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Sample records for plasma cvd technique

  1. Characterization of nanocrystalline gold/DLC composite films synthesized by plasma CVD technique

    NASA Astrophysics Data System (ADS)

    Paul, R.; Hussain, S.; Pal, A. K.

    2009-06-01

    Composite films containing gold nanoparticles embedded in diamond-like carbon (Au-DLC) matrix were deposited on glass and Si (1 0 0) substrates by using capacitatively coupled plasma (CCP) chemical vapour deposition technique (CVD). Particle size and metal volume fraction were tailored by varying the relative amount of argon in the methane + argon gas mixture in the plasma. Optical constants of the films were evaluated. Bonding environment in these films were obtained from Raman and Fourier transformed infrared spectra (FTIR) studies. Blue-shift of the surface plasmon resonance peak in the optical absorbance spectra of the films could be associated with the reduction of the particle size while red shift was observed with the increase in volume fraction of metal particles in the DLC films. Absorption spectra recorded in the reflection mode indicated dichromatism in these films.

  2. Synthesis and characterization of composite films of silver nanoparticles embedded in DLC matrix prepared by plasma CVD technique

    NASA Astrophysics Data System (ADS)

    Paul, R.; Gayen, R. N.; Hussain, S.; Khanna, V.; Bhar, R.; Pal, A. K.

    2009-07-01

    Composite films containing silver nanoparticles embedded in diamond-like carbon (DLC) matrix were deposited on glass substrates by using capacitatively coupled plasma (CCP) chemical vapour deposition techninique (CVD). Particle size and metal volume fraction were tailored by varying the relative amount of methane of a gas mixture of methane + argon in the plasma. Optical constants of the films were evaluated. Bonding environment in these films were obtained from Raman and FTIR studies. Blue-shift of the surface plasmon resonance peak in the optical absorbance spectra of the films could be associated with the reduction of the particle size while red shift was associated with the increase in volume fraction of metal particles. The experimental results have been discussed in light of the existing Mie theory.

  3. Plasma CVD of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Delzeit, Lance; Cruden, B.; Hash, D.; Meyyappan, M.; DeVincenzi, Donald L. (Technical Monitor)

    2001-01-01

    Carbon nanotubes(CNT) exhibit remarkable mechanical and unique electronic properties and thus have created excitement in the research community about their potential in electronics, computing, sensor and structural applications. Realization of these applications critically depends on the ability to control the properties(such as diameter, chirality) as well purity. We have investigated CNT growth using an inductively coupled plasma(ICP) process using hydrocarbon feedstock. The catalyst required for nanotube growth consists of thin sputtered layers of aluminum and iron(10 nm each) and aligned carbon nanotubes have been obtained. Optical emission diagnostics as well as a plasma modeling effort have been undertaken to understand growth mechanisms. This presentation will discuss growth characteristics under various pressure, power and feedgas compositions and our understanding from modeling and diagnostics.

  4. Investigation of the Millimeter-Wave Plasma Assisted CVD Reactor

    SciTech Connect

    Vikharev, A; Gorbachev, A; Kozlov, A; Litvak, A; Bykov, Y; Caplan, M

    2005-07-21

    A polycrystalline diamond grown by the chemical vapor deposition (CVD) technique is recognized as a unique material for high power electronic devices owing to unrivaled combination of properties such as ultra-low microwave absorption, high thermal conductivity, high mechanical strength and chemical stability. Microwave vacuum windows for modern high power sources and transmission lines operating at the megawatt power level require high quality diamond disks with a diameter of several centimeters and a thickness of a few millimeters. The microwave plasma-assisted CVD technique exploited today to produce such disks has low deposition rate, which limits the availability of large size diamond disk windows. High-electron-density plasma generated by the millimeter-wave power was suggested for enhanced-growth-rate CVD. In this paper a general description of the 30 GHz gyrotron-based facility is presented. The output radiation of the gyrotron is converted into four wave-beams. Free localized plasma in the shape of a disk with diameter much larger than the wavelength of the radiation is formed in the intersection area of the wave-beams. The results of investigation of the plasma parameters, as well as the first results of diamond film deposition are presented. The prospects for commercially producing vacuum window diamond disks for high power microwave devices at much lower costs and processing times than currently available are outlined.

  5. Fabrication of graphene-based films using remote plasma CVD

    NASA Astrophysics Data System (ADS)

    Hiramatsu, Mineo; Tsukada, Ryosuke; Kashima, Yohei; Naito, Masateru; Kondo, Hiroki; Hori, Masaru

    2012-10-01

    Plasma-enhanced CVD (PECVD) employing methane/hydrogen gases has been used to grow diamond, diamond-like carbon, and carbon nanotubes. In the case of microwave PECVD with methane/hydrogen system without catalyst nanoparticles at temperatures of 700--850 ^oC, where the substrate is exposed to the plasma, vertical nano-graphenes and carbon nanoflakes have been easily grown even on Cu substrate due to the ion bombardment and local electric field forces. In this work, we demonstrate the synthesis of planar few-layer graphene-based film using PECVD with remote plasma configuration. In the case using microwave plasma of cylindrical resonant cavity type, by simply installing grounded grid over the substrate plate for obtaining remote plasma configuration, we have successfully fabricated graphene-based films on Cu substrate, which was confirmed by the Raman spectrum and SEM image of deposit. Similar method will be applied to other plasmas such as low-pressure inductively coupled plasma, in order to verify the effectiveness of remote plasma configuration for the growth of planar graphene using PECVD technique. We will discuss the planar graphene growth mechanism in terms of precursors and their surface reaction.

  6. Plasma lipoprotein (a), homocysteine, and other cardiovascular disease (CVD) risk factors in Nigerians with CVD.

    PubMed

    Ebesunun, M O; Agbedana, E O; Taylor, G O L; Oladapo, O O

    2008-04-01

    Elevated plasma lipoprotein (a) (Lp(a)) and total homocysteine (tHcy) concentrations, as well as fat distributions, are associated with cardiovascular disease (CVD) risk. The purpose of this study was to evaluate plasma Lp(a), tHcy, percentage body fat, anthropometric indices, and blood pressure (BP) and their relationships with each other in well-defined, hospital-based, CVD patients in a Nigerian African community. One hundred seventy patients suffering from hypertensive heart disease, hypertension, ischaemic heart disease, and myocardial infraction with the mean age of 45.3 +/- 1.3 years and 58 apparently healthy volunteers with the mean age of 44.8 +/-1.2 years were selected. Anthropometric indices and BP were measured. Percentage body fat, body mass index, and waist-to-hip ratio (WHR) were calculated. Plasma Lp(a) and tHcy concentrations were determined. The results showed significant increases in BP, skinfold thickness (SFT) variables, and WHR in all of the CVD patients. Plasma Lp(a) was also significantly increased (p < 0.001), whereas the slight increase in the mean tHcy was not statistically significant. Positive significant correlations were found between systolic BP, triceps, SFT, and percentage body fat (p < 0.01), whereas significant correlations were found between some body composition variables, tHcy, and systolic BP (p < 0.05). Our findings provide supportive evidence for altered plasma Lp(a) concentration in addition to some other traditional CVD risk factors in Nigerians. The role of homocysteine is not well defined.

  7. Toroidal plasma enhanced CVD of diamond films

    SciTech Connect

    Zvanya, John Cullen, Christopher Morris, Thomas Krchnavek, Robert R.; Holber, William Basnett, Andrew Basnett, Robert; Hettinger, Jeffrey

    2014-09-01

    An inductively coupled toroidal plasma source is used as an alternative to microwave plasmas for chemical vapor deposition of diamond films. The source, operating at a frequency of 400 kHz, synthesizes diamond films from a mixture of argon, methane, and hydrogen. The toroidal design has been adapted to create a highly efficient environment for diamond film deposition: high gas temperature and a short distance from the sample to the plasma core. Using a toroidal plasma geometry operating in the medium frequency band allows for efficient (≈90%) coupling of AC line power to the plasma and a scalable path to high-power and large-area operation. In test runs, the source generates a high flux of atomic hydrogen over a large area, which is favorable for diamond film growth. Using a deposition temperature of 900–1050 °C and a source to sample distance of 0.1–2.0 cm, diamond films are deposited onto silicon substrates. The results showed that the deposition rate of the diamond films could be controlled using the sample temperature and source to sample spacing. The results also show the films exhibit good-quality polycrystalline diamond as verified by Raman spectroscopy, x-ray diffraction, and scanning electron microscopy. The scanning electron microscopy and x-ray diffraction results show that the samples exhibit diamond (111) and diamond (022) crystallites. The Raman results show that the sp{sup 3} peak has a narrow spectral width (FWHM 12 ± 0.5 cm{sup −1}) and that negligible amounts of the sp{sup 2} band are present, indicating good-quality diamond films.

  8. Substrate temperature measurement and control during thermal plasma CVD

    SciTech Connect

    Zhuang, Q.D.; Guo, H.; Han, Q.Y.; Heberlein, J.V.R.; Pfender, E.

    1993-09-01

    A technique is proposed for substrate temperature control, with emphasis on temperature uniformity across substrate. The technique includes a substrate holder design employing non-uniform water cooling and a means of substrate attachment featured by controlled thermal contact resistance for a given heat flux distribution from the plasma. The technique was applied to deposit diamond films over a 5 cm diameter area in a DC thermal plasma reactor, and proved adequate. Performance of single-color (0.655 {mu}m) and two-color (2.1 and 2.4 {mu}m) pyrometers were evaluated against DC thermo.] plasma radiation. It was found that both line and continuum emission of plasma jets caused large errors in temperature measurement of the single-color pyrometer. The two-color pyrometer, however, is shown to be less sensitive to the plasma radiation. The way the substrate temperature was controlled and monitored in this study is in general applicable to other TPCVD processes where intense local heating and a bright plasma background exist.

  9. Advanced Functional Thin Films Prepared by Plasma CVD

    NASA Astrophysics Data System (ADS)

    Takai, Osamu

    1998-10-01

    Recently water repellency has been required for many types of substrate (e.g. glass, plastics, fibers, ceramics and metals) in various industrial fields. This paper reports on the preparation of highly water-repellent thin films by plasma CVD (PCVD). We have prepared transparent water-repellent thin films at low substrate temperatures by two types of PCVD, rf PCVD and microwave PCVD, using fluoro-alkyl silanes (FASs) as source gases. Silicon oxide thin films contained fluoro-alkyl functions were deposited onto glass and plastics, and realized the excellent water repellency like polytetrafluoroetylene (PTFE) and the high transparency like glass. Increasing the deposition pressure we have formed ultra water-repellent (contact angle for a water drop of over about 150 degrees) thin films by microwave PCVD using a multiple gas mixture of tetramethylsilane (TMS), (heptadecafluoro-1,1,2,2-tetrahydro-decyl)-1-trimethoxysilane (FAS-17) and argon. Ultra water-repellency appears at higher total pressures over 40 Pa because the surface becomes rough due to the growth of large particles. The color of these ultra water-repellent films is slightly white because of the scattering of light by the large particles. Recently we have also deposited transparent ultra water-repellent thin films at low substrate temperatures by microwave PCVD using organosilicon compounds without fluorine as source gases. We evaluated water repellency, optical transmittance, surface morphology and chemical composition of the deposited films. At the suitable substrate position the deposited film gave the contact angle of about 150 degrees and the transmittance of over 80 visible region for a coated glass (thickness was about 1 micron). The control of the surface morphology of the deposited films is most important to obtain the transparent ultra water-repellent films.

  10. Use of a remote plasma source for CVD chamber clean and exhaust gas abatement applications

    SciTech Connect

    Holber, W.; Chen, X.; Smith, D.; Besen, M.

    1999-07-01

    Remote plasma sources have traditionally been used in semiconductor processing applications such as dry removal of photoresist, where the capability of delivering a large flux of atomic oxygen into a semiconductor process chamber, with little of the associated plasma used to dissociate the oxygen, has made them attractive. With the development of fluorine-compatible remote plasma sources, a range of new application opportunities has opened up. In remote cleaning of CVD chambers, the remote plasma source is positioned before the process chamber, and a stream of atomic fluorine from the source is flowed into the chamber, where it can effectively clean a wide variety of materials such as SiO{sub 2}, Si{sub 3}N{sub 4}, and W. The cleaning process is purely chemical, with no associated in-situ plasma which can cause degradation of the process chamber. In exhaust gas abatement, the remote plasma source is located between the outlet of the etch or deposition process chamber and the mechanical pump. By adding appropriate gases, the exhaust stream from the chamber can be converted to form which can be managed more readily. Using a robust toroidal plasma source design, the ASTRON{trademark} remote plasma source has been used to address both of these areas. As an atomic fluorine source, over the typical operating range of 2--10 Torr several SLM of gases such as NF{sub 3} can be fully dissociated. As an exhaust gas abatement device, with operating pressure in the 0.1--1.0 Torr regime, abatement of perfluorocompounds (PFC's) at greater than 95% levels has been demonstrated. Using a variety of techniques--FTIR, RGA, and sample etching--the operation of this source technology and issues such as transport of atomic fluorine over substantial distances has been investigated.

  11. Photo-oxidation of Polymers Synthesized by Plasma and Initiated CVD

    DOE PAGES

    Baxamusa, Salmaan H.; Suresh, Aravind; Ehrmann, Paul; Laurence, Ted; Hanania, Jiries; Hayes, Jeff; Harley, Stephen; Burkey, Daniel D.

    2015-11-09

    Plasma polymers are often limited by their susceptibility to spontaneous and photo-oxidation. We show that the unusual photoluminescence (PL) behavior of a plasma polymer of trans-2-butene is correlated with its photoluminescence strength. These photo-processes occur under blue light illumination (λ=405 nm), distinguishing them from traditional ultraviolet degradation of polymers. These photo-active defects are likely formed during the plasma deposition process and we show that a polymer synthesized using initiated (i)CVD, non-plasma method, has 1000× lower PL signal and enhanced photo-stability. In conclusion, non-plasma methods such as iCVD may therefore be a route to overcoming material aging issues that limit themore » adoption of plasma polymers.« less

  12. Photo-oxidation of Polymers Synthesized by Plasma and Initiated CVD

    SciTech Connect

    Baxamusa, Salmaan H.; Suresh, Aravind; Ehrmann, Paul; Laurence, Ted; Hanania, Jiries; Hayes, Jeff; Harley, Stephen; Burkey, Daniel D.

    2015-11-09

    Plasma polymers are often limited by their susceptibility to spontaneous and photo-oxidation. We show that the unusual photoluminescence (PL) behavior of a plasma polymer of trans-2-butene is correlated with its photoluminescence strength. These photo-processes occur under blue light illumination (λ=405 nm), distinguishing them from traditional ultraviolet degradation of polymers. These photo-active defects are likely formed during the plasma deposition process and we show that a polymer synthesized using initiated (i)CVD, non-plasma method, has 1000× lower PL signal and enhanced photo-stability. In conclusion, non-plasma methods such as iCVD may therefore be a route to overcoming material aging issues that limit the adoption of plasma polymers.

  13. Few layers isolated graphene domains grown on copper foils by microwave surface wave plasma CVD using camphor as a precursor

    NASA Astrophysics Data System (ADS)

    Ram Aryal, Hare; Adhikari, Sudip; Uchida, Hideo; Wakita, Koichi; Umeno, Masayoshi

    2016-03-01

    Few layers isolated graphene domains were grown by microwave surface wave plasma CVD technique using camphor at low temperature. Graphene nucleation centers were suppressed on pre-annealed copper foils by supplying low dissociation energy. Scanning electron microscopy study of time dependent growth reveals that graphene nucleation centers were preciously suppressed, which indicates the possibility of controlled growth of large area single crystal graphene domains by plasma processing. Raman spectroscopy revealed that the graphene domains are few layered which consist of relatively low defects.

  14. Moisture barrier properties of thin organic-inorganic multilayers prepared by plasma-enhanced ALD and CVD in one reactor

    NASA Astrophysics Data System (ADS)

    Bülow, Tim; Gargouri, Hassan; Siebert, Mirko; Rudolph, Rolf; Johannes, Hans-Hermann; Kowalsky, Wolfgang

    2014-05-01

    A widely used application of the atomic layer deposition (ALD) and chemical vapour deposition (CVD) methods is the preparation of permeation barrier layers against water vapour. Especially in the field of organic electronics, these films are highly demanded as such devices are very sensitive to moisture and oxygen. In this work, multilayers of aluminium oxide (AlO x ) and plasma polymer (PP) were coated on polyethylene naphthalate substrates by plasma-enhanced ALD and plasma-enhanced CVD at 80℃ in the same reactor, respectively. As precursor, trimethylaluminium was used together with oxygen radicals in order to prepare AlO x , and benzene served as precursor to deposit the PP. This hybrid structure allows the decoupling of defects between the single AlO x layers and extends the permeation path for water molecules towards the entire barrier film. Furthermore, the combination of two plasma techniques in a single reactor system enables short process times without vacuum breaks. Single aluminium oxide films by plasma-enhanced ALD were compared to thermally grown layers and showed a significantly better barrier performance. The water vapour transmission rate (WVTR) was determined by means of electrical calcium tests. For a multilayer with 3.5 dyads of 25-nm AlO x and 125-nm PP, a WVTR of 1.2 × 10 -3 g m -2 d -1 at 60℃ and 90% relative humidity could be observed.

  15. Moisture barrier properties of thin organic-inorganic multilayers prepared by plasma-enhanced ALD and CVD in one reactor.

    PubMed

    Bülow, Tim; Gargouri, Hassan; Siebert, Mirko; Rudolph, Rolf; Johannes, Hans-Hermann; Kowalsky, Wolfgang

    2014-01-01

    A widely used application of the atomic layer deposition (ALD) and chemical vapour deposition (CVD) methods is the preparation of permeation barrier layers against water vapour. Especially in the field of organic electronics, these films are highly demanded as such devices are very sensitive to moisture and oxygen. In this work, multilayers of aluminium oxide (AlO x ) and plasma polymer (PP) were coated on polyethylene naphthalate substrates by plasma-enhanced ALD and plasma-enhanced CVD at 80â"ƒ in the same reactor, respectively. As precursor, trimethylaluminium was used together with oxygen radicals in order to prepare AlO x , and benzene served as precursor to deposit the PP. This hybrid structure allows the decoupling of defects between the single AlO x layers and extends the permeation path for water molecules towards the entire barrier film. Furthermore, the combination of two plasma techniques in a single reactor system enables short process times without vacuum breaks. Single aluminium oxide films by plasma-enhanced ALD were compared to thermally grown layers and showed a significantly better barrier performance. The water vapour transmission rate (WVTR) was determined by means of electrical calcium tests. For a multilayer with 3.5 dyads of 25-nm AlO x and 125-nm PP, a WVTR of 1.2 × 10 (-3) gm (-2) d (-1) at 60â"ƒ and 90% relative humidity could be observed.

  16. Moisture barrier properties of thin organic-inorganic multilayers prepared by plasma-enhanced ALD and CVD in one reactor

    PubMed Central

    2014-01-01

    A widely used application of the atomic layer deposition (ALD) and chemical vapour deposition (CVD) methods is the preparation of permeation barrier layers against water vapour. Especially in the field of organic electronics, these films are highly demanded as such devices are very sensitive to moisture and oxygen. In this work, multilayers of aluminium oxide (AlO x ) and plasma polymer (PP) were coated on polyethylene naphthalate substrates by plasma-enhanced ALD and plasma-enhanced CVD at 80℃ in the same reactor, respectively. As precursor, trimethylaluminium was used together with oxygen radicals in order to prepare AlO x , and benzene served as precursor to deposit the PP. This hybrid structure allows the decoupling of defects between the single AlO x layers and extends the permeation path for water molecules towards the entire barrier film. Furthermore, the combination of two plasma techniques in a single reactor system enables short process times without vacuum breaks. Single aluminium oxide films by plasma-enhanced ALD were compared to thermally grown layers and showed a significantly better barrier performance. The water vapour transmission rate (WVTR) was determined by means of electrical calcium tests. For a multilayer with 3.5 dyads of 25-nm AlO x and 125-nm PP, a WVTR of 1.2 × 10 −3 gm−2d−1 at 60℃ and 90% relative humidity could be observed. PMID:24936155

  17. Moisture barrier properties of thin organic-inorganic multilayers prepared by plasma-enhanced ALD and CVD in one reactor.

    PubMed

    Bülow, Tim; Gargouri, Hassan; Siebert, Mirko; Rudolph, Rolf; Johannes, Hans-Hermann; Kowalsky, Wolfgang

    2014-01-01

    A widely used application of the atomic layer deposition (ALD) and chemical vapour deposition (CVD) methods is the preparation of permeation barrier layers against water vapour. Especially in the field of organic electronics, these films are highly demanded as such devices are very sensitive to moisture and oxygen. In this work, multilayers of aluminium oxide (AlO x ) and plasma polymer (PP) were coated on polyethylene naphthalate substrates by plasma-enhanced ALD and plasma-enhanced CVD at 80â"ƒ in the same reactor, respectively. As precursor, trimethylaluminium was used together with oxygen radicals in order to prepare AlO x , and benzene served as precursor to deposit the PP. This hybrid structure allows the decoupling of defects between the single AlO x layers and extends the permeation path for water molecules towards the entire barrier film. Furthermore, the combination of two plasma techniques in a single reactor system enables short process times without vacuum breaks. Single aluminium oxide films by plasma-enhanced ALD were compared to thermally grown layers and showed a significantly better barrier performance. The water vapour transmission rate (WVTR) was determined by means of electrical calcium tests. For a multilayer with 3.5 dyads of 25-nm AlO x and 125-nm PP, a WVTR of 1.2 × 10 (-3) gm (-2) d (-1) at 60â"ƒ and 90% relative humidity could be observed. PMID:24936155

  18. Microwave plasma CVD of NANO structured tin/carbon composites

    DOEpatents

    Marcinek, Marek; Kostecki, Robert

    2012-07-17

    A method for forming a graphitic tin-carbon composite at low temperatures is described. The method involves using microwave radiation to produce a neutral gas plasma in a reactor cell. At least one organo tin precursor material in the reactor cell forms a tin-carbon film on a supporting substrate disposed in the cell under influence of the plasma. The three dimensional carbon matrix material with embedded tin nanoparticles can be used as an electrode in lithium-ion batteries.

  19. Low-temperature synthesis of carbon nitride by microwave plasma CVD

    NASA Astrophysics Data System (ADS)

    Tanaka, Ippei; Sakamoto, Yukihiro

    2016-01-01

    Investigation of the low temperature synthesis of carbon nitride was carried out by microwave plasma CVD. Carbon nitride was synthesized using an improved microwave plasma CVD apparatus. Si was used as the substrate. A mixture of CH4 and N2 gas was used as a reaction gas. Synthesis pressure was varied from 1.1 to 4.0 kPa, microwave power was varied from 400 to 800 W. Faceted particles were obtained at a microwave power of 800 W and a substrate temperature of 880 K. Faceted particles were obtained at various synthesis pressures and a substrate temperature of as low as 740 K. Also, β-Si3N4 and α-C3N4 peaks were observed in the X-ray diffraction (XRD) pattern. As a result of studies of the low-temperature synthesis of carbon nitride by microwave plasma CVD, the morphology of deposits was found to depend on substrate temperature, and faceted particles were obtained at a substrate temperature as low as 740 K.

  20. Field emission from carbon nanotubes produced using microwave plasma assisted CVD

    SciTech Connect

    Zhang, Q.; Yoon, S.F.; Ahn, J.; Gan, B.; Rusli; Yu, M.B.; Cheah, L.K.; Shi, X.

    2000-01-30

    Electron field emission from carbon nanotubes prepared using microwave plasma assisted CVD has been investigated. The nanotubes, ranging from 50 to 120 nm in diameter and a few tens of microns in length, were formed under methane and hydrogen plasma at 720 C with the aid of iron-oxide particles. The morphology and growth direction of the nanotubes are found to be strongly influenced by the flow ratio of methane to hydrogen. However, the electron field emission from these massive nanotubes show similar characteristics, i.e., high emission current at low electric fields.

  1. Effects of Time Parameter in Pulse Plasma CVD on Narrow-Chirality Distributed growth of Single-Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Xu, Bin; Kato, Toshiaki; Kaneko, Toshiro

    2015-09-01

    Single-walled carbon nanotubes (SWNTs) are promising materials in industry application, since they have many brilliant characteristics However, since the electronic and optical properties of SWNTs strongly depend on chirality, the selective synthesis of SWNTs with desired chiralities is one of the major challenges in nanotubes science and applications. In this study, time-controlled pulse plasma CVD has been developed aiming for the mass production of narrow chirality distributed SWNTs. Through the comparison of continuous plasma CVD and pulse plasma CVD, it is found that the amount of SWNTs can be increased in keeping with the initial narrow chirality distribution by repeating pulse plasma CVD. The effects of pulse time parameter, plasma off time, on the chirality distribution of SWNTs are also investigated. The chirality distribution becomes narrow with an increase in the plasma off time up to 60 sec, then it becomes broad with an increase in the off time. These indicate, adjustment of plasma time parameter in pulse plasma CVD can improve the uniformity of chirality distribution, resulting in the mass production of very narrow chirality distributed SWNTs. This work was supported by a Grant-in-Aid for JSPS Fellows Grant Number 15J01481.

  2. A thermocouple-based remote temperature controller of an electrically floated sample to study plasma CVD growth of carbon nanotube

    NASA Astrophysics Data System (ADS)

    Miura, Takuya; Xie, Wei; Yanase, Takashi; Nagahama, Taro; Shimada, Toshihiro

    2015-09-01

    Plasma chemical vapor deposition (CVD) is now gathering attention from a novel viewpoint, because it is easy to combine plasma processes and electrochemistry by applying a bias voltage to the sample. In order to explore electrochemistry during the plasma CVD, the temperature of the sample must be controlled precisely. In traditional equipment, the sample temperature is measured by a radiation thermometer. Since emissivity of the sample surface changes in the course of the CVD growth, it is difficult to measure the exact temperature using the radiation thermometer. In this work, we developed new equipment to control the temperature of electrically floated samples by thermocouple with Wi-Fi transmission. The growth of the CNT was investigated using our plasma CVD equipment. We examined the temperature accuracy and stability controlled by the thermocouple with monitoring the radiation thermometer. We noticed that the thermocouple readings were stable, whereas the readings of the radiation thermometer changes significantly (20 °C) during plasma CVD. This result clearly shows that the sample temperature should be measured with direct connection. On the result of CVD experiment, different structures of carbon including CNT were obtained by changing the bias voltages.

  3. Microwave engineering of plasma-assisted CVD reactors for diamond deposition

    NASA Astrophysics Data System (ADS)

    Silva, F.; Hassouni, K.; Bonnin, X.; Gicquel, A.

    2009-09-01

    The unique properties of CVD diamond make it a compelling choice for high power electronics. In order to achieve industrial use of CVD diamond, one must simultaneously obtain an excellent control of the film purity, very low defect content and a sufficiently rapid growth rate. Currently, only microwave plasma-assisted chemical vapour deposition (MPACVD) processes making use of resonant cavity systems provide enough atomic hydrogen to satisfy these requirements. We show in this paper that the use of high microwave power density (MWPD) plasmas is necessary to promote atomic hydrogen concentrations that are high enough to ensure the deposition of high purity diamond films at large growth rates. Moreover, the deposition of homogeneous films on large surfaces calls for the production of plasma with appropriate shapes and large volumes. The production of such plasmas needs generating a fairly high electric field over extended regions and requires a careful design of the MW coupling system, especially the cavity. As far as MW coupling efficiency is concerned, the presence of a plasma load represents a mismatching perturbation to the cavity. This perturbation is especially important at high MWPD where the reflected fraction of the input power may be quite high. This mismatch can lead to a pronounced heating of the reactor walls. It must therefore be taken into account from the very beginning of the reactor design. This requires the implementation of plasma modelling tools coupled to detailed electromagnetic simulations. This is discussed in section 3. We also briefly discuss the operating principles of the main commercial plasma reactors before introducing the reactor design methodology we have developed. Modelling results for a new generation of reactors developed at LIMHP, working at very high power density, will be presented. Lastly, we show that scaling up this type of reactor to lower frequencies (915 MHz) can result in high density plasmas allowing for fast and

  4. Mechanical properties of nanostructured carbon layers grown by CVD and PLD techniques

    NASA Astrophysics Data System (ADS)

    Mangione, A.; Lanzara, G.; Torrisi, L.; Caridi, F.

    2010-10-01

    Pulsed laser deposition (PLD) and chemical vapour deposition (CVD) have been proven to be among the most successful techniques for growing the entire spectrum of carbon films, which can be used in a wide range of technical applications. Here an investigation has been performed to explore the effect of different growing techniques (PLD and CVD) and process parameters (such as deposition time and substrate type) on the films' morphology and mechanical properties. The mechanical properties of the grown thin films were characterised by means of nano/micro indentation and scratch test techniques. It was observed that the thickness of the Al2O3 interlayer (between the Fe catalyst nanoparticles and the silicon substrate) is a critical parameter that can be used to significantly enhance the adhesion strength of PLD-grown carbon films. PLD-grown carbon films were in fact found to have higher adhesion to the substrate than CVD-grown carbon nanotubes (CNT), and the adhesion strength was found to increase with increasing thickness of the Al2O3 interlayer. On the other hand, CVD-grown carbon films (made of aligned CNTs) seem to offer a greater response in terms of elastic modulus. A thorough scanning electron microscopy characterisation suggested that the observed mechanical responses might be correlated to the films' morphology at the nano/microscale. It was in fact observed that, in PLD-grown samples, an increasing deposition time and Al2O3 content leads to a grain size increase and to a clustering effect, thus to a loss in film uniformity.

  5. Simultaneous synthesis of nanodiamonds and graphene via plasma enhanced chemical vapor deposition (MW PE-CVD) on copper.

    PubMed

    Gottlieb, Steven; Wöhrl, Nicolas; Schulz, Stephan; Buck, Volker

    2016-01-01

    The simultaneous growth of both nanodiamonds and graphene on copper samples is described for the first time. A PE-CVD process is used to synthesize graphene layers and nanodiamond clusters from a hydrogen/methane gas mixture as it is typically done successfully in thermal CVD processes for graphene synthesis. However, the standard thermal CVD process is not without problems since the deposition of graphene is affected by the evaporation of a notable amount of copper caused by the slow temperature increase typical for thermal CVD resulting in a long process time. In sharp contrast, the synthesis of graphene by PE-CVD can circumvent this problem by substantially shortening the process time at holding out the prospect of a lower substrate temperature. The reduced thermal load and the possibility to industrially scale-up the PE-CVD process makes it a very attractive alternative to the thermal CVD process with respect to the graphene production in the future. Nanodiamonds are synthesized in PE-CVD reactors for a long time because these processes offer a high degree of control over the film's nanostructure and simultaneously providing a significant high deposition rate. To model the co-deposition process, the three relevant macroscopic parameters (pressure, gas mixture and microwave power) are correlated with three relevant process properties (plasma ball size, substrate temperature and C2/Hα-ratio) and the influence on the quality of the deposited carbon allotropes is investigated. For the evaluation of the graphene as well as the nanodiamond quality, Raman spectroscopy used whereas the plasma properties are measured by optical methods. It is found that the diamond nucleation can be influenced by the C2/Hα-ratio in the plasma, while the graphene quality remains mostly unchanged by this parameter. Moreover it is derived from the experimental data that the direct plasma contact with the copper surface is beneficial for the nucleation of the diamond while the growth and

  6. Simultaneous synthesis of nanodiamonds and graphene via plasma enhanced chemical vapor deposition (MW PE-CVD) on copper.

    PubMed

    Gottlieb, Steven; Wöhrl, Nicolas; Schulz, Stephan; Buck, Volker

    2016-01-01

    The simultaneous growth of both nanodiamonds and graphene on copper samples is described for the first time. A PE-CVD process is used to synthesize graphene layers and nanodiamond clusters from a hydrogen/methane gas mixture as it is typically done successfully in thermal CVD processes for graphene synthesis. However, the standard thermal CVD process is not without problems since the deposition of graphene is affected by the evaporation of a notable amount of copper caused by the slow temperature increase typical for thermal CVD resulting in a long process time. In sharp contrast, the synthesis of graphene by PE-CVD can circumvent this problem by substantially shortening the process time at holding out the prospect of a lower substrate temperature. The reduced thermal load and the possibility to industrially scale-up the PE-CVD process makes it a very attractive alternative to the thermal CVD process with respect to the graphene production in the future. Nanodiamonds are synthesized in PE-CVD reactors for a long time because these processes offer a high degree of control over the film's nanostructure and simultaneously providing a significant high deposition rate. To model the co-deposition process, the three relevant macroscopic parameters (pressure, gas mixture and microwave power) are correlated with three relevant process properties (plasma ball size, substrate temperature and C2/Hα-ratio) and the influence on the quality of the deposited carbon allotropes is investigated. For the evaluation of the graphene as well as the nanodiamond quality, Raman spectroscopy used whereas the plasma properties are measured by optical methods. It is found that the diamond nucleation can be influenced by the C2/Hα-ratio in the plasma, while the graphene quality remains mostly unchanged by this parameter. Moreover it is derived from the experimental data that the direct plasma contact with the copper surface is beneficial for the nucleation of the diamond while the growth and

  7. Low pressure plasma diagnostics by cars and other techniques

    SciTech Connect

    Hata, N. )

    1989-01-01

    Within the past several years, intensive research activities relating amorphous-silicon technology have stimulated plasma-chemical-vapor-deposition (plasma-CVD) diagnostics by laser-spectroscopic techniques. Among them, coherent anti-Stokes Raman spectroscopy (CARS) has attracted much attention because of its great success in combustion diagnostics, and has been employed for low-pressure-plasma studies. Gas-phase species such as SiH{sub 4}, H{sub 2}, Si{sub 2}H{sub 6}, SiH{sub 2}, and GeH{sub 4} have been detected, time dependences of their concentration and spatial profiles of their concentration and rotational temperature have been determined, and the gas-phase mechanisms have been discussed. This talk will employ those results as examples, and discuss (1) the potential of CARS for gas-phase analysis in CVD (including (i) what species are monitored, (ii) what information is obtained, and (iii) what are the advantages and limitations), and (2) some other diagnostic techniques that provide additional information for better understandings of CVD mechanisms.

  8. Diagnostic techniques for thermal plasmas

    SciTech Connect

    Fincke, J.R.; Snyder, S.C.; Swank, W.D.; Haggard, D.C.; Reynolds, L.D.

    1994-12-31

    The plasma diagnostic techniques discussed are Rayleigh and coherent Thomson scattering, Coherent-Anti-Stokes-Raman Spectroscopy (CARS) and enthalpy probes. The quantities measured are heavy species and electron temperature, ionized fraction, plasma composition, and velocity. Examples of results from both subsonic and supersonic jets are presented and limitations discussed.

  9. Synthesis and characterization of carbon-encapsulated magnetic nanoparticles via arc-plasma assisted CVD

    SciTech Connect

    Li, Z.T.; Hu, C.; Yu, C.; Qiu, J.S.

    2009-12-15

    Carbon-encapsulated magnetic nanoparticles (CEMNs) were fabricated on a large scale by arc-plasma assisted CVD in acetylene. The coal-derived metal-containing (Fe, Co and Ni) carbon rods were used as anodes, while a high-purity graphite rod was used as a cathode that remained unchanged during the arcing process. The CEMNs obtained were characterized by TEM, XRD, Raman spectroscopy, N{sub 2} adsorption isotherms and VSM. The diameter distribution of the obtained CEMNs varies from 10 to 70 nm, of which the metal cores are proximately 5-50 nm. The core phases in Fe ) nanoparticles are body-centered cubic Fe and orthorhombic Fe3C while Co ) nanoparticles and Ni ) nanoparticles show the characteristic of a face-centered cubic structure. The Fe ), Co ) and Ni ) nanoparticles with well-ordered graphitic shells have the surface area of 89 m{sup 2}/g, 72 m{sup 2}/g and 75 m{sup 2}/g, respectively. The CEMNs show ferromagnetic of which was characterized by a ratio of remnant magnetization (MR) to saturation magnetization (MS).

  10. A symmetrical bi-electrode electrochemical technique for high-efficiency transfer of CVD-grown graphene

    NASA Astrophysics Data System (ADS)

    Shi, Liangjing; Liu, Yangqiao; Yang, Fan; Gao, Lian; Sun, Jing

    2014-04-01

    Graphene transfer is a critical process in the journey from CVD-grown graphene to device application. The current transfer techniques use a chemical-etching method to oxidize the metal catalyst, which is heavily time-consuming and involves a high material cost. In this study, a highly efficient symmetrical bi-electrode technique has been developed to simultaneously delaminate the CVD-grown graphene from the metal catalyst at both the anode and cathode of the electrolytic cell. Raman spectra, UV-visible transmittance, and four-probe measurements confirm that this transfer process is nondestructive and can produce similar electrical properties to those produced by the conventional metal-etching transfer method. This bi-electrode transfer technique possesses the advantages of high efficiency, recyclable use of metal catalyst, and high electrical conductivity, and it can be potentially applied for industrial applications.

  11. Epitaxial thin film GaAs solar cells using OM-CVD techniques. [Organometallics

    NASA Technical Reports Server (NTRS)

    Stirn, R. J.; Wang, K. L.; Yeh, Y. C. M.

    1981-01-01

    A new approach has been initiated at JPL to fabricate thin-film, high efficiency GaAs solar cells on low-cost, single-crystal Si substrates having a thin CVD interlayer of Ge to minimize the lattice and thermal expansion mismatch. For initial experiments, n(+)/p GaAs cells were grown by OM-CVD on single-crystal GaAs and Ge wafers. Details of the growths and performance results will be presented. Subsequently, a combined epitaxial structure of OM-CVD GaAs on a strongly adherent Ge interlayer on (100) Si was grown. This is the first report of the successful growth of this composite structure. Low module costs projected by JPL SAMICS methodology calculations and the potential for 400-600W/kg space solar arrays will be discussed.

  12. System for the growth of bulk SiC crystals by modified CVD techniques

    NASA Technical Reports Server (NTRS)

    Steckl, Andrew J.

    1994-01-01

    The goal of this program was the development of a SiC CVD growth of films thick enough to be useful as pseudo-substrates. The cold-walled CVD system was designed, assembled, and tested. Extrapolating from preliminary evaluation of SiC films grown in the system at relatively low temperatures indicates that the growth rate at the final temperatures will be high enough to make our approach practical. Modifications of the system to allow high temperature growth and cleaner growth conditions are in progress. This program was jointly funded by Wright Laboratory, Materials Directorate and NASA LeRC and monitored by NASA.

  13. Atmospheric pressure plasma CVD as a tool to functionalise wound dressings.

    PubMed

    Spange, Sebastian; Pfuch, Andreas; Wiegand, Cornelia; Beier, Oliver; Hipler, Uta C; Grünler, Bernd

    2015-02-01

    The main goal of this investigation was the preparation of an antibacterial layer system for additional modification of wound dressings with atmospheric plasma. Furthermore, the modified wound dressings were checked on there bactericidal and cytotoxic activity. The layer system was applied by using a novel atmospheric pressure plasma chemical vapour deposition technique on a variety of textile substrates which are suitable as wound dressing materials. The layer system composed of silicon dioxide with in situ generated embedded silver nanoparticles. The bactericidal activity of the produced wound dressings was investigated against different bacteria like Staphylococcus aureus and Klebsiella pneumoniae while the cytotoxic potential of the coated wound dressings was verified using human keratinocytes. Even at low concentrations of silver precursor a strong antibacterial effect was observed in direct contact with S. aureus and K. pneumoniae. Furthermore, extractions produced from the coated textiles showed a good antibacterial effect. By means of optimised coating parameters a therapeutic window for those wound dressings could be identified. Consequently, the atmospheric pressure plasma chemical vapour deposition technique promise an effective and low cost modification of wound dressing materials.

  14. In situ growth rate measurement and nucleation enhancement for microwave plasma CVD of diamond

    NASA Astrophysics Data System (ADS)

    Stoner, B. R.; Williams, B. E.; Wolter, S. D.; Nishimura, K.; Glass, J. T.

    1992-02-01

    Laser reflection interferometry (LRI) has been shown to be a useful in situ technique for measuring growth rate of diamond during microwave plasma chemical vapor deposition (MPCVD). Current alternatives to LRI usually involve ex situ analysis such as cross-sectional SEM or profilometry. The ability to measure the growth rate in 'real-time' has allowed the variation of processing parameters during a single deposition and thus the extraction of much more information in a fraction of the time. In situ monitoring of growth processes also makes it possible to perform closed loop process control with better reproducibility and quality control. Unfortunately, LRI requires a relatively smooth surface to avoid surface scattering and the commensurate drop in reflected intensity. This problem was remedied by greatly enhancing the diamond particle nucleation via the deposition of an intermediate carbon layer using substrate biasing. When an unscratched silicon wafer is pretreated by biasing negatively relative to ground while in a methane-hydrogen plasma, nucleation densities much higher than those achieved on scratched silicon wafers are obtained. The enhanced nucleation allows a complete film composed of small grains to form in a relatively short time, resulting in a much smoother surface than is obtained from a film grown at lower nucleation densities.

  15. Plasma-Enhanced Chemical Vapor Deposition (PE-CVD) yields better Hydrolytical Stability of Biocompatible SiOx Thin Films on Implant Alumina Ceramics compared to Rapid Thermal Evaporation Physical Vapor Deposition (PVD).

    PubMed

    Böke, Frederik; Giner, Ignacio; Keller, Adrian; Grundmeier, Guido; Fischer, Horst

    2016-07-20

    Densely sintered aluminum oxide (α-Al2O3) is chemically and biologically inert. To improve the interaction with biomolecules and cells, its surface has to be modified prior to use in biomedical applications. In this study, we compared two deposition techniques for adhesion promoting SiOx films to facilitate the coupling of stable organosilane monolayers on monolithic α-alumina; physical vapor deposition (PVD) by thermal evaporation and plasma enhanced chemical vapor deposition (PE-CVD). We also investigated the influence of etching on the formation of silanol surface groups using hydrogen peroxide and sulfuric acid solutions. The film characteristics, that is, surface morphology and surface chemistry, as well as the film stability and its adhesion properties under accelerated aging conditions were characterized by means of X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and tensile strength tests. Differences in surface functionalization were investigated via two model organosilanes as well as the cell-cytotoxicity and viability on murine fibroblasts and human mesenchymal stromal cells (hMSC). We found that both SiOx interfaces did not affect the cell viability of both cell types. No significant differences between both films with regard to their interfacial tensile strength were detected, although failure mode analyses revealed a higher interfacial stability of the PE-CVD films compared to the PVD films. Twenty-eight day exposure to simulated body fluid (SBF) at 37 °C revealed a partial delamination of the thermally deposited PVD films whereas the PE-CVD films stayed largely intact. SiOx layers deposited by both PVD and PE-CVD may thus serve as viable adhesion-promoters for subsequent organosilane coupling agent binding to α-alumina. However, PE-CVD appears to be favorable for long-term direct film exposure to aqueous

  16. Plasma-Enhanced Chemical Vapor Deposition (PE-CVD) yields better Hydrolytical Stability of Biocompatible SiOx Thin Films on Implant Alumina Ceramics compared to Rapid Thermal Evaporation Physical Vapor Deposition (PVD).

    PubMed

    Böke, Frederik; Giner, Ignacio; Keller, Adrian; Grundmeier, Guido; Fischer, Horst

    2016-07-20

    Densely sintered aluminum oxide (α-Al2O3) is chemically and biologically inert. To improve the interaction with biomolecules and cells, its surface has to be modified prior to use in biomedical applications. In this study, we compared two deposition techniques for adhesion promoting SiOx films to facilitate the coupling of stable organosilane monolayers on monolithic α-alumina; physical vapor deposition (PVD) by thermal evaporation and plasma enhanced chemical vapor deposition (PE-CVD). We also investigated the influence of etching on the formation of silanol surface groups using hydrogen peroxide and sulfuric acid solutions. The film characteristics, that is, surface morphology and surface chemistry, as well as the film stability and its adhesion properties under accelerated aging conditions were characterized by means of X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and tensile strength tests. Differences in surface functionalization were investigated via two model organosilanes as well as the cell-cytotoxicity and viability on murine fibroblasts and human mesenchymal stromal cells (hMSC). We found that both SiOx interfaces did not affect the cell viability of both cell types. No significant differences between both films with regard to their interfacial tensile strength were detected, although failure mode analyses revealed a higher interfacial stability of the PE-CVD films compared to the PVD films. Twenty-eight day exposure to simulated body fluid (SBF) at 37 °C revealed a partial delamination of the thermally deposited PVD films whereas the PE-CVD films stayed largely intact. SiOx layers deposited by both PVD and PE-CVD may thus serve as viable adhesion-promoters for subsequent organosilane coupling agent binding to α-alumina. However, PE-CVD appears to be favorable for long-term direct film exposure to aqueous

  17. Microwave plasma CVD-grown graphene-CNT hybrids for enhanced electron field emission applications

    NASA Astrophysics Data System (ADS)

    Kaushik, Vishakha; Shukla, A. K.; Vankar, V. D.

    2014-12-01

    The growth and electron emission characteristics were investigated from a hybrid structure of multiwalled carbon nanotubes (MWCNTs) and multilayer layer graphene (MLG) deposited on silicon substrate coated with iron catalyst and an interlayer of aluminium. The hybrid structures were synthesized in a two-step process by microwave plasma-enhanced chemical vapour deposition technique. The formation of MWCNTs takes place by absorption and precipitation of carbon radicals into the catalyst particles. Thereafter, ample carbon forms MLG on tip of the MWCNTs resulting in a MLG-MWCNTs hybrid nanostructure. MLG was observed to grow branching out of the tips and sidewalls of the MWCNTs and is expected to attach by Van der Walls bonds. Transmission electron microscopy and micro-Raman spectroscopy confirmed the crystalline nature of the hybrid structures. Electron emission studies were carried out using a diode-type field emission setup. The enhancement factor was found to be ~3,500 for bare MWCNTs, ~4,070 to ~5,000 for hybrid structures and ~6,500 for N-doped MLG-MWCNTs hybrid structures. Modification in the defects structure and enhancement of emission sites are suggested to be responsible for the increase of the field emission characteristics.

  18. Insights into gold-catalyzed plasma-assisted CVD growth of silicon nanowires

    NASA Astrophysics Data System (ADS)

    Chen, Wanghua; Roca i Cabarrocas, Pere

    2016-07-01

    Understanding and controlling effectively the behavior of metal catalyst droplets during the Vapor-Liquid-Solid growth of nanowires are crucial for their applications. In this work, silicon nanowires are produced by plasma-assisted Chemical Vapor Deposition using gold as a catalyst. The influence of hydrogen plasma on nanowire growth is investigated experimentally and theoretically. Interestingly, in contrast to conventional chemical vapor deposition, the growth rate of silicon nanowires shows a decrease as a function of their diameters, which is consistent with the incorporation of silicon via sidewall diffusion. We show that Ostwald ripening of catalyst droplets during nanowire growth is inhibited in the presence of a hydrogen plasma. However, when the plasma is off, the diffusion of Au atoms on the nanowire sidewall can take place. Based on this observation, we have developed a convenient method to grow silicon nanotrees.

  19. Fabrication of Ultrasensitive Field-Effect Transistor DNA Biosensors by a Directional Transfer Technique Based on CVD-Grown Graphene.

    PubMed

    Zheng, Chao; Huang, Le; Zhang, Hong; Sun, Zhongyue; Zhang, Zhiyong; Zhang, Guo-Jun

    2015-08-12

    Most graphene field-effect transistor (G-FET) biosensors are fabricated through a routine process, in which graphene is transferred onto a Si/SiO2 substrate and then devices are subsequently produced by micromanufacture processes. However, such a fabrication approach can introduce contamination onto the graphene surface during the lithographic process, resulting in interference for the subsequent biosensing. In this work, we have developed a novel directional transfer technique to fabricate G-FET biosensors based on chemical-vapor-deposition- (CVD-) grown single-layer graphene (SLG) and applied this biosensor for the sensitive detection of DNA. A FET device with six individual array sensors was first fabricated, and SLG obtained by the CVD-growth method was transferred onto the sensor surface in a directional manner. Afterward, peptide nucleic acid (PNA) was covalently immobilized on the graphene surface, and DNA detection was realized by applying specific target DNA to the PNA-functionalized G-FET biosensor. The developed G-FET biosensor was able to detect target DNA at concentrations as low as 10 fM, which is 1 order of magnitude lower than those reported in a previous work. In addition, the biosensor was capable of distinguishing the complementary DNA from one-base-mismatched DNA and noncomplementary DNA. The directional transfer technique for the fabrication of G-FET biosensors is simple, and the as-constructed G-FET DNA biosensor shows ultrasensitivity and high specificity, indicating its potential application in disease diagnostics as a point-of-care tool.

  20. Fabrication of Ultrasensitive Field-Effect Transistor DNA Biosensors by a Directional Transfer Technique Based on CVD-Grown Graphene.

    PubMed

    Zheng, Chao; Huang, Le; Zhang, Hong; Sun, Zhongyue; Zhang, Zhiyong; Zhang, Guo-Jun

    2015-08-12

    Most graphene field-effect transistor (G-FET) biosensors are fabricated through a routine process, in which graphene is transferred onto a Si/SiO2 substrate and then devices are subsequently produced by micromanufacture processes. However, such a fabrication approach can introduce contamination onto the graphene surface during the lithographic process, resulting in interference for the subsequent biosensing. In this work, we have developed a novel directional transfer technique to fabricate G-FET biosensors based on chemical-vapor-deposition- (CVD-) grown single-layer graphene (SLG) and applied this biosensor for the sensitive detection of DNA. A FET device with six individual array sensors was first fabricated, and SLG obtained by the CVD-growth method was transferred onto the sensor surface in a directional manner. Afterward, peptide nucleic acid (PNA) was covalently immobilized on the graphene surface, and DNA detection was realized by applying specific target DNA to the PNA-functionalized G-FET biosensor. The developed G-FET biosensor was able to detect target DNA at concentrations as low as 10 fM, which is 1 order of magnitude lower than those reported in a previous work. In addition, the biosensor was capable of distinguishing the complementary DNA from one-base-mismatched DNA and noncomplementary DNA. The directional transfer technique for the fabrication of G-FET biosensors is simple, and the as-constructed G-FET DNA biosensor shows ultrasensitivity and high specificity, indicating its potential application in disease diagnostics as a point-of-care tool. PMID:26203889

  1. Plasma-enhanced CVD preparation of isotopes of group IV and VI elements

    NASA Astrophysics Data System (ADS)

    Sennikov, P. G.; Kornev, R. A.

    2016-03-01

    The plasma-chemical reduction was studied experimentally of molybdenum, sulfur and germanium fluorides with different isotopic composition by hydrogen in plasmas sustained by inductively coupled (IC) and capacitively-coupled (CC) RF discharges. The emission spectra of plasmas recorded under different experimental conditions are discussed. Reaction mechanisms are proposed. In the case of 98MoF6 reduction in CCP, the combined radical-atomic mechanism including intermediate MoF3 resulting in bulk and powder 98Mo formation was established. In the emission spectrum of the 32SF6 + H2 system in ICP at 0.2 Torr, only lines assigned to SiF2, SiF and F2 * originating from the decomposition of 32SF6 and a fast reaction of its products with the reactor's quartz walls were observed. Due to this etching process, the yield of 32S was moderate. Increasing the pressure in the reactor above 1 Torr resulted in an increase of the 32S yield. The mechanism of 72GeF4 reduction depends on the pressure and plasma type. At 0.25 Torr in ICP, a 72Ge deposit was formed via the 72GeF radical; however, at 3.5 Torr in CCP, the mechanism changed to a molecular one. Results of the study of the structure and the isotopic and chemical purity of isotope samples obtained are briefly presented.

  2. Analysis of the Response of CVD Diamond Detectors for UV and sX-Ray Plasma Diagnostics Installed at JET

    NASA Astrophysics Data System (ADS)

    Caiffi, B.; Coffey, I.; Pillon, M.; Osipenko, M.; Prestopino, G.; Ripani, M.; Taiuti, M.; Verona, C.; Verona-Rinati, G.

    Diamond detectors are very promising candidates for plasma diagnostics in a harsh environment. In fact, they have several proprieties which make them suitable for magnetic fusion devices: radiation hardness, high thermal conductivity, high resistivity, high carrier mobility and a large bandgap (5.5 eV). The latter makes them insensitive to visible radiation and allows low noise measurements without any cooling. In 2008 two CVD (Chemical Vapour Deposition) single crystal diamond (SCD) detectors were installed at the JET tokamak as extreme UV and soft X-Ray diagnostics [1]. In this work the neutron background in these detectors was measured shielding the UV and soft X-Ray radiation by closing a local vacuum valve. The UV detector was found to be insensitive to the neutron flux, while the soft X Ray detector signal exhibited spikes during the highest neutron rate pulse (neutron rate 1016n/s, which corresponds to a flux of φn ˜105n/cm2s in the detector location). These spikes were found to be due to the (n,p) reaction within the plastic filter in front of the soft X-Ray detector. The UV SCD was also used to perform time of flight (ToF) measurements in laser ablation experiments. ToFs were found to be an order of magnitude higher than expected if only the drift velocity is considered. This discrepancy could be due to a delay between the arrival time of the impurities in the plasma and their emission in an energy range which SCD is sensitive to (Eph >5.5 eV). The delay is found to be comparable with the expected ionization times for edge plasma conditions.

  3. Dendrimer-templated Fe nanoparticles for the growth of single-wall carbon nanotubes by plasma-enhanced CVD.

    PubMed

    Amama, Placidus B; Maschmann, Matthew R; Fisher, Timothy S; Sands, Timothy D

    2006-06-01

    A fourth-generation (G4) poly(amidoamine) (PAMAM) dendrimer (G4-NH2) has been used as a template to deliver nearly monodispersed catalyst nanoparticles to SiO2/Si, Ti/Si, sapphire, and porous anodic alumina (PAA) substrates. Fe2O3 nanoparticles obtained after calcination of the immobilized Fe3+/G4-NH2 composite served as catalytic "seeds" for the growth of single-wall carbon nanotubes (SWNTs) by microwave plasma-enhanced CVD (PECVD). To surmount the difficulty associated with SWNT growth via PECVD, reaction conditions that promote the stabilization of Fe nanoparticles, resulting in enhanced SWNT selectivity and quality, have been identified. In particular, in situ annealing of Fe catalyst in an N2 atmosphere was found to improve SWNT selectivity and quality. H2 prereduction at 900 degrees C for 5 min was also found to enhance SWNT selectivity and quality for SiO2/Si supported catalyst, albeit of lower quality for sapphire supported catalyst. The application of positive dc bias voltage (+200 V) during SWNT growth was shown to be very effective in removing amorphous carbon impurities while enhancing graphitization, SWNT selectivity, and vertical alignment. The results of this study should promote the use of exposed Fe nanoparticles supported on different substrates for the growth of high-quality SWNTs by PECVD. PMID:16771309

  4. Characteristics of indium oxide plasma filters deposited by atmospheric pressure CVD

    SciTech Connect

    Langlois, E.; Murthy, S.D.; Bhat, I.; Gutmann, R.; Brown, E.; Dziendziel, R.; Freeman, M.; Choudhury, N.

    1995-07-01

    Thin films of undoped and tin-doped In{sub 2}O{sub 3} are being investigated for use as plasma filters in spectral control applications for thermal photovoltaic cells. These films are required to exhibit high reflectance at wavelengths longer than the plasma wavelength {lambda}{sub p}, high transmittance at wavelengths shorter than {lambda}{sub p} and low absorption throughout the spectrum. Both types of films were grown via atmospheric pressure chemical vapor deposition (APCVD) on Si (100) and fused silica substrates using trimethylindium (TMI), tetraethyltin (TET), and oxygen as the precursors. Fourier Transform InfraRed (FTIR) spectroscopy was used to measure the filter transmittance and reflectance between 1.8--20 {micro}m. Nominal conditions used during the growth of undoped In{sub 2}O{sub 3} were a substrate temperature of 450 C and partial pressures of 1.4 {times} 10{sup {minus}4} atm. and 1 {times} 10{sup {minus}3} atm. for TMI and O{sub 2} respectively. The O{sub 2}/TMI partial pressure ratio and substrate temperature were systematically varied to control the filter characteristics. The plasma wavelength {lambda}{sub p} was found to be a sensitive function of these parameters. Post-growth annealing of the films was done in inert as well as air ambient at elevated temperatures, but was found to have no beneficial effect. Tin-doped In{sub 2}O{sub 3} was grown under similar conditions as above, with a typical TET partial pressure of 4 {times} 10{sup {minus}6} atm. Here also, the material properties and consequently the optical response were found to be strongly dependent on growth conditions such as O{sub 2} and TET partial pressures. Both undoped and tin-doped In{sub 2}O{sub 3} grown on fused silica exhibited enhanced transmittance due to the close matching of refractive indices of In{sub 2}O{sub 3} and silica. X-ray diffractometer measurements indicated that all these films were polycrystalline and highly textured towards the (111) direction. The best

  5. Novel Diamond Films Synthesis Strategy: Methanol and Argon Atmosphere by Microwave Plasma CVD Method Without Hydrogen.

    PubMed

    Yang, Li; Jiang, Caiyi; Guo, Shenghui; Zhang, Libo; Gao, Jiyun; Peng, Jinhui; Hu, Tu; Wang, Liang

    2016-12-01

    Diamond thin films are grown on silicon substrates by only using methanol and argon mixtures in microwave plasma chemical vapor deposition (MPCVD) reactor. It is worth mentioning that the novel strategy makes the synthesis reaction works smoothly without hydrogen atmosphere, and the substrates temperature is only 500 °C. The evidence of surface morphology and thickness under different time is obtained by characterizing the samples using scanning electron microscopy (SEM). X-ray diffractometer (XRD) spectrum reveals that the preferential orientation of (111) plane sample is obtained. The Raman spectra indicate that the dominant component of all the samples is a diamond. Moreover, the diamond phase content of the targeted films was quantitatively analyzed by X-ray photoelectron spectroscopy (XPS) method, and the surface roughness of diamond films was investigated by atomic force microscope (AFM). Meanwhile, the possible synthesis mechanism of the diamond films in methanol- and argon-mixed atmosphere was discussed. PMID:27644241

  6. Novel Diamond Films Synthesis Strategy: Methanol and Argon Atmosphere by Microwave Plasma CVD Method Without Hydrogen

    NASA Astrophysics Data System (ADS)

    Yang, Li; Jiang, Caiyi; Guo, Shenghui; Zhang, Libo; Gao, Jiyun; Peng, Jinhui; Hu, Tu; Wang, Liang

    2016-09-01

    Diamond thin films are grown on silicon substrates by only using methanol and argon mixtures in microwave plasma chemical vapor deposition (MPCVD) reactor. It is worth mentioning that the novel strategy makes the synthesis reaction works smoothly without hydrogen atmosphere, and the substrates temperature is only 500 °C. The evidence of surface morphology and thickness under different time is obtained by characterizing the samples using scanning electron microscopy (SEM). X-ray diffractometer (XRD) spectrum reveals that the preferential orientation of (111) plane sample is obtained. The Raman spectra indicate that the dominant component of all the samples is a diamond. Moreover, the diamond phase content of the targeted films was quantitatively analyzed by X-ray photoelectron spectroscopy (XPS) method, and the surface roughness of diamond films was investigated by atomic force microscope (AFM). Meanwhile, the possible synthesis mechanism of the diamond films in methanol- and argon-mixed atmosphere was discussed.

  7. Study of high quality spinel zinc gallate nanowires grown using CVD and ALD techniques.

    PubMed

    Kumar, Sudheer; Sarau, G; Tessarek, C; Göbelt, M; Christiansen, S; Singh, R

    2015-08-21

    High quality single crystalline zinc gallate (ZnGa2O4) nanowires (NWs) were grown using a combination of chemical vapor deposition and atomic layer deposition techniques. Morphological, structural and optical investigations revealed the formation of Ga2O3-ZnO core-shell NWs and their conversion into ZnGa2O4 NWs after annealing via a solid state reaction. This material conversion was systematically confirmed for single NWs by various measurement techniques including scanning and transmission electron microscopy, Raman spectroscopy and voltage-dependent cathodoluminescence. Moreover, a model system based on the obtained results has been provided explaining the formation mechanism of the ZnGa2O4 NWs.

  8. Temperature dependent growth of GaN nanowires using CVD technique

    NASA Astrophysics Data System (ADS)

    Kumar, Mukesh; Kumar, Vikram; Singh, R.

    2016-05-01

    Growth of GaN nanowires have been carried out on sapphire substrates with Au as a catalyst using chemical vapour deposition technique. GaN nanowires growth have been studied with the experimental parameter as growth temperature. Diameter of grown GaN nanowires are in the range of 50 nm to 100 nm while the nanowire length depends on growth temperature. Morphology of the GaN nanowires have been studied by scanning electron microscopy. Crystalline nature has been observed by XRD patterns. Optical properties of grown GaN nanowires have been investigated by photoluminescence spectra.

  9. Plasma techniques for reprocessing nuclear wastes

    SciTech Connect

    Siciliano, E.R.; Lucoff, D.M.; Omberg, R.P.; Walter, A.E.

    1993-06-01

    A newly emerging plasma-based system, currently under development for material dissociation and mass separation applications in the area of high-level radioactive waste treatment, may have possible applications as a central processing unit for spent nuclear fuel reprocessing. Because this system has no moving parts and obtains separations by electromagnetic techniques, it offers a distinct advantage over chemically based separation techniques, in that the total waste volume does not increase. The basic concepts underlying the operation of this plasma-based system are discussed, along with the demonstrated and expected capabilities of this system. Possible fuel reprocessing configurations using this plasma-based technology are also mentioned.

  10. Comparative Study of Solid-Phase Crystallization of Amorphous Silicon Deposited by Hot-Wire CVD, Plasma-Enhanced CVD, and Electron-Beam Evaporation

    SciTech Connect

    Stradins, P.; Kunz, O.; Young, D. L.; Yan, Y.; Jones, K. M.; Xu, Y.; Reedy, R. C.; Branz, H. M.; Aberle, A. G.; Wang, Q.

    2007-01-01

    Solid-phase crystallization (SPC) rates are compared in amorphous silicon films prepared by three different methods: hot-wire chemical vapor deposition (HWCVD), plasma-enhanced chemical vapor deposition (PECVD), and electron-beam physical vapor deposition (e-beam). Random SPC proceeds approximately 5 and 13 times slower in PECVD and e-beam films, respectively, as compared to HWCVD films. Doping accelerates random SPC in e-beam films but has little effect on the SPC rate of HWCVD films. In contrast, the crystalline growth front in solid-phase epitaxy experiments propagates at similar speed in HWCVD, PECVD, and e-beam amorphous Si films. This strongly suggests that the observed large differences in random SPC rates originate from different nucleation rates in these materials while the grain growth rates are relatively similar. The larger grain sizes observed for films that exhibit slower random SPC support this suggestion.

  11. Plasma diagnostic techniques using particle beam probes

    SciTech Connect

    Jennings, W C

    1980-07-01

    A brief overview is given of particle beam probing. The fundamental concepts common to all techniques are discussed as well as the design considerations for choosing a particular diagnostic technique. The capabilities of existing and proposed techniques, and the present status of the techniques in major magnetic confinement geometries is also presented. Techniques which involve the injection of a beam of neutral particles into the plasma are then considered. The techniques of beam attenuation, beam scattering, and active charge exchange using a beam of light particles such as hydrogen or helium are first presented. Optical measurements of the Zeeman splitting of the radiation from a neutral lithium beam is then discussed, including a new proposal for significantly improving this technique through the addition of a dye laser. Two techniques involving the injection of heavy neutral particles are then presented, and the section concludes with two proposed techniques for measuring the properties of the alpha particles produced from actual fusion reactions. The diagnostic techniques which are based upon the injection of a beam of charged particles into the plasma are next described. The advantages and limitations of these techniques in comparison with the neutral techniques are discussed, followed by a description of specific techniques.

  12. Solution-based mist CVD technique for CH3NH3Pb(Br1- x Cl x )3 inorganic-organic perovskites

    NASA Astrophysics Data System (ADS)

    Nishinaka, Hiroyuki; Yoshimoto, Masahiro

    2016-10-01

    We report the growth of inorganic-organic perovskites using a solution-based mist chemical vapor deposition (mist CVD) technique and the successful growth of the alloying CH3NH3Pb(Br1- x Cl x )3 using mixture solutions of Br and Cl precursors. The formation mechanism of the inorganic-organic perovskite grown by the laminar flow-type mist CVD is suggested to be a vapor phase reaction, although solution precursors are used. The near-band-edge emissions from photoluminescence can be tuned from 500 to 550 nm by considering Br/Cl ratios in the solution without crystal phase segregation by incorporating Cl into crystalline CH3NH3PbBr3 films.

  13. Plasma mass filtering techniques: applications and requirements

    NASA Astrophysics Data System (ADS)

    Gueroult, Renaud; Fisch, Nathaniel J.

    2013-10-01

    Plasma mass filters differ from conventional chemical filtering techniques in that elements are dissociated, and can therefore be processed without regard to chemical form. In addition, plasma filters can be in principle operated at larger velocities compared to their gaseous and/or liquid counterparts, so that larger throughputs are possible. On the other hand, one has to pay the price of ionization, which sets a lower limit for the processing cost. Plasma mass filtering techniques are consequently foreseen as a promising solution for separation processes which are simultaneously chemically challenging and of high added value. Such separation processes can be, for example, found within the context of nuclear waste remediation, or nuclear spent fuel reprocessing. However, although plasma separation techniques appear globally attractive for these distinct needs, the plasma parameters required to fulfill a particular separation process are expected to depend strongly on the process's attributes (volume, composition, mass difference), which may vary significantly. Such operating parameters' variations are shown to be well accommodated by a particular configuration, called the Magnetic Centrifugal Mass Filter. Work supported by US DOE under contract Nos DE-AC02-09CH11466 and DE-FG02-06ER54851.

  14. Plasma filtering techniques for nuclear waste remediation

    SciTech Connect

    Gueroult, Renaud; Hobbs, David T.; Fisch, Nathaniel J.

    2015-04-24

    The economical viability of nuclear waste cleanup e orts could, in some cases, be put at risk due to the difficulties faced in handling unknown and complex feedstocks. Plasma filtering, which operates on dissociated elements, offers advantages over chemical techniques for the processing of such wastes. In this context, the economic feasibility of plasma mass filtering for nuclear waste pretreatment before ultimate disposal is analyzed. Results indicate similar costs for chemical and plasma solid-waste pretreatment per unit mass of waste, but suggest significant savings potential as a result of a superior waste mass minimization. This performance improvement is observed over a large range of waste chemical compositions, representative of legacy waste's heterogeneity. Although smaller, additional savings arise from the absence of a secondary liquid waste stream, as typically produced by chemical techniques.

  15. Plasma filtering techniques for nuclear waste remediation

    DOE PAGES

    Gueroult, Renaud; Hobbs, David T.; Fisch, Nathaniel J.

    2015-04-24

    The economical viability of nuclear waste cleanup e orts could, in some cases, be put at risk due to the difficulties faced in handling unknown and complex feedstocks. Plasma filtering, which operates on dissociated elements, offers advantages over chemical techniques for the processing of such wastes. In this context, the economic feasibility of plasma mass filtering for nuclear waste pretreatment before ultimate disposal is analyzed. Results indicate similar costs for chemical and plasma solid-waste pretreatment per unit mass of waste, but suggest significant savings potential as a result of a superior waste mass minimization. This performance improvement is observed overmore » a large range of waste chemical compositions, representative of legacy waste's heterogeneity. Although smaller, additional savings arise from the absence of a secondary liquid waste stream, as typically produced by chemical techniques.« less

  16. Bond dissociation mechanism of ethanol during carbon nanotube synthesis via alcohol catalytic CVD technique: Ab initio molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Oguri, Tomoya; Shimamura, Kohei; Shibuta, Yasushi; Shimojo, Fuyuki; Yamaguchi, Shu

    2014-03-01

    supergrowth CVD technique) [26]. Recently, several experimental studies have been carried out in an attempt to understand these complicated dissociation processes. For example, Tomie et al. [27] performed in situ mass spectroscopic analysis during CNT synthesis by the ACCVD technique and revealed that ethylene molecules are formed by the dissociation of ethanol, which means that C-O bonds in the ethanol molecules are dissociated during CNT synthesis. Moreover, Xiang et al. [28] employed isotopically labeled ethanol (i.e., 12CH3-13CH2-OH, 13CH3-12CH2-OH, and so forth) to trace the carbon atoms during CNT synthesis and revealed that the carbon further away from the hydroxyl group in the ethanol is preferentially incorporated into the SNWT structure, which was confirmed from the different G band peaks of the Raman spectra. This experimental finding shows that the C-C bonds in ethanol molecules are dissociated during CNT synthesis. Although many experimental studies [29-32] have revealed part of the dissociation process during CNT growth, it is not yet well understood how the initial dissociation of carbon source molecules affects the subsequent formation process of CNTs.In parallel with the many experimental studies, there has been numerous computational works focusing on the formation process of CNTs. However, most of these studies [9-16] did not take the dissociation of carbon source molecules into account and examined the cap formation process starting from isolated carbon atoms. This is mainly due to the fact that a low-impact interatomic potential appropriately describing the dissociation of carbon source molecules has not been established for classical molecular dynamics (MD) simulation. Meanwhile, several classical MD simulations using the ReaxFF potential [33], which describes chemical reactions with a reasonable degree of accuracy but has a high computational cost, have demonstrated the dissociation of hydrocarbons on a nickel cluster [34] and a flat metal surface [35

  17. Effect of hydrogen dilution on photoluminescent properties of nanocrystalline SiC films deposited by helicon wave plasma CVD

    NASA Astrophysics Data System (ADS)

    Yu, Wei; Du, Jie; Zhang, Li; Cui, Shuang Kui; Han, Li; Fu, Guang Sheng

    2007-11-01

    Nanocrystalline silicon carbide (nc-SiC) thin films were deposited by helicon wave plasma enhanced chemical vapor deposition (HW-PECVD) technique at different hydrogen dilution ratio (RH). The PL peak energy and intensity were systemically analyzed using photoluminescent (PL) and photoluminescent excitation (PLE) methods. As a whole, the PL intensity shows an increasing trend and the PL peak energy presents continuous blue shifts with increasing hydrogen dilution ratio. In addition, it is found that the spectra band of samples deposited at low RH are composed of two components, the high energy band comes from quantum confinement effect and the low energy band is related to radiation of surface defect. The low energy band has a decreasing trend with increasing hydrogen dilution ratio and even disappears finally at high RH. We explain dependence of PL properties in terms of the variation of film microstructure induced by hydrogen dilution during film deposition. The increasing of PL intensity and the decreasing of the low energy band can both be accounted by the microstructure improvement. The decrease of PL peak energy is related to the size decrease of SiC nanocrystals.

  18. Low temperature plasma enhanced CVD epitaxial growth of silicon on GaAs: a new paradigm for III-V/Si integration

    PubMed Central

    Cariou, Romain; Chen, Wanghua; Maurice, Jean-Luc; Yu, Jingwen; Patriarche, Gilles; Mauguin, Olivia; Largeau, Ludovic; Decobert, Jean; Roca i Cabarrocas, Pere

    2016-01-01

    The integration of III-V semiconductors with silicon is a key issue for photonics, microelectronics and photovoltaics. With the standard approach, namely the epitaxial growth of III-V on silicon, thick and complex buffer layers are required to limit the crystalline defects caused by the interface polarity issues, the thermal expansion, and lattice mismatches. To overcome these problems, we have developed a reverse and innovative approach to combine III-V and silicon: the straightforward epitaxial growth of silicon on GaAs at low temperature by plasma enhanced CVD (PECVD). Indeed we show that both GaAs surface cleaning by SiF4 plasma and subsequent epitaxial growth from SiH4/H2 precursors can be achieved at 175 °C. The GaAs native oxide etching is monitored with in-situ spectroscopic ellipsometry and Raman spectroscopy is used to assess the epitaxial silicon quality. We found that SiH4 dilution in hydrogen during deposition controls the layer structure: the epitaxial growth happens for deposition conditions at the transition between the microcrystalline and amorphous growth regimes. SIMS and STEM-HAADF bring evidences for the interface chemical sharpness. Together, TEM and XRD analysis demonstrate that PECVD enables the growth of high quality relaxed single crystal silicon on GaAs. PMID:27166163

  19. Low temperature plasma enhanced CVD epitaxial growth of silicon on GaAs: a new paradigm for III-V/Si integration

    NASA Astrophysics Data System (ADS)

    Cariou, Romain; Chen, Wanghua; Maurice, Jean-Luc; Yu, Jingwen; Patriarche, Gilles; Mauguin, Olivia; Largeau, Ludovic; Decobert, Jean; Roca I Cabarrocas, Pere

    2016-05-01

    The integration of III-V semiconductors with silicon is a key issue for photonics, microelectronics and photovoltaics. With the standard approach, namely the epitaxial growth of III-V on silicon, thick and complex buffer layers are required to limit the crystalline defects caused by the interface polarity issues, the thermal expansion, and lattice mismatches. To overcome these problems, we have developed a reverse and innovative approach to combine III-V and silicon: the straightforward epitaxial growth of silicon on GaAs at low temperature by plasma enhanced CVD (PECVD). Indeed we show that both GaAs surface cleaning by SiF4 plasma and subsequent epitaxial growth from SiH4/H2 precursors can be achieved at 175 °C. The GaAs native oxide etching is monitored with in-situ spectroscopic ellipsometry and Raman spectroscopy is used to assess the epitaxial silicon quality. We found that SiH4 dilution in hydrogen during deposition controls the layer structure: the epitaxial growth happens for deposition conditions at the transition between the microcrystalline and amorphous growth regimes. SIMS and STEM-HAADF bring evidences for the interface chemical sharpness. Together, TEM and XRD analysis demonstrate that PECVD enables the growth of high quality relaxed single crystal silicon on GaAs.

  20. Low temperature plasma enhanced CVD epitaxial growth of silicon on GaAs: a new paradigm for III-V/Si integration.

    PubMed

    Cariou, Romain; Chen, Wanghua; Maurice, Jean-Luc; Yu, Jingwen; Patriarche, Gilles; Mauguin, Olivia; Largeau, Ludovic; Decobert, Jean; Roca I Cabarrocas, Pere

    2016-01-01

    The integration of III-V semiconductors with silicon is a key issue for photonics, microelectronics and photovoltaics. With the standard approach, namely the epitaxial growth of III-V on silicon, thick and complex buffer layers are required to limit the crystalline defects caused by the interface polarity issues, the thermal expansion, and lattice mismatches. To overcome these problems, we have developed a reverse and innovative approach to combine III-V and silicon: the straightforward epitaxial growth of silicon on GaAs at low temperature by plasma enhanced CVD (PECVD). Indeed we show that both GaAs surface cleaning by SiF4 plasma and subsequent epitaxial growth from SiH4/H2 precursors can be achieved at 175 °C. The GaAs native oxide etching is monitored with in-situ spectroscopic ellipsometry and Raman spectroscopy is used to assess the epitaxial silicon quality. We found that SiH4 dilution in hydrogen during deposition controls the layer structure: the epitaxial growth happens for deposition conditions at the transition between the microcrystalline and amorphous growth regimes. SIMS and STEM-HAADF bring evidences for the interface chemical sharpness. Together, TEM and XRD analysis demonstrate that PECVD enables the growth of high quality relaxed single crystal silicon on GaAs. PMID:27166163

  1. New novel cleaning technique for extending mean time between mechanical cleans in a Genus tungsten CVD reactor

    SciTech Connect

    Lujan, R.D.; Fleming, J.G.; Baird, J.L.; Gentry, M.S.

    1994-12-31

    During the chemical vapor deposition of blanket tungsten from the reduction of tungsten hexafluoride (WF{sub 6}), metallic parts within the reaction chamber accumulate metallic tungsten, tungsten oxyfluorides, and other related tungsten species. The usual method for removal of the chamber deposits is to open the chamber and perform a labor intensive mechanical clean, which involves the use of hydrogen peroxide (H{sub 2}O{sub 2}) and deionized (DI) water, or an in-situ fluorine-base plasma clean. The authors have investigated the use of repetitive in-situ nitrogen trifluoride (NF{sub 3}) plasma cleans during the course of operating a Genuse 8721 tungsten chemical vapor deposition reactor. The Genuse reactor has been retrofitted with self-ratchetting linear slides, which allow the wafer clamps to be extended into the NF{sub 3} plasma. They have extended the mean time between failures (MTBF) due to the use of 10 minute plasma clean every 75--100 wafers. Deposition for this process is 8,000 angstroms per wafer, using 6 deposition sites. The total tungsten deposition for a 0.5 micron tungsten plug is 4 microns, per a 25 wafer lot. Instead of a total removal of the accumulated tungsten from the chamber hardware, a partial etchback of the deposition from the wafer clamps and wafer chucks was performed. With this, sources for particles and backside deposition were eliminated. They see an increase in wafer-to-wafer uniformity, lot-to-lot repeatability, and particle reduction due to the use of frequent plasma clean. Recovery time after a plasma clean is excellent and no detrimental effects from hydrogen fluoride ``poisoning`` were seen.

  2. Interlayer utilization (including metal borides) for subsequent deposition of NSD films via microwave plasma CVD on 316 and 440C stainless steels

    NASA Astrophysics Data System (ADS)

    Ballinger, Jared

    . Surface boriding was implemented using the novel method of microwave plasma CVD with a mixture of hydrogen and diborane gases. On 440C bearings, dual phase boride layers of Fe2B and FeB were formed which supported adhered nanostructured diamond films. Continuity of the films was not seamless with limited regions remaining uncoated potentially corresponding to delamination of the film as evidenced by the presence of tubular structures presumably composed of sp2 bonded carbon. Surface boriding of 316 stainless steel discs was conducted at various powers and pressures to achieve temperatures ranging from 550-800 °C. The substrate boriding temperature was found to substantially influence the resultant interlayer by altering the metal boride(s) present. The lowest temperatures produced an interlayer where CrB was the single detected phase, higher temperatures yielded the presence of only Fe2B, and a combination of the two phases resulted from an intermediate boriding temperature. Compared with the more common, commercialized boriding methods, this a profound result given the problems posed by the FeB phase in addition to other advantages offered by CVD processes and microwave generated plasmas in general. Indentation testing of the boride layers revealed excellent adhesion strength for all borided interlayers, and above all, no evidence of cracking was observed for a sole Fe2B phase. As with boriding of 440C bearings, subsequent diamond deposition was achieved on these interlayers with substantially improved adhesion strength relative to diamond coated TiN interlayers. Both XRD and Raman spectroscopy confirmed a nanostructured diamond film with interfacial chromium carbides responsible for enhanced adhesion strength. Interlayers consisting solely of Fe2B have displayed an ability to support fully continuous nanostructured diamond films, yet additional study is required for consistent reproduction. This is in good agreement with initial work on pack borided high alloy steels

  3. Comparative evaluation of CVD diamond technologies

    SciTech Connect

    Anthony, T.R.

    1993-01-01

    Chemical vapor deposition (CVD) of diamonds occurs from hydrogen-hydrocarbon gas mixtures in the presence of atomic hydrogen at subatmospheric pressures. Most CVD methods are based on different means of generating and transporting atomic hydrogen in a particular system. Evaluation of these different techniques involves their capital costs, material costs, energy costs, labor costs and the type and quality of diamond that they produce. Currently, there is no universal agreement on which is the best technique and technique selection has been largely driven by the professional background of the user as well as the particular application of interest. This article discusses the criteria for evaluating a process for low-pressure deposition of diamond. Next, a brief history of low-pressure diamond synthesis is reviewed. Several specific processes are addressed, including the hot filament process, hot filament electron-assisted chemical vapor deposition, and plasma generation of atomic hydrogen by glow discharge, microwave discharge, low pressure radio frequency discharge, high pressure DC discharge, high pressure microwave discharge jets, high pressure RF discharge, and high and low pressure flames. Other types of diamond deposition methods are also evaluated. 101 refs., 15 figs.

  4. Hot-Wire CVD Amorphous Si Materials for Solar Cell Application

    SciTech Connect

    Wang, Q.

    2009-01-01

    Hydrogenated amorphous silicon (a-Si:H) thin films and their application to solar cells fabricated using the hot-wire chemical vapor deposition (HWCVD) or (CAT)-CVD will be reviewed. This review will focus on the comparison to the standard plasma enhance (PE) CVD in the terms of deposition technique, film properties, and solar cell performance. The advantages of using HWCVD for a-Si:H solar cell research as well as the criteria for industry's adaptation of this technique for mass production will be addressed.

  5. Low-temperature-deposited insulating films of silicon nitride by reactive sputtering and plasma-enhanced CVD: Comparison of characteristics

    NASA Astrophysics Data System (ADS)

    Sato, Masaru; Takeyama, Mayumi B.; Nakata, Yoshihiro; Kobayashi, Yasushi; Nakamura, Tomoji; Noya, Atsushi

    2016-04-01

    The characteristics of SiN x films deposited by reactive sputtering and plasma-enhanced chemical vapor deposition (PECVD) are examined to obtain high-density films at low deposition temperatures. PECVD SiN x films deposited at 200 °C show low densities of 2.14-2.20 g/cm3 regardless of their composition, while their refractive index varies depending on their composition. PECVD requires the substrate temperature to obtain high-density films, because a possible cause of low-density films is the amount of Si-H bond, rather than that of N-H bond, in the films originating from hydrogen incorporated by the insufficient decomposition of SiH4 molecules at low temperatures. The sputtered SiN x films with high density are obtained at a temperature lower than 200 °C and considered a promising candidate for insulating films at low process temperatures.

  6. Photodetectors on the basis of Ge/Si(001) heterostructures grown by the hot-wire CVD technique

    SciTech Connect

    Shengurov, V. G. Chalkov, V. Yu.; Denisov, S. A.; Alyabina, N. A.; Guseinov, D. V.; Trushin, V. N.; Gorshkov, A. P.; Volkova, N. S.; Ivanova, M. M.; Kruglov, A. V.; Filatov, D. O.

    2015-10-15

    The fabrication of photodetectors for the wavelength range of communications λ = 1.3–1.55 µm on the basis of Ge/Si(001) heterostructures with thick (∼0.5 µm) Ge layers grown by the hot-wire technique at reduced growth temperatures (350°C) is reported. The single-crystal Ga layers are distinguished by a low density of threading dislocations (∼10{sup 5} cm{sup –2}). The photodetectors exhibit a rather high quantum efficiency (∼0.05 at λ = 1.5 µm and 300 K) at moderate reverse saturation current densities (∼10{sup –2} A cm{sup –2}). Thus, it is shown that the hot-wire technique offers promise for the formation of integrated photodetectors for the wavelength range of communications, especially in the case of limitations on the conditions of heat treatments.

  7. Direct synthesis and characterization of optically transparent conformal zinc oxide nanocrystalline thin films by rapid thermal plasma CVD

    PubMed Central

    2011-01-01

    We report a rapid, self-catalyzed, solid precursor-based thermal plasma chemical vapor deposition process for depositing a conformal, nonporous, and optically transparent nanocrystalline ZnO thin film at 130 Torr (0.17 atm). Pure solid zinc is inductively heated and melted, followed by ionization by thermal induction argon/oxygen plasma to produce conformal, nonporous nanocrystalline ZnO films at a growth rate of up to 50 nm/min on amorphous and crystalline substrates including Si (100), fused quartz, glass, muscovite, c- and a-plane sapphire (Al2O3), gold, titanium, and polyimide. X-ray diffraction indicates the grains of as-deposited ZnO to be highly textured, with the fastest growth occurring along the c-axis. The individual grains are observed to be faceted by (103) planes which are the slowest growth planes. ZnO nanocrystalline films of nominal thicknesses of 200 nm are deposited at substrate temperatures of 330°C and 160°C on metal/ceramic substrates and polymer substrates, respectively. In addition, 20-nm- and 200-nm-thick films are also deposited on quartz substrates for optical characterization. At optical spectra above 375 nm, the measured optical transmittance of a 200-nm-thick ZnO film is greater than 80%, while that of a 20-nm-thick film is close to 100%. For a 200-nm-thick ZnO film with an average grain size of 100 nm, a four-point probe measurement shows electrical conductivity of up to 910 S/m. Annealing of 200-nm-thick ZnO films in 300 sccm pure argon at temperatures ranging from 750°C to 950°C (at homologous temperatures between 0.46 and 0.54) alters the textures and morphologies of the thin film. Based on scanning electron microscope images, higher annealing temperatures appear to restructure the ZnO nanocrystalline films to form nanorods of ZnO due to a combination of grain boundary diffusion and bulk diffusion. PACS: films and coatings, 81.15.-z; nanocrystalline materials, 81.07.Bc; II-VI semiconductors, 81.05.Dz. PMID:22040295

  8. Effect of plasma CVD operating temperature on nanomechanical properties of TiC nanostructured coating investigated by atomic force microscopy

    SciTech Connect

    Shanaghi, Ali; Rouhaghdam, Ali Reza Sabour; Ahangarani, Shahrokh; Chu, Paul K.

    2012-09-15

    Highlights: ► The TiC{sub x} nanostructure coatings have been deposited by PACVD method. ► Dominant mechanism of growth structure at 490 °C is island-layer type. ► TiC{sub x} nanostructure coating applied at 490 °C, exhibits lowest friction coefficient. ► Young's moduli are 289.9, 400 and 187.6 GPa for 470, 490 and 510 °C, respectively. ► This higher elastic modulus and higher hardness of nanocoating obtain at 490 °C. -- Abstract: The structure, composition, and mechanical properties of nanostructured titanium carbide (TiC) coatings deposited on H{sub 11} hot-working tool steel by pulsed-DC plasma assisted chemical vapor deposition at three different temperatures are investigated. Nanoindentation and nanoscratch tests are carried out by atomic force microscopy to determine the mechanical properties such as hardness, elastic modulus, surface roughness, and friction coefficient. The nanostructured TiC coatings prepared at 490 °C exhibit lower friction coefficient (0.23) than the ones deposited at 470 and 510 °C. Increasing the deposition temperature reduces the Young's modulus and hardness. The overall superior mechanical properties such as higher hardness and lower friction coefficient render the coatings deposited at 490 °C suitable for wear resistant applications.

  9. Atmospheric Pressure Plasma CVD of Amorphous Hydrogenated Silicon Carbonitride (a-SiCN:H) Films Using Triethylsilane and Nitrogen

    SciTech Connect

    Srinivasan Guruvenket; Steven Andrie; Mark Simon; Kyle W. Johnson; Robert A. Sailer

    2011-10-04

    Amorphous hydrogenated silicon carbonitride (a-SiCN:H) thin films are synthesized by atmospheric pressure plasma enhanced chemical vapor (AP-PECVD) deposition using the Surfx Atomflow{trademark} 250D APPJ source with triethylsilane (HSiEt{sub 3}, TES) and nitrogen as the precursor and the reactive gases, respectively. The effect of the substrate temperature (T{sub s}) on the growth characteristics and the properties of a-SiCN:H films was evaluated. The properties of the films were investigated via scanning electron microscopy (SEM), atomic force microscopy (AFM) for surface morphological analyses, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) for chemical and compositional analyses; spectroscopic ellipsometry for optical properties and thickness determination and nanoindentation to determine the mechanical properties of the a-SiCN:H films. Films deposited at low T{sub s} depict organic like features, while the films deposited at high T{sub s} depict ceramic like features. FTIR and XPS studies reveal that an increases in T{sub s} helps in the elimination of organic moieties and incorporation of nitrogen in the film. Films deposited at T{sub s} of 425 C have an index of refraction (n) of 1.84 and hardness (H) of 14.8 GPa. A decrease in the deposition rate between T{sub s} of 25 and 250 C and increase in deposition rate between T{sub s} of 250 and 425 C indicate that the growth of a-SiCN:H films at lower T{sub s} are surface reaction controlled, while at high temperatures film growth is mass-transport controlled. Based on the experimental results, a potential route for film growth is proposed.

  10. Effect of incorporation of deuterium on vacancy-type defects of a-C:H films prepared by plasma CVD

    NASA Astrophysics Data System (ADS)

    Ozeki, K.; Sekiba, D.; Uedono, A.; Hirakuri, K. K.; Masuzawa, T.

    2015-03-01

    Amorphous deuterated carbon (a-C:D) films were prepared using plasma-enhanced chemical vapor deposition (PECVD) from CH4/CD4 and CH4/D2 source gases. For CH4/CD4, the gas flow ratio of CD4/(CD4 + CH4) was varied from 0 to 100%. For CH4/D2, the additional partial gas pressure of D2 was increased from 1 to 7 Pa as the flow rate increased, and the partial gas pressure and the flow rate of CH4 were maintained at 10 Pa and 10 sccm, respectively. The concentrations of hydrogen (H) and deuterium (D) relative to carbon (C) in the films and the film densities were determined by elastic recoil detection analysis (ERDA) and Rutherford backscattering spectroscopy (RBS). Positron annihilation spectroscopy (PAS) was performed to measure the vacancy-type defect of the film. The S value obtained from PAS measurement correlates to the vacancy-type defect in the film. The film hardness was also measured using a nanoindenter. For CH4/CD4, the D concentration in the film increased when the CD4/(CH4 + CD4) gas ratio increased, whereas the concentration of H decreased. For CH4/D2, the D concentration in the film increased with increasing D2 partial pressure, whereas the concentration of H decreased. From the PAS results, the S value increased with increasing CD4/(CH4 + CD4) gas ratio for CH4/CD4, whereas the S value did not change with any D2 partial pressure for CH4/D2. The hardness and the mass density of the films decreased when the CD4/(CH4 + CD4) gas ratio increased for CH4/CD4, whereas the hardness and the density did not change with any D2 partial pressure for CH4/D2. A correlation among the S value, the film hardness and the film density was observed, and the S value, the film hardness and the film density did not correlate to the D concentration in the film. These findings suggest that information about the vacancy-type defect of the hydrogenated amorphous carbon films is crucial for evaluation of their mechanical properties and density.

  11. Electrical properties of carbon nanotubes synthesis by double furnace thermal-CVD technique at different temperatures on porous silicon template

    NASA Astrophysics Data System (ADS)

    Husairi, F. S.; Zobir, S. A. M.; Rusop, M.; Abdullah, S.

    2013-06-01

    Multiwalled Carbon Nanotubes (MWCNs) were synthesized using double-furnace thermal chemical vapor deposition technique at 700 - 900 °C on porous silicon nanostructure (PSiNs). Palm oil used as a carbon natural source, ferrocene as a catalyst and nitrogen gas as a carrier gas. The precursor were vaporized at 475 °C carried by nitrogen gas which flow at constant rate 150 sccm/min. Carbon nanotubes characterized by using Raman Spectroscopy and field emission scanning electron microscopy (FESEM) to check its structure and crystallites before tested with I-V probe. Au contact used as a metal contact deposited on CNTs layer. Carbon nanotubes (CNTs) with uniform diameter were found grown on porous silicon for each temperature used. Based on micro-Raman spectroscopy result, the peak of carbon nanotubes (around 1 300 to 1 600 nm) was detected. The I-V characteristic of CNTs deposited had different profile when deposited at different temperature.

  12. Comparative analyses of plasma probe diagnostics techniques

    SciTech Connect

    Godyak, V. A.; Alexandrovich, B. M.

    2015-12-21

    The subject of this paper is a comparative analysis of the plasma parameters inferred from the classical Langmuir probe procedure, from different theories of the ion current to the probe, and from measured electron energy distribution function (EEDF) obtained by double differentiation of the probe characteristic. We concluded that the plasma parameters inferred from the classical Langmuir procedure can be subjected to significant inaccuracy due to the non-Maxwellian EEDF, uncertainty of locating the plasma potential, and the arbitrariness of the ion current approximation. The plasma densities derived from the ion part of the probe characteristics diverge by as much as an order of magnitude from the density calculated according to Langmuir procedure or calculated as corresponding integral of the measured EEDF. The electron temperature extracted from the ion part is always subjected to uncertainty. Such inaccuracy is attributed to modification of the EEDF for fast electrons due to inelastic electron collisions, and to deficiencies in the existing ion current theories; i.e., unrealistic assumptions about Maxwellian EEDFs, underestimation of the ion collisions and the ion ambipolar drift, and discounting deformation of the one-dimensional structure of the region perturbed by the probe. We concluded that EEDF measurement is the single reliable probe diagnostics for the basic research and industrial applications of highly non-equilibrium gas discharge plasmas. Examples of EEDF measurements point up importance of examining the probe current derivatives in real time and reiterate significance of the equipment technical characteristics, such as high energy resolution and wide dynamic range.

  13. Comparative analyses of plasma probe diagnostics techniques

    NASA Astrophysics Data System (ADS)

    Godyak, V. A.; Alexandrovich, B. M.

    2015-12-01

    The subject of this paper is a comparative analysis of the plasma parameters inferred from the classical Langmuir probe procedure, from different theories of the ion current to the probe, and from measured electron energy distribution function (EEDF) obtained by double differentiation of the probe characteristic. We concluded that the plasma parameters inferred from the classical Langmuir procedure can be subjected to significant inaccuracy due to the non-Maxwellian EEDF, uncertainty of locating the plasma potential, and the arbitrariness of the ion current approximation. The plasma densities derived from the ion part of the probe characteristics diverge by as much as an order of magnitude from the density calculated according to Langmuir procedure or calculated as corresponding integral of the measured EEDF. The electron temperature extracted from the ion part is always subjected to uncertainty. Such inaccuracy is attributed to modification of the EEDF for fast electrons due to inelastic electron collisions, and to deficiencies in the existing ion current theories; i.e., unrealistic assumptions about Maxwellian EEDFs, underestimation of the ion collisions and the ion ambipolar drift, and discounting deformation of the one-dimensional structure of the region perturbed by the probe. We concluded that EEDF measurement is the single reliable probe diagnostics for the basic research and industrial applications of highly non-equilibrium gas discharge plasmas. Examples of EEDF measurements point up importance of examining the probe current derivatives in real time and reiterate significance of the equipment technical characteristics, such as high energy resolution and wide dynamic range.

  14. Plasma filtering techniques for nuclear waste remediation.

    PubMed

    Gueroult, Renaud; Hobbs, David T; Fisch, Nathaniel J

    2015-10-30

    Nuclear waste cleanup is challenged by the handling of feed stocks that are both unknown and complex. Plasma filtering, operating on dissociated elements, offers advantages over chemical methods in processing such wastes. The costs incurred by plasma mass filtering for nuclear waste pretreatment, before ultimate disposal, are similar to those for chemical pretreatment. However, significant savings might be achieved in minimizing the waste mass. This advantage may be realized over a large range of chemical waste compositions, thereby addressing the heterogeneity of legacy nuclear waste.

  15. Plasma filtering techniques for nuclear waste remediation

    DOE PAGES

    Gueroult, Renaud; Hobbs, David T.; Fisch, Nathaniel J.

    2015-04-24

    Nuclear waste cleanup is challenged by the handling of feed stocks that are both unknown and complex. Plasma filtering, operating on dissociated elements, offers advantages over chemical methods in processing such wastes. The costs incurred by plasma mass filtering for nuclear waste pretreatment, before ultimate disposal, are similar to those for chemical pretreatment. However, significant savings might be achieved in minimizing the waste mass. As a result, this advantage may be realized over a large range of chemical waste compositions, thereby addressing the heterogeneity of legacy nuclear waste.

  16. Plasma filtering techniques for nuclear waste remediation.

    PubMed

    Gueroult, Renaud; Hobbs, David T; Fisch, Nathaniel J

    2015-10-30

    Nuclear waste cleanup is challenged by the handling of feed stocks that are both unknown and complex. Plasma filtering, operating on dissociated elements, offers advantages over chemical methods in processing such wastes. The costs incurred by plasma mass filtering for nuclear waste pretreatment, before ultimate disposal, are similar to those for chemical pretreatment. However, significant savings might be achieved in minimizing the waste mass. This advantage may be realized over a large range of chemical waste compositions, thereby addressing the heterogeneity of legacy nuclear waste. PMID:25956646

  17. A comparative study of electrical probe techniques for plasma diagnostics

    NASA Technical Reports Server (NTRS)

    Szuszczewicz, E. P.

    1972-01-01

    Techniques for using electrical probes for plasma diagnostics are reviewed. Specific consideration is given to the simple Langmuir probe, the symmetric double probe of Johnson and Malter, the variable-area probe of Fetz and Oeschsner, and a floating probe technique. The advantages and disadvantages of each technique are discussed.

  18. Plasma Sheet Velocity Measurement Techniques for the Pulsed Plasma Thruster SIMP-LEX

    NASA Technical Reports Server (NTRS)

    Nawaz, Anuscheh; Lau, Matthew

    2011-01-01

    The velocity of the first plasma sheet was determined between the electrodes of a pulsed plasma thruster using three measurement techniques: time of flight probe, high speed camera and magnetic field probe. Further, for time of flight probe and magnetic field probe, it was possible to determine the velocity distribution along the electrodes, as the plasma sheet is accelerated. The results from all three techniques are shown, and are compared for one thruster geometry.

  19. Positron plasma control techniques for the production of cold antihydrogen

    SciTech Connect

    Funakoshi, R.; Hayano, R. S.; Amoretti, M.; Macri, M.; Testera, G.; Variola, A.; Bonomi, G.; Bowe, P. D.; Hangst, J. S.; Madsen, N.; Canali, C.; Carraro, C.; Lagomarsino, V.; Manuzio, G.; Cesar, C. L.; Charlton, M.; Joergensen, L. V.; Mitchard, D.; Werf, D. P. van der; Doser, M.

    2007-07-15

    An observation of a clear dependence of antihydrogen production on positron plasma shapes is reported. For this purpose a plasma control method has been developed combining the plasma rotating-wall technique with a mode diagnostic system. With the help of real-time and nondestructive observations, the rotating-wall parameters have been optimized. The positron plasma can be manipulated into a wide range of shapes (aspect ratio 6.5{<=}{alpha} < or approx. 80) and densities (1.5x10{sup 8}{<=}n < or approx. 7x10{sup 9} cm{sup -3}) within a short duration (25 s) compatible with the ATHENA antihydrogen production cycle.

  20. Plasma Technology as a New Preservation Technique

    NASA Astrophysics Data System (ADS)

    Rincón, R.; Calzada, M. D.

    The preliminary results of using the surface wave discharge at the atmospheric pressure on groups of lentils and sherry Fino wine samples are presented. In this research, the capability of active species and UV radiation from the plasma, has been assessed on preservation of food. Besides, the generation and emission of both excited molecules in a metastable state N2}(B3Π {g-> A3}Σ u{+) and the de-excitation of species NO(A2}Σ {+) producing UV radiation have been also studied.

  1. Diagnostic techniques in thermal plasma processing (Part II). Volume 2

    SciTech Connect

    Boulos, M.; Fauchais, P.; Pfender, E.

    1986-02-01

    Techniques for diagnostics for thermal plasmas are discussed. These include both optical techniques and in-flight measurements of particulate matter. In the core of the plasma, collisional excitation of the various chemical species is so strong that the population of the corresponding quantum levels becomes high enough for net emission from the plasma. In that case, the classical methods of emission spectroscopy may be applied. But in the regions where the temperatures are below 4000/sup 0/K (these regions are of primary importance for plasma processing), the emission from the plasma is no longer sufficient for emission spectroscopy. In this situation, the population of excited levels must be increased by the absorption of the light from an external source. Such sources, as for example pulsed tunable dye lasers, are now commercially available. The use of such new devices leads to various techniques such as laser induced fluorescence (LIF) or Coherent Anti Stockes Raman Spectroscopy (CARS) that can be used for analyzing plasmas. Particle velocity measurements can be achieved by photography and laser Doppler anemometry. Particle flux measurements are typically achieved by collecting particles on a substrate. Particle size measurements are based on intensity of scattered light. (WRF)

  2. Enhanced surface functionality via plasma modification and plasma deposition techniques to create more biologically relevant materials

    NASA Astrophysics Data System (ADS)

    Shearer, Jeffrey C.

    Functionalizing nanoparticles and other unusually shaped substrates to create more biologically relevant materials has become central to a wide range of research programs. One of the primary challenges in this field is creating highly functionalized surfaces without modifying the underlying bulk material. Traditional wet chemistry techniques utilize thin film depositions to functionalize nanomaterials with oxygen and nitrogen containing functional groups, such as --OH and --NHx. These functional groups can serve to create surfaces that are amenable to cell adhesion or can act as reactive groups for further attachment of larger structures, such as macromolecules or antiviral agents. Additional layers, such as SiO2, are often added between the nanomaterial and the functionalized coating to act as a barrier films, adhesion layers, and to increase overall hydrophilicity. However, some wet chemistry techniques can damage the bulk material during processing. This dissertation examines the use of plasma processing as an alternative method for producing these highly functionalized surfaces on nanoparticles and polymeric scaffolds through the use of plasma modification and plasma enhanced chemical vapor deposition techniques. Specifically, this dissertation will focus on (1) plasma deposition of SiO2 barrier films on nanoparticle substrates; (2) surface functionalization of amine and alcohol groups through (a) plasma co-polymerization and (b) plasma modification; and (3) the design and construction of plasma hardware to facilitate plasma processing of nanoparticles and polymeric scaffolds. The body of work presented herein first examines the fabrication of composite nanoparticles by plasma processing. SiOxC y and hexylamine films were coated onto TiO2 nanoparticles to demonstrate enhanced water dispersion properties. Continuous wave and pulsed allyl alcohol plasmas were used to produce highly functionalized Fe2 O3 supported nanoparticles. Specifically, film composition was

  3. First fusion proton measurements in TEXTOR plasmas using activation technique

    SciTech Connect

    Bonheure, G.; Wassenhove, G. Van; Mlynar, J.; Hult, M.; Gonzalez de Orduna, R.; Lutter, G.; Vermaercke, P.; Huber, A.; Schweer, B.; Esser, G.; Biel, W.

    2012-10-15

    MeV particle loss measurements from fusion plasmas, in particular alpha particles, remain difficult in large fusion devices and further R and D is needed for ITER. This paper describes the first attempt to measure 3 MeV escaping fusion protons emitted from TEXTOR tokamak plasmas using activation technique. This technique was successfully demonstrated, initially, in 2006 on the JET tokamak. An ion camera equipped with a collimator and several types of activation detectors was installed inside the TEXTOR vacuum vessel to perform these measurements. After irradiation, the detectors were analyzed using ultra low level gamma-ray spectrometry at the HADES underground laboratory. 3 MeV escaping fusion protons were detected in larger number -{approx}6 times more - compared to earlier measurements using this technique on JET. Another major progress was the reduction of the cooling time by a factor of 50, which made possible to detect radionuclides with half-life of less than 90 min.

  4. Dynamics of blood plasma by spectropolarimetry and biochemical techniques

    NASA Astrophysics Data System (ADS)

    Voloshynska, Katerina; Ilashchuka, Tetjana; Prydij, Olexander; Gruia, Maria

    2014-08-01

    The aim of the study was to establish objective parameters of the field of laser and incoherent radiation of different spectral ranges (UV, visible, IR) as a non-invasive optical method of interaction with different samples of biological tissues and fluids of patients to determine the dynamics of metabolic syndrome and choosing the best personal treatment. As diagnostic methods have been used ultraviolet spectrometry samples of blood plasma in the liquid state, infrared spectroscopy middle range (2,5 - 25 microns) dry residue of plasma polarization and laser diagnostic technique of thin histological sections of biological tissues.

  5. Diagnostic techniques for measuring suprathermal electron dynamics in plasmas (invited)

    SciTech Connect

    Coda, S.

    2008-10-15

    Plasmas, both in the laboratory and in space, are often not in thermodynamic equilibrium, and the plasma electron distribution function is accordingly non-Maxwellian. Suprathermal electron tails can be generated by external drives, such as rf waves and electric fields, or internal ones, such as instabilities and magnetic reconnection. The variety and importance of the phenomena in which suprathermal electrons play a significant role explains an enduring interest in diagnostic techniques to investigate their properties and dynamics. X-ray bremsstrahlung emission has been studied in hot magnetized plasmas for well over two decades, flanked progressively by electron-cyclotron emission in geometries favoring the high-energy end of the distribution function (high-field-side, vertical, oblique emission), by electron-cyclotron absorption, by spectroscopic techniques, and at lower temperatures, by Langmuir probes and electrostatic analyzers. Continuous progress in detector technology and in measurement and analysis techniques, increasingly sophisticated layouts (multichannel and tomographic systems, imaging geometries), and highly controlled suprathermal generation methods (e.g., perturbative rf modulation) have all been brought to bear in recent years on an increasingly detailed, although far from complete, understanding of suprathermal electron dynamics.

  6. Plasma and trap-based techniques for science with positrons

    NASA Astrophysics Data System (ADS)

    Danielson, J. R.; Dubin, D. H. E.; Greaves, R. G.; Surko, C. M.

    2015-01-01

    In recent years, there has been a wealth of new science involving low-energy antimatter (i.e., positrons and antiprotons) at energies ranging from 102 to less than 10-3 eV . Much of this progress has been driven by the development of new plasma-based techniques to accumulate, manipulate, and deliver antiparticles for specific applications. This article focuses on the advances made in this area using positrons. However, many of the resulting techniques are relevant to antiprotons as well. An overview is presented of relevant theory of single-component plasmas in electromagnetic traps. Methods are described to produce intense sources of positrons and to efficiently slow the typically energetic particles thus produced. Techniques are described to trap positrons efficiently and to cool and compress the resulting positron gases and plasmas. Finally, the procedures developed to deliver tailored pulses and beams (e.g., in intense, short bursts, or as quasimonoenergetic continuous beams) for specific applications are reviewed. The status of development in specific application areas is also reviewed. One example is the formation of antihydrogen atoms for fundamental physics [e.g., tests of invariance under charge conjugation, parity inversion, and time reversal (the CPT theorem), and studies of the interaction of gravity with antimatter]. Other applications discussed include atomic and materials physics studies and the study of the electron-positron many-body system, including both classical electron-positron plasmas and the complementary quantum system in the form of Bose-condensed gases of positronium atoms. Areas of future promise are also discussed. The review concludes with a brief summary and a list of outstanding challenges.

  7. A polarization-based Thomson scattering technique for burning plasmas

    NASA Astrophysics Data System (ADS)

    Parke, E.; Mirnov, V. V.; Den Hartog, D. J.

    2014-02-01

    The traditional Thomson scattering diagnostic is based on measurement of the wavelength spectrum of scattered light, where electron temperature measurements are inferred from thermal broadening of the spectrum. At sufficiently high temperatures, especially those predicted for ITER and other burning plasmas, relativistic effects cause a change in the degree of polarization (P) of the scattered light; for fully polarized incident laser light, the scattered light becomes partially polarized. The resulting reduction of polarization is temperature dependent and has been proposed by other authors as a potential alternative to the traditional spectral decomposition technique. Following the previously developed Stokes vector approach, we analytically calculate the degree of polarization for incoherent Thomson scattering. For the first time, we obtain exact results valid for the full range of incident laser polarization states, scattering angles, and electron temperatures. While previous work focused only on linear polarization, we show that circularly polarized incident light optimizes the degree of depolarization for a wide range of temperatures relevant to burning plasmas. We discuss the feasibility of a polarization based Thomson scattering diagnostic for ITER-like plasmas with both linearly and circularly polarized light and compare to the traditional technique.

  8. Recent Advances in High-Growth Rate Single-Crystal CVD Diamond

    SciTech Connect

    Liang, Q.; Yan, C; Meng, Y; Lai, J; Krasnicki, S; Mao, H; Hemley, R

    2009-01-01

    There have been important advances in microwave plasma chemical vapor deposition (MPCVD) of large single-crystal CVD diamond at high growth rates and applications of this diamond. The types of gas chemistry and growth conditions, including microwave power, pressure, and substrate surface temperatures, have been varied to optimize diamond quality and growth rates. The diamond has been characterized by a variety of spectroscopic and diffraction techniques. We have grown single-crystal CVD diamond over ten carats and above 1 cm in thickness at growth rates of 50-100 {micro}m/h. Colorless and near colorless single crystals up to two carats have been produced by further optimizing the process. The nominal Vickers fracture toughness of this high-growth rate diamond can be tuned to exceed 20 MPa m{sup 1/2} in comparison to 5-10 MPa m{sup 1/2} for conventional natural and CVD diamond. Post-growth high-pressure/high-temperature (HPHT) and low-pressure/high-temperature (LPHT) annealing have been carried out to alter the optical, mechanical, and electronic properties. Most recently, single-crystal CVD diamond has been successfully annealed by LPHT methods without graphitization up to 2200 C and < 300 Torr for periods of time ranging from a fraction of minute to a few hours. Significant changes observed in UV, visible, infrared, and photoluminescence spectra are attributed to changes in various vacancy centers and extended defects.

  9. Nano powders, components and coatings by plasma technique

    NASA Technical Reports Server (NTRS)

    McKechnie, Timothy N. (Inventor); Antony, Leo V. M. (Inventor); O'Dell, Scott (Inventor); Power, Chris (Inventor); Tabor, Terry (Inventor)

    2009-01-01

    Ultra fine and nanometer powders and a method of producing same are provided, preferably refractory metal and ceramic nanopowders. When certain precursors are injected into the plasma flame in a reactor chamber, the materials are heated, melted and vaporized and the chemical reaction is induced in the vapor phase. The vapor phase is quenched rapidly to solid phase to yield the ultra pure, ultra fine and nano product. With this technique, powders have been made 20 nanometers in size in a system capable of a bulk production rate of more than 10 lbs/hr. The process is particularly applicable to tungsten, molybdenum, rhenium, tungsten carbide, molybdenum carbide and other related materials.

  10. Nano powders, components and coatings by plasma technique

    DOEpatents

    McKechnie, Timothy N.; Antony, Leo V. M.; O'Dell, Scott; Power, Chris; Tabor, Terry

    2009-11-10

    Ultra fine and nanometer powders and a method of producing same are provided, preferably refractory metal and ceramic nanopowders. When certain precursors are injected into the plasma flame in a reactor chamber, the materials are heated, melted and vaporized and the chemical reaction is induced in the vapor phase. The vapor phase is quenched rapidly to solid phase to yield the ultra pure, ultra fine and nano product. With this technique, powders have been made 20 nanometers in size in a system capable of a bulk production rate of more than 10 lbs/hr. The process is particularly applicable to tungsten, molybdenum, rhenium, tungsten carbide, molybdenum carbide and other related materials.

  11. Plasma deposition and surface modification techniques for wear resistance

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1982-01-01

    The ion-assisted or plasma coating technology is discussed as it applies to the deposition of hard, wear resistant refractory compound films. Of the many sputtering and ion plating modes and configurations the reactive magnetron sputtering and the reactive triode ion plating techniques are the preferred ones to deposit wear resistant coatings for tribological applications. Both of these techniques incorporate additional means to enhance the ionization efficiency and chemical reaction to precision tailor desirable tribological characteristics. Interrelationships between film formation, structure, and ribological properties are strictly controlled by the deposition parameters and the substrate condition. The enhanced ionization contributes to the excellent adherence and coherence, reduced internal stresses and improved structural growth to form dense, cohesive, equiaxed grain structure for improved wear resistance and control.

  12. Homocysteine, B-vitamins and CVD.

    PubMed

    McNulty, Helene; Pentieva, Kristina; Hoey, Leane; Ward, Mary

    2008-05-01

    There is considerable interest in plasma homocysteine (tHcy) as a CVD risk factor. Although the secondary prevention trials published to date have been inconclusive in confirming a benefit of tHcy-lowering treatment with B-vitamins on CVD events generally, such studies are widely recognised to have been insufficiently powered to detect a significant effect for the predicted magnitude of association between tHcy and heart disease risk, and therefore cannot be interpreted as evidence that no relationship exists. In fact, a recent meta-analysis of clinical trials has confirmed that folic acid supplementation reduces the risk of stroke, particularly in individuals without a history of stroke. Evidence supporting a causal relationship between elevated tHcy and heart disease also comes from genetic studies. The most important genetic determinant of tHcy in the general population is the common C677T variant in methylenetetrahydrofolate reductase (MTHFR) that results in higher tHcy. Individuals with the homozygous mutant (TT) genotype have a significantly higher (14-21%) risk of heart disease. Plasma tHcy is very responsive to intervention with the B-vitamins required for its metabolism, in particular folic acid, and to a lesser extent vitamins B12 and B6. Thus, although primarily aimed at reducing neural-tube defects, folic acid fortification may have an important role in the primary prevention of CVD via tHcy lowering. Besides folate, riboflavin is required as a cofactor for MTHFR and enhanced riboflavin status results in a marked lowering in tHcy specifically in individuals with the TT genotype, presumably by neutralising the variant form of the enzyme. About 10% of the UK and Irish populations have the TT genotype. In the present paper the potential role of folate and related B-vitamins in the primary prevention of CVD and the implications for nutrition policy are explored. PMID:18412997

  13. Nuts and CVD.

    PubMed

    Ros, Emilio

    2015-04-01

    Nuts are nutrient-dense foods with complex matrices rich in unsaturated fatty acids and other bioactive compounds, such as l-arginine, fibre, healthful minerals, vitamin E, phytosterols and polyphenols. By virtue of their unique composition, nuts are likely to beneficially affect cardiovascular health. Epidemiological studies have associated nut consumption with a reduced incidence of CHD in both sexes and of diabetes in women, but not in men. Feeding trials have clearly demonstrated that consumption of all kinds of nuts has a cholesterol-lowering effect, even in the context of healthy diets. There is increasing evidence that nut consumption has a beneficial effect on oxidative stress, inflammation and vascular reactivity. Blood pressure, visceral adiposity and the metabolic syndrome also appear to be positively influenced by nut consumption. Contrary to expectations, epidemiological studies and clinical trials suggest that regular nut consumption is not associated with undue weight gain. Recently, the PREvención con DIeta MEDiterránea randomised clinical trial of long-term nutrition intervention in subjects at high cardiovascular risk provided first-class evidence that regular nut consumption is associated with a 50 % reduction in incident diabetes and, more importantly, a 30 % reduction in CVD. Of note, incident stroke was reduced by nearly 50 % in participants allocated to a Mediterranean diet enriched with a daily serving of mixed nuts (15 g walnuts, 7.5 g almonds and 7.5 g hazelnuts). Thus, it is clear that frequent nut consumption has a beneficial effect on CVD risk that is likely to be mediated by salutary effects on intermediate risk factors. PMID:26148914

  14. Nuts and CVD.

    PubMed

    Ros, Emilio

    2015-04-01

    Nuts are nutrient-dense foods with complex matrices rich in unsaturated fatty acids and other bioactive compounds, such as l-arginine, fibre, healthful minerals, vitamin E, phytosterols and polyphenols. By virtue of their unique composition, nuts are likely to beneficially affect cardiovascular health. Epidemiological studies have associated nut consumption with a reduced incidence of CHD in both sexes and of diabetes in women, but not in men. Feeding trials have clearly demonstrated that consumption of all kinds of nuts has a cholesterol-lowering effect, even in the context of healthy diets. There is increasing evidence that nut consumption has a beneficial effect on oxidative stress, inflammation and vascular reactivity. Blood pressure, visceral adiposity and the metabolic syndrome also appear to be positively influenced by nut consumption. Contrary to expectations, epidemiological studies and clinical trials suggest that regular nut consumption is not associated with undue weight gain. Recently, the PREvención con DIeta MEDiterránea randomised clinical trial of long-term nutrition intervention in subjects at high cardiovascular risk provided first-class evidence that regular nut consumption is associated with a 50 % reduction in incident diabetes and, more importantly, a 30 % reduction in CVD. Of note, incident stroke was reduced by nearly 50 % in participants allocated to a Mediterranean diet enriched with a daily serving of mixed nuts (15 g walnuts, 7.5 g almonds and 7.5 g hazelnuts). Thus, it is clear that frequent nut consumption has a beneficial effect on CVD risk that is likely to be mediated by salutary effects on intermediate risk factors.

  15. Simplex-in-cell technique for collisionless plasma simulations

    NASA Astrophysics Data System (ADS)

    Kates-Harbeck, Julian; Totorica, Samuel; Zrake, Jonathan; Abel, Tom

    2016-01-01

    We extend the simplex-in-cell (SIC) technique recently introduced in the context of collisionless dark matter fluids [1,2] to the case of collisionless plasmas. The six-dimensional phase space distribution function f (x , v) is represented by an ensemble of three-dimensional manifolds, which we refer to as sheets. The electric potential field is obtained by solving the Poisson equation on a uniform mesh, where the charge density is evaluated by a spatial projection of the phase space sheets. The SIC representation of phase space density facilitates robust, high accuracy numerical evolution of the Vlasov-Poisson system using significantly fewer tracer particles than comparable particle-in-cell (PIC) approaches by reducing the numerical shot-noise associated with the latter. We introduce the SIC formulation and describe its implementation in a new code, which we validate using standard test problems including plasma oscillations, Landau damping, and two stream instabilities in one dimension. Merits of the new scheme are shown to include higher accuracy and faster convergence rates in the number of particles. We finally motivate and outline the efficient application of SIC to higher dimensional problems.

  16. Oriented carbon nanostructures grown by hot-filament plasma-enhanced CVD from self-assembled Co-based catalyst on Si substrates

    NASA Astrophysics Data System (ADS)

    Fleaca, Claudiu Teodor; Morjan, Ion; Rodica, Alexandrescu; Dumitrache, Florian; Soare, Iuliana; Gavrila-Florescu, Lavinia; Sandu, Ion; Dutu, Elena; Le Normand, François; Faerber, Jacques

    2012-03-01

    We report the synthesis of coral- and caterpillar-like carbon nanostructures assemblies starting from cobalt nitrate ethanol solutions deposited by drop-casting onto blank or carbon nanoparticles film covered Si(1 0 0) substrates. The seeded films were pre-treated with glow discharge hydrogen plasma aided by hot-filaments at 550 °C followed by introduction of acetylene at 700 °C. The resultant carbon nanostructure assemblies contain a high density of aligned carbon nanotubes/nanofibers (CNTs/CNFs). The influence of the forces that act during liquid-mediated self-assembly of Co catalyst precursor is discussed.

  17. Atmospheric pressure plasma-initiated chemical vapor deposition (AP-PiCVD) of poly(diethylallylphosphate) coating: a char-forming protective coating for cellulosic textile.

    PubMed

    Hilt, Florian; Boscher, Nicolas D; Duday, David; Desbenoit, Nicolas; Levalois-Grützmacher, Joëlle; Choquet, Patrick

    2014-01-01

    An innovative atmospheric pressure chemical vapor deposition method toward the deposition of polymeric layers has been developed. This latter involves the use of a nanopulsed plasma discharge to initiate the free-radical polymerization of an allyl monomer containing phosphorus (diethylallylphosphate, DEAP) at atmospheric pressure. The polymeric structure of the film is evidence by mass spectrometry. The method, highly suitable for the treatment of natural biopolymer substrate, has been carried out on cotton textile to perform the deposition of an efficient and conformal protective coating.

  18. Growth process of hydrogenated amorphous carbon films synthesized by atmospheric pressure plasma enhanced CVD using nitrogen and helium as a dilution gas

    NASA Astrophysics Data System (ADS)

    Mori, Takanori; Sakurai, Takachika; Sato, Taiki; Shirakura, Akira; Suzuki, Tetsuya

    2016-04-01

    Hydrogenated amorphous carbon films with various thicknesses were synthesized by dielectric barrier discharge-based plasma deposition under atmospheric pressure diluted with nitrogen (N2) and helium (He) at various pulse frequencies. The C2H2/N2 film showed cauliflower-like-particles that grew bigger with the increase in film’s thickness. At 5 kHz, the film with a thickness of 2.7 µm and smooth surface was synthesized. On the other hand, the films synthesized from C2H2/He had a smooth surface and was densely packed with domed particles. The domed particles extended with the increase in the film thickness, enabling it to grow successfully to 37 µm with a smooth surface.

  19. CVD-Enabled Graphene Manufacture and Technology

    PubMed Central

    2015-01-01

    Integrated manufacturing is arguably the most challenging task in the development of technology based on graphene and other 2D materials, particularly with regard to the industrial demand for “electronic-grade” large-area films. In order to control the structure and properties of these materials at the monolayer level, their nucleation, growth and interfacing needs to be understood to a level of unprecedented detail compared to existing thin film or bulk materials. Chemical vapor deposition (CVD) has emerged as the most versatile and promising technique to develop graphene and 2D material films into industrial device materials and this Perspective outlines recent progress, trends, and emerging CVD processing pathways. A key focus is the emerging understanding of the underlying growth mechanisms, in particular on the role of the required catalytic growth substrate, which brings together the latest progress in the fields of heterogeneous catalysis and classic crystal/thin-film growth. PMID:26240694

  20. Effect of Depositing Temperature on the Interfacial Adhesion of Nanocrystalline Diamond Films Grown on Titanium by Microwave Plasma Assisted Cvd Process

    NASA Astrophysics Data System (ADS)

    Askari, Syed Jawid; Merchant, Ali Imran

    In contrast to their exceptional mechanical properties, titanium and its alloys possess poor friction and wear characteristics. Nanocrystalline diamond (NCD) films appear to be a promising solution for their tribological problem due to their smooth surfaces and small grain size. However, the synthesis of a well adherent NCD film on titanium and its alloys is always complicated due to the different thermal expansion coefficients of the two materials, the complex nature of the interlayer formed during diamond deposition, and the difficulty in achieving very high nucleation density. In this work NCD thin films have been deposited on pure Ti substrates in a microwave plasma chemical vapor deposition (MWPCVD) reactor under fixed pressure and methane concentration in hydrogen but over a wide temperature range. The effects of depositing temperatures on the adhesion of films are evaluated using Rockwell indentation tests. It is found that by increasing the deposition temperature the films bonding deteriorates. The films synthesized are characterized by field emission scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and X-ray diffraction.

  1. Synthesis of graphene by cobalt-catalyzed decomposition of methane in plasma-enhanced CVD: Optimization of experimental parameters with Taguchi method

    NASA Astrophysics Data System (ADS)

    Mehedi, H.-A.; Baudrillart, B.; Alloyeau, D.; Mouhoub, O.; Ricolleau, C.; Pham, V. D.; Chacon, C.; Gicquel, A.; Lagoute, J.; Farhat, S.

    2016-08-01

    This article describes the significant roles of process parameters in the deposition of graphene films via cobalt-catalyzed decomposition of methane diluted in hydrogen using plasma-enhanced chemical vapor deposition (PECVD). The influence of growth temperature (700-850 °C), molar concentration of methane (2%-20%), growth time (30-90 s), and microwave power (300-400 W) on graphene thickness and defect density is investigated using Taguchi method which enables reaching the optimal parameter settings by performing reduced number of experiments. Growth temperature is found to be the most influential parameter in minimizing the number of graphene layers, whereas microwave power has the second largest effect on crystalline quality and minor role on thickness of graphene films. The structural properties of PECVD graphene obtained with optimized synthesis conditions are investigated with Raman spectroscopy and corroborated with atomic-scale characterization performed by high-resolution transmission electron microscopy and scanning tunneling microscopy, which reveals formation of continuous film consisting of 2-7 high quality graphene layers.

  2. C(1) metabolism and CVD outcomes in older adults.

    PubMed

    McNulty, Helene; Strain, J J; Pentieva, Kristina; Ward, Mary

    2012-05-01

    CVD is the most common cause of death in people over 65 years. This review considers the latest evidence for a potential protective effect of C(1) donors (folate and the metabolically related B-vitamins) in CVD. Such an effect may or may not be mediated via the role of these nutrients in maintaining plasma homocysteine concentrations within a desirable range. Despite predictions from epidemiological studies that lowering plasma homocysteine would reduce cardiovascular risk, several secondary prevention trials in at-risk patients published since 2004 have failed to demonstrate a benefit of homocysteine-lowering therapy with B-vitamins on CVD events generally. All these trials were performed in CVD patients with advanced disease; thus current evidence suggests that intervention with high-dose folic acid is of no benefit in preventing another event, at least in the case of heart disease. The evidence at this time, however, is stronger for stroke, with meta-analyses of randomised trials showing that folic acid reduces the risk of stroke, particularly in people with no history of stroke. Genetic studies provide convincing evidence to support a causal relationship between sub-optimal B-vitamin status and CVD. People homozygous for the common C677T variant in the gene encoding the folate-metabolising enzyme, methylenetetrahydrofolate reductase (MTHFR), typically have a 14-21% higher risk of CVD. Apart from folate, riboflavin is required as a co-factor for MTHFR. New evidence shows that riboflavin intervention results in marked lowering of blood pressure, specifically in patients with the MTHFR 677TT genotype. This novel gene-nutrient interaction may provide insights as to the mechanism that links C(1) metabolism with CVD outcomes. PMID:22152927

  3. Equation of State Measurement Technique for Strongly Coupled Plasmas

    NASA Astrophysics Data System (ADS)

    Tierney, T.; Benage, J.; Evans, S.; Kyrala, G.; Montoya, R.; Roberts, J.; Taylor, T.; Workman, J.

    2000-09-01

    Low-temperature ( ~ 1eV), high-density(n_e ~10^21 cm-3) plasmas are called strongly coupled (SCP) when the coulomb interaction energy is comparable to the thermal kinetic energy. We intend to measure the SCP equation of state (EOS) by modifying the standard EOS shock technique. A square column of aluminum SCP ( ~0.1 g/ cm^3, ~1 eV) is shocked by a 2-3 J, 0.8 ns frequency-doubled Nd:Yag laser pulse, producing a ~1 g/cm^3, ~20 eV SCP. The densities of the pre-shocked and shocked regions are measured by Ti K-shell (4.75 keV) x-ray absorption. Mg K-shell x-ray (1.35 keV) absorption, imaged through a high-resolution 1-D microscope onto a streak camera, provides shock speed measurements. Filtered PMTs provide the temperature and an initial internal energy estimate. Using these measurements in the Rankine-Hugoniot conservation equations we determine the pressure, final internal energy and, thus, the SCP EOS. We present the preliminary measurements of the aluminum conditions with emphasis on determining the EOS. * Work performed under the auspices of DOE

  4. Effect of active screen plasma nitriding pretreatment on wear behavior of TiN coating deposited by PACVD technique

    NASA Astrophysics Data System (ADS)

    Raoufi, M.; Mirdamadi, Sh.; Mahboubi, F.; Ahangarani, Sh.; Mahdipoor, M. S.; Elmkhah, H.

    2012-08-01

    Titanium based alloys are used extensively for improving wear properties of different parts due to their high hardness contents. Titanium nitride (TiN) is among these coatings which can be deposited on surface using various techniques such as CVD, PVD and PACVD. Their weak interface with substrate is one major drawback which can increase the total wear in spite of favorite wear behavior of TiN. Disc shaped samples from AISI H13 (DIN 1.2344) steel were prepared in this study. Single TiN coating was deposited on some of them while others have experienced a TiN deposition by active screen plasma nitriding (ASPN). Hardness at the surface and depth of samples was measured through Vickers micro hardness test which revealed 1810 Hv hardness as the maximum values for a dual-layered ASPN-TiN. Pin-on-disc wear test was done in order to study the wear mechanism. In this regard, the wear behavior of samples was investigated against pins from 100Cr6 (Din 1.3505) bearing steel and tungsten carbide-cobalt (WC-Co) steel. It was evidenced that the dual-layer ASPN-TiN coating has shown the least weight loss with the best wearing behavior because of its high hardness values, stable interface and acceptable resistance against peeling during wearing period.

  5. Structure and spectroscopic analysis of the graphene monolayer film directly grown on the quartz substrate via the HF-CVD technique

    NASA Astrophysics Data System (ADS)

    Mahmoud, Waleed E.; Al-Hazmi, Farag S.; Al-Ghamdi, A. A.; Shokr, F. S.; Beall, Gary W.; Bronstein, Lyudmila M.

    2016-08-01

    Direct growth of a monolayer graphene film on a quartz substrate by a hot filament chemical vapor deposition technique is reported. The monolayer graphene film prepared was characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), selected area electron diffraction (SAED), and atomic force microscopy (AFM). The optical properties were studied by spectroscopic elliposmetry. The experimental data were fitted by the Forouhi-Bloomer model to estimate the extinction coefficient and the refractive index of the monolayer graphene film. The refractive index spectrum in the visible region was studied based on the harmonic oscillator model. The lattice dielectric constant, real and imaginary dielectric constants and the ratio of the charge carrier number to the effective mass were determined. The surface and volume energy loss parameters were also found and showed that the value of the surface energy loss is greater than the volume energy loss. The determination of these optical constants will open new avenue for novel applications of graphene films in the field of wave plates, light modulators, ultrahigh-frequency signal processing and LCDs.

  6. Arc Plasma Synthesis of Nanostructured Materials: Techniques and Innovations

    SciTech Connect

    Das, A. K.; Bhoraskar, S. V.; Kakati, M.; Karmakar, Soumen

    2008-10-23

    Arc plasma aided synthesis of nanostructured materials has the potential of producing complex nano phase structures in bulk quantities. Successful implementation of this potential capability to industrial scale nano generation needs establishment of a plasma parameter control regime in terms of plasma gas, flow pattern, pressure, local temperature and the plasma fields to obtain the desired nano phase structures. However, there is a need to design innovative in situ experiments for generation of an extensive database and subsequently to correlate plasma parameters to the size, shape and phase of the generated nanostructures. The present paper reviews the various approaches utilized in the field of arc plasma nanosynthesis in general and in the authors' laboratories in particular. Simple plasma diagnostics and monitoring schemes have been used in conjunction with nano materials characterization tools to explore the possibility of controlling the size, shape, yield and phase composition of the arc generated nanostructures through plasma control. Case studies related to synthesis of AlN, Al2O3, TiO2, ZrO2, ZnO), magnetic (e.g. {gamma}-Fe2O3, Fe3O4) and single elemental materials (e.g. carbon nanotubes) are presented.

  7. CVD Diamond Dielectric Accelerating Structures

    SciTech Connect

    Schoessow, P.; Kanareykin, A.; Gat, R.

    2009-01-22

    The electrical and mechanical properties of diamond make it an ideal candidate material for use in dielectric accelerating structures: high RF breakdown field, extremely low dielectric losses and the highest available thermoconductive coefficient. Using chemical vapor deposition (CVD) cylindrical diamond structures have been manufactured with dimensions corresponding to fundamental TM{sub 01} mode frequencies in the GHz to THz range. Surface treatments are being developed to reduce the secondary electron emission (SEE) coefficient below unity to reduce the possibility of multipactor. The diamond CVD cylindrical waveguide technology developed here can be applied to a variety of other high frequency, large-signal applications.

  8. Argan oil improves surrogate markers of CVD in humans.

    PubMed

    Sour, Souad; Belarbi, Meriem; Khaldi, Darine; Benmansour, Nassima; Sari, Nassima; Nani, Abdelhafid; Chemat, Farid; Visioli, Francesco

    2012-06-01

    Limited - though increasing - evidence suggests that argan oil might be endowed with potential healthful properties, mostly in the areas of CVD and prostate cancer. We sought to comprehensively determine the effects of argan oil supplementation on the plasma lipid profile and antioxidant status of a group of healthy Algerian subjects, compared with matched controls. A total of twenty healthy subjects consumed 15 g/d of argan oil - with toasted bread - for breakfast, during 4 weeks (intervention group), whereas twenty matched controls followed their habitual diet, but did not consume argan oil. The study lasted 30 d. At the end of the study, argan oil-supplemented subjects exhibited higher plasma vitamin E concentrations, lower total and LDL-cholesterol, lower TAG and improved plasma and cellular antioxidant profile, when compared with controls. In conclusion, we showed that Algerian argan oil is able to positively modulate some surrogate markers of CVD, through mechanisms which warrant further investigation.

  9. Argan oil improves surrogate markers of CVD in humans.

    PubMed

    Sour, Souad; Belarbi, Meriem; Khaldi, Darine; Benmansour, Nassima; Sari, Nassima; Nani, Abdelhafid; Chemat, Farid; Visioli, Francesco

    2012-06-01

    Limited - though increasing - evidence suggests that argan oil might be endowed with potential healthful properties, mostly in the areas of CVD and prostate cancer. We sought to comprehensively determine the effects of argan oil supplementation on the plasma lipid profile and antioxidant status of a group of healthy Algerian subjects, compared with matched controls. A total of twenty healthy subjects consumed 15 g/d of argan oil - with toasted bread - for breakfast, during 4 weeks (intervention group), whereas twenty matched controls followed their habitual diet, but did not consume argan oil. The study lasted 30 d. At the end of the study, argan oil-supplemented subjects exhibited higher plasma vitamin E concentrations, lower total and LDL-cholesterol, lower TAG and improved plasma and cellular antioxidant profile, when compared with controls. In conclusion, we showed that Algerian argan oil is able to positively modulate some surrogate markers of CVD, through mechanisms which warrant further investigation. PMID:22082585

  10. Analyses of Different Techniques for the Plasma Probe Diagnostics

    NASA Astrophysics Data System (ADS)

    Godyak, Valery; Alexandrovich, Benjamin

    2015-09-01

    The subject of this publication is comparison of the plasma parameters inferred from classical Langmuir probe procedure, from different theories of the ion current to the probe, and from measured EEDF using double differentiation of the probe characteristic We concluded that the plasma parameters inferred by the classical Langmuir procedure are subjected to significant inaccuracy due to non-Maxwellian EEDF, uncertainty of locating the plasma potential and arbitrariness in approximation of the ion current. The plasma density inferred from the ion part of the probe characteristic was found to diverge by as much as an order of magnitude from the density calculated as the EEDF integral, while the electron temperature is derived with significant uncertainty. Such inaccuracy is attributed to deficiencies in the ion current theories, i.e. unrealistic assumptions about Maxwellian-shaped EEDFs, underestimation of the ion collisions and the ion ambipolar drift, and some others. We concluded that for highly non-equilibrium gas discharge plasmas at low gas pressure the probe measurements based on EEDF diagnostics is single reliable tool of for the basic research and industrial applications. Examples of EEDF measurements reiterate significance of the instrument technical characteristics, such as high energy resolution and wide dynamic range and importance of displaying the probe current derivatives in real time.

  11. Atomistic modelling of CVD synthesis of carbon nanotubes and graphene

    NASA Astrophysics Data System (ADS)

    Elliott, James A.; Shibuta, Yasushi; Amara, Hakim; Bichara, Christophe; Neyts, Erik C.

    2013-07-01

    We discuss the synthesis of carbon nanotubes (CNTs) and graphene by catalytic chemical vapour deposition (CCVD) and plasma-enhanced CVD (PECVD), summarising the state-of-the-art understanding of mechanisms controlling their growth rate, chiral angle, number of layers (walls), diameter, length and quality (defects), before presenting a new model for 2D nucleation of a graphene sheet from amorphous carbon on a nickel surface. Although many groups have modelled this process using a variety of techniques, we ask whether there are any complementary ideas emerging from the different proposed growth mechanisms, and whether different modelling techniques can give the same answers for a given mechanism. Subsequently, by comparing the results of tight-binding, semi-empirical molecular orbital theory and reactive bond order force field calculations, we demonstrate that graphene on crystalline Ni(111) is thermodynamically stable with respect to the corresponding amorphous metal and carbon structures. Finally, we show in principle how a complementary heterogeneous nucleation step may play a key role in the transformation from amorphous carbon to graphene on the metal surface. We conclude that achieving the conditions under which this complementary crystallisation process can occur may be a promising method to gain better control over the growth processes of both graphene from flat metal surfaces and CNTs from catalyst nanoparticles.

  12. Atomistic modelling of CVD synthesis of carbon nanotubes and graphene.

    PubMed

    Elliott, James A; Shibuta, Yasushi; Amara, Hakim; Bichara, Christophe; Neyts, Erik C

    2013-08-01

    We discuss the synthesis of carbon nanotubes (CNTs) and graphene by catalytic chemical vapour deposition (CCVD) and plasma-enhanced CVD (PECVD), summarising the state-of-the-art understanding of mechanisms controlling their growth rate, chiral angle, number of layers (walls), diameter, length and quality (defects), before presenting a new model for 2D nucleation of a graphene sheet from amorphous carbon on a nickel surface. Although many groups have modelled this process using a variety of techniques, we ask whether there are any complementary ideas emerging from the different proposed growth mechanisms, and whether different modelling techniques can give the same answers for a given mechanism. Subsequently, by comparing the results of tight-binding, semi-empirical molecular orbital theory and reactive bond order force field calculations, we demonstrate that graphene on crystalline Ni(111) is thermodynamically stable with respect to the corresponding amorphous metal and carbon structures. Finally, we show in principle how a complementary heterogeneous nucleation step may play a key role in the transformation from amorphous carbon to graphene on the metal surface. We conclude that achieving the conditions under which this complementary crystallisation process can occur may be a promising method to gain better control over the growth processes of both graphene from flat metal surfaces and CNTs from catalyst nanoparticles. PMID:23774798

  13. CVD diamond - fundamental phenomena

    SciTech Connect

    Yarbrough, W.A.

    1993-01-01

    This compilation of figures and diagrams addresses the basic physical processes involved in the chemical vapor deposition of diamond. Different methods of deposition are illustrated. For each method, observations are made of the prominent advantages and disadvantages of the technique. Chemical mechanisms of nucleation are introduced.

  14. CVD boron on calcium chromate powder

    SciTech Connect

    Coonen, R.M.

    1984-09-01

    This study was an experimental effort to improve the compositional homogeneity of a pyrotechnic mixture of boron and calcium chromate (CaCrO/sub 4/). Boron was deposited onto calcium chromate powders at 350/sup 0/C from a diborane and hydrogen gas mixture at a pressure of 40 torr by Chemical Vapor Deposition (CVD). The B:CaCrO/sub 4/ ratio of the coated powders was analyzed by inductively-coupled plasma spectroscopy and the distribution of the two phases was observed by electron microprobe analysis. The pyrotechnic activity was determined by differential thermal analysis. In addition to varying the composition of the mixture, an attempt was made to vary the boron distribution by coating both sized and unsized CaCrO/sub 4/ powders. Boron was deposited for 2 h onto sized CaCrO/sub 4/ powder, which resulted in a higher weight percentage of boron in comparison to the unsized powder. CVD coated CaCrO/sub 4/ powders began their pyrotechnic activity at an auto ignition temperature that was lower than the auto ignition temperature observed for mechanically blended mixtures. The coating of sized CaCrO/sub 4/ powder improved the uniformity of boron deposition of CaCrO/sub 4/, but it also decreased the pyrotechnic activity.

  15. Synthesis of Carbon Nanotubes Array by CVD

    NASA Technical Reports Server (NTRS)

    Zhu, S.; Su, C.; Cochrane, J. C.; Lehoczky, S. L.; Muntele, I.; Ila, D.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Since the properties of multi-wall carbon nanotubes (MWCNT) are superior in many devices such as electronics and sensors, many efforts have been involved in synthesizing particular structural or dimensional MWCNT. Uniform aligned MWCNT array is one of the prototype structures for devices such as filed emission device and microelectromechanical systems in which a large length to diameter ratio may also be required. Most aligned MWCNT recently synthesized by plasma enhanced chemical vapor deposition (CVD) have cone shaped structures. This presentation will illustrate aligned MWCNT array synthesized on silicon substrates using thermal CVD that could produce MWCNT with uniform diameter. An array of nickel particles was used as catalyst for MWCNT growth. A thin Ti or Au buffer layer was coated on the substrate prior to depositing nickel particles. Because the MWCNT size depends on the catalyst particle size, the nickel particle size annealed at various temperatures was investigated. MWCNT were grown on the substrate in the temperature range of 700 C - 1000 C and the pressure range of 1 to 300 torr. Methane and hydrogen gases with methane content of 1 - 10 % were used for the MWCNT synthesis. Morphology, length and diameter of MWCNT were determined by scanning electron microscopy and Raman spectroscopy. The detailed results of synthesis and characterizations will be discussed in the presentation.

  16. Thin film silicon by a microwave plasma deposition technique: Growth and devices, and, interface effects in amorphous silicon/crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Jagannathan, Basanth

    Thin film silicon (Si) was deposited by a microwave plasma CVD technique, employing double dilution of silane, for the growth of low hydrogen content Si films with a controllable microstructure on amorphous substrates at low temperatures (<400sp°C). The double dilution was achieved by using a Ar (He) carrier for silane and its subsequent dilution by Hsb2. Structural and electrical properties of the films have been investigated over a wide growth space (temperature, power, pressure and dilution). Amorphous Si films deposited by silane diluted in He showed a compact nature and a hydrogen content of ˜8 at.% with a photo/dark conductivity ratio of 10sp4. Thin film transistors (W/L = 500/25) fabricated on these films, showed an on/off ratio of ˜10sp6 and a low threshold voltage of 2.92 volts. Microcrystalline Si films with a high crystalline content (˜80%) were also prepared by this technique. Such films showed a dark conductivity ˜10sp{-6} S/cm, with a conduction activation energy of 0.49 eV. Film growth and properties have been compared for deposition in Ar and He carrier systems and growth models have been proposed. Low temperature junction formation by undoped thin film silicon was examined through a thin film silicon/p-type crystalline silicon heterojunctions. The thin film silicon layers were deposited by rf glow discharge, dc magnetron sputtering and microwave plasma CVD. The hetero-interface was identified by current transport analysis and high frequency capacitance methods as the key parameter controlling the photovoltaic (PV) response. The effect of the interface on the device properties (PV, junction, and carrier transport) was examined with respect to modifications created by chemical treatment, type of plasma species, their energy and film microstructure interacting with the substrate. Thermally stimulated capacitance was used to determine the interfacial trap parameters. Plasma deposition of thin film silicon on chemically clean c-Si created electron

  17. Investigation of plasma diagnostics using a dual frequency harmonic technique

    SciTech Connect

    Kim, Dong-Hwan; Kim, Young-Do; Cho, Sung-Won; Kim, Yu-Sin; Chung, Chin-Wook

    2014-09-07

    Plasma diagnostic methods using harmonic currents analysis of electrostatic probes were experimentally investigated to understand the differences in their measurement of the plasma parameters. When dual frequency voltage (ω{sub 1},ω{sub 2}) was applied to a probe, various harmonic currents (ω{sub 1}, 2ω{sub 1},ω{sub 2}, 2ω{sub 2},ω{sub 2}±ω{sub 1},ω{sub 2}±2ω{sub 1}) were generated due to the non-linearity of the probe sheath. The electron temperature can be obtained from the ratio of the two harmonics of the probe currents. According to the combinations of the two harmonics, the sensitivities in the measurement of the electron temperature differed, and this results in a difference of the electron temperature. From experiments and simulation, it is shown that this difference is caused by the systematic and random noise.

  18. Advanced modeling techniques in application to plasma pulse treatment

    NASA Astrophysics Data System (ADS)

    Pashchenko, A. F.; Pashchenko, F. F.

    2016-06-01

    Different approaches considered for simulation of plasma pulse treatment process. The assumption of a significant non-linearity of processes in the treatment of oil wells has been confirmed. Method of functional transformations and fuzzy logic methods suggested for construction of a mathematical model. It is shown, that models, based on fuzzy logic are able to provide a satisfactory accuracy of simulation and prediction of non-linear processes observed.

  19. Computational technique for plasma parameters determination using Langmuir probe data

    SciTech Connect

    Negrea, C.; Manea, V.; Covlea, V.; Jipa, A.

    2011-05-15

    In the present work, we consider a new numerical method for processing the experimental information on the electron energy distribution function obtained with a Langmuir probe in a low-pressure plasma. This method offers the possibility to establish the temperature and concentration of the electrons for different forms of the distribution function. Some specific difficulties of the previous methods used to do such estimations are surpassed using the method proposed in this work.

  20. Power Efficient Plasma Technique for Rapid Water Sterilization

    NASA Astrophysics Data System (ADS)

    Hershcovitch, Ady

    2015-11-01

    Water especially good quality drinking water is a dwindling resource for significant segments of the world population. The BBC quoted this article (http://www.ft.com/cms/s/2/8e42bdc8-0838-11e4-9afc-00144feab7de.html) for a claim that water shortage is a bigger problem than climate change. One option for increasing the water supply is to recycle waste and polluted water by inexpensive, environmentally friendly methods. First steps involve filtrations while the last step is water disinfection. Presently disinfection is done chemically and/or UV radiation. Some chemicals cannot be used in large quantity due to residual toxicity, while UV disinfection systems consume a great deal electricity. Plasmas in water are very attractive for water sterilization due to UV radiation, ozone, etc. generation inside the water volume. Commercially available devices like NK-03 Blue Ballast System are used aboard ships for water purification. But, presently utilized plasmas: glow, pulsed arcs are not power efficient. Vortex stabilized plasmas, which are power efficient, can even degrade medications (antibiotics) advancing the state-of-the-art by orders of magnitude, especially when combined with electron beams. Disinfection scheme will be presented. Work supported by Contract No. DE-AC02-98CH1-886 with the US DOE.

  1. Experimental Manipulation of a Non-Neutral Ion Plasma Using FT-ICR Techniques

    NASA Astrophysics Data System (ADS)

    Williams, Chad; Peterson, Bryan

    2010-10-01

    The goal of our project is to experimentally determine the half life of beryllium-7. We plan to do this by singly ionizing beryllium atoms and containing them in a non-neutral plasma state as they decay. In order to correctly make this measurement, however, we need a clean plasma of high density containing solely Be-7 atoms. Due to the variable amounts of impurities in the Be-7 samples produced in our lab, it is necessary to implement the technique of Fourier Transform Ion Cyclotron Resonance (FT-ICR). By exciting the cyclotron radius of these particles trapped in a magnetic field we seek to expel these impurities from the plasma, leaving pure Be-7. Also, a technique has been developed for successfully stacking multiple pulses of plasma inside of our Malmberg-Penning trap. Recent changes in the internal structure of trap confinement rings will grant us greater efficiency in the use of these techniques.

  2. Primary prevention of CVD: diet

    PubMed Central

    2014-01-01

    Introduction Diet is important in the cause of many chronic diseases. Individual change in dietary behaviour has the potential to decrease the burden of chronic disease, particularly cardiovascular disease (CVD). Methods and outcomes We conducted a systematic review and aimed to answer the following clinical question: What are the effects of dietary advice in generally healthy adults without existing CVD or increased CVD risk factors to improve cardiovascular outcomes (mortality, cardiovascular events, and cardiovascular risk factors)? We searched: Medline, Embase, The Cochrane Library, and other important databases up to March 2014 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). Results We found 14 studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. Conclusions In this systematic review, we present information relating to the effectiveness and safety of the following interventions: advice to increase fibre intake alone, advice to increase fruit and vegetable intake alone, advice to reduce and/or modify fat intake alone, and advice to reduce sodium intake alone. PMID:25268279

  3. Comparison of ionospheric plasma drifts obtained by different techniques

    NASA Astrophysics Data System (ADS)

    Kouba, Daniel; Arikan, Feza; Arikan, Orhan; Toker, Cenk; Mosna, Zbysek; Gok, Gokhan; Rejfek, Lubos; Ari, Gizem

    2016-07-01

    Ionospheric observatory in Pruhonice (Czech Republic, 50N, 14.9E) provides regular ionospheric sounding using Digisonde DPS-4D. The paper is focused on F-region vertical drift data. Vertical component of the drift velocity vector can be estimated by several methods. Digisonde DPS-4D allows sounding in drift mode with direct output represented by drift velocity vector. The Digisonde located in Pruhonice provides direct drift measurement routinely once per 15 minutes. However, also other different techniques can be found in the literature, for example the indirect estimation based on the temporal evolution of measured ionospheric characteristics is often used for calculation of the vertical drift component. The vertical velocity is thus estimated according to the change of characteristics scaled from the classical quarter-hour ionograms. In present paper direct drift measurement is compared with technique based on measuring of the virtual height at fixed frequency from the F-layer trace on ionogram, technique based on variation of h`F and hmF. This comparison shows possibility of using different methods for calculating vertical drift velocity and their relationship to the direct measurement used by Digisonde. This study is supported by the Joint TUBITAK 114E092 and AS CR 14/001 projects.

  4. The extended growth of graphene oxide flakes using ethanol CVD

    NASA Astrophysics Data System (ADS)

    Huang, Jingfeng; Larisika, Melanie; Fam, W. H. Derrick; He, Qiyuan; Nimmo, Myra A.; Nowak, Christoph; Tok, I. Y. Alfred

    2013-03-01

    We report the extended growth of Graphene Oxide (GO) flakes using atmospheric pressure ethanol Chemical Vapor Deposition (CVD). GO was used to catalyze the deposition of carbon on a substrate in the ethanol CVD with Ar and H2 as carrier gases. Raman, SEM, XPS and AFM characterized the growth to be a reduced GO (RGO) of <5 layers. This newly grown RGO possesses lower defect density with larger and increased distribution of sp2 domains than chemically reduced RGO. Furthermore this method without optimization reduces the relative standard deviation of electrical conductivity between chips, from 80.5% to 16.5%, enabling RGO to be used in practical electronic devices.We report the extended growth of Graphene Oxide (GO) flakes using atmospheric pressure ethanol Chemical Vapor Deposition (CVD). GO was used to catalyze the deposition of carbon on a substrate in the ethanol CVD with Ar and H2 as carrier gases. Raman, SEM, XPS and AFM characterized the growth to be a reduced GO (RGO) of <5 layers. This newly grown RGO possesses lower defect density with larger and increased distribution of sp2 domains than chemically reduced RGO. Furthermore this method without optimization reduces the relative standard deviation of electrical conductivity between chips, from 80.5% to 16.5%, enabling RGO to be used in practical electronic devices. Electronic supplementary information (ESI) available: The ethanol CVD setup, TEM of CVD treated RGO, graphite 2D Raman spectra, GO synthesis, transfer and reduction methods and details of characterization techniques are described in the document. See DOI: 10.1039/c3nr33704a

  5. Feasibility of measuring density and temperature of laser produced plasmas using spectroscopic techniques.

    SciTech Connect

    Edens, Aaron D.

    2008-09-01

    A wide variety of experiments on the Z-Beamlet laser involve the creation of laser produced plasmas. Having a direct measurement of the density and temperature of these plasma would an extremely useful tool, as understanding how these quantities evolve in space and time gives insight into the causes of changes in other physical processes, such as x-ray generation and opacity. We propose to investigate the possibility of diagnosing the density and temperature of laser-produced plasma using temporally and spatially resolved spectroscopic techniques that are similar to ones that have been successfully fielded on other systems. Various researchers have measured the density and temperature of laboratory plasmas by looking at the width and intensity ratio of various characteristic lines in gases such as nitrogen and hydrogen, as well as in plasmas produced off of solid targets such as zinc. The plasma conditions produce two major measurable effects on the characteristic spectral lines of that plasma. The 1st is the Stark broadening of an individual line, which depends on the electron density of the plasma, with higher densities leading to broader lines. The second effect is a change in the ratio of various lines in the plasma corresponding to different ionization states. By looking at the ratio of these lines, we can gain some understanding of the plasma ionization state and consequently its temperature (and ion density when coupled with the broadening measurement). The hotter a plasma is, the higher greater the intensity of lines corresponding to higher ionization states. We would like to investigate fielding a system on the Z-Beamlet laser chamber to spectroscopically study laser produced plasmas from different material targets.

  6. Plasma diagnostic techniques in thermal-barrier tandem-mirror fusion experiments

    SciTech Connect

    Silver, E.H.; Clauser, J.F.; Carter, M.R.; Failor, B.H.; Foote, J.H.; Hornady, R.S.; James, R.A.; Lasnier, C.J.; Perkins, D.E.

    1986-08-29

    We review two classes of plasma diagnostic techniques used in thermal-barrier tandem-mirror fusion experiments. The emphasis of the first class is to study mirror-trapped electrons at the thermal-barrier location. The focus of the second class is to measure the spatial and temporal behavior of the plasma space potential at various axial locations. The design and operation of the instruments in these two categories are discussed and data that are representative of their performance is presented.

  7. ECR plasma cleaning: an in-situ processing technique for RF cavities

    SciTech Connect

    Wu, G.; Moeller, W-D.; Antoine, C.; Jiang, H.; Pechenezhskiy, I.; Cooley, L.; Khabiboulline, T.; Terechkine, Y.; Edwards, H.; Koeth, T.; Romanenko, A.; /Cornell U., Phys. Dept. /Jefferson Lab

    2008-01-01

    A condition for Electron Cyclotron Resonance (ECR) can be established inside a fully assembled RF cavity without the need for removing high-power couplers. As such, plasma generated by this process can be used as a final cleaning step, or as an alternative cleaning step in place of other techniques. Tests showed filtered dry air plasma can successfully remove sulfur particles on niobium surface while the surface oxygen content remains intact.

  8. Optical properties of surface modified polypropylene by plasma immersion ion implantation technique

    SciTech Connect

    Ahmed, Sk. Faruque; Moon, Myoung-Woon; Kim, Chansoo; Lee, Kwang-Ryeol; Jang, Yong-Jun; Han, Seonghee; Choi, Jin-Young; Park, Won-Woong

    2010-08-23

    The optical band gap and activation energy of polypropylene (PP) induced by an Ar plasma immersion ion implantation technique were studied in detail. It was revealed that the structural alternation with an increase in polymer chain cross-linking in the ion beam affected layer enhanced the optical properties of PP. The optical band gap, calculated from the transmittance spectra, decreased from 3.44 to 2.85 eV with the Ar plasma ion energy from 10 to 50 keV. The activation energy, determined from the band tail of the transmittance spectra, decreased while the electrical conductivity increased with the Ar plasma ion energy.

  9. A penalization technique to model plasma facing components in a tokamak with temperature variations

    NASA Astrophysics Data System (ADS)

    Paredes, A.; Bufferand, H.; Ciraolo, G.; Schwander, F.; Serre, E.; Ghendrih, P.; Tamain, P.

    2014-10-01

    To properly address turbulent transport in the edge plasma region of a tokamak, it is mandatory to describe the particle and heat outflow on wall components, using an accurate representation of the wall geometry. This is challenging for many plasma transport codes, which use a structured mesh with one coordinate aligned with magnetic surfaces. We propose here a penalization technique that allows modeling of particle and heat transport using such structured mesh, while also accounting for geometrically complex plasma-facing components. Solid obstacles are considered as particle and momentum sinks whereas ionic and electronic temperature gradients are imposed on both sides of the obstacles along the magnetic field direction using delta functions (Dirac). Solutions exhibit plasma velocities (M=1) and temperatures fluxes at the plasma-wall boundaries that match with boundary conditions usually implemented in fluid codes. Grid convergence and error estimates are found to be in agreement with theoretical results obtained for neutral fluid conservation equations. The capability of the penalization technique is illustrated by introducing the non-collisional plasma region expected by the kinetic theory in the immediate vicinity of the interface, that is impossible when considering fluid boundary conditions. Axisymmetric numerical simulations show the efficiency of the method to investigate the large-scale transport at the plasma edge including the separatrix and in realistic complex geometries while keeping a simple structured grid.

  10. Ionospheric Plasma Drift Analysis Technique Based On Ray Tracing

    NASA Astrophysics Data System (ADS)

    Ari, Gizem; Toker, Cenk

    2016-07-01

    Ionospheric drift measurements provide important information about the variability in the ionosphere, which can be used to quantify ionospheric disturbances caused by natural phenomena such as solar, geomagnetic, gravitational and seismic activities. One of the prominent ways for drift measurement depends on instrumentation based measurements, e.g. using an ionosonde. The drift estimation of an ionosonde depends on measuring the Doppler shift on the received signal, where the main cause of Doppler shift is the change in the length of the propagation path of the signal between the transmitter and the receiver. Unfortunately, ionosondes are expensive devices and their installation and maintenance require special care. Furthermore, the ionosonde network over the world or even Europe is not dense enough to obtain a global or continental drift map. In order to overcome the difficulties related to an ionosonde, we propose a technique to perform ionospheric drift estimation based on ray tracing. First, a two dimensional TEC map is constructed by using the IONOLAB-MAP tool which spatially interpolates the VTEC estimates obtained from the EUREF CORS network. Next, a three dimensional electron density profile is generated by inputting the TEC estimates to the IRI-2015 model. Eventually, a close-to-real situation electron density profile is obtained in which ray tracing can be performed. These profiles can be constructed periodically with a period of as low as 30 seconds. By processing two consequent snapshots together and calculating the propagation paths, we estimate the drift measurements over any coordinate of concern. We test our technique by comparing the results to the drift measurements taken at the DPS ionosonde at Pruhonice, Czech Republic. This study is supported by TUBITAK 115E915 and Joint TUBITAK 114E092 and AS CR14/001 projects.

  11. Immunoelectrophoresis and ELISA techniques for assay of plasma beta 2 glycoprotein-1 and the influence of plasma lipids.

    PubMed

    McNally, T; Mackie, I J; Isenberg, D A; Machin, S J

    1993-11-15

    Beta 2 glycoprotein-1 (beta 2GP1) has been identified as a cofactor for the binding of some antiphospholipid antibodies to anionic phospholipids and has been demonstrated to possess anticoagulant properties in vitro. We have investigated Laurell rocket immunoelectrophoresis (IEP) and ELISA techniques for measurement of beta 2GP1. Western blotting and crossed immunoelectrophoresis (CIE) of plasma demonstrated free beta 2GP1 and beta 2GP1 complexed with unidentified plasma constituents. The free and complexed forms were not distinguished in immunoelectrophoresis assays, allowing measurement of total beta 2GP1. Standard and detergent modified IEP and ELISA techniques were compared: significant correlation was demonstrated between unmodified and detergent modified IEP, detergent modified IEP and ELISA and unmodified IEP and ELISA. The intra-assay co-efficients of variation (CVs) of the unmodified and modified IEPs and ELISA were 7.5, 3.7 and 7.9%. Inter-assay CVs determined for the modified IEP and ELISA were 5.8 and 9.1% respectively. The purified beta 2GP1 used to standardise the assays was shown to have subfraction selectivity and different calibration values were obtained for pooled normal plasma by the unmodified IEP (242 mg/l) and modified IEP and ELISA (201 mg/l). We have also investigated the influence of some pre-test variables on beta 2GP1 levels and shown that heparin, citrate or EDTA plasma and serum samples are suitable for assay of this glycoprotein and that levels are unaffected by repeated freeze/thawing. The influence of plasma lipids on beta 2GP1 measurement was also examined and we demonstrated no significant differences between pre and postprandial samples, which suggests that fasting status is not an important consideration for assay of beta 2GP1 in healthy subjects.

  12. Using a Filtration Technique to Isolate Platelet Free Plasma for Assaying Pyrophosphate

    PubMed Central

    TOLOUIAN, RAMIN; CONNERY, SEAN M.; O’NEILL, W. CHARLES; GUPTA, AJAY

    2015-01-01

    SUMMARY Background Vascular calcification (VC) is a strong prognostic marker of mortality from cardiovascular disease. Extracellular inorganic pyrophosphate (PPi) is a critical inhibitor of vascular calcification and it has been reported that hemodialysis patients have reduced plasma PPi levels, suggesting that altered PPi metabolism could contribute to VC in hemodialysis patients. Platelets are rich in PPi and release of PPi from platelets during storage or processing of plasma can lead to falsely elevated plasma PPi levels. To prepare plasma samples that are suitable for measuring PPi levels, ultracentrifugation has been used to remove platelets. Consequently, plasma PPi measurements have been limited to research laboratories since the majority of clinical laboratories do not have access to an ultracentrifuge. The purpose of the present study was to test the validity of an improved method of preparing platelet free plasma that uses filtration with a 300,000 Dalton molecular weight cut-off filter to exclude platelets, while minimizing their release of PPi. Methods In 20 maintenance hemodialysis patients, PPi levels were measured in plasma samples prepared by the conventional technique of low-speed centrifugation to remove red and white blood cells versus a novel filtration technique. Results Plasma prepared by filtration had significantly lower platelet counts (0 vs. 3 – 7 103/μL) and PPi levels (1.39 ± 0.30 μM vs. 2.74 ± 1.19 μM; mean ± SD, p < 0.01). Conclusions The filtration method appears effective in excluding platelets without causing trauma to platelets and can be used by clinical laboratories to prepare platelet-depleted plasma for PPi measurement. PMID:23289181

  13. Application of Soft Computing Techniques to Experimental Space Plasma Turbulence Observations - Genetic Algorithms

    NASA Astrophysics Data System (ADS)

    Bates, I.; Lawton, A.; Breikin, T.; Dunlop, M.

    Space Systems Group, University of Sheffield, U.K. Automatic Control and Systems Engineering, University of Sheffield, U.K. 3 Imperial College, London, U.K.A Genetic Algorithm (GA) approach is presented to solve a problem for turbulent space plasma system modelling in the form of Generalised Frequency Response Functions (GFRFs), using in-situ multi-satellite magnetic field measurements of the plasma turbulence. Soft Computing techniques have now been used for many years in Industry for nonlinear system identification. These techniques approach the problem of understanding a system, e.g. a chemical plant or a jet engine, by model structure selection and fitting parameters of the chosen model for the system using measured inputs and outputs of the system, which can then be used to determine physical characteristics of the system. GAs are one such technique that has been developed, providing essentially a series of solutions that evolve in a way to improve the model. Experimental space plasma turbulence studies have benefited from these System Identification techniques. Multi-point satellite observations provide input and output measurements of the turbulent plasma system. In previous work it was found natural to fit parameters to GFRFs, which derive from Volterra series and lead to quantitative measurements of linear wave-field growth and higher order wave-wave interactions. In previous work these techniques were applied using a Least Squares (LS) parameter fit. Results using GAs are compared to results obtained from the LS approach.

  14. A penalization technique to model plasma facing components in a tokamak with temperature variations

    SciTech Connect

    Paredes, A.; Bufferand, H.; Ciraolo, G.; Schwander, F.; Serre, E.; Ghendrih, P.; Tamain, P.

    2014-10-01

    To properly address turbulent transport in the edge plasma region of a tokamak, it is mandatory to describe the particle and heat outflow on wall components, using an accurate representation of the wall geometry. This is challenging for many plasma transport codes, which use a structured mesh with one coordinate aligned with magnetic surfaces. We propose here a penalization technique that allows modeling of particle and heat transport using such structured mesh, while also accounting for geometrically complex plasma-facing components. Solid obstacles are considered as particle and momentum sinks whereas ionic and electronic temperature gradients are imposed on both sides of the obstacles along the magnetic field direction using delta functions (Dirac). Solutions exhibit plasma velocities (M=1) and temperatures fluxes at the plasma–wall boundaries that match with boundary conditions usually implemented in fluid codes. Grid convergence and error estimates are found to be in agreement with theoretical results obtained for neutral fluid conservation equations. The capability of the penalization technique is illustrated by introducing the non-collisional plasma region expected by the kinetic theory in the immediate vicinity of the interface, that is impossible when considering fluid boundary conditions. Axisymmetric numerical simulations show the efficiency of the method to investigate the large-scale transport at the plasma edge including the separatrix and in realistic complex geometries while keeping a simple structured grid.

  15. Preparation of Fe/Mo/molecular sieves by CVD

    SciTech Connect

    Yoo, Jin S.; Donohu, J.A.; Choi-Feng, C.

    1995-12-01

    A series of mixed metal oxide catalysts was prepared via the chemical vapor deposition (CVD) technique by using the silanol moiety existing on various zeolite matrices as an anchoring site for metals. The novel CVD Fe/Mo/DBH catalyst was made by depositing FeCl{sub 3} and then MoO{sub 2}Cl{sub 2} on the partially deboronated borosilicate (DBH). The catalyst precursor was activated by calcining it at 650-690{degrees}C for prolonged period. Among the zeolite matrices such as borosilicate, silicalite, ZSM-5, {beta}-zeolite and {Upsilon}-zeolite, the DBH exhibited a unique papra-selective oxidation property for the gas-phase O{sub 2} oxidation of polymethylated benzenes. Terephthaldehyde was produced in the oxidation of p-xylene. The impregnated catalyst was also prepared by the incipient wetness method. The catalyst performance and the stability of the impregnated catalyst were compared with those of the CVD counterpart. The CVD catalyst was more active and showed better stability than the impregnated catalyst. These catalysts were characterized by ammonia TPD, Raman spectroscopy, and electron microscopy with an objective of explaining these findings.

  16. An inexpensive technique for the time resolved laser induced plasma spectroscopy

    NASA Astrophysics Data System (ADS)

    Ahmed, Rizwan; Ahmed, Nasar; Iqbal, J.; Baig, M. Aslam

    2016-08-01

    We present an efficient and inexpensive method for calculating the time resolved emission spectrum from the time integrated spectrum by monitoring the time evolution of neutral and singly ionized species in the laser produced plasma. To validate our assertion of extracting time resolved information from the time integrated spectrum, the time evolution data of the Cu II line at 481.29 nm and the molecular bands of AlO in the wavelength region (450-550 nm) have been studied. The plasma parameters were also estimated from the time resolved and time integrated spectra. A comparison of the results clearly reveals that the time resolved information about the plasma parameters can be extracted from the spectra registered with a time integrated spectrograph. Our proposed method will make the laser induced plasma spectroscopy robust and a low cost technique which is attractive for industry and environmental monitoring.

  17. CVD diamond detectors for radiation pulse characterisation

    NASA Astrophysics Data System (ADS)

    Foulon, F.; Bergonzo, P.; Jany, C.; Gicquel, A.; Pochet, T.

    Polycrystalline diamond films deposited by microwave plasma-enhanced chemical vapour deposition (MPCVD) have been used for the fabrication of resistive photoconductors. Such detectors can be used to measure the intensity and the temporal shape of pulsed radiation such as IR, visible, UV and X-rays. The photodetector response times were characterised under fast Nd:Yag laser pulses ( λ = 266 nm, τL = 30 ps at FWHM). The detector sensitivities were measured under both pulsed UV laser and steady-state X-ray excitations (40 keV). The detector response time strongly depends on the CVD diamond film structural and physical properties, i.e., the film growth conditions. They exhibit a response signal presenting full widths at half maximum down to about 100 ps and decay times down to about 130 ps. The diamond detector responses are compared to the responses measured on typical ultrafast photoconductors made from gallium arsenide pre-irradiated at 3 × 10 15 neutrons/cm 2 as well as from natural type IIa bulk diamond.

  18. Beams, brightness, and background: Using active spectroscopy techniques for precision measurements in fusion plasma research

    SciTech Connect

    Thomas, Dan M.

    2012-05-15

    The use of an injected neutral beam-either a dedicated diagnostic beam or the main heating beams-to localize and enhance plasma spectroscopic measurements can be exploited for a number of key physics issues in magnetic confinement fusion research, yielding detailed profile information on thermal and fast ion parameters, the radial electric field, plasma current density, and turbulent transport. The ability to make these measurements has played a significant role in much of our recent progress in the scientific understanding of fusion plasmas. The measurements can utilize emission from excited state transitions either from plasma ions or from the beam atoms themselves. The primary requirement is that the beam 'probe' interacts with the plasma in a known fashion. Advantages of active spectroscopy include high spatial resolution due to the enhanced localization of the emission and the use of appropriate imaging optics, background rejection through the appropriate modulation and timing of the beam and emission collection/detection system, and the ability of the beam to populate emitter states that are either nonexistent or too dim to utilize effectively in the case of standard or passive spectroscopy. In addition, some active techniques offer the diagnostician unique information because of the specific quantum physics responsible for the emission. This paper will describe the general principles behind a successful active spectroscopic measurement, emphasize specific techniques that facilitate the measurements and include several successful examples of their implementation, briefly touching on some of the more important physics results. It concludes with a few remarks about the relevance and requirements of active spectroscopic techniques for future burning plasma experiments.

  19. Experimental, theoretical and computational study of frequency upshift of electromagnetic radiation using plasma techniques

    SciTech Connect

    Joshi, C.

    1992-09-01

    This is a second year progress report on Experimental, Theoretical and Computational Study of Frequency Upshift of Electromagnetic Radiation Using Plasma Techniques.'' The highlights are: (I) Ionization fronts have been shown to frequency upshift e.m. radiation by greater than a factor 5. In the experiments, 33 GHz microwave radiation is upshifted to more than 175 GHz using a relativistically propagating ionization front created by a laser beam. (II) A Letter describing the results has been published in Physical Review Letters and an invited'' paper has been submitted to IEEE Trans. in Plasma Science.

  20. Development of a novel plasma scanning technique for high-quality anodic bonding

    NASA Astrophysics Data System (ADS)

    Wu, Jim-Wei; Yang, Chii-Rong; Huang, Che-Yi

    2016-04-01

    Anodic bonding is a type of nonintermediate wafer bonding technique that has been widely used in microelectromechanical systems for sealing devices or assembling microstructures. However, the conventional anodic bonding method has a limitation. The specimens being bonded must typically be in contact with the anode and cathode electrodes during the bonding process. In general, the initial bonding position corresponds to the contact area of the two electrodes; subsequently, the bonded region gradually extends to cover the entire target region. Nevertheless, the traditional diffuse bonding method provides limited bonding efficiency in industrial applications. Therefore, this paper proposes a novel plasma bonding technique for 2D scanning anodic bonding. In this technique, the plasma is positioned to simultaneously heat and bond specimens. We conducted an experiment that entailed bonding 4-inch silicon/glass wafers by using N2 plasma. The results revealed that an almost bubble-free bonded interface and an average bonding strength exceeding 37 MPa were achieved for a bonding time of 15 min 53 s, bonding voltage of 2 kV, noncontact distance (between the cathode electrode and the bonding specimens) of 3 mm, variable raster scan path, scan speed of 3 mm s-1, and continuous scan steps of 2.5 mm in the x- and y-axes. A comprehensive series of experiments were performed to validate the bonding performance of the proposed technique.

  1. A novel technique for plasma density measurement using surface-wave transmission spectra

    NASA Astrophysics Data System (ADS)

    Dine, S.; Booth, J.-P.; Curley, G. A.; Corr, C. S.; Jolly, J.; Guillon, J.

    2005-11-01

    A technique for the measurement of the absolute electron density in low-pressure plasmas using microwaves is described. It is based on observing the propagation of electromagnetic surface waves (SW) at a plasma-sheath boundary, guided by a dielectric cylinder immersed in the plasma. The transmission spectrum is measured between two antennas situated at either end of the dielectric cylinder and connected to a network analyser. Analytical theory based on the Trivelpiece-Gould work (Trivelpiece and Gould 1959 J. Appl. Phys. 30 1784, Trivelpiece 1967 Slow-Wave Propagation in Plasma Waveguides) indicates that the lowest frequency at which the SW can propagate is equal to 1/\\sqrt{2} of the plasma frequency, which is directly related to the electron number density at the plasma-sheath boundary. We call this probe the plasma transmission probe (PTP) in contrast to the plasma absorption probe proposed by Sugai and co-workers (Kokura et al 1999 Japan. J. Appl. Phys. 38 5262). The PTP is promising for the measurement of low densities (>=109 cm-3) at relatively high gas pressure (<=1 Torr). An axi-symmetric finite element model of the probe is presented and used to calculate transmission spectra. Experimental spectra measured in a radio-frequency capacitively coupled discharge in argon at various plasma densities and pressures (40-750 mTorr) are presented and compared with the calculated ones. Plasma densities derived from the transmission spectra were compared with those obtained with a Langmuir probe. The PTP was also compared with a microwave 1/4-wave resonator ('hairpin probe') at low pressure (5-45 mTorr) in an ICP discharge in argon. The densities determined by the PTP were found to be lower by a factor of 0.5-0.7 compared with those obtained with a Langmuir and a hairpin probe. We believe this can be attributed to the pre-sheath plasma density gradient, as the PTP determines the sheath edge electron density, not the bulk value.

  2. Determination of bevantolol in human plasma by high performance liquid chromatography using solid phase extraction technique.

    PubMed

    Trung, Tran Quoc; Long, Pham Hai; Al-Abd, Ahmed M; Ku, Hyo Jeong; Lee, Ho Yoon; Hwang, Sung Joo; Kim, Kyeong Ho

    2007-07-01

    A method was developed and fully validated for the determination of bevantolol, an adrenergic-receptor blocker, in human plasma. Bevantolol and betaxolol as internal standard (I.S) were extracted from 1 mL of human plasma by solid phase extraction technique using Sep-pak silica cartridge. Chromatographic separation was accomplished under isocratic conditions using a reverse-phase C8 analytical column and mixture of dibasic ammonium phosphate (pH 5.7; 50 mM)-acetonitrile (75:25, v/v) as mobile phase, with a detection wavelength at 220 nm. The method was proved to be specific by testing six different human plasma sources. Linearity was established for the concentration ranges of 40-1600 ng/mL with correlation coefficent of 0.9995. The lower limit of quantification 40 ng/mL with precision of 10.9% as C.V%.

  3. Ultratough CVD single crystal diamond and three dimensional growth thereof

    DOEpatents

    Hemley, Russell J.; Mao, Ho-kwang; Yan, Chih-shiue

    2009-09-29

    The invention relates to a single-crystal diamond grown by microwave plasma chemical vapor deposition that has a toughness of at least about 30 MPa m.sup.1/2. The invention also relates to a method of producing a single-crystal diamond with a toughness of at least about 30 MPa m.sup.1/2. The invention further relates to a process for producing a single crystal CVD diamond in three dimensions on a single crystal diamond substrate.

  4. Radiation monitoring with CVD diamonds in BABAR

    NASA Astrophysics Data System (ADS)

    Edwards, A. J.; Bruinsma, M.; Burchat, P.; Kagan, H.; Kass, R.; Kirkby, D.; Petersen, B. A.; Pulliam, T.

    2005-10-01

    The BABAR experiment has been using two polycrystalline chemical-vapor-deposition (pCVD) diamonds for radiation monitoring for nearly 2 years. In July 2005, an additional 12 diamond based radiation sensors will be installed inside the BABAR detector. These diamonds will take over the function of 12 silicon PIN-diodes that are currently used in the radiation protection and monitoring system. We describe our highly successful experience with using pCVD diamond radiation sensors in a high energy physics experiment. We also detail our findings of persistent signal currents and magnetically suppressed erratic dark currents in pCVD diamond based radiation sensors.

  5. Status of Plasma Physics Techniques for the Deposition of Tribological Coatings

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1984-01-01

    The plasma physics deposition techniques of sputtering and ion-plating are reviewed. Their characteristics and potentials are discussed in terms of synthesis or deposition of tribological coatings. Since the glow discharge or plasma generated in the conventional sputtering and ion-plating techniques has a low ionization efficiency, rapid advances have been made in equipment design to further increase the ionization efficiency. The enhanced ionization favorably affects the nucleation and growth sequence of the coating. This leads to improved adherence and coherence, higher density, favorable morphological growth, and reduced internal stresses in the coatings. As a result, desirable coating characteristics can be precision tailored. Tribological coating characteristics of sputtered solid film lubricants such as MoS2, ion-plated soft gold and lead metallic films, and sputtered and ion-plated wear-resistant refractory compound films such as nitrides and carbides are discussed.

  6. Underwater plasma-MIG arc welding: Shielding technique and pressure reduction by a centrifugal pump

    SciTech Connect

    Creutz, M.; Mewes, D.; Bartzsch, J.; Draugelates, U.

    1995-12-31

    In comparison to hyperbaric underwater welding in diving chambers, wet welding techniques promise higher flexibility and lower costs. One technique for creating a local dry and pressure reduced welding zone is the use of a centrifugal pump. Results of experimental investigations in combination with a plasma-MIG arc welding system are presented in this paper. Special importance is attached to the local pressure reduction in view of the fact that low pressure, i.e. a high pressure difference between surrounding water and dry welding area, is a good condition for welding but is difficult to be obtained with other shielding systems than pressure chambers. Plasma-MIG welding has been done under water with a good result on the weld quality. Values of the hardness of the joint and the appearance of the weld structure are nearly comparable to atmospheric welds.

  7. Studies on non-oxide coating on carbon fibers using plasma enhanced chemical vapor deposition technique

    NASA Astrophysics Data System (ADS)

    Patel, R. H.; Sharma, S.; Prajapati, K. K.; Vyas, M. M.; Batra, N. M.

    2016-05-01

    A new way of improving the oxidative behavior of carbon fibers coated with SiC through Plasma Enhanced Chemical Vapor Deposition technique. The complete study includes coating of SiC on glass slab and Stainless steel specimen as a starting test subjects but the major focus was to increase the oxidation temperature of carbon fibers by PECVD technique. This method uses relatively lower substrate temperature and guarantees better stoichiometry than other coating methods and hence the substrate shows higher resistance towards mechanical and thermal stresses along with increase in oxidation temperature.

  8. New plasma technique for the deposition of silica layers for integrated optics applications

    NASA Astrophysics Data System (ADS)

    Panciatichi, Cristina; Natascia De Leo, Maria C.

    2000-03-01

    An inductively coupled plasma torch has been used for the synthesis of high-purity, low OH concentration, fused silica layers, for integrated optics applications. This technique is very versatile and the same apparatus can be used to deposit silica layers doped with different elements but this work is particularly devoted to the germanium-doped silica layers. The torch, designed and built in-house, operates at atmospheric pressure and is posed by a 13.56 MHz, 5.4 kW, RF generator. The gaseous reactants are injected in the plasma tail flame by a silica nozzle. Planar silica targets are suitably moved over the torch exit in order to obtain the desired deposition. The samples made by means of this chemical vapor deposition process have been chemically and physically analyzed using various techniques: optical microscopy, scanning electron microscopy, atomic force microscopy, x-ray diffractometer, UV, visible and IR spectroscopy, to test their morphological, geometrical, chemical and optical characteristics. By this plasma- assisted technique it has been possible to achieve the deposition of pure and germanium doped silica layers with good optical and morphological characteristics. Preliminary direct UV photoinduction experiments are very promising: a high refractive index change has been measured.

  9. Fracture Characteristics of Monolayer CVD-Graphene

    PubMed Central

    Hwangbo, Yun; Lee, Choong-Kwang; Kim, Sang-Min; Kim, Jae-Hyun; Kim, Kwang-Seop; Jang, Bongkyun; Lee, Hak-Joo; Lee, Seoung-Ki; Kim, Seong-Su; Ahn, Jong-Hyun; Lee, Seung-Mo

    2014-01-01

    We have observed and analyzed the fracture characteristics of the monolayer CVD-graphene using pressure bulge testing setup. The monolayer CVD-graphene has appeared to undergo environmentally assisted subcritical crack growth in room condition, i.e. stress corrosion cracking arising from the adsorption of water vapor on the graphene and the subsequent chemical reactions. The crack propagation in graphene has appeared to be able to be reasonably tamed by adjusting applied humidity and stress. The fracture toughness, describing the ability of a material containing inherent flaws to resist catastrophic failure, of the CVD-graphene has turned out to be exceptionally high, as compared to other carbon based 3D materials. These results imply that the CVD-graphene could be an ideal candidate as a structural material notwithstanding environmental susceptibility. In addition, the measurements reported here suggest that specific non-continuum fracture behaviors occurring in 2D monoatomic structures can be macroscopically well visualized and characterized. PMID:24657996

  10. Multiwalled carbon nanotube CVD synthesis, modification, and composite applications

    NASA Astrophysics Data System (ADS)

    Qian, Dali

    Well-aligned carbon multiwall nanotube (MWNT) arrays have been continuously synthesized by a floating catalytic chemical vapor deposition (CVD) method involving the pyrolysis of xylene-ferrocene mixtures. The CVD parameters have been studied to selectively synthesize nanotubes with required dimensions. A mixed tip-root growth model has been proposed for the floating catalytic CVD synthesis. Coarsening of the catalyst particle at the root end promoted MWNT wall coarsening (addition of new concentric graphene shells), while the smaller catalyst particle at the tip contributed to MWNT elongation. A two-step process in which ferrocene was fed for only five minutes to nucleate the DTs was developed to understand if a continuous supply of catalyst was necessary for continued growth. The results show that the ferrocene was only necessary for initial nucleation. To simplify the CVD process further, another two-step synthesis method was developed in which the ferrocene was pre-decomposed so that the nanotube nucleation could be isolated from the growth, enabling quantification of growth mechanisms and kinetics. Mass spectra and hydrocarbon analyses of the CVD reactor tail gas were performed to understand the pyrolysis chemistry. Well-aligned N-doped and Ru-doped MWNT arrays have been produced by pyrolysis of pyridine ferrocene mixtures and xylene-ferrocene-ruthenocene mixtures, respectively. Various material characterization techniques were used to measure the dopant distributions and correlate the catalyst phase with the novel nanotube structures. High-temperature annealing has been shown to be a viable means to remove both the catalyst particles and certain microstructural defects within the CVD-derived DTs. The phase transformation of catalyst during annealing has also been studied. Homogeneous distribution of MWNTs in polystyrene matrices was achieved by an ultrasonic assisted solution-evaporation method. Addition of only 1 wt % DTs to polystyrene increased the polymer

  11. Development of CVD mullite coatings for Si-based ceramics

    NASA Astrophysics Data System (ADS)

    Auger, Michael Lawrence

    1999-09-01

    To raise fuel efficiencies, the next generation of engines and fuel systems must be lighter and operate at higher temperatures. Ceramic-based materials, which are considerably lighter than metals and can withstand working temperatures of up to 1400sp°C, have been targeted to replace traditional metal-based components. The materials used in combustion environments must also be capable of withstanding erosion and corrosion caused by combustion gases, particulates, and deposit-forming corrodants. With these demanding criteria, silicon-based ceramics are the leading candidate materials for high temperature engine and heat exchanger structural components. However, these materials are limited in gaseous environments and in the presence of molten salts since they form liquid silicates on exposed surfaces at temperatures as low as 800sp°C. Protective coatings that can withstand higher operating temperatures and corrosive atmospheres must be developed for silicon-based ceramics. Mullite (3Alsb2Osb3{*}2SiOsb2) was targeted as a potential coating material due to its unique ability to resist corrosion, retain its strength, resist creep, and avoid thermal shock failure at elevated temperatures. Several attempts to deposit mullite coatings by various processing methods have met with limited success and usually resulted in coatings that have had pores, cracks, poor adherence, and required thermal post-treatments. To overcome these deficiencies, the direct formation of chemically vapor deposited (CVD) mullite coatings has been developed. CVD is a high temperature atomistic deposition technique that results in dense, adherent crystalline coatings. The object of this dissertation was to further the understanding of the CVD mullite deposition process and resultant coating. The kinetics of CVD mullite deposition were investigated as a function of the following process parameters: temperature, pressure, and the deposition reactor system. An empirical kinetic model was developed

  12. Single-crystal CVD diamonds as small-angle X-ray scattering windows for high-pressure research

    PubMed Central

    Wang, Suntao; Meng, Yu-fei; Ando, Nozomi; Tate, Mark; Krasnicki, Szczesny; Yan, Chih-shiue; Liang, Qi; Lai, Joseph; Mao, Ho-kwang; Gruner, Sol M.; Hemley, Russell J.

    2012-01-01

    Small-angle X-ray scattering (SAXS) was performed on single-crystal chemical vapor deposition (CVD) diamonds with low nitrogen concentrations, which were fabricated by microwave plasma-assisted chemical vapor deposition at high growth rates. High optical quality undoped 500 µm-thick single-crystal CVD diamonds grown without intentional nitrogen addition proved to be excellent as windows on SAXS cells, yielding parasitic scattering no more intense than a 7.5 µm-thick Kapton film. A single-crystal CVD diamond window was successfully used in a high-pressure SAXS cell. PMID:22675230

  13. Fermented dairy food and CVD risk.

    PubMed

    Tapsell, Linda C

    2015-04-01

    Fermented dairy foods such as yoghurt and cheese are commonly found in the Mediterranean diet. Recent landmark research has confirmed the effect of the Mediterranean diet on reducing the CVD risk, but the relative contributions of fermented dairy foods have not been fully articulated. The present study provides a review of the relationship between fermented dairy foods consumption and CVD risk in the context of the whole diet. Studies show that people who eat healthier diets may be more likely to consume yoghurt, so there is a challenge in attributing separate effects to yoghurt. Analyses from large population studies list yoghurt as the food most negatively associated with the risk of weight gain (a problem that may lead to CVD). There is some suggestion that fermented dairy foods consumption (yoghurt or cheese) may be associated with reduced inflammatory biomarkers associated with the development of CVD. Dietary trials suggest that cheese may not have the same effect on raising LDL-cholesterol levels as butter with the same saturated fat content. The same might be stated for yoghurt. The use of different probiotic cultures and other aspects of study design remain a problem for research. Nevertheless, population studies from a range of countries have shown that a reduced risk of CVD occurs with the consumption of fermented dairy foods. A combination of evidence is necessary, and more research is always valuable, but indications remain that fermented dairy foods such as cheese and yoghurt are integral to diets that are protective against CVD.

  14. Characterization and performance of carbon films deposited by plasma and ion beam based techniques

    SciTech Connect

    Walter, K.C.; Kung, H.; Levine, T.

    1994-12-31

    Plasma and ion beam based techniques have been used to deposit carbon-based films. The ion beam based method, a cathodic arc process, used a magnetically mass analyzed beam and is inherently a line-of-sight process. Two hydrocarbon plasma-based, non-line-of-sight techniques were also used and have the advantage of being capable of coating complicated geometries. The self-bias technique can produce hard carbon films, but is dependent on rf power and the surface area of the target. The pulsed-bias technique can also produce hard carbon films but has the additional advantage of being independent of rf power and target surface area. Tribological results indicated the coefficient of friction is nearly the same for carbon films from each deposition process, but the wear rate of the cathodic arc film was five times less than for the self-bias or pulsed-bias films. Although the cathodic arc film was the hardest, contained the highest fraction of sp{sup 3} bonds and exhibited the lowest wear rate, the cathodic arc film also produced the highest wear on the 440C stainless steel counterface during tribological testing. Thus, for tribological applications requiring low wear rates for both counterfaces, coating one surface with a very hard, wear resistant film may detrimentally affect the tribological behavior of the counterface.

  15. PREFACE: IX International Conference on Modern Techniques of Plasma Diagnostics and their Application

    NASA Astrophysics Data System (ADS)

    Savjolov, A. S.; Dodulad, E. I.

    2016-01-01

    The IX Conference on ''Modern Techniques of Plasma Diagnosis and their Application'' was held on 5 - 7 November, 2014 at National Research Nuclear University MEPhI (NRNU MEPhI). The goal of the conference was an exchange of information on both high-temperature and low-temperature plasma diagnostics as well as deliberation and analysis of various diagnostic techniques and their applicability in science, industry, ecology, medicine and other fields. The Conference also provided young scientists from scientific centres and universities engaged in plasma diagnostics with an opportunity to attend the lectures given by the leading specialists in this field as well as present their own results and findings. The first workshop titled ''Modern problems of plasma diagnostics and their application for control of chemicals and the environment'' took place at Moscow Engineering and Physics Institute (MEPhI) in June 1998 with the support of the Section on Diagnostics of the Council of Russian Academic of Science on Plasma Physics and since then these forums have been held at MEPhI every two years. In 2008 the workshop was assigned a conference status. More than 150 specialists on plasma diagnostics and students took part in the last conference. They represented leading Russian scientific centres (such as Troitsk Institute of Innovative and Thermonuclear Research, National Research Centre ''Kurchatov Institute'', Russian Federal Nuclear Centre - All-Russian Scientific Research Institute of Experimental Physics and others) and universities from Belarus, Ukraine, Germany, USA, Belgium and Sweden. About 30 reports were made by young researchers, students and post-graduate students. All presentations during the conference were broadcasted online over the internet with viewers in Moscow, Prague, St. Petersburgh and other cities. The Conference was held within the framework of the Centre of Plasma, Laser Research and Technology supported by MEPhI Academic Excellence Project (Russian

  16. CVD silicon carbide characterization. Final report, August 1992-October 1993

    SciTech Connect

    Graves, G.A.; Iden, D.

    1994-08-01

    Chemically vapor deposited (CVD) silicon carbide is a candidate material for high quality ground and space-based mirror substrates and high quality reflective optics. Statistically valid material property data has not been available, however, to make durability and lifetime predictions for such optics. The primary purpose of this study was to determine the Weibull and slow crack growth parameters for CVD silicon carbide. Specimens were cut from various locations in a 25 mm thick, 50 cm diameter piece of SiC to analyze bulk material property homogeneity. Flexural strength was measured using a four-point bend technique. In addition to mechanical testing for strength, hardness, and fracture toughness, the material crystallography and microstructure were studied. Thermal expansion, thermal diffusivity, specific heat, optical absorption, and infrared reflectivity measurements were also conducted. Raman spectroscopy was used to check for any residual stress. Test results show this CVD silicon carbide is a high-purity, homogeneous, fine-grained substrate material with very good mechanical, optical, and thermal properties.

  17. Crystallographic anisotropy of growth and etch rates of CVD diamond

    SciTech Connect

    Wolfer, M; Biener, J; El-dasher, B S; Biener, M M; Hamza, A V; Kriele, A; Wild, C

    2008-08-05

    The investigation of orientation dependent crystal growth and etch processes can provide deep insights into the underlying mechanisms and thus helps to validate theoretical models. Here, we report on homoepitaxial diamond growth and oxygen etch experiments on polished, polycrystalline CVD diamond wafers by use of electron backscatter diffraction (EBSD) and white-light interferometry (WLI). Atomic force microscopy (AFM) was applied to provide additional atomic scale surface morphology information. The main advantage of using polycrystalline diamond substrates with almost random grain orientation is that it allows determining the orientation dependent growth (etch) rate for different orientations within one experiment. Specifically, we studied the effect of methane concentration on the diamond growth rate, using a microwave plasma CVD process. At 1 % methane concentration a maximum of the growth rate near <100> and a minimum near <111> is detected. Increasing the methane concentration up to 5 % shifts the maximum towards <110> while the minimum stays at <111>. Etch rate measurements in a microwave powered oxygen plasma reveal a pronounced maximum at <111>. We also made a first attempt to interpret our experimental data in terms of local micro-faceting of high-indexed planes.

  18. Z-pinch diagnostics, plasma and liner instabilities and new x-ray techniques

    SciTech Connect

    Oona, H.; Anderson, B.; Benage, J.

    1996-09-01

    Pulse power experiments of the last several decades have contributed greatly to the understanding of high temperature and high density plasmas and, more recently, to the study of hydrodynamic effects in thick imploding cylinders. Common to all these experiments is the application of a large current pulse to a cylindrically symmetric load, with the resulting Lorenz force compressing the load to produce hydrodynamic motion and/or high temperature, high density plasma. In Los Alamos, Pulsed power experiments are carried out at two facilities. Experiments at low current (from several million to ten million Amperes) are conducted on the Pegasus II capacitor bank. Experiments with higher currents (10`s to 100`s MA range) are performed in Ancho Canyon with the explosively driven Procyon and MAGO magnetic flux compression generator systems. In this paper, the authors present a survey of diagnostic capabilities and results from several sets of experiments. First, they discuss the initiation and growth of instabilities in plasmas generated from the implosion of hollow z-pinches in the pegasus and Procyon experiments. Next they discuss spectroscopic data from the plasmas produced by the MAGO system. They also show time resolved imaging data from thick ({approximately} .4 mm) liner implosions. Finally, the authors discuss improvements to x-ray and visible light imaging and spectrographic diagnostic techniques. The emphasis of this paper is not so much a detailed discussion of the experiments, but a presentation of imaging and spectroscopic results and the implications of these observations to the experiments.

  19. Tracer techniques for the assessment of material migration and surface modification of plasma-facing components

    NASA Astrophysics Data System (ADS)

    Rubel, M.; Weckmann, A.; Ström, P.; Petersson, P.; Garcia-Carrasco, A.; Brezinsek, S.; Coenen, J.; Kreter, A.; Möller, S.; Wienhold, P.; Wauters, T.; Fortuna-Zaleśna, E.

    2015-08-01

    Tracer techniques were used in the TEXTOR tokamak to determine high-Z metal migration and the deposition of species used for plasma edge cooling or wall conditioning under different types of operation conditions. Volatile molybdenum hexa-fluoride, nitrogen-15 and oxygen-18 were used as markers in tokamak or ion cyclotron wall conditioning discharges (ICWC). The objective was to obtain qualitative and quantitative of a global and local deposition pattern and material mixing effects. The deposition and retention was studied on plasma-facing components, collector probes and test limiters. Optical spectroscopy and ex-situ analysis techniques were used to determine the plasma response to tracer injection and the modification of surface composition. Molybdenum and light isotopes were detected on all types of limiters and short-term probes retrieved from the vessel showing that both helium and nitrogen are trapped following wall conditioning and edge cooling. Only small amounts below 1 × 1019 m-2 of 18O were detected on surfaces treated by oxygen-assisted ICWC.

  20. Electroluminescent and photosensitive films prepared by DTC-CVD method

    NASA Astrophysics Data System (ADS)

    Zavyalova, Ludmila V.; Svechnikov, George S.

    1997-08-01

    The original chemical vapor deposition (CVD) method used in fabrication A2B6 films, photodetectors and electro- luminescent emitters based on these films have been reported. The basic idea behind this method is thermal decomposition of dithiocarbamates (DTC). The proposed method does not require expensive materials and vacuum equipment. Moreover, the DTC-CVD method differs from the known CVD methods in source material delivery method, a low deposition temperature and a non-sealed reactor geometry. Both CdS and CdS1-xSex were obtained at temperature of 240- 280 degrees C and were activated directly in the grown process by Cu and In, or by annealing in mixture CdS: Cu, Cl. Photodetectors with absorption maxima at 500-750 nm have dark conductivity (sigma) D EQ 10-9 divided by 10-8 (Omega) -1 cm-1 and photoconductivity (sigma) ph equals 10-2 divided by 10-1 (Omega) -1 cm-1 at 200 lux. CdS films with thickness of 6 divided by 12 micrometers have been used as sandwich-type photoconductor detectors. Electroluminescence ZnS:Mn films prepared by DTC-CVD method at the substrate temperature of 200 DIV 300 degrees C without additional annealing have high luminance and luminous efficiency. Deposition at a law temperature makes it possible to use flexible polymer films or low cost glasses as substrates. Because the technique is rather simple and can be applied to obtain all types of thin film electroluminescence structure layers, we expect a low price of light sources based on these films.

  1. Synthesis of Proton-Exchange Membranes by a Plasma Polymerization Technique

    NASA Astrophysics Data System (ADS)

    Jiang, Zhongqing; Meng, Yuedong; Shi, Yicai

    2008-08-01

    An after-glow capacitively coupled discharge technique has been used to fabricate ultra-thin proton-exchange composite membranes in a plasma polymerization reactor, where styrene and acrylic acid are used as starting materials. During the preparation, the energy of the ionized particles extracted from the radio frequency glow discharge region to the plasma polymerization region can be easily controlled by adjusting the bias voltage applied to the screen grids and substrate. Therefore, the degradation of monomers can be effectively avoided, and the contents of the proton exchange groups on the obtained membranes could reach to a higher extent. The synthesized membranes are dense with uniform structure and are demonstrated as good proton conductors.

  2. CVD 908, CVD 908-htrA, and CVD 909 live oral typhoid vaccines: a logical progression.

    PubMed

    Tacket, Carol O; Levine, Myron M

    2007-07-15

    Typhoid fever remains an important public health problem in many parts of the world. Despite the availability of oral Ty21a (Vivotif; Berna Biotech) and parenteral Vi polysaccharide vaccine (Typhim Vi; Aventis Pasteur), improved typhoid fever vaccines have been sought. These include a series of vaccine candidates developed at the Center for Vaccine Development, University of Maryland, based on attenuation of Salmonella enterica serovar Typhi by deletions in the aroC, aroD, and htrA genes. These vaccine candidates, designated "CVD 908," "CVD 908-htrA," and "CVD 909," have been developed and tested in volunteers with variable success. This review summarizes the clinical data that directed the logical progression of this vaccine development strategy.

  3. Optimization of non-oxidative carbon-removal techniques by nitrogen-containing plasmas

    NASA Astrophysics Data System (ADS)

    Ferreira, J. A.; Tabarés, F. L.; Tafalla, D.

    2009-06-01

    The continuous control of tritium inventory in ITER calls for the development of new conditioning techniques [G. Federici et al., Nucl. Fus. 41 (2001) 1967]. For carbon plasma-facing components, this implies the removal of the T-rich carbon co-deposits. In the presence of strong oxygen getters, such Be, the use of oxygen-based techniques will be discouraged. In addition, tritiated water generated by these techniques poses extra problems in terms of safety issues [G. Saji, Fus. Eng. Des. 69 (2003) 631; G. Bellanger, J.J. Rameau, Fus. Technol. 32 (1997) 196; T. Hayashi, et al., Fus. Eng. Des. 81 (2006) 1365]. In the present work, oxygen-free (nitrogen and ammonia) glow discharge plasmas for carbon film removal were investigated. The following gas mixtures were fed into a DC glow discharge running in a ˜200 nm carbon film coated chamber. Erosion rate was measured in situ by laser interferometry, RGA (Residual Gas Analysis) and CTAMS (Cryotrapping Assisted Mass Spectrometry) [J.A. Ferreira, F.L. Tabarés, J. Vac. Sci. Technol. A25(2) (2007) 246] were used for the characterization of the reaction products. Very high erosion rates (similar to those obtained in helium-oxygen glow discharge [J.A. Ferreira et al., J. Nucl. Mater. 363-365 (2007) 252]) were recorded for ammonia glow discharge.

  4. Sex specific differences in the predictive value of cholesterol homeostasis markers and 10-Year CVD event rate in Framingham Offspring Study participants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Available data are inconsistent on factors influencing plasma cholesterol homeostasis marker concentrations and their value in predicting subsequent cardiovascular disease (CVD) events. To address this issue the relationship between markers of cholesterol absorption (campesterol, sitosterol, cholest...

  5. High T(sub c) superconductors fabricated by plasma aerosol mist deposition technique

    NASA Technical Reports Server (NTRS)

    Wang, X. W.; Vuong, K. D.; Leone, A.; Shen, C. Q.; Williams, J.; Coy, M.

    1995-01-01

    We report new results on high T(sub c) superconductors fabricated by a plasma aerosol mist deposition technique, in atmospheric environment. Materials fabricated are YBaCuO, BiPbSrCaCuO, BaCaCuO precursor films for TlBaCaCuO, and other buffers such as YSZ. Depending on processing conditions, sizes of crystallites and/or particles are between dozens of nano-meters and several micrometers. Superconductive properties and other material characteristics can also be tailored.

  6. Application of the coded long-pulse technique to plasma line studies of the ionosphere

    NASA Technical Reports Server (NTRS)

    Djuth, Frank T.; Sulzer, Michael P.; Elder, John H.

    1994-01-01

    Recently, the coded long-pulse radar technique was tested at Arecibo Observatory, Puerto Rico using photoelectron-enhanced plasma lines in the daytime ionosphere. The technique immediately proved to be a powerful diagnostic tool for studying natural ionospheric phenomena. Our initial observations indicate that extremely accurate measurements of absolute electron density (0.01 to 0.03% error bars) can be achieved with an altitude resolution of 150 m and a temporal resolution of approx. 2 s. In addition, the technique provides information about electron density structure within a 150-m altitude cell and yields parameters from which the energy spectrum of suprathermal electrons (equal to or greater than 5 eV) can be deduced. Our earliest measurements are used to illustrate applications of the coded long-pulse technique to several aeronomic/ionsospheric areas of current interest. These include studies of neutral wave motions in the lower thermosphere, measurements of ion composition in the F(sub 1) region/upper ionosphere, and investigations of electron-gas thermal balance and photoelectron energy loss processes. The technique can be utilized to examine irregularity formation in the F region, probe electron acceleration processes in ionospheric modification experiments, verify the magnetic field dependence of Langmuir wave damping, and more generally test higher order corrections suggested for the Langmuir dispersion relation. It is anticipated that the latter tests will facilitate measurements of ionospheric currents.

  7. Iridium-coated rhenium thrusters by CVD

    NASA Technical Reports Server (NTRS)

    Harding, J. T.; Kazaroff, J. M.; Appel, M. A.

    1989-01-01

    Operation of spacecraft thrusters at increased temperature reduces propellant requirements. Inasmuch as propellant comprises the bulk of a satellite's mass, even a small percentage reduction makes possible a significant enhancement of the mission in terms of increased payload. Because of its excellent high temperature strength, rhenium is often the structural material of choice. It can be fabricated into free-standing shapes by chemical vapor deposition (CVD) onto an expendable mandrel. What rhenium lacks is oxidation resistance, but this can be provided by a coating of iridium, also by CVD. This paper describes the process used by Ultramet to fabricate 22-N (5-lbf) and, more recently, 445-N (100-lbf) Ir/Re thrusters; characterizes the CVD-deposited materials; and summarizes the materials effects of firing these thrusters. Optimal propellant mixture ratios can be employed because the materials withstand an oxidizing environment up to the melting temperature of iridium, 2400 C (4350 F).

  8. Iridium-coated rhenium thrusters by CVD

    NASA Technical Reports Server (NTRS)

    Harding, John T.; Kazaroff, John M.; Appel, Marshall A.

    1988-01-01

    Operation of spacecraft thrusters at increased temperature reduces propellant requirements. Inasmuch as propellant comprises the bulk of a satellite's mass, even a small percentage reduction makes possible a significant enhancement of the mission in terms of increased payload. Because of its excellent high temperature strength, rhenium is often the structural material of choice. It can be fabricated into free-standing shapes by chemical vapor deposition (CVD) onto an expendable mandrel. What rhenium lacks is oxidation resistance, but this can be provided by a coating of iridium, also by CVD. This paper describes the process used by Ultramet to fabricate 22-N (5-lbf) and, more recently, 445-N (100-lbf) Ir/Re thrusters; characterizes the CVD-deposited materials; and summarizes the materials effects of firing these thrusters. Optimal propellant mixture ratios can be employed because the materials withstand an oxidizing environment up to the meltimg temperature of iridium, 2400 C (4350 F).

  9. Determination of trace elements in petroleum products by inductively coupled plasma techniques: A critical review

    NASA Astrophysics Data System (ADS)

    Sánchez, Raquel; Todolí, José Luis; Lienemann, Charles-Philippe; Mermet, Jean-Michel

    2013-10-01

    The fundamentals, applications and latter developments of petroleum products analysis through inductively coupled plasma optical emission spectrometry (ICP-OES) and mass spectrometry (ICP-MS) are revisited in the present bibliographic survey. Sample preparation procedures for the direct analysis of fuels by using liquid sample introduction systems are critically reviewed and compared. The most employed methods are sample dilution, emulsion or micro-emulsion preparation and sample decomposition. The first one is the most widely employed due to its simplicity. Once the sample has been prepared, an organic matrix is usually present. The performance of the sample introduction system (i.e., nebulizer and spray chamber) depends strongly upon the nature and properties of the solution finally obtained. Many different devices have been assayed and the obtained results are shown. Additionally, samples can be introduced into the plasma by using an electrothermal vaporization (ETV) device or a laser ablation system (LA). The recent results published in the literature showing the feasibility, advantages and drawbacks of latter alternatives are also described. Therefore, the main goal of the review is the discussion of the different approaches developed for the analysis of crude oil and its derivates by inductively coupled plasma (ICP) techniques.

  10. The Deflection Plate Analyzer: A Technique for Space Plasma Measurements Under Highly Disturbed Conditions

    NASA Technical Reports Server (NTRS)

    Wright, Kenneth H., Jr.; Dutton, Ken; Martinez, Nelson; Smith, Dennis; Stone, Nobie H.

    2004-01-01

    A technique has been developed to measure the characteristics of space plasmas under highly disturbed conditions; e.g., non-Maxwellian plasmas with strong drifting populations and plasmas contaminated by spacecraft outgassing. The present method is an extension of the capabilities of the Differential Ion Flux Probe (DIFP) to include a mass measurement that does not include either high voltage or contamination sensitive devices such as channeltron electron multipliers or microchannel plates. This reduces the complexity and expense of instrument fabrication, testing, and integration of flight hardware as compared to classical mass analyzers. The new instrument design is called the Deflection Plate Analyzer (DPA) and can deconvolve multiple ion streams and analyze each stream for ion flux intensity (density), velocity (including direction of motion), mass, and temperature (or energy distribution). The basic functionality of the DPA is discussed. The performance characteristics of a flight instrument as built for an electrodynamic tether mission, the Propulsive Small Expendable Deployer System (ProSEDS), and the instrument s role in measuring key experimental conditions are also discussed.

  11. Removal Dynamics of Nitric Oxide (NO) Pollutant Gas by Pulse-Discharged Plasma Technique

    PubMed Central

    Zhang, Lianshui; Wang, Xiaojun; Lai, Weidong; Cheng, Xueliang; Zhao, Kuifang

    2014-01-01

    Nonthermal plasma technique has drawn extensive attentions for removal of air pollutants such as NOx and SO2. The NO removal mechanism in pulse discharged plasma is discussed in this paper. Emission spectra diagnosis indicates that the higher the discharge voltage is, the more the NO are removed and transformed into O, N, N2, NO2, and so forth. Plasma electron temperature Te is ranged from 6400 K at 2.4 kV discharge voltage to 9500 K at 4.8 kV. After establishing a zero-dimensional chemical reaction kinetic model, the major reaction paths are clarified as the electron collision dissociation of NO into N and O during discharge and followed by single substitution of N on NO to form N2 during and after discharge, compared with the small fraction of NO2 formed by oxidizing NO. The reaction directions can be adjusted by N2 additive, and the optimal N2/NO mixing ratio is 2 : 1. Such a ratio not only compensates the disadvantage of electron competitive consumption by the mixed N2, but also heightens the total NO removal extent through accelerating the NO oxidization process. PMID:24737985

  12. A computationally assisted spectroscopic technique to measure secondary electron emission coefficients in radio frequency plasmas

    NASA Astrophysics Data System (ADS)

    Daksha, M.; Berger, B.; Schuengel, E.; Korolov, I.; Derzsi, A.; Koepke, M.; Donkó, Z.; Schulze, J.

    2016-06-01

    A computationally assisted spectroscopic technique to measure secondary electron emission coefficients (γ-CAST) in capacitively-coupled radio-frequency plasmas is proposed. This non-intrusive, sensitive diagnostic is based on a combination of phase resolved optical emission spectroscopy and particle-based kinetic simulations. In such plasmas (under most conditions in electropositive gases) the spatio-temporally resolved electron-impact excitation/ionization rate features two distinct maxima adjacent to each electrode at different times within each RF period. While one maximum is the consequence of the energy gain of electrons due to sheath expansion, the second maximum is produced by secondary electrons accelerated towards the plasma bulk by the sheath electric field at the time of maximum voltage drop across the adjacent sheath. Due to these different excitation/ionization mechanisms, the ratio of the intensities of these maxima is very sensitive to the secondary electron emission coefficient γ. This sensitvity, in turn, allows γ to be determined by comparing experimental excitation profiles and simulation data obtained with various γ-coefficients. The diagnostic, tested here in a geometrically symmetric argon discharge, yields an effective secondary electron emission coefficient of γ =0.066+/- 0.01 for stainless steel electrodes.

  13. Thermal plasma processing of materials

    SciTech Connect

    Pfender, E.; Heberlein, J.

    1992-02-01

    Emphasis has been on plasma synthesis of fine powders, plasma Chemical Vapor Deposition (CVD), on related diagnostics, and on modeling work. Since plasma synthesis as well as plasma CVD make frequent use of plasma jets, the beginning has been devoted of plasma jets and behavior of particulates injected into such plasma jets. Although most of the construction of the Triple-Torch Plasma Reactor (TTPR) has already been done, modifications have been made in particular modifications required for plasma CVD of diamond. A new reactor designed for Counter-Flow Liquid Injection Plasma Synthesis (CFLIPS) proved to be an excellent tool for synthesis of fine powders as well as for plasma CVD. An attempt was made to model flow and temperature fields in this reactor. Substantial efforts were made to single out those parameters which govern particle size, size distribution, and powder quality in our plasma synthesis experiments. This knowledge is crucial for controlling the process and for meaningful diagnostics and modeling work. Plasma CVD of diamond films using both reactors has been very successful and we have been approached by a number of companies interested in using this technology for coating of tools.

  14. Strain Relaxation in CVD Graphene: Wrinkling with Shear Lag.

    PubMed

    Bronsgeest, Merijntje S; Bendiab, Nedjma; Mathur, Shashank; Kimouche, Amina; Johnson, Harley T; Coraux, Johann; Pochet, Pascal

    2015-08-12

    We measure uniaxial strain fields in the vicinity of edges and wrinkles in graphene prepared by chemical vapor deposition (CVD), by combining microscopy techniques and local vibrational characterization. These strain fields have magnitudes of several tenths of a percent and extend across micrometer distances. The nonlinear shear-lag model remarkably captures these strain fields in terms of the graphene-substrate interaction and provides a complete understanding of strain-relieving wrinkles in graphene for any level of graphene-substrate coherency. PMID:26171667

  15. Transient current electric field profiling of single crystal CVD diamond

    NASA Astrophysics Data System (ADS)

    Isberg, J.; Gabrysch, M.; Tajani, A.; Twitchen, D. J.

    2006-08-01

    The transient current technique (TCT) has been adapted for profiling of the electric field distribution in intrinsic single crystal CVD diamond. It was found that successive hole transits do not appreciably affect the electric field distribution within the sample. Transits of holes can therefore be used to probe the electric field distribution and also the distribution of trapped charge. Electron transits, on the other hand, cause an accumulation of negative charge in the sample. Illumination with blue or green light was shown to lead to accumulation of positive charge. Low concentrations of trapped charge can be detected in diamond using TCT, corresponding to an ionized impurity concentration below N = 1010 cm-3.

  16. Recent results on CVD diamond radiation sensors

    NASA Astrophysics Data System (ADS)

    Weilhammer, P.; Adam, W.; Bauer, C.; Berdermann, E.; Bogani, F.; Borchi, E.; Bruzzi, M.; Colledani, C.; Conway, J.; Dabrowski, W.; Delpierre, P.; Deneuville, A.; Dulinski, W.; v. d. Eijk, R.; van Eijk, B.; Fallou, A.; Fish, D.; Fried, M.; Gan, K. K.; Gheeraert, E.; Grigoriev, E.; Hallewell, G.; Hall-Wilton, R.; Han, S.; Hartjes, F.; Hrubec, J.; Husson, D.; Kagan, H.; Kania, D.; Kaplon, J.; Kass, R.; Knopfle, K. T.; Krammer, M.; Manfredi, P. F.; Meier, D.; LeNormand; Pan, L. S.; Pernegger, H.; Pernicka, M.; Plano, R.; Re, V.; Riester, J. L.; Roe, S.; Roff; Rudge, A.; Schieber, M.; Schnetzer, S.; Sciortino, S.; Speziali, V.; Stelzer, H.; Stone, R.; Tapper, R. J.; Tesarek, R.; Thomson, G. B.; Trawick, M.; Trischuk, W.; Turchetta, R.; RD 42 Collaboration

    1998-02-01

    CVD diamond radiation sensors are being developed for possible use in trackers in the LHC experiments. The diamond promises to be radiation hard well beyond particle fluences that can be tolerated by Si sensors. Recent results from the RD 42 collaboration on charge collection distance and on radiation hardness of CVD diamond samples will be reported. Measurements with diamond tracking devices, both strip detectors and pixel detectors, will be discussed. Results from beam tests using a diamond strip detector which was read out with fast, 25 ns shaping time, radiation-hard pipeline electronics will be presented.

  17. A facile process for soak-and-peel delamination of CVD graphene from substrates using water

    PubMed Central

    Gupta, Priti; Dongare, Pratiksha D.; Grover, Sameer; Dubey, Sudipta; Mamgain, Hitesh; Bhattacharya, Arnab; Deshmukh, Mandar M.

    2014-01-01

    We demonstrate a simple technique to transfer chemical vapour deposited (CVD) graphene from copper and platinum substrates using a soak-and-peel delamination technique utilizing only hot deionized water. The lack of chemical etchants results in cleaner CVD graphene films minimizing unintentional doping, as confirmed by Raman and electrical measurements. The process allows the reuse of substrates and hence can enable the use of oriented substrates for growth of higher quality graphene, and is an inherently inexpensive and scalable process for large-area production. PMID:24457558

  18. Surface Modification of Graphene Oxides by Plasma Techniques and Their Application for Environmental Pollution Cleanup.

    PubMed

    Wang, Xiangxue; Fan, Qiaohui; Chen, Zhongshan; Wang, Qi; Li, Jiaxing; Hobiny, Aatef; Alsaedi, Ahmed; Wang, Xiangke

    2016-02-01

    Graphene oxides (GOs) have come under intense multidisciplinary study because of their unique physicochemical properties and possible applications. The large amount of oxygen-containing functional groups on GOs leads to a high sorption capacity for the removal of various kinds of organic and inorganic pollutants from aqueous solutions in environmental pollution cleanup. However, the lack of selectivity results in difficulty in the selective removal of target pollutants from aqueous solutions in the presence of other coexisting pollutants. Herein, the surface grafting of GOs with special oxygen-containing functional groups using low-temperature plasma techniques and the application of the surface-modified GOs for the efficient removal of organic and inorganic pollutants in environmental pollution are reviewed. This paper gives an account of our research on the application of GO-based nanomaterials in environmental pollution cleanup, including: (1) the synthesis and surface grafting of functional groups on GOs, summarizing various types of low-temperature plasma techniques for the synthesis of graphene/GOs; and (2) the application of graphene/GOs and their composites for the efficient removal of organic and inorganic pollutants from aqueous solutions, including the interaction mechanism according to recently published results.

  19. Plasma cortisol and prolactin secretion rhythms in cattle under varying external environments and management techniques.

    PubMed

    Ogino, Mizuna; Matsuura, Akihiro; Yamazaki, Atusi; Irimajiri, Mami; Suzuki, Yoshihiro; Kushibiki, Shiro; Singu, Hroyuki; Kasuya, Etsuko; Hasegawa, Yoshihisa; Hodate, Koichi

    2014-01-01

    The secretion rhythms of plasma cortisol (CORT) and prolactin (PRL), hormones related to stress responsiveness and biological rhythm and controlled by light and temperature, were investigated under varying external environments and different management techniques. Serial blood samples were collected from female cattle reared in free-stall and freely fed (FF) conditions (n = 4) or in tie-stall and restricted feeding (RF) conditions (hay and concentrate twice daily, n = 4). Plasma CORT and PRL concentrations, eating behavior, and environmental parameters were analyzed. Cyclic patterns for each parameter were examined using spectral analysis, and correlations between CORT, PRL and other parameters were investigated using cross-spectral analysis. Under FF conditions, CORT secretion was not related to the lighting intensity and eating behavior. However, under RF conditions, the CORT secretion rhythm showed a distinct correlation with lighting intensity and eating behavior. Under FF conditions, the PRL secretion rhythm was similar in all seasons. However, under RF conditions, the PRL rhythm oscillated with high frequency in summer and low frequency in winter, indicating a seasonal change in rhythm. The present study demonstrates that hormone secretion rhythms change under different environments and management techniques.

  20. Thin CVD Coating Protects Titanium Aluminide Alloys

    NASA Technical Reports Server (NTRS)

    Clark, Ronald; Wallace, Terryl; Cunnington, George; Robinson, John

    1994-01-01

    Feasibility of using very thin CVD coatings to provide both protection against oxidation and surfaces of low catalytic activity for thin metallic heat-shield materials demonstrated. Use of aluminum in compositions increases emittances of coatings and reduces transport of oxygen through coatings to substrates. Coatings light in weight and applied to foil-gauge materials with minimum weight penalties.

  1. CVD-produced boron filaments

    NASA Technical Reports Server (NTRS)

    Wawner, F. E.; Debolt, H. E.; Suplinskas, R. D.

    1980-01-01

    A technique for producing boron filaments with an average tensile strength of 6.89 GPa has been developed which involves longitudinal splitting of the filament and core (substrate) removal by etching. Splitting is accomplished by a pinch wheel device which continuously splits filaments in lengths of 3.0 m by applying a force to the side of the filament to create a crack which is then propagated along the axis by a gentle sliding action. To facilitate the splitting, a single 10 mil tungsten substrate is used instead of the usual 0.5 mil substrate. A solution of hot 30% hydrogen peroxide is used to remove the core without attacking the boron. An alternative technique is to alter the residual stress by heavily etching the filament. Average strengths in the 4.83-5.52 GPa range have been obtained by etching an 8 mil filament to 4 mil.

  2. Study of the triton-burnup process in different JET scenarios using neutron monitor based on CVD diamond

    NASA Astrophysics Data System (ADS)

    Nemtsev, G.; Amosov, V.; Meshchaninov, S.; Popovichev, S.; Rodionov, R.

    2016-11-01

    We present the results of analysis of triton burn-up process using the data from diamond detector. Neutron monitor based on CVD diamond was installed in JET torus hall close to the plasma center. We measure the part of 14 MeV neutrons in scenarios where plasma current varies in a range of 1-3 MA. In this experiment diamond neutron monitor was also able to detect strong gamma bursts produced by runaway electrons arising during the disruptions. We can conclude that CVD diamond detector will contribute to the study of fast particles confinement and help predict the disruption events in future tokamaks.

  3. Selected Topics in CVD Diamond Research

    NASA Astrophysics Data System (ADS)

    Koizumi, Satoshi; Nebel, Christoph E.; Nesladek, Milos

    2006-10-01

    Since the discovery of Chemical Vapor Deposition (CVD) diamond growth in 1976, the steady scientific progress often resulted in surprising new discoveries and breakthroughs. This brought us to the idea to publish the special issue Selected Topics in CVD Diamond Research in physica status solidi (a), reflecting such advancements and interesting results at the leading edge of diamond research.The present issue summarizes this progress in the CVD diamond field by selecting contributions from several areas such as superconductivity, super-excitonic radiation, quantum computing, bio-functionalization, surface electronic properties, the nature of phosphorus doping, transport properties in high energy detectors, CVD growth and properties of nanocrystalline diamond. In all these directions CVD diamond appears to be very competitive in comparison with other semiconducting materials.As Editors of this special issue, we must admit that the selection is biased by our opinion. Nonetheless, we are sure that each contribution introduces new ideas and results which will improve the understanding of the current level of physics and chemistry of this attractive wide-bandgap semiconductor and which will help to bring it closer to applications.All submissions were invited based on the contributions of the authors to their specific research field. The Feature Articles have the format of topical reviews to give the reader a comprehensive summary. Partially, however, they are written in research paper style to report new results of ongoing research.We hope that this issue will attract the attention of a broad community of scientists and engineers, and that it will facilitate the utilization of diamond in electronic applications and technologies of the future.

  4. Superconductivity in CVD Diamond Films

    NASA Astrophysics Data System (ADS)

    Takano, Yoshihiko

    2005-03-01

    The recent news of superconductivity 2.3K in heavily boron-doped diamond synthesized by high pressure sintering was received with considerable surprise (1). Opening up new possibilities for diamond-based electrical devices, a systematic investigation of these phenomena clearly needs to be achieved. Application of diamond to actual devices requires it to be made into the form of wafers or thin films. We show unambiguous evidence for superconductivity in a heavily boron-doped diamond thin film deposited by the microwave plasma assisted chemical vapor deposition (MPCVD) method (2). An advantage of the MPCVD deposited diamond is that it can control boron concentration in its wider range, particularly in (111) oriented films. The temperature dependence of resistivity for (111) and (100) homoepitaxial thin films were measured under several magnetic fields. Superconducting transition temperatures of (111) homoepitaxial film are determined to be 11.4K for Tc onset and 7.2K for zero resistivity. And the upper critical field is estimated to be about 8T. These values are 2-3 times higher than these ever reported (1,3). On other hand, for (100) homoepitaxial film, Tc onset and Tc zero resistivity were estimated to be 6.3 and 3.2K respectively. The superconductivity in (100) film was strongly suppressed even at the same boron concentration. These differences of superconductivity in film orientation will be discussed. These findings established the superconductivity as a universal property of boron-doped diamond, demonstrating that device application is indeed a feasible challenge. 1. E. A. Ekimov et al. Nature, 428, 542 (2004). 2. Y. Takano et al., Appl. Phys. Lett. 85, 2851 (2004). 3. E. Bustarret et al., ond-mat 0408517.

  5. Non-thermal plasma as preparative technique to evaluate olive oil adulteration.

    PubMed

    Van Durme, Jim; Vandamme, Jeroen

    2016-10-01

    In recent years adulteration of pure extra virgin olive oil (EVOO) with other types of vegetable oils has become an important issue. In this study, non-thermal plasma (NTP) is investigated as an innovative preparative analytical technique enabling classification of adulterated olive oil from an ascertained authentic batch of olive oil in a more sensitive manner. Non-thermal plasma discharges are a source of highly oxidative species such as singlet oxygen, and atomic oxygen. It was assumed that NTP-induced oxidation triggers unique lipid oxidation mechanisms depending on the specific composition of the oil matrix and minor constituents. In this work EVOO samples were adulterated with sunflower oil (1-3%) and submitted to NTP treatment. Results showed that while untreated samples could not be classified from the authentic olive oil reference, NTP treatments of 60min (Ar/O2 0.1%) on the oil batches resulted in the formation of a unique set of secondary volatile lipid oxidation products enabling classification of adulterated oil samples.

  6. Non-thermal plasma as preparative technique to evaluate olive oil adulteration.

    PubMed

    Van Durme, Jim; Vandamme, Jeroen

    2016-10-01

    In recent years adulteration of pure extra virgin olive oil (EVOO) with other types of vegetable oils has become an important issue. In this study, non-thermal plasma (NTP) is investigated as an innovative preparative analytical technique enabling classification of adulterated olive oil from an ascertained authentic batch of olive oil in a more sensitive manner. Non-thermal plasma discharges are a source of highly oxidative species such as singlet oxygen, and atomic oxygen. It was assumed that NTP-induced oxidation triggers unique lipid oxidation mechanisms depending on the specific composition of the oil matrix and minor constituents. In this work EVOO samples were adulterated with sunflower oil (1-3%) and submitted to NTP treatment. Results showed that while untreated samples could not be classified from the authentic olive oil reference, NTP treatments of 60min (Ar/O2 0.1%) on the oil batches resulted in the formation of a unique set of secondary volatile lipid oxidation products enabling classification of adulterated oil samples. PMID:27132839

  7. Measurement of xenon plasma properties in an ion thruster using laser Thomson scattering technique

    SciTech Connect

    Yamamoto, N.; Tomita, K.; Sugita, K.; Kurita, T.; Nakashima, H.; Uchino, K.

    2012-07-15

    This paper reports on the development of a method for measuring xenon plasma properties using the laser Thomson scattering technique, for application to ion engine system design. The thresholds of photo-ionization of xenon plasma were investigated and the number density of metastable atoms, which are photo-ionized by a probe laser, was measured using laser absorption spectroscopy, for several conditions. The measured threshold energy of the probe laser using a plano-convex lens with a focal length of 200 mm was 150 mJ for a xenon mass flow rate of 20 {mu}g/s and incident microwave power of 6 W; the probe laser energy was therefore set as 80 mJ. Electron number density was found to be (6.2 {+-} 0.4) Multiplication-Sign 10{sup 17} m{sup -3} and electron temperature was found to be 2.2 {+-} 0.4 eV at a xenon mass flow rate of 20 {mu}g/s and incident microwave power of 6 W. The threshold of the probe laser intensity against photo-ionization in a miniature xenon ion thruster is almost constant for various mass flow rates, since the ratio of population of the metastable atoms to the electron number density is little changed.

  8. The use of laser-induced plasma spectroscopy technique for the characterization of boiler tubes

    NASA Astrophysics Data System (ADS)

    Nicolas, G.; Mateo, M. P.; Yañez, A.

    2007-12-01

    The present work focuses on the characterization of boiler tube walls using laser-induced plasma spectroscopy technique with visual inspection by optical and scanning electron microscopy of the cross-sections of these tubes. In a watertube boiler, water runs through tubes that are surrounded by a heating source. As a result, the water is heated to very high temperatures, causing accumulation of deposits on the inside surfaces of the tubes. These deposits play an important role in the efficiency of the boiler tube because they produce a reduction of the boiler heat rate and an increase in the number of tube failures. The objectives are to determine the thickness and arrangement of deposits located on the highest heat area of the boiler and compare them with tube parts where the heat flux is lower. The major deposits found were copper and magnetite. These deposits come mainly from the boiler feedwater and from the reaction between iron and water, and they do not form on the tube walls at a uniform rate over time. Their amount depends on the areas where they are collected. A Nd:YAG laser operating at 355 nm has been used to perform laser-induced plasma spectra and depth profiles of the deposits.

  9. CVD diamond Brewster window: feasibility study by FEM analyses

    NASA Astrophysics Data System (ADS)

    Aiello, G.; Grossetti, G.; Meier, A.; Scherer, T.; Schreck, S.; Spaeh, P.; Strauss, D.; Vaccaro, A.

    2012-09-01

    Chemical vapor deposition (CVD) diamond windows are a crucial component in heating and current drive (H&CD) applications. In order to minimize the amount of reflected power from the diamond disc, its thickness must match the desired beam wavelength, thus proper targeting of the plasma requires movable beam reflectors. This is the case, for instance, of the ITER electron cyclotron H&CD system. However, looking at DEMO, the higher heat loads and neutron fluxes could make the use of movable parts close to the plasma difficult. The issue might be solved by using gyrotrons able to tune the beam frequency to the desired resonance, but this concept requires transmission windows that work in a given frequency range, such as the Brewster window. It consists of a CVD diamond disc brazed to two copper cuffs at the Brewster angle. The brazing process is carried out at about 800°C and then the temperature is decreased down to room temperature. Diamond and copper have very different thermal expansion coefficients, therefore high stresses build up during the cool down phase that might lead to failure of the disc. Considering also the complex geometry of the window with the skewed position of the disc, analyses are required in the first place to check its feasibility. The cool down phase was simulated by FEM structural analyses for several geometric and constraint configurations of the window. A study of indirect cooling of the window by water was also performed considering a HE11 mode beam. The results are here reported.

  10. Novel 3D Tissue Engineered Bone Model, Biomimetic Nanomaterials, and Cold Atmospheric Plasma Technique for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Wang, Mian

    This thesis research is consist of four chapters, including biomimetic three-dimensional tissue engineered nanostructured bone model for breast cancer bone metastasis study (Chapter one), cold atmospheric plasma for selectively ablating metastatic breast cancer (Chapter two), design of biomimetic and bioactive cold plasma modified nanostructured scaffolds for enhanced osteogenic differentiation of bone marrow derived mesenchymal stem cells (Chapter three), and enhanced osteoblast and mesenchymal stem cell functions on titanium with hydrothermally treated nanocrystalline hydroxyapatite/magnetically treated carbon nanotubes for orthopedic applications (Chapter four). All the thesis research is focused on nanomaterials and the use of cold plasma technique for various biomedical applications.

  11. The MDF technique for the analysis of tokamak edge plasma fluctuations

    NASA Astrophysics Data System (ADS)

    Lafouti, M.; Ghoranneviss, M.; Meshkani, S.; Elahi, A. Salar; Elahi

    2014-02-01

    Tokamak edge plasma was analyzed by applying the multifractal detrend fluctuation analysis (MF-DFA) technique. This method has found wide application in the analysis of correlations and characterization of scaling behavior of the time-series data in physiology, finance, and natural sciences. The time evolution of the ion saturation current (Is ), the floating potential fluctuation (Vf ), the poloidal electric field (Ep ), and the radial particle flux (Γ r ) has been measured by using a set of Langmuir probes consisting of four tips on the probe head. The generalized Hurst exponents (h(q)), local fluctuation function (Fq(s)), the Rényi exponents (τ(q)) as well as the multifractal spectrum f(α h ) have been calculated by applying the MF-DFA method to Is , Vf , and the magnetohydrodynamic (MHD) fluctuation signal. Furthermore, we perform the shuffling and the phase randomization techniques to detect the sources of multifractality. The nonlinearity shape of τ(q) reveals a multifractal behavior of the time-series data. The results show that in the presence of biasing, Is , Vf , Ep , and Γ r reduce about 25%, 90%, 70%, and 50%, respectively, compared with the situation with no biasing. Also, they reduce about 15%, 90%, 35%, and 25%, respectively, after resonant helical magnetic field (RHF) application. In the presence of biasing or RHF, the amplitude of the power spectrum of Is , Vf , Γ r , and MHD activity reduce remarkably in all the ranges of frequency, while their h(q) increase. The values of h(q) have been restricted between 0.6 and 0.68. These results are evidence of the existence of long-range correlations in the plasma edge turbulence. They also show the self-similar nature of the plasma edge fluctuations. Biasing or RHF reduces the amount of Fq(s). The multifractal spectrum width of Is , Vf , and MHD fluctuation amplitude reduce about 60%, 70%, and 42%, respectively, by applying biasing. In the presence of RHF, their width reduces about 60%, 85%, and 75

  12. Contribution to the application of the Langmuir probe technique for plasma monitoring in the Ar and n-hexane mixture plasma during the polymerisation process

    NASA Astrophysics Data System (ADS)

    Adámek, P.; Kalčík, J.; Šícha, M.; Tichý, M.; Biederman, H.; Soukup, L.; Jastrabík, L.

    1999-12-01

    In the present paper the Langmuir probe technique was applied for plasma monitoring in the Ar and n-hexane mixture plasma during the polymerisation process. The experiments were performed in a stainless steel DC magnetron reactor with a planar magnetron cathode. Within the investigated range of the gas pressure, no time-stable condition of the discharge was found. The regular oscillations, of a frequency of approximately 32 kHz, were observed in the Ar and 20% n-hexane mixture at the total pressure of 10 Pa and the discharge current of 8 mA. The experimentally obtained probe characteristics were used to determine the density and the average energy of electrons. In the DC magnetron stainless steel reactor the electron average energy in the Ar and n-hexane mixture plasma was about one order of magnitude smaller than in the case in which the working gas inside the reactor was the pure Ar. The probe measurements in the magnetron reactor were supplemented by the experiment in the customary glass discharge tube with a hollow cathode. In the glass discharge tube and in the Ar and 10% n-hexane mixture plasma a region of plasma parameters was found, in which the plasma was stable and no instabilities were observed. At such conditions the experiments in the glass discharge tube were used for the study of the efficiency of the probe surface cleaning methods used.

  13. Synthesis of Few-Layer Graphene Using DC PE-CVD

    NASA Astrophysics Data System (ADS)

    Kim, Jeong Hyuk; Castro, Edward Joseph D.; Hwang, Yong Gyoo; Lee, Choong Hun

    2011-12-01

    Few layer graphene (FLG) had been successfully grown on polycrystalline Ni films or foils on a large scale using DC Plasma Enhanced Chemical Vapor Deposition (DC PE-CVD) as a result of the Raman spectra drawn out of the sample. The size of graphene films is dependent on the area of the Ni film as well as the DC PE-CVD chamber size. Synthesis time has an effect on the quality of graphene produced. However, further analysis and experiments must be pursued to further identify the optimum settings and conditions of producing better quality graphene. Applied plasma voltage on the other hand, had an influence on the minimization of defects in the graphene grown. It has also presented a method of producing a free standing PMMA/graphene membrane on a FeCl3(aq) solution which could then be transferred to a desired substrate.

  14. The validation of the Z-Scan technique for the determination of plasma glucose

    NASA Astrophysics Data System (ADS)

    Alves, Sarah I.; Silva, Elaine A. O.; Costa, Simone S.; Sonego, Denise R. N.; Hallack, Maira L.; Coppini, Ornela L.; Rowies, Fernanda; Azzalis, Ligia A.; Junqueira, Virginia B. C.; Pereira, Edimar C.; Rocha, Katya C.; Fonseca, Fernando L. A.

    2013-11-01

    Glucose is the main energy source for the human body. The concentration of blood glucose is regulated by several hormones including both antagonists: insulin and glucagon. The quantification of glucose in the blood is used for diagnosing metabolic disorders of carbohydrates, such as diabetes, idiopathic hypoglycemia and pancreatic diseases. Currently, the methodology used for this determination is the enzymatic colorimetric with spectrophotometric. This study aimed to validate the use of measurements of nonlinear optical properties of plasma glucose via the Z-Scan technique. For this we used samples of calibrator patterns that simulate commercial samples of patients (ELITech ©). Besides calibrators, serum glucose levels within acceptable reference values (normal control serum - Brazilian Society of Clinical Pathology and Laboratory Medicine) and also overestimated (pathological control serum - Brazilian Society of Clinical Pathology and Laboratory Medicine) were used in the methodology proposal. Calibrator dilutions were performed and determined by the Z-Scan technique for the preparation of calibration curve. In conclusion, Z-Scan method can be used to determinate glucose levels in biological samples with enzymatic colorimetric reaction and also to apply the same quality control parameters used in biochemistry clinical.

  15. Leakage current measurements of a pixelated polycrystalline CVD diamond detector

    NASA Astrophysics Data System (ADS)

    Zain, R. M.; Maneuski, D.; O'Shea, V.; Bates, R.; Blue, A.; Cunnigham, L.; Stehl, C.; Berderman, E.; Rahim, R. A.

    2013-01-01

    Diamond has several desirable features when used as a material for radiation detection. With the invention of synthetic growth techniques, it has become feasible to look at developing diamond radiation detectors with reasonable surface areas. Polycrystalline diamond has been grown using a chemical vapour deposition (CVD) technique by the University of Augsburg and detector structures fabricated at the James Watt Nanofabrication Centre (JWNC) in the University of Glasgow in order to produce pixelated detector arrays. The anode and cathode contacts are realised by depositing gold to produce ohmic contacts. Measurements of I-V characteristics were performed to study the material uniformity. The bias voltage is stepped from -1000V to 1000V to investigate the variation of leakage current from pixel to pixel. Bulk leakage current is measured to be less than 1nA.

  16. Mutual relation among lattice distortion, Hall effect property and band edge cathodoluminescence of heavily-boron-doped microwave-plasma CVD diamond films homoepitaxially grown on vicinal (001) high-pressure/high-temperature-synthesized Ib substrates

    NASA Astrophysics Data System (ADS)

    Mori, Reona; Maida, Osamu; Ito, Toshimichi

    2015-04-01

    We have investigated properties of heavily-B-doped diamond (HBD) films homoepitaxially grown with boron-to-carbon (B/C) mole ratios ranging from 1000 to 5000 ppm in the source gas mainly by using X-Ray diffraction (XRD), cathodoluminescence (CL), and Hall effect measurements. Each HBD layer was deposited on a vicinal (001) substrate of high-pressure/high-temperature synthesized Ib-type diamond with 5° misorientation angle by means of high-power-density microwave-plasma chemical-vapor-deposition method with a source gas composed of 4% CH4 in H2 and H2-diluted B(CH3)3. XRD data indicated that the lattice constant of the B-doped layer slightly decreased for the B/C ratios≤3000 ppm while slightly increasing for that of 5000 ppm, suggesting that for the latter HBD sample a part of the incorporated B atoms behaved differently from the remaining other B atoms. By contrast the Hall data indicated that all the HBD samples had a degenerate feature only at temperatures well below room temperature (RT), above which a semiconducting feature was evident, and that the density of the degenerate holes steeply increased from 1.3×1019 to 1.2×1021 cm-3 with increases in the incorporated B density, [B], from 1.2×1020 to 5.9×1020 cm-3. This drastic change in the hole density strongly suggested the presence of a [B]-dependent impurity band. Their evident near-band-edge CL spectra taken at RT and 85 K demonstrated that radiative transition features in the HBD layers considerably varied for the B/C ratios studied. The CL peaks were consistently assigned by assuming both the presence of an impurity band and a slight bandgap shrinkage. These observed features are discussed in relation to the energy separation between the low-mobility impurity band assumed and the valence band in the high-quality HBD layer which are not merged in energy.

  17. Recent Results with CVD Diamond Trackers

    NASA Astrophysics Data System (ADS)

    Adam, W.; Bauer, C.; Berdermann, E.; Bergonzo, P.; Bogani, F.; Borchi, E.; Brambilla, A.; Bruzzi, M.; Colledani, C.; Conway, J.; Dabrowski, W.; Delpierre, P.; Deneuville, A.; Dulinski, W.; van Eijk, B.; Fallou, A.; Fizzotti, F.; Foulon, F.; Friedl, M.; Gan, K. K.; Gheeraert, E.; Grigoriev, E.; Hallewell, G.; Hall-Wilton, R.; Han, S.; Hartjes, F.; Hrubec, J.; Husson, D.; Kagan, H.; Kania, D.; Kaplon, J.; Karl, C.; Kass, R.; Knöpfle, K. T.; Krammer, M.; Logiudice, A.; Lu, R.; Manfredi, P. F.; Manfredotti, C.; Marshall, R. D.; Meier, D.; Mishina, M.; Oh, A.; Pan, L. S.; Palmieri, V. G.; Pernicka, M.; Peitz, A.; Pirollo, S.; Polesello, P.; Pretzl, K.; Procario, M.; Re, V.; Riester, J. L.; Roe, S.; Roff, D.; Rudge, A.; Runolfsson, O.; Russ, J.; Schnetzer, S.; Sciortino, S.; Speziali, V.; Stelzer, H.; Stone, R.; Suter, B.; Tapper, R. J.; Tesarek, R.; Trawick, M.; Trischuk, W.; Vittone, E.; Walsh, A. M.; Wedenig, R.; Weilhammer, P.; White, C.; Ziock, H.; Zoeller, M.; RD42 Collaboration

    1999-08-01

    We present recent results on the use of Chemical Vapor Deposition (CVD) diamond microstrip detectors for charged particle tracking. A series of detectors was fabricated using 1 x 1 cm 2 diamonds. Good signal-to-noise ratios were observed using both slow and fast readout electronics. For slow readout electronics, 2 μs shaping time, the most probable signal-to-noise ratio was 50 to 1. For fast readout electronics, 25 ns peaking time, the most probable signal-to-noise ratio was 7 to 1. Using the first 2 x 4 cm 2 diamond from a production CVD reactor with slow readout electronics, the most probable signal-to-noise ratio was 23 to 1. The spatial resolution achieved for the detectors was consistent with the digital resolution expected from the detector pitch.

  18. CVD diamond substrate for microelectronics. Final report

    SciTech Connect

    Burden, J.; Gat, R.

    1996-11-01

    Chemical Vapor Deposition (CVD) of diamond films has evolved dramatically in recent years, and commercial opportunities for diamond substrates in thermal management applications are promising. The objective of this technology transfer initiative (TTI) is for Applied Science and Technology, Inc. (ASTEX) and AlliedSignal Federal Manufacturing and Technologies (FM&T) to jointly develop and document the manufacturing processes and procedures required for the fabrication of multichip module circuits using CVD diamond substrates, with the major emphasis of the project concentrating on lapping/polishing prior to metallization. ASTEX would provide diamond films for the study, and FM&T would use its experience in lapping, polishing, and substrate metallization to perform secondary processing on the parts. The primary goal of the project was to establish manufacturing processes that lower the manufacturing cost sufficiently to enable broad commercialization of the technology.

  19. Scrolling of Suspended CVD Graphene Sheets

    NASA Astrophysics Data System (ADS)

    Martynov, Oleg; Yeom, Sinchul; Bockrath, Marc; UC: Riverside Team

    Carbon Nanoscrolls, one dimensional spiral forms of graphitic carbon, have attracted recent interest due to their novel proposed properties. Although various production methods and studies of carbon nanoscrolls have been performed, low yield and poor controllability of their synthesis have slowed progress in this field. Suspended graphene membranes and carbon nanotubes have been predicted as promising systems for the formation of graphene scrolls. We have suspended chemical vapor deposition (CVD)-grown graphene over large holes in a Si/SiO2 substrate to make suspended membranes upon which nanotubes are placed. Initial experiments have been performed showing that tears or cuts of the suspended sheet can initiate scrolling. Our latest progress towards carbon nanotube initiated formation of graphene scrolls and suspended CVD graphene scrolling, along with measurements of these novel structures will be presented.

  20. Enhanced nonlinear iterative techniques applied to a non-equilibrium plasma flow

    SciTech Connect

    Knoll, D.A.; McHugh, P.R.

    1996-12-31

    We study the application of enhanced nonlinear iterative methods to the steady-state solution of a system of two-dimensional convection-diffusion-reaction partial differential equations that describe the partially-ionized plasma flow in the boundary layer of a tokamak fusion reactor. This system of equations is characterized by multiple time and spatial scales, and contains highly anisotropic transport coefficients due to a strong imposed magnetic field. We use Newton`s method to linearize the nonlinear system of equations resulting from an implicit, finite volume discretization of the governing partial differential equations, on a staggered Cartesian mesh. The resulting linear systems are neither symmetric nor positive definite, and are poorly conditioned. Preconditioned Krylov iterative techniques are employed to solve these linear systems. We investigate both a modified and a matrix-free Newton-Krylov implementation, with the goal of reducing CPU cost associated with the numerical formation of the Jacobian. A combination of a damped iteration, one-way multigrid and a pseudo-transient continuation technique are used to enhance global nonlinear convergence and CPU efficiency. GMRES is employed as the Krylov method with Incomplete Lower-Upper(ILU) factorization preconditioning. The goal is to construct a combination of nonlinear and linear iterative techniques for this complex physical problem that optimizes trade-offs between robustness, CPU time, memory requirements, and code complexity. It is shown that a one-way multigrid implementation provides significant CPU savings for fine grid calculations. Performance comparisons of the modified Newton-Krylov and matrix-free Newton-Krylov algorithms will be presented.

  1. Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents.

    PubMed

    Yager-Elorriaga, D A; Steiner, A M; Patel, S G; Jordan, N M; Lau, Y Y; Gilgenbach, R M

    2015-11-01

    In this work, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ∼600 kA with ∼200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. This technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines. PMID:26628134

  2. Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents

    SciTech Connect

    Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; Jordan, N. M.; Lau, Y. Y.; Gilgenbach, R. M.

    2015-11-19

    In this study, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ~600 kA with ~200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. As a result, this technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.

  3. Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents

    DOE PAGES

    Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; Jordan, N. M.; Lau, Y. Y.; Gilgenbach, R. M.

    2015-11-19

    In this study, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ~600 kA with ~200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. As amore » result, this technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.« less

  4. Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents

    NASA Astrophysics Data System (ADS)

    Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; Jordan, N. M.; Lau, Y. Y.; Gilgenbach, R. M.

    2015-11-01

    In this work, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ˜600 kA with ˜200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. This technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.

  5. Tomography of homogenized laser-induced plasma by Radon transform technique

    NASA Astrophysics Data System (ADS)

    Eschlböck-Fuchs, S.; Demidov, A.; Gornushkin, I. B.; Schmid, T.; Rössler, R.; Huber, N.; Panne, U.; Pedarnig, J. D.

    2016-09-01

    Tomography of a laser-induced plasma in air is performed by inverse Radon transform of angle-resolved plasma images. Plasmas were induced by single laser pulses (SP), double pulses (DP) in collinear geometry, and by a combination of single laser pulses with pulsed arc discharges (SP-AD). Images of plasmas on metallurgical steel slags were taken at delay times suitable for calibration-free laser-induced breakdown spectroscopy (CF-LIBS). Delays ranged from few microseconds for SP and DP up to tens of microseconds for SP-AD excitation. The white-light and the spectrally resolved emissivity ε(x,y,z) was reconstructed for the three plasma excitation schemes. The electron number density Ne(x,y,z) and plasma temperature Te(x,y,z) were determined from Mg and Mn emission lines in reconstructed spectra employing the Saha-Boltzmann plot method. The SP plasma revealed strongly inhomogeneous emissivity and plasma temperature. Re-excitation of plasma by a second laser pulse (DP) and by an arc discharge (SP-AD) homogenized the plasma and reduced the spatial variation of ε and Te. The homogenization of a plasma is a promising approach to increase the accuracy of calibration-free LIBS analysis of complex materials.

  6. Raman spectroscopic investigation of polycrystalline structures of CVD-grown graphene by isotope labeling

    NASA Astrophysics Data System (ADS)

    Wang, Shengnan; Suzuki, Satoru; Hibino, Hiroki

    2014-10-01

    Topological defects, such as point defects, dislocations and grain boundaries, have a dramatic influence on the chemical and physical properties of large-scale graphene grown by chemical vapor deposition (CVD) method. Here we demonstrate the Raman visualization of polycrystalline structures in an isotopically modified CVD graphene. By means of the reversible reaction of methane on a copper catalyst, the etching of 12C-lattice and surface deposition of 13C-atoms occur in CVD graphene by sequentially introducing hydrogen and isotopic methane after standard growth of graphene with full monolayer coverage. Spatial Raman spectroscopic mapping on labeled graphene reveals pronounced network-like 13C-rich regions, which are further identified to exist along the grain boundaries of graphene by low-energy electron microscopy. The structural defects inside the graphene grains are also targeted in the isotope labeling process. Our work opens a new way to investigate multiple grain structures in CVD graphene with a simple spectroscopic technique.Topological defects, such as point defects, dislocations and grain boundaries, have a dramatic influence on the chemical and physical properties of large-scale graphene grown by chemical vapor deposition (CVD) method. Here we demonstrate the Raman visualization of polycrystalline structures in an isotopically modified CVD graphene. By means of the reversible reaction of methane on a copper catalyst, the etching of 12C-lattice and surface deposition of 13C-atoms occur in CVD graphene by sequentially introducing hydrogen and isotopic methane after standard growth of graphene with full monolayer coverage. Spatial Raman spectroscopic mapping on labeled graphene reveals pronounced network-like 13C-rich regions, which are further identified to exist along the grain boundaries of graphene by low-energy electron microscopy. The structural defects inside the graphene grains are also targeted in the isotope labeling process. Our work opens a new

  7. CVD risk factors and ethnicity--a homogeneous relationship?

    PubMed

    Forouhi, Nita G; Sattar, Naveed

    2006-04-01

    Current understanding of cardiovascular disease risk (CVD) is derived largely from studies of Caucasians of European origin. However, people of certain ethnic groups experience a disproportionately greater burden of CVD including coronary heart disease (CHD) and stroke. Adoption of a Westernised lifestyle has different effects on metabolic and vascular dysfunction across populations, e.g. South Asians have a higher prevalence of coronary heart disease (CHD) and cardiovascular mortality compared with Europeans. African-Americans demonstrate higher rates of CHD and stroke while African/Caribbeans in the UK have lower CHD rates and higher stroke rates than British Europeans. Other non-European groups such as the Chinese and Japanese exhibit consistently high rates of stroke but not CHD, while Mexican Americans have a higher prevalence of both stroke and CHD, and North American native Indians also have high rates of CHD. While conventional cardiovascular risk factors such as smoking, blood pressure and total cholesterol predict risk within these ethnic groups, they do not fully account for the differences in risk between ethnic groups, suggesting that alternative explanations might exist. Ethnic groups show differences in levels of visceral adiposity, insulin resistance, and novel risk markers such as C-reactive protein (CRP), adiponectin and plasma homocysteine. The marked differences across racial and ethnic groups in disease risk are likely due in part to each of genetic, host susceptibility and environmental factors, and can provide valuable aetiological clues to differences in patterns of disease presentation, therapeutic needs and response to treatment. Ongoing studies should increase understanding of ethnicity as a potential independent risk factor, thus enabling better identification of treatment targets and selection of therapy in specific populations.

  8. Coupled Electro-Thermo-Mechanical Finite Element Modeling of the Spark Plasma Sintering Technique

    NASA Astrophysics Data System (ADS)

    Schwertz, Maxime; Katz, Aurélien; Sorrel, Emmanuel; Lemonnier, Sébastien; Barraud, Elodie; Carradò, Adele; d'Astorg, Sophie; Leriche, Anne; Nardin, Michel; Vallat, Marie-France; Kosior, Francis

    2016-04-01

    This paper deals with the development of a novel and predictive finite element method (FEM) model coupling electrical, thermal, and mechanical time-dependent contributions for simulating the behavior of a powdery material submitted to a spark plasma sintering (SPS) treatment by using COMSOL Multiphysics® software. The original approach of this work lies in the use of the modified Cam-Clay model to solve the mechanical phenomenon occurring during a SPS sintering treatment. As the powder properties and behaviors are different from the final sintered material and display a nonlinear dependence as a function of temperature and pressure, the model includes the description of the sample densification. In this way, numerical and experimental results obtained on conductive model material (aluminum) such as temperature, stress distributions, and shrinkage, were directly compared. This FEM model demonstrated the ability to predict the powder behavior during temperature-controlled experiments precisely, as they are typically performed in the SPS technique. This approach exhibits a remarkable level of interest because it takes into account the nature of the material and also the specific characteristics of the powder studied.

  9. Amidoxime-grafted multiwalled carbon nanotubes by plasma techniques for efficient removal of uranium(VI)

    NASA Astrophysics Data System (ADS)

    Wang, Yun; Gu, Zexing; Yang, Jijun; Liao, Jiali; Yang, Yuanyou; Liu, Ning; Tang, Jun

    2014-11-01

    A novel solid-phase extractant, amidoxime-grafted multiwalled carbon nanotubes (AO-g-MWCNTs), has been synthesized using plasma techniques to selectively separate uranium from nuclear industrial effluents. The adsorbent was characterized by Fourier transform infrared spectra (FT-IR), elemental analysis, Raman, scanning electron microscopy (SEM), and thermal gravity analysis (TGA). Sorption behaviors of uranium(VI) on AO-g-MWCNTs were investigated by varying pH, contact time, initial uranium concentration, and temperature. An optimum sorption capacity of 145 mg g-1 (0.61 mmol g-1) for U(VI) was obtained at pH 4.5. X-ray photoelectron spectroscopy (XPS) has been used to explore the sorption mechanism of U(VI) on AO-g-MWCNTs. Furthermore, AO-g-MWCNTs could selectively adsorb U(VI) in aqueous solution containing co-existing ions (Mn2+, Co2+, Ni2+, Zn2+, Sr2+, Ba2+ and Cs+). This study shows that AO-g-MWCNTs are potential adsorbent for effective removal of U(VI) from aqueous solution.

  10. On the OES line-ratio technique in argon and argon-containing plasmas

    NASA Astrophysics Data System (ADS)

    Siepa, Sarah; Danko, Stephan; Tsankov, Tsanko V.; Mussenbrock, Thomas; Czarnetzki, Uwe

    2014-11-01

    Optical emission spectroscopy is used to investigate capacitively coupled argon and argon-hydrogen-silane plasmas. The argon collisional-radiative model (CRM) used to extract the electron density and temperature from the spectra is presented. The electron energy distribution function, which is an input parameter to the model, is discussed in detail. Its strong variation with pressure is found to significantly influence the results for the (effective) temperature. For the analysis of the spectra the common line-ratio technique is applied. Special attention is paid to the choice of lines and a pair of line-ratios for optimum accuracy is suggested. For the argon gas mixture at high partial pressure of the admixed molecular gases the CRM reduces to a corona-like model, extended by a quenching term. The line-ratio method is found to fail under these conditions due to the strong depopulation of the argon 1s states. As a consequence, individual line intensities have to be used and an absolute calibration is required. An easy calibration method, which relies on the results obtained by the line-ratio method in pure argon, is proposed and applied.

  11. Insights in the plasma-assisted growth of carbon nanotubes through atomic scale simulations: effect of electric field.

    PubMed

    Neyts, Erik C; van Duin, Adri C T; Bogaerts, Annemie

    2012-01-18

    Carbon nanotubes (CNTs) are nowadays routinely grown in a thermal CVD setup. State-of-the-art plasma-enhanced CVD (PECVD) growth, however, offers advantages over thermal CVD. A lower growth temperature and the growth of aligned freestanding single-walled CNTs (SWNTs) makes the technique very attractive. The atomic scale growth mechanisms of PECVD CNT growth, however, remain currently entirely unexplored. In this contribution, we employed molecular dynamics simulations to focus on the effect of applying an electric field on the SWNT growth process, as one of the effects coming into play in PECVD. Using sufficiently strong fields results in (a) alignment of the growing SWNTs, (b) a better ordering of the carbon network, and (c) a higher growth rate relative to thermal growth rate. We suggest that these effects are due to the small charge transfer occurring in the Ni/C system. These simulations constitute the first study of PECVD growth of SWNTs on the atomic level. PMID:22126536

  12. Dimensionless Numbers Expressed in Terms of Common CVD Process Parameters

    NASA Technical Reports Server (NTRS)

    Kuczmarski, Maria A.

    1999-01-01

    A variety of dimensionless numbers related to momentum and heat transfer are useful in Chemical Vapor Deposition (CVD) analysis. These numbers are not traditionally calculated by directly using reactor operating parameters, such as temperature and pressure. In this paper, these numbers have been expressed in a form that explicitly shows their dependence upon the carrier gas, reactor geometry, and reactor operation conditions. These expressions were derived for both monatomic and diatomic gases using estimation techniques for viscosity, thermal conductivity, and heat capacity. Values calculated from these expressions compared well to previously published values. These expressions provide a relatively quick method for predicting changes in the flow patterns resulting from changes in the reactor operating conditions.

  13. A controlled atmosphere tube furnace was designed for thermal CVD

    NASA Astrophysics Data System (ADS)

    Rashid, M.; Bhatti, J. A.; Hussain, F.; Imran, M.; Khawaja, I. U.; Chaudhary, K. A.; Ahmad, S. A.

    2013-06-01

    High quality materials were used for the fabrication of hi-tech tube furnace. The furnace was especially suitable for thermal Chemical Vapor Deposition (CVD). High density alumina tube was used for the fabrication of furnace. The tube furnace was found to have three different temperature zones with maximum temperature at central zone was found to be 650°C. The flexible heating tape with capacity of 760°C was wrapped on the tube. To minimize the heat losses, asbestos and glass wool were used on heating tape. The temperature of the tube furnace was controlled by a digital temperature controller had accuracy of ±1°C. Methanol was taken as the representative of hydrocarbon sources, to give thin film of carbon. The a-C: H structure was investigated by conventional techniques using optical microscopy, FT-IR and SEM.

  14. RMF concept: a rotating-magnetic-field technique for driving steady plasma currents in compact toroid devices

    SciTech Connect

    McKenna, K.F.

    1980-09-01

    The generation and/or sustaining of a Compact Toroid (CT) configuration using the RMF technique is a relatively new and unknown concept. In this report the basic principles, historical development, and current theoretical understanding of this concept are reviewed. Significant experimental and theoretical results, potential problem areas, and recommendations for the direction of future work are discussed. An illustrative analysis of the application of the RMF technique to a CT reactor is presented. The results of a recent experiment, the Rotamak, in which a Spheromak-like CT plasma was produced using the RMF technique, are presented.

  15. Observation of twinning in diamond CVD films

    NASA Astrophysics Data System (ADS)

    Marciniak, W.; Fabisiak, K.; Orzeszko, S.; Rozploch, F.

    1992-10-01

    Diamond particles prepared by dc-glow-discharge enhanced HF-CVD hybrid method, from a mixture of acetone vapor and hydrogen gas have been examined by TEM, RHEED and dark field method of observation. Results suggest the presence of twinned diamond particles, which can be reconstructed by a sequence of twinning operations. Contrary to the 'stick model' of the lattice, very common five-fold symmetry of diamond microcrystals may be obtained by applying a number of edge dislocations rather than the continuous deformation of many tetrahedral C-C bonds.

  16. Techniques for the remote sensing of space plasma in the heliosphere via energetic neutral atoms - A review

    NASA Technical Reports Server (NTRS)

    Hsieh, K. C.; Curtis, C. C.; Fan, C. Y.; Gruntman, M. A.

    1992-01-01

    A survey is conducted for state-of-the-art techniques for detecting energetic neutral atoms (ENAs) in the 100-300 keV range, in regions from the heliospheric boundary to the auroral zones where the solar wind plays a crucial role. While ENA spectrometry allows sampling of the mass and energy distributions of a distant plasma, ENA imaging gives a global view of the structures and dynamics of an extended plasma. The ENA instrument designs discussed share many components which exhibit excellent flight performance as elements in charged-particle analyzers for space missions.

  17. Study of atmospheric pressure weakly ionized plasma as surface compatibilization technique for improved plastic composites loaded with cellulose based fillers

    NASA Astrophysics Data System (ADS)

    Lekobou, William Pimakouon

    Atmospheric pressure plasmas have gained considerable interest from researchers recently for their unique prospective of engineering surfaces with plasma without the need of vacuum systems. They offer the advantage of low energy consumption, minimal capital cost and their simplicity as compared to conventional low pressure plasmas make them easy to upscale from laboratory to industry size. The present dissertation summarizes results of our attempt at applying atmospheric pressure weakly ionized plasma (APWIP) to the engineering of plastic composites filled with cellulose based substrates. An APWIP reactor was designed and built based on a multipoint-to-grounded ring and screen configurations. The carrier gas was argon and acetylene serves as the precursor molecule. The APWIP reactors showed capability of depositing plasma polymerized coating rich in carbon on substrates positioned within the electrode gap as well as downstream of the plasma discharge into the afterglow region. Our findings show that films grow by forming islands which for prolonged deposition time grow into thin films showing nodules, aggregates of nodules and microspheres. They also show chemical structure similar to films deposited from hydrocarbons with other conventional plasma techniques. The plasma polymerized deposits were used on substrates to modify their surface properties. Results show the surface of wood veneer and wood flour can be finely tuned from hydrophilic to hydrophobic. It was achieved by altering the topography of the surfaces along with their chemical composition. The wettability of wood veneer was investigated with contact angle measurements on capacitive drops and the capillary effect was utilized to assess surface properties of wood flour exposed to the discharges.

  18. The characterization of boron carbide nanowires grown by PECVD and CVD

    NASA Astrophysics Data System (ADS)

    Alkhateeb, Abdullah; Zhang, Daqing; McIlroy, D. N.; Norton, M. Grant

    2001-03-01

    The growth of boron carbide nanowires by chemical vapor deposition (CVD) and plasma enhanced chemical vapor deposition (PECVD) has been compared. In both cases the single source compound orthocarborane (C2B10H12) was used. The two processes vary dramatically from one another primarily due to the differences in fragmentation pathways of the precursor orthocarborane, which is extremely stable. For simple CVD the process is limited by thermal fragmentation of the precursor at the surface. However, for plasma enhanced CVD there are many more fragmentation pathways and the fragmentation can occur far away from the surface. This study has shown that there is competition between thin film growth and nanowire growth that strongly depends on the fragmentation process of the precursor. It has been determined that nanowires growth can be promoted over thin film growth by reducing the fragmentation pathways of orthocarborane and that probability of thermal fragmentation is higher at the surface of the catalyst (NiB) than at the substrate (silicon).

  19. Man-made vitreous fiber produced from incinerator ash using the thermal plasma technique and application as reinforcement in concrete.

    PubMed

    Yang, Sheng-Fu; Wang, To-Mai; Lee, Wen-Cheng; Sun, Kin-Seng; Tzeng, Chin-Ching

    2010-10-15

    This study proposes using thermal plasma technology to treat municipal solid waste incinerator ashes. A feasible fiberization method was developed and applied to produce man-made vitreous fiber (MMVF) from plasma vitrified slag. MMVF were obtained through directly blending the oxide melt stream with high velocity compressed air. The basic technological characteristics of MMVF, including morphology, diameter, shot content, length and chemical resistance, are described in this work. Laboratory experiments were conducted on the fiber-reinforced concrete. The effects of fibrous content on compressive strength and flexural strength are presented. The experimental results showed the proper additive of MMVF in concrete can enhance its mechanical properties. MMVF products produced from incinerator ashes treated with the thermal plasma technique have great potential for reinforcement in concrete.

  20. Method for growth of CVD diamond on thin film refractory coatings and glass ceramic materials

    NASA Astrophysics Data System (ADS)

    Moran, Mark B.; Johnson, Linda F.; Klemm, Karl A.

    1994-09-01

    This paper describes a new method for significantly improving diamond film quality and growth rate on insulating substrates and thin films. The usual method of abrading the substrate surface with diamond particles yields good quality CVD diamond films at reasonable deposition rates on semiconducting materials like silicon. However, on insulating materials like fused silica and sapphire, the conventional method of diamond seeding and surface abrasion almost always results in slow growth rates and poor quality films. Current in-house diamond nucleation and growth studies have focused on depositing CVD diamond on substrates such as fused silica, sapphire, and glass ceramics. Diamond was grown successfully on these types of materials using a sacrificial metal layer method called metal induced nucleation of diamond (MIND). This technique offers a way to deposit diamond on glassy materials with improved adhesion and at lower deposition temperatures (less than 650 degree(s)C). In addition, the MIND technique can be used in combination with metal masking and conventional etching to deposit patterns of diamond. The MIND method was combined with another in-house developed technique called sputtered refractory interlayer nucleation technique (SPRINT). Diamond-crystallite size and orientation can be controlled with SPRINT to fabricate low-scatter diamond films. Both techniques are discussed. A reliable, efficient method for growing diamond on insulating materials significantly enhances the feasibility for practical applications of CVD diamond technology. For example, further development of the MIND technique may provide low-scatter, protective diamond films on sapphire and glass ceramics for visible-wavelength windows and missile domes. For electronic applications, reduction in the growth temperature makes CVD diamond more compatible with existing semiconductor processes. The lower growth temperature also helps to alleviate diffusion problems in metal alloys and facilitates

  1. Grazing incidence technique to obtain spatially resolved spectra from laser heated plasmas

    NASA Technical Reports Server (NTRS)

    Behring, W. E.; Underwood, J. H.; Brown, C. M.; Feldman, U.; Seely, John F.

    1988-01-01

    An experimental method is described in which a grazing incidence spectrograph is used to obtain spatially resolved spectra of laser heated plasmas in the 6-370-A region. In the experiment, small target spheres were irradiated by tightly focused laser beams. A tilted grazing incidence elliptical mirror placed 1.3 m from the target focuses the plasma radiation on the spectrograph slit at a distance of 0.7 m producing a useful degree of spatial resolution in the recorded spectral lines. The spectrum from a copper target is presented together with an X-ray pinhole camera image of the plasma.

  2. Raman spectroscopic investigation of polycrystalline structures of CVD-grown graphene by isotope labeling.

    PubMed

    Wang, Shengnan; Suzuki, Satoru; Hibino, Hiroki

    2014-11-21

    Topological defects, such as point defects, dislocations and grain boundaries, have a dramatic influence on the chemical and physical properties of large-scale graphene grown by chemical vapor deposition (CVD) method. Here we demonstrate the Raman visualization of polycrystalline structures in an isotopically modified CVD graphene. By means of the reversible reaction of methane on a copper catalyst, the etching of (12)C-lattice and surface deposition of (13)C-atoms occur in CVD graphene by sequentially introducing hydrogen and isotopic methane after standard growth of graphene with full monolayer coverage. Spatial Raman spectroscopic mapping on labeled graphene reveals pronounced network-like (13)C-rich regions, which are further identified to exist along the grain boundaries of graphene by low-energy electron microscopy. The structural defects inside the graphene grains are also targeted in the isotope labeling process. Our work opens a new way to investigate multiple grain structures in CVD graphene with a simple spectroscopic technique. PMID:25303722

  3. Hexagonal Boron Nitride assisted transfer and encapsulation of large area CVD graphene

    NASA Astrophysics Data System (ADS)

    Shautsova, Viktoryia; Gilbertson, Adam M.; Black, Nicola C. G.; Maier, Stefan A.; Cohen, Lesley F.

    2016-07-01

    We report a CVD hexagonal boron nitride (hBN-) assisted transfer method that enables a polymer-impurity free transfer process and subsequent top encapsulation of large-area CVD-grown graphene. We demonstrate that the CVD hBN layer that is utilized in this transfer technique acts as a buffer layer between the graphene film and supporting polymer layer. We show that the resulting graphene layers possess lower doping concentration, and improved carrier mobilities compared to graphene films produced by conventional transfer methods onto untreated SiO2/Si, SAM-modified and hBN covered SiO2/Si substrates. Moreover, we show that the top hBN layer used in the transfer process acts as an effective top encapsulation resulting in improved stability to ambient exposure. The transfer method is applicable to other CVD-grown 2D materials on copper foils, thereby facilitating the preparation of van der Waals heterostructures with controlled doping.

  4. Hexagonal Boron Nitride assisted transfer and encapsulation of large area CVD graphene

    PubMed Central

    Shautsova, Viktoryia; Gilbertson, Adam M.; Black, Nicola C. G.; Maier, Stefan A.; Cohen, Lesley F.

    2016-01-01

    We report a CVD hexagonal boron nitride (hBN-) assisted transfer method that enables a polymer-impurity free transfer process and subsequent top encapsulation of large-area CVD-grown graphene. We demonstrate that the CVD hBN layer that is utilized in this transfer technique acts as a buffer layer between the graphene film and supporting polymer layer. We show that the resulting graphene layers possess lower doping concentration, and improved carrier mobilities compared to graphene films produced by conventional transfer methods onto untreated SiO2/Si, SAM-modified and hBN covered SiO2/Si substrates. Moreover, we show that the top hBN layer used in the transfer process acts as an effective top encapsulation resulting in improved stability to ambient exposure. The transfer method is applicable to other CVD-grown 2D materials on copper foils, thereby facilitating the preparation of van der Waals heterostructures with controlled doping. PMID:27443219

  5. Plasma microcontact patterning (PμCP): a technique for the precise control of surface patterning at small-scale.

    PubMed

    Picone, Remigio; Baum, Buzz; McKendry, Rachel

    2014-01-01

    Plasma microcontact patterning (PμCP) is a simple, efficient, and cost-effective method for the precise patterning of molecules on surfaces. It combines the use of low-pressure plasma with an elastomeric 3D mask to spatially control the removal of molecules, such as proteins, from a surface. The entire PμCP process is subdivided into three main steps: surface precoating, plasma micropatterning, and a surface postcoating step. Surfaces are first precoated with a molecular species and then placed in close contact with the 3D mask. This allows the formation of two distinct regions: an un-masked open-region which is accessible to the plasma, from which the surface layer is removed, and, a contact region which is physically protected from exposure to the plasma. In the final step, a second molecule is added to back-fill the pattern generated through plasma-treatment. The PμCP technique allows the patterning of virtually any organic molecules on different surface materials and geometries (e.g., flat, curved surfaces, and 3D microstructures). Moreover, it is a simple and robust procedure. The main advantages of this approach over traditional microcontact printing are twofold: The stability of molecule binding to plasma-treated surfaces, and the separation of the surface functionalization step from the actual micropatterning step, which enables the precise control of concentration and uniformity of patterned molecules. In conclusion, PμCP is a simple way to generate surface patterns that are highly reproducible, stable and uniform, making it a useful method for many applications. PMID:24439280

  6. Quantum cascade laser absorption spectroscopy with the amplitude-to-time conversion technique for atmospheric-pressure plasmas

    SciTech Connect

    Yumii, Takayoshi; Kimura, Noriaki; Hamaguchi, Satoshi

    2013-06-07

    The NO{sub 2} concentration, i.e., density, in a small plasma of a nitrogen oxide (NOx) treatment reactor has been measured by highly sensitive laser absorption spectroscopy. The absorption spectroscopy uses a single path of a quantum cascade laser beam passing through a plasma whose dimension is about 1 cm. The high sensitivity of spectroscopy is achieved by the amplitude-to-time conversion technique. Although the plasma reactor is designed to convert NO in the input gas to NO{sub 2}, it has been demonstrated by this highly sensitive absorption spectroscopy that NO{sub 2} in a simulated exhaust gas that enters the reactor is decomposed by the plasma first and then NO{sub 2} is formed again, possibly more than it was decomposed, through a series of gas-phase reactions by the time the gas exits the reactor. The observation is consistent with that of an earlier study on NO decomposition by the same type of a plasma reactor [T. Yumii et al., J. Phys. D 46, 135202 (2013)], in which a high concentration of NO{sub 2} was observed at the exit of the reactor.

  7. X-ray spectroscopic technique for energetic electron transport studies in short-pulse laser/plasma interactions

    SciTech Connect

    Tutt, T.E.

    1994-12-01

    When a solid target is irradiated by a laser beam, the material is locally heated to a high temperature and a plasma forms. The interaction of the laser with plasma can produce energetic electrons. By observing the behavior of these {open_quotes}hot{close_quotes} electrons, we hope to obtain a better understanding of Laser/Plasma Interactions. In this work we employ a layered-fluorescer technique to study the transport, and therefore the energetics, of the electrons. The plasma forms on a thin foil of metallic Pd which is bonded to thin layer of metallic Sn. Electrons formed from the plasma penetrate first the Pd and then the Sn. In both layers the energetic electrons promote inner (K) shell ionization of the metallic atoms which leads to the emission of characteristic K{sub {alpha}} x-rays of the fluorescers. By recording the x-ray spectrum emitted by the two foils, we can estimate the energy-dependent range of the electrons and their numbers.

  8. Determination of glomerular filtration rate by single-plasma sampling technique following injection of radioiodinated diatrizoate

    SciTech Connect

    Tauxe, W.N.

    1986-01-01

    Measurement of glomerular filtration rate (GFR) based on the radioactivity concentration in a single-plasma sample obtained after the injection of radioiodinated diatrizoate (DTZ) has been described. Simultaneous determinations of GFR by use of DTZ based on multiple-sample plasma disappearance curves and inulin correlate highly. Certain theoretical volumes of distribution (injection dose counts divided by plasma concentration expressed as counts per liter of plasma) correlate highly with GFR determined by the multiple-sample plasma disappearance curves. For patients with relatively high GFR (greater than 100 ml/min) best correlations were obtained at 120 min; for patients with GFR 60-100 ml/min, best correlations were obtained at sampling times of 150 min after injection and for patients with GFR less than 60 ml/min, the ideal sampling time was 230 min after injection. For general use the 180-min sampling time may suffice. Since the formulae were found to produce nearly identical GFR values for data obtained from the use of diethylenetriaminepentaacetic acid and DTZ, the former radiopharmaceutical can probably be substituted for diatrizoate using these formulae and sampling times as long as absence of plasma protein binding of the labeled chelate can be demonstrated.

  9. Development of Field-Reversed Configuration Plasma Gun Formation Techniques for Magnetized Target Fusion

    NASA Astrophysics Data System (ADS)

    Lynn, Alan; Gilmore, Mark; Wynkoop, Tyler; Intrator, Thomas; Weber, Thomas

    2012-10-01

    Magnetized Target Fusion (MTF) is an innovative approach for a relatively fast and cheap path to the production of fusion energy that utilizes magnetic confinement to assist in the compression of a hot plasma to thermonuclear conditions by an external driver. Los Alamos National Laboratory (LANL) is currently pursing demonstration of the MTF concept via compression of an FRC (field-reversed configuration) plasma by a metal liner z-pinch in conjunction with the Air Force Research Laboratory in Albuquerque, NM. A key physics issue for the FRC as an MTF target lies in the initial pre-ionization (PI) stage. The PI formation process determines the amount of magnetic flux that can be trapped to form the FRC. This trapped flux plays an important role in the FRC's final equilibrium, transport, and stability properties. It also provides the route to greatest potential gains in FRC lifetime, which is essential to provide enough time to translate and compress the FRC effectively. In conjunction with LANL we plan to test and characterize a new system to improve the initial PI plasma formation. This system will use an array of plasma guns to form the initial plasma. Initial characterization of the plasma gun behavior will be presented.

  10. CVD fabrication of thermionic converter and heat pipe

    SciTech Connect

    Reagan, P.; Lieb, D.; Miskolczy, G.; Goodale, D.; Huffman, F.

    1983-07-01

    Thermionic converters and heat pipes fabricated by chemical-vapor deposition (CVD) have operated for extended periods of more than 12,500 hours in natural gas flames at temperatures more than 1700 K. These CVD-trilayer silicon carbide, graphite, and tungsten structures have survived thermal shock and thermal cycle tests.

  11. Cold Vacuum Drying (CVD) Set Point Determination

    SciTech Connect

    PHILIPP, B.L.

    2000-01-12

    This document provides the calculations used to determine the error of safety class signals used for the CVD process These errors are used with the Parameter limits to arrive at the initial set point. The Safety Class Instrumentation and Control (SCIC) system provides active detection and response to process anomalies that, if unmitigated would result in a safety event. Specifically actuation of the SCIC system includes two portions. The portion which isolates the MCO and initiates the safety-class helium (SCHe) purge, and the portion which detects and stops excessive heat input to the MCO on high tempered water MCO inlet temperature. For the MCO isolation and purge the SCIC receives signals from MCO pressure (both positive pressure and vacuum) helium flow rate, bay high temperature switches, seismic trips and time under vacuum trips.

  12. Nanoelectronic biosensors based on CVD grown graphene

    NASA Astrophysics Data System (ADS)

    Huang, Yinxi; Dong, Xiaochen; Shi, Yumeng; Li, Chang Ming; Li, Lain-Jong; Chen, Peng

    2010-08-01

    Graphene, a single-atom-thick and two-dimensional carbon material, has attracted great attention recently. Because of its unique electrical, physical, and optical properties, graphene has great potential to be a novel alternative to carbon nanotubes in biosensing. We demonstrate the use of large-sized CVD grown graphene films configured as field-effect transistors for real-time biomolecular sensing. Glucose or glutamate molecules were detected by the conductance change of the graphene transistor as the molecules are oxidized by the specific redox enzyme (glucose oxidase or glutamic dehydrogenase) functionalized onto the graphene film. This study indicates that graphene is a promising candidate for the development of real-time nanoelectronic biosensors.Graphene, a single-atom-thick and two-dimensional carbon material, has attracted great attention recently. Because of its unique electrical, physical, and optical properties, graphene has great potential to be a novel alternative to carbon nanotubes in biosensing. We demonstrate the use of large-sized CVD grown graphene films configured as field-effect transistors for real-time biomolecular sensing. Glucose or glutamate molecules were detected by the conductance change of the graphene transistor as the molecules are oxidized by the specific redox enzyme (glucose oxidase or glutamic dehydrogenase) functionalized onto the graphene film. This study indicates that graphene is a promising candidate for the development of real-time nanoelectronic biosensors. Electronic supplementary information (ESI) available: AFM images of graphene film before and after functionalization, transfer curves of graphene after every step, SEM image of CNT-net, and detection results using CNT-net devices. See DOI: 10.1039/c0nr00142b

  13. Final Report on Development of Optimized Field-Reversed Configuration Plasma Formation Techniques for Magnetized Target Fusion

    SciTech Connect

    Lynn, Alan

    2013-11-01

    The University of New Mexico (UNM) proposed a collaboration with Los Alamos National Laboratory (LANL) to develop and test methods for improved formation of field-reversed configuration (FRC) plasmas relevant to magnetized target fusion (MTF) energy research. MTF is an innovative approach for a relatively fast and cheap path to the production of fusion energy that utilizes magnetic confinement to assist in the compression of a hot plasma to thermonuclear conditions by an external driver. LANL is currently pursing demonstration of the MTF concept via compression of an FRC plasma by a metal liner z-pinch in conjunction with the Air Force Research Laboratory in Albuquerque, NM. A key physics issue for the FRC's ultimate success as an MTF target lies in the initial pre-ionization (PI) stage. The PI plasma sets the initial conditions from which the FRC is created. In particular, the PI formation process determines the amount of magnetic flux that can be trapped to form the FRC. A ringing theta pinch ionization (RTPI) technique, such as currently used by the FRX-L device at LANL, has the advantages of high ionization fraction, simplicity (since no additional coils are required), and does not require internal electrodes which can introduce impurities into the plasma. However RTPI has been shown to only trap 50% of the initial bias flux at best and imposes additional engineering constraints on the capacitor banks. The amount of trapped flux plays an important role in the FRC's final equilibrium, transport, and stability properties, and provides increased ohmic heating of the FRC through induced currents as the magnetic field decays. Increasing the trapped flux also provides the route to greatest potential gains in FRC lifetime, which is essential to provide enough time to translate and compress the FRC effectively. In conjunction with LANL we initially planned to develop and test a microwave break- down system to improve the initial PI plasma formation. The UNM team would

  14. Organochlorine contaminants in loggerhead sea turtle blood: extraction techniques and distribution among plasma and red blood cells.

    PubMed

    Keller, J M; Kucklick, J R; McClellan-Green, P D

    2004-02-01

    Few studies have described the organochlorine (OC) contaminant concentrations found in sea turtle tissues. These studies have relied on the opportunistic sampling of either eggs or tissues from stranded carcasses. In this study, the use of whole blood samples as well as both blood components (plasma and red blood cells) were examined as a non-destructive alternative for monitoring OCs in free-ranging loggerhead sea turtles (Caretta caretta). Blood samples were collected from juvenile loggerhead sea turtles (n = 12) captured in Core Sound, North Carolina, USA and analyzed for 55 polychlorinated biphenyl (PCB) congeners and 24 OC pesticides by gas chromatography with electron capture detection and mass spectrometry. Using pooled loggerhead sea turtle whole blood, three different liquid:liquid extraction techniques were compared. Results were similar in terms of recovery of internal standards, lipids, and OC concentrations. An extraction technique, employing formic acid and 1:1 methyl-tert-butyl-ether: hexane, was found to be satisfactory. This method was applied to the extraction of OCs from whole blood, plasma, and red blood cell (RBC) samples from five loggerhead sea turtles. Plasma contained the highest OC concentrations on a wet mass basis, followed by whole blood and RBCs. The majority of each OC compound was found in the plasma rather than the RBCs, suggesting that OC compounds preferentially partition into the plasma. On average (SD), 89.4% (3.1 %) of total PCBs, 83.4% (11.9%) of total chlordanes, 74.3% (15.1%) of mirex, 72.6% (4.8%) of total DDTs, and 80.1% (16.6%) of dieldrin were found in the plasma. The concentrations of total PCBs, mirex, total chlordanes, and total DDTs measured in both components of the blood significantly correlated to those in whole blood. These are the first reported OC concentrations in sea turtle blood. They were found to be similar to previously reported levels in blood components of humans and of reptiles from relatively clean

  15. Fabrication of copper-based anodes via atmosphoric plasma spraying techniques

    SciTech Connect

    Lu, Chun

    2012-04-24

    A fuel electrode anode (18) for a solid oxide fuel cell is made by presenting a solid oxide fuel cell having an electrolyte surface (15), mixing copper powder with solid oxide electrolyte in a mixing step (24, 44) to provide a spray feedstock (30,50) which is fed into a plasma jet (32, 52) of a plasma torch to melt the spray feed stock and propel it onto an electrolyte surface (34, 54) where the spray feed stock flattens into lamellae layer upon solidification, where the layer (38, 59) is an anode coating with greater than 35 vol. % based on solids volume.

  16. Electronic properties of embedded graphene: doped amorphous silicon/CVD graphene heterostructures

    NASA Astrophysics Data System (ADS)

    Arezki, Hakim; Boutchich, Mohamed; Alamarguy, David; Madouri, Ali; Alvarez, José; Cabarrocas, Pere Roca i.; Kleider, Jean-Paul; Yao, Fei; Lee, Young Hee

    2016-10-01

    Large-area graphene film is of great interest for a wide spectrum of electronic applications, such as field effect devices, displays, and solar cells, among many others. Here, we fabricated heterostructures composed of graphene (Gr) grown by chemical vapor deposition (CVD) on copper substrate and transferred to SiO2/Si substrates, capped by n- or p-type doped amorphous silicon (a-Si:H) deposited by plasma-enhanced chemical vapor deposition. Using Raman scattering we show that despite the mechanical strain induced by the a-Si:H deposition, the structural integrity of the graphene is preserved. Moreover, Hall effect measurements directly on the embedded graphene show that the electronic properties of CVD graphene can be modulated according to the doping type of the a-Si:H as well as its phase i.e. amorphous or nanocrystalline. The sheet resistance varies from 360 Ω sq-1 to 1260 Ω sq-1 for the (p)-a-Si:H/Gr (n)-a-Si:H/Gr, respectively. We observed a temperature independent hole mobility of up to 1400 cm2 V-1 s-1 indicating that charge impurity is the principal mechanism limiting the transport in this heterostructure. We have demonstrated that embedding CVD graphene under a-Si:H is a viable route for large scale graphene based solar cells or display applications.

  17. Electronic properties of embedded graphene: doped amorphous silicon/CVD graphene heterostructures.

    PubMed

    Arezki, Hakim; Boutchich, Mohamed; Alamarguy, David; Madouri, Ali; Alvarez, José; Cabarrocas, Pere Roca I; Kleider, Jean-Paul; Yao, Fei; Hee Lee, Young

    2016-10-12

    Large-area graphene film is of great interest for a wide spectrum of electronic applications, such as field effect devices, displays, and solar cells, among many others. Here, we fabricated heterostructures composed of graphene (Gr) grown by chemical vapor deposition (CVD) on copper substrate and transferred to SiO2/Si substrates, capped by n‑ or p-type doped amorphous silicon (a-Si:H) deposited by plasma-enhanced chemical vapor deposition. Using Raman scattering we show that despite the mechanical strain induced by the a-Si:H deposition, the structural integrity of the graphene is preserved. Moreover, Hall effect measurements directly on the embedded graphene show that the electronic properties of CVD graphene can be modulated according to the doping type of the a-Si:H as well as its phase i.e. amorphous or nanocrystalline. The sheet resistance varies from 360 Ω sq(-1) to 1260 Ω sq(-1) for the (p)-a-Si:H/Gr (n)-a-Si:H/Gr, respectively. We observed a temperature independent hole mobility of up to 1400 cm(2) V(-1) s(-1) indicating that charge impurity is the principal mechanism limiting the transport in this heterostructure. We have demonstrated that embedding CVD graphene under a-Si:H is a viable route for large scale graphene based solar cells or display applications. PMID:27506254

  18. A Novel Technique to Treat Air Leak Following Lobectomy: Intrapleural Infusion of Plasma

    PubMed Central

    Konstantinou, Froso; Potaris, Konstantinos; Syrigos, Konstantinos N.; Tsipas, Panteleimon; Karagkiouzis, Grigorios; Konstantinou, Marios

    2016-01-01

    Background Persistent air leak following pulmonary lobectomy can be very difficult to treat and results in prolonged hospitalization. We aimed to evaluate the efficacy of a new method of postoperative air leak management using intrapleurally infused fresh frozen plasma via the chest tube. Material/Methods Between June 2008 and June 2014, we retrospectively reviewed 98 consecutive patients who underwent lobectomy for lung cancer and postoperatively developed persistent air leak treated with intrapleural instillation of fresh frozen plasma. Results The study identified 89 men and 9 women, with a median age of 65.5 years (range 48–77 years), with persistent postoperative air leak. Intrapleural infusion of fresh frozen plasma was successful in stopping air leaks in 90 patients (92%) within 24 hours, and in 96 patients (98%) within 48 hours, following resumption of the procedure. In the remaining 2, air leak ceased at 14 and 19 days. Conclusions Intrapleural infusion of fresh frozen plasma is a safe, inexpensive, and remarkably effective method for treatment of persistent air leak following lobectomy for lung cancer. PMID:27079644

  19. Depolymerization of chitosan-metal complexes via a solution plasma technique.

    PubMed

    Pornsunthorntawee, Orathai; Katepetch, Chaiyapruk; Vanichvattanadecha, Chutima; Saito, Nagahiro; Rujiravanit, Ratana

    2014-02-15

    Chitosan-metal complexes were depolymerized under acidic conditions using a solution plasma system. Four different types of metal ions, including Ag(+), Zn(2+), Cu(2+), and Fe(3+) ions, were added to the chitosan solution at a metal-to-chitosan molar ratio of 1:8. The depolymerization rate was affected by the types of metal ions that form complexes with chitosan. The complexation of chitosan with Cu(2+) or Fe(3+) ions strongly promoted the depolymerization rate of chitosan using a solution plasma treatment. However, chitosan-Ag(+) and chitosan-Zn(2+) complexes exhibited no change in the depolymerization rate compared to chitosan. After plasma treatment of the chitosan-metal complexes, the depolymerized chitosan products were separated into water-insoluble and water-soluble fractions. The water-soluble fraction containing low-molecular-weight chitosan was obtained in a yield of less than 57% for the depolymerization of chitosan-Fe(3+) complex with the plasma treatment time of 180 min. PMID:24507312

  20. Parallel-beam correlation technique for measuring density fluctuations in plasmas with strong magnetic shear

    SciTech Connect

    Jacobson, A.R.

    1981-04-01

    A laser diagnostic scheme is described which facilitates localization of density fluctuations along the line of sight. The method exploits both the generally observed anisotropy of density fluctuations in low-beta plasmas, as well as the twisting of the magnetic field which occurs across the minor diameter of reversed-field pinches, spheromaks, etc. Both interferometric and schlieren variations are discussed.

  1. Imaging of the magnetic field structure in megagauss plasmas by combining pulsed polarimetry with an optical Kerr effect shutter technique.

    PubMed

    Smith, R J

    2010-10-01

    Pulsed polarimetry in combination with a high speed photographic technique based on the optical Kerr effect is described. The backscatter in a pulsed polarimeter is directed through a scattering cell and photographed using an ∼1 ps shutter, essentially freezing the intensity pattern. The image provides both the local electron density and magnetic field distributions along and transverse to the laser sightline. Submillimeter spatial resolution is possible for probing wavelengths in the visible due to the high densities and strong optical activity. Pulsed polarimetry is thereby extended to centimeter-sized plasmas with n(e)>10(19)-10(20) cm(-3) and B>20-100 T (MG) produced by multiterawatt, multimega-ampere electrical drivers, wire Z pinches, and liner imploded magnetized plasmas. PMID:21033885

  2. A study of the Interaction Between Cetirizine and Plasma Membrane of Eosinophils, Neutrophils, Platelets and Lymphocytes using A fluorescence Technique

    PubMed Central

    Oggiano, N.; Giorgi, P. L.; Rihoux, J-P.

    1994-01-01

    The effect of cetirizine on plasma membrane fluidity and heterogeneity of human eosinophils, neutrophils, platelets and lymphocytes was investigated using a fluorescence technique. Membrane fluidity and heterogeneity were studied by measuring the steady-state fluorescence anisotropy and fluorescence decay of 1-(4- trimethylammonium-phenyl)-6-phenyl-1, 3, 5-hexatriene (TMA-DPH) incorporated in the membrane. The results demonstrate that cetirizine (1 μg/ml) induced a significant increase in the Hpid order in the exterior part of the membrane and a decrease in membrane heterogeneity in eosinophils, neutrophils and platelets. Moreover, cetirizine blocked the PAF induced changes in membrane fluidity in these cells. Cetirizine did not influence significantly the plasma membrane of lymphocytes. These data may partially explain the effect ofcetirizine on inflammatory cell activities. PMID:18472948

  3. Imaging of the magnetic field structure in megagauss plasmas by combining pulsed polarimetry with an optical Kerr effect shutter technique

    SciTech Connect

    Smith, R. J.

    2010-10-15

    Pulsed polarimetry in combination with a high speed photographic technique based on the optical Kerr effect is described. The backscatter in a pulsed polarimeter is directed through a scattering cell and photographed using an {approx}1 ps shutter, essentially freezing the intensity pattern. The image provides both the local electron density and magnetic field distributions along and transverse to the laser sightline. Submillimeter spatial resolution is possible for probing wavelengths in the visible due to the high densities and strong optical activity. Pulsed polarimetry is thereby extended to centimeter-sized plasmas with n{sub e}>10{sup 19}-10{sup 20} cm{sup -3} and B>20-100 T (MG) produced by multiterawatt, multimega-ampere electrical drivers, wire Z pinches, and liner imploded magnetized plasmas.

  4. Mechanistic studies of the CVD of silicon nitride from SiF[sub 4] and NH[sub 3

    SciTech Connect

    Buss, R J; Ho, P

    1992-01-01

    An industrial process for the CVD of silicon nitride from SiF[sub 4] and NH[sub 3] was studied with a wide variety of techniques, ranging from numerical models of the coupled chemistry and fluid mechanics to experimental studies of chemical reactions. The latter includes a set of molecular beam experiments that probed the temperature and flux dependencies of the reaction of SiF[sub 4] and NH[sub 3] at the surface. These experiments showed that the CVD reactor chemistry was dominated by surface kinetics rather than gas-phase decomposition.

  5. Euromech 260: Advanced non-intrusive experimental techniques in fluid and plasma flows

    NASA Astrophysics Data System (ADS)

    The following topics are discussed: coherent anti-Stokes and elastic Rayleigh scattering; elastic scattering and non linear dynamics; fluorescence; molecular tracking techniques and particle image velocimetry.

  6. How Gene Networks Can Uncover Novel CVD Players

    PubMed Central

    Parnell, Laurence D; Casas-Agustench, Patricia; Iyer, Lakshmanan K; Ordovas, Jose M

    2014-01-01

    Cardiovascular diseases (CVD) are complex, involving numerous biological entities from genes and small molecules to organ function. Placing these entities in networks where the functional relationships among the constituents are drawn can aid in our understanding of disease onset, progression and prevention. While networks, or interactomes, are often classified by a general term, say lipids or inflammation, it is a more encompassing class of network that is more informative in showing connections among the active entities and allowing better hypotheses of novel CVD players to be formulated. A range of networks will be presented whereby the potential to bring new objects into the CVD milieu will be exemplified. PMID:24683432

  7. A low-level activation technique for monitoring thermonuclear fusion plasma conditions.

    PubMed

    Gasparro, Joël; Hult, Mikael; Bonheure, Georges; Johnston, Peter N

    2006-01-01

    Optimisation of the confinement and sustainability of a thermonuclear plasma requires methods to monitor processes in the plasma. In this work three materials were used as activation targets (Ti, MgF2 and a TiVAl compound). They were placed inside the joint European Torus (JET) vacuum chamber. Certain gamma-ray emitting radionuclides (7Be, 54Mn, 56Co, 57Co, 58Co and 46Sc) were measured using ultra low-level gamma-ray spectrometry in an underground laboratory 1-2 months after activation. They were found to arise from neutron activation of bulk sample material and surface contaminants sputtered from other Tokamak parts. Decision thresholds for some activation products were determined in order to aid in giving upper bounds for the flux of charged particles.

  8. Characteristics of heat-annealed silicon homojunction infrared photodetector fabricated by plasma-assisted technique

    NASA Astrophysics Data System (ADS)

    Hammadi, Oday A.

    2016-09-01

    In this work, the effect of thermal annealing on the characteristics of silicon homojunction photodetector was studied. This homojunction photodetector was fabricated by means of plasma-induced etching of p-type silicon substrate and plasma sputtering of n-type silicon target in vacuum. The electrical and spectral characteristics of this photodetector were determined and optimized before and after the annealing process. The maximum surface reflectance of 1.89% and 1.81%, the maximum responsivity of 0.495 A/W and 0.55 A/W, the ideality factor of 1.80 and 1.99, the maximum external quantum efficiency of 76% and 83.5%, and the built-in potential of 0.79 V and 0.72 V were obtained before and after annealing, respectively.

  9. Impurities and Growth Morphology in Diamond CVD

    NASA Astrophysics Data System (ADS)

    Koidl, Peter

    1996-03-01

    This paper reports on recent investigations of the structural evolution and morphogical control in the low-pressure deposition of diamond. It will be shown that minor gas contaminations may drastically influence the film structure and morphology. Gas additions that are substitutionally incorporated like nitrogen and boron are of special importance. Nitrogen at concentrations on the ppm level has been found to promote <100> textured growth and thus assists in forming smooth films with coplanar 100 facets.(R. Locher, C. Wild, N. Herres, D. Behr, P. Koidl, Appl. Phys. Lett. 65), 34 (1994) Boron - on the other hand - is shown to have an opposite effect: it destabilizes the 100 surface.(R. Locher, J. Wagner, F. Fuchs, M. Maier, P. Gonon, P. Koidl, Diamond Relat. Mater. 4), 678 (1995) In addition, both types of gas contaminations do influence the twin formation. The structure and morphology of CVD diamond films are strongly affected by competitive growth between 100- and 111-growth sectors as determined by the relative growth rate parameter α = √3 v_100/v_111.(C. Wild, R. Kohl, N. Herres, W. Müller-Sebert, P. Koidl, Diamond Relat. Mater. 3), 373 (1994) Using in-situ interferometry, it has been shown that nitrogen selectively increases the growth rate of 100 faces, while additional boron reduces it. The structural implications of nitrogen and boron additions are discussed as a result of their growth sector dependent reaction and incorporation and the resulting change of α.

  10. Application of Smoothed Particle MHD (SPMHD) techniques to the simulation of magnetically confined plasma dynamics

    NASA Astrophysics Data System (ADS)

    Vela-Vela, Luis; Sanchez, Raul; Reynolds-Barredo, J. Miguel

    2015-11-01

    Magnetically confined plasmas relevant for fusion scenarios are, to first approximation, well described by ideal and resistive MHD. This includes the description of their equilibrium and stability properties, as well as their medium-to-long term nonlinear evolution under external forcing. In many of these cases, one needs to deal with magnetic topologies that include magnetic islands, stochastic regions or that require the consideration of free-moving boundaries. The present work is part of an on-going effort to develop of a numerical code capable of dealing with these situations by taking advantage of the SPMHD formalism that, although widely used in astrophysical plasmas, is not widespread within the fusion community. SPMHD is a particle (i.e., Lagrangian) method particularly well-suited to deal with complicated boundaries while retaining great parallelization benefits. Here, we will report on the adaptation of the SPMHD equations to the case of magnetically confined plasmas, several benchmarking tests typical for MHD codes, and some preliminary results obtained for more elaborate scenarios. Our results suggest that our new code (EVA) can be very advantageous to deal with problems of current interest for the fusion community, including tokamaks and stellarators.

  11. The influence of heating rate on superconducting characteristics of MgB2 obtained by spark plasma sintering technique

    NASA Astrophysics Data System (ADS)

    Aldica, G.; Burdusel, M.; Popa, S.; Enculescu, M.; Pasuk, I.; Badica, P.

    2015-12-01

    Superconducting bulks of MgB2 were obtained by the Spark Plasma Sintering (SPS) technique. Different heating rates of 20, 100, 235, 355, and 475 °C/min were used. Samples have high density, above 95%. The onset critical temperature Tc, is about 38.8 K. There is an optimum heating rate of ∼100 °C/min to maximize the critical current density Jc0, the irreversibility field Hirr, the product (Jc0 x μ0Hirr), and to partially avoid formation of undesirable flux jumps at low temperatures. Significant microstructure differences were revealed for samples processed with low and high heating rates in respect to grain boundaries.

  12. Electrochemical delamination of CVD-grown graphene film: toward the recyclable use of copper catalyst.

    PubMed

    Wang, Yu; Zheng, Yi; Xu, Xiangfan; Dubuisson, Emilie; Bao, Qiaoliang; Lu, Jiong; Loh, Kian Ping

    2011-12-27

    The separation of chemical vapor deposited (CVD) graphene from the metallic catalyst it is grown on, followed by a subsequent transfer to a dielectric substrate, is currently the adopted method for device fabrication. Most transfer techniques use a chemical etching method to dissolve the metal catalysts, thus imposing high material cost in large-scale fabrication. Here, we demonstrate a highly efficient, nondestructive electrochemical route for the delamination of CVD graphene film from metal surfaces. The electrochemically delaminated graphene films are continuous over 95% of the surface and exhibit increasingly better electronic quality after several growth cycles on the reused copper catalyst, due to the suppression of quasi-periodical nanoripples induced by copper step edges. The electrochemical delamination process affords the advantages of high efficiency, low-cost recyclability, and minimal use of etching chemicals.

  13. Pulse-shape analysis for gamma background rejection in thermal neutron radiation using CVD diamond detectors

    NASA Astrophysics Data System (ADS)

    Kavrigin, P.; Finocchiaro, P.; Griesmayer, E.; Jericha, E.; Pappalardo, A.; Weiss, C.

    2015-09-01

    A novel technique for the rejection of gamma background from charged-particle spectra was demonstrated using a CVD diamond detector with a 6Li neutron converter installed at a thermal neutron beamline of the TRIGA research reactor at the Atominstitut (Vienna University of Technology). Spectra of the alpha particles and tritons of 6Li(n,T)4He thermal neutron capture reaction were separated from the gamma background by a new algorithm based on pulse-shape analysis. The thermal neutron capture in 6Li is already used for neutron flux monitoring, but the ability to remove gamma background allows using a CVD diamond detector for thermal neutron counting. The pulse-shape analysis can equally be applied to all cases where the charged products of an interaction are absorbed in the diamond and to other background particles that fully traverse the detector.

  14. Electrochemical delamination of CVD-grown graphene film: toward the recyclable use of copper catalyst.

    PubMed

    Wang, Yu; Zheng, Yi; Xu, Xiangfan; Dubuisson, Emilie; Bao, Qiaoliang; Lu, Jiong; Loh, Kian Ping

    2011-12-27

    The separation of chemical vapor deposited (CVD) graphene from the metallic catalyst it is grown on, followed by a subsequent transfer to a dielectric substrate, is currently the adopted method for device fabrication. Most transfer techniques use a chemical etching method to dissolve the metal catalysts, thus imposing high material cost in large-scale fabrication. Here, we demonstrate a highly efficient, nondestructive electrochemical route for the delamination of CVD graphene film from metal surfaces. The electrochemically delaminated graphene films are continuous over 95% of the surface and exhibit increasingly better electronic quality after several growth cycles on the reused copper catalyst, due to the suppression of quasi-periodical nanoripples induced by copper step edges. The electrochemical delamination process affords the advantages of high efficiency, low-cost recyclability, and minimal use of etching chemicals. PMID:22034835

  15. Wide-Gap Thin Film Si n-i-p Solar Cells Deposited by Hot-Wire CVD: Preprint

    SciTech Connect

    Wang, Q.; Iwaniczko, E.; Yang, J.; Lord, K.; Guha, S.; Wang, K.; Han, D.

    2002-05-01

    High-voltage wide bandgap thin-film Si n-i-p solar cells have been made using the hot-wire chemical vapor deposition (HWCVD) technique. The best open-circuit voltage (Voc) has exceeded 0.94 V in solar cells using HWCVD in the entire n-i-p structure. A Voc of 0.97V has been achieved using HWCVD in the n and i layers and plasma-enhanced (PE) CVD for the p layer. The high voltages are attributed to the wide-gap i layer and an improved p/i interface. The wide-gap i layer is obtained by using low substrate temperatures and sufficient hydrogen dilution during the growth of the i layer to arrive at the amorphous-to-microcrystalline phase transition region. The optical band gap (E04) of the i layer is found to be 1.90 eV. These high-voltage cells also exhibit good fill factors exceeding 0.7 with short-circuit-current densities of 8 to 10 mA/cm2 on bare stainless steel substrates. We have also carried out photoluminescence (PL) spectroscopy studies and found a correlation between Voc and the PL peak energy position.

  16. The Use of Plasma Vortexes in Creating Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Leith, Alexander; Alexander Leith Collaboration

    2016-03-01

    Carbon nanotubes have been created in a variety of ways such as arc discharge, laser ablation, and chemical vapor deposition (CVD). Each of these techniques has been proven to produce carbon nanotubes in small quantities in a lab setting. This is the problem that we have been addressing. Over the course of 16 months, we have been working on a new method of carbon nanotube production that is based around fluid dynamics and plasma. We have created the basic components to test this new way to produce carbon nanotubes. This research will ideally provide a new avenue for carbon nanotube production. Worked with Dr. Randal Tagg of the University of Colorado Denver.

  17. CVD facility electrical system captor/dapper study

    SciTech Connect

    SINGH, G.

    1999-10-28

    Project W-441, CVD Facility Electrical System CAPTOWDAPPER Study validates Meier's hand calculations. This study includes Load flow, short circuit, voltage drop, protective device coordination, and transient motor starting (TMS) analyses.

  18. Determination of rare earth elements in tomato plants by inductively coupled plasma mass spectrometry techniques.

    PubMed

    Spalla, S; Baffi, C; Barbante, C; Turetta, C; Turretta, C; Cozzi, G; Beone, G M; Bettinelli, M

    2009-10-30

    In recent years identification of the geographical origin of food has grown more important as consumers have become interested in knowing the provenance of the food that they purchase and eat. Certification schemes and labels have thus been developed to protect consumers and genuine producers from the improper use of popular brand names or renowned geographical origins. As the tomato is one of the major components of what is considered to be the healthy Mediterranean diet, it is important to be able to determine the geographical origin of tomatoes and tomato-based products such as tomato sauce. The aim of this work is to develop an analytical method to determine rare earth elements (RRE) for the control of the geographic origin of tomatoes. The content of REE in tomato plant samples collected from an agricultural area in Piacenza, Italy, was determined, using four different digestion procedures with and without HF. Microwave dissolution with HNO3 + H2O2 proved to be the most suitable digestion procedure. Inductively coupled plasma quadrupole mass spectrometry (ICPQMS) and inductively coupled plasma sector field plasma mass spectrometry (ICPSFMS) instruments, both coupled with a desolvation system, were used to determine the REE in tomato plants in two different laboratories. A matched calibration curve method was used for the quantification of the analytes. The detection limits (MDLs) of the method ranged from 0.03 ng g(-1) for Ho, Tm, and Lu to 2 ng g(-1) for La and Ce. The precision, in terms of relative standard deviation on six replicates, was good, with values ranging, on average, from 6.0% for LREE (light rare earth elements) to 16.5% for HREE (heavy rare earth elements). These detection limits allowed the determination of the very low concentrations of REE present in tomato berries. For the concentrations of REE in tomato plants, the following trend was observed: roots > leaves > stems > berries.

  19. Wear behavior of AISI 1090 steel modified by pulse plasma technique

    SciTech Connect

    Ayday, Aysun; Durman, Mehmet

    2012-09-06

    AISI 1090 steel was pulse plasma treated (PPT) using a Molybdenum electrode. Two different pulse numbers were chosen to obtain modified layers of 20{+-}5 {mu}m thickness. The dry sliding wear studies performed on this steel with and without PPT against an alumina ball counterpart showed that the PPT improved the wear resistance. The pulse number of the PPT modified layer was found to be highly influential in imparting the wear resistance to this steel, due to enhancement of surface hardness depending on treatment time.

  20. Locally conformal finite-difference time-domain techniques for particle-in-cell plasma simulation

    NASA Astrophysics Data System (ADS)

    Clark, R. E.; Welch, D. R.; Zimmerman, W. R.; Miller, C. L.; Genoni, T. C.; Rose, D. V.; Price, D. W.; Martin, P. N.; Short, D. J.; Jones, A. W. P.; Threadgold, J. R.

    2011-02-01

    The Dey-Mittra [S. Dey, R. Mitra, A locally conformal finite-difference time-domain (FDTD) algorithm for modeling three-dimensional perfectly conducting objects, IEEE Microwave Guided Wave Lett. 7 (273) 1997] finite-difference time-domain partial cell method enables the modeling of irregularly shaped conducting surfaces while retaining second-order accuracy. We present an algorithm to extend this method to include charged particle emission and absorption in particle-in-cell codes. Several examples are presented that illustrate the possible improvements that can be realized using the new algorithm for problems relevant to plasma simulation.

  1. Application of plasma gas modulation technique for improvement of the measurement of Mn emission intensity in ICP-AES.

    PubMed

    Kubota, K; Wagatsuma, K

    2001-01-01

    A phase-sensitive detection technique associated with a digital lock-in amplifier was applied for an improvement of the detection in ICP-AES. The lock-in amplifier works as an extremely narrow band pass filter. It can pick up the modulated signal, which has the same frequency as the reference signal, from any noise and thus it can improve the signal-to-noise ratio. Modulation of the ICP can be performed by mixing small amounts of air to argon as the outer gas cyclically, because the emission intensities of ionic lines are enhanced by using the mixed gas. An electromagnetic valve, which is placed in the outer-gas flow path, causes periodic variation in the air gas in the outer-gas flow, and thus switching the valve on/off can modulate the ICP. By choosing the appropriate conditions, the addition of air gas enhances the emission intensity of ionic lines more than that of the background, thus leading to improved signal-to-background ratios. At the same time the lock-in amplifier further enhances the ionic emissions because it picks up only the modulated part of the signal. By applying the plasma gas flow modulation technique the detection and the determination limits of the Mn II 257.610 nm line are improved in comparison with the conventional method. A change in plasma shape corresponding to the modulation frequency is observed when the ICP is modulated. PMID:11225355

  2. Electron-beam manipulation techniques in the SINBAD Linac for external injection in plasma wake-field acceleration

    NASA Astrophysics Data System (ADS)

    Marchetti, B.; Assmann, R.; Behrens, C.; Brinkmann, R.; Dorda, U.; Floettmann, K.; Hartl, I.; Huening, M.; Nie, Y.; Schlarb, H.; Zhu, J.

    2016-09-01

    The SINBAD facility (Short and INnovative Bunches and Accelerators at Desy) is foreseen to host various experiments in the field of production of ultra-short electron bunches and novel high gradient acceleration techniques. Besides studying novel acceleration techniques aiming to produce high brightness short electron bunches, the ARD group at DESY is working on the design of a conventional RF accelerator that will allow the production of low charge (0.5 pC - few pC) ultra-short electron bunches (having full width half maximum, FWHM, length ≤ 1 fs - few fs). The setup will allow the direct experimental comparison of the performance achievable by using different compression techniques (velocity bunching, magnetic compression, hybrid compression schemes). At a later stage the SINBAD linac will be used to inject such electron bunches into a laser driven Plasma Wakefield Accelerator, which imposes strong requirements on parameters such as the arrival time jitter and the pointing stability of the beam. In this paper we review the compression techniques that are foreseen at SINBAD and we underline the differences in terms of peak current, beam quality and arrival time stability.

  3. Techniques For Injection Of Pre-Charaterized Dust Into The Scrape Off Layer Of Fusion Plasma

    SciTech Connect

    Roquemore, A. L.; John, B.; Friesen, F.; Hartzfeld, K.; Mansfield, D. K.

    2011-07-21

    Introduction of micron-sized dust into the scrape-off layer (SOL) of a plasma has recently found many applications aimed primarily at determining dust behavior in future fusion reactors. The dust particles are typically composed of materials intrinsic to a fusion reactor. On DIII-D and TEXTOR carbon dust has been introduced into the SOL using a probe inserted from below into the divertor region. On NSTX, both Li and tungsten dust have been dropped from the top of the machine into the SOL throughout the duration of a discharge, by utilizing a vibrating piezoelectric based particle dropper. The original particle dropper was developed to inject passivated Li powder {approx} 40 {mu}m in diameter into the SOL to enhance plasma performance. A simplified version of the dropper was developed to introduce trace amounts of tungsten powder for only a few discharges, thus not requiring a large powder reservoir. The particles emit visible light from plasma interactions and can be tracked by either spectroscopic means or by fast frame rate visible cameras. This data can then be compared with dust transport codes such as DUSTT to make predictions of dust behavior in next-step devices such as ITER. For complete modeling results, it is desired to be able to inject pre-characterized dust particles in the SOL at various known poloidal locations, including near the vessel midplane. Purely mechanical methods of injecting particles are presently being studied using a modified piezoelectric-based powder dropper as a particle source and one of several piezo-based transducers to deflect the particles into the SOL. Vibrating piezo fans operating at 60 Hz with a deflection of {+-}2.5 cm can impart a significant horizontal boost in velocity. The highest injection velocities are expected from rotating paddle wheels capable of injecting particles at 10's of meters per second depending primarily on the rotation velocity and diameter of the wheel. Several injection concepts have been tested and

  4. Radioimmunoassay of human growth hormone: technique and application to plasma, cerebrospinal fluid, and pituitary extracts

    PubMed Central

    Thomas, Frances J.; Lloyd, H. M.; Thomas, M. J.

    1972-01-01

    A radioimmunoassay for human growth hormone using activated charcoal is described and its precision, accuracy, and sensitivity are defined. Results are presented for growth hormone measurements in plasma obtained during hypoglycaemia induced with insulin in patients of short stature and during glucose tolerance tests in patients with acromegaly. The method was used to measure growth hormone concentrations in cerebrospinal fluid and in extracts of pituitary tumours. No growth hormone was detected in the cerebrospinal fluid of patients without acromegaly. In patients with acromegaly, the concentration of growth hormone in cerebrospinal fluid was measurable and was considerably elevated in one patient with extrasellar extension of a pituitary tumour. Extracts of chromophobe pituitary tumours contained very small concentrations of growth hormone. In extracts of pituitary tumours removed from acromegalic patients, concentrations fell either below or within the normal range. PMID:5086220

  5. Determination of the Mechanical Properties of Plasma-Sprayed Hydroxyapatite Coatings Using the Knoop Indentation Technique

    NASA Astrophysics Data System (ADS)

    Hasan, Md. Fahad; Wang, James; Berndt, Christopher

    2015-06-01

    The microhardness and elastic modulus of plasma-sprayed hydroxyapatite coatings were evaluated using Knoop indentation on the cross section and on the top surface. The effects of indentation angle, testing direction, measurement location and applied load on the microhardness and elastic modulus were investigated. The variability and distribution of the microhardness and elastic modulus data were statistically analysed using the Weibull modulus distribution. The results indicate that the dependence of microhardness and elastic modulus on the indentation angle exhibits a parabolic shape. Dependence of the microhardness values on the indentation angle follows Pythagoras's theorem. The microhardness, Weibull modulus of microhardness and Weibull modulus of elastic modulus reach their maximum at the central position (175 µm) on the cross section of the coatings. The Weibull modulus of microhardness revealed similar values throughout the thickness, and the Weibull modulus of elastic modulus shows higher values on the top surface compared to the cross section.

  6. Hydrogen analysis of zircaloy tube used in nuclear power station using laser plasma technique

    SciTech Connect

    Kurniawan, Koo Hendrik; Lie, Tjung Jie; Idris, Nasrullah; Kobayashi, Takao; Maruyama, Tadashi; Kagawa, Kiichiro; Tjia, May On; Chumakov, Alexander Nikitich

    2004-12-01

    It is shown that remarkable improvements essential to a quantitative spectrochemical analysis of hydrogen emissions from the zircaloy samples were achieved when the low-pressure surrounding air used in the previous experiment of Nd-YAG laser-induced shockwave plasma was replaced by an inert gas. Using the high-purity (99.999%) nitrogen gas at 1.5 Torr, a linear calibration curve of the HI 656.2 nm emission line was obtained with a zero intercept from the zircaloy samples prepared with various hydrogen concentrations. Further, when the surrounding nitrogen gas was replaced by a helium gas, more than an order of magnitude enhancement was obtained on the signal-to-noise ratio, yielding a detection limit of less than 5 ppm.

  7. Automated standardization technique for an inductively-coupled plasma emission spectrometer

    USGS Publications Warehouse

    Garbarino, J.R.; Taylor, H.E.

    1982-01-01

    The manifold assembly subsystem described permits real-time computer-controlled standardization and quality control of a commercial inductively-coupled plasma atomic emission spectrometer. The manifold assembly consists of a branch-structured glass manifold, a series of microcomputer-controlled solenoid valves, and a reservoir for each standard. Automated standardization involves selective actuation of each solenoid valve that permits a specific mixed standard solution to be pumped to the nebulizer of the spectrometer. Quality control is based on the evaluation of results obtained for a mixed standard containing 17 analytes, that is measured periodically with unknown samples. An inaccurate standard evaluation triggers restandardization of the instrument according to a predetermined protocol. Interaction of the computer-controlled manifold assembly hardware with the spectrometer system is outlined. Evaluation of the automated standardization system with respect to reliability, simplicity, flexibility, and efficiency is compared to the manual procedure. ?? 1982.

  8. Radio Frequency Transistors and Circuits Based on CVD MoS2.

    PubMed

    Sanne, Atresh; Ghosh, Rudresh; Rai, Amritesh; Yogeesh, Maruthi Nagavalli; Shin, Seung Heon; Sharma, Ankit; Jarvis, Karalee; Mathew, Leo; Rao, Rajesh; Akinwande, Deji; Banerjee, Sanjay

    2015-08-12

    We report on the gigahertz radio frequency (RF) performance of chemical vapor deposited (CVD) monolayer MoS2 field-effect transistors (FETs). Initial DC characterizations of fabricated MoS2 FETs yielded current densities exceeding 200 μA/μm and maximum transconductance of 38 μS/μm. A contact resistance corrected low-field mobility of 55 cm(2)/(V s) was achieved. Radio frequency FETs were fabricated in the ground-signal-ground (GSG) layout, and standard de-embedding techniques were applied. Operating at the peak transconductance, we obtain short-circuit current-gain intrinsic cutoff frequency, fT, of 6.7 GHz and maximum intrinsic oscillation frequency, fmax, of 5.3 GHz for a device with a gate length of 250 nm. The MoS2 device afforded an extrinsic voltage gain Av of 6 dB at 100 MHz with voltage amplification until 3 GHz. With the as-measured frequency performance of CVD MoS2, we provide the first demonstration of a common-source (CS) amplifier with voltage gain of 14 dB and an active frequency mixer with conversion gain of -15 dB. Our results of gigahertz frequency performance as well as analog circuit operation show that large area CVD MoS2 may be suitable for industrial-scale electronic applications. PMID:26134588

  9. Synthesis and Characterization of Large-Area Graphene Directly CVD-Grown on h-BN

    NASA Astrophysics Data System (ADS)

    Kim, Minwoo; Song, Young; Wang, Min; Jang, Seong-Kyu; Lee, Sungjoo; Jang, Won-Jun; Kahng, Se-Jong; Graphene synthesis Collaboration; Characterization Collaboration

    2013-03-01

    As an ideal substrate for graphene, hexagonal boron nitride (h-BN) has been utilized and studied extensively by transfer technique, which still has a high chance to have impurities at the graphene/h-BN interface. Here we report direct CVD growth of graphene on large area h-BN film. AFM and Raman spectroscopy measurements show that there is only one monolayer of graphene, and whose unperturbed electronic structures are also confirmed by electron transport measurements and scanning tunneling spectroscopy. High resolution TEM images for cross-section taken before and after transferring graphene/h-BN on to SiO2 indicate this CVD-grown hybrid structure is robust enough. Based on this new method, high quality and large area graphene on h-BN film with a clean interface can be synthesized for the application of electronic devices, and can fill the missing steps to grow fully CVD-grown super-structure of graphene and h-BN. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (Grant Numbers: 2009-0083540, 2012R1A1A2020089 and 2012R1A1A1041416).

  10. Uniform and selective CVD growth of carbon nanotubes and nanofibres on arbitrarily microstructured silicon surfaces

    NASA Astrophysics Data System (ADS)

    Hart, A. J.; Boskovic, B. O.; Chuang, A. T. H.; Golovko, V. B.; Robertson, J.; Johnson, B. F. G.; Slocum, A. H.

    2006-03-01

    Carbon nanotubes (CNTs) and nanofibres (CNFs) are grown on bulk-micromachined silicon surfaces by thermal and plasma-enhanced chemical vapour deposition (PECVD), with catalyst deposition by electron beam evaporation or from a colloidal solution of cobalt nanoparticles. Growth on the peaked topography of plasma-etched silicon 'micrograss' supports, as well as on sidewalls of vertical structures fabricated by deep-reactive ion etching demonstrates the performance of thermal CVD and PECVD in limiting cases of surface topography. In thermal CVD, uniform films of tangled single-walled CNTs (SWNTs) coat the structures despite oblique-angle effects on the thickness of the catalyst layers deposited by e-beam evaporation. In PECVD, forests of aligned CNFs protrude from areas which are favourably wet by the colloidal catalyst, demonstrating selective growth based on surface texture. These surface preparation principles can be used to grow a wide variety of nanostructures on microstructured surfaces having arbitrary topography, giving substrates with hierarchical microscale and nanoscale surface textures. Such substrates could be used to study cell and neuronal growth, influence liquid-solid wetting behaviour, and as functional elements in microelectronic and micromechanical devices.

  11. Compositional study of silicon oxynitride thin films deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition technique

    SciTech Connect

    Baumann, H.; Sah, R.E.

    2005-05-01

    We have used backscattering spectrometry and {sup 15}N({sup 1}H,{alpha},{gamma}){sup 12}C nuclear reaction analysis techniques to study in detail the variation in the composition of silicon oxynitride films with deposition parameters. The films were deposited using 2.45 GHz electron cyclotron resonance plasma-enhanced chemical vapor deposition (PECVD) technique from mixtures of precursors argon, nitrous oxide, and silane at deposition temperature 90 deg. C. The deposition pressure and nitrous oxide-to-silane gas flow rates ratio have been found to have a pronounced influence on the composition of the films. When the deposition pressure was varied for a given nitrous oxide-to-silane gas flow ratio, the amount of silicon and nitrogen increased with the deposition pressure, while the amount of oxygen decreased. For a given deposition pressure, the amount of incorporated nitrogen and hydrogen decreased while that of oxygen increased with increasing nitrous oxide-to-silane gas flow rates ratio. For nitrous oxide-to-silane gas flow ratio of 5, we obtained films which contained neither chemically bonded nor nonbonded nitrogen atoms as revealed by the results of infrared spectroscopy, backscattering spectrometry, and nuclear reaction analysis. Our results demonstrate the nitrogen-free nearly stoichiometric silicon dioxide films can be prepared from a mixture of precursors argon, nitrous oxide, and silane at low substrate temperature using high-density PECVD technique. This avoids the use of a hazardous and an often forbidden pair of silane and oxygen gases in a plasma reactor.

  12. Scalable graphene production: perspectives and challenges of plasma applications.

    PubMed

    Levchenko, Igor; Ostrikov, Kostya Ken; Zheng, Jie; Li, Xingguo; Keidar, Michael; B K Teo, Kenneth

    2016-05-19

    Graphene, a newly discovered and extensively investigated material, has many unique and extraordinary properties which promise major technological advances in fields ranging from electronics to mechanical engineering and food production. Unfortunately, complex techniques and high production costs hinder commonplace applications. Scaling of existing graphene production techniques to the industrial level without compromising its properties is a current challenge. This article focuses on the perspectives and challenges of scalability, equipment, and technological perspectives of the plasma-based techniques which offer many unique possibilities for the synthesis of graphene and graphene-containing products. The plasma-based processes are amenable for scaling and could also be useful to enhance the controllability of the conventional chemical vapour deposition method and some other techniques, and to ensure a good quality of the produced graphene. We examine the unique features of the plasma-enhanced graphene production approaches, including the techniques based on inductively-coupled and arc discharges, in the context of their potential scaling to mass production following the generic scaling approaches applicable to the existing processes and systems. This work analyses a large amount of the recent literature on graphene production by various techniques and summarizes the results in a tabular form to provide a simple and convenient comparison of several available techniques. Our analysis reveals a significant potential of scalability for plasma-based technologies, based on the scaling-related process characteristics. Among other processes, a greater yield of 1 g × h(-1) m(-2) was reached for the arc discharge technology, whereas the other plasma-based techniques show process yields comparable to the neutral-gas based methods. Selected plasma-based techniques show lower energy consumption than in thermal CVD processes, and the ability to produce graphene flakes of

  13. Scalable graphene production: perspectives and challenges of plasma applications.

    PubMed

    Levchenko, Igor; Ostrikov, Kostya Ken; Zheng, Jie; Li, Xingguo; Keidar, Michael; B K Teo, Kenneth

    2016-05-19

    Graphene, a newly discovered and extensively investigated material, has many unique and extraordinary properties which promise major technological advances in fields ranging from electronics to mechanical engineering and food production. Unfortunately, complex techniques and high production costs hinder commonplace applications. Scaling of existing graphene production techniques to the industrial level without compromising its properties is a current challenge. This article focuses on the perspectives and challenges of scalability, equipment, and technological perspectives of the plasma-based techniques which offer many unique possibilities for the synthesis of graphene and graphene-containing products. The plasma-based processes are amenable for scaling and could also be useful to enhance the controllability of the conventional chemical vapour deposition method and some other techniques, and to ensure a good quality of the produced graphene. We examine the unique features of the plasma-enhanced graphene production approaches, including the techniques based on inductively-coupled and arc discharges, in the context of their potential scaling to mass production following the generic scaling approaches applicable to the existing processes and systems. This work analyses a large amount of the recent literature on graphene production by various techniques and summarizes the results in a tabular form to provide a simple and convenient comparison of several available techniques. Our analysis reveals a significant potential of scalability for plasma-based technologies, based on the scaling-related process characteristics. Among other processes, a greater yield of 1 g × h(-1) m(-2) was reached for the arc discharge technology, whereas the other plasma-based techniques show process yields comparable to the neutral-gas based methods. Selected plasma-based techniques show lower energy consumption than in thermal CVD processes, and the ability to produce graphene flakes of

  14. Scalable graphene production: perspectives and challenges of plasma applications

    NASA Astrophysics Data System (ADS)

    Levchenko, Igor; Ostrikov, Kostya (Ken); Zheng, Jie; Li, Xingguo; Keidar, Michael; B. K. Teo, Kenneth

    2016-05-01

    Graphene, a newly discovered and extensively investigated material, has many unique and extraordinary properties which promise major technological advances in fields ranging from electronics to mechanical engineering and food production. Unfortunately, complex techniques and high production costs hinder commonplace applications. Scaling of existing graphene production techniques to the industrial level without compromising its properties is a current challenge. This article focuses on the perspectives and challenges of scalability, equipment, and technological perspectives of the plasma-based techniques which offer many unique possibilities for the synthesis of graphene and graphene-containing products. The plasma-based processes are amenable for scaling and could also be useful to enhance the controllability of the conventional chemical vapour deposition method and some other techniques, and to ensure a good quality of the produced graphene. We examine the unique features of the plasma-enhanced graphene production approaches, including the techniques based on inductively-coupled and arc discharges, in the context of their potential scaling to mass production following the generic scaling approaches applicable to the existing processes and systems. This work analyses a large amount of the recent literature on graphene production by various techniques and summarizes the results in a tabular form to provide a simple and convenient comparison of several available techniques. Our analysis reveals a significant potential of scalability for plasma-based technologies, based on the scaling-related process characteristics. Among other processes, a greater yield of 1 g × h-1 m-2 was reached for the arc discharge technology, whereas the other plasma-based techniques show process yields comparable to the neutral-gas based methods. Selected plasma-based techniques show lower energy consumption than in thermal CVD processes, and the ability to produce graphene flakes of various

  15. Expert system and process optimization techniques for real-time monitoring and control of plasma processes

    NASA Astrophysics Data System (ADS)

    Cheng, Jie; Qian, Zhaogang; Irani, Keki B.; Etemad, Hossein; Elta, Michael E.

    1991-03-01

    To meet the ever-increasing demand of the rapidly-growing semiconductor manufacturing industry it is critical to have a comprehensive methodology integrating techniques for process optimization real-time monitoring and adaptive process control. To this end we have accomplished an integrated knowledge-based approach combining latest expert system technology machine learning method and traditional statistical process control (SPC) techniques. This knowledge-based approach is advantageous in that it makes it possible for the task of process optimization and adaptive control to be performed consistently and predictably. Furthermore this approach can be used to construct high-level and qualitative description of processes and thus make the process behavior easy to monitor predict and control. Two software packages RIST (Rule Induction and Statistical Testing) and KARSM (Knowledge Acquisition from Response Surface Methodology) have been developed and incorporated with two commercially available packages G2 (real-time expert system) and ULTRAMAX (a tool for sequential process optimization).

  16. Effluents from MBT plants: Plasma techniques for the treatment of VOCs

    SciTech Connect

    Ragazzi, Marco; Tosi, Paolo; Rada, Elena Cristina; Torretta, Vincenzo; Schiavon, Marco

    2014-11-15

    Highlights: • Dielectric Barrier Discharge was applied to remove methyl ethyl ketone from air. • Methyl ethyl ketone was chosen since it represents emissions from MBT plants. • The removal efficiency was linearly dependent on time, power and energy density. • Besides CO{sub 2}, methyl nitrate and 2,3-butanedione were the main byproducts formed. • The removal efficiency can be increased by increasing the convective flow. - Abstract: Mechanical–biological treatments (MBTs) of urban waste are growing in popularity in many European countries. Recent studies pointed out that their contribution in terms of volatile organic compounds (VOCs) and other air pollutants is not negligible. Compared to classical removal technologies, non-thermal plasmas (NTP) showed better performances and low energy consumption when applied to treat lowly concentrated streams. Therefore, to study the feasibility of the application of NTP to MBTs, a Dielectric Barrier Discharge reactor was applied to treat a mixture of air and methyl ethyl ketone (MEK), to simulate emissions from MBTs. The removal efficiency of MEK was linearly dependent upon time, power and specific input energy. Only 2–4% of MEK was converted to carbon dioxide (CO{sub 2}), the remaining carbon being involved in the formation of byproducts (methyl nitrate and 2,3-butanedione, especially). For future development of pilot-scale reactors, acting on residence time, power, convective flow and catalysts will help finding a compromise between energy consumption, desired abatement and selectivity to CO{sub 2}.

  17. Pressure dependent tailored attributes of silicon nanoneedles grown by VHF plasma technique

    NASA Astrophysics Data System (ADS)

    Mohammed, Yasir Hussein; Sakrani, Samsudi Bin; Rohani, Md Supar

    2016-06-01

    Gold (Au) catalysts assisted well-aligned silicon nanoneedles (SiNNs) are synthesized using very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) method. The tailored morphology and the optical reflectance of such NNs are inspected as a function of varying reactor pressure (200-800 mTorr). FESEM images revealed the growth of high density SiNNs with diameter ranging from 45 to 600 nm and length as much as 5.66 ± 0.2 μm. Overall morphology of these NNs are found to be highly sensitive to the pressure variation, where appreciably aligned thinner NNs are achieved at 600 mTorr pressure. The presence of globule at the NNs tip authenticated their VLS mechanism mediated growth. The reactor pressure sensitivity of the aspect ratio, lattice parameters, Raman modes, and reflectance are demonstrated. XRD patterns manifested SiNNs cubic crystalline phase with preferred orientation along <111> direction. The occurrence of NNs high crystallinity is further supported by the Raman and HRTEM data. The reflectance of SiNNs grown at 600 mTorr exhibited remarkable reduction (˜6.3%) than those obtained at other pressures. This reactor pressure dependent significant modification in the physical properties of synthesized SiNNs may be prospective for the development of optoelectronics.

  18. Techniques for mass resolution improvement achieved by typical plasma mass analyzers: Modeling and simulations

    NASA Astrophysics Data System (ADS)

    Nicolaou, Georgios; Yamauchi, Masatoshi; Wieser, Martin; Barabash, Stas; Fedorov, Andrei

    2016-04-01

    Mass separation and particularly distinction between atomic ions and molecular ions are essential in understanding a wide range of plasma environments, with each consisted of different species with various properties. In this study we present the optimization results of light-weight (about 2 kg) magnetic mass analyzers with high g-factor for Rosetta (Ion Composition Analyser: ICA) and for Mars Express and Venus Express (Ion Mass Analyser: IMA). For the instrument's optimization we use SIMION, a 3D ion tracing software in which we can trace particle beams of several energies and directions, passing through the instrument's units. We first reproduced ICA and IMA results, which turned out to be different from simple models for low energy (< 100 eV). We then change the mechanical structure of several units of the instrument and we quantify the new mass resolution achieved with each change. Our goal is to find the optimal instrument's structure, which will allow us to achieve a proper mass resolution to distinguish atomic nitrogen from atomic oxygen for the purposes of a future magnetospheric mission.

  19. Effluents from MBT plants: plasma techniques for the treatment of VOCs.

    PubMed

    Ragazzi, Marco; Tosi, Paolo; Rada, Elena Cristina; Torretta, Vincenzo; Schiavon, Marco

    2014-11-01

    Mechanical-biological treatments (MBTs) of urban waste are growing in popularity in many European countries. Recent studies pointed out that their contribution in terms of volatile organic compounds (VOCs) and other air pollutants is not negligible. Compared to classical removal technologies, non-thermal plasmas (NTP) showed better performances and low energy consumption when applied to treat lowly concentrated streams. Therefore, to study the feasibility of the application of NTP to MBTs, a Dielectric Barrier Discharge reactor was applied to treat a mixture of air and methyl ethyl ketone (MEK), to simulate emissions from MBTs. The removal efficiency of MEK was linearly dependent upon time, power and specific input energy. Only 2-4% of MEK was converted to carbon dioxide (CO2), the remaining carbon being involved in the formation of byproducts (methyl nitrate and 2,3-butanedione, especially). For future development of pilot-scale reactors, acting on residence time, power, convective flow and catalysts will help finding a compromise between energy consumption, desired abatement and selectivity to CO2.

  20. Pressure dependent tailored attributes of silicon nanoneedles grown by VHF plasma technique

    NASA Astrophysics Data System (ADS)

    Mohammed, Yasir Hussein; Sakrani, Samsudi Bin; Rohani, Md Supar

    2016-06-01

    Gold (Au) catalysts assisted well-aligned silicon nanoneedles (SiNNs) are synthesized using very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) method. The tailored morphology and the optical reflectance of such NNs are inspected as a function of varying reactor pressure (200-800 mTorr). FESEM images revealed the growth of high density SiNNs with diameter ranging from 45 to 600 nm and length as much as 5.66 ± 0.2 μm. Overall morphology of these NNs are found to be highly sensitive to the pressure variation, where appreciably aligned thinner NNs are achieved at 600 mTorr pressure. The presence of globule at the NNs tip authenticated their VLS mechanism mediated growth. The reactor pressure sensitivity of the aspect ratio, lattice parameters, Raman modes, and reflectance are demonstrated. XRD patterns manifested SiNNs cubic crystalline phase with preferred orientation along <111> direction. The occurrence of NNs high crystallinity is further supported by the Raman and HRTEM data. The reflectance of SiNNs grown at 600 mTorr exhibited remarkable reduction (∼6.3%) than those obtained at other pressures. This reactor pressure dependent significant modification in the physical properties of synthesized SiNNs may be prospective for the development of optoelectronics.

  1. Progress Toward a New Technique for Measuring Local Electric Field Fluctuations in High Temperature Plasmas

    NASA Astrophysics Data System (ADS)

    Bakken, M. R.; Burke, M. G.; Fonck, R. J.; Lewicki, B. T.; Liben, M. M.; Thompson, D. S.; Winz, G. R.

    2015-11-01

    A new diagnostic measuring local Ez(r,t) fluctuations is being developed at the Pegasus Toroidal Experiment. A novel multiple volume phase holographic grating spectrometer, designed to have high resolution (0.25Å) and high étendue (U = 0.01cm2-ster), measures the line separation of the π components of the Hα motional Stark spectrum of emitted beam light. The spectra are recorded at high frequency (fNy ~ 500kHz) by a high speed CMOS imaging detector. The groove density of the objective grating is varied linearly along its surface to counter geometric Doppler broadening. A low divergence (Ω ~ 0.5o) , 80kV, 2.5A H0 diagnostic neutral beam is being deployed on Pegasus. The beam uses a washer-stack arc ion source to maximize full energy species fraction in the injected neutral beam. Laboratory tests of the ion source demonstrate stable, repeatable plasmas with Te <= 20eV and ne ~ 5x1017m-3, sufficient to sustain a 6mA/cm2 current density at the focal plane for up to 20ms. A three phase resonant converter power supply, with low amplitude (δV/80kV ~ 0.05%), high frequency (frip ~ 280kHz) ripple, is in development to provide the 80kV accelerator power. This research supported by US D.O.E. Grant DE-FG02-89ER53296.

  2. Remote sensing of auroral E region plasma structures by radio, radar, and UV techniques at solar minimum

    SciTech Connect

    Basu, S.; Valladares, C.E. ); Basu, S.; Eastes, R.; Huffman, R.E. ); Daniell, R.E. ); Chaturvedi, P.K. ); Livingston, R.C. )

    1993-02-01

    The unique capability of the Polar BEAR satellite to simultaneously image auroral luminosities at multiple ultraviolet (UV) wavelengths and to remote sense large-scale (hundreds to tens of kilometers) and small-scale (kilometers to hundreds of meters) plasma density structures with its multifrequency beacon package is utilized to probe the auroral E region in the vicinity of the incoherent scatter radar (ISR) facility near Sondrestrom. In particular, we present coordinated observations on two nights obtained during the sunspot minimum (sunspot number < 10) January-February 1987 period when good spatial and temporal conjunction was obtained between Polar BEAR overflights and Sondrestrom ISR measurements. With careful coordinated observations we were able to confirm that the energetic particle precipitation responsible for the UV emissions causes the electron density increases in the E region. The integrations up to the topside of these ISR electron density profiles were consistent with the total electron content (TEC) measured by the Polar BEAR satellite. An electron transport model was utilized to determine quantitatively the electron density profiles which could be produced by the particle precipitation, which also produced multiple UV emissions measured by the imager; these profiles were found to be in good agreement with the observed ISR profiles in the E region. This outer scale size is also consistent with the measured phase to amplitude scintillation ratio. An estimate of the linear growth rate of the gradient-drift instability in the E region shows that these plasma density irregularities could have been generated by this process. The mutual consistency of these different sets of measurements provides confidence in the ability of the different techniques to remote sense large- and small-scale plasma density structures in the E region at least during sunspot minimum when the convection-dominated high-latitude F region is fairly weak. 56 refs., 16 figs.

  3. Multi-energy soft-x-ray technique for impurity transport measurements in the fusion plasma edge

    NASA Astrophysics Data System (ADS)

    Clayton, D. J.; Tritz, K.; Stutman, D.; Finkenthal, M.; Kaye, S. M.; Kumar, D.; LeBlanc, B. P.; Paul, S.; Sabbagh, S. A.

    2012-10-01

    A new diagnostic technique was developed to produce high-resolution impurity transport measurements of the steep-gradient edge of fusion plasmas. Perturbative impurity transport measurements were performed for the first time in the NSTX plasma edge (r/a ˜ 0.6 to the SOL) with short neon gas puffs, and the resulting line and continuum emission was measured with the new edge multi-energy soft-x-ray (ME-SXR) diagnostic. Neon transport is modeled with the radial impurity transport code STRAHL and the resulting x-ray emission is computed using the ADAS atomic database. The radial transport coefficient profiles D(r) and v(r), and the particle flux from the gas puff Φ(t), are the free parameters in this model and are varied to find the best fit to experimental x-ray emissivity measurements, with bolometry used to constrain the impurity source. Initial experiments were successful and results were consistent with previous measurements of core impurity transport and neoclassical transport calculations. New diagnostic tools will be implemented on NSTX-U to further improve these transport measurements.

  4. Growth of controllable ZnO film by atomic layer deposition technique via inductively coupled plasma treatment

    SciTech Connect

    Huang, Hsin-Wei; Chang, Wen-Chih; Lin, Su-Jien; Chueh, Yu-Lun

    2012-12-15

    An inductively coupled plasma technique (ICP), namely, remote-plasma treatment was introduced to ionize the water molecules as the precursor for the deposition of ZnO film via the atomic layer deposition processes. Compared with the H{sub 2}O gas as the precursor for the ALD growth, the ionized water molecules can provide a lesser energy to uniformly stabilize oxidization processes, resulting in a better film quality with a higher resistivity owing to less formation of intrinsic defects at a lower growth temperature. The relationship between resistivity and formation mechanisms have been discussed and investigated through analyses of atomic force microscopy, photonluminescence, and absorption spectra, respectively. Findings indicate that the steric hindrance of the ligands plays an important rule for the ALD-ZnO film sample with the ICP treatment while the limited number of bonding sites will be dominant for the ALD-ZnO film without the ICP treatment owing to decreasing of the reactive sites via the ligand-exchange reaction during the dissociation process. Finally, the enhanced aspect-ratio into the anodic aluminum oxide with the better improved uniform coating of ZnO layer after the ICP treatment was demonstrated, providing an important information for a promising application in electronics based on ZnO ALD films.

  5. Changes in CVD risk factors in the activity counseling trial

    PubMed Central

    Baruth, Meghan; Wilcox, Sara; Sallis, James F; King, Abby C; Marcus, Bess H; Blair, Steven N

    2011-01-01

    Primary care facilities may be a natural setting for delivering interventions that focus on behaviors that improve cardiovascular disease (CVD) risk factors. The purpose of this study was to examine the 24-month effects of the Activity Counseling Trial (ACT) on CVD risk factors, to examine whether changes in CVD risk factors differed according to baseline risk factor status, and to examine whether changes in fitness were associated with changes in CVD risk factors. ACT was a 24-month multicenter randomized controlled trial to increase physical activity. Participants were 874 inactive men and women aged 35–74 years. Participants were randomly assigned to one of three arms that varied by level of counseling, intensity, and resource requirements. Because there were no significant differences in change over time between arms on any of the CVD risk factors examined, all arms were combined, and the effects of time, independent of arm, were examined separately for men and women. Time × Baseline risk factor status interactions examined whether changes in CVD risk factors differed according to baseline risk factor status. Significant improvements in total cholesterol, high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol, the ratio of total cholesterol to HDL-C, and triglycerides were seen in both men and women who had high (or low for HDL-C) baseline levels of risk factors, whereas significant improvements in diastolic blood pressure were seen only in those men with high baseline levels. There were no improvements in any risk factors among participants with normal baseline levels. Changes in fitness were associated with changes in a number of CVD risk factors. However, most relationships disappeared after controlling for changes in body weight. Improvements in lipids from the ACT interventions could reduce the risk of coronary heart disease in people with already high levels of lipids by 16%–26% in men and 11%–16% in women

  6. Preparation and mechanism of nanometer Al{sub 5}O{sub 6}N via shock wave plasma technique

    SciTech Connect

    Lei Fengbin; Wang Zuoshan Zhao Baoguo

    2009-01-08

    Cubic Al{sub 5}O{sub 6}N nanocrystals were successfully synthesized via a novel strategy called shock wave plasma technique, using trinitrotoluene (TNT) and aluminum powder as raw materials and water as protection medium. The precursor including carbon and Al{sub 5}O{sub 6}N was engendered firstly during the detonation of compound dynamite, and then the pure Al{sub 5}O{sub 6}N nanoparticles were obtained when the carbon was removed through calcining at high temperature. The precursor and the final as-synthesized Al{sub 5}O{sub 6}N powder were characterized by X-ray diffraction (XRD), Raman spectrum and high-resolution transmission electron microscope (HRTEM), respectively. The calcining temperature schedule of the precursor was decided through DTA/TG analysis. The results indicate that the precursor consists of 37.7% carbon and 62.3 deg. C Al{sub 5}O{sub 6}N. After calcining at 600 deg. C for 1 h, the average diameter of the as-synthesized Al{sub 5}O{sub 6}N nanocrystal is 30-40 nm and the morphology micrograph takes on uniform spherical shape. The lattice parameters are consistent completely with the standard cubic Al{sub 5}O{sub 6}N (JCPDS 48-0686). The well-dispersed Al{sub 5}O{sub 6}N nanocrystals synthesized by shock wave plasma technique can be attributed to the covering of carbon and fast cooling of water medium. A possible reaction mechanism was also proposed preliminarily based on the experimental results.

  7. Choice of anesthetic technique on plasma concentrations of interleukins and cell adhesion molecules

    PubMed Central

    2013-01-01

    Background Whether inflammatory responses to surgery are comparably activated during total intravenous anesthesia (TIVA) and during volatile anesthesia remains unclear. We thus compared the perioperative effects of TIVA and isoflurane anesthesia on plasma concentrations of proinflammatory and anti-inflammatory interleukins and cell adhesion molecules. Methods Patients having laparoscopic cholecystectomies were randomly allocated to two groups: 44 were assigned to TIVA and 44 to isoflurane anesthesia. IL-1β, IL-6, IL-8, IL-10, IL-13, and the cellular adhesion molecules intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 were determined preoperatively, before incision, and at 2 and 24 hours postoperatively. Our primary outcomes were area-under-the-curve cytokine and adhesion molecule concentrations over 24 postoperative hours. Results The only statistically significant difference in area-under-the-curve concentrations was for IL-6, which was greater in patients given isoflurane:78 (95% confidence interval (CI): 52 to 109) pg/ml versus 33 (22 to 50) pg/ml, P= 0.006. Two hours after surgery, IL-6 was significantly greater than baseline in patients assigned to isoflurane: 47 (95% CI: 4 to 216, P<0.001) pg/ml versus 18 (95%CI: 4 to 374, P<0.001) pg/ml in the TIVA group. In contrast, IL-10 was significantly greater in patients assigned to TIVA: 20 (95% CI: 2 to 140, P<0.001) pg/ml versus 12 (95% CI: 3 to 126, P<0.001) pg/ml. By 24 hours after surgery, concentrations were generally similar between study groups and similar to baseline values. Conclusion The only biomarker whose postoperative area-under-the-curve concentrations differed significantly as a function of anesthetic management was IL-6. Two hours after surgery, IL-6 concentrations were significantly greater in patients given isoflurane than TIVA. However, the differences were modest and seem unlikely to prove clinically important. Further studies are needed. PMID:24472144

  8. Alternative Techniques for Injecting Massive Quantities of Gas for Plasma Disruption Mitigation

    SciTech Connect

    Combs, Stephen Kirk; Meitner, Steven J; Caughman, John B; Commaux, Nicolas JC; Fehling, Dan T; Foust, Charles R; Jernigan, Thomas C; McGill, James M; Parks, P. B.; Rasmussen, David A

    2010-01-01

    Injection of massive quantities of noble gases or D2 has proven to be effective at mitigating some of the deleterious effects of disruptions in tokamaks. Two alternative methods that might offer some advantages over the present technique for massive gas injection are shattering massive pellets and employing closecoupled rupture disks. Laboratory testing has been carried out to evaluate their feasibility. For the study of massive pellets, a pipe gun pellet injector cooled with a cryogenic refrigerator was fitted with a relatively large barrel (16.5 mm bore), and D2 and Ne pellets were made and were accelerated to speeds of ~600 and 300 m/s, respectively. Based on the successful proof-of-principle testing with the injector and a special double-impact target to shatter pellets, a similar system has been prepared and installed on DIII-D, with preliminary experiments already carried out. To study the applicability of rupture disks for disruption mitigation, a simple test apparatus was assembled in the lab. Commercially available rupture disks of 1 in. nominal diameter were tested at conditions relevant for the application on tokamaks, including tests with Ar and He gases and rupture pressures of ~54 bar. Some technical and practical issues of implementing this technique on a tokamak are discussed.

  9. Circulating and Dietary Omega‐3 and Omega‐6 Polyunsaturated Fatty Acids and Incidence of CVD in the Multi‐Ethnic Study of Atherosclerosis

    PubMed Central

    de Oliveira Otto, Marcia C.; Wu, Jason H. Y.; Baylin, Ana; Vaidya, Dhananjay; Rich, Stephen S.; Tsai, Michael Y.; Jacobs, David R.; Mozaffarian, Dariush

    2013-01-01

    Background Dietary guidelines support intake of polyunsaturated fatty acids (PUFAs) in fish and vegetable oils. However, some controversy remains about benefits of PUFAs, and most prior studies have relied on self‐reported dietary assessment in relatively homogeneous populations. Methods and Results In a multiethnic cohort of 2837 US adults (whites, Hispanics, African Americans, Chinese Americans), plasma phospholipid PUFAs were measured at baseline (2000–2002) using gas chromatography and dietary PUFAs estimated using a food frequency questionnaire. Incident cardiovascular disease (CVD) events (including coronary heart disease and stroke; n=189) were prospectively identified through 2010 during 19 778 person‐years of follow‐up. In multivariable‐adjusted Cox models, circulating n‐3 eicosapentaenoic acid and docosahexaenoic acid were inversely associated with incident CVD, with extreme‐quartile hazard ratios (95% CIs) of 0.49 for eicosapentaenoic acid (0.30 to 0.79; Ptrend=0.01) and 0.39 for docosahexaenoic acid (0.22 to 0.67; Ptrend<0.001). n‐3 Docosapentaenoic acid (DPA) was inversely associated with CVD in whites and Chinese, but not in other race/ethnicities (P‐interaction=0.01). No significant associations with CVD were observed for circulating n‐3 alpha‐linolenic acid or n‐6 PUFA (linoleic acid, arachidonic acid). Associations with CVD of self‐reported dietary PUFA were consistent with those of the PUFA biomarkers. All associations were similar across racial‐ethnic groups, except those of docosapentaenoic acid. Conclusions Both dietary and circulating eicosapentaenoic acid and docosahexaenoic acid, but not alpha‐linolenic acid or n‐6 PUFA, were inversely associated with CVD incidence. These findings suggest that increased consumption of n‐3 PUFA from seafood may prevent CVD development in a multiethnic population. PMID:24351702

  10. Two-compartment, two-sample technique for accurate estimation of effective renal plasma flow: Theoretical development and comparison with other methods

    SciTech Connect

    Lear, J.L.; Feyerabend, A.; Gregory, C.

    1989-08-01

    Discordance between effective renal plasma flow (ERPF) measurements from radionuclide techniques that use single versus multiple plasma samples was investigated. In particular, the authors determined whether effects of variations in distribution volume (Vd) of iodine-131 iodohippurate on measurement of ERPF could be ignored, an assumption implicit in the single-sample technique. The influence of Vd on ERPF was found to be significant, a factor indicating an important and previously unappreciated source of error in the single-sample technique. Therefore, a new two-compartment, two-plasma-sample technique was developed on the basis of the observations that while variations in Vd occur from patient to patient, the relationship between intravascular and extravascular components of Vd and the rate of iodohippurate exchange between the components are stable throughout a wide range of physiologic and pathologic conditions. The new technique was applied in a series of 30 studies in 19 patients. Results were compared with those achieved with the reference, single-sample, and slope-intercept techniques. The new two-compartment, two-sample technique yielded estimates of ERPF that more closely agreed with the reference multiple-sample method than either the single-sample or slope-intercept techniques.

  11. Characterization of interfaces in mosaic CVD diamond crystal

    NASA Astrophysics Data System (ADS)

    Muchnikov, Anatoly B.; Radishev, Dmitry B.; Vikharev, Anatoly L.; Gorbachev, Alexei M.; Mitenkin, Anatoly V.; Drozdov, Mikhail N.; Drozdov, Yuri N.; Yunin, Pavel A.

    2016-05-01

    Detailed description of a way to accrete diamond single crystals in one plate using the CVD method is presented. It was found that each region of the mosaic CVD diamond crystal grown over a certain seed substrate "inherits" the crystallographic orientation of its substrate. No correlation was found between the value of misorientation of the accreted crystals and entrance of hydrogen to the boundary. It is shown that successful accretion of single crystal diamond plates in a single mosaic crystal occurs even in the case of great misorientation of crystals. The mechanical stresses appear during the fabrication of the mosaic CVD diamond crystal. Stresses accumulate during accretion of the regions, which grow over substrates with different orientations, in a common structure.

  12. Development of In-Situ Erosion Measurement Techniques for Application to Real-Time Determination of Plasma Thruster Component Lifetimes

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This research has resulted in advancing the laser-based diagnostic capability and the ion optics development in the ion propulsion program at NASA GRC. Laser-based plasma diagnostics have been demonstrated in tabletop experiments and, in the case of LDI, on laboratory hollow cathodes. Assessment by GRC of its resources and priorities two years into the grant lead to a refocusing of the research effort away from the development of a real-time erosion rate measurement technique. The extension of the diagnostic techniques to diagnostic tools has been transferred to graduate students under the technical direction of the PI. These diagnostics may facilitate the development of ion thruster with significantly improved throughput capability for lower-power (10 kW) missions High-Isp, Long-lived ion optics development has proceeded from simple extensions of state-of-the-art geometries to radically different geometries and materials. Full-scale testing of these ion optics has demonstrated a significant advance in the throughput capability of ion thrusters enabling significantly more demanding missions. The capability to predict the throughput was developed and will continue to be upgraded. The performance models have been validated via full-scale testing. Partial validation of the throughput prediction will be completed via an upcoming wear test of the ion optics.

  13. Elimination of sulphur odours at landfills by bioconversion and the corona discharge plasma technique.

    PubMed

    Xia, Fangfang; Liu, Xin; Kang, Ying; He, Ruo; Wu, Zucheng

    2015-01-01

    Hydrogen sulphide (H2S) contributes a lot to odours at landfills, which is a threat to the environment and the health of the staff therein. To mitigate its emission, the bioconversion within landfill cover soils (LCSs) was introduced. H2S emission and concentration both in the field air above the landfill and in microcosm testing were surveyed. Results indicated that H2S emission and concentration in the landfill varied with landfill seasons and sites. There existed relationship between H2S concentration and fluxes spatially and temporally. To characterize and assess the spatial and temporal diversity of sulphur-oxidizing bacteria (SOB) and sulphate-reducing bacteria (SRB) in the LCSs, the terminal-restriction fragment length polymorphism technique was employed. Using the functional genes of dsrB and soxB, SOB, including Halothiobacillus, Rhodothalassium, Paracocccus, Allochromatium, and Thiobacillus, and SRB, including Desulfovibrio, Syntrophobacter, Desulfomonile and Desulfobacca, were identical and exhibited the dominant role in the LCSs. By employing an alternative available corona reactor, more than 90% removal efficiencies of sulphides were demonstrated, suggesting that the LCSs for eliminating odours in a lower concentration would be feasible.

  14. Tractable Chemical Models for CVD of Silicon and Carbon

    NASA Technical Reports Server (NTRS)

    Blanquet, E.; Gokoglu, S. A.

    1993-01-01

    Tractable chemical models are validated for the CVD of silicon and carbon. Dilute silane (SiH4) and methane (CH4) in hydrogen are chosen as gaseous precursors. The chemical mechanism for each systems Si and C is deliberately reduced to three reactions in the models: one in the gas phase and two at the surface. The axial-flow CVD reactor utilized in this study has well-characterized flow and thermal fields and provides variable deposition rates in the axial direction. Comparisons between the experimental and calculated deposition rates are made at different pressures and temperatures.

  15. CVD Growth of Carbon Nanotubes: Structure, Catalyst, and Growth

    NASA Technical Reports Server (NTRS)

    Delzeit, Lance

    2003-01-01

    Carbon nanotubes (CNTs) exhibit extraordinary mechanical and unique electronic properties and hence have been receiving much attention in recent years for their potential in nanoelectronics, field emission devices, scanning probes, high strength composites and many more applications. Catalytic decomposition of hydrocarbon feedstock with the aid of supported transition metal catalysts - also known as chemical vapor deposition (CVD) - has become popular to produce single-walled and multi-walled nanotubes (SWNTs, MWNTs) and multiwalled nanofibers (MWNFs). The ability to grow CNTs on patterned substrates and in vertically aligned arrays, and the simplicity of the process, has made CVD growth of CNTs an attractive approach.

  16. Origin of residual particles on transferred graphene grown by CVD

    NASA Astrophysics Data System (ADS)

    Yasunishi, Tomohiro; Takabayashi, Yuya; Kishimoto, Shigeru; Kitaura, Ryo; Shinohara, Hisanori; Ohno, Yutaka

    2016-08-01

    Large-area single-layer graphene can be grown on Cu foil by CVD, but for device applications, the layer must to be transferred onto an insulating substrate. As residual particles are often observed on transferred graphene, we investigated their origin using scanning electron microscopy and energy-dispersive X-ray spectrometry (EDX). The results show that these residual particles are composed either of silicon or an alloy of a few metals, and hence, likely originate from the quartz tube of the CVD furnace and the impurities contained in the Cu foil.

  17. Nanoparticle removal using laser induced plasma (LIP) technique and study of detachment modes based on molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Peri, M. D. Murthy

    Nanoparticle contamination is a major problem in many industries. In the semiconductor industry, as the device (integrated circuit) size shrinks with each technological node (DRAM half-pitch), the feature size that has to be fabricated shrinks. Consequently, the minimum tolerable particle defect size also reduces to sub-100 nm level. In order to attain the stringent small size features, Extreme Ultraviolet Lithography (EUVL) technique is being explored in the semiconductor industry. As the EUVL masks are reflective and pellicle free, the cleaning techniques employed to remove the native particle defects must be more effective for the removal of the sub-100 nm particles without any substrate damage. The effectiveness of Laser Induced Plasma (LIP) technique, considered as a next generation cleaning method, for removal of 30 nm PSL particles from silicon substrate was previously demonstrated by our group. In the current study, the removal of 100 nm PSL particles from photomask and 300 nm PSL particles from 500 nm patterns was investigated. It was observed that the patterns were damaged which could be attributed to the radiation heating of the plasma, and this necessitated pressure amplification techniques to amplify the transient pressure and minimize the risk of damage. As a potential solution, shocktubes were designed and transient pressure measurements were carried out in air medium. Also, plasma was generated in water, in order to take advantage of the density of the medium, to generate stronger shocks and consequently higher pressure. The performance of the shocktubes was characterized based on their pressure amplification factor. The shocktubes resulted in a pressure amplification factor of 11 in air. The particle removal experiments with shocktubes on 150 nm patterns were performed and no damage to the patterns was observed. However, there were particle adders due to the ablation of the shocktube material. Molecular Dynamics (MD) simulations were initiated and

  18. Experimental Evaluation of Multi-spacecraft Data Analysis Techniques in a Laboratory Plasma

    SciTech Connect

    Jongsoo Yoo and Masaaki Yamada

    2012-03-27

    The Magnetic Reconnection Experiment (MRX)[1] has been utilized to assess the effectiveness of minimum variance analysis on the magnetic field (MVAB) and boundary-crossing time analysis (BCTA). The neutral sheet is swept, or jogged, in a controlled manner with respect to the stationary probes by pulsed internal coil currents. Magnetic field data from measurement points resembling data from multi-spacecraft flying though a reconnecting current sheet is used to check both techniques to deduce a proper normal vector. We examine discharges with the two-dimensional (2-D) X-line structure as well as cases in which a flux rope forms within the layer. All discharges are in a two-fluid regime in which electrons are magnetized but not ions. Boundary-crossing time analysis with four sample measurement points forming a tetrahedron generates a reasonable unit normal vector and relative velocity along the normal vector for all of the tested cases. On the other hand, MVAB sometimes fails to predict a proper normal direction. This is because the X-line magnetic geometry is fundamentally 2-D or 3-D. However, the direction along the reconnecting field determined by MVAB does not deviate much from the real magnetic geometry documented by 2-D magnetic probe arrays and one additional probe at a different toroidal location. Based on these observations, we suggest a procedure for determining a local coordinate system for data from the Magnetospheric Multi-Scale (MMS) mission when spacecraft passes through a reconnecting current sheet. The distance between measurement points on the order of the ion skin depth (c/{omega}{sub pi}) is pertinent to determination of the magnetic geometry.

  19. Effects of Surface Treatments on Secondary Electron Emission from CVD Diamond Films

    NASA Technical Reports Server (NTRS)

    Mearini, G. T.; Krainsky, I. L.; Dayton, J. A., Jr.; Zorman, Christian; Wang, Yaxin; Lamouri, A.

    1995-01-01

    Secondary electron emission (SEE) properties of polycrystalline diamond films grown by chemical vapor deposition (CVD) were measured. The total secondary yield (sigma) from as-grown samples was observed to be as high as 20 at room temperature and 48 while heating at 700 K in vacuum. Electron-beam-activated, alkali-terminated diamond films have shown stable values of sigma as high as 60 when coated with CsI and similarly high values when coated with other alkali halides. Diamond coated with BaF2 had a stable sigma of 6, but no enhancement of the SEE properties was observed with coatings of Ti or Au. Hydrogen was identified to give rise to this effect in as-grown films. However, electron beam exposure led to a reduction in sigma values as low as 2. Exposure to a molecular hydrogen environment restored sigma to its original value after degradation, and enabled stable secondary emission during electron beam exposure. Atomic hydrogen and hydrogen plasma treatments were performed on diamond/Mo samples in an attempt to increase the near-surface hydrogen concentration which might lead to increased stability in the secondary emission. Raman scattering analysis, scanning electron microscopy, and Auger electron spectroscopy (AES) confirmed that hydrogen plasma and atomic hydrogen treatments improved the quality of the CVD diamond significantly. Elastic recoil detection (ERD) showed that heating as-grown diamond targets to 7OO K, which was correlated with an increase in sigma, removed contaminants from the surface but did not drive hydrogen from the diamond bulk. ERD showed that the hydrogen plasma treatment produced an increase in the hydrogen concentration in the near-surface region which did not decrease while heating in vacuum at 700 K, but no improvement in the SEE properties was observed.

  20. Faraday effect of bismuth iron garnet thin film prepared by mist CVD method

    NASA Astrophysics Data System (ADS)

    Yao, Situ; Sato, Takafumi; Kaneko, Kentaro; Murai, Shunsuke; Fujita, Koji; Tanaka, Katsuhisa

    2015-06-01

    Metastable bismuth iron garnet (BIG, an abbreviation of Bi3Fe5O12), one kind of garnet-type ferrites, is known to manifest very large Faraday rotation as well as low optical absorption in the visible to infrared region. We report on successful synthesis of thin film composed of single-phase BIG epitaxially grown on single-crystalline gadolinium gallium garnet (Gd3Ga5O12, GGG) substrate by using mist chemical vapor deposition (CVD) method, which is an emerging technique for preparation of thin films. The crystal structure, surface morphology, and magnetic, optical and magneto-optical properties of the resultant thin films have been explored. The BIG thin film has a relatively flat surface free from roughness compared to those prepared by other vapor deposition methods. Saturation magnetization is about 1620 G at room temperature, which is close to that expected from the ideal magnetic structure of BIG. The maximum value of Faraday rotation angle reaches 54.3 deg/µm at a wavelength of 424 nm. This value is rather large when compared with those reported for BIG thin films prepared by other techniques. The wavelength dependence of Faraday rotation angle is analyzed well in terms of the crystal electric field (CEF) level schema. Our result suggests that the mist CVD method is a simple and effective technique to synthesize BIG thin film with excellent magneto-optical properties.

  1. Simulation Based on Ion-Ion Plasma Techniques of Electric propulsion In Mars Mission Using Chlorine Gas

    NASA Astrophysics Data System (ADS)

    Sathiyavel, C.

    Abstract:The recently(Nov-5/2013) launched Mangalyan by the Indian space Research Organization (ISRO) to Mars orbit with Mankalyan contained by small liquid engine(MMH+N2O4).This will take long time to reach the Mars orbit that is around the 9 Months. Bi-Propellant rocket system has good thrust but low specific impulse and velocity. In future we need a rocket with good high specific impulse and high velocity of rocket system, to reduce the trip time to Mars. Electric propulsion rocket system is expected to become popular with the development of ion-ion pair techniques because this needs low propellant, Design thrust range is 1.5 N with high efficiency. An ion - ion pair of Electric propulsion rocket system is proposed in this work. Ion-Ion(positive ion- negative ion) Based Rocket system consists of three parts 1.The negative ionization stage with electro negative propellant 2. Ion-Ion plasma formation and ion accelerator 3. Exhaust of Nozzle. The Negative ions from electro negative gas are produced by adding up the gas, such as chlorine with electron emitted from an Electron gun ionization chamber. The formulate of large stable negative ion is achievable in chlorine gas with respect to electron affinity (∆E). When a neutral chlorine atom in the gaseous form picks up an electron to form a Cl- ion, it releases energy of 3.6eV. The negative ion density becomes several orders of magnitude larger than that of the electrons, hence forming ion-ion (positive ion - negative ion) plasma at the periphery of the discharge. The distance between ion- ions is important for the evaluate the rocket thrust and it also that the distance is determined by the exhaust velocity of the propellant. Accelerate the ion-ion plasma to a high velocity in the thrust vector direction via electron gun and the exhaust of ions through Nozzle. The simulation of the ion propulsion system has been carried out by MATLAB. By comparing the simulation results with the theoretical and previous results, we

  2. Correlation of p-doping in CVD Graphene with Substrate Surface Charges

    PubMed Central

    Goniszewski, S.; Adabi, M.; Shaforost, O.; Hanham, S. M.; Hao, L.; Klein, N.

    2016-01-01

    Correlations between the level of p-doping exhibited in large area chemical vapour deposition (CVD) graphene field effect transistor structures (gFETs) and residual charges created by a variety of surface treatments to the silicon dioxide (SiO2) substrates prior to CVD graphene transfer are measured. Beginning with graphene on untreated thermal oxidised silicon, a minimum conductivity (σmin) occurring at gate voltage Vg = 15 V (Dirac Point) is measured. It was found that more aggressive treatments (O2 plasma and UV Ozone treatments) further increase the gate voltage of the Dirac point up to 65 V, corresponding to a significant increase of the level of p-doping displayed in the graphene. An electrowetting model describing the measured relationship between the contact angle (θ) of a water droplet applied to the treated substrate/graphene surface and an effective gate voltage from a surface charge density is proposed to describe biasing of Vg at σmin and was found to fit the measurements with multiplication of a correction factor, allowing effective non-destructive approximation of substrate added charge carrier density using contact angle measurements. PMID:26956096

  3. Correlation of p-doping in CVD Graphene with Substrate Surface Charges

    NASA Astrophysics Data System (ADS)

    Goniszewski, S.; Adabi, M.; Shaforost, O.; Hanham, S. M.; Hao, L.; Klein, N.

    2016-03-01

    Correlations between the level of p-doping exhibited in large area chemical vapour deposition (CVD) graphene field effect transistor structures (gFETs) and residual charges created by a variety of surface treatments to the silicon dioxide (SiO2) substrates prior to CVD graphene transfer are measured. Beginning with graphene on untreated thermal oxidised silicon, a minimum conductivity (σmin) occurring at gate voltage Vg = 15 V (Dirac Point) is measured. It was found that more aggressive treatments (O2 plasma and UV Ozone treatments) further increase the gate voltage of the Dirac point up to 65 V, corresponding to a significant increase of the level of p-doping displayed in the graphene. An electrowetting model describing the measured relationship between the contact angle (θ) of a water droplet applied to the treated substrate/graphene surface and an effective gate voltage from a surface charge density is proposed to describe biasing of Vg at σmin and was found to fit the measurements with multiplication of a correction factor, allowing effective non-destructive approximation of substrate added charge carrier density using contact angle measurements.

  4. THE RELATIONSHIP BETWEEN OZONE-INDUCED LUNG INJURY, ANTIOXIDANT COMPENSATION AND UNDERLYING CARDIOVASCULAR DISEASE (CVD).

    EPA Science Inventory

    Increased levels of oxidants and compromised compensatory response are associated with CVD susceptibility. We hypothesized that rat strains demonstrating genetic CVD will have lower levels of antioxidants and greater ozone-induced pulmonary injury relative to healthy strains. Mal...

  5. COMPARATIVE EVALUATION OF RISK FACTORS FOR CARDIOVASCULAR DISEASE (CVD) IN GENETICALLY PREDISPOSED RATS

    EPA Science Inventory

    Rodent CVD models are increasingly used for understanding individual differences in susceptibility to environmental stressors such as air pollution. We characterized pathologies and a number of known human risk factors of CVD in genetically predisposed, male young adult Spontaneo...

  6. CVD diamond film oxidation resistance research

    NASA Astrophysics Data System (ADS)

    Jing, Longwei; Wang, Xiaoping; Wang, Lijun; Pan, Xiufang; Sun, Yiqing; Wang, Jinye; Sun, Hongtao

    2013-12-01

    Diamond films were deposited on a silicon substrate by microwave plasma chemical vapor deposition system, and its oxidation experiments were carried out in atmospheric environmental condition by using a muffle furnace. Inatmospheric environment (the temperature is from 400°C to 900°C) the oxidation resistance of diamond thin films was investigated. The results indicate that under the atmospheric environment diamond thin film surface morphology did not change after 6 hours at 400°C. Diamond thin film surface morphology began to change after 2 hours at 600°C, and when time was extended to 4 hours, the diamond thin film surface morphology changed significantly. The surface morphology of diamond films began to change after 15 minutes at a 700°C condition and when time was extended to 6 hours diamond films were all destroyed. All the diamond films on the silicon substrate disappeared completely in 20 minutes at 900°C. The intact crystal face is the reason that natural diamond has stable chemical property. The crystal face of synthetic diamond film has a lot of defects, especially on the side. Oxidation of the diamond films begin with the grain boundary and defects.

  7. Capacitive behavior of amorphous and crystalline RuO 2 composite electrode fabricated by spark plasma sintering technique

    NASA Astrophysics Data System (ADS)

    Bharali, P.; Kuratani, K.; Takeuchi, T.; Kiyobayashi, T.; Kuriyama, N.

    This study is intended to determine if the capacitive properties are improved when a specific amount of crystalline ruthenium oxide (c-RuO 2) is added to an amorphous hydrous ruthenium oxide (a-RuO 2) electrode fabricated by the spark plasma sintering technique. For at the cyclic voltammetry scan rates higher than 10 mV s -1, the capacitance of a highly pseudo-capacitive, but less electron-conductive a-RuO 2 electrode is augmented by adding 5-20 wt.% of c-RuO 2 which is less capacitive, but more electron-conductive than a-RuO 2. The capacitance fades when more than 20 wt.% of c-RuO 2 is added because the less capacitive nature of c-RuO 2 prevails. The proximate cause of this phenomenon is the electronic conductivity, σ, of the composite electrode as we observe a maximum in σ at around a 5-20 wt.% c-RuO 2 content. The fact that c-RuO 2 is composed of smaller particles than a-RuO 2 seems to be related to the maximum σ value for a certain c-RuO 2 content of the composite electrode.

  8. Characterization of RF He-N2/Ar mixture plasma via Langmuir probe and optical emission spectroscopy techniques

    NASA Astrophysics Data System (ADS)

    Younus, Maria; Rehman, N. U.; Shafiq, M.; Hussain, S. S.; Zakaullah, M.; Zaka-ul-Islam, M.

    2016-08-01

    A Magnetic Pole Enhanced inductively coupled RF H e - N 2 / A r plasma is characterized using a Langmuir probe and optical emission spectroscopy (OES) techniques. The effect of helium mixing on electron density ( n e ) and temperature ( T e ) , electron energy probability functions (EEPFs), [ N ] atomic density, and N 2 dissociation is investigated. A Langmuir probe and a zero slope method based on trace rare gas-optical emission spectroscopy (TRG-OES) are employed to measure the electron temperature. It is noted that the electron temperature shows an increasing trend for both methods. However, the temperature measured by a zero slope method T e ( Z . S ) approaches the temperature measured by a Langmuir probe; T e ( L . P ) at 56% and above helium concentration in the discharge. "Advance actinometry" is employed to monitor the variation in [ N ] atomic density with helium concentration and gas pressure. It is noted that [ N ] atomic density increases at 56% and above helium in the discharge, which is consistent with the trend of electron temperature and EEPFs. A drastic enhancement in N 2 dissociation fraction D 1 determined by "advance actinometry" is noted at 56% and above helium concentration in the mixture due to modifications in different population and depopulation mechanisms. However, it is also noted that the dissociation fraction D 2 determined by intensity ratio method increases linearly with helium addition.

  9. Bacteria Adherence Properties of Nitrogen-Doped TiO2 Coatings by Plasma Surface Alloying Technique

    NASA Astrophysics Data System (ADS)

    Wang, Hefeng; Tang, Bin; Li, Xiuyan; Fan, Ailan

    Titanium nitride coatings on 316L stainless steel (S. S) were obtained by plasma surface alloying technique. Nitrogen-doped titanium dioxide (TiO2-xNx) was synthesized by oxidative annealing the resulted TiNx coatings in air. The reference TiO2 samples were also prepared by oxidation of sputtered Ti coatings. The as-prepared coatings were characterized by X-ray diffraction, glow discharge optical emission spectrometer (GDOES), scanning electron microscopy, X-ray hotoelectron spectroscopy and UV-Vis spectrophotometry, respectively. The bacteria adherence property of the TiO2-xNx coatings on stainless steel on the oral bacteria Streptococcus Mutans was investigated and compared with that of stainless steel by fluorescence microscopy. The mechanism of the bacteria adherence was discussed. The results show that the TiO2-xNx coatings are composed of anatase crystalline structure. SEM measurement indicates a rough surface morphology with three-dimensional homogenous protuberances after annealing treatment. Optical properties reveal an extended tailing of the absorption edge toward the visible region due to nitrogen presence. The band gap of the N-doped sample is reduced from 2.29 eV to 1.90 eV compared with the pure TiO2 one. Because of the different roughness and microstructure, the TiO2-xNx coatings inhibit the bacteria adherence.

  10. Investigation of impurity transport using laser blow-off technique in the HL-2A Ohmic and ECRH plasmas

    NASA Astrophysics Data System (ADS)

    Kai, Zhang; Zheng-Ying, Cui; Ping, Sun; Chun-Feng, Dong; Wei, Deng; Yun-Bo, Dong; Shao-Dong, Song; Min, Jiang; Yong-Gao, Li; Ping, Lu; Qing-Wei, Yang

    2016-06-01

    Impurity transports in two neighboring discharges with and without electron cyclotron resonance heating (ECRH) are studied in the HL-2A tokamak by laser blow-off (LBO) technique. The progression of aluminium ions as the trace impurity is monitored by soft x-ray (SXR) and bolometer detector arrays with good temporal and spatial resolutions. Obvious difference in the time trace of the signal between the Ohmic and ECRH L-mode discharges is observed. Based on the numerical simulation with one-dimensional (1D) impurity transport code STRAHL, the radial profiles of impurity diffusion coefficient D and convective velocity V are obtained for each shot. The result shows that the diffusion coefficient D significantly increases throughout the plasma minor radius for the ECRH case with respect to the Ohmic case, and that the convection velocity V changes from negative (inward) for the Ohmic case to partially positive (outward) for the ECRH case. The result on HL-2A confirms the pump out effect of ECRH on impurity profile as reported on various other devices.

  11. Studies of gas phase reactions, nucleation and growth mechanisms of plasma promoted chemical vapor deposition of aluminum using dimethylethylamine alane as source percursor

    NASA Astrophysics Data System (ADS)

    Knorr, Andreas H.

    The work presented herein focuses on the use of plasma promoted chemical vapor deposition (PPCVD) of aluminum (Al) using dimethylethylamine alane (DMEAA) as source precursor to provide an integrated, low temperature alternative to currently employed Al deposition methods in ultra large sale integration ULSI multilevel metal wiring schemes. In this respect, key findings are reported and discussed from critical scientific and technical aspects of an research and development effort, which was successfully executed to identify a viable Al CVD deposition process. In this respect, advanced atomic scale analytical techniques were successfully employed to characterize the PPCVD deposition process at the molecular level, and document the dependence of film's structural and compositional properties on key process parameters. This led to the development and optimization of a PPCVD Al process for ULSI applications. In addition, gas phase quadrupole mass spectrometry (QMS) was employed to study the gas phase evolution during TCVD and PPCVD in order to gain a thorough understanding of the potential chemical and physical reactions that could occur in the gas phase and derive corresponding optimized reaction pathways for both CVD processes. Key reaction mechanisms involved in thermal and plasma promoted CVD as a function of processing parameters were investigated, including the role of hydrogen plasma in providing an efficient pathway to aluminum nucleation and growth. The resulting reaction mechanisms were then employed to identify the most likely precursor decomposition pathways and explore relevant implications for thermal and plasma promoted CVD Al. Furthermore, the nucleation and growth of Al in both TCVD and PPCVD were thoroughly characterized. Time evolution studies were carried out employing a variety of relevant liners and seed layers under selected surface chemical states. The surface morphology of the resulting films were analyzed by means of scanning probe microscopy

  12. Thermal plasma processing of materials. Progress report, September 1, 1988--January 31, 1992

    SciTech Connect

    Pfender, E.; Heberlein, J.

    1992-02-01

    Emphasis has been on plasma synthesis of fine powders, plasma Chemical Vapor Deposition (CVD), on related diagnostics, and on modeling work. Since plasma synthesis as well as plasma CVD make frequent use of plasma jets, the beginning has been devoted of plasma jets and behavior of particulates injected into such plasma jets. Although most of the construction of the Triple-Torch Plasma Reactor (TTPR) has already been done, modifications have been made in particular modifications required for plasma CVD of diamond. A new reactor designed for Counter-Flow Liquid Injection Plasma Synthesis (CFLIPS) proved to be an excellent tool for synthesis of fine powders as well as for plasma CVD. An attempt was made to model flow and temperature fields in this reactor. Substantial efforts were made to single out those parameters which govern particle size, size distribution, and powder quality in our plasma synthesis experiments. This knowledge is crucial for controlling the process and for meaningful diagnostics and modeling work. Plasma CVD of diamond films using both reactors has been very successful and we have been approached by a number of companies interested in using this technology for coating of tools.

  13. CVD growth of graphene under exfoliated hexagonal boron nitride for vertical hybrid structures

    SciTech Connect

    Wang, Min; Jang, Sung Kyu; Song, Young Jae; Lee, Sungjoo

    2015-01-15

    Graphical abstract: We have demonstrated a novel yet simple method for fabricating graphene-based vertical hybrid structures by performing the CVD growth of graphene at an h-BN/Cu interface. Our systematic Raman measurements combined with plasma etching process indicate that a graphene film is grown under exfoliated h-BN rather than on its top surface, and that an h-BN/graphene vertical hybrid structure has been fabricated. Electrical transport measurements of this h-BN/graphene, transferred on SiO2, show the carrier mobility up to approximately 2250 cm{sup 2} V{sup −1} s{sup −1}. The developed method would enable the exploration of the possibility of novel hybrid structure integration with two-dimensional material systems. - Abstract: We have demonstrated a novel yet simple method for fabricating graphene-based vertical hybrid structures by performing the CVD growth of graphene at an h-BN/Cu interface. Our systematic Raman measurements combined with plasma etching process indicate that a graphene film is grown under exfoliated h-BN rather than on its top surface, and that an h-BN/graphene vertical hybrid structure has been fabricated. Electrical transport measurements of this h-BN/graphene, transferred on SiO{sub 2}, show the carrier mobility up to approximately 2250 cm{sup 2} V{sup −1} s{sup −1}. The developed method would enable the exploration of the possibility of novel hybrid structure integration with two-dimensional material systems.

  14. Innovative Plasma Disinfection Technique with the Reduced-pH Method and the Plasma-Treated Water (PTW) -Safety and Powerful Disinfection with Cryopreserved PTW-

    NASA Astrophysics Data System (ADS)

    Kitano, Katsuhisa; Ikawa, Satoshi; Nakashima, Yoichi; Tani, Atsushi; Yokoyama, Takashi; Ohshima, Tomoko

    2015-09-01

    Among the applications of the plasma disinfection to human body, plasma sterilization in liquid is crucial. We found that the plasma-treated water (PTW) has strong bactericidal activity under low pH condition and the half-lives of its activity depend on temperature. Lower temperature brings longer half-life and the bactericidal activity of PTW can be kept by cryopreservation. These physicochemical properties were in accordance with Arrhenius equation both in liquid and solid states. From the experimental results of ESR (Electron Spin Resonance) measurement of O2-in liquid against PTW with spin trapping method, half-lives of PTW were also in accordance with Arrhenius equation. It suggests that high concentration PTW as integrated value can be achieved by cooling of plasma apparatus. Pure PTW has disinfection power of 22 log reduction (B. subtilis). This corresponds to 65% H2O2, 14% hypochlorous acid and 0.33% peracetic acid, which are deadly poison for human. On the other hand, PTW is deactivated soon at body temperature. This indicates that toxicity to human body seems to be low. PTW, which is a sort of indirect plasma exposure, with pH and temperature controls could be applied for safety and powerful disinfection. MEXT (15H03583, 23340176, 25108505). NCCE (23-A-15).

  15. Experimental, theoretical and computational study of frequency upshift of electromagnetic radiation using plasma techniques. Annual technical report, January 15, 1992--January 14, 1993

    SciTech Connect

    Joshi, C.

    1992-09-01

    This is a second year progress report on ``Experimental, Theoretical and Computational Study of Frequency Upshift of Electromagnetic Radiation Using Plasma Techniques.`` The highlights are: (I) Ionization fronts have been shown to frequency upshift e.m. radiation by greater than a factor 5. In the experiments, 33 GHz microwave radiation is upshifted to more than 175 GHz using a relativistically propagating ionization front created by a laser beam. (II) A Letter describing the results has been published in Physical Review Letters and an ``invited`` paper has been submitted to IEEE Trans. in Plasma Science.

  16. Kinetics of low pressure CVD growth of SiO2 on InP and Si

    NASA Technical Reports Server (NTRS)

    Iyer, R.; Lile, D. L.

    1988-01-01

    The kinetics of low pressure CVD growth of SiO2 from SiH4 and O2 has been investigated for the case of an indirect (remote) plasma process. Homogeneous (gas phase) and heterogeneous operating ranges have been experimentally identified. The process was shown to be consistent within the heterogeneous surface-reaction dominated range of operation. A kinetic rate equation is given for growth at 14 W RF power input and 400 mtorr total pressure on both InP and Si substrates. The process exhibits an activation energy of 8.4 + or - 0.6 kcal/mol.

  17. Design of a CVD reactor for the deposition of diamond in a microgravity environment

    NASA Technical Reports Server (NTRS)

    Languell, Michael L.; Davidson, J. L.; Strauss, A. M.

    1992-01-01

    There is a growing body of theoretical and experimental evidence suggesting that the uniformity, rate, adhesion, quality, and other key properties of Chemical Vapor Deposition (CVD) diamond coatings are influenced by the gas mixing kinetics in the thermal plasma environment of the reaction chamber. The implementation of, for example, Microwave Plasma Enhanced Chemical Vapor Deposition (MPECVD) process in microgravity has, thus, been suggested. Such a diamond deposition system, which overcomes the limitations of present systems and which is distiguishable from them by the use of high pressure MPECVD and recirculation of the would be effluent hydrogen and carbon, is described. Given the key fact that there is nothing in the effluent of the MPECVD process that is truly a byproduct or 'waste', the system can, at least in principle, lend itself to being closed loop yet dynamic. The exhaust contains hydrogen and carbon species which can be recirculated to the plasma reactor, that is, since there are no unusable reaction byproducts, the effluent can be fed back to the reaction chamber with no detriment, thus allowing deployment in a microgravity environment.

  18. P-type ZnO films by phosphorus doping using plasma immersion ion-implantation technique

    NASA Astrophysics Data System (ADS)

    Nagar, S.; Chakrabarti, S.

    2013-03-01

    ZnO has been a subject of intense research in the optoelectronics community owing to its wide bandgap (3.3eV) and large exciton binding energy (60meV). However, difficulty in doping it p-type posts a hindrance in fabricating ZnO-based devices. In order to make p-type ZnO films, phosphorus implantation, using plasma immersion ion-implantation technique (2kV, 900W, 10μs pulse width) for 30 seconds, was performed on ZnO thin film deposited by RF Magnetron Sputtering (Sample A). The implanted samples were subsequently rapid thermal annealed at 700°C and 1000°C (Samples B and C) in oxygen environment for 30 seconds. Low temperature (8K) photoluminescence spectra reveal dominant donor-bound exciton (D°X) peak at 3.36eV for samples A and B. However, for Sample B the peaks around 3.31eV and 3.22eV corresponding to the free electron-acceptor (FA) and donor to acceptor pair peaks (DAP) are also observed. A dominant peak around 3.35eV, corresponding to acceptor bound exciton (A°X) peak, is detected for Sample C along with the presence of FA and DAP peaks around 3.31eV and 3.22eV. Moreover, the deep level peak around 2.5eV is higher for Sample B which may be due to implantation and acceptor related defects. However, for Sample C, the deep level peaks are very weak compared to the near band edge peaks confirming that these peaks are mainly due to intrinsic defects and not related to acceptors. These results clearly show us a promising way to achieve p-type ZnO films using phosphorus doping.

  19. Ultrasonic cavity preparation using CVD coated diamond bur: A case report

    PubMed Central

    de Vasconcellos, Beatriz Tholt; Thompson, Jeffrey Y.; de Paula Macedo, Manoel Roberto; de Oliveira Maia, Janaína Monalisa; Oda, Margareth; Garone-Netto, Narciso

    2013-01-01

    Before any restorative procedure can be undertaken a proper cavity preparation is required. This clinical step is the mechanical alteration of the tooth to receive a restorative material with which a satisfactory form, function and the esthetics of the tooth will be established. In recent years improvements in materials and techniques have been devised and new technologies are now available for this purpose. The aim of the present study is to report two clinical cases in which a CVD coated diamond bur coupled to an ultrasonic handpiece is used in dental preparation. This technique provides an accurate and conservative tooth preparation with ideal access and visibility and because of enhanced efficiency can also play a role in eliminating some of the patient discomfort of the dental treatment. PMID:23408140

  20. Ultrasonic cavity preparation using CVD coated diamond bur: A case report.

    PubMed

    de Vasconcellos, Beatriz Tholt; Thompson, Jeffrey Y; de Paula Macedo, Manoel Roberto; de Oliveira Maia, Janaína Monalisa; Oda, Margareth; Garone-Netto, Narciso

    2013-01-01

    Before any restorative procedure can be undertaken a proper cavity preparation is required. This clinical step is the mechanical alteration of the tooth to receive a restorative material with which a satisfactory form, function and the esthetics of the tooth will be established. In recent years improvements in materials and techniques have been devised and new technologies are now available for this purpose. The aim of the present study is to report two clinical cases in which a CVD coated diamond bur coupled to an ultrasonic handpiece is used in dental preparation. This technique provides an accurate and conservative tooth preparation with ideal access and visibility and because of enhanced efficiency can also play a role in eliminating some of the patient discomfort of the dental treatment.

  1. Deposition of duplex Al 2O 3/aluminum coatings on steel using a combined technique of arc spraying and plasma electrolytic oxidation

    NASA Astrophysics Data System (ADS)

    Gu, Weichao; Shen, Dejiu; Wang, Yulin; Chen, Guangliang; Feng, Wenran; Zhang, Guling; Fan, Songhua; Liu, Chizi; Yang, Size

    2006-02-01

    Plasma electrolytic oxidation (PEO) is a cost-effective technique that can be used to prepare ceramic coatings on metals such as Ti, Al, Mg, Nb, etc., and their alloys, but this promising technique cannot be used to modify the surface properties of steels, which are the most widely used materials in engineering. In order to prepare metallurgically bonded ceramic coatings on steels, a combined technique of arc spraying and plasma electrolytic oxidation (PEO) was adopted. In this work, metallurgically bonded ceramic coatings on steels were obtained using this method. We firstly prepared aluminum coatings on steels by arc spraying, and then obtained the metallurgically bonded ceramic coatings on aluminum coatings by PEO. The characteristics of duplex coatings were analyzed by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The corrosion and wear resistance of the ceramic coatings were also studied. The results show that, duplex Al 2O 3/aluminum coatings have been deposited on steel substrate after the combined treatment. The ceramic coatings are mainly composed of α-Al 2O 3, γ-Al 2O 3, θ-Al 2O 3 and some amorphous phase. The duplex coatings show favorable corrosion and wear resistance properties. The investigations indicate that the combination of arc spraying and plasma electrolytic oxidation proves a promising technique for surface modification of steels for protective purposes.

  2. THERMAL DIFFUSIVITY/CONDUCTIVITY OF IRRADIATED MONOLITHIC CVD-SIC

    SciTech Connect

    Youngblood, Gerald E.; Senor, David J.; Jones, Russell H.

    2003-03-31

    Several thermal diffusivity disc samples of high purity CVD-SiC were neutron-irradiated to equivalent doses of about 5-8 dpa-SiC at temperatures from 252 up to 800 C. For this temperature range, the degradation in the thermal diffusivity ranged from about 95 percent down to 89 percent, respectively. The reciprocal thermal diffusivity method was used to estimate the phonon mean free paths and defect concentrations before and after the irradiations for these materials. Even though the CVD-SiC material is an excellent monitor of certain neutron irradiation effects, the degradation in the thermal diffusivity (conductivity) appears to be more than a factor of two greater than predicted by recent theoretical model simulations.

  3. CVD Diamonds in the BaBar Radiation Monitoring System

    NASA Astrophysics Data System (ADS)

    Bruinsma, M.; Burchat, P.; Edwards, A. J.; Kagan, H.; Kass, R.; Kirkby, D.; Petersen, B. A.

    2006-01-01

    To prevent excessive radiation damage to its Silicon Vertex Tracker, the BaBar experiment at SLAC uses a radiation monitoring and protection system that triggers a beam abort whenever radiation levels are anomalously high. The existing system, which employs large area Si PIN diodes as radiation sensors, has become increasingly difficult to operate due to radiation damage. We have studied CVD diamond sensors as a potential alternative for these silicon sensors. Two diamond sensors have been routinely used since their installation in the Vertex Tracker in August 2002. The experience with these sensors and a variety of tests in the laboratory have shown CVD diamonds to be a viable solution for dosimetry in high radiation environments. However, our studies have also revealed surprising side-effects.

  4. Cold Vacuum Drying (CVD) OCRWM Loop Error Determination

    SciTech Connect

    PHILIPP, B.L.

    2000-07-26

    Characterization is specifically identified by the Richland Operations Office (RL) for the Office of Civilian Radioactive Waste Management (OCRWM) of the US Department of Energy (DOE), as requiring application of the requirements in the Quality Assurance Requirements and Description (QARD) (RW-0333P DOE 1997a). Those analyses that provide information that is necessary for repository acceptance require application of the QARD. The cold vacuum drying (CVD) project identified the loops that measure, display, and record multi-canister overpack (MCO) vacuum pressure and Tempered Water (TW) temperature data as providing OCRWM data per Application of the Office of Civilian Radioactive Waste Management (OCRWM) Quality Assurance Requirements to the Hanford Spent Nuclear Fuel Project HNF-SD-SNF-RPT-007. Vacuum pressure transmitters (PT 1*08, 1*10) and TW temperature transmitters (TIT-3*05, 3*12) are used to verify drying and to determine the water content within the MCO after CVD.

  5. Catalytic CVD of SWCNTs at Low Temperatures and SWCNT Devices

    NASA Astrophysics Data System (ADS)

    Seidel, Robert; Liebau, Maik; Unger, Eugen; Graham, Andrew P.; Duesberg, Georg S.; Kreupl, Franz; Hoenlein, Wolfgang; Pompe, Wolfgang

    2004-09-01

    New results on the planar growth of single-walled carbon nanotubes (SWCNTs) by catalytic chemical vapor deposition (CVD) at low temperatures will be reported. Optimizing catalyst, catalyst support, and growth parameters yields SWCNTs at temperatures as low as 600 °C. Growth at such low temperatures largely affects the diameter distribution since coalescence of the catalyst is suppressed. A phenomenological growth model will be suggested for CVD growth at low temperatures. The model takes into account surface diffusion and is an alternative to the bulk diffusion based vapor-liquid-solid (VLS) model. Furthermore, carbon nanotubes field effect transistors based on substrate grown SWCNTs will be presented. In these devices good contact resistances could be achieved by electroless metal deposition or metal evaporation of the contacts.

  6. Infrared absorption of fs-laser textured CVD diamond

    NASA Astrophysics Data System (ADS)

    Calvani, P.; Bellucci, A.; Girolami, M.; Orlando, S.; Valentini, V.; Polini, R.; Mezzetti, A.; Di Fonzo, F.; Trucchi, D. M.

    2016-03-01

    Nanoscale periodic texturing on polycrystalline CVD diamond surface was performed to obtain a significant increase in optical absorptance to visible and near-infrared radiation. Surface texturing, obtained by the use of fs-laser ultrashort pulses, has been demonstrated to induce a controlled periodicity of ripples of about 170 nm and length of several µm, able to drastically increase the diamond capability of interacting with solar radiation from its intrinsic visible blindness. Ultraviolet and visible Raman spectroscopy has been used to confirm the absence of non-diamond phases resulting from the process for the fs-laser-textured sample. Moreover, here we investigate the optical properties in the range 200 nm-25 µm. Absorbance of fs-laser-textured CVD diamond is considerably higher than the untreated one at every wavelength, resulting in a remarkable increase in the emittance: It points out the need for an optimization of process parameters to enhance the selective absorption capability.

  7. Development of CVD diamond detectors for clinical dosimetry

    NASA Astrophysics Data System (ADS)

    Piliero, M. A.; Hugtenburg, R. P.; Ryde, S. J. S.; Oliver, K.

    2014-11-01

    The use of chemical vapour deposition (CVD) methods for the manufacture of diamonds could lead to detectors for high-resolution radiotherapy dosimetry that are cheaper and more reproducible than detectors based on natural diamonds. In this work two prototype designs (Diamond Detectors Ltd, Poole) of CVD diamond detectors were considered. The detectors were encapsulated in a water-proof housing in a form-factor that would be suitable for dosimetry measurements in water, as well as solid material phantoms. Stability of the dosimeter over time, the dose-response, dose-rate response and angular-response were examined. The study demonstrated that the detector behaviour conformed with theory in terms of the dose-rate response and had acceptable properties for use in the clinic.

  8. Evidence relating sodium intake to blood pressure and CVD.

    PubMed

    O'Donnell, Martin; Mente, Andrew; Yusuf, Salim

    2014-01-01

    Sodium is an essential nutrient, mostly ingested as salt (sodium chloride). Average sodium intake ranges from 3 to 6 g per day (7.5-15 g/day of salt) in most countries, with regional variations. Increasing levels of sodium intake have a positive association with higher blood pressure. Randomized controlled trials report a reduction in blood pressure with reducing sodium intake from moderate to low levels, which is the evidence that forms the basis for international guidelines recommending all people consume less than 2.0 g of sodium per day. However, no randomized trials have demonstrated that reducing sodium leads to a reduction in cardiovascular disease (CVD). In their absence, the next option is to examine the association between sodium consumption and CVD in prospective cohort studies. Several recent prospective cohort studies have indicated that while high intake of sodium (>6 g/d) is associated with higher risk of CVD compared to those with moderate intake (3 to 5 g/d), lower intake (<3 g/day) is also associated with a higher risk (despite lower blood pressure levels). However, most of these studies were conducted in populations at increased risk of cardiovascular disease. Current epidemiologic evidence supports that an optimal level of sodium intake is in the range of about 3-5 g/day, as this range is associated with lowest risk of CVD in prospective cohort studies. Randomized controlled trials, comparing the effect of low sodium intake to moderate intake on incidence of cardiovascular events and mortality, are required to truly define optimal intake range.

  9. Underestimating risk in women delays diagnosis of CVD.

    PubMed

    Keteepe-Arachi, Tracey; Sharma, Sanjay

    2016-03-01

    CVD remains the most common cause of mortality in women. In 2007, the annual mortality in women secondary to CAD was 4.7 times that of breast cancer. Around 2.8 million women are living with CVD in the UK. There has been an increase in the prevalence of MI in women aged 35 to 54, while a decline in prevalence was observed in age-matched men. Difficulty in evaluating symptoms of ischaemic heart disease in women is well documented and remains challenging because of their atypical nature. The main gender difference is that women tend to present less frequently with exertional symptoms of chest pain before an AMI. Although men and women share classic cardiovascular risk factors the relative importance of each risk factor may be gender specific. The impact of smoking is greater in women than men, especially in those under 50. Diabetes is a more potent risk factor for fatal CHD in women than men. Risk factors specific to women include postmenopausal status, hysterectomy and complications during pregnancy. Women who develop gestational diabetes mellitus or pre-eclampsia more than double their risk of CVD later in life. Transition to the menopause is associated with a worsening CHD risk profile. After the menopause women may experience an increase in weight, alteration in fat distribution and an increase in other CVD risk factors such as diabetes and a more adverse lipid profile. Pharmacological stress testing is preferred for diagnosing CAD in females with lower exercise capacity. Stress cardiomyopathy is triggered by intense, unexpected emotional or physical stress and is characterised by transient apical systolic dysfunction or ballooning of the left ventricle. The syndrome predominantly affects postmenopausal women. Women presenting with STEMI have worse outcomes compared with men. However, in those presenting with NSTEMI there were no differences in outcomes. PMID:27214974

  10. Controlled growth of CNT in mesoporous AAO through optimized conditions for membrane preparation and CVD operation

    NASA Astrophysics Data System (ADS)

    Ciambelli, P.; Arurault, L.; Sarno, M.; Fontorbes, S.; Leone, C.; Datas, L.; Sannino, D.; Lenormand, P.; Le Blond Du Plouy, S.

    2011-07-01

    Anodic aluminium oxide (RAAO) membranes with a mesoporous structure were prepared under strictly controlling experimental process conditions, and physically and chemically characterized by a wide range of experimental techniques. Commercial anodic aluminium oxide (CAAO) membranes were also investigated for comparison. We demonstrated that RAAO membranes have lower content of both water and phosphorus and showed better porosity shape than CAAO. The RAAO membranes were used for template growth of carbon nanotubes (CNT) inside its pores by ethylene chemical vapour deposition (CVD) in the absence of a catalyst. A composite material, containing one nanotube for each channel, having the same length as the membrane thickness and an external diameter close to the diameter of the membrane holes, was obtained. Yield, selectivity and quality of CNTs in terms of diameter, length and arrangement (i.e. number of tubes for each channel) were optimized by investigating the effect of changing the experimental conditions for the CVD process. We showed that upon thermal treatment RAAO membranes were made up of crystallized allotropic alumina phases, which govern the subsequent CNT growth, because of their catalytic activity, likely due to their Lewis acidity. The strict control of experimental conditions for membrane preparation and CNT growth allowed us to enhance the carbon structural order, which is a critical requisite for CNT application as a substitute for copper in novel nano-interconnects.

  11. Deposition of moisture barrier films by catalytic CVD using hexamethyldisilazane

    NASA Astrophysics Data System (ADS)

    Ohdaira, Keisuke; Matsumura, Hideki

    2014-01-01

    Hexamethyldisilazane (HMDS) is utilized to deposit moisture barrier films by catalytic chemical vapor deposition (Cat-CVD). An increase in the thickness of silicon oxynitride (SiOxNy) films leads to a better water-vapor transmission rate (WVTR), indicating that Cat-CVD SiOxNy films deposited using HMDS do not severely suffer from cracking. A WVTR on the order of 10-3 g m-2 day-1 can be realized by a Cat-CVD SiOxNy film formed using HMDS on a poly(ethylene terephthalate) (PET) substrate without any stacking structures at a substrate temperature of as low as 60 °C. X-ray reflectivity (XRR) measurement reveals that a film density of >2.0 g/cm3 is necessary for SiOxNy films to demonstrate an effective moisture barrier ability. The use of HMDS will give us safer production of moisture barrier films because of its non-explosive and non-toxic nature.

  12. Approach to diabetes management in patients with CVD.

    PubMed

    Lathief, Sanam; Inzucchi, Silvio E

    2016-02-01

    Epidemiologic analyses have established a clear association between diabetes and macrovascular disease. Vascular dysfunction caused by metabolic abnormalities in patients with diabetes is associated with accelerated atherosclerosis and increased risk of myocardial infarction (MI), stroke, and peripheral arterial disease. Patients with diabetes are at two to four fold higher CV risk as compared to non-diabetic individuals, and CVD remains the leading cause of mortality in patients with this condition. One strategy to reduce CVD burden in patients with diabetes has been to focus on controlling the major metabolic abnormality in this condition, namely hyperglycemia. However, this has not been unequivocally demonstrated to reduced CV events, in contrast to controlling other CVD risk factors linked to hyperglycemia, such as blood pressure, dyslipidemia, and platelet dysfunction. However, In contradistinction, accrued data from a number of large, randomized clinical trials in both type 1 (T1DM) and type 2 diabetes (T2DM) over the past 3 decades have proven that more intensive glycemic control retards the onset and progression of microvascular disease. In this review, we will summarize the key glucose-lowering CV outcomes trials in diabetes, provide an overview of the different drugs and their impact on the CV system, and describe our approach to management of the frequently encountered patient with T2DM and coronary artery disease (CAD) and/or heart failure (HF).

  13. Controlled CVD growth of Cu-Sb alloy nanostructures

    NASA Astrophysics Data System (ADS)

    Chen, Jing; Yin, Zongyou; Sim, Daohao; Tay, Yee Yan; Zhang, Hua; Ma, Jan; Hng, Huey Hoon; Yan, Qingyu

    2011-08-01

    Sb based alloy nanostructures have attracted much attention due to their many promising applications, e.g. as battery electrodes, thermoelectric materials and magnetic semiconductors. In many cases, these applications require controlled growth of Sb based alloys with desired sizes and shapes to achieve enhanced performance. Here, we report a flexible catalyst-free chemical vapor deposition (CVD) process to prepare Cu-Sb nanostructures with tunable shapes (e.g. nanowires and nanoparticles) by transporting Sb vapor to react with copper foils, which also serve as the substrate. By simply controlling the substrate temperature and distance, various Sb-Cu alloy nanostructures, e.g. Cu11Sb3 nanowires (NWs), Cu2Sb nanoparticles (NPs), or pure Sb nanoplates, were obtained. We also found that the growth of Cu11Sb3 NWs in such a catalyst-free CVD process was dependent on the substrate surface roughness. For example, smooth Cu foils could not lead to the growth of Cu11Sb3 nanowires while roughening these smooth Cu foils with rough sand papers could result in the growth of Cu11Sb3 nanowires. The effects of gas flow rate on the size and morphology of the Cu-Sb alloy nanostructures were also investigated. Such a flexible growth strategy could be of practical interest as the growth of some Sb based alloy nanostructures by CVD may not be easy due to the large difference between the condensation temperature of Sb and the other element, e.g. Cu or Co.

  14. In-vitro study on the competitive binding of diflunisal and uraemic toxins to serum albumin and human plasma using a potentiometric ion-probe technique.

    PubMed

    Davilas, A; Koupparis, M; Macheras, P; Valsami, G

    2006-11-01

    The competitive binding of diflunisal and three well-known uraemic toxins (3-indoxyl sulfate, indole-3-acetic acid and hippuric acid) to bovine serum albumin (BSA), human serum albumin (HSA) and human plasma was studied by direct potentiometry. The method used the potentiometric drug ion-probe technique with a home-made ion sensor (electrode) selective to the drug anion. The site-oriented Scatchard model was used to describe the binding of diflunisal to BSA, HSA and human plasma, while the general competitive binding model was used to calculate the binding parameters of the three uraemic toxins to BSA. Diflunisal binding parameters, number of binding sites, n(i) and association constants for each class of binding site, K(i), were calculated in the absence and presence of uraemic toxins. Although diflunisal exhibits high binding affinity for site I of HSA and the three uraemic toxins bind primarily to site II, strong interaction was observed between the drug and the three toxins, which were found to affect the binding of diflunisal on its primary class of binding sites on both BSA and HSA molecules and on human plasma. These results are strong evidence that the decreased binding of diflunisal that occurs in uraemic plasma may not be solely attributed to the lower albumin concentration observed in many patients with renal failure. The uraemic toxins that accumulate in uraemic plasma may displace the drug from its specific binding sites on plasma proteins, resulting in increased free drug plasma concentration in uraemic patients. PMID:17132209

  15. Analysis of buprenorphine in rat plasma using a solid-phase extraction technique and high-performance liquid chromatography with electrochemical detection.

    PubMed

    Salem, A; Pierce, T L; Hope, W

    1997-03-01

    A solid-phase extraction method and sensitive reversed phase high-performance liquid chromatography analysis with electrochemical detection of buprenorphine and its metabolite, norbuprenorphine, in rat plasma is described. Adequate separation of the compounds of interest was achieved on a Phenomenex C18 reversed-phase column using a mobile phase comprising phosphate buffer: acetonitrile (75:25, pH 3.0) and 0.25 mM 1-octane-sulfonic acid, at a flow rat of 1 ml/min. Electrochemical detection was performed at a potential of 0.75 V and sensitivity of 2 nA. Buprenorphine and norbuprenorphine were extracted from plasma by solid-phase extraction technique using naltrindole as an internal standard (IS). Recoveries of buprenorphine and norbuprenorphine following the extraction method were high (70%-89%) over the concentration range used (25-100 ng/ml) and no endogenous substances in plasma interfered with any of the sample components. The retention times for norbuprenorphine, IS, and buprenorphine were 8, 12.5, and 30.5 min, respectively. The limits of detection of buprenorphine and norbuprenorphine in spiked plasma samples were 25 and 5 ng/ml, respectively. Using this method, buprenorphine was detected in rat plasma in animals acutely treated with the drug (5 mg/kg, s.c.).

  16. Improvement of interfacial adhesion and nondestructive damage evaluation for plasma-treated PBO and Kevlar fibers/epoxy composites using micromechanical techniques and surface wettability.

    PubMed

    Park, Joung-Man; Kim, Dae-Sik; Kim, Sung-Ryong

    2003-08-15

    Comparison of interfacial properties and microfailure mechanisms of oxygen-plasma treated poly(p-phenylene-2,6-benzobisoxazole (PBO, Zylon) and poly(p-phenylene terephthalamide) (PPTA, Kevlar) fibers/epoxy composites were investigated using a micromechanical technique and nondestructive acoustic emission (AE). The interfacial shear strength (IFSS) and work of adhesion, Wa, of PBO or Kevlar fiber/epoxy composites increased with oxygen-plasma treatment, due to induced hydrogen and covalent bondings at their interface. Plasma-treated Kevlar fiber showed the maximum critical surface tension and polar term, whereas the untreated PBO fiber showed the minimum values. The work of adhesion and the polar term were proportional to the IFSS directly for both PBO and Kevlar fibers. The microfibril fracture pattern of two plasma-treated fibers appeared obviously. Unlike in slow cooling, in rapid cooling, case kink band and kicking in PBO fiber appeared, whereas buckling in the Kevlar fiber was observed mainly due to compressive and residual stresses. Based on the propagation of microfibril failure toward the core region, the number of AE events for plasma-treated PBO and Kevlar fibers increased significantly compared to the untreated case. The results of nondestructive AE were consistent with microfailure modes.

  17. Improvement of interfacial adhesion and nondestructive damage evaluation for plasma-treated PBO and Kevlar fibers/epoxy composites using micromechanical techniques and surface wettability.

    PubMed

    Park, Joung-Man; Kim, Dae-Sik; Kim, Sung-Ryong

    2003-08-15

    Comparison of interfacial properties and microfailure mechanisms of oxygen-plasma treated poly(p-phenylene-2,6-benzobisoxazole (PBO, Zylon) and poly(p-phenylene terephthalamide) (PPTA, Kevlar) fibers/epoxy composites were investigated using a micromechanical technique and nondestructive acoustic emission (AE). The interfacial shear strength (IFSS) and work of adhesion, Wa, of PBO or Kevlar fiber/epoxy composites increased with oxygen-plasma treatment, due to induced hydrogen and covalent bondings at their interface. Plasma-treated Kevlar fiber showed the maximum critical surface tension and polar term, whereas the untreated PBO fiber showed the minimum values. The work of adhesion and the polar term were proportional to the IFSS directly for both PBO and Kevlar fibers. The microfibril fracture pattern of two plasma-treated fibers appeared obviously. Unlike in slow cooling, in rapid cooling, case kink band and kicking in PBO fiber appeared, whereas buckling in the Kevlar fiber was observed mainly due to compressive and residual stresses. Based on the propagation of microfibril failure toward the core region, the number of AE events for plasma-treated PBO and Kevlar fibers increased significantly compared to the untreated case. The results of nondestructive AE were consistent with microfailure modes. PMID:16256662

  18. Green`s function for a switched plasma medium and a perturbation technique for the study of wave propagation in a transient plasma with a small rise time

    SciTech Connect

    Kalluri, D.K.

    1996-12-31

    The main effect of switching a medium (creating a temporal discontinuity in the properties of a medium) is the splitting of the source (incident) wave into new waves whose frequencies are different. Lightning induced effects in the ionosphere cause a temporary enhancement of ionization. Such transient plasmas have a time-varying plasma frequency {omega}{sub p} (t) with a rise time T{sub r}. If the period t{sub 0} of a source wave existing before the transient effect begins is much larger than the rise time, the ionization change may be idealized as a sudden switching of the medium. The solution to this initial value problem with a step-change in the electron density profile is known and this profile will be considered as a reference profile. The topic of this paper is the solution of the initial value problem when t{sub 0} is comparable to the rise time T{sub r}. The initial motivation for investigating the problem is given below. There is considerable interest in the ionospheric physics community to investigate the recently discovered Sprites phenomenon which are red emissions in the lower D region induced by the lightning discharges from a cloud to the ground. The preliminary indications are that the Sprite is a plasma with electron density enhanced by about 10{sup 1} to 10{sup 3}/cc in a rise time of about 100 {micro}s.

  19. A novel technique for guided bone regeneration using platelet-rich plasma and osteogenic progenitor cells: Literature-based rationale and case report.

    PubMed

    Kwon, TaeHyun; Grieco, Peter C; Levin, Liran; Intini, Giuseppe

    2016-03-01

    Achieving predictable guided bone regeneration in critical size defects for future endosseous dental implant therapy poses a great challenge to clinicians. A novel technique utilizing autogenous osteogenic progenitor cells, calcium sulfate activated platelet-rich plasma in addition to particulate allograft was successfully used to augment a severely deficient maxillary anterior edentulous ridge. After 6 months of healing, satisfactory radiographic and clinical bone gain was noted with significant increase in alveolar ridge width. Endosseous implants were placed and restored successfully. The techniques with underlying clinical and biologic rationales are presented and discussed in this report.

  20. Low temperature growth of diamond films on optical fibers using Linear Antenna CVD system

    NASA Astrophysics Data System (ADS)

    Ficek, M.; Drijkoningen, S.; Karczewski, J.; Bogdanowicz, R.; Haenen, K.

    2016-01-01

    It is not trivial to achieve a good quality diamond-coated fibre interface due to a large difference in the properties and composition of the diamond films (or use coating even) and the optical fibre material, i.e. fused silica. One of the biggest problems is the high temperature during the deposition which influences the optical fibre or optical fibre sensor structure (e.g. long-period gratings (LPG)). The greatest advantage of a linear antenna microwave plasma enhanced chemical vapor deposition system (LA MW CVD) is the fact that it allows to grow the diamond layers at low temperature (below 300°C) [1]. High quality nanocrystalline diamond (NCD) thin films with thicknesses ranging from 70 nm to 150 nm, were deposited on silicon, glass and optical fibre substrates [2]. Substrates pretreatment by dip-coating and spin coating process with a dispersion consisting of detonation nanodiamond (DND) in dimethyl sulfoxide (DMSO) with polyvinyl alcohol (PVA) has been applied. During the deposition process the continuous mode of operation of the LA MW CVD system was used, which produces a continuous wave at a maximum power of 1.9 kW (in each antenna). Diamond films on optical fibres were obtained at temperatures below 350°C, providing a clear improvement of results compared to our earlier work [3]. The samples were characterized by scanning electron microscopy (SEM) imaging to investigate the morphology of the nanocrystalline diamond films. The film growth rate, film thickness, and optical properties in the VIS-NIR range, i.e. refractive index and extinction coefficient will be discussed based on measurements on reference quartz plates by using spectroscopic ellipsometry (SE).

  1. Effects of Light Intensity Activity on CVD Risk Factors: A Systematic Review of Intervention Studies

    PubMed Central

    Batacan, Romeo B.; Duncan, Mitch J.; Dalbo, Vincent J.; Tucker, Patrick S.; Fenning, Andrew S.

    2015-01-01

    The effects of light intensity physical activity (LIPA) on cardiovascular disease (CVD) risk factors remain to be established. This review summarizes the effects of LIPA on CVD risk factors and CVD-related markers in adults. A systematic search of four electronic databases (PubMed, Academic Search Complete, SPORTDiscus, and CINAHL) examining LIPA and CVD risk factors (body composition, blood pressure, glucose, insulin, glycosylated hemoglobin, and lipid profile) and CVD-related markers (maximal oxygen uptake, heart rate, C-reactive protein, interleukin-6, tumor necrosis factor-alpha, and tumor necrosis factor receptors 1 and 2) published between 1970 and 2015 was performed on 15 March 2015. A total of 33 intervention studies examining the effect of LIPA on CVD risk factors and markers were included in this review. Results indicated that LIPA did not improve CVD risk factors and CVD-related markers in healthy individuals. LIPA was found to improve systolic and diastolic blood pressure in physically inactive populations with a medical condition. Reviewed studies show little support for the role of LIPA to reduce CVD risk factors. Many of the included studies were of low to fair study quality and used low doses of LIPA. Further studies are needed to establish the value of LIPA in reducing CVD risk. PMID:26543862

  2. Effects of Light Intensity Activity on CVD Risk Factors: A Systematic Review of Intervention Studies.

    PubMed

    Batacan, Romeo B; Duncan, Mitch J; Dalbo, Vincent J; Tucker, Patrick S; Fenning, Andrew S

    2015-01-01

    The effects of light intensity physical activity (LIPA) on cardiovascular disease (CVD) risk factors remain to be established. This review summarizes the effects of LIPA on CVD risk factors and CVD-related markers in adults. A systematic search of four electronic databases (PubMed, Academic Search Complete, SPORTDiscus, and CINAHL) examining LIPA and CVD risk factors (body composition, blood pressure, glucose, insulin, glycosylated hemoglobin, and lipid profile) and CVD-related markers (maximal oxygen uptake, heart rate, C-reactive protein, interleukin-6, tumor necrosis factor-alpha, and tumor necrosis factor receptors 1 and 2) published between 1970 and 2015 was performed on 15 March 2015. A total of 33 intervention studies examining the effect of LIPA on CVD risk factors and markers were included in this review. Results indicated that LIPA did not improve CVD risk factors and CVD-related markers in healthy individuals. LIPA was found to improve systolic and diastolic blood pressure in physically inactive populations with a medical condition. Reviewed studies show little support for the role of LIPA to reduce CVD risk factors. Many of the included studies were of low to fair study quality and used low doses of LIPA. Further studies are needed to establish the value of LIPA in reducing CVD risk. PMID:26543862

  3. Aerosol-assisted delivery of precursors for chemical vapour deposition: expanding the scope of CVD for materials fabrication.

    PubMed

    Marchand, Peter; Hassan, Iman A; Parkin, Ivan P; Carmalt, Claire J

    2013-07-14

    The production of thin films of materials has become the attention of a great deal of research throughout academia and industry worldwide owing to the array of applications which utilise them, including electronic devices, gas sensors, solar cells, window coatings and catalytic systems. Whilst a number of deposition techniques are in common use, chemical vapour deposition (CVD) is an attractive process for the production of a wide range of materials due to the control it offers over film composition, coverage and uniformity, even on large scales. Conventional CVD processes can be limited, however, by the need for suitably volatile precursors. Aerosol-assisted (AA)CVD is a solution-based process which relies on the solubility of the precursor, rather than its volatility and thus vastly extends the range of potentially applicable precursors. In addition, AACVD offers extra means to control film morphology and concurrently the properties of the deposited materials. In this perspective we discuss the AACVD process, the influence of deposition conditions on film characteristics and a number of materials and applications to which AACVD has been found beneficial. PMID:23629474

  4. Carbon-coated hexagonal magnetite nanoflakes production by spray CVD of alcohols in mixture with water

    NASA Astrophysics Data System (ADS)

    Reyes-Reyes, Marisol; Hernández-Arriaga, Daniel; López-Sandoval, Román

    2014-12-01

    In this study, we report a successful technique for synthesizing magnetite hexagonal nanoflakes coated with carbon layers using spray thermal decomposition, which is a reproducible method that is easy to scale up. We investigated the effects of mixing different volumes of deionized (DI) water with alcohol on the population and quality of single-crystalline Fe3O4 hexagonal nanoflakes. Methanol and ethanol were used as the carbon and oxygen source, while ferrocene was mainly used as the Fe source. To obtain a large quantity of hexagonal structures, a strongly oxidative atmosphere was required. The DI water was used to enhance the oxidative environment during the reaction and was an important component for obtaining well-shaped hexagonal magnetite crystalline nanoflakes. The use of alcohols, water and the spray chemical vapor deposition (CVD) method make this procedure easy to use. In addition, this method provides a one-step process for synthesizing carbon-coated hexagonal Fe3O4 nanocrystals.

  5. Pulsed electrodeposition into AAO templates for CVD growth of carbon nanotube arrays

    NASA Astrophysics Data System (ADS)

    Sklar, G. P.; Paramguru, K.; Misra, M.; La Combe, J. C.

    2005-08-01

    Anodic aluminium oxide (AAO) templates for multi-walled carbon nanotube (MWCNT) growth were produced by anodization of aluminium followed by pulse-reverse electrodeposition of cobalt inside the AAO pores. Cobalt functioned as the catalyst for H2/C2H2 chemical vapour deposition (CVD) growth of fairly well graphitized MWCNTs initiating inside the majority of the AAO pores and quickly growing beyond the pore confines. A technique is introduced for the production of AAO templates that fill evenly during pulsed electrodeposition. The electrodeposition produced an active metallic catalyst in the pore bottoms, with minimal over-filling. This process also eliminates the reduction step necessary when alternating current (AC) electrodeposition is used for filling AAO pores.

  6. A Bayesian method to estimate the neutron response matrix of a single crystal CVD diamond detector

    SciTech Connect

    Reginatto, Marcel; Araque, Jorge Guerrero; Nolte, Ralf; Zbořil, Miroslav; Zimbal, Andreas; Gagnon-Moisan, Francis

    2015-01-13

    Detectors made from artificial chemical vapor deposition (CVD) single crystal diamond are very promising candidates for applications where high resolution neutron spectrometry in very high neutron fluxes is required, for example in fusion research. We propose a Bayesian method to estimate the neutron response function of the detector for a continuous range of neutron energies (in our case, 10 MeV ≤ E{sub n} ≤ 16 MeV) based on a few measurements with quasi-monoenergetic neutrons. This method is needed because a complete set of measurements is not available and the alternative approach of using responses based on Monte Carlo calculations is not feasible. Our approach uses Bayesian signal-background separation techniques and radial basis function interpolation methods. We present the analysis of data measured at the PTB accelerator facility PIAF. The method is quite general and it can be applied to other particle detectors with similar characteristics.

  7. Epigenetic modifications and human pathologies: cancer and CVD.

    PubMed

    Duthie, Susan J

    2011-02-01

    Epigenetic changes are inherited alterations in DNA that affect gene expression and function without altering the DNA sequence. DNA methylation is one epigenetic process implicated in human disease that is influenced by diet. DNA methylation involves addition of a 1-C moiety to cytosine groups in DNA. Methylated genes are not transcribed or are transcribed at a reduced rate. Global under-methylation (hypomethylation) and site-specific over-methylation (hypermethylation) are common features of human tumours. DNA hypomethylation, leading to increased expression of specific proto-oncogenes (e.g. genes involved in proliferation or metastasis) can increase the risk of cancer as can hypermethylation and reduced expression of tumour suppressor (TS) genes (e.g. DNA repair genes). DNA methyltransferases (DNMT), together with the methyl donor S-adenosylmethionine (SAM), facilitate DNA methylation. Abnormal DNA methylation is implicated not only in the development of human cancer but also in CVD. Polyphenols, a group of phytochemicals consumed in significant amounts in the human diet, effect risk of cancer. Flavonoids from tea, soft fruits and soya are potent inhibitors of DNMT in vitro, capable of reversing hypermethylation and reactivating TS genes. Folates, a group of water-soluble B vitamins found in high concentration in green leafy vegetables, regulate DNA methylation through their ability to generate SAM. People who habitually consume the lowest level of folate or with the lowest blood folate concentrations have a significantly increased risk of developing several cancers and CVD. This review describes how flavonoids and folates in the human diet alter DNA methylation and may modify the risk of human colon cancer and CVD.

  8. Oats and CVD risk markers: a systematic literature review.

    PubMed

    Thies, Frank; Masson, Lindsey F; Boffetta, Paolo; Kris-Etherton, Penny

    2014-10-01

    High consumption of whole-grain food such as oats is associated with a reduced risk of CVD and type 2 diabetes. The present study aimed to systematically review the literature describing long-term intervention studies that investigated the effects of oats or oat bran on CVD risk factors. The literature search was conducted using Embase, Medline and the Cochrane library, which identified 654 potential articles. Seventy-six articles describing sixty-nine studies met the inclusion criteria. Most studies lacked statistical power to detect a significant effect of oats on any of the risk factors considered: 59 % of studies had less than thirty subjects in the oat intervention group. Out of sixty-four studies that assessed systemic lipid markers, thirty-seven (58 %) and thirty-four (49 %) showed a significant reduction in total cholesterol (2-19 % reduction) and LDL-cholesterol (4-23 % reduction) respectively, mostly in hypercholesterolaemic subjects. Few studies (three and five, respectively) described significant effects on HDL-cholesterol and TAG concentrations. Only three out of twenty-five studies found a reduction in blood pressure after oat consumption. None of the few studies that measured markers of insulin sensitivity and inflammation found any effect after long-term oat consumption. Long-term dietary intake of oats or oat bran has a beneficial effect on blood cholesterol. However, there is no evidence that it favourably modulates insulin sensitivity. It is still unclear whether increased oat consumption significantly affects other risk markers for CVD risk, and comprehensive, adequately powered and controlled intervention trials are required to address this question.

  9. Controlled CVD growth of Cu-Sb alloy nanostructures.

    PubMed

    Chen, Jing; Yin, Zongyou; Sim, Daohao; Tay, Yee Yan; Zhang, Hua; Ma, Jan; Hng, Huey Hoon; Yan, Qingyu

    2011-08-12

    Sb based alloy nanostructures have attracted much attention due to their many promising applications, e.g. as battery electrodes, thermoelectric materials and magnetic semiconductors. In many cases, these applications require controlled growth of Sb based alloys with desired sizes and shapes to achieve enhanced performance. Here, we report a flexible catalyst-free chemical vapor deposition (CVD) process to prepare Cu-Sb nanostructures with tunable shapes (e.g. nanowires and nanoparticles) by transporting Sb vapor to react with copper foils, which also serve as the substrate. By simply controlling the substrate temperature and distance, various Sb-Cu alloy nanostructures, e.g. Cu(11)Sb(3) nanowires (NWs), Cu(2)Sb nanoparticles (NPs), or pure Sb nanoplates, were obtained. We also found that the growth of Cu(11)Sb(3) NWs in such a catalyst-free CVD process was dependent on the substrate surface roughness. For example, smooth Cu foils could not lead to the growth of Cu(11)Sb(3) nanowires while roughening these smooth Cu foils with rough sand papers could result in the growth of Cu(11)Sb(3) nanowires. The effects of gas flow rate on the size and morphology of the Cu-Sb alloy nanostructures were also investigated. Such a flexible growth strategy could be of practical interest as the growth of some Sb based alloy nanostructures by CVD may not be easy due to the large difference between the condensation temperature of Sb and the other element, e.g. Cu or Co. PMID:21757793

  10. Specific identification of fibrin polymers, fibrinogen degradation products, and crosslinked fibrin degradation products in plasma and serum with a new sensitive technique.

    PubMed

    Connaghan, D G; Francis, C W; Lane, D A; Marder, V J

    1985-03-01

    A new method is described for identifying low concentrations of circulating derivatives of fibrinogen and fibrin, even when present in heterogeneous mixtures. This technique is applicable to plasma and serum and uses electrophoresis in 2% agarose in the presence of sodium dodecyl sulfate (SDS) followed by immunological identification of separated derivatives, using radiolabeled antifibrinogen antiserum and autoradiography. Unique electrophoretic patterns distinguish plasmic derivatives of crosslinked fibrin from those of fibrinogen and also identify crosslinked fibrin polymers produced by the combined action of thrombin and factor XIII on fibrinogen. The assay is sensitive to a concentration of 0.1 micrograms/mL of fibrinogen in serum or plasma. Fibrin polymers, plasmic degradation products of fibrinogen, and plasmic degradation products of crosslinked fibrin were detected in the plasma or serum of a patient with disseminated intravascular coagulation. Plasmic derivatives of both fibrinogen and crosslinked fibrin appeared in serum in the course of fibrinolytic therapy for pulmonary embolism, whereas during acute myocardial infarction a marked increase in the proportion of fibrin polymers in plasma was found in comparison with normal controls. Thus, the procedure can distinguish between the simultaneous processes of fibrin polymer formation, fibrinogenolysis, and fibrinolysis, and is sufficiently sensitive to detect relevant quantities of derivatives in pathologic conditions.

  11. Development of CVD Mullite Coatings for SiC Fibers

    SciTech Connect

    Sarin, V.K.; Varadarajan, S.

    2000-03-15

    A process for depositing CVD mullite coatings on SiC fibers for enhanced oxidation and corrosion, and/or act as an interfacial protective barrier has been developed. Process optimization via systematic investigation of system parameters yielded uniform crystalline mullite coatings on SiC fibers. Structural characterization has allowed for tailoring of coating structure and therefore properties. High temperature oxidation/corrosion testing of the optimized coatings has shown that the coatings remain adherent and protective for extended periods. However, preliminary tests of coated fibers showed considerable degradation in tensile strength.

  12. Paralinear Oxidation of CVD SiC in Water Vapor

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Hann, Raiford E., Jr.

    1997-01-01

    The oxidation kinetics of CVD SiC were monitored by thermogravimetric analysis (TGA) in a 50% H2O/50% O2 gas mixture flowing at 4.4 cm/s for temperatures between 1200 and 1400 C. Paralinear weight change kinetics were observed as the water vapor oxidized the SiC and simultaneously volatilized the silica scale. The long-term degradation rate of SiC is determined by the volatility of the silica scale. Rapid SiC surface recession rates were estimated from these data for actual aircraft engine combustor conditions.

  13. Selective, pulsed CVD of platinum on microfilament gas sensors

    SciTech Connect

    Manginell, R.P.; Smith, J.H.; Ricco, A.J.; Moreno, D.J.; Hughes, R.C.; Huber, R.J.; Senturia, S.D.

    1996-05-01

    A post-processing, selective micro-chemical vapor deposition (``micro-CVD``) technology for the deposition of catalytic films on surface-micromachined, nitride-passivated polysilicon filaments has been investigated. Atmospheric pressure deposition of Pt on microfilaments was accomplished by thermal decomposition of Pt acetylacetonate; deposition occurs selectively only on those filaments which are electrically heated. Catalyst morphology, characterized by SEM, can be controlled by altering deposition time, filament temperature, and through the use of pulsed heating of the filament during deposition. Morphology plays an important role in determining the sensitivity of these devices when used as combustible gas sensors.

  14. Spray CVD for Making Solar-Cell Absorber Layers

    NASA Technical Reports Server (NTRS)

    Banger, Kulbinder K.; Harris, Jerry; Jin, Michael H.; Hepp, Aloysius

    2007-01-01

    Spray chemical vapor deposition (spray CVD) processes of a special type have been investigated for use in making CuInS2 absorber layers of thin-film solar photovoltaic cells from either of two subclasses of precursor compounds: [(PBu3) 2Cu(SEt)2In(SEt)2] or [(PPh3)2Cu(SEt)2 In(SEt)2]. The CuInS2 films produced in the experiments have been characterized by x-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and four-point-probe electrical tests.

  15. The Oxidation of CVD Silicon Carbide in Carbon Dioxide

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Nguyen, QuynchGiao N.

    1997-01-01

    Chemically-vapor-deposited silicon carbide (CVD SiC) was oxidized in carbon dioxide (CO2) at temperatures of 1200-1400 C for times between 100 and 500 hours at several gas flow rates. Oxidation weight gains were monitored by thermogravimetric analysis (TGA) and were found to be very small and independent of temperature. Possible rate limiting kinetic laws are discussed. Oxidation of SiC by CO2 is negligible compared to the rates measured for other oxidants typically found in combustion environments: oxygen and water vapor.

  16. Departures from local thermodynamic equilibrium in cutting arc plasmas derived from electron and gas density measurements using a two-wavelength quantitative Schlieren technique

    SciTech Connect

    Prevosto, L.; Mancinelli, B.; Artana, G.; Kelly, H.

    2011-03-15

    A two-wavelength quantitative Schlieren technique that allows inferring the electron and gas densities of axisymmetric arc plasmas without imposing any assumption regarding statistical equilibrium models is reported. This technique was applied to the study of local thermodynamic equilibrium (LTE) departures within the core of a 30 A high-energy density cutting arc. In order to derive the electron and heavy particle temperatures from the inferred density profiles, a generalized two-temperature Saha equation together with the plasma equation of state and the quasineutrality condition were employed. Factors such as arc fluctuations that influence the accuracy of the measurements and the validity of the assumptions used to derive the plasma species temperature were considered. Significant deviations from chemical equilibrium as well as kinetic equilibrium were found at elevated electron temperatures and gas densities toward the arc core edge. An electron temperature profile nearly constant through the arc core with a value of about 14000-15000 K, well decoupled from the heavy particle temperature of about 1500 K at the arc core edge, was inferred.

  17. A novel fast and flexible technique of radical kinetic behaviour investigation based on pallet for plasma evaluation structure and numerical analysis

    NASA Astrophysics Data System (ADS)

    Malinowski, Arkadiusz; Takeuchi, Takuya; Chen, Shang; Suzuki, Toshiya; Ishikawa, Kenji; Sekine, Makoto; Hori, Masaru; Lukasiak, Lidia; Jakubowski, Andrzej

    2013-07-01

    This paper describes a new, fast, and case-independent technique for sticking coefficient (SC) estimation based on pallet for plasma evaluation (PAPE) structure and numerical analysis. Our approach does not require complicated structure, apparatus, or time-consuming measurements but offers high reliability of data and high flexibility. Thermal analysis is also possible. This technique has been successfully applied to estimation of very low value of SC of hydrogen radicals on chemically amplified ArF 193 nm photoresist (the main goal of this study). Upper bound of our technique has been determined by investigation of SC of fluorine radical on polysilicon (in elevated temperature). Sources of estimation error and ways of its reduction have been also discussed. Results of this study give an insight into the process kinetics, and not only they are helpful in better process understanding but additionally they may serve as parameters in a phenomenological model development for predictive modelling of etching for ultimate CMOS topography simulation.

  18. Low-temperature oxidizing plasma surface modification and composite polymer thin-film fabrication techniques for tailoring the composition and behavior of polymer surfaces

    NASA Astrophysics Data System (ADS)

    Tompkins, Brendan D.

    This dissertation examines methods for modifying the composition and behavior of polymer material surfaces. This is accomplished using (1) low-temperature low-density oxidizing plasmas to etch and implant new functionality on polymers, and (2) plasma enhanced chemical vapor deposition (PECVD) techniques to fabricate composite polymer materials. Emphases are placed on the structure of modified polymer surfaces, the evolution of polymer surfaces after treatment, and the species responsible for modifying polymers during plasma processing. H2O vapor plasma modification of high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), and 75A polyurethane (PU) was examined to further our understanding of polymer surface reorganization leading to hydrophobic recovery. Water contact angles (wCA) measurements showed that PP and PS were the most susceptible to hydrophobic recovery, while PC and HDPE were the most stable. X-ray photoelectron spectroscopy (XPS) revealed a significant quantity of polar functional groups on the surface of all treated polymer samples. Shifts in the C1s binding energies (BE) with sample age were measured on PP and PS, revealing that surface reorganization was responsible for hydrophobic recovery on these materials. Differential scanning calorimetry (DSC) was used to rule out the intrinsic thermal properties as the cause of reorganization and hydrophobic recovery on HDPE, LDPE, and PP. The different contributions that polymer cross-linking and chain scission mechanisms make to polymer aging effects are considered. The H2O plasma treatment technique was extended to the modification of 0.2 microm and 3.0 microm track-etched polycarbonate (PC-TE) and track-etched polyethylene terephthalate (PET-TE) membranes with the goal of permanently increasing the hydrophilicity of the membrane surfaces. Contact angle measurements on freshly treated and aged samples confirmed the wettability of the

  19. Full-length, glycosylated NSP4 is localized to plasma membrane caveolae by a novel raft isolation technique.

    PubMed

    Storey, Stephen M; Gibbons, Thomas F; Williams, Cecelia V; Parr, Rebecca D; Schroeder, Friedhelm; Ball, Judith M

    2007-06-01

    Rotavirus NSP4, initially characterized as an endoplasmic reticulum intracellular receptor, is a multifunctional viral enterotoxin that induces diarrhea in murine pups. There have been recent reports of the secretion of a cleaved NSP4 fragment (residues 112 to 175) and of the association of NSP4 with LC3-positive autophagosomes, raft membranes, and microtubules. To determine if NSP4 traffics to a specific subset of rafts at the plasma membrane, we isolated caveolae from plasma membrane-enriched material that yielded caveola membranes free of endoplasmic reticulum and nonraft plasma membrane markers. Analyses of the newly isolated caveolae from rotavirus-infected MDCK cells revealed full-length, high-mannose glycosylated NSP4. The lack of Golgi network-specific processing of the caveolar NSP4 glycans supports studies showing that NSP4 bypasses the Golgi apparatus. Confocal imaging showed the colocalization of NSP4 with caveolin-1 early and late in infection, elucidating the temporal and spatial NSP4-caveolin-1 association during infection. These data were extended with fluorescent resonance energy transfer analyses that confirmed the NSP4 and caveolin-1 interaction in that the specific fluorescently tagged antibodies were within 10 nm of each other during infection. Cells transfected with NSP4 showed patterns of staining and colocalization with caveolin-1 similar to those of infected cells. This study presents an endoplasmic reticulum contaminant-free caveola isolation protocol; describes the presence of full-length, endoglycosidase H-sensitive NSP4 in plasma membrane caveolae; provides confirmation of the NSP4-caveolin interaction in the presence and absence of other viral proteins; and provides a final plasma membrane destination for Golgi network-bypassing NSP4 transport. PMID:17376898

  20. Oxide Dispersion Strengthened Iron Aluminide by CVD Coated Powders

    SciTech Connect

    Asit Biswas Andrew J. Sherman

    2006-09-25

    This I &I Category2 program developed chemical vapor deposition (CVD) of iron, aluminum and aluminum oxide coated iron powders and the availability of high temperature oxidation, corrosion and erosion resistant coating for future power generation equipment and can be used for retrofitting existing fossil-fired power plant equipment. This coating will provide enhanced life and performance of Coal-Fired Boilers components such as fire side corrosion on the outer diameter (OD) of the water wall and superheater tubing as well as on the inner diameter (ID) and OD of larger diameter headers. The program also developed a manufacturing route for readily available thermal spray powders for iron aluminide coating and fabrication of net shape component by powder metallurgy route using this CVD coated powders. This coating can also be applid on jet engine compressor blade and housing, industrial heat treating furnace fixtures, magnetic electronic parts, heating element, piping and tubing for fossil energy application and automotive application, chemical processing equipment , heat exchanger, and structural member of aircraft. The program also resulted in developing a new fabrication route of thermal spray coating and oxide dispersion strengthened (ODS) iron aluminide composites enabling more precise control over material microstructures.

  1. VOx effectively doping CVD-graphene for transparent conductive films

    NASA Astrophysics Data System (ADS)

    Ji, Qinghua; Shi, Liangjing; Zhang, Qinghong; Wang, Weiqi; Zheng, Huifeng; Zhang, Yuzhi; Liu, Yangqiao; Sun, Jing

    2016-11-01

    Chemical vapor deposition(CVD)-synthesized graphene is potentially an alternative for tin-doped indium oxide (ITO) transparent conductive films (TCFs), however its sheet resistance is still too high to meet many demands. Vanadium oxide has been widely applied as smart window materials, however, no study has been reported to use it as dopant to improve the conductivity of graphene TCFs. In this study, we firstly reported that VOx doping can effectively lower the sheet resistance of CVD-graphene films while keeping its good optical properties, whose transmittance is as high as 86-90%. The optimized VOx-doped graphene exhibits a sheet resistance as low as 176 Ω/□, which decreases by 56% compared to the undoped graphene films. The doping process is convenient, stable, economical and easy to operate. What is more, VOx can effectively increase the work function(WF) of the film, making it more appropriate for use in solar cells. The evolution of the VOx species annealed at different temperatures below 400 °C has been detailed studied for the first time, based on which the doping mechanism is proposed. The prepared VOx doped graphene is expected to be a promising candidate for transparent conductive film purposes.

  2. Dopant Incorporation Efficiency in CVD Silicon Carbide Epilayers

    NASA Technical Reports Server (NTRS)

    Larkin, D. J.

    1996-01-01

    In order to ensure reproducible and reliable SiC semiconductor device characteristics, controlled dopant incorporation must be accomplished. Some of the many factors which greatly influence dopant incorporation are the site-competition effect, SiC(0001) substrate polarity, substrate temperature, and the dopant-source reactor concentration. In this paper, dopant incorporation is considered and compared for various dopants in the context of dopant incorporation efficiency. By using secondary ion mass spectrometry (SIMS), the relative dopant incorporation efficiencies were calculated by dividing the SIMS determined dopant concentration in the resulting epitaxial layer by the intentional gas phase dopant concentration used during the SiC CVD. Specifically, the relative magnitudes of dopant incorporation efficiencies for nitrogen, phosphorus, and boron in 6H-SiC (0001) Si-face epitaxial layers are compared as a function of the site-competition effect and the dopant-source reactor concentrations. This serves as a first approximation for comparison of the relative 'doping potencies' of some common dopants used in SiC CVD epitaxial growth.

  3. Thermoluminescence in CVD diamond films: application to actinometric dosimetry.

    PubMed

    Barboza-Flores, M; Meléndrez, R; Chernov, V; Castañeda, B; Pedroza-Montero, M; Gan, B; Ahn, J; Zhang, Q; Yoon, S F

    2002-01-01

    Diamond is considered a tissue-equivalent material since its atomic number (Z =6) is close to the effective atomic number of biological tissue (Z =7.42). Such a situation makes it suitable for radiation detection purposes in medical applications. In the present work the analysis is reported of the thermoluminescence (TL) and dosimetric features of chemically vapour deposited (CVD) diamond film samples subjected to ultraviolet (UV) irradiation in the actinometric region. The TL glow curve shows peaks at 120, 220), 320 and 370 degrees C. The 120 and 370 degrees C peaks are too weak and the first one fades away in a few seconds after exposure. The overall room temperature fading shows a 50% TL decay 30 min after exposure. The 320 degrees C glow peak is considered to be the most adequate for dosimetric applications due to its low fading and linear TL behaviour as a function of UV dose in the 180-260 nm range. The TL excitation spectrum presents a broad band with at least two overlapped components around 205 and 220 nm. The results indicate that the TL behaviour of CVD diamond film can be a good alternative to the currently available dosemeter and detector in the actinometric region as well as in clinical and medical applications. PMID:12382917

  4. CVD Rhenium Engines for Solar-Thermal Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Williams, Brian E.; Fortini, Arthur J.; Tuffias, Robert H.; Duffy, Andrew J.; Tucker, Stephen P.

    1999-01-01

    Solar-thermal upper-stage propulsion systems have the potential to provide specific impulse approaching 900 seconds, with 760 seconds already demonstrated in ground testing. Such performance levels offer a 100% increase in payload capability compared to state-of-the-art chemical upper-stage systems, at lower cost. Although alternatives such as electric propulsion offer even greater performance, the 6- to 18- month orbital transfer time is a far greater deviation from the state of the art than the one to two months required for solar propulsion. Rhenium metal is the only material that is capable of withstanding the predicted thermal, mechanical, and chemical environment of a solar-thermal propulsion device. Chemical vapor deposition (CVD) is the most well-established and cost-effective process for the fabrication of complex rhenium structures. CVD rhenium engines have been successfully constructed for the Air Force ISUS program (bimodal thrust/electricity) and the NASA Shooting Star program (thrust only), as well as under an Air Force SBIR project (thrust only). The bimodal engine represents a more long-term and versatile approach to solar-thermal propulsion, while the thrust-only engines provide a potentially lower weight/lower cost and more near-term replacement for current upper-stage propulsion systems.

  5. Plasma Cleaning

    NASA Technical Reports Server (NTRS)

    Hintze, Paul E.

    2016-01-01

    NASA's Kennedy Space Center has developed two solvent-free precision cleaning techniques: plasma cleaning and supercritical carbon dioxide (SCCO2), that has equal performance, cost parity, and no environmental liability, as compared to existing solvent cleaning methods.

  6. Microstructural study of as sprayed and heat treated Ni3Al coatings deposited by air plasma spraying technique

    NASA Astrophysics Data System (ADS)

    Mehmood, K.; Rafiq, M. A.; Nusair Khan, A.; Rauf, M. M.

    2016-08-01

    Air plasma spraying system was utilized to deposit Ni3Al coatings on AISI 321 steel samples. After plasma spraying the coatings were heat treated at different temperatures i.e. 500 °C to 800 °C for 10 to 100 hours. The characterization tools such as, X-Ray diffraction analysis, optical and scanning electron microscopy were used. By comparing the XRD scan data of as sprayed and heat treated coating, it was observed that the formation of NiO increases drastically with time and temperature. Due to the formation of NiO, hardness was also enhanced. The oxidation behavior was observed by using optical microscope and when it was studied that the oxidation was increasing with time and temperature. Further, the SEM tool was utilized to study the detail microstructural behavior such as shrinkage cavity and oxide particles. The other phases like alumina and spinel phases were determined by using Energy dispersive spectrometer method.

  7. Evaluation technique for plasma-induced SiOC dielectric damage by capacitance-voltage hysteresis monitoring

    NASA Astrophysics Data System (ADS)

    Nishida, Kentaro; Okada, Yukimasa; Takao, Yoshinori; Eriguchi, Koji; Ono, Kouichi

    2016-06-01

    We propose an electrical method, named capacitance-voltage (C-V) monitoring, for quantifying plasma-induced damage (PID) to interlayer dielectrics. By this method, we measure the C-V hysteresis loops to assign carrier trap sites created by PID, and simultaneously obtain the change in the dielectric constant and thickness. We optimized the bias-sweep configuration for measuring the hysteresis curves. It is found that the C-V curve shifted in the negative direction during the optimized voltage sweep from accumulation to inversion in a pseudo-metal-oxide-semiconductor (MOS) structure. This implies the appearance of net positively charged sites owing to PID, presumably near the surface of the SiOC film. We estimate the density of defects created near the surface by monitoring the obtained C-V hysteresis curve shift. Since the degradation of interlayer dielectrics affects the circuit performance, the proposed quantitative method should be used for plasma process designs.

  8. Generation and characterization of plasma channels in gas puff targets using soft X-ray radiography technique

    SciTech Connect

    Wachulak, P. W. Bartnik, A.; Jarocki, R.; Fok, T.; Węgrzyński, Ł.; Kostecki, J.; Szczurek, M.; Jabczyński, J.; Fiedorowicz, H.

    2014-10-15

    We present our recent results of a formation and characterization of plasma channels in elongated krypton and xenon gas puff targets. The study of their formation and temporal expansion was carried out using a combination of a soft X-ray radiography (shadowgraphy) and pinhole camera imaging. Two high-energy short laser pulses were used to produce the channels. When a pumping laser pulse was shaped into a line focus, using cylindrical and spherical lenses, the channels were not produced because much smaller energy density was deposited in the gas puff target. However, when a point focus was obtained, using just a spherical lens, the plasma channels appeared. The channels were up to 9 mm in length, had a quite uniform density profile, and expanded in time with velocities of about 2 cm/μs.

  9. A multi-technique analysis of deuterium trapping and near-surface precipitate growth in plasma-exposed tungsten

    DOE PAGES

    Kolasinski, Robert; Shimada, Masashi; Oya, Yasuhisa; Buchenauer, Dean A.; Chikada, Takumi; Cowgill, Donald F.; Donovan, David; Friddle, Raymond William; Michibayashi, Katsu; Sato, Misaki

    2015-08-17

    We examine how deuterium becomes trapped in plasma-exposed tungsten and forms near-surface platelet-shaped precipitates. How these bubbles nucleate and grow, as well as the amount of deuterium trapped within, is crucial for interpreting the experimental database. Here, we use a combined experimental/theoretical approach to provide further insight into the underlying physics. With the Tritium Plasma Experiment, we exposed a series of ITER-gradetungsten samples to high flux D plasmas (up to 1.5 × 1022 m-2 s-1) at temperatures ranging between 103 and 554 °C. Retention of deuterium trapped in the bulk, assessed through thermal desorption spectrometry, reached a maximum at 230more » °C and diminished rapidly thereafter for T > 300 °C. Post-mortem examination of the surfaces revealed non-uniform growth of bubbles ranging in diameter between 1 and 10 μm over the surface with a clear correlation with grain boundaries. Electron back-scattering diffraction maps over a large area of the surface confirmed this dependence; grains containing bubbles were aligned with a preferred slip vector along the <111> directions. Focused ion beam profiles suggest that these bubbles nucleated as platelets at depths of 200 nm–1 μm beneath the surface and grew as a result of expansion of sub-surface cracks. Furthermore, to estimate the amount of deuterium trapped in these defects relative to other sites within the material, we applied a continuum-scale treatment of hydrogen isotope precipitation. Additionally, we propose a straightforward model of near-surface platelet expansion that reproduces bubble sizes consistent with our measurements. For the tungsten microstructure considered here, we find that bubbles would only weakly affect migration of D into the material, perhaps explaining why deep trapping was observed in prior studies with plasma-exposed neutron-irradiated specimens. We foresee no insurmountable issues that would prevent the theoretical framework developed here from

  10. A multi-technique analysis of deuterium trapping and near-surface precipitate growth in plasma-exposed tungsten

    SciTech Connect

    Kolasinski, R. D. Buchenauer, D. A.; Cowgill, D. F.; Donovan, D. C.; Shimada, M.; Oya, Y.; Chikada, T.; Sato, M.; Friddle, R. W.; Michibayashi, K.

    2015-08-21

    In this work, we examine how deuterium becomes trapped in plasma-exposed tungsten and forms near-surface platelet-shaped precipitates. How these bubbles nucleate and grow, as well as the amount of deuterium trapped within, is crucial for interpreting the experimental database. Here, we use a combined experimental/theoretical approach to provide further insight into the underlying physics. With the Tritium Plasma Experiment, we exposed a series of ITER-grade tungsten samples to high flux D plasmas (up to 1.5 × 10{sup 22 }m{sup −2} s{sup −1}) at temperatures ranging between 103 and 554 °C. Retention of deuterium trapped in the bulk, assessed through thermal desorption spectrometry, reached a maximum at 230 °C and diminished rapidly thereafter for T > 300 °C. Post-mortem examination of the surfaces revealed non-uniform growth of bubbles ranging in diameter between 1 and 10 μm over the surface with a clear correlation with grain boundaries. Electron back-scattering diffraction maps over a large area of the surface confirmed this dependence; grains containing bubbles were aligned with a preferred slip vector along the <111> directions. Focused ion beam profiles suggest that these bubbles nucleated as platelets at depths of 200 nm–1 μm beneath the surface and grew as a result of expansion of sub-surface cracks. To estimate the amount of deuterium trapped in these defects relative to other sites within the material, we applied a continuum-scale treatment of hydrogen isotope precipitation. In addition, we propose a straightforward model of near-surface platelet expansion that reproduces bubble sizes consistent with our measurements. For the tungsten microstructure considered here, we find that bubbles would only weakly affect migration of D into the material, perhaps explaining why deep trapping was observed in prior studies with plasma-exposed neutron-irradiated specimens. We foresee no insurmountable issues that would prevent the

  11. A multi-technique analysis of deuterium trapping and near-surface precipitate growth in plasma-exposed tungsten

    SciTech Connect

    Kolasinski, Robert; Shimada, Masashi; Oya, Yasuhisa; Buchenauer, Dean A.; Chikada, Takumi; Cowgill, Donald F.; Donovan, David; Friddle, Raymond William; Michibayashi, Katsu; Sato, Misaki

    2015-08-17

    We examine how deuterium becomes trapped in plasma-exposed tungsten and forms near-surface platelet-shaped precipitates. How these bubbles nucleate and grow, as well as the amount of deuterium trapped within, is crucial for interpreting the experimental database. Here, we use a combined experimental/theoretical approach to provide further insight into the underlying physics. With the Tritium Plasma Experiment, we exposed a series of ITER-gradetungsten samples to high flux D plasmas (up to 1.5 × 1022 m-2 s-1) at temperatures ranging between 103 and 554 °C. Retention of deuterium trapped in the bulk, assessed through thermal desorption spectrometry, reached a maximum at 230 °C and diminished rapidly thereafter for T > 300 °C. Post-mortem examination of the surfaces revealed non-uniform growth of bubbles ranging in diameter between 1 and 10 μm over the surface with a clear correlation with grain boundaries. Electron back-scattering diffraction maps over a large area of the surface confirmed this dependence; grains containing bubbles were aligned with a preferred slip vector along the <111> directions. Focused ion beam profiles suggest that these bubbles nucleated as platelets at depths of 200 nm–1 μm beneath the surface and grew as a result of expansion of sub-surface cracks. Furthermore, to estimate the amount of deuterium trapped in these defects relative to other sites within the material, we applied a continuum-scale treatment of hydrogen isotope precipitation. Additionally, we propose a straightforward model of near-surface platelet expansion that reproduces bubble sizes consistent with our measurements. For the tungsten microstructure considered here, we find that bubbles would only weakly affect migration of D into the material, perhaps explaining why deep trapping was observed in prior studies with plasma-exposed neutron-irradiated specimens. We foresee no insurmountable issues that would prevent the theoretical

  12. Dusty plasmas

    SciTech Connect

    Jones, M.E.; Winske, D.; Keinigs, R.; Lemons, D.

    1996-05-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project has been to develop a fundamental understanding of dusty plasmas at the Laboratory. While dusty plasmas are found in space in galactic clouds, planetary rings, and cometary tails, and as contaminants in plasma enhanced fabrication of microelectronics, many of their properties are only partially understood. Our work has involved both theoretical analysis and self-consistent plasma simulations to understand basic properties of dusty plasmas related to equilibrium, stability, and transport. Such an understanding can improve the control and elimination of plasma dust in industrial applications and may be important in the study of planetary rings and comet dust tails. We have applied our techniques to the study of charging, dynamics, and coagulation of contaminants in plasma processing reactors for industrial etching and deposition processes and to instabilities in planetary rings and other space plasma environments. The work performed in this project has application to plasma kinetics, transport, and other classical elementary processes in plasmas as well as to plasma waves, oscillations, and instabilities.

  13. Synthesis of carbon nanowall by plasma-enhanced chemical vapor deposition method.

    PubMed

    Liu, Rulin; Chi, Yaqing; Fang, Liang; Tang, Zhensen; Yi, Xun

    2014-02-01

    Plasma-enhanced chemical vapor deposition (PECVD) is widely used for the synthesis of carbon materials, such as diamond-like carbons (DLCs), carbon nanotubes (CNTs) and carbon nanowalls (CNWs). Advantages of PECVD are low synthesis temperature compared with thermal CVD and the ability to grow vertically, free-standing structures. Due to its self-supported property and high specific surface area, CNWs are a promising material for field emission devices and other chemical applications. This article reviews the recent process on the synthesis of CNW by the PECVD method. We briefly introduce the structure and properties of CNW with characterization techniques. Growth mechanism is also discussed to analyze the influence of plasma conditions, substrates, temperature, and other parameters to the final film, which will give a suggestion on parameter modulation for desired film. PMID:24749447

  14. Laser-Plasma Instabilities by Avoiding the Strong Ion Landau Damping Limit: The Central Role of Statistical, Ultrafast, Nonlinear Optical Laser Techniques (SUNOL)

    NASA Astrophysics Data System (ADS)

    Afeyan, Bedros; Hüller, Stefan; Montgomery, David; Moody, John; Froula, Dustin; Hammer, James; Jones, Oggie; Amendt, Peter

    2014-10-01

    In mid-Z and high-Z plasmas, it is possible to control crossed bean energy transfer (CBET) and subsequently occurring single or multiple beam instabilities such as Stimulated Raman Scattering (SRS) by novel means. These new techniques are inoperative when the ion acoustic waves are in their strong damping limit, such as occurs in low Z plasmas with comparable electron and ion temperatures. For mid-Z plasmas, such as Z = 10, and near the Mach 1 surface, the strong coupling regime (SCR) can be exploited for LPI mitigation. While at higher Z values, it is thermal filamentation in conjunction with nonlocal heat transport that are useful to exploit. In both these settings, the strategy is to induce laser hot spot intensity dependent, and thus spatially dependent, frequency shifts to the ion acoustic waves in the transient response of wave-wave interactions. The latter is achieved by the on-off nature of spike trains of uneven duration and delay, STUD pulses. The least taxing use of STUD pulses is to modulate the beams at the 10 ps time scale and to choose which crossing beams are overlapping in time and which are not. Work supported by a grant from the DOE NNSA-OFES joint program on HEDP

  15. The influence of DC biasing on the uniformity of a-C:H films for three-dimensional substrates by using a plasma-based ion implantation technique

    NASA Astrophysics Data System (ADS)

    Watanabe, Toshiya; Yamamoto, Kazuhiro; Tsuda, Osamu; Tanaka, Akihiro; Koga, Yoshinori; Takai, Osamu

    2003-05-01

    Amorphous hydrogenated carbon (a-C:H) films were synthesized by the use of a PBII technique using an electron cyclotron resonance plasma source with a mirror field, and the influence of the biasing conditions on the properties and the uniformity of the three-dimensional surfaces of a-C:H films was investigated. For convex faces, the film thickness was almost constant, independent of the deposition conditions, because a uniform plasma surrounded the substrates. For concave faces, the thickness of the films that formed without biasing and with only the application of a pulse bias decreased when the microwave-incident angle was decreased. On the other hand, when a DC bias was applied to the substrate in addition to a pulse bias, the uniformity of the thickness was much improved with a distribution within ±10%. The improvement in the uniformity was assumed to be the result of the continuous supply of ions in the plasma to the surfaces by the DC biasing.

  16. Low temperature deposition of SiO 2 and PSG using SiH 4, N 2O and phosphorous vapour for damage-free passivation of InP-based PIN diodes by plasma- and photo-assisted LPCVD

    NASA Astrophysics Data System (ADS)

    Riemenschneider, R.; DasGupta, N.; Schütz, R.; Hartnagel, H. L.; Kräutle, H.

    1993-05-01

    An improved deposition technique of phospho-silicate glass (PSG) for the passivation of InP has been developed using a low-temperature plasma-enhanced chemical vapour deposition (PECVD). Leakage-current measurements, capacitance-voltage analyses ( C-V curves) and deep-level transient spectroscopy (DLTS) have been employed to compare this passivation technique with a commonly applied plasma CVD and a photo-assisted CVD of silicon oxide. Improvements regarding interface states and deep-level traps have been achieved with a phosphorous vapour present during the insulator growth. The measurement of leakage on a semi-insulating InP surface, which is very relevant for the reliability and performance of InP-based PIN diodes, provides reliable results to detect surface damage and material degradation. The optimised plasma deposition of phospho-silicate glass at a temperature of 300°C with a low phosphorous concentration (<10 wt% P) prevents surface leakage and does not show plasma damage.

  17. Combined single-crystalline and polycrystalline CVD diamond substrates for diamond electronics

    SciTech Connect

    Vikharev, A. L. Gorbachev, A. M.; Dukhnovsky, M. P.; Muchnikov, A. B.; Ratnikova, A. K.; Fedorov, Yu. Yu.

    2012-02-15

    The fabrication of diamond substrates in which single-crystalline and polycrystalline CVD diamond form a single wafer, and the epitaxial growth of diamond films on such combined substrates containing polycrystalline and (100) single-crystalline CVD diamond regions are studied.

  18. A novel femtosecond-gated, high-resolution, frequency-shifted shearing interferometry technique for probing pre-plasma expansion in ultra-intense laser experiments

    SciTech Connect

    Feister, S. Orban, C.; Nees, J. A.; Morrison, J. T.; Frische, K. D.; Chowdhury, E. A.; Roquemore, W. M.

    2014-11-15

    Ultra-intense laser-matter interaction experiments (>10{sup 18} W/cm{sup 2}) with dense targets are highly sensitive to the effect of laser “noise” (in the form of pre-pulses) preceding the main ultra-intense pulse. These system-dependent pre-pulses in the nanosecond and/or picosecond regimes are often intense enough to modify the target significantly by ionizing and forming a plasma layer in front of the target before the arrival of the main pulse. Time resolved interferometry offers a robust way to characterize the expanding plasma during this period. We have developed a novel pump-probe interferometry system for an ultra-intense laser experiment that uses two short-pulse amplifiers synchronized by one ultra-fast seed oscillator to achieve 40-fs time resolution over hundreds of nanoseconds, using a variable delay line and other techniques. The first of these amplifiers acts as the pump and delivers maximal energy to the interaction region. The second amplifier is frequency shifted and then frequency doubled to generate the femtosecond probe pulse. After passing through the laser-target interaction region, the probe pulse is split and recombined in a laterally sheared Michelson interferometer. Importantly, the frequency shift in the probe allows strong plasma self-emission at the second harmonic of the pump to be filtered out, allowing plasma expansion near the critical surface and elsewhere to be clearly visible in the interferograms. To aid in the reconstruction of phase dependent imagery from fringe shifts, three separate 120° phase-shifted (temporally sheared) interferograms are acquired for each probe delay. Three-phase reconstructions of the electron densities are then inferred by Abel inversion. This interferometric system delivers precise measurements of pre-plasma expansion that can identify the condition of the target at the moment that the ultra-intense pulse arrives. Such measurements are indispensable for correlating laser pre-pulse measurements

  19. CVD synthesis of graphene nanoplates on MgO support

    NASA Astrophysics Data System (ADS)

    Jugade, Ravin M.; Sharma, Shalini; Gokhale, Suresh

    2014-06-01

    Synthesis of graphene directly on MgO has been carried out and the structural properties of the obtained material have been investigated. Few-layered graphene was produced by simple thermal decomposition of methane over MgO powder at 950 °C in a CVD reactor. The samples were purified by 10 N HNO3 treatment, and studied by TEM, Raman spectroscopy, EDAX and SEM. TEM clearly indicated the formation of graphene. EDAX showed that the purified sample contained only carbon and no traces of MgO. The characteristic Raman features of graphene were also seen as D-band at 1316 cm-1, G-band at 1602 cm-1, and a small 2D-band at 2700 cm-1 in the Raman spectra. The strong D-band suggests that the graphene possess large number of boundary defects. The small 2D-band indicates the formation of few-layered graphene.

  20. Low temperature CVD of TaB/sub 2/

    SciTech Connect

    Randich, E.

    1980-01-01

    Crystalline TaB/sub 2/ has been deposited using the CVD reaction of TaCl/sub 5/ and B/sub 2/H/sub 6/ in the temperature range of 773-1200/sup 0/K. Thermodynamic calculations have been made which compare the use of both B/sub 2/H/sub 6/ and BCl/sub 3/ as B source gases. The deposits obtained with B/sub 2/H/sub 6/ exhibited extremely small crystal size and contained amorphous B when the deposition temperature was below approx. 873/sup 0/K but were substoichiometric in B above this temperature. Carbon analysis indicated that C may substitute for B and thereby stabilize the diboride structure at high deposition temperatures. Microhardness of the coatings decreased with increasing B/Ta ratio and decreasing crystal size.

  1. Application of HOPG and CVD graphene as ion beam detectors

    NASA Astrophysics Data System (ADS)

    Kozubek, Roland; Ochedowski, Oliver; Zagoranskiy, Igor; Karlušić, Marko; Schleberger, Marika

    2014-12-01

    Highly ordered pyrolytic graphite and graphene created via chemical vapor deposition have been irradiated with high energetic I6+ ions. By Raman mapping an increase of the ID /IG ratio could be identified which arises from the ion induced defects. This ratio grows with increasing fluence. Using this as a tool, HOPG and graphene can be utilized to determine the ion beam spot size and its homogeneity. Both systems seem to be suitable for size determination of the spot. But due to the much higher sensitivity of graphene to ion irradiation, more detailed information regarding the homogeneity of the beam can only be derived using this 2D system. By comparison of both systems we conclude, that CVD graphene is more suitable as an ion beam detector, while HOPG is sufficient for a rough spot size analysis.

  2. Study of magnetotransport across the neutrality point in CVD graphene

    NASA Astrophysics Data System (ADS)

    Mani, Ramesh G.

    Hall effect compensation and a residual resistivity ρxx ~ h / 4e2 are experimentally examined over the p <-->n transition about the nominal Dirac point in CVD graphene. The observed characteristics are reproduced in a model with a parabolic distribution f (VN) of neutrality potentials, VN, and simultaneous electron- and hole- conduction. The results suggest that, broadly about the gate-induced n <--> p transition, charge transport is characterized by domain confined ambipolar currents, which leads to compensation in the global Hall effect and the observed residual resistivity. DOE-BES, Mat'l. Sci. & Eng. Div., DE-SC0001762; ARO W911NF-14-2-0076; ARO W911NF-15-1-0433.

  3. Tip-based patterning of HOPG and CVD graphene

    NASA Astrophysics Data System (ADS)

    Hicks, Bryan T.; Yoshimizu, Norimasa; O'Connell, Christopher; Lal, Amit; Pollock, Clifford R.

    2011-06-01

    Nanometer-scale patterning of graphite and graphene has been accomplished through local anodic oxidation using an AFM tip. The underlying mechanism is explained. To date, protrusions, holes, trenches, and even words have been patterned in HOPG over scales ranging from 1nm2 to 1mm2 and depths ranging from sub nm to as deep as 200nm with less than 5 nm variation on the feature size and placement. This same method has also been applied to CVD-grown graphene providing a resist-free process for patterning graphene at the single nanometer scale. This capability could provide a method to rival e-beam lithography resolution but without any pre- or post-processing.

  4. Fast fabrication of nano-structured anti-reflection layers for enhancement of solar cells performance using plasma sputtering and infrared assisted roller embossing techniques.

    PubMed

    Liu, Shih-Jung; Liao, Che-Ting

    2012-02-27

    This paper reports the continuous fabrication of dual-side nano-structured anti-reflection protective layer for performance enhancement of solar cells using plasma sputtering and infrared assisted roller embossing techniques. Nano-structures were first deposited onto the surface of glass substrates using the plasma sputtering technique. After electroforming, a nickel master mold containing nano-array of 30 nm was obtained. The mold was then attached to the surfaces of the two metallic rollers in an infrared assisted roll-to-roll embossing facility. The embossing facility was used to replicate the nano-structures onto 60 μm thick polyethylene terephthalate (PET) films in the experiments. The embossed films were characterized using UV-vis spectrophotometer, atomic force microscope (AFM), and scanning electron microscope (SEM); its total conversion efficiency for solar cells was also measured by a solar simulator. The experimental results showed that the fabricated films could effectively reduce the reflectance and increase the conversion efficiency of solar cells. The proposed method shows great potential for fast fabrication of the anti-reflection protective layer of solar cells due to its simplicity and versatility.

  5. Cs/sup +/ + Cs/sup +/ charge-transfer and ionization cross-section measurements by a plasma-target technique

    SciTech Connect

    Stalder, K.R.

    1982-05-01

    A Q machine plasma target using cesium was constructed to serve as a target for a beam of Cs/sup +/ ions. The sum of charge transfer and ionization cross sections was determined by measuring the growth of the Cs/sup + +/ component of the beam as a function of the plasma radial line density. The measured cross section varies approximately linearly with energy between 50 and 110 keV. This loss cross section is 0.47 +- .11 x 10/sup -16/ cm/sup 2/ at 110 keV. These results have been compared to the cross section determined by a crossed-beam technique. The agreement between the results of the experiments is good at energies above 75 keV. A discrepancy between the results at lower energies indicated a systematic error in one of the techniques. Theoretical estimates of the cross section recently have begun to agree with the magnitude of the cross section but have not fully explained the energy dependence.

  6. Transfer printing of CVD graphene FETs on patterned substrates

    NASA Astrophysics Data System (ADS)

    Abhilash, T. S.; de Alba, R.; Zhelev, N.; Craighead, H. G.; Parpia, J. M.

    2015-08-01

    We describe a simple and scalable method for the transfer of CVD graphene for the fabrication of field effect transistors. This is a dry process that uses a modified RCA-cleaning step to improve the surface quality. In contrast to conventional fabrication routes where lithographic steps are performed after the transfer, here graphene is transferred to a pre-patterned substrate. The resulting FET devices display nearly zero Dirac voltage, and the contact resistance between the graphene and metal contacts is on the order of 910 +/- 340 Ω μm. This approach enables formation of conducting graphene channel lengths up to one millimeter. The resist-free transfer process provides a clean graphene surface that is promising for use in high sensitivity graphene FET biosensors.We describe a simple and scalable method for the transfer of CVD graphene for the fabrication of field effect transistors. This is a dry process that uses a modified RCA-cleaning step to improve the surface quality. In contrast to conventional fabrication routes where lithographic steps are performed after the transfer, here graphene is transferred to a pre-patterned substrate. The resulting FET devices display nearly zero Dirac voltage, and the contact resistance between the graphene and metal contacts is on the order of 910 +/- 340 Ω μm. This approach enables formation of conducting graphene channel lengths up to one millimeter. The resist-free transfer process provides a clean graphene surface that is promising for use in high sensitivity graphene FET biosensors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03501e

  7. Simultaneous Quantitative Analysis of Olmesartan Medoxomil and Amlodipine Besylate in Plasma by High-performance Liquid Chromatography Technique

    PubMed Central

    Shah, SK; Asnani, AJ; Kawade, DP; Dangre, SC; Arora, SK; Yende, SR

    2012-01-01

    A rapid, simple and sensitive high-performance liquid chromatography (HPLC) method has been developed for quantification of olmesartan medoxomil (OLM) and amlodipine besylate (AM) in plasma. The assay enables the measurement of OLM and AM for therapeutic drug monitoring with a minimum detectable limit of 2 ng mL. The method involves a simple, one-step extraction procedure and analytical recovery was above 50%. The separation was performed on an analytical 250 × 4.6 mm Eurospher 100-5 C18 column. The wavelength was set at 239 nm. The mobile phase was a mixture of acetonitrile:0.05 M ammonium acetate buffer: 0.1 mL triethylamine at pH 6.8 was selected at a flow rate of 1.0 mL min. The calibration curve for the determination of OLM and AM in plasma was linear over the range 2–2500 and 8–10,000 ng mL AM and OLM. The coefficients of variation for interday and intraday assay were found to be <15%. The method can be applied to a pharmacokinetic and pharmacodynamic study of OLM and AM in a combined dosage form. PMID:22754260

  8. Association between plasma omega-3 fatty acids and cardiovascular disease risk factors.

    PubMed

    Garneau, Véronique; Rudkowska, Iwona; Paradis, Ann-Marie; Godin, Gaston; Julien, Pierre; Pérusse, Louis; Vohl, Marie-Claude

    2013-03-01

    The consumption of omega-3 (n-3) fatty acids (FA), namely eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have been linked to reduced cardiovascular disease (CVD) risk. The objective of this study was to examine the relation between n-3 FA in plasma phospholipid (PL) levels and CVD risk factors. n-3 FA levels in plasma PL were determined using gas chromatography in 100 obese (body mass index (BMI), ≥30 kg·m(-2)) and 100 nonobese selected individuals from the Quebec City metropolitan area. The CVD risk factors analysed were BMI, blood pressure, plasma lipids levels, and fasting plasma glucose. Significantly higher levels of alpha-linolenic acid (ALA) and docosapentaenoic acid (DPA) were observed in obese subjects, whereas significantly higher levels of DHA were observed in nonobese subjects. For CVD risk factors, ALA levels were positively correlated with plasma triglyceride concentrations and negatively associated with diastolic blood pressure. None of the CVD risk factors studied was linked to EPA levels. In addition, DPA was negatively related to high-density lipoprotein cholesterol (HDL-C) and positively correlated with the total cholesterol/HDL-C ratio. DHA levels were negatively correlated with BMI, waist circumference, and plasma triglyceride levels, whereas a positive association was observed with HDL-C levels. Total n-3 FA percentages were negatively correlated with BMI. In conclusion, higher DHA percentages in plasma PL are associated with a more favourable CVD risk profile, whereas higher DPA percentages in plasma PL are associated with a more deteriorated CVD risk profile.

  9. Identification of gunshot residues in fabric targets using sector field inductively coupled plasma mass spectrometry technique and ternary graphs.

    PubMed

    Freitas, João Carlos D; Sarkis, Jorge E Souza; Negrini Neto, Osvaldo; Viebig, Sônia Bocamino

    2012-03-01

    During criminal investigations involving firearms, the detection of gunshot residues (GSRs) is one of the most important evidences. In the present study, a new method to identify trace evidences of GSRs, deposited around the bullet entrance hole, in different types of fabrics used as targets, is described. The experiments were carried out using a 0.38-inch caliber revolver, and 9-mm and 0.40-inch caliber pistols. Testimonies of 2.25 cm(2) of the fabrics were cut around the bullet entrance and digested with 10% nitric acid. Antimony, barium, and lead were analyzed in the remaining solution using a sector field inductively coupled plasma mass spectrometer. The concentrations of the elements were detected at levels up to few microgram per square centimeter. The use of ternary graphics allowed us to identify specific patterns of distribution for blank samples and the clear distinction between the revolver and pistols used.

  10. Multirate Particle-in-Cell Time Integration Techniques of Vlasov-Maxwell Equations for Collisionless Kinetic Plasma Simulations

    SciTech Connect

    Chen, Guangye; Chacon, Luis; Knoll, Dana Alan; Barnes, Daniel C

    2015-07-31

    A multi-rate PIC formulation was developed that employs large timesteps for slow field evolution, and small (adaptive) timesteps for particle orbit integrations. Implementation is based on a JFNK solver with nonlinear elimination and moment preconditioning. The approach is free of numerical instabilities (ωpeΔt >>1, and Δx >> λD), and requires many fewer dofs (vs. explicit PIC) for comparable accuracy in challenging problems. Significant gains (vs. conventional explicit PIC) may be possible for large scale simulations. The paper is organized as follows: Vlasov-Maxwell Particle-in-cell (PIC) methods for plasmas; Explicit, semi-implicit, and implicit time integrations; Implicit PIC formulation (Jacobian-Free Newton-Krylov (JFNK) with nonlinear elimination allows different treatments of disparate scales, discrete conservation properties (energy, charge, canonical momentum, etc.)); Some numerical examples; and Summary.

  11. Influence of the source gas ratio on the hydrogen and deuterium content of a-C:H and a-C:D films: Plasma-enhanced CVD with CH4/H2, CH4/D2, CD4/H2 and CD4/D2

    NASA Astrophysics Data System (ADS)

    Ozeki, K.; Sekiba, D.; Suzuki, T.; Kanda, K.; Niibe, M.; Hirakuri, K. K.; Masuzawa, T.

    2013-01-01

    Amorphous hydrogenated carbon (a-C:H) and amorphous deuterated carbon (a-C:D) films were prepared using plasma-enhanced chemical vapor deposition (PECVD) from CD4, H2, CD4 and D2 source gases. Fourteen different samples were prepared by changing the source gas ratios of CH4/H2, CH4/D2, CD4/H2, and CD4/D2. The concentrations of hydrogen (H) and deuterium (D) relative to carbon (C) in the films were determined by elastic recoil detection analysis (ERDA) and Rutherford backscattering spectroscopy (RBS). The sp2/(sp2 + sp3) ratios of the films were analyzed by near-edge X-ray absorption fine structure (NEXAFS) measurements. Hardness and mass density of the films were measured using a nanoindenter and X-ray reflectivity (XRR), respectively. For all combinations of source gas, the H and D concentrations varied by only 4.0 at.%. For the CH4/D2 source gas, the D concentration in the film increased from 0 at.% with the D2/(CH4 + D2) source gas combination to 11.2 at.% for the 80% D2/(CH4 + D2) source gas combination. The increase in D concentration exceeded the increase in total H and D concentration (3.4 at.%). For CH4/D2 source gas, the H concentration decreased as the D concentration increased. For the CD4/H2 source gas, we observed the opposite tendency. Additionally, an isotope effect between the a-C:H films and the a-C:D films was observed, with preferential incorporation of H over D. From the NEXAFS measurements, the sp2/(sp2 + sp3) ratios in all of the samples were between 38.8% and 40.8%. A correlation between the sp2/(sp2 + sp3) ratio and the H2 or D2 gas source ratio was not observed. The hardness and density of the films decreased when the H2 or D2 source gas ratio increased. Even though the H concentration in the a-C:H films was higher than the D concentration in the a-C:D films, the a-C:D films had lower hardness and mass density values. These findings suggest that information concerning the voids, nanostructures, sp2/sp3 ratios and H concentrations of

  12. Linear electric field mass analysis: a technique for three-dimensional high mass resolution space plasma composition measurements.

    PubMed

    McComas, D J; Nordholt, J E; Bame, S J; Barraclough, B L; Gosling, J T

    1990-08-01

    A revolutionary type of three-dimensional space plasma composition analyzer has been developed that combines very high-resolution mass composition measurements on a fraction of the incident ions simultaneously with lower mass resolution but high sensitivity measurements of the remaining population in a single compact and robust sensor design. Whereas the lower mass resolution measurements are achieved using conventional energy/charge (E/q) and linear time-of-flight analysis, the high mass resolution measurements are made by timing reflected E/q analyzed ions in a linear electric field (LEF). In a LEF the restoring (reflecting) force that an ion experiences in the direction parallel to the field is proportional to the depth it travels into the LEF region, and its equation of motion in that direction is that of a simple harmonic oscillator. Consequently, an ion's travel time is independent of its initial angle and energy and is simply proportional to the square root of the ion's mass/charge (m/q). The measured m/q resolution, (m/q)/Delta(m/q), for a small LEF-based prototype that we have developed and tested is approximately 20. In addition, our laboratory measurements with the prototype instrument show that characteristic time-of-flight spectra allow the resolution of atomic and molecular species with nearly identical m/q values. The measured response of the prototype is in excellent agreement with computer simulations of the device. Advanced design work using this computer simulation indicates that three-dimensional plasma composition analyzers with m/q resolutions of at least 50 are readily achievable.

  13. Efficacy of bipolar “button” plasma vaporization of the prostate for benign prostatic obstruction, compared to the standard technique

    PubMed Central

    Aboutaleb, Hamdy

    2015-01-01

    Objective: The objective of the following study is to evaluate the efficiency of transurethral plasma vaporization of the prostate in saline bipolar plasma vaporization of the prostate (BPVP) using the button electrode and comparing it to the standard transurethral resection of the prostate (TURP). Patients and Methods: During the period of the year between 2007 and 2013, 152 patients with benign prostatic hyperplasia were rolled in our study. Fifty-two patients were underwent BPVP and 100 TURP. All patients were evaluated preoperatively, 24 h and at 3 months postoperatively. International Prostate Symptom Score (I-PSS), quality-of-life (QOL) score, Qmax and Qave and post void residual (PVR) urine. Operative time, hospital stay, catheterization time, and complications were reported. Mean serum Hb, hematocrit and serum sodium changes were reported preoperatively and within 24 h postoperatively in both groups. Statistical analysis is performed using SPSS program version 20 for windows. Results: Mean age at surgery was 60.8 ± 8 (range 63- 92) and 66 ± 8.6 (range 50-83) for BPVP and TURP groups, respectively. Mean prostatic volume was 46 ± 11 (range 30-92) and 43 ± 8 (range 30-80) in both groups, respectively. Patients from both series had similar preoperative characteristics. The mean operative duration 53 ± 21 1 ± 2.1 (range 1-7) versus 3 ± 3.3 (range 3-8) days (P value 0.0001) were significantly (range 20-80) versus 62 ± 16 min (range 30-126) (P value 0.004), catheterization period 2 ± 0.28 ( range 2-4) versus 3 ± 3.2 (range 2-7) days (P value 0.03). Conclusions: BPVP has superior efficacy in short-term results and less complication rates compared with classic TURP. PMID:26692662

  14. Masked-backlighter technique used to simultaneously image x-ray absorption and x-ray emission from an inertial confinement fusion plasma

    SciTech Connect

    Marshall, F. J. Radha, P. B.

    2014-11-15

    A method to simultaneously image both the absorption and the self-emission of an imploding inertial confinement fusion plasma has been demonstrated on the OMEGA Laser System. The technique involves the use of a high-Z backlighter, half of which is covered with a low-Z material, and a high-speed x-ray framing camera aligned to capture images backlit by this masked backlighter. Two strips of the four-strip framing camera record images backlit by the high-Z portion of the backlighter, while the other two strips record images aligned with the low-Z portion of the backlighter. The emission from the low-Z material is effectively eliminated by a high-Z filter positioned in front of the framing camera, limiting the detected backlighter emission to that of the principal emission line of the high-Z material. As a result, half of the images are of self-emission from the plasma and the other half are of self-emission plus the backlighter. The advantage of this technique is that the self-emission simultaneous with backlighter absorption is independently measured from a nearby direction. The absorption occurs only in the high-Z backlit frames and is either spatially separated from the emission or the self-emission is suppressed by filtering, or by using a backlighter much brighter than the self-emission, or by subtraction. The masked-backlighter technique has been used on the OMEGA Laser System to simultaneously measure the emission profiles and the absorption profiles of polar-driven implosions.

  15. Effect of intake on fasting heat production, respiratory quotient and plasma metabolites measured using the washed rumen technique

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective was to investigate the effect of intake prior to fasting on concentrations of metabolites and hormones, respiratory quotient (RQ) and fasting heat production (HP) using the washed rumen technique and to compare these values with those from the fed state. Six Holstein steers (360 ± 22 k...

  16. Enhanced graphitization of c-CVD grown multi-wall carbon nanotube arrays assisted by removal of encapsulated iron-based phases under thermal treatment in argon

    NASA Astrophysics Data System (ADS)

    Boncel, Slawomir; Koziol, Krzysztof K. K.

    2014-05-01

    The effect of annealing on multi-walled carbon nanotube (MWCNT) arrays grown via catalytic Chemical Vapour Deposition (c-CVD) was studied. The treatment enabled to decrease number of defects/imperfections in the graphene walls of MWCNTs', which was reflected in Raman spectroscopy by reduction of the ID/IG ratio by 27%. Moreover, the vertical alignment from the as-synthesized nanotube arrays was found intact after annealing. Not only graphitization of the nanotube walls occurred under annealing, but the amount of metal iron-based catalyst residues (interfering with numerous physicochemical properties, and hence applications of MWCNTs) was reduced from 9.00 wt.% (for pristine MWCNTs) to 0.02 wt.% as detected by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). This value, established by a new analytical protocol, is the lowest recorded by now for purified c-CVD MWCNTs and, due to operating under atmospheric pressure, medium temperature regime (as for annealing processes), reasonable time-scale and metal residue non-specificity, it could lay the foundation for commercial purification of c-CVD derived MWCNTs.

  17. Preparation of tantalum-based alloys by a unique CVD process

    NASA Technical Reports Server (NTRS)

    Bryant, W. A.; Meier, G. H.

    1975-01-01

    The paper describes a sequential pulsing technique for deposition of refractory alloys and evaluates the technique for the deposition of the tantalum-base alloys Ta-10W (Ta-10 st% W) and T-111 (Ta-8 wt% W-2 wt% Hf). The deposition cycle for Ta-10W was chosen as alternate injections of TaCl5 plus hydrogen and WCl6 plus hydrogen. The cycle for T-111 was chosen as injections of TaCl5 plus hydrogen interspersed with injections of WCl6 plus hydrogen. A temperature range of 900-1300 C was chosen for both alloys. The ability of the pulse process to blanket a uniformly heated section of substrate with a mixture of gases, whose composition varies not with position on the substrate but instead with time of residence in the reactor, allows metal of uniform thickness to be deposited. It is shown that Ta and W can be deposited at high temperature with the formation of a dense columnar grain structure, so that the feasibility of preparing uniformly thick deposits of these elements by a 'pulsing' modification of CVD is demonstrated. A similar attempt to deposit T-111 was unsuccessful due to the difficulty in reducing HfCl4.

  18. Study of HF-induced plasma turbulence by SEE and ISR technique during 2011 HAARP experimental campaign

    NASA Astrophysics Data System (ADS)

    Grach, Savely; Bernhardt, Paul; Sergeev, Evgeny; Shindin, Alexey; Broughton, Matt; Labelle, James; Bricinsky, Stanley; Mishin, Evgeny; Isham, Brett; Watkins, Brenton

    A concise review of the results of the 20 March - 4 April 2011 experimental campaign at the HAARP heating facility, Gakona, Alaska is presented. The campaign goals were to study the physical processes that determine the interaction of high-power HF radio waves with the F-region ionosphere. The stimulated electromagnetic emission (SEE) observational sites A/B/C were located along the magnetic meridian to the south of the HAARP facility at about 11/83/113 km distant. Site A (B) was nearly under the region during injections at vertical (Magnetic Zenith, MZ). Enhanced plasma line (PL) radar echoes were measured by the modular UHF incoherent scatter radar (MUIR) located at HAARP. Specially designed 'diagnostic' regimes of the pump wave radiation were used to account for the characteristic times of the excitation and fading of the plasma waves (Delta t_w ˜ 1-10 ms) and small-scale field-aligned irregularities (FAI, Delta t_{fai} ˜ 1-10 s). They include mainly (I) alternation low-duty cycles consisting of short (a few Delta t_w) pulses with long (Delta t_{fai}) pauses between them and high duty cycles, i.e. long injection pulses (≫ t_w) with a short pauses of 20-30 ms. The low-duty regime is aimed to study the excited Langmuir turbulence and at to specify the evolution of FAI and their scale-lengths related to different SEE spectral features. The main objective of the high-duty regime is to explore the excitation and fading of upper-hybrid and electron Bernstein plasma waves, with FAI fixed. (II) Concurrent injection of the pump wave f_0 in the regime I, and another wave at a frequency f_1≠q f_0 in the low duty cycle. Since these waves reflect/refract at different altitudes, the altitudinal distribution of FAI can be obtained. (III) Fast (within some seconds) sweeping the pump frequency about electron gyroharmonics s f_c (s=2,3,4) in order to determine the contribution of various nonlinear interaction processes to the excitation of the HF part of the pump

  19. Gene-centric association signals for haemostasis and thrombosis traits identified with the HumanCVD BeadChip.

    PubMed

    Gaunt, T R; Zabaneh, D; Shah, S; Guyatt, A; Ladroue, C; Kumari, M; Drenos, F; Shah, T; Talmud, P J; Casas, J P; Lowe, G; Rumley, A; Lawlor, D A; Kivimaki, M; Whittaker, J; Hingorani, A D; Humphries, S E; Day, I N

    2013-11-01

    Coagulation phenotypes show strong intercorrelations, affect cardiovascular disease risk and are influenced by genetic variants. The objective of this study was to search for novel genetic variants influencing the following coagulation phenotypes: factor VII levels, fibrinogen levels, plasma viscosity and platelet count. We genotyped the British Women's Heart and Health Study (n=3,445) and the Whitehall II study (n=5,059) using the Illumina HumanCVD BeadArray to investigate genetic associations and pleiotropy. In addition to previously reported associations (SH2B3, F7/F10, PROCR, GCKR, FGA/FGB/FGG, IL5), we identified novel associations at GRK5 (rs10128498, p=1.30x10(-6)), GCKR (rs1260326, p=1.63x10(-6)), ZNF259-APOA5 (rs651821, p=7.17x10(-6)) with plasma viscosity; and at CSF1 (rs333948, p=8.88x10(-6)) with platelet count. A pleiotropic effect was identified in GCKR which associated with factor VII (p=2.16x10(-7)) and plasma viscosity (p=1.63x10(-6)), and, to a lesser extent, ZNF259-APOA5 which also associated with factor VII and fibrinogen (p<1.00x10-²) and plasma viscosity (p<1.00x10(-5)). Triglyceride associated variants were overrepresented in factor VII and plasma viscosity associations. Adjusting for triglyceride levels resulted in attenuation of associations at the GCKR and ZNF259-APOA5 loci. In addition to confirming previously reported associations, we identified four single nucleotide polymorphisms (SNPs) associated with plasma viscosity and platelet count and found evidence of pleiotropic effects with SNPs in GCKR and ZNF259-APOA5. These triglyceride-associated, pleiotropic SNPs suggest a possible causal role for triglycerides in coagulation.

  20. Predictive Properties of Plasma Amino Acid Profile for Cardiovascular Disease in Patients with Type 2 Diabetes

    PubMed Central

    Kume, Shinji; Araki, Shin-ichi; Ono, Nobukazu; Shinhara, Atsuko; Muramatsu, Takahiko; Araki, Hisazumi; Isshiki, Keiji; Nakamura, Kazuki; Miyano, Hiroshi; Koya, Daisuke; Haneda, Masakazu; Ugi, Satoshi; Kawai, Hiromichi; Kashiwagi, Atsunori; Uzu, Takashi; Maegawa, Hiroshi

    2014-01-01

    Prevention of cardiovascular disease (CVD) is an important therapeutic object of diabetes care. This study assessed whether an index based on plasma free amino acid (PFAA) profiles could predict the onset of CVD in diabetic patients. The baseline concentrations of 31 PFAAs were measured with high-performance liquid chromatography-electrospray ionization-mass spectrometry in 385 Japanese patients with type 2 diabetes registered in 2001 for our prospective observational follow-up study. During 10 years of follow-up, 63 patients developed cardiovascular composite endpoints (myocardial infarction, angina pectoris, worsening of heart failure and stroke). Using the PFAA profiles and clinical information, an index (CVD-AI) consisting of six amino acids to predict the onset of any endpoints was retrospectively constructed. CVD-AI levels were significantly higher in patients who did than did not develop CVD. The area under the receiver-operator characteristic curve of CVD-AI (0.72 [95% confidence interval (CI): 0.64–0.79]) showed equal or slightly better discriminatory capacity than urinary albumin excretion rate (0.69 [95% CI: 0.62–0.77]) on predicting endpoints. A multivariate Cox proportional hazards regression analysis showed that the high level of CVD-AI was identified as an independent risk factor for CVD (adjusted hazard ratio: 2.86 [95% CI: 1.57–5.19]). This predictive effect of CVD-AI was observed even in patients with normoalbuminuria, as well as those with albuminuria. In conclusion, these results suggest that CVD-AI based on PFAA profiles is useful for identifying diabetic patients at risk for CVD regardless of the degree of albuminuria, or for improving the discriminative capability by combining it with albuminuria. PMID:24971671

  1. CVD and obesity in transitional Syria: a perspective from the Middle East

    PubMed Central

    Barakat, Hani; Barakat, Hanniya; Baaj, Mohamad K

    2012-01-01

    Purpose Syria is caught in the middle of a disruptive nutritional transition. Its healthcare system is distracted by challenges and successes in other areas while neglecting to address the onslaught of Syria’s cardiovascular disease (CVD) epidemic. Despite the official viewpoint touting improvement in health indicators, current trends jeopardize population health, and several surveys in the Syrian population signal the epidemic spreading far and wide. The goal is to counteract the indifference towards obesity as a threat to Syrian’s health, as the country is slowly becoming a leader in CVD mortality globally. Methods PubMed, World Health Organization, and official government websites were searched for primary surveys in Syria related to CVD morbidity, mortality, and risk factors. Inclusion criteria ensured that results maximized relevance while producing comparable studies. Statistical analysis was applied to detect the most common risk factor and significant differences in risk factor prevalence and CVD rates. Results Obesity remained the prevailing CVD risk factor except in older Syrian men, where smoking and hypertension were more common. CVD mortality was more common in males due to coronary disease, while stroke dominated female mortality. The young workforce is especially impacted, with 50% of CVD mortality occurring before age 65 years and an 81% prevalence of obesity in women over 45 years. Conclusion Syria can overcome its slow response to the CVD epidemic and curb further deterioration by reducing obesity and, thus, inheritance and clustering of risk factors. This can be achieved via multilayered awareness and intensive parental and familial involvement. Extinguishing the CVD epidemic is readily achievable as demonstrated in other countries. PMID:22454558

  2. Development of Micro and Nano Crystalline CVD Diamond TL/OSL Radiation Detectors for Clinical Applications

    NASA Astrophysics Data System (ADS)

    Barboza-Flores, Marcelino

    2015-03-01

    Modern radiotherapy methods requires the use of high photon radiation doses delivered in a fraction to small volumes of cancer tumors. An accurate dose assessment for highly energetic small x-ray beams in small areas, as in stereotactic radiotherapy, is necessary to avoid damage to healthy tissue surrounding the tumor. Recent advances on the controlled synthesis of CVD diamond have demonstrated the possibility of using high quality micro and nano crystalline CVD as an efficient detector and dosimeter suitable for high energy photons and energetic particle beams. CVD diamond is a very attractive material for applications in ionizing radiation dosimetry, particularly in the biomedical field since the radiation absorption by a CVD diamond is very close to that of soft tissue. Furthermore, diamond is stable, non-toxic and radiation hard. In the present work we discuss the CVD diamond properties and dosimeter performance and discuss its relevance and advantages of various dosimetry methods, including thermally stimulated luminescence (TL) as well as optically stimulated luminescence (OSL). The recent CVD improved method of growth allows introducing precisely controlled impurities into diamond to provide it with high dosimetry sensitivity. For clinical dosimetry applications, high accuracy of dose measurements, low fading, high sensitivity, good reproducibility and linear dose response characteristics are very important parameters which all are found in CVD diamonds specimens. In some cases, dose linearity and reproducibility in CVD diamond have been found to be higher than standard commercial TLD materials like LiF. In the present work, we discuss the state-of-the art developments in dosimetry applications using CVD diamond. The financial support from Conacyt (Mexico) is greatly acknowledged

  3. Calculations of the Electron Energy Distribution Function in a Uranium Plasma by Analytic and Monte Carlo Techniques. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Bathke, C. G.

    1976-01-01

    Electron energy distribution functions were calculated in a U235 plasma at 1 atmosphere for various plasma temperatures and neutron fluxes. The distributions are assumed to be a summation of a high energy tail and a Maxwellian distribution. The sources of energetic electrons considered are the fission-fragment induced ionization of uranium and the electron induced ionization of uranium. The calculation of the high energy tail is reduced to an electron slowing down calculation, from the most energetic source to the energy where the electron is assumed to be incorporated into the Maxwellian distribution. The pertinent collisional processes are electron-electron scattering and electron induced ionization and excitation of uranium. Two distinct methods were employed in the calculation of the distributions. One method is based upon the assumption of continuous slowing and yields a distribution inversely proportional to the stopping power. An iteration scheme is utilized to include the secondary electron avalanche. In the other method, a governing equation is derived without assuming continuous electron slowing. This equation is solved by a Monte Carlo technique.

  4. Ellipsometric and Rutherford Back scattering Spectrometry studies of SiO(X)N(Y) films elaborated by plasma-enhanced chemical vapour deposition technique.

    PubMed

    Mahamdi, R; Boulesbaa, M; Saci, L; Mansour, F; Molliet, C; Collet, M; Temple-Boyer, P

    2011-10-01

    Silicon oxynitride (SiO(X)N(Y)) thin films were deposited by plasma-enhanced chemical vapour deposition technique (PECVD) from silane (SiH4), nitrous oxide (N2O), ammonia (NH3) and nitrogen (N2) mixture. Spectroscopic ellipsometry (SE), in the range of wavelengths 450-900 nm, was used to define the film thickness and therefore the deposition rate, as well as the refractive index as a function of the N2O gaseous flow. While considering the (Si3N4, SiO2, H2 or void) heterogeneous mixture, Maxwell Garnett (MG) theory allows to fit the SE measurements and to define the volume fraction of the different phases. Finally, Rutherford Backscattering Spectrometry (RBS) results showed that x = O/Si ratio increases gradually with increasing the N2O flow, allowing the correlation of the SiO(X)N(Y) films main parameters. PMID:22400311

  5. Radiation monitoring with CVD diamonds and PIN diodes at BaBar

    NASA Astrophysics Data System (ADS)

    Bruinsma, M.; Burchat, P.; Curry, S.; Edwards, A. J.; Kagan, H.; Kass, R.; Kirkby, D.; Majewski, S.; Petersen, B. A.

    2007-12-01

    The BaBar experiment at the Stanford Linear Accelerator Center has been using two polycrystalline chemical vapor deposition (pCVD) diamonds and 12 silicon PIN diodes for radiation monitoring and protection of the Silicon Vertex Tracker (SVT). We have used the pCVD diamonds for more than 3 years, and the PIN diodes for 7 years. We will describe the SVT and SVT radiation monitoring system as well as the operational difficulties and radiation damage effects on the PIN diodes and pCVD diamonds in a high-energy physics environment.

  6. Controlled incorporation of mid-to-high Z transition metals in CVD diamond

    SciTech Connect

    Biener, M M; Biener, J; Kucheyev, S O; Wang, Y M; El-Dasher, B; Teslich, N E; Hamza, A V; Obloh, H; Mueller-Sebert, W; Wolfer, M; Fuchs, T; Grimm, M; Kriele, A; Wild, C

    2010-01-08

    We report on a general method to fabricate transition metal related defects in diamond. Controlled incorporation of Mo and W in synthetic CVD diamond was achieved by adding volatile metal precursors to the diamond chemical vapor deposition (CVD) growth process. Effects of deposition temperature, grain structure and precursor exposure on the doping level were systematically studied, and doping levels of up to 0.25 at.% have been achieved. The metal atoms are uniformly distributed throughout the diamond grains without any indication of inclusion formation. These results are discussed in context of the kinetically controlled growth process of CVD diamond.

  7. CVD graphene vs. highly ordered pyrolytic graphite for use in electroanalytical sensing.

    PubMed

    Brownson, Dale A C; Gorbachev, Roman V; Haigh, Sarah J; Banks, Craig E

    2012-02-21

    We explore and contrast the electroanalytical performance of a commercially available CVD grown graphene electrode with that of edge- and basal-plane pyrolytic graphite electrodes constructed from highly ordered pyrolytic graphite for the sensing of biologically important analytes, namely β-nicotinamide adenine dinucleotide (NADH) and uric acid (UA). We demonstrate that for the analytes studied here, in the best case, the electroanalytical performance of the CVD-graphene mimics that of edge plane pyrolytic graphite, suggesting no significant advantage of utilising CVD-graphene in this context.

  8. Are your patients with risk of CVD getting the viscous soluble fiber they need?

    PubMed

    Shamliyan, Tatyana A; Jacobs, David R; Raatz, Susan K; Nordstrom, David L; Keenan, Joseph M

    2006-09-01

    A diet that includes 5 to 10 g/d of viscous soluble fiber reduces cardiovascular disease (CVD) events and death independent of baseline risk. Consuming foods rich in viscous soluble fiber reduces low-density lipoprotein cholesterol (LDL-C) blood levels 10% to 15% with expected reduction in CVD events by 10% to 15%. Routinely counsel adults at risk of CVD to promote a healthy diet: assess dietary fiber consumption; recommend specific foods rich in viscous soluble fiber; monitor LDL-C levels and encourage increased dietary fiber intake at follow-up visits; motivate patients to comply with recommendations.

  9. Radiation monitoring with CVD Diamonds and PIN Diodes at BaBar

    SciTech Connect

    Bruinsma, M.; Burchat, P.; Curry, S.; Edwards, A.J.; Kagan, H.; Kass, R.; Kirkby, D.; Majewski, S.; Petersen, B.A.; /UC, Irvine /SLAC /Ohio State U.

    2008-02-13

    The BaBar experiment at the Stanford Linear Accelerator Center has been using two polycrystalline chemical vapor deposition (pCVD) diamonds and 12 silicon PIN diodes for radiation monitoring and protection of the Silicon Vertex Tracker (SVT). We have used the pCVD diamonds for more than 3 years, and the PIN diodes for 7 years. We will describe the SVT and SVT radiation monitoring system as well as the operational difficulties and radiation damage effects on the PIN diodes and pCVD diamonds in a high-energy physics environment.

  10. Analysis of the Plasma-Coma of Comet P/Halley by Image Processing Techniques of Bochum's Photoplates

    NASA Astrophysics Data System (ADS)

    Voelzke, Marcos Rincon

    1996-10-01

    Photographic and photoelectric observations of comet P/Halley's ion gas coma from CO+ at 4250A were part of the Bochum Halley Monitoring Program, conducted from 1986 February 17, to April 17 at the European Southern Observatory on La Silla (Chile). In this spectral range it is possible to watch the continuous formation, motion and expansion of plasma structures. To observe the morphology of these structures 32 CO$^+$ photos (glass plates) from P/Halley's comet have been analysed. They have a field of view of 28 degrees 6 X 28 degrees 6 and were obtained from 1986 March 29, to April 17 with exposure times between 20 and 120 minutes. All photos were digitized with a PDS 2020 GM (Photometric Data System) microdensitometer at the Astronomisches Institut der Westfalischen Wilhelms-Universitat in Munster (one pixel = 25 microns X 25 microns approximately 46 arcsec 88 X 46 arcsec 88). After digitization the data were reduced to relative intensities, and the part with proper calibrations were also converted to absolute intensities, expressed in terms of column densities using the image data systems MIDAS (Munich Image Data Analysis System; ESO - Image Processing Group, 1988) and IHAP (Image Handling And Processing; Middleburg, 1983). With the help of the Stellingwerf-Theta-Minimum-Method (Stellingwerf, 1978) a period of (2.22 +/- 0.09) days results from analysis of structures in the plasma-coma by subtracting subsequent images. The idea behind subtracting subsequent images is that rotation effects are only 10% phenomena on gas distribution. Difference images are than used to supress the static component of the gas cloud. The CO+ column density data (in molecules cm^-2) were compared with the data of CN column density from Schulz (1990) in all common days. The results show that the relations between CO+ and CN in average column density values (N_CO^+ /N_CN) are 11.6 for a circular slit with average diameter (Phi) of 6 arcminute 1 which corresponds to a distance from the

  11. Use of a parallel path nebulizer for capillary-based microseparation techniques coupled with an inductively coupled plasma mass spectrometer for speciation measurements

    NASA Astrophysics Data System (ADS)

    Yanes, Enrique G.; Miller-Ihli, Nancy J.

    2004-06-01

    A low flow, parallel path Mira Mist CE nebulizer designed for capillary electrophoresis (CE) was evaluated as a function of make-up solution flow rate, composition, and concentration, as well as the nebulizer gas flow rate. This research was conducted in support of a project related to the separation and quantification of cobalamin (vitamin B-12) species using microseparation techniques combined with inductively coupled plasma mass spectrometry (ICP-MS) detection. As such, Co signals were monitored during the nebulizer characterization process. Transient effects in the ICP were studied to evaluate the suitability of using gradients for microseparations and the benefit of using methanol for the make-up solution was demonstrated. Co signal response changed significantly as a function of changing methanol concentrations of the make-up solution and maximum signal enhancement was seen at 20% methanol with a 15 μl/min flow rate. Evaluation of the effect of changing the nebulizer gas flow rates showed that argon flows from 0.8 to 1.2 l/min were equally effective. The Mira Mist CE parallel path nebulizer was then evaluated for interfacing capillary microseparation techniques including capillary electrophoresis (CE) and micro high performance liquid chromatography (μHPLC) to inductively coupled plasma mass spectrometry (ICP-MS). A mixture of four cobalamin species standards (cyanocobalamin, hydroxocobalamin, methylcobalamin, and 5' deoxyadenosylcobalamin) and the corrinoid analogue cobinamide dicyanide were successfully separated using both CE-ICP-MS and μHPLC-ICP-MS using the parallel path nebulizer with a make-up solution containing 20% methanol with a flow rate of 15 μl/min.

  12. Efficacy of platelet-rich plasma as a shielding technique after endoscopic mucosal resection in rat and porcine models

    PubMed Central

    Lorenzo-Zúñiga, Vicente; Boix, Jaume; Moreno de Vega, Vicente; Bon, Ignacio; Marín, Ingrid; Bartolí, Ramón

    2016-01-01

    Background and study aims: The aims were to assess the efficacy of endoscopic application of Platelet-rich plasma (PRP) to prevent delayed perforation and to induce mucosal healing after endoscopic resections. Patients and methods: Colonic induced lesions were performed in rats (n = 16) and pigs (n = 4). Animals were randomized to receive onto the lesions saline (control) or PRP. Animals underwent endoscopic follow-up. Thermal injury was assessed with a 1 – 4 scale: (1) mucosal necrosis; (2) submucosal necrosis; (3) muscularis propria necrosis; and (4) serosal necrosis Results: Saline treatment showed 50 % of mortality in rats (P = 0.02). Mean ulcerated area after 48 hours and 7 days was significantly smaller with PRP than with saline (0.27 ± 0.02 cm2 and 0.08 ± 0.01 cm2 vs. 0.56 ± 0.1 cm2 and 0.40 ± 0.06 cm2; P < 0.001). The incidence of thermal injury was significantly lower with PRP (1.25 ± 0.46) than in controls (2.25 ± 0.50); P = 0.006. The porcine model showed a trend toward higher mucosal restoration in animals treated with PRP than with saline at weeks 1 and 2 (Median area in cm2: 0.55 and 0.40 vs. 1.32 and 0.79) Conclusions: Application of PRP to colonic mucosal lesions showed strong healing properties in rat and porcine models. PMID:27540573

  13. Carbon Nanotubes Growth by CVD on Graphite Fibers

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, Ching-Hua; Cochrane, J. C.; Lehoczky, S. L.; Muntele, I.; Ila, D.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Due to the superior electrical and mechanical properties of carbon nanotubes (CNT), synthesizing CNT on various substances for electronics devices and reinforced composites have been engaged in many efforts for applications. This presentation will illustrate CNT synthesized on graphite fibers by thermal CVD. On the fiber surface, iron nanoparticles as catalysts for CNT growth are coated. The growth temperature ranges from 600 to 1000 C and the pressure ranges from 100 Torr to one atmosphere. Methane and hydrogen gases with methane content of 10% to 100% are used for the CNT synthesis. At high growth temperatures (greater than or equal to 900 C), the rapid inter-diffusion of the transition metal iron on the graphite surface results in the rough fiber surface without any CNT grown on it. When the growth temperature is relative low (650-800 C), CNT with catalytic particles on the nanotube top ends are fabricated on the graphite surface. (Methane and hydrogen gases with methane content of 10% to 100% are used for the CNT synthesis.) (By measuring the samples) Using micro Raman spectroscopy in the breath mode region, single-walled or multi-walled CNT (MWCNT), depending on growth concentrations, are found. Morphology, length and diameter of these MWCNT are determined by scanning electron microscopy and Raman spectroscopy. The detailed results of syntheses and characterizations will be discussed in the presentation.

  14. Recovery of CVD Diamond Detectors using Laser Double Pulses

    SciTech Connect

    Dauffy, L S; Lerche, R A; Schmid, G J; Koch, J A; Silbenagel, C

    2005-09-27

    A 5 x 0.25 mm Chemical Vapor Deposited (CVD) diamond detector, with a voltage bias of + 250V, was excited by a 400 nm laser (3.1 eV photons) in order to study the saturation of the wafer and its associated electronics. In a first experiment, the laser beam energy was increased from a few tens of a pJ to about 100 {micro}J, and the signal from the diamond was recorded until full saturation of the detection system was achieved. Clear saturation of the detection system was observed at about 40 V, which corresponds with the expected saturation at 10% of the applied bias (250V). The results indicate that the interaction mechanism of the 3.1 eV photons in the diamond (E{sub bandgap} = 5.45 eV) is not a multi-photon process but is linked to the impurities and defects of the crystal. In a second experiment, the detector was irradiated by a saturating first laser pulse and then by a delayed laser pulse of equal or smaller amplitude with delays of 5, 10, and 20 ns. The results suggest that the diamond and associated electronics recover within 10 to 20 ns after a strong saturating pulse.

  15. Contact resistance study of various metal electrodes with CVD graphene

    NASA Astrophysics Data System (ADS)

    Gahoi, Amit; Wagner, Stefan; Bablich, Andreas; Kataria, Satender; Passi, Vikram; Lemme, Max C.

    2016-11-01

    In this study, the contact resistance of various metals to chemical vapor deposited (CVD) monolayer graphene is investigated. Transfer length method (TLM) structures with varying channel widths and separation between contacts have been fabricated and electrically characterized in ambient air and vacuum condition. Electrical contacts are made with five metals: gold, nickel, nickel/gold, palladium and platinum/gold. The lowest value of 92 Ω μm is observed for the contact resistance between graphene and gold, extracted from back-gated devices at an applied back-gate bias of -40 V. Measurements carried out under vacuum show larger contact resistance values when compared with measurements carried out in ambient conditions. Post processing annealing at 450 °C for 1 h in argon-95%/hydrogen-5% atmosphere results in lowering the contact resistance value which is attributed to the enhancement of the adhesion between metal and graphene. The results presented in this work provide an overview for potential contact engineering for high performance graphene-based electronic devices.

  16. High Efficiency CVD Graphene-lead (Pb) Cooper Pair Splitter

    PubMed Central

    Borzenets, I. V.; Shimazaki, Y.; Jones, G. F.; Craciun, M. F.; Russo, S.; Yamamoto, M.; Tarucha, S.

    2016-01-01

    Generation and manipulation of quantum entangled electrons is an important concept in quantum mechanics, and necessary for advances in quantum information processing; but not yet established in solid state systems. A promising device is a superconductor-two quantum dots Cooper pair splitter. Early nanowire based devices, while efficient, are limited in scalability and further electron manipulation. We demonstrate an optimized, high efficiency, CVD grown graphene-based Cooper pair splitter. Our device is designed to induce superconductivity in graphene via the proximity effect, resulting in both a large superconducting gap Δ = 0.5 meV, and coherence length ξ = 200 nm. The flat nature of the device lowers parasitic capacitance, increasing charging energy EC. Our design also eases geometric restrictions and minimizes output channel separation. As a result we measure a visibility of up to 86% and a splitting efficiency of up to 62%. This will pave the way towards near unity efficiencies, long distance splitting, and post-splitting electron manipulation. PMID:26971450

  17. High Efficiency CVD Graphene-lead (Pb) Cooper Pair Splitter.

    PubMed

    Borzenets, I V; Shimazaki, Y; Jones, G F; Craciun, M F; Russo, S; Yamamoto, M; Tarucha, S

    2016-01-01

    Generation and manipulation of quantum entangled electrons is an important concept in quantum mechanics, and necessary for advances in quantum information processing; but not yet established in solid state systems. A promising device is a superconductor-two quantum dots Cooper pair splitter. Early nanowire based devices, while efficient, are limited in scalability and further electron manipulation. We demonstrate an optimized, high efficiency, CVD grown graphene-based Cooper pair splitter. Our device is designed to induce superconductivity in graphene via the proximity effect, resulting in both a large superconducting gap Δ = 0.5 meV, and coherence length ξ = 200 nm. The flat nature of the device lowers parasitic capacitance, increasing charging energy EC. Our design also eases geometric restrictions and minimizes output channel separation. As a result we measure a visibility of up to 86% and a splitting efficiency of up to 62%. This will pave the way towards near unity efficiencies, long distance splitting, and post-splitting electron manipulation. PMID:26971450

  18. Purification of carbon nanotubes grown by thermal CVD

    NASA Astrophysics Data System (ADS)

    Porro, S.; Musso, S.; Vinante, M.; Vanzetti, L.; Anderle, M.; Trotta, F.; Tagliaferro, A.

    2007-03-01

    We show the results of a set of purifications on carbon nanotubes (CNT) by acid and basic treatments. CNTs were obtained by thermal decomposition of camphor at 850 °C in a CVD growth system, by means of a growth process catalyzed by iron clusters originating from the addition of ferrocene in the precursors mixture. The purification procedures involved HNO 3, H 2SO 4, HSO 3Cl and NaOH for different process temperatures. As-grown CNTs showed a consistent presence of metal catalyst (about 6 wt%), evidenced by TGA. The purification treatments led to a certain amount of opening of the CNT tips, with a consequent loss of metal catalyst encapsulated in tips. This is also confirmed by BET analysis, which showed an increase of the surface area density of CNT after the purification. FT-IR and XPS revealed the presence of carboxylic groups on the CNT surface chemically modified by the harsh environment of the purification process. Among the various treatments that have been tested, the 1:3 solution of nitric and sulphuric acid was the most effective in modifying the CNT surface and inducing the formation of functional groups.

  19. The evaluation of radiation damage parameter for CVD diamond

    NASA Astrophysics Data System (ADS)

    Grilj, V.; Skukan, N.; Jakšić, M.; Pomorski, M.; Kada, W.; Kamiya, T.; Ohshima, T.

    2016-04-01

    There are a few different phenomenological approaches that aim to track the dependence of signal height in irradiated solid state detectors on the fluence of damaging particles. However, none of them are capable to provide a unique radiation hardness parameter that would reflect solely the material capability to withstand high radiation environment. To extract such a parameter for chemical vapor deposited (CVD) diamond, two different diamond detectors were irradiated with proton beams in MeV energy range and subjected afterwards to ion beam induced charge (IBIC) analysis. The change in charge collection efficiency (CCE) due to defects produced was investigated in context of a theoretical model that was developed on the basis of the adjoint method for linearization of the continuity equations of electrons and holes. Detailed modeling of measured data resulted with the first known value of the kσ product for diamond, where k represents the number of charge carriers' traps created per one simulated primary lattice vacancy and σ represents the charge carriers' capture cross section. As discussed in the text, this product could be considered as a true radiation damage parameter.

  20. High Efficiency CVD Graphene-lead (Pb) Cooper Pair Splitter

    NASA Astrophysics Data System (ADS)

    Borzenets, I. V.; Shimazaki, Y.; Jones, G. F.; Craciun, M. F.; Russo, S.; Yamamoto, M.; Tarucha, S.

    2016-03-01

    Generation and manipulation of quantum entangled electrons is an important concept in quantum mechanics, and necessary for advances in quantum information processing; but not yet established in solid state systems. A promising device is a superconductor-two quantum dots Cooper pair splitter. Early nanowire based devices, while efficient, are limited in scalability and further electron manipulation. We demonstrate an optimized, high efficiency, CVD grown graphene-based Cooper pair splitter. Our device is designed to induce superconductivity in graphene via the proximity effect, resulting in both a large superconducting gap Δ = 0.5 meV, and coherence length ξ = 200 nm. The flat nature of the device lowers parasitic capacitance, increasing charging energy EC. Our design also eases geometric restrictions and minimizes output channel separation. As a result we measure a visibility of up to 86% and a splitting efficiency of up to 62%. This will pave the way towards near unity efficiencies, long distance splitting, and post-splitting electron manipulation.

  1. Carbon Nanotubes Grown By CVD in Various Conditions

    NASA Technical Reports Server (NTRS)

    Zhu, S.; Su, C.; Cochrane, J. C.; Lehoczky. S. L.; Muntele, I.; Ila, D.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Since the superior properties of multi-wall carbon nanotubes (MWCNT) could be used in numerous devices such as electronics and sensors, many efforts have been engaged in synthesizing particular structural or dimensional MWCNT. This presentation will illustrate MWCNT synthesized on silicon substrates by thermal CVD. On the substrate, an array of catalysts is coated using sputtering deposition. A thin Ti buffer layer is also coated on some Si substrates prior to depositing catalyst particles. Nickel, cobalt or iron transition metals are used as catalysts for the MWCNT growth. Since the diameter of MWCNT depends on the size of catalyst particles, the catalyst particle size is investigated after annealed at various temperatures. MWCNT are grown on the substrate in the temperature range of 700 to 1000 C and the pressure range of 100 torr to one atmosphere. Methane and hydrogen gases with methane content of 10% to 100% are used for the MWCNT synthesis. Morphology, length and diameter of these MWCNT are determined by scanning electron microscopy and Raman spectroscopy. The detailed results of syntheses and characterizations will be discussed in the presentation.

  2. Carbon Nanotubes Growth by CVD in Various Conditions

    NASA Technical Reports Server (NTRS)

    Zhu, S.; Su, C. H.; Cochrane, J. C.; Lehoczky, S. L.; Gorti, S.; Muntele, I.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Since the superior properties of multi-wall carbon nanotubes (MWCNT could be used in numerous devices such as electronics and sensors, many efforts have been engaged in synthesizing particular structural or dimensional MWCNT. This presentation will illustrate MWCNT synthesized on silicon substrates by thermal CVD. On the substrate, an array of catalysts is coated using sputtering deposition. A thin Ti buffer layer is also coated on some Si substrates prior to depositing catalyst particles. Nickel, cobalt or iron transition metals are used as catalysts for the MWCNT growth. Since the diameter of MWCNT depends on the size of catalyst particles, the catalyst particle size is investigated after annealed at various temperatures. MWCNT are grown on the substrate in the temperature range of 700 to 1000 C and the pressure range of 100 torr to one atmosphere. Methane and hydrogen gases with methane content of 10% to 100% are used for the MWCNT synthesis. Morphology, length and diameter of these MWCNT are determined by scanning electron microscopy and Raman spectroscopy. The detailed results of syntheses and characterizations will be discussed in the presentation.

  3. Plasma and magnetospheric research

    NASA Technical Reports Server (NTRS)

    Comfort, R. H.; Horwitz, J. L.

    1985-01-01

    Research and development in plasmas and magnetospheric environments is reported. Topics discussed include: analysis and techniques of software development; data analysis and modeling; spacecraft sheath effects; laboratory plasma flow studies; instrument development.

  4. 13C(n,α0)10Be cross section measurement with sCVD diamond detector

    NASA Astrophysics Data System (ADS)

    Kavrigin, P.; Griesmayer, E.; Belloni, F.; Plompen, A. J. M.; Schillebeeckx, P.; Weiss, C.

    2016-06-01

    This paper presents 13C(n, α0)10Be cross section measurements performed at the Van de Graaff facility of the Joint Research Centre Geel. The 13C(n, α0)10Be cross section was measured relative to the 12C(n, α0)9Be cross section at 14.3 MeV and 17.0 MeV neutron energies. The measurements were performed with an sCVD (single-crystal chemical vapor deposition) diamond detector which acted as sample and as sensor simultaneously. A novel analysis technique was applied, which is based on the pulse-shape analysis of the detector's ionization current. This technique resulted in an efficient separation of background events and consequently in a well-determined selection of the nuclear reaction channels 12C(n, α0)9Be and 13C(n, α0)10Be.

  5. Physicochemical characterization of titanium dioxide pigments using various techniques for size determination and asymmetric flow field flow fractionation hyphenated with inductively coupled plasma mass spectrometry.

    PubMed

    Helsper, Johannes P F G; Peters, Ruud J B; van Bemmel, Margaretha E M; Rivera, Zahira E Herrera; Wagner, Stephan; von der Kammer, Frank; Tromp, Peter C; Hofmann, Thilo; Weigel, Stefan

    2016-09-01

    Seven commercial titanium dioxide pigments and two other well-defined TiO2 materials (TiMs) were physicochemically characterised using asymmetric flow field flow fractionation (aF4) for separation, various techniques to determine size distribution and inductively coupled plasma mass spectrometry (ICPMS) for chemical characterization. The aF4-ICPMS conditions were optimised and validated for linearity, limit of detection, recovery, repeatability and reproducibility, all indicating good performance. Multi-element detection with aF4-ICPMS showed that some commercial pigments contained zirconium co-eluting with titanium in aF4. The other two TiMs, NM103 and NM104, contained aluminium as integral part of the titanium peak eluting in aF4. The materials were characterised using various size determination techniques: retention time in aF4, aF4 hyphenated with multi-angle laser light spectrometry (MALS), single particle ICPMS (spICPMS), scanning electron microscopy (SEM) and particle tracking analysis (PTA). PTA appeared inappropriate. For the other techniques, size distribution patterns were quite similar, i.e. high polydispersity with diameters from 20 to >700 nm, a modal peak between 200 and 500 nm and a shoulder at 600 nm. Number-based size distribution techniques as spICPMS and SEM showed smaller modal diameters than aF4-UV, from which mass-based diameters are calculated. With aF4-MALS calculated, light-scattering-based "diameters of gyration" (Øg) are similar to hydrodynamic diameters (Øh) from aF4-UV analyses and diameters observed with SEM, but much larger than with spICPMS. A Øg/Øh ratio of about 1 indicates that the TiMs are oblate spheres or fractal aggregates. SEM observations confirm the latter structure. The rationale for differences in modal peak diameter is discussed. PMID:27469116

  6. Physicochemical characterization of titanium dioxide pigments using various techniques for size determination and asymmetric flow field flow fractionation hyphenated with inductively coupled plasma mass spectrometry.

    PubMed

    Helsper, Johannes P F G; Peters, Ruud J B; van Bemmel, Margaretha E M; Rivera, Zahira E Herrera; Wagner, Stephan; von der Kammer, Frank; Tromp, Peter C; Hofmann, Thilo; Weigel, Stefan

    2016-09-01

    Seven commercial titanium dioxide pigments and two other well-defined TiO2 materials (TiMs) were physicochemically characterised using asymmetric flow field flow fractionation (aF4) for separation, various techniques to determine size distribution and inductively coupled plasma mass spectrometry (ICPMS) for chemical characterization. The aF4-ICPMS conditions were optimised and validated for linearity, limit of detection, recovery, repeatability and reproducibility, all indicating good performance. Multi-element detection with aF4-ICPMS showed that some commercial pigments contained zirconium co-eluting with titanium in aF4. The other two TiMs, NM103 and NM104, contained aluminium as integral part of the titanium peak eluting in aF4. The materials were characterised using various size determination techniques: retention time in aF4, aF4 hyphenated with multi-angle laser light spectrometry (MALS), single particle ICPMS (spICPMS), scanning electron microscopy (SEM) and particle tracking analysis (PTA). PTA appeared inappropriate. For the other techniques, size distribution patterns were quite similar, i.e. high polydispersity with diameters from 20 to >700 nm, a modal peak between 200 and 500 nm and a shoulder at 600 nm. Number-based size distribution techniques as spICPMS and SEM showed smaller modal diameters than aF4-UV, from which mass-based diameters are calculated. With aF4-MALS calculated, light-scattering-based "diameters of gyration" (Øg) are similar to hydrodynamic diameters (Øh) from aF4-UV analyses and diameters observed with SEM, but much larger than with spICPMS. A Øg/Øh ratio of about 1 indicates that the TiMs are oblate spheres or fractal aggregates. SEM observations confirm the latter structure. The rationale for differences in modal peak diameter is discussed.

  7. CVD of polymeric thin films: applications in sensors, biotechnology, microelectronics/organic electronics, microfluidics, MEMS, composites and membranes

    NASA Astrophysics Data System (ADS)

    Ozaydin-Ince, Gozde; Coclite, Anna Maria; Gleason, Karen K.

    2012-01-01

    Polymers with their tunable functionalities offer the ability to rationally design micro- and nano-engineered materials. Their synthesis as thin films have significant advantages due to the reduced amounts of materials used, faster processing times and the ability to modify the surface while preserving the structural properties of the bulk. Furthermore, their low cost, ease of fabrication and the ability to be easily integrated into processing lines, make them attractive alternatives to their inorganic thin film counterparts. Chemical vapor deposition (CVD) as a polymer thin-film deposition technique offers a versatile platform for fabrication of a wide range of polymer thin films preserving all the functionalities. Solventless, vapor-phase deposition enable the integration of polymer thin films or nanostructures into micro- and nanodevices for improved performance. In this review, CVD of functional polymer thin films and the polymerization mechanisms are introduced. The properties of the polymer thin films that determine their behavior are discussed and their technological advances and applications are reviewed.

  8. Urchin-like artificial gallium oxide nanowires grown by a novel MOCVD/CVD-based route for random laser application

    NASA Astrophysics Data System (ADS)

    de Melo, Ronaldo P.; Oliveira, Nathalia Talita C.; Dominguez, Christian Tolentino; Gomes, Anderson S. L.; Falcão, Eduardo H. L.; Alves, Severino; da Luz, Leonis L.; Chassagnon, Remi; de Araújo, Cid B.; Sacilotti, Marco

    2016-04-01

    A novel procedure based on a two-step method was developed to obtain β-Ga2O3 nanowires by the chemical vapor deposition (CVD) method. The first step consists in the gallium micro-spheres growth inside a metal-organic chemical vapor deposition environment, using an organometallic precursor. Nanoscale spheres covering the microspheres were obtained. The second step involves the CVD oxidization of the gallium micro-spheres, which allow the formation of β-Ga2O3 nanowires on the micro-sphere surface, with the final result being a nanostructure mimicking nature's sea urchin morphology. The grown nanomaterial is characterized by several techniques, including X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, and photoluminescence. A discussion about the growth mechanism and the optical properties of the β-Ga2O3 material is presented considering its unknown true bandgap value (extending from 4.4 to 5.68 eV). As an application, the scattering properties of the nanomaterial are exploited to demonstrate random laser emission (around 570 nm) when it is permeated with a laser dye liquid solution.

  9. Is the risk and nature of CVD the same in type 1 and type 2 diabetes?

    PubMed

    Duca, Lindsey; Sippl, Rachel; Snell-Bergeon, Janet K

    2013-06-01

    The incidence of both type 1 and type 2 diabetes is increasing globally, most likely explained by environmental changes, such as changing exposures to foods, viruses, and toxins, and by increasing obesity. While cardiovascular disease (CVD) mortality has been declining recently, this global epidemic of diabetes threatens to stall this trend. CVD is the leading cause of death in both type 1 and type 2 diabetes, with at least a two- to fourfold increased risk in patients with diabetes. In this review, the risk factors for CVD are discussed in the context of type 1 and type 2 diabetes. While traditional risk factors such as dyslipidemia, hypertension, and obesity are greater in type 2 patients than in type 1 diabetes, they explain only about half of the increased CVD risk. The role for diabetes-specific risk factors, including hyperglycemia and kidney complications, is discussed in the context of new study findings. PMID:23519720

  10. Effect of intake on fasting heat production, respiratory quotient and plasma metabolites measured using the washed rumen technique.

    PubMed

    Kim, D H; McLeod, K R; Koontz, A F; Foote, A P; Klotz, J L; Harmon, D L

    2015-01-01

    The objective was to investigate the effect of intake before fasting on concentrations of metabolites and hormones, respiratory quotient (RQ) and fasting heat production (HP) using the washed rumen technique and to compare these values with those from the fed state. Six Holstein steers (360±22 kg) were maintained at 21°C and fed three different energy intakes within a replicated 3×3 Latin square design with 21-day periods. Steers were fed alfalfa cubes to provide 1.0, 1.5 and 2.0×NEm during 19 days of each experimental period. Steers were placed in individual metabolism stalls fitted with indirect calorimetry head-boxes on day 20 of each experimental period (FED steers) and fed their normal meal. On day 21 of each period the reticulorumen was emptied, washed and refilled with ruminal buffer (NaCl=96; NaHCO3=24; KHCO3=30; K2HPO4=2; CaCl2=1.5; MgCl2=1.5 mmol/kg of buffer) aerated with 75% N2 and 25% CO2 before introduction to the rumen (steers were not fed; WASHED steers). Each gas exchange was measured over 24 h. HP for 1.0, 1.5 and 2.0×NEm were 479, 597 and 714 kJ/daykg0.75 (s.e.m. =16), respectively. The plateau RQ was 0.756, 0.824 and 0.860 for the 1.0, 1.5 and 2.0×NEm intakes for the FED steers, respectively. After rumen washing, fasting HP was 331, 359 and 400 kJ/daykg0.75 (s.e.m.=13) for 1.0, 1.5, and 2.0×NEm intakes before fasting, respectively. The RQ for WASHED rumen steers was 0.717, 0.710 and 0.719, respectively. Cortisol and β-hydroxybutyrate concentrations in WASHED rumen steers did not exceed threshold levels for severe energy deficit and stress as can be induced from prolonged fasting. This study demonstrates that a fasting state can be emulated using the washed rumen technique, minimizing the time required as opposed to traditional fasting methodologies, without causing a severe energy deficit and stress.

  11. Association Between Leukocyte Telomere Length and Plasma Homocysteine in a Singapore Chinese Population

    PubMed Central

    Rane, Grishma; Koh, Woon-Puay; Kanchi, Madhu Mathi; Wang, Renwei; Yuan, Jian-Min

    2015-01-01

    Abstract Rationale: Leukocyte telomere length (LTL) and plasma homocysteine (HCY) have been independently associated with cardiovascular disease (CVD) morbidity and mortality. However, few studies have investigated the association between LTL and HCY levels. Objective: This study investigated the association of LTL with CVD risk factors, including HCY, in an overt CVD-free Singapore Chinese population comprised of middle aged and elderly, the age group at risk of developing CVD. Approach: The association of plasma HCY and other CVD biomarkers with LTL were assessed in 100 samples drawn from the Singapore Chinese Health Study (SCHS). SCHS, a population-based cohort, recruited Chinese individuals, aged 45–74 years, between 1993 and 1998. Questionnaire data were collected via face-to-face interviews. Known CVD biomarkers were measured from the blood collected at the time of recruitment, and LTL was measured using the conventional Southern blot method. Results: After adjustment for age, gender, smoking status, education, and dialect, LTL was found to be inversely associated with plasma HCY levels (p for trend=0.014). Serum urate showed a weak association (p for trend=0.056). Other CVD risk factors and nutrients, namely total cholesterol, low-density lipoprotein (LDL), triglycerides and creatinine, high-density lipoprotein (HDL), folate, and vitamin B6 showed the expected trend with LTL, but did not reach statistical significance. Conclusion: LTL displayed an inverse association with plasma HCY. This LTL–HCY inverse association in subjects lacking obvious cardiovascular events suggests that telomere length may be an intermediary in the biological mechanism by which elevated HCY leads to CVD. PMID:25546508

  12. Thermal conductivity of giant mono- to few-layered CVD graphene supported on an organic substrate.

    PubMed

    Liu, Jing; Wang, Tianyu; Xu, Shen; Yuan, Pengyu; Xu, Xu; Wang, Xinwei

    2016-05-21

    The thermal conductivity (k) of supported graphene is a critical property that reflects the graphene-substrate interaction, graphene structure quality, and is needed for thermal design of a graphene device. Yet the related k measurement has never been a trivial work and very few studies are reported to date, only at the μm level. In this work, for the first time, the k of giant chemical vapor decomposition (CVD) graphene supported on poly(methyl methacrylate) (PMMA) is characterized using our transient electro-thermal technique based on a differential concept. Our graphene size is ∼mm, far above the samples studied in the past. This giant graphene measurement eliminates the thermal contact resistance problems and edge phonon scattering encountered in μm-scale graphene k measurement. Such mm-scale measurement is critical for device/system-level thermal design since it reflects the effect of abundant grains in graphene. The k of 1.33-layered, 1.53-layered, 2.74-layered and 5.2-layered supported graphene is measured as 365 W m(-1) K(-1), 359 W m(-1) K(-1), 273 W m(-1) K(-1) and 33.5 W m(-1) K(-1), respectively. These values are significantly lower than the k of supported graphene on SiO2, and are about one order of magnitude lower than the k of suspended graphene. We speculate that the abundant C atoms in the PMMA promote more ready energy and momentum exchange with the supported graphene, and give rise to more phonon scattering than the SiO2 substrate. This leads to a lower k of CVD graphene on PMMA than that on SiO2. We attribute the existence of disorder in the sp(2) domain, graphene oxide (GO) and stratification in the 5.2-layered graphene to its more k reduction. The Raman linewidth (G peak) of the 5.2-layered graphene is also twice larger than that of the other three kinds of graphene, indicating the much more phonon scattering and shorter phonon lifetime in it. Also the electrical conductivity of the 5.2-layered graphene is about one-fifth of that for the

  13. Thermal conductivity of giant mono- to few-layered CVD graphene supported on an organic substrate

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Wang, Tianyu; Xu, Shen; Yuan, Pengyu; Xu, Xu; Wang, Xinwei

    2016-05-01

    The thermal conductivity (k) of supported graphene is a critical property that reflects the graphene-substrate interaction, graphene structure quality, and is needed for thermal design of a graphene device. Yet the related k measurement has never been a trivial work and very few studies are reported to date, only at the μm level. In this work, for the first time, the k of giant chemical vapor decomposition (CVD) graphene supported on poly(methyl methacrylate) (PMMA) is characterized using our transient electro-thermal technique based on a differential concept. Our graphene size is ~mm, far above the samples studied in the past. This giant graphene measurement eliminates the thermal contact resistance problems and edge phonon scattering encountered in μm-scale graphene k measurement. Such mm-scale measurement is critical for device/system-level thermal design since it reflects the effect of abundant grains in graphene. The k of 1.33-layered, 1.53-layered, 2.74-layered and 5.2-layered supported graphene is measured as 365 W m-1 K-1, 359 W m-1 K-1, 273 W m-1 K-1 and 33.5 W m-1 K-1, respectively. These values are significantly lower than the k of supported graphene on SiO2, and are about one order of magnitude lower than the k of suspended graphene. We speculate that the abundant C atoms in the PMMA promote more ready energy and momentum exchange with the supported graphene, and give rise to more phonon scattering than the SiO2 substrate. This leads to a lower k of CVD graphene on PMMA than that on SiO2. We attribute the existence of disorder in the sp2 domain, graphene oxide (GO) and stratification in the 5.2-layered graphene to its more k reduction. The Raman linewidth (G peak) of the 5.2-layered graphene is also twice larger than that of the other three kinds of graphene, indicating the much more phonon scattering and shorter phonon lifetime in it. Also the electrical conductivity of the 5.2-layered graphene is about one-fifth of that for the other three. This

  14. Flow-injection technique for determination of uranium and thorium isotopes in urine by inductively coupled plasma mass spectrometry.

    PubMed

    Benkhedda, Karima; Epov, Vladimir N; Evans, R Douglas

    2005-04-01

    A sensitive and efficient flow-injection (FI) preconcentration and matrix-separation technique coupled to sector field ICP-mass spectrometry (SF-ICP-MS) has been developed and validated for simultaneous determination of ultra-low levels of uranium (U) and thorium (Th) in human urine. The method is based on selective retention of U and Th from a urine matrix, after microwave digestion, on an extraction chromatographic TRU resin, as an alternative to U/TEVA resin, and their subsequent elution with ammonium oxalate. Using a 10 mL sample, the limits of detection achieved for 238U and 232Th were 0.02 and 0.03 ng L(-1), respectively. The accuracy of the method was checked by spike-recovery measurements. Levels of U and Th in human urine were found to be in the ranges 1.86-5.50 and 0.176-2.35 ng L(-1), respectively, well in agreement with levels considered normal for non-occupationally exposed persons. The precision obtained for five replicate measurements of a urine sample was 2 and 3% for U and Th, respectively. The method also enables on-line measurements of the 235U/238U isotope ratios in urine. Precision of 0.82-1.04% (RSD) was obtained for 235U/238U at low ng L(-1) levels, using the FI transient signal approach.

  15. The High performance of nanocrystalline CVD diamond coated hip joints in wear simulator test.

    PubMed

    Maru, M M; Amaral, M; Rodrigues, S P; Santos, R; Gouvea, C P; Archanjo, B S; Trommer, R M; Oliveira, F J; Silva, R F; Achete, C A

    2015-09-01

    The superior biotribological performance of nanocrystalline diamond (NCD) coatings grown by a chemical vapor deposition (CVD) method was already shown to demonstrate high wear resistance in ball on plate experiments under physiological liquid lubrication. However, tests with a close-to-real approach were missing and this constitutes the aim of the present work. Hip joint wear simulator tests were performed with cups and heads made of silicon nitride coated with NCD of ~10 μm in thickness. Five million testing cycles (Mc) were run, which represent nearly five years of hip joint implant activity in a patient. For the wear analysis, gravimetry, profilometry, scanning electron microscopy and Raman spectroscopy techniques were used. After 0.5 Mc of wear test, truncation of the protruded regions of the NCD film happened as a result of a fine-scale abrasive wear mechanism, evolving to extensive plateau regions and highly polished surface condition (Ra<10nm). Such surface modification took place without any catastrophic features as cracking, grain pullouts or delamination of the coatings. A steady state volumetric wear rate of 0.02 mm(3)/Mc, equivalent to a linear wear of 0.27 μm/Mc favorably compares with the best performance reported in the literature for the fourth generation alumina ceramic (0.05 mm(3)/Mc). Also, squeaking, quite common phenomenon in hard-on-hard systems, was absent in the present all-NCD system.

  16. All optical read-out radiation dosimeter using CVD synthetic diamond

    NASA Astrophysics Data System (ADS)

    Preciado-Flores, S.; Schreck, M.; Meléndrez, R.; Chernov, V.; Pedroza-Montero, M.; Barboza-Flores, M.

    2006-09-01

    In the present work, we evaluate the optically stimulated luminescence (OSL) dosimetric properties of two polycrystalline 10 m thick films, undoped and 750 ppm nitrogen doped, grown on (100) silicon substrates exposed to beta radiation. The samples were optically stimulated to free and to induce radiative recombination of the trapped charges caused by radiation absorption. This all optical technique uses IR laser 830 nm light for stimulation and a PMT coupled to a BG-39 (300-600 nm) filter for light intensity measurements. The OSL of both samples is very similar in output intensity and hyperbolic decay type. The OSL signal of non doped samples involves localized trapping states around the 373-653 K as compared to nitrogen doped sample which involves the charge detrapping of localized states in the 353-550 K range. The OSL signal in the first 0.16 s shows two linearity regions for 0-35 Gy and 35-100 Gy dose ranges. An obvious advantage of OSL over TL/TSC methods is that no heating is required, it may also open the possibility of using CVD diamond coupled to optical fibers for stimulation and read-out light signals allowing in situ and real time dose measurements.

  17. The Electronic Properties of Nanoscale Meta-lattice Made by High Pressure CVD

    NASA Astrophysics Data System (ADS)

    Huang, Zhaohui; Crespi, Vincent

    Meta-lattice can be defined as an artificial 3D superlattice with periodic structural modulation occurred at 10nm scale. One viable route to synthesize can be as follows: A template is first prepared by close-packed nanometer-sized silica spheres, then Si/Ge or a binary semiconductor is infiltrated into voids by high pressure chemical vapor deposition (CVD). Later silica spheres can be removed by chemical method, and voids in the inverse meta-latice offer the opportunity for a second infiltration. Due to the characteristic length of voids, meta-lattice provides a platform to test novel mesoscopic electronic and thermal phenomena. A meta-lattice solid can show novel physical properties that each constituent infiltrate material does not have. Since a significan portion of atoms are located on the surface, the interface structure details are expected to play a critical role. Here we investigate Si/Ge inverse meta-lattices with or without silica template present. Tight-binding, DFT and GW/BSE techniques are employed to look into the electronic and optical properties.

  18. Ultrathin antifouling coatings with stable surface zwitterionic functionality by initiated chemical vapor deposition (iCVD).

    PubMed

    Yang, Rong; Gleason, Karen K

    2012-08-21

    Antifouling thin films of poly[N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)-co-2-(dimethylamino)ethyl methacrylate-co-ethylene glycol dimethacrylate] (PDDE) were synthesized via a substrate-independent and all-dry-initiated chemical vapor deposition (iCVD) technique followed by a diffusion-limited vapor-phase reaction with 1,3-propane sultone. Coated surfaces exhibited very low absorption of various foulants including bovine serum albumin (BSA), humic acid (HA), and sodium alginate (SA), as measured with the quartz crystal microbalance with dissipation monitoring (QCM-D). The fouling by humic acid was dependent on the presence of divalent cations such as Ca(2+). Both depth profiling and angle-resolved X-ray photoelectron spectroscopy (XPS) measurements indicated that the zwitterionic groups were highly concentrated in the top ~3 nm of the film. The contact angle measurements revealed a limited degree of surface chain reorganization upon contacting water. The dynamic contact angles remained unchanged after 100 days of storage in air, indicating the stability of the interface. The coating was substrate-independent, and the film was conformal on surface nanostructures including trenches, reverse osmosis membranes, and electrospun nanofiber mats. PMID:22873558

  19. Fabrication of contamination-free CVD Graphene devices using soak and peel method

    NASA Astrophysics Data System (ADS)

    Sebastian, Abhilash; Kakatkar, Aniket; de Alba, Roberto; Zhelev, Nikolay; McEuen, Paul; Craighead, Harold; Parpia, Jeevak

    2014-03-01

    Large area graphene-based devices are commonly fabricated by transferring the CVD grown graphene from metal foils to semiconductor substrates. However, during device fabrication, the transfer process involves chemical etching of metal that leads to the degradation of electrical properties of graphene. Recently, a clean transfer of graphene to devices with improved electrical properties, by delamination of graphene from metal substrates by soak and peel using DI-water has been demonstrated. We employed the soak and peel scheme to fabricate graphene transistor arrays on a SiO2/Si substrate with a back gate configuration. The source-drain contacts are patterned using Ti/Pt with graphene channel length varying from 2-50um. The graphene is transferred subsequently to the substrate and yields a high quality junction between metal electrodes and graphene. The contact resistance is low and the Dirac peak is observed across the array. The suitability of the graphene transistors for chemical functionalization will be presented. Possible application of this transfer technique for fabricating large area suspended nano-electro mechanical systems will be discussed.

  20. CVD Diamond, DLC, and c-BN Coatings for Solid Film Lubrication

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Murakawa, Masao; Watanabe, Shuichi; Takeuchi, Sadao; Miyake, Shojiro; Wu, Richard L. C.

    1998-01-01

    The main criteria for judging coating performance were coefficient of friction and wear rate, which had to be less than 0.1 and 10(exp -6) cubic MM /(N*m), respectively. Carbon- and nitrogen-ion-implanted, fine-grain, chemical-vapor-deposited (CVD) diamond and diamondlike carbon (DLC) ion beam deposited on fine-grain CVD diamond met the criteria regardless of environment (vacuum, nitrogen, and air).

  1. Simulation of a perfect CVD diamond Schottky diode steep forward current-voltage characteristic

    NASA Astrophysics Data System (ADS)

    Kukushkin, V. A.

    2016-10-01

    The kinetic equation approach to the simulation of the perfect CVD diamond Schottky diode current-voltage characteristic is considered. In result it is shown that the latter has a significantly steeper forward branch than that of perfect devices of such a type on usual semiconductors. It means that CVD diamond-based Schottky diodes have an important potential advantage over analogous devices on conventional materials.

  2. CVD Diamond, DLC, and c-BN Coatings for Solid Film Lubrication

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1998-01-01

    When the main criteria for judging coating performance were coefficient of friction and wear rate, which had to be less than 0.1 and 10(exp -6) mm(exp 3)/N-m, respectively, carbon- and nitrogen-ion-implanted, fine-grain CVD diamond and DLC ion beam deposited on fine-grain CVD diamond met the requirements regardless of environment (vacuum, nitrogen, and air).

  3. Tribological Characteristics and Applications of Superhard Coatings: CVD Diamond, DLC, and c-BN

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Murakawa, Masao; Watanabe, Shuichi; Takeuchi, Sadao; Wu, Richard L. C.

    1999-01-01

    Results of fundamental research on the tribological properties of chemical-vapor-deposited (CVD) diamond, diamondlike carbon, and cubic boron nitride films in sliding contact with CVD diamond in ultrahigh vacuum, dry nitrogen, humid air, and water are discussed. Furthermore, the actual and potential applications of the three different superhard coatings in the field of tribology technology, particularly for wear parts and tools, are reviewed.

  4. Ion beam induced surface graphitization of CVD diamond for x-ray beam position monitor applications

    SciTech Connect

    Liu, Chian; Shu, D.; Kuzay, T.M.; Wen, L.; Melendres, C.A. |

    1996-12-31

    The Advanced Photon Source at ANL is a third-generation synchrotron facility that generates powerful x-ray beams on its undulator beamlines. It is important to know the position and angle of the x- ray beam during experiments. Due to very high heat flux levels, several patented x-ray beam position monitors (XBPM) exploiting chemical vapor deposition (CVD) diamond have been developed. These XBPMs have a thin layer of low-atomic-mass metallic coating so that photoemission from the x rays generate a minute but measurable current for position determination. Graphitization of the CVD diamond surface creates a very thin, intrinsic and conducting layer that can stand much higher temperatures and minimal x-ray transmission losses compared to the coated metallic layers. In this paper, a laboratory sputter ion source was used to transform selected surfaces of a CVD diamond substrate into graphite. The effect of 1-5 keV argon ion bombardment on CVD diamond surfaces at various target temperatures from 200 to 500 C was studied using Auger electron spectroscopy and in-situ electrical resistivity measurements. Graphitization after the ion bombardment has been confirmed and optimum conditions for graphitization studied. Raman spectroscopy was used to identify the overall diamond structure in the bulk of CVD diamond substrate after the ion bombardments. It was found that target temperature plays an important role in stability and electrical conductivity of the irradiated CVD diamonds.

  5. Defects in CVD Diamond Films from Their Response as Nuclear Detectors

    NASA Astrophysics Data System (ADS)

    Marinelli, Marco; Milani, Enrico; Tucciarone, Aldo; Rinati, Gianluca Verona

    CVD diamond films can be used to realize nuclear detectors with outstanding working capability in harsh environments. Since efficient particle detection requires high drift lengths of the carriers produced by the ionizing particle, the presence of defects severely limits the performance of these detectors. This is a major issue because the fabrication technology of CVD diamond is much less advanced than that of more conventional materials like silicon. The different kinds of defects in CVD diamond and their influence on the detector response are discussed. The connections between the microscopic structure of CVD diamond and the priming (or pumping) effect, which is widely used to increase CVD diamond detector performance, are elucidated. The analysis of the response of CVD diamond-based detectors is used to extract qualitative and quantitative information on the properties of defects limiting the free movement of charge carriers in the detector (e.g., carrier type for which the traps are active, activation energies, geometrical distribution in the film, etc.). Milani-begin

  6. On the chemistry of a-SiO 2 deposition by plasma enhanced CVD

    NASA Astrophysics Data System (ADS)

    Wickramanayaka, Sunil; Nakanishi, Y.; Hatanaka, Y.

    1997-04-01

    The chemistry in depositing a-SiO 2 using tetraethoxysilane, Si(OC 2H 5) 4, (TEOS) and tetraisocyanatesilane, Si(NCO) 4, (TICS) with an oxidant is comparatively studied. In both cases, absorption and desorption reactions of intermediate precursors are seen to be dominant. TEOS/O 2 chemistry, where there is no N atom in the source gas, yields conformal step coverage over patterned surfaces. The precursor or precursors generated in TICS/O 2 chemistry are expected to contain N atom or atoms and have no surface migration property. The N atom in the precursor is believed to limit the surface migration property. This results in an uneven step coverage over patterned surfaces similar to that of SiH 4/O 2 chemistry.

  7. Cluster control plasma CVD for fabrication of stable a-Si:H solar cells

    NASA Astrophysics Data System (ADS)

    Shiratani, Masaharu; Hashimoto, Yuuji; Kanemitsu, Yoshinori; Seo, Hyunwoong; Kamataki, Kunihiro; Uchida, Giichiro; Itagaki, Naho; Koga, Kazunori

    2013-09-01

    Light-induced degradation of a-Si:H is the key issue for a-Si:H solar cells, because light exposure initially causes a significant reduction of the efficiency of the cells due to the degradation. In SiH4 discharges employed for a-Si:H deposition, there coexist three deposition precursors; SiH3 radicals, HOS radicals, and amorphous clusters (nanoparticles). SiH3 radicals are the main deposition precursors for ``good'' quality films, whereas clusters are the precursors to cause the light induced degradation. To suppress cluster incorporation into films, we employ, 1) magnetic field which modifies EEDF, 2) gas heating to suppress polymerization reactions in gas phase, 3) gas flow which drives clusters downstream, 4) thermophoretic force which supresses cluster deposition, and 5) a cluster eliminating filter. Our a-Si:H films deposited at 3 nm/s show a low stabilized defect density of 5 × 1015 cm-3 . To evaluate their quality as an I layer of PIN solar cells, we have measured Fill Factor (FF) of N-type c-Si/a-Si:H/Ni Schottky cells of such cluster-free a-Si:H films. Our cell shows high initial FF of 0.516, high stable FF of 0.514, and little light induced degradation ratio of 0.39%. Work supported by NEDO, PVTEC, and MEXT.

  8. Laser ablation inductively coupled plasma mass spectrometry: A new technique for the determination of trace and ultra-trace elements in silicates

    SciTech Connect

    Perkins, W.T.; Pearce, N.J.G.; Jeffries, T.E. )

    1993-01-01

    This paper describes recent work applying a laser ablation system coupled to an inductively coupled plasma mass spectrometer (LA-ICP-MS) for the direct analysis of solid geological materials. This work demonstrates the potential of LA-ICP-MS for the determination of a wide range of petrogenetically important trace and ultra-trace elements (including for example REE, Hf, Ta, Nb, Th, U) following a routine method of sample preparation. Powdered geological materials have been prepared as both pressed powder disks and fused glasses; both common methods of sample preparation for X-ray fluorescence (XRF) analysis. The solid materials were sampled by ablation using a pulsed Nd:YAG laser operating at 1,064 nm. Analyses can be produced at approximately 10 samples per hour. This instrumental method has limits of detection at or close to those in chondritic meteorites and gives linear calibrations over four orders of magnitude. The accuracy of the technique has been evaluated using reference materials to calibrate the instrument and treating Geological Survey of Japan basalts JB-1a, JB-2, and JB-3 as unknowns.' Detection limits are better than routine XRF analysis and compare favorably with Instrumental Neutron Activation Analysis. Laser ablation overcomes the problems of sample dissolution employed in standard wet chemical techniques, whilst the fused glasses provide homogeneous solid samples. The fused glass technique has been applied to a wide range of reference materials from ultra-basic rocks through basalts and andesites to granites, as well as syenite, mica schist, and black shale. For all of the elements commonly used to generate multi-element discrimination diagrams the data obtained define straight line calibrations. This method is therefore capable of analyzing the complete range of silicate compositions normally encountered with a single calibration (i.e., there is no apparent matrix effect). 47 refs., 4 figs., 5 tabs.

  9. Synthesis of Carbon Nanotubes by CVD and Spray Pyrolysis and Their Characterization by Scattering Techniques

    NASA Astrophysics Data System (ADS)

    Bahadur, J.; Prakash, J.; Sen, D.; Mazumder, S.; Sathiyamoorthy, D.

    2011-07-01

    Carbon nanotubes have been synthesized by catalytic chemical vapor deposition and spray pyrolysis methods. Synthesized nanotubes were characterized by Small-angle neutron scattering, X-ray diffraction and Raman spectroscopy. Scattering data reveals the aggregated nature of nanotubes, the average diameter and average length have also been estimated. It has been observed that the nanotubes, synthesized by spray pyrolysis methods, possess fewer defects in their graphitic nature of wall. The X-ray diffraction data reveals that the nanotubes possess metal oxide impurities.

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

    PubMed

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

    2014-10-21

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

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

    PubMed

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

    2014-10-21

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

  12. Microstructure evolution and non-diamond carbon incorporation in CVD diamond thin films grown at low substrate temperatures

    NASA Astrophysics Data System (ADS)

    Michler, J.; Stiegler, J.; von Kaenel, Y.; Moeckli, P.; Dorsch, W.; Stenkamp, D.; Blank, E.

    1997-03-01

    We investigated the development of the microstructure and the incorporation of non-diamond carbon close to the low temperature border of the CVD diamond domain. Thin diamond films were deposited at low substrate temperatures (560°C-275°C) by microwave plasma-assisted CVD on silicon, varying only the substrate temperature. At elevated temperatures (560°C-430°C) the film mainly consists of nearly defect free near 112 oriented grains with smooth 111 facets, exhibiting steps and risers at the surface. Decreasing the substrate temperature an apparently sharp transition occurs, below which the film quality undergoes a rapid deterioration as evidenced by Raman spectroscopy, while crystalline faceted grains with a size of several microns and a growth texture of <100> remain. However, X-ray diffraction reveals a strongly decreasing crystal size (from about 1 μm to 10 nm) which can be attributed to an increased twin density within the macroscopic grains. High resolution transmission electron microscopy reveals that these twins consist of small twin lamellae with a spacing of only several atomic planes. Transmission electron microscopy of near surface areas evidences re-entrant corners at the grain surfaces formed by twin lamellae and the presence of steps and risers. Non-diamond carbon was detected in the form of amorphous inclusions at incoherent twin boundaries and probably at higher order twin boundaries. The observations will be discussed by means of two different competing nucleation mechanisms: above the low temperature limit the grains grow by lateral ledge motion and preferential nucleation at re-entrant corners. Approaching the low temperature limit, two-dimensional nucleation at growth facets becomes an alternate nucleation mechanism, which introduces a high density of microtwins. If two-dimensional nuclei grow together, non-diamond carbon is incorporated during growth at this interface.

  13. Layer-controlled CVD growth of large-area two-dimensional MoS2 films

    NASA Astrophysics Data System (ADS)

    Jeon, Jaeho; Jang, Sung Kyu; Jeon, Su Min; Yoo, Gwangwe; Jang, Yun Hee; Park, Jin-Hong; Lee, Sungjoo

    2015-01-01

    In spite of the recent heightened interest in molybdenum disulfide (MoS2) as a two-dimensional material with substantial bandgaps and reasonably high carrier mobility, a method for the layer-controlled and large-scale synthesis of high quality MoS2 films has not previously been established. Here, we demonstrate that layer-controlled and large-area CVD MoS2 films can be achieved by treating the surfaces of their bottom SiO2 substrates with the oxygen plasma process. Raman mapping, UV-Vis, and PL mapping are performed to show that mono, bi, and trilayer MoS2 films grown on the plasma treated substrates fully cover the centimeter scale substrates with a uniform thickness. Our TEM images also present the single crystalline nature of the monolayer MoS2 film and the formation of the layer-controlled bi- and tri-layer MoS2 films. Back-gated transistors fabricated on these MoS2 films are found to exhibit the high current on/off ratio of ~106 and high mobility values of 3.6 cm2 V-1 s-1 (monolayer), 8.2 cm2 V-1 s-1 (bilayer), and 15.6 cm2 V-1 s-1 (trilayer). Our results are expected to have a significant impact on further studies of the MoS2 growth mechanism as well as on the scaled layer-controlled production of high quality MoS2 films for a wide range of applications.In spite of the recent heightened interest in molybdenum disulfide (MoS2) as a two-dimensional material with substantial bandgaps and reasonably high carrier mobility, a method for the layer-controlled and large-scale synthesis of high quality MoS2 films has not previously been established. Here, we demonstrate that layer-controlled and large-area CVD MoS2 films can be achieved by treating the surfaces of their bottom SiO2 substrates with the oxygen plasma process. Raman mapping, UV-Vis, and PL mapping are performed to show that mono, bi, and trilayer MoS2 films grown on the plasma treated substrates fully cover the centimeter scale substrates with a uniform thickness. Our TEM images also present the single

  14. Implementation of a new atomic basis for the He I equilibrium line ratio technique for electron temperature and density diagnostic in the SOL for H-mode plasmas in DIII-D

    NASA Astrophysics Data System (ADS)

    Muñoz Burgos, J. M.; Schmitz, O.; Unterberg, E. A.; Loch, S. D.; Ballance, C. P.

    2011-08-01

    Evaluating the ratio of selected helium lines allows for measurement of electron densities and temperatures. This technique is applied for L-mode plasmas at TEXTOR (O. Schmitz et al., Plasma Phys. Control. Fusion 50 (2008) 115004). We report our first efforts to extend it to H-mode plasma diagnostics in DIII-D. This technique depends on the accuracy of the atomic data used in the collisional radiative model (CRM). We present predictions for the electron temperatures and densities by using recently calculated R-Matrix With Pseudostates (RMPS) and Convergent Close-Coupling (CCC) electron-impact excitation and ionization data. We include contributions from higher Rydberg states by means of the projection matrix. These effects become significant for high electron density conditions, which are typical in H-mode. We apply a non-equilibrium model for the time propagation of the ionization balance to predict line emission profiles from experimental H-mode data from DIII-D.

  15. Friction Properties of Polished Cvd Diamond Films Sliding against Different Metals

    NASA Astrophysics Data System (ADS)

    Lin, Zichao; Sun, Fanghong; Shen, Bin

    2016-11-01

    Owing to their excellent mechanical and tribological properties, like the well-known extreme hardness, low coefficient of friction and high chemical inertness, chemical vapor deposition (CVD) diamond films have found applications as a hard coating for drawing dies. The surface roughness of the diamond films is one of the most important attributes to the drawing dies. In this paper, the effects of different surface roughnesses on the friction properties of diamond films have been experimentally studied. Diamond films were fabricated using hot filament CVD. The WC-Co (Co 6wt.%) drawing dies were used as substrates. A gas mixture of acetone and hydrogen gas was used as the feedstock gas. The CVD diamond films were polished using mechanical polishing. Polished diamond films with three different surface roughnesses, as well as the unpolished diamond film, were fabricated in order to study the tribological performance between the CVD diamond films and different metals with oil lubrication. The unpolished and polished CVD diamond films are characterized with scanning electron microscope (SEM), atomic force microscope (AFM), surface profilometer, Raman spectrum and X-ray diffraction (XRD). The friction examinations were carried out by using a ball-on-plate type reciprocating friction tester. Low carbide steel, stainless steel, copper and aluminum materials were used as counterpart balls. Based on this study, the results presented the friction coefficients between the polished CVD films and different metals. The friction tests demonstrate that the smooth surface finish of CVD diamond films is beneficial for reducing their friction coefficients. The diamond films exhibit low friction coefficients when slid against the stainless steel balls and low carbide steel ball, lower than that slid against copper ball and aluminum ball, attributed to the higher ductility of copper and aluminum causing larger amount of wear debris adhering to the sliding interface and higher adhesive

  16. Applications of atmospheric plasmas

    NASA Astrophysics Data System (ADS)

    Oldham, Christopher John

    Surface modification techniques using plasmas have historically been completed in a low pressure environment due to Pd (pressure x gap distance) considerations influencing the behavior of plasma generation. Generally, plasmas produced in a low pressure environment are of a non-thermal or cold nature. The basic feature of non-thermal plasmas is the majority of electrical energy used to generate the plasma is primarily used to produce energetic electrons for generating chemical species. Low pressure plasmas serve many purposes for materials processing. Since the plasma environment is contained within a closed vessel, the plasma can be controlled very easily. Low pressure plasmas have been used in many industries but the complexity associated with the large pumping stations and limitation to batch processing has motivated new work in the area of atmospheric plasmas. Atmospheric plasmas offer both economic and technical justification for use over low pressure plasmas. Since atmospheric plasmas can be operated at ambient conditions, lower costs associated with continuous processing and a decrease in the complexity of equipment validate atmospheric plasma processing as a next generation plasma-aided manufacturing process. In an effort to advance acceptance of atmospheric plasma processing into industry, a process was developed, the dielectric barrier discharge (DBD), in order to generate a homogeneous and non-thermal plasma discharge at ambient conditions. The discharge was applied to the reduction of known food borne pathogens, deposition of thin film materials, and modification of lignocellulosic biomass.

  17. Collaborative study for establishment of a European Pharmacopoei Biological Reference Preparation (BRP) for B19 virus DNA testing of plasma pools by nucleic acid amplification technique.

    PubMed

    Nübling, C M; Daas, A; Buchheit, K H

    2004-01-01

    The goal of the collaborative study was to calibrate the B19 DNA content of a candidate Biological Reference Preparation (BRP) that is intended to be used for the validation of the analytical procedure, as threshold control and/or as quantitative reference material in the Nucleic Acid Amplification Technique (NAT) test of plasma pools for detection of B19 contamination. The candidate BRP was calibrated against the 1st International Standard for B19 DNA NAT assays. According to the European Pharmacopoeia monograph Human anti-D immunoglobulin, the threshold control needs to have a titre of 10( 4) IU/ml of B19 virus DNA. The lyophilised candidate BRP was prepared from 0.5 ml aliquots of a plasma pool spiked with B19 virus. The B19 virus originated from a "B19 virus window phase" blood donation (anti-B19 negative, B19-DNA high titre positive) and was diluted in a plasma pool tested negative by both serological and NAT assays for Hepatitis B Virus, Hepatitis C Virus and Human Immunodeficiency Virus 1 to obtain a B19-DNA concentration level in the range of 10( 6) copies/ml. The residual water content of the lyophilised candidate BRP was determined as 0.98 +/- 0.65% (mean +/- relative standard deviation). Sixteen laboratories (Official Medicine Control Laboratories, manufacturers of plasma derivatives, NAT test laboratories and NAT kit manufacturers) from nine countries participated. Participants were requested to test the candidate BRP and the International Standard (99/800) in four independent test runs on different days using their in-house qualitative and/or quantitative NAT methods. Sixteen laboratories reported results. Thirteen laboratories reported results from qualitative assays and 5 laboratories reported results from quantitative assays. Two laboratories reported results from both types of assay. For the qualitative assays a weighted combined potency of 5.64 log( 10) IU/ml with 95 per cent confidence limits of +/- 0.17 log( 10) which corresponds to 67 to 150

  18. Collaborative study for establishment of a European Pharmacopoei Biological Reference Preparation (BRP) for B19 virus DNA testing of plasma pools by nucleic acid amplification technique.

    PubMed

    Nübling, C M; Daas, A; Buchheit, K H

    2004-01-01

    The goal of the collaborative study was to calibrate the B19 DNA content of a candidate Biological Reference Preparation (BRP) that is intended to be used for the validation of the analytical procedure, as threshold control and/or as quantitative reference material in the Nucleic Acid Amplification Technique (NAT) test of plasma pools for detection of B19 contamination. The candidate BRP was calibrated against the 1st International Standard for B19 DNA NAT assays. According to the European Pharmacopoeia monograph Human anti-D immunoglobulin, the threshold control needs to have a titre of 10( 4) IU/ml of B19 virus DNA. The lyophilised candidate BRP was prepared from 0.5 ml aliquots of a plasma pool spiked with B19 virus. The B19 virus originated from a "B19 virus window phase" blood donation (anti-B19 negative, B19-DNA high titre positive) and was diluted in a plasma pool tested negative by both serological and NAT assays for Hepatitis B Virus, Hepatitis C Virus and Human Immunodeficiency Virus 1 to obtain a B19-DNA concentration level in the range of 10( 6) copies/ml. The residual water content of the lyophilised candidate BRP was determined as 0.98 +/- 0.65% (mean +/- relative standard deviation). Sixteen laboratories (Official Medicine Control Laboratories, manufacturers of plasma derivatives, NAT test laboratories and NAT kit manufacturers) from nine countries participated. Participants were requested to test the candidate BRP and the International Standard (99/800) in four independent test runs on different days using their in-house qualitative and/or quantitative NAT methods. Sixteen laboratories reported results. Thirteen laboratories reported results from qualitative assays and 5 laboratories reported results from quantitative assays. Two laboratories reported results from both types of assay. For the qualitative assays a weighted combined potency of 5.64 log( 10) IU/ml with 95 per cent confidence limits of +/- 0.17 log( 10) which corresponds to 67 to 150

  19. Thermal plasma processing

    SciTech Connect

    Boulos, M.I. . Dept. of Chemical Engineering)

    1991-12-01

    This paper is a review of the fundamental aspects involved in material processing using thermal plasma technology. The description of plasma-generating devices covers dc plasma torches, dc transferred arcs, radio-frequency (RF) inductively coupled plasma torches, and hybrid combinations of them. Emphasis is given to the identification of the basic energy-coupling mechanism in each case and the principal characteristics of the flow and temperature fields in the plasma. Materials-processing techniques using thermal plasmas are grouped in two broad categories, depending on the role played by the plasma in the process. Only typical examples are given in this review of each type of processes. The simplest and most widely used processes such as spheroidization, melting, deposition, and spray-coating make use of the plasma only as a high-temperature energy source. Thermal plasma technology is also used in applications involving chemical synthesis in which the plasma acts as a source of chemically active species.

  20. The Role of Plasma in Plasma Enhanced Chemical Vapour Deposition of Nanostructure Growth

    NASA Technical Reports Server (NTRS)

    Hash, David B.; Meyyappan, M.; Teo, Kenneth B. K.; Lacerda, Rodrigo G.; Rupesinghe, Nalin L.

    2004-01-01

    Chemical vapour deposition (CVD) has become the preferred process for high yield growth of carbon nanotubes and nanofibres because of its ability to pattern growth through lithographic positioning of transition metal catalysts on substrates. Many potential applications of nanotubes such as field emitters [1] require not only patterned growth but also vertical alignment. Some degree of ali,ment in thermal CVD processes can be obtained when carbon nanotubes are grown closely together as a result of van der Waals interactions. The ali,onment however is marginal, and the van der Waals prerequisite makes growth of freestanding nanofibres with thermal CVD unrealizable. The application of electric fields as a means of ali,onment has been shown to overcome this limitation [2-5], and highly aligned nanostructures can be grown if electric fields on the order of 0.5 V/microns are employed. Plasma enhanced CVD in various configurations including dc, rf, microwave, inductive and electron cyclotron resonance has been pursued as a means of enabling alignment in the CVD process. However, the sheath fields for the non-dc sources are in general not sufficient for a high degree of ali,pment and an additional dc bias is usually applied to the growth substrate. This begs the question as to the actual role of the plasma. It is clear that the plasma itself is not required for aligned growth as references [3] and [4] employed fields through small applied voltages (3-20 V) across very small electrode spacings (10-100 microns) and thus avoided striking a discharge.

  1. SY 04-1 CVD RISK PREDICTION IN HIGH-RISK VERSUS LOW-RISK POPULATIONS.

    PubMed

    Kim, Hyeon Chang

    2016-09-01

    Disease risk prediction models have been developed to assess the impact of multiple risk factors and to estimate an individual's absolute disease risk. Accurate disease prediction is essential for personalized prevention, because the benefits, risks, and costs of alternative strategies must be weighed to choose the best preventive strategy for individual patients. Cardiovascular disease (CVD) prediction is the earliest example of individual risk predictions. Since the Framingham study reported a CVD risk prediction method in 1976, an increasing number of risk assessment tools have been developed to CVD risk in various settings. The Framingham study results are fundamental evidence for the prediction of CVD risk. However, the clinical utility of a disease prediction model can be population-specific because the baseline disease risk, subtype distribution of the disease, and level of exposure to risk factors differ by region and ethnicity.It has been proved that CVD prediction models which were developed in high-risk populations, such as the Framingham Risk Score, overestimate an individual's disease risk when applied to a low-risk population without re-calibration. Thus countries of relatively low CVD risk are trying to re-calibrate the existing CVD prediction models or to develop a new prediction model analyzing their own population data. However, even the re-calibrated or newly-developed CVD prediction models are often of little clinical value in a low-risk population. A good example is the CVD prediction in the Korean population. Compared to Western populations, the Korean population has much lower incidence of coronary heart disease. Therefore, the vast majority of individuals fall into the low-risk group when their disease risk is assessed with a prediction model. Even a well-validated prediction model may not identify high-risk individuals who merit aggressive preventive treatment.A few alternative approaches have been suggested for CVD risk prediction in a low

  2. Movers and stayers: The geography of residential mobility and CVD hospitalisations in Auckland, New Zealand.

    PubMed

    Exeter, Daniel J; Sabel, Clive E; Hanham, Grant; Lee, Arier C; Wells, Susan

    2015-05-01

    The association between area-level disadvantage and health and social outcomes is unequivocal. However, less is known about the health impact of residential mobility, particularly at intra-urban scales. We used an encrypted National Health Index (eNHI) number to link individual-level data recorded in routine national health databases to construct a cohort of 641,532 participants aged 30+ years to investigate the association between moving and CVD hospitalisations in Auckland, New Zealand. Residential mobility was measured for participants according to changes in the census Meshblock of usual residence, obtained from the Primary Health Organisation (PHO) database for every calendar quarter between 1/1/2006 and 31/12/2012. The NZDep2006 area deprivation score at the start and end of a participant's inclusion in the study was used to measure deprivation mobility. We investigated the relative risk of movers being hospitalised for CVD relative to stayers using multi-variable binomial regression models, controlling for age, gender, deprivation and ethnicity. Considered together, movers were 1.22 (1.19-1.26) times more likely than stayers to be hospitalised for CVD. Using the 5×5 deprivation origin-destination matrix to model a patient's risk of CVD based on upward, downward or sideways deprivation mobility, movers within the least deprived (NZDep2006 Quintile 1) areas were 10% less likely than stayers to be hospitalised for CVD, while movers within the most deprived (NZDep2006 Q5) areas were 45% more likely than stayers to have had their first CVD hospitalisation in 2006-2012 (RR: 1.45 [1.35-1.55]). Participants who moved upward also had higher relative risks of having a CVD event, although their risk was less than those observed for participants experiencing downward deprivation mobility. This research suggests that residential mobility is an important determinant of CVD in Auckland. Further investigation is required to determine the impact moving has on the risk of

  3. Enhanced cold wall CVD reactor growth of horizontally aligned single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Mu, Wei; Kwak, Eun-Hye; Chen, Bingan; Huang, Shirong; Edwards, Michael; Fu, Yifeng; Jeppson, Kjell; Teo, Kenneth; Jeong, Goo-Hwan; Liu, Johan

    2016-05-01

    HASynthesis of horizontally-aligned single-walled carbon nanotubes (HA-SWCNTs) by chemical vapor deposition (CVD) directly on quartz seems very promising for the fabrication of future nanoelectronic devices. In comparison to hot-wall CVD, synthesis of HA-SWCNTs in a cold-wall CVD chamber not only means shorter heating, cooling and growth periods, but also prevents contamination of the chamber. However, since most synthesis of HA-SWCNTs is performed in hot-wall reactors, adapting this well-established process to a cold-wall chamber becomes extremely crucial. Here, in order to transfer the CVD growth technology from a hot-wall to a cold-wall chamber, a systematic investigation has been conducted to determine the influence of process parameters on the HA-SWCNT's growth. For two reasons, the cold-wall CVD chamber was upgraded with a top heater to complement the bottom substrate heater; the first reason to maintain a more uniform temperature profile during HA-SWCNTs growth, and the second reason to preheat the precursor gas flow before projecting it onto the catalyst. Our results show that the addition of a top heater had a significant effect on the synthesis. Characterization of the CNTs shows that the average density of HA-SWCNTs is around 1 - 2 tubes/ μm with high growth quality as shown by Raman analysis. [Figure not available: see fulltext.

  4. Applicability of the Existing CVD Risk Assessment Tools to Type II Diabetics in Oman: A Review.

    PubMed

    Al-Rawahi, Abdulhakeem; Lee, Patricia

    2015-09-01

    Patients with type II diabetes (T2DM) have an elevated risk for cardiovascular disease (CVD), and it is considered to be a leading cause of morbidity and premature mortality in these patients. Many traditional risk factors such as age, male sex, hypertension, dyslipidemia, glycemic control, diabetes duration, renal dysfunction, obesity, and smoking have been studied and identified as independent factors for CVD. Quantifying the risk of CVD among diabetics using the common risk factors in order to plan the treatment and preventive measures is important in the management of these patients as recommended by many clinical guidelines. Therefore, several risk assessment tools have been developed in different parts of the world for this purpose. These include the tools that have been developed for general populations and considered T2DM as a risk factor, and the tools that have been developed for T2DM populations specifically. However, due to the differences in sociodemographic factors and lifestyle patterns, as well as the differences in the distribution of various CVD risk factors in different diabetic populations, the external applicability of these tools on different populations is questionable. This review aims to address the applicability of the existing CVD risk models to the Omani diabetic population.

  5. Methane as an effective hydrogen source for single-layer graphene synthesis on Cu foil by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Kim, Yong Seung; Lee, Jae Hong; Kim, Young Duck; Jerng, Sahng-Kyoon; Joo, Kisu; Kim, Eunho; Jung, Jongwan; Yoon, Euijoon; Park, Yun Daniel; Seo, Sunae; Chun, Seung-Hyun

    2013-01-01

    A single-layer graphene is synthesized on Cu foil in the absence of H2 flow by plasma enhanced chemical vapor deposition (PECVD). In lieu of an explicit H2 flow, hydrogen species are produced during the methane decomposition process into their active species (CHx<4), assisted with the plasma. Notably, the early stage of growth depends strongly on the plasma power. The resulting grain size (the nucleation density) has a maximum (minimum) at 50 W and saturates when the plasma power is higher than 120 W because hydrogen partial pressures are effectively tuned by a simple control of the plasma power. Raman spectroscopy and transport measurements show that decomposed methane alone can provide a sufficient amount of hydrogen species for high-quality graphene synthesis by PECVD.A single-layer graphene is synthesized on Cu foil in the absence of H2 flow by plasma enhanced chemical vapor deposition (PECVD). In lieu of an explicit H2 flow, hydrogen species are produced during the methane decomposition process into their active species (CHx<4), assisted with the plasma. Notably, the early stage of growth depends strongly on the plasma power. The resulting grain size (the nucleation density) has a maximum (minimum) at 50 W and saturates when the plasma power is higher than 120 W because hydrogen partial pressures are effectively tuned by a simple control of the plasma power. Raman spectroscopy and transport measurements show that decomposed methane alone can provide a sufficient amount of hydrogen species for high-quality graphene synthesis by PECVD. Electronic supplementary information (ESI) available: Schematic diagram of the ICP-CVD system, substrate heating by plasma, differential-pumping technique for mass spectra measurement, and transport properties of a single-domain graphene device. See DOI. 10.1039/c2nr33034b

  6. Gaseous product mixture from Fischer-Tropsch synthesis as an efficient carbon feedstock for low temperature CVD growth of carbon nanotube carpets

    NASA Astrophysics Data System (ADS)

    Almkhelfe, Haider; Carpena-Núñez, Jennifer; Back, Tyson C.; Amama, Placidus B.

    2016-07-01

    Low-temperature chemical vapor deposition (CVD) growth of carbon nanotube (CNT) carpets from Fe and Fe-Cu catalysts using a gaseous product mixture from Fischer-Tropsch synthesis (FTS-GP) as a superior carbon feedstock is demonstrated. This growth approach addresses a persistent issue of obtaining thick CNT carpets on temperature-sensitive substrates at low temperatures using a non-plasma CVD approach without catalyst pretreatment and/or preheating of the carbon feedstock. The efficiency of the process is evidenced by the highly dense, vertically aligned CNT structures from both Fe and Fe-Cu catalysts even at temperatures as low as 400 °C - a record low growth temperature for CNT carpets obtained via conventional thermal CVD. The grown CNTs exhibit a straight morphology with hollow interior and parallel graphitic planes along the tube walls. The apparent activation energies for CNT carpet growth on Fe and Fe-Cu catalysts are 0.71 and 0.54 eV, respectively. The synergistic effect of Fe and Cu show a strong dependence on the growth temperature, with Cu being more influential at temperatures higher than 450 °C. The low activation energies and long catalyst lifetimes observed are rationalized based on the unique composition of FTS-GP and Gibbs free energies for the decomposition reactions of the hydrocarbon components. The use of FTS-GP facilitates low-temperature growth of CNT carpets on traditional (alumina film) and nontraditional substrates (aluminum foil) and has the potential of enhancing CNT quality, catalyst lifetime, and scalability.Low-temperature chemical vapor deposition (CVD) growth of carbon nanotube (CNT) carpets from Fe and Fe-Cu catalysts using a gaseous product mixture from Fischer-Tropsch synthesis (FTS-GP) as a superior carbon feedstock is demonstrated. This growth approach addresses a persistent issue of obtaining thick CNT carpets on temperature-sensitive substrates at low temperatures using a non-plasma CVD approach without catalyst

  7. Onset conditions for gas phase reaction and nucleation in the CVD of transition metal oxides

    NASA Technical Reports Server (NTRS)

    Collins, J.; Rosner, D. E.; Castillo, J.

    1992-01-01

    A combined experimental/theoretical study is presented of the onset conditions for gas phase reaction and particle nucleation in hot substrate/cold gas CVD of transition metal oxides. Homogeneous reaction onset conditions are predicted using a simple high activation energy reacting gas film theory. Experimental tests of the basic theory are underway using an axisymmetric impinging jet CVD reactor. No vapor phase ignition has yet been observed in the TiCl4/O2 system under accessible operating conditions (below substrate temperature Tw = 1700 K). The goal of this research is to provide CVD reactor design and operation guidelines for achieving acceptable deposit microstructures at the maximum deposition rate while simultaneously avoiding homogeneous reaction/nucleation and diffusional limitations.

  8. Cold Vacuum Dryer (CVD) Facility Fire Protection System Design Description (SYS 24)

    SciTech Connect

    SINGH, G.

    2000-10-17

    This system design description (SDD) addresses the Cold Vacuum Drying (CVD) Facility fire protection system (FPS). The primary features of the FPS for the CVD are a fire alarm and detection system, automatic sprinklers, and fire hydrants. The FPS also includes fire extinguishers located throughout the facility and fire hydrants to assist in manual firefighting efforts. In addition, a fire barrier separates the operations support (administrative) area from the process bays and process bay support areas. Administrative controls to limit combustible materials have been established and are a part of the overall fire protection program. The FPS is augmented by assistance from the Hanford Fire Department (HED) and by interface systems including service water, electrical power, drains, instrumentation and controls. This SDD, when used in conjunction with the other elements of the definitive design package, provides a complete picture of the FPS for the CVD Facility.

  9. Polymer Adsorption on Graphite and CVD Graphene Surfaces Studied by Surface-Specific Vibrational Spectroscopy.

    PubMed

    Su, Yudan; Han, Hui-Ling; Cai, Qun; Wu, Qiong; Xie, Mingxiu; Chen, Daoyong; Geng, Baisong; Zhang, Yuanbo; Wang, Feng; Shen, Y R; Tian, Chuanshan

    2015-10-14

    Sum-frequency vibrational spectroscopy was employed to probe polymer contaminants on chemical vapor deposition (CVD) graphene and to study alkane and polyethylene (PE) adsorption on graphite. In comparing the spectra from the two surfaces, it was found that the contaminants on CVD graphene must be long-chain alkane or PE-like molecules. PE adsorption from solution on the honeycomb surface results in a self-assembled ordered monolayer with the C-C skeleton plane perpendicular to the surface and an adsorption free energy of ∼42 kJ/mol for PE(H(CH2CH2)nH) with n ≈ 60. Such large adsorption energy is responsible for the easy contamination of CVD graphene by impurity in the polymer during standard transfer processes. Contamination can be minimized with the use of purified polymers free of PE-like impurities.

  10. A direct comparison of CVD-grown and exfoliated MoS2 using optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Plechinger, G.; Mann, J.; Preciado, E.; Barroso, D.; Nguyen, A.; Eroms, J.; Schüller, C.; Bartels, L.; Korn, T.

    2014-06-01

    MoS2 is a highly interesting material, which exhibits a crossover from an indirect band gap in the bulk crystal to a direct gap for single layers. Here, we perform a direct comparison between large-area MoS2 films grown by chemical vapor deposition (CVD) and MoS2 flakes prepared by mechanical exfoliation from mineral bulk crystal. Raman spectroscopy measurements show differences between the in-plane and out-of-plane phonon mode positions in CVD-grown and exfoliated MoS2. Photoluminescence (PL) mapping reveals large regions in the CVD-grown films that emit strong PL at room-temperature, and low-temperature PL scans demonstrate a large spectral shift of the A exciton emission as a function of position. Polarization-resolved PL measurements under near-resonant excitation conditions show a strong circular polarization of the PL, corresponding to a valley polarization.

  11. iCVD Cyclic Polysiloxane and Polysilazane as Nanoscale Thin-Film Electrolyte: Synthesis and Properties.

    PubMed

    Chen, Nan; Reeja-Jayan, B; Liu, Andong; Lau, Jonathan; Dunn, Bruce; Gleason, Karen K

    2016-03-01

    A group of crosslinked cyclic siloxane (Si-O) and silazane (Si-N) polymers are synthesized via solvent-free initiated chemical vapor deposition (iCVD). Notably, this is the first report of cyclic polysilazanes synthesized via the gas-phase iCVD method. The deposited nanoscale thin films are thermally stable and chemically inert. By iCVD, they can uniformly and conformally cover nonplanar surfaces having complex geometry. Although polysiloxanes are traditionally utilized as dielectric materials and insulators, our research shows these cyclic organosilicon polymers can conduct lithium ions (Li(+) ) at room temperature. The conformal coating and the room temperature ionic conductivity make these cyclic organosilicon polymers attractive for use as thin-film electrolytes in solid-state batteries. Also, their synthesis process and properties have been systemically studied and discussed. PMID:26785633

  12. Effect of current stress during thermal CVD of multilayer graphene on cobalt catalytic layer

    NASA Astrophysics Data System (ADS)

    Ueno, Kazuyoshi; Ichikawa, Hiroyasu; Uchida, Takaki

    2016-04-01

    To improve the crystallinity of multilayer graphene (MLG) by CVD at a low temperature, the effect of current stress during thermal CVD on a cobalt (Co) catalytic layer was investigated. The crystallinity of MLG obtained by CVD with current was higher than that without current at the same temperature. This indicates that current has effects besides the Joule heating effect. The current effects on the Co catalytic layer and the MLG growth reaction were investigated, and it was found that current had small effects on the grain size and crystal structure of the Co catalyst and large effects on the MLG growth reaction such as large grain growth and a low activation energy of 0.49 eV, which is close to the value reported for carbon surface diffusion on Co. It is considered that the enhancement of MLG growth reaction by current leads to the improved crystallinity of MLG at a relatively low temperature.

  13. Metal infiltration into biomaterials by ALD and CVD: a comparative study.

    PubMed

    Lee, Seung-Mo; Pippel, Eckhard; Knez, Mato

    2011-03-14

    Atomic layer deposition (ALD) is a subset of chemical vapor deposition (CVD) and both use very similar chemistry. Recently, it has been reported that ALD has the potential to realize a new design paradigm of bioinorganic materials through metal infiltration, which in nature has been employed as a hardening strategy for many tissues in diverse biological organisms. Herein, using a spider dragline silk and a collagen membrane as targets, we have performed a comparative study to elucidate the difference of the metal infiltration effect by ALD and CVD. From the comparison of mechanical properties, concentration of the infiltrated metal, and structural changes induced by the infiltrated metal, it has been proven that the metal can effectively infiltrate biomaterials by ALD and the infiltrated metal leads to highly improved mechanical properties accompanied by substantial changes in the protein structures, whereas CVD is less effective.

  14. iCVD Cyclic Polysiloxane and Polysilazane as Nanoscale Thin-Film Electrolyte: Synthesis and Properties.

    PubMed

    Chen, Nan; Reeja-Jayan, B; Liu, Andong; Lau, Jonathan; Dunn, Bruce; Gleason, Karen K

    2016-03-01

    A group of crosslinked cyclic siloxane (Si-O) and silazane (Si-N) polymers are synthesized via solvent-free initiated chemical vapor deposition (iCVD). Notably, this is the first report of cyclic polysilazanes synthesized via the gas-phase iCVD method. The deposited nanoscale thin films are thermally stable and chemically inert. By iCVD, they can uniformly and conformally cover nonplanar surfaces having complex geometry. Although polysiloxanes are traditionally utilized as dielectric materials and insulators, our research shows these cyclic organosilicon polymers can conduct lithium ions (Li(+) ) at room temperature. The conformal coating and the room temperature ionic conductivity make these cyclic organosilicon polymers attractive for use as thin-film electrolytes in solid-state batteries. Also, their synthesis process and properties have been systemically studied and discussed.

  15. Microbiota and the nitrogen cycle: Implications in the development and progression of CVD and CKD.

    PubMed

    Briskey, David; Tucker, Patrick S; Johnson, David W; Coombes, Jeff S

    2016-07-01

    Chronic kidney disease (CKD) is associated with an increased risk of death from cardiovascular disease (CVD). One factor involved in CVD development is nitric oxide (NO), which acts as a powerful vasodilator. NO is produced via the nitrogen cycle, through the reduction of nitrate to nitrite with the process mainly occurring in the mouth by commensal microbiota. People with CKD have compromised microbiota (dysbiosis) with an increased abundance of potentially pathogenic and pro-inflammatory bacteria capable of producing uremic toxins that contribute to CKD development and reduce enzymatic NO production. However, to date, few studies have comprehensively documented the gut or saliva microbiota in the CKD population or investigated the role of NO in people with CKD. This review will discuss NO pathways that are linked to the progression of CKD and CVD and therapeutic options for targeting these pathways. PMID:27164294

  16. Gaseous product mixture from Fischer-Tropsch synthesis as an efficient carbon feedstock for low temperature CVD growth of carbon nanotube carpets.

    PubMed

    Almkhelfe, Haider; Carpena-Núñez, Jennifer; Back, Tyson C; Amama, Placidus B

    2016-07-21

    Low-temperature chemical vapor deposition (CVD) growth of carbon nanotube (CNT) carpets from Fe and Fe-Cu catalysts using a gaseous product mixture from Fischer-Tropsch synthesis (FTS-GP) as a superior carbon feedstock is demonstrated. This growth approach addresses a persistent issue of obtaining thick CNT carpets on temperature-sensitive substrates at low temperatures using a non-plasma CVD approach without catalyst pretreatment and/or preheating of the carbon feedstock. The efficiency of the process is evidenced by the highly dense, vertically aligned CNT structures from both Fe and Fe-Cu catalysts even at temperatures as low as 400 °C - a record low growth temperature for CNT carpets obtained via conventional thermal CVD. The grown CNTs exhibit a straight morphology with hollow interior and parallel graphitic planes along the tube walls. The apparent activation energies for CNT carpet growth on Fe and Fe-Cu catalysts are 0.71 and 0.54 eV, respectively. The synergistic effect of Fe and Cu show a strong dependence on the growth temperature, with Cu being more influential at temperatures higher than 450 °C. The low activation energies and long catalyst lifetimes observed are rationalized based on the unique composition of FTS-GP and Gibbs free energies for the decomposition reactions of the hydrocarbon components. The use of FTS-GP facilitates low-temperature growth of CNT carpets on traditional (alumina film) and nontraditional substrates (aluminum foil) and has the potential of enhancing CNT quality, catalyst lifetime, and scalability.

  17. Comprehensive process maps for synthesizing high density aluminum oxide-carbon nanotube coatings by plasma spraying for improved mechanical and wear properties

    NASA Astrophysics Data System (ADS)

    Keshri, Anup Kumar

    Plasma sprayed aluminum oxide ceramic coating is widely used due to its outstanding wear, corrosion, and thermal shock resistance. But porosity is the integral feature in the plasma sprayed coating which exponentially degrades its properties. In this study, process maps were developed to obtain Al2O3-CNT composite coatings with the highest density (i.e. lowest porosity) and improved mechanical and wear properties. Process map is defined as a set of relationships that correlates large number of plasma processing parameters to the coating properties. Carbon nanotubes (CNTs) were added as reinforcement to Al2O 3 coating to improve the fracture toughness and wear resistance. Two novel powder processing approaches viz spray drying and chemical vapor growth were adopted to disperse CNTs in Al2O3 powder. The degree of CNT dispersion via chemical vapor deposition (CVD) was superior to spray drying but CVD could not synthesize powder in large amount. Hence optimization of plasma processing parameters and process map development was limited to spray dried Al2O3 powder containing 0, 4 and 8 wt. % CNTs. An empirical model using Pareto diagram was developed to link plasma processing parameters with the porosity of coating. Splat morphology as a function of plasma processing parameter was also studied to understand its effect on mechanical properties. Addition of a mere 1.5 wt. % CNTs via CVD technique showed ˜27% and ˜24% increase in the elastic modulus and fracture toughness respectively. Improved toughness was attributed to combined effect of lower porosity and uniform dispersion of CNTs which promoted the toughening by CNT bridging, crack deflection and strong CNT/Al2O3 interface. Al2O 3-8 wt. % CNT coating synthesized using spray dried powder showed 73% improvement in the fracture toughness when porosity reduced from 4.7% to 3.0%. Wear resistance of all coatings at room and elevated temperatures (573 K, 873 K) showed improvement with CNT addition and decreased porosity

  18. Dietary flavonoid intakes and CVD incidence in the Framingham Offspring Cohort.

    PubMed

    Jacques, Paul F; Cassidy, Aedin; Rogers, Gail; Peterson, Julia J; Dwyer, Johanna T

    2015-11-14

    This study examines the relationship between long-term intake of six flavonoid classes and incidence of CVD and CHD, using a comprehensive flavonoid database and repeated measures of intake, while accounting for possible confounding by components of a healthy dietary pattern. Flavonoid intakes were assessed using a FFQ among the Framingham Offspring Cohort at baseline and three times during follow-up. Cox proportional hazards regression was used to characterise prospective associations between the natural logarithms of flavonoid intakes and CVD incidence using a time-dependent approach, in which intake data were updated at each examination to represent average intakes from previous examinations. Mean baseline age was 54 years, and 45 % of the population was male. Over an average 14·9 years of follow-up among 2880 participants, there were 518 CVD events and 261 CHD events. After multivariable adjustment, only flavonol intake was significantly associated with lower risk of CVD incidence (hazard ratios (HR) per 2·5-fold flavonol increase=0·86, P trend=0·05). Additional adjustment for total fruit and vegetable intake and overall diet quality attenuated this observation (HR=0·89, P trend=0·20 and HR=0·92, P trend=0·33, respectively). There were no significant associations between flavonoids and CHD incidence after multivariable adjustment. Our findings suggest that the observed association between flavonol intake and CVD risk may be a consequence of better overall diet. However, the strength of this non-significant association was also consistent with relative risks observed in previous meta-analyses, and therefore a modest benefit of flavonol intake on CVD risk cannot be ruled out.

  19. Concentration profiling of minerals in iliac crest bone tissue of opium addicted humans using inductively coupled plasma and discriminant analysis techniques.

    PubMed

    Mani-Varnosfaderani, Ahmad; Jamshidi, Mahbobeh; Yeganeh, Ali; Mahmoudi, Mani

    2016-02-20

    Opium addiction is one of the main health problems in developing countries and induces serious defects on the human body. In this work, the concentrations of 32 minerals including alkaline, heavy and toxic metals have been determined in the iliac crest bone tissue of 22 opium addicted individuals using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The bone tissues of 30 humans with no physiological and metabolomic diseases were used as the control group. For subsequent analyses, the linear and quadratic discriminant analysis techniques have been used for classification of the data into "addicted" and "non-addicted" groups. Moreover, the counter-propagation artificial neural network (CPANN) has been used for clustering of the data. The results revealed that the CPANN is a robust model and thoroughly classifies the data. The area under the curve for the receiver operating characteristic curve for this model was more than 0.91. Investigation of the results revealed that the opium consumption causes a deficiency in the level of Calcium, Phosphate, Potassium and Sodium in iliac crest bone tissue. Moreover, this type of addiction induces an increment in the level of toxic and heavy metals such as Co, Cr, Mo and Ni in iliac crest tissue. The correlation analysis revealed that there were no significant dependencies between the age of the samples and the mineral content of their iliac crest, in this study. The results of this work suggest that the opium addicted individuals need thorough and restricted dietary and medical care programs after recovery phases, in order to have healthy bones.

  20. Direct analysis of ultra-trace semiconductor gas by inductively coupled plasma mass spectrometry coupled with gas to particle conversion-gas exchange technique.

    PubMed

    Ohata, Masaki; Sakurai, Hiromu; Nishiguchi, Kohei; Utani, Keisuke; Günther, Detlef

    2015-09-01

    An inductively coupled plasma mass spectrometry (ICPMS) coupled with gas to particle conversion-gas exchange technique was applied to the direct analysis of ultra-trace semiconductor gas in ambient air. The ultra-trace semiconductor gases such as arsine (AsH3) and phosphine (PH3) were converted to particles by reaction with ozone (O3) and ammonia (NH3) gases within a gas to particle conversion device (GPD). The converted particles were directly introduced and measured by ICPMS through a gas exchange device (GED), which could penetrate the particles as well as exchange to Ar from either non-reacted gases such as an air or remaining gases of O3 and NH3. The particle size distribution of converted particles was measured by scanning mobility particle sizer (SMPS) and the results supported the elucidation of particle agglomeration between the particle converted from semiconductor gas and the particle of ammonium nitrate (NH4NO3) which was produced as major particle in GPD. Stable time-resolved signals from AsH3 and PH3 in air were obtained by GPD-GED-ICPMS with continuous gas introduction; however, the slightly larger fluctuation, which could be due to the ionization fluctuation of particles in ICP, was observed compared to that of metal carbonyl gas in Ar introduced directly into ICPMS. The linear regression lines were obtained and the limits of detection (LODs) of 1.5 pL L(-1) and 2.4 nL L(-1) for AsH3 and PH3, respectively, were estimated. Since these LODs revealed sufficiently lower values than the measurement concentrations required from semiconductor industry such as 0.5 nL L(-1) and 30 nL L(-1) for AsH3 and PH3, respectively, the GPD-GED-ICPMS could be useful for direct and high sensitive analysis of ultra-trace semiconductor gas in air.

  1. Concentration profiling of minerals in iliac crest bone tissue of opium addicted humans using inductively coupled plasma and discriminant analysis techniques.

    PubMed

    Mani-Varnosfaderani, Ahmad; Jamshidi, Mahbobeh; Yeganeh, Ali; Mahmoudi, Mani

    2016-02-20

    Opium addiction is one of the main health problems in developing countries and induces serious defects on the human body. In this work, the concentrations of 32 minerals including alkaline, heavy and toxic metals have been determined in the iliac crest bone tissue of 22 opium addicted individuals using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The bone tissues of 30 humans with no physiological and metabolomic diseases were used as the control group. For subsequent analyses, the linear and quadratic discriminant analysis techniques have been used for classification of the data into "addicted" and "non-addicted" groups. Moreover, the counter-propagation artificial neural network (CPANN) has been used for clustering of the data. The results revealed that the CPANN is a robust model and thoroughly classifies the data. The area under the curve for the receiver operating characteristic curve for this model was more than 0.91. Investigation of the results revealed that the opium consumption causes a deficiency in the level of Calcium, Phosphate, Potassium and Sodium in iliac crest bone tissue. Moreover, this type of addiction induces an increment in the level of toxic and heavy metals such as Co, Cr, Mo and Ni in iliac crest tissue. The correlation analysis revealed that there were no significant dependencies between the age of the samples and the mineral content of their iliac crest, in this study. The results of this work suggest that the opium addicted individuals need thorough and restricted dietary and medical care programs after recovery phases, in order to have healthy bones. PMID:26717018

  2. AB006. Erectile dysfunction (ED) as a marker for cardiovascular diseases (CVD)

    PubMed Central

    Torres, Luiz Otavio

    2015-01-01

    In 1973 V. Michal, a vascular surgeon said “Erectile dysfunction (ED) is related to diseases of the vascular bed”. And this makes sense since ED and cardiovascular diseases (CVD) share many risk factors like aging, obesity, inactivity, smoking, depression, dyslipidemia, hypertension, diabetes/insuline resistance. These conditions may lead to an oxidative stress which ultimately can promote vasoconstriction, thrombosis, atherosclerosis and finally ED and CVD. One of the most accepted Idea is that small vessels plug earlier, it means, small arteries when have for example 50% of obstruction will probably have a clinical manifestation before bigger arteries!

  3. A numerical and experimental analysis of reactor performance and deposition rates for CVD on monofilaments

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Kuczmarski, M.; Veitch, L.; Tsui, P.; Chait, A.

    1990-01-01

    The computational fluid dynamics (CFD) code FLUENT is adopted to simulate a cylindrical upflow reactor designed for chemical vapor deposition (CVD) on monofilaments. Equilibrium temperature profiles along the fiber and quartz reactor wall are experimentally measured and used as boundary conditions in numerical simulations. Two-dimensional axisymmetric flow and temperature fields are calculated for hydrogen and argon; the effect of free convection is assessed. The gas and surface chemistry is included for predicting silicon deposition from silane. The model predictions are compared with experimentally measured silicon CVD rates. Inferences are made for optimum conditions to obtain uniformity.

  4. Direct growth of macroscopic fibers composed of large diameter SWNTs by CVD

    NASA Astrophysics Data System (ADS)

    Yang, Q. H.; Bai, S.; Fournier, T.; Li, F.; Wang, G.; Cheng, H. M.; Bai, J. B.

    2003-03-01

    Macroscopic nanotube fibers, composed of aligned large diameter single-walled carbon nanotubes (SWNTs), were prepared by a simple CVD method. These fibers, which constitute the nanotube ropes of loose structure like hemp cords, can be divided into the nanotube threads (mesoscopically) and subdivided into nanotube bundles (microscopically). The samples show good alignment at different scales. The fibers, several micrometers in diameter, have a relatively stable structure and only dissociated partially under ultrasonic dispersion. The obtained SWNTs have good crystalline structure and good purity. The influence of the CVD conditions on the fiber morphology was also investigated.

  5. [A case of malignant pheochromocytoma treated with 131I-metaiodobenzylguanidine and CVD regimen].

    PubMed

    Ukimura, O; Kojima, M; Hosoi, S; Itoh, H; Watanabe, H; Minamikawa, T

    1994-05-01

    A 44-year-old male had multiple metastasis to the lung, liver, kidney and paraaortic lymph node from primary adrenal malignant pheochromocytoma. Radiation therapy with 131I-metaiodobenzylguanidine (131I-MIBG), was first performed, which was followed by chemotherapy with cyclophosphamide, vincristine and dacarbazine (CVD). A total amount of 4810 MBq of 131I-MIBG was administered then 7 cycles of CVD regimen were added. He was survived for sixteen months with tumor response in primary tumor, paraaortic lymph node and liver metastasis tumors, in addition to hormonal response. It was considered that the survival was prolonged in spite of advanced case with inoperative primary tumor.

  6. Temperature threshold and water role in CVD growth of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Geng, Junfeng; Motta, Marcelo; Angels, Volker; Luo, Jikui; Johnson, Brian

    2016-02-01

    An in-depth understanding of the growth process of single walled carbon nanotubes is of vital importance to the control of the yield of the material and its carbon structure. Using a nickel/silica (Ni/SiOx) catalyst we have conducted a series of growth experiments with a chemical vapour deposition (CVD) system. We find that there is a temperature threshold in the CVD process, and if the reaction temperature sets above this threshold there will be no growth of the nanotubes. In association with this temperature effect, water plays an important role in the promotion or termination of the growth of single walled carbon nanotubes.

  7. The Effect of Annealing at 1500 C on Migration and Release of Ion Implanted Silver in CVD Silicon Carbide

    SciTech Connect

    HJ MacLean; RG Ballinger; LE Kolaya; SA Simonson; N Lewis; M Hanson

    2004-10-07

    The transport of silver in CVD {beta}-SiC has been studied using ion implantation. Silver ions were implanted in {beta}-SiC using the ATLAS accelerator facility at the Argonne National Laboratory. Ion beams with energies of 93 and 161 MeV were used to achieve deposition with peak concentrations at depths of approximately 9 and 13 {micro}m, respectively. As-implanted samples were then annealed at 1500 C for 210 or 480 hours. XPS, SEM, TEM, STEM, and optical methods were used to analyze the material before and after annealing. Silver concentration profiles were determined using XPS before and after annealing. STEM and SEM equipped with quantitative chemical analysis capability were used to more fully characterize the location and morphology of the silver before and after annealing. The results show that, within the uncertainty of measurement techniques, there is no silver migration, via either inter- or intragrannular paths, for the times and temperature studied. Additionally, the silver was observed to phase separate within the SiC after annealing. The irradiation damage from the implantation process resulted in a three-layer morphology in the as-implanted condition: (1) a layer of unaltered SiC, followed by (2) a layer of crystallized SiC, followed by (3) an amorphized layer which contained essentially all of the implanted silver. After annealing the layer structure changed. Layer 1 was unaltered. The grains in layer 2 recrystallized to form an epitaxial (columnar) layer. Layer 3 recrystallized to form a fine grain equiaxed layer. The results of this work do not support the long held assumption that silver release from CVD SiC, used for gas-reactor coated particle fuel, is dominated by grain boundary diffusion.

  8. Carbon Nanotubes/Nanofibers by Plasma Enhanced Chemical Vapour Deposition

    NASA Technical Reports Server (NTRS)

    Teo, K. B. K.; Hash, D. B.; Bell, M. S.; Chhowalla, M.; Cruden, B. A.; Amaratunga, G. A. J.; Meyyappan, M.; Milne, W. I.

    2005-01-01

    Plasma enhanced chemical vapour deposition (PECVD) has been recently used for the production of vertically aligned carbon nanotubedfibers (CN) directly on substrates. These structures are potentially important technologically as electron field emitters (e.g. microguns, microwave amplifiers, displays), nanoelectrodes for sensors, filter media, superhydrophobic surfaces and thermal interface materials for microelectronics. A parametric study on the growth of CN grown by glow discharge dc-PECVD is presented. In this technique, a substrate containing thin film Ni catalyst is exposed to C2H2 and NH3 gases at 700 C. Without plasma, this process is essentially thermal CVD which produces curly spaghetti-like CN as seen in Fig. 1 (a). With the plasma generated by biasing the substrate at -6OOV, we observed that the CN align vertically during growth as shown in Fig. l(b), and that the magnitude of the applied substrate bias affects the degree of alignment. The thickness of the thin film Ni catalyst was found to determine the average diameter and inversely the length of the CN. The yield and density of the CN were controlled by the use of different diffusion barrier materials under the Ni catalyst. Patterned CN growth [Fig. l(c)], with la variation in CN diameter of 4.1% and 6.3% respectively, is achieved by lithographically defining the Ni thin film prior to growth. The shape of the structures could be varied from very straight nanotube-like to conical tip-like nanofibers by increasing the ratio of C2H2 in the gas flow. Due to the plasma decomposition of C2H2, amorphous carbon (a-C) is an undesirable byproduct which could coat the substrate during CN growth. Using a combination of depth profiled Auger electron spectroscopy to study the substrate and in-situ mass spectroscopy to examine gas phase neutrals and ions, the optimal conditions for a-C free growth of CN is determined.

  9. Synthesis and characterization of Al{sub 2}O{sub 3} and SiO{sub 2} films with fluoropolymer content using rf-plasma magnetron sputtering technique

    SciTech Connect

    Islam, Mohammad; Inal, Osman T.

    2008-03-15

    Pure and molecularly mixed inorganic films for protection against atomic oxygen in lower earth orbit were prepared using radio-frequency (rf) plasma magnetron sputtering technique. Alumina (Al{sub 2}O{sub 3}) and silica (SiO{sub 2}) films with average grain size in the range of 30-80 nm and fully dense or dense columnar structure were synthesized under different conditions of pressure and power. Simultaneous oxide sputtering and plasma polymerization (PP) of hexafluoropropylene (HFP) led to the formation of molecularly mixed films with fluoropolymer content. The degree of plasma polymerization was strongly influenced by total chamber pressure and the argon to HFP molar ratio (n{sub Ar}/n{sub M}). An order of magnitude increase in pressure due to argon during codeposition changed the plasma-polymerization mechanism from radical-chain- to radical-radical-type processes. Subsequently, a shift from linear CH{sub 2} group based chain polymerization to highly disordered fluoropolymer content with branching and cross-linking was observed. Fourier transform infrared spectroscopy studies revealed chemical interaction between depositing SiO{sub 2} and PP-HFP through appearance of absorption bands characteristic of Si-F stretching and expansion of SiO{sub 2} network. The relative amount and composition of plasma-polymerized fluoropolymer in such films can be controlled by changing argon to HFP flow ratio, total chamber pressure, and applied power. These films offer great potential for use as protective coatings in aerospace applications.

  10. Using X-Rays to Test CVD Diamond Detectors for Areal Density Measurement at the National Ignition Facility

    SciTech Connect

    Dauffy, L S; Koch, J A; Tommasini, R; Izumi, N

    2008-05-06

    At the National Ignition Facility (NIF), 192 laser beams will compress a target containing a mixture of deuterium and tritium (DT) that will release fusion neutrons, photons, and other radiation. Diagnostics are being designed to measure this emitted radiation to infer crucial parameters of an ignition shot. Chemical Vapor Deposited (CVD) diamond is one of the ignition diagnostics that will be used as a neutron time-of-flight detector for measuring primary (14.1 MeV) neutron yield, ion temperature, and plasma areal density. This last quantity is the subject of this study and is inferred from the number of downscattered neutrons arriving late in time, divided by the number of primary neutrons. We determine in this study the accuracy with which this detector can measure areal density, when the limiting factor is detector and electronics saturation. We used laser-produced x-rays to reproduce NIF signals in terms of charge carriers density, time between pulses, and amplitude contrast and found that the effect of the large pulse on the small pulse is at most 8.4%, which is less than the NIF accuracy requirement of {+-} 10%.

  11. Highly Crystalline CVD-grown Multilayer MoSe2 Thin Film Transistor for Fast Photodetector

    PubMed Central

    Jung, Chulseung; Kim, Seung Min; Moon, Hyunseong; Han, Gyuchull; Kwon, Junyeon; Hong, Young Ki; Omkaram, Inturu; Yoon, Youngki; Kim, Sunkook; Park, Jozeph

    2015-01-01

    Hexagonal molybdenum diselenide (MoSe2) multilayers were grown by chemical vapor deposition (CVD). A relatively high pressure (>760 Torr) was used during the CVD growth to achieve multilayers by creating multiple nuclei based on the two-dimensional crystal growth model. Our CVD-grown multilayer MoSe2 thin-film transistors (TFTs) show p-type-dominant ambipolar behaviors, which are attributed to the formation of Se vacancies generated at the decomposition temperature (650 °C) after the CVD growth for 10 min. Our MoSe2 TFT with a reasonably high field-effect mobility (10 cm2/V · s) exhibits a high photoresponsivity (93.7 A/W) and a fast photoresponse time (τrise ~ 0.4 s) under the illumination of light, which demonstrates the practical feasibility of multilayer MoSe2 TFTs for photodetector applications. PMID:26477744

  12. Evidence for CVD 103-HgR as an effective single-dose oral cholera vaccine.

    PubMed

    Jackson, Sarah S; Chen, Wilbur H

    2015-01-01

    We propose the ideal oral cholera vaccine (OCV) should be an inexpensive, single, oral dose that rapidly confers immunity for a long duration, and is well tolerated by individuals vulnerable to cholera. Vaccine trials in industrialized countries of a single oral dose of 5 × 10(8) colony forming units (CFU) of the live, attenuated cholera strain CVD 103-HgR have shown 88-97% serum vibriocidal antibody seroconversion rates, a correlate of protection and documented vaccine efficacy of ≥80% using volunteer challenge studies with wild-type cholera. For individuals of developing countries, a 5 × 10(9) CFU dose of CVD 103-HgR is necessary to elicit similar antibody responses. Presently, a reformulation of CVD 103-HgR is in late-stage clinical development for prospective US FDA licensure; making a cholera vaccine for US travelers potentially accessible in 2016. The availability of CVD 103-HgR should be a welcome addition to the currently available OCVs.

  13. Evidence for CVD 103-HgR as an effective single-dose oral cholera vaccine.

    PubMed

    Jackson, Sarah S; Chen, Wilbur H

    2015-01-01

    We propose the ideal oral cholera vaccine (OCV) should be an inexpensive, single, oral dose that rapidly confers immunity for a long duration, and is well tolerated by individuals vulnerable to cholera. Vaccine trials in industrialized countries of a single oral dose of 5 × 10(8) colony forming units (CFU) of the live, attenuated cholera strain CVD 103-HgR have shown 88-97% serum vibriocidal antibody seroconversion rates, a correlate of protection and documented vaccine efficacy of ≥80% using volunteer challenge studies with wild-type cholera. For individuals of developing countries, a 5 × 10(9) CFU dose of CVD 103-HgR is necessary to elicit similar antibody responses. Presently, a reformulation of CVD 103-HgR is in late-stage clinical development for prospective US FDA licensure; making a cholera vaccine for US travelers potentially accessible in 2016. The availability of CVD 103-HgR should be a welcome addition to the currently available OCVs. PMID:26228388

  14. CVD of SiC and AlN using cyclic organometallic precursors

    NASA Technical Reports Server (NTRS)

    Interrante, L. V.; Larkin, D. J.; Amato, C.

    1992-01-01

    The use of cyclic organometallic molecules as single-source MOCVD precursors is illustrated by means of examples taken from our recent work on AlN and SiC deposition, with particular focus on SiC. Molecules containing (AlN)3 and (SiC)2 rings as the 'core structure' were employed as the source materials for these studies. The organoaluminum amide, (Me2AlNH2)3, was used as the AlN source and has been studied in a molecular beam sampling apparatus in order to determine the gas phase species present in a hot-wall CVD reactor environment. In the case of SiC CVD, a series of disilacyclobutanes (Si(XX')CH2)2 (with X and X' = H, CH3, and CH2SiH2CH3), were examined in a cold-wall, hot-stage CVD reactor in order to compare their relative reactivities and prospective utility as single-source CVD precursors. The parent compound, disilacyclobutane, (SiH2CH2)2, was found to exhibit the lowest deposition temperature (ca. 670 C) and to yield the highest purity SiC films. This precursor gave a highly textured, polycrystalline film on the Si(100) substrates.

  15. Control of Reaction Surface in Low Temperature CVD to Enhance Nucleation and Conformal Coverage

    ERIC Educational Resources Information Center

    Kumar, Navneet

    2009-01-01

    The Holy Grail in CVD community is to find precursors that can afford the following: good nucleation on a desired substrate and conformal deposition in high AR features. Good nucleation is not only necessary for getting ultra-thin films at low thicknesses; it also offers films that are smooth at higher thickness values. On the other hand,…

  16. Towards a general growth model for graphene CVD on transition metal catalysts

    NASA Astrophysics Data System (ADS)

    Cabrero-Vilatela, Andrea; Weatherup, Robert S.; Braeuninger-Weimer, Philipp; Caneva, Sabina; Hofmann, Stephan

    2016-01-01

    The chemical vapour deposition (CVD) of graphene on three polycrystalline transition metal catalysts, Co, Ni and Cu, is systematically compared and a first-order growth model is proposed which can serve as a reference to optimize graphene growth on any elemental or alloy catalyst system. Simple thermodynamic considerations of carbon solubility are insufficient to capture even basic growth behaviour on these most commonly used catalyst materials, and it is shown that kinetic aspects such as carbon permeation have to be taken into account. Key CVD process parameters are discussed in this context and the results are anticipated to be highly useful for the design of future strategies for integrated graphene manufacture.The chemical vapour deposition (CVD) of graphene on three polycrystalline transition metal catalysts, Co, Ni and Cu, is systematically compared and a first-order growth model is proposed which can serve as a reference to optimize graphene growth on any elemental or alloy catalyst system. Simple thermodynamic considerations of carbon solubility are insufficient to capture even basic growth behaviour on these most commonly used catalyst materials, and it is shown that kinetic aspects such as carbon permeation have to be taken into account. Key CVD process parameters are discussed in this context and the results are anticipated to be highly useful for the design of future strategies for integrated graphene manufacture. Electronic supplementary information (ESI) available: Fig. S1. See DOI: 10.1039/c5nr06873h

  17. Advanced Synthesis of Spinnable MWCNT Forests by RF-Induction Heating Enhanced CVD Process

    NASA Astrophysics Data System (ADS)

    Zakhidov, Anvar; Holmes, William; UTD Solarno Team; Solarno UTD Team

    2015-03-01

    We demonstrate here an advanced method to effectively grow tall multi-wall carbon nanotubes (MWCNT) vertically oriented forests which are highly spinnable. Heating of the Fe catalyst is achieved extremely fast by RF induction heating using coils outside the quartz tube. This method and the new apparatus designed and presented in this paper allow separate control over the temperature of the substrate and the temperature of the incoming gases. In addition to temperature control, the fast T-ramping of the substrate preserves the catalyst nanoclusters from Ostwald ripening and other growth quenching effects such as carbon overgrowth of the catalyst. We show that the parametric sweet spot or bell curve of substrate spinnability can be increased significantly with this improved RF-CVD method. The catalyst nanoclusters also show a wide band of density arrangements that very positively effect spinnability and the drawing ratio. Drawing ratios can vary from 2 meters to 12 meters of sheets drawn from only 1cm of forest. RF-CVD method allows to grow fast (in several minuts) higher CNT forests at higher temperature of synthesis up to 800 K, and obtain dry-spinable CNTs, Characterization results of the samples created in the newRF-CVD system will be presented and compared to previous CNT sheet samples by conventional three-zone resistive heating CVD to measure the extent of property improvements of the CNT sheets and forests. Specifics of the experimental system will be addressed in detail and future property improvements and applications explored.

  18. Human Plasma Lipidome Is Pleiotropically Associated with Cardiovascular Risk Factors and Death

    PubMed Central

    Mamtani, Manju; Kent, Jack W.; Wong, Gerard; Weir, Jacquelyn M.; Barlow, Christopher K.; Diego, Vincent; Almeida, Marcio; Dyer, Thomas D.; Göring, Harald H.H.; Almasy, Laura; Mahaney, Michael C.; Comuzzie, Anthony G.; Williams-Blangero, Sarah; Meikle, Peter J.; Blangero, John; Curran, Joanne E.

    2014-01-01

    Background Cardiovascular disease (CVD) is the most common cause of death in the United States and is associated with a high economic burden. Prevention of CVD focuses on controlling or improving the lipid profile of patients at risk. The human lipidome is made up of thousands of ubiquitous lipid species. By studying biologically simple canonical lipid species, we investigated whether the lipidome is genetically redundant and whether its genetic influences can provide clinically relevant clues of CVD risk. Methods and Results We performed a genetic study of the human lipidome in 1,212 individuals from 42 extended Mexican American families. High-throughput mass spectrometry enabled rapid capture of precise lipidomic profiles, providing 319 unique species. Using variance-component based heritability analyses and bivariate trait analyses, we detected significant genetic influences on each lipid assayed. Median heritability of the plasma lipid species was 0.37. Hierarchical clustering based on complex genetic correlation patterns identified 12 genetic clusters that characterized the plasma lipidome. These genetic clusters were differentially but consistently associated with risk factors of CVD, including central obesity, obesity, type 2 diabetes, raised serum triglycerides and metabolic syndrome. Also these clusters consistently predicted occurrence of cardiovascular deaths during follow-up. Conclusions The human plasma lipidome is heritable. Shared genetic influences reduce the dimensionality of the human lipidome into clusters that are associated with risk factors of CVD. PMID:25363705

  19. Measurements of He metastable atom density profile in front of substrate in ECR plasma flow by laser-induced fluorescence technique.

    NASA Astrophysics Data System (ADS)

    Toyota, H.; Takiyama, K.; Oda, T.

    1998-10-01

    Metastable atoms of rare gases affect on the etching processes and the radical formation processes in a reactive plasma because of their high internal energy. Fundamental understanding is required of the creation and annihilation mechanisms of the metastable atoms in the plasma, especially in the boundary region between plasma and substrate. We have measured spatial profile of He metastable (2^1S) atom density in plasma flow from an ECR plasma source by polarized laser-induced fluorescence (LIF) spectroscopy [1]. It has been shown that the metastable atoms near the outlet of the plasma flow are created by collisional-radiative processes. However, the remarkable decrease near the substrate placed in the downstream has not been clearly understood. Observation of the polarized LIF due to forbidden excitation is made with high spatial resolution in the vicinity of the substrate to obtain the detailed density profile. Based on these results, possible annihilation mechanism of the metastable atoms will be briefly discussed. [1] H. Toyota et al.; Jpn. J. Appl. Phys. 36 (1997) 4670.

  20. Study of the effect of low-power pulse laser on arc plasma and magnesium alloy target in hybrid welding by spectral diagnosis technique

    NASA Astrophysics Data System (ADS)

    Liu, Liming; Hao, Xinfeng

    2008-10-01

    In order to study the effect of laser pulses on arc plasma and target metal in the hybrid welding process, the spectra of the plasmas in the welding process of magnesium alloys are analysed in this paper. The acquisition system of plasma spectra is set up and the spectral lines of welding plasma are acquired. Compared with tungsten-inert gas (TIG) welding, the intensities of the spectral lines of magnesium increase sharply while those of Ar decrease for strong evaporation and ionization of magnesium alloys in low-power laser/arc hybrid welding. The electron temperature and density are estimated by the Boltzmann plot method and the Stark broadening effect. The result shows that the electron temperature of arc plasma in the hybrid welding process is much lower than that in TIG welding, especially in the laser beam-affected zone. In contrast, the electron density of the plasma is enhanced. The influences of laser parameters on electron temperature are also studied. The changes in electron temperature and density indicate that the effect of laser pulse on the target metal is the dominant factor influencing the electron temperature and density in low-power laser/arc hybrid welding.