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Sample records for pulse radiolysis method

  1. One-electron oxidations of ferrocenes: A pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Faraggi, Moshe; Weinraub, Dany; Broitman, Federico; DeFelippis, Michael R.; Klapper, Michael H.

    Using the pulse radiolysis technique we have studied the oxidation by various inorganic radicals of four water soluble ferrocene derivatives, hydroxyethyl, dimethylaminomethyl, monocarboxylic acid and dicarboxylic acid. We report the second order rate constants for these reactions, the stabilities and spectral properties of the ferrocinium products, and the electrochemically determined ferrocinium/ferrocene redox potentials. We also present preliminary estimates of tyrosine and tryptophan radical redox potentials obtained with the dicarboxylic acid ferrocene derivative as reference, and we discuss the relationship between redox potential differences and the reactivities of the ferrocenes with the inorganic radicals.

  2. Development of nanosecond time-resolved infrared detection at the LEAF pulse radiolysis facility

    SciTech Connect

    Grills, David C. Farrington, Jaime A.; Layne, Bobby H.; Preses, Jack M.; Wishart, James F.; Bernstein, Herbert J.

    2015-04-15

    When coupled with transient absorption spectroscopy, pulse radiolysis, which utilizes high-energy electron pulses from an accelerator, is a powerful tool for investigating the kinetics and thermodynamics of a wide range of radiation-induced redox and electron transfer processes. The majority of these investigations detect transient species in the UV, visible, or near-IR spectral regions. Unfortunately, the often-broad and featureless absorption bands in these regions can make the definitive identification of intermediates difficult. Time-resolved vibrational spectroscopy would offer much improved structural characterization, but has received only limited application in pulse radiolysis. In this paper, we describe in detail the development of a unique nanosecond time-resolved infrared (TRIR) detection capability for condensed-phase pulse radiolysis on a new beam line at the LEAF facility of Brookhaven National Laboratory. The system makes use of a suite of high-power, continuous wave external-cavity quantum cascade lasers as the IR probe source, with coverage from 2330 to 1051 cm{sup −1}. The response time of the TRIR detection setup is ∼40 ns, with a typical sensitivity of ∼100 μOD after 4-8 signal averages using a dual-beam probe/reference normalization detection scheme. This new detection method has enabled mechanistic investigations of a range of radiation-induced chemical processes, some of which are highlighted here.

  3. Development of nanosecond time-resolved infrared detection at the LEAF pulse radiolysis facility

    SciTech Connect

    Grills, David C.; Farrington, Jaime A.; Layne, Bobby H.; Preses, Jack M.; Bernstein, Herbert J.; Wishart, James F.

    2015-04-27

    When coupled with transient absorption spectroscopy, pulse radiolysis, which utilizes high-energy electron pulses from an accelerator, is a powerful tool for investigating the kinetics and thermodynamics of a wide range of radiation-induced redox and electron transfer processes. The majority of these investigations detect transient species in the UV, visible, or near-IR spectral regions. Unfortunately, the often-broad and featureless absorption bands in these regions can make the definitive identification of intermediates difficult. Time-resolved vibrational spectroscopy would offer much improved structural characterization, but has received only limited application in pulse radiolysis. In this paper, we describe in detail the development of a unique nanosecond time-resolved infrared (TRIR) detection capability for condensed-phase pulse radiolysis on a new beam line at the LEAF facility of Brookhaven National Laboratory. The system makes use of a suite of high-power, continuous wave external-cavity quantum cascade lasers as the IR probe source, with coverage from 2330-1051 cm⁻¹. The response time of the TRIR detection setup is ~40 ns, with a typical sensitivity of ~100 µOD after 4-8 signal averages using a dual-beam probe/reference normalization detection scheme. As a result, this new detection method has enabled mechanistic investigations of a range of radiation-induced chemical processes, some of which are highlighted here.

  4. Development of nanosecond time-resolved infrared detection at the LEAF pulse radiolysis facility

    DOE PAGES

    Grills, David C.; Farrington, Jaime A.; Layne, Bobby H.; ...

    2015-04-27

    When coupled with transient absorption spectroscopy, pulse radiolysis, which utilizes high-energy electron pulses from an accelerator, is a powerful tool for investigating the kinetics and thermodynamics of a wide range of radiation-induced redox and electron transfer processes. The majority of these investigations detect transient species in the UV, visible, or near-IR spectral regions. Unfortunately, the often-broad and featureless absorption bands in these regions can make the definitive identification of intermediates difficult. Time-resolved vibrational spectroscopy would offer much improved structural characterization, but has received only limited application in pulse radiolysis. In this paper, we describe in detail the development of amore » unique nanosecond time-resolved infrared (TRIR) detection capability for condensed-phase pulse radiolysis on a new beam line at the LEAF facility of Brookhaven National Laboratory. The system makes use of a suite of high-power, continuous wave external-cavity quantum cascade lasers as the IR probe source, with coverage from 2330-1051 cm⁻¹. The response time of the TRIR detection setup is ~40 ns, with a typical sensitivity of ~100 µOD after 4-8 signal averages using a dual-beam probe/reference normalization detection scheme. As a result, this new detection method has enabled mechanistic investigations of a range of radiation-induced chemical processes, some of which are highlighted here.« less

  5. Pulse radiolysis and spectrophotometric studies on the binding of organic cations with heparin

    NASA Astrophysics Data System (ADS)

    Jakubowska, Małgorzata; Adamus, Jan; Gębicki, Jerzy; Marcinek, Andrzej; Sikora, Adam

    2014-06-01

    Here we present the spectroscopic and pulse radiolysis studies of the interactions of heparin and some organic cations:methylene blue (MB), 1-methylnicotinamide (MNA+), and its dimer 1,3-bis(1-methylnicotinamide)propane (bis(MNA+)).

  6. Pulse radiolysis of catalase in solution—II. Reactions of primary products from water radiolysis with catalase

    NASA Astrophysics Data System (ADS)

    Gȩbicka, Lidia; Gȩbicki, Jerzy L.

    The mechanism of the reaction of catalase with e -aq, H and OH has been studied by pulse radiolysis at room temperature. Some evidences have been found that e -eq/H react with porphyrin ring of catalase to form π-radical without reduction of heme iron within investigated time span of 1 s after the pulse. OH radicals react mainly with the protein moiety of the enzyme but the formation and decay of compound I, an intermediate of the catalytic reaction of catalase can be observed as well.

  7. A pulse radiolysis study of the dynamics of ascorbic acid free radicals within a liposomal environment.

    PubMed

    Kobayashi, Kazuo; Seike, Yumiko; Saeki, Akinori; Kozawa, Takahiro; Takeuchi, Fusako; Tsubaki, Motonari

    2014-10-06

    The dynamics of free-radical species in a model cellular system are examined by measuring the formation and decay of ascorbate radicals within a liposome with pulse radiolysis techniques. Upon pulse radiolysis of an N2O-saturated aqueous solution containing ascorbate-loaded liposome vesicles, ascorbate radicals are formed by the reaction of OH(·) radicals with ascorbate in unilamellar vesicles exclusively, irrespective of the presence of vesicle lipids. The radicals are found to decay rapidly compared with the decay kinetics in an aqueous solution. The distinct radical reaction kinetics in the vesicles and in bulk solution are characterized, and the kinetic data are analyzed.

  8. Radiolytic reactions of nitro blue tetrazolium under oxidative and reductive conditions: a pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Kovacs, A.; Wojnarovits, L.; Baranyai, M.; Moussa, A.; Othman, I.; McLaughlin, W. L.

    1999-08-01

    The radiolytic reactions of the ditetrazolium salt nitro blue tetrazolium chloride (NBTCl 2) were studied by pulse radiolysis technique in aqueous solution under reducing and oxidising conditions with the aim of potential dosimetry application. Under reducing conditions the fast formation of the tetrazolinyl radical is observed that is followed by the appearance of monoformazan (MF +), i.e. one of the tetrazolium rings is reduced to formazan. The formation of the water-insoluble diformazan, i.e. the result of the second reduction step was not observed in pulse radiolysis. Formazan formation was not found under oxidative conditions.

  9. Radiation-induced pink nickel oligomeric clusters in water. Pulse radiolysis study.

    PubMed

    Hioul, Mohamed Larbi; Lin, Mingzhang; Belloni, Jacqueline; Keghouche, Nassira; Marignier, Jean-Louis

    2014-10-09

    γ-rays and pulse radiolysis of aqueous solutions of Ni(2+) ions in the presence of polyacrylate (PA(-)) and 2-propanol leads to the formation of metastable species absorbing at 540 nm that are ascribed to "pink" oligomeric clusters of a few nickel atoms only. The molar absorption coefficient is evaluated as ε540 nm = 3300 ± 300 L mol(-1) cm(-1) per Ni(0) atom. The successive steps from the reduction of Ni(2+) into Ni(+) ions to the formation of the pink clusters at 540 nm under conditions of complexation by PA(-) are investigated by pulse radiolysis. The yield of the formation of pink clusters increases markedly with the irradiation dose rate, demonstrating the occurrence of the disproportionation of the [Ni(+), PA(-)] complex after a single electron pulse. The reduction and nucleation mechanisms, including rate constants, in competition with the back oxidation by protons, particularly at low dose rate, are discussed.

  10. Hydroxyl radical-induced degradation of fenuron in pulse and gamma radiolysis: kinetics and product analysis.

    PubMed

    Kovács, Krisztina; Mile, Viktoria; Csay, Tamás; Takács, Erzsébet; Wojnárovits, László

    2014-11-01

    Radiolytic reactions of phenylureas were studied in detail with fenuron model compound in dilute aqueous solutions using pulse radiolysis for detection of the intermediates, gamma radiolysis with UV-Vis and HPLC-MS techniques for analysis of the final products. The kinetics of oxidation was followed by COD, TOC and toxicity measurements. During radiolysis of aerated solutions hydroxyl radical ((•)OH), eaq (-), H(•) and O2 (•-)/HO2 (•) reactive intermediates are produced, the degradation of solute takes place practically entirely through (•)OH reactions. Therefore, the product distribution is similar to the distributions reported in other advanced oxidation processes with (•)OH as main reactant. (•)OH mainly reacts with the aromatic ring, forming cyclohexadienyl radical as an intermediate. This radical in pulse radiolysis has a wide absorption band in the 310-390 nm wavelength range with a maximum at 350 nm. Cyclohexadienyl radical reacts with dissolved O2 with a rate coefficient of ∼ 4 × 10(8) mol(-1) dm(3) s(-1) forming peroxy radical. The latter may eliminate HO2 (•) giving phenols or undergoes fragmentation. The one-electron oxidant (•)OH on average induces more than two-electron oxidations. The toxicity first increases with absorbed dose, then decreases. This increase is partly due to phenols formed during the first degradation period.

  11. Pulse radiolysis studies of berkelium(III): preparation and identification of berkelium(II) in aqueous perchlorate media. [Pulsed Electrons

    SciTech Connect

    Sullivan, J.C.; Schmidt, K.H.; Morss, L.R.; Pippin, C.G.; Williams, C. )

    1988-02-24

    The first direct evidence for the formation of Bk(II) in aqueous solutions as a result of pulse radiolysis is reported herein. The barrier that the necessity of a high pH has presented for this reaction was circumvented by using bicarbonate to adjust the pH, by maintaining rigorously oxygen-free conditions, and by using ethanol to suppress radiolysis products. The absorption ascribed to Bk(II) occurs at 310nm, and the molar absorptivity at this wavelength is consistent with theoretical considerations advanced by Carnall and Crosswhite. 10 references, 2 figures.

  12. Pulsed electron beam water radiolysis for submicrosecond hydroxyl radical protein footprinting.

    PubMed

    Watson, Caroline; Janik, Ireneusz; Zhuang, Tiandi; Charvátová, Olga; Woods, Robert J; Sharp, Joshua S

    2009-04-01

    Hydroxyl radical footprinting is a valuable technique for studying protein structure, but care must be taken to ensure that the protein does not unfold during the labeling process due to oxidative damage. Footprinting methods based on submicrosecond laser photolysis of peroxide that complete the labeling process faster than the protein can unfold have been recently described; however, the mere presence of large amounts of hydrogen peroxide can also cause uncontrolled oxidation and minor conformational changes. We have developed a novel method for submicrosecond hydroxyl radical protein footprinting using a pulsed electron beam from a 2 MeV Van de Graaff electron accelerator to generate a high concentration of hydroxyl radicals by radiolysis of water. The amount of oxidation can be controlled by buffer composition, pulsewidth, dose, and dissolved nitrous oxide gas in the sample. Our results with ubiquitin and beta-lactoglobulin A demonstrate that one submicrosecond electron beam pulse produces extensive protein surface modifications. Highly reactive residues that are buried within the protein structure are not oxidized, indicating that the protein retains its folded structure during the labeling process. Time-resolved spectroscopy indicates that the major part of protein oxidation is complete in a time scale shorter than that of large scale protein motions.

  13. Pulsed Electron Beam Water Radiolysis for Sub-Microsecond Hydroxyl Radical Protein Footprinting

    PubMed Central

    Watson, Caroline; Janik, Ireneusz; Zhuang, Tiandi; Charvátová, Olga; Woods, Robert J.; Sharp, Joshua S.

    2009-01-01

    Hydroxyl radical footprinting is a valuable technique for studying protein structure, but care must be taken to ensure that the protein does not unfold during the labeling process due to oxidative damage. Footprinting methods based on sub-microsecond laser photolysis of peroxide that complete the labeling process faster than the protein can unfold have been recently described; however, the mere presence of large amounts of hydrogen peroxide can also cause uncontrolled oxidation and minor conformational changes. We have developed a novel method for sub-microsecond hydroxyl radical protein footprinting using a pulsed electron beam from a 2 MeV Van de Graaff electron accelerator to generate a high concentration of hydroxyl radicals by radiolysis of water. The amount of oxidation can be controlled by buffer composition, pulsewidth, dose, and dissolved nitrous oxide gas in the sample. Our results with ubiquitin and β-lactoglobulin A demonstrate that one sub-microsecond electron beam pulse produces extensive protein surface modifications. Highly reactive residues that are buried within the protein structure are not oxidized, indicating that the protein retains its folded structure during the labeling process. Time-resolved spectroscopy indicates that the major part of protein oxidation is complete in a timescale shorter than that of large scale protein motions. PMID:19265387

  14. Studies on the transient species formed in the pulse radiolysis of benzotriazole

    NASA Astrophysics Data System (ADS)

    Naik, D. B.; Moorthy, P. N.

    1995-09-01

    Rate constants for the reaction of benzotriazole (BTZ) with the primary species of water radiolysis (e.g. eaq-, OH, H and O -) have been determined at different pHs using the pulse radiolysis technique. Absorption spectra of the transient intermediates formed have been recorded in the region 220-650 nm. Semireduced radicals formed by eaq- reaction with benzotriazole are found to be strongly reducing in nature and they transfer electrons to various acceptors such as thionine, methylene blue, paraquat with diffusion controlled rate constants. Only SO 4- radicals were found to oxidize benzotriazole. Reactivity of BTZ towards eaq- and specific oxidants has been compared with that of indole. Evidence for characterization of both semireduced and semioxidized benzotriazole as three electron bonded species are given.

  15. Pulse radiolysis study of the reactions of catechins with nitrogen dioxide

    NASA Astrophysics Data System (ADS)

    Gebicki, Jerzy L.; Meisner, Piotr; Stawowska, Katarzyna; Gebicka, Lidia

    2012-12-01

    Nitrogen dioxide (•NO2), one of the oxidizing radicals formed in vivo is suspected to play a role in various pathophysiological processes. The reactions of •NO2 with dietary catechins, the group of flavonoids present in high amounts in green tea and red wine, have been investigated by pulse radiolysis method. The kinetics of the reaction of •NO2 with gallic acid have been also studied for comparison. The spectra of transient intermediates are presented. The rate constants of the reaction of •NO2 with catechin, epigallocatechin, epigallocatechin gallate and gallic acid determined by the competition method with 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) at pH 7.0 and room temperature have been found to be 0.9, 1.0, 2.3 and 0.5×108 M-1 s-1, respectively. The values for catechins are among the highest reported for the reactions of •NO2 with non-radical compounds.

  16. Reactivity of OH radicals with chlorobenzoic acids—A pulse radiolysis and steady-state radiolysis study

    NASA Astrophysics Data System (ADS)

    Zona, Robert; Solar, Sonja; Getoff, Nikola; Sehested, Knud; Holcman, Jerzy

    2010-05-01

    The reactions of OH radicals with 2-, 3-, 4-chlorobenzoic acids (ClBzA) and chlorobenzene (ClBz), k( rad OH+substrates)=(4.5-6.2)×10 9 dm 3 mol -1 s -1, have been studied by pulse radiolysis in N 2O saturated solutions. The absorption maxima of the OH-adducts were in the range of 320-340 nm. Their decay was according to a second-order reaction, 2 k=(1-9)×10 8 dm 3 mol -1 s -1. In the presence of N 2O/O 2 the formation of peroxyl radicals was detectable for 2-, 4-ClBzA and ClBz, k(OH-adduct+O 2)=(2-4)×10 7 dm 3 mol -1 s -1, while this reaction for 3-ClBzA was too slow to be registered. In the presence of N 2O the degradation rates induced by gamma radiation were very similar for all chlorobenzoic acids, yet the chloride formation was distinctly higher for 3-ClBzA. In the presence of oxygen the initial degradation of 2-and 4-ClBzA equaled the OH-radical concentration, whereas in case of 3-ClBzA only ˜60% of rad OH led to degradation. The order for the efficiency of dehalogenation was 4->2->3-ClBzA. Several primary radiolytic products could be detected by HPLC. To evaluate the toxicity of final products a bacterial bioluminescence test was carried out.

  17. Reaction between ortho-semiquinones and oxygen: pulse radiolysis, electron spin resonance, and oxygen uptake studies.

    PubMed

    Kalyanaraman, B; Korytowski, W; Pilas, B; Sarna, T; Land, E J; Truscott, T G

    1988-10-01

    The cytotoxicity to tumor cells or cardiotoxic side effects of certain para-quinone antitumor drugs have been attributed to the corresponding semiquinones and derived superoxide and hydroxyl radicals. It has also been suggested that ortho-semiquinones, including those that arise during melanogenesis, produced via either the one-electron oxidation of catechol(amine)s or the one-electron reduction of the corresponding quinones, react with molecular oxygen to give superoxide and hydrogen peroxide. Furthermore it has been shown that catechol(amine)s which form noncyclizable quinones are more cytotoxic toward melanogenic cells than those forming cyclizable quinones. In order to provide further kinetic information on the interaction of oxygen with ortho-semiquinones, using pulse radiolysis we directly measured the rates of reaction of various ortho-semiquinones with molecular oxygen. The semiquinones of the corresponding catechol(amine)s were also produced by the horseradish peroxidase/hydrogen peroxide system, and detected by electron spin resonance spectroscopy using the spin stabilization method. Oxygen consumption was monitored using a standard Clark oxygen electrode. Our data indicate that while ortho-semiquinones from catechol(amine)s and catechol estrogens do not react with molecular oxygen at a rate equal to or greater than k less than or equal to 10(5) M-1 s-1, semiquinones from hydroxy-substituted catechol(amine)s react with dioxygen with rates in the range k = 10(6)-10(7) M-1 s-1.

  18. Pulse Radiolysis Using Very-high-energy Ions for Optimizing Cancer Therapy.

    PubMed

    Getoff, Nikola

    2016-01-01

    Cancer therapy by means of high-energy ions is very efficient. As a consequence of the linear-energy-transfer effect only a negligible part of the produced free radicals can escape combination processes to form molecular products and to cause undesired side processes. Positrons (e⁺) and γ-rays, generated by the nuclear interaction of high-energy ions in the medium, serve in monitoring the radiation dose absorbed by the tumor. However, due to the dipole nature of water molecules a small proportion of thermalized positrons (e⁺th) can become solvated (e⁺aq). Hence, they are stabilized, live longer and can initiate side reactions. In addition, positronium (Ps), besides solvated electrons (e⁺aq), can be generated and involved in the reaction mechanisms. For a better understanding of the reaction mechanisms involved and to improve cancer therapy, a time-resolved pulse radiolysis instrument using high-energy particles is discussed here. The proposed method is examined and recommended by CERN experts. It is planned to be realized at the MedAustron Radiation Therapy and Research Centre in Wiener Neustadt, Austria.

  19. The reduction process of phytic acid silver ion system: A pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Joshi, Ravi; Mukherjee, Tulsi

    2007-05-01

    Reduction of silver ion in a silver-phytic acid (1:1 ratio) system has been studied using pulse radiolysis technique. Time-resolved transformation of the intermediates, Ag +→Ag 0→Ag 2+→Ag 32+, has been clearly observed in the reduction of silver-phytic acid (1:1) system. The effect of phytic acid on the formation and decay of initial silver clusters has been also studied. The surface plasmon absorption band of stable silver nanoparticle (410 nm) and dynamic light scattering technique has been used to characterize the nanoparticles and measure the average size ( Rav=100 nm).

  20. Pulse radiolysis system of OPU-LINAC in RIAST, Osaka Prefecture University

    NASA Astrophysics Data System (ADS)

    Kojima, Takao; Taniguchi, Ryoichi; Furuta, Masakazu; Okuda, Shuichi; Hara, Masayuki; Fujita, Shin'ichi

    2004-09-01

    Micro- to milli-second pulse radiolysis apparatus using short electron pulse form 18 MeV linear accelerator (Linac) is in-service at the Research institute for advanced science and technology (RIAST), Osaka Prefecture University. This apparatus is an effective tool, not only for investigation of primary process on radiation chemistry, but also for research of electron transfer mechanism playing an important role in chemistry and bioscience. This apparatus is composed of an 18 MeV electron linear accelerator (electron pulse duration: about 4 μs) and a transient light absorption measurement system. We introduce the outline of this system, transient absorption spectrum of thiocyanate aqueous solution as an example of measured data and future plan.

  1. Pulsed radiolysis of model aromatic polymers and epoxy based matrix materials

    NASA Technical Reports Server (NTRS)

    Gupta, A.; Moacanin, J.; Liang, R.; Coulter, D.

    1982-01-01

    Models of primary processes leading to deactivation of energy deposited by a pulse of high energy electrons were derived for epoxy matrix materials and polyl-vinyl naphthalene. The basic conclusion is that recombination of initially formed charged states is complete within 1 nanosecond, and subsequent degradation chemistry is controlled by the reactivity of these excited states. Excited states in both systems form complexes with ground state molecules. These excimers or exciplexes have their characteristics emissive and absorptive properties and may decay to form separated pairs of ground state molecules, cross over to the triplet manifold or emit fluorescence. ESR studies and chemical analyses subsequent to pulse radiolysis were performed in order to estimate bond cleavage probabilities and net reaction rates. The energy deactivation models which were proposed to interpret these data have led to the development of radiation stabilization criteria for these systems.

  2. Pulse radiolysis of supercritical water II. Reaction of nitrobenzene with hydrated electrons and hydroxyl radicals.

    SciTech Connect

    Marin, T. W.; Cline, J. A.; Bartels, D. M.; Jonah, C. D.; Takahashi, K.; Chemistry; Hakkaido Univ.

    2003-12-26

    The rate constants for the reactions of nitrobenzene with the hydroxyl radical (OH{sup {sm_bullet}}) and hydrated electron ((e{sup -}){sub aq}) in water have been measured from room temperature to 400 {sup o}C using electron pulse radiolysis and transient absorption spectroscopy. The diffusion-limited reaction of nitrobenzene with (e{sup 0}){sub aq} exhibits temperature-insensitive activation energy up to 300 {sup o}C, indicating that the activation energy for electron diffusion remains high over this range. The (e{sup -}){sub aq} reactivity is explained as a long-range electron transfer, and the results are interpreted in terms of extended Marcus theory and Smoluchowski relationships. At 380 {sup o}C, the rate constant has a density dependence similar to that previously reported for other (e{sup -}){sub aq} scavenging reactions. The reaction rate of nitrobenzene with OH{sup {sm_bullet}} is very insensitive to temperature from room temperature up to 300 {sup o}C, in agreement with previous studies. Above 300 {sup o}C, the rate constant increases as the critical temperature is approached and exceeded. Time-resolved electronic absorption spectra of the nitrobenzene radiolysis transients reveal complex kinetics involving multiple absorbing species.

  3. Antioxidative properties of hydroxycinnamic acid derivatives and a phenylpropanoid glycoside. A pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Lin, Weizhen; Navaratnam, Suppiah; Yao, Side; Lin, Nianyun

    1998-10-01

    Spectral and redox properties of the phenoxyl radicals from hydroxycinnamic acid derivatives and one selected component of phenylpropanoid glycosides, verbascoside, were studied using pulse radiolysis techniques. On the basis of the pH dependence of phenoxyl radical absorptions, the p Ka values for deprotonation of sinapic acid radical and ferulic acid radical are 4.9 and 5.2. The rate constants of one electron oxidation of those antioxidants by azide radical and bromide radical ion were determined at pH 7. The redox potentials of those antioxidants were determined as 0.59-0.71 V vs NHE at pH 7 with reference standard 4-methoxyphenol and resorcinol.

  4. Dynamic spectral shifts of molecular anions in organic glasses. [Pulse radiolysis

    SciTech Connect

    Huddleston, R.K.; Miller, J.R.

    1982-06-24

    Time-dependent spectra of the radical anions of pyromellitic dianhydride and p-dinitrobenzene have been observed after formation by pulse radiolysis in frozen 2-methyltetrahydrofuran and triacetin glasses. At temperatures near the glass transition, the spectra shift toward the blue over the entire observed time range 100 ns to 100 s), while at temperatures well below the glass transition, the spectral shifts can be stopped or greatly slowed. The magnitudes of the shifts are not large (typically approx. = to 10 nm), but because they are larger than the vibrational line widths, dramatic kinetics may be observed: the absorbance grows or decays by more than a factor of five at some wavelengths. The observations are consistent with a solvent molecule reorientation mechanism for spectral shifts of molecular ions in low-temperature organic glasses. 6 figures.

  5. Competition reactions of H2O•+ radical in concentrated Cl- aqueous solutions: picosecond pulse radiolysis study.

    PubMed

    El Omar, Abdel Karim; Schmidhammer, Uli; Rousseau, Bernard; LaVerne, Jay; Mostafavi, Mehran

    2012-11-29

    Picosecond pulse-probe radiolysis measurements of highly concentrated Cl(-) aqueous solutions are used to probe the oxidation mechanism of the Cl(-). The transient absorption spectra are measured from 340 to 710 nm in the picosecond range for the ultrafast electron pulse radiolysis of halide solutions at different concentrations up to 8 M. The amount of Cl(2)(•-) formation within the electron pulse increases notably with increasing Cl(-) concentration. Kinetic measurements reveal that the direct ionization of Cl(-) cannot solely explain the significant amount of fast Cl(2)(•-) formation within the electron pulse. The results suggest that Cl(-) reacts with the precursor of the OH(•) radical, i.e., H(2)O(•+) radical, to form Cl(•) atom within the electron pulse and the Cl(•) atom reacts subsequently with Cl(-) to form Cl(2)(•-) on very short time scales. The proton transfer reaction between H(2)O(•+) and the water molecule competes with the electron transfer reaction between Cl(-) and H(2)O(•+). Molecular dynamics simulations show that number of water molecules in close proximity decreases with increasing concentration of the salt (NaCl), confirming that for highly concentrated solutions the proton transfer reaction between H(2)O(•+) and a water molecule becomes less efficient. Diffusion-kinetic simulations of spur reactions including the direct ionization of Cl(-) and hole scavenging by Cl(-) show that up to 30% of the H(2)O(•+) produced by the irradiation could be scavenged for solutions containing 5.5 M Cl(-). This process decreases the yield of OH(•) radical in solution on the picosecond time scale. The experimental results for the same concentration of Cl(-) at a given absorbed dose show that the radiation energy absorbed by counterions is transferred to Cl(-) or water molecules and the effect of the countercation such as Li(+), K(+), Na(+), and Mg(2+) on the oxidation yield of Cl(-) is negligible.

  6. Pulse radiolysis study of ion-species effects on the solvated electron in alkylammonium ionic liquids

    NASA Astrophysics Data System (ADS)

    Kondoh, Takafumi; Asano, Akira; Yang, Jinfeng; Norizawa, Kimihiro; Takahashi, Kenji; Taguchi, Mitsumasa; Nagaishi, Ryuji; Katoh, Ryuzi; Yoshida, Yoichi

    2009-12-01

    The spectra and kinetic behavior of solvated electrons (e sol-) in alkyl ammonium ionic liquids (ILs), i.e. N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide (DEMMA-TFSI), N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium tetrafluoroborate (DEMMA-BF 4), N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide (TMPA-TFSI), N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13-TFSI), N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P13-TFSI), and N-methyl-N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P14-TFSI) were investigated by the pulse radiolysis method. The e sol- in each of the ammonium ILs has an absorption peak at 1100 nm, with molar absorption coefficients of 1.5-2.3×10 4 dm 3 mol -1 cm -1. The e sol- decayed by first order with a rate constant of 1.4-6.4×10 6 s -1. The reaction rate constant of the solvated electron with pyrene (Py) was 1.5-3.5×10 8 dm 3 mol -1 s -1 in the various ILs. These values were about one order of magnitude higher than the diffusion-controlled limits calculated from measured viscosities. The radiolytic yields ( G-value) of the e sol- were 0.8-1.7×10 -7 mol J -1. The formation rate constant of e sol- in DEMMA-TFSI was 3.9×10 10 s -1. The dry electron (e dry-) in DEMMA-TFSI reacts with Py with a rate constant of 7.9×10 11 dm 3 mol -1 s -1, three orders of magnitude higher than that of the e sol- reactions. The G-value of the e sol- in the picosecond time region is 1.2×10 -7 mol J -1. The capture of e dry- by scavengers was found to be very fast in ILs.

  7. Pulse radiolysis of alkanes: A time-resolved electron paramagnetic resonance study

    SciTech Connect

    Shkrob, I.A.; Trifunac, A.D.

    1994-02-14

    Time-resolved spin-echo-detected electron paramagnetic resonance (EPR) was applied to examine short-lived alkyl radicals formed in pulse radiolysis of liquid alkanes. It was found that the ratio of yields of penultimate and interior radicals in n-alkanes at the instant of their generation is temperature-independent and is ca. 1.25 times greater than the statistical quantity. This higher-than-statistical production of penultimate radicals indicates that the fast ion molecule reactions involving radical cations are a significant route of radical generation. The analysis of spin-echo kinetics in n-alkanes suggests that the alkyl radicals are emissively polarized in spur reactions. this initial polarization rapidly increases with shortening of the aliphatic chain. Another finding is that a long-chain structure of these radicals results in much higher rate of Heisenberg spin exchange relative to the recombination rate. The relative yields of hydrogen abstraction and fragmentation for various branched alkanes are estimated. It is concluded that the fragmentation occurs prior to the formation of radicals in an excited precursor species. Effects of phenolic and alkene additives in radiolysis of n-alkanes are examined. It is demonstrated that phenoxy radicals are produced in dissociative capture of electrons and alkane holes. Another route is a reaction of phenols with free hydrogen atoms. A rapid transfer of singlet correlation from the geminate radical ion pairs is responsible for unusual polarization patterns in the phenoxy and cyclohexadienyl radicals. The significance of these results in the context of cross-linking in polyethylene and higher paraffins is discussed. 56 refs.

  8. One-electron transfer reactions of the couple NAD. /NADH. [Pulse radiolysis

    SciTech Connect

    Grodkowski, J.; Neta, P.; Carlson, B.W.; Miller, L.

    1983-08-04

    One-electron transfer reactions involving nicotinamide-adenine dinucleotide in its oxidized and reducd forms (NAD./NADH) were studied by pulse radiolysis in aqueous solutions. One-electron oxidation of NADH by various phenoxyl radicals and phenothiazine cation radicals was found to take place with rate constants in the range of 10/sup 5/ to 10/sup 8/ M/sup -1/ s/sup -1/, depending on the redox potential of the oxidizing species. In all cases, NAD. is formed quantitatively with no indication for the existence of the protonated form (NADH/sup +/.). The spectrum of NAD., as well as the rates of oxidation of NADH by phenoxyl and by (chlorpromazine)/sup +/. were independent of pH between pH 4.5 and 13.5. Reaction of deuterated NADH indicated only a small kinetic isotope effect. All these findings point to an electron transfer mechanism. On the other hand, attempts to observe the reverse electron transfer, i.e., one-electron reduction of NAD. to NADH by radicals such as semiquinones, showed that k was less than 10/sup 4/ to 10/sup 5/ M/sup -1/ s/sup -1/, so that it was unobservable. Consequently, it was not possible to achieve equilibrium conditions which would have permitted the direct measurement of the redox potential for NAD./NADH. One-electron reduction of NAD. appears to be an unlikely process. 1 table.

  9. Pulse radiolysis studies of mangiferin: A C- glycosyl xanthone isolated from Mangifera indica

    NASA Astrophysics Data System (ADS)

    Mishra, B.; Priyadarsini, K. Indira; Sudheerkumar, M.; Unnikrishhnan, M. K.; Mohan, H.

    2006-01-01

    Pulse radiolysis technique has been employed to study the reaction of different oxidizing and reducing radicals with mangiferin. The reaction of rad OH radical showed the formation of transient species absorbing in 380-390 and 470-480 nm region. The reaction with specific one-electron oxidants (N 3rad , CCl 3O 2rad ) also showed the formation of similar transient absorption bands and is assigned to phenoxyl radicals. The p Ka values of the transient species have been determined to be 6.3 and 11.9. One-electron oxidation potential of mangiferin at pH 9 has been found to be 0.62 V vs. NHE. The reaction of e aq- showed the formation of transient species with λmax at 340 nm, which is assigned to the ketyl anion radical formed on addition of e aq- at carbonyl site. Reactions of one-electron oxidised mangiferin radicals with ascorbic acid have also been studied.

  10. Pulse radiolysis of silybin: One-electron oxidation of the flavonoid at neutral pH

    NASA Astrophysics Data System (ADS)

    György, I.; Antus, S.; Földiák, G.

    One-electron oxidation of silybin, a flavonoid drug used in human therapy of liver, was investigated by pulse radiolysis at neutral pH. Phenoxyl radicals formed from the substrate by oxidising N .3 radicals were identified by comparing the transient optical absorption spectra with those obtained from model compounds. The orto-methoxy-phenolic structure (ring B) is the exclusive target for one-electron oxidation of silybin. The 5.7-dihydroxy-chromanone moiety (ring A) withstands free-radical attack at neutral pH due to the chelatic H-bond (p Ka = 10.2) existing between the 5-OH and 4-oxo groups. Hydroxyl radicals react with silybin at diffusion controlled rate ( k = 1.8 x 10 10 dm 3 mol -1 s -1). The reactivity of silybin towards free radicals at neutral pH is conform with the assumption that the physiological activity of the flavonoid is due to its chain-breaking antioxidant behaviour.

  11. A direct demonstration of the catalytic action of monodehydroascorbate reductase by pulse radiolysis.

    PubMed

    Kobayashi, K; Tagawa, S; Sano, S; Asada, K

    1995-11-17

    To elucidate the catalytic mechanism of monodehydroascorbate (MDA) reductase from cucumber, its interaction with MDA radical was investigated by the use of pulse radiolysis. When approximately equimolar MDA radical to the fully reduced MDA reductase was generated, the fully reduced enzyme reacted first with MDA radical to form the red semiquinone, and the semiquinone further reacted with MDA radical to form the oxidized enzyme. At a low ratio (< 20) of MDA radical to enzyme concentration, the fully reduced enzyme reacted quantitatively with MDA radical to form the semiquinone with a second-order rate constant of 2.6 x 10(8) M-1 s-1 at pH 7.4. At excess MDA radical to enzyme concentration, a similar rate constant was obtained from the decay of MDA radical. These results suggest that the reaction of the semiquinone with MDA radical occurs at the same rate or rate-limiting step of the oxidation of the fully reduced enzyme by MDA radical. The rate constants decreased with an increase in NaCl concentration, suggesting that the localization of cationic groups of amino acid residue near the active site may provide electrostatic guidance to the anionic substrate of MDA radical.

  12. Photoreduction of azaoxoisoaporphines by amines: laser flash and steady-state photolysis and pulse radiolysis studies.

    PubMed

    de la Fuente, Julio R; Aliaga, Christian; Cañete, Alvaro; Kciuk, Gabriel; Szreder, Tomasz; Bobrowski, Krzysztof

    2013-01-01

    Photoreduction of 7H-benzo[e]perimidin-7-one (3-AOIA, A1) and its 2-methyl derivative (2-Me-3-AOIA, A2) by non-H-donating amines (1,4-diazabicyclo[2.2.2]octane [DABCO]; 2,2,6,6-tetramethylpiperidine [TMP]), and a hydrogen-donating amine (triethylamine [TEA]), has been studied in deaerated neat acetonitrile solutions using laser flash photolysis (LFP) and steady-state photolysis. The triplet excited states of A1 and A2 were characterized by a strong absorption band with λmax = 440 nm and lifetimes of 20 and 27 μs respectively. In the presence of tertiary amines, both triplet excited states were quenched with rate constants close to the diffusional limit (kq ranged between 10(9) and 10(10) M(-1) s(-1)). The transient absorption spectra observed after quenching with DABCO and TMP were characterized by maxima located at 460 nm and broad shoulders in the range of 500-600 nm. These transient species are attributed to solvent-separated radical ion pairs and/or to isolated radical anions. In the presence of TEA, these transients undergo proton transfer, leading to the neutral hydrogenated radicals, protonated over the N1- and O-atoms. Transient absorption spectra of these transients were characterized by maxima located at 400 and 520 nm and 430 nm respectively. Additional support for these spectral assignments was provided by pulse radiolysis (PR) experiments in acetonitrile and 2-propanol solutions.

  13. Pulse radiolysis studies of 3,5-dimethyl pyrazole derivatives of selenoethers.

    PubMed

    Barik, Atanu; Singh, Beena G; Sharma, Asmita; Jain, Vimal K; Priyadarsini, K Indira

    2014-11-06

    One electron redox reaction of two asymmetric 3,5-dimethyl pyrazole derivatives of selenoethers attached to ethanoic acid (DPSeEA) and propionic acid (DPSePA) were studied by pulse radiolysis technique using transient absorption detection. The reaction of the hydroxyl ((•)OH) radical with DPSeEA or DPSePA at pH 7 produced transients absorbing at 500 nm and at 300 nm, respectively. The absorbance at 500 nm increased with increasing parent concentration indicating formation of dimer radical cations. From the absorbance changes, the equilibrium constants for the formation of dimer radical cation of DPSeEA and DPSePA were estimated as 2020 and 1608 M(-1), respectively. The rate constants at pH 7 for the reaction of the (•)OH radical with DPSeEA and DPSePA were determined to be 9.6 × 10(9) and 1.4 × 10(10) M(-1) s(-1), respectively. The dimer radical cation of DPSeEA and DPSePA decayed by first order kinetics with a rate constant of 2.8 × 10(4) and 5.5 × 10(3) s(-1), respectively. The yield of radical cations of DPSeEA and DPSePA were estimated from the secondary electron transfer reaction, which corresponds to 38% and 48% of (•)OH radical yield, respectively. Some fraction of monomer radical cation undergoes decarboxylation reaction, and the yield of decarboxylation was 25% and 20% for DPSeEA and DPSePA, respectively. These results have implication in understanding their antioxidant activity. The reaction of trichloromethyl peroxyl radical, glutathione, and ascorbic acid further support their antioxidant behavior.

  14. Acid proliferation to improve the sensitivity of EUV resists: a pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Enomoto, Kazuyuki; Arimitsu, Koji; Yoshizawa, Atsutaro; Yamamoto, Hiroki; Oshima, Akihiro; Kozawa, Takahiro; Tagawa, Seiichi

    2011-04-01

    The yields of acid have been measured in the electron-beam irradiation of triphenylsulfonium triflate (TPS-Tf) and pinanediol monosulfonates, which consist of tosylate (PiTs), 4-fluorobenzenesulfonate (Pi1F), or 4-trifluoromethylbenzenesulfonate (Pi3F), as an acid amplifier blended in 4-hydroxystyrene matrixes. The acid yields efficiency decreases when PiTs is present, while its efficiency increases in the presence of Pi3F. Reactions of the electrons with TPS-Tf and pinanediol monosulfonates have been studied using pulse radiolysis in liquid tetrahydrofuran (THF) to evaluate the kinetic contributions to acid production. The THF-solvated electrons react with PiTs, Pi1F, and Pi3F to produce the corresponding radical anions; the rate constants are estimated to be 4.1, 5.1, and 9.2 × 1010 M-1 s-1, respectively. Electron transfer from PiTs•-, Pi1F•-, and Pi3F•- radical anions to TPS-Tf occurs with the rate constants of 5.7×1010, 1.2×1011, and 6.3 × 1010 M-1 s-1, respectively. The long-lived Pi3F•- efficiently undergoes the electron transfer to TPS-Tf to form the TPS-Tf•-, which subsequently decompose to generate TfOH. On the other hand, the decay channels of PiTs•- and Pi1F•-, which possess a relatively short lifetime, are presumably dependent on its reactions with solvated protons (charge recombination) rather than the electron transfer to TPS-Tf. The novel acid production pathway via the electron transfer from pinanediol monosulfonate radical anions to TPS-Tf is presented.

  15. Mechanism of oxidative conversion of Amplex® Red to resorufin: Pulse radiolysis and enzymatic studies.

    PubMed

    Dębski, Dawid; Smulik, Renata; Zielonka, Jacek; Michałowski, Bartosz; Jakubowska, Małgorzata; Dębowska, Karolina; Adamus, Jan; Marcinek, Andrzej; Kalyanaraman, Balaraman; Sikora, Adam

    2016-06-01

    Amplex® Red (10-acetyl-3,7-dihydroxyphenoxazine) is a fluorogenic probe widely used to detect and quantify hydrogen peroxide in biological systems. Detection of hydrogen peroxide is based on peroxidase-catalyzed oxidation of Amplex® Red to resorufin. In this study we investigated the mechanism of one-electron oxidation of Amplex® Red and we present the spectroscopic characterization of transient species formed upon the oxidation. Oxidation process has been studied by a pulse radiolysis technique with one-electron oxidants (N3(•), CO3(•-),(•)NO2 and GS(•)). The rate constants for the Amplex® Red oxidation by N3(•) ((2)k=2.1·10(9)M(-1)s(-1), at pH=7.2) and CO3(•-) ((2)k=7.6·10(8)M(-1)s(-1), at pH=10.3) were determined. Two intermediates formed during the conversion of Amplex® Red into resorufin have been characterized. Based on the results obtained, the mechanism of transformation of Amplex® Red into resorufin, involving disproportionation of the Amplex® Red-derived radical species, has been proposed. The results indicate that peroxynitrite-derived radicals, but not peroxynitrite itself, are capable to oxidize Amplex® Red to resorufin. We also demonstrate that horseradish peroxidase can catalyze oxidation of Amplex® Red not only by hydrogen peroxide, but also by peroxynitrite, which needs to be considered when employing the probe for hydrogen peroxide detection.

  16. Radiation-Induced Chemical Reactions in Hydrogel of Hydroxypropyl Cellulose (HPC): A Pulse Radiolysis Study.

    PubMed

    Yamashita, Shinichi; Ma, Jun; Marignier, Jean-Louis; Hiroki, Akihiro; Taguchi, Mitsumasa; Mostafavi, Mehran; Katsumura, Yosuke

    2016-12-01

    We performed studies on pulse radiolysis of highly transparent and shape-stable hydrogels of hydroxypropyl cellulose (HPC) that were prepared using a radiation-crosslinking technique. Several fundamental aspects of radiation-induced chemical reactions in the hydrogels were investigated. With radiation doses less than 1 kGy, degradation of the HPC matrix was not observed. The rate constants of the HPC composing the matrix, with two water decomposition radicals [hydroxyl radical ((•)OH) and hydrated electron ([Formula: see text])] in the gels, were determined to be 4.5 × 10(9) and 1.8 × 10(7) M(-1) s(-1), respectively. Direct ionization of HPC in the matrix slightly increased the initial yield of [Formula: see text], but the additionally produced amount of [Formula: see text] disappeared immediately within 200 ps, indicating fast recombination of [Formula: see text] with hole radicals on HPC or on surrounding hydration water molecules. Reactions of [Formula: see text] with nitrous oxide (N2O) and nitromethane (CH3NO2) were also examined. Decay of [Formula: see text] due to scavenging by N2O and CH3NO2 were both slower in hydrogels than in aqueous solutions, showing slower diffusions of the reactants in the gel matrix. The degree of decrease in the decay rate was more effective for N2O than for CH3NO2, revealing lower solubility of N2O in gel than in water. It is known that in viscous solvents, such as ethylene glycol, CH3NO2 exhibits a transient effect, which is a fast reaction over the contact distance of reactants and occurs without diffusions of reactants. However, such an effect was not observed in the hydrogel used in the current study. In addition, the initial yield of [Formula: see text], which is affected by the amount of the scavenged precursor of [Formula: see text], in hydrogel containing N2O was slightly higher than that in water containing N2O, and the same tendency was found for CH3NO2.

  17. Effects of oxidation on copper-binding properties of Aβ1-16 peptide: a pulse radiolysis study.

    PubMed

    Ramteke, S N; Ginotra, Y P; Walke, G R; Joshi, B N; Kumbhar, A S; Rapole, S; Kulkarni, P P

    2013-12-01

    The reaction of hydroxyl radicals ((•)OH) with Aβ1-16 peptide was carried out using pulse radiolysis to understand the effect of oxidation of peptide on its copper-binding properties. This reaction produced oxidized, dimeric and trimeric Aβ1-16 peptide species. The formation of these products was established with the help of fluorescence spectroscopy and mass spectrometry. The mass spectral data indicate that the major site of oxidation is at His6, while the site for dimerization is at Tyr10. Diethyl pyrocarbonate-treated Aβ1-16 peptide did not produce any trimeric species upon oxidation with (•)OH. The quantitative chemical modification studies indicated that one of the three histidine residues is covalently modified during pulse radiolysis. The copper-binding studies of the oxidized peptide revealed that it has similar copper-binding properties as the unoxidized peptide. Further, the cytotoxicity studies point out that both oxidized and unoxidized Aβ1-16 peptide are equally efficient in producing free radicals in presence of copper and ascorbate that resulted in comparable cell death.

  18. Picosecond pulse radiolysis of highly concentrated sulfuric acid solutions: evidence for the oxidation reactivity of radical cation H2O(•+).

    PubMed

    Ma, Jun; Schmidhammer, Uli; Mostafavi, Mehran

    2014-06-12

    Aqueous solution of sulfuric acid is used as a suitable system to investigate the reactivity of the short-lived radical cation H2O(•+) which is generated by radiation in water. Ten aqueous solutions containing sulfuric acid with concentration from 1 to 18 mol L(-1) are studied by picosecond pulse radiolysis. The absorbance of the secondary radical SO4(•-) (or HSO4(•)) formed within the 10 ps electron pulse is measured by a pulse-probe method in the visible range. The analysis of the kinetics show that the radicals of sulfuric acid are formed within the picosecond electron pulse via two parallel mechanisms: direct electron detachment by the electron pulse and oxidation by the radical cation of water H2O(•+). In highly concentrated solution when SO4(2-) is in contact with H2O(•+), the electron transfer becomes competitive against proton transfer with another water molecule. Therefore, H2O(•+) may act as an extremely strong oxidant. The maximum radiolytic yield of scavenged H2O(•+) is estimated to be 5.3 ± 0.1 × 10(-7) mol J(-1).

  19. One-electron oxidation of mitomycin C and its corresponding peroxyl radicals. A steady-state and pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Getoff, Nikola; Solar, Sonja; Quint, Ruth M.

    1997-12-01

    The one-electron oxidation of Mitomycin C (MMC) as well as the formation of the corresponding peroxyl radicals were investigated by both steady-state and pulse radiolysis. The steady-state MMC-radiolysis by OH-attack followed at both absorption bands showed different yields: at 218 nm G i (-MMC) = 3.0 and at 364 nm G i (-MMC) = 3.9, indicating the formation of various not yet identified products, among which ammonia was determined, G(NH 3) = 0.81. By means of pulse radiolysis it was established a total κ (OH + MMC) = (5.8 ± 0.2) × 10 9 dm 3 mol -1 s -1. The transient absorption spectrum from the one-electron oxidized MMC showed absorption maxima at 295 nm ( ɛ = 9950 dm 3 mol -1 cm t-1 ), 410 nm ( ɛ = 1450 dm 3 mol -1 cm -1) and 505 nm ( ɛ = 5420 dm 3 mol -1 cm -1). At 280-320 and 505 nm and above they exhibit in the first 150 μs a first order decay, κ1 = (0.85 ± 0.1) × 10 3 s -1, and followed upto ms time range, by a second order decay, 2 κ = (1.3 ± 0.3) × 10 8 dm 3 mol -1 s -1. Around 410 nm the kinetics are rather mixed and could not be resolved. The steady-state MMC-radiolysis in the presence of oxygen featured a proportionality towards the absorbed dose for both MMC-absorption bands, resulting in a G i (-MMC) = 1.5. Among several products ammonia-yield was determined G(NH 3) = 0.52. The formation of MMC-peroxyl radicals was studied by pulse radiolysis, likewise in neutral aqueous solution, but saturated with a gas mixture of 80% N 2O and 20% O 2. The maxima of the observed transient spectrum are slightly shifted compared to that of the one-electron oxidized MMC-species, namely: 290 nm ( ɛ = 10100 dm 3 mol -1 cm -1), 410 nm ( ɛ = 2900 dm 3 mol -1 cm -1) and 520 nm ( ɛ = 5500 dm 3 mol -1 cm -1). The O 2-addition to the MMC-one-electron oxidized transients was found to be at 290 to 410 nm gk(MMC·OH + O 2) = 5 × 10 7 dm 3 mol -1 s -1, around 480 nm κ = 1.6 × 10 8 dm 3 mol -1 s -1 and at 510 nm and above, κ = 3 × 10 8 dm 3 mol -1 s -1. The

  20. EPR and NMR detection of transient radicals and reaction products. [Radiolysis of methanol and aqueous potassium acetate

    SciTech Connect

    Trifunac, A.D.

    1981-01-01

    Magnetic resonance methods in radiation chemistry are illustrated. The most recent developments in pulsed EPR and NMR studies in pulse radiolysis are outlined with emphasis on the study of transient radicals and their reaction products. 12 figures.

  1. Free radical mechanisms for the oxidation of substituted ascorbates. A pulse radiolysis study of L-ascorbic acid-2-sulfate

    SciTech Connect

    Cabelli, D.E.; Comstock, D.A.; Bielski, B.H.J.

    1983-09-01

    The oxidations of L-ascorbate 2-sulfate by Br/sub 2//sup -/ and OH radicals generated in aqueous solutions (pH 4.5 to 9.5) were studied by pulse radiolysis. The (2-SO/sub 4/A)./sup -/ radical, generated in an electron transfer reaction between Br/sub 2//sup -/ and the parent compound, loses sulfate (tau approx. 500 ..mu..sec) to give ascorbate free radical (A./sup -/) with a G(A./sup -/) = 2.0. The oxidation of L-ascorbate 2sulfate by OH radicals is complex, yielding both (2-SO/sub 4/A)/sup -/ and OH radical adducts. Some of these transients subsequently yield A./sup -/. HPLC studies corroborate the overall mechanism postulated for the oxidation of L-ascorbate 2-sulfate by OH radicals.

  2. Effect of ionic micellar medium on kinetics and mechanism of oxidation of bovine serum albumin: A pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Joshi, Ravi; Mukherjee, Tulsi

    2010-09-01

    Effect of protein-micelle interaction on bovine serum albumin (BSA) oxidation by trichloromethyl peroxyl radical (CCl 3O 2·) in anionic sodium dodecyl sulfate (SDS) and cationic cetyltrimethyl ammonium bromide (CTAB) micellar media has been studied using nanosecond pulse radiolysis technique. Viscosity measurement and light scattering studies have suggested that SDS and CTAB micelles produce BSA-micelle aggregates of different sizes and polydispersity. Oxidation kinetics and transients have been affected both by anionic SDS and cationic CTAB micelles but in a different manner. Tryptophanyl-CCl 3O 2· adduct radical to tyrosyl radical transformation in BSA has been observed in anionic SDS micelles but not in cationic CTAB micelles. Similar studies have also been done with tryptophan and tyrosine amino acids, which undergo oxidation in BSA. The study suggests that Coulombic and hydrophobic interactions between micelles and protein affect the structure of the protein to shield its functional amino acids, like tryptophan and tyrosine, to neutral oxidizing radical.

  3. Pulse radiolysis of tetrazolium violet in aqueous and aqueous-alcoholic solutions under oxidative and reductive conditions

    NASA Astrophysics Data System (ADS)

    Kovács, A.; Wojnárovits, L.; Pálfi, T.; Emi-Reynolds, G.; Fletcher, J.

    2008-09-01

    The radiolytic reduction of colourless tetrazolium salts to coloured formazans in liquid and solid state is suggested for dosimetry purposes. In order to clarify the reaction mechanism, a pulse radiolysis study was conducted in aqueous and aqueous-alcoholic solutions under oxidative and reductive conditions. Under reducing conditions, fast formation of the electron adduct tetrazolinyl radical was observed: coloured formazan final product formed during the decay of electron adduct. Both the decay of the tetrazolinyl radical and the formation of the formazan were found to be second order. The spectra of the formazan were similar in neutral and alkaline solutions, but with higher absorbance in the latter solutions due to the higher molar absorption coefficient. Under oxidative conditions formazan did not form; hydroxylated products through OH-adducts were observed in the pH range studied.

  4. Fundamental reactions in TiO 2 nanocrystallite aqueous solutions studied by pulse radiolysis

    NASA Astrophysics Data System (ADS)

    Gao, Ruomei; Safrany, Agnes; Rabani, Joseph

    2002-12-01

    Reactions of the hydrated electron, H atoms, 2-propanol, and methanol radicals with the TiO 2 nano-particles have been studied either directly or by competition kinetics. The radicals were produced by radiolysis of 2-propanol, t-butanol, or methanol aqueous solutions in acid pH's. The reactions involve electron injection to the conduction band. As expected, the t-butanol radical is inert towards TiO 2 under our conditions, while the other reducing radicals react with TiO 2. The reactivity decreases in the order: e aq->H>CH 3COHCH 3>CH 2OH. Two TiO 2 nanocrystallite sizes, with average diameters of 1.0 and 4.7 nm were compared. For equal concentrations (in terms of TiO 2 molecules), the rate of electron injection shows relatively little dependency on particle size. The rates of interfacial electron transfer and transfer coefficient are also reported.

  5. Kinetics and mechanism of superoxide radical reactions with some biologically important compounds in aqueous solutions. Pulse radiolysis

    NASA Astrophysics Data System (ADS)

    Revina, A. A.; Amiragova, M. I.; Volod'ko, V. V.; Vannikov, A. V.

    Microsecond pulse radiolysis of oxygenated aqueous solutions containing 0.02 mol dm -3 sodium formate and 2 mmol dm -3 phosphate buffer at pH 7 was used to generate superoxide anion radicals. The influence of some biologically important compounds upon the rate of O ⨪2 decay was monitored spectrophotometrically in the range of 245-300 nm. Hematoporphyrin (HP), hemin C (HC), catalase (Cat), cobalt sulfophthalocyanine (CoTSPc) were studied. Among the investigated compounds only Cat was found to show a high catalytic efficiency towards the self-decay of O ⨪2. A red shift of O ⨪2 absorption band and slowing down of its decay were observed to take place by adding HP or CoTSPc to the solutions containing formate ions in excess. This effect is associated with the formation of a transient superoxo-complex. An appearance of an intermediate species with absorption maxima at 350 nm and half-life of about 2s was observed to accompany the superoxo-complex of CoTSPc decay. In the aerated solution of HP the intensity of absorbance at 260 nm was found to be independent of the presence of formate ions.

  6. Examination of the formation process of pre-solvated and solvated electron in n-alcohol using femtosecond pulse radiolysis

    NASA Astrophysics Data System (ADS)

    Toigawa, Tomohiro; Gohdo, Masao; Norizawa, Kimihiro; Kondoh, Takafumi; Kan, Koichi; Yang, Jinfeng; Yoshida, Yoichi

    2016-06-01

    The formation process of pre-solvated and solvated electron in methanol (MeOH), ethanol (EtOH), n-butanol (BuOH), and n-octanol (OcOH) were investigated using a fs-pulse radiolysis technique by observing the pre-solvated electron at 1400 nm. The formation time constants of the pre-solvated electrons were determined to be 1.2, 2.2, 3.1, and 6.3 ps for MeOH, EtOH, BuOH, and OcOH, respectively. The formation time constants of the solvated electrons were determined to be 6.7, 13.6, 22.2, and 32.9 ps for MeOH, EtOH, BuOH, and OcOH, respectively. The formation dynamics and structure of the pre-solvated and solvated electrons in n-alcohols were discussed based on relation between the obtained time constant and dielectric relaxation time constant from the view point of kinetics. The observed formation time constants of the solvated electrons seemed to be strongly correlated with the second component of the dielectric relaxation time constants, which are related to single molecule motion. On the other hand, the observed formation time constants of the pre-solvated electrons seemed to be strongly correlated with the third component of the dielectric relaxation time constants, which are related to dynamics of hydrogen bonds.

  7. Pulse radiolysis and 77 K matrix. gamma. irradiation of dimethyl truxinates and trans-methyl cinnamate in 2-methyltetrahydrofuran

    SciTech Connect

    Takamuku, S.; Kigawa, H.; Suematsu, H.; Susumu, T.; Tsumori, K.; Sakurai, H.

    1982-05-13

    One-electron reduction of dimethyl ..mu..-truxinate (..mu..-DMT), dimethyl ..beta..-truxinate (..beta..-DMT), and dimethyl ..cap alpha..-truxillate (..cap alpha..-DMT) has been investigated by pulse radiolysis and 77 K matrix ..gamma.. irradiation of the 2-methyltetrahydrofuran solutions. Cycloreversion of the radical anions formed by an electron attachment to these cyclobutanes was observed in all cases, even at 77 K. The orientation of the cycloreversion was dependent on the stereochemistry of the cyclobutanes, and the selectivity was reasonably explained by a so-called cis effect; the best possible release of steric hindrance decides the primary step of the reaction. In 77 K matrix ..gamma.. irradiation of ..cap alpha..-DMT, an intense IR absorption was found after the photobleaching of trapped electrons with light > 690 nm. In other DMTs, the IR absorption band was not observed while the cycloreversion of DMT by mobile electrons occurred. Thus, the IR band in the case of ..cap alpha..-DMT was assigned to an associated dimer anion due to the interaction between the radical anion and the neutral molecule pair of trans-methyl cinnamate orginally formed by the cycloreversion of ..cap alpha..-DMT. The dimer anion was presumed to be oriented in a head-to-tail structure in a solvent cage on the basis of the original configuration of ..cap alpha..-DMT.

  8. Favism inducing agents: a pulse radiolysis study of isouramil and convicine. Progress report, December 1, 1979 - November 30, 1980

    SciTech Connect

    Chevion, M.; Ilan, Y.A.

    1980-01-01

    Isouramil and covicine, substances implicated in precipitating favic crises in glucose-6-phosphate dehydrogenase deficient individuals, have been studied in N/sub 2/O-saturated aqueous solutions by pulse radiolysis, and the kinetics of the reactions of both substances with OH radicals were determined. The products of these reactions are addition intermediates absorbing above 330 nm. The decay of the intermediate(s) formed in the isouramil reaction is a biphasic one, while the decay of the corresponding intermediate for the convicine reaction is characterized by a single constant. By analogy to uracil, it is suggested that the OH radical is added to the double bond at either positions 5 or 6 of the pyrimidine ring forming two different intermediates. Each of these intermediates loses a molecule of water indicated by the observed biphasic decay reaction. For convicine on the other hand, position 5 is blocked by the O-gucosidic bond and the addition of the OH radical could take place only at position 6. Thus, a single intermediate is formed and its decay is a single-phase one. It has been shown that although free radicals could not be detected in the course of the reactions between isouramil and oxygen or with cellular components by electron paramagnetic resonance, isouramil can participate in a uni-electron transfer reacton and can form relatively stable intermediates. Thus, it is speculated that in the red blood cells isouramil could give rise to deleterious free radicals.

  9. Pulse-radiolysis studies on the interaction of one-electron-reduced species with ascorbate oxidase in aqueous solution.

    PubMed Central

    O'Neill, P; Fielden, E M; Finazzi-Agrò, A; Avigliano, L

    1983-01-01

    The interaction of e-aq., CO2-. and one-electron reduced nitroaromatics (RNO2-.) with ascorbate oxidase (AAO) was studied in aqueous solution at pH 6.0 and 7.5 by using the technique of pulse radiolysis. From observations at 330, 410 and 610 nm, interaction of e-aq. and CO2-. with AAO results in non-specific reduction of the protein followed by reduction of Type 1 Cu in a rate-determining intramolecular step. Only a few per cent of the reducing equivalents ultimately results in reduction of Type 1 Cu. With large excesses of reducing equivalents (e-aq. and CO2-.) with respect to the copper concentration, the amount of Type 1 copper reduced never exceeds 50% of the total amount of Type 1 copper after a single radiation pulse. With less-powerful reducing agents, e.g. RNO2-. reduction of Type 1 Cu occurs via a bimolecular step, and there is no evidence for formation of radicals on protein residues. From observations at 330 nm it is evident that Type 2 and/or Type 3 Cu may also be reduced along with Type 1 Cu. Almost stoichiometric reduction of AAO by RNO2-. was observed, e.g. the protein accepts 6-7 reducing equivalents. It is inferred that the various types of redox couples Cu2+/Cu+ are in equilibrium and that intramolecular electron transfer between the different types of Cu is not rate-determining when using RNO2-. as reducing agent. PMID:6405732

  10. Design of a high pressure system for pulse radiolysis studies up to 400 MPa with flow regulation

    NASA Astrophysics Data System (ADS)

    NGuyen Le, D.-T.; Pin, S.; Anjoure, D.; Chopineau, P.; Baldacchino, G.

    2013-03-01

    This article reports details of a new setup including an optical flow cell and devices which can increase pressure up to 400 MPa by controlling the ramp rate. It is composed of two high pressure syringe pumps which can make liquids flowing up to 4 cm3/mn. The optical flow cell can contains aqueous solutions and allow carry out pulse radiolysis experiments with a pulsed 10-MeV electron beam by performing in situ and time resolved optical analysis, such as transient UV-visible absorption or fluorescence spectroscopy. A Labview-program has been developed to drive and monitor automatons which regulate pressure, make solution flow under pressure, carry out operations such as filling, emptying or cleaning the system under safe conditions. Two results are exhibited: 1/associated to phosphate buffer, the fluorescence spectrum of the fluorescein pH-sensor has been performed under pressure. Phosphate pKa is confirmed to be very sensitive to pressure increase even up to 300 MPa. 2/a time-resolved absorption spectroscopy of hydrated electron in deaerated water has been conducted up to 350 MPa with a continuous flow of sample. In presence of tertio-butanol and bisTris pH7-buffer in solution, the spectral shift of hydrated electron is finely reproduced. BisTris is also confirmed as insensitive buffer under high pressure and its reduction by hydrated electron remains constant with a rate constant of (4.6 ± 0.6) × 108 M-1 s-1.

  11. OH-radical induced degradation of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 4-chloro-2-methylphenoxyacetic acid (MCPA): A pulse radiolysis and gamma-radiolysis study

    NASA Astrophysics Data System (ADS)

    Zona, Robert; Solar, Sonja; Sehested, Knud

    2012-02-01

    The reactions of rad OH, H rad and e aq- with 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 4-chloro-2-methylphenoxyacetic acid (MCPA) were studied by pulse radiolysis. The site of rad OH-radicals addition to the aromatic ring of 2,4,5-T was found to be—C1: ˜18%, C2/C4/C5: total ˜28% and C3/C6: total ˜41%. The overall rate constants with OH-radicals were k( rad OH+2,4,5-T)=6.4 (±0.5)×10 9 mol dm -3 s -1 and k( rad OH+MCPA)=8.5 (±0.8)×10 9 mol dm -3 s -1. The radiation induced decomposition of the pesticides, chloride- and product formation (phenolic compounds, aliphatic acids) was studied by gamma radiolysis as a function of dose. A mechanism for acetate formation is discussed. The presence of oxygen during irradiation affected the decomposition rate only indiscernibly, however, chloride elimination, ring fragmentation (formation of aliphatic acids), TOC- and toxicity reduction were strongly enhanced. For complete removal of 500 μmol dm -3 herbicides a dose of ˜4 kGy was required. Using air saturation during irradiation a reduction of 37-40% of the TOC was observable at 5 kGy, detoxification (luminescence inhibition <20%) was achieved with 10 kGy.

  12. Laser pulse stacking method

    DOEpatents

    Moses, Edward I.

    1992-01-01

    A laser pulse stacking method is disclosed. A problem with the prior art has been the generation of a series of laser beam pulses where the outer and inner regions of the beams are generated so as to form radially non-synchronous pulses. Such pulses thus have a non-uniform cross-sectional area with respect to the outer and inner edges of the pulses. The present invention provides a solution by combining the temporally non-uniform pulses in a stacking effect to thus provide a more uniform temporal synchronism over the beam diameter.

  13. Laser pulse stacking method

    DOEpatents

    Moses, E.I.

    1992-12-01

    A laser pulse stacking method is disclosed. A problem with the prior art has been the generation of a series of laser beam pulses where the outer and inner regions of the beams are generated so as to form radially non-synchronous pulses. Such pulses thus have a non-uniform cross-sectional area with respect to the outer and inner edges of the pulses. The present invention provides a solution by combining the temporally non-uniform pulses in a stacking effect to thus provide a more uniform temporal synchronism over the beam diameter. 2 figs.

  14. Radiolysis of herbs

    NASA Astrophysics Data System (ADS)

    Jilan, Wu; Xujia, Zhang; Rongyao, Yuan; Yongke, He

    1995-08-01

    Radiolysis of 124 types of herbs was studied. The majority were stable under γ-irradiation with absorbed dose up to 10 kGy. Radiolytic decomposition was detected at 10 kGy for 16 types of herbs (12.9%) and at 5 kGy for 6 types (4.8%). No detectable radiolytic decomposition was found at <2 kGy. The model system study showed: 1, γ-radiolysis is different from thermohydrolysis and photolysis; 2, water adsorbed on herbs evidently affects the radiolytic decomposition of herbs. Pulse and γ-radiolysis of baicalin, 1,8-dihydroxyanthraquinone-β- D-glycoside, glycyrrhizin and corydalic-B showed that some new compounds were formed due to the attack of OH radical. The addition of fructose and glucose can inhibit the γ-radiolytic decomposition of herbs. Chemical clearance displays fruitful and hopeful prospect to disinfect herbs by γ-ray, but important measure and step should be adopted. That is: 1, the herbs must exist in dry state; 2, it is preferred to make bolus by mixing powdered Chinese medicine and honey, as the latter can inhibit the radiolysis of herbs; 3, the producer must pay attention to executing strictly manufacture procedure to reduce the microbiological contamination, thus subsequently lower the applied dose.

  15. A pulse-radiolysis study of the catalytic mechanism of the iron-containing superoxide dismutase from Photobacterium leiognathi.

    PubMed

    Lavelle, F; McAdam, M E; Fielden, E M; Roberts, P B

    1977-01-01

    The mechanism of the enzymic reaction of an iron-containing superoxide dismutase purified from the marine bacterium Photobacterium leiognathi was studied by using pulse radiolysis. Measurements of activity were done with two different preparations of enzyme containing either 1.6 or 1.15 g-atom of iron/mol. In both cases, identical values of the second-order rate constant for reaction between superoxide dismutase and the superoxide ion in the pH range 6.2-9.0 (k=5.5 X 10(8) M-1-S-1 at pH 8.0) were found. As with the bovine erythrocuprein, there was no evidence for substrate saturation. The effects of reducing agents (H2O2, sodium ascorbate or CO2 radicals) on the visible and the electron-paramagnetic-resonance spectra of the superoxide dismutase containing 1.6 g-atom of ferric iron/mol indicate that this enzyme contains two different types of iron. Turnover experiments demonstrate that only that fraction of the ferric iron that is reduced by H2O2 is involved in the catalysis, being alternately oxidized and reduced by O2; both the oxidation and the reduction steps have a rate constant equal to that measured under turnover conditions. These results are interpreted by assuming that the superoxide dismutase isolated from the organism contains 1 g-atom of catalytic iron/mol and a variable amount of non-catalytic iron. This interpretation is discused in relation to the stoicheiometry reported for iron-containing superoxide dismutases prepared from several other organisms.

  16. Photoreduction of oxoisoaporphines by amines: laser flash and steady-state photolysis, pulse radiolysis, and TD-DFT studies.

    PubMed

    De la Fuente, Julio R; Aliaga, Christian; Poblete, Cristian; Zapata, Gerald; Jullian, Carolina; Saitz, Claudio; Cañete, Alvaro; Kciuk, Gabriel; Sobarzo-Sanchez, Eduardo; Bobrowski, Krzysztof

    2009-07-09

    Photoreduction of oxoisoaporphine (OIA) (1-aza-benzo-[de]anthracen-7-one) and its 5-methoxy (5-MeO-OIA) derivative by selected amines (two non-alpha-hydrogen-donating amines (1,4-diaza[2.2.2]-bicyclooctane (DABCO) and 2,2,6,6-tetramethylpiperidine (TMP)) and three alpha-hydrogen-donating amines (triethylamine (TEA), diethylmethylamine (DEMA), and dimethylethylamine (DMEA))) has been studied in deaerated neat acetonitrile solutions using laser flash and steady-state photolysis. The triplet excited states of OIA and 5-MeO-OIA are characterized by intense absorption maxima located at lambda(max) = 450 nm and lifetimes of 34.7 +/- 0.5 and 44.6 +/- 0.4 micros, respectively. In the presence of tertiary amines, both triplets are quenched with a rate constant that varies from the near diffusion limit (>10(9) M(-1) s(-1)) to a rather low value (approximately 10(7) M(-1) s(-1)) and shows the expected dependence on the reduction potential for one-electron-transfer reactions. The transient absorption spectra observed after quenching of the respective triplet states are characterized by distinct absorption maxima located at lambda(max) = 480 and 490 nm (for OIA and 5-MeO-OIA, respectively) and accompanied by broad shoulders in the range of 510-560 nm. They were assigned to either solvent-separated radical ion pairs and/or isolated radical anions. In the presence of alpha-hydrogen-donating amines these species undergo protonation that leads to the formation of neutral hydrogenated radicals A1H(*)/A2H(*) with two possible sites of protonation, N and O atoms. Pulse radiolysis and molecular modeling together with TD-DFT calculations were used to support the conclusions about the origin of transients.

  17. Yields and decay kinetics of the solvated electron in pulse radiolysis of 1-alkanols

    NASA Astrophysics Data System (ADS)

    Kalachandra, S.; Farhataziz; Foyt, David C.

    The products of the yields of the solvated electron in 1-alkanols, G(e alk-, and the extinction coefficient of e alk- at its absorption maximum, ɛ(e alk-) max, relative to the same product for the hydrated electron, G(e aq-)ɛ(e aq-) max, for a 60 nsec irradiation at room temperature are given in parentheses after the name of each 1-alkanol: methanol (0.38), ethanol (0.42), 1-propanol (0.33), 1-butanol (0.30), 1-pentanol (0.28), 1-hexanol (0.31), 1-heptanol (0.27), 1-octanol (0.29), 1-nonanol (0.26), and 1-decanol (0.24). The decay kinetics of e alk- after 60 or 400 nsec of pulse irradiation of 1-alkanols, C 1-C 10, fit competitive pseudo-first order and second order (initial concentrations of both reactants the same) processes. Except for 1-propanol to 1-pentanol, the observed second order specific rates are a function of the dose per pulse. A mechanism is proposed for the above given decay kinetics of e alk- in C 1C 10 1-alkanols.

  18. Dynamics of radical cations of poly(4-hydroxystyrene) in the presence and absence of triphenylsulfonium triflate as determined by pulse radiolysis of its highly concentrated solution

    NASA Astrophysics Data System (ADS)

    Okamoto, Kazumasa; Ishida, Takuya; Yamamoto, Hiroki; Kozawa, Takahiro; Fujiyoshi, Ryoko; Umegaki, Kikuo

    2016-07-01

    Pulse radiolysis of highly concentrated poly(4-hydroxystyrene) (PHS) solutions in cyclohexanone and p-dioxane was performed both with and without an onium-type photoacid generator (PAG). With increasing PHS concentration, the rate constant of deprotonation of PHS radical cations was found to decrease. In the presence of PAG, the yield of the multimer radical cation of PHS was shown to decrease. We found that pairing between the anions produced by the attachment of dissociative electrons of PAGs and the monomer PHS radical cations restrict local molecular motions, leading to the formation of the multimer PHS radical cations.

  19. Measuring hydrogen peroxide due to water radiolysis using a modified horseradish peroxidase based biosensor as an alternative dosimetry method.

    PubMed

    Tavakoli, Hassan; Baghbanan, Amin Azam

    2015-08-01

    H2O2 generated during water radiolysis was measured electrochemically as an alternative dosimetry method. A biosensor was fabricated by immobilising modified horseradish peroxidase (HRP) on a glassy carbon electrode (GCE) followed by evaluation of its analytical parameters. Anthraquinone 2-carboxylic acid was used to modify HRP. To assess sensor performance, phosphate buffer solutions were irradiated with 0.510 Gy of gamma ray emitted from (60)Co. The results showed that this sensor can detect low quantities of hydrogen peroxide in water radiolysis. Sensitivity, detection limit and linear range of the biosensor were 260 nA/Gy, 0.392 Gy and 0.5-5 Gy, respectively. Long term stability studies showed that sensor responses were stable for at least a month. The cathodic peak current, as biosensor response, subsequently decreased to 20% of its initial value.

  20. A new approach to the study of intramolecular electron-transfer reactions of metalloproteins: Pulse radiolysis of NO[sub 2]-modified tyrosine derivatives of plastocyanin

    SciTech Connect

    Govindaraju, K.; Christensen, H.E.M.; Lloyd, E.; Tomkinson, N.P.; Sykes, A.G. ); Olsen, M. ); Salmon, G.A. )

    1993-01-06

    Single NO[sub 2]-modified derivatives of plastocyanin, with modifications at Tyr83 (spinach) and Tyr83/Tyr62 (parsley, deletions at 57 and 58), have been prepared and characterized by peptide mapping. All three products give a TyrNO[sub 2] UV-vis absorbance band at 355 nm ([epsilon] = 3,900 M[sup [minus]1] cm[sup [minus]1]) at pH < 7.5, assigned to NO[sub 2], which shifts to 428 nm on increasing the pH to > 9.0 due to acid dissociation of the phenolic group. Pulse radiolysis experiments in which the reductant CO[sub 2][sup [sm bullet][minus

  1. Pulse measurement apparatus and method

    DOEpatents

    Marciante, John R.; Donaldson, William R.; Roides, Richard G.

    2011-10-25

    An embodiment of the invention is directed to a pulse measuring system that measures a characteristic of an input pulse under test, particularly the pulse shape of a single-shot, nano-second duration, high shape-contrast optical or electrical pulse. An exemplary system includes a multi-stage, passive pulse replicator, wherein each successive stage introduces a fixed time delay to the input pulse under test, a repetitively-gated electronic sampling apparatus that acquires the pulse train including an entire waveform of each replica pulse, a processor that temporally aligns the replicated pulses, and an averager that temporally averages the replicated pulses to generate the pulse shape of the pulse under test. An embodiment of the invention is directed to a method for measuring an optical or an electrical pulse shape. The method includes the steps of passively replicating the pulse under test with a known time delay, temporally stacking the pulses, and temporally averaging the stacked pulses. An embodiment of the invention is directed to a method for increasing the dynamic range of a pulse measurement by a repetitively-gated electronic sampling device having a rated dynamic range capability, beyond the rated dynamic range of the sampling device; e.g., enhancing the dynamic range of an oscilloscope. The embodied technique can improve the SNR from about 300:1 to 1000:1. A dynamic range enhancement of four to seven bits may be achieved.

  2. Effect of isopropyl alcohol on the surface localization and recombination of conduction-band electrons in Degussa P25 TiO sub 2. A pulse-radiolysis time-resolved microwave conductivity study. [Accelerated electrons

    SciTech Connect

    Warman, J.M.; Hass, M.P. de ); Pichat, P. ); Serpone, N. Concordia Univ., Montreal, Quebec )

    1991-10-31

    Conduction-band electrons, formed by pulse radiolysis of Degussa P25 TiO{sub 2} particles, have been monitored by time-resolved microwave conductivity and found to undergo equilibrium localization and eventual recombination at the particle surface. In the presence of isopropyl alcohol recombination is retarded due to surface hole scavenging. The particle bulk can then be pumped with mobile electrons, which survive for seconds.

  3. Temperature dependence of the rate constant for hydrogen atom reaction with Cl2-• in water by pulse radiolysis of aqueous HCl solution

    NASA Astrophysics Data System (ADS)

    Kazmierczak, L.; Szala-Bilnik, J.; Wolszczak, M.; Swiatla-Wojcik, D.

    2015-12-01

    The temperature dependence of the rate constant for the reaction of dichloride anion radical (Cl2- •) with atomic hydrogen (H•) in water up to 75 °C has been determined by pulse radiolysis of deaerated 0.1 M HCl solution. The room temperature value is (6.1±0.6)×109 M-1 s-1. The activation energy of (13.2±0.6) kJ mol-1 is less than 16.7 kJ mol-1, expected for the diffusion-controlled reaction. Based on the temperature dependence of the rate constant for the reactions H•+Cl2- • and H•+Cl2, derived in this work, and on that reported earlier (Szala-Bilnik et al., 2014) for Cl2- • + Cl2- • , we show that a value of (10±2) M-1 s-1 determined by Hartig and Getoff (1982) for k (H•+H2O) in water at 25 °C is overestimated by at least two orders of magnitude.

  4. Laser beam pulse formatting method

    DOEpatents

    Daly, Thomas P.; Moses, Edward I.; Patterson, Ralph W.; Sawicki, Richard H.

    1994-01-01

    A method for formatting a laser beam pulse (20) using one or more delay loops (10). The delay loops (10) have a partially reflective beam splitter (12) and a plurality of highly reflective mirrors (14) arranged such that the laser beam pulse (20) enters into the delay loop (10) through the beam splitter (12) and circulates therein along a delay loop length (24) defined by the mirrors (14). As the laser beam pulse (20) circulates within the delay loop (10) a portion thereof is emitted upon each completed circuit when the laser beam pulse (20) strikes the beam splitter (12). The laser beam pulse (20) is thereby formatted into a plurality of sub-pulses (50, 52, 54 and 56). The delay loops (10) are used in combination to produce complex waveforms by combining the sub-pulses (50, 52, 54 and 56) using additive waveform synthesis.

  5. Chemical, pulse radiolysis and density functional studies of a new, labile 5,6-indolequinone and its semiquinone.

    PubMed

    Pezzella, Alessandro; Crescenzi, Orlando; Natangelo, Anna; Panzella, Lucia; Napolitano, Alessandra; Navaratnam, Suppiah; Edge, Ruth; Land, Edward J; Barone, Vincenzo; d'Ischia, Marco

    2007-03-02

    The chemical and spectroscopic characterization of 5,6-indolequinones and their semiquinones, key transient intermediates in the oxidative conversion of 5,6-dihydroxyindoles to eumelanin biopolymers, is a most challenging task. In the present paper, we report the characterization of a novel, relatively long-lived 5,6-indolequinone along with its semiquinone using an integrated chemical, pulse radiolytic, and computational approach. The quinone was obtained by oxidation of 5,6-dihydroxy-3-iodoindole (1a) with o-chloranil in cold ethyl acetate or aqueous buffer: it displayed electronic absorption bands around 400 and 600 nm, was reduced to 1a with Na2S2O4, and reacted with o-phenylenediamine to give small amounts of 3-iodo-1H-pyrrolo[2,3-b]phenazine (2). The semiquinone exhibited absorption maxima at 380 nm (sh) and 520 nm and was detected as the initial species produced by pulse radiolytic oxidation of 1a at pH 7.0. DFT investigations indicated the 6-phenoxyl radical and the N-protonated radical anion as the most stable tautomers for the neutral and anion forms of the semiquinone, respectively. Calculated absorption spectra in water gave bands at 350 (sh) and 500 nm for the neutral form and at 310 and 360 (sh) nm for the anion. Disproportionation of the semiquinone with fast second-order kinetics (2k = 1.1 x 1010 M-1 s-1) gave a chromophore with absorption bands resembling those of chemically generated 1a quinone. Computational analysis predicted 1a quinone to exist in vacuo as the quinone-methide tautomer, displaying low energy transitions at 380 and 710 nm, and in water as the o-quinone, with calculated absorption bands around 400 and 820 nm. A strong participation of a p orbital on the iodine atom in the 360-380 nm electronic transitions of the o-quinone and quinone-methide was highlighted. The satisfactory agreement between computational and experimental electronic absorption data would suggest partitioning of 1a quinone between the o-quinone and quinone

  6. Pulsed ultrasonic stir welding method

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    A method of performing ultrasonic stir welding uses a welding head assembly to include a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. In the method, the rod is rotated about its longitudinal axis during a welding operation. During the welding operation, a series of on-off ultrasonic pulses are applied to the rod such that they propagate parallel to the rod's longitudinal axis. At least a pulse rate associated with the on-off ultrasonic pulses is controlled.

  7. Radiolysis of boiling water

    NASA Astrophysics Data System (ADS)

    Yang, Shuang; Katsumura, Yosuke; Yamashita, Shinichi; Matsuura, Chihiro; Hiroishi, Daisuke; Lertnaisat, Phantira; Taguchi, Mitsumasa

    2016-06-01

    γ-radiolysis of boiling water has been investigated. The G-value of H2 evolution was found to be very sensitive to the purity of water. In high-purity water, both H2 and O2 gases were formed in the stoichiometric ratio of 2:1; a negligible amount of H2O2 remained in the liquid phase. The G-values of H2 and O2 gas evolution depend on the dose rate: lower dose rates produce larger yields. To clarify the importance of the interface between liquid and gas phase for gas evolution, the gas evolution under Ar gas bubbling was measured. A large amount of H2 was detected, similar to the radiolysis of boiling water. The evolution of gas was enhanced in a 0.5 M NaCl aqueous solution. Deterministic chemical kinetics simulation elucidated the mechanism of radiolysis in boiling water.

  8. Interfacial electron-transfer equilibria and flat-band potentials of. cap alpha. -Fe/sub 2/O/sub 3/ and TiO/sub 2/ colloids studied by pulse radiolysis

    SciTech Connect

    Dimitrijevic, N.M.; Savic, D.; Micic, O.I.; Nozik, A.J.

    1984-09-13

    The kinetics and equilibria of electron transfer between methylviologen cation radicals and ..cap alpha..-Fe/sub 2/O/sub 3/ or TiO/sub 2/ colloidal particles were studied with the pulse-radiolysis technique. The rates of electron transfer to both colloids are lower than those predicted for a diffusion-controlled reaction. For higher pHs (TiO/sub 2/, pH > 2; ..cap alpha..-Fe/sub 2/O/sub 3/, pH > 9) the established equilibrium MV/sup +/ in equilibrium MV/sup 2 +/ + (e/sup -/)/sub coll/ is strongly influenced by the MV/sup 2 +/ concentration and pH. The MV/sup +/ equilibrium concentration can be exploited to derive the flat-band potential of the semiconductor colloids. The method for determining the flat-band potential of the particles is independent of whether the injected electrons are free or trapped, and whether the electrons raise the bulk Fermi level toward the conduction band or just produce a space charge. The flat-band potentials for both colloids appear to be somewhat more negative (-0.1 to -0.2 V) than the corresponding single-crystal electrodes. Also, the flat-band potentials become slightly more negative with increasing radiation dose (initial MV/sup +/ concentration). The effect of absorbed radiation dose is explained by the corresponding changes in the ratio of oxidized to reduced forms of the redox couple, which in turn changes the adsorbed ionic charge on the semiconductor surface. For colloidal particles of TiO/sub 2/ stabilized by poly(vinyl alcohol) (PVA), the flat-band potentials were almost the same as those for PVA-free TiO/sub 2/ sols. The decrease of particle diameter from 800 to 70 A does not affect the value of the flat-band potentials for TiO/sub 2/ and ..cap alpha..-Fe/sub 2/O/sub 3/ colloids. 28 references, 9 figures.

  9. Radiolysis Process Model

    SciTech Connect

    Buck, Edgar C.; Wittman, Richard S.; Skomurski, Frances N.; Cantrell, Kirk J.; McNamara, Bruce K.; Soderquist, Chuck Z.

    2012-07-17

    Assessing the performance of spent (used) nuclear fuel in geological repository requires quantification of time-dependent phenomena that may influence its behavior on a time-scale up to millions of years. A high-level waste repository environment will be a dynamic redox system because of the time-dependent generation of radiolytic oxidants and reductants and the corrosion of Fe-bearing canister materials. One major difference between used fuel and natural analogues, including unirradiated UO2, is the intense radiolytic field. The radiation emitted by used fuel can produce radiolysis products in the presence of water vapor or a thin-film of water (including OH• and H• radicals, O2-, eaq, H2O2, H2, and O2) that may increase the waste form degradation rate and change radionuclide behavior. H2O2 is the dominant oxidant for spent nuclear fuel in an O2 depleted water environment, the most sensitive parameters have been identified with respect to predictions of a radiolysis model under typical conditions. As compared with the full model with about 100 reactions it was found that only 30-40 of the reactions are required to determine [H2O2] to one part in 10–5 and to preserve most of the predictions for major species. This allows a systematic approach for model simplification and offers guidance in designing experiments for validation.

  10. Magnetic Alignment of Pulsed Solenoids Using the Pulsed Wire Method

    SciTech Connect

    Arbelaez, D.; Madur, A.; Lipton, T.M.; Waldron, W.L.; Kwan, J.W.

    2011-04-01

    A unique application of the pulsed-wire measurement method has been implemented for alignment of 2.5 T pulsed solenoid magnets. The magnetic axis measurement has been shown to have a resolution of better than 25 {micro}m. The accuracy of the technique allows for the identification of inherent field errors due to, for example, the winding layer transitions and the current leads. The alignment system is developed for the induction accelerator NDCX-II under construction at LBNL, an upgraded Neutralized Drift Compression experiment for research on warm dense matter and heavy ion fusion. Precise alignment is essential for NDCX-II, since the ion beam has a large energy spread associated with the rapid pulse compression such that misalignments lead to corkscrew deformation of the beam and reduced intensity at focus. The ability to align the magnetic axis of the pulsed solenoids to within 100 pm of the induction cell axis has been demonstrated.

  11. Oxidation of amino-containing disulfides by Br/sub 2//sup -/ and OH: a pulse-radiolysis study. [1. 5 MeV electrons

    SciTech Connect

    Elliot, A.J.; McEachern, R.J.; Armstrong, D.A.

    1981-01-08

    The rate constant for reaction of Br/sub 2/ radicals with dithiodipropionic acid (approx. 4.2 x 10/sup 8/ mol/sup -1/dm/sup 3/s/sup -1/) was independent of pH in the range 6.6-11.0 and was approx. 4.5 times smaller than those for the neutral dimethyl and diethyl disulfides Br/sub 2//sup -/ only reacted with the disulfides of cysteamine, cysteine, and penicillamine with an appreciable rate (> 10/sup 8/mol/sup -1/dm/sup 3/s/sup -1/) when one or both of the amino groups were unprotonated. Homocystine was less sensitive to the degree of protonation. While the reaction of Br/sub 2/ radicals with dithiodipropionic acid yielded a transient (lambda/sub max/ approx. = 450 nm) which possessed the characteristics of a disulfide cation, the amino-containing disulfides cited above produced transients which adsorbed with a lambda/sub max/ near 380 nm. The latter transients decayed by second-order kinetics over the pH range studied, and they gave no evidence of reaction with OH/sup -/. These species have been tentatively identified as perthiyl (RSS.) radicals. Hydroxyl radicals produced composite spectra consisting of the 380-nm species and other transients which absorbed below 350 nm. Oxidized glutathione gave only weak absorptions on reaction with Br/sub 2/ and OH radicals. The yields of sulfydryl molecules have been measured for cystine and dithiodipropionic acid. The mechanisms of radiolysis are discussed in the light of present results and earlier studies.

  12. Radiolysis of berberine or palmatine in aqueous solution

    NASA Astrophysics Data System (ADS)

    Marszalek, Milena; Wolszczak, Marian

    2011-01-01

    The reactions of hydrated electron (eaq-), hydrogen atom (H rad ) (reducing species) and Cl2•-, Br2•-, N,O•H radicals (oxidizing species) with berberine or palmatine in aqueous solution have been studied by steady-state and pulse radiolysis. The spectra of transient intermediates, leading to the final products, are presented. The rate constants of the reaction of eaq- and rad OH radical with both alkaloids in the homogenous solution and in the presence of DNA are reported. It is demonstrated that the primary products of the reaction of berberine and palmatine with eaq- and radicals generated during radiolysis are unstable and undergo further reactions.

  13. Reaction mechanisms in the radiolysis of peptides, polypeptides and proteins

    SciTech Connect

    Garrison, W.M.

    1985-01-01

    The purpose of this review is to bring together and to correlate the wide variety of experimental studies that provide information on the reaction products and reaction mechanisms involved in the radiolysis of peptides, polypeptides and proteins (including chromosomal proteins) in both aqueous and solid-state systems. The comparative radiation chemistry of these systems is developed in terms of specific reactions of the peptide main-chain and the aliphatic, aromatic-unsaturated and sulfur-containing side-chains. Information obtained with the various experimental techniques of product analysis, competition kinetics, spin-trapping, pulse radiolysis and ESR spectroscopy is included. 147 refs.

  14. A pulse-radiolysis study on the kinetics of reaction of PW{sub 12}O{sub 40}{sup 4{minus}} heteropolytungstate blue with Np(VI) ions in aqueous acid solutions

    SciTech Connect

    Gogolev, A.V.; Shilov, V.P.; Fedoseev, A.M.

    1994-11-01

    Data on the kinetics of redox reactions with the participation of heteropoly compounds may be of interest in photochemistry, radiation chemistry, catalysis, and other branches of physical chemistry. The structure of heteropoly blues is the same as that of the initial heteropoly compounds. Because of this, the oxidation of blues by metal ions can proceed quite readily. Presently, data on the interaction of blues with 5f-element ions is lacking. As a part of a systematic study on the reactivity of free radicals and excited species to actinide ions, the authors used a pulse-radiolysis technique to determine the rate constant of the reaction: Np(VI) + PW{sub 12}O{sub 40}{sup 4{minus}} {yields} Np(V) + PW{sub 12}O{sub 40}{sup 3{minus}}, k{sub 1} = ? The ions of Np(VI) were chosen as oxidizing agents because of their relatively high redox potential (1.13 V), and the resemblance of the structure of Np(VI) and Np(V) ions.

  15. Reduction potential of the sulfhydryl radical: Pulse radiolysis and laser flash photolysis studies of the formation and reactions of {sm_bullet}SH and HSSH{sm_bullet}{sup {minus}} in aqueous solutions

    SciTech Connect

    Das, T.N.; Huie, R.E.; Neta, P.; Padmaja, S.

    1999-07-08

    H{sub 2}S, which is a very toxic gas, has a large number of natural and anthropogenic sources, and the safe removal of this substance has been a matter of ongoing industrial concern. Formation and reactions of the {sm_bullet}SH/{sm_bullet}S{sup {minus}} and HSSH{sm_bullet}{sup {minus}}/HSS{sm_bullet}{sup 2{minus}} radicals in aqueous solutions have been studied by excimer laser flash photolysis and by pulse radiolysis. Acidic H{sub 2}S solutions can be photolyzed with 193 nm laser pulses and produce a transient species with {lambda}{sub max} at 240 nm, ascribed to the {sm_bullet}SH/{sm_bullet}S{sup {minus}} radical. Solutions of SH{sup {minus}} can be photolyzed also with 248 nm laser pulses to produce the {sm_bullet}SH/{sm_bullet}S{sup {minus}} reacts with SH{sup {minus}} ({kappa}{sub f} = 4 {times} 10{sup 9} L/mol s, {kappa}{sub r} = 5 {times} 10{sup 5} s{sup {minus}1}) to form HSSH{sm_bullet}{sup {minus}}/HSS{sm_bullet}{sup 2{minus}}, with {lambda}{sub max} at 380 nm. Both {sm_bullet}SH/{sm_bullet}S{sup {minus}} and HSSH{sm_bullet}{sup {minus}}/HSS{sm_bullet}{sup 2{minus}} react rapidly with O{sub 2}; the former produces SO{sub 2}{sm_bullet}{sup {minus}} ({kappa} = 5 {times} 10{sup 9} L/mol s), and the latter produces O{sub 2}{sm_bullet} ({kappa} = 4 {times} 10{sup 8} L/mol s). Both radicals react with olefinic compounds. The monomeric radical oxidizes Fe(CN){sub 6}{sup 4{minus}}, SO{sub 3}{sup 2{minus}}, ClO{sub 2}{sup {minus}}, and chlorpromazine. The dimeric radical is a weaker oxidant toward ferrocyanide but reduces N-methylpyridinium compounds. The reduction potential for the dimeric radical at pH 7 was determined from one-electron transfer equilibria with Mo(CN){sub 8}{sup 3{minus}} and with the 4-methoxyaniline radical cation and found to be 0.69 V vs NHE. From the equilibrium constant K = [HSS{sm_bullet}{sup 2{minus}}]/[SH{sup {minus}}][{sm_bullet}S{sup {minus}}] = 8 {times} 10{sup 3} L/mol, the reduction potential for ({sm_bullet}S{sup {minus

  16. Excited states and reduced and oxidized forms of a textile diazo dye, naphthol blue black. Spectral characterization using laser flash photolysis and pulse radiolysis studies

    NASA Astrophysics Data System (ADS)

    Nasr, Chouhaid; Vinodgopal, K.; Hotchandani, Surat; Chattopadhyay, A. K.; Kamat, Prashant V.

    1997-01-01

    The excited singlet and triplet states of a diazo textile dye (Naphthol Blue Black) have been investigated by pico and nanosecond flash photolysis. The excited singlet state shows a difference absorption maximum at 500 nm and has a lifetime of 25-30 ps in ethanol. The triplet excited state generated by triplet-triplet energy transfer shows an absorption maxima at 710-730 nm. The oxidized form as well as the reduced form of the diazo dye have been generated pulse radiolytically by reacting with azide and e aq radicals, respectively. Preliminary results of the photoelectrochemical irreversible reduction of Naphthol Blue Black in colloidal TiO 2 are also reported.

  17. Interaction of radicals from water radiolysis with melanin.

    PubMed

    Sarna, T; Pilas, B; Land, E J; Truscott, T G

    1986-08-06

    Melanins are considered to be natural photoprotectors in the melanocytes and keratinocytes of the skin. These pigments have also been suggested to play an important role in protection of melanin-containing cells against ionising radiation. Various mechanisms have been proposed to explain the protective role of melanin which invoke the radical scavenging properties of the polymer. In the present work the reactions of melanins with radicals generated in aqueous media by pulse radiolysis have been studied. Time-resolved changes in absorbance of the melanin or the radical species were recorded at selected wavelengths. Experiments were carried out on synthetic dopa- and 5-S-cysteinyldopa-melanins and a natural melanin in phosphate buffer (pH 7.4). Under the conditions employed, melanin reacted predominantly with either oxidising (OH., N3.) or reducing (eaq-, CO2-) species. We were also able to monitor the interaction of melanin with superoxide radical, which was reducing in this case. Detailed analysis of transient changes in melanin absorbance, detected at different wavelengths, was demonstrated to be a convenient method for studying redox processes of this substance, as shown by model experiments using ferricyanide and dithionite as oxidising and reducing agents, respectively. Among the radicals studied, OH. exhibited the strongest reactivity with melanins. Apparent rate constants for the reactions of radicals with autoxidative dopa-melanin (1.5 X 10(9) M-1 X s-1, 2.6 X 10(8) M-1 X s-1, 1.8 X 10(8) M-1 X s-1, 5 X 10(5) M-1 X s-1, 10(6)-10(7) M-1 X s-1 for OH., eaq-, N.3. O2- and CO2-, respectively) are reported. The reactivity of melanins with radicals from water radiolysis and their effect on pigment properties are discussed in terms of the structure and possible biological role of the pigments.

  18. Pulsed Electric Propulsion Thrust Stand Calibration Method

    NASA Technical Reports Server (NTRS)

    Wong, Andrea R.; Polzin, Kurt A.; Pearson, J. Boise

    2011-01-01

    The evaluation of the performance of any propulsion device requires the accurate measurement of thrust. While chemical rocket thrust is typically measured using a load cell, the low thrust levels associated with electric propulsion (EP) systems necessitate the use of much more sensitive measurement techniques. The design and development of electric propulsion thrust stands that employ a conventional hanging pendulum arm connected to a balance mechanism consisting of a secondary arm and variable linkage have been reported in recent publications by Polzin et al. These works focused on performing steady-state thrust measurements and employed a static analysis of the thrust stand response. In the present work, we present a calibration method and data that will permit pulsed thrust measurements using the Variable Amplitude Hanging Pendulum with Extended Range (VAHPER) thrust stand. Pulsed thrust measurements are challenging in general because the pulsed thrust (impulse bit) occurs over a short timescale (typically 1 micros to 1 millisecond) and cannot be resolved directly. Consequently, the imparted impulse bit must be inferred through observation of the change in thrust stand motion effected by the pulse. Pulsed thrust measurements have typically only consisted of single-shot operation. In the present work, we discuss repetition-rate pulsed thruster operation and describe a method to perform these measurements. The thrust stand response can be modeled as a spring-mass-damper system with a repetitive delta forcing function to represent the impulsive action of the thruster.

  19. Generic Sensor Modeling Using Pulse Method

    NASA Technical Reports Server (NTRS)

    Helder, Dennis L.; Choi, Taeyoung

    2005-01-01

    Recent development of high spatial resolution satellites such as IKONOS, Quickbird and Orbview enable observation of the Earth's surface with sub-meter resolution. Compared to the 30 meter resolution of Landsat 5 TM, the amount of information in the output image was dramatically increased. In this era of high spatial resolution, the estimation of spatial quality of images is gaining attention. Historically, the Modulation Transfer Function (MTF) concept has been used to estimate an imaging system's spatial quality. Sometimes classified by target shapes, various methods were developed in laboratory environment utilizing sinusoidal inputs, periodic bar patterns and narrow slits. On-orbit sensor MTF estimation was performed on 30-meter GSD Landsat4 Thematic Mapper (TM) data from the bridge pulse target as a pulse input . Because of a high resolution sensor s small Ground Sampling Distance (GSD), reasonably sized man-made edge, pulse, and impulse targets can be deployed on a uniform grassy area with accurate control of ground targets using tarps and convex mirrors. All the previous work cited calculated MTF without testing the MTF estimator's performance. In previous report, a numerical generic sensor model had been developed to simulate and improve the performance of on-orbit MTF estimating techniques. Results from the previous sensor modeling report that have been incorporated into standard MTF estimation work include Fermi edge detection and the newly developed 4th order modified Savitzky-Golay (MSG) interpolation technique. Noise sensitivity had been studied by performing simulations on known noise sources and a sensor model. Extensive investigation was done to characterize multi-resolution ground noise. Finally, angle simulation was tested by using synthetic pulse targets with angles from 2 to 15 degrees, several brightness levels, and different noise levels from both ground targets and imaging system. As a continuing research activity using the developed sensor

  20. Chaotic carrier pulse position modulation communication system and method

    DOEpatents

    Abarbanel, Henry D. I.; Larson, Lawrence E.; Rulkov, Nikolai F.; Sushchik, Mikhail M.; Tsimring, Lev S.; Volkovskii, Alexander R.

    2001-01-01

    A chaotic carrier pulse position modulation communication system and method is disclosed. The system includes a transmitter and receiver having matched chaotic pulse regenerators. The chaotic pulse regenerator in the receiver produces a synchronized replica of a chaotic pulse train generated by the regenerator in the transmitter. The pulse train from the transmitter can therefore act as a carrier signal. Data is encoded by the transmitter through selectively altering the interpulse timing between pulses in the chaotic pulse train. The altered pulse train is transmitted as a pulse signal. The receiver can detect whether a particular interpulse interval in the pulse signal has been altered by reference to the synchronized replica it generates, and can therefore detect the data transmitted by the receiver. Preferably, the receiver predicts the earliest moment in time it can expect a next pulse after observation of at least two consecutive pulses. It then decodes the pulse signal beginning at a short time before expected arrival of a pulse.

  1. Radiolysis of Bicarbonate and Carbonate Aqueous Solutions: Product Analysis and Simulation of Radiolytic Processes

    SciTech Connect

    Cai Zhongli; Li Xifeng; Katsumura, Yosuke; Urabe, Osamu

    2001-11-15

    An understanding of the radiation-induced effects in groundwater is essential to evaluate the safe geological disposal of spent fuel. In groundwater, the bicarbonate ion is the predominant and common anion; this work investigated radiation-induced chemical reactions of (bi)carbonate aqueous solutions with steady-state irradiation and pulse radiolysis methods. Aqueous solutions of sodium (bi)carbonate as high as 50 mmol.dm{sup -3} were used. The formation of formate, oxalate, and H{sub 2}O{sub 2} were measured under different conditions. A complete set of reaction steps and reliable kinetic data for the radiolysis of (bi)carbonate aqueous solutions at ionic strength close to the groundwater were proposed. Kinetic calculations were completed based on the proposed reaction steps and the kinetic data obtained in the present work. The results from the calculation are in good agreement with the experimental results. With these proposed reaction steps and kinetic data, computer simulation can be performed to predict the yield of radiolytic products of (bi)carbonate aqueous solutions as a function of irradiation time and used to evaluate the safety of geological disposal options of spent fuel.

  2. Pulsed source ion implantation apparatus and method

    DOEpatents

    Leung, K.N.

    1996-09-24

    A new pulsed plasma-immersion ion-implantation apparatus that implants ions in large irregularly shaped objects to controllable depth without overheating the target, minimizing voltage breakdown, and using a constant electrical bias applied to the target. Instead of pulsing the voltage applied to the target, the plasma source, for example a tungsten filament or a RF antenna, is pulsed. Both electrically conducting and insulating targets can be implanted. 16 figs.

  3. Pulsed source ion implantation apparatus and method

    DOEpatents

    Leung, Ka-Ngo

    1996-01-01

    A new pulsed plasma-immersion ion-implantation apparatus that implants ions in large irregularly shaped objects to controllable depth without overheating the target, minimizing voltage breakdown, and using a constant electrical bias applied to the target. Instead of pulsing the voltage applied to the target, the plasma source, for example a tungsten filament or a RF antenna, is pulsed. Both electrically conducting and insulating targets can be implanted.

  4. Studies on oxidative radiolysis of ibuprofen in presence of potassium persulfate

    NASA Astrophysics Data System (ADS)

    Paul (Guin), Jhimli; Naik, D. B.; Bhardwaj, Y. K.; Varshney, Lalit

    2014-07-01

    The radiolysis of ibuprofen (IBP), a model pharmaceutical compound, was studied by gamma irradiation in an aqueous solution in the presence and absence of potassium persulfate (K2S2O8). The extent of mineralization was investigated by measuring the UV-visible spectra, decrease in the chemical oxygen demand (COD) and the total organic carbon (TOC) content of aqueous IBP solution at different doses. The gamma radiolysis, in the presence of K2S2O8, required much lesser dose compared to in the absence of K2S2O8 for the same extent of mineralization of aqueous IBP solution. The pulse radiolysis of IBP was carried out under different radiolytic conditions to understand the mechanism of efficient mineralization of IBP during gamma radiolysis in the presence of K2S2O8. It was found that unlike radOH radical, SO4rad - radical preferentially produces benzyl type of radicals via the formation of the benzene radical cation. The results concluded that the gamma radiolysis in presence of K2S2O8 could be one of the efficient advanced oxidation processes for degradation of pharmaceutical compounds present in the aqueous solution.

  5. Stably operating pulse combustor and method

    DOEpatents

    Zinn, B.T.; Reiner, D.

    1990-05-29

    A pulse combustor apparatus is described which is adapted to burn either a liquid fuel or a pulverized solid fuel within a preselected volume of the combustion chamber. The combustion process is substantially restricted to an optimum combustion zone in order to attain effective pulse combustion operation. 4 figs.

  6. Stably operating pulse combustor and method

    DOEpatents

    Zinn, Ben T.; Reiner, David

    1990-01-01

    A pulse combustor apparatus adapted to burn either a liquid fuel or a pulverized solid fuel within a preselected volume of the combustion chamber. The combustion process is substantially restricted to an optimum combustion zone in order to attain effective pulse combustion operation.

  7. Pulse front adaptive optics: a new method for control of ultrashort laser pulses.

    PubMed

    Sun, Bangshan; Salter, Patrick S; Booth, Martin J

    2015-07-27

    Ultrafast lasers enable a wide range of physics research and the manipulation of short pulses is a critical part of the ultrafast tool kit. Current methods of laser pulse shaping are usually considered separately in either the spatial or the temporal domain, but laser pulses are complex entities existing in four dimensions, so full freedom of manipulation requires advanced forms of spatiotemporal control. We demonstrate through a combination of adaptable diffractive and reflective optical elements - a liquid crystal spatial light modulator (SLM) and a deformable mirror (DM) - decoupled spatial control over the pulse front (temporal group delay) and phase front of an ultra-short pulse was enabled. Pulse front modulation was confirmed through autocorrelation measurements. This new adaptive optics technique, for the first time enabling in principle arbitrary shaping of the pulse front, promises to offer a further level of control for ultrafast lasers.

  8. Apparatus and method for optical pulse measurement

    DOEpatents

    Trebino, Rick P.; Tsang, Thomas; Fittinghoff, David N.; Sweetser, John N.; Krumbuegel, Marco A.

    1999-12-28

    Practical third-order frequency-resolved optical grating (FROG) techniques for characterization of ultrashort optical pulses are disclosed. The techniques are particularly suited to the measurement of single and/or weak optical pulses having pulse durations in the picosecond and subpicosecond regime. The relative quantum inefficiency of third-order nonlinear optical effects is compensated for through i) use of phase-matched transient grating beam geometry to maximize interaction length, and ii) use of interface-enhanced third-harmonic generation.

  9. In honour of N. Yngve Öhrn: surveying proton cancer therapy reactions with Öhrn's electron nuclear dynamics method. Aqueous clusters radiolysis and DNA-base damage by proton collisions

    NASA Astrophysics Data System (ADS)

    Mclaurin, Patrick M.; Privett, Austin J.; Stopera, Christopher; Grimes, Thomas V.; Perera, Ajith; Morales, Jorge A.

    2015-02-01

    Proton cancer therapy (PCT) utilises high-energy H+ projectiles to cure cancer. PCT healing arises from its DNA damage in cancerous cells, which is mostly inflicted by the products from PCT water radiolysis reactions. While clinically established, a complete microscopic understanding of PCT remains elusive. To help in the microscopic elucidation of PCT, Professor Öhrn's simplest-level electron nuclear dynamics (SLEND) method is herein applied to H+ + (H2O)3-4 and H+ + DNA-bases at ELab = 1.0 keV. These are two types of computationally feasible prototypes to study water radiolysis reactions and H+-induced DNA damage, respectively. SLEND is a time-dependent, variational, non-adiabatic and direct-dynamics method that adopts a nuclear classical-mechanics description and an electronic single-determinantal wavefunction. Additionally, our SLEND + effective-core-potential method is herein employed to simulate some computationally demanding PCT reactions. Due to these attributes, SLEND proves appropriate for the simulation of various types of PCT reactions accurately and feasibly. H+ + (H2O)3-4 simulations reveal two main processes: H+ projectile scattering and the simultaneous formation of H and OH fragments; the latter process is quantified through total integrals cross sections. H+ + DNA-base simulations reveal atoms and groups displacements, ring openings and base-to-proton electron transfers as predominant damage processes. The authors warmly dedicate this SLEND investigation in honour of Professor N. Yngve Öhrn on the occasion of his 80th birthday celebration during the 54th Sanibel Symposium in St. Simons' Island, Georgia, on February 16-21, 2014. Associate Professor Jorge A. Morales was a former chemistry PhD student under the mentorship of Professor Öhrn and Dr Ajith Perera took various quantum chemistry courses taught by Professor Öhrn during his chemistry PhD studies. Both Jorge and Ajith look back to those great times of their scientific formation under

  10. A new method to produce short pulses

    NASA Astrophysics Data System (ADS)

    Germer, Rudolf

    2005-03-01

    If a coaxial cable or a strip line has an open end, then the incoming signal is reflected there. Due to the propagation velocity, an incoming rectangular pulse has a length in space which depends on its length in time. If the pulse length is twice the cable length, then after the reflection at the end, the pulse energy is distributed in an electrical field along the cable. Input and output current are compensating. At this time, it is possible to take out the energy simultanously through several switched connections at the same time. The result is a shorter pulse of much higher power which can drive a load of low impedance or with the pulse transformer presented at the 25th ICHSPP give a short pulse of very high voltage. This concentration in time of the electrical energy is planed to be used for x-ray flash systems. If the input pulse is not rectangular, then it is possible to take off the energy at the time of best peak power. Bei einem Bandleiter oder Koaxialkabel mit offenem Ende wird das auf der Leitung laufende Signal reflektiert. Die Ausdehnung eines Rechteckimpulses auf einer solchen Leitung entspricht seiner Dauer und der Ausbreitungsgeschwindigkeit auf der Leitung. Wenn die Impulsausdehnung doppelt so gross ist wie die Leitungslange, dann kann die gesamte Energie des Impulses nach der Reflexion im elektrischen Feld gespeichert sein, Eingangs und Reflexionsstrom kompensieren sich. Zu dieser Zeit ist es moglich, fast die ganze Energie gleichzeitig seitlich durch einen ausgedehnten oder mit mehreren einzelnen Schaltern an einen niederohmigen Verbraucher weiterzuleiten oder mit einem Impulstransformator ( gezeigt auf dem 25. ICHSPP ) an dessen Impedanz anzupassen. Der Ausgangsimpuls ist sehr kurz und von vervielfachter Leistung. Diese zeitliche Energiekonzentration soll spater fur Rontgenbltzsysteme verwendet werden. Im Falle eines nicht rechteckformigen Eingangsimpulses kann die Energie wahrend der hochsten Spitzenleistung entnommen werden.

  11. Laser pulse stretcher method and apparatus

    DOEpatents

    Hawkins, Jon K.; Williams, William A.

    1990-01-01

    The output of an oscillator stage of a laser system is monitored by a photocell which is coupled to a feedback section to control a Pockels Cell and change the light output of the oscillator stage. A synchronizing pulse is generated in timed relation to the initiation of operation of the oscillator stage and is applied to a forward feed section which cooperates with the feedback section to maintain the light output constant for an extended time interval.

  12. Laser pulse detection method and apparatus

    NASA Technical Reports Server (NTRS)

    Goss, W.; Janesick, J. R. (Inventor)

    1984-01-01

    A sensor is described for detecting the difference in phase of a pair of returned light pulse components, such as two components of a light pulse of an optical gyro. In an optic gyro, the two light components have passed in opposite directions through a coil of optical fiber, with the difference in phase of the returned light components determining the intensity of light shining on the sensor. The sensor includes a CCD (charge coupled device) that receives the pair of returned light components to generate a charge proportional to the number of photons in the received light. The amount of the charge represents the phase difference between the two light components. At a time after the transmission of the light pulse and before the expected time of arrival of the interfering light components, charge accumulating in the CCD as a result of reflections from components in the system, are repeatedly removed from the CCD, by transferring out charges in the CCD and dumping these charges.

  13. Laser pulse detection method and apparatus

    NASA Technical Reports Server (NTRS)

    Goss, Willis C. (Inventor); Janesick, James R. (Inventor)

    1987-01-01

    A sensor is described for detecting the difference in phase of a pair of returned light pulse components, such as the two components of a light pulse of an optical gyro. In an optic gyro, the two light components have passed in opposite directions through a coil of optical fiber, with the difference in phase of the returned light components determining the intensity of light shining on the sensor. The sensor includes a CCD (charge coupled device) that receives the pair of returned light components to generate a charge proportional to the number of photons in the received light. The amount of the charge represents the phase difference between the two light components. At a time after the transmission of the light pulse and before the expected time of arrival of the interfering light components, charge accumulating in the CCD as a result of reflections from optical components in the system, are repeatedly removed from the CCD, by transferring out charges in the CCD and dumping these charges.

  14. Radiolysis of water in sealed aluminum capsules - Its prediction and inhibition.

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.

    1971-01-01

    This report presents the results of an investigation into methods of inhibiting the radiolysis of water in sealed aluminum capsules in the Plum Brook Reactor of NASA. Experimental design techniques are employed to identify the measured effects of eight variables and their interactions which control water decomposition and the resultant pressure buildup. Multiple regression analyses are used to develop predictive models for the pressure rise observed in an inpile capsule system. Predictive equations are derived for pressure rise due to the radiolysis of water with air as a cover gas or with helium cover gas containing air as an impurity or mixtures of hydrogen, oxygen, and nitrogen as impurities. Radiation induced reaction products of nitrogen and oxygen are identified as the key to radiolysis behavior. The prevention of radiolysis depends on the exclusion of air or mixtures of nitrogen and oxygen from the system. Pure inert gases, helium, neon, and argon prove to be satisfactory radiolysis inhibitors. This is demonstrated for helium by inpile tests lasting up to 14 days (one reactor cycle) in the Plum Brook Reactor.

  15. Optimal pulse design in quantum control: A unified computational method

    PubMed Central

    Li, Jr-Shin; Ruths, Justin; Yu, Tsyr-Yan; Arthanari, Haribabu; Wagner, Gerhard

    2011-01-01

    Many key aspects of control of quantum systems involve manipulating a large quantum ensemble exhibiting variation in the value of parameters characterizing the system dynamics. Developing electromagnetic pulses to produce a desired evolution in the presence of such variation is a fundamental and challenging problem in this research area. We present such robust pulse designs as an optimal control problem of a continuum of bilinear systems with a common control function. We map this control problem of infinite dimension to a problem of polynomial approximation employing tools from geometric control theory. We then adopt this new notion and develop a unified computational method for optimal pulse design using ideas from pseudospectral approximations, by which a continuous-time optimal control problem of pulse design can be discretized to a constrained optimization problem with spectral accuracy. Furthermore, this is a highly flexible and efficient numerical method that requires low order of discretization and yields inherently smooth solutions. We demonstrate this method by designing effective broadband π/2 and π pulses with reduced rf energy and pulse duration, which show significant sensitivity enhancement at the edge of the spectrum over conventional pulses in 1D and 2D NMR spectroscopy experiments. PMID:21245345

  16. Pulsed interrupter and method of operation

    SciTech Connect

    Drake, Joel Lawton; Kratz, Robert

    2015-06-09

    Some embodiments provide interrupter systems comprising: a first electrode; a second electrode; a piston movably located at a first position and electrically coupled with the first and second electrodes establishing a closed state, the piston comprises an electrical conductor that couples with the first and second electrodes providing a conductive path; an electromagnetic launcher configured to, when activated, induce a magnetic field pulse causing the piston to move away from the electrical coupling with the first and second electrodes establishing an open circuit between the first and second electrodes; and a piston control system comprising a piston arresting system configured to control a deceleration of the piston following the movement of the piston induced by the electromagnetic launcher such that the piston is not in electrical contact with at least one of the first electrode and the second electrode when in the open state.

  17. Method and apparatus for analog pulse pile-up rejection

    DOEpatents

    De Geronimo, Gianluigi

    2013-12-31

    A method and apparatus for pulse pile-up rejection are disclosed. The apparatus comprises a delay value application constituent configured to receive a threshold-crossing time value, and provide an adjustable value according to a delay value and the threshold-crossing time value; and a comparison constituent configured to receive a peak-occurrence time value and the adjustable value, compare the peak-occurrence time value with the adjustable value, indicate pulse acceptance if the peak-occurrence time value is less than or equal to the adjustable value, and indicate pulse rejection if the peak-occurrence time value is greater than the adjustable value.

  18. Method and circuit for shaping laser output pulses

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P. (Inventor)

    1990-01-01

    The invention is a method and circuit for shaping laser pulses 17' in which a laser medium 12' in a laser resonator 10' that includes a Q-switch 14' and polarizer 13' which act in combination to control the loss of the resonator 10' and provide the laser output 17' representative of such loss. An optical diode 22' senses the level of the output pulse 17' and provides an output signal 23' that when amplified is used with a control voltage from a supply 29' provide a control signal 19' which is applied to Q-switch 14' to control the shape of the output pulse 17' by adjusting its length.

  19. Method and apparatus for analog pulse pile-up rejection

    DOEpatents

    De Geronimo, Gianluigi

    2014-11-18

    A method and apparatus for pulse pile-up rejection are disclosed. The apparatus comprises a delay value application constituent configured to receive a threshold-crossing time value, and provide an adjustable value according to a delay value and the threshold-crossing time value; and a comparison constituent configured to receive a peak-occurrence time value and the adjustable value, compare the peak-occurrence time value with the adjustable value, indicate pulse acceptance if the peak-occurrence time value is less than or equal to the adjustable value, and indicate pulse rejection if the peak-occurrence time value is greater than the adjustable value.

  20. Frequency-Domain Methods for Characterization of Pulsed Power Diagnostics

    SciTech Connect

    White, A D; Anderson, R A; Ferriera, T J; Goerz, D A

    2009-07-27

    This paper discusses methods of frequency-domain characterization of pulsed power sensors using vector network analyzer and spectrum analyzer techniques that offer significant simplification over time-domain methods, while mitigating or minimizing the effect of the difficulties present in time domain characterization. These methods are applicable to characterization of a wide variety of sensors.

  1. Neural network and area method interpretation of pulsed experiments

    SciTech Connect

    Dulla, S.; Picca, P.; Ravetto, P.; Canepa, S.

    2012-07-01

    The determination of the subcriticality level is an important issue in accelerator-driven system technology. The area method, originally introduced by N. G. Sjoestrand, is a classical technique to interpret flux measurement for pulsed experiments in order to reconstruct the reactivity value. In recent times other methods have also been developed, to account for spatial and spectral effects, which were not included in the area method, since it is based on the point kinetic model. The artificial neural network approach can be an efficient technique to infer reactivities from pulsed experiments. In the present work, some comparisons between the two methods are carried out and discussed. (authors)

  2. Gamma Ray Radiolysis of the FPEX Solvent

    SciTech Connect

    B. J. Mincher; S. P. Mezyk; D. R. Peterman

    2006-09-01

    Slide presentation. FPEX contains a calixarene for Cs extraction, a crown ether for Sr extraction, Cs7SB modifier, and TOA to aid in stripping, in Isopar L diluent. The radiation stability FPEX must be evaluated prior to process use. Radiolytic degradation of species in solution are due to reaction with the direct radiolysis products of the diluent. In Isopar L, the reactive species produced include e-, •H and alkane radicals, resulting in a reducing environment. However, in nitric acid, oxidizing hydroxyl (•OH) and nitro (•NO2) radicals dominate system chemistry. Thus, the nature of diluent and the presence of radical scavengers affect the results of irradiation. We report the preliminary results of a new program to investigate the radiolysis of FPEX using the 60Co irradiation of FPEX neat solvent, acid pre-equilibrated solvent and mixed aerated phases. The Cs and Sr distribution ratios were used as metrics.

  3. Spur decay kinetics of the solvated electron in heavy water radiolysis.

    SciTech Connect

    Bartels, D. M.; Gosztola, D.; Jonah, C. D.; Chemistry

    2001-08-30

    Spur decay kinetics of the hydrated electron following picosecond pulse radiolysis of heavy water have been measured using a time-correlated absorption spectroscopy (TCAS) technique. The TCAS data collected for the first 40 ns of the decay was matched up with single-shot transient digitizer data out to microsecond time scales. The decay shape in heavy water looks exactly like the decay in light water except in the first 10 ns. The 'time zero' solvated electron yield in heavy water radiolysis must be approximately 7% larger than in light water, to match the best available scavenger product measurements. We propose an explanation in terms of the larger distances traveled by electrons in heavy water prior to localization. The implication is that presolvated H{sub 2}O{sup +} 'holes' are very efficient scavengers for the presolvated conduction band electrons.

  4. Pulsed Plasma Lubrication Device and Method

    NASA Technical Reports Server (NTRS)

    Hofer, Richard R. (Inventor); Bickler, Donald B. (Inventor); D'Agostino, Saverio A. (Inventor)

    2016-01-01

    Disclosed herein is a lubrication device comprising a solid lubricant disposed between and in contact with a first electrode and a second electrode dimensioned and arranged such that application of an electric potential between the first electrode and the second electrode sufficient to produce an electric arc between the first electrode and the second electrode to produce a plasma in an ambient atmosphere at an ambient pressure which vaporizes at least a portion of the solid lubricant to produce a vapor stream comprising the solid lubricant. Methods to lubricate a surface utilizing the lubrication device in-situ are also disclosed.

  5. Arterial pulse system: modern methods for traditional Indian medicine.

    PubMed

    Joshi, Aniruddha; Chandran, Sharat; Jayaraman, V K; Kulkarni, B D

    2007-01-01

    Ayurveda is one of the most comprehensive healing systems in the world and has classified the body system according to the theory of Tridosha to overcome ailments. Diagnosis similar to the traditional pulse-based method requires a system of clean input signals, and extensive experiments for obtaining classification features. In this paper we briefly describe our system of generating pulse waveforms and use various feature detecting methods to show that an arterial pulse contains typical physiological properties. The beat-to-beat variability is captured using a complex B-spline mother wavelet based peak detection algorithm. We also capture--to our knowledge for the first time--the self-similarity in the physiological signal, and quantifiable chaotic behavior using recurrence plot structures.

  6. Effect of oxygen on the radiolysis of tyrosine in aqueous solutions

    SciTech Connect

    Cudina, I.; Josimovic, L.

    1987-02-01

    The effect of oxygen on the radiolysis of tyrosine in aqueous solutions was investigated by using gamma and pulsed electron irradiation. Steady-state radiolysis was reexamined and extended to include the effect of pH and determination of hydrogen peroxide. The loss of tyrosine, G(-Tyr), during irradiation and yields of 3,4-dihydroxyphenylalanine, G(DOPA), and hydrogen peroxide, G(H2O2), are determined in the pH range from 1 to 9. In the whole pH range used G(-Tyr) equals G(DOPA), and a higher G(H2O2) than expected was observed. In slightly acid and neutral media, both G(-Tyr) and G(DOPA) equal the yield of hydroxyl radicals, GOH, formed in the radiolysis of water, while the excess of hydrogen peroxide equals 1/2 GOH. Hence it was concluded that all tyrosine OH-adducts react with oxygen yielding peroxy radicals. In acid and alkaline media all measured yields decrease. This is caused by formation of tyrosine phenoxyl radicals (TyrO), which react with superoxide anion (O2-) and hydroperoxy (HO2) radicals regenerating tyrosine. By using pulse radiolysis K(TyrO + O2) less than or equal to 2 X 10(5) mol-1 dm3 s-1 and k(TyrO + O2-) = (1.7 +/- 0.2) X 10(9) mol-1 dm3 s-1 were determined. On the basis of the results, a reaction mechanism is proposed.

  7. Methods and devices for generation of broadband pulsed radiation

    DOEpatents

    Borguet, Eric; Isaienko, Oleksandr

    2013-05-14

    Methods and apparatus for non-collinear optical parametric ampliffication (NOPA) are provided. Broadband phase matching is achieved with a non-collinear geometry and a divergent signal seed to provide bandwidth gain. A chirp may be introduced into the pump pulse such that the white light seed is amplified in a broad spectral region.

  8. Method and apparatus for characterizing reflected ultrasonic pulses

    NASA Technical Reports Server (NTRS)

    Yost, William T. (Inventor); Cantrell, John H., Jr. (Inventor)

    1991-01-01

    The invention is a method of and apparatus for characterizing the amplitudes of a sequence of reflected pulses R1, R2, and R3 by converting them into corresponding electric signals E1, E2, and E3 to substantially the same value during each sequence thereby restoring the reflected pulses R1, R2, and R3 to their initial reflection values by timing means, an exponential generator, and a time gain compensator. Envelope and baseline reject circuits permit the display and accurate location of the time spaced sequence of electric signals having substantially the same amplitude on a measurement scale on a suitable video display or oscilloscope.

  9. About the OH yield in the radiolysis of an aqueous/H2O2 system. Its optimisation for water treatment

    NASA Astrophysics Data System (ADS)

    Emmi, Salvatore S.; Caminati, Serena; Esposito, Biagio; Saracino, Michela

    2012-09-01

    Unless the radiolytic reducing species are neutralised or converted into oxidising species, an EB remediation system cannot be considered a true Advanced Oxidation Processes (AOP). A water/H2O2 system irradiated by UVC mercury lamps constitutes a widely used OH production method. Employing H2O2 in radiolysis as well, an enhancement of the oxidative efficiency of an EB treatment can be obtained. Pulse radiolysis measurements of an aerated aqueous/H2O2/KSCN system have been systematically undertaken to assess the optimal H2O2 concentration. By linearly fitting a competition kinetics relationship, it is found that the scavengeable extra-yield of OH is ΔG(OH)=0.24 μmol J-1 (R=0,9958), while the maximum experimental yield is measured G(OH)max=(0.52±0.02) μmol J-1 when [H2O2]=5-10 mM. Exceeding these concentrations the OH yield drops off.

  10. Influence Pulse Duration Methodical Error of Determination of Thermal Translucent Materials Laser Flash Method

    NASA Astrophysics Data System (ADS)

    Katz, Mark M.; Katz, Ilija M.

    2016-02-01

    The analysis of errors in the determination of thermal diffusivity of a typical semiconductor material - Germany, due to radiative energy transfer in the heated layer of material, under conditions consistent with the implementation of the method under the influence of the laser pulse on the surface of the collimated laser pulse of finite duration.

  11. Comparison of pulse phase and thermographic signal reconstruction processing methods

    NASA Astrophysics Data System (ADS)

    Oswald-Tranta, Beata; Shepard, Steven M.

    2013-05-01

    Active thermography data for nondestructive testing has traditionally been evaluated by either visual or numerical identification of anomalous surface temperature contrast in the IR image sequence obtained as the target sample cools in response to thermal stimulation. However, in recent years, it has been demonstrated that considerably more information about the subsurface condition of a sample can be obtained by evaluating the time history of each pixel independently. In this paper, we evaluate the capabilities of two such analysis techniques, Pulse Phase Thermography (PPT) and Thermographic Signal Reconstruction (TSR) using induction and optical flash excitation. Data sequences from optical pulse and scanned induction heating are analyzed with both methods. Results are evaluated in terms of signal-tobackground ratio for a given subsurface feature. In addition to the experimental data, we present finite element simulation models with varying flaw diameter and depth, and discuss size measurement accuracy and the effect of noise on detection limits and sensitivity for both methods.

  12. Long-laser-pulse method of producing thin films

    DOEpatents

    Balooch, Mehdi; Olander, Donald K.; Russo, Richard E.

    1991-01-01

    A method of depositing thin films by means of laser vaporization employs a long-pulse laser (Nd-glass of about one millisecond duration) with a peak power density typically in the range 10.sup.5 -10.sup.6 W/cm.sup.2. The method may be used to produce high T.sub.c superconducting films of perovskite material. In one embodiment, a few hundred nanometers thick film of YBa.sub.2 Cu.sub.3 O.sub.7-x is produced on a SrTiO.sub.3 crystal substrate in one or two pulses. In situ-recrystallization and post-annealing, both at elevated temperature and in the presence of an oxidizing agen The invention described herein arose in the course of, or under, Contract No. DE-C03-76SF0098 between the United States Department of Energy and the University of California.

  13. Radiolysis of cyanocobalamin (vitamin B 12)

    NASA Astrophysics Data System (ADS)

    Juanchi, X.; Albarran, G.; Negron-Mendoza, A.

    2000-03-01

    Research on the radiolysis of vitamins is of considerable interest since these compounds are important nutritional constituents in foods and in dietetic supplements. In spite of these considerations there are few data and very often difficult to compare for the radiolytic behavior of vitamins. In this work we focused our attention on to the study of the radiolysis of cyanocobalamin (vitamin B 12) in solid state and in aqueous solutions. The procedure was followed by HPLC and UV-spectroscopy. The results obtained in aqueous solutions showed a dependence of the decomposition as a linear function of the dose. The G of decomposition for a 1×10 -5 M solution was 3.3. In the solid state the vitamin was very stable towards the irradiation in the conditions used in this study with a G=2.1×10 -3. A study made with Serratia marcescens as a microbiological contaminant showed that at the sterilization dose there is a destruction of the vitamin in aqueous solution. In the solid state the degree of decomposition was 7%.

  14. A new pulsed laser deposition technique: Scanning multi-component pulsed laser deposition method

    SciTech Connect

    Fischer, D.; Jansen, M.; Fuente, G. F. de la

    2012-04-15

    The scanning multi-component pulsed laser deposition (PLD) method realizes uniform depositions of desired coatings by a modified pulsed laser deposition process, preferably with a femto-second laser-system. Multi-component coatings (single or multilayered) are thus deposited onto substrates via laser induced ablation of segmented targets. This is achieved via horizontal line-scanning of a focused laser beam over a uniformly moving target's surface. This process allows to deposit the desired composition of the coating simultaneously, starting from the different segments of the target and adjusting the scan line as a function of target geometry. The sequence and thickness of multilayers can easily be adjusted by target architecture and motion, enabling inter/intra layer concentration gradients and thus functional gradient coatings. This new, simple PLD method enables the achievement of uniform, large-area coatings. Case studies were performed with segmented targets containing aluminum, titanium, and niobium. Under the laser irradiation conditions applied, all three metals were uniformly ablated. The elemental composition within the rough coatings obtained was fixed by the scanned area to Ti-Al-Nb = 1:1:1. Crystalline aluminum, titanium, and niobium were found to coexist side by side at room temperature within the substrate, without alloy formation up to 600 deg. C.

  15. A new pulsed laser deposition technique: scanning multi-component pulsed laser deposition method.

    PubMed

    Fischer, D; de la Fuente, G F; Jansen, M

    2012-04-01

    The scanning multi-component pulsed laser deposition (PLD) method realizes uniform depositions of desired coatings by a modified pulsed laser deposition process, preferably with a femto-second laser-system. Multi-component coatings (single or multilayered) are thus deposited onto substrates via laser induced ablation of segmented targets. This is achieved via horizontal line-scanning of a focused laser beam over a uniformly moving target's surface. This process allows to deposit the desired composition of the coating simultaneously, starting from the different segments of the target and adjusting the scan line as a function of target geometry. The sequence and thickness of multilayers can easily be adjusted by target architecture and motion, enabling inter/intra layer concentration gradients and thus functional gradient coatings. This new, simple PLD method enables the achievement of uniform, large-area coatings. Case studies were performed with segmented targets containing aluminum, titanium, and niobium. Under the laser irradiation conditions applied, all three metals were uniformly ablated. The elemental composition within the rough coatings obtained was fixed by the scanned area to Ti-Al-Nb = 1:1:1. Crystalline aluminum, titanium, and niobium were found to coexist side by side at room temperature within the substrate, without alloy formation up to 600 °C.

  16. Method and means of transmitting and receiving broad-band unipolar, ultrasonic pulses for ultrasonic inspection

    DOEpatents

    Thompson, Donald O.; Hsu, David K.

    1993-12-14

    The invention includes a means and method for transmitting and receiving broadband, unipolar, ultrasonic pulses for ultrasonic inspection. The method comprises generating a generally unipolar ultrasonic stress pulse from a low impedance voltage pulse transmitter along a low impedance electrical pathway to an ultrasonic transducer, and receiving the reflected echo of the pulse by the transducer, converting it to a voltage signal, and passing it through a high impedance electrical pathway to an output. The means utilizes electrical components according to the method. The means and method allow a single transducer to be used in a pulse/echo mode, and facilitates alternatingly transmitting and receiving the broadband, unipolar, ultrasonic pulses.

  17. Method and means of transmitting and receiving broad-band unipolar, ultrasonic pulses for ultrasonic inspection

    DOEpatents

    Thompson, D.O.; Hsu, D.K.

    1993-12-14

    The invention includes a means and method for transmitting and receiving broadband, unipolar, ultrasonic pulses for ultrasonic inspection. The method comprises generating a generally unipolar ultrasonic stress pulse from a low impedance voltage pulse transmitter along a low impedance electrical pathway to an ultrasonic transducer, and receiving the reflected echo of the pulse by the transducer, converting it to a voltage signal, and passing it through a high impedance electrical pathway to an output. The means utilizes electrical components according to the method. The means and method allow a single transducer to be used in a pulse/echo mode, and facilitates alternatingly transmitting and receiving the broadband, unipolar, ultrasonic pulses. 25 figures.

  18. Radiolysis Model Sensitivity Analysis for a Used Fuel Storage Canister

    SciTech Connect

    Wittman, Richard S.

    2013-09-20

    This report fulfills the M3 milestone (M3FT-13PN0810027) to report on a radiolysis computer model analysis that estimates the generation of radiolytic products for a storage canister. The analysis considers radiolysis outside storage canister walls and within the canister fill gas over a possible 300-year lifetime. Previous work relied on estimates based directly on a water radiolysis G-value. This work also includes that effect with the addition of coupled kinetics for 111 reactions for 40 gas species to account for radiolytic-induced chemistry, which includes water recombination and reactions with air.

  19. Radiolysis Concerns for Water Shielding in Fission Surface Power Applications

    SciTech Connect

    Schoenfeld, Michael P.; Anghaie, Samim

    2008-01-21

    This paper presents an overview of radiolysis concerns with regard to water shields for fission surface power. A review of the radiolysis process is presented and key parameters and trends are identified. From this understanding of the radiolytic decomposition of water, shield pressurization and corrosion are identified as the primary concerns. Existing experimental and modeling data addressing concerns are summarized. It was found that radiolysis of pure water in a closed volume results in minimal, if any net decomposition, and therefore reduces the potential for shield pressurization and corrosion.

  20. Reaction mechanisms in the radiolysis of peptides, polypeptides, and proteins. I. Reactions of the peptide main-chain in model systems

    SciTech Connect

    Garrison, W.M.

    1982-08-01

    The object of this review is to bring together and to correlate our present knowledge of products and mechanisms in the radiolysis of peptides, polypeptides and proteins in both aqueous and solid-state systems. Results obtained with various experimental techniques such as product analysis, competition kinetics, ESR spectroscopy and pulse radiolysis are included. Here in part I the emphasis is on the various radiation-induced reactions of the peptide main-chain in model systems. In part II the emphasis is on the radiation chemistry of side-chain loci of the aliphatic, sulfur-containing, aromatic and other unsaturated amino acid residues in similar systems. And, in part III this information on model systems is used in interpreting the mechanisms of chemical change in the radiolysis of proteins in aqueous solution and in the solid state. 60 references.

  1. A pulse radiolysis study of zinc(II)-insulin.

    PubMed

    Elliot, A J; Wilkinson, F; Armstrong, D A

    1980-07-01

    Reactions of eaq with zinc(II)-insulin at pH 6.6 and 9.0 yielded relatively low disulphide anion absorptions, suggesting eaq reacts at other sites than S-S. A similar conclusion was reached for the reation of CO2 where an even lower yield of disulphide anion was found. However, here the disulphide anion yield increased with 'prepulsing'. Simultaneously the rate constant decreased, implying that a more reactive site was 'cleaned up'. While no reaction of Br2 with insulin was observed, both OH and Cl2 reacted rapidly and predominantly at the tyrosine residues. The second order rate constants, calculated in terms of insulin monomer concentrations, are reported for eaq, CO2 and Cl2. The transient spectra qualitatively support evidence regarding the accessibility of S-S bonds and tryosine residues in the various forms of insulin as predicted from earlier studies.

  2. Pulse

    MedlinePlus

    ... the underside of the opposite wrist, below the base of the thumb. Press with flat fingers until ... determine if the patient's heart is pumping. Pulse measurement has other uses as well. During or immediately ...

  3. A robust method for pulse peak determination in a digital volume pulse waveform with a wandering baseline.

    PubMed

    Jang, Dae-Geun; Farooq, Umar; Park, Seung-Hun; Hahn, Minsoo

    2014-10-01

    This paper presents a robust method for pulse peak determination in a digital volume pulse (DVP) waveform with a wandering baseline. A proposed new method uses a modified morphological filter (MMF) to eliminate a wandering baseline signal of the DVP signal with minimum distortion and a slope sum function (SSF) with an adaptive thresholding scheme to detect pulse peaks from the baseline-removed DVP signal. Further in order to cope with over-detected and missed pulse peaks, knowledge based rules are applied as a postprocessor. The algorithm automatically adjusts detection parameters periodically to adapt to varying beat morphologies and fluctuations. Compared with conventional methods (highpass filtering, linear interpolation, cubic spline interpolation, and wavelet adaptive filtering), our method performs better in terms of the signal-to-error ratio, the computational burden (0.125 seconds for one minute of DVP signal analysis with the Intel Core 2 Quad processor @ 2.40 GHz PC), the true detection rate (97.32% with an acceptance level of 4 ms ) as well as the normalized error rate (0.18%). In addition, the proposed method can detect true positions of pulse peaks more accurately and becomes very useful for pulse transit time (PTT) and pulse rate variability (PRV) analyses.

  4. The Radiolysis of AmVI Solutions

    SciTech Connect

    Bruce J. Mincher

    2013-06-01

    The reduction of bismuthate-produced AmVI by 60Co gamma-rays was measured using post-irradiation UV/Vis spectroscopy. The reduction of AmVI by radiolysis was rapid, producing AmV as the sole product. Relatively low absorbed doses in the ~0.3 kGy range quantitatively reduced a solution of 2.5 x 10-4 M AmVI. The addition of bismuthate to samples during irradiation did not appear to protect AmVI from radiolytic reduction during these experiments. It was also shown here that AmV is very stable toward radiation. The quantitative reduction of the AmVI concentration here corresponds to 1.4 hours of exposure to a process solution, however the actual americium concentrations will be higher and the expected contact times short when using centrifugal contactors. Thus, the reduction rate found in these initial experiments may not be excessive.

  5. Method of pressure pulse cleaning a tube bundle heat exchanger

    SciTech Connect

    Scharton, T.D.; Taylor, G.B.

    1987-04-07

    A method is described of removing the products of corrosion, oxidation, sedimentation and comparable chemical reactions collectively known as sludge which settle on the bottom of a tube bundle heat exchange and form a pile of sludge. The tube bundle heat exchanger is characterized by a tube bundle heat exchanger wall and a thick metal plate known as a tube sheet near the lower portion of the tube bundle heat exchanger wall's interior surface. The tube sheet serves to support the lower ends of a multiplicity of heat exchanger tubes within the tube bundle heat exchanger. The tube bundle heat exchange wall further comprises a multiplicity of small holes known as hand holes, manways, drain lines and vents, located around its circumference and above the tube sheet. The method is described of removing the pile of sludge which settles on the tube sheet comprising: a. locating at least one air-gun type pressure pulse shock wave source outside the tube bundle heat exchanger so as to be able to introduce pressure pulse shock waves through one or more of the multiplicity of hand holes, manways, drain lines and vents; and b. filling the tube bundle heat exchanger with a liquid to a level above the pile of sludge.

  6. The radiolysis and radioracemization of amino acids on clays

    NASA Technical Reports Server (NTRS)

    Bonner, W. A.; Hall, H.; Chow, G.; Yi, L.; Lemmon, R. M.

    1985-01-01

    The effects of the surfaces of kaolinite and bentonite clays on the radiolysis and radioracemization of L-leucine and its hydrochloride salt have been investigated experimentally. L-leucine and its hydrochloride salt were deposited on the clays and the amino acid/clay preparations were irradiated by a Co-60 gamma-ray source which induced 2-89 percent radiolysis. The efficiency of radiolysis and radioracemization were measured using gas chromatography. Results were obtained for leucine in 0.1 M aqueous solution for comparison with the clay-deposted leucine and leucine hydrochloride. It is found that radiolysis and radioracemization in the samples occurred according to a pseudo-first-order rate law. Comparison of the specific rate constants showed that leucine and its hydrochloride salt were the most resistant to both radiolysis and radioracemization, followed by leucine and its hydrochloride salt on kaolin. Leucine and its HCl salt on bentonite, and leucine in aqueous solution were found to be the least resistant to radiolysis and radioracemization. The experimental results are intepreted with respect to the Vester-Ulbricht mechanism for the origin of optical activity.

  7. Method of estimating pulse response using an impedance spectrum

    SciTech Connect

    Morrison, John L; Morrison, William H; Christophersen, Jon P; Motloch, Chester G

    2014-10-21

    Electrochemical Impedance Spectrum data are used to predict pulse performance of an energy storage device. The impedance spectrum may be obtained in-situ. A simulation waveform includes a pulse wave with a period greater than or equal to the lowest frequency used in the impedance measurement. Fourier series coefficients of the pulse train can be obtained. The number of harmonic constituents in the Fourier series are selected so as to appropriately resolve the response, but the maximum frequency should be less than or equal to the highest frequency used in the impedance measurement. Using a current pulse as an example, the Fourier coefficients of the pulse are multiplied by the impedance spectrum at corresponding frequencies to obtain Fourier coefficients of the voltage response to the desired pulse. The Fourier coefficients of the response are then summed and reassembled to obtain the overall time domain estimate of the voltage using the Fourier series analysis.

  8. Radiolysis of water with aluminum oxide surfaces

    NASA Astrophysics Data System (ADS)

    Reiff, Sarah C.; LaVerne, Jay A.

    2017-02-01

    Aluminum oxide, Al2O3, nanoparticles with water were irradiated with γ-rays and 5 MeV He ions followed by the determination of the production of molecular hydrogen, H2, and characterization of changes in the particle surface. Surface analysis techniques included: diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), nitrogen absorption with the Brunauer - Emmett - Teller (BET) methodology for surface area determination, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Production of H2 by γ-ray radiolysis was determined for samples with adsorbed water and for Al2O3 - water slurries. For Al2O3 samples with adsorbed water, the radiation chemical yield of H2 was measured as 80±20 molecules/100 eV (1 molecule/100 eV=1.04×10-7 mol/J). The yield of H2 was observed to decrease as the amount of water present in the Al2O3 - water slurries increased. Surface studies indicated that the α-phase Al2O3 samples changed phase following irradiation by He ions, and that the oxyhydroxide layer, present on the pristine sample, is removed by γ-ray and He ion irradiation.

  9. Multi-wavelength photoplethysmography method for skin arterial pulse extraction

    PubMed Central

    Liu, Jing; Yan, Bryan Ping-Yen; Dai, Wen-Xuan; Ding, Xiao-Rong; Zhang, Yuan-Ting; Zhao, Ni

    2016-01-01

    In this work, we present a multi-wavelength (MW) PPG method exploiting the wavelength dependence of light penetration in skin tissue to provide depth resolution of skin blood pulsation. The MW PPG system requires two to three light sources in different wavelengths and extracts the arterial blood pulsation through a multi-wavelength multi-layer light-skin interaction model, which removes the capillary pulsation (determined from the short-wavelength PPG signal) from the long-wavelength PPG signal using absorption weighting factors that are quasi-analytically calibrated. The extracted pulsations are used to calculate blood pressure (BP) through pulse transit time (PTT), and the results are compared with those obtained from the single wavelength PPG method. The comparative study is clinically performed on 20 subjects including 10 patients diagnosed with cardiovascular diseases and 10 healthy subjects. The result demonstrates that the MW PPG method significantly improves the measurement accuracy of systolic BP (SBP), reducing the mean absolute difference between the reference and the estimated SBP values from 5.7 mmHg (for single-wavelength PPG) to 2.9 mmHg (for three-wavelength PPG). PMID:27867733

  10. The radiolysis and radioracemization of amino acids on silica surfaces

    NASA Technical Reports Server (NTRS)

    Bonner, W. A.; Lemmon, R. M.

    1981-01-01

    Results are presented of experiments on the radioracemization of amino acids in the presence of silica surfaces such as may have been found on the prebiotic earth. L-leucine and a DL-leucine mixture deposited on samples of 1-quartz and an amorphous silica preparation (Syloid 63) was subjected to Co-60 gamma-ray irradiation, then analyzed by gas chromatography to determine the radiolysis and racemization rates. The quartz surface is found to have a marginal efficacy in enhancing radiolysis when compared with a crystalline L-leucine control, although enhancing radioracemization symmetrically by a factor of two. Both the radiolysis and radioracemization of L-leucine and DL-leucine on a Syloid-63 silica surface are observed to increase with increasing radiation dose, and to be substantially greater than in the crystalline controls. Additional experiments with the nonprotein amino acid isovaline deposited on Syloid 63 confirm the greater radiolysis susceptibility of amino acids deposited on silica with respect to the crystalline state, although racemization is not observed. The observations suggest that the presence of a silica surface would have a deleterious effect on any mechanism for the origin of molecular chirality relying on stereoselective beta-radiolysis.

  11. Plutonium and Americium Alpha Radiolysis of Nitric Acid Solutions.

    PubMed

    Horne, Gregory P; Gregson, Colin R; Sims, Howard E; Orr, Robin M; Taylor, Robin J; Pimblott, Simon M

    2017-02-02

    The yield of HNO2, as a function of absorbed dose and HNO3 concentration, from the α-radiolysis of aerated HNO3 solutions containing plutonium or americium has been investigated. There are significant differences in the yields measured from solutions of the two different radionuclides. For 0.1 mol dm(-3) HNO3 solutions, the radiolytic yield of HNO2 produced by americium α-decay is below the detection limit, whereas for plutonium α-decay the yield is considerably greater than that found previously for γ-radiolysis. The differences between the solutions of the two radionuclides are a consequence of redox reactions involving plutonium and the products of aqueous HNO3 radiolysis, in particular H2O2 and HNO2 and its precursors. This radiation chemical behavior is HNO3 concentration dependent with the differences between plutonium and americium α-radiolysis decreasing with increasing HNO3 concentration. This change may be interpreted as a combination of α-radiolysis direct effects and acidity influencing the plutonium oxidation state distribution, which in turn affects the radiation chemistry of the system.

  12. Monitoring of concrete structures using the ultrasonic pulse velocity method

    NASA Astrophysics Data System (ADS)

    Karaiskos, G.; Deraemaeker, A.; Aggelis, D. G.; Van Hemelrijck, D.

    2015-11-01

    Concrete is the material most produced by humanity. Its popularity is mainly based on its low production cost and great structural design flexibility. Its operational and ambient loadings including environmental effects have a great impact in the performance and overall cost of concrete structures. Thus, the quality control, the structural assessment, the maintenance and the reliable prolongation of the operational service life of the existing concrete structures have become a major issue. In the recent years, non-destructive testing (NDT) is becoming increasingly essential for reliable and affordable quality control and integrity assessment not only during the construction of new concrete structures, but also for the existing ones. Choosing the right inspection technique is always followed by a compromise between its performance and cost. In the present paper, the ultrasonic pulse velocity (UPV) method, which is the most well known and widely accepted ultrasonic concrete NDT method, is thoroughly reviewed and compared with other well-established NDT approaches. Their principles, inherent limitations and reliability are reviewed. In addition, while the majority of the current UPV techniques are based on the use of piezoelectric transducers held on the surface of the concrete, special attention is paid to a very promising technique using low-cost and aggregate-size piezoelectric transducers embedded in the material. That technique has been evaluated based on a series of parameters, such as the ease of use, cost, reliability and performance.

  13. Method and apparatus for stabilizing pulsed microwave amplifiers

    DOEpatents

    Hopkins, Donald B.

    1993-01-01

    Phase and amplitude variations at the output of a high power pulsed microwave amplifier arising from instabilities of the driving electron beam are suppressed with a feed-forward system that can stabilize pulses which are too brief for regulation by conventional feedback techniques. Such variations tend to be similar during successive pulses. The variations are detected during each pulse by comparing the amplifier output with the low power input signal to obtain phase and amplitude error signals. This enables storage of phase and amplitude correction signals which are used to make compensating changes in the low power input signal during the following amplifier output pulse which suppress the variations. In the preferred form of the invention, successive increments of the correction signals for each pulse are stored in separate channels of a multi-channel storage. Sequential readout of the increments during the next pulse provides variable control voltages to a voltage controlled phase shifter and voltage controlled amplitude modulator in the amplifier input signal path.

  14. Method and apparatus for stabilizing pulsed microwave amplifiers

    DOEpatents

    Hopkins, D.B.

    1993-01-26

    Phase and amplitude variations at the output of a high power pulsed microwave amplifier arising from instabilities of the driving electron beam are suppressed with a feed-forward system that can stabilize pulses which are too brief for regulation by conventional feedback techniques. Such variations tend to be similar during successive pulses. The variations are detected during each pulse by comparing the amplifier output with the low power input signal to obtain phase and amplitude error signals. This enables storage of phase and amplitude correction signals which are used to make compensating changes in the low power input signal during the following amplifier output pulse which suppress the variations. In the preferred form of the invention, successive increments of the correction signals for each pulse are stored in separate channels of a multi-channel storage. Sequential readout of the increments during the next pulse provides variable control voltages to a voltage controlled phase shifter and voltage controlled amplitude modulator in the amplifier input signal path.

  15. Modeling of water radiolysis at spallation neutron sources

    SciTech Connect

    Daemen, L.L.; Kanner, G.S.; Lillard, R.S.; Butt, D.P.; Brun, T.O.; Sommer, W.F.

    1998-12-01

    In spallation neutron sources neutrons are produced when a beam of high-energy particles (e.g., 1 GeV protons) collides with a (water-cooled) heavy metal target such as tungsten. The resulting spallation reactions produce a complex radiation environment (which differs from typical conditions at fission and fusion reactors) leading to the radiolysis of water molecules. Most water radiolysis products are short-lived but extremely reactive. When formed in the vicinity of the target surface they can react with metal atoms, thereby contributing to target corrosion. The authors describe the results of calculations and experiments performed at los alamos to determine the impact on target corrosion of water radiolysis in the spallation radiation environment. The computational methodology relies on the use of the Los Alamos radiation transport code, LAHET, to determine the radiation environment, and the AEA code, FACSIMILE, to model reaction-diffusion processes.

  16. Summary Report on Gamma Radiolysis of TBP/n-dodecane in the Presence of Nitric Acid Using the Radiolysis/Hydrolysis Test Loop

    SciTech Connect

    Dean R. Peterman; Bruce J. Mincher; Catherine L. Riddle; Richard D. Tillotson

    2010-08-01

    processes containing TBP that are being developed to support advanced aqueous separations processes. Initial experimental results are consistent with existing literature reports regarding TBP/n-dodecane radiolysis. Additionally, the gamma dose rate has been characterized within the test loop and analytical methods have been developed for the characterization and quantification of radiolytic degradation products.

  17. Methods of Attosecond X-Ray Pulse Generation

    SciTech Connect

    Zholents, Alexander

    2005-05-08

    We review several proposals for generation of solitary attosecond pulses using two types of free electron lasers which are envisioned as future light sources for studies of ultra-fast dynamics using soft and hard x-rays.

  18. Further Methods for the Generation of Ultrashort Optical Pulses

    NASA Astrophysics Data System (ADS)

    Hirlimann, C.

    Up to the beginning of the sixties, the shortest measurable time duration was of the order of one nanosecond (10-9 s). Short pulses were produced through the generation of short electrical discharges. After the laser was invented in 1960, the situation quite rapidly changed. In 1965, the picosecond (10-12 s) regime was reached by placing a saturable absorber inside a laser cavity. Twenty years of continuous progress led to the production of light pulses of less than 10 femtoseconds. In the race towards ever shorter pulses, recent developments in the generation of tabletop X-ray lasers have opened the way to dynamical studies in the attosecond (10-18 s)regime [4.1-2]. In the meantime, progress was made on the tunability of the pulsed-laser sources. Today's tunability extends from the near ultraviolet to the near infrared [4.2-6].

  19. Apparatus and method for characterizing ultrafast polarization varying optical pulses

    DOEpatents

    Smirl, Arthur; Trebino, Rick P.

    1999-08-10

    Practical techniques are described for characterizing ultrafast potentially ultraweak, ultrashort optical pulses. The techniques are particularly suited to the measurement of signals from nonlinear optical materials characterization experiments, whose signals are generally too weak for full characterization using conventional techniques.

  20. The radiolysis and racemization of leucine on proton irradiation

    NASA Technical Reports Server (NTRS)

    Bonner, W. A.; Lemmon, R. M.; Conzett, H. E.

    1982-01-01

    D- and L-Leucine have been subjected to 39-55 percent radiolysis using 0.11 MeV protons, both with the proton beam passing through the sample or being absorbed by it and with quenching the sample immediately on completion of irradiation or after a 21-day interval. Racemization was small (1.1-1.7 percent) and comparable in all cases, suggesting that radioracemization and secondary degradative effects were not important factors in the recent unsuccessful attempts to induce optical activity in DL-Leucine by partial radiolysis using 0-11 MeV longitudinally polarized protons.

  1. TRUEX Radiolysis Testing Using the INL Radiolysis Test Loop: FY-2012 Status Report

    SciTech Connect

    Dean R. Peterman; Lonnie G. Olson; Richard D. Tillotson; Rocklan G. McDowell; Jack D. Law

    2012-09-01

    The INL radiolysis test loop has been used to evaluate the affect of radiolytic degradation upon the efficacy of the strip section of the TRUEX flowsheet for the recovery of trivalent actinides and lanthanides from acidic solution. The nominal composition of the TRUEX solvent used in this study is 0.2 M CMPO and 1.4 M TBP dissolved in n-dodecane and the nominal composition of the TRUEX strip solution is 1.5 M lactic acid and 0.050 M diethylenetriaminepentaacetic acid. Gamma irradiation of a mixture of TRUEX process solvent and stripping solution in the test loop does not adversely impact flowsheet performance as measured by stripping americium ratios. The observed increase in americium stripping distribution ratios with increasing absorbed dose indicates the radiolytic production of organic soluble degradation compounds.

  2. Summary of TRUEX Radiolysis Testing Using the INL Radiolysis Test Loop

    SciTech Connect

    Dean R. Peterman; Lonnie G. Olson; Rocklan G. McDowell; Gracy Elias; Jack D. Law

    2012-03-01

    The INL radiolysis and hydrolysis test loop has been used to evaluate the effects of hydrolytic and radiolytic degradation upon the efficacy of the TRUEX flowsheet for the recovery of trivalent actinides and lanthanides from acidic solution. Repeated irradiation and subsequent re-conditioning cycles did result in a significant decrease in the concentration of the TBP and CMPO extractants in the TRUEX solvent and a corresponding decrease in americium and europium extraction distributions. However, the build-up of solvent degradation products upon {gamma}-irradiation, had little impact upon the efficiency of the stripping section of the TRUEX flowsheet. Operation of the TRUEX flowsheet would require careful monitoring to ensure extraction distributions are maintained at acceptable levels.

  3. Apparatus for and method of operating a cylindrical pulsed induction mass launcher

    DOEpatents

    Cowan, M. Jr.; Duggin, B.W.; Widner, M.M.

    1992-06-30

    An electromagnetic cylindrical projectile mass launcher and a method of operation is provided which includes a cylindrical projectile having a conducting armature, a cylindrical barrel in which the armature is received, a plurality of electromagnetic drive coil stages, a plurality of pulse energy sources, and a pulsed power arrangement for generating magnetic pulses forming a pulsed magnetic wave along the length of the launcher barrel. The pulsed magnetic wave provides a propelling force on the projectile along the drive coil. The pulsed magnetic wave of the drive coil stages is advanced along the armature faster than the projectile to thereby generate an induced current wave in the armature. The pulsed generation of the magnetic wave minimizes electromagnetic heating of the projectile and provides for smooth acceleration of the projectile through the barrel of the launcher. 2 figs.

  4. Apparatus for and method of operating a cylindrical pulsed induction mass launcher

    DOEpatents

    Cowan, Jr., Maynard; Duggin, Billy W.; Widner, Melvin M.

    1992-01-01

    An electromagnetic cylindrical projectile mass launcher and a method of operation is provided which includes a cylindrical projectile having a conducting armature, a cylindrical barrel in which the armature is received, a plurality of electromagnetic drive coil stages, a plurality of pulse energy sources, and a pulsed power arrangement for generating magnetic pulses forming a pulsed magnetic wave along the length of the launcher barrel. The pulsed magnetic wave provides a propelling force on the projectile along the drive coil. The pulsed magnetic wave of the drive coil stages is advanced along the armature faster than the projectile to thereby generate an induced current wave in the armature. The pulsed generation of the magnetic wave minimizes electromagnetic heating of the projectile and provides for smooth acceleration of the projectile through the barrel of the launcher.

  5. METHOD AND APPARATUS FOR PULSING A CHARGED PARTICLE BEAM

    DOEpatents

    Aaland, K.; Kuenning, R.W.; Harmon, R.K.

    1961-05-01

    A system is offered for pulsing a continuous beam of charged particles to form beam pulses that are consistently rectangular and of precise time durations which may be varied over an extremely wide range at a widely variable range of repetition rates. The system generally comprises spaced deflection plates on opposite sides of a beam axis in between which a unidirectional bias field is established to deflect the beam for impingement on an off-axis collector. The bias field is periodically neutralized by the application of fast rise time substantially rectangular pulses to one of the deflection plates in opposition to the bias field and then after a time delay to the other deflection plate in aiding relation to the bias field and during the flat crest portion of the bias opposing pulses. The voltage distribution of the resulting deflection field then includes neutral or zero portions which are of symmetrical substantially rectangular configuration relative to time and during which the beam axially passes the collector in the form of a substantially rectangular beam pulse.

  6. Method for generating high-energy and high repetition rate laser pulses from CW amplifiers

    DOEpatents

    Zhang, Shukui

    2013-06-18

    A method for obtaining high-energy, high repetition rate laser pulses simultaneously using continuous wave (CW) amplifiers is described. The method provides for generating micro-joule level energy in pico-second laser pulses at Mega-hertz repetition rates.

  7. Method for spatially modulating X-ray pulses using MEMS-based X-ray optics

    DOEpatents

    Lopez, Daniel; Shenoy, Gopal; Wang, Jin; Walko, Donald A.; Jung, Il-Woong; Mukhopadhyay, Deepkishore

    2015-03-10

    A method and apparatus are provided for spatially modulating X-rays or X-ray pulses using microelectromechanical systems (MEMS) based X-ray optics. A torsionally-oscillating MEMS micromirror and a method of leveraging the grazing-angle reflection property are provided to modulate X-ray pulses with a high-degree of controllability.

  8. Electrochemical synthesis of nanosized hydroxyapatite by pulsed direct current method

    SciTech Connect

    Nur, Adrian; Rahmawati, Alifah; Ilmi, Noor Izzati; Affandi, Samsudin; Widjaja, Arief

    2014-02-24

    Synthesis of nanosized of hydroxyapatite (HA) by electrochemical pulsed direct current (PDC) method has been studied. The aim of this work is to study the influence of various PDC parameters (pH initial, electrode distance, duty cycle, frequency, and amplitude) on particle surface area of HA powders. The electrochemical synthesis was prepared in solution Ca{sup 2+}/EDTA{sup 4−}/PO{sub 4}{sup 3+} at concentration 0.25/0.25/0.15 M for 24 h. The electrochemical cell was consisted of two carbon rectangular electrodes connected to a function generator to produce PDC. There were two treatments for particles after electrosynthesized, namely without aging and aged for 2 days at 40 °C. For both cases, the particles were filtered and washed by demineralized water to eliminate the impurities and unreacted reactants. Then, the particles were dried at 100 °C for 2 days. The dried particles were characterized by X-ray diffraction, surface area analyzer, scanning electron microscopy (SEM), Fourier transform infrared spectra and thermogravimetric and differential thermal analysis. HA particles can be produced when the initial pH > 6. The aging process has significant effect on the produced HA particles. SEM images of HA particles showed that the powders consisted of agglomerates composed of fine crystallites and have morphology plate-like and sphere. The surface area of HA particles is in the range of 25 – 91 m{sup 2}/g. The largest particle surface area of HA was produced at 4 cm electrode distance, 80% cycle duty, frequency 0.1 Hz, amplitude 9 V and with aging process.

  9. Experimental validation of a high voltage pulse measurement method.

    SciTech Connect

    Cular, Stefan; Patel, Nishant Bhupendra; Branch, Darren W.

    2013-09-01

    This report describes X-cut lithium niobates (LiNbO3) utilization for voltage sensing by monitoring the acoustic wave propagation changes through LiNbO3 resulting from applied voltage. Direct current (DC), alternating current (AC) and pulsed voltage signals were applied to the crystal. Voltage induced shift in acoustic wave propagation time scaled quadratically for DC and AC voltages and linearly for pulsed voltages. The measured values ranged from 10 - 273 ps and 189 ps 2 ns for DC and non-DC voltages, respectively. Data suggests LiNbO3 has a frequency sensitive response to voltage. If voltage source error is eliminated through physical modeling from the uncertainty budget, the sensors U95 estimated combined uncertainty could decrease to ~0.025% for DC, AC, and pulsed voltage measurements.

  10. Valine radiolysis by MeV ions

    NASA Astrophysics Data System (ADS)

    Da Silveira, Enio

    2016-07-01

    Valine, (CH3)2 CHCH (NH2) COOH, is a protein amino acid that has been identified in extraterrestrial environments and in the Murchison meteorite [1]. The knowledge of half-lives of small organic molecules under ionizing radiation is important for the setup of models describing the spread out of prebiotics across the Solar System or the Galaxy. We have investigated typical effects of MeV cosmic ray ions on prebiotic molecules in laboratory by impinging ions produced by the PUC-Rio Van de Graaff accelerator. Pure valine films, deposited by evaporation on KBr substrates, were irradiated by H ^{+}, He ^{+} and N ^{+} ion beams, from 0.5 to 1.5 MeV and up to a fluence of 10 ^{15} projectiles/cm ^{2}. The sample temperature was varied from 10 K to 300 K. The irradiation was interrupted several times for Mid-FTIR analysis of the sample. The main findings are: 1- The column density of the valine decreases exponentially with fluence. 2- In some cases, a second exponential appears in the beginning of irradiation; this feature has been attributed to sample compaction by the ion beam [2]. 3- Destruction cross sections of valine are in the 10 ^{-15} cm ^{2} range, while compaction cross sections are in the 10 ^{-14} cm ^{2} range. 4- Destruction cross section increases with the stopping power of the beam and also with the sample temperature. 5- Surprisingly, during the radiolysis of valine, just CO _{2} is seen by as a daughter molecule formed in the bulk. 6- After long beam fluence, also a CO peak appears in the infrared spectrum; this species is however interpreted as a fragment of the formed CO2 molecules. 7- Considering the flux ratio between laboratory experiments and actual galactic cosmic rays, half-life of valine is predicted for ISM conditions [3]. This work on pure valine is the first measurement of a series. New experiments are planned for determining cross sections of valine dissolved in H _{2}O or CO _{2}, inspired by the study performed for glycine [4]. [1] P

  11. Apparatus for and method of operating a cylindrical pulsed induction mass launcher

    SciTech Connect

    Cowan, M. Jr.; Duggin, B.W.; Widner, M.M.

    1990-12-06

    In accordance with the one aspect of the invention, an electromagnetic projectile launcher is provided which comprises: a conducting projectile, a barrel that receives the projectile, a plurality of electromagnetic drive coils, a plurality of pulsed energy sources, and pulse power means for generating a sequence of pulses forming a pulsed magnetic wave within the drive coil for propelling the projectile along the barrel, wherein the pulsed magnetic wave of the drive coil is advanced along the barrel faster than the projectile to thereby induce a current wave in the armature of the projectile and thereby minimize electromagnetic heating of the projectile and provide nearly constant acceleration of the projectile. In accordance with another aspect of the invention, a method is provided for propelling a projectile within a pulsed induction electromagnetic coil launcher, wherein the method comprises the steps of: generating a sequence of pulses forming a pulsed magnetic wave within the coil launcher, applying the pulsed magnetic wave initially at the aft end of the projectile to accelerate the projectile within the coil launcher, and advancing the position of the pulsed magnetic wave relative to the projectile to thereby generate an induced current wave in the armature, such that electromagnetic heating of the projectile is minimized and acceleration is nearly constant.

  12. Leach and radiolysis data for FUETAP concretes containing SRP wastes

    SciTech Connect

    Dole, L.R.; Rogers, G.C.; Morgan, M.T.; Stinton, D.P.; Kessler, J.H.; Robinson, S.M.; Moore, J.G.

    1983-04-01

    This supplement to ORNL/TM-8579 contains experimental results for leach tests and alpha-radiolysis tests made on FUETAP concretes containing Savannah River Plant waste. The results, presented in two sections, consist of both the raw data and calculated values for individual experiments. This information is summarized and analyzed in Sections 5 and 7 of ORNL/TM-8579.

  13. Enhancement of Zirconolite Dissolution Due to Water Radiolysis

    SciTech Connect

    Tribet, Magaly; Moncoffre, Nathalie

    2007-07-01

    Zirconolite is a candidate host material for conditioning minor tri- and tetra-valent actinides arising from enhanced nuclear spent fuel reprocessing and partitioning, in the case of disposal of the nuclear waste. Its chemical durability has been studied here under charged particle-induced radiolysis (He{sup 2+} and proton external beams) to identify the possible effects of water radiolysis on the dissolution rates in pure water and to describe the alteration mechanisms. Two experimental geometries have been used in order to evaluate the influence of the following parameters: solid irradiation, water radiolysis. In the first geometry the beam gets through the sample before stopping at the surface/water interface. In the second one the beam stops before the surface/water interface. Results on the elemental releases due to the enhanced dissolution of the zirconolite surface during charged particle-induced irradiation of water are presented. Under radiolysis, an increase of one order of magnitude is observed in the Ti, Zr and Nd elemental releases. No difference in the total elemental releases can be noticed when the solid is also irradiated. (authors)

  14. Systolic Blood Pressure Accuracy Enhancement in the Electronic Palpation Method Using Pulse Waveform

    DTIC Science & Technology

    2007-11-02

    1 of 4 SYSTOLIC BLOOD PRESSURE ACCURACY ENHANCEMENT IN THE ELECTRONIC PALPATION METHOD USING PULSE WAVEFORM H. S. S. Sorvoja1, R. A. Myllylä1...systolic blood pressure measurements based on pulse waveform. A set of measurement was carried out with elderly cardiac surgery patients. The experiments... blood pressure . Systolic pressure errors were defined and correlations with other specific values, like pressure rise time, pulse wave velocity

  15. Apparatus and method for characterizing ultrafast polarization varying optical pulses

    DOEpatents

    Smirl, A.; Trebino, R.P.

    1999-08-10

    Practical techniques are described for characterizing ultrafast potentially ultraweak, ultrashort optical pulses. The techniques are particularly suited to the measurement of signals from nonlinear optical materials characterization experiments, whose signals are generally too weak for full characterization using conventional techniques. 2 figs.

  16. A Novel Sterilization Method Using Pulsed Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Wang, Xi-lu; Akira, Mizuno; Shijin, Katsura

    1998-01-01

    Pulsed discharge plasma(PDP) has been used to kill bacteria and the curves of the survival rate of bacteria against treatment time are obtained. Irreversible structural change in the cell membrane is caused by PDP and the cell is thus killed. The sterilization mechanism is analyzed.

  17. Method and apparatus for producing durationally short ultraviolet or X-ray laser pulses

    DOEpatents

    MacGowan, Brian J.; Matthews, Dennis L.; Trebes, James E.

    1988-01-01

    A method and apparatus is disclosed for producing ultraviolet or X-ray laser pulses of short duration (32). An ultraviolet or X-ray laser pulse of long duration (12) is progressively refracted, across the surface of an opaque barrier (28), by a streaming plasma (22) that is produced by illuminating a solid target (16, 18) with a pulse of conventional line focused high power laser radiation (20). The short pulse of ultraviolet or X-ray laser radiation (32), which may be amplified to high power (40, 42), is separated out by passage through a slit aperture (30) in the opaque barrier (28).

  18. Method and apparatus for producing durationally short ultraviolet or x-ray laser pulses

    DOEpatents

    MacGowan, B.J.; Matthews, D.L.; Trebes, J.E.

    1987-05-05

    A method and apparatus is disclosed for producing ultraviolet or x- ray laser pulses of short duration. An ultraviolet or x-ray laser pulse of long duration is progressively refracted, across the surface of an opaque barrier, by a streaming plasma that is produced by illuminating a solid target with a pulse of conventional line focused high power laser radiation. The short pulse of ultraviolet or x-ray laser radiation, which may be amplified to high power, is separated out by passage through a slit aperture in the opaque barrier.

  19. Method of eliminating effects of spurious free induction decay NMR signal caused by imperfect 180 degrees pulses

    SciTech Connect

    Bottomley, P.A.; Edelstein, W.A.

    1984-11-20

    A method for eliminating the effects of a spurious free induction decay (FID) NMR signal due to imperfect 180/sup 0/ RF pulses comprises applying a large magnitude, short duration magnetic field gradient pulse, termed the ''crusher'' pulse immediately following the 180/sup 0/ pulse. When the method is employed with NMR pulse sequences in which the 180/sup 0/ pulse is part of a spin echo type refocusing RF pulse sequence, the 180/sup 0/ pulse is preceded by a magnetic field gradient pulse termed the ''primer'', having an equal integral with respect to time as the crusher pulse. The method is effective in removing NMR image artifacts produced by spurious FID in both planar and three-dimensional NMR imaging methods.

  20. Method and apparatus for sputtering utilizing an apertured electrode and a pulsed substrate bias

    NASA Technical Reports Server (NTRS)

    Przybyszewski, J. S.; Shaltens, R. K. (Inventor)

    1973-01-01

    The method and equipment used for sputtering by use of an apertured electrode and a pulsed substrate bias are discussed. The technique combines the advantages of ion plating with the versatility of a radio frequency sputtered source. Electroplating is accomplished by passing a pulsed high voltage direct current to the article being plated during radio frequency sputtering.

  1. Hazardous and Corrosive Gas Production in the Radiolysis of Water/Organic Mixtures in Model TRU Waste

    SciTech Connect

    LaVerne, Jay A.

    2004-12-01

    - from 1,2-DCE and from 1,1-DCE solutions is very significantly higher ({approx} x 3-4) than from deoxygenated solution. Furthermore, the observed yield is both dose and dose rate dependent. The mechanisms for Cl- production in aerated aqueous solutions of 1,2-DCE and of 1,1-DCE are currently under investigation. Rate coefficients for the reaction of eaq- and -OH with chlorinated hydrocarbons. There is considerable disagreement over the rate coefficients for the reaction of the primary radiation-produced reducing and oxidizing radicals from water, eaq- and -OH respectively, with 1,2-DCE and with 1,1-DCE. Electron pulse-radiolysis experiments monitoring the decay of eaq- have been used to measure the rate coefficients: 1,2 DCE eaq- + CH2Cl-CH2Cl ' CH2Cl-CH2- + Cl- k1 = 2.3 x 109 dm3 mole-1 s-1 1,1 DCE eaq- + CH3Cl-CHCl2 ' CH3-CHCl- + Cl- k2 = 3.5 x 109 dm3 mole-1 s-1 while competition kinetic experiments were employed to determine the rate coefficients: 1,2 DCE -OH + CH2Cl-CH2Cl ' CH2Cl-CHCl- + H2O k3 = 1.8 x 108 dm3 mole-1 s-1 1,1 DCE -OH + CH3Cl-CHCl2 ' CH3-CCl2- + H2O k4 = 1.1 x 108 dm3 mole-1 s-1 The values obtained are similar to those measured by Asmus and co-workers, but there is a significant discrepancy from the estimate of Getoff and co-workers for k1. Rate coefficient for the reaction of OH with thiocyanide ion. The rate coefficient for the reaction of the -OH radical with a chlorinated hydrocarbon is obtained by a competition experiment, in which the change in the radiation-induced yield of (SCN)2-- from an aqueous SCN- solution is monitored on the addition of the hydrocarbon. The mechanism for the radiation-induced formation of (SCN)2-- from a SCN- is complex and involves a number of equilibria. Careful electron pulse radiolysis experiments have been performed and analyzed, employing the full, complex reaction mechanism, to re-evaluated the rate coefficient for the fundamental reaction -OH + SCN- ' (HOSCN)-- k5 = 1.4 x 1010 dm3 mole-1 s-1 This reaction is

  2. Digital pulse deconvolution method for current tails of NaI(Tl) detectors

    NASA Astrophysics Data System (ADS)

    Zeng, Guo-Qiang; Yang, Jian; Yu, Ming-Fu; Zhang, Kai-Qi; Ge, Qing; Ge, Liang-Quan

    2017-01-01

    To overcome the problem of pulse pile-up at high count rates, a digital deconvolution algorithm is used to remove the exponential current tails of NaI(Tl) detectors, so as to obtain a current unit impulse. Then a narrow pulse can be obtained through pulse shaping. The pulse deconvolution technique can thoroughly eliminate the influences of ballistic deficit and improve traditional pulse shaping systems in both pulse throughput and energy resolution. To demonstrate this method, the energy spectrum of a 137Cs radioactive source was measured. When the shaping time constant is 1.5 μs, traditional pulse shaping systems yielded a 6.99% energy resolution and 68 kcps count rate, while the new pulse deconvolution technique, used to improve traditional pulse shaping systems, yielded a 6.37% energy resolution and 102 kcps count rate. Supported by National Natural Science Foundation of China (41474159), Sichuan Youth Science & Technology Foundation (2015JQ0035) and Key Laboratory of Applied Nuclear Techniques in Geosciences Sichuan (gnzds2014006)

  3. VERSE-Guided Numerical RF Pulse Design: A Fast Method for Peak RF Power Control

    PubMed Central

    Lee, Daeho; Grissom, William A.; Lustig, Michael; Kerr, Adam B.; Stang, Pascal P.; Pauly, John M.

    2013-01-01

    In parallel excitation, the computational speed of numerical radiofrequency (RF) pulse design methods is critical when subject dependencies and system nonidealities need to be incorporated on-the-fly. One important concern with optimization-based methods is high peak RF power exceeding hardware or safety limits. Hence, online controllability of the peak RF power is essential. Variable-rate selective excitation pulse reshaping is ideally suited to this problem due to its simplicity and low computational cost. In this work, we first improve the fidelity of variable-rate selective excitation implementation for discrete-time waveforms through waveform oversampling such that variable-rate selective excitation can be robustly applied to numerically designed RF pulses. Then, a variable-rate selective excitation-guided numerical RF pulse design is suggested as an online RF pulse design framework, aiming to simultaneously control peak RF power and compensate for off-resonance. PMID:22135085

  4. Method and apparatus for electrical cable testing by pulse-arrested spark discharge

    DOEpatents

    Barnum, John R.; Warne, Larry K.; Jorgenson, Roy E.; Schneider, Larry X.

    2005-02-08

    A method for electrical cable testing by Pulse-Arrested Spark Discharge (PASD) uses the cable response to a short-duration high-voltage incident pulse to determine the location of an electrical breakdown that occurs at a defect site in the cable. The apparatus for cable testing by PASD includes a pulser for generating the short-duration high-voltage incident pulse, at least one diagnostic sensor to detect the incident pulse and the breakdown-induced reflected and/or transmitted pulses propagating from the electrical breakdown at the defect site, and a transient recorder to record the cable response. The method and apparatus are particularly useful to determine the location of defect sites in critical but inaccessible electrical cabling systems in aging aircraft, ships, nuclear power plants, and industrial complexes.

  5. A method for pressure-pulse suppression in fluid-filled piping

    SciTech Connect

    Shin, Y.W.; Bielick, E.F. ); Wiedermann, A.H. ); Ockert, C.E. )

    1989-01-01

    A simple, nondestructive method to suppress pressure pulses in fluid-filled piping was proposed and theoretically analyzed earlier. In this paper, the proposed method is verified experimentally. The results of experiments performed for the range of parameters of practical importance indicated that the attenuation of pressure pulses was in accordance with the theoretical predictions. This paper describes the experimental setup and the test models of the proposed pulse suppression devices and discusses the experimental results. In particular, the measured attenuation factors are presented and compared with the theoretical predictions. 8 ref., 17 fig., 2 tab.

  6. Radiolysis gas formation and pressure increase during a criticality excursion

    SciTech Connect

    Barbry, F.; Rozain, J.P.

    1989-01-01

    During a criticality excursion occurring in fissile solution, most of the energy released is transformed into thermal heating and the formation of gas by radiolytic decomposition of water. In addition, for fast kinetics excursions, a pressure increase in the internal solution is observed. This pressure increases and hydrogen generation can pose a safety concern. To understand and to model these phenomena, the Commissariat a l'Energie Atomique (CEA) Institute for Nuclear Protection and Safety has carried out specific experiments at the SILENE facility to: measure the pressure increase accompanying the power peak and determine the volume of radiolysis gas formed as a function of the energy and medium. These results are interrelated, and it should be possible to make use of pressure, energy, and radiolysis gas data to set up an equation of state of fissile solution and, consequently, to improve currently existing calculation models.

  7. Pulsed voltage electrospray ion source and method for preventing analyte electrolysis

    DOEpatents

    Kertesz, Vilmos [Knoxville, TN; Van Berkel, Gary [Clinton, TN

    2011-12-27

    An electrospray ion source and method of operation includes the application of pulsed voltage to prevent electrolysis of analytes with a low electrochemical potential. The electrospray ion source can include an emitter, a counter electrode, and a power supply. The emitter can include a liquid conduit, a primary working electrode having a liquid contacting surface, and a spray tip, where the liquid conduit and the working electrode are in liquid communication. The counter electrode can be proximate to, but separated from, the spray tip. The power system can supply voltage to the working electrode in the form of a pulse wave, where the pulse wave oscillates between at least an energized voltage and a relaxation voltage. The relaxation duration of the relaxation voltage can range from 1 millisecond to 35 milliseconds. The pulse duration of the energized voltage can be less than 1 millisecond and the frequency of the pulse wave can range from 30 to 800 Hz.

  8. Production of pulsed atomic oxygen beams via laser vaporization methods

    NASA Technical Reports Server (NTRS)

    Brinza, David E.; Coulter, Daniel R.; Liang, Ranty H.; Gupta, Amitava

    1986-01-01

    The generation of energetic pulsed atomic oxygen beams by laser-driven evaporation of cryogenically frozen ozone/oxygen films and thin indium-tin oxide (ITO) films is reported. Mass spectroscopy is used in the mass and energy characterization of beams from the ozone/oxygen films, and a peak flux of 3 x 10 to the 20th/sq m per sec at 10 eV is found. Analysis of the time-of-flight data suggests that several processes contribute to the formation of the oxygen beam. Results show the absence of metastable states such as the 2p(3)3s(1)(5S) level of atomic oxygen blown-off from the ITO films. The present process has application to the study of the oxygen degradation problem of LEO materials.

  9. Radiolysis and Photolysis of Icy Satellite Surfaces: Experiments and Theory

    NASA Technical Reports Server (NTRS)

    Cassidy, T.; Coll, P.; Raulin, F.; Carlson, R. W.; Hand, K. P.; Johnson, R. E.; Loeffler, M. J.; Baragiola, R. A.

    2010-01-01

    The transport and exchange of material between bodies in the outer solar system is often facilitated by their exposure to ionizing radiation. With this in mind we review the effects of energetic ions, electrons and UV photons on materials present in the outer solar system. We consider radiolysis, photolysis, and sputtering of low temperature solids. Radiolysis and photolysis are the chemistry that follows the bond breaking and ionization produced by incident radiation, producing, e.g., O2 and H2 from irradiated H2O ice. Sputtering is the ejection of molecules by incident radiation. Both processes are particularly effective on ices in the outer solar system. Materials reviewed include H2O ice, sulfur-containing compounds (such as S02 and S8), carboncontajning compounds (such as CH4), nitrogen-containing compounds (such as NH3 and N2), and mixtures of those compounds. We also review the effects of ionizing radiation on a mixture of N2 and CH4 gases, as appropriate to Titan's upper atmosphere, where radiolysis and photolysis produce complex organic compounds (tholins).

  10. Radiolysis and Photolysis of Icy Satellite Surfaces: Experiments and Theory

    NASA Astrophysics Data System (ADS)

    Cassidy, T.; Coll, P.; Raulin, F.; Carlson, R. W.; Johnson, R. E.; Loeffler, M. J.; Hand, K. P.; Baragiola, R. A.

    2010-06-01

    The transport and exchange of material between bodies in the outer solar system is often facilitated by their exposure to ionizing radiation. With this in mind we review the effects of energetic ions, electrons and UV photons on materials present in the outer solar system. We consider radiolysis, photolysis, and sputtering of low temperature solids. Radiolysis and photolysis are the chemistry that follows the bond breaking and ionization produced by incident radiation, producing, e.g., O2 and H2 from irradiated H2O ice. Sputtering is the ejection of molecules by incident radiation. Both processes are particularly effective on ices in the outer solar system. Materials reviewed include H2O ice, sulfur-containing compounds (such as SO2 and S8), carbon-containing compounds (such as CH4), nitrogen-containing compounds (such as NH3 and N2), and mixtures of those compounds. We also review the effects of ionizing radiation on a mixture of N2 and CH4 gases, as appropriate to Titan’s upper atmosphere, where radiolysis and photolysis produce complex organic compounds (tholins).

  11. Radiolysis and Hydrolysis of TRUEX-NPH solvent.

    SciTech Connect

    Simonzadeh, N.; Crabtree, A. M.; Trevorrow, L. E.; Vandegrift, G. F.

    1992-07-01

    The TRUEX solvent extraction process separates transuranic (TRU) elements from aqueous nitrate and chloride solutions. During contact with high-level wastes, which may be highly radioactive and highly acidic, the radiolysis and hydrolysis ofTRUEX-NPH solvent can affect the process not only by destroying the extractant CMPO in the solvent, but also by generating products of CMPO destruction, some of which are powerful extractants at low acidities and can prevent the stripping of Am and Pu from solvent that is to be recycled. To provide an experimental basis from which mathematical expressions of these effects could be derived, samples of solvent were degraded by radiolysis and hydrolysis while in contact with acidic aqueous solutions. Following this treatment, the distribution of americium between degraded solvent and aqueous HNO3 was used as a measure of the extent of degradation. Mathematical expressions were derived to represent the distribution coefficient, DAm, as a function of hydrolysis time and/or radiation dose. Assumptions about the dependence of DAm on CMPO concentration were used to derive expressions for the hydrolysis rate for CMPO and also to calculate values of radiation chemical yield for CMPO radiolysis. Also experimentally investigated were changes in acidity of both the aqueous and organic phases as functions of contact time, the effects of a carbonate wash in removing acidic degradation products that function as extractants at low acidities, and changes in compositions of some of the aqueous and organic phases during contact.

  12. Computationally efficient method for Fourier transform of highly chirped pulses for laser and parametric amplifier modeling.

    PubMed

    Andrianov, Alexey; Szabo, Aron; Sergeev, Alexander; Kim, Arkady; Chvykov, Vladimir; Kalashnikov, Mikhail

    2016-11-14

    We developed an improved approach to calculate the Fourier transform of signals with arbitrary large quadratic phase which can be efficiently implemented in numerical simulations utilizing Fast Fourier transform. The proposed algorithm significantly reduces the computational cost of Fourier transform of a highly chirped and stretched pulse by splitting it into two separate transforms of almost transform limited pulses, thereby reducing the required grid size roughly by a factor of the pulse stretching. The application of our improved Fourier transform algorithm in the split-step method for numerical modeling of CPA and OPCPA shows excellent agreement with standard algorithms.

  13. Method to precisely measure the phase of few-cycle laser pulses.

    PubMed

    Liao, Qing; Lu, Peixiang; Lan, Pengfei; Yang, Zhenyu; Li, Yunhua

    2008-04-28

    A new method of accurately measuring the carrier-envelope phase (CEP) of few-cycle pulses is presented. The high-energy photo-electron spectrum by a few-cycle pulse is dominated by photoelectrons bursting in very few short time intervals near the maximum of the pulse envelope. For high laser intensities, the positions of interference fringes in the high-energy cutoff region are very sensitive to the CEP, which can be used to measure and stabilize the CEP precisely. The measurement precision of the CEP strongly depends on the laser intensity for the fastest photoelectrons.

  14. Production of pulsed atomic oxygen beams via laser vaporization methods

    NASA Technical Reports Server (NTRS)

    Brinza, David E.; Coulter, Daniel R.; Liang, Ranty H.; Gupta, Amitava

    1987-01-01

    Energetic pulsed atomic oxygen beams were generated by laser-driven evaporation of cryogenically frozen ozone/oxygen films and thin films of indium-tin oxide (ITO). Mass and energy characterization of beams from the ozone/oxygen films were carried out by mass spectrometry. The peak flux, found to occur at 10 eV, is estimated from this data to be 3 x 10(20) m(-2) s(-1). Analysis of the time-of-flight data indicates a number of processes contribute to the formation of the atomic oxygen beam. The absence of metastable states such as the 2p(3) 3s(1) (5S) level of atomic oxygen blown off from ITO films is supported by the failure to observe emission at 777.3 nm from the 2p(3) 3p(1) (5P sub J) levels. Reactive scattering experiments with polymer film targets for atomic oxygen bombardment are planned using a universal crossed molecular beam apparatus.

  15. Evaluation of the pulse-contour method of determining stroke volume in man.

    NASA Technical Reports Server (NTRS)

    Alderman, E. L.; Branzi, A.; Sanders, W.; Brown, B. W.; Harrison, D. C.

    1972-01-01

    The pulse-contour method for determining stroke volume has been employed as a continuous rapid method of monitoring the cardiovascular status of patients. Twenty-one patients with ischemic heart disease and 21 patients with mitral valve disease were subjected to a variety of hemodynamic interventions. The pulse-contour estimations, using three different formulas derived by Warner, Kouchoukos, and Herd, were compared with indicator-dilution outputs. A comparison of the results of the two methods for determining stroke volume yielded correlation coefficients ranging from 0.59 to 0.84. The better performing Warner formula yielded a coefficient of variation of about 20%. The type of hemodynamic interventions employed did not significantly affect the results using the pulse-contour method. Although the correlation of the pulse-contour and indicator-dilution stroke volumes is high, the coefficient of variation is such that small changes in stroke volume cannot be accurately assessed by the pulse-contour method. However, the simplicity and rapidity of this method compared to determination of cardiac output by Fick or indicator-dilution methods makes it a potentially useful adjunct for monitoring critically ill patients.

  16. Silver-halide sensitized gelatin (SHSG) processing method for pulse holograms recorded on VRP plates

    NASA Astrophysics Data System (ADS)

    Evstigneeva, Maria K.; Drozdova, Olga V.; Mikhailov, Viktor N.

    2002-06-01

    One of the most important area of holograph applications is display holography. In case of pulse recording the requirement for vibration stability is easier than compared to CW exposure. At the same time it is widely known that the behavior of sliver-halide holographic materials strongly depends on the exposure duration. In particular the exposure sensitivity drastically decreases under nanosecond pulse duration. One of the effective ways of the diffraction efficiency improvement is SHSG processing method. This processing scheme is based on high modulation of refractive index due to microvoids appearance inside emulsion layer. It should be mentioned that the SHSG method was used earlier only in the cases when the holograms were recorded by use of CW lasers. This work is devoted to the investigation of SHSG method for pulse hologram recording on VRP plates. We used a pulsed YLF:Nd laser with pulse duration of 25 nanoseconds and wavelength of 527 nm. Both transmission and reflection holograms were recorded. The different kinds of bleaching as well as developing solutions were investigated. Our final processing scheme includes the following stages: 1) development in non-tanning solution, 2) rehalogenating bleach, 3) intermediate alcohol drying, 4) uniform second exposure, 5) second development in diluted developer, 6) reverse bleaching, 7) fixing and 8) gradient drying in isopropyl alcohol. Diffraction efficiency of transmission holograms was of about 60 percent and reflection mirror holograms was of about 45 percent. Thus we have demonstrated the SHSG processing scheme for producing effective holograms on VRP plates under pulse exposure.

  17. Method and Apparatus for Pressure Pulse Arcjet Starting

    NASA Technical Reports Server (NTRS)

    Sankovic, John M. (Inventor); Curran, Francis M. (Inventor)

    1999-01-01

    The invention disclosed is directed to a method and apparatus for an arcjet starter. The invention discloses a method of moving an arc from the subsonic region of the thruster to the supersonic region by introducing a pressurized propellant into the casuty of the anode.

  18. Method and apparatus for pressure pulse arcjet starting

    NASA Technical Reports Server (NTRS)

    Sankovic, John M. (Inventor); Curran, Francis M. (Inventor)

    1996-01-01

    The invention disclosed is directed to a method and apparatus for an arcjet starter. The invention discloses a method of moving an arc from the subsonic region of the thruster to the supersonic region by introducing a pressurized propellant into the casuty of the anode.

  19. Scintillation event energy measurement via a pulse model based iterative deconvolution method

    NASA Astrophysics Data System (ADS)

    Deng, Zhenzhou; Xie, Qingguo; Duan, Zhiwen; Xiao, Peng

    2013-11-01

    This work focuses on event energy measurement, a crucial task of scintillation detection systems. We modeled the scintillation detector as a linear system and treated the energy measurement as a deconvolution problem. We proposed a pulse model based iterative deconvolution (PMID) method, which can process pileup events without detection and is adaptive for different signal pulse shapes. The proposed method was compared with digital gated integrator (DGI) and digital delay-line clipping (DDLC) using real world experimental data. For singles data, the energy resolution (ER) produced by PMID matched that of DGI. For pileups, the PMID method outperformed both DGI and DDLC in ER and counts recovery. The encouraging results suggest that the PMID method has great potentials in applications like photon-counting systems and pulse height spectrometers, in which multiple-event pileups are common.

  20. Facile time-of-flight methods for characterizing pulsed superfluid helium droplet beams

    SciTech Connect

    He, Yunteng; Zhang, Jie; Li, Yang; Freund, William M.; Kong, Wei

    2015-08-15

    We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He{sub 2}{sup +} and He{sub 4}{sup +}, which are signatures of superfluid helium droplets. Without ionizing any helium atoms, multiphoton non-resonant laser ionization of CCl{sub 4} doped in superfluid helium droplets at 266 nm generates complex cluster ions of dopant fragments with helium atoms, including (He){sub n}C{sup +}, (He){sub n}Cl{sup +}, and (He){sub n}CCl{sup +}. Using both methods, we have characterized our cryogenic pulsed valve—the Even-Lavie valve. We have observed a primary pulse with larger helium droplets traveling at a slower speed and a rebound pulse with smaller droplets at a faster speed. In addition, the pickup efficiency of dopant is higher for the primary pulse when the nozzle temperature is higher than 13 K, and the total time duration of the doped droplet pulse is only on the order of 20 μs. These results stress the importance of fast and easy characterization of the droplet beam for sensitive measurements such as electron diffraction of doped droplets.

  1. [A calibrated method for blood pressure measurement based on volume pulse wave].

    PubMed

    Youde, Ding; Qinkai, Deng; Feixue, Liang; Jinseng, Guo

    2010-01-01

    Physiology parameters measurement based on volume pulse wave is suitable for the monitoring blood pressure continuously. This paper described that the systolic blood pressure (SBP) and diastolic blood pressure (DBP) can be calibrated by measuring the pulse propagation time, just on one point of finger tip. The volume pulse wave was acquired by lighting the red and infrared LED alternately, and after signal processing, an accelerated pulse wave was obtained. Then by measuring the pulse wave propagation time between the progressive wave and reflected wave, we can find the relationship of the time and the blood pressure, and establish the related systolic blood pressure measurement equation. At the same time, based on the relationship between alternating current and direct current components in the volume pulse waveforms and through regression analysising, the relevant diastolic blood pressure measurement equation can be established. 33 clinical experimentation cases have been worked by dividing them into two groups: training group (18 cases) and control group (15 cases), by comparing with the measuring results of the OMRON electronic sphygmomanometer. The results indicated that the two methods had good coherence. The measurement described is simple and reliable, and may be served as a new method for noninvasively and continuously measurement of blood pressure.

  2. Facile time-of-flight methods for characterizing pulsed superfluid helium droplet beams.

    PubMed

    He, Yunteng; Zhang, Jie; Li, Yang; Freund, William M; Kong, Wei

    2015-08-01

    We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He2(+) and He4(+), which are signatures of superfluid helium droplets. Without ionizing any helium atoms, multiphoton non-resonant laser ionization of CCl4 doped in superfluid helium droplets at 266 nm generates complex cluster ions of dopant fragments with helium atoms, including (He)(n)C(+), (He)(n)Cl(+), and (He)(n)CCl(+). Using both methods, we have characterized our cryogenic pulsed valve—the Even-Lavie valve. We have observed a primary pulse with larger helium droplets traveling at a slower speed and a rebound pulse with smaller droplets at a faster speed. In addition, the pickup efficiency of dopant is higher for the primary pulse when the nozzle temperature is higher than 13 K, and the total time duration of the doped droplet pulse is only on the order of 20 μs. These results stress the importance of fast and easy characterization of the droplet beam for sensitive measurements such as electron diffraction of doped droplets.

  3. Pulse shape discrimination and classification methods for continuous depth of interaction encoding PET detectors

    NASA Astrophysics Data System (ADS)

    Roncali, Emilie; Phipps, Jennifer E.; Marcu, Laura; Cherry, Simon R.

    2012-10-01

    In previous work we demonstrated the potential of positron emission tomography (PET) detectors with depth-of-interaction (DOI) encoding capability based on phosphor-coated crystals. A DOI resolution of 8 mm full-width at half-maximum was obtained for 20 mm long scintillator crystals using a delayed charge integration linear regression method (DCI-LR). Phosphor-coated crystals modify the pulse shape to allow continuous DOI information determination, but the relationship between pulse shape and DOI is complex. We are therefore interested in developing a sensitive and robust method to estimate the DOI. Here, linear discriminant analysis (LDA) was implemented to classify the events based on information extracted from the pulse shape. Pulses were acquired with 2×2×20 mm3 phosphor-coated crystals at five irradiation depths and characterized by their DCI values or Laguerre coefficients. These coefficients were obtained by expanding the pulses on a Laguerre basis set and constituted a unique signature for each pulse. The DOI of individual events was predicted using LDA based on Laguerre coefficients (Laguerre-LDA) or DCI values (DCI-LDA) as discriminant features. Predicted DOIs were compared to true irradiation depths. Laguerre-LDA showed higher sensitivity and accuracy than DCI-LDA and DCI-LR and was also more robust to predict the DOI of pulses with higher statistical noise due to low light levels (interaction depths further from the photodetector face). This indicates that Laguerre-LDA may be more suitable to DOI estimation in smaller crystals where lower collected light levels are expected. This novel approach is promising for calculating DOI using pulse shape discrimination in single-ended readout depth-encoding PET detectors.

  4. The method of pulsed x-ray detection with a diode laser

    NASA Astrophysics Data System (ADS)

    Liu, Jun; Ouyang, Xiaoping; Zhang, Zhongbing; Sheng, Liang; Chen, Liang; Tan, Xinjian; Weng, Xiufeng

    2016-12-01

    A new class of pulsed X-ray detection methods by sensing carrier changes in a diode laser cavity has been presented and demonstrated. The proof-of-principle experiments on detecting pulsed X-ray temporal profile have been done through the diode laser with a multiple quantum well active layer. The result shows that our method can achieve the aim of detecting the temporal profile of a pulsed X-ray source. We predict that there is a minimum value for the pre-bias current of the diode laser by analyzing the carrier rate equation, which exists near the threshold current of the diode laser chip in experiments. This behaviour generally agrees with the characterizations of theoretical analysis. The relative sensitivity is estimated at about 3.3 × 10-17 C ṡ cm2. We have analyzed the time scale of about 10 ps response with both rate equation and Monte Carlo methods.

  5. Method and Apparatus for Pressure Pulse Arcjet Starting

    NASA Technical Reports Server (NTRS)

    Sandkovic, John M. (Inventor); Curran, Francis M. (Inventor)

    1997-01-01

    The invention disclosed is directed to a model and apparatus for an arcjet starter. The invention discloses a method of moving an arc from the subsonic region of the thruster to the supersonic region by introducing a pressurized propellant into the annular area of the anode.

  6. Method and apparatus for pulse width modulation control of an AC induction motor

    NASA Technical Reports Server (NTRS)

    Geppert, Steven (Inventor); Slicker, James M. (Inventor)

    1984-01-01

    An inverter is connected between a source of DC power and a three-phase AC induction motor, and a micro-processor-based circuit controls the inverter using pulse width modulation techniques. In the disclosed method of pulse width modulation, both edges of each pulse of a carrier pulse train are equally modulated by a time proportional to sin .THETA., where .THETA. is the angular displacement of the pulse center at the motor stator frequency from a fixed reference point on the carrier waveform. The carrier waveform frequency is a multiple of the motor stator frequency. The modulated pulse train is then applied to each of the motor phase inputs with respective phase shifts of 120.degree. at the stator frequency. Switching control commands of electronic switches in the inverter are stored in a random access memory (RAM) and the locations of the RAM are successively read out in a cyclic manner, each bit of a given RAM location controlling a respective phase input of the motor. The DC power source preferably comprises rechargeable batteries and all but one of the electronic switches in the inverter can be disabled, the remaining electronic switch being part of a flyback DC-DC converter circuit for recharging the battery.

  7. Method and apparatus for pulse width modulation control of an AC induction motor

    DOEpatents

    Geppert, Steven; Slicker, James M.

    1984-01-01

    An inverter is connected between a source of DC power and a three-phase AC induction motor, and a micro-processor-based circuit controls the inverter using pulse width modulation techniques. In the disclosed method of pulse width modulation, both edges of each pulse of a carrier pulse train are equally modulated by a time proportional to sin .THETA., where .THETA. is the angular displacement of the pulse center at the motor stator frequency from a fixed reference point on the carrier waveform. The carrier waveform frequency is a multiple of the motor stator frequency. The modulated pulse train is then applied to each of the motor phase inputs with respective phase shifts of 120.degree. at the stator frequency. Switching control commands of electronic switches in the inverter are stored in a random access memory (RAM) and the locations of the RAM are successively read out in a cyclic manner, each bit of a given RAM location controlling a respective phase input of the motor. The DC power source preferably comprises rechargeable batteries and all but one of the electronic switches in the inverter can be disabled, the remaining electronic switch being part of a "flyback" DC-DC converter circuit for recharging the battery.

  8. Noninvasive Method for Measuring Local Pulse Wave Velocity by Dual Pulse Wave Doppler: In Vitro and In Vivo Studies

    PubMed Central

    Wang, Zhen; Yang, Yong; Yuan, Li-jun; Liu, Jie; Duan, Yun-you; Cao, Tie-sheng

    2015-01-01

    Objectives To evaluate the validity and reproducibility of a noninvasive dual pulse wave Doppler (DPWD) method, which involves simultaneous recording of flow velocity of two independent sample volumes with a measurable distance, for measuring the local arterial pulse wave velocity (PWV) through in vitro and in vivo studies. Methods The DPWD mode of Hitachi HI Vision Preirus ultrasound system with a 5–13MHz transducer was used. An in vitro model was designed to compare the PWV of a homogeneous rubber tubing with the local PWV of its middle part measured by DPWD method. In the in vivo study, local PWV of 45 hypertensive patients (25 male, 49.8±3.1 years) and 45 matched healthy subjects (25 male, 49.3±3.0 years) were investigated at the left common carotid artery (LCCA) by DPWD method. Results In the in vitro study, the local PWV measured by DPWP method and the PWV of the homogeneous rubber tubing did not show statistical difference (5.16 ± 0.28 m/s vs 5.03 ± 0.15 m/s, p = 0.075). The coefficient of variation (CV) of the intra- and inter- measurements for local PWV were 3.46% and 4.96%, for the PWV of the homogeneous rubber tubing were 0.99% and 1.98%. In the in vivo study, a significantly higher local PWV of LCCA was found in the hypertensive patients as compared to that in healthy subjects (6.29±1.04m/s vs. 5.31±0.72m/s, P = 0.019). The CV of the intra- and inter- measurements in hypertensive patients were 2.22% and 3.94%, in healthy subjects were 2.07% and 4.14%. Conclusions This study demonstrated the feasibility of the noninvasive DPWD method to determine the local PWV, which was accurate and reproducible not only in vitro but also in vivo studies. This noninvasive echocardiographic method may be illuminating to clinical use. PMID:25786124

  9. Determination of diffusion coefficients in polypyrrole thin films using a current pulse relaxation method

    NASA Technical Reports Server (NTRS)

    Penner, Reginald M.; Vandyke, Leon S.; Martin, Charles R.

    1987-01-01

    The current pulse E sub oc relaxation method and its application to the determination of diffusion coefficients in electrochemically synthesized polypyrrole thin films is described. Diffusion coefficients for such films in Et4NBF4 and MeCN are determined for a series of submicron film thicknesses. Measurement of the double-layer capacitance, C sub dl, and the resistance, R sub u, of polypyrrole thin films as a function of potential obtained with the galvanostatic pulse method is reported. Measurements of the electrolyte concentration in reduced polypyrrole films are also presented to aid in the interpretation of the data.

  10. Apparatus and method for recharging a string a avalanche transistors within a pulse generator

    DOEpatents

    Fulkerson, E. Stephen

    2000-01-01

    An apparatus and method for recharging a string of avalanche transistors within a pulse generator is disclosed. A plurality of amplification stages are connected in series. Each stage includes an avalanche transistor and a capacitor. A trigger signal, causes the apparatus to generate a very high voltage pulse of a very brief duration which discharges the capacitors. Charge resistors inject current into the string of avalanche transistors at various points, recharging the capacitors. The method of the present invention includes the steps of supplying current to charge resistors from a power supply; using the charge resistors to charge capacitors connected to a set of serially connected avalanche transistors; triggering the avalanche transistors; generating a high-voltage pulse from the charge stored in the capacitors; and recharging the capacitors through the charge resistors.

  11. Coupling the Mixed Potential and Radiolysis Models for Used Fuel Degradation

    SciTech Connect

    Buck, Edgar C.; Jerden, James L.; Ebert, William L.; Wittman, Richard S.

    2013-08-30

    The primary purpose of this report is to describe the strategy for coupling three process level models to produce an integrated Used Fuel Degradation Model (FDM). The FDM, which is based on fundamental chemical and physical principals, provides direct calculation of radionuclide source terms for use in repository performance assessments. The G-value for H2O2 production (Gcond) to be used in the Mixed Potential Model (MPM) (H2O2 is the only radiolytic product presently included but others will be added as appropriate) needs to account for intermediate spur reactions. The effects of these intermediate reactions on [H2O2] are accounted for in the Radiolysis Model (RM). This report details methods for applying RM calculations that encompass the effects of these fast interactions on [H2O2] as the solution composition evolves during successive MPM iterations and then represent the steady-state [H2O2] in terms of an “effective instantaneous or conditional” generation value (Gcond). It is anticipated that the value of Gcond will change slowly as the reaction progresses through several iterations of the MPM as changes in the nature of fuel surface occur. The Gcond values will be calculated with the RM either after several iterations or when concentrations of key reactants reach threshold values determined from previous sensitivity runs. Sensitivity runs with RM indicate significant changes in G-value can occur over narrow composition ranges. The objective of the mixed potential model (MPM) is to calculate the used fuel degradation rates for a wide range of disposal environments to provide the source term radionuclide release rates for generic repository concepts. The fuel degradation rate is calculated for chemical and oxidative dissolution mechanisms using mixed potential theory to account for all relevant redox reactions at the fuel surface, including those involving oxidants produced by solution radiolysis and provided by the radiolysis model (RM). The RM calculates

  12. Pulsing Depolarization: New Method of In-Vivo Blood Glucometry

    NASA Astrophysics Data System (ADS)

    Romanov, Dmitri; Shvartsman, Leonid; Fine, Ilya

    2002-03-01

    We propose a new system of non-invasive measurements enabling one to monitor in-vivo the glucose content of the blood. The proposed method is based on the transmission oximetry technique [1] and on the model of red blood cell aggregation [2]. We utilize the known birefregence of glucose solutions (in this case, the blood plasma) and the absence of this optical activity on the part of the red cells. Thus, we model the blood as a birefrigent host medium filled with optically non-active inclusions of spheroidal shape, arbitrarily oriented and having one semiaxis growing with time during the cell aggregation. We trace the evolution of initially linearly polarized laser beam in this system, and calculate the ellipticity and the azimuthal angle of the resulting partially depolarized light. The azimuthal angle is obtained as time-independent quantity being a function of the hematocrit, glucose content and thickness of the host medium layer, while the ellipticity depends also on the red cell aggregation, and thus oscillates with the heartbeats. Measurements of both the azimuthal angle and the ellipticity provide us with sufficient data to determine the glucose content of the blood. [1] I. Fine, A. Weinreb, Med. and Biol. Eng. and Comput., 31, 516 (1993). [2] L.D. Shvartsman, I. Fine, SPIE Proc., 4162, 120 (2000).

  13. Radiolysis Model Formulation for Integration with the Mixed Potential Model

    SciTech Connect

    Buck, Edgar C.; Wittman, Richard S.

    2014-07-10

    The U.S. Department of Energy Office of Nuclear Energy (DOE-NE), Office of Fuel Cycle Technology has established the Used Fuel Disposition Campaign (UFDC) to conduct the research and development activities related to storage, transportation, and disposal of used nuclear fuel (UNF) and high-level radioactive waste. Within the UFDC, the components for a general system model of the degradation and subsequent transport of UNF is being developed to analyze the performance of disposal options [Sassani et al., 2012]. Two model components of the near-field part of the problem are the ANL Mixed Potential Model and the PNNL Radiolysis Model. This report is in response to the desire to integrate the two models as outlined in [Buck, E.C, J.L. Jerden, W.L. Ebert, R.S. Wittman, (2013) “Coupling the Mixed Potential and Radiolysis Models for Used Fuel Degradation,” FCRD-UFD-2013-000290, M3FT-PN0806058

  14. Radiolysis of aqueous adenine (vitamin B4) and 8-hydroxyadenine

    NASA Astrophysics Data System (ADS)

    Hartmann, J.; Quint, R. M.; Getoff, N.

    2007-05-01

    The radiolysis of adenine (vitamin B4) was studied in aqueous solution (pH˜7.4) saturated either with argon (operating radicals: 44% e -aq, 46% OH, 10% H) or with air (46% OH, 54% O 2rad - ) and with N 2O (90% OH, 10% H), respectively. The obtained initial Gi-values are: 0.88, 1.16 and 1.45. As main radiolytic product was determined 8-hydroxyadenine (8-HOA), whose yield depends on the OH concentration in the reacting media. Hence, under the same experimental conditions the Gi-values are in media saturated with argon: 0.1, in air: 0.15 and in N 2O: 0.29. In aerated solution also a mixture of aldehydes as well as of carboxylic acids were formed, but they were not identified. 8-HOA is of some biological interest; therefore, its radiolysis was also investigated under the same conditions. The determined Gi(-8HOA)-values were in airfree solution negligible, in aerated solutions: 3.1 and in the presence of N 2O: 4.0. For explanation of the product formation some probable reaction mechanisms were given.

  15. Pulsed holographic microscopy as a measurement method of dynamic fracture toughness for fast propagating cracks

    NASA Astrophysics Data System (ADS)

    Suzuki, Shinichi; Homma, Hiroomi; Kusaka, Riichiro

    A METHOD OF pulsed holographic microscopy is applied to take instantaneous microscopic photographs of the neighborhoods of crack tips propagating through PMMA or through AISI 4340 steel specimens at a speed of several hundred meters per second. The cracks are in the opening mode. A fast propagating crack is recorded as a hologram at an instant during its propagation. A microscopic photograph of the crack is taken with a conventional microscope to magnify the reconstructed image from the hologram. From the microscopic photograph, crack opening displacement (COD) is measured along the crack in the vicinity of the crack tip. The COD is of the order often to one hundred microns, and in proportion to the square root of the distance from the crack tip. The dynamic fracture toughness KID is obtained using the formula for COD in the singular stress field of a fast propagating crack. Simultaneous KID measurement both through pulsed holographic microscopy and through the caustic method is furthermore carried out with PMMA specimens. The values of KID obtained through pulsed holographic microscopy are in agreement with those through the caustic method. Microcracks accompanied by a main crack are also photographed with the method of pulsed holographic microscopy.

  16. Pulse method of structural and parametric identification of models of heterogeneous catalytic processes

    SciTech Connect

    Kafarov, V.V.; Pisarenko, V.N.; Usacheva, I.I.

    1986-04-01

    A description is given of a pulse method for the investigation of heterogeneous catalytic processes, through which the parameters of a model can be evaluated with high accuracy. An example is given of the application of the procedure to an alloy catalyst.

  17. Assay of brines for common radiolysis products

    SciTech Connect

    MacDougall, C.S.

    1981-01-01

    Brines are assayed for four common products of radiolytic reaction. Free chlorine is determined spectrophotometrically after reaction with o-tolidine. The test is specific for chlorine, and quantities of chlorine from 0.1 to 6 ..mu..g in the test aliquot are determined with a precision of about +- 5%. Hydrogen peroxide is reacted with xylenol orange and determined spectrophotometrically with a precision of +- 5% on 2-..mu..g quantities of peroxide. A spectrophotometric method using thiocyanate is employed in the chlorate assay. After subtracting the bias caused by any H/sub 2/O/sub 2/ or Cl/sub 2/, 1-..mu..g quantities of chlorate can be determined with a precision of +- 10%. Perchlorate ion quantities of 1 ppM can be determined directly in brines by ion chromatography with a precision of about +- 15%.

  18. An ultrasound-based method for determining pulse wave velocity in superficial arteries.

    PubMed

    Rabben, Stein Inge; Stergiopulos, Nikos; Hellevik, Leif Rune; Smiseth, Otto A; Slørdahl, Stig; Urheim, Stig; Angelsen, Bjørn

    2004-10-01

    In this paper, we present a method for estimating local pulse wave velocity (PWV) solely from ultrasound measurements: the area-flow (QA) method. With the QA method, PWV is estimated as the ratio between change in flow and change in cross-sectional area (PWV = dQ/dA) during the reflection-free period of the cardiac cycle. In four anaesthetized dogs and 21 human subjects (age 23-74) we measured the carotid flow and cross-sectional area non-invasively by ultrasound. As a reference method we used the Bramwell-Hill (BH) equation which estimates PWV from pulse pressure and cross-sectional area. Additionally, we therefore measured brachial pulse pressure by oscillometry in the human subjects, and central aortic pulse pressure by micro-manometry in the dogs. As predicted by the pressure dependency of arterial stiffness, the estimated PWV decreased when the aortic pressure was lowered in two of the dogs. For the human subjects, the QA and BH estimates were correlated (R=0.43, p<0.05) and agreed on average (mean difference of -0.14 m/s). The PWV by the BH method increased with age (p<0.01) whereas the PWV by the QA method tended to increase with age (p<0.1). This corresponded to a larger residual variance (residual = deviation of the estimated PWV from the regression line) for the QA method than for the BH method, indicating different precisions for the two methods. This study illustrates that the simple equation PWV = dQ/dA gives estimates correlated to the PWV of the reference method. However, improvements in the basic measurements seem necessary to increase the precision of the method.

  19. Method and circuit for controlling the evolution time interval of a laser output pulse

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P. (Inventor)

    1992-01-01

    The invention is a method and circuit for controlling the evolution time interval of a laser output pulse used for making precise spectral measurements. It comprises the means for pumping a laser medium in a resonator that includes a Q-switch and polarizer that act in combination to control the loss in the resonator. A photodiode senses the resulting fluorescence which is applied to a two level Q-switch and polarizer from high to intermediate to substantially zero loss states to control the evolution time interval of the resulting laser output pulse.

  20. Practical method and device for enhancing pulse contrast ratio for lasers and electron accelerators

    DOEpatents

    Zhang, Shukui; Wilson, Guy

    2014-09-23

    An apparatus and method for enhancing pulse contrast ratios for drive lasers and electron accelerators. The invention comprises a mechanical dual-shutter system wherein the shutters are placed sequentially in series in a laser beam path. Each shutter of the dual shutter system has an individually operated trigger for opening and closing the shutter. As the triggers are operated individually, the delay between opening and closing first shutter and opening and closing the second shutter is variable providing for variable differential time windows and enhancement of pulse contrast ratio.

  1. Split-Step Fourier Method for Laser Pulse Propagation in Particulate Media,

    DTIC Science & Technology

    1981-10-01

    AD-A109 50 5 DEFENCE RESEARCH ESTABLISHMENT VALCARTIER (QUEBEC) F/9 20/6 SPLIT-STEP FOURIER METHO0D FOR LASER PULSE PROPAGATION IN PARTIC--ETCIU...SPLIT-STEP FOURIER METHOD FOR LASER PULSE PROPAGATION IN PARTICULATE MEDIA by W.G. Tam CENTRE DE RECHERCHES POUR LA DEFENSE DEFENCE RESEARCH...la fonction de coh6rence mutuelle est d6termin6e A l1’aide d’une transforma- tion Fourier ’split-step’. Cette approche nous permet d𔄀viter l’utili

  2. Multi-Gaussian fitting for pulse waveform using Weighted Least Squares and multi-criteria decision making method.

    PubMed

    Wang, Lu; Xu, Lisheng; Feng, Shuting; Meng, Max Q-H; Wang, Kuanquan

    2013-11-01

    Analysis of pulse waveform is a low cost, non-invasive method for obtaining vital information related to the conditions of the cardiovascular system. In recent years, different Pulse Decomposition Analysis (PDA) methods have been applied to disclose the pathological mechanisms of the pulse waveform. All these methods decompose single-period pulse waveform into a constant number (such as 3, 4 or 5) of individual waves. Furthermore, those methods do not pay much attention to the estimation error of the key points in the pulse waveform. The estimation of human vascular conditions depends on the key points' positions of pulse wave. In this paper, we propose a Multi-Gaussian (MG) model to fit real pulse waveforms using an adaptive number (4 or 5 in our study) of Gaussian waves. The unknown parameters in the MG model are estimated by the Weighted Least Squares (WLS) method and the optimized weight values corresponding to different sampling points are selected by using the Multi-Criteria Decision Making (MCDM) method. Performance of the MG model and the WLS method has been evaluated by fitting 150 real pulse waveforms of five different types. The resulting Normalized Root Mean Square Error (NRMSE) was less than 2.0% and the estimation accuracy for the key points was satisfactory, demonstrating that our proposed method is effective in compressing, synthesizing and analyzing pulse waveforms.

  3. Application of P4 Polyphase codes pulse compression method to air-coupled ultrasonic testing systems.

    PubMed

    Li, Honggang; Zhou, Zhenggan

    2017-03-03

    Air-coupled ultrasonic testing systems are usually restricted by low signal-to-noise ratios (SNR). The use of pulse compression techniques based on P4 Polyphase codes can improve the ultrasound SNR. This type of codes can generate higher Peak Side Lobe (PSL) ratio and lower noise of compressed signal. This paper proposes the use of P4 Polyphase sequences to code ultrasound with a NDT system based on air-coupled piezoelectric transducer. Furthermore, the principle of selecting parameters of P4 Polyphase sequence for obtaining optimal pulse compression effect is also studied. Successful results are presented in molded composite material. A hybrid signal processing method for improvement in SNR up to 12.11dB and in time domain resolution about 35% are achieved when compared with conventional pulse compression technique.

  4. Method and apparatus for generating high power laser pulses in the two to six micron wavelength range

    DOEpatents

    MacPherson, David C.; Nelson, Loren D.; O'Brien, Martin J.

    1996-01-01

    Apparatus performs a method of generating one or more output laser pulses in a range of 2 to 6 microns. When a plurality of the output laser pulses are generated, a first output pulse has any selected wavelength within the range and a second output pulse is temporally closely spaced relative to the first output pulse and has a chosen wavelength differing from the selected wavelength. An oscillator laser cavity is provided with a tunable oscillator rod capable of generating initial laser pulses within a range of from 750 to 1000 nm, and a tuning element is coupled to the rod. A flashlamp is operable to pump the rod. For two pulse operation, the flashlamp has a given duration. A Q-switch provides the initial laser pulses upon operation of the tuning element and the flashlamp. A Raman device coupled to the rod shifts the wavelength of such initial laser pulse into the range of from 2 to 6 microns to form the output laser pulse having a wavelength within the range. For multiple pulses, a controller causes the Q-switch to provide first and second ones of the initial laser pulses, spaced by a time interval less than the given duration. Also, a selector coupled to the tuning element is operable within such duration to successively select the wavelength of the first output pulse and the chosen wavelength of the second initial pulse. The Raman device is responsive to each of the initial light pulses to generate radiation at first and second Stokes wavelengths, each of said the output laser pulses being radiation at the second Stokes wavelength.

  5. Method and apparatus for generating high power laser pulses in the two to six micron wavelength range

    DOEpatents

    MacPherson, D.C.; Nelson, L.D.; O`Brien, M.J.

    1996-12-10

    Apparatus performs a method of generating one or more output laser pulses in a range of 2 to 6 microns. When a plurality of the output laser pulses are generated, a first output pulse has any selected wavelength within the range and a second output pulse is temporally closely spaced relative to the first output pulse and has a chosen wavelength differing from the selected wavelength. An oscillator laser cavity is provided with a tunable oscillator rod capable of generating initial laser pulses within a range of from 750 to 1000 nm, and a tuning element is coupled to the rod. A flashlamp is operable to pump the rod. For two pulse operation, the flashlamp has a given duration. A Q-switch provides the initial laser pulses upon operation of the tuning element and the flashlamp. A Raman device coupled to the rod shifts the wavelength of such initial laser pulse into the range of from 2 to 6 microns to form the output laser pulse having a wavelength within the range. For multiple pulses, a controller causes the Q-switch to provide first and second ones of the initial laser pulses, spaced by a time interval less than the given duration. Also, a selector coupled to the tuning element is operable within such duration to successively select the wavelength of the first output pulse and the chosen wavelength of the second initial pulse. The Raman device is responsive to each of the initial light pulses to generate radiation at first and second Stokes wavelengths, each of said the output laser pulses being radiation at the second Stokes wavelength. 30 figs.

  6. Sample preparation method for glass welding by ultrashort laser pulses yields higher seam strength

    SciTech Connect

    Cvecek, K.; Miyamoto, I.; Strauss, J.; Wolf, M.; Frick, T.; Schmidt, M.

    2011-05-01

    Glass welding by ultrashort laser pulses allows joining without the need of an absorber or a preheating and postheating process. However, cracks generated during the welding process substantially impair the joining strength of the welding seams. In this paper a sample preparation method is described that prevents the formation of cracks. The measured joining strength of samples prepared by this method is substantially higher than previously reported values.

  7. The RMT method for describing many-electron atoms in intense short laser pulses

    NASA Astrophysics Data System (ADS)

    Lysaght, M. A.; Moore, L. R.; Nikolopoulos, L. A. A.; Parker, J. S.; van der Hart, H. W.; Taylor, K. T.

    2012-11-01

    We describe how we have extended the underlying methods of the HELIUM code to describe multi-electron systems exposed to intense short-pulse laser light. We achieve this extension through exploiting the powerful R-matrix division-of-space concept to bring together a numerical method (basis set) most appropriate to the multi-electron finite inner region and a different numerical method (finite difference) most appropriate to the one-electron outer region. In order for the method to exploit massively parallel supercomputers efficiently, we time-propagate the wave function in both regions by employing schemes based on the Arnoldi method, long employed in HELIUM.

  8. Water Sorption and Gamma Radiolysis Studies for Uranium Oxides

    SciTech Connect

    Icenhour, A.S.

    2002-02-27

    During the development of a standard for the safe, long-term storage of {sup 233}U-containing materials, several areas were identified that needed additional experimental studies. These studies were related to the perceived potential for the radiolytic generation of large pressures or explosive concentrations of gases in storage containers. This report documents the results of studies on the sorption of water by various uranium oxides and on the gamma radiolysis of uranium oxides containing various amounts of sorbed moisture. In all of the experiments, {sup 238}U was used as a surrogate for the {sup 233}U. For the water sorption experiments, uranium oxide samples were prepared and exposed to known levels of humidity to establish the water uptake rate. Subsequently, the amount of water removed was studied by heating samples in a oven at fixed temperatures and by thermogravimetric analysis (TGA)/differential thermal analysis (DTA). It was demonstrated that heating at 650 C adequately removes all moisture from the samples. Uranium-238 oxides were irradiated in a {sup 60}Co source and in the high-gamma-radiation fields provided by spent nuclear fuel elements of the High Flux Isotope Reactor. For hydrated samples of UO{sub 3}, H{sub 2} was the primary gas produced; but the total gas pressure increase reached steady value of about 10 psi. This production appears to be a function of the dose and the amount of water present. Oxygen in the hydrated UO{sub 3} sample atmosphere was typically depleted, and no significant pressure rise was observed. Heat treatment of the UO{sub 3} {center_dot} xH{sub 2}O at 650 C would result in conversion to U{sub 3}O{sub 8} and eliminate the H{sub 2} production. For all of the U{sub 3}O{sub 8} samples loaded in air and irradiated with gamma radiation, a pressure decrease was seen and little, if any, H{sub 2} was produced--even for samples with up to 9 wt % moisture content. Hence, these results demonstrated that the efforts to remove trace

  9. A FBG pulse wave demodulation method based on PCF modal interference filter

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng; Xu, Shan; Shen, Ziqi; Zhao, Junfa; Miao, Changyun; Bai, Hua

    2016-10-01

    Fiber optic sensor embedded in textiles has been a new direction of researching smart wearable technology. Pulse signal which is generated by heart beat contains vast amounts of physio-pathological information about the cardiovascular system. Therefore, the research for textile-based fiber optic sensor which can detect pulse wave has far-reaching effects on early discovery and timely treatment of cardiovascular diseases. A novel wavelength demodulation method based on photonic crystal fiber (PCF) modal interference filter is proposed for the purpose of developing FBG pulse wave sensing system embedded in smart clothing. The mechanism of the PCF modal interference and the principle of wavelength demodulation based on In-line Mach-Zehnder interferometer (In-line MZI) are analyzed in theory. The fabricated PCF modal interferometer has the advantages of good repeatability and low temperature sensitivity of 3.5pm/°C from 25°C to 60°C. The designed demodulation system can achieve linear demodulation in the range of 2nm, with the wavelength resolution of 2.2pm and the wavelength sensitivity of 0.055nm-1. The actual experiments' result indicates that the pulse wave can be well detected by this demodulation method, which is in accordance with the commercial demodulation instrument (SM130) and more sensitive than the traditional piezoelectric pulse sensor. This demodulation method provides important references for the research of smart clothing based on fiber grating sensor embedded in textiles and accelerates the developments of wearable fiber optic sensors technology.

  10. Various methods of optimizing control pulses for quantum systems with decoherence

    NASA Astrophysics Data System (ADS)

    Pawela, Łukasz; Sadowski, Przemysław

    2016-05-01

    We design control setting that allows the implementation of an approximation of an unitary operation of a quantum system under decoherence using various quantum system layouts and numerical algorithms. We focus our attention on the possibility of adding ancillary qubits which help to achieve a desired quantum map on the initial system. Furthermore, we use three methods of optimizing the control pulses: genetic optimization, approximate evolution method and approximate gradient method. To model the noise in the system we use the Lindblad equation. We obtain results showing that applying the control pulses to the ancilla allows one to successfully implement unitary operation on a target system in the presence of noise, which is not possible which control field applied to the system qubits.

  11. Differential time domain method improves performance of pulsed laser ranging and three-dimensional imaging.

    PubMed

    Cao, Jie; Hao, Qun; Cheng, Yang; Peng, Yuxin; Zhang, Kaiyu; Mu, Jiaxing; Wang, Peng

    2016-01-10

    A ranging method based on the differential time domain method (DTDM) is proposed in order to improve ranging accuracy and the range of active measurement based on peak discriminator (PD). We develop mathematical models and deduce that zero-crossing sensitivity is an important factor, which affects the ranging error of DTDM. Additionally, zero-crossing sensitivity is determined by delayed time. We carried out relative experiments and obtained the smallest ranging error when delayed time is receiving pulse width. We also compare ranging, three-dimensional (3D) point clouds and depth images based on two methods under same testing conditions. The results show that DTDM is beneficial in improving performance of pulse laser ranging and 3D imaging.

  12. General implementation of the ERETIC method for pulsed field gradient probe heads.

    PubMed

    Ziarelli, Fabio; Viel, Stéphane; Caldarelli, Stefano; Sobieski, Daniel N; Augustine, Matthew P

    2008-10-01

    A capacitive coupling between a secondary radiofrequency (rf) channel and the gradient coil of a standard commercially available high resolution NMR spectrometer and probe head is described and used to introduce a low level exponentially damped rf signal near the frequency of the primary rf channel to serve as an external concentration standard, in analogy to the so-called ERETIC method. The stability of this inexpensive and simple to implement method, here referred to as the Pulse Into the Gradient (PIG) approach, is superb over a 14-h period and both gradient tailored water suppression and one-dimensional imaging applications are provided. Since the low level signal is introduced via the pulsed field gradient coil, the coupling is identical to that for a free induction signal and thus the method proves to be immune (within 5%) to sample ionic strength effects up to the 2M NaCl solutions explored here.

  13. Comparison of parabolic filtration methods for 3D filtered back projection in pulsed EPR imaging

    NASA Astrophysics Data System (ADS)

    Qiao, Zhiwei; Redler, Gage; Epel, Boris; Halpern, Howard J.

    2014-11-01

    Pulse electron paramagnetic resonance imaging (Pulse EPRI) is a robust method for noninvasively measuring local oxygen concentrations in vivo. For 3D tomographic EPRI, the most commonly used reconstruction algorithm is filtered back projection (FBP), in which the parabolic filtration process strongly influences image quality. In this work, we designed and compared 7 parabolic filtration methods to reconstruct both simulated and real phantoms. To evaluate these methods, we designed 3 error criteria and 1 spatial resolution criterion. It was determined that the 2 point derivative filtration method and the two-ramp-filter method have unavoidable negative effects resulting in diminished spatial resolution and increased artifacts respectively. For the noiseless phantom the rectangular-window parabolic filtration method and sinc-window parabolic filtration method were found to be optimal, providing high spatial resolution and small errors. In the presence of noise, the 3 point derivative method and Hamming-window parabolic filtration method resulted in the best compromise between low image noise and high spatial resolution. The 3 point derivative method is faster than Hamming-window parabolic filtration method, so we conclude that the 3 point derivative method is optimal for 3D FBP.

  14. Evaluation of cardiac output by 5 arterial pulse contour techniques using trend interchangeability method

    PubMed Central

    Fischer, Marc-Olivier; Diouf, Momar; de Wilde, Robert B.P.; Dupont, Hervé; Hanouz, Jean-Luc; Lorne, Emmanuel

    2016-01-01

    Abstract Cardiac output measurement with pulse contour analysis is a continuous, mini-invasive, operator-independent, widely used, and cost-effective technique, which could be helpful to assess changes in cardiac output. The 4-quadrant plot and the polar plot have been described to compare the changes between 2 measurements performed under different conditions, and the direction of change by using different methods of measurements. However, the 4-quadrant plot and the polar plot present a number of limitations, with a risk of misinterpretation in routine clinical practice. We describe a new trend interchangeability method designed to objectively define the interchangeability of each change of a variable. Using the repeatability of the reference method, we classified each change as either uninterpretable or interpretable and then as either noninterchangeable, in the gray zone or interchangeable. An interchangeability rate can then be calculated by the number of interchangeable changes divided by the total number of interpretable changes. In this observational study, we used this objective method to assess cardiac output changes with 5 arterial pulse contour techniques (Wesseling's method, LiDCO, PiCCO, Hemac method, and Modelflow) in comparison with bolus thermodilution technique as reference method in 24 cardiac surgery patients. A total of 172 cardiac output variations were available from the 199 data points: 88 (51%) were uninterpretable, according to the first step of the method. The second step of the method, based on the 84 (49%) interpretable variations, showed that only 18 (21%) to 30 (36%) variations were interchangeable regardless of the technique used. None of pulse contour cardiac output technique could be interchangeable with bolus thermodilution to assess changes in cardiac output using the trend interchangeability method in cardiac surgery patients. Future studies may consider using this method to assess interchangeability of changes between different

  15. The radiolysis of iodine in aqueous solutions containing methane

    NASA Astrophysics Data System (ADS)

    Paquette, Jean; Ford, Beverly L.

    The γ-radiolysis of iodine, iodine, iodate and periodate solutions containing methane has been investigated. Iodoalkanes are produced in these solutions upon irradiation. In the case of unbuffered iodine, iodate and periodate solutions at an initial concentration of 1.0 × 10 -4 mol dm -3, nearly all of the initial iodine is transformed into iodoalkanes after the absorption of a 4 kGy radiation dose. The yield of iodoalkanes is lower for iodine solutions and for iodide solutions buffered at neutral pH. It is concluded that the main reactions leading to the formation of iodoalkanes are CH 3+I 2→CH 3I+I and CH 3+I→CH 3I. In the case of iodate and periodate, these reactions could be preceeded by reactions involving the methyl radical and oxyiodine species: CH 3+IO x→CH 2O+HIO x-1.

  16. Effect of alpha-radiolysis on TRUEX-NPH solvent

    SciTech Connect

    Buchholz, B.A.; Nunez, L.; Vandegrift, G.F.

    1994-10-01

    An unexpectedly high degradation of the TRUEX (TRansUranic EXtraction) solvent occurred during the treatment of waste solutions from the New Brunswick Laboratory. The waste solutions treated contained approximately 1 g/L of Pu-239 and 20 mg/L of Am-241. Earlier studies of {alpha}-radiolysis using carbon tetrachloride (CCl{sub 4}) rather than normal paraffinic hydrocarbons (NPH) as a diluent indicated greater resistance to radiation damage than observed. For this study, the TRUEX-NPH solvent was loaded with Am-241 in nitric acid, irradiated with doses up to 3.5 Mrad, and monitored for decline in extraction capability as a function of absorbed dose. Results of this study are being used to improve the Generic TRUEX Model (GTM), a thermodynamic model that permits flowsheet design for solvent extraction processing.

  17. Formation of stable radicals in the radiolysis of fluoroorganic compounds

    NASA Astrophysics Data System (ADS)

    Goldanskii, V. I.; Barkalov, I. M.

    The existence of anomally long-living radicals (life time in liquid more than 100 days at 300 K) which arise in the process of radiolysis has been discovered in liquid perfluorocarbons. The ESR spectra analysis has allowed the singling out of two types of radical: (1) the perfluoroalkyl radical in which the unpaired electron stabilization is thought to be connected with the steric isolation of the surrounding perfluoromethyl groups and (2) the perfluoroalkyl radical whose stabilization is connected with the delocalization of the unpaired electron conjugated with the double CC bond. These stable radicals may be employed in the synthesis and modification of fluoropolymers as initiators and regulators, in the dosimetry of reactor irradiation, as well as in medico-biological investigations as spin-labelled compounds.

  18. Radiolysis of alanine adsorbed in a clay mineral

    SciTech Connect

    Aguilar-Ovando, Ellen Y.; Negron-Mendoza, Alicia

    2013-07-03

    Optical activity in molecules is a chemical characteristic of living beings. In this work, we examine the hypothesis of the influence of different mineral surfaces on the development of a specific chirality in organic molecules when subjected to conditions simulating the primitive Earth during the period of chemical evolution. By using X-ray diffraction techniques and HPLC/ELSD to analyze aqueous suspensions of amino acids adsorbed on minerals irradiated in different doses with a cobalt-60 gamma source, the experiments attempt to prove the hypothesis that some solid surfaces (like clays and meteorite rocks) may have a concentration capacity and protective role against external sources of ionizing radiation (specifically {gamma}-ray) for some organic compounds (like some amino acids) adsorbed on them. Preliminary results show a slight difference in the adsorption and radiolysis of the D-and L-alanine.

  19. The RMT method for describing many-electron atoms in intense short laser pulses

    NASA Astrophysics Data System (ADS)

    Lysaght, M. A.; Moore, L. R.; Nikolopoulos, L. A. A.; Parker, J. S.; van der Hart, H. W.; Taylor, K. T.

    2012-11-01

    We describe how we have developed an ab initio R-Matrix incorporating Time (RMT) method to provide an accurate description of the single ionization of a general many-electron atom exposed to short intense laser pulses. The new method implements the "division-of-space" concept central to R-matrix theory and takes over the sophisticated time-propagation algorithms of the HELIUM code. We have tested the accuracy of the new method by calculating multiphoton ionization rates of He and Ne and have found excellent agreement with other highly accurate and well-established methods.

  20. Development of ultrasonic pulse-train Doppler method for velocity profile and flowrate measurement

    NASA Astrophysics Data System (ADS)

    Wada, Sanehiro; Furuichi, Noriyuki; Shimada, Takashi

    2016-11-01

    We present a novel technique for measuring the velocity profile and flowrate in a pipe. This method, named the ultrasonic pulse-train Doppler method (UPTD), has the advantages of expanding the velocity range and setting the smaller measurement volume with low calculation and instrument costs in comparison with the conventional ultrasonic pulse Doppler method. The conventional method has limited measurement of the velocity range due to the Nyquist sampling theorem. In addition, previous reports indicate that a smaller measurement volume increases the accuracy of the measurement. In consideration of the application of the conventional method to actual flow fields, such as industrial facilities and power plants, the issues of velocity range and measurement volume are important. The UPTD algorithm, which exploits two pulses of ultrasound with a short interval and envelope detection, is proposed. Velocity profiles calculated by this algorithm were examined through simulations and excellent agreement was found in all cases. The influence of the signal-to-noise ratio (SNR) on the algorithm was also estimated. The result indicates that UPTD can measure velocity profiles with high accuracy, even under a small SNR. Experimental measurements were conducted and the results were evaluated at the national standard calibration facility of water flowrate in Japan. Every detected signal forms a set of two pulses and the enveloped line can be observed clearly. The results show that UPTD can measure the velocity profiles over the pipe diameter, even if the velocities exceed the measurable velocity range. The measured flowrates were under 0.6% and the standard deviations for all flowrate conditions were within  ±0.38%, which is the uncertainty of the flowrate measurement estimated in the previous report. In conclusion, UPTD provides superior accuracy and expansion of the velocity range.

  1. Compressive strength evaluation of structural lightweight concrete by non-destructive ultrasonic pulse velocity method.

    PubMed

    Bogas, J Alexandre; Gomes, M Glória; Gomes, Augusto

    2013-07-01

    In this paper the compressive strength of a wide range of structural lightweight aggregate concrete mixes is evaluated by the non-destructive ultrasonic pulse velocity method. This study involves about 84 different compositions tested between 3 and 180 days for compressive strengths ranging from about 30 to 80 MPa. The influence of several factors on the relation between the ultrasonic pulse velocity and compressive strength is examined. These factors include the cement type and content, amount of water, type of admixture, initial wetting conditions, type and volume of aggregate and the partial replacement of normal weight coarse and fine aggregates by lightweight aggregates. It is found that lightweight and normal weight concretes are affected differently by mix design parameters. In addition, the prediction of the concrete's compressive strength by means of the non-destructive ultrasonic pulse velocity test is studied. Based on the dependence of the ultrasonic pulse velocity on the density and elasticity of concrete, a simplified expression is proposed to estimate the compressive strength, regardless the type of concrete and its composition. More than 200 results for different types of aggregates and concrete compositions were analyzed and high correlation coefficients were obtained.

  2. Common products from gamma-radiolysis and ultraviolet photolysis of metronidazole

    NASA Astrophysics Data System (ADS)

    Moore, Douglas E.; Wilkins, Brian J.

    u.v. Photolysis of metronidazole in aqueous solution at pH 7.0 results in rearrangement through an imino-ketone to an oxadiazole. These compounds were also found following γ-radiolysis of metronidazole, being about 10% of the products. Saturation of the solution with nitrous oxide caused a slight increase in the yield of imino-ketone in radiolysis. Conversely, the imino-ketone was not detected on addition of sodium formate or propan-2-ol to the radiolysis, but an increased yield of other products was observed. It is suggested that formation of the imino-ketone and oxadiazole in both photolysis and radiolysis occurs via processes which do not involve the nitro radical anion as first transient species.

  3. Determining the sizes of micropores in activated charcoals by the pulsed NMR method

    NASA Astrophysics Data System (ADS)

    Gogelashvili, G. Sh.; Khozina, E. V.; Vartapetyan, R. Sh.; Ladychuk, D. V.; Grunin, Yu. B.

    2011-07-01

    The pulsed NMR method was used to measure the nuclear spin-spin relaxation of protons of water adsorbed in micropores of activated charcoal (AC) samples with different porous structures. A correlation was found between the spin-spin relaxation time of water protons in AC with completely filled micropores and the volume density of water primary adsorption centers in the AC samples. An equation for approximating obtained dependences is proposed that allows us to determine the volume of micropores in AC.

  4. Method and apparatus for improving the quality and efficiency of ultrashort-pulse laser machining

    DOEpatents

    Stuart, Brent C.; Nguyen, Hoang T.; Perry, Michael D.

    2001-01-01

    A method and apparatus for improving the quality and efficiency of machining of materials with laser pulse durations shorter than 100 picoseconds by orienting and maintaining the polarization of the laser light such that the electric field vector is perpendicular relative to the edges of the material being processed. Its use is any machining operation requiring remote delivery and/or high precision with minimal collateral dames.

  5. Pulse wave detection method based on the bio-impedance of the wrist

    NASA Astrophysics Data System (ADS)

    He, Jianman; Wang, Mengjun; Li, Xiaoxia; Li, Gang; Lin, Ling

    2016-05-01

    The real-time monitoring of pulse rate can evaluate the heart health to some extent, and the measurement of bio-impedance has the potential in wearable health monitoring system. In this paper, an effective method, which contains self-balancing bridge, flexible electrode, and high-speed digital lock-in algorithm (DLIA) with over-sampling, was designed to detect the impedance pulse wave at the wrist. By applying the self-balancing bridge, the basic impedance can be compensated as much as possible, and the low amplitude of impedance variation related to heart pulse can be obtained more easily. And the flexible conductive rubber electrode used in our experiment is human-friendly. Besides, the over-sampling method and high-speed DLIA are used to enhance the effective resolution of the existing data sampled by analog to digital converter. With the high-speed data process and simple circuit above, this proposed method has the potential in wrist-band wearable systems and it can satisfy quests of small volume and low power consumption.

  6. Development of glucose measurement system based on pulsed laser-induced ultrasonic method

    NASA Astrophysics Data System (ADS)

    Ren, Zhong; Wan, Bin; Liu, Guodong; Xiong, Zhihua

    2016-09-01

    In this study, a kind of glucose measurement system based on pulsed-induced ultrasonic technique was established. In this system, the lateral detection mode was used, the Nd: YAG pumped optical parametric oscillator (OPO) pulsed laser was used as the excitation source, the high sensitivity ultrasonic transducer was used as the signal detector to capture the photoacoustic signals of the glucose. In the experiments, the real-time photoacoustic signals of glucose aqueous solutions with different concentrations were captured by ultrasonic transducer and digital oscilloscope. Moreover, the photoacoustic peak-to-peak values were gotten in the wavelength range from 1300nm to 2300nm. The characteristic absorption wavelengths of glucose were determined via the difference spectral method and second derivative method. In addition, the prediction models of predicting glucose concentrations were established via the multivariable linear regression algorithm and the optimal prediction model of corresponding optimal wavelengths. Results showed that the performance of the glucose system based on the pulsed-induced ultrasonic detection method was feasible. Therefore, the measurement scheme and prediction model have some potential value in the fields of non-invasive monitoring the concentration of the glucose gradient, especially in the food safety and biomedical fields.

  7. Density dependence of the yield of hydrated electrons in the low-LET radiolysis of supercritical water at 400 °C: influence of the geminate recombination of subexcitation-energy electrons prior to thermalization.

    PubMed

    Meesungnoen, Jintana; Sanguanmith, Sunuchakan; Jay-Gerin, Jean-Paul

    2013-10-21

    Monte Carlo simulations were used to calculate the yield of hydrated electrons (eaq(-)) in the low-linear energy transfer radiolysis of supercritical water at 400 °C as a function of water density over the range of ~0.15 to 0.6 g cm(-3). Very good agreement was found between our calculations and picosecond pulse radiolysis experimental data at ~60 ps and 1 ns at high density (>0.35 g cm(-3)). At densities lower than ~0.35 g cm(-3), our eaq(-) yields were lower than the experimental data, especially at ~60 ps. However, if we incorporated into the simulations a prompt geminate electron-cation (H2O˙(+)) recombination (prior thermalization of the electron) that decreased as the density decreased, our computed eaq(-) yields at ~60 ps and 1 ns compared fairly well with the experimental data for the entire density range studied.

  8. Robust segmentation methods with an application to aortic pulse wave velocity calculation.

    PubMed

    Babin, Danilo; Devos, Daniel; Pižurica, Aleksandra; Westenberg, Jos; Vansteenkiste, Ewout; Philips, Wilfried

    2014-04-01

    Aortic stiffness has proven to be an important diagnostic and prognostic factor of many cardiovascular diseases, as well as an estimate of overall cardiovascular health. Pulse wave velocity (PWV) represents a good measure of the aortic stiffness, while the aortic distensibility is used as an aortic elasticity index. Obtaining the PWV and the aortic distensibility from magnetic resonance imaging (MRI) data requires diverse segmentation tasks, namely the extraction of the aortic center line and the segmentation of aortic regions, combined with signal processing methods for the analysis of the pulse wave. In our study non-contrasted MRI images of abdomen were used in healthy volunteers (22 data sets) for the sake of non-invasive analysis and contrasted magnetic resonance (MR) images were used for the aortic examination of Marfan syndrome patients (8 data sets). In this research we present a novel robust segmentation technique for the PWV and aortic distensibility calculation as a complete image processing toolbox. We introduce a novel graph-based method for the centerline extraction of a thoraco-abdominal aorta for the length calculation from 3-D MRI data, robust to artifacts and noise. Moreover, we design a new projection-based segmentation method for transverse aortic region delineation in cardiac magnetic resonance (CMR) images which is robust to high presence of artifacts. Finally, we propose a novel method for analysis of velocity curves in order to obtain pulse wave propagation times. In order to validate the proposed method we compare the obtained results with manually determined aortic centerlines and a region segmentation by an expert, while the results of the PWV measurement were compared to a validated software (LUMC, Leiden, the Netherlands). The obtained results show high correctness and effectiveness of our method for the aortic PWV and distensibility calculation.

  9. Methods and optical fibers that decrease pulse degradation resulting from random chromatic dispersion

    DOEpatents

    Chertkov, Michael; Gabitov, Ildar

    2004-03-02

    The present invention provides methods and optical fibers for periodically pinning an actual (random) accumulated chromatic dispersion of an optical fiber to a predicted accumulated dispersion of the fiber through relatively simple modifications of fiber-optic manufacturing methods or retrofitting of existing fibers. If the pinning occurs with sufficient frequency (at a distance less than or are equal to a correlation scale), pulse degradation resulting from random chromatic dispersion is minimized. Alternatively, pinning may occur quasi-periodically, i.e., the pinning distance is distributed between approximately zero and approximately two to three times the correlation scale.

  10. [Application of three heat pulse technique-based methods to determine the stem sap flow].

    PubMed

    Wang, Sheng; Fan, Jun

    2015-08-01

    It is of critical importance to acquire tree transpiration characters through sap flow methodology to understand tree water physiology, forest ecology and ecosystem water exchange. Tri-probe heat pulse sensors, which are widely utilized in soil thermal parameters and soil evaporation measurement, were applied to implement Salix matsudana sap flow density (Vs) measurements via heat-ratio method (HRM), T-Max method (T-Max) and single-probe heat pulse probe (SHPP) method, and comparative analysis was conducted with additional Grainer's thermal diffusion probes (TDP) measured results. The results showed that, it took about five weeks to reach a stable measurement stage after TPHP installation, Vs measured with three methods in the early stage after installation was 135%-220% higher than Vs in the stable measurement stage, and Vs estimated via HRM, T-Max and SHPP methods were significantly linearly correlated with Vs estimated via TDP method, with R2 of 0.93, 0.73 and 0.91, respectively, and R2 for Vs measured by SHPP and HRM reached 0.94. HRM had relatively higher precision in measuring low rates and reverse sap flow. SHPP method seemed to be very promising to measure sap flow for configuration simplicity and high measuring accuracy, whereas it couldn' t distinguish directions of flow. T-Max method had relatively higher error in sap flow measurement, and it couldn' t measure sap flow below 5 cm3 · cm(-2) · h(-1), thus this method could not be used alone, however it could measure thermal diffusivity for calculating sap flow when other methods were imposed. It was recommended to choose a proper method or a combination of several methods to measure stem sap flow, based on specific research purpose.

  11. Method and apparatus for rapidly growing films on substrates using pulsed supersonic jets

    DOEpatents

    Eres, Diula; Lowndes, Douglas H.

    1992-01-01

    A method and apparatus for the rapid and economical deposition of uniform and high quality films upon a substrate for subsequent use in producing electronic devices, for example. The resultant films are either epitaxial (crystalline) or amorphous depending upon the incidence rate and the temperature and structure of the substrate. The deposition is carried out in a chamber maintained at about 10.sup.-6 Torr. A gaseous source of the material for forming the deposit is injected into the deposition chamber in the form of a pulsed supersonic jet so as to obtain a high incidence rate. The supersonic jet is produced by a pulsed valve between a relatively high presure reservoir, containing the source gaseous molecules, and the deposition chamber; the valve has a small nozzle orifice (e.g., 0.1-1.0 mm diameter). The type of deposit (crystalline amorphous) is then dependent upon the temperature and structure of the substrate. Very high deposition rates are achieved, and the deposit is very smooth and of uniform thickness. Typically the deposition rate is about 100 times that of much more expensive conventional molecular beam methods for deposition, and comparable to certain expensive plasma-assisted CVD methods of the art. The high growth rate of this method results in a reduced contamination of the deposit from other elements in the environment. The method is illustrated by the deposition of epitaxial and amorphour germanium films upon GaAs substrates.

  12. Method and apparatus for measuring the intensity and phase of an ultrashort light pulse

    DOEpatents

    Kane, Daniel J.; Trebino, Rick P.

    1998-01-01

    The pulse shape I(t) and phase evolution x(t) of ultrashort light pulses are obtained using an instantaneously responding nonlinear optical medium to form a signal pulse. A light pulse, such a laser pulse, is split into a gate pulse and a probe pulse, where the gate pulse is delayed relative to the probe pulse. The gate pulse and the probe pulse are combined within an instantaneously responding optical medium to form a signal pulse functionally related to a temporal slice of the gate pulse corresponding to the time delay of the probe pulse. The signal pulse is then input to a wavelength-selective device to output pulse field information comprising intensity vs. frequency for a first value of the time delay. The time delay is varied over a range of values effective to yield an intensity plot of signal intensity vs. wavelength and delay. In one embodiment, the beams are overlapped at an angle so that a selected range of delay times is within the intersection to produce a simultaneous output over the time delays of interest.

  13. Investigation of a pulsed current annealing method in reusing MOSFET dosimeters for in vivo IMRT dosimetry

    SciTech Connect

    Luo, Guang-Wen; Qi, Zhen-Yu Deng, Xiao-Wu; Rosenfeld, Anatoly

    2014-05-15

    Purpose: To explore the feasibility of pulsed current annealing in reusing metal oxide semiconductor field-effect transistor (MOSFET) dosimeters forin vivo intensity modulated radiation therapy (IMRT) dosimetry. Methods: Several MOSFETs were irradiated atd{sub max} using a 6 MV x-ray beam with 5 V on the gate and annealed with zero bias at room temperature. The percentage recovery of threshold voltage shift during multiple irradiation-annealing cycles was evaluated. Key dosimetry characteristics of the annealed MOSFET such as the dosimeter's sensitivity, reproducibility, dose linearity, and linearity of response within the dynamic range were investigated. The initial results of using the annealed MOSFETs for IMRT dosimetry practice were also presented. Results: More than 95% of threshold voltage shift can be recovered after 24-pulse current continuous annealing in 16 min. The mean sensitivity degradation was found to be 1.28%, ranging from 1.17% to 1.52%, during multiple annealing procedures. Other important characteristics of the annealed MOSFET remained nearly consistent before and after annealing. Our results showed there was no statistically significant difference between the annealed MOSFETs and their control samples in absolute dose measurements for IMRT QA (p = 0.99). The MOSFET measurements agreed with the ion chamber results on an average of 0.16% ± 0.64%. Conclusions: Pulsed current annealing provides a practical option for reusing MOSFETs to extend their operational lifetime. The current annealing circuit can be integrated into the reader, making the annealing procedure fully automatic.

  14. A method for pulsed scannerless laser imaging using focal plane array

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-peng; Wang, Ke-yong; Deng, Jia-hao; Hai, Yan

    2011-06-01

    Laser imaging techniques have advantages for EMI (Electro Magnetic Interference) immunity and abundant image information. This contribution describes the research activity on the scannerless laser imaging detection technique using direct detection aimed at laser fuze applications. The technique using a pulsed laser to illuminate the target and a focal plane array can be used as a receiver. The range information is achieved by means of a direct time of light measurement. Information about the reflectivity of the target is gathered by recording the amplitude of the received pulse. In this paper a high-repetition-frequency, narrow pulse semiconductor laser floodlight emitting system is designed; corresponding optics is used to generate the homogenously illuminated FOI (field of illumination). The echo of laser is collected by receiving optical system fed to focal plane array. Some experiments were done with the emitting and receiving systems that had been designed. Experiments show the validity and rationality of this method. The scannerless structure is robust and provides instantaneous snapshot-type imaging. Avoiding any moving mechanical parts, scannerless laser imaging system have distinct characteristics such as small, compact, high frame rate, wide field of view and high reliability. It is an optimal approach to realize laser imaging fuze.

  15. Method and apparatus for fast laser-pulse detection using gaseous plasmas

    DOEpatents

    McLellan, E.J.; Webb, J.A.

    1981-06-18

    The method and device of the instant invention is a detector of pulsed laser radiation which utilizes the electromotive force generated by the plasma formed when such radiation is focused onto a surface. Measurements are made with a 10.6 ..mu..m CO/sub 2/ laser capable of producing peak intensities of 10/sup 13/ W/cm/sup 2/ when directed through a converging lens. Evacuated detector response to such laser intensity if 1 kV signal peak amplitude and subnanosecond risetimes into a 50 ..cap omega.. load. Detector performance is found to be greatly altered with the introduction of a background gas. For example, with one atmosphere of air, the detector produces prompt signals of the order of 1 V with subnanosecond response for pulse trains lasting 100 ns. With argon, krypton, or zenon at pressures of the order of 10 torr, the detector generates trigger pulses of about 250 V amplitude and 0.2 ns risetimes. Such detectors are quite robust when irradiated with high intensity laser radiation and are useful for qualitative laser beam monitoring.

  16. Method and apparatus for fast laser pulse detection using gaseous plasmas

    DOEpatents

    McLellan, Edward J.; Webb, John A.

    1984-01-01

    The method and device of the instant invention is a detector of pulsed laser radiation which utilizes the electromotive force generated by the plasma formed when such radiation is focused onto a surface (1). Measurements are made with a 10.6 .mu.m CO.sub.2 laser capable of producing peak intensities of 10.sup.13 W/cm.sup.2 when directed through a converging lens (2). Evacuated detector response to such laser intensity is 1 kV signal peak amplitude and subnanosecond risetimes into a 50.OMEGA. load (3). Detector performance is found to be greatly altered with the introduction of a background gas (4). For example, with one atmosphere of air, the detector produces prompt signals of the order of 1 V with subnanosecond response for pulse trains lasting 100 ns. With argon, krypton, or zenon at pressures of the order of 10 torr, the detector generates "trigger pulses" of about 250 V amplitude and 0.2 ns risetimes. Such detectors are quite robust when irradiated with high intensity laser radiation and are useful for qualitative laser beam monitoring.

  17. Doppler ultrasound in the measurement of pulse wave velocity: agreement with the Complior method

    PubMed Central

    2011-01-01

    Aortic stiffness is an independent predictor factor for cardiovascular risk. Different methods for determining pulse wave velocity (PWV) are used, among which the most common are mechanical methods such as SphygmoCor or Complior, which require specific devices and are limited by technical difficulty in obtaining measurements. Doppler guided by 2D ultrasound is a good alternative to these methods. We studied 40 patients (29 male, aged 21 to 82 years) comparing the Complior method with Doppler. Agreement of both devices was high (R = 0.91, 0.84-0.95, 95% CI). The reproducibility analysis revealed no intra-nor interobserver differences. Based on these results, we conclude that Doppler ultrasound is a reliable and reproducible alternative to other established methods for the measurement of aortic PWV. PMID:21496271

  18. A new method for measurement of pulse wave velocity in arterial wall

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoming; Kinnick, Randall R.; Fatemi, Mostafa; Greenleaf, James F.

    2003-10-01

    Arterial wall stiffness can be associated with various diseases. The stiffness of an artery can be assessed by measurement of the pulse wave velocity (PWV). PWV is directly related to the Youngs modulus by the well-known Moens-Korteweg equation. Usually, PWV is estimated using the foot-to-foot method. However, the foot of the pressure wave is not very clear due to reflected waves. Also, the pressure wave is normally at a low frequency, hence, the time resolution is low. PWV is an average indicator of artery stiffness between the two measuring points, therefore it is not easy to identify local stiffness. We propose producing a very short pulse wave in the arterial wall using ultrasound radiation force and measuring its propagation speed along the artery by laser. The temporal resolution of this method is in the range of microseconds, which allows PWV to be measured accurately over a few millimeters. Experiments were carried out on a silicone tube in gelatin. PWV was measured by two scanning methods: (1) fixed source and scanning detector, (2) scanning source and fixed detector. Results: PWV was measured at 2 mm/40 μs by both methods. The Doppler technique was also tested which is potentially suitable for clinical applications.

  19. AFM and pulsed laser ablation methods for Cultural Heritage: application to archeometric analysis of stone artifacts

    NASA Astrophysics Data System (ADS)

    Barberio, M.; Veltri, S.; Stranges, F.; Bonanno, A.; Xu, F.; Antici, P.

    2015-09-01

    In this paper, we introduce the use of the atomic force microscope (AFM) and of the pulsed laser ablation as methods for morphological diagnostic with nanoscale precision of archeological artifacts and corrosive patina removal from stone artifacts. We test our methodology on stone artifacts extracted from the Church of Sotterra (located in Calabria, South Italy). The AFM microscopy was compared with different petrographic, chemical, optical and morphological analysis methods for identifying the textural characteristics, evaluating the state of preservation and formulating some hypotheses about the provenance and composition of the impurity patina located on the artifact surfaces. We demonstrate that with the nanometric precision obtained with AFM microscopy, it is possible to distinguish the different states of preservation, much better than using conventional petrographic methods. The surface's roughness is evaluated from very small artifact's fragments, reducing the coring at micrometric scale with a minimal damage to the artworks. After the diagnosis, we performed restoration tests using the pulsed laser ablation (PLA) method and compared it with the more common micro-sandblasting under dry conditions. We find that the PLA is highly effective for the removal of the surficial patina, with a control of a few hundreds of nanometers in the cleaning of surface, without introducing chemical or morphological damages to the artifacts. Moreover, PLA can be easily implemented in underwater conditions; this has the great advantage that stone and pottery artifacts for marine archeological sites do not need to be removed from the site.

  20. Application of the Marquardt least-squares method to the estimation of pulse function parameters

    NASA Astrophysics Data System (ADS)

    Lundengârd, Karl; Rančić, Milica; Javor, Vesna; Silvestrov, Sergei

    2014-12-01

    Application of the Marquardt least-squares method (MLSM) to the estimation of non-linear parameters of functions used for representing various lightning current waveshapes is presented in this paper. Parameters are determined for the Pulse, Heidler's and DEXP function representing the first positive, first and subsequent negative stroke currents as given in IEC 62305-1 Standard Ed.2, and also for some other fast- and slow-decaying lightning current waveshapes. The results prove the ability of the MLSM to be used for the estimation of parameters of the functions important in lightning discharge modeling.

  1. Pulse-shape discrimination in neutron depth profiling radioanalytical methods. Part II

    NASA Astrophysics Data System (ADS)

    Vacík, J.; Červená, J.; Hnatowicz, V.; Havránek, V.; Hoffmann, J.; Pošta, S.; Fink, D.

    1999-01-01

    Pulse shape discrimination (PSD) is used for the reduction of radiation background in the depth sensitive neutron depth profiling method (NDP) based on the detection of charged particles from the (n, α) and (n, p) nuclear reactions induced by thermal neutrons on some light elements. The experimental NDP-PSD arrangement is described and its performance is demonstrated on the measurement of real samples. Background reduction by several orders of magnitude in the region below 1 MeV leads to a corresponding sensitivity improvement and to an extension of the measurable depth region for some light elements.

  2. Noncontact single-pulse optical method to measure interfacial properties in intact systems.

    PubMed

    Clark, David C; Kim, Myung K

    2012-12-15

    We introduce a noncontact purely optical approach to measuring the localized surface properties of an interface within a system using a single optical pressure pulse and a time-resolved digital holographic quantitative phase-imaging technique to track the propagating nanometric capillary disturbance. We demonstrate the proposed method's ability to measure the surface energy of deionized water, methanol, and chemical monolayers formed by surfactants with good agreement to published values. The development of this technique boasts immediate application to static and dynamic systems and near-future applications for living biological cell membranes.

  3. Pulse retrieval in frequency-resolved optical gating based on the method of generalized projections

    SciTech Connect

    DeLong, K.W.; Fittinghoff, D.N.; Trebino, R. ); Kohler, B.; Wilson, K. )

    1994-12-15

    We use the algorithmic method of generalized projections (GP's) to retrieve the intensity and phase of an ultrashort laser pulse from the experimental trace in frequency-resolved optical gating (FROG). Using simulations, we show that the use of GP's improves significantly the convergence properties of the algorithm over the basic FROG algorithm. In experimental measurements, the GP-based algorithm achieves significantly lower errors than previous algorithms. The use of GP's also permits the inclusion of an arbitrary material response function in the FROG problem.

  4. A Heuristic Fast Method to Solve the Nonlinear Schroedinger Equation in Fiber Bragg Gratings with Arbitrary Shape Input Pulse

    SciTech Connect

    Emami, F.; Hatami, M.; Keshavarz, A. R.; Jafari, A. H.

    2009-08-13

    Using a combination of Runge-Kutta and Jacobi iterative method, we could solve the nonlinear Schroedinger equation describing the pulse propagation in FBGs. By decomposing the electric field to forward and backward components in fiber Bragg grating and utilizing the Fourier series analysis technique, the boundary value problem of a set of coupled equations governing the pulse propagation in FBG changes to an initial condition coupled equations which can be solved by simple Runge-Kutta method.

  5. X-ray pulse preserving single-shot optical cross-correlation method for improved experimental temporal resolution

    SciTech Connect

    Beye, M.; Krupin, O.; Hays, G.; Jong, S. de; Lee, S.; Coffee, R.; Holmes, M. R.; Fry, A. R.; White, W. E.; Bostedt, C.; Schlotter, W. F.; Reid, A. H.; Rupp, D.; Lee, W.-S.; Scherz, A. O.; Chuang, Y.-D.; Cryan, J. P.; Glownia, J. M.; Foehlisch, A.; Durr, H. A.

    2012-03-19

    We measured the relative arrival time between an optical pulse and a soft x-ray pulse from a free-electron laser. This femtosecond cross-correlation measurement was achieved by observing the change in optical reflectivity induced through the absorption of a fraction of the x-ray pulse. The main x-ray pulse energy remained available for an independent pump-probe experiment where the sample may be opaque to soft x-rays. The method was employed to correct the two-pulse delay data from a canonical pump-probe experiment and demonstrate 130 {+-} 20 fs (FWHM) temporal resolution. We further analyze possible timing jitter sources and point to future improvements.

  6. Pulsed arrays: A new method of flaw detection by generating a frequency dependent angle of propagation

    NASA Astrophysics Data System (ADS)

    Hill, S. J.; Dixon, S. M.

    2012-05-01

    A new method of using an array of generation sources, pulsed simultaneously to generate a wavefront with a frequency dependant angle of propagation, has been developed. If pulsed arrays are used to generate a wave with a frequency dependent angle of propagation, the angle at which the wave was launched can be identified by measuring the frequency of the detected wave. In an isotropic material this means that it is possible use a second transducer to locate the position of the scatterer, whereas with a conventional single element generator method, it can only be located onto an ellipse. In addition to an increased scan speed, the resolution of detection should also be improved. A theoretical framework is put forward to explain how the wavefront is created from the superposition of the waves from the individual elements, and how the frequency varies along the wavefront. Finite element models and experimental measurements were also carried out, and both agreed with the analytic model. This method will have applications within NDE, but could also extend to sonar and radar techniques.

  7. Calculation of photon pulse height distribution using deterministic and Monte Carlo methods

    NASA Astrophysics Data System (ADS)

    Akhavan, Azadeh; Vosoughi, Naser

    2015-12-01

    Radiation transport techniques which are used in radiation detection systems comprise one of two categories namely probabilistic and deterministic. However, probabilistic methods are typically used in pulse height distribution simulation by recreating the behavior of each individual particle, the deterministic approach, which approximates the macroscopic behavior of particles by solution of Boltzmann transport equation, is being developed because of its potential advantages in computational efficiency for complex radiation detection problems. In current work linear transport equation is solved using two methods including collided components of the scalar flux algorithm which is applied by iterating on the scattering source and ANISN deterministic computer code. This approach is presented in one dimension with anisotropic scattering orders up to P8 and angular quadrature orders up to S16. Also, multi-group gamma cross-section library required for this numerical transport simulation is generated in a discrete appropriate form. Finally, photon pulse height distributions are indirectly calculated by deterministic methods that approvingly compare with those from Monte Carlo based codes namely MCNPX and FLUKA.

  8. Pulsed Dilution Method for the Recovery of Aggregated Mouse TNF-α

    PubMed Central

    Mahmoodi, Merat; Ghodsi, Maryam; Moghadam, Malihe; Sankian, Mojtaba

    2017-01-01

    Background: The expression of mouse tumor necrosis factor alpha (TNF-α) in Escherichia coli is a favorable way to get high yield of protein; however, the formation of cytoplasmic inclusion bodies, which is the consequence of insoluble accumulated proteins, is a major obstacle in this system. To overcome this obstacle, we used a pulsed dilution method to convert the product to its native conformation Methods: Reducing agent and guanidine hydrochloride were used to solubilize inclusion bodies formed after TNF-(α) expression. Then, the refolding procedure was performed by pulsed dilution of the denatured protein into a refolding buffer. The properly-folded protein was purified by metal affinity chromatography. Results: SDS-PAGE showed a 19.9 kDa band related to the mature TNF-(α) protein. The protein was recognized by anti-mouse TNF-(α) on western blots. The final concentration of the purified recombinant TNF-(α) was 62.5 µg/mL Conclusions: Our study demonstrates the efficiency of this method to produce a high yield of folded mature TNF- (α). PMID:28367471

  9. Calibration of pulsed electroacoustic method considering electrode-dielectric interface status and porosity

    NASA Astrophysics Data System (ADS)

    Huang, Meng; Zhou, Yuanxiang; Chen, Weijiang; Lu, Licheng; Jin, Fubao; Huang, Jianwen

    2014-10-01

    Pulsed electroacoustic (PEA) method is widely used, but measurement conditions not always agree with the underlying PEA assumptions. This necessitates space charge recovery; however, existing research only addresses the attenuation and dispersion in lossy media. The effects of electrode-dielectric interface contact status and porosity on the accuracy of space charge distribution are discussed in the present article. It is shown that the presence of nonlinear interface and porosity can introduce severe error. However, because the properties of acoustic propagation of waves (which are generated from charge on the electrode and in the bulk) are different, the conventional recovery algorithm is no longer suitable for calibrating the charge density. To obtain accurate space charge profiles, it is necessary to eliminate these effects. A method has been proposed which is based on the original measurement process. The validity of the proposed method was tested by reasonable post-recovery electric field distributions.

  10. Pulse-fitting - A novel method for the evaluation of pulse measurements, demonstrated for the low frequency behavior of lithium-ion cells

    NASA Astrophysics Data System (ADS)

    Schmidt, Jan Philipp; Ivers-Tiffée, Ellen

    2016-05-01

    The impedance of a commercial lithium ion cell (2 Ah) is evaluated over a wide frequency range of 10-5 Hz < f < 102 Hz using a new approach. The so-called pulse-fitting method (PFM) derives the cell impedance from time domain measurements, which are transferred into frequency data by a using a newly developed evaluation algorithm in combination with the distribution of relaxation times (DRT). The time constants of the individual polarization processes taking place during charging/discharging were analyzed at 20 different state-of-charge levels at 23 °C in a wide frequency range spanning from 10-5 Hz < f < 102 Hz. The pulse-fitting method seems to be especially useful for monitoring the change of individual polarization losses in the course of time, as self-discharge effects can be sorted out.

  11. A method for the formation of Pt metal nanoparticle arrays using nanosecond pulsed laser dewetting

    SciTech Connect

    Owusu-Ansah, Ebenezer; Horwood, Corie A.; Birss, Viola I.; Shi, Yujun J.; El-Sayed, Hany A.

    2015-05-18

    Nanosecond pulsed laser dewetting of Pt thin films, deposited on a dimpled Ta (DT) surface, has been studied here in order to form ordered Pt nanoparticle (NP) arrays. The DT substrate was fabricated via a simple electrochemical anodization process in a highly concentrated H{sub 2}SO{sub 4} and HF solution. Pt thin films (3–5 nm) were sputter coated on DT and then dewetted under vacuum to generate NPs using a 355 nm laser radiation (6–9 ns, 10 Hz). The threshold laser fluence to fully dewet a 3.5 nm thick Pt film was determined to be 300 mJ/cm{sup 2}. Our experiments have shown that shorter irradiation times (≤60 s) produce smaller nanoparticles with more uniform sizes, while longer times (>60 s) give large nanoparticles with wider size distributions. The optimum laser irradiation time of 1 s (10 pulses) has led to the formation of highly ordered Pt nanoparticle arrays with an average nanoparticle size of 26 ± 3 nm with no substrate deformation. At the optimum condition of 1 s and 500 mJ/cm{sup 2}, as many as 85% of the dewetted NPs were found neatly in the well-defined dimples. This work has demonstrated that pulsed laser dewetting of Pt thin films on a pre-patterned dimpled substrate is an efficient and powerful technique to produce highly ordered Pt nanoparticle arrays. This method can thus be used to produce arrays of other high-melting-point metal nanoparticles for a range of applications, including electrocatalysis, functionalized nanomaterials, and analytical purposes.

  12. A method for the formation of Pt metal nanoparticle arrays using nanosecond pulsed laser dewetting

    NASA Astrophysics Data System (ADS)

    Owusu-Ansah, Ebenezer; Horwood, Corie A.; El-Sayed, Hany A.; Birss, Viola I.; Shi, Yujun J.

    2015-05-01

    Nanosecond pulsed laser dewetting of Pt thin films, deposited on a dimpled Ta (DT) surface, has been studied here in order to form ordered Pt nanoparticle (NP) arrays. The DT substrate was fabricated via a simple electrochemical anodization process in a highly concentrated H2SO4 and HF solution. Pt thin films (3-5 nm) were sputter coated on DT and then dewetted under vacuum to generate NPs using a 355 nm laser radiation (6-9 ns, 10 Hz). The threshold laser fluence to fully dewet a 3.5 nm thick Pt film was determined to be 300 mJ/cm2. Our experiments have shown that shorter irradiation times (≤60 s) produce smaller nanoparticles with more uniform sizes, while longer times (>60 s) give large nanoparticles with wider size distributions. The optimum laser irradiation time of 1 s (10 pulses) has led to the formation of highly ordered Pt nanoparticle arrays with an average nanoparticle size of 26 ± 3 nm with no substrate deformation. At the optimum condition of 1 s and 500 mJ/cm2, as many as 85% of the dewetted NPs were found neatly in the well-defined dimples. This work has demonstrated that pulsed laser dewetting of Pt thin films on a pre-patterned dimpled substrate is an efficient and powerful technique to produce highly ordered Pt nanoparticle arrays. This method can thus be used to produce arrays of other high-melting-point metal nanoparticles for a range of applications, including electrocatalysis, functionalized nanomaterials, and analytical purposes.

  13. Comparison of the soluble products from radiolysis and photolysis of CS2

    NASA Astrophysics Data System (ADS)

    Cataldo, F.; Heymann, D.

    2001-05-01

    Soluble products from the radiolysis of CS2 with gamma variable rays from 60Co, include elemental sulfur and CmSn compounds. These compounds were essentially the same as those that had already been reported for the UV photolysis of CS2. The amount of sulfur formed was proportional to the irradiation dose. The radiolysis also formed a dark colored, insoluble polymer in amounts proportional to the irradiation dose. The soluble CmSn molecules found in this work were most likely due to `aborted polymerization'. Radiolysis and photolysis of CS2 may contribute important C-S compounds for the cosmochemistry of circumstellar and interstellar media as well as of comets and atmospheres of the giant planets.

  14. Vitroceramic interface deposited on titanium substrate by pulsed laser deposition method.

    PubMed

    Voicu, Georgeta; Miu, Dana; Dogaru, Ionut; Jinga, Sorin Ion; Busuioc, Cristina

    2016-08-30

    Pulsed laser deposition (PLD) method was used to obtain biovitroceramic thin film coatings on titanium substrates. The composition of the targets was selected from SiO2-CaO-P2O5-(CaF2) systems and the corresponding masses were prepared using the sol-gel method. The depositions were performed in oxygen atmosphere (100mTorr), while the substrates were heated at 400°C. The PLD deposited films were analysed through different experimental techniques: X-ray diffraction, scanning (SEM, EDX) and transmission (HRTEM, SAED) electron microscopy and infra-red spectroscopy coupled with optical microscopy. They were also biologically tested by in vitro cell culture and the contact angle was determined. The bioevaluation results indicate a high biocompatibilty of the obtained materials, demonstrating their potential use for biomedical applications.

  15. Fabrication of Nanocomposite Thermoelectric Materials by a Pulsed Laser Deposition Method

    NASA Astrophysics Data System (ADS)

    Matsubara, Masato; Azuma, Hirozumi; Asahi, Ryoji

    2011-05-01

    We applied a pulsed laser deposition (PLD) technique to fabricate nanocomposite half-Heusler thermoelectrics by employing two different methods: a dry process and a wet process. First, we tried to obtain nanosized thermoelectric particles by using PLD in a liquid solvent. Nanosized (<100 nm) spherical and crystalline half-Heusler particles containing Ti, Zr, Hf, Ni, and Sn elements were obtained by this method, showing good controllability of stoichiometry. The key is to select a solvent that prevents oxidation. Second, the dry PLD process was employed to coat the thermoelectric powder with metal oxides. To this end, we developed a PLD coating apparatus. After sintering the coated powder using the spark plasma sintering (SPS) technique, we confirmed that a nanosized layer of the metal oxides was uniformly formed at the grain boundaries of the half-Heusler matrix. With these two examples, the capability of the PLD techniques to fabricate well-controlled nanocomposite thermoelectric materials is demonstrated.

  16. A new oscillometric method for pulse wave analysis: comparison with a common tonometric method

    PubMed Central

    Wassertheurer, S; Kropf, J; Weber, T; van der Giet, M; Baulmann, J; Ammer, M; Hametner, B; Mayer, C C; Eber, B; Magometschnigg, D

    2010-01-01

    In the European Society of Cardiology–European Society of Hypertension guidelines of the year 2007, the consequences of arterial stiffness and wave reflection on cardiovascular mortality have a major role. But the investigators claimed the poor availability of devices/methods providing easy and widely suitable measuring of arterial wall stiffness or their surrogates like augmentation index (AIx) or aortic systolic blood pressure (aSBP). The aim of this study was the validation of a novel method determining AIx and aSBP based on an oscillometric method using a common cuff (ARCSolver) against a validated tonometric system (SphygmoCor). aSBP and AIx measured with the SphygmoCor and ARCSolver method were compared for 302 subjects. The mean age was 56 years with an s.d. of 20 years. At least two iterations were performed in each session. This resulted in 749 measurements. For aSBP the mean difference was −0.1 mm Hg with an s.d. of 3.1 mm Hg. The mean difference for AIx was 1.2% with an s.d. of 7.9%. There was no significant difference in reproducibility of AIx for both methods. The variation estimate of inter- and intraobserver measurements was 6.3% for ARCSolver and 7.5% for SphygmoCor. The ARCSolver method is a novel method determining AIx and aSBP based on an oscillometric system with a cuff. The results agree with common accepted tonometric measurements. Its application is easy and for widespread use. PMID:20237499

  17. The radiation chemistry of CMPO: Part 2. Alpha radiolysis

    SciTech Connect

    Bruce J. Mincher; Stephen P. Mezyk; Gary S. Groenewold; Christian Ekberg; Gunnar Skarnemark; Jay A. LaVerne; Mikael Nilsson; Jeremy Pearson; Nicholas C. Schmitt; Richard D. Tillotson; Lonnie G. Olson; Gracy Elias

    2014-01-01

    Octylphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) dissolved in dodecane was subjected to a-irradiation using a He-ion beam, 244 Cm isotopic a-rays, and He and Li ions created by the n,a reaction of 10B in a nuclear reactor. Post-irradiation samples were analyzed for the radiolytically-induced decrease in CMPO concentration, the appearance of degradation products, and their Am solvent extraction distribution ratios. The –G CMPO-value for the radiolytic degradation of CMPO was found to be very low compared to values previously reported for ?-irradiation. Additionally, isotopic irradiation to absorbed a-doses as high as 600 kGy in aerated solution had no effect on Am solvent extraction or stripping. The main CMPO radiolysis products identified in He-ion beam irradiated samples by ESI-MS include amides, an acidic amide, and amines produced by bond rupture on either side of the CMPO carbonyl group. Deaerated samples irradiated using the reactor in the absence of an aqueous phase, or with a dilute nitric acid aqueous phase showed small but measurable decreases in CMPO concentration with increasing absorbed doses. Higher concentrations of nitric acid resulted in lower decomposition rates for the CMPO. The radio-protection by dissolved oxygen and nitric acid previously found for ?-irradiated CMPO also occurs for a-irradiation. This suggests that similar free-radical mechanisms operate in the high-LET system, but with lower degradation yields due to the lower overall radical concentrations produced.

  18. Method for producing H.sub.2 using a rotating drum reactor with a pulse jet heat source

    DOEpatents

    Paulson, Leland E.

    1990-01-01

    A method of producing hydrogen by an endothermic steam-carbon reaction using a rotating drum reactor and a pulse jet combustor. The pulse jet combustor uses coal dust as a fuel to provide reaction temperatures of 1300.degree. to 1400.degree. F. Low-rank coal, water, limestone and catalyst are fed into the drum reactor where they are heated, tumbled and reacted. Part of the reaction product from the rotating drum reactor is hydrogen which can be utilized in suitable devices.

  19. Methods on handling missing rainfall data with Neyman-Scott rectangular pulse modeling

    NASA Astrophysics Data System (ADS)

    Yendra, Rado; Jemain, Abdul Aziz; Zahari, Marina; Wan Zin, Wan Zawiah

    2013-04-01

    Rainfall data from rain-gauge stations suffers the risk of being missing due to factors such as human negligence, faulty equipment and disasters. In this paper, complete monthly rainfall data from 1985 to 1992 in Payakangsar station is used as the base data to determine the appropriate method for handling missing data. A portion of this complete data is then omitted at random by as much as 5%, 10% and 15% of the total number of data. Three methods of missing data replacement are considered that is, replacement of the missing data with zero (NR), single imputation (SI) and multiple imputation (MI) methods. The Neyman-Scott Rectangular Pulse (NSRP) rainfall stochastic model is then fitted to the resulting data from these three methods. Data from the month of October and November are selected for further analysis as these two months represent the months with highest rainfall amount received. To assess the performance of these three methods, a goodness-of-fit test based on the mean absolute error is applied. Results from the goodness-of-fit test indicate that NR method is the best for each case of missing data in the month of October, and also for the 5% case in November. On the other hand, method of imputation with 4 stages (MI) is superior for cases of 10% and 15% in November.

  20. Poly(arylsulfone imide) as E-beam resist: synthesis and radiolysis. Technical report

    SciTech Connect

    Chien, J.C.; Cheng, Z.S.

    1989-01-01

    Aromatic diamines containing -SO/sub 2/-and-S- moieties were used to prepare soluble polyimides with ditrifluoromethyl methane bis(phthalic anhydride) (F-series polyimides) and polyamic acid with pyromellitic dianhydride (P-series). Gamma radiolysis gave G(S) values for scission between 1 to 2 with no crosslinking. Significant weight loss occurred with radiolysis is attributable to efficient -SO/sub 2/-bond scission for the R-series polyimides, as well as imidization in the cases of P-series polyamic acids.

  1. A new method for compensation of the effect of charging transformer's leakage inductance on PFN voltage regulation in Klystron pulse modulators

    NASA Astrophysics Data System (ADS)

    Patel, Akhil; Kale, Umesh; Shrivastava, Purushottam

    2017-04-01

    The Line type modulators have been widely used to generate high voltage rectangular pulses to power the klystron for high power RF generation. In Line type modulator, the Pulse Forming Network (PFN) which is a cascade combination of lumped capacitors and inductors is used to store the electrical energy. The charged PFN is then discharged into a klystron by firing a high voltage Thyratron switch. This discharge generates a high voltage rectangular pulse across the klystron electrodes. The amplitude and phase of Klystron's RF output is governed by the high voltage pulse amplitude. The undesired RF amplitude and phase stability issues arises at the klystron's output due to inter-pulse and during the pulse amplitude variations. To reduce inter-pulse voltage variations, the PFN is required to be charged at the same voltage after every discharge cycle. At present, the combination of widely used resonant charging and deQing method is used to regulate the pulse to pulse PFN voltage variations but the charging transformer's leakage inductance puts an upper bound on the regulation achievable by this method. Here we have developed few insights of the deQing process and devised a new compensation method to compensate this undesired effect of charging transformer's leakage inductance on the pulse to pulse PFN voltage stability. This compensation is accomplished by the controlled partial discharging of the split PFN capacitor using a low voltage MOSFET switch. Theoretically, very high values of pulse to pulse voltage stability may be achieved using this method. This method may be used in deQing based existing modulators or in new modulators, to increase the pulse to pulse voltage stability, without having a very tight bound on charging transformer's leakage inductance. Given a stable charging power supply, this method may be used to further enhance the inter-pulse voltage stability of modulators which employ the direct charging, after replacing the direct charging with the

  2. Amplifiable DNA from Gram-negative and Gram-positive bacteria by a low strength pulsed electric field method

    PubMed Central

    Vitzthum, Frank; Geiger, Georg; Bisswanger, Hans; Elkine, Bentsian; Brunner, Herwig; Bernhagen, Jürgen

    2000-01-01

    An efficient electric field-based procedure for cell disruption and DNA isolation is described. Isoosmotic suspensions of Gram-negative and Gram-positive bacteria were treated with pulsed electric fields of <60 V/cm. Pulses had an exponential decay waveform with a time constant of 3.4 µs. DNA yield was linearly dependent on time or pulse number, with several thousand pulses needed. Electrochemical side-effects and electrophoresis were minimal. The lysates contained non-fragmented DNA which was readily amplifiable by PCR. As the method was not limited to samples of high specific resistance, it should be applicable to physiological fluids and be useful for genomic and DNA diagnostic applications. PMID:10734214

  3. A two-dose-rate method for general recombination correction for liquid ionization chambers in pulsed beams

    NASA Astrophysics Data System (ADS)

    Tölli, Heikki; Sjögren, Rickard; Wendelsten, Mikael

    2010-08-01

    The correction for general recombination losses in liquid ionization chambers (LICs) is more complex than that in air-filled ionization chambers. The reason for this is that the saturation charge in LICs, i.e. the charge that escapes initial recombination, depends on the applied voltage. This paper presents a method, based on measurements at two different dose rates in a pulsed beam, for general recombination correction in LICs. The Boag theory for pulsed beams is used and the collection efficiency is determined by numerical methods which are equivalent to the two-voltage method used in dosimetry with air-filled ionization chambers. The method has been tested in experiments in water in a 20 MeV electron beam using two LICs filled with isooctane and tetramethylsilane. The dose per pulse in the electron beam was varied between 0.1 mGy/pulse and 8 mGy/pulse. The relative standard deviations of the collection efficiencies determined with the two-dose-rate method ranged between 0.1% and 1.5%. The dose-rate variations of the general recombination corrected charge measured with the LICs are in excellent agreement with the corresponding values obtained with an air-filled plane parallel ionization chamber.

  4. A novel defect depth measurement method based on Nonlinear System Identification for pulsed thermographic inspection

    NASA Astrophysics Data System (ADS)

    Zhao, Yifan; Mehnen, Jörn; Sirikham, Adisorn; Roy, Rajkumar

    2017-02-01

    This paper introduces a new method to improve the reliability and confidence level of defect depth measurement based on pulsed thermographic inspection by addressing the over-fitting problem. Different with existing methods using a fixed model structure for all pixels, the proposed method adaptively detects the optimal model structure for each pixel thus targeting to achieve better model fitting while using less model terms. Results from numerical simulations and real experiments suggest that (a) the new method is able to measure defect depth more accurately without a pre-set model structure (error is usually within 1 % when SNR>32 dB) in comparison with existing methods, (b) the number of model terms should be 8 for signals with SNR∈ [ 30 dB , 40 dB ] , 8-10 for SNR>40 dB and 5-8 for SNR<30 dB, and (c) a data length with at least 100 data points and 2-3 times of the characteristic time usually produces the best results.

  5. Method for continuous control of composition and doping of pulsed laser deposited films

    DOEpatents

    Lowndes, Douglas H.; McCamy, James W.

    1995-01-01

    A method for growing a deposit upon a substrate of semiconductor material involves the utilization of pulsed laser deposition techniques within a low-pressure gas environment. The substrate and a target of a first material are positioned within a deposition chamber and a low-pressure gas atmosphere is developed within the chamber. The substrate is then heated, and the target is irradiated, so that atoms of the target material are ablated from the remainder of the target, while atoms of the gas simultaneously are adsorbed on the substrate/film surface. The ablated atoms build up upon the substrate, together with the adsorbed gas atoms to form the thin-film deposit on the substrate. By controlling the pressure of the gas of the chamber atmosphere, the composition of the formed deposit can be controlled, and films of continuously variable composition or doping can be grown from a single target of fixed composition.

  6. Method for continuous control of composition and doping of pulsed laser deposited films by pressure control

    DOEpatents

    Lowndes, Douglas H.; McCamy, James W.

    1996-01-01

    A method for growing a deposit upon a substrate of semiconductor material involves the utilization of pulsed laser deposition techniques within a low-pressure gas environment. The substrate and a target of a first material are positioned within a deposition chamber and a low-pressure gas atmosphere is developed within the chamber. The substrate is then heated, and the target is irradiated, so that atoms of the target material are ablated from the remainder of the target, while atoms of the gas simultaneously are adsorbed on the substrate/film surface. The ablated atoms build up upon the substrate, together with the adsorbed gas atoms to form the thin-film deposit on the substrate. By controlling the pressure of the gas of the chamber atmosphere, the composition of the formed deposit can be controlled, and films of continuously variable composition or doping can be grown from a single target of fixed composition.

  7. Method and apparatus for the control of fluid dynamic mixing in pulse combustors

    DOEpatents

    Bramlette, T. Tazwell; Keller, Jay O.

    1992-06-02

    In a method and apparatus for controlling total ignition delay time in a pulse combustor, and thus controlling the mixing characteristics of the combustion reactants and the combustion products in the combustor, the total ignition delay time is controlled by adjusting the inlet geometry of the inlet to the combustion chamber. The inlet geometry may be fixed or variable for controlling the mixing characteristics. A feedback loop may be employed to sense actual combustion characteristics, and, in response to the sensed combustion characteristics, the inlet geometry may be varied to obtain the total ignition delay time necessary to achieve the desired combustion characteristics. Various embodiments relate to the varying of the mass flow rate of reactants while holding the radius/velocity ratio constant.

  8. Apparatus and method for pulsed laser deposition of materials on wires and pipes

    NASA Technical Reports Server (NTRS)

    Fernandez, Felix E. (Inventor)

    2003-01-01

    Methods and apparatuses are disclosed which allow uniform coatings to be applied by pulsed laser deposition (PLD) on inner and outer surfaces of cylindrical objects, such as rods, pipes, tubes, and wires. The use of PLD makes this technique particularly suitable for complex multicomponent materials, such as superconducting ceramics. Rigid objects of any length, i.e., pipes up to a few meters, and with diameters from less than 1 centimeter to over 10 centimeters can be coated using this technique. Further, deposition is effected simultaneously onto an annular region of the pipe wall. This particular arrangement simplifies the apparatus, reduces film uniformity control difficulties, and can result in faster operation cycles. In addition, flexible wires of any length can be continuously coated using the disclosed invention.

  9. Pulse-Echo Ultrasonic Imaging Method for Eliminating Sample Thickness Variation Effects

    NASA Technical Reports Server (NTRS)

    Roth, Don J. (Inventor)

    1997-01-01

    A pulse-echo, immersion method for ultrasonic evaluation of a material which accounts for and eliminates nonlevelness in the equipment set-up and sample thickness variation effects employs a single transducer and automatic scanning and digital imaging to obtain an image of a property of the material, such as pore fraction. The nonlevelness and thickness variation effects are accounted for by pre-scan adjustments of the time window to insure that the echoes received at each scan point are gated in the center of the window. This information is input into the scan file so that, during the automatic scanning for the material evaluation, each received echo is centered in its time window. A cross-correlation function calculates the velocity at each scan point, which is then proportionalized to a color or grey scale and displayed on a video screen.

  10. Pulse-echo ultrasonic imaging method for eliminating sample thickness variation effects

    NASA Technical Reports Server (NTRS)

    Roth, Don J. (Inventor)

    1995-01-01

    A pulse-echo, immersion method for ultrasonic evaluation of a material is discussed. It accounts for and eliminates nonlevelness in the equipment set-up and sample thickness variation effects employs a single transducer, automatic scanning and digital imaging to obtain an image of a property of the material, such as pore fraction. The nonlevelness and thickness variation effects are accounted for by pre-scan adjusments of the time window to insure that the echoes received at each scan point are gated in the center of the window. This information is input into the scan file so that, during the automatic scanning for the material evaluation, each received echo is centered in its time window. A cross-correlation function calculates the velocity at each scan point, which is then proportionalized to a color or grey scale and displayed on a video screen.

  11. Method and apparatus for the control of fluid dynamic mixing in pulse combustors

    DOEpatents

    Bramlette, T.T.; Keller, J.O.

    1992-06-02

    In a method and apparatus for controlling total ignition delay time in a pulse combustor, and thus controlling the mixing characteristics of the combustion reactants and the combustion products in the combustor, the total ignition delay time is controlled by adjusting the inlet geometry of the inlet to the combustion chamber. The inlet geometry may be fixed or variable for controlling the mixing characteristics. A feedback loop may be employed to sense actual combustion characteristics, and, in response to the sensed combustion characteristics, the inlet geometry may be varied to obtain the total ignition delay time necessary to achieve the desired combustion characteristics. Various embodiments relate to the varying of the mass flow rate of reactants while holding the radius/velocity ratio constant. 10 figs.

  12. Applicability of the polynomial chaos expansion method for personalization of a cardiovascular pulse wave propagation model.

    PubMed

    Huberts, W; Donders, W P; Delhaas, T; van de Vosse, F N

    2014-12-01

    Patient-specific modeling requires model personalization, which can be achieved in an efficient manner by parameter fixing and parameter prioritization. An efficient variance-based method is using generalized polynomial chaos expansion (gPCE), but it has not been applied in the context of model personalization, nor has it ever been compared with standard variance-based methods for models with many parameters. In this work, we apply the gPCE method to a previously reported pulse wave propagation model and compare the conclusions for model personalization with that of a reference analysis performed with Saltelli's efficient Monte Carlo method. We furthermore differentiate two approaches for obtaining the expansion coefficients: one based on spectral projection (gPCE-P) and one based on least squares regression (gPCE-R). It was found that in general the gPCE yields similar conclusions as the reference analysis but at much lower cost, as long as the polynomial metamodel does not contain unnecessary high order terms. Furthermore, the gPCE-R approach generally yielded better results than gPCE-P. The weak performance of the gPCE-P can be attributed to the assessment of the expansion coefficients using the Smolyak algorithm, which might be hampered by the high number of model parameters and/or by possible non-smoothness in the output space.

  13. Determination of bosentan in pharmaceutical preparations by linear sweep, square wave and differential pulse voltammetry methods.

    PubMed

    Atila, Alptug; Yilmaz, Bilal

    2015-01-01

    In this study, simple, fast and reliable cyclic voltammetry (CV), linear sweep voltammetry (LSV), square wave voltammetry (SWV) and differential pulse voltammetry (DPV) methods were developed and validated for determination of bosentan in pharmaceutical preparations. The proposed methods were based on electrochemical oxidation of bosentan at platinum electrode in acetonitrile solution containing 0.1 M TBACIO4. The well-defined oxidation peak was observed at 1.21 V. The calibration curves were linear for bosentan at the concentration range of 5-40 µg/mL for LSV and 5-35 µg/mL for SWV and DPV methods, respectively. Intra- and inter-day precision values for bosentan were less than 4.92, and accuracy (relative error) was better than 6.29%. The mean recovery of bosentan was 100.7% for pharmaceutical preparations. No interference was found from two tablet excipients at the selected assay conditions. Developed methods in this study are accurate, precise and can be easily applied to Tracleer and Diamond tablets as pharmaceutical preparation.

  14. Investigation of molecular mechanisms in photodynamic action and radiobiology with nanosecond flash photolysis and pulse radiolysis

    NASA Astrophysics Data System (ADS)

    Grossweiner, L. I.

    1981-06-01

    A formula was proposed for predicting enzyme inactivation quantum yields. The predictions were in good agreement with measurements on six important enzymes at 254 nm and 280 nm. Kinetics models were developed and tested for important stages in the photosensitization of DNA to near ultraviolet radiation by furocoumarin compounds currently used for PUVA therapy (psoralen plus UV-A) of psoriasis and other human skin diseases. Experiments on photobinding of psoralen (Ps) and 8-methoxypsoralen (8-MOP) to calf thymus DNA were consistent with the assumption that equilibrium dark complexing of the furocoumarin to the DNA is a precondition for the formation of covalent monoadducts and crosslinks. Singlet oxygen generation by furocoumarins has been investigated with liposomes and human erythrocytes (rbc). Results were obtained with 3-carbethoxypsoralen (3-CPs), and experimental alternate interacts with liposome and rbc membranes in the dark.

  15. Radiation induced primary processes of aqueous 8-methoxy-psoralen. A pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Solar, S.; Quint, R.

    The spectroscopic characteristics as well as the formation and decay kinetics of the 8-MOP radical cation (8-MOP .+), radical anion (8-MOP .-), H-adduct (8-MOP.H) and OH-adduct (8-MOP.OH) are presented.

  16. Cross modulation method of transformation of the spatial coherence of pulsed laser radiation in a nonlinear medium

    SciTech Connect

    Kitsak, M A; Kitsak, A I

    2008-04-30

    The cross modulation method of transformation of the spatial coherence of low-power pulsed laser radiation in a nonlinear medium is proposed. The method is realised experimentally in a multimode optical fibre. The estimates of the degree of spatial coherence of radiation subjected to the phase cross modulation demonstrated the high efficiency of this radiation decorrelation mechanism. (control of laser radiation parameters)

  17. A real-time receive method of wideband radar based on subband pulse compression

    NASA Astrophysics Data System (ADS)

    Li, Ming; Fu, Wei; Zhang, Peng; Wu, Yan

    2011-10-01

    The data rate with high capacity and speed of wideband signal makes its real-time processing limited by hardware and software. In this paper, wideband signal is made pulse compression based on subband pulse compression system. It is used uniform complex modulation to generate analysis filter bank and synthesis filter bank, then signals are processed in each subband. The processed results of simulated and measured datas indicate, that the parallel means of subband pulse compression raises the operation speed and improves real-time processing performance of the system, selecting proper subband number according to the data quantity when the result closed to that of directed pulse compression.

  18. Detection of volatile impurities in turbine oils by the heat-pulse testing method

    NASA Astrophysics Data System (ADS)

    Skripov, P. V.; Demin, V. A.; Shangin, V. V.; Starostin, A. A.

    2016-07-01

    The research is aimed at development and implementation of methods and devices to control critical sections of the oil system of the power equipment that operates in the real time mode. The task was to develop a method for rapid detection of volatile impurities in turbine oils. The approach to the study is based on quantitative assessment of the short-term thermal stability of the substance that is formally associated with the content of the volatile impurity. The approach was selected on the basis of the results of search experiments taking into consideration the formulation of requirements for the method and the device, viz., (1) the method should reliably determine the moisture content in the range of 10-150 g of the impurity per ton of oil and (2) the device is to be applicable "in situ." For this purpose, a variant of the method of the controlled pulse heating of a wire probe, a resistance thermometer, has been developed. The advantages of the method are its speed, sensitivity to small contents of volatile impurities regardless of the nature of the impurity, and smallness of methodologically contributed perturbation. The heating conditions of the probe most sensitive to the appearance of moisture— including its trace amounts—in the system, has been defined. The duration of the measurement is on the order of milliseconds; the heat flux density through the surface of the probe reaches 1 MW/m2. The essence of the method consists in measuring, in the characteristic time interval, the temperature of the thermal instability onset associated with the content of the volatile impurity. The approach proposed by the authors is aimed at increasing the lifetime of the oil and preventing unpredictable failures of the operating equipment.

  19. A new method for evaluating the degeneration of articular cartilage using pulse-echo ultrasound

    NASA Astrophysics Data System (ADS)

    Sun, Anyu; Bai, Xiaolong; Ju, Bing-Feng

    2015-03-01

    This paper presents a novel nondestructive ultrasonic technique for measuring the sound speed and acoustic impedance of articular cartilage using the pulsed V(z,t) technique. V(z,t) data include a series of pulsed ultrasonic echoes collected using different distances between the ultrasonic transducer and the specimen. The 2D Fourier transform is applied to the V(z,t) data to reconstruct the 2D reflection spectrum R(θ,ω). To obtain the reflection coefficient of articular cartilage, the V(z,t) data from a reference specimen with a well-known reflection coefficient are obtained to eliminate the dependence on the general system transfer function. The ultrasound-derived aggregate modulus (Ha) is computed based on the measured reflection coefficient and the sound speed. In the experiment, 32 cartilage-bone samples were prepared from bovine articular cartilage, and 16 samples were digested using 0.25% trypsin solution. The sound speed and Ha of these cartilage samples were evaluated before and after degeneration. The magnitude of the sound speed decreased with trypsin digestion (from 1663 ± 5.6 m/s to 1613 ± 5.3 m/s). Moreover, the Young's modulus in the corresponding degenerative state was measured and was correlated with the ultrasound-derived aggregate modulus. The ultrasound-derived aggregate modulus was determined to be highly correlated with the Young's modulus (n = 16, r>0.895, p<0.003, Pearson correlation test for each measurement). The results demonstrate the effectiveness of using the proposed method to assess the changes in sound speed and the ultrasound-derived aggregate modulus of cartilage after degeneration.

  20. A harmonic pulse testing method for leakage detection in deep subsurface storage formations

    NASA Astrophysics Data System (ADS)

    Sun, Alexander Y.; Lu, Jiemin; Hovorka, Susan

    2015-06-01

    Detection of leakage in deep geologic storage formations (e.g., carbon sequestration sites) is a challenging problem. This study investigates an easy-to-implement frequency domain leakage detection technology based on harmonic pulse testing (HPT). Unlike conventional constant-rate pressure interference tests, HPT stimulates a reservoir using periodic injection rates. The fundamental principle underlying HPT-based leakage detection is that leakage modifies a storage system's frequency response function, thus providing clues of system malfunction. During operations, routine HPTs can be conducted at multiple pulsing frequencies to obtain experimental frequency response functions, using which the possible time-lapse changes are examined. In this work, a set of analytical frequency response solutions is derived for predicting system responses with and without leaks for single-phase flow systems. Sensitivity studies show that HPT can effectively reveal the presence of leaks. A search procedure is then prescribed for locating the actual leaks using amplitude and phase information obtained from HPT, and the resulting optimization problem is solved using the genetic algorithm. For multiphase flows, the applicability of HPT-based leakage detection procedure is exemplified numerically using a carbon sequestration problem. Results show that the detection procedure is applicable if the average reservoir conditions in the testing zone stay relatively constant during the tests, which is a working assumption under many other interpretation methods for pressure interference tests. HPT is a cost-effective tool that only requires periodic modification of the nominal injection rate. Thus it can be incorporated into existing monitoring plans with little additional investment.

  1. A new method for evaluating the degeneration of articular cartilage using pulse-echo ultrasound.

    PubMed

    Sun, Anyu; Bai, Xiaolong; Ju, Bing-Feng

    2015-03-01

    This paper presents a novel nondestructive ultrasonic technique for measuring the sound speed and acoustic impedance of articular cartilage using the pulsed Vz,t technique. Vz,t data include a series of pulsed ultrasonic echoes collected using different distances between the ultrasonic transducer and the specimen. The 2D Fourier transform is applied to the Vz,t data to reconstruct the 2D reflection spectrum Rθ,ω. To obtain the reflection coefficient of articular cartilage, the Vz,t data from a reference specimen with a well-known reflection coefficient are obtained to eliminate the dependence on the general system transfer function. The ultrasound-derived aggregate modulus (Ha) is computed based on the measured reflection coefficient and the sound speed. In the experiment, 32 cartilage-bone samples were prepared from bovine articular cartilage, and 16 samples were digested using 0.25% trypsin solution. The sound speed and Ha of these cartilage samples were evaluated before and after degeneration. The magnitude of the sound speed decreased with trypsin digestion (from 1663 ± 5.6 m/s to 1613 ± 5.3 m/s). Moreover, the Young's modulus in the corresponding degenerative state was measured and was correlated with the ultrasound-derived aggregate modulus. The ultrasound-derived aggregate modulus was determined to be highly correlated with the Young's modulus (n = 16, r>0.895, p<0.003, Pearson correlation test for each measurement). The results demonstrate the effectiveness of using the proposed method to assess the changes in sound speed and the ultrasound-derived aggregate modulus of cartilage after degeneration.

  2. Transport critical current of MgB2 wires: pulsed current of varying rate compared to direct current method

    NASA Astrophysics Data System (ADS)

    See, K. W.; Xu, X.; Horvat, J.; Cook, C. D.; Dou, S. X.

    2011-10-01

    The measurement of transport critical current (Ic) for MgB2 wires and tapes has been investigated with two different techniques, the conventional four-probe arrangement with direct current (DC) power source, and a tailored triangle pulse at different rates of current change. The DC method has been widely used and practiced by various groups, but suffers from inevitable heating effects when high currents are used at low magnetic fields. The pulsed current method has no heating effects, but the critical current can depend on the rate of the current change (dI/dt) in the pulse. Our pulsed current measurements with varying dI/dt show that the same values of Ic are obtained as with the DC method, but without the artifacts of heating. Our method is particularly useful at low field regions which are often inaccessible by DC methods. We also performed a finite element method (FEM) analysis to obtain the time dependent heat distribution in MgB2 due to the electric potential produced at the current contacts to the superconducting sample and its gradient around the contacts. This gradient is defined as the current transfer length (CTL) of the samples and leads to Joule heating of the wire near the contacts. The FEM results provide further evidence of the limitation of the DC method in obtaining high transport critical current.

  3. Gamma-Radiolysis of Cysteine-Cysteamine Disulfide in Aqueous Solution,

    DTIC Science & Technology

    Gamma-radiolysis of a mixed disulfide, cysteine- cysteamine disulfide, in unbuffered aqueous solution (0.3 mM) was investigated in the presence and...absence of oxygen. The principal products were the thiols (cysteine and cysteamine ), the corresponding sulfinic and sulfonic acids, the symmetrical

  4. Pressurized liquid extraction as a sample preparation method for the analysis of isoflavones in pulses.

    PubMed

    Delgado-Zamarreño, María Milagros; Pérez-Martín, Lara; Bustamante-Rangel, Myriam; Carabias-Martínez, Rita

    2012-08-01

    In this work, we describe a rapid and simple analytical method that exploits pressurized liquid extraction (PLE) and liquid chromatography with diode array detection for the determination of isoflavones in samples of Spanish pulses. Confirmation of the analytes present was performed using ion-trap mass spectrometry. To optimize the PLE extraction, variables such as the dispersing agent, type of solvent and sample amount, and the experimental parameters, such as temperature and the number of extraction cycles, were studied. Separation was carried out using a reverse-phase C18 with polar endcapping as the stationary phase and acetonitrile/water with 0.2 % of formic acid, under a gradient regime, as the mobile phase. Optimal extraction of formononetin and biochanin-A from chickpeas with PLE was achieved using Hydromatrix as a dispersant agent, methanol/water (50:50), a temperature of 90 °C, and three cycles. The same optimal conditions-except methanol/water (75:25)-for solvent extraction were obtained for the extraction of daidzin, genistin, and formononetin from lentils. Recoveries ranged from 97 to 110 %, and standard deviations lower than 20 % were obtained. The contents obtained for daidzin in lentils using the proposed method were not significantly different from those obtained using another official method of analysis.

  5. Electrodeposition and characterization of Ni-ZrO2 nanocomposites by direct and pulse current methods.

    PubMed

    Kumar, K Arunsunai; Mohan, P; Kalaignan, G Paruthimal; Muralidharan, V S

    2012-11-01

    Direct Current (DC) and Pulse current (PC) methods were used to get nanocrystalline Ni-ZrO2 composites from tri-ammonium citrate bath. In the electrocomposite formation, the ZrO2 particles were transported to the surface by mechanical action and got entrapped in the nickel matrix. Incorporation of ZrO2 in the nickel matrix was found to increase with current densities when DC was employed. Beyond 2 A/dm2, their incorporation became saturated when PC was used. PC method offered better electrocomposites than DC method producing finer grains and uniform surface. Scanning electron micrographs (SEM) reveals that smaller grains and uniform distribution of Zirconia particles in the nickel matrix. The increased hardness of Ni-ZrO2 electrocomposite coatings is due to incorporation of ZrO2 particles in the nickel matrix and also changes in grain size. Incorporation of ZrO2 particles in Ni-matrix favoured the enhanced microhardness and corrosion resistance of the deposit.

  6. Radical ions and excited states in radiolysis. Optically detected time resolved EPR

    SciTech Connect

    Trifunac, A.D.; Smith, J.P.

    1981-01-01

    Excited-state production and radical-ion recombination kinetics in pulse-irradiated solutions of aromatic solutes in cyclohexane are studied by a new method of optical detection of time-resolved electron paramagnetic resonance (EPR) spectra. 7 figures.

  7. The effect of interfacial mass transfer on steady-state water radiolysis

    NASA Astrophysics Data System (ADS)

    Yakabuskie, Pamela A.; Joseph, Jiju M.; Clara Wren, J.

    2010-07-01

    The effect of aqueous-gas interfacial transfer of volatile species on the γ-radiolysis of water was studied as a function of gas-to-liquid volume ratio at various solution pHs and cover gas compositions. Water samples with cover-gas headspace were irradiated at an absorbed dose rate of 2.5 Gy s -1 and the radiolytic productions of H 2 in the cover gas and H 2O 2 in the water phase were monitored as a function of irradiation time. The experimental results were compared with computer simulations using a water radiolysis kinetics model that included primary radiolysis, subsequent reactions of the primary radiolysis products in the aqueous phase, and aqueous-gas interfacial transfer of the volatile species H 2 and O 2. This study shows that the impact of the interfacial mass transfer strongly depends on pH. At pH≤8 (lower than the pKa of •H of 9.6) the effect of aqueous-to-gas phase transfer of the volatile species on the steady-state concentrations of the other radiolysis products is negligible. At higher pHs (≥8), radiolytic production of O 2 is slow but considerable, which results in significant increase in the steady-state concentrations of H 2 and H 2O 2 compared to those at lower pHs. Thus, in the presence of headspace, the interfacial transfer of both H 2 and O 2 becomes significant, and the aqueous concentrations of H 2 and O 2 are no longer independent of the interfacial surface area and water volume. Nevertheless, the accumulated mass of H 2(g) in the headspace is proportional to the aqueous concentration of H 2 at all pHs, and the gaseous concentration of H 2 in the headspace can be used to infer the aqueous concentration of H 2.

  8. HPLC method validation for Digitalis and its analogue by pulsed amperometric detection.

    PubMed

    Kwon, Ha-Jeong; Sim, Hee-Jung; Lee, Sa-im; Lee, Yong-Moon; Park, Yong-Duk; Hong, Seon-Pyo

    2011-01-05

    We developed a highly sensitive and selective reversed-phase HPLC-pulsed amperometric detection (RP-HPLC-PAD) method for cardiac glycoside detection. Eight cardiac glycosides were completely separated within 45 min on a reversed-phase column using a water-acetonitrile gradient, and were detected using a PAD under NaOH alkaline conditions. The detection (S/N=3) and quantification (S/N=10) limits for the cardiac glycosides were 0.1-0.3 and 0.3-0.8 ng, respectively. The linear regression coefficient was 0.9962-0.9998 for concentrations of 1-25 μg/mL. Cardiac glycosides in the Digitalis purpurea leaf displayed intra- and inter-day precisions (RSDs) of <9.30% and average recoveries of 98.63-99.94%. The contents of gitoxin, digitonin, and digitoxin in the D. purpurea were 0.197, 0.11, and 0.379 mg/g for leaf dried at 60 °C, 0.058, 0.11, and 0.090 mg/g for leaf dried at ambient temperature, and N.D. (not detected), and 18.379 mg/g, N.D. for seed, respectively. We conclude that our method shows good precision and accuracy.

  9. A method for determining transverse permeability of tight reservoir cores by radial pressure pulse decay measurement

    NASA Astrophysics Data System (ADS)

    Yang, Zehao; Dong, Mingzhe; Zhang, Shaojie; Gong, Houjian; Li, Yajun; Long, Feifei

    2016-10-01

    A transverse pressure pulse decay (TPPD) method is presented to measure transverse permeability of tight reservoir cores in a cell with finite volume. Given appropriate assumptions, a mathematical model based on the specially designed experiment is formulated, and its general solution is proposed. Early-time and late-time techniques are further presented for convenient postprocessing applications of experimental data. Meanwhile, sensitivity analysis of TPPD method is given. It is found that a good TPPD experimental principle can be obtained by adjusting test gas, experimental pressure, dimension of core sample, and volume ratio (λ). The volume ratio error (λerror) analysis reveals the following: (1) a larger λerror results in increased transverse permeability error (kerror); (2) the volume ratio (λ) is better not very close to 0.754; (3) when λ is equal to or greater than 1, the kerror resulting from λerror is monotonic decreasing as the volume ratio increases. In practice, λ is usually equal to or greater than 1 due to the very small pore volume of a tight core. But this does not mean that the volume ratio should be as large as possible. The reason for this is that a pressure transducer with higher resolution is needed to record pressure change. That means experimental apparatus is much more costly. And such a TPPD experiment requires a much longer time to attain the late-time straight line behavior. The best choice is to find an optimal balance point among experimental cost, time, and accuracy.

  10. Lattice Boltzmann method for short-pulsed laser transport in a multi-layered medium

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Yi, Hong-Liang; Tan, He-Ping

    2015-04-01

    We construct a lattice Boltzmann method (LBM) for transient radiative transfer in one-dimensional multi-layered medium with distinct refractive index in each layer. The left boundary is irradiated normally by a short-pulsed laser. The Fresnel interfaces conditions, which incorporate reflection and refraction, are used at the boundaries and the interfaces. Based on the Fresnel's law and Snell's law, the interfacial intensity formulas are introduced. The collimated and diffuse intensities are treated individually. At a transient time step, the collimated component is first solved by LBM and then embedded into the transient radiative transfer equation as a source term. To keep the consistency of the directions in all the layers, angular interpolation of the intensities at the interfaces is adopted. The transient radiative transfer in a two-layer medium is first investigated, and the time-resolved results are validated by comparing with those by the Monte Carlo method (MCM). Of particular interest, the angular intensities along the slab at different times are presented to illustrate a variety of interesting phenomena, and the discontinuous nature of the intensity at the interfaces is discussed. The effects of various parameters on the time-resolved signals are examined.

  11. Fixed and pulsed gradient diffusion methods in low-field core analysis.

    PubMed

    Leu, Gabriela; Fordham, Edmund J; Hürlimann, Martin D; Frulla, Phil

    2005-02-01

    We review diffusion-weighted relaxation protocols for two-dimensional diffusion/relaxation time (D, T(2)) distributions and their application to fluid-saturated sedimentary rocks at low fields typical of oil-well logging tools (< or = 2 MHz for 1H). Fixed field gradient (FFG) protocols may be implemented in logging tools and in the laboratory; there, pulsed field gradient (PFG) protocols are also available. In either category, direct or stimulated echoes may be used for the diffusion evolution periods. We compare the results of several variant FFG and PFG protocols obtained on liquids and two contrasting sedimentary rocks. For liquids and rocks of negligible internal gradients (g(int)), results are comparable, as expected, for all the studied protocols. For rocks of strong g(int), protocol-dependent artifacts are seen in the joint (D, T2) distributions, consistent with the effects of the internal fields. For laboratory petrophysics, the PFG methods offer several advantages: (a) significantly improved signal-to-noise ratio and acquisition times for repetitions over many samples; (b) freedom from heteronuclear contamination when fluorinated liquids are used in core holders; and (c) a palette of variants--one comparable with the FFG--for the study of rocks of significant g(int). Given suitable hardware, both PFG and FFG methods can be implemented in the same bench-top apparatus, providing a versatile test bed for application in a petrophysical laboratory.

  12. Breast mass segmentation in digital mammography based on pulse coupled neural network and level set method

    NASA Astrophysics Data System (ADS)

    Xie, Weiying; Ma, Yide; Li, Yunsong

    2015-05-01

    A novel approach to mammographic image segmentation, termed as PCNN-based level set algorithm, is presented in this paper. Just as its name implies, a method based on pulse coupled neural network (PCNN) in conjunction with the variational level set method for medical image segmentation. To date, little work has been done on detecting the initial zero level set contours based on PCNN algorithm for latterly level set evolution. When all the pixels of the input image are fired by PCNN, the small pixel value will be a much more refined segmentation. In mammographic image, the breast tumor presents big pixel value. Additionally, the mammographic image with predominantly dark region, so that we firstly obtain the negative of mammographic image with predominantly dark region except the breast tumor before all the pixels of an input image are fired by PCNN. Therefore, in here, PCNN algorithm is employed to achieve mammary-specific, initial mass contour detection. After that, the initial contours are all extracted. We define the extracted contours as the initial zero level set contours for automatic mass segmentation by variational level set in mammographic image analysis. What's more, a new proposed algorithm improves external energy of variational level set method in terms of mammographic images in low contrast. In accordance with the gray scale of mass region in mammographic image is higher than the region surrounded, so the Laplace operator is used to modify external energy, which could make the bright spot becoming much brighter than the surrounded pixels in the image. A preliminary evaluation of the proposed method performs on a known public database namely MIAS, rather than synthetic images. The experimental results demonstrate that our proposed approach can potentially obtain better masses detection results in terms of sensitivity and specificity. Ultimately, this algorithm could lead to increase both sensitivity and specificity of the physicians' interpretation of

  13. Pulse radiolytic studies of electron transfer processes and applications to solar photochemistry. Progress report, [March 1992--March 1993

    SciTech Connect

    Neta, P.

    1993-04-01

    Electron transfer and other reactions of various short-lived intermediates have been studied by pulse radiolysis and laser flash photolysis. Highlights of results during the past year are summarized under two main sections: Metalloporphyrin electron transfer and associated reactions, and solvent effects on reactions of inorganic radicals and organic peroxyl radicals.

  14. Non-contact thrust stand calibration method for repetitively pulsed electric thrusters.

    PubMed

    Wong, Andrea R; Toftul, Alexandra; Polzin, Kurt A; Pearson, J Boise

    2012-02-01

    A thrust stand calibration technique for use in testing repetitively pulsed electric thrusters for in-space propulsion has been developed and tested using a modified hanging pendulum thrust stand. In the implementation of this technique, current pulses are applied to a solenoid to produce a pulsed magnetic field that acts against a permanent magnet mounted to the thrust stand pendulum arm. The force on the magnet is applied in this non-contact manner, with the entire pulsed force transferred to the pendulum arm through a piezoelectric force transducer to provide a time-accurate force measurement. Modeling of the pendulum arm dynamics reveals that after an initial transient in thrust stand motion the quasi-steady average deflection of the thrust stand arm away from the unforced or "zero" position can be related to the average applied force through a simple linear Hooke's law relationship. Modeling demonstrates that this technique is universally applicable except when the pulsing period is increased to the point where it approaches the period of natural thrust stand motion. Calibration data were obtained using a modified hanging pendulum thrust stand previously used for steady-state thrust measurements. Data were obtained for varying impulse bit at constant pulse frequency and for varying pulse frequency. The two data sets exhibit excellent quantitative agreement with each other. The overall error on the linear regression fit used to determine the calibration coefficient was roughly 1%.

  15. Phase retrieval and time-frequency methods in the measurement of ultrashort laser pulses

    SciTech Connect

    DeLong, K.W.; Fittinghoff, D.N.; Ladera, C.L.; Trebino, R.

    1995-02-01

    Recently several techniques have become available to measure the time- (or frequency-) dependent intensity and phase of ultrashort laser pulses. One of these, Frequency-Resolved Optical Gating (FROG), is rigorous and has achieved single-laser-shot operation. FROG combines the concepts of time-frequency analysis in the form of spectrogram generation (in order to create a two-dimensional problem), and uses a phase-retrieval-based algorithm to invert the experimental data to yield the intensity and phase of the laboratory laser pulse. In FROG it is easy to generate a spectrogram of the unknown signal, and inversion of the spectrogram to recover the signal is the main goal. Because the temporal width of a femtosecond laser pulse is much shorter than anything achievable by electronics, FROG uses the pulse to measure itself. In FROG, the laser pulse is split into two replicas of itself by a partially reflecting beamsplitter, and the two replicas interact with each other in a medium with an instantaneous nonlinear-optical response. This interaction generates a signal field that is then frequency-resolved using a spectrometer. The spectrum of the signal field is measured for all relevant values of the temporal delay between the two pulses. Here, the authors employ FROG and FROG related techniques to measure the time-dependent intensity and phase of an ultrashort laser pulse.

  16. Method specificity of non-invasive blood pressure measurement: oscillometry and finger pulse pressure vs acoustic methods.

    PubMed Central

    De Mey, C; Schroeter, V; Butzer, R; Roll, S; Belz, G G

    1995-01-01

    1. The agreement of blood pressure measurements by stethoscope auscultation (SBPa, DBPa-IV and DBPa-V), oscillometry (Dinamap; SBPo, and DBPo) and digital photoplethysmography (Finapres; SBPf, and DBPf) with the graphical analysis of the analogue microphone signals of vascular wall motion sound (SBPg and DBPg) was evaluated in eight healthy subjects in the presence of responses to the intravenous infusion of 1 microgram min-1 isoprenaline. 2. In general, there was good agreement between the SBP/DBP-measurements based on auscultatory Korotkoff-I- and IV-criteria and the reference method; the average method difference in estimating the isoprenaline responses for SBPa-SBPg was: -1.1, 95% CI: -5.4 to 3.1 mm Hg with a within-subject between-method repeatability coefficient (REP) of 11.6 mm Hg and for DBPa-IV-DBPg: 3.5, 95% CI: -0.5 to 6.5 mm Hg, REP: 11.5 mm Hg. The ausculatation of Korotkoff-V substantially overestimated the isoprenaline induced reduction of DBP: method difference DBPa-V-DBPg: -11.3, 95% CI: -17.8 to -4.7 mm Hg, REP: 31.8 mm Hg. 3. Oscillometry yielded good approximations for the SBP response to isoprenaline (average method difference SBPo-SBPg: -2.9, 95% CI: -9.0 to 3.3 mm Hg, REP: 17.6 mm Hg) but was poorly sensitive with regard to the DBP responses: method difference DBPo-DBPg: 6.5, 95% CI: -1.3 to 14.3 mm Hg, REP: 25.7 mm Hg. 4. Whilst the finger pulse pressure agreed well with regard to DBP (method difference for the DBP responses to isoprenaline: DBPf-DBPg: 1.8, 95% CI: -5.1 to 8.6 mm Hg, REP: 18.5 mm Hg) it was rather unsatisfactory with regard to SBP (method difference SBPf-SBPg: -14.1, 95% CI: -28.2 to -0.1 mm Hg, REP: 49.9 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8554929

  17. Method and apparatus for fine tuning an orifice pulse tube refrigerator

    DOEpatents

    Swift, Gregory W.; Wollan, John J.

    2003-12-23

    An orifice pulse tube refrigerator uses flow resistance, compliance, and inertance components connected to a pulse tube for establishing a phase relationship between oscillating pressure and oscillating velocity in the pulse tube. A temperature regulating system heats or cools a working gas in at least one of the flow resistance and inertance components. A temperature control system is connected to the temperature regulating system for controlling the temperature of the working gas in the at least one of the flow resistance and inertance components and maintains a control temperature that is indicative of a desired temporal phase relationship.

  18. Method of production H/sub 2/ using a rotating drum reactor with a pulse jet heat source

    DOEpatents

    Paulson, L.E.

    1988-05-13

    A method of producing hydrogen by an endothermic steam-carbon reaction using a rotating drum reactor and a pulse jet combustor. The pulse jet combustor uses coal dust as a fuel to provide reaction temperatures of 1300/degree/ to 1400/degree/F. Low-rank coal, water, limestone and catalyst are fed into the drum reactor where they are heated, tumbled and reacted. Part of the reaction product from the rotating drum reactor is hydrogen which can be utilized in suitable devices. 1 fig.

  19. Are rivers just big streams? A pulse method to quantify nitrogen demand in a large river.

    PubMed

    Tank, Jennifer L; Rosi-Marshall, Emma J; Baker, Michelle A; Hall, Robert O

    2008-10-01

    Given recent focus on large rivers as conduits for excess nutrients to coastal zones, their role in processing and retaining nutrients has been overlooked and understudied. Empirical measurements of nutrient uptake in large rivers are lacking, despite a substantial body of knowledge on nutrient transport and removal in smaller streams. Researchers interested in nutrient transport by rivers (discharge >10000 L/s) are left to extrapolate riverine nutrient demand using a modeling framework or a mass balance approach. To begin to fill this knowledge gap, we present data using a pulse method to measure inorganic nitrogen. (N) transport and removal in the Upper Snake River, Wyoming, USA (seventh order, discharge 12000 L/s). We found that the Upper Snake had surprisingly high biotic demand relative to smaller streams in the same river network for both ammonium (NH4+) and nitrate (NO3-). Placed in the context of a meta-analysis of previously published nutrient uptake studies, these data suggest that large rivers may have similar biotic demand for N as smaller tributaries. We also found that demand for different forms of inorganic N (NH4+ vs. NO3-) scaled differently with stream size. Data from rivers like the Upper Snake and larger are essential for effective water quality management at the scale of river networks. Empirical measurements of solute dynamics in large rivers are needed to understand the role of whole river networks (as opposed to stream reaches) in patterns of nutrient export at regional and continental scales.

  20. A noncontacting method for measuring sheet grammage and thickness using acoustic pulse techniques

    NASA Astrophysics Data System (ADS)

    Vuohelainen, Reijo Antero

    A new way to use an acoustic pulse transmission method to measure the basis weight and the thickness of paper and other thin materials was developed. The apparatus consisted of a sound source, a microphone, a digital oscilloscope, and a microcomputer. A short acoustic tone burst is transmitted through the sample and the transmission loss is defined as the ratio of the receiver voltage amplitude measured with the sample present to the voltage amplitude measured without the sample. This attenuation is a function of the basis weight of the sample and of the frequency used in the measurement. Different types of paper and plastic foils were measured with good accuracy. The measurement frequencies vary from 5 kHz to 40 kHz depending on the sample parameters. With the optimum frequency for the specific sample the accuracy is about +/-1% and the resolution is 0.5% of the grammage of the sample. This system can be used to measure both transparent and opaque foils, which makes it useful for many industrial and laboratory applications.

  1. Designing Pulse Laser Surface Modification of H13 Steel Using Response Surface Method

    NASA Astrophysics Data System (ADS)

    Aqida, S. N.; Brabazon, D.; Naher, S.

    2011-01-01

    This paper presents a design of experiment (DOE) for laser surface modification process of AISI H13 tool steel in achieving the maximum hardness and minimum surface roughness at a range of modified layer depth. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). The response surface method with Box-Behnken design approach in Design Expert 7 software was used to design the H13 laser surface modification process. Metallographic study and image analysis were done to measure the modified layer depth. The modified surface roughness was measured using two-dimensional surface profilometer. The correlation of the three laser processing parameters and the modified surface properties was specified by plotting three-dimensional graph. The hardness properties were tested at 981 mN force. From metallographic study, the laser modified surface depth was between 37 μm and 150 μm. The average surface roughness recorded from the 2D profilometry was at a minimum value of 1.8 μm. The maximum hardness achieved was between 728 and 905 HV0.1. These findings are significant to modern development of hard coatings for wear resistant applications.

  2. Determination of lithium sulphur batteries internal resistance by the pulsed method during galvanostatic cycling

    NASA Astrophysics Data System (ADS)

    Kolosnitsyn, V. S.; Kuzmina, E. V.; Mochalov, S. E.

    2014-04-01

    The pulsed method of measuring impedance is described. The cell is galvanostatically stimulated by a bipolar current signal of square shape. The cell response is registered by sampling U+[i], U-[i] with selected period Δt. The impedance spectra are calculated by direct Fourier transform. The internal resistance of the lithium sulphur cell is characteristically minimum in the calculated impedance diagrams in the frequency range of 0.035-5 Hz. It is shown that the lithium sulphur cells have maximum internal resistance at the transient between high and low voltage plateaus of charge and discharge curves. The internal resistance increases significantly during the initial stages of cycling because of the formation of passivation layers at the electrodes. It was found that the internal resistance of the lithium sulphur cell in the same charge state is governed by the way in which it is achieved. This is explained by differences in molar volumes of products generated in the sulphur electrode by electrochemical reaction during charging and discharging.

  3. Cargo and Container X-Ray Inspection with Intra-Pulse Multi-Energy Method for Material Discrimination

    NASA Astrophysics Data System (ADS)

    Saverskiy, Aleksandr Y.; Dinca, Dan-Cristian; Rommel, J. Martin

    The Intra-Pulse Multi-Energy (IPME) method of material discrimination mitigates main disadvantages of the traditional "interlaced" approach: ambiguity caused by sampling different regions of cargo and reduction of effective scanning speed. A novel concept of creating multi-energy probing pulses using a standing-wave structure allows maintaining a constant energy spectrum while changing the time duration of each sub-pulse and thus enables adaptive cargo inspection. Depending on the cargo density, the dose delivered to the inspected object is optimized for best material discrimination, maximum material penetration, or lowest dose to cargo. A model based on Monte-Carlo simulation and experimental reference points were developed for the optimization of inspection conditions.

  4. Method and means for generating a synchronizing pulse from a repetitive wave of varying frequency

    DOEpatents

    DeVolpi, Alexander; Pecina, Ronald J.; Travis, Dale J.

    1976-01-01

    An event that occurs repetitively at continuously changing frequencies can be used to generate a triggering pulse which is used to synchronize or control. The triggering pulse is generated at a predetermined percentage of the period of the repetitive waveform without regard to frequency. Counts are accumulated in two counters, the first counting during the "on" fraction of the period, and the second counting during the "off" fraction. The counts accumulated during each cycle are compared. On equality the trigger pulse is generated. Count input rates to each counter are determined by the ratio of the on-off fractions of the event waveform and the desired phase relationship. This invention is of particular utility in providing a trigger or synchronizing pulse during the open period of the shutter of a high-speed framing camera during its acceleration as well as its period of substantially constant speed.

  5. Solid cartridge for a pulse weld forming electrode and method of joining tubular members

    DOEpatents

    Bonnen, John Joseph Francis; Golovashchenko, Sergey Fedorovich; Mamutov, Alexander; Maison, Lloyd Douglas; Dawson, Scott Alwyn; deVries, James

    2016-02-23

    A cartridge assembly is disclosed for a pulse welding a first tube supported on a mandrel to a second tube. An outer tool is assembled over the second tube and a stored charge is discharged in the cartridge assembly. The cartridge comprises an annular conductor and a solid casing enveloping the conductor. The stored charge is electrically connected to the conductor and discharged through the conductor to compress the second tube and pulse weld the second tube to the first tube.

  6. Determination of intrinsic mobility of a bilayer oxide thin-film transistor by pulsed I-V method.

    PubMed

    Woo, Hyunsuk; Kim, Taeho; Hur, Jihyun; Jeon, Sanghun

    2017-04-28

    Amorphous oxide semiconductor thin-film transistors (TFT) have been considered as outstanding switch devices owing to their high mobility. However, because of their amorphous channel material with a certain level of density of states, a fast transient charging effect in an oxide TFT occurs, leading to an underestimation of the mobility value. In this paper, the effects of the fast charging of high-performance bilayer oxide semiconductor TFTs on mobility are examined in order to determine an accurate mobility extraction method. In addition, an approach based on a pulse I D -V G measurement method is proposed to determine the intrinsic mobility value. Even with the short pulse I D -V G measurement, a certain level of fast transient charge trapping cannot be avoided as long as the charge-trap start time is shorter than the pulse rising time. Using a pulse-amplitude-dependent threshold voltage characterization method, we estimated a correction factor for the apparent mobility, thus allowing us to determine the intrinsic mobility.

  7. Method for Thermal Spraying of Coatings Using Resonant-Pulsed Combustion

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E.

    2008-01-01

    A method has been devised for high-volume, high-velocity surface deposition of protective metallic coatings on otherwise vulnerable surfaces. Thermal spraying is used whereby the material to be deposited is heated to the melting point by passing through a flame. Rather than the usual method of deposition from the jet formed from the combustion products, this innovation uses non-steady combustion (i.e. high-frequency, periodic, confined bursts), which generates not only higher temperatures and heat transfer rates, but exceedingly high impingement velocities an order of magnitude higher than conventional thermal systems. Higher impingement rates make for better adhesion. The high heat transfer rates developed here allow the deposition material to be introduced, not as an expensive powder with high surface-area-to-volume, but in convenient rod form, which is also easier and simpler to feed into the system. The nonsteady, resonant combustion process is self-aspirating and requires no external actuation or control and no high-pressure supply of fuel or air. The innovation has been demonstrated using a commercially available resonant combustor shown in the figure. Fuel is naturally aspirated from the tank through the lower Tygon tube and into the pulsejet. Air for starting is ported through the upper Tygon tube line. Once operation commences, this air is no longer needed as additional air is naturally aspirated through the inlet. A spark plug on the device is needed for starting, but the process carries on automatically as the operational device is resonant and reignites itself with each 220-Hz pulse.

  8. Film dosimetry calibration method for pulsed-dose-rate brachytherapy with an 192Ir source.

    PubMed

    Schwob, Nathan; Orion, Itzhak

    2007-05-01

    192Ir sources have been widely used in clinical brachytherapy. An important challenge is to perform dosimetric measurements close to the source despite the steep dose gradient. The common, inexpensive silver halide film is a classic two-dimensional integrator dosimeter and would be an attractive solution for these dose measurements. The main disadvantage of film dosimetry is the film response to the low-energy photon. Since the photon energy spectrum is known to vary with depth, the sensitometric curves are expected to be dependent on depth. The purpose of this study is to suggest a correction method for silver halide film dosimetry that overcomes the response changes at different depths. Sensitometric curves have been obtained at different depths with verification film near a 1 Ci 192Ir pulsed-dose-rate source. The depth dependence of the film response was observed and a correction function was established. The suitability of the method was tested through measurement of the radial dose profile and radial dose function. The results were compared to Monte Carlo-simulated values according to the TG43 formalism. Monte Carlo simulations were performed separately for the beta and gamma source emissions, using the EGS4 code system, including the low-energy photon and electron transport optimization procedures. The beta source emission simulation showed that the beta dose contribution could be neglected and therefore the film-depth dependence could not be attributed to this part of the source radioactivity. The gamma source emission simulations included photon-spectra collection at several depths. The results showed a depth-dependent softening of the photon spectrum that can explain the film-energy dependence.

  9. A standardized method to determine the concentration of extracellular vesicles using tunable resistive pulse sensing

    PubMed Central

    Vogel, Robert; Coumans, Frank A. W.; Maltesen, Raluca G.; Böing, Anita N.; Bonnington, Katherine E.; Broekman, Marike L.; Broom, Murray F.; Buzás, Edit I.; Christiansen, Gunna; Hajji, Najat; Kristensen, Søren R.; Kuehn, Meta J.; Lund, Sigrid M.; Maas, Sybren L. N.; Nieuwland, Rienk; Osteikoetxea, Xabier; Schnoor, Rosalie; Scicluna, Benjamin J.; Shambrook, Mitch; de Vrij, Jeroen; Mann, Stephen I.; Hill, Andrew F.; Pedersen, Shona

    2016-01-01

    Background Understanding the pathogenic role of extracellular vesicles (EVs) in disease and their potential diagnostic and therapeutic utility is extremely reliant on in-depth quantification, measurement and identification of EV sub-populations. Quantification of EVs has presented several challenges, predominantly due to the small size of vesicles such as exosomes and the availability of various technologies to measure nanosized particles, each technology having its own limitations. Materials and Methods A standardized methodology to measure the concentration of extracellular vesicles (EVs) has been developed and tested. The method is based on measuring the EV concentration as a function of a defined size range. Blood plasma EVs are isolated and purified using size exclusion columns (qEV) and consecutively measured with tunable resistive pulse sensing (TRPS). Six independent research groups measured liposome and EV samples with the aim to evaluate the developed methodology. Each group measured identical samples using up to 5 nanopores with 3 repeat measurements per pore. Descriptive statistics and unsupervised multivariate data analysis with principal component analysis (PCA) were used to evaluate reproducibility across the groups and to explore and visualise possible patterns and outliers in EV and liposome data sets. Results PCA revealed good reproducibility within and between laboratories, with few minor outlying samples. Measured mean liposome (not filtered with qEV) and EV (filtered with qEV) concentrations had coefficients of variance of 23.9% and 52.5%, respectively. The increased variance of the EV concentration measurements could be attributed to the use of qEVs and the polydisperse nature of EVs. Conclusion The results of this study demonstrate the feasibility of this standardized methodology to facilitate comparable and reproducible EV concentration measurements. PMID:27680301

  10. Alpha Radiolysis of Sorbed Water on Uranium Oxides and Uranium Oxyfluorides

    SciTech Connect

    Icenhour, A.S.

    2003-09-10

    The radiolysis of sorbed water and other impurities contained in actinide oxides has been the focus of a number of studies related to the establishment of criteria for the safe storage and transport of these materials. Gamma radiolysis studies have previously been performed on uranium oxides and oxyfluorides (UO{sub 3}, U{sub 3}O{sub 8}, and UO{sub 2}F{sub 2}) to evaluate the long-term storage characteristics of {sup 233}U. This report describes a similar study for alpha radiolysis. Uranium oxides and oxyfluorides (with {sup 238}U as the surrogate for {sup 233}U) were subjected to relatively high alpha radiation doses (235 to 634 MGy) by doping with {sup 244}Cm. The typical irradiation time for these samples was about 1.5 years, which would be equivalent to more than 50 years irradiation by a {sup 233}U sample. Both dry and wet (up to 10 wt % water) samples were examined in an effort to identify the gas pressure and composition changes that occurred as a result of radiolysis. This study shows that several competing reactions occur during radiolysis, with the net effect that only very low pressures of hydrogen, nitrogen, and carbon dioxide are generated from the water, nitrate, and carbon impurities, respectively, associated with the oxides. In the absence of nitrate impurities, no pressures greater than 1000 torr are generated. Usually, however, the oxygen in the air atmosphere over the oxides is consumed with the corresponding oxidation of the uranium oxide. In the presence of up to 10 wt % water, the oxides first show a small pressure rise followed by a net decrease due to the oxygen consumption and the attainment of a steady-state pressure where the rate of generation of gaseous components is balanced by their recombination and/or consumption in the oxide phase. These results clearly demonstrate that alpha radiolysis of either wet or dry {sup 233}U oxides will not produce deleterious pressures or gaseous components that could compromise the long-term storage of

  11. Sculpting 3D spatial selectivity with pairs of 2D pulses: A comparison of methods

    NASA Astrophysics Data System (ADS)

    Farkash, Gil; Dumez, Jean-Nicolas; Frydman, Lucio

    2016-12-01

    Enhancing the specificity of the spins' excitation can improve the capabilities of magnetic resonance. Exciting voxels with tailored 3D shapes reduces partial volume effects and enhances contrast, particularly in cases where cubic voxels or other simple geometries do not provide an optimal localization. Spatial excitation profiles of arbitrary shapes can be implemented using so-called multidimensional RF pulses, which are often limited in practice to 2D implementations owing to their sensitivity to field inhomogeneities. Recent work has shown the potential of spatio-temporally encoded (SPEN) pulses towards alleviating these constraints. In particular, 2D pulses operating in a so-called hybrid scheme where the "low-bandwidth" spatial dimension is sculpted by a SPEN strategy while an orthogonal axis is shaped by regular k-space encoding, have been shown resilient to chemical shift and B0 field inhomogeneities. In this work we explore the use of pairs of 2D pulses, with one of these addressing geometries in the x-y plane and the other in the x-z dimension, to sculpt complex 3D volumes in phantoms and in vivo. To overcome limitations caused by the RF discretization demanded by these 2D pulses, a number of "unfolding" techniques yielding images from the centerband RF excitation while deleting sideband contributions - even in cases where center- and side-bands severely overlap - were developed. Thus it was possible to increase the gradient strengths applied along the low bandwidth dimensions, significantly improving the robustness of this kind of 3D sculpting pulses. Comparisons against conventional pulses designed on the basis of pure k-space trajectories, are presented.

  12. Non-Contact Thrust Stand Calibration Method for Repetitively-Pulsed Electric Thrusters

    NASA Technical Reports Server (NTRS)

    Wong, Andrea R.; Toftul, Alexandra; Polzin, Kurt A.; Pearson, J. Boise

    2011-01-01

    A thrust stand calibration technique for use in testing repetitively-pulsed electric thrusters for in-space propulsion has been developed and tested using a modified hanging pendulum thrust stand. In the implementation of this technique, current pulses are applied to a solenoidal coil to produce a pulsed magnetic field that acts against the magnetic field produced by a permanent magnet mounted to the thrust stand pendulum arm. The force on the magnet is applied in this non-contact manner, with the entire pulsed force transferred to the pendulum arm through a piezoelectric force transducer to provide a time-accurate force measurement. Modeling of the pendulum arm dynamics reveals that after an initial transient in thrust stand motion the quasisteady average deflection of the thrust stand arm away from the unforced or zero position can be related to the average applied force through a simple linear Hooke s law relationship. Modeling demonstrates that this technique is universally applicable except when the pulsing period is increased to the point where it approaches the period of natural thrust stand motion. Calibration data were obtained using a modified hanging pendulum thrust stand previously used for steady-state thrust measurements. Data were obtained for varying impulse bit at constant pulse frequency and for varying pulse frequency. The two data sets exhibit excellent quantitative agreement with each other as the constant relating average deflection and average thrust match within the errors on the linear regression curve fit of the data. Quantitatively, the error on the calibration coefficient is roughly 1% of the coefficient value.

  13. A Time-Domain Reflectometry Method with Variable Needle Pulse Width for Measuring the Dielectric Properties of Materials

    PubMed Central

    Wilczek, Andrzej; Szypłowska, Agnieszka; Kafarski, Marcin; Skierucha, Wojciech

    2016-01-01

    Time-domain reflectometry (TDR) methods used for measuring the dielectric properties of materials mostly utilize step or needle electrical pulses of constant amplitudes and shapes. Our novel approach enables determining the dielectric relaxation time of a sample using the analysis of the amplitudes of reflected pulses of two widths, in addition to bulk dielectric permittivity and electrical conductivity commonly obtained by the TDR technique. The method was developed for various values of electrical conductivity and relaxation time using numerical simulations of a five-rod probe placed in a material with complex dielectric permittivity described by the Debye model with an added electrical conductivity term. The characterization of amplitudes of two pulses of selected widths was done with regard to the dielectric parameters of simulated materials. The required probe parameters were obtained solely from numerical simulations. Verification was performed for the probe placed in aqueous KCl solutions with 14 different electrical conductivity values. The determined relaxation time remained roughly constant and independent of electrical conductivity. The obtained electrical conductivity agreed with the reference values. Our results indicate that the relaxation time, dielectric permittivity and electrical conductivity of the tested solutions can be simultaneously determined using a simple analysis of the amplitude and reflection time of two needle pulses of different widths. PMID:26861318

  14. Using the compensated heat pulse method to monitor trends in stem water content in standing trees.

    PubMed

    López-Bernal, Álvaro; Testi, Luca; Villalobos, Francisco J

    2012-11-01

    Studying the dynamics of stem water content (θ) in living trees has an outstanding physiological interest but all the available techniques to measure θ exhibit major drawbacks. In this work, we present a new methodology to estimate variations in θ along with sap velocity using the compensated heat pulse (CHP) technique. One lab experiment was performed on several wooden blocks obtained from three different tree species. Samples were slowly dried and their moisture loss was monitored by both gravimetric approaches and time-domain reflectometry (TDR) or CHP probes in order to contrast the validity of our methodology (volumetric specific heat (VSH)-CHP) over a range of water contents. In addition, a field experiment was conducted to monitor θ fluctuations in standing olive trees (Olea europaea L. cv. 'Arbequina') growing under three different irrigation regimes. In the lab test, the actual θ values deduced gravimetrically differed from the estimates yielded by the VSH-CHP method. However, it could successfully track relative changes in the water stored for the range of θ expected in living wood. Furthermore, the field experiment showed a seasonal change in θ, which was similar in shape and magnitude to those reported in the literature for olive and other Mediterranean tree species. On the other hand, differences in the seasonal patterns of θ between irrigation treatments strongly corresponded with those of sap flow and some leaf water potential measurements. The results of this work suggest that the CHP technique could be employed to monitor the dynamics of both θ and sap flow simultaneously in standing trees and evidence that seasonal changes in θ might be used as a long-term water status indicator.

  15. Radiolysis as a solution for accelerated ageing studies of electrolytes in Lithium-ion batteries

    PubMed Central

    Ortiz, Daniel; Steinmetz, Vincent; Durand, Delphine; Legand, Solène; Dauvois, Vincent; Maître, Philippe; Le Caër, Sophie

    2015-01-01

    Diethyl carbonate and dimethyl carbonate are prototype examples of eco-friendly solvents used in lithium-ion batteries. Nevertheless, their degradation products affect both the battery performance and its safety. Therefore, it is of paramount importance to understand the reaction mechanisms involved in the ageing processes. Among those, redox processes are likely to play a critical role. Here we show that radiolysis is an ideal tool to generate the electrolytes degradation products. The major gases detected after irradiation (H2, CH4, C2H6, CO and CO2) are identified and quantified. Moreover, the chemical compounds formed in the liquid phase are characterized by different mass spectrometry techniques. Reaction mechanisms are then proposed. The detected products are consistent with those of the cycling of Li-based cells. This demonstrates that radiolysis is a versatile and very helpful tool to better understand the phenomena occurring in lithium-ion batteries. PMID:25907411

  16. Radiolysis, racemization and the origin of molecular asymmetry in the biosphere

    NASA Technical Reports Server (NTRS)

    Bonner, W. A.; Lemmon, R. M.

    1978-01-01

    An investigation has been undertaken to determine whether ionizing radiation might engender racemization of optically active amino acids, along with their usual radiolysis. As prototypes, crystalline Dand L-leucine, as well as aqueous solutions of their sodium salts were exposed to the radiation from a 3000 Ci Co-60 gamma-ray source. Gamma-ray doses which caused about 68% radiolysis of solid leucine left a residue which was about 5% racemized, while racemization proved even greater at lower doses for the dissolved sodium salts. In aqueous solution both percent degradation and percent racemization of the sodium salts were proportional to gamma-ray dosage within the range employed (1,000,000-27,000,000 rads). Implications of these observations for the origin of molecular asymmetry by the beta-decay parity violation mechanism are discussed.

  17. Radiolysis as a solution for accelerated ageing studies of electrolytes in Lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Ortiz, Daniel; Steinmetz, Vincent; Durand, Delphine; Legand, Solène; Dauvois, Vincent; Maître, Philippe; Le Caër, Sophie

    2015-04-01

    Diethyl carbonate and dimethyl carbonate are prototype examples of eco-friendly solvents used in lithium-ion batteries. Nevertheless, their degradation products affect both the battery performance and its safety. Therefore, it is of paramount importance to understand the reaction mechanisms involved in the ageing processes. Among those, redox processes are likely to play a critical role. Here we show that radiolysis is an ideal tool to generate the electrolytes degradation products. The major gases detected after irradiation (H2, CH4, C2H6, CO and CO2) are identified and quantified. Moreover, the chemical compounds formed in the liquid phase are characterized by different mass spectrometry techniques. Reaction mechanisms are then proposed. The detected products are consistent with those of the cycling of Li-based cells. This demonstrates that radiolysis is a versatile and very helpful tool to better understand the phenomena occurring in lithium-ion batteries.

  18. Radiolysis as a solution for accelerated ageing studies of electrolytes in Lithium-ion batteries.

    PubMed

    Ortiz, Daniel; Steinmetz, Vincent; Durand, Delphine; Legand, Solène; Dauvois, Vincent; Maître, Philippe; Le Caër, Sophie

    2015-04-24

    Diethyl carbonate and dimethyl carbonate are prototype examples of eco-friendly solvents used in lithium-ion batteries. Nevertheless, their degradation products affect both the battery performance and its safety. Therefore, it is of paramount importance to understand the reaction mechanisms involved in the ageing processes. Among those, redox processes are likely to play a critical role. Here we show that radiolysis is an ideal tool to generate the electrolytes degradation products. The major gases detected after irradiation (H2, CH4, C2H6, CO and CO2) are identified and quantified. Moreover, the chemical compounds formed in the liquid phase are characterized by different mass spectrometry techniques. Reaction mechanisms are then proposed. The detected products are consistent with those of the cycling of Li-based cells. This demonstrates that radiolysis is a versatile and very helpful tool to better understand the phenomena occurring in lithium-ion batteries.

  19. Muon radiolysis affected by density inhomogeneity in near-critical fluids.

    PubMed

    Cormier, P J; Alcorn, C; Legate, G; Ghandi, K

    2014-04-01

    In this article we show the significant tunability of radiation chemistry in supercritical ethane and to a lesser extent in near critical CO2. The information was obtained by studies of muonium (Mu = μ(+)e(-)), which is formed by the thermalization of positive muons in different materials. The studies of the proportions of three fractions of muon polarization, PMu, diamagnetic PD and lost fraction, PL provided the information on radiolysis processes involved in muon thermalization. Our studies include three different supercritical fluids, water, ethane and carbon dioxide. A combination of mobile electrons and other radiolysis products such as (•)C2H5 contribute to interesting behavior at densities ∼40% above the critical point in ethane. In carbon dioxide, an increase in electron mobility contributes to the lost fraction. The hydrated electron in water is responsible for the lost fraction and decreases the muonium fraction.

  20. The radiolysis of simple gas mixtures—III. the production of ``trace organics''

    NASA Astrophysics Data System (ADS)

    Dyer, Alan; Moores, Graham E.

    Carbon dioxide based gas mixtures, similar to those used as coolants in the Advanced Gas-cooled Nuclear Reactors, have been radiolyzed at the comparatively low dose rate of 3 Gy s -1 using γ-radiation from a 60Co source. The concentrations of certain C 4 and C 5 alkanes, ethanal and propanone, produced by radiolysis, have been determined under different conditions of temperature, pressure, gas composition, and surface area. Observations showed that these compounds were produced in concentrations of the order of 1/1000 of the methane concentration and that the production of these "trace organics" varied in a complex way with the experimental parameters. Mechanisms for the production of these organics have been proposed. Some unidentified products of radiolysis were observed and suggestions are made as to their nature.

  1. Realizing up-conversion fluorescence tuning in lanthanide-doped nanocrystals by femtosecond pulse shaping method

    PubMed Central

    Zhang, Shian; Yao, Yunhua; Shuwu, Xu; Liu, Pei; Ding, Jingxin; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong

    2015-01-01

    The ability to tune color output of nanomaterials is very important for their applications in laser, optoelectronic device, color display and multiplexed biolabeling. Here we first propose a femtosecond pulse shaping technique to realize the up-conversion fluorescence tuning in lanthanide-doped nanocrystals dispersed in the glass. The multiple subpulse formation by a square phase modulation can create different excitation pathways for various up-conversion fluorescence generations. By properly controlling these excitation pathways, the multicolor up-conversion fluorescence can be finely tuned. This color tuning by the femtosecond pulse shaping technique is realized in single material by single-color laser field, which is highly desirable for further applications of the lanthanide-doped nanocrystals. This femtosecond pulse shaping technique opens an opportunity to tune the color output in the lanthanide-doped nanocrystals, which may bring a new revolution in the control of luminescence properties of nanomaterials. PMID:26290391

  2. A Method for Evaluating Electron Transport Parameters on a Pulsed Townsend Experiment

    SciTech Connect

    Ridenti, M. A.; Pascholati, P. R.; Vivaldini, T. C.; Lima, I. B.

    2010-05-21

    In this work, we present a physical model that links fundamental theory of electron kinetics on weakly ionized gases to direct measurements of induced pulsed signals in a Resistive Plate Chamber. It is also presented preliminary measurements of electron transport parameters in nitrogen obtained for reduced electric fields ranging from 129 Td up to 216 Td. These parameters were indirectly determined by fitting the proposed model to the time dependent pulse current induced on the parallel plate chamber electrodes by an electron avalanche triggered near the cathode by a N{sub 2} laser pulse. Experimental results are compared with previous measurements, Monte Carlo simulation results from Magboltz and results from classical two-term expansion Boltzmann equation solution from Bolsig+.

  3. Methods for the shaping high-power picosecond laser pulses with a high-contrast ratio

    SciTech Connect

    Malinov, V. A.; Charukchev, A. V.; Chernov, V. N.; Nikitin, N. V.; Potapov, S. L.; Efanov, V. M.; Yarin, P. M.

    1998-02-20

    We present the performance of the electrooptical system based on four Pockels cells with 10 and 20 mm diameters, each of them is driving by its own drift step recovery diode pulse generator. We are developing electro-optic deflector system for CPA laser using two identical deflectors (diverging and converging) and three spatial filters. The results of numerical modeling of the time-dependent distributions of the intensity in the beam are presented. A peak-to-background intensity ratio more than five orders is achieved by this technique. We have developed a new pulse generator based on single drift step recovery diode producing two identical electrical pulses with output voltage up to 15 kV, FWHM of 1.5 ns, rise time of 0.7 ns and jitter of 100 ps at a 100 Hz repetition rate to electro-optic deflectors.

  4. Sensitivity of UO2 Stability in a Reducing Environment on Radiolysis Model Parameters

    SciTech Connect

    Wittman, Richard S.; Buck, Edgar C.

    2012-09-01

    Results for a radiolysis model sensitivity study of radiolytically produced H2O2 are presented as they relate to Spent (or Used) Light Water Reactor uranium oxide (UO2) nuclear fuel (UNF) oxidation in a low oxygen environment. The model builds on previous reaction kinetic studies to represent the radiolytic processes occurring at the nuclear fuel surface. Hydrogen peroxide (H2O2) is the dominant oxidant for spent nuclear fuel in an O2-depleted water environment.

  5. EVIDENCE OF CORROSIVE GAS FORMED BY RADIOLYSIS OF CHLORIDE SALTS IN PLUTONIUM-BEARING MATERIALS

    SciTech Connect

    Dunn, K.; Louthan, M.

    2010-02-01

    Corrosion and pitting have been observed in headspace regions of stainless steel containers enclosing plutonium oxide/salt mixtures. These observations are consistent with the formation of a corrosive gas, probably HCl, and transport of that gas to the headspace regions of sealed containers. The NH{sub 4}Cl films found on the walls of the sealed containers is also indicative of the presence of HCl gas. Radiolysis of hydrated alkaline earth salts is the probable source of HCl.

  6. Accelerated Monte Carlo simulation on the chemical stage in water radiolysis using GPU

    NASA Astrophysics Data System (ADS)

    Tian, Zhen; Jiang, Steve B.; Jia, Xun

    2017-04-01

    The accurate simulation of water radiolysis is an important step to understand the mechanisms of radiobiology and quantitatively test some hypotheses regarding radiobiological effects. However, the simulation of water radiolysis is highly time consuming, taking hours or even days to be completed by a conventional CPU processor. This time limitation hinders cell-level simulations for a number of research studies. We recently initiated efforts to develop gMicroMC, a GPU-based fast microscopic MC simulation package for water radiolysis. The first step of this project focused on accelerating the simulation of the chemical stage, the most time consuming stage in the entire water radiolysis process. A GPU-friendly parallelization strategy was designed to address the highly correlated many-body simulation problem caused by the mutual competitive chemical reactions between the radiolytic molecules. Two cases were tested, using a 750 keV electron and a 5 MeV proton incident in pure water, respectively. The time-dependent yields of all the radiolytic species during the chemical stage were used to evaluate the accuracy of the simulation. The relative differences between our simulation and the Geant4-DNA simulation were on average 5.3% and 4.4% for the two cases. Our package, executed on an Nvidia Titan black GPU card, successfully completed the chemical stage simulation of the two cases within 599.2 s and 489.0 s. As compared with Geant4-DNA that was executed on an Intel i7-5500U CPU processor and needed 28.6 h and 26.8 h for the two cases using a single CPU core, our package achieved a speed-up factor of 171.1–197.2.

  7. The radiolysis of CMPO: effects of acid, metal complexation and alpha vs. gamma radiation

    SciTech Connect

    Bruce J. Mincher; Stephen P. Mezyk; Gary S. Groenewold

    2016-05-01

    Abstract The group actinide/lanthanide complexing agent octylphenylcarbamoylmethyl phosphine oxide (CMPO) has been examined for its radiation stability by measuring the kinetics of its reactions with free radicals in both the aqueous and organic phases for the free and metal-complexed ligand, identifying its degradation products for both alpha and gamma irradiation, measuring the effects on solvent extraction performance, and measuring the G-values for its degradation under various conditions. This includes the G-values for CMPO in the absence of, and in contact with the acidic aqueous phase, where it is shown that the acidic aqueous phase provides radio-protection for this ligand. It was found that both solvent and metal complexation affect the kinetics of the reaction of the •NO3 radical, a product of HNO3 radiolysis, with CMPO. For example, CMPO complexed with lanthanides has a rate constant for this reaction an order of magnitude higher than for the free ligand, and the reaction for the free ligand in the organic phase is about three times faster than in the aqueous phase. In steady state radiolysis kinetics it was determined that HNO3, although not NO3- anion, provides radio-protection to CMPO, with the G-value for its degradation decreasing with increasing acidity, until it was almost completely suppressed by irradiation in contact with 5 M HNO3. The same degradation products were produced by irradiation with alpha and gamma-sources, except that the relative abundances of these products varied. For example, the product of C-C bond scission was produced only in low amounts for gamma-radiolysis, but it was an important product for samples irradiated with a He ion beam. These results are compared to the new data appearing in the literature on DGA radiolysis, since CMPO and the DGAs both contain the amide functional group.

  8. A simple method of calculating pulse amplitudes and shapes arising from reflection from linear segments

    SciTech Connect

    Erickson, S.A. Jr.

    1988-01-02

    A new formulation for the amplitude and pulse shape from reflections from a linear segment for a bistatic planar geometry is presented. The formulation is useful in calculating reverberation from high intensity signals in an deep ocean basin where long range propagation can occur. This reverberation is important in calculating the acoustic interference to sonar arising from the detonation of nuclear or large chemical explosives, and for modeling long range active sonar. The reflections computed with the new formulation are significantly different from those of earlier versions of the reverberation model, with pulses generally shorter and more intense, leading to predictions of louder but more sporadic reverberation than previously estimated. 9 refs

  9. A Method for Removal of CO from Exhaust Gas Using Pulsed Corona Discharge.

    PubMed

    Li, Xiaohong; Yang, Lin; Lei, Yuyong; Wang, Jiansheng; Lu, Yiyu

    2000-10-01

    An experimental study of the oxidation of CO in exhaust gas from a motorcycle has been carried out using plasma chemical reactions in a pulsed corona discharge. In the process, some main parameters, such as the initial CO concentration, amplitude and frequency of pulses, residence time, reactor volume, and relative humidity (RH), as well as their effects on CO removal characteristics, were investigated. O3, which is beneficial to reducing CO, was produced during CO removal . When the exhaust gas was at ambient temperature, more than 80% CO removal efficiency was realized at an initial concentration of 288 ppm in a suitable range of the parameters.

  10. A method for removal of CO from exhaust gas using pulsed corona discharge.

    PubMed

    Li, X; Yang, L; Lei, Y; Wang, J; Lu, Y

    2000-10-01

    An experimental study of the oxidation of CO in exhaust gas from a motorcycle has been carried out using plasma chemical reactions in a pulsed corona discharge. In the process, some main parameters, such as the initial CO concentration, amplitude and frequency of pulses, residence time, reactor volume, and relative humidity (RH), as well as their effects on CO removal characteristics, were investigated. O3, which is beneficial to reducing CO, was produced during CO removal. When the exhaust gas was at ambient temperature, more than 80% CO removal efficiency was realized at an initial concentration of 288 ppm in a suitable range of the parameters.

  11. The frequency-domain method of calculation for the pulsed electromagnetic field in a conductive ferromagnetic plate

    NASA Astrophysics Data System (ADS)

    Nosov, G. V.; Kuleshova, E. O.; Lefebvre, S.; Plyusnin, A. A.; Tokmashev, D. M.

    2017-02-01

    The technique for parameters determination of magnetic skin effect on ferromagnetic plate at a specified pulse of magnetic field intensity on the plate surface is proposed. It is based on a frequency-domain method and could be applied for a pulsing transformer, a dynamoelectric pulse generator and a commutating inductor that contains an imbricated core. Due to this technique, such plate parameters as specific heat loss energy, the average power of this energy and the plate temperature raise, the magnetic flux attenuation factor and the plate q-factor could be calculated. These parameters depend on the steel type, the amplitude, the rms value, the duration and the form of the magnetic field intensity impulse on the plate surface. The plate thickness is defined by the value of the flux attenuation factor and the plate q-factor that should be maximal. The reliability of the proposed technique is built on a common frequency-domain usage applicable for pulse transient study under zero boundary conditions of the electric circuit and the conformity of obtained results with the sinusoidal steady-state mode.

  12. Fundamental aspects of pulse phase-locked loop technology-based methods for measurement of ultrasonic velocity

    NASA Technical Reports Server (NTRS)

    Yost, William T.; Cantrell, John H.; Kushnick, Peter W.

    1992-01-01

    A new instrument based on a constant frequency pulse phase-locked loop concept has been developed to accurately measure the ultrasonic phase velocity in condensed matter. Measurements of the sound velocity in ultrapure water are reported in which both damped and undamped transducers are used with the instrument together with reflectors of various thicknesses placed in the sound propagation path. An analysis of measurements made with the new instrument and similar measurements, taken under identical experimental conditions, using a popular variable frequency pulsed-phase-locked loop instrument is reported. Uncertainties in both measurement systems are analyzed and discussed. A method for measuring inherent phase shifts, not addressed by previous investigations, within the variable frequency pulsed phase-locked loop system and a derivation of the equations that govern the overall use of variable frequency systems using phase-sensitive comparisons are presented. The effects of a finite pulse length on the measurements of phase velocity in dispersive media are addressed in detail.

  13. A remote and non-contact method for obtaining the blood-pulse waveform with a laser Doppler vibrometer

    NASA Astrophysics Data System (ADS)

    Desjardins, Candida L.; Antonelli, Lynn T.; Soares, Edward

    2007-02-01

    The use of lasers to remotely and non-invasively detect the blood pressure waveform of humans and animals would provide a powerful diagnostic tool. Current blood pressure measurement tools, such as a cuff, are not useful for burn and trauma victims, and animals require catheterization to acquire accurate blood pressure information. The purpose of our sensor method and apparatus invention is to remotely and non-invasively detect the blood pulse waveform of both animals and humans. This device is used to monitor an animal or human's skin in proximity to an artery using radiation from a laser Doppler vibrometer (LDV). This system measures the velocity (or displacement) of the pulsatile motion of the skin, indicative of physiological parameters of the arterial motion in relation to the cardiac cycle. Tests have been conducted that measures surface velocity with an LDV and a signal-processing unit, with enhanced detection obtained with optional hardware including a retro-reflector dot. The blood pulse waveform is obtained by integrating the velocity signal to get surface displacement using standard signal processing techniques. Continuous recording of the blood pulse waveform yields data containing information on cardiac health and can be analyzed to identify important events in the cardiac cycle, such as heart rate, the timing of peak systole, left ventricular ejection time and aortic valve closure. Experimental results are provided that demonstrates the current capabilities of the optical, non-contact sensor for the continuous, non-contact recording of the blood pulse waveform without causing patient distress.

  14. Room temperature synthesis of Ni-based alloy nanoparticles by radiolysis.

    SciTech Connect

    Nenoff, Tina Maria; Berry, Donald T.; Lu, Ping; Leung, Kevin; Provencio, Paula Polyak; Stumpf, Roland Rudolph; Huang, Jian Yu; Zhang, Zhenyuan

    2009-09-01

    Room temperature radiolysis, density functional theory, and various nanoscale characterization methods were used to synthesize and fully describe Ni-based alloy nanoparticles (NPs) that were synthesized at room temperature. These complementary methods provide a strong basis in understanding and describing metastable phase regimes of alloy NPs whose reaction formation is determined by kinetic rather than thermodynamic reaction processes. Four series of NPs, (Ag-Ni, Pd-Ni, Co-Ni, and W-Ni) were analyzed and characterized by a variety of methods, including UV-vis, TEM/HRTEM, HAADF-STEM and EFTEM mapping. In the first focus of research, AgNi and PdNi were studied. Different ratios of Ag{sub x}- Ni{sub 1-x} alloy NPs and Pd{sub 0.5}- Ni{sub 0.5} alloy NP were prepared using a high dose rate from gamma irradiation. Images from high-angle annular dark-field (HAADF) show that the Ag-Ni NPs are not core-shell structure but are homogeneous alloys in composition. Energy filtered transmission electron microscopy (EFTEM) maps show the homogeneity of the metals in each alloy NP. Of particular interest are the normally immiscible Ag-Ni NPs. All evidence confirmed that homogeneous Ag-Ni and Pd-Ni alloy NPs presented here were successfully synthesized by high dose rate radiolytic methodology. A mechanism is provided to explain the homogeneous formation of the alloy NPs. Furthermore, studies of Pd-Ni NPs by in situ TEM (with heated stage) shows the ability to sinter these NPs at temperatures below 800 C. In the second set of work, CoNi and WNi superalloy NPs were attempted at 50/50 concentration ratios using high dose rates from gamma irradiation. Preliminary results on synthesis and characterization have been completed and are presented. As with the earlier alloy NPs, no evidence of core-shell NP formation occurs. Microscopy results seem to indicate alloying occurred with the CoNi alloys. However, there appears to be incomplete reduction of the Na{sub 2}WO{sub 4} to form the W

  15. Composition analysis of oxide films formed on titanium surface under pulsed laser action by method of chemical thermodynamics

    NASA Astrophysics Data System (ADS)

    Ageev, E. I.; Andreeva, Ya M.; Karlagina, Yu Yu; Kolobov, Yu R.; Manokhin, S. S.; Odintsova, G. V.; Slobodov, A. A.; Veiko, V. P.

    2017-04-01

    A pulsed fiber laser with a wavelength of 1.06 µm was used to treat a commercial pure titanium surface in the air at intensities below the ablation threshold to provide oxide formation. Laser oxidation results are predicted by the chemical thermodynamic method and confirmed by experimental techniques (x-ray diffraction, energy dispersive x-ray spectroscopy). For the first time, the chemical thermodynamic method was used for determining the qualitative and quantitative phase-chemical composition of the compounds formed by a pulsed laser heating of commercial titanium in the air, and its applicability is proven. The simulation shows that multilayered composite film appears on a surface, the lower layers of which consist of Ti2O3 and TiO oxides with the addition of titanium nitride; and the thin upper layer consists of transparent titanium dioxide. Also, the chemical composition of films remains unchanged within a temperature range of 881–2000 K.

  16. Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

    DOEpatents

    Konrad, Charles E.; Boothe, Richard W.

    1996-01-01

    A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements.

  17. Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

    DOEpatents

    Konrad, C.E.; Boothe, R.W.

    1994-02-15

    A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements. 6 figures.

  18. Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

    DOEpatents

    Konrad, Charles E.; Boothe, Richard W.

    1994-01-01

    A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements.

  19. Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

    DOEpatents

    Konrad, C.E.; Boothe, R.W.

    1996-01-23

    A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements. 6 figs.

  20. Method for optimizing output in ultrashort-pulse multipass laser amplifiers with selective use of a spectral filter

    DOEpatents

    Backus, Sterling J.; Kapteyn, Henry C.

    2007-07-10

    A method for optimizing multipass laser amplifier output utilizes a spectral filter in early passes but not in later passes. The pulses shift position slightly for each pass through the amplifier, and the filter is placed such that early passes intersect the filter while later passes bypass it. The filter position may be adjust offline in order to adjust the number of passes in each category. The filter may be optimized for use in a cryogenic amplifier.

  1. Bubble population phenomena in sonochemical reactor: I estimation of bubble size distribution and its number density with pulsed sonication - laser diffraction method.

    PubMed

    Iida, Yasuo; Ashokkumar, Muthupandian; Tuziuti, Toru; Kozuka, Teruyuki; Yasui, Kyuichi; Towata, Atsuya; Lee, Judy

    2010-02-01

    To characterize the bubble populations (size and its number distribution) in a sonochemical reactor, a simple but powerful technique based on the Fraunhofer laser diffraction (LD) has been proposed. In this method, the acoustic wave disturbance to the laser probe in the sonochemical reaction field was eliminated by the temporal separation using pulsed sonication (pulsed LD). With this relatively simple strategy, the temporal development of the bubble size distribution could be evaluated by pulsed LD. A number density of bubbles was estimated by using a calibration data obtained with monosized standard particles. In addition, the effect of pulse length and a surfactant on the bubble population phenomena in a multibubble system are discussed.

  2. A comparison of three types of pulse tube refrigerators - New methods for reaching 60 K

    NASA Technical Reports Server (NTRS)

    Radebaugh, Ray; Zimmerman, James; Smith, David R.; Louie, Beverly

    1986-01-01

    The three types of pulse tube refrigerator, namely the resonant, basic, and orifice designs, are compared with each other and with such common refrigerators as the Joule-Thomson and Stirling types, using an apparatus able to measure their intrinsic behavior from 30 to 300 K. Orifice pulse tubes are found capable of reaching 60 K temperature drops in a single stage. Additional advantages of the type are (1) a single, room-temperature moving part, (2) the use of moderate pressures and pressure ratios, (3) good intrinsic efficiency, and (4) the ability to operate several stages from the same pressure wave generator. The low refrigeration rate/unit mass flow means, however, that better regenerator units are required.

  3. Effect of Catalytic Pyrolysis Conditions Using Pulse Current Heating Method on Pyrolysis Products of Wood Biomass

    PubMed Central

    Honma, Sensho; Hata, Toshimitsu; Watanabe, Takashi

    2014-01-01

    The influence of catalysts on the compositions of char and pyrolysis oil obtained by pyrolysis of wood biomass with pulse current heating was studied. The effects of catalysts on product compositions were analyzed using GC-MS and TEM. The compositions of some aromatic compounds changed noticeably when using a metal oxide species as the catalyst. The coexistence or dissolution of amorphous carbon and iron oxide was observed in char pyrolyzed at 800°C with Fe3O4. Pyrolysis oil compositions changed remarkably when formed in the presence of a catalyst compared to that obtained from the uncatalyzed pyrolysis of wood meal. We observed a tendency toward an increase in the ratio of polyaromatic hydrocarbons in the pyrolysis oil composition after catalytic pyrolysis at 800°C. Pyrolysis of biomass using pulse current heating and an adequate amount of catalyst is expected to yield a higher content of specific polyaromatic compounds. PMID:25614894

  4. Antimicrobial activity of biopolymer-antibiotic thin films fabricated by advanced pulsed laser methods

    NASA Astrophysics Data System (ADS)

    Cristescu, R.; Popescu, C.; Dorcioman, G.; Miroiu, F. M.; Socol, G.; Mihailescu, I. N.; Gittard, S. D.; Miller, P. R.; Narayan, R. J.; Enculescu, M.; Chrisey, D. B.

    2013-08-01

    We report on thin film deposition by matrix assisted pulsed laser evaporation (MAPLE) of two polymer-drug composite thin film systems. A pulsed KrF* excimer laser source (λ = 248 nm, τ = 25 ns, ν = 10 Hz) was used to deposit composite thin films of poly(D,L-lactide) (PDLLA) containing several gentamicin concentrations. FTIR spectroscopy was used to demonstrate that MAPLE-transferred materials exhibited chemical structures similar to those of drop cast materials. Scanning electron microscopy data indicated that MAPLE may be used to fabricate thin films of good morphological quality. The activity of PDLLA-gentamicin composite thin films against Staphylococcus aureus bacteria was demonstrated using drop testing. The influence of drug concentration on microbial viability was also assessed. Our studies indicate that polymer-drug composite thin films prepared by MAPLE may be used to impart antimicrobial activity to implants, medical devices, and other contact surfaces.

  5. Quickbird Satellite in-orbit Modulation Transfer Function (MTF) Measurement Using Edge, Pulse and Impulse Methods for Summer 2003

    NASA Technical Reports Server (NTRS)

    Helder, Dennis; Choi, Taeyoung; Rangaswamy, Manjunath

    2005-01-01

    The spatial characteristics of an imaging system cannot be expressed by a single number or simple statement. However, the Modulation Transfer Function (MTF) is one approach to measure the spatial quality of an imaging system. Basically, MTF is the normalized spatial frequency response of an imaging system. The frequency response of the system can be evaluated by applying an impulse input. The resulting impulse response is termed the Point Spread function (PSF). This function is a measure of the amount of blurring present in the imaging system and is itself a useful measure of spatial quality. An underlying assumption is that the imaging system is linear and shift-independent. The Fourier transform of the PSF is called the Optical Transfer Function (OTF) and the normalized magnitude of the OTF is the MTF. In addition to using an impulse input, a knife-edge in technique has also been used in this project. The sharp edge exercises an imaging system at all spatial frequencies. The profile of an edge response from an imaging system is called an Edge Spread Function (ESF). Differentiation of the ESF results in a one-dimensional version of the Point Spread Function (PSF). Finally, MTF can be calculated through use of Fourier transform of the PSF as stated previously. Every image includes noise in some degree which makes MTF of PSF estimation more difficult. To avoid the noise effects, many MTF estimation approaches use smooth numerical models. Historically, Gaussian models and Fermi functions were applied to reduce the random noise in the output profiles. The pulse-input method was used to measure the MTF of the Landsat Thematic Mapper (TM) using 8th order even functions over the San Mateo Bridge in San Francisco, California. Because the bridge width was smaller than the 30-meter ground sample distance (GSD) of the TM, the Nyquist frequency was located before the first zero-crossing point of the sinc function from the Fourier transformation of the bridge pulse. To avoid

  6. Novel image fusion method based on adaptive pulse coupled neural network and discrete multi-parameter fractional random transform

    NASA Astrophysics Data System (ADS)

    Lang, Jun; Hao, Zhengchao

    2014-01-01

    In this paper, we first propose the discrete multi-parameter fractional random transform (DMPFRNT), which can make the spectrum distributed randomly and uniformly. Then we introduce this new spectrum transform into the image fusion field and present a new approach for the remote sensing image fusion, which utilizes both adaptive pulse coupled neural network (PCNN) and the discrete multi-parameter fractional random transform in order to meet the requirements of both high spatial resolution and low spectral distortion. In the proposed scheme, the multi-spectral (MS) and panchromatic (Pan) images are converted into the discrete multi-parameter fractional random transform domains, respectively. In DMPFRNT spectrum domain, high amplitude spectrum (HAS) and low amplitude spectrum (LAS) components carry different informations of original images. We take full advantage of the synchronization pulse issuance characteristics of PCNN to extract the HAS and LAS components properly, and give us the PCNN ignition mapping images which can be used to determine the fusion parameters. In the fusion process, local standard deviation of the amplitude spectrum is chosen as the link strength of pulse coupled neural network. Numerical simulations are performed to demonstrate that the proposed method is more reliable and superior than several existing methods based on Hue Saturation Intensity representation, Principal Component Analysis, the discrete fractional random transform etc.

  7. An Improved Method of Mitigating Laser Induced Surface Damage Growth in Fused Silica Using a Rastered, Pulsed CO2 Laser

    SciTech Connect

    Bass, I L; Guss, G M; Nostrand, M J; Wegner, P L

    2010-10-21

    A new method of mitigating (arresting) the growth of large (>200 m diameter and depth) laser induced surface damage on fused silica has been developed that successfully addresses several issues encountered with our previously-reported large site mitigation technique. As in the previous work, a tightly-focused 10.6 {micro}m CO{sub 2} laser spot is scanned over the damage site by galvanometer steering mirrors. In contrast to the previous work, the laser is pulsed instead of CW, with the pulse length and repetition frequency chosen to allow substantial cooling between pulses. This cooling has the important effect of reducing the heat-affected zone capable of supporting thermo-capillary flow from scale lengths on the order of the overall scan pattern to scale lengths on the order of the focused laser spot, thus preventing the formation of a raised rim around the final mitigation site and its consequent down-stream intensification. Other advantages of the new method include lower residual stresses, and improved damage threshold associated with reduced amounts of redeposited material. The raster patterns can be designed to produce specific shapes of the mitigation pit including cones and pyramids. Details of the new technique and its comparison with the previous technique will be presented.

  8. Simultaneous voltammetric determination of morphine and noscapine by adsorptive differential pulse stripping method and least-squares support vector machines.

    PubMed

    Niazi, Ali; Ghasemi, Jahanbakhsh; Zendehdel, Mojgan

    2007-11-30

    An adsorptive differential pulse stripping method for the simultaneous determination of morphine and noscapine is proposed. The procedure involves an adsorptive accumulation of morphine and noscapine on a hanging mercury drop electrode (HMDE), followed by oxidation of adsorbed morphine and noscapine by voltammetric scan using differential pulse modulation. The optimum experimental conditions are: pH 10.0, accumulation potential of -100 mV versus Ag/AgCl, accumulation time of 150 s, scan rate of 40 mV s(-1) and pulse height of 100 mV. Morphine and noscapine peak currents were observed in same potential region at about +0.25 V. The simultaneous determination of morphine and noscapine by using voltammetry is a difficult problem in analytical chemistry, due to voltammogram interferences. The resolution of mixture of morphine and noscapine by the application of least-squares support vector machines (LS-SVM) was performed. The linear dynamic ranges were 0.01-3.10 and 0.015-2.75 microg mL(-1) and detection limits were 3 and 7 ng mL(-1) for morphine and noscapine, respectively. The capability of the method for the analysis of real samples was evaluated by the determination of morphine and noscapine in addict's human plasma with satisfactory results.

  9. Spectral encoding method for measuring the relative arrival time between x-ray/optical pulses

    SciTech Connect

    Bionta, M. R.; Hartmann, N.; Weaver, M.; French, D.; Glownia, J. M.; Bostedt, C.; Chollet, M.; Ding, Y.; Fritz, D. M.; Fry, A. R.; Krzywinski, J.; Lemke, H. T.; Messerschmidt, M.; Schorb, S.; Zhu, D.; White, W. E.; Nicholson, D. J.; Cryan, J. P.; Baker, K.; Kane, D. J.; and others

    2014-08-15

    The advent of few femtosecond x-ray light sources brings promise of x-ray/optical pump-probe experiments that can measure chemical and structural changes in the 10–100 fs time regime. Widely distributed timing systems used at x-ray Free-Electron Laser facilities are typically limited to above 50 fs fwhm jitter in active x-ray/optical synchronization. The approach of single-shot timing measurements is used to sort results in the event processing stage. This has seen wide use to accommodate the insufficient precision of active stabilization schemes. In this article, we review the current technique for “measure-and-sort” at the Linac Coherent Light Source at the SLAC National Accelerator Laboratory. The relative arrival time between an x-ray pulse and an optical pulse is measured near the experimental interaction region as a spectrally encoded cross-correlation signal. The cross-correlation provides a time-stamp for filter-and-sort algorithms used for real-time sorting. Sub-10 fs rms resolution is common in this technique, placing timing precision at the same scale as the duration of the shortest achievable x-ray pulses.

  10. Microcomputer-based system for the measurement of transpiration rate in trees by the heat pulse method

    NASA Astrophysics Data System (ADS)

    Ben-Yaakov, Sam; Cohen, Yeheskel; Roshansky, Magenia

    1985-08-01

    A microcomputer-based system was designed to measure water transport in trees by the heat pulse method. The system comprises a heater probe as a heat source and a thermistor, incorporated into a bridge which is automatically balanced by the microcomputer. The overall dynamic range of the system for temperature is 22 bits and the resolution for temperature determination is about 1.45×10-4 °C. The elapsed time between the heat pulse injection and the thermal peak at the thermistor is calculated by the microcomputer. The computation program includes algorithms for base-line slope correction and a noise immune derivative evaluating routine for peak recognition. The system was tested in the laboratory and in the field on a citrus tree.

  11. Simultaneous polarographic determination of 2-nitrophenol and 4-nitrophenol by differential pulse polarography method and support vector regression.

    PubMed

    Asadpour-Zeynali, Karim; Soheili-Azad, Payam

    2012-01-01

    A differential pulse polarography (DPP) for the simultaneous determination of 2-nitrophenol and 4-nitrophenol was proposed. It was found that under optimum experimental conditions (pH = 5, scan rate = 5 mV/s, pulse amplitude = -50 mV), 2-nitrophenol and 4-nitrophenol had well-defined polarographic reduction waves with peak potentials at -317 and -406 mV, respectively. In the mixture of two compounds overlapping polarographic peaks were observed. In this study, support vector regression (SVR) was applied to resolve the overlapped polarograms. Furthermore, a comparison was made between the performance of SVR and partial least square (PLS) on data set. The results demonstrated that SVR is a better well-performing alternative for the analysis and modeling of DPP data than the commonly applied PLS technique. The proposed method was used for the determination of 2-nitrophenol and 4-nitrophenol in industrial waste water.

  12. Theoretical analysis of the pulse-clamp method as applied to neural stimulating electrodes.

    SciTech Connect

    Stefan, I. C.; Tolmachev, Y. V.; Nagy, Z.; Minkoff, M.; Merrill, D. R.; Mortimer, J. T.; Scherson, D. A.; Case Western Reserve Univ.

    2001-02-01

    A mathematical model was developed to simulate potential pulse clamp experiments at inert-electrode/aqueous solution interfaces in the absence of dioxygen or other adventitious redox active species. This model incorporates a potential invariant interfacial capacitor, a kinetically slow redox couple with parameters consistent with the H{sub 2}O/H{sub 2} reaction on polycrystalline Au in acid electrolytes as the only faradaic process involved, and diffusion as the only mode of mass transport in solution phase. Numerical integration of the resulting system of differential equations was found to yield results in good agreement with experimental data reported by Mortimer and co-workers for Au in dearated sulfuric acid solutions. A detailed analysis of these calculations identified the fast and slow recoverable charges to be capacitive and the unrecoverable charges to be faradaic. The results obtained indicated that for small overpotentials the charge is stored in the interfacial capacitor, and that significant faradaic processes occur only when the overpotential is large. Furthermore, during the delay, and despite the fact that no current flows through the external circuit, the capacitor discharges via the faradaic reaction, increasing the total amount of product generated. More importantly, under the conditions selected for the simulations, none of the faradaic charge is recovered during the potential controlled stage of the sequence. These results provide insight into the relationships between stimulus parameters and charge injected into irreversible faradaic reactions, which may generate biologically harmful species. In general, as stimulus pulse durations increase, unrecoverable charge increases. Also, as the delay increases between the end of the primary and beginning of the secondary pulse, unrecoverable charge increases. Furthermore, based on the mathematical model used herein, the use of an electrode material with a small exchange current density would allow

  13. Apparatus and method for measurement of weak optical absorptions by thermally induced laser pulsing

    DOEpatents

    Cremers, D.A.; Keller, R.A.

    1982-06-08

    The thermal lensing phenomenon is used as the basis for measurement of weak optical absorptions when a cell containing the sample to be investigated is inserted into a normally continuous-wave operation laser-pumped dye laser cavity for which the output coupler is deliberately tilted relative to intracavity circulating laser light, and pulsed laser output ensues, the pulsewidth of which can be rlated to the sample absorptivity by a simple algorithm or calibration curve. A minimum detection limit of less than 10/sup -5/ cm/sup -1/ has been demonstrated using this technique.

  14. Apparatus and method for measurement of weak optical absorptions by thermally induced laser pulsing

    DOEpatents

    Cremers, David A.; Keller, Richard A.

    1985-01-01

    The thermal lensing phenomenon is used as the basis for measurement of weak optical absorptions when a cell containing the sample to be investigated is inserted into a normally continuous-wave operation laser-pumped dye laser cavity for which the output coupler is deliberately tilted relative to intracavity circulating laser light, and pulsed laser output ensues, the pulsewidth of which can be related to the sample absorptivity by a simple algorithm or calibration curve. A minimum detection limit of less than 10.sup.-5 cm.sup.-1 has been demonstrated using this technique.

  15. Apparatus and method for measurement of weak optical absorptions by thermally induced laser pulsing

    DOEpatents

    Cremers, D.A.; Keller, R.A.

    1985-10-01

    The thermal lensing phenomenon is used as the basis for measurement of weak optical absorptions when a cell containing the sample to be investigated is inserted into a normally continuous-wave operation laser-pumped dye laser cavity for which the output coupler is deliberately tilted relative to intracavity circulating laser light, and pulsed laser output ensues, the pulsewidth of which can be related to the sample absorptivity by a simple algorithm or calibration curve. A minimum detection limit of less than 10[sup [minus]5] cm[sup [minus]1] has been demonstrated using this technique. 6 figs.

  16. Evaluation of Methods to Increase Beam Pulse Width on the DARHT Axis-II Accelerator

    DTIC Science & Technology

    2013-06-01

    lanl.gov Abstract The second axis (Axis II) of the Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility at Los Alamos National Laboratory ( LANL ...of the cell pulses are of less importance than 665U.S. Government work not protected by U.S. copyright Report Documentation Page Form ApprovedOMB No...19th). Held in San Francisco, CA on 16-21 June 2013., The original document contains color images. 14. ABSTRACT The second axis (Axis II) of the Dual

  17. Application of wavelet filtering and Barker-coded pulse compression hybrid method to air-coupled ultrasonic testing

    NASA Astrophysics Data System (ADS)

    Zhou, Zhenggan; Ma, Baoquan; Jiang, Jingtao; Yu, Guang; Liu, Kui; Zhang, Dongmei; Liu, Weiping

    2014-10-01

    Air-coupled ultrasonic testing (ACUT) technique has been viewed as a viable solution in defect detection of advanced composites used in aerospace and aviation industries. However, the giant mismatch of acoustic impedance in air-solid interface makes the transmission efficiency of ultrasound low, and leads to poor signal-to-noise (SNR) ratio of received signal. The utilisation of signal-processing techniques in non-destructive testing is highly appreciated. This paper presents a wavelet filtering and phase-coded pulse compression hybrid method to improve the SNR and output power of received signal. The wavelet transform is utilised to filter insignificant components from noisy ultrasonic signal, and pulse compression process is used to improve the power of correlated signal based on cross-correction algorithm. For the purpose of reasonable parameter selection, different families of wavelets (Daubechies, Symlet and Coiflet) and decomposition level in discrete wavelet transform are analysed, different Barker codes (5-13 bits) are also analysed to acquire higher main-to-side lobe ratio. The performance of the hybrid method was verified in a honeycomb composite sample. Experimental results demonstrated that the proposed method is very efficient in improving the SNR and signal strength. The applicability of the proposed method seems to be a very promising tool to evaluate the integrity of high ultrasound attenuation composite materials using the ACUT.

  18. Accuracy improvement in leak detection of charcoal adsorbers by halide pulse integration method

    SciTech Connect

    Kovach, B.J.; Banks, E.M.

    1997-08-01

    Due to the phaseout of the supply of R-11, which is used as a charcoal adsorber leak-testing agent, several new substitutes have been suggested and tested. Pulse testing using agents with higher boiling points produced longer response times (due to prolonged evaporation and dispersion times). This longer evaporation time alters the pulse shape and lowers the peak concentration. Since the dispersion and evaporation time under different ambient condition are unpredictable, the peak concentration becomes unpredictable as well. One way to eliminate this unpredictability is to determine the area under the curve (of concentration versus time) after test-agent injection rather than the peak concentration (height). This value should be independent of the injection time and evaporation rate as long as the volume of the test agent injected remains constant. Thus, tests were performed with a constant volume injection of test agent but with different injection times and evaporation rates. The area under the curve of concentration versus time was then compared with the peak concentration for each injection. 4 refs., 1 fig.

  19. A Potential Mechanism for Perchlorate Formation on Mars: Surface-Radiolysis-Initiated Atmospheric Chemistry

    NASA Astrophysics Data System (ADS)

    Wilson, Eric; Atreya, Sushil K.; Kaiser, Ralf-Ingo; Mahaffy, Paul

    2016-10-01

    Perchlorate (ClO4-) is prevalent on Earth, and with observations of perchlorate on lunar samples and chondrite meteorites, along with recent observations indicating the presence of perchlorate (ClO4-) in the Martian surface by the Phoenix lander and the Sample Analysis at Mars (SAM) on the Mars Science Laboratory (MSL) rover, it appears that the existence of perchlorate is widespread throughout the solar system. However, the abundance and isotopic composition of Martian perchlorate suggest that the perchlorate formation mechanism on Mars may involve a different path than perchlorate found elsewhere in the solar system. Motivated by this, we employ a one-dimensional chemical model to investigate the viability of perchlorate formation in the atmosphere of Mars, instigated by the radiolysis of the Martian surface by galactic cosmic rays. The surface-atmosphere interaction to produce Martian perchlorate involves the sublimation of chlorine oxides into the atmosphere, through surface radiolysis, and their subsequent synthesis to form perchloric acid (HClO4), followed by surface deposition and mineralization to form surface perchlorates. Considering the chlorine oxide, OClO, we find an OClO surface flux as low as 3.2x107 molecules cm-2 s-1, sublimated into the atmosphere from the surface could produce sufficient HClO4 to explain the perchlorate concentration on Mars, assuming an accumulation depth of 30 cm and integrated over the Amazonian period. Radiolysis provides an efficient pathway for the oxidation of chlorine, bypassing the efficient Cl/HCl recycling mechanism that characterizes HClO4 formation mechanisms proposed for the Earth but not Mars.

  20. Identification of tetraphenylborate radiolysis products in a simulated feedstock for radioactive waste processing

    SciTech Connect

    Eibling, R.E.; Bartlett, M.G.; Carlson, R.E.; Testino, S.A. Jr.; Kunkel, G.J.; Browner, R.F.; Busch, K.L.

    1994-10-01

    The first step towards immobilization of the soluble radioactive species in borosilicate glass is the addition of sodium tetraphenylborate (TPB) and sodium titanate to the radioactive aqueous solution. Initial studies of the TPB hydrolysis process have found that some component of the radiolysis mixture inactivates the Cu catalyst. The interaction of organic materials with the catalyst, and the subsequent interference with the hydrolysis process, would have presented problems with the use of the vitrification process. Prevention of the catalyst deactivation is obtained by washing the irradiated TPB precipitate in the Late Wash Facility prior to hydrolysis to remove the soluble radiolysis products. Identification of the organic radiolysis products, their distribution in the Late Wash Facility, and their interactions with the Cu catalyst has become an important analytical issue. To further investigate the reaction products of the TPB precipitation process, a simulated feedstock was created from compounds known to be present in the starting materials. This simulated feedstock was precipitated with sodium TPB and then exposed to Co-60 gamma radiation to simulate two years of additional storage time prior to the hydrolysis process. The irradiated product was divided into two parts, the filtered supernatant liquid and the precipitate slurry, which contains the TPB and the solid sodium titanate. Using gas chromatography/mass spectrometry, liquid secondary ion mass spectrometry, inductively coupled plasma/mass spectrometry, ion chromatography, and high performance liquid chromatography, over 50 organic and inorganic species have been identified in the aqueous portion of a simulated feedstock for TPB hydrolysis. The major organic species present are benzene, phenol, benzamide and a variety of substituted phenylphenols. The major inorganic species present are sodium, nitrite, and oxalate ions.

  1. A Review of Radiolysis Concerns for Water Shielding in Fission Surface Power Applications

    NASA Technical Reports Server (NTRS)

    Schoenfeld, Michael P.

    2008-01-01

    This paper presents an overview of radiolysis concerns with regard to water shields for fission surface power. A review of the radiolysis process is presented and key parameters and trends are identified. From this understanding of the radiolytic decomposition of water, shield pressurization and corrosion are identified as the primary concerns. Existing experimental and modeling data addressing concerns are summarized. It was found that radiolysis of pure water in a closed volume results in minimal, if any net decomposition, and therefore reduces the potential for shield pressurization and corrosion. With the space program focus m emphasize more on permanent return to the Moon and eventually manned exploration of Mars, there has been a renewed look at fission power to meet the difficult technical & design challenges associated with this effort. This is due to the ability of fission power to provide a power rich environment that is insensitive to solar intensity and related aspects such as duration of night, dusty environments, and distance from the sun, etc. One critical aspect in the utilization of fission power for these applications of manned exploration is shielding. Although not typically considered for space applications, water shields have been identified as one potential option due to benefits in mass savings and reduced development cost and technical risk (Poston, 2006). However, the water shield option requires demonstration of its ability to meet key technical challenges including such things as adequate natural circulation for thermal management and capability for operational periods up to 8 years. Thermal management concerns have begun to be addressed and are not expected to be a problem (Pearson, 2007). One significant concern remaining is the ability to maintain the shield integrity through its operational lifetime. Shield integrity could be compromised through shield pressurization and corrosion resulting from the radiolytic decomposition of water.

  2. GAMMA-RADIOLYSIS OF DISULFIDES IN AQUEOUS SOLUTION. II. D-PENICILLAMINE DISULFIDE,

    DTIC Science & Technology

    The gamma-radiolysis of D- penicillamine disulfide (PenSSPen) in an aqueous solution has been studied under aerated and deaerated conditions. G...values were determined for the following products: penicillamine sulfinic acid (PenSO2H), penicillaminic acid (PenSO3H), beta-hydroxyvaline (PenOH), 2...amino-3-methylbut-3-enoic acid (HOOC.CH(NH2).C(CH3)=CH2), penicillamine (PenSH), penicillamine disulfide-S-monoxide (PenS(O)SPen), valine (PenH

  3. Radiolysis of selected antibiotics and their toxic effects on various aquatic organisms

    NASA Astrophysics Data System (ADS)

    Kim, Hyun Y.; Yu, Seung H.; Lee, Myun J.; Kim, Tae H.; Kim, Sang D.

    2009-04-01

    This study was conducted to investigate the decomposition of three γ-irradiated antibiotics (e.g., tetracycline, sulfamethazine, and lincomycin) and to compare the toxic effects on Daphnia magna, Vibrio fischeri, and Pseudokirchneriella subcapitata. The median cell growth inhibition concentrations (IC 50) of tetracycline, lincomycin, and sulfamethazine for P. subcapitata dramatically increased (e.g., toxicity decreased) after radiolysis. The results demonstrated that γ-radiation treatment was efficient to decompose antibiotics and thereby their toxicity on P. subcaptitata remarkably decreased due to reduced parent compounds.

  4. Evaluation of B/A nonlinear parameter using an acoustic self-calibrated pulse-echo method

    SciTech Connect

    Vander Meulen, F.; Haumesser, L.

    2008-05-26

    The objective of this work is to develop an easy-to-build and robust setup for measuring the nonlinearity parameter B/A in fluids using ultrasound. The method is based on the pulse-echo technique, using a single element broadband acoustic transducer, and requires electrical signal measurements. Results obtained in water and denatured alcohol validate the proposed procedure. The choice of a suitable primary wave frequency is discussed with regard to the transducer sensitivity. Further, the influence of the perturbations introduced by the experimental device nonlinearities, and the role of the reflector on the measured second harmonic field amplitude are investigated.

  5. Long pulse production from short pulses

    DOEpatents

    Toeppen, J.S.

    1994-08-02

    A method of producing a long output pulse from a short pump pulse is disclosed, using an elongated amplified fiber having a doped core that provides an amplifying medium for light of one color when driven into an excited state by light of a shorter wavelength and a surrounding cladding. A seed beam of the longer wavelength is injected into the core at one end of the fiber and a pump pulse of the shorter wavelength is injected into the cladding at the other end of the fiber. The counter-propagating seed beam and pump pulse will produce an amplified output pulse having a time duration equal to twice the transit time of the pump pulse through the fiber plus the length of the pump pulse. 3 figs.

  6. Long pulse production from short pulses

    DOEpatents

    Toeppen, John S.

    1994-01-01

    A method of producing a long output pulse (SA) from a short pump pulse (P), using an elongated amplified fiber (11) having a doped core (12) that provides an amplifying medium for light of one color when driven into an excited state by light of a shorter wavelength and a surrounding cladding 13. A seed beam (S) of the longer wavelength is injected into the core (12) at one end of the fiber (11) and a pump pulse (P) of the shorter wavelength is injected into the cladding (13) at the other end of the fiber (11). The counter-propagating seed beam (S) and pump pulse (P) will produce an amplified output pulse (SA) having a time duration equal to twice the transit time of the pump pulse (P) through the fiber (11) plus the length of the pump pulse (P).

  7. Electrochemical properties of Sn-based nanopowders synthesized by a pulsed wire evaporation method and effect of binder coating

    SciTech Connect

    Ha, Jong-Keun; Song, Ju-Seok; Cho, Gyu-Bong; Ahn, Jou-Hyeon; Ahn, Hyo-Jun; Cho, Kwon-Koo

    2016-10-15

    Highlights: • Sn-based nanoparticles are fabricated by using the pulsed wire evaporation method. • The electrodes are prepared by mixing the graphene and coating the surface. • Coating the surface of electrode is used with brushing of simple and facile method. • The electrochemical measurements are performed with galvanostatic experiments. • The coating electrode maintains capacity nearly of 501 mAh g{sup −1} up to 100 cycles. - Abstract: Sn-based nanoparticles are prepared with the O{sub 2} concentrations in chamber of Ar atmosphere (by v/v) by using the pulsed wire evaporation (PWE) method. The prepared electrodes are only Sn-based powder electrode, its binder coating electrode and Sn-based powder/graphene nanocomposite electrode. Morphology and structure of the synthesized powders and electrodes are investigated with a field emission scanning electron microscope (FE-SEM) and an X-ray diffraction (XRD) analysis. The electrochemical measurements were performed with galvanostatic cycling experiments using a coin type cell of CR2032 (Ø20, T3.2 mm). The binder coating electrode is superior to others and maintains delithiation capacity nearly of 501 mAh g{sup −1} as 58.3% of first delithiation capacity at 0.2 C-rate up to 100 cycles.

  8. Variable frequency pulsed phase-locked loop method for measuring material nonlinearity

    NASA Technical Reports Server (NTRS)

    Yost, William T.; Cantrell, John H.

    1992-01-01

    The design of a pressure vessel with an isothermal volume to measure changes in the natural velocities of material continuously over a wide temperature range is reported. Highly sensitive pulsed phase-locked loop technology is used to measure the natural velocity of fatigued aluminum 2024-T4 as a function of pressure at different temperatures. Second derivative variations with respect to pressure and temperature are found to exhibit order-of-magnitude changes at a gauge pressure near 950 kPa at room temperature. This indicates a significant change in certain combinations of second-order and higher-order elastic constants at relatively low pressures. Fractional frequency change as a function of applied pressure for aluminum 2024-T4 with fatigue damage is illustrated.

  9. High power pulsed magnetron sputtering: A method to increase deposition rate

    SciTech Connect

    Raman, Priya McLain, Jake; Ruzic, David N; Shchelkanov, Ivan A.

    2015-05-15

    High power pulsed magnetron sputtering (HPPMS) is a state-of-the-art physical vapor deposition technique with several industrial applications. One of the main disadvantages of this process is its low deposition rate. In this work, the authors report a new magnetic field configuration, which produces deposition rates twice that of conventional magnetron's dipole magnetic field configuration. Three different magnet pack configurations are discussed in this paper, and an optimized magnet pack configuration for HPPMS that leads to a higher deposition rate and nearly full-face target erosion is presented. The discussed magnetic field produced by a specially designed magnet assembly is of the same size as the conventional magnet assembly and requires no external fields. Comparison of deposition rates with different power supplies and the electron trapping efficiency in complex magnetic field arrangements are discussed.

  10. Method for pulse control in a laser including a stimulated brillouin scattering mirror system

    DOEpatents

    Dane, C. Brent; Hackel, Lloyd; Harris, Fritz B.

    2007-10-23

    A laser system, such as a master oscillator/power amplifier system, comprises a gain medium and a stimulated Brillouin scattering SBS mirror system. The SBS mirror system includes an in situ filtered SBS medium that comprises a compound having a small negative non-linear index of refraction, such as a perfluoro compound. An SBS relay telescope having a telescope focal point includes a baffle at the telescope focal point which blocks off angle beams. A beam splitter is placed between the SBS mirror system and the SBS relay telescope, directing a fraction of the beam to an alternate beam path for an alignment fiducial. The SBS mirror system has a collimated SBS cell and a focused SBS cell. An adjustable attenuator is placed between the collimated SBS cell and the focused SBS cell, by which pulse width of the reflected beam can be adjusted.

  11. Apparatus and method for tuned unsteady flow purging of high pulse rate spark gaps

    DOEpatents

    Thayer, III, William J.

    1990-01-01

    A spark gap switch apparatus is disclosed which is capable of operating at a high pulse rate which comprises an insulated housing; a pair of spaced apart electrodes each having one end thereof within a first bore formed in the housing and defining a spark gap therebetween; a pressure wave reflector in the first bore in the housing and spaced from the spark gap and capable of admitting purge flow; and a second enlarged bore contiguous with the first bore and spaced from the opposite side of the spark gap; whereby pressure waves generated during discharge of a spark across the spark gap will reflect off the wave reflector and back from the enlarged bore to the spark gap to clear from the spark gap hot gases residues generated during the discharge and simultaneously restore the gas density and pressure in the spark gap to its initial value.

  12. RADIOLYSIS OF ORGANIC COMPOUNDS IN THE ADSORBED STATE

    DOEpatents

    Sutherland, J.W.; Allen, A.O.

    1961-10-01

    >A method of forming branch chained hydrocarbons by means of energetic penetrating radiation is described. A solid zeolite substrate is admixed with a cobalt ion and is irradiated with a hydrocarbon adsorbed therein. Upon irradiation with gamma rays, there is an increased yield of branched and lower molecular straight chain compounds. (AEC)

  13. Comparison of an Oscillometric Method with Cardiac Magnetic Resonance for the Analysis of Aortic Pulse Wave Velocity

    PubMed Central

    Feistritzer, Hans-Josef; Reinstadler, Sebastian J.; Klug, Gert; Kremser, Christian; Seidner, Benjamin; Esterhammer, Regina; Schocke, Michael F.; Franz, Wolfgang-Michael; Metzler, Bernhard

    2015-01-01

    Objectives Pulse wave velocity (PWV) is the proposed gold-standard for the assessment of aortic elastic properties. The aim of this study was to compare aortic PWV determined by a recently developed oscillometric device with cardiac magnetic resonance imaging (CMR). Methods PWV was assessed in 40 volunteers with two different methods. The oscillometric method (PWVOSC) is based on a transfer function from the brachial pressure waves determined by oscillometric blood pressure measurements with a common cuff (Mobil-O-Graph, I.E.M. Stolberg, Germany). CMR was used to determine aortic PWVCMR with the use of the transit time method based on phase-contrast imaging at the level of the ascending and abdominal aorta on a clinical 1.5 Tesla scanner (Siemens, Erlangen, Germany). Results The median age of the study population was 34 years (IQR: 24–55 years, 11 females). A very strong correlation was found between PWVOSC and PWVCMR (r = 0.859, p < 0.001). Mean PWVOSC was 6.7 ± 1.8 m/s and mean PWVCMR was 6.1 ± 1.8 m/s (p < 0.001). Analysis of agreement between the two measurements using Bland-Altman method showed a bias of 0.57 m/s (upper and lower limit of agreement: 2.49 m/s and -1.34 m/s). The corresponding coefficient of variation between both measurements was 15%. Conclusion Aortic pulse wave velocity assessed by transformation of the brachial pressure waveform showed an acceptable agreement with the CMR-derived transit time method. PMID:25612307

  14. Analytical new method to generation of nonlinear optical pulses in wave guides and analysis of its stability

    NASA Astrophysics Data System (ADS)

    Amaro de Faria Júnior, A. C.

    2015-09-01

    We have developed a analitical method based on the general theory of modulation of Whitham7 where the variational method is a particular case to generate nonlinear optical pulses and Optical Solitons. We show the equivalence of the solutions of the Nonlinear Schrödinger Equation (NLS) and the solutions derived from the method proposed here, demonstrating that these solutions lead to the Optical Solitons. We developed a new method to check the stability of the NLS equations. We show that the Optical Solitons obtained from a Lagrangian density can propagate through a waveguide such as an optical fiber, and are equivalent to Optical Solitons guided by an optical fiber. To analyze the stability of system solutions we have expanded the Lagrangian density and from the expanded Lagrangian we obtain the system equations of motion and restrict the solutions that have oscillating behavior when disturbed. The stability analysis can also be performed by expansion of the optical field as it is presented in section 4. Thus obtain a self-value equation whose spectrum is positive indicating that the solutions with the characteristics of reproducing the NLS solutions are stable. This method can be used and implemented computationally for linear stability analysis of any optical system or any NLS solution. Another important aspect of our research has been the discovery of a relationship between the Lagrangian of optical system and the optical pulse propagating through a waveguide. The paper is organized as follows. Section 1 is devoted to a quick presentation of NLS systems. The section 2 provides a description of modeling of an optical network. Section 3 and 4 are devoted to the presentation of the proposed method for obtaining this class of solutions and their stability analysis. Section 5 presents conclusions and comments and section 6 provides references.

  15. Method of optical self-mixing for pulse wave transit time in comparison with other methods and correlation with blood pressure

    NASA Astrophysics Data System (ADS)

    Meigas, Kalju; Lass, Jaanus; Kattai, Rain; Karai, Deniss; Kaik, Juri

    2004-07-01

    This paper is a part of research to develop convenient method for continuous monitoring of arterial blood pressure by non-invasive and non-oscillometric way. A simple optical method, using self-mixing in a diode laser, is used for detection of skin surface vibrations near the artery. These vibrations, which can reveal the pulsate propagation of blood pressure waves along the vasculature, are used for pulse wave registration. The registration of the Pulse Wave Transit Time (PWTT) is based on computing the time delay in different regions of the human body using an ECG as a reference signal. In this study, the comparison of method of optical self-mixing with other methods as photoplethysmographic (PPG) and bioimpedance (BI) for PWTT is done. Also correlation of PWTT, obtained with different methods, with arterial blood pressure is calculated. In our study, we used a group of volunteers (34 persons) who made the bicycle exercise test. The test consisted of cycling sessions of increasing workloads during which the HR changed from 60 to 180 beats per minute. In addition, a blood pressure (NIBP) was registered with standard sphygmomanometer once per minute during the test and all NIBP measurement values were synchronized to other signals to find exact time moments where the systolic blood pressure was detected (Korotkoff sounds starting point). Computer later interpolated the blood pressure signal in order to get individual value for every heart cycle. The other signals were measured continuously during all tests. At the end of every session, a recovery period was included until person's NIBP and heart rate (HR) normalized. As a result of our study it turned out that time intervals that were calculated from plethysmographic (PPG) waveforms were in the best correlation with systolic blood pressure. The diastolic pressure does not correlate with any of the parameters representing PWTT. The pulse wave signals measured by laser and piezoelectric transducer are very similar

  16. Representation Method for Spectrally Overlapping Signals in Flow Cytometry Based on Fluorescence Pulse Time-Delay Estimation.

    PubMed

    Zhang, Wenchang; Lou, Xiaoping; Meng, Xiaochen; Zhu, Lianqing

    2016-11-23

    Flow cytometry is being applied more extensively because of the outstanding advantages of multicolor fluorescence analysis. However, the intensity measurement is susceptible to the nonlinearity of the detection method. Moreover, in multicolor analysis, it is impossible to discriminate between fluorophores that spectrally overlap; this influences the accuracy of the fluorescence pulse signal representation. Here, we focus on spectral overlap in two-color analysis, and assume that the fluorescence follows the single exponential decay model. We overcome these problems by analyzing the influence of the spectral overlap quantitatively, which enables us to propose a method of fluorescence pulse signal representation based on time-delay estimation (between fluorescence and scattered pulse signals). First, the time delays are estimated using a modified chirp Z-transform (MCZT) algorithm and a fine interpolation of the correlation peak (FICP) algorithm. Second, the influence of hardware is removed via calibration, in order to acquire the original fluorescence lifetimes. Finally, modulated signals containing phase shifts associated with these lifetimes are created artificially, using a digital signal processing method, and reference signals are introduced in order to eliminate the influence of spectral overlap. Time-delay estimation simulation and fluorescence signal representation experiments are conducted on fluorescently labeled cells. With taking the potentially overlap of autofluorescence as part of the observed fluorescence spectrum, rather than distinguishing the individual influence, the results show that the calculated lifetimes with spectral overlap can be rectified from 8.28 and 4.86 ns to 8.51 and 4.63 ns, respectively, using the comprehensive approach presented in this work. These values agree well with the lifetimes (8.48 and 4.67 ns) acquired for cells stained with single-color fluorochrome. Further, these results indicate that the influence of spectral

  17. Representation Method for Spectrally Overlapping Signals in Flow Cytometry Based on Fluorescence Pulse Time-Delay Estimation

    PubMed Central

    Zhang, Wenchang; Lou, Xiaoping; Meng, Xiaochen; Zhu, Lianqing

    2016-01-01

    Flow cytometry is being applied more extensively because of the outstanding advantages of multicolor fluorescence analysis. However, the intensity measurement is susceptible to the nonlinearity of the detection method. Moreover, in multicolor analysis, it is impossible to discriminate between fluorophores that spectrally overlap; this influences the accuracy of the fluorescence pulse signal representation. Here, we focus on spectral overlap in two-color analysis, and assume that the fluorescence follows the single exponential decay model. We overcome these problems by analyzing the influence of the spectral overlap quantitatively, which enables us to propose a method of fluorescence pulse signal representation based on time-delay estimation (between fluorescence and scattered pulse signals). First, the time delays are estimated using a modified chirp Z-transform (MCZT) algorithm and a fine interpolation of the correlation peak (FICP) algorithm. Second, the influence of hardware is removed via calibration, in order to acquire the original fluorescence lifetimes. Finally, modulated signals containing phase shifts associated with these lifetimes are created artificially, using a digital signal processing method, and reference signals are introduced in order to eliminate the influence of spectral overlap. Time-delay estimation simulation and fluorescence signal representation experiments are conducted on fluorescently labeled cells. With taking the potentially overlap of autofluorescence as part of the observed fluorescence spectrum, rather than distinguishing the individual influence, the results show that the calculated lifetimes with spectral overlap can be rectified from 8.28 and 4.86 ns to 8.51 and 4.63 ns, respectively, using the comprehensive approach presented in this work. These values agree well with the lifetimes (8.48 and 4.67 ns) acquired for cells stained with single-color fluorochrome. Further, these results indicate that the influence of spectral

  18. Study of the shower maximum depth by the method of detection of the EAS Cerenkov light pulse shape

    NASA Technical Reports Server (NTRS)

    Aliev, N.; Alimov, T.; Kakhkharov, M.; Khakimov, N.; Makhmudov, B. M.; Rakhimova, N.; Tashpulatov, R.; Khristiansen, G. B.; Prosin, V. V.; Zhukov, V. Y.

    1985-01-01

    The results of processing the data on the shape of the EAS Cerenkov light pulses recorded by the extensive air showers (EAS) array are presented. The pulse FWHM is used to find the mean depth of EAS maximum.

  19. Water radiolysis by low-energy carbon projectiles from first-principles molecular dynamics

    PubMed Central

    Kohanoff, Jorge

    2017-01-01

    Water radiolysis by low-energy carbon projectiles is studied by first-principles molecular dynamics. Carbon projectiles of kinetic energies between 175 eV and 2.8 keV are shot across liquid water. Apart from translational, rotational and vibrational excitation, they produce water dissociation. The most abundant products are H and OH fragments. We find that the maximum spatial production of radiolysis products, not only occurs at low velocities, but also well below the maximum of energy deposition, reaching one H every 5 Å at the lowest speed studied (1 Bohr/fs), dissociative collisions being more significant at low velocity while the amount of energy required to dissociate water is constant and much smaller than the projectile’s energy. A substantial fraction of the energy transferred to fragments, especially for high velocity projectiles, is in the form of kinetic energy, such fragments becoming secondary projectiles themselves. High velocity projectiles give rise to well-defined binary collisions, which should be amenable to binary approximations. This is not the case for lower velocities, where multiple collision events are observed. H secondary projectiles tend to move as radicals at high velocity, as cations when slower. We observe the generation of new species such as hydrogen peroxide and formic acid. The former occurs when an O radical created in the collision process attacks a water molecule at the O site. The latter when the C projectile is completely stopped and reacts with two water molecules. PMID:28267804

  20. Radiolysis of astrophysical ices by heavy ion irradiation: Destruction cross section measurement

    NASA Astrophysics Data System (ADS)

    de Barros, A. L. F.; Boduch, P.; Domaracka, A.; Rothard, H.; da Silveira, E. F.

    2012-08-01

    Many solar system objects, such as planets and their satellites, dust grains in rings, and comets, are known to either be made of ices or to have icy surfaces. These ices are exposed to ionizing radiation including keV, MeV and GeV ions from solar wind or cosmic rays. Moreover, icy dust grains are present in interstellar space and, in particular, in dense molecular clouds. Radiation effects include radiolysis (the destruction of molecules leading to formation of radicals), the formation of new molecules following radiolysis, the desorption or sputtering of atoms or molecules from the surface, compaction of porous ices, and phase changes. This review discusses the application of infrared spectroscopy FTIR to study the evolution of the chemical composition of ices containing the most abundant molecular species found in the solar system and interstellar medium, such as H2O, CO, CO2 and hydrocarbons. We focus on the evolution of chemical composition with ion fluence in order to deduce the corresponding destruction and formation cross sections. Although initial approach focused on product identification, it became increasingly necessary to work toward a comprehensive understanding of ice chemistry. The abundances of these molecules in different phases of ice mantles provide important clues to the chemical processes in dense interstellar clouds, and therefore it is of importance to accurately measure the quantities such as dissociation and formation cross sections of the infrared features of these molecules. We also are able to obtain the scaling of these cross sections with deposited energy.

  1. Perchlorate formation on Mars through surface radiolysis-initiated atmospheric chemistry: A potential mechanism.

    PubMed

    Wilson, Eric H; Atreya, Sushil K; Kaiser, Ralf I; Mahaffy, Paul R

    2016-08-01

    Recent observations of the Martian surface by the Phoenix lander and the Sample Analysis at Mars indicate the presence of perchlorate (ClO4(-)). The abundance and isotopic composition of these perchlorates suggest that the mechanisms responsible for their formation in the Martian environment may be unique in our solar system. With this in mind, we propose a potential mechanism for the production of Martian perchlorate: the radiolysis of the Martian surface by galactic cosmic rays, followed by the sublimation of chlorine oxides into the atmosphere and their subsequent synthesis to form perchloric acid (HClO4) in the atmosphere, and the surface deposition and subsequent mineralization of HClO4 in the regolith to form surface perchlorates. To evaluate the viability of this mechanism, we employ a one-dimensional chemical model, examining chlorine chemistry in the context of Martian atmospheric chemistry. Considering the chlorine oxide, OClO, we find that an OClO flux as low as 3.2 × 10(7) molecules cm(-2) s(-1) sublimated into the atmosphere from the surface could produce sufficient HClO4 to explain the perchlorate concentration on Mars, assuming an accumulation depth of 30 cm and integrated over the Amazonian period. Radiolysis provides an efficient pathway for the oxidation of chlorine, bypassing the efficient Cl/HCl recycling mechanism that characterizes HClO4 formation mechanisms proposed for the Earth but not Mars.

  2. Perchlorate formation on Mars through surface radiolysis-initiated atmospheric chemistry: A potential mechanism

    NASA Astrophysics Data System (ADS)

    Wilson, Eric H.; Atreya, Sushil K.; Kaiser, Ralf I.; Mahaffy, Paul R.

    2016-08-01

    Recent observations of the Martian surface by the Phoenix lander and the Sample Analysis at Mars indicate the presence of perchlorate (ClO4-). The abundance and isotopic composition of these perchlorates suggest that the mechanisms responsible for their formation in the Martian environment may be unique in our solar system. With this in mind, we propose a potential mechanism for the production of Martian perchlorate: the radiolysis of the Martian surface by galactic cosmic rays, followed by the sublimation of chlorine oxides into the atmosphere and their subsequent synthesis to form perchloric acid (HClO4) in the atmosphere, and the surface deposition and subsequent mineralization of HClO4 in the regolith to form surface perchlorates. To evaluate the viability of this mechanism, we employ a one-dimensional chemical model, examining chlorine chemistry in the context of Martian atmospheric chemistry. Considering the chlorine oxide, OClO, we find that an OClO flux as low as 3.2 × 107 molecules cm-2 s-1 sublimated into the atmosphere from the surface could produce sufficient HClO4 to explain the perchlorate concentration on Mars, assuming an accumulation depth of 30 cm and integrated over the Amazonian period. Radiolysis provides an efficient pathway for the oxidation of chlorine, bypassing the efficient Cl/HCl recycling mechanism that characterizes HClO4 formation mechanisms proposed for the Earth but not Mars.

  3. Water radiolysis by low-energy carbon projectiles from first-principles molecular dynamics.

    PubMed

    Kohanoff, Jorge; Artacho, Emilio

    2017-01-01

    Water radiolysis by low-energy carbon projectiles is studied by first-principles molecular dynamics. Carbon projectiles of kinetic energies between 175 eV and 2.8 keV are shot across liquid water. Apart from translational, rotational and vibrational excitation, they produce water dissociation. The most abundant products are H and OH fragments. We find that the maximum spatial production of radiolysis products, not only occurs at low velocities, but also well below the maximum of energy deposition, reaching one H every 5 Å at the lowest speed studied (1 Bohr/fs), dissociative collisions being more significant at low velocity while the amount of energy required to dissociate water is constant and much smaller than the projectile's energy. A substantial fraction of the energy transferred to fragments, especially for high velocity projectiles, is in the form of kinetic energy, such fragments becoming secondary projectiles themselves. High velocity projectiles give rise to well-defined binary collisions, which should be amenable to binary approximations. This is not the case for lower velocities, where multiple collision events are observed. H secondary projectiles tend to move as radicals at high velocity, as cations when slower. We observe the generation of new species such as hydrogen peroxide and formic acid. The former occurs when an O radical created in the collision process attacks a water molecule at the O site. The latter when the C projectile is completely stopped and reacts with two water molecules.

  4. Phenol formation in gamma radiolysis of aqueous benzene solution with sodium hypochlorite.

    PubMed

    Takeda, Kazuhiko; Nagano, Koki

    2013-03-07

    Phenol formation by gamma radiolysis of an aqueous benzene solution containing sodium hypochlorite is reported. The phenol formation in a benzene solution containing sodium hypochlorite irradiated with (60)Co γ-rays is about six times higher than that without sodium hypochlorite. Ten micromolar sodium hypochlorite enhanced the formation of phenol up to a total dose of 6 Gy. Above 6 Gy in solutions containing sodium hypochlorite, the rate of phenol yield sharply decreased and was essentially the same as that without sodium hypochlorite. The yield of phenol with sodium hypochlorite is 0.89 μmol J(-1) and is larger than the sum of yield for the radicals and reactive oxygen species by water radiolysis such as •OH, e(-), H, H2, and H2O2. The formation of phenol with sodium hypochlorite was reduced by NaCl. Results suggest that the radiolytic formation of phenol in a benzene solution with sodium hypochlorite relates to the reaction process involving chlorine atoms. Sodium hypochlorite can be applied as a sensitizer for a benzene chemical dosimetry system. The lower limit of dose detection calculated from the detection limit of phenol and the G value of phenol was estimated to be 1 × 10(-3) Gy.

  5. Radiolysis and photolysis of sodium sulfate crystalline hydrate

    NASA Astrophysics Data System (ADS)

    Tenchurina, A. R.; Sal'keeva, A. K.

    2016-03-01

    The thermal treatment of sodium sulfate was found to affect its optical and luminescent properties when activated with trivalent rare-earth ions. The influence of crystal water molecules on radiation processes in sodium sulfate was studied. The interactions of atomic hydrogen with ions and radicals were calculated by the semiempirical MNDO quantum-chemical method. The hydrogen atom was found to form stable complexes with all ions and radicals. The ions and radicals of the sulfate subsystem play the role of traps for hydrogen atoms and escape recombination, giving rise to recombination luminescence at 150 K during UV excitation of the crystalline hydrate.

  6. Simultaneous determination of oxygen, nitrogen and hydrogen in metals by pulse heating and time of flight mass spectrometric method.

    PubMed

    Shen, Xuejing; Wang, Peng; Hu, Shaocheng; Yang, Zhigang; Ma, Hongquan; Gao, Wei; Zhou, Zhen; Wang, Haizhou

    2011-05-30

    The inert gas fusion and infrared absorption and thermal conductivity methods are widely used for quantitative determination of oxygen(O), nitrogen(N) and hydrogen(H) in metals. However, O, N and H cannot be determined simultaneously with this method in most cases and the sensitivity cannot meet the requirement of some new metal materials. Furthermore, there is no equipment or method reported for determination of Argon(Ar) or Helium(He) in metals till now. In this paper, a new method for simultaneous quantitative determination of O, N, H and Ar(or He) in metals has been described in detail, which combined the pulse heating inert gas fusion with time of flight mass spectrometric detection. The whole analyzing process was introduced, including sample retreatment, inert gas fusion, mass spectral line selection, signal acquisition, data processing and calibration. The detection limit, lower quantitative limit and linear range of each element were determined. The accuracy and precision of the new method have also been verified by measurements of several kinds of samples. The results were consistent with that obtained by the traditional method. It has shown that the new method is more sensitive and efficient than the existing method.

  7. Fast assessment of planar chromatographic layers quality using pulse thermovision method.

    PubMed

    Suszyński, Zbigniew; Świta, Robert; Loś, Joanna; Zarzycka, Magdalena B; Kaleniecka, Aleksandra; Zarzycki, Paweł K

    2014-12-19

    The main goal of this paper is to demonstrate capability of pulse thermovision (thermal-wave) methodology for sensitive detection of photothermal non-uniformities within light scattering and semi-transparent planar stationary phases. Successful visualization of stationary phases defects required signal processing protocols based on wavelet filtration, correlation analysis and k-means 3D segmentation. Such post-processing data handling approach allows extremely sensitive detection of thickness and structural changes within commercially available planar chromatographic layers. Particularly, a number of TLC and HPTLC stationary phases including silica, cellulose, aluminum oxide, polyamide and octadecylsilane coated with adsorbent layer ranging from 100 to 250μm were investigated. Presented detection protocol can be used as an efficient tool for fast screening the overall heterogeneity of any layered materials. Moreover, described procedure is very fast (few seconds including acquisition and data processing) and may be applied for fabrication processes online controlling. In spite of planar chromatographic plates this protocol can be used for assessment of different planar separation tools like paper based analytical devices or micro total analysis systems, consisted of organic and non-organic layers.

  8. Pulse Wave Velocity and Cardiac Output vs. Heart Rate in Patients with an Implanted Pacemaker Based on Electric Impedance Method Measurement

    NASA Astrophysics Data System (ADS)

    Soukup, Ladislav; Vondra, Vlastimil; Viščor, Ivo; Jurák, Pavel; Halámek, Josef

    2013-04-01

    The methods and device for estimation of cardiac output and measurement of pulse wave velocity simultaneously is presented here. The beat-to-beat cardiac output as well as pulse wave velocity measurement is based on application of electrical impedance method on the thorax and calf. The results are demonstrated in a study of 24 subjects. The dependence of pulse wave velocity and cardiac output on heart rate during rest in patients with an implanted pacemaker was evaluated. The heart rate was changed by pacemaker programming while neither exercise nor drugs were applied. The most important result is that the pulse wave velocity, cardiac output and blood pressure do not depend significantly on heart rate, while the stroke volume is reciprocal proportionally to the heart rate.

  9. Method for wavelength stabilization of pulsed difference frequency laser at 1572 nm for CO(2) detection lidar.

    PubMed

    Gong, Wei; Ma, Xin; Han, Ge; Xiang, Chengzhi; Liang, Ailin; Fu, Weidong

    2015-03-09

    High-accuracy on-line wavelength stabilization is required for differential absorption lidar (DIAL), which is ideal for precisely measuring atmospheric CO(2) concentration. Using a difference-frequency laser, we developed a ground-based 1.57-μm pulsed DIAL for performing atmospheric CO(2) measurements. Owing to the system complexity, lacking phase, and intensity instability, the stabilization method was divided into two parts-wavelength calibration and locking-based on saturated absorption. After obtaining the on-line laser position, accuracy verification using statistical theory and locking stabilization using a one-dimensional template matching method, namely least-squares matching (LSM), were adopted to achieve wavelength locking. The resulting system is capable of generating a stable wavelength.

  10. The new methods of treatment for age-related macular degeneration using the ultra-short pulsed laser

    NASA Astrophysics Data System (ADS)

    Iwamoto, Yumiko; Awazu, Kunio; Suzuki, Sachiko; Ohshima, Tetsuro; Sawa, Miki; Sakaguchi, Hirokazu; Tano, Yasuo; Ohji, Masahito

    2007-02-01

    The non-invasive methods of treatments have been studying for the improvement of quality of life (QOL) of patients undergoing treatment. A photodynamic therapy (PDT) is one of the non-invasive treatments. PDT is the methods of treatment using combination of a laser and a photosensitizer. PDT has few risks for patients. Furthermore, PDT enables function preservation of a disease part. PDT has been used for early cancer till now, but in late years it is applied for age-related macular degeneration (AMD). AMD is one of the causes of vision loss in older people. However, PDT for AMD does not produce the best improvement in visual acuity. The skin photosensivity by an absorption characteristic of a photosensitizer is avoided. We examined new PDT using combination of an ultra-short pulsed laser and indocyanine green (ICG).

  11. Study of vesicle size distribution dependence on pH value based on nanopore resistive pulse method

    NASA Astrophysics Data System (ADS)

    Lin, Yuqing; Rudzevich, Yauheni; Wearne, Adam; Lumpkin, Daniel; Morales, Joselyn; Nemec, Kathleen; Tatulian, Suren; Lupan, Oleg; Chow, Lee

    2013-03-01

    Vesicles are low-micron to sub-micron spheres formed by a lipid bilayer shell and serve as potential vehicles for drug delivery. The size of vesicle is proposed to be one of the instrumental variables affecting delivery efficiency since the size is correlated to factors like circulation and residence time in blood, the rate for cell endocytosis, and efficiency in cell targeting. In this work, we demonstrate accessible and reliable detection and size distribution measurement employing a glass nanopore device based on the resistive pulse method. This novel method enables us to investigate the size distribution dependence of pH difference across the membrane of vesicles with very small sample volume and rapid speed. This provides useful information for optimizing the efficiency of drug delivery in a pH sensitive environment.

  12. Measurement of Space Charges in Dielectric Materials by Pulse Electro-acoustic Method after Irradiation by High-energy Electron Beam

    NASA Astrophysics Data System (ADS)

    Xiaogang, Qin; Kai, Li; Mayali; Xiaoquan, Zheng; Xiaodong, Liu

    2009-01-01

    Dielectric materials are widely used in space environment. When they are irradiated, charges will accumulate in the bulk and on the surface of the material, leading to pulse discharge events that can cause permanent changes in their physical and chemical structure. In this paper, a special method called PEA (pulse electro-acoustic) was used to measure and analyze the space charging of several dielectric materials after they have been irradiated by different high-energy electron beams.

  13. An extended field method solution for a pulse loaded thin plate

    NASA Technical Reports Server (NTRS)

    Donaldson, B. K.; Starkey, N. B.

    1980-01-01

    This paper deals with a new extension of a weighted residual method of analysis called the extended field method. The extended field method is applied for the first time to the problem of the transient vibration of a uniformly thin elastic plate. Numerical results have been obtained which validate the analysis procedure and show better solution convergence than is obtainable by standard methods of analysis for the same number of degrees of freedom. Further studies are necessary to obtain still better convergence.

  14. Water accessibility in a membrane-inserting peptide comparing Overhauser DNP and pulse EPR methods

    NASA Astrophysics Data System (ADS)

    Segawa, Takuya F.; Doppelbauer, Maximilian; Garbuio, Luca; Doll, Andrin; Polyhach, Yevhen O.; Jeschke, Gunnar

    2016-05-01

    Water accessibility is a key parameter for the understanding of the structure of biomolecules, especially membrane proteins. Several experimental techniques based on the combination of electron paramagnetic resonance (EPR) spectroscopy with site-directed spin labeling are currently available. Among those, we compare relaxation time measurements and electron spin echo envelope modulation (ESEEM) experiments using pulse EPR with Overhauser dynamic nuclear polarization (DNP) at X-band frequency and a magnetic field of 0.33 T. Overhauser DNP transfers the electron spin polarization to nuclear spins via cross-relaxation. The change in the intensity of the 1H NMR spectrum of H2O at a Larmor frequency of 14 MHz under a continuous-wave microwave irradiation of the nitroxide spin label contains information on the water accessibility of the labeled site. As a model system for a membrane protein, we use the hydrophobic α-helical peptide WALP23 in unilamellar liposomes of DOPC. Water accessibility measurements with all techniques are conducted for eight peptides with different spin label positions and low radical concentrations (10-20 μM). Consistently in all experiments, the water accessibility appears to be very low, even for labels positioned near the end of the helix. The best profile is obtained by Overhauser DNP, which is the only technique that succeeds in discriminating neighboring positions in WALP23. Since the concentration of the spin-labeled peptides varied, we normalized the DNP parameter ɛ, being the relative change of the NMR intensity, by the electron spin concentration, which was determined from a continuous-wave EPR spectrum.

  15. Nanopore formation on the surface oxide of commercially pure titanium grade 4 using a pulsed anodization method in sulfuric acid.

    PubMed

    Williamson, R S; Disegi, J; Griggs, J A; Roach, M D

    2013-10-01

    Titanium and its alloys form a thin amorphous protective surface oxide when exposed to an oxygen environment. The properties of this oxide layer are thought to be responsible for titanium and its alloys biocompatibility, chemical inertness, and corrosion resistance. Surface oxide crystallinity and pore size are regarded to be two of the more important properties in establishing successful osseointegration. Anodization is an electrochemical method of surface modification used for colorization marking and improved bioactivity on orthopedic and dental titanium implants. Research on titanium anodization using sulphuric acid has been reported in the literature as being primarily conducted in molarity levels 3 M and less using either galvanostatic or potentiostatic methods. A wide range of pore diameters ranging from a few nanometers up to 10 μm have been shown to form in sulfuric acid electrolytes using the potentiostatic and galvanostatic methods. Nano sized pores have been shown to be beneficial for bone cell attachment and proliferation. The purpose of the present research was to investigate oxide crystallinity and pore formation during titanium anodization using a pulsed DC waveform in a series of sulfuric acid electrolytes ranging from 0.5 to 12 M. Anodizing titanium in increasing sulfuric acid molarities showed a trend of increasing transformations of the amorphous natural forming oxide to the crystalline phases of anatase and rutile. The pulsed DC waveform was shown to produce pores with a size range from ≤0.01 to 1 μm(2). The pore size distributions produced may be beneficial for bone cell attachment and proliferation.

  16. Pulsed IR inductive lasers

    NASA Astrophysics Data System (ADS)

    Razhev, A. M.; Churkin, D. S.; Kargapol'tsev, E. S.

    2014-07-01

    Pulsed inductive discharge is a new alternative method of pumping active gas laser media. The work presents results of experimental investigations of near, mid, and far IR inductive gas lasers (H2, HF, and CO2) operating at different transitions of atoms and molecules with different mechanisms of formation of inversion population. The excitation systems of a pulsed inductive cylindrical discharge (pulsed inductively coupled plasma) and pulsed RF inductive discharge in the gases are developed. Various gas mixtures including H2, N2, He, Ne, F2, NF3, and SF6 are used. Characteristics of near IR H2 laser radiation are investigated. Maximal pulse peak power of 7 kW is achieved. The possibility of using a pulsed inductive discharge as a new method of pumping HF laser active medium is demonstrated. The pulsed RF inductive CO2 laser is created and a total efficiency of 17% is achieved.

  17. Method and system based on pulsed neutron generator for fissile material detection in luggage

    NASA Astrophysics Data System (ADS)

    Bogolubov, Ye. P.; Korotkov, S. A.; Korytko, L. A.; Morukov, V. G.; Nazarov, V. I.; Polkanov, Yu. G.; Khasaev, T. O.

    2004-01-01

    The paper discusses the problem of fissile material (FM) detection in passenger luggage. Different methods of control of unauthorized FM movement were analyzed. Application of differential die-away technique was substantiated. Experimental prototype with sensitivity of uranium-235 detection equal to 5 g during 5 s was described. A method for revealing deliberate FM masking by neutron-absorbing shields is suggested.

  18. Application of the pulsed fast/thermal neutron method for soil elemental analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil science is a research field where physic concepts and experimental methods are widely used, particularly in agro-chemistry and soil elemental analysis. Different methods of analysis are currently available. The evolution of nuclear physics (methodology and instrumentation) combined with the ava...

  19. Can stroke volume and cardiac output be determined reliably in a tilt-table test using the pulse contour method?

    PubMed

    Nieminen, T; Kööbi, T; Turjanmaa, V

    2000-11-01

    The applicability of the finger pressure-derived pulse contour (PC) technique was evaluated in the measurement of stroke volume (SV), cardiac output (CO) and their changes in different phases of the tilt-table test. The reference method was whole-body impedance cardiography (ICG). A total number of 40 physically active patients, aged 41 +/- 19 years, were randomly chosen from a pool of 230. Specifically speaking, 20 of the patients experienced (pre)syncope (tilt+ patients) during the head-up tilt (HUT), and 20 did not (tilt-). A total number of three measurement periods, 30-60 s each, were analysed: supine position, 5 min after the commencement of HUT, and 1 min before set down. SV and CO values measured by PC underestimated significantly those measured by ICG (biases +/- SD 19 +/- 14 ml and 1.55 +/- 1.14 l min-1, respectively) in agreement with earlier reports. The bias between the methods was almost the same in the different phases of the test. However, the SD of the bias was bigger for tilt+ (P < 0.05). When the bias between the methods was eliminated by scaling the first measurement to 100%, the agreement between the methods in the second and third measurements was clearly better than without scaling. Both methods showed a physiological drop in SV after the commencement of HUT. These results indicate that PC suffices in tracking the changes in CO and SV, but for absolute values it is not reliable.

  20. Improving sensitivity of an inductive pulse sensor for detection of metallic wear debris in lubricants using parallel LC resonance method

    NASA Astrophysics Data System (ADS)

    Du, Li; Zhu, Xiaoliang; Han, Yu; Zhao, Liang; Zhe, Jiang

    2013-07-01

    Detection of small metallic wear debris is critical to identify abnormal wear conditions for prognosis of pending machinery failure. In this paper we applied an inductance-capacitance (LC) resonance method to an inductive pulse debris sensor to increase the sensitivity. By adding an external capacitor to the sensing coil of the sensor, a parallel LC resonance circuit is formed that has a unique resonant frequency. At an excitation frequency close to the resonant frequency, impedance change (and thus change in voltage output) of the LC circuit caused by the passage of a debris particle is amplified due to sharp change in impedance at the resonant peak; thus signal-to-noise ratio and sensitivity are significantly improved. Using an optimized measurement circuit, iron particles ranging from 32 to 96 µm and copper particles ranging from 75 to 172 µm were tested. Results showed that the parallel LC resonance method is capable of detecting a 20 µm iron particle and a 55 µm copper particle while detection limits for the non-resonance method are 45 and 125 µm, respectively. In contrast to the non-resonant method, the sensitivity of the resonance method has been significantly improved.

  1. Fabrication of Co thin films using pulsed laser deposition method with or without employing external magnetic field

    NASA Astrophysics Data System (ADS)

    Ehsani, M. H.; Mehrabad, M. Jalali; Kameli, P.

    2016-11-01

    In this work, the external magnetic field effects on growth condition during deposition processes of the Co thin films were studied. Two specimens of Co films with different condition (with and without external magnetic field) were synthesized by pulsed laser deposition method. Structural and magnetic properties of the Co thin films were systematically studied, using atomic force microscope analysis and magnetization measurement, respectively. During the deposition processes, the external applied magnetic field had been provided by a permanent magnet. The experimental results show that the external magnetic field enables one to tune the magnetic properties of the deposited thin films. To clarify this effect, using Multi-Physics COMSOL simulation environment, a study of vapor flux by applied magnetic field during deposition were performed. Comparison between experimental data and output data of the simulation show promising accommodation and approve the existence of a strong correlation between the structural and magnetic properties of the specimens, and deposition rate of Co thin films.

  2. A novel and practical approach for determination of the acoustic nonlinearity parameter using a pulse-echo method

    NASA Astrophysics Data System (ADS)

    Jeong, Hyunjo; Zhang, Shuzeng; Barnard, Dan; Li, Xiongbing

    2016-02-01

    Measurements of the acoustic nonlinearity parameter β are frequently made for early detection of damage in various materials. The practical implementation of the measurement technique has been limited to the through-transmission setup for determining the nonlinearity parameter of the second harmonic wave. In this work, a feasibility study is performed to assess the possibility of using pulse-echo methods in determining the nonlinearity parameter β of solids with a stress-free boundary. The multi-Gaussian beam model is developed based on the quasilinear theory of the KZK equation. Simulation results and discussion are presented for the reflected beam fields of the fundamental and second harmonic waves, the uncorrected β behavior and the properties of total correction that incorporate reflection, attenuation and diffraction effects.

  3. Synthesis of carbon films using pulsed laser deposition method with frozen CH 4 and CO 2 targets

    NASA Astrophysics Data System (ADS)

    Ishiguro, Takashi; Esaki, Kotaro; Hiroshima, Yasushi

    1998-05-01

    A novel pulsed laser deposition (PLD) process with frozen CH 4 and/or CO 2 is developed. Frozen CH 4 and/or CO 2 formed on the graphitic carbon (GC) target at 12 K, then co-ablated with the GC target, using a KrF excimer laser. The present method is effective in enhancing the dissociation of raw materials and suppressing the large splashing particles. The characteristics of the deposited carbon films depend on the target material and on the substrate temperature. Under the proper conditions, the films show the characteristics of diamond-like carbon in the Raman spectrum. According to the high resolution transmission electron microscopy, these films contain nanometer-sized diamond embryos.

  4. Paired Pulse Basis Functions for the Method of Moments EFIE Solution of Electromagnetic Problems Involving Arbitrarily-shaped, Three-dimensional Dielectric Scatterers

    NASA Technical Reports Server (NTRS)

    MacKenzie, Anne I.; Rao, Sadasiva M.; Baginski, Michael E.

    2007-01-01

    A pair of basis functions is presented for the surface integral, method of moment solution of scattering by arbitrarily-shaped, three-dimensional dielectric bodies. Equivalent surface currents are represented by orthogonal unit pulse vectors in conjunction with triangular patch modeling. The electric field integral equation is employed with closed geometries for dielectric bodies; the method may also be applied to conductors. Radar cross section results are shown for dielectric bodies having canonical spherical, cylindrical, and cubic shapes. Pulse basis function results are compared to results by other methods.

  5. Method of Producing a Film Coating by Matrix Assisted Pulsed Laser Deposition

    DTIC Science & Technology

    1997-05-28

    N.C. 78,117 PATENT APPLICATION Inventor’s Name: R. Andrew McGill and Douglas B. Chrisey 1 in a technique called spin coating . These techniques have...several disadvantages. It is difficult with 2 the spin coating or spray coating methods to control the coating thickness precisely, or to ensure 3... Spin coating potentially provides a more uniform 5 coating surface than does spray coating, but nevertheless this method has the disadvantage that 6

  6. Pulsed microwave heating method for preparation of dye-sensitized solar cells for greener, faster, cheaper production of photovoltaic materials

    NASA Astrophysics Data System (ADS)

    Murphy, Clifford B.; Cotta, Robert; Blais, Timothy; Hall, Charles B.

    2015-05-01

    Microwave heating methods are very popular for developing chemical syntheses that are achieved much more rapidly or with less solvent than via conventional heating methods. Their application to solar cell development has been primarily in developing improvements in the synthesis of dyes and curing of polymer substrates, but not in assisting the photoanode construction of dye-sensitized solar cells. Microwave heating of conducting substrates can lead to arcing of electricity in the reactor, which in turn, can lead to extensive degradation or complete destruction of the photoanode. Here we present our work in applying a pulsed microwave heating method that affords quicker dye deposition times in comparison to conventional heating (μw 40 min, conventional 60 min) with similar dye concentrations as characterized by UV-Vis absorbance, contact angle measurements, and cyclic voltammetry. Our photoanodes are constructed with anatase TiO2 cured onto FTO glass, and deposition of the N719 ruthenium dye either directly to the TiO2 layer or through amide bond formation to a silane layer that has been deposited on the TiO2 layer. Modest improvements in the solar energy conversion efficiency are shown through the microwave method in comparison to conventional heating (μw 0.78% vs. conventional 0.25% reported by K. Szpakolski, et. Al. Polyhedron, 2013, 52, 719-732.)

  7. A two-pulse, pump-probe method for short-range, remote standoff detection of chemical warfare agents

    NASA Astrophysics Data System (ADS)

    Bisson, Scott E.; Headrick, Jeffrey M.; Reichardt, Thomas A.; Farrow, Roger L.; Kulp, Thomas J.

    2011-05-01

    We describe a photofragment laser-induced fluorescence (PF-LIF) method that can be applied to the short-range-standoff detection of low-volatility organophosphonate chemical warfare agents (OP-CWAs) on surfaces. It operates by photofragmenting a surface-bound analyte and then actively interrogating a released phosphorous monoxide (PO) fragment using LIF. We demonstrate a single-pulse-pair (pump = 500 μJ @ 266 nm; probe = 20 μJ @ 248 nm) surface detection sensitivity of 30 μg/cm2 for the organophosphonate diisopropyl isothiocyanate phosphonate (DIPP) on aluminum and 210 μg/cm2 for the same analyte on a more porous concrete surface. By detecting the PO photofragment, the method indicates the presence of organophosphonates; however, we show that it also responds to other phosphorouscontaining compounds. Because of its limited specificity, we believe that the method may have most immediate use as a mapping tool to rapidly identify "hotspots" of OP-CWAs. These would then be confirmed using a more specific tool. As one method of confirming the presence of OP-CWAs (and identifying the agent), we demonstrate that the probe beam can be used to acquire Raman-scattering spectra of the target area.

  8. Development of a noninvasive multifunctional measurement method using nanosecond pulsed laser for evaluation of regenerative medicine for articular cartilage

    NASA Astrophysics Data System (ADS)

    Ishihara, Miya; Sato, Masato; Kaneshiro, Nagatoshi; Mitani, Genya; Sato, Shunichi; Ishihara, Masayuki; Mochida, Joji; Kikuchi, Makoto

    2006-02-01

    We demonstrated the capability of a photoacoustic method for viscoelastic measurement. The measurement method has already proved to be useful for evaluation of regenerative medicine of articular cartilage. However, characterization of the extracellular matrix as well as determination of the viscoelastic property should be carried out for evaluation of regenerative medicine because the extracellular matrix plays an important role. We therefore developed a method for characterization of the extracellular matrix that can be performed simultaneously with the photoacoustic measurement. Since collagen molecules, which are the major contents of the cartilage extracellular matrix, are well known as endogenous fluorescent molecules, it is possible that fluorescence measurement will enable characterization of the extracellular matrix. Third harmonic Q-switched Nd:YAG laser pulses were used as an excitation light source. The time-resolved fluorescence spectroscopy was obtained by using a photonic multi-channel analyzer. Tissue-engineered cartilages cultured under different conditions for various periods were used as samples. Different culture conditions resulted in different extracellular matrix formations. There were significant differences in the measured fluorescent parameters among the culture conditions of cartilage because chondrocytes produce a specific extracellular matrix depending on its culture condition. The specific extracellular matrix contained a specific type of collagen such as collagen type I or type II, which each have specific fluorescent features. Thus, the fluorescent parameters enabled characterization of synthesis of cartilage-associated extracellular matrix. Therefore, the combination of fluorescence and photoacoustic measurement is expected to become a useful evaluation method in regenerative medicine.

  9. Digital pulse shape discrimination methods for n-γ separation in an EJ-301 liquid scintillation detector

    NASA Astrophysics Data System (ADS)

    Wan, Bo; Zhang, Xue-Ying; Chen, Liang; Ge, Hong-Lin; Ma, Fei; Zhang, Hong-Bin; Ju, Yong-Qin; Zhang, Yan-Bin; Li, Yan-Yan; Xu, Xiao-Wei

    2015-11-01

    A digital pulse shape discrimination system based on a programmable module NI-5772 has been established and tested with an EJ-301 liquid scintillation detector. The module was operated by running programs developed in LabVIEW, with a sampling frequency up to 1.6 GS/s. Standard gamma sources 22Na, 137Cs and 60Co were used to calibrate the EJ-301 liquid scintillation detector, and the gamma response function was obtained. Digital algorithms for the charge comparison method and zero-crossing method have been developed. The experimental results show that both digital signal processing (DSP) algorithms can discriminate neutrons from γ-rays. Moreover, the zero-crossing method shows better n-γ discrimination at 80 keVee and lower, whereas the charge comparison method gives better results at higher thresholds. In addition, the figure-of-merit (FOM) for detectors of two different dimensions were extracted at 9 energy thresholds, and it was found that the smaller detector presented better n-γ separation for fission neutrons. Supported by National Natural Science Foundation of China (91226107, 11305229) and the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA03030300)

  10. Remote sensing image fusion method in CIELab color space using nonsubsampled shearlet transform and pulse coupled neural networks

    NASA Astrophysics Data System (ADS)

    Jin, Xin; Zhou, Dongming; Yao, Shaowen; Nie, Rencan; Yu, Chuanbo; Ding, Tingting

    2016-04-01

    In CIELab color space, we propose a remote sensing image fusion technique based on nonsubsampled shearlet transform (NSST) and pulse coupled neural network (PCNN), which aim to improve the efficiency and performance of the remote sensing image fusion by combining the excellent properties of the two methods. First, panchromatic (PAN) and multispectral (MS) are transformed into CIELab color space to get different color components. Second, PAN and L component of MS are decomposed by the NSST to obtain corresponding the low-frequency coefficients and high-frequency coefficients. Third, the low-frequency coefficients are fused by intersecting cortical model (ICM); the high-frequency coefficients are divided into several sub-blocks to calculate the average gradient (AG), and the linking strength β of PCNN model is determined by the AG, so that the parameters β can be adaptively set according to the quality of the sub-block images, then the sub-blocks image are input into PCNN to get the oscillation frequency graph (OFG), the method can get the fused high-frequency coefficients according to the OFG. Finally, the fused L component is obtained by inverse NSST, and the fused RGB color image is obtained through inverse CIELab transform. The experimental results demonstrate that the proposed method provide better effect compared with other common methods.

  11. Means and method for characterizing high power, ultra short laser pulses in a real time, on line manner

    DOEpatents

    Veligdan, James T.

    1994-01-01

    An ultra short (<10 ps), high power laser pulse is temporally characterized by a system that uses a physical measurement of a wavefront that has been altered in a known manner. The system includes a first reflection switch to remove a portion of a pulse from a beam of pulses, then includes a second reflection switch, operating in a mode that is opposite to the first reflection switch, to slice off a portion of that removed portion. The sliced portion is then directed to a measuring device for physical measurement. The two reflection switches are arranged with respect to each other and with respect to the beam of ultra short pulses such that physical measurement of the sliced portion is related to the temporal measurement of the ultra short pulse by a geometric or trigonometric relationship. The reflection switches are operated by a control pulse that is directed to impinge on each of the reflection switches at a 90.degree. angle of incidence.

  12. Method of using deuterium-cluster foils for an intense pulsed neutron source

    DOEpatents

    Miley, George H.; Yang, Xiaoling

    2013-09-03

    A method is provided for producing neutrons, comprising: providing a converter foil comprising deuterium clusters; focusing a laser on the foil with power and energy sufficient to cause deuteron ions to separate from the foil; and striking a surface of a target with the deuteron ions from the converter foil with energy sufficient to cause neutron production by a reaction selected from the group consisting of D-D fusion, D-T fusion, D-metal nuclear spallation, and p-metal. A further method is provided for assembling a plurality of target assemblies for a target injector to be used in the previously mentioned manner. A further method is provided for producing neutrons, comprising: splitting a laser beam into a first beam and a second beam; striking a first surface of a target with the first beam, and an opposite second surface of the target with the second beam with energy sufficient to cause neutron production.

  13. CONTROL OF LASER RADIATION PARAMETERS: Cross modulation method of transformation of the spatial coherence of pulsed laser radiation in a nonlinear medium

    NASA Astrophysics Data System (ADS)

    Kitsak, M. A.; Kitsak, A. I.

    2008-04-01

    The cross modulation method of transformation of the spatial coherence of low-power pulsed laser radiation in a nonlinear medium is proposed. The method is realised experimentally in a multimode optical fibre. The estimates of the degree of spatial coherence of radiation subjected to the phase cross modulation demonstrated the high efficiency of this radiation decorrelation mechanism.

  14. Radiolysis of ammonia-containing ices by heavy cosmic rays inside dense molecular clouds

    NASA Astrophysics Data System (ADS)

    Pilling, Sergio; Seperuelo Duarte, Eduardo; da Silveira, Enio F.; Balanzat, Emmanuel; Rothard, Hermann; Domaracka, Alicja; Boduch, Philippe

    2010-03-01

    We present experimental studies on the interaction of heavy, highly charged and energetic ions (46 MeV 58Ni13+) with interstellar ammonia-containing (H2O:NH3:CO) ice analog in an attempt to simulate the physical chemistry induced by heavy ion cosmic rays inside dense astrophysical environments. The measurements were performed at the heavy ion accelerator GANIL in Caen, France. In-situ analysis have been performed by a Fourier transform infrared spectrometer. The averaged values for the dissociation cross section of water, ammonia and carbon monoxide are determined and the estimated half life for the studied species inside dense molecular clouds is 2-3 × 106 years. The IR spectra of organic residue produced by the radiolysis have revealed, at room temperature, five bands that are tentatively assigned to vibration modes of the zwitterionic glycine (NH3+CH2COO-).

  15. The radiolysis of tryptophan and leucine with P-32 beta-radiation

    NASA Technical Reports Server (NTRS)

    Blair, N. E.; Bonner, W. A.

    1980-01-01

    The paper extends earlier experiments on the radiolysis of DL-tryptophan using P-32 beta-radiation to longer reaction times, observing complete destruction of tryptophan by secondary, nonradiolytic processes. In addition DL-leucine is irradiated with P-32 beta-irradiation at -196 C, leading to radiolyses to the extents of about 20-30%, but observing no concomitant asymmetric bias. The complete absence of asymmetric bias in the present and earlier (Bonner et al., 1979) radiolyses of aqueous tryptophan at -25 C and the present radiolyses of water-free leucine at -196 C using P-32 beta-radiation and its accompanying bremsstrahlung leave it an open question whether or not the Vester-Ulbricht beta-decay/bremsstrahlung mechanism for the origin of optical activity is a viable one.

  16. Photocatalytic oxidation of 4-chlorophenol on titanium dioxide: A comparison with {gamma}-radiolysis

    SciTech Connect

    Stafford, U.; Gray, K.A.; Kamat, P.V.

    1994-02-01

    To gain useful insight into the mechanistic details of the TiO{sub 2} photocatalyzed oxidation of halogenated organic compounds, the intermediates produced during the photocatalytic degradation of 4-chlorophenol (4-CP) have been compared with those produced during {gamma}-radiolysis. Photocatalytic degradation of 4-CP produces aromatic intermediates consistent with {gamma}-radiolytic hydroxyl radical oxidation, but the distribution of the intermediates differs. The surface area of TiO{sub 2} has an important influence on the intermediate distribution suggesting that the presence of surface influences the reaction pathway. The course of photocatalytic transformation of 4-CP involves a combination of hydroxyl radical oxidation, direct electron transfer and surface chemical reactions contributing to the disappearance of 4-CP and its reaction intermediates in TiO{sub 2} slurries.

  17. Prediction of size distribution of Ag nanoparticles synthesized via gamma-ray radiolysis

    NASA Astrophysics Data System (ADS)

    Liang, Jia-liang; Shen, Sheng-wen; Ye, Sheng-ying; Ye, Lü-meng

    2015-09-01

    The spherical shape Ag nanoparticles synthesized via gamma-ray radiolysis were observed with the transmission electron microscope (TEM). Diameters of Ag nanoparticles were measured from the TEM photographs. Statistical analysis showed that the particle diameter complied with a linear-converted Poisson distribution. The distribution parameter, which was the average of diameters, was related to the ultraviolet-visible spectrum peak position of the nanosilver collosol. An empirical equation was established to predicting size distribution of Ag nanoparticles with the peak position. Nanosilver of different sizes could be synthesized by adjusting the intensity of γ-irradiation, the kind and the addition amount of the stabilizing agent. Because particle size affects the physiochemical properties of nanosilver material, results of this paper would be of practical significance for the application of nanosilver.

  18. The effects of radiolysis on the corrosion and stress corrosion behavior of 316 stainless steels

    SciTech Connect

    Duquette, D.J.; Steiner, D.

    1993-09-01

    This program is focused on the corrosion, stress corrosion and corrosion fatigue behavior of Type 316 stainless steel (316SS) at 50, 90, and 130 C in high-purity water. Irradiated solution tests are performed using high-energy photon radiation. Purpose of this work is to determine the effects of radiolysis products on the environmental stability of 316SS in support of the ITER first wall/shield/blanket design. Preliminary results suggest that irradiation of pure water at 50 C results in a shift in the electrochemical potential for 316SS of approximately 100mV in the active direction and nearly an order of magnitude increase in the passive current density as compared to non-irradiated conditions. This proposal outlines a three-year program to develop corrosion design criteria for the use of 316SS in an ITER environment.

  19. Radiolysis of Amino Acids in Outer Solar-System Ice Analogs

    NASA Technical Reports Server (NTRS)

    Gerakines, Perry A.; Hudson, Reggie L.

    2011-01-01

    Amino acids have been found in cometary dust particles and in the organic component of meteorites. These molecules, important for pre-biotic chemistry and for active biological systems, might be formed in cold planetary or interstellar environments and then delivered to H20-rich surfaces in the outer solar system. Many models for the availability of organic species on Earth and elsewhere depend on the ability of these molecules to survive in radiation-rich space environments. This poster presents results of O.8-MeV proton radiolysis of ice films at lS-140K. using infrared spectroscopy, the destruction rates of glycine, alanine, and phenylalanine have been determined for both pure films and those containing amino acids diluted in H2o. our results are discussed in terms of the survivability of these molecules in the icy surfaces present in the outer solar system and the possibility of their detection by instruments on board the New Horizons spacecraft

  20. Method of characterizing residual stress in ferromagnetic materials using a pulse histogram of acoustic emission signals

    NASA Technical Reports Server (NTRS)

    Namkung, Min (Inventor); Yost, William T. (Inventor); Kushnick, Peter W. (Inventor); Grainger, John L. (Inventor)

    1992-01-01

    The invention is a method and apparatus for characterizing residual uniaxial stress in a ferromagnetic test member by distinguishing between residual stresses resulting from positive (tension) forces and negative (compression) forces by using the distinct and known magnetoacoustic (MAC) and a magnetoacoustic emission (MAE) measurement circuit means. A switch permits the selective operation of the respective circuit means.

  1. Ability of melanins to protect against the radiolysis of thymine and thymidine.

    PubMed

    Hill, H Z; Huselton, C; Pilas, B; Hill, G J

    1987-01-01

    Individuals with black skin rarely get skin cancer, and melanomas, tumors arising from pigmented cells, are generally resistant to radiation therapy. The role of melanin in these two phenomena has not been defined, but oxygen-radical species have been implicated in both effects. These studies were undertaken to determine the ability of various melanins to compete for ionizing radiation-produced radicals which destroy nucleic acid bases. The ability of Sigma eumelanin (S-eumelanin) to protect against the radiolysis of thymidine in buffered solutions was compared to the protective ability of seven amino acids, including melanin precursors; bovine serum albumin, as a model protein; ficoll, as a model polysaccharide; and DNA. Both proteins and polysaccharides are known to scavenge hydroxyl radicals in cells. The concentration of thymidine after exposure to gamma radiation was determined by High Performance Liquid Chromatography (HPLC) analysis after removal of insoluble melanin by acid precipitation. S-eumelanin was more effective at competing with thymidine for free radicals than bovine serum albumin, Ficoll, or DNA, but less effective than certain of the small molecules. Several of the above compounds were also examined for ability to protect against thymine radiolysis. In addition, melanins from other sources were compared to S-eumelanin. Of these, enzymatically synthesized phaeomelanin was the most effective. The results indicate that melanins can compete for base- and nucleoside-damaging free radicals more effectively than other cellular macromolecules. Of the small molecules, the phenolic compounds had the greatest scavenging ability. In vivo, melanins are found in melanosomes bound to protein. Therefore, the relevance of these findings to the photo- and radiobiology of melanins in vivo has yet to be determined.

  2. Characterization of ultrashort pulses by a modified grating-eliminated no-nonsense observation of ultrafast incident laser light E fields (GRENOUILLE) method

    NASA Astrophysics Data System (ADS)

    Heisler, Ismael A.; Correia, Ricardo R. B.; Cunha, Silvio L. S.

    2005-06-01

    The measurement and characterization of ultrashort laser pulses remains an arduous task. The most commonly used pulse-measurement method is known as frequency-resolved optical gating (FROG), and another version with great experimental simplification and low-priced setup is known as grating-eliminated no-nonsense observation of ultrafast incident laser light E fields (GRENOUILLE). Nevertheless, there is interest in elaborating other, more accessible or simpler and cheaper, setups with equal or better assets. We explored modification of the GRENOUILLE method in which we replaced the original Fresnel biprism with a beam splitter and two mirrors and used a cheap webcam to measure the pulse traces. We have evaluated our system, and we propose a method to correct border effects caused by the beam intensity's profile based on the characterization of three pulse classes: Fourier-transform limited, double, and chirped. We compare the recovered electric field with further spectral and second-order correlation data of the corresponding pulses.

  3. An innovative method to reduce count loss from pulse pile-up in a photon-counting pixel for high flux X-ray applications

    NASA Astrophysics Data System (ADS)

    Lee, D.; Lim, K.; Park, K.; Lee, C.; Alexander, S.; Cho, G.

    2017-03-01

    In this study, an innovative fast X-ray photon-counting pixel for high X-ray flux applications is proposed. A computed tomography system typically uses X-ray fluxes up to 108 photons/mm2/sec at the detector and thus a fast read-out is required in order to process individual X-ray photons. Otherwise, pulse pile-up can occur at the output of the signal processing unit. These superimposed signals can distort the number of incident X-ray photons leading to count loss. To minimize such losses, a cross detection method was implemented in the photon-counting pixel. A maximum count rate under X-ray tube voltage of 90 kV was acquired which reflect electrical test results of the proposed photon counting pixel. A maximum count of 780 kcps was achieved with a conventional photon-counting pixel at the pulse processing time of 500 ns, which is the time for a pulse to return to the baseline from the initial rise. In contrast, the maximum count of about 8.1 Mcps was achieved with the proposed photon-counting pixel. From these results, it was clear that the maximum count rate was increased by approximately a factor 10 times by adopting the cross detection method. Therefore, it is an innovative method to reduce count loss from pulse pile-up in a photon-counting pixel while maintaining the pulse processing time.

  4. A unique method to study acoustic transmission through ducts using signal synthesis and averaging of acoustic pulses

    NASA Technical Reports Server (NTRS)

    Salikuddin, M.; Ramakrishnan, R.; Ahuja, K. K.; Brown, W. H.

    1981-01-01

    An acoustic impulse technique using a loudspeaker driver is developed to measure the acoustic properties of a duct/nozzle system. A signal synthesis method is used to generate a desired single pulse with a flat spectrum. The convolution of the desired signal and the inverse Fourier transform of the reciprocal of the driver's response are then fed to the driver. A signal averaging process eliminates the jet mixing noise from the mixture of jet noise and the internal noise, thereby allowing very low intensity signals to be measured accurately, even for high velocity jets. A theoretical analysis is carried out to predict the incident sound field; this is used to help determine the number and locations of the induct measurement points to account for the contributions due to higher order modes present in the incident tube method. The impulse technique is validated by comparing experimentally determined acoustic characteristics of a duct-nozzle system with similar results obtained by the impedance tube method. Absolute agreement in the comparisons was poor, but the overall shapes of the time histories and spectral distributions were much alike.

  5. Evaluation and calibration of a pulsed neutron method for total hydrogen determination in mineral and concrete samples

    NASA Astrophysics Data System (ADS)

    Bennun, L.; Santibañez, M.; Gomez, J.; Santisteban, J. R.

    2011-11-01

    We studied the feasibility of a nondestructive method to determine hydrogen concentrations in concrete and mineral samples. The amount of total hydrogen in the sample is directly related to the proportion of water included in the paste preparation; and also considers all subsequent processes which can add or remove hydrogen in a real sample (like rain, evaporation, etc.). The hydrogen proportion is a critical variable in the curing concrete process; its excess or deficiency impacts negatively in the quality of the final product. The proposed technique is based on a pulsed neutron source and the technical support of the time of flight, which allow discriminating epithermal neutrons interacting with hydrogen (inelastic scattering) from the elastic and quasi-isotropic scattering produced by other kinds of atoms. The method was externally calibrated in limestone rocks fragments (CaCO3-main material used in cement fabrication) and in steel, allowing an easy retrieval of the required information. The technique's simplicity may facilitate the development of a mobile measuring device in order to make determinations "in situ." In this paper, we describe the foundations of the proposed method and various analysis results.

  6. A Direct Method to Extract Transient Sub-Gap Density of State (DOS) Based on Dual Gate Pulse Spectroscopy

    PubMed Central

    Dai, Mingzhi; Khan, Karim; Zhang, Shengnan; Jiang, Kemin; Zhang, Xingye; Wang, Weiliang; Liang, Lingyan; Cao, Hongtao; Wang, Pengjun; Wang, Peng; Miao, Lijing; Qin, Haiming; Jiang, Jun; Xue, Lixin; Chu, Junhao

    2016-01-01

    Sub-gap density of states (DOS) is a key parameter to impact the electrical characteristics of semiconductor materials-based transistors in integrated circuits. Previously, spectroscopy methodologies for DOS extractions include the static methods, temperature dependent spectroscopy and photonic spectroscopy. However, they might involve lots of assumptions, calculations, temperature or optical impacts into the intrinsic distribution of DOS along the bandgap of the materials. A direct and simpler method is developed to extract the DOS distribution from amorphous oxide-based thin-film transistors (TFTs) based on Dual gate pulse spectroscopy (GPS), introducing less extrinsic factors such as temperature and laborious numerical mathematical analysis than conventional methods. From this direct measurement, the sub-gap DOS distribution shows a peak value on the band-gap edge and in the order of 1017–1021/(cm3·eV), which is consistent with the previous results. The results could be described with the model involving both Gaussian and exponential components. This tool is useful as a diagnostics for the electrical properties of oxide materials and this study will benefit their modeling and improvement of the electrical properties and thus broaden their applications. PMID:27297030

  7. A Direct Method to Extract Transient Sub-Gap Density of State (DOS) Based on Dual Gate Pulse Spectroscopy.

    PubMed

    Dai, Mingzhi; Khan, Karim; Zhang, Shengnan; Jiang, Kemin; Zhang, Xingye; Wang, Weiliang; Liang, Lingyan; Cao, Hongtao; Wang, Pengjun; Wang, Peng; Miao, Lijing; Qin, Haiming; Jiang, Jun; Xue, Lixin; Chu, Junhao

    2016-06-14

    Sub-gap density of states (DOS) is a key parameter to impact the electrical characteristics of semiconductor materials-based transistors in integrated circuits. Previously, spectroscopy methodologies for DOS extractions include the static methods, temperature dependent spectroscopy and photonic spectroscopy. However, they might involve lots of assumptions, calculations, temperature or optical impacts into the intrinsic distribution of DOS along the bandgap of the materials. A direct and simpler method is developed to extract the DOS distribution from amorphous oxide-based thin-film transistors (TFTs) based on Dual gate pulse spectroscopy (GPS), introducing less extrinsic factors such as temperature and laborious numerical mathematical analysis than conventional methods. From this direct measurement, the sub-gap DOS distribution shows a peak value on the band-gap edge and in the order of 10(17)-10(21)/(cm(3)·eV), which is consistent with the previous results. The results could be described with the model involving both Gaussian and exponential components. This tool is useful as a diagnostics for the electrical properties of oxide materials and this study will benefit their modeling and improvement of the electrical properties and thus broaden their applications.

  8. Development of a microchip-pulsed electrochemical method for rapid determination of L-DOPA and tyrosine in Mucuna pruriens.

    PubMed

    Li, Xinchun; Chen, Zuanguang; Yang, Fan; Pan, Jianbin; Li, Yinbao

    2013-05-01

    L-3,4-dihydroxyphenylalanine (L-DOPA) is a well-recognized therapeutic compound to Parkinson's disease. Tyrosine is a precursor for the biosynthesis of L-DOPA, both of which are widely found in traditional medicinal material, Mucuna pruriens. In this paper, we described a validated novel analytical method based on microchip capillary electrophoresis with pulsed electrochemical detection for the simultaneous measurement of L-DOPA and tyrosine in M. pruriens. This protocol adopted end-channel amperometric detection using platinum disk electrode on a homemade glass/polydimethylsiloxane electrophoresis microchip. The background buffer consisted of 10 mM borate (pH 9.5) and 0.02 mM cetyltrimethylammonium bromide, which can produce an effective resolution for the two analytes. In the optimal condition, sufficient electrophoretic separation and sensitive detection for the target analytes can be realized within 60 s. Both tyrosine and L-DOPA yielded linear response in the concentration range of 5.0-400 μM (R(2) > 0.99), and the LOD were 0.79 and 1.1 μM, respectively. The accuracy and precision of the established method were favorable. The present method shows several merits such as facile apparatus, high speed, low cost and minimal pollution, and provides a means for the pharmacologically active ingredients assay in M. pruriens.

  9. Influence of the Duration of Thermal Action on the Errors in Determining the Thermophysical Characteristics of Ceramic Materials by a Laser Pulse Method

    NASA Astrophysics Data System (ADS)

    Kuznetsov, G. V.; Kats, M. D.

    2016-05-01

    An analysis of the errors involved in determining the thermophysical characteristics of a special-purpose ceramic material — zirconium carbide — is made. It is shown that the errors of determining the heat capacity and thermal diffusivity of the indicated material under conditions corresponding to the implementation of the laser pulse method vary nonmonotonically depending on the pulse duration. The possibility of attaining minimum values of methodical errors by appropriately selecting the thickness of a sample and of the time of its heating is shown.

  10. Method and Apparatus for Thermal Spraying of Metal Coatings Using Pulsejet Resonant Pulsed Combustion

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E. (Inventor)

    2014-01-01

    An apparatus and method for thermal spraying a metal coating on a substrate is accomplished with a modified pulsejet and optionally an ejector to assist in preventing oxidation. Metal such as Aluminum or Magnesium may be used. A pulsejet is first initiated by applying fuel, air, and a spark. Metal is inserted continuously in a high volume of metal into a combustion chamber of the pulsejet. The combustion is thereafter controlled resonantly at high frequency and the metal is heated to a molten state. The metal is then transported from the combustion chamber into a tailpipe of said pulsejet and is expelled therefrom at high velocity and deposited on a target substrate.

  11. Pulse shaping with transmission lines

    DOEpatents

    Wilcox, R.B.

    1985-08-15

    A method and apparatus for forming shaped voltage pulses uses passive reflection from a transmission line with nonuniform impedance. The impedance of the reflecting line varies with length in accordance with the desired pulse shape. A high voltage input pulse is transmitted to the reflecting line. A reflected pulse is produced having the desired shape and is transmitted by pulse removal means to a load. Light activated photoconductive switches made of silicon can be utilized. The pulse shaper can be used to drive a Pockels cell to produce shaped optical pulses.

  12. Pulse shaping with transmission lines

    DOEpatents

    Wilcox, Russell B.

    1987-01-01

    A method and apparatus for forming shaped voltage pulses uses passive reflection from a transmission line with nonuniform impedance. The impedance of the reflecting line varies with length in accordance with the desired pulse shape. A high voltage input pulse is transmitted to the reflecting line. A reflected pulse is produced having the desired shape and is transmitted by pulse removal means to a load. Light activated photoconductive switches made of silicon can be utilized. The pulse shaper can be used to drive a Pockels cell to produce shaped optical pulses.

  13. Methods, systems and apparatus for adjusting duty cycle of pulse width modulated (PWM) waveforms

    DOEpatents

    Gallegos-Lopez, Gabriel; Kinoshita, Michael H; Ransom, Ray M; Perisic, Milun

    2013-05-21

    Embodiments of the present invention relate to methods, systems and apparatus for controlling operation of a multi-phase machine in a vector controlled motor drive system when the multi-phase machine operates in an overmodulation region. The disclosed embodiments provide a mechanism for adjusting a duty cycle of PWM waveforms so that the correct phase voltage command signals are applied at the angle transitions. This can reduce variations/errors in the phase voltage command signals applied to the multi-phase machine so that phase current may be properly regulated thus reducing current/torque oscillation, which can in turn improve machine efficiency and performance, as well as utilization of the DC voltage source.

  14. Method and Apparatus for Thermal Spraying of Metal Coatings Using Pulsejet Resonant Pulsed Combustion

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E. (Inventor)

    2010-01-01

    An apparatus and method [or thermal spraying a metal coating on a substrate is accomplished with a modified pulsejet and optionally an ejector to assist in preventing oxidation. Metal such a Aluminum or Magnesium may be used. A pulsejet is first initiated by applying fuel, air. and a spark. Metal is inserted continuously in a high volume of meta1 into a combustion chamber of the pulsejet. The combustion is thereafter. controlled resonantly at high frequency and the metal is heated to a molten state. The metal is then transported from the combustion chamber into a tail pipe of said pulsejet and is expelled therefrom at high velocity and deposited on a target substrate.

  15. Investigation of the first-order phase transition kinetics using the method of pulsed photothermal surface deformation: radial measurements

    NASA Astrophysics Data System (ADS)

    Vintzentz, S. V.; Sandomirsky, V. B.

    1992-09-01

    An extension of the photothermal surface deformation (PTSD) method to study the macroscopic kinetics of the first-order phase transition (PTr) is given. The movement of the phase interface (PI) over a surface with a PTr locally induced in the subsurface volume by a focused laser pulse is investigated for the first time using radial measurements of the PTSD kinetics. For the known metal-to-semiconductor PTr in VO 2 (a good model system) a procedure is suggested for measuring the maximum size rsm of the "hot" (metal) phase on the surface (a parameter most difficult to determine) as well as for estimating the velocity of the PI movement over the surface, vs, and in the bulk, vb. Besides, it is shown that the PTSD method may be used to determine the "local" threshold energy E0 needed for the laser-induced PTr and the "local" latent heat L of the PTr. This demonstrates the feasibility of scanning surface E0- and L-microscopy.

  16. Fabrication of one-dimensional alumina photonic crystals by anodization using a modified pulse-voltage method

    SciTech Connect

    Li, Shou-Yi; Wang, Jian; Wang, Gang; Wang, Ji-Zhou; Wang, Cheng-Wei

    2015-08-15

    Highlights: • The alumina multilayer structure with alternating high and low refractive index is fabricated. • This multilayer shows a strong photonic band gap (PBG) and vivid film colors. • The first PBG could be modulated easily by varying the duration time of constant high or low voltages. • Fabrication of the photonic crystal is obtained by directly electrochemical anodization. • The formation mechanism of multilayer is also discussed. - Abstract: The alumina nanolayer structure with alternating high and low porosities is conveniently fabricated by applying a modified pulse voltage waveform with constant high and low voltage. This structure shows the well-defined layer in a long-range structural periodicity leads to a strong photonic band gap (PBG) from visible to near infrared and brilliant film colors. Compared with the previous reported tuning method, this method is more simple and flexible in tuning the PBG of photonic crystals (PCs). The effect of duration time of high, low and 0 V voltages on PBG is discussed. The first PBG could be modulated easily from the visible to near infrared region by varying the duration time of constant high or low voltages. It is also found that the 0 V lasting for appropriate time is helpful to improve the quality of the PCs. The formation mechanism of multilayer is also discussed.

  17. Analysis of exosome purification methods using a model liposome system and tunable-resistive pulse sensing.

    PubMed

    Lane, Rebecca E; Korbie, Darren; Anderson, Will; Vaidyanathan, Ramanathan; Trau, Matt

    2015-01-06

    Exosomes are vesicles which have garnered interest due to their diagnostic and therapeutic potential. Isolation of pure yields of exosomes from complex biological fluids whilst preserving their physical characteristics is critical for downstream applications. In this study, we use 100 nm-liposomes from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and cholesterol as a model system as a model system to assess the effect of exosome isolation protocols on vesicle recovery and size distribution using a single-particle analysis method. We demonstrate that liposome size distribution and ζ-potential are comparable to extracted exosomes, making them an ideal model for comparison studies. Four different purification protocols were evaluated, with liposomes robustly isolated by three of them. Recovered yields varied and liposome size distribution was unaltered during processing, suggesting that these protocols do not induce particle aggregation. This leads us to conclude that the size distribution profile and characteristics of vesicles are stably maintained during processing and purification, suggesting that reports detailing how exosomes derived from tumour cells differ in size to those from normal cells are reporting a real phenomenon. However, we hypothesize that larger particles present in most purified exosome samples represent co-purified contaminating non-exosome debris. These isolation techniques are therefore likely nonspecific and may co-isolate non-exosome material of similar physical properties.

  18. Analysis of exosome purification methods using a model liposome system and tunable-resistive pulse sensing

    NASA Astrophysics Data System (ADS)

    Lane, Rebecca E.; Korbie, Darren; Anderson, Will; Vaidyanathan, Ramanathan; Trau, Matt

    2015-01-01

    Exosomes are vesicles which have garnered interest due to their diagnostic and therapeutic potential. Isolation of pure yields of exosomes from complex biological fluids whilst preserving their physical characteristics is critical for downstream applications. In this study, we use 100 nm-liposomes from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and cholesterol as a model system as a model system to assess the effect of exosome isolation protocols on vesicle recovery and size distribution using a single-particle analysis method. We demonstrate that liposome size distribution and ζ-potential are comparable to extracted exosomes, making them an ideal model for comparison studies. Four different purification protocols were evaluated, with liposomes robustly isolated by three of them. Recovered yields varied and liposome size distribution was unaltered during processing, suggesting that these protocols do not induce particle aggregation. This leads us to conclude that the size distribution profile and characteristics of vesicles are stably maintained during processing and purification, suggesting that reports detailing how exosomes derived from tumour cells differ in size to those from normal cells are reporting a real phenomenon. However, we hypothesize that larger particles present in most purified exosome samples represent co-purified contaminating non-exosome debris. These isolation techniques are therefore likely nonspecific and may co-isolate non-exosome material of similar physical properties.

  19. Fast numerical design of spatial-selective rf pulses in MRI using Krotov and quasi-Newton based optimal control methods.

    PubMed

    Vinding, Mads S; Maximov, Ivan I; Tošner, Zdenĕk; Nielsen, Niels Chr

    2012-08-07

    The use of increasingly strong magnetic fields in magnetic resonance imaging (MRI) improves sensitivity, susceptibility contrast, and spatial or spectral resolution for functional and localized spectroscopic imaging applications. However, along with these benefits come the challenges of increasing static field (B(0)) and rf field (B(1)) inhomogeneities induced by radial field susceptibility differences and poorer dielectric properties of objects in the scanner. Increasing fields also impose the need for rf irradiation at higher frequencies which may lead to elevated patient energy absorption, eventually posing a safety risk. These reasons have motivated the use of multidimensional rf pulses and parallel rf transmission, and their combination with tailoring of rf pulses for fast and low-power rf performance. For the latter application, analytical and approximate solutions are well-established in linear regimes, however, with increasing nonlinearities and constraints on the rf pulses, numerical iterative methods become attractive. Among such procedures, optimal control methods have recently demonstrated great potential. Here, we present a Krotov-based optimal control approach which as compared to earlier approaches provides very fast, monotonic convergence even without educated initial guesses. This is essential for in vivo MRI applications. The method is compared to a second-order gradient ascent method relying on the Broyden-Fletcher-Goldfarb-Shanno (BFGS) quasi-Newton method, and a hybrid scheme Krotov-BFGS is also introduced in this study. These optimal control approaches are demonstrated by the design of a 2D spatial selective rf pulse exciting the letters "JCP" in a water phantom.

  20. Investigation of molecular mechanisms in photodynamic action and radiobiology with nanosecond flash photolysis and pulse radiolysis. Progress report, 1982

    SciTech Connect

    Grossweiner, L.I.

    1983-01-01

    Liposomes have been employed as membrane models applicable to photosensitization in phototherapy procedures. The results with 8-methoxypsoralen, the sensitizer in PUVA therapy of psoriasis, show that singlet oxygen generated by near-uv (uv-A) irradiation induces membrane damage leading to lysis. A similar role of singlet oxygen has been shown for photosensitization of liposomes by methylene blue, with the new observation that hydrodynamic forces promote the lytic action initiated by singlet oxygen attack on an unsaturated site of phosphatidylcholine. Liposome photosensitization by hematoporphyrin follows a Type II mechanism mediated by singlet oxygen for low sensitizer concentrations, and a Type I, anoxic, mechanism when the hematoporphyrin is aggregated. Similar concentration effects obtain with hematoporphyrin derivative (hpd), the photosensitizer in photoradiation therapy of malignant tumors. Studies on the components of hpd separated by gel chromatography show that the putative biological active fraction can photosensitize membrane damage under oxic and anoxic conditions. The oxic pathway was suppressed by binding to human serum albumin, as involved in serum transport of hpd prior to localization in tumor tissue. A study on hematoporphyrin photosensitization of targets other than membranes has shown that singlet oxygen is responsible for the photosensitized inactivation of subtilisin BPN' and photooxidation of tryptophan in human and bovine serum albumin. In the case of the serum proteins, the singlet oxygen is generated by the sensitizer-protein complex and it may react with all protein in the system. 11 references.

  1. Efficient optical pulse stacker system

    DOEpatents

    Seppala, Lynn G.; Haas, Roger A.

    1982-01-01

    Method and apparatus for spreading and angle-encoding each pulse of a multiplicity of small area, short pulses into several temporally staggered pulses by use of appropriate beam splitters, with the optical elements being arranged so that each staggered pulse is contiguous with one or two other such pulses, and the entire sequence of stacked pulses comprising a single, continuous long pulse. The single long pulse is expanded in area, and then doubly passed through a nonstorage laser amplifier such as KrF. After amplification, the physically separated, angle-encoded and temporally staggered pulses are recombined into a single pulse of short duration. This high intensity output beam is well collimated and may be propagated over long distance, or used for irradiating inertial confinement fusion targets.

  2. The effects of γ-irradiation on garlic oil content in garlic bulbs and on the radiolysis of allyl trisulfide

    NASA Astrophysics Data System (ADS)

    Genshuan, Wei; Guanghui, Wang; Ruipu, Yang; Jilan, Wu

    1996-02-01

    A study of the effects of γ-radiation on garlic oil content in garlic bulbs and on the radiolysis of allyl trisulfide and disulfide was carried out. The content of garlic oil in fresh garlic bulbs treated by gamma ray keeps nearly constant when stored for 10 months. The main components of garlic oil are allyl trisulfide (about 60%) and allyl disulfide (about 30%). The G values of radiolysis products of allyl disulfide and trisulfide in ethanol system were determined. The results show that allyl trisulfide is a very effective solvated electron scavenger and can oxidize CH 3CHOH radical into acetaldehyde, which means that the formation of 2,3-butanediol is extensively inhibited.

  3. Passive and active pulse stacking scheme for pulse shaping

    DOEpatents

    Harney, Robert C.; Schipper, John F.

    1977-01-01

    Apparatus and method for producing a sequence of radiation pulses with a pulse envelope of time variation which is controllable by an external electromagnetic signal applied to an active medium or by a sectored reflector, through which the radiation passes.

  4. Usefulness and limitation of measurement methods for evaluation of tissue-engineered cartilage function and characterization using nanosecond pulsed laser

    NASA Astrophysics Data System (ADS)

    Ishihara, Miya; Sato, Masato; Kaneshiro, Nagatoshi; Mitani, Genya; Nagai, Toshihiro; Kutsuna, Toshiharu; Ishihara, Masayuki; Mochida, Joji; Kikuchi, Makoto

    2007-02-01

    There is a demand in the field of regenerative medicine for measurement technology that enables determination of functions and characterizations of engineered tissue. Regenerative medicine involving the articular cartilage in particular requires measurement of viscoelastic properties and characterization of the extracellular matrix, which plays a major role in articular cartilage. To meet this demand, we previously proposed a noninvasive method for determination of the viscoelasticity using laser-induced thermoelastic wave (1,2). We also proposed a method for characterization of the extracellular matrix using time-resolved autofluorescence spectroscopy, which could be performed simultaneously with laser-induced thermoelastic wave measurement(3). The purpose of this study was to verify the usefulness and limitation of these methods for evaluation of actual engineered cartilage. 3rd Q-SW Nd:YAG laser pulses, which are delivered through optical fiber, were used for the light source. Laser-induced thermoelastic waves were detected by a sensor consisting of a piezoelectric transducer, which was designed for use in arthroscopy(4). The time-resolved fluorescence spectroscopy was measured by a photonic multichannel analyzer with 4ch digital signal generator. Various tissue-engineered cartilages were developed as samples. Only a limited range of sample thickness could be measured, however, the measured viscoelastic parameters had a positive correlation with culture time, that is, the degree of formation of extracellular matrix(5,6). There were significant differences in the fluorescent parameters among the phenotypic expressions of cartilage because chondrocyte produces specific extracellular matrix as in collagen types depending on its phenotype.

  5. SNMR pulse sequence phase cycling

    DOEpatents

    Walsh, David O; Grunewald, Elliot D

    2013-11-12

    Technologies applicable to SNMR pulse sequence phase cycling are disclosed, including SNMR acquisition apparatus and methods, SNMR processing apparatus and methods, and combinations thereof. SNMR acquisition may include transmitting two or more SNMR pulse sequences and applying a phase shift to a pulse in at least one of the pulse sequences, according to any of a variety cycling techniques. SNMR processing may include combining SNMR from a plurality of pulse sequences comprising pulses of different phases, so that desired signals are preserved and indesired signals are canceled.

  6. Construction of a magnetic bottle spectrometer and its application to pulse duration measurement of X-ray laser using a pump-probe method

    SciTech Connect

    Namba, S.; Hasegawa, N.; Kishimoto, M.; Nishikino, M.; Ishino, M.; Kawachi, T.

    2015-11-15

    To characterize the temporal evolution of ultrashort X-ray pulses emitted by laser plasmas using a pump-probe method, a magnetic bottle time-of-flight electron spectrometer is constructed. The design is determined by numerical calculations of a mirror magnetic field and of the electron trajectory in a flight tube. The performance of the spectrometer is characterized by measuring the electron spectra of xenon atoms irradiated with a laser-driven plasma X-ray pulse. In addition, two-color above-threshold ionization (ATI) experiment is conducted for measurement of the X-ray laser pulse duration, in which xenon atoms are simultaneously irradiated with an X-ray laser pump and an IR laser probe. The correlation in the intensity of the sideband spectra of the 4d inner-shell photoelectrons and in the time delay of the two laser pulses yields an X-ray pulse width of 5.7 ps, in good agreement with the value obtained using an X-ray streak camera.

  7. Simulation of temperature and thermally induced stress of human tooth under CO2 pulsed laser beams using finite element method.

    PubMed

    Sabaeian, Mohammad; Shahzadeh, Mohammadreza

    2015-02-01

    The authors report the simulation of temperature distribution and thermally induced stresses of human tooth under CO2 pulsed laser beam. A detailed tooth structure comprising enamel, dentin, and pulp with realistic shapes and thicknesses were considered, and a numerical method of finite element was adopted to solve time-dependent bio-heat and stress equations. The realistic boundary conditions of constant temperature for those parts embedded in the gingiva and heat flux condition for those parts out of the gingiva were applied. The results which were achieved as a function of energy density (J/cm(2)) showed when laser beam is irradiated downward (from the top of the tooth), the temperature and thermal stresses decrease quickly as a function of depth that is a result of strong absorption of CO2 beams by enamel. This effect is so influential that one can use CO2 beams to remove micrometer layers while underlying tissues, especially the pulp, are safe from thermal effects.

  8. A Reliable Split-Step Fourier Method for the Propagation Equation of Ultra-Fast Pulses in Single-Mode Optical Fibers

    SciTech Connect

    Deiterding, Ralf; Glowinski, R.; Oliver, Hilde; Poole, Stephen W

    2013-01-01

    The extension to the split-step Fourier method (SSFM) for Schrodinger-type pulse propagation equations that we propose in this article is designed with the accurate simulation of pulses in the femto-second regime in single-mode communication fibers in mind. We show that via an appropriate operator splitting scheme, Kerr nonlinearity and the self-steepening and stimulated Raman scattering terms can be combined into a single sub-step consisting of an inhomogeneous quasilinear first-order hyperbolic system for the real-valued quantities intensity and phase. First- and second-order accurate shock-capturing upwind schemes have been developed specifically for this nonlinear sub-step, which enables the accurate and oscillation-free simulation of signals under the influence of Raman scattering and extreme self-steepening with the SSFM. Benchmark computations of ultra-fast Gaussian pulses in fibers with strong nonlinearity demonstrate the superior approximation properties of the proposed approach.

  9. A comparison of the y-Radiolysis of TODGA and T(EH)DGA using UHPLC-ESI-MS analysis

    SciTech Connect

    Zarzana, Christopher A.; Groenewold, Gary S.; Mincher, Bruce J.; Mezyk, Stephen P.; Wilden, Andreas; Schmidt, Holger; Modolo, Giuseppe; Wishart, James F.; Cook, Andrew R.

    2015-04-27

    Solutions of the diglycolamide extractants TODGA and T(EH)DGA in n-dodecane were subjected to γ- irradiation in the presence and absence of an acidic aqueous phase. These solutions were then analyzed using UHPLC-ESI-MS to determine the rates of radiolytic decay of the two extractants neat and in contact with respect to the acidity of the contacted aqueous phase, as well as to identify radiolysis products. The presence or absence of an acidic aqueous phase was shown to have no influence on the measured decay rates, nor did the side-chain have an influence. A number of radiolysis products were identified, consistent with those previously identified for these two compounds using GC-MS. The identity of these radiolysis products suggests that the bonds most vulnerable to radiolytic attack are those in the dyglycolamide center of these molecules, and not on the side-chains.  The agreement of these results with previous work using GC-MS indicates supports the further use of UHPLC-ESI-MS as a tool for studying diglycolamide extractant systems.

  10. A comparison of the y-Radiolysis of TODGA and T(EH)DGA using UHPLC-ESI-MS analysis

    DOE PAGES

    Zarzana, Christopher A.; Groenewold, Gary S.; Mincher, Bruce J.; ...

    2015-04-27

    Solutions of the diglycolamide extractants TODGA and T(EH)DGA in n-dodecane were subjected to γ- irradiation in the presence and absence of an acidic aqueous phase. These solutions were then analyzed using UHPLC-ESI-MS to determine the rates of radiolytic decay of the two extractants neat and in contact with respect to the acidity of the contacted aqueous phase, as well as to identify radiolysis products. The presence or absence of an acidic aqueous phase was shown to have no influence on the measured decay rates, nor did the side-chain have an influence. A number of radiolysis products were identified, consistent with thosemore » previously identified for these two compounds using GC-MS. The identity of these radiolysis products suggests that the bonds most vulnerable to radiolytic attack are those in the dyglycolamide center of these molecules, and not on the side-chains.  The agreement of these results with previous work using GC-MS indicates supports the further use of UHPLC-ESI-MS as a tool for studying diglycolamide extractant systems.« less

  11. Pulse Oximetry

    MedlinePlus

    ... www.thoracic.org amount of gases (oxygen and carbon dioxide) that are in your blood. To get ... Also, a pulse oximeter does not measure your carbon dioxide level. How accurate is the pulse oximeter? ...

  12. Prediction of back-scatter radiations to a beam monitor chamber of medical linear accelerators by use of the digitized target-current-pulse analysis method.

    PubMed

    Suzuki, Yusuke; Hayashi, Naoki; Kato, Hideki; Fukuma, Hiroshi; Hirose, Yasujiro; Kawano, Makoto; Nishii, Yoshio; Nakamura, Masaru; Mukouyama, Takashi

    2013-01-01

    In small-field irradiation, the back-scattered radiation (BSR) affects the counts measured with a beam monitor chamber (BMC). In general, the effect of the BSR depends on the opened-jaw size. The effect is significantly large in small-field irradiation. Our purpose in this study was to predict the effect of BSR on LINAC output accurately with an improved target-current-pulse (TCP) technique. The pulse signals were measured with a system consisting of a personal computer and a digitizer. The pulse signals were analyzed with in-house software. The measured parameters were the number of pulses, the change in the waveform and the integrated signal values of the TCPs. The TCPs were measured for various field sizes with four linear accelerators. For comparison, Yu's method in which a universal counter was used was re-examined. The results showed that the variance of the measurements by the new method was reduced to approximately 1/10 of the variance by the previous method. There was no significant variation in the number of pulses due to a change in the field size in the Varian Clinac series. However, a change in the integrated signal value was observed. This tendency was different from the result of other investigations in the past. Our prediction method is able to define the cutoff voltage for the TCP acquired by digitizer. This functionality provides the capability of clearly classifying TCPs into signals and noise. In conclusion, our TCP analysis method can predict the effect of BSR on the BMC even for small-field irradiations.

  13. Means and method for characterizing high power, ultra short laser pulses in a real time, on line manner

    DOEpatents

    Veligdan, J.T.

    1994-03-08

    An ultra short (<10 ps), high power laser pulse is temporally characterized by a system that uses a physical measurement of a wavefront that has been altered in a known manner. The system includes a first reflection switch to remove a portion of a pulse from a beam of pulses, then includes a second reflection switch, operating in a mode that is opposite to the first reflection switch, to slice off a portion of that removed portion. The sliced portion is then directed to a measuring device for physical measurement. The two reflection switches are arranged with respect to each other and with respect to the beam of ultra short pulses such that physical measurement of the sliced portion is related to the temporal measurement of the ultra short pulse by a geometric or trigonometric relationship. The reflection switches are operated by a control pulse that is directed to impinge on each of the reflection switches at a 90[degree] angle of incidence. 8 figures.

  14. Extrusion cooking: Legume pulses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Extrusion is used commercially to produce high value breakfast and snack foods based on cereals such as wheat or corn. However, this processing method is not being commercially used for legume pulses seeds due to the perception that they do not expand well in extrusion. Extrusion cooking of pulses (...

  15. Critical evaluation of pulse-echo ultrasonic test method for the determination of setting and mechanical properties of acrylic bone cement: influence of mixing technique.

    PubMed

    Hagan, Christopher P; Orr, John F; Mitchell, Christina A; Dunne, Nicholas J

    2015-02-01

    Currently there is no reliable objective method to quantify the setting properties of acrylic bone cements within an operating theatre environment. Ultrasonic technology can be used to determine the acoustic properties of the polymerising bone cement, which are linked to material properties and provide indications of the physical and chemical changes occurring within the cement. The focus of this study was the critical evaluation of pulse-echo ultrasonic test method in determining the setting and mechanical properties of three different acrylic bone cement when prepared under atmospheric and vacuum mixing conditions. Results indicated that the ultrasonic pulse-echo technique provided a highly reproducible and accurate method of monitoring the polymerisation reaction and indicating the principal setting parameters when compared to ISO 5833 standard, irrespective of the acrylic bone cement or mixing method used. However, applying the same test method to predict the final mechanical properties of acrylic bone cement did not prove a wholly accurate approach. Inhomogeneities within the cement microstructure and specimen geometry were found to have a significant influence on mechanical property predictions. Consideration of all the results suggests that the non-invasive and non-destructive pulse-echo ultrasonic test method is an effective and reliable method for following the full polymerisation reaction of acrylic bone cement in real-time and then determining the setting properties within a surgical theatre environment. However the application of similar technology for predicting the final mechanical properties of acrylic bone cement on a consistent basis may prove difficult.

  16. Exploring water radiolysis in proton cancer therapy: Time-dependent, non-adiabatic simulations of H+ + (H2O)1-6.

    PubMed

    Privett, Austin J; Teixeira, Erico S; Stopera, Christopher; Morales, Jorge A

    2017-01-01

    To elucidate microscopic details of proton cancer therapy (PCT), we apply the simplest-level electron nuclear dynamics (SLEND) method to H+ + (H2O)1-6 at ELab = 100 keV. These systems are computationally tractable prototypes to simulate water radiolysis reactions-i.e. the PCT processes that generate the DNA-damaging species against cancerous cells. To capture incipient bulk-water effects, ten (H2O)1-6 isomers are considered, ranging from quasi-planar/multiplanar (H2O)1-6 to "smallest-drop" prism and cage (H2O)6 structures. SLEND is a time-dependent, variational, non-adiabatic and direct method that adopts a nuclear classical-mechanics description and an electronic single-determinantal wavefunction in the Thouless representation. Short-time SLEND/6-31G* (n = 1-6) and /6-31G** (n = 1-5) simulations render cluster-to-projectile 1-electron-transfer (1-ET) total integral cross sections (ICSs) and 1-ET probabilities. In absolute quantitative terms, SLEND/6-31G* 1-ET ICS compares satisfactorily with alternative experimental and theoretical results only available for n = 1 and exhibits almost the same accuracy of the best alternative theoretical result. SLEND/6-31G** overestimates 1-ET ICS for n = 1, but a comparable overestimation is also observed with another theoretical method. An investigation on H+ + H indicates that electron direct ionization (DI) becomes significant with the large virtual-space quasi-continuum in large basis sets; thus, SLEND/6-31G** 1-ET ICS is overestimated by DI contributions. The solution to this problem is discussed. In relative quantitative terms, both SLEND/6-31* and /6-31G** 1-ET ICSs precisely fit into physically justified scaling formulae as a function of the cluster size; this indicates SLEND's suitability for predicting properties of water clusters with varying size. Long-time SLEND/6-31G* (n = 1-4) simulations predict the formation of the DNA-damaging radicals H, OH, O and H3O. While "smallest-drop" isomers are included, no early

  17. Determination of diffusion parameters of thermal neutrons for non-moderator media by a pulsed method and a time independent method

    NASA Astrophysics Data System (ADS)

    Boufraqech, A.

    1991-02-01

    Two methods for determining the diffusion parameters of thermal neutrons for non-moderator and non-multiplicator media have been developed. The first one, which is a pulsed method, is based on thermal neutrons relaxation coefficients measurement in a moderator, with and without the medium of interest that plays the role of reflector. For the experimental results interpretation using the diffusion theory, a corrective factor which takes into account the neutron cooling by diffusion has been introduced. Its dependence on the empirically obtained relaxation coefficients is in a good agreement with the calculations made in P3L2 approximation. The difference between linear extrapolation lengths of the moderator and the reflector has been taken into account, by developing the scalar fluxes in Bessel function series which automatically satisfy the boundary conditions at the extrapolated surfaces of the two media. The obtained results for iron are in a good agreement with those in the literature. The second method is time independent, based on the 'flux albedo' measurements interpretation (concept introduced by Amaldi and Fermi) by P3 approximation in the one group transport theory. The independent sources are introduced in the Marshak boundary conditions. An angular albedo matrix has been used to deal with multiple reflections and to take into account the distortion of the current vector when entering a medium, after being reflected by this latter. The results obtained by this method are slightly different from those given in the literature. The analysis of the possible sources causing this discrepancy, particulary the radial distribution of flux in cylindrical geometry and the flux depression at medium-black body interface, has shown that the origin of this discrepancy is the neutron heating by diffusion.

  18. PULSE GENERATOR

    DOEpatents

    Roeschke, C.W.

    1957-09-24

    An improvement in pulse generators is described by which there are produced pulses of a duration from about 1 to 10 microseconds with a truly flat top and extremely rapid rise and fall. The pulses are produced by triggering from a separate input or by modifying the current to operate as a free-running pulse generator. In its broad aspect, the disclosed pulse generator comprises a first tube with an anode capacitor and grid circuit which controls the firing; a second tube series connected in the cathode circuit of the first tube such that discharge of the first tube places a voltage across it as the leading edge of the desired pulse; and an integrator circuit from the plate across the grid of the second tube to control the discharge time of the second tube, determining the pulse length.

  19. INSTRUMENTS AND METHODS OF INVESTIGATION: Giant pulses of thermal neutrons in large accelerator beam dumps. Possibilities for experiments

    NASA Astrophysics Data System (ADS)

    Stavissky, Yurii Ya

    2006-12-01

    A short review is presented of the development in Russia of intense pulsed neutron sources for physical research — the pulsating fast reactors IBR-1, IBR-30, IBR-2 (Joint Institute for Nuclear Research, Dubna), and the neutron-radiation complex of the Moscow meson factory — the 'Troitsk Trinity' (RAS Institute for Nuclear Research, Troitsk, Moscow region). The possibility of generating giant neutron pulses in beam dumps of superhigh energy accelerators is discussed. In particular, the possibility of producing giant pulsed thermal neutron fluxes in modified beam dumps of the large hadron collider (LHD) under construction at CERN is considered. It is shown that in the case of one-turn extraction ov 7-TeV protons accumulated in the LHC main rings on heavy targets with water or zirconium-hydride moderators placed in the front part of the LHC graphite beam-dump blocks, every 10 hours relatively short (from ~100 µs) thermal neutron pulses with a peak flux density of up to ~1020 neutrons cm-2 s-1 may be produced. The possibility of applying such neutron pulses in physical research is discussed.

  20. Use of the correct heat conduction-convection equation as basis for heat-pulse sap flow methods in anisotropic wood.

    PubMed

    Vandegehuchte, Maurits W; Steppe, Kathy

    2012-05-01

    Heat-pulse methods to determine sap flux density in trees are founded on the theory of heat conduction and heat convection in an isotropic medium. However, sapwood is clearly anisotropic, implying a difference in thermal conductivity along and across the grain, and hence necessitates the theory for an anisotropic medium. This difference in thermal conductivities, which can be up to 50%, is, however, not taken into account in the key equation leading to the currently available heat-pulse methods. Despite this major flaw, the methods remain theoretically correct as they are based on derivations of the key equation, ruling out any anisotropic aspects. The importance of specifying the thermal characteristics of the sapwood according to axial, tangential or radial direction is revealed as well as referring to and using the proper anisotropic theory in order to avoid confusion and misinterpretation of thermal properties when dealing with sap flux density measurements or erroneous results when modelling heat transport in sapwood.

  1. Diagnostics of atmospheric-pressure pulsed-dc discharge with metal and liquid anodes by multiple laser-aided methods

    NASA Astrophysics Data System (ADS)

    Urabe, Keiichiro; Shirai, Naoki; Tomita, Kentaro; Akiyama, Tsuyoshi; Murakami, Tomoyuki

    2016-08-01

    The density and temperature of electrons and key heavy particles were measured in an atmospheric-pressure pulsed-dc helium discharge plasma with a nitrogen molecular impurity generated using system with a liquid or metal anode and a metal cathode. To obtain these parameters, we conducted experiments using several laser-aided methods: Thomson scattering spectroscopy to obtain the spatial profiles of electron density and temperature, Raman scattering spectroscopy to obtain the neutral molecular nitrogen rotational temperature, phase-modulated dispersion interferometry to determine the temporal variation of the electron density, and time-resolved laser absorption spectroscopy to analyze the temporal variation of the helium metastable atom density. The electron density and temperature measured by Thomson scattering varied from 2.4  ×  1014 cm-3 and 1.8 eV at the center of the discharge to 0.8  ×  1014 cm-3 and 1.5 eV near the outer edge of the plasma in the case of the metal anode, respectively. The electron density obtained with the liquid anode was approximately 20% smaller than that obtained with the metal anode, while the electron temperature was not significantly affected by the anode material. The molecular nitrogen rotational temperatures were 1200 K with the metal anode and 1650 K with the liquid anode at the outer edge of the plasma column. The density of helium metastable atoms decreased by a factor of two when using the liquid anode.

  2. Water radiolysis in exchanged-montmorillonites: the H2 production mechanisms.

    PubMed

    Fourdrin, C; Aarrachi, H; Latrille, C; Esnouf, S; Bergaya, F; Le Caër, S

    2013-08-20

    The radiolysis of water confined in montmorillonites is studied as a function of the composition of the montmorillonite, the nature of the exchangeable cation, and the relative humidity by following the H2 production under electron irradiation. It is shown that the main factor influencing this H2 production is the water amount in the interlayer space. The effect of the exchangeable cation is linked to its hydration enthalpy. When the water amount is high enough to get a basal distance higher than 1.3 nm, then a total energy transfer from the montmorillonite sheets to the interlayer space occurs, and the H2 production measured is very similar to the one obtained in bulk water. For a basal distance smaller than 1.3 nm, the H2 production increases with the relative humidity and thus with the water amount. Lastly, electron paramagnetic resonance measurements evidence the formation of a new defect induced by ionizing radiation. It consists of a hydrogen radical (H2 precursor) trapped in the structure. This implies that structural hydroxyl bonds can be broken under irradiation, potentially accounting for the observed H2 production.

  3. Characterization of CMPO and its radiolysis products by Direct Infusion ESI-MS

    SciTech Connect

    G. S. Groenewold; G. Elias; B. J. Mincher; S. P. Mezyk

    2012-09-01

    Direct infusion electrospray ionization-mass spectrometry (ESI-MS) approaches were developed for rapid identification of octyl,phenyl,(N,N-(diisobutyl)carbamoylmethyl) phosphine oxide (CMPO) and impurity compounds formed during alpha and gamma irradiation experiments. CMPO is an aggressive Lewis base, and produces extremely abundant metal complex ions in the ESI-MS analysis that make identification of low abundance compounds that are less nucleophilic challenging. Radiolysis products were identified using several approaches including restricting ion trapping so as to exclude the abundant natiated CMPO ions, extraction of acidic products using aqueous NaOH, and extraction of basic products using HNO3. These approaches generated protonated, natiated and deprotonated species derived from CMPO degradation products formed via radiolytic cleavages of several different bonds. Cleavages of the amide and methylene-phosphoryl bonds appear to be favored by both forms of irradiation, while alpha irradiation also appears to induce cleavage of the methylene-carbonyl bond. The degradation products observed are formed from recombination of the initially formed radicals with hydrogen, methyl, isopropyl and hydroxyl radicals that are derived either from CMPO, or the dodecane solvent.

  4. Simulation of the radiolysis of water using Green's functions of the diffusion equation.

    PubMed

    Plante, I; Cucinotta, F A

    2015-09-01

    Radiation chemistry is of fundamental importance in the understanding of the effects of ionising radiation, notably with regard to DNA damage by indirect effect (e.g. damage by ·OH radicals created by the radiolysis of water). In the recent years, Green's functions of the diffusion equation (GFDEs) have been used extensively in biochemistry, notably to simulate biochemical networks in time and space. In the present work, an approach based on the GFDE will be used to refine existing models on the indirect effect of ionising radiation on DNA. As a starting point, the code RITRACKS (relativistic ion tracks) will be used to simulate the radiation track structure and calculate the position of all radiolytic species formed during irradiation. The chemical reactions between these radiolytic species and with DNA will be done by using an efficient Monte Carlo sampling algorithm for the GFDE of reversible reactions with an intermediate state that has been developed recently. These simulations should help the understanding of the contribution of the indirect effect in the formation of DNA damage, particularly with regards to the formation of double-strand breaks.

  5. On the Radiolysis of Ethylene Ices by Energetic Electrons and Implications to the Extraterrestrial Hydrocarbon Chemistry

    NASA Astrophysics Data System (ADS)

    Zhou, Li; Maity, Surajit; Abplanalp, Matt; Turner, Andrew; Kaiser, Ralf I.

    2014-07-01

    The chemical processing of ethylene ices (C2H4) by energetic electrons was investigated at 11 K to simulate the energy transfer processes and synthesis of new molecules induced by secondary electrons generated in the track of galactic cosmic ray particles. A combination of Fourier transform infrared spectrometry (solid state) and quadrupole mass spectrometry (gas phase) resulted in the identification of six hydrocarbon molecules: methane (CH4), the C2 species acetylene (C2H2), ethane (C2H6), the ethyl radical (C2H5), and—for the very first time in ethylene irradiation experiments—the C4 hydrocarbons 1-butene (C4H8) and n-butane (C4H10). By tracing the temporal evolution of the newly formed molecules spectroscopically online and in situ, we were also able to fit the kinetic profiles with a system of coupled differential equations, eventually providing mechanistic information, reaction pathways, and rate constants on the radiolysis of ethylene ices and the inherent formation of smaller (C1) and more complex (C2, C4) hydrocarbons involving carbon-hydrogen bond ruptures, atomic hydrogen addition processes, and radical-radical recombination pathways. We also discuss the implications of these results on the hydrocarbon chemistry on Titan's surface and on ice-coated, methane-bearing interstellar grains as present in cold molecular clouds such as TMC-1.

  6. Pulse stretcher

    DOEpatents

    Horton, J.A.

    1994-05-03

    Apparatus for increasing the length of a laser pulse to reduce its peak power without substantial loss in the average power of the pulse is disclosed. The apparatus uses a White cell having a plurality of optical delay paths of successively increasing number of passes between the field mirror and the objective mirrors. A pulse from a laser travels through a multi-leg reflective path between a beam splitter and a totally reflective mirror to the laser output. The laser pulse is also simultaneously injected through the beam splitter to the input mirrors of the optical delay paths. The pulses from the output mirrors of the optical delay paths go simultaneously to the laser output and to the input mirrors of the longer optical delay paths. The beam splitter is 50% reflective and 50% transmissive to provide equal attenuation of all of the pulses at the laser output. 6 figures.

  7. Measurement of spatio-temporal field distribution of THz pulses in electro-optic crystal by interferometry method

    SciTech Connect

    Chizhov, P A; Ushakov, A A; Bukin, V V; Garnov, S V

    2015-05-31

    We propose a scheme for measuring the spatial distribution of the THz pulse electric field strength in an electro-optic crystal using optical interferometry. The resulting images of the field distribution from a test source with a spherical wave front are presented. (extreme light fields and their applications)

  8. Pulsed power

    NASA Astrophysics Data System (ADS)

    Stone, David H.

    Pulsed power systems are critical elements for such prospective weapons technologies as high-power microwaves, electrothermal and electromagnetic projectile launchers, neutral particle beams, space-based FELs, ground-based lasers, and charged particle beams. Pulsed power will also be essential for the development of nonweapon military systems such as lidars and ultrawideband radars, and could serve as the bases for nuclear weapon effect simulators. The pulsed power generation requirements for each of these systems is considered.

  9. A pulsed electron beam synthesis of PEDOT conducting polymers by using sulfate radicals as oxidizing species

    NASA Astrophysics Data System (ADS)

    Coletta, Cecilia; Cui, Zhenpeng; Dazzi, Alexandre; Guigner, Jean-Michel; Néron, Stéphane; Marignier, Jean-Louis; Remita, Samy

    2016-09-01

    In this study, an original radiolytic method, based on pulsed electron beam irradiation, is used for the synthesis of conducting PEDOT in an aqueous solution containing EDOT monomers in the presence of potassium persulfate, K2S2O8, at 0 °C. At this low temperature, EDOT monomers are not chemically oxidized by S2O82- anions, initiating PEDOT polymerization, but are rather oxidized by sulfate radicals, SO4•-, which are radiolytically generated by the reaction of solvated electrons, produced by water radiolysis, with persulfate anions. Successfully, as demonstrated by UV-vis absorption spectrophotometry and ATR-FTIR spectroscopy, irradiating the aqueous solution, by using a series of accumulated electron pulses, enables complete EDOT oxidation and quantitative in situ PEDOT polymerization through a step-by-step oxidation mechanism. The morphology of PEDOT polymers, mixed with unreacted K2S2O8 salt, is characterized by Cryo-TEM microscopy in aqueous solution and by SEM after deposition. Successfully, in the absence of any washing step, high resolution AFM microscopy, coupled with infrared nanospectroscopy, is used to discriminate between the organic polymers and the inorganic salt and to probe the local chemical composition of PEDOT nanostructures. The results demonstrate that PEDOT polymers form globular self-assembled nanostructures which preferentially adsorb onto unreacted K2S2O8 solid nanoplates. The present results first demonstrate the efficiency of sulfate radicals as oxidizing species for the preparation of nanostructured PEDOT polymers and second highlight the promising potentiality of electron accelerators in the field of conducting polymers synthesis.

  10. Pulse Voltammetry

    NASA Astrophysics Data System (ADS)

    Stojek, Zbigniew

    The idea of imposing potential pulses and measuring the currents at the end of each pulse was proposed by Barker in a little-known journal as early as in 1958 [1]. However, the first reliable trouble-free and affordable polarographs offering voltammetric pulse techniques appeared on the market only in the 1970s. This delay was due to some limitations on the electronic side. In the 1990s, again substantial progress in electrochemical pulse instrumentation took place. This was related to the introduction of microprocessors, computers, and advanced software.

  11. Estimating water use by sugar maple trees: considerations when using heat-pulse methods in trees with deep functional sapwood.

    PubMed

    Pausch, Roman C.; Grote, Edmund E.; Dawson, Todd E.

    2000-03-01

    Accurate estimates of sapwood properties (including radial depth of functional xylem and wood water content) are critical when using the heat pulse velocity (HPV) technique to estimate tree water use. Errors in estimating the volumetric water content (V(h)) of the sapwood, especially in tree species with a large proportion of sapwood, can cause significant errors in the calculations ofsap velocity and sap flow through tree boles. Scaling to the whole-stand level greatly inflates these errors. We determined the effects of season, tree size and radial wood depth on V(h) of wood cores removed from Acer saccharum Marsh. trees throughout 3 years in upstate New York. We also determined the effects of variation in V(h) on sap velocity and sap flow calculations based on HPV data collected from sap flow gauges inserted at four depths. In addition, we compared two modifications of Hatton's weighted average technique, the zero-step and zero-average methods, for determining sap velocity and sap flow at depths beyond those penetrated by the sap flow gauges. Parameter V(h) varied significantly with time of year (DOY), tree size (S), and radial wood depth (RD), and there were significant DOY x S and DOY x RD interactions. Use of a mean whole-tree V(h) value resulted in differences ranging from -6 to +47% for both sap velocity and sap flow for individual sapwood annuli compared with use of the V(h) value determined at the specific depth where a probe was placed. Whole-tree sap flow was 7% higher when calculated on the basis of the individual V(h) value compared with the mean whole-tree V(h) value. Calculated total sap flow for a tree with a DBH of 48.8 cm was 13 and 19% less using the zero-step and the zero-average velocity techniques, respectively, than the value obtained with Hatton's weighted average technique. Smaller differences among the three methods were observed for a tree with a DBH of 24.4 cm. We conclude that, for Acer saccharum: (1) mean V(h) changes significantly

  12. Effectiveness of quenchers to reduce radiolysis of (111)In- or (177)Lu-labelled methionine-containing regulatory peptides. Maintaining radiochemical purity as measured by HPLC.

    PubMed

    de Blois, Erik; Chan, Ho Sze; Konijnenberg, Mark; de Zanger, Rory; Breeman, Wouter A P

    2012-01-01

    An overview how to measure and to quantify radiolysis by the addition of quenchers and to maintain Radio-Chemical Purity (RCP) of vulnerable methionine-containing regulatory peptides is presented. High RCP was only achieved with a combination of quenchers. However, quantification of RCP is not standardized, and therefore comparison of radiolabelling and RCP of regulatory peptides between different HPLC-systems and between laboratories is cumbersome. Therefore we suggest a set of standardized requirements to quantify RCP by HPLC for radiolabelled DTPA- or DOTA-peptides. Moreover, a dosimetry model was developed to calculate the doses in the reaction vials during radiolabelling and storage of the radiopeptides, and to predict RCP in the presence and absence of quenchers. RCP was measured by HPLC, and a relation between radiation dose and radiolysis of RCP was established. The here described quenchers are tested individually as ƒ(concentration) to investigate efficacy to reduce radiolysis of radiolabelled methionine-containing regulatory peptides.

  13. Radiolysis of astrophysical ice analogs by energetic ions: the effect of projectile mass and ice temperature.

    PubMed

    Pilling, Sergio; Duarte, Eduardo Seperuelo; Domaracka, Alicja; Rothard, Hermann; Boduch, Philippe; da Silveira, Enio F

    2011-09-21

    An experimental study of the interaction of highly charged, energetic ions (52 MeV (58)Ni(13+) and 15.7 MeV (16)O(5+)) with mixed H(2)O : C(18)O(2) astrophysical ice analogs at two different temperatures is presented. This analysis aims to simulate the chemical and the physicochemical interactions induced by cosmic rays inside dense, cold astrophysical environments, such as molecular clouds or protostellar clouds as well at the surface of outer solar system bodies. The measurements were performed at the heavy ion accelerator GANIL (Grand Accelerateur National d'Ions Lourds) in Caen, France. The gas samples were deposited onto a CsI substrate at 13 K and 80 K. In situ analysis was performed by a Fourier transform infrared (FTIR) spectrometer at different fluences. Radiolysis yields of the produced species were quantified. The dissociation cross section at 13 K of both H(2)O and CO(2) is about 3-4 times smaller when O ions are employed. The ice temperature seems to affect differently each species when the same projectile was employed. The formation cross section at 13 K of molecules such as C(18)O, CO (with oxygen from water), and H(2)O(2) increases when Ni ions are employed. The formation of organic compounds seems to be enhanced by the oxygen projectiles and at lower temperatures. In addition, because the organic production at 13 K is at least 4 times higher than the value at 80 K, we also expect that interstellar ices are more organic-rich than the surfaces of outer solar system bodies.

  14. Radiolysis of H2O:CO2 ices by heavy energetic cosmic ray analogs

    NASA Astrophysics Data System (ADS)

    Pilling, S.; Seperuelo Duarte, E.; Domaracka, A.; Rothard, H.; Boduch, P.; da Silveira, E. F.

    2010-11-01

    An experimental study of the interaction of heavy, highly charged, and energetic ions (52 MeV 58Ni13+) with pure H2O, pure CO2 and mixed H2O:CO2 astrophysical ice analogs is presented. This analysis aims to simulate the chemical and the physicochemical interactions induced by heavy cosmic rays inside dense and cold astrophysical environments, such as molecular clouds or protostellar clouds. The measurements were performed at the heavy ion accelerator GANIL (Grand Accélérateur National d'Ions Lourds in Caen, France). The gas samples were deposited onto a CsI substrate at 13 K. In-situ analysis was performed by a Fourier transform infrared (FTIR) spectrometer at different fluences. Radiolysis yields of the produced species were quantified. The dissociation cross sections of pure H2O and CO2 ices are 1.1 and 1.9 × 10-13 cm2, respectively. For mixed H2O:CO2 (10:1), the dissociation cross sections of both species are about 1 × 10-13 cm2. The measured sputtering yield of pure CO2 ice is 2.2 × 104 molec ion-1. After a fluence of 2-3 × 1012 ions cm-2, the CO2/CO ratio becomes roughly constant (~0.1), independent of the initial CO2/H2O ratio. A similar behavior is observed for the H2O2/H2O ratio, which stabilizes at 0.01, independent of the initial H2O column density or relative abundance.

  15. Low LET radiolysis escape yields for reducing radicals and H2 in pressurized high temperature water

    NASA Astrophysics Data System (ADS)

    Sterniczuk, Marcin; Yakabuskie, Pamela A.; Wren, J. Clara; Jacob, Jasmine A.; Bartels, David M.

    2016-04-01

    Low Linear Energy Transfer (LET) radiolysis escape yields (G values) are reported for the sum (G(radH)+G(e-)aq) and for G(H2) in subcritical water up to 350 °C. The scavenger system 1-10 mM acetate/0.001 M hydroxide/0.00048 M N2O was used with simultaneous mass spectroscopic detection of H2 and N2 product. Temperature-dependent measurements were carried out with 2.5 MeV electrons from a van de Graaff accelerator, while room temperature calibration measurements were done with a 60Co gamma source. The concentrations and dose range were carefully chosen so that initial spur chemistry is not perturbed and the N2 product yield corresponds to those reducing radicals that escape recombination in pure water. In comparison with a recent review recommendation of Elliot and Bartels (AECL report 153-127160-450-001, 2009), the measured reducing radical yield is seven percent smaller at room temperature but in fairly good agreement above 150 °C. The H2 escape yield is in good agreement throughout the temperature range with several previous studies that used much larger radical scavenging rates. Previous analysis of earlier high temperature measurements of Gesc(radOH) is shown to be flawed, although the actual G values may be nearly correct. The methodology used in the present report greatly reduces the range of possible error and puts the high temperature escape yields for low-LET radiation on a much firmer quantitative foundation than was previously available.

  16. Effect of Perchlorates on Electron Radiolysis of Glycine with Application to Mars

    NASA Astrophysics Data System (ADS)

    Góbi, Sándor; Abplanalp, Matthew J.; Kaiser, Ralf I.

    2016-05-01

    This work explores the radiolytic decomposition of glycine (H2NCH2COOH) under simulated Martian conditions in the presence of perchlorates ({{{ClO}}4}-), which are abundant oxidizers on the surface of Mars, by energetic electrons at 10, 160, 210, and 260 K, mimicking the radiation exposure of the Martian regolith in the first 5-10 cm depths over about 250 million years. Our experiments present quantitative evidence that the rate constants of the glycine decomposition in the presence of magnesium perchlorate hexahydrate (Mg(ClO4)2 · 6H2O) were a factor of about two higher than that of the pure glycine, suggesting that energetic oxygen atoms (O) released from the {{{ClO}}4}- have a significant effect on the decomposition rates and accelerate them by providing a unique oxidizing environment in the radiolyzed samples. Hence, two decay mechanisms exist: radiolysis by the electrons and oxidation by the O atoms. Within the Mars-relevant temperature range covering 160-260 K, the destruction rates are nearly temperature invariant with rates varying as little as 5%. Further, the formation rates of carbon dioxide (CO2) and carbon monoxide (CO) are both accelerated in the presence of {{{ClO}}4}- by a factor of three to five, supporting our conclusion of an active oxygen-initiated chemistry. In addition, the degradation rates are significantly higher than the formation rates of CO2 and CO. This suggests that, besides the decarboxylation, alternative degradation pathways such as a polymerization of glycine must exist. Finally, besides CO2 and CO, three alternative products were identified tentatively: methylamine (CH3NH2), methane (CH4), and ammonia (NH3).

  17. On the radiolysis of ethylene ices by energetic electrons and implications to the extraterrestrial hydrocarbon chemistry

    SciTech Connect

    Zhou, Li; Maity, Surajit; Abplanalp, Matt; Turner, Andrew; Kaiser, Ralf I.

    2014-07-20

    The chemical processing of ethylene ices (C{sub 2}H{sub 4}) by energetic electrons was investigated at 11 K to simulate the energy transfer processes and synthesis of new molecules induced by secondary electrons generated in the track of galactic cosmic ray particles. A combination of Fourier transform infrared spectrometry (solid state) and quadrupole mass spectrometry (gas phase) resulted in the identification of six hydrocarbon molecules: methane (CH{sub 4}), the C2 species acetylene (C{sub 2}H{sub 2}), ethane (C{sub 2}H{sub 6}), the ethyl radical (C{sub 2}H{sub 5}), and—for the very first time in ethylene irradiation experiments—the C4 hydrocarbons 1-butene (C{sub 4}H{sub 8}) and n-butane (C{sub 4}H{sub 10}). By tracing the temporal evolution of the newly formed molecules spectroscopically online and in situ, we were also able to fit the kinetic profiles with a system of coupled differential equations, eventually providing mechanistic information, reaction pathways, and rate constants on the radiolysis of ethylene ices and the inherent formation of smaller (C1) and more complex (C2, C4) hydrocarbons involving carbon-hydrogen bond ruptures, atomic hydrogen addition processes, and radical-radical recombination pathways. We also discuss the implications of these results on the hydrocarbon chemistry on Titan's surface and on ice-coated, methane-bearing interstellar grains as present in cold molecular clouds such as TMC-1.

  18. Pulse oximetry

    PubMed Central

    Jubran, Amal

    1999-01-01

    Pulse oximetry is one of the most commonly employed monitoringmodalities in the critical care setting. This review describes the latesttechnological advances in the field of pulse oximetry. Accuracy of pulseoximeters and their limitations are critically examined. Finally, the existingdata regarding the clinical applications and cost-effectiveness of pulseoximeters are discussed. PMID:11094477

  19. Effects of the duty ratio on the niobium oxide film deposited by pulsed-DC magnetron sputtering methods.

    PubMed

    Eom, Ji Mi; Oh, Hyun Gon; Cho, Il Hwan; Kwon, Sang Jik; Cho, Eou Sik

    2013-11-01

    Niobium oxide (Nb2O5) films were deposited on p-type Si wafers and sodalime glasses at a room temperature using in-line pulsed-DC magnetron sputtering system with various duty ratios. The different duty ratio was obtained by varying the reverse voltage time of pulsed DC power from 0.5 to 2.0 micros at the fixed frequency of 200 kHz. From the structural and optical characteristics of the sputtered NbOx films, it was possible to obtain more uniform and coherent NbOx films in case of the higher reverse voltage time as a result of the cleaning effect on the Nb2O5 target surface. The electrical characteristics from the metal-insulator-semiconductor (MIS) fabricated with the NbOx films shows the leakage currents are influenced by the reverse voltage time and the Schottky barrier diode characteristics.

  20. Method for determining the position, angle and other injection parameters of a short pulsed beam in the Brookhaven AGS

    SciTech Connect

    Gardner, C.; Ahrens, L.

    1985-01-01

    As part of the effort to improve the monitoring of the injection process at the Brookhaven Alternating Gradient Synchrotron (AGS), we have developed a beam diagnostics package which processes the signals from the plates of a pick-up electrode (PUE) located near the injection region of the AGS and provides measurements of the position and angle (with respect to the equilibrium orbit) of the injected beam at the stripping foil where the incident H/sup -/ beam is converted into protons. In addition the package provides measurements of the tune and chromaticity of the AGS at injection, and a measurement of the momentum spread of the injected beam. Since these parameters are obtained for a short-pulsed beam at injection we shall refer to the diagnostics package as PIP which stands for Pulsed Injection Parameters.

  1. Comparative Study of As-Deposited ZnO Thin Films by Thermal Evaporation, Pulsed Laser Deposition and RF Sputtering Methods for Electronic and Optoelectronic Applications

    NASA Astrophysics Data System (ADS)

    Vyas, Sumit; Giri, Pushpa; Singh, Shaivalini; Chakrabarti, P.

    2015-10-01

    Zinc oxide (ZnO) thin films have been deposited on Si substrate and glass substrate using thermal evaporation, pulsed laser deposition (PLD) and radio-frequency (RF) sputtering methods. The structural, surface morphological, optical and electrical properties of ZnO thin films deposited by these three methods were investigated and compared systematically using x-ray diffractometer, atomic force microscopy, ellipsometric and current-voltage ( I- V) measurement. The ZnO films deposited by RF sputtering method were highly oriented along the (002) plane. The ZnO films grown by thermal evaporation and PLD methods exhibited a polycrystalline nature. The surface roughness was found to be the least and the transparency in the visible region was the highest for the films grown by the RF sputtering method as compared to the films grown by the other two methods. The I- V characteristics reveal that the Pd:Au/ZnO (RF-sputtered) Schottky contact exhibited a better value of ideality factor, series resistance and barrier height as compared to the values obtained for Pd:Au/ZnO (thermally evaporated and pulse laser-deposited) Schottky contacts. The optical bandgap was found to be almost the same for the films grown by all three methods and was estimated to be around 3.2 eV.

  2. Hazardous and Corrosive Gas Production in the Radiolysis of Water/Organic Mixtures in Model TRU Waste

    SciTech Connect

    LaVerne, Jay A.

    2005-06-01

    Experiments in combination with diffusion-kinetic modeling incorporating track structure simulations are used to examine the radiation chemistry of aqueous systems containing chlorinated hydrocarbons. Irradiations with both Co-60 gamma rays and alpha particles are employed in order to simulate typical mixed radiation environments encountered in waste management. The goal is to determine fundamental mechanisms, kinetics, and yields for the formation of potentially explosive gases and corrosive agents, such as H2 and HCl, respectively, in the radiolysis of water-organic mixtures. The radiation chemical systems studied are found throughout the DOE portfolio and are important in radioactive waste remediation and management.

  3. Alpha Radiolysis of Nuclear Solvent Extraction Ligands Used for An(III) and Ln(III) Separations

    SciTech Connect

    Mezyk, Stephen P.; Mincher, Bruce J.; Nilsson, Mikael

    2016-08-01

    This document is the final report for the Nuclear Energy Universities Program (NEUP) grant 10-910 (DE-AC07-05ID14517) “Alpha Radiolysis of Nuclear Solvent Extraction Ligands used for An(III) and Ln(III) Separations”. The goal of this work was to obtain a quantitative understanding of the impacts of both low Linear Energy Transfer (LET, gamma-rays) and high LET (alpha particles) radiation chemistry occurring in future large-scale separations processes. This quantitative understanding of the major radiation effects on diluents and ligands is essential for optimal process implementation, and could result in significant cost savings in the future.

  4. LASERS: Ultrashort-pulse erbium-doped fibre laser using a saturable absorber based on single-wall carbon nanotubes synthesised by the arc-discharge method

    NASA Astrophysics Data System (ADS)

    Tausenev, A. V.; Obraztsova, E. D.; Lobach, A. S.; Konov, V. I.; Konyashchenko, A. V.; Kryukov, P. G.; Dianov, E. M.

    2007-09-01

    An erbium-doped fibre laser operating in self-mode-locked regime achieved with the help of a saturable absorber based on single-wall carbon nanotubes synthesised by the arc-discharge method is fabricated and studied. Due to the development of an original method for preparing samples, films of the optical quality containing individual single-wall carbon nanotubes were synthesised. The study of the dependence of resonance absorption at a wavelength of 1.5 μm on the laser radiation intensity transmitted through a film showed that these films have nonlinear transmission and can be used in fibre lasers as saturable absorbers to provide self-mode locking. Stable transform-limited pulses having the shape of optical solitons were generated at a wavelength of 1557.5 nm in the laser with a ring resonator. The pulse duration was 1.13 ps at a pulse repetition rate of 20.5 MHz. The continuous output power achieved 1.1 mW upon pumping by a 25-mW laser diode at 980 nm.

  5. PULSE AMPLIFIER

    DOEpatents

    Johnstone, C.W.

    1958-06-17

    The improvement of pulse amplifiers used with scintillation detectors is described. The pulse amplifier circuit has the advantage of reducing the harmful effects of overloading cause by large signal inputs. In general the pulse amplifier circuit comprises two amplifier tubes with the input pulses applied to one amplifier grid and coupled to the second amplifier tube through a common cathode load. The output of the second amplifier is coupled from the plate circuit to a cathode follower tube grid and a diode tube in connected from grid to cathode of the cathode follower tube. Degenerative feedback is provided in the second amplifier by coupling a signal from the cathode follower cathode to the second amplifier grid. The circuit proqides moderate gain stability, and overload protection for subsequent pulse circuits.

  6. Pulse radiolytic studies of electron transfer processes and applications to solar photochemistry. Progress report

    SciTech Connect

    Neta, P.

    1995-02-01

    The pulse radiolysis technique is applied to the study of electron transfer processes in a variety of chemical systems. Reactive intermediates are produced in solution by electron pulse irradiation and the kinetics of their reactions are followed by time resolved absorption spectrophotometry. Complementary experiments are carried out with excimer laser flash photolysis. These studies are concerned with mechanisms, kinetics, and thermodynamics of reactions of organic and inorganic radicals and unstable oxidation states of metal ions. Reactions are studied in both aqueous and non-aqueous solutions. The studies focus on the unique ability of pulse radiolysis to provide absolute rate constants for reactions of many inorganic radicals and organic peroxyl radicals, species that are key intermediates in many chemical processes. A special concern of this work is the study of electron transfer reactions of metalloporphyrins, which permits evaluation of these molecules as intermediates in solar energy conversion. Metalloporphyrins react with free radicals via electron transfer, involving the ligand or the metal center, or via bonding to the metal, leading to a variety of chemical species whose behavior is also investigated. The highlights of the results during the past three years are summarized below under the following sections: (a) electron transfer reactions of peroxyl radicals, concentrating on the characterization of new peroxyl radicals derived from vinyl, phenyl, other aryl, and pyridyl; (b) solvent effects on electron transfer reactions of inorganic and organic peroxyl radicals, including reactions with porphyrins, and (c) electron transfer and alkylation reactions of metalloporphyrins and other complexes.

  7. Magnetic-Field-Induced Strain of Shape-Memory Alloy Fe3Pt Studied by a Capacitance Method in a Pulsed Magnetic Field

    NASA Astrophysics Data System (ADS)

    Sakon, Takuo; Takaha, Atsuo; Obara, Kenji; Dejima, Koutatsu; Nojiri, Hiroyuki; Motokawa, Mitsuhiro; Fukuda, Takashi; Kakeshita, Tomoyuki

    2007-01-01

    The precise magnetic-field-induced strain (MFIS) and magnetization of the martensite metallic compound Fe3Pt in a martensitic phase were studied in a pulsed magnetic field using the capacitance method at low temperatures down to 4.2 K, which is much lower than the martensitic transformation temperature TM=85 K. After zero field cooling, a pulsed magnetic field with a maximum frequency of 160 Hz was applied parallel to the [001]p axis. A large MFIS was measured. The value of the MFIS is Δ L/L=-1.7%. When the magnetic field was decreased, the recovery of the strain was observed. In the second applied field, a strain of about 0.6% was observed. This means that MFIS occurs even in short-pulse magnetic fields. MFIS was observed below 70 K. The largest strain was observed at 20 K. These results are almost the same as the MFIS in a steady magnetic field using a superconducting magnet.

  8. Oxygen Gas Barrier Properties of Hydrogenated Amorphous Carbon Thin Films Deposited with a Pulse-Biased Inductively Coupled Plasma Chemical Vapor Deposition Method

    NASA Astrophysics Data System (ADS)

    Baek, Sang-min; Shirafuji, Tatsuru; Cho, Sung-pyo; Saito, Nagahiro; Takai, Osamu

    2010-08-01

    Hydrogenated amorphous carbon (a-C:H) films have been deposited on poly(ethylene terephthalate) (PET) films with an pulse-biased inductively coupled plasma chemical vapor deposition method using CH4 and C2H2 gases. We have investigated the effects of the pulse-bias frequency on the oxygen transmission rate (OTR) of the a-C:H-coated PET sample, and discussed relationship between the OTR characteristics and the structure of the films based on the results of Raman and infrared absorption spectroscopy. In case of CH4 plasmas, the OTR of the sample has been reduced down to 1.12 cm3/(m2·day·atm) by increasing the bias-frequency to 2 kHz, and the structure of the a-C:H films has been modified from polymer-like to tetrahedral one. In case of C2H2 plasmas, the OTR of the samples has been 1.18 cm3/(m2·day·atm) with the lower bias frequency of 0.5 kHz, and has not shown strong dependence on the pulse-bias frequency. This has been explained by the fact that the films prepared with C2H2 plasma can be modified to tetrahedral structures by applying the bias with the lower frequency.

  9. Examination of the effect of alpha radiolysis on plutonium(V) sorption to quartz using multiple plutonium isotopes.

    PubMed

    Hixon, Amy E; Arai, Yuji; Powell, Brian A

    2013-08-01

    The objective of this research was to determine if radiolysis at the mineral surface was a plausible mechanism for surface-mediated reduction of plutonium. Batch sorption experiments were used to monitor the amount of plutonium sorbed to high-purity quartz as a function of time, pH, and total alpha radioactivity. Three systems were prepared using both (238)Pu and (242)Pu in order to increase the total alpha radioactivity of the mineral suspensions while maintaining a constant plutonium concentration. The fraction of sorbed plutonium increased with increasing time and pH regardless of the total alpha radioactivity of the system. Increasing the total alpha radioactivity of the solution had a negligible effect on the sorption rate. This indicated that surface-mediated reduction of Pu(V) in these systems was not due to radiolysis. Additionally, literature values for the Pu(V) disproportionation rate constant did not describe the experimental results. Therefore, Pu(V) disproportionation was also not a main driver for surface-mediated reduction of plutonium. Batch desorption experiments and X-ray absorption near edge structure spectroscopy were used to show that Pu(IV) was the dominant oxidation state of sorbed plutonium. Thus, it appears that the observed surface-mediated reduction of Pu(V) in the presence of high-purity quartz was based on the thermodynamic favorability of a Pu(IV) surface complex.

  10. On the possibility of galactic cosmic ray-induced radiolysis-powered life in subsurface environments in the Universe

    PubMed Central

    2016-01-01

    Photosynthesis is a mechanism developed by terrestrial life to utilize the energy from photons of solar origin for biological use. Subsurface regions are isolated from the photosphere, and consequently are incapable of utilizing this energy. This opens up the opportunity for life to evolve alternative mechanisms for harvesting available energy. Bacterium Candidatus Desulforudis audaxviator, found 2.8 km deep in a South African mine, harvests energy from radiolysis, induced by particles emitted from radioactive U, Th and K present in surrounding rock. Another radiation source in the subsurface environments is secondary particles generated by galactic cosmic rays (GCRs). Using Monte Carlo simulations, it is shown that it is a steady source of energy comparable to that produced by radioactive substances, and the possibility of a slow metabolizing life flourishing on it cannot be ruled out. Two mechanisms are proposed through which GCR-induced secondary particles can be utilized for biological use in subsurface environments: (i) GCRs injecting energy in the environment through particle-induced radiolysis and (ii) organic synthesis from GCR secondaries interacting with the medium. Laboratory experiments to test these hypotheses are also proposed. Implications of these mechanisms on finding life in the Solar System and elsewhere in the Universe are discussed. PMID:27707907

  11. On the possibility of galactic cosmic ray-induced radiolysis-powered life in subsurface environments in the Universe.

    PubMed

    Atri, Dimitra

    2016-10-01

    Photosynthesis is a mechanism developed by terrestrial life to utilize the energy from photons of solar origin for biological use. Subsurface regions are isolated from the photosphere, and consequently are incapable of utilizing this energy. This opens up the opportunity for life to evolve alternative mechanisms for harvesting available energy. Bacterium Candidatus Desulforudis audaxviator, found 2.8 km deep in a South African mine, harvests energy from radiolysis, induced by particles emitted from radioactive U, Th and K present in surrounding rock. Another radiation source in the subsurface environments is secondary particles generated by galactic cosmic rays (GCRs). Using Monte Carlo simulations, it is shown that it is a steady source of energy comparable to that produced by radioactive substances, and the possibility of a slow metabolizing life flourishing on it cannot be ruled out. Two mechanisms are proposed through which GCR-induced secondary particles can be utilized for biological use in subsurface environments: (i) GCRs injecting energy in the environment through particle-induced radiolysis and (ii) organic synthesis from GCR secondaries interacting with the medium. Laboratory experiments to test these hypotheses are also proposed. Implications of these mechanisms on finding life in the Solar System and elsewhere in the Universe are discussed.

  12. Pulse Voltammetry.

    ERIC Educational Resources Information Center

    Osteryoung, Janet

    1983-01-01

    Discusses the nature of pulse voltammetry, indicating that its widespread use arises from good sensitivity and detection limits and from ease of application and low cost. Provides analytical and mechanistic applications of the procedure. (JN)

  13. Interactions between butterfly-shaped pulses in the inhomogeneous media

    SciTech Connect

    Liu, Wen-Jun; Huang, Long-Gang; Pan, Nan; Lei, Ming

    2014-10-15

    Pulse interactions affect pulse qualities during the propagation. Interactions between butterfly-shaped pulses are investigated to improve pulse qualities in the inhomogeneous media. In order to describe the interactions between butterfly-shaped pulses, analytic two-soliton solutions are derived. Based on those solutions, influences of corresponding parameters on pulse interactions are discussed. Methods to control the pulse interactions are suggested. - Highlights: • Interactions between butterfly-shaped pulses are investigated. • Methods to control the pulse interactions are suggested. • Analytic two-soliton solutions for butterfly-shaped pulses are derived.

  14. Dependence of the specific features of two PAPVD methods: Impulse Plasma Deposition (IPD) and Pulsed Magnetron Sputtering (PMS) on the structure of Fe-Cu alloy layers

    NASA Astrophysics Data System (ADS)

    Nowakowska-Langier, Katarzyna; Chodun, Rafal; Nietubyc, Robert; Minikayev, Roman; Zdunek, Krzysztof

    2013-06-01

    This paper describes the study of the structural properties of the alloy layers prepared by two different, impulsively working PAPVD methods: the Pulsed Magnetron Sputtering (PMS) and the Impulse Plasma Deposition (IPD). The Fe-Cu alloy layers were synthesized. The results of our investigation revealed a nanocrystalline structure of the layers. The differences in the phase composition of the Fe-Cu alloy layers produced by these two methods were observed. The synthesis of the Fe-Cu layers by using the Pulsed Magnetron Sputtering method resulted in obtaining the two-phase, polycrystalline structures (fcc-Cu and bcc-Fe). In this case the clear evidence of mixing between the iron and copper atoms was not observed. The Fe-Cu layers deposited by the Impulse Plasma Deposition method were characterized by the non-equilibrium phase composition - the presence of one-phase supersaturated solid solution (fcc-Cu(Fe) or bcc-Fe(Cu)) was formed in immiscible systems. These results suggest a short-distance diffusion between the neighboring nanoparticles of the two metals (Cu and Fe) occurring during the IPD layers growth.

  15. GLM Proxy Data Generation: Methods for Stroke/Pulse Level Inter-Comparison of Ground-Based Lightning Reference Networks

    NASA Technical Reports Server (NTRS)

    Cummins, Kenneth L.; Carey, Lawrence D.; Schultz, Christopher J.; Bateman, Monte G.; Cecil, Daniel J.; Rudlosky, Scott D.; Petersen, Walter Arthur; Blakeslee, Richard J.; Goodman, Steven J.

    2011-01-01

    In order to produce useful proxy data for the GOES-R Geostationary Lightning Mapper (GLM) in regions not covered by VLF lightning mapping systems, we intend to employ data produced by ground-based (regional or global) VLF/LF lightning detection networks. Before using these data in GLM Risk Reduction tasks, it is necessary to have a quantitative understanding of the performance of these networks, in terms of CG flash/stroke DE, cloud flash/pulse DE, location accuracy, and CLD/CG classification error. This information is being obtained through inter-comparison with LMAs and well-quantified VLF/LF lightning networks. One of our approaches is to compare "bulk" counting statistics on the spatial scale of convective cells, in order to both quantify relative performance and observe variations in cell-based temporal trends provided by each network. In addition, we are using microsecond-level stroke/pulse time correlation to facilitate detailed inter-comparisons at a more-fundamental level. The current development status of our ground-based inter-comparison and evaluation tools will be presented, and performance metrics will be discussed through a comparison of Vaisala s Global Lightning Dataset (GLD360) with the NLDN at locations within and outside the U.S.

  16. EVALUATION OF RADIOLYSIS INDUCED HYDROGEN GENERATION IN DOT 6M DRUMS FROM INTEC

    SciTech Connect

    Vinson, D

    2007-06-18

    Three DOT 6M 30-gallon drums are scheduled to be shipped from the Idaho Nuclear Technology Engineering Center (INTEC) at the Idaho National Laboratory (INL) to L-Area at the Savannah River Site (SRS). These three drums contain radioactive materials that resulted from the material recovery effort following a small explosion that had occurred in the Idaho Chemical Processing Plant (ICPP) hot chemistry laboratory (HCL). In support of the shipment and subsequent storage of the three DOT 6M drums, an evaluation of the potential for molecular hydrogen production in the drums has been completed and documented herein. The potential sources of hydrogen evaluated in the current report include radiolytic decomposition of polymeric materials in the DOT 6M drums No.3031 and No.3598 and the radiolytic decomposition of water in drum No.20102. No other potential sources have been identified based upon reported drum contents and packaging configuration. A parametric approach was used to evaluate the maximum quantity of molecular hydrogen that can be expected to evolve in two DOT 6M 30-gallon drums in support of receipt and subsequent interim storage prior to canyon processing. These drums are two of three drums scheduled for shipment from INTEC to SRS as part of the decommissioning effort of the INTEC facility. The three DOT 6M drums will be received at L-Area in SRS and stored for up to 13-years prior to final disposition at HB-Line in 2020. Results of the current analysis do not include parametric analysis of drum No.20102 containing 114/133 SAL (salvage) which contains UO{sub 3} powder. This drum has not been identified as containing polymeric materials and a conservative calculation indicates that the maximum gross molecular hydrogen production due to the radiolysis of adsorbed moisture would yield a production rate of 5.1-cm{sup 3}/yr, driven primarily by the large surface are to volume ratio of the oxide powder. The remaining two drums, No.3031 and No.3598 contain polymer

  17. Harmonic generation with a dual frequency pulse.

    PubMed

    Keravnou, Christina P; Averkiou, Michalakis A

    2014-05-01

    Nonlinear imaging was implemented in commercial ultrasound systems over the last 15 years offering major advantages in many clinical applications. In this work, pulsing schemes coupled with a dual frequency pulse are presented. The pulsing schemes considered were pulse inversion, power modulation, and power modulated pulse inversion. The pulse contains a fundamental frequency f and a specified amount of its second harmonic 2f. The advantages and limitations of this method were evaluated with both acoustic measurements of harmonic generation and theoretical simulations based on the KZK equation. The use of two frequencies in a pulse results in the generation of the sum and difference frequency components in addition to the other harmonic components. While with single frequency pulses, only power modulation and power modulated pulse inversion contained odd harmonic components, with the dual frequency pulse, pulse inversion now also contains odd harmonic components.

  18. Pulse stretcher

    DOEpatents

    Horton, James A.

    1994-01-01

    Apparatus (20) for increasing the length of a laser pulse to reduce its peak power without substantial loss in the average power of the pulse. The apparatus (20) uses a White cell (10) having a plurality of optical delay paths (18a-18d) of successively increasing number of passes between the field mirror (13) and the objective mirrors (11 and 12). A pulse (26) from a laser (27) travels through a multi-leg reflective path (28) between a beam splitter (21) and a totally reflective mirror (24) to the laser output (37). The laser pulse (26) is also simultaneously injected through the beam splitter (21) to the input mirrors (14a-14d) of the optical delay paths (18a-18d). The pulses from the output mirrors (16a-16d) of the optical delay paths (18a-18d) go simultaneously to the laser output (37) and to the input mirrors ( 14b-14d) of the longer optical delay paths. The beam splitter (21) is 50% reflective and 50% transmissive to provide equal attenuation of all of the pulses at the laser output (37).

  19. Pulsed-neutron monochromator

    DOEpatents

    Mook, H.A. Jr.

    1984-01-01

    In one aspect, the invention is an improved pulsed-neutron monochromator of the vibrated-crystal type. The monochromator is designed to provide neutron pulses which are characterized both by short duration and high density. A row of neutron-reflecting crystals is disposed in a neutron beam to reflect neutrons onto a common target. The crystals in the row define progressively larger neutron-scattering angles and are vibrated sequentially in descending order with respect to the size of their scattering angles, thus generating neutron pulses which arrive simultaneously at the target. Transducers are coupled to one end of the crystals to vibrate them in an essentially non-resonant mode. The transducers propagate transverse waves in the crystal which progress longitudinally therein. The waves are absorbed at the undriven ends of the crystals by damping material mounted thereon. In another aspect, the invention is a method for generating neutron pulses characterized by high intensity and short duration.

  20. Pulsed-neutron monochromator

    DOEpatents

    Mook, Jr., Herbert A.

    1985-01-01

    In one aspect, the invention is an improved pulsed-neutron monochromator of the vibrated-crystal type. The monochromator is designed to provide neutron pulses which are characterized both by short duration and high density. A row of neutron-reflecting crystals is disposed in a neutron beam to reflect neutrons onto a common target. The crystals in the row define progressively larger neutron-scattering angles and are vibrated sequentially in descending order with respect to the size of their scattering angles, thus generating neutron pulses which arrive simultaneously at the target. Transducers are coupled to one end of the crystals to vibrate them in an essentially non-resonant mode. The transducers propagate transverse waves in the crystal which progress longitudinally therein. The wave are absorbed at the undriven ends of the crystals by damping material mounted thereon. In another aspect, the invention is a method for generating neutron pulses characterized by high intensity and short duration.