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Sample records for alpha xn reactions

  1. Development of a neutron long-counter system for astrophysical (α , xn) reaction studies

    NASA Astrophysics Data System (ADS)

    Ahn, Sunghoon; Montes, Fernando; Ong, Wei Jia; Meisel, Zachary; Perello, Jesus; Joint InstituteNuclear Astrophysics-Center Evolution of the Elements Collaboration; National Superconducting Cyclotron Laboratory Collaboration

    2015-10-01

    Recent studies on the discrepancy of Z = 38 - 47 abundances between metal poor stars have proposed (α , xn) reactions as the main reaction pathway for early nucleosynthesis in the wind with the condition of (n , γ) - (γ , n) equilibrium and temperatures between 3.5 and 5.5 GK. Uncertainties in (α , xn) reaction rates directly affect calculated abundances with an impact that is comparable to that from astrophysical uncertainties. At present, reaction rate uncertainties are relatively large since little experimental data exists for (α , xn) cross sections involved in the nucleosynthesis calculation. We are developing a neutron detector which counts emitted neutrons from the (α , xn) reactions. The detector consists of 80 gas-filled BF3 and 3He proportional tubes oriented in rings along the beam axis embedded in a polyethylene matrix. The configuration of the tubes in the matrix is determined by both a high average neutron detection efficiency and the efficiency as a function of energy to be as constant as possible from En = 0 . 1 - 19 . 5 MeV, since neutron energy information will be lost due to neutron moderation. Details of the detector design and a status report on the device will be presented.

  2. Alpha-induced reactions in iridium

    SciTech Connect

    Bhardwaj, M.K.; Rizvi, I.A.; Chaubey, A.K. )

    1992-05-01

    The excitation function of ({alpha},{ital xn}) reactions on {sup 191}Ir (abundance 37.3%) and on {sup 193}Ir (abundance 62.7%) has been measured for the 17--55 MeV alpha-particle bombarding energy range. The stacked foil activation technique and {gamma}-ray spectroscopy were used to determine the cross sections. The experimental data were compared with calculated values obtained by means of a geometry-dependent hybrid model. The initial exciton number {ital n}{sub 0}=4 with {ital n}=2, {ital p}=2, and {ital h}=0 gives the best agreements with the presently measured results. To calculate the excitation function theoretically a computer code was used. This set of excitation functions provides a data basis for probing the validity of combined equilibrium and preequilibrium reaction models in a considerable energy range.

  3. Measurement of excitation functions in the reactions 197Au(11C, xn)208-xAt using a radioactive 11C beam

    PubMed

    Joosten; Powell; Guo; Haustein; Larimer; McMahan; Norman; O'Neil; Rowe; VanBrocklin; Wutte; Xu; Cerny

    2000-05-29

    A light-element radioactive ion-beam capability has been developed at the LBNL 88-Inch Cyclotron. The system is based on the coupled-cyclotrons method and utilizes short-lived species, e.g., 11C, 14O, 13N produced by (p,n) and (p,alpha) reactions at the LBNL Biomedical Isotope Facility Cyclotron. In a first experiment, 197Au(11C,xn)208-xAt excitation functions have been measured for energies ranging from the Coulomb barrier up to 110 MeV using a beam of 11C with intensities up to (1-2)x10(8) ions/sec on target. The results of this experiment are compared to measurements of 197Au(12C, xn)209-xAt excitation functions. PMID:10990868

  4. The Measurement of the Evaporation Residues Excitation Functions in the Fusion Reactions 144Sm (40Ar,xn) and 166Er(40Ar,xn)

    NASA Astrophysics Data System (ADS)

    Chernysheva, E. V.; Rodin, A. M.; Belozerov, A. V.; Dmitriev, S. N.; Gulyaev, A. V.; Gulyaeva, A. V.; Itkis, M. G.; Novoselov, A. S.; Oganessian, Yu. Ts.; Salamatin, V. S.; Stepantsov, S. V.; Vedeneev, V. Yu.; Yukhimchuk, S. A.; Krupa, L.; Kliman, J.; Motycak, S.; Sivacek, I.

    2015-06-01

    The evaporation residues excitation functions for the reactions 40Ar+144Sm→184Hg and 40Ar+166Er→206Rn were measured at the energies below and above the Coulomb barrier (Elab=142-207 MeV) using a mass-separator MASHA. The experimental data were compared with theoretical calculations using a Channel Coupling Model. The influence of experimental beam energy spread on the excitation functions was taking into account. It was found that structure of xn-cross sections correlate strongly with the nuclear structure of colliding nuclei.

  5. {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.

  6. 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.

  7. Alpha Induced Reaction Cross Section Calculations of Tantalum Nucleus

    NASA Astrophysics Data System (ADS)

    Tel, E.; Ugur, F. A.; Gokce, A. A.

    2013-04-01

    The fusion energy is attractive as an energy source because the fusion will not produce CO2 or SO2 and so fusion will not contribute to environmental problems, such as particulate pollution and excessive CO2 in the atmosphere. The fusion reaction does not produce radioactive nuclides and it is not self-sustaining, as is a fission reaction when a critical mass of fissionable material is assembled. Since the fusion reaction is easily and quickly quenched the primary sources of heat to drive such an accident are heat from radioactive decay and heat from chemical reactions. Both the magnitude and time dependence of the generation of heat from radioactive decay can be controlled by proper selection and design of materials. Tantalum is one of the candidate materials for the first wall of fusion reactors and for component parts of irradiation chambers. Accurate experimental cross-section data of alpha induced reactions on Tantalum are also of great importance for thermonuclear reaction rate determinations since the models used in the study of stellar nucleosynthesis are strongly dependent on these rates (Santos et al. in J Phys G 26:301, 2000). In this study, neutron-production cross sections for target nuclei 181Ta have been investigated up to 100 MeV alpha energy. The excitation functions for (α, xn) reactions (x = 1, 2, 3) have been calculated by pre-equilibrium reaction mechanism. And also neutron emission spectra for 181Ta (α, xn) reactions at 26.8 and 45.2 MeV have been calculated. The mean free path multiplier parameters has been investigated. The pre-equilibrium results have been calculated by using the hybrid model, the geometry dependent hybrid (GDH) model. Calculation results have been also compared with the available measurements in literature.

  8. Measurement of high energy neutrons via Lu(n,xn) reactions

    SciTech Connect

    Henry, E.A.; Becker, J.A.; Archer, D.E.; Younes, W.; Stoyer, M.A.; Slaughter, D.

    1997-07-01

    High energy neutrons can be assayed by the use of the nuclear diagnostic material lutetium. We are measuring the (n,xn) cross sections for natural lutetium in order to develop it as a detector material. We are applying lutetium to diagnose the high energy neutrons produced in test target/blanket systems appropriate for the Accelerator Production of Tritium Project. 3 refs., 5 figs., 1 tab.

  9. 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.

  10. Statistical theory of light-nucleus reactions and application to the 9Be (p,xn) reaction

    NASA Astrophysics Data System (ADS)

    Sun, Xiaojun; Zhang, Jingshang

    2016-01-01

    A statistical theory of light nucleus reactions (STLN) is proposed to describe both neutron and light charged particle induced nuclear reactions with 1 p -shell light nuclei involved. The dynamics of STLN is described by the unified Hauser-Feshbach and exciton model, in which the angular momentum and parity conservations are strictly considered in equilibrium and pre-equilibrium processes. The Coulomb barriers of the incoming and outgoing charged particles, which significantly influence the open channels of the reaction, can be reasonably considered in the incident channel and different outgoing channels. In kinematics, the recoiling effects in various emission processes are strictly taken into account. The analytical double-differential cross sections of the reaction products in sequential and simultaneous emission processes are obtained in terms of the new integral formula proposed in our recent paper [Phys. Rev. C 92, 061601(R) (2015), 10.1103/PhysRevC.92.061601]. Taking the 9Be(p ,x n ) reaction as an example, we calculate the double-differential cross sections of outgoing neutrons and charged particles using the punf code in the frame of STLN. The existing experimental double-differential cross sections of neutrons at Ep=18 MeV can be remarkably well reproduced, which indicates that the punf code is a powerful tool to set up "file-6" in the reaction data library for light charged particle induced nuclear reactions with 1 p -shell light nuclei involved.

  11. Heavy-ion reaction mechanisms studied with the spin spectrometer

    SciTech Connect

    Halbert, M.L.

    1983-01-01

    Experimental data and statistical-model calculations for xn and ..cap alpha..xn products of the reaction /sup 20/Ne + /sup 146/Nd at 136 MeV are shown to be in generally good agreement, indicating that equilibrium processes are dominant. Preliminary results on the heavy-ion ejectiles from /sup 19/F + /sup 159/Tb are presented.

  12. Alternate Alpha Induced Reactions for NIF Radiochemistry

    SciTech Connect

    Shaughnessy, D A; Moody, K J; Bernstein, L A

    2010-02-26

    Radiochemical analysis of NIF capsule residues has been identified as a potential diagnostic of NIF capsule performance. In particular, alpha-induced nuclear reactions that occur on tracer elements added to the NIF capsule have been shown through simulation to be a very sensitive diagnostic for mix. The short range of the alpha particles makes them representative of the hot spot where they are created through the fusion of deuterium and tritium. Reactions on elements doped into the innermost part of the capsule ablator would therefore be sensitive to material that had mixed into the hot spot. Radiochemical determinations of activated detector elements may perhaps be the only true measure of mix that occurs in a NIF capsule, particularly in cases when the capsule fails.

  13. Alpha resonant scattering for astrophysical reaction studies

    NASA Astrophysics Data System (ADS)

    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.

    2014-05-01

    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 7Be+α resonant scattering is discussed. Based on the result of the experiment, we evaluated the contributions of high-lying resonances for the 7Be(α,γ) reaction, and proposed a new cluster band in 11C.

  14. 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.

  15. 89Y(γ,xn) reaction cross-section measurements with bremsstrahlung end-point energies of 50-65 MeV

    NASA Astrophysics Data System (ADS)

    Zaman, Muhammad; Kim, Guinyun; Kim, Kwangsoo; Shahid, Muhammad; Naik, Haladhara; Yang, Sungchul; Shin, Sung-Gyun; Cho, Moo-Hyun

    2015-10-01

    The cross-sections for 89Y(γ, n)88Y, 89Y(γ, 2n)87Y, 89Y(γ, 3n)86Y, and 89Y(γ, 4n)85Y reactions for the end-point bremsstrahlung energies of 50 and 65 MeV were determined by using an activation and an off-line γ-ray spectrometric techniques with the electron linear accelerator at the Pohang Accelerator laboratory (PAL), Korea. The photon-induced reaction cross-sections of 89Y as functions of the photon energy were taken from the TENDL-2013 nuclear data library based on the TALYS 1.6 program. For comparison with our experimental results, the flux-weighted average cross-sections for the existing experimental data with mono-energetic photons and the theoretical values from TENDL-2013 were obtained. The reaction cross-section values measured at different end-point bremsstrahlung energies from the present work and from literature are found to be in good agreement with the theoretical values. The 89Y(γ, xn, x = 1 - 4) reaction cross-sections were observed to increase sharply from their threshold values to certain energies, until the next reaction channel opens, after which it remained constant for a while until the next reaction channel opened. Then, it decrease slowly with increasing of end-point bremsstrahlung energy due to the opening of different reaction channels.

  16. 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.

  17. From γ emissions to (n,xn) cross sections of interest: The role of GAINS and GRAPhEME in nuclear reaction modeling

    NASA Astrophysics Data System (ADS)

    Kerveno, M.; Bacquias, A.; Borcea, C.; Dessagne, Ph.; Henning, G.; Mihailescu, L. C.; Negret, A.; Nyman, M.; Olacel, A.; Plompen, A. J. M.; Rouki, C.; Rudolf, G.; Thiry, J. C.

    2015-12-01

    During the last 10 years, in the general context of nuclear energy applications and future reactors development, our collaboration has performed measurements of (n, x nγ cross sections to study (n, xn) reactions. Large sets of new and accurate experimental data have been produced on a variety of nuclei from 7Li to 238U. Comparisons with nuclear reaction code calculations have shown that the predictions of these exclusive cross sections are a real challenge for the theoretical codes. Indeed many processes are involved as evaporation, fission if fissionable nucleus, direct and pre-equilibrium reactions, etc. All these processes should be simultaneously well described by the models that using nuclear structure description for optical potential, level densities, decay scheme, etc. In this article, we review what we have learned since the last P(ND)2 workshop held in 2005 (A.J.M. Plompen, Proceedings of the Perspectives on Nuclear data for the Next Decade Workshop, Bruyères-le-Châtel, France, 26-28 September 2005, NEA Report N° 6121, p. 151) and highlight how we can further progress in this field in order to provide new, complete, accurate and relevant experimental data.

  18. Measurement of flux-weighted average cross sections for 197Au(γ, xn) reactions and isomeric yield ratios of 196m,gAu with bremsstrahlung

    NASA Astrophysics Data System (ADS)

    Naik, Haladhara; Kim, Guinyun; Kim, Kwangsoo; Zaman, Muhammad; Goswami, Ashok; Lee, Man Woo; Yang, Sung-Chul; Lee, Young-Ouk; Shin, Sung-Gyun; Cho, Moo-Hyun

    2016-04-01

    Photo-neutron cross sections of 197Au were experimentally determined for the bremsstrahlung end-point energies of 50, 60, and 70 MeV, by utilizing activation and off-line γ-ray spectrometric technique, using the 100 MeV electron linac at the Pohang Accelerator Laboratory (PAL), Pohang, Korea. The 197Au(γ, xn; x = 1- 6) reaction cross sections were calculated as a function of the bombarding photon energy by using the TALYS 1.6 computer code with default parameters. The flux-weighted average cross sections were obtained from the literature data and the theoretical values of TALYS 1.6 and TENDL-2014, for mono-energetic photons, and are found to be in good agreement with the present data. Isomeric yield ratios of 196m2,gAu from the 197Au(γ, n) reaction were also determined for the bremsstrahlung end-point energies of 50, 60, and 70 MeV, from the reaction cross sections of m2- and g-states, based on the present experimental data, and are found to be in good agreement with the theoretical values based on TALYS 1.6 and TENDL-2014.

  19. 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.

  20. 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.

  1. 196Pt(n,xn yp γ) reactions using spallation neutrons from En=1 to 250 MeV

    NASA Astrophysics Data System (ADS)

    Tavukcu, E.; Bernstein, L. A.; Hauschild, K.; Becker, J. A.; Garrett, P. E.; McGrath, C. A.; McNabb, D. P.; Younes, W.; Chadwick, M. B.; Nelson, R. O.; Johns, G. D.; Mitchell, G. E.

    2001-11-01

    Neutron-induced reactions on 196Pt were studied over the neutron energy range from 1 to 250 MeV. A ``white'' neutron beam was provided by the spallation neutron source of the Weapons Neutron Research facility at the Los Alamos Neutron Science Center. The prompt reaction γ rays were measured with the large-scale Compton-suppressed Ge spectrometer GEANIE. The incident neutron energy was determined by the time-of-flight technique. Excitation functions for γ-ray transitions in 184,186,188,190-196Pt and 189,191,193Ir isotopes are compared with enhanced Hauser-Feshbach reaction modeling, as implemented in the reaction code GNASH. Overall, the model predictions agree well with the measured γ-ray yields. Discrepancies appear, however, due to inadequate discrete-level information in the calculations describing the preequilibrium process.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Pavlik, A.; Baumann, P.; Borcea, C.; Jericha, E.; Jokić, S.; Kerveno, M.; Lukić, S.; Meulders, J. P.; Mihailescu, L. C.; Nolte, R.; Plompen, A. J. M.; Raškinytė, I.; N Tof Collaboration

    2005-05-01

    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 Université 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.

  4. 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.

  5. 207,208Pb(n,xnγ) reactions for neutron energies from 3 to 200 MeV

    NASA Astrophysics Data System (ADS)

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

    1994-10-01

    High-resolution γ-ray spectra from the interaction of neutrons in the energy range from 3 to 200 MeV with 207,208Pb were measured with the white neutron source at the weapons neutron research (WNR) facility at Los Alamos National Laboratory. From these data, excitation functions for prominent γ transitions in 200,202,204,206,207,208Pb were derived from threshold to 200 MeV incident neutron energy. These γ-production cross sections reflect the excitation cross sections for the respective 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 nucleus 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 of this work clearly demonstrate that multiple preequilibrium emission has to be taken into account above about 40 MeV, and that the level density model of Ignatyuk, which accounts for the gradual disappearance of shell effects with increasing excitation energy, should be used instead of the Gilbert-Cameron and backshifted Fermi-gas models if excitation energies exceed about 30 MeV. No indication for a reduction of the nuclear moment of inertia below the rigid body value was found.

  6. Reaction of. cap alpha. ,. cap alpha. ,omega-trihydroperfluoroalkanols with thionyl chloride

    SciTech Connect

    Krolevets, A.A.; Ragulin, L.I.; Popov, A.G.

    1987-06-10

    The effect of catalysts on the reaction of thionyl chloride with ..cap alpha..,..cap alpha..,omega-trihydroperfluoroalkanols was investigated. It was shown that the use of calcium chloride, aluminum chloride, ferric chloride, and magnesium chloride as catalysts makes it possible to obtain polyfluoroalkyl chlorosulfites and bis(polyfluoroalkyl) sulfites with good yields.

  7. 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.

  8. Reaction of alpha-gem-trichlorocarbonyl compounds with conjugated alkadienes

    SciTech Connect

    Startsev, V.V.; Zubritskii, L.M.; Gorbunkov, V.D.; Petrov, A.A.

    1986-04-10

    Chloral and gem-trichloroacetone add to 1,3-alkadienes in the presence of copper(I) chloride with the formation of the corresponding ..gamma..,delta-unsaturated ..cap alpha..,..cap alpha..epsilon-trichlorocarbonyl compounds as mixtures of the E and Z isomers in a ratio in the order of 85:15. The reaction takes place under mild conditions and gives a high yield of the final products.

  9. Alcoholysis reactions from starch with alpha-amylases.

    PubMed

    Santamaría, R I; Del Río, G; Saab, G; Rodríguez, M E; Soberón, X; López-Manguía, A

    1999-06-11

    The ability of alpha-amylases from different sources to carry out reactions of alcoholysis was studied using methanol as substrate. It was found that while the enzymes from Aspergillus niger and Aspergillus oryzae, two well-studied saccharifying amylases, are capable of alcoholysis reactions, the classical bacterial liquefying alpha-amylases from Bacillus licheniformis and Bacillus stearothermophilus are not. The effect of starch and methanol concentration, temperature and pH on the synthesis of glucosides with alpha-amylase from A. niger was studied. Although methanol may inactivate alpha-amylase, a 90% substrate relative conversion can be obtained in 20% methanol at a high starch concentration (15% w/v) due to a stabilizing effect of starch on the enzyme. As the products of alcoholysis are a series of methyl-oligosaccharides, from methyl-glucoside to methyl-hexomaltoside, alcoholysis was indirectly quantified by high performance liquid chromatography analysis of the total methyl-glucoside produced after the addition of glucoamylase to the alpha-amylase reaction products. More alcoholysis was obtained from intact soluble starch than with maltodextrins or pre-hydrolyzed starch. The biotechnological implications of using starch as substrate for the production of alkyl-glucosides is analyzed in the context of these results. PMID:10386619

  10. Studies of alpha-induced astrophysical reactions at CRIB

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

    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, (α,p) reactions, and others were performed in recent years mainly for studying astrophysical reactions and exotic nuclear structure. Among them, the results on the 7Li+α resonance scatterings are presented.

  11. Indirect Measurements for (p,{alpha}) Reactions Involving Boron Isotopes

    SciTech Connect

    Lamia, L.; Spitaleri, C.; Romano, S.; Cherubini, S.; Crucilla, V.; Gulino, M.; La Cognata, M.; Pizzone, R. G.; Puglia, S. M. R.; Sergi, M. L.; Tudisco, S.; Tumino, A.; Carlin, N.; Szanto, M. G. del; Liguori Neto, R.; Moura, M. M. de; Munhoz, M. G.; Souza, F. A.; Suaide, A. A. P.; Szanto, E.

    2008-04-06

    Light elements lithium, beryllium and boron (LiBeB) were used in the last years as 'possible probe' for a deeper understanding of some extra-mixing phenomena occurring in young Main-Sequence stars. They are mainly destroyed by (p,{alpha}) reactions and cross section measurements for such channels are then needed. The Trojan Horse Method (THM) allows one to extract the astrophysical S(E)-factor without the experience of tunneling through the Coulomb barrier. In this work a resume of the recent results about the {sup 11}B(p,{alpha}{sub 0}){sup 8}Be and {sup 10}B(p,{alpha}){sup 7}Be reactions is shown.

  12. The astrophysical reaction rate for the {sup 18}F(p,{alpha}){sup 15}O reaction

    SciTech Connect

    Rehm, K.E.; Paul, M.; Roberts, A.D.

    1996-03-01

    Proton and alpha widths for a 3/2{sup +} ({ell}{sub p} = 0) state in {sup 19}Ne at E{sub x} = 7.1 MeV have been extracted using the results of recent measurements of the {sup 18}F(p,{alpha}){sup 15}O reaction. This {ell}{sub p} = 0 resonance dominates the astrophysical reaction rates at temperatures T{sub 9} > 0.5.

  13. Neutron, Proton and Alpha Emission Spectra of Nickel Isotopes for Proton Induced Reactions

    NASA Astrophysics Data System (ADS)

    Tel, E.; Kara, A.

    2012-06-01

    The fusion energy is attractive as an energy source because the fusion will not produce CO2 or SO2 and so fusion will not contribute to environmental problems, such as particulate pollution and excessive CO2 in the atmosphere. The fusion reaction does not produce radioactive nuclides and it is not self-sustaining, as is a fission reaction when a critical mass of fissionable material is assembled. Since the fusion reaction is easily and quickly quenched the primary sources of heat to drive such an accident are heat from radioactive decay and heat from chemical reactions. Both the magnitude and time dependence of the generation of heat from radioactive decay can be controlled by proper selection and design of materials. Nickel (Ni) is an important structural material in fusion (and also fission) reactor technologies and many other fields. So, the working out the reaction cross sections of the Ni isotopes is very important for selection of the fusion materials. In this study, 58Ni(p,xn), 58Ni(p,xp), 60Ni(p,xp), 60Ni(p,xα) and 62Ni(p,xp) reactions have been investigated using nuclear reaction models. And also the 58Ni(p,xn) reaction has been calculated through a method of offered by Tel et al. The calculated results are discussed and compared with the experimental data taken from EXFOR database.

  14. 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.

  15. 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).

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Synthesis of rutherfordium isotopes in the {sup 238}U({sup 26}Mg, xn){sup 264-x}Rf reaction and study of their decay properties

    SciTech Connect

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

    2008-03-15

    Isotopes of rutherfordium ({sup 258-261}Rf) were produced in irradiations of {sup 238}U targets with {sup 26}Mg beams. Excitation functions were measured for the 4n,5n, and 6n exit channels. Production of {sup 261}Rf in the 3n exit channel with a cross section of 28{sub -26}{sup +92} pb was observed. {alpha}-decay of {sup 258}Rf 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 {sup 259}Rf, the electron capture/total-decay branching ratio was measured to be 0.15{+-}0.04. The measured half-lives for {sup 258}Rf, {sup 259}Rf, and {sup 260}Rf were 14.7{sub -1.0}{sup +1.2} ms, 2.5{sub -0.3}{sup +0.4} s, and 22.2{sub -2.4}{sup +3.0} 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)

  1. Cross sections for the formation of {sup 195}Hg{sup m,g}, {sup 197}Hg{sup m,g}, and {sup 196}Au{sup m,g} in {alpha} and {sup 3}He-particle induced reactions on Pt: Effect of level density parameters on the calculated isomeric cross-section ratio

    SciTech Connect

    Sudar, S.; Qaim, S.M.

    2006-03-15

    Excitation functions were measured for the reactions {sup nat}Pt({sup 3}He,xn){sup 195}Hg{sup m,g},{sup nat}Pt({sup 3}He,xn){sup 197}Hg{sup m,g},{sup nat}Pt({sup 3}He,= x){sup 196}Au{sup m,g}, and {sup nat}Pt({alpha},xn){sup 197}Hg{sup m,g} over the energy range of 18-35 MeV for {sup 3}He particles and 17-26 MeV for {alpha} particles. The reactions {sup 197}Au(p,n){sup 197}Hg{sup m,g} were also investigated over the proton energy range of 6-20 MeV. The three projectiles were produced at the Juelich variable-energy compact cyclotron (CV 28). Use was made of the activation technique in combination with conventional high-resolution as well as low-energy HPGe-detector {gamma}-ray spectroscopy. For most of the reactions, the present measurements provide the first consistent sets of data. From the available experimental data, isomeric cross-section ratios were determined for the above-mentioned reactions. Nuclear model calculations using the code STAPRE, which employs the Hauser-Feshbach (statistical model) and exciton model (precompound effects) formalisms, were undertaken to describe the formation of both the isomeric and the ground states of the products. The calculations were compared with the results of the EMPIRE-II code. The excitation functions of the ({sup 3}He,xn) and ({alpha},xn) processes are described well by the theory. In the case of ({sup 3}He,pxn) reactions, however, considerable deviations were observed between the experiment and the theory, presumably due to strong contributions from direct interactions. A description of the isomeric cross-section ratio by the model was possible only with a very low value of {eta}, i.e., the {theta}{sub eff}/{theta}{sub rig} ratio. A mass dependence of {eta} is proposed.

  2. Measurement of Isomeric Yield Ratio of 143m,gSm from natSm(γ,xn) Reaction with End-Point Bremsstrahlung Energies of 40-60 MeV

    NASA Astrophysics Data System (ADS)

    Yang, S. C.; Kim, K.; Kim, G. N.; Kim, H. I.; Lee, Y. O.; Lee, M. W.; Pham, D. K.; Nguyen, V. D.; Shin, S. G.; Cho, M. H.

    2014-05-01

    The isomeric yield ratios (IR) of 143m,gSm from the natSm(γ, xn) reaction with the end-point bremsstrahlung energies of 40, 50 and 60 MeV were measured by the activation method and using the 100 MeV electron linac of the Pohang Accelerator Laboratory (PAL), Korea. A high-purity natSm foil in disc shape was used for the irradiation and the induced photo-peak activity of the γ-rays of 143m,gSm in the irradiated sample was measured with a HPGe detector. The experimental data were analyzed through the Gamma Vision program and IR was obtained using a decay equation. The present results are compared with the literature data at other energies. It was found that the IR of 143m,gSm increases sharply from 12 to 20 MeV due to the GDR effect and thereafter remains nearly constant or increases slowly with the end-point bremsstrahlung energy.

  3. 18F({alpha},p)21Ne Reaction: Neutron Source For r-Process In Supernovae

    SciTech Connect

    Lee, H.-Y.; Beard, M.; Couder, M.; Couture, A.; Goerres, J.; Lamm, L.; LeBlanc, P.; O'Brien, S.; Palumbo, A.; Stech, E.; Strandberg, E.; Tan, W.; Ugalde, C.; Wiescher, M.; Becker, H.-W.

    2006-03-13

    The reaction rate of 18F({alpha},p)21Ne has been studied using the inverse reaction 21Ne(p,{alpha})18F. This has been measured by the activation method in the energy range of the relevant Gamow window. Experimental results will be discussed and compared with the results of Hauser-Feshbach calculations and previous measurements.

  4. Model for alpha particle induced nuclear reactions: /sup 93/Nb(. cap alpha. ,x. cap alpha. ypzn) from 40--140 MeV

    SciTech Connect

    Gadioli, E.; Gadioli-Erba, E.; Hogan, J.J.; Jacak, B.V.

    1984-01-01

    A comprehensive model is introduced for alpha particle induced nuclear reactions. Five different mechanisms are examined and discussed. These include inelastic scattering of the incident alpha particle, nucleon pickup, binary fragmentation, dissolution of the alpha in the nuclear field, and preequilibrium processes initiated by alpha-nucleon collisions. A series of experiments was performed to measure the excitation functions of many nuclides produced from the irradiation of /sup 93/Nb by 40--140 MeV alpha particles. Together with alpha particle and proton spectra measured by other authors, these data form the basis of a test of the model introduced. A detailed analysis of the comparison between the calculated and experimental results, with particular emphasis on the interpretation of breakup processes, leads to the conclusion that breakup to four nucleons is preferred to the more commonly assumed binary fragmentation in that a much broader range of experimental data may be reproduced.

  5. Glauber model for {alpha}-nucleus total reaction cross section

    SciTech Connect

    Chauhan, Deeksha; Khan, Z. A.

    2009-11-15

    The Coulomb-modified Glauber model is employed to calculate the total reaction cross section ({sigma}{sub R}) for {alpha} particles from {sup 9}Be, {sup 12}C, {sup 16}O, {sup 28}Si, {sup 40}Ca, {sup 58,60}Ni, {sup 112,116,120,124}Sn, and {sup 208}Pb at 117.2, 163.9, and 192.4 MeV and from the lighter nuclei also at 69.6 MeV. Our main focus in this work is to assess the suitability of semiphenomenological parametrization of the NN amplitude (SPNN), used recently [Deeksha Chauhan and Z. A. Khan, Eur. Phys. J. A 41, 179 (2009)], in the analysis of {sigma}{sub R} at the energies under consideration. Using the realistic form factors for the colliding nuclei, it is found that the SPNN works reasonably well and we have quite a satisfactory account of the {sigma}{sub R} data in all the cases. Moreover, our analysis suggests that the SPNN could be taken as fairly stable to describe simultaneously the elastic angular distribution and the {sigma}{sub R} for a wide range of target nuclei in the relatively low-energy region.

  6. Analysis of {alpha}-induced reactions on {sup 151}Eu below the Coulomb barrier

    SciTech Connect

    Avrigeanu, V.; Avrigeanu, M.

    2011-01-15

    Novel measurements of ({alpha},{gamma}) and ({alpha},n) reaction cross sections on the target nucleus {sup 151}Eu, close to the reaction thresholds, support the choice of recently proposed parameters of the {alpha}-particle optical model potential below the Coulomb barrier. A better understanding of the {alpha}-particle optical potential at these energies leads to a statistical model analysis of additional partial cross sections that were measured but not considered within a former model analysis. On this basis we have tentatively assigned a modified J{sup {pi}}=9{sup -} spin and parity to the 22.7-h isomer in {sup 154}Tb.

  7. 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.

  8. Enhancement of hydroxyl radical generation in the Fenton reaction by alpha-hydroxy acid.

    PubMed

    Ali, M A; Konishi, T

    1998-09-01

    The effect of various organic acids on hydroxyl radical (.OH) generation in the Fenton reaction were examined by the ESR spin trapping technique, where 5,5-dimethyl-1-pyroline-N-nitroxide (DMPO) and alpha-phenyl-tert-butyl nitrone (PBN) were used as the spin trapping reagents. alpha-Hydroxy acids such as lactic acid, glycolic acid and 2-hydroxy isobutyric acid were found to markedly enhance .OH generation in the reaction. In contrast, beta-hydroxy acid, alpha-keto acid, esters of alpha-hydroxy acids, aldehydes and other straight chain organic acids had no such enhancing activity. alpha-Amino acids had also no enhancing effect. The results suggest that the alpha-hydroxy acid moiety is prerequisite for the enhancement of .OH generation in the Fenton reaction. Superoxide dismutase did not inhibit the enhancing effect of alpha-hydroxy acids whereas catalase completely inhibited the .OH generation. Thus, alpha-hydroxy acids directly enhanced the .OH generation via the Fenton reaction but not the Haber-Weiss reaction. Possible role of lactic acid manipulating .OH generation is discussed in relation to the ischemia-reperfusion cell damage. PMID:9784848

  9. The {sup 59}Co(n,{alpha}) reaction from threshold to 30 MeV

    SciTech Connect

    Lee, T.M.; Sterbenz, S.M.; Bateman, F.B.

    1994-06-01

    Neutron-induced reactions that result in alpha-particle emission have been investigated for the target nucleus {sup 59}Co over the neutron energy range from threshold to 30 MeV with the spallation neutron source at WNR/LAMPF. Double-differential cross sections were measured at alpha-particle emission angles of 30, 60, 90 and 135{degree}. Integrated cross sections agree well with activation data below 14 MeV where only the {sup 59}Co(n,{alpha}){sup 56}Mn reaction contributes to alpha-particle emission. At higher energies, the integrated alpha-particle emission cross section exceeds the activation data. The results will be interpreted in terms of statistical and pre-compound reaction mechanisms. The sensitivity to nuclear level density parameters will be discussed.

  10. Measurement of isomeric yield ratios of 197m,gPt and 190m2,g+m1Ir from the 198Pt(γ,n) and natPt(γ,xn1p) reactions induced by 55-, 60-, and 65-MeV bremsstrahlung

    NASA Astrophysics Data System (ADS)

    Kye, Yong-Uk; Shin, Sung-Gyun; Cho, Moo-Hyun; Kim, Kyung Sook; Namkung, Won; Kim, Guinyun; Kim, Kwangsoo; Kang, Yeong-Rok; Lee, Man-Woo; Yang, Sung-Chul; Nguyen, Van Do; Pham, Duc Khue; Kim, Tien Thanh; Naik, Haladhara

    2015-05-01

    We have measured the isomeric yield ratios of 197m,gPt from the 198Pt(γ,n) reaction and 190m2,g+m1Ir from the natPt(γ,xn1p) reaction, induced with the bremsstrahlung end-point energies of 55-, 60-, and 65-MeV. The measurements were carried out by the activation method in combination with the direct γ-spectrometry. The experiments were performed at the 100 MeV electron linac of the Pohang Accelerator Laboratory (PAL). The obtained results at 55-, 60- and 65-MeV for the 197m,gPt from the 198Pt(γ,n) reaction are 0.166 ± 0.012, 0.174 ± 0.011, and 0.175 ± 0.011, whereas for the 190m2,g+m1Ir from the natPt(γ,xn1p) reaction are 0.072 ± 0.006, 0.084 ± 0.006 and 0.087 ± 0.006, respectively. The present results are measured for the first time over the investigated energy range. The present data are compared with the similar literature data at lower energy to examine the role of excitation energy.

  11. Nucleon-nucleon charge symmetry breaking and the dd{yields}{alpha}{pi}{sup 0} reaction

    SciTech Connect

    Fonseca, A. C.; Machleidt, R.; Miller, G. A.

    2009-08-15

    We show that using parameters consistent with the charge symmetry violating difference between the strong nn and pp scattering lengths provides significant constraints on the calculated amplitude for the dd{yields}{alpha}{pi}{sup 0} reaction.

  12. Study of the Pygmy Dipole Resonance in {sup 124}Sn by means of the ({alpha},{alpha}'{gamma}) reaction

    SciTech Connect

    Endres, J.; Zilges, A.; Pietralla, N.; Savran, D.; Sonnabend, K.; Harakeh, M. N.; Stoica, V.; Woertche, H.; Butler, P.; Herzberg, R. D.; Scheck, M.; Kruecken, R.; Popescu, L.; Harissopulos, S.; Lagoyannis, A.

    2009-01-28

    In recent years {alpha}-{gamma} coincidence experiments at 136 MeV incident energy on {sup 48}Ca, {sup 140}Ce, {sup 138}Ba and {sup 124}Sn were performed at the KVI in Groningen to study the isospin character of electric dipole excitations below the particle threshold, frequently called Pygmy Dipole Resonance (PDR). An array of HPGe {gamma}-detectors has been used in coincidence with the Big-Bite Spectrometer (BBS) and a resolution of about 10 keV in the {gamma}-ray energy has been achieved. The results show that the excitation patterns of the PDR in the ({alpha},{alpha}') reaction seem to differ significantly from results obtained in Nuclear Resonance Fluorescence (NRF)({gamma},{gamma}') measurements. The PDR, which until now has been assigned to one excitation mode, splits up into two parts: One that is excited in ({alpha},{alpha}'{gamma}) and ({gamma},{gamma}') reactions (denoting a dominant isoscalar character), and one that is only excited in ({gamma},{gamma}')(denoting a dominant isovector character). This indicates that two different excitation mechanisms produce these low-lying E1 excitations [1], The preliminary results of the latest measurements on the N = 82 nucleus {sup 138}Ba and the Z = 50 nucleus {sup 124}Sn show that this break up into two parts is a common feature of the PDR in semi-magic nuclei.

  13. 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.

  14. 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.

  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. Trojan horse particle invariance studied with the {sup 6}Li(d,{alpha}){sup 4}He and {sup 7}Li(p,{alpha}){sup 4}He reactions

    SciTech Connect

    Pizzone, R. G.; Spitaleri, C.; Lamia, L.; Cherubini, S.; La Cognata, M.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Bertulani, C.; Mukhamedzhanov, A.; Blokhintsev, L.; Burjan, V.; Hons, Z.; Kroha, V.; Mrazek, J.; Piskor, S.; Kiss, G. G.; Li, C.; Tumino, A.

    2011-04-15

    The Trojan horse nucleus invariance for the binary reaction cross section extracted from the Trojan horse reaction was tested using the quasifree {sup 3}He({sup 6}Li,{alpha}{alpha})H and {sup 3}He({sup 7}Li,{alpha}{alpha}){sup 2}H reactions. The cross sections for the {sup 6}Li(d,{alpha}){sup 4}He and {sup 7}Li(p,{alpha}){sup 4}He binary processes were extracted in the framework of the plane wave approximation. They are compared with direct behaviors as well as with cross sections extracted from previous indirect investigations of the same binary reactions using deuteron as the Trojan horse nucleus instead of {sup 3}He. The very good agreement confirms the applicability of the plane wave approximation which suggests the independence of the binary indirect cross section on the chosen Trojan horse nucleus, at least for the investigated cases.

  17. Total reaction cross sections from elastic {alpha}-nucleus scattering angular distributions around the Coulomb barrier

    SciTech Connect

    Mohr, P.; Galaviz, D.; Fueloep, Zs.; Gyuerky, Gy.; Kiss, G. G.; Somorjai, E.

    2010-10-15

    The total reaction cross section {sigma}{sub reac} is a valuable measure for the prediction of {alpha}-induced reaction cross sections within the statistical model and for the comparison of scattering of tightly bound projectiles to weakly bound and exotic projectiles. Here we provide the total reaction cross sections {sigma}{sub reac} derived from our previously published angular distributions of elastic {alpha}-nucleus scattering on {sup 89}Y, {sup 92}Mo, {sup 112,124}Sn, and {sup 144}Sm at energies around the Coulomb barrier.

  18. 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.

  19. 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.

  20. Chimerogenesis in estimation of specificity and pathway directions for cytochrome p45017alpha catalyzed reactions.

    PubMed

    Gilep, A A; Estabrook, R W; Usanov, S A

    2004-04-01

    Cytochrome P45017alpha is a key enzyme in steroid hormone biosynthesis. It catalyzes the reaction of 17alpha-hydroxylation of progesterone (P4) and pregnenolone (P5) and the 17,20-lyase reaction resulting in side chain cleavage of C21 steroids to form C19 steroids. Depending on the activity of cytochrome P45017alpha, steroid hormone biosynthesis pathways are directed either for biosynthesis of mineralocorticoids and glucocorticoids or sex hormones. The formation of sex hormones starts from biosynthesis of androstenedione. Androstenedione formation is a result of two reactions: 17,20-lyase reaction of 17alpha-hydroxyprogesterone (Delta4-pathway) and 3beta-hydroxysteroid dehydrogenase/Delta4,Delta5-isomerase reaction using dehydroepiandrosterone as substrate (Delta5-pathway). In case of exclusive direction of the 17,20-lyase reaction either through the Delta4- or the Delta5-pathway, the formation of sex hormones depends more on specificity and activity of 3beta-hydroxysteroid-dehydrogenase/Delta4,Delta5-isomerase. Depending on species, the cytochromes P45017alpha can utilize as a substrate for 17,20-lyase activity Delta4-steroids, Delta5-steroids, or both types of steroids. To identify the structural elements of cytochrome P45017alpha responsible for substrate recognition, in the present work we used exchange of homologous fragments of cytochrome P45017alpha having different types of activities. We engineered more than 10 different types of chimeric cytochrome P45017alpha. Chimeric cytochromes P45017alpha have been expressed in E. coli and purified. The expression of chimeric cytochrome P45017alpha with the point of exchange between exons III and IV results in inability of the recombinant hemeprotein to properly bind heme. The determination of activity of chimeric cytochromes P45017alpha shows that the structural element responsible for switching activity between Delta4- or Delta5-pathway is located in the region of polypeptide chain coded by exons II-V of CYP17 gene

  1. Recoil range distributions of residues from. cap alpha. + /sup 59/Co reactions

    SciTech Connect

    Gadioli, E.; Gadioli Erba, E.; Parker, D.J.; Asher, J.

    1985-10-01

    The recoil range distributions of /sup 61/Cu, /sup 60/Cu, /sup 58/Co, /sup 57/Co, /sup 56/Co, /sup 54/Mn, and /sup 52/Mn residual nuclei produced in ..cap alpha.. particle bombardment of /sup 59/Co at 38, 50, 65, and 85 MeV have been measured and analyzed. Analysis of these measurements, as well as other recently published measurements of longitudinal linear momentum transfer to residue isobars at energies extending up to roughly-equal200 MeV, in the same reaction, shows that calculations based on the exciton model and a realistic description of the ..cap alpha..-nucleus interaction allow a quantitatively correct description of ..cap alpha..-induced reactions. Contrary to recent suggestions, data of this kind do not seem to indicate a change in the general character of the ..cap alpha..-nucleus interaction for incident energies below roughly-equal50 MeV/nucleon.

  2. Three-body effects in the /sup 7/Li (/ital d/,. cap alpha cap alpha. /ital n/) reaction

    SciTech Connect

    Arena, N.; Cavallaro, S.; Fazio, G.; Giardina, G.; Italiano, A.; Herman, M.; Bruno, M.; Cannata, F.; D'Agostino, M.

    1989-07-01

    Measurements of the differential cross sections for the/sup 7/Li(/ital d/,..cap alpha cap alpha..n) reaction have been performed at deuteron incident energy /ital E/(/ital d/)=6.8 MeV. The kinematical configurations were chosen so as to optimize the population of the /sup 5/He/sup **/ 3/2/sup +/ state with 16.76 MeV excitation energy. The parameters of this resonance are deduced from the experimental data; deviations from the standard values indicate the relevance of three-body effects and/or rescattering. Some phenomenological considerations give a qualitative explanation of the results obtained. In particular, as far as the width is concerned, we observe a broadening with respect to the standard value, which may be related to the presence of a shadow pole.

  3. 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.

  4. 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.

  5. Bifunctional mechanism of catalysis in reactions leading to formation of /alpha/-amino ketones

    SciTech Connect

    Popov, A.F.; Anikeev, A.V.

    1988-10-20

    The kinetics of the reaction of /alpha/-bromoacetophenone and benzyl bromide with aniline and pyridine in the presence of additions of acetic acid and phenol in benzene at 30/degree/C were investigated. The catalytic effects due to the activity of the uncombined forms of the catalyst, their dimers, and their 1:1 complexes with the amines were separated quantitatively. The change in the catalytic activity of the respective particles in the solutions with variation in the structure of the reagents is examined, and possible mechanisms for the catalytic reactions are discussed on this basis. It is concluded that there is a bifunctional mechanism of catalysis by acetic acid in the reaction of /alpha/-bromoacetophenone with aniline.

  6. 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. PMID:17677960

  7. Initial-state Coulomb interaction in the dd{yields}{alpha}{pi}{sup 0} reaction

    SciTech Connect

    Laehde, Timo A.; Miller, Gerald A.

    2007-05-15

    The effects of initial-state Coulomb interactions in the charge-symmetry-breaking reaction dd{yields}{alpha}{pi}{sup 0} are investigated within a previously published formalism. This is a leading order effect in which the Coulomb interaction between the two initial state protons leads to the breakup of the two deuterons into a continuum state that is well connected to the final {alpha}{pi}{sup 0} state by the strong emission of a pion. As a first step, we use a simplified set of d and {alpha} wave functions and a plane-wave approximation for the initial dd state. This Coulomb mechanism, by itself, yields cross sections that are much larger than the experimental ones, and which are comparable in size to the contributions from other mechanisms. Inclusion of this mechanism is therefore necessary in a realistic calculation.

  8. 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

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    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, (α, p) reactions, and other types of measurements (β-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 7Li+α/7Be+α resonant scatterings are presented.

  10. Improved information on the 7Li+p{yields}{alpha}+{alpha} reaction via the Trojan Horse Method applied to the 3He break-up

    SciTech Connect

    Tumino, A.; Spitaleri, C.; Sergi, M. L.; Cherubini, S.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Romano, S.; Tudisco, S.; Kroha, V.; Burjan, V.; Novac, J.; Vincour, J.; Fulop, S.; Somorjai, E.

    2006-04-26

    The astrophysically relevant 7Li+p{yields}{alpha}+{alpha} reaction was investigated via the THM by selecting the quasi-free contribution to the measured 3He+7Li{yields}{alpha}+{alpha}+d three-body process. This investigation is mainly aimed at testing the validity of the pole approximation in the THM against the bound structure of the Trojan-horse nucleus. The three-body experiment was performed at 33 MeV, corresponding to a 7Li-p relative energy ranging from 0.2 to 7 MeV. The quasi-free 7Li+p cross-section was compared with the free reaction cross-section as well as with indirect data from a previous THM experiment. The good agreement between data sets throughout the energy range investigated provided a very important validity test of the pole approximation for the THM.

  11. [4 + 2] Dimerization and Cycloaddition Reactions of alpha,beta-Unsaturated Selenoaldehydes and Selenoketones.

    PubMed

    Li, Guang Ming; Niu, Shuqiang; Segi, Masahito; Zingaro, Ralph A.; Yamamoto, Hiroaki; Watanabe, Kentaro; Nakajima, Tadashi; Hall, Michael B.

    1999-03-01

    The reactions of alpha,beta-unsaturated aldehydes and ketones with bis(dimethylaluminum) selenide, (Me(2)Al)(2)Se, yield the corresponding alpha,beta-unsaturated selenoaldehydes and selenoketones. They are too unstable to be isolated in the monomeric form, but they undergo regioselective [4 + 2] dimerization via a "head-to-head" oriented transition state to afford diselenin derivatives (trans and cis isomers). Theoretical calculations at the density functional theory level show that this selectivity occurs because the "head-to-head" dimerization is thermodynamically favored over the "head-to-tail" by about 14 kcal/mol. Both dimerization reactions have low energy barriers: 1.5 and 2.8 kcal/mol for the former and 0.9 and 1.3 kcal/mol for the latter. In the presence of norbornadiene, these compounds function as 4pi heterodienes (C=C-C=Se) to give the respective cycloadduct products. On the other hand, they act as 2pi dienophiles (C=Se) in the reactions with cyclopentadiene except for selenoacrolein which serves as a 4pi diene and only one C=C bond (2pi) in cyclopentadiene is involved in the reaction. Theoretical calculations have been carried out in order to better understand these observations. PMID:11674220

  12. Reaction kinetics in dehydrochlorination of. cap alpha. -isomer of hexachlorocyclohexane in the presence of a phase transfer catalyst

    SciTech Connect

    Sirovskii, F.S.; Chimishkyan, A.L.; Panova, M.V.; Treger, Y.A.; Velichko, S.M.

    1986-01-01

    This paper presents a kinetic study of the reaction of aqueous caustic dehydrochlorination of the alpha-isomer of hexachlorocyclohexane (alpha-HCCH) with catalysis by tetrabutyl-ammonium hydroxide. It has been shown that the process is described by a scheme of phase transfer catalysis.

  13. Study of the {sup 10}B(p,alpha){sup 7}Be Reaction through the Indirect Trojan Horse Method

    SciTech Connect

    Puglia, S. M. R.; Romano, S.; Lamia, L.; Spitaleri, C.; Cherubini, S.; Gulino, M.; La Cognata, M.; Pizzone, R. G.; Rapisarda, G. G.; Sergi, M. L.; Tudisco, S.; Del Santo, M. G.; Carlin, N.; Souza, F.; Szanto de Toledo, A.; Kroha, V.; Kubono, S.; Wakabayashi, Y.; Yamaguchi, H.; Li, C.

    2010-03-01

    The {sup 10}B(p,alpha){sup 7}Be reaction is the main responsible for {sup 10}B destruction in stellar interior. In such environments the process takes places mainly through a resonant state of the compound {sup 11}C nucleus. The {sup 10}B(p,alpha){sup 7}Be reaction has been studied by means of the Trojan Horse Method using the {sup 2}H({sup 10}B,alpha{sup 7}Be)n three-body reaction. The experiment was performed at the Laboratori Nazionali del Sud in Catania. The {sup 10}B(p,alpha){sup 7}Be reaction cross section has been extracted at low neutron momentum.

  14. 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.

  15. 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.

  16. 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.

  17. Synthetic approaches to borocarbonitrides, BC{sub x}N (x=1-2)

    SciTech Connect

    Kumar, Nitesh; Raidongia, Kalyan; Mishra, Abhishek K.; Waghmare, Umesh V.; Sundaresan, A.; Rao, C.N.R.

    2011-11-15

    In order to synthesize borocarbonitrides of the general formula BC{sub x}N where x varies between 1 and 2, we have carried out high-temperature gas phase reaction of BBr{sub 3} with a mixture of ethylene and ammonia. The composition of the product was close to BC{sub 1.6}N as shown by x-ray photon spectroscopy (XPS) and electron energy loss spectroscopy (EELS). The products were further characterized by infra-red, Raman and other spectroscopic techniques. The borocarbonitrides obtained from the gas phase reaction have low surface areas, in contrast to those of similar compositions prepared by the urea method. First principles calculations show that the most stable structures of the compositions BCN and BC{sub 2}N contain BN-rich and carbon-rich domains where BN{sub 3} and NB{sub 3} units are present. - Graphical abstract: Vapor phase synthesis of BC{sub x}N (x=1-2) by the reaction of BBr{sub 3}, ethylene and ammonia leads to the formation of pan-like structure. Highlights: > We have carried out vapor phase reaction of BBr{sub 3}, ethylene and ammonia to synthesize BC{sub x}N (x=1-2). > HRTEM and AFM show the formation of pan-like structures with the central region formed of single layer of BC{sub x}N. > Borocarbonitrides formed by vapor phase synthesis show limited adsorption properties as compared to the urea route. > First principles calculations show that the most stable structure of the compositions BCN and BC{sub 2}N contain BN-rich and carbon-rich domains where BN{sub 3} and NB{sub 3} units are present.

  18. 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.

  19. Lifetime and g-factor measurements of excited states using Coulomb excitation and alpha transfer reactions

    NASA Astrophysics Data System (ADS)

    Guevara, Z. E.; Torres, D. A.

    2016-07-01

    In this contribution the challenges in the use of a setup to simultaneously measure lifetimes and g-factor values will be presented. The simultaneous use of the transient field technique and the Doppler Shift Attenuation Method, to measure magnetic moments and lifetimes respectively, allows to obtain a complete characterization of the currents of nucleons and the deformation in excited states close to the ground state. The technique is at the moment limited to Coulomb excitation and alpha-transfer reactions, what opens an interesting perspective to consider this type of experiments with radioactive beams. The use of deep-inelastic and fusion-evaporation reactions will be discussed. An example of a setup that makes use of a beam of 106Cd to study excited states of 110Sn and the beam nuclei itself will be presented.

  20. Thin-target excitation functions, cross-sections and optimised thick-target yields for natMo(p,xn)(94g ,95m,95g,96(m + g))Tc nuclear reactions induced by protons from threshold up to 44 MeV. No Carrier Added radiochemical separation and quality control.

    PubMed

    Bonardi, Mauro; Birattari, Claudio; Groppi, Flavia; Sabbioni, Enrico

    2002-11-01

    This work describes the method adopted in our laboratories, to produce 94gTc, 95gTc, 95mTc and 96gTc radionuclides via proton-cyclotron irradiation on molybdenum targets of natural isotopic composition. A new set of experimental thin-target excitation functions and "effective" cross-sections for direct natMo(p,xn)(A)Tc [with A = 94, 95, 95, 96] nuclear reactions, with incident proton energy in the range from threshold up to 44 MeV is presented. Some definitions of the equations used and nuclear data traceability are reported. Thick-target yield values were calculated and optimised, by numerical fitting and integration of the measured excitation functions. These values allow optimisation of production yield of one radionuclide, minimising at the same time the yield of the others. Radiochemical separation on NCA technetium radionuclides from both molybdenum target and niobium, zirconium and yttrium radioactive by-products is reported. Quality control tests of the radiotracers were developed for the applications envisaged in environmental metallo-biochemical toxicology. PMID:12433035

  1. 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…

  2. Degradation mechanism of SiC/super {alpha}{sub 2} composite due to interfacial reaction

    SciTech Connect

    Ochiai, S.; Inoue, T.; Fujita, T.; Hojo, M.; Dudek, H.J.; Leucht, R.

    1999-10-01

    The degradation mechanism of SiC(SCS-6)/Super {alpha}{sub 2} composite due to the interfacial reaction was studied using single-fiber composite specimens fabricated by the sputtering method, heat treated at 1,273 K for various times, and tensile tested at room temperature. The main results are summarized as follows. (1) The tensile strength was reduced with progress of interfacial reaction by the formed defects on the fiber surface, while the formation of the reaction layers in the matrix side was not the direct reason for the reduction. (2) From the fracture mechanical analysis of the experimentally observed relation of the size and shape of the surface defects to the fiber strength, the fracture toughness of the fiber employed in the present work was estimated to be 2 to 4 MPa {radical}m. (3) The change in distribution of strength of the reacted fiber with progressing reaction was simulated successfully by combining the Monte Carlo method with the Weibull distribution function for the strength of the unreacted fiber, the Gumbell distribution function for the maximum effective size of the surface defect of the reacted fiber, and the fracture mechanics.

  3. 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.

  4. Astrophysical Reaction Rate for the Neutron-Generator Reaction {sup 13}C({alpha},n){sup 16}O in Asymptotic Giant Branch Stars

    SciTech Connect

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

    2006-11-10

    The reaction {sup 13}C({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{sup +} 6.356 MeV subthreshold resonance in {sup 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 ({sup 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.

  5. Systematics Studies of (n,{alpha}) reaction cross sections at 14.5 MeV neutrons energy

    SciTech Connect

    Belgaid, M.; Kadem, F.; Amokrane, A.

    2008-05-12

    A new semi-empirical formula for the calculation of the (n,{alpha}) cross section at 14.5 MeV neutron energy is obtained. It is based on the pre-equilibrium exciton and evaporation models and uses the Droplet model of Myers and Swiatecki to express the reaction energy Q(n,{alpha}). The systematics behavior of the different terms of the Droplet model involved in Q(n,{alpha}) was checked individually before choosing the pertinent terms and setting up the formula. Fitting this formula to the existing cross section data on 120 nuclei with 40{<=}A{<=}209, the adjustable parameters have been determined and the systematics of the (n,{alpha}) reaction have been studied. The predictions of this formula are compared with those of the existing formulae and with the experimental data. The formula with five parameters is found to give a better fit to the data than the previous comparable formulae.

  6. 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.

  7. 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.

  8. 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.

  9. Investigation of the role of break-up processes on the fusion of {sup 16}O induced reactions

    SciTech Connect

    Singh, Devendra P.; Unnati; Singh, Pushpendra P.; Yadav, Abhishek; Singh, B. P.; Prasad, R.; Sharma, Manoj Kumar; Golda, K. S.; Kumar, Rakesh; Sinha, A. K.

    2009-07-15

    An experiment was carried out to explore heavy ion incomplete fusion reaction dynamics, within the framework of the break-up fusion model, at energies near and above the Coulomb barrier. Excitation functions for several radionuclides produced via xn, pxn, and {alpha}xn channels were measured in the {sup 16}O+{sup 181}Ta system at energies of {approx_equal}76-100 MeV. The experimental excitation functions were compared with those calculated using the theoretical model code PACE4. It was observed that excitation functions of xn/pxn channels are in good agreement with theoretical predictions. However, a significant enhancement in the measured excitation functions of {alpha}-emitting channels was observed and attributed to the incomplete fusion processes. The incomplete fusion fraction (F{sub ICF}) that gives the relative importance of complete and incomplete fusion processes was found to increase with energy. The results are discussed in terms of {alpha}-cluster structure of the projectile on various fusion reactions.

  10. 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. PMID:24144496

  11. 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.

  12. [Boron in dental hard tissues studied by 11B(p,alpha)8Be nuclear reaction].

    PubMed

    Torrisi, L; Rapisarda, E; Cicero, G

    1989-09-01

    Boron's low atomic number and low concentration make its measurement in hard dental tissues difficult. Using nuclear reaction, the 11B(p,alpha)8Be*, enamel, dentine and radicular cement of 18 dental elements, ten healthy and eight decayed teeth, both permanent and deciduous were studied. The highest Boron concentrations were found in the two most superficial microns of the vestibular enamel in non-decayed incisors, particularly deciduous ones. Premolar and molar teeth showed lower Boron concentrations than frontal ones, decayed teeth revealed hardly any Boron. In confirmation of the prevailing exogenous contribution of this karyostatic trace element, on average, Boron concentrations were 2.5 times as high as dentine and 10 times as high as cement. PMID:2811808

  13. DEPENDENCE OF s-PROCESS NUCLEOSYNTHESIS IN MASSIVE STARS ON TRIPLE-ALPHA AND {sup 12}C({alpha}, {gamma}){sup 16}O REACTION RATE UNCERTAINTIES

    SciTech Connect

    Tur, Clarisse; Austin, Sam M.; Heger, Alexander E-mail: austin@nscl.msu.edu

    2009-09-10

    We have studied the sensitivity of s-process nucleosynthesis in massive stars to {+-}2{sigma} variations in the rates of the triple-{alpha} and {sup 12}C({alpha}, {gamma}){sup 16}O reactions. We simulated the evolution of massive stars from H burning through Fe-core collapse, followed by a supernova explosion. We found that the production factors of s-process nuclides between {sup 58}Fe and {sup 96}Zr change strongly with changes in the He burning reaction rates; using the Lodders solar abundances rather than those of Anders and Grevesse reduces s-process nucleosynthesis; later burning phases beyond core He burning and shell C burning have a significant effect on post-explosive production factors. We also discuss the implications of the uncertainties in the helium burning rates for evidence of a new primary neutron capture process (LEPP) in massive stars.

  14. Width measurement of the {sup 6}Li{sub 4.31} state by the {sup 7}Li({sup 3}He, {alpha}d){alpha} reaction

    SciTech Connect

    Arena, N.; Cavallaro, S.; D`Agostino, P.; D`Arrigo, A.; Fazio, G.; Giardina, G.; Sacchi, M.; Eremin, N.V.; Klochko, T.U.; Lombardi, M.

    1995-02-01

    The J{sup {pi}} = 2{sup +}, T = 0 {sup 6}Li state at E{sub x} = 4.31 MeV was populated by the {sup 7}Li({sup 3}He, {alpha}d){alpha} reaction performed at 4, 5, and 6 MeV {sup 3}He incident energies. The values obtained for {Gamma}({sup 6}Li{sub 4.31}) were compared with those deduced from the above reaction at E({sup 3}He) = 2.5 MeV. In contrast to the findings of other authors, no dependence of the above parameter on incident energy was observed. 23 refs., 1 fig., 2 tabs.

  15. The OXYGEN-15(ALPHA, GAMMA)NEON-19 Reaction Rate and the Rapid-Proton Capture Process

    NASA Astrophysics Data System (ADS)

    Magnus, Paul Vogt

    The energetics and the rates of the various nuclear reaction chains active in stars play a critical role in the stars' evolution and in the isotopic abundances resulting from this nucleosynthesis. One can therefore gain information about the structure and evolution of stars by examining these nuclear reaction chains and the resulting elemental and isotopic abundances. The abundances of a number of isotopes (e.g., 13C and ^ {15}N) point to the importance of explosive hydrogen burning which takes place on time scales which are short compared to the relevant beta-decay lifetimes. Explosive hydrogen burning is expected to occur at high temperatures (rm T>2times10^8K) in many astrophysical environments such as super-massive stars, accreting neutron stars, red giants with neutron star cores, novae, and supernovae. In these environments it is usually assumed that hydrogen burning occurs via the Hot-CNO (HCNO) cycle which is responsible for the observed abundance of 15N. At sufficiently high temperatures, however, the ^ {15}O(alpha,gamma)^{19 }Ne reaction can break the HCNO cycle and initiate a reaction chain called the rapid-proton capture (rp) process. The rp process transforms CNO nuclei to heavier nuclei (up to iron and nickel) by a chain of successive proton captures and beta decays. Hydrogen and helium-burning reactions, including the 15O( alpha,gamma)19Ne breakout reaction and the subsequent rp process, are thought to be the energy source for novae on the surface of accreting neutron stars and are possibly responsible for the unusual concentrations of heavy elements recently observed in novae. At astrophysically important temperatures, the 15O(alpha,gamma) 19Ne reaction rate is determined by the properties of several resonances just above the alpha-particle threshold in 19 Ne (Ecm<1.2 MeV). This thesis involves a series of experiments which determine the reaction rate for the 15O(alpha,gamma)^ {19}Ne reaction by measuring the properties of these resonances. The ^{15

  16. Reaction of HO/sub 2//O/sub 2//sup -/ with. cap alpha. -tocopherol in ethanolic solutions

    SciTech Connect

    Arudi, R.L.; Sutherland, M.W.; Bielski, B.H.J.

    1982-01-01

    The HO/sub 2/ perhydroxyl radical reacts with ..cap alpha..-tocopherol in 85% ethanol containing some H/sub 2/SO/sub 4/, EDTA, and O/sub 2/. The resulting transient has a spectral maximum near 390 ..mu... The final product is mostly ..cap alpha..-tocopherylquinone. Best reproducibility for reaction of O/sub 2//sup -/ with ..cap alpha..-tocopherol was obtained in a deoxygenated reaction mixture of 26 +- 3 ..mu..M O/sub 2//sup -/, 0.0565M ..cap alpha..-tocopherol, 5..mu..M EDTA, and 0.005 M KOH in 85% EtOH; the upper limit for the reaction was 6.0 +- 3.0 M/sup -1/ s/sup -1/, indicating that for all practical purposes O/sub 2//sup -/ does not react at all with ..cap alpha..-tocopherol. Preliminary experiments with Trolox, a vitamin E model compound, indicates that it too reacts with HO/sub 2/ but not with O/sub 2//sup -/. Membrane-bound tocopherols in vivo may fulfil a dual antioxidant role. (DLC)

  17. A novel alpha-arylation of ketones, aldehydes, and esters via a photoinduced SN1 reaction through 4-aminophenyl cations.

    PubMed

    Fraboni, Andrea; Fagnoni, Maurizio; Albini, Angelo

    2003-06-13

    4-Aminophenyl cations (expediently generated by photolysis of 4-chloroaniline and its N,N-dimethyl derivative by photolysis in MeCN) added to enamines and gave the corresponding alpha-(4-aminophenyl) ketones in satisfactory yields. The yields of the same ketones were increased when silyl enol ethers were used in the place of enamines. The alpha-arylation of silyl enol ethers of aldehydes occurred with lower yields and only with the N,N-dimethyl derivative. The procedure was successful with ketene silyl acetals giving in a single step a good yield of alpha-(4-aminophenyl)propionic(acetic) esters, known intermediates for the preparation of analgesic compounds. The reaction of the aryl cation with Danishefsky's diene gave the arylated beta-methoxy enone. The method is complementary to the recently developed palladium-catalyzed alpha-arylation and occurs under neutral conditions. PMID:12790595

  18. 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.

  19. Characterization of a slow folding reaction for the alpha subunit of tryptophan synthase.

    PubMed

    Hurle, M R; Michelotti, G A; Crisanti, M M; Matthews, C R

    1987-01-01

    The equilibria and kinetics of urea-induced unfolding and refolding of the alpha subunit of tryptophan synthase of E. coli have been examined for their dependences on viscosity, pH, and temperature in order to investigate the properties of one of the rate-limiting steps, domain association. A viscosity enhancer, 0.58 M sucrose, was found to slow unfolding and accelerate refolding. This apparently anomalous result was shown to be due to the stabilizing effect of sucrose on the folding reaction. After accounting for this stabilization effect by using linear free-energy plots, the unfolding and refolding kinetics were found to have a viscosity dependence. A decrease in pH was found to stabilize the domain association reaction by increasing the refolding rate and decreasing the unfolding rate. This effect was accounted for by protonation of a single residue with a pK value of 8.8 in the native state and 7.1 in the intermediate, in which the two domains are not yet associated. The activation energy of unfolding is 4.8 kcal/mol, close to the diffusion limit. The negative activation entropy of unfolding, -47 cal/deg-mol, which controls this reaction, may result from ordering of solvent about the newly exposed domain interface of the transition state. These results may provide information on the types of noncovalent interactions involved in domain association and improve the ability to interpret the folding of mutants with single amino-acid substitutions at the interface. PMID:3328859

  20. 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.

  1. 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.

  2. /sup 12/C(/sup 6/Li,d)/sup 16/O. -->. cap alpha. +/sup 12/C reaction mechanism by means of angular correlation measurements

    SciTech Connect

    Cunsolo, A.; Foti, A.; Imme, G.; Pappalardo, G.; Raciti, G.; Saunier, N.

    1980-06-01

    The particle-particle angular correlation method is applied to the reaction /sup 12/C(/sup 6/Li,d)/sup 16/O ..-->.. ..cap alpha..+/sup 12/C. Deuterons were detected at theta/sup lab//sub d/=10/sup 0/. Information on the reaction mechanism is obtained by analyzing the shape and the angular shift of the experimental data. A dominant direct transfer mechanism is found for the primary reaction. The ratios GAMMA..cap alpha../sub 0//GAMMA and the ..cap alpha..-reduced widths ..gamma cap alpha../sub 0/ are deduced.

  3. Excitation energy deposition in {sup 209}Bi({alpha},{alpha}{sup {prime}}) reactions at 240 MeV

    SciTech Connect

    Fabris, D.; Lunardon, M.; Nebbia, G.; Viesti, G.; Fioretto, E.; Napoli, D.R.; Prete, G.; Natowitz, J.B.; Wada, R.; Gonthier, P.; Majka, Z.; Alfarro, R.; Zhao, Y.; Mdeiwayeh, N.; Ho, T.

    1998-08-01

    The energy deposition associated with inelastic {alpha} particle scattering on {sup 209}Bi at 240 MeV has been determined using the TAMU neutron ball. A comparison of the reconstructed average excitation energies with the beam energy losses demonstrates that only part of the missing beam energy is usually deposited as thermal excitation in the target nucleus. Requiring an additional coincidence with a light charged particle or fission fragment leads to selection of a significant higher average excitation energy. {copyright} {ital 1998} {ital The American Physical Society}

  4. 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.

  5. Measurement of excitation functions in alpha-induced reactions on yttrium

    NASA Astrophysics Data System (ADS)

    Shahid, Muhammad; Kim, Kwangsoo; Naik, Haladhara; Zaman, Muhammad; Kim, Guinyun; Yang, Sung-Chul; Song, Tae-Young

    2015-01-01

    The excitation functions of 89g,m,90,91m,92mNb,88,89Zr, and 87g,m,88,90m,91mY from alpha-induced reactions on 89Y were measured from their respective threshold to 45 MeV by using a stacked-foil activation technique at the MC-50 cyclotron of the Korean Institute of Radiological and Medical Sciences. The results were compared with the earlier reported data as well as with the theoretical values obtained from the TENDL-2013 library based on the TALYS1.6 code. Our measurements in the energy region from the threshold energy to 45 MeV are in general good agreement with the other experimental data and calculated results. The integral yields for thick target of the produced radionuclides were also deduced from their measured cross sections and the stopping power of 89Y. The measured excitation functions find importance in various practical applications including nuclear medicine and improvement of nuclear model calculations.

  6. Investigation of activation cross-sections of alpha-induced nuclear reactions on natural cadmium

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    We measured production cross-sections of Sn, In, and Cd radionuclides from alpha-induced reactions on natCd from their respective threshold to 45 MeV by using a stacked-foil activation technique at the MC-50 cyclotron of the Korea Institute of Radiological and Medical Sciences. The results were compared with the earlier measurements as well as with the theoretical values obtained from the TENDL-2012 library based on the TALYS 1.4 code. Our measurements for the 110,113g,117mSn, 108m,108g,109g,110m,110g,111g,113m,114m,115m,116m,117m,117gIn, and 111m,115gCd radionuclides in the energy region from the threshold energy to 45 MeV are in general good agreement with the other experimental data and calculated results. The integral yields for thick target were also deduced using the measured cross-sections and the stopping power of natural cadmium target and found in agreement with the directly measured yields available in the literature. The measured cross-sections find importance in various practical applications including nuclear medicine and improvement of nuclear model calculations.

  7. 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.

  8. Pole approximation validation in the study of the {sup 6}Li(d,{alpha}){sup 4}He reaction

    SciTech Connect

    Pizzone, R. G.; Kiss, G. G.; Spitaleri, C.; Lamia, L.; Cherubini, S.; La Cognata, M.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Burjan, V.; Hons, Z.; Kroha, V.; Mrazek, J.; Piskor, S.; Li, C.; Tumino, A.

    2010-11-24

    The Trojan Horse Method (THM) was applied to the {sup 3}He+{sup 6}Li interaction in order to investigate the quasi-free {sup 6}Li(d,{alpha}){sup 4}He reaction. The experiment was performed at 17 MeV at the Cyclotron Institute of the Czech Academy of Science. The extracted {sup 6}Li(d,{alpha}){sup 4}He quasi-free cross-section was compared with the behavior of direct data. A good agreement between data sets shows up throughout the energy range investigated, providing a very important validity test of the pole approximation for the THM above the Coulomb barrier.

  9. 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

  10. An analysis of 25Al energy levels observed in the 28Si(p,alpha)25Al reaction

    SciTech Connect

    Pittman, S. T.; Bardayan, Daniel W; Blackmon, Jeff C; Kozub, R. L.; Smith, Michael Scott

    2009-01-01

    The level structure of {sup 25}Al has been studied at the ORNL Holifield Radioactive Ion Beam Facility (HRIBF) by measuring the angular and energy distributions of alpha particles from the {sup 28}Si(p,{alpha}){sup 25}Al reaction. Proton beams ({approx}10 nA) at laboratory energies of 40- and 42-MeV were generated by the 25 MV tandem accelerator and bombarded a natural silicon target (50 {micro}g/cm{sup 2}). Alpha particles were detected and identified in the Silicon Detector Array (SIDAR) in the 'telescope' configuration [1]. Eighteen levels have been observed and spins for several have been constrained through a distorted-wave Born approximation (DWBA) analysis of the angular distributions.

  11. Contribution of endothelial selectins and alpha 4 integrins to eosinophil trafficking in allergic and nonallergic inflammatory reactions in skin.

    PubMed

    Teixeira, M M; Hellewell, P G

    1998-09-01

    The role of endothelial selectins in mediating eosinophil recruitment was assessed using the trafficking of 111In-labeled blood eosinophils in mouse skin. An intradermal injection of chemoattractants (leukotriene B4, macrophage inflammatory protein-l alpha, and eotaxin) resulted in a rapid accumulation of 111In eosinophils that was reduced 49 to 91% by anti-P-selectin mAb. An anti-E-selectin mAb was ineffective, although a combined E- and P-selectin blockade resulted in >95% inhibition of all responses. The accumulation of a pulse of 111In eosinophils at sites of active cutaneous anaphylaxis (ACA) at 4 to 8 h and at 20 to 24 h after Ag challenge was completely dependent upon E- and P-selectin in combination, but not in isolation. In contrast, at 20 to 24 h after Ag challenge in a delayed-type hypersensitivity (DTH) reaction in skin, 111In eosinophil accumulation was largely independent of endothelial selectins, even when L-selectin was also blocked. An anti-alpha 4 integrin mAb significantly reduced 111In eosinophil trafficking in both allergic reactions but was slightly more effective in the DTH reaction compared with the ACA reaction. These results show that P-selectin and to a lesser extent E-selectin mediate eosinophil recruitment in skin in acute inflammatory reactions. In allergic, late-onset inflammatory reactions, neither P- nor E-selectin alone are sufficient to mediate eosinophil accumulation; when combined, they are essential for trafficking in ACA but are less important in the DTH reaction. Whether alpha 4 integrin-based strategies will be more effective than selectin-based strategies at inhibiting eosinophil recruitment in human disease remains to be determined. PMID:9725251

  12. Review of Experimental Data on Alpha-Induced Reactions on Some Nuclei (Mg-24, Si-28, S-32, Ar-36, Ca-40) in Terms of Astrophysical Applications

    SciTech Connect

    Dunaeva, S.A.; McLane, V.; Savin, M.; Taova, S.

    2005-05-24

    The present report gives a detailed analysis of experimental works and a review of alpha-induced reaction cross-section data of five alpha-alpha nuclei, Mg-24, Si-28, S-32, Ar-36 and Ca-40, for incident alpha energy up to 20 MeV. Alpha-induced reactions play an important role in the helium burning stage of stars, novae, and supernovae. These reactions are basic to the CNO and Al-Mg cycles, and also to the production of neutrons producing S and R processes occurring in stars. Thus, the availability of cross-section data for these reactions is a prime need for the study of nuclear interactions taking place in stars.These data have been compiled as part of an international collaboration, funded in part by the Civilian Research and Development Foundation, and are available in the EXFOR databases.

  13. Microanalytical techniques for boron analysis using the 10B(n,alpha)7Li reaction.

    PubMed

    Fairchild, R G; Gabel, D; Laster, B H; Greenberg, D; Kiszenick, W; Micca, P L

    1986-01-01

    In order to predict the efficacy of boronated compounds for neutron capture therapy (NCT), it is mandatory that the boron concentration in tissues be known. Various techniques for measurement of trace amounts of boron (1-100 ppm) are available, including chemical and physical procedures. Experience has shown that, with the polyhedral boranes and carboranes in particular, the usual colorimetric and spark emission spectroscopic methods are not reliable. Although these compounds may be traced with additional radiolabels, direct physical detection of boron by nondestructive methods is clearly preferable. Boron analysis via detection of the prompt-gamma ray from the 10B(n, alpha)7Li reaction has been shown to be a reliable technique. Two prompt-gamma facilities developed at Brookhaven National Laboratory are described. One, at the 60-MW high flux beam reactor, uses sophisticated beam extraction techniques to enhance thermal neutron intensity and reduce fast neutron and gamma contamination. The other was constructed at Brookhaven's 5-MW medical research reactor and uses conventional shielding and electronics to provide an "on-line" boron analysis facility adjacent to beams designed for NCT, thus satisfying one of the requisites for clinical application of this procedure. Technical restrictions attendant upon the synthesis and testing of boronated biomolecules often require the measurement of trace amounts of boron in extremely small (mg) samples. A track-etching technique capable of detecting ng amounts of boron in mg liquid or cell samples is described. Thus it is possible to measure the boron content in small amounts (mg samples) of antibodies, or boron uptake in cells grown in tissue culture. PMID:3951409

  14. Differential cross section measurements for the 6Li(n,t)alpha reaction in the few MeV region

    SciTech Connect

    Devlin, Matthew J; Taddeucci, Terence N; Hale, Gerald M; Haight, Robert C; O' Donnell, Johhn M

    2008-01-01

    New measured differential cross sections of tritons and alpha particles following the {sup 6}Li(n,t){alpha} reaction are reported for incident neutron energies between 0.2 and approximately 20 MeV. The neutrons were produced by spallation at the WNR facility at the Los Alamos Neutron Science CEnter (LANSCE), with the incident neutron energy determined by the time-of-flight method. Four E-{Delta}E telescopes were used at eight laboratory angles. These data have been incorporated into a prior R-matrix fit for the compound {sup 7}Li system, and result in an (n,t) reaction cross section that is 4% to 10% higher than previous evaluations in the 1-3 MeV incident neutron energy region.

  15. Trojan Horse Method and RIBs: The {sup 18}F(p,{alpha}){sup 15}O reaction at astrophysical energies

    SciTech Connect

    Cherubini, S.; Gulino, M.; Rapisarda, G. G.; Spitaleri, C.; La Cognata, M.; Lamia, L.; Kubono, S.; Yamaguchi, H.; Hayakawa, S.; Wakabayashi, Y.; Iwasa, N.; Kato, S.; Komatsubara, H.; Teranishi, T.; Coc, A.; De Sereville, N.; Hammache, F.

    2012-11-12

    The abundance of {sup 18}F in Nova explosions is an important issue for the understanding of this astrophysical phenomenon. For this reason it is necessary to study the nuclear reactions that produce or destroy this isotope in novae. Among these latter processes, the {sup 18}F(p,{alpha}){sup 15}O is one of the main {sup 18}F destruction channels. We report here on the preliminary results of the first experiment that applies the Trojan Horse Method to a Radioactive Ion Beam induced reaction. The experiment was performed using the CRIB apparatus of the Center for Nuclear Study of The Tokyo University.

  16. Triethylaluminum- or triethylborane-induced free radical reaction of alkyl iodides and alpha,beta-unsaturated compounds.

    PubMed

    Liu, Jing-Yuan; Jang, Yoeng-Jiunn; Lin, Wen-Wei; Liu, Ju-Tsung; Yao, Ching-Fa

    2003-05-16

    A series of alpha,beta-unsaturated compounds, 1a-c, 9, 13, and 17, were used as reactants in free radical conjugate addition reactions with different radicals generated from alkyl iodides such as 3, 4, or 5 in the presence of triethylborane-oxygen in air or via the use of triethylaluminum-benzoyl peroxide as a free radical initiator. When the reactions were carried out using triethylborane-air, the products, in most cases, were clean and were easily purified. However, higher yields of the 1,4-adducts and less side reactions occurred when less reactive substrates were used as Michael acceptors in reactions with triethylaluminum-benzoyl peroxide and alkyl iodide under similar conditions. A mechanism for this is proposed in Scheme 1. PMID:12737587

  17. Study of {sup 17}O(p,{alpha}){sup 14}N reaction via the Trojan Horse Method for application to {sup 17}O nucleosynthesis

    SciTech Connect

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

    2008-05-21

    Because of the still present uncertainties on its rate, the {sup 17}O(p,{alpha}){sup 14}N is one of the most important reaction to be studied in order to get more information about the fate of {sup 17}O in different astrophysical scenarios. The preliminary study of the three-body reaction {sup 2}H({sup 17}O,{alpha}{sup 14}N)n is presented here as a first stage of the indirect study of this important {sup 17}O(p,{alpha}){sup 14}N reaction through the Trojan Horse Method (THM)

  18. 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.

  19. Reexamination of the astrophysical S factor for the {alpha}+d{yields}{sup 6}Li+{gamma} reaction

    SciTech Connect

    Mukhamedzhanov, A. M.; Blokhintsev, L. D.; Irgaziev, B. F.

    2011-05-15

    Recently, a new measurement of the {sup 6}Li (150 A MeV)dissociation in the field of {sup 208}Pb has been reported [Hammache et al., Phys. Rev. C 82, 065803 (2010)] to study the radiative capture {alpha}+d{yields}{sup 6}Li+{gamma} process. However, the dominance of the nuclear breakup over the Coulomb one prevented the information about the {alpha}+d{yields}{sup 6}Li+{gamma} process from being obtained from the breakup data. The astrophysical S{sub 24}(E) factor has been calculated within the {alpha}-d two-body potential model with potentials determined from the fits to the {alpha}-d elastic scattering phase shifts. However, the scattering phase shift, according to the theorem of the inverse scattering problem, does not provide a unique {alpha}-d bound-state potential, which is the most crucial input when calculating the S{sub 24}(E) astrophysical factor at astrophysical energies. In this work, we emphasize the important role of the asymptotic normalization coefficient (ANC) for {sup 6}Li{yields}{alpha}+d, which controls the overall normalization of the peripheral {alpha}+d{yields}{sup 6}Li+{gamma} process and is determined by the adopted {alpha}-d bound-state potential. Since the potential determined from the elastic scattering data fit is not unique, the same is true for the ANC generated by the adopted potential. However, a unique ANC can be found directly from the elastic scattering phase shift, without invoking intermediate potential, by extrapolation the scattering phase shift to the bound-state pole [Blokhintsev et al., Phys. Rev. C 48, 2390 (1993)]. We demonstrate that the ANC previously determined from the {alpha}-d elastic scattering s-wave phase shift [Blokhintsev et al., Phys. Rev. C 48, 2390 (1993)], confirmed by ab initio calculations, gives S{sub 24}(E), which at low energies is about 38% less than the other one reported [Hammache et al., Phys. Rev. C 82, 065803 (2010)]. We recalculate also the reaction rates, which are lower than those obtained in

  20. 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.

  1. Stopped-flow kinetic studies of the reaction of barley alpha-amylase/subtilisin inhibitor and the high pI barley alpha-amylase.

    PubMed

    Sidenius, U; Olsen, K; Svensson, B; Christensen, U

    1995-03-20

    The interaction of alpha-amylase/subtilisin inhibitor (BASI) from barley seeds and the high pI barley alpha-amylase (AMY2) de novo synthesized during seed germination, has been studied at pH 8.0, 25 degrees C, using stopped-flow fluorescence spectroscopy, equilibrium fluorescence titration and kinetic analysis of the displacement of BASI from the BASI-AMY2 complex by the substrate blue starch. The results are in accordance with a two-step reaction model: [formula: see text] The resulting values of the kinetic parameters were: k2/K1 = (1.0 +/- 0.2) x 10(6) M-1.s-1, K1 = 0.4 +/- 0.21 mM, k2 = 320 +/- 150 s-1, k-2 = (7.2 +/- 0.6) x 10(-5)s-1, and the overall dissociation constant Kd = (0.7 +/- 0.1) x 10(-10) M. BASI thus is best characterized as a fast reacting, tight-binding inhibitor of AMY2. PMID:7698332

  2. 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.

  3. Free radical reactions might contribute to severe alpha amanitin hepatotoxicity--a hypothesis.

    PubMed

    Zheleva, Antoaneta; Tolekova, Anna; Zhelev, Momchil; Uzunova, Veselina; Platikanova, Magdalena; Gadzheva, Vesselina

    2007-01-01

    Alpha amanitin is a powerful natural hepatotoxin that belongs to the amatoxins isolated from deadly poisonous Amanita phalloides mushroom. The basic molecular mechanism of their toxicity was attributed to inhibition of RNA polymerase II of the eukaryotic cells. At present, the most effective clinical antidote to acute Amanita phalloides mushroom poisoning is silybin, an antioxidant possessing free radical scavenger activity and inhibiting lipid peroxidation, stabilizing membrane structure and protecting enzymes under conditions of oxidative stress. Bearing in mind the biological mechanism of silybin action and the fact that for different amatoxins (alpha, beta, and est. amanitins) does not established straight correlation between their in vivo LD50 and inhibitory constants (Ki) toward RNA polymerase III in vitro determined we supposed some additional toxic effects of these toxins might contribute to their severe hepatotoxicity. Our formerly in vitro experiments demonstrated that alpha amanitin could act either as an antioxidant or as a prooxidant depending on the treatment conditions and toxin concentration. By UV-visible spectroscopy we also shown that alpha amanitin was sensitive to oxidation by a system of lactoperoxidase/H(2)O(2) and assumed formation of free radical toxin intermediates. Having in mind some exogenic compounds including natural toxins can induce increased production of reactive oxygen species (ROS) we suggested similar generation of ROS provoked by alpha amanitin. Our recently in vitro studies have demonstrated that the alpha amanitin could increase superoxide dismutase (SOD) activity and inhibit catalase (CAT) activity to a considerable degree after together incubation of the toxin with any of enzymes. We have also shown that in vitro increased SOD activity was due to superoxide anion radical scavenging activity (SSA) of the toxin. This therefore informed the decision to study the in vivo effect of alpha amanitin on SOD and CAT activity and the

  4. 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. PMID:17705431

  5. 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.

  6. Particle Leaking, Cross-Section Ratio 10B(n,{alpha})/238U(n,fission), and Excitation Function of the Reaction 10B(n,{alpha})7Li at MeV Energies

    SciTech Connect

    Giorginis, Georgios; Khryachkov, Vitali

    2005-05-24

    The 10B(n,{alpha})7Li reaction was studied in the energy range between 1.5 MeV and 5.6 MeV at the 7-MV Van de Graaff accelerator of IRMM by using a gridded ionisation chamber, signal digitisation, and an intrinsic 238U neutron monitor. The aim was to obtain accurate data for the IAEA Coordinated Research Project (CRP) on the improvement of standard cross sections for light elements. The effect of particle leaking was discovered and its implications investigated. The determination of the cross section {sigma}({alpha}0+{alpha}1) strongly benefits from it but measurements of angular distributions, individual cross sections {sigma}({alpha}0) and {sigma}({alpha}1), and the branching ratio {alpha}0/{alpha}1 are negatively affected. The correct number of reaction events was obtained by identification of unknown particle signatures in the energy spectra as 10B(n,{alpha})7Li events in the form of quasi 7Li+{alpha} particles created by particle leaking. The cross-section ratio 10B(n,{alpha})7Li/238U(n,fission) was measured and the excitation function of 10B(n,{alpha})7Li determined by simultaneously detecting the charged particles from the boron disintegration in the forward hemisphere and the 238U fission fragments in the backward hemisphere. The IRMM cross sections are compared to experimental data of other groups and to predictions of the ENDF/B-VI.8, JENDL-3.3, and JEF-2.2 evaluations.

  7. 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.

  8. Calculation of excitation functions of proton, alpha and deuteron induced reactions for production of medical radioisotopes 122-125I

    NASA Astrophysics Data System (ADS)

    Artun, Ozan; Aytekin, Hüseyin

    2015-02-01

    In this work, the excitation functions for production of medical radioisotopes 122-125I with proton, alpha, and deuteron induced reactions were calculated by two different level density models. For the nuclear model calculations, the Talys 1.6 code were used, which is the latest version of Talys code series. Calculations of excitation functions for production of the 122-125I isotopes were carried out by using the generalized superfluid model (GSM) and Fermi-gas model (FGM). The results have shown that generalized superfluid model is more successful than Fermi-gas model in explaining the experimental results.

  9. Production and separation of {sup 55}Co via the {sup 58}Ni(p,{alpha}){sup 55}Co reaction

    SciTech Connect

    Mastren, T.; Sultan, D.; Lapi, S. E.

    2012-12-19

    {sup 55}Co is a positron emitting isotope that is of interest to the nuclear medicine imaging community. {sup 55}Co was produced by the {sup 58}Ni(p,{alpha}){sup 55}Co reaction and purified by chromatography. Our method has produced {sup 55}Co in millicurie quantities with a final recovery of 78% and an effective specific activity of 28{mu}Ci/{mu}mol. The only radioactive impurity recovered with {sup 55}Co is {sup 57}Co(271.8d) and is at a concentration of {approx}0.182% that of {sup 55}Co.

  10. {sup 117}In and {sup 118}Sn Homologous State Identification via the {sup 120}Sn(p-vector,alpha){sup 117}In and {sup 121}Sb(p-vector,alpha){sup 118}Sn Reactions

    SciTech Connect

    Zetta, L.; Guazzoni, P.; Cavallaro, M.; Faestermann, T.; Graw, G.; Hertenberger, R.; Wirth, H.-F.; Jaskola, M.

    2009-08-04

    To investigate the spectator role of the 1g{sub 5/2} unpaired proton outside the Z = 50 closed shell, the {sup 120}Sn(p-vector,alpha){sup 117}In and {sup 121}Sb(p-vector,alpha){sup 118}Sn reactions have been measured in high resolution experiments at 23 MeV incident proton energy of the Munich MP Tandem accelerator, using the Stern-Gerlach type polarized hydrogen ion source and the Q3D magnetic spectrograph.

  11. Direct measurement of the {sup 18}F(p,{alpha}){sup 15}O reaction at nova temperatures

    SciTech Connect

    Beer, C. E.; Laird, A. M.; Bentley, M. A.; Diget, C. A.; Fox, S. P.; Fulton, B. R.; Murphy, A. St. J.; Davinson, T.; Salter, P.; Buchman, L.; Davids, B.; Hager, U.; Howell, D.; Martin, L.; Ruiz, C.; Ruprecht, G.; Vockenhuber, C.; Walden, P.

    2011-04-15

    The {sup 18}F(p,{alpha}){sup 15}O reaction rate is crucial for understanding the final abundance of {sup 18}F predicted by nova models. The {gamma}-ray emission in the first few hours after a nova outburst is expected to be dominated by 511 keV annihilation photons from the decay of {sup 18}F, and so understanding its production can provide important constraints on the conditions during the outburst when compared with observations. Results are presented from the lowest-energy direct measurement to date, performed at the Isotope Separator and Accelerator radioactive beam facility at the TRIUMF laboratory, Canada. Cross section measurements at center-of-mass energies of 250, 330, 453, and 673 keV are obtained and the results compared to previous data and R-matrix calculations. The implications for the overall reaction rate in the context of nova explosions have been discussed.

  12. On the reaction pathways and determination of transition-state structures for retaining alpha-galactosyltransferases.

    PubMed

    André, Isabelle; Tvaroska, Igor; Carver, Jeremy P

    2003-04-22

    The catalytic mechanism of retaining glycosyltransferases is not yet completely understood, but one possible mechanism, by analogy with retaining glycosidases, is a double-displacement mechanism via a covalent glycosyl-enzyme intermediate (CGE). We have investigated various reaction pathways for this mechanism using non-empirical quantum mechanical methods. Because a double-displacement mechanism presumes a reaction happening in two steps, we have used predefined reaction coordinates to calculate the potential energy surface describing each step of the mechanism. By investigating several potential candidates to act as a catalytic base, this study attempts to shed some light on the unclear mechanism of the second step of the reaction. All intermediates and transition states on the reaction pathways were characterized using basis sets up to the DFT/B3LYP/6-311++G**//DFT/B3LYP/6-31G* level. Reaction pathways and structural changes were compared with the results previously obtained for inverting glycosyltransferases. The outcome of this study indicates, that among the reaction models investigated, the energetically favorable one is also the most plausible given the existing experimental data. This model requires the presence of only one catalytic acid in the active site with the UDP functioning as a general base in the second step of the reaction. This mechanism is in agreement with both kinetic data in the literature and the description of X-ray structures of retaining glycosyltransferases solved up to today. PMID:12681911

  13. Cross-section measurement of the 18F(alpha,p)21Ne reaction and possible implication for neutron production in explosive helium burning

    SciTech Connect

    Couture, Aaron Joseph; Lee, Hye Young; Couder, Manoel; Falahat, Sascha; Gorres, Joachim; Lamm, Larry O; Le Blanc, P J; O' Brien, Shawn P; Palumbo, Annalia; Stech, Edward J; Strandberg, Elizabeth; Tan, Wanpeng; Ugalde, Claudio; Wiescher, Michael C. F.

    2009-01-01

    At the high temperature and density conditions of hot or explosive helium burning, the {sup 18}F({alpha},p){sup 21}Ne reaction may compete successfully wilh the {sup 18}F({beta}{sup +}{nu}) decay. This suggesls {sup 21}Ne({alpha},n) as an alternative neutron source in Ihe r-process. We have determined the total cross section of the {sup 18}F({alpha},p){sup 21}Ne reaction by studying the time-reverse reaction {sup 21}Ne(p,{alpha}){sup 18}F. Using the activation technique, the total reaction yield was measured in the proton beam energy range of 2.3-4.0 MeV, which corresponds to energies of 0.5-2.1 MeV in the {sup 18}F + {alpha} system. The resulting yield curve was analyzed in terms of the thick target formalism and the R-matrix theory. The reaction rate was deduced experimentally for the first time for the temperature of 0.1 < T{sub 9} < I. The experimemal reaction rate was compared with Hauser-Feshbach predictions. The astrophysical implications of the new rate are discussed.

  14. 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.

  15. Measurement of the 20 and 90 keV resonances in the 18O(p,alpha)15N reaction via the Trojan horse method.

    PubMed

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

    2008-10-10

    The 18O(p,alpha)15N 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 18O(p,alpha)15N 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. PMID:18999593

  16. 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.

  17. Structural analysis of specificity: alpha-lytic protease complexes with analogues of reaction intermediates.

    PubMed

    Bone, R; Frank, D; Kettner, C A; Agard, D A

    1989-09-19

    To better understand the structural basis of enzyme specificity, the structures of complexes formed between alpha-lytic protease, an extracellular serine protease of Lysobacter enzymogenes, and five inhibitory peptide boronic acids (R2-boroX, where R2 is methoxysuccinyl-Ala-Ala-Pro- and boroX is the alpha-aminoboronic acid analogue of Ala, Val, Ile, Norleu, or Phe) have been studied at high resolution by X-ray crystallography. The enzyme has primary specificity for Ala in the P1 position of peptide substrates with catalytic efficiency decreasing with increasing side-chain volume. Enzyme affinity for inhibitors with boroVal, boroIle, and boroPhe residues is much higher than expected on the basis of the catalytic efficiencies of homologous substrates. Covalent tetrahedral adducts are formed between the active-site serine and the boronic acid moieties of R2-boroAla, R2-boroVal R2-boroIle, and R2-boroNorleu. Though R2-boroVal is a slowly bound inhibitor and R2-boroAla is rapidly bound [Kettner, C. A., Bone, R., Agard, D. A., & Bachovchin, W. W. (1988) Biochemistry 27, 7682-7688], there appear to be no structural differences that could account for slow binding. The removal from solution of 20% more hydrophobic surface on binding accounts for the improved affinity of alpha-lytic protease for R2-boroVal relative to R2-boroAla. The high affinity of the enzyme for R2-boroIle derives from the selective binding of the L-allo stereoisomer of the boroIle residue, which can avoid bad steric interactions in the binding pocket.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2611204

  18. Reaction of /alpha/,/beta/-unsaturated acyl isothiocyanates with salts of dithiocarbamic acids

    SciTech Connect

    Krus, K.; Masias, A.; Beletskaya, I.P.

    1989-01-10

    The reaction of unsaturated isothiocyanates with the sodium and calcium salts of N-alkyl- and N,N-dialkyldithiocarbamic acids was studied. Depending on the structure of the dithiocarbamate, the reaction products are thiazines or acyl dithiocarbamates. For the salts of methyldithiocarbamic acid the effect of the concentration and the nature of the metal on the relative yields of 6-phenyl-3-methylpropiorhodanine and 6-phenylpropiorhodanine was studied. A method is proposed for the synthesis of 3-substituted propiorhodanines.

  19. Isoforms of alpha1E voltage-gated calcium channels in rat cerebellar granule cells--detection of major calcium channel alpha1-transcripts by reverse transcription-polymerase chain reaction.

    PubMed

    Schramm, M; Vajna, R; Pereverzev, A; Tottene, A; Klöckner, U; Pietrobon, D; Hescheler, J; Schneider, T

    1999-01-01

    In primary cultures of rat cerebellar granule cells, transcripts of voltage-gated Ca2+ channels have been amplified by reverse transcription-polymerase chain reaction and identified by sequencing of subcloned polymerase chain reaction products. In these neurons cultured for six to eight days in vitro, fragments of the three major transcripts alpha1C, alpha1A, and alpha1E are detected using degenerated oligonucleotide primer pairs under highly stringent conditions. Whole-cell Ca2+ current recordings from six to eight days in vitro granule cells show that most of the current is due to L-type (25%), P-type (33%) and R-type (30%) Ca2+ channels. These data support the correlation between alpha1A and P-type Ca2+ channels (G1) and between alpha1E and R-type channels (G2 and G3). By including specific primer pairs for alpha1E the complimentary DNA fragments of indicative regions of alpha1E isoforms are amplified corresponding to the three most variable regions of alpha1E, the 5'-end, the II/III-loop, and the central part of the 3'-end. Although the complementary DNA fragments of the 5'-end of rat alpha1E yield a uniform reverse transcription-polymerase chain reaction product, its structure is unusual in the sense that it is longer than in the cloned rat alpha1E complementary DNA. It corresponds to the alpha1E isoform reported for mouse and human brain and is also expressed in cerebellum and cerebrum of rat brain as the major or maybe even the only variant of alpha1E. While fragments of a new rat alpha1E isoform are amplified from the 5'-end, three known fragments of the II/III-loop and two known isoforms homologue to the 3'-coding region are detected, which in the last case are discriminated by a 129 base pair insertion. The shift of the alpha1E expression from a pattern seen in cerebellum (alpha1Ee) to a pattern identified in other regions of the brain (alpha1E-3) is discussed. These data show that: (i) alpha1E is expressed in rat brain as a structural homologue to the

  20. [The decomposition of Maillard reaction products by amylolytic enzymes. 1. Reversible inhibition of alpha- and glucoamylase and alpha-glucosidase by oligosaccharide Amidori compounds].

    PubMed

    Schumacher, D; Kroh, L W

    1994-10-01

    The influence of Amadori-compounds (fructosyl-, maltulosyl- and maltotriulosylglycin) on the activity of the enzymes alpha-glucosidase (from Saccharomyces cerevisiae), glucoamylase (from Aspergillus niger) and alpha-amylase (from porcine pancreas) was studied. Fructosylglycin was not hydrolyzed by all three enzymes. alpha-Glucosidase hydrolyzes maltulosylglycin 10 times slower than maltotriulosylglycin. Glucoamylase and alpha-amylase catalyze only the cleavage of maltotriulosylglycin to form glucose and maltulosylglycin. The activities of alpha-glucosidase and glucoamylase are inhibited through the Amadori-compounds fructosyl- and maltulosylglycin. These Amadori-compounds don't influence the activity of alpha-amylase. Electronic effects or interactions between the secondary amino function of Amadori-compounds and the carboxyl- or carboxylate groups of active centres could be responsible for such an inhibition. PMID:7839734

  1. Measurement of cross sections for the 63Cu(alpha,gamma)67Ga reaction from 5.9-8.7 MeV

    SciTech Connect

    Basunia, M. Shamsuzzoha; Norman, Eric B.; Shugart, Howard A.; Smith, Alan R.; Dolinski, Michelle J.; Quiter, Brian J.

    2004-09-23

    We have measured cross sections for the 63Cu(alpha,gamma)67Ga reaction in the 5.9-8.7 MeV energy range using an activation technique. Natural Cu foils were bombarded with alpha beams from the 88 Cyclotron at Lawrence Berkeley National Laboratory (LBNL). Activated foils were counted using gamma spectrometry system at LBNL's Low Background Facility. The 63Cu(alpha,gamma)67Ga cross-sections were determined and compared with the latest NON-SMOKER theoretical values. Experimental cross sections were found to be in agreement with theoretical values.

  2. 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.

  3. 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.

  4. The {beta}-delayed {alpha}-spectrum of {sup 16}N and the astrophysical aspects of the {sup 12}C({alpha},{gamma}){sup 16}O reaction

    SciTech Connect

    Azuma, R.E.; Buchmann, L.; Barker, F.C.

    1995-08-01

    Radiative alpha-capture by {sup 12}C is a key process occurring during the helium-burning phase in red giant stars, and its rate remains one of the most significant uncertainties in the nucleosynthetic calculations for massive stars. This is largely due to the lack of precise experimental information concerning the values of the reduced {alpha}-particle widths of the J{sup {pi}} = 1{sup {minus}} and 2{sup +} subthreshold states in {sup 16}O to which the higher-energy radiative capture data are only weakly sensitive. Of these two states, the reduced {alpha}-width of the E{sub x} = 7.12 MeV J{sup {pi}} = 1{sup {minus}} level has been predicted to have a considerable effect on the structure of the hitherto unmeasured low-energy region of the {beta}-delayed {alpha}-particle spectrum of {sup 16}N. Experiments using the TRIUMF isotope separator TISOL have been performed to measure this {alpha}-spectrum down to an energy of E{sub {alpha}} = 600 keV, utilizing a coincidence technique which also accounts completely for the detector response function. The {alpha}-spectrum, containing 10{sup 6} counts, has been incorporated into both R- and K-matrix analyses along with the previously measured {sup 12}C({alpha},{gamma}){sup 16}O cross section and the {sup 12}C + {alpha} elastic phase shifts to yield a much improved value for S{sub E1}(300) keV. In light of this new determination of S{sub E1}(300), the available radiative capture data and elastic scattering phase shifts are re-analyzed, along with {beta}-delayed {alpha}-spectrum of {sup 16}N in an attempt also to place improved limits on the S{sub E1}(300) contribution to the {sup 12}C({alpha},{gamma}){sup 16}O cross section.

  5. 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.

  6. Energetic ion, atom, and molecule reactions and excitation in low-current H2 discharges: H(alpha) Doppler profiles.

    PubMed

    Petrović, Z Lj; Phelps, A V

    2009-12-01

    Absolute spectral emissivities for Doppler broadened H(alpha) profiles are measured and compared with predictions of energetic hydrogen ion, atom, and molecule behavior in low-current electrical discharges in H2 at very high electric field E to gas density N ratios E/N and low values of Nd , where d is the parallel-plate electrode separation. These observations reflect the energy and angular distributions for the excited atoms and quantitatively test features of multiple-scattering kinetic models in weakly ionized hydrogen in the presence of an electric field that are not tested by the spatial distributions of H(alpha) emission. Absolute spectral intensities agree well with predictions. Asymmetries in Doppler profiles observed parallel to the electric field at 4reactions among H+, H2+, H3 , H, and H2 leading to fast H atoms and then fast excited H(n=3) atoms. PMID:20365280

  7. 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

  8. A system for measuring total body calcium in man using the 40Ca(n, alpha)37 Ar reaction.

    PubMed

    Lewellen, T K; Nelp, W B; Murano, R; Palmer, H E; Hinn, G M

    1979-01-01

    A technique to measure total body calcium using the 40Ca(n, alpha)37 Ar reaction has been developed. The technique is based on collecting 37Ar exhaled in the breath following a 10 mrad uniform total body irradiation by 14 MeV neutrons. The 37Ar in the exhaled breath is extracted by selective absorption and its radioactivity is measured inside a low-background proportional detector. The facilities developed include an activation facility providing a +/-2.7% activation uniformity, a closed circuit rebreathing and gas collection system, and a gas purification and counting system. The technique provides a precision of +/-2.4% as determined by repetitive measurements of human volunteers and has an accuracy for determination of total body calcium in grams of +/-5%. PMID:432261

  9. Improved determination of the astrophysical S(0) factor of the {sup 15}N(p,{alpha}){sup 12}C reaction

    SciTech Connect

    La Cognata, M.; Spitaleri, C.; Goldberg, V. Z.; Mukhamedzhanov, A. M.; Tribble, R. E.

    2009-07-15

    We present new improved R matrix fits of direct data and indirect Trojan Horse data for the {sup 15}N(p,{alpha}){sup 12}C reaction and provide a more accurate recommended value of S(0)=73.0{+-}5.0 MeV b from direct Redder data [A. Redder et al., Z. Phys. A 305, 325 (1982)] and S(0)=70.0{+-}13.5 MeV b from the Trojan Horse data [M. La Cognata et al., Phys. Rev. C 76, 065804 (2007)]. We also analyze a recent fit by Barker [F. C. Barker, Phys. Rev. C 78, 044611 (2008)] and demonstrate that when all the uncertainties are taken into account, our results overlap with his. We also provide a fit of the Trojan Horse data that properly takes into account finite residual energy resolution of the data.

  10. Application of the BINS superheated drop detector spectrometer to the {sup 9}Be(p,xn) neutron energy spectrum determination

    SciTech Connect

    Di Fulvio, A.; Ciolini, R.; Mirzajani, N.; Romei, C.; D'Errico, F.; Bedogni, R.; Esposito, J.; Zafiropoulos, D.; Colautti, P.

    2013-07-18

    In the framework of TRASCO-BNCT project, a Bubble Interactive Neutron Spectrometer (BINS) device was applied to the characterization of the angle-and energy-differential neutron spectra generated by the {sup 9}Be(p,xn)reaction. The BINS spectrometer uses two superheated emulsion detectors, sequentially operated at different temperatures and thus provides a series of six sharp threshold responses, covering the 0.1-10 MeV neutron energy range. Spectrum unfolding of the data was performed by means of MAXED code. The obtained angle, energy-differential spectra were compared with those measured with a Bonner sphere spectrometer, a silicon telescope spectrometer and literature data.

  11. Alpha-particle capture reactions in inverse kinematics relevant to p-process nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Ujić, P.; Lagoyannis, A.; Mertzimekis, T. J.; de Oliveira Santos, F.; Harissopulos, S.; Demetriou, P.; Perrot, L.; Stodel, Ch.; Saint-Laurent, M.-G.; Kamalou, O.; Lefebvre-Schuhl, A.; Spyrou, A.; Amthor, M. A.; Grevy, S.; Caceres, L.; Koivisto, H.; Laitinen, M.; Uusitalo, J.; Julin, R.

    2011-10-01

    The first feasibility study of an α-particle capture reaction in inverse kinematics at energies relevant to the p process was performed at the Wien Filter of the LISE spectrometer at GANIL. Hereby, the 4He(78Kr,γ)82Sr reaction was investigated using as target an 4He-implanted thin Al foil. The analysis of the data has shown that the determination of (α,γ) reaction cross sections at rather low energies around 2 MeV/u in inverse kinematics is indeed feasible regarding the high rejection rate of the primary beam, which in the present work was better than a factor of 109. However, the expected position of the recoils of interest was completely masked by particles of currently unknown origin that could hardly be attributed to scattering of the primary beam. The most probable explanation for the origin of these "pollutants" could be microscopic dust particles of 10 μm diameter and less, that are extremely difficult to avoid in standard experimental conditions. Hence, the use of a gas-jet target instead of a solid one is compulsory.

  12. Stereochemistry and mechanism of a new single-turnover, half-transamination reaction catalyzed by the tryptophan synthase alpha 2 beta 2 complex

    SciTech Connect

    Miles, E.W.

    1987-01-27

    Tryptophan synthase is a versatile enzyme that catalyzes a wide variety of pyridoxal phosphate dependent reactions that are also catalyzed in model systems. These include beta-replacement, beta-elimination, racemization, and transamination reactions. We now show that the apo-alpha 2 beta 2 complex of tryptophan synthase will bind two unnatural substrates, pyridoxamine phosphate and indole-3-pyruvic acid, and will convert them by a single-turnover, half-transamination reaction to pyridoxal phosphate and L-tryptophan, the natural coenzyme and a natural product, respectively. This enzyme-catalyzed reaction is more rapid and more stereospecific than an analogous model reaction. The pro-S 4'-methylene proton of pyridoxamine phosphate is removed during the reaction, and the product is primarily L-tryptophan. We conclude that pyridoxal phosphate enzymes may be able to catalyze some unnatural reactions involving bound reactants and bound coenzyme since the coenzyme itself has the intrinsic ability to promote a variety of reactions.

  13. Astrophysically Important 19Ne States Studied with the 2H(18F,alpha+15O)n Reaction

    SciTech Connect

    Adekola, Aderemi S; Bardayan, Daniel W; Blackmon, Jeff C; Brune, C.; Chae, K. Y.; Champagne, A. E.; Domizioli, Carlo P; Greife, U.; Heinen, Z.; Hornish, M.; Johnson, Micah; Jones, K. L.; Kapler, R.; Livesay, Jake; Ma, Zhanwen; Massey, T.; Moazen, Brian; Nesaraja, Caroline D; Pain, Steven D; ShrinerJr., J. F.; Thomas, J. S.; Smith, Nathan A; Smith, Michael Scott; Visser, D. W.; Voinov, A.

    2009-01-01

    The nuclear structure of {sup 19}Ne near the proton threshold is of interest for understanding the rates of proton-induced reactions on {sup 18}F in novae. Analogues for several states in the mirror nucleus {sup 19}F have not yet been identified in {sup 19}Ne indicating the level structure of {sup 19}Ne in this region is incomplete. The {sup 18}F(d;n){sup 19}Ne and {sup 18}F(d,p){sup 19}F reactions have been measured simultaneously at E{sub c.m.} = 14.9 MeV. The experiments were performed at the Holifield Radioactive Ion Beam Facility (HRIBF) of Oak Ridge National Laboratory (ORNL) by bombarding a 720-mg/cm{sub 2} CD{sub 2} target with a radioactive {sup 18}F beam. The {sup 19}Ne states of interest near the proton threshold decay by breakup into a and {sup 15}O particles. These decay products were detected in coincidence with position-sensitive E-{Delta}E silicon telescopes. The {alpha} and {sup 15}N particles from the break up of the mirror nucleus {sup 19}F were also measured with these detectors. Particle identification, coincidence, and Q-value requirements enable us to distinguish the reaction of interest from other reactions. The reconstruction of relative energy of the detected particles reveals the excited states of {sup 19}Ne and {sup 19}F which are populated. The neutron (proton) angular distributions for states in {sup 19}Ne ({sup 19}F) were extracted using momentum conservation. The observed states in {sup 19}Ne and {sup 19}F will be presented.

  14. Efficient one-pot enzymatic synthesis of alpha-(1-->4)-glucosidic disaccharides through a coupled reaction catalysed by Lactobacillus acidophilus NCFM maltose phosphorylase.

    PubMed

    Nakai, Hiroyuki; Dilokpimol, Adiphol; Abou Hachem, Maher; Svensson, Birte

    2010-05-27

    Lactobacillus acidophilus NCFM maltose phosphorylase (LaMalP) of glycoside hydrolase family 65 catalysed enzymatic synthesis of alpha-(1-->4)-glucosidic disaccharides from maltose and five monosaccharides in a coupled phosphorolysis/reverse phosphorolysis one-pot reaction. Thus phosphorolysis of maltose to beta-glucose 1-phosphate circumvented addition of costly beta-glucose 1-phosphate for reverse phosphorolysis with different monosaccharide acceptors, resulting in 91%, 89%, 88%, 86% and 84% yield of alpha-d-glucopyranosyl-(1-->4)-N-acetyl-D-glucosaminopyranose [N-acetyl-maltosamine], alpha-D-glucopyranosyl-(1-->4)-D-glucosaminopyranose [maltosamine], alpha-D-glucopyranosyl-(1-->4)-D-mannopyranose, alpha-D-glucopyranosyl-(1-->4)-L-fucopyranose and alpha-D-glucopyranosyl-(1-->4)-D-xylopyranose, respectively, from 0.1M maltose, 0.5M N-acetyl glucosamine, 0.1M glucosamine, 0.1M mannose, 1M L-fucose and 0.5M xylose in 0.2M phosphate-citrate pH 6.2. These current yields of 0.27-0.34 g of disaccharide products from 10 mL reaction mixtures are easy to scale up and moreover the strategy can be applied to large-scale production of other oligosaccharides from low-cost disaccharides as catalysed by phosphorylases with different substrate specificities. PMID:20392438

  15. 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. PMID:25439920

  16. Nova Nucleosynthesis with a New 18F(p,alpha) Reaction Rate

    NASA Astrophysics Data System (ADS)

    Smith, Michael; Kozub, Raymond; Brune, Carl; Starrfield, Sumner

    2005-04-01

    The long-lived radionuclide ^18F is synthesized in nova outbursts and its decay may serve as an observational tracer of the explosion mechanism. Because the ^18F(p,α)^15O reaction is the dominant destruction mechanism for ^18F, the flux of gamma rays from ^18F decay is very sensitive to the rate of this reaction. A revised ^18F(p,α)^15O rate was determined from recent ORNL measurements of ^1H(^18F,p)^18F and ^2H(^18F,p)^19F, combined with a reanalysis of archival ^15N(α,α)^15N data. We used this new rate in nova element synthesis calculations and compared new predictions of the synthesized abundance ^18F (and other nuclides) to that obtained using the two most recent (p,α) rates. We used a post- processing approach with temperature and density histories of 28 zones of ejected material determined from separate hydrodynamics calculations. The implications for satellite observations of novae will be discussed. These calculations were performed and visualized with the Computational Infrastructure for Nuclear Astrophysics, an online suite of codes available at nucastrodata.org.

  17. 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). PMID:25897880

  18. Cross-section measurement for the 10B(n, alpha)7Li reaction at 4.0 and 5.0 MeV.

    PubMed

    Zhang, Guohui; Guo, Li'an; Cao, Rongtai; Zhang, Jiaguo; Chen, Jinxiang

    2008-10-01

    Cross-sections of the (10)B(n, alpha)(7)Li reaction were measured at En=4.0 and 5.0 MeV. A gridded ionization chamber (GIC) was used as charged particle detector. Neutrons were produced through the D(d, n)(3)He reaction with a deuterium gas target. Experiments were performed at the 4.5 MV Van de Graaff accelerator of Peking University. Cross-section data of the (238)U(n, f) reaction were employed as standard. The measured cross-sections of the (10)B(n, alpha)(7)Li reaction at 4.0 and 5.0 MeV are 211+/-17 and 169+/-14 mb, respectively, and they are compared with existing results of measurements and evaluations. PMID:18387305

  19. 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.

  20. Direct measurement of the {sup 11}C({alpha},p){sup 14}N reaction at CRIB: A path from pp-chain to CNO

    SciTech Connect

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

    2012-11-20

    We determined the total reaction rate of the {sup 11}C({alpha},p){sup 14}N reaction 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 performed the identification of the ground-state transition and excited-state transitions using time-of-flight information for the first time.

  1. 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.

  2. {alpha}-decaying states in {sup 10,12}Be populated in the {sup 10}Be({sup 14}C,{sup 10,12}Be) reaction

    SciTech Connect

    Curtis, N.; Ashwood, N.I.; Bloxham, T.R.; Freer, M.; McEwan, P.; Price, D.L.; Baby, L.T.; Caussyn, D.D.; Spingler, D.; Wiedenhover, I.; Baldwin, T.D.; Catford, W.N.; Harlin, C.W.

    2006-05-15

    A search has been made for the {sup 6}He+{sup 6}He and {alpha} + {sup 8}He decay of the molecular rotational band in {sup 12}Be using the {sup 10}Be({sup 14}C,{sup 12}Be*){sup 12}C reaction at 88.5 MeV. Although the {alpha} + {sup 6}He decay of {sup 10}Be was observed in the data set there is no evidence for the breakup of {sup 12}Be. The cross-section upper limits for the {sup 10}Be({sup 14}C,{sup 6}He {sup 6}He){sup 12}C and {sup 10}Be({sup 14}C,{alpha} {sup 8}He){sup 12}C reactions are 50 and 300 nb respectively.

  3. Equilibrium and pre-equilibrium processes in the {sup 55}Mn({sup 6}Li,xp) and {sup 57}Fe({alpha},xp) reactions

    SciTech Connect

    Voinov, A. V.; Grimes, S. M.; Brune, C. R.; Massey, T. N.; Buerger, A.; Goergen, A.; Guttormsen, M.; Larsen, A. C.; Siem, S.; Kalbach, C.

    2011-05-15

    Spectra of outgoing neutrons and protons from the {sup 6}Li + {sup 55}Mn reaction and protons from the {alpha} + {sup 57}Fe reaction have been measured with beams of 15-MeV {sup 6}Li ions and 30-MeV {alpha} particles. These reactions proceed through the same {sup 61}Ni nucleus at the same excitation energy, thus allowing the difference in reaction mechanisms to be studied. It is shown that spectra from the first reaction measured at backward angles are due to emission from a traditional compound nucleus reaction, in which the intermediate nucleus has reached statistical equilibrium; the spectra from the second reaction contain a significant fraction of pre-equilibrium emission at all angles. Level density parameters of the residual nucleus {sup 60}Co have been obtained from the first reaction. Both emission spectra and angular distributions have been measured for the second reaction. It was found that the pre-equilibrium component exhibits a forward-peaked angular distribution, as expected, but with a steeper slope than predicted and with an unusual slight rise at angles above 120 deg. The backward-angle rise is explained qualitatively by the dominance of the multistep compound mechanism at backward angles.

  4. Bicyclic Guanidine Catalyzed Asymmetric Tandem Isomerization Intramolecular-Diels-Alder Reaction: The First Catalytic Enantioselective Total Synthesis of (+)-alpha-Yohimbine.

    PubMed

    Feng, Wei; Jiang, Danfeng; Kee, Choon-Wee; Liu, Hongjun; Tan, Choon-Hong

    2016-02-01

    Hydroisoquinoline derivatives were prepared in moderate to good enantioselectivities via a bicyclic guanidine-catalyzed tandem isomerization intramolecular-Diels-Alder (IMDA) reaction of alkynes. With this synthetic method, the first enantioselective synthesis of (+)-alpha-yohimbine was completed in 9 steps from the IMDA products. PMID:25932622

  5. THE RGB AND AGB STAR NUCLEOSYNTHESIS IN LIGHT OF THE RECENT {sup 17}O(p, {alpha}){sup 14}N AND {sup 18}O(p, {alpha}){sup 15}N REACTION-RATE DETERMINATIONS

    SciTech Connect

    Palmerini, S.; Sergi, M. L.; La Cognata, M.; Pizzone, R. G.; Spitaleri, C.; Lamia, L.

    2013-02-20

    In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on A = 17 and A = 18 oxygen isotopes, overcoming extrapolation procedures and enhancement effects due to electron screening. In particular, the strengths of the 20 keV and 65 keV resonances in the {sup 18}O(p, {alpha}){sup 15}N and {sup 17}O(p, {alpha}){sup 14}N reactions, respectively, have been extracted, as well as the contribution of the tail of the broad 656 keV resonance in the {sup 18}O(p, {alpha}){sup 15}N reaction inside the Gamow window. The strength of the 65 keV resonance in the {sup 17}O(p, {alpha}){sup 14}N reaction, measured by means of the THM, has been used to renormalize the corresponding resonance strength in the {sup 17}O + p radiative capture channel. As a result, more accurate reaction rates for the {sup 18}O(p, {alpha}){sup 15}N, {sup 17}O(p, {alpha}){sup 14}N, and {sup 17}O(p, {gamma}){sup 18}F processes have been deduced, devoid of systematic errors due to extrapolation or the electron screening effect. Such rates have been introduced into state-of-the-art red giant branch and asymptotic giant branch (AGB) models for proton-capture nucleosynthesis coupled with extra-mixing episodes. The predicted abundances have been compared with isotopic compositions provided by geochemical analysis of presolar grains. As a result, an improved agreement is found between the models and the isotopic mix of oxide grains of AGB origins, whose composition is the signature of low-temperature proton-capture nucleosynthesis. The low {sup 14}N/{sup 15}N found in SiC grains cannot be explained by the revised nuclear reaction rates and remains a serious problem that has not been satisfactorily addressed.

  6. 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.

  7. Asymmetric Strecker-Type Reaction of alpha-Aryl Ketones. Synthesis of (S)-alphaM4CPG, (S)-MPPG, (S)-AIDA, and (S)-APICA, the Antagonists of Metabotropic Glutamate Receptors.

    PubMed

    Ma, Dawei; Tian, Hongqi; Zou, Guixiang

    1999-01-01

    Heating a mixture of alpha-aryl ketone with (R)-phenylglycinol produces a mixture of imine and 1,3-dioxazolidine. Treatment of this mixture with trimethylsilyl cyanide followed by transformation of nitrile to ester gives Strecker-type reaction products. The diastereoselectivity of the generated alpha-amino esters is from 2/1 to 7/1, and the (R,S)isomer is found as the major product. The (R,S) and (R,R)isomers can be separated by conversion to their N-Cbz or cyclization derivatives. Using this methodology, four antagonists of metabotropic glutamate receptors, (S)-alphaM4CPG, (S)-MPPG, (S)-AIDA, and (S)-APICA, are synthesized. PMID:11674092

  8. Stromal fibrosis reaction in rat prostates induced by alpha 1 adrenergic stimulation.

    PubMed

    Rosenzweig-Bublil, Nurit; Abramovici, Armand

    2006-01-01

    Most of the publications dealing with the experimental induction of prostatic neoplasia have focused on the description of epithelial lesions, but little attention has been paid to the involvement of their stromal alterations. The present study is a first attempt to assess the stromal changes in both collagen and elastic fibrils as well as in its cellular constituents, which accompany prostatic intraepithelial neoplastic (PIN)-like lesions induced by phenylephrine (PE) in rats. Adolescent rats received subcutaneous injections of PE daily (10 mg/kg/d) for 1 month. At the end of the experimental period the rats were sacrificed; the dissected ventral prostates were fixed in Stieve solution and paraffin-embedded; and sections were cut and stained accordingly. Most of the stromal cells were identified by immunohistochemistry techniques using primary antibodies to ED2 (resident macrophages), actin (fibrocytes and vascular smooth muscle cells), vimentin (mesenchymal cells), and 5'-bromo-2'-deoxyuridine (S-phase proliferating cells). Collagen stromal mass was visualized by Gomori trichrome and individual collagen fibers by picrosirius red staining under polarized light, whereas the fine fibrils were stained according to the Pinkus method. The untreated rat prostates are characterized by a delicate interacinar stroma with scanty cells and fibrils. The PE-treated prostates showed a significant increase in both cellular and fibrillar elements as well as an increase in arteriolar density, in addition to the typical PIN lesions. The presence of such an interstitial fibrosis, which also includes inflammatory cells, neoangiogenesis, and synthesis de novo of collagen and fibers, might be regarded as a desmoplastic reaction. It is suggested that these changes could be related to a tissue repair process occurring subsequent to the inflammatory exudate that takes place during the incipient phases of the PE treatment. PMID:16304211

  9. Cross-section measurements for (n, 2n) and (n, alpha) reactions on yttrium at neutron energies from 13.5 to 14.6 MeV.

    PubMed

    Zhou, Fengqun; Zhang, Hongwei; Huang, Hongchun; Li, Kuohu; Yi, Yanling; Tuo, Fei; Kong, Xiangzhong

    2008-12-01

    The cross sections for the reactions (89)Y(n, 2n) (88m+g)Y and (89)Y(n, alpha) (86m+g)RB induced by 14MeV neutrons have been measured using the activation technique and a coaxial HPGe gamma-ray detector. Spectroscopically pure Y(2)O(3) powder was used. Fast neutrons were produced by the T(d, n) (4)He reaction. The neutron fluencies were determined using the monitor reaction (93)Nb(n, 2n) (92m)Nb. PMID:18650098

  10. Adverse skin reactions due to pegylated interferon alpha 2b plus ribavirin combination therapy in a patient with chronic hepatitis C virus.

    PubMed

    Hashimoto, Yuki; Kanto, Hiromi; Itoh, Masatoshi

    2007-08-01

    Pegylated interferon (IFN)-alpha-2b with ribavirin has recently replaced "standard" IFN-alpha for the treatment of chronic hepatitis C. The most common side-effect of pegylated IFN-alpha-2b plus ribavirin combination therapy is localized inflammatory skin lesions at the site of injection. A 66-year-old female treated with once-weekly pegylated IFN-alpha-2b plus ribavirin for active chronic hepatitis C developed inflammatory skin lesions 2 months after starting antiviral treatment. The type of skin reactions observed were vesicle erythematous eruptions at the injection sites, and pruritic papular erythematous eruptions located on the face, neck, distal limbs, dorsa of the hands, trunk and buttocks away from the injection sites. Histological examination was performed on the pruritic papular erythematous eruption located on the left forearm, away from the injection sites. It showed epidermal spongiosis, a spongiotic microvesicle, and perivascular infiltration of the upper dermis with lymphocytes. The treatment was interrupted subsequently and the patient was rechallenged with pegylated IFN-alpha-2b plus ribavirin combination therapy, oral prednisolone with olopatadine hydrochloride and topical 0.1% diflucortolone valerate, which led to a significant improvement of skin lesions. Erythema with infiltration can occur at the injection sites of pegylated IFN-alpha-2b. However, the occurrence of vesicle erythematous eruptions away from the injection sites and autosensitization dermatitis apart from injection sites have not yet been frequently reported. PMID:17683392

  11. THE FLUORINE DESTRUCTION IN STARS: FIRST EXPERIMENTAL STUDY OF THE {sup 19}F(p, {alpha}{sub 0}){sup 16}O REACTION AT ASTROPHYSICAL ENERGIES

    SciTech Connect

    La Cognata, M.; Spitaleri, C.; Indelicato, I.; Cherubini, S.; Gulino, M.; Kiss, G. G.; Lamia, L.; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Mukhamedzhanov, A. M.; Aliotta, M.; Burjan, V.; Hons, Z.; Kroha, V.; Mrazek, J.; Piskor, S.; Coc, A.

    2011-10-01

    The {sup 19}F(p, {alpha}){sup 16}O reaction is an important fluorine destruction channel in the proton-rich outer layers of asymptotic giant branch (AGB) stars and it might also play a role in hydrogen-deficient post-AGB star nucleosynthesis. So far, available direct measurements do not reach the energy region of astrophysical interest (E {sub cm} {approx}< 300 keV), because of the hindrance effect of the Coulomb barrier. The Trojan Horse (TH) method was thus used to access this energy region, by extracting the quasi-free contribution to the {sup 2}H({sup 19}F, {alpha}{sup 16}O)n and the {sup 19}F({sup 3}He, {alpha}{sup 16}O)d reactions. The TH measurement of the {alpha}{sub 0} channel shows the presence of resonant structures not observed before, which cause an increase of the reaction rate at astrophysical temperatures up to a factor of 1.7, with potential consequences for stellar nucleosynthesis.

  12. 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).

  13. A DIAMANT Wedding For AFRODITE: Probing Structure and Characterizing Reaction Properties Via Charged-Particle-{gamma} Correlations

    SciTech Connect

    Mullins, S. M.; Murray, S. H. T.; Bark, R. A.; Gueorguieva, E.; Lawrie, J. J.; Lieder, E. O.; Lieder, R. M.; Papka, P.; Nyako, B. M.; Timar, J.; Berek, G.; Gal, J.; Kalinka, G.; Molnar, J.; Krasznahorkay, A.; Zolnai, L.; Juhasz, K.; Lipoglavsek, M.; Ntshangase, S. S.; Scheurer, J. N.

    2008-05-12

    The DIAMANT-AFRODITE combination has been used to investigate incomplete fusions reactions via the {sup 13}C+{sup 170}Er entrance channel. The intensity of {sup 176}Hf (populated via the {alpha} 3n exit channel) is {approx}8% of {sup 178}W (populated via 5n evaporation) which is {approx}8 times stronger than that expected from complete fusion. Moreover, 2{alpha}xn exit channels leading to Yb nuclei are observed with intensities that are {approx}30-to-40% of {sup 176}Hf, for which no yield is expected from complete fusion. A comparison of the intensities from the two-{alpha}- and one-{alpha}-gated data is consistent with fragmentation of the {sup 13}C beam into ({alpha}-{alpha}-{alpha}-n) which suggests that the population of Yb nuclei results from fusion (or ''massive transfer'') of one the break-up {alpha}-particles. A campaign of measurements is scheduled for late 2007 with further investigations planned for 2008, including the continuation of the study of superdeformation in {sup 32}S.

  14. Neonatal alpha1-antitrypsin screening: parents' views and reactions 20 years after the identification of the deficiency state.

    PubMed

    Sveger, T; Thelin, T; McNeil, T F

    1999-03-01

    During 1972-74, 200000 Swedish neonates were screened for alpha1-antitrypsin deficiency (alpha1ATD). The parents of the 22-23-y-old alpha1ATD children were asked about their views on the screening study, information and follow-up of their children as well as physical and psychosomatic problems, which were compared with a matched control (MC) group. Of the original 122 alpha1ATD and MC parents, 85 alpha1ATD and 89 MC parents decided to participate. The neonatal period was considered the best time for screening by 88% of the responding parents. The care of the alpha1ATD individuals was assessed as positive or very positive by 84% of the parents. About 70% of the parents thought that the awareness of their child's alpha1ATD had affected their lives, the most common comment being an increased consciousness of smoky and dusty environments. No significant difference between alpha1ATD and control parents was found concerning worry about the child's health and future. When asked about symptoms related to their mental health, no difference was found concerning headache, sleep problems, stomach troubles or tiredness. Alpha1ATD mothers had statistically significantly more anxiety than control mothers (chi2 p<0.01, Wilcoxon p<0.02). The knowledge derived from the present and previous parts of the alpha1AT screening study is important with regard to presymptomatic testing for adult-onset disease in children. PMID:10229044

  15. Electron-transfer photochemistry of. cap alpha. -silylamine-cyclohexenone systems. Medium effects on reaction pathways followed

    SciTech Connect

    Yoon, U.C.; Kim, J.U.; Hasegawa, E.; Mariano, P.S.

    1987-07-08

    Previously, the authors demonstrated how photostimulated electron-transfer (SET) processes of ..cap alpha..-trialkylsilyl-substituted electron donors can be employed to generate free radical systems. Initial efforts focused on SET processes of iminium salts. Recently, the authors expanded this methodology to include arenecarbonitriles. In this communication they report on the SET photochemistry of ..cap alpha..,..beta..-unsaturated cyclohexenones with an ..cap alpha..-silyl tertiary amine donor.

  16. Photodimerization of the alpha'-polymorph of ortho-ethoxy-trans-cinnamic acid in the solid state. I. Monitoring the reaction at 293 K.

    PubMed

    Fernandes, M A; Levendis, D C

    2004-06-01

    Structural changes that occur during the [2 + 2] photodimerization of the metastable alpha'-polymorph of ortho-ethoxy-trans-cinnamic acid at 293 K are presented here. Crystals of the alpha'-polymorph were first stabilized by exposing the alpha-polymorph to UV light for a short period of time at 343 K. The photodimerization reaction was then carried out at 293 K and observed in situ by single-crystal X-ray diffraction. The alpha'-polymorph contains three molecules in the asymmetric unit, labelled A, B and C, which are arranged to form two potential reaction sites. The intermolecular distance between the C=C bonds of molecules A and B (making up the AB site) is 3.6 A, and these were observed to undergo photodimerization at 293 K. The corresponding distance between centrosymmetrically related C=C bonds in the CC site (made up of C molecules) is 4.6 A, and these remain unreacted even after 60 h irradiation at 293 K. The crystal of the final product, which corresponds to a 66.7% conversion (only two out of three molecules in the asymmetric unit take part in the photodimerization reaction at 293 K), contains an ordered arrangement of the photodimer and unreacted monomer. The crystal retains many structural features of the original monomer crystal, including carboxylic acid hydrogen bonds and C-H.O interactions. Single-crystal X-ray diffraction was used to monitor changes in the unit-cell parameters, reacting molecules and molecular conformations as the reaction progressed. The conformation of the photodimer obtained from the solid-state reaction differs from that of the photodimer obtained by recrystallization from solution. PMID:15148435

  17. 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.

  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. Inhibition of bovine viral diarrhea virus in vitro by xanthohumol: comparisons with ribavirin and interferon-alpha and implications for the development of anti-hepatitis C virus agents.

    PubMed

    Zhang, Ni; Liu, Zhengwen; Han, Qunying; Chen, Jinghong; Lou, Sai; Qiu, Jianming; Zhang, Guoyu

    2009-11-01

    Xanthohumol (XN) is a natural compound with potential antiviral activity. In this study, the ability of XN to inhibit bovine viral diarrhea virus (BVDV), a surrogate model of hepatitis C virus (HCV), was investigated. The antiviral activity of XN was compared with that of ribavirin (RBV) and interferon (IFN)-alpha. The results showed that XN could inhibit BVDV induced cytopathic effects (CPE). At 1000 TCID(50) and 100 TCID(50), the values of 50% effective concentration (EC(50)) were 3.24+/-0.02 mg/l and 2.77+/-0.19 mg/l, respectively, and the therapeutic indices were >7.72 and >9.03, respectively. XN inhibited BVDV E2 expression and viral RNA levels in a dose-dependent manner. At 6.25mg/l, XN decreased the viral RNA from released virus by 3.83 log 10 at 1000 TCID(50) and to an undetectable level at 100 TCID(50), and decreased the viral RNA level in whole cell culture by 3.36 log 10 and 2.88 log 10 at 1000 TCID(50) and 100 TCID(50), respectively. The inhibitory activity of XN on CPE, BVDV E2 expression and viral RNA levels was stronger than that of RBV and weaker than that of IFN-alpha. These results indicate the need to investigate the anti-HCV potential of XN. PMID:19720145

  20. FA-SIFT study of reactions of protonated water and ethanol clusters with [alpha]-pinene and linalool in view of their selective detection by CIMS

    NASA Astrophysics Data System (ADS)

    Dhooghe, F.; Amelynck, C.; Rimetz-Planchon, J.; Schoon, N.; Vanhaecke, F.

    2010-02-01

    The use of protonated water clusters and protonated ethanol clusters as reagent ions has been evaluated for the resolution of an interference encountered in CIMS when measuring monoterpenes (C10H16) and linalool (C10H18O) simultaneously. To this end, the reactions of H3O+.(H2O)n (n = 1-3), (C2H5OH)mH+ (m = 1-3) and (C2H5OH.H2O)H+ with [alpha]-pinene and linalool have been characterized in a flowing afterglow-selected ion flow tube (FA-SIFT) instrument at a SIFT He buffer gas pressure of 1.43 hPa and a temperature of 298 K. All reactions with linalool were found to occur at the collision limit. The reaction of (C2H5OH)2H+ with [alpha]-pinene proceeds at half the collision rate and both the reactions of (C2H5OH)3H+ and H3O+.(H2O)3 with [alpha]-pinene have a very low rate constant. All other reactions involving [alpha]-pinene proceed at the collision rate. The reactions of H3O+.H2O, H3O+.(H2O)2, C2H5OH2+, (C2H5OH.H2O)H+ and (C2H5OH)2H+ with [alpha]-pinene mainly proceed by proton transfer. Additionally, ligand switching channels have been observed for the reactions of (C2H5OH)2H+ and H3O+.(H2O)2 with [alpha]-pinene. Protonated linalool was observed as a minor product for the reactions of (C2H5OH.H2O)H+ and H3O+.(H2O)n (n = 1-3) with linalool. For all linalool reactions, a contribution of the dissociative proton transfer product at m/z 137 was found and this ion was the main product ion for the reactions with H3O+.H2O, C2H5OH2+ and (C2H5OH.H2O)H+. For the (C2H5OH.H2O)H+/linalool reaction, ligand switching with both water and ethanol has been observed. Major ligand switching channels were observed for the reactions of (C2H5OH)2H+, (C2H5OH)3H+ and H3O+.(H2O)2 with linalool. Also, for the H3O+.(H2O)3/linalool reaction, several ligand switching channels have been observed. These results are discussed in view of their applicability for the selective detection of monoterpenes and linalool with CIMS instrumentation such as SIFT-MS, PTR-MS and APCI-MS.

  1. Experimental determination of the {sup 17}O(p,{alpha}){sup 14}N and {sup 17}O(p,{gamma}){sup 18}F reaction rates

    SciTech Connect

    Chafa, A.; Ouichaoui, S.; Tatischeff, V.; Coc, A.; Garrido, F.; Kiener, J.; Lefebvre-Schuhl, A.; Thibaud, J.-P.; Aguer, P.; Barhoumi, S.; Hernanz, M.; Jose, J.; Sereville, N. de

    2007-03-15

    The {sup 17}O(p,{alpha}){sup 14}N and {sup 17}O(p,{gamma}){sup 18}F reactions are of major importance to hydrogen-burning nucleosynthesis in a number of different stellar sites. In particular, {sup 17}O and {sup 18}F nucleosynthesis in classical novae is strongly dependent on the thermonuclear rates of these two reactions. The previously estimated rate for {sup 17}O(p,{alpha}){sup 14}N carries very large uncertainties in the temperature range of classical novae (T=0.01-0.4 GK), whereas a recent measurement has reduced the uncertainty of the {sup 17}O(p,{gamma}){sup 18}F rate. We report on the observation of a previously undiscovered resonance at E{sub c.m.}=183.3 keV in the {sup 17}O(p,{alpha}){sup 14}N reaction, with a measured resonance strength {omega}{gamma}{sub p{alpha}}=(1.6{+-}0.2)x10{sup -3} eV. We studied in the same experiment the {sup 17}O(p,{gamma}){sup 18}F reaction by an activation method, and the resonance strength was found to amount to {omega}{gamma}{sub p{gamma}}=(2.2{+-}0.4)x10{sup -6} eV. The excitation energy of the corresponding level in {sup 18}F was determined to be 5789.8{+-}0.3 keV in a Doppler shift attenuation method measurement, which yielded a value of {tau}<2.6 fs for the level lifetime. The {sup 17}O(p,{alpha}){sup 14}N and {sup 17}O(p,{gamma}){sup 18}F reaction rates were calculated using the measured resonance properties and reconsidering some previous analyses of the contributions of other levels or processes. The {sup 17}O(p,{alpha}){sup 14}N rate is now well established below T=1.5 GK, with uncertainties reduced by orders of magnitude in the temperature range T=0.1-0.4 GK. The uncertainty in the {sup 17}O(p,{gamma}){sup 18}F rate is somewhat larger because of remaining obscurities in the knowledge of the direct capture process. These new resonance properties have important consequences for {sup 17}O nucleosynthesis and {gamma}-ray emission of classical novae.

  2. Experimental determination of the {sup 26}Al(n,{alpha}){sup 23}Na reaction cross section and calculation of the Maxwellian averaged cross section at stellar temperatures

    SciTech Connect

    Smet, L. de; Wagemans, C.; Wagemans, J.; Heyse, J.; Gils, J. van

    2007-10-15

    The {sup 26}Al(n,{alpha}){sup 23}Na reaction cross section has been studied at the linear accelerator GELINA of the Institute for Reference Materials and Measurements in Geel, Belgium, and has been determined up to a neutron energy of about 100 keV using the time-of-flight technique. Six resonances could be observed in this energy region, whereas before only one had been identified experimentally. For four of them, resonance parameters such as resonance energy, total width, area, and spin of the state could be determined. From the obtained {sup 26}Al(n,{alpha}){sup 23}Na cross section data, Maxwellian averaged cross section (MACS) values were calculated by numerical integration. Since neutron induced reactions are among the major destruction mechanisms of {sup 26}Al in our Galaxy, these new MACS values contribute to a better understanding of the observed {sup 26}Al abundance.

  3. EFFECT OF HIGH-ENERGY RESONANCES ON THE {sup 18}O(p, {alpha}){sup 15}N REACTION RATE AT AGB AND POST-AGB RELEVANT TEMPERATURES

    SciTech Connect

    La Cognata, M.; Spitaleri, C.; Mukhamedzhanov, A. M.

    2010-11-10

    The {sup 18}O(p, {alpha}){sup 15}N reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as {sup 19}F, {sup 18}O, and {sup 15}N. Fluorine is synthesized in the intershell region of asymptotic giant branch (AGB) stars, together with s-elements, by {alpha} radiative capture on {sup 15}N, which in turn is produced in the {sup 18}O proton-induced destruction. Peculiar {sup 18}O abundances are observed in R-Coronae Borealis stars, having {sup 16}O/{sup 18}O {approx}< 1, hundreds of times smaller than the galactic value. Finally, there is no definite explanation of the {sup 14}N/{sup 15}N ratio in pre-solar grains formed in the outer layers of AGB stars. Again, such an isotopic ratio is influenced by the {sup 18}O(p, {alpha}){sup 15}N reaction. In this work, a high accuracy {sup 18}O(p, {alpha}){sup 15}N reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. Indeed, current determinations are uncertain because of the poor knowledge of the resonance parameters of key levels of {sup 19}F. In particular, we have focused on the study of the broad 660 keV 1/2{sup +} resonance corresponding to the 8.65 MeV level of {sup 19}F. Since {Gamma} {approx} 100-300 keV, it determines the low-energy tail of the resonant contribution to the cross section and dominates the cross section at higher energies. Here, we provide a reaction rate that is a factor of two larger above T {approx} 0.5 10{sup 9} K based on our new improved determination of its resonance parameters, which could strongly influence present-day astrophysical model predictions.

  4. /sup 194/ /sup 196/ /sup 198/Pt(t,. cap alpha. )/sup 193/ /sup 195/ /sup 197/Ir reactions with polarized tritons. [17 MeV

    SciTech Connect

    Cizewski, J.A.; Flynn, E.R.; Sunier, J.W.; Brown, R.E.; Burke, D.G.

    1980-01-01

    The /sup 194/ /sup 196/ /sup 198/Pt(t vector, ..cap alpha..)/sup 193/ /sup 195/ /sup 197/Ir reactions were measured. Angular distributions of cross sections and analyzing powers for levels up to approx. 2.5 MeV in each residual nuclide were obtained, and comparisons with DWBA predictions allowed spins, parities, and pickup spectroscopic strengths to be determined. The results are being analyzed with the aim of testing the existence of supersymmmetric structures in nature. 2 figures.

  5. Cross section measurement for the (95)Mo(n, alpha)(92)Zr reaction at 4.0, 5.0 and 6.0MeV.

    PubMed

    Zhang, Guohui; Wu, Hao; Zhang, Jiaguo; Liu, Jiaming; Yin, Yuxiang; Chen, Jinxiang; Gledenov, Yu M; Sedysheva, M V; Khuukhenkhuu, G; Koehler, P E; Szalanski, P J

    2010-01-01

    Measurements of cross sections of the (95)Mo(n, alpha)(92)Zr reaction at E(n)=4.0, 5.0 and 6.0MeV were carried out at the 4.5MV Van de Graaff of Peking University, China. A twin gridded ionization chamber and two large-area (95)Mo samples were adopted. Fast neutrons were produced through the D(d, n)(3)He reaction by using a deuterium gas target. A small (238)U fission chamber was employed for absolute neutron flux determination. Present data are compared with existing evaluations and measurement. PMID:19811925

  6. 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.

  7. Cross sections of the {sup 67}Zn(n,{alpha}){sup 64}Ni reaction at 4.0, 5.0, and 6.0 MeV

    SciTech Connect

    Zhang Guohui; Liu Jiaming; Wu Hao; Liu Xiang; Chen Jinxiang; Gledenov, Yu. M.; Sedysheva, M. V.; Stolupin, V. A.; Khuukhenkhuu, G.; Szalanski, P. J.

    2010-11-15

    Experimental cross section data of the {sup 67}Zn(n,{alpha}){sup 64}Ni reaction are very scanty because the residual nucleus {sup 64}Ni is stable and the commonly used activation method is not feasible. As a result, very large deviations (about 10 times) exist among different nuclear data libraries. In the present work, cross sections of the partial {sup 67}Zn(n,{alpha}{sub 0}){sup 64}Ni and total {sup 67}Zn(n,{alpha}){sup 64}Ni reactions are measured at neutron energies of 4.0 and 5.0 MeV for the first time, and those of 6.0 MeV are remeasured for consistency checking. A twin-gridded ionization chamber was used as the charged-particle detector and two enriched back-to-back-set {sup 67}Zn samples were adopted. Experiments were performed at the 4.5 MV Van de Graaff Accelerator of Peking University. Neutrons were produced through the {sup 2}H(d,n){sup 3}He reaction using a deuterium gas target. Absolute neutron flux was determined by counting the fission fragments from a {sup 238}U sample placed inside the gridded ionization chamber while a BF{sub 3} long counter was employed as neutron flux monitor. Present data are compared with results of previous measurements, evaluations, and talys code calculations.

  8. The fluorine destruction in stars: First experimental study of the {sup 19}F(p,{alpha}){sup 16}O reaction at astrophysical energies

    SciTech Connect

    La Cognata, M.; Mukhamedzhanov, A.; Spitaleri, C.; Indelicato, I.; Aliotta, M.; Burjan, V.; Cherubini, S.; Coc, A.; Gulino, M.; Hons, Z.; Kiss, G. G.; Kroha, V.; Lamia, L.; Mrazek, J.; Palmerini, S.; Piskor, S.; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; and others

    2012-11-12

    The {sup 19}F(p,{alpha}){sup 16}O reaction is an important fluorine destruction channel in the proton-rich outer layers of asymptotic giant branch (AGB) stars and it might also play a role in hydrogendeficient post-AGB star nucleosynthesis. So far, available direct measurements do not reach the energy region of astrophysical interest (E{sub cm}{approx} 300 keV), because of the hindrance effect of the Coulomb barrier. The Trojan Horse (TH) method was thus used to access this energy region, by extracting the quasi-free contribution to the {sup 2}H({sup 19}F,{alpha}{sup 16}O)n reaction. The TH measurement of the {alpha}{sub 0} channel, which is the dominant one at such energies, shows the presence of resonant structures not observed before that cause an increase of the reaction rate at astrophysical temperatures up to a factor of 1.7, with potential important consequences for stellar nucleosynthesis.

  9. Cross Section Measurement for the 95Mo(n, {alpha})92Zr Reaction at 4.0, 5.0 and 6.0 MeV

    SciTech Connect

    Zhang, Guohui; Wu, Hao; Zhang, Jiaguo; Liu, Jiaming; Yin, Yuxiang; Chen, Jinxiang; Gledenov, Youri Mikhailovich; Sedysheva, M. V.; Khuukhenkhuu, G; Koehler, Paul Edward; Szalanski, P.

    2011-01-01

    For the {sup 95}Mo(n, {alpha}){sup 92}Zr reaction cross section, there is only one experimental datum in the MeV neutron energy region with large uncertainty. As a result, very large deviations exist in different evaluated nuclear data libraries. This paper report the measurement of cross sections of the {sup 95}Mo(n, {alpha}){sup 92}Zr reaction at En = 4.0, 5.0 and 6.0 MeV. Experiments were performed at the 4.5 MV Van de Graaff of Peking University, China. A twin gridded ionization chamber was used as alpha particle detector and two large area {sup 95}Mo samples placed back to back were adopted. Fast neutrons were produced through the D(d, n){sup 3}He reaction by using a deuterium gas target. A small {sup 238}U fission chamber was adopted for absolute neutron flux determination and a BF{sub 3} long counter was used for neutron flux monitor. Present experimental data are compared with existing evaluations and measurement.

  10. Observation of asymmetric fission of /sup 213/At in the reaction /sup 209/Bi (. cap alpha. ,f)

    SciTech Connect

    Gruzintsev, E.N.; Itkis, M.G.; Okolovich, V.N.; Rusanov, A.Y.; Smirenkin, G.N.; Tolstikov, V.N.

    1982-05-20

    The fragment mass distribution in the fission of the nucleus /sup 213/At by 36-MeV ..cap alpha.. particles is a bell-shaped curve Y/sub s/ (M) with a clearly expressed asymmetric admixture Y/sub ..cap alpha../ (M), for which the ratio of the yields at the peaks is Y/sup max//sub s//Y/sup max//sub ..cap alpha../ approx. = 2.5 x 10/sup 2/. This new type of fission of preactinide nuclei exhibits several of the properties typical of the asymmetric fission of heavy nuclei.

  11. Estimation of free energy barriers in the cytoplasmic and mitochondrial aspartate aminotransferase reactions probed by hydrogen-exchange kinetics of C alpha-labeled amino acids with solvent

    SciTech Connect

    Julin, D.A.; Wiesinger, H.; Toney, M.D.; Kirsch, J.F. )

    1989-05-02

    The existence of the postulated quinonoid intermediate in the cytoplasmic aspartate amino-transferase catalyzed transamination of aspartate to oxaloacetate was probed by determining the extent of transfer of tritium from the C alpha position of tritiated L-aspartate to pyridoxamine 5'-phosphate in single turnover experiments in which washout from the back-reaction was obviated by product trapping. The maximum amount of transferred tritium observed was 0.7%, consistent either with a mechanism in which a fraction of the net transamination reaction proceeds through a quinonoid intermediate or with a mechanism in which this intermediate is formed off the main reaction pathway. It is shown that transfer of labeled hydrogen from the amino acid to cofactor cannot be used to differentiate a stepwise from a concerted transamination mechanism. The amount of tritium transferred is a function of the rate constant for torsional equilibration about the epsilon-amino group of Lys-258, the presumptive abstractor of the C alpha proton; the relative rate constants for hydrogen exchange with solvent versus cofactor protonation; and the tritium isotope effect on this ratio. The free energy barriers facing the covalent intermediate between aldimine and keto acid product (i.e., ketimine and possibly quinonoid) were evaluated relatively by comparing the rates of C alpha-hydrogen exchange in starting amino acid with the rates of keto acid formation. The value of theta (= kexge/kprod) was found to be 2.6 for the reaction of cytoplasmic isozyme with aspartate and ca. 0.5 for that of the mitochondrial form with glutamate.

  12. Theoretical evaluation of the reaction rates for {sup 26}Al(n,p){sup 26}Mg and {sup 26}Al(n,{alpha}){sup 23}Na

    SciTech Connect

    Oginni, B. M.; Iliadis, C.; Champagne, A. E.

    2011-02-15

    The reactions that destroy {sup 26}Al in massive stars have significance in a number of astrophysical contexts. We evaluate the reaction rates of {sup 26}Al(n,p){sup 26}Mg and {sup 26}Al(n,{alpha}){sup 23}Na using cross sections obtained from the codes empire and talys. These have been compared to the published rates obtained from the non-smoker code and to some experimental data. We show that the results obtained from empire and talys are comparable to those from non-smoker. We also show how the theoretical results vary with respect to changes in the input parameters. Finally, we present recommended rates for these reactions using the available experimental data and our new theoretical results.

  13. Molecular beam epitaxy of free-standing wurtzite AlxGa1-xN layers

    NASA Astrophysics Data System (ADS)

    Novikov, S. V.; Staddon, C. R.; Martin, R. W.; Kent, A. J.; Foxon, C. T.

    2015-09-01

    Recent developments with group III nitrides present AlxGa1-xN based LEDs as realistic devices for new alternative deep ultra-violet light sources. Because there is a significant difference in the lattice parameters of GaN and AlN, AlxGa1-xN substrates would be preferable to either GaN or AlN for ultraviolet device applications. We have studied the growth of free-standing wurtzite AlxGa1-xN bulk crystals by plasma-assisted molecular beam epitaxy (PA-MBE). Thick wurtzite AlxGa1-xN films were grown by PA-MBE on 2-in. GaAs (111)B substrates and were removed from the GaAs substrate after growth to provide free standing AlxGa1-xN samples. X-ray microanalysis measurements confirm that the AlN fraction is uniform across the wafer and mass spectroscopy measurements show that the composition is also uniform in depth. We have demonstrated that free-standing wurtzite AlxGa1-xN wafers can be achieved by PA-MBE for a wide range of AlN fractions. In order to develop a commercially viable process for the growth of wurtzite AlxGa1-xN substrates, we have used a novel Riber plasma source and have demonstrated growth rates of GaN up to 1.8 μm/h on 2-in. diameter GaAs and sapphire wafers.

  14. 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.

  15. 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.

  16. 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. PMID:18374585

  17. High sensitivity boron quantification in bulk silicon using the {sup 11}B(p,{alpha}{sub 0}){sup 8}Be nuclear reaction

    SciTech Connect

    Moro, Marcos V.; Silva, Tiago F. da; Added, Nemitala; Rizutto, Marcia A.; Tabacniks, Manfredo H.; Neira, John B.; Neto, Joao B. F.

    2013-05-06

    There is a great need to quantify sub-ppm levels of boron in bulk silicon. There are several methods to analyze B in Si: Nuclear Reaction Analysis using the {sup 11}B(p,{alpha}{sub 0}){sup 8}Be reaction exhibits a quantification limit of some hundreds ppm of B in Si. Heavy Ion Elastic Recoil Detection Analysis offers a detection limit of 5 to 10 at. ppm. Secondary Ion Mass Spectrometry is the method of choice of the semiconductor industry for the analysis of B in Si. This work verifies the use of NRA to quantify B in Si, and the corresponding detection limits. Proton beam with 1.6 up to 2.6 MeV was used to obtain the cross-section of the {sup 11}B(p,{alpha}{sub 0}){sup 8}Be nuclear reaction at 170 Degree-Sign scattering angle. The results show good agreementwith literature indicating that the quantification of boron in silicon can be achieved at 100 ppm level (high sensitivity) at LAMFI-IFUSP with about 16% uncertainty. Increasing the detection solid angle and the collected beam charge, can reduce the detection limit to less than 100 ppm meeting present technological needs.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Electrospray ionization mass spectrometric investigations of [alpha]-dicarbonyl compounds--Probing intermediates formed in the course of the nonenzymatic browning reaction of l-ascorbic acid

    NASA Astrophysics Data System (ADS)

    Schulz, Anke; Trage, Claudia; Schwarz, Helmut; Kroh, Lothar W.

    2007-05-01

    A new method is presented which allows the simultaneous detection of various [alpha]-dicarbonyl compounds generated in the course of the nonenzymatic browning reaction initiated by thermal treatment of l-ascorbic acid, namely: glyoxal, methylglyoxal, diacetyl, 3-deoxy-l-pentosone, and l-threosoneE 3-Deoxy-l-threosone was successfully identified as a new C4-[alpha]-dicarbonyl structure for the first time in the degradation of Vitamin C by application of this non-chromatographic mass spectrometric approach. Moreover, a more detailed elucidation of the mechanistic scenario with respect to the oxidative and nonoxidative pathways is presented by using dehydro-l-ascorbic acid and 2,3-diketo-l-gulonic acid instead of l-ascorbic acid as a starting material. Furthermore, the postulated pathways are corroborated with the aid of 13C-isotopic labeling studies. The investigations were extended to baby food, and the successful detection of [alpha]-dicarbonyl compounds characteristic for Vitamin C degradation proved the matrix tolerance of the introduced method.

  4. Measurement of cross sections for the 147Sm(n, alpha)144Nd reaction at 5.0 and 6.0 MeV.

    PubMed

    Zhang, Guohui; Zhang, Jiaguo; Guo, Li'an; Wu, Hao; Chen, Jinxiang; Tang, Guoyou; Gledenov, Yu M; Sedysheva, M V; Khuukhenkhuu, G; Szalanski, P J

    2009-01-01

    Cross sections of the (147)Sm(n, alpha)(144)Nd reaction were measured at En=5.0 and 6.0MeV. A twin gridded ionization chamber was used as a charged particle detector and two large area (147)Sm(2)O(3) samples placed back to back were employed. Experiments were performed at the 4.5MV Van de Graaff accelerator of Peking University. Neutrons were produced through the D(d, n)(3)He reaction with a deuterium gas target. Absolute neutron flux was determined by a small (238)U fission chamber. Present cross-section data are compared with existing results of evaluations and measurements. PMID:18707895

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

    PubMed

    André, G; Tran, V

    2004-10-01

    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. PMID:15356864

  6. The effect of functional differences in the alpha and beta chains on the cooperativity of the osidation reduction reaction of hemoglobin.

    PubMed

    Edelstein, S J; Gibson, W H

    1975-02-10

    Partially oxidized solutions of hemoglobin have been reacted with azide to determine the extent of oxidation, of the alpha and beta chains according to the method of McQuarrie and Gibson (J. Biol. Chem. (1971) 246, 517-522) In 2, 2'2'' nitriloethanol buffer the fraction of oxidized material represented by the beta chains decreases with decreasing extent of total oxidation, of the alpha chains. Upon addition of insitol hexaphosphate, the degree of perferntial oxidation in terms of a two-state model similar to the description of oxygenation by Edelstein (nature(1971) 230, 224-227) but with the incorporation of chain heterogeneity. The results indicate that the pH-dependent cooperativity of the oxidation-reduction reaction can be described in terms of a bell curbe of n versus log l, the allosteric somewhat lower and shifted slightly to the left, due in part to an affnity of beta chains for electrons approximately twince that of alpha chains. Because the curve is shifted to the left, oxidation-reduction equilibria at l values corresponding to pH 6 to lie on the right side of the bell curve where cooperativity the preferntial affity of beta chains for electrons rises to about 4 times that of alpha chains. As a consequence, the coreesponding bell curve is lowered with the Hill coeficient falling to unity or below in the range of l encountered. Thus the principal cause of decreased cooperativity is chain heterogeneity and not stabilization in the t state as suggested by Perutz; under these conditions the molecules of methemoglobin in the t state are only a fractional part of the population. PMID:234445

  7. {gamma}-ray production by proton and {alpha}-particle induced reactions on {sup 12}C, {sup 16}O, {sup 24}Mg, and Fe

    SciTech Connect

    Belhout, A.; Kiener, J.; Coc, A.; Duprat, J.; Engrand, C.; Fitoussi, C.; Gounelle, M.; Lefebvre-Schuhl, A.; Sereville, N. de; Tatischeff, V.; Thibaud, J.-P.; Chabot, M.; Hammache, F.; Benhabiles-Mezhoud, H.

    2007-09-15

    {gamma}-ray production cross sections for proton and {alpha}-particle interactions with {sup 12}C, {sup 16}O, {sup 24}Mg, and Fe have been measured in the energy range 5-25 MeV with proton beams and 5-40 MeV with {alpha}-particle beams. Isotopically pure foils of {sup 24}Mg and foils of natural isotopical composition of C, MgO, and Fe have been used. {gamma}-ray angular distributions were obtained with five high-purity Ge detectors with bismuth germanate Compton shields placed at angles of 45 deg. to 157.5 deg. Cross sections for more than 50 different {gamma}-ray transitions were extracted, and for many of them no data have been published before. Comparison of present data with data available in the literature shows mostly good to excellent agreement. In addition to the production cross sections, high-statistics, low-background line shapes of the 4.438 MeV {sup 12}C {gamma} ray from inelastic scattering off {sup 12}C and spallation of {sup 16}O were obtained. Comparison with nuclear reaction calculations shows that these data place interesting constraints on nuclear reaction models.

  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. PMID:27016709

  9. 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.

  10. Excitation functions of alpha particle induced reactions on natTi up to 40 MeV

    NASA Astrophysics Data System (ADS)

    Uddin, M. S.; Scholten, B.

    2016-08-01

    Excitation functions of the reactions natTi(α,x)48Cr, natTi(α,x)48V and natTi(α,x)46,48Sc were determined by the stacked-foil activation technique up to 40 MeV. The radioactivities produced in the natTi target were measured by γ-ray spectrometry using HPGe detector. The reaction natTi(α,x)51Cr was used to determine the beam parameters. New experimental values for the above reactions have been obtained. An intercomparison of our data with the available literature values has been done. The cross section results obtained in this work could be useful in defining new monitor reactions, radiation safety and isotope production.

  11. 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/.

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

    SciTech Connect

    Patin, Joshua B.

    2002-05-24

    The study of the reactions between heavy ions and {sup 208}Pb, {sup 209}Bi, {sup 238}U, and {sup 248} 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 {sup 238}U({sup 18}O,xn){sup 256-x}Fm, {sup 238}U({sup 22}Ne,xn){sup 260-x}No, and {sup 248}Cm({sup 15}N,xn){sup 263-x}Lr 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 {sup 208}Pb({sup 48}Ca,xn){sup 256-x}No, {sup 208}Pb({sup 50}Ti,xn){sup 258-x}Rf, {sup 208}Pb({sup 51}V,xn){sup 259-x}Db, {sup 209}Bi({sup 50}Ti,xn){sup 259-x}Db, and {sup 209}Bi({sup 51}V,xn){sup 260-x}Sg 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.

  13. Rh(II)-catalyzed reaction of alpha-diazocarbonyl compounds bearing beta-trichloroacetylamino substituent: C-H insertion versus 1,2-H shift.

    PubMed

    Zhang, Zhenhua; Shi, Weifeng; Zhang, Jian; Zhang, Bo; Liu, Bingge; Liu, Yiyang; Fan, Bo; Xiao, Fengping; Xu, Feng; Wang, Jianbo

    2010-05-01

    The Rh(II)-carbene reaction is dramatically affected by the neighboring substituents. If the neighboring substituent is an OH group, a1,2-H shift is the exclusive pathway. If it is an OAc group, a 1,2-acetoxy migration is observed. If it is p-toluenesulfonyl group, 1,3 and 1,5-C-H insertion are the major pathways, and the 1,2-H shift is completely suppressed. If the adjacent substituent is a trichloroacetyl amino group, 1,5-C-H insertion competes with the 1,2-hydride shift, and no 1,3-C-H insertion can be observed. Both electronic and steric factors are responsible for the switching of the Rh(II)-carbene reaction pathway. The highly stereoselective 1,5-C-H insertions in Rh(II)-catalyzed reaction of alpha-diazocarbonyl compounds, bearing beta-trichloroacetylamino substituent, can be utilized as a novel way to synthesize five-membered cyclic beta-amino acid derivatives. PMID:20013998

  14. Comments on a peak of AlxGa1-xN observed by infrared reflectance

    NASA Astrophysics Data System (ADS)

    Marx, G.; Engelbrecht, J. A. A.; Lee, M. E.; Wagener, M. C.; Henry, A.

    2016-05-01

    AlxGa1-xN epilayers, grown on c-plane oriented sapphire substrates by metal organic chemical vapour deposition (MOCVD), were evaluated using FTIR infrared reflectance spectroscopy. A peak at ∼850 cm-1 in the reflectance spectra, not reported before, was observed. Possible origins for this peak are considered and discussed.

  15. 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

  16. Synthesis of the isotopes of elements 118 and 116 in the 249Cf and 245Cm+48Ca fusion reactions

    SciTech Connect

    Oganessian, Y T; Utyonkov, V K; Lobanov, Y V; Abdullin, F S; Polyakov, A N; Sagaidak, R N; Shirokovsky, I V; Tsyganov, Y S; Voinov, A A; Gulbekian, G G; Bogomolov, S L; Gikal, B N; Mezentsev, A N; Iliev, S; Subbotin, V G; Sukhov, A M; Subotic, K; Zagrebaev, V I; Vostokin, G K; Itkis, M G; Moody, K J; . Patin, J B; Shaughnessy, D A; Stoyer, M A; Stoyer, N J; Wilk, P A; Kenneally, J M; Landrum, J H; Wild, J F; Lougheed, R W

    2006-01-31

    The decay properties of {sup 290}116 and {sup 291}116, and the dependence of their production cross sections on the excitation energies of the compound nucleus, {sup 293}116, have been measured in the {sup 245}Cm({sup 48}Ca,xn){sup 293-x}116 reaction. These isotopes of element 116 are the decay daughters of element 118 isotopes, which are produced via the {sup 249}Cf+{sup 48}Ca reaction. They performed the element 118 experiment at two projectile energies, corresponding to {sup 297}118 compound nucleus excitation energies of E* = 29.2 {+-} 2.5 and 34.4 {+-} 2.3 MeV. During an irradiation with a total beam dose of 4.1 x 10{sup 19} {sup 48}Ca projectiles, three similar decay chains consisting of two or three consecutive {alpha} decays and terminated by a spontaneous fission (SF) with high total kinetic energy of about 230 MeV were observed. The three decay chains originated from the even-even isotope {sup 294}118 (E{sub {alpha}} = 11.65 {+-} 0.06 MeV, T{sub {alpha}} = 0.89{sub -0.31}{sup +1.07} ms) produced in the 3n-evaporation channel of the {sup 249}Cf+{sup 48}Ca reaction with a maximum cross section of 0.5{sub -0.3}{sup +1.6} pb.

  17. Astrophysical S(E) factor of the {sup 15}N(p,{alpha}){sup 12}C reaction at sub-Coulomb energies via the Trojan horse method

    SciTech Connect

    La Cognata, M.; Romano, S.; Spitaleri, C.; Cherubini, S.; Crucilla, V.; Gulino, M.; Lamia, L.; Pizzone, R. G.; Tumino, A.; Tribble, R.; Fu, Changbo; Goldberg, V. Z.; Mukhamedzhanov, A. M.; Schmidt, D.; Tabacaru, G.; Trache, L.; Irgaziev, B. F.

    2007-12-15

    The low-energy bare-nucleus cross section for {sup 15}N(p,{alpha}){sup 12}C is extracted by means of the Trojan horse method applied to the {sup 2}H({sup 15}N,{alpha}{sup 12}C)n reaction at E{sub beam}=60 MeV. For the first time we applied the modified half-off-energy-shell resonant R-matrix method that takes into account off-energy-shell effects and initial- and final-state interactions. In particular it has been shown that inclusion of Coulomb {sup 15}N-d scattering and off-shell effects do not affect the determination of the astrophysical factor. Also the simple plane-wave approximation used in previous analyses is justified. The results extracted via the Trojan horse method are compared to direct data in the same energy region and show very good agreement in the energy interval 70-312 keV. These results confirm the extrapolations of the S factor reported in literature.

  18. Measurement of the 58Ni(n,t)56Co, 59Co(n,p)59Fe, and 63Cu(n,{alpha})60Co Reaction Cross Sections from 14 to 20 MeV

    SciTech Connect

    Semkova, V.; Plompen, A.J.M.; Smith, D.L.

    2005-05-24

    Neutron activation cross sections for the 63Cu(n,{alpha})60Co, 59Co(n,p)59Fe, and 58Ni(n,t)56Co reactions were measured in the energy range from 13 to 21 MeV. The irradiations were carried out at the 7-MV Van de Graaff accelerator at IRMM, Geel. Quasi-monoenergetic neutrons were produced via the 3H(d,n)4He reaction at 1-, 2-, 3-, and 4-MeV incident deuteron energy. All reaction cross sections measured in the present work are referenced to the 27Al(n,{alpha})24Na standard reaction cross section. Neutron flux spectra were determined by an activation spectral index method in combination with TOF spectrum measurements. Standard {gamma}-ray spectrometry was employed for the measurement of radioactivity. The measured results are compared with work by other authors, TALYS-0.57 and EMPIRE-II model calculations, and current evaluated data files. The new results contribute substantially to the experimental database of the measured reactions. Recommendations are provided for the best evaluations for the 59Co(n,p)59Fe, and 63Cu(n,{alpha})60Co reactions. For the 58Ni(n,t)56Co reaction no current evaluation is in good agreement with all available data. For this reaction further measurements would help to guide new modeling efforts.

  19. 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}.

  20. 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.

  1. Selective alpha particle decay of 12C+12C resonances to excited 20Ne rotational bands observed in the 12C(12C,α)20Ne reaction

    NASA Astrophysics Data System (ADS)

    Ledoux, R. J.; Ordon¯Ez, C. E.; Bechara, M. J.; Al-Juwair, H. A.; Lavelle, G.; Cosman, E. R.

    1984-09-01

    Excitation functions of the 12C(12C,α)20Ne reaction were measured at θlab=7.5° between Ec.m.=14-40 MeV and angular distributions were measured from Ec.m.=17.8 to 20.6 MeV. Summed yields reveal prominent intermediate structure resonances over the entire range which correlate well to resonances previously observed in elastic data. The resonances show enhanced decays to excited rotational bands in 20Ne with reduced widths comparable to those for the elastic channel and an order of magnitude greater than those for the 20Ne ground state band. A discussion is given of the resonances as shape-isomeric states in a shell model secondary minimum in 24Mg, and of the selective alpha decay as being transitions to states of related configuration in 20Ne.

  2. 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.

  3. Paradoxical reactions induced by tumor necrosis factor-alpha antagonists: A literature review based on 46 cases.

    PubMed

    Olteanu, Rodica; Zota, Alexandra

    2016-01-01

    Anti-tumor necrosis factor (TNFα) agents have acquired a prominent place in the treatment options for inflammatory disorders. Among the side effects of these agents are the so-called paradoxical reactions which have increasingly been reported in recent years. A review of literature was carried out using Medline (PubMed) database from January 2010 to December 2014 to collect all published articles on cases of anti-TNFα-induced psoriasis and psoriatic arthritis. Published articles were identified, reviewed and the relevant data extracted. A total of 22 studies (46 patients) fulfilled the inclusion criteria and were selected for analysis. Of the 46 patients, 45 (97.8%) developed psoriasis and 1 (2.1%) psoriatic arthritis. The mean age of patients was 47 years; three (6.5%) patients had a past history of psoriasis. Infliximab caused cutaneous reactions in the most number, 26 (56.5%) cases. Thirty seven (80.4%). patients developed primary plaque-type psoriasis. Women accounted for 86.9% of patients. There was complete resolution of psoriasis in 12 (26%) patients despite differences in the therapeutic approach. Cessation of the incriminated drug led to resolution of cutaneous lesions in 5 (10.8%), switching to another TNFα antagonist led to resolution in 6 (13%) and one (2.1%) patient improved despite continuation of the drug. As for the lone case of psoriatic arthritis, drug withdrawal did not result in improvement; only switching to another anti-TNFα agent helped. Since our sample was small, it was not adequately powered to draw any firm conclusions. However, in this analysis, we found that paradoxical reactions occurred predominantly in adult women, there were only isolated cases with a personal history of psoriasis, infliximab was responsible for most cases of these reactions and the most prevalent form was plaque-type psoriasis. The decision whether to continue or discontinue the triggering anti-TNFα agent should be individualized as results are highly variable

  4. Reactions of Vinyl Groups on a Model Chromia Surface: Vinyl Chloride on Stoichiometric Alpha-Cr2O3 (1012)

    SciTech Connect

    McKee, M.; Ma, Q; Mullins, D; Neurock, M; Cox, D

    2009-01-01

    The thermal reaction of vinyl chloride on nearly-stoichiometric ?-Cr2O3 View the MathML source produces gas phase acetylene, ethylene, 1,3-butadiene, and dihydrogen, and results in the deposition of chlorine adatoms. No surface carbon or combustion products (CO, CO2, H2O) are observed. Thermal desorption and spectroscopic studies indicate that the surface reaction of vinyl chloride proceeds through C-Cl bond cleavage to form Cl adatoms and surface vinyl groups which dehydrogenate to acetylene, hydrogenate to ethylene, and couple to form butadiene. Cl adatoms affect surface reactivity in two ways: (1) by increasing the barrier to vinyl dehydrogenation from 145 to 160 kJ/mol, and (2) by blocking Cr3+ sites which shuts down the surface chemistry. Selectivity to butadiene is dependent on Cl adatom coverage, where the increased stability of vinyl intermediates at lower Cl coverages gives rise to more butadiene coupling product. At higher Cl coverages, Cl appears to inhibit the mobility of surface vinyl and decreases the reaction probability for coupling. Photoemission and near edge X-ray absorption fine structure (NEXAFS) spectra show that a mixed monolayer of molecular and dissociated vinyl chloride is formed at 130 K. The polarization dependence of the NEXAFS indicates that vinyl chloride ?-bonds with the molecular plane nominally parallel to the surface, while vinyl intermediates ?-bond at Cr centers with the molecular plane nominally perpendicular to the surface, in agreement with DFT predictions of the adsorption geometries.

  5. 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. PMID:25976524

  6. 2,4,6-Trihydroxy-alpha-p-methoxyphenylacetophenone (Compound D-58) is a potent inhibitor of allergic reactions.

    PubMed

    Malaviya, R; Vassilev, A; Uckun, F M

    2001-01-01

    The authors investigated the effects of 2,4,6-trihydroxy-alpha-p-methoxyphenylacetophenone (compound D-58), a potent inhibitor of protein tyrosine kinases SYK and Bruton's tyrosine kinase (BTK), on IgE receptor/FcepsilonRI-triggered mast cell-mediated acute allergic responses in vitro and in vivo. Compound D-58 abrogated IgE receptor/FcepsilonRI-mediated SYK and BTK activation as well as calcium mobilization in mast cells. Mast-cell degranulation and leukotriene (LT) C(4) release was inhibited by compound D-58 in a concentration-dependent fashion. Notably, compound D-58 prevented the mast cell mediator-induced vascular hyperpermeability in an in vivo murine model of passive cutaneous anaphylaxis as measured by the prevention of extravasation of systemically administered Evans blue dye. The results uniquely indicate that compound D-58 has potent antiallergic properties. Therefore, further development of compound D-58 may provide the basis for new and effective treatment programs for severe allergic disorders. PMID:11704780

  7. Studies of reaction variables for lipase-catalyzed production of alpha-linolenic acid enriched structured lipid and oxidative stability with antioxidants.

    PubMed

    Mitra, Kanika; Shin, Jung-Ah; Lee, Jeung-Hee; Kim, Seong-Ai; Hong, Soon-Taek; Sung, Chang-Keun; Xue, Cheng Lian; Lee, Ki-Teak

    2012-01-01

    Alpha-linolenic acid (ALA) enriched structured lipid (SL) was produced by lipase-catalyzed interesterification from perilla oil (PO) and corn oil (CO). The effects of different reaction conditions (substrate molar ratio [PO/CO 1:1 to 1:3], reaction time [0 to 24 h], and reaction temperature [55 to 65 °C]) were studied. Lipozyme RM IM from Rhizomucor miehei was used as biocatalyst. We obtained 32.39% of ALA in SL obtained under the optimized conditions (molar ratio-1:1 [PO:CO], temperature-60 °C, reaction time-15 h). In SL, the major triacylglycerol (TAG) species (linolenoyl-linolenoyl-linolenoyl glycerol [LnLnLn], linolenoyl-linolenoyl-linoleoyl glycerol [LnLnL]) mainly from PO and linoleoyl-linoleoyl-oleoyl glycerol (LLO), linoleoyl-oleoyl-oleoyl glycerol (LOO), palmitoyl-linoleoyl-oleoyl glycerol (PLO) from CO decreased while linolenoyl-linolenoyl-oleoyl glycerol (LnLnO) (18.41%), trilinolein (LLL) (9.06%), LLO (16.66%), palmitoyl-linoleoyl-linoleoyl glycerol (PLL) (9.69%) were increased compared to that of physical blend. Total tocopherol content (28.01 mg/100 g), saponification value (SV) (192.2), and iodine value (IV) (161.9) were obtained. Furthermore, oxidative stability of the SL was also investigated by addition of 3 different antioxidants (each 200 ppm of rosemary extract [SL-ROS], BHT [SL-BHT], catechin [SL-CAT]) was added into SL and stored in 60 °C oven for 30 d. 2-Thiobabituric acid-reactive substances (TBARS) value was 0.16 mg/kg in SL-CAT and 0.18 mg/kg in SL-ROS as compared with 0.22 mg/kg in control (SL) after oxidation. The lowest peroxide value (POV, 200.9 meq/kg) and longest induction time (29.88 h) was also observed in SL-CAT. PMID:22122200

  8. 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

  9. Ab initio alpha-alpha scattering.

    PubMed

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

    2015-12-01

    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

  10. FLUORINE-18 Production for PET and AN Investigation of the FLUORINE-18(P, ALPHA)OXYGEN-15 Reaction with a Radioactive Beam.

    NASA Astrophysics Data System (ADS)

    Roberts, Andrew David

    1995-01-01

    Improved methods for the production of ^{18}F have been developed. The isotope, a beta^{+} emitter with a 110 min half-life, serves a vital role in positron emission tomography (PET), and more recently has become important in the emerging field of a radioactive beam development for nuclear reaction studies. Aside from increasing some PET radiopharmaceutical yields by factors of 2-20, the present work made possible a factor of 10 ^3-10^4 improvement in ^{18}F ion beam intensity over previously published methods. ^{18}F production targetry was developed for an 11.4 MeV, 6-8 mm FWHM, 50 muA proton beam from the UW cyclotron. Nucleophilic aqueous (^ {18}F) fluoride is produced via the ^{18}O(p,n)^ {18}F reaction on an enriched ( ^{18}O) water target. The target yield is (80 +/- 15)% of the theoretical maximum for beam currents up to 40 muA, with the highest yield to date of 70 GBq. Gas targets for the production of electrophilic (^ {18}F] F_2 were developed with a saturation bombardment yield of 3.10 +/- 0.40 GBq/muA for beam currents up to 45 muA, and a maximum yield to date of 45.5 GBq. The ^{18} F in either form has important applications in the labeling of PET radiopharmaceuticals, and the applicability of each to radioactive beam technology has been investigated. An ^{18}F ion beam was generated by a dual-accelerator method incorporating off-line chemical separation. ^ {18}F was produced on the UW radioisotope production cyclotron, then delivered to Argonne National Laboratory (ANL) for beam formation on the tandem accelerator on ATLAS. An average ^{18}F ^{-} beam intensity of 1ppA was achieved from a cesium vapor, sputter negative ion source (SNICS) with a peak intensity of 4.5 ppA. This was sufficient to allow direct measurements of the ^{18}F(p,alpha) ^{15}O reaction cross section at energies of astrophysical interest. Cyclotron targetry studies, radioactive beam production techniques and results from the ^{18 }F(p,alpha)^ {15}O experiment are presented.

  11. 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.

  12. Evidence for alpha-cluster condensation in the 0{sub 2}{sup +} state at E{sub x} = 7.654 MeV in {sup 12}C via the (p,p') reaction at 300 MeV

    SciTech Connect

    Okamoto, A.; Yamagata, T.; Akimune, H.; Hara, K. Y.; Kinoshita, M.; Utsunomiya, H.; Warashina, N.; Fujiwara, M.; Fushimi, K.; Hayami, R.; Nakayama, S.; Greenfield, M. B.; Hara, K.; Hashimoto, H.; Kawase, K.; Nakanishi, N.; Yosoi, M.; Hirabayashi, H.; Tanaka, M.

    2010-06-01

    We measured the differential cross sections for the 0{sub 2}{sup +} state at E{sub x} = 7.654 MeV in {sup 12}C via the (p,p') reaction at an incident energy of 300 MeV, and in an angular range from 2.7 deg. to 40 deg. We analyzed the data with the distorted-wave Born-approximation (DWBA) employing transition densities obtained in a macroscopic collective model, a microscopic alpha-cluster model, and a microscopic alpha-cluster condensation model. It is concluded that the present results for the {sup 12}C(p,p') reaction at 300 MeV is quite consistent with the assumption that the 0{sub 2}{sup +} state at E{sub x} = 7.654 MeV has the wave function with the alpha-cluster condensation.

  13. Reactions of vinyl groups on a model chromia surface: vinyl chloride on stoichiometric alpha-Cr2O3 (101-2) .

    SciTech Connect

    Mullins, David R; McKee, Mary M.; MA, Qiang; Cox, David F.; Neurock, Matthew

    2009-01-01

    The thermal reaction of vinyl chloride on nearly-stoichiometric {alpha}-Cr{sub 2}O{sub 3}{sub (10{bar 1}2)} produces gas phase acetylene, ethylene, 1,3-butadiene, and dihydrogen, and results in the deposition of chlorine adatoms. No surface carbon or combustion products (CO, CO{sub 2}, H{sub 2}O) are observed. Thermal desorption and spectroscopic studies indicate that the surface reaction of vinyl chloride proceeds through C-Cl bond cleavage to form Cl adatoms and surface vinyl groups which dehydrogenate to acetylene, hydrogenate to ethylene, and couple to form butadiene. Cl adatoms affect surface reactivity in two ways: (1) by increasing the barrier to vinyl dehydrogenation from 145 to 160 kJ/mol, and (2) by blocking Cr{sup 3+} sites which shuts down the surface chemistry. Selectivity to butadiene is dependent on Cl adatom coverage, where the increased stability of vinyl intermediates at lower Cl coverages gives rise to more butadiene coupling product. At higher Cl coverages, Cl appears to inhibit the mobility of surface vinyl and decreases the reaction probability for coupling. Photoemission and near edge X-ray absorption fine structure (NEXAFS) spectra show that a mixed monolayer of molecular and dissociated vinyl chloride is formed at 130 K. The polarization dependence of the NEXAFS indicates that vinyl chloride {pi}-bonds with the molecular plane nominally parallel to the surface, while vinyl intermediates {sigma}-bond at Cr centers with the molecular plane nominally perpendicular to the surface, in agreement with DFT predictions of the adsorption geometries.

  14. 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

  15. 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

  16. Production of the doubly magic nucleus Sn100 in fusion and quasifission reactions via light particle and cluster emission channels

    NASA Astrophysics Data System (ADS)

    Kalandarov, Sh. A.; Adamian, G. G.; Antonenko, N. V.; Wieleczko, J. P.

    2014-08-01

    The possibilities of production of the doubly magic nucleus Sn100 in complete fusion and quasifission reactions with stable and radioactive ion beams are investigated within a dinuclear system model. The excitation functions for production of the exotic nuclei 100-103Sn and 112,114Ba via xn, pxn, αxn, and 12,14Cxn emission channels are predicted for future experiments.

  17. Band gap bowing and electron localization of (GaxIn1-x)N

    SciTech Connect

    Lee, Byounghak; Wang, Lin-Wang

    2006-05-09

    The band gap bowing and the electron localization ofGaxIn1-xN are calculated using both the local density approximation (LDA)and screened-exchange local density functional (sX-LDA) methods. Thecalculated sX-LDA band gaps are in good agreement with the experimentallyobserved values, with errors of -0.26 and 0.09 eV for bulk GaN and InN,respectively. The LDA band gap errors are 1.33 and 0.81 eV for GaN andInN, in order. In contrast to the gap itself, the band gap bowingparameter is found to be very similar in sX-LDA and LDA. We identify thelocalization of hole states in GaxIn1-xN alloys along In-N-In chains. Thepredicted localizationis stronger in sX-LDA.

  18. Production possibility of 60,61,62Cu radioisotopes by alpha induced reactions on cobalt for PET studies

    NASA Astrophysics Data System (ADS)

    Szelecsényi, Ferenc; Suzuki, Kazutoshi; Kovács, Zoltán; Takei, Makoto; Okada, Kazuhiro

    2002-02-01

    Excitation functions were measured by the stacked-foil technique for 59Co( α, n) 62Cu, 59Co( α,2 n) 61Cu and 59Co( α,3 n) 60Cu nuclear reactions up to 60 MeV. The excitation functions were compared with the published data. The optimum energy range for the production of 61Cu and 62Cu was found to be 39 → 18 and 18.5 → 6 MeV, respectively. The calculated thick target yield of 61Cu in this energy range was 21.0 mCi/ μA (supposing one half-life activation time); and 16.2 mCi/ μA (supposing three half-life activation time) for 62Cu. The level of 60Cu and 62Cu impurities at 61Cu production decreases to around 1% after a 1 h cooling time. The practical yield in this case is 17.2 mCi/ μA. For production of 62Cu the contamination level of 61Cu increases continuously after EOB, but remains below 1% if the cooling time is less than 0.5 h ( 1.9 mCi/ μA at 0.5 h after EOB). Unfortunately, in the case of 60Cu production, the contamination level of 61Cu and 62Cu at EOB was found to be 18.4% and 47.9%, respectively, of the produced 60Cu activity ( 6.4 mCi/ μA, after 60 min irradiation time, in the energy interval 60 → 44 MeV).

  19. OPTICAL PROPERTIES OF THE CUBIC AlxGa1-xN ALLOY

    NASA Astrophysics Data System (ADS)

    Hadji, S.; Berrah, S.; Abid, H.

    2013-07-01

    In this paper, we present numerical calculations based on the full potential augmented plane wave (FP-LAPW) method within the local density approximation (LDA) to study the optical properties of the ternary alloy AlxGa1-xN. The shape of the dielectric function, the refractive index, and the absorption coefficient versus photon energy were presented. From the results, we deduce the possibility of this alloy to be used in the optoelectronic and photovololtaic area.

  20. Structure and electronic properties of conducting, ternary TixTa1-xN films

    NASA Astrophysics Data System (ADS)

    Matenoglou, G. M.; Lekka, Ch. E.; Koutsokeras, L. E.; Karras, G.; Kosmidis, C.; Evangelakis, G. A.; Patsalas, P.

    2009-05-01

    We report on the electronic structure and optical properties of conducting ternary transition metal nitrides consisting of metals of different groups of the periodic table of elements. For the study of the bonding, electronic structure, and optical properties of conducting TixTa1-xN film growth, optical spectroscopy and ab initio calculations were used. Despite the different valence electron configuration of the constituent elements, Ta(d3s2) and Ti(d2s2), we show that TiN and TaN are completely soluble due to the hybridization of the d and sp electrons of the metals and N, respectively, that stabilizes the ternary TixTa1-xN systems to the rocksalt structure. The optical properties of TixTa1-xN have been studied using spectroscopic methods and detailed electronic structure calculations, revealing that the plasma energy of the fully dense TixTa1-xN is varying between 7.8 and 9.45 eV. Additional optical absorption bands are manifested due to the N p →Ti/Ta d interband transition the t2g→eg transition due to splitting of the metals' d band, with the major exception of the Ti0.50Ta0.50N, where the eg unoccupied states are not manifested due to the local structure of the ternary system; this finding is observed for the first time and proves previous assignments of optical transitions in TaN.

  1. Tunnel optical radiation in InxGa1-xN

    NASA Astrophysics Data System (ADS)

    Alexandrov, Dimiter; Skerget, Shawn

    2014-02-01

    An investigation of tunnel optical radiation in epitaxial layers of n-type InxGa1-xN grown on p-type GaN by novel plasma based migration enhanced epitaxy is presented. Experimental results of electro-luminescence spectra for InxGa1-xN/p-GaN hetero-junctions were obtained and they show two well expressed optical bands - one in range 500-540 nm and other in range 550-610 nm. An interesting detail is that each band begins and ends by sharp drops of the radiation, which nearly approach zero. A theoretical investigation of the unusual behavior of these spectra was done using LCAO electron band structure calculations. The optical ranges of these bands show that the radiation occurs in the InxGa1-xN region. In fact, substitutions of In atoms in Ga sites creates defects in the structure of InxGa1-xN and the corresponding LCAO matrix elements are found on this basis. The LCAO electron band structures are calculated considering the interactions between nearest-neighbor orbitals. Electron energy pockets are found in both the conduction and the valence bands at the Γ point of the electron band structures. Also it is found that these pockets are separated by distances, for which there is overlapping between the electron wave functions describing localized states belonging to the pockets, and as a result tunnel optical radiation can take place. This type of electron transition - between such a pocket in the conduction band and a pocket in the valence band - occurs in InxGa1-xN, causing the above described optical bands. This conclusion concurs with the fact that the shapes of these bands change with change of the applied voltage.

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

    DOE PAGESBeta

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

    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

  3. Creep and precipitation behaviors of AL6XN austenitic steel at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Meng, L. J.; Sun, J.; Xing, H.

    2012-08-01

    Creep behaviors of the solution-treated AL6XN austenitic stainless steel have been investigated at 873-1023 K and 120-260 MPa. The results showed that the creep stress exponent and activation energy of the AL6XN steel are 5 and 395.4 kJ/mol, respectively in the power-law breakdown regime. TEM observations revealed that dislocations distributed homogenously in grains. The creep deformation mechanism is mainly attributed to viscous dislocation glide. Precipitates in the steel after creep deformation were additionally analyzed by TEM, and the results showed that there are four different types of precipitates, such as M23C6, M6C, σ phase and Laves phase. The M23C6 carbides were observed at grain boundaries in the steel after creep at 873 K. The M6C, σ phase and Laves phase precipitates were found when the creep temperature increases to 923-1023 K. Although the AL6XN steel exhibited low steady state creep rates, a high volume fraction of brittle precipitates of σ and Laves phases reduced the creep lifetime of the steel at elevated temperatures.

  4. Modulation of adhesion molecule expression on endothelial cells during the late asthmatic reaction: role of macrophage-derived tumour necrosis factor-alpha.

    PubMed Central

    Lassalle, P; Gosset, P; Delneste, Y; Tsicopoulos, A; Capron, A; Joseph, M; Tonnel, A B

    1993-01-01

    In a previous work we have demonstrated that in patients exhibiting a late allergic reaction (LAR), alveolar macrophages (AM) collected 18 h after bronchial allergen challenge produced high levels of IL-6 and tumour necrosis factor-alpha (TNF) which is known to up-regulate the endothelial cell expression of adhesion molecules participating in the development of the inflammatory reaction in bronchial asthma. For these reasons, we evaluated the effect of AM supernatants from asthmatic patients developing an LAR on intercellular adhesion molecule-1 (ICAM-1) and endothelial leucocyte adhesion molecule-1 (ELAM-1) expression by human endothelial cells. The expression of adhesion molecules was assessed by an ELISA method and compared with the effect of an optimal dose of human recombinant (hr) TNF. Results showed that AM supernatants, from challenged asthmatics developing an LAR, increased significantly the ICAM-1 and ELAM-1 expression on endothelial cells to a level similar to that obtained in the presence of hrTNF (500 U/ml) (P < 0.001 in both cases, respectively 90.4% and 75.2% of the level obtained with hrTNF). In contrast, AM supernatants from asthmatics at baseline or exhibiting, after challenge, a single early reaction had no significant effect on these parameters (P = NS in both cases, respectively 23.5% and 24.7% of the ICAM-1 expression, 22.7% and 15.3% of the ELAM-1 expression obtained with hrTNF). AM-derived TNF present in these supernatants was thought to play a key role in endothelial cell stimulation, since: (i) TNF concentration in AM supernatants correlated with its effect on ICAM-1 (r = 0.80, P < 10(-4)) and ELAM-1 expression (r = 0.88, P < 10(-5)); and (ii) a neutralizing anti-TNF antibody decreased their effect (68% and 80% respectively on ICAM-1 and ELAM-1 expression). Moreover, the role of IL-6 was excluded on the basis both of the hrIL-6 inefficiency to induce ICAM-1 and ELAM-1 synthesis, even in costimulation with hrTNF, and of anti-IL-6 antibody

  5. Inclusive cross-sections of (p,xp) and (p,x{alpha}) reactions on {sup 56}Fe at E{sub p}=29.9 MeV

    SciTech Connect

    Duisebayev, A.; Ismailov, K.M.; Boztosun, I.

    2005-11-01

    In this paper, we present new experimental data measured at E{sub p}= 29.9 MeV for the inclusive reactions (p,xp) and (p,x{alpha}) on nucleus {sup 56}Fe. We investigate the adequacy of the theoretical models in explaining the measured experimental data, and we determine the contributions of multistep direct and multistep compound processes in the formation of the cross-sections. We show that the traditional frameworks are valid for the description of the new experimental data, and our measurements agree with previous measurements for the (p,xp) and (p,x{alpha}) reactions on the {sup 54}Fe nucleus. The only exception is within the energy region of E{sub p}= 15 and 25 MeV for both reactions, where the cross-section for the {sup 56}Fe nucleus is smaller than the cross-section for the {sup 54}Fe nucleus.

  6. 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

  7. SYNTHESIS OF ALPHA-AMINO GAMMA-LACTONE VIA A NOVEL TANDEM THREE-COMPONENT REACTION OF ALKENES, GLYOXYLATES AND AMINES. (R822668)

    EPA Science Inventory

    Abstract

    alpha.gif" alt="small alpha, Greek" border=0>-Amino small gamma, Greek-lactones were generated by an InCl3...

  8. 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. PMID:18468910

  9. Strong enhancement of piezoelectric constants in ScxAl1-xN: First-principles calculations

    NASA Astrophysics Data System (ADS)

    Momida, Hiroyoshi; Teshigahara, Akihiko; Oguchi, Tamio

    2016-06-01

    We theoretically investigate the piezoelectricity of ScxAl1-xN in the entire range of x by first-principles calculations. We find that the piezoelectric constants of wurtzite-type ScxAl1-xN significantly enhance as x increases from 0 to 0.75. However, the energy stability analyses between structure phases show that the cubic-type phases become more stable than the wurtzite-type phases at x of approximately 0.5 and higher, interfering with the ability of wurtzite-type ScxAl1-xN to realize the maximum piezoelectricity. Moreover, our study on element combination dependences on piezoelectricity in A0.5B0.5N (A = Sc, Y, La and B = Al, Ga, In) indicates that Sc, Y, and La have the strongest effect on the enhancement of piezoelectric constants in AlN, GaN, and InN, respectively.

  10. Measurement of the 4. 8-MeV /sup 9/B state width by the reaction /sup 10/B(/sup 3/He,. cap alpha. )/sup 9/B(. cap alpha. ) /sup 5/Li at E( /sup 3/He) = 2. 3 and 5. 0 MeV

    SciTech Connect

    Arena, N.; Cavallaro, S.; Fazio, G.; Giardina, G.; Italiano, A.; Mezzanares, F.

    1986-10-13

    The analog of the 4.7-MeV state of the /sup 9/Be nucleus has been observed in its mirror /sup 9/B by the reaction /sup 10/B(/sup 3/He, ..cap alpha..)/sup 9/B(..cap alpha..) /sup 5/Li (g.s.) at E( /sup 3/He) = 2.3 and 5.0 MeV. The excitation energy and width of the state have been deduced. The value of 1.5 +- 0.3 MeV found for the width is in line with the value deduced by the reaction /sup 7/Li(/sup 3/He,n) /sup 9/B, but it is larger by a factor of about 4 than the one measured by the proton following the ..beta../sup +/ decay of the /sup 9/C nucleus.

  11. Alpha Particle

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    Term that is sometimes used to describe a helium nucleus, a positively charged particle that consists of two protons and two neutrons, bound together. Alpha particles, which were discovered by Ernest Rutherford (1871-1937) in 1898, are emitted by atomic nuclei that are undergoing alpha radioactivity. During this process, an unstable heavy nucleus spontaneously emits an alpha particle and transmut...

  12. 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.

  13. 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}.

  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. Binding of tumor necrosis factor alpha to activated forms of human plasma alpha 2 macroglobulin.

    PubMed Central

    Wollenberg, G. K.; LaMarre, J.; Rosendal, S.; Gonias, S. L.; Hayes, M. A.

    1991-01-01

    We tested the hypothesis that human plasma alpha 2 macroglobulin (alpha 2M) is a latent binding glycoprotein for human tumor necrosis factor alpha (TNF-alpha). Human recombinant 125I-TNF-alpha was incubated for 2 hours (37 degrees C) with purified native alpha 2M and with alpha 2M that was modified by reaction with methylamine or various proteinases. 125I-TNF-alpha/alpha 2M complexes were detected by nondenaturing polyacrylamide gel electrophoresis after autoradiography or by liquid chromatography on Superose-6. 125I-TNF-alpha bound strongly but noncovalently to alpha 2M-plasmin and alpha 2M-methylamine. There was minimal binding of 125I-TNF-alpha to native alpha 2M, alpha 2M-trypsin, or alpha 2M-thrombin. A 10(6) molar excess of porcine heparin did not reduce the binding of 125I-TNF-alpha to alpha 2M-methylamine or alpha 2M-plasmin. alpha 2M-plasmin or alpha 2M-methylamine added to human plasma or serum preferentially bound 125I-TNF-alpha in the presence of native alpha 2M. 125I-TNF-alpha also bound to 'fast' alpha-macroglobulins in methylamine-reacted human, rat, mouse, swine, equine, and bovine plasma. However, TNF-alpha, preincubated with either alpha 2M-plasmin or alpha 2M-methylamine, remained a potent necrogen for cultured L929 cells. Purified 125I-TNF-alpha/alpha 2M-plasmin complex injected intravenously in CD-1 mice rapidly cleared from the circulation, unless the alpha 2M-receptor pathway was blocked by coinjection of excess alpha 2M-trypsin. These findings demonstrate that alpha 2M is a latent plasmin-activated binding glycoprotein for TNF-alpha and that TNF-alpha/alpha 2M-plasmin complexes can be removed from the circulation by the alpha 2M-receptor pathway. This suggests that alpha 2M may be an important regulator of the activity and distribution of TNF-alpha in vivo. Images Figure 1 Figure 3 PMID:1704186

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

    DOE PAGESBeta

    Sands, Timothy D.; Stach, Eric A.; Saha, Bivas; Saber, Sammy; Naik, Gururaj V.; Boltasseva, Alexandra; Kvam, Eric P.

    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

  17. 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.

  18. High accuracy {sup 18}O(p,{alpha}){sup 15}N reaction rate in the 8{center_dot}10{sup 6}-5{center_dot}10{sup 9} K temperature range

    SciTech Connect

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

    2011-10-28

    The {sup 18}O(p,{alpha}){sup 15}N reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as {sup 19}F, {sup 18}O and {sup 15}N. In this work, a high accuracy {sup 18}O(p,{alpha}){sup 15}N reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. In particular, we have focused on the study of the broad 660 keV 1/2{sup +} resonance. Since {Gamma}{approx}100-300 keV, it strongly influences the nearly-zero-energy region of the cross section by means of the low-energy tail of the resonant contribution and dominates the cross section at higher energies. Here we provide a factor of 2 larger reaction rate above T{approx}0.5 10{sup 9} K based over our new improved determination of its resonance parameters.

  19. AlxGa1-xN materials and device technology for solar blind ultraviolet photodetector applications

    NASA Astrophysics Data System (ADS)

    McClintock, Ryan; Sandvik, Peter M.; Mi, Kan; Shahedipour, Fatemeh; Yasan, Alireza; Jelen, Christopher L.; Kung, Patrick; Razeghi, Manijeh

    2001-06-01

    There has been a growing interest for the development of solar blind ultraviolet (UV) photodetectors for use in a variety of applications, including early missile threat warning, flame monitoring, UV radiation monitoring and chemical/biological reagent detection. The AlxGa1-xN material system has emerged as the most promising approach for such devices. However, the control of the material quality and the device technology are still rather immature. We report here the metalorganic chemical vapor deposition, the n-type and the p-type doping of high quality AlxGa1-xN thin films on sapphire substrates over a wide range of Al concentration. The quality of this AlxGa1-xN material was verified through the demonstration of high performance visible and solar blind ultraviolet p-i-n photodiodes with a cut-off wavelength continuously tunable from 227 to 365 nm, internal quantum efficiencies up to 86% when operated in photovoltaic mode, and a ultraviolet-to-visible rejection ratio as high as six orders of magnitude. Both front and back side illuminated p-i-n photodiodes were realized. Photodetector devices were also demonstrated on GaN material obtained using lateral epitaxial overgrowth. The technology for such AlxGa1-xN based devices was improved in an effort to enhance their performance, including the development of ohmic metal contacts to both n-type and p-type AlxGa1-xN films with an Al concentration up to 40%.

  20. Isomeric yield ratios of 87m,gY from different nuclear reactions

    NASA Astrophysics Data System (ADS)

    Naik, H.; Kim, G. N.; Kim, K.; Zaman, M.; Sahid, M.; Yang, S.-C.; Lee, M. W.; Kang, Y. R.; Shin, S. G.; Cho, M.-H.; Goswami, A.; Song, T. Y.

    2014-07-01

    The independent isomeric yield ratios of 87m,gY produced from the 93Nb( γ, α2n) and natZr( γ, p xn) reactions with the end-point bremsstrahlung energy of 45-70 MeV have been determined by an off-line γ-ray spectrometric technique using 100 MeV electron linac at the Pohang accelerator laboratory, Korea. The isomeric yield ratios of 87m,gY were also determined from the natZr(p, αxn) and the 89Y(p,p2n) reactions with E P = 15-45 MeV as well as those from the 89Y( α, α2n) reaction with E α = 32-43 MeV using the MC-50 cyclotron at the Korea Institute of Radiological and Medical Science, Korea. The isomeric yield ratios of 87m,gY from the present work in the 93Nb( γ, α2n), natZr( γ, p xn), natZr(p, αxn), 89Y(p,p2n), and 89Y( α, α2n) reactions were compared with those of the literature data in the 85Rb( α, 2n), the 86,87,88Sr(d, xn), 89Y(n,3n), and the 89Y( γ, 2n) reactions to examine the role of target, projectiles, and ejectiles through compound nucleus excitation energy and input angular momentum. The isomeric yield ratios of 87m,gY in the above eleven reactions were also calculated using the computer code TALYS 1.4 and compared with the experimental data. The different behaviors between photon- and neutron-induced reactions and charged-particle-induced reactions are discussed from the viewpoint of compound and non-compound (pre-equilibrium) process.

  1. Origin of background electron concentration in InxGa1-xN alloys

    NASA Astrophysics Data System (ADS)

    Pantha, B. N.; Wang, H.; Khan, N.; Lin, J. Y.; Jiang, H. X.

    2011-08-01

    The origin of high background electron concentration (n) in InxGa1-xN alloys has been investigated. A shallow donor was identified as having an energy level (ED1) that decreases with x (ED1 = 16 meV at x = 0 and ED1 = 0 eV at x ˜ 0.5) and that crossover the conduction band at x ˜ 0.5. This shallow donor is believed to be the most probable cause of high n in InGaN. This understanding is consistent with the fact that n increases sharply with an increase in x and becomes constant for x > 0.5. A continuous reduction in n was obtained by increasing the V/III ratio during the epilayer growth, suggesting that nitrogen vacancy-related impurities are a potential cause of the shallow donors and high background electron concentration in InGaN.

  2. Origin of background electron concentration in InxGa1-xN alloys

    DOE PAGESBeta

    Pantha, B. N.; Wang, H.; Khan, N.; Lin, J. Y.; Jiang, H. X.

    2011-08-15

    The origin of high background electron concentration (n) in InxGa1-xN alloys has been investigated. A shallow donor was identified as having an energy level (ED1) that decreases with x (ED1 = 16 meV at x = 0 and ED1 = 0 eV at x ~ 0.5) and that crossover the conduction band at x ~ 0.5. This shallow donor is believed to be the most probable cause of high n in InGaN. This understanding is consistent with the fact that n increases sharply with an increase in x and becomes constant for x > 0.5. A continuous reduction in nmore » was obtained by increasing the V/III ratio during the epilayer growth, suggesting that nitrogen vacancy-related impurities are a potential cause of the shallow donors and high background electron concentration in InGaN« less

  3. 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}.

  4. Thermoelectric properties of InxGa1-xN alloys

    NASA Astrophysics Data System (ADS)

    Pantha, B. N.; Dahal, R.; Li, J.; Lin, J. Y.; Jiang, H. X.; Pomrenke, G.

    2008-01-01

    Thermoelectric (TE) properties of InxGa1-xN alloys grown by metal organic chemical vapor deposition have been investigated. It was found that as indium concentration increases, the thermal conductivity decreases and power factor increases, which leads to an increase in the TE figure of merit (ZT). The value of ZT was found to be 0.08 at 300K and reached 0.23 at 450K for In0.36Ga0.64N alloy, which is comparable to those of SiGe based alloys. The results indicate that InGaN alloys could be potentially important TE materials for many applications, especially for prolonged TE device operation at high temperatures, such as for recovery of waste heat from automobile, aircrafts, and power plants due to their superior physical properties, including the ability of operating at high temperature/high power conditions, high mechanical strength and stability, and radiation hardness.

  5. 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.

  6. Neutron Reactions in Accreting Neutron Stars: A New Pathway to Efficient Crust Heating

    SciTech Connect

    Gupta, Sanjib S.; Kawano, Toshihiko; Moeller, Peter

    2008-12-05

    In our calculation of neutron star crust heating we include several key new model features. In earlier work electron capture (EC) only allowed neutron emission from the daughter ground state; here we calculate, in a deformed quasi-random-phase approximation (QRPA) model, EC decay rates to all states in the daughter that are allowed by Gamow-Teller selection rules and energetics. The subsequent branching ratios between the 1n,...,xn channels and the competing {gamma} decay are calculated in a Hauser-Feshbach model. In our multicomponent plasma model a single (EC, xn) reaction step can produce several neutron-deficient nuclei, each of which can further decay by (EC, xn). Hence, the neutron emission occurs more continuously with increasing depth as compared to that in a one-component plasma model.

  7. Measurement of the -3 keV resonance in the {sup 13}C({alpha},n){sup 16}O reaction and its influence on the synthesis of s-process nuclei

    SciTech Connect

    La Cognata, M.; Spitaleri, C.; Trippella, O.; Kiss, G. G.; Rogachev, G. V.; Mukhamedzhanov, A. M.; Avila, M.; Guardo, G. L.; Koshchiy, E.; Kuchera, A.; Lamia, L.; Puglia, S. M. R.; Romano, S.; Santiago, D.; Sparta, R.; and others

    2012-11-20

    The {sup 13}C({alpha},n){sup 16}O reaction is the neutron source for the main component of the s-process, responsible of the production of most nuclei in the mass range 90 < A < 204. It is active inside the helium-burning shell in asymptotic giant branch stars, at temperatures < 10{sup 8} K, corresponding to an energy interval where the {sup 13}C({alpha},n){sup 16}O is effective of 140 - 230 keV. In this region, the astrophysical S(E)-factor is dominated by the -3 keV sub-threshold resonance due to the 6.356 MeV level in {sup 17}O, giving rise to a steep increase of the S-factor. Notwithstanding that it plays a crucial role in astrophysics, no direct measurements exist. Therefore, we have applied the Trojan Horse Method (THM) to the {sup 13}C({sup 6}Li,n{sup 16}O)d quasi-free reaction to achieve an experimental estimate of such contribution. For the first time, the ANC for the 6.356 MeV level has been deduced through the THM as well as the n-partial width, allowing to attain an unprecedented accuracy in the {sup 13}C({alpha},n){sup 16}O study. Though a larger ANC for the 6.356 MeV level is measured, our experimental S(E) factor agrees with the most recent extrapolation in the literature in the 140 - 230 keV energy interval, the accuracy being greatly enhanced thanks to this innovative approach.

  8. Dichloromethyl alkyl ethers and sulfides in the Reformatskii reaction

    SciTech Connect

    Lapkin, I.I.; Fotin, V.V.

    1986-09-10

    A study was carried out on the reaction of dichloromethyl alkyl ethers and sulfides with ..cap alpha..-brominated esters in the presence of zinc resulting in the formation of either ..cap alpha..-alkyl-..beta..-alkoxyacrylates (or ..cap alpha..-alkyl-..beta..-alkylthioacrylates) or ..cap alpha..,..cap alpha..,..cap alpha..',..cap alpha..'-tetramethyl-..beta..-alkoxyglutaric acid (or ..cap alpha..,..cap alpha..,..cap alpha..',..cap alpha..'-tetramethyl-..beta..-alkylthioglutaric acid) depending on the structure of the starting bromoester. PMR and IR spectroscopy indicates the geometry of the ..cap alpha..-alkyl-..beta..-alkoxyacrylates and ..cap alpha..-alkyl-..beta..-alkylthioacrylates.

  9. Calculation of induced reactions of 3He-particles on natSb in 10-34MeV energy range.

    PubMed

    Gul, K

    2009-01-01

    Calculations for the excitation functions of the (121)Sb((3)He, xn) (121,122,123)I, and (123)Sb((3)He xn) (122,123,124,125)I reactions have been carried out using statistical and pre-equilibrium nuclear reaction models in 10-34MeV energy range. These excitation functions have been used to derive the excitation functions of the (nat)Sb((3)He, xn)(121,123,124)I reactions and compared with reported measurements. For studying the improvement with measurements two values of the diffuseness parameter a(w) equal to 0.9 and 0.7fm have been used in the calculations. The dependence of pre-equilibrium calculations on the initial exciton numbers has also been considered. PMID:18951811

  10. Growth and characterization of Al xGa 1-xN via NH 3-based metal-organic molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Billingsley, Daniel; Henderson, Walter; Pritchett, David; Alan Doolittle, W.

    2009-02-01

    Growth and characterization of ammonia-based metal-organic molecular beam epitaxy (NH 3-MOMBE) Al xGa 1-xN epitaxial films has been conducted. Al xGa 1-xN films spanning the entire range of aluminum compositions were grown on GaN templates. This is the first reported successful growth of Al xGa 1-xN via NH 3-MOMBE, using triethylgallium (TEGa), triethylaluminum (TEAl) and ammonia (NH 3) as the precursors. These films were characterized via optical interferometry (OI), atomic force microscopy (AFM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). High-quality Al xGa 1-xN films, as inferred by XRD, are achievable in films without cracking. The catalytic effect of Al on NH 3 is found to play a major part in the growth rate of the Al xGa 1-xN films. The excessive nitrogen produced through this catalytic effect hinders the growth rate at lower Al composition while increasing the growth rate of Al xGa 1-xN ( x>0.4) films. Stress in the deposited films is found to be partially relieved through surface cracking along the <1 1 2¯ 0> direction in the film. These cracks provide dislocation gettering centers, with the dislocation pit density decreasing with increasing Al composition. A basic understanding on the factors affecting the growth of Al xGa 1-xN is determined and will become the basis for further investigations into the optimization of Al xGa 1-xN growth.

  11. Raman characterization of alpha- and beta-LiFe{sub 5}O{sub 8} prepared through a solid-state reaction pathway

    SciTech Connect

    Cook, W.; Manley, M.

    2010-02-15

    Lithium ferrite, a mixed-inverse spinel of type A{sub x}B{sub y}[A{sub 1-x}B{sub 1-y}]O{sub 4} was produced through solid state synthesis by calcining a Li{sub 2}CO{sub 3}/Fe{sub 2}O{sub 3} mixture at 900 deg. C. The presence of both the ordered alpha-phase and disordered beta-phase of LiFe{sub 5}O{sub 8} was confirmed by XRD analysis, while formation of the latter was achieved by air quenching from high temperature. Laser Raman analysis was performed on both the alpha-LiFe{sub 5}O{sub 8} and beta-LiFe{sub 5}O{sub 8} powders in order to achieve a reference set of Raman shifts for the spinel. The strongest, characteristic Raman peaks were determined to be 493, 382, 358, 300, and 263 cm{sup -1} for both phases while smaller peaks at 202 and 236 cm{sup -1} present in the alpha-phase were diminishing in intensity when the beta-phase was present, thus providing unique identifiers for the presence of the disordered ferrite structure. SEM images taken of the synthesized LiFe{sub 5}O{sub 8} powders showed particle sizes of less than 300 nm and an even particle size distribution. - Graphical abstract: The disordered, beta-phase of lithium ferrite is sustained by air quenching from 900 deg. C. Shown is a SEM image of beta-LiFe{sub 5}O{sub 8} exhibiting even particle sizes less than 300 nm.

  12. Optimisation of cyclotron production parameters for the 209Bi(alpha, 2n) 211At reaction related to biomedical use of 211At.

    PubMed

    Henriksen, G; Messelt, S; Olsen, E; Larsen, R H

    2001-05-01

    The cyclotron alpha beam production of 211At and of the contaminant 210At related to beam energy were studied. Radiochemical purification of 211At from the other main contaminant, 210Po, by an extraction procedure was also evaluated. To avoid impurities 28MeV has previously been considered as a maximum beam energy, but by using instead 29.1 MeV as a limit a large increase in EOB yield and sufficient radiochemical purity of extracted 211At were obtained. More cyclotrons could thereby deliver quantities useful for clinical cancer trials. PMID:11258534

  13. Difference in linear polarization of biaxially strained I nxG a1 -xN alloys on nonpolar a -plane and m -plane GaN

    NASA Astrophysics Data System (ADS)

    Zhang, Siyuan; Cui, Ying; Griffiths, James T.; Fu, Wai Y.; Freysoldt, Christoph; Neugebauer, Jörg; Humphreys, Colin J.; Oliver, Rachel A.

    2015-12-01

    I nxG a1 -xN structures epitaxially grown on a -plane or m -plane GaN exhibit in-plane optical polarization. Linear elasticity theory treats the two planes equivalently and is hence unable to explain the experimentally observed higher degree of linear polarization for m -plane than a -plane I nxG a1 -xN . Using density functional theory, we study the response of I nxG a1 -xN random alloys to finite biaxial strains on both nonpolar planes. The calculated m -plane I nxG a1 -xN valence band splitting is larger than that of the a plane, due to a greater degree of structural relaxation in a -plane I nxG a1 -xN . We provide a parametrization of the valence band splitting of I nxG a1 -xN strained to a -plane and m -plane GaN for In compositions between 0 and 0.5, which agrees with experimental measurements and qualitatively explains the experimentally observed difference between a -plane and m -plane polarization.

  14. High temperature stability of ScxAl1-xN (x=0.27) thin films

    NASA Astrophysics Data System (ADS)

    Mayrhofer, P. M.; Bittner, A.; Schmid, U.

    2015-05-01

    The stability of piezoelectric scandium aluminium nitride (ScxAl1-xN) thin films with x= 27% was investigated after post deposition annealings up to 1000°C. The ScxAl1-xN thin films targeted for applications in micro-electromechanical systems (MEMS) were deposited close to room-temperature applying DC magnetron sputtering. Varying deposition parameters yielded films with different microstructural properties and piezoelectric constants. Upon annealing, the crystalline quality of thin films with c-axis orientation increased, as found via characterization techniques such as X-ray diffractometry and fourier transform infrared absorbance measurements. Additionally, piezoelectric constants after annealing steps up to 1000°C are reported as obtained via a Berlincourt measurement principle. Furthermore, modifications in chemical composition during temperature loads up to 1000°C were recorded by thermal effusion measurements.

  15. Metalorganic Vapor-Phase Epitaxial Growth and Characterization of Cubic AlxGa1-xN Alloy

    NASA Astrophysics Data System (ADS)

    Nakadaira, Atsushi; Tanaka, Hidenao

    1998-03-01

    Cubic AlxGa1-xN alloy films in the range 0≤x≤0.51 were grown on GaAs (100) substrates using low-pressure metalorganic vapor-phase epitaxy. The lattice constants of the alloys, which were estimated from the X-ray diffraction peaks, obeyed Vegard's rule. The optical quality of the alloys was improved by using triethylaluminum as the aluminum precursor. In photoluminescence measurements, AlxGa1-xN in the range x≤0.42 exhibited strong near band edge emissions, while that with x around 0.5 did not. The peak energy of the photoluminescence depended on the relationship E=3.20+1.85x in the range x≤0.42, while that around x=0.5 was less than that given by this relationship.

  16. Optical and electronic properties of Ti{sub 1-x}Nb{sub x}N thin films

    SciTech Connect

    Vasu, K.; Gopikrishnan, G. M.; Krishna, M. Ghanashyam; Padmanabhan, K. A.

    2012-06-05

    Ti{sub 1-x}Nb{sub x}N thin films with x=0, 0.26, 0.41, 0.58 and 1 were deposited on silicon (311) substrate by RF magnetron sputtering. The dielectric functions of these films were calculated by fitting measured reflectance spectra to the Drude-Lorentz model. The measured reflectance spectra exhibits a minimum in the visible region and this feature shifts to higher energy (shorter wavelength) with increase in x. The observed behavior can be modeled as the response of four Lorentz oscillators. The real part of the dielectric function is characterized by a screened plasma energy of 2.26 eV for x=0 which increased to 2.80 eV for x=0.58 in the Ti{sub 1-x}Nb{sub x}N film.

  17. Effect of native defects on optical properties of In{sub x}Ga{sub 1-x}N alloys

    SciTech Connect

    Li, S.X.; Haller, E.E.; Yu, K.M.; Walukiewicz, W.; Ager, J.W. III; Wu, J.; Shan, W.; Lu Hai; Schaff, William J.

    2005-10-17

    The energy position of the optical-absorption edge and the free-carrier populations in In{sub x}Ga{sub 1-x}N ternary alloys can be controlled using high-energy {sup 4}He{sup +} irradiation. The blueshift of the absorption edge after irradiation in In-rich material (x>0.34) is attributed to the band-filling effect (Burstein-Moss shift) due to the native donors introduced by the irradiation. In Ga-rich material, optical-absorption measurements show that the irradiation-introduced native defects are inside the band gap, where they are incorporated as acceptors. The observed irradiation-produced changes in the optical-absorption edge and the carrier populations in In{sub x}Ga{sub 1-x}N are in excellent agreement with the predictions of the amphoteric defect model.

  18. 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 ...

  19. The changes in small metal cluster size with adsorption Be13Xn, X = H, O, S, Cl and F

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.

    1985-01-01

    The Be-Be and Be-adsorbate distances are optimized for small Be13Xn clusters,s assuming only two independent degrees of freedom. Results for chemisorption into the three-fold hollows are quite similar to those found for small metal clusters on supports. It is predicted that Cl and F will have the same effect on the metal-metal bond lengths, and so will O and S.

  20. Role of biaxial strain and microscopic ordering for structural and electronic properties of InxGa1 -xN

    NASA Astrophysics Data System (ADS)

    Cui, Ying; Lee, Sangheon; Freysoldt, Christoph; Neugebauer, Jörg

    2015-08-01

    The structural and electronic properties of InxGa1 -xN alloys are studied as a function of c -plane biaxial strain and In ordering by density functional theory with the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional. A nonlinear variation of the c lattice parameter with In content is observed in biaxial strain and should be taken into account when deducing In content from interplanar distances. From compressive to tensile strain, the character of the top valence-band state changes, leading to a nonlinear variation of the band gap in InxGa1 -xN . Interestingly, the well-known bowing of the InxGa1 -xN band gap is largely removed for alloys grown strictly coherently on GaN, while the actual values for band gaps at x <0.33 are hardly affected by strain. Ordering plays a minor role for lattice constants but may induce changes of the band gap up to 0.15 eV.

  1. New investigations of the 10B(p,{\\alpha }_{0})7Be reaction at bombarding energies between 0.6 and 1 MeV

    NASA Astrophysics Data System (ADS)

    Lombardo, I.; Dell'Aquila, D.; Conte, F.; Francalanza, L.; La Cognata, M.; Lamia, L.; La Torre, R.; Spadaccini, G.; Spitaleri, C.; Vigilante, M.

    2016-08-01

    We measured the 10B(p,{α }0)7Be reaction in the bombarding energy domain of 0.6-1.0 MeV, a region where very few data (with large uncertainties) have been reported in the literature. Despite the experimental difficulties, due to the unfavourable reaction kinematics and the presence of contaminants in the 10B target, we were able to measure excitation functions at both forward and backward angles thanks to the use of the inverse absorber technique. The obtained angular distributions show a continuous shape evolution, testifying to the contributions of several resonant states in the 11C compound nucleus. An R-matrix analysis of some reaction and scattering channels allows us to refine the spectroscopy of 11C excited states.

  2. Cluster-transfer reactions with radioactive beams: A spectroscopic tool for neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Bottoni, S.; Leoni, S.; Fornal, B.; Raabe, R.; Rusek, K.; Benzoni, G.; Bracco, A.; Crespi, F. C. L.; Morales, A. I.; Bednarczyk, P.; Cieplicka-Oryńczak, N.; Królas, W.; Maj, A.; Szpak, B.; Callens, M.; Bouma, J.; Elseviers, J.; De Witte, H.; Flavigny, F.; Orlandi, R.; Reiter, P.; Seidlitz, M.; Warr, N.; Siebeck, B.; Hellgartner, S.; Mücher, D.; Pakarinen, J.; Vermeulen, M.; Bauer, C.; Georgiev, G.; Janssens, R. V. F.; Balabanski, D.; Sferrazza, M.; Kowalska, M.; Rapisarda, E.; Voulot, D.; Lozano Benito, M.; Wenander, F.

    2015-08-01

    An exploratory experiment performed at REX-ISOLDE to investigate cluster-transfer reactions with radioactive beams in inverse kinematics is presented. The aim of the experiment was to test the potential of cluster-transfer reactions at the Coulomb barrier as a mechanism to explore the structure of exotic neutron-rich nuclei. The reactions 7Li(98Rb,α xn ) and 7Li(98Rb,t xn ) were studied through particle-γ coincidence measurements, and the results are presented in terms of the observed excitation energies and spins. Moreover, the reaction mechanism is qualitatively discussed as a transfer of a clusterlike particle within a distorted-wave Born approximation framework. The results indicate that cluster-transfer reactions can be described well as a direct process and that they can be an efficient method to investigate the structure of neutron-rich nuclei at medium-high excitation energies and spins.

  3. 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.

  4. 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.

  5. Structure and strain relaxation effects of defects in InxGa1-xN epilayers

    NASA Astrophysics Data System (ADS)

    Rhode, S. L.; Fu, W. Y.; Moram, M. A.; Massabuau, F. C.-P.; Kappers, M. J.; McAleese, C.; Oehler, F.; Humphreys, C. J.; Dusane, R. O.; Sahonta, S.-L.

    2014-09-01

    The formation of trench defects is observed in 160 nm-thick InxGa1-xN epilayers with x ≤ 0.20, grown on GaN on (0001) sapphire substrates using metalorganic vapour phase epitaxy. The trench defect density increases with increasing indium content, and high resolution transmission electron microscopy shows an identical structure to those observed previously in InGaN quantum wells, comprising meandering stacking mismatch boundaries connected to an I1-type basal plane stacking fault. These defects do not appear to relieve in-plane compressive strain. Other horizontal sub-interface defects are also observed within the GaN pseudosubstrate layer of these samples and are found to be pre-existing threading dislocations which form half-loops by bending into the basal plane, and not basal plane stacking faults, as previously reported by other groups. The origins of these defects are discussed and are likely to originate from a combination of the small in-plane misorientation of the sapphire substrate and the thermal mismatch strain between the GaN and InGaN layers grown at different temperatures.

  6. Sample stability for complete blood cell count using the Sysmex XN haematological analyser

    PubMed Central

    Daves, Massimo; Zagler, Elmar M.; Cemin, Roberto; Gnech, Flora; Joos, Alexandra; Platzgummer, Stefan; Lippi, Giuseppe

    2015-01-01

    Background Sample stability is a crucial aspect for the quality of results of a haematology laboratory. This study was conducted to investigate the reliability of haematological testing using Sysmex XN in samples stored for up to 24 h at different temperatures. Materials and methods Haematological tests were performed on whole blood samples collected from 16 ostensibly healthy outpatients immediately after collection and 3 h, 6 h or 24 h afterwards, with triple aliquots kept at room temperature, 4 °C or 37 °C. Results No meaningful bias was observed after 3 h under different storage conditions, except for red blood cell distribution width (RDW) and platelet count (impedance technique, PLT-I) at 37 °C. After 6 h, meaningful bias was observed for mean corpuscular haemoglobin (MCH) and mean corpuscular volume (MCV) at room temperature, red blood cell (RBC) count, mean corpuscular haemoglobin concentration (MCHC), MCH, MCV and PLT-I at 4 °C, and RBC, RDW, MCHC, MCH and PLT-I at 37 °C. After 24 h, a meaningful bias was observed for MCHC, MCV, platelet count (fluorescent technique, PLT-F) and mean platelet volume (MPV) at room temperature, MCHC, MCV, PLT-I and MPV at 4 °C, and all parameters except RBC count and MPV at 37 °C. Discussion Great caution should be observed when analysing results of haematological tests conducted more than 3 h after sample collection. PMID:26057491

  7. Reactions of Ethyl Groups on a Model Chromia Surface: Ethyl Chloride on Stoichiometric Alpha-Cr2O3(1012)

    SciTech Connect

    Brooks, J.; Ma, Q; Cox, D

    2009-01-01

    The reaction of CH3CH2Cl over the nearly-stoichiometric ?-Cr2O3 (1 0 View the MathML source 2) surface yields gas phase CH2double bond; length as m-dashCH2, CH3CH3, H2 and surface chlorine adatoms. The decomposition reaction is initiated via C-Cl bond cleavage to give a surface ethyl (CH3CH2-) intermediate. A rate-limiting ?-hydride elimination from the surface ethyl species produces gas phase CH2double bond; length as m-dashCH2 and surface hydrogen atoms. Two parallel competing reactions form CH3CH3, via ?-hydride addition to remaining surface ethyl species (reductive elimination), and H2, via the combination of two surface hydrogen atoms. The chlorine freed from the dissociation of CH3CH2Cl binds at the five-coordinate surface Cr3+ sites on the stoichiometric surface and inhibits the surface chemistry via simple site blocking. No surface carbon deposition is observed from the thermal reaction of ethyl chloride, suggesting that ethyl intermediates are not primary coke forming intermediates in the dehydrogenation of ethane over (1 0 View the MathML source 2) facets of ?-Cr2O3.

  8. Study of the excitation region 45--57 MeV of the /sup 7/Be nucleus in the reaction /sup 6/Li(p,. cap alpha. )/sup 3/He

    SciTech Connect

    Nemets, O.F.; Ostashko, V.V.; Povoroznik, O.M.; Urin, V.N.; Yasnogorodskii, A.M.; Barit, I.Y.; Zuev, S.V.

    1984-07-01

    To investigate the excitation region 45--57 MeV of the /sup 7/Be nucleus we have studied the reaction /sup 6/Li(p,..cap alpha..)/sup 3/He at proton energies E/sub p/ = 47.8--62.5 MeV. The measurements were made in the U-240 isochronous cyclotron at our institute. The energy dependences obtained for the angular distributions have been analyzed by parametrization in terms of expansions in Legendre polynomials. A departure of the expansion coefficients from a monotonic dependence is observed in the proton-energy region near 55 MeV, which corresponds to a /sup 7/Be excitation energy of about 50 MeV.

  9. Experimental determination of the {sup 36}Cl(n,p){sup 36}S and {sup 36}Cl(n,{alpha}){sup 33}P reaction cross sections and the consequences on the origin of {sup 36}S

    SciTech Connect

    Smet, L. de; Wagemans, C.; Goeminne, G.; Heyse, J.; Gils, J. van

    2007-03-15

    The {sup 36}Cl(n,p){sup 36}S and {sup 36}Cl(n,{alpha}){sup 33}P reaction cross sections have been studied with resonance neutrons at the linear accelerator GELINA of the IRMM in Geel (Belgium) and have been determined up to approximately 250 keV using the time-of-flight technique. In this energy region, 17 resonances were observed, whereas eight were identified before. For some resonances the resonance strength, the spin, and the total width could be determined. From the obtained cross section data, the MACS has been calculated by numerical integration. These updated MACS values were used in stellar models to trace the origin of the rare isotope {sup 36}S.

  10. Dependence of s-Process Nucleosynthesis in Massive Stars on Triple-Alpha and 12C(α, γ)16O Reaction Rate Uncertainties

    NASA Astrophysics Data System (ADS)

    Tur, Clarisse; Heger, Alexander; Austin, Sam M.

    2009-09-01

    We have studied the sensitivity of s-process nucleosynthesis in massive stars to ±2σ variations in the rates of the triple-α and 12C(α, γ)16O reactions. We simulated the evolution of massive stars from H burning through Fe-core collapse, followed by a supernova explosion. We found that the production factors of s-process nuclides between 58Fe and 96Zr change strongly with changes in the He burning reaction rates; using the Lodders solar abundances rather than those of Anders and Grevesse reduces s-process nucleosynthesis; later burning phases beyond core He burning and shell C burning have a significant effect on post-explosive production factors. We also discuss the implications of the uncertainties in the helium burning rates for evidence of a new primary neutron capture process (LEPP) in massive stars.

  11. 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. PMID:26178835

  12. Modeling and experiment reveal an unexpected stereoelectronic effect on conformation and scalar couplings of alpha-aminoorganostannanes, with possible relevance to the tin-lithium exchange reaction.

    PubMed

    Santiago, Marcelina; Low, Eddy; Chambournier, Gilles; Gawley, Robert E

    2003-10-31

    The solution conformation of N-methyl-2-(tributylstannyl)piperidines has been determined through the use of vicinal 119Sn-13C coupling constants, revealing a conformational distortion caused by an unexpected stereoelectronic effect in some cases. Specifically, the "equatorial" conformer is distorted into a half-chair, in which the nitrogen lone pair eclipses the C-Sn bond. This distortion, which "costs" approximately 1 kcal/mol, correlates with a conformational dependence of geminal 119Sn-15N couplings and a possible correlation with reactivity in the tin-lithium exchange reaction. PMID:14575474

  13. Alpha-1 Antitrypsin Deficiency

    MedlinePlus

    ... Liver Disease Information > Alpha-1 Antitrypsin Deficiency Alpha-1 Antitrypsin Deficiency Explore this section to learn more about alpha-1 antitrypsin deficiency, including a description of the disorder ...

  14. Paradoxical Autoinflammatory Skin Reaction to Tumor Necrosis Factor Alpha Blockers Manifesting as Amicrobial Pustulosis of the Folds in Patients With Inflammatory Bowel Diseases

    PubMed Central

    Marzano, Angelo V.; Tavecchio, Simona; Berti, Emilio; Gelmetti, Carlo; Cugno, Massimo

    2015-01-01

    Abstract The therapy of inflammatory bowel disease, particularly with tumor necrosis factor (TNF) blockers, may be associated with a number of cutaneous adverse effects, including psoriasis-like, eczema-like, and lichenoid eruptions. Other rare skin complications are neutrophilic dermatoses such as amicrobial pustulosis of the folds (APF), which is a chronic relapsing pustular disorder classified in this spectrum. The authors analyzed clinical, histopathologic, and cytokine expression profiles of 3 inflammatory bowel disease patients with APF triggered by adalimumab (patient 1) and infliximab (patients 2 and 3). All 3 patients presented with sterile pustules involving the cutaneous folds, genital regions, and scalp 6 months after starting adalimumab (patient 1) and 9 months after starting infliximab (patients 2 and 3). Histology was characterized by epidermal spongiform pustules with a dermal neutrophilic and lymphocytic infiltrate. Tumor necrosis factor blocker withdrawal associated with topical and systemic corticosteroids induced complete remission of APF in all 3 patients. The expressions of interleukin (IL)-1 beta and its receptors as well as TNF alpha and its receptors were significantly higher in APF than in controls. Also IL-17, leukocyte selectin, and chemokines, such as IL-8, [C-X-C motif] chemokine ligand 1/2/3 (C = cysteine, X = any amino acid), [C-X-C motif] chemokine ligand 16 (C = cysteine, X = any amino acid), and RANTES (regulated on activation, normal T cell expressed and secreted) were significantly overexpressed. Finally, the authors found significant overexpression of both metalloproteinases 2/9 and their inhibitors 1/2. The observation of 3 patients with APF following anti-TNF therapy expands not only the clinical context of APF but also the spectrum of anti-TNF side effects. Overexpression of cytokines/chemokines and molecules amplifying the inflammatory network supports the view that APF is autoinflammatory in origin. PMID

  15. Protonation of acyllithium reagents by dichloromethane and dichloroarylmethane. A new method for the synthesis of {alpha},{alpha}-dichloro alcohols

    SciTech Connect

    Kabalka, G.W.; Li, N.S.; Yu, S.

    1995-04-01

    The first example of the protonation of acylithium reagents by dichloromethane and dichloroarylmethane is described. The reaction affords the corresponding {alpha},{alpha}-dichloro alcohols in excellent yields. 23 refs., 1 tab.

  16. Glycyl-histidyl-lysine (GHK) is a quencher of alpha,beta-4-hydroxy-trans-2-nonenal: a comparison with carnosine. insights into the mechanism of reaction by electrospray ionization mass spectrometry, 1H NMR, and computational techniques.

    PubMed

    Beretta, Giangiacomo; Artali, Roberto; Regazzoni, Luca; Panigati, Monica; Facino, Roberto Maffei

    2007-09-01

    Histidine-containing oligopeptides are currently studied as detoxifying agents against cytotoxic alpha,beta-unsaturated aldehydes (prototype: 4-hydroxy-2-nonenal, HNE), electrophilic end products formed by decomposition of omega-6 polyunsaturated fatty acids, associated with severe pathologies such as diabetes, nephropathy, retinopathy, and neurodegenerative diseases. This study evaluated the quenching reaction against HNE of the endogenous tripeptide l-glycyl- l-histidyl- l-lysine (GHK), an oligopeptide discovered to be a growth-modulating factor and also a strong activator of wound healing. We first evaluated the HNE consumption (50 microM, HPLC-UVDAD method) in the presence of GHK (1 mM) in physiomimetic conditions (phosphate buffer, pH 7.4) and confirmed GHK/HNE adduct formation by mass spectrometric analysis (ESI-MS/MS) and (1)H NMR analyses. These results indicated that GHK was an effective quencher of HNE, although significantly less potent than the reference compound carnosine, and that HNE modulation by GHK can contribute to the satisfactory outcome of the wound-healing process. In the second part of the study, we investigated the quenching reaction between GHK and HNE, in parallel to carnosine, using (1)H NMR and computational analyses. At a mechanistic level, this explained the different reactivity of the two peptides: (i) The greater stability of the macrocyclic intermediate HNE/carnosine was compared to HNE/GHK. (ii) GHK in solution has a quasi-folded conformation due to the interaction of four intramolecular hydrogen bonds, three of which need to be broken for the transition state to form (energy barrier, approximately 20 kcal/mol). By contrast, carnosine, with an extended conformation and only one hydrogen bond, requires less energy to reach the transition state ( approximately 7 kcal/mol). (iii) The different stereoelectronic features of the transition state lead to the intramolecular Michael reaction, that is, the favorable superimposition of

  17. Azimuthal distributions of fission fragments and. alpha. particles emitted in the reactions sup 36 Ar+ sup 238 U at E / A =20 and 35 MeV and sup 14 N+ sup 238 U at E / A =50 MeV

    SciTech Connect

    Tsang, M.B.; Kim, Y.D.; Carlin, N.; Chen, Z.; Gelbke, C.K.; Gong, W.G.; Lynch, W.G.; Murakami, T.; Nayak, T.; Ronningen, R.M.; Xu, H.M.; Zhu, F. Department of Physics Astronomy, Michigan State University, East Lansing, MI ); Sobotka, L.G.; Stracener, D.W.; Sarantites, D.G.; Majka, Z.; Abenante, V. )

    1990-07-01

    Azimuthal correlations between coincident fission fragments and {alpha} particles were measured for the reactions {sup 36}Ar+{sup 238}U at {ital E}/{ital A}=20 and 35 MeV and {sup 14}N+{sup 238}U at {ital E}/{ital A}=50 MeV. At all energies, coplanar emission is enhanced. The azimuthal distributions for fission fragments and {alpha} particles are decoupled using a simple parametrization. Both azimuthal distributions are highly anisotropic at lower incident energies; these anisotropies decrease with energy. At the highest incident energies, energetic {alpha} particles emitted at large transverse momenta appear to be more suited than fission fragments to tag the orientation of the entrance channel reaction plane.

  18. 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.

  19. Structural and compositional evolutions of InxAl1-xN core-shell nanorods grown on Si(111) substrates by reactive magnetron sputter epitaxy.

    PubMed

    Serban, Elena Alexandra; Åke Persson, Per Ola; Poenaru, Iuliana; Junaid, Muhammad; Hultman, Lars; Birch, Jens; Hsiao, Ching-Lien

    2015-05-29

    Catalystless growth of InxAl(1-x)N core-shell nanorods have been realized by reactive magnetron sputter epitaxy onto Si(111) substrates. The samples were characterized by scanning electron microscopy, x-ray diffraction, scanning transmission electron microscopy, and energy dispersive x-ray spectroscopy. The composition and morphology of InxAl(1-x)N nanorods are found to be strongly influenced by the growth temperature. At lower temperatures, the grown materials form well-separated and uniform core-shell nanorods with high In-content cores, while a deposition at higher temperature leads to the formation of an Al-rich InxAl(1-x)N film with vertical domains of low In-content as a result of merging Al-rich shells. The thickness and In content of the cores (domains) increase with decreasing growth temperature. The growth of the InxAl(1-x)N is traced to the initial stage, showing that the formation of the core-shell nanostructures starts very close to the interface. Phase separation due to spinodal decomposition is suggested as the origin of the resultant structures. Moreover, the in-plane crystallographic relationship of the nanorods and substrate was modified from a fiber textured to an epitaxial growth with an epitaxial relationship of InxAl(1-x)N[0001]//Si[111] and InxAl(1-x)N[1120]//Si[110 by removing the native SiOx layer from the substrate. PMID:25944838

  20. 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.

  1. 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.

  2. Structural and compositional evolutions of InxAl1-xN core-shell nanorods grown on Si(111) substrates by reactive magnetron sputter epitaxy

    NASA Astrophysics Data System (ADS)

    Serban, Elena Alexandra; Åke Persson, Per Ola; Poenaru, Iuliana; Junaid, Muhammad; Hultman, Lars; Birch, Jens; Hsiao, Ching-Lien

    2015-05-01

    Catalystless growth of InxAl1-xN core-shell nanorods have been realized by reactive magnetron sputter epitaxy onto Si(111) substrates. The samples were characterized by scanning electron microscopy, x-ray diffraction, scanning transmission electron microscopy, and energy dispersive x-ray spectroscopy. The composition and morphology of InxAl1-xN nanorods are found to be strongly influenced by the growth temperature. At lower temperatures, the grown materials form well-separated and uniform core-shell nanorods with high In-content cores, while a deposition at higher temperature leads to the formation of an Al-rich InxAl1-xN film with vertical domains of low In-content as a result of merging Al-rich shells. The thickness and In content of the cores (domains) increase with decreasing growth temperature. The growth of the InxAl1-xN is traced to the initial stage, showing that the formation of the core-shell nanostructures starts very close to the interface. Phase separation due to spinodal decomposition is suggested as the origin of the resultant structures. Moreover, the in-plane crystallographic relationship of the nanorods and substrate was modified from a fiber textured to an epitaxial growth with an epitaxial relationship of InxAl1-xN[0001]//Si[111] and InxAl1-xN[11\\bar{2}0]//Si[1\\bar{1}0] by removing the native SiOx layer from the substrate.

  3. Mechanical, tribological, and electrochemical behavior of Cr 1- xAl xN coatings deposited by r.f. reactive magnetron co-sputtering method

    NASA Astrophysics Data System (ADS)

    Sanchéz, J. E.; Sanchéz, O. M.; Ipaz, L.; Aperador, W.; Caicedo, J. C.; Amaya, C.; Landaverde, M. A. Hernández; Beltran, F. Espinoza; Muñoz-Saldaña, J.; Zambrano, G.

    2010-02-01

    Chromium aluminum nitride (Cr 1- xAl xN) coatings were deposited onto AISI H13 steel and silicon substrates by r.f. reactive magnetron co-sputtering in (Ar/N 2) gas mixture from chromium and aluminum targets. Properties of deposited Cr 1- xAl xN coatings such as compositional, structural, morphological, electrochemical, mechanical and tribological, were investigated as functions of aluminum content. X-ray diffraction patterns of Cr 1- xAl xN coatings with different atomic concentrations of aluminum (0.51 < x < 0.69) showed the presence and evolution of (1 1 1), (2 0 0), and (1 0 2) crystallographic orientations associated to the Cr 1- xAl xN cubic and w-AlN phases, respectively. The rate of corrosion of the steel coated with Cr 1- xAl xN varied with the applied power; however, always being clearly lower when compared to the uncoated substrate. The behavior of the protective effect of the Cr 1- xAl xN coatings is based on the substitution of Cr for Al, when the power applied to the aluminum target increases. The mechanical properties were also sensitive to the power applied, leading to a maximum in hardness and a reduced elastic modulus of 30 and 303 GPa at 350 W and a monotonic decrease to 11 and 212 GPa at 450 W, respectively. Finally, the friction coefficient measured by pin-on disk revealed values between 0.45 and 0.70 in humid atmosphere.

  4. 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.

  5. Band gap bowing and crossing of BxGa1-xN alloy investigated by hybrid functional method

    NASA Astrophysics Data System (ADS)

    Jiaping, Jiang; Yanqin, Gai; Gang, Tang

    2016-02-01

    The electronic properties of zinc-blende BxGa1-xN alloys are comparatively investigated by employing both the Perdewe-Burkee-Ernzerhof generalized-gradient approximation (PBE-GGA) and the Heyd-Scuseria-Ernzerhof screened hybrid functional methods (HSE06). HSE06 reproduced much closer ground-state properties to experiments. Large and composition-dependent bowing parameters bγ for the direct band gaps were obtained from both PBE and HSE06. The crossover composition where alloy switches from direct to indirect was predicted to occur at very similar x from PBE and HSE06. We can obtain direct gap BxGa1-xN with a gap value much larger than that of GaN by alloying x < 0.557 boron into GaN. Project supported by the Fundamental Research Funds for the Central Universities (No. 2010LKWL03), the Special Fund for Theoretical Physics (No. 11047130), and the National Natural Science Foundation of China (No. 11104345).

  6. Microstructure and dielectric properties of piezoelectric magnetron sputtered w-ScxAl1-xN thin films

    SciTech Connect

    Zukauskaite, Agne; Wingqvist, Gunilla; Palisaitis, Justinas; Jensen, Jens; Persson, Per; Matloub, Ramin; Muralt, Paul; Kim, Yunseok; Birch, Jens; Hultman, Lars

    2012-01-01

    Piezoelectric wurtzite ScxAl1 xN (x = 0, 0.1, 0.2, 0.3) thin films were epitaxially grown by reactive magnetron co-sputtering from elemental Sc and Al targets. Al2O3(0001) wafers with TiN(111) seed and electrode layers were used as substrates. X-ray diffraction shows that an increase in the Sc content results in the degradation of the crystalline quality. Samples grown at 400 C possess true dielectric behavior with quite low dielectric losses and the leakage current is negligible. For ScAlN samples grown at 800 C, the crystal structure is poor and leakage current is high. Transmission electron microscopy with energy dispersive x-ray spectroscopy mapping shows a mass separation into ScN-rich and AlN-rich domains for x 0.2 when substrate temperature is increased from 400 to 800 C. The piezoelectric response of epitaxial ScxAl1 xN films measured by piezoresponse force microscopy and double beam interferometry shows up to 180% increase by the addition of Sc up to x = 0.2 independent of substrate temperature, in good agreement with previous theoretical predictions based on density-functional theory.

  7. AIN content influence on the properties of Al xGa 1-xN doped with Pr ions

    NASA Astrophysics Data System (ADS)

    Fialho, M.; Magalhães, S.; Alves, L. C.; Marques, C.; Maalej, R.; Monteiro, T.; Lorenz, K.; Alves, E.

    2012-02-01

    The purpose of this work is the study of the structural and optical properties of Al xGa 1-xN films grown on (0 0 0 1) sapphire substrates with different AlN molar fraction implanted with 150 keV of praseodymium ions with a fluence of 2.5 × 10 14 cm -2. The main goal is to achieve the optical doping of Al xGa 1-xN with the rare earth Pr. Structural properties, damage accumulation and Pr lattice site location were studied combining Rutherford backscattering/channeling spectrometry and high resolution X-ray diffraction. The channeling data clearly indicate a higher resistance of the lattice to irradiation damage with the increase of the AlN content. Detailed angular scans reveal a fraction above 90% of Pr incorporated in near substitutional sites. A pronounced narrowing at the bottom of the Pr angular curve along the c-axis suggests the presence of a minor fraction with a higher displacement towards the center of the channel. The displacement is less pronounced with the increase of Ga content in the samples. Ionoluminescence with a 1H + microbeam reveal an enhancement of the optical activity when the AlN content is in the intermediate range of concentrations.

  8. Effect of annealing temperature on microstructure, hardness and adhesion properties of TiSi xN y superhard coatings

    NASA Astrophysics Data System (ADS)

    Lu, Y. H.; Wang, J. P.; Tao, S. L.; Zhou, Z. F.

    2011-05-01

    A series of TiSi xN y superhard coatings with different Si contents were prepared on M42 steel substrates using two Ti and two Si targets by reactive magnetron sputtering at 500 °C. These samples were subsequently vacuum-annealed at 500, 600, 700, 800 and 900 °C, respectively. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), microindenter, Rockwell hardness tester and scratch tester were applied to investigate the microstructure, phase configuration, hardness and adhesion properties of as-deposited and annealed samples. The results indicated that there were two bonds, TiN and Si 3N 4, in all presently deposited TiSi xN y thin films, that structure was nanocomposite of nanocrystalline (nc-) TiN embedded into amorphous Si 3N 4 matrices. Annealing treatment below 900 °C played a little role in microstructure and hardness of the coatings although it greatly affected those of steel substrates. The film-substrate adhesion strength was slightly increased, followed by an abrupt decrease with increasing annealing temperature. Its value got to the maximum at 600 °C. Annealing had little effect on the friction coefficient with its value varying in the range of 0.39-0.40.

  9. 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.

  10. 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.

  11. Aluminum incorporation in Ti{sub 1-x}Al{sub x}N films studied by x-ray absorption near-edge structure

    SciTech Connect

    Gago, R.; Redondo-Cubero, A.; Endrino, J. L.; Jimenez, I.; Shevchenko, N.

    2009-06-01

    The local bonding structure of titanium aluminum nitride (Ti{sub 1-x}Al{sub x}N) films grown by dc magnetron cosputtering with different AlN molar fractions (x) has been studied by x-ray absorption near-edge structure (XANES) recorded in total electron yield mode. Grazing incidence x-ray diffraction (GIXRD) shows the formation of a ternary solid solution with cubic structure (c-Ti{sub 1-x}Al{sub x}N) that shrinks with the incorporation of Al and that, above a solubility limit of xapprox0.7, segregation of w-AlN and c-Ti{sub 1-x}Al{sub x}N phases occurs. The Al incorporation in the cubic structure and lattice shrinkage can also be observed using XANES spectral features. However, contrary to GIXRD, direct evidence of w-AlN formation is not observed, suggesting a dominance and surface enrichment of cubic environments. For x>0.7, XANES shows the formation of Ti-Al bonds, which could be related to the segregation of w-AlN. This study shows the relevance of local-order information to assess the atomic structure of Ti{sub 1-x}Al{sub x}N solutions.

  12. On Positive Solutions for the Rational Difference Equation Systems xn+1 = A/xnyn2, and yn+1 = Byn/xn−1yn−1

    PubMed Central

    Ma, Hui-li; Feng, Hui

    2014-01-01

    Our aim in this paper is to investigate the behavior of positive solutions for the following systems of rational difference equations: xn+1 = A/xnyn2, and yn+1 = Byn/xn−1yn−1, n = 0,1,…, where x−1, x0, y−1, and y0 are positive real numbers and A and B are positive constants.

  13. XN2Y-1 Model Being Prepared for Spin Tunnel Tests

    NASA Technical Reports Server (NTRS)

    1935-01-01

    Model of XN2Y-1 biplane mounted on a special test rig to determine moments of inertia prior to spin tests in the Langley 15-Foot Spin Tunnel. This was one of two balsa wood models (the other was a 1/12- scale model of the F4B-2) for initial testing and calibration of the new tunnel. Researchers were very concerned that the results they might achieve with models in the tunnel would not correlate with the spinning behavior of full-scale airplanes. They noted that: 'comparisons between results from the N.A.C.A. spinning balance and full-scale flight tests have indicated considerable scale effect upon aerodynamic characteristics in spinning attitudes.' Thus, these first two models were chosen for testing in the new tunnel because their full-scale spinning characteristics were already well known. These first tests proved encouraging to the researchers but they did not achieve the precise degree of reliability hoped for. The facility's opening however, does signify the advent of a serious and long term commitment to studying the problem of aircraft spinning. From NACA TR No. 557: 'At the beginning of a test the model is mounted upon a launching spindle about the axis of which it is free to rotate. This spindle is on the end of a wooden rod and is held in the center of the tunnel by one of the operators standing in the observation chamber. With the spindle vertical the attitude of the model is such that the fuselage axis is approximately 35L to the horizontal, nose down, and the wings are 10L to the horizontal with the left wing tip the lower (for a right spin). When the model is in this attitude, air flowing upward through the tunnel causes it to rotate fairly rapidly. The air speed is increased by a second operator until the air force on the model is equal to its weight. The model then automatically disengages itself from the spindle and continues to float in the air stream entirely free of mechanical restraint. The launching spindle is immediately withdrawn from the

  14. XN2Y-1 Model Being Prepared for Spin Tunnel Tests

    NASA Technical Reports Server (NTRS)

    1935-01-01

    Model of XN2Y-1 biplane mounted on a special test rig to determine moments of inertia prior to spin tests in the Langley 15-Foot Spin Tunnel. This was one of two balsa wood models (the other was a 1/12- scale model of the F4B-2) for initial testing and calibration of the new tunnel. Researchers were very concerned that the results they might achieve with models in the tunnel would not correlate with the spinning behavior of full-scale airplanes. They noted that: 'comparisons between results from the N.A.C.A. spinning balance and full-scale flight tests have indicated considerable scale effect upon aerodynamic characteristics in spinning attitudes.' Thus, these first two models were chosen for testing in the new tunnel because their full-scale spinning characteristics were already well known. These first tests proved encouraging to the researchers but they did not achieve the precise degree of reliability hoped for. The facility's opening however, does signify the advent of a serious and long term commitment to studying the problem of aircraft spinning. Charles Zimmerman wrote in NACA TR No. 557: 'At the beginning of a test the model is mounted upon a launching spindle about the axis of which it is free to rotate. This spindle is on the end of a wooden rod and is held in the center of the tunnel by one of the operators standing in the observation chamber. With the spindle vertical the attitude of the model is such that the fuselage axis is approximately 35 to the horizontal, nose down, and the wings are 10 to the horizontal with the left wing tip the lower (for a right spin). When the model is in this attitude, air flowing upward through the tunnel causes it to rotate fairly rapidly. The air speed is increased by a second operator until the air force on the model is equal to its weight. The model then automatically disengages itself from the spindle and continues to float in the air stream entirely free of mechanical restraint. The launching spindle is immediately

  15. Alpha-1 Antitrypsin Deficiency

    MedlinePlus

    ... from the NHLBI on Twitter. What Is Alpha-1 Antitrypsin Deficiency? Alpha-1 antitrypsin (an-tee-TRIP-sin) deficiency, or AAT ... as it relates to lung disease. Overview Alpha-1 antitrypsin, also called AAT, is a protein made ...

  16. 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.

  17. The role of dislocation-induced scattering in electronic transport in GaxIn1-xN alloys

    NASA Astrophysics Data System (ADS)

    Donmez, Omer; Gunes, Mustafa; Erol, Ayse; Arikan, Cetin M.; Balkan, Naci; Schaff, William J.

    2012-08-01

    Electronic transport in unintentionally doped GaxIn1-xN alloys with various Ga concentrations ( x = 0.06, 0.32 and 0.52) is studied. Hall effect measurements are performed at temperatures between 77 and 300 K. Temperature dependence of carrier mobility is analysed by an analytical formula based on two-dimensional degenerate statistics by taking into account all major scattering mechanisms for a two-dimensional electron gas confined in a triangular quantum well between GaxIn1-xN epilayer and GaN buffer. Experimental results show that as the Ga concentration increases, mobility not only decreases drastically but also becomes less temperature dependent. Carrier density is almost temperature independent and tends to increase with increasing Ga concentration. The weak temperature dependence of the mobility may be attributed to screening of polar optical phonon scattering at high temperatures by the high free carrier concentration, which is at the order of 1014 cm-2. In our analytical model, the dislocation density is used as an adjustable parameter for the best fit to the experimental results. Our results reveal that in the samples with lower Ga compositions and carrier concentrations, alloy and interface roughness scattering are the dominant scattering mechanisms at low temperatures, while at high temperatures, optical phonon scattering is the dominant mechanism. In the samples with higher Ga compositions and carrier concentrations, however, dislocation scattering becomes more significant and suppresses the effect of longitudinal optical phonon scattering at high temperatures, leading to an almost temperature-independent behaviour.

  18. 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.

  19. Phosphorylation-independent stimulation of DNA topoisomerase II alpha activity.

    PubMed

    Kimura, K; Saijo, M; Tanaka, M; Enomoto, T

    1996-05-01

    It has been suggested that casein kinase II phosphorylates DNA topoisomerase II alpha (topo II alpha) in mouse FM3A cells, by comparison of phosphopeptide maps of topo II alpha labeled in intact cells and of topo II alpha phosphorylated by various kinases in vitro. The phosphorylation of purified topo II alpha by casein kinase II, which attached a maximum of two phosphate groups per topo II alpha molecule, had no effect on the activity of topo II alpha. Dephosphorylation of purified topo II alpha by potato acid phosphatase, which almost completely dephosphorylated the topo II alpha, did not reduce the activity of topo II alpha. The incubation itself, regardless of phosphorylation or dephosphorylation status, stimulated the enzyme activity in both reactions. Topo II alpha activity was stimulated by incubation in a medium containing low concentrations of glycerol but not in that containing high concentrations of glycerol, such as the 50% in which purified topo II alpha is stored. The stimulation of topo II alpha activity by incubation was dependent on the concentration of topo II alpha, requiring a relatively high concentration of topo II alpha. PMID:8631919

  20. Alpha-particle scattering from sup 6 Li near the. alpha. - d breakup threshold

    SciTech Connect

    Samanta, C.; Ghosh, S.; Lahiri, M. ); Ray, S. ); Banerjee, S.R. )

    1992-04-01

    The {sup 6}Li({alpha},{alpha}{prime}) reaction was studied at {ital E}{sub {alpha}}=50 MeV. The angular distribution of the continuum region near the {sup 6}Li{r arrow}{alpha}+{ital d} breakup threshold (1.475 MeV) was measured for {theta}{sub lab}=7{degree}--40{degree}. The data were analyzed in terms of plane-wave and distorted-wave impulse approximation calculations. To study the possible effects of recombination of the breakup clusters in the exit channel, distorted-wave Born approximation calculations were also performed.

  1. GaN Epitaxial Layer Grown with Conductive Al(x)Ga(1-x)N Buffer Layer on SiC Substrate Using Metal Organic Chemical Vapor Deposition.

    PubMed

    So, Byeongchan; Lee, Kyungbae; Lee, Kyungjae; Heo, Cheon; Pyeon, Jaedo; Ko, Kwangse; Jang, Jongjin; Nam, Okhyun

    2016-05-01

    This study investigated GaN epitaxial layer growth with a conductive Al(x)Ga(1-x)N buffer layer on n-type 4H-SiC by high-temperature metalorganic chemical vapor deposition (HT-MOCVD). The Al composition of the Al(x)Ga(1-x)N buffer was varied from 0% to 100%. In terms of the crystal quality of the GaN layer, 79% Al was the optimal composition of the Al(x)Ga(1-x)N buffer layer in our experiment. A vertical conductive structure was fabricated to measure the current voltage (I-V) characteristics as a function of Al composition, and the I-V curves showed that the resistance increased with increasing Al concentration of the Al(x)Ga(1-x)N buffer layer. PMID:27483845

  2. Computational Replication of the Primary Isotope Dependence of Secondary Kinetic Isotope Effects in Solution Hydride-Transfer Reactions: Supporting the Isotopically Different Tunneling Ready State Conformations.

    PubMed

    Derakhshani-Molayousefi, Mortaza; Kashefolgheta, Sadra; Eilers, James E; Lu, Yun

    2016-06-30

    We recently reported a study of the steric effect on the 1° isotope dependence of 2° KIEs for several hydride-transfer reactions in solution (J. Am. Chem. Soc. 2015, 137, 6653). The unusual 2° KIEs decrease as the 1° isotope changes from H to D, and more in the sterically hindered systems. These were explained in terms of a more crowded tunneling ready state (TRS) conformation in D-tunneling, which has a shorter donor-acceptor distance (DAD) than in H-tunneling. To examine the isotopic DAD difference explanation, in this paper, following an activated motion-assisted H-tunneling model that requires a shorter DAD in a heavier isotope transfer process, we computed the 2° KIEs at various H/D positions at different DADs (2.9 Å to 3.5 Å) for the hydride-transfer reactions from 2-propanol to the xanthylium and thioxanthylium ions (Xn(+) and TXn(+)) and their 9-phenyl substituted derivatives (Ph(T)Xn(+)). The calculated 2° KIEs match the experiments and the calculated DAD effect on the 2° KIEs fits the observed 1° isotope effect on the 2° KIEs. These support the motion-assisted H-tunneling model and the isotopically different TRS conformations. Furthermore, it was found that the TRS of the sterically hindered Ph(T)Xn(+) system does not possess a longer DAD than that of the (T)Xn(+) system. This predicts a no larger 1° KIE in the former system than in the latter. The observed 1° KIE order is, however, contrary to the prediction. This implicates the stronger DAD-compression vibrations coupled to the bulky Ph(T)Xn(+) reaction coordinate. PMID:27232375

  3. 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.

  4. 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.

  5. On the reliable analysis of indium mole fraction within InxGa1-xN quantum wells using atom probe tomography

    NASA Astrophysics Data System (ADS)

    Riley, James R.; Detchprohm, Theeradetch; Wetzel, Christian; Lauhon, Lincoln J.

    2014-04-01

    Surface crystallography and polarity are shown to influence the detection probability of In, Ga, and N ions during atom probe tomography analysis of InxGa1-xN m-plane, c-plane, and (202¯1¯) quantum wells. A N deficit is observed in regions of the reconstruction generated from Ga-polar surfaces, and the probability of detecting group-III atoms is lower in InxGa1-xN quantum wells than in GaN barrier layers. Despite these artifacts, the detected In mole fraction is consistent throughout a given quantum well regardless of the crystal orientation of the quantum well or the evaporation surface from which the reconstruction was generated.

  6. 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.

  7. 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.

  8. 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.

  9. Deexcitation processes in nuclear reactions. [Dept. of Chemistry, Purdue Univ

    SciTech Connect

    Porile, N.T.

    1980-08-01

    The following studies, currently in progress, are discussed: angular distributions and differential ranges of Ba fragments from the interaction of /sup 238/U with 0.8-to 400- GeV protons; target A dependence of the angular distribution of Sc fragments emitted in 400-GeV proton interactions; energy spectra of isotopically resolved fragments emitted in high-energy proton interactions with noble gases; comparative study of fragments emission in the interaction of Cu-U with relativistic /sup 12/C ions and high-energy protons; excitation functions of the /sup 127/I(..pi../sup + -/,..pi../sup + -/xn) reactions. 7 figures.

  10. 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.

  11. 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.

  12. 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.

  13. Nanoscale Electrostructural Characterization of Compositionally Graded Al(x)Ga(1-x)N Heterostructures on GaN/Sapphire (0001) Substrate.

    PubMed

    Kuchuk, Andrian V; Lytvyn, Petro M; Li, Chen; Stanchu, Hryhorii V; Mazur, Yuriy I; Ware, Morgan E; Benamara, Mourad; Ratajczak, Renata; Dorogan, Vitaliy; Kladko, Vasyl P; Belyaev, Alexander E; Salamo, Gregory G

    2015-10-21

    We report on AlxGa1-xN heterostructures resulting from the coherent growth of a positive then a negative gradient of the Al concentration on a [0001]-oriented GaN substrate. These polarization-doped p-n junction structures were characterized at the nanoscale by a combination of averaging as well as depth-resolved experimental techniques including: cross-sectional transmission electron microscopy, high-resolution X-ray diffraction, Rutherford backscattering spectrometry, and scanning probe microscopy. We observed that a small miscut in the substrate orientation along with the accumulated strain during growth led to a change in the mosaic structure of the AlxGa1-xN film, resulting in the formation of macrosteps on the surface. Moreover, we found a lateral modulation of charge carriers on the surface which were directly correlated with these steps. Finally, using nanoscale probes of the charge density in cross sections of the samples, we have directly measured, semiquantitatively, both n- and p-type polarization doping resulting from the gradient concentration of the AlxGa1-xN layers. PMID:26431166

  14. Epitaxial growth of (111)-oriented ZrxTi1-xN thin films on c-plane Al2O3 substrates

    NASA Astrophysics Data System (ADS)

    Li, Ruiteng; Gandhi, Jateen S.; Pillai, Rajeev; Forrest, Rebecca; Starikov, David; Bensaoula, Abdelhak

    2014-10-01

    A systematic study is presented on the effects of process parameters of S-gun configured DC magnetron sputtered ZrN thin films on c-plane Al2O3 substrates. Using a quartz crystal microbalance the deposition rate of ZrN is investigated as a function of Ar and N2 flow rates, target power, chamber pressure and gas injection position in the chamber. Selected growth conditions for ZrN show the interrelation of growth parameters on film orientation and crystallinity. (111) oriented ZrN thin films exhibit X-ray diffraction rocking curve FWHM as low as 0.36°. Additionally, (111) oriented ternary ZrxTi1-xN thin films (0≤x≤1) are also deposited on c-plane Al2O3 substrates. High resolution X-ray diffraction characterization shows that ZrxTi1-xN (x=0, 0.64, 0.80, 0.93, 1) layers exhibit rocking curve FWHM values of 0.0045-0.006° for the (111) reflection, indicating highly crystalline thin films. Atomic force microscopy characterizations show ZrxTi1-xN thin films with a surface roughness between 1.2 nm and 2.9 nm.

  15. 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

  16. Raman and photoluminescence mapping of InxGa1-xN (x ˜ 0.4) at high pressure: Optical determination of composition and stress

    NASA Astrophysics Data System (ADS)

    Gkrana, V.; Filintoglou, K.; Arvanitidis, J.; Christofilos, D.; Bazioti, C.; Dimitrakopulos, G. P.; Katsikini, M.; Ves, S.; Kourouklis, G. A.; Zoumakis, N.; Georgakilas, A.; Iliopoulos, E.

    2014-09-01

    The pressure response of a polar wurtzite InxGa1-xN (x = 0.37) film epitaxially grown on a GaN/sapphire template was studied by means of combined Raman and photoluminescence (PL) mappings. The pressure slopes of the Raman peaks (∂ω/∂P ˜ 4.7 cm-1.GPa-1) of the studied alloy are indicative of its intermediate stiffness between the end members of the InxGa1-xN system. The data analysis suggests that in our experiments the obtained slopes have marginal contribution, if any, from the substrate. Furthermore, the similarity of the ambient pressure value of the PL peak energy (˜1.97 eV) and its pressure slope (∂EPL/∂P ˜ 30 meV.GPa-1) with those obtained by absorption measurements implies that PL can be used to follow the pressure evolution of the energy bandgap. Finally, we demonstrate that all-optical characterization of the composition and residual stress of InxGa1-xN samples is feasible.

  17. 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.

  18. Calculation for the excitation functions of the {sup 93}Nb(p,n){sup 93}Mo{sup m}, {sup 93}Nb(p,{alpha}n){sup 89}Zr, and {sup 93}Nb(p,np+pn){sup 92}Nb{sup m} reactions

    SciTech Connect

    Gul, K.

    2009-04-15

    Statistical model calculation has been carried out for the excitation functions of the {sup 93}Nb(p,n){sup 93}Mo{sup m}, {sup 93}Nb(p,{alpha}n){sup 89}Zr, and {sup 93}Nb(p,np+pn){sup 92}Nb{sup m} reactions up to a 20-MeV proton energy range using global reaction parameters. The results are compared and discussed with reported measurements. The calculation for the excitation function of the {sup 93}Nb(p,n){sup 93}Mo{sup m} reaction can only match the measured magnitudes of cross sections if we postulate the existence of two energy levels with spin-parity values of 19/2{sup +} and 17/2{sup -} lying immediately above the 2.425 MeV (21/2{sup +}) isomeric state. The existence of the hypothetical levels has been discussed in the light of reported shell-model calculations.

  19. 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

  20. Methylation of alpha-type embryonic globin gene alpha pi represses transcription in primary erythroid cells.

    PubMed

    Singal, Rakesh; vanWert, Jane M; Ferdinand, Larry

    2002-12-01

    The inverse relationship between expression and methylation of beta-type globin genes is well established. However, little is known about the relationship between expression and methylation of avian alpha-type globin genes. The embryonic alpha(pi)-globin promoter was unmethylated, and alpha(pi)-globin RNA was easily detected in 5-day chicken erythroid cells. A progressive methylation of the CpG dinucleotides in the alpha(pi) promoter associated with loss of expression of alpha(pi)-globin gene was seen during development in primary erythroid cells. A 315-bp alpha(pi)-globin promoter region was cloned in an expression construct (alpha(pi)pGL3E) containing a luciferase reporter gene and SV40 enhancer. The alpha(pi)pGL3E construct was transfected into primary erythroid cells derived from 5-day-old chicken embryos. Methylation of alpha(pi)pGL3E plasmid and alpha(pi)-globin promoter alone resulted in a 20-fold and 7-fold inhibition of expression, respectively. The fully methylated but not the unmethylated 315-bp alpha(pi)-globin gene promoter fragment formed a methyl cytosine-binding protein complex (MeCPC). Chromatin immunoprecipitation assays were combined with quantitative real-time polymerase chain reaction to assess histone acetylation associated with the alpha(pi)-globin gene promoter. Slight hyperacetylation of histone H3 but a marked hyperacetylation of histone H4 was seen in 5-day when compared with 14-day erythroid cells. These results demonstrate that methylation can silence transcription of an avian alpha-type embryonic globin gene in homologous primary erythroid cells, possibly by interacting with an MeCPC and histone deacetylase complex. PMID:12393573

  1. A study of non-elastic reaction rates for the ADS materials in the environment of spallation neutrons produced by 1.6 GeV d-beam.

    PubMed

    Bhatia, Chitra; Adam, J; Kumar, V; Katovsky, K; Majerle, M; Solnyshkin, A A; Tsoupko-Sitnikov, V M

    2012-07-01

    For the design and modeling of Accelerator Driven sub-critical System (ADS) a detailed study of response of ADS materials to the spallation neutrons is required. For this purpose reaction rates of different reactions like (n, xn) and (n, xnyp) in 209Bi, natMo, 56Fe, natNi, 55Mn, natTi and natCo materials are determined in an experiment conducted at Nuclotron of JINR, Dubna, using 1.6 GeV d-beam in the 'Energy+Transmutation' set-up. Reaction rates of various (n, xn) and (n, xnyp) reactions are studied in these samples. Results of reaction rates deduced from all the gamma peaks observed in case of 209Bi (n, xn) reactions with x=3-9, natMo (n, γ), (n, 3n), (n, 6n), 56Fe (n, p), (n, p2n), (n, p4n), natNi (n, 2n), (n, 3n), (n, p), (n, d), (n, t), 55Mn (n, γ), (n, 2n), (n, 4n), natTi (n, p), (n, d), (n, t) and natCo (n, γ), (n, xn) reactions with x=2-5 along with (n, p), (n, 2p2n), (n, 2p4n) and (n, 2p6n) are presented. The measured reaction rates for all the elements show good consistency for all the reaction channels and all observed Eγ's of the product nucleus. For all the above mentioned reactions, both experimental as well as theoretical spectrum average cross-sections (σsp.av.cs) are deduced and compared. A close agreement is found between the experimental σsp.av.cs and theoretical σsp.av.cs values. PMID:22204785

  2. 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.

  3. 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.

  4. Immature platelet fraction measured on the Sysmex XN hemocytometer predicts thrombopoietic recovery after autologous stem cell transplantation

    PubMed Central

    van der Linden, Noreen; Klinkenberg, Lieke JJ; Meex, Steven JR; Beckers, Erik AM; de Wit, Norbert CJ; Prinzen, Lenneke

    2014-01-01

    Objectives A period of thrombocytopenia is common after stem cell transplantation (SCT). To prevent serious bleeding complications, prophylactic platelet transfusions are administered. Previous studies have shown that a rise in immature platelets precedes recovery of platelet count. Our aim was to define a cutoff value for immature platelets predicting thrombopoietic recovery within 2 d. Methods Hematological parameters were measured on the Sysmex XN hemocytometer. We calculated reference change values (RCV) for platelets in eight healthy individuals as marker for platelet recovery. To define a cutoff value, we performed ROC analysis using data from 16 autologous SCT patients. Results RCV for platelet concentration was 14.1%. Platelet recovery was observed 13 (median; range 9–31) days after SCT. Increase in immature platelet fraction (IPF) before platelet recovery was seen in all autologous SCT patients. Optimal cutoff IPF was found to be 5.3% for platelet recovery within 2 d (specificity 0.98, sensitivity 0.47, positive predictive value 0.93). Conclusions We identified an optimal cutoff value for IPF 5.3% to predict platelet recovery after autologous SCT within 2 d. Implementing this cutoff value in transfusion strategy may reduce the number of prophylactic platelet transfusions. PMID:24660761

  5. Alpha-1 Antitrypsin Test

    MedlinePlus

    ... measures the level of the protein AAT in blood. Alpha-1 antitrypsin phenotype testing evaluates the amount and type of AAT being produced and compares it to normal patterns. Alpha-1 antitrypsin genotype testing ( DNA testing) can ...

  6. Alpha-1 antitrypsin test

    MedlinePlus

    ... page: //medlineplus.gov/ency/article/003715.htm Alpha-1 antitrypsin test To use the sharing features on this page, please enable JavaScript. Alpha-1 antitrypsin is a laboratory test to measure the ...

  7. 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.

  8. 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)

  9. The alloantigenic sites of alpha3alpha4alpha5(IV) collagen: pathogenic X-linked alport alloantibodies target two accessible conformational epitopes in the alpha5NC1 domain.

    PubMed

    Kang, Jeong Suk; Kashtan, Clifford E; Turner, A Neil; Heidet, Laurence; Hudson, Billy G; Borza, Dorin-Bogdan

    2007-04-01

    Anti-glomerular basement membrane (GBM) antibody nephritis is caused by an autoimmune or alloimmune reaction to the NC1 domains of alpha3alpha4alpha5(IV) collagen. Some patients with X-linked Alport syndrome (XLAS) develop post-transplant nephritis mediated by pathogenic anti-GBM alloantibodies to collagen IV chains present in the renal allograft but absent from the tissues of the patient. In this work, the epitopes targeted by alloantibodies from these patients were identified and characterized. All XLAS alloantibodies recognized conformational epitopes in the NC1 domain of alpha5(IV) collagen, which were mapped using chimeric alpha1/alpha5 NC1 domains expressed in mammalian cells. Allograft-eluted alloantibodies mainly targeted two conformational alloepitopes mapping to alpha5NC1 residues 1-45 and 114-168. These regions also encompassed the major epitopes of circulating XLAS alloantibodies, which in some patients additionally targeted alpha5NC1 residues 169-229. Both kidney-eluted and circulating alloantibodies to alpha5NC1 distinctively targeted epitopes accessible in the alpha3alpha4alpha5NC1 hexamers of human GBM, unlike anti-GBM autoantibodies, which targeted sequestered alpha3NC1 epitopes. The results identify two immunodominant alpha5NC1 epitopes as major alloantigenic sites of alpha3alpha4alpha5(IV) collagen specifically implicated in the pathogenesis of post-transplant nephritis in XLAS patients. The contrast between the accessibility of these alloepitopes and the crypticity of autoepitopes indicates that distinct molecular forms of antigen may initiate the immunopathogenic processes in the two forms of anti-GBM disease. PMID:17293596

  10. Effects of deuterium substitution alpha and beta to the reaction centre, 18O substitution in the leaving group, and aglycone acidity on hydrolyses of aryl glucosides and glucosyl pyridinium ions by yeast alpha-glucosidase. A probable failure of the antiperiplanar-lone-pair hypothesis in glycosidase catalysis.

    PubMed

    Hosie, L; Sinnott, M L

    1985-03-01

    Neither kcat. nor kcat./Km for five aryl alpha-D-glucopyranosides correlates with aglycone pKa, and isotope effects, described according to the convention used by Cleland [(1982) CRC Crit. Rev. Biochem. 13, 385-428], of 18(V) = 1.002 +/- 0.008, alpha D(V) = 1.01 +/- 0.04 and alpha D(V/K) = 0.969 +/- 0.035 are observed for p-nitrophenyl, and one of beta D(V) = 1.02 +/- 0.04 for phenyl alpha-D-glucopyranoside; kcat. but not kcat./Km, correlates with aglycone pKa for five alpha-D-glucopyranosyl pyridinium ions with a Brønsted coefficient of -0.61 +/- 0.06, and isotope effects of alpha D(V) = 1.22 +/- 0.02, beta D(V) = 1.13 +/- 0.01 and alpha D(V/K) = 1.018 +/- 0.046 for the 4-bromoisoquinolinium, and alpha D(V) = 1.15 +/- 0.02 and beta D(V) = 1.085 +/- 0.011 for the pyridinium salts are observed. These data require that a non-covalent event, fast in the case of the N-glycosides but slow in the case of the O-glycosides, precedes bond-breaking, and that bond-breaking involves substantial charge development on the glycone and near-perpendicularity of the C2-H bond to the planar oxocarbonium ion system. A model meeting these requirements is that the non-covalent event is a conjoint change of protein and substrate conformation which puts the pyranose ring in the 2,5B conformation of the bond-breaking transition state. This model also explains the contrast between the powerful inhibition of the enzyme by deoxynojirimycin (Ki = 23 +/- 3 microM) and feeble inhibition by castanospermine [Saul, Chambers, Molyneux & Elbein (1983) Arch. Biochem. Biophys. 221, 593-597], but is directly contrary to the predictions of Deslongchamps' 'Theory of Stereoelectronic Control' [Deslongchamps (1975) Tetrahedron 31, 2463-2490; (1983) Stereoelectronic Effects in Organic Chemistry, p. 39, Pergamon Press, Oxford]. PMID:3888191

  11. Alpha-gal anaphylaxis: the first case report in Italy.

    PubMed

    Calamari, A M; Poppa, M; Villalta, D; Pravettoni, V

    2015-09-01

    We report the case of a 55-year-old man who went into anaphylactic shock six hours after eating a meal containing meat. He reported having had several tick bites in months before the reaction. The serum specific IgE showed strong positivity to alpha-gal. This is clearly alpha-gal anaphylaxis with delayed onset after meat ingestion caused by tick bite, confirmed by alpha-gal IgE positivity. PMID:26357002

  12. Human alpha 2-adrenergic receptor subtype distribution: widespread and subtype-selective expression of alpha 2C10, alpha 2C4, and alpha 2C2 mRNA in multiple tissues.

    PubMed

    Eason, M G; Liggett, S B

    1993-07-01

    At present, molecular cloning and pharmacological studies have delineated three human alpha 2-adrenergic receptor (alpha 2AR) subtypes, alpha 2C10, alpha 2C4, and alpha 2C2. Assignment of the alpha 2AR subtypes to specific functions has been limited by an unclear definition of tissue alpha 2AR expression outside of the central nervous system. It has been suggested that alpha 2C4 expression is confined to the brain, that alpha 2C2 expression is only in the liver and kidney, and that there is nearly ubiquitous expression of alpha 2C10. However, this is based on studies of a limited number of rat tissues or on studies using non-species-specific approaches. Therefore, to define alpha 2C10, alpha 2C4, and alpha 2C2 tissue expression, we used reverse transcription of total RNA isolated from 20 human tissues, followed by amplification of alpha 2AR cDNA using the polymerase chain reaction. This technique provided two advantages: high sensitivity and, with the use of subtype-specific oligonucleotide primers and probes, differentiation between the alpha 2AR subtypes. The tissues studied were aorta, vena cava, heart (epicardium and endocardium), lung, skeletal muscle, liver, pancreas (head and tail), fat (perinephric and subcutaneous), kidney (cortex and medulla), prostate, stomach, ileum, jejunum, colon, adrenal gland, and spleen. We found that the majority of these tissues expressed alpha 2C10, with the exceptions being the head of the pancreas, subcutaneous fat, colon, and spleen. In marked distinction to other studies, however, we found a prolific expression of the alpha 2C4 and alpha 2C2 subtypes. Expression of alpha 2C4 was found in all tissues with the exception of liver, fat, stomach, and colon, and a virtually ubiquitous expression of alpha 2C2 was found, with the exception of epicardium. Of all tissues studied, only colon and subcutaneous fat expressed a single alpha 2AR subtype, which was alpha 2C2. Thus, the alpha 2AR subtypes do not have a confined expression but

  13. Calibration issues in delta alpha /alpha .

    NASA Astrophysics Data System (ADS)

    Molaro, Paolo; Centurión, Miriam; Levshakov, Sergei

    Laser Comb Wavelength calibration shows that the ThAr one is locally unreliable with possible deviations of up to 100 {m s}-1 within one order range, while delivering an overall 1 {m s}-1 accuracy (Wilken et al 2009). Such deviation corresponds to delta alpha /alpha ≈ 7* 10-6 for a Fe II-Mg II pair. Comparison of line shifts among the 5 Fe II lines, with almost identical sensitivity to fine structure constant changes, offers a clean way to directly test the presence of possible local wavelength calibration errors of whatever origin. We analyzed 5 absorption systems, with zabs ranging from 1.15 to 2.19 towards 3 bright QSOs. The results show that while some lines are aligned within 20 {m s}-1, others reveal large deviations reaching 200 {m s}-1 or higher and corresponding to a delta alpha /alpha > 10-5 level. The origin of these deviations is not clearly identified but could be related to the adaptation of wavelength calibration to CCD manufacturing irregularities. These results suggest that to draw conclusions from delta alpha /alpha analysis based on one or only few lines must be done with extreme care.

  14. Experimental investigation and theoretical calculation for 3He induced nuclear reactions on vanadium

    NASA Astrophysics Data System (ADS)

    Ali, B. M.; Al-Abyad, M.; Seddik, U.; El-Kameesy, S. U.; Ditrói, F.; Takács, S.; Tárkányi, F.

    2016-04-01

    Using stacked-foil activation technique and gamma-ray spectrometry, excitation functions for 3He induced nuclear reactions on natV were measured. Cross-sections for natV(3He, xn)52m,gMn and natV(3He, pxn)51Cr nuclear reactions were measured up to 27 MeV utilizing the MGC-20E cyclotron of ATOMKI. The measurements establish for the first time consistent excitation curves. Comparisons with results for values derived from different theoretical codes were included. Integral yield were calculated.

  15. Hyperbranched Polycarbosilanes via Nucleophilic Substitution Reactions

    NASA Astrophysics Data System (ADS)

    Interrante, L.; Shen, Q.

    Nucleophilic substitution reactions involving organomagnesium (Grignard) [1] and organolithium reagents have been used extensively for many years to form Si—C bonds (see Reaction Scheme 12.1). However, their use for the construction of hyperbranched polymers whose backbone contains, as a major structural component, silicon—carbon bonds, i.e., polycarbosilanes [2] is relatively more recent. (12.1) begin{array}{l} {{R}}_3 {{SiX + MR'}} to {{R}}_3 {{SiR' + MX}} \\ left({{{R,R' = alkyl}} {{or aryl;}} {{M = Mg(X),}} {{Li,}} {{Na}};{{X = halogen, OR''}}} right) \\ This chapter focuses on the application of such nucleophilic substitution reactions toward the synthesis of hyperbranched polycarbosilanes, with particular emphasis on those preparations that have resulted in relatively well characterized products. These syntheses are organized by the type of ABn monomer unit used (see Section 1.2), where A and B refer to the (C)X and (Si)Xn, respectively, functional ends of the monomer unit and where the nature of the coupling reaction leads to entirely or primarily Si—C bond formation. In most cases, these are “one-pot” reactions that employ monomers that bear halogen or alkoxy groups on the C and Si ends of the unit. Indeed, hyperbranched polycarbosilanes have been described, in general, as “obtained in one synthetic step via a random, one-pot polymerization of multifunctional monomers of AB n type” [2]. Treatment of the ABn monomer with either elemental Mg or an organolithium reagent, ideally (but not always) forms a complexed carbanion (the nucleophile) by reaction with the C-X end of the monomer unit, resulting in an intermediate of the type, (XxM)CSiXn, where M = Mg or Li, X = halogen or alkoxy, and x = 1 (Mg) or 0 (Li). Self-coupling of this reagent via reactions of the type shown in Reaction Scheme 12.1 leads to oligomeric and polymeric products that are connected primarily through Si—C bonds and yield an inorganic MXx by-product.

  16. Action of human pancreatic and salivary alpha-amylases on maltooligosaccharides: evaluation of kinetic parameters.

    PubMed

    Saito, N; Horiuchi, T; Yoshida, M; Imai, T

    1979-10-01

    The kinetic studies on the reactions of human pancreatic and salivary alpha-amylases with several maltooligosaccharides (maltotetraose, maltopentaose, maltohexaose, and maltoheptaose) were carried out. The susceptibility to hydrolysis with human pancreatic alpha-amylase decreased in the order of maltopentaose, maltohexaose, maltotetraose, and maltoheptaose, while with human salivary alpha-amylase maltopentaose was hydrolysed slightly slower than maltohexaose but fairly faster than maltotetraose or maltoheptaose from a viewpoint of the rates of reactions based on the amount of substrate changed. The relative rates of production of substrates, utilized in the coupled yeast alpha-glucosidase reaction, increased in the order of maltoheptaose, maltohexaose, maltotetraose, and maltopentaose with human pancreatic alpha-amylase, while with human salivary alpha-amylase in the order of maltoheptaose, maltotetraose, maltohexaose, and maltopentaose. Thus, maltopentaose was considered to be the best substrate over maltotetraose, maltohexaose or maltoheptaose for the alpha-glucosidase coupled method of alpha-amylase determination. PMID:385176

  17. Photo-neutron reaction cross-sections for natMo in the bremsstrahlung end-point energies of 12-16 and 45-70 MeV

    NASA Astrophysics Data System (ADS)

    Naik, H.; Kim, G. N.; Kapote Noy, R.; Schwengner, R.; Kim, K.; Zaman, M.; Shin, S. G.; Gey, Y.; Massarczyk, R.; John, R.; Junghans, A.; Wagner, A.; Cho, M.-H.

    2016-07-01

    The natMo( γ, xn)90, 91, 99Mo reaction cross-sections were experimentally determined for the bremsstrahlung end-point energies of 12, 14, 16, 45, 50, 55, 60 and 70MeV by activation and off-line γ -ray spectrometric technique and using the 20MeV electron linac (ELBE) at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany, and the 100MeV electron linac at the Pohang Accelerator Laboratory (PAL), Pohang, Korea. The natMo( γ, xn)88, 89, 90, 91, 99Mo reaction cross-sections as a function of photon energy were also calculated using the computer code TALYS 1.6. The flux-weighted average cross-sections were obtained from the literature data and the calculated values of TALYS based on mono-energetic photons and are found to be in general agreement with the present results. The flux-weighted average experimental and theoretical cross-sections for the natMo( γ, xn)88, 89, 90, 91, 99Mo reactions increase with the bremsstrahlung end-point energy, which indicates the role of excitation energy. After a certain energy, the individual natMo( γ, xn) reaction cross-sections decrease with the increase of bremsstrahlung energy due to opening of other reactions, which indicates sharing of energy in different reaction channels. The 100Mo( γ, n) reaction cross-section is important for the production of 99Mo , which is a probable alternative to the 98Mo(n, γ) and 235U(n, f ) reactions.

  18. Renal deposition of alpha interferon in systemic lupus erythematosus.

    PubMed Central

    Panem, S; Ordóñez, N; Vilcek, J

    1983-01-01

    Earlier studies from several laboratories showed that interferon-alpha (IFN-alpha) is present in the sera of a large percentage of patients with systemic lupus erythematosus (SLE). We now report the detection of IFN-alpha by indirect immunofluorescence in renal sections of three patients with SLE but not in six control kidneys. The immunofluorescence reaction was mediated by three hyperimmune antisera to IFN-alpha raised in three different species, but not by any preimmune serum. The reaction was specifically blocked by absorption of the anti-IFN-alpha sera with purified IFN-alpha made by recombinant DNA techniques or with IFN-alpha isolated from the serum of an SLE patient, but not by bovine serum albumin or human immunoglobulin G. In contrast, antisera to IFN-beta or IFN-gamma did not mediate immunofluorescence. The pattern of IFN-alpha deposition resembled that seen with anti-human immunoglobulin G, suggesting association with immune complexes. Immune complexes were then preparatively eluted from the homogenate of an SLE kidney by treatment with buffer at pH 2.8. Biologically active IFN was found in this eluate and was demonstrated to be IFN-alpha by specific neutralization with IFN antisera. These results extend the specific association of IFN-alpha with SLE. Images PMID:6413415

  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. Excited levels of /sup 238/Np from spectroscopic measurements of the /sup 237/Np(n,. gamma. )/sup 238/Np reaction and /sup 242m/Am alpha decay

    SciTech Connect

    Hoff, R.; Ruhter, W.; Mann, L.

    1981-06-01

    The gamma rays and conversion electrons emitted following neutron capture in a /sup 237/Np target have been measured by use of the GAMS and BILL spectrometers at Grenoble. Gamma ray and alpha particle measurements of /sup 242m/Am alpha decay (Ge(Li)..gamma.. singles, ..gamma..-..gamma.. coincidences, ..cap alpha.. singles) have been made at Livermore. The data from these measurements have been combined with earlier measurements (Ionescu 1979, Asaro 1964) to produce a more detailed level scheme for /sup 238/Np. Approximately 36 levels have been identified from all of the experimental evidence. The experimentally-observed bandhead energies can be compared with predicted values derived from a simple linear addition of excitation energies observed in neighboring odd-mass nuclei. Values for the Gallagher-Moszkowski splitting of each configurational pair were obtained from theoretical calculations (Piepenbring 1978). We have assigned configurations to ten rotational bands whose bandhead energies range from 0 to 342 keV and which represent all but one of the configurations predicted to occur below 385 keV.

  1. Effects of alloy disorder on the transport properties of Al{sub x}Ga{sub 1-x}N epilayers probed by persistent photoconductivity

    SciTech Connect

    Zeng, K. C.; Lin, J. Y.; Jiang, H. X.

    2000-03-27

    The effects of alloy fluctuations on the transport properties of Al{sub x}Ga{sub 1-x}N alloys (x{approx}0.35) have been probed through the use of persistent photoconductivity (PPC). In the PPC state, the electron mobility, {mu}{sub e}, as a function of electron concentration, n, in a single sample can be obtained under controlled light illumination conditions. It was found that {mu}{sub e} is a constant when n is below a critical value n{sub c} and it then increases with n at n>n{sub c}. This mobility behavior was attributed to the effects of alloy fluctuations in Al{sub x}Ga{sub 1-x}N alloys. As a result, the initial PPC buildup kinetics seen in Al{sub x}Ga{sub 1-x}N alloys was quite different from those in better understood semiconductor alloys, such as AlGaAs and ZnCdSe, and is a direct consequence of the observed unique dependence of {mu}{sub e} on n. From these measurements, the total density of the tail states below the mobility edge in the conduction band was estimated to be 1.46x10{sup 17} cm{sup -3} in a Al{sub 0.35}Ga{sub 0.65}N sample. The results were compared with those in II-VI semiconductor alloys and their implications on III-nitride device applications were discussed. (c) 2000 American Institute of Physics.

  2. Optical constants of In(x)Ga(1-x)N (0 ≤ x ≤ 0.73) in the visible and near-infrared wavelength regimes.

    PubMed

    Hazari, Arnab; Bhattacharya, Aniruddha; Frost, Thomas; Zhao, Songrui; Baten, Md Zunaid; Mi, Zetian; Bhattacharya, Pallab

    2015-07-15

    Complex refractive indices of In(x)Ga(1-x)N epitaxial layers have been determined from analysis of data obtained by spectroscopic ellipsometry. The measurements were made in the wavelength range of 400-1687 nm. The samples were grown by plasma-assisted molecular beam epitaxy on (001) silicon substrate and are of the wurtzite crystalline form. A comparison of the fundamental absorption edge derived from analysis of measured data and the measured photoluminescence peak emission energy indicates a Stokes shift present in the alloys. PMID:26176455

  3. Impact of cation-based localized electronic states on the conduction and valence band structure of Al{sub 1−x}In{sub x}N alloys

    SciTech Connect

    Schulz, S.; Caro, M. A.; O'Reilly, E. P.

    2014-04-28

    We demonstrate that cation-related localized states strongly perturb the band structure of Al{sub 1−x}In{sub x}N leading to a strong band gap bowing at low In content. Our first-principles calculations show that In-related localized states are formed both in the conduction and the valence band in Al{sub 1−x}In{sub x}N for low In composition, x, and that these localized states dominate the evolution of the band structure with increasing x. Therefore, the commonly used assumption of a single composition-independent bowing parameter breaks down when describing the evolution both of the conduction and of the valence band edge in Al{sub 1−x}In{sub x}N.

  4. Temperature Dependence of Surface Acoustic Wave Propagation Velocity in InxGa1-xN Films Obtained by High-Resolution Brillouin Spectroscopy: Determination of Temperature Coefficient of Frequency

    NASA Astrophysics Data System (ADS)

    Riobóo, Rafael J. Jiménez; Prieto, Carlos; Cuscó, Ramón; Artús, Lluís; Boney, Chris; Bensaoula, Abdelhak; Yamaguchi, Tomohiro; Nanishi, Yasushi

    2013-05-01

    Temperature-dependent surface acoustic wave (SAW) propagation velocity and temperature coefficient of frequency (TCF) have been determined for the first time in InxGa1-xN alloys by means of high-resolution Brillouin spectroscopy (HRBS). HRBS offers an alternative way of determining TCF. The obtained TCF values present a non-linear behavior with the In concentration. TCF of pure InN (-13.75 ppm/K) is similar to those of AlN and GaN (-19 and -17.7 ppm/K, respectively). InxGa1-xN samples exhibit frequency values that are very stable against temperature changes, which makes InxGa1-xN a good candidate for current SAW-based technological applications.

  5. [Alpha1-adrenoceptor subtypes and alpha1-adrenoceptor antagonists].

    PubMed

    Muramatsu, Ikunobu; Suzuki, Fumiko; Tanaka, Takashi; Yamamoto, Hatsumi; Morishima, Shigeru

    2006-03-01

    Alpha(1)-adrenoceptors are widely distributed in the human body and play important physiologic roles. Three alpha(1)-adrenoceptor subtypes (alpha(1A), alpha(1B) and alpha(1D)) have been cloned and show different pharmacologic profiles. In addition, a putative alpha(1)-adrenoceptor (alpha(1L) subtype) has also been proposed. Recently, three drugs (tamsulosin, naftopidil, and silodosin) have been developed in Japan for the treatment of urinary obstruction in patients with benign prostatic hyperplasia. In this review, we describe recent alpha(1)-adrenoceptor subclassifications and the pharmacologic characteristics (subtype selectivity and clinical relevance) of alpha(1)-adrenoceptor antagonists. PMID:16518082

  6. Alpha-thalassemia mutations in Gilan Province, North Iran.

    PubMed

    Hadavi, Valeh; Jafroodi, Maryam; Hafezi-Nejad, Nima; Moghadam, Sousan Dehnadi; Eskandari, Fatemeh; Tarashohi, Shahin; Pourfahim, Hamideh; Oberkanins, Christian; Law, Hai-Yang; Najmabadi, Hossein

    2009-01-01

    One hundred and three patients from Gilan Province, Iran, presenting with hypochromic and microcytic anemia parameters without iron deficiency were included in this study. Using gap-polymerase chain reaction (gap-PCR), reverse hybridization StripAssay and DNA sequencing, we detected a total of 113 alpha-globin mutations in 94 (91.3%) of these patients. Most prevalent of the 16 different alpha-thalassemia (alpha-thal) alleles was -alpha(3.7) (42.5%), followed by the polyadenylation signal (poly A2) (AATAAA>AATGAA) (12.4%), Hb Constant Spring [Hb CS, alpha142, Term-->Gln (TAA>CAA in alpha2] (10.6%), --(MED) (8.8%), IVS-I donor site [GAG GTG AGG>GAG G-----, alpha(-5 nt) (-TGAGG)] (7.1%), -alpha(4.2) (4.4%) and poly A1 (AATAAA>AATAAG) (3.5%). An additional nine mutations were observed at frequencies below 2%. We also found two novel alpha1 gene mutations: alpha(-9) (HBA1: c.-9 G>C) and alpha(IVS-I-4) (HBA1: c.95+4 A>G). Our new findings will be valuable for improving targeted thalassemia screening and prevention strategies in this area. PMID:19657838

  7. {alpha} decay of even-even superheavy elements

    SciTech Connect

    Denisov, V. Yu.; Khudenko, A. A.

    2010-03-15

    The {alpha}-decay half-lives of even-even superheavy elements within the range of proton number 104<=Z<=126, which can be formed by possible cold and hot fusion reactions, are calculated in the framework of various approaches for {alpha}-decay half-life evaluation and by using the Q values of {alpha} transitions obtained within different approximations for atomic masses. The dependencies of {alpha}-decay half-lives of superheavy elements on model approaches for both the Q values and half-life calculations are discussed in detail.

  8. 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.

  9. 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.

  10. Polymorphism of tumour necrosis factor-alpha (TNF-alpha) at position -308 in relation to ankylosing spondylitis.

    PubMed Central

    Verjans, G M; Brinkman, B M; Van Doornik, C E; Kijlstra, A; Verweij, C L

    1994-01-01

    In addition to HLA-B27, other genetic factors are thought to be involved in the pathogenesis of ankylosing spondylitis (AS). Because of the localization, in the proximity of the HLA-B locus, and the biological activities of TNF-alpha, we investigated the association between AS and a single base polymorphism located at position -308 of the TNF-alpha gene. An allele-specific polymerase chain reaction was developed to monitor this polymorphism. The frequency of the TNF-alpha alleles was determined in 66 AS patients and 37 healthy controls. The TNF-alpha allele frequency was not significantly different between AS patients and controls. PMID:8033419

  11. On the vibrational spectra and structural parameters of some XN 3 molecules (X=H, F, Cl, Br)

    NASA Astrophysics Data System (ADS)

    Shen, Shiyu; Durig, James R.

    2003-12-01

    Ab initio calculations with full electron correlation by the perturbation method to second order and hybrid density functional theory calculations by the B3LYP method utilizing the 6-31G* and 6-311+G** basis sets have been carried out for the XN 3 molecules (X=H, F, Cl, Br). From these calculations, force constants, infrared intensities, Raman activities, depolarization ratios, vibrational frequencies, and structural parameters have been determined. These calculations support the assignment of the HN 3 and DN 3 out-of-plane bending modes (ν 6, A″) at 602 and 591 cm -1, respectively, which was proposed [J. Chem. Phys. 44 (1966) 4108] earlier and show the recent assignments at 637 and 638 cm -1 [J. Mol. Struct. (Theochem) 434 (1998) 1], respectively, for these modes are in error. Also the usually used frequency of 588 cm -1 for ν 6 for the HN 3 from nitrogen matrix studies for comparison to ab initio predicted values is also clearly in error. The predicted intensity of ν 6 is only 0.2-0.6 km/mol which is 10 3 times less than the stronger bands which explains why it is so weak in the nitrogen matrix compared to its intensity in the gas phase where it drastically increased by Coriolis coupling with ν 5. For ClN 3 there is extensive coupling of the N 3 deformation at 719 cm -1 with the Cl-N stretch at 545 cm -1 where the latter mode is 71% Cl-N stretch. For BrN 3 the coupling is mainly between the N 3 deformation (682 cm -1) and the BrNN bend which is predicted in the 180 cm -1 region. The predicted force constants for FN 3 are compared to those obtained earlier from frequency and distortion data. By combining previously reported rotational constants for HN 3, FN 3 and ClN 3 with the ab initio MP2/6-311+G** predicted parameters, adjusted r0 parameters have been obtained for all three molecules. The structural parameters for hydrazoic acid are: r(H-N), 1.015(5); r(N 1N 2), 1.243(5); r(N 2N 3), 1.134(2)Å; ∠HN 1N 2, 108.8(5); ∠N 1N 2N 3, 171.8(5)°. It is

  12. Influence of carbon content and nitrogen vacancies on the bonding structure and mechanical performance of graphite-like BC{sub x}N thin films

    SciTech Connect

    Caretti, Ignacio; Jimenez, Ignacio

    2012-09-15

    X-ray absorption near edge structure (XANES) was used to investigate two sets of graphite-like BC{sub x}N thin films with similar B:C:N ratios but different amounts of nitrogen vacancies, which become oxygen-filled in the surface-most region. The two sets of samples were grown on Si (100) at room temperature by ion beam assisted deposition using two different ion/atom ratios. Nitrogen vacancy defects were detected in the B1s XANES spectra due to an oxygen decoration mechanism taking place at the film surface, which is correctly described by a core-level shift model. Analysis of the O1s XANES spectra showed two different types of oxygen incorporation in the samples under study. The tribomechanical properties of the BC{sub x}N samples were tested by the pin-on-disk technique, revealing the substantial role played by both the carbon intake in the hexagonal BCN planes and the concentration of nitrogen vacancies generated during the growth.

  13. Microstructure and dielectric properties of piezoelectric magnetron sputtered w-Sc{sub x}Al{sub 1-x}N thin films

    SciTech Connect

    Zukauskaite, Agne; Wingqvist, Gunilla; Palisaitis, Justinas; Jensen, Jens; Persson, Per O. A.; Birch, Jens; Hultman, Lars; Matloub, Ramin; Muralt, Paul; Kim, Yunseok

    2012-05-01

    Piezoelectric wurtzite Sc{sub x}Al{sub 1-x}N (x = 0, 0.1, 0.2, 0.3) thin films were epitaxially grown by reactive magnetron co-sputtering from elemental Sc and Al targets. Al{sub 2}O{sub 3}(0001) wafers with TiN(111) seed and electrode layers were used as substrates. X-ray diffraction shows that an increase in the Sc content results in the degradation of the crystalline quality. Samples grown at 400 deg. C possess true dielectric behavior with quite low dielectric losses and the leakage current is negligible. For ScAlN samples grown at 800 deg. C, the crystal structure is poor and leakage current is high. Transmission electron microscopy with energy dispersive x-ray spectroscopy mapping shows a mass separation into ScN-rich and AlN-rich domains for x {>=} 0.2 when substrate temperature is increased from 400 to 800 deg. C. The piezoelectric response of epitaxial Sc{sub x}Al{sub 1-x}N films measured by piezoresponse force microscopy and double beam interferometry shows up to 180% increase by the addition of Sc up to x = 0.2 independent of substrate temperature, in good agreement with previous theoretical predictions based on density-functional theory.

  14. The impact of argon admixture on the c-axis oriented growth of direct current magnetron sputtered ScxAl1-xN thin films

    NASA Astrophysics Data System (ADS)

    Mayrhofer, P. M.; Eisenmenger-Sittner, C.; Stöger-Pollach, M.; Euchner, H.; Bittner, A.; Schmid, U.

    2014-05-01

    The piezoelectric properties of wurtzite aluminium nitride (w-AlN) are enhanced by alloying with scandium (Sc), thus offering superior properties for applications in micro electro-mechanical systems devices. ScxAl1-xN thin films have been prepared by DC reactive magnetron sputtering on Si (100) substrates from a single target. When targeting a concentration range from x = 0 up to x = 0.15, the preparation conditions have been optimized by varying the Ar/N2 ratio in the sputtering gas. To incorporate an increasing Sc concentration, a higher Ar/N2 ratio has to be applied during the deposition process. Hence, the argon concentration in the sputtering gas becomes a crucial parameter for microstructure-related parameters. To determine phase purity, degree of c-axis orientation, lattice parameter, and grain size, the ScxAl1-xN thin films were investigated by techniques, such as scanning electron microscopy, transmission electron microscopy, and X-ray diffraction.

  15. Spin-glass-like behavior and negative thermal expansion in antiperovskite Mn{sub 3}Ni{sub 1−x}Cu{sub x}N compounds

    SciTech Connect

    Ding, Lei; Wang, Cong Sun, Ying; Colin, Claire V.; Chu, Lihua

    2015-06-07

    The Cu-doping effect on the lattice and magnetic properties in Mn{sub 3}Ni{sub 1−x}Cu{sub x}N (x = 0, 0.3, 0.5, 0.7, 1.0) was extensively investigated. We observed that the Cu-doping at the Ni site complicated the magnetic ground states, which induced the competition of antiferromagnetic and ferromagnetic interactions. Spin-glass-like behavior, arising from possible site-randomness and competing interactions of magnetism, was observed in compounds with x = 0.3, 0.5, and 0.7, and typically discussed by means of the measurement of ac magnetic susceptibility for x = 0.7. The negative thermal expansion (NTE) behavior, due to the magnetic ordering transition, was observed in Mn{sub 3}Ni{sub 1−x}Cu{sub x}N compounds using variable temperature x-ray diffraction. It reveals that the introduction of Cu effectively broadens the temperature range displaying negative thermal expansion. The relationship between the local lattice distortion and the competing magnetic ground states might play an important role in broadening the NTE temperature range in this antiperovskite compound.

  16. 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.

  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. 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.

  19. 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.

  20. 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.

  1. Alpha-synuclein expression in the developing human brain.

    PubMed

    Raghavan, Ravi; Kruijff, Loes de; Sterrenburg, Monique D; Rogers, Beverly B; Hladik, Christa L; White, Charles L

    2004-01-01

    Alpha (alpha)-synuclein is a presynaptic protein, abnormal expression of which has been associated with neurodegenerative and neoplastic diseases. It is abundant in the developing vertebrate central nervous system (CNS), but less is known about its developmental expression in the human CNS. Immunohistochemical expression of alpha-synuclein was studied in 39 fetal, perinatal, pediatric, and adolescent brains. Perikaryal expression of alpha-synuclein is observed as early as 11-wk gestation in the cortical plate. Several discrete neuronal groups in the hippocampus, basal ganglia, and brain stem express perikaryal alpha-synuclein by 20-wk gestation, persisting through the first few years of life. In the cerebellum, alpha-synuclein is present by 21-wk gestation and persists into adult life as a coarse granular neuropil reaction product in the internal granular layer, and as a diffuse neuropil "blush" in the molecular layer. The germinal matrix, glia, endothelial cells, external granular layer, Pukinje cells, and dentate neurons are consistently negative for alpha-synuclein. We conclude that alpha-synuclein is expressed very early in human gestation, and that its distribution and temporal sequence of expression varies in discrete neuronal groups. Perikaryal alpha-synuclein starts disappearing from the neuronal cytosol in early childhood, and only the neuropil retains immunoreactivity into adulthood. The reappearance of alpha-synuclein in the adult neuronal cytosol in certain disease processes may represent reemergence of cues from an earlier developmental stage as part of a stress response. PMID:15547775

  2. 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.

  3. The status of alpha-particle diagnostics

    SciTech Connect

    Young, K.M.; Johnson, D.W.

    1992-01-01

    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.

  4. Alpha-thalassaemia.

    PubMed

    Harteveld, Cornelis L; Higgs, Douglas R

    2010-01-01

    Alpha-thalassaemia is inherited as an autosomal recessive disorder characterised by a microcytic hypochromic anaemia, and a clinical phenotype varying from almost asymptomatic to a lethal haemolytic anaemia.It is probably the most common monogenic gene disorder in the world and is especially frequent in Mediterranean countries, South-East Asia, Africa, the Middle East and in the Indian subcontinent. During the last few decades the incidence of alpha thalassaemia in North-European countries and Northern America has increased because of demographic changes. Compound heterozygotes and some homozygotes have a moderate to severe form of alpha thalassaemia called HbH disease. Hb Bart's hydrops foetalis is a lethal form in which no alpha-globin is synthesized. Alpha thalassaemia most frequently results from deletion of one or both alpha genes from the chromosome and can be classified according to its genotype/phenotype correlation. The normal complement of four functional alpha-globin genes may be decreased by 1, 2, 3 or all 4 copies of the genes, explaining the clinical variation and increasing severity of the disease. All affected individuals have a variable degree of anaemia (low Hb), reduced mean corpuscular haemoglobin (MCH/pg), reduced mean corpuscular volume (MCV/fl) and a normal/slightly reduced level of HbA2. Molecular analysis is usually required to confirm the haematological observations (especially in silent alpha-thalassaemia and alpha-thalassaemia trait). The predominant features in HbH disease are anaemia with variable amounts of HbH (0.8-40%). The type of mutation influences the clinical severity of HbH disease. The distinguishing features of the haemoglobin Bart's hydrops foetalis syndrome are the presence of Hb Bart's and the total absence of HbF. The mode of transmission of alpha thalassaemia is autosomal recessive. Genetic counselling is offered to couples at risk for HbH disease or haemoglobin Bart's Hydrops Foetalis Syndrome. Carriers of alpha+- or

  5. 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.

  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. Observation of a Double-humped {gamma}-Ray Fold Distribution in {sup 142}Eu

    SciTech Connect

    Lieder, R. M.; Pasternak, A. A.; Lieder, E. O.; Gast, W.; De Angelis, G.; Bazzacco, D.

    2008-05-12

    An investigation of {gamma}-ray fold distributions has been carried out for the {sup 97}Mo({sup 51}V,z{alpha} yp xn) reaction. For the {alpha}2n channel leading to {sup 142}Eu a double-humped fold distribution was found. An explanation in terms of an incomplete-fusion reaction mechanism is proposed.

  8. Polyfluorinated. cap alpha. ,. beta. -unsaturated ketons

    SciTech Connect

    Latypov, R.R.; Belogai, V.D.; Pashkevich, K.I.

    1986-07-10

    The ..cap alpha..,..beta..-unsaturated ketones (..cap alpha..,..beta..-UK), particularly those groups containing fluoroalkyl groups, are of interest as highly reactive compounds having two nonequivalent electrophilic centers. In the present investigation, by boiling polyfluorinated aldehydes with methylketones in glacial acetic acid, they have obtained for the first time the polyfluorinated ..beta..-hydroxy-ketones, the dehydration of which has been used to synthesize the corresponding polyfluorinated ..cap alpha..,..beta..-UK, and their structure and reactions with the nucleophiles NH/sub 3/, PhNH/sub 2/, MeOH have been studied. In the PMR spectra of the ..cap alpha..,..beta..-UK (X)-(XVI) two doublets of triplets are observed at 6.9 and 7.9 ppm, caused by the spin-spin coupling of the olefin protons with the CF/sub 2/ group of the substituent. For ..cap alpha..,..beta..-UK, apart from the cis-trans isomerism relative to the C=C bond, a rotational isomerism is possible, caused by rotation around the C-C single bond. The presence in the IR spectra of absorption bands from nonplanar torsion-deformation vibrations of C-H for a double bond (nu = 975-980 cm/sup -1/) and the high value of the spin-spin coupling constant of the olefin protons (J/sub HH/ = 15 Hz) indicate unambiguously the transconfiguration of the olefin protons.

  9. 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.

  10. Synthesis of all nineteen appropriately protected chiral alpha-hydroxy acid equivalents of the alpha-amino acids for Boc solid-phase depsi-peptide synthesis.

    PubMed

    Deechongkit, Songpon; You, Shu-Li; Kelly, Jeffery W

    2004-02-19

    [reaction: see text] The preparation of depsi-peptides, amide-to-ester-substituted peptides used to probe the role of hydrogen bonding in protein folding energetics, is accomplished by replacing specific l-alpha-amino acid residues by their alpha-hydroxy acid counterparts in a solid-phase synthesis employing a t-Boc strategy. Herein we describe the efficient stereoselective synthesis of all 19 appropriately protected alpha-hydroxy acid equivalents of the l-alpha-amino acids, employing commercially available materials, expanding the number of available alpha-hydroxy acids from 9 to 19. PMID:14961607

  11. 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.

  12. alpha-thalassemia mutations in Khuzestan Province, Southwest Iran.

    PubMed

    Zandian, Khodamorad; Nateghi, Jamal; Keikhaie, Bijan; Pedram, Mohammad; Hafezi-Nejad, Nima; Hadavi, Valeh; Oberkanins, Christian; Azarkeivan, Azita; Law, Hai-Yang; Najmabadi, Hossein

    2008-01-01

    Although alpha-thalassemia (alpha-thal) is the most common hereditary hemoglobin (Hb) disorder in Iran, no comprehensive data are so far available on the prevalence of the disease in the province of Khuzestan in Southwest Iran. This study investigates the spectrum of alpha-thal mutations in this region. One hundred and twenty-one subjects from Khuzestan Province, Iran, were initially tested for the three most common Iranian alpha-thal mutations (- alpha3.7, -alpha4.2, and --MED) by gap-polymerase chain reaction (gap-PCR). Reverse hybridization test strips and DNA sequencing were used to identify additional alpha-globin mutations. A total of 131 mutated alpha-globin alleles were identified in these patients. Of the 13 mutations that were detected in Khuzestan Province, Iran, the - alpha3.7 single gene deletion was the most frequently identified variant, representing 62.6% of the total; we also observed significant numbers of individuals with compound heterozygous mutations. On the basis of our results, we strongly recommend screening for the most common mutations to improve the molecular diagnosis of anemia in this region. PMID:19065332

  13. 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.

  14. The Structural Quality of AlxGa1-xN Epitaxial Layers Grown by Digitally-AlloyedModulated Precursor Epitaxy Determined by Transmission Electron Microscopy

    SciTech Connect

    Hawkridge, Michael E; Liliental-Weber, Zuzanna; Kim, Hee Jin; Choi, Suk; Yoo, Dongwon; Ryou, Jae-Hyun; Dupuis, Russell

    2008-10-13

    Al(x)Ga(1-x)N layers of varying composition (0.5

  15. 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.

  16. 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.

  17. Correlated high-resolution x-ray diffraction photoluminescence and atom probe tomography analysis of continuous and discontinuous InxGa1-xN quantum wells

    DOE PAGESBeta

    Ren, Xiaochen; Riley, James R.; Koleske, Daniel; Lauhon, Lincoln J.

    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

  18. Influence of c-axis orientation and scandium concentration on infrared active modes of magnetron sputtered ScxAl1-xN thin films

    NASA Astrophysics Data System (ADS)

    Mayrhofer, P. M.; Eisenmenger-Sittner, C.; Euchner, H.; Bittner, A.; Schmid, U.

    2013-12-01

    Doping of wurtzite aluminium nitride (AlN) with scandium (Sc) significantly enhances the piezoelectric properties of AlN. ScxAl1-xN thin films with different Sc concentrations (x = 0 to 0.15) were deposited by DC reactive magnetron sputtering. Infrared (IR) absorbance spectroscopy was applied to investigate the Sc concentration dependent shift of the IR active modes E1(TO) and A1(TO). These results are compared to ab initio simulations, being in excellent agreement with the experimental findings. In addition, IR spectroscopy is established as an economical and fast method to distinguish between thin films with a high degree of c-axis orientation and those exhibiting mixed orientations.

  19. Synthesis and characterization of novel rocksalt-type oxynitrides, LiTi nO xN y ( n=1, 2, 3, 4 and 8)

    NASA Astrophysics Data System (ADS)

    Katsumata, Tetsuhiro; Takaki, Seiko; Inaguma, Yoshiyuki; Shan, Yue Jin

    2004-12-01

    Novel oxynitrides, LiTi nO xN y ( n=1, 2, 3, 4 and 8) were synthesized by sintering under NH 3 gas atmosphere. These compounds have rocksalt-type structure and the existence of cation vacancies is suggested. While the lattice parameters of these compound slightly vary, obvious tendency for the Li or nitride content is not found. For these compounds, the temperature dependence of the electronic conductivity shows the semiconducting behavior. However, the measurement of magnetic susceptibility and the Seebeck coefficient suggest that the transport in these compound is metallic. The electric conductivity seems to be dominated by the resistance of the grain boundary and the transport property of these compounds is metallic.

  20. Magnetic properties of Mn{sub x}Ti{sub 1-x}N thin films grown by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Wu, S. X.; Xia, Y. Q.; Yu, X. L.; Liu, Y. J.; Li, S. W.

    2007-09-15

    High-quality Mn{sub x}Ti{sub 1-x}N thin films were grown on MgO(001) substrates using plasma-assisted molecular beam epitaxy. Magnetic measurements evidence the presence of ferromagnetism with Curie temperature exceeding 380 K. X-ray photoelectron spectroscopy indicates that the Mn ions are in a divalent state and uniformly substitute on Ti cation sites, consistent with the ferromagnetism that correlates with Mn substitution on Ti sites. The origin of the ferromagnetism might be attributed to itinerant-carrier mediated Rudermann-Kittel-Kasuya-Yosida (RKKY)-type long-range coupling which allows for arbitrary itinerant-carrier spin polarization and dynamic correlations.

  1. 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

  2. Expression of human. alpha. sub 2 -macroglobulin cDNA in baby hamster kidney fibroblasts: Secretion of high levels of active. alpha. sub 2 -macroglobulin

    SciTech Connect

    Boel, E.; Mortensen, S.B. ); Kristensen, T.; Sottrup-Jensen, L. ); Petersen, C.M. )

    1990-05-01

    Human {alpha}{sub 2}-macroglobulin ({alpha}{sub 2}M) is a unique 720-kDa proteinase inhibitor with a broad specificity. Unlike most other proteinase inhibitors, it does not inhibit proteolytic activity by blocking the active site of the proteinase. During complex formation with a proteinase {alpha}{sub 2}M entraps the proteinase molecule in a reaction that involves large conformational changes in {alpha}{sub 2}M. The authors describe the molecular cloning of {alpha}{sub 2}M cDNA from the human hepatoblastoma cell line HepG2. The cDNA was subcloned under control of the adenovirus major late promoter in a mammalian expression vector and introduced into the baby hamster kidney (BHK) cell line. Transformed clones were isolated and tested for production of human {alpha}{sub 2}M with a specific enzyme-linked immunosorbent assay. Human recombinant {alpha}{sub 2}M (r{alpha}{sub 2}M), secreted and purified form isolated transfected BHK cell lines, was structurally and functionally compared to {alpha}{sub 2}M purified from human serum. The results show that r{alpha}{sub 2}M was secreted from the BHK cells as an active proteinase-binding tetramer with functional thiol esters. Cleavage reactions of r{alpha}{sub 2}M with methylamine and trypsin showed that the recombinant product, which was correctly processed at the N-terminus, exhibited molecular characteristics similar to those of the human serum derived reference.

  3. Helium-induced reactions in astrophysics

    SciTech Connect

    Hale, G.M.

    1997-11-01

    Helium-induced reactions play a crucial role in stellar nucleosynthesis. Carbon and oxygen are produced mainly during the helium-burning phase by the chain of reactions {sup 8}Be({alpha}, {gamma} + e{sup +}e{sup {minus}}){sup 12}C({alpha}, {gamma}){sup 16}O. The first step, often called triple-{alpha} capture, was proposed by Hoyle to bypass the mass stability gap at {sup 8}Be. The second step gives rise to the largest uncertainty in most of the calculated stellar abundances. Later {alpha}-captures on {sup 13}C are believed to be a major source of s-process neutrons. The status of each of these important reactions is reviewed here.

  4. 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.

  5. 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.

  6. Synthesis of alpha-methylenebeutyrolactams as potential antitumor agents.

    PubMed

    Kornet, M J

    1979-03-01

    A series of 1-aryl-3-methylene-2-pyrrolidinones was synthesized via a three-step reaction sequence. 1,4-Bis-[N-(3-methylene-2-oxopyrrolidino)]benzene, which can undergo alkylation at two sites, was also prepared. These compounds are related to the known antitumor agents alpha-methylenebutyrolactones. Attempts to prepare bis-alpha-methylenelactams, in which the heterocyclic rings are joined through their nitrogen atoms by an alkylene bridge, were unsuccessful. All of the alpha-methylenelactams were screened in B16 melanocarcinoma and P-388 lymphocytic leukemia tumor systems but failed to show significant activity. PMID:423127

  7. 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.

  8. 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.

  9. The Lyman alpha coronagraph

    NASA Technical Reports Server (NTRS)

    Kohl, J. L.; Reeves, E. M.; Kirkham, B.

    1977-01-01

    The rocket-borne Lyman alpha coronagraph (RLAC) is to be used in the absence of a natural solar eclipse to determine coronal temperatures from measurements of the line width of Lyman-alpha and to determine neutral hydrogen densities of coronal material from the absolute intensity. The coronagraph consists of a 75-cm Fastie-Ebert scanning spectrometer with an AMR 641 photoelectric detection system, an off-axis parabolic primary mirror, and an occulting system. A special optical arrangement achieves rejection of radiation from the solar disk.

  10. 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

  11. A tumour necrosis factor alpha polymorphism is not associated with rheumatoid arthritis.

    PubMed Central

    Wilson, A G; de Vries, N; van de Putte, L B; Duff, G W

    1995-01-01

    OBJECTIVE--To determine whether a polymorphism within the tumour necrosis factor alpha (TNF alpha) gene is associated with susceptibility to, or severity of, rheumatoid arthritis (RA). METHODS--Consecutive patients with recent onset RA were enrolled in a prospective trial. DNA was collected, disease activity was measured at presentation, and radiographic progression at three years was assessed. Typing of TNF alpha was by polymerase chain reaction and single stranded conformation polymorphism analysis. RESULTS--No association of TNF alpha alleles and susceptibility to, or severity of, RA was demonstrated. CONCLUSIONS--These results indicate that this TNF alpha polymorphism does not play a part in the genetic background of RA. PMID:7668906

  12. Trifluoroethanol-containing RP-HPLC mobile phases for the separation of transmembrane peptides human glycophorin-A, integrin alpha-1, and p24: analysis and prevention of potential side reactions due to formic acid.

    PubMed

    Hara, Toshiaki; Huang, Yue; Ito, Akihiro; Kawakami, Toru; Hojo, Hironobu; Murata, Michio

    2015-02-01

    Reversed-phase high-pressure liquid chromatography analysis and purification of three hydrophobic, aggregation-prone peptides, composed mainly of the transmembrane (TM) sequence, were performed using elution systems containing 2,2,2-trifluoroethanol (TFE). The addition of 10-16% TFE to a common mobile phase, such as a water/acetonitrile/propanol (PrOH) or a water/PrOH/formic acid system, markedly improved the chromatographic separation of these peptides. The superior performance of TFE-containing systems in separating peptides over water/PrOH/formic acid systems [Bollhagen R. et al., J. Chromatogr. A, 1995; 711: 181-186.] clearly demonstrated that adding TFE to the mobile phase is one of best methods for TM-peptide purification. Characterization of the potential side reactions using MALDI and ESI-LIT/Orbitrap mass spectrometry indicated that prolonged incubation of peptides in a mixture of TFE-formic acid possibly induces O-formylation of the Ser residue and N-formylation of the N-terminus of peptides. The conditions for selective removal of the formyl groups from TM peptides were also screened. We believe that these results will expand our ability to analyze and prepare hydrophobic, aggregation-prone TM peptides and proteins. PMID:25504594

  13. Activation cross sections of α-particle induced nuclear reactions on hafnium and deuteron induced nuclear reaction on tantalum: production of ¹⁷⁸W/(178m)Ta generator.

    PubMed

    Tárkányi, F; Takács, S; Ditrói, F; Hermanne, A; Ignatyuk, A V; Uddin, M S

    2014-09-01

    In the frame of a systematic study of charged particle production routes of medically relevant radionuclei, the excitation function for indirect production of (178m)Ta through (nat)Hf(α,xn)(178)W-(178m)Ta nuclear reaction was measured for the first time up to 40 MeV. In parallel, the side reactions (nat)Hf(α,x)(179,177,176,175)W, (183,182,178g,177,176,175)Ta, (179m,177m,175)Hf were also assessed. Stacked foil irradiation technique and γ-ray spectrometry were used. New experimental cross section data for the (nat)Ta(d,xn)(178)W reaction are also reported up to 40 MeV. The measured excitation functions are compared with the results of the ALICE-IPPE, and EMPIRE nuclear reaction model codes and with the TALYS 1.4 based data in the TENDL-2013 library. The thick target yields were deduced and compared with yields of other charged particle ((p,4n), (d,5n) and ((3)He,x)) production routes for (178)W. PMID:24926946

  14. [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…

  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. 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.

  17. 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.

  18. Description of fusion and evaporation residue formation cross sections in reactions leading to the formation of element Z =122 within the Langevin approach

    NASA Astrophysics Data System (ADS)

    Litnevsky, V. L.; Kosenko, G. I.; Ivanyuk, F. A.

    2016-06-01

    We describe the evolution of the compact system formed by the touching of two colliding ions in reactions 58Fe+248Cm → 306-x122 + xn, 64Ni+244Pu → 308-x122 + xn, and 90Zr+208Pb → 298-x122 + xn. The description is carried out within the dynamical multidimensional stochastic approach, based on Langevin equations for the shape degrees of freedom of colliding ions and the compact system. For the approach stage we take into account the shell structure of colliding ions, their orientation in the space, and the effect of tunneling of ions through the Coulomb barrier. By describing the evolution of the compact system formed after the touching of incident ions, the shell structure of the compact system is also taken into account. Within this approach we have calculated the compound nucleus and evaporation residue formation cross sections. These can be compared with the experimental data. We have also clarified the impact of the tunneling effect in the entrance channel on the fusion and evaporation residue cross sections.

  19. [The interaction of human alpha 1-antitrypsin with human plasmin].

    PubMed

    Sakurama, S

    1984-01-01

    The interaction of alpha 1-antitrypsin (alpha 1-AT) with plasmin was investigated, and the molecular weight of the inhibitor was also re-evaluated. The value of molecular weight of alpha 1-AT determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) method showed a difference depending on the presence or absence of the reducing agent, resulting in 72,000 dalton before reduction and 59,000 dalton after reduction. Conclusively, the molecular weight of alpha 1-AT was appropriate to be 59,000 dalton from considering the molecular shape of the protein. The interaction of alpha 1-AT with plasmin was analysed by SDS-PAGE method. Unreduced analysis revealed that two kinds of complexes with different molecular weight (the major of 155,000 dalton and the minor of 140,000 dalton) were formed time dependently, suggesting that the former was a native complex and the latter was a degraded product. Reduced analysis disclosed that the light chain of plasmin involved the complex formation with the inhibitor, and a peptide of 16,000 dalton appeared during the reaction. From these observations, the mechanism of action was summarized as follows. First, alpha 1-AT inhibited all of the plasmin activities by forming a 1: 1 stoichiometric complex with the enzyme, presumably with the active center of the enzyme, whose complex is undissociable in the presence of denaturing or reducing agents or both. Secondly, the native complex broke into a degraded product and a released peptide by limited proteolysis with the free plasmin which existed in the reaction mixture even with an excess of alpha 1-AT due to the reaction of complex formation being time consuming. The clinical significance of alpha 1-AT on fibrinolysis was also subject for discussion. PMID:6232193

  20. alpha-Macroglobulins are present in some gram-negative bacteria: characterization of the alpha2-macroglobulin from Escherichia coli.

    PubMed

    Doan, Ninh; Gettins, Peter G W

    2008-10-17

    alpha-Macroglobulins (alphaMs) are large glycoproteins that have been identified in a wide range of vertebrate and invertebrate species and are mostly thiol ester containing proteinase inhibitors. A recent analysis of bacterial genomes ( Budd, A., Blandin, S., Levashina, E. A., and Gibson, T. J. (2004) Genome Biol. 5, R38 ) identified many alpha-macroglobulin-like sequences that appear to have been acquired by Gram-negative bacteria from their metazoan hosts. We report the first expression and characterization of such a bacterial alpha-macroglobulin, that from Escherichia coli. This is also the first alpha-macroglobulin to be characterized that is predicted to be membrane-anchored. We found that the 183-kDa protein contains an intact thiol ester, is monomeric, and is localized to the periplasmic space. Reaction with proteinase results in limited cleavage within a bait region, rapid activation of the thiol ester, cross-linking to the attacking proteinase or other available nucleophiles, and partial protection of the proteinase against macromolecular substrates. Given these properties and the co-occurrence of the alphaM gene with one for a repair transglycosylase, this suggests a possible role for bacterial alphaMs in cell defense following host attack. Such a role would make bacterial alphaMs appropriate novel targets for antibiotic drugs. PMID:18697741

  1. 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

  2. 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.

  3. Alpha Condensates in Atomic Nuclei

    SciTech Connect

    Suzuki, Y.; Matsumura, H.

    2005-11-21

    Recent issues on Bose-Einstein condensation (BEC) of {alpha}-particles in nuclei are reviewed. A candidate of condensates is discussed for some states in 12C and 16O by defining the amount of {alpha} condensation.

  4. Identification of hydrogen peroxide oxidation sites of alpha A- and alpha B-crystallins.

    PubMed

    Smith, J B; Jiang, X; Abraham, E C

    1997-02-01

    The alpha-crystallins are the most abundant structural proteins of the lens and, because of their chaperone activity, contribute to the solubility of the other crystallins. With aging, the lens crystallins undergo a variety of modifications which correlate with a loss of solubility and the development of cataract. A recent study demonstrating that alpha-crystallins exposed in vitro to FeCl3 and H2O2 exhibit decreased chaperone activity, implicates metal catalyzed oxidations of alpha-crystallins in this loss of solubility. The present study has determined that alpha-crystallins incubated with FeCl3 and H2O2 are modified by the nearly complete oxidation of all methionine residues to methionine sulfoxide, with no other detectable reaction products. The modifications were identified from the molecular weights of peptides formed by enzymatic digestion of the alpha-crystallins and located by tandem mass spectrometric analysis of the fragmentation pattern of the mass spectra of the fragments from peptides with oxidized methionine is loss of 64 Da, which corresponds to loss of CH3SOH from the methionine sulfoxide. These fragments are useful in identifying peptides that include oxidized methionine residues. PMID:9257122

  5. AlGaN composition dependence of the band offsets for epitaxial Gd2O3/AlxGa1-xN (0 ≤ x ≤ 0.67) heterostructures

    NASA Astrophysics Data System (ADS)

    Ihlefeld, Jon F.; Brumbach, Michael; Allerman, Andrew A.; Wheeler, David R.; Atcitty, Stanley

    2014-07-01

    Gd2O3 films were prepared on (0001)-oriented AlxGa1-xN (0 ≤ x ≤ 0.67) thin film substrates via reactive molecular-beam epitaxy. X-ray diffraction revealed that these films possessed the cubic bixbyite structure regardless of substrate composition and were all 111-oriented with in-plane rotations to account for the symmetry difference between the oxide film and nitride epilayer. Valence band offsets were characterized by X-ray photoelectron spectroscopy and were determined to be 0.41 ± 0.02 eV, 0.17 ± 0.02 eV, and 0.06 ± 0.03 eV at the Gd2O3/AlxGa1-xN interfaces for x = 0, 0.28, and 0.67, respectively.

  6. Study of near-stability nuclei populated as fission fragments in heavy-ion fusion reactions

    SciTech Connect

    Fotiadis, Nikolaos; Nelson, Ronald O; Devlin, Matthew; Cizewski, Jolie A; Krucken, Reiner; Clark, R M; Fallon, Paul; Lee, I Yang; Macchiavelli, Agusto O; Becker, John A; Younes, Walid

    2010-01-01

    Examples are presented to illustrate the power of prompt {gamma}-ray spectroscopy of fission fragments from compound nuclei with A {approx} 200 formed in fusion-evaporation reactions in experiments using the Gammasphere Ge-detector array. Complementary methods, such as Coulomb excitation and deep-inelastic processes, are also discussed. In other cases (n, xn{gamma}) reactions on stable isotopes have been used to establish neutron excitation functions for {gamma}-rays using a pulsed 'white'-neutron source, coupled to a high-energy-resolution germanium-detector array. The excitation functions can unambiguously assign {gamma}-rays to a specific reaction product. Results from all these methods bridge the gaps in the systematics of high-spin states between the neutron-deficient and neutron-rich nuclei. Results near shell closures should motivate new shell model calculations.

  7. Development and identification of monoclonal antibodies against meso-Tetra (alpha,alpha,alpha,alpha,-O-phenylacetamide benzene) porphyrin.

    PubMed

    Wang, Fengyang; Huang, Xueying; Du, Li; Li, Weiguo; Qi, Chao

    2007-04-01

    The small molecule meso-Tetra (alpha,alpha,alpha,alpha-o-phenylacetamide benzene) porphyrin was synthesized through the condensation of o-nitrobenzaldehyde and pyrrole followed by reduction of the meso-tetra (o-nitrophenyl) porphyrin. The small molecule, without carrier, was used as complete antigen to immunize BALB/ C mice. Spleen cells producing high titer antibody were removed and fused with myeloma cells of SP2/0 origin. Using a conventional immunization protocol, stable murine monoclonal antibodies (MAbs) producing cell lines to meso-Tetra (alpha,alpha,alpha,alpha-o-phenylacetamide benzene) porphyrin 1F2 were obtained. Subclass determination showed that the clones produce IgG2a types of MAbs. The analytical results of HPLC and MALDI/TOFMS suggest that the purity of MAb 1F2 is 100%, and MAb 1F2 has a relative molecular weight of 156678.8 Da. Our results demonstrated that small molecule meso-Tetra (alpha,alpha,alpha,alpha-o-phenylacetamide benzene) porphyrin, as semiantigen without carrier, can elicit the formation of MAbs. PMID:17451352

  8. 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.

  9. Oil compositions containing alkyl mercaptan derivatives of copolymers of an alpha olefin or an alkyl vinyl ether and an unsaturated alpha, beta-dicarboxylic compound

    SciTech Connect

    Le, H.T.

    1991-10-08

    This paper describes an oil composition. It comprises: a major amount of an oil selected from a mineral oil or synthetic oil and a manor amount of an alkyl mercaptan derivative of an alpha olefin or alkyl vinyl either and an unsaturated alpha, beta-dicarboxylic compound copolymer having pour point depressant properties, the copolymer comprising the reaction product of an alpha a olefin having from about 2 to about 30 carbon atoms or mixtures of alpha olefins having from about 2 to about 30 carbonates or an alkyl vinyl ether or mixture of alkyl vinyl ethers.

  10. 7-alpha-hydroxylation of cholestanol by rat liver microsomes.

    PubMed

    Shefer, S; Hauser, S; Mosbach, E H

    1968-05-01

    In a study of the mechanism whereby 5alpha-bile acids are formed from cholestanol, the 7alpha-hydroxylation of cholestanol was investigated in rat liver preparations in vitro. It was found that in the presence of NADPH and oxygen, rat liver microsomes catalyzed the 7alpha-hydroxylation of cholestanol to the same extent as that of cholesterol. The rate of the hydroxylation was enhanced by prior treatment of the experimental rats with cholestyramine (a bile acid sequestrant) or by establishment of bile fistulas-i.e., by partial or complete removal of bile acids from the enterohepatic circulation. The 7-hydroxylation reaction was further stimulated by pretreatment of the animals with phenobarbital, a drug known to produce increased biosynthesis of hepatic endoplasmic membranes. The 7alpha-hydroxylase was inhibited by the reaction product, by sterols with 7-keto or 7beta-hydroxyl groups, and also by mono- and dihydroxy bile acids of the 5beta-series, although cholic acid or taurocholate produced no inhibition unless added in high concentrations. The results of these studies are in accord with the concept that the presence of a Delta(5)-double bond is not required for the enzymatic formation of the 7alpha-hydroxy derivative. The rate of this hydroxylation reaction in vitro appears to depend on the concentration of bile salts in the enterohepatic circulation of the experimental animals from whom the microsomes were obtained. PMID:5650927

  11. 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.

  12. Alpha-globin loci in homozygous beta-thalassemia intermedia.

    PubMed

    Triadou, P; Lapoumeroulie, C; Girot, R; Labie, D

    1983-01-01

    Homozygous beta-thalassemia intermediate (TI) differs from thalassemia major (TM) in being less severe clinically. Associated alpha-thalassemia could account for the TI phenotype by reducing the alpha/non-alpha chain imbalance. We have analyzed the alpha loci of 9 TI and 11 TM patients by restriction endonuclease mapping. All the TM and 7 of the TI patients have the normal complement of four alpha-globin genes (alpha alpha/alpha alpha). One TI patient has three alpha-globin genes (alpha alpha/-alpha), and another TI patient has five alpha genes (alpha alpha/alpha alpha alpha). PMID:6305827

  13. Classification and evolution of alpha-amylase genes in plants.

    PubMed

    Huang, N; Stebbins, G L; Rodriguez, R L

    1992-08-15

    The DNA sequences for 17 plant genes for alpha-amylase (EC 3.2.1.1) were analyzed to determine their phylogenetic relationship. A phylogeny for these genes was obtained using two separate approaches, one based on molecular clock assumptions and the other based on a comparison of sequence polymorphisms (i.e., small and localized insertions) in the alpha-amylase genes. These polymorphisms are called "alpha-amylase signatures" because they are diagnostic of the gene subfamily to which a particular alpha-amylase gene belongs. Results indicate that the cereal alpha-amylase genes fall into two major classes: AmyA and AmyB. The AmyA class is subdivided into the Amy1 and Amy2 subfamilies previously used to classify alpha-amylase genes in barley and wheat. The AmyB class includes the Amy3 subfamily to which most of the alpha-amylase genes of rice belong. Using polymerase chain reaction and oligonucleotide primers that flank one of the two signature regions, we show that the AmyA and AmyB gene classes are present in approximately equal amounts in all grass species examined except barley. The AmyB (Amy3 subfamily) genes in the latter case are comparatively underrepresented. Additional evidence suggests that the AmyA genes appeared recently and may be confined to the grass family. PMID:1502164

  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. Modelling and analysis of nucleon emission from deuteron-induced reactions at incident energies up to 100 MeV

    NASA Astrophysics Data System (ADS)

    Nakayama, Shinsuke; Kouno, Hiroshi; Watanabe, Yukinobu; Iwamoto, Osamu; Ye, Tao; Ogata, Kazuyuki

    2016-06-01

    We have so far developed a computational code system dedicated to deuteron-induced reactions in combination with some theoretical models. In our previous works, the code system was successfully applied to systematic analyses of double-differential cross sections (DDXs) of (d,xp) reactions for 12C, 27Al, and 58Ni at incident energies up to 100 MeV. In the present work, we apply the code system to neutron emission from deuteron-induced reactions. Since there is few experimental data of DDXs of (d,xn) reactions, double-differential thick target neutron yields (TTNYs) are calculated and compared with experimental data instead of DDXs. The calculation using the code system reproduces the measured TTNYs for carbon at incident energies up to 50 MeV.

  16. 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

  17. In situ Eu doping into AlxGa1-xN grown by organometallic vapor phase epitaxy to improve luminescence properties

    NASA Astrophysics Data System (ADS)

    Koizumi, Atsushi; Kawabata, Kosuke; Lee, Dong-gun; Nishikawa, Atsushi; Terai, Yoshikazu; Ofuchi, Hironori; Honma, Tetsuo; Fujiwara, Yasufumi

    2015-03-01

    We have succeeded in situ Eu doping into AlxGa1-xN grown by organometallic vapor phase epitaxy and investigated the effects of the growth pressure and Al composition on the photoluminescence (PL) properties of Eu3+ ions. The intensity of red emission due to the 5D0-7F2 transition of Eu3+ ions decreased with increasing Al content in the case of growth at atmospheric pressure. The effect of the reactor pressure on the Eu concentration and Eu3+ PL properties showed that low-pressure growth is effective in increasing the Eu doping concentration and luminescence efficiency. The PL intensity increased with the Al composition and reached a maximum intensity at approximately x = 0.24. At Al compositions of higher than 0.24, X-ray absorption near-edge structure analysis revealed that the concentration of Eu2+ ions increased with increasing Al composition, leading to a reduction in the concentration of optically active Eu3+ ions.

  18. Strain relaxation in GaN/AlxGa1-xN superlattices grown by plasma-assisted molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Kotsar, Y.; Doisneau, B.; Bellet-Amalric, E.; Das, A.; Sarigiannidou, E.; Monroy, E.

    2011-08-01

    We have investigated the misfit relaxation process in GaN/AlxGa1-xN (x = 0.1, 0.3, 0.44) superlattices (SL) deposited by plasma-assisted molecular beam epitaxy. The SLs under consideration were designed to achieve intersubband absorption in the mid-infrared spectral range. We have considered the case of growth on GaN (tensile stress) and on AlGaN (compressive stress) buffer layers, both deposited on GaN-on-sapphire templates. Using GaN buffer layers, the SL remains almost pseudomorphic for x = 0.1, 0.3, with edge-type threading dislocation densities below 9 × 108 cm-2 to 2 × 109 cm-2. Increasing the Al mole fraction to 0.44, we observe an enhancement of misfit relaxation resulting in dislocation densities above 1010 cm-2. In the case of growth on AlGaN, strain relaxation is systematically stronger, with the corresponding increase in the dislocation density. In addition to the average relaxation trend of the SL, in situ measurements indicate a periodic fluctuation of the in-plane lattice parameter, which is explained by the different elastic response of the GaN and AlGaN surfaces to the Ga excess at the growth front. The results are compared with GaN/AlN SLs designed for near-infrared intersubband absorption.

  19. Spinning Characteristics of the XN2Y-1 Airplane Obtained from the Spinning Balance and Compared with Results from the Spinning Tunnel and from Flight Tests

    NASA Technical Reports Server (NTRS)

    Bamber, M J; House, R O

    1937-01-01

    Report presents the results of tests of a 1/10-scale model of the XN2Y-1 airplane tested in the NACA 5-foot vertical wind tunnel in which the six components of forces and moments were measured. The model was tested in 17 attitudes in which the full-scale airplane had been observed to spin, in order to determine the effects of scale, tunnel, and interference. In addition, a series of tests was made to cover the range of angles of attack, angles of sideslip, rates of rotation, and control setting likely to be encountered by a spinning airplane. The data were used to estimate the probable attitudes in steady spins of an airplane in flight and of a model in the free-spinning tunnel. The estimated attitudes of steady spin were compared with attitudes measured in flight and in the spinning tunnel. The results indicate that corrections for certain scale and tunnel effects are necessary to estimate full-scale spinning attitudes from model results.

  20. Impact of inhomogeneous broadening on optical polarization of high-inclination semipolar and nonpolar InxGa1 -xN /GaN quantum wells

    NASA Astrophysics Data System (ADS)

    Mounir, Christian; Schwarz, Ulrich T.; Koslow, Ingrid L.; Kneissl, Michael; Wernicke, Tim; Schimpke, Tilman; Strassburg, Martin

    2016-06-01

    We investigate the influence of inhomogeneous broadening on the optical polarization properties of high-inclination semipolar and nonpolar InxGa1 -xN /GaN quantum wells. Different planar m-plane and (20 2 ¯1 ¯) samples were grown (including core-shell microrods) and have been characterized by excitation-dependent polarization-resolved confocal micro-photoluminescence. The measured degree of linear polarization (DLP) is compared to theoretical predictions obtained by Fermi-Dirac statistical filling of the electronic band structure calculated by the k .p envelope function method. We show that our measured DLP at room temperature, as well as values reported by other groups, are systematically higher than the theoretical predictions. We propose to solve this discrepancy between theory and experiment by introducing inhomogeneous broadening in our calculations. Considering indium content fluctuations and the localization lengths of electrons and holes, different effective broadenings are applied to different subsets of subbands. We thereby show that inhomogeneous broadening leads to an increase of the DLP at room temperature. Furthermore, the dependence of the optical properties on the excitation density is better reproduced. Looking at the DLP as a function of the temperature gives us insight into the thermalization dynamics of charge carriers.

  1. 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.

  2. 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.

  3. Structural and optical analyses of AlxGa1-xN thin films grown by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Kucukgok, Bahadir; Lu, Na; Ferguson, Ian T.; Wang, Shu Chang; Zhang, Xiong; Feng, Zhe Chuan

    2015-02-01

    A series of AlxGa1-xN thin films with x = 0.20-0.60 were grown by metal organic chemical vapor deposition (MOCVD) on sapphire (0001) substrate using AlN buffer layer. High resolution X-ray diffraction (HRXRD) was performed for (0002), (0004), and (0006) reflections to investigate the threading dislocation density in variation with Al composition by X-ray analysis technique; Williamson-Hall (WH) plot. A symmetric high resolution 2θ-ω scans exhibit high crystal quality for all the AlGaN samples. A room temperature deep ultraviolet (DUV) photoluminescence (PL) spectroscopy (excitation at 248 nm) has also been employed to investigate the effect of various Al compositions on crystal structure of the thin film layers. It was observed that the band edge transition peak energy blueshifts from 3.87 eV for x = 0.23 to 4.55 eV for x = 0.47. In addition to the band edge transition, each spectrum also shows deep impurity transitions.

  4. Strain relaxation in GaN/Al{sub x}Ga{sub 1-x}N superlattices grown by plasma-assisted molecular-beam epitaxy

    SciTech Connect

    Kotsar, Y.; Bellet-Amalric, E.; Das, A.; Monroy, E.; Sarigiannidou, E.

    2011-08-01

    We have investigated the misfit relaxation process in GaN/Al{sub x}Ga{sub 1-x}N (x = 0.1, 0.3, 0.44) superlattices (SL) deposited by plasma-assisted molecular beam epitaxy. The SLs under consideration were designed to achieve intersubband absorption in the mid-infrared spectral range. We have considered the case of growth on GaN (tensile stress) and on AlGaN (compressive stress) buffer layers, both deposited on GaN-on-sapphire templates. Using GaN buffer layers, the SL remains almost pseudomorphic for x = 0.1, 0.3, with edge-type threading dislocation densities below 9 x 10{sup 8} cm{sup -2} to 2 x 10{sup 9} cm{sup -2}. Increasing the Al mole fraction to 0.44, we observe an enhancement of misfit relaxation resulting in dislocation densities above 10{sup 10} cm{sup -2}. In the case of growth on AlGaN, strain relaxation is systematically stronger, with the corresponding increase in the dislocation density. In addition to the average relaxation trend of the SL, in situ measurements indicate a periodic fluctuation of the in-plane lattice parameter, which is explained by the different elastic response of the GaN and AlGaN surfaces to the Ga excess at the growth front. The results are compared with GaN/AlN SLs designed for near-infrared intersubband absorption.

  5. Point defects in hexagonal BN, BC{sub 3} and BC{sub x}N compounds studied by x-ray absorption near-edge structure

    SciTech Connect

    Caretti, Ignacio; Jimenez, Ignacio

    2011-07-15

    The generation of point defects in highly oriented pyrolytic boron nitride (HOPBN) after Ar{sup +} ion bombardment in ultrahigh vacuum and subsequent exposure to air was studied by angle-resolved x-ray absorption near edge structure (XANES). The pristine HOPBN showed well-oriented boron nitride (BN) basal planes parallel to the surface, with a negligible amount of defects. Amorphization of the BN structure took place after Ar{sup +} sputtering, as indicated by the broadening of the XANES spectra and significant decrease of the characteristic {pi}* states. Following air exposure, the XANES analysis revealed a spontaneous reorganization of the sample structure. The appearance of four new B1s {pi}* excitonic peaks indicates an oxygen decoration process of the nitrogen vacancies created by ion bombardment. A core-level shift model is presented to support this statement. This model is successfully extended to the case of oxygen substitutional defects in hexagonal BC{sub 3} and BC{sub x}N (0 < x < 4) materials, which can be applied to any B-based sp{sup 2}-bonded honeycomb structure.

  6. The palladium assisted transfer reduction of. alpha. ,. beta. -unsaturated nitroalkenes to oximes using ammonium formate

    SciTech Connect

    Kabalka, G.W.; Pace, R.D.; Wadgaonkar, P.P. )

    1990-01-01

    {alpha},{beta}-Unsaturated nitroalkenes are readily reduced to the corresponding oximes in good yields using ammonium formate in the presence of palladium. The reactions occur rapidly at room temperature in a solvent system of methanol and tetrahydrofuran.

  7. 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.

  8. 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.

  9. Formation of hydroxyapatite by hydrolysis of alpha-tricalcium phosphate

    NASA Astrophysics Data System (ADS)

    Durucan, Caner

    Low-temperature cement-type formation of hydroxyapatite [Ca10(PO4)6(OH)2 or HAp) has value in terms of developing synthetic compounds similar in compositions to those formed by natural mineralization of bone. Understanding the in vitro kinetics of formation of the synthetic composition could produce insights into developing hard tissue analogs. The kinetics and chemistry of cement-type formation of HAp by hydrolysis of particulate alpha-tricalcium phosphate (alpha-Ca 3(PO4)2 or alpha-TCP) were examined. In particular, the effects of reaction temperature, synthesis route, inorganic salt additives and presence of biodegradable polymers (poly(alpha-hydroxyl acids) on the hydrolysis rate and microstructural/mechanical properties of HAp were determined using the following analytical techniques: isothermal calorimetry, x-ray diffraction, scanning electron microscsopy (SEM), fourier transform infrared spectroscopy (FTIR), solution chemistry, diametrical compression and 3-point bending tests. For the phase-pure alpha-TCP/water system the complete reaction times and morphologies of the resultant HAp were found to be strongly dependent on reaction temperature over a range of 37°C to 56°C. Isothermal calorimetry analyses revealed a thermally activated hydrolysis mechanism, leading to higher reaction rates with an increase in hydrolysis temperature. The microstructure of the resultant HAp typically had entangled, flake-like morphology, with HAp formed at 37°C having a smaller crystalline size than that formed at 45°C and 56°C. The cement hardening contributed to entanglement at the microstructural level. In all cases the hydrated product was phase pure calcium-deficient hydroxyapatite [Ca10-x(HPO4) x(PO4)6-x(OH)2-x], and no other intermediates or by-products were formed through the complete transformation. According to the proposed kinetic model, a two-step mechanism was found to control the overall hydrolysis reaction and thereby HAp formation at 37°C. During the first

  10. Alpha-mannosidosis

    PubMed Central

    Malm, Dag; Nilssen, Øivind

    2008-01-01

    Alpha-mannosidosis is an inherited lysosomal storage disorder characterized by immune deficiency, facial and skeletal abnormalities, hearing impairment, and intellectual disability. It occurs in approximately 1 of 500,000 live births. The children are often born apparently normal, and their condition worsens progressively. Some children are born with ankle equinus or develop hydrocephalus in the first year of life. Main features are immune deficiency (manifested by recurrent infections, especially in the first decade of life), skeletal abnormalities (mild-to-moderate dysostosis multiplex, scoliosis and deformation of the sternum), hearing impairment (moderate-to-severe sensorineural hearing loss), gradual impairment of mental functions and speech, and often, periods of psychosis. Associated motor function disturbances include muscular weakness, joint abnormalities and ataxia. The facial trait include large head with prominent forehead, rounded eyebrows, flattened nasal bridge, macroglossia, widely spaced teeth, and prognathism. Slight strabismus is common. The clinical variability is significant, representing a continuum in severity. The disorder is caused by lysosomal alpha-mannosidase deficiency. Alpha-mannosidosis is inherited in an autosomal recessive fashion and is caused by mutations in the MAN2B1 gene located on chromosome 19 (19 p13.2-q12). Diagnosis is made by measuring acid alpha-mannosidase activity in leukocytes or other nucleated cells and can be confirmed by genetic testing. Elevated urinary secretion of mannose-rich oligosaccharides is suggestive, but not diagnostic. Differential diagnoses are mainly the other lysosomal storage diseases like the mucopolysaccharidoses. Genetic counseling should be given to explain the nature of the disease and to detect carriers. Antenatal diagnosis is possible, based on both biochemical and genetic methods. The management should be pro-active, preventing complications and treating manifestations. Infections must be

  11. Reactions in water: alkyl nitrile coupling reactions using Fenton's reagent.

    PubMed

    Keller, Christopher L; Dalessandro, James D; Hotz, Richard P; Pinhas, Allan R

    2008-05-01

    The coupling reaction of water-soluble alkyl nitriles using Fenton's reagent (Fe(II) and H2O2) is described. The best metal for the reaction is iron(II), and the greatest yields are obtained when the concentration of the metal is kept low. Hydrogen-atom abstraction is selective, preferentially producing the radical alpha to the nitrile. In order to increase the production of dinitrile, in situ reduction of iron(III) to iron(II), using a variety of reducing agents, was investigated. PMID:18363368

  12. 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)

  13. 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.

  14. 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.

  15. Proteinaceous alpha-amylase inhibitors.

    PubMed

    Svensson, Birte; Fukuda, Kenji; Nielsen, Peter K; Bønsager, Birgit C

    2004-02-12

    Proteins that inhibit alpha-amylases have been isolated from plants and microorganisms. These inhibitors can have natural roles in the control of endogenous alpha-amylase activity or in defence against pathogens and pests; certain inhibitors are reported to be antinutritional factors. The alpha-amylase inhibitors belong to seven different protein structural families, most of which also contain evolutionary related proteins without inhibitory activity. Two families include bifunctional inhibitors acting both on alpha-amylases and proteases. High-resolution structures are available of target alpha-amylases in complex with inhibitors from five families. These structures indicate major diversity but also some similarity in the structural basis of alpha-amylase inhibition. Mutational analysis of the mechanism of inhibition was performed in a few cases and various protein engineering and biotechnological approaches have been outlined for exploitation of the inhibitory function. PMID:14871655

  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. Long range alpha particle detector

    DOEpatents

    MacArthur, Duncan W.; Wolf, Michael A.; McAtee, James L.; Unruh, Wesley P.; Cucchiara, Alfred L.; Huchton, Roger L.

    1993-01-01

    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.

  18. 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.

  19. Direct Measurement of 21Na+α Stellar Reaction

    NASA Astrophysics Data System (ADS)

    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.

    2010-08-01

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

  20. The reaction of ornithine aminotransferase with ornithine.

    PubMed Central

    Williams, J A; Bridge, G; Fowler, L J; John, R A

    1982-01-01

    Rat liver ornithine aminotransferase is found to exchange the pro-S hydrogen on the delta-carbon atom of ornithine exclusively, thus showing that the mammalian enzyme transfers the delta-amino group and not the alpha-amino group as has been demonstrated with the plant enzyme [Mestichelli, Gupta & Spenser (1979) J. Biol. Chem. 254, 640-647]. The enzyme also transfers the alpha-amino group of glutamate and the kinetics of the half reactions between the enzyme and both amino acids are compared. Rate and dissociation constants for both reactions are determined. PMID:6282258

  1. 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.

  2. ISS Update: Alpha Magnetic Spectrometer

    NASA Video Gallery

    NASA Public Affairs Officer Kelly Humphries interviews Trent Martin, Johnson Space Center project manager for the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. Questions...

  3. An enzymatically produced novel cyclic tetrasaccharide, cyclo-{-->6)-alpha-D-Glcp-(1-->4)-alpha-D-Glcp-(1-->6)-alpha-D-Glcp-(1-->4)-alpha-D-Glcp-(1-->} (cyclic maltosyl-(1-->6)-maltose), from starch.

    PubMed

    Mukai, Kazuhisa; Watanabe, Hikaru; Oku, Kazuyuki; Nishimoto, Tomoyuki; Kubota, Michio; Chaen, Hiroto; Fukuda, Shigeharu; Kurimoto, Masashi

    2005-06-13

    A bacterial strain M6, isolated from soil and identified as Arthrobacter globiformis, produced a novel nonreducing oligosaccharide. The nonreducing oligosaccharide was produced from starch using a culture supernatant of the strain as enzyme preparation. The oligosaccharide was purified as a crystal preparation after alkaline treatment and deionization of the reaction mixture. The structure of the oligosaccharide was determined by methylation analysis, mass spectrometry, and (1)H and (13)C NMR spectroscopy, and it was demonstrated that the oligosaccharide had a cyclic structure consisting of four glucose residues joined by alternate alpha-(1-->4)- and alpha-(1-->6)-linkages. The cyclic tetrasaccharide, cyclo-{-->6)-alpha-D-Glcp(1-->4)-alpha-D-Glcp(1-->6)-alpha-D-Glcp(1-->4)-alpha-D-Glcp(1-->}, was found to be a novel oligosaccharide, and was tentatively called cyclic maltosyl-maltose (CMM). CMM was not hydrolyzed by various amylases, such as alpha-amylase, beta-amylase, glucoamylase, isoamylase, pullulanase, maltogenic alpha-amylase, and alpha-glucosidase, but hydrolyzed by isomalto-dextranase to give rise to isomaltose. This is the first report of the cyclic tetrasaccharide, which has alternate alpha-(1-->4)- and alpha-(1-->6)-glucosidic linkages. PMID:15882856

  4. Mouse egg integrin alpha 6 beta 1 functions as a sperm receptor.

    PubMed

    Almeida, E A; Huovila, A P; Sutherland, A E; Stephens, L E; Calarco, P G; Shaw, L M; Mercurio, A M; Sonnenberg, A; Primakoff, P; Myles, D G; White, J M

    1995-06-30

    Binding between sperm and egg plasma membranes is an essential step in fertilization. Whereas fertilin, a mammalian sperm surface protein, is involved in this crucial interaction, sperm receptors on the egg plasma membrane have not been identified. Because fertilin contains a predicted integrin ligand domain, we investigated the expression and function of integrin subunits in unfertilized mouse eggs. Polymerase chain reactions detected mRNAs for alpha 5, alpha 6, alpha v, beta 1, beta 3, and beta 5. Immunofluorescence revealed alpha 6 beta 1 and alpha v beta 3 on the plasma membrane. GoH3, a function-blocking anti-alpha 6 monoclonal antibody, abolished sperm binding, but a nonfunction-blocking anti-alpha 6 monoclonal antibody, a function-blocking anti-alpha v beta 3 polyclonal antibody, and an RGD peptide had no effect. Somatic cells bound sperm avidly, but only if they expressed alpha 6 beta 1. A peptide analog of the fertilin integrin ligand domain inhibited sperm binding to eggs and alpha 6 beta 1+ cells and diminished GoH3 staining of eggs. Our results indicate a novel role for the integrin alpha 6 beta 1 as a cell-cell adhesion receptor that mediates sperm-egg binding. PMID:7600577

  5. 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

  6. 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.

  7. Alpha Heating and Burning Plasmas in Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Christopherson, A. R.

    2015-11-01

    In inertial confinement fusion, a spherical capsule of cryogenic DT is accelerated inward at a high velocity. Near stagnation, a dense hot spot is formed where the deuterium and tritium ions begin to fuse, creating a 3.5-MeV alpha particle per reaction. These alpha particles deposit energy back into the plasma, thereby increasing the pressure, temperature, and reaction rate. This feedback process is called ``alpha heating,'' and ignition is a direct consequence of this thermal instability. The onset of a burning-plasma regime occurs when the total alpha-particle energy produced exceeds the shell compression work. Using an analytic compressible-shell model for the implosion, it is found that the onset of the burning-plasma regime is a unique function of the neutron yield enhancement caused by alpha particles for any target, direct or indirect drive. This yield enhancement can then be inferred from experimentally measureable quantities, such as the Lawson parameter. From this analysis, the onset of a burning plasma occurs at yields exceeding 50 kJ for implosions at the National Ignition Facility. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and DE-FC02-04ER54789 (Fusion Science Center).

  8. 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…

  9. Characterization of the bovine C alpha gene.

    PubMed Central

    Brown, W R; Rabbani, H; Butler, J E; Hammarström, L

    1997-01-01

    The complete genomic sequence of a bovine C alpha gene is reported here. The genomic sequence was obtained from a C alpha phage clone that had been cloned from a genomic EMBL4 phage vector library. The C alpha sequence had previously been expressed as a chimeric antibody and identified as IgA using IgA-specific antibodies. Intron/exon boundaries were determined by comparison of the genomic sequence with an expressed bovine C alpha sequence obtained from spleen by reverse transcription-polymerase chain reaction (RT-PCR). Analysis of 50 Swedish bovine genomic DNA samples using genomic blots and five different restriction enzymes failed to detect evidence of polymorphism. However, PstI digests of Brown Swiss DNA showed a restriction fragment length polymorphism (RFLP), suggesting that at least two allelic variants of bovine IgA exist. Comparison of the deduced amino acid sequence of bovine IgA with sequences available for other species indicated that the highest homology was with that of swine, another artiodactyl. This was the highest homology observed for all mammalian IgA compared except for that between IgA1 and IgA2 in humans. Bovine IgA shares with rabbit IgA3 and IgA4, an additional N-linked glycosylation site at position 282. However, the collective data indicate that cattle are like swine and rodents and unlike rabbits in having a single locus of the gene encoding IgA of this species. Images Figure 4 PMID:9203958

  10. Determination of neutron-induced alpha-particle cross sections on carbon using the response of a liquid scintillation detector

    SciTech Connect

    Brede, H.J.; Dietze, G.; Klein, H.; Schoelermann, H. )

    1991-01-01

    This paper presents the sums of the cross section {sup 12}C(n, {alpha}{sub 0}) {sup 9}Be and {sup 12}C(n, N{prime}3{alpha}) determined in the neutron energy range between 7.4 and 11 MeV. An NE-213 scintillation detector is simultaneously used as a carbon target, an alpha-particle detector, and a neutron fluence monitor. By comparing the measured and calculated response spectra, the neutron-induced alpha-particle events in the scintillation volume are separated and the cross sections {sigma}{sub n,{alpha}0} + {sigma}{sub n,n{prime}3{alpha}} are determined relative to the n-p scattering cross section. The pulse-height distribution due to alpha particles allows the angular distribution to be extracted on the basis of the reaction kinematics and an accurately determined light output function for alpha particles in the NE-213 detector.

  11. 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.

  12. 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.

  13. 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.

  14. Negative exchange bias in single-phase D y1 -xN dxCr O3 induced by Nd doping

    NASA Astrophysics Data System (ADS)

    McDannald, A.; dela Cruz, C. R.; Seehra, M. S.; Jain, M.

    2016-05-01

    Observation of significant negative exchange bias (HE) is reported in solid solutions of single-phase samples of D y1 -xN dxCr O3 for x = 0.33 ,0.67 , and 1 with corresponding Néel temperatures at TNCr= 175 K ,200 K , and 225 K, respectively, and the spin-reorientation transitions TS R at 48 K, 58 K, and 38 K, respectively. In contrast, no HE was observed for the sample with x =0 (i.e., DyCr O3 ) shows no HE below its TNCr= 145 K , and no reorientation of spins at lower temperatures was observed. More importantly, the (negative) HE for the x = 0.33 ,0.67 , and 1 samples is observed only in the temperature range between TN and TS R with the corresponding observation of magnetic coercivity. These results show that the canted antiferromagnetic Γ7 ,Cr structure of the C r3 + moments present between TNCr and TS R is essential for the observed HE. By comparing this result to the literature, common features of single-phase materials with HE were identified. The present bulk powder samples were prepared by the citrate method and structurally characterized by x-ray diffraction and Raman spectroscopy techniques. Neutron diffraction measurements for the x = 0.33 ,0.67 , and 1 samples at select temperatures were done to verify the presence of the Γ7 ,Cr structure between TNCr and TS R and the Γ1 ,Cr structure (with no canting of C r3 + moments) below TS R.

  15. Conciliatory Inductive Model Explaining the Origin of Changes in the η(2)-SiH Bond Length Caused by Presence of Strongly Electronegative Atoms X (X = F, Cl) in Cp(OC)2Mn[η(2)-H(SiH3-nXn)] (n = 0-3) Complexes.

    PubMed

    Jabłoński, Mirosław

    2016-06-23

    Using three theoretical methods, QTAIM, IQA, and NCI, we analyze an influence of halogen atoms X (X = F, Cl) substituted at various positions in the -SiH3-nXn group on the charge density distribution within the η(2)-SiH bond and on the SiH bond energies in Cp(OC)2Mn[η(2)-H(SiH3-nXn)] complexes and isolated HSiH3-nXn molecules. It is shown that shortening of the η(2)-SiH bond in Cp(OC)2Mn[η(2)-H(SiH3-nXn)] complexes should be considered as a normal inductive result of halogenation. This η(2)-SiH bond's compression may, however, be overcome by a predominant elongation resulting from a contingent presence of a halogen atom at position trans to the η(2)-SiH bond. This trans effect is particularly large for bulky and highly polarizable chlorine. Moreover, peculiar properties of the trans chlorine atom are manifested in several ways. To explain the origin of all the observed changes in both the length and the electron charge distribution of the η(2)-SiH bond in investigated Cp(OC)2Mn[η(2)-H(SiH3-nXn)] complexes a new model, called the Conciliatory Inductive Model, is being proposed. PMID:27232528

  16. Alpha-amylase gene transcription in tissues of normal dog.

    PubMed

    Mocharla, H; Mocharla, R; Hodes, M E

    1990-02-25

    We studied the distribution of alpha-amylase mRNA in normal dog tissues by northern blotting (NB) and reverse transcription-polymerase chain reaction (RT-PCR) with human pancreatic (AMY2) and salivary (AMY1) alpha-amylase cDNA-specific primers. Analysis of poly(A+) RNA from various normal tissues by NB indicated the presence of detectable levels of alpha-amylase mRNA transcripts only in pancreas. Dot-blot analysis of DNA amplified with primers common to both (human) isoamylase mRNAs showed presence of alpha-amylase gene transcripts not only in pancreas but also in liver, small intestine, large intestine and fallopian tube. Traces of amylase gene transcripts were also observed in ovary, uterus and lung. Interestingly, amylase transcripts were not detectable in the parotid gland by NB or RT-PCR. We have also localized alpha-amylase mRNA transcripts to dog pancreas by in situ transcription and in situ hybridization. Our results suggest that there is high degree of homology between the alpha-amylase mRNA sequences in dog and human at least in the exon 3-4 regions of the human gene. PMID:2315015

  17. Alpha glucosidase inhibitors.

    PubMed

    Kalra, Sanjay

    2014-04-01

    Alpha glucosidase inhibitors (AGIs) are a unique class of anti-diabetic drugs. Derived from bacteria, these oral drugs are enzyme inhibitors which do not have a pancreato -centred mechanism of action. Working to delay carbohydrate absorption in the gastrointestinal tract, they control postprandial hyperglycaemia and provide unquestioned cardiovascular benefit. Specially suited for a traditional Pakistani carbohydrate-rich diet, AGIs have been termed the 'untapped diamonds' of diabetology. The use of these oral antidiabetic drugs (OADs) that target pathophysiology in the early stages of type 2 diabetes, notably to reduce postprandial hyperglycaemia and hyperinsulinaemia will inevitably increase with time. This review describes the history of their development, mechanism of action, basic and clinical pharmacology, and suggests practical, evidence-based guidance for their optimal use. PMID:24864650

  18. 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...

  19. Analysis of deuteron breakup reactions on {sup 7}Li for energies up to 100 MeV

    SciTech Connect

    Ye, Tao; Watanabe, Yukinobu; Ogata, Kazuyuki

    2009-07-15

    Inclusive nucleon spectra from deuteron breakup reactions on {sup 7}Li are analyzed in terms of the continuum discretized coupled channels theory for the elastic breakup process and the Glauber model for the nucleon stripping process. Both theoretical models use the same phenomenological nucleon optical potential of {sup 7}Li and have no other free parameters. The calculations reproduce well a prominent bump observed around half the incident energy in experimental inclusive spectra of 40-MeV (d,xn) and 100-MeV (d,xp) reactions at forward angles. The analysis shows that the stripping process is more important than the elastic breakup process in deuteron breakup reactions on {sup 7}Li.

  20. 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.

  1. Stability of superheavy nuclei produced in actinide-based complete fusion reactions: Evidence for the next magic proton number at Z{>=}120

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Sargsyan, V. V.

    2009-05-15

    Using the experimental evaporation residue cross sections in the {sup 48}Ca-induced complete fusion reactions and the complete fusion cross sections calculated within the dinuclear system model, the survival probabilities of superheavy nuclei with charge numbers Z=112-116 and 118 in the xn-evaporation channels are extracted. The effects of angular momentum and deformations of colliding nuclei are taken into account. The obtained dependence of the survival probability on Z indicates the next doubly magic nucleus beyond {sup 208}Pb at Z{>=}120.

  2. 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.

  3. 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

  4. 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)

  5. Alpha-Decay Half-Lives of Superheavy Nuclei

    SciTech Connect

    Budaca, A. I.; Silisteanu, I.; Silisteanu, A. O.; Anghel, C. I.

    2010-11-24

    Half-lives given by self-consistent models for the {alpha}-clustering and resonance scattering are calculated and compared with data and empirical estimates. The major influence of the pairing, deformed shell closures and screening corrections is evidenced in the systematics of half-lives and provides a convenient basis for the interpretation of observed trends of the data and for prediction of new results. The very small widths of {alpha}-resonances observed experimentally in fusion-evaporation reactions, are interpreted as resonance levels of radioactive products, and such a correlation contributes directly to the study of the nuclear structure on the basis of decay data.

  6. Determination via luminescence spectroscopy and x-ray diffraction of the strain and composition of GaN and Al(x)Ga(1-x)N thin films grown on 6H-SiC(0001) substrates

    NASA Astrophysics Data System (ADS)

    Perry, William George

    1997-12-01

    This dissertation describes the luminescence and x-ray diffraction characterization of GaN and AlxGa1-xN thin films that were deposited on 6H-SiC(0001) substrates. These materials have applications for optoelectronic devices that are operational in the UV to green regions of the spectrum and for high-temperature, high-frequency and high-power microelectronic devices. The primary tools used in this research were photoluminescence and cathodoluminescence spectroscopies and high-resolution x-ray diffraction. Biaxial strains resulting from the mismatches in thermal expansion coefficients and lattice parameters in GaN films grown on AlN buffer layers previously deposited on vicinal and on-axis 6H-SiC(0001) substrates were measured using photoluminescence. A linear relationship between the bound exciton energy (EBX) and the biaxial strain along the c-axis direction was observed. A marked variation in the biaxial strain in GaN films deposited on off- and on-axis SiC was determined. It was attributed to the difference in the density and nature of the microstructural defects that originate at the steps on the SiC surface. The strain in the GaN films was either in tension or compression; whereas, only tensile strains were reported in all previous studies using SiC wafers. This indicated that the lattice mismatch strain in the former films was not fully relieved by defect formation. This result was confirmed by the observation via HRTEM of a 0.9% residual compressive strain at the GaN/AlN interface. Cathodoluminescence was used to determine the optical spectra in AlxGa1-xN films over the entire composition range of x. A bowing parameter of b = 1.65 eV for the bound exciton peak was observed. This bound exciton peak became more localized as the Al mole fraction increased. This was attributed to the increase in the ionization energy (ED) of the donor to which the exciton was bound. The donor-acceptor pair (DAP) band and the so-called 'yellow' emission band that are commonly

  7. Alpha Schottky junction energy source

    NASA Astrophysics Data System (ADS)

    Litz, Marc S.; Fan, Zhaoyang; Carroll, James J.; Bayne, Stephen

    2012-06-01

    Isotope batteries offer solutions for long-lived low-power sensor requirements. Alpha emitting isotopes have energy per decay 103 times that of beta emitters. Alpha particles are absorbed within 20 μm of most materials reducing shielding mitigation. However, damage to materials from the alphas limits their practical use. A Schottky Barrier Diode (SBD) geometry is considered with an alpha emitting contact-layer on a diamond-like crystal semiconductor region. The radiation tolerance of diamond, the safety of alpha particles, combined with the internal field of the SBD is expected to generate current useful for low-power electronic devices over decades. Device design parameters and calculations of the expected current are described.

  8. 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)

  9. 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.

  10. Measurement of the 330-keV resonance in 18F(p,alpha)15O

    SciTech Connect

    Moazen, Brian; Blackmon, Jeff C; Bardayan, Daniel W; Chae, K. Y.; Chipps, K.; Jones, K. L.; Kozub, R. L.; Matei, Catalin; Nesaraja, Caroline D; Pain, Steven D; ShrinerJr., J. F.; Smith, Michael Scott

    2009-03-01

    While recent measurements have substantially improved our understanding of the {sup 18}F(p, {alpha}){sup 15}O reaction that is important in novae, the production of {sup 18}F is still uncertain by more than 2 orders of magnitude, due in large part to the contribution of a resonance located at E{sub cm} = 330 keV. We developed a new technique to study resonant (p, {alpha}) reactions and employed it to measure properties of the E{sub cm} = 183 keV resonance in {sup 17}O(p, {alpha}){sup 14}N which had been previously reported to decrease {sup 18}F production in ONeMg novae by as much as a factor of 10. The previous results were confirmed using the new technique and we now propose to use this technique to study the {sup 18}F(p, {alpha}){sup 15}O reaction.

  11. Hb Oegstgeest [alpha104(G11)Cys-->Ser (alpha1)]. A new hemoglobin variant associated with a mild alpha-thalassemia phenotype.

    PubMed

    Harteveld, Cornelis L; Rozendaal, Lieke; Blom, Nico A; Lo-A-Njoe, Shirley; Akkerman, Nicole; Arkestijn, Sandra; Van Delft, Peter; Giordano, Piero C

    2005-01-01

    A microcytic hypochromic anemic state was observed in an 8-year old Black female of Surinam origin during pre-operative Hb S [beta6(A3)Glu-->Val] screening. Her high zinc protoporphyrin (ZPP) level suggested a chronic iron depletion but, in contrast, the high red blood cell (RBC) count (5.85 x 10(12)/L) was indicative of a possible coexisting thalassemia. No abnormal hemoglobin (Hb) bands were present on high performance liquid chromatography (HPLC) or alkaline electrophoresis and the Hb A2 level was normal. Break point polymerase chain reaction (PCR) failed to reveal any of the common alpha-thalassemia (thal) mutations but selective DNA sequencing of both alpha-globin genes disclosed a TGC-->AGC transversion at codon 104 of the alpha1 gene. Cystine at codon 104 is involved in alpha/beta globin contact and has been described to be a critical amino acid of the alpha2 chain when substituted by a tyrosine (Hb Sallanches), inducing Hb H (beta4) disease in the homozygous state. Our heterozygous patient had a moderate anemia of 12.2 g/dL and a borderline haptoglobin suggesting some degree of hemolysis. PMID:16114179

  12. First principles calculations of electronic structure and magnetic properties of Cr-based magnetic semiconductors Al{sub 1-x}Cr{sub x}X (X=N, P, As, Sb)

    SciTech Connect

    Saeed, Y.; Shaukat, A.; Nazir, S.; Ikram, N.; Hussain Reshak, Ali

    2010-01-15

    First principles calculations based on the density functional theory (DFT) within the local spin density approximation are performed to investigate the electronic structure and magnetic properties of Cr-based zinc blende diluted magnetic semiconductors Al{sub 1-x}Cr{sub x}X (X=N, P, As, Sb) for 0<=x<=0.50.The behaviour of magnetic moment of Al{sub 1-x}Cr{sub x}X at each Cr site as well as the change in the band gap value due to spin down electrons has been studied by increasing the concentration of Cr atom and through changing X from N to Sb. Furthermore, the role of p-d hybridization is analyzed in the electronic band structure and exchange splitting of d-dominated bands. The interaction strength is stronger in Al{sub 1-x}Cr{sub x}N and becomes weaker in Al{sub 1-x}Cr{sub x}Sb. The band gap due to the spin down electrons decreases with the increased concentration of Cr in Al{sub 1-x}Cr{sub x}X, and as one moves down along the isoelectronic series in the group V from N to Sb. Our calculations also verify the half-metallic ferromagnetic character in Cr doped AlX. - Graphical abstract: The prototype structures of Cr doped AlX (X=N, P, As, Sb) compounds: (A) zinc blende AlP for x=0, (B) Cr{sub 1}Al{sub 7}P{sub 8} for x=0.125, (C) Cr{sub 1}Al{sub 3}P{sub 4} for x=0.25, (D) Cr{sub 1}Al{sub 1}P{sub 2} for x=0.5.

  13. Characterization of homogeneous recombinant rat ovarian 20alpha-hydroxysteroid dehydrogenase: fluorescent properties and inhibition profile.

    PubMed Central

    Ma, H; Penning, T M

    1999-01-01

    In rat ovary, 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD), a member of the aldo-keto reductase (AKR) superfamily, converts progesterone into the inactive progestin 20alpha-hydroxyprogesterone and has been implicated in the termination of pregnancy. Here we report a convenient overexpression system that permits the purification of milligram quantities of homogeneous recombinant 20alpha-HSD with wild-type enzyme activity. The availability of this enzyme has permitted detailed kinetic, inhibition and fluorescence analyses. The enzyme exhibited narrow steroid specificity, catalysing reactions only at C-20; it reduced progesterone and 17alpha-hydroxyprogesterone and oxidized 20alpha-hydroxypregnanes. It also turned over common AKR substrates, such as 9, 10-phenanthrenequinone and 4-nitrobenzaldehyde. The intrinsic fluorescence spectrum of 20alpha-HSD was characterized and was quenched on the binding of NADP(H), yielding a KNADPd of 0.36 microM and a KNADPHd of 0.64 microM. NADP(H) binding generated an energy transfer band that could not be quenched by steroids. Inhibition studies conducted with non-steroidal and steroidal anti-inflammatory drugs and synthetic oestrogens indicated that even though rat ovarian 20alpha-HSD and rat liver 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) share more than 67% amino acid identity, their inhibition profiles are markedly different. Unlike 3alpha-HSD, most of these compounds did not inhibit 20alpha-HSD. Only meclofenamic acid and hexoestrol were potent competitive inhibitors for 20alpha-HSD, yielding K(i) values of 18.9 and 14.3 microM respectively. These studies suggest that selective non-steroidal AKR inhibitors could be developed for 20alpha-HSD that might be useful in maintaining pregnancy and that specific inhibitors might be developed from either N-phenylanthranilates or biphenols. PMID:10417353

  14. Characterization of homogeneous recombinant rat ovarian 20alpha-hydroxysteroid dehydrogenase: fluorescent properties and inhibition profile.

    PubMed

    Ma, H; Penning, T M

    1999-08-01

    In rat ovary, 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD), a member of the aldo-keto reductase (AKR) superfamily, converts progesterone into the inactive progestin 20alpha-hydroxyprogesterone and has been implicated in the termination of pregnancy. Here we report a convenient overexpression system that permits the purification of milligram quantities of homogeneous recombinant 20alpha-HSD with wild-type enzyme activity. The availability of this enzyme has permitted detailed kinetic, inhibition and fluorescence analyses. The enzyme exhibited narrow steroid specificity, catalysing reactions only at C-20; it reduced progesterone and 17alpha-hydroxyprogesterone and oxidized 20alpha-hydroxypregnanes. It also turned over common AKR substrates, such as 9, 10-phenanthrenequinone and 4-nitrobenzaldehyde. The intrinsic fluorescence spectrum of 20alpha-HSD was characterized and was quenched on the binding of NADP(H), yielding a KNADPd of 0.36 microM and a KNADPHd of 0.64 microM. NADP(H) binding generated an energy transfer band that could not be quenched by steroids. Inhibition studies conducted with non-steroidal and steroidal anti-inflammatory drugs and synthetic oestrogens indicated that even though rat ovarian 20alpha-HSD and rat liver 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) share more than 67% amino acid identity, their inhibition profiles are markedly different. Unlike 3alpha-HSD, most of these compounds did not inhibit 20alpha-HSD. Only meclofenamic acid and hexoestrol were potent competitive inhibitors for 20alpha-HSD, yielding K(i) values of 18.9 and 14.3 microM respectively. These studies suggest that selective non-steroidal AKR inhibitors could be developed for 20alpha-HSD that might be useful in maintaining pregnancy and that specific inhibitors might be developed from either N-phenylanthranilates or biphenols. PMID:10417353

  15. 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 ...

  16. Reaction of sulfur halides with unsaturated compounds. New type of reaction of sulfur dichloride with olefins

    SciTech Connect

    Tolstikov, G.A.; Lerman, B.M.; Umanskaya, L.I.; Struchkov, Y.T.

    1982-09-20

    This report focuses on a new type of reaction between sulfur dichloride and olefins which has been discovered, leading to epithio compounds and chloro-substituted olefins. Depending on conditions, the reaction between adamantylideneadamantane and SC1/sub 2/ at an equimolar ratio of the reagents leads preferably to 2,2'-epithio-2-(2'-adamantyl) adamantane, or 4e-chloro-2,2'-epithio-2-(2'-adamatyl) adamantane, or 4e-chloroadamantylideneadamantane. The structure of 4e-chloro-2,2'-epithio-2(2'-adamantyl)adamatane was confirmed by x-ray diffraction analysis. Results indicated that in the reaction between adamantylideneadamantane and an excess of SC1/sub 2/, 4e,4'e-dichloro-, 4e,4'e,8..cap alpha..-trichloro- and 4e,4'e,8..cap alpha..,8'..cap alpha..-tetrachloroadamantylideneadamatanes are formed.

  17. Genetics Home Reference: alpha-mannosidosis

    MedlinePlus

    ... Me Understand Genetics Home Health Conditions alpha-mannosidosis alpha-mannosidosis Enable Javascript to view the expand/collapse boxes. Download PDF Open All Close All Description Alpha-mannosidosis is a rare inherited disorder that causes ...

  18. Fusion hindrance in reactions with very heavy ions: Border between normal and hindered fusion

    SciTech Connect

    Shen Caiwan; Li Qingfeng; Boilley, David; Shen Junjie; Abe, Yasuhisa

    2011-05-15

    The fusion hindrance in heavy-ion collisions is studied in the framework of the two-center liquid drop model. It appears that the neck and the radial degrees of freedom might both be hampered by an inner potential barrier on their path between the contact configuration to the compound nucleus. Heavy-ion reactions with and without the two kinds of fusion hindrance are classified through systematic calculations. It is found that the number of reactions without radial fusion hindrance is much smaller than that without neck fusion hindrance, and for both kinds of fusion hindrance the number of reactions without fusion hindrance at small mass-asymmetry parameter {alpha} is smaller than that at large {alpha}. In the formation of a given compound nucleus, if a reaction with {alpha}{sub c} is not hindered, then other reactions with {alpha}>{alpha}{sub c} are also not hindered, as is well known experimentally.

  19. 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.

  20. 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