Science.gov

Sample records for alpha xn reactions

  1. Cross Sections for (gamma)-ray Production in the 191Ir (n,xn(gamma)) Reactions

    SciTech Connect

    Fotiades, N; Nelson, R O; Devlin, M; Chadwick, M B; Talou, P; Becker, J A; Garrett, P E; Younes, W

    2005-01-11

    Discrete {gamma}-ray spectra have been measured for nuclei populated in {sup 191}Ir(n{sub 4}xn{gamma}) with x{<=}11, as a function of incident neutron energy using neutrons from the 'white' neutron source at the Los Alamos Neutron Science Center's WNR facility. The energy of the neutrons was determined using the time-of-flight technique. The data were taken using the GEANIE spectrometer. The cross sections for emission of 202 {gamma} rays of {sup 181-191}Ir were determined for neutron energies 0.2 MeV < E{sub n} < 300 MeV. Comparison with model calculations, using the GNASH reaction model, and with GEANIE results from the similar {sup 193}Ir(n{sub 4}xn{gamma}) reactions is made.

  2. Probing reaction dynamics with the {sup 196}Pt(n,xn{gamma}) reactions for x{le}15

    SciTech Connect

    Bernstein, L.A.; Becker, J.A.; Younes, W.; Archer, D.E.; Hauschild, K.; Nelson, R.O.; Wilburn, W.S. Drake, D.M.

    1998-06-01

    Discrete {gamma}-ray spectra have been measured as a function of incident neutron energy for nuclei produced in the {sup 196}Pt(n,xn{gamma}) reactions. Spectroscopy was done using the large-scale Compton suppressed Ge {gamma}-ray spectrometer GEANIE. The {open_quotes}white{close_quotes} source neutron beam was produced at the Los Alamos Neutron Science WNR facility. Reaction neutron energy was determined using the time-of-flight technique. Reaction-channel yields were inferred from the measured intensity sum of the 2{sub 1}{sup +}{r_arrow}0{sub 1}{sup +} and the 2{sub 2}{sup +}{r_arrow}0{sub 1}{sup +} transitions for the {sup 196}Pt(n,xn) reactions for x{le}15. Weisskopf-Ewing calculations (including precompound) done with the HMS-ALICE code correctly predict the bulk of the (n,xn) reaction products for low multiplicity. However, they do not accurately predict yield ratios of the different (n,xn) reactions for x{ge}9. In addition, there is no consistent experimental indication of charged-particle reaction channels (n,pxn) for incident neutron energies above 60 MeV where they are predicted to account for approximately 1/3 of the total reaction cross section. Several possible causes are discussed for these discrepancies. Finally, the region of E-J phase space populated in this reaction is probed for several of the strongest reaction channels through the observation of relative yields for different yrast and off-yrast states. {copyright} {ital 1998} {ital The American Physical Society}

  3. GRAPhEME: a setup to measure (n, xn γ) reaction cross sections

    SciTech Connect

    Henning, Greg; Bacquias, A.; Capdevielle, O.; Dessagne, P.; Kerveno, M.; Rudolf, G.; Borcea, C.; Negret, A.; Olacel, A.; Drohe, J.C.; Plompen, A.J.M.; Nyman, M.

    2015-07-01

    Most of nuclear reactor developments are using evaluated data base for numerical simulations. However, the considered databases present still large uncertainties and disagreements. To improve their level of precision, new measurements are needed, in particular for (n, xn) reactions, which are of great importance as they modify the neutron spectrum, the neutron population, and produce radioactive species. The IPHC group started an experimental program to measure (n, xn gamma) reaction cross sections using prompt gamma spectroscopy and neutron energy determination by time of flight. Measurements of (n, xn gamma) cross section have been performed for {sup 235,238}U, {sup 232}Th, {sup nat,182,183,184,186}W, {sup nat}Zr. The experimental setup is installed at the neutron beam at GELINA (Geel, Belgium). The setup has recently been upgraded with the addition of a highly segmented 36 pixels planar HPGe detector. Significant efforts have been made to reduce radiation background and electromagnetic perturbations. The setup is equipped with a high rate digital acquisition system. The analysis of the segmented detector data requires a specific procedure to account for cross signals between pixels. An overall attention is paid to the precision of the measurement. The setup characteristic and the analysis procedure will be presented along with the acquisition and analysis challenges. Examples of results and their impact on models will be discussed. (authors)

  4. {sup 248}Cm({sup 22}Ne,xn){sup 270-x}Sg reaction and the decay properties of {sup 265}Sg reexamined

    SciTech Connect

    Duellmann, Ch. E.; Tuerler, A.

    2008-06-15

    Recent studies of the hot fusion reaction {sup 248}Cm({sup 26}Mg,xn){sup 274-x}Hs have provided new nuclear decay data on {sup 265,266}Sg and confirmed the existence of an isomeric state in {sup 261}Rf. The results reported in [J. Dvorak et al., Phys. Rev. Lett. 100, 132503 (2008)] suggest that all decay chains observed in previous studies of the reaction {sup 248}Cm({sup 22}Ne,xn){sup 270-x}Sg, which were originally attributed to {sup 266}Sg, originated from {sup 265}Sg. Here, the decay properties of {sup 265}Sg are reevaluated. Indications for the existence of an isomeric state in {sup 265}Sg are found. The half-lives and main {alpha} particle energies of the two {sup 265}Sg states are 8.9 s/8.85 MeV and 16.2 s/8.70 MeV, respectively. Direct production of this isotope as an evaporation residue of a nuclear fusion reaction populates both states with similar intensity while {alpha} decay of {sup 269}Hs into {sup 265}Sg preferentially populates the longer-lived state, which in turn decays almost exclusively into the short-lived state in {sup 261}Rf. The cross section of the reaction {sup 248}Cm({sup 22}Ne,5n){sup 265}Sg is reanalyzed and found to be of the order of a few hundred pb, assuming that {alpha} decay is the only decay mode of {sup 265}Sg. A decay scheme that is consistent with the published data on {sup 265}Sg and {sup 261}Rf is proposed, which can serve as a working hypothesis in the design of new experiments dedicated to study the production and decay of these two isotopes.

  5. Comparison of reactions for the production of 258,257Db: 208Pb(51V,xn) and 209Bi(50Ti,xn)

    SciTech Connect

    Gates, Jacklyn M.; Nelson, Sarah L.; Gregorich, Kenneth E.; Dragojevic, Irena; Dullmann, Christoph E.; Ellison, Paul A.; Folden III, Charles M.; Garcia, Mitch A.; Stavsetra, Liv; Sudowe, Ralf; Hoffman, Darleane C.; Nitsche, Heino

    2008-09-29

    Excitation functions for the 1n and 2n exit channels of the 208Pb(51V,xn)259-xDb reaction were measured. A maximum cross section of the 1n exit channel of 2070+1100/-760 pb was measured at an excitation energy of 16.0 +- 1.8 MeV. For the 2n exit channel, a maximum cross section of 1660+450/-370 pb was measured at 22.0 +- 1.8 MeV excitation energy. The 1n excitation function for the 209Bi(50Ti,n)258Db reaction was remeasured, resulting in a cross section of 5480+1750/-1370 pb at an excitation energy of 16.0 +- 1.6 MeV, in agreement with previous values [F. P. Hebberger, et al., Eur. Phys. J. A 12, 57 (2001)]. Differences in cross section maxima are discussed in terms of the fusion probability below the barrier.

  6. Inclusive measurement of (p,. pi. /sup -/xn) double charge exchange reactions on bismuth from threshold to 800 MeV

    SciTech Connect

    Dombsky, M.; D'Auria, J.M.; Kelson, I.; Yavin, A.I.; Ward, T.E.; Clark, J.L.; Ruth, T.; Sheffer, G.

    1985-07-01

    The energy dependence of the total angle-integrated cross section for the production of astatine isotopes from (p,..pi../sup -/xn) double charge exchange reactions on bismuth (/sup 209/Bi) was measured from 120 to 800 MeV using activation and radiochemical techniques. Chemical yields were estimated by direct radioassaying of /sup 211/At activity in thin (approx.1 mg/cm/sup 2/), irradiated bismuth targets. Calculations of the contributions of secondary (two-step) reactions to these measured astatine yields were performed, based partially upon the observed /sup 211/At activity although even at the highest energies, the contribution to products lighter than /sup 207/At was negligible. These data for products with as many as seven neutrons removed from the doubly coherent product (/sup 210/At) display nearly Gaussian shapes for the mass distributions of the astatine residues, with the maximum occurring for about /sup 204/At. The most probable momentum transfer deduced from these distributions for the initial ..pi../sup -/ production step was 335 MeV/c. The observed excitation functions display a behavior similar to that observed for the yield of /sup 210/Po from a (p,..pi../sup 0/) reaction on /sup 209/Bi, but radically different from that observed for inclusive ..pi../sup -/ reactions on a heavy nucleus. These data are discussed in terms of recent theoretical approaches to negative pion production from bismuth. In addition, a simple, schematic model is developed to treat the rapidly decreasing percentage of the total inclusive ..pi../sup -/ emission which is observed for this double charge exchange reaction. This model reflects the opacity of a nucleus to a source of internal energetic protons.

  7. Lead 207, 208 (n, xn gamma) reactions for neutron energies up to 200 MeV

    SciTech Connect

    Pavlik, A.; Vonach, H.; Chadwick, M.B.; Haight, R.C.; Nelson, R.O.; Wender, S.A.; Young, P.G.

    1994-07-01

    High-resolution {gamma}-ray spectra from the interaction of neutrons in the energy range from 3 to 200 MeV with {sup 207,208}Pb were measured with the white neutron source at the WNR facility at Los Alamos National Laboratory. From these data, excitation functions for prominent {gamma} transitions in {sup 200,202,204,206,207,208}Pb were derived from threshold to 200 MeV incident neutron energy. These {gamma}-production cross sections represent formation cross sections for excited states of the residual nuclei. The results are compared with the predictions of nuclear reaction calculations based on the exciton model for precompound emission, the Hauser-Feshbach theory for compound nuclear decay, and coupled channels calculations to account for direct excitation of collective levels. Good agreement was obtained over the entire energy range covered in the experiment with reasonable model parameters. The results demonstrate that multiple preequilibrium emission has to be taken into account above about 40 MeV, and that the level density model of Ignatyuk should be used instead of the Gilbert-Cameron and back-shifted Fermi-gas models if excitation energies exceed about 30 MeV.

  8. Comparison of reactions for the production of {sup 258,257}Db: {sup 208}Pb({sup 51}V,xn) and {sup 209}Bi({sup 50}Ti,xn)

    SciTech Connect

    Gates, J. M.; Nelson, S. L.; Dragojevic, I.; Duellmann, Ch. E.; Ellison, P. A.; Folden III, C. M.; Garcia, M. A.; Hoffman, D. C.; Nitsche, H.; Gregorich, K. E.; Stavsetra, L.; Sudowe, R.

    2008-09-15

    Excitation functions for the 1n and 2n exit channels of the {sup 208}Pb({sup 51}V,xn){sup 259-x}Db reaction were measured. A maximum cross section of the 1n exit channel of 2070{sub -760}{sup +1100} pb was measured at an excitation energy of 16.0 {+-} 1.8 MeV. For the 2n exit channel, a maximum cross section of 1660{sub -370}{sup +450} pb was measured at 22.0 {+-} 1.8 MeV excitation energy. The 1n excitation function for the {sup 209}Bi({sup 50}Ti,n){sup 258}Db reaction was remeasured, resulting in a cross section of 5480{sub -1370}{sup +1730} pb at an excitation energy of 16.0 {+-} 1.6 MeV, in agreement with previous values [F. P. Hessberger et al., Eur. Phys. J. A 12, 57 (2001)]. Differences in cross section maxima are discussed in terms of the fusion probability below the barrier.

  9. Measurement of flux-weighted average cross-sections and isomeric yield ratios for 103Rh(γ,xn) reactions in the bremsstrahlung end-point energies of 55 and 60 MeV

    NASA Astrophysics Data System (ADS)

    Shakilur Rahman, Md.; Kim, Kwangsoo; Kim, Guinyun; Naik, Haladhara; Nadeem, Muhammad; Thi Hien, Nguyen; Shahid, Muhammad; Yang, Sung-Chul; Cho, Young-Sik; Lee, Young-Ouk; Shin, Sung-Gyun; Cho, Moo-Hyun; Woo Lee, Man; Kang, Yeong-Rok; Yang, Gwang-Mo; Ro, Tae-Ik

    2016-07-01

    We measured the flux-weighted average cross-sections and the isomeric yield ratios of 99m, g, 100m, g, 101m, g, 102m, gRh in the 103Rh( γ, xn) reactions with the bremsstrahlung end-point energies of 55 and 60MeV by the activation and the off-line γ-ray spectrometric technique, using the 100MeV electron linac at the Pohang Accelerator Laboratory (PAL), Korea. The flux-weighted average cross-sections were calculated by using the computer code TALYS 1.6 based on mono-energetic photons, and compared with the present experimental data. The flux-weighted average cross-sections of 103Rh( γ, xn) reactions in intermediate bremsstrahlung energies are the first time measurement and are found to increase from their threshold value to a particular value, where the other reaction channels open up. Thereafter, it decreases with bremsstrahlung energy due to its partition in different reaction channels. The isomeric yield ratios (IR) of 99m, g, 100m, g, 101m, g, 102m, gRh in the 103Rh( γ, xn) reactions from the present work were compared with the literature data in the 103Rh(d, x), 102-99Ru(p, x) , 103Rh( α, αn) , 103Rh( α, 2p3n) , 102Ru(3He, x), and 103Rh( γ, xn) reactions. It was found that the IR values of 102, 101, 100, 99Rh in all these reactions increase with the projectile energy, which indicates the role of excitation energy. At the same excitation energy, the IR values of 102, 101, 100, 99Rh are higher in the charged particle-induced reactions than in the photon-induced reaction, which indicates the role of input angular momentum.

  10. Alpha resonant scattering for astrophysical reaction studies

    SciTech Connect

    Yamaguchi, H.; Kahl, D.; Nakao, T.; Wakabayashi, Y.; Kubano, S.; Hashimoto, T.; Hayakawa, S.; Kawabata, T.; Iwasa, N.; Teranishi, T.; Kwon, Y. K.; Binh, D. N.; Khiem, L. H.; Duy, N. G.

    2014-05-02

    Several alpha-induced astrophysical reactions have been studied at CRIB (CNS Radioactive Ion Beam separator), which is a low-energy RI beam separator at Center for Nuclear Study (CNS) of the University of Tokyo. One of the methods to study them is the α resonant scattering using the thick-target method in inverse kinematics. Among the recent studies at CRIB, the measurement of {sup 7}Be+α resonant scattering is discussed. Based on the result of the experiment, we evaluated the contributions of high-lying resonances for the {sup 7}Be(α,γ) reaction, and proposed a new cluster band in {sup 11}C.

  11. Depth profile of production yields of natPb(p, xn) 206,205,204,203,202,201Bi nuclear reactions

    NASA Astrophysics Data System (ADS)

    Mokhtari Oranj, Leila; Jung, Nam-Suk; Kim, Dong-Hyun; Lee, Arim; Bae, Oryun; Lee, Hee-Seock

    2016-11-01

    Experimental and simulation studies on the depth profiles of production yields of natPb(p, xn) 206,205,204,203,202,201Bi nuclear reactions were carried out. Irradiation experiments were performed at the high-intensity proton linac facility (KOMAC) in Korea. The targets, irradiated by 100-MeV protons, were arranged in a stack consisting of natural Pb, Al, Au foils and Pb plates. The proton beam intensity was determined by activation analysis method using 27Al(p, 3p1n)24Na, 197Au(p, p1n)196Au, and 197Au(p, p3n)194Au monitor reactions and also by Gafchromic film dosimetry method. The yields of produced radio-nuclei in the natPb activation foils and monitor foils were measured by HPGe spectroscopy system. Monte Carlo simulations were performed by FLUKA, PHITS/DCHAIN-SP, and MCNPX/FISPACT codes and the calculated data were compared with the experimental results. A satisfactory agreement was observed between the present experimental data and the simulations.

  12. Measurement of flux-weight average cross-sections of natZn(γ,xn) reactions in the bremsstrahlung end-point energies of 50, 55, 60, and 65 MeV

    NASA Astrophysics Data System (ADS)

    Zaman, Muhammad; Kim, Guinyun; Naik, Haladhara; Kim, Kwangsoo; Cho, Young-Sik; Lee, Young-Ok; Shin, Sung-Gyun; Cho, Moo-Hyun; Kang, Yeong-Rok; Lee, Man-Woo

    2017-04-01

    The flux-weighted average cross-sections of (γ , xn) reactions on natZn induced by the bremsstrahlung end-point energies of 50, 55, 60, and 65 MeV have been determined by activation and off-line γ-ray spectrometric technique, using the 100 MeV electron linac at the Pohang Accelerator Laboratory (PAL), Pohang, Korea. The theoretical photon-induced reaction cross-sections of natZn as a function of photon energy were taken from TENDL-2014 nuclear data library based on TALYS 1.6 program. The flux-weighted average cross-sections were obtained from the literature data and the theoretical values of TENDL-2014 based on mono-energetic photon. The flux-weighted reaction cross-sections from the present work and literature data at different bremsstrahlung end-point energies are in good agreement with the theoretical values. It was found that the individual natZn(γ , xn) reaction cross-sections increase sharply from reaction threshold to certain values where the next reaction channel opens. There after it remains constant for a while, where the next reaction channel increases. Then it decreases slowly with increase of bremsstrahlung end-point energy due to opening of different reaction channels.

  13. Theoretical analyses of (n,xn) reactions on sup 235 U, sup 238 U, sup 237 Np, and sup 239 Pu for ENDF/B-VI

    SciTech Connect

    Young, P.G.; Arthur, E.D.

    1991-01-01

    Theoretical analyses were performed of neutron-induced reactions on {sup 235}U, {sup 238}U, {sup 237}Np, and {sup 239}Pu between 0.01 and 20 MeV in order to calculate neutron emission cross sections and spectra for ENDF/B-VI evaluations. Coupled-channel optical model potentials were obtained for each target nucleus by fitting total, elastic, and inelastic scattering cross section data, as well as low-energy average resonance data. The resulting deformed optical model potentials were used to calculate direct (n,n{prime}) cross sections and transmission coefficients for use in Hauser-Feshbach statistical theory analyses. A fission model with multiple barrier representation, width fluctuation corrections, and preequilibrium corrections were included in the analyses. Direct cross sections for higher-lying vibrational states were calculated using DWBA theory, normalized using B(E{ell}) values determined from (d,d{prime}) and Coulomb excitation data, where available, and from systematics otherwise. Initial fission barrier parameters and transition state density enhancements appropriate to the compound systems involved were obtained from previous analyses, especially fits to charged-particle fission probability data. The parameters for the fission model were adjusted for each target system to obtain optimum agreement with direct (n,f) cross section measurements, taking account of the various multichance fission channels, that is, the different compound systems involved. The results from these analyses were used to calculate most of the neutron (n,n), (n,n{prime}), and (n,xn) cross section data in the ENDF/B/VI evaluations for the above nuclei, and all of the energy-angle correlated spectra. The deformed optical model and fission model parameterizations are described. Comparisons are given between the results of these analyses and the previous ENDF/B-V evaluations as well as with the available experimental data. 14 refs., 3 figs., 1 tab.

  14. Cross-Section Measurements for (n,xn) Reactions by In-Beam Gamma-Ray Spectroscopy

    SciTech Connect

    Pavlik, A.; Baumann, P.; Kerveno, M.; Rudolf, G.; Borcea, C.; Mihailescu, L.C.; Jericha, E.; Raskinyte, I.; Jokic, S.; Lukic, S.; Meulders, J.P.; Nolte, R.; Plompen, A.J.M.

    2005-05-24

    The nuclear reactions 207Pb(n,2n)206Pb and 232Th(n,5n)228Th were studied by measuring prompt gamma-ray emission spectra from the interaction of neutrons with an enriched 207Pb sample and a natTh sample. For 207Pb the measurements were performed at the white neutron beam of the GELINA neutron source at IRMM Geel in the neutron energy range up to 20 MeV. The Th measurements were done at the quasi-monoenergetic 7Li(p,n)7Be neutron source at the Universite Catholique de Louvain for five peak neutron energies in the range 29 MeV to 42 MeV. The measurements were complemented by model calculations using the code system EMPIRE-II.

  15. Direct Measurement of {sup 21}Na+{alpha} Stellar Reaction

    SciTech Connect

    Binh, D. N.; Kubono, S.; Yamaguchi, H.; Hayakawa, S.; Hashimoto, T.; Kahl, D.; Teranishi, T.; Iwasa, N.; Kume, N.; Kato, S.; Khiem, L. H.; Tho, N. T.; Wakabayashi, Y.

    2010-08-12

    The measurement of the resonant alpha scattering and the {sup 21}Na({alpha}, p) reaction were performed for the first time in inverse kinematics with the thick target method using a {sup 21}Na radioisotope (RI) beam. This paper reports the current result of alpha scattering measurement and its astrophysics implication.

  16. Studies of alpha-induced astrophysical reactions at CRIB

    SciTech Connect

    Yamaguchi, H.; Hashimoto, T.; Hayakawa, S.; Binh, D. N.; Kahl, D.; Kubono, S.

    2010-08-12

    CRIB (CNS Radioactive Ion Beam separator) is a low-energy RI beam separator at the Center for Nuclear Study (CNS) of the University of Tokyo. Using the RI beams at CRIB, many measurements on proton alpha resonance scatterings, ({alpha},p) reactions, and others were performed in recent years mainly for studying astrophysical reactions and exotic nuclear structure. Among them, the results on the {sup 7}Li+{alpha} resonance scatterings are presented.

  17. Non-resonant triple alpha reaction rate at low temperature

    SciTech Connect

    Itoh, T.; Tamii, A.; Aoi, N.; Fujita, H.; Hashimoto, T.; Miki, K.; Ogata, K.; Carter, J.; Donaldson, L.; Sideras-Haddad, E.; Furuno, T.; Kawabata, T.; Kamimura, M.; Nemulodi, F.; Neveling, R.; Smit, F. D.; Swarts, C.

    2014-05-02

    Our experimental goal is to study the non-resonant triple alpha reaction rate at low temperture (T < 10{sup 8} K). The {sup 13}C(p,d) reaction at 66 MeV has been used to probe the alpha-unbound continuum state in {sup 12}C just below the 2{sup nd} 0{sup +} state at 7.65 MeV. The transition strength to the continuum state is predicted to be sensitive to the non-resonant triple alpha reaction rate. The experiment has been performed at iThemba LABS. We report the present status of the experiment.

  18. Pauli-blocking effects in neutron-alpha reactions

    SciTech Connect

    Avrigeanu, M. |; Avrigeanu, V.; Antonov, A.N.; Chadwick, M.B.; Hodgson, P.E.; Stoitsov, M.V.

    1994-06-01

    We present a knockout model for direct (n,{alpha}) reactions in which the residual nucleus is left in a continuum excited state. The interaction of the neutron with a preformed alpha particle inside the nucleus is related to the free neutron-alpha scattering cross-section, with modifications to account for nuclear medium effects, including Fermi motion, Pauli-blocking, and barrier penetration. Phase space restrictions for the four nucleons of the alpha-particle after the knockout are imposed by a Pauli-blocking function. We apply this model, along with evaporation contributions, to analyze excitation functions of (n,{alpha} reactions on {sup 48}Ti, {sup 51}V, {sup 52}Cr, {sup 54}Fe, {sup 55}Mn, and {sup 59}Co. Good agreement is obtained between our calculations and experimental measurements. Values for the local Fermi energy in the region from where knockout occurs indicate a surface reaction.

  19. Benchmarking the External Surrogate Ratio Method using the (alpha,alpha' f) reaction at STARS

    SciTech Connect

    Lesher, S R; Bernstein, L A; Ai, H; Beausang, C W; Bleuel, D; Burke, J T; Clark, R M; Fallon, P; Gibelin, J; Lee, I Y; Lyles, B F; Macchiavelli, A O; McMahan, M A; Moody, K J; Norman, E B; Phair, L; Rodriguez-Vieitez, E; Wiedeking, M

    2008-01-09

    We measured the ratio of the fission probabilities of {sup 234}U* relative to {sup 236}U* formed via an ({alpha},{alpha}{prime}) direct reactions using the STARS array at the 88-inch cyclotron at the Lawrence Berkeley National Laboratory. This ratio has a shape similar to the ratio of neutron capture probabilities from {sup 233}U(n; f) and {sup 235}U(n; f), indicating the alpha reactions likely formed a compound nucleus. This result indicates that the ratios of fission exit channel probabilities for two actinide nuclei populated via ({alpha}, {alpha}{prime}) can be used to determine an unknown fission cross section relative to a known one. The validity of the External Surrogate Ratio Method (ESRM) is tested and the results support the conclusions of Burke et al. [1].

  20. Contribution from 3 alpha-Condensed States to the Triple-Alpha Reaction

    SciTech Connect

    Kato, Kiyoshi; Kurokawa, Chie; Arai, Koji

    2010-06-01

    The alpha-condensed state in nuclear systems has been proposed by Tohsaki et al. and has given rise to interesting discussions. The Hoyle state of {sup 12}C has been studied as the most typical example of such an alpha-condensed state. A new resonant 0{sub 3}{sup +} state (E{sub r} = 1.66 MeV, GAMMA = 1.48 MeV) is predicted as an excited alpha-condensed state in addition to the second 0{sup +} state of the Hoyle state by calculations of the 3 alpha orthogonality condition model (3 alpha OCM) using the complex scaling method. Based on this result, the breakup strengths of the inversion reaction for sequential ({sup 8}Be+alpha->{sup 12}C+gamma) and direct (alpha+alpha+alpha->{sup 12}C+gamma) processes are calculated. It is discussed that a large reaction strength calculated recently by Ogata et al. in non-resonant energies is considered as a contribution from the excited 0{sub 3}{sup +} state.

  1. Enantioselective reactions of donor/acceptor carbenoids derived from alpha-aryl-alpha-diazoketones.

    PubMed

    Denton, Justin R; Davies, Huw M L

    2009-02-19

    The reaction of a variety of alpha-aryl-alpha-diazo ketones with activated olefins, catalyzed by the adamantyl glycine-derived dirhodium complex Rh(2)(S-PTAD)(4), generates cyclopropyl ketones with high diastereoselectivity (up to >95:5 dr) and enantioselectivity (up to 98% ee). Intermolecular C-H functionalization of 1,4-cyclohexadiene by means of carbenoid-induced C-H insertion was also possible with this type of carbenoid.

  2. Plans for Studies of (alpha,n) Reactions Relevant to Astrophysics via Inverse Reactions

    NASA Astrophysics Data System (ADS)

    Shima, T.; Nagai, Y.; Kii, T.; Kikuchi, T.; Baba, T.; Kobayashi, T.; Okazaki, F.

    1996-08-01

    (alpha,n) reactions in the keV energy region play important roles in astrophysical nucleosynthesis. In the primordial nucleosynthesis, it has been pointed out that a fluctuation of the baryon density distribution could be formed if the QCD phase transition from quark-gluon plasma to hadron gas occurred by first order. In that case the space was separated into the high density proton-rich zones and the low density neutron-rich ones, and in the neutron-rich zones nucleosynthesis could proceed beyond the mass gap at A = 8 via the reaction chains such as H-1(n,gamma)H-2(n,gamma)H-3(d,n)He-4(t,gamma)Li-7(n,gamma)Li-8(alpha,n)B- 11(n,ga mma)B-12(e(sup-)nu)C-12(n,gamma)C-13(n,gamma)C-14(n,gamma)C-15 ......, and so on. In the above nuclear reactions, the Li-8(alpha,n)B reaction plays quite a crucial role, because it can break through the mass gap at A = 8. (alpha,n) reactions of some light nuclei are also important as neutron sources for slow neutron capture process (s-process) of nucleosynthesis in stars. In low-mass and intermediate-mass (M < 10 Solar Mass) stars, neutrons are supposed to be supplied mainly by the C-13(alpha,n)O-16 reaction. On the other hand, the Ne-22(alpha,n)Mg-25 reaction is a candidate of the neutron source in massive stars with M > or = 10 Solar Mass. The contribution of the O-18(alpha,n)Ne-21 reaction to s-process in massive stars is still unknown. Since the temperatures of the above astrophysical sites correspond to the energy range of between a few ten and a few hundred keV, accurate data of the (alpha,n) reaction cross sections in the energy range are required for investigating nucleosynthesis. In order to measure these cross sections, not only direct (alpha,n) reactions but also inverse (n,alpha) reactions can be studied. In the following we would like to show experimental designs for studying several (alpha,n) reactions of astrophysical importance.

  3. Faddeev Three-body Calculation of Triple-Alpha Reaction

    NASA Astrophysics Data System (ADS)

    Ishikawa, Souichi

    2013-03-01

    The triple-alpha (3 α) process, in which three 4He nuclei are transformed into a 12C nucleus, is studied in terms of a three-alpha (3- α) model. The reaction rate of the process is calculated via an inverse process, 3- α photodisintegration of a 12C nucleus. Both of 3- α bound and -continuum states are calculated by a Faddeev method with accommodating the long range Coulomb interaction. Results of the 3 α reaction rate are about 103 times larger than a standard rate from the Nuclear Astrophysics Compilation of Reaction Rates (NACRE) at a low temperature ( T = 107 K), which means our results are remarkably smaller than recent three-body calculations by the method of continuum-discretized coupled-channel.

  4. Excitation functions of 125Te(p, xn)-reactions from their respective thresholds up to 100 MeV with special reference to the production of 124I.

    PubMed

    Hohn, A; Nortier, F M; Scholten, B; van der Walt, T N; Coenen, H H; Qaim, S M

    2001-08-01

    Excitation functions of the nuclear reactions 125Te(p, xn) (119,120m, 120g, 121,122,123,124,125)I were measured for the first time from their respective thresholds up to 100 MeV using the stacked-foil technique. Thin samples were prepared by electrolytic deposition of 98.3% enriched 125Te on Ti-backing. In addition to experimental studies, excitation functions were calculated by the modified hybrid model code ALICE-IPPE. The experimental and theoretical data generally showed good agreement. From the measured cross section data, integral yields of (123,124,125)I were calculated. The energy range Ep 21 --> 15 MeV appears to be very suitable for the production of the medically interesting radionuclide 124I (T(1/2) = 4.18 d; I(beta)+ = 25%). The thick target yield of 124I amounts to 81 MBq/microA h and the level of 125I-impurity to 0.9%. The 125Te(p,2n)124I reaction gives 124I yield about four times higher than the commonly used 124Te(p,n)124I and 124Te(d,2n)124I reactions. The proposed production energy range is too high for small cyclotrons but large quantities of 124I can be produced with medium-sized commercial machines.

  5. Excitation functions of 124Te(d,xn)124,125I reactions from threshold up to 14 MeV: comparative evaluation of nuclear routes for the production of 124I.

    PubMed

    Bastian, T H; Coenen, H H; Qaim, S M

    2001-09-01

    Excitation functions of the nuclear reactions 124Te(d,xn)124-125I were measured from their respective thresholds up to 14.0 MeV via the stacked-foil technique. Thin samples were prepared by electrolytic deposition of 99.8% enriched 124Te on Ti-backing. The excitation function of the 124Te(d,n)125I reaction was measured for the first time. The present data for the 124Te(d,2n)124I reaction are by an order of magnitude higher than the literature experimental data but are in good agreement with the results of a hybrid model calculation. From the measured cross sections, integral yields of 124,125I were calculated. The energy range Ed = 14 --> 10 MeV appears to be the best compromise between 124I-yield and 1251-impurity. The calculated 124I-yield amounts to 17.5 MBq/microA h and the 125I-impurity to 1.7%. A critical evaluation of the three nuclear routes for the production of 124I, viz. 124Te(d,2n)-, 124Te(p,n)- and 125Te(p,2n)-processes, is given. The reaction studied in this work proved to be least suitable. The 124Te(p,n)-reaction gives 124I of the highest radionuclidic purity, and a small-sized cyclotron is adequate for production purposes. The 125Te(p,2n)-reaction is more suitable at a medium-sized cyclotron: the yield of 124I is four times higher than in the other two reactions but the level of 0.9% 125I-impurity is relatively high.

  6. Li production in alpha-alpha reactions. [relation to gamma ray observation

    NASA Technical Reports Server (NTRS)

    Kozlovsky, B.; Ramaty, R.

    1974-01-01

    The cross section for Li-7 production in alpha-alpha reactions is shown to be increased by about a factor of 2 due to the excitation levels of Li-7 and Be-7 at 478 keV and 431 keV, respectively. The cross section for Li-6 production, however, remains the same as calculated on the basis of the detailed balance principle. The lines at 478 keV and 431 keV may link Li-7 production to feasible gamma-ray observations.

  7. Synthesis of rutherfordium isotopes in the 238U(26Mg, xn)264-xRf reaction and study of their decay properties

    SciTech Connect

    Gates, Jacklyn M; Gates, J.M.; Garcia, M.A.; Gregorich, K.E.; Dullmann, Ch.E.; Dragojevic, I.; Dvorak, J.; Eichler, R.; Folden III, C.M.; Loveland, W.; Nelson, S.L.; Pang, G.K.; Stavsetra, L.; Sudowe, R.; Turler, A.; Nitsche, H.

    2008-01-15

    Isotopes of rutherfordium (258-261Rf) were produced in irradiations of 238U targets with 26Mg beams. Excitation functions were measured for the 4n, 5n and 6n exit channels. Production of 261Rf in the 3n exit channel with a cross section of 28+92-26 pb was observed. Alpha decay of 258Rf was observed for the first time with an alpha-particle energy of 9.05+-0.03 MeV and an alpha/total decay branching ratio of 0.31+-0.11. In 259Rf, the electron capture/total decay branching ratio was measured to be 0.15+-0.04. The measured half-lives for 258Rf, 259Rf and 260Rf were 14.7+1.2-1.0 ms, 2.5+0.4-0.3 s and 22.2+3.0-2.4 ms, respectively, in agreement with literature data. The systematics of the alpha decay Q values and of the partial spontaneous fission half-lives were evaluated for even-even nuclides in the region of the N = 152, Z = 100 deformed shell. The influence of the N = 152 shell on the alpha decay Q values for rutherfordium was observed to be similar to that of the lighter elements (96<_ Z<_ 102). However, the N = 152 shell does not stabilize the rutherfordium isotopes against spontaneous fission, as it does in the lighter elements (96<_ Z<_102).

  8. Measurements and analysis of alpha-induced reactions of importance for nuclear astrophysics

    NASA Astrophysics Data System (ADS)

    de Messieres, Genevieve Escande

    2011-11-01

    Reactions during stellar helium burning are of primary importance for understanding nucleosynthesis. A detailed understanding of the critical reaction chain 4He(2alpha, gamma)12C( alpha, gamma)16O(alpha, gamma) 20Ne is necessary both because it is the primary energy source and because it determines the ratio of 12C to 16O produced, which in turn significantly effects subsequent nucleosynthesis. Also during Helium burning, the reactions 22Ne(alpha, n)25Mg and 22Ne(alpha, gamma )26Mg are crucial in determining the amount of neutrons available for the astrophysical s-process. This thesis presents new experimental results concerning the 16O(alpha, gamma) 20Ne, 22Ne(alpha, n)25Mg, and 22Ne(alpha, gamma)26Mg reaction rates. These results are then applied to the calculation of the associated stellar reaction rates in order to achieve better accuracy.

  9. Triple-{alpha} reaction rate constrained by stellar evolution models

    SciTech Connect

    Suda, Takuma; Hirschi, Raphael; Fujimoto, Masayuki Y.

    2012-11-12

    We investigate the quantitative constraint on the triple-{alpha} reaction rate based on stellar evolution theory, motivated by the recent significant revision of the rate proposed by nuclear physics calculations. Targeted stellar models were computed in order to investigate the impact of that rate in the mass range of 0.8{<=}M/M{sub Circled-Dot-Operator }{<=}25 and in the metallicity range between Z= 0 and Z= 0.02. The revised rate has a significant impact on the evolution of low-and intermediate-mass stars, while its influence on the evolution of massive stars (M > 10M{sub Circled-Dot-Operator }) is minimal. We find that employing the revised rate suppresses helium shell flashes on AGB phase for stars in the initial mass range 0.8{<=}M/M{sub Circled-Dot-Operator }{<=}6, which is contradictory to what is observed. The absence of helium shell flashes is due to the weak temperature dependence of the revised triple-{alpha} reaction cross section at the temperature involved. In our models, it is suggested that the temperature dependence of the cross section should have at least {nu} > 10 at T = 1-1.2 Multiplication-Sign 10{sup 8}K where the cross section is proportional to T{sup {nu}}. We also derive the helium ignition curve to estimate the maximum cross section to retain the low-mass first red giants. The semi-analytically derived ignition curves suggest that the reaction rate should be less than {approx} 10{sup -29} cm{sup 6} s{sup -1} mole{sup -2} at Almost-Equal-To 10{sup 7.8} K, which corresponds to about three orders of magnitude larger than that of the NACRE compilation.

  10. STELLAR EVOLUTION CONSTRAINTS ON THE TRIPLE-{alpha} REACTION RATE

    SciTech Connect

    Suda, Takuma; Fujimoto, Masayuki Y.; Hirschi, Raphael

    2011-11-01

    We investigate the quantitative constraint on the triple-{alpha} reaction rate based on stellar evolution theory, motivated by the recent significant revision of the rate proposed by nuclear physics calculations. Targeted stellar models were computed in order to investigate the impact of that rate in the mass range of 0.8 {<=} M/M{sub sun} {<=} 25 and in the metallicity range between Z = 0 and Z = 0.02. The revised rate has a significant impact on the evolution of low- and intermediate-mass stars, while its influence on the evolution of massive stars (M {approx}> 10 M{sub sun}) is minimal. We find that employing the revised rate suppresses helium shell flashes on asymptotic giant branch phase for stars in the initial mass range 0.8 {<=} M/M{sub sun} {<=} 6, which is contradictory to what is observed. The absence of helium shell flashes is due to the weak temperature dependence of the revised triple-{alpha} reaction cross section at the temperature involved. In our models, it is suggested that the temperature dependence of the cross section should have at least {nu} > 10 at T = (1-1.2) Multiplication-Sign 10{sup 8} K where the cross section is proportional to T {sup {nu}}. We also derive the helium ignition curve to estimate the maximum cross section to retain the low-mass first red giants. The semi-analytically derived ignition curves suggest that the reaction rate should be less than {approx}10{sup -29} cm{sup 6} s{sup -1} mole{sup -2} at Almost-Equal-To 10{sup 7.8} K, which corresponds to about three orders of magnitude larger than that of the NACRE compilation. In an effort to compromise with the revised rates, we calculate and analyze models with enhanced CNO cycle reaction rates to increase the maximum luminosity of the first giant branch. However, it is impossible to reach the typical red giant branch tip luminosity even if all the reaction rates related to CNO cycles are enhanced by more than 10 orders of magnitude.

  11. Triple-alpha reaction rate studied with the Faddeev three-body formalism

    SciTech Connect

    Ishikawa, Souichi

    2012-11-12

    The triple-alpha (3{alpha}) reaction, {sup 4}He+{sup 4}He+{sup 4}He{yields}{sup 12}C+{gamma}, which plays a significant role in the stellar evolution scenarios, is studied in terms of a three-alpha (3-{alpha}) model. The reaction rate of the process is calculated via an inverse process, 3-{alpha} photodisintegration of a {sup 12}C nucleus. Both of 3-{alpha} bound and-continuum states are calculated by a Faddeev method with accommodating the long range Coulomb interaction. With being adjusted to the empirical E2-strength for {sup 12}C(0{sub 2}{sup +}){yields}{sup 12}C(2{sub 1}{sup +}) transition, results of the 3{alpha} reaction rate <{alpha}{alpha}{alpha}> at higher temperature (T > 10{sup 8} K), where the reaction proceeds mainly through the {sup 8}Be and {sup 12}C(0{sub 2}{sup +}) resonant states, almost agree with those of the Nuclear Astrophysics Compilation of Reaction Rates (NACRE). On the other hand, calculated values of <{alpha}{alpha}{alpha}> are about 10{sup 3} times larger than the NACRE rate at a low temperature (T= 10{sup 7} K), which means our results are remarkably smaller than recent CDCC results.

  12. Experimental Study of the Cross Sections of {alpha}-Particle Induced Reactions on 209Bi

    SciTech Connect

    Hermanne, A.; Tarkanyi, F.; Takacs, S.; Szucs, Z.

    2005-05-24

    Alpha particle induced reactions for generation of 211At used in therapeutic nuclear medicine and possible contaminants were investigated with the stacked foil activation technique on natural bismuth targets up to E{alpha}=39 MeV. Excitation functions for the reactions 209Bi({alpha},2n)211At, 209Bi({alpha},3n)210At, 209Bi({alpha},x) 210Po obtained from direct alpha emission measurements and gamma spectra from decay products are compared with earlier literature values. Thick target yields have been deduced from the experimental cross sections.

  13. Quantum three-body calculation of nonresonant triple-{alpha} reaction rate at low temperatures

    SciTech Connect

    Ogata, Kazuyuki; Kan, Masataka; Kamimura, Masayasu

    2010-08-12

    Triple-{alpha} reaction rate is re-evaluated by directly solving the three-body Schroedinger equation. The resonant and nonresonant processes are treated on the same footing using the continuum-discretized coupled-channels method for three-body scattering. An accurate description of the {alpha}-{alpha} nonresonant states significantly quenches the Coulomb barrier between the first two {alpha}-particles and the third {alpha}-particle. Consequently, the{alpha}-{alpha} nonresonant continuum states give a markedly larger contribution at low temperatures than that reported in previous studies. We show that Nomoto's method for three-body nonresonant capture processes, which is adopted in the NACRE compilation and many other studies, is a crude approximation of the accurate quantum three-body model calculation. We find an increase in triple-{alpha} reaction rate by about 20 orders of magnitude around 10{sup 7} K compared with the rate of NACRE.

  14. Quantum three-body calculation of nonresonant triple-alpha reaction rate at low temperatures

    SciTech Connect

    Ogata, Kazuyuki; Kan, Masataka; Kamimura, Masayasu

    2010-06-01

    Triple-alpha reaction rate is re-evaluated by directly solving the three-body Schroedinger equation. The resonant and nonresonant processes are treated on the same footing using the continuum-discretized coupled-channels method for three-body scattering. An accurate description of the alpha-alpha nonresonant states significantly quenches the Coulomb barrier between the first two alpha-particles and the third alpha-particle. Consequently, the alpha-alpha nonresonant continuum states give a markedly larger contribution at low temperatures than that reported in previous studies. We show that Nomoto's method for three-body nonresonant capture processes, which is adopted in the NACRE compilation and many other studies, is a crude approximation of the accurate quantum three-body model calculation. We find an increase in triple-alpha reaction rate by 26 orders of magnitude around 10{sup 7} K compared with the rate of NACRE.

  15. The Consolidated Fleet XN2Y-1

    NASA Technical Reports Server (NTRS)

    1935-01-01

    The Consolidated Fleet XN2Y-1 was a Fleet 1 trainer purchased by the Navy for evaluation. The purchase of several N2Y-1 aircraft followed, for use as trainers for the pilots who would fly the 'parasite' fighters attached to the airships Akron and Macon. The XN2Y-1 was turned over to the NACA for research work. Note the that vertical surfaces are instrumented for NACA spin work.

  16. Alpha-induced reaction studies using low-energy RI beams at CRIB

    SciTech Connect

    Yamaguchi, H.; Kahl, D.; Hu, J.; Kubono, S.; Hayakawa, S.; Hashimoto, T.

    2012-11-12

    CRIB (CNS Radioactive Ion Beam separator) is a low-energy RI beam separator at the Center for Nuclear Study (CNS) of the University of Tokyo. Studies on proton and alpha resonance scatterings, ({alpha}, p) reactions, and other types of measurements ({beta}-decay lifetimes etc.) have been performed using RI beams at CRIB, motivated by interests on astrophysical reactions and exotic nuclear structure. Among the studies at CRIB, the measurement of {sup 7}Li+{alpha}/{sup 7}Be+{alpha} resonant scatterings are presented.

  17. Reactions of. cap alpha. -oxides in the presence of hexamethylenetetramine and glycerine diphenyl ether

    SciTech Connect

    Nikolaev, P.V.; Sveshnikova, N.F.; Ignatov, V.A.

    1987-11-20

    Hexamethylenetetramine (HMTA) is widely used as a catalyst for the condensation and hardening of compositions based on epoxide oligomer. To provide objective information about the reaction scheme and the kinetics of reactions in which epoxide oligomers participate we studied a model reaction system. The model epoxide oligomer selected was phenyl glycidyl ether (PGE) and the ..cap alpha..,..gamma..-diphenyl ether of glycerine (GDPE). The reference substances in the differential thermal analysis were magnesium oxide, aluminum oxide, and GDPE. Monitoring of the progress of the isothermal reaction was effected by determining the ..cap alpha..-oxide group mercurimetrically. The concentration of HMTA was determined iodometrically.

  18. Probable new type of reaction mechanism: Double. cap alpha. direct transfer process

    SciTech Connect

    Xu Shu-wei; Wu Guo-hua; Miao Rong-zhi; Han Fei

    1983-10-01

    It is assumed that /sup 8/Be consists of two ..cap alpha.. particles which are close to each other in configuration space. A spectroscopic density of /sup 8/Be cluster in the residue nuclei is then obtained, which is proportional to the square of the preformation probability of ..cap alpha.. particle at nuclear surface. Using the improved method of parametrization of EFR-DWBA overlap integral,/sup 1//sup en-dash//sup 2/ we calculate the double differential energy spectra and angular distributions of ..cap alpha.. particles for the reactions /sup 209/Bi (/sup 12/C, ..cap alpha..) /sup 217/Fr and extract the preformation probability of ..cap alpha.. particle at the surface of /sup 217/Fr nuclei from fitting the experimental data. The agreement within the range of calculation error between the preformation probabilities extracted from transfer reactions and ..cap alpha.. decay suggests that the reaction /sup 209/Bi(/sup 12/C, ..cap alpha..) /sup 217/Fr may be explained as a double ..cap alpha.. direct transfer process.

  19. Population of mixed-symmetry states via {alpha} transfer reactions

    SciTech Connect

    Alonso, C. E.; Arias, J. M.; Fortunato, L.; Vitturi, A.; Pietralla, N.

    2008-07-15

    Within the neutron-proton interacting boson model we study the population of mixed-symmetry states via {alpha} transfer processes. Closed expressions are deduced in the case of the limiting U{sub {pi}}{sub +{nu}}(5) and SU{sub {pi}}{sub +{nu}}(3). We find that the population of the lowest mixed-symmetry 2{sup +} state, vanishing along the N{sub {pi}}=N{sub {nu}} line, depends on the number of active bosons and is normally smaller than that of the lowest full symmetric 2{sup +} state. In particular, for deformed nuclei where the number of bosons is normally large, the relative population of the mixed-symmetry 2{sup +} state is of the order of a few percent. More favorable cases can be found near shell closures, as in the case of {alpha} transfer leading to {sup 140}Ba.

  20. Thick target measurement of the 40Ca(alpha,gamma)44Ti reaction rate

    SciTech Connect

    Sheets, S A; Burke, J T; Scielzo, N D; Phair, L; Bleuel, D; Norman, E B; Grant, P G; Hurst, A M; Tumey, S; Brown, T A; Stoyer, M

    2009-02-06

    The thick-target yield for the {sup 40}Ca({alpha},{gamma}){sup 44}Ti reaction has been measured for E{sub beam} = 4.13, 4.54, and 5.36 MeV using both an activation measurement and online {gamma}-ray spectroscopy. The results of the two measurements agree. From the measured yield a reaction rate is deduced that is smaller than statistical model calculations. This implies a smaller {sup 44}Ti production in supernova compared to recently measured {sup 40}Ca({alpha},{gamma}){sup 44}Ti reaction rates.

  1. Nuclear reactions induced by high-energy alpha particles

    NASA Technical Reports Server (NTRS)

    Shen, B. S. P.

    1974-01-01

    Experimental and theoretical studies of nuclear reactions induced by high energy protons and heavier ions are included. Fundamental data needed in the shielding, dosimetry, and radiobiology of high energy particles produced by accelerators were generated, along with data on cosmic ray interaction with matter. The mechanism of high energy nucleon-nucleus reactions is also examined, especially for light target nuclei of mass number comparable to that of biological tissue.

  2. Tumor necrosis factor-alpha release during systemic reaction in cold urticaria.

    PubMed

    Tillie-Leblond, I; Gosset, P; Janin, A; Dalenne, R; Joseph, M; Wallaert, B; Tonnel, A B

    1994-02-01

    Primary cold urticaria (PCU) characterized by the association of urticaria, angioedema, and sometimes a shock-like reaction after cold exposure, is usually considered to be linked with histamine and prostaglandin D2 release by mast cells. To determine the involvement of cytokines, we studied the release of tumor necrosis factor-alpha (TNF-alpha) in the blood of the efferent vein after immersion of the hand in chilled water. Five patients with PCU were compared with a control population (three patients with nonphysical urticaria and three healthy subjects). Among patients with PCU who underwent the cold immersion test, two exhibited a shock-like reaction with a large urticarial plaque (patients 1 and 2), one had only a mild cutaneous reaction, and two had no reaction. Patient 1 was reevaluated after 6 months of treatment with H1 and H2 antihistamines: he did not respond to this challenge. All controls were strictly negative. Histamine was released within the first minute after the challenge in the three patients with PCU, but at a higher level for the two patients who had a systemic reaction. TNF-alpha was undetectable in the blood of the patient with only a mild cutaneous reaction, whereas TNF-alpha release was observed for the two patients with a systemic reaction, 2 and 6 minutes after the end of the cold immersion test. The two other patients and the control subjects released neither histamine nor TNF-alpha. In parallel, pathologic and immunohistochemical (with a rabbit anti-TNF-alpha antibody) studies were performed on skin biopsy specimens collected 10 minutes after ice-cube test.(ABSTRACT TRUNCATED AT 250 WORDS)

  3. Imaginary time approach for reaction rate of triple-alpha process

    NASA Astrophysics Data System (ADS)

    Yabana, Kazuhiro; Akahori, Takahiko; Funaki, Yasuro

    2014-09-01

    We propose a new theoretical approach for the radiative capture reaction rate, which we call the imaginary-time theory. In the theory, inverse temperature is identified with the temperature. Since reaction rates can be calculated without solving any scattering problem in the theory, it is ideally suited for the triple-alpha process in which scattering problem of three charged particles has caused difficulties. Using the imaginary-time theory, we obtain the triple-alpha reaction rate in the quantum three-body model treating alpha particles as structureless point particles. The calculated rate is almost identical to the standard NACRE rate. We have also found that the reaction mechanism of the triple-alpha process changes at exactly the same temperatures as those in empirical theories. We may show that it is possible to derive an analytical formula close to that of the NACRE rate, if we introduce some assumptions in the three-body model. We demonstrate that, if we introduce a coupled-channel expansion with a truncation, reaction rate is substantially overestimated. This finding may help to explain the very different reaction rates obtained so far using different theoretical approaches.

  4. Isomeric cross-section ratio for the formation of 58Com,g in neutron, proton, deuteron, and alpha-particle induced reactions in the energy region up to 25 MeV

    NASA Astrophysics Data System (ADS)

    Sudár, S.; Qaim, S. M.

    1996-06-01

    Excitation functions were determined for 58Fe(p,n)58Com, natFe(d,xn)58Com, 55Mn(α,n)58Com, and 59Co(n,2n)58Com reactions from the respective thresholds to 14.12 MeV in work with protons, 12.97 MeV with deuterons, 13 MeV with neutrons, and 25.52 MeV with alpha particles. The radioactivity of the activation product 58Com(T1/2=9.15 h) was determined by high resolution γ-ray and x-ray spectrometry. Using the present σm results and the (σm+σg) data reported earlier, the isomeric cross-section ratio σm/(σm+σg) was determined for each reaction. Statistical model calculations taking into account the precompound effects were performed for the above-mentioned four reactions as well as for the 58Ni(n,p)58Com,g process. A consistent set of model parameters was used. The isomeric cross-section ratio for the pair 58Com,g strongly depends on the level scheme and branching ratios of the known levels of 58Co. Different reactions produced different angular momentum distributions of the compound nucleus, resulting in different isomeric cross-section ratio at the same excitation of the compound nucleus. The ratio was found to be relatively high for target nuclei with high spin values.

  5. [Development of highly stereoselective reactions utilizing heteroatoms--asymmetric synthesis of alpha-substituted serines].

    PubMed

    Sano, S

    2000-01-01

    This article reviews the efficient methods for diastereoselective and enantioselective syntheses of alpha-substituted serines. A newly designed bislactim ether, ethyl (5S)- or (5R)-3,6-diethoxy-2,5-dihydro-5-isopropyl-2-pyrazinecarboxylate, was treated with base or Lewis acid-tertiary amine to generate an enolate or enaminate (imine anion, metalloenamine). Alkylation or aldol-type reaction with the resultant enolate or enaminate proceeded in a highly diastereoselective manner to give the corresponding alkylated or aldol products, respectively. Reduction of these products with diisobutylaluminum hydride (DIBAL) followed by hydrolysis with hydrochloric acid afforded the desirable alpha-substituted serines. The enantioselective aldol-type reaction of an achiral bislactim ether, ethyl 3,6-diethoxy-2,5-dihydro-2-pyrazinecarboxylate, was also investigated by employing Sn(OSO2CF3)2-triethylamine in the presence of an external chiral ligand, (--)-sparteine. Not only a stoichiometric amount, but also a catalytic amount of (--)-sparteine promoted the highly enantioselective aldol-type reactions. Interestingly, the stereoselective outcome of the Sn(II)-mediated reaction differed from that of the Mg(II)-mediated one in the aldol-type reaction of the bislactim ethers with aliphatic aldehydes. On the other hand, chemoenzymatic synthesis of enantiomerically pure alpha-substituted serines must also be a convenient and useful procedure. Porcine liver esterase (PLE) or rabbit liver esterase (RLE) catalyzed hydrolysis of the pro-S ester group of diethyl alpha-alkyl-alpha-(benzyloxycarbonylamino)malonates to afford (R)-ethyl alpha-alkyl-alpha-(benzyloxycarbonylamino)malonates each in excellent enantiomeric excess. Enantiodivergent reductions of these acid esters readily proceeded to furnish both the corresponding enantiomeric alpha-substituted serines. Finally, the application of these methodologies mentioned above to a total synthesis of ISP-I (a potent immunosuppressive principle in

  6. Three-body calculation of triple-alpha reaction at low energies

    NASA Astrophysics Data System (ADS)

    Ishikawa, Souichi

    2011-09-01

    The reaction rate of the triple-alpha (3α) process at low temperatures, where resonant reaction is not dominant, is calculated through the inverse process, the photodisintegration of a 12C nucleus. For this, Schrödinger equations in a three-alpha (3-α) model of 12C are directly solved by a Faddeev method, which has been successfully applied to three-nucleon problem so far. The nuclear Hamiltonian consists of an α-α potential, which reproduces the 8Be resonance state, together with three-body potentials to reproduce 12C properties. Our results of the 3α reaction rate are about 103 times larger at low temperature (T = 107 K) than a standard rate from the Nuclear Astrophysics Compilation of Reaction Rates (NACRE), which means our results are remarkably smaller than recent results of quantum-mechanical three-body calculations by Ogata et al.

  7. Reaction cross sections of intermediate energy {alpha} particles within a relativistic optical model

    SciTech Connect

    Ait-Tahar, S.; Nedjadi, Y.

    1995-07-01

    The suggestion made recently by H. Abele {ital et} {ital al}. that relativistic effects in the interaction of alpha particles with various nuclei at intermediate energies may remove the existing discrepancy between the theoretical predictions and the experimental data for the reaction cross section is investigated. We use a relativistic model based on the Kemmer-Duffin-Petiau equation and find that relativistic effects do not lead to a reduction in the reaction cross section within the present approach. Alternative explanations are discussed.

  8. Reaction of. cap alpha. ,. cap alpha. , omega-trihydroperfluoroalkanols with phosphorus tribromide

    SciTech Connect

    Krolevets, A.A.; Ragulin, L.I.; Shevchenko, V.I.; Lyubimova, E.I.

    1986-08-20

    The authors investigate the bromination and phosphorylation of the title alkanol by phosphorus tribromide and determine the structure and composition of the resulting phosphorus and bromine compounds using IR and NMR spectroscopy with phosphorus 31, fluorine 19, and hydrogen 1. An extensive analysis of chemical shifts and spin-spin coupling constants is performed. The reaction of fluorine-containing trialkyl phosphites with sulfuric acid anhydride was found to lead to the formation of the corresponding fluorinated trialkyl phosphates in a quantitative yield.

  9. Alpha-decay of light protactinium isotopes

    SciTech Connect

    Faestermann, T.; Gillitzer, A.; Hartel, K.; Henning, W.; Kienle, P.

    1987-12-10

    Light protactinium isotopes have been produced with /sup 204/Pb (/sup 19/F,xn) reactions. ..cap alpha..-activities with E/sub ..cap alpha../ = 9.90(5) MeV, T/sub 1/2/ = 53(10) ns and E/sub ..cap alpha../ = 9.65(5) MeV, T/sub 1/2/ = 0.78(16) ..mu..s could be attributed to the previously unobserved nuclei /sup 219/Pa and /sup 220/Pa with the help of excitation functions. The peak cross sections for the 4n and 3n evaporation channels are on the order of 10 ..mu..b. The decay energies as well as the halflives fit well into the systematics of these nuclei close to the magic neutron number N = 126. /sup 219/Pa is the shortest lived nuclide known with directly measured halflife.

  10. Zeolite-directed cascade reactions: cycliacyarylation versus decarboxyarylation of alpha,beta-unsaturated carboxylic acids.

    PubMed

    Chassaing, Stefan; Kumarraja, Mayilvasagam; Pale, Patrick; Sommer, Jean

    2007-09-27

    The interaction of alpha,beta-unsaturated carboxylic acids with benzene derivatives was investigated in H-zeolites and led to two distinct but competing processes, cycliacyarylation and decarboxyarylation. Interestingly, H-USY selectively induced the cycliacyarylation cascade reaction, whereas H-ZSM5 selectively promoted the decarboxyarylation cascade.

  11. Lost alpha-particle diagnostics from a D-T plasma by using nuclear reactions

    SciTech Connect

    Sasao, Mamiko; Wada, Motoi; Isobe, Mitsutaka

    2014-08-21

    Among various methods proposed for alpha-particles loss measurement, we studied on those by measuring gamma rays of three cases, from (1) nuclear reactions induced by alpha particles, (2) those from short-life-time activities and (3) those from long-life-time activities induced by alpha particles. The time evolution of local alpha flux may possibly be measured by using the {sup 9}Be (a, n) {sup 12}C reaction (1). Using the same system, but with a target set up close to the first wall, activation measurement on site right after turning-off the discharge is possible (2). Nuclear reaction, {sup 25}Mg (a, p) {sup 28}Al, that produce radioisotopes of short lifetime of 2.2 minutes in one of the best candidates. As to the activation to a long lifetime (3), it is predicted that the gamma ray yield from {sup 19}F (a, n) {sup 22}Na reaction is enough for the measurement at the reactor site.

  12. Synthesis of pyrroles by consecutive multicomponent reaction/[4 + 1] cycloaddition of alpha-iminonitriles with isocyanides.

    PubMed

    Fontaine, Patrice; Masson, Géraldine; Zhu, Jieping

    2009-04-02

    [4 + 1] Cycloaddition of alpha,beta-unsaturated imidoyl cyanide (2-cyano-1-azadienes) with isocyanides in the presence of a catalytic amount of AlCl(3) afforded polysubstituted 2-amino-5-cyanopyrroles in good to excellent yields. In combination with the IBX/TBAB-mediated oxidative Strecker reaction, this important heterocycle is readily synthesized in two steps from simple starting materials.

  13. {alpha}-cluster states in {sup 38}Ar observed via the {sup 34}S({sup 7}Li,t{alpha}){sup 34}S reaction

    SciTech Connect

    Fukada, M.; Ohmura, M.; Harima, F.; Ogino, K.; Takimoto, K.; Ohkubo, S.

    2005-06-01

    To study the {alpha}-cluster states in the {sup 38}Ar nucleus, angular correlation functions between t and {alpha} in the {sup 34}S({sup 7}Li, t{alpha}){sup 38}Ar reaction have been measured. Seven states at 10.2, 10.8, 11.4, 12.2, 12.7, 14.3, and 15.0 MeV were newly observed.

  14. Study of the 30P({alpha},p){sup 33}S reaction using a gas-filled magnetic spectrograph

    SciTech Connect

    Figueira, J. M.; Deibel, C. M.; Fernandez Niello, J. O.; Greene, J.; Jiang, C. L.; Lee, H. Y.; Pardo, R. C.; Rehm, K. E.; Ugalde, C.; Zinkann, G.; Marley, S. T.; Patel, N.; Paul, M.

    2010-08-04

    We have developed a technique using a gas-filled magnetic spectrograph which enables us to study ({alpha},p) transfer reactions of astrophysical interest in inverse kinematics and by means of the time-inverse reactions. We present preliminary experimental results of the reaction {sup 30}P({alpha},p){sup 33}S which confirm that the technique permits the study of these kinds of transfer reactions.

  15. 15O(alpha,gamma)19Ne breakout reaction and impact on X-ray bursts.

    PubMed

    Tan, W P; Fisker, J L; Görres, J; Couder, M; Wiescher, M

    2007-06-15

    The breakout reaction 15O(alpha,gamma)19Ne, which regulates the flow between the hot CNO cycle and the rp process, is critical for the explanation of the burst amplitude and periodicity of x-ray bursters. We report on the first successful measurement of the critical alpha-decay branching ratios of relevant states in 19Ne populated via 19F(3He,t)19Ne. Based on the experimental results and our previous lifetime measurements of these states, we derive the first experimental rate of 15O(alpha,gamma)19Ne. The impact of our experimental results on the burst pattern and periodicity for a range of accretion rates is analyzed.

  16. Investigation of the triple-alpha reaction in a full three-body approach

    NASA Astrophysics Data System (ADS)

    Nguyen, Ngoc Bich

    We have developed a new three-body method to compute the triple-alpha reaction rate at low temperatures where measurements are impossible and many numerical attempts have failed before. In this work, the triple-alpha is modeled as a three-body Borromean system in hyperspherical harmonics coordinates. In the low temperature region, the triple-alpha proceeds through a quadrupole transition from the 0+ continuum to the 2+1 bound state in 12C. The 2+1 bound state is obtained by solving a set of coupled channels equations in hyper-radius coordinates for negative energy with a boundary condition that requires the wavefunction to go to zero at large distances. The same approach can not be applied to the 0+ continuum state because it requires an exact boundary condition for the three charged particles. We therefore combine the R-matrix expansion, the R-matrix propagation method, and the screening technique in the hyperspherical harmonics basis to obtain a numerically stable three-body continuum wavefunction for the alpha + alpha + alpha system. We employ the Ali-Bodmer potential for the alpha-alpha interaction which reproduces the low energy phase shifts as well as the 0+ resonance of 8Be. We add a three-body force to fit experimental data. Both the 2+1 bound state and the 0+2 resonant state in 12C are well reproduced in our framework. We find a dominant triangle three-alpha configuration for the Hoyle resonance by studying the density distribution function. The resonant and non-resonant continuum states of 12C(0+) are obtained simultaneously, allowing us to include these two processes on the same footing. Long range Coulomb interactions show important effects especially in the low temperature regime. We also present a detailed convergence study of the triple-alpha reaction rate with respect to the screening radius and the size of the model space. The new rate agrees with the NACRE rate for temperatures greater than 0.07 GK, but a large enhancement at lower temperatures is

  17. Alpha'-hydroxyenones as mechanistic probes and scope-expanding surrogates for alpha,beta-unsaturated aldehydes in N-heterocyclic carbene-catalyzed reactions.

    PubMed

    Chiang, Pei-Chen; Rommel, Michael; Bode, Jeffrey W

    2009-06-24

    N-heterocyclic carbene-catalyzed reactions of alpha,beta-unsaturated aldehydes and a variety of electrophiles allow the facile preparation of a diverse array of annulation products including trisubstituted cyclopentenes, gamma-lactams, and bicyclic beta-lactams. The substrate scope of these reactions, however, is limited by the difficulties of preparing the starting alpha,beta-unsaturated aldehydes. We now report that alpha'-hydroxyenones, which can be prepared in a single convenient step from aromatic and heteroaromatic aldehydes, can serve as efficient surrogates for enals in the annulation reactions. This protocol allows the facile preparation and use of substrates bearing nitrogen heterocycles. These reagents have also allowed us to demonstrate that, in contrast to other classes of aldehydes, the formation of the Breslow intermediate from enals and N-heterocyclic carbenes is irreversible under the reaction conditions.

  18. OH-initiated oxidation of monoterpenes: reaction of alpha-pinene.

    PubMed

    Librando, Vito; Tomaselli, Gaetano; Tringali, Giuseppe

    2003-04-01

    The aim of this paper is to study the reaction products of alpha-pinene, beta-pinene, limonene, 3-carene and sabinene with OH radicals by FT-IR spectroscopy and by HPLC-MS-MS, to evaluate the secondary aerosol formation. All gas phase reaction products were quantified using reference compounds. As source of OH radicals were used H2O2 and CH3ONO. The experiments were performed at low terpene concentration (0.9-2.1 ppm) and at high terpene concentration (4.1-13.2 ppm), using H2O2 and CH3ONO as sources of OH radicals.

  19. Coupling reactions of alpha-bromocarboxylate with non-aromatic N-heterocycles.

    PubMed

    Brychtova, Katerina; Slaba, Barbora; Placek, Lukas; Jampilek, Josef; Raich, Ivan; Csollei, Jozef

    2009-08-13

    The conditions for the C-N bond forming reaction (C-N coupling reaction) between alpha-bromocarboxylate and nitrogen-containing non-aromatic heterocyclic rings under heterogeneous copper(I) oxide catalysis are investigated in this paper. All the generated compounds were fully characterized by IR, NMR and MS spectroscopy. Ab initio/DFT calculations of partial charges on nitrogen atoms in all the discussed heterocycles and on C((2)) of carboxylate under applied conditions were predicted. These in silico results correlate relatively with the experimental observations.

  20. Crosschecking of alpha particle monitor reactions up to 50 MeV

    NASA Astrophysics Data System (ADS)

    Takács, S.; Ditrói, F.; Szűcs, Z.; Haba, H.; Komori, Y.; Aikawa, M.; Saito, M.

    2017-04-01

    Selected reactions with well-defined excitation functions can be used to monitor the parameters of charged particle beams. The frequently used reactions for monitoring alpha particle beams are the 27Al(α,x)22,24Na, natTi(α,x)51Cr, natCu(α,x)66,67Ga and natCu(α,x)65Zn reactions. The excitation functions for these reactions were studied using the activation method and stacked target irradiation technique to crosscheck and to compare the above six reactions. Thin metallic foils with natural isotopic composition and well defined thickness were stacked together in sandwich targets and were irradiated at the AVF cyclotron of RIKEN with an alpha particle beam of 51.2 MeV. The activity of the target foils were assessed by using high-resolution gamma spectrometers of high purity Ge detectors. The data sets of the six processes were crosschecked with each other to provide consistent, cross-linked numerical cross section data.

  1. Effects of a new 3-alpha reaction on the s-process in massive stars

    SciTech Connect

    Kikuch, Yukihiro; Ono, Masaomi; Matsuo, Yasuhide; Hashimoto, Masa-aki; Fujimoto, Shin-ichiro

    2012-11-12

    Effect of a new 3-alpha reaction rate on the s-process during the evolution of a massive star of 25 solar mass is investigated for the first time, because the s-process in massive stars have been believed to be established with only minor change. We find that the s-process with use of the new rate during the core helium burning is very inefficient compared to the case with the previous 3-alpha rate. However, the difference of the overproduction is found to be largely compensated by the subsequent carbon burning. Since the s-process in massive stars has been attributed so far to the neutron irradiation during core helium burning, our finding reveals for the first time the importance of the carbon burning for the s-process during the evolution of massive stars.

  2. High-precision (p,t) reaction measurement to determine {sup 18}Ne({alpha},p){sup 21}Na reaction rates

    SciTech Connect

    Matic, A.; Berg, A. M. van den; Harakeh, M. N.; Woertche, H. J.; Berg, G. P. A.; Couder, M.; Fisker, J. L.; Goerres, J.; LeBlanc, P.; O'Brien, S.; Wiescher, M.; Fujita, K.; Hatanaka, K.; Sakemi, Y.; Shimizu, Y.; Tameshige, Y.; Tamii, A.; Yosoi, M.; Adachi, T.; Fujita, Y.

    2009-11-15

    x-ray bursts are identified as thermonuclear explosions in the outer atmosphere of accreting neutron stars. The thermonuclear runaway is fueled by the {alpha}p process that describes a sequence of ({alpha},p) reactions triggered by the {sup 18}Ne({alpha},p){sup 21}Na breakout reaction from the hot CNO cycles. We studied the level structure of the compound nucleus {sup 22}Mg by measuring the {sup 24}Mg(p,t){sup 22}Mg reaction at the Grand Raiden spectrometer at Research Center for Nuclear Physics, Osaka. A large number of {alpha}-unbound states was identified and precise excitation energies were determined. Based on shell model and {alpha}-cluster model calculations we predict the level parameters for determining the stellar reaction rate of {sup 18}Ne({alpha},p){sup 21}Na for a wide temperature range. x-ray burst simulations have been performed to study the impact of the reaction on the x-ray burst luminosity.

  3. First Experimental Measurement of the {sup 18}O(p,{alpha}){sup 15}N Reaction at Astrophysical Energies

    SciTech Connect

    La Cognata, M.; Sergi, M. L.; Spitaleri, C.; Cherubini, S.; Gulino, M.; Kiss, G.; Lamia, L.; Pizzone, R. G.; Romano, S.; Mukhamedzhanov, A.; Goldberg, V.; Tribble, R.; Coc, A.; Hammache, F.; Sereville, N. de; Tumino, A.

    2010-11-24

    The {sup 18}O(p,{alpha}){sup 15}N and {sup 17}O(p,{alpha}){sup 14}N reactions are of primary importance in several as-trophysical scenarios, including nucleosynthesis inside Asymptotic Giant Branch stars and oxygen and nitrogen isotopic ratios in meteorite grains. They are also key reactions to understand exotic systems such as R-Coronae Borealis stars and novae. Thus, the measurement of their cross sections in the low energy region can be crucial to reduce the nuclear uncertainty on theoretical predictions, because the resonance parameters are poorly determined. The Trojan Horse Method, in its newly developed form particularly suited to investigate low-energy resonances, has been applied to the {sup 2}H({sup 18}O,{alpha}{sup 15}N)n and {sup 2}H({sup 17}O,{alpha}{sup 14}N)n reactions to deduce the {sup 18}O(p,{alpha}){sup 15}N and {sup 17}O(p,{alpha}){sup 14}N cross sections at low energies. Resonances in the {sup 18}O(p,{alpha}){sup 15}N and {sup 17}O(p,{alpha}){sup 14}N excitation functions have been studied and the resonance parameters deduced.

  4. Alpha capture reaction cross section measurements on Sb isotopes by activation method

    NASA Astrophysics Data System (ADS)

    Korkulu, Z.; Özkan, N.; Kiss, G. G.; Szücs, T.; Fülöp, Zs; Güray, R. T.; Gyürky, Gy; Halász, Z.; Somorjai, E.; Török, Zs; Yalçin, C.

    2016-01-01

    Alpha induced reactions on natural and enriched antimony targets were investigated via the activation technique in the energy range from 9.74 MeV to 15.48 MeV, close to the upper end of the Gamow window at a temperature of 3 GK relevant to the γ-process. The experiments were carried out at the Institute for Nuclear Research, the Hungarian Academy of Sciences (MTA Atomki). 121Sb(α,γ)125I, 121Sb(α,n)124I and 123Sb(α,n)126I reactions were measured using a HPGe detector. In this work, the 121Sb(α,n)124 cross section results and the comparison with the theoretical predictions (obtained with standard settings of the statistical model codes NON-SMOKER and TALYS) were presented.

  5. Cluster states and container picture in light nuclei, and triple-alpha reaction rate

    NASA Astrophysics Data System (ADS)

    Funaki, Yasuro

    2015-04-01

    The excited states in 12C are investigated by using an extended version of the so- called Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave function, where both the 3α condensate and 8Be + α cluster asymptotic configurations are included. We focus on the structures of the “Hoyle band” states, 2+2, and 4+2 states, which are recently observed above the Hoyle state, and of the 0+3 and 0+4 states, which are also quite recently identified in experiment. We show that the Hoyle band is not simply considered to be the 8Be(0+) + α rotation as suggested by previous cluster model calculations, nor to be a rotation of a rigid-body triangle-shaped object composed of the 3α particles. We also discuss the rate of the triple-alpha radiative capture reaction, applyng the imaginary-time method. Results of the triple-alpha reaction rate are consistent with NACRE rate for both high (≈ 109K) and low (≈ 107 K) temperatures. We show that the rate of the imaginary-time calculation in coupled-channels approach has a large enhancement for low temperatures if we truncate the number of channels.

  6. Solvent-Free Conversion of Alpha-Naphthaldehyde to 1-Naphthoic Acid and 1-Naphthalenemethanol: Application of the Cannizzaro Reaction

    ERIC Educational Resources Information Center

    Esteb, John J.; Gligorich, Keith M.; O'Reilly, Stacy A.; Richter, Jeremy M.

    2004-01-01

    A mixture of potassium hydroxide and alpha-naphthaldehyde (1) are heated under solvent-free conditions to produce 1-naphthoic acid (2) and 1-naphthalenemethanol (3). The experiment offers several advantages over many existing exercises including the ease of reaction workup, shorter reaction time, relative environmental friendliness of the…

  7. High-precision {sup 28}Si(p,t){sup 26}Si reaction to determine {sup 22}Mg({alpha},p){sup 25}Al reaction rates

    SciTech Connect

    Matic, A.; Berg, A. M. van den; Harakeh, M. N.; Woertche, H. J.; Beard, M.; Berg, G. P. A.; Goerres, J.; LeBlanc, P.; O'Brien, S.; Wiescher, M.; Fujita, K.; Hatanaka, K.; Sakemi, Y.; Shimizu, Y.; Tameshige, Y.; Tamii, A.; Yosoi, M.; Adachi, T.; Fujita, Y.; Shimbara, Y.

    2011-08-15

    The rise time of stellar x-ray bursts is a signature of thermonuclear runaway processes in the atmosphere of neutron stars and is highly sensitive to a series of ({alpha},p) reactions via high-lying resonances in sd-shell nuclei. Lacking data for the relevant resonance levels, the stellar reaction rates have been calculated using statistical, Hauser-Feshbach models, assuming a high-level density. This assumption may not be correct in view of the selectivity of the ({alpha},p) reaction to natural parity states. We measured the {sup 28}Si(p,t){sup 26}Si reaction with a high-resolution spectrometer to identify resonance levels in {sup 26}Si above the {alpha}-emission threshold at 9.164 MeV excitation energy. These resonance levels are used to calculate the stellar reaction rate of the {sup 22}Mg({alpha},p){sup 25}Al reaction and to test the validity of the statistical assumption.

  8. Astrophysical reaction rate for the neutron-generator reaction 13C(alpha,n)16O in asymptotic giant branch stars.

    PubMed

    Johnson, E D; Rogachev, G V; Mukhamedzhanov, A M; Baby, L T; Brown, S; Cluff, W T; Crisp, A M; Diffenderfer, E; Goldberg, V Z; Green, B W; Hinners, T; Hoffman, C R; Kemper, K W; Momotyuk, O; Peplowski, P; Pipidis, A; Reynolds, R; Roeder, B T

    2006-11-10

    The reaction 13C(alpha,n) is considered to be the main source of neutrons for the s process in asymptotic giant branch stars. At low energies, the cross section is dominated by the 1/2+ 6.356 MeV subthreshold resonance in (17)O whose contribution at stellar temperatures is uncertain by a factor of 10. In this work, we performed the most precise determination of the low-energy astrophysical S factor using the indirect asymptotic normalization (ANC) technique. The alpha-particle ANC for the subthreshold state has been measured using the sub-Coulomb alpha-transfer reaction ((6)Li,d). Using the determined ANC, we calculated S(0), which turns out to be an order of magnitude smaller than in the nuclear astrophysics compilation of reaction rates.

  9. Synthesis of complex pyridine bases in the reaction of. cap alpha. ,omega-nitrileacetylenes with acetylene, catalyzed by cobalt complexes

    SciTech Connect

    Dzhemilev, U.M.; Selimov, F.A.; Khafizov, V.R.

    1987-01-20

    It has been shown that ..cap alpha..,omega-nitrileacetylenes under the action of homogeneous cobalt-containing catalysts undergo transformations into pyridine derivatives. In order to expand the scope of this method for synthesis of complex pyridine bases, for investigation of the reactivity of nitrileacetylenes of various structure in the reaction of cooligomerization with acetylene, as well as for the introduction to these reactions of new types of ..cap alpha..,omega-nitrileacetylenes, containing in their molecules an oxygen atom, they studied the homo- and codimerization of ..cap alpha..,omega-nitrileacetylenes with acetylene under the action of a Co(2-ethyl hexanoate)/sub 2/-AIR/sub 3/ catalyst in a toluene solution. Cyclodimerization of acetylene with ..cap alpha..,omega-nitrileacetylenes, catalyzed by a Co(2-ethyl hexanoate)/sub 2/-AlEt/sub 3/ system gives new types of mono- and bicyclic pyridines.

  10. S(N)2 reaction of sulfur nucleophiles with hindered sulfamidates: enantioselective synthesis of alpha-methylisocysteine.

    PubMed

    Avenoza, Alberto; Busto, Jesús H; Jiménez-Osés, Gonzalo; Peregrina, Jesús M

    2006-02-17

    The work described here demonstrates that the five-membered cyclic alpha-methylisoserine-derived sulfamidate, (R)-1, behaves as an excellent chiral building block for the ring-opening reaction by S(N)2 attack with sulfur nucleophiles at the quaternary carbon. As a synthetic application of this methodology, and to show that this sulfamidate is a valuable starting material, the synthesis of two new alpha-methylisocysteine derivatives has been carried out to cover the lack of alpha- and beta-methylated amino acids that incorporate the cysteine or isocysteine skeleton. These compounds are two new alpha,alpha-disubstituted beta-amino acids (beta(2,2)-amino acids), and the synthetic routes involve nucleophilic ring opening followed by acid hydrolysis.

  11. Measurement of alpha-induced reaction cross sections on erbium isotopes for γ process studies

    NASA Astrophysics Data System (ADS)

    Kiss, G. G.; Szücs, T.; Török, Zs.; Fülöp, Zs.; Gyürky, Gy.; Halász, Z.; Somorjai, E.; Rauscher, T.

    2014-05-01

    The cross sections of the 162Er(α,γ)166Yb and 162,164,166Er(α,n)165,167,169Yb reactions have been measured at MTA Atomki. The radiative alpha capture reaction cross section was measured between Ec.m. = 11.21 MeV and Ec.m. = 16.09 MeV just above the astrophysically relevant energy region (which lies between 7.8 and 11.48 MeV at T9 = 3 GK). The 162Er(α,n)165Yb, 164Er(α,n)167Yb and 166Er(α,n)169Yb reactions were studied between Ec.m. = 12.19 and 16.09 MeV, Ec.m. = 13.17 and 16.59 MeV and Ec.m. = 12.68 and 17.08 MeV, respectively. The aim of this work is to provide experimental data for modeling the γ process which is thought to be responsible for the production of the proton-rich isotopes heavier than iron.

  12. Measurement of alpha-induced reaction cross sections on erbium isotopes for γ process studies

    SciTech Connect

    Kiss, G. G.; Szücs, T.; Török, Zs.; Fülöp, Zs.; Gyürky, Gy.; Halász, Z.; Somorjai, E.; Rauscher, T.

    2014-05-02

    The cross sections of the {sup 162}Er(α,γ){sup 166}Yb and {sup 162,164,166}Er(α,n){sup 165,167,169}Yb reactions have been measured at MTA Atomki. The radiative alpha capture reaction cross section was measured between E{sub c.m.} = 11.21 MeV and E{sub c.m.} = 16.09 MeV just above the astrophysically relevant energy region (which lies between 7.8 and 11.48 MeV at T{sub 9} = 3 GK). The {sup 162}Er(α,n){sup 165}Yb, {sup 164}Er(α,n){sup 167}Yb and {sup 166}Er(α,n){sup 169}Yb reactions were studied between E{sub c.m.} = 12.19 and 16.09 MeV, E{sub c.m.} = 13.17 and 16.59 MeV and E{sub c.m.} = 12.68 and 17.08 MeV, respectively. The aim of this work is to provide experimental data for modeling the γ process which is thought to be responsible for the production of the proton-rich isotopes heavier than iron.

  13. 40Ca(alpha, gamma)44Ti reaction in the energy regime of supernova nucleosynthesis.

    PubMed

    Nassar, H; Paul, M; Ahmad, I; Ben-Dov, Y; Caggiano, J; Ghelberg, S; Goriely, S; Greene, J P; Hass, M; Heger, A; Heinz, A; Henderson, D J; Janssens, R V F; Jiang, C L; Kashiv, Y; Nara Singh, B S; Ofan, A; Pardo, R C; Pennington, T; Rehm, K E; Savard, G; Scott, R; Vondrasek, R

    2006-02-03

    The 44Ti(t1/2=59 yr) nuclide, an important signature of supernova nucleosynthesis, has recently been observed as live radioactivity by gamma-ray astronomy from the Cas A remnant. We investigate in the laboratory the major 44Ti production reaction 40Ca(alpha, gamma)44Ti (Ec.m. approximately 0.6-1.2 MeV/u by direct off-line counting of 44Ti nuclei. The yield, significantly higher than inferred from previous experiments, is analyzed in terms of a statistical model using microscopic nuclear inputs. The associated stellar rate has important astrophysical consequences, increasing the calculated supernova 44Ti yield by a factor approximately 2 over previous estimates and bringing it closer to Cas A observations.

  14. 12C(alpha,gamma)16O: the key reaction in stellar nucleosynthesis.

    PubMed

    Kunz, R; Jaeger, M; Mayer, A; Hammer, J W; Staudt, G; Harissopulos, S; Paradellis, T

    2001-04-09

    The angular distributions of gamma rays from the 12C(alpha,gamma)16O reaction have been measured at 20 energy points in the energy range E(cm) = 0.95 to 2.8 MeV. The sensitivity of the present experiment compared to previous direct investigations was raised by 1-2 orders of magnitude, by using an array of highly efficient ( 100%) Ge detectors shielded actively with BGOs, as well as high beam currents of up to 500 microA that were provided by the Stuttgart Dynamitron accelerator. The S(E1) and S(E2) factors deduced from the gamma angular distributions have been extrapolated to the range of helium burning temperatures applying the R-matrix method, which yielded S(300)(E1) = (76+/-20) keV b and S(300)(E2) = (85+/-30) keV b.

  15. Theory of (3He,(alpha)) surrogate reactions for deformed uranium nuclei

    SciTech Connect

    Thompson, I; Escher, J E

    2006-11-08

    We present the one-step theory of neutron-pickup transfer reactions with {sup 3}He projectiles on {sup 235}U and {sup 238}U. We find all the neutron eigenstates in a deformed potential, and use those in a given energy range for ({sup 3}He, {alpha}) DWBA pickup calculations to find the spin and parity distributions of the residual target nuclei. A simple smoothing convolution is used to take into account the spreading width of the single-neutron hole states into the more complicated compound nuclear states. We assume that the initial target is an even-even rotor, but can take into account spectator neutrons outside such a rotor by recombining their spin and parity at the end of the calculations.

  16. EEG alpha spindles and prolonged brake reaction times during auditory distraction in an on-road driving study.

    PubMed

    Sonnleitner, Andreas; Treder, Matthias Sebastian; Simon, Michael; Willmann, Sven; Ewald, Arne; Buchner, Axel; Schrauf, Michael

    2014-01-01

    Driver distraction is responsible for a substantial number of traffic accidents. This paper describes the impact of an auditory secondary task on drivers' mental states during a primary driving task. N=20 participants performed the test procedure in a car following task with repeated forced braking on a non-public test track. Performance measures (provoked reaction time to brake lights) and brain activity (EEG alpha spindles) were analyzed to describe distracted drivers. Further, a classification approach was used to investigate whether alpha spindles can predict drivers' mental states. Results show that reaction times and alpha spindle rate increased with time-on-task. Moreover, brake reaction times and alpha spindle rate were significantly higher while driving with auditory secondary task opposed to driving only. In single-trial classification, a combination of spindle parameters yielded a median classification error of about 8% in discriminating the distracted from the alert driving. Reduced driving performance (i.e., prolonged brake reaction times) during increased cognitive load is assumed to be indicated by EEG alpha spindles, enabling the quantification of driver distraction in experiments on public roads without verbally assessing the drivers' mental states.

  17. Kinetic isotope effects of peptidylglycine alpha-hydroxylating mono-oxygenase reaction.

    PubMed Central

    Takahashi, K; Onami, T; Noguchi, M

    1998-01-01

    Many bioactive polypeptides or neuropeptides possess a C-terminal alpha-amide group as a critical determinant for their optimal bioactivities. The amide functions are introduced by the sequential actions of peptidylglycine alpha-hydroxylating mono-oxygenase (PHM; EC 1.14.17.3) and peptidylamidoglycollate lyase (PAL; EC 4.3.2.5) from their glycine-extended precursors. In the present study we examined the kinetic isotope effects of the frog PHM reaction by competitive and non-competitive approaches. In the competitive approach we employed the double-label tracer method with D-Tyr-[U-14C]Val-Gly, D-Tyr-[3,4-3H]Val-[2,2-2H2]-Gly, and D-Tyr-Val-(R,S)[2-3H]Gly as substrates, and we determined the deuterium and tritium effects on Vmax/Km as 1.625+/-0.041 (mean+/-S. D.) and 2.71+/-0.16 (mean+/-S.D.), respectively. The intrinsic deuterium isotope effect (Dk) on the glycine hydroxylation reaction was estimated to be 6.5-10.0 (mean 8.1) by the method of Northrop [Northrop (1975) Biochemistry 14, 2644-2651]. In the non-competitive approach with N,N-dimethyl-1,4-phenylenediamine as a reductant, however, the deuterium effect on Vmax (DV) was approximately unity, although the deuterium effect on Vmax/Km (DV/K) was comparable to that obtained by the competitive approach. These results indicated that DV was completely masked by the presence of one or more steps much slower than the glycine hydroxylation step and that DV/K was diminished from Dk by a large forward commitment to catalysis. The addition of PAL, however, increased the apparent DV from 1.0 to 1.2, implying that the product release step was greatly accelerated by PAL. These results suggest that the product release is rate-limiting in the overall PHM reaction. The large Dk indicated that the glycine hydroxylation catalysed by PHM might proceed in a stepwise mechanism similar to that proposed for the dopamine beta-hydroxylase reaction [Miller and Klinman (1983) Biochemistry 22, 3091-3096]. PMID:9806894

  18. Reactions of the alkoxy radicals formed following OH-addition to alpha-pinene and beta-pinene. C-C bond scission reactions.

    PubMed

    Dibble, T S

    2001-05-09

    The atmospheric degradation pathways of the atmospherically important terpenes alpha-pinene and beta-pinene are studied using density functional theory. We employ the correlation functional of Lee, Yang, and Parr and the three-parameter HF exchange functional of Becke (B3LYP) together with the 6-31G(d) basis set. The C-C bond scission reactions of the beta-hydroxyalkoxy radicals that are formed after OH addition to alpha-pinene and beta-pinene are investigated. Both of the alkoxy radicals formed from the alpha-pinene-OH adduct possess a single favored C-C scission pathway with an extremely low barrier (approximately 3 kcal/mol) leading to the formation of pinonaldehyde. Neither of these pathways produces formaldehyde, and preliminary computational results offer some support for suggestions that 1,5 or 1,6 H-shift (isomerization) reactions of alkoxy radicals contribute to formaldehyde production. In the case of the alkoxy radical formed following OH addition to the methylene group of beta-pinene, there exists two C-C scission reactions with nearly identical barrier heights (approximately 7.5 kcal/mol); one leads to known products (nopinone and formaldehyde) but the ultimate products of the competing reaction are unknown. The single C-C scission pathway of the other alkoxy radical from beta-pinene possesses a very low (approximately 4 kcal/mol) barrier. The kinetically favored C-C scission reactions of all four alkoxy radicals appear to be far faster than expected rates of reaction with O2. The rearrangement of the alpha-pinene-OH adduct, a key step in the proposed mechanism of formation of acetone from alpha-pinene, is determined to possess a barrier of 11.6 kcal/mol. This value is consistent with another computational result and is broadly consistent with the modest acetone yields observed in product yield studies.

  19. An easy stereoselective access to beta,gamma-aziridino alpha-amino ester derivatives via mannich reaction of benzophenone imines of glycine esters with N-sulfonyl alpha-chloroaldimines.

    PubMed

    Kiss, Loránd; Mangelinckx, Sven; Sillanpää, Reijo; Fülöp, Ferenc; De Kimpe, Norbert

    2007-09-14

    Mannich-type addition of benzophenone imine glycinates across newly synthesized N-(p-toluenesulfonyl) alpha-chloroaldimines afforded gamma-chloro-alpha,beta-diamino ester derivatives with moderate diastereoselectivity as separable mixtures of anti and syn diastereomers. The gamma-chloro-alpha,beta-diamino esters were efficiently cyclized under basic conditions to the corresponding beta,gamma-aziridino alpha-amino ester derivatives, representing a new class of conformationally constrained heterocyclic alpha,beta-diamino acid derivatives. The relative configuration of the aziridines was determined via X-ray diffraction analysis. Mechanisms and intermediate transition states to explain the stereochemical outcome of the Mannich reaction with different substrates or under different conditions are proposed. The synthetic importance of the beta,gamma-aziridino alpha-amino ester derivatives is demonstrated by their conversion into the corresponding Boc-protected derivatives and ring opening reactions to alpha,beta-diamino esters and a gamma-amino alpha,beta-unsaturated amino ester.

  20. Complementary optical-potential analysis of {alpha}-particle elastic scattering and induced reactions at low energies

    SciTech Connect

    Avrigeanu, M. Obreja, A.C.; Roman, F.L.; Avrigeanu, V.; Oertzen, W. von

    2009-07-15

    A previously derived semi-microscopic analysis based on the Double Folding Model, for {alpha}-particle elastic scattering on A{approx}100 nuclei at energies below 32 MeV, is extended to medium mass A{approx}50-120 nuclei and energies from {approx}13 to 50 MeV. The energy-dependent phenomenological imaginary part for this semi-microscopic optical model potential was obtained including the dispersive correction to the microscopic real potential, and used within a concurrent phenomenological analysis of the same data basis. A regional parameter set for low-energy {alpha}-particles entirely based on elastic scattering data analysis was also obtained for nuclei within the above mentioned mass and energy ranges. Then, an ultimate assessment of ({alpha},{gamma}), ({alpha},n), and ({alpha},p) reaction cross sections considered target nuclei from {sup 45}Sc to {sup 118}Sn and incident energies below {approx}12 MeV. The former diffuseness of the real part of optical potential as well as the surface imaginary potential depth have been found to be responsible for the actual difficulties in the description of these data, and modified in order to obtain an optical potential which describes equally well both the low-energy elastic scattering and induced reaction data for {alpha}-particles.

  1. Witnessing quantum discord in 2xN systems

    SciTech Connect

    Bylicka, Bogna; Chruscinski, Dariusz

    2010-06-15

    Bipartite states with vanishing quantum discord are necessarily separable and hence positive partial transpose (PPT). We show that 2xN states satisfy additional property: the positivity of their partial transposition is recognized with respect to the canonical factorization of the original density operator. We call such states strong PPT (SPPT). Therefore, we provide a natural witness for a quantum discord: if a 2xN state is not SPPT it must contain nonclassical correlations measured by quantum discord. It is an analog of the celebrated Peres-Horodecki criterion: if a state is not PPT it must be entangled.

  2. Alpha Resonances in {sup 13}C Excited by the {sup 9}Be ({sup 6}Li,d) Reaction

    SciTech Connect

    Rodrigues, M. R. D.; Borello-Lewin, T.; Horodynski-Matsushigue, L. B.; Duarte, J. L. M.; Rodrigues, C. L.; Souza, M. A.; Miyake, H.; Cunsolo, A.; Cappuzzello, F.; Ukita, G. M.

    2010-05-21

    The {sup 9}Be({sup 6}Li,d){sup 13}C reaction was used to investigate alpha resonant states in {sup 13}C up to 13 MeV of excitation. The reaction was measured at a bombarding energy of 25.5 MeV employing the Sao Paulo Pelletron-Enge-Spectrograph facility and the nuclear emulsion detection technique. The resolution of 50 keV allowed for the separation of the resonant contributions to the known 7/2{sup -} at 10.753 MeV and (5/2{sup -}) at 10.818 MeV {sup 13}C states. The alpha resonance seen at the (3alpha+n) threshold was not previously reported. The experimental angular distributions are presented in comparison with DWBA predictions.

  3. Excitation functions of some (n,p) and (n,{alpha}) reactions from threshold to 16 MeV

    SciTech Connect

    Doczi, R.; Buczko, C.M.; Csikai, J.; Semkova, V.; Fenyvesi, A.; Yamamuro, N.

    1998-06-01

    Precise cross sections were measured for the {sup 90}Zr(n,{alpha}){sup 87m}Sr, {sup 94}Zr(n,{alpha}){sup 91}Sr, {sup 92}Mo(n,{alpha}){sup 89m+g}Zr, {sup 45}Sc(n,{alpha}){sup 42}K, {sup 51}V(n,{alpha}){sup 48}Sc, {sup 59}Co(n,{alpha}){sup 56}Mn, {sup 93}Nb(n,{alpha}){sup 90m}Y, {sup 92}Mo(n,p){sup 92m}Nb, {sup 96}(n,p){sup 96}Nb, {sup 97}Mo(n,p){sup 97m+g}Nb, {sup 90}Zr(n,p){sup 90m}Y, {sup 91}Zr(n,p){sup 91m}Y, {sup 92}Zr(n,p){sup 92}Y, and {sup 60}Ni(n,p){sup 60m+g}Co reactions in the 7- to 14.7-MeV neutron energy range. Excitation functions were completed with a number of new differential data. Spectrum-averaged (n,{alpha}) and (n,p) cross sections were measured for the {sup 54}Fe(n,{alpha}){sup 51}Cr, {sup 68}Zn(n,{alpha}){sup 65}Ni, {sup 27}Al(n,{alpha}){sup 24}Na, {sup 58}Ni(n,p){sup 58m+g}Co, {sup 64}Zn(n,p){sup 64}Cu, {sup 59}Co(n,p){sup 59}Fe, {sup 94}Zr(n,p){sup 94}Y, {sup 56}Fe(n,p){sup 56}Mn, {sup 46}Ti(n,p){sup 46m+g}Sc, {sup 47}Ti(n,p){sup 47}Sc, {sup 48}Ti(n,p){sup 48}Sc, and {sup 62}Ni(n,{alpha}){sup 59}Fe reactions in addition to those aforementioned using a thick target Be(d,n) neutron field at E{sub d} = 9.72 MeV. Results were compared with the ENDF/B-VI, IRDF90, JENDL-3, BROND, JEF-2, CENDL-2, and ADL-3 data files and the SINCROS-II system for testing the validation of differential data and the nuclear model calculations.

  4. Analyzing power of the {sup 40}Ca(p-vector,p{alpha}) reaction at 100 MeV

    SciTech Connect

    Neveling, R.; Buthelezi, Z.; Foertsch, S. V.; Lawrie, J. J.; Steyn, G. F.; Smit, F. D.; Cowley, A. A.; Fujita, H.; Hillhouse, G. C.; Wyngaardt, S. M.; Botha, N. T.; Mudau, L.; Ntshangase, S. S.

    2008-03-15

    Analyzing powers have been measured for the {sup 40}Ca(p-vector,p{alpha}){sup 36}Ar reaction at an incident energy of 100 MeV for coplanar scattering angles corresponding to zero recoil momentum of the residual nucleus. Predictions based on the distorted wave impulse approximation fail to reproduce the data.

  5. Comment on 'Low-energy cross sections in the {sup 12}C({alpha},{gamma}){sup 16}O reaction'

    SciTech Connect

    Descouvemont, P.; Dufour, M.

    2010-02-15

    We show that the E1 and E2 S factors recommended by Katsuma [Phys. Rev. C 78, 034606 (2008)] do not include well-known constraints and that the model is inappropriate for the {sup 12}C({alpha},{gamma}){sup 16}O reaction.

  6. Use of Be(p,{alpha}) and Be(p,d) Reactions to Determine Be Content in Sapphire

    SciTech Connect

    Franklyn, C. B.

    2011-12-13

    Since natural coloured sapphire ({alpha}-Al{sub 2}O{sub 3}) commands a high gem stone market price there is a need for a reliable method of identifying artificially coloured sapphire that has an inherently lower value. Diffusing beryllium into sapphire at high temperatures results in a coloured stone virtually indistinguishable from a natural one. Beryllium can occur naturally in sapphire but at levels of <1 ppma. Beryllium diffused sapphire typically contains >10 ppma, which is difficult to determine in a non destructive way. It is possible to utilize nuclear reaction analysis techniques to determine the beryllium content in a macroscopically non destructive way. Kinematically ideal reactions are Be(p,{alpha}) and Be(p,d) which, for Ep = 0.5 to 0.9 MeV, exhibit distinct reaction product signatures well separated from other proton induced reactions in aluminium or oxygen. Due to the lack of comprehensive cross section data for the Be(p,{alpha}) and Be(p,d) reactions in the energy range of interest, a series of measurements were made at the Van de Graaff accelerator facility at Necsa to create a new data base. A further outcome of these measurements was a deviation in reported values for the non-Rutherfordian proton back-scatter cross section. These new data bases, which extend to Ep = 2.6MeV, can now facilitate a procedure for determining beryllium content in sapphire.

  7. The 44Ti(alpha,p) reaction and its implication on the 44Ti yield in supernovae

    PubMed

    Sonzogni; Rehm; Ahmad; Borasi; Bowers; Brumwell; Caggiano; Davids; Greene; Harss; Heinz; Henderson; Janssens; Jiang; McMichael; Nolen; Pardo; Paul; Schiffer; Segel; Seweryniak; Siemssen; Truran; Uusitalo; Wiedenhover; Zabransky

    2000-02-21

    Cross sections for the 44Ti(alpha,p)47V reaction which significantly affects the yield of 44Ti in supernovae were measured in the energy range 5.7 MeVreaction rates are larger than the results from theoretical calculations by about a factor of 2. The implications of this increase in the reaction rate for the search of supernovae using space-based gamma detectors are discussed.

  8. Intramolecular condensation reactions of {alpha},{omega}-bis(triethoxysilyl)alkanes. Formation of cyclic disilsesquioxanes

    SciTech Connect

    Loy, D.A.; Carpenter, J.P.; Myers, S.A.; Assink, R.A.; Small, J.H.; Greaves, J.; Shea, K.J.

    1996-09-04

    In this paper, we used mass spectrometry and {sup 29}Si NMR spectroscopy to discover that the length of the alkylene-bridging groups had a pronounced effect on the competition between cyclization and polymerization of {alpha},{omega}-bis(triethoxysilyl)alkanes and on the formation of polymeric gels. While the intramolecular reaction clearly slows gelation, the cyclic disilsesquioxanes are still tetrafunctional monomers theoretically capable of forming polymeric gels. If the ring structures, which bear a striking resemblence to carbohydrates, are preserved through the polymerization, the resulting poly(cyclic disilsesquioxane) gels may have structural similarities to branched or cross-linked carbohydrates, such as cellulose or chitosan. Under base-catalyzed sol-gel polymerization conditions, 3 and 4 (six- and seven-membered cyclic disilsesquioxanes, respectively) quickly reacted to give gels with significant ring opening as determined from the {sup 29}Si chemical shifts in solid-state (CP MAS) NMR spectra. However, gels prepared under acidic conditions reveal some or all of the cyclic disilsesquioxane functionality was preserved in the polymers. 13 refs., 1 fig.

  9. Alpha adrenergic modulation on effects of norepinephrine transporter inhibitor reboxetine in five-choice serial reaction time task

    PubMed Central

    Liu, Yia-Ping; Lin, Yu-Lung; Chuang, Chia-Hsin; Kao, Yu-Cheng; Chang, Shang-Tang; Tung, Che-Se

    2009-01-01

    The study examined the effects of a norepinephrine transporter (NET) inhibitor reboxetine (RBX) on an attentional performance test. Adult SD rats trained with five-choice serial reaction time task (5-CSRTT) were administered with RBX (0, 3.0 and 10 mg/kg) in the testing day. Alpha-1 adrenergic receptor antagonist PRA and alpha-2 adrenergic receptor antagonist RX821002 were used to clarify the RBX effect. Results revealed that rat received RBX at 10 mg/kg had an increase in the percentage of the correct response and decreases in the numbers of premature response. Alpha-1 adrenergic receptor antagonist Prazosin (PRA) at 0.1 mg/kg reversed the RBX augmented correct responding rate. However, alpha-2 adrenergic receptor antagonist RX821002 at 0.05 and 0.1 mg/kg dose dependently reversed the RBX reduced impulsive responding. Our results suggested that RBX as a norepinephrine transporter inhibitor can be beneficial in both attentional accuracy and response control and alpha-1 and alpha-2 adrenergic receptors might be involved differently. PMID:19678962

  10. Reactions of ozone with. alpha. -pinene and. beta. -pinene in air: Yields of gaseous and particulate products

    SciTech Connect

    Hatakeyama, S.; Izumi, K.; Fukuyama, T.; Akimoto, H. )

    1989-09-20

    Reactions of ozone with {alpha}-prinene and {beta}-pinene were studied for the purpose of obtaining the quantitative yields of gaseous and particulate products. Major gaseous products from {alpha}-pinene were CO, CO{sub 2}, HCHO, and aldehydes mainly composed of pinonaldehyde and nor-pinonaldehyde, while those from {beta}-pinene were CO{sub 2}, HCHO, and 6,6-dimethylbicyclo(3.1.1)heptan-2-one. Average molar yields from {alpha}-pinene were CO; 9{plus minus}1%, CO{sub 2}; 30{plus minus}2%, HCHO; 22{plus minus}1%, and aldehydes; 51{plus minus}6%. Average molar yields from {beta}-pinene were CO{sub 2}; 27{plus minus}2%, HCHO; 76{plus minus}2%, and 6,6-dimethylbicyclo(3.1.1)heptan-2-one; 40{plus minus}2%. Particulate products were found to include pinonaldehyde, nor-pinonaldehyde, pinonic acid, and nor-pinonic acid from {alpha}-pinene. The yields of the particulate aldehydes decreased with the reaction time, whereas the yields of the acids increased. This observation suggests the sequential oxidation of aldehydes to carboxylic acids. From {beta}-pinene, only 6,6-dimethylbicyclo(3.1.1)heptan-2-one was identified as a particulate product. For {alpha}-pinene, most of the products are explainable in terms of the reaction mechanism similar to that for the cyclohexene/ozone reaction, whereas for {beta}-pinene the principal reaction path is that of the doubly substituted Criegee intermediate. The total yields of organic aerosols from both {alpha}- and {beta}-pinene were measured with their concentrations at a lower ppb level. The yields were found almost constant in a pinene concentration range from 10 up to 100 ppb, being 18.3{plus minus}1.1 and 13.8{plus minus}0.8% for {alpha}- and {beta}-pinene, respectively, which are much lower than the previously reported values. {copyright} American Geophysical Union 1989

  11. [Determination of rate constants of gas-phase reactions of alpha-pinene and beta-pinene with ozone].

    PubMed

    Liu, Z R; Hu, D

    2001-10-01

    alpha-pinene and beta-pinene are the most dominating species among natural terpenes. Terpenes are mainly emitted from forest trees, flowers and grass. In the lower troposphere terpenes can react fast with OH radical, ozone, NO3 radical and ground state oxygen atom. These reactions may contribute to the occurring of aerosols, peroxides (hydrogen peroxide and organic peroxide), carbon cycle (mainly CO), acid rain (organic acids, NO3- and SO4(2-), ozone and active radicals such as OH radical. Reactions with ozone occur both in the daytime and in the night. The study in this field in China began in the late 1980. The main work focus on the source emission and the experimental simulation has just started. It is most of our group's work. In this paper preliminary experimental simulation of the gas-phase reactions of alpha-pinene and beta-pinene with ozone were carried out in the quartz chamber. The rate constants of these reactions were measured using long-path Fourier transform infra-red combined with relative rate constant method. And the rate constants for the gas-phase reactions of alpha-pinene, beta-pinene with ozone were determined as 2.83 x 10(17) cm3.molecule-1.s-1 and 1.48 x 10(17) cm3.molecule-1.s-1 at 1.0 x 10(5) Pa and 296 +/- 3 K. The results are quite similar to the data from Atkinson group. No cyclohexane was added to the reaction system during the measurement to restrain the formation of OH radical. The formation of OH radical could not be quantified, so that the effect of subsidiary reactions induced by OH radical has not been calculated. In the later simulation study and model this effect should be considered.

  12. Inhibition of radical reaction of apolipoprotein B-100 and alpha-tocopherol in human plasma by green tea catechins.

    PubMed

    Hashimoto, R; Yaita, M; Tanaka, K; Hara, Y; Kojo, S

    2000-12-01

    (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), (-)-epigallocatechin gallate (EGCg), and Trolox inhibited the decreases of apolipoprotein B-100 (apoB) and alpha-tocopherol in a radical reaction of human plasma initiated by Cu(2+). The concentrations of EC, EGC, ECg, EGCg, and Trolox for 50% inhibition (IC50) of apoB fragmentation were 39.1, 42.2, 14.6, 21.3, and 36.2 microM, respectively. Similar IC50 values were observed for alpha-tocopherol consumption, indicating the close relationship between apoB fragmentation and alpha-tocopherol consumption. These results demonstrate that tea catechins serve as an effective antioxidant in plasma and that the gallate group has a strong antioxidative activity.

  13. Theoretical analysis of kinetic isotope effects on proton transfer reactions between substituted alpha-methoxystyrenes and substituted acetic acids.

    PubMed

    Wong, Kin-Yiu; Richard, John P; Gao, Jiali

    2009-10-07

    Primary kinetic isotope effects (KIEs) on a series of carboxylic acid-catalyzed protonation reactions of aryl-substituted alpha-methoxystyrenes (X-1) to form oxocarbenium ions have been computed using the second-order Kleinert variational perturbation theory (KP2) in the framework of Feynman path integrals (PI) along with the potential energy surface obtained at the B3LYP/6-31+G(d,p) level. Good agreement with the experimental data was obtained, demonstrating that this novel computational approach for computing KIEs of organic reactions is a viable alternative to the traditional method employing Bigeleisen equation and harmonic vibrational frequencies. Although tunneling makes relatively small contributions to the lowering of the free energy barriers for the carboxylic acid catalyzed protonation reaction, it is necessary to include tunneling contributions to obtain quantitative estimates of the KIEs. Consideration of anharmonicity can further improve the calculated KIEs for the protonation of substituted alpha-methoxystyrenes by chloroacetic acid, but for the reactions of the parent and 4-NO(2) substituted alpha-methoxystyrene with substituted carboxylic acids, the correction of anharmonicity overestimates the computed KIEs for strong acid catalysts. In agreement with experimental findings, the largest KIEs are found in nearly ergoneutral reactions, DeltaG(o) approximately 0, where the transition structures are nearly symmetric and the reaction barriers are relatively low. Furthermore, the optimized transition structures are strongly dependent on the free energy for the formation of the carbocation intermediate, that is, the driving force DeltaG(o), along with a good correlation of Hammond shift in the transition state structure.

  14. Measurement of the OXYGEN-17(PROTON, Alpha Particle) Nitrogen -14 Cross Section at Stellar Energies (proton Energies, Resonant Reaction)

    NASA Astrophysics Data System (ADS)

    Blackmon, Jeffery Curtis

    The isotopic abundance ratio 16O/17O has been shown to be a good probe of mass flow and mixing in stars. This ratio is sensitive to the depth of convective mixing which occurs on the giant branch and to the amount of nonconvective mixing occurring on the main sequence. The interpretation of recent observations of this ratio in red giants is limited by a large uncertainty in the value of the 17O(p, alpha)14N reaction rate. This reaction rate is dominated at stellar energies by a resonance at E_{rm x} = 5673 keV in the compound nucleus 18 F, whose strength was previously uncertain. We have carried out a measurement of the ^ {17}O(p,alpha)^{14 }N cross section at proton energies of 75 keV and 65 keV. Thick, high-purity rm Ta_2O _5 targets enriched to 77% ^ {17}O were used in conjunction with beam currents of 0.45 mA and large-solid-angle detectors. The background for the experiment was measured using targets of natural isotopic composition. The resonance peak was observed in the data collected at 75 keV, and we determined the proton width of the 5673 keV state to be 22 +/- 4 neV. This implies a rate for the 17O(p,alpha)^ {14}N reaction that is ten times greater than the typical rates used previously in stellar models.

  15. Near Fermi Energy reaction dynamics and clustering in alpha-conjugate systems

    NASA Astrophysics Data System (ADS)

    Cao, Xiguang; Schmidt, Katarzyna; Kim, E.-J.; Hagel, K.; Barbui, M.; Wuenschel, S.; Natowitz, J. B.; Zheng, H.; Blando, N.; Bonasera, A.; Giuliani, G.

    2015-10-01

    Theoretical study predicted that the self-organizing of alpha cluster is favored over deuteron below a critical density with moderate temperature, where the possible Bose-Einstein condensation (BEC) is expected to occur. However the experimental information about the alpha states at low density is scarce. It is natural to pursue experiments with α conjugate beams and advanced detection apparatus to explore the collective dynamics of alpha clustered systems at low density. Systematical experiments were carried out with 40Ca and 28Si beams at 10, 25, 35 MeV/u incident on 28Si, 12C, 40Ca and 180Ta targets, detected with the NIMROD-ISiS 4 Pi detector array. It is found that there is a strong neck-like emission, which consists mainly of alpha-like fragments. The characteristic of the α emission source is explored by shape analysis, multi-particle correlation and quantum fluctuation approaches. How these observables reveal the possible alpha BEC in low density and possible exotic toroidal and linear chain configurations made out of alpha clusters is discussed.

  16. Atmospheric fate of OH initiated oxidation of terpenes. Reaction mechanism of alpha-pinene degradation and secondary organic aerosol formation.

    PubMed

    Librando, Vito; Tringali, Giuseppe

    2005-05-01

    This paper studies the reaction products of alpha-pinene, beta-pinene, sabinene, 3-carene and limonene with OH radicals and of alpha-pinene with ozone using FT-IR spectroscopy for measuring gas phase products and HPLC-MS-MS to measure products in the aerosol phase. These techniques were used to investigate the secondary organic aerosol (SOA) formation from the terpenes. The gas phase reaction products were all quantified using reference compounds. At low terpene concentrations (0.9-2.1 ppm), the molar yields of gas phase reaction products were: HCHO 16-92%, HCOOH 10-54% (OH source: H2O2, 6-25 ppm); HCHO 127-148%, HCOOH 4-6% (OH source: CH3ONO, 5-8 ppm). At high terpene concentrations (4.1-13.2 ppm) the results were: HCHO 9-27%, HCOOH 15-23%, CH3(CO)CH3 0-14%, CH3COOH 0-5%, nopinone 24% (only from beta-pinene oxidation), limona ketone 61% (only from limonene oxidation), pinonaldehyde was identified during alpha-pinene degradation (OH source H2O2, 23-30 ppm); HCHO 76-183%, HCOOH 12-15%, CH3(CO)CH3 0-12%, nopinone 17% (from beta-pinene oxidation), limona ketone 48% (from limonene oxidation), pinonaldehyde was identified during alpha-pinene degradation (OH source CH3ONO, 14-16 ppm). Pinic acid, pinonic acid, limonic acid, limoninic acid, 3-caric acid, 3-caronic acid and sabinic acid were identified in the aerosol phase. On the basis of these results, we propose a formation mechanism for pinonic and pinic acid in the aerosol phase explaining how degradation products could influence SOA formation and growth in the troposphere.

  17. Radiochemical study of the medium energy pion double charge exchange reactions: /sup 209/Bi(pi/sup +/pi/sup -/)/sup 209-x/At

    SciTech Connect

    Clark, J.L.

    1980-01-01

    Carrier-free radiochemical techniques have been used to measure cross sections for the double charge exchange reactions of the type /sup 209/Bi(pi/sup +/, pi/sup -/xn)/sup 209-x/At for 100, 180, and 300 MeV incident pions. The observed formation of astatine products with mass numbers ranging from 208 to 205 is interpreted as evidence of processes in which energy deposited in the initial double charge exchange interaction is subsequently dissipated through neutron evaporation. The excitation functions for these reactions are seen to rise rapidly with decreasing incident pion energy with the maximum results for this study at 100 MeV. The astatine production cross secions measured for these positive pion irradiations of thick bismuth targets must be corrected for secondary processes, particularly the pion induced production of fast alpha particles which can contribute to the total cross sections through reactions like /sup 209/Bi(alpha,xn)/sup 213-x/At. The importance of these secondary contributions was studied through a series of negative pion irradiations of bismuth in which secondary pathways furnish the only means of producing astatine. The failure of evaporation calculations to reproduce the astatine product mass yields observed in these secondary studies suggests that direct mechanisms for energetic complex particle formation are quite important. Values for the alpha decay branches of /sup 207/At, /sup 208/At, and /sup 209/At were determined through a study of the electron capture and alpha decay characteristics of chemically purified astatine fractions.

  18. Thermal stability and chemical bonding states of AlO xN y/Si gate stacks revealed by synchrotron radiation photoemission spectroscopy

    NASA Astrophysics Data System (ADS)

    He, G.; Toyoda, S.; Shimogaki, Y.; Oshima, M.

    2010-12-01

    Annealing-temperature dependence of the thermal stability and chemical bonding states of AlO xN y/SiO 2/Si gate stacks grown by metalorganic chemical vapor deposition (MOCVD) using new chemistry was investigated by synchrotron radiation photoemission spectroscopy (SRPES). Results have confirmed the formation of the AlN and AlNO compounds in the as-deposited samples. Annealing the AlO xN y samples in N 2 ambient in 600-800 °C promotes the formation of SiO 2 component. Meanwhile, there is no formation of Al-O-Si and Al-Si binding states, suggesting no interdiffusion of Al with the Si substrate. A thermally induced reaction between Si and AlO xN y to form volatile SiO and Al 2O is suggested to be responsible for the full disappearance of the Al component that accompanies annealing at annealing temperature of 1000 °C. The released N due to the breakage of the Al-N bonding will react with the SiO 2 interfacial layer and lead to the formation of the Si 3-N-O/Si 2-N-O components at the top of Si substrate. These results indicate high temperature processing induced evolution of the interfacial chemistry and application range of AlO xN y/Si gate stacks in future CMOS devices.

  19. Low-energy cross sections in the {sup 12}C({alpha},{gamma}){sup 16}O reaction

    SciTech Connect

    Katsuma, M.

    2008-09-15

    The low-energy {sup 12}C({alpha},{gamma}){sup 16}O reaction is analyzed with the potential model. The potentials are chosen from the deep potential describing the {alpha}-particle nuclear rainbow phenomena at high energies. Below E{sub c.m.}=1 MeV, the cross section is found to be dominated by the E2 transition to the ground state of {sup 16}O. No enhancement of the E1 component at low energies is predicted. The extrapolated astrophysical S-factors at E{sub c.m.}=0.3 MeV are S{sub E2}=150 keV b and S{sub E1}=3 keV b.

  20. Reaction of N-vinylic phosphazenes with alpha,beta-unsaturated aldehydes. Azatriene-mediated synthesis of dihydropyridines and pyridines derived from beta-amino acids.

    PubMed

    Palacios, Francisco; Herran, Esther; Alonso, Concepción; Rubiales, Gloria; Lecea, Begoña; Ayerbe, Mirari; Cossío, Fernando P

    2006-08-04

    Aza-Wittig reaction of N-vinylic phosphazenes (1,2 addition), derived from diphenylmethylphosphine or derived from trimethylphosphine with alpha,beta-unsaturated aldehydes, leads to the formation of 3-azatrienes through a [2 + 2]-cycloaddition-cycloreversion sequence. The presence of an alkyl substituent in position 3 of N-vinylic phosphazenes increases the steric interactions, and [4 + 2] periselectivity (1,4 addition) is observed. Reaction of azatrienes with alpha,beta-unsaturated aldehydes yields pyridines.

  1. Side feeding patterns and nuclear lifetime determinations by the Doppler shift attenuation method in ({alpha},n{gamma}) reactions

    SciTech Connect

    Mihai, C.; Filipescu, D.; Ivascu, M.; Bucurescu, D.; Cata-Danil, G.; Cata-Danil, I.; Deleanu, D.; Ghita, D.; Glodariu, T.; Marginean, N.; Marginean, R.; Negret, A.; Pascu, S.; Sava, T.; Stroe, L.; Suliman, G.; Zamfir, N. V.; Pasternak, A. A.; Lobach, Yu. N.

    2010-03-15

    {gamma} rays were measured at several angles in both singles and coincidence mode in the {sup 119}Sn({alpha},n{gamma}){sup 122}Te reaction at 15 MeV on a thick target. Lifetimes of excited states in {sup 122}Te were determined from a Monte Carlo Doppler shift attenuation method (DSAM) analysis of the Doppler broadened lines shapes of {gamma} rays de-exciting the levels. A comparison of several deduced lifetimes with recent results obtained with the (n,n{sup '}) reaction allowed us to validate the choice of a parameter used to calculate the contribution of the side feeding times. The ingredients of the DSAM line-shape analysis (stopping power, description of instrumental line shapes, and side feeding evaluation) are presented in some detail. It is concluded that with proper treatment of side feeding, a DSAM line-shape analysis of peaks in singles or coincidence spectra obtained following the ({alpha},n{gamma}) reaction is able to provide rather accurate values for the lifetimes of levels with low and medium spins.

  2. Threshold states in 19Ne and the CNO breakout reaction 15O({alpha},{gamma})19Ne

    SciTech Connect

    Tan, W. P.; Goerres, J.; Daly, J.; Couder, M.; Couture, A.; Lee, H. Y.; Stech, E.; Strandberg, E.; Ugalde, C.; Wiescher, M.

    2006-03-13

    The 15O({alpha},{gamma})19Ne reaction is one of the most important breakout reactions for the hot CNO cycles. However, the relevant states in 19Ne at excitation energies of 4-5 MeV have not been well studied. The lifetimes of these states are not known and are only constrained by experimental upper/lower limits. In particular, the accurate knowledge of the {gamma}- and {alpha}- decay widths of the 4.03 MeV state of 19Ne is important, since the resonance strength of this level dominates the reaction rate for the astrophysically relevant temperatures T9 < 0.6. In this work, we employed an improved DSAM approach to obtain lifetime values of this and other states via 17O(3He,n - {gamma})19Ne. For the 4.03 MeV state, the measured excitation energy is 4034.5{+-}0.8 keV and the mean lifetime, measured here for the first time, is 13{sub -6}{sup +9} fs at the confidence level of 1{sigma} and 13{sub -9}{sup +16} fs at the confidence level of 2{sigma}. This result is in excellent agreement with the 9 fs prediction by Langanke, Wiescher, Fowler, and Goerres.

  3. A gas-tight Cu K alpha x-ray transparent reaction chamber for high-temperature x-ray diffraction analyses of halide gas/solid reactions.

    PubMed

    Shian, Samuel; Sandhage, Kenneth H

    2009-11-01

    An externally heated, x-ray transparent reaction chamber has been developed to enable the dynamic high temperature x-ray diffraction (HTXRD) analysis of a gas/solid [TiF(4)(g)/SiO(2)(s)] reaction involving a halide gas reactant formed at elevated temperatures (up to 350 degrees C) from a condensed source (TiF(4) powder) sealed within the chamber. The reaction chamber possessed x-ray transparent windows comprised of a thin (13 microm) internal layer of Al foil and a thicker (125 microm) external Kapton film. After sealing the SiO(2) specimens (diatom frustules or Stober spheres) above TiF(4) powder within the reaction chamber, the chamber was heated to a temperature in the range of 160-350 degrees C to allow for internal generation of TiF(4)(g). The TiF(4)(g) underwent a metathetic reaction with the SiO(2) specimen to yield a TiOF(2)(s) product. HTXRD analysis, using Cu K alpha x rays passed through the Kapton/Al windows of the chamber, was used to track the extent of SiO(2) consumption and/or TiOF(2) formation with time. The Al foil inner layer of the windows protected the Kapton film from chemical attack by TiF(4)(g), whereas the thicker, more transparent Kapton film provided the mechanical strength needed to contain this gas. By selecting an appropriate combination of x-ray transparent materials to endow such composite windows with the required thermal, chemical, and mechanical performance, this inexpensive reaction chamber design may be applied to the HTXRD analyses of a variety of gas/solid reactions.

  4. Transition metal-catalyzed/mediated reaction of allenes with a nucleophilic functionality connected to the alpha-carbon atom.

    PubMed

    Ma, Shengming

    2003-09-01

    Allenes with a nucleophilic functionality connected to the alpha-carbon atom have been shown to be versatile building blocks for the syn-thesis of gamma-butenolides, gamma-lactams, gamma-iminolactones, vinylic epoxides, 4-amino-2-alkenols, 2-amino-3-alkenols, 2,5-dihydrofurans, furans, vinylic cyclopropanes, and cyclopentenes, depending on the nature of the nucleophilic centers. The reaction may proceed via the carbometalation-nucleophilic attack mechanism or nucleometallation-reductive elimination. The stereochemical outcomes by these two pathways are different.

  5. The role of nuclear reactions and {alpha}-particle transport in the dynamics of inertial confinement fusion capsules

    SciTech Connect

    Garnier, Josselin; Cherfils-Clerouin, Catherine

    2008-10-15

    This paper is devoted to the study of the deceleration phase of inertial confinement capsules. The purpose is to obtain a zero-dimensional model that has the form of a closed system of ordinary differential equations for the main hydrodynamic quantities. The model takes into account the energy released by nuclear reactions, a nonlocal model for the {alpha}-particle energy deposition process, and radiation loss by electron bremsstrahlung. The asymptotic analysis is performed in the case of a strong temperature dependence of the thermal conductivity. We finally study the beginning of the expansion phase after stagnation to derive an ignition criterion.

  6. Measurement of the inelastic branch of the {sup 14}O({alpha},p){sup 17}F reaction: Implications for explosive burning in novae and x-ray bursters

    SciTech Connect

    He, J. J.; Woods, P. J.; Davinson, T.; Aliotta, M.; Murphy, A. St. J.; Buescher, J.; Neyskens, P.; Raabe, R.; Clement, E.; Delahaye, P.; Voulot, D.; Walle, J. van der; Wenander, F.; Hass, M.; Kumar, V.; Jenkins, D. G.; Robinson, A. P.; Warr, N.

    2009-10-15

    A measurement of the inelastic component of the key astrophysical resonance in the {sup 14}O({alpha},p){sup 17}F reaction for burning and breakout from hot carbon-nitrogen-oxygen (CNO) cycles is reported. The inelastic component is found to be comparable to the ground-state branch and will enhance the {sup 14}O({alpha},p){sup 17}F reaction rate. The current results for the reaction rate confirm that the {sup 14}O({alpha},p){sup 17}F reaction is unlikely to contribute substantially to burning and breakout from the CNO cycles under novae conditions. The reaction can, however, contribute strongly to the breakout from the hot CNO cycles under the more extreme conditions found in x-ray bursters.

  7. Theoretical cross section calculations of medical 13N and 18F radioisotope using alpha induced reaction

    NASA Astrophysics Data System (ADS)

    Kılınç, F.; Karpuz, N.; ćetin, B.

    2017-02-01

    In medical physics, radionuclides are needed to diagnose functional disorders of organs and to diagnose and treat many diseases. Nuclear reactions are significant for the productions of radionuclides. It is important to analyze the cross sections for much different energy. In this study, reactional cross sections calculations on 13N, 18F radioisotopes are with TALYS 1.6 nuclear reaction simulation code. Cross sections calculated and experimental data taken from EXFOR library were compared

  8. Characterization of products formed in the reaction of ozone with alpha-pinene: case for organic peroxides.

    PubMed

    Venkatachari, Prasanna; Hopke, Philip K

    2008-08-01

    The generation of reactive oxygen species (ROS) and their subsequent induced pulmonary and systemic oxidative stress has been implicated as an important molecular mechanism of PM-mediated toxicity. However, recent work has shown that there is significant ROS associated with ambient PM. In order to understand the formation mechanisms as well as understand the potential health effects of particle-bound oxidative species, the alpha-pinene-O(3) oxidation chemical system was studied to elucidate the structures of reaction products using liquid chromatography-multiple stage mass spectrometry (LC-MS(n)). The classes of compounds identified based on their multiple stage-MS fragmentation patterns, mechanistic considerations of alpha-pinene-O(3) oxidation, and general fragmentation rules, of the products from this reaction system were highly oxygenated species, predominantly containing hydroperoxide and peroxide functional groups. The oxidant species observed were clearly stable for the 1-3 h that elapsed during aerosol collection and analysis, and probably for much longer, thus rendering it possible for these species to bind onto particles forming fine particulate organic peroxides that concentrate on the particles and could deliver concentrated doses of ROS in vivo to tissue.

  9. Reactions of Ethylidene on a Model Chromia Surface: 1 1-Dichloroethane on Stoichiometric alpha-Cr2O3 (1012)

    SciTech Connect

    J Brooks; T Chen; D Mullins; D Cox

    2011-12-31

    The reaction of CH{sub 3}CHCl{sub 2} over the nearly-stoichiometric {alpha}-Cr{sub 2}O{sub 3} (10{sub {bar 1}} > 2) surface produces an ethylidene intermediate that yields primarily gas phase CH{sub 2}{double_bond}CH{sub 2} and surface chlorine adatoms; however, trace amounts of HC{triple_bond}CH, CH{sub 3}CH{sub 3}, H{sub 2} and CH{sub 3}CH{double_bond}CHCH{sub 3} are also observed. A rate-limiting intramolecular isomerization (2,1-hydrogen shift) in the surface ethylidene species produces gas phase CH{sub 2}{double_bond}CH{sub 2}. The chlorine freed from the dissociation of CH{sub 3}CHCl{sub 2} binds at the five-coordinate surface Cr{sup 3+} sites on the stoichiometric surface, completing the octahedral coordination sphere, and inhibits the surface chemistry by simple site blocking. No surface carbon deposition is observed from the thermal reaction of 1,1-dichloroethane under the conditions of this study, demonstrating that the ethylidene intermediate is not a primary coke forming intermediate over (10{sub {bar 1}} > 2) facets of {alpha}-Cr{sub 2}O{sub 3} under the conditions of this study.

  10. Measurement of the 20 and 90 keV Resonances in the {sup 18}O(p,{alpha}){sup 15}N Reaction via the Trojan Horse Method

    SciTech Connect

    La Cognata, M.; Spitaleri, C.; Cherubini, S.; Crucilla, V.; Gulino, M.; Lamia, L.; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Tumino, A.; Mukhamedzhanov, A. M.; Tribble, R. E.; Banu, A.; Goldberg, V. Z.; Tabacaru, G.; Trache, L.; Irgaziev, B.; Coc, A.

    2008-10-10

    The {sup 18}O(p,{alpha}){sup 15}N reaction is of primary importance in several astrophysical scenarios, including fluorine nucleosynthesis inside asymptotic giant branch stars as well as oxygen and nitrogen isotopic ratios in meteorite grains. Thus the indirect measurement of the low energy region of the {sup 18}O(p,{alpha}){sup 15}N reaction has been performed to reduce the nuclear uncertainty on theoretical predictions. In particular the strength of the 20 and 90 keV resonances has been deduced and the change in the reaction rate evaluated.

  11. (n,p) and (n,alpha) measurements using LENZ instrument to improve reaction model prediction

    NASA Astrophysics Data System (ADS)

    Lee, Hye Young; Devlin, Matthew; Haight, Robert; Manning, Brett; Mosby, Shea

    2015-10-01

    Understanding neutron-induced charged particle reactions is of interest for nuclear astrophysics and applied nuclear energy. Often, direct measurements of these reactions are not feasible at neutron beam facilities due to the short half-lives of the targets and the reduced cross sections at astrophysically relevant energies given the large Coulomb barriers. Instead, the Hauser-Feshbach formalism is used to study this reaction mechanism for predicting cross sections. We have developed the LENZ (Low Energy n,z) instrument to measure the (n,p) and (n, α) reactions using a time-of-flight method for incident neutron energies from thermal to several tens of MeV at LANSCE. The LENZ has improved capabilities including a large solid angle, a low detection threshold, and good signal-to-background ratios using waveform digitizers. We have performed an in-beam commissioning measurement on 59Co(n, α/p) at En = 0.7 - 12 MeV. In this paper, we will discuss the results of the 59Co(n, α/p) measurements and present the status of the reaction studies on 16O(n, α) for nuclear energy applications and 77Se(n,p) for reaction mechanism studies. This work is funded by the US Department of Energy-Los Alamos National Security, LLC under Contract DE-AC52-06NA25396.

  12. Synthesis of 19-oxygenated 4beta,5beta-epoxy derivatives of 16alpha-hydroxyandrostenedione as mechanistic and catalytic probes for aromatase reaction.

    PubMed

    Numazawa, M; Yoshimura, A

    2000-09-01

    4Beta,5beta-epoxy derivatives of 16alpha-hydroxyandrostenedione (2), one of the natural substrates for aromatase, and its 19-oxygenated compounds 4 and 5 were synthesized as mechanistic and catalytic probes for the enzyme reaction. Treatment of 16alpha-bromoandrostenedione (13) or its 19-hydroxy analog 19 which was prepared from 3beta-hydroxy-19-(tert-butyldimethylsiloxy)androst-5-en-17-one (16) in three steps, with H2O2 and NaOH followed by controlled alkaline hydrolysis with NaOH in aqueous pyridine stereospecifically yielded 4beta,5beta-epoxy-16alpha-ol 15 or 4beta,5beta-epoxy-16alpha,19-diol 22, respectively. Oxidation of 16beta-bromo-4beta,5beta-epoxy-19-ol 21 with pyridinium dichromate followed by controlled alkaline hydrolysis produced 4beta,5beta-epoxy-16alpha-hydroxy-19-al 24.

  13. Reactions between a <111> screw dislocation and <100> interstitial dislocation loops in alpha-iron modelled at atomic-scale

    SciTech Connect

    Terentyev, Dmitry; Bacon, David J; Osetskiy, Yury N

    2010-03-01

    Interstitial dislocation loops with Burgers vector of <100> type are observed in {alpha}-iron irradiated by neutrons or heavy ions, and their population increases with increasing temperature. Their effect on motion of a 1/2<111> edge dislocation was reported earlier 1. Results are presented of a molecular dynamics study of interactions between a 1/2<111> screw dislocation and <100> loops in iron at temperature in the range 100 to 600 K. A variety of reaction mechanisms and outcomes are observed and classified in terms of the resulting dislocation configuration and the maximum stress required for the dislocation to break away. The highest obstacle resistance arises when the loop is absorbed to form a helical turn on the screw dislocation line, for the dislocation cannot glide away until the turn closes and a loop is released with the same Burgers vector as the line. Other than one situation found, in which no dislocation-loop reaction occurs, the weakest obstacle strength is found when the original <100> loop is restored at the end of the reaction. The important role of the cross-slip and the influence of model boundary conditions are emphasised and demonstrated by examples.

  14. Xanthohumol, a main prenylated chalcone from hops, reduces liver damage and modulates oxidative reaction and apoptosis in hepatitis C virus infected Tupaia belangeri.

    PubMed

    Yang, Mingbo; Li, Na; Li, Fang; Zhu, Qianqian; Liu, Xi; Han, Qunying; Wang, Yawen; Chen, Yanping; Zeng, Xiaoyan; Lv, Yi; Zhang, Pingping; Yang, Cuiling; Liu, Zhengwen

    2013-08-01

    Hepatitis C virus (HCV) infection in Tupaia belangeri (Tupaia) represents an important model of HCV infection. Xanthohumol (XN), a major prenylated chalcone from hops, has various biological activities including hepatopreventive and anti-viral activities. In this study, Tupaias infected with HCV RNA positive serum were used to evaluate the effects of XN on liver damage, oxidative reaction, apoptosis and viral protein expression in liver tissues. The Tupaias inoculated with HCV positive serum had elevated serum aminotransferase levels and inflammation, especially hepatic steatosis, and HCV core protein expression in liver tissue. In the animals inoculated with HCV positive serum, XN significantly decreased aminotransferase levels, histological activity index, hepatic steatosis score and transforming growth factor β1 expression in liver tissue compared with the animals without XN intervention. XN reduced HCV core protein expression in liver tissue compared with those without XN intervention but the difference was not significant. XN significantly decreased malondialdehyde, potentiated superoxide dismutase and glutathione peroxidase, reduced Bax expression, promoted Bcl-xL and inhibited caspase 3 activity in liver tissues compared with the animals without XN intervention. These results indicate that XN may effectively improve hepatic inflammation, steatosis and fibrosis induced by HCV in Tupaias primarily through inhibition of oxidative reaction and regulation of apoptosis and possible suppression of hepatic stellate cell activation. The anti-HCV potential of XN needs further investigation.

  15. Structural Basis on the Catalytic Reaction Mechanism of Novel 1,2-Alpha L-Fucosidase (AFCA) From Bifidobacterium Bifidum

    SciTech Connect

    Nagae, M.; Tsuchiya, A.; Katayama, T.; Yamamoto, K.; Wakatsuki, S.; Kato, R.

    2009-06-03

    1,2-alpha-L-fucosidase (AfcA), which hydrolyzes the glycosidic linkage of Fucalpha1-2Gal via an inverting mechanism, was recently isolated from Bifidobacterium bifidum and classified as the first member of the novel glycoside hydrolase family 95. To better understand the molecular mechanism of this enzyme, we determined the x-ray crystal structures of the AfcA catalytic (Fuc) domain in unliganded and complexed forms with deoxyfuconojirimycin (inhibitor), 2'-fucosyllactose (substrate), and L-fucose and lactose (products) at 1.12-2.10 A resolution. The AfcA Fuc domain is composed of four regions, an N-terminal beta region, a helical linker, an (alpha/alpha)6 helical barrel domain, and a C-terminal beta region, and this arrangement is similar to bacterial phosphorylases. In the complex structures, the ligands were buried in the central cavity of the helical barrel domain. Structural analyses in combination with mutational experiments revealed that the highly conserved Glu566 probably acts as a general acid catalyst. However, no carboxylic acid residue is found at the appropriate position for a general base catalyst. Instead, a water molecule stabilized by Asn423 in the substrate-bound complex is suitably located to perform a nucleophilic attack on the C1 atom of L-fucose moiety in 2'-fucosyllactose, and its location is nearly identical near the O1 atom of beta-L-fucose in the products-bound complex. Based on these data, we propose and discuss a novel catalytic reaction mechanism of AfcA.

  16. Reaction rate sensitivity of 44Ti production in massive stars and implications of a thick target yield measurement of 40Ca(alpha,gamma)44Ti

    SciTech Connect

    Hoffman, R D; Sheets, S A; Burke, J T; Scielzo, N D; Rauscher, T; Norman, E B; Tumey, S; Brown, T A; Grant, P G; Hurst, A M; Phair, L; Stoyer, M A; Wooddy, T; Fisker, J L; Bleuel, D

    2010-02-16

    We evaluate two dominant nuclear reaction rates and their uncertainties that affect {sup 44}Ti production in explosive nucleosynthesis. Experimentally we develop thick-target yields for the {sup 40}Ca({alpha},{gamma}){sup 44}Ti reaction at E{sub {alpha}} = 4.13, 4.54, and 5.36 MeV using {gamma}-ray spectroscopy. At the highest beam energy, we also performed an activation measurement which agrees with the thick target result. From the measured yields a stellar reaction rate was developed that is smaller than current statistical-model calculations and recent experimental results, which would suggest lower {sup 44}Ti production in scenarios for the {alpha}-rich freeze out. Special attention has been paid to assessing realistic uncertainties of stellar reaction rates produced from a combination of experimental and theoretical cross sections. With such methods, we also develop a re-evaluation of the {sup 44}Ti({alpha},p){sup 47}V reaction rate. Using these two rates we carry out a sensitivity survey of {sup 44}Ti synthesis in eight expansions representing peak temperature and density conditions drawn from a suite of recent supernova explosion models. Our results suggest that the current uncertainty in these two reaction rates could lead to as large an uncertainty in {sup 44}Ti synthesis as that produced by different treatments of stellar physics.

  17. PRODUCTION OF {sup 9}Be THROUGH THE {alpha}-FUSION REACTION OF METAL-POOR COSMIC RAYS AND STELLAR FLARES

    SciTech Connect

    Kusakabe, Motohiko; Kawasaki, Masahiro E-mail: kawasaki@icrr.u-tokyo.ac.jp

    2013-04-10

    Spectroscopic observations of metal-poor stars have indicated possible {sup 6}Li abundances that are much larger than the primordial abundance predicted in the standard big bang nucleosynthesis model. Possible mechanisms of {sup 6}Li production in metal-poor stars include pregalactic and cosmological cosmic-ray (CR) nucleosynthesis and nucleosynthesis by flare-accelerated nuclides. We study {sup 9}Be production via two-step {alpha}-fusion reactions of CR or flare-accelerated {sup 3,4}He through {sup 6}He and {sup 6,7}Li, in pregalactic structure, intergalactic medium, and stellar surfaces. We solve transfer equations of CR or flare particles and calculate nuclear yields of {sup 6}He, {sup 6,7}Li, and {sup 9}Be taking account of probabilities of processing {sup 6}He and {sup 6,7}Li into {sup 9}Be via fusions with {alpha} particles. Yield ratios, i.e., {sup 9}Be/{sup 6}Li, are then calculated for the CR and flare nucleosynthesis models. We suggest that the future observations of {sup 9}Be in metal-poor stars may find enhanced abundances originating from metal-poor CR or flare activities.

  18. Characterization of radicals and high-molecular weight species from alpha-pinene/ozone reaction and ambient aerosol samples

    NASA Astrophysics Data System (ADS)

    Pavlovic, Jelica

    Secondary organic aerosol formed during oxidation of different volatile organic compounds is composed from a number of final and intermediate reaction products. The final products include compounds in both low and high molecular weight range called also oligomer species. These compounds can be highly volatile, as well as being semi- or low-volatility compounds. This study characterized intermediate reactive radical products formed from previously often studied alpha-pinene/ozone reaction. In order to passivate those radical species nitrone spin traps were used. 5,5-dimethyl-4,5-dihydro-3H-pyrrole-N-oxide (DMPO), and 5-dietoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) traps were able to successfully trap oxygen- and carbon-centered radicals produced from alpha-pinene/ozone reaction. Electrospray ionization (ESI) in negative ion mode with mass spectrometry (MS) detection was used to scan spectra of formed spin trap adducts and the tandem mass spectrometry (MSn) to elucidate its structures as well as structures of captured radicals. The same method was applied to analyze radical species present in ambient PM2.5 samples. Few carbon- (alkyl) and oxygen- (alkoxyl) centered radicals were captured with DMPO and DEPMPO traps. The second part of this study was focused on high molecular weight (high-MW) species formed from the same reaction (alpha-pinene/ozone), but found also in fine particulate matter fractions of ambient samples. LC/MS/MS analysis of dimer species from chamber study revealed fragments that can originate from peroxide structures. Proposed reaction for these peroxide dimer formation is self reaction of two peroxyl radicals, followed by the loss of oxygen molecule. These findings emphasize the role of peroxyl (ROO) radicals in formation of high-MW products and are in line with the high O:C ratio results reported in other studies. Water soluble organic carbon (WSOC) extracts of three size fractions of the ambient aerosol, PM1--2.5, PM0.1--1, and PM<0

  19. Investigation of excitation functions of alpha induced reactions on natXe: Production of the therapeutic radioisotope 131Cs

    NASA Astrophysics Data System (ADS)

    Tárkányi, F.; Hermanne, A.; Király, B.; Takács, S.; Ditrói, F.; Sonck, M.; Kovalev, S. F.; Ignatyuk, A. V.

    2009-03-01

    Excitation functions were measured for alpha-particle induced nuclear reactions on natural xenon leading to the formation of the radionuclides 129m(rel),129g,131m,131mg,133m,135m,137m,139cumBa and 129cum,130mg,132,134m,135m,136mg,138mgCs from the respective thresholds up to 40 MeV. No earlier experimental cross section data were found in the literature. The experimental data were compared to and analyzed with the results of the theoretical model code ALICE-IPPE. The feasibility of the production of the therapeutic radioisotope 131Cs by using gas target technology was investigated. Comparison of reactor and cyclotron production routes of 131Cs was given.

  20. Contribution from 3 α-Condensed States to the Triple-Alpha Reaction

    NASA Astrophysics Data System (ADS)

    Katō, Kiyoshi; Kurokawa, Chie; Arai, Koji

    2010-06-01

    The α-condensed state in nuclear systems has been proposed by Tohsaki et al. and has given rise to interesting discussions. The Hoyle state of 12C has been studied as the most typical example of such an α-condensed state. A new resonant 03+ state (Er = 1.66 MeV, Γ = 1.48 MeV) is predicted as an excited α-condensed state in addition to the second 0+ state of the Hoyle state by calculations of the 3 α orthogonality condition model (3 α OCM) using the complex scaling method. Based on this result, the breakup strengths of the inversion reaction for sequential (8Be+α-->12C+γ) and direct (α+α+α-->12C+γ) processes are calculated. It is discussed that a large reaction strength calculated recently by Ogata et al. in non-resonant energies is considered as a contribution from the excited 03+ state.

  1. Diastereoselectivity in the Mukaiyama-Michael Reaction Employing alpha-Acyl beta,gamma-Unsaturated Phosphonates.

    PubMed

    Telan, Leila A.; Poon, Chi-Duen; Evans, Slayton A.

    1996-10-18

    The unique electronic and structural nature of the alpha-acylphosphonate functional group affords both dimeric and chelated complexes of diethyl crotonyl phosphonate (1; DECP) with stannic chloride (SnCl(4)). The dimeric complex, SnCl(4).(DECP)(2) (5) results from the coordination of two DECP molecules, ligated via the phosphoryl oxygens to the tin atom. The chelated complex, SnCl(4).(DECP) (6), is best represented with both phosphoryl and carbonyl oxygens coordinated to the metal center. Both metal ligated and chelated complexes have unique (13)C (31)P, and (119)Sn NMR spectra. In complex 5, the (13)C NMR resonances attributed to the carbonyl carbons were shifted upfield of free DECP. A monocoordinating Lewis acid, BF(3).OEt(2), produced a similar chemical shift trend in both the (13)C and (31)P NMR spectra of the BF(3).DECP complex. Essentially quantitative yields and moderate diastereomeric excesses favoring anti (or trans) diethyl 6-phenyl-4,5-dimethyl-6-(trimethylsilyloxy)-2-dihydropyranphosphonate (3) and diethyl 5-phenyl-3,4-dimethyl-1,5-dioxopentanephosphonate (4) were obtained from both chelated and dimeric SnCl(4).(DECP)(n) (n = 1, 2) when treated with either diastereomeric (Z)- or (E)-1-phenyl-1-(trimethylsilyloxy)-1-propene 2. Diethyl crotonylphosphonate (1), 3, and 4 were fully characterized.

  2. Participation of Two Carbonic Anhydrases of the Alpha Family in Photosynthetic Reactions in Arabidopsis thaliana.

    PubMed

    Zhurikova, E M; Ignatova, L K; Rudenko, N N; Mudrik, V A; Vetoshkina, D V; Ivanov, B N

    2016-10-01

    The expression of genes of two carbonic anhydrases (CA) belonging to the α-family, α-CA2 and α-CA4 (according to the nomenclature in N. Fabre et al. (2007) Plant Cell Environ., 30, 617-629), was studied in arabidopsis (Arabidopsis thaliana, var. Columbia) leaves. The expression of the At2g28210 gene coding α-CA2 decreased under increase in plant illumination, while the expression of the At4g20990 gene coding α-CA4 increased. Under conditions close to optimal for photosynthesis, in plants with gene At2g28210 knockout, the effective quantum yield of photosystem 2 and the light-induced accumulation of hydrogen peroxide in leaves were lower than in wild type plants, while the coefficient of non-photochemical quenching of leaf chlorophyll a fluorescence and the rate of CO2 assimilation in leaves were higher. In plants with At4g20990 gene knockout, the same characteristics changed in opposite ways relative to wild type. Possible mechanisms of the participation of α-CA2 and α-CA4 in photosynthetic reactions are discussed, taking into account that protons can be either consumed or released in the reactions they catalyze.

  3. Effects of alpha-amylase reaction mechanisms on analysis of resistant-starch contents.

    PubMed

    Moore, Samuel A; Ai, Yongfeng; Chang, Fengdan; Jane, Jay-lin

    2015-01-22

    This study aimed to understand differences in the resistant starch (RS) contents of native and modified starches obtained using two standard methods of RS content analysis: AOAC Method 991.43 and 2002.02. The largest differences were observed in native potato starch, cross-linked wheat distarch phosphate, and high-amylose corn starch stearic-acid complex (RS5) between using AOAC Method 991.43 with Bacillus licheniformis α-amylase (BL) and AOAC Method 2002.02 with porcine pancreatic α-amylase (PPA). To determine possible reasons for these differences, we hydrolyzed raw-starch granules with BL and PPA with equal activity at pH 6.9 and 37°C for up to 84 h and observed the starch granules displayed distinct morphological differences after the hydrolysis. Starches hydrolyzed by BL showed erosion on the surface of the granules; those hydrolyzed by PPA showed pitting on granule surfaces. These results suggested that enzyme reaction mechanisms, including the sizes of the binding sites and the reaction patterns of the two enzymes, contributed to the differences in the RS contents obtained using different methods of RS analysis.

  4. Human alpha-fetal protein immunoassay using fluorescence suppression with fluorescent-bead/antibody conjugate and enzymatic reaction.

    PubMed

    Ahn, Junhyoung; Shin, Yong-Beom; Lee, JaeJong; Kim, Min-Gon

    2015-09-15

    The aim of the study was to develop a simple and rapid immunoassay using fluorescent microbeads and enzyme-substrate reactions to measure alpha-fetal protein (AFP) concentrations. We demonstrated the functionality of the fluorescent immunosensor using antibody-conjugated fluorescent latex beads (AB-FLBs) and horseradish peroxidase (HRP) to catalyze a reaction, where the products would precipitate and suppress the fluorescence of AB-FLBs. First, the AB-FLBs were incubated with antigen, biotinylated antibodies (bABs), and streptavidin-HRP (SAv-HRP) to form a sandwich-type immunoreaction. The mixture was then filtered through a membrane to concentrate the beads on a small area. After washing to remove unbound bABs and SAv-HRP, a chromogenic HRP substrate and H2O2 were added to form precipitates on the FLB surface. The suppression of the fluorescence was measured with a fluorescent image analyzer system. Under optimized conditions, AFP could be measured at concentrations as low as 1 pg mL(-1) with a dynamic range up to 100 ng mL(-1).

  5. Measurement of excitation functions in alpha induced reactions on natCu

    NASA Astrophysics Data System (ADS)

    Shahid, Muhammad; Kim, Kwangsoo; Kim, Guinyun; Zaman, Muhammad; Nadeem, Muhammad

    2015-09-01

    The excitation functions of 66,67,68Ga, 62,63,65Zn, 61,64Cu, and 58,60Co radionuclides in the natCu(α, x) reaction were measured in the energy range from 15 to 42 MeV by using a stacked-foil activation method at the MC-50 cyclotron of the Korean Institute of Radiological and Medical Sciences. The measured results were compared with the literature data as well as the theoretical values obtained from the TENDL-2013 and TENDL-2014 libraries based on the TALYS-1.6 code. The integral yields for thick targets of the produced radionuclides were also determined from the measured excitation functions and the stopping power of natural copper.

  6. Production cross sections of short-lived silver radionuclides from natPd(p,xn) nuclear processes

    NASA Astrophysics Data System (ADS)

    Khandaker, Mayeen Uddin; Kim, Kwangsoo; Kim, Guinyun

    2012-03-01

    Production cross-sections of short-lived 103Ag, 104mAg and 104gAg radionuclides from proton-induced reactions on natural palladium (Pd) were measured up to 41 MeV by using a stacked-foil activation technique combined with high resolution γ-ray spectrometry. The present results are compared with the available literature values as well as theoretical data calculated by the TALYS and the ALICE-IPPE computer codes. Note that production cross-sections of the 104mAg radionuclide from natPd(p,xn) processes has been measured here for the first time. Physical thick target yields for the investigated radionuclides were deduced from the respective threshold energy to 41 MeV taking into account that the total energy is absorbed in the targets. Measured data of the short-lived 103Ag radionuclide are noteworthy due to its possible applications as a precursor for the indirect production of widely used therapeutic 103Pd radionuclide via natPd(p,xn)103Ag → 103Pd processes. On the other hand, the investigated 104Ag radionuclide finds importance due to its potential use as a diagnostic and positron emission tomography (PET) imaging analogue. Above all, measured data will enrich the literature database leading to various applications in science and technology.

  7. Direct measurement of the breakout reaction {sup 11}C({alpha},p){sup 14}N in explosive hydrogen-burning process

    SciTech Connect

    Hayakawa, S.; Kubono, S.; Kahl, D.; Yamaguchi, H.; Binh, Dam N.; Hashimoto, T.; Wakabayashi, Y.; He, J. J.; Iwasa, N.; Kato, S.; Komatsubara, T.; Kwon, Y. K.; Teranishi, T.; Wanajo, S.

    2012-11-12

    We determined the {sup 11}C({alpha},p){sup 14}N reaction rate relevant to the nucleosynthesis in explosive hydrogen-burning stars. The measurement was performed by means of the thick target method in inverse kinematics with {sup 11}C RI beams. We derived the excitation functions for the ground-state transition and excited-state transitions using time-of-flight information for the first time. The present reaction rate is compared to the previous one.

  8. Decellularization of bovine anterior cruciate ligament tissues minimizes immunogenic reactions to alpha-gal epitopes by human peripheral blood mononuclear cells.

    PubMed

    Yoshida, Ryu; Vavken, Patrick; Murray, Martha M

    2012-10-01

    Rupture of ACL is a common injury. While the current surgical treatments are effective, many patients still suffer from precocious osteoarthritis, and there is an increasing interest in bioengineering approaches to improve ACL repair. Bovine collagen is a material currently in use for tissue engineering of ligaments. The alpha-gal epitopes found on bovine cells are a source of immunogenic stimulus for human cells. In this study, we wished to determine if those epitopes could be removed sufficiently to mitigate an immunogenic response using either a decellularization protocol or decellularization followed by alpha-galactosidase treatment. Bovine ACLs were treated with Triton-X, sodium deoxycholate, ribonuclease, and deoxyribonuclease to remove cells. A subset of the decellularized tissues was further treated with alpha-galactosidase. Human peripheral blood mononuclear cells (PBMCs) were exposed to untreated, decellularized, and alpha-galactosidase-treated tissues, and PBMC migration and IL-6 release were measured. PBMCs were significantly more attracted to untreated ACL compared to decellularized or alpha-galactosidase-treated tissue, but no difference was seen between the two treatment groups. PBMCs also released significantly more IL-6 when exposed to untreated tissue compared to decellularized ACL or alpha-galactosidase-treated ACL, but no difference was seen between the two treatment groups. Immunohistochemistry using anti-alpha-gal antibody detected the epitopes throughout the untreated ACL, but similar areas of reaction were not seen on decellularized or alpha-galactosidase-treated ACL. These results suggest that our decellularization protocol minimizes the immunogenic reactions of human PBMCs to bovine ACL tissue. Therefore, decellularized bovine ACL tissue may be a safe, effective biomaterial for ACL injury treatments.

  9. Intramolecular condensation reactions of {alpha}, {omega}- bis(triethoxy-silyl)alkanes. Formation of cyclic disilsesquioxanes

    SciTech Connect

    Loy, D.A.; Carpenter, J.P.; Myers, S.A.; Assink, R.A.; Small, J.H.; Greaves, J.; Shea, K.J.

    1996-08-01

    Under acidic sol-gel polymerization conditions, 1,3-bis(triethoxysilyl)-propane (1) and 1,4-bis(triethoxysilyl)butane (2) were shown to preferentially form cyclic disilsesquioxanes 3 and 4 rather than the expected 1,3-propylene- and 1,4-butylene-bridged polysilsesquioxane gels. Formation of 3 and 4 is driven by a combination of an intramolecular cyclization to six and seven membered rings, and a pronounced reduction in reactivity under acidic conditions as a function of increasing degree of condensation. The ease with which these relatively unreactive cyclic monomers and dimers are formed (under acidic conditions) helps to explain the difficulties in forming gels from 1 and 2. The stability of cyclic disilsesquioxanes was confirmed withe the synthesis of 3 and 4 in gram quantities; the cyclic disilsesquioxanes react slowly to give tricyclic dimers containing a thermodynamically stable eight membered siloxane ring. Continued reactions were shown to perserve the cyclic structure, opening up the possibility of utilizing cyclic disilsesquioxanes as sol-gel monomers. Preliminary polymerization studies with these new, carbohydrate-like monomers revealed the formation of network poly(cyclic disilsesquioxanes) under acidic conditions and polymerization with ring-opening under basic conditions.

  10. Reich-Moore Parameterization of ({alpha},n) Reactions on Light Nuclei: Impact on a Neutron Source Calculation in an Oxide Fuel

    SciTech Connect

    Babut, Richard; Bouland, Olivier; Fort, Eric

    2005-10-15

    Evaluated data are adjusted on experimental measurements using nuclear reaction models. Among these data, those concerning alpha-particle interactions on light nuclei are not well known, although crucial for neutron emission problems via ({alpha},n) processes in nuclear fuels (oxide, carbide, nitride). Examples of applications are reprocessing, packaging and storage of radioactive waste, and intrinsic neutron source term evaluation in critical and subcritical reactors (accelerator-driven systems). The goal is the modeling of ({alpha},n) reactions on oxygen isotopes to extract the resonance parameters. The SAMMY code, which relies on the Reich-Moore approximation of the R-matrix theory, is used. In the most recent version, the SAMMY code allows the study of the in- and outgoing charged-particle channels. An important validation of this new feature has been made. In addition, a manifest lack of experimental data for this type of reaction has been underlined. Finally, the impact of the new pointwise description of the ({alpha},n) reaction cross section on the energy distribution calculation of the intrinsic neutron source of an irradiated mixed-oxide fuel pin is shown and compared to the standard calculation, which uses average cross sections.

  11. NEW DETERMINATION OF THE {sup 13}C({alpha}, n){sup 16}O REACTION RATE AND ITS INFLUENCE ON THE s-PROCESS NUCLEOSYNTHESIS IN AGB STARS

    SciTech Connect

    Guo, B.; Li, Z. H.; Li, Y. J.; Su, J.; Yan, S. Q.; Bai, X. X.; Chen, Y. S.; Fan, Q. W.; Jin, S. J.; Li, E. T.; Li, Z. C.; Lian, G.; Liu, J. C.; Liu, X.; Shu, N. C.; Lugaro, M.; Buntain, J.; Pang, D. Y.; Karakas, A. I.; Shi, J. R. E-mail: guobing@ciae.ac.cn; and others

    2012-09-10

    We present a new measurement of the {alpha}-spectroscopic factor (S{sub {alpha}}) and the asymptotic normalization coefficient for the 6.356 MeV 1/2{sup +} subthreshold state of {sup 17}O through the {sup 13}C({sup 11}B, {sup 7}Li){sup 17}O transfer reaction and we determine the {alpha}-width of this state. This is believed to have a strong effect on the rate of the {sup 13}C({alpha}, n){sup 16}O reaction, the main neutron source for slow neutron captures (the s-process) in asymptotic giant branch (AGB) stars. Based on the new width we derive the astrophysical S-factor and the stellar rate of the {sup 13}C({alpha}, n){sup 16}O reaction. At a temperature of 100 MK, our rate is roughly two times larger than that by Caughlan and Fowler and two times smaller than that recommended by the NACRE compilation. We use the new rate and different rates available in the literature as input in simulations of AGB stars to study their influence on the abundances of selected s-process elements and isotopic ratios. There are no changes in the final results using the different rates for the {sup 13}C({alpha}, n){sup 16}O reaction when the {sup 13}C burns completely in radiative conditions. When the {sup 13}C burns in convective conditions, as in stars of initial mass lower than {approx}2 M{sub Sun} and in post-AGB stars, some changes are to be expected, e.g., of up to 25% for Pb in our models. These variations will have to be carefully analyzed when more accurate stellar mixing models and more precise observational constraints are available.

  12. Structural effects on the beta-scission reaction of tertiary arylcarbinyloxyl radicals. The role of alpha-cyclopropyl and alpha-cyclobutyl groups.

    PubMed

    Bietti, Massimo; Gente, Giacomo; Salamone, Michela

    2005-08-19

    A product and time-resolved kinetic study on the reactivity of tertiary arylcarbinyloxyl radicals bearing alpha-cyclopropyl and alpha-cyclobutyl groups has been carried out. Both the 1-cyclopropyl-1-phenylethoxyl (1.) and alpha,alpha-dicyclopropylphenylmethoxyl (2.) radicals undergo beta-scission to give cyclopropyl phenyl ketone as the major or exclusive product with rate constants higher than that measured for the cumyloxyl radical. It is proposed that in the transition state for beta-scission of 1. and 2., formation of the C=O double bond is assisted by overlap with the C-C bonding orbitals of the cyclopropane ring. With tertiary arylcarbinyloxyl radicals bearing alpha-cyclobutyl groups such as the 1-cyclobutyl-1-phenylethoxyl (4.) and 1-cyclobutyl-1-phenylpropoxyl (5.) radicals, the fragmentation regioselectivity is essentially governed by the stability of the radical formed by beta-scission. Accordingly, 4. undergoes exclusive C-cyclobutyl bond cleavage to give acetophenone, whereas with 5., competition between C-cyclobutyl and C-ethyl bond cleavage, leading to propiophenone and cyclobutylphenyl ketone in a 2:1 ratio, is observed.

  13. Prolonged paradoxical reaction to anti-tuberculous treatment after discontinuation of TNF-alpha- blocker therapy with adalimumab. Rare clinical documentation

    PubMed Central

    Husemann, Kim; Kohlhäufl, Martin

    2015-01-01

    In the past decades, tumor necrosis factor alpha (TNF-a) antagonist has been a milestone in the treatment of many chronic inflammatory diseases. TNF antagonist can increase patients’ susceptibility to many different kinds of infections especially those requiring granuloma formations despite regular performance of Screening for latent tuberculosis infection (LTBI). We report 2 cases of patients who developed tuberculosis under treatment with adalimumab, which was discontinued after the diagnosis of tuberculosis. During the tuberculosis therapy they unexpectedly developed a prolonged paradoxical reaction. In both cases we were only able to manage the progress of the paradoxical reaction through high steroid doses. Patients undergoing therapy with TNF- alpha-blocker are prone to develop tuberculosis infection, which could in turn lead to severe prolonged paradoxical reaction during anti-tuberculous treatment. An increased steroid dose may be required and is sometimes necessary.

  14. Organophosphate inhibitors: the reactions of bis(p-nitrophenyl) methyl phosphate with liver carboxylesterases and alpha-chymotrypsin.

    PubMed

    Hamilton, S E; Dudman, A P; De Jersey, J; Stoops, J K; Zerner, B

    1975-02-19

    Bis(p-nitrophenyl) methyl phosphate (BNMP) has been tested as a spectrophotometric titrant for a group of serine hydrolases. Bis(p-nitrophenyl) methyl phosphate reacts rapidly with liver carboxylesterases from chicken, sheep, and horse, and more slowly with alpha-chymotrypsin, releasing 2 mol of p-nitrophenol per active site titrated, and producing a phosphorylated enzyme very stable to dephosphorylation. However, pig liver carboxylesterase produces 2.2 mol of p-nitrophenol per active site titratedmreaction of pig and chicken liver carboxylesterases with bis(p-nitrophenyl) [3H]methyl [32P]phosphate clarified this differencemone molecule of the chicken enzyme reacts with one molecule of bis(p-nitrophenyl) methyl phosphate, releasing both p-nitrophenol residues, and resulting in an inhibited enzyme with one phosphorus atom and one methyl group covalently bound. Pig enzyme reacts rapidly, forming (presumably) methyl p-nitrophenyl phosphoryl-carboxylesterasemthis further reacts, concurrently producing methyl phosphoryl-carboxylesterase plus p-nitrophenol, or free enzyme plus methyl p-nitrophenyl phosphate, in the ratio of about 5 : 1 at pH 7.55. The free enzyme produced undergoes further reaction with bis(p-nitrophenyl) methyl phosphate until all the carboxylesterase is inhibited.

  15. Low-temperature sequential pulsed chemical vapor deposition of ternary B{sub x}Ga{sub 1-x}N and B{sub x}In{sub 1-x}N thin film alloys

    SciTech Connect

    Haider, Ali E-mail: biyikli@unam.bilkent.edu.tr; Kizir, Seda; Ozgit-Akgun, Cagla; Biyikli, Necmi E-mail: biyikli@unam.bilkent.edu.tr; Okyay, Ali Kemal

    2016-01-15

    In this work, the authors have performed sequential pulsed chemical vapor deposition of ternary B{sub x}Ga{sub 1-x}N and B{sub x}In{sub 1-x}N alloys at a growth temperature of 450 °C. Triethylboron, triethylgallium, trimethylindium, and N{sub 2} or N{sub 2}/H{sub 2} plasma have been utilized as boron, gallium, indium, and nitrogen precursors, respectively. The authors have studied the compositional dependence of structural, optical, and morphological properties of B{sub x}Ga{sub 1-x}N and B{sub x}In{sub 1-x}N ternary thin film alloys. Grazing incidence X-ray diffraction measurements showed that boron incorporation in wurtzite lattice of GaN and InN diminishes the crystallinity of B{sub x}Ga{sub 1-x}N and B{sub x}In{sub 1-x}N sample. Refractive index decreased from 2.24 to 1.65 as the B concentration of B{sub x}Ga{sub 1-x}N increased from 35% to 88%. Similarly, refractive index of B{sub x}In{sub 1-x}N changed from 1.98 to 1.74 for increase in B concentration value from 32% to 87%, respectively. Optical transmission band edge values of the B{sub x}Ga{sub 1-x}N and B{sub x}In{sub 1-x}N films shifted to lower wavelengths with increasing boron content, indicating the tunability of energy band gap with alloy composition. Atomic force microscopy measurements revealed an increase in surface roughness with boron concentration of B{sub x}Ga{sub 1-x}N, while an opposite trend was observed for B{sub x}In{sub 1-x}N thin films.

  16. Reactions of OH with. alpha. -pinene and. beta. -pinene in air: Estimate of global CO production from the atmosphere oxidation of terpenes

    SciTech Connect

    Hatakeyama, Shiro; Izumi, Katsuyuki; Fukuyama, Tsutomu; Akimoto, Hajime; Washida, Nobuaki )

    1991-01-20

    Reactions of OH with {alpha}-pinene and {beta}-pinene were studied for the purpose of obtaining the basic data to estimate the emission rate of CO from the photooxidation of terpenes in the atmosphere. In the presence of NO the main product was pinonaldehyde and 6,6-dimethylbicyclo(3.1.1)heptan-2-one from {alpha}- and {beta}-pinene, respectively, and the yield was 56{plus minus}4 and 79{plus minus}8%, respectively. In the absence of NO the yield was remarkably lower, and the yield of organic aerosols was enhanced. For {alpha}-pinene 56 {plus minus} 3% was obtained as a yield of aerosols on the carbon number basis. Gross annual emission of CO from the reactions of OH with terpenes was estimated to be 22 Tg C/yr (50 Tg CO/yr) by regarding {alpha}-pinene as the representative of terpenes, on the basis of the annual emission rate of terpenes, estimated lifetime of pinenes in the atmosphere, the apparent rate constant for the intermediate to form CO, and the estimated yield of CO from the secondary oxidation of pinonaldehyde. The ultimate yield of CO from the tropospheric oxidation of terpenes (including both ozone and OH reactions) was estimated to be 20% on the carbon number basis, and the total annual emission of CO was evaluated to be 96 Tg C/yr (222 Tg CO/yr).

  17. The stem of sinomenium acutum inhibits mast cell-mediated anaphylactic reactions and tumor necrosis factor-alpha production from rat peritoneal mast cells.

    PubMed

    Kim, H M; Moon, P D; Chae, H J; Kim, H R; Chung, J G; Kim, J J; Lee, E J

    2000-05-01

    The aqueous extract of Sinomenium acutum stem (SSAE) (0.1-1000 mg/kg) dose-dependently inhibited systemic anaphylactic reaction induced by compound 48/80 in mice. In particular, SSAE reduced compound 48/80-induced anaphylactic reaction with 50% at the dose of 1000 mg/kg. SSAE (100-1000 mg/kg) also significantly inhibited local anaphylactic reaction activated by anti-dinitrophenyl (DNP) IgE. When mice were pretreated with SSAE at a concentration ranging from 0.1 to 1000 mg/kg, the plasma histamine levels were reduced in a dose-dependent manner. SSAE (1-1000 microg/ml) dose-dependently inhibited histamine release from the rat peritoneal mast cells (RPMCs) activated by compound 48/80 or anti-DNP IgE. In addition, SSAE (0.1 microg/ml) had a significant inhibitory effect on anti-DNP IgE-induced tumor necrosis factor-alpha (TNF-alpha) production. These results indicate that SSAE inhibits mast cell-mediated anaphylactic reactions and TNF-alpha production from mast cells.

  18. A compilation of information on the {sup 31}P(p,{alpha}){sup 28}Si reaction and properties of excited levels in the compound nucleus {sup 32}S

    SciTech Connect

    Miller, R.E.; Smith, D.L.

    1997-11-01

    This report documents a survey of the literature, and provides a compilation of data contained therein, for the {sup 31}P(p,{alpha}){sup 28}Si reaction. Attention is paid here to resonance states in the compound-nuclear system {sup 32}S formed by {sup 31}P + p, with emphasis on the alpha-particle decay channels, {sup 28}Si + {alpha} which populate specific levels in {sup 28}Si. The energy region near the proton separation energy for {sup 32}S is especially important in this context for applications in nuclear astrophysics. Properties of the excited states in {sup 28}Si are also considered. Summaries of all the located references are provided and numerical data contained in them are compiled in EXFOR format where applicable.

  19. Measurement of the cross section for the reaction {sup 20}Ne(n,{alpha}){sup 17}O in the neutron-energy between 4 and 7 MeV

    SciTech Connect

    Khryachkov, V. A.; Bondarenko, I. P.; Kuzminov, B. D.; Semenova, N. N.; Sergachev, A. I.

    2012-04-15

    The cross section for the reaction {sup 20}Ne(n, {alpha}){sup 17}O was measured in the neutron-energy range 4-7 MeV. An ionization chamber equipped with a Frisch grid combined with a pulse-shape digitizer was used as a detector. Gaseous neon that served as a target on which the reaction being studied proceeded was added to the gas filling the ionization chamber. The partial cross sections for the {alpha}{sub 0}, {alpha}{sub 1}, {alpha}{sub 2}, and {alpha}{sub 3} channels of the reaction {sup 20}Ne(n, {alpha}){sup 17}O were obtained for the first time.

  20. Measurement of natW(p,xn)177,178,179Re excitation function of natural tungsten by using a 100-MeV proton beam

    NASA Astrophysics Data System (ADS)

    Yoon, Jungran; Lee, Jieun; Lee, Samyol

    2017-01-01

    Measurements of the proton-induced excitation function for the natW(p,xn)177,178,179Re nuclear reaction has been measured in the energy region below 100 MeV by using the 100-MeV proton linear accelerator at the Korea Multi-Purpose Accelerator Complex. The stacked foil activation technique was adopted in the present study. The gamma-rays generated from the proton-irradiated samples were measured by using a gamma-ray spectroscopy system with a HPGe detector. The 27Al(p,3p+n)24Na reaction was used as a monitor reaction for proton flux monitoring. The nuclear reactions of natW(p,xn)177,178,179Re were observed in the present study. The proton-induced excitation functions of natural tungsten were derived from the delayed gamma-ray yield of the produced nucleus. The present results were compared with the previous experimental excitation function data of Yu. E. Titarenko et al. [1].

  1. Temperature dependence of the rate coefficient for the alpha-pinene reaction with ozone in the range between 243 K and 303 K.

    PubMed

    Tillmann, Ralf; Saathoff, Harald; Brauers, Theo; Kiendler-Scharr, Astrid; Mentel, Thomas F

    2009-04-07

    The absolute rate coefficient for the reaction of alpha-pinene with ozone was determined in the temperature range between 243 K and 303 K at atmospheric pressure. In total, 30 experiments were performed in the large (85 m3) temperature-controlled simulation chamber AIDA, where the concentrations of the reactants ozone and alpha-pinene were measured directly. An Arrhenius expression for the alpha-pinene + ozone reaction was derived with a pre-exponential factor of (1.4 +/- 0.4) x 10(-15) cm3 s(-1) and a temperature coefficient of (833 +/- 86) K. This rate coefficient is in good agreement (-5%) with the current IUPAC (IUPAC 2007) recommendation at 298 K. The IUPAC recommendation is significantly larger (+27%), around 243 K where the recommended values were extrapolated from higher temperatures. This finding is relevant for tropical regions where strong updrafts can rapidly transport reactive hydrocarbons like alpha-pinene from the boundary layer into the cold regions of the free troposphere.

  2. Interference effects between /sup 17/O states populated in the /sup 13/C(/sup 6/Li,d)/sup 17/O*. --> cap alpha. +/sup 13/C reaction

    SciTech Connect

    Cardella, G.; Cunsolo, A.; Foti, A.; Imme, G.; Pappalardo, G.; Raciti, G.; Rizzo, F.; Alamanos, N.; Berthier, B.; Saunier, N.

    1987-12-01

    An analysis of the /sup 13/C(/sup 6/Li,d..cap alpha..)/sup 13/C reaction in the collinear (theta/sub d/ = 0/sup 0/) and noncollinear (theta/sub d/ = 10/sup 0/,8/sup 0/) geometry is made for two peaks observed in the deuteron energy spectrum and corresponding to excitation energies of 16.1 and 13.6 MeV in the /sup 17/O nucleus. It is shown that the reaction proceeds via a direct alpha-transfer process which populates doublets of interfering /sup 17/O levels. Spins, weights, and parities of these levels are obtained by means of a least square procedure.

  3. Comparison of the (p,xn) cross sections from /sup 238/U, /sup 235/U, and /sup 232/Th targets irradiated with 200-MeV protons

    SciTech Connect

    Chu, Y.Y.; Zhou, M.L.

    1982-01-01

    We have measured absolute cross sections for (p,xn) reactions (x ranges from 0 to 8) from /sup 238/U, /sup 235/U, and /sup 232/Th targets irradiated with 200-MeV protons at the Brookhaven AGS Linac injector. Chemical yields were determined by using /sup 239/Np and /sup 233/Pa as tracers. Yield patterns obtained in this work can be compared to the experimental results and theoretical calculations from earlier work, and they are consistent within the framework of intranuclear cascade followed by neutron evaporation and fission competition.

  4. Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors

    NASA Technical Reports Server (NTRS)

    Stern, Jeffrey A.; Farr, William H.; Leduc, Henry G.; Bumble, Bruce

    2008-01-01

    Superconducting-nanowire single-photon detectors (SNSPDs) in which Nb(x)Ti(1-x)N (where x<1) films serve as the superconducting materials have shown promise as superior alternatives to previously developed SNSPDs in which NbN films serve as the superconducting materials. SNSPDs have potential utility in optical communications and quantum cryptography. Nb(x)Ti(1-x)N is a solid solution of NbN and TiN, and has many properties similar to those of NbN. It has been found to be generally easier to stabilize Nb(x)Ti(1-x)N in the high-superconducting-transition temperature phase than it is to so stabilize NbN. In addition, the resistivity and penetration depth of polycrystalline films of Nb(x)Ti(1-x)N have been found to be much smaller than those of films of NbN. These differences have been hypothesized to be attributable to better coupling at grain boundaries within Nb(x)Ti(1-x)N films.

  5. Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors

    NASA Technical Reports Server (NTRS)

    Stem, Jeffrey A.; Farr, William H.; Leduc, Henry G.; Bumble, Bruce

    2008-01-01

    Superconducting-nanowire singlephoton detectors (SNSPDs) in which Nb(x)Ti(1-x)N (where x<1) films serve as the superconducting materials have shown promise as superior alternatives to previously developed SNSPDs in which NbN films serve as the superconducting materials. SNSPDs have potential utility in optical communications and quantum cryptography. Nb(x)Ti(1-x)N is a solid solution of NbN and TiN, and has many properties similar to those of NbN. It has been found to be generally easier to stabilize NbxTi1 xN in the high-superconducting-transitiontemperature phase than it is to so stabilize NbN. In addition, the resistivity and penetration depth of polycrystalline films of Nb(x)Ti(1-x)N have been found to be much smaller than those of films of NbN. These differences have been hypothesized to be attributable to better coupling at grain boundaries within Nb(x)Ti(1-x)N films.

  6. Wurtzite Al xGa 1- xN bulk crystals grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Novikov, S. V.; Staddon, C. R.; Powell, R. E. L.; Akimov, A. V.; Luckert, F.; Edwards, P. R.; Martin, R. W.; Kent, A. J.; Foxon, C. T.

    2011-05-01

    We have studied the growth of wurtzite GaN and Al xGa 1- xN layers and bulk crystals by molecular beam epitaxy (MBE). MBE is normally regarded as an epitaxial technique for the growth of very thin layers with monolayer control of their thickness. However, we have used the MBE technique for bulk crystal growth and have produced 2 in diameter wurtzite Al xGa 1- xN layers up to 10 μm in thickness. Undoped wurtzite Al xGa 1- xN films were grown on GaAs (1 1 1)B substrates by a plasma-assisted molecular beam epitaxy (PA-MBE) method and were removed from the GaAs substrate after the growth. The fact that free-standing ternary Al xGa 1- xN wafers can be grown is very significant for the potential future production of wurtzite Al xGa 1- xN substrates optimized for AlGaN-based device structures.

  7. Multichannel study of the {sup 13}C({alpha},n){sup 16}O and {sup 16}O(n,{gamma}){sup 17}O reactions

    SciTech Connect

    Dufour, M.; Descouvemont, P.

    2005-07-01

    The {sup 13}C({alpha},n){sup 16}O reaction is investigated in a microscopic two-cluster model with an effective interaction recently developed for transfer reactions. The wave functions are defined in the generator coordinate method. The basis includes all {sup 13}C+{alpha} and {sup 16}O+n channels with {sup 13}C and {sup 16}O described in the p shell. Particle-hole excitations in the sd shell are also taken into account in order to include the {sup 16}O(3{sup -})+n channel. The {sup 17}O spectroscopy is in good agreement with experiment. In particular, the width of the astrophysically relevant 1/2{sub 2}{sup +} state is well reproduced ({gamma}=121 keV as compared to the experimental value {gamma}=124{+-}12 keV). The calculation of the {sup 13}C({alpha},n){sup 16}O S factor shows the importance of the 3/2{sub 3}{sup +} resonance, and provides S(0.2 MeV)=2.1x10{sup 6} MeV b, slightly lower than the NACRE recommended value (2.5x10{sup 6} MeV b). The same model is applied to the {sup 16}O(n,{gamma}){sup 17}O radiative-capture reaction at thermal and astrophysical energies.

  8. Nondeletional alpha-thalassemia: first description of alpha Hph alpha and alpha Nco alpha mutations in a Spanish population.

    PubMed

    Ayala, S; Colomer, D; Aymerich, M; Pujades, A; Vives-Corrons, J L

    1996-07-01

    Several different deletions underlie the molecular basis of alpha-thalassemia. The most common alpha-thalassemia determinant in Spain is the rightward deletion (-alpha 3.7). To our knowledge, however, no cases of alpha-thalassemia due to nondeletional mutations have so far been described in this particular Mediterranean area. Here, we report the existence of nondeletional forms of alpha-thalassemia in ten Spanish families. The alpha 2-globin gene was characterized in ten unrelated patients and their relatives only when the presence of deletional alpha-thalassemia was ruled out. The alpha 2-globin gene analysis was performed using the polymerase chain reaction (PCR) followed by restriction enzyme analysis or by allelespecific priming. This allowed the identification of a 5-base pair (bp) deletion at the donor site of IVS I (alpha Hph alpha) in 9 cases and the alpha 2 initiation codon mutation (alpha Nco alpha) in one case. Although these alpha 2-globin gene mutations are found in other mediterranean areas, our results demonstrate their presence in the Spanish population and suggest that the alpha Hph alpha/alpha alpha genotype is probably the most common nondeletional form of alpha-thalassemia in Spain.

  9. Structure-activity relationships of 2alpha-substituted androstenedione analogs as aromatase inhibitors and their aromatization reactions.

    PubMed

    Numazawa, Mitsuteru; Handa, Wakako; Hasegawa, Chie; Takahashi, Madoka

    2005-12-01

    Aromatase catalyzes the conversion of androstenedione (1a, AD) to estrone through three sequential oxygenations of the 19-methyl group. To gain insight into the spatial nature of the AD binding (active) site of aromatase in relation to the catalytic function of the enzyme, we tested for the ability of 2alpha-substituted (halogeno, alkyl, hydroxy, and alkoxy) ADs (1b-1i) to inhibit aromatase in human placental microsomes as well as their ability to serve as a substrate for the enzyme. All of the steroids inhibited the enzyme in a competitive manner with the apparent K(i)'s ranging from 45 to 1150 nM. 2alpha-Halogeno (F, Cl, and Br) and 2alpha-alkyl (CH3 and CH2CH3) steroids 1b-1f were powerful to good inhibitors (Ki=45-171 nM) whereas steroids 1g-1i, having an oxygen function (hydroxy or alkoxy) at C-2alpha, were poor inhibitors (Ki=670-1150 nM). Aromatization of some of the steroids with placental microsomes was analyzed by gas chromatography-mass spectrometry, indicating that the aromatization rate of the bromide 1d was about two-fold that of the natural substrate AD and that of 2alpha-methoxide 1h was similar to that of AD. Kinetic analysis of the aromatization of androgens revealed that a good substrate was not essentially a good inhibitor for aromatase.

  10. Resonances in (11)C observed in the (4)He((7)Be, alpha)(7)Be and (4)He((7)Be, p)(10)B reactions

    SciTech Connect

    Freer, M.; Ashwood, N. I.; Curtis, N.; Malcolm, J.; Munoz-Britton, T.; Price, D.; Wheldon, C.; Achouri, N. L.; Demaret, P.; Bardayan, Daniel W; Pain, Steven D; Brown, S.; Catford, W.; Harlin, Christopher W; Thomas, J. S.; Wilson, G.; Chipps, K.; Milin, M.; Raabe, R.; Soic, N.

    2012-01-01

    Measurements of the {sup 4}He({sup 7}Be,{alpha}){sup 7}Be and {sup 4}He({sup 7}Be,p){sup 10}B reactions were performed using {sup 7}Be beam energies of 7.1 and 23 MeV and a helium-4 target, employing the thick target technique. Resonances were observed between E{sub x}({sup 11}C) = 8.6 to 13.8 MeV. An R-matrix analysis was performed to characterize the spins and partial widths. This analysis showed that the observed sequence of states was consistent with that found for {sup 7}Li + {alpha} resonant scattering populating resonances in {sup 11}B. A comparison of the proposed partial widths for decay with the Wigner limit indicates that several of the states are associated with cluster-like structures.

  11. Enantioselective alpha-arylation of aldehydes via organo-SOMO catalysis. An ortho-selective arylation reaction based on an open-shell pathway.

    PubMed

    Conrad, Jay C; Kong, Jongrock; Laforteza, Brian N; MacMillan, David W C

    2009-08-26

    The intramolecular alpha-arylation of aldehydes has been accomplished using singly occupied molecular orbital (SOMO) catalysis. Selective oxidation of chiral enamines (formed by the condensation of an aldehyde and a secondary amine catalyst) leads to the formation of a 3pi-electron radical species. These chiral SOMO-activated radical cations undergo enantioselective reaction with an array of pendent electron-rich aromatics and heterocycles thus efficiently providing cyclic alpha-aryl aldehyde products (10 examples: > or = 70% yield and > or = 90% ee). In accordance with our radical mechanism, when there is a choice between arylation at the ortho or para position of anisole substrates, we find that arylation proceeds selectively at the ortho position.

  12. Nuclear gamma rays from 720-MeV alpha-induced reactions on Al-27 and Si-28

    NASA Technical Reports Server (NTRS)

    Lieb, B. J.; Plendl, H. S.; Funsten, H. O.; Stronach, C. E.; Lind, V. G.

    1980-01-01

    Prompt gamma rays from the interaction of 720-MeV alpha particles with Al-27 and Si-28 were detected and analyzed to identify residual nuclei and to determine cross sections for production of specific levels. No gamma-ray transitions were detected from nuclei heavier than the target. From Doppler broadening, the momentum of the residual nuclei was estimated. The results are compared with previous results for 140- and 1600-MeV alphas on Al-27 and approximately 200-MeV positive or negative pions on Al-27 and Si-28 and fitted to a spallation-yield formula.

  13. Indirect study of the {sup 13}C({alpha},n){sup 16}O reaction via the {sup 13}C({sup 7}Li,t){sup 17}O transfer reaction

    SciTech Connect

    Pellegriti, M. G.; Hammache, F.; Roussel, P.; Audouin, L.; Beaumel, D.; Fortier, S.; Vilmay, M.; Descouvemont, P.; Gaudefroy, L.; Kiener, J.; Lefebvre-Schuhl, A.; Tatischeff, V.; Stanoiu, M.

    2008-04-15

    The {sup 13}C({alpha},n){sup 16}O reaction is considered the main neutron source for the s process in low mass asymptotic giant branch (AGB) stars. In the Gamow peak, the cross section sensitively depends on the 1/2{sup +} subthreshold state of {sup 17}O (E{sub x}=6.356 MeV). In this work, we determined the astrophysical S factor through an evaluation of the {alpha} spectroscopic factor and the corresponding asymptotic normalization factor (ANC) of the 6.356 MeV state using the transfer reaction {sup 13}C({sup 7}Li,t){sup 17}O at two different incident energies. Our result confirms that the contribution of the 1/2{sup +} state is dominant at astrophysical energies. Our reaction rate at T=0.09 GK is slightly lower than the value adopted in the Nuclear Astrophysics Compilation of REaction rates (NACRE), but two times larger than the one obtained in a recent ANC measurement.

  14. Multiplex polymerase chain reaction-based deletion analysis of spontaneous, gamma ray- and alpha-induced hprt mutants of CHO-K1 cells.

    PubMed

    Schwartz, J L; Rotmensch, J; Sun, J; An, J; Xu, Z; Yu, Y; Hsie, A W

    1994-11-01

    Independent Chinese hamster ovary (CHO)-K1 cell mutants at the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus were isolated from untreated, 60Co gamma ray- and 212Bi alpha-exposed cells and the genetic changes underlying the mutation determined by multiplex polymerase chain reaction (PCR)-based exon deletion analysis. In the 71 spontaneous mutants analyzed, 77.5% of the clones showed no change in exon number or size, 15.5% showed a loss of a single exon, 4.2% showed a loss of 2-8 exons, and 2.8% showed loss of all nine hprt exons (total gene deletion). Exposure to 6 Gy of gamma rays, which reduced survival levels to 10%, produced a significantly different deletion spectrum that was shifted toward deletions with 45% of the 20 mutants analyzed showing a loss of a single exon and 30% showing a loss of all nine exons. Exposure to 2 Gy alpha radiation from 212Bi, a 220Rn daughter, a dose which also reduced survival levels to about 10%, resulted in a deletion spectrum similar to the gamma-ray spectrum in that more than 75% of the 49 mutants analyzed were deletions. The alpha spectrum, however, was significantly different from both the spontaneous and gamma spectra with 55.1% of the alpha mutants showing a loss of all nine exons, 10.2% showing loss of a single exon, and 14.3% showing loss of 2-8 exons. Thus, alpha-radiation appears to produce larger intragenic deletions than gamma radiation. The results suggest that intragenic deletion size should be considered when low- and high linear energy transfer (LET) mutation spectra are compared.

  15. Polymerase chain reaction-deletion analysis of spontaneous, gamma ray-, and alpha-induced hprt mutants of CHO-K1 cells.

    SciTech Connect

    Schwartz, J. L.; Rotmensch, J.; Sun, J.; An, J.; Xu, Z.; Yu, Y.; Hsie, A. W.; Center for Mechanistic Biology and Biotechnology; Univ. of Chicago; Univ. of Texas Medical Branch

    1994-01-01

    Independent Chinese hamster ovary (CHO)-K1 cell mutants at the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus were isolated from untreated, {sup 60}Co {gamma} ray-and {sup 212}Bi {alpha}-exposed cells and the genetic changes underlying the mutation determined by multiplex polymerase chain reaction (PCR)-based exon deletion analysis. In the 71 spontaneous mutants analyzed, 77.5% of the clones showed no change in exon number or size, 15.5% showed a loss of a single exon, 4.2% showed a loss of 2-8 exons, and 2.8% showed loss of all nine hprt exons (total gene deletion). Exposure to 6 Gy of {gamma} rays, which reduced survival levels to 10%, produced a significantly different deletion spectrum that was shifted toward deletions with 45% of the 20 mutants analyzed showing a loss of a single exon and 30% showing a loss of all nine exons. Exposure to 2 Gy {alpha} radiation from 212Bi, a 220Rn daughter, a dose which also reduced survival levels to about 10%, resulted in a deletion spectrum similar to the {gamma}-ray spectrum in that more than 75% of the 49 mutants analyzed were deletions. The {alpha} spectrum, however, was significantly different from both the spontaneous and {gamma} spectra with 55.1% of the {alpha} mutants showing a loss of all nine exons, 10.2% showing loss of a single exon, and 14.3% showing loss of 2-8 exons. Thus, {alpha}-radiation appears to produce larger intragenic deletions than {gamma} radiation. The results suggest that intragenic deletion size should be considered when low- and high linear energy transfer (LET) mutation spectra are compared.

  16. Measurement of activation cross-sections for high-energy neutron-induced reactions of Bi and Pb

    NASA Astrophysics Data System (ADS)

    Zaman, Muhammad; Kim, Guinyun; Kim, Kwangsoo; Naik, Haladhara; Shahid, Muhammad; Lee, Manwoo

    2015-08-01

    The cross-sections for 209Bi(n, 4n)206Bi, 209Bi(n, 5n)205Bi, natPb(n, xn)204mPb, natPb(n, xn)203Pb, natPb(n, xn)202mPb,natPb(n, xn)201Pb, natPb(n, xn)200Pb, natPb(n, αxn)203Hg and natPb(n, p xn)202Tl reactions were determined at the Korean Institute of Radiological and Medical Sciences (KIRAMS), Korea in the neutron energy range of 15.2 to 37.2 MeV. The above cross-sections were obtained by using the activation and off-line γ-ray spectrometric technique. The quasi-monoenergetic neutron used for the above reactions are based on the 9Be(p, n) reaction. Simulations of the spectral flux from the Be target were done using the MCNPX program. The cross-sections were estimated with the TALYS 1.6 code using the default parameter. The data from the present work and literature were compared with the data from the EAF-2010 and the TENDL-2013 libraries, and calculated values of TALYS 1.6 code. It shows that appropriate level density model, the γ-ray strength function, and the spin cut-off parameter are needed to obtain a good agreement between experimental data and theoretical values from TALYS 1.6 code.

  17. Cross-sections of the reaction 232Th(p,3n)230Pa for production of 230U for targeted alpha therapy.

    PubMed

    Morgenstern, Alfred; Apostolidis, Christos; Bruchertseifer, Frank; Capote, Roberto; Gouder, Thomas; Simonelli, Federica; Sin, Mihaela; Abbas, Kamel

    2008-10-01

    (230)U/(226)Th is a promising novel alpha-emitter system for application in targeted alpha therapy of cancer. The therapeutic nuclides can be produced by proton irradiation of natural (232)Th according to the reaction (232)Th(p,3n)(230)Pa, followed by subsequent beta decay of (230)Pa to (230)U. In this study, the experimental excitation function for the (232)Th(p,3n)(230)Pa reaction up to 34 MeV proton energy has been measured using the stacked-foil technique. The proton energies in the various foils were calculated with the SRIM 2003 code and gamma-ray spectrometry was used to measure the activities of the various radioisotopes produced. The measured cross-sections are in good agreement with selected literature values and with model calculations using the EMPIRE II code. The reaction (232)Th(p,3n)(230)Pa allows the production of carrier-free (230)U in clinically relevant levels.

  18. AN UPDATED {sup 6}Li(p, {alpha}){sup 3}He REACTION RATE AT ASTROPHYSICAL ENERGIES WITH THE TROJAN HORSE METHOD

    SciTech Connect

    Lamia, L.; Spitaleri, C.; Sergi, M. L.; Pizzone, R. G.; Tumino, A.; La Cognata, M.; Tognelli, E.; Degl'Innocenti, S.; Prada Moroni, P. G.; Pappalardo, L.

    2013-05-01

    The lithium problem influencing primordial and stellar nucleosynthesis is one of the most interesting unsolved issues in astrophysics. {sup 6}Li is the most fragile of lithium's stable isotopes and is largely destroyed in most stars during the pre-main-sequence (PMS) phase. For these stars, the convective envelope easily reaches, at least at its bottom, the relatively low {sup 6}Li ignition temperature. Thus, gaining an understanding of {sup 6}Li depletion also gives hints about the extent of convective regions. For this reason, charged-particle-induced reactions in lithium have been the subject of several studies. Low-energy extrapolations of these studies provide information about both the zero-energy astrophysical S(E) factor and the electron screening potential, U{sub e} . Thanks to recent direct measurements, new estimates of the {sup 6}Li(p, {alpha}){sup 3}He bare-nucleus S(E) factor and the corresponding U{sub e} value have been obtained by applying the Trojan Horse method to the {sup 2}H({sup 6}Li, {alpha} {sup 3}He)n reaction in quasi-free kinematics. The calculated reaction rate covers the temperature window 0.01 to 2T{sub 9} and its impact on the surface lithium depletion in PMS models with different masses and metallicities has been evaluated in detail by adopting an updated version of the FRANEC evolutionary code.

  19. Structural Studies of Geosmin Synthase, a Bifunctional Sesquiterpene Synthase with Alpha-Alpha Domain Architecture that Catalyzes a Unique Cyclization-Fragmentation Reaction Sequence

    PubMed Central

    Harris, Golda G.; Lombardi, Patrick M.; Pemberton, Travis A.; Matsui, Tsutomu; Weiss, Thomas M.; Cole, Kathryn E.; Köksal, Mustafa; Murphy, Frank V.; Vedula, L. Sangeetha; Chou, Wayne K.W.; Cane, David E.; Christianson, David W.

    2015-01-01

    Geosmin synthase from Streptomyces coelicolor (ScGS) catalyzes an unusual, metal-dependent terpenoid cyclization and fragmentation reaction sequence. Two distinct active sites are required for catalysis: the N-terminal domain catalyzes the ionization and cyclization of farnesyl diphosphate to form germacradienol and inorganic pyrophosphate (PPi), and the C-terminal domain catalyzes the protonation, cyclization, and fragmentation of germacradienol to form geosmin and acetone through a retro-Prins reaction. A unique αα domain architecture is predicted for ScGS based on amino acid sequence: each domain contains the metal-binding motifs typical of a class I terpenoid cyclase, and each domain requires Mg2+ for catalysis. Here, we report the X-ray crystal structure of the unliganded N-terminal domain of ScGS and the structure of its complex with 3 Mg2+ ions and alendronate. These structures highlight conformational changes required for active site closure and catalysis. Although neither full-length ScGS nor constructs of the C-terminal domain could be crystallized, homology models of the C-terminal domain were constructed based on ~36% sequence identity with the N-terminal domain. Small-angle X-ray scattering experiments yield low resolution molecular envelopes into which the N-terminal domain crystal structure and the C-terminal domain homology model were fit, suggesting possible αα domain architectures as frameworks for bifunctional catalysis. PMID:26598179

  20. HPLC-MS determination of the oxidation products of the reaction between alpha- and beta-pinene and OH radicals.

    PubMed

    Van den Bergh, V; Coeckelberghs, H; Vanhees, I; De Boer, R; Compernolle, F; Vinckier, C

    2002-03-01

    Biogenic non-methane hydrocarbons such as isoprene, alpha-pinene, and beta-pinene, are emitted by forests in very large quantities. To evaluate the role of alpha- and beta-pinene and their contribution to the global production of trace gases and especially aerosol precursors, a study of the oxidation mechanism of alpha- and beta-pinene with hydroxyl radicals must be conducted. The degradation products of both monoterpenes with hydroxyl radicals were identified and quantified in a fast-flow reactor. The products were collected on a liquid-nitrogen trap coated with a 2,4-DNPH solution to which two internal standards (benzaldehyde-2,4-DNPH and tolualdehyde-2,4-DNPH) had been added. The collection method was based on the in situ conversion of aldehyde and/or ketone compounds to their 2,4-dinitrophenylhydrazone derivatives. The derivatives were analyzed by HPLC-MS using APCI(-). TIC chromatograms and mass spectral data for the various oxidation products are presented. For alpha-pinene, pinonaldehyde is the most important degradation product, with smaller amounts of acetone, formaldehyde, campholenealdehyde, and acetaldehyde. For beta-pinene, nopinone and formaldehyde are the most abundant products, of almost equal importance, whereas acetone and acetaldehyde are minor compounds.

  1. Lifetime measurements by the Doppler-shift attenuation method in the {sup 115}Sn({alpha},n{gamma}){sup 118}Te reaction

    SciTech Connect

    Mihai, C.; Pasternak, A. A.; Pascu, S.; Filipescu, D.; Ivascu, M.; Bucurescu, D.; Cata-Danil, I.; Deleanu, D.; Ghita, D. G.; Glodariu, T.; Marginean, N.; Marginean, R.; Negret, A.; Sava, T.; Stroe, L.; Suliman, G.; Zamfir, N. V.; Cata-Danil, G.

    2011-05-15

    {gamma} rays were measured at several angles in both singles and coincidence modes in the {sup 115}Sn({alpha},n{gamma}){sup 118}Te reaction at 15 MeV on a thick target. Multipolarities and mixing ratios were determined from the {gamma}-ray angular distribution analysis. Lifetimes of 11 low- and medium-spin excited states in {sup 118}Te were determined from a Monte Carlo Doppler-shift attenuation method analysis of the Doppler broadened line shapes of {gamma} rays deexciting the levels. The results are discussed in comparison with the predictions of the interacting boson model.

  2. The preparation of nitrogen-doped TiO 2- xN x photocatalyst coated on hollow glass microbeads

    NASA Astrophysics Data System (ADS)

    Shifu, Chen; Xuqiang, Liu; Yunzhang, Liu; Gengyu, Cao

    2007-01-01

    In this paper, the effective method for nitrogen-doped TiO 2- xN x photocatalyst coated on hollow glass microbeads is described, which uses titanium tetraisopropoxide [Ti( iso-OC 3H 7) 4] as the raw materials and gaseous ammonia as a heat treatment atmosphere. The effects of heat treatment temperature and time on the photocatalytic activity of TiO 2- xN x/beads are studied. The photocatalyst is characterized by the UV-vis diffuse reflection spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis and scanning electron microscopy (SEM). The results show that when the TiO 2- xN x/beads is heated at 650 °C for 5 h, the photocatalytic activity of the TiO 2- xN x/beads is the best. Compared with TiO 2, the photoabsorption wavelength range of nitrogen-doped TiO 2- xN x red shifts of about 60 nm, and the photoabsorption intensity increases as well. The photocatalytic activity of the TiO 2- xN x/beads is higher than that of the TiO 2/beads under visible light irradiation. The presence of nitrogen neither influences on the transformation of anatase to rutile, nor creates new crystal phases. When the TiO 2- xN x/beads is heated at 650 °C for 5 h, the amount of nitrogen-doped is 0.53 wt.% in the TiO 2- xN x. As the density of TiO 2- xN x/beads prepared is lower than 1.0 g/cm 3, it may float on water surface and use broader sunlight spectrum directly.

  3. A microdosimetric study of {sup 10}B(n,{alpha}){sup 7}Li and {sup 157}Gd(n,{gamma}) reactions for neutron capture therapy

    SciTech Connect

    Wang, C.K.C.; Sutton, M.; Evans, T.M.; Laster, B.H.

    1996-12-31

    This paper presents the microdosimetric analysis for the most interesting cell survival experiment recently performed at the Brookhaven National Laboratory (BNL). In this experiment, the cells were first treated with a gadolinium (Gd) labeled tumor-seeking boronated porphyrin (Gd-BOPP) or with BOPP alone, and then irradiated with thermal neutrons. The resulting cell survival curves indicate that the {sup 157}Gd(n,{gamma}) reactions is very effective in cell killing. The death of a cell treated with GD-BOPP were attributed to either the {sup 10}B(n,{alpha}) {sup 7}Li reactions or the {sup 157}Gd(n,{gamma}) reactions (or both). However, the quantitative relationship between the two types of reaction and the cell survival fraction was not clear. This paper presents the microdosimetric analysis for the BNL experiment based on the measured experimental parameters, and the results clearly suggest a quantitative relationship between the two types of reaction and the cell survival fraction. The results also suggest new research in Gadolinium neutron capture therapy (GDNCT) which may lead to a more practical modality than the boron neutron capture therapy (BNCT) for treating cancers.

  4. A microdosimetric study of {sup 10}B(n,{alpha}){sup 7}Li and {sup 157}Gd(n,{gamma}) reactions for neutron capture therapy

    SciTech Connect

    Wang, C.K.C.; Sutton, M.; Evans, T.M.; Laster, B.H.

    1999-01-01

    This paper presents the microdosimetric analysis for the most interesting cell survival experiment recently performed at the Brookhaven National Laboratory (BNL). In this experiment, the cells were first treated with a gadolinium (Gd) labeled tumor-seeking boronated porphyrin (Gd-BOPP) or with BOPP alone, and then irradiated with thermal neutrons. The resulting cell-survival curves indicate that the {sup 157}Gd(n,{gamma}) reactions are very effective in cell killing. The death of a cell treated with Gd-BOPP was attributed to either the {sup 10}B(n,{alpha}){sup 7}Li reactions or the {sup 157}Gd(n,{gamma}) reactions (or both). However, the quantitative relationship between the two types of reaction and the cell-survival fraction was not clear. This paper presents the microdosimetric analysis for the BNL experiment based on the measured experimental parameters, and the results clearly suggest a quantitative relationship between the two types of reaction and the cell survival fraction. The results also suggest new research in gadolinium neutron capture therapy (GdNCT) which may lead to a more practical modality than the boron neutron capture therapy (BNCT) for treating cancers.

  5. Putative implication of alpha-amylase loop 7 in the mechanism of substrate binding and reaction products release.

    PubMed

    André, G; Tran, V

    2004-10-05

    Alpha-amylases are widespread endo-enzymes involved in the hydrolysis of internal alpha-(1,4) glycosidic linkages of starch polymers. Molecular modeling of amylose-amylase interactions is a step toward enzymatic mechanism understanding and rational design of new enzymes. From the crystallographic complex of barley alpha-amylase AMY2-acarbose, the static aspects of amylose-amylase docking have been characterized with a model of maltododecaose (DP12) (G. André, A. Buléon, R. Haser, and V. Tran, Biopolymers 1999, Vol. 50, pp. 751-762; G. André and V. Tran, Special Publication no. 246 1999, The Royal Society of Chemistry, H. J. Gilbert, G. J. Davies, B. Henrissat, and B. Svensson, Eds., Cambridge, pp. 165-174). These studies, consistent with the experimental subsite mapping (K. Bak-Jensen, G. André, V. Tran, and B. Svensson, Journal of Biological Chemistry, to be published), propose a propagation scheme for an amylose chain in the active cleft of AMY2. The topographical overview of alpha-amylases identified loop 7 as a conserved segment flanking the active site. Since some crystallographic experiments suspected its high flexibility, its putative motion was explored through a robotic scheme, an alternate route to dynamics simulations that consume CPU time. The present article describes the characteristics of the flexibility of loop 7: location and motion in AMY2. A back-and-forth motion with a large amplitude of more than 0.6 nm was evaluated. This movement could be triggered by two hinge residues. It results in the loop flipping over the active site to enhance the docking of the native helical substrate through specific interactions, it positions the catalytic residues, it distorts the substrate towards its transition state geometry, and finally monitors the release of the products after hydrolysis. The residues involved in the process are now rational mutation points in the hands of molecular biologists.

  6. [Serum protein binding of fentanyl. The effect of postoperative acute phase reaction with elevated alpha 1-acid glycoprotein and methodologic problems in determination by equilibrium dialysis].

    PubMed

    Wiesner, G; Taeger, K; Peter, K

    1996-04-01

    Numerous basic drugs are extensively bound to alpha 1-acid glycoprotein. Fentanyl, with a pKa value of 8.43, is also a basic drug. Protein binding studies have yielded contradictory results concerning binding of fentanyl to alpha 1-acid glycoprotein. In this study we investigated time courses of serum protein concentrations and serum protein binding of fentanyl during postoperative acute phase reaction, assuming that an increase of alpha 1-acid glycoprotein is accompanied by an increase of serum protein binding, if fentanyl is extensively bound to alpha 1-acid glycoprotein. Fentanyl protein binding measurements using equilibrium dialysis can be affected by volume shifts and pH changes. Therefore, volume shifts from buffer to serum and the influence of various phosphate buffers on increasing pH due to loss of CO2 were also evaluated. METHODS. Thirteen patients with no history of renal or hepatic disease undergoing an operation with a significant acute phase reaction were studied. Preoperatively and on the first 3 postoperative days serum concentrations of alpha 1-acid glycoprotein, albumin, total protein and apolipoprotein A and B were determined by rocket immunoeolectrophoresis, biuret method and laser nephelometry, respectively. Corresponding serum protein binding of fentanyl was measured by adding 40 ng of fentanyl to 1 ml serum followed by equilibrium dialysis at 37 degrees C for 4 h. A 0.167 M phosphate buffer (pH 7.27), which gave a final pH of 7.40, was used. Volume shifts from buffer to serum were measured. Fentanyl concentration in serum before dialysis (FS) was determined by gas chromatography, and fentanyl concentration in buffer after dialysis (FB) was determined by radioimmunoassay. Serum protein binding (SPB) was calculated by the formula: SPB = (FS - FB - FB*c)/(FS - FB) where c is a correction factor. Ten randomly selected patient sera were dialyzed against four phosphate buffers of different pH values and molarities, and the serum pH at the end of

  7. Measurement of the LITHIUM-8(DEUTERON, NEUTRON)BERYLLIUM-9 and LITHIUM-8(ALPHA, NEUTRON)BORON-11 Reaction Cross Sections at Astrophysical Energies by Radioactive Beam Techniques

    NASA Astrophysics Data System (ADS)

    Corn, Philip Bennet

    A preliminary direct measurement of the ^8Li(d,n)^9Be cross section has been obtained by means of a radioactive beam facility used with the Lawrence Livermore National Laboratory FN van de Graaff accelerator. The cross section at a ^8Li energy of 13.3 MeV agrees plausibly with values estimated from data for the reverse reaction, ^9Be(n,d)^8Li, and for the related ^7Li(d,n) ^8Be reaction to within the large estimated experimental error. This result thus demonstrates the feasibility of the technique. In addition, a design for a similar radioactive beam measurement of the ^8Li(alpha,n) 11B reaction cross section is given. The two reactions figure prominently in network calculations for current inhomogeneous models of primordial nucleosynthesis in the early universe, and because of the short 838 millisecond half life of the radioactive ^8Li nuclide, their cross sections have not been measured directly before. The radioactive beam apparatus employs a 16.0 MeV ^7Li beam from the accelerator incident on a thin, deuterated polyethylene primary reaction target foil. A secondary beam containing ^8Li produced in the ^7 Li(d,p)^8Li reaction is concentrated by a spectrometer incorporating twin triplet magnetic quadrupole elements and an electrostatic dipole, and is focussed on a second deuterated polyethylene reaction target foil in which the reaction of interest takes place. Reaction products are identified and measured by means of a pair of surface barrier charged particle detector telescopes, and ^8Li flux is measured via a CaF_2 scintillator and photomultiplier tube at the rear of the detector chamber. Future efforts will use improved gas cell production and reaction targets and detector systems, and will focus in the near term on a definitive measurement of the ^8Li(d,n)^9 Be cross section at several energies. The experiments and apparatus described are part of a continuing program of studies of astrophysically interesting reactions on radioactive nuclides carried out with

  8. Evaluation of nuclear reaction cross section data for the production of (87)Y and (88)Y via proton, deuteron and alpha-particle induced transmutations.

    PubMed

    Zaneb, H; Hussain, M; Amjad, N; Qaim, S M

    2016-06-01

    Proton, deuteron and alpha-particle induced reactions on (87,88)Sr, (nat)Zr and (85)Rb targets were evaluated for the production of (87,88)Y. The literature data were compared with nuclear model calculations using the codes ALICE-IPPE, TALYS 1.6 and EMPIRE 3.2. The evaluated cross sections were generated; therefrom thick target yields of (87,88)Y were calculated. Analysis of radio-yttrium impurities and yield showed that the (87)Sr(p, n)(87)Y and (88)Sr(p, n)(88)Y reactions are the best routes for the production of (87)Y and (88)Y respectively. The calculated yield for the (87)Sr(p, n)(87)Y reaction is 104 MBq/μAh in the energy range of 14→2.7MeV. Similarly, the calculated yield for the (88)Sr(p, n)(88)Y reaction is 3.2 MBq/μAh in the energy range of 15→7MeV.

  9. Radiative corrections to e/sup +/e/sup -/ reactions to all orders in. cap alpha. using the renormalization group

    SciTech Connect

    Tsai, Y.S.

    1983-01-01

    Renormalization group technique is used to improve the accuracy of the lowest order radiative corrections in QED. The exponentiation of infrared terms comes automatically. It also leads to exponentiation of the vertex functions. It predicts the existence of conversion of photons into pairs and the result agrees with the Kroll-Wada relation. Kinoshita-Lee-Nauenberg cancellation of mass singularities occurs to all order in ..cap alpha.. in leading log approximation in the final state if we sum over all the final states. Higher order corrections to the order ..cap alpha../sup 3/ asymmetry is shown to be small. The results are used to derive useful formulas for the radiative corrections to processes such as e/sup +/e/sup -/ ..-->.. ..mu../sup +/..mu../sup -/, e/sup +/e/sup -/ ..-->.. ..mu../sup +/..mu../sup -/..gamma.., e/sup +/e/sup -/ ..-->.. hadron continuum, e/sup +/e/sup -/ ..-->.. very narrow resonance such as phi, and e/sup +/e/sup -/ ..-->.. not very narrow resonance such as Z/sup 0/.

  10. Significant elastic anisotropy in Ti{sub 1-x}Al{sub x}N alloys

    SciTech Connect

    Tasnadi, Ferenc; Abrikosov, Igor A.; Rogstroem, Lina; Johansson, Mats P.; Oden, Magnus; Almer, Jonathan

    2010-12-06

    Strong compositional-dependent elastic properties have been observed theoretically and experimentally in Ti{sub 1-x}Al{sub x}N alloys. The elastic constant, C{sub 11}, changes by more than 50% depending on the Al-content. Increasing the Al-content weakens the average bond strength in the local octahedral arrangements resulting in a more compliant material. On the other hand, it enhances the directional (covalent) nature of the nearest neighbor bonds that results in greater elastic anisotropy and higher sound velocities. The strong dependence of the elastic properties on the Al-content offers new insight into the detailed understanding of the spinodal decomposition and age hardening in Ti{sub 1-x}Al{sub x}N alloys.

  11. Shallow and deep defects in Al xGa 1-xN structures

    NASA Astrophysics Data System (ADS)

    Seghier, D.; Gislason, H. P.

    2007-12-01

    We report electrical characterization of Al xGa 1-xN materials grown by MOCVD. The techniques used in this study were admittance spectroscopy and photocurrent measurements. We identify a continuum of shallow donors with ionization energies ranging from 50 to 110 meV in Al xGa 1-xN alloys with values of the Al mole fraction x=0.1 and 0.3. Investigations of the photocurrent buildup kinetics allow identification of a deep center with optical ionization energy of 1.2 eV. This center controls the buildup of the photocurrent when the materials are illuminated with sub-bandgap photon energy. In the light of this finding we discuss the broad spectrum of DX-like defects that may contribute to the persistent photocurrent and the collapse in the drain current observed in AlGaN-related structures.

  12. Physical properties and applications of InxGa1-xN nanowires

    NASA Astrophysics Data System (ADS)

    Segura-Ruiz, J.; Gómez-Gómez, M.; Garro, N.; Martínez-Criado, G.; Cantarero, A.; Denker, C.; Malindretos, J.; Rizzi, A.

    2014-05-01

    We have successfully grown InxGa1-xN nanowires by plasma-assisted molecular beam epitaxy on silicon substrates. The alloy composition and crystal quality have been analyzed by Raman scattering, photoluminescence spectroscopy and x-ray fluorescence nanoprobe techniques. InxGa1-xN is an one-mode alloy, where the different optical modes have an intermediate frequency of that of pure InN and GaN. The sample composition can be derived from the Raman data. On the other hand, by using the optical gap provided by the emission spectra, we conclude that the samples have a lower Ga content than that provided by the Raman analysis. X-ray fluorescence maps and photoluminescence measured in single nanowires help to explain this contradictory result.

  13. Low-temperature growth of InxGa1-xN films by radio-frequency magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Wang, J.; Shi, X. J.; Zhu, J.

    2013-01-01

    The low-temperature growth of InxGa1-xN films on quartz glass substrates utilizing radio-frequency magnetron sputtering is investigated. In the InxGa1-xN films prepared using an In-Ga alloy target, grazing incidence X-ray diffraction (GIXRD) peaks corresponding to wurtzite structure were observed. X-ray photoelectron spectroscopy (XPS) was applied to study the extent of oxygen contamination and chemical states, and secondary ion mass spectrometry (SIMS) was used to evaluate the distribution profiles of oxygen impurity in the as-grown InxGa1-xN thin films. XPS and SIMS analysis indicate that the entire thin films have oxide phases. However, no evidence of In2O3, Ga2O3, or indium oxynitride phases was shown in XRD studies. It may be predicted that the oxygen impurities formed amorphous oxide phases embedded in InxGa1-xN matrix. According to our findings, indium is a major phase in the InxGa1-xN thin films which suggests that a significant amount of indium remains un-reacted with N2. The optical transmittance spectra of the as-grown films show interference fringe patterns. The indium fraction x of the as-deposited InxGa1-xN thin films can be calculated out by the transmittance data.

  14. Distribution of cations in wurtzitic InxGa1-xN and InxAl1-xN alloys: Consequences for energetics and quasiparticle electronic structures

    NASA Astrophysics Data System (ADS)

    de Carvalho, Luiz Cláudio; Schleife, André; Furthmüller, Jürgen; Bechstedt, Friedhelm

    2012-03-01

    The ternary, isostructural, wurtzite-derived group-III mononitride alloys InxGa1-xN and InxAl1-xN are reexamined within a cluster expansion approach. Using density functional theory together with the AM05 exchange-correlation functional, the total energies and the optimized atomic geometries of all 22 clusters classes of the cluster expansion for each material system are calculated. The computationally demanding calculation of the corresponding quasiparticle electronic structures is achieved for all cluster classes by means of a recently developed scheme to approximately solve the quasiparticle equation based on the HSE06 hybrid functional and the G0W0 approach. Using two different alloy statistics, the configurational averages for the lattice parameters, the mixing enthalpies, and the bulk moduli are calculated. The composition-dependent electronic structures of the alloys are discussed based on configurationally averaged electronic states, band gaps, and densities of states. Ordered cluster arrangements are found to be energetically rather unfavorable, however, they possess the smallest energy gaps and, hence, contribute to light emission. The influence of the alloy statistics on the composition dependencies and the corresponding bowing parameters of the band gaps is found to be significant and should, hence, lead to different signatures in the optical-absorption or -emission spectra.

  15. Distribution of cations in wurtzitic InxGa1-xN and InxAl1-xN alloys: Consequences for energetics and quasiparticle electronic structures

    DOE PAGES

    de Carvalho, Luiz Cláudio; Schleife, André; Furthmüller, Jürgen; ...

    2012-03-27

    The ternary, isostructural, wurtzite-derived group-III mononitride alloys InxGa1-xN andInxAl1-xN are reexamined within a cluster expansion approach. Using density functional theory together with the AM05 exchange-correlation functional, the total energies and the optimized atomic geometries of all 22 clusters classes of the cluster expansion for each material system are calculated. The computationally demanding calculation of the corresponding quasiparticle electronic structures is achieved for all cluster classes by means of a recently developed scheme to approximately solve the quasiparticle equation based on the HSE06 hybrid functional and the G₀W₀ approach. Using two different alloy statistics, the configurational averages for the lattice parameters,more » the mixing enthalpies, and the bulk moduli are calculated. The composition-dependent electronic structures of the alloys are discussed based on configurationally averaged electronic states, band gaps, and densities of states. Ordered cluster arrangements are found to be energetically rather unfavorable, however, they possess the smallest energy gaps and, hence, contribute to light emission. The influence of the alloy statistics on the composition dependencies and the corresponding bowing parameters of the band gaps is found to be significant and should, hence, lead to different signatures in the optical-absorption or -emission spectra.« less

  16. Kinetics of the Reaction of beta-Methoxy-alpha-nitrostilbene with Cyanamide in 50 DMSO-50 Water. Failure to Detect the S(N)V Intermediate.

    PubMed

    Bernasconi, Claude F.; Leyes, Aquiles E.; Rappoport, Zvi

    1999-04-16

    A kinetic study of the reaction of beta-methoxy-alpha-nitrostilbene (1-OMe) with cyanamide (CNA) over a pH range from 8.5 to 12.4 shows that it is the anion (CNA(-), pK(a) = 11.38) rather than the neutral amine that is the reactive species. Attempts at monitoring the reaction with the neutral CNA at low pH were unsuccessful because of competing hydrolysis. It is shown that the nucleophilic reactivity of CNA is abnormally low, probably because of a resonance effect, and that the reactivity of CNA(-) is high, higher than that of strongly basic oxyanion because of relatively weak solvation. The high reactivity of both 1-OMe and CNA(-) appeared to constitute favorable conditions conducive to the detection of the S(N)V intermediate, as has been the case in the reactions of 1-OMe with thiolate ions, alkoxide ions, and some amines. However, no intermediate was observed. Reasons for this failure are discussed.

  17. Excitation function of the alpha particle induced nuclear reactions on enriched 116Cd, production of the theranostic isotope 117mSn

    NASA Astrophysics Data System (ADS)

    Ditrói, F.; Takács, S.; Haba, H.; Komori, Y.; Aikawa, M.; Szűcs, Z.; Saito, M.

    2016-10-01

    117mSn is one of the radioisotopes can be beneficially produced through alpha particle irradiation. The targets were prepared by deposition of 116Cd metal onto high purity 12 μm thick Cu backing. The average deposited thickness was 21.9 μm. The beam energy was thoroughly measured by Time of Flight (TOF) methods and proved to be 51.2 MeV. For the experiment the well-established stacked foil technique was used. In addition to the Cd targets, Ti foils were also inserted into the stacks for energy and intensity monitoring. The Cu backings were also used for monitoring and as recoil catcher of the reaction products from the cadmium layer. The activities of the irradiated foils were measured with HPGe detector for gamma-ray spectrometry and cross section values were determined. As a result excitation functions for the formation of 117mSn, 117m,gIn, 116mIn, 115mIn and 115m,gCd from enriched 116Cd were deduced and compared with the available literature data and with the results of the nuclear reaction model code calculations EMPIRE 3.2 and TALYS 1.8. Yield curves were also deduced for the measured nuclear reactions and compared with the literature.

  18. Phase degradation in BxGa1-xN films grown at low temperature by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Gunning, Brendan P.; Moseley, Michael W.; Koleske, Daniel D.; Allerman, Andrew A.; Lee, Stephen R.

    2017-04-01

    Using metalorganic vapor phase epitaxy, a comprehensive study of BxGa1-xN growth on GaN and AlN templates is described. BGaN growth at high-temperature and high-pressure results in rough surfaces and poor boron incorporation efficiency, while growth at low-temperature and low-pressure (750-900 °C and 20 Torr) using nitrogen carrier gas results in improved surface morphology and boron incorporation up to 7.4% as determined by nuclear reaction analysis. However, further structural analysis by transmission electron microscopy and x-ray pole figures points to severe degradation of the high boron composition films, into a twinned cubic structure with a high density of stacking faults and little or no room temperature photoluminescence emission. Films with <1% triethylboron (TEB) flow show more intense, narrower x-ray diffraction peaks, near-band-edge photoluminescence emission at 362 nm, and primarily wurtzite-phase structure in the x-ray pole figures. For films with >1% TEB flow, the crystal structure becomes dominated by the cubic phase. Only when the TEB flow is zero (pure GaN), does the cubic phase entirely disappear from the x-ray pole figure, suggesting that under these growth conditions even very low boron compositions lead to mixed crystalline phases.

  19. Regulation of acetylcholine receptor alpha subunit variants in human myasthenia gravis. Quantification of steady-state levels of messenger RNA in muscle biopsy using the polymerase chain reaction.

    PubMed Central

    Guyon, T; Levasseur, P; Truffault, F; Cottin, C; Gaud, C; Berrih-Aknin, S

    1994-01-01

    Myasthenia gravis (MG) is an autoimmune disease mediated by auto-antibodies that attack the nicotinic acetylcholine receptor (AChR). To elucidate the molecular mechanisms underlying the decrease in AChR levels at the neuromuscular junction, we investigated the regulation of AChR expression by analyzing mRNA of the two AChR alpha subunit isoforms (P3A+ and P3A-) in muscle samples from myasthenic patients relative to controls. We applied a quantitative method based on reverse transcription of total RNA followed by polymerase chain reaction (PCR), using an internal standard we constructed by site-directed mutagenesis. An increased expression of mRNA coding for the alpha subunit of the AChR isoforms was observed in severely affected patients (P < 0.003 versus controls) but not in moderately affected patients, independently of the anti-AChR antibody titer. Study of mRNA precursor levels indicates a higher expression in severely affected patients compared to controls, suggesting an enhanced rate of transcription of the message coding for the alpha subunit isoforms in these patients. We have also reported that mRNA encoding both isoforms are expressed at an approximate 1:1 ratio in controls and in patients. We have thus identified a new biological parameter correlated with disease severity, and provide evidence of a compensatory mechanism to balance the loss of AChR in human myasthenia gravis, which is probably triggered only above a certain degree of AChR loss. Images PMID:8040257

  20. Measurements of cross sections and decay properties of the isotopes of elements 112, 114, and 116 produced in the fusion reactions {sup 233,238}U, {sup 242}Pu, and {sup 248}Cm+{sup 48}Ca

    SciTech Connect

    Oganessian, Yu.Ts.; Utyonkov, V.K.; Lobanov, Yu.V.; Abdullin, F.Sh.; Polyakov, A.N.; Shirokovsky, I.V.; Tsyganov, Yu.S.; Gulbekian, G.G.; Bogomolov, S.L.; Gikal, B.N.; Mezentsev, A.N.; Iliev, S.; Subbotin, V.G.; Sukhov, A.M.; Voinov, A.A.; Buklanov, G.V.; Subotic, K.; Zagrebaev, V.I.; Itkis, M.G.; Patin, J.B.

    2004-12-01

    We have studied the dependence of the production cross sections of the isotopes {sup 282,283}112 and {sup 286,287}114 on the excitation energy of the compound nuclei {sup 286}112 and {sup 290}114. The maximum cross section values of the xn-evaporation channels for the reaction {sup 238}U({sup 48}Ca,xn){sup 286-x}112 were measured to be {sigma}{sub 3n}=2.5{sub -1.1}{sup +1.8} pb and {sigma}{sub 4n}=0.6{sub -0.5}{sup +1.6} pb; for the reaction {sup 242}Pu({sup 48}Ca,xn){sup 290-x}114: {sigma}{sub 2n}{approx}0.5 pb, {sigma}{sub 3n}=3.6{sub -1.7}{sup +3.4} pb, and {sigma}{sub 4n}=4.5{sub -1.9}{sup +3.6} pb. In the reaction {sup 233}U({sup 48}Ca,2-4n){sup 277-279}112 at E*=34.9=2.2 MeV we measured an upper cross section limit of {sigma}{sub xn}{<=}0.6 pb. The observed shift of the excitation energy associated with the maximum sum evaporation residue cross section {sigma}{sub ER}(E*) to values significantly higher than that associated with the calculated Coulomb barrier can be caused by the orientation of the deformed target nucleus in the entrance channel of the reaction. An increase of {sigma}{sub ER} in the reactions of actinide targets with {sup 48}Ca is consistent with the expected increase of the survivability of the excited compound nucleus upon closer approach to the closed neutron shell N=184. In the present work we detected 33 decay chains arising in the decay of the known nuclei {sup 282}112, {sup 283}112, {sup 286}114, {sup 287}114, and {sup 288}114. In the decay of {sup 287}114({alpha}){yields}{sup 283}112({alpha}){yields}{sup 279}110(SF), in two cases out of 22, we observed decay chains of four and five sequential {alpha} transitions that end in spontaneous fission of {sup 271}Sg (T{sub {alpha}}{sub /SF}=2.4{sub -1.0}{sup +4.3} min) and {sup 267}Rf (T{sub SF}{approx}2.3 h), longer decay chains than reported previously. We observed the new nuclide {sup 292}116 (T{sub {alpha}}=18{sub -6}{sup +16} ms,E{sub {alpha}}=10.66{+-}0.07 MeV) in the irradiation of the

  1. Selectivity guidelines and a reductive elimination-based model for predicting the stereochemical course of conjugate addition reactions of organocuprates to gamma-alkoxy-alpha,beta-enoates.

    PubMed

    Kireev, Artem S; Manpadi, Madhuri; Kornienko, Alexander

    2006-03-31

    Current models used to predict the stereochemical outcome of organocopper conjugate addition processes focus on the nucleophilic addition step as stereochemistry-determining. Recent kinetic, NMR, kinetic isotope effect, and theoretical density functional studies strongly support the proposal that stereochemical preferences in these processes are dictated by the reductive elimination step, transforming Cu(III) to Cu(I) intermediates. A new model that considers various steric and stereoelectronic factors involved in the transition state of the reductive elimination step is proposed and then used to interpret the results of systematic studies of arylcuprate conjugate addition reactions with cis and trans gamma-alkoxy-alpha,beta-enoates. The results give rise to the following selectivity guidelines for this process. To achieve high anti-addition diastereoselectivities the use of trans esters with a bulky nonalkoxy substituent at the gamma-position is recommended. While stereoelectronics disfavor syn-addition, a judicious choice of properly sized gamma-substituents may lead to the predominant formation of syn-products, especially with cis enoates. However, high syn-selectivities may be achieved by using gamma-amino-alpha,beta-enoates.

  2. Data on photoneutron reactions from various experiments for 133Cs, 138Ba and 209Bi nuclei

    NASA Astrophysics Data System (ADS)

    Varlamov, V. V.; Ishkhanov, B. S.; Orlin, V. N.; Peskov, N. N.

    2016-07-01

    Basic methods for determining cross sections for photoneutron partial reactions are examined. They are obtained directly in experiments with quasimonoeneregetic annihilation photons or from the cross section for the ( γ, xn) = ( γ, 1 n) + 2( γ, 2 n) + 3( γ, 3 n) +... neutron-yield reaction in experiments with bremsstrahlung photons by introducing corrections based on statistical nuclear-reaction theory. The difference in the conditions of these experiments, which leads to discrepancies between their results because of sizable systematic errors, is analyzed. Physical criteria are used to study the reliability of data on the photodisintegration of 133Cs, 138Ba, and 209Bi nuclei. The cross sections for partial and total reactions satisfying the reliability criteria are evaluated within the experimental-theoretical method ( σ eval( γ, in) = F i theor × σ expt( γ, xn)) on the basis of the experimental cross sections σ expt( γ, xn) and the results of the calculations within the combined model of photonuclear reactions.

  3. Measurement of the parity-violating triton emission asymmetry in the reaction {sup 6}Li(n,{alpha}){sup 3}H with polarized cold neutrons

    SciTech Connect

    Vesna, V. A.; Shulgina, E. V.; Gledenov, Yu. M.; Sedyshev, P. V.; Nesvizhevsky, V. V.; Petoukhov, A. K.; Soldner, T.; Zimmer, O.

    2008-03-15

    We describe measurements of the parity-violating (P-odd) triton emission asymmetry coefficient a{sub P-odd} in the {sup 6}Li(n,{alpha}){sup 3}H reaction with polarized cold neutrons. Experiments were carried out at the Petersburg Nuclear Physics Institute (Gatchina, Russia) and at the Institut Laue-Langevin (Grenoble, France). We employed an ionisation chamber in a configuration allowing us to suppress the left-right asymmetry well below 10{sup -8}. An additional test for a false asymmetry due to eventual target impurities (''zero test'') resulted in a{sub 0-test}=(0.0{+-}0.5)x10{sup -8}. As final result of this series of experiments we obtained a{sub P-odd}=(-8.8{+-}2.1)x10{sup -8}.

  4. Liquid chromatography-electrospray ionization-mass spectrometry method in multiple reaction monitoring mode to determine 17alpha-ethynylestradiol residues in cattle hair without previous digestion.

    PubMed

    Pedreira, S; Lolo, M; Vázquez, B I; Franco, C M; Cepeda, A; Fente, C

    2007-11-14

    A liquid chromatography-mass spectrometric (LC-MS/MS) method has been developed for determination of ethynylestradiol residues in cattle hair. Hair samples were pulverized with a cryogenic mill followed by a simple extraction with acetonitrile. A dansyl derivatization procedure to improve ethynylestradiol detection was used before the LC-MS/MS analysis in multiple reaction monitoring (MRM) mode using alpha-estradiol as an internal standard. The method was validated following the latest EU guidelines using blank hair samples spiked at 2 ng g(-1). The detection capability (CCbeta) was less than 2 ng g(-1), and the decision limit (CCalpha) was 1 ng g(-1). Incurred samples obtained 56 days after cow treatment with ethynylestradiol were analyzed, and the presence of ethynylestradiol in the hair was confirmed in all cases.

  5. Diagnosis of. alpha. sub 1 -antitrypsin deficiency by enzymatic amplification of human genomic DNA and direct sequencing of polymerase chain reaction products

    SciTech Connect

    Newton, C.R.; Graham, A.; Powell, S.; Gammack, A.; Riley, J.; Markham, A.F. ); Kalsheker, N. )

    1988-09-12

    The authors have compared sequencing of cloned polymerase chain reaction (PCR) products and the direct sequencing of PCR products in the examination of individuals from six families affected with {alpha}{sub 1}-antitrypsin (AAT) deficiency. In families where paternity was in question they confirmed consanguinity by DNA fingerprinting using a panel of locus-specific minisatellite probes. They demonstrate that direct sequencing of PCR amplification products is the method of choice for the absolutely specific diagnosis of AAT deficiency and can distinguish normals, heterozygotes and homozygotes in a single, rapid and facile assay. Furthermore, they demonstrate the reproducibility of the PCR and a rapid DNA isolation procedure. They have also shown that two loci can be simultaneously amplified and that the PCR product from each locus can be independently examined by direct DNA sequencing.

  6. Novel 4{pi} Detection System for the Measurement of the {sup 6}Li(n,{alpha}){sup 3}H Reaction Cross Section

    SciTech Connect

    Giorginis, Georgios; Bencardino, Raffaele

    2011-12-13

    A dedicated one-dimensional Time Projection Chamber (1D-TPC) was designed and produced at IRMM to determine the {sup 6}Li(n,{alpha}){sup 3}H cross section in the 0.4-2.8 MeV energy range, aiming at 5% accuracy. The basic TPC components were a twin gridded ionisation chamber (GIC) with interwired electrodes and fast digitisation of the anode and cathode signals. The energy of both reaction products emitted from a thin {sup 6}LiF sample at the common TPC cathode was measured. A Kr(97%)CO{sub 2}(3%) mixture was used as the detector gas at a pressure up to 3.5 bar. A {sup 238}U sample mounted on the cathode of an ionisation chamber without grid was used as the neutron flux monitor. Special care was taken to reduce the experimental sources of uncertainty. The beam-monitor {sup 238}U sample was characterised at IRMM by low-geometry {alpha}-counting with an accuracy of 0.1%. A {sup 6}Li sample was produced at IRMM by vacuum evaporation of {sup 6}LiF onto transparent aluminium backing. The number of {sup 6}Li atoms will be measured via Thermal Neutron Depth Profiling with an expected accuracy of 2% with respect to an IRMM Standard Reference Material. First test measurements were performed using a monoenergetic neutron beam produced by the T(p,n){sup 3}He reaction at the IRMM 7 MV Van de Graaff accelerator. The experimental method and preliminary results are presented.

  7. Surface reaction rate and probability of ozone and alpha-terpineol on glass, polyvinyl chloride, and latex paint surfaces.

    PubMed

    Shu, Shi; Morrison, Glenn C

    2011-05-15

    Ozone can react homogeneously with unsaturated organic compounds in buildings to generate undesirable products. However, these reactions can also occur on indoor surfaces, especially for low-volatility organics. Conversion rates of ozone with α-terpineol, a representative low-volatility compound, were quantified on surfaces that mimic indoor substrates. Rates were measured for α-terpineol adsorbed to beads of glass, polyvinylchloride (PVC), and dry latex paint, in a plug flow reactor. A newly defined second-order surface reaction rate coefficient, k(2), was derived from the flow reactor model. The value of k(2) ranged from 0.68 × 10(-14) cm(4)s(-1)molecule(-1) for α-terpineol adsorbed to PVC to 3.17 × 10(-14) cm(4)s(-1)molecule(-1) for glass, but was insensitive to relative humidity. Further, k(2) is only weakly influenced by the adsorbed mass but instead appears to be more strongly related to the interfacial activity α-terpineol. The minimum reaction probability ranged from 3.79 × 10(-6) for glass at 20% RH to 6.75 × 10(-5) for PVC at 50% RH. The combination of high equilibrium surface coverage and high reactivity for α-terpineol suggests that surface conversion rates are fast enough to compete with or even overwhelm other removal mechanisms in buildings such as gas-phase conversion and air exchange.

  8. Reaction of germinal centers in the T-cell-independent response to the bacterial polysaccharide alpha(1-->6)dextran.

    PubMed Central

    Wang, D; Wells, S M; Stall, A M; Kabat, E A

    1994-01-01

    Primary immunization of BALB/c mice with alpha(1-->6)dextran (DEX), a native bacterial polysaccharide, induces an unexpected pattern of splenic B-cell responses. After a peak of antibody-secreting B-cell response at day 4, deposition of dextran-anti-dextran immune complexes, as revealed by staining with both dextran and antibodies to dextran, occurs and persists in splenic follicles until at least the fourth week after immunization. Antigen-specific B cells appear and proliferate in such follicles, leading by day 11 to development of DEX-specific germinal centers as characterized by the presence of distinct regions of DEX+ peanut agglutinin-positive (PNA+) cells. At this time, fluorescence-activated cell sorter analysis also reveals the appearance of a distinct population of DEX+ PNA+ splenic B cells. In contrast, DEX+ PNA- cells, characterized by intense cytoplasmic staining, are present outside of splenic follicles, peak at day 4 to day 5, and persist until at least day 28. The frequency of these cells correlates with DEX-specific antibody-secreting cells, as detected by the ELISA-spot assay. Thus, in addition to the expected plasma cellular response, the typical T-cell-independent type II antigen, DEX, surprisingly also elicits the formation of antigen-specific germinal centers. These observations raise fundamental questions about the roles of germinal centers in T-cell-independent immune responses. Images PMID:7511812

  9. A fluid response: Alpha-amylase reactions to acute laboratory stress are related to sample timing and saliva flow rate.

    PubMed

    Nagy, Tamás; van Lien, René; Willemsen, Gonneke; Proctor, Gordon; Efting, Marieke; Fülöp, Márta; Bárdos, György; Veerman, Enno C I; Bosch, Jos A

    2015-07-01

    Salivary alpha-amylase (sAA) is used as a sympathetic (SNS) stress marker, though its release is likely co-determined by SNS and parasympathetic (PNS) activation. The SNS and PNS show asynchronous changes during acute stressors, and sAA responses may thus vary with sample timing. Thirty-four participants underwent an eight-minute memory task (MT) and cold pressor task (CPT). Cardiovascular SNS (pre-ejection period, blood pressure) and PNS (heart rate variability) activity were monitored continuously. Unstimulated saliva was collected repeatedly during and after each laboratory stressor, and sAA concentration (U/ml) and secretion (U/minute) determined. Both stressors increased anxiety. The MT caused an immediate and continued cardiac SNS activation, but sAA concentration increased at task cessation only (+54%); i.e., when there was SNS-PNS co-activation. During the MT sAA secretion even decreased (-35%) in conjunction with flow rate and vagal tone. The CPT robustly increased blood pressure but not sAA. In summary, sAA fluctuations did not parallel changes in cardiac SNS activity or anxiety. sAA responses seem contingent on sample timing and flow rate, likely involving both SNS and PNS influences. Verification using other stressors and contexts seems warranted.

  10. Stereochemical course of hydrolytic reaction catalyzed by alpha-galactosidase from cold adaptable marine bacterium of genus Pseudoalteromonas

    NASA Astrophysics Data System (ADS)

    Bakunina, Irina; Balabanova, Larissa; Golotin, Vasiliy; Slepchenko, Lyubov; Isakov, Vladimir; Rasskazov, Valeriy

    2014-10-01

    The recombinant α-galactosidase of the marine bacterium (α-PsGal) was synthesized with the use of the plasmid 40Gal, consisting of plasmid pET-40b (+) (Novagen) and the gene corresponding to the open reading frame of the mature α-galactosidase of marine bacterium Pseudoalteromonas sp. KMM 701, transformed into the E. coli Rosetta(DE3) cells. In order to understand the mechanism of action, the stereochemistry of hydrolysis of 4-nitrophenyl α-D-galactopyranoside (4-NPGP) by α-PsGal was measured by 1H NMR spectroscopy. The kinetics of formation of α- and β-anomer of galactose showed that α-anomer initially formed and accumulated, and then an appreciable amount of β-anomer appeared as a result of mutarotation. The data clearly show that the enzymatic hydrolysis of 4-NPGP proceeds with the retention of anomeric configuration, probably, due to a double displacement mechanism of reaction.

  11. Stereochemistry of the allylation and crotylation reactions of alpha-methyl-beta-hydroxy aldehydes with allyl- and crotyltrifluorosilanes. Synthesis of anti,anti-dipropionate stereotriads and stereodivergent pathways for the reactions with 2,3-anti- and 2,3-syn-alpha-methyl-beta-hydroxy aldehydes.

    PubMed

    Chemler, Sherry R; Roush, William R

    2003-02-21

    A new method for the stereoselective synthesis of the anti,anti-dipropionate stereotriad via the reaction of alpha-methyl-beta-hydroxy aldehydes with (Z)-crotyltrifluorosilane (24) is described. These reactions were designed to occur through bicyclic transition states (e.g., 31) in which the silane reagent is covalently bound to the beta-hydroxyl group of the aldehyde and the crotyl group is transferred intramolecularly. This methodology was used to synthesize the C(7)-C(16) segment (58) of zincophorin, which contains a synthetically challenging all-anti stereopentad unit. Surprisingly, 2,3-anti- and 2,3-syn-alpha-methyl-beta-hydroxy aldehydes react in a stereodivergent manner with 24: 2,3-anti-beta-hydroxy aldehydes give the targeted anti,anti-dipropionate adducts with high selectivity, but the reactions of 2,3-syn-beta-hydroxy aldehydes are poorly selective. The stereodivergent behavior of 2,3-syn- vs 2,3-anti-alpha-methyl-beta-hydroxy aldehydes is also exhibited in their reactions with the allyl- (68) and (E)-crotyltrifluorosilanes (27). Competition experiments performed with beta-hydroxy aldehydes 37a (anti) and the corresponding p-methoxybenzyl (PMB) ether 48, and between aldehyde 39 (syn) and the PMB ether 90, established that the 2,3-anti-beta-hydroxy aldehydes react predominantly through bicyclic transition states while the 2,3-syn aldehydes react predominantly through conventional Zimmerman-Traxler transition states. NMR studies established that both the 2,3-syn and the 2,3-anti aldehydes form stable, pentavalent silicate intermediates (98 and 100) with PhSiF(3), but chelated structures 99 and 101 could not be detected. The activation energies for the competing bicyclic and conventional Zimmerman-Traxler transition states were calculated by using semiemperical methods (MNDO/d). These calculations indicate that the stereodivergent behavior of the 2,3-syn-beta-hydroxy aldehydes and the 2,3-anti-beta-hydroxy aldehydes is due to differences in nonbonded

  12. Ab initio alpha-alpha scattering.

    PubMed

    Elhatisari, Serdar; Lee, Dean; Rupak, Gautam; Epelbaum, Evgeny; Krebs, Hermann; Lähde, Timo A; Luu, Thomas; Meißner, Ulf-G

    2015-12-03

    Processes such as the scattering of alpha particles ((4)He), the triple-alpha reaction, and alpha capture play a major role in stellar nucleosynthesis. In particular, alpha capture on carbon determines the ratio of carbon to oxygen during helium burning, and affects subsequent carbon, neon, oxygen, and silicon burning stages. It also substantially affects models of thermonuclear type Ia supernovae, owing to carbon detonation in accreting carbon-oxygen white-dwarf stars. In these reactions, the accurate calculation of the elastic scattering of alpha particles and alpha-like nuclei--nuclei with even and equal numbers of protons and neutrons--is important for understanding background and resonant scattering contributions. First-principles calculations of processes involving alpha particles and alpha-like nuclei have so far been impractical, owing to the exponential growth of the number of computational operations with the number of particles. Here we describe an ab initio calculation of alpha-alpha scattering that uses lattice Monte Carlo simulations. We use lattice effective field theory to describe the low-energy interactions of protons and neutrons, and apply a technique called the 'adiabatic projection method' to reduce the eight-body system to a two-cluster system. We take advantage of the computational efficiency and the more favourable scaling with system size of auxiliary-field Monte Carlo simulations to compute an ab initio effective Hamiltonian for the two clusters. We find promising agreement between lattice results and experimental phase shifts for s-wave and d-wave scattering. The approximately quadratic scaling of computational operations with particle number suggests that it should be possible to compute alpha scattering and capture on carbon and oxygen in the near future. The methods described here can be applied to ultracold atomic few-body systems as well as to hadronic systems using lattice quantum chromodynamics to describe the interactions of

  13. Ab initio alpha-alpha scattering

    NASA Astrophysics Data System (ADS)

    Elhatisari, Serdar; Lee, Dean; Rupak, Gautam; Epelbaum, Evgeny; Krebs, Hermann; Lähde, Timo A.; Luu, Thomas; Meißner, Ulf-G.

    2015-12-01

    Processes such as the scattering of alpha particles (4He), the triple-alpha reaction, and alpha capture play a major role in stellar nucleosynthesis. In particular, alpha capture on carbon determines the ratio of carbon to oxygen during helium burning, and affects subsequent carbon, neon, oxygen, and silicon burning stages. It also substantially affects models of thermonuclear type Ia supernovae, owing to carbon detonation in accreting carbon-oxygen white-dwarf stars. In these reactions, the accurate calculation of the elastic scattering of alpha particles and alpha-like nuclei—nuclei with even and equal numbers of protons and neutrons—is important for understanding background and resonant scattering contributions. First-principles calculations of processes involving alpha particles and alpha-like nuclei have so far been impractical, owing to the exponential growth of the number of computational operations with the number of particles. Here we describe an ab initio calculation of alpha-alpha scattering that uses lattice Monte Carlo simulations. We use lattice effective field theory to describe the low-energy interactions of protons and neutrons, and apply a technique called the ‘adiabatic projection method’ to reduce the eight-body system to a two-cluster system. We take advantage of the computational efficiency and the more favourable scaling with system size of auxiliary-field Monte Carlo simulations to compute an ab initio effective Hamiltonian for the two clusters. We find promising agreement between lattice results and experimental phase shifts for s-wave and d-wave scattering. The approximately quadratic scaling of computational operations with particle number suggests that it should be possible to compute alpha scattering and capture on carbon and oxygen in the near future. The methods described here can be applied to ultracold atomic few-body systems as well as to hadronic systems using lattice quantum chromodynamics to describe the interactions of

  14. Reaction mechanisms in {sup 16}O+{sup 40}Ca at an incident energy of E({sup 16}O) =86 MeV through inclusive measurements of {alpha} and proton spectra

    SciTech Connect

    Basu, Chinmay; Adhikari, S.; Ghosh, S. K.; Roy, S.; Behera, B. R.; Datta, S. K.

    2007-09-15

    The {alpha} and proton spectra from the {sup 16}O+{sup 40}Ca reaction is measured at E({sup 16}O) =86 MeV at several laboratory angles between 54 deg. and 138 deg. Analysis in terms of the statistical model for compound nuclear reactions show that an event-by-event calculation of the evaporation spectra removes discrepancy observed with standard calculations.

  15. Effects of optically active 1-(alpha-methylbenzyl)-3-(3,4-dichlorophenyl)urea on reactions of mitochondria and chloroplasts.

    PubMed

    Moreland, D E; Boots, M R

    1971-01-01

    Effects of the R- and S-isomers and racemate of 1-(alpha-methylbenzyl)-3-(3,4-dichlorophenyl)urea (MBPU) were measured on phosphorylation and electron transport in mung bean (Phaseolus aureus L.) mitochondria and spinach (Spinacia oleracea L.) chloroplasts.In chloroplasts, S-MBPU inhibited basal and methylamine-uncoupled electron transport with ferricyanide as the oxidant, both photoreduction and coupled photophosphorylation with water as the electron donor and with ferricyanide and nicotinamide adenine dinucleotide phosphate (NADP) as oxidants, and cyclic photophosphorylation with phenazine methosulfate as the electron mediator under an argon gas phase. With ascorbate 2,6-dichloro-phenolindophenol as the electron donor, phosphorylation coupled to NADP reduction was inhibited, but the reduction of NADP was not inhibited. The R-isomer of MBPU, like the S-isomer, inhibited all of the photophosphorylation reactions studied. However, unlike the S-isomer, the R-isomer either did not inhibit or was a very weak inhibitor of all photoreduction reactions. The effects of the MBPUs on the chloroplast reactions can be explained by action at two different sites: an optically specific site near photosystem II and the oxygen evolution pathway, and a second optically nonspecific site associated with the generation of ATP.In mitochondria, both the R- and S-isomers stimulated state 4 respiration, inhibited state 3 respiration, and released oligomycin-inhibited respiration with malate, succinate, and NADH as substrates. Both enantiomers were equally active in all studies with malate and succinate as substrates. However, with NADH as substrate, R-MBPU was a stronger inhibitor of state 3 respiration and a weaker stimulator of state 4 respiration than S-MBPU.

  16. Does Dietary Deoxynivalenol Modulate the Acute Phase Reaction in Endotoxaemic Pigs?—Lessons from Clinical Signs, White Blood Cell Counts, and TNF-Alpha

    PubMed Central

    Tesch, Tanja; Bannert, Erik; Kluess, Jeannette; Frahm, Jana; Kersten, Susanne; Breves, Gerhard; Renner, Lydia; Kahlert, Stefan; Rothkötter, Hermann-Josef; Dänicke, Sven

    2015-01-01

    We studied the interaction between deoxynivalenol (DON)-feeding and a subsequent pre- and post-hepatic immune stimulus with the hypothesis that the liver differently mediates the acute phase reaction (APR) in pigs. Barrows (n = 44) were divided into a DON-(4.59 mg DON/kg feed) and a control-diet group, surgically equipped with permanent catheters pre- (V. portae hepatis) and post-hepatic (V. jugularis interna) and infused either with 0.9% NaCl or LPS (7.5 µg/kg BW). Thus, combination of diet (CON vs. DON) and infusion (CON vs. LPS, jugular vs. portal) created six groups: CON_CONjug.-CONpor., CON_CONjug.-LPSpor., CON_LPSjug.-CONpor., DON_CONjug.-CONpor., DON_CONjug.-LPSpor., DON_LPSjug.-CONpor.. Blood samples were taken at −30, 15, 30, 45, 60, 75, 90, 120, 150, 180 min relative to infusion and analyzed for leukocytes and TNF-alpha. Concurrently, clinical signs were scored and body temperature measured during the same period. LPS as such induced a dramatic rise in TNF-alpha (p < 0.001), hyperthermia (p < 0.01), and severe leukopenia (p < 0.001). In CON-fed pigs, an earlier return to physiological base levels was observed for the clinical complex, starting at 120 min post infusionem (p < 0.05) and persisting until 180 min. DON_LPSjug.-CONpor. resulted in a lower temperature rise (p = 0.08) compared to CON_LPSjug.-CONpor.. In conclusion, APR resulting from a post-hepatic immune stimulus was altered by chronic DON-feeding. PMID:26703732

  17. Does Dietary Deoxynivalenol Modulate the Acute Phase Reaction in Endotoxaemic Pigs?--Lessons from Clinical Signs, White Blood Cell Counts, and TNF-Alpha.

    PubMed

    Tesch, Tanja; Bannert, Erik; Kluess, Jeannette; Frahm, Jana; Kersten, Susanne; Breves, Gerhard; Renner, Lydia; Kahlert, Stefan; Rothkötter, Hermann-Josef; Dänicke, Sven

    2015-12-23

    We studied the interaction between deoxynivalenol (DON)-feeding and a subsequent pre- and post-hepatic immune stimulus with the hypothesis that the liver differently mediates the acute phase reaction (APR) in pigs. Barrows (n = 44) were divided into a DON-(4.59 mg DON/kg feed) and a control-diet group, surgically equipped with permanent catheters pre- (V. portae hepatis) and post-hepatic (V. jugularis interna) and infused either with 0.9% NaCl or LPS (7.5 µg/kg BW). Thus, combination of diet (CON vs. DON) and infusion (CON vs. LPS, jugular vs. portal) created six groups: CON_CON(jug.)-CON(por.), CON_CON(jug.)-LPS(por.), CON_LPS(jug.)-CON(por.), DON_CON(jug.)-CON(por.), DON_CON(jug.)-LPS(por.), DON_LPS(jug.)-CON(por.). Blood samples were taken at -30, 15, 30, 45, 60, 75, 90, 120, 150, 180 min relative to infusion and analyzed for leukocytes and TNF-alpha. Concurrently, clinical signs were scored and body temperature measured during the same period. LPS as such induced a dramatic rise in TNF-alpha (p < 0.001), hyperthermia (p < 0.01), and severe leukopenia (p < 0.001). In CON-fed pigs, an earlier return to physiological base levels was observed for the clinical complex, starting at 120 min post infusionem (p < 0.05) and persisting until 180 min. DON_LPS(jug.)-CON(por.) resulted in a lower temperature rise (p = 0.08) compared to CON_LPS(jug.)-CON(por.). In conclusion, APR resulting from a post-hepatic immune stimulus was altered by chronic DON-feeding.

  18. The FLUORINE-17(PROTON, PHOTON)NEON-18 and Oxygen -14(ALPHA Particle, PROTON)FLUORINE-17 Reaction Rates and the Structure of NEON-18 (NEON-18, FLUORINE-17, Oxygen -14, Astrophysical Hydrogen Burning)

    NASA Astrophysics Data System (ADS)

    Hahn, Kevin Insik

    1993-01-01

    The 14O(alpha,p) 17F and ^ {17}F(p,gamma)18Ne reactions play crucial roles in the advanced stages of astrophysical hydrogen burning. The ^{14 }O(alpha,p)^ {17}F(p,gamma) ^ {18}Ne(beta^+nu) 18F(p,alpha)^ {15}O reaction sequence can provide a path around the relatively slow positron decay of 14O in the HCNO cycle, while the similar reaction sequence, ^{14 }O(alpha ,p) 17F(p,gamma)^ {18}Ne(beta ^+nu) 18F(p,gamma)^ {19}Ne, can provide an alternate path from the HCNO cycle to the rp-process. The 17F(p,gamma)18Ne reaction rate could provide the principal source of 18O. Under some astrophysical conditions, the ^{14 }O(alpha,p)^ {17}F reaction is expected to compete with the 15O(alpha, gamma)19Ne reaction in providing a path through which nuclei involved in the HCNO cycle can be transformed into heavier nuclei with Z >= 10.. In order to better determine the rates of these two reactions, we measured the properties of the resonances in 18Ne; the excitation energies, the spins, and the partial and total widths of the relevant resonances. By comparing the previously observed states in 18Ne to the well-studied isospin mirror nucleus, ^{18 }O, it is clear that there are a number of missing levels in 18Ne in the region rm Ex > 4 MeV. These missing states in ^ {18}Ne could be important in determining the 17F(p, gamma)18rm Ne and 14O(alpha ,p)17F reaction rates. We have studied the ^{12 }C(12C,^6He)^{18 }Ne, 20rm Ne(p{,}t)18Ne, and 16O(^3He{, }n)18Ne reactions to measure new nuclear structure information of ^{18 }Ne. From our experiments, we have the following major results: (a) an evidence of the 3^+ <=vel at E_{rm x} = 4.56 MeV, (b) new levels at E_ {rm x} = 6.15 MeV, 7.12 MeV, 7.35 MeV, 7.62 MeV, 8.30 MeV, (8.45 MeV), 8.55 MeV, 8.94 MeV, and 9.58 MeV. (c) new J^pi assignments to the 5.11/5.15-MeV doublet and the 6.15-MeV state. Our discovery of the 3^+<=vel at an energy ~230 keV higher than calculated by Wiescher, Gorres, and Thielemann causes the contribution of the 17 F

  19. F-actin sequesters elongation factor 1alpha from interaction with aminoacyl-tRNA in a pH-dependent reaction

    PubMed Central

    1996-01-01

    The machinery of eukaryotic protein synthesis is found in association with the actin cytoskeleton. A major component of this translational apparatus, which is involved in the shuttling of aa-tRNA, is the actin- binding protein elongation factor 1alpha (EF-1alpha). To investigate the consequences for translation of the interaction of EF-1alpha with F- actin, we have studied the effect of F-actin on the ability of EF- 1alpha to bind to aa-tRNA. We demonstrate that binding of EF-1alpha:GTP to aa-tRNA is not pH sensitive with a constant binding affinity of approximately 0.2 microM over the physiological range of pH. However, the sharp pH dependence of binding of EF-1alpha to F-actin is sufficient to shift the binding of EF-1alpha from F-actin to aa-tRNA as pH increases. The ability of EF-1alpha to bind either F-actin or aa- tRNA in competition binding experiments is also consistent with the observation that EF-1alpha's binding to F-actin and aa-tRNA is mutually exclusive. Two pH-sensitive actin-binding sequences in EF-1alpha are identified and are predicted to overlap with the aa-tRNA-binding sites. Our results suggest that pH-regulated recruitment and release of EF- 1alpha from actin filaments in vivo will supply a high local concentration of EF-1alpha to facilitate polypeptide elongation by the F-actin-associated translational apparatus. PMID:8922379

  20. Asteroid Lightcurve Analysis at Riverland Dingo Observatory (RDO): 185 Eunike, (17252) 2000 GJ127, and (152858) 1999 XN35

    NASA Astrophysics Data System (ADS)

    Hills, Kevin

    2013-04-01

    Lightcurves for three asteroids selected from the Collaborative Asteroid Lightcurve Link (CALL; Warner 2011) were obtained at Riverland Dingo Observatory (RDO) in the period October 13 through December 5, 2012: 185 Eunike, (17252) 2000 GJ127, and (152858) 1999 XN35.

  1. Development of epitaxial AlxSc1-xN for artificially structured metal/semiconductor superlattice metamaterials

    DOE PAGES

    Sands, Timothy D.; Stach, Eric A.; Saha, Bivas; ...

    2015-02-01

    Epitaxial nitride rocksalt metal/semiconductor superlattices are emerging as a novel class of artificially structured materials that have generated significant interest in recent years for their potential application in plasmonic and thermoelectric devices. Though most nitride metals are rocksalt, nitride semiconductors in general have hexagonal crystal structure. We report rocksalt aluminum scandium nitride (Al,Sc)N alloys as the semiconducting component in epitaxial rocksalt metal/semiconductor superlattices. The AlxSc1-xN alloys when deposited directly on MgO substrates are stabilized in a homogeneous rocksalt (single) phase when x < 0.51. Employing 20 nm TiN as a seed layer on MgO substrates, the homogeneity range for stabilizingmore » the rocksalt phase has been extended to x < 0.82 for a 120 nm film. The rocksalt AlxSc1-xN alloys show moderate direct bandgap bowing with a bowing parameter, B = 1.41 ± 0.19 eV. The direct bandgap of metastable rocksalt AlN is extrapolated to be 4.70 ± 0.20 eV. The tunable lattice parameter, bandgap, dielectric permittivity, and electronic properties of rocksalt AlxSc1-xN alloys enable high quality epitaxial rocksalt metal/AlxSc1-xN superlattices with a wide range of accessible metamaterials properties.« less

  2. BetaQ114N and betaT110V Mutations Reveal a Critically Important Role of the Substrate alpha-Carboxylte Site in the Reaction Specificity of Tryptophan Synthase

    SciTech Connect

    Blumenstein,L.; Domratcheva, T.; Niks, D.; Ngo, H.; Seidel, R.; Dunn, M.; Schlichting, I.

    2007-01-01

    In the PLP-requiring {alpha}2{beta}2 tryptophan synthase complex, recognition of the substrate l-Ser at the {beta}-site includes a loop structure (residues {beta}110-115) extensively H-bonded to the substrate {alpha}-carboxylate. To investigate the relationship of this subsite to catalytic function and to the regulation of substrate channeling, two loop mutants were constructed: {beta}Thr110 {yields} Val, and {beta}Gln114 {yields} Asn. The {beta}T110V mutation greatly impairs both catalytic activity in the {beta}-reaction, and allosteric communication between the {alpha}- and {beta}-sites. The crystal structure of the {beta}T110V mutant shows that the modified l-Ser carboxylate subsite has altered protein interactions that impair {beta}-site catalysis and the communication of allosteric signals between the {alpha}- and {beta}-sites. Purified {beta}Q114N consists of two species of mutant protein, one with a reddish color ({lambda}max = 506 nm). The reddish species is unable to react with l-Ser. The second {beta}Q114N species displays significant catalytic activities; however, intermediates obtained on reaction with substrate l-Ser and substrate analogues exhibit perturbed UV/vis absorption spectra. Incubation with l-Ser results in the formation of an inactive species during the first 15 min with {lambda}max 320 nm, followed by a slower conversion over 24 h to the species with ?max = 506 nm. The 320 and 506 nm species originate from conversion of the {alpha}-aminoacrylate external aldimine to the internal aldimine and {alpha}-aminoacrylate, followed by the nucleophilic attack of {alpha}-aminoacrylate on C-4' of the internal aldimine to give a covalent adduct with PLP. Subsequent treatment with sodium hydroxide releases a modified coenzyme consisting of a vinylglyoxylic acid moiety linked through C-4' to the 4-position of the pyridine ring. We conclude that the shortening of the side chain accompanying the replacement of {beta}114-Gln by Asn relaxes the steric

  3. Structural and EPR characterisation of single electron and alkyl transfer products from reaction of dimethyl magnesium with bulky alpha-diimine ligands.

    PubMed

    Bailey, Philip J; Coxall, Robert A; Dick, Caroline M; Fabre, Sylvie; Parsons, Simon; Yellowlees, Lesley J

    2005-09-28

    Treatment of dimethylmagnesium with bulky alpha-diimine ligands provides either the biradical methyl-bridged complexes [(alpha-diimine-.)Mg+(mu-CH3)]2 via single electron transfer (SET), or the product of methyl transfer to an imine carbon atom depending upon conditions.

  4. Quantitation of mRNA levels of steroid 5alpha-reductase isozymes: A method that combines one-step reverse transcription-polymerase chain reaction and separation by capillary electrophoresis.

    PubMed

    Torres, Jesús M; Ortega, Esperanza

    2004-02-01

    We developed an accurate, rapid, and modestly labor-intensive method to precisely quantitate mRNA species by one-step reverse transcription-polymerase chain reaction (RT-PCR). This approach combines the high specificity of quantitative competitive PCR with the sensitivity of laser-induced fluorescence capillary electrophoresis (LIF-CE). Both cDNA synthesis and PCR amplification are performed with the same enzyme and site-specific primers, improving the efficiency of cDNA synthesis. The specific target mRNA and a mimic DNA fragment, used as a competitive internal standard, were coamplified in a single reaction in which the same primers are used. The 5' forward primers were end-labeled with 6-carboxy-fluorescein (6-FAM). The ratio of fluorescence intensity between amplified products of the target cDNA and the competitive DNA was determined quantitatively after separation by CE and fluorescence analysis. Using this method, we have been able to precisely quantify the mean amount of steroid 5alpha-reductase (5alpha-R) isozyme mRNA levels in ventral prostate of the rat, detecting 10-fold difference for 5alpha-R1 and 50-fold difference for 5alpha-R2, respectively, in comparison with our previously reported two-step method. Because the competitive RT-PCR presented in this paper enables a more efficient quantitative determination of mRNAs, low-level gene expression could be quantified.

  5. Ga{sub 1-x}Mn{sub x}N epitaxial films with high magnetization

    SciTech Connect

    Kunert, G.; Kruse, C.; Figge, S.; Hommel, D.; Dobkowska, S.; Jakiela, R.; Stefanowicz, W.; Sawicki, M.; Li, Tian; Bonanni, A.; Reuther, H.; Grenzer, J.; Borany, J. von; Dietl, T.

    2012-07-09

    We report on the fabrication of pseudomorphic wurtzite Ga{sub 1-x}Mn{sub x}N grown on GaN with Mn concentrations up to 10% using molecular beam epitaxy. According to Rutherford backscattering, the Mn ions are mainly at the Ga-substitutional positions, and they are homogeneously distributed according to depth-resolved Auger-electron spectroscopy and secondary-ion mass-spectroscopy measurements. A random Mn distribution is indicated by transmission electron microscopy, and no Mn-rich clusters are present for optimized growth conditions. A linear increase of the c-lattice parameter with increasing Mn concentration is found using x-ray diffraction. The ferromagnetic behavior is confirmed by superconducting quantum-interference measurements showing saturation magnetizations of up to 150 emu/cm{sup 3}.

  6. Synthesis of a peroxime proliferator activated receptor (PPAR) alpha/gamma agonist via stereocontrolled Williamson ether synthesis and stereospecific SN2 reaction of S-2-chloro propionic acid with phenoxides.

    PubMed

    Aikins, James A; Haurez, Michael; Rizzo, John R; Van Hoeck, Jean-Pierre; Brione, Willy; Kestemont, Jean-Paul; Stevens, Christophe; Lemair, Xavier; Stephenson, Gregory A; Marlot, Eric; Forst, Mindy; Houpis, Ioannis N

    2005-06-10

    The stereospecific synthesis of the PPAR alpha/gamma agonist 1 was accomplished via ethylation of the optically pure trihydroxy derivative 6, itself derived via an enzymatic resolution. The ethylation can be accomplished without epimerization only under strict control of the reaction conditions and the choice of base (sodium tert-amylate), temperature (-30 degrees C), order of addition, and solvent (DMF). The key diastereospecific SN2 reaction of the phenol 4 with S-2-chloropropionic acid is best achieved via the sodium phenoxide of 4 derived from Na0 as the reagent of choice. The structure elucidation and key purification protocols to achieve pharmaceutical purity will also be described.

  7. Cross sections for (n, 2n), (n, p) and (n, <alpha>) reactions on osmium isotopes in the neutron energy range of 13.5-14.8 MeV.

    PubMed

    Zhao, Liangyong; Yuan, Jilong; Tuo, Fei; Zhang, Yanbin; Kong, Xiangzhong; Liu, Rong; Jiang, Li

    2008-10-01

    Cross sections for (n, 2n), (n, p) and (n, alpha) reactions on the osmium isotopes were measured in the neutron energies 13.5-14.8 MeV by the activation technique with the monitor reaction (93)Nb(n, 2n)(92 m)Nb. Our measurements were carried out by gamma-detection using a coaxial high-purity germanium (HPGe) detector. Natural high-purity osmium powder (99.9%) was fabricated as the samples. The neutron energies were determined by the cross-section ratios for (93)Nb(n, 2n)(92 m)Nb and (90)Zr(n, 2n)(89 m+g)Zr reactions. The fast neutrons were produced by the T(d, n)(4)He reaction. The results obtained were compared with previous data.

  8. Synthesis of a precursor for the preparation of 9 alpha,11 alpha-tritiated 5 alpha-androstane-3 alpha,17 beta-diol 17-glucuronide

    SciTech Connect

    Rao, P.N.; Damodaran, K.M.

    1984-03-01

    Starting from 11 beta-hydroxytestosterone, the synthesis of a strategic precursor, C-9 (11) unsaturated 5 alpha-androstane-3 alpha, 17 beta-diol 17-glucuronide (9a), for the preparation of 9 alpha,11 alpha-tritiated 5 alpha-androstane-3 alpha, 17 beta-diol 17-glucuronide has been achieved. The authors optimized the reaction conditions for catalytic reduction employing hydrogen and subsequent base hydrolysis followed by purification on Amberlite XAD-2 resin to obtain the saturated 5 alpha-androstane-3 alpha, 17 beta-diol 17-glucuronide.

  9. Acid-, base-, and lewis-acid-catalyzed heterolysis of methoxide from an alpha-hydroxy-beta-methoxy radical: models for reactions catalyzed by coenzyme B12-dependent diol dehydratase.

    PubMed

    Xu, Libin; Newcomb, Martin

    2005-11-11

    [Reaction: see text].A model for glycol radicals was employed in laser flash photolysis kinetic studies of catalysis of the fragmentation of a methoxy group adjacent to an alpha-hydroxy radical center. Photolysis of a phenylselenylmethylcyclopropane precursor gave a cyclopropylcarbinyl radical that rapidly ring opened to the target alpha-hydroxy-beta-methoxy radical (3). Heterolysis of the methoxy group in 3 gave an enolyl radical (4a) or an enol ether radical cation (4b), depending upon pH. Radicals 4 contain a 2,2-diphenylcyclopropane reporter group, and they rapidly opened to give UV-observable diphenylalkyl radicals as the final products. No heterolysis was observed for radical 3 under neutral conditions. In basic aqueous acetonitrile solutions, specific base catalysis of the heterolysis was observed; the pK(a) of radical 3 was determined to be 12.5 from kinetic titration plots, and the ketyl radical formed by deprotonation of 3 eliminated methoxide with a rate constant of 5 x 10(7) s(-1). In the presence of carboxylic acids in acetonitrile solutions, radical 3 eliminated methanol in a general acid-catalyzed reaction, and rate constants for protonation of the methoxy group in 3 by several acids were measured. Radical 3 also reacted by fragmentation of methoxide in Lewis-acid-catalyzed heterolysis reactions; ZnBr2, Sc(OTf)3, and BF3 were found to be efficient catalysts. Catalytic rate constants for the heterolysis reactions were in the range of 3 x 10(4) to 2 x 10(6) s(-1). The Lewis-acid-catalyzed heterolysis reactions are fast enough for kinetic competence in coenzyme B12 dependent enzyme-catalyzed reactions of glycols, and Lewis-acid-catalyzed cleavages of beta-ethers in radicals might be applied in synthetic reactions.

  10. Cross sections of the reaction {sup 231}Pa(d,3n){sup 230}U for the production of {sup 230}U/{sup 226}Th for targeted {alpha} therapy

    SciTech Connect

    Morgenstern, A.; Bruchertseifer, F.; Zielinska, B.; Apostolidis, C.; Lebeda, O.; Stursa, J.; Capote, R.; Sin, M.

    2009-11-15

    {sup 230}U and its daughter nuclide {sup 226}Th are novel therapeutic nuclides for application in targeted {alpha} therapy of cancer. We investigated the feasibility of producing {sup 230}U/{sup 226}Th via deuteron irradiation of {sup 231}Pa according to the reaction {sup 231}Pa(d,3n){sup 230}U. The experimental excitation function for a deuteron-induced reaction on {sup 231}Pa is reported for the first time. Cross sections were measured using thin targets of {sup 231}Pa prepared by electrodeposition and {sup 230}U yields were analysed using {alpha} spectrometry. Beam energies were calculated from measured beam orbits and compared with the values obtained via monitor reactions on aluminium foils using high-resolution {gamma} spectrometry and IAEA recommended cross sections. Beam intensities were determined using a beam current integrator. The experimental cross sections are in excellent agreement with model calculations allowing for deuteron breakup using the EMPIRE 3 code. According to thick-target yields calculated from the experimental excitation function, the reaction {sup 231}Pa(d,3n){sup 230}U allows the production of {sup 230}U/{sup 226}Th at moderate levels.

  11. Measurement of the astrophysical S-factor for the {sup 18}F(p,{alpha}) reaction at E = 662 keV/u with a {sup 18}F radioactive beam

    SciTech Connect

    Rehm, K.E.; Blumenthal, D.J.; Gehring, J.

    1995-08-01

    {sup 18}F is produced in stars during the so-called breakout from the hot CNO cycle and is important as one of the links connecting the HCNO cycle with the rp-process by producing {sup 19}Ne via the {sup 18}F(p,{gamma}) reaction. There is, however, a competing reaction {sup 18}F(p,{alpha}){sup 15}O which leads back into the CNO cycle. The importance of {sup 18}F for producing {sup 19}Ne therefore depends strongly on the (p,{gamma}) to (p,{alpha}) cross sections ratio. We have begun to study the {sup 18}F(p,{alpha}){sup 15}O reaction using a {sup 18}F beam. {sup 18}F, which is a well-studied PET isotope, is generated at the medical cyclotron of the University of Wisconsin. Aqueous [{sup 18}F] fluoride ions are produced via the {sup 18}O(p,n){sup 18}F reaction using a 30-{mu}A, 11.4-MeV proton beam bombarding a 95% enriched [{sup 18}O] water target and electroplated onto the end of a 3-mm diameter Al anode. After electroplating, the anodized Al is pressed into a copper cathode insert for the National Electrostatics Corporation SNICS ion source, transported to Argonne National Laboratory and installed in the ion source of the Tandem accelerator at ATLAS. With an activity at the end of the electroplating process of 530 mCi, the starting activity after 2 h, which is the time needed to transport and install the material in the SNICS source, was 250 mCi, corresponding to a total number of {sup 18}F atoms of 8.8 x 10{sup 13}.

  12. Structural and electronic properties of GaN nanowires with embedded InxGa1-xN nanodisks

    NASA Astrophysics Data System (ADS)

    Kioseoglou, J.; Pavloudis, Th.; Kehagias, Th.; Komninou, Ph.; Karakostas, Th.; Latham, C. D.; Rayson, M. J.; Briddon, P. R.; Eickhoff, M.

    2015-07-01

    In the present study, the effects of various types of strain and indium concentration on the total energy and optoelectronic properties of GaN nanowires (NWs) with embedded InxGa1-xN nanodisks (NDs) are examined. In particular, the bi-axial, hydrostatic, and uniaxial strain states of the embedded InxGa1-xN NDs are investigated for multiple In concentrations. Density functional theory is employed to calculate the band structure of the NWs. The theoretical analysis finds that the supercell-size-dependent characteristics calculated for our 972-atom NW models are very close to the infinite supercell-size limit. It is established that the embedded InxGa1-xN NDs do not induce deep states in the band gap of the NWs. A bowing parameter of 1.82 eV is derived from our analysis in the quadratic Vegard's formula for the band gaps at the various In concentrations of the investigated InxGa1-xN NDs in GaN NW structures. It is concluded that up to ˜10% of In, the hydrostatic strain state is competitive with the bi-axial due to the radial absorption of the strain on the surfaces. Above this value, the dominant strain state is the bi-axial one. Thus, hydrostatic and bi-axial strain components coexist in the embedded NDs, and they are of different physical origin. The bi-axial strain comes from growth on lattice mismatched substrates, while the hydrostatic strain originates from the lateral relaxation of the surfaces.

  13. Chemically ordered Al{sub x}Ga{sub 1-x}N alloys: Spontaneous formation of natural quantum wells

    SciTech Connect

    Albrecht, M.; Lymperakis, L.; Neugebauer, J.; Northrup, J.E.; Kirste, L.; Leroux, M.; Grzegory, I.; Porowski, S.; Strunk, H.P.

    2005-01-15

    We combine transmission electron microscopy, high-resolution x-ray diffraction, cathodoluminescence, and photoluminescence experiments with first-principles calculations to study the formation, thermodynamic stability, structural, and optical properties of chemically ordered Al{sub x}Ga{sub 1-x}N alloys (0x}N alloys. The ordered alloys have unique properties: (i) the band gap is redshifted up to 110 meV with respect to the disordered alloy of the same composition and (ii) the band gap reduction is caused by localization of the band edge wave functions in the GaN layer. Ordered Al{sub x}Ga{sub 1-x}N thus can be seen as a natural quantum well structure where electrons and holes are localized and confined in monolayer GaN quantum wells.

  14. The alpha channeling effect

    SciTech Connect

    Fisch, N. J.

    2015-12-10

    Alpha particles born through fusion reactions in a tokamak reactor tend to slow down on electrons, but that could take up to hundreds of milliseconds. Before that happens, the energy in these alpha particles can destabilize on collisionless timescales toroidal Alfven modes and other waves, in a way deleterious to energy confinement. However, it has been speculated that this energy might be instead be channeled into useful energy, so as to heat fuel ions or to drive current. Such a channeling needs to be catalyzed by waves Waves can produce diffusion in energy of the alpha particles in a way that is strictly coupled to diffusion in space. If these diffusion paths in energy-position space point from high energy in the center to low energy on the periphery, then alpha particles will be cooled while forced to the periphery. The energy from the alpha particles is absorbed by the wave. The amplified wave can then heat ions or drive current. This process or paradigm for extracting alpha particle energy collisionlessly has been called alpha channeling. While the effect is speculative, the upside potential for economical fusion is immense. The paradigm also operates more generally in other contexts of magnetically confined plasma.

  15. Diphenylprolinol silyl ether as catalyst of an asymmetric, catalytic, and direct Michael reaction of nitroalkanes with alpha,beta-unsaturated aldehydes.

    PubMed

    Gotoh, Hiroaki; Ishikawa, Hayato; Hayashi, Yujiro

    2007-12-06

    A catalytic enantioselective direct conjugate addition of nitroalkanes to alpha,beta-unsaturated aldehydes using diphenylprolinol silyl ether as an organocatalyst has been developed. Using this methodology as a key step, short syntheses of therapeutically useful compounds have also been accomplished.

  16. Asymmetric hydrogenation of alpha,beta-unsaturated phosphonates with Rh-BisP* and Rh-MiniPHOS catalysts: scope and mechanism of the reaction.

    PubMed

    Gridnev, Ilya D; Yasutake, Masaya; Imamoto, Tsuneo; Beletskaya, Irina P

    2004-04-13

    Optically active 1,2-bis(alkylmethylphosphino)ethanes and bis(alkylmethylphosphino)methanes are unique diphosphine ligands combining the simple molecular structure and P-stereogenic asymmetric environment. This work shows that these ligands exhibit excellent enantioselectivity in rhodium-catalyzed asymmetric hydrogenation of alpha,beta-unsaturated phosphonic acid derivatives. The enantioselective hydrogenation mechanism elucidated by NMR study is also described.

  17. InxAl1-xN chiral nanorods mimicking the polarization features of scarab beetles

    NASA Astrophysics Data System (ADS)

    Magnusson, R.; Birch, J.; Hsiao, C.-L.; Sandström, P.; Arwin, H.; Järrendahl, K.

    2015-03-01

    The scarab beetle Cetonia aurata is known to reflect light with brilliant colors and a high degree of circular polarization. Both color and polarization effects originate from the beetles exoskeleton and have been attributed to a Bragg reflection of the incident light due to a twisted laminar structure. Our strategy for mimicking the optical properties of the Cetonia aurata was therefore to design and fabricate transparent, chiral films. A series of films with tailored transparent structures of helicoidal InxAl1-xN nanorods were grown on sapphire substrates using UHV magnetron sputtering. The value of x is tailored to gradually decrease from one side to the other in each nanorod normal to its growth direction. This introduces an in-plane anisotropy with different refractive indices in the direction of the gradient and perpendicular to it. By rotating the sample during film growth the in-plane optical axis will be rotated from bottom to top and thereby creating a chiral film. Based on Muellermatrix ellipsometry, optical modeling has been done suggesting that both the exoskeleton of Cetonia aurata and our artificial material can be modeled by an anisotropic film made up of a stack of thin layers, each one with its in-plane optical axis slightly rotated with respect to the previous layer. Simulations based on the optical modeling were used to investigate how pitch and thickness of the film together with the optical properties of the constitutive materials affects the width and spectral position of the Bragg reflection band.

  18. Luminescence studies in InxGa1-xN epitaxial layers with different indium contents

    NASA Astrophysics Data System (ADS)

    Wu, T. Y.; Chang, C. C.; Tiong, K. K.; Lee, Y. C.; Hu, S. Y.; Lin, L. Y.; Lin, T. Y.; Feng, Z. C.

    2013-08-01

    The optical properties of InxGa1-xN epitaxial layers (x = 0.02, 0.04, 0.11, 0.15, 0.30 and 0.33) grown by metalorganic chemical vapor deposition (MOCVD) have been investigated by temperature-dependent photoluminescence (PL) measurement. The surface morphologies of InGaN samples are studied by scanning electron microscopy (SEM) images. The PL feature at 12 K has shown an increase in full-width at half-maximum (FWHM) with increasing In content. An anomalous S-shaped temperature dependence of the PL peak energy exhibited by InGaN films with higher In content enabled the evaluation of the exciton localization energy. The broadened FWHM and S-shaped emission shift are attributed to larger compositional fluctuation due to compositional inhomogeneity of In. Additionally, the luminescence mechanism relating to the phase separation has to be considered for the much larger FWHM value and the pronounced S-shaped behavior for the InGaN samples with In content of 0.30 and 0.33.

  19. Fragmented red cells reference range (Sysmex XN(®) automated blood cell counter).

    PubMed

    Lesesve, Jean-François; Daigney, Amandine; Henry, Sylvain; Speyer, Elodie

    2015-01-01

    Fragmented red cells (FRCs) is a new parameter automatedly determined by recent blood cell counters. Their count might be of interest because FRCs are supposed to reflect schistocytes counts measured on a stained peripheral blood smear observed under the microscope. But FRCs depend from the technical procedure used to detect them and thus reference ranges are device-dependent. The XN-9000(®) is one of the last model from Sysmex series. We aimed to establish reference range for FRCs, from 2389 controls. The mean ± SD was 0.32% ± 0.81, the median 0.02% (95% confidence interval ot the mean: 0.29-0.35%). We observed that the percentage of red blood cells with less than 17 pg of hemoglobin content (Hypo-He) was correlated to FRC increase, Hypo-He increase resulting in spurious FRCs majoration. FRCs reference range should be useful for: 1) laboratory staff in order to select which blood smears to check optically; 2) Sysmex company to set-up more optimal rules proposed with the counter (automated making of blood smear).

  20. Alpha Particle Diagnostic

    SciTech Connect

    Fisher, Ray, K.

    2009-05-13

    The study of burning plasmas is the next frontier in fusion energy research, and will be a major objective of the U.S. fusion program through U.S. collaboration with our international partners on the ITER Project. For DT magnetic fusion to be useful for energy production, it is essential that the energetic alpha particles produced by the fusion reactions be confined long enough to deposit a significant fraction of their initial ~3.5 MeV energy in the plasma before they are lost. Development of diagnostics to study the behavior of energetic confined alpha particles is a very important if not essential part of burning plasma research. Despite the clear need for these measurements, development of diagnostics to study confined the fast confined alphas to date has proven extremely difficult, and the available techniques remain for the most part unproven and with significant uncertainties. Research under this grant had the goal of developing diagnostics of fast confined alphas, primarily based on measurements of the neutron and ion tails resulting from alpha particle knock-on collisions with the plasma deuterium and tritium fuel ions. One of the strengths of this approach is the ability to measure the alphas in the hot plasma core where the interesting ignition physics will occur.

  1. Sequential and selective hydrogenation of the C(alpha)-C(beta) and M-C(alpha) double bonds of an allenylidene ligand coordinated to osmium: new reaction patterns between an allenylidene complex and alcohols.

    PubMed

    Bolaño, Tamara; Castarlenas, Ricardo; Esteruelas, Miguel A; Oñate, Enrique

    2007-07-18

    Complex [OsH(=C=C=CPh2)(CH3CN)2(PiPr3)2]BF4 (1) reacts with primary and secondary alcohols to give the corresponding dehydrogenated alcohols and the hydride-carbene derivative [OsH(=CHCH=CPh2)(CH3CN)2(PiPr3)2]BF4 (2), as a result of hydrogen transfer reactions from the alcohols to the Calpha-Cbeta double bond of the allenylidene ligand of 1. The reactions with phenol and t-butanol, which do not contain any beta-hydrogen, afford the alkoxy-hydride-carbyne complexes [OsH(OR)(CCH=CPh2)(CH3CN)(PiPr3)2]BF4 (R = Ph (3), tBu (4)), as a consequence of the 1,3-addition of the O-H bond of the alcohols to the metallic center and the Cbeta atom of the allenylidene of 1. On the basis of the reactions of 1 with these tertiary alcohols, deuterium labeling experiments, and DFT calculations, the mechanism of the hydrogenation is proposed. In acetonitrile under reflux, the Os-C double bond of 2 undergoes hydrogenation to give 1,1-diphenylpropene and [Os{CH2CH(CH3)PiPr2(CH3CN)3(PiPr3)]BF4 (11), containing a metalated phosphine ligand. This reaction is a first-order process with activation parameters of DeltaH = 89.0 +/- 6.3 kJ mol-1 and DeltaS = -43.5 +/- 9.6 J mol-1 K-1. The X-ray structures of 2 and 3 are also reported.

  2. Band-edge exciton transitions in (Ga 1- xMn x)N diluted magnetic semiconductor films with above room temperature ferromagnetic transition

    NASA Astrophysics Data System (ADS)

    Jeon, H. C.; Kang, T. W.; Kim, T. W.; Cho, Y. H.

    2006-06-01

    (Ga 1- xMn x)N thin films grown on GaN buffer layers by using molecular beam epitaxy were investigated with the goal of producing diluted magnetic semiconductors (DMSs) with band-edge exciton transitions for applications in optomagnetic devices. The magnetization curve as a function of the magnetic field at 5 K indicated that ferromagnetism existed in the (Ga 1- xMn x)N thin films, and the magnetization curve as a function of the temperature showed that the ferromagnetic transition temperature of the (Ga 1- xMn x)N thin film was above room temperature. Photoluminescence and photoluminescence excitation spectra showed that band-edge exciton transitions in (Ga 1- xMn x)N thin films appeared. These results indicate that the (Ga 1- xMn x)N DMSs with a magnetic single phase hold promise for potential applications in spin optoelectronic devices in the blue region of the spectrum.

  3. Luteal 3beta-hydroxysteroid dehydrogenase and 20alpha-hydroxysteroid dehydrogenase activities in the rat corpus luteum of pseudopregnancy: Effect of the deciduoma reaction

    PubMed Central

    Clementi, Marisa A; Deis, Ricardo P; Telleria, Carlos M

    2004-01-01

    Background In the rat, the maintenance of gestation is dependent on progesterone production from the corpora lutea (CL), which are under the control of pituitary, decidual and placental hormones. The luteal metabolism of progesterone during gestation has been amply studied. However, the regulation of progesterone synthesis and degradation during pseudopregnancy (PSP), in which the CL are mainly under the control of pituitary prolactin (PRL), is not well known. The objectives of this investigation were: i) to study the luteal metabolism of progesterone during PSP by measuring the activities of the enzymes 3beta-hydroxysteroid dehydrogenase (3betaHSD), involved in progesterone biosynthesis, and that of 20alpha-hydroxysteroid dehydrogenase (20alphaHSD), involved in progesterone catabolism; and ii) to determine the role of decidualization on progesterone metabolism in PSP. Methods PSP was induced mechanically at 10:00 h on the estrus of 4-day cycling Wistar rats, and the stimulus for decidualization was provided by scratching the uterus on day 4 of PSP. 3betaHSD and 20alphaHSD activities were measured in the CL isolated from ovaries of PSP rats using a spectrophotometric method. Serum concentrations of progesterone, PRL, androstenedione, and estradiol were measured by radioimmunoassay (RIA). Results The PSP stage induced mechanically in cycling rats lasted 11.3 ± 0.09 days (n = 14). Serum progesterone concentration was high until day 10 of PSP, and declined thereafter. Serum PRL concentration was high on the first days of PSP but decreased significantly from days 6 to 9, having minimal values on days 10 and 11. Luteal 3betaHSD activities were elevated until day 6 of PSP, after which they progressively declined, reaching minimal values at the end of PSP. Luteal 20alphaHSD activities were very low until day 9, but abruptly increased at the end of PSP. When the deciduoma was induced by scratching the uterus of pseudopregnant animals on day 4 (PSP+D), PSP was extended to

  4. First-Principles Calculations for the Structural and Electronic Properties of ScxAl1-xN Alloys

    NASA Astrophysics Data System (ADS)

    Mohammad, Rezek; Katircioğlu, Şenay

    2013-10-01

    The first-principles calculations based on Density Functional Theory (DFT) within generalized gradient approximation (GGA) of Engel-Vosko-Perdew-Wang and modified exact exchange potential of Becke-Johnson have been introduced for the structural and electronic properties of the ScxAl1-xN alloys, respectively. The present lattice constants calculated for the ScAlN alloys and the end compounds (AlN and ScN) are found to be in very good agreement with the available experimental and theoretical ones. The stable ground state structures of the ScxAl1-xN alloys are determined to be wurtzite for the Sc concentration less than 0.403 and rock-salt for the higher Sc concentrations. The present electronic band structure calculations within Becke-Johnson scheme are found to be capable of providing energy band gaps of the AlN and ScN compounds very close to the ones of the available experiments and expensive calculations. According to the calculations of Becke-Johnson potential, the ScxAl1-xN alloys in the wurtzite and zinc-blende structures are direct band gap materials for the Sc concentrations in the ranges of (0.056 ≤ x ≤ 0.833) and (0.03125 ≤ x ≤ 0.0625, 0.375 ≤ x ≤ 0.96875), respectively. However, the ScAlN alloys in the rock-salt phase are determined to be direct band gap materials for total range of the Sc concentration considered in this work. While the energy gaps of the RS-AlScN alloys are found to be extending from near ultraviolet to near infrared with a large (negative) bowing, the ones of the WZ-AlScN and ZB-AlScN alloys are determined to be varying in a small energy range around near ultraviolet with a small (negative) bowing.

  5. Thick target neutron yields and spectra from the Li(d,xn) reaction at 35 MeV

    SciTech Connect

    Johnson, D.L.; Mann, F.M.; Watson, J.W.; Brady, F.P.; Ullmann, J.L.; Romero, J.L.; Castaneda, C.M.; Zanelli, C.I.; Wyckoff, W.G.

    1980-05-01

    Measurements were performed using a 35 MeV deuteron beam from the isochronous cyclotron at the University of California at Davis. Data were obtained using the time-of-flight technique with an NE213 liquid scintillator. One set of measurements was used to observe the neutron spectrum from approx. 1 MeV to approx. 50 MeV, the maximum kinematically allowed energy. Observation angles were from 0/sup 0/ to 150/sup 0/ with emphasis on forward angles. Spectral data below approx. 1.5 MeV had poor accuracy. It was felt that a significant fraction of the neutron yield might lie at still lower energies, therefore a second set of measurements was performed to investigate the spectra to as low an energy as possible. Additional measurements were performed with a target enriched in the isotope /sup 6/Li replacing the natural lithium target used in previous measurements. The main advantage of a /sup 6/Li target is that the maximum kinematically allowed neutron energy is only about 38 MeV, hence reducing shielding requirements. The experiments, preliminary results, and future needs will be described.

  6. Temperature-controlled epitaxy of In{sub x}Ga{sub 1-x}N alloys and their band gap bowing

    SciTech Connect

    Liu, S. T.; Wang, X. Q.; Chen, G.; Zhang, Y. W.; Feng, L.; Huang, C. C.; Xu, F. J.; Tang, N.; Shen, B.; Sang, L. W.; Sumiya, M.

    2011-12-01

    In{sub x}Ga{sub 1-x}N alloys (0 {<=} x {<=} 1) have been grown on GaN/sapphire templates by molecular beam epitaxy. Growth temperature controlled epitaxy was proposed to modulate the In composition so that each In{sub x}Ga{sub 1-x}N layer was grown at a temperature as high as possible and thus their crystalline quality was improved. The bandgap energies of the In{sub x}Ga{sub 1-x}N alloys have been precisely evaluated by optical transmission spectroscopy, where the effect of residual strain and electron concentration (the Burstein-Moss effect) on the bandgap energy shift has been considered. Finally, a bowing parameter of {approx}1.9 {+-} 0.1 eV has been obtained by the well fitting In-composition dependent bandgap energy.

  7. Alpha Blockers

    MedlinePlus

    ... conditions such as high blood pressure and benign prostatic hyperplasia. Find out more about this class of medication. ... these conditions: High blood pressure Enlarged prostate (benign prostatic hyperplasia) Though alpha blockers are commonly used to treat ...

  8. Alpha fetoprotein

    MedlinePlus

    ... Alpha fetoprotein - series References Cunningham FG, Leveno KJ, Bloom SL, et al. Prenatal diagnosis and fetal therapy. In: Cunningham FG, Leveno KJ, Bloom SL, et al, eds. Williams Obstetrics . 23rd ed. ...

  9. Alpha Thalassemia

    MedlinePlus

    ... an apparently normal individual has a child with hemoglobin H disease or alpha thalassemia minor. It can ... gene on one chromosome 25% 25% 25% 25% hemoglobin H disease there is a 25% chance with ...

  10. Influence of Alpha-Beams with Energy of 30 MeV on Wave Propagation in the Belousov-Zhabotinsky Reaction

    SciTech Connect

    Artamonov, D. N.; Priselkova, A. B.; Spassky, A. V.; Trukhanov, K. A.

    2007-11-26

    The generation of leading centers was observed in an oscillatory reaction of the Belousov-Zhabotinsky type under the action of collimated radiation with high linear energy transfer. Threshold values of the absorbed dose for the generation and complete quenching of autowaves were estimated. For modeling the effect of hard ionizing radiation on the Belousov-Zhabotinsky reaction, we proposed a modified radicalator model taking into account the interaction of reactants with {sup {center_dot}}OH radical, which is produced in the course of irradiation as a result of the radiolysis of water.

  11. Lattice damage and compositional changes in Xe ion irradiated InxGa1-xN (x = 0.32-1.0) single crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Limin; Jiang, Weilin; Dissanayake, Amila; Peng, Jinxin; Ai, Wensi; Zhang, Jiandong; Zhu, Zihua; Wang, Tieshan; Shutthanandan, Vaithiyalingam

    2016-06-01

    Lattice disorder and compositional changes in InxGa1-xN (x = 0.32, 0.47, 0.7, 0.8, and 1.0) films on GaN/Al2O3 substrates, induced by room-temperature irradiation of 5 MeV Xe ions, have been investigated using both Rutherford backscattering spectrometry under ion-channeling conditions and time-of-flight secondary ion mass spectrometry. The results show that for a fluence of 3 × 1013 cm-2, the relative level of lattice disorder in InxGa1-xN increases monotonically from 59% to 90% with increasing indium concentration x from 0.32 to 0.7; a further increase in x up to 1.0 leads to little increase in the disorder level. In contrast to Ga-rich InxGa1-xN (x = 0.32 and 0.47), significant volume swelling of up to ˜25% accompanied with oxidation in In-rich InxGa1-xN (x = 0.7, 0.8, and 1.0) is observed. In addition, irradiation-induced atomic mixing occurs at the interface of In-rich InxGa1-xN and GaN. The results from this study indicate an extreme susceptibility of the high In-content InxGa1-xN to heavy-ion irradiation, and suggest that cautions must be exercised in applying ion-implantation techniques to these materials at room temperature. Further studies of the irradiation behavior at elevated temperatures are warranted.

  12. Influence of the Al distribution on the structure, elastic properties, and phase stability of supersaturated Ti{sub 1-x}Al{sub x}N

    SciTech Connect

    Mayrhofer, P. H.; Music, D.; Schneider, J. M.

    2006-11-01

    Ti{sub 1-x}Al{sub x}N films and/or their alloys are employed in many industrial applications due to their excellent mechanical and thermal properties. Synthesized by plasma-assisted vapor deposition, Ti{sub 1-x}Al{sub x}N is reported to crystallize in the cubic NaCl (c) structure for AlN mole fractions below 0.4-0.91, whereas at larger Al contents the hexagonal ZnS-wurtzite (w) structure is observed. Here we use ab initio calculations to analyze the effect of composition and Al distribution on the metal sublattice on phase stability, structure, and elastic properties of c-Ti{sub 1-x}Al{sub x}N and w-Ti{sub 1-x}Al{sub x}N. We show that the phase stability of supersaturated c-Ti{sub 1-x}Al{sub x}N not only depends on the chemical composition but also on the Al distribution of the metal sublattice. An increase of the metastable solubility limit of AlN in c-Ti{sub 1-x}Al{sub x}N from 0.64 to 0.74 is obtained by decreasing the number of Ti-Al bonds. This can be understood by considering the Al distribution induced changes of the electronic structure, bond energy, and configurational entropy. This may in part explain the large variation of the metastable solubility limit reported in the literature.

  13. Lattice damage and compositional changes in Xe ion irradiated InxGa1-xN (x = 0.32-1.0) single crystals

    SciTech Connect

    Zhang, Limin; Jiang, Weilin; Dissanayake, Amila C.; Peng, Jinxin; Ai, Wensi; Zhang, Jiandong; Zhu, Zihua; Wang, Tieshan; Shutthanandan, V.

    2016-06-27

    Lattice disorder and compositional changes in InxGa1-xN (x=0.32, 0.47, 0.7, 0.8 and 1.0) films on GaN/Al2O3 substrates, induced by room-temperature irradiation of 5 MeV Xe ions, have been investigated using both Rutherford backscattering spectrometry under ion-channeling conditions and time-of-flight secondary ion mass spectrometry. The results show that for a fluence of 3E13 cm-2, the relative level of lattice disorder in InxGa1-xN increases monotonically from 59% to 90% with increasing indium concentration x from 0.32 to 0.7; a further increase in x up to 1.0 leads to little increase in the disorder level. In contrast to Ga-rich InxGa1-xN (x=0.32 and 0.47), significant volume swelling of up to ~25% accompanied with oxidation in In-rich InxGa1-xN (x=0.7, 0.8 and 1.0) is observed. In addition, irradiation-induced atomic mixing occurs at the interface of In-rich InxGa1-xN and GaN. The results from this study indicate an extreme susceptibility of the high In-content InxGa1-xN to heavy-ion irradiation, and suggest that cautions must be exercised in applying ion-implantation techniques to these materials at room temperature. Further studies of the irradiation behavior at elevated temperatures are warranted.

  14. Role of electronic excitations and nuclear collisions for color center creation in AlxGa1-xN semiconductors

    NASA Astrophysics Data System (ADS)

    Moisy, F.; Grygiel, C.; Ribet, A.; Sall, M.; Balanzat, E.; Monnet, I.

    2016-07-01

    In this work, AlxGa1-xN (x = 0; 0.1; 0.3; 0.5; 0.65; 0.7; 0.8; 1) wurtzite epilayers, grown on c-plane sapphire substrates, have been irradiated with Swift Heavy Ions at GANIL facility. Modifications induced by irradiation are characterized with in-situ optical absorption spectroscopy at 15 K. Spectra of these irradiated alloys exhibit optical absorption band formation, related to new energy levels in their bandgaps, whose positions only depend on the composition of the layer. However, these absorption bands are not observed in the AlxGa1-xN with Al molar fraction less than 0.3, likely because the energy level of the corresponding defect is located above the conduction band. Moreover, using different irradiation conditions, a coupled effect between nuclear collisions and electronic excitations for these color center creation have been investigated. A synergy between these two phenomena has been shown and appears to be independent of the composition of the alloy.

  15. Spectroscopic analysis of the NIR emission in Tm implanted AlxGa1-xN layers

    NASA Astrophysics Data System (ADS)

    Rodrigues, J.; Fialho, M.; Esteves, T. C.; Santos, N. F.; Ben Sedrine, N.; Rino, L.; Neves, A. J.; Lorenz, K.; Alves, E.; Monteiro, T.

    2016-08-01

    AlxGa1-xN samples, with different AlN molar fractions, x = 0, 0.15, 0.77, and 1, grown by halide vapor phase epitaxy were implanted with Tm ions. Photoluminescence (PL) measurements revealed that after thermal annealing all the samples exhibit intraionic Tm3+ luminescence. In samples with x > 0, the low temperature emission is dominated by the lines that appear in the near infrared (NIR) spectral region, corresponding to the overlapped 1G4 → 3H5 and 3H4 → 3H6 multiplet transitions. A detailed spectroscopic analysis of NIR emission of the thulium implanted and annealed AlxGa1-xN layers is presented by using temperature dependent steady-state PL, room temperature PL excitation, and time resolved PL. The results indicate that the excitonic features sensitive to the alloy disorder are involved in the excitation population processes of the Tm3+ luminescence and the highest thermal stability for the NIR emission occurs for the AlN:Tm sample.

  16. Higher reactivity of apolipoprotein B-100 and alpha-tocopherol compared to sialic acid moiety of low-density lipoprotein (LDL) in radical reaction.

    PubMed

    Matsukawa, Nao; Nariyama, Yoko; Hashimoto, Ryoko; Kojo, Shosuke

    2003-09-01

    Radical reaction of low-density lipoprotein (LDL) is a key step in atherogenesis and causes both a decrease in the sialic acid moiety and modification of apolipoprotein B-100 (apoB). Although apoB modification (cross-link and fragmentation) increases in atherosclerosis, the change in apoB-bound sialic acid in atherosclerosis is controversial. To elucidate the physiological implications of desialylation of LDL by radical reaction, the reactivity of sialic acid of LDL was compared with that of apoB, which underwent facile fragmentation in radical reactions. ApoB was determined by immunoblot analysis with anti-apoB antiserum, and the sialic acid moiety was measured by blot analysis with a biotin-bound lectin [biotin-SSA from Japanese elderberry (Sambucus sieboldiana)] specific to sialic acid. When human LDL was oxidized with Cu(2+) at 37 degrees C, apoB and apoB-attached sialic acid decreased simultaneously. Comparison of the staining bands with anti-apoB and with biotin-SSA shows that sialic acid moieties still remain on fragmented apoB proteins, indicating that the decrease in sialic acid is much slower than that of apoB fragmentation. In addition, human plasma was oxidized with 400 microM of Cu(2+) at 37 degrees C. Similar analysis indicates that the decrease in sialic acid attached to apoB also results from the fragmentation of apoB. This study indicates that the fragmentation of apoB proceeds at a much faster rate than the decrease in sialic acid content when a free radical reaction is induced in isolated LDL as well as in plasma LDL exposed to Cu(2+)-induced oxidative stress. On the basis of these results, the modification of apoB is much more sensitive than the decrease in sialic acid as an indicator of oxidative stress.

  17. Antioxidant-enzyme reaction to the oxidative stress due to alpha-cypermethrin, chlorpyriphos, and pirimicarb in tomato (Lycopersicon esculentum Mill.).

    PubMed

    Chahid, Karim; Laglaoui, Amin; Zantar, Said; Ennabili, Abdeslam

    2015-11-01

    Tomato (Lycopersicon esculentum Mill.) becomes one of the world's foremost vegetables, and its world production and consumption have increased fairly quickly. The capacity to induce oxidative stress in tomato plant, exposed to three xenobiotics such as alpha-cypermethrin, chlorpyriphos, and pirimicarb, was investigated by the evaluation of lipid peroxidation by measuring malondialdehyde (MDA) rate; also, we studied the response of tomato to this stress by assessing the response of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), glutathione-s-transferase (GST), and glutathione reductase (GR). The effect of the insecticides was observed using four concentrations (25, 50, 75, and 100%) for germinating seeds and only the recommended concentration in agriculture (100%) for growing plants. Our results show an important accumulation of MDA, demonstrating the increase of lipid peroxidation in consequence of the excessive reactive oxygen species (ROS) production due to insecticide treatment. In response to this oxidative stress in tomato seedlings and plants, the activities of antioxidant-enzyme system were generally enhanced. The electrophoretic analysis showed also the apparition of new isoenzymes as the case for CAT and POD.

  18. Synthesis of alpha-phosphorylated alpha,beta-unsaturated imines and their selective reduction to vinylogous and saturated alpha-aminophosphonates.

    PubMed

    Palacios, Francisco; Vicario, Javier; Maliszewska, Agnieszka; Aparicio, Domitila

    2007-03-30

    An efficient synthesis of alpha,beta-unsaturated imines derived from alpha-aminophosphonates is achieved through aza-Wittig reaction of P-trimethyl phosphazenes with beta,gamma-unsaturated alpha-ketophosphonates. Selective 1,2-reduction of such 1-azadienes affords beta,gamma-unsaturated alpha-aminophosphonates, phosphorylated analogs of vinylglycines, which are hydrogenated to yield saturated alpha-aminophosphonate derivatives.

  19. New approach to description of (d,xn) spectra at energies below 50 MeV in Monte Carlo simulation by intra-nuclear cascade code with Distorted Wave Born Approximation

    NASA Astrophysics Data System (ADS)

    Hashimoto, S.; Iwamoto, Y.; Sato, T.; Niita, K.; Boudard, A.; Cugnon, J.; David, J.-C.; Leray, S.; Mancusi, D.

    2014-08-01

    A new approach to describing neutron spectra of deuteron-induced reactions in the Monte Carlo simulation for particle transport has been developed by combining the Intra-Nuclear Cascade of Liège (INCL) and the Distorted Wave Born Approximation (DWBA) calculation. We incorporated this combined method into the Particle and Heavy Ion Transport code System (PHITS) and applied it to estimate (d,xn) spectra on natLi, 9Be, and natC targets at incident energies ranging from 10 to 40 MeV. Double differential cross sections obtained by INCL and DWBA successfully reproduced broad peaks and discrete peaks, respectively, at the same energies as those observed in experimental data. Furthermore, an excellent agreement was observed between experimental data and PHITS-derived results using the combined method in thick target neutron yields over a wide range of neutron emission angles in the reactions. We also applied the new method to estimate (d,xp) spectra in the reactions, and discussed the validity for the proton emission spectra.

  20. Chemical modification of hydroxynitrile lyase by selective reaction of an essential cysteine-SH group with alpha, beta-unsaturated propiophenones as pseudo-substrates.

    PubMed

    Jaenicke, L; Preun, J

    1984-01-16

    3-Oxo-3-phenylpropyne and 3-oxo-3-phenylpropene were synthesized as active-site-directed irreversible inhibitors of the bitter almond hydroxynitrile lyase (EC 4.1.2.10), an FAD-protein. The substrate and competitors (e.g. benzoate) decrease the rate of the inhibitor-mediated deactivation of the enzyme. By excess addition of either one of the two inhibitors, the deactivation process is shown to be pseudo-first order. The reaction with equimolar amounts of 3-oxo-3-phenylpropyne with the enzyme is accompanied by a shift in the ultraviolet spectrum of the inhibitor, allowing direct measurement of the enzyme-inactivation process. The spectral change has second-order kinetics. Incubation with 3-oxo-3-[p-3H]phenylpropyne or 3-oxo-3-[1-14C]phenylpropene shows a one-to-one stoichiometry for the inhibitory-enzyme reaction. Dissociation of the 3-oxo-3[p-3H]phenylpropyne-inactivated holoenzyme with acid ammonium sulfate yields a labeled apoenzyme; the inhibitor does not react with free or enzyme-bound FAD. After boranate reduction and exhaustive hydrolysis of the 3-oxo-3-[1-14C]phenylpropene-inactivated enzyme, a labeled cysteine derivative was isolated which was identified by chromatographic and mass spectroscopic comparison with synthetic references as L-2-amino-4-thia-DL-7-hydroxy-7-phenylhepatanoic acid, the reduced, linear addition product of the inhibitor to a cysteine-SH group.

  1. Experimental Cross Sections for Reactions of Heavy Ions and 208Pb, 209Bi, 238U, and 248Cm Targets

    SciTech Connect

    Patin, Joshua Barnes

    2002-01-01

    The study of the reactions between heavy ions and 208Pb, 209Bi, 238U, and 248Cm Cm targets was performed to look at the differences between the cross sections of hot and cold fusion reactions. Experimental cross sections were compared with predictions from statistical computer codes to evaluate the effectiveness of the computer code in predicting production cross sections. Hot fusion reactions were studied with the MG system, catcher foil techniques and the Berkeley Gas-filled Separator (BGS). 3n- and 4n-exit channel production cross sections were obtained for the 238U(18O,xn)256-xFm, 238U(22Ne,xn)260-xNo, and 248Cm(15N,xn)263-xLr reactions and are similar to previous experimental results. The experimental cross sections were accurately modeled by the predictions of the HIVAP code using the Reisdorf and Schaedel parameters and are consistent with the existing systematics of 4n exit channel reaction products. Cold fusion reactions were examined using the BGS. The 48Pb(238Ca,xn)256-xNo, 208Pb(50Ti,xn)258-xRf, 208Pb(51V,xn)259-xDb, 50Bi(238Ti,xn)259-xDb, and 209Bi(51V,xn)260-xSg reactions were studied. The experimental production cross sections are in agreement with the results observed in previous experiments. It was necessary to slightly alter the Reisdorf and Schaedel parameters for use in the HIVAP code in order to more accurately model the experimental data. The cold fusion experimental results are in agreement with current 1n- and 2n-exit channel systematics.

  2. Mechanical properties of AlxGa1-xN films with high Al composition grown on AlN/sapphire templates

    NASA Astrophysics Data System (ADS)

    Xu, F. J.; Shen, B.; Wang, M. J.; Xu, J.; Lu, L.; Miao, Z. L.; Yang, Z. J.; Qin, Z. X.; Zhang, G. Y.; Lin, B.; Bai, S. L.

    2007-08-01

    Mechanical properties of AlxGa1-xN thin films with high Al composition (0.33⩽x⩽1) grown on AlN/sapphire templates have been investigated by means of the nanoindentation technique. It is found that Young's modulus E of the films increases with increasing Al composition. In addition, it is also found that the occurrence of the clear and sudden displacement discontinuity ("pop-in") in the plastic deformation (PD) process is dependent on Al composition in AlxGa1-xN films. The higher Al composition results in less occurrence of the pop-in in the PD process of the films. With increasing Al composition, it is believed that the increase of the bond strength and the decrease of the lattice mismatch between AlxGa1-xN films and AlN/sapphire templates result in greater resistance to the formation of dislocations, which is responsible for the pop-in behavior in AlxGa1-xN films.

  3. Analogs of the giant dipole and spin-dipole resonances in {sup 4}He and in {alpha} clusters of {sup 6,7}Li studied by the {sup 4}He,{sup 6,7}Li({sup 7}Li,{sup 7}Be{gamma}) reactions

    SciTech Connect

    Nakayama, S.; Matsumoto, E.; Fushimi, K.; Hayami, R.; Kawasuso, H.; Yasuda, K.; Yamagata, T.; Akimune, H.; Ikemizu, H.; Asaji, S.; Ishida, T.; Kudoh, T.; Sagara, K.; Fujiwara, M.; Hashimoto, H.; Kawase, K.; Nakanishi, K.; Oota, T.; Yosoi, M.; Greenfield, M. B.

    2008-07-15

    We studied analogs of the giant dipole resonance (GDR) and spin-dipole resonance (SDR) in {sup 4}He and in the {alpha} clusters of {sup 6,7}Li via the ({sup 7}Li,{sup 7}Be{gamma}) reactions on {sup 4}He, {sup 6}Li, and {sup 7}Li at an incident energy of 455 MeV and at a scattering angle of 0 deg. by measuring spin-nonflip and spin-flip spectra. The reaction Q-values for the analogs of the GDR and SDR in the {alpha} clusters of {sup 6,7}Li were found to be more negative than those in {sup 4}He by 2.0{+-}0.5 MeV. The ratios of the cross section for the analog of the GDR to that for the analog of the SDR in {sup 4}He and in the {alpha} clusters of {sup 6}Li and {sup 7}Li were found to be the same within errors, 0.5{+-}0.1. The cross sections for the analogs of the GDR as well as those for the analogs of the SDR in the {alpha} clusters of {sup 6,7}Li were 0.6{approx}0.8 times smaller than those in {sup 4}He. These results suggest that excitations of {alpha} clusters embedded in nuclei are suppressed as compared with excitations of free {alpha} particles.

  4. Growth of free-standing bulk wurtzite AlxGa1-xN layers by molecular beam epitaxy using a highly efficient RF plasma source

    NASA Astrophysics Data System (ADS)

    Novikov, S. V.; Staddon, C. R.; Sahonta, S.-L.; Oliver, R. A.; Humphreys, C. J.; Foxon, C. T.

    2016-12-01

    The recent development of group III nitrides allows researchers world-wide to consider AlGaN based light emitting diodes as a possible new alternative deep ultra-violet light source for surface decontamination and water purification. In this paper we will describe our recent results on plasma-assisted molecular beam epitaxy (PA-MBE) growth of free-standing wurtzite AlxGa1-xN bulk crystals using the latest model of Riber's highly efficient nitrogen RF plasma source. We have achieved AlGaN growth rates up to 3 μm/h. Wurtzite AlxGa1-xN layers with thicknesses up to 100 μm were successfully grown by PA-MBE on 2-inch and 3-inch GaAs (111)B substrates. After growth the GaAs was subsequently removed using a chemical etch to achieve free-standing AlxGa1-xN wafers. Free-standing bulk AlxGa1-xN wafers with thicknesses in the range 30-100 μm may be used as substrates for further growth of AlxGa1-xN-based structures and devices. High Resolution Scanning Transmission Electron Microscopy (HR-STEM) and Convergent Beam Electron Diffraction (CBED) were employed for detailed structural analysis of AlGaN/GaAs (111)B interface and allowed us to determine the N-polarity of AlGaN layers grown on GaAs (111)B substrates. The novel, high efficiency RF plasma source allowed us to achieve free-standing AlxGa1-xN layers in a single day's growth, making this a commercially viable process.

  5. Enzymatic synthesis of a selective inhibitor for alpha-glucosidases: alpha-acarviosinyl-(1-->9)-3-alpha-D-glucopyranosylpropen.

    PubMed

    Lee, Young-Su; Lee, Myoung-Hee; Lee, Hee-Seob; Lee, Seung-Jae; Kim, Young-Wan; Zhang, Ran; Withers, Stephen G; Kim, Kwan Soo; Lee, Sung-Joon; Park, Kwan-Hwa

    2008-07-09

    Here, we describe the enzymatic synthesis of novel inhibitors using acarviosine-glucose as a donor and 3-alpha-D-glucopyranosylpropen (alphaGP) as an acceptor. Maltogenic amylase from Thermus sp. (ThMA) catalyzed the transglycosylation of the acarviosine moiety to alphaGP. The two major reaction products were isolated using chromatographies. Structural analyses revealed that acarviosine was transferred to either C-7 or C-9 of the alphaGP, which correspond to C-4 and C-6 of glucose. Both inhibited rat intestine alpha-glucosidase competitively but displayed a mixed-type inhibition mode against human pancreatic alpha-amylase. The alpha-acarviosinyl-(1-->7)-3-alpha-D-glucopyranosylpropen showed weaker inhibition potency than acarbose against both alpha-glycosidases. In contrast, the alpha-acarviosinyl-(1-->9)-3-alpha-D-glucopyranosylpropen exhibited a 3.0-fold improved inhibition potency against rat intestine alpha-glucosidase with 0.3-fold inhibition potency against human pancreatic alpha-amylase relative to acarbose. In conclusion, alpha-acarviosinyl-(1-->9)-3-alpha-D-glucopyranosylpropen is a novel alpha-glucosidase-selective inhibitor with 10-fold enhanced selectivity toward alpha-glucosidase over alpha-amylase relative to acarbose, and it could be applied as a potent hypoglycemic agent.

  6. Luminescence and superradiance in electron-beam-excited Al{sub x}Ga{1-sub x}N

    SciTech Connect

    Bokhan, P. A.; Gugin, P. P.; Zakrevsky, Dm. E.; Malin, T. V.; Zhuravlev, K. S.; Osinnykh, I. V.; Solomonov, V. I.; Spirina, A. V.

    2014-09-21

    Luminescence and superradiance characteristics of 0.5–1.2-μm thick Al{sub x}Ga{sub 1-x}N films grown by molecular-beam epitaxy on sapphire substrates were studied under excitation of the films with low-energy (<20 keV) and high-energy (170 keV) electron beams. In both cases, the luminescence spectra looked quite similarly; they exhibited a band-edge luminescence with x-dependent wavelength ranging from 365 nm to 310 nm and a broadband emission taking over the whole visible spectral region. Superradiance within the broad band was obtained by pumping the samples with powerful an electron beam in the form of an open-discharge-generated filament.

  7. Half metallic ferromagnetism in alkaline-earth metal nitrides XN (X=Ca, Sr and Ba): A first principles study

    NASA Astrophysics Data System (ADS)

    Palanichamy, R. Rajeswara; Priyanga, G. Sudha; Cinthia, A. Jemmy; Murugan, A.; Meenaatci, A. T. Asvini; Iyakutti, K.

    2013-11-01

    The structural, electronic, mechanical and magnetic properties of 3 alkaline-earth metal nitrides (XN: X=Ca, Sr, and Ba) are investigated by the first principles calculations based on density functional theory using the Vienna ab-initio simulation code. At ambient pressure all the 3 nitrides are stable in the ferromagnetic state with a cubic NaCl structure. The calculated lattice parameters are in good agreement with the available results. The electronic structure reveals that these materials are half metallic ferromagnets at normal pressure. A pressure-induced structural phase transition from NaCl (B1) to CsCl (B2) phase is observed in CaN, SrN and BaN. On further increasing the pressure, a half metallic to metallic transition is also observed in these nitrides. Ferromagnetism is quenched in all the 3 nitrides at high pressures.

  8. Phase diagram, chemical bonds, and gap bowing of cubic InxAl1-xN alloys: Ab initio calculations

    NASA Astrophysics Data System (ADS)

    Teles, L. K.; Scolfaro, L. M. R.; Leite, J. R.; Furthmüller, J.; Bechstedt, F.

    2002-12-01

    Thermodynamic, structural, and electronic properties of cubic InxAl1-xN alloys are studied by combining first-principles total energy calculations and the generalized quasichemical approach. Results for bond-lengths, second-nearest-neighbors distances, and bond angles in the alloy are presented. The calculated phase diagram of the alloy shows a broad and asymmetric miscibility gap. The gap fluctuations in the alloy allow for the definition of a minimum gap and an average gap with different bowing parameters, that can provide an explanation for the discrepancies found in the experimental values for the bowing parameter. It is also found that lattice matched In0.2Al0.8N with GaN is suitable to form a barrier material for electronic and optoelectronic nitride based devices.

  9. Barrier height of Pt-InxGa1-xN (0<=x<=0.5) nanowire Schottky diodes

    NASA Astrophysics Data System (ADS)

    Guo, Wei; Banerjee, Animesh; Zhang, Meng; Bhattacharya, Pallab

    2011-05-01

    The barrier height of Schottky diodes made on InxGa1-xN nanowires have been determined from capacitance-voltage measurements. The nanowires were grown undoped on n-type (001) silicon substrates by plasma-assisted molecular beam epitaxy. The length, diameter and density of the nanowires are ˜1 μm, 20 nm, and 1×1011 cm-2. The Schottky contact was made on the top surface of the nanowires with Pt after planarizing with parylene. The measured barrier height ΦB varies from 1.4 eV (GaN) to 0.44 eV (In0.5Ga0.5N) and agrees well with the ideal barrier heights in the Schottky limit.

  10. Involvement of metals in enzymatic and nonenzymatic decomposition of C-terminal alpha-hydroxyglycine to amide: an implication for the catalytic role of enzyme-bound zinc in the peptidylamidoglycolate lyase reaction.

    PubMed

    Takahashi, Kenichi; Harada, Saori; Higashimoto, Yuichiro; Shimokawa, Chizu; Sato, Hideaki; Sugishima, Masakazu; Kaida, Yasuhiko; Noguchi, Masato

    2009-02-24

    The peptide C-terminal amide group essential for the full biological activity of many peptide hormones is produced by consecutive actions of peptidylglycine alpha-hydroxylating monooxygenase (PHM) and peptidylamidoglycolate lyase (PAL); PHM catalyzes the hydroxylation of C-terminal glycine, and PAL decomposes the peptidyl-alpha-hydroxyglycine to an amidated peptide and glyoxylate. PAL contains 1 mol of zinc, but its role, catalytic or structural, has not yet been clarified. In this study, we found that a series of transition metals, Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), and Cd(2+), catalyze the nonenzymatic decomposition of the hydroxyglycine intermediate in a concentration-dependent manner. The second-order rate constant of the metal catalysis increased with elevation of pH, indicating that the hydrated metal acts as a general base. Extensive removal of the enzyme-bound metals remarkably diminished the PAL activity; k(cat) of the metal-depleted enzyme retaining 0.1 mol of zinc decreased to 3.2 s(-1) from 25.7 s(-1) of the wild-type enzyme. Among a series of divalent metals tested, Zn(2+), Co(2+), and Cd(2+) could fully restore the PAL activity of the metal-depleted enzyme. Especially, Zn substitution reproduced the steady-state parameters of the wild-type enzyme. On the other hand, Co and Cd substitution largely altered the kinetic parameters; the k(cat) increased 3- and 5-fold and the K(m) for the substrate increased 2.5- and 4-fold, respectively. These observations support that the enzyme-bound zinc plays a catalytic role, rather than a structural role, in the PAL reaction through the action of zinc-bound water as a general base.

  11. Possibilities of synthesis of unknown isotopes of superheavy nuclei with charge numbers Z > 108 in asymmetric actinide-based complete fusion reactions

    NASA Astrophysics Data System (ADS)

    Hong, Juhee; Adamian, G. G.; Antonenko, N. V.

    2016-10-01

    The possibilities of production of new isotopes of superheavy nuclei with charge numbers Z = 109-114 in various asymmetric hot fusion reactions are studied for the first time. The excitation functions of the formation of these isotopes in the xn evaporation channels are predicted and the optimal conditions for the synthesis are proposed. The products of the suggested reactions can fill a gap of unknown isotopes between the isotopes of the heaviest nuclei obtained in cold and hot complete fusion reactions.

  12. Nuclear diagnostic for fast alpha particles

    DOEpatents

    Grisham, L.R.; Post, D.E. Jr.; Dawson, J.M.

    1983-11-23

    This invention relates generally to high energy confined plasmas and more particularly is directed to measuring the velocity distribution of confined energetic alpha particles resulting from deuterium-tritium fusion reactions in a confined energetic plasma.

  13. Cloning and targeted mutations of G alpha 7 and G alpha 8, two developmentally regulated G protein alpha-subunit genes in Dictyostelium.

    PubMed Central

    Wu, L; Gaskins, C; Zhou, K; Firtel, R A; Devreotes, P N

    1994-01-01

    GTP-binding protein (G protein)-mediated signal transduction pathways play essential roles during the aggregation and differentiation process of Dictyostelium. In addition to the five known G protein alpha-subunit genes, we recently identified three novel alpha-subunit genes, G alpha 6, G alpha 7, and G alpha 8, using the polymerase chain reaction technique. We present here a more complete analysis of G alpha 7 and G alpha 8. The cDNAs of these two genes were cloned, and their complete nucleotide sequences were determined. Sequence analyses indicate that G alpha 8 possesses some unusual features. It lacks the "TCATDT" motif, a sequence of amino acids highly conserved among G alpha subunits, and has an additional 50 amino acids at its C-terminus consisting of long stretches of asparagine. Moreover, G alpha 8 is unusually resistant to protease digestion, which may indicate a slow GTP hydrolysis rate. The possible functions of these alpha-subunits were assessed by generating mutants lacking G alpha 7 or G alpha 8 by gene targeting through homologous recombination and by overexpressing G alpha 7 or G alpha 8 protein. Overexpression of G alpha 7 resulted in abnormal morphogenesis starting at the slug stage, whereas analysis of the other strains failed to reveal any obvious growth or developmental defects under either normal or stressful conditions. The implications of these results are discussed. Images PMID:7949425

  14. Unified studies of structure and reactions in light unstable nuclei

    NASA Astrophysics Data System (ADS)

    Ito, Makoto

    2016-06-01

    The generalized two-center cluster model (GTCM), which can treat covalent, ionic and atomic configurations in general systems with two inert cores plus valence nucleons, is formulated in the basis of the microscopic cluster model. In this model, the covalent configurations constructed by the molecular orbital (MO) method and the atomic (or ionic) configuration obtained by the valence bonding (VB) method can be described in a consistent manner. GTCM is applied to the light neutron-rich system, 10,12Be = α + α + XN (X = 2,4), and the unified studies of the structural changes and the reaction problem are performed. In the structure study, the calculated energy levels are characterized in terms of the chemical bonding like structures, such as the covalent MO or ionic VB structures. The chemical bonding structures changes from level to level within a small energy interval. In the unbound region, the structure problem with the total system of α + α + XN and the reaction problem, induced by the collision of an asymptotic VB state of α+6,8He, are combined by GTCM. The properties of unbound resonant states are discussed in a close connection to the reaction mechanism, and some enhancement factors originated from the properties of the intrinsic states are predicted in the reaction observables. The unified calculation of the structures and the reactions is applied to the Coulomb shift problem in the mirror system, such the 10Be and 10C nuclei. The Coulomb displacement energy of the mirror systems are discussed.

  15. Near-zero temperature coefficient of resistivity associated with magnetic ordering in antiperovskite Mn3+xNi1-xN

    NASA Astrophysics Data System (ADS)

    Deng, Sihao; Sun, Ying; Wang, Lei; Wu, Hui; Shi, Kewen; Hu, Pengwei; Huang, Qingzhen; Wang, Cong

    2016-01-01

    The near-zero temperature coefficient of resistivity (NZ-TCR) behavior is reported in the antiperovskite compounds Mn3+xNi1-xN (0 ≤ x ≤ 0.333). Our results indicate that the broad temperature range (above 275 K extending to above 220 K) of NZ-TCR is obtained by Mn doping at the Ni site. The short-range magnetic ordering is revealed by both neutron powder diffraction and inverse magnetic susceptibility. Further, we find a strong correlation between the anomalous resistivity change of Mn3+xNi1-xN from the metal-like to the NZ-TCR behavior and the lack of the long-range magnetic ordering. The possible mechanism of NZ-TCR behavior is discussed using the spin-disorder scattering model.

  16. Growth and oxidization stability of cubic Zr{sub 1−x}Gd{sub x}N solid solution thin films

    SciTech Connect

    Höglund, C.; Alling, B.; Jensen, J.; Hultman, L.; Birch, J.; Hall-Wilton, R.

    2015-05-21

    We report Zr{sub 1−x}Gd{sub x}N thin films deposited by magnetron sputter deposition. We show a solid solubility of the highly neutron absorbing GdN into ZrN along the whole compositional range, which is in excellent agreement with our recent predictions by first-principles calculations. An oxidization study in air shows that Zr{sub 1−x}Gd{sub x}N with x reaching from 1 to close to 0 fully oxidizes, but that the oxidization is slowed down by an increased amount of ZrN or stopped by applying a capping layer of ZrN. The crystalline quality of Zr{sub 0.5}Gd{sub 0.5}N films increases with substrate temperatures increasing from 100 °C to 900 °C.

  17. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Growth and Characteristics of Epitaxial AlxGa1-xN by MOCVD

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Guo, Li-Wei; Chen, Yao; Xu, Pei-Qiang; Ding, Guo-Jian; Peng, Ming-Zeng; Jia, Hai-Qiang; Zhou, Jun-Ming; Chen, Hong

    2009-06-01

    AlxGa1-xN epilayers with a wide Al composition range (0.2 <= x <= 0.68) were grown on AlN/sapphire templates by low-pressure metalorganic chemical vapour deposition (LP-MOCVD). X-ray diffraction results reveal that both the (0002) and (10bar 15) full widths at half-maximum (FWHM) of the AlxGa1-xN epilayer decrease with increasing Al composition due to the smaller lattice mismatch to the AlN template. However, the surface morphology becomes rougher with increasing Al composition due to the weak migration ability of Al atoms. Low temperature photoluminescence (PL) spectra show pronounced near band edge (NBE) emission and the NBE FWHM becomes broader with increasing Al composition mainly caused by alloy disorder. Meanwhile, possible causes of the low energy peaks in the PL spectra are discussed.

  18. Efficient synthesis of 1-azadienes derived from alpha-aminoesters. Regioselective preparation of alpha-dehydroamino acids, vinylglycines, and alpha-amino acids.

    PubMed

    Palacios, Francisco; Vicario, Javier; Aparicio, Domitila

    2006-09-29

    An efficient synthesis of 1-azadienes derived from alpha-aminoesters is achieved through an aza-Wittig reaction of phosphazenes with beta,gamma-unsaturated alpha-ketoesters. Regioselective 1,2-reduction of these functionalized 1-azadienes affords vinylglycine derivatives, while conjugative 1,4-reduction gives alpha-dehydroamino acid compounds. Reduction of both the carbon-carbon and the imine-carbon-nitrogen double bonds leads to the formation of alpha-amino acid derivatives.

  19. Bandgap measurements and the peculiar splitting of E2H phonon modes of InxAl1-xN nanowires grown by plasma assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Tangi, Malleswararao; Mishra, Pawan; Janjua, Bilal; Ng, Tien Khee; Anjum, Dalaver H.; Prabaswara, Aditya; Yang, Yang; Albadri, Abdulrahman M.; Alyamani, Ahmed Y.; El-Desouki, Munir M.; Ooi, Boon S.

    2016-07-01

    The dislocation free InxAl1-xN nanowires (NWs) are grown on Si(111) by nitrogen plasma assisted molecular beam epitaxy in the temperature regime of 490 °C-610 °C yielding In composition ranges over 0.50 ≤ x ≤ 0.17. We study the optical properties of these NWs by spectroscopic ellipsometry (SE), photoluminescence, and Raman spectroscopies since they possesses minimal strain with reduced defects comparative to the planar films. The optical bandgap measurements of InxAl1-xN NWs are demonstrated by SE where the absorption edges of the NW samples are evaluated irrespective of substrate transparency. A systematic Stoke shift of 0.04-0.27 eV with increasing x was observed when comparing the micro-photoluminescence spectra with the Tauc plot derived from SE. The micro-Raman spectra in the NWs with x = 0.5 showed two-mode behavior for A1(LO) phonons and single mode behavior for E2H phonons. As for x = 0.17, i.e., high Al content, we observed a peculiar E2H phonon mode splitting. Further, we observe composition dependent frequency shifts. The 77 to 600 K micro-Raman spectroscopy measurements show that both AlN- and InN-like modes of A1(LO) and E2H phonons in InxAl1-xN NWs are redshifted with increasing temperature, similar to that of the binary III group nitride semiconductors. These studies of the optical properties of the technologically important InxAl1-xN nanowires will path the way towards lasers and light-emitting diodes in the wavelength of the ultra-violet and visible range.

  20. Negative anisotropic magnetoresistance resulting from minority spin transport in NixFe4-xN (x = 1 and 3) epitaxial films

    NASA Astrophysics Data System (ADS)

    Takata, Fumiya; Kabara, Kazuki; Ito, Keita; Tsunoda, Masakiyo; Suemasu, Takashi

    2017-01-01

    We grew 50 nm-thick NixFe4-xN (x = 1 and 3) epitaxial films on a SrTiO3(001) single-crystal substrate by molecular beam epitaxy and measured their anisotropic magnetoresistance (AMR) ratios rAMR in the temperature range of 5-300 K with current directions set along either NixFe4-xN [100] or [110]. A negative rAMR was obtained up to 200 K or higher. Their magnitude | rAMR | increased with decreasing temperature. From the negative AMR effect and the negative spin-polarization of density of states for NixFe4-xN at the Fermi level, it can be stated that the minority spin transport is dominant in NixFe4-xN, similar to Fe4N and Co3FeN. The rAMR depends on the current direction that arises from the current direction dependence of s-d scattering. In the case of Ni3FeN, the rAMR decreased to nearly zero at 260 K. This temperature agreed well with the Curie temperature determined from the temperature dependence of magnetization. The AMR curves were reproduced well by using both cos2ϕ and cos4ϕ components below 100 K, whereas a cos2ϕ component was enough to fit those obtained above 100 K. It is assumed that the tetragonal crystal field was enhanced at low temperatures (<100 K) similar to Fe4N (<50 K).

  1. Complete Genome Sequence of Staphylococcus aureus XN108, an ST239-MRSA-SCCmec III Strain with Intermediate Vancomycin Resistance Isolated in Mainland China

    PubMed Central

    Zhang, Xia; Xu, Xiaomeng; Yuan, Wenchang; Hu, Qiwen; Shang, Weilong; Hu, Xiaomei

    2014-01-01

    ST239-MRSA-SCCmec III (ST239, sequence type 239; MRSA, methicillin-resistant Staphylococcus aureus; SCCmec III, staphylococcal cassette chromosome mec type III) is the most predominant clone of hospital-acquired methicillin-resistant S. aureus in mainland China. We report here the complete genome sequence of XN108, the first vancomycin-intermediate S. aureus strain isolated from a steam-burned patient with a wound infection. PMID:25059856

  2. M5-brane defect and quantum Hall effect in AdS{sub 4}xN(1,1)/N=3 superconformal field theory

    SciTech Connect

    Fujita, Mitsutoshi

    2011-05-15

    We study the d=11 gravity dual AdS{sub 4}xN(1,1) of the d=3 N=3 flavored Chern-Simons-matter theory. In the dual gravity side, we analyze the M5-brane filling AdS{sub 3} inside AdS{sub 4} and derive the quantized Hall conductivity of the dual gauge theory. In the gauge theory side, this M5-brane intersects the gauge theory at the codimension-one defect.

  3. Establishment of Age- and Gender-Specific Reference Ranges for 36 Routine and 57 Cell Population Data Items in a New Automated Blood Cell Analyzer, Sysmex XN-2000

    PubMed Central

    Park, Sang Hyuk; Lee, Bo-Ra; Kim, Mi-Jeong; Han, Min-Young; Cho, Young-Uk; Jang, Seongsoo

    2016-01-01

    We established age- and gender-specific reference ranges for the 36 routine complete blood cell (CBC) and 57 cell population data (CPD) items in the Sysmex XN-2000 (Sysmex, Japan). In total, 280 peripheral blood samples were obtained from an equal number of healthy adults. Values for 36 routine items and 57 CPD items were obtained for each sample, and the results were categorized into six subgroups (N>39 in each subgroup) according to patient age (20-40, 41-60, and >60 yr) and gender (male and female), and compared with respect to age and gender differences. The majority of data items (22 of 36 routine CBC items and 44 of 57 CPD items) exhibited significant differences (P≤0.05) in their results with respect to age or gender, and several red cell-, lymphocyte-, and platelet-related data tended to decrease in women or older adults. These results provide a basis for establishing age- and gender-specific reference ranges for routine and CPD items in Sysmex XN-2000. Furthermore, these reference ranges could be used to determine clinical significance for new items of Sysmex XN-2000 in further studies. PMID:26915613

  4. Point defects introduced by InN alloying into InxGa1-xN probed using a monoenergetic positron beam

    NASA Astrophysics Data System (ADS)

    Uedono, A.; Tsutsui, T.; Watanabe, T.; Kimura, S.; Zhang, Y.; Lozac'h, M.; Sang, L. W.; Ishibashi, S.; Sumiya, M.

    2013-03-01

    Native defects in InxGa1-xN (x = 0.06-0.14) grown by metal organic chemical vapor deposition were studied using a monoenergetic positron beam. Measurements of Doppler broadening spectra of the annihilation radiation as a function of incident positron energy for InxGa1-xN showed that vacancy-type defects were introduced with increasing InN composition, and the major defect species was identified as complexes between a cation vacancy and a nitrogen vacancy. The concentration of the divacancy, however, was found to be suppressed by Mg doping. The momentum distribution of electrons at the InxGa1-xN/GaN interface was close to that in defect-free GaN or InxGa1-xN, which was attributed to localization of positrons at the interface due to the built-in electric field, and to suppression of positron trapping by vacancy-type defects. We have also shown that the diffusion property of positrons is sensitive to an electric field near the InxGa1-xN/GaN interface.

  5. Stress controlled pulsed direct current co-sputtered Al{sub 1−x}Sc{sub x}N as piezoelectric phase for micromechanical sensor applications

    SciTech Connect

    Fichtner, Simon; Reimer, Tim; Chemnitz, Steffen; Wagner, Bernhard; Lofink, Fabian

    2015-11-01

    Scandium alloyed aluminum nitride (Al{sub 1−x}Sc{sub x}N) thin films were fabricated by reactive pulsed direct current co-sputtering of separate scandium and aluminum targets with x ≤ 0.37. A significant improvement of the clamped transversal piezoelectric response to strain e{sub 31,f} from −1.28 C/m{sup 2} to −3.01 C/m{sup 2} was recorded, while dielectric constant and loss angle remain low. Further, the built-in stress level of Al{sub 1−x}Sc{sub x}N was found to be tuneable by varying pressure, Ar/N{sub 2} ratio, and Sc content. The thus resulting enhancement of the expectable signal to noise ratio by a factor of 2.1 and the ability to control built-in stress make the integration of Al{sub 1−x}Sc{sub x}N as the piezoelectric phase of micro-electro-mechanical system sensor applications highly attractive.

  6. Establishment of Age- and Gender-Specific Reference Ranges for 36 Routine and 57 Cell Population Data Items in a New Automated Blood Cell Analyzer, Sysmex XN-2000.

    PubMed

    Park, Sang Hyuk; Park, Chan Jeoung; Lee, Bo Ra; Kim, Mi Jeong; Han, Min Young; Cho, Young Uk; Jang, Seongsoo

    2016-05-01

    We established age- and gender-specific reference ranges for the 36 routine complete blood cell (CBC) and 57 cell population data (CPD) items in the Sysmex XN-2000 (Sysmex, Japan). In total, 280 peripheral blood samples were obtained from an equal number of healthy adults. Values for 36 routine items and 57 CPD items were obtained for each sample, and the results were categorized into six subgroups (N>39 in each subgroup) according to patient age (20-40, 41-60, and >60 yr) and gender (male and female), and compared with respect to age and gender differences. The majority of data items (22 of 36 routine CBC items and 44 of 57 CPD items) exhibited significant differences (P≤0.05) in their results with respect to age or gender, and several red cell-, lymphocyte-, and platelet-related data tended to decrease in women or older adults. These results provide a basis for establishing age- and gender-specific reference ranges for routine and CPD items in Sysmex XN-2000. Furthermore, these reference ranges could be used to determine clinical significance for new items of Sysmex XN-2000 in further studies.

  7. Point defects introduced by InN alloying into In{sub x}Ga{sub 1-x}N probed using a monoenergetic positron beam

    SciTech Connect

    Uedono, A.; Tsutsui, T.; Watanabe, T.; Kimura, S.; Zhang, Y.; Lozac'h, M.; Sang, L. W.; Sumiya, M.; Ishibashi, S.

    2013-03-28

    Native defects in In{sub x}Ga{sub 1-x}N (x = 0.06-0.14) grown by metal organic chemical vapor deposition were studied using a monoenergetic positron beam. Measurements of Doppler broadening spectra of the annihilation radiation as a function of incident positron energy for In{sub x}Ga{sub 1-x}N showed that vacancy-type defects were introduced with increasing InN composition, and the major defect species was identified as complexes between a cation vacancy and a nitrogen vacancy. The concentration of the divacancy, however, was found to be suppressed by Mg doping. The momentum distribution of electrons at the In{sub x}Ga{sub 1-x}N/GaN interface was close to that in defect-free GaN or In{sub x}Ga{sub 1-x}N, which was attributed to localization of positrons at the interface due to the built-in electric field, and to suppression of positron trapping by vacancy-type defects. We have also shown that the diffusion property of positrons is sensitive to an electric field near the In{sub x}Ga{sub 1-x}N/GaN interface.

  8. [Interferon alpha-2b modified with polyethylene glycol].

    PubMed

    Wu, Yingxin; Zhai, Yanqin; Lei, Jiandu; Ma, Guanghui; Su, Zhiguo

    2008-09-01

    In order to obtain a more stable PEGylated interferon alpha-2b, and prolong its half life, interferon alpha-2b (IFN alpha-2b) was modified with monomethoxy polyethylene glycol propionaldehyde (mPEG-ALD) 20000. It was found that the optimized reaction condition for the maximum bioactivity and highest PEGylation degree of the mono PEGylated interferon alpha-2b was as follows: in 20 mmol/L, pH 6.5, citric acid and sodium dihydrogen phosphate buffer, the concentration of IFN alpha-2b was 4 mg/mL, and the molar ratio of PEG/IFN alpha-2b was 8:1, and the reaction time was 20 h at 4 degrees C. Under the optimized reaction condition, the mono PEGylation degree reached to 55%. Ion exchange chromatography was used to separate and purify mono PEGylated interferon alpha-2b from the reaction mixture. The purity of mono PEGylated interferon alpha-2b was higher than 97% characterized by HPLC. The bioactivity of the mono PEGylated interferon alpha-2b was 13.4% of the native IFN alpha-2b, while its half life in SD rat is much longer than the native IFN alpha-2b. The mono PEGylated interferon alpha-2b is also stable in aqueous.

  9. Electrical characteristics of AlxGa1-xN Schottky diodes prepared by a two-step surface treatment

    NASA Astrophysics Data System (ADS)

    Motayed, Abhishek; Sharma, Ashok; Jones, Kenneth A.; Derenge, Michael A.; Iliadis, Agis A.; Mohammad, S. Noor

    2004-09-01

    Near-ideal Schottky barrier contacts to n-type Al0.22Ga0.78N have been developed by a two-step surface treatment technique. Plasma etching of the AlxGa1-xN surface prior to Schottky metal deposition, combined with sequential chemical treatment of the etched surface, holds promise for developing high quality low-leakage Schottky contacts for low noise applications and for recessed gate high electron mobility transistors. In this work, the effect of postetch chemical treatment of the n-type Al0.22Ga0.78N surface on the performance of the Ni /Au based Schottky contact has been investigated. Three different types of chemical treatment: viz, reactive ion etching, reactive ion etching plus dipping in hot aqua regia, and reactive ion etching plus dipping in hot KOH, are studied. Detailed current-voltage studies of three different surface treated diodes and a comparison with as-deposited diodes reveal significant improvement in the diode characteristics. The latter surface treatment yields Ni /Au Schottky diodes with very low reverse leakage currents, breakdown voltages greater than 44V, and an ideality factor as low as 1.14.

  10. Impact of implantation geometry and fluence on structural properties of AlxGa1-xN implanted with thulium

    NASA Astrophysics Data System (ADS)

    Fialho, M.; Magalhães, S.; Chauvat, M. P.; Ruterana, P.; Lorenz, K.; Alves, E.

    2016-10-01

    AlxGa1-xN (x = 0.15 and 0.77) films, grown by halide vapor phase epitaxy, were implanted with 300 keV Tm ions. Implantation damage accumulation is investigated with Rutherford backscattering spectrometry/channeling (RBS/C), transmission electron microscopy (TEM), and high resolution X-ray diffraction (XRD). Distinct damage behavior for samples with different AlN contents was found. Surface nanocrystallization occurs for samples with x = 0.15, similar to implantation effects observed in GaN. Samples with x = 0.77 approach the behavior of AlN. In particular, surface nanocrystallization is suppressed and the depth range of the stacking fault network, typical for implanted III-nitrides, is decreased. The crystalline quality of the sample with x = 0.15 was investigated to compare random and channeled implantation, showing less concentration of damage but with a higher range for channeled implantation. Surprisingly, the strain field caused by the implantation reaches much deeper into the sample than the defect profiles measured by RBS/C and TEM. This is attributed to the fact that XRD is much more sensitive to low defect densities caused by ions which are channeled to deep regions of the sample.

  11. Clinical significance of cell population data (CPD) on Sysmex XN-9000 in septic patients with our without liver impairment

    PubMed Central

    Seghezzi, Michela; Vavassori, Mauro; Dominoni, Paola; Apassiti Esposito, Sara; Manenti, Barbara; Mecca, Tommaso; Marchesi, Gianmariano; Castellucci, Enrico; Azzarà, Giovanna; Ottomano, Cosimo; Lippi, Giuseppe

    2016-01-01

    Background This study evaluated the clinical significance of cell population data (CPD) parameters obtained on Sysmex XN-9000 in septic patients admitted to intensive care unit (ICU) and stratified according to liver function. Methods The study population consisted in 84 patients, 44 of whom did not develop sepsis (NS), whereas the remaining 40 developed sepsis (SE) (n=24) or septic shock (SS) (n=16). Two hundred ostensibly healthy blood donors [healthy subjects (HS)], undergoing routine blood testing before a regular blood donation, were studied. Results Except for neutrophils and lymphocytes cell size (NE-FCS and LY-Z), all other CPD values were significantly different in ICU patients compared to HS. Neutrophils and monocytes fluorescence intensity (NE-SFL and MO-X) values were significantly higher in SS compared to sepsis and not develop sepsis patients. The value of many parameters was also different according to liver function. Overall, MO-X and neutrophils fluorescence intensity (NE-SFL) exhibited the best performance for diagnosing sepsis in all patients (AUC, 0.75 and 0.72), as well as in those with (AUC, 0.95 and 0.89) or without (AUC, 0.72 for both) liver impairment. These parameters were also significantly correlated with Sequential Organ Failure Assessment (SOFA) score. Conclusions This study suggested that some novel CPD parameters (namely NE-SFL and MO-X) may provide useful information for diagnosis and management of sepsis. PMID:27942509

  12. Band-gap Engineering in Sputter Deposited Amorphous/Microcrystalline Sc(x)Ga(1-x)N

    NASA Technical Reports Server (NTRS)

    Little, Mark E.; Kordesch, Martin E.; Bushnell, Dennis M. (Technical Monitor)

    2001-01-01

    Reactive sputtering was used to grow thin films of Sc(x)Ga(1-x)N with scandium concentrations of 20%-70% on quartz substrates at temperatures of 300-675 K. X-ray diffraction (XRD) of the films showed either weak or no structure, suggesting the films are amorphous or microcrystalline. Optical absorption spectra were taken of each sample and the optical band gap was determined. The band gap varied linearly with increasing Ga concentration between 2.0 and 3.5 eV. Ellipsometry was used to confirm the band gap measurements and provide optical constants in the range 250-1200 nm. ScN and GaN have different crystal structures (rocksalt and wurzite, respectively), and thus may form a heterogeneous mixture as opposed to an alloy. Since the XRD data were inconclusive, bilayers of ScN/GaN were grown and optical absorption spectra taken. A fundamental difference in the spectra between the bilayer films and alloy films was seen, suggesting the films are alloys, not heterogeneous mixtures.

  13. Temperature-dependent elastic properties of Ti{sub 1−x}Al{sub x}N alloys

    SciTech Connect

    Shulumba, Nina; Hellman, Olle; Rogström, Lina; Raza, Zamaan; Tasnádi, Ferenc; Odén, Magnus; Abrikosov, Igor A.

    2015-12-07

    Ti{sub 1−x}Al{sub x}N is a technologically important alloy that undergoes a process of high temperature age-hardening that is strongly influenced by its elastic properties. We have performed first principles calculations of the elastic constants and anisotropy using the symmetry imposed force constant temperature dependent effective potential method, which include lattice vibrations and therefore the effects of temperature, including thermal expansion and intrinsic anharmonicity. These are compared with in situ high temperature x-ray diffraction measurements of the lattice parameter. We show that anharmonic effects are crucial to the recovery of finite temperature elasticity. The effects of thermal expansion and intrinsic anharmonicity on the elastic constants are of the same order, and cannot be considered separately. Furthermore, the effect of thermal expansion on elastic constants is such that the volume change induced by zero point motion has a significant effect. For TiAlN, the elastic constants soften non-uniformly with temperature: C{sub 11} decreases substantially when the temperature increases for all compositions, resulting in an increased anisotropy. These findings suggest that an increased Al content and annealing at higher temperatures will result in a harder alloy.

  14. Optical investigation of semi-polar (11-22) AlxGa1-xN with high Al composition

    NASA Astrophysics Data System (ADS)

    Li, Z.; Wang, L.; Jiu, L.; Bruckbauer, J.; Gong, Y.; Zhang, Y.; Bai, J.; Martin, R. W.; Wang, T.

    2017-02-01

    Exciton localization generally disturbs uniform population inversion, leading to an increase in the threshold current for lasing. High Al content AlGaN is required for the fabrication of deep ultra-violet (DUV) laser diodes (LDs), and this also generates exciton localization. Temperature-dependent photoluminescence and room temperature cathodoluminescence measurements have been performed on high quality semi-polar (11-22) AlxGa1-xN alloys with high Al composition ranging from 0.37 to 0.56 in order to systematically study the optical properties (in particular, exciton localization) of both the near-band-edge emission and the basal-plane stacking faults related emission, demonstrating different behaviours. Further comparison with the exciton localization of their c-plane counterparts has been performed, exhibiting that the exciton localization in semi-polar (11-22) AlGaN is much smaller than that in c-plane AlGaN. As a consequence, semi-polar (11-22) AlGaN demonstrates a greater potential than its c-plane counterpart in terms of the growth of DUV LDs.

  15. Optical and structural properties of Eu-implanted In{sub x}Al{sub 1-x}N

    SciTech Connect

    Roqan, I. S.; O'Donnell, K. P.; Martin, R. W.; Trager-Cowan, C.; Matias, V.; Vantomme, A.; Lorenz, K.; Alves, E.; Watson, I. M.

    2009-10-15

    Off-axis implantation of 80 keV Eu ions into epitaxial c-plane InAlN/GaN bilayers confines rare-earth (RE) doping largely to the InAlN layer. Rutherford backscattering spectrometry and x-ray diffraction show good correlations between the Eu{sup 3+} emission linewidth and key structural parameters of In{sub x}Al{sub 1-x}N films on GaN in the composition range near lattice matching (xapprox0.17). In contrast to GaN:Eu, selectively excited photoluminescence (PL) and PL excitation spectra reveal the presence of a single dominant optical center in InAlN. Eu{sup 3+} emission from In{sub 0.13}Al{sub 0.87}N:Eu also shows significantly less thermal quenching than GaN:Eu. InAlN films are therefore superior to GaN for RE optical doping.

  16. Maximum Torque and Momentum Envelopes for Reaction Wheel Arrays

    NASA Technical Reports Server (NTRS)

    Reynolds, R. G.; Markley, F. Landis

    2001-01-01

    Spacecraft reaction wheel maneuvers are limited by the maximum torque and/or angular momentum which the wheels can provide. For an n-wheel configuration, the torque or momentum envelope can be obtained by projecting the n-dimensional hypercube, representing the domain boundary of individual wheel torques or momenta, into three dimensional space via the 3xn matrix of wheel axes. In this paper, the properties of the projected hypercube are discussed, and algorithms are proposed for determining this maximal torque or momentum envelope for general wheel configurations. Practical implementation strategies for specific wheel configurations are also considered.

  17. Electrospray tandem mass spectrometry of alkali-cationized BocN-carbo-alpha,beta- and -beta,alpha-peptides: Differentiation of positional isomers.

    PubMed

    Reddy, P Nagi; Srikanth, R; Srinivas, R; Sharma, V U M; Sharma, G V M; Nagendar, P

    2006-01-01

    Dissociation pathways of a series of alkali-cationized hybrid peptides, viz., Boc-alpha,beta- and -beta,alpha-carbopeptides, synthesized from C-linked carbo-beta3-amino acids [Caa (S)] and alpha-alanine (L-Ala), have been investigated by electrospray ionization tandem mass spectrometry. The positional isomers (six pairs) of the cationized alpha,beta- and beta,alpha-peptides can be differentiated by the collision-induced dissociation (CID) spectra of their [M + Cat-Boc + H]+ ions which give characteristic series of alkali-cationized C- (x(n)+, y(n)+, z(n)+) and N-terminal (a(n)+, b(n)+, c(n)+) ions. Another noteworthy difference is cationized beta,alpha-peptides eliminate a molecule of ammonia whereas this pathway is absent for alpha,beta-peptides. This is useful for identifying the presence of a beta-amino acid at the N-terminus. The CID spectra of [M + Cat-Boc + H]+ ions of these peptide acids show abundant rearrangement [b(n) + 17 + Cat]+ (n = 1 to n-1) ions which is diagnostic for distinguishing between alpha- and beta-amino acid at the C-terminus. MS(n) experiments of [b(n) + Li-H]+ ions from these hybrid peptides showed the loss of CO and 72 u giving rise to [a(n) + Li-H]+ and cationized nitrile product ions which render support to earlier proposals that b(n)+ or [b(n) + Cat-H]+ ions have protonated or cationized oxazolinone structures, respectively.

  18. NUCLEAR REACTION MODELING FOR RIA ISOL TARGET DESIGN

    SciTech Connect

    S. MASHNIK; ET AL

    2001-03-01

    Los Alamos scientists are collaborating with researchers at Argonne and Oak Ridge on the development of improved nuclear reaction physics for modeling radionuclide production in ISOL targets. This is being done in the context of the MCNPX simulation code, which is a merger of MCNP and the LAHET intranuclear cascade code, and simulates both nuclear reaction cross sections and radiation transport in the target. The CINDER code is also used to calculate the time-dependent nuclear decays for estimating induced radioactivities. They give an overview of the reaction physics improvements they are addressing, including intranuclear cascade (INC) physics, where recent high-quality inverse-kinematics residue data from GSI have led to INC spallation and fission model improvements; and preequilibrium reactions important in modeling (p,xn) and (p,xnyp) cross sections for the production of nuclides far from stability.

  19. Evaluation of micromechanical properties of buckled SiO xN y-loaded membranes by combining the Twyman-Green interferometry with nanoindentation and point-wise deflection technique

    NASA Astrophysics Data System (ADS)

    Józwik, Michal; Gorecki, Christophe; Sabac, Andrei; Delobelle, Patrick; Kujawińska, Małgorzata

    2004-05-01

    In view of applications in MOEMS technology, an interferometric technique has been developed for determination of micromechanical properties of PECVD-deposited SiO xN y thin films. By combining the Twyman-Green interferometry with nanoindentation technique, an original "point-wise" deflection method is proposed, particularly appropriated to measure the residual stress in the case of silicon membranes compressively prestressed by SiO xN y deposition. For such SiO xN y membranes, operating at the first mode of buckling, the nonindentation permits the extraction of Young's modulus and interferometry measures the out-of-plan displacements, respectively. The proposed point-wise deflection technique combines both the interferometric and Young's modulus data, giving the access to the distribution of residual stress versus the optical quality of SiO xN y films. The residual stress is monitored as a function of the refractive index of SiO xN y, establishing the relationship between the optical and micromechanical properties of deposited thin films. High measuring accuracy and resolution have been demonstrated, allowing measurements to be used to enhance PECVD process control

  20. Mass spectrometric study of three-body ion-molecule clustering reactions of CpHq+ ions with N2 or CH4 in N2-CH4 mixtures.

    PubMed

    Speller, C V; Vacher, J R; Duc, E; Fitaire, M

    1995-01-01

    Thermochemical data for several ion-molecule clustering of hydrocarbon ions with N2 or CH4 were obtained from clustering equilibria studies in gas mixtures irradiated by alpha-particles. High-pressure mass spectrometry was used to determine the enthalpy and entropy changes of clustering (delta H0 and delta S0, respectively) for the reactions X+(N2)n-1 + 2N2 <==> X(+)(N2)n + N2 with X = CH5, n = 1-2; X = C2H5, n = 1-4; and X = C3H7, n = 1. For X = CH5, the values (delta H0; delta S0) are found to be (-6.8 kcal mol-1; -19.7 cal mol-1 K-1) for n = 1, and (-5.3 kcal mol-1; -15.9 cal mol-1 K-1) for n = 2. For X = C2H5, (delta H0; delta S0) = (-6.9 kcal mol-1; -18.2 cal mol-1 K-1), for n = 1, and (-4.6 kcal mol-1; -20.8 cal mol-1 K-1) for n = 2. From the equilibrium measurements at 129 K, estimates of the thermochemical values could be obtained for n = 3-4. The results obtained for the free energy, delta G0, were -1.4 kcal mol-1 for n = 3, and -1.1 kcal mol-1 for n = 4. For X = C3H7 we found delta G0 = -0.7 kcal mol-1 at 213 K. The association reactions X+ + 2CH4 <==> X+(CH4) + CH4 with X = CH5, C2H5, C2H7, and C3H7 were also studied, resulting in free energy values at 206 K of -3.1, -1.9, -0.5 and -1.3 kcal mol-1, respectively. The results for CH5, C2H5 and C3H7 are compared with previously reported measurements.

  1. High-Temperature Ferromagnetism in Cr- and Mn-Implanted Al(sub x)Ga(sub 1-x)N

    DTIC Science & Technology

    2007-09-23

    films of AlxGa1-xN that display ferromagnetism. Although recent advances in ion-implantation doping of group-III nitrides with Cr and Mn are making...annealed from 675 to 775 oC at AFIT in an Oxy -Gon furnace using the rapid thermal annealing method in an N2 environment for 5 min to anneal out the...layer). After implantation, the samples were annealed in an Oxy -Gon annealing furnace at temperatures between 650 and 775 oC for 5 min. Before

  2. Catalytic Mechanism of Human Alpha-galactosidase

    SciTech Connect

    Guce, A.; Clark, N; Salgado, E; Ivanen, D; Kulinskaya, A; Brumer, H; Garman, S

    2010-01-01

    The enzyme {alpha}-galactosidase ({alpha}-GAL, also known as {alpha}-GAL A; E.C. 3.2.1.22) is responsible for the breakdown of {alpha}-galactosides in the lysosome. Defects in human {alpha}-GAL lead to the development of Fabry disease, a lysosomal storage disorder characterized by the buildup of {alpha}-galactosylated substrates in the tissues. {alpha}-GAL is an active target of clinical research: there are currently two treatment options for Fabry disease, recombinant enzyme replacement therapy (approved in the United States in 2003) and pharmacological chaperone therapy (currently in clinical trials). Previously, we have reported the structure of human {alpha}-GAL, which revealed the overall structure of the enzyme and established the locations of hundreds of mutations that lead to the development of Fabry disease. Here, we describe the catalytic mechanism of the enzyme derived from x-ray crystal structures of each of the four stages of the double displacement reaction mechanism. Use of a difluoro-{alpha}-galactopyranoside allowed trapping of a covalent intermediate. The ensemble of structures reveals distortion of the ligand into a {sup 1}S{sub 3} skew (or twist) boat conformation in the middle of the reaction cycle. The high resolution structures of each step in the catalytic cycle will allow for improved drug design efforts on {alpha}-GAL and other glycoside hydrolase family 27 enzymes by developing ligands that specifically target different states of the catalytic cycle. Additionally, the structures revealed a second ligand-binding site suitable for targeting by novel pharmacological chaperones.

  3. Nuclear diagnostic for fast alpha particles

    DOEpatents

    Grisham, Larry R.; Post Jr., Douglass E.; Dawson, John M.

    1986-06-03

    Measurement of the velocity distribution of confined energetic alpha particles resulting from deuterium-tritium fusion reactions in a magnetically contained plasma is provided. The fusion plasma is seeded with energetic boron neutrals for producing, by means of the reaction .sup.10 B (.alpha.,n) .sup.13 N reaction, radioactive nitrogen nuclei which are then collected by a probe. The radioactivity of the probe is then measured by conventional techniques in determining the energy distribution of the alpha particles in the plasma. In a preferred embodiment, diborane gas (B.sub.2 H.sub.6) is the source of the boron neutrals to produce .sup.13 N which decays almost exclusively by positron emission with a convenient half-life of 10 minutes.

  4. Nuclear diagnostic for fast alpha particles

    DOEpatents

    Grisham, Larry R.; Post, Jr., Douglass E.; Dawson, John M.

    1986-01-01

    Measurement of the velocity distribution of confined energetic alpha particles resulting from deuterium-tritium fusion reactions in a magnetically contained plasma is provided. The fusion plasma is seeded with energetic boron neutrals for producing, by means of the reaction .sup.10 B (.alpha.,n) .sup.13 N reaction, radioactive nitrogen nuclei which are then collected by a probe. The radioactivity of the probe is then measured by conventional techniques in determining the energy distribution of the alpha particles in the plasma. In a preferred embodiment, diborane gas (B.sub.2 H.sub.6) is the source of the boron neutrals to produce .sup.13 N which decays almost exclusively by positron emission with a convenient half-life of 10 minutes.

  5. Fibrinogen {alpha} genes: Conservation of bipartite transcripts and carboxy-terminal-extended {alpha} subunits in vertebrates

    SciTech Connect

    Fu, Y.; Cao, Y.; Hertzberg, K.M.; Grieninger, G.

    1995-11-01

    All three well-studied subunits of the clotting protein fibrinogen ({alpha}, {beta}, {gamma}) share N-terminal structural homologies, but until recently only the {beta} and {gamma} chains were recognized as having similar globular C-termini. With the discovery of an extra exon in the human fibrinogen {alpha} gene (exon VI), a minor form of the {alpha} subunit ({alpha}{sub E}) with an extended {beta}- and {gamma}-like C-terminus has been identified. In the present study, the polymerase chain reaction has been used to identify sequences that encode counterparts to {alpha}{sub E} in chicken, rabbit, rat, and baboon. The basic six-exon structure of the fibrinogen {alpha} genes is shown to be conserved among mammals and birds, as are the intron positions. Bipartite transcripts - still bearing an intron prior to the last exon - are found among the products of the various vertebrate fibrinogen {alpha} genes. The last exon represents the largest conserved segment of the gene and, in each species examined, encodes exactly 236 amino acids. The C-termini of these {alpha}{sub E} chains align without a single gap and are between 76 and 99% identical. Since the exon VI-encoded domain of {alpha}{sub E} is as well conserved as the corresponding regions of the {beta} and {gamma} chains, it follows that it is equally important and that {alpha}{sub E}-fibrinogen plays a vital, if as-yet unrecognized physiological role. 21 refs., 7 figs., 1 tab.

  6. alpha-Hexachlorocyclohexane (alpha-HCH)

    Integrated Risk Information System (IRIS)

    alpha - Hexachlorocyclohexane ( alpha - HCH ) ; CASRN 319 - 84 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Ass

  7. The murine alpha B-crystallin/small heat shock protein enhancer: identification of alpha BE-1, alpha BE-2, alpha BE-3, and MRF control elements.

    PubMed

    Gopal-Srivastava, R; Piatigorsky, J

    1993-11-01

    The murine alpha B-crystallin gene (a member of the small heat shock protein family) is expressed constitutively at high levels in the lens and at lower levels in many other tissues, including skeletal muscle. We have previously used the herpes simplex virus thymidine kinase promoter fused to the human growth hormone gene to identify an alpha B-crystallin enhancer at positions -427 to -259 that has high activity in muscle and low activity in lens cell lines. In the study reported here, we performed DNase I footprinting, transfection, mutagenesis, and electrophoretic mobility shift experiments using the murine C2C12 muscle and alpha TN4-1 lens cell lines and the rabbit N/N1003A lens cell line to identify sequences responsible for activity of this enhancer. Enhancer activity in both the muscle and lens cells was dependent on novel elements called alpha BE-1 (-407 to -397), alpha BE-2 (-360 to -327), and alpha BE-3 (-317 to -306). These elements were also weakly occupied by nuclear proteins in L929 cells, which appear to express the alpha B-crystallin gene at a very low level (detectable only by the polymerase chain reaction). A fourth element containing a consensus muscle regulatory factor-binding site called MRF (-300 to -288) was occupied and used only by the C2C12 muscle cells. Cotransfection in NIH 3T3 cells and antibody-gel shift experiments using C2C12 nuclear extracts indicated that MyoD, myogen, or a similar member of this family can activate the alpha B-crystallin enhancer by interaction with the MRF site. Taken together, we conclude that the alpha BE-1, alpha BE-2, and alpha BE-3 elements are shared by both lens and muscle cells, but the MRF element is used only in muscle cells, providing the first example of a muscle-specific control element in a crystallin gene.

  8. Incorporation of Mn in AlxGa1 -xN probed by x-ray absorption and emission spectroscopy, high-resolution microscopy, x-ray diffraction, and first-principles calculations

    NASA Astrophysics Data System (ADS)

    Rovezzi, Mauro; Schlögelhofer, Wolfgang; Devillers, Thibaut; Szwacki, Nevill Gonzalez; Li, Tian; Adhikari, Rajdeep; Glatzel, Pieter; Bonanni, Alberta

    2015-09-01

    Synchrotron radiation x-ray absorption and emission spectroscopy techniques, complemented by high-resolution transmission electron microscopy methods and density functional theory calculations, are employed to investigate the effect of Mn in AlxGa1 -xN :Mn samples with an Al content up to 100%. The atomic and electronic structure of Mn is established together with its local environment and valence state. A dilute alloy without precipitation is obtained for AlxGa1 -xN :Mn with Al concentrations up to 82%, and the surfactant role of Mn in the epitaxial process is confirmed.

  9. Alpha Hydroxy Acids

    MedlinePlus

    ... Cosmetics Home Cosmetics Products & Ingredients Ingredients Alpha Hydroxy Acids Share Tweet Linkedin Pin it More sharing options ... for Industry: Labeling for Cosmetics Containing Alpha Hydroxy Acids The following information is intended to answer questions ...

  10. On the microstructure of Al{sub x}Ga{sub 1-x}N layers grown on 6H-SiC(0001) substrates

    SciTech Connect

    Kroeger, Roland; Einfeldt, Sven; Chierchia, Rosa; Hommel, Detlef; Reitmeier, Zachary J.; Davis, Robert F.; Liu, Quincy K.K.

    2005-04-15

    The microstructural as well as the compositional evolution of Al{sub x}Ga{sub 1-x}N (x{approx}0.15) layers grown on 6H-SiC(0001) substrates by metalorganic vapor phase epitaxy were analyzed by atomic force microscopy, X-ray diffraction, and transmission electron microscopy in conjunction with energy dispersive X-ray spectroscopy. The epitaxial growth was followed from the early nucleation stage on the substrate to the development of a thick bulk-like film. Phase separation was observed during the early stage of growth; that is, islands of two different shapes formed whose Al mole fractions were about 0.035 and 0.18, respectively. The Al{sub x}Ga{sub 1-x}N coalesced at a film thickness of about 100 nm with the domains of varying Al content being fully coherent. Such domains were not only found at the film/substrate interface but also further away from the interface. They were arranged in layers that were shifted laterally against each other; that is, Al-deficient domains formed on top of Al-rich domains and vice versa. Increasing the film thickness to more than 100 nm finally led to a homogeneous Al distribution. Finite-element simulations were performed to calculate the strain distribution in these inhomogeneous systems. They allowed the experimental results to be explained by an interplay of strain minimization in the epitaxial film and growth kinetics.

  11. SQUID measurements of MnxSc(1-x)N and Fe0.1Sc0.9N Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Chia, Han-Jong; Constantin, Costel; Wang, Kangkang; Chinchore, Abhijit; Smith, Arthur; Markert, John

    2009-03-01

    We report SQUID magnetic measurements on N-rich and N-poor MnxSc(1-x)N and Fe0.1Sc0.9N films grown on ScN(001)/MgO(001) substrates by radio frequency plasma assisted molecular beam epitaxy. Ferromagnetism is present in both the Mn doped (x ranging from 3 to 15%) and the Fe doped ScN samples. Measurements on N-poor Mn0.03Sc0.97N and Mn0.15Sc0.85N (x=15%) show Curie temperatures of 383 K and 361 K, respectively. The Fe0.1Sc0.9N film shows a Curie temperature above 350 K as well. Further studies will be required to determine the origin of the ferromagnetism and the Curie temperature of the remaining MnxSc(1-x)N films. This work is supported by: Seton Hall: University Research Council; Ohio University: DOE-BES Grant No. DE-FG02-06ER46317 and NSF Grant No. 0730257; and UT Austin: NSF Grant Nos. DMR-0605828 and DGE-0549417, Welch Foundation Grant No. F-1191.

  12. The Alpha Centauri System.

    ERIC Educational Resources Information Center

    Soderblom, David R.

    1987-01-01

    Describes the Alpha Centauri star system, which is the closest star system to the sun. Discusses the difficulties associated with measurements involving Alpha Centauri, along with some of the recent advances in stellar seismology. Raises questions about the possibilities of planets around Alpha Centauri. (TW)

  13. Alpha Backgrounds in the SNO ^3He Proportional Counter Array

    NASA Astrophysics Data System (ADS)

    Stonehill, Laura

    2006-04-01

    The Sudbury Neutrino Observatory (SNO) has recently deployed an array of proportional counters known as Neutral Current Detectors (NCDs) to detect thermalized neutrons via the ^3He(n,p)^3H reaction. The primary physics background to the neutron-capture signal is alpha particle emission from uranium- and thorium-chain decays in the NCD walls. The expected capture rate of neutrons from the neutral-current neutrino reaction on deuterium is three per day and the intrinsic alpha background rate is approximately 250 alphas per day. Fewer than 10% of these alphas fall into the energy range where neutron-capture signals occur, and a substantial number of these can be eliminated by pulse-shape analysis. This talk will focus on measurements of the alpha backgrounds in the NCDs and the extent to which these alphas contaminate the neutron-capture signal region.

  14. New data on ({gamma}, n), ({gamma}, 2n), and ({gamma}, 3n) partial photoneutron reactions

    SciTech Connect

    Varlamov, V. V. Ishkhanov, B. S.; Orlin, V. N.; Peskov, N. N.; Stepanov, M. E.

    2013-11-15

    Systematic discrepancies between the results of various experiments devoted to determining cross sections for total and partial photoneutron reactions are analyzed by using objective criteria of reliability of data in terms of the transitional photoneutron-multiplicity function F{sub i} = {sigma}({gamma}, in)/{sigma}({gamma}, xn), whose values for i = 1, 2, 3, ... cannot exceed by definition 1.00, 0.50, 0.33, ..., respectively. It was found that the majority of experimental data on the cross sections obtained for ({gamma}, n), ({gamma}, 2n), and ({gamma}, 3n) reactions with the aid of methods of photoneutron multiplicity sorting do not meet objective criteria (in particular, F{sub 2} > 0.50 for a vast body of data). New data on the cross sections for partial reactions on {sup 181}Ta and {sup 208}Pb nuclei were obtained within a new experimental-theoretical method that was proposed for the evaluation of cross sections for partial reactions and in which the experimental neutron yield cross section {sigma}{sup expt}({gamma}, xn) = {sigma}({gamma}, n) + 2{sigma}({gamma}, 2n) + 3{sigma}({gamma}, 3n) + ..., which is free from problems associated with determining neutron multiplicities, is used simultaneously with the functions F{sub i}{sup theor} calculated within a combined model of photonuclear reactions.

  15. Identification of Dictyostelium G alpha genes expressed during multicellular development.

    PubMed Central

    Hadwiger, J A; Wilkie, T M; Strathmann, M; Firtel, R A

    1991-01-01

    Guanine nucleotide-binding protein (G protein)-mediated signal transduction constitutes a common mechanism by which cells receive and respond to a diverse set of environmental signals. Many of the signals involved in the developmental life cycle of the slime mold Dictyostelium have been postulated to be transduced by such pathways and, in some cases, these pathways have been demonstrated to be dependent on specific G proteins. Using the polymerase chain reaction, we have identified two additional Dictyostelium G alpha genes, G alpha 4 and G alpha 5, that are developmentally regulated. Transcripts from both of these genes are primarily expressed during the multicellular stages of development, suggesting possible roles in cell differentiation or morphogenesis. The entire G alpha 4 gene was sequenced and found to encode a protein consisting of 345 amino acids. The G alpha 4 subunit is homologous to other previously identified G alpha subunits, including the Dictyostelium G alpha 1 (43% identity) and G alpha 2 (41% identity) subunits. However, the G alpha 4 subunit contains some unusual sequence divergences in residues highly conserved among most eukaryotic G alpha subunits, suggesting that G alpha 4 may be a member of another class of G alpha subunits. Images PMID:1910174

  16. Effect of nitrogen flow rate on structural, morphological and optical properties of In-rich InxAl1-xN thin films grown by plasma-assisted dual source reactive evaporation

    NASA Astrophysics Data System (ADS)

    Alizadeh, M.; Ganesh, V.; Goh, B. T.; Dee, C. F.; Mohmad, A. R.; Rahman, S. A.

    2016-08-01

    In-rich InxAl1-xN thin films were deposited on quartz substrate at various nitrogen flow rates by plasma-assisted dual source reactive evaporation technique. The elemental composition, surface morphology, structural and optical properties of the films were investigated by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), Raman spectroscopy, X-ray diffraction (XRD), UV-vis spectrophotometer and photoluminescence (PL) measurements. XPS results revealed that the indium composition (x) of the InxAl1-xN films increases from 0.90 to 0.97 as the nitrogen flow rate is increased from 40 to 100 sccm, respectively. FESEM images of the surface and cross-sectional microstructure of the InxAl1-xN films showed that by increasing the N2 flow rate, the grown particles are highly agglomerated. Raman and XRD results indicated that by increasing nitrogen flow rate the In-rich InxAl1-xN films tend to turn into amorphous state. It was found that band gap energy of the films are in the range of 0.90-1.17 eV which is desirable for the application of full spectra solar cells.

  17. Effect of substitution of nitrogen ions to red-emitting Sr 3B 2O 6-3/2 xN x:Eu 2+ oxy-nitride phosphor for the application to white LED

    NASA Astrophysics Data System (ADS)

    Hoon Jung, Sang; Seok Kang, Dong; Young Jeon, Duk

    2011-07-01

    The luminescence properties of orange-red-emitting Eu 2+ activated Sr 3B 2O 6-3/2 xN x were optimized for application to blue/near UV light-emitting diodes (LEDs). Sr 3B 2O 6-3/2 xN x:Eu 2+ phosphor showed broad orange-red emission peaking at 600-650 nm under blue and n-UV excitations of 450 and 360 nm, respectively; the emission peak of phosphor was affected by nitrogen ion substitution. Boron nitride raw materials affect luminescence properties of phosphor; a small amount of BN reacts as a flux for synthesis of Sr 3B 2O 6 and a large amount of BN helps Sr 3B 2O 6-3/2 xN x:Eu 2+ phosphor to have longer-wavelength emission peak. A 447 nm-emitting blue LED-pumped white LED with a mixture of Sr 3B 2O 6-3/2 xN x:Eu 2+ ( x=1) and Ba 2SiO 4:Eu 2+ green-emitting phosphor was fabricated; it is observed that it showed color coordinates of (0.3648, 0.3605) and CRI value of 96.

  18. First-principles study of the structural and elastic properties of Cr{sub 2}AlX (X=N, C) compounds

    SciTech Connect

    Cui Shouxin; Wei Dongqing; Hu Haiquan; Feng Wenxia; Gong Zizheng

    2012-07-15

    The structural, electronic and elastic properties of Cr{sub 2}AlX, with X=N, C, have been investigated at the density functional theory level by applying a plane-wave pseudopotential approach. The band structure and density of states reveal the metallic features of Cr{sub 2}AlX. The total and projected density of states indicate that the bonding is achieved through a hybridization of Cr 3d states with Al and X-atom p states. The Cr 3d-X2p bonds are lower in energy and are stiffer than Cr 3d-Al 3p bonds. The charge density distributions indicate that there exist soft Cr-Al and relatively strong Cr-X covalent bonds, which might be responsible for their hardness. The elastic constants were obtained in the pressure range 0-100 GPa, and satisfy the stability conditions for hexagonal crystal, which indicates that these two compounds are stable in the pressure regime studied. By analyzing bulk modulus to shear modulus ratio and Cauchy pressure, Cr{sub 2}AlC is predicted to be brittleness and Cr{sub 2}AlN is ductile. The Debye temperature was obtained from the average sound velocity. - Graphical abstract: The heterogeneity of chemical bonds in Cr{sub 2}AlX (X=N, C) is observed: soft Cr-Al and relatively strong Cr-X covalent bonds might be contributed to their hardness. Highlights: Black-Right-Pointing-Pointer Cr 3d-X2p (X=N, C) bonds are lower in energy and stiffer than Cr 3d-Al 3p bonds for Cr{sub 2}AlX. Black-Right-Pointing-Pointer The hardness of Cr{sub 2}AlX might be ascribed to soft Cr-Al and relatively strong Cr-X covalent bonds. Black-Right-Pointing-Pointer The predicted brittleness of Cr{sub 2}AlC and ductility of Cr{sub 2}AlN originated from their novel structure.

  19. Producing a compound Nucleus via Inelastic Scattering: The 90Zr(alpha,alpha')90Zr* Case

    SciTech Connect

    Escher, J E; Dietrich, F S

    2008-05-23

    In a Surrogate reaction a compound nucleus is produced via a direct reaction (pickup, stripping, or inelastic scattering). For a proper application of the Surrogate approach it is necessary to predict the resulting angular momentum and parity distribution in the compound nucleus. A model for determining these distributions is developed for the case of inelastic alpha scattering off a spherical nucleus. The focus is on obtaining a first, simple description of the direct-reaction process that produces the compound nucleus and on providing the basis for a more complete treatment of the problem. The approximations employed in the present description are discussed and the extensions required for a more rigorous treatment of the problem are outlined. To illustrate the formalism, an application to {sup 90}Zr({alpha},{alpha}{prime}){sup 90}Zr* is presented.

  20. Intentional anisotropic strain relaxation in (112{sup ¯}2) oriented Al{sub 1−x}In{sub x}N one-dimensionally lattice matched to GaN

    SciTech Connect

    Buß, E. R. Rossow, U.; Bremers, H.; Hangleiter, A.; Meisch, T.; Caliebe, M.; Scholz, F.

    2014-09-22

    We report on (112{sup ¯}2) oriented Al{sub 1−x}In{sub x}N grown by low pressure metal organic vapor phase epitaxy on (112{sup ¯}2) GaN templates on patterned r-plane sapphire. The indium incorporation efficiency as well as the growth rate of (112{sup ¯}2) oriented layers are similar to c-plane oriented Al{sub 1−x}In{sub x}N layers. Deposition of thick Al{sub 1−x}In{sub x}N layers does not lead to additional roughening like in case of c-plane oriented Al{sub 1−x}In{sub x}N. Independent of the thickness, the degree of relaxation of layers lattice matched in m-direction is in the range of 33%–45% in [112{sup ¯}3{sup ¯}]-direction. Associated with the relaxation in [112{sup ¯}3{sup ¯}]-direction, there is a tilt of the Al{sub 1−x}In{sub x}N layers around the [11{sup ¯}00] axis due to slip of threading dislocations on the basal (0001)-plane. Relaxation in m-direction is not observable for layers lattice matched in [112{sup ¯}3{sup ¯}] direction. The possibility to adjust the lattice parameter of AlInN in [112{sup ¯}3{sup ¯}] direction without changing the lattice parameter in m-direction by anisotropic strain relaxation opens up opportunities for subsequent growth of optically active structures. One possibility is to form relaxed buffer layers for GaInN quantum well structures.

  1. Recent results of measurements of the {sup 14}N(n,p){sup 14}C, {sup 35}Cl(n,p){sup 35}S, {sup 36}Cl(n,p){sup 36}S, and {sup 36}Cl(n,{alpha}){sup 33}P reaction cross sections

    SciTech Connect

    Gledenov, Y.M.; Salatski, V.I.; Sedyshev, P.V.; Sedysheva, M.V.; Koehler, P.E.; Vesna, V.A.; Okunev, I.S.

    1995-02-05

    Experiments are reported for measuring the cross section of the {sup 14}N(n,p){sup 14}C reaction over the neutron energy range from thermal energy to 150 keV at the IBR-30 pulsed booster at JNR, Dubna and the WWR-M reactor at INR, Kiev. The reaction cross section values were found for the thermal energy and for the neutron energies of 24 keV, 54 keV, 144 keV. The {sup 36}Cl(n,p){sup 36}S cross section was measured for the neutron energies from thermal energy to approximately 800 keV at the neutron source of LANSCE, Los Alamos. The contributions of the {sup 36}Cl(n,p){sup 36}S and {sup 36}Cl(n,{alpha}){sup 33}P reactions to resonances at 0.9 keV and 1.3 keV were identified. Also, at the WWR-M reactor of PINR, Gatchina, preliminary measurements of the {sup 36}Cl(n,p){sup 36}S cross section at the thermal neutron energy were conducted. The {sup 35}Cl(n,p){sup 35}S reaction cross section was measured at the IBR-30 pulsed booster. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  2. Synthesis of 4-amino-5-H-2,3-dihydroisothiazole-1,1-dioxide ring systems on sugar templates via carbanion-mediated sulfonamide intramolecular cyclization reactions (CSIC protocols) of glyco-alpha-sulfonamidonitriles.

    PubMed

    Domínguez, Laura; van Nhien, Albert Nguyen; Tomassi, Cyrille; Len, Christophe; Postel, Denis; Marco-Contelles, José

    2004-02-06

    The carbanion-mediated sulfonate intramolecular cyclizations (CSIC protocols) of glyco-alpha-sulfonamidonitriles derived from readily available monosaccharides have been extensively investigated using potassium carbonate, cesium carbonate, n-BuLi, and LDA as bases. As a result, a series of enantiomerically pure spiro(4-amino-5-H-2,3-dihydroisothiazole-1,1-dioxide) derivatives have been prepared efficiently and isolated in good yield. The synthesis of these new bicyclic systems is key to accessing a novel range of aza analogues of TSAO nucleosides (ATSAOs).

  3. Crystal structure study of dielectric oxynitride perovskites La1-xSrxTiO2+xN1-x (x=0, 0.2)

    NASA Astrophysics Data System (ADS)

    Habu, Daiki; Masubuchi, Yuji; Torii, Shuki; Kamiyama, Takashi; Kikkawa, Shinichi

    2016-05-01

    As is the case with SrTaO2N, both cis-ordering of nitride anions and octahedral titling are also preferable in La1-xSrxTiO2+xN1-x (x=0, 0.2) oxynitride perovskites. A larger dielectric constant of εr≈5.0×103 was estimated for the pure oxynitride with x=0.2, compared with εr≈750 for the product with x=0, by extrapolating the εr values obtained from powders mixed with paraffin at various mixing ratios. The crystal structure of x=0.2 with larger tolerance factor than x=0 increased the octahedral tilting, which contributes to the increased dielectric constant. The increased dielectric constant supports the exchange mechanism for the dielectric property between two kinds of -Ti-N- helical coils (clockwise and anticlockwise) derived from the above cis-ordering of nitride anions.

  4. Vacancy-type defects in In{sub x}Ga{sub 1-x}N alloys probed using a monoenergetic positron beam

    SciTech Connect

    Uedono, A.; Watanabe, T.; Ishibashi, S.; Wang, X. Q.; Liu, S. T.; Chen, G.; Shen, B.; Sang, L. W.; Sumiya, M.

    2012-07-01

    Native defects in In{sub x}Ga{sub 1-x}N grown by plasma-assisted molecular beam epitaxy were probed by a monoenergetic positron beam. Doppler broadening spectra of the annihilation radiation were measured, and these were compared with results obtained using first-principles calculation. The defect concentration increased with increasing In composition x and reached the maximum at x = 0.44{approx}0.56. A clear correlation between the line-width of photoluminescence and the defect concentration was obtained. The major defect species detected by positron annihilation was identified as cation vacancies coupled with multiple nitrogen vacancies (V{sub N}s), and their introduction mechanism is discussed in terms of the strain energy due to bond-length/angle distortions and the suppression of the V{sub N} formation energy by neighboring In atoms.

  5. Anomalous Hall effect in epitaxial ferrimagnetic anti-perovskite Mn{sub 4−x}Dy{sub x}N films

    SciTech Connect

    Meng, M.; Wu, S. X. Zhou, W. Q.; Ren, L. Z.; Wang, Y. J.; Wang, G. L.; Li, S. W.

    2015-08-07

    Anomalous Hall effect (AHE) has been studied for ferrimagnetic antiperovskite Mn{sub 4−x}Dy{sub x}N films grown by molecular-beam epitaxy. The introduction of Dy changes the AHE dramatically, even changes its sign, while the variations in magnetization are negligible. Two sign reversals of the AHE (negative-positive-negative) are ascribed to the variation of charge carriers as a result of Fermi surface reconstruction. We further demonstrate that the AHE current J{sub AH} is dissipationless (independent of the scattering rate), by confirming that anomalous Hall conductivity, σ{sub AH}, is proportional to the carrier density n at 5 K. Our study may provide a route to further utilize antiperovskite manganese nitrides in spintronics.

  6. High efficiency ultraviolet emission from AlxGa1-xN core-shell nanowire heterostructures grown on Si (111) by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Wang, Q.; Nguyen, H. P. T.; Cui, K.; Mi, Z.

    2012-07-01

    High crystalline quality, vertically aligned AlxGa1-xN nanowire heterostructures are grown on GaN nanowire templates on Si (111) substrates by plasma-assisted molecular beam epitaxy. The nanowires exhibit unique core-shell structures, with enhanced Al compositions in the near-surface region. The emission wavelength can be varied across nearly the entire ultraviolet A (˜3.10-3.94 eV) and B (˜3.94-4.43 eV) spectral range by controlling the Al compositions. Such nanowire structures can exhibit extremely high internal quantum efficiency (up to ˜58%) at room-temperature, which is attributed to the superior carrier confinement offered by the core-shell structures and to the use of defect-free GaN nanowire templates.

  7. Texture and microstructure evolution in single-phase Ti{sub x}Ta{sub 1-x}N alloys of rocksalt structure

    SciTech Connect

    Koutsokeras, L. E.; Abadias, G.; Patsalas, P.

    2011-08-15

    The mechanisms controlling the structural and morphological features (texture and microstructure) of ternary transition metal nitride thin films of the Ti{sub x}Ta{sub 1-x}N system, grown by various physical vapor deposition techniques, are reported. Films deposited by pulsed laser deposition, dual cathode magnetron sputtering, and dual ion beam sputtering have been investigated by means of x-ray diffraction in various geometries and scanning electron microscopy. We studied the effects of composition, energetic, and kinetics in the evolution of the microstructure and texture of the films. We obtain films with single and mixed texture as well as films with columnar ''zone-T'' and globular type morphology. The results have shown that the texture evolution of ternary transition metal nitrides as well as the microstructural features of such films can be well understood in the framework of the kinetic mechanisms proposed for their binary counterparts, thus giving these mechanisms a global application.

  8. Correlated high-resolution x-ray diffraction photoluminescence and atom probe tomography analysis of continuous and discontinuous InxGa1-xN quantum wells

    DOE PAGES

    Ren, Xiaochen; Riley, James R.; Koleske, Daniel; ...

    2015-07-14

    In this study, atom probe tomography (APT) is used to characterize the influence of hydrogen dosing duringGaN barrier growth on the indium distribution of InxGa1-xN quantum wells, and correlatedmicro-photoluminescence is used to measure changes in the emission spectrum and efficiency. We found that relative to the control growth, hydrogen dosing leads to a 50% increase in emission intensity arising from discontinuous quantum wells that are narrower, of lower indium content, and with more abrupt interfaces. Additionally, simulations of carrier distributions based on APT composition profiles indicate that the greater carrier confinement leads to an increased radiative recombination rate. Furthermore, APTmore » analysis of quantum well profiles enables refinement of x-ray diffractionanalysis for more accurate nondestructive measurements of composition.« less

  9. Interpreting EEG alpha activity.

    PubMed

    Bazanova, O M; Vernon, D

    2014-07-01

    Exploring EEG alpha oscillations has generated considerable interest, in particular with regards to the role they play in cognitive, psychomotor, psycho-emotional and physiological aspects of human life. However, there is no clearly agreed upon definition of what constitutes 'alpha activity' or which of the many indices should be used to characterize it. To address these issues this review attempts to delineate EEG alpha-activity, its physical, molecular and morphological nature, and examine the following indices: (1) the individual alpha peak frequency; (2) activation magnitude, as measured by alpha amplitude suppression across the individual alpha bandwidth in response to eyes opening, and (3) alpha "auto-rhythmicity" indices: which include intra-spindle amplitude variability, spindle length and steepness. Throughout, the article offers a number of suggestions regarding the mechanism(s) of alpha activity related to inter and intra-individual variability. In addition, it provides some insights into the various psychophysiological indices of alpha activity and highlights their role in optimal functioning and behavior.

  10. N-carbamoyl-alpha-amino acids rather than free alpha-amino acids formation in the primitive hydrosphere: a novel proposal for the emergence of prebiotic peptides.

    PubMed

    Taillades, J; Beuzelin, I; Garrel, L; Tabacik, V; Bied, C; Commeyras, A

    1998-02-01

    Our previous kinetic and thermodynamic studies upon the reactional system HCHO/HCN/NH3 in aqueous solutions are completed. In the assumed prebiotic conditions of the primitive earth ([HCHO] and [HCN] near 1 g L-1, T = 25 degrees C, pH = 8, [NH3] very low), this system leads to 99.9% of alpha-hydroxyacetonitrile and 0.1% of alpha-aminoacetonitrile (precursor of the alpha-amino acid). The classical base-catalyzed hydration of nitriles, slow and not selective, can not modify significantly this proportion. On the contrary, we found two specific and efficient reactions of alpha-aminonitriles which shift the initial equilibrium in favor of the alpha-aminonitrile pathway. The first reaction catalyzed by formaldehyde generates alpha-aminoamides, precursors of alpha-aminoacids. The second reaction catalyzed by carbon dioxide affords hydantoins, precursors of N-carbamoyl-alpha-aminoacids. In the primitive hydrosphere, where the concentration in carbon dioxide was estimated to be higher than that of formaldehyde, the formation of hydantoins was consequently more efficient. The rates of hydrolysis of the alpha-aminoacetamide and of the hydantoin at pH 8 being very similar, the synthesis of the N-carbamoyl-alpha-amino acid seems then to be the fatal issue of the HCHO/HCN/NH3 system that nature used to perform its evolution. These N-protected alpha-amino acids offer new perspectives in prebiotic chemistry, in particular for the emergence of peptides on the prebiotic earth.

  11. {alpha} cluster states in {sup 44,46,52}Ti

    SciTech Connect

    Fukada, M.; Takimoto, M. K.; Ogino, K.; Ohkubo, S.

    2009-12-15

    {alpha} decaying states of {sup 44,46,52}Ti were investigated with angular correlation functions between t and {alpha} with the {sup 40,42,48}Ca({sup 7}Li,t{alpha}){sup 40,42,48}Ca reactions at E=26.0 MeV. Many {alpha} cluster states were newly observed in the 10-15 MeV excitation energy of {sup 44}Ti and their spin-parities were assigned, in which J{sup {pi}}=7{sup -} state was found at 11.95 MeV as a candidate for the member of the K=0{sub 1}{sup -} negative parity band. In {sup 46}Ti many {alpha} cluster states were also found in the 11-17 MeV excitation energy with the {sup 42}Ca({sup 7}Li,t{alpha}){sup 42}Ca reaction, though its strength is weak compared with {sup 44}Ti. No {alpha} cluster states were detected for the {sup 48}Ca({sup 7}Li,t{alpha}){sup 48}Ca reaction, in which the number of coincidence events decaying from {sup 48}Ca was very small.

  12. ALPHA CONTAMINATION MONITORING

    DTIC Science & Technology

    This project was conducted to determine the alpha hazard existing in the vicinity of the missile launch pad following the destruction of a missile ...were used for plutonium particle collection. Because all warhead-carrying missiles were properly launched after Project 2.3 was approved, no alpha contamination data was obtained.

  13. Imaging alpha particle detector

    DOEpatents

    Anderson, David F.

    1985-01-01

    A method and apparatus for detecting and imaging alpha particles sources is described. A conducting coated high voltage electrode (1) and a tungsten wire grid (2) constitute a diode configuration discharge generator for electrons dislodged from atoms or molecules located in between these electrodes when struck by alpha particles from a source (3) to be quantitatively or qualitatively analyzed. A thin polyester film window (4) allows the alpha particles to pass into the gas enclosure and the combination of the glass electrode, grid and window is light transparent such that the details of the source which is imaged with high resolution and sensitivity by the sparks produced can be observed visually as well. The source can be viewed directly, electronically counted or integrated over time using photographic methods. A significant increase in sensitivity over other alpha particle detectors is observed, and the device has very low sensitivity to gamma or beta emissions which might otherwise appear as noise on the alpha particle signal.

  14. Imaging alpha particle detector

    DOEpatents

    Anderson, D.F.

    1980-10-29

    A method and apparatus for detecting and imaging alpha particles sources is described. A dielectric coated high voltage electrode and a tungsten wire grid constitute a diode configuration discharge generator for electrons dislodged from atoms or molecules located in between these electrodes when struck by alpha particles from a source to be quantitatively or qualitatively analyzed. A thin polyester film window allows the alpha particles to pass into the gas enclosure and the combination of the glass electrode, grid and window is light transparent such that the details of the source which is imaged with high resolution and sensitivity by the sparks produced can be observed visually as well. The source can be viewed directly, electronically counted or integrated over time using photographic methods. A significant increase in sensitivity over other alpha particle detectors is observed, and the device has very low sensitivity to gamma or beta emissions which might otherwise appear as noise on the alpha particle signal.

  15. Event counting alpha detector

    DOEpatents

    Bolton, Richard D.; MacArthur, Duncan W.

    1996-01-01

    An electrostatic detector for atmospheric radon or other weak sources of alpha radiation. In one embodiment, nested enclosures are insulated from one another, open at the top, and have a high voltage pin inside and insulated from the inside enclosure. An electric field is produced between the pin and the inside enclosure. Air ions produced by collision with alpha particles inside the decay volume defined by the inside enclosure are attracted to the pin and the inner enclosure. With low alpha concentrations, individual alpha events can be measured to indicate the presence of radon or other alpha radiation. In another embodiment, an electrical field is produced between parallel plates which are insulated from a single decay cavity enclosure.

  16. Event counting alpha detector

    DOEpatents

    Bolton, R.D.; MacArthur, D.W.

    1996-08-27

    An electrostatic detector is disclosed for atmospheric radon or other weak sources of alpha radiation. In one embodiment, nested enclosures are insulated from one another, open at the top, and have a high voltage pin inside and insulated from the inside enclosure. An electric field is produced between the pin and the inside enclosure. Air ions produced by collision with alpha particles inside the decay volume defined by the inside enclosure are attracted to the pin and the inner enclosure. With low alpha concentrations, individual alpha events can be measured to indicate the presence of radon or other alpha radiation. In another embodiment, an electrical field is produced between parallel plates which are insulated from a single decay cavity enclosure. 6 figs.

  17. Alpha-particle diagnostics

    SciTech Connect

    Young, K.M.

    1991-01-01

    This paper will focus on the state of development of diagnostics which are expected to provide the information needed for {alpha}- physics studies in the future. Conventional measurement of detailed temporal and spatial profiles of background plasma properties in DT will be essential for such aspects as determining heating effectiveness, shaping of the plasma profiles and effects of MHD, but will not be addressed here. This paper will address (1) the measurement of the neutron source, and hence {alpha}-particle birth profile, (2) measurement of the escaping {alpha}-particles and (3) measurement of the confined {alpha}-particles over their full energy range. There will also be a brief discussion of (4) the concerns about instabilities being generated by {alpha}-particles and the methods necessary for measuring these effects. 51 refs., 10 figs.

  18. {alpha} resonance structure in {sup 11}B studied via resonant scattering of {sup 7}Li+{alpha}

    SciTech Connect

    Yamaguchi, H.; Hashimoto, T.; Hayakawa, S.; Binh, D. N.; Kahl, D.; Kubono, S.; Wakabayashi, Y.; Kawabata, T.; Teranishi, T.

    2011-03-15

    A new measurement of {alpha} resonant scattering on {sup 7}Li was performed over the excitation energy of 10.2-13.0 MeV in {sup 11}B at the low-energy RI beam facility CNS Radioactive Ion Beam separator (CRIB) of the Center for Nuclear Study (CNS), University of Tokyo. The excitation function of {sup 7}Li+{alpha} at 180 deg. in the center-of-mass system was successfully measured for the first time with the inverse kinematics method, providing important information on the {alpha} cluster structure in {sup 11}B and the reaction rate of {sup 7}Li({alpha},{gamma}), which is relevant to the {sup 11}B production in the {nu} process in core-collapse supernovae. The excitation function of the {sup 7}Li({alpha},p) reaction cross section for 11.7-13.1 MeV was also measured.

  19. Reexamination of the {alpha}-{alpha}''fishbone'' potential

    SciTech Connect

    Day, J. P.; McEwen, J. E.; Elhanafy, M.; Smith, E.; Woodhouse, R.; Papp, Z.

    2011-09-15

    The fishbone potential of composite particles simulates the Pauli effect by nonlocal terms. We determine the {alpha}-{alpha} fishbone potential by simultaneously fitting to two-{alpha} resonance energies, experimental phase shifts, and three-{alpha} binding energies. We found that, essentially, a simple Gaussian can provide a good description of two-{alpha} and three-{alpha} experimental data without invoking three-body potentials.

  20. Electron transfer in acetohydroxy acid synthase as a side reaction of catalysis. Implications for the reactivity and partitioning of the carbanion/enamine form of (alpha-hydroxyethyl)thiamin diphosphate in a "nonredox" flavoenzyme.

    PubMed

    Tittmann, Kai; Schröder, Kathrin; Golbik, Ralph; McCourt, Jennifer; Kaplun, Alexander; Duggleby, Ronald G; Barak, Ze'ev; Chipman, David M; Hübner, Gerhard

    2004-07-13

    Acetohydroxy acid synthases (AHAS) are thiamin diphosphate- (ThDP-) and FAD-dependent enzymes that catalyze the first common step of branched-chain amino acid biosynthesis in plants, bacteria, and fungi. Although the flavin cofactor is not chemically involved in the physiological reaction of AHAS, it has been shown to be essential for the structural integrity and activity of the enzyme. Here, we report that the enzyme-bound FAD in AHAS is reduced in the course of catalysis in a side reaction. The reduction of the enzyme-bound flavin during turnover of different substrates under aerobic and anaerobic conditions was characterized by stopped-flow kinetics using the intrinsic FAD absorbance. Reduction of enzyme-bound FAD proceeds with a net rate constant of k' = 0.2 s(-1) in the presence of oxygen and approximately 1 s(-1) under anaerobic conditions. No transient flavin radicals are detectable during the reduction process while time-resolved absorbance spectra are recorded. Reconstitution of the binary enzyme-FAD complex with the chemically synthesized intermediate 2-(hydroxyethyl)-ThDP also results in a reduction of the flavin. These data provide evidence for the first time that the key catalytic intermediate 2-(hydroxyethyl)-ThDP in the carbanionic/enamine form is not only subject to covalent addition of 2-keto acids and an oxygenase side reaction but also transfers electrons to the adjacent FAD in an intramolecular redox reaction yielding 2-acetyl-ThDP and reduced FAD. The detection of the electron transfer supports the idea of a common ancestor of acetohydroxy acid synthase and pyruvate oxidase, a homologous ThDP- and FAD-dependent enzyme that, in contrast to AHASs, catalyzes a reaction that relies on intercofactor electron transfer.

  1. A model reaction assesses contribution of H-tunneling and coupled motions to enzyme catalysis.

    PubMed

    Liu, Qi; Zhao, Yu; Hammann, Blake; Eilers, James; Lu, Yun; Kohen, Amnon

    2012-08-17

    To assess the contribution of physical features to enzyme catalysis, the enzymatic reaction has to be compared to a relevant uncatalyzed reaction. While such comparisons have been conducted for some hydrolytic and radical reactions, it is most challenging for biological hydride transfer and redox reactions in general. Here, the same experimental tools used to study the H-tunneling and coupled motions for enzymatic hydride transfer between two carbons were used in the study of an uncatalyzed model reaction. The enzymatic oxidations of benzyl alcohol and its substituted analogues mediated by alcohol dehydrogenases were compared to the oxidations by 9-phenylxanthylium cation (PhXn(+)). The PhXn(+) serves as an NAD(+) model, while the solvent, acetonitrile, models the protein environment. Experimental comparisons included linear free energy relations with Hammett reaction constant (ρ) of zero versus -2.7; temperature-independent versus temperature-dependent primary KIEs; deflated secondary KIEs with deuteride transfer (i.e., primary-secondary coupled motion) versus no coupling between secondary KIEs and H- or D-transfer; and large versus small secondary KIEs for the enzymatic versus uncatalyzed alcohol oxidation. Some of the differences may come from differences in the order of microscopic steps between the catalyzed versus uncatalyzed reactions. However, several of these comparative experiments indicate that in contrast to the uncatalyzed reaction the transition state of the enzymatic reaction is better reorganized for H-tunneling and its H-donor is better rehybridized prior to the C-H→C transfer. These findings suggest an important role for these physical features in enzyme catalysis.

  2. Chemical synthesis of (22E)-3alpha,6alpha,7alpha,12alpha-Tetrahydroxy-5beta-chol-22-en-24-oic acid and its N-acylamidated conjugates with glycine or taurine: precursors of the [22,23-(3)H] labelled tracers.

    PubMed

    Ogawa, Shoujiro; Adachi, Yuuki; Kakiyama, Genta; Shimada, Miki; Mano, Nariyasu; Goto, Junichi; Iida, Takashi

    2010-08-01

    (22E)-3alpha,6alpha,7alpha,12alpha-Tetrahydroxy-5beta-chol-22-en-24-oic acid and its N-acylamidated conjugates with glycine or taurine were synthesized from cholic acid. The key reactions employed are: 1) degradation of the side chain in intermediary C(24) 3alpha,6alpha,7alpha,12alpha-tetrahydroxylated bile acid to the corresponding C(22) 23,24-dinor-aldehyde, followed by Wittig reaction with methyl (triphenylphosphoranylidene)acetate and 2) N-acylamidation of the unconjugated tetrahydroxy-Delta(22)-5beta-cholenoic acid with glycine (or taurine) in the presence of diethylphosphorocyanide and triethylamine as coupling reagents.

  3. [Pharmacological significance of alpha lipoic acid in up to date treatment of diabetic neuropathy].

    PubMed

    Becić, Fahir; Kapić, Elvedina; Rakanović-Todić, Maida

    2008-01-01

    Alpha lipoic acid is important intramolecular redox system. It is coenzyme of piruvate dehydrogenase and ketoglutarate dehydrogenase. Alpha lipoic acid has enzymatic and cytoprotective effect. It has key role in citric acid cycle, as a coenzyme. Therapeutic efficacy of alpha lipoic acid in diabetic neuropathy is based on reaction with free radicals and lipophylic antioxydans properties. Clinical studies results showed efficacy and safety of alpha liponic acid application in patients with diabetic neuropathy.

  4. The status of alpha-particle diagnostics

    SciTech Connect

    Young, K.M.; Johnson, D.W.

    1992-08-01

    There is a flurry of activity to complete alpha-particle diagnostics so that they can undergo some experimental testing in DT plasmas on JET or TFTR prior to implementation on ITER. Successful measurements of escaping charged fusion products have been made in DD plasmas, and the {alpha}-particle source can be well characterized by neutron profile measurement. These methods can be extrapolated to DT plasmas. Measurement of the confined {alpha}-particles requires a new technique. Collective Thomson scattering, methods involving charge-exchange interactions and nuclear reactions with impurities will be discussed. Some assessment is given of the capabilities of these techniques, bearing in mind the potential for their use in the physics phase of the ITER program.

  5. Alpha One Foundation

    MedlinePlus

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  6. Metathesis process for preparing an alpha, omega-functionalized olefin

    DOEpatents

    Burdett, Kenneth A.; Mokhtarzadeh, Morteza; Timmers, Francis J.

    2010-10-12

    A cross-metathesis process for preparing an .alpha.,.omega.-functionalized olefin, such as methyl 9-decenoate, and an .alpha.-olefin having three or more carbon atoms, such as 1-decene. The process involves contacting in a first reaction zone an .alpha.-functionalized internal olefin, such as methyl oleate, and an .alpha.-olefinic monomer having three or more carbon atoms, such as 1-decene, with a first metathesis catalyst to prepare an effluent stream containing the .alpha.,.omega.-functionalized olefin, such as methyl 9-decenoate, an unfunctionalized internal olefin, such as 9-octadecene, unconverted reactant olefins, and optionally, an .alpha.,.omega.-difunctionalized internal olefinic dimer, such as dimethyl 9-octadecen-1,18-dioate; separating said effluent streams; then contacting in a second reaction zone the unfunctionalized internal olefin with ethylene in the presence of a second metathesis catalyst to obtain a second product effluent containing the .alpha.-olefinic monomer having three or more carbon atoms; and cycling a portion of the .alpha.-olefinic monomer stream(s) to the first zone.

  7. alpha-Terpineol from hydration of crude sulfate turpentine oil.

    PubMed

    Pakdel, H; Sarron, S; Roy, C

    2001-09-01

    Hydration of alpha-pinene under various conditions was studied and compared with the literature. Optimal reaction conditions have been established for the hydration of alpha-pinene and crude turpentine oil in the absence of catalyst and using a low volume of acetone. A detailed reaction product analysis is reported. The main hydration product, alpha-terpineol, was obtained at a yield of 67 wt % of the initial alpha-pinene by reacting with 15% aqueous sulfuric acid and an excess of acetone in an oil bath heated to 80-85 degrees C over the course of 4 h. A progressive transformation of alpha-terpineol to 4-(2-hydroxypropyl)-1-methylcyclohexanol (1,8-terpine) takes place as the hydration time exceeds 4 h. A crude turpentine oil sample was also hydrated under conditions similar to those of alpha-pinene. The alpha-terpineol yield was 77 wt % of the initial alpha-pinene in the crude turpentine oil. The chemical analysis of the crude turpentine oil before and after hydration was carried out, and the distribution of the products was discussed.

  8. Coaching the alpha male.

    PubMed

    Ludeman, Kate; Erlandson, Eddie

    2004-05-01

    Highly intelligent, confident, and successful, alpha males represent about 70% of all senior executives. Natural leaders, they willingly take on levels of responsibility most rational people would find overwhelming. But many of their quintessential strengths can also make alphas difficult to work with. Their self-confidence can appear domineering. Their high expectations can make them excessively critical. Their unemotional style can keep them from inspiring their teams. That's why alphas need coaching to broaden their interpersonal tool kits while preserving their strengths. Drawing from their experience coaching more than 1,000 senior executives, the authors outline an approach tailored specifically for the alpha. Coaches get the alpha's attention by inundating him with data from 360-degree feedback presented in ways he will find compelling--both hard-boiled metrics and vivid verbatim comments from colleagues about his strengths and weaknesses. A 360-degree assessment is a wake-up call for most alphas, providing undeniable proof that their behavior doesn't work nearly as well as they think it does. That paves the way for a genuine commitment to change. In order to change, the alpha must venture into unfamiliar--and often uncomfortable--psychological territory. He must admit vulnerability, accept accountability not just for his own work for others', connect with his underlying emotions, learn to motivate through a balance of criticism and validation, and become aware of unproductive behavior patterns. The goal of executive coaching is not simply to treat the alpha as an individual problem but to improve the entire team dynamic. Initial success creates an incentive to persevere, and the virtuous cycle reverberates throughout the entire organization.

  9. alpha2-Adrenoreceptor antagonists.

    PubMed

    Mayer, P; Imbert, T

    2001-06-01

    A review of the literature relating to the therapeutic potential of alpha2-adrenoceptor antagonists published between 1990 and 2000 is presented. Although extensively studied since the early 1970s in a wide spectrum of therapeutic applications, the distinction of alpha2-adrenoceptor subtypes and some emerging evidence concerning new applications in neurodegenerative disorders, such as Alzheimer's and Parkinson's diseases, obesity and schizophrenia, have refreshed an interest in this class of agents.

  10. Summary of alpha-neutron sources in GADRAS.

    SciTech Connect

    Mitchell, Dean James; Thoreson, Gregory G.; Harding, Lee T.

    2012-05-01

    A common source of neutrons for calibration and testing is alpha-neutron material, named for the alpha-neutron nuclear reaction that occurs within. This material contains a long-lived alpha-emitter and a lighter target element. When the alpha particle from the emitter is absorbed by the target, neutrons and gamma rays are released. Gamma Detector Response and Analysis Software (GADRAS) includes built-in alpha-neutron source definitions for AcC, AmB, AmBe, AmF, AmLi, CmC, and PuC. In addition, GADRAS users may create their own alpha-neutron sources by placing valid alpha-emitters and target elements in materials within their one-dimensional models (1DModel). GADRAS has the ability to use pre-built alpha-neutron sources for plotting or as trace-sources in 1D models. In addition, if any material (existing or user-defined) specified in a 1D model contains both an alpha emitter in conjunction with a target nuclide, or there is an interface between such materials, then the appropriate neutron-emission rate from the alpha-neutron reaction will be computed. The gamma-emissions from these sources are also computed, but are limited to a subset of nine target nuclides. If a user has experimental data to contribute to the alpha-neutron gamma emission database, it may be added directly or submitted to the GADRAS developers for inclusion. The gadras.exe.config file will be replaced when GADRAS updates are installed, so sending the information to the GADRAS developers is the preferred method for updating the database. This is also preferable because it enables other users to benefit from your efforts.

  11. Maximum Torque and Momentum Envelopes for Reaction Wheel Arrays

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Reynolds, Reid G.; Liu, Frank X.; Lebsock, Kenneth L.

    2009-01-01

    Spacecraft reaction wheel maneuvers are limited by the maximum torque and/or angular momentum that the wheels can provide. For an n-wheel configuration, the torque or momentum envelope can be obtained by projecting the n-dimensional hypercube, representing the domain boundary of individual wheel torques or momenta, into three dimensional space via the 3xn matrix of wheel axes. In this paper, the properties of the projected hypercube are discussed, and algorithms are proposed for determining this maximal torque or momentum envelope for general wheel configurations. Practical strategies for distributing a prescribed torque or momentum among the n wheels are presented, with special emphasis on configurations of four, five, and six wheels.

  12. Excitation function and yield for the (103)Rh(d,2n)(103)Pd nuclear reaction: Optimization of the production of palladium-103.

    PubMed

    Manenti, Simone; Alí Santoro, María Del Carmen; Cotogno, Giulio; Duchemin, Charlotte; Haddad, Ferid; Holzwarth, Uwe; Groppi, Flavia

    2017-03-06

    Deuteron-induced nuclear reactions for the generation of (103)Pd were investigated using the stacked-foil activation technique on rhodium targets at deuteron energies up to Ed=33MeV. The excitation functions of the reactions (103)Rh(d,xn)(101,103)Pd, (103)Rh(d,x)(100g,cum,101m,g,102m,g)Rh and (103)Rh(d,2p)(103)Ru have been measured, and the Thick-Target Yield for (103)Pd has been calculated.

  13. Molecular cloning and expression of cDNAs encoding human alpha-mannosidase II and a previously unrecognized alpha-mannosidase IIx isozyme.

    PubMed Central

    Misago, M; Liao, Y F; Kudo, S; Eto, S; Mattei, M G; Moremen, K W; Fukuda, M N

    1995-01-01

    Golgi alpha-mannosidase II (alpha-MII) is an enzyme involved in the processing of N-linked glycans. Using a previously isolated murine cDNA clone as a probe, we have isolated cDNA clones encompassing the human alpha-MII cDNA open reading frame and initiated isolation of human genomic clones. During the isolation of genomic clones, genes related to that encoding alpha-MII were isolated. One such gene was found to encode an isozyme, designated alpha-MIIx. A 5-kb cDNA clone encoding alpha-MIIx was then isolated from a human melanoma cDNA library. However, comparison between alpha-MIIx and alpha-MII cDNAs suggested that the cloned cDNA encodes a truncated polypeptide with 796 amino acid residues, while alpha-MII consists of 1144 amino acid residues. To reevaluate the sequence of alpha-MIIx cDNA, polymerase chain reaction (PCR) was performed with lymphocyte mRNAs. Comparison of the sequence of PCR products with the alpha-MIIx genomic sequence revealed that alternative splicing of the alpha-MIIx transcript can result in an additional transcript encoding a 1139-amino acid polypeptide. Northern analysis showed transcription of alpha-MIIx in various tissues, suggesting that the alpha-MIIx gene is a housekeeping gene. COS cells transfected with alpha-MIIx cDNA containing the full-length open reading frame showed an increase of alpha-mannosidase activity. The alpha-MIIx gene was mapped to human chromosome 15q25, whereas the alpha-MII gene was mapped to 5q21-22. Images Fig. 5 PMID:8524845

  14. Alpha particle induced reactions on natCr up to 39 MeV: Experimental cross-sections, comparison with theoretical calculations and thick target yields for medically relevant 52gFe production

    NASA Astrophysics Data System (ADS)

    Hermanne, A.; Adam Rebeles, R.; Tárkányi, F.; Takács, S.

    2015-08-01

    Thin natCr targets were obtained by electroplating, using 23.75 μm Cu foils as backings. In five stacked foil irradiations, followed by high resolution gamma spectroscopy, the cross sections for production of 52gFe, 49,51cumCr, 52cum,54,56cumMn and 48cumV in Cr and 61Cu,68Ga in Cu were measured up to 39 MeV incident α-particle energy. Reduced uncertainty is obtained by simultaneous remeasurement of the natCu(α,x)67,66Ga monitor reactions over the whole energy range. Comparisons with the scarce literature values and results from the TENDL-2013 on-line library, based on the theoretical code family TALYS-1.6, were made. A discussion of the production routes for 52gFe with achievable yields and contamination rates was made.

  15. alpha-DNA II. Synthesis of unnatural alpha-anomeric oligodeoxyribonucleotides containing the four usual bases and study of their substrate activities for nucleases.

    PubMed Central

    Morvan, F; Rayner, B; Imbach, J L; Thenet, S; Bertrand, J R; Paoletti, J; Malvy, C; Paoletti, C

    1987-01-01

    This paper describes for the first time the synthesis of alpha-oligonucleotides containing the four usual bases. Two unnatural hexadeoxyribonucleotides: alpha-[d(CpApTpGpCpG)] and alpha-[d(CpGpCpApTpG)], consisting only of alpha-anomeric nucleotide units, were obtained by an improved phosphotriester method, in solution. Starting material was the four base-protected alpha-deoxyribonucleosides 3a-d. Pyrimidine alpha-deoxynucleosides 3a and 3b were prepared by self-anomerization reactions followed by selective deprotection of sugar hydroxyles, while the two purine alpha-deoxynucleosides 3c and 3d were prepared by glycosylation reactions. In the case of guanine alpha-nucleoside derivative a supplementary base-protecting group: N,N-diphenylcarbamoyl was introduced on O6-position in order to avoid side-reactions during oligonucleotide assembling. The hexadeoxynucleotide alpha-[d(CpApTpGpCpG)] was tested as substrate of selected endo- and exonucleases. In conditions where the natural corresponding beta-hexamer was completely degradated by nuclease S1 and calf spleen phosphodiesterase, the alpha-oligonucleotide remained almost intact. PMID:3575096

  16. Pre-nitridation induced In incorporation in InxGa1-xN nanorods on Si(111) grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    De, Arpan; Tangi, Malleswararao; Shivaprasad, S. M.

    2015-07-01

    We address the issue of obtaining high quality green emitting InGaN nanorods without any phase separation. Role of pre-nitridation of the Si(111) substrate and growth, temperature on the morphology, structural and optical properties of InxGa1-xN films grown by plasma assisted molecular beam epitaxy, has been studied. The nitrogen rich growth environment and surface nitridation results in the formation of vertically well-aligned single crystalline nanorods that are coalesced and isolated at 400 °C and 500 °C, respectively. In incorporation is also seen to be enhanced to ≈28% at 400 °C to yield a stable green emission, while the nanorods grown at 500 °C show blue band-edge emission. The orientation, phase separations, and optical properties characterized by Reflection High Energy Electron Diffraction, Field Emission Scanning Electron Microscopy, high resolution x-ray diffraction, x-ray photoelectron spectroscopy, and photoluminescence are corroborated to understand the underlying mechanism. The study optimizes conditions to grow high quality catalyst-free well-aligned InGaN rods on nitrided Si surface, whose band-edge emission can be tuned from blue to green by sheer control of the substrate temperature.

  17. Phase separation in single In(x)Ga(1-x)N nanowires revealed through a hard X-ray synchrotron nanoprobe.

    PubMed

    Segura-Ruiz, J; Martínez-Criado, G; Denker, C; Malindretos, J; Rizzi, A

    2014-03-12

    In this work, we report on the composition, short- and long-range structural order of single molecular beam epitaxy grown In(x)Ga(1-x)N nanowires using a hard X-ray synchrotron nanoprobe. Nano-X-ray fluorescence mapping reveals an axial and radial heterogeneous elemental distribution in the single wires with Ga accumulation at their bottom and outer regions. Polarization-dependent nano-X-ray absorption near edge structure demonstrates that despite the elemental modulation, the tetrahedral order around the Ga atoms remains along the nanowires. Nano-X-ray diffraction mapping on single nanowires shows the existence of at least three different phases at their bottom: an In-poor shell and two In-rich phases. The alloy homogenizes toward the top of the wires, where a single In-rich phase is observed. No signatures of In-metallic precipitates are observed in the diffraction spectra. The In-content along the single nanowires estimated from X-ray fluorescence and diffraction data are in good agreement. A rough picture of these phenomena is briefly presented. We anticipate that this methodology will contribute to a greater understanding of the underlying growth concepts not only of nanowires but also of many nanostructures in materials science.

  18. Simulation of the EXAFS and Raman spectra of InxGa1-xN utilizing the equation of motion routine of FEFF8.

    NASA Astrophysics Data System (ADS)

    Katsikini, M.; Pinakidou, F.; Paloura, E. C.; Arvanitidis, J.; Ves, S.; Reinholz, U.; Papadomanolaki, E.; Iliopoulos, E.

    2016-05-01

    A combined analysis of EXAFS and Raman spectra is applied for the study of InxGa1-xN alloys with 0.3

  19. Spontaneous core–shell elemental distribution in In-rich In(x)Ga1-xN nanowires grown by molecular beam epitaxy.

    PubMed

    Gómez-Gómez, M; Garro, N; Segura-Ruiz, J; Martinez-Criado, G; Cantarero, A; Mengistu, H T; García-Cristóbal, A; Murcia-Mascarós, S; Denker, C; Malindretos, J; Rizzi, A

    2014-02-21

    The elemental distribution of self-organized In-rich In(x)Ga1-xN nanowires grown by plasma-assisted molecular beam epitaxy has been investigated using three different techniques with spatial resolution on the nanoscale. Two-dimensional images and elemental profiles of single nanowires obtained by x-ray fluorescence and energy-dispersive x-ray spectroscopy, respectively, have revealed a radial gradient in the alloy composition of each individual nanowire. The spectral selectivity of resonant Raman scattering has been used to enhance the signal from very small volumes with different elemental composition within single nanowires. The combination of the three techniques has provided sufficient sensitivity and spatial resolution to prove the spontaneous formation of a core–shell nanowire and to quantify the thicknesses and alloy compositions of the core and shell regions. A theoretical model based on continuum elastic theory has been used to estimate the strain fields present in such inhomogeneous nanowires. These results suggest new strategies for achieving high quality nonpolar heterostructures.

  20. Pulsed laser deposition of novel nitride solid solution films Ni xTi 1- xN y on MgO(0 0 1)

    NASA Astrophysics Data System (ADS)

    Sakamoto, Koyo; Inumaru, Kei; Yamanaka, Shoji

    2002-10-01

    A novel nitride solid solution, Ni xTi 1- xN y (0≤ x≤0.31, 0.59≤ y≤1) was grown on MgO(0 0 1) using a pulsed laser deposition (PLD) method combined with RF nitrogen radical irradiation. Compressed disks made of mixtures of titanium hydride and nickel metal were used as the PLD targets. Simple Ti-Ni alloyed targets gave no crystalline nitride. High-resolution X-ray diffraction reciprocal space mapping revealed that the deposited films were epitaxially grown on MgO(0 0 1) and that the lattice of the films shrunk to fit the lattice of MgO(0 0 1) in the plane. The lattice constant perpendicular to the plane decreased linearly as the Ni content increased up to x=0.31, demonstrating the incorporation of Ni atoms into the crystal structure. These thin films were metallic conductors. X-ray photoelectron spectra showed that the substitution of Ti for Ni brought about the formation of large amounts of nitrogen vacancies.

  1. Polar catastrophe and the structure of KT a1 - xN bxO3 surfaces: Results from elastic and inelastic helium atom scattering

    NASA Astrophysics Data System (ADS)

    Flaherty, F. A.; Trelenberg, T. W.; Li, J. A.; Fatema, R.; Skofronick, J. G.; Van Winkle, D. H.; Safron, S. A.; Boatner, L. A.

    2015-07-01

    The structure and dynamics of cleaved (001 ) surfaces of potassium tantalates doped with niobium, KT a1 - xN bxO3 (KTN), with x ranging from 0 % to 30 % , were measured by helium atom scattering (HAS). Through HAS time-of-flight (TOF) experiments, a dispersionless branch (Einstein phonon branch) with energy of 13 -14 meV was observed across the surface Brillouin zone in all samples. When this observation is combined with the results from earlier experimental and theoretical studies on these materials, a consistent picture of the stable surface structure emerges: After cleaving the single-crystal sample, the surface should be composed of equal areas of KO and Ta O2/Nb O2 terraces. The data, however, suggest that K+ and O2 - ions migrate from the bulk to the surface, forming a charged KO lattice that is neutralized primarily by additional K+ ions bridging pairs of surface oxygens. This structural and dynamic modification at the (001 ) surface of KTN appears due to its formally charged KO (-1 ) and Ta O2/Nb O2(+1 ) layers and avoids a "polar catastrophe." This behavior is contrasted with the (001 ) surface behavior of the fluoride perovskite KMn F3 with its electrically neutral KF and Mn F2 layers.

  2. SEMICONDUCTOR PHYSICS: Pressure influence on bound polarons in a strained wurtzite GaN/AlxGa1-xN heterojunction under an electric field

    NASA Astrophysics Data System (ADS)

    Min, Zhang; Shiliang, Ban

    2010-05-01

    The binding energies of bound polarons near the interface of a strained wurtzite GaN/AlxGa1-xN heterojunction are studied by using a modified LLP variational method and a simplified coherent potential approximation under hydrostatic pressure and an external electric field. Considering the biaxial strain due to lattice mismatch or epitaxial growth, the uniaxial strain effects and the influences of the electron-phonon interaction as well as impurity-phonon interaction including the effects of interface-optical phonon modes and half-space phonon modes, the binding energies as functions of pressure, the impurity position, areal electron density and the phonon effect on the Stark energy shift are investigated. The numerical result shows that the contributions from the interface optical phonon mode with higher frequency and the LO-like half space mode to the binding energy and the Stark energy shift are important and obviously increase with increasing hydrostatic pressure, whereas the interface optical phonon mode with lower frequency and the TO-like half space mode are extremely small and are insensitive to the impurity position and hydrostatic pressure. It is also shown that the conductive band bending should not be neglected.

  3. Magnetotransport properties of nearly-free electrons in two-dimensional hexagonal metals and application to the Mn +1A Xn phases

    NASA Astrophysics Data System (ADS)

    Ouisse, T.; Shi, L.; Piot, B. A.; Hackens, B.; Mauchamp, V.; Chaussende, D.

    2015-07-01

    We propose a general, yet simple model for describing the weak field magnetotransport properties of nearly-free electrons in two-dimensional hexagonal metals. We modify this model so as to apply it to the magnetotransport properties of the Mn +1A Xn phases, a particular class of nanolamellar carbides and nitrides. We argue that the values of the in-plane Hall coefficient and the in-plane parabolic magnetoresistance are due to the specific shape of the Fermi surface of almost two-dimensional hole and electron bands. If the contribution of the electron pockets to in-plane resistivity is often (but not always) predicted to be a minor one, in contrast, both holes and electrons should substantially contribute to the overall value of the in-plane Hall coefficient. The relevance of our model is supported by elementary considerations and a set of experimental data obtained from single crystals of V2AlC and C r2AlC . In particular, we obtain a high ratio between the in-plane (ρa b) and parallel to the c axis (ρc) resistivities.

  4. Optical doping of Al{sub x}Ga{sub 1-x}N compounds by ion implantation of Tm ions

    SciTech Connect

    Fialho, M.; Lorenz, K.; Magalhaes, S.; Redondo-Cubero, A.; Rodrigues, J.; Santos, N. F.; Monteiro, T.; Alves, E.

    2012-11-06

    Al{sub x}Ga{sub 1-x}N (0 axis for samples with AlN contents of 0.15 and 0.77 suggest a relation between the AlN content and Tm specific sites in the lattice. Rapid thermal annealing treatments under N{sub 2} ambient were performed to remove damage and promote optical activation of rare earth intra-4f{sup n} transitions. After annealing the observed intraionic emissions of Tm{sup 3+} ions were characterized by photoluminescence.

  5. Spontaneous core-shell elemental distribution in In-rich InxGa1-xN nanowires grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Gómez-Gómez, M.; Garro, N.; Segura-Ruiz, J.; Martinez-Criado, G.; Cantarero, A.; Mengistu, H. T.; García-Cristóbal, A.; Murcia-Mascarós, S.; Denker, C.; Malindretos, J.; Rizzi, A.

    2014-02-01

    The elemental distribution of self-organized In-rich InxGa1-xN nanowires grown by plasma-assisted molecular beam epitaxy has been investigated using three different techniques with spatial resolution on the nanoscale. Two-dimensional images and elemental profiles of single nanowires obtained by x-ray fluorescence and energy-dispersive x-ray spectroscopy, respectively, have revealed a radial gradient in the alloy composition of each individual nanowire. The spectral selectivity of resonant Raman scattering has been used to enhance the signal from very small volumes with different elemental composition within single nanowires. The combination of the three techniques has provided sufficient sensitivity and spatial resolution to prove the spontaneous formation of a core-shell nanowire and to quantify the thicknesses and alloy compositions of the core and shell regions. A theoretical model based on continuum elastic theory has been used to estimate the strain fields present in such inhomogeneous nanowires. These results suggest new strategies for achieving high quality non-polar heterostructures.

  6. Cloning and functional expression of a cDNA encoding coffee bean alpha-galactosidase.

    PubMed

    Zhu, A; Goldstein, J

    1994-03-25

    Purified coffee bean alpha-galactosidase (alpha Gal) has been used for removing terminal alpha-galactose residues from the glyco-conjugates at the red cell surface, in studies of blood group conversion. Here, we report the isolation and sequence of the full-length clone for coffee bean alpha Gal by using the polymerase chain reaction (PCR) and rapid amplification of cDNA ends (RACE) techniques. The cDNA clone (1.4 kb) contains a single open reading frame which encodes a protein of 378 amino acids (aa). Its authenticity is confirmed by perfect alignment of aa sequences obtained from purified coffee bean alpha Gal, and by immune reaction with the antibody raised against the enzyme. Furthermore, the protein produced in insect cells shows enzymatic activity towards a synthetic alpha Gal substrate, p-nitro-phenyl-alpha-galactopyranoside.

  7. Alpha irradiation modeling

    SciTech Connect

    Keeton, S C; Mount, M E

    1999-03-26

    With the end of the Cold War and the associated limitations imposed on the nuclear weapons stockpile by strategic arms treaties, much has changed in the stockpile stewardship program. Weapons that were originally designed for stockpile lives on the order of 15 to 20 years are now being evaluated for much longer periods: in some cases as much as 60 years. As such, issues that were once considered to be of no consequence are being reexamined. Among these is the extent of the radiation dose received by secondary organics over time that results from the intrinsic alpha source of the weapon components. This report describes the results of work performed to estimate the alpha radiation deposition in the organic components of an LLNL system at specific points in its stockpile life. Included are discussions of the development of the intrinsic time- and energy-dependent alpha source term per unit mass, estimation of the effective source and absorber material thicknesses, development of a simplified model for the total intrinsic alpha source term and energy deposition in the absorber, and the alpha radiation deposition in the organic components of a selected LLNL weapon.

  8. Evidence for Alpha Receptors in the Human Ureter

    NASA Astrophysics Data System (ADS)

    Madeb, Ralph; Knopf, Joy; Golijanin, Dragan; Bourne, Patricia; Erturk, Erdal

    2007-04-01

    An immunohistochemical and western blot expression analysis of human ureters was performed in order to characterize the alpha-1-adrenergic receptor distribution along the length of the human ureteral wall. Mapping the distribution will assist in understanding the potential role alpha -1-adrenergic receptors and their subtype density might have in the pathophysiology of ureteral colic and stone passage. Patients diagnosed with renal cancer or bladder cancer undergoing nephrectomy, nephroureterectomy, or cystectomy had ureteral specimens taken from the proximal, mid, distal and tunneled ureter. Tissues were processed for fresh frozen examination and fixed in formalin. None of the ureteral specimens were involved with cancer. Serial histologic sections and immunohistochemical studies were performed using antibodies specific for alpha-1-adrenergic receptor subtypes (alpha 1a, alpha 1b, alpha 1d). The sections were examined under a light microscope and scored as positive or negative. In order to validate and quantify the alpha receptor subtypes along the human ureter. Western blotting techniques were applied. Human ureter stained positively for alpha -1-adrenergic receptors. Immunostaining appeared red, with intense reaction in the smooth muscle of the ureter and endothelium of the neighboring blood vessels. There was differential expression between all the receptors with the highest staining for alpha-1D subtype. The highest protein expression for all three subtypes was in the renal pelvis and decreased with advancement along the ureter to the distal ureter. At the distal ureter, there was marked increase in expression as one progressed towards the ureteral orifice. The same pattern of protein expression was exhibited for all three alpha -1-adrenergic receptor subtypes. We provide preliminary evidence for the ability to detect and quantify the alpha-1-receptor subtypes along the human ureter which to the best of our knowledge has never been done with

  9. ALPHA MIS: Reference manual

    SciTech Connect

    Lovin, J.K.; Haese, R.L.; Heatherly, R.D.; Hughes, S.E.; Ishee, J.S.; Pratt, S.M.; Smith, D.W.

    1992-02-01

    ALPHA is a powerful and versatile management information system (MIS) initiated and sponsored and by the Finance and Business Management Division of Oak Ridge National Laboratory, who maintain and develop it in concert with the Business Systems Division for its Information Center. A general-purpose MIS, ALPHA allows users to access System 1022 and System 1032 databases to obtain and manage information. From a personal computer or a data terminal, Energy Systems employees can use ALPHA to control their own report reprocessing. Using four general commands (Database, Select, Sort, and Report) they can (1) choose a mainframe database, (2) define subsets within it, (3) sequentially order a subset by one or more variables, and (4) generate a report with their own or a canned format.

  10. The Apollo Alpha Spectrometer.

    NASA Technical Reports Server (NTRS)

    Jagoda, N.; Kubierschky, K.; Frank, R.; Carroll, J.

    1973-01-01

    Located in the Science Instrument Module of Apollo 15 and 16, the Alpha Particle Spectrometer was designed to detect and measure the energy of alpha particles emitted by the radon isotopes and their daughter products. The spectrometer sensor consisted of an array of totally depleted silicon surface barrier detectors. Biased amplifier and linear gate techniques were utilized to reduce resolution degradation, thereby permitting the use of a single 512 channel PHA. Sensor identification and in-flight radioactive calibration were incorporated to enhance data reduction.

  11. Contemporary Issues in Ultra-Low Alpha Particle Counting

    NASA Astrophysics Data System (ADS)

    Gordon, Michael

    Single-Event Upsets (SEU) in CMOS devices are caused by the passage of ionizing radiation either from terrestrial neutrons or from the natural alpha particle radiation within the materials surrounding the transistors. Interactions of the neutrons with the silicon cause spallation reactions which emit energetic highly ionizing elements. Alpha particles, on the other hand, can upset the devices through direct ionization rather than through a nuclear reaction as in the case of the neutrons. In order to minimize the alpha-particle component of SEU, the radiation from the materials within a distance 100 μm of the transistors, currently needs to have an alpha particle emissivity of less than 2 alpha particles per khr per square centimeter. Many alpha particle detectors have background levels that are larger than this, which can make these measurements inaccurate and time consuming. This talk will discuss what is involved in making alpha particle emissivity measurements of materials used in the semiconductor industry using an ultra-low background commercially-available ionization detector. Detector calibration and efficiency, radon adsorption on the samples, and the effect of surface charge on electrically insulating samples will be discussed.

  12. Systematic analysis of astrophysical S-factors and thermonuclear reaction rates

    SciTech Connect

    Katsuma, M.

    2008-05-12

    The astrophysical S-factors of the {sup 13}C({alpha},n){sup 16}O, {sup 17}O({alpha},n){sup 20}Ne, {sup 21}Ne({alpha},n){sup 24}Mg and {sup 25}Mg({alpha},n){sup 28}Si reactions are analyzed with DWBA. The gross structures of the experimental data are reproduced by the DWBA calculations. The resulting reaction rates are compared with those in the CF88 and NACRE compilations.

  13. Diabetes and Alpha Lipoic Acid

    PubMed Central

    Golbidi, Saeid; Badran, Mohammad; Laher, Ismail

    2011-01-01

    Diabetes mellitus is a multi-faceted metabolic disorder where there is increased oxidative stress that contributes to the pathogenesis of this debilitating disease. This has prompted several investigations into the use of antioxidants as a complementary therapeutic approach. Alpha lipoic acid, a naturally occurring dithiol compound which plays an essential role in mitochondrial bioenergetic reactions, has gained considerable attention as an antioxidant for use in managing diabetic complications. Lipoic acid quenches reactive oxygen species, chelates metal ions, and reduces the oxidized forms of other antioxidants such as vitamin C, vitamin E, and glutathione. It also boosts antioxidant defense system through Nrf-2-mediated antioxidant gene expression and by modulation of peroxisome proliferator activated receptors-regulated genes. ALA inhibits nuclear factor kappa B and activates AMPK in skeletal muscles, which in turn have a plethora of metabolic consequences. These diverse actions suggest that lipoic acid acts by multiple mechanisms, many of which have only been uncovered recently. In this review we briefly summarize the known biochemical properties of lipoic acid and then discussed the oxidative mechanisms implicated in diabetic complications and the mechanisms by which lipoic acid may ameliorate these reactions. The findings of some of the clinical trials in which lipoic acid administration has been tested in diabetic patients during the last 10 years are summarized. It appears that the clearest benefit of lipoic acid supplementation is in patients with diabetic neuropathy. PMID:22125537

  14. Chemical synthesis of methyl 6'-alpha-maltosyl-alpha-maltotrioside and its use for investigation of the action of starch synthase II.

    PubMed

    Damager, Iben; Olsen, Carl Erik; Blennow, Andreas; Denyer, Kay; Møller, Birger Lindberg; Motawia, Mohammed Saddik

    2003-01-20

    The branched pentasaccharide methyl 6'-alpha-maltosyl-alpha-maltotrioside was chemically synthesised and investigated as a primer for particulate starch synthase II (SSII) using starch granules prepared from the low-amylose pea mutant lam as the enzyme source. For chemical synthesis, the trichloroacetimidate activation method was used to synthesise methyl O-(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl)-(1-->4)-O-(2,3,6-tri-O-benzyl-alpha-D-glucopyranosyl)-(1-->6)-O-[(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl-(1-->4)]-O-(2,3-di-O-benzyl-alpha-D-glucopyranosyl)-(1-->4)-2,3,6-tri-O-benzyl-alpha-D-glucopyranoside, which was then debenzylated to provide the desired branched pentasaccharide methyl 6'-alpha-maltosyl-alpha-maltotrioside as documented by 1H and 13C NMR spectroscopy. Using a large excess of the maltoside, the pentasaccharide was tested as a substrate for starch synthase II (SSII). Both of the non-reducing ends of methyl 6'-alpha-maltosyl-alpha-maltotrioside were extended equally resulting in two hexasaccharide products in nearly equal amounts. Thus, SSII catalyses an equimolar and non-processive elongation reaction of this substrate. Accordingly, the presence of the alpha-1,6 linkages does not dictate a specific structure of the pentasaccharide in which only one of the two non-reducing ends are available for extension.

  15. From Alpha to Omega

    ERIC Educational Resources Information Center

    Czaja, Paul Clement

    2006-01-01

    The Alpha point of the authors' life as a Montessori educator began in 1959, when he was a graduate student studying philosophy at Fordham University in the Bronx, New York. While studying the works of the great American philosopher William James, the author came across the writings of Maria Montessori and immediately became captivated by her…

  16. [alpha]-Oxocarboxylic Acids

    ERIC Educational Resources Information Center

    Kerber, Robert C.; Fernando, Marian S.

    2010-01-01

    Several [alpha]-oxocarboxylic acids play key roles in metabolism in plants and animals. However, there are inconsistencies between the structures as commonly portrayed and the reported acid ionization constants, which result because the acids are predominantly hydrated in aqueous solution; that is, the predominant form is RC(OH)[subscript 2]COOH…

  17. Radial-velocity variations in Alpha Ori, Alpha Sco, and Alpha Her

    SciTech Connect

    Smith, M.A.; Patten, B.M.; Goldberg, L. Computer Sciences Corp., Seabrook, MD Iowa State Univ., Ames )

    1989-12-01

    Radial-velocity observations of Alpha Ori, Alpha Sco A, and Alpha Her A are used to study radial-velocity periodicities in M supergiants. The data refer to several metallic lines in the H-alpha region and to H-alpha itself. It is shown that Alpha Ori and Alpha Sco A have cycle lengths of about 1 yr and semiamplitudes of 2 km/s. It is suggested that many semiregular red supergiant varibles such as Alpha Ori may be heading toward chaos. All three stars show short-term stochastic flucutations with an amplitude of 1-2 km/s. It is found that the long-term variability of H-alpha velocities may be a consequence of intermittent failed ejections. 58 refs.

  18. Synthesis of stabilized alpha-helical peptides.

    PubMed

    Bernal, Federico; Katz, Samuel G

    2014-01-01

    Stabilized alpha-helical (SAH) peptides are valuable laboratory tools to explore important protein-protein interactions. Whereas most peptides lose their secondary structure when isolated from the host protein, stapled peptides incorporate an all-hydrocarbon "staple" that reinforces their natural alpha-helical structure. Thus, stapled peptides retain their functional ability to bind their native protein targets and serve multiple experimental uses. First, they are useful for structural studies such as NMR or crystal structures that map and better define binding sites. Second, they can be used to identify small molecules that specifically target that interaction site. Third, stapled peptides can be used to test the importance of specific amino acid residues or posttranslational modifications to the binding. Fourth, they can serve as structurally competent bait to identify novel binding partners to specific alpha-helical motifs. In addition to markedly improved alpha-helicity, stapled peptides also display resistance to protease cleavage and enhanced cell permeability. Most importantly, they are useful for intracellular experiments that explore the functional consequences of blocking particular protein interactions. Because of their remarkable stability, stapled peptides can be applied to whole-animal, in vivo studies. Here we describe a protocol for the synthesis of a peptide that incorporates an all-hydrocarbon "staple" employing a ring-closing olefin metathesis reaction. With proper optimization, stapled peptides can be a fundamental, accurate laboratory tool in the modern chemical biologist's armory.

  19. Electron Screening Effects on {alpha}-decay

    SciTech Connect

    Musumarra, A.; Bonasera, A.; Del Zoppo, A.; Di Pietro, A.; Figuera, P.; Kimura, S.; Lattuada, M.; Pellegriti, M. G.; Scuderi, V.; Torresi, D.; Farinon, F.; Geissel, H.; Knoebel, R.; Prochazka, A.; Scheidenberger, C.; Nociforo, C.; Behr, K.-H.; Bosch, F.; Boutin, D.; Bruenle, A.

    2009-08-26

    An open problem in Nuclear Astrophysics concerns the understanding of electron-screening effects on nuclear reaction rates at stellar energies. In this framework, we have proposed to investigate the influence of the electron cloud on {alpha}-decay by measuring Q-values and {alpha}-decay half-lives of fully stripped, H-like and He-like ions. These kinds of measurements have been feasible just recently for highly-charged radioactive nuclides by fragmentation of {sup 238}U at relativistic energies at the FRS-ESR facility at GSI. In this way it is possible to produce, efficiently separate and store highly-charged {alpha}-emitters. Candidates for the proposed investigation were carefully selected and will be studied by using the Schottky Mass Spectroscopy technique. In order to establish a solid reference data set, lifetimes and Q{sub {alpha}}-value measurements of the corresponding neutrals have been performed directly at the FRS, by implanting the separated ions into an active Silicon stopper.

  20. Breakup effects on alpha spectroscopic factors of 16O

    NASA Astrophysics Data System (ADS)

    Adhikari, S.; Basu, C.; Sugathan, P.; Jhinghan, A.; Behera, B. R.; Saneesh, N.; Kaur, G.; Thakur, M.; Mahajan, R.; Dubey, R.; Mitra, A. K.

    2017-01-01

    The triton angular distribution for the 12C(7Li,t)16O* reaction is measured at 20 MeV, populating discrete states of 16O. Continuum discretized coupled reaction channel calculations are used to to extract the alpha spectroscopic properties of 16O states instead of the distorted wave born approximation theory to include the effects of breakup on the transfer process. The alpha reduced width, spectroscopic factors and the asymptotic normalization constant (ANC) of 16O states are extracted. The error in the spectroscopic factor is about 35% and in that of the ANC about 27%.

  1. Formation and Dissociation of the Interstrand i-Motif by the Sequences d(XnC4Ym) Monitored with Electrospray Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Cao, Yanwei; Qin, Yujiao; Bruist, Michael; Gao, Shang; Wang, Bing; Wang, Huixin; Guo, Xinhua

    2015-06-01

    Formation and dissociation of the interstrand i-motifs by DNA with the sequence d(XnC4Ym) (X and Y represent thymine, adenine, or guanine, and n, m range from 0 to 2) are studied with electrospray ionization mass spectrometry (ESI-MS), circular dichroism (CD), and UV spectrophotometry. The ion complexes detected in the gas phase and the melting temperatures (Tm) obtained in solution show that a non-C base residue located at 5' end favors formation of the four-stranded structures, with T > A > G for imparting stability. Comparatively, no rule is found when a non-C base is located at the 3' end. Detection of penta- and hexa-stranded ions indicates the formation of i-motifs with more than four strands. In addition, the i-motifs seen in our mass spectra are accompanied by single-, double-, and triple-stranded ions, and the trimeric ions were always less abundant during annealing and heat-induced dissociation process of the DNA strands in solution (pH = 4.5). This provides a direct evidence of a strand-by-strand formation and dissociation pathway of the interstrand i-motif and formation of the triple strands is the rate-limiting step. In contrast, the trimeric ions are abundant when the tetramolecular ions are subjected to collision-induced dissociation (CID) in the gas phase, suggesting different dissociation behaviors of the interstrand i-motif in the gas phase and in solution. Furthermore, hysteretic UV absorption melting and cooling curves reveal an irreversible dissociation and association kinetic process of the interstrand i-motif in solution.

  2. New approach to analyzing and evaluating cross sections for partial photoneutron reactions

    SciTech Connect

    Varlamov, V. V. Ishkhanov, B. S.; Orlin, V. N.

    2012-11-15

    The presence of substantial systematic discrepancies between the results of different experiments devoted to determining cross sections for partial photoneutron reactions-first of all, ({gamma}, n), ({gamma}, 2n), and ({gamma}, 3n) reactions-is a strong motivation for studying the reliability and authenticity of these data and for developing methods for taking into account and removing the discrepancies in question. In order to solve the first problem, we introduce objective absolute criteria involving transitional photoneutron-multiplicity functions F{sub 1}, F{sub 2}, F{sub 3}, Horizontal-Ellipsis ; by definition, their values cannot exceed 1.0, 0.5, 0.33, Horizontal-Ellipsis , respectively. With the aim of solving the second problem, we propose a new experimental-theoretical approach. In this approach, reaction cross sections are evaluated by simultaneously employing experimental data on the cross section for the total photoneutron yield, {sigma}{sup expt}({gamma}, xn) = {sigma}{sup expt}({gamma}, n) + 2{sigma}{sup expt}({gamma}, 2n) + 3{sigma}{sup expt}({gamma}, 3n) + Horizontal-Ellipsis , which are free from drawbacks plaguing experimental methods for sorting neutrons in multiplicity, and the results obtained by calculating the functions F{sub theor}{sup 1}, F{sub theor}{sup 2}, F{sub theor}{sup 3}, Horizontal-Ellipsis on the basis of the modern model of photonuclear reactions. The reliability and authenticity of data on the cross sections for ({gamma}, n), ({gamma}, 2n), and ({gamma}, 3n) partial reactions-{sigma}{sup eval}({gamma}, in) = F{sub i}{sup theor}{sigma}{sup expt}({gamma}, xn)-were evaluated for the {sup 90}Zr, {sup 115}In, {sup 112,114,116,117,118,119,120,122,124}Sn, {sup 159}Tb, and {sup 197}Au nuclei.

  3. Summary of Alpha Particle Transport

    SciTech Connect

    Medley, S.S.; White, R.B.; Zweben, S.J.

    1998-08-19

    This paper summarizes the talks on alpha particle transport which were presented at the 5th International Atomic Energy Agency's Technical Committee Meeting on "Alpha Particles in Fusion Research" held at the Joint European Torus, England in September 1997.

  4. Interleukin-1alpha and tumor necrosis factor-alpha expression during the early phases of orthodontic tooth movement in rats.

    PubMed

    Bletsa, Athanasia; Berggreen, Ellen; Brudvik, Pongsri

    2006-10-01

    Remodelling of the periodontium after application of mechanical forces constitutes the basis of clinical orthodontics and various immunoregulatory molecules are involved in this process. The aim of this study was to investigate the expression of the cytokines interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha) in dental tissues during the early phases of orthodontic tooth movement. Eightteen male Wistar rats were used. All maxillary right first molars were moved orthodontically, with a force of 0.5 N, for 3 h, 1 d, and 3 d. The contralateral sides served as untreated controls. Parasagittal sections of the maxillary molars and the surrounding tissues were subjected to immunohistochemical staining for IL-1alpha or TNF-alpha, and were evaluated with light microscopy. IL-1alpha and TNF-alpha were expressed in the bone and periodontal ligament (PDL) along the roots of the orthodontically moved molars and in the gingiva. Increased expression of both cytokines was observed in the aforementioned areas after 1 and 3 d of tooth movement. The pulp tissue exhibited only minor changes in cytokine expression during tooth movement. The results suggest that mechanical stress results in almost immediate inflammatory reactions in various dental tissues.

  5. Alpha storage regime in high temperature sub-ignited D-T tokamaks

    SciTech Connect

    Zweben, S.J.; Furth, H.P.; Mikkelsen, D.R.; Redi, M.H.; Strachan, J.D.

    1988-07-01

    Alpha particle parameters in sub-ignited D-T tokamaks like TFTR can be optimized in a high temperature ''alpha storage regime '' in which the alpha particle thermalization time /tau//sub ..cap alpha../ is long (approx.1.0 sec) and in which the alpha particle source rate S/sub ..cap alpha../ is enhanced due to a beam-target and beam-beam reactions (by a factor of approx.2-3). Near reactor-level alpha instability parameters ..beta../sub ..cap alpha../(0) approx. n/sub ..cap alpha../(0)/n/sub e/(O) approx. 1% are predicted by simulation codes when Q approx. 0.5-1, while present TFTR ''supershots'' already have ..beta../sub ..cap alpha../(O) approx. n/sub /alpha/(O)/n/sub e/(O) /approx/ 0.1-0.2%. Plasmas in this regime can be used to test theories of collective alpha instabilities for the first time, and can be used to provide a strong (but transient) alpha heating pulse. An experimental scenario to exploit this regime is described. 28 refs., 5 figs., 5 tabs.,

  6. HB Hillingdon [alpha46(CE4)Phe-->Val (alpha1 Or alpha2)]: a new alpha chain hemoglobin variant.

    PubMed

    Babb, Anna; Solaiman, Susannah; Green, Brian N; Mantio, Debbie; Patel, Ketan

    2009-01-01

    Routine antenatal hemoglobinopathy screening detected a new alpha chain variant that eluted with Hb A(2) on cation exchange high performance liquid chromatography (HPLC) in a lady of Sri Lankan origin who had normal hematological indices. The mutation was identified by electrospray ionization mass spectrometry (ESI-MS) as alpha46(CE4)Phe-->Val, inferring that the variant was due to a single base change at codon 46 (TTC>GTC) of the alpha1- or alpha2-globin genes.

  7. Molecular design of hybrid tumour necrosis factor alpha with polyethylene glycol increases its anti-tumour potency.

    PubMed Central

    Tsutsumi, Y.; Kihira, T.; Tsunoda, S.; Kanamori, T.; Nakagawa, S.; Mayumi, T.

    1995-01-01

    This study was conducted to increase the anti-tumour potency and reduce the toxic side-effects of tumour necrosis factor alpha (TNF-alpha). Natural human TNF-alpha was chemically conjugated with monomethoxy polyethylene glycol (PEG) using succinimidyl coupling of lysine amino groups of TNF-alpha. The number-average molecular weight of PEG-modified TNF-alpha (PEG-TNF-alpha) increased with an increase in the reaction time and the initial molar ratio of PEG relative to TNF-alpha. The resulting modified TNF-alpha was separated into fractions of various molecular weights. The specific activity of separated PEG-TNF-alpha s relative to that of native TNF-alpha gradually decreased with an increase in the degree of PEG modification, but the plasma half-life was drastically increased with the increase in molecular weight of modified TNF-alpha. PEG-TNF-alpha s, in which 29% and 56% of lysine residues were coupled to PEG, had anti-tumour activity approximately 4 and 100 times greater than unmodified TNF-alpha in the murine Meth-A fibrosarcoma model. Extensive PEG modification did not increase its in vivo activity. A high dose of unmodified TNF-alpha induced toxic side-effects, but these were not observed with the modified TNF-alpha s. Optimal PEG modification of TNF-alpha markedly increased its bioavailability and may facilitate its potential anti-tumour therapeutic use. PMID:7734321

  8. Alpha-Cluster Dominance in the αp Process in Explosive Hydrogen Burning

    NASA Astrophysics Data System (ADS)

    Kubono, S.; Dam, N.; Hayakawa, S.; Hashimoto, H.; Kahl, D.; Yamaguchi, H.; Wakabayashi, Y.; Teranishi, T.; Iwasa, N.; Komatsubara, T.; Kato, S.; Chen, A.; Cherubini, S.; Choi, S.; Hahn, I.; He, J.; Le, H. K.; Lee, C.; Kwon, Y.; Wanajo, S.; Janka, H.

    Nucleosynthesis by alpha particles and heavier 4n nuclei are of great interest as they would involve nuclear cluster resonances. The role of nuclear clustering is discussed for nucleosynthesis with the Cluster Nucleosynthesis Diagram (CND) proposed before, especially those involving alpha induced reactions, based on our recent works of (α,p) reactions with low energy RI beams. We present experimental results that alpha resonances play a crucial role for the (α,p) reaction cross sections. Molecular resonances are also briefly discussed along this line for O- and C-burning.

  9. Measurements of 15.11-MeV gamma-ray flux produced in the reactions C-12(p, p')-C-12*(15.11 MeV) and O-16(p, p' alpha)-C-12*(15.11 MeV)

    NASA Technical Reports Server (NTRS)

    Lapides, J. R.; Crannell, C. J.; Crannell, H.; Hornyak, W. F.; Seltzer, S. M.; Trombka, J. I.; Wall, N. S.

    1978-01-01

    The flux of 15.11 MeV gamma rays relative to the flux of 4.44 MeV gamma rays which are emitted from the corresponding states of C-12 are a sensitive measure of the spectrum of exciting particles in solar flares and other cosmic sources. Emission of 15.11 MeV gamma rays may result not only from the direct excitation of C-12 but also from the interaction O-16 (p,p' alpha) C-12* sup 15.11 MeV. Although the cross sections for the direct reaction was studied extensively, the cross section for the spallation interaction with O-16 is not reported in the literature. Preliminary measurements demonstrated the feasibility of measuring the production of 15.11 MeV gamma rays by proton interactions with O-16 using the University of Maryland cyclotron facility. For both carbon and oxygen targets the flux of 15.11 MeV gamma rays is being measured relative to the flux of 4.44 MeV gamma rays. The gamma ray emission from de-excitation of the giant dipole resonances is being measured.

  10. A role of hydrocarbon reaction for NO{sub x} formation and reduction in fuel-rich pulverized coal combustion

    SciTech Connect

    Taniguchi, Masayuki; Kamikawa, Yuki; Okazaki, Teruyuki; Yamamoto, Kenji; Orita, Hisayuki

    2010-08-15

    We have investigated an index for modeling a NO{sub x} reaction mechanism of pulverized coal combustion. The reaction mechanism of coal nitrogen was examined by drop-tube furnace experiments under various burning conditions. We proposed the gas phase stoichiometric ratio (SRgas) as a key index to evaluate NO{sub x} concentration in fuel-rich flames. The SRgas was defined as: SRgas {identical_to} amount of fuel required for stoichiometry combustion/amount of gasified fuel where, the amount of gasified fuel was defined as the amount of fuel which had been released to the gas phase by pyrolysis, oxidation and gasification reactions. When SRgas < 1.0, NO{sub x} concentration was strongly influenced by the value of SRgas. In this condition, the NO{sub x} concentration was hardly influenced by coal type, particle diameter, or reaction time. We developed a model to analyze NO{sub x} and XN(HCN, NH{sub 3}) concentrations for pulverized coal/air combustion and coal/CO{sub 2}/O{sub 2} combustion, based on the index. NO{sub x} and XN concentrations did not reproduce the experimental results without considering reactions between hydrocarbons and NO{sub x}. The hydrocarbon reaction was important for both NO{sub x} and XN, especially for air combustion. In the present model, an empirical formula was used to estimate the total concentration of hydrocarbons in coal flame. The reaction of heavy hydrocarbons which had plural aromatic rings was very important to analyze the reaction mechanism of hydrocarbons for coal combustion in detail. When burning temperature and SRgas were the same, total hydrocarbon concentration in a coal flame was larger than that of a light gaseous hydrocarbon flame. Total hydrocarbon concentration in oxy-fuel combustion was lower than that in air combustion. We verified the proposed model by experimental results obtained for a drop-tube furnace and a laboratory-scale furnace that had an installed low-NO{sub x} burner. (author)

  11. Simultaneous quantification of GABAergic 3alpha,5alpha/3alpha,5beta neuroactive steroids in human and rat serum.

    PubMed

    Porcu, Patrizia; O'Buckley, Todd K; Alward, Sarah E; Marx, Christine E; Shampine, Lawrence J; Girdler, Susan S; Morrow, A Leslie

    2009-01-01

    The 3alpha,5alpha- and 3alpha,5beta-reduced derivatives of progesterone, deoxycorticosterone, dehydroepiandrosterone and testosterone enhance GABAergic neurotransmission and produce inhibitory neurobehavioral and anti-inflammatory effects. Despite substantial information on the progesterone derivative (3alpha,5alpha)-3-hydroxypregnan-20-one (3alpha,5alpha-THP, allopregnanolone), the physiological significance of the other endogenous GABAergic neuroactive steroids has remained elusive. Here, we describe the validation of a method using gas chromatography-mass spectrometry to simultaneously identify serum levels of the eight 3alpha,5alpha- and 3alpha,5beta-reduced derivatives of progesterone, deoxycorticosterone, dehydroepiandrosterone and testosterone. The method shows specificity, sensitivity and enhanced throughput compared to other methods already available for neuroactive steroid quantification. Administration of pregnenolone to rats and progesterone to women produced selective effects on the 3alpha,5alpha- and 3alpha,5beta-reduced neuroactive steroids, indicating differential regulation of their biosynthetic pathways. Pregnenolone administration increased serum levels of 3alpha,5alpha-THP (+1488%, p<0.001), (3alpha,5alpha)-3,21-dihydroxypregnan-20-one (3alpha,5alpha-THDOC, +205%, p<0.01), (3alpha,5alpha)-3-hydroxyandrostan-17-one (3alpha,5alpha-A, +216%, p<0.001), (3alpha,5alpha,17beta)-androstane-3,17-diol (3alpha,5alpha-A-diol, +190%, p<0.01). (3alpha,5beta)-3-hydroxypregnan-20-one (3alpha,5beta-THP) and (3alpha,5beta)-3-hydroxyandrostan-17-one (3alpha,5beta-A) were not altered, while (3alpha,5beta)-3,21-dihydroxypregnan-20-one (3alpha,5beta-THDOC) and (3alpha,5beta,17beta)-androstane-3,17-diol (3alpha,5beta-A-diol) were increased from undetectable levels to 271+/-100 and 2.4+/-0.9 pg+/-SEM, respectively (5/8 rats). Progesterone administration increased serum levels of 3alpha,5alpha-THP (+1806%, p<0.0001), 3alpha,5beta-THP (+575%, p<0.001), 3alpha,5alpha

  12. Heterologous expression of the cloned guinea pig alpha 2A, alpha 2B, and alpha 2C adrenoceptor subtypes. Radioligand binding and functional coupling to a CAMP-responsive reporter gene.

    PubMed

    Svensson, S P; Bailey, T J; Porter, A C; Richman, J G; Regan, J W

    1996-02-09

    Functional studies have shown that 6-chloro-9-[(3-methyl-2-butenyl)oxy]-3-methyl-1H-2,3,4,5-tetrahydro-3- benzazepine (SKF 104078) has very low affinity for prejunctional alpha 2-adrenoceptors (alpha 2-AR) in the guinea pig atrium. In this study, we have cloned guinea pig homologues of the human alpha 2-C10, alpha 2-C4 AR subtypes and have studied them in isolation by heterologous expression in cultured mammalian cells. Oligonucleotide primers, designed from conserved areas of the human alpha 2-ARs were used in a polymerase chain reaction (PCR) with template cDNA synthesized from guinea pig atrial mRNA. Three PCR products were obtained that shared identity with the three human alpha 2-AR subtypes. A guinea pig (gp) genomic library was screened with a cDNA clone encoding a portion of the gp-alpha 2A, and genes containing the complete coding sequences of the guinea pig alpha 2A, alpha 2B, and alpha 2C AR subtypes were obtained. These guinea pig genes were subcloned into a eukaryotic expression plasmid and were expressed transiently in COS-7 cells. The binding of the alpha 2-selective antagonist [3H]MK-912 to membranes prepared from these cells was specific and of high affinity with Kd values of 810 pM for gp-alpha 2A, 2700 pM for gp-alpha 2B and 110 pM for gp-alpha 2C. Competition for the binding of [3H]MK-912 by SKF 104078 indicated that it was of moderately high affinity (approximately 100 nM) but that it was not selective for any of the guinea pig alpha 2-AR subtypes. Co-expression of guinea pig alpha 2-AR subtypes with a cyclicAMP-responsive chloramphenicol acetyltransferase (CAT) reporter gene resulted in agonist-dependent modulation of CAT activity. For the gp-alpha 2 A, a biphasic response was obtained with low concentrations of noradrenaline (NE) decreasing forskolin-stimulated CAT activity and high concentrations causing a reversal. For the gp-alpha 2B, NE produced mostly potentiation of forskolin-stimulated activity, and for the gp-alpha 2C, NE caused

  13. The ALPHA Magnetic Spectrometer

    NASA Astrophysics Data System (ADS)

    Viertel, G. M.; Capell, M.

    1998-12-01

    The ALPHA Magnetic Spectrometer (AMS) will be the first large magnetic spectrometer in space. It is scheduled to be installed on the future International Space Station ALPHA (ISSA) in the year 2002 to perform measurements of the charged particle composition to answer fundamental questions in particle physics and astrophysics. Before installation on ISSA, AMS will fly on the shuttle DISCOVERY for a period of 10 days starting in May 1998. This will enable AMS to perform a test of the apparatus and first measurements. The AMS detector has five major components: A permanent NdFeB magnet, six planes of Silicon double-sided microstrip detectors, a plastic scintillator time of flight hodoscope, a plastic scintillator anticoincidence counter and an Aerogel Cherenkov threshold counter. In addition, there are electronics, support infrastructure and interfaces.

  14. Surrogate Reactions in the Actinide Region

    SciTech Connect

    Burke, J T; Bernstein, L A; Scielzo, N D; Bleuel, D L; Lesher, S R; Escher, J; Ahle, L; Dietrich, F S; Hoffman, R D; Norman, E B; Sheets, S A; Phair, L; Fallon, P; Clark, R M; Gibelin, J; Jewett, C; Lee, I Y; Macchiavelli, A O; McMahan, M A; Moretto, L G; Rodriguez-Vieitez, E; Wiedeking, M; Lyles, B F; Beausang, C W; Allmond, J M; Ai, H; Cizewski, J A; Hatarik, R; O'Malley, P D; Swan, T

    2008-01-30

    Over the past three years we have studied various surrogate reactions (d,p), ({sup 3}He,t), ({alpha},{alpha}{prime}) on several uranium isotopes {sup 234}U, {sup 235}U, {sup 236}U, and {sup 238}U. An overview of the STARS/LIBERACE surrogate research program as it pertains to the actinides is discussed. A summary of results to date will be presented along with a discussion of experimental difficulties encountered in surrogate experiments and future research directions.

  15. Substrate specificity of THCA-CoA oxidases from rat liver light mitochondrial fractions on dehydrogenation of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid CoA thioester.

    PubMed

    Ikegawa, S; Goto, T; Mano, N; Goto, J

    1998-11-01

    The substrate specificity of rat liver peroxisomal 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoyl-CoA (THCA-CoA) oxidases, which catalyze the dehydrogenation of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid (THCA) CoA thioester, having an asymmetric center at C-25, to form (24E)-3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholest-24-enoic acid (delta 24-THCA) CoA thioester, was studied. The stable isotope labeled substrates, [3,7,12-18O3]-(25R)- and (25S)-THCA CoA thioesters were synthesized by an exchange reaction of carbonyl oxygens on a steroid nucleus of 3,7,12-trioxo-5 beta-cholestanoic acid, followed by metal hydride reduction and condensation reaction with CoA. After incubation of a mixture of unlabeled (25R)- and 18O-labeled (25S)-THCA CoA thioester, or vice versa, with hepatic peroxisomal THCA-CoA oxidases, biotransformed delta 24-THCA was determined by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry. The delta 24-THCA was derived only from (25S)-THCA CoA thioester, indicating that the 25S epimer of THCA is a preferential substrate on dehydrogenation by THCA-CoA oxidases.

  16. The influence of projectile neutron number in the 208Pb(48Ti, n)255Rf and 208Pb(50Ti, n)257Rf reactions

    SciTech Connect

    Dragojevic, Irena; Dragojevic, I.; Gregorich, K.E.; Dullmann, Ch.E.; Garcia, M.A.; Gates, J.M.; Nelson, S.L.; Stavsetra, L.; Sudowe, R.; Nitsche, H.

    2008-07-11

    Four isotopes of rutherfordium,254-257Rf, were produced by the 208Pb(48Ti, xn)256-xRf and 208Pb(50Ti, xn)258-xRf reactions (x = 1, 2) at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. Excitation functions were measured for the 1n and 2n exit channels. A maximum likelihood technique, which correctly accounts for the changing cross section at all energies subtended by the targets, was used to fit the 1n data to allow a more direct comparison between excitation functions obtained under different experimental conditions. The maximum 1n crosssections of the 208Pb(48Ti, n)255Rf and 208Pb(50Ti, n)257Rf reactions obtained from fits to the experimental data are 0.38 +/- 0.07 nb and 40 +/-5 nb, respectively. Excitation functions for the 2n exit channel were also measured, with maximum cross sections of nb for the 48Ti induced reaction, and 15.7 +/- 0.2 nb for the 50Ti induced reaction. The impact of the two neutron difference in the projectile on the 1n cross section is discussed. The results are compared to the Fusion by Diffusion model developed by Swiatecki, Wilczynska, and Wilczynski.

  17. Alpha decay of {sup 181}Pb

    SciTech Connect

    Davids, C.N.; Henderson, D.J.; Hermann, R.

    1995-08-01

    The {alpha}-decay energy of {sup 181}Pb was measured as 7211(10) keV and 7044(15). In the first study the isotope was produced in {sup 90}Zr bombardments of {sup 94}Mo and, after traversing a velocity filter, implanted in a position-sensitive Si detector; no half life for {sup 181}Pb was reported. In the second study the isotope was produced in {sup 40}Ca bombardments of {sup 144}Sm and transported to a position in front of a Si(Au) surface barrier detector with a fast He-gas-jet capillary system; an estimate of 50 ms was determined for the {sup 181}Pb half life. Recently we investigated {sup 181}Pb {alpha} decay at ATLAS as part of a survey experiment in which a l-pnA beam of 400-MeV {sup 92}Mo was used to irradiate targets of {sup 89}Y, {sup 90,92,94}Zr, and {sup 92}Mo to examine yields for one- and two-nucleon evaporation products from symmetric cold-fusion reactions. Recoiling nuclei of interest were passed through the Fragment Mass Analyzer and implanted in a double-sided silicon strip detector for {alpha}-particle assay. With the {sup 90}Zr target we observed a group at 7065(20) keV which was correlated with A = 181 recoils and had a half life of 45(20) ms. Our new results for {sup 181}Pb therefore agreed with those of the second study. There was no indication in the {sup 90}Zr + {sup 92}Mo data of the 7211(10)-keV {alpha} particles seen by Keller et al. The interested reader is referred to the 1993 atomic mass evaluation wherein the input {alpha}-decay energies and resultant masses of the light Pb isotopes (including {sup 181}Pb) are discussed.

  18. Exploring the {alpha}p-process with Grand Raiden

    SciTech Connect

    O'Brien, S.; Berg, G. P. A.; Couder, M.; Goerres, J.; Patel, D.; Sault, K.; Wiescher, M.; Adachi, T.; Hatanaka, K.; Ishikawa, D.; Matsubara, H.; Okamura, H.; Ong, H. J.; Suzuki, T.; Tamii, A.; Zenihiro, J.; Dozono, M.; Wakasa, T.; Fujita, H.; Fujita, Y.

    2009-01-28

    {sup 22}Mg, {sup 30}S, {sup 34}Ar and {sup 38}Ca have been investigated using (p,t) reactions at RCNP with the intent of identifying energy levels in nuclei that determine the reaction rates along the pathway of the {alpha}p-process. These experiments exploit the high resolution and 0 deg. capabilities of the Grand Raiden spectrometer and the WS beamline, which can deliver a fully dispersion matched beam to target. The level information is vital to understanding the nucleosynthesis occurring during explosive hydrogen burning, which, for example, is thought to occur during type I X-ray bursts. In the case of {sup 22}Mg, new reaction rate calculations have been performed for the {sup 18}Ne({alpha},p){sup 21}Na reaction. The experimental technique will be discussed, and the experimental results will be presented.

  19. Generation of superoxide anion radical by alpha-terthienyl in the anal gills of mosquito larvae Aedes aegypti: a new aspect in alpha-terthienyl phototoxicity.

    PubMed

    Nivsarkar, M; Kumar, G P; Laloraya, M; Laloraya, M M

    1992-01-01

    The present study documents that the secondary plant metabolites, especially alpha-terthienyl, exert phototoxic action through inhibition of certain enzymes and generation of singlet oxygen. Some of the reports have emerged exhibiting involvement of free radical generation in vitro by alpha-terthienyl. We provide evidence for the generation of a free radical viz., superoxide anion radical, by alpha-terthienyl employing spin-trapping techniques, probably due to the extension of the latter reaction. On the basis of this observation the phototoxic action of alpha-terthienyl on Aedes aegypti larvae is explained.

  20. The primary transcription unit of the human alpha 2 globin gene defined by quantitative RT/PCR.

    PubMed Central

    Owczarek, C M; Enriquez-Harris, P; Proudfoot, N J

    1992-01-01

    We have set up an experimental system to map the primary transcription unit of the human alpha 2 globin gene. The duplicated human alpha globin genes (alpha 2-alpha 1) were linked to the alpha globin locus Positive Regulatory Element (PRE) and stably transfected into murine erythroleukaemia cells. We then developed a quantitative reverse transcriptase, polymerase chain reaction assay to map alpha 2 primary transcripts using primer pairs derived from different parts of the alpha 2 globin gene and its 3' flanking region. This approach has revealed the presence of steady state nuclear RNA past the poly(A) site of the alpha 2 globin gene at approximately 40% of the level of unspliced intron transcript. Furthermore, these 3' flanking transcripts diminish 500 bp into the 3' flanking region, identifying this part of the alpha 2 globin gene as the principal region of termination of transcription. Images PMID:1371868

  1. Gas-phase chemistry of (alpha-terpineol with ozone and OH radical: rate constants and products.

    PubMed

    Wells, J R

    2005-09-15

    A bimolecular rate constant, kOH+alpha-terpineol, of (1.9 +/- 0.5) x 10(-10) cm3 molecule(-1) s(-1) was measured using gas chromatography/mass spectrometry and the relative rate technique for the reaction of the hydroxyl radical (OH) with alpha-terpineol (1-methyl-4-isopropyl-1-cyclohexen-8-ol) at (297 +/- 3) K and 1 atm total pressure. Additionally, a bimolecular rate constant, kO3+alpha-terpineol, of (3.0 +/- 0.2) x 10(-16) cm3 molecule(-1) s(-1) was measured by monitoring the first order decrease in ozone concentration as a function of excess alpha-terpineol. To better understand alpha-terpineol's gas-phase transformation in the indoor environment, the products of the alpha-terpineol + OH and alpha-terpineol + 03 reactions were also investigated. The positively identified alpha-terpineol/OH reaction products were acetone, ethanedial (glyoxal, HC(=O)C(=O)H), and 2-oxopropanal (methyl glyoxal, CH3C(=O)C(=O)H). The positively identified alpha-terpineol/O3 reaction product was 2-oxopropanal (methyl glyoxal, CH3C(=O)C(=O)H). The use of derivatizing agents O-(2,3,4,5,6-pentalfluorobenzyl)hydroxylamine (PFBHA) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) clearly indicated that several other reaction products were formed. The elucidation of these other reaction products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible alpha-terpineol/OH and alpha-terpineol/O3 reaction mechanisms based on previously published volatile organic compound/ OH and volatile organic compound/O3 gas-phase reaction mechanisms.

  2. Transfer-type products accompanying cold fusion reactions

    SciTech Connect

    Adamian, G.G.; Antonenko, N.V.

    2005-12-15

    Production of nuclei heavier than the target is treated for projectile-target combinations used in cold fusion reactions leading to superheavy nuclei. These products are related to transfer-type or to asymmetry-exit-channel quasifission reactions. The production of isotopes in the transfer-type reactions emitting of {alpha} particles with large energies is discussed.

  3. A radioimmunoassay for alpha- and beta-gliadins.

    PubMed

    Ciclitira, P J; Lennox, E S

    1983-06-01

    1. A rapid, sensitive specific radioimmunoassay for alpha- and beta-gliadin has been developed using an antiserum raised in rabbits to A-gliadin, a component of alpha-gliadin. 2. The antigen used in the assay was alpha-gliadin labelled with 125I; antigen-antibody complexes were collected after adsorption to Staphylococcus aureus in suspension. 3. The sensitivity of the assay, as judged by competitive binding with unlabelled antigen, was 1 ng of alpha- or beta-gliadin, which show complete cross-reaction with this antiserum. 4. Cross-reactivity to other wheat proteins was less than 1% and no cross-reactivity to extracts of rye, barley or oats was observed. 5. This radioimmunoassay for alpha- and beta-gliadin has been used to measure their amount in different varieties of wheat flour, several foods prepared from flour, e.g. bread, biscuits and products prepared as 'gluten free'. The possibility of assaying for alpha-gliadin in prepared foods is of special value since alpha-, beta-, gamma- and omega-gliadin have been shown to exacerbate coeliac disease.

  4. Extension of activation cross section data of deuteron induced nuclear reactions on rhodium up to 50 MeV

    NASA Astrophysics Data System (ADS)

    Hermanne, A.; Tárkányi, F.; Takács, S.; Ditrói, F.

    2015-11-01

    In the frame of the systematical study of light ion induced nuclear reactions activation cross sections for deuteron induced reactions on monoisotopic 103Rh were extended to 50 MeV incident energy. Excitation functions were measured in the 49.8-36.6 MeV energy range for the 103Rh(d,xn)100,101Pd, 103Rh(d,pxn)99m,99g,100,101m,101g,102m,102gRh and 103Rh(d,x)97,103Ru reactions by using the stacked foil irradiation technique and off-line high resolution γ-ray spectrometry. The experimental results are compared to our previous results and to the theoretical predictions in the TENDL-2014 library (TALYS 1.6 code).

  5. Production cross section of At radionuclides from 7Li+natPb and 9Be+natTl reactions

    NASA Astrophysics Data System (ADS)

    Maiti, Moumita; Lahiri, Susanta

    2011-12-01

    Earlier we reported theoretical studies on the probable production of astatine radionuclides from 6,7Li- and 9Be-induced reactions on natural lead and thallium targets, respectively. The production of astatine radionuclides were investigated experimentally with two heavy-ion-induced reactions: 9Be + natTl and 7Li + natPb. Formation cross sections of the evaporation residues, 207,208,209,210At, produced in the (HI,xn) channel, were measured by the stacked-foil technique followed by off-line γ spectrometry at low incident energies (<50 MeV). Measured excitation functions were interpreted in terms of a compound nuclear reaction mechanism using Weisskopf-Ewing and Hauser-Feshbach models. Measured cross-section values are lower than the respective theoretical predictions.

  6. Release of alpha 2-plasmin inhibitor from plasma fibrin clots by activated coagulation factor XIII. Its effect on fibrinolysis.

    PubMed Central

    Mimuro, J; Kimura, S; Aoki, N

    1986-01-01

    When blood coagulation takes place in the presence of calcium ions, alpha 2-plasmin inhibitor (alpha 2PI) is cross-linked to fibrin by activated coagulation Factor XIII (XIIIa) and thereby contributes to the resistance of fibrin to fibrinolysis. It was previously shown that the cross-linking reaction is a reversible one, since the alpha 2PI-fibrinogen cross-linked complex could be dissociated. In the present study we have shown that the alpha 2PI-fibrin cross-linking reaction is also a reversible reaction and alpha 2PI which had been cross-linked to fibrin can be released from fibrin by disrupting the equilibrium, resulting in a decrease of its resistance to fibrinolysis. When the fibrin clot formed from normal plasma in the presence of calcium ions was suspended in alpha 2PI-deficient plasma of buffered saline, alpha 2PI was gradually released from fibrin on incubation. When alpha 2PI was present in the suspending milieu, the release was decreased inversely to the concentrations of alpha 2PI in the suspending milieu. The release was accelerated by supplementing XIIIa or the presence of a high concentration of the NH2-terminal 12-residue peptide of alpha 2PI (N-peptide) which is cross-linked to fibrin in exchange for the release of alpha 2PI. When the release of alpha 2PI from fibrin was accelerated by XIIIa or N-peptide, the fibrin became less resistant to the fibrinolytic process, resulting in an acceleration of fibrinolysis which was proportional to the degree of the release of alpha 2PI. These results suggest the possibility that alpha 2PI could be released from fibrin in vivo by disrupting the equilibrium of the alpha 2PI-fibrin cross-linking reaction, and that the release would result in accelerated thrombolysis. Images PMID:2419360

  7. Expedient synthesis of substituted (S)-N-(alpha-methylbenzyl)aziridines.

    PubMed

    Bew, Sean P; Hughes, David L; Savic, Vladimir; Soapi, Katy M; Wilson, Martin A

    2006-09-07

    We report for the first time that after O-acylation the conjugate addition products of (S)-N-(alpha-methylbenzyl)hydroxylamine undergo an efficient diastereoselective 3-exo-tet ring-closure reaction affording 2- and 2,3-disubstituted-N-alkylaziridines in good to excellent yields.

  8. Organocatalytic enantioselective indole alkylations of alpha,beta-unsaturated ketones.

    PubMed

    Chen, Wei; Du, Wei; Yue, Lei; Li, Rui; Wu, Yong; Ding, Li-Sheng; Chen, Ying-Chun

    2007-03-07

    The C3-selective enantioselective Michael-type Friedel-Crafts alkylations of indoles with nonchelating alpha,beta-unsaturated alkyl ketones, catalysed by a chiral primary amine derived from natural cinchonine, were investigated. The reactions, in the presence of 30 mol% catalyst, were smoothly conducted at 0 to -20 degrees C. Moderate to good ee (47-89%) has been achieved.

  9. Resonance damping of the terahertz-frequency transverse acoustic phonon in the relaxor ferroelectric KT a1 -xN bxO3

    NASA Astrophysics Data System (ADS)

    Toulouse, J.; Iolin, E.; Hennion, B.; Petitgrand, D.; Erwin, R.

    2016-12-01

    The damping (Γ a ) of the transverse acoustic (TA) phonon in single crystals of the relaxor KT a1 -xN bxO3 with x =0.15 -0.17 was studied by means of high resolution inelastic cold neutron scattering near the (200) Brillouin Zone (BZ) point where diffuse scattering is absent, although it is present near (110). In a wide range of temperatures centered on the phase transition, T =195 K ÷108 K , the TA phonon width (damping) exhibits a step increase around momentum q =0.07 , goes through a shallow maximum at q =0.09 -0.12 , and remains high above and up to the highest momentum studied of q =0.16 . These experimental results are explained in terms of a resonant interaction between the TA phonon and the collective or correlated reorientation through tunneling of the off-center N b+5 ions. The observed TA damping is successfully reproduced in a simple model that includes an interaction between the TA phonon and a dispersionless localized mode (LM) with frequency ωL and damping ΓL(ΓL<ωL) , itself coupled to the transverse optic (TO) mode. Maximum damping of the TA phonon occurs when its frequency is ωa≈ωL . The values of ωL and ΓL are moderately dependent on temperature, but the oscillator strength, M2, of the resonant damping exhibits a strong maximum in the range T ˜120 K ÷150 K in which neutron diffuse scattering near the (110) BZ point is also maximum and the dielectric susceptibility exhibits the relaxor behavior. The maximum value of M appears to be due to the increasing number of polar nanodomains. In support of the proposed model, the observed value of ωL≈0.7 THz is found to be similar to the estimate previously obtained by Girshberg and Yacoby [J. Phys.: Condens. Matter 24, 015901 (2012)], 10.1088/0953-8984/24/1/015901. Alternatively, the TA phonon damping can be successfully fitted in the framework of an empirical Havriliak-Negami (HN) relaxation model that includes a strong resonancelike transient contribution.

  10. Design and one-pot synthesis of alpha-aminophosphonates and bis(alpha-aminophosphonates) by iron(III) chloride and cytotoxic activity.

    PubMed

    Rezaei, Zahra; Firouzabadi, Habib; Iranpoor, Nasser; Ghaderi, Abbas; Jafari, Mohammad Reza; Jafari, Abbas Ali; Zare, Hamid Reza

    2009-11-01

    In this study, we used a solution of FeCl(3) in THF to facilitate the Mannich-type reaction of aldehyde, amine and phosphite compounds to form corresponding alpha-aminophosphonates in a one-pot, three-component reaction. Selected alpha-aminophosphonates were entered into a biological assay test and were studied by docking methods, using Autodock 3.0. The results showed that the reactions were carried out mildly and eco-friendly to form alpha-aminophosphonates in high yields. Some were found to have cytotoxic activity on the cell lines RAJI, JURKAT and MCF-7. An indole derived bis(alpha-aminophosphonates) showed maximum cytotoxic effect comparable to doxorubicin. Although the FDE (Final Docking Energy) for the most cytotoxic compound was of the most negative value, there is no correlation between FDE and cytotoxicity.

  11. Background canceling surface alpha detector

    DOEpatents

    MacArthur, D.W.; Allander, K.S.; Bounds, J.A.

    1996-06-11

    A background canceling long range alpha detector which is capable of providing output proportional to both the alpha radiation emitted from a surface and to radioactive gas emanating from the surface. The detector operates by using an electrical field between first and second signal planes, an enclosure and the surface or substance to be monitored for alpha radiation. The first and second signal planes are maintained at the same voltage with respect to the electrically conductive enclosure, reducing leakage currents. In the presence of alpha radiation and radioactive gas decay, the signal from the first signal plane is proportional to both the surface alpha radiation and to the airborne radioactive gas, while the signal from the second signal plane is proportional only to the airborne radioactive gas. The difference between these two signals is proportional to the surface alpha radiation alone. 5 figs.

  12. Background canceling surface alpha detector

    DOEpatents

    MacArthur, Duncan W.; Allander, Krag S.; Bounds, John A.

    1996-01-01

    A background canceling long range alpha detector which is capable of providing output proportional to both the alpha radiation emitted from a surface and to radioactive gas emanating from the surface. The detector operates by using an electrical field between first and second signal planes, an enclosure and the surface or substance to be monitored for alpha radiation. The first and second signal planes are maintained at the same voltage with respect to the electrically conductive enclosure, reducing leakage currents. In the presence of alpha radiation and radioactive gas decay, the signal from the first signal plane is proportional to both the surface alpha radiation and to the airborne radioactive gas, while the signal from the second signal plane is proportional only to the airborne radioactive gas. The difference between these two signals is proportional to the surface alpha radiation alone.

  13. Effects of electron acceptors and radical scavengers on nonchain radical nucleophilic substitution reactions

    SciTech Connect

    Xianman Zhang; Dilun Yang; Youcheng Liu )

    1993-01-01

    The yields of reaction products from thermal nucleophilic substitution reactions in dimethyl sulfoxide (DMSO) of six o- and p-nitrohalobenzenes with the sodium salt of ethyl [alpha]-cyanoacetate carbanion [Na[sup +][sup [minus

  14. Are alpha-gliadins glycosylated?

    PubMed

    Turner, J B; Garner, G V; Gordon, D B; Brookes, S J; Smith, C A

    2002-02-01

    Alpha-gliadins isolated by carboxymethylcellulose chromatography contain noncovalently bound glucose probably due to contaminating proteoglycans and to material shed from the column. Traces of carbohydrate remain strongly bound to alpha-gliadins even after harsh denaturation, but our results indicate alpha-gliadins are not glycoproteins. Suggestions that gliadins are glycoproteins are probably due to contamination with this glucose and the presence of these proteoglycans.

  15. Long range alpha particle detector

    DOEpatents

    MacArthur, D.W.; Wolf, M.A.; McAtee, J.L.; Unruh, W.P.; Cucchiara, A.L.; Huchton, R.L.

    1993-02-02

    An alpha particle detector capable of detecting alpha radiation from distant sources. In one embodiment, a high voltage is generated in a first electrically conductive mesh while a fan draws air containing air molecules ionized by alpha particles through an air passage and across a second electrically conductive mesh. The current in the second electrically conductive mesh can be detected and used for measurement or alarm. The detector can be used for area, personnel and equipment monitoring.

  16. An alpha particle instrument with alpha, proton, and X-ray modes for planetary chemical analyses

    NASA Technical Reports Server (NTRS)

    Economou, T. E.; Turkevich, A. L.

    1976-01-01

    The interaction of alpha particles with matter is employed in a compact instrument that could provide rather complete in-situ chemical analyses of surfaces and thin atmospheres of extraterrestrial bodies. The instrument is a miniaturized and improved version of the Surveyor lunar instrument. The backscattering of alpha particles and (alpha, p) reactions provide analytical data on the light elements (carbon-iron). An X-ray mode that detects the photons produced by the alpha sources provides sensitivity and resolution for the chemical elements heavier than about silicon. The X-rays are detected by semiconductor detectors having a resolution between 150 and 250 eV at 5.9 keV. Such an instrument can identify and determine with good accuracy 99 percent of the atoms (except hydrogen) in rocks. For many trace elements, the detecting sensitivity is a few ppm. Auxiliary sources could be used to enhance the sensitivities for elements of special interest. The instrument could probably withstand the acceleration involved in semi-hard landings.

  17. T-cell receptor V alpha and C alpha alleles associated with multiple and myasthenia gravis.

    PubMed Central

    Oksenberg, J R; Sherritt, M; Begovich, A B; Erlich, H A; Bernard, C C; Cavalli-Sforza, L L; Steinman, L

    1989-01-01

    Polymorphic markers in genes encoding that alpha chain of the human T-cell receptor (TcR) have been detected by Southern blot analysis in Pss I digests. Polymorphic bands were observed at 6.3 and 2.0 kilobases (kb) with frequencies of 0.30 and 0.44, respectively, in the general population. Using the polymerase chain reaction (PCR) method, we amplified selected sequences derived from the full-length TcR alpha cDNA probe. These PCR products were used as specific probes to demonstrate that the 6.3-kb polymorphic fragment hybridizes to the variable (V)-region probe and the 2.0-kb fragment hybridizes to the constant (C)-region probe. Segregation of the polymorphic bands was analyzed in family studies. To look for associations between these markers and autoimmune diseases, we have studied the restriction fragment length polymorphism distribution of the Pss I markers in patients with multiple sclerosis, myasthenia gravis, and Graves disease. Significant differences in the frequency of the polymorphic V alpha and C alpha markers were identified between patients and healthy individuals. Images PMID:2915992

  18. Modeling Solar Lyman Alpha Irradiance

    NASA Technical Reports Server (NTRS)

    Pap, J.; Hudson, H. S.; Rottman, G. J.; Willson, R. C.; Donnelly, R. F.; London, J.

    1990-01-01

    Solar Lyman alpha irradiance is estimated from various solar indices using linear regression analyses. Models developed with multiple linear regression analysis, including daily values and 81-day running means of solar indices, predict reasonably well both the short- and long-term variations observed in Lyman alpha. It is shown that the full disk equivalent width of the He line at 1083 nm offers the best proxy for Lyman alpha, and that the total irradiance corrected for sunspot effect also has a high correlation with Lyman alpha.

  19. Binding and modification of proteins by methylglyoxal under physiological conditions. A kinetic and mechanistic study with N alpha-acetylarginine, N alpha-acetylcysteine, and N alpha-acetyllysine, and bovine serum albumin.

    PubMed

    Lo, T W; Westwood, M E; McLellan, A C; Selwood, T; Thornalley, P J

    1994-12-23

    The physiological alpha-oxoaldehyde methylglyoxal binds and modifies arginine, lysine, and cysteine residues in proteins. The kinetics and mechanism of these reactions were investigated with N alpha-acetylamino acids and bovine serum albumin at pH 7.4 and 37 degrees C. The reaction of methylglyoxal with N alpha-acetylarginine involved the initial reversible formation of glycosylamine and 4,5-dihydroxy-5-methylimidazolidine derivatives, with further slow irreversible conversion to an imidazolone, N alpha-acetyl-N delta- (5-methyl-4-imidazolon-2-yl)ornithine. The imidazolone was fluorescent with an excitation lambda max value of 320 nm and an emission lambda max value of 398 nm. Methylglyoxal reacted reversibly with N alpha-acetyllysine to form glycosylamine and bisglycosylamine derivatives. Further reaction of these glycosylamines occurred to form brown, fluorescent oligomers that were not characterized. Methylglyoxal reacted rapidly and reversibly with N alpha-acetylcysteine to form the hemithioacetal adduct. The reaction of methylglyoxal with bovine serum albumin (BSA) at pH 7.4 and 37 degrees C involved the reversible and irreversible formation of methylglyoxal-BSA adducts. Irreversible modification of BSA occurred mainly on arginine residues to form imidazolone. The formation of methylglyoxal-modified proteins involves glycoxidation leading to advanced glycation end product-like fluorescence. It is expected to be increased in diabetes mellitus and may be linked to the development of diabetic complications.

  20. Drug Reactions

    MedlinePlus

    Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions. One problem is ...

  1. Purification and characterization of a Bacillus licheniformis phosphatase specific for D-alpha-glycerophosphate.

    PubMed

    Skraly, F A; Cameron, D C

    1998-01-01

    Bacillus licheniformis ("Ford's type") was found to contain a novel enzyme, D-alpha-glycerophosphatase. The enzyme is highly specific for D-alpha-glycerophosphate, effecting little or no hydrolysis of L-alpha- or beta-glycerophosphate or other similar compounds. All other known alpha-glycerophosphatases preferentially hydrolyze the L isomer. The products of the D-alpha-glycerophosphatase reaction were identified as glycerol and inorganic phosphate. The enzyme is a monomer with an apparent molecular mass of approximately 25 kDa. As with most phosphatases, it requires divalent magnesium for activity, but unlike the nonspecific acid and alkaline phosphatases, its optimum pH is around neutral. Its K(m) for D-alpha-glycerophosphate in the presence of 1 mM Mg2+ was found to be 4.3 mM. D-alpha-glycerophosphatase was produced in B. licheniformis fermentations whether or not high levels of phosphate were present; the same was true of glycerol formation. D-alpha-glycerophosphatase is not strongly inhibited by inorganic phosphate and would therefore be capable of catalyzing the formation of glycerol in the presence of high levels of phosphate. The D-alpha-glycerophosphatase of B. licheniformis is similar in characteristics to L-alpha-glycerophosphatases known to synthesize glycerol in vivo, suggesting that D-alpha-glycerophosphatase may be the final enzyme in the fermentative glycerol formation pathway of B. licheniformis.

  2. Alpha Kappa Alpha Sorority's Reading Improvement Program for Minorities.

    ERIC Educational Resources Information Center

    Marable, June Morehead

    This document discusses the founding and establishment of Alpha Kappa Alpha Sorority's reading experience pilot project. The efforts of this project were aligned with those of Right to Read and Reading Is Fundamental (RIF). Because of the response from parents and children, plans are being made to increase present operations within the next…

  3. Molecular characterization of alpha 1- and alpha 2-adrenoceptors.

    PubMed

    Harrison, J K; Pearson, W R; Lynch, K R

    1991-02-01

    Three 'alpha 1-adrenoceptors' and three 'alpha 2-adrenoceptors' have now been cloned. How closely do these receptors match the native receptors that have been identified pharmacologically? What are the properties of these receptors, and how do they relate to other members of the cationic amine receptor family? Kevin Lynch and his colleagues discuss these questions in this review.

  4. Complete remission of multiple myeloma after autoimmune hemolytic anemia: possible association with interferon-alpha.

    PubMed

    Gesundheit, Benjamin; Zelig, Orly; Shapira, Michael Y; Ackerstein, Aliza; Avgil, Meytal; Or, Reuven

    2007-06-01

    A patient with multiple myeloma (MM) was being maintained on human recombinant interferon-alpha (INF-alpha) after VAD and autologous bone marrow transplantation (pretreated with melphalan). An episode of immune thrombocytopenia and (Coombs positive) autoimmune hemolytic anemia (AIHA) was noted while on maintenance INF-alpha, which remitted when it was withdrawn. Following this event, he achieved a state of stable disease that persists (more than 3 years) with no specific myeloma treatment. This sequence of events suggests a relationship between an immunological reaction induced by INF-alpha and the prolonged phase of stable disease.

  5. Microscopic cluster model of {alpha}+n, {alpha}+p, {alpha}+ {sup 3}He, and {alpha}+{alpha} elastic scattering from a realistic effective nuclear interaction

    SciTech Connect

    Dohet-Eraly, J.; Baye, D.

    2011-07-15

    An effective nucleon-nucleon interaction adapted to cluster-model calculations of collisions is derived from the realistic Argonne potential AV18 with the unitary correlation operator method. The unitary correlation is determined from the {alpha}+{alpha} elastic phase shifts calculated in a cluster approach by the generator coordinate method coupled with the microscopic R-matrix method. With this interaction, the elastic phase shifts for the {alpha}+n, {alpha}+p, and {alpha}+{sup 3}He collisions are calculated within the same model. Without further adjustment, a good agreement with experimental data is obtained with a small model space.

  6. Alpha-particle microdosimetry.

    PubMed

    Chouin, Nicolas; Bardies, Manuel

    2011-07-01

    With the increasing availability of alpha emitters, targeted α-particle therapy has emerged as a solution of choice to treat haematological cancers and micrometastatic and minimal residual diseases. Alpha-particles are highly cytotoxic because of their high linear energy transfer (LET) and have a short range of a few cell diameters in tissue, assuring good treatment specificity. These radiologic features make conventional dosimetry less relevant for that context. Stochastic variations in the energy deposited in cell nuclei are important because of the microscopic target size, low number of α- particle traversals, and variation in LET along the α-particle track. Microdosimetry provides a conceptual framework that aims at a systematic analysis of the stochastic distribution of energy deposits in irradiated matter. The different quantities of microdosimetry and the different methods of microdosimetric calculations were described in the early eighties. Since then, numerous models have been published through the years and applied to analyse experimental data or to model realistic therapeutic situations. Major results have been an accurate description of the high toxicity of α-particles, and the description of the predominant effect of activity distribution at the cellular scale on toxicity or efficacy of potential targeted α-particle therapies. This last factor represents a major limitation to the use of microdosimetry in vivo because determination of the source - target distribution is complicated. The future contributions of microdosimetry in targeted α-particle therapy research will certainly depend on the ability to develop high-resolution detectors and on the implementation of pharmaco-kinetic models at the tumour microenvironment scale.

  7. Substitutional and Interstitial Diffusion in alpha2-Ti3Al(O)

    NASA Technical Reports Server (NTRS)

    Copland, Evan; Young, David J.; Gleeson, Brian; Jacobson, Nathan

    2007-01-01

    The reaction between Al2O3 and alpha2-Ti3Al was studied with a series of Al2O3/alpha2-Ti3Al multiphase diffusion couples annealed at 900, 1000 and 1100 C. The diffusion-paths were found to strongly depend on alpha2- Ti3Al(O) composition. For alloys with low oxygen concentrations the reaction involved the reduction of Al2O3, the formation of a gamma-TiAl reaction-layer and diffusion of Al and O into the alpha2-Ti3Al substrate. Measured concentration profiles across the interaction-zone showed "up-hill" diffusion of O in alpha2-Ti3Al(O) indicating a significant thermodynamic interaction between O and Al, Ti or both. Diffusion coefficients for the interstitial O in alpha2-Ti3Al(O) were determined independently from the interdiffusion of Ti and Al on the substitutional lattice. Diffusion coefficients are reported for alpha2-Ti3Al(O) as well as gamma-TiAl. Interpretation of the results were aided with the subsequent measurement of the activities of Al, Ti and O in alpha 2-Ti3Al(O) by Knudsen effusion-cell mass spectrometry.

  8. Action pattern of human pancreatic and salivary alpha-amylase on 1,4-alpha-D-nitrophenylmaltooligosaccharides. 1,4-alpha-D-nitrophenylmaltooligosaccharides as substrates of alpha-amylse, I.

    PubMed

    Wallenfels, K; Laule, G; Meltzer, B

    1982-08-01

    High performance liquid chromatography (HPLC) was used to monitor the purity of the substrates and to establish the patterns of hydrolysis of ortho- and para-nitrophenylmaltooligosaccharides (2-7 glucose residues) catalysed by human pancreatic and salivary alpha-amylase. Separation of the reaction products from the remaining substrate was performed on a TSK-G-2000 PW or a RP18 column. By measuring the quantitative distribution of products, and assuming a 5-subsite model for the active site of alpha-amylase, differential activities for the hydrolysis of the different glycosidic bonds in the 2 series of substrates were deduced. A highly sensitive coupled continuous assay system is based on the formation of phenyloligosaccharides with 1-4 glucose residues by the action of the amylase under test, coupled to hydrolysis of these products by yeast alpha-glucosidase. The most suitable test substrates were shown to be para-nitrophenyl-alpha-D-maltotetraoside and -pentaoside. Direct production of nitrophenol from ortho-nitrophenyl-alpha-D-maltotrioside is recommended for the measurement of the alpha-amylase activity of pancreatic and salivary gland secretions and extracts.

  9. Airway epithelial cell wound repair mediated by alpha-dystroglycan.

    PubMed

    White, S R; Wojcik, K R; Gruenert, D; Sun, S; Dorscheid, D R

    2001-02-01

    Dystroglycans (DGs) bind laminin matrix proteins in skeletal and cardiac muscle and are expressed in other nonmuscle tissues. However, their expression in airway epithelial cells has not been demonstrated. We examined expression of DGs in the human airway epithelial cell line 1HAEo(-), and in human primary airway epithelial cells. Expression of the common gene for alpha- and beta-DG was demonstrated by reverse transcriptase/ polymerase chain reaction in 1HAEo(-) cells. Protein expression of beta-DG was demonstrated by both Western blot and flow cytometry in cultured cells. Localization of alpha-DG, using both a monoclonal antibody and the alpha-DG binding lectin wheat-germ agglutinin (WGA), was to the cell membrane and nucleus. We then examined the function of DGs in modulating wound repair over laminin matrix. Blocking alpha-DG binding to laminin in 1HAEo(-) monolayers using either glycosyaminoglycans or WGA attenuated cell migration and spreading after mechanical injury. alpha-DG was not expressed in epithelial cells at the wound edge immediately after wound creation, but localized to the cell membrane in these cells within 12 h of injury. These data demonstrate the presence of DGs in airway epithelium. alpha-DG is dynamically expressed and serves as a lectin to bind laminin during airway epithelial cell repair.

  10. DFT CONFORMATIONAL STUDIES OF ALPHA-MALTOTRIOSE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recent DFT optimization studies on alpha-maltose improved our understanding of the preferred conformations of alpha-maltose and the present study extends these studies to alpha-maltotriose with three alpha-D-glucopyranose residues linked by two alpha-[1-4] bridges, denoted herein as DP-3's. Combina...

  11. Prothymosin alpha in human blood.

    PubMed Central

    Panneerselvam, C; Haritos, A A; Caldarella, J; Horecker, B L

    1987-01-01

    The major cross-reacting peptide in human plasma detected with a radioimmunoassay (RIA) for thymosin alpha 1 was identified as prothymosin alpha, based on its elution properties in gel-filtration chromatography and its amino acid composition after purification by HPLC. A small quantity (less than 10%) of the total cross-reacting material was recovered in fractions corresponding to lower molecular weight thymosin alpha 1-like peptides. The total quantity of cross-reacting material detected in human blood, expressed as thymosin alpha 1 equivalents, was 11-14 pmol/ml (approximately 90% was recovered in the leukocyte fraction, approximately 10% was in the plasma fraction, and 1-2% was in the erythrocyte fraction). The peptide present in leukocytes was also identified as prothymosin alpha. After correction for the 5-times lower molar reactivity of prothymosin alpha in the thymosin alpha 1 RIA employed in these experiments, we estimate that the content of prothymosin alpha in human blood is 55-70 pmol/ml (0.6-0.8 microgram/ml). The relatively small quantities recovered in the erythrocyte and plasma fractions may be attributed to contamination of the former by leukocytes or to leakage from leukocytes into the plasma. PMID:3474615

  12. EEG Alpha Power and Intelligence.

    ERIC Educational Resources Information Center

    Doppelmayr, M.; Klimesch, W.; Stadler, W.; Pollhuber, D.; Heine, C.

    2002-01-01

    Tested whether alpha power in different sub-bands is selectively related to intelligence. For 74 Austrian subjects, the EEG was recorded during a resting session and 2 different intelligence tests were performed. Findings show a strong positive correlation between intelligence and alpha power. (SLD)

  13. Alpha particle emitters in medicine

    SciTech Connect

    Fisher, D.R.

    1989-09-01

    Radiation-induced cancer of bone, liver and lung has been a prominent harmful side-effect of medical applications of alpha emitters. In recent years, however, the potential use of antibodies labeled with alpha emitting radionuclides against cancer has seemed promising because alpha particles are highly effective in cell killing. High dose rates at high LET, effectiveness under hypoxic conditions, and minimal expectancy of repair are additional advantages of alpha emitters over antibodies labeled with beta emitting radionuclides for cancer therapy. Cyclotron-produced astatine-211 ({sup 211}At) and natural bismuth-212 ({sup 212}Bi) have been proposed and are under extensive study in the United States and Europe. Radium-223 ({sup 223}Ra) also has favorable properties as a potential alpha emitting label, including a short-lived daughter chain with four alpha emissions. The radiation dosimetry of internal alpha emitters is complex due to nonuniformly distributed sources, short particle tracks, and high relative specific ionization. The variations in dose at the cellular level may be extreme. Alpha-particle radiation dosimetry, therefore, must involve analysis of statistical energy deposition probabilities for cellular level targets. It must also account fully for nonuniform distributions of sources in tissues, source-target geometries, and particle-track physics. 18 refs., 4 figs.

  14. Optical and electron transport properties of rock-salt Sc{sub 1−x}Al{sub x}N

    SciTech Connect

    Deng, Ruopeng; Zheng, P. Y.; Gall, D.

    2015-07-07

    Epitaxial single-crystal Sc{sub 1−x}Al{sub x}N ternary alloy layers deposited by magnetron co-sputtering on MgO(001) substrates at 950 °C exhibit a solid solution rock-salt phase for x = 0–0.2 without decomposition. Optical absorption indicates a linear increase in the optical gap from 2.51 eV for ScN to 3.05 eV for Sc{sub 0.8}Al{sub 0.2}N and, after correction due to the Moss-Burstein shift, a direct X point interband transition energy E{sub g}(X) = 2.15 + 2.75 x (eV). Correspondingly, the direct transition at the zone center increases with Al concentration according to E{sub g}(Γ) = 3.80 + 1.45 x (eV), as determined from a feature in the reflection spectra. All layers are degenerate n-type semiconductors with a room temperature mobility that decreases from 22 to 6.7 to 0.83 cm{sup 2}/V s as x increases from 0 to 0.11 to 0.20. The corresponding carrier densities are 9.2 × 10{sup 20}, 7.9 × 10{sup 20}, and 0.95 × 10{sup 20 }cm{sup −3} as determined from Hall measurements and consistent with optical free carrier absorption below photon energies of 1 eV. Temperature dependent transport measurements indicate metallic conduction for ScN, but weak localization that leads to a resistivity minimum at 85 and 210 K for x = 0.051 and 0.15, respectively, and a negative temperature coefficient over the entire measured 4–300 K range for Sc{sub 0.8}Al{sub 0.2}N. The decreasing mobility is attributed to alloy scattering at randomly distributed Al atoms on cation sites, which also cause the weak localization. The carrier density is primarily due to unintentional F doping from the Sc target and decreases strongly for x > 0.15, which is attributed to trapping in defect states due to the deterioration of the crystalline quality, as evidenced by the x-ray diffraction peak width that exhibits a minimum of 0.14° for x = 0.11 but increases to 0.49° for x = 0.20. This is consistent with asymmetric x

  15. Investigation of a stereoselective co-mediated rearrangement reaction.

    PubMed

    Carbery, David R; Reignier, Serge; Miller, Neil D; Adams, Harry; Harrity, Joseph P A

    2003-05-30

    A stereocontrolled approach to alpha-alkyl beta-alkynyl cyclohexanones is reported through a Lewis acid mediated rearrangement reaction of enol ethers bearing an Co-alkyne moiety. The reaction proceeds with high levels of stereoselectivity in the presence of Ti- and B-Lewis acids to provide a range of alpha,beta-disubstituted cyclohexanones in high yield although the products are prone to epimerization at the alpha-position in the presence of the B-promoter system. The potential for an enantioselective variant of this process is outlined, and a rationale for the observed stereochemical trends and detailed structural analyses of the ketone products are described.

  16. The solid-phase Nicholas reaction: scope and limitations.

    PubMed

    Gachkova, Natalie; Cassel, Johan; Leue, Stefanie; Kann, Nina

    2005-01-01

    Two libraries of alpha-substituted alkynes has been prepared on solid phase using a sequential Sonogashira/Nicholas reaction approach. The scope of nucleophiles in the Nicholas reaction on solid phase has been investigated, including carbon, oxygen, nitrogen, sulfur, fluoride, and hydride nucleophiles. The conditions for the reaction sequence have been optimized in terms of Lewis acid, catalyst for the Sonogashira step, temperature, reaction time, and decomplexation method, enabling the five-step sequence to be performed in 1 day.

  17. Metals, a Plasma of the Poor Man: Electron Screening in 7Li(p,{alpha}){alpha} and 6Li(p,{alpha})3He for Different Environments

    SciTech Connect

    Rolfs, C.

    2006-05-24

    The electron screening in the 7Li(p,{alpha}){alpha} reaction has been studied at Ep = 30 to 100 keV for different environments: Li2WO4 insulator, Li metal, and PdLi alloys. For the insulator a screening potential energy of Ue = 185{+-}150 eV was observed, consistent with previous work and the atomic adiabatic limit. However, for the Li metal and the PdLi alloys we find large values of Ue = 1280{+-}60 and 3790{+-}330 eV, respectively: the values can be explained by the plasma model of Debye applied to the quasi-free metallic electrons in these samples. Similar results have been found for the 6Li(p,{alpha})3He reaction supporting the hypothesis of the isotopic independence of the electron screening effect. The data together with previous studies of d(d,p)t and 9Be(p,{alpha})6Li in metals verify the Debye model scaling Ue {proportional_to} Zt (charge number of target)

  18. Face-selective Diels-Alder reactions between unsymmetrical cyclohexadienes and symmetric trans-dienophile: an experimental and computational investigation.

    PubMed

    Lahiri, Saswati; Yadav, Somnath; Banerjee, Srirupa; Patil, Mahendra P; Sunoj, Raghavan B

    2008-01-18

    A combined experimental and theoretical study of the Diels-Alder reactions between 2-trimethylsiloxy-1,3-cyclohexadienes (2-11) and (E)-1,4-diphenylbut-2-ene-1,4-dione (1) is reported. Two diastereomeric products, 5-endo-6-exo- (nx) and 5-exo-6-endo- (xn) dibenzoyl derivatives, are possible with symmetric trans-dienophile (1). While in many cases 5-endo-6-exo product is preferred over the corresponding 5-exo-6-endo product, the product ratio nx:xn is found to vary with the position of substituents on the diene. The density functional theory studies with the mPW1PW91/6-31G* as well as the B3LYP/6-31G* levels reveal that the electrostatic repulsion between the oxygen lone pairs on the diene and the dienophile is critical to the observed product selectivities. The optimized transition state geometries though appeared to involve secondary orbital interactions, careful examination of the frontier Kohn-Sham orbitals as well as calculations with the natural bond orbital (NBO) analyses confirm the absence of SOI in these transition states. In the case of methyl-substituted dienes, a cumulative effect of steric and electrostatic interactions between the diene and the dienophile is found to be the controlling element toward the observed selectivity.

  19. Exploring clustering in alpha-conjugate nuclei using the thick target inverse kinematic technique for multiple alpha emission

    NASA Astrophysics Data System (ADS)

    Barbui, M.; Hagel, K.; Gauthier, J.; Wuenschel, S.; Goldberg, V. Z.; Zheng, H.; Giuliani, G.; Rapisarda, G.; Kim, E.-J.; Liu, X.; Natowitz, J. B.; Desouza, R. T.; Hudan, S.; Fang, D.

    2015-10-01

    Searching for alpha cluster states analogous to the 12C Hoyle state in heavier alpha-conjugate nuclei can provide tests of the existence of alpha condensates in nuclear matter. Such states are predicted for 16O, 20Ne, 24Mg, etc. at excitation energies slightly above the decay threshold. The Thick Target Inverse Kinematics (TTIK) technique can be successfully used to study the breakup of excited self-conjugate nuclei into many alpha particles. The reaction 20Ne + α at 11 and 13 AMeV was studied at Cyclotron Institute at Texas A&M University. Here the TTIK method was used to study both single α-particle emission and multiple α-particle decays. Due to the limited statistics, only events with alpha multiplicity up to three were analyzed. The analysis of the three α-particle emission data allowed the identification of the Hoyle state and other 12C excited states decaying into three alpha particles. The results will be shown and compared with other data available in the literature. Another experiment is planned in August 2015 to study the system 28Si + α at 15 AMeV. Preliminary results will be shown. Supported by the U.S. DOE and the Robert A. Welch Foundation, Grant No. A0330.

  20. TNF-alpha SNP haplotype frequencies in equidae.

    PubMed

    Brown, J J; Ollier, W E R; Thomson, W; Matthews, J B; Carter, S D; Binns, M; Pinchbeck, G; Clegg, P D

    2006-05-01

    Tumour necrosis factor alpha (TNF-alpha) is a pro-inflammatory cytokine that plays a crucial role in the regulation of inflammatory and immune responses. In all vertebrate species the genes encoding TNF-alpha are located within the major histocompatability complex. In the horse TNF-alpha has been ascribed a role in a variety of important disease processes. Previously two single nucleotide polymorphisms (SNPs) have been reported within the 5' un-translated region of the equine TNF-alpha gene. We have examined the equine TNF-alpha promoter region further for additional SNPs by analysing DNA from 131 horses (Equus caballus), 19 donkeys (E. asinus), 2 Grant's zebras (E. burchellii boehmi) and one onager (E. hemionus). Two further SNPs were identified at nucleotide positions 24 (T/G) and 452 (T/C) relative to the first nucleotide of the 522 bp polymerase chain reaction product. A sequence variant at position 51 was observed between equidae. SNaPSHOT genotyping assays for these and the two previously reported SNPs were performed on 457 horses comprising seven different breeds and 23 donkeys to determine the gene frequencies. SNP frequencies varied considerably between different horse breeds and also between the equine species. In total, nine different TNF-alpha promoter SNP haplotypes and their frequencies were established amongst the various equidae examined, with some haplotypes being found only in horses and others only in donkeys or zebras. The haplotype frequencies observed varied greatly between different horse breeds. Such haplotypes may relate to levels of TNF-alpha production and disease susceptibility and further investigation is required to identify associations between particular haplotypes and altered risk of disease.

  1. Prevalence of -alpha(3.7) and alpha alpha alpha(anti3.7) alleles in sickle cell trait and beta-thalassemia patients in Mexico.

    PubMed

    Nava, María Paulina; Ibarra, Bertha; Magaña, María Teresa; de la Luz Chávez, María; Perea, F Javier

    2006-01-01

    The aim of this study was to determine the frequency of alpha-globin gene mutations in three groups of Mexican unrelated individuals. The first two groups were normal and sickle cell trait individuals from the Costa Chica region, a place with a 12.8% frequency of HbS carriers, and the third group comprised of Mexican mestizo patients with beta-thalassemia. We searched for -alpha(3.7) and -alpha(4.2) alpha(+)-thalassemia deletion alleles, as well as the alpha alpha alpha(anti3.7) triplication through long-gap PCR. The alleles -alpha(3.7) and alpha alpha alpha(anti3.7) were found in the heterozygote state only; 19% of the normal subjects had the -alpha(3.7) allele, and 2% showed the alpha alpha alpha(anti3.7) allele. In individuals with the sickle cell trait, 17% had the -alpha(3.7) deletion, and the alpha alpha alpha(anti3.7) triplication was observed in 3% of these individuals. We revealed that 16% of the subjects with beta-thalassemia showed the -alpha(3.7) deletion and 28% the alpha alpha alpha(anti3.7) triplication. The -alpha(4.2) deletion was not detected in any individual. The frequency of the -alpha(3.7) allele was roughly the same in the three groups studied; this can be explained by the fact that the three groups have common genes from Africa and the Mediterranean, where a high prevalence of alpha(+)-thalassemia has been observed. To our knowledge, the frequency of alpha alpha alpha(anti3.7) triplication observed in the Mexican beta-thalassemia patients is the highest reported. As the -alpha(3.7) and alpha alpha alpha(anti3.7) alleles are very common in our selected populations, we believe that there is a need to investigate systematically the alpha-globin gene mutations in all hemoglobinopathies in the Mexican population.

  2. The human alpha 2-macroglobulin receptor: identification of a 420-kD cell surface glycoprotein specific for the activated conformation of alpha 2-macroglobulin

    PubMed Central

    1990-01-01

    Ligand affinity chromatography was used to purify a cell surface alpha 2-macroglobulin (alpha 2M) receptor. Detergent extracts of human placenta were applied to an affinity matrix consisting of alpha 2M, previously reacted with methylamine, coupled to Sepharose. Elution with EDTA specifically released polypeptides with apparent molecular masses of 420 and 39 kD. In some preparations, small amounts of a 90-kD polypeptide were observed. The 420- and 39-kD polypeptides appear specific for the forms of alpha 2M activated by reaction with proteinases or methylamine and do not bind to an affinity matrix consisting of native alpha 2M coupled to Sepharose. Separation of these two polypeptides was accomplished by anion exchange chromatography, and binding activity was exclusively associated with the 420-kD polypeptide. The purified 420-kD protein binds to the conformationally altered forms of alpha 2M that are known to specifically interact with alpha 2M receptors and does not bind to native alpha 2M. Binding of the 420-kD polypeptide to immobilized wheat germ agglutinin indicates that this polypeptide is a glycoprotein. The cell surface localization of the 420-kD glycoprotein was confirmed by affinity chromatography of extracts from surface radioiodinated fibroblasts. These properties suggest that the 420-kD polypeptide is a cell surface receptor for the activated forms of alpha 2M. PMID:1691187

  3. A molecular map of G protein alpha chains in microdissected rat nephron segments.

    PubMed Central

    Senkfor, S I; Johnson, G L; Berl, T

    1993-01-01

    Membrane-associated guanine nucleotide binding proteins regulate many receptor-mediated signals. Heterogeneity of biochemical and functional properties in nephron segments could be due to differences in G protein expression. To ascertain whether such heterogeneity of G proteins is present in various nephron segments, this study examines the distribution and relative abundance of G protein alpha chains in microdissected medullary thick ascending limb, cortical collecting tubules, outer medullary collecting tubules, proximal inner medullary tubules, and distal inner medullary tubules. Reverse transcription and polymerase chain reactions were employed using oligonucleotides encoding highly conserved regions of all known alpha chains. The cDNA was sequenced for alpha chain identification. The alpha i2 versus alpha s distribution was different in the outer medullary collecting tubules, when compared with the medullary thick ascending limb (P < 0.001) or the cortical collecting tubule, the proximal inner medullary tubules, and the distal inner medullary tubules (P < 0.05). These latter four segments did not significantly differ from each other. A similar analysis was applied to the frequently used line of kidney cells, LLC-PK1, whose exact cellular origin remains unclear. Interestingly, we detected both alpha i2 and alpha i3, while only alpha i2 was detected in the rat distal nephron. No alpha o or alpha z reverse transcription PCR products were detected. In contrast alpha 11 and alpha 14 members of the more recently described alpha q family were detected in the outer medullary collecting tubules and the proximal inner medullary tubules, respectively. We conclude that the majority of nephron segments have a relatively constant distribution of G protein alpha chains. Images PMID:8349818

  4. Allergic Reactions

    MedlinePlus

    ... that is right for you. In many instances, allergy immunotherapy in the form of shots or tablets is an effective, cost-efficient long term treatment approach. While there is not yet ... Healthy Tips • Allergy symptoms are the result of a chain reaction ...

  5. Reaction of Tris(cyclopentadienyl)uranium compounds with amines, azides, and related ligands

    SciTech Connect

    Rosen, R.K.

    1989-12-01

    The trivalent uranium compound, (MeC{sub 5}H{sub 4}){sub 3}U(thf), serves as a one- or two-electron reducing agent towards azides, RN{sub 3}. These reactions produce either the uranium(IV) azide, (MeC{sub 5}H{sub 4}){sub 3}UN{sub 3}, or uranium(V) imides, (MeC{sub 5}H{sub 4}){sub 3}UNR. The role of steric and electronic effects upon this reaction has been investigated using several series of azides. For Me{sub 3}XN{sub 3}, the imides are produced when X = C or Si, both products are formed when X = Ge, and the azide is produced when X = Sn. For Ph{sub 3}XN{sub 3}, the azide is produced when X = C or Sn. For Ph{sub 3-x}CH{sub 3}N{sub 3}, the imide is produced when x = 2 and both compounds are produced when x = 1. For substituted phenylazides, RC{sub 6}H{sub 4}N{sub 3}, only the imides are produced. The magnetic properties of uranium diimides, ((MeC{sub 5}H{sub 4}){sub 3}U){sub 2}({mu}-NRN), were investigated. Several uranium(III) amines, (MeC{sub 5}H{sub 4}){sub 3}U(NH{sub 2}R), were produced from (MeC{sub 5}H{sub 4}){sub 3}U(thf) and RNH{sub 2}, and NH{sub 3} was found to be a better ligand towards (MeC{sub 5}H{sub 4}){sub 3}U than is PMe{sub 3}.

  6. Oxidative inactivation of alpha 1-proteinase inhibitor by alveolar epithelial type II cells.

    PubMed

    Wallaert, B; Aerts, C; Gressier, B; Gosset, P; Voisin, C

    1993-12-01

    The aim of this work was to evaluate the ability of guinea pig alveolar epithelial type II cells to generate significant amounts of reactive oxygen species to inactivate alpha 1-proteinase inhibitor (alpha 1-PI). Inactivation of alpha 1-PI was evaluated by its inhibitory activity against porcine pancreatic elastase and was expressed as a percentage. The same experiments were performed in parallel with alveolar macrophages (AM) obtained from the same animals and with MRC-5 fibroblasts. Both type II cells and AM released significant amounts of hydrogen peroxide and superoxide, whereas the fibroblasts did not. Unstimulated type II cells (0.5 +/- 2%), AM (1.2 +/- 1.5%), and fibroblasts (0.5 +/- 0.5%) were unable to inactivate alpha 1-PI. Addition of phorbol myristate acetate did not increase their ability to inactivate alpha 1-PI. In contrast, type II cells (79.7 +/- 7%) and AM (80.1 +/- 8%) dramatically inactivated alpha 1-PI in the presence of myeloperoxidase (25 mU/ml), whereas fibroblasts did not. Addition of catalase to the reaction significantly prevented the inactivation of alpha 1-PI. Western blot analysis of alpha 1-PI did not reveal a significant proteolysis of alpha 1-PI, which supports the hypothesis that, in the presence of neutrophil-derived myeloperoxidase, type II cells may oxidatively inactivate alpha 1-PI.

  7. Venus - Alpha Regio

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The eastern edge of Alpha Regio is shown in this image centered at 30 degrees south latitude and 11.8 degrees east longitude (longitude on Venus is measured from 0 degrees to 360 degrees east). Seven circular, dome-like hills, averaging 25 kilometers (15 miles) in diameter with maximum heights of 750 meters (2,475 feet) dominate the scene. These features are interpreted as very thick lava flows that came from an opening on the relatively level ground, which allowed the lava to flow in an even pattern outward from the opening. The complex fractures on top of the domes suggest that if the domes were created by lava flows, a cooled outer layer formed and then further lava flowing in the interior stretched the surface. The domes may be similar to volcanic domes on Earth. Another interpretation is that the domes are the result of molten rock or magma in the interior that pushed the surface layer upward. The near-surface magma then withdrew to deeper levels, causing the collapse and fracturing of the dome surface. The bright margins possibly indicate the presence of rock debris on the slopes of the domes. Some of the fractures on the plains cut through the domes, while others appear to be covered by the domes. This indicates that active processes pre date and post date the dome-like hills. The prominent black area in the northeast corner of the image is a data gap. North is at the top of the image.

  8. Manganese(II)-azido/thiocyanato complexes of naphthylazoimidazoles: X-ray structures of Mn(β-NaiEt) 2(X) 2 (β-NaiEt = 1-ethyl-2-(naphthyl-β-azo)imidazole; X=N3-, NCS -)

    NASA Astrophysics Data System (ADS)

    Das, D.; Chand, B. G.; Wu, J. S.; Lu, T.-H.; Sinha, C.

    2007-10-01

    Manganese(II)-naphthylazoimidazole complexes using N3- and NCS - as counter ions are characterized as Mn(β-NaiR) 2(X) 2(β-NaiEt = 1-alkyl-2-(naphthyl-β-azo)imidazole; X=N3-, NCS -). The ligands are unsymmetric N(imidazole), N(azo) chelating agents. The microanalytical, spectral (FT-IR, UV-vis), magnetic (bulk moment and EPR) and electrochemical data establish the structure and composition of the complexes. The single crystal X-ray diffraction studies of Mn(β-NaiEt) 2(N 3) 2 and Mn(β-NaiEt) 2(NCS) 2(β-NaiEt = 1-ethyl-2-(naphthyl-β-azo)imidazole) have confirmed the three dimensional structure of the complexes. Cyclic voltammetry exhibits high potential Mn(III)/Mn(II) couple along with azo reductions. The EPR spectra show usual pattern.

  9. KOH based selective wet chemical etching of AlN, AlxGa1-xN, and GaN crystals: A way towards substrate removal in deep ultraviolet-light emitting diode

    SciTech Connect

    Guo, W; Kirste, R; Bryan, I; Bryan, Z; Hussey, L; Reddy, P; Tweedie, J; Collazo, R; Sitar, Z

    2015-02-23

    A controllable and smooth potassium hydroxide-based wet etching technique was developed for the AlGaN system. High selectivity between AlN and AlxGa1-xN (up to 12 x) was found to be critical in achieving effective substrate thinning or removal for AlGaN-based deep ultraviolet light emitting diodes, thus increasing light extraction efficiency. The mechanism of high selectivity of AlGaN as a function of Al composition can be explained as related to the formation and dissolution of oxide/hydroxide on top of N-polar surface. Cross-sectional transmission electron microscopic analysis served as ultimate proof that these hillocks were not related to underlying threading dislocations. (C) 2015 AIP Publishing LLC.

  10. Alpha-particle spectrometer experiment

    NASA Technical Reports Server (NTRS)

    Gorenstein, P.; Bjorkholm, P.

    1972-01-01

    Mapping the radon emanation of the moon was studied to find potential areas of high activity by detection of radon isotopes and their daughter products. It was felt that based on observation of regions overflown by Apollo spacecraft and within the field of view of the alpha-particle spectrometer, a radon map could be constructed, identifying and locating lunar areas of outgassing. The basic theory of radon migration from natural concentrations of uranium and thorium is discussed in terms of radon decay and the production of alpha particles. The preliminary analysis of the results indicates no significant alpha emission.

  11. Sputter deposition of high transparent TiO 2- xN x/TiO 2/ZnO layers on glass for development of photocatalytic self-cleaning application

    NASA Astrophysics Data System (ADS)

    Nejand, B. Abdollahi; Sanjabi, S.; Ahmadi, V.

    2011-10-01

    In this study, TiO 2- xN x/TiO 2 double layers thin film was deposited on ZnO (80 nm thickness)/soda-lime glass substrate by a dc reactive magnetron sputtering. The TiO 2 film was deposited under different total gas pressures of 1 Pa, 2 Pa, and 4 Pa with constant oxygen flow rate of 0.8 sccm. Then, the deposition was continued with various nitrogen flow rates of 0.4, 0.8, and 1.2 sccm in constant total gas pressure of 4 Pa. Post annealing was performed on as-deposited films at various annealing temperatures of 400, 500, and 600 °C in air atmosphere to achieve films crystallinity. The structure and morphology of deposited films were evaluated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). The chemical composition of top layer doped by nitrogen was evaluated by X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of samples was measured by degradation of Methylene Blue (MB) dye. The optical transmittance of the multilayer film was also measured using ultraviolet-visible light (UV-vis) spectrophotometer. The results showed that by nitrogen doping of a fraction (˜1/5) of TiO 2 film thickness, the optical transmittance of TiO 2- xN x/TiO 2 film was compared with TiO 2 thin film. Deposited films showed also good photocatalytic and hydrophilicity activity at visible light.

  12. Structural and optical properties of AlxGa1-xN (0.33 ≤ x ≤ 0.79) layers on high-temperature AlN interlayer grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Xu, Qingjun; Liu, Bin; Zhang, Shiying; Tao, Tao; Dai, Jiangping; He, Guotang; Xie, Zili; Xiu, Xiangqian; Chen, Dunjun; Chen, Peng; Han, Ping; Zhang, Rong

    2017-01-01

    High-Al-content AlxGa1-xN films with x varying from 0.33 to 0.79 were grown on GaN templates with the high temperature AlN (HT-AlN) interlayer by metal organic chemical vapor deposition (MOCVD). The best crystalline quality, among these AlxGa1-xN alloys, can be obtained for an AlN mole fraction x = 0.55, where the full-width at half-maximum of the Al0.55Ga0.45N (0002) diffraction peak was measured to be 259 arcsec by high resolution X-ray diffraction (HRXRD). The screw threading dislocation (TDs) density was 2 × 108 cm-2 evaluated by transmission electron microscope (TEM), which agreed with the calculations from Williamson-Hall plots. Moreover, cross-sectional TEM indicated that the HT-AlN interlayer could sufficiently reduce the threading dislocations (TDs) through generation of V trenches in the HT-AlN interlayer, since the TDs propagated along the V trenches, then bent into basal planes and annihilated with other dislocations. The study of optical properties indicated that obvious S-shape of temperature dependence on emission energy was observed for Al0.55Ga0.45N layers, which was attributed to exciton localization with energy (Eloc) ∼14.95 meV at 10 K resulting from potential fluctuation and band tail states. The time-resolved photoluminescence (TRPL) curves showed a bi-exponential decay at low temperature. The fast decay time implied the presence of the localized excitons enhancing radiative recombination, while the quite slow one was due to the dominance of trapping mechanisms originating from cation vacancy complexes and the VIII-related complexes.

  13. Assessment of errors and biases in retrievals of XCO2, XCH4, XCO, and XN2O from a 0.5 cm–1 resolution solar-viewing spectrometer

    DOE PAGES

    Hedelius, Jacob K.; Viatte, Camille; Wunch, Debra; ...

    2016-08-03

    Bruker™ EM27/SUN instruments are commercial mobile solar-viewing near-IR spectrometers. They show promise for expanding the global density of atmospheric column measurements of greenhouse gases and are being marketed for such applications. They have been shown to measure the same variations of atmospheric gases within a day as the high-resolution spectrometers of the Total Carbon Column Observing Network (TCCON). However, there is little known about the long-term precision and uncertainty budgets of EM27/SUN measurements. In this study, which includes a comparison of 186 measurement days spanning 11 months, we note that atmospheric variations of Xgas within a single day are wellmore » captured by these low-resolution instruments, but over several months, the measurements drift noticeably. We present comparisons between EM27/SUN instruments and the TCCON using GGG as the retrieval algorithm. In addition, we perform several tests to evaluate the robustness of the performance and determine the largest sources of errors from these spectrometers. We include comparisons of XCO2, XCH4, XCO, and XN2O. Specifically we note EM27/SUN biases for January 2015 of 0.03, 0.75, –0.12, and 2.43 % for XCO2, XCH4, XCO, and XN2O respectively, with 1σ running precisions of 0.08 and 0.06 % for XCO2 and XCH4 from measurements in Pasadena. We also identify significant error caused by nonlinear sensitivity when using an extended spectral range detector used to measure CO and N2O.« less

  14. The electrophoretically 'slow' and 'fast' forms of the alpha 2-macroglobulin molecule.

    PubMed Central

    Barrett, A J; Brown, M A; Sayers, C A

    1979-01-01

    alpha 2-Macroglobulin (alpha 2M) was isolated from human plasma by a four-step procedure: poly(ethylene glyco) fractionation, gel chromatography, euglobulin precipitation and immunoadsorption. No contaminants were detected in the final preparations by electrophoresis or immunoprecipitation. The protein ran as a single slow band in gel electrophoresis, and was designated 'S-alpha 2M'. S-alpha 2M bound about 2 mol of trypsin/mol. Treatment of S-alpha 2M with a proteinase or ammonium salts produced a form of the molecule more mobile in electrophoresis, and lacking proteinase-binding activity (F-alpha 2M). The electrophoretic mobility of the F-alpha 2M resulting from reaction with NH4+ salts was identical with that of proteinase complexes. We attribute the change in electrophoretic mobility of the alpha 2M to a conformation change, but there was no evidence of a change in pI or Strokes radius. Electrophoresis of S-alpha 2M in the presence of sodium dodecylsulphate gave results consistent with the view that the alpha 2M molecule is a tetramer of identical subunits, assembled as a non-covalent pair of disulphide-linked dimers. Some of the subunits seemed to be 'nicked' into two-thires-length and one-third-length chains, however. This was not apparent with F-alpha 2M produced by ammonium salts. F-alpha 2M produced by trypsin showed two new bands attributable to cleavage of the subunit polypeptide chain near the middle. Immunoassays of F-alpha 2M gave 'rockets' 12-29% lower than those with S-alpha 2M. The nature of the interactions between subunits in S-alpha 2M and F-alpha 2M was investigated by treating each form with glutaraldehyde before electrophoresis in the presence of sodium dodecyl sulphate. A much greater degree of cross-linking was observed with the F-alpha 2M, indicating that the subunits interact most closely in this form of the molecule. Exposure of S-alpha 2M to 3 M-urea or pH3 resulted in dissociation to the disulphide-bonded half-molecules; these did not

  15. Alpha Magnetic Spectrometer (AMS) Overview

    NASA Video Gallery

    The Alpha Magnetic Spectrometer (AMS) is flying to the station on STS-134. The AMS experiment is a state-of-the-art particle physics detector being operated by an international team composed of 60 ...

  16. Genetics Home Reference: alpha thalassemia

    MedlinePlus

    ... a blood disorder that reduces the production of hemoglobin . Hemoglobin is the protein in red blood cells that ... alpha thalassemia , a reduction in the amount of hemoglobin prevents enough oxygen from reaching the body's tissues. ...

  17. Analysis of T cell antigen receptor (TCR) expression by human peripheral blood CD4-8- alpha/beta T cells demonstrates preferential use of several V beta genes and an invariant TCR alpha chain

    PubMed Central

    1993-01-01

    CD4-CD8- (double negative [DN]) alpha/beta T cells are a largely uncharacterized subpopulation of unknown function. To investigate whether these cells are selected to recognize particular antigens or antigen-presenting molecules, DN alpha/beta T cells were purified from the peripheral blood of five normal donors and their T cell receptor (TCR) alpha and beta chains were examined. Random cloning of TCR alpha chains by single-sided polymerase chain reaction (PCR) amplification identified an invariant rearrangement between V alpha 24 and J alpha Q, with no N region diversity, which was expressed preferentially by DN alpha/beta T cells from all donors. Random cloning also identified a precise V alpha 7.2-J alpha (IGRJa14) rearrangement, with two variable amino acids encoded in the V-J junction, which was enriched in the DN alpha/beta T cell preparations from some, but not all, donors. Analysis of TCR beta chains by quantitative PCR amplification demonstrated that the expression of four V beta gene families, V beta 2, 8, 11, and 13, was markedly increased in these DN alpha/beta T cell preparations. The expression of particular TCRs by DN alpha/beta T cells from multiple donors indicates that these cells, or at least a subpopulation of cells with this phenotype, recognize a limited spectrum of antigens and suggests that they may use nonpolymorphic antigen-presenting molecules. PMID:8391057

  18. Supernova shock revival by nuclear reactions

    SciTech Connect

    Nakamrua, Ko; Takiwaki, Tomoya; Kotake, Kei; Nishimura, Nobuya

    2012-11-12

    We performed hydrodynamic simulations of core collapse and bounce for a progenitor model with 15.0 solar mass, using ZEUS-MP code in axi-symmetric coordinate. Our numerical code is equipped with a nuclear reaction network including 13 alpha nuclei form {sup 4}He to {sup 56}Ni to investigate the potential role played by nuclear reactions in reviving a stalled shock wave at the central region of core-collapse supernovae. We found that the energy released by nuclear reactions is significantly helpful in accelerating shock waves and is able to produce energetic explosion even if inputted neutrino luminosity is low.

  19. Novel alpha1-adrenergic receptor signaling pathways: secreted factors and interactions with the extracellular matrix.

    PubMed

    Shi, Ting; Duan, Zhong-Hui; Papay, Robert; Pluskota, Elzbieta; Gaivin, Robert J; de la Motte, Carol A; Plow, Edward F; Perez, Dianne M

    2006-07-01

    alpha1-Adrenergic receptor (alpha1-ARs) subtypes (alpha1A, alpha1B, and alpha1D) regulate multiple signal pathways, such as phospholipase C, protein kinase C (PKC), and mitogen-activated protein kinases. We employed oligonucleotide microarray technology to explore the effects of both short- (1 h) and long-term (18 h) activation of the alpha1A-AR to enable RNA changes to occur downstream of earlier well characterized signaling pathways, promoting novel couplings. Polymerase chain reaction (PCR) studies confirmed that PKC was a critical regulator of alpha1A-AR-mediated gene expression, and secreted interleukin (IL)-6 also contributed to gene expression alterations. We next focused on two novel signaling pathways that might be mediated through alpha1A-AR stimulation because of the clustering of gene expression changes for cell adhesion/motility (syndecan-4 and tenascin-C) and hyaluronan (HA) signaling. We confirmed that alpha1-ARs induced adhesion in three cell types to vitronectin, an interaction that was also integrin-, FGF7-, and PKC-dependent. alpha1-AR activation also inhibited cell migration, which was integrin- and PKC-independent but still required secretion of FGF7. alpha1-AR activation also increased the expression and deposition of HA, a glycosaminoglycan, which displayed two distinct structures: pericellular coats and long cable structures, as well as increasing expression of the HA receptor, CD44. Long cable structures of HA can bind leukocytes, which this suggests that alpha1-ARs may be involved in proinflammatory responses. Our results indicate alpha1-ARs induce the secretion of factors that interact with the extracellular matrix to regulate cell adhesion, motility and proinflammatory responses through novel signaling pathways.

  20. Synthesis of Antitumor Lycorines by Intramolecular Diels-Alder Reaction.

    PubMed

    Pérez, Dolores; Burés, Gema; Guitián, Enrique; Castedo, Luis

    1996-03-08

    Pharmacologically interesting lycorines were obtained by a short, efficient method based on an intramolecular Diels-Alder reaction between an alpha-pyrone and an alkyne, followed by loss of CO(2) in a retro Diels-Alder reaction. The cyclization precursors (pyrones 9) were obtained in good yields in two or three steps from the corresponding homophthalic acid or anhydride.

  1. Few-nucleon transfer reactions on deformed nuclei

    SciTech Connect

    van den Berg, A.M.

    1985-01-01

    Recent developments discussed include: alpha-transfer reactions on deformed nuclei, quasi-elastic neutron transfer reactions induced by /sup 58/Ni beams on spherical and deformed samarium nuclei, and the population of low-lying states in neutron rich nuclei using (particle,..gamma..) or (particle,e) coincidence methods. 37 refs., 10 figs. (LEW)

  2. Progesterone's 5 alpha-reduced metabolite, 3 alpha,5 alpha-THP, mediates lateral displacement of hamsters.

    PubMed

    Frye, Cheryl A; Rhodes, Madeline E

    2005-03-15

    5 alpha-Pregnan-3 alpha-ol-20-one (3 alpha,5 alpha-THP), progesterone (P4)'s 5 alpha-reduced, 3 alpha-hydroxysteroid oxidoreduced product, facilitates lordosis of rodents in part via agonist-like actions at GABA(A)/benzodiazepine receptor complexes in the ventral tegmental area (VTA). Whether 3 alpha,5 alpha-THP influences another reproductively-relevant behavior, lateral displacement, of hamsters was investigated. Lateral displacement is the movement that female hamsters make with their perineum towards male-like tactile stimulation. This behavior facilitates, and is essential for, successful mating. Hamsters in behavioral estrus had greater lateral displacement responses when endogenous progestin levels were elevated compared to when progestin levels were lower. Administration of P4, a prohormone for 3 alpha,5 alpha-THP, dose-dependently (500 > 200 > 100, 50, or 0 microg) enhanced lateral displacement of ovariectomized hamsters that had been primed with SC estradiol benzoate (5 or 10 microg). Inhibiting P4's metabolism to 3 alpha,5 alpha-THP by co-administering finasteride, a 5 alpha-reductase inhibitor, or indomethacin, a 3 alpha-hydroxysteroid oxidoreductase inhibitor, either systemically or to the VTA, significantly decreased lateral displacement and midbrain progestin levels of naturally receptive or hormone-primed hamsters compared to controls. These data suggest that lateral displacement is progestin-sensitive and requires the formation of 3 alpha,5 alpha-THP in the midbrain VTA.

  3. Radiative capture reactions with heavy beams: extending the capabilities of DRAGON

    NASA Astrophysics Data System (ADS)

    Simon, Anna; Fallis, Jennifer; Spyrou, Artemis; Laird, Alison M.; Ruiz, Chris; Buchmann, Lothar; Fulton, Brian R.; Hutcheon, Dave; Martin, Lars; Ottewell, Dave; Rojas, Alex

    2013-05-01

    Understanding the nucleosynthesis of stable proton-rich nuclei requires knowledge of the cross sections for both proton and alpha capture reactions. As some of the nucleosynthesis paths responsible for the production of these nuclei involve reactions on unstable isotopes, it is of particular importance to develop techniques to investigate these reactions. This requires radioactive beams and measurements in inverse kinematics, thus making recoil separators an ideal tool for direct measurements of proton and alpha capture reactions. Here, the application of the DRAGON recoil separator for measurements of capture reactions for heavy beams is presented. The performance of the separator was tested using the 58Ni(p,γ)59Cu reaction.

  4. Cross-section measurements of neutron threshold reactions in various materials

    NASA Astrophysics Data System (ADS)

    Vrzalová, J.; Svoboda, O.; Kugler, A.; Suchopár, M.; Wagner, V.

    As members of international collaboration "Energy and Transmutation of radioactive Waste" we routinely use (n,xn) threshold reactions in various materials to measure high energy neutron flux from spallation reactions. The cross-sections of many reactions important for our activation detectors are missing. To improve situation, we studied the neutron cross-sections using different quasi-monoenergetic neutron sources based on proton reaction on 7Li target. The measurements were performed in Nuclear Physics Institute of the Academy of Sciences of the Czech Republic in Řež near Prague and in The Svedberg Laboratory in Uppsala (Sweden). We used neutron energies 17, 22, 30 and 35 MeV from the quasi-monoenergetic neutron source in Řež and neutron energies 22, 47 and 94 MeV in Uppsala. The last experiment was carried out in February 2010 in Uppsala using neutron energies 59, 66, 72 and 89 MeV. The study of neutron threshold reactions in yttrium was performed first time during this irradiation. We have developed procedure for the subtraction of contribution of the background neutrons. We studied various materials in the form of thin foils and observed good agreement with the data in EXFOR database and also with the calculations performed in deterministic code TALYS. Many cross-sections were measured in the energy regions where no experimental data are available so far.

  5. Thionation of some alpha,beta-unsaturated steroidal ketones.

    PubMed

    Krstić, Natalija M; Bjelaković, Mira S; Dabović, Milan M; Pavlović, Vladimir D

    2010-05-12

    The reactions of selected alpha,beta-unsaturated steroidal ketones with Lawesson's reagent (LR) in CH(2)Cl(2) and toluene under the standard reaction conditions and with a combination of phosphorus pentasulfide with hexamethyldisiloxane (P(4)S(10)/HMDO) in 1,2-dichlorobenzene (ODCB) under microwave irradiation were investigated and for this purpose several cholestane, androstane and pregnane carbonyl derivatives were chosen. Depending on the reagent and the solvent, 19 new sulfur containing compounds, including dithiones 4c and 4d, alpha,beta-unsaturated 3-thiones 3a-e, dimer-sulfides 2a-e, 1,2,4-trithiolanes 5a-e and phosphonotrithioates 6b-e were synthesized. All newly prepared compounds were characterized by IR, (1)H- and (13)C-NMR spectroscopy and elemental analysis.

  6. Gas phase hydrogen permeation in alpha titanium and carbon steels

    NASA Technical Reports Server (NTRS)

    Johnson, D. L.; Shah, K. K.; Reeves, B. H.; Gadgeel, V. L.

    1980-01-01

    Commercially pure titanium and heats of Armco ingot iron and steels containing from 0.008-1.23 w/oC were annealed or normalized and machined into hollow cylinders. Coefficients of diffusion for alpha-Ti and alpha-Fe were determined by the lag-time technique. Steady state permeation experiments yield first power pressure dependence for alpha-Ti and Sievert's law square root dependence for Armco iron and carbon steels. As in the case of diffusion, permeation data confirm that alpha-titanium is subject to at least partial phase boundary reaction control while the steels are purely diffusion controlled. The permeation rate in steels also decreases as the carbon content increases. As a consequence of Sievert's law, the computed hydrogen solubility decreases as the carbon content increases. This decreases in explained in terms of hydrogen trapping at carbide interfaces. Oxidizing and nitriding the surfaces of alpha-titanium membranes result in a decrease in the permeation rate for such treatment on the gas inlet surfaces but resulted in a slight increase in the rate for such treatment on the gas outlet surfaces. This is explained in terms of a discontinuous TiH2 layer.

  7. {alpha} decay of {sup 194}At

    SciTech Connect

    Andreyev, A. N.; Antalic, S.; Streicher, B.; Saro, S.; Venhart, M.; Ackermann, D.; Heinz, S.; Hessberger, F. P.; Kojouharov, I.; Kindler, B.; Lommel, B.; Mann, R.; Sulignano, B.; Bianco, L.; Page, R. D.; Sapple, P.; Thomson, J.; Franchoo, S.; Hofmann, S.; Huyse, M.

    2009-06-15

    Detailed {alpha}-decay studies of the neutron-deficient isotope {sup 194}At have been performed in the complete fusion reaction {sup 56}Fe+{sup 141}Pr{yields}{sup 194}At+3n at the velocity filter SHIP. Two {alpha}-decaying isomeric states with half-lives of T{sub 1/2}({sup 194}At{sup m1})=310(8) ms and T{sub 1/2}({sup 194}At{sup m2})=253(10) ms were identified in this nucleus. Their complex decays to the states in the daughter nucleus {sup 190}Bi are discussed in the article. We propose that similar to the case of the neighboring {sup 191,192,193,195}At isotopes, the oblate-deformed configurations based on the proton 1/2{sup +}[440] and/or 7/2{sup -}[514] Nilsson orbitals become important in {sup 194}At. A new isomeric state with the half-life of 175(8) ns was observed in {sup 190}Bi.

  8. {sup 17}O({alpha},{gamma}){sup 21}Ne and {sup 17}O({alpha},n){sup 20}Ne for the weak s process

    SciTech Connect

    Best, A.; Goerres, J.; Beard, M.; Couder, M.; Boer, R. de; Falahat, S.; Gueray, R. T.; Kontos, A.; Kratz, K.-L.; LeBlanc, P. J.; Li, Q.; O'Brien, S.; Oezkan, N.; Pignatari, M.; Sonnabend, K.; Talwar, R.; Tan, W.; Uberseder, E.; Wiescher, M.

    2012-11-20

    The ratio of the reaction rates of the competing channels {sup 17}O({alpha}{gamma}){sup 21}Ne and {sup 17}O({alpha},n){sup 20}Ne determines the efficiency of {sup 16}O as a neutron poison in the s process in low metallicity rotating stars. It has a large impact on the element production, either producing elements to the mass range of A=90 in case of a significant poisoning effect or extending the mass range up to the region of A=150 if the {gamma} channel is of negligible strength. We present an improved study of the reaction {sup 17}O({alpha},n){sup 20}Ne, including an independent measurement of the {sup 17}O({alpha},n{sub 1}){sup 20}Ne channel. A simultaneous R-Matrix fit to both the n{sub 0} and the n{sub 1} channels has been performed. New reaction rates, including recent data on the {sup 17}O({alpha},{gamma}){sup 21}Ne reaction, have been calculated and used as input for stellar network calculations and their impact on the s process in rotating massive stars is discussed.

  9. Purification, characterization, and synergistic action of phytate-resistant alpha-amylase and alpha-glucosidase from Geobacillus thermodenitrificans HRO10.

    PubMed

    Ezeji, Thaddeus C; Bahl, Hubert

    2006-08-20

    The alpha-amylase (1, 4-alpha-d-glucanohydrolase; EC 3.2.1.1) and alpha-glucosidase (alpha-d-glucoside glucohydrolase; EC 3.2.1.20) secreted by Geobacillus thermodenitrificans HRO10 were purified to homogeneity (13.6-fold; 11.5% yield and 25.4-fold; 32.0% yield, respectively) through a series of steps. The molecular weight of alpha-amylase was 58kDa, as estimated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The alpha-amylase activity on potato starch was optimal at pH 5.5 and 80 degrees Celsius. In the presence of Ca(2+), the alpha-amylase had residual activity of more than 92% after 1h of incubation at 70 degrees Celsius. The alpha-amylase did not lose any activity in the presence of phytate (a selective alpha-amylase inhibitor) at concentrations as high as 10mM, rather it retained 90% maximal activity after 1h of incubation at 70 degrees Celsius. EGTA and EDTA were strong inhibitory substances of the enzyme. The alpha-amylase hydrolyzed soluble starch at 80 degrees Celsius, with a K(m) of 3.05mgml(-1) and a V(max) of 7.35Uml(-1). The molecular weight of alpha-glucosidase was approximately 45kDa, as determined by SDS-PAGE. The enzyme activity was optimal at pH 6.5-7.5 and 55 degrees Celsius. Phytate did not inhibit G. thermodenitrificans HRO10 alpha-glucosidase activity, whereas pCMB was a potent inhibitor of the enzyme. The alpha-glucosidase exhibited Michaelis-Menten kinetics with maltose at 55 degrees Celsius (K(m): 17mM; V(max): 23micromolmin(-1)mg(-1)). Thin-layer chromatography studies with G. thermodenitrificans HRO10 alpha-amylase and alpha-glucosidase showed an excellent synergistic action and did not reveal any transglycosylation catalyzed reaction by the alpha-glucosidase.

  10. Highly regioselective hydrogenolysis of bis(alpha-methylbenzyl)amine derivatives affected by the trifluoromethyl substituent on the aromatic ring.

    PubMed

    Kanai, Masatomi; Yasumoto, Manabu; Kuriyama, Yokusu; Inomiya, Kenjin; Katsuhara, Yutaka; Higashiyama, Kimio; Ishii, Akihiro

    2003-04-03

    [reaction: see text] The highly regioselective hydrogenolysis of bis(alpha-methylbenzyl)amine derivatives proceeded with influence not from the electronic effect but from the steric effect of the trifluoromethyl substituent on the aromatic ring to provide a practical asymmetric synthesis of trifluoromethyl-substituted alpha-phenylethylamines.

  11. Soluble polymer supported synthesis of alpha-amino acid derivatives.

    PubMed

    Sauvagnat, B; Kulig, K; Lamaty, F; Lazaro, R; Martinez, J

    2000-01-01

    A Schiff base activated glycine supported on a soluble polymer (poly(ethylene glycol) (PEG)) was readily alkylated with a wide variety of electrophiles in the presence of a carbonate base in acetonitrile. The presence of the polymer provided a phase-transfer catalysis environment which accelerated the reaction. Effects of various carbonate bases and leaving groups have been also studied. Completion of the PEG-supported reaction was obtained without using a large excess of reagents or an extra phase-transfer catalyst, even in the case of unreactive or hindered electrophiles. After cleavage from the polymer, alpha-amino esters are obtained in good yields.

  12. Cyclotron production of Ac-225 for targeted alpha therapy.

    PubMed

    Apostolidis, C; Molinet, R; McGinley, J; Abbas, K; Möllenbeck, J; Morgenstern, A

    2005-03-01

    The feasibility of producing Ac-225 by proton irradiation of Ra-226 in a cyclotron through the reaction Ra-226(p,2n)Ac-225 has been experimentally demonstrated for the first time. Proton energies were varied from 8.8 to 24.8 MeV and cross-sections were determined by radiochemical analysis of reaction yields. Maximum yields were reached at incident proton energies of 16.8 MeV. Radiochemical separation of Ac-225 from the irradiated target yielded a product suitable for targeted alpha therapy of cancer.

  13. Unusual antioxidant behavior of alpha- and gamma-terpinene in protecting methyl linoleate, DNA, and erythrocyte.

    PubMed

    Li, Guo-Xiang; Liu, Zai-Qun

    2009-05-13

    The antioxidant effects of alpha-terpinene (alpha-TH) and gamma-terpinene (gamma-TH) on the oxidation of methyl linoleate (LH), DNA, and erythrocytes induced by 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH) were investigated. The results from erythrocytes and DNA were treated by means of chemical kinetic equations. It was found that either alpha- or gamma-TH was able to scavenge approximately 0.4 radicals when they protected DNA. alpha-TH can trap approximately 0.7 radicals when protecting erythrocytes and can trap approximately 0.5 radicals when protecting LH. gamma-TH can trap approximately 1.2 radicals when protecting erythrocytes and LH. Therefore, the antioxidant effectiveness of gamma-TH was higher than alpha-TH. gamma-TH contained a nonconjugated diene, and the diene in alpha-TH was conjugated. The obtained results implied that the nonconjugated diene benefited for antioxidant capacity more than a conjugated diene. Moreover, the reactions of alpha- and gamma-TH with 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) cation radical (ABTS(+) (*)) and 2,2'-diphenyl-1-picrylhydrazyl (DPPH) implicated that alpha- and gamma-TH were able to scavenge radicals directly. However, alpha- and gamma-TH promoted AAPH-induced hemolysis with a high concentration employed.

  14. Mechanism of alpha-tocopheryl-phosphate (alpha-TP) transport across the cell membrane

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We have reported that alpha-TP is synthesized and hydrolyzed in animal cells and tissues; it modulates also several cell functions (FRBM 39:970, and UBMB Life, 57:23, 2005). While it is similar to alpha-tocopherol (alpha-T), alpha-TP appears to be more potent than alpha-T in inhibiting cell prolifer...

  15. Technique for measuring the losses of alpha particles to the wall in TFTR

    SciTech Connect

    England, A.C.

    1984-03-01

    It is proposed to measure the losses of alpha particles to the wall in the Tokamak Fusion Test Reactor (TFTR) or any large deuterium-tritium (D-T) burning tokamak by a nuclear technique. For this purpose, a chamber containing a suitable fluid would be mounted near the wall of the tokamak. Alpha particles would enter the chamber through a thin window and cause nuclear reactions in the fluid. The material would then be transported through a tube to a remote, low-background location for measurement of the activity. The most favorable reaction suggested here is /sup 10/B(..cap alpha..,n)/sup 13/N, although /sup 14/N(..cap alpha..,..gamma..)/sup 18/F and others may be possible. The system, the sensitivity, the probe design, and the sources of error are described.

  16. [Development of highly stereoselective reactions utilizing heteroatoms--new approach to the stereoselective Horner-Wadsworth-Emmons reaction].

    PubMed

    Sano, S

    2000-05-01

    This article reviews a new approach to stereoselective Horner-Wadsworth-Emmons (HWE) reactions. The HWE reaction is one of the most efficient methods for the preparation of alpha,beta-unsaturated esters, which play an important role in the synthesis of biologically active compounds. The reactions of aldehydes with phosphonates bearing alpha-substituents which stabilize the carbanion, preferentially furnish the corresponding E-alkenes. However, the stereoselectivity of the HWE reactions with ketones has never been investigated in detail because of their low reactivity and low stereoselectivity. The conventional HWE reactions of aryl alkyl ketones with ethyl diethylphosphonoacetate in the presence of sodium hydride gave the corresponding alpha,beta-unsaturated esters with modest E-selectivity. On the other hand, the treatment of aryl alkyl ketones with ethyl diethylphosphonoacetate in the presence of Sn(OSO2CF3)2 and N-ethylpiperidine afforded alpha,beta-unsaturated esters in a highly Z-selective fashion. A significant improvement in the selectivity and yield was found when the Still's reagent, methyl bis(trifluoroethyl)phosphonoacetate, was used under Sn(II)-mediated conditions. On the basis of the experimental results, the high Z-selectivity in the Sn(II)-mediated HWE reactions of aryl alkyl ketones with these phosphonates can be rationalized in terms of six-membered transition state involving Sn(II) chelation. Similarly, the HWE reactions of aryl alkyl ketones with ethyl 2-fluoro-2-diethylphosphonoacetate in the presence of Sn(OSO2CF3)2 and N-ethylpiperidine gave the corresponding alpha-fluoro-alpha,beta-unsaturated esters in a highly E-selective manner. Finally, the Sn(II)-mediated asymmetric HWE reactions of isopropyl 2-fluoro-2-diethylphosphonoacetate with 4-tert-butylcyclohexanone in the presence of a chiral diamine is described.

  17. Workshop on Precision Measurements of $\\alpha_s$

    SciTech Connect

    Bethke, Siegfried; Hoang, Andre H.; Kluth, Stefan; Schieck, Jochen; Stewart, Iain W.; Aoki, S.; Beneke, M.; Bethke, S.; Blumlein, J.; Brambilla, N.; Brodsky, S.; /MIT, LNS

    2011-10-01

    These are the proceedings of the Workshop on Precision Measurements of {alpha}{sub s} held at the Max-Planck-Institute for Physics, Munich, February 9-11, 2011. The workshop explored in depth the determination of {alpha}{sub s}(m{sub Z}) in the {ovr MS} scheme from the key categories where high precision measurements are currently being made, including DIS and global PDF fits, {tau}-decays, electro-weak precision observables and Z-decays, event-shapes, and lattice QCD. These proceedings contain a short summary contribution from the speakers, as well as the lists of authors, conveners, participants, and talks.

  18. Immunodiagnosis of alpha chain disease.

    PubMed Central

    Doe, W F; Danon, F; Seligmann, M

    1979-01-01

    Since the early diagnosis of alpha chain disease (alphaCD)) is essential to successful treatment and to epidemiological studies, the available immunodiagnostic techniques were compared for their sensitivity, specificity and ease of performance on a panel of sixteen sera, comprising ten alphaCD sera and six control sera containing either IgA myeloma protein or high levels of polyclonal IgA. Immunoselection by immunoelectrophoresis into gel containing a specially developed anti-Fabalpha antiserum provided the most sensitive and specific detection system for alphaCD protein. The same technique using anti-light chain antiserum for immunoselection was also highly sensitive, but proved less specific, being prone to false positives with difficult IgA myeloma proteins. Somewhat less sensitive, but specific and simple to perform, was immunoelectrophoresis using an antiserum recognizing the conformational specificities of Fabalpha as well as those of the constant region of alpha chains. Immunoselection using the Ouchterlony or rocket techniques proved to be less sensitive and prone to false positives when some IgA myeloma sera were tested. Images FIG. 1 FIG. 2 FIG. 3 FIG. 4 FIG. 5 FIG. 6 FIG. 7 PMID:113152

  19. Photonuclear reaction to test cluster structure of Lithium

    SciTech Connect

    Akkurt, Iskender

    2008-11-11

    The lithium can be pictured as an {alpha} particle with 2 extra nucleon surrounding it. A photonuclear reaction experiment has been performed to test this structure at Maxlab in Lund-Sweden. The cross-section of the {sup 6}Li({gamma},n) reaction have been measured using TOF methods and the results were compared with results of {sup 6}Li({gamma},p) and also {sup 4}He({gamma},n) reaction.

  20. Pd-catalyzed arylation of silyl enol ethers of substituted alpha-fluoroketones.

    PubMed

    Guo, Yong; Twamley, Brendan; Shreeve, Jean'ne M

    2009-04-21

    Alpha-fluoro-alpha-aryl-ketones were synthesized by the Pd-catalyzed cross-coupling of aryl bromides with either alpha-fluoroketones or their corresponding silyl enol ethers. The direct arylation with an alpha-fluoroketone requires a strong base, such as potassium tert-butoxide, and under these conditions the presence of a base-sensitive functional group is not compatible. However, good functional tolerance was achieved when the anionic coupling moieties were generated from the silyl enol ethers obtained by reacting alpha-fluoroketones with tetrabutylammonium (tripheny1silyl)difluorosilicate (TBAT) as the fluoride source under nearly neutral conditions. The aryl halides with a carbmethoxy, nitro, cyano or carbonyl group were used. The reaction with nonfluorinated silyl enol ether 1h gave a cross-coupling product in low yield.

  1. The anti-HIV activity of the phytochemical alpha-terthienyl.

    PubMed

    Hudson, J B; Harris, L; Teeple, A; Towers, G H

    1993-01-01

    The plant trithiophene, alpha-terthienyl (alpha T), was evaluated for activity against the human immunodeficiency virus (HIV-1). Antiviral activity specifically required long wavelength light (UVA, 320-400 nm). The compound had little or no activity in visible light or in the dark. The anti-HIV effect was UVA-dose dependent and was proportional to the concentration of alpha T, according to several parameters of virus infectivity and replication. The efficacy was decreased to some extent by the presence of bovine serum in the reactions; but under optimal conditions 0.1 microgram/ml. alpha T (3 x 10(-7) M) could inactivate 10(4)-10(5) infectious particles. In contrast poliovirus and Coxsackievirus infectivity were relatively resistant to alpha T + UVA.

  2. Short term integrative meditation improves resting alpha activity and stroop performance.

    PubMed

    Fan, Yaxin; Tang, Yi-Yuan; Tang, Rongxiang; Posner, Michael I

    2014-12-01

    Our previous research showed that short term meditation training reduces the time to resolve conflict in the flanker task. Studies also show that resting alpha increases with long term meditation practice. The aim of this study is to determine whether short term meditation training both increases resting alpha activity and reduces the time to resolve conflict in the Stroop task and whether these two effects are related. Forty-three Chinese undergraduates were randomly assigned an experiment group given 5 days meditation training using integrative body-mind training (IBMT) and a relaxation training control. After training, only the IBMT group showed decreased conflict reaction time (RT), and increased resting mean alpha power. Moreover, the higher the enhancement of resting alpha power, the stronger the improvement of conflict RT. The results indicate that short term meditation diffusely enhances alpha and improves the ability to deal with conflict and moreover these two effects are positively related.

  3. Three-component synthesis of alpha-branched amines under Barbier-like conditions.

    PubMed

    Le Gall, Erwan; Haurena, Caroline; Sengmany, Stéphane; Martens, Thierry; Troupel, Michel

    2009-10-16

    An array of alpha-branched amines has been prepared by using an expedient three-component Mannich-type reaction among organic halides, aldehyde derivatives, and amines. The experimental procedure, which is characterized by its simplicity, employs zinc dust for the in situ generation of organozinc reagents. We show that this Barbier-like protocol constitutes a useful entry to diarylmethylamines, 1,2-diarylethylamines, alpha- or beta-amino esters, benzylamines, and beta-arylethylamines.

  4. Bioisosteric phentolamine analogs as selective human alpha(2)- versus alpha(1)-adrenoceptor ligands.

    PubMed

    Bavadekar, Supriya A; Hong, Seoung-Soo; Lee, Sang-Ii; Miller, Duane D; Feller, Dennis R

    2008-08-20

    Phentolamine is known to act as a competitive, non-subtype-selective alpha-adrenoceptor antagonist. In an attempt to improve alpha(2)- versus alpha(1)-adrenoceptor selectivity and alpha(2)-adrenoceptor subtype-selectivity, two new chemical series of bioisosteric phentolamine analogs were prepared and evaluated. These compounds were evaluated for binding affinities on alpha(1)- (alpha(1A)-, alpha(1B)-, alpha(1D)-) and alpha(2)- (alpha(2A)-, alpha(2B)-, alpha(2C)-) adrenoceptor subtypes that had been stably expressed in human embryonic kidney and Chinese hamster ovary cell lines, respectively. Methylation of the phenolic hydroxy group and replacement of the 4-methyl group of phentolamine with varying lipophilic substituents yielded bioisosteric analogs selective for the alpha(2)- versus alpha(1)-adrenoceptors. Within the alpha(2)-adrenoceptors, these analogs bound with higher affinity at the alpha(2A)- and alpha(2C)-subtypes as compared to the alpha(2B)-subtype. In particular, the t-butyl analog was found to be the most selective, its binding at the alpha(2C)-adrenoceptor (Ki=3.6 nM) being 37- to 173-fold higher than that at the alpha(1)-adrenoceptors, and around 2- and 19-fold higher than at the alpha(2A)- and alpha(2B)-adrenoceptors, respectively. Data from luciferase reporter gene assays confirmed the functional antagonist activities of selected compounds from the bioisosteric series on human alpha(1A)- and alpha(2C)-adrenoceptors. Thus, the results with these bioisosteric analogs of phentolamine provide a lead to the rational design of potent and selective alpha(2)-adrenoceptor ligands that may be useful in improving the therapeutic profile of this drug class for human disorders.

  5. Space Station alpha joint bearing

    NASA Technical Reports Server (NTRS)

    Everman, Michael R.; Jones, P. Alan; Spencer, Porter A.

    1987-01-01

    Perhaps the most critical structural system aboard the Space Station is the Solar Alpha Rotary Joint which helps align the power generation system with the sun. The joint must provide structural support and controlled rotation to the outboard transverse booms as well as power and data transfer across the joint. The Solar Alpha Rotary Joint is composed of two transition sections and an integral, large diameter bearing. Alpha joint bearing design presents a particularly interesting problem because of its large size and need for high reliability, stiffness, and on orbit maintability. The discrete roller bearing developed is a novel refinement to cam follower technology. It offers thermal compensation and ease of on-orbit maintenance that are not found in conventional rolling element bearings. How the bearing design evolved is summarized. Driving requirements are reviewed, alternative concepts assessed, and the selected design is described.

  6. NACA Physicist Studying Alpha Rays

    NASA Technical Reports Server (NTRS)

    1957-01-01

    NACA Physicits studying Alpha Rays in a continuous cloud chamber. A cloud chamber is used by Lewis scientists to obtain information aimed at minimizing undesirable effects of radiation on nuclear-powered aircraft components. Here, alpha particles from a polonium source emit in a flower-like pattern at the cloud chamber's center. The particles are made visible by means of alcohol vapor diffusing from an area at room temperature to an area at minus -78 deg. Centigrade. Nuclear-powered aircraft were never developed and aircraft nuclear propulsion systems were canceled in the early 1960s.

  7. Bremsstrahlung in {alpha} Decay Reexamined

    SciTech Connect

    Boie, H.; Scheit, H.; Jentschura, U. D.; Koeck, F.; Lauer, M.; Schwalm, D.; Milstein, A. I.; Terekhov, I. S.

    2007-07-13

    A high-statistics measurement of bremsstrahlung emitted in the {alpha} decay of {sup 210}Po has been performed, which allows us to follow the photon spectra up to energies of {approx}500 keV. The measured differential emission probability is in good agreement with our theoretical results obtained within the quasiclassical approximation as well as with the exact quantum mechanical calculation. It is shown that, due to the small effective electric dipole charge of the radiating system, a significant interference between the electric dipole and quadrupole contributions occurs, which is altering substantially the angular correlation between the {alpha} particle and the emitted photon.

  8. Alpha Channeling in Mirror Machines

    SciTech Connect

    Fisch, Nathaniel J.

    2014-07-16

    This Final Report for DE-FG02-06ER54851, Alpha Channeling in Mirror Machines, was in fact submitted on April 9, 2010. Some confusion arose because it was submitted as an initial progress report on a related grant, Alpha Channeling in Open- System Magnetic Devices. The original text is reproduced below, except that the publication record is undated. Note that the articles published in 2009 and 2010 reflect work in fact done under DE-FG02-06ER54851.

  9. Test chamber for alpha spectrometry

    DOEpatents

    Larsen, Robert P.

    1977-01-01

    Alpha emitters for low-level radiochemical analysis by measurement of alpha spectra are positioned precisely with respect to the location of a surface-barrier detector by means of a chamber having a removable threaded planchet holder. A pedestal on the planchet holder holds a specimen in fixed engagement close to the detector. Insertion of the planchet holder establishes an O-ring seal that permits the chamber to be pumped to a desired vacuum. The detector is protected against accidental contact and resulting damage.

  10. Kinetics of molecular encapsulation of 1-methylcyclopropene into alpha-cyclodextrin.

    PubMed

    Neoh, Tze Loon; Yamauchi, Kousuke; Yoshii, Hidefumi; Furuta, Takeshi

    2007-12-26

    1-methylcyclopropene (1-MCP), an ethylene inhibiting regulator, is commercially available in the form of an inclusion complex with alpha-cyclodextrin (alpha-CD). In this study, molecular encapsulation of gaseous 1-MCP into aqueous alpha-CD was investigated in a closed, agitated vessel with a flat gas-liquid interface. Molecular encapsulation of gaseous 1-MCP by alpha-CD is a simultaneous two-step reaction which involves the aqueous dissolution of gaseous 1-MCP and the encapsulation of the dissolved molecules by alpha-CD. The kinetics and mechanism of molecular encapsulation were analyzed based on the depletion rate of 1-MCP in the headspace of the vessel. The encapsulation rates could be explained quantitatively by the gas absorption theory with a pseudo-first-order reaction between 1-MCP and alpha-CD. The negative value of the calculated apparent activation energy of encapsulation (-24.4 kJ/mol) implied the significant effect of exothermic aqueous dissolution of 1-MCP. An encapsulation temperature of 15 degrees C was optimal; at this temperature, the highest 1-MCP yield and best inclusion ratio of inclusion complex were obtained. Changes in the X-ray diffraction pattern suggested that the crystal lattice structure of alpha-CD was altered upon inclusion of 1-MCP.

  11. Angular correlation measurements for 4-{alpha} decaying states in {sup 16}O

    SciTech Connect

    Wuosmaa, A.H.; Back, B.B.; Betts, R.R.

    1995-08-01

    Previous measurements of the {sup 12}C({sup 12}C,{sup 8}Be){sup 16}O{sup *}(4 {alpha}) reaction identified discrete levels in {sup 16}O which decay by breakup into 4 {alpha} particles through a number of different decay sequences, including {sup 16}O{sup *} {yields} {sup 8}Be + {sup 8}Be and {alpha} + {sup 12}C (O{sub 2}{sup +}). These states are observed in a range of excitation energies where resonances are observed in inelastic {alpha} + {sup 12}C scattering leading to the {sup 8}Be + {sup 8}Be and {alpha} + {sup 12}C final states. These resonances were associated with 4 {alpha}-particle chain configurations in {sup 16}O. Should the states populated in the {sup 12}C + {sup 12}C reaction possess this same extended structure, it would serve as an important piece of evidence supporting the idea that even more deformed structures are formed in the {sup 24}Mg compound system. In order to more firmly make this association, it is important to determine the spins of the states populated in the {sup 12}C + {sup 12}C reaction.

  12. Capture reactions on C-14 in nonstandard big bang nucleosynthesis

    NASA Technical Reports Server (NTRS)

    Wiescher, Michael; Gorres, Joachim; Thielemann, Friedrich-Karl

    1990-01-01

    Nonstandard big bang nucleosynthesis leads to the production of C-14. The further reaction path depends on the depletion of C-14 by either photon, alpha, or neutron capture reactions. The nucleus C-14 is of particular importance in these scenarios because it forms a bottleneck for the production of heavier nuclei A greater than 14. The reaction rates of all three capture reactions at big bang conditions are discussed, and it is shown that the resulting reaction path, leading to the production of heavier elements, is dominated by the (p, gamma) and (n, gamma) rates, contrary to earlier suggestions.

  13. Visible light photocatalytic decomposition of 2-naphthol by anodic-biased alpha-Fe2O3 film.

    PubMed

    Kawahara, Tetsuro; Yamada, Kei-Ichi; Tada, Hiroaki

    2006-02-15

    Transparent alpha-Fe2O3 films with varying film thickness were formed on a SnO2 transparent conducting film-coated glass substrate by metal organic deposition. Under anodic-biased conditions, the alpha-Fe2O3 film showed a high photocatalytic activity for the decomposition of 2-NAP with visible light irradiation. The alpha-Fe2O3 is transformed to inactive hydroxide as the reaction proceeds, while the activity of alpha-Fe2O3 is almost maintained in acetonitrile.

  14. A ruthenium-grafted hydrotalcite as a multifunctional catalyst for direct alpha-alkylation of nitriles with primary alcohols.

    PubMed

    Motokura, Ken; Nishimura, Daisuke; Mori, Kohsuke; Mizugaki, Tomoo; Ebitani, Kohki; Kaneda, Kiyotomi

    2004-05-12

    Treatment of a hydrotacite, Mg6Al2(OH)16CO3, with an aqueous solution of RuCl3.nH2O afforded a monomeric Ru(IV) species on the surface of the hydrotalcite. This novel Ru-grafted hydrotalcite (Ru/HT) efficiently catalyzed alpha-alkylation of nitriles with primary alcohols through the cooperative catalysis between the Ru species and the surface base sites. The catalyst system could be further extended for the one-pot synthesis of alpha,alpha-dialkylated phenylacetonitriles via the base-catalyzed Michael reaction of alpha-alkylated phenylacetonitrile with activate olefins.

  15. Excitation function for deuteron induced nuclear reactions on natural ytterbium for production of high specific activity 177g Lu in no-carrier-added form for metabolic radiotherapy.

    PubMed

    Manenti, Simone; Groppi, Flavia; Gandini, Andrea; Gini, Luigi; Abbas, Kamel; Holzwarth, Uwe; Simonelli, Federica; Bonardi, Mauro

    2011-01-01

    Deuteron-induced nuclear reactions for generation of no-carrier-added Lu radionuclides were investigated using the stacked-foil activation technique on natural Yb targets at energies up to E(d)=18.18 MeV. Excitation functions of the reactions (nat)Yb(d,xn)(169,170,171,172,173,174g,174m,176m,177g)Lu and (nat)Yb(d,pxn)(169,175,177)Yb have been measured, among them three ((169)Lu, (174m)Lu and (176m)Lu) are reported for the first time. The upper limit of the contamination from the long-lived metastable level (177m)Lu was evaluated too. Thick-target yields for all investigated radionuclides are calculated.

  16. The alpha 4 integrin chain is a ligand for alpha 4 beta 7 and alpha 4 beta 1

    PubMed Central

    1995-01-01

    The heterodimeric alpha 4 integrins alpha 4 beta 7 lymphocyte Peyer's patch adhesion molecule ([LPAM]-1) and alpha 4 beta 1 (very late antigen-4) are cell surface adhesion molecules involved in lymphocyte trafficking and lymphocyte-cell and matrix interactions. Known cellular ligands include vascular cell adhesion molecule (VCAM)-1, which binds to alpha 4 beta 1 and alpha 4 beta 7, and the mucosal addressin cell adhesion molecule (MAdCAM)-1, which binds to alpha 4 beta 7. Here we show that the alpha 4 chain of these integrins can itself serve as a ligand. The alpha 4 chain, immunoaffinity purified and immobilized on glass slides, binds thymocytes and T lymphocytes. Binding exhibits divalent cation requirements and temperature sensitivity which are characteristic of integrin-mediated interactions, and is specifically inhibited by anti-alpha 4 integrin antibodies, which exert their effect at the cell surface. Cells expressing exclusively alpha 4 beta 7 (TK-1) or alpha 4 beta 1 (L1-2) both bound avidly, whereas alpha 4-negative cells did not. A soluble 34-kD alpha 4 chain fragment retained binding activity, and it inhibited lymphocyte adhesion to alpha 4 ligands. It has been shown that alpha 4 integrin binding to fibronectin involves an leucine-aspartic acid-valine (LDV) motif in the HepII/IIICS region of fibronectin (CS-1 peptide), and homologous sequences are important in binding to VCAM-1 and MAdCAM-1. Three conserved LDV motifs occur in the extracellular sequence of alpha 4. A synthetic LDV-containing alpha 4- derived oligopeptide supports alpha 4-integrin-dependent lymphocyte adhesion and blocks binding to the 34-kD alpha 4 chain fragment. Our results suggest that alpha 4 beta 7 and alpha 4 beta 1 integrins may be able to bind to the alpha 4 subunit on adjacent cells, providing a novel mechanism for alpha 4 integrin-mediated and activation-regulated lymphocyte interactions during immune responses. PMID:7629498

  17. Comparison of the Luminous Efficiencies of Ga- and N-Polar InxGa1 -xN /InyGa1 -yN Quantum Wells Grown by Plasma-Assisted Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Fernández-Garrido, Sergio; Lähnemann, Jonas; Hauswald, Christian; Korytov, Maxim; Albrecht, Martin; Chèze, Caroline; Skierbiszewski, Czesław; Brandt, Oliver

    2016-09-01

    We investigate the luminescence of Ga- and N-polar InxGa1 -xN /InyGa1 -yN quantum wells grown by plasma-assisted molecular beam epitaxy on freestanding GaN as well as 6H -SiC substrates. In striking contrast to their Ga-polar counterparts, the N-polar quantum wells prepared on freestanding GaN do not exhibit any detectable photoluminescence even at 10 K. Theoretical simulations of the band profiles combined with resonant excitation of the quantum wells allow us to rule out carrier escape and subsequent surface recombination as the reason for this absence of luminescence. To explore the hypothesis of a high concentration of nonradiative defects at the interfaces between wells and barriers, we analyze the photoluminescence of Ga- and N-polar quantum wells prepared on 6H -SiC as a function of the well width. Intense luminescence is observed for both Ga- and N-polar samples. As expected, the luminescence of the Ga-polar quantum wells quenches and redshifts with increasing well width due to the quantum confined Stark effect. In contrast, both the intensity and the energy of the luminescence from the N-polar samples are essentially independent of the well width. Transmission electron microscopy reveals that the N-polar quantum wells exhibit abrupt interfaces and homogeneous composition, excluding emission from In-rich clusters as the reason for this anomalous behavior. The microscopic origin of the luminescence in the N-polar samples is elucidated using spatially resolved cathodoluminescence spectroscopy. Regardless of well width, the luminescence is found to not originate from the N-polar quantum wells but from the semipolar facets of ∨ -pit defects. These results cast serious doubts on the potential of N-polar InxGa1 -xN /InyGa1 -yN quantum wells grown by plasma-assisted molecular beam epitaxy for the development of long-wavelength light-emitting diodes.

  18. Total syntheses of (-)-alpha-kainic acid and (+)-alpha-allokainic acid via stereoselective C-H insertion and efficient 3,4-stereocontrol.

    PubMed

    Jung, Young Chun; Yoon, Cheol Hwan; Turos, Edward; Yoo, Kyung Soo; Jung, Kyung Woon

    2007-12-21

    Reported herein is a novel approach to the total syntheses of (-)-alpha-kainic acid and (+)-alpha-allokainic acid, where the stereochemistries on C(2), C(3), and C(4) of the pyrrolidine core were introduced efficiently and selectively. A regio- and stereoselective C-H insertion reaction was utilized to prepare the gamma-lactam as an intermediate. A Michael-type cyclization of phenylsulfone with a conjugated acetylenic ketone was developed to prepare the tricyclic ketone as a key intermediate for (-)-alpha-kainic acid. Subsequently, a stereoselective dephenylsulfonylation was carried out successfully to secure the cis relationship at C(3) and C(4) centers. An unprecedented acetylation on the phenylsulfone, followed by a stereoselective dephenylsulfonylation, secured the trans relationship at C(3) and C(4) centers in (+)-alpha-allokainic acid.

  19. Ozonolysis of alpha-pinene and beta-pinene: kinetics and mechanism.

    PubMed

    Zhang, Dan; Zhang, Renyi

    2005-03-15

    A combined quantum-chemical and RRKM/ME (ME--master equation) approach is employed to investigate the structures, energetics, and kinetics of intermediate and stable species, and the yields of stabilized carbonyl oxides and OH radicals from the alpha-pinene and beta-pinene ozonolysis reactions. The cycloaddition of O(3) is highly exothermic, with the reaction energies of 55.1 and 51.1 kcal mol(-1) for alpha- and beta-pinenes, respectively. Cleavage of primary ozonides yields carbonyl oxides with the barrier height of 12.2-17.5 kcal mol(-1). For the prompt reactions of carbonyl oxides from alpha- and beta-pinene ozonolysis, H migration to hydroperoxides represents the dominant pathway over ring closure to dioxiranes. The kinetic calculations indicate a significant portion of stabilization for alpha- and beta-carbonyl oxides. The yields of stabilized carbonyl oxides are estimated to be 0.34 for alpha-pinene and 0.22 for beta-pinene. The applicability of theoretical methods for investigation of oxidation reactions of large hydrocarbon molecules is demonstrated.

  20. Alpha proton x ray spectrometer

    NASA Technical Reports Server (NTRS)

    Rieder, Rudi; Waeke, H.; Economou, T.

    1994-01-01

    Mars Pathfinder will carry an alpha-proton x ray spectrometer (APX) for the determination of the elemental chemical composition of Martian rocks and soils. The instrument will measure the concentration of all major and some minor elements, including C, N, and O at levels above typically 1 percent.

  1. Sparse Coding for Alpha Matting.

    PubMed

    Johnson, Jubin; Varnousfaderani, Ehsan Shahrian; Cholakkal, Hisham; Rajan, Deepu

    2016-07-01

    Existing color sampling-based alpha matting methods use the compositing equation to estimate alpha at a pixel from the pairs of foreground ( F ) and background ( B ) samples. The quality of the matte depends on the selected ( F,B ) pairs. In this paper, the matting problem is reinterpreted as a sparse coding of pixel features, wherein the sum of the codes gives the estimate of the alpha matte from a set of unpaired F and B samples. A non-parametric probabilistic segmentation provides a certainty measure on the pixel belonging to foreground or background, based on which a dictionary is formed for use in sparse coding. By removing the restriction to conform to ( F,B ) pairs, this method allows for better alpha estimation from multiple F and B samples. The same framework is extended to videos, where the requirement of temporal coherence is handled effectively. Here, the dictionary is formed by samples from multiple frames. A multi-frame graph model, as opposed to a single image as for image matting, is proposed that can be solved efficiently in closed form. Quantitative and qualitative evaluations on a benchmark dataset are provided to show that the proposed method outperforms the current stateoftheart in image and video matting.

  2. Sparse Coding for Alpha Matting.

    PubMed

    Johnson, Jubin; Varnousfaderani, Ehsan; Cholakkal, Hisham; Rajan, Deepu

    2016-04-21

    Existing color sampling based alpha matting methods use the compositing equation to estimate alpha at a pixel from pairs of foreground (F) and background (B) samples. The quality of the matte depends on the selected (F,B) pairs. In this paper, the matting problem is reinterpreted as a sparse coding of pixel features, wherein the sum of the codes gives the estimate of the alpha matte from a set of unpaired F and B samples. A non-parametric probabilistic segmentation provides a certainty measure on the pixel belonging to foreground or background, based on which a dictionary is formed for use in sparse coding. By removing the restriction to conform to (F,B) pairs, this method allows for better alpha estimation from multiple F and B samples. The same framework is extended to videos, where the requirement of temporal coherence is handled effectively. Here, the dictionary is formed by samples from multiple frames. A multi-frame graph model, as opposed to a single image as for image matting, is proposed that can be solved efficiently in closed form. Quantitative and qualitative evaluations on a benchmark dataset are provided to show that the proposed method outperforms current state-of-the-art in image and video matting.

  3. Alcoholism, Alpha Production, and Biofeedback

    ERIC Educational Resources Information Center

    Jones, Frances W.; Holmes, David S.

    1976-01-01

    Electroencephalograms of 20 alcoholics and 20 nonalcoholics were obtained. Data indicated that alcoholics produced less alpha than nonalcoholics. In one training condition subjects were given accurate biofeedback, whereas in the other condition subjects were given random (noncontingent) feedback. Accurate biofeedback did not result in greater…

  4. Intracellular target for alpha-terthienyl photosensitization: involvement of lysosomal membrane damage.

    PubMed

    Sasaki, M; Koyama, S; Tokiwa, K; Fujita, H

    1993-05-01

    Intracellular targets for the photosensitizer alpha-terthienyl (alpha T) were examined by fluorescence microscopy and microfluorospectrometry using human nonkeratinized buccal cells. Intracellular distribution of alpha T was observed as fluorescent patches widely dispersed in the cytoplasm. The distribution of the fluorescent patches was compared with that of acid phosphatase activity visualized as an azo dye produced by the fast garnet 2-methyl-4-[(2-methyl-phenyl)azo]benzenediasonium sulfate reaction. Because both the distribution sites coincided, lysosomes were the likely sites of intracellular affinity of alpha T. However, because acid phosphatase is not a specific lysosomal marker, we tried to detect another lysosomal enzyme, beta-galactosidase, to confirm if the fluorescent patches were lysosomes, using fluorescein-di-(beta-D-galactopyranoside) (FDG) as a fluorogenic substrate. Without UV-A (320-400 nm) irradiation of the cells after uptake of alpha T and FDG, no significant fluorescence was observed. In contrast, with prior UV-A irradiation in the presence of alpha T and FDG, the bright yellow fluorescence of fluorescein, which is the digested product of FDG, was clearly detected in the cells by fluorescence microscopy. This observation implied that inflow of external FDG into the lysosomes is caused by lysosomal membrane damage on alpha T photosensitization. The present results indicated that lysosomes are the primary photosensitization site of alpha T.

  5. Acetylation of lysine 40 in alpha-tubulin is not essential in Tetrahymena thermophila

    PubMed Central

    1995-01-01

    In Tetrahymena, at least 17 distinct microtubule structures are assembled from a single primary sequence type of alpha- and beta- tubulin heterodimer, precluding distinctions among microtubular systems based on tubulin primary sequence isotypes. Tetrahymena tubulins also are modified by several types of posttranslational reactions including acetylation of alpha-tubulin at lysine 40, a modification found in most eukaryotes. In Tetrahymena, axonemal alpha-tubulin and numerous other microtubules are acetylated. We completely replaced the single type of alpha-tubulin gene in the macronucleus with a version encoding arginine instead of lysine 40 and therefore cannot be acetylated at this position. No acetylated tubulin was detectable in these transformants using a monoclonal antibody specific for acetylated lysine 40. Surprisingly, mutants lacking detectable acetylated tubulin are indistinguishable from wild-type cells. Thus, acetylation of alpha- tubulin at lysine 40 is non-essential in Tetrahymena. In addition, isoelectric focusing gel analysis of axonemal tubulin from cells unable to acetylate alpha-tubulin leads us to conclude that: (a) most or all ciliary alpha-tubulin is acetylated, (b) other lysines cannot be acetylated to compensate for loss of acetylation at lysine 40, and (c) acetylated alpha-tubulin molecules in wild-type cells contain one or more additional charge-altering modifications. PMID:7775576

  6. Photoreactivity of. cap alpha. -fluorinated phenyl alkyl ketones

    SciTech Connect

    Wagner, P.J.; Thomas, M.J.; Puchalski, A.E.

    1986-11-26

    The photoreactivities of the mono-, di-, and tri-..cap alpha..-fluorinated acetophenones have been compared to that of acetophenone itself. All four ketones have similar triplet excitation energies; the three fluorinated ketones have reduction potentials 0.5-0.7 eV lower than that of acetophenone. Triplet reactivity toward alkylbenzenes keeps increasing with fluorine substitution, since the rate-determining step becomes charge-transfer complexation as the ketone reduction potential decreases. The primary/tertiary C-H selectivity toward p-cymene increases with the number of fluorines. Triplet reactivity toward cyclopentane also is increased by fluorination but peaks at two fluorines, since the lowest triplet switches from n,..pi..* to ..pi..,..pi..* with two or three fluorines and ..pi..,..pi..* triplets are unreactive in simple hydrogen atom abstraction. In contrast, ..cap alpha..-fluorination of valerophenone does not significantly increase the rate of triplet ..gamma..-hydrogen abstraction. The inductive effect on reactivity apparently is offset by a conformational effect. The ..cap alpha..-fluorinated phenones give predominantly cyclobutanols instead of Norrish type II elimination. ..cap alpha..-Fluoroacetophenone forms predominantly acetophenone and HF when irradiated with 2-propanol, in what appears to be a short chain process involving electron transfer to ketone followed by fluoride ion loss. Finally, the radical coupling products in these reactions are formed in varying yields, depending on solvent and additives.

  7. Activation cross sections for reactions induced by 14 MeV neutrons on natural tantalum

    SciTech Connect

    Luo Junhua; Tuo Fei; Kong Xiangzhong

    2009-05-15

    Cross sections for (n,2n), (n,p), (n,n{sup '}{alpha}), (n,t), (n,d{sup '}), and (n,{alpha}) reactions have been measured on tantalum isotopes at the neutron energies of 13.5 to 14.7 MeV using the activation technique. Data are reported for the following reactions: {sup 181}Ta(n,2n){sup 180}Ta{sup g}, {sup 181}Ta(n,p){sup 181}Hf, {sup 181}Ta(n,n{sup '}{alpha}){sup 177}Lu{sup m}, {sup 181}Ta(n,t){sup 179}Hf{sup m2}, {sup 181}Ta(n,d{sup '}){sup 180}Hf{sup m}, and {sup 181}Ta(n,{alpha}){sup 178}Lu{sup m}. The neutron fluences were determined using the monitor reaction {sup 27}Al(n,{alpha}){sup 24}Na. Results were discussed and compared with the previous works.

  8. Interleukin-6 enhances whereas tumor necrosis factor alpha and interferons inhibit integrin expression and adhesion of human mast cells to extracellular matrix proteins.

    PubMed

    Schoeler, Dagmar; Grützkau, Andreas; Henz, Beate M; Küchler, Jens; Krüger-Krasagakis, Sabine

    2003-05-01

    Integrins are expressed on mast cells and constitute an essential prerequisite for the accumulation of the cells at sites of inflammation. In order to clarify a potential contribution of inflammatory cytokines to this process, we have studied the modulation of integrin expression and adhesion of immature human mast cells (HMC-1) to extracellular matrix proteins by interleukin-6, tumor necrosis factor alpha, interferon-alpha and interferon-gamma. Corticosteroids were used for comparison. On fluorescence-activated cell sorter analysis, preincubation of cells for 48 h with different concentrations of interleukin-6 induced a significant, up to 40%, increase of alpha v alpha 5, CD49b (alpha 2), CD49e (alpha 5), CD49f (alpha 6), and CD51 (alpha v). In contrast, different concentrations of tumor necrosis factor alpha, interferon-alpha, interferon-gamma, and dexamethasone (10-8-10-10 M) inhibited expression of adhesion receptors by up to 60%, reaching significance for some but not all integrins. On semiquantitative polymerase chain reaction analysis, interleukin-6, the other cytokines, and corticosteroids significantly modulated expression of alpha1, alpha v and alpha 5 integrin chains at mRNA level. Functional significance of these findings was proven in adhesion assays using fibronectin, laminin, and vitronectin, with interleukin-6 causing significant enhancement of adhesion in all cases, tumor necrosis factor alpha and dexamethasone inducing significant reduction of adhesion to fibronectin and laminin, and interferon-gamma significantly inhibiting adhesion to fibronectin only. Specificity of interleukin-6-induced changes was demonstrated using antibodies against alpha1 and alpha 5 integrins in unstimulated and interleukin-6-prestimulated cells. These data show that interleukin-6 stimulates mast cell adhesion to extracellular matrix and thus allows for the accumulation of the cells at tissue sites by enhancing integrin expression, whereas tumor necrosis factor alpha

  9. Synthesis of chiral alpha-amino aldehydes linked by their amine function to solid support.

    PubMed

    Cantel, Sonia; Heitz, Annie; Martinez, Jean; Fehrentz, Jean-Alain

    2004-09-01

    The anchoring of an alpha-amino-acid derivative by its amine function on to a solid support allows some chemical reactions starting from the carboxylic acid function. This paper describes the preparation of alpha-amino aldehydes linked to the support by their amine function. This was performed by reduction with LiAlH4 of the corresponding Weinreb amide linked to the resin. The aldehydes obtained were then involved in Wittig or reductive amination reactions. In addition, the linked Weinreb amide was reacted with methylmagnesium bromide to yield the corresponding ketone. After cleavage from the support, the compounds were obtained in good to excellent yields and characterized.

  10. A model for sequential threading of alpha-cyclodextrin onto a guest: a complete thermodynamic and kinetic study in water.

    PubMed

    Saudan, C; Dunand, F A; Abou-Hamdan, A; Bugnon, P; Lye, P G; Lincoln, S F; Merbach, A E

    2001-10-24

    The first variable-temperature and variable-pressure stopped-flow spectrophotometric study of the sequential threading of alpha-cyclodextrin (alpha-CD) onto the guest dye Mordant Orange 10, S, is reported. Complementary (1)H one-dimensional (1D) variable-temperature kinetic studies and two-dimensional (2D) rotating-frame nuclear Overhauser effect spectroscopy (ROESY) and EXSY NMR studies are also reported. In aqueous solution at 298.2 K, the first alpha-CD threads onto S to form a 1:1 complex S.alpha-CD with a forward rate constant k(1,f) = 15 200 +/- 200 M(-1) s(-1) and dethreads with a reverse rate constant k(1,r) = 4.4 +/- 0.3 s(-1). Subsequently, S.alpha-CD isomerizes to S.alpha-CD (k(3,f) = 0.158 +/- 0.006 s(-1), k(3,f) = 0.148 +/- 0.006 s(-1)). This process can be viewed as a thermodynamically controlled molecular shuttle. A second alpha-CD threads onto S.alpha-CD to form a 1:2 complex, S.(alpha-CD)(2), with k(2,f) = 98 +/- 2 M(-1) s(-1) and k(2,r) = 0.032 +/- 0.002 s(-1). A second alpha-CD also threads onto S.alpha-CD to form another 1:2 complex, S.(alpha-CD)(2), characterized by k(4,f) = 9640 +/- 1800 M(-1) s(-1) and k(4,r) = 61 +/- 6 s(-1). Direct interconvertion between S.(alpha-CD)(2) and S.(alpha-CD)(2) was not detected; instead, they interconvert by dethreading the second alpha-CD and through the isomerization equilibrium between S.alpha-CD and S.alpha-CD. The reaction volumes, DeltaV(0), were found to be negative for the first three equilibria and positive for the fourth equilibrium. For the first three forward and reverse reactions, the volumes of activation are substantially more negative, indicating a compression of the transition state in comparison with the ground states. These data were used in conjunction with DeltaH, DeltaH degrees, DeltaS, and DeltaS degrees data to deduce the dominant mechanistic threading processes, which appear to be largely controlled by changes in hydration and van der Waals interactions, and possibly by conformational

  11. Coexistence of {alpha}+{alpha}+n+n and {alpha}+t+t cluster structures in {sup 10}Be

    SciTech Connect

    Itagaki, N.; Ito, M.; Milin, M.; Hashimoto, T.; Ishiyama, H.; Miyatake, H.

    2008-06-15

    The coexistence of the {alpha}+{alpha}+n+n and {alpha}+t+t cluster structures in the excited states of {sup 10}Be has been discussed. In the previous analysis, all the low-lying states of {sup 10}Be were found to be well described by the motion of the two valence neutrons around two {alpha} clusters. However, the {alpha}+t+t cluster structure was found to coexist with the {alpha}+{alpha}+n+n structure around E{sub x}=15 MeV, close to the corresponding threshold. We have introduced a microscopic model to solve the coupling effect between these two configurations. The K=0 and K=1 states are generated from the {alpha}+t+t configurations due to the spin coupling of two triton clusters. The present case of {sup 10}Be is one of the few examples in which completely different configurations of triton-type ({alpha}+t+t three-center) and {alpha}-type ({alpha}+{alpha}+n+n two-center) clusters coexist in a single nucleus in the same energy region.

  12. Characterization of alpha-glucosyltransferase from Pseudomonas mesoacidophila MX-45.

    PubMed

    Nagai, Y; Sugitani, T; Tsuyuki, K

    1994-10-01

    alpha-Glucosyltransferase was purified from Pseudomonas mesoacidophila MX-45. The molecular weight was estimated to be 63,000 by SDS-PAGE, and the isoelectric point was pI 5.4. For enzyme activity based on sucrose decomposition, the optimum pH and the optimum temperature were pH 5.8 and 40 degrees C, respectively. The ranges of stable pH and temperature were pH 5.1-6.7 and below 40 degrees C, respectively. The purified enzyme of MX-45 converted sucrose into trehalulose (1-O-alpha-D-glucopyranosyl- D-fructose) and isomaltulose (palatinose, 6-O-alpha-D-glucopyranosyl-D-fructose) simultaneously, and the ratio of trehalulose to isomaltulose increased at lower reaction temperatures. Therefore, optimum conditions for trehalulose production were pH 5.5-6.5 at 20 degrees C. The yield of trehalulose from sucrose (20-40% solution) was 91%. The Km for sucrose was 19.2 +/- 3.3 mM estimated by the Hanes-Woolf plot. Product inhibition was observed, and the product inhibition constant was 0.17 M. Hg2+, Fe3+, Cu2+, Mg2+, Ag+, Pb2+, glucono-1,5-lactone, and Tris(hydroxymethyl)aminomethane inhibited the reaction.

  13. Production of medical Sc radioisotopes with an alpha particle beam.

    PubMed

    Szkliniarz, Katarzyna; Sitarz, Mateusz; Walczak, Rafał; Jastrzębski, Jerzy; Bilewicz, Aleksander; Choiński, Jarosław; Jakubowski, Andrzej; Majkowska, Agnieszka; Stolarz, Anna; Trzcińska, Agnieszka; Zipper, Wiktor

    2016-12-01

    The internal α-particle beam of the Warsaw Heavy Ion Cyclotron was used to produce research quantities of the medically interesting Sc radioisotopes from natural Ca and K and isotopically enriched (42)Ca targets. The targets were made of metallic calcium, calcium carbonate and potassium chloride. New data on the production yields and impurities generated during the target irradiations are presented for the positron emitters (43)Sc, (44g)Sc and (44m)Sc. The different paths for the production of the long lived (44m)Sc/(44g)Sc in vivo generator, proposed by the ARRONAX team, using proton and deuteron beams as well as alpha-particle beams are discussed. Due to the larger angular momentum transfer in the formation of the compound nucleus in the case of the alpha particle induced reactions, the isomeric ratio of (44m)Sc/(44g)Sc at a bombarding energy of 29MeV is five times larger than previously determined for a deuteron beam and twenty times larger than for proton induced reactions on enriched CaCO3 targets. Therefore, formation of this generator via the alpha-particle route seems a very attractive way to form these isotopes. The experimental data presented here are compared with theoretical predictions made using the EMPIRE evaporation code. Reasonable agreement is generally observed.

  14. A synopsis of collective alpha effects and implications for ITER

    SciTech Connect

    Sigmar, D.J.

    1990-10-01

    This paper discusses the following: Alpha Interaction with Toroidal Alfven Eigenmodes; Alpha Interaction with Ballooning Modes; Alpha Interaction with Fishbone Oscillations; and Implications for ITER.

  15. Alpha-toxin of Staphylococcus aureus.

    PubMed Central

    Bhakdi, S; Tranum-Jensen, J

    1991-01-01

    Alpha-toxin, the major cytotoxic agent elaborated by Staphylococcus aureus, was the first bacterial exotoxin to be identified as a pore former. The protein is secreted as a single-chain, water-soluble molecule of Mr 33,000. At low concentrations (less than 100 nM), the toxin binds to as yet unidentified, high-affinity acceptor sites that have been detected on a variety of cells including rabbit erythrocytes, human platelets, monocytes and endothelial cells. At high concentrations, the toxin additionally binds via nonspecific absorption to lipid bilayers; it can thus damage both cells lacking significant numbers of the acceptor and protein-free artificial lipid bilayers. Membrane damage occurs in both cases after membrane-bound toxin molecules collide via lateral diffusion to form ring-structured hexamers. The latter insert spontaneously into the lipid bilayer to form discrete transmembrane pores of effective diameter 1 to 2 nm. A hypothetical model is advanced in which the pore is lined by amphiphilic beta-sheets, one surface of which interacts with lipids whereas the other repels apolar membrane constitutents to force open an aqueous passage. The detrimental effects of alpha-toxin are due not only to the death of susceptible targets, but also to the presence of secondary cellular reactions that can be triggered via Ca2+ influx through the pores. Well-studied phenomena include the stimulation of arachidonic acid metabolism, triggering of granule exocytosis, and contractile dysfunction. Such processes cause profound long-range disturbances such as development of pulmonary edema and promotion of blood coagulation.(ABSTRACT TRUNCATED AT 250 WORDS) Images PMID:1779933

  16. What Causes Alpha-1 Antitrypsin Deficiency?

    MedlinePlus

    ... Causes Alpha-1 Antitrypsin Deficiency? Alpha-1 antitrypsin (AAT) deficiency is an inherited disease. "Inherited" means it's ... parents to children through genes. Children who have AAT deficiency inherit two faulty AAT genes, one from ...

  17. How Is Alpha-1 Antitrypsin Deficiency Treated?

    MedlinePlus

    ... Alpha-1 Antitrypsin Deficiency Treated? Alpha-1 antitrypsin (AAT) deficiency has no cure, but its related lung ... pulmonary disease). If you have symptoms related to AAT deficiency, your doctor may recommend: Medicines called inhaled ...

  18. New, tritium-release assay for 25-hydroxyvitamin D-1. cap alpha. -hydroxylase

    SciTech Connect

    Brown, A.J.; Perlman, K.; DeLuca, H.F.

    1986-05-01

    A new, rapid assay for 25-hydroxyvitamin D (25-OH-D)-1..cap alpha..-hydroxylase has been developed using 25-OH-(1..cap alpha..-/sup 3/H)D/sub 3/ as substrate. This compound was prepared by reduction of 1-oxo-25-hydroxycyclovitamin D/sub 3/ with (/sup 3/H)NaBH/sub 4/, separation of the 1..cap alpha..- and 1..beta..-hydroxy products by HPLC, subsequent treatments with methylsulfonylchloride and lithium aluminum hydride, cycloreversion, and saponification. The 1..cap alpha..- and 1..beta..-tritiated substrates were tested in the solubilized and reconstituted chick 1..cap alpha..-hydroxylase system. After incubation, the reaction mixture was passed through a reversed phase silica cartridge to separate (/sup 3/H)H/sub 2/O from the labeled substrate. The cartridges were then washed with methanol to elute all vitamin D metabolites, and the amount of 1,25-(OH)/sub 2/(/sup 3/H)D/sub 3/ was measured by HPLC. In addition, identical reaction mixtures using 25-OH-(26,27-/sup 3/H)D/sub 3/ as substrate were extracted and analyzed by HPLC for 1,25-(OH)/sub 2/(/sup 3/H)D/sub 3/. Reactions with 25-OH-(1..cap alpha..-/sup 3/H)D/sub 3/ produced (/sup 3/H)H/sub 2/O comparable to the amount of 1,25-(OH)/sub 2/(26,27-/sup 3/H)D/sub 3/ and negligible (/sup 3/H) in 1,25-(OH)/sub 2/D/sub 3/. Conversely, reactions with 25-OH-(1..beta..-/sup 3/H)D/sub 3/ produced negligible (/sup 3/H)H/sub 2/O but produced 1,25-(OH)/sub 2/(/sup 3/H)D/sub 3/ comparable to that from reactions with 25-OH-(26,27-/sup 3/H)D/sub 3/. The results indicate that 1..cap alpha..-hydroxylation specifically displaces the 1..cap alpha..-hydrogen of 25-OH-D/sub 3/ and that the release of the 1..cap alpha..-/sup 3/H provides an accurate measure of vitamin D 1..cap alpha..-hydroxylation.

  19. T-cell receptor V sub. alpha. and C sub. alpha. alleles associated with multiple sclerosis and myasthenia gravis

    SciTech Connect

    Oksenberg, J.R.; Cavalli-Sforza, L.L.; Steinman, L. ); Sherritt, M.; Bernard, C.C. ); Begovich, A.B.; Erlich, H.A. )

    1989-02-01

    Polymorphic markers in genes encoding the {alpha} chain of the human T-cell receptor (TcR) have been detected by Southern blot analysis in Pss I digests. Polymorphic bands were observed at 6.3 and 2.0 kilobases (kb) with frequencies of 0.30 and 0.44, respectively, in the general population. Using the polymerase chain reaction (PCR) method, the authors amplified selected sequences derived from the full-length TcR {alpha} cDNA probe. These PcR products were used as specific probes to demonstrate that the 6.3-kb polymorphic fragment hybridizes to the variable (V)-region probe and the 2.0-kb fragment hybridizes to the constant (C)-region probe. Segregation of the polymorphic bands was analyzed in family studies. To look for associations between these markers and autoimmune diseases, the authors have studied the restriction fragment length polymorphism distribution of the Pss I markers in patients with multiple sclerosis, myasthenia gravis, and Graves disease. Significant differences in the frequency of the polymorphic V{sub {alpha}} and C{sub {alpha}} markers were identified between patients and healthy individuals.

  20. Epitaxial growth of In{sub x}Ga{sub 1-x}N alloy films on sapphire and silicon by reactive co-sputtering of GaAs and indium

    SciTech Connect

    Mohan, Shyam Major, S. S.; Srinivasa, R. S.

    2015-06-24

    In{sub x}Ga{sub 1-x}N alloy films (0.2