WorldWideScience

Sample records for al excitation function

  1. Precise measurement of the 27Al(n,2n)26gAl excitation function near threshold and its relevance for fusion-plasma technology

    International Nuclear Information System (INIS)

    A new accurate measurement of the 27Al(n,2n)26Al excitation function leading to the ground state of 26Al(t1/2=7.1 x 105 years) in the near-threshold region (Eth=13.55 MeV) was performed, with the goal to achieve relative cross-sections with the highest accuracy possible using proven methods. In addition, the measurements were also designed to provide good absolute cross-section values, since absolute cross-sections are important for radioactive waste predictions in future fusion reactor materials. Samples of Al metal were irradiated with neutrons in the energy range near threshold (En=13.5-14.8 MeV) in Vienna and St. Petersburg, and at 14.8 MeV in Tokai-mura. In addition, irradiations with neutrons of higher energies (17 and 19 MeV) were performed in Tuebingen, to obtain also cross-section values well above threshold. The amount of 26Al produced during the irradiations was measured via accelerator mass spectrometry (AMS). With this system, a background as low as 3 x 10-15 for 26Al/27Al isotope ratios was obtained, corresponding to a (n,2n) cross-section of 0.04 mb. Utilizing AMS, cross-sections with much higher precision and considerably closer to the threshold than in previous investigations were measured. A substantial improvement in the knowledge of this excitation function was obtained. Its expected strongly non-linear behaviour near threshold makes the production of 26Al sensitive to temperature changes in a deuterium-tritium (D-T) fusion plasma. The prerequisite for such an application as a temperature monitor, namely a very well-known shape of the excitation function, was met. A quantitative prediction of the sensitivity of this method for monitoring the temperature in a D-T fusion plasma was therefore possible. (orig.)

  2. Cross-Correlation of Excitation Functions for Different Fragments and Different Scattering Angles in 27Al(19F, x) y Reactions

    Institute of Scientific and Technical Information of China (English)

    HAN Jian-Long; WU He-Yu; LI Zhi-Chang; LU Xiu-Qin; ZHAO Kui; ZHOU Ping; LIU Jian-Cheng; XU Guo-Ji; Sergey Yu Kun; WANG Qi; BAI Zhen; DONG Yu-Chuan; LI Song-Lin; DUAN Li-Min; XU Hu-Shan; XU Hua-Gen; CHEN Ruo-Fu

    2008-01-01

    @@ Excitation functions have been measured for different projectile-like fragments produced in 27 Al(19 F,x)y reactions at incident energies from 110.25 to 118. 75 Me V in 250 ke V steps. Strong cross section fluctuations of the excitation functions are observed. The cross-correlation coefficients of the excitation functions for different atomic number Z and for different scattering angle θcm have been deduced. These coefficients are much larger than the statistical theoretical calculated ones. This indicates that there are strong correlations between different exit channels in the dissipative heavy ion collision of 27 Al(19 F,x )y.

  3. Study of the excitation functions of 27Al(n,α)24Na, 27Al(n,p)27Mg and 28Si(n,p)28Al reactions

    International Nuclear Information System (INIS)

    Cross sections for the reactions 27Al(n, p)27Mg and 28Si(n, p)28Al were measured by activation method between 13.40 and 14.83 MeV neutron energy. An accuracy of about 4% was achieved using the 27Al(n, α)24Na reaction as a reference at 14.1 MeV where the relative excitation function has also been measured. Results obtained were compared to a recent compilation and that calculated by the Hauser-Feshbach model. Using the back-shifted level density formula and taking into account the contribution of the separated levels, the calculations were extended to the energy range from the threshold to 18 MeV. A structure was observed in the 27Al(n, α)24Na reaction cross section curve around 14 MeV neutron energy. (orig.)

  4. Precise measurement of the sup 2 sup 7 Al(n,2n) sup 2 sup 6 sup g Al excitation function near threshold and its relevance for fusion-plasma technology

    CERN Document Server

    Wallner, A; Priller, A; Steier, P; Vonach, H; Chuvaev, S V; Filatenkov, A A; Ikeda, Y; Mertens, G; Rochow, W

    2003-01-01

    A new accurate measurement of the sup 2 sup 7 Al(n,2n) sup 2 sup 6 Al excitation function leading to the ground state of sup 2 sup 6 Al(t sub 1 sub / sub 2 =7.1 x 10 sup 5 years) in the near-threshold region (E sub t sub h =13.55 MeV) was performed, with the goal to achieve relative cross-sections with the highest accuracy possible using proven methods. In addition, the measurements were also designed to provide good absolute cross-section values, since absolute cross-sections are important for radioactive waste predictions in future fusion reactor materials. Samples of Al metal were irradiated with neutrons in the energy range near threshold (E sub n =13.5-14.8 MeV) in Vienna and St. Petersburg, and at 14.8 MeV in Tokai-mura. In addition, irradiations with neutrons of higher energies (17 and 19 MeV) were performed in Tuebingen, to obtain also cross-section values well above threshold. The amount of sup 2 sup 6 Al produced during the irradiations was measured via accelerator mass spectrometry (AMS). With this...

  5. Measurement of nuclear potentials from fusion excitation functions

    International Nuclear Information System (INIS)

    The basis for measuring nuclear potentials from fusion excitation functions at energies above barrier is reviewed. It is argued that because of experimental and conceptual problems fusion excitation functions at high energies cannot lead to model independent measurements of internuclear potential at small separations. The Al 27 + Ne 20 reaction previously analyzed by others is used as an example of problems arising from the inability to distinguish complete and incomplete fusion in experimental data

  6. Evaluation of Excitation Function for 64Zn

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>Present work concerns the evaluated neutron induced excitation function data for 64Zn, and mainly on (n, γ) reaction channel. The related experimental data were collected, analyzed and corrected for 64Zn

  7. Evaluation of Excitation Function for 182Ta

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>Present work concerns the evaluated neutron induced excitation function data for 182Ta, and mainly on (n, γ) reaction channel. The related experimental data were collected, analyzed and corrected for 182Ta

  8. Neutron excitation function guide for reactor dosimetry

    International Nuclear Information System (INIS)

    Neutron Excitation Function Guide for Reactor Dosimetry (NEFGRD) has been prepared in the Ukrainian Nuclear Data Center (UKRNDC) using ZVV 9.2 code for graphical data presentation. The data can be retrieved through Web or obtained on CD-ROM or as hard copy report. NEFGRD contains graphical and text information for 56 nuclides (81 dosimetry reactions). Each reaction is provided by the information part and several graphical function blocks (from one to nine). (author)

  9. Photoluminescence and excitation spectra of GaAs-Ga(Al)As strongly coupled double well superlattice

    International Nuclear Information System (INIS)

    The electron and holes mini-bands are calculated as a function of the parallel momentum for a strongly coupled double well structure. Photoluminescence and excitation spectra for 45A GaAs wells separated by 12A Ga(Al)As barrier is analyzed. (Author)

  10. Excitation functions for the production of radionuclides by neutron-induced reactions on C, O, Mg, Al, Si, Fe, Co, Ni, Cu, Ag, Te, Pb, and U up to 180 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Michel, R., E-mail: michel@irs.uni-hannover.de [Institute for Radioecology and Radiological Protection, Leibniz University Hannover (Germany); Hansmann, D. [Institute for Radioecology and Radiological Protection, Leibniz University Hannover (Germany); Neumann, S. [Institute for Radioecology and Radiological Protection, Leibniz University Hannover (Germany); Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany); Glasser, W. [Institute for Radioecology and Radiological Protection, Leibniz University Hannover (Germany); Schuhmacher, H.; Dangendorf, V.; Nolte, R. [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany); Herpers, U. [Dept. for Nuclear Chemistry, University of Cologne (Germany); Smirnov, A.N.; Ryzhov, I.V. [V. G. Khlopin Radium Institute, St. Petersburg (Russian Federation); Prokofiev, A.V. [The Svedberg Laboratory (TSL), Uppsala University (Sweden); Dept. of Physics and Astronomy, Uppsala University (Sweden); Malmborg, P. [The Svedberg Laboratory (TSL), Uppsala University (Sweden); Kollár, D. [Dept. of Nuclear Physics, Comenius University, Bratislava (Slovakia); Meulders, J.-P. [Université Catholique de Louvain (UCL), Louvain-la-Neuve (Belgium)

    2015-01-15

    Irradiation experiments with well-characterized, quasi mono-energetic neutrons of energies between 32.7 MeV and 175.4 MeV were performed at UCL/Louvain-la-Neuve and TSL/Uppsala. The abundances of relatively short-lived residual radionuclides from 13 different target elements were determined by γ-spectrometry. More than 100 excitation functions of neutron-induced reactions were unfolded based on the neutron spectra and the radionuclide abundances with the aid of additional information that was provided by “guess” excitation functions calculated by the TALYS 1.0 code. The results are compared with the sparse existing data from other authors. The new excitation functions were validated by calculation of and comparison with experimental thick-target production rates. Consistency with neutron excitation functions up to 1.6 GeV, which were derived earlier by unfolding the thick-target production rates, was so demonstrated.

  11. Excitation functions for the production of radionuclides by neutron-induced reactions on C, O, Mg, Al, Si, Fe, Co, Ni, Cu, Ag, Te, Pb, and U up to 180 MeV

    International Nuclear Information System (INIS)

    Irradiation experiments with well-characterized, quasi mono-energetic neutrons of energies between 32.7 MeV and 175.4 MeV were performed at UCL/Louvain-la-Neuve and TSL/Uppsala. The abundances of relatively short-lived residual radionuclides from 13 different target elements were determined by γ-spectrometry. More than 100 excitation functions of neutron-induced reactions were unfolded based on the neutron spectra and the radionuclide abundances with the aid of additional information that was provided by “guess” excitation functions calculated by the TALYS 1.0 code. The results are compared with the sparse existing data from other authors. The new excitation functions were validated by calculation of and comparison with experimental thick-target production rates. Consistency with neutron excitation functions up to 1.6 GeV, which were derived earlier by unfolding the thick-target production rates, was so demonstrated

  12. A new measurement of pantip excitation functions

    International Nuclear Information System (INIS)

    In a recent experiment at the CERN Proton Synchrotron (PS) the proton-antiproton excitation functions of the annihilation as well as of the elastic channel have been measured in the laboratory momentum range from 370 to 1000 MeV/c. The experiment was characterized by a r.m.s. mass resolution of 0.4 MeV/c2 and a statistical accuracy of 1.2% for the annihilation channel. With this precision a narrow structure, about 4 MeV/c2 wide, at a mass of 1936 MeV/c2 is observed in the annihilation channel

  13. Fusion excitation functions involving transitional nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Rehm, K.E.; Jiang, C.L.; Esbensen, H. [and others

    1995-08-01

    Measurements of fusion excitation functions involving transitional nuclei {sup 78}Kr and {sup 100}Mo showed a different behavior at low energies, if compared to measurements with {sup 86}Kr and {sup 92}Mo. This points to a possible influence of nuclear structure on the fusion process. One way to characterize the structure of vibrational nuclei is via their restoring force parameters C{sub 2} which can be calculated from the energy of the lowest 2{sup +} state and the corresponding B(E2) value. A survey of the even-even nuclei between A = 28-150 shows strong variations in C{sub 2} values spanning two orders of magnitude. The lowest values for C{sub 2} are observed for {sup 78}Kr, {sup 104}Ru and {sup 124}Xe followed by {sup 74,76}Ge, {sup 74,76}Se, {sup 100}Mo and {sup 110}Pd. In order to learn more about the influence of {open_quotes}softness{close_quotes} on the sub-barrier fusion enhancement, we measured cross sections for evaporation residue production for the systems {sup 78}Kr + {sup 104}Ru and {sup 78}Kr + {sup 76}Ge with the gas-filled magnet technique. For both systems, fusion excitation functions involving the closed neutron shell nucleus {sup 86}Kr were measured previously. The data are presently being analyzed.

  14. Study of incomplete fusion dynamics: analysis of excitation functions

    International Nuclear Information System (INIS)

    With a view to study complete fusion and incomplete fusion in several projectile target combinations, a programme of precise measurements of cross-sections and analysis of excitation functions has been undertaken. As a part of the ongoing programme, excitation functions for six reactions in 16O + 169Tm system have been measured

  15. Excited states of hydrogen shallow impurities in GaAs-Ga Al As quantum wells

    International Nuclear Information System (INIS)

    The study of shallow impurities in semiconductor heterostructures, such as quantum and superlattices, has been of continuous interest over the last years. Successful comparisons between experimental results photoluminescence: N.N Ledentsov et al., Appl. Phys. A 54, 261 (1992) and theoretical calculations [L.E. Oliveira and G.D. Mahan, Phys. Rev. B 47, 2406 (1993)] constitute a strong motivation for an in-depth theoretical study. We present a variational calculation of the binding energies of shallow donors in a Ga-As-AlGaAs quantum well. The energies and variational wave functions associated to the ground state (1s-like) as well as some excited states (2s, 2pxy, 2pxy, 3s, 3pxy, and 3p like) are obtained as functions of the position of the impurity (zi) in the well. The density of impurity states, intra-donor transition strengths and the infrared absorption spectra are calculated for some of these excited states and results compared with previous theoretical [S. Fraizzoli, F. Bassani, and R. Buczko, Phys. rev. B 41, 5096 (1990)] and experimental works [N.C. Jarosik et al., Phys. Rev. Lett. 54, 1283 (1985). (author)

  16. Empirical systematics for selection of threshold reaction excitation functions

    International Nuclear Information System (INIS)

    This report is devoted to empirical excitation functions systematics of threshold reactions (n,p), (n,α), (n,2n) and (n,3n). The shapes and maximum cross sections of excitation functions were analysed as functions of neutron excess (N-Z) and mass number A. Some systematical trends are shown for the fission and (n,2n) cross sections of fissile isotopes. (author)

  17. Exact ensemble density-functional theory for excited states

    CERN Document Server

    Yang, Zeng-hui; Pribram-Jones, Aurora; Burke, Kieron; Needs, Richard J; Ullrich, Carsten A

    2014-01-01

    We construct exact Kohn-Sham potentials for the ensemble density-functional theory (EDFT) of excited states from the ground and excited states of helium. The exchange-correlation potential is compared with current approximations, which miss prominent features. The ensemble derivative discontinuity is tested, and the virial theorem is proven and illustrated.

  18. Functional Integrals and Collective Excitations in Boson-Fermion Model

    Institute of Scientific and Technical Information of China (English)

    YAN Jun

    2006-01-01

    In this paper, collective excitations in the boson-fermion model are investigated by means of functional integration method. The equations of energy gap and excitation spectrum are derived. Moreover, the Bose energy spectrum of zero wave vector Fermi fields is also calculated.

  19. Excitation Spectra of Nucleobases with Multiconfigurational Density Functional Theory

    DEFF Research Database (Denmark)

    Hubert, Mickaël; Jensen, Hans Jørgen Aa; Hedegård, Erik D.

    2016-01-01

    Range-separated hybrid methods between wave function theory and density functional theory (DFT) can provide high-accuracy results, while correcting some of the inherent flaws of both the underlying wave function theory and DFT. We here assess the accuracy for excitation energies of the nucleobases...... linear response extension of CAS-srDFT, we compare the first 7-8 excited states of the nucleobases with perturbative multireference approaches as well as coupled cluster based methods. Our results show that the CAS-srDFT method can provide accurate excitation energies in good correspondence with the...

  20. Efficient basis for the Dicke model: II. Wave function convergence and excited states

    International Nuclear Information System (INIS)

    An extended bosonic coherent basis has been shown by Chen et al (2008 Phys. Rev. A 78 051801) and Liu T et al (2009 Phys. Rev. A 80 165308) to provide numerically exact solutions of the finite-size Dicke model. The advantages in employing this basis, as compared with the photon number (Fock) basis, are exhibited to be valid for a large region of the Hamiltonian parameter space and many excited states by analyzing the convergence in the wave functions. (paper)

  1. Density functional theory generalized to degenerate excited states

    International Nuclear Information System (INIS)

    In this paper it is shown that the density functional theory can be generalized to systems with degenerate excited states. There is a one-to-one map between the subspace, spanned by the ground state and any one of the first degenerate excited states, and the sum of their densities. But only a one way correspondence exists between external potential and subspace, as well as between external potential and the sum of densities. The extension of the Hohenberg-Kohn-Sham theory for degenerate excited states has also been developed. (author)

  2. Excitation Spectra of Nucleobases with Multiconfigurational Density Functional Theory.

    Science.gov (United States)

    Hubert, Mickaël; Jensen, Hans Jørgen Aa; Hedegård, Erik D

    2016-01-14

    Range-separated hybrid methods between wave function theory and density functional theory (DFT) can provide high-accuracy results, while correcting some of the inherent flaws of both the underlying wave function theory and DFT. We here assess the accuracy for excitation energies of the nucleobases thymine, uracil, cytosine, and adenine, using a hybrid between complete active space self-consistent field (CASSCF) and DFT methods. The method is based on range separation, thereby avoiding all double-counting of electron correlation and is denoted long-range CASSCF short-range DFT (CAS-srDFT). Using a linear response extension of CAS-srDFT, we compare the first 7-8 excited states of the nucleobases with perturbative multireference approaches as well as coupled cluster based methods. Our results show that the CAS-srDFT method can provide accurate excitation energies in good correspondence with the computationally more expensive methods. PMID:26669578

  3. The systematics of (n,2n) reaction excitation function

    International Nuclear Information System (INIS)

    Based on the constant temperature evaporation model taking the competition of (n,3n) reaction and the contribution of preequilibrium emission into account, the systematics formulae of (n,2n) reaction excitation function have been established. The systematics behaviours of (n,2n) reaction excitation function have been studied. There are two systematics parameters T and σn,M, and can be adjusted in the formulae. For getting the two parameters, the new evaluated data of (n,2n) reactions were adopted and fitted by means of the nonlinear least squares method. The fitted results agree fairly well with the measured data at 45≤A≤210 below 30 MeV. Based on a body of new measurements, the reliability to predict (n,2n) reaction excitation function is improved. Hence more accurate systematics prediction for unmeasured nucleus or energy range may be provided.

  4. The systematics of (n,2n) reaction excitation function

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jimin, E-mail: jmwang@ciae.ac.c [China Institute of Atomic Energy, P.O. Box 275(41), Beijing 102413 (China); Tao Xi; Huang Xiaolong; Zhuang Youxiang [China Institute of Atomic Energy, P.O. Box 275(41), Beijing 102413 (China)

    2010-07-01

    Based on the constant temperature evaporation model taking the competition of (n,3n) reaction and the contribution of preequilibrium emission into account, the systematics formulae of (n,2n) reaction excitation function have been established. The systematics behaviours of (n,2n) reaction excitation function have been studied. There are two systematics parameters T and {sigma}{sub n,M}, and can be adjusted in the formulae. For getting the two parameters, the new evaluated data of (n,2n) reactions were adopted and fitted by means of the nonlinear least squares method. The fitted results agree fairly well with the measured data at 45{<=}A{<=}210 below 30 MeV. Based on a body of new measurements, the reliability to predict (n,2n) reaction excitation function is improved. Hence more accurate systematics prediction for unmeasured nucleus or energy range may be provided.

  5. Excitations and benchmark ensemble density functional theory for two electrons

    International Nuclear Information System (INIS)

    A new method for extracting ensemble Kohn-Sham potentials from accurate excited state densities is applied to a variety of two-electron systems, exploring the behavior of exact ensemble density functional theory. The issue of separating the Hartree energy and the choice of degenerate eigenstates is explored. A new approximation, spin eigenstate Hartree-exchange, is derived. Exact conditions that are proven include the signs of the correlation energy components and the asymptotic behavior of the potential for small weights of the excited states. Many energy components are given as a function of the weights for two electrons in a one-dimensional flat box, in a box with a large barrier to create charge transfer excitations, in a three-dimensional harmonic well (Hooke's atom), and for the He atom singlet-triplet ensemble, singlet-triplet-singlet ensemble, and triplet bi-ensemble

  6. Excitations and benchmark ensemble density functional theory for two electrons

    CERN Document Server

    Pribram-Jones, Aurora; Trail, John R; Burke, Kieron; Needs, Richard J; Ullrich, Carsten A

    2014-01-01

    A new method for extracting ensemble Kohn-Sham potentials from accurate excited state densities is applied to a variety of two electron systems, exploring the behavior of exact ensemble density functional theory. The issue of separating the Hartree energy and the choice of degenerate eigenstates is explored. A new approximation, spin eigenstate Hartree-exchange (SEHX), is derived. Exact conditions that are proven include the signs of the correlation energy components, the virial theorem for both exchange and correlation, and the asymptotic behavior of the potential for small weights of the excited states. Many energy components are given as a function of the weights for two electrons in a one-dimensional flat box, in a box with a large barrier to create charge transfer excitations, in a three-dimensional harmonic well (Hooke's atom), and for the He atom singlet-triplet ensemble, singlet-triplet-singlet ensemble, and triplet bi-ensemble.

  7. Fluctuations in the excitation functions of dissipative heavy ion collisions

    International Nuclear Information System (INIS)

    Excitation functions have been measured for different charge products of the 28Si+64Ni reaction in the energy range 120-126.75 MeV in 250 keV steps (lab). Dissipative cross sections have shown fluctuations with coherence energies in the range 200-800 keV (CM). The formation of a dinuclear intermediate system is suggested. (orig.)

  8. El strength function at high spin and excitation energy

    International Nuclear Information System (INIS)

    Recently giant dipole resonance-like concentration of the dipole strength function in nuclei was observed at both high excitation energies and high spins. This observation raises the possibility of obtaining new information on the shape of rapidly rotating heated nuclei. Recent experimental results on this subject are reviewed

  9. A study of the ground and excited states of Al3 and Al3-. II. Computational analysis of the 488 nm anion photoelectron spectrum and a reconsideration of the Al3 bond dissociation energy

    Science.gov (United States)

    Miller, Stephen R.; Schultz, Nathan E.; Truhlar, Donald G.; Leopold, Doreen G.

    2009-01-01

    Computational results are reported for the ground and low-lying excited electronic states of Al3- and Al3 and compared with the available spectroscopic data. In agreement with previous assignments, the six photodetachment transitions observed in the vibrationally resolved 488nm photoelectron spectrum of Al3- are assigned as arising from the ground X˜A1'1(A11) and excited B23 states of Al3- and accessing the ground X˜A1'2(A12) and excited A2″2(B12), A24, and B22 states of Al3 (with C2v labels for D3h states in parentheses). Geometries and vibrational frequencies obtained by PBE0 hybrid density functional calculations using the 6-311+G(3d2f) basis set and energies calculated using coupled cluster theory with single and double excitations and a quasiperturbative treatment of connected triple excitations (CCSD(T)) with the aug-cc-pVxZ {x =D, T, Q} basis sets with exponential extrapolation to the complete basis set limit are in good agreement with experiment. Franck-Condon spectra calculated in the harmonic approximation, using either the Sharp-Rosenstock-Chen method which includes Duschinsky rotation or the parallel-mode Hutchisson method, also agree well with the observed spectra. Possible assignments for the higher-energy bands observed in the previously reported UV photoelectron spectra are suggested. Descriptions of the photodetachment transition between the Al3- and Al3 ground states in terms of natural bond order (NBO) analyses and total electron density difference distributions are discussed. A reinterpretation of the vibrational structure in the resonant two-photon ionization spectrum of Al3 is proposed, which supports its original assignment as arising from the X˜A1'2 ground state, giving an Al3 bond dissociation energy, D0(Al2-Al), of 2.403±0.001eV. With this reduction by 0.3eV from the currently recommended value, the present calculated dissociation energies of Al3, Al3-, and Al3+ are consistent with the experimental data.

  10. Dielectric Function and Electronic Excitations of Functionalized DNA Thin Films

    Science.gov (United States)

    Lee, Hosuk; Lee, Hosun; Lee, Jung Eun; Rha Lee, U.; Choi, Dong Hoon

    2010-06-01

    We measure the dielectric functions of organic-soluble, functionalized DNAs bearing functional moieties in the near-infrared, visible, and ultra-violet spectra by using spectroscopic ellipsometry. Natural double-stranded DNA is dissolved in water and reacted with carbazole-based trimethyl ammonium bromide, cetyltrimethylammonium bromide, and chalcone-terminated trimethyl ammonium bromide. The functional DNA products are all precipitated and filtered for washing and drying. We successfully prepare functionalized DNAs that are insoluble in water but soluble in organic solvents. The thin films are fabricated by using the spin coating technique after preparing solutions in either homogeneous or mixed organic solvents. We measure the ultraviolet-visible absorbance spectra of the films. The absorbance spectra show that the optical energy gaps of the functionalized DNAs change little even though the DNAs are connected to the complex molecules by electrostatic interaction. From the measured ellipsometric angles, we estimate the dielectric functions by using parametric optical constant model and layer model analysis. Depending on the nature of the attached complex molecules, the dielectric functions change, new optical structures develop below and above band gaps arising from the side molecules, and the optical energy gaps of the DNAs are altered slightly by weak coupling to the tethered complex molecules.

  11. Reduction of nonlinear resonance excitation from insertion devices in the ALS

    International Nuclear Information System (INIS)

    Theoretical studies of Lawrence Berkeley Laboratory's Advanced Light Source (ALS) storage ring predict strong field insertion devices will break the rings symmetry, increasing resonance excitation that may reduce the dynamic aperture and thus the beam lifetime. The authors have embarked on an experimental program to study the strength of nonlinear resonance excitation in the ALS when insertion devices are present. They observe an enhancement in the resonance excitation of a third-order resonance when the gap of the insertion device is narrowed. They also find that it is possible to suppress this resonance by detuning two quadruples on either side of the insertion device. The results of this study are presented in this paper

  12. Excitation Functions of Deuteron Induced Nuclear Reactions on Iron

    International Nuclear Information System (INIS)

    The excitation functions were measured for nuclear reactions induced by deuterons on natural iron leading to the production of 52g,54Mn and 55,56,57,58gCo radionuclides in the energy range from threshold energy up to 10 MeV. The measured data were compared with other measured data and also with the results of theoretical calculations using the default parameters of the codes EMPIRE-3.0 and TALYS. The coulomb barrier Bc for iron target was calculated and the excitation curves were discussed taking in consideration the deuteron breakup and the pre-equilibrium emission processes. The integral yields of 55,56,57,58gCO radionuclides were calculated as a function of deuteron energy

  13. Leptin regulation of neuronal excitability and cognitive function

    OpenAIRE

    Harvey., Jenni

    2007-01-01

    Leptin, a hormone produced by adipocytes, provides signals to specific regions of the hypothalamus to control energy homeostasis. However, the past decade of research has not only revealed that leptin receptors are widely expressed in the CNS, but has also identified numerous additional functions for this hormone in the brain. In particular, there is evidence that leptin influences neuronal excitability via the activation as well as trafficking of specific potassium channels in several brain ...

  14. Excitation and de-excitation mechanisms of Er-doped GaAs and AlGaAs. Doctoral thesis

    Energy Technology Data Exchange (ETDEWEB)

    Elsaesser, D.W.

    1992-12-01

    Electrical and optical characterization have been performed on GaAs and AlxGa1-xAs samples doped with Er either by ion implantation or during Molecular Beam Epitaxial (MBE) growth. Deep Level Transient Spectroscopy (DLTS) and Temperature-Dependent Hall Effect (TDH) measurements indicated the presence of two hole traps in Er-doped GaAs, at 35 and 360 meV above the valence band maximum. The former (shallower) center was thought to be due to Er substituting for a Ga atom (ErGa) and giving rise to an isoelectronic impurity potential. The second center was attributed to an Er atom occupying an interstitial position (Er(i)). Annealing studies performed on Er-implanted GaAs indicated that the ErGa center preferentially formed at higher annealing temperatures ( > 850 deg C), with the Er(i) reaching a maximum concentration at an annealing temperature of around 750 deg C. Optical characterization performed by Photoluminescence (PL) measurements showed that the Er(i) center gave a much stronger Er-related intra-4f shell emission. Mechanisms for the excitation of the 4f shells of these two centers are discussed. Similar optically active Eri centers may be forming in AlGaAs....Rare earth, Er, DLTS, Isoelectronic, GaAs, AlGaAs, Ion implantation, MBE, Luminescence, Hall effect.

  15. Coupled cluster Green function: Model involving single and double excitations

    Science.gov (United States)

    Bhaskaran-Nair, Kiran; Kowalski, Karol; Shelton, William A.

    2016-04-01

    In this paper, we report on the development of a parallel implementation of the coupled-cluster (CC) Green function formulation (GFCC) employing single and double excitations in the cluster operator (GFCCSD). A key aspect of this work is the determination of the frequency dependent self-energy, Σ(ω). The detailed description of the underlying algorithm is provided, including approximations used that preserve the pole structure of the full GFCCSD method, thereby reducing the computational costs while maintaining an accurate character of methodology. Furthermore, for systems with strong local correlation, our formulation reveals a diagonally dominate block structure where as the non-local correlation increases, the block size increases proportionally. To demonstrate the accuracy of our approach, several examples including calculations of ionization potentials for benchmark systems are presented and compared against experiment.

  16. Evaluation of cross-section data from threshold to 40-60 MeV for specific neutron reactions important for neutron dosimetry applications. Part 1: Evaluation of the excitation functions for the 27Al(n,α)24Na, 55Mn(n,2n)54Mn, 59Co(n,p)59Fe, 59Co(n,2n)58m+gCo and 90Zr(n,2n)89m+gZr reactions

    International Nuclear Information System (INIS)

    Evaluations of cross sections and their associated covariance matrices have been carried out for five dosimetry reactions: - excitation functions were re-evaluated for the 27Al(n,α)24Na, 55Mn(n,2n)54Mn and 90Zr(n,2n)89m+gZr reactions over the neutron energy range from threshold to 40 MeV; - excitation functions were re-evaluated for the 59Co(n,p)59Fe and 59Co(n,2n)58m+gCo reactions over the neutron energy range from threshold to 60 MeV. Uncertainties in the cross sections for all of those reactions were also derived in the form of relative covariance matrices. Benchmark calculations performed for 235U thermal fission and 252Cf spontaneous fission neutron spectra show that the integral cross sections calculated from the newly evaluated excitation functions exhibit improved agreement with related experimental data when compared with the equivalent data from the IRDF-2002 library. (author)

  17. Aluminum resistance in wheat involves maintenance of leaf Ca(2+) and Mg(2+) content, decreased lipid peroxidation and Al accumulation, and low photosystem II excitation pressure.

    Science.gov (United States)

    Moustaka, Julietta; Ouzounidou, Georgia; Bayçu, Gülriz; Moustakas, Michael

    2016-08-01

    The phytotoxic aluminum species (Al(3+)) is considered as the primary factor limiting crop productivity in over 40 % of world's arable land that is acidic. We evaluated the responses of two wheat cultivars (Triticum aestivum L.) with differential Al resistance, cv. Yecora E (Al-resistant) and cv. Dio (Al-sensitive), exposed to 0, 37, 74 and 148 μM Al for 14 days in hydroponic culture at pH 4.5. With increasing Al concentration, leaf Ca(2+) and Mg(2+) content decreased, as well as the effective quantum yield of photosystem II (PSII) photochemistry (Φ PSII ), while a gradual increase in leaf membrane lipid peroxidation, Al accumulation, photoinhibition (estimated as F v /F m ), and PSII excitation pressure (1 - q p ) occurred. However, the Al-resistant cultivar with lower Al accumulation, retained larger concentrations of Ca(2+) and Mg(2+) in the leaves and kept a larger fraction of the PSII reaction centres (RCs) in an open configuration, i.e. a higher ratio of oxidized to reduced quinone A (QA), than plants of the Al-sensitive cultivar. Four times higher Al concentration in the nutrient solution was required for Al-resistant plants (148 μM Al) than for Al-sensitive (37 μM Al), in order to establish the same closed RCs. Yet, the decline in photosynthetic efficiency in the cultivar Dio was not only due to closure of PSII RCs but also to a decrease in the quantum yield of the open RCs. We suggest that Al(3+) toxicity may be mediated by nutrient deficiency and oxidative stress, and that Al-resistance of the wheat cultivar Yecora E, may be due at least partially, from the decreased Al accumulation that resulted to decreased reactive oxygen species (ROS) formation. However, under equal internal Al accumulation (exposure Al concentration: Dio 74 μM, Yecora E 148 μM) that resulted to the same oxidative stress, the reduced PSII excitation pressure and the better PSII functioning of the Al-resistant cultivar was probably due to the larger concentrations of Ca

  18. Proton and deuteron induced reactions on natGa: Experimental and calculated excitation functions

    Science.gov (United States)

    Hermanne, A.; Adam-Rebeles, R.; Tárkányi, F.; Takács, S.; Ditrói, F.

    2015-09-01

    Cross-sections for reactions on natGa, induced by protons (up to 65 MeV) and deuterons (up to 50 MeV), producing γ-emitting radionuclides with half-lives longer than 1 h were measured in a stacked-foil irradiation using thin Ga-Ni alloy (70-30%) targets electroplated on Cu or Au backings. Excitation functions for generation of 68,69Ge, 66,67,68,72Ga and 65,69mZn on natGa are discussed, relative to the monitor reactions natAl(d,x)24,22Na, natAl(p,x)24,22Na, natCu(p,x)62Zn and natNi(p,x)57Ni. The results are compared to our earlier measurements, the scarce literature values and to the results of the code TALYS 1.6 (online database TENDL-2014).

  19. Moments for Generating Functions of Al-Salam-Carlitz Polynomials

    OpenAIRE

    Jian Cao

    2012-01-01

    We employ the moment representations for Al-Salam-Carlitz polynomials and show how to deduce bilinear, trilinear, and multilinear generating functions for Al-Salam-Carlitz polynomials. Moreover, we obtain two terminating generating functions for Al-Salam-Carlitz polynomials by the method of moments.

  20. Some light-ion excitation-function measurements on titanium, yttrium, and europium, and associated results

    Energy Technology Data Exchange (ETDEWEB)

    West, H.I. Jr. [ed.; Lanier, R.G.; Mustafa, M.G.; Nuckolls, R.M.; Nagle, R.J.; O`Brien, H. [Lawrence Livermore National Lab., CA (United States); Frehaut, J.; Adam, A.; Philis, C. [Service de Physique et Techniques Nucleaires, Centre d`Etudes Bruyeres-le-Chatel, Boite Postale 12 (France)

    1993-11-01

    This report discusses: Fabrication of Plastic-Matrix-Encapsulated Accelerator Targets and Their Use in Measuring Nuclear Excitation Functions; Correcting Excitation Function Data in the Low Energy Region for Finite Thickness of the Target Foils, Including Effects of Straggling; Excitation Functions for the Nuclear Reactions on Titanium Leading to the Production {sup 48}V, {sup 44}Sc and {sup 47}Sc by Proton, Deuteron and Triton Irradiations at 0--35 MeV; Some Excitation Functions of Proton and Deuteron Induced Reactions on {sup 89}Y; Measurements of the Excitation Functions of the Isobaric Chain {sup 87}Y, {sup 87}Y{sup m}, {sup 87}Y{sup g} and {sup 87}Sr{sup m}; Levels in {sup 87}Y Observed in the Decay of {sup 87}Zr; and Nuclear Reaction Excitation Functions from the Irradiation of {sup 151,153}Eu with Protons And deuterons up to 35 MeV.

  1. Optimization of Ground- and Excited-State Wave Functions and van der Waals Clusters

    International Nuclear Information System (INIS)

    A quantum Monte Carlo method is introduced to optimize excited-state trial wave functions. The method is applied in a correlation function Monte Carlo calculation to compute ground- and excited-state energies of bosonic van der Waals clusters of up to seven particles. The calculations are performed using trial wave functions with general three-body correlations

  2. Predictions of Excitation Functions of Super-Heavy Elements

    International Nuclear Information System (INIS)

    A long-standing theoretical change is predictions of optimum incident systems, optimum incident energies, as well as those of maximum residue cross sections for synthesis of super-heavy elements (SHE). Theoretical predictions, however, have ambiguities stemming from two causes: unknown masses or shell correction energies (SCE) of SHE nuclei themselves and unexplained mechanism of the fusion hindrance, experimentally known since many years ago. On the former, there are rather precise predictions by structure studies, but they are different with each other, so predicted SCE's are not reliable precisely, because 1 MeV difference in them results in change in residue cross section about one order of magnitude through so-called survival probability (It should be noted that fission barrier of SHE is given totally by SCE). On the latter, there was no reaction theory encompassing the hindrance mechanism. The present authors have proposed the two-step model for the fusion process, which explains the hindrance qualitatively [1], and which is applicable to the cold as well as to the hot fusion paths [2]. However, the model overestimates the absolute values of the cross sections, if the masses predicted by P. Moeller et al. [3] are used. Examples of the calculated excitations are shown in Fig. 1 [4] and 2, with only one free parameter f, a factor for SCE, in order to reproduce order of magnitude of the cross sections. As for the formation step of the spherical compound nucleus, the present authors recently have made a closer analysis of fusion dynamics from di-nucleus to mono-nucleus, which improves predictions of fusion probability quantitatively [5]. That is expected to make a free parameter f to be unnecessary to introduce. Furthermore, the neck dynamics is found to depend on mass-asymmetry and thus, fusion probability depends on incident channel with the neck dynamics unknown so far. In connection with the question on which path is more favorable when we proceed to heavier

  3. Electronic excitations: density-functional versus many-body Green's-function approaches

    Science.gov (United States)

    Onida, Giovanni; Reining, Lucia; Rubio, Angel

    2002-04-01

    Electronic excitations lie at the origin of most of the commonly measured spectra. However, the first-principles computation of excited states requires a larger effort than ground-state calculations, which can be very efficiently carried out within density-functional theory. On the other hand, two theoretical and computational tools have come to prominence for the description of electronic excitations. One of them, many-body perturbation theory, is based on a set of Green's-function equations, starting with a one-electron propagator and considering the electron-hole Green's function for the response. Key ingredients are the electron's self-energy Σ and the electron-hole interaction. A good approximation for Σ is obtained with Hedin's GW approach, using density-functional theory as a zero-order solution. First-principles GW calculations for real systems have been successfully carried out since the 1980s. Similarly, the electron-hole interaction is well described by the Bethe-Salpeter equation, via a functional derivative of Σ. An alternative approach to calculating electronic excitations is the time-dependent density-functional theory (TDDFT), which offers the important practical advantage of a dependence on density rather than on multivariable Green's functions. This approach leads to a screening equation similar to the Bethe-Salpeter one, but with a two-point, rather than a four-point, interaction kernel. At present, the simple adiabatic local-density approximation has given promising results for finite systems, but has significant deficiencies in the description of absorption spectra in solids, leading to wrong excitation energies, the absence of bound excitonic states, and appreciable distortions of the spectral line shapes. The search for improved TDDFT potentials and kernels is hence a subject of increasing interest. It can be addressed within the framework of many-body perturbation theory: in fact, both the Green's functions and the TDDFT approaches profit

  4. Two-body correlation function and its application to the excited states of He-like ions

    International Nuclear Information System (INIS)

    The two-body correlation method, proposed by Wilets et al. and developed by the authors for calculating the correlation structure of light atoms, is further investigated and applied to He-like ion excited states. In this formalism, the variational calculation of the full atomic wave function is predicted in detail. The calculated atomic correlation energy results agree very well with that of other more complicated correlation methods such as CI and 1/Z perturbation expansion etc

  5. Is There a Linear Building Transfer Function for Small Excitation?

    Science.gov (United States)

    Clinton, J. F.; Heaton, T. H.

    2003-12-01

    In the absence of actual building accelerometer data, the linear response of a structure to strong ground motion is estimated by the convolution of the dynamic response of the structure with an input ground motion. The input motion is usually provided by a local `reference' station record. In this study, we look at whether actual recorded ground motion at two instrumented buildings with well studied dynamic properties can be satisfactorily modeled using a local ground station. All stations record continuous 24-bit data streams on the CISN network, so analysis of a variety of weak earthquake motions, as well as ambient noise, is possible. Our buildings are the 9-story reinforced concrete Millikan Library (CISN Station MIK) and the 3-story braced steel frame Broad Center (CBC), both on the Caltech Campus. Motions recorded on their upper floors are compared with motions from ground stations located in the basement of a lightweight wood-frame house (GSA), and in a subsurface vault (CRP). All stations are within 200m of each other. Recent work using the new continuous datastream indicates that the natural frequencies of these structures can vary by up to 5% during normal ambient conditions, due to such factors as changing building usage, diurnal temperature variation, and wind/rainfall events. These shifts can be sudden, and models of building motions are sensitive to these previously un-documented changes. Further, during stronger motions, such as forced vibration testing, and minor earthquake shaking, natural frequencies are shown to drop by up to 10% (2003 M5.4 Big Bear Earthquake, Δ = 119km), with near-instantaneous recovery once the excitation is over. Moderate earthquakes can temporarily reduce frequencies by up to 30% with no apparent structural damage (1971 M6.6 San Fernando Earthquake, Δ = 31km). Post-event permanent reductions of about 10% have been observed. The ability to monitor these evolving dynamic characteristics makes a re-evaluation of the

  6. Excitations

    Energy Technology Data Exchange (ETDEWEB)

    Dorner, B. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1996-12-31

    A short introduction to instrumental resolution is followed by a discussion of visibilities of phonon modes due to their eigenvectors. High precision phonon dispersion curves in GaAs are presented together with `ab initio` calculations. Al{sub 2}O{sub 3} is taken as an example of selected visibility due to group theory. By careful determination of phonon intensities eigenvectors can be determined, such as in Silicon and Diamond. The investigation of magnon modes is shown for the garnet Fe{sub 2}Ca{sub 3}(GeO{sub 4}){sub 3}, where also a quantum gap due to zero point spin fluctuations was observed. The study of the splitting of excitons in CsFeCl{sub 3} in an applied magnetic field demonstrates the possibilities of neutron polarisation analysis, which made it possible to observe a mode crossing. An outlook to inelastic X-ray scattering with very high energy resolution of synchrotron radiation is given with the examples of phonons in Beryllium and in water. (author) 19 figs., 36 refs.

  7. Excitations

    International Nuclear Information System (INIS)

    A short introduction to instrumental resolution is followed by a discussion of visibilities of phonon modes due to their eigenvectors. High precision phonon dispersion curves in GaAs are presented together with 'ab initio' calculations. Al2O3 is taken as an example of selected visibility due to group theory. By careful determination of phonon intensities eigenvectors can be determined, such as in Silicon and Diamond. The investigation of magnon modes is shown for the garnet Fe2Ca3(GeO4)3, where also a quantum gap due to zero point spin fluctuations was observed. The study of the splitting of excitons in CsFeCl3 in an applied magnetic field demonstrates the possibilities of neutron polarisation analysis, which made it possible to observe a mode crossing. An outlook to inelastic X-ray scattering with very high energy resolution of synchrotron radiation is given with the examples of phonons in Beryllium and in water. (author) 19 figs., 36 refs

  8. Wave Function Frozen-Density Embedding: Coupled Excitations.

    Science.gov (United States)

    Höfener, Sebastian; Visscher, Lucas

    2016-02-01

    We report quasi-ab initio correlated ground-state and excitation-energy calculations for agglomerates consisting of several molecules with total system sizes of up to more than one hundred atoms using a combination of a density-fitted, approximate second-order coupled-cluster singles and doubles (RICC2) method and frozen-density embedding (FDE), denoted RICC2-in-RICC2. Working equations are presented for CC2 ground-state energies and approximate coupled excitation energies, which are a necessary prerequisite for investigations of potential energy surfaces (PESs) of both ground and excited states. The approach is applicable to all systems that can be decomposed into interacting individual molecules for which the RICC2 calculation itself is feasible. Because of the absence of exact exchange in the formalism and the possibility to efficiently evaluate Coulomb coupling integrals using density fitting or a dipole approximation, the coupling step is insignificant in terms of computation time. PMID:26653851

  9. Measuring excitation functions needed to interpret cosmogenic nuclide production in lunar rocks

    International Nuclear Information System (INIS)

    Radionuclides produced in lunar rocks by cosmic ray interactions are measured using Accelerator Mass Spectrometry or gamma-ray spectroscopy. From these measurements, estimates of the solar proton flux over time periods characterized by the half-life of the isotope under study can be made, if all the cross sections for all the reactions of all cosmic ray particles with all elements found in lunar rocks are known. Proton production cross sections are very important because ∼98% of solar cosmic rays and ∼87% of galactic cosmic rays are protons in the lunar environment. Many of the needed cross sections have never been measured. Targets of C, Al, Si, SiO2, Mg, K, Ca, Fe and Ni have been irradiated using three accelerators to cover a proton energy range of 25 endash 500 MeV. Excitation functions for 7Be, 10Be, 22Na, and 26Al production from Mg and Al will be reported, and the consequences of using these new cross section values to estimate solar proton fluxes discussed. copyright 1997 American Institute of Physics

  10. Local density approximation for exchange in excited-state density functional theory

    OpenAIRE

    Harbola, Manoj K.; Samal, Prasanjit

    2004-01-01

    Local density approximation for the exchange energy is made for treatment of excited-states in density-functional theory. It is shown that taking care of the state-dependence of the LDA exchange energy functional leads to accurate excitation energies.

  11. High precision fusion excitation function measurements; what can we learn from them?

    International Nuclear Information System (INIS)

    Excitation functions for the reactions 154Sm+16O, 186W+16O, 144Sm+16O and 144Sm+17O have been measured at small energy intervals and with high precision. These excitation functions are sensitive to the nuclear structure of the interacting nuclei and this is most clearly demonstrated when they are displayed as barrier distributions. (author). 20 refs., 9 figs

  12. The effect of the excitation and of the temperature on the photoluminescence circular polarization of AlInAs/AlGaAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Sellami, N. [Unite de Recherche de Physique des Semiconducteurs et Capteurs, Institut Preparatoire aux Etudes Scientifiques et Techniques, La Marsa 2070 (Tunisia); Melliti, A., E-mail: adnenmelliti@yahoo.fr [Unite de Recherche de Physique des Semiconducteurs et Capteurs, Institut Preparatoire aux Etudes Scientifiques et Techniques, La Marsa 2070 (Tunisia); Sahli, A.; Maaref, M.A. [Unite de Recherche de Physique des Semiconducteurs et Capteurs, Institut Preparatoire aux Etudes Scientifiques et Techniques, La Marsa 2070 (Tunisia); Testelin, C. [Institut des NanoSciences de Paris, Campus Boucicaut, Universites Paris 6 et 7, CNRS, UMR7588, 140 rue de Lourmel, 75015 Paris (France); Kuszelewiez, R. [Laboratoire de Photonique et Nanostructures, CNRS, UPR 20 (France)

    2009-12-15

    In this paper, we present a study of photoluminescence (PL) from AlInAs/AlGaAs quantum dots (QDs) structures grown by molecular beam epitaxy. Specifically, we describe the effects of the temperature and of the excitation density on the photoluminescence circular polarization. We have found that the circular polarization degree depends on temperature. On the other hand, the study of the excitation density dependent circular polarization PL degree shows that the last increases in the case of the sample of weak dot density. However, in the case of large dot density, it is almost constant in the excitation density range from 0.116 W cm{sup -2} to 9 W cm{sup -2}.

  13. The effect of the excitation and of the temperature on the photoluminescence circular polarization of AlInAs/AlGaAs quantum dots

    International Nuclear Information System (INIS)

    In this paper, we present a study of photoluminescence (PL) from AlInAs/AlGaAs quantum dots (QDs) structures grown by molecular beam epitaxy. Specifically, we describe the effects of the temperature and of the excitation density on the photoluminescence circular polarization. We have found that the circular polarization degree depends on temperature. On the other hand, the study of the excitation density dependent circular polarization PL degree shows that the last increases in the case of the sample of weak dot density. However, in the case of large dot density, it is almost constant in the excitation density range from 0.116 W cm-2 to 9 W cm-2.

  14. Orientation of Al3Ti platelets in Al-Al3Ti functionally graded material manufactured by centrifugal method

    International Nuclear Information System (INIS)

    Al-Al3Ti functionally graded materials (FGMs) were manufactured by the centrifugal method with a commercial ingot of Al-5 mass% Ti master alloy. The alloy was melted at a liquid/solid coexisting temperature, at which Al3Ti remains as a solid, and then it was cast into a thick-walled ring. It was found that the Al-Al3Ti functionally graded material can be successfully fabricated by the centrifugal method. It was also found that the volume fraction of the Al3Ti can be increased by repetition of the centrifugal method. Since the shape of Al3Ti particles in a commercial alloy ingot is that of a platelet, the Al3Ti particles are arranged with their platelet planes nearly perpendicular to the radial direction. The orientation effects become stronger when the G number becomes larger. Although the final centrifugal casting was conducted under a very large centrifugal force for the specimen cast three times, the orientation effects were weaker than those in the specimen cast one time. From these observations, it is concluded that the origin of orientation of Al3Ti platelets can be attributed to the angular velocity gradient of the melt along the radial direction produced by the difference in the viscosity. (orig.)

  15. Excitation functions of reactions from d + Ti, d + Mo, p + Ti and p + Mo

    International Nuclear Information System (INIS)

    The excitation functions for the products of 48V, from P + Ti and d + Ti and of 95Tcm,g, 96Tcg and 99Mo from P + Mo and d + Mo were studied. The excitation functions were measured by the conventional stacked foil method. The experiments were carried out at the HI-13 tandem accelerator of CIAE in the energy range from threshold to 22 Mev. The excitation functions leading to the formation of 48V, 95Tcm,g, 96Tcg and 99Mo are presented

  16. Self-Consistent Optimization of Excited States within Density-Functional Tight-Binding.

    Science.gov (United States)

    Kowalczyk, Tim; Le, Khoa; Irle, Stephan

    2016-01-12

    We present an implementation of energies and gradients for the ΔDFTB method, an analogue of Δ-self-consistent-field density functional theory (ΔSCF) within density-functional tight-binding, for the lowest singlet excited state of closed-shell molecules. Benchmarks of ΔDFTB excitation energies, optimized geometries, Stokes shifts, and vibrational frequencies reveal that ΔDFTB provides a qualitatively correct description of changes in molecular geometries and vibrational frequencies due to excited-state relaxation. The accuracy of ΔDFTB Stokes shifts is comparable to that of ΔSCF-DFT, and ΔDFTB performs similarly to ΔSCF with the PBE functional for vertical excitation energies of larger chromophores where the need for efficient excited-state methods is most urgent. We provide some justification for the use of an excited-state reference density in the DFTB expansion of the electronic energy and demonstrate that ΔDFTB preserves many of the properties of its parent ΔSCF approach. This implementation fills an important gap in the extended framework of DFTB, where access to excited states has been limited to the time-dependent linear-response approach, and affords access to rapid exploration of a valuable class of excited-state potential energy surfaces. PMID:26587877

  17. Functional patterned multiphoton excitation deep inside scattering tissue

    Science.gov (United States)

    Papagiakoumou, Eirini; Bègue, Aurélien; Leshem, Ben; Schwartz, Osip; Stell, Brandon M.; Bradley, Jonathan; Oron, Dan; Emiliani, Valentina

    2013-04-01

    Stochastic distortion of light beams in scattering samples makes in-depth photoexcitation in brain tissue a major challenge. A common solution for overcoming scattering involves adaptive pre-compensation of the unknown distortion. However, this requires long iterative searches for sample-specific optimized corrections, which is a problem when applied to optical neurostimulation where typical timescales in the system are in the millisecond range. Thus, photoexcitation in scattering media that is independent of the properties of a specific sample would be an ideal solution. Here, we show that temporally focused two-photon excitation with generalized phase contrast enables photoexcitation of arbitrary spatial patterns within turbid tissues with remarkable robustness to scattering. We demonstrate three-dimensional confinement of tailored photoexcitation patterns >200 µm in depth, both in numerical simulations and through brain slices combined with patch-clamp recording of photoactivated channelrhodopsin-2.

  18. 35Cl + 12C asymmetrical fission excitation functions

    International Nuclear Information System (INIS)

    The fully energy-damped yields from the 35Cl + 12C reaction have been systematically investigated using particle-particle coincidence techniques at a 35Cl bombarding energy of ∼ 8 MeV/nucleon. The fragment-fragment correlation data show that the majority of events arises from a binary-decay process with rather large numbers of secondary light-charged particles emitted from the two excited exit fragments. No evidence is observed for ternary breakup events. The binary-process results of the present measurement, along with those of earlier, inclusive experimental data obtained at several lower bombarding energies are compared with predictions of two different kinds of statistical model calculations. The methods give comparable predictions and are both in good agreement with the experimental results thus confirming the fusion-fission origin of the fully-damped yields. (author)

  19. Coherent calculations of spectra and excitation functions within the Griffin model

    International Nuclear Information System (INIS)

    Particles spectra and excitation functions are calculated within a coherent approach of the exciton model by solving exactly the set of master equations. Comparisons with experimental results are presented. (author)

  20. Multiple-Resonance Local Wave Functions for Accurate Excited States in Quantum Monte Carlo.

    Science.gov (United States)

    Zulfikri, Habiburrahman; Amovilli, Claudio; Filippi, Claudia

    2016-03-01

    We introduce a novel class of local multideterminant Jastrow-Slater wave functions for the efficient and accurate treatment of excited states in quantum Monte Carlo. The wave function is expanded as a linear combination of excitations built from multiple sets of localized orbitals that correspond to the bonding patterns of the different Lewis resonance structures of the molecule. We capitalize on the concept of orbital domains of local coupled-cluster methods, which is here applied to the active space to select the orbitals to correlate and construct the important transitions. The excitations are further grouped into classes, which are ordered in importance and can be systematically included in the Jastrow-Slater wave function to ensure a balanced description of all states of interest. We assess the performance of the proposed wave function in the calculation of vertical excitation energies and excited-state geometry optimization of retinal models whose π → π* state has a strong intramolecular charge-transfer character. We find that our multiresonance wave functions recover the reference values of the total energies of the ground and excited states with only a small number of excitations and that the same expansion can be flexibly used at very different geometries. Furthermore, significant computational saving can also be gained in the orbital optimization step by selectively mixing occupied and virtual orbitals based on spatial considerations without loss of accuracy on the excitation energy. Our multiresonance wave functions are therefore compact, accurate, and very promising for the calculation of multiple excited states of different character in large molecules. PMID:26761421

  1. High photo-excited carrier multiplication by charged InAs dots in AlAs/GaAs/AlAs resonant tunneling diode

    OpenAIRE

    Wang, Wangping; Hou, Ying; Xiong, Dayuan; Li, Ning; Lu, Wei

    2007-01-01

    We present an approach for the highly sensitive photon detection based on the quantum dots (QDs) operating at temperature of 77K. The detection structure is based on an AlAs/GaAs/AlAs double barrier resonant tunneling diode combined with a layer of self-assembled InAs QDs (QD-RTD). A photon rate of 115 photons per second had induced 10nA photocurrent in this structure, corresponding to the photo-excited carrier multiplication factor of 10^7. This high multiplication factor is achieved by the ...

  2. The decay of excited He from Stochastic Density-Functional Theory: a quantum measurement theory interpretation

    OpenAIRE

    Bushong, Neil; Di Ventra, Massimiliano

    2007-01-01

    Recently, time-dependent current-density functional theory has been extended to include the dynamical interaction of quantum systems with external environments [Phys. Rev. Lett. {\\bf 98}, 226403 (2007)]. Here we show that such a theory allows us to study a fundamentally important class of phenomena previously inaccessible by standard density-functional methods: the decay of excited systems. As an example we study the decay of an ensemble of excited He atoms, and discuss these results in the c...

  3. Investigation of Multiconfigurational Short-Range Density Functional Theory for Electronic Excitations in Organic Molecules

    DEFF Research Database (Denmark)

    Hubert, Mickaël; Hedegård, Erik D.; Jensen, Hans Jørgen Aa

    2016-01-01

    inadequate when the molecule has near-degeneracies and/or low-lying double-excited states. To address these issues we have recently proposed multiconfiguration short-range density-functional theory-MC-srDFT-as a new tool in the toolbox. While initial applications for systems with multireference character and......-srDFT for a selected benchmark set of electronic excitations of organic molecules, covering the most common types of organic chromophores. This investigation confirms the expectation that the MC-srDFT method is accurate for a broad range of excitations and comparable to accurate wave function methods such...

  4. Excitation functions and thick target yields for deuteron induced reactions on zirconium

    International Nuclear Information System (INIS)

    Production cross sections of Zr-89, Zr-97, Y-90m, Nb-90g and Y-92 formed by the irradiation of natural zirconium with deuterons were measured. Thick-target yields for Zr-90 (d, t) Zr-89 reaction were determined for different irradiation times and as functions of deuteron energy. Stacks of zirconium foils were irradiated with the external beam of the Buenos Aires synchrocyclotron. The targets were prepared with natural zirconium foils of high purity. Their thickness was 13 mg.cm-2. The target foils were placed between aluminium degrading foils of known thicknesses. The energy of deuterons at the middle of each target foil of the stack was determined from the tables of Williamson, Boujot and Picard. The energy straggling in the target was estimated to be about 0.5 MeV for the foil in which the deuterons had been slowed down to 16 MeV. The excitation function of the Al-27(d, αp) Na-24 reaction is supposed to be well known and from the yield of radioactive isotopes in the zirconium foils relative to that of Na-24 in the aluminium foils the absolute cross sections for the deuteron reactions on zirconium were calculated. (T.I.)

  5. Range-separated density-functional theory for molecular excitation energies

    International Nuclear Information System (INIS)

    Linear-response time-dependent density-functional theory (TDDFT) is nowadays a method of choice to compute molecular excitation energies. However, within the usual adiabatic semi-local approximations, it is not able to describe properly Rydberg, charge-transfer or multiple excitations. Range separation of the electronic interaction allows one to mix rigorously density-functional methods at short range and wave function or Green's function methods at long range. When applied to the exchange functional, it already corrects most of these deficiencies but multiple excitations remain absent as they need a frequency-dependent kernel. In this thesis, the effects of range separation are first assessed on the excitation energies of a partially-interacting system in an analytic and numerical study in order to provide guidelines for future developments of range-separated methods for excitation energy calculations. It is then applied on the exchange and correlation TDDFT kernels in a single-determinant approximation in which the long-range part of the correlation kernel vanishes. A long-range frequency-dependent second-order correlation kernel is then derived from the Bethe-Salpeter equation and added perturbatively to the range-separated TDDFT kernel in order to take into account the effects of double excitations. (author)

  6. Study of the excited states of 28Si using the 27Al(p,γ)28Si radiative capture

    International Nuclear Information System (INIS)

    The gamma decay of 28Si levels excited in the 27Al(p,γ)28Si reaction has been investigated in the energy range Esub(p)3 classification. A part from the K=0+ rotational band based on the ground state, the SU3 previsions are not substantiated, but can not definitely rejected, and a few experiment are suggested. On the other band, many results are consistent with the shell model calculations

  7. Seismic functional limitation test (emergency diesel generator) in FY 2010. Governor shaking table excitation test

    International Nuclear Information System (INIS)

    'Seismic design review guide of nuclear power facilities' updated in September 2006 requested evaluation of 'residual risks' beyond basic earthquake ground motion Ss as well as revision of active fault and Ss evaluation method. Data on equipment's strength and functional limitations (seismic capacity) were needed for 'residual risks' evaluation using seismic PSA. Equipment's seismic capacity test had been continued at the JNES since 2003. This report summarized results of governor shaking table excitation test, which finished as part of seismic capacity test (emergency diesel generator) started in 2009. Test results confirmed no significant difference on governor's work period between no excitation (standstill state) and excitation in horizontal and vertical direction, and governor function was maintained up to acceleration of horizontal 4 g and vertical 2 g. Results of governor functional maintenance could be used for evaluation of maintenance of dynamic function and functional limitation of emergency diesel generator. (T. Tanaka)

  8. Benchmarks for electronically excited states: Time-dependent density functional theory and density functional theory based multireference configuration interaction

    DEFF Research Database (Denmark)

    Silva-Junior, Mario R.; Schreiber, Marko; Sauer, Stephan P. A.;

    2008-01-01

    Time-dependent density functional theory (TD-DFT) and DFT-based multireference configuration interaction (DFT/MRCI) calculations are reported for a recently proposed benchmark set of 28 medium-sized organic molecules. Vertical excitation energies, oscillator strengths, and excited-state dipole...... moments are computed using the same geometries (MP2/6-31G*) and basis set (TZVP) as in our previous ab initio benchmark study on electronically excited states. The results from TD-DFT (with the functionals BP86, B3LYP, and BHLYP) and from DFT/MRCI are compared against the previous high-level ab initio......-DFT/B3LYP (0.27 and 0.44 eV, respectively), whereas TD-DFT/BP86 and TD-DFT/BHLYP are significantly less accurate. The energies of singlet states with double excitation character are generally overestimated by TD-DFT, whereas triplet state energies are systematically underestimated by the currently...

  9. Nuclear charge-exchange excitations in localized covariant density functional theory

    International Nuclear Information System (INIS)

    The recent progress in the studies of nuclear charge-exchange excitations with localized covariant density functional theory is briefly presented, by taking the fine structure of spin-dipole excitations in 16O as an example. It is shown that the constraints introduced by the Fock terms of the relativistic Hartree-Fock scheme into the particle-hole residual interactions are straightforward and robust. (authors)

  10. Nuclear charge-exchange excitations in localized covariant density functional theory

    CERN Document Server

    Liang, H Z; Nakatsukasa, T; Niu, Z M; Ring, P; Roca-Maza, X; Van Giai, N; Zhao, P W

    2014-01-01

    The recent progress in the studies of nuclear charge-exchange excitations with localized covariant density functional theory is briefly presented, by taking the fine structure of spin-dipole excitations in 16O as an example. It is shown that the constraints introduced by the Fock terms of the relativistic Hartree-Fock scheme into the particle-hole residual interactions are straightforward and robust.

  11. Sum rule analysis of vector and axial-vector spectral functions with excited states in vacuum

    OpenAIRE

    Hohler, Paul M.; Rapp, Ralf

    2012-01-01

    We simultaneously analyze vector and axial-vector spectral functions in vacuum using hadronic models constrained by experimental data and the requirement that Weinberg-type sum rules are satisfied. Upon explicit inclusion of an excited vector state, viz. rho', and the requirement that the perturbative continua are degenerate in vector and axial-vector channels, we deduce the existence of an excited axial-vector resonance state, a1', in order that the Weinberg sum rules are satisfied. The resu...

  12. Hardness Measurement of (TiB2-TiAl)/TiAl Symmetrically Function Gradient Materials

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    (TiB2-TiAl)/TiAl symmetrically function gradient materials (FGM) were prepared by spark plasma sintering (SPS). Owing to the difference of the thermal expansion coefficients between TiB2 and TiAl, a compressive surface stress was introduced to the FGM by the thermal expansion mismatch. The hardness values of the uniform materials and the FGM were tested, respectively. For the FGM with a compressive surface stress, hardness is obviously superior to that of the uniform material.When the FGM was subjected to heat treatment,the hardness decreased due to a partial relaxation of the compressive surface stress.

  13. Proton-proton elastic scattering excitation functions at intermediate energies: Cross sections and analyzing powers

    International Nuclear Information System (INIS)

    The EDDA experiment at the cooler synchrotron COSY measures proton-proton elastic scattering excitation functions in the momentum range 0.8 - 3.4 GeV/c. In phase 1 of the experiment, spin-averaged differential cross sections were measured continuously during acceleration with an internal polypropylene (CH2) fiber target, taking particular care to monitor luminosity as a function of beam momentum. In phase 2, excitation functions of the analyzing power AN and the polarization correlation parameters ANN, ASS and ASL are measured using a polarized proton beam and a polarized atomic hydrogen beam target. The paper presents recent dσ/dΩ and AN data. The results provide excitation functions and angular distributions of high precision and internal consistency. No evidence for narrow structures was found. The data are compared to recent phase shift solutions

  14. Communication: Exciton analysis in time-dependent density functional theory: How functionals shape excited-state characters

    Science.gov (United States)

    Mewes, Stefanie A.; Plasser, Felix; Dreuw, Andreas

    2015-11-01

    Excited-state descriptors based on the one-particle transition density matrix referring to the exciton picture have been implemented for time-dependent density functional theory. State characters such as local, extended ππ∗, Rydberg, or charge transfer can be intuitively classified by simple comparison of these descriptors. Strong effects of the choice of the exchange-correlation kernel on the physical nature of excited states can be found and decomposed in detail leading to a new perspective on functional performance and the design of new functionals.

  15. Two-Step Electron Beam Excitation of Al2O3:Cr by Gallium Nitride Recombination Radiation

    Science.gov (United States)

    Zehe, A.; Ramírez, A.; Seifert, W.

    We report on a two-step excitation process of a GaN/A2O3:Cr specimen by an external electron beam of 30 keV. The epitaxial growth of GaN on the (0001) faces of ruby is described, as well as the experimental technique applied in the excitation and recording of the combined luminescence spectrum. It is known that the spinel and ruby are frequently used as substrate materials for the epitaxial deposition of GaN. At the same time is ruby one of the most useful layer materials with a red emission line λ = 694 nm. Due to its dielectric character, the pumping of ruby is performed usually subjecting it to the light of an intense flash lamp. Electron beam excitation, on the other hand, which could be more powerful, is impaired with electrical insulator material. This discrepancy can be removed by a two-step excitation, where at first the semiconducting GaN-layer, epitaxially grown on a (0001)Al2O3:Cr (ruby) crystal is excited to radiation emission by an external electron beam. The following internal absolption process, by the ruby crystal, of the GaN luminescence radiation provides for the characteristic 2E to 4A2-transition at 1.786 eV. We found a strong and sharp emission line of that photon energy, which additionally displays polarization, typical for the anisotropic uniaxial ruby crystal. Such an indirect electron-beam excitation of ruby allows to generate almost monochromatic red light, and might point into a direction of interesting practical applications.

  16. Generalized variational principle for excited states using nodes of trial functions

    International Nuclear Information System (INIS)

    The familiar variational principle provides an upper bound to the ground-state energy of a given Hamiltonian. This allows one to optimize a trial wave function by minimizing the expectation value of the energy. This approach is also trivially generalized to excited states, so that given a trial wave function of a certain symmetry, one can compute an upper bound to the lowest-energy level of that symmetry. In order to generalize further and build an upper bound of an arbitrary excited state of the desired symmetry, a linear combination of basis functions is generally used to generate an orthogonal set of trial functions, all bounding their respective states. However, sometimes a compact wave-function form is sought, and a basis-set expansion is not desirable or possible. Here we present an alternative generalization of the variational principle to excited states that does not require explicit orthogonalization to lower-energy states. It is valid for one-dimensional systems and, with additional information, to at least some n-dimensional systems. This generalized variational principle exploits information about the nodal structure of the trial wave function, giving an upper bound to the exact energy without the need to build a linear combination of basis functions. To illustrate the theorem we apply it to a nontrivial example: the 1s2s 1 S excited state of the helium atom.

  17. Magnetospectroscopy of excited states in charge-tunable GaAs/AlGaAs [111] quantum dots

    Science.gov (United States)

    Durnev, M. V.; Vidal, M.; Bouet, L.; Amand, T.; Glazov, M. M.; Ivchenko, E. L.; Zhou, P.; Wang, G.; Mano, T.; Ha, N.; Kuroda, T.; Marie, X.; Sakoda, K.; Urbaszek, B.

    2016-06-01

    We present a combined experimental and theoretical study of highly charged and excited electron-hole complexes in strain-free (111) GaAs/AlGaAs quantum dots grown by droplet epitaxy. We address the complexes with one of the charge carriers residing in the excited state, namely, the "hot" trions X-* and X+*, and the doubly negatively charged exciton X2 -. Our magnetophotoluminescence experiments performed on single quantum dots in the Faraday geometry uncover characteristic emission patterns for each excited electron-hole complex, which are very different from the photoluminescence spectra observed in (001)-grown quantum dots. We present a detailed theory of the fine structure and magnetophotoluminescence spectra of X-*,X+*, and X2 - complexes, governed by the interplay between the electron-hole Coulomb exchange interaction and the heavy-hole mixing, characteristic for these quantum dots with a trigonal symmetry. Comparison between experiment and theory allows for precise charge state identification, as well as extraction of electron-hole exchange interaction constants and g factors for the charge carriers occupying excited states.

  18. Study of excitation function for alpha induced reactions in natural iridium

    International Nuclear Information System (INIS)

    Excitation function of (α, χn) reactions on 191Ir (37.3%) and on 191Ir (62.7%) have been measured for 17-55 MeV alpha particle bombarding energy range. Stacked foil activation technique and gamma spectroscopy were used to determine the cross-sections. The experimental data were compared with calculated values obtained by means of geometry dependent hybrid model. The initial exciton number no = 4 with n = 2, p = 2 and h = 0 gives the best agreements with the presently measured values. To calculate the excitation function theoretically the ALICE/LIVERMORE-82 computer code was used. This set of excitation functions provides a data basis for probing the validity of combined equilibrium and pre-equilibrium reaction models in a considerable energy range. (author). 34 refs, 9 figs

  19. Development of Al2O3/Cu functionally gradient material

    International Nuclear Information System (INIS)

    In order to insure reliability of the thermoelectric module, we had applied FGM layer with composition of Cu and Si3N4 to the bonding parts in the module and decided the functionally graded compositional profile based on thermal stress analysis. And the Si3N4/Cu FGM had been fabricated by the hot press based on the analysis results. But many cracks initiated in FGM after sintering process with dependence of compositional profile and specimen geometries and bonding strength was very low because of a large difference of sintering temperature between Cu and Si3N4. In this study, Al2O3/Cu FGM was developed based on residual stress analysis by using high-purity Al2O3 particle with character of very small particle radius and low sintering temperature. Obtained results are summarized as follow, (1) Al2O3/Cu composites could be fabricated under low sintering temperature (1473 K). And temperature dependence of mechanical properties of the Al2O3/Cu composites was measured. (2) In order to minimize residual stress in the FGM after sintering process, functionally graded profile of Al2O3/Cu FGM was examined based on finite element analysis using the mechanical properties of Al2O3/Cu composites. (3) Al2O3/Cu FGM was fabricated based on the above residual stress analysis results. It was found that the FGM could be fabricated if residual stress in the FGM was lower than the bending strength the Al2O3/Cu composites. (author)

  20. Excitation wavelength dependence of the anomalous circular photogalvanic effect in undoped InGaAs/AlGaAs quantum wells

    International Nuclear Information System (INIS)

    The excitation wavelength dependence of the anomalous circular photogalvanic effect (ACPGE) current arising from the reciprocal spin Hall effect (RSHE) in undoped InGaAs/AlGaAs quantum wells is measured under normal incidence of circularly polarized light at room temperature. We found that the spot location with the maximum ACPGE current is wavelength independent. And the normalized ACPGE current decreases at smaller wavelengths, which can be attributed to the sharp decrease of the spin relaxation time (τs) and the hot electron relaxation time (τ1) at smaller wavelengths. The study of the excitation wavelength dependence of ACPGE current is a good supplement to the in-depth investigation of RSHE

  1. Investigation of Multiconfigurational Short-Range Density Functional Theory for Electronic Excitations in Organic Molecules.

    Science.gov (United States)

    Hubert, Mickaël; Hedegård, Erik D; Jensen, Hans Jørgen Aa

    2016-05-10

    Computational methods that can accurately and effectively predict all types of electronic excitations for any molecular system are missing in the toolbox of the computational chemist. Although various Kohn-Sham density-functional methods (KS-DFT) fulfill this aim in some cases, they become inadequate when the molecule has near-degeneracies and/or low-lying double-excited states. To address these issues we have recently proposed multiconfiguration short-range density-functional theory-MC-srDFT-as a new tool in the toolbox. While initial applications for systems with multireference character and double excitations have been promising, it is nevertheless important that the accuracy of MC-srDFT is at least comparable to the best KS-DFT methods also for organic molecules that are typically of single-reference character. In this paper we therefore systematically investigate the performance of MC-srDFT for a selected benchmark set of electronic excitations of organic molecules, covering the most common types of organic chromophores. This investigation confirms the expectation that the MC-srDFT method is accurate for a broad range of excitations and comparable to accurate wave function methods such as CASPT2, NEVPT2, and the coupled cluster based CC2 and CC3. PMID:27058733

  2. Relativistic time-dependent density functional calculations for the excited states of the cadmium dimer

    Energy Technology Data Exchange (ETDEWEB)

    Kullie, Ossama, E-mail: kullie@uni-kassel.de [Institute de Chimie de Strasbourg, CNRS et Université de Strasbourg, Laboratoire de Chimie Quantique, 4 rue Blaise Pascal, 67070 Strasbourg (France); Theoretical Physics, Institute for Physics, Department of Mathematics and Natural Science, University of Kassel (Germany)

    2013-03-29

    Highlights: ► The achievement of CAMB3LYP functional for excited states in framework of TD-DFT. ► Relativistic 4-components calculations for the excited states of the Cd{sub 2} dimer. ► Relativistic Spin-Free calculations for the excited states of Cd{sub 2} dimer. ► A comparison of the achievements of different types of DFT approximations upon Cd{sub 2}. - Abstract: In this paper we present a time-dependent density functional study for the ground-state as well the 20-lowest laying excited states of the cadmium dimer Cd{sub 2}, we analyze its spectrum obtained from all electrons calculations performed with time-depended density functional for the relativistic Dirac-Coulomb- and relativistic spin-free-Hamiltonian as implemented in DIRAC-PACKAGE. The calculations were obtained with different density functional approximations, and a comparison with the literature is given as far as available. Our result is very encouraging, especially for the lowest excited states of this dimer, and is expected to be enlightened for similar systems. The result shows that only long-range corrected functionals such as CAMB3LYP, gives the correct asymptotic behavior for the higher states. A comparable but less satisfactory results were obtained with B3LYP and PBE0 functionals. Spin-free-Hamiltonian is shown to be very efficient for systems containing heavy elements such as Cd{sub 2} in frameworks of (time-dependent) density functional without introducing large errors.

  3. High spin states excited in the 27Al(α,p) reaction

    International Nuclear Information System (INIS)

    The 27Al(α,p)30Si reaction at three bombarding energies: 26.2, 26.45, 26.7 MeV has been studied. Angular distributions for states populated in 30Si have been compared with the Hauser-Feshbach theory and DWBA calculations to determine the reaction mechanism and to deduce spectroscopic informations. The results of this analysis indicate high spin selectivity in 27Al(α,p)30Si reaction. (Author)

  4. Time-dependent density functional study on the excitation spectrum of point defects in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Gali, Adam [Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, PO Box 49, Budapest 1525 (Hungary); Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki ut 8, 1111 Budapest (Hungary)

    2011-06-15

    A common fingerprint of the electrically active point defects in semiconductors is the transition between their localized defect states upon excitation, which may result in characteristic absorption or photoluminescence spectrum. While density functional calculations have been very successful in exploring the ground-state properties like formation energies or hyperfine tensors the density functional theory (DFT), in principle, is not capable of providing reliable excitation spectrum. Time-dependent (TD)-DFT, however, addresses this issue which makes possible to study the properties of point defects associated with their excited states. In this paper, we apply the TD-DFT on two characteristic examples: the well-known nitrogen-vacancy defect in diamond and the less known divacancy in silicon carbide. The former defect is a leading candidate in solid state quantum bit applications where detailed knowledge about the excitation spectrum is extremely important. The excitation property of divacancy will be also studied and its relevance in different applications will be discussed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. The systematics research on (p,n) and (p,2n) reaction excitation functions

    International Nuclear Information System (INIS)

    On the basis of Planck formula of black body radiation and experimental excitation functions of (p,n) and (p,2n) reactions, an empirical systematics formula with two parameters is presented, which can describe experimental data of (p,n) and (p,2n) reactions well for incident proton energies from threshold to 150 MeV, target masses from 30 to 243

  6. Excitation function measurement of 16O + 175Lu system below 6 MeV/nucleon

    International Nuclear Information System (INIS)

    In the present work, we have measured and analyzed the excitation functions of evaporation residues produced in 16O + 175Lu reactions at energies ranging from 4.3-6.2 MeV/nucleon to study both the CF and ICF processes involved. To the best of our knowledge no earlier measurements are reported in the literature for this system

  7. Preparation of thin gadolinium samples via electrodeposition for excitation function studies

    International Nuclear Information System (INIS)

    A preparation method for gadolinium targets with a thickness up to 4 mg/cm2 on aluminum supports from aqueous electrolytes was developed. These electrodeposited adhesive and mechanically stable natGd layers were used to measure excitation functions of Gd + p nuclear reactions relevant to the production of medically important 152Tb (PET) and 155Tb (SPECT) radioisotopes. (author)

  8. Calculations of Excitation Functions of Some Structural Fusion Materials for ( n, t) Reactions up to 50 MeV Energy

    Science.gov (United States)

    Tel, E.; Durgu, C.; Aktı, N. N.; Okuducu, Ş.

    2010-06-01

    Fusion serves an inexhaustible energy for humankind. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. Tritium self-sufficiency must be maintained for a commercial power plant. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. So, the working out the systematics of ( n, t) reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at different energies. In this study, ( n, t) reactions for some structural fusion materials such as 27Al, 51V, 52Cr, 55Mn, and 56Fe have been investigated. The new calculations on the excitation functions of 27Al( n, t)25Mg, 51V( n, t)49Ti, 52Cr( n, t)50V, 55Mn( n, t)53Cr and 56Fe( n, t)54Mn reactions have been carried out up to 50 MeV incident neutron energy. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. The pre-equilibrium calculations involve the new evaluated the geometry dependent hybrid model, hybrid model and the cascade exciton model. Equilibrium effects are calculated according to the Weisskopf-Ewing model. Also in the present work, we have calculated ( n, t) reaction cross-sections by using new evaluated semi-empirical formulas developed by Tel et al. at 14-15 MeV energy. The calculated results are discussed and compared with the experimental data taken from the literature.

  9. Influence of two particles-two holes excitations in the longitudinal response function

    International Nuclear Information System (INIS)

    The influence of two particles-two holes excitations in the longitudinal response function was studied for the quasi-elastic electron dispersion on nuclei. Since the momenta delt with are large, the nuclear matter approximation is used. The study is restricted to exclusive type reactions, that is, where only the dispersed electron is detected. It is found that inclusion of these excitations leads to a decrease in entity for low energies and increase for high energies. An estimation of the Coulomb adding rule was also made. (Author)

  10. Prediction of Excitation Energies for Conjugated Oligomers and Polymers from Time-Dependent Density Functional Theory

    Directory of Open Access Journals (Sweden)

    Jianmin Tao

    2010-05-01

    Full Text Available With technological advances, light-emitting conjugated oligomers and polymers have become competitive candidates in the commercial market of light-emitting diodes for display and other technologies, due to the ultralow cost, light weight, and flexibility. Prediction of excitation energies of these systems plays a crucial role in the understanding of their optical properties and device design. In this review article, we discuss the calculation of excitation energies with time-dependent density functional theory, which is one of the most successful methods in the investigation of the dynamical response of molecular systems to external perturbation, owing to its high computational efficiency.

  11. Surface Energy and Work Function Control of AlOx/Al Surfaces by Fluorinated Benzylphosphonic Acids.

    Science.gov (United States)

    Abraham, Ffion; Ford, William E; Scholz, Frank; Nelles, Gabriele; Sandford, Graham; von Wrochem, Florian

    2016-05-11

    The performance of organic electronic devices can be significantly improved by modifying metal electrodes with organic monolayers, which alter the physical and chemical nature of the interface between conductor and semiconductor. In this paper we examine a series of 12 phosphonic acid compounds deposited on the native oxide layer of aluminum (AlOx/Al), an electrode material with widespread applications in organic electronics. This series includes dodecylphosphonic acid as a reference and 11 benzylphosphonic acids, seven of which are fluorinated, including five newly synthesized derivatives. The monolayers are experimentally characterized by contact angle goniometry and by X-ray photoemission spectroscopy (XPS), and work function data obtained by low-intensity XPS are correlated with molecular dipoles obtained from DFT calculations. We find that monolayers are formed with molecular areas ranging from 17.7 to 42.9 Å(2)/molecule, and, by the choice of appropriate terminal groups, the surface energy can be tuned from 23.5 mJ/m(2) to 70.5 mJ/m(2). Depending on the number and position of fluorine substituents on the aromatic rings, a variation in the work function of AlOx/Al substrates over a range of 0.91 eV is achieved, and a renormalization procedure based on molecular density yields a surprising agreement of work function changes with interface dipoles as expected from Helmholtz' equation. The ability to adjust energetics and adhesion at organic semiconductor/AlOx interfaces has immediate applications in devices such as OLEDs, OTFTs, organic solar cells, and printed organic circuits. PMID:27093557

  12. Density-functional calculations of field-dependent ionization potentials and excitation energies of aromatic molecules

    International Nuclear Information System (INIS)

    Highlights: • A model for the calculation of field-dependent ionization potential is presented. • A limitation of the model for polyaromatic molecules is investigated and cured. • Excitation energies are also calculated for molecules used as insulating liquids. • The IP decreases in the field, while the excitation energies remain constant. • The excitations vanish at certain fields, different for different types of molecules. - Abstract: A recent method based on constrained density functional theory (CDFT) has been used to calculate the field-dependent ionization potential by determining the dissociation barrier for the interaction between a cation and an electron in an electric field. In the CDFT model, we rely on that the barrier is located somewhere outside the cation, which has limited the applicability for polyaromatic molecules where the barrier is located closer to the cation than for other molecules. Different density functionals, basis sets and choices of constraints in the CDFT calculations are tested for benzene as a case study. The field-dependent ionization potential calculated by constraining the charge with the B3LYP functional and the cc-pVDZ basis set shows a good agreement with our previous work and has a low computational cost for the larger aromatic molecules included here. In addition, field-dependent excitation energies are investigated using time-dependent DFT

  13. Localized operator partitioning method for electronic excitation energies in the time-dependent density functional formalism

    CERN Document Server

    Nagesh, Jayashree; Brumer, Paul; Izmaylov, Artur F

    2016-01-01

    We extend the localized operator partitioning method (LOPM) [J. Nagesh, A.F. Izmaylov, and P. Brumer, J. Chem. Phys. 142, 084114 (2015)] to the time-dependent density functional theory (TD-DFT) framework to partition molecular electronic energies of excited states in a rigorous manner. A molecular fragment is defined as a collection of atoms using Stratman-Scuseria-Frisch atomic partitioning. A numerically efficient scheme for evaluating the fragment excitation energy is derived employing a resolution of the identity to preserve standard one- and two-electron integrals in the final expressions. The utility of this partitioning approach is demonstrated by examining several excited states of two bichromophoric compounds: 9-((1-naphthyl)-methyl)-anthracene and 4-((2-naphthyl)-methyl)-benzaldehyde. The LOPM is found to provide nontrivial insights into the nature of electronic energy localization that are not accessible using simple density difference analysis.

  14. Measurement of fusion excitation functions in the system {sup 78}Kr + {sup 100}Mo

    Energy Technology Data Exchange (ETDEWEB)

    Rehm, K.E.; Jiang, C.L.; Esbensen, H. [and others

    1995-08-01

    Earlier measurements of fusion reactions involving {sup 78}Kr and {sup 100}Mo projectiles and Ni-targets showed surprisingly large fusion yields at low energies which could not be explained by coupled-channels calculations. The main difference to similar measurements involving the neighboring {sup 86}Kr and {sup 92}Mo isotopes was the different slope of the excitation functions at sub-barrier energies. An analysis of a variety of experiments showed a correlation between the nuclear structure and the slope of the excitation functions, with the {open_quotes}soft{close_quotes} transitional nuclei ({sup 78}Kr, {sup 100}Mo) exhibiting shallower slopes than the {open_quotes}stiff{close_quotes} nuclei ({sup 86}Kr, {sup 92}Mo) measured at the same energies with respect to the barrier. In this experiment we studied the fusion excitation function involving two transitional nuclei {sup 78}Kr + {sup 100}Mo. The measurements were performed with {sup 78}Kr beams from the ECR source at energies between 285-370 MeV. Separation of the evaporation nucleus from the elastically scattered particles was achieved by measuring time-of-flight and magnetic rigidity in the gas-filled spectrograph. The data were completely analyzed. A comparison of the cross sections with measurements for the system {sup 86}Kr + {sup 92}Mo populating the same compound nucleus {sup 178}Pt. It shows good agreement at the highest energies, but quite different falloffs of the excitation functions toward lower energies. Coupled-channels calculations, including multi-phonon excitation for the two systems, are being performed.

  15. Aluminum matrix texture in Al-Al3Ti functionally graded materials analyzed by electron back-scattering diffraction

    Science.gov (United States)

    Watanabe, Yoshimi; Sequeira, Paulo D.; Sato, Hisashi; Inamura, Tomonari; Hosoda, Hideki

    2016-01-01

    Al matrix functionally graded materials (FGMs) with oriented Al3Ti platelets were fabricated by a centrifugal solid-particle method. The applied centrifugal forces were 30, 60, and 120G (units of gravity). The orientation and volume fraction gradients of the Al3Ti platelets within the samples were measured. Since a good lattice correspondence was reported for the close-packed directions and the close-packed planes between Al and Al3Ti, the Al matrix in the Al-Al3Ti FGMs fabricated by the centrifugal solid-particle method should have some texture. Al matrix texture was, therefore, analyzed by electron back-scattering diffraction (EBSD). Analysis of the resulting pole figures indicates a preferred orientation along the (200) plane for the Al matrix crystals. Furthermore, increasing the applied centrifugal force enhances the orientation effect. A correlation appears to exist between platelet orientation and the preferred texture of the Al matrix.

  16. Fabrication of Al-Al3Ti/Ti3Al Functionally Graded Materials under a Centrifugal Force

    Directory of Open Access Journals (Sweden)

    Yoshimi Watanabe

    2010-09-01

    Full Text Available Fabrication of Al-Al3Ti functionally graded materials (FGMs under the centrifugal force has recently attracted some attention. The controlled compositional gradient of the fabricated FGMs, the low cost of the process, and the good mold filling, are the main advantages of the centrifugal method (CM. Using the conventional CM techniques such as the centrifugal solid-particle method and centrifugal in-situ method, FGMs rings with gradually distributed properties could be achieved. As a more practical choice, the centrifugal mixed-powder method (CMPM was recently proposed to obtain FGMs containing nano-particles selectively dispersed in the outer surface of the fabricated parts. However, if a control of the particles morphology, compound formulas or sizes, is desired, another CM technique is favored. As a development of CMPM, our novel reaction centrifugal mixed-powder method (RCMPM has been presented. Using RCMPM, Al‑Al3Ti/Ti3Al FGMs with good surface properties and temperature controlled compositional gradient could be achieved. In this short review, this novel method will be discussed in detail and the effect of RCMPM processing temperature on the reinforcement particles morphology, size and distribution through the fabricated samples, will be reviewed.

  17. Functional neuroimaging of inner fields-of-view with 2D-selective RF excitations.

    Science.gov (United States)

    Finsterbusch, Jürgen

    2013-09-01

    Echo-planar imaging is widely used in functional neuroimaging but suffers from its pronounced sensitivity to field inhomogeneities that cause geometric distortions and image blurring which both limit the effective in-plane resolution achievable. In this work, it is shown how inner-field-of-view techniques based on 2D-selective RF excitations (2DRF) can be applied to reduce the field-of-view in the phase-encoding direction without aliasing and increase the in-plane resolution accordingly. Free-induction-decay (FID) EPI and echo-train-shifted (T2*-weighted) and standard (T2-weighted) spin-echo (SE) EPI with in-plane resolutions of up to 0.5×1.0mm(2) (slice thickness 5mm) were acquired at 3T. Unwanted signal contributions of 2DRF side excitations were shifted out of the object (FID-EPI) or of the refocusing plane by tilting the excitation plane (SE-EPI). Brain activation in healthy volunteers was investigated with checkerboard and finger-tapping block-design paradigms. Brain activation could be detected with all sequences and contrasts, most reliably with FID-EPI due to its higher signal amplitude and the longer 2DRF excitation that are more sensitive to magnetic field inhomogeneities. In conclusion, inner-FOV EPI based on 2DRF excitations could help to improve the spatial resolution of fMRI of focal target regions, e.g., for applications in the spinal cord. PMID:23602726

  18. Hydrogen-bonded Intramolecular Charge Transfer Excited State of Dimethylaminobenzophenone using Time Dependent Density Functional Theory

    Institute of Scientific and Technical Information of China (English)

    Yu-ling Chu; Zhong Yang; Zhe-feng Pan; Jing Liu; Yue-yi Han; Yong Ding; Peng Song

    2012-01-01

    Density functional theory and time-dependent density-functional theory have been used to investigate the photophysical properties and relaxation dynamics of dimethylaminobenzophenone (DMABP) and its hydrogen-bonded DMABP-MeOH dimer.It is found that,in nonpolar aprotic solvent,the transitions from S0 to S1 and S2 states of DMABP have both n→π* and π→π* characters,with the locally excited feature mainly located on the C=O group and the partial CT one characterized by electron transfer mainly from the dimethylaminophenyl group to the C=O group.But when the intermolecular hydrogen bond C=O…H-O is formed,the highly polar intramolecular charge transfer character switches over to the first excited state of DMABP-MeOH dimer and the energy difference between the two lowlying electronically excited states increases.To gain insight into the relaxation dynamics of DMABP and DMABP-MeOH dimer in the excited state,the potential energy curves for conformational relaxation are calculated.The formation of twisted intramolecular charge transfer state via diffusive twisting motion of the dimethylamino/dimethylaminophenyl groups is found to be the major relaxation process.In addition,the decay of the S1 state of DMABP-MeOH dimer to the ground state,through nonradiative intermolecular hydrogen bond stretching vibrations,is facilitated by the formation of the hydrogen bond between DMABP and alcohols.

  19. Skyrme energy-density functional approach to collective modes of excitation in exotic nuclei

    International Nuclear Information System (INIS)

    Low-frequency collective modes of excitation in neutron-rich nuclei are investigated in the framework of the nuclear energy-density functional method. It is shown that the collective Hamiltonian approach gives the quantitative description of the low-lying states in transitional nuclei with the Skyrme and pairing energy-density functionals as a microscopic input. The inertial functions for large-amplitude vibration and rotation are evaluated by the local normal modes along the axial quadrupole collective coordinate. The time-odd components of the mean fields are fully included in the derived masses

  20. Generating functions and stability study of multivariate self-excited epidemic processes

    Science.gov (United States)

    Saichev, A. I.; Sornette, D.

    2011-09-01

    We present a stability study of the class of multivariate self-excited Hawkes point processes, that can model natural and social systems, including earthquakes, epileptic seizures and the dynamics of neuron assemblies, bursts of exchanges in social communities, interactions between Internet bloggers, bank network fragility and cascading of failures, national sovereign default contagion, and so on. We present the general theory of multivariate generating functions to derive the number of events over all generations of various types that are triggered by a mother event of a given type. We obtain the stability domains of various systems, as a function of the topological structure of the mutual excitations across different event types. We find that mutual triggering tends to provide a significant extension of the stability (or subcritical) domain compared with the case where event types are decoupled, that is, when an event of a given type can only trigger events of the same type.

  1. Study of excitation functions in Rh(α,xn) Ag reactions

    International Nuclear Information System (INIS)

    The excitation functions for the reaction 103Rh(α,n)106mAg, 103Rh(α,2n)105Ag and 103Rh(α,3n)104Ag have been measured between 10 and 40 MeV α-particle energy, using stacked foil activation technique. Excitation functions are also calculated theoretically using geometry dependent hybrid (GDH) model. The computer code ALICE/LIVERMORE-82 has been used which takes into account the pre-equilibrium contribution along with the equilibrium decay of the compound nucleus. It has been found that initial exciton number n0 = 4 gives a satisfactory reproduction of experimental data. (author). 25 refs, 4 figs, 1 tab

  2. Sub-Coulomb fusion excitation function for 12 C + 12 C

    International Nuclear Information System (INIS)

    Fusion excitation functions are measured for the o, p and n evaporation channels in the fusion of the 12 C + 12 C system at center of mass energies between 4.5 and 6.5 MeV, with energy steps of 75 keV. The X-ray technique is used with a new absolute normalization method which is independent of charge collection and allows at the same time to monitor the Carbon buildup on the target. Good agreement is obtained with absolute cross section values previously measured using particle detection techniques, but smaller energy steps are used in the present experiment. As in previous works much structure is seen in the excitation function which is consistent with the positions of resonances reported in the literature for this system. (Author)

  3. Application of Excitation Function to the Prediction of RI Level Caused by Corona Discharge

    Institute of Scientific and Technical Information of China (English)

    ZHU Lingyu; JI Shengchang; HUI Sisi; GUO Jun; LI Yansong; FU Chenzhao

    2012-01-01

    Radio interference (RI), as an aftereffect of corona discharge, is an important research topic in the field of electromagnetic compatibility, where excitation function is applied broadly to the prediction of RI level. This paper presents the theory of excitation function method used in the RI level prediction. Then, some practical problems related to this method are discussed. The propagation procedure of corona current is solved by the phase-modal transformation, and the impedance matrix of multi transmission lines is calculated by a double logarithmic approximate model of Carson's Ground-Return impedance. At the same time, in order to calculate the RI level when total line corona is assumed, an analytical formula is deduced for integral operation. Based on the above solutions, an algorithm is presented and applied to the prediction of RI level of a practical overhead transmission line. Comparison of prediction and measurement results indicates that the algorithm proposed in this paper is effective and feasible.

  4. Melittin restores proteasome function in an animal model of ALS

    Directory of Open Access Journals (Sweden)

    Lee Sang Min

    2011-06-01

    Full Text Available Abstract Amyotrophic lateral sclerosis (ALS is a paralyzing disorder characterized by the progressive degeneration and death of motor neurons and occurs both as a sporadic and familial disease. Mutant SOD1 (mtSOD1 in motor neurons induces vulnerability to the disease through protein misfolding, mitochondrial dysfunction, oxidative damage, cytoskeletal abnormalities, defective axonal transport- and growth factor signaling, excitotoxicity, and neuro-inflammation. Melittin is a 26 amino acid protein and is one of the components of bee venom which is used in traditional Chinese medicine to inhibit of cancer cell proliferation and is known to have anti-inflammatory and anti-arthritic effects. The purpose of the present study was to determine if melittin could suppress motor neuron loss and protein misfolding in the hSOD1G93A mouse, which is commonly used as a model for inherited ALS. Meltittin was injected at the 'ZuSanLi' (ST36 acupuncture point in the hSOD1G93A animal model. Melittin-treated animals showed a decrease in the number of microglia and in the expression level of phospho-p38 in the spinal cord and brainstem. Interestingly, melittin treatment in symptomatic ALS animals improved motor function and reduced the level of neuron death in the spinal cord when compared to the control group. Furthermore, we found increased of α-synuclein modifications, such as phosphorylation or nitration, in both the brainstem and spinal cord in hSOD1G93A mice. However, melittin treatment reduced α-synuclein misfolding and restored the proteasomal activity in the brainstem and spinal cord of symptomatic hSOD1G93A transgenic mice. Our research suggests a potential functional link between melittin and the inhibition of neuroinflammation in an ALS animal model.

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

    Energy Technology Data Exchange (ETDEWEB)

    Bokhan, P. A.; Gugin, P. P.; Zakrevsky, Dm. E.; Malin, T. V. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, 13, Lavrentieva av., Novosibirsk 630090 (Russian Federation); Zhuravlev, K. S.; Osinnykh, I. V. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, 13, Lavrentieva av., Novosibirsk 630090 (Russian Federation); Novosibirsk State University, 2 Pirogova Str., Novosibirsk 630090 (Russian Federation); Solomonov, V. I.; Spirina, A. V. [Institute of Electrophysics, Ural Division of the Russian Academy of Sciences, 106, Amundsen str., Ekaterinburg 620016 (Russian Federation)

    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.

  6. Excitation functions and production of arsenic radioisotopes for environmental toxicology and biomedical purposes

    Energy Technology Data Exchange (ETDEWEB)

    Basile, D.; Birattari, C.; Bonard, M.; Salomone, A. (Istituto Nazionale di Fisica Nucleare, Milan (Italy)); Goetz, L.; Sabbioni, E. (Commission of the European Communities, Ispra (Italy). Joint Research Centre)

    1981-06-01

    Many arsenic radionuclides have come to be used as tracers in biology and in the study of environmental pollution of both water and soil. In nuclear medicine, radioactive /sup 74/As has been employed as a positron emitter for the localization of brain tumors, cerebral occlusive vascular lesions, arterious-venous malformations, etc. The aim of the work described was to study the excitation functions for the production of the arsenic radioisotopes from targets of natural germanium via nuclear reactions (p, xn).

  7. Integral measurement of break-up excitation function using a multiple silicon telescope

    International Nuclear Information System (INIS)

    A simple method is proposed for measuring the inclusive break-up excitation function which the experimental device, consisting of a set of successive silicon detectors, serves the double purpose of decreasing the incident beam energy and of detecting and identifying the reaction products. Monte Carlo simulations revealed the merits and the limitations of the method. Finally, experimental data for tritons are treated in order to obtain relevant physical informations (authors). 9 refs., 9 figs

  8. Study of np2P1/2,3/2 Rydberg series of AlI by the method of laser stepwise excitation and ionization by electric field

    International Nuclear Information System (INIS)

    Frequencies of the 4s2S1/2-np2P1/2,3/2 transitions are measured and the energies of high-lying P states, as well as the ionization energy of aluminum atoms, are determined by the method of two-step laser excitation and ionization of excited atoms of AlI by an electric field. 4 refs., 3 figs., 1 tab

  9. Energy levels, radiative rates and electron impact excitation rates for transitions in Al X

    CERN Document Server

    Aggarwal, K M

    2013-01-01

    Energy levels, radiative rates and lifetimes are calculated among the lowest 98 levels of the n <= 4 configurations of Be-like Al X. The GRASP (General-purpose Relativistic Atomic Structure Package) is adopted and data are provided for all E1, E2, M1 and M2 transitions. Similar data are also obtained with the Flexible Atomic Code (FAC) to assess the accuracy of the calculations. Based on comparisons between calculations with the two codes as well as with available measurements, our listed energy levels are assessed to be accurate to better than 0.3%. However, the accuracy for radiative rates and lifetimes is estimated to be about 20%. Collision strengths are also calculated for which the Dirac Atomic R-matrix Code (DARC) is used. A wide energy range (up to 380 Ryd) is considered and resonances resolved in a fine energy mesh in the thresholds region. The collision strengths are subsequently averaged over a Maxwellian velocity distribution to determine effective collision strengths up to a temperature of 1.6...

  10. The effect of wave function orthogonality on the simultaneous ionization and excitation of helium

    International Nuclear Information System (INIS)

    Within the framework of the first-order Born approximation, the triple differential cross sections (TDCSs) for simultaneous ionization and excitation of helium are calculated. The wave function of the ejected electron is chosen to be orthogonal or non-orthogonal to the wave function of the bound electron before ionization. It is found that the orthogonality has a strong effect on the TDCS, especially when plane waves and Coulomb waves are used to describe the projectile and the ejected electron. (atomic and molecular physics)

  11. Excited State Contributions to the Heavy Baryon Fragmentation Functions in a Quark-Diquark Model

    CERN Document Server

    Adamov, A D; Goldstein, Gary R.

    2001-01-01

    Spin dependent fragmentation functions for heavy flavor quarks to fragment into heavy baryons are calculated in a quark-diquark model. The production of intermediate spin 1/2 and 3/2 excited states is explicity included. The resulting $\\Lambda_b$ production rate and polarization at LEP energies are in agreement with experiment. The $\\Lambda_c$ and $\\Xi_c$ functions are also obtained. The spin independent $f_1(z)$ is compared to data. The integrated values for production rates agree with the data.

  12. Temperatures and excitation energies for hot nuclei formed in the Ar on Al reactions from 36 to 65MeV/u

    International Nuclear Information System (INIS)

    Temperatures and excitation energies have been independently measured for hot nuclei formed in the Ar on Al reactions from 36 to 65MeV/u. Charged products have been measured in a geometry close to 4π in the center of mass with multidetectors MUR and TONNEAU. At each incident energy, the temperature and excitation energy are both increasing when the impact parameter value decreases. For central collisions (b < 2 fm), the temperature increases with the incident energy until 45 MeV/u and reaches a value of 7 MeV and the excitation energy per nucleon increases at least until 55 MeV/u

  13. Scaling of heavy ion fusion excitation functions with regard to Wongs expression

    International Nuclear Information System (INIS)

    Cross sections for heavy ion reactions below the Coulomb barrier is characterized by a marked enhancement of the fusion cross sections over the predictions of the one dimensional barrier penetration model, as also the associated isotope dependence. A large number of experimental data has accumulated over the years for such sub-barrier fusion enhancements. The fusion enhancements is usually ascribed to coupling of the fusion channel with other degrees of freedom such as nuclear deformation, low lying collective excitations as well as by nucleon transfer etc. An alternative approach applied to many cases has been the distribution of barriers. With the accumulation of large volume of experimental data it would be desirable to have a general scaling of appropriate parameters describing the fusion excitation functions

  14. A relativistic time-dependent density functional study of the excited states of the mercury dimer

    Energy Technology Data Exchange (ETDEWEB)

    Kullie, Ossama, E-mail: kullie@uni-kassel.de, E-mail: ossama.kullie@unistra.fr [Institute de Chimie de Strasbourg, CNRS et Université de Strasbourg, Laboratoire de Chimie Quantique, 4 rue Blaise Pascal, 67070 Strasbourg, France and Theoretical Physics, Institute for Physics, Department of Mathematics and Natural Science, University of Kassel, D-34127 Kassel (Germany)

    2014-01-14

    In previous works on Zn{sub 2} and Cd{sub 2} dimers we found that the long-range corrected CAMB3LYP gives better results than other density functional approximations for the excited states, especially in the asymptotic region. In this paper, we use it to present a time-dependent density functional (TDDFT) study for the ground-state as well as the excited states corresponding to the (6s{sup 2} + 6s6p), (6s{sup 2} + 6s7s), and (6s{sup 2} + 6s7p) atomic asymptotes for the mercury dimer Hg{sub 2}. We analyze its spectrum obtained from all-electron calculations performed with the relativistic Dirac-Coulomb and relativistic spinfree Hamiltonian as implemented in DIRAC-PACKAGE. A comparison with the literature is given as far as available. Our result is excellent for the most of the lower excited states and very encouraging for the higher excited states, it shows generally good agreements with experimental results and outperforms other theoretical results. This enables us to give a detailed analysis of the spectrum of the Hg{sub 2} including a comparative analysis with the lighter dimers of the group 12, Cd{sub 2}, and Zn{sub 2}, especially for the relativistic effects, the spin-orbit interaction, and the performance of CAMB3LYP and is enlightened for similar systems. The result shows, as expected, that spinfree Hamiltonian is less efficient than Dirac-Coulomb Hamiltonian for systems containing heavy elements such as Hg{sub 2}.

  15. Short periodic variations of polar motion and hemispheric atmospheric angular momentum excitation functions in the period 1984-1992

    Directory of Open Access Journals (Sweden)

    J. Nastula

    Full Text Available Short periodic oscillations with the periods from 10 up to 110 days of the hemispheric components of effective atmospheric angular momentum (EAAM excitation function and their correlation with polar motion excitation function have been analyzed. The EAAM data of the Japan Meteorological Agency (JMA computed for the two hemispheres and the very long baseline interferometry (VLBI polar motion NGS 92 R01 data (NGS 1992, determined by the National Geodetic Survey were applied. The distinct oscillations with periods of about 28, 35-55 and 60-80 days were detected in the χy-component of both polar motion excitation function and northern EAAM excitation functions containing wind and pressure, with and without inverted barometric correction terms. The χy-component of the polar motion excitation function is significanly correlated (correlation coefficient equal to 0.55-0.75 with the χy-components of the northern EAAM excitation functions mentioned above, which are mostly induced by the atmospheric circulation over lands. No meaningful correlation between polar motion excitation function and the southern EAAM excitation functions was found. The χx-components of the EAAM and polar motion excitation functions are not significantly correlated. The strong short periodic variation of the length of day (LOD and χy in the early 1988 seems to be caused by the above-mentioned 35-55 days oscillations of the northern hemisphere atmosphere. This variation can be related to the rapid passing from the El Niño to the La Niña phenomenon or from the minimum to the maximum in the Southern Oscillation Index in 1987-1989.

  16. Excitation function measurements and integral yields estimation for natZn(p,x) reactions at low energies

    International Nuclear Information System (INIS)

    Excitation functions have been measured for a number of proton-induced nuclear reactions on natural zinc in the energy range from 27.5 MeV down to their threshold energy, using the activation method on stacked foils. Excitation functions and thick target yield for the reactions leading to the formation of 67Ga,66Ga,68Ga,62Zn and 65Zn are presented and compared with earlier reported experimental data. The experimental cross-sections and the production yields are tabulated; the excitation functions and the thick target yield curves are plotted in graphs

  17. Beyond Time-Dependent Density Functional Theory Using Only Single Excitations: Methods for Computational Studies of Excited States in Complex Systems.

    Science.gov (United States)

    Herbert, John M; Zhang, Xing; Morrison, Adrian F; Liu, Jie

    2016-05-17

    Single-excitation methods, namely, configuration interaction singles and time-dependent density functional theory (TDDFT), along with semiempirical versions thereof, represent the most computationally affordable electronic structure methods for describing electronically excited states, scaling as [Formula: see text] absent further approximations. This relatively low cost, combined with a treatment of electron correlation, has made TDDFT the most widely used excited-state quantum chemistry method over the past 20+ years. Nevertheless, certain inherent problems (beyond just the accuracy of this or that exchange-correlation functional) limit the utility of traditional TDDFT. For one, it affords potential energy surfaces whose topology is incorrect in the vicinity of any conical intersection (CI) that involves the ground state. Since CIs are the conduits for transitions between electronic states, the TDDFT description of photochemistry (internal conversion and intersystem crossing) is therefore suspect. Second, the [Formula: see text] cost can become prohibitive in large systems, especially those that involve multiple electronically coupled chromophores, for example, the antennae structures of light-harvesting complexes or the conjugated polymers used in organic photovoltaics. In such cases, the smallest realistic mimics might already be quite large from the standpoint of ab initio quantum chemistry. This Account describes several new computational methods that address these problems. Topology around a CI can be rigorously corrected using a "spin-flip" version of TDDFT, which involves an α → β spin-flipping transition in addition to occupied → virtual excitation of one electron. Within this formalism, singlet states are generated via excitation from a high-spin triplet reference state, doublets from a quartet, etc. This provides a more balanced treatment of electron correlation between ground and excited states. Spin contamination is problematic away from the

  18. The Role of Potential Structure in Excitation Functions of Synthesizing Superheavy Nuclei

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The excitation functions of two very similar reaction channels, 58Fe+2O8Pb→265Hs+1n and 58Fe+2O8Pb→209Bi→266Mt+1n are studied in the framework of the dinucleai system conception. The fusion probabilities are found to be strongly subject to the structure of the driving potential. Usually the fusion probability is hindered by a barrier from the injection channel towards the compound nuclear configuration. The barrier towards the mass symmetrical direction, however, also plays an important role for the fusion probability, because the barrier hinders the quasi-Gssion, and therefore helps fusion.

  19. Excitation Function for the 74Se(18O,p3n) Reaction

    OpenAIRE

    Gates, Jacklyn

    2009-01-01

    The 74Se(18O,p3n)88gNb excitation function was measured and a maximum cross section of 495+-5 mb was observed at and 18O energy of 74.0 MeV. Experimental cross sections were compared to theoretical calculations using the computer code ALICE-91 and the values were found to be in good agreement. The half life of 88gNb was determined to be around 14.56+-0.11 min.

  20. Measurement and analysis of the excitation function for alpha induced reaction on Ga and Sb isotopes

    International Nuclear Information System (INIS)

    Excitation functions for the reactions 69Ga(αxn)sup(73-x)As, 69Ga(α,p3n)69Ge, 69Ga(α,2p4n)67Ga, 71Ga(α,xn)sup(75-x)As, 121Sb(α,xn)sup(125-x)I, 121Sb(α,p3n)121Te and 123Sb(α,xn)sup(127-x)I were obtained from the measurements of the residual activity of stacked foils of gallium nitrate evaporated on aluminium backings from threshold to 65 MeV. The excitation functions for the production of 74As, 72As, 71As, 69Ge and 67Ga from α - induced reactions on Ga and 126I, 124I, 123I, 121I and 121Te from α - induced reactions on Sb are presented. The experimental data are compared with calculations considering equilibrium as well as pre-equilibrium reaction mechanism according to the hybrid model of Blann (1971). The high energy part of the excitation functions are dominated by the pre-equilibrium reaction mechanism. Calculations were done using the a priori calculational method of Overlaid Alice Code of Blann. From the reactions 71Ga(α,3n)72As and 123Sb(α,3n)124I an initial exciton number nsub(o)=4(nsub(n)=2, nsub(p)=2, nsub(h)=0) with the mean free path multiplier parameter k set to 2 has been deduced for both the targets. However, there are a few exceptions (i) the theory overestimates the cross-section for the 69Ga(α,2p4n)67Ga reaction whereas it underestimate the cross-section for the 121Sb(α,p3n)121Te reaction and the high energy tail of 121Sb(α,2n)123I excitation function. Factors to which these discrepancies between theory and experiment in case of these reactions may be attributed are indicated. Barring these reactions the overall agreement between theory and experiment is good taking into account the limitations of the theory. (author). 43 refs., 7 tabs., 19 figs

  1. Excitation spectrum and correlation functions of the Z3 chiral Potts quantum spin chain

    International Nuclear Information System (INIS)

    We study the excitation spectrum and the correlation functions of the Z3 chiral Potts model in the massive high-temperature phase using perturbation expansions and numerical diagonalization. We are mainly interested in results for general chiral angles but we consider also the superintegrable case. For the parameter values considered, we find that the band structure of the low-lying part of the excitation spectrum has the form expected from a quasiparticle picture with two fundamental particles. Studying the chain-size dependence of the spectrum, we find a remarkable stability of the second fundamental particle in a limited range of the momentum, even when its energy becomes so high that it lies very high up among the multiparticle scattering states. This is not a phenomenon restricted to the superintegrable line. Calculating a non-translationally invariant correlation function, we give evidence that it is oscillating. Within our numerical accuracy we find a relation between the oscillation length and the dip position of the momentum dispersion of the lightest particle which seems to be quite independent of the chiral angles. ((orig.))

  2. Excitation function of elastic $pp$ scattering from a unitarily extended Bialas-Bzdak model

    CERN Document Server

    Nemes, F; Csanád, M

    2015-01-01

    The Bialas-Bzdak model of elastic proton-proton scattering assumes a purely imaginary forward scattering amplitude, which consequently vanishes at the diffractive minima. We extended the model to arbitrarily large real parts in a way that constraints from unitarity are satisfied. The resulting model is able to describe elastic $pp$ scattering not only at the lower ISR energies but also at $\\sqrt{s}=$7~TeV in a statistically acceptable manner, both in the diffractive cone and in the region of the first diffractive minimum. The total cross-section as well as the differential cross-section of elastic proton-proton scattering is predicted for the future LHC energies of $\\sqrt{s}=$13, 14, 15~TeV and also to 28~TeV. A non-trivial, significantly non-exponential feature of the differential cross-section of elastic proton-proton scattering is analyzed and the excitation function of the non-exponential behavior is predicted. The excitation function of the shadow profiles is discussed and related to saturation at small ...

  3. Excitation function of elastic $pp$ scattering from a unitarily extended Bialas-Bzdak model

    CERN Document Server

    Nemes, F; Csanád, M

    2014-01-01

    The Bialas-Bzdak model of elastic proton-proton scattering assumes a purely imaginary forward scattering amplitude, which consequently vanishes at the diffractive minima. We extended the model to arbitrarily large real parts in a way that constraints from unitarity are satisfied. The resulting model is able to describe elastic $pp$ scattering not only at the lower ISR energies but also at $\\sqrt{s}=$7 TeV in a statistically acceptable manner, both in the diffractive cone and in the region of the first diffractive minimum. The total cross-section as well as the differential cross-section of elastic proton-proton scattering is predicted for the future LHC energies of $\\sqrt{s}=$8, 13, 14, 15 TeV and also to 28 TeV. A non-trivial, significantly non-exponential feature of the differential cross-section of elastic proton-proton scattering is analyzed and the excitation function of the non-exponential behavior is predicted. The excitation function of the shadow profiles is discussed and related to saturation at sma...

  4. Calculation of excitation functions for the production of Cu and Co medical isotopes

    International Nuclear Information System (INIS)

    Copper and cobalt radioisotopes have been used for both diagnostic and therapeutic purposes in the field of nuclear medicine. There is considerable interest in 60,61,64,67Cu and 55,57Co radioisotopes for some applications like PET, SPECT imaging and targeted radiotherapy of tumors. In present study, the production of 60,61,64,67Cu and 55,57Co via 64Zn(p,a)61Cu, 67Zn(p,a)64Cu, 70Zn(p,a)67Cu, 58Ni(p,a)55Co, 60Ni(p,a)57Co, 64Zn(p,na)60Cu and 68Zn(p,na)64Cu reactions have been investigated in the range of 5-40 MeV proton incident energy. The new version of the code ALICE-2011 is used to determine the excitation functions of these nuclear reactions. The calculated excitation functions were compared with experimental results and semi-empirical cross section values of a previously developed model. (orig.)

  5. High excitation of the species in nitrogen–aluminum plasma generated by electron cyclotron resonance microwave discharge of N2 gas and pulsed laser ablation of Al target

    International Nuclear Information System (INIS)

    A reactive nitrogen–aluminum plasma generated by electron cyclotron resonance (ECR) microwave discharge of N2 gas and pulsed laser ablation of an Al target is characterized spectroscopically by time-integrated and time-resolved optical emission spectroscopy (OES). The vibrational and rotational temperatures of N2 species are determined by spectral simulation. The generated plasma strongly emits radiation from a variety of excited species including ambient nitrogen and ablated aluminum and exhibits unique features in optical emission and temperature evolution compared with the plasmas generated by a pure ECR discharge or by the expansion of the ablation plume. The working N2 gas is first excited by ECR discharge and the excitation of nitrogen is further enhanced due to the fast expansion of the aluminum plume induced by target ablation, while the excitation of the ablated aluminum is prolonged during the plume expansion in the ECR nitrogen plasma, resulting in the formation of strongly reactive nitrogen–aluminum plasma which contains highly excited species with high vibrational and rotational temperatures. The enhanced intensities and the prolonged duration of the optical emissions of the combined plasma would provide an improved analytical capability for spectrochemical analysis. - Highlights: • ECR discharge and pulsed laser ablation generate highly excited ECR–PLA plasma. • The expansion of PLA plasma results in excitation enhancement of ECR plasma species. • The ECR plasma leads to excitation prolongation of PLA plasma species. • The ECR–PLA plasma emits strong emissions from a variety of excited species. • The ECR–PLA plasma maintains high vibrational–rotational temperatures for a long time

  6. Monte-Carlo modeling of excitation of the electron subsystem of Al{sub 2}O{sub 3} and polyethylene after swift heavy ion impact

    Energy Technology Data Exchange (ETDEWEB)

    Rymzhanov, R.A., E-mail: r.a.rymzhanov@gmail.com [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); Medvedev, N.A. [Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg (Germany); Volkov, A.E. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); National Research Centre ‘Kurchatov Institute’, Kurchatov Square 1, 123182 Moscow (Russian Federation); Lebedev Physical Institute of the Russian Academy of Sciences, Leninskij pr., 53, 119991 Moscow (Russian Federation)

    2014-05-01

    The Monte-Carlo (MC) model simulating the femto-second kinetics of the electron subsystem in a track of a swift heavy ion decelerated in the electronic stopping regime is developed. The complex dielectric function (CDF) formalism is used to calculate the cross sections of interactions of an ion and fast electrons with the electron subsystem of a target. It accounts for all collective modes in the electron ensemble. The applied method of CDF reconstruction from the experimental optical data provided a very good agreement of the calculated electron inelastic mean free paths with the NIST database as well as of the calculated SHI energy loss with those from SRIM and CasP codes. The MC model was applied to determine the radial distributions of delocalized electrons and their energy density in tracks of Au (2187 MeV) ions in insulators (Al{sub 2}O{sub 3} and polyethylene) at different times. The femtosecond electron kinetics reveals two fronts of the spatial propagation: the primary fast delta-electrons form the front of excitations while electrons appearing due to decay of plasmons generated in a track form the second slow front following behind.

  7. Synthesis of BaAl12O19:Mn2+ nanophosphors by a reverse microemulsion method and its photoluminescence properties under VUV excitation

    International Nuclear Information System (INIS)

    BaAl12O19:Mn2+ nanoparticles were successfully synthesized by a reverse microemulsion method. The nanoparticles were characterized by transmission electron microscopy, X-ray diffraction and photoluminescence measurements. The results indicate that BaAl12O19:Mn2+ with spherical morphology can be synthesized at 1200 deg. C, which is about 300 deg. C lower than that of solid state reaction with size ranging from 40 to 100 nm. Monitored at 515 nm, the excitation spectra of as-prepared BaAl12O19:x Mn2+ (0.1≤x≤0.5) and bulk BaAl12O19:0.1 Mn2+ are similar. The bands at 130 and 156 nm were observed and assigned to the optical absorption of AlO4 and AlO6 groups, respectively. The emission band position of nano-BaAl12O19:0.1 Mn2+ is 6 nm shorter than that of the bulk due to the low symmetry of crystal field near the surface of nano-BaAl12O19:Mn2+. The optimum emission intensity was obtained at x=0.2 of Mn2+ doping. Furthermore, the decay behaviors of nano-sized and bulk BaAl12O19:0.1 Mn2+ have also been discussed

  8. Spin contamination-free N-electron wave functions in the excitation-based configuration interaction treatment

    Science.gov (United States)

    Alcoba, Diego R.; Torre, Alicia; Lain, Luis; Massaccesi, Gustavo E.; Oña, Ofelia B.; Capuzzi, Pablo

    2016-07-01

    This work deals with the spin contamination in N-electron wave functions provided by the excitation-based configuration interaction methods. We propose a procedure to ensure a suitable selection of excited N-electron Slater determinants with respect to a given reference determinant, required in these schemes. The procedure guarantees the construction of N-electron wave functions which are eigenfunctions of the spin-squared operator S ˆ 2 , avoiding any spin contamination. Our treatment is based on the evaluation of the excitation level of the determinants by means of the expectation value of an excitation operator formulated in terms of spin-free replacement operators. We report numerical determinations of energies and expectation values, arising from our proposal as well as from traditional configuration interaction methods, in selected open-shell systems, in order to compare the behavior of these procedures and their computational costs.

  9. The thermotidal exciting function for water vapour absorption of solar radiation

    Directory of Open Access Journals (Sweden)

    M. BONAFEDE

    1976-06-01

    Full Text Available The thermotidal exciting function J is considered, for
    the absorption of solar radiation by water vapour, according to the model
    derived by Siebert. The Mugge-Moller formula for water vapour absorption
    is integrated numerically, using experimental data for the water vapour
    concentration in the troposphere and the stratosphere. It appears that
    Siebort's formula is a reasonable approximation at low tropospheric levels
    but it dramatically overestimates the water vapour thermotidal heating
    in the upper troposphere and in the stratosphere. It seems thus possible
    that, if the correct vertical profile is employed for J , the amplitudes and
    phases of the diurnal temperature oscillations and of the tidal wind speeds
    may suffer significant changes from those previously calculated and possibly explain the three hours delay of the observed phases from the computed values.

  10. Excitation function of elastic scattering on 12C + 4He system, at low energies

    International Nuclear Information System (INIS)

    Interactions in the 12C + 4He system are of great interest in astrophysics and to help determine the relative abundances of elements in stars, at the end of helium burning [1, 2]. The Instituto Nacional de Investigaciones Nucleares (ININ) in Mexico, have made measurements of elastic scattering for this system, using the inverse kinematics method with thick white gas [3, 4], for E CM (0.5 - 4 MeV) θ CM = 180o. In this work we obtain excitation functions of elastic scattering of 12C + 4He system with angular and energy dependence; ECM = 0.5 - 4 MeV and θCM 100o -170o.Using inverse kinematics method with thick white gas and energy loss tables. (Author)

  11. New calculations of excitation functions for some light deformed medical radionuclides

    International Nuclear Information System (INIS)

    In this study, the new calculations on the excitation functions of 51V(p,n)51Cr, 57Fe(p,n)57Co, 58Fe(p,n)58Co, 75As(p,n)75Se, 81Br (p,n)81Kr, 82Se(p,n)82Br and 85Rb(p,n)85Sr reactions have been carried for incident proton energy up to 50 MeV. In these calculations the pre-equilibrium and equilibrium effects have been investigated. The pre-equilibrium calculations involve hybrid model, geometry dependent hybrid model, the cascade exciton model and full exciton model. Equilibrium effects have been calculated according to Weisskopf-Ewing model. The calculated results have been compared with the experimental data taken from the literature.

  12. Description of excitations in odd non-magic nuclei by the Green's function method

    International Nuclear Information System (INIS)

    General equations for one-particle Green function in non-magic nuclei are derived where a pairing mechanism is singled out explicitly. A refining procedure for the phenomenological single-particle energies and pairing gaps is formulated to avoid double counting of the phonon mixing if the initial data of the problem are these phenomenological quantities. The general equations obtained are written in the squared phonon creation amplitude approximation. Using this approximation the secular equation to calculate excitations of odd non-magic nuclei are obtained. The equation takes ground state correlations into account completely and contains only the squared energy variable. Distributions of single-particle strength in 119 Sn and 121 Sn are calculated and reasonable agreement with the available experiment is obtained

  13. Excitation functions of the proton induced nuclear reactions on natural zirconium

    Energy Technology Data Exchange (ETDEWEB)

    Uddin, M.S. [Department of Physics, Kyungpook National University, 1370 Sankyok-dong, Buk-gu, Daegu 702-701 (Korea, Republic of); Institute of Nuclear Science and Technology, Atomic Energy Research Establishment, Savar, GPO Box No 3787, Dhaka 1000 (Bangladesh); Khandaker, M.U.; Kim, K.S.; Lee, Y.S.; Lee, M.W. [Department of Physics, Kyungpook National University, 1370 Sankyok-dong, Buk-gu, Daegu 702-701 (Korea, Republic of); Kim, G.N. [Department of Physics, Kyungpook National University, 1370 Sankyok-dong, Buk-gu, Daegu 702-701 (Korea, Republic of)], E-mail: gnkim@knu.ac.kr

    2008-01-15

    Excitation functions for the {sup nat}Zr(p,xn){sup 90,92m,95g,96}Nb, {sup nat}Zr(p,pxn){sup 88,89}Zr, and {sup nat}Zr(p,{alpha}xn){sup 86,87m,87mg,88}Y reactions were measured by using a stacked-foil activation technique in combination with HPGe {gamma}-ray spectroscopy using the MC50 cyclotron at the Korean Institute of Radiological and Medical Sciences, Korea. In this way the proton beam energy range 4-40 MeV was covered. We report new data for these processes. The data were compared with the results of precompound-hybrid model calculations, whereby only a partial agreement was obtained.

  14. Excitation functions of parameters in Erlang distribution, Schwinger mechanism, and Tsallis statistics in RHIC BES program

    CERN Document Server

    Gao, Li-Na; Lacey, Roy A

    2016-01-01

    Experimental results of the transverse momentum distributions of phi mesons and $\\Omega$ hyperons produced in gold-gold (Au-Au) collisions with different centrality intervals, measured by the STAR Collaboration at different energies (7.7, 11.5, 19.6, 27, and 39 GeV) in the beam energy scan (BES) program at the relativistic heavy ion collider (RHIC), are approximately described by the single Erlang distribution and the two-component Schwinger mechanism. Meanwhile, the STAR experimental transverse momentum distributions of negatively charged particles, produced in Au-Au collisions at RHIC BES energies, are approximately described by the two-component Erlang distribution and the single Tsallis statistics. The excitation functions of free parameters are obtained from the fit to the experimental data. A weak softest point in the string tension in $\\Omega$ hyperon spectra is observed at 7.7 GeV.

  15. Measurement of excitation functions in 16O + 93Nb at energies above the Coulomb barrier

    International Nuclear Information System (INIS)

    From past few decades it has become the topic of great interest to study heavy ion (HI) induced reaction at intermediate energy range. It has been observed that at energies just above the Coulomb barrier both the complete fusion (CF) and incomplete fusion (ICF) reaction may dominant. In CF processes whole projectile fuses with the target while in ICF processes only a part of projectile fuses with the target and remaining part passes with almost beam energy. Some studies show that ICF competes with CF just above the Coulomb barrier. Several theoretical models have been presented to explain the ICF reaction dynamics, such as Exciton model, Breakup fusion model, Promptly emitted particles model, Multistep direct reaction theory and Hot spot model etc. In the present work an effort has been made to investigate the mechanism involve in HI reaction with measurement of excitation functions for thirteen evaporation residues (ERs) identified in the interaction of 16O+93Nb system.

  16. Integral excitation functions as a tool to decipher the solar record in extraterrestrial matter

    International Nuclear Information System (INIS)

    A large variety of stable and radioactive nuclides is produced by the interaction of cosmic ray particles with extraterrestrial matter. In order to interpret these cosmogenic nuclides in lunar samples, in meteorites and cosmic dust, one has to differentiate between p- and α-induced reactions with solar and galactic cosmic rays. In particular, for a satisfactory description of the interaction of solar particles with dense matter, a detailed knowledge of the cross section of the respective nuclear reactions is necessary. On the basis of integral excitation functions, model calculations of the depth dependent radionuclide productions by solar protons and α-particles in the lunar surface and in meteorites are presented. Theoretical profiles are compared with experimental data and several cosmochemical applications are discussed, concerning questions about the constancy of the cosmic radiation in time and space. (Auth.)

  17. Validation of Earth orientation parameters (EOP), geophysical excitation functions ( EF) and the second degree gravity field coefficients (GFC)

    Science.gov (United States)

    Heiker, A.; Schmidt, M.

    2012-04-01

    The project P9 of the research group "Earth rotation and geophysical processes" aims at the combined analysis and validation of Earth rotation observations and models (see Göttl et al. EGU 2012 poster). The EOP, EF and GFC are linked by the Earth tensor of inertia. This link is used for a sophisticated mutual validation. A least squares adjustment model which estimate the unknown tensor of inertia was developed for this purpose. Additionally variance and covariance components are estimated. The results of the adjustment model are the residuals for each data series and the adjusted tensor of inertia. It is assumed that the residuals contain the inconsistencies between the various time series. A thorough analysis of the residuals in the time and frequency domain reveals the systematic effects within the residuals. The adjusted variance and covariance components allow to check the standard deviations and in some cases the correlations given by the data centers. We present the results obtained from the combined analysis of IERS EOP, two different atmospheric and oceanic excitation functions (NCEP/ECCO from the Jet Propulsion Laboratory and ERAInterim/OMCT from the GeoForschungsZentrum (GFZ) Potsdam) and six different gravity field solutions (five GRACE solutions and one SLR solution).

  18. Temperatures and excitation energies for hot nuclei formed in the Ar on Al reactions from 36 to 65MeV/u. Temperatures et energies d'excitation des noyaux chauds formes dans les collisions Ar + Al de 36 a 65 MeV/u

    Energy Technology Data Exchange (ETDEWEB)

    Cussol, D.; Peter, J.; Sullivan, J.P.; Bizard, G.; Brou, R.; Durand, D.; Louvel, M.; Patry, J.P.; Regimbart, R.; Steckmeyer, J.C.; Tamain, B.; Motobayashi, T. (Caen Univ., 14 (FR). Lab. de Physique Corpusculaire); Crema, E.; Doubre, H.; Hagel, K.; Jin, G.M.; Peghaire, A.; Saint-Laurent, F.; Motobayashi, T. (Grand Accelerateur National d' Ions Lourds (GANIL), 14 - Caen (FR)); Cassagnou, Y.; Legrain, R. (CEA Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (FR). Dept. de Physique Nucleaire); Lebrun, C. (Nantes Univ., 44 (FR). Lab. de Spectroscopie Nucleaire); Rosato, E. (Naples Univ. (IT). Ist. di Fisica); Hagel, K. (Texas A and M Univ., College Station, TX (US). Cyclotron Inst.); Mac Grath, R. (State Univ. of New York, Stony Brook, NY (US)); Jin, G.M. (Lanzhou Univ., GS (CN). Dept. of Modern Physics); Jeong, S.G.; Lee, S.M.; Nagashima, Y.; Nakagawa, T.; Ogihara, M.; Kasagi, J. (Tsukuba Univ., Ibaraki (JP). Inst. of Physics); Kasagi, J. (Tokyo Inst. of Techn. (JP). Dept

    1991-03-01

    Temperatures and excitation energies have been independently measured for hot nuclei formed in the Ar on Al reactions from 36 to 65MeV/u. Charged products have been measured in a geometry close to 4{pi} in the center of mass with multidetectors MUR and TONNEAU. At each incident energy, the temperature and excitation energy are both increasing when the impact parameter value decreases. For central collisions (b < 2 fm), the temperature increases with the incident energy until 45 MeV/u and reaches a value of 7 MeV and the excitation energy per nucleon increases at least until 55 MeV/u.

  19. Spectrographic determination of impurities in ammonium bifluoride. III. Study of the processes of vaporization, transport and excitation of the elements Al, B, Cu and Cr

    International Nuclear Information System (INIS)

    The influences of the processes of vaporization, transport and excitation on the shape of the volatilization-excitation curves and on the values of the spectral-line intensities have been investigated in a method for the spectrographic determination of Al, B, Cu and Cr In ammonium bifluoride samples by direct current are excitation in Scribner type electrodes, with addition of different matrices (graphite, 63203, GeO2, MgO and Zn0). The reaction products in the electrode cavity have been identified by X-ray powder diffraction analysis and the percentages of vaporized and diffused element evaluated through analysis by total-burning spectrographic methods. In addition, the values of both the number of particles entering the discharge column and the transport efficiencies have been calculated. Thus, the origin of most observed differences has been explained. (Author) 11 refs

  20. Influence of Exchange-Correlation Functional in the Calculations of Vertical Excitation Energies of Halogenated Copper Phthalocyanines using Time-Dependent Density Functional Theory (TD-DFT)

    International Nuclear Information System (INIS)

    The accurate prediction of vertical excitation energies is very important for the development of new materials in the dye and pigment industry. A time-dependent density functional theory (TD-DFT) approach coupled with 22 different exchange-correlation functionals was used for the prediction of vertical excitation energies in the halogenated copper phthalocyanine molecules in order to find the most appropriate functional and to determine the accuracy of the prediction of the absorption wavelength and observed spectral shifts. Among the tested functional, B3LYP functional provides much more accurate vertical excitation energies and UV-vis spectra. Our results clearly provide a benchmark calibration of the TD-DFT method for phthalocyanine based dyes and pigments used in industry

  1. Influence of Exchange-Correlation Functional in the Calculations of Vertical Excitation Energies of Halogenated Copper Phthalocyanines using Time-Dependent Density Functional Theory (TD-DFT)

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Uck [Univ. of Ulsan, Ulsan (Korea, Republic of)

    2013-08-15

    The accurate prediction of vertical excitation energies is very important for the development of new materials in the dye and pigment industry. A time-dependent density functional theory (TD-DFT) approach coupled with 22 different exchange-correlation functionals was used for the prediction of vertical excitation energies in the halogenated copper phthalocyanine molecules in order to find the most appropriate functional and to determine the accuracy of the prediction of the absorption wavelength and observed spectral shifts. Among the tested functional, B3LYP functional provides much more accurate vertical excitation energies and UV-vis spectra. Our results clearly provide a benchmark calibration of the TD-DFT method for phthalocyanine based dyes and pigments used in industry.

  2. A study of excitation functions for the radio-active isotopes produced by α-induced reactions in gold

    International Nuclear Information System (INIS)

    Excitation functions for the reactions 197Au(α,xn)201-xTl(x=1-4) have been measured in the energy range approx. 30-60 MeV using stacked foil technique. Ge(Li) gamma ray spectroscopy has been used for the analysis of irradiated samples. Excitation functions have also been calculated theoretically using two different computer codes (ACT and ALICE) with and without the inclusion of pre-equilibrium emission. As expected inclusion of pre-equilibrium emission to the compound nucleon calculations agree well with the experimentally measured excitation functions. An interesting trend in pre-equilibrium fraction with energy has been observed. (author). 33 refs, 6 figs

  3. A study of the reactions occurring in 16O+159Tb system: Measurement of excitation functions and recoil range distributions

    International Nuclear Information System (INIS)

    In order to study complete and incomplete fusion in heavy ion reactions, the excitation functions for several residues produced in the system 16O+159Tb have been measured in the energy range ∼70-95 MeV, employing activation technique. The measured excitation functions have been compared with those calculated using computer codes CASCADE, PACE2 and ALICE-91. Comparison of measured and theoretically calculated excitation functions has indicated significant contributions from incomplete fusion in some α-emission channels. In the present experiment, the recoil range distributions of several residues at ∼90 MeV incident beam energy have also been measured using recoil catcher technique and off-line gamma ray spectrometry. Analysis of the recoil range distributions has further confirmed the presence of contributions from incomplete fusion reactions. An attempt has been made to separate out the relative contributions of complete and incomplete fusion channels

  4. Linear interpolation method in ensemble Kohn-Sham and range-separated density-functional approximations for excited states

    CERN Document Server

    Senjean, Bruno; Jensen, Hans Jørgen Aa; Fromager, Emmanuel

    2015-01-01

    The computation of excitation energies in range-separated ensemble density-functional theory (DFT) is discussed. The latter approach is appealing as it enables the rigorous formulation of a multi-determinant state-averaged DFT method. In the exact theory, the short-range density functional, that complements the long-range wavefunction-based ensemble energy contribution, should vary with the ensemble weights even when the density is held fixed. This weight dependence ensures that the range-separated ensemble energy varies linearly with the ensemble weights. When the (weight-independent) ground-state short-range exchange-correlation functional is used in this context, curvature appears thus leading to an approximate weight-dependent excitation energy. In order to obtain unambiguous approximate excitation energies, we simply propose to interpolate linearly the ensemble energy between equiensembles. It is shown that such a linear interpolation method (LIM) effectively introduces weight dependence effects. LIM has...

  5. Measurement and analysis of excitation functions in 16O + 103Rh system in the excitation energy range ≅ 2-4 MeV/A

    International Nuclear Information System (INIS)

    In the present work, excitation functions for seven evaporation residues (ERs) produced via complete fusion and incomplete fusion processes in 16O + 103Rh system have been measured in the energy range ≅ 47-85 MeV, using recoil catcher technique followed by off-line gamma-ray spectrometry. Comparison of the experimental data with statistical model based computer code PACE 2 revealed dominance of incomplete fusion in reactions involving alpha-emission channels. To the best of our knowledge these reactions are being reported for the first time

  6. Modified linear response for time-dependent density-functional theory: Application to Rydberg and charge-transfer excitations

    International Nuclear Information System (INIS)

    We present an improved ab initio time-dependent density-functional theory (TDDFT) approach to electronic excitations. A conventional TDDFT scheme within the local-density approximation (LDA) inaccurately predicts Rydberg and charge-transfer excitation energies, mainly because the electron-hole (e-h) interaction is inappropriately described in these excitations, as can be found by analyzing the linear response formula [M. Petersilka, U. J. Gossmann, and E. K. U. Gross, Phys. Rev. Lett. 76, 1212 (1996)]. When the formula is averaged over the electron occupation, the inappropriate e-h interaction within LDA is corrected to become explicitly similar to that of the exact exchange system. As anticipated from the similarity, our proposed scheme of modified linear response greatly improves the prediction of the problematic excitations, which are exemplified for typical molecules

  7. Performance of Popular XC-Functionals for the Description of Excitation Energies in GFP-Like Chromophore Models

    DEFF Research Database (Denmark)

    List, Nanna Holmgaard; Olsen, Jógvan Magnus Haugaard; Rocha-Rinza, Tomás;

    2012-01-01

    Understanding and rationalization of the optical properties of fluorescent proteins are of great importance for life sciences due to their numerous applications as fluorescent biomarkers. Time-dependent density functional theory (TD-DFT) is a computationally appealing approach to accomplish this...... task. We present an evaluation of the performance of commonly used XC-functionals for the prediction of excitation energies of GFP-like chromophores. In particular, we have considered the TD-DFT vertical excitation energies of chromophores displaying different charge states. We compare the quality of...... six XC-functionals, belonging to the GGA, hybrid and Coulomb-attenuated classes of XC-functionals, by comparison with RI-CC2 results. We find that none of the tested XC-functionals are capable of providing a simultaneous good description of all charge states and, interestingly, the hybrid functionals...

  8. Excited States of DNA Base Pairs Using Long-Range Corrected Time-Dependent Density Functional Theory

    Science.gov (United States)

    Jensen, Lasse; Govind, Niranjan

    2009-08-01

    In this work, we present a study of the excitation energies of adenine, cytosine, guanine, thymine, and the adenine-thymine (AT) and guanine-cytosine (GC) base pairs using long-range corrected (LC) density functional theory. We compare three recent LC functionals, BNL, CAM-B3LYP, and LC-PBE0, with B3LYP and coupled cluster results from the literature. We find that the best overall performance is for the BNL functional based on LDA. However, in order to achieve this good agreement, a smaller attenuation parameter is needed, which leads to nonoptimum performance for ground-state properties. B3LYP, on the other hand, severely underestimates the charge-transfer (CT) transitions in the base pairs. Surprisingly, we also find that the CAM-B3LYP functional also underestimates the CT excitation energy for the GC base pair but correctly describes the AT base pair. This illustrates the importance of retaining the full long-range exact exchange even at distances as short as that of the DNA base pairs. The worst overall performance is obtained with the LC-PBE0 functional, which overestimates the excitations for the individual bases as well as the base pairs. It is therefore crucial to strike a good balance between the amount of local and long-range exact exchange. Thus, this work highlights the difficulties in obtained LC functionals, which provides a good description of both ground- and excited-state properties.

  9. Ghost interaction correction in ensemble density-functional theory for excited states with and without range separation

    CERN Document Server

    Alam, Md Mehboob; Fromager, Emmanuel

    2016-01-01

    Ensemble density-functional theory (eDFT) suffers from the "ghost-interaction" (GI) error when approximate exchange-correlation functionals are used. In this letter, we present a rigorous GI correction (GIC) in the context of multideterminantal range-separated eDFT. The method, which relies on a double generalized adiabatic connection for ensembles, is equally applicable to standard Kohn-Sham eDFT. We show that GIC reduces the curvature of approximate ensemble energies drastically while providing considerably more accurate excitation energies, even for charge-transfer and double excitations.

  10. Excitation function of elliptic flow in Au+Au collisions and the nuclear matter equation of state

    CERN Document Server

    Andronic, A; Basrak, Z; Bastid, N; Benabderrahmane, L; Berek, G; Caplar, R; Cordier, E; Crochet, Philippe; Dupieux, P; Dzelalija, M; Fodor, Z; Gasparic, I; Grishkin, Yu; Hartmann, O N; Herrmann, N; Hildenbrand, K D; Hong, B; Kecskeméti, J; Kim, Y J; Kirejczyk, M; Koczón, P; Korolija, M; Kotte, R; Kress, T; Lebedev, A; Leifels, Y; López, X; Mangiarotti, A; Merschmeyer, M; Neubert, W; Pelte, D; Petrovici, M; Rami, F; Reisdorf, W; de Schauenburg, B; Schüttauf, A; Seres, Z; Sikora, B; Sim, K S; Simion, V; Siwek-Wilczynska, K; Smolyankin, V T; Stockmeier, M R; Stoicea, G; Tyminski, Z; Wagner, P; Wisniewski, K; Wohlfarth, D; Xiao, Z G; Yushmanov, I E; Zhilin, A

    2005-01-01

    We present measurements of the excitation function of elliptic flow at midrapidity in Au+Au collisions at beam energies from 0.09 to 1.49 GeV per nucleon. For the integral flow, we discuss the interplay between collective expansion and spectator shadowing for three centrality classes. A complete excitation function of transverse momentum dependence of elliptic flow is presented for the first time in this energy range, revealing a rapid change with incident energy below 0.4 AGeV, followed by an almost perfect scaling at the higher energies. The equation of state of compressed nuclear matter is addressed through comparisons to microscopic transport model calculations.

  11. Corrosion behaviour of Al/Al3Ti and Al/Al3Zr functionally graded materials produced by centrifugal solid-particle method: Influence of the intermetallics volume fraction

    OpenAIRE

    Ferreira, S. C.; L. A. Rocha; Ariza, E.; Sequeira, P. D.; WATANABE, Yoshimi; Fernandes, J. C. S.

    2011-01-01

    Intermetallic particles, Al3Ti and Al3Zr were formed in Al–5mass%Ti and Al–5mass%Zr alloys, respectively, by centrifugal casting, in order to create functionally graded materials (FGMs). At present, no information is available on the influence of the amount of intermetallics on the electrochemical properties of these alloys. In this paper, the corrosion resistance of Al/Al3Ti and Al/Al3Zr FGMs was investigated by open-circuit measurements, potentiodynamic polarization and electrochemical ...

  12. Synthesis and characterization of Al/SiC and Ni/Al2O3 functionally graded materials

    International Nuclear Information System (INIS)

    Two-multilayered functionally graded materials (FGMs), namely aluminium-silicon carbide (Al/SiC) and nickel-alumina (Ni/Al2O3) systems are designed, synthesized and characterized considering 10, 20, 30 and 40 vol.% ceramic concentrations. Two, three and five-layered FGMs are fabricated into flat beam samples following powder metallurgy route for Al/SiC and thermal spraying technique for Ni/Al2O3 system. Apart from microstructural studies, porosity content and microhardness are also determined. Three bulk properties are evaluated for FGM characterizations, namely effective flexural strength, thermal fatigue behavior and thermal shock resistance. Progressive and appreciable enhancement in FGM performance is observed as the number of layers is increased from two to five keeping the extreme layers same. Microhardness variation across the interfaces is found to be consistent with the analytically obtained jump in the inplane stresses at the interfaces

  13. Change of Work Function of Pd, Ag, K on Al(001) as a Function of External Electric Field

    Institute of Scientific and Technical Information of China (English)

    侯柱峰; 黄美纯; 朱梓忠; 黄荣彬; 郑兰荪

    2001-01-01

    We present a local density functional calculation of the effect of an external electric field on the work function change of Pd and Ag adsorption on an Al(001) surface. The adsorption of K has also been considered for comparison. We found that the work functions for all the systems increased linearly when the strength of the external electric field was increased. Since the polarized electrons at the interstitial regions between the adsorbate and substrate for Pd/Al(001) and Ag/Al(001) react to the external electric field differently, the subtle differences between Pd/Al(001) and Ag/Al(001) bondings has been characterized through the comparison of the slopes of the work function change versus electric field.

  14. Relativistic time-dependent density functional theory, a study of the ground and excited states of the zinc dimer

    Energy Technology Data Exchange (ETDEWEB)

    Kullie, Ossama [CNRS et Universite de Strasbourg, Institut de Chimie, Laboratoire de Chimie Quantique, 1 Rue Blaise Pascal, F- 67008 Strasbourg cedex (France)

    2012-07-01

    In this poster I present a (time-dependent) density functional study of the 20 low-lying excited states as well the ground states of the zinc dimer Zn{sub 2}. I analyze the spectrum of the dimer obtained form all electrons calculations which are performed using time-depended density functional with a relativistic 4-components-, and spin-free-Hamiltonian. I show results for different well-known density functional approximations, in comparing with literature and experimental values, the results are very encouraging, especially for the lowest excited states of these dimers. However, the results show that only the long-range corrected functionals such CAMB3LYP gives the correct asymptotic behavior for the higher states, for which the best result is obtained, and a comparable result is obtained from PBE0 functional.

  15. Magnetophonon resonance in photoluminescence excitation spectra of magnetoexcitons in GaAs/Al0.3Ga0.7As superlattice

    DEFF Research Database (Denmark)

    Dickmann, S.; Tartakovskii, A. I.; Timofeev, V. B.;

    2000-01-01

    to the sample layers. While varying B, the intensities of the PLE peaks have been measured as functions of energy separation Delta E between excited ME peaks and the ground state of the system. The resonance profiles have been found to have maxima at Delta E-max close to the energy of the GaAs LO...

  16. The excitation functions of 187Re(n,2n) 186m,gRe reactions

    Science.gov (United States)

    Huang, Xiao-Long; Kang, Meng-Xiao; Liu, Li-Le; Wang, Ji-Min; Chen, Xiong-Jun

    2016-08-01

    A new value for the emission probability of 137.144 keV γ-rays from 186gRe decay is recommended to be (9.47±0.03)/%. Using this value the measured cross sections for 187Re(n,2n)186mRe and 187Re(n,2n)186gRe reactions around 14 MeV are analyzed, and the cross section for 187Re(n,2n)186m+gRe reaction at 14.8 MeV is (2213±116) mb. The UNF code was adopted to calculate the cross sections for the 187Re(n,2n)186m+gRe reaction below 20 MeV, fitting to the value (2213±116) mb at 14.8 MeV using a set of optimum neutron optical potential parameters which were obtained based on the relevant experimental data of rhenium. The isomeric cross section ratio for the 187Re(n,2n)186m,gRe reaction was analyzed using the V-H method based on nuclear statistical theory. Combining these calculated results, the excitation functions for the 187Re(n,2n)186mRe and 187Re(n,2n)186gRe reactions were obtained. The obtained results are in good agreement with the available experimental data.

  17. Excitation Function of the nat-Ta(p,x)178m2-Hf Reaction

    CERN Document Server

    Titarenko, Yu E; Rogov, V I; Titarenko, A Yu; Yuldashev, S N; Zhivun, V M; Ignatyuk, A V; Mashnik, S G; Leray, S; Boudard, A; David, J -C; Mancusi, D; Cugnon, J; Yariv, Y; Nishihara, K; Matsuda, N; Kumawat, H; Stankovskiy, A Yu

    2013-01-01

    178m2-Hf is an extremely interesting isomeric state due to its potential energy capacity level. One possible way to obtain it is by irradiation of a nat-Ta sample with a high-current proton accelerator. Up to now, there was no information in the international experimental nuclear data base (EXFOR) for this reaction. Irradiations of nat-Ta samples performed for other purposes provide an opportunity to address this question. This paper presents the 172m2-Hf independent production cross-sections determined by gamma-ray spectrometry. The nat-Ta(p,x)172m2-Hf excitation function is studied in the 20-3500 MeV energy range. Comparisons with results by several nuclear models (ISABEL, Bertini, INCL4.5+ABLA07, PHITS, CASCADE07, and CEM03.02) used as event-generators in modern transport codes are also reported. However, since such models are generally not able to separately predict ground and isomeric states of reaction products, only 178-Hf independent and cumulative cross-section data are compared.

  18. A ΔE-E Telescope with Ionization Chamber Used in Excitation Function Measurement

    Institute of Scientific and Technical Information of China (English)

    LiSonglin; WangQi; DongYuchuan; XuHuagen; ChenRuofu

    2003-01-01

    A thorough study of excitation function in dissipative heavy ion collision requires the identification of the nuclear charge number Z of the reaction products. For this purpose, a special designed ΔE-E telescope is employed, which consists of a gas filled ionization chamber to detect the energy loss and a position sensitive semiconductor Si detector (300μm in thickness and 8 mm×45 mm in active area) as the residual energy detector. The ionization chamber with a sensitive length of about 60 mm, is divided into two parts of ΔE1 and ΔE2, each with length of 30 mm. The trajectory of the incident particles is parallel to the direction of the electric field in the ionization chamber. The anodes of ΔE1 and ΔE2 are realized through the rectangular empty metallic frames. In order to collect ionized charge produced by the incident particle inside the ionization chamber effectively, two equipotential frame-shape electrodes were placed on both sides of each anode, to form a strong electric focused field toward the anode. The advantages of this type of the detector arc as follows: (1)lower energy detection threshold; (2) wide dynamical range both for the light particles and the heavy fragments;(3) larger solid angle coverage with a relatively smaller detector size based on the position information from the Si detector.

  19. High-sensitivity measurements of the excitation function for Bhabha scattering at MeV energies

    International Nuclear Information System (INIS)

    Using a monochromatic e+ beam scattered on a Be foil and a high-resolution detector device, the excitation function for elastic e+e- scattering was measured with a statistical accuracy of 0.25% in 1.4 keV steps in the c.m.-energy range between 770 keV and 840 keV (1.79 - 1.86 MeV/c2) at c.m. scattering angles between 800 and 1000 (FWHM). Within the experimental sensitivity of 0.5 b.eV/sr (c.m.) for the energy-integrated differential cross section no resonances were observed (97% CL). From this limit we infer that a hypothetical spinless resonant state should have a width of less than 1.9 meV corresponding to a lifetime limit of 3.5x10-13 s. This limit establishes the most stringent bound for new particles in this mass range derived from Bhabha scattering and is independent of assumptions about the internal structure of the hypothetical particles. Less sensitivite limits were, in addition, derived around 520 keV c.m. energy (≅ 1.54 MeV/c2) from an investigation with a thorium and a mylar foil as scatterers. (orig.)

  20. Dynamics of laser excited colloidal gold nanoparticles functionalized with cysteine derivatives

    International Nuclear Information System (INIS)

    The ultrafast dynamics of Au colloidal nanoparticles excited with femtosecond laser pulses is investigated experimentally. The transient absorption signal presents a bleaching of the surface plasmon band and a transient absorption at the wings of the band. The kinetics of the “hot” electrons in Au nanoparticles show a fast component of around 1 ps and a slower one of approximately 300 ps. Additionally, we found that the time of the ground state population recovery of Au nanoparticles depends on the pump wavelength. Furthermore, the interaction of Au nanoparticles with cysteine and cystine is studied at different pump wavelengths. The increase of the ligand concentration produces a variation of the relaxation times, as well as a delay of the time zero kinetics due to the adsorption of the ligands to the Au surface. - Highlights: • The ultrafast dynamics of AuNPs were investigated using femtosecond laser pulses. • The “hot” electrons dynamics shows two components: fast (1 ps) and slow (300 ps). • We studied the transient absorption behavior of the S-ligands functionalized AuNPs. • The relaxation times varied with increasing the ligand fraction

  1. Sub-barrier fusion excitation function data and energy dependent Woods-Saxon potential

    Science.gov (United States)

    Gautam, Manjeet Singh

    2016-07-01

    This paper analyzed the role of intrinsic degrees of freedom of colliding nuclei in the enhancement of sub-barrier fusion cross-section data of various heavy ion fusion reactions. The influences of inelastic surface vibrations of colliding pairs are found to be dominant and their couplings result in the significantly larger fusion enhancement over the predictions of the one dimensional barrier penetration model at sub-barrier energies. The theoretical calculations are performed by using energy dependent Woods-Saxon potential model (EDWSP model) in conjunction with the one dimensional Wong formula. The effects of dominant intrinsic channels are entertained within framework of the coupled channel calculations obtained by using the code CCFULL. It is quite interesting to note that the energy dependence in Woods-Saxon potential simulates the effects of inelastic surface vibrational states of reactants wherein significantly larger value of diffuseness parameter ranging from a = 0.85 fm to a = 0.95 fm is required to address the observed fusion excitation function data of the various heavy ion fusion reactions.

  2. The formulation of a self-consistent constricted variational density functional theory for the description of excited states

    International Nuclear Information System (INIS)

    Graphical abstract: In constricted variational density functional theory suggested here we perform a unitary transformation (Part A) among the occupied φocc and virtual φvir ground state orbitals to any order in the variational parameter matrix U to obtain the new occupied φocc′ and virtual φvir′ exited state orbitals. From φocc′ we calculate the excited state energy E(U) and optimize it with respect to U under the constraint (Part B) that one electron is transferred from the occupied orbital space to the virtual orbital space. Highlights: ► We outline a self-consistent density functional approach to the calculation of transition energies. ► The approach is an improvement over a previous scheme [Ziegler et al. Chem. Phys. 130, 154102 (2009)]. ► We describe how our method is related to other schemes based on density functional theory. - Abstract: We outline here a self-consistent approach to the calculation of transition energies within density functional theory. The method is based on constricted variational theory (CV-DFT). It constitutes in the first place an improvement over a previous scheme [T. Ziegler, M. Seth, M. Krykunov, J. Autschbach, F. Wang, Chem. Phys. 130 (2009) 154102] in that it includes terms in the variational parameters to any desired order n including n = ∞. For n = 2, CV(n)-DFT is similar to TD-DFT. Adiabatic TD-DFT becomes identical to CV(2)-DFT after the Tamm–Dancoff approximation is applied to both theories. We have termed the new scheme CV(n)-DFT. In the second place, the scheme can be implemented self-consistently, SCF-CV(n)-DFT. The procedure outlined here could also be used to formulate a SCF-CV(n) Hartree–Fock theory. The approach is further kindred to the ΔSCF-DFT procedures predating TD-DFT and we describe how adiabatic TD-DFT and ΔSCF-DFT are related through different approximations to SCF-CV(n)-DFT.

  3. A separately excited synchronous motor as high efficient drive in electric vehicles; Die stromerregte Synchronmaschine als hocheffizienter Traktionsmotor in Elektrofahrzeugen

    Energy Technology Data Exchange (ETDEWEB)

    Illiano, Enzo [ETH Zuerich, Zurich (Switzerland). Inst. fuer Werkzeugmaschinen und Fertigung; Brusa Elektronik AG, Sennfeld (Switzerland)

    2013-08-15

    The separately excited synchronous motor has several advantages which make this topology a very promising traction drive for electric vehicles. The comparison of the separately excited motor with other common topologies also shows the proper regulation of the current in the rotor will rise the complexity of the entire system. In addition the presence of a rotor current has a negative effect on the continuous power of the motor, as the investigations of ETH Zuerich and Brusa show. An optimised motor regulation and an accurate rotor shape design are indispensible to reduce the power deficit. (orig.)

  4. Analytical Hessian of electronic excited states in time-dependent density functional theory with Tamm-Dancoff approximation.

    Science.gov (United States)

    Liu, Jie; Liang, WanZhen

    2011-07-01

    We present the analytical expression and computer implementation for the second-order energy derivatives of the electronic excited state with respect to the nuclear coordinates in the time-dependent density functional theory (TDDFT) with Gaussian atomic orbital basis sets. Here, the Tamm-Dancoff approximation to the full TDDFT is adopted, and therefore the formulation process of TDDFT excited-state Hessian is similar to that of configuration interaction singles (CIS) Hessian. However, due to the replacement of the Hartree-Fock exchange integrals in CIS with the exchange-correlation kernels in TDDFT, many quantitative changes in the derived equations are arisen. The replacement also causes additional technical difficulties associated with the calculation of a large number of multiple-order functional derivatives with respect to the density variables and the nuclear coordinates. Numerical tests on a set of test molecules are performed. The simulated excited-state vibrational frequencies by the analytical Hessian approach are compared with those computed by CIS and the finite-difference method. It is found that the analytical Hessian method is superior to the finite-difference method in terms of the computational accuracy and efficiency. The numerical differentiation can be difficult due to root flipping for excited states that are close in energy. TDDFT yields more exact excited-state vibrational frequencies than CIS, which usually overestimates the values. PMID:21744894

  5. Coupled cluster and density functional studies on geometries and energies of excited C2v states of ozone

    Science.gov (United States)

    Grein, Friedrich

    2009-03-01

    The performance of single-determinant methods for finding geometries and energies of excited states is tested on the ozone molecule. Geometries for low-lying singlet and triplet states of ozone were optimized by CCSD(T) and density functional theory (DFT) (with BPW91 functional) methods. DFT geometries were found to lie close to CCSD(T) values. Most CCSD(T) and DFT geometries and energies are in good agreement with available experimental and recent high-level theoretical values, with deviations lying within 0.02 Å, 2°, and 0.3 eV. An exception is the 1 B12 state, having a larger deviation of bond distance and energy. A multiconfigurational treatment is required for this state. DFT geometry optimizations and calculations of vibrational frequencies were extended to higher states, covering over 30 excited states of ozone, with adiabatic excitation energies up to about 6 eV. Calculated harmonic frequencies showed several states, including 1 B12, to be saddle points. Multireference configuration interaction (MRCI) bending potentials for first and second singlet and triplet states were used in verifying the CCSD(T) and DFT geometries and for locating additional minima. For first states, DFT bending potentials are compared with MRCI potentials. As a criterion for the quality of single-determinant geometries and energies of excited states, comparison of their vertical excitation energies with MRCI or time-dependent DFT values is recommended.

  6. A Preliminary Transcranial Magnetic Stimulation Study of Cortical Inhibition and Excitability in High-Functioning Autism and Asperger Disorder

    Science.gov (United States)

    Enticott, Peter G.; Rinehart, Nicole J.; Tonge, Bruce J.; Bradshaw, John L.; Fitzgerald, Paul B.

    2010-01-01

    Aim: Controversy surrounds the distinction between high-functioning autism (HFA) and Asperger disorder, but motor abnormalities are associated features of both conditions. This study examined motor cortical inhibition and excitability in HFA and Asperger disorder using transcranial magnetic stimulation (TMS). Method: Participants were diagnosed by…

  7. Isobaric analog states of neutron-rich nuclei. Doppler shift as a measurement tool for resonance excitation functions

    International Nuclear Information System (INIS)

    We present a new approach for the measurement of resonance excitation functions of neutron-rich nuclei using Doppler shift information. Preliminary data from the first application of the method is presented in the spectroscopy studies of 7He isobaric analog states in 7Li. (orig.)

  8. Relative importance of energy dependent diffuseness parameter and barrier position in the analysis of fusion excitation function data

    International Nuclear Information System (INIS)

    We have investigated the relative importance of the energy dependence of diffuseness parameter and barrier position in the description of the fusion excitation function data of some heavy ion systems in near barrier energy region. The effects of the energy dependent diffuseness parameter are found to be much more prominent in comparison to those of barrier position. (authors)

  9. Channels Active in the Excitability of Nerves and Skeletal Muscles across the Neuromuscular Junction: Basic Function and Pathophysiology

    Science.gov (United States)

    Goodman, Barbara E.

    2008-01-01

    Ion channels are essential for the basic physiological function of excitable cells such as nerve, skeletal, cardiac, and smooth muscle cells. Mutations in genes that encode ion channels have been identified to cause various diseases and disorders known as channelopathies. An understanding of how individual ion channels are involved in the…

  10. The 90deg excitation function for elastic 12C+12C scattering. The importance of Airy elephants

    International Nuclear Information System (INIS)

    The 90deg excitation function for elastic 12C+12C scattering, at laboratory energies between the Coulomb barrier and 130 MeV, exhibits a complex structure of peaks and valleys whose nature has remained an unsolved mystery for more than 20 years. The problem has primarily been caused by the difficulty of choosing from a plethora of discretely ambiguous optical potentials. However, data accumulated above 150 MeV over the last decade have determined unique potentials at these higher energies, and the requirement of continuity downward in energy has recently permitted the determination of a unique set of potentials for angular distributions at energies below 130 MeV, where the excitation-function data exist. These new potentials are used to provide a mean-field (i.e., nonresonant) interpretation of the structure in the 12C+12C 90deg excitation function between 70 and 130 MeV. Its most prominent minima are found to be Airy minima from nuclear rainbows, with the remaining structure arising primarily from more elementary optical phenomena related to Fraunhofer diffraction. These same potentials are also successful in explaining the details of excitation functions measured very recently at other angles by Morsad. (orig.)

  11. Tuning of the excited state properties of phenylenevinylene oligomers : A time-dependent density functional theory study

    NARCIS (Netherlands)

    Grozema, FC; Telesca, R; Snijders, JG; Siebbeles, LDA

    2003-01-01

    This paper discusses a time-dependent density functional theory study of the effect of molecular structure on the excited state polarizability of conjugated molecules. A short phenylenevinylene oligomer containing three phenyl rings (PV2, distyryl benzene) is taken as a model system. Introduction of

  12. Studying the excitation function of the full cross section of a reaction using a modified transmission technique: Initial results

    Czech Academy of Sciences Publication Activity Database

    Sobolev, Yuri, G.; Penionyhkevich, Y. E.; Borcha, K.; Ivanov, M. P.; Kugler, Andrej; Kulko, A. A.; Kroha, Václav; Maslov, V. A.; Mrázek, Jaromír; Negret, A.; Rvenko, R. V.; Savrov, Ya. Yu.; Skobelev, N. K.; Trzaska, V. G.

    2012-01-01

    Roč. 76, č. 8 (2012), s. 952-957. ISSN 1062-8738 R&D Projects: GA MŠk LA08002 Institutional support: RVO:61389005 Keywords : cross sections * excitation functions * radioactive beams Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders

  13. Relative importance of energy dependent diffuseness parameter and barrier position in the analysis of fusion excitation function data

    Directory of Open Access Journals (Sweden)

    Kharab Rajesh

    2014-03-01

    Full Text Available We have investigated the relative importance of the energy dependence of diffuseness parameter and barrier position in the description of the fusion excitation function data of some heavy ion systems in near barrier energy region. The effects of the energy dependent diffuseness parameter are found to be much more prominent in comparison to those of barrier position.

  14. Melittin restores proteasome function in an animal model of ALS

    OpenAIRE

    Lee Sang Min; Yang Sun Choel; Kim Seon Hwy; Yang Eun Jin; Choi Sun-Mi

    2011-01-01

    Abstract Amyotrophic lateral sclerosis (ALS) is a paralyzing disorder characterized by the progressive degeneration and death of motor neurons and occurs both as a sporadic and familial disease. Mutant SOD1 (mtSOD1) in motor neurons induces vulnerability to the disease through protein misfolding, mitochondrial dysfunction, oxidative damage, cytoskeletal abnormalities, defective axonal transport- and growth factor signaling, excitotoxicity, and neuro-inflammation. Melittin is a 26 amino acid p...

  15. Aromatic Lateral Substituents Influence the Excitation Energies of Hexaaza Lanthanide Macrocyclic Complexes: A Wave Function Theory and Density Functional Study.

    Science.gov (United States)

    Rabanal-León, Walter A; Murillo-López, Juliana A; Páez-Hernández, Dayán; Arratia-Pérez, Ramiro

    2015-09-24

    The high interest in lanthanide chemistry, and particularly in their luminescence, has been encouraged by the need of understanding the lanthanide chemical coordination and how the design of new luminescent materials can be affected by this. This work is focused on the understanding of the electronic structure, bonding nature, and optical properties of a set of lanthanide hexaaza macrocyclic complexes, which can lead to potential optical applications. Here we found that the DFT ground state of the open-shell complexes are mainly characterized by the manifold of low lying f states, having small HOMO-LUMO energy gaps. The results obtained from the wave function theory calculations (SO-RASSI) put on evidence the multiconfigurational character of their ground state and it is observed that the large spin-orbit coupling and the weak crystal field produce a strong mix of the ground and the excited states. The electron localization function (ELF) and the energy decomposition analysis (EDA) support the idea of a dative interaction between the macrocyclic ligand and the lanthanide center for all the studied systems; noting that, this interaction has a covalent character, where the d-orbital participation is evidenced from NBO analysis, leaving the f shell completely noninteracting in the chemical bonding. From the optical part we observed in all cases the characteristic intraligand (IL) (π-π*) and ligand to metal charge-transfer (LMCT) bands that are present in the ultraviolet and visible regions, and for the open-shell complexes we found the inherent f-f electronic transitions on the visible and near-infrared region. PMID:26325624

  16. Validation of geophysical excitation functions by a rigorous combination with Earth orientation parameters and gravity field coefficients

    Science.gov (United States)

    Heiker, A.; Kutterer, H.

    2010-12-01

    Geophysical excitation functions model the re-distribution of atmospheric, oceanic and hydrologic masses. The change of the mass distribution of the Earth affects polar motion and length of day as well as gravity field coefficients of second degree. As all these quantities are related to the unknown Earth's tensor of inertia, a combined analysis allows to identify inconsistencies between the data and to determine the tensor of inertia. Usually, this physical relation between the Earth rotation parameters, excitation functions and second degree gravity field coefficients which is induced by the tensor of inertia, is not considered. In our study, we rigorously exploit it for the independent mutual validation based on least-squares estimation including variance-covariance component estimation. The functional model is based on the well known linear approximation of the Euler-Liouville equation. The construction of an appropriate stochastic model is hindered in practice due to insufficient knowledge on variances and covariances. Here, the missing stochastic information is determined empirically by analyzing the input data. Improved Earth orientation parameters, second degree gravity field coefficients and improved excitation functions are obtained as estimation results. Furthermore the unknown tensor of inertia is determined. The observation residuals indicate the degree of mutual consistency of the data. We give a short overview of our adjustment model. We present and discuss some results obtained from two different oceanic and atmospheric excitations (NCEP + ECCO and ECMWF + OMCT). The analysis and discussion of the resulting estimated excitation functions is emphasized. The work regarding the mutual validation is performed within the project P9 “Combined analysis and validation of Earth rotation models and observations” of the Research Unit FOR 584 (“Earth rotation and global dynamic processes”) which is funded by the German research funding organization DFG.

  17. Vertical electric field induced suppression of fine structure splitting of excited state excitons in a single GaAs/AlGaAs island quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Ghali, Mohsen [Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577 (Japan); Laboratory of Nanophotonics, Physics Department, Faculty of Science, Kafrelsheikh University, 33516 Kafrelsheikh (Egypt); Ohno, Yuzo; Ohno, Hideo [Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577 (Japan)

    2015-09-21

    We report experimentally on fine structure splitting (FSS) of various excitonic transitions in single GaAs island quantum dots, formed by a monolayer thickness fluctuation in the narrow GaAs/AlGaAs quantum well, and embedded in an n-i-Schottky diode device. By applying a forward vertical electric field (F) between the top metallic contact and the sample substrate, we observed an in-plane polarization rotation of both the ground and the excited state excitons with increasing the electric field. The polarization rotations were accompanied with a strong decrease in the FSS of the ground as well as the excited state excitons with the field, until the FSS vanished as F approached 30 kV/cm.

  18. The effect of initial wave functions on electron-impact-induced ionization-excitation reaction of helium

    International Nuclear Information System (INIS)

    In the reaction of electron-impact-induced ionization-excitation of helium, under distorted wave Born approximation model, the triple differential cross sections (TDCS) have been calculated through two kinds of He atom initial wave functions. And the theoretical results are compared with experimental data. These comparisons demonstrate that the TDCS results of the Silverman wave function which contains radial and angular correlations are much better in agreement with experimental results. (authors)

  19. Production and de-excitation modes of hot nuclei in the 84Kr + 12C, 84Kr + 27Al, 84Kr + Nat Ti reactions at 26.4, 34.4 and 45.4 MeV/nucleon

    International Nuclear Information System (INIS)

    The inclusive characteristics of nuclear fragments, of mass greater than 10 uma, from KR + C, Al and Ti reactions at 25, 35 and 45 MeV/u, are investigated. The inverse kinematic method is applied. The analysis of velocity and fragment (mass < 40 uma) spatial distribution show a stable source emission component. Monte Carlo calculations confirm these results, except in the case of Kr + Al and Ti at 45.4 MeV/nucleon. Moreover, part of the events come from non-equilibrium or dissipative processes. For the Kr + C reaction at 25 and 35 MeV/u total fusion, which corresponds to 0.1 of the evaporation croks section. In the other cases, incomplete transfer momentum, higher than the one for evaporation, is observed. Complex nuclear fragment yield determines the reaction hotest nuclei. The source velocities, associated to the evaporation residues and to the complex fragments becomes lower as a function of the system's symmetry. For the Kr + C system, the calculated and experimental data of the source velocity and the mass of evaporation residues are in good agreement. These parameters are overestimated for Ti target. The calculated maximal excitation energies increase as a function of the available energy, reaching 5.8 MeV/u. The complex fragment production cross sections increase with the target's mass. As the available energy increases, the ratio between the production of evaporation residues and complex fragments diminishes. A statistical de-excitation model, which takes into account complex fragment emissions, is applied. The excitation energy remains inferior to 4.2 MeV/nucleon and to the value of the mass transfer hypothesis

  20. Excitation function of the 60Ni(p ,γ )61Cu reaction from threshold to 16 MeV

    Science.gov (United States)

    Uddin, M. S.; Sudár, S.; Spahn, I.; Shariff, M. A.; Qaim, S. M.

    2016-04-01

    Excitation function of the reaction 60Ni(p ,γ )61Cu was measured via the activation technique in the energy range of 1.3-16.0 MeV using a low-energy accelerator and a small cyclotron. The results are comparable to those previously obtained via prompt γ counting. In addition excitation functions of the more common competing 60Ni(p ,n )60Cu and 60Ni(p ,α )57Co reactions were also measured. Theoretical calculations on proton-induced reactions on 60Ni were performed using the nuclear model code talys. The results suggest that near the threshold of the reaction the compound nucleus mechanism dominates. Thereafter the contribution of direct interactions becomes rather strong, especially between 4 and 6 MeV, i.e., just below the threshold of the 60Ni(p ,n )60Cu reaction. The cross section at the maximum of the excitation function of each of the three reactions, namely, 60Ni(p ,γ )61Cu,60Ni(p ,n )60Cu , and 60Ni(p ,α )57Co , amounts to 2, 320, and 85 mb, respectively. The (p ,n ) reaction is thus the most commonly occurring process, and the (p ,γ ) reaction is the weakest, possibly due to higher probability of particle emission than γ-ray emission from the highly excited intermediate nucleus 61Cu formed in the interaction of a proton with the target nucleus 60Ni.

  1. Altered neuronal excitability underlies impaired hippocampal function in an animal model of psychosis

    Directory of Open Access Journals (Sweden)

    Thomas eGrüter

    2015-05-01

    Full Text Available Psychosis is accompanied by severe attentional deficits, and impairments in associational-memory processing and sensory information processing that are ascribed to dysfunctions in prefrontal and hippocampal function. Disruptions of glutamatergic signalling may underlie these alterations: Antagonism of the N-methyl-D-aspartate receptor (NMDAR results in similar molecular, cellular, cognitive and behavioural changes in rodents and/or humans as those that occur in psychosis, raising the question as to whether changes in glutamatergic transmission may be intrinsic to the pathophysiology of the disease. In an animal model of psychosis that comprises treatment with the irreversible NMDAR-antagonist, MK801, we explored the cellular mechanisms that may underlie hippocampal dysfunction in psychosis. MK801-treatment resulted in a profound loss of hippocampal LTP that was evident 4 weeks after treatment. Whereas neuronal expression of the immediate early gene, Arc, was enhanced in the hippocampus by spatial learning in controls, MK801-treated animals failed to show activity-dependent increases in Arc expression. By contrast, a significant increase in basal Arc expression in the absence of learning was evident compared to controls. Paired-pulse facilitation was increased at the 40 ms interval indicating that NMDAR and/or fast GABAergic-mediated neurotransmission was disrupted. In line with this, MK801-treatment resulted in a significant decrease in GABA(A, and increase in GABA(B-receptor-expression in PFC, along with a significant increase of GABA(B- and NMDAR-GluN2B expression in the dentate gyrus. NMDAR-GluN1 or GluN2A subunit expression was unchanged. These data suggest that in psychosis, deficits in hippocampus-dependent memory may be caused by a loss of hippocampal LTP that arises through enhanced hippocampal neuronal excitability, altered GluN2B and GABA receptor expression and an uncoupling of the hippocampus-prefrontal cortex circuitry.

  2. Microscopic description of collective excitations in spherical nuclei: Response functions, transition densities, current and velocity fields

    International Nuclear Information System (INIS)

    Self-consistent Hartree-Fock and RPA calculations with Skyrme-type interactions have been used for a systematic investigation of the natural-parity spin-independent collective excitations with multipolarities λ ≤ 3 in 40Ca and λ ≤ 5 in 208Pb. The nuclear response function to different probes and the correlation energy shift were studied. Low-lying and high-lying (giant resonance) vibrations of both surface and compression type were identified. Transition densities, convection current and velocity fields were calculated and displayed for these states. Contrary to the assumption that collective vibrations have irrotational incompressible flow, a large variety of velocity fields were obtained. Some of them display strong vortices. The possibility to measure the transition currents (and even identify such vortices) in inelastic electron scattering experiments was investigated in detail for the 2+ (4.085 MeV) and 3- (2.615 MeV) states in 208Pb. Theoretical DWBA calculations reproduce the experimental data quite well and show that for 900 and 1600 (where data are available) the transversal currents play only a negligible role. However for 1800 they modify the cross section in a very characteristic way (compared to the longitudinal contribution) and enhance it to values as large as the measured cross sections. This confirms that backward scattering experiments are a unique tool for determing the currents of vibrating nuclei and at the same time strongly supports the feasibility of such measurements. The contribution of the magnetization currents and their possible quenching is also discussed. (orig.)

  3. Hydrogen sulfide regulates cardiovascular function by influencing the excitability of subfornical organ neurons.

    Directory of Open Access Journals (Sweden)

    Markus Kuksis

    Full Text Available Hydrogen sulfide (H2S, a gasotransmitter endogenously found in the central nervous system, has recently been suggested to act as a signalling molecule in the brain having beneficial effects on cardiovascular function. This study was thus undertaken to investigate the effect of NaHS (an H2S donor in the subfornical organ (SFO, a central nervous system site important to blood pressure regulation. We used male Sprague-Dawley rats for both in vivo and in vitro experiments. We first used RT-PCR to confirm our previous microarray analyses showing that mRNAs for the enzymes required to produce H2S are expressed in the SFO. We then used microinjection techniques to investigate the physiological effects of NaHS in SFO, and found that NaHS microinjection (5 nmol significantly increased blood pressure (mean AUC = 853.5±105.7 mmHg*s, n = 5. Further, we used patch-clamp electrophysiology and found that 97.8% (88 of 90 of neurons depolarized in response to NaHS. This response was found to be concentration dependent with an EC50 of 35.6 µM. Coupled with the depolarized membrane potential, we observed an overall increase in neuronal excitability using an analysis of rheobase and action potential firing patterns. This study has provided the first evidence of NaHS and thus H2S actions and their cellular correlates in SFO, implicating this brain area as a site where H2S may act to control blood pressure.

  4. The effect of Al segregation on Schottky barrier height and effective work function in TiAl/TiN/HfO2 gate stacks

    Science.gov (United States)

    Kim, Geun-Myeong; Oh, Young Jun; Chang, K. J.

    2016-07-01

    We perform first-principles density functional calculations to investigate the effects of Al incorporation on the p-type Schottky barrier height ≤ft({φ\\text{p}}\\right) and the effective work function for various high-k/metal gate stacks, such as TiN/HfO2 with interface Al impurities, Ti1‑x Al x N/HfO2, and TiAl/TiN/HfO2. When Al atoms substitute for the interface Ti atoms at TiN/HfO2 interface, interface dipole fields become stronger, leading to the increase of {φ\\text{p}} and thereby the n-type shift of effective work function. In Ti1‑x Al x N/HfO2 interface, {φ\\text{p}} linearly increases with the Al content, attributed to the presence of interface Al atoms. On the other hand, in TiAl/TiN/HfO2 interface, where Al is assumed not to segregate from TiAl to TiN, {φ\\text{p}} is nearly independent of the thickness of TiAl. Our results indicate that Al impurities at the metal/dielectric interface play an important role in controlling the effective work function, and provide a clue to understanding the n-type shift of the effective work function observed in TiAl/TiN/HfO2 gate stacks fabricated by using thegate-last process.

  5. Analytical approach for the excited-state Hessian in time-dependent density functional theory: Formalism, implementation, and performance

    Science.gov (United States)

    Liu, Jie; Liang, WanZhen

    2011-11-01

    The paper presents the formalism, implementation, and performance of the analytical approach for the excited-state Hessian in the time-dependent density functional theory (TDDFT) that extends our previous work [J. Liu and W. Z. Liang, J. Chem. Phys. 135, 014113 (2011)] on the analytical Hessian in TDDFT within Tamm-Dancoff approximation (TDA) to full TDDFT. In contrast to TDA-TDDFT, an appreciable advantage of full TDDFT is that it maintains the oscillator strength sum rule, and therefore yields more precise results for the oscillator strength and other related physical quantities. For the excited-state harmonic vibrational frequency calculation, however, full TDDFT does not seem to be advantageous since the numerical tests demonstrate that the accuracy of TDDFT with and without TDA are comparable to each other. As a common practice, the computed harmonic vibrational frequencies are scaled by a suitable scale factor to yield good agreement with the experimental fundamental frequencies. Here we apply both the optimized ground-state and excited-state scale factors to scale the calculated excited-state harmonic frequencies and find that the scaling decreases the root-mean-square errors. The optimized scale factors derived from the excited-state calculations are slightly smaller than those from the ground-state calculations.

  6. Theoretical study of excited states of DNA base dimers and tetramers using optimally tuned range-separated density functional theory.

    Science.gov (United States)

    Sun, Haitao; Zhang, Shian; Zhong, Cheng; Sun, Zhenrong

    2016-03-15

    Excited states of various DNA base dimers and tetramers including Watson-Crick H-bonding and stacking interactions have been investigated by time-dependent density functional theory using nonempirically tuned range-separated exchange (RSE) functionals. Significant improvements are found in the prediction of excitation energies and oscillator strengths, with results comparable to those of high-level coupled-cluster (CC) models (RI-CC2 and EOM-CCSD(T)). The optimally-tuned RSE functional significantly outperforms its non-tuned (default) version and widely-used B3LYP functional. Compared to those high-level CC benchmarks, the large mean absolute deviations of conventional functionals can be attributed to their inappropriate amount of exact exchange and large delocalization errors which can be greatly eliminated by tuning approach. Furthermore, the impacts of H-bonding and π-stacking interactions in various DNA dimers and tetramers are analyzed through peak shift of simulated absorption spectra as well as corresponding change of absorption intensity. The result indicates the stacking interaction in DNA tetramers mainly contributes to the hypochromicity effect. The present work provides an efficient theoretical tool for accurate prediction of optical properties and excited states of nucleobase and other biological systems. © 2015 Wiley Periodicals, Inc. PMID:26666212

  7. Fabrication of Al-W Functionally Graded Impact Material via Vacuum Hot-Pressing Sintering Method

    International Nuclear Information System (INIS)

    Dense graded material as a type of functionally graded material (FGM) changes its wave impedance gradually along the thickness direction. In this investigation, Al-W functionally graded material was fabricated via vacuum hot-pressing sintering method (VHPS). The results showed that densified Al-W composite was fabricated at 550°C-300MPa-120min which the relative density was higher than 98.5% without intermetallic compounds. The density graded material of Al-W FGM was attained at the optimized parameters which the component of Al was from 10% to 100%. The micro structure of Al-W FGM composite indicated that W particles in single-layer composite were distributed homogeneously. The density of each layer in Al-W FGM composite was consistent with the design value.

  8. Excitation functions of proton induced reactions on natOs up to 65 MeV: Experiments and comparison with results from theoretical codes

    International Nuclear Information System (INIS)

    Activation of thin natOs targets, electrodeposited on Ni backings, was investigated for the first time in stacked foil irradiations with 65 MeV and 34 MeV proton beams. Assessments of the produced radionuclides by high resolution gamma-ray spectroscopy yielded excitation functions for formation of 184, 185, 186m,m+g, 187m+g, 188m+g, 189m2+m1+g, 190m2,m1+g, 192m1+gIr and 185cum, 191m+gOs, 183m+gRe. Where available comparisons with the reaction cross sections obtained in 2 earlier studies on enriched 192Os were made. Reduced uncertainty on cross sections is obtained by simultaneous remeasurement of the 27Al(p,x)22,24Na, natNi(p,x)57Ni and natTi(p,x)48V monitor reactions over wide relevant energy ranges. Confirmation of monitoring took place by assessment of excitation functions of 61Cu, 56Ni, 55,56,57,58Co and 52Mn induced in the Ni backings and comparison with a recent compilation for most of these radionuclides. Contributing reactions and overall cross sections are discussed and were evaluated in comparison with the results of the theoretical code TALYS 1.6 (values from the on-line library TENDL-2013)

  9. Dynamics of electron excitations in densely packed plasmonic Ag/Na3AlF6 nanostructures under pulsed laser action

    Science.gov (United States)

    Buganov, O. V.; Zamkovets, A. D.; Ponyavina, A. N.; Tikhomirov, S. A.; Baran, L. V.

    2011-11-01

    Differential transient absorption spectra have been studied for planar densely packed Ag/Na3AlF6 nanostructures under ultrashort laser pulse excitation. The nanostructures were fabricated by sequential thermal evaporation of cryolite (Na3AlF6) and silver in vacuo onto glass and quartz substrates. A nonmonotonic variation in relaxation times of induced changes in a surface plasmon resonance band was observed with an increase in the metal surface density that resulted in nanoparticle size growth and structural modification of the densely packed layer. The tendency of the relaxation times to vary nonmonotonically is explained by both features of intrinsic size effects and electron-tunneling processes in plasmonic densely packed nanostructures of various topologies.

  10. Dynamics of electron excitations in densely packed plasmonic Ag/Na3AlF6 nanostructures under pulsed laser action

    International Nuclear Information System (INIS)

    Differential transient absorption spectra have been studied for planar densely packed Ag/Na3AlF6 nanostructures under ultrashort laser pulse excitation. The nanostructures were fabricated by sequential thermal evaporation of cryolite (Na3AlF6) and silver in vacuo onto glass and quartz substrates. A nonmonotonic variation in relaxation times of induced changes in a surface plasmon resonance band was observed with an increase in the metal surface density that resulted in nanoparticle size growth and structural modification of the densely packed layer. The tendency of the relaxation times to vary nonmonotonically is explained by both features of intrinsic size effects and electron-tunneling processes in plasmonic densely packed nanostructures of various topologies. (authors)

  11. Density functional theory study of neutral AlSn(n = 2–9) clusters

    International Nuclear Information System (INIS)

    This paper investigates the geometrical structures and relative stabilities of neutral AlSn(n = 2–9) using the density functional theory. Structural optimisation and frequency analysis are performed at the B3LYP/6–311G(d) level. The ground state structures of the AlSn show that the sulfur atoms prefer not only to evenly distribute on both sides of the aluminum atom but also to form stable structures in AlSn clusters. The structures of pure Sn are fundamentally changed due to the doping of the Al atom. The fragmentation energies and the second-order energy differences are calculated and discussed. Among neutral AlSn(n = 2–9) clusters, AIS4 and AlS6 are the most stable. (atomic and molecular physics)

  12. Nonlinear electronic excitations in crystalline solids using meta-generalized gradient approximation and hybrid functional in time-dependent density functional theory

    Science.gov (United States)

    Sato, Shunsuke A.; Taniguchi, Yasutaka; Shinohara, Yasushi; Yabana, Kazuhiro

    2015-12-01

    We develop methods to calculate electron dynamics in crystalline solids in real-time time-dependent density functional theory employing exchange-correlation potentials which reproduce band gap energies of dielectrics; a meta-generalized gradient approximation was proposed by Tran and Blaha [Phys. Rev. Lett. 102, 226401 (2009)] (TBm-BJ) and a hybrid functional was proposed by Heyd, Scuseria, and Ernzerhof [J. Chem. Phys. 118, 8207 (2003)] (HSE). In time evolution calculations employing the TB-mBJ potential, we have found it necessary to adopt the predictor-corrector step for a stable time evolution. We have developed a method to evaluate electronic excitation energy without referring to the energy functional which is unknown for the TB-mBJ potential. For the HSE functional, we have developed a method for the operation of the Fock-like term in Fourier space to facilitate efficient use of massive parallel computers equipped with graphic processing units. We compare electronic excitations in silicon and germanium induced by femtosecond laser pulses using the TB-mBJ, HSE, and a simple local density approximation (LDA). At low laser intensities, electronic excitations are found to be sensitive to the band gap energy: they are close to each other using TB-mBJ and HSE and are much smaller in LDA. At high laser intensities close to the damage threshold, electronic excitation energies do not differ much among the three cases.

  13. Nonlinear electronic excitations in crystalline solids using meta-generalized gradient approximation and hybrid functional in time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Shunsuke A. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); Taniguchi, Yasutaka [Center for Computational Science, University of Tsukuba, Tsukuba 305-8571 (Japan); Department of Medical and General Sciences, Nihon Institute of Medical Science, 1276 Shimogawara, Moroyama-Machi, Iruma-Gun, Saitama 350-0435 (Japan); Shinohara, Yasushi [Max Planck Institute of Microstructure Physics, 06120 Halle (Germany); Yabana, Kazuhiro [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); Center for Computational Science, University of Tsukuba, Tsukuba 305-8571 (Japan)

    2015-12-14

    We develop methods to calculate electron dynamics in crystalline solids in real-time time-dependent density functional theory employing exchange-correlation potentials which reproduce band gap energies of dielectrics; a meta-generalized gradient approximation was proposed by Tran and Blaha [Phys. Rev. Lett. 102, 226401 (2009)] (TBm-BJ) and a hybrid functional was proposed by Heyd, Scuseria, and Ernzerhof [J. Chem. Phys. 118, 8207 (2003)] (HSE). In time evolution calculations employing the TB-mBJ potential, we have found it necessary to adopt the predictor-corrector step for a stable time evolution. We have developed a method to evaluate electronic excitation energy without referring to the energy functional which is unknown for the TB-mBJ potential. For the HSE functional, we have developed a method for the operation of the Fock-like term in Fourier space to facilitate efficient use of massive parallel computers equipped with graphic processing units. We compare electronic excitations in silicon and germanium induced by femtosecond laser pulses using the TB-mBJ, HSE, and a simple local density approximation (LDA). At low laser intensities, electronic excitations are found to be sensitive to the band gap energy: they are close to each other using TB-mBJ and HSE and are much smaller in LDA. At high laser intensities close to the damage threshold, electronic excitation energies do not differ much among the three cases.

  14. Nonlinear electronic excitations in crystalline solids using meta-generalized gradient approximation and hybrid functional in time-dependent density functional theory

    International Nuclear Information System (INIS)

    We develop methods to calculate electron dynamics in crystalline solids in real-time time-dependent density functional theory employing exchange-correlation potentials which reproduce band gap energies of dielectrics; a meta-generalized gradient approximation was proposed by Tran and Blaha [Phys. Rev. Lett. 102, 226401 (2009)] (TBm-BJ) and a hybrid functional was proposed by Heyd, Scuseria, and Ernzerhof [J. Chem. Phys. 118, 8207 (2003)] (HSE). In time evolution calculations employing the TB-mBJ potential, we have found it necessary to adopt the predictor-corrector step for a stable time evolution. We have developed a method to evaluate electronic excitation energy without referring to the energy functional which is unknown for the TB-mBJ potential. For the HSE functional, we have developed a method for the operation of the Fock-like term in Fourier space to facilitate efficient use of massive parallel computers equipped with graphic processing units. We compare electronic excitations in silicon and germanium induced by femtosecond laser pulses using the TB-mBJ, HSE, and a simple local density approximation (LDA). At low laser intensities, electronic excitations are found to be sensitive to the band gap energy: they are close to each other using TB-mBJ and HSE and are much smaller in LDA. At high laser intensities close to the damage threshold, electronic excitation energies do not differ much among the three cases

  15. Ab initio geometry and bright excitation of carotenoids: Quantum Monte Carlo and Many Body Green's Function Theory calculations on peridinin

    CERN Document Server

    Coccia, Emanuele; Guidoni, Leonardo

    2014-01-01

    In this letter we report the singlet ground state structure of the full carotenoid peridinin by means of variational Monte Carlo (VMC) calculations. The VMC relaxed geometry has an average bond length alternation of 0.1165(10) {\\AA}, larger than the values obtained by DFT (PBE, B3LYP and CAM-B3LYP) and shorter than that calculated at the Hartree-Fock (HF) level. TDDFT and EOM-CCSD calculations on a reduced peridinin model confirm the HOMO-LUMO major contribution of the Bu+-like (S2) bright excited state. Many Body Green's Function Theory (MBGFT) calculations of the vertical excitation energy of the Bu+-like state for the VMC structure (VMC/MBGFT) provide excitation energy of 2.62 eV, in agreement with experimental results in n-hexane (2.72 eV). The dependence of the excitation energy on the bond length alternation in the MBGFT and TDDFT calculations with different functionals is discussed.

  16. Communication: Hole localization in Al-doped quartz SiO2 within ab initio hybrid-functional DFT

    International Nuclear Information System (INIS)

    We investigate the long-standing problem of hole localization at the Al impurity in quartz SiO2, using a relatively recent DFT hybrid-functional method in which the exchange fraction is obtained ab initio, based on an analogy with the static many-body COHSEX approximation to the electron self-energy. As the amount of the admixed exact exchange in hybrid functionals has been shown to be determinant for properly capturing the hole localization, this problem constitutes a prototypical benchmark for the accuracy of the method, allowing one to assess to what extent self-interaction effects are avoided. We obtain good results in terms of description of the charge localization and structural distortion around the Al center, improving with respect to the more popular B3LYP hybrid-functional approach. We also discuss the accuracy of computed hyperfine parameters, by comparison with previous calculations based on other self-interaction-free methods, as well as experimental values. We discuss and rationalize the limitations of our approach in computing defect-related excitation energies in low-dielectric-constant insulators

  17. Communication: Hole localization in Al-doped quartz SiO{sub 2} within ab initio hybrid-functional DFT

    Energy Technology Data Exchange (ETDEWEB)

    Gerosa, Matteo [Department of Energy, Politecnico di Milano, via Ponzio 34/3, 20133 Milano (Italy); Di Valentin, Cristiana; Pacchioni, Gianfranco [Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi 55, 20125 Milan (Italy); Bottani, Carlo Enrico, E-mail: carlo.bottani@polimi.it [Department of Energy, Politecnico di Milano, via Ponzio 34/3, 20133 Milano (Italy); Center for Nano Science and Technology @Polimi, Istituto Italiano di Tecnologia, via Pascoli 70/3, 20133 Milano (Italy); Onida, Giovanni [Dipartimento di Fisica dell’ Universita’ degli Studi di Milano and European Theoretical Spectroscopy Facility (ETSF), Via Celoria 16, 20133 Milan (Italy)

    2015-09-21

    We investigate the long-standing problem of hole localization at the Al impurity in quartz SiO{sub 2}, using a relatively recent DFT hybrid-functional method in which the exchange fraction is obtained ab initio, based on an analogy with the static many-body COHSEX approximation to the electron self-energy. As the amount of the admixed exact exchange in hybrid functionals has been shown to be determinant for properly capturing the hole localization, this problem constitutes a prototypical benchmark for the accuracy of the method, allowing one to assess to what extent self-interaction effects are avoided. We obtain good results in terms of description of the charge localization and structural distortion around the Al center, improving with respect to the more popular B3LYP hybrid-functional approach. We also discuss the accuracy of computed hyperfine parameters, by comparison with previous calculations based on other self-interaction-free methods, as well as experimental values. We discuss and rationalize the limitations of our approach in computing defect-related excitation energies in low-dielectric-constant insulators.

  18. Enhanced excitation efficiency of Eu ions in Eu-doped GaN/AlGaN multiple quantum well structures grown by organometallic vapor phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Arai, Takanori; Timmerman, Dolf; Wakamatsu, Ryuta; Lee, Dong-gun; Koizumi, Atsushi; Fujiwara, Yasufumi, E-mail: fujiwara@mat.eng.osaka-u.ac.jp

    2015-02-15

    We have grown Eu-doped GaN (GaN:Eu)/AlGaN multiple quantum well (MQW:Eu) structures by organometallic vapor phase epitaxy and investigated their Eu luminescence properties. The MQW:Eu structures exhibited enhancement of Eu photoluminescence (PL) intensity with an integrated intensity which was three times higher than that of conventional GaN:Eu structures. PL and time-resolved PL measurements suggest that this enhancement is due to the improvement of the excitation efficiency of Eu ions in the MQW:Eu structure. Following these results, we have successfully fabricated a light-emitting diode based on the MQW:Eu structures, which demonstrated an improved output power efficiency of red light. - Highlights: • Eu doped GaN quantum well structures were grown by OMVPE. • The luminescence properties of these structures were studied. • Both electrical and optical excitations of Eu ions are possible. • Both excitation methods show an increased efficiency. • The mechanism behind the increased efficiency is discussed.

  19. Enhanced excitation efficiency of Eu ions in Eu-doped GaN/AlGaN multiple quantum well structures grown by organometallic vapor phase epitaxy

    International Nuclear Information System (INIS)

    We have grown Eu-doped GaN (GaN:Eu)/AlGaN multiple quantum well (MQW:Eu) structures by organometallic vapor phase epitaxy and investigated their Eu luminescence properties. The MQW:Eu structures exhibited enhancement of Eu photoluminescence (PL) intensity with an integrated intensity which was three times higher than that of conventional GaN:Eu structures. PL and time-resolved PL measurements suggest that this enhancement is due to the improvement of the excitation efficiency of Eu ions in the MQW:Eu structure. Following these results, we have successfully fabricated a light-emitting diode based on the MQW:Eu structures, which demonstrated an improved output power efficiency of red light. - Highlights: • Eu doped GaN quantum well structures were grown by OMVPE. • The luminescence properties of these structures were studied. • Both electrical and optical excitations of Eu ions are possible. • Both excitation methods show an increased efficiency. • The mechanism behind the increased efficiency is discussed

  20. Pre-equilibrium analysis of the excitation functions of (α, xn) reactions up to 50 MeV

    International Nuclear Information System (INIS)

    Stacked foil activation technique has been employed for the investigation of alpha particle induced reactions in the target element indium up to 50 MeV. Four excitation functions for the (α, xn) type of reactions were studied using high resolution Ge(Li) gamma ray spectroscopy. Three new energy point cross sections were measured for the first time. A comparison with pre-equilibrium hybrid model and the more recent index model has been made using the initial exciton number n0 = 4(4p0h). In general the shapes of the excitation functions were rather fairly reproduced with both the models. However, hybrid model gives better agreement than index model in the high energy region. (author). 24 refs., 3 figs., 1 tab

  1. Excitation functions for (d,x) reactions on (133)Cs up to Ed=40MeV.

    Science.gov (United States)

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

    2016-04-01

    In the frame of a systematic study of excitation functions of deuteron induced reactions the excitation functions of the (133)Cs(d,x)(133m,133mg,131mg)Ba,(134,)(132)Cs and (12)(9m)Xe nuclear reactions were measured up to 40MeV deuteron energies by using the stacked foil irradiation technique and γ-ray spectroscopy of activated samples. The results were compared with calculations performed with the theoretical nuclear reaction codes ALICE-IPPE-D, EMPIRE II-D and TALYS calculation listed in the TENDL-2014 library. A moderate agreement was obtained. Based on the integral yields deduced from our measured cross sections, production of (131)Cs via the (133)Cs(d,4n)(131)Ba→(131)Cs reaction and (133)Ba via (133)Cs(d,2n) reactions is discussed in comparison with other charged particle production routes. PMID:26773822

  2. Electron Emission by Doppler-Mediated Formation of Doubly Excited H -** in Grazing Incidence of Protons on Clean Al(111)

    Czech Academy of Sciences Publication Activity Database

    Lörinčík, Jan; Šroubek, Zdeněk; Aumayr, H.; Winter, H. P.

    2001-01-01

    Roč. 54, č. 5 (2001), s. 633-639. ISSN 0295-5075 R&D Projects: GA AV ČR IAA1067801 Institutional research plan: CEZ:AV0Z4040901 Keywords : ion scattering from surfaces * Doppler-mediated formation * Al(111) Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.304, year: 2001

  3. The program TXRES - convolution of sharp excitation cross-section with triple-axis resolution function

    International Nuclear Information System (INIS)

    The program TXRES can be used to calculate the intensity at points on a triple-axis spectrometer scan by evaluating a convolution integral to determine the sharp excitation spectrum with no intrinsic broadening. Having described the program, subroutines called in the program, the use of the program, input date, output, availability, storage, and CPU time taken, are explained. (U.K.)

  4. Local scale transformation method with more than one scalar functions for description of monopole excitations in nuclei

    International Nuclear Information System (INIS)

    An extension of the Local-Scale Transformation Method (LSTM) by inclusion of N scalar functions is suggested. An application of LSTM to the Hartree-Fock theory is considered. By means of the suggested approach an investigation of the 'breathing' monopole excitation mode within the Adiabatic limit of the Time-Dependent Hartree-Fock Theory (ATDHF) is carried out. Numeric results in a particular case of pure scale transformation using the Skyrme forces for the nucleus 16O are obtained

  5. Excitation Functions of Fusion and Fission for 32S+170Er at Energies Near and Below Coulomb Barrier

    Institute of Scientific and Technical Information of China (English)

    BAO; Peng-fei; LIN; Cheng-jian; YANG; Feng; JIA; Hui-ming; XU; Xin-xing; YANG; Lei; SUN; Li-jie; MA; Nan-ru; ZHANG; Huan-qiao; LIU; Zu-hua

    2013-01-01

    Excitation functions of fusion evaporation residue(ER)and fission for 32S+170Er system at near barrier energy region were measured,respectively.With the comparison to the calculations of coupledchannels effects,it is accessible to investigate the impacts on the fusion and fission processes of target deformation and the dependence on the entrance-channel.The experiment was performed at Beijing HI-13 Tandem Accelerator.Fission and fusion evaporation

  6. Optical and magnetic excitations of metal-encapsulating Si cages: A systematic study by time-dependent density functional theory

    OpenAIRE

    Oliveira, Micael J. T.; Medeiros, Paulo V. C.; Sousa, José R. F.; Nogueira, Fernando; Gueorguiev, Gueorgui K.

    2013-01-01

    Systematic study of the optical and magnetic excitations of twelve MSi$_{12}$ and four MSi$_{10}$ transition metal encapsulating Si cages has been carried out by employing real time time-dependent density functional theory. Criteria for the choice of transition metals (M) are clusters' stability, synthesizability, and diversity. It was found that both the optical absorption and the spin-susceptibility spectra are mainly determined by, in decreasing order of importance: 1) the cage shape, 2) t...

  7. Variation of Excited-State Dynamics in Trifluoromethyl Functionalized C60 Fullerenes

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jaehong; Ramirez, Jessica J.; Clikeman, Tyler T.; Larson, Bryon W.; Boltalina, Olga V.; Strauss, Steven H.; Rumbles, Garry

    2016-09-07

    We report on electronically excited-state dynamics of three different trifluoromethyl C60 fullerenes (TMFs, C60(CF3)n: C60/4-1, C60/6-2, and C60/10-1, featuring four, six, and ten trifluoromethyl groups, respectively) using steady-state and time-resolved optical spectroscopy as well as ultrafast pump/probe transient absorption spectroscopy. C60/4-1 and C60/6-2 dissolved in toluene solvent show near-unity S1--T1 intersystem crossing quantum yield (..phi..ISC), ca. 1 ns S1-state lifetimes, and microsecond-timescale T1-state lifetimes, which are typical of the fullerene class. On the other hand, C60/10-1 exhibits a dominant sub-nanosecond nonradiative S1--S0 relaxation mechanism and negligible ..phi..ISC, therefore decreasing the average excited-state lifetime (..tau..avg) by about 5 orders of magnitude compared to that of C60/4-1 and C60/6-2 (..tau..avg approx. 17 us and 54 us for C60/4-1 and C60/6-2, respectively, whereas ..tau..avg approx. 100 ps for C60/10-1). These excited-state characteristics of C60/4-1 and C60/6-2 are preserved in polymer matrix, suggesting that fullerene/polymer interactions do not modulate intrinsic photophysics of trifluoromethyl-substituted fullerenes. The contrasting excited- state study results of C60/4-1 and C60/6-2 to that of C60/10-1 infer that intrinsic optical properties and excited-state dynamics can be affected by the substitution on the fullerene.

  8. Variation of excited-state dynamics in trifluoromethyl functionalized C60 fullerenes.

    Science.gov (United States)

    Park, Jaehong; Ramirez, Jessica J; Clikeman, Tyler T; Larson, Bryon W; Boltalina, Olga V; Strauss, Steven H; Rumbles, Garry

    2016-08-17

    We report on electronically excited-state dynamics of three different trifluoromethyl C60 fullerenes (TMFs, C60(CF3)n: C60/4-1, C60/6-2, and C60/10-1, featuring four, six, and ten trifluoromethyl groups, respectively) using steady-state and time-resolved optical spectroscopy as well as ultrafast pump/probe transient absorption spectroscopy. C60/4-1 and C60/6-2 dissolved in toluene solvent show near-unity S1 → T1 intersystem crossing quantum yield (ΦISC), ca. 1 ns S1-state lifetimes, and microsecond-timescale T1-state lifetimes, which are typical of the fullerene class. On the other hand, C60/10-1 exhibits a dominant sub-nanosecond nonradiative S1 → S0 relaxation mechanism and negligible ΦISC, therefore decreasing the average excited-state lifetime (τavg) by about 5 orders of magnitude compared to that of C60/4-1 and C60/6-2 (τavg ≈ 17 μs and 54 μs for C60/4-1 and C60/6-2, respectively, whereas τavg ≈ 100 ps for C60/10-1). These excited-state characteristics of C60/4-1 and C60/6-2 are preserved in polymer matrix, suggesting that fullerene/polymer interactions do not modulate intrinsic photophysics of trifluoromethyl-substituted fullerenes. The contrasting excited-state study results of C60/4-1 and C60/6-2 to that of C60/10-1 infer that intrinsic optical properties and excited-state dynamics can be affected by the substitution on the fullerene. PMID:27485768

  9. Measurement and analysis of excitation functions and observation of mass-asymmetry effect on incomplete fusion dynamics

    Directory of Open Access Journals (Sweden)

    Rashid M.H.

    2011-10-01

    Full Text Available Excitation functions for sixteen evaporation residues produced in the interaction of 20Ne with 165Ho have been measured in the projectile energy range ≈88-164 MeV, using catcher foil activation technique followed by gamma-ray spectrometry. It has been found in general that the excitation functions of evaporation residues produced via xn/pxn channels satisfactorily reproduced with the statistical model code PACE-2 after subtraction of precursor decay contribution. The significant enhancement in the measured excitation functions for the residues produced in alpha emission channels over the PACE-2 predictions has been observed. These alpha emission channels are attributed to incomplete fusion reaction process. The results indicate the occurrence of incomplete fusion involving break-up of projectile 20Ne into 4He + 16O and /or 8Be + 12C followed by fusion of one of the fragments with target nucleus 165Ho. The analysis of the present data suggest that probability of incomplete fusion increases with projectile energy. The ICF fraction FICF also increases with increasing mass-asymmetry of the entrance channel.

  10. Relative level excitation in ion-atom collisions as a function of the orbital angular momentum quantum number

    International Nuclear Information System (INIS)

    In a previous study of projectile Rydberg state excitations in the collisions Be+, Mg+-He at 10-75 keV it was found, for a fixed value of the principal quantum number n, that the ratio of the s, p, and d level cross sections was close to 1:3:5, whereas the f and g level cross sections drop to approximately the same value as for s levels. Blaney and Berry (1976) found essentially the same increase in cross section for electron transfer into excited Li I states in the Li+-H2 collision. In contrast to this behavior, beam-foil excitations oscillate as a function of the orbital angular momentum quantum number with maxima at odd values of l (p, f,...) and minima at even l (s, d, g,...). Since no model is available to describe these features, the measurements have been extended to other systems to test their general validity. A large conjugated molecule (benzene) was chosen as target gas in one experiment to bridge the gap between ion-atom and ion-foil excitations. The data presented here have all been obtained by optical spectrometry. A quasi molecular approach is used to explain the results. (Auth.)

  11. NiAl(110)/Cr(110) interface: A density functional theory study

    Science.gov (United States)

    Liu, W.; Li, J. C.; Zheng, W. T.; Jiang, Q.

    2006-05-01

    The optimal geometries, thermodynamic properties, and electronic structures of NiAl(110)/Cr(110) interface are studied using a first-principle density functional plane-wave ultrasoft pseudopotential method. Surface energies of different NiAl surfaces are compared with those obtained based on the classical broken-bond rule. Simulation results indicate that the structure of Ni and Al placed in the hollow sites of Cr atoms at the interface is more thermodynamically stable, and the NiCr bonding is dominated by 3d electrons of Ni and Cr. It is found that NiAl(110)/Cr(110) alloying could lower brittleness of NiAl compounds. With simulated values of adhesion work and interface energy for NiAl(110)/Cr(110) system, its mechanical and thermodynamic properties are also discussed.

  12. Formation of Sm2+ ions in femtosecond laser excited Al2O3 - SiO2 glasses

    International Nuclear Information System (INIS)

    Al2O3 - SiO2 glasses doped with Sm3+ ions were irradiated with an 800 nm wavelength femtosecond laser pulse and the formation of Sm2+ ions was investigated. The Sm3+ ions were reduced to Sm2+ within a few minutes of laser irradiation. Electron spin resonance spectra indicated that the hole was trapped in non-bridging oxygen bound to Al3+, while the electron was captured in the Sm3+, leading to the Sm2+ formation. The thermal stability of the photoinduced Sm2+ ions was also investigated by fluorescence spectroscopy. The Sm2+ ions were converted to Sm3+ ions by heating the glasses in air at 300- 400 deg. C

  13. Cosmogenic nuclide production rates as a function of latitude and altitude calculated via a physics based model and excitation functions

    Science.gov (United States)

    Argento, D.; Reedy, R. C.; Stone, J. O.

    2012-12-01

    Cosmogenic nuclides have been used to develop a set of tools critical to the quantification of a wide range of geomorphic and climatic processes and events (Dunai 2010). Having reliable absolute measurement methods has had great impact on research constraining ice age extents as well as providing important climatic data via well constrained erosion rates, etc. Continuing to improve CN methods is critical for these sciences. While significant progress has been made in the last two decades to reduce uncertainties (Dunai 2010; Gosse & Phillips 2001), numerous aspects still need to be refined in order to achieve the analytic resolution desired by glaciologists and geomorphologists. In order to investigate the finer details of the radiation responsible for cosmogenic nuclide production, we have developed a physics based model which models the radiation cascade of primary and secondary cosmic-rays through the atmosphere. In this study, a Monte Carlo method radiation transport code, MCNPX, is used to model the galactic cosmic-ray (GCR) radiation impinging on the upper atmosphere. Beginning with a spectrum of high energy protons and alpha particles at the top of the atmosphere, the code tracks the primary and resulting secondary particles through a model of the Earth's atmosphere and into the lithosphere. Folding the neutron and proton flux results with energy dependent cross sections for nuclide production provides production rates for key cosmogenic nuclides (Argento et al. 2012, in press; Reedy 2012, in press). Our initial study for high latitude shows that nuclides scale at different rates for each nuclide (Argento 2012, in press). Furthermore, the attenuation length for each of these nuclide production rates increases with altitude, and again, they increase at different rates. This has the consequence of changing the production rate ratio as a function of altitude. The earth's geomagnetic field differentially filters low energy cosmic-rays by deflecting them away

  14. Influence of neglected covariances on the estimation of Earth rotation parameters, geophysical excitation functions and second degree gravity field coefficients

    Science.gov (United States)

    Heiker, Andrea; Kutterer, Hansjörg

    2010-05-01

    The Earth rotation variability is redundantly described by the combination of Earth rotation parameters (polar motion and length of day), geophysical excitation functions and second degree gravity field coefficients. There exist some publications regarding the comparison of the Earth rotation parameters and excitation functions. However, most authors do not make use of the redundancy. In addition, existing covariances between the input parameters are not considered. As shown in previous publications we use the redundancy for the independent mutual validation of the Earth rotation parameters, excitation functions and second degree gravity field coefficients based on an extended Gauss-Markov model and least-squares adjustment. The work regarding the mutual validation is performed within the project P9 "Combined analysis and validation of Earth rotation models and observations" of the research Unit FOR 584 ("Earth rotation and global dynamic processes") which is funded by the German Research Unit (DFG); see also abstract "Combined Analysis and Validation of Earth Rotation Models and Observations". The adjustment model is determined at first by the joint functional relations between the parameters and second by the stochastic model of the input data. A variance-covariance component estimation is included in the adjustment model. The functional model is based on the linearized Euler-Liouville equation. The construction of an appropriate stochastic model is prevented in practice by insufficient knowledge on variances and covariances. However, some numerical results derived from arbitrarily chosen stochastic models indicate that the stochastic model may be crucial for a correct estimation. The missing information is approximated by analyzing the input data. Synthetic variance-covariance matrices are constructed by considering empirical auto- and cross-correlation functions. The influence of neglected covariances is quantified and discussed by comparing the results derived

  15. Double excitations and state-to-state transition dipoles in π-π∗ excited singlet states of linear polyenes: Time-dependent density-functional theory versus multiconfigurational methods

    Science.gov (United States)

    Mikhailov, Ivan A.; Tafur, Sergio; Masunov, Artëm E.

    2008-01-01

    The effect of static and dynamic electron correlation on the nature of excited states and state-to-state transition dipole moments is studied with a multideterminant wave function approach on the example of all-trans linear polyenes ( C4H6 , C6H8 , and C8H10 ). Symmetry-forbidden singlet nAg states were found to separate into three groups: purely single, mostly single, and mostly double excitations. The excited-state absorption spectrum is dominated by two bright transitions: 1Bu-2Ag and 1Bu-mAg , where mAg is the state, corresponding to two-electron excitation from the highest occupied to lowest unoccupied molecular orbital. The richness of the excited-state absorption spectra and strong mixing of the doubly excited determinants into lower- nAg states, reported previously at the complete active space self-consistent field level of theory, were found to be an artifact of the smaller active space, limited to π orbitals. When dynamic σ-π correlation is taken into account, single- and double-excited states become relatively well separated at least at the equilibrium geometry of the ground state. This electronic structure is closely reproduced within time-dependent density-functional theory (TD DFT), where double excitations appear in a second-order coupled electronic oscillator formalism and do not mix with the single excitations obtained within the linear response. An extension of TD DFT is proposed, where the Tamm-Dancoff approximation (TDA) is invoked after the linear response equations are solved (a posteriori TDA). The numerical performance of this extension is validated against multideterminant-wave-function and quadratic-response TD DFT results. It is recommended for use with a sum-over-states approach to predict the nonlinear optical properties of conjugated molecules.

  16. Excitation energies,for a benchmark set of molecules obtained within time-dependent current-density functional theory using the Vignale-Kohn functional

    OpenAIRE

    van Faassen, M.; de Boeij, PL

    2004-01-01

    In this article we explain how the existing linear response theory of time-dependent density-functional theory can be extended to. obtain excitation.,energies in the framework of time-dependent current-density-functional theory. We use the Vignale-Kohn current-functional [G. Vignale and W. Kohn, Phys. Rev. Lett. 77, 2037 (1996)] which has proven to be successful for describing ultranonlocal exchange-correlation effects in the case of the axial polarizability of molecular chains [M. van Faasse...

  17. Multi-functional smart aggregate-based structural health monitoring of circular reinforced concrete columns subjected to seismic excitations

    International Nuclear Information System (INIS)

    In this paper, a recently developed multi-functional piezoceramic-based device, named the smart aggregate, is used for the health monitoring of concrete columns subjected to shake table excitations. Two circular reinforced concrete columns instrumented with smart aggregates were fabricated and tested with a recorded seismic excitation at the structural laboratory at the University of Nevada—Reno. In the tests, the smart aggregates were used to perform multiple monitoring functions that included dynamic seismic response detection, structural health monitoring and white noise response detection. In the proposed health monitoring approach, a damage index was developed on the basis of the comparison of the transfer function with the baseline function obtained in the healthy state. A sensor-history damage index matrix is developed to monitor the damage evolution process. Experimental results showed that the acceleration level can be evaluated from the amplitude of the dynamic seismic response; the damage statuses at different locations were evaluated using a damage index matrix; the first modal frequency obtained from the white noise response decreased with increase of the damage severity. The proposed multi-functional smart aggregates have great potential for use in the structural health monitoring of large-scale concrete structures

  18. Investigating the contribution of VAPB/ALS8 loss of function in amyotrophic lateral sclerosis.

    Science.gov (United States)

    Kabashi, Edor; El Oussini, Hajer; Bercier, Valérie; Gros-Louis, François; Valdmanis, Paul N; McDearmid, Jonathan; Mejier, Inge A; Dion, Patrick A; Dupre, Nicolas; Hollinger, David; Sinniger, Jérome; Dirrig-Grosch, Sylvie; Camu, William; Meininger, Vincent; Loeffler, Jean-Philippe; René, Frédérique; Drapeau, Pierre; Rouleau, Guy A; Dupuis, Luc

    2013-06-15

    The mutations P56S and T46I in the gene encoding vesicle-associated membrane protein-associated protein B/C (VAPB) cause ALS8, a familial form of amyotrophic lateral sclerosis (ALS). Overexpression of mutant forms of VAPB leads to cytosolic aggregates, suggesting a gain of function of the mutant protein. However, recent work suggested that the loss of VAPB function could be the major mechanism leading to ALS8. Here, we used multiple genetic and experimental approaches to study whether VAPB loss of function might be sufficient to trigger motor neuron degeneration. In order to identify additional ALS-associated VAPB mutations, we screened the entire VAPB gene in a cohort of ALS patients and detected two mutations (A145V and S160Δ). To directly address the contribution of VAPB loss of function in ALS, we generated zebrafish and mouse models with either a decreased or a complete loss of Vapb expression. Vapb knockdown in zebrafish led to swimming deficits. Mice knocked-out for Vapb showed mild motor deficits after 18 months of age yet had innervated neuromuscular junctions (NMJs). Importantly, overexpression of VAPB mutations were unable to rescue the motor deficit caused by Vapb knockdown in zebrafish and failed to cause a toxic gain-of-function defect on their own. Thus, Vapb loss of function weakens the motor system of vertebrate animal models but is on its own unable to lead to a complete ALS phenotype. Our findings are consistent with the notion that VAPB mutations constitute a risk factor for motor neuron disease through a loss of VAPB function. PMID:23446633

  19. Hole trapping at Al impurities in silica: A challenge for density functional theories

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper; Stokbro, Kurt

    2001-01-01

    The atomic geometry and electronic structure around a neutral substitutional Al impurity in silica is investigated using either the unrestricted Hartree-Fock (UHF) approximation, or Beckes three-parameter hybrid functional (B3LYP). It is found that the B3LYP functional fails to describe the...

  20. Two-photon excited fluorescence of intrinsic fluorophores enables label-free assessment of adipose tissue function

    Science.gov (United States)

    Alonzo, Carlo Amadeo; Karaliota, Sevasti; Pouli, Dimitra; Liu, Zhiyi; Karalis, Katia P.; Georgakoudi, Irene

    2016-01-01

    Current methods for evaluating adipose tissue function are destructive or have low spatial resolution. These limit our ability to assess dynamic changes and heterogeneous responses that occur in healthy or diseased subjects, or during treatment. Here, we demonstrate that intrinsic two-photon excited fluorescence enables functional imaging of adipocyte metabolism with subcellular resolution. Steady-state and time-resolved fluorescence from intracellular metabolic co-factors and lipid droplets can distinguish the functional states of excised white, brown, and cold-induced beige fat. Similar optical changes are identified when white and brown fat are assessed in vivo. Therefore, these studies establish the potential of non-invasive, high resolution, endogenous contrast, two-photon imaging to identify distinct adipose tissue types, monitor their functional state, and characterize heterogeneity of induced responses. PMID:27491409

  1. Spin transport in undoped InGaAs/AlGaAs multiple quantum well studied via spin photocurrent excited by circularly polarized light.

    Science.gov (United States)

    Zhu, Laipan; Liu, Yu; Huang, Wei; Qin, Xudong; Li, Yuan; Wu, Qing; Chen, Yonghai

    2016-12-01

    The spin diffusion and drift at different excitation wavelengths and different temperatures have been studied in undoped InGaAs/AlGaAs multiple quantum well (MQW). The spin polarization was created by optical spin orientation using circularly polarized light, and the reciprocal spin Hall effect was employed to measure the spin polarization current. We measured the ratio of the spin diffusion coefficient to the mobility of spin-polarized carriers. From the wavelength dependence of the ratio, we found that the spin diffusion and drift of holes became as important as electrons in this undoped MQW, and the ratio for light holes was much smaller than that for heavy holes at room temperature. From the temperature dependence of the ratio, the correction factors for the common Einstein relationship for spin-polarized electrons and heavy holes were firstly obtained to be 93 and 286, respectively. PMID:26744148

  2. Density functional theory and evolution algorithm calculations of elastic properties of AlON

    International Nuclear Information System (INIS)

    Different models for aluminum oxynitride (AlON) were calculated using density functional theory and optimized using an evolutionary algorithm. Evolutionary algorithm and density functional theory (DFT) calculations starting from several models of AlON with different Al or O vacancy locations and different positions for the N atoms relative to the vacancy were carried out. The results show that the constant anion model [McCauley et al., J. Eur. Ceram. Soc. 29(2), 223 (2009)] with a random distribution of N atoms not adjacent to the Al vacancy has the lowest energy configuration. The lowest energy structure is in a reasonable agreement with experimental X-ray diffraction spectra. The optimized structure of a 55 atom unit cell was used to construct 220 and 440 atom models for simulation cells using DFT with a Gaussian basis set. Cubic elastic constant predictions were found to approach the experimentally determined AlON single crystal elastic constants as the model size increased from 55 to 440 atoms. The pressure dependence of the elastic constants found from simulated stress-strain relations were in overall agreement with experimental measurements of polycrystalline and single crystal AlON. Calculated IR intensity and Raman spectra are compared with available experimental data

  3. Advisory function of the Tales of the Prophets (Qiṣaṣ al-anbiyāʾ)

    OpenAIRE

    Helewa, Sami

    2012-01-01

    This thesis examines the advisory function of the tales of three prophets (Joseph, David and Solomon) in al-Ṭabarī’s (d. 923/310 AH) History and al-Thaʿlabī’s (d. 1025/416) Tales of the Prophets within their religio-political contexts in Baghdād and Nīshāpūr respectively. The hypothesis is that by reading the tales through the prism of Islamic advice literature, in particular the works of Ibn al-Muqaffaʿ (d. 757 / 139) and Kay Kāʾūs (d. 1084 /476), one sees how these stories co...

  4. Modeling Spin Fluctuations and Magnetic Excitations from Time-Dependent Density Functional Theory

    Science.gov (United States)

    Gorni, Tommaso; Timrov, Iurii; Dal Corso, Andrea; Baroni, Stefano

    Harnessing spin fluctuations and magnetic excitations in materials is key in many fields of technology, spanning from memory devices to information transfer and processing, to name but a few. A proper understanding of the interplay between collective and single-particle spin excitations is still lacking, and it is expected that first-principle simulations based on TDDFT may shed light on this interplay, as well as on the role of important effects such as relativistic ones and related magnetic anisotropies. All the numerical approaches proposed so far to tackle this problem are based on the computationally demanding solution of the Sternheimer equations for the response orbitals or the even more demanding solution of coupled Dyson equations for the spin and charge susceptibilities. The Liouville-Lanczos approach to TDDFT has already proven to be a valuable alternative, the most striking of its features being the avoidance of sums over unoccupied single-particle states and the frequency-independence of the main numerical bottleneck. In this work we present an extension of this methodology to magnetic systems and its implementation in the Quantum ESPRESSO distribution, together with a few preliminary results on the magnon dispersions in bulk Fe.

  5. Generalized adiabatic connection in ensemble density-functional theory for excited states: example of the H2 molecule

    CERN Document Server

    Franck, Odile

    2013-01-01

    A generalized adiabatic connection for ensembles (GACE) is presented. In contrast to the traditional adiabatic connection formulation, both ensemble weights and interaction strength can vary along a GACE path while the ensemble density is held fixed. The theory is presented for non-degenerate two-state ensembles but it can in principle be extended to any ensemble of fractionally occupied excited states. Within such a formalism an exact expression for the ensemble exchange-correlation density-functional energy, in terms of the conventional ground-state exchange-correlation energy, is obtained by integration over the ensemble weight. Stringent constraints on the functional are thus obtained when expanding the ensemble exchange-correlation energy through second order in the ensemble weight. For illustration purposes, the analytical derivation of the GACE is presented for the H2 model system in a minimal basis, leading thus to a simple density-functional approximation to the ensemble exchange-correlation energy. ...

  6. Time-dependent density functional study of the electronic potential energy curves and excitation spectrum of the oxygen molecule

    Science.gov (United States)

    Guan, Jingang; Wang, Fan; Ziegler, Tom; Cox, Hazel

    2006-07-01

    Orbital energies, ionization potentials, molecular constants, potential energy curves, and the excitation spectrum of O2 are calculated using time-dependent density functional theory (TDDFT) with Tamm-Dancoff approximation (TDA). The calculated negative highest occupied molecular orbital energy (-ɛHOMO) is compared with the energy difference ionization potential for five exchange correlation functionals consisting of the local density approximation (LDAxc), gradient corrected Becke exchange plus Perdew correlation (B88X+P86C), gradient regulated asymptotic correction (GRAC), statistical average of orbital potentials (SAOP), and van Leeuwen and Baerends asymptotically correct potential (LB94). The potential energy curves calculated using TDDFT with the TDA at internuclear distances from 1.0to1.8Å are divided into three groups according to the electron configurations. The 1πu41πg2 electron configuration gives rise to the XΣg-3, aΔg1, and bΣg +1 states; the 1πu31πg3 electron configuration gives rise to the cΣu -1, CΔu3, and AΣu +3 states; and the BΣu -3, AΔu1, and fΣu +1 states are determined by the mixing of two or more electron configurations. The excitation spectrum of the oxygen molecule, calculated with the aforementioned exchange correlation functionals, shows that the results are quite sensitive to the choice of functional. The LDAxc and the B88X+P86C functionals produce similar spectroscopic patterns with a single strongly absorbing band positioned at 19.82 and 19.72eV, respectively, while the asymptotically corrected exchange correlation functionals of the SAOP and the LB94 varieties yield similar excitation spectra where the computed strongly absorbing band is located at 16.09 and 16.42eV, respectively. However, all of the exchange correlation functionals yield only one strongly absorbing band (oscillator strength greater than 0.1) in the energy interval of 0-20eV, which is assigned to a XΣg -3 to Σu-3 transition. Furthermore, the oxygen

  7. Coupled cluster method with single and double excitations tailored by matrix product state wave functions

    CERN Document Server

    Veis, Libor; Neese, Frank; Legeza, Örs; Pittner, Jiří

    2016-01-01

    We present an alternative method for accurate treatment of strongly correlated systems which combines the coupled cluster (CC) theory with the density matrix renormalization group method (DMRG). The connection is done in the spirit of the tailored CC method [T. Kinoshita, O. Hino, and R. J. Bartlett, \\textit{J. Chem. Phys.} {\\bf 123} (2005) 074106]. In the first step, the configuration interaction (CI) coefficients corresponding to single and double excitations within the DMRG active space are computed by contraction of the matrix product state (MPS) matrices. These coefficients are subsequently transformed into CC amplitudes. In the second step, the CC amplitudes are used to define a "tailored" single reference CCSD wavefunction. As a result, the DMRG method is responsible for the proper description of non-dynamic correlation, whereas the dynamic correlation is incorporated through the framework of the CC theory. We illustrate the potential of this method on prominent multireference model systems like N$_2$ ...

  8. Quantum Monte Carlo, time-dependent density functional theory, and density functional theory calculations of diamondoid excitation energies and Stokes shifts

    CERN Document Server

    Marsusi, F; Drummond, N D

    2011-01-01

    We have computed the absorption and emission energies and hence Stokes shifts of small diamondoids as a function of size using different theoretical approaches, including density functional theory and quantum Monte Carlo (QMC) calculations. The absorption spectra of these molecules were also investigated by time-dependent density functional theory (TD-DFT) and compared with experiment. We have analyzed the structural distortion and formation of a self-trapped exciton in the excited state, and we have studied the effects of these on the Stokes shift as a function of size. Compared to recent experiments, QMC overestimates the excitation energies by about 0.8(1) eV on average. Benefiting from a cancellation of errors, the optical gaps obtained in DFT calculations with the B3LYP functional are in better agreement with experiment. It is also shown that TD-B3LYP calculations can reproduce most of the features found in the experimental spectra. According to our calculations, the structures of diamondoids in the exci...

  9. Group-II acceptors in wurtzite AlN: A screened hybrid density functional study

    OpenAIRE

    Szabo, Aron; Tien Son, Ngyen; Janzén, Erik; Gali, Adam

    2010-01-01

    We systematically studied the group-II acceptors in wurtzite AlN by screened hybrid density functional calculations. We show that the shallowest isolated group-II substitutional defect is Mg, while codoping of Mg and O may yield even shallower acceptor level. Original Publication:Aron Szabo, Ngyen Tien Son, Erik Janzén and Adam Gali, Group-II acceptors in wurtzite AlN: A screened hybrid density functional study, 2010, APPLIED PHYSICS LETTERS, (96), 19, 192110.http://dx.doi.org/10.1063/1.3...

  10. Peripheral monocytes are functionally altered and invade the CNS in ALS patients.

    Science.gov (United States)

    Zondler, Lisa; Müller, Kathrin; Khalaji, Samira; Bliederhäuser, Corinna; Ruf, Wolfgang P; Grozdanov, Veselin; Thiemann, Meinolf; Fundel-Clemes, Katrin; Freischmidt, Axel; Holzmann, Karlheinz; Strobel, Benjamin; Weydt, Patrick; Witting, Anke; Thal, Dietmar R; Helferich, Anika M; Hengerer, Bastian; Gottschalk, Kay-Eberhard; Hill, Oliver; Kluge, Michael; Ludolph, Albert C; Danzer, Karin M; Weishaupt, Jochen H

    2016-09-01

    Amyotrophic lateral sclerosis (ALS) is a devastating progressive neurodegenerative disease affecting primarily the upper and lower motor neurons. A common feature of all ALS cases is a well-characterized neuroinflammatory reaction within the central nervous system (CNS). However, much less is known about the role of the peripheral immune system and its interplay with CNS resident immune cells in motor neuron degeneration. Here, we characterized peripheral monocytes in both temporal and spatial dimensions of ALS pathogenesis. We found the circulating monocytes to be deregulated in ALS regarding subtype constitution, function and gene expression. Moreover, we show that CNS infiltration of peripheral monocytes correlates with improved motor neuron survival in a genetic ALS mouse model. Furthermore, application of human immunoglobulins or fusion proteins containing only the human Fc, but not the Fab antibody fragment, increased CNS invasion of peripheral monocytes and delayed the disease onset. Our results underline the importance of peripheral monocytes in ALS pathogenesis and are in agreement with a protective role of monocytes in the early phase of the disease. The possibility to boost this beneficial function of peripheral monocytes by application of human immunoglobulins should be evaluated in clinical trials. PMID:26910103

  11. Investigations of the potential functions of weakly bound diatomic molecules and laser-assisted excitive Penning ionization

    International Nuclear Information System (INIS)

    Three variations on the Dunham series expansion function of the potential of a diatomic molecule are compared. The differences among these expansions lie in the choice of the expansion variable, lambda. The functional form of these variables are lambda/sub s/ = l-r/sub e//r for the Simon-Parr-Finlan version, lambda/sub T/ - 1-(r/sub e//r)/sup p/ for that of Thakkar, and lambda/sub H/ = 1-exp(-rho(r/r/sub e/-1) for that of Huffaker. A wide selection of molecular systems are examined. It is found that, for potentials in excess of thirty kcal/mole, the Huffaker expansion provides the best description of the three, extrapolating at large internuclear separation to a value within 10% of the true dissociation energy. For potentials that result from the interaction of excited states, all series expansions show poor behavior away from the equilibrium internuclear separation of the molecule. The series representation of the potentials of weakly bound molecules are examined in more detail. The ground states of BeAr+, HeNe+, NaAr, and Ar2 and the excited states of HeNe+, NaNe, and NaAr are best described by the Thakkar expansion. Finally, the observation of laser-assisted excitive Penning ionization in a flowing afterglow is reported. The reaction Ar(3P2) + Ca + h nu → Ar + Ca+(5p 2P/sub J/) + e- occurs when the photon energy, h nu, is approximately equal to the energy difference between the metastable argon and one of the fine structure levels of the ion's doublet. By monitoring the cascade fluorescence of the above reaction and comparing it to the flourescence from the field-free process Ar(3P2) + Ca → Ar + Ca+(4p 2P/sub J/) + e- a surprisingly large cross section of 6.7 x 103 A2 is estimated

  12. Complete and incomplete fusion reactions in the 16O+169Tm system: Excitation functions and recoil range distributions

    International Nuclear Information System (INIS)

    With the view to study complete and incomplete fusion in heavy ion induced reactions, experiments have been carried out for measuring excitation functions for several reactions in the system 16O+169Tm at energies near the Coulomb barrier to well above it, using an activation technique. The measured excitation functions have been compared with those calculated theoretically using three different computer codes viz., ALICE-91, CASCADE and PACE2. The enhancement of experimentally measured cross sections for alpha emission channels over their theoretical prediction has been attributed to the fact that these residues are formed not only by complete fusion but also through incomplete fusion. In order to separate out the relative contributions of complete and incomplete fusion, the recoil range distributions of eight residues produced in the interaction of 16O with 169Tm at ≅87 MeV have been measured. The recoil range distributions indicate significant contributions from incomplete fusion at ≅87 MeV for some of the channels

  13. Measurement and analysis of excitation functions and forward recoil range distributions in 12C + 59Co system

    International Nuclear Information System (INIS)

    With the motivation of studying complete and incomplete fusion reactions in a 12C+59Co projectile target system, the excitation functions for (C, p3n), (C, 2p2n), (C, αn), (C, α2n), (C, αp3n) and (C, 2α2n) reactions have been measured up to 80 MeV. The well-known activation technique followed by offline high purity Ge γ-ray spectroscopy was used. The measured experimental values were compared with the statistical model calculations by using the ALICE-91 and CASCADE codes. For the calculations obtained by CASCADE, the variation of parameter Fθ, which is the ratio of actual moment of inertia to the rigid body value have also been studied. Considerable enhancement of the measured excitation functions compared to theoretical predictions for some channels clearly indicates the presence of incomplete fusion with complete fusion in the present projectile energy range. The measurements of forward recoil range distribution of evaporation residues at 80 MeV projectile energy confirm these observations. (author)

  14. New excitation functions for proton induced reactions on natural titanium, nickel and copper up to 70 MeV

    Science.gov (United States)

    Garrido, E.; Duchemin, C.; Guertin, A.; Haddad, F.; Michel, N.; Métivier, V.

    2016-09-01

    New excitation functions for proton induced nuclear reactions on natural titanium, nickel and copper were measured, using the stacked-foil technique and gamma spectrometry, up to 70 MeV. The experimental cross sections were measured using the Ti-nat(p,x) V-48, Ni-nat(p,x) Ni-57 and Cu-nat(p,x) Zn-62,Co-56 monitor reactions recommended by the International Atomic Energy Agency (IAEA), depending on the investigated energy range. Data have been extracted for the Ti-nat(p,x) Sc-43,44m,46,47,48, V-48, K-42,43, Ni-nat(p,x) Ni-56,57, Co-55,56,57,58, Mn-52,54, Cu-nat(p,x) Cu-61,64, Ni-57, Co-56,57,58,60, Zn-62,65, Mn-54 reactions. Our results are discussed and compared to the existing ones as well as with the TALYS code version 1.6 calculations using default models. Our experimental data are in overall good agreement with the literature. TALYS is able to reproduce, in most cases, the experimental trend. Our new experimental results allow to expand our knowledge on these excitation functions, to confirm the existing trends and to give additional values on a large energy range. This work is in line with the new Coordinated Research Project (CRP) launched by the IAEA to expand the database of monitor reactions.

  15. Charge-displacement analysis for excited states

    Energy Technology Data Exchange (ETDEWEB)

    Ronca, Enrico, E-mail: enrico@thch.unipg.it; Tarantelli, Francesco, E-mail: francesco.tarantelli@unipg.it [Istituto CNR di Scienze e Tecnologie Molecolari, via Elce di Sotto 8, I-06123 Perugia (Italy); Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, via Elce di Sotto 8, I-06123 Perugia (Italy); Pastore, Mariachiara, E-mail: chiara@thch.unipg.it; Belpassi, Leonardo; De Angelis, Filippo [Istituto CNR di Scienze e Tecnologie Molecolari, via Elce di Sotto 8, I-06123 Perugia (Italy); Angeli, Celestino; Cimiraglia, Renzo [Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Ferrara, via Borsari 46, I-44100 Ferrara (Italy)

    2014-02-07

    We extend the Charge-Displacement (CD) analysis, already successfully employed to describe the nature of intermolecular interactions [L. Belpassi et al., J. Am. Chem. Soc. 132, 13046 (2010)] and various types of controversial chemical bonds [L. Belpassi et al., J. Am. Chem. Soc. 130, 1048 (2008); N. Salvi et al., Chem. Eur. J. 16, 7231 (2010)], to study the charge fluxes accompanying electron excitations, and in particular the all-important charge-transfer (CT) phenomena. We demonstrate the usefulness of the new approach through applications to exemplary excitations in a series of molecules, encompassing various typical situations from valence, to Rydberg, to CT excitations. The CD functions defined along various spatial directions provide a detailed and insightful quantitative picture of the electron displacements taking place.

  16. Ejected-electron excitation functions of the (4p55s2)2P3/2,1/2 autoionizing states of rubidium atoms excited by 15 to 640 eV electrons

    International Nuclear Information System (INIS)

    Ejected-electron excitation functions of the (4p55s2)2P3/2,1/2 leading autoionizing doublet in rubidium atoms were measured for the incident electron energy ranges from threshold up to 640 eV. The excitation functions show strong negative-ion resonances near threshold and broad maxima, typical for dipole-allowed transitions, around 100 eV. The excitation cross sections reach the maximum value of 1.1·10−17 cm2 at 15.9 eV and 0.3·10−17 cm2 at 16.9 eV for 2P3/2 and 2P1/2 states, respectively.

  17. Variational polaron self-interaction-corrected total-energy functional for charge excitations in insulators

    Science.gov (United States)

    Sadigh, Babak; Erhart, Paul; Ã berg, Daniel

    2015-08-01

    We conduct a detailed investigation of the polaron self-interaction (pSI) error in standard approximations to the exchange-correlation (XC) functional within density-functional theory (DFT). The pSI leads to delocalization error in the polaron wave function and energy, as calculated from the Kohn-Sham (KS) potential in the native charge state of the polaron. This constitutes the origin of the systematic failure of DFT to describe the polaron formation in band insulators. It is shown that the delocalization error in these systems is, however, largely absent in the KS potential of the closed-shell neutral charge state. This leads to a modification of the DFT total-energy functional that corrects the pSI in the XC functional. The resulting pSIC-DFT method constitutes an accurate parameter-free ab initio methodology for calculating polaron properties in insulators at a computational cost that is orders of magnitude smaller than hybrid XC functionals. Unlike approaches that rely on parametrized localized potentials such as DFT+U , the pSIC-DFT method properly captures both site and bond-centered polaron configurations. This is demonstrated by studying formation and migration of self-trapped holes in alkali halides (bond-centered) as well as self-trapped electrons in an elpasolite compound (site-centered). The pSIC-DFT approach consistently reproduces the results obtained by hybrid XC functionals parametrized by DFT+G0W0 calculations. Finally, we generalize the pSIC approach to hybrid functionals, and show that in stark contrast to conventional hybrid calculations of polaron energies, the pSIC-hybrid method is insensitive to the parametrization of the hybrid XC functional. On this basis, we further rationalize the success of the pSIC-DFT approach.

  18. Exact wave functions and excitation spectra of the one-dimensional double-exchange model with one mobile electron

    International Nuclear Information System (INIS)

    Motivated by recent studies of the in-gap (or nonquasiparticle) states in the half-metallic ferromagnets, we study the one-dimensional double-exchange model with one mobile electron. We solve the Schrödinger equation analytically and obtain the energies and wave functions for all the eigenstates exactly. As an application, we compute the single-particle Green's function. We show that the single-particle spectrum is entirely incoherent and the lowest band has an infinite band mass; i.e., the single electron is localized due to its interaction with the spin excitations. Implication on the observed in-gap states in the half-metallic ferromagnets is considered.

  19. Excitation spectra and rf response near the polaron-to-molecule transition from the functional renormalization group

    International Nuclear Information System (INIS)

    A light impurity in a Fermi sea undergoes a transition from a polaron to a molecule for increasing interaction. We develop a method to compute the spectral functions of the polaron and molecule in a unified framework based on the functional renormalization group with full self-energy feedback. We discuss the energy spectra and decay widths of the attractive and repulsive polaron branches as well as the molecular bound state, and confirm the scaling of the excited-state decay rate near the transition. The quasiparticle weight of the polaron shifts from the attractive to the repulsive branch across the transition, while the molecular bound state has a very small residue characteristic for a composite particle. We propose an experimental procedure to measure the repulsive branch in a 6Li Fermi gas using rf spectroscopy and calculate the corresponding spectra.

  20. Determination of the default curve for the unfolding procedure in the measurement of threshold neutron excitation functions

    Energy Technology Data Exchange (ETDEWEB)

    Jovancevic, Nikola; Daraban, Laura; Oberstedt, Stephan, E-mail: stephan.oberstedt@ec.europa.eu

    2014-03-01

    In this study we have improved the technique for measuring the neutron activation cross-section using wide energy neutron beams (NAXSUN). We propose a method for the determination of the default function for the unfolding procedure, which is an important and critical part for extracting reaction cross-sections from this type of measurements. The new method was tested on the measurement of the excitation function from the threshold energy up to 5.6 MeV for the {sup 113}In(n,n'){sup 113m}In and {sup 115}In(n,n'){sup 115m}In reactions. - Highlights: • Determination of default curve for unfolding procedure solely based on actual measurement. • No input from data libraries or model calculations necessary.

  1. Determination of the default curve for the unfolding procedure in the measurement of threshold neutron excitation functions

    International Nuclear Information System (INIS)

    In this study we have improved the technique for measuring the neutron activation cross-section using wide energy neutron beams (NAXSUN). We propose a method for the determination of the default function for the unfolding procedure, which is an important and critical part for extracting reaction cross-sections from this type of measurements. The new method was tested on the measurement of the excitation function from the threshold energy up to 5.6 MeV for the 113In(n,n')113mIn and 115In(n,n')115mIn reactions. - Highlights: • Determination of default curve for unfolding procedure solely based on actual measurement. • No input from data libraries or model calculations necessary

  2. Formative versus Reflective Measurement in Executive Functions: A Critique of Willoughby et al.

    Science.gov (United States)

    Peterson, Eric; Welsh, Marilyn C.

    2014-01-01

    Research into executive functioning (EF) has indeed grown exponentially across the past few decades, but as the Willoughby et al. critique makes clear, there remain fundamental questions to be resolved. The crux of their argument is built upon an examination of the confirmatory factor analysis (CFA) approach to understanding executive processes.…

  3. Functional properties of the sintered tool materials with (Ti,AlN coating

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2009-10-01

    Full Text Available Purpose: The paper presents investigation results of functional properties of the sintered tool materials: high-speed steel matrix composites (HSSMC, cemented carbides, cermets and Al2O3 type oxide tool ceramics with (Ti,AlN coating deposited in the cathodic arc evaporation CAE-PVD method and comparing them with the uncoated tool materials.Design/methodology/approach: Analysis of the mechanical and functional properties: surface roughness, microhardness tests, scratch tests, cutting tests. X-ray qualitative microanalysis of elements.Findings: Deposition of (Ti,AlN coating onto high-speed steel matrix composites (HSSMC, cemented carbides, cermet and Al2O3 type oxide tool ceramics substrate causes increase of wear resistance as well as reduces the exceeding of steady stresses critical levels. It causes multiple (up to 800% increase of tool life. As a result of metallographic observations it was stated that linear and uniform character of wear was achieved in case of all deposited samples.Practical implications: Employment of the hard coatings deposited onto sintered tool materials is reckoned as one of the most important achievements last year in the area of improvement of functional properties of cutting tools.Originality/value: Combination of substrates (especially coatings deposited on high-speed steel matrix composite is unique and very interesting in respect of achieved functional properties.

  4. Does the regulation of local excitation-inhibition balance aid in recovery of functional connectivity? A computational account.

    Science.gov (United States)

    Vattikonda, Anirudh; Surampudi, Bapi Raju; Banerjee, Arpan; Deco, Gustavo; Roy, Dipanjan

    2016-08-01

    Computational modeling of the spontaneous dynamics over the whole brain provides critical insight into the spatiotemporal organization of brain dynamics at multiple resolutions and their alteration to changes in brain structure (e.g. in diseased states, aging, across individuals). Recent experimental evidence further suggests that the adverse effect of lesions is visible on spontaneous dynamics characterized by changes in resting state functional connectivity and its graph theoretical properties (e.g. modularity). These changes originate from altered neural dynamics in individual brain areas that are otherwise poised towards a homeostatic equilibrium to maintain a stable excitatory and inhibitory activity. In this work, we employ a homeostatic inhibitory mechanism, balancing excitation and inhibition in the local brain areas of the entire cortex under neurological impairments like lesions to understand global functional recovery (across brain networks and individuals). Previous computational and empirical studies have demonstrated that the resting state functional connectivity varies primarily due to the location and specific topological characteristics of the lesion. We show that local homeostatic balance provides a functional recovery by re-establishing excitation-inhibition balance in all areas that are affected by lesion. We systematically compare the extent of recovery in the primary hub areas (e.g. default mode network (DMN), medial temporal lobe, medial prefrontal cortex) as well as other sensory areas like primary motor area, supplementary motor area, fronto-parietal and temporo-parietal networks. Our findings suggest that stability and richness similar to the normal brain dynamics at rest are achievable by re-establishment of balance. PMID:27177761

  5. On the excited state wave functions of Dirac fermions in the random gauge potential

    Indian Academy of Sciences (India)

    H Milani Moghaddam

    2010-04-01

    In the last decade, it was shown that the Liouville field theory is an effective theory of Dirac fermions in the random gauge potential (FRGP). We show that the Dirac wave functions in FRGP can be written in terms of descendents of the Liouville vertex operator. In the quasiclassical approximation of the Liouville theory, our model predicts 22.2 that the localization length scales with the energy as $ ∼ E^{−b^{2}(1+b^{2})^{2}}$, where is the strength of the disorder. The self-duality of the theory under the transformation → 1/ is discussed. We also calculate the distribution functions of 0 = |0 ()|2, (i.e. (0); 0 () is the ground state wave function), which behaves as the log-normal distribution function. It is also shown that in small 0, (0) behaves as a chi-square distribution.

  6. Parallel transmit excitation at 1.5 T based on the minimization of a driving function for device heating

    International Nuclear Information System (INIS)

    Purpose: To provide a rapid method to reduce the radiofrequency (RF) E-field coupling and consequent heating in long conductors in an interventional MRI (iMRI) setup. Methods: A driving function for device heating (W) was defined as the integration of the E-field along the direction of the wire and calculated through a quasistatic approximation. Based on this function, the phases of four independently controlled transmit channels were dynamically changed in a 1.5 T MRI scanner. During the different excitation configurations, the RF induced heating in a nitinol wire immersed in a saline phantom was measured by fiber-optic temperature sensing. Additionally, a minimization of W as a function of phase and amplitude values of the different channels and constrained by the homogeneity of the RF excitation field (B1) over a region of interest was proposed and its results tested on the benchtop. To analyze the validity of the proposed method, using a model of the array and phantom setup tested in the scanner, RF fields and SAR maps were calculated through finite-difference time-domain (FDTD) simulations. In addition to phantom experiments, RF induced heating of an active guidewire inserted in a swine was also evaluated. Results: In the phantom experiment, heating at the tip of the device was reduced by 92% when replacing the body coil by an optimized parallel transmit excitation with same nominal flip angle. In the benchtop, up to 90% heating reduction was measured when implementing the constrained minimization algorithm with the additional degree of freedom given by independent amplitude control. The computation of the optimum phase and amplitude values was executed in just 12 s using a standard CPU. The results of the FDTD simulations showed similar trend of the local SAR at the tip of the wire and measured temperature as well as to a quadratic function of W, confirming the validity of the quasistatic approach for the presented problem at 64 MHz. Imaging and heating

  7. Enhancing phosphate adsorption by Mg/Al layered double hydroxide functionalized biochar with different Mg/Al ratios.

    Science.gov (United States)

    Li, Ronghua; Wang, Jim J; Zhou, Baoyue; Awasthi, Mukesh Kumar; Ali, Amjad; Zhang, Zengqiang; Gaston, Lewis A; Lahori, Altaf Hussain; Mahar, Amanullah

    2016-07-15

    Mg/Al ratio plays a significant role for anion adsorption by Mg/Al-layered double hydroxides (Mg/Al-LDHs) modified biochar. In this study, Mg/Al-LDHs biochar with different Mg/Al ratios (2, 3, 4) were prepared by co-precipitation for phosphate removal from aqueous solution. Factors on phosphate adsorption including Mg/Al ratio, pH, and the presence of other inorganic anions were investigated through batch experiments. Increasing Mg/Al ratio in the Mg/Al-LDHs biochar composites generally enhanced phosphate adsorption with Langmuir adsorption maximum calculated at 81.83mg phosphorous (P) per gram of 4:1Mg/Al-LDHs biochar at pH3.0. The adsorption process was best described by the pseudo-second-order kinetic model. Solution pH had greater effects on the phosphate adsorption by Mg/Al LDHs biochar composites with lower Mg/Al ratios. The presence of other inorganic anions decreased the phosphate adsorption efficiency in the order of F(-) > SO4(2-) > NO2(-) >Cl(-). Phosphate adsorption mechanism involves ion exchange, electrostatic attraction and surface inner-sphere complex formation. Overall, Mg/Al-LDHs biochar composites offer a potential alternative of carbon-based adsorbent for phosphate removal from aqueous solution. PMID:27058131

  8. Proton hole response function on 196Pt and 197Au transitional target nuclei up to high excitation energy

    International Nuclear Information System (INIS)

    The proton hole response functions have been studied on the transitional target nuclei 196Pt and 197Au via the (d, 3He) reaction at Ed = 108.4 MeV, up to 6 MeV and 18.5 MeV excitation energy respectively. 196Pt low lying levels have been studied in addition at Ed = 50 MeV. Spectroscopic information gained on the low lying levels in the 195Ir and 196Pt residual nuclei allows the discussion of the 3s1/2 and 2d3/2 orbital filling. For both 195Ir and 196Pt, new 2d5/2 and 1h11/2 levels or groups are observed. The 196Pt spectra exhibit a broad bump between 6 and 15 MeV excitation energy riding over a continuous background. The study of the excitation energy spectra up to 27 MeV leads to a consistent subtraction of the background. The contributions of the 1g9/2, 2p and 1f inner hole strengths are deduced by least square fits of DWBA angular distributions. About the whole 1g9/2 and 2p inner hole strengths and 50% of the 1f strengths are found below Ex = 18.5 MeV. The background correction is also used to reanalyse previous data obtained via the same reaction on the spherical 208Pb target for comparison. Experimental results on centroid separation energies are compared with Hartree Fock predictions. The spreading widths and specific features of the strength distribution shapes in 195Ir and 196Pt and 207Tl are discussed in connection with the dominant quadrupole collective degrees of freedom of the two first nuclei contrasting with the strong vibrational modes in 207Tl. The valence hole fragmentation in 195Ir is described in the framework of the Core-Quasi-Particle-Coupling-Model

  9. Stability domains of wind-excited random nonlinear systems throughLyapunov function

    Czech Academy of Sciences Publication Activity Database

    Náprstek, Jiří

    2001-01-01

    Roč. 89, č. 11 (2001), s. 1149-1512. ISSN 0167-6105 R&D Projects: GA ČR GA103/99/0122; GA ČR GA103/99/0756 Keywords : stochastic stability, Lyapunov function, stability domains Subject RIV: JM - Building Engineering Impact factor: 0.358, year: 2001

  10. Phase instability in ZrO2 endash NiAl functionally graded materials

    International Nuclear Information System (INIS)

    Sedimentation in organic solvents was followed by hot-pressing to produce 2 mole% yttria stabilized zirconia-NiAl functionally graded materials (FGM close-quote s). These FGM close-quote s were better able to accommodate high levels of residual stress than alumina-NiAl FGM close-quote s; this is possibly due to enhanced tetragonal phase retention. However, we found that the zirconia layer in these FGM close-quote s subsequently experiences room temperature transformation of t-ZrO2 to m-ZrO2. copyright 1997 Materials Research Society

  11. Excited electronic states of MnO4−: Challenges for wavefunction and density functional response theories

    International Nuclear Information System (INIS)

    Highlights: • Linear response coupled cluster hierarchy CCS, CC2, CCSD, CC3 applied to lowest excited states of MnO4−. • Unphysical results obtained for approximate CCn methods. • Failure traced to very large singles amplitudes. • HF and RASSCF calculations on ground state show strong correlations give very poor HF single particle picture. • TD-CAM-B3LYP describes LMCT states with reasonable accuracy. - Abstract: The lowest excited electronic states of the permanganate ion MnO4− are calculated using a hierarchy of coupled cluster response approaches, as well as time-dependent density functional theory. It is shown that while full linear response coupled cluster with singles and doubles (or higher) performs well, that permanganate represents a stern test for approximate coupled cluster response models, and that problems can be traced to very large orbital relaxation effects. TD-DFT is reasonably robust although errors around 0.6 eV are still observed. In order to further investigate the strong correlations prevalent in the electronic ground state large-scale RASSCF calculations were also performed. Again very large orbital relaxation in the correlated wavefunction is observed. Although the system can qualitatively be described by a single configuration, multi-reference diagnostic values show that care must be taken in this and similar metal complexes

  12. Interaction of bathocuproine with metals (Ca, Mg, Al, Ag, and Au) studied by density functional theory

    International Nuclear Information System (INIS)

    Electronic structure of the interface between a bathocuproine (BCP) molecule and metal surface was studied by density functional theory. The bond energy of BCP with metal surface increased with decreasing work function of metals, that is, Au, Ag, Al, Mg, and Ca in this order. The charge transfer also increased with decreasing metal work function. It was analyzed that the Fermi level and the lowest unoccupied molecular orbital of BCP are composed of both BCP and metal orbital component, and electron transport properties across the BCP and metal is discussed based on these analyses.

  13. Excitation functions of longer lived radionuclides formed by deuteron irradiation of germanium

    International Nuclear Information System (INIS)

    The cross sections of nuclear reactions induced by deuteron particles on natural germanium were investigated by using the stacked target technique, activation method and standard high resolution gamma spectrometry. Targets were natural germanium, vacuum evaporated onto 25 micron thick polyimide (kapton) foils with nominal thickness of about 2 μm. The stack was composed of 26 kapton–Ge–Ge–kapton sandwich targets foils and 24 aluminum and 25 titanium foils with nominal thickness of 50 and 11 μm respectively. The Al foils served as monitors and at the same time as energy degraders in the high energy part of the stack. Ti foils were included in the stack to monitor the beam parameters in the low energy region. The irradiation was done with 50 MeV deuteron particles with a beam current of about 50 nA for about 1 h. Activation cross sections were determined for production of the 70,71,72,73,74,76As, 69,75,77Ge and 66,67,73Ga radionuclides. The deduced experimental cross sections were compared to the results of theoretical calculations taken from the TENDL-2013 data library based on the TALYS computer code. A comparison was made with available experimental data measured earlier. Thick target yields were deduced from the experimental cross sections and were compared with the data published before. The possible production routes of arsenic radioisotopes are discussed

  14. Excitation functions of longer lived radionuclides formed by deuteron irradiation of germanium

    Energy Technology Data Exchange (ETDEWEB)

    Takács, S., E-mail: stakacs@atomki.hu [Institute for Nuclear Research, Hungarian Academy of Sciences, 4026 Debrecen (Hungary); Takács, M.P. [Institute for Nuclear Research, Hungarian Academy of Sciences, 4026 Debrecen (Hungary); Institute of Physics, University of Debrecen, 4026 Debrecen (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel, Brussels 1090 Belgium (Belgium); Tárkányi, F. [Institute for Nuclear Research, Hungarian Academy of Sciences, 4026 Debrecen (Hungary); Adam-Rebeles, R. [Cyclotron Laboratory, Vrije Universiteit Brussel, Brussels 1090 Belgium (Belgium)

    2014-10-01

    The cross sections of nuclear reactions induced by deuteron particles on natural germanium were investigated by using the stacked target technique, activation method and standard high resolution gamma spectrometry. Targets were natural germanium, vacuum evaporated onto 25 micron thick polyimide (kapton) foils with nominal thickness of about 2 μm. The stack was composed of 26 kapton–Ge–Ge–kapton sandwich targets foils and 24 aluminum and 25 titanium foils with nominal thickness of 50 and 11 μm respectively. The Al foils served as monitors and at the same time as energy degraders in the high energy part of the stack. Ti foils were included in the stack to monitor the beam parameters in the low energy region. The irradiation was done with 50 MeV deuteron particles with a beam current of about 50 nA for about 1 h. Activation cross sections were determined for production of the {sup 70,71,72,73,74,76}As, {sup 69,75,77}Ge and {sup 66,67,73}Ga radionuclides. The deduced experimental cross sections were compared to the results of theoretical calculations taken from the TENDL-2013 data library based on the TALYS computer code. A comparison was made with available experimental data measured earlier. Thick target yields were deduced from the experimental cross sections and were compared with the data published before. The possible production routes of arsenic radioisotopes are discussed.

  15. Excitation functions of longer lived radionuclides formed by deuteron irradiation of germanium

    Science.gov (United States)

    Takács, S.; Takács, M. P.; Hermanne, A.; Tárkányi, F.; Adam-Rebeles, R.

    2014-10-01

    The cross sections of nuclear reactions induced by deuteron particles on natural germanium were investigated by using the stacked target technique, activation method and standard high resolution gamma spectrometry. Targets were natural germanium, vacuum evaporated onto 25 micron thick polyimide (kapton) foils with nominal thickness of about 2 μm. The stack was composed of 26 kapton-Ge-Ge-kapton sandwich targets foils and 24 aluminum and 25 titanium foils with nominal thickness of 50 and 11 μm respectively. The Al foils served as monitors and at the same time as energy degraders in the high energy part of the stack. Ti foils were included in the stack to monitor the beam parameters in the low energy region. The irradiation was done with 50 MeV deuteron particles with a beam current of about 50 nA for about 1 h. Activation cross sections were determined for production of the 70,71,72,73,74,76As, 69,75,77Ge and 66,67,73Ga radionuclides. The deduced experimental cross sections were compared to the results of theoretical calculations taken from the TENDL-2013 data library based on the TALYS computer code. A comparison was made with available experimental data measured earlier. Thick target yields were deduced from the experimental cross sections and were compared with the data published before. The possible production routes of arsenic radioisotopes are discussed.

  16. Faraday waves under time-reversed excitation.

    Science.gov (United States)

    Pietschmann, Dirk; Stannarius, Ralf; Wagner, Christian; John, Thomas

    2013-03-01

    Do parametrically driven systems distinguish periodic excitations that are time mirrors of each other? Faraday waves in a Newtonian fluid are studied under excitation with superimposed harmonic wave forms. We demonstrate that the threshold parameters for the stability of the ground state are insensitive to a time inversion of the driving function. This is a peculiarity of some dynamic systems. The Faraday system shares this property with standard electroconvection in nematic liquid crystals [J. Heuer et al., Phys. Rev. E 78, 036218 (2008)]. In general, time inversion of the excitation affects the asymptotic stability of a parametrically driven system, even when it is described by linear ordinary differential equations. Obviously, the observed symmetry has to be attributed to the particular structure of the underlying differential equation system. The pattern selection of the Faraday waves above threshold, on the other hand, discriminates between time-mirrored excitation functions. PMID:23496716

  17. Density-functional prediction of a surface magnetic phase in SrTiO(3)/LaAlO(3) heterostructures induced by Al vacancies.

    Science.gov (United States)

    Weston, L; Cui, X Y; Ringer, S P; Stampfl, C

    2014-10-31

    Based on first-principles density functional calculations we propose a novel Al vacancy induced ferromagnetism occurring at the LaAlO(3) surface of SrTiO(3)/LaAlO(3) bilayers. Magnetism at cation vacancies away from the surface is quenched due to charge compensation. Magnetic surface Al vacancies are stabilized due to the built-in electric field inside the LaAlO(3) region that raises the energy of the defect level, making charge compensation unfavorable. Surface Al vacancies prefer to form clusters and exhibit two-dimensional ferromagnetic alignment mediated by a long-range magnetic interaction. These results are discussed in light of recent experimental observations. PMID:25396383

  18. Malondialdehyde suppresses cerebral function by breaking homeostasis between excitation and inhibition in turtle Trachemys scripta.

    Directory of Open Access Journals (Sweden)

    Fangxu Li

    Full Text Available The levels of malondialdehyde (MDA are high in the brain during carbonyl stress, such as following daily activities and sleep deprivation. To examine our hypothesis that MDA is one of the major substances in the brain leading to fatigue, the influences of MDA on brain functions and neuronal encodings in red-eared turtle (Trachemys scripta were studied. The intrathecal injections of MDA brought about sleep-like EEG and fatigue-like behaviors in a dose-dependent manner. These changes were found associated with the deterioration of encoding action potentials in cortical neurons. In addition, MDA increased the ratio of γ-aminobutyric acid to glutamate in turtle's brain, as well as the sensitivity of GABAergic neurons to inputs compared to excitatory neurons. Therefore, MDA, as a metabolic product in the brain, may weaken cerebral function during carbonyl stress through breaking the homeostasis between excitatory and inhibitory neurons.

  19. Description of Excitations in Odd Non-magic Nuclei by the Green's Function Method

    OpenAIRE

    Avdeenkov, A.V.; Kamerdzhiev, S. P.

    2000-01-01

    General equations for one- particle Green function in non- magic nuclei have been derived where a pairing mechanism, which is analogous to the Bardeen- Cooper- Schrieffer one, has been singled out explicitely. A "refining" procedure for the phenomenological single- particle energies and pairing gaps is formulated to avoid double counting of the phonon mixing if the initial data of the problem are these phenomenological quantities. The general equations obtained have been written in the square...

  20. Influence of RF excitation during pulsed laser deposition in oxygen atmosphere on the structural properties and luminescence of nanocrystalline ZnO:Al thin films

    International Nuclear Information System (INIS)

    Thin ZnO:Al layers were deposited by pulsed laser deposition in vacuum and in oxygen atmosphere at gas pressures between 10 and 70 Pa and by applying radio-frequency (RF) plasma. Grazing incidence small angle x-ray scattering and grazing incidence x-ray diffraction (GIXRD) data showed that an increase in the oxygen pressure leads to an increase in the roughness, a decrease in the sample density, and changes in the size distribution of nanovoids. The nanocrystal sizes estimated from GIXRD were around 20 nm, while the sizes of the nanovoids increased from 1 to 2 nm with the oxygen pressure. The RF plasma mainly influenced the nanostructural properties and point defects dynamics. The photoluminescence consisted of three contributions, ultraviolet (UV), blue emission due to Zn vacancies, and red emission, which are related to an excess of oxygen. The RF excitation lowered the defect level related to blue emission and narrowed the UV luminescence peak, which indicates an improvement of the structural ordering. The observed influence of the deposition conditions on the film properties is discussed as a consequence of two main effects: the variation of the energy transfer from the laser plume to the growing film and changes in the growth chemistry

  1. Influence of RF excitation during pulsed laser deposition in oxygen atmosphere on the structural properties and luminescence of nanocrystalline ZnO:Al thin films

    Energy Technology Data Exchange (ETDEWEB)

    Meljanac, Daniel, E-mail: dmeljan@irb.hr; Plodinec, Milivoj; Siketić, Zdravko; Gracin, Davor [Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb (Croatia); Juraić, Krunoslav [Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia and Institute of Inorganic Chemistry, Graz University of Technology, Stremayrgasse 9/IV, 8010 Graz (Austria); Krstulović, Nikša; Salamon, Krešimir; Skenderović, Hrvoje; Kregar, Zlatko; Rakić, Iva Šrut [Institute of Physics, Bijenička 46, 10000 Zagreb (Croatia); Bernstorff, Sigrid [Elettra-Sincrotrone Trieste, SS 14, Km 163.5, I-34049 Basovizza (TS) (Italy)

    2016-03-15

    Thin ZnO:Al layers were deposited by pulsed laser deposition in vacuum and in oxygen atmosphere at gas pressures between 10 and 70 Pa and by applying radio-frequency (RF) plasma. Grazing incidence small angle x-ray scattering and grazing incidence x-ray diffraction (GIXRD) data showed that an increase in the oxygen pressure leads to an increase in the roughness, a decrease in the sample density, and changes in the size distribution of nanovoids. The nanocrystal sizes estimated from GIXRD were around 20 nm, while the sizes of the nanovoids increased from 1 to 2 nm with the oxygen pressure. The RF plasma mainly influenced the nanostructural properties and point defects dynamics. The photoluminescence consisted of three contributions, ultraviolet (UV), blue emission due to Zn vacancies, and red emission, which are related to an excess of oxygen. The RF excitation lowered the defect level related to blue emission and narrowed the UV luminescence peak, which indicates an improvement of the structural ordering. The observed influence of the deposition conditions on the film properties is discussed as a consequence of two main effects: the variation of the energy transfer from the laser plume to the growing film and changes in the growth chemistry.

  2. Unrestricted density functional theory based on the fragment molecular orbital method for the ground and excited state calculations of large systems

    International Nuclear Information System (INIS)

    We extended the fragment molecular orbital (FMO) method interfaced with density functional theory (DFT) into spin unrestricted formalism (UDFT) and developed energy gradients for the ground state and single point excited state energies based on time-dependent DFT. The accuracy of FMO is evaluated in comparison to the full calculations without fragmentation. Electronic excitations in solvated organic radicals and in the blue copper protein, plastocyanin (PDB code: 1BXV), are reported. The contributions of solvent molecules to the electronic excitations are analyzed in terms of the fragment polarization and quantum effects such as interfragment charge transfer

  3. Aluminum-activated citrate and malate transporters encoded by distinct Al tolerance genes function independently in Arabidopsis

    Science.gov (United States)

    Aluminum (Al) -activated malate and citrate exudation from roots plays an important role in conferring Al tolerance to many plant species. Here, we report on the identification and characterization of AtMATE, the gene encoding an Al-activated root citrate efflux transporter that functions in Arabid...

  4. Preparation of Al/Si functionally graded materials using ultrasonic separation method

    Directory of Open Access Journals (Sweden)

    Zhang Zhongtao

    2008-08-01

    Full Text Available Functionally graded materials (FGM have been widely used in many industries such as aerospace, energy and electronics. In this experimental study of fabricating FGM, an approach was developed to prepare Al/Si FGM using power ultrasonic separation method. Material sample with continuously changing composition and performance/properties was successfully produced. Results showed that the microstructure of the FGM sample transited, from its top to bottom, from the hypereutectic structure with a large quantity of primary Si gradually to the eutectic, and fi nally to the hypoeutectic with numerous primary Al dendrites. The distribution of primary Si and microhardness of the FGM sample also presented graded characteristics, resulting that the wear resistance of the FGM sample decreased from top to bottom. Preliminary discussion was made on the mechanism of the formation of Al/Si FGM.

  5. Dual functions of TiC nanoparticles on tribological performance of Al/graphite composites

    Science.gov (United States)

    Fallahdoost, Hamid; Nouri, Alireza; Azimi, Amin

    2016-06-01

    In this study, the effect of TiC nanoparticles as a reinforcement on the mechanical and tribological properties of Aluminum-based self lubricating composite was investigated. The microstructure, relative density, hardness, and tribological properties of Al/graphite and Al/TiC/graphite composites were examined as a function of graphite content. The tribo-surfaces of the samples were analyzed using SEM and EDS elemental mapping. The results indicated that the addition of TiC nanoparticles not only decreased the wear rate and coefficient of friction of the composites, but also facilitated the formation of a stable graphite layer at longer sliding distances and high sliding velocities by forming a durable graphite/TiC composite on the tribo-surface. Therefore, the stability of graphite layer can be considered as a possible cause for decrease in wear rate of the Al/TiC/graphite composite.

  6. Fission excitation function for 19F + 194,196,198Pt at near and above barrier energies

    Directory of Open Access Journals (Sweden)

    Singh Varinderjit

    2015-01-01

    Full Text Available Fission excitation functions for 19F + 194,196,198Pt reactions populating 213,215,217Fr compound nuclei are reported. Out of these three compound nuclei, 213Fr is a shell closed (N=126 compound nucleus and the other two are away from the shell closure. From a comparison of the experimental fission cross-sections with the statistical model predictions, it is observed that the fission cross-sections are underestimated by the statistical model predictions using shell corrected finite range rotating liquid drop model (FRLDM fission barriers. Further the FRLDM fission barriers are reduced to fit the fission cross-sections over the entire measured energy range.

  7. Excitation functions of reactions of production of radioisotopes 201Tl, 201Pb, 201Bi (experimental and theoretical data)

    International Nuclear Information System (INIS)

    The results of calculations of charged particle induced reactions for the production of neutron deficient radioisotopes 201Tl, 201Pb, 201Bi and concomitant ones are discussed. The excitation functions for reactions 202Hg(p,xn), 197Au(a,xn), 203,205Tl(p,xn), 203,205Tl(d,xn), 203,205Tl(p,pxn), 204Pb(p,xn), 204Pb(p,p3n), 206Pb(p,6n), 206Pb(p,p5n), 207Pb(p,7n), 207Pb(p,p6n), 208Pb(p,xn) and 208Pb(p,p7n) are calculated on the base of statistical model in energy range up to 80 MeV. For the most reactions producing 201Tl the data on the calculated and practical yields under optimum conditions are given and the main admixture levels are pointed out. 30 refs., 9 figs

  8. Calculation of excitation functions of the 54,56,57,58Fe(, ) reaction from threshold to 30 MeV

    Indian Academy of Sciences (India)

    Damewan Suchiang; J Joseph Jeremiah; B M Jyrwa

    2014-10-01

    The cross-sections for the formation of 54,56,57,58Co in the 54,56,57,58Fe(, ) reaction from threshold to 30 MeV protons have been theoretically calculated using the TALYS-1.4 nuclear model code, whereby we have studied major nuclear reaction mechanisms, including direct, preequilibrium and compound nuclear reaction. Subsequently, the level density and shell damping parameters have been adjusted and at the same time, the odd–even effects are well comprehended. The excitation functions have been compared with experimental nuclear data. It is observed that the theoretical cross-sections match fairly well. Proton-induced reaction cross-sections provide clues to understand the nuclear structure and offers a good testing ground for ideas about nuclear forces. In addition, complete information in this field is very much required for application in accelerator-driven subcritical system.

  9. Investigation of incomplete fusion dynamics by measurement of excitation functions in the 20Ne + 59Co system

    International Nuclear Information System (INIS)

    In the present work, an attempt has been made to address some important aspects of CF and ICF dynamics for the system 20Ne + 59Co in the projectile energy range ≈ 62–150 MeV by using recoil catcher activation technique with the following off-line γ-ray spectroscopy. Excitation Functions (EFs) for the following reactions: 59Co(Ne, α p4n)70Ga, 59Co(Ne, 3αp3n) 63Zn, 59Co (Ne, 3αp4n) 62Zn and 59Co (Ne, 4α3n) 60Cu have been measured. No precursor decay contribution has been observed for these measured evaporation residues. The measured values of total fusion cross-sections of the above evaporation residues have been compared with the theoretical total complete fusion cross sections calculated by code PACE-2, which do not take into account ICF contribution

  10. Comparative assessment of density functional methods for evaluating essential parameters to simulate SERS spectra within the excited state energy gradient approximation.

    Science.gov (United States)

    Mohammadpour, Mozhdeh; Jamshidi, Zahra

    2016-05-21

    The prospect of challenges in reproducing and interpretation of resonance Raman properties of molecules interacting with metal clusters has prompted the present research initiative. Resonance Raman spectra based on the time-dependent gradient approximation are examined in the framework of density functional theory using different methods for representing the exchange-correlation functional. In this work the performance of different XC functionals in the prediction of ground state properties, excitation state energies, and gradients are compared and discussed. Resonance Raman properties based on time-dependent gradient approximation for the strongly low-lying charge transfer states are calculated and compared for different methods. We draw the following conclusions: (1) for calculating the binding energy and ground state geometry, dispersion-corrected functionals give the best performance in comparison to ab initio calculations, (2) GGA and meta GGA functionals give good accuracy in calculating vibrational frequencies, (3) excited state energies determined by hybrid and range-separated hybrid functionals are in good agreement with EOM-CCSD calculations, and (4) in calculating resonance Raman properties GGA functionals give good and reasonable performance in comparison to the experiment; however, calculating the excited state gradient by using the hybrid functional on the hessian of GGA improves the results of the hybrid functional significantly. Finally, we conclude that the agreement of charge-transfer surface enhanced resonance Raman spectra with experiment is improved significantly by using the excited state gradient approximation. PMID:27208944

  11. Plane wave/pseudopotential implementation of excited state gradients in density functional linear response theory: a new route via implicit differentiation

    OpenAIRE

    Doltsinis, Nikos L.; Kosov, D. S.

    2005-01-01

    This work presents the formalism and implementation of excited state nuclear forces within density functional linear response theory (TDDFT) using a plane wave basis set. An implicit differentiation technique is developed for computing nonadiabatic coupling between Kohn-Sham molecular orbital wavefunctions as well as gradients of orbital energies which are then used to calculate excited state nuclear forces. The algorithm has been implemented in a plane wave/pseudopotential code taking into a...

  12. Accurate electronic excitations for two alkali-halide systems obtained by density-functional theory and verified by multi-configuration self-consistent field calculations

    OpenAIRE

    Hellman, A.; Slabanja, M.

    2004-01-01

    Use of density-functional theory in a $\\Delta$self-consistent field framework result in both the ground- and two lowest electronicly excited states of the NaCl and LiCl. The accuracy of this method is confirmed using a multi-configuration self-consistent field method to obtain the same states. The overall good agreement between the calculated ground and excited potential-energy surfaces speaks promising for the computationally simple $\\Delta$self-consistent field method.

  13. Taking account of vibrational states in the description of energy-level density and excitation functions of (n, 2n) reaction for spherical nuclei

    International Nuclear Information System (INIS)

    Basing on a phenomenological approach accounting for the shell structure, pair correlations and coherent excitations of vibrational type, the energy dependence is discussed of the coefficient of vibrational level density increase for spherical nuclei with A approximately equal to 60. The relationship found is satisfactorily describing the level density for a number of nuclei, the neutron spectra and excitation functions of the 56Fe(n, 2n)55Fe reaction

  14. Electronically Excited States of Vitamin B12: Benchmark Calculations Including Time-Dependent Density Functional Theory and Correlated Ab Initio Methods

    OpenAIRE

    Kornobis, Karina; Kumar, Neeraj; Wong, Bryan M.; Lodowski, Piotr; Jaworska, Maria; Andruniów, Tadeusz; Rudd, Kenneth; Kozlowski, Pawel M.

    2011-01-01

    Time-dependent density functional theory (TD-DFT) and correlated ab initio methods have been applied to the electronically excited states of vitamin B12 (cyanocobalamin or CNCbl). Different experimental techniques have been used to probe the excited states of CNCbl, revealing many issues that remain poorly understood from an electronic structure point of view. Due to its efficient scaling with size, TD-DFT emerges as one of the most practical tools that can be used to predict the electronic p...

  15. Investigation of excitation functions using new evaluated empirical and semi-empirical systematic for 14-15 MeV (n, t) reaction cross sections

    International Nuclear Information System (INIS)

    The hybrid reactor is a combination of the fusion and fission processes. In the fusion-fission hybrid reactor, tritium self-sufficiency must be maintained for a commercial power plant. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. Working out the systematics of (n,t) reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at energies up to 20 MeV. In this study, we have investigated the asymmetry term effect for the (n,t) reaction cross sections at 14-15 neutron incident energy. It has been discussed the odd even effect and the pairing effect considering binding energy systematic of the nuclear shell model for the new experimental data and new cross section formulas (n,t) reactions developed by Tel et al. We have determined a different parameter groups by the classification of nuclei into even-even, even-odd and odd-even for (n,t) reactions cross sections. The obtained empirical formulas by fitting two parameter for (n,t) reactions were given. All calculated results have been compared with the experimental data. By using the new cross sections formulas (n,t) reactions the obtained results have been discussed and compared with the available experimental data

  16. Investigations of the potential functions of weakly bound diatomic molecules and laser-assisted excitive Penning ionization

    Energy Technology Data Exchange (ETDEWEB)

    Goble, J.H. Jr.

    1982-05-01

    Three variations on the Dunham series expansion function of the potential of a diatomic molecule are compared. The differences among these expansions lie in the choice of the expansion variable, lambda. The functional form of these variables are lambda/sub s/ = l-r/sub e//r for the Simon-Parr-Finlan version, lambda/sub T/ - 1-(r/sub e//r)/sup p/ for that of Thakkar, and lambda/sub H/ = 1-exp(-rho(r/r/sub e/-1) for that of Huffaker. A wide selection of molecular systems are examined. It is found that, for potentials in excess of thirty kcal/mole, the Huffaker expansion provides the best description of the three, extrapolating at large internuclear separation to a value within 10% of the true dissociation energy. For potentials that result from the interaction of excited states, all series expansions show poor behavior away from the equilibrium internuclear separation of the molecule. The series representation of the potentials of weakly bound molecules are examined in more detail. The ground states of BeAr/sup +/, HeNe/sup +/, NaAr, and Ar/sub 2/ and the excited states of HeNe+, NaNe, and NaAr are best described by the Thakkar expansion. Finally, the observation of laser-assisted excitive Penning ionization in a flowing afterglow is reported. The reaction Ar(/sup 3/P/sub 2/) + Ca + h nu ..-->.. Ar + Ca/sup +/(5p /sup 2/P/sub J/) + e/sup -/ occurs when the photon energy, h nu, is approximately equal to the energy difference between the metastable argon and one of the fine structure levels of the ion's doublet. By monitoring the cascade fluorescence of the above reaction and comparing it to the flourescence from the field-free process Ar(/sup 3/P/sub 2/) + Ca ..-->.. Ar + Ca/sup +/(4p /sup 2/P/sub J/) + e/sup -/ a surprisingly large cross section of 6.7 x 10/sup 3/ A/sup 2/ is estimated.

  17. Density functional investigation of the electronic structure and charge transfer excited states of a multichromophoric antenna

    Science.gov (United States)

    Basurto, Luis; Zope, Rajendra R.; Baruah, Tunna

    2016-05-01

    We report an electronic structure study of a multichromophoric molecular complex containing two of each borondipyrromethane dye, Zn-tetraphenyl-porphyrin, bisphenyl anthracene and a fullerene. The snowflake shaped molecule behaves like an antenna capturing photon at different frequencies and transferring the photon energy to the porphyrin where electron transfer occurs from the porphyrin to the fullerene. The study is performed within density functional formalism using large polarized Guassian basis sets (12,478 basis functions in total). The energies of the HOMO and LUMO states in the complex, as adjudged by the ionization potential and the electron affinity values, show significant differences with respect to their values in participating subunits in isolation. These differences are also larger than the variations of the ionization potential and electron affinity values observed in non-bonded C60-ZnTPP complexes in co-facial arrangement or end-on orientations. An understanding of the origin of these differences is obtained by a systematic study of the effect of structural strain, the presence of ligands, the effect of orbital delocalization on the ionization energy and the electron affinity. Finally, a few lowest charge transfer energies involving electronic transitions from the porphyrin component to the fullerene subunit of the complex are predicted.

  18. Excited states studied with density functional theory using local and non-local potentials

    International Nuclear Information System (INIS)

    Density Functional Theory (DFT) is a very popular tool for numerical simulations of the electronic structure of materials. The reason is that it is very efficient and quite accurate in many cases. However, one of its main weaknesses is the description of unoccupied states. These are important because they determine the response of a system to external influences. For example the optical properties of a material or the electrical conductivity of a semiconductor are heavily dependent on the unoccupied electronic states. DFT-based simulations are not capable of describing these states correctly. The most obvious shortcoming is the underestimation of the band gap, which is defined as the difference between the ionization energy and the electron affinity, as compared to the experimental value. An impressive number of different approaches (such as many-body perturbation theory, hybrid DFT, DFT+U, scissor operators) has been created and is used to deal with this problem. However, none of them has yet been established as the one main method, which is superior to the others. The focus of this thesis is on two of these approaches: Tran and Blaha's modified Becke-Johnson (TB-mBJ) exchange potential and hybrid DFT. The main principle of hybrid DFT is the combination of Hartree-Fock (exact) exchange with DFT. This makes it necessary to calculate the same exchange integrals as in Hartree-Fock calculations which means that the calculations are as expensive as in the Hartree-Fock method. However, recently screened hybrid functionals have been introduced and the screening of the long-range Coulomb-potential makes faster calculations possible. The standard form of such a screened hybrid functional contains two parameters. One determines the amount of Hartree-Fock based exchange and the other one the screening length. These parameters can be kept fixed and applied to different systems without changing, but the quality of the results is not the same for small-gap semiconductors

  19. Preparation of Al/Si functionally graded materials using ultrasonic separation method

    OpenAIRE

    Zhang Zhongtao; Li Tingju; Yue Hongyun

    2008-01-01

    Functionally graded materials (FGM) have been widely used in many industries such as aerospace, energy and electronics. In this experimental study of fabricating FGM, an approach was developed to prepare Al/Si FGM using power ultrasonic separation method. Material sample with continuously changing composition and performance/properties was successfully produced. Results showed that the microstructure of the FGM sample transited, from its top to bottom, from the hypereutectic structure with a ...

  20. Optical properties of Al nanostructures from time dependent density functional theory

    KAUST Repository

    Mokkath, Junais Habeeb

    2016-04-05

    The optical properties of Al nanostructures are investigated by means of time dependent density functional theory, considering chains of varying length and ladders/stripes of varying aspect ratio. The absorption spectra show redshifting for increasing length and aspect ratio. For the chains the absorption is dominated by HOMO → LUMO transitions, whereas ladders and stripes reveal more complex spectra of plasmonic nature above a specific aspect ratio.

  1. Fabrication of Al/Diamond Particles Functionally Graded Materials by Centrifugal Sintered-Casting Method

    International Nuclear Information System (INIS)

    The continuous graded structure of functionally graded materials (FGMs) can be created under a centrifugal force. Centrifugal sintered-casting (CSC) method, proposed by the authors, is one of the fabrication methods of FGM under centrifugal force. This method is a combination of the centrifugal sintering method and centrifugal casting method. In this study, Al/diamond particle FGM was fabricated by the proposed method.

  2. Fabrication of Al/Diamond Particles Functionally Graded Materials by Centrifugal Sintered-Casting Method

    Science.gov (United States)

    Watanabe, Yoshimi; Shibuya, Masafumi; Sato, Hisashi

    2013-03-01

    The continuous graded structure of functionally graded materials (FGMs) can be created under a centrifugal force. Centrifugal sintered-casting (CSC) method, proposed by the authors, is one of the fabrication methods of FGM under centrifugal force. This method is a combination of the centrifugal sintering method and centrifugal casting method. In this study, Al/diamond particle FGM was fabricated by the proposed method.

  3. Rapid development of Purkinje cell excitability, functional cerebellar circuit, and afferent sensory input to cerebellum in zebrafish

    Directory of Open Access Journals (Sweden)

    Jui-Yi Hsieh

    2014-12-01

    Full Text Available The zebrafish has significant advantages for studying the morphological development of the brain. However, little is known about the functional development of the zebrafish brain. We used patch clamp electrophysiology in live animals to investigate the emergence of excitability in cerebellar Purkinje cells, functional maturation of the cerebellar circuit, and establishment of sensory input to the cerebellum. Purkinje cells are born at 3 days post-fertilization (dpf. By 4 dpf, Purkinje cells spontaneously fired action potentials in an irregular pattern. By 5 dpf, the frequency and regularity of tonic firing had increased significantly and most cells fired complex spikes in response to climbing fiber activation. Our data suggest that, as in mammals, Purkinje cells are initially innervated by multiple climbing fibers that are winnowed to a single input. To probe the development of functional sensory input to the cerebellum, we investigated the response of Purkinje cells to a visual stimulus consisting of a rapid change in light intensity. At 4 dpf, sudden darkness increased the rate of tonic firing, suggesting that afferent pathways carrying visual information are already active by this stage. By 5 dpf, visual stimuli also activated climbing fibers, increasing the frequency of complex spiking. Our results indicate that the electrical properties of zebrafish and mammalian Purkinje cells are highly conserved and suggest that the same ion channels, Nav1.6 and Kv3.3, underlie spontaneous pacemaking activity. Interestingly, functional development of the cerebellum is temporally correlated with the emergence of complex, visually-guided behaviors such as prey capture. Because of the rapid formation of an electrically-active cerebellum, optical transparency, and ease of genetic manipulation, the zebrafish has great potential for functionally mapping cerebellar afferent and efferent pathways and for investigating cerebellar control of motor behavior.

  4. Excitation Functions for Charged Particle Induced Reactions in Light Elements at Low Projectile Energies

    International Nuclear Information System (INIS)

    The present chapter has been formulated with the aim of making it useful in various fields of nuclear applications with emphasis on charged particle activation analysis. Activation analysis of light elements using charged particles has proved to be an important tool in solving various problems in analytical chemistry, e g those associated with metal surfaces. Scientists desiring to evaluate the distribution of light elements in the surface of various matrices using charged particle reactions require accurate data on cross sections in the MeV-region. A knowledge of cross section data and yield-functions is of great interest in many applied fields involving work with charged particles, such as radiological protection and health physics, material research, semiconductor material investigations and corrosion chemistry. The authors therefore decided to collect a limited number of data which find use in these fields. Although the compilation is far from being complete, it is expected to be of assistance in devising measurements of charged particle reactions in Van de Graaff or other low energy accelerators

  5. Assessment of charge-transfer excitations with time-dependent, range-separated density functional theory based on long-range MP2 and multiconfigurational self- consistent field wave functions

    DEFF Research Database (Denmark)

    Hedegård, Erik D.; Jensen, Hans Jørgen Aagaard; Knecht, Stefan;

    2013-01-01

    Charge transfer excitations can be described within Time-Dependent Density Functional Theory (TD-DFT), not only by means of the Coulomb Attenuated Method (CAM) but also with a combination of wave function theory and TD-DFT based on range separation. The latter approach enables a rigorous formulat......Charge transfer excitations can be described within Time-Dependent Density Functional Theory (TD-DFT), not only by means of the Coulomb Attenuated Method (CAM) but also with a combination of wave function theory and TD-DFT based on range separation. The latter approach enables a rigorous...... displays multireference character in the ground state and both excited states exhibit considerable double excitation character, which in turn cannot be described within standard TD-DFT, due to the adiabatic approximation. However, a TD-MC-srDFT approach can account for the multireference character, and...

  6. Half-metallic ferromagnetism in Al1-xCrxP and superlattices (AlP)n/(CrP)m by density functional calculations

    Science.gov (United States)

    Merabet, M.; Rached, D.; Benalia, S.; Reshak, A. H.; Bettahar, N.; Righi, H.; Baltache, H.; Soyalp, F.; Labair, M.

    2014-01-01

    Using the first-principles full-potential linear muffin-tin orbital (FP-LMTO) method based on density functional theory, we have investigated the electronic structure and magnetism of order dilute ferromagnetic semiconductor Al1-xCrxP (x = 0.125, 0.25 and 0.50) and the superlattices (AlP)1/(CrP)1 and (AlP)3/(CrP)1. For the exchange-correlation functional, the generalized gradient approximation (GGA) has been used. It is shown that these compounds are half-metallic ferromagnets. Calculations of the s-d exchange constant N0α and p-d exchange constant N0β clearly indicate the magnetic nature of these compounds. We observe that p-d hybridization reduces the local magnetic moment of Cr from its free space charge value and produces small local magnetic moments on the non-magnetic Al and P sites.

  7. C-E Translation of Internet Neologisms from the Perspective of Function-al Equivalence

    Institute of Scientific and Technical Information of China (English)

    张利梅

    2015-01-01

    With the rapid development of China's economy and society,neologisms are involved in every field and continue to boom.However,Internet neologisms have an important influence on our mind and language form and update the way of information transmission and communication as well.It rapidly steps into people's life with different style and reflect social phenomenon and special cultural connotation with its unique charm.It is necessary to be aware of Internet neologisms translation when applying them into the language system.To those foreign readers who differ from Chinese mind and culture,inappropriate translation could result in misunderstanding and further cause communication failure.Hence,English translation for Internet neologisms should be placed considerable value.This paper will employ Eugene A.Nida's functional equivalence to probe into translation methods of In-ternet neologisms in order to find out appropriate translation.

  8. Density functional theory study of the adsorption and incorporation of Sc and Y on the AlN(0001) surface

    Science.gov (United States)

    González-Hernández, Rafael; González-Garcia, Alvaro; López-Perez, William

    2016-06-01

    Density functional theory (DFT) calculations were carried out in order to study the adsorption and incorporation of scandium and yttrium atoms on the AlN(0001) surface aiming to gain insight into epitaxial growth of ScxAl1-x N and YxAl1-x N layers on AlN. The adsorption energy, geometry, formation energy, band structure and density of states of Sc (and Y) adatom/AlN(0001) systems are calculated. The calculations showed that the interaction between Sc (and Y) adatom and the AlN(0001) surface is strong (~ 3.9 eV) and it prefers to adsorb on N-top site (T4). However, formation energy calculations reveal that the incorporation of Sc and Y atoms in the Al-substitutional site is energetically more favorable compared with the adsorption on the top layers, which can be attributed to the lower enthalpy of formation of ScN and YN with respect to that of AlN. The results also suggest that the Sc and Y atoms prefer to incorporate in top AlN surface layers. At full coverage, calculations show the formation of metallic ScxN and YxAl1-x N layers on the AlN polar surface over the entire range of Al chemical potentials, in agreement with experimental observations. In addition, we found that for high coverage Sc atoms couple ferromagnetically in the Al-substitutional sites on the AlN(0001) surface.

  9. Damage detection of metro tunnel structure through transmissibility function and cross correlation analysis using local excitation and measurement

    Science.gov (United States)

    Feng, Lei; Yi, Xiaohua; Zhu, Dapeng; Xie, Xiongyao; Wang, Yang

    2015-08-01

    In a modern metropolis, metro rail systems have become a dominant mode for mass transportation. The structural health of a metro tunnel is closely related to public safety. Many vibration-based techniques for detecting and locating structural damage have been developed in the past several decades. However, most damage detection techniques and validation tests are focused on bridge and building structures; very few studies have been reported on tunnel structures. Among these techniques, transmissibility function and cross correlation analysis are two well-known diagnostic approaches. The former operates in frequency domain and the latter in time domain. Both approaches can be applied to detect and locate damage through acceleration data obtained from sensor arrays. Furthermore, the two approaches can directly utilize structural response data without requiring excitation measurement, which offers advantages in field testing on a large structure. In this research, a numerical finite element model of a metro tunnel is built and different types of structural defects are introduced at multiple locations of the tunnel. Transmissibility function and cross correlation analysis are applied to perform structural damage detection and localization, based on simulated structural vibration data. Numerical results demonstrate that the introduced defects can be successfully identified and located. The sensitivity and feasibility of the two approaches have been verified when sufficient distribution of measurement locations is available. Damage detection results of the two different approaches are compared and discussed.

  10. Catalytic characterization of bi-functional catalysts derived from Pd–Mg–Al layered double hydroxides

    Indian Academy of Sciences (India)

    N N Das; S C Srivastava

    2002-08-01

    Hydrotalcite like precursors containing PdII–MgII–AlIII with varying molar ratios, (Pd + Mg)/Al ≈ 3 and Mg/Pd ≈ 750 to 35, were prepared by coprecipitation of metal nitrates at constant pH. Characterization of samples as synthesized and their calcined products by elemental analyses, powder XRD, TG–DTA, FT–IR spectroscopy, TPR and N2 physisorption indicated a well crystalline hydrotalcite like structure with incorporation of Pd2+ in the brucite layers. Thermal decomposition of hydrotalcite precursors at intermediate temperatures led to amorphous mixed oxides, Pd/MgAl(O), which on reduction yielded bi-functional catalyst, Pd°/MgAl(O). The resultant catalysts with acid, base and hydrogenating sites, were highly active and selective for one-step synthesis of methyl isobutyl ketone (MIBK) from acetone and hydrogen. The results showed an optimal balance between acid-base and metallic sites were required to increase the selectivity of MIBK and stability of the catalysts.

  11. Calculation of excitation functions of proton, alpha and deuteron induced reactions for production of medical radioisotopes {sup 122–125}I

    Energy Technology Data Exchange (ETDEWEB)

    Artun, Ozan, E-mail: ozanartun@yahoo.com; Aytekin, Hüseyin, E-mail: huseyinaytekin@gmail.com

    2015-02-15

    In this work, the excitation functions for production of medical radioisotopes {sup 122–125}I 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 {sup 122–125}I 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.

  12. Effect of nuclear level density on the calculation of excitation function for production of cesium, xenon, iodine, thallium, lead and bismuth radionuclides

    International Nuclear Information System (INIS)

    Excitation functions for the production of radionuclides Cs, Xe, I, Pb, Tl, Bi and some others for charged particle energies ranging from 5-100 MeV have been calculated. The well known experimental results have been compared to excitation functions calculated by two versions of the most widely used computer code ALICE. The generalized superfluid model of nuclei was used for level density description. The results of calculation for the ALICE-87 and ALICE-92 codes are discussed. Modified ALICE-92 code takes into account γ-ray competition, as well as cluster's preequilibrium emission. 43 refs.; 29 figs.; 3 tabs

  13. Is the existence of a softest point in the directed flow excitation function an unambiguous signal for the creation of a quark-gluon plasma?

    CERN Document Server

    Bleicher, M; Bleicher, Marcus

    2005-01-01

    The excitation function of the in-plane directed flow of nucleons is studied within a non-equilibrium transport approach. It is demonstrated that a local minimum in the excitation function of the directed flow develops, which is not related to a transition into a quark-gluon plasma (QGP) phase. It is a consequence of the dynamical softening of the underlying equation of state, due to the onset of resonance matter and particle production. Thus, the interpretation of this minimum as a 'smoking gun' signature for the creation of a QGP is premature.

  14. Is the existence of a softest point in the directed flow excitation function an unambiguous signal for the creation of a quark-gluon plasma?

    OpenAIRE

    Bleicher, Marcus; Aichelin, Jörg

    2002-01-01

    The excitation function of the in-plane directed flow of nucleons is studied within a non-equilibrium transport approach. It is demonstrated that a local minimum in the excitation function of the directed flow develops, which is not related to a transition into a quark-gluon plasma (QGP) phase. It is a consequence of the dynamical softening of the underlying equation of state, due to the onset of resonance matter and particle production. Thus, the interpretation of this minimum as a 'smoking ...

  15. Formation of Feshbach resonances associated with doubly excited He states in slow collisions of He[sup ++] ions with low work function surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Brenten, H.; Mueller, H.; Kempter, V. (Physikalisches Institut der Technischen Universitaet Clausthal, W-3392 Clausthal-Zellerfeld (Germany))

    1993-01-04

    We report electron energy spectra from He[sup ++] (100 eV) ions colliding under grazing incidence with partially cesiated W(110). We propose that at low surface work functions ([le]2 eV) the formation of Feshbach resonances associated with the doubly excited He states of the configuration (2[ital l]2[ital l][prime]) occurs. This is concluded from the variation of the relative population of the doubly excited He states with the surface work function. Furthermore, a peak can be identified in the spectra which appears to be due to the decay of the Feshbach resonances by one-electron emission.

  16. A simple and rapid method for direct determination of Al(III) based on the enhanced resonance Rayleigh scattering of hemin-functionalized graphene-Al(III) system

    Science.gov (United States)

    Ling, Yu; Chen, Ling Xiao; Dong, Jiang Xue; Li, Nian Bing; Luo, Hong Qun

    2016-03-01

    A novel method for direct determination of Al(III) by using hemin-functionalized graphene (H-GO) has been established based on the enhancement of resonance Rayleigh scattering (RRS) intensity. The characteristics of RRS spectra, the optimum reaction conditions, and the reaction mechanism have been investigated. In this experiment, the Al(III) would exist in sol-gel Al(OH)3 species under the condition of pH 5.9 in aqueous solutions. When H-GO existed in the solution, the sol-gel Al(OH)3 would react with H-GO and result in enhancement of RRS intensity, owing to the enhanced hydrophobicity of H-GO surface. Therefore, a simple and rapid sensor for Al(III) was developed. The increased intensity of RRS is directly proportional to the concentration of Al(III) in the range of 10 nM-6 μM, along with a detection limit of 0.87 nM. Moreover, the sensor has been applied to determination of Al(III) concentration in real water and aspirin tablet samples with satisfactory results. Therefore, the proposed method is promising as an effective means for selective and sensitive determination of Al(III).

  17. Multiresolution quantum chemistry in multiwavelet bases: excited states from time-dependent Hartree-Fock and density functional theory via linear response.

    Science.gov (United States)

    Yanai, Takeshi; Fann, George I; Beylkin, Gregory; Harrison, Robert J

    2015-12-21

    A fully numerical method for the time-dependent Hartree-Fock and density functional theory (TD-HF/DFT) with the Tamm-Dancoff (TD) approximation is presented in a multiresolution analysis (MRA) approach. From a reformulation with effective use of the density matrix operator, we obtain a general form of the HF/DFT linear response equation in the first quantization formalism. It can be readily rewritten as an integral equation with the bound-state Helmholtz (BSH) kernel for the Green's function. The MRA implementation of the resultant equation permits excited state calculations without virtual orbitals. The integral equation is efficiently and adaptively solved using a numerical multiresolution solver with multiwavelet bases. Our implementation of the TD-HF/DFT methods is applied for calculating the excitation energies of H2, Be, N2, H2O, and C2H4 molecules. The numerical errors of the calculated excitation energies converge in proportion to the residuals of the equation in the molecular orbitals and response functions. The energies of the excited states at a variety of length scales ranging from short-range valence excitations to long-range Rydberg-type ones are consistently accurate. It is shown that the multiresolution calculations yield the correct exponential asymptotic tails for the response functions, whereas those computed with Gaussian basis functions are too diffuse or decay too rapidly. We introduce a simple asymptotic correction to the local spin-density approximation (LSDA) so that in the TDDFT calculations, the excited states are correctly bound. PMID:25711489

  18. Preparation of Al/Si functionally graded materials using ultrasonic separation method

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhongtao; LI Tingju; Yue Hongyun; Zhang Jian; Li Jie

    2008-01-01

    Functionally graded materials (FGM) have been widely used in many industries such as aerospace, energy and electronics. In this experimental study of fabricating FGM, an approach was developed to prepare Al/Si FGM using power ultrasonic separation method. Material sample with continuously changing composition and performance/properties was successfully produced. Results showed that the microstructure of the FGM sample transited, from its top to bottom, from the hypereutectic structure with a large quantity of primary Si gradually to the eutectic, and finally to the hypoeutectic with numerous primary AI dendrites. The distribution of primary Si and microhardness of the FGM sample also presented graded characteristics, resulting that the wear resistance of the FGM sample decreased from top to bottom. Preliminary discussion was made on the mechanism of the formation of Al/Si FGM.

  19. Role of physiological ClC-1 Cl- ion channel regulation for the excitability and function of working skeletal muscle

    DEFF Research Database (Denmark)

    Pedersen, Thomas Holm; Riisager, Anders; de Paoli, Frank Vincenzo;

    2016-01-01

    permeability for Cl- ions. Thus, in resting human muscle, ClC-1 Cl- ion channels account for ∼80% of the membrane conductance, and because active Cl- transport is limited in muscle fibers, the equilibrium potential for Cl- lies close to the resting membrane potential. These conditions—high membrane conductance...... and passive distribution—enable ClC-1 to conduct membrane current that inhibits muscle excitability. This depressing effect of ClC-1 current on muscle excitability has mostly been associated with skeletal muscle hyperexcitability in myotonia congenita, which arises from loss-of-function mutations in...... the CLCN1 gene. However, given that ClC-1 must be drastically inhibited (∼80%) before myotonia develops, more recent studies have explored whether acute and more subtle ClC-1 regulation contributes to controlling the excitability of working muscle. Methods were developed to measure ClC-1 function with...

  20. The excitation function for Li+HF-->LiF+H at collision energies below 80 meV

    CERN Document Server

    Bobbenkamp, Rolf; Mudrich, Marcel; Stienkemeier, Frank

    2011-01-01

    We have measured the dependence of the relative integral cross section of the reaction Li+HF-->LiF+H on the collision energy using crossed molecular beams. By varying the intersection angle of the beams from 37{\\deg} to 90{\\deg} we covered the energy range 25 meV < E_tr < 131 meV. We observe a monotonous rise of the cross section with decreasing energy over the entire energy range indicating that a possible translational energy threshold to the reaction is significantly smaller than 25 meV. The steep rise is quantitatively recovered by a Langevin-type excitation function based on a vanishing threshold and a mean interaction potential energy ~R^-2.5 where R is the distance between the reactants. To date all threshold energies deduced from ab-initio potentials and zero-point vibrational energies are at variance with our results, however, our findings support recent quantum scattering calculations that predict significant product formation at collision energies far below these theoretical thresholds.

  1. Optical and magnetic excitations of metal-encapsulating Si cages: A systematic study by time-dependent density functional theory

    CERN Document Server

    Oliveira, Micael J T; Sousa, José R F; Nogueira, Fernando; Gueorguiev, Gueorgui K

    2013-01-01

    Systematic study of the optical and magnetic excitations of twelve MSi$_{12}$ and four MSi$_{10}$ transition metal encapsulating Si cages has been carried out by employing real time time-dependent density functional theory. Criteria for the choice of transition metals (M) are clusters' stability, synthesizability, and diversity. It was found that both the optical absorption and the spin-susceptibility spectra are mainly determined by, in decreasing order of importance: 1) the cage shape, 2) the group in the Periodic Table M belongs to, and 3) the period of M in the Periodic Table. Cages with similar structures and metal species that are close to each other in the Periodic Table possess spectra sharing many similarities, e. g., the optical absorption spectra of the MSi$_{12}$ (M = V, Nb, Ta, Cr, Mo, and W), which are highly symmetric and belong to groups 4 and 5 of the Periodic Table, all share a very distinctive peak at around 4 eV. In all cases, although some of the observed transitions are located at the Si...

  2. Excitation functions of (d,x) nuclear reactions on natural titanium up to 24 MeV

    International Nuclear Information System (INIS)

    Excitation functions of the natTi(d,x)48V and natTi(d,x)43,44m,44g,46,47,48Sc nuclear reactions were measured up to a 24-MeV deuteron energy by using a stacked-foil activation technique combined with γ-ray spectrometry with a high-purity germanium detector at the AVF cyclotron of the RIKEN RI Beam Factory, Wako, Japan. An overall good agreement is found between the measured cross-sections and the literature ones, whereas partial agreements are obtained for the theoretical calculations based on the TALYS code. Physical thick target yields, i.e., induced radioactivities per unit fluence of the 24-MeV deuteron were also deduced, and they were compared with the directly measured ones in the literature. The present results will have an important role in enrichment of the literature database of the deuteron-induced reactions on natural titanium leading to various applications

  3. Excitation functions of the proton induced nuclear reactions on {sup nat}Zn up to 40 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Uddin, M.S. [Department of Physics, Kyungpook National University, 1370 Sankyok-dong, Buk-gu, Daegu 702-701 (Korea, Republic of); Institute of Nuclear Science and Technology, Atomic Energy Research Establishment, Savar, GPO Box No. 3787, Dhaka-1000 (Bangladesh); Khandaker, M.U. [Department of Physics, Kyungpook National University, 1370 Sankyok-dong, Buk-gu, Daegu 702-701 (Korea, Republic of); Kim, K.S. [Department of Physics, Kyungpook National University, 1370 Sankyok-dong, Buk-gu, Daegu 702-701 (Korea, Republic of); Lee, Y.S. [Department of Physics, Kyungpook National University, 1370 Sankyok-dong, Buk-gu, Daegu 702-701 (Korea, Republic of); Kim, G.N. [Department of Physics, Kyungpook National University, 1370 Sankyok-dong, Buk-gu, Daegu 702-701 (Korea, Republic of)]. E-mail: gnkim@knu.ac.kr

    2007-05-15

    We measured the excitation functions of the {sup nat}Zn(p,xn){sup 66,67}Ga, {sup nat}Zn(p,pxn){sup 62,65,69m}Zn, and {sup nat}Zn(p,{alpha}xn){sup 61}Cu nuclear processes up to 40 MeV by using a stacked-foil activation technique at the MC50 cyclotron of the Korea Institute of Radiological and Medical Sciences. The results were compared with the earlier reported experimental data and theoretical calculations based on the ALICE-IPPE code. We have given new data points for the formation of the above radionuclides. The present values are in good agreement with some well-measured literature values. Integral yields were also deduced from the measured cross-sections. The reported direct measured thick target yields for the formation of the {sup 66}Ga and {sup 67}Ga radionuclides at 22 MeV support our deduced yields. The optimum formation of the {sup 66}Ga and {sup 61}Cu radionuclides with minimum impurities can be obtained at 8-15 MeV and 10-20 MeV energy range, respectively. The yields and decay characteristics of the nuclide {sup 65}Zn are suitable for thin layer activation analysis.

  4. New evolution equations for the joint response-excitation probability density function of stochastic solutions to first-order nonlinear PDEs

    Science.gov (United States)

    Venturi, D.; Karniadakis, G. E.

    2012-08-01

    By using functional integral methods we determine new evolution equations satisfied by the joint response-excitation probability density function (PDF) associated with the stochastic solution to first-order nonlinear partial differential equations (PDEs). The theory is presented for both fully nonlinear and for quasilinear scalar PDEs subject to random boundary conditions, random initial conditions or random forcing terms. Particular applications are discussed for the classical linear and nonlinear advection equations and for the advection-reaction equation. By using a Fourier-Galerkin spectral method we obtain numerical solutions of the proposed response-excitation PDF equations. These numerical solutions are compared against those obtained by using more conventional statistical approaches such as probabilistic collocation and multi-element probabilistic collocation methods. It is found that the response-excitation approach yields accurate predictions of the statistical properties of the system. In addition, it allows to directly ascertain the tails of probabilistic distributions, thus facilitating the assessment of rare events and associated risks. The computational cost of the response-excitation method is order magnitudes smaller than the one of more conventional statistical approaches if the PDE is subject to high-dimensional random boundary or initial conditions. The question of high-dimensionality for evolution equations involving multidimensional joint response-excitation PDFs is also addressed.

  5. New evolution equations for the joint response-excitation probability density function of stochastic solutions to first-order nonlinear PDEs

    International Nuclear Information System (INIS)

    By using functional integral methods we determine new evolution equations satisfied by the joint response-excitation probability density function (PDF) associated with the stochastic solution to first-order nonlinear partial differential equations (PDEs). The theory is presented for both fully nonlinear and for quasilinear scalar PDEs subject to random boundary conditions, random initial conditions or random forcing terms. Particular applications are discussed for the classical linear and nonlinear advection equations and for the advection–reaction equation. By using a Fourier–Galerkin spectral method we obtain numerical solutions of the proposed response-excitation PDF equations. These numerical solutions are compared against those obtained by using more conventional statistical approaches such as probabilistic collocation and multi-element probabilistic collocation methods. It is found that the response-excitation approach yields accurate predictions of the statistical properties of the system. In addition, it allows to directly ascertain the tails of probabilistic distributions, thus facilitating the assessment of rare events and associated risks. The computational cost of the response-excitation method is order magnitudes smaller than the one of more conventional statistical approaches if the PDE is subject to high-dimensional random boundary or initial conditions. The question of high-dimensionality for evolution equations involving multidimensional joint response-excitation PDFs is also addressed.

  6. Study of the transferred angular momentum as a function of the excitation energy in the Kr + U reaction at 35 A.MeV

    International Nuclear Information System (INIS)

    The aim of this study is to measure the angular momentum transferred to the target-like product, in the Kr + U reaction at 35 A.MeV, as a function of the excitation energy. The measured neutron multiplicity, as seen by the detector ORION, was used as the basic event selection criterion. This multiplicity also allows an estimation of the excitation energy transferred to the target-like product on an event by event basis. The study of the behaviour of the projectile-like component allows one to characterize two-body mechanisms, which are associated with a large energy dissipation for less peripheral collisions. The spin transferred to the target-like component is deduced from the out-plane angular distributions of the fission fragments. The study of the angular correlation between these fission fragments confirms that the dominant mechanism is essentially a two-body process. We show that the angular momentum values obtained, as a function of the excitation energy of the target-like product, have little dependence on the time taken for the nucleus to reach the saddle point. We observe a constant increase in the target-like component's spin, varying from 15ℎ to 60ℎ, as the excitation energy increases from roughly 8 to 400 MeV. For the higher excitation energies the spin does not increase. This behaviour reflects the vanishing binary fission mechanism at high angular momenta. (author)

  7. Assessment of Charge-Transfer Excitations in Organic Dyes obtained from TD-srDFT Based on Long-Range MP2 and MCSCF Wave Functions

    CERN Document Server

    Hedegård, Erik D; Knecht, Stefan; Fromager, Emmanuel; Jensen, Hans Jørgen Aa

    2013-01-01

    Charge transfer excitations can be described within TD-DFT, not only by means of long-range corrected exchange functionals but also with a combination of wave function theory and TD-DFT based on range separation. The latter approach enables a rigorous formulation of multi-determinantal TD-DFT schemes where excitation classes, which are absent in conventional TD-DFT spectra (like for example double excitations), can be addressed. This paper investigates the combination of both the long-range MCSCF and SOPPA ans\\"atze with a short-range DFT (srDFT) description. We find that the combinations of SOPPA or MCSCF with TD-DFT yield better results than could be expected from the pure wave function schemes. For the Time-Dependent MCSCF short-range DFT ansatz (TD-MC-srDFT) excitation energies calculated over a larger benchmark set of molecules with predominantly single reference character yield good agreement with their reference values, and are in general comparable to the long-range corrected functional CAM-B3LYP. The...

  8. Plane wave density functional molecular dynamics study of exothermic reactions of Al/CuO thermites

    Science.gov (United States)

    Oloriegbe, Suleiman; Sewell, Thomas; Chen, Zhen; Jiang, Shan; Gan, Yong

    2014-03-01

    Exothermic reactions between nanosize aluminum (Al) and copper oxide (CuO) structures are of current interest because of their high reaction enthalpy and energy density which exceed those of traditional monomolecular energetic compounds such as TNT, RDX, and HMX. In this work, molecular dynamics simulations with forces obtained from plane wave density functional theory are used to investigate the atomic-scale and electronic processes that occur during the fast thermite reactions between Al and CuO nanostructures under adiabatic conditions. Aluminum surfaces in contact with O-exposed and Cu-exposed CuO surfaces are studied. Starting from initial temperature T = 800 K, we have observed: faster chemical reaction at the oxygen-rich interface during the initial 0.5 ps, linear temperature rise, and fast oxygen diffusion into the Al region with the rate 1.87 X 10-3 cm2/s. The density-derived electrostatic and chemical method is used to evaluate the net atomic charges and charge transfer during the important redox processes. High charge density around the oxygen-exposed interface may be responsible for the faster initial reactions at that interface. The overall reaction rate, determined using the time evolution of Cu-O charge orbital overlap population, is approximately first order.

  9. Hot nuclei study: Is there a limit for the excitation energy that a nucleus can endure. Application to 40Ca + 27Al system at 25 and 35 MeV/u

    International Nuclear Information System (INIS)

    Hot nuclei produced in the 40Ca+27Al reaction have been studied at 25 and 35 MeV/u. In a first part, we remind the experimental context which brings us to perform this experiment and to use the AMPHORA multidetector. AMPHORA's efficiency for the most violent collisions has then been verified. The hot nuclei study requires the definition of a criterion to select central collisions. We established that a light particles multiplicity greater or equal to 9 selected a special class of these collisions. We exhibit the experimental results deduced from these hot nuclei study: source velocity, excitation energy, temperature. After comparison with an evaporation code, we deduce excitation energies per nucleon of 6 MeV/u at 25 MeV/u and 7.5 MeV/u at 35 MeV/u. Despite the significant increase of hot nuclei excitation energies, we do not observe a strong evolution for the associated charge distributions and heavy fragments multiplicities. Rare events where 75% of total charge are carried away by light particles have then been studied. They are associated with very hot nuclei and we call them vaporization events. The comparison between experimental results and those of a statistical evaporation code confirms that we selected nuclei with high excitation energy. The agreement is generally good except for charge distributions evolution depending on the source's excitation energy. However, these problems should not challenge the statistical nature of evaporation mechanisms

  10. Band parameters of (Al,Ga,In)N polytypes from different XC functionals

    International Nuclear Information System (INIS)

    Actually a detailed knowledge of the band parameters of the group-III nitrides is necessary to interpret experimental data and understand theoretical results. The most successful theoretical approach is the Density Functional Theory (DFT), but its accuracy depends on the exchange-correlation (XC) functional. Different XC functionals yield slightly varying results for the structural and electronic properties. However, this effect is less important in comparison to the drastic changes of the electronic band structures by solving the quasiparticle (QP) equation. In this work we present and discuss the qualitative and quantitative influence of the XC functionals LDA, GGA, and AM05 induced by structural changes on the band parameters of the AlN, GaN and InN mononitrides. DFT as implemented in VASP code is used to calculate the structural and elastic properties of zinc-blende and wurtzite polytypes. The QP band structures including the XC self-energy within Hedin's GW approximation are obtained taking almost self-consistency into account using HSE03 hybrid XC functional as a starting point. The gap energies, crystal-fields splittings, momentum matrix elements, effective masses and spin-orbit coupling are computed from the QP band structures. We compare our results with experimental values reported in the literature.

  11. Excitation functions and isomeric ratios for the isomeric pair 106Ag(m) and 106Ag(g) in the 107Ag(d,t) reaction

    International Nuclear Information System (INIS)

    Excitation functions and isomeric cross section ratios have been measured for the 107Ag(d,t) reaction in which the isomeric pair 106Ag(m/g) is produced. Thick-target yields have been determined for different irradiation times and as a function of deuteron energy. Stacked silver foils with aluminium foils as monitors were bombarded with deuterons up to 27 MeV and the activities of products measured with a calibrated Ge(Li) counter. (orig.)

  12. Elastic and Thermodynamic Properties of Complex Mg-Al Intermetallic Compounds via Orbital-Free Density Functional Theory

    Science.gov (United States)

    Zhuang, Houlong; Chen, Mohan; Carter, Emily A.

    2016-06-01

    Magnesium-aluminum (Mg-Al) alloys are important metal alloys with a wide range of engineering applications. We investigate the elastic and thermodynamic properties of Mg, Al, and four stoichiometric Mg-Al compounds including Mg17Al12 , Mg13Al14 , and Mg23Al30 , and MgAl2 with orbital-free density-functional theory (OFDFT). We first calculate the lattice constants, zero-temperature formation energy, and independent elastic constants of these six materials and compare the results to those computed via Kohn-Sham DFT (KSDFT) benchmarks. We obtain excellent agreement between these two methods. Our calculated elastic constants of hexagonal close-packed Mg and face-centered-cubic Al are also consistent with available experimental data. We next compute their phonon spectra using the force constants extracted from the very fast OFDFT calculations, because such calculations are computationally challenging using KSDFT. This is especially the case for the Mg23Al30 compound, whose 3 ×3 ×3 supercell consists of 1431 atoms. We finally employ the quasiharmonic approximation to investigate temperature-dependent thermodynamic properties, including formation energies, heat capacities, and thermal expansion of the four Mg-Al intermetallic compounds. The calculated heat capacity and thermal expansion of both Mg and Al agree well with experimental data. We additionally find that Mg13Al14 and MgAl2 are both unstable, consistent with their absence from the equilibrium Mg-Al phase diagram. Our work demonstrates that OFDFT is an efficient and accurate quantum-mechanical computational tool for predicting elastic and thermodynamic properties of complicated Mg-Al alloys and also should be applicable to many other engineering alloys.

  13. Synthesis and luminescence properties of polymeric complexes of Cu(II), Zn(II) and Al(III) with functionalized polybenzimidazole containing 8-hydroxyquinoline side group

    Science.gov (United States)

    Zhong, Chaofan; Wu, Qian; Guo, Rongfang; Zhang, Hailiang

    2008-02-01

    The polymeric ligand PBI-8Q ( 2) (functionalized polybenzimidazole containing 8-hydroxyquinoline side group) was successfully synthesized by the reaction of polybenzimidazole (PBI) ( 1) with 5-chloro-8-hydroxyquinoline (5-Cl-8Q) in DMSO solvent by using NaH as deprotonation reagent. Its corresponding metal complexes of Cu(II), Zn(II) and Al(III) were prepared and characterized through FT-IR, 1H NMR, molar conductance measurements and thermal analysis. The luminescence properties of all compounds were also studied by UV-vis and fluorescence spectra at ambient temperature. When excited from 338 to 415 nm, these compounds emit blue light of about 415 nm in solution and blue/green light from 483 to 552 nm in solid state, respectively. Thermal properties measurement and analysis show that they have good thermal stabilities.

  14. Optical excitation function of H(1s-2p) produced by electron impact from threshold to 1.8 keV

    International Nuclear Information System (INIS)

    The optical excitation function of prompt Lyman-α radiation, produced by electron impact on atomic hydrogen, has been measured over the extended energy range from threshold to 1.8 keV. Measurements were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source. A vacuum-ultraviolet monochromator system was used to measure the emitted Lyman-α radiation. The absolute H(1s-2p) electron impact excitation cross section was obtained from the experimental optical excitation function by normalizing to the accepted optical oscillator strength, with corrections for polarization and cascade. Our data are significantly different from the earlier experimental results and which are limited to energies below 200 eV. Statistical and known systematic uncertainties in our data range from ±4% near threshold to ±2% at 1.8 keV. Multistate coupling affecting the shape of the excitation function up to 1 keV impact energy is apparent in both the present experimental data and present theoretical results obtained with convergent close-coupling (CCC) theory. This shape function effect leads to an uncertainty in absolute cross sections at the 10% level in the analysis of the experimental data. The derived optimized absolute cross sections are within 7% of the CCC calculations over the 14 eV endash 1.8 keV range. The present CCC calculations converge on the Bethe-Fano profile for H(1s-2p) excitation at high energy. For this reason agreement with the CCC values to within 3% is achieved in a nonoptimal normalization of the experimental data to the Bethe-Fano profile. The fundamental H(1s-2p) electron impact cross section is thereby determined to an unprecedented accuracy over the 14 eV endash 1.8 keV energy range. (Abstract Truncated)

  15. Role of resonance-enhanced multiphoton excitation in high-harmonic generation of N2: A time-dependent density-functional-theory study

    Science.gov (United States)

    Chu, Xi; Groenenboom, Gerrit C.

    2013-01-01

    A minimum at ˜39 eV is observed in the high-harmonic-generation spectra of N2 for several laser intensities and frequencies. This minimum appears to be invariant for different molecular orientations. We reproduce this minimum for a set of laser parameters and orientations in time-dependent density-functional-theory calculations, which also render orientation-dependent maxima at 23-26 eV. Photon energies of these maxima overlap with ionization potentials of excited states observed in photoelectron spectra. Time profile analysis shows that these maxima are caused by resonance-enhanced multiphoton excitation. We propose a four-step mechanism, in which an additional excitation step is added to the well-accepted three-step model. Excitation to a linear combination of Rydberg states c4'1Σu+ and c31Πu gives rise to an orientation-invariant minimum analogous to the “Cooper minimum” in argon. When the molecular axis is parallel to the polarization direction of the field, a radial node goes through the atomic centers, and hence the Cooper-like minimum coincides with the minimum predicted by a modified two-center interference model that considers the de-excitation of the ion and symmetry of the Rydberg orbital.

  16. Dielectric function and electro-optical properties of (Al,Ga)N/GaN-heterostructures; Dielektrische Funktion und elektrooptische Eigenschaften von (Al,Ga)N/GaN-Heterostrukturen

    Energy Technology Data Exchange (ETDEWEB)

    Buchheim, Carsten

    2010-04-23

    In this work extensive investigations on nitride semiconductors by optical spectroscopy are presented. The ordinary and the extraordinary component of the dielectric function of GaN in the spectral range from 1.2 to 9.8 eV is shown for the first time. It is demonstrated, that the transparent spectral range is clearly influenced by higher energetic critical points of the band structure. The optical selection rules for GaN and AlN are verified considering the actual strain state. The change of the valence band ordering of AlN in comparison to GaN is proven and the crystal field splitting is estimated for AlN. The ordinary dielectric function of AlGaN is determined for different Al contents. The data are used for developing an analytical model, which includes excitonic effects and bowings. It allows the calculation of the dielectric function for arbitrary alloy compositions. (GaN/)AlGaN/GaN heterostructures are investigated by spectroscopic ellipsometry as well as by photoreflectance and electroreflectance. The optical data yields the electric field strengths of the individual layers to determine the density of the two-dimensional carrier gases at the heterointerfaces with high accuracy. The surface potential is calculated from the combination of experiments and Schroedinger-Poisson calculations. Its dependency on the Al content is quantified. For the special case of thick cap layers the coexistence of electron and hole gases in one sample is experimentally proven for the first time. Several interband transitions between quantized states in AlN/GaN superlattices are observed by electroreflectance. The comparison to quantum mechanical calculations demonstrates the influence of strain and electrical fields (quantum confined Stark effect). For both the ratio of the thicknesses of quantum wells and barriers is crucial. From the dielectric function of the superlattices it becomes obvious, that quantum size effects are not only important for the vicinity of the bandgap, but

  17. Tight-Binding Approximations to Time-Dependent Density Functional Theory - a fast approach for the calculation of electronically excited states

    CERN Document Server

    Rüger, Robert; Heine, Thomas; Visscher, Lucas

    2016-01-01

    We propose a new method of calculating electronically excited states that combines a density functional theory (DFT) based ground state calculation with a linear response treatment that employs approximations used in the time-dependent density functional based tight binding (TD-DFTB) approach. The new method termed TD-DFT+TB does not rely on the DFTB parametrization and is therefore applicable to systems involving all combinations of elements. We show that the new method yields UV/Vis absorption spectra that are in excellent agreement with computationally much more expensive time-dependent density functional theory (TD-DFT) calculations. Errors in vertical excitation energies are reduced by a factor of two compared to TD-DFTB.

  18. Tight-binding approximations to time-dependent density functional theory - A fast approach for the calculation of electronically excited states.

    Science.gov (United States)

    Rüger, Robert; van Lenthe, Erik; Heine, Thomas; Visscher, Lucas

    2016-05-14

    We propose a new method of calculating electronically excited states that combines a density functional theory based ground state calculation with a linear response treatment that employs approximations used in the time-dependent density functional based tight binding (TD-DFTB) approach. The new method termed time-dependent density functional theory TD-DFT+TB does not rely on the DFTB parametrization and is therefore applicable to systems involving all combinations of elements. We show that the new method yields UV/Vis absorption spectra that are in excellent agreement with computationally much more expensive TD-DFT calculations. Errors in vertical excitation energies are reduced by a factor of two compared to TD-DFTB. PMID:27179467

  19. Tight-binding approximations to time-dependent density functional theory — A fast approach for the calculation of electronically excited states

    Science.gov (United States)

    Rüger, Robert; van Lenthe, Erik; Heine, Thomas; Visscher, Lucas

    2016-05-01

    We propose a new method of calculating electronically excited states that combines a density functional theory based ground state calculation with a linear response treatment that employs approximations used in the time-dependent density functional based tight binding (TD-DFTB) approach. The new method termed time-dependent density functional theory TD-DFT+TB does not rely on the DFTB parametrization and is therefore applicable to systems involving all combinations of elements. We show that the new method yields UV/Vis absorption spectra that are in excellent agreement with computationally much more expensive TD-DFT calculations. Errors in vertical excitation energies are reduced by a factor of two compared to TD-DFTB.

  20. Electronically Excited States of Vitamin B12: Benchmark Calculations Including Time-Dependent Density Functional Theory and Correlated Ab Initio Methods

    CERN Document Server

    Kornobis, Karina; Wong, Bryan M; Lodowski, Piotr; Jaworska, Maria; Andruniów, Tadeusz; Rudd, Kenneth; Kozlowski, Pawel M; 10.1021/jp110914y

    2011-01-01

    Time-dependent density functional theory (TD-DFT) and correlated ab initio methods have been applied to the electronically excited states of vitamin B12 (cyanocobalamin or CNCbl). Different experimental techniques have been used to probe the excited states of CNCbl, revealing many issues that remain poorly understood from an electronic structure point of view. Due to its efficient scaling with size, TD-DFT emerges as one of the most practical tools that can be used to predict the electronic properties of these fairly complex molecules. However, the description of excited states is strongly dependent on the type of functional used in the calculations. In the present contribution, the choice of a proper functional for vitamin B12 was evaluated in terms of its agreement with both experimental results and correlated ab initio calculations. Three different functionals, i.e. B3LYP, BP86, and LC-BLYP, were tested. In addition, the effect of relative contributions of DFT and HF to the exchange-correlation functional ...

  1. Fabrication of Al2O3-W Functionally Graded Materials by Slipcasting Method

    International Nuclear Information System (INIS)

    We have successfully fabricated a functionally graded material (FGM) from tungsten and alumina powders by a slip-casting method. This FGM has applications as a sealing and conducting component for high-intensity discharge lamps (HiDLs) that have a translucent alumina envelope. Two types of W powder, with different oxidizing properties, were used as the raw powders for the Al2O3-W FGM. 'Oxidized W' was prepared by heat-treatment at 200 deg. C for 180 min in air. Alumina and each of the W powders were mixed in ultrapure water by ultrasonic stirring. The slurry was then cast into a cylindrical acrylic mold, which had a base of porous alumina, under controlled pressure. The green compacts were subsequently dried, and then sintered using a vacuum furnace at 1600 deg. C for a fixed time. The microstructures of the FGMs were observed by scanning electron microscopy (SEM) of the polished section. The Al2O3-W FGM with the 'oxidized W' powder resulted in a microscopic compositional gradient. However, the FGM with 'as-received W' showed no compositional gradient. This result was mainly attributed to the difference between the ζ-potentials of the W powders with the different oxidizing conditions; basically 'oxidized W' powder tends to disperse because of the larger ζ-potential of the oxide layer coated on the W powder core.

  2. Microstructure and Functional Mechanism of Friction Layer in Ni3Al Matrix Composites with Graphene Nanoplatelets

    Science.gov (United States)

    Xue, Bing; Zhu, Qingshuai; Shi, Xiaoliang; Zhai, Wenzheng; Yang, Kang; Huang, Yuchun

    2016-08-01

    Microstructure and functional mechanism of friction layer need to be further researched. In the present work, the friction coefficients and wear rates are analyzed through response surface methodology to obtain an empirical model for the best response. Fitting results show that the tribological performance of Ni3Al matrix composites (NMCs) with graphene nanoplatelets (GNPs) is better than that of NMCs without GNPs, especially at high sliding velocities and high loads. Further research suggests that the formation of integrated friction layer, which consists of a soft microfilm on a hard coating, is the major reason to cause the differences. Of which, the wear debris layer (WDL) with a low shear strength can reduce the shear force. The ultrafine layer (UL), which is much harder and finer, can effectively avoid fracture and improve the load support capacity. Moreover, the GNPs in WDL and UL can be easily sheared and help to withstand the loads, trending to be parallel to the direction of shear force.

  3. Lowest excited states and optical absorption spectra of donor–acceptor copolymers for organic photovoltaics: a new picture emerging from tuned long-range corrected density functionals

    KAUST Repository

    Pandey, Laxman

    2012-01-01

    Polymers with low optical gaps are of importance to the organic photovoltaics community due to their potential for harnessing a large portion of the solar energy spectrum. The combination along their backbones of electron-rich and electron-deficient fragments contributes to the presence of low-lying excited states that are expected to display significant charge-transfer character. While conventional hybrid functionals are known to provide unsatisfactory results for charge-transfer excitations at the time-dependent DFT level, long-range corrected (LRC) functionals have been reported to give improved descriptions in a number of systems. Here, we use such LRC functionals, considering both tuned and default range-separation parameters, to characterize the absorption spectra of low-optical-gap systems of interest. Our results indicate that tuned LRC functionals lead to simulated optical-absorption properties in good agreement with experimental data. Importantly, the lowest-lying excited states (excitons) are shown to present a much more localized nature than initially anticipated. © 2012 the Owner Societies.

  4. Effect of Excess Target Nucleons on The Main Features of Excitation Functions For Some Proton Induced Reactions Depending on Alice-IPPE Calculations

    International Nuclear Information System (INIS)

    Proton induced nuclear reactions at low proton energies are commonly used for production of radioactive isotopes which are important for many different applications. The production yield depends on excitation function features for the used nuclear reaction. In this work the excitation functions for more than 80 protons induced nuclear reactions were constructed using the ALICE-IPPE code which depends on the pre equilibrium model. Four groups of different isotopes were chosen to study the effect of the excess target neutrons on the threshold energy (Ethr), maximum reaction cross section (σmax) and the energy at maximum cross section (Emax). The selected groups were the natural isotopes of Ti, Cr, Fe and Ni. For the study of the effect of excess target protons on the same previous parameters, the excitation functions for the reactions on the isotones group 54Cr, 55Mn, 56Fe and 58Ni were performed at the same proton energy range. In order to understand the effect of the neutron to proton ratio on the previously mentioned parameters, proton reactions on the group of isobars 50Ti, 50V and 50Cr had been studied. In each case three protons induced reactions were undertaken, manly (p,n), (p,2n) and (p,3n). Each of the three previously mentioned parameters for each reaction were tabulated as a function of the excess number of nucleons and curve fit were constructed in order to get some phenomenological formulae for the behavior of these parameters

  5. Nickel-63 production in copper samples exposed to the Hiroshima atomic bomb: estimation based on an excitation function obtained by neutron irradiation experiments.

    Science.gov (United States)

    Takamiya, K; Imanaka, T; Ota, Y; Akamine, M; Shibata, S; Shibata, T; Ito, Y; Imamura, M; Uwamino, Y; Nogawa, N; Baba, M; Iwasaki, S; Matsuyama, S

    2008-07-01

    The upper and lower limits of the excitation function of the (63)Cu(n,p)(63)Ni reaction were experimentally determined, and the number of (63)Ni nuclei produced in copper samples exposed to atomic bomb neutrons in Hiroshima was estimated by using the experimental excitation functions and the neutron fluences given in the DS02 dosimetry system. The estimated number of (63)Ni nuclei was compared with that measured and with that calculated using the DS02 dosimetry system and the corresponding ENDF/B-VI cross section. In comparison with DS02, there is about a 60% maximum difference in (63)Ni production at the hypocenter when the experimental upper cross section values are used. The difference becomes smaller at greater distances from the hypocenter and decreases, for example, to less than 30 and 5% when using the upper and lower experimental cross sections at 1,000 m, respectively. PMID:18496703

  6. Excitation functions of some neutron threshold reactions on 89Y in the energy range of 7.8 to 14.7 MeV

    International Nuclear Information System (INIS)

    Excitation functions were measured for 89Y(n,2n)88Y, 89Y(n,p)89Sr and 89Y(n,α)86Rb reactions from their respective thresholds up to 14.7 MeV using the activation technique. Quasi-monoenergetic neutrons in the energy range of 7.8 to 13.3 MeV were produced via the 2H(d,n)3He reaction on a D2 gas target at the Juelich compact cyclotron (CV 28), and monoenergetic neutrons in the range of 13.8 to 14.7 MeV using the D-T neutron generator at Debrecen. For characterization of 88Y and 86Rb, high-resolution γ-ray spectrometry was applied. The latter product was also separated radiochemically and characterized by low-level β- counting; the results obtained using the two counting methods were generally in good agreement. The product 89Sr is a pure β- emitter: its activity was exclusively assayed via radiochemical separation and β- counting. Our results agree with the literature values on the (n,2n) reaction and provide the first consistent set of data on the (n,p) and (n,α) reactions near their thresholds. Statistical model calculations incorporating precompound effects were performed on the three excitation functions under consideration. The experimental and theoretical results were found to be in good agreement. Some systematic trends in the excitation functions in this mass region are discussed. (orig.)

  7. Functions and mechanism of modification elements in eutectic solidification of Al-Si alloys: A brief review

    Directory of Open Access Journals (Sweden)

    Zu Fangqiu

    2014-07-01

    Full Text Available Being used more and more widely in engineering, Al-Si alloys comprise about 80% of all kinds of aluminum alloys, which are the most widely utilized nonferrous alloys. Although most Al-Si alloys consist of multiple components, the eutectics in the structure accounts for 50%-90% of the sum volume of such alloys. Therefore, understanding the modification mechanism and function rules of the Al-Si eutectic solidification is the technical key in controlling the structures and properties of such casting alloys. The present paper chiefly reviews recent investigation developments and important conclusions along the lines of the functions of modification elements and their modification mechanism in the eutectic solidification of Al-Si alloys.

  8. Density functional theory study of phase stability, vibrational and electronic properties of $Mo_3Al_2C$

    OpenAIRE

    Reith, D.; Blaas-Schenner, C.; Podloucky, R.

    2012-01-01

    Based on density functional theory the noncentrosymmetric superconductor Mo_3Al_2C in its well established {\\beta}-Mn type ($P4_{1}32$) crystal structure is investigated. In particular, its thermodynamical and dynamical stabilities are studied by calculating lattice vibrations within the harmonic approximation. It is found that the fully stoichiometric compound is dynamically unstable. However, compounds with carbon vacancies, i.e., Mo_3Al_2C_{1-x}, can be dynamically stabilized for vacancy c...

  9. Organic electronic materials: Recent advances in the dft description of the ground and excited states using tuned range-separated hybrid functionals

    KAUST Repository

    Körzdörfer, Thomas

    2014-11-18

    Density functional theory (DFT) and its time-dependent extension (TD-DFT) are powerful tools enabling the theoretical prediction of the ground- and excited-state properties of organic electronic materials with reasonable accuracy at affordable computational costs. Due to their excellent accuracy-to-numerical-costs ratio, semilocal and global hybrid functionals such as B3LYP have become the workhorse for geometry optimizations and the prediction of vibrational spectra in modern theoretical organic chemistry. Despite the overwhelming success of these out-of-the-box functionals for such applications, the computational treatment of electronic and structural properties that are of particular interest in organic electronic materials sometimes reveals severe and qualitative failures of such functionals. Important examples include the overestimation of conjugation, torsional barriers, and electronic coupling as well as the underestimation of bond-length alternations or excited-state energies in low-band-gap polymers.In this Account, we highlight how these failures can be traced back to the delocalization error inherent to semilocal and global hybrid functionals, which leads to the spurious delocalization of electron densities and an overestimation of conjugation. The delocalization error for systems and functionals of interest can be quantified by allowing for fractional occupation of the highest occupied molecular orbital. It can be minimized by using long-range corrected hybrid functionals and a nonempirical tuning procedure for the range-separation parameter.We then review the benefits and drawbacks of using tuned long-range corrected hybrid functionals for the description of the ground and excited states of π-conjugated systems. In particular, we show that this approach provides for robust and efficient means of characterizing the electronic couplings in organic mixed-valence systems, for the calculation of accurate torsional barriers at the polymer limit, and for the

  10. Highly efficient implementation of pseudospectral time-dependent density-functional theory for the calculation of excitation energies of large molecules.

    Science.gov (United States)

    Cao, Yixiang; Hughes, Thomas; Giesen, Dave; Halls, Mathew D; Goldberg, Alexander; Vadicherla, Tati Reddy; Sastry, Madhavi; Patel, Bhargav; Sherman, Woody; Weisman, Andrew L; Friesner, Richard A

    2016-06-15

    We have developed and implemented pseudospectral time-dependent density-functional theory (TDDFT) in the quantum mechanics package Jaguar to calculate restricted singlet and restricted triplet, as well as unrestricted excitation energies with either full linear response (FLR) or the Tamm-Dancoff approximation (TDA) with the pseudospectral length scales, pseudospectral atomic corrections, and pseudospectral multigrid strategy included in the implementations to improve the chemical accuracy and to speed the pseudospectral calculations. The calculations based on pseudospectral time-dependent density-functional theory with full linear response (PS-FLR-TDDFT) and within the Tamm-Dancoff approximation (PS-TDA-TDDFT) for G2 set molecules using B3LYP/6-31G*(*) show mean and maximum absolute deviations of 0.0015 eV and 0.0081 eV, 0.0007 eV and 0.0064 eV, 0.0004 eV and 0.0022 eV for restricted singlet excitation energies, restricted triplet excitation energies, and unrestricted excitation energies, respectively; compared with the results calculated from the conventional spectral method. The application of PS-FLR-TDDFT to OLED molecules and organic dyes, as well as the comparisons for results calculated from PS-FLR-TDDFT and best estimations demonstrate that the accuracy of both PS-FLR-TDDFT and PS-TDA-TDDFT. Calculations for a set of medium-sized molecules, including Cn fullerenes and nanotubes, using the B3LYP functional and 6-31G(**) basis set show PS-TDA-TDDFT provides 19- to 34-fold speedups for Cn fullerenes with 450-1470 basis functions, 11- to 32-fold speedups for nanotubes with 660-3180 basis functions, and 9- to 16-fold speedups for organic molecules with 540-1340 basis functions compared to fully analytic calculations without sacrificing chemical accuracy. The calculations on a set of larger molecules, including the antibiotic drug Ramoplanin, the 46-residue crambin protein, fullerenes up to C540 and nanotubes up to 14×(6,6), using the B3LYP functional and 6-31G

  11. HgNO3 sensitivity of AlGaN/GaN field effect transistors functionalized with phytochelating peptides

    Science.gov (United States)

    Rohrbaugh, Nathaniel; Hernandez-Balderrama, Luis; Kaess, Felix; Kirste, Ronny; Collazo, Ramon; Ivanisevic, Albena

    2016-06-01

    This study examined the conductance sensitivity of AlGaN/GaN field effect transistors in response to varying Hg/HNO3 solutions. FET surfaces were covalently functionalized with phytochelatin-5 peptides in order to detect Hg in solution. Results showed a resilience of peptide-AlGaN/GaN bonds in the presence of strong HNO3 aliquots, with significant degradation in FET ID signal. However, devices showed strong and varied response to Hg concentrations of 1, 10, 100, and 1000 ppm. The gathered statistically significant results indicate that peptide terminated AlGaN/GaN devices are capable of differentiating between Hg solutions and demonstrate device sensitivity.

  12. Tunnel spin injection into graphene using Al2O3 barrier grown by atomic layer deposition on functionalized graphene surface

    OpenAIRE

    Yamaguchi, Takehiro; Masubuchi, Satoru; Iguchi, Kazuyuki; Moriya, Rai; Machida, Tomoki

    2011-01-01

    We demonstrate electrical tunnel spin injection from a ferromagnet to graphene through a high-quality Al2O3 grown by atomic layer deposition (ALD). The graphene surface is functionalized with a self-assembled monolayer of 3,4,9,10-perylene tetracarboxylic acid (PTCA) to promote adhesion and growth of Al2O3 with a smooth surface. Using this composite tunnel barrier of ALD-Al2O3 and PTCA, a spin injection signal of 30 ohm has been observed from non-local magnetoresistance measurements at 45 K, ...

  13. Critical Assessment of Time-Dependent Density Functional Theory for Excited States of Open-Shell Systems: II. Doublet-Quartet Transitions.

    Science.gov (United States)

    Li, Zhendong; Liu, Wenjian

    2016-06-14

    Compared with closed-shell systems, open-shell systems place three additional challenges to time-dependent density functional theory (TD-DFT) for electronically excited states: (a) the spin-contamination problem is a serious issue; (b) the exchange-correlation (XC) kernel may be numerically instable; and (c) the single-determinant description of open-shell ground states readily becomes energetically instable. Confined to flip-up single excitations, the spin-contamination problem can largely be avoided by using the spin-flip TD-DFT (SF-TD-DFT) formalism, provided that a noncollinear XC kernel is employed. As for the numerical instabilities associated with such a kernel, only an ad hoc scheme has been proposed so far, viz., the ALDA0 kernel, which amounts to setting the divergent components (arising from density gradients and kinetic energy density) simply to zero. The ground-state instability problem can effectively be avoided by introducing the Tamm-Dancoff approximation (TDA) to TD-DFT. Therefore, on a general basis, the SF-TDA/ALDA0 Ansatz is so far the only promising means within the TD-DFT framework for flip-up single excitations of open-shell systems. To assess systematically the performance of SF-TDA/ALDA0, in total 61 low-lying quartet excited states of the benchmark set of 11 small radicals [J. Chem. Theory Comput. 2016, 12, 238] are investigated with various XC functionals. Taking the MRCISD+Q (multireference configuration interaction with singles and doubles plus the Davidson correction) results as benchmark, it is found that the mean absolute errors of SF-TDA/ALDA0 with the SAOP (statistical averaging of model orbital potentials), global hybrid, and range-separated hybrid functionals are in the range of 0.2-0.4 eV. This is in line not only with the typical accuracy of TD-DFT for singlet and triplet excited states of closed-shell systems but also with the gross accuracy of spin-adapted TD-DFT for spin-conserving excited states of open-shell systems. PMID

  14. Synthesis and functionalization of monodisperse near-ultraviolet and visible excitable multifunctional Eu3+, Bi3+:REVO4 nanophosphors for bioimaging and biosensing applications

    Science.gov (United States)

    Escudero, Alberto; Carrillo-Carrión, Carolina; Zyuzin, Mikhail V.; Ashraf, Sumaira; Hartmann, Raimo; Núñez, Nuria O.; Ocaña, Manuel; Parak, Wolfgang J.

    2016-06-01

    Near-ultraviolet and visible excitable Eu- and Bi-doped NPs based on rare earth vanadates (REVO4, RE = Y, Gd) have been synthesized by a facile route from appropriate RE precursors, europium and bismuth nitrate, and sodium orthovanadate, by homogeneous precipitation in an ethylene glycol/water mixture at 120 °C. The NPs can be functionalized either by a one-pot synthesis with polyacrylic acid (PAA) or by a Layer-by-Layer approach with poly(allylamine hydrochloride) (PAH) and PAA. In the first case, the particle size can also be tuned by adjusting the amount of PAA. The Eu- Bi-doped REVO4 based nanophosphors show the typical red luminescence of Eu(iii), which can be excited through an energy transfer process from the vanadate anions, resulting in a much higher luminescence intensity in comparison to the direct excitation of the europium cations. The incorporation of Bi into the REVO4 structure shifts the original absorption band of the vanadate anions towards longer wavelengths, giving rise to nanophosphors with an excitation maximum at 342 nm, which can also be excited in the visible range. The suitability of such nanophosphors for bioimaging and biosensing applications, as well as their colloidal stability in different buffer media of biological interest, their cytotoxicity, their degradability at low pH, and their uptake by HeLa cells have been evaluated. Their suitability for bioimaging and biosensing applications is also demonstrated.Near-ultraviolet and visible excitable Eu- and Bi-doped NPs based on rare earth vanadates (REVO4, RE = Y, Gd) have been synthesized by a facile route from appropriate RE precursors, europium and bismuth nitrate, and sodium orthovanadate, by homogeneous precipitation in an ethylene glycol/water mixture at 120 °C. The NPs can be functionalized either by a one-pot synthesis with polyacrylic acid (PAA) or by a Layer-by-Layer approach with poly(allylamine hydrochloride) (PAH) and PAA. In the first case, the particle size can also be

  15. Corrosion and wear behavior of functionally graded Al2024/SiC composites produced by hot pressing and consolidation

    International Nuclear Information System (INIS)

    Highlights: • Functionally graded Al2024/SiC composites were produced by hot pressing. • Effect of the number of graded layers was investigated on the corrosion behavior. • Functionally graded composites has the most corrosion resistant than composites. • Wear mechanisms of Al2024/SiC composites were explained. - Abstract: Functionally graded Al2024/SiC composites (FGMs) with varying percentage of SiC (30–60%) were produced by hot pressing and consolidation method. The effects of SiC content and number of layers of Al2024/SiC FGMs on the corrosion and wear behaviors were investigated. The microstructures of these composites were characterized by a scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). The corrosion performances of composites were evaluated by potentiodynamic polarization scans in 3.5% NaCl solution. Corrosion experiments shows that corrosion rate (1109 mpy) of two layered FGMs which containing 50 wt.% SiC were much higher than Al2024 matrix (2569 mpy) and Al2024/50 wt.% SiC composite (2201 mpy). Mechanical properties of these composites were evaluated by microhardness measurements and ball-on-disk wear tests. As the applied load change from 15 to 20 N, the wear rates of the Al2024 increased significantly and wear mechanism transformed from mild to severe wear regime. It has been shown that Al2024/40 wt.% SiC composite has lower wear rate where adhesive and abrasive wear mechanisms play a major role

  16. Corrosion and wear behavior of functionally graded Al2024/SiC composites produced by hot pressing and consolidation

    Energy Technology Data Exchange (ETDEWEB)

    Erdemir, Fatih; Canakci, Aykut, E-mail: aykut@ktu.edu.tr; Varol, Temel; Ozkaya, Serdar

    2015-09-25

    Highlights: • Functionally graded Al2024/SiC composites were produced by hot pressing. • Effect of the number of graded layers was investigated on the corrosion behavior. • Functionally graded composites has the most corrosion resistant than composites. • Wear mechanisms of Al2024/SiC composites were explained. - Abstract: Functionally graded Al2024/SiC composites (FGMs) with varying percentage of SiC (30–60%) were produced by hot pressing and consolidation method. The effects of SiC content and number of layers of Al2024/SiC FGMs on the corrosion and wear behaviors were investigated. The microstructures of these composites were characterized by a scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). The corrosion performances of composites were evaluated by potentiodynamic polarization scans in 3.5% NaCl solution. Corrosion experiments shows that corrosion rate (1109 mpy) of two layered FGMs which containing 50 wt.% SiC were much higher than Al2024 matrix (2569 mpy) and Al2024/50 wt.% SiC composite (2201 mpy). Mechanical properties of these composites were evaluated by microhardness measurements and ball-on-disk wear tests. As the applied load change from 15 to 20 N, the wear rates of the Al2024 increased significantly and wear mechanism transformed from mild to severe wear regime. It has been shown that Al2024/40 wt.% SiC composite has lower wear rate where adhesive and abrasive wear mechanisms play a major role.

  17. Time-dependent density functional study on the electronic excitation energies of polycyclic aromatic hydrocarbon radical cations of naphthalene, anthracene, pyrene, and perylene

    International Nuclear Information System (INIS)

    Time-dependent density functional theory (TDDFT) and its modification, the Tamm - Dancoff approximation to TDDFT, are employed to calculate the electronic excitation energies and oscillator strengths for a series of polycyclic aromatic hydrocarbon radical cations. For the radical cations of naphthalene and anthracene, TDDFT using the Becke - Lee - Yang - Parr functional and the 6-31G** basis set provides the excitation energies that are roughly within 0.3 eV of the experimental data. The assignments of the electron transitions proposed by TDDFT accord with the previous assignments made by accurate ab initio calculations, except that TDDFT indicates the existence of a few additional transitions of π*left-arrow σ character among the several low-lying transitions. The calculated energies for these π*left-arrow σ transitions are found to be consistent with the onset of a σ electron ionization manifold in the photoelectron spectra. For the pyrene radical cation, TDDFT supports the previous assignments made by semiempirical calculations, whereas for the perylene radical cation, TDDFT suggests the energy ordering of the three lowest-lying excited states be changed from those of the semiempirical results. copyright 1999 American Institute of Physics

  18. On the truncation of the number of excited states in density functional theory sum-over-states calculations of indirect spin spin coupling constants

    Energy Technology Data Exchange (ETDEWEB)

    Zarycz, M. Natalia C., E-mail: mnzarycz@gmail.com; Provasi, Patricio F., E-mail: patricio@unne.edu.ar [Department of Physics, University of Northeastern - CONICET, Av. Libertad 5500, Corrientes W3404AAS (Argentina); Sauer, Stephan P. A., E-mail: sauer@kiku.dk [Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø (Denmark)

    2015-12-28

    It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCCs), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections of the Polarization Propagator (IPPP-CLOPPA) approach to analyzing SSCCs in terms of localized orbitals. As a test set we have studied the nine simple compounds, CH{sub 4}, NH{sub 3}, H{sub 2}O, SiH{sub 4}, PH{sub 3}, SH{sub 2}, C{sub 2}H{sub 2}, C{sub 2}H{sub 4}, and C{sub 2}H{sub 6}. The excited (pseudo)states were obtained from time-dependent density functional theory (TD-DFT) calculations with the B3LYP exchange-correlation functional and the specialized core-property basis set, aug-cc-pVTZ-J. We investigated both how the calculated coupling constants depend on the number of (pseudo)states included in the summation and whether the summation can be truncated in a systematic way at a smaller number of states and extrapolated to the total number of (pseudo)states for the given one-electron basis set. We find that this is possible and that for some of the couplings it is sufficient to include only about 30% of the excited (pseudo)states.

  19. On the truncation of the number of excited states in density functional theory sum-over-states calculations of indirect spin spin coupling constants

    International Nuclear Information System (INIS)

    It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCCs), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections of the Polarization Propagator (IPPP-CLOPPA) approach to analyzing SSCCs in terms of localized orbitals. As a test set we have studied the nine simple compounds, CH4, NH3, H2O, SiH4, PH3, SH2, C2H2, C2H4, and C2H6. The excited (pseudo)states were obtained from time-dependent density functional theory (TD-DFT) calculations with the B3LYP exchange-correlation functional and the specialized core-property basis set, aug-cc-pVTZ-J. We investigated both how the calculated coupling constants depend on the number of (pseudo)states included in the summation and whether the summation can be truncated in a systematic way at a smaller number of states and extrapolated to the total number of (pseudo)states for the given one-electron basis set. We find that this is possible and that for some of the couplings it is sufficient to include only about 30% of the excited (pseudo)states

  20. Optical excitation function of H(1s-2p) produced by electron impact from threshold to 1.8 keV

    Energy Technology Data Exchange (ETDEWEB)

    James, G.K. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States); Slevin, J.A. [Department of Experimental Physics, St. Patricks College, Maynooth, County Kildare (Ireland); Shemansky, D.E. [Department of Aerospace Engineering, University of Southern California, Los Angeles, California 90089 (United States); McConkey, J.W. [Department of Physics, University of Windsor, Windsor, Ontario, N9B3P4 (CANADA); Bray, I. [Electronic Structure of Materials Centre, The Flinders University of South Australia, G.P.O. Box 2100, Adelaide 5001 (Australia); Dziczek, D. [Institute of Physics, Nicholas Copernicus University, 87-100 Torun (Poland); Kanik, I.; Ajello, J.M. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States)

    1997-02-01

    The optical excitation function of prompt Lyman-{alpha} radiation, produced by electron impact on atomic hydrogen, has been measured over the extended energy range from threshold to 1.8 keV. Measurements were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source. A vacuum-ultraviolet monochromator system was used to measure the emitted Lyman-{alpha} radiation. The absolute H(1s-2p) electron impact excitation cross section was obtained from the experimental optical excitation function by normalizing to the accepted optical oscillator strength, with corrections for polarization and cascade. Our data are significantly different from the earlier experimental results and which are limited to energies below 200 eV. Statistical and known systematic uncertainties in our data range from {plus_minus}4{percent} near threshold to {plus_minus}2{percent} at 1.8 keV. Multistate coupling affecting the shape of the excitation function up to 1 keV impact energy is apparent in both the present experimental data and present theoretical results obtained with convergent close-coupling (CCC) theory. This shape function effect leads to an uncertainty in absolute cross sections at the 10{percent} level in the analysis of the experimental data. The derived optimized absolute cross sections are within 7{percent} of the CCC calculations over the 14 eV{endash}1.8 keV range. The present CCC calculations converge on the Bethe-Fano profile for H(1s-2p) excitation at high energy. For this reason agreement with the CCC values to within 3{percent} is achieved in a nonoptimal normalization of the experimental data to the Bethe-Fano profile. The fundamental H(1s-2p) electron impact cross section is thereby determined to an unprecedented accuracy over the 14 eV {endash} 1.8 keV energy range. (Abstract Truncated)

  1. Anharmonicity of multi-octupole-phonon excitations in $^{208}$Pb: analysis with multi-reference covariant density functional theory and subbarrier fusion of $^{16}$O+$^{208}$Pb

    CERN Document Server

    Yao, J M

    2016-01-01

    We discuss anharmonicity of the multi-octupole-phonon states in $^{208}$Pb based on a covariant density functional theory, by fully taking into account the interplay between the quadrupole and the octupole degrees of freedom. Our results indicate the existence of a large anharmonicity in the transition strengths, even though the excitation energies are similar to those in the harmonic limit. We also show that the quadrupole-shape fluctuation significantly enhances the fragmentation of the two-octupole-phonon states in $^{208}$Pb. Using those transition strengths as inputs to coupled channels calculations, we then discuss the fusion reaction of $^{16}$O+$^{208}$Pb at energies around the Coulomb barrier. We show that the anharmonicity of the octupole vibrational excitation considerably improves previous coupled-channels calculations in the harmonic oscillator limit, significantly reducing the height of the main peak in the fusion barrier distribution.

  2. Microstructural analysis of the radial distribution function for liquid and amorphous Al

    CERN Document Server

    Li, G X; Zhu, Z G; Liu, C S

    2003-01-01

    Constant-pressure molecular dynamics simulations and analysis of the local atomic structures have been performed to study the conventional and 'inherent' structural evolution of liquid Al during rapid solidification. The results show that the radial distribution functions g(r) exhibit a second-peak splitting feature not only for the general structures of the amorphous states but also for the inherent structure of liquid states. The second peak of g(r) decomposes into three main components, each corresponding to different pairs. The first subpeak in the inherent structure of the liquid arises from 2211 and 2331 pairs (which correspond to triangles with a common side and the tetrahedra sharing a face respectively), while the first subpeak in the amorphous state arises from 2331 pairs; in both cases the second subpeak is due to the 2101 pairs (linear trimers). The existence of a shoulder or the splitting in the second peak of g(r) in the amorphous state, and even in the undercooled liquid state, results mainly f...

  3. Microstructural analysis of the radial distribution function for liquid and amorphous Al

    International Nuclear Information System (INIS)

    Constant-pressure molecular dynamics simulations and analysis of the local atomic structures have been performed to study the conventional and 'inherent' structural evolution of liquid Al during rapid solidification. The results show that the radial distribution functions g(r) exhibit a second-peak splitting feature not only for the general structures of the amorphous states but also for the inherent structure of liquid states. The second peak of g(r) decomposes into three main components, each corresponding to different pairs. The first subpeak in the inherent structure of the liquid arises from 2211 and 2331 pairs (which correspond to triangles with a common side and the tetrahedra sharing a face respectively), while the first subpeak in the amorphous state arises from 2331 pairs; in both cases the second subpeak is due to the 2101 pairs (linear trimers). The existence of a shoulder or the splitting in the second peak of g(r) in the amorphous state, and even in the undercooled liquid state, results mainly from the increase in number of and aggregation of the tetrahedra, which in turn give rise to the presence of entities with local icosahedral order

  4. Ni–Fe–Al$_2$O$_3$ electrodeposited nanocomposite coating with functionally graded microstructure

    Indian Academy of Sciences (India)

    V TORABINEJAD; A SABOUR ROUHAGHDAM; M ALIOFKHAZRAEI; M H ALLAHYARZADEH

    2016-06-01

    In this study, a Ni–Fe–Al$_2$O$_3$ nanocomposite coating was deposited on the substrate of low-carbon steel by electrodeposition from a sulphate-based bath. The effects of frequency and duty cycle were investigated to producethe functionally graded (FG) coating. For this purpose, first, the coatings with duty cycle-decreased method (DDM) were deposited in eight steps from 88 to 11%. At the second step, frequency-increased method (FIM) was utilized from 50 to 6400 Hz during eight steps. Assessing of coatings was carried out by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), potentiodynamic test, Vickers microhardness test and wear test.Microstructure evaluations gained by SEM and EDS demonstrated that the continuous alterations of duty cycle contribute for manufacturing of FG coatings, so that the maximum particle fraction was in the free surface of the coating and its amount was gradually decreased to the interface. These investigations showed that FIM had no effect on production of graded structure. Corrosion and wear tests indicated high corrosion and wear resistance of DDM coatings in comparison to FIM coatings. Investigating the best coatings obtained from both above methods exhibited 50 and 20% reduction in corrosion current density and wear rate, respectively, for DDM specimen in comparison to FIM sample.

  5. Temporal evolution of ion energy distribution functions and ion charge states of Cr and Cr-Al pulsed arc plasmas

    International Nuclear Information System (INIS)

    To study the temporal evolution of ion energy distribution functions, charge-state-resolved ion energy distribution functions of pulsed arc plasmas from Cr and Cr-Al cathodes were recorded with high time resolution by using direct data acquisition from a combined energy and mass analyzer. The authors find increases in intensities of singly charged ions, which is evidence that charge exchange reactions took place in both Cr and Cr-Al systems. In Cr-Al plasmas, the distributions of high-charge-state ions exhibit high energy tails 50 μs after discharge ignition, but no such tails were observed at 500 μs. The energy ratios of ions of different charge states at the beginning of the pulse, when less neutral atoms were in the space in front of the cathode, suggest that ions are accelerated by an electric field. The situation is not so clear after 50 μs due to particle collisions. The initial mean ion charge state of Cr was about the same in Cr and in Cr-Al plasmas, but it decreased more rapidly in Cr-Al plasmas compared to the decay in Cr plasma. The faster decay of the mean ion charge state and ion energy caused by the addition of Al into a pure Cr cathode suggests that the mean ion charge state is determined not only by ionization processes at the cathode spot but also by inelastic collision between different elements

  6. Temporal evolution of ion energy distribution functions and ion charge states of Cr and Cr-Al pulsed arc plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Koichi, E-mail: tanak@mmc.co.jp [Central Research Institute, Mitsubishi Materials Corporation, 1002-14 Mukohyama, Naka-shi, Ibaraki 311-0102 (Japan); Anders, André [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 53, Berkeley, California 94720 (United States)

    2015-11-15

    To study the temporal evolution of ion energy distribution functions, charge-state-resolved ion energy distribution functions of pulsed arc plasmas from Cr and Cr-Al cathodes were recorded with high time resolution by using direct data acquisition from a combined energy and mass analyzer. The authors find increases in intensities of singly charged ions, which is evidence that charge exchange reactions took place in both Cr and Cr-Al systems. In Cr-Al plasmas, the distributions of high-charge-state ions exhibit high energy tails 50 μs after discharge ignition, but no such tails were observed at 500 μs. The energy ratios of ions of different charge states at the beginning of the pulse, when less neutral atoms were in the space in front of the cathode, suggest that ions are accelerated by an electric field. The situation is not so clear after 50 μs due to particle collisions. The initial mean ion charge state of Cr was about the same in Cr and in Cr-Al plasmas, but it decreased more rapidly in Cr-Al plasmas compared to the decay in Cr plasma. The faster decay of the mean ion charge state and ion energy caused by the addition of Al into a pure Cr cathode suggests that the mean ion charge state is determined not only by ionization processes at the cathode spot but also by inelastic collision between different elements.

  7. Excitation functions and yields of proton induced reactions at intermediate energies leading to important diagnostics radioisotopes of 52Fe, 77Br, 82Rb, 97Ru, 111In, 123I, 127Xe, 128Cs, 178Ta and 201Tl

    International Nuclear Information System (INIS)

    This report describes investigations of the excitation functions of the proton induced reactions on 14 targets (Mn, Co, Br, Rb, 99Tc, 113Cd, 114Cd, Cd, I, Cs, Ta, 206,207,208Pb) leading directly or indirectly to the formation of radionuclides 52Fe, 77Br, 82Rb, 97Ru, 111In, 123I, 127Xe, 128Cs, 178Ta and 201Tl frequently used in diagnostic procedures of nuclear medicine. The measurements of the excitation functions were made over a wide proton energy range from the reaction threshold up to 100 MeV using the stacked foil (or pellet) technique. Small energy steps were used to allow for accurate determination of the structure of excitation functions. For 97Ru, 111In and 127Xe formation with protons, new reaction channels and targets were used and data concerning this method are published for the first time. The data for 52Fe, 77Br, 82Rb, 123I, 128Cs and 201Tl obtained in the present work for the Ep=70-100 MeV region are also published for the first time. The measured excitation functions for the formation of desired (and undesired) radionuclides (altogether 28 excitation functions) are compared with the theoretical ones calculated on the basis of a hybrid model of nuclear reactions in the form of the Overlaid Alice computer code. In order to determine the contribution of the competitive reaction channels to the purity of the produced, desired radionuclide, the excitation functions of the accompanying reactions were also calculated. The 122 calculated excitation functions for the possible contaminant are given in the present work. The comparison of experimental excitation functions with the results of model calculations showed satisfactory agreement, especially if one considers, that no parameter adjustment for individual reaction products was undertaken. From the measured excitation functions the production yields for 28 radionuclides mentioned above have been determined (author). 262 refs, 65 figs, 34 tabs

  8. Nuclear excitation in plasma

    International Nuclear Information System (INIS)

    4 main electromagnetic excitation processes of atomic nuclei in hot dense plasma are reviewed: the black body photon absorption, the electron inelastic scattering, the nuclear excitation by electron capture (NEEC effect) and the nuclear excitation by electron transition (NEET effect). Experimental results on Ta181m are commented and an experiment showing the NEEC effect on Fe57 is described. A model including all the phenomena of excitation and de-excitation of a nuclear state in plasma, has been developed. Predictions about the evolution of the life-time of a nuclear excited state as a function of the temperature and density are made. A complete calculation of the NEET effect of the first excited state of U235 in a local thermodynamic equilibrium plasma is presented. Some experimental works on the excitation of U235m in a laser-produced plasma are discussed. The NEET effect on Hg201 in a laser-produced plasma is also considered in both theoretical and experimental aspects

  9. Excited-state dynamics of Yb.sup.2+./sup. in LiCaAlF.sub.6./sub. single crystal

    Czech Academy of Sciences Publication Activity Database

    Bensalah, A.; Nikl, Martin; Mihóková, Eva; Solovieva, Natalia; Vedda, A.; Sato, H.; Fukuda, T.; Boulon, G.

    2004-01-01

    Roč. 38, - (2004), s. 545-548. ISSN 1350-4487 R&D Projects: GA AV ČR(CZ) IAA1010305 Institutional research plan: CEZ:AV0Z1010914 Keywords : LiCaAlF 6 Yb 2+ * photoluminescence * thermoluminescence * decay kinetics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.664, year: 2004

  10. Time-course of corticospinal excitability and autonomic function interplay during and following monopolar tDCS

    Directory of Open Access Journals (Sweden)

    Emiliano eSantarnecchi

    2014-07-01

    Full Text Available While polarity-specific after-effects of monopolar transcranial direct current stimulation (tDCS on cortico-spinal excitability are well-documented, modulation of vital parameters due to current spread through the brainstem is still a matter of debate, raising potential concerns about its use through the general public, as well as for neurorehabilitation purposes. We monitored online and after-effects of monopolar tDCS (primary motor cortex in ten healthy subjects by adopting a neuronavigated transcranial magnetic stimulation (TMS/tDCS combined protocol. Motor evoked potentials (MEPs together with vital parameters (e.g. blood pressure, heart-rate variability and sympathovagal balance were recorded and monitored before, during and after anodal, cathodal or sham tDCS. Ten MEPs every 2.5-minute time windows were recorded from the right First Dorsal Interosseus (FDI, while 5-minute epochs were used to record vital parameters. The protocol included 15 minutes of pre-tDCS and of online-tDCS, (anodal, cathodal or sham. After effects were recorded for 30 minutes. We showed a polarity-independent stabilization of cortical excitability level, a polarity-specific after-effects for cathodal and anodal stimulation, and an absence of persistent excitability changes during online stimulation. No significant effects on vital parameters emerged both during and after tDCS, while a linear increase in systolic/diastolic blood pressure and heart-rate variability was observed during each tDCS condition, as a possible unspecific response to experimental demands. Taken together, current findings provide new insights on the safety of monopolar tDCS, promoting its application both in research and clinical settings.

  11. Excitable Scale Free Networks

    CERN Document Server

    Copelli, Mauro

    2007-01-01

    When a simple excitable system is continuously stimulated by a Poissonian external source, the response function (mean activity versus stimulus rate) generally shows a linear saturating shape. This is experimentally verified in some classes of sensory neurons, which accordingly present a small dynamic range (defined as the interval of stimulus intensity which can be appropriately coded by the mean activity of the excitable element), usually about one or two decades only. The brain, on the other hand, can handle a significantly broader range of stimulus intensity, and a collective phenomenon involving the interaction among excitable neurons has been suggested to account for the enhancement of the dynamic range. Since the role of the pattern of such interactions is still unclear, here we investigate the performance of a scale-free (SF) network topology in this dynamic range problem. Specifically, we study the transfer function of disordered SF networks of excitable Greenberg-Hastings cellular automata. We obser...

  12. Determination and systematics of excitation functions for the production of {sup 36}Cl by means of AMS

    Energy Technology Data Exchange (ETDEWEB)

    Sudbrock, F.; Herpers, U. [Koeln Univ. (Germany); Synal, H.A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Suter, M. [Eidgenoessische Technische Hochschule, Zurich (Switzerland); Gloris, M.; Michel, R. [Hannover Univ. (Germany)

    1997-09-01

    Studies concerning the production of the long-lived radionuclides {sup 10}Be, {sup 26}Al and {sup 36}Cl measured via accelerator mass spectrometry have been continued. Recently measured data on the production of {sup 36}Cl by medium and high energy protons are discussed. (author) 1 figs., 4 refs.

  13. Free electrons and ionic liquids: study of excited states by means of electron-energy loss spectroscopy and the density functional theory multireference configuration interaction method.

    Science.gov (United States)

    Regeta, Khrystyna; Bannwarth, Christoph; Grimme, Stefan; Allan, Michael

    2015-06-28

    The technique of low energy (0-30 eV) electron impact spectroscopy, originally developed for gas phase molecules, is applied to room temperature ionic liquids (IL). Electron energy loss (EEL) spectra recorded near threshold, by collecting 0-2 eV electrons, are largely continuous, assigned to excitation of a quasi-continuum of high overtones and combination vibrations of low-frequency modes. EEL spectra recorded by collecting 10 eV electrons show predominantly discrete vibrational and electronic bands. The vibrational energy-loss spectra correspond well to IR spectra except for a broadening (∼0.04 eV) caused by the liquid surroundings, and enhanced overtone activity indicating a contribution from resonant excitation mechanism. The spectra of four representative ILs were recorded in the energy range of electronic excitations and compared to density functional theory multireference configuration interaction (DFT/MRCI) calculations, with good agreement. The spectra up to about 8 eV are dominated by π-π* transitions of the aromatic cations. The lowest bands were identified as triplet states. The spectral region 2-8 eV was empty in the case of a cation without π orbitals. The EEL spectrum of a saturated solution of methylene green in an IL band showed the methylene green EEL band at 2 eV, indicating that ILs may be used as a host to study nonvolatile compounds by this technique in the future. PMID:26018044

  14. Revisiting the carbonyl n → π* electronic excitation through topological eyes: expanding, enriching and enhancing the chemical language using electron number distribution functions and domain averaged Fermi holes.

    Science.gov (United States)

    Ferro-Costas, David; Francisco, Evelio; Pendás, Ángel Martín; Mosquera, Ricardo A

    2015-10-21

    The theory of chemical bonding is underdeveloped in electronic excited states, even in small molecules. Fortunately, real space tools may be used to offer rich images of simple excitation processes, as is shown in this work. The statistics of electron populations, through a fruitful combination of electron distribution functions (EDFs) and domain averaged Fermi holes (DAFHs), was used to enlighten our chemical knowledge of a paradigmatic process: the n → π* excitation in formaldehyde. Interestingly, our results are perfectly compatible with an alternative perception of the electronic transition: the rotation of one averaged-electron in the oxygen lone pair. This topological model does not require inter-orbital jumps to explain the final electron distribution and, in our humble opinion, this fact makes it, to some extent, more realistic. Finally, other far-reaching conclusions emerge smoothly from our analysis: (i) the σ link may contribute less to the total bond order (as measured by the delocalization index) of a polar double bond than the π one; (ii) populating an antibonding orbital does not necessarily imply decreasing the bond order of its corresponding bond. PMID:26168082

  15. Excited states

    CERN Document Server

    Lim, Edward C

    1974-01-01

    Excited States, Volume I reviews radiationless transitions, phosphorescence microwave double resonance through optical spectra in molecular solids, dipole moments in excited states, luminescence of polar molecules, and the problem of interstate interaction in aromatic carbonyl compounds. The book discusses the molecular electronic radiationless transitions; the double resonance techniques and the relaxation mechanisms involving the lowest triplet state of aromatic compounds; as well as the optical spectra and relaxation in molecular solids. The text also describes dipole moments and polarizab

  16. Formation of Sm sup 2 sup + ions in femtosecond laser excited Al sub 2 O sub 3 - SiO sub 2 glasses

    CERN Document Server

    Park, G J; Nogami, M

    2003-01-01

    Al sub 2 O sub 3 - SiO sub 2 glasses doped with Sm sup 3 sup + ions were irradiated with an 800 nm wavelength femtosecond laser pulse and the formation of Sm sup 2 sup + ions was investigated. The Sm sup 3 sup + ions were reduced to Sm sup 2 sup + within a few minutes of laser irradiation. Electron spin resonance spectra indicated that the hole was trapped in non-bridging oxygen bound to Al sup 3 sup + , while the electron was captured in the Sm sup 3 sup + , leading to the Sm sup 2 sup + formation. The thermal stability of the photoinduced Sm sup 2 sup + ions was also investigated by fluorescence spectroscopy. The Sm sup 2 sup + ions were converted to Sm sup 3 sup + ions by heating the glasses in air at 300- 400 deg. C.

  17. An analysis of fluctuations connected with the precompound and compound emission in the 27Al(3He,p) reaction

    International Nuclear Information System (INIS)

    Recent measurements on the 27Al(3He,p) reaction have shown fluctuations in the excitation functions of some low-lying levels of the residual nucleus: coherence energy GAMMA was found varying between 50 and 200 KeV. The excitation functions have been re-analyzed by means of the generalized auto-correlation function recently proposed by Friedman et al., and GAMMA values have been interpreted by means of the statistical multi-step compound emission. (author)

  18. Laser excited novel near-infrared photoluminescence bands in fast neutron-irradiated MgO·nAl2O3

    Science.gov (United States)

    Rahman, Abu Zayed Mohammad Saliqur; Haseeb, A. S. M. A.; Xu, Qiu; Evslin, Jarah; Cinausero, Marco

    2016-08-01

    New near-infrared photoluminescence bands were observed in neutron-irradiated spinel single crystal upon excitation by a 532 nm laser. The surface morphology of the unirradiated and fast neutron-irradiated samples was investigated using atomic force microscopy and scanning probe microscopy. Fast neutron-irradiated samples show a strong emission peak at 1685 nm along with weak bands at 1065 and 2365 nm. The temperature dependence of the photoluminescence intensity was also measured. At lower temperatures, the dominant peak at 1685 nm shifts toward lower energy whereas the other peaks remain fixed. Activation energies of luminescence quenching were estimated to be 5.7 and 54.6 meV for the lower and higher temperature regions respectively.

  19. Electronic Excitations in Push-Pull Oligomers and Their Complexes with Fullerene from Many-Body Green's Functions Theory with Polarizable Embedding.

    Science.gov (United States)

    Baumeier, Björn; Rohlfing, Michael; Andrienko, Denis

    2014-08-12

    We present a comparative study of excited states in push-pull oligomers of PCPDTBT and PSBTBT and prototypical complexes with a C60 acceptor using many-body Green's functions theory within the GW approximation and the Bethe-Salpeter equation. We analyze excitations in oligomers up to a length of 5 nm and find that for both materials the absorption energy practically saturates for structures larger than two repeat units due to the localized nature of the excitation. In the bimolecular complexes with C60, the transition from Frenkel to charge transfer excitons is generally exothermic and strongly influenced by the acceptor's position and orientation. The high CT binding energy of the order of 2 eV results from the lack of an explicit molecular environment. External polarization effects are then modeled in a GW-BSE based QM/MM approach by embedding the donor-acceptor complex into a polarizable lattice. The lowest charge transfer exciton is energetically stabilized by about 0.5 eV, while its binding energy is reduced to about 0.3 eV. We also identify a globally unbound charge transfer state with a more delocalized hole at higher energy while still within the absorption spectrum, which opens another potential pathway for charge separation. For both PCPDTBT and PSBTBT, the energetics are largely similar with respect to absorption and the driving force to form intermediate charge transfer excitations for free charge generation. These results support that the higher power conversion efficiency observed for solar cells using PSBTBT as donor material is a result of molecular packing rather than of the electronic structure of the polymer. PMID:26588281

  20. Patterns of conductivity in excitable automata with updatable intervals of excitations

    OpenAIRE

    Adamatzky A.

    2012-01-01

    We define a cellular automaton where a resting cell excites if number of its excited neighbours belong to some specified interval and boundaries of the interval change depending on ratio of excited and refractory neighbours in the cell's neighbourhood. We calculate excitability of a cell as a number of possible neighbourhood configurations that excite the resting cell. We call cells with maximal values of excitability conductive. In exhaustive search of functions of excitation interval update...

  1. Time-dependent density functional theory applied to ligand-field excitations and their circular dichroism in some transition metal complexes

    International Nuclear Information System (INIS)

    Graphical abstract: Ligand-field (LF) transitions in [Co(en)3]3+ and [Rh(en)3]2+ and the low-energy part of the electronic circular dichroism (CD) spectrum of [Fe(phen)3]2+ are investigated with time-dependent density functional theory (TDDFT). There is a strong functional dependence for [Co(en)3]3+ and [Fe(phen)3]2+. ΔSCF methods reproduce the ligand-field singlet excitation energies of [Co(en)3]3+ and [Rh(en)3]2+ well. For the LF transitions of [Co(en)3]3+ TDDFT with a hybrid functional with around 25correction/Coulomb attenuation offers little improvement for the LF transitions in [Co(en)3]3+ because the occupied and unoccupied orbitals involved are in close spatial proximity. Highlights: ► TDDFT Ligand-field (LF) excitations in 3d metal complexes are functional dependent. ► Study of Co(en)3(3+) links sensitivity to correlation/self-interaction balance. ► Correlation effects on the LF spectra are very large. ► Range separated functionals offer limited improvement due to spatial proximity of orbitals. - Abstract: Ligand-field transitions in [Co(en)3]3+ and [Rh(en)3]3+ as well as the low-energy part of the electronic spectrum of [Fe(phen)3]2+ are investigated with time-dependent density functional theory (TDDFT). There is a strong functional dependence for [Co(en)3]3+ and [Fe(phen)3]2+. ΔSCF methods reproduce the ligand-field singlet excitation energies of [Co(en)3]3+ and [Rh(en)3]3+ very well. The case of [Co(en)3]3+ is analyzed in some detail, in particular regarding the possibility of applying a charge-transfer (CT) correction [M.E. Casida, F. Gutierrez, J. Guan, F.-X. Gadea, D.R. Salahub, J.-P. Daudey, J. Chem. Phys. 113 (2000) 7062]. A simple CT correction would not be sufficient, but the magnitude of the charge transfer correction term in comparison with the calculated excitation energy appears to be indicative of self-interaction problems in the ground state electronic structure and in the calculated excitation energies. For the ligand

  2. Measurement of excitation functions and isomeric ratios of the 197Au(3He,xn)200- sup(x)Tl reactions, where x=2,3 and 4

    International Nuclear Information System (INIS)

    The excitation functions and isomer ratios of the 197Au(3He,xn)200- sup(x)Tl reactions, with x = 2, 3 and 4, were measured at bombarding energies in the range from 15 to 36 MeV. The measured values were compared to those obtained with the use of the statistical an hybrid modeles, calculated by the ALICE code. Best fit was achieved using the simple statistical model. The results were also compared to those found in literature for the (3He,xn) and (4He,xn) reactions in gold. (Author)

  3. Gain-of-function mutations in the ALS8 causative gene VAPB have detrimental effects on neurons and muscles

    Directory of Open Access Journals (Sweden)

    Mario Sanhueza

    2013-12-01

    Amyotrophic Lateral Sclerosis (ALS is a motor neuron degenerative disease characterized by a progressive, and ultimately fatal, muscle paralysis. The human VAMP-Associated Protein B (hVAPB is the causative gene of ALS type 8. Previous studies have shown that a loss-of-function mechanism is responsible for VAPB-induced ALS. Recently, a novel mutation in hVAPB (V234I has been identified but its pathogenic potential has not been assessed. We found that neuronal expression of the V234I mutant allele in Drosophila (DVAP-V260I induces defects in synaptic structure and microtubule architecture that are opposite to those associated with DVAP mutants and transgenic expression of other ALS-linked alleles. Expression of DVAP-V260I also induces aggregate formation, reduced viability, wing postural defects, abnormal locomotion behavior, nuclear abnormalities, neurodegeneration and upregulation of the heat-shock-mediated stress response. Similar, albeit milder, phenotypes are associated with the overexpression of the wild-type protein. These data show that overexpressing the wild-type DVAP is sufficient to induce the disease and that DVAP-V260I is a pathogenic allele with increased wild-type activity. We propose that a combination of gain- and loss-of-function mechanisms is responsible for VAPB-induced ALS.

  4. Study on the preparation of the SiCp/Al-20Si-3Cu functionally graded material using spray deposition

    International Nuclear Information System (INIS)

    Research highlights: → The SiCp/Al-20Si-3Cu functionally gradient material (FGM) was successfully prepared via the spray deposition technique. → The SiCp/Al-20Si-3Cu functionally gradient material (FGM) was successfully prepared via the spray deposition technique. → In the experimental setup, the novel devices play an important role in adjusting the output of SiCp to prepare the FGM. → The experiment results reveal that the SiCp weight fraction of the as-deposited preform from the top to the bottom ranges almost continuously from 0% to 30%. → The fraction of SiC particles has no obvious influence on the phase constitutions of the SiCp/Al-20Si-3Cu FGM. - Abstract: The SiCp/Al-20Si-3Cu functionally gradient material (FGMs) was successfully prepared via the spray deposition technique accompanied with an automatic control system. The results reveal that the SiCp weight fraction of the as-deposited preform from the top to the bottom ranges almost continuously from 0% to 30%. The part with the higher SiCp weight fraction exhibits a relatively smaller density than that with the lower SiCp weight fraction. However, the microhardness and the porosity increase with the increasing SiCp weight fraction in the as-deposited preform. The X-ray diffraction results exhibit that the secondary phases in the regions with the different amount of SiC particles are the same such as Al2Cu and AlCuMg. The spray deposition technology is promising to produce a wide range of other FGMs.

  5. Study on the preparation of the SiCp/Al-20Si-3Cu functionally graded material using spray deposition

    Energy Technology Data Exchange (ETDEWEB)

    Su, B. [College of Materials Science and Engineering, Hunan University, 410082 Changsha (China); Yan, H.G., E-mail: subindier2008@126.com [College of Materials Science and Engineering, Hunan University, 410082 Changsha (China); Chen, G.; Shi, J.L.; Chen, J.H.; Zeng, P.L. [College of Materials Science and Engineering, Hunan University, 410082 Changsha (China)

    2010-09-25

    Research highlights: {yields} The SiCp/Al-20Si-3Cu functionally gradient material (FGM) was successfully prepared via the spray deposition technique. {yields} The SiCp/Al-20Si-3Cu functionally gradient material (FGM) was successfully prepared via the spray deposition technique. {yields} In the experimental setup, the novel devices play an important role in adjusting the output of SiCp to prepare the FGM. {yields} The experiment results reveal that the SiCp weight fraction of the as-deposited preform from the top to the bottom ranges almost continuously from 0% to 30%. {yields} The fraction of SiC particles has no obvious influence on the phase constitutions of the SiCp/Al-20Si-3Cu FGM. - Abstract: The SiCp/Al-20Si-3Cu functionally gradient material (FGMs) was successfully prepared via the spray deposition technique accompanied with an automatic control system. The results reveal that the SiCp weight fraction of the as-deposited preform from the top to the bottom ranges almost continuously from 0% to 30%. The part with the higher SiCp weight fraction exhibits a relatively smaller density than that with the lower SiCp weight fraction. However, the microhardness and the porosity increase with the increasing SiCp weight fraction in the as-deposited preform. The X-ray diffraction results exhibit that the secondary phases in the regions with the different amount of SiC particles are the same such as Al{sub 2}Cu and AlCuMg. The spray deposition technology is promising to produce a wide range of other FGMs.

  6. Ultrastructural studies of ALS mitochondria connect altered function and permeability with defects of mitophagy and mitochondriogenesis

    OpenAIRE

    Alessandro Frati; Francesco Fornai

    2015-01-01

    The key role of mitochondria in patients affected by amyotrophic lateral sclerosis (ALS) is well documented by electron microscopy studies of motor neurons within spinal cord and brainstem. Nonetheless, recent studies challenged the role of mitochondria placed within the cell body of motor neuron. In fact, it was demonstrated that, despite preservation of mitochondria placed within this compartment, there is no increase in the lifespan of transgenic mouse models of ALS. Thus, the present mini...

  7. Atomic to Nanoscale Investigation of Functionalities of Al2O3 Coating Layer on Cathode for Enhanced Battery Performance

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Pengfei; Zheng, Jianming; Zhang, Xiaofeng; Xu, Rui; Amine, Khalil; Xiao, Jie; Zhang, Jiguang; Wang, Chong M.

    2016-01-06

    Surface coating of cathode has been identified as an effective approach for enhancing the capacity retention of layered structure cathode. However, the underlying operating mechanism of such a thin layer of coating, in terms of surface chemical functionality and capacity retention, remains unclear. In this work, we use aberration corrected scanning transmission electron microscopy and high efficient spectroscopy to probe the delicate functioning mechanism of Al2O3 coating layer on Li1.2Ni0.2Mn0.6O2 cathode. We discovered that in terms of surface chemical function, the Al2O3 coating suppresses the side reaction between cathode and the electrolyte upon the battery cycling. At the same time, the Al2O3 coating layer also eliminates the chemical reduction of Mn from the cathode particle surface, therefore avoiding the dissolution of the reduced Mn into the electrolyte. In terms of structural stability, we found that the Al2O3 coating layer can mitigate the layer to spinel phase transformation, which otherwise will initiate from the particle surface and propagate towards the interior of the particle with the progression of the battery cycling. The atomic to nanoscale effects of the coating layer observed here provide insight for optimized design of coating layer on cathode to enhance the battery properties.

  8. Novel joining of dissimilar ceramics in the Si3N4-Al2O3 system using polytypoid functional gradients

    OpenAIRE

    Lee, Caroline Sunyong

    2001-01-01

    A unique approach to crack-free joining of heterogeneous ceramics is demonstrated by the use of sialon polytypoids as Functionally Graded Materials (FGM) as defined by the phase diagram in the system, Si3N4-Al2O3. Polytypoids in the Al2O3-Si3N4 system offer a path to compatibility for such heterogeneous ceramics. The first part of the dissertation describes successful hot press sintering of multilayered FGM's with 20 layers of thickness 500 mm each. Transmission Electron Microscopy was ...

  9. Description of electron transfer in the ground and excited states of organic donor–acceptor systems by single-reference and multi-reference density functional methods

    International Nuclear Information System (INIS)

    Electron transfer in the ground and excited states of a model donor–acceptor (D–A) system is investigated using the single-reference and multi-reference density functional theory (DFT) methods. To analyze the results of the calculations, a simple two-site multi-reference model was derived that predicts a stepwise electron transfer in the S0 state and a wave-like dependence of the S1 electron transfer on the external stimulus. The standard single-reference Kohn-Sham (KS) DFT approach and the time-dependent DFT (TDDFT) method failed to describe the correct dependence of the S0 and S1 electron transfer on the external electric field applied along the donor–acceptor system. The multi-reference DFT approach, the spin-restricted ensemble-referenced KS (REKS) method, was able to successfully reproduce the correct behavior of the S0 and S1 electron transfer on the applied field. The REKS method was benchmarked against experimentally measured gas phase charge transfer excitations in a series of organic donor–acceptor complexes and displayed its ability to describe this type of electronic transitions with a very high accuracy, mean absolute error of 0.05 eV with the use of the standard range separated density functionals. On the basis of the calculations undertaken in this work, it is suggested that the non-adiabatic coupling between the S0 and S1 states may interfere with the electron transfer in a weakly coupled donor–acceptor system. It is also suggested that the electronic excitation of a D+–A− system may play a dual role by assisting the further electron transfer at certain magnitudes of the applied electric field and causing the backward transfer at lower electric field strengths

  10. Bonding in Zintl phase hydrides: density functional calculations for SrAlSiH, SrAl2H2, SrGa2H2 and BaGa2H2

    Energy Technology Data Exchange (ETDEWEB)

    Subedi, Alaska P [ORNL; Singh, David J [ORNL

    2008-01-01

    We investigate the bonding characteristics of SrAlSiH, SrAl{sub 2}H{sub 2}, SrGa{sub 2}H{sub 2}, and BaGa{sub 2}H{sub 2} using density functional calculations. The mixed bonding characteristic of other families of Zintl phases is found, with the formation of covalent sp{sup 2} bonds in the Al/Ga/Al-Si planes of the various compounds. On the other hand the Sr and Ba atoms occur as divalent cations, while the H is anionic. The results indicate that insulating SrSiAlH may be a switchable ferroelectric.

  11. Ultrastructural studies of ALS mitochondria connect altered function and permeability with defects of mitophagy and mitochondriogenesis

    Directory of Open Access Journals (Sweden)

    Alessandro Frati

    2015-09-01

    Full Text Available The key role of mitochondria in patients affected by amyotrophic lateral sclerosis (ALS is well documented by electron microscopy studies of motor neurons within spinal cord and brainstem. Nonetheless, recent studies challenged the role of mitochondria placed within the cell body of motor neuron. In fact, it was demonstrated that, despite preservation of mitochondria placed within this compartment, there is no increase in the lifespan of transgenic mouse models of ALS. Thus, the present mini-review comments on morphological findings of mitochondrial alterations in ALS patients in connection with novel findings about mitochondrial dynamics within various compartments of motor neurons. The latter issue was recently investigated in relationship with altered calcium homeostasis and autophagy, which affect mitochondria in ALS. In fact, it was recently indicated that a pathological mitophagy, mitochondriogenesis and calcium homeostasis produce different ultrastructural effects within specific regions of motor neurons. This might explain why specific compartments of motor neurons possess different thresholds to mitochondrial damage. In particular, it appears that motor axons represent the most sensitive compartment which undergoes the earliest and most severe alterations in the course of ALS. It is now evident that altered calcium buffering is compartment-dependent, as well as mitophagy and mitochondriogenesis. On the other hand, mitochondrial homeostasis strongly relies on calcium handling, the removal of altered mitochondria through the autophagy flux (mitophagy and the biogenesis of novel mitochondria (mitochondriogenesis. Thus, recent findings related to altered calcium storage and impaired autophagy flux in ALS may help to understand the occurrence of mitochondrial alterations as a hallmark in ALS patients. At the same time, the compartmentalization of such dysfunctions may be explained considering the compartments of calcium dynamics and

  12. Multireference configuration interaction potential curve and analytical potential energy function of the ground and low-lying excited states of CdSe

    Institute of Scientific and Technical Information of China (English)

    Gao Feng; Yang Chuan-Lu; Hu Zhen-Yan; Wang Mei-Shan

    2007-01-01

    The potential energy curves (PECs) of the ground state (3Π) and three low-lying excited states (1∑, 3∑,1Π) of CdSe dimer have been studied by emploging quasirelativistic effective core potentials on the basis of the complete active space self-consistent field method followed by multireference configuration interaction calculation. The four PECs are fitted to analytical potential energy functions using the Murrel-Sorbie potential function. Based on the PECs,the vibrational levels of the four states are determined by solving the Schr(o)dinger equation of nuclear motion, and corresponding spectroscopic contants are accurately calculated. The equilibrium positions as well as the spectroscopic constants and the vibrational levels are reported. By our analysis, the 3Π state, of which the dissociation asymptote is Cd(1S) + Se(3p), is identified as a ground state of CdSe dimer, and the corresponding dissociation energy is estimated to be 0.39eV. However, the first excited state is only 1132.49cm-1 above the ground state and the 3∑ state is the highest in the four calculated states.

  13. Ultrasensitive detection of Hg2+ using oligonucleotide-functionalized AlGaN/GaN high electron mobility transistor

    International Nuclear Information System (INIS)

    An oligonucleotide-functionalized ion sensitive AlGaN/GaN high electron mobility transistor (HEMT) was fabricated to detect trace amounts of Hg2+. The advantages of ion sensitive AlGaN/GaN HEMT and highly specific binding interaction between Hg2+ and thymines were combined. The current response of this Hg2+ ultrasensitive transistor was characterized. The current increased due to the accumulation of Hg2+ ions on the surface by the highly specific thymine-Hg2+-thymine recognition. The dynamic linear range for Hg2+ detection has been determined in the concentrations from 10−14 to 10−8 M and a detection limit below 10−14 M level was estimated, which is the best result of AlGaN/GaN HEMT biosensors for Hg2+ detection till now.

  14. Novel joining of dissimilar ceramics in the Si3N4-Al2O3 system using polytypoid functional gradients

    International Nuclear Information System (INIS)

    A unique approach to crack-free joining of heterogeneous ceramics is demonstrated by the use of sialon polytypoids as Functionally Graded Materials (FGM) as defined by the phase diagram in the system, Si3N4-Al2O3. Polytypoids in the Al2O3-Si3N4 system offer a path to compatibility for heterogeneous ceramics. This paper describes successful hot press sintering of multilayered FGM's with 20 layers of thickness 500 mm each. Transmission Electron Microscopy was used to identify the polytypoids at the interfaces of different areas of the joint. It has been found that the 15R polytypoid was formed in the Al2O3-contained layers and the 12H polytypoid was formed in the Si3N4-contained layers

  15. Excitation energies with linear response density matrix functional theory along the dissociation coordinate of an electron-pair bond in N-electron systems.

    Science.gov (United States)

    van Meer, R; Gritsenko, O V; Baerends, E J

    2014-01-14

    Time dependent density matrix functional theory in its adiabatic linear response formulation delivers exact excitation energies ωα and oscillator strengths fα for two-electron systems if extended to the so-called phase including natural orbital (PINO) theory. The Löwdin-Shull expression for the energy of two-electron systems in terms of the natural orbitals and their phases affords in this case an exact phase-including natural orbital functional (PILS), which is non-primitive (contains other than just J and K integrals). In this paper, the extension of the PILS functional to N-electron systems is investigated. With the example of an elementary primitive NO functional (BBC1) it is shown that current density matrix functional theory ground state functionals, which were designed to produce decent approximations to the total energy, fail to deliver a qualitatively correct structure of the (inverse) response function, due to essential deficiencies in the reconstruction of the two-body reduced density matrix (2RDM). We now deduce essential features of an N-electron functional from a wavefunction Ansatz: The extension of the two-electron Löwdin-Shull wavefunction to the N-electron case informs about the phase information. In this paper, applications of this extended Löwdin-Shull (ELS) functional are considered for the simplest case, ELS(1): one (dissociating) two-electron bond in the field of occupied (including core) orbitals. ELS(1) produces high quality ωα(R) curves along the bond dissociation coordinate R for the molecules LiH, Li2, and BH with the two outer valence electrons correlated. All of these results indicate that response properties are much more sensitive to deficiencies in the reconstruction of the 2RDM than the ground state energy, since derivatives of the functional with respect to both the NOs and the occupation numbers need to be accurate. PMID:24437859

  16. Improved wear resistance of functional diamond like carbon coated Ti-6Al-4V alloys in an edge loading conditions.

    Science.gov (United States)

    Choudhury, Dipankar; Lackner, Jürgen M; Major, Lukasz; Morita, Takehiro; Sawae, Yoshinori; Bin Mamat, Azuddin; Stavness, Ian; Roy, Chanchal K; Krupka, Ivan

    2016-06-01

    This study investigates the durability of functional diamond-like carbon (DLC) coated titanium alloy (Ti-6Al-4V) under edge loading conditions for application in artificial hip joints. The multilayered (ML) functional DLC coatings consist of three key layers, each of these layers were designed for specific functions such as increasing fracture strength, adapting stress generation and enhancing wear resistance. A 'ball-on-disk' multi-directional wear tester was used in the durability test. Prior to the wear testing, surface hardness, modulus elasticity and Raman intensity were measured. The results revealed a significant wear reduction to the DLC coated Ti-6Al-4V disks compared to that of non-coated Ti-6Al-4V disks. Remarkably, the counterpart Silicon Nitride (Si3N4) balls also yielded lowered specific wear rate while rubbed against the coated disks. Hence, the pairing of a functional multilayered DLC and Si3N4 could be a potential candidate to orthopedics implants, which would perform a longer life-cycle against wear caused by edge loading. PMID:27085502

  17. Solvent effects on optical excitations of poly para phenylene ethynylene studied by QM/MM simulations based on Many-Body Green's Functions Theory

    CERN Document Server

    Bagheri, Behnaz; Baumeier, Björn

    2016-01-01

    Electronic excitations in dilute solutions of poly para phenylene ethynylene (poly-PPE) are studied using a QM/MM approach combining many-body Green's functions theory within the $GW$ approximation and the Bethe-Salpeter equation with polarizable force field models. Oligomers up to a length of 7.5\\,nm (10 repeat units) functionalized with nonyl side chains are solvated in toluene and water, respectively. After equilibration using atomistic molecular dynamics (MD), the system is partitioned into a quantum region (backbone) embedded into a classical (side chains and solvent) environment. Optical absorption properties are calculated solving the coupled QM/MM system self-consistently and special attention is paid to the effects of solvents. The model allows to differentiate the influence of oligomer conformation induced by the solvation from electronic effects related to local electric fields and polarization. It is found that the electronic environment contributions are negligible compared to the conformational ...

  18. Analysis of fragmentation excitation functions of lead by carbon ions up to 400 MeV/u

    International Nuclear Information System (INIS)

    Fragmentation reaction cross-sections of lead bombarded by carbon ions below 400 MeV/u are measured and compared with those simulated with Monte-Carlo radiation transport code PHITS to pinpoint the problems of simulation based on the quantum molecular dynamics model and the statistical decay model. Cross-sections for 32 fragments from A = 24 to 85 and those from A = 121 to 175 are measured within a reasonable uncertainty. Contribution of secondary particles to production of measured fragments are generally less than 20%. Comparison shows production cross-sections for fragments from A = 20 to 60 and those from A = 110 to 130 are underestimated by one order of magnitude. Further simulation shows production of each group of fragments in simulation are attributed to evaporation of fission fragments and to evaporation of highly excited prefragments, respectively. The lower the energy is, the more this trend is pronounced. Observed underestimation indicates presence of nuclear reaction mechanisms not considered in the current simulation such as multi-fragmentation

  19. On the excitation spectra of Cr{sup 3+}/Cr{sup 2+} and V{sup 3+} co-doped ZnAl{sub 2}S{sub 4} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Anghel, S., E-mail: anggell@gmail.com [Institute of Applied Physics, Academiei Str 5, Chis,inău MD-2028, Republic of Moldova (Moldova, Republic of); Ruhr-Universität Bochum, Anorganische Chemie III, Universitätsstrasse 150, D-44801 Bochum (Germany); Brik, M.G. [College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); Institute of Physics, University of Tartu, Ravila 14 C, Tartu 50411 (Estonia); Institute of Physics, Jan Dlugosz University, Armii Krajowej 13/15, PL-42200 Czestochowa (Poland); Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-668 Warsaw (Poland); Ma, C.-G. [College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); Sushkevich, K. [State University of Moldova, Mateevici Str 60, Chis,inău MD-2009, Republic of Moldova (Moldova, Republic of); Kulyuk, L. [Institute of Applied Physics, Academiei Str 5, Chis,inău MD-2028, Republic of Moldova (Moldova, Republic of)

    2015-10-15

    The excitation spectra of the ZnAl{sub 2}S{sub 4} spinel crystals codoped with chromium and vanadium are investigated in order to explain some features of the Cr{sup 3+} ions optical spectra and the inconsistency of the experimental absorption/emission bands position with the Tanabe–Sugano diagram, as well as the “missing” band in the absorption spectrum of V{sup 3+} ion although this band should be present as it is due to a spin allowed transition. The unusual high Racah parameters of the C/B ratio for Cr{sup 3+} ions have been induced to recalculate the Tanabe–Sugano diagram for the d{sup 3} electron configuration and the ratio C/B=8 in order to use it for the experimental results interpretation. The presence of Cr{sup 2+} ions in the low spin electron configurations in the octahedral coordination was confirmed; the temperature dependence of the Cr{sup 2+} emission at about 1.9 eV was studied and the Huang–Rhys factors were estimated for different temperatures. Despite the fact that the V{sup 3+}C/B ratio has a different value compared to the case of Cr{sup 3+} ions, the electron–phonon interaction is similar for both ions, with the Huang–Rhys parameter equal to 10 in both cases. Further research into optimizing the ZnAl{sub 2}S{sub 4}:Cr, V system to get an efficient enhancement of the vanadium emission on account on re-absorbing the chromium emission is suggested. - Highlights: • The spectroscopic properties of Cr and V codoped α-ZnAI{sub 2}S{sub 4} have been investigated. • The crystal field calculations have been performed. • The Huang–Rhys factors have been estimated for different temperatures. • The theoretical calculations have been correlated with the excitation spectra.

  20. Adsorption and dissociation of H2O on Al(1 1 1) surface by density functional theory calculation

    International Nuclear Information System (INIS)

    Highlights: • O2 on Al(1 1 1) surface can spontaneously dissociate, but H2O can not. • H2O, OH and H on top sites are favorable on Al(1 1 1) surface. • O on the hollow (fcc) site is preferred. • O which plays a key role in the dissociate reaction of H2O. - Abstract: Using the first-principles calculations method based on the density functional theory, we systematically study the adsorption behavior of a single molecular H2O on a clean and a pre-adsorbed O atom Al(1 1 1) surface, and also its corresponding dissociation reactions. The equilibrium configuration on top, bridge, and hollow (fcc and hcp) site were determined by relaxation of the system relaxation. The adsorptions of H2O, OH and H on top sites are favorable on the Al(1 1 1) surface, while that of O on the hollow (fcc) site is preferred. The results show that the hydrogen atom dissociating from H2O needs a 248.32 kJ/mol of energy on clean Al(1 1 1) surface, while the dissociating energy decreases to 128.53 kJ/mol with the aid of the O absorption. On the other hand, these phenomena indicate that the dehydrogenated reaction energy barrier of the pre-adsorbed O on metal surface is lower than that of on a clean one, because O can promote the dehydrogenation of H2O

  1. Time-dependent density functional theory study of first excited singlet states of phenyl-5C-tetrazole derivatives

    International Nuclear Information System (INIS)

    Electronic transition energies for phenyl-5C-tetrazole and four of its p-substituted derivatives were calculated through time-dependent density functional theory using a series of hybrid density functionals. For three of the compounds, maxima of the experimental UV absorption bands could be exactly reproduced, for the remaining two - maxima of the calculated bands occurred at lower wavelengths than those of the experimental ones

  2. Functionalizing Aluminum Oxide by Ag Dendrite Deposition at the Anode during Simultaneous Electrochemical Oxidation of Al.

    Science.gov (United States)

    Rafailović, Lidija D; Gammer, Christoph; Rentenberger, Christian; Trišović, Tomislav; Kleber, Christoph; Karnthaler, Hans Peter

    2015-11-01

    A novel synthesis strategy is presented for depositing metallic Ag at the anode during simultaneous electrochemical oxidation of Al. This unexpected result is achieved based on galvanic coupling. Metallic dendritic nanostructures well-anchored in a high surface area supporting matrix are envisioned to open up a new avenue of applications. PMID:26398487

  3. Application of X-ray microtomography to the microstructural characterization of Al-based functionally graded materials

    OpenAIRE

    Velhinho, A.; Fernandes, F. M. Braz; Ferreira, S. C.; L. A. Rocha; Vignoles, G.; Cloetens, P.

    2006-01-01

    This paper provides a brief overview of the possibilities offered by X-ray computed microtomography, and particularly synchrotron radiation X-ray microtomography, regarding metal matrix composite characterization, emphasis being placed in the case of Al-based functionally graded materials. Examples are provided concerning the characterization of the reinforcement population, interfacial properties, in-situ transformation and damage evolution. The specific needs of the technique and limitation...

  4. Optical excitation and electron relaxation dynamics at semiconductor surfaces: a combined approach of density functional and density matrix theory applied to the silicon (001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Buecking, N.

    2007-11-05

    In this work a new theoretical formalism is introduced in order to simulate the phononinduced relaxation of a non-equilibrium distribution to equilibrium at a semiconductor surface numerically. The non-equilibrium distribution is effected by an optical excitation. The approach in this thesis is to link two conventional, but approved methods to a new, more global description: while semiconductor surfaces can be investigated accurately by density-functional theory, the dynamical processes in semiconductor heterostructures are successfully described by density matrix theory. In this work, the parameters for density-matrix theory are determined from the results of density-functional calculations. This work is organized in two parts. In Part I, the general fundamentals of the theory are elaborated, covering the fundamentals of canonical quantizations as well as the theory of density-functional and density-matrix theory in 2{sup nd} order Born approximation. While the formalism of density functional theory for structure investigation has been established for a long time and many different codes exist, the requirements for density matrix formalism concerning the geometry and the number of implemented bands exceed the usual possibilities of the existing code in this field. A special attention is therefore attributed to the development of extensions to existing formulations of this theory, where geometrical and fundamental symmetries of the structure and the equations are used. In Part II, the newly developed formalism is applied to a silicon (001)surface in a 2 x 1 reconstruction. As first step, density-functional calculations using the LDA functional are completed, from which the Kohn-Sham-wave functions and eigenvalues are used to calculate interaction matrix elements for the electron-phonon-coupling an the optical excitation. These matrix elements are determined for the optical transitions from valence to conduction bands and for electron-phonon processes inside the

  5. Renormalization of Optical Excitations in Molecules near a Metal Surface

    DEFF Research Database (Denmark)

    García Lastra, Juan Maria; Thygesen, Kristian Sommer

    2011-01-01

    consequence we find that close to the metal surface the optical gap of benzene can exceed its quasiparticle gap. A classical image charge model for the screened Coulomb interaction can account for all these effects which, on the other hand, are completely missed by standard time-dependent density functional......The lowest electronic excitations of benzene and a set of donor-acceptor molecular complexes are calculated for the gas phase and on the Al(111) surface using the many-body Bethe-Salpeter equation. The energy of the charge-transfer excitations obtained for the gas phase complexes are found to be...

  6. Atomic Layer Deposition of Al2O3 on WSe2 Functionalized by Titanyl Phthalocyanine.

    Science.gov (United States)

    Park, Jun Hong; Fathipour, Sara; Kwak, Iljo; Sardashti, Kasra; Ahles, Christopher F; Wolf, Steven F; Edmonds, Mary; Vishwanath, Suresh; Xing, Huili Grace; Fullerton-Shirey, Susan K; Seabaugh, Alan; Kummel, Andrew C

    2016-07-26

    To deposit an ultrathin dielectric onto WSe2, monolayer titanyl phthalocyanine (TiOPc) is deposited by molecular beam epitaxy as a seed layer for atomic layer deposition (ALD) of Al2O3 on WSe2. TiOPc molecules are arranged in a flat monolayer with 4-fold symmetry as measured by scanning tunneling microscopy. ALD pulses of trimethyl aluminum and H2O nucleate on the TiOPc, resulting in a uniform deposition of Al2O3, as confirmed by atomic force microscopy and cross-sectional transmission electron microscopy. The field-effect transistors (FETs) formed using this process have a leakage current of 0.046 pA/μm(2) at 1 V gate bias with 3.0 nm equivalent oxide thickness, which is a lower leakage current than prior reports. The n-branch of the FET yielded a subthreshold swing of 80 mV/decade. PMID:27305595

  7. Excited Delirium

    Directory of Open Access Journals (Sweden)

    Takeuchi, Asia

    2011-02-01

    Full Text Available Excited (or agitated delirium is characterized by agitation, aggression, acute distress and sudden death, often in the pre-hospital care setting. It is typically associated with the use of drugs that alter dopamine processing, hyperthermia, and, most notably, sometimes with death of the affected person in the custody of law enforcement. Subjects typically die from cardiopulmonary arrest, although the cause is debated. Unfortunately an adequate treatment plan has yet to be established, in part due to the fact that most patients die before hospital arrival. While there is still much to be discovered about the pathophysiology and treatment, it is hoped that this extensive review will provide both police and medical personnel with the information necessary to recognize and respond appropriately to excited delirium. [West J Emerg Med. 2011;12(1:77-83.

  8. Excited baryons

    International Nuclear Information System (INIS)

    The status of the theory of the low-energy approach to hadron structure is reviewed briefly by surveying a few relevant models. A few examples of tests needed to sort out the predictions of different models pertaining to the quark-gluon structure of hadrons are discussed, and given the resulting physics objectives, a few experimental options for excited baryon research at CFBAF are suggested

  9. An efficient formulation and implementation of the analytic energy gradient method to the single and double excitation coupled-cluster wave function - Application to Cl2O2

    Science.gov (United States)

    Rendell, Alistair P.; Lee, Timothy J.

    1991-01-01

    The analytic energy gradient for the single and double excitation coupled-cluster (CCSD) wave function has been reformulated and implemented in a new set of programs. The reformulated set of gradient equations have a smaller computational cost than any previously published. The iterative solution of the linear equations and the construction of the effective density matrices are fully vectorized, being based on matrix multiplications. The new method has been used to investigate the Cl2O2 molecule, which has recently been postulated as an important intermediate in the destruction of ozone in the stratosphere. In addition to reporting computational timings, the CCSD equilibrium geometries, harmonic vibrational frequencies, infrared intensities, and relative energetics of three isomers of Cl2O2 are presented.

  10. Ab initio calculations of accurate dissociation energy and analytic potential energy function for the second excited state B1П of 7LiH

    Institute of Scientific and Technical Information of China (English)

    Shi De-Heng; Liu Yu-Fang; Sun Jin-Feng; Zhu Zun-Lùe; Yang Xiang-Dong

    2006-01-01

    The reasonable dissociation limit of the second excited singlet state B1П of 7LiH molecule is obtained. The obtained over the internuclear distance ranging from about 0.10 nm to 0.54 nm, and has a least-square fit to the analytic compared with previous theoretical results. The equilibrium internuclear distance obtained by geometry optimization is found to be quite different from that obtained by single-point energy scanning under the same calculation condition.comparison of the theoretical calculations of dissociation energies, equilibrium interatomic distances and the analytic potential energy function with those obtained by previous theoretical results clearly shows that the present work is more theories.

  11. Effect of entrance channel parameters on the fusion of two heavy ions: Excitation functions of reaction products in 16O+66Zn and 37Cl + 45Sc reactions

    Indian Academy of Sciences (India)

    Suparne Sodaye; B S Tomar; A Goswami

    2006-06-01

    Excitation functions of reaction products formed in 16O+66Zn and 37Cl + 45Sc systems, leading to the same compound nucleus, 82Sr, were measured using recoilcatcher technique and off-line -ray spectrometry. The contribution of non-compound processes like transfer and incomplete fusion (ICF) reactions to the cross-sections of different evaporation residues were delineated by comparing the experimental data with the predictions of Monte Carlo simulation code PACE2. The results show that non-compound processes become a significant fraction of the total reaction cross-section in 16O+66Zn systems in the beam energy range studied, while 37Cl + 45Sc gives mainly compound nucleus products. The mass asymmetry dependence of the fusion and non-compound cross-sections have been analysed in terms of the static fusion model and sum rule model.

  12. Measurement of excitation functions and isomeric ratios of the reactions 103Rh(3He, xn) sup(106-x)Ag where x=2, 3 and 4

    International Nuclear Information System (INIS)

    The excitation functions and isomer ratios for the reactions 103Rh(3He, xn) sup(106-x)Ag, where x=2, 3 and 4, were measured with projectile Lab energy varying from 23 to 35 MeV. Since the half-life of sup(103m)Ag is equal to 5.7 s. the use of a recoil nucleous gas jet transport system became necessary. The values measured for the cross-sections were compared to those yielded by the ALICE code. The experimental isomer ratios are smaller than those calculated using the residual nucleus spin distribution obtained with the ALICE code. By-pass fractions as expected in this mass region were also obtained. (Author)

  13. A spectroscopic and computational study of the singlet and triplet excited states of synthetic β-functionalized chlorins

    Science.gov (United States)

    Brückner, Christian; McCarthy, Jason R.; Daniell, Heather W.; Pendon, Zeus D.; Ilagan, Robielyn P.; Francis, Tasha M.; Ren, Lei; Birge, Robert R.; Frank, Harry A.

    2003-11-01

    This paper presents a comparative investigation of the absorption, fluorescence, electron paramagnetic resonance (EPR), and transient triplet-triplet absorption spectroscopic properties and triplet state dynamics of two functionalized, synthetic, meso-phenylchlorins. The chromophores investigated are the novel 2-hydroxy-3-oxa-5,10,15,20-tetrakisphenylchlorin ( 3) and the known 2,3-dioxo-5,10,15,20-tetrakisphenylchlorin ( 4). In these chromophores, one peripheral CHCH bond of the parent porphyrin meso-tetrakisphenylporphyrin (TPP, 1) was formally replaced by a CH(OH)O (lactol) or a β-diketone moiety. The spectroscopic data are compared with results from investigations on the parent porphyrin TPP studied here and the parent chlorin 5,10,15,20-tetrakisphenylchlorin (TPC, 2) from the literature. The spectroscopic observables are examined both qualitatively within the framework of the four orbital model and quantitatively using MNDO-PSDCI methods. The results delineate the role of β-lactol and β-dicarbonyl moieties in controlling the electronic and spectroscopic properties of these chromophores. This investigation serves as the foundation from which to derive a general understanding of the effects of β-functionalization on the electronic properties of chlorin-type chromophores. This knowledge is required for the design and understanding of long-wavelength absorbing and fluorescing chromophores to be used in light harvesting systems and photomedicine.

  14. Operating function tests of the PWR type RHR pump for engineering safety system under simulated strong ground excitation

    International Nuclear Information System (INIS)

    Results are described of operating function verification tests of a PWR RHR pump during an earthquake. Of the active reactor components, the PWR residual heat removal pump was chosen from view points of aseismic classification, safety function, structural complexity and past aseismic tests. Through survey of the service conditions and structure of this pump, seismic test conditions such as acceleration level, simulated seismic wave form and earthquake duration were decided for seismicity of the operating pump. Then, plans were prepared to evaluate vibration chracteristics of the pump and to estimate its aseismic design margins. Subsequently, test facility and instrumentation system were designed and constructed. Experimental results could thus be acquired on vibration characteristics of the pump and its dynamic behavior during different kinds and levels of simulated earthquake. In conclusion: (1) Stiffeners attached to the auxiliary system piping do improve aseismic performance of the pump. (2) The rotor-shaft-bearing system is secure unless it is subjected to transient disturbunces having high frequency content. (3) The motor and pump casing having resonance frequencies much higher than frequency content of the seismic wave show only small amplifications. (4) The RHR pump possesses an aseismic design margin more than 2.6 times the expected ultimate earthquake on design basis. (author)

  15. Soft multipole excitations

    International Nuclear Information System (INIS)

    The origin of soft multipole states in halo nuclei is discussed by using a double square well potential. It is found that the huge enhancement of the transition strength near particle threshold energy is caused by the coherent contribution of particle and hole wave functions from an extremely large radial distance R=10∼45 fm. The soft excitation is thus characterized as an independent particle-hole excitation rather than a coherent superposition of particle-hole states. The characteristic feature of the soft mode is demonstrated to manifest itself in the response to the momentum dependent transition operator. (author) 12 refs., 4 figs., 1 tab

  16. The function of self-esteem in terror management theory and sociometer theory: comment on Pyszczynski et al. (2004).

    Science.gov (United States)

    Leary, Mark R

    2004-05-01

    By applying different standards of evidence to sociometer theory than to terror management theory (TMT), T. Pyszczynski, J. Greenberg, S. Solomon, J. Arndt, and J. Schimel's (2004) review offers an imbalanced appraisal of the theories' merits. Many of Pyszczynski et al.'s (2004) criticisms of sociometer theory apply equally to TMT. and others are based on misconstruals of the theory or misunderstandings regarding how people respond when rejected. Furthermore, much of their review is only indirectly relevant to TMT's position on the function of self-esteem, and the review fails to acknowledge logical and empirical challenges to TMT. A more balanced review suggests that each theory trumps the other in certain respects, both have difficulty explaining all of the evidence regarding self-esteem, and the propositions of each theory can be roughly translated into the concepts of the other. For these reasons, declaring a theoretical winner at this time is premature. PMID:15122933

  17. Structural Analysis of Al, Ni, and Cu Using the Maximum Entropy Method, Multipole and Pair Distribution Function

    Science.gov (United States)

    Robert, Muthaian Charles; Saravanan, Ramachandran; Saravanakumar, Krishnamoorthy; Rani, Murugesan Prema

    2009-06-01

    The average and local structures of the metals Al, Ni, and Cu have been elucidated for the first time using the MEM (maximum entropy method), multipole and PDF (pair distribution function). The bonding between the constituent atoms in all these systems is found to be well pronounced and clearly seen from the electron density maps. The MEM maps of all three systems show the spherical core nature of the atoms. The mid bond electron density profiles of Al, Ni, and Cu reveal the metallic nature of the bonding. The local structure using the PDF profile of Ni is compared with that of previously reported results. The R value in the present work using low Q XRD data for the PDF analysis of Ni is close to the value in the literature using high Q synchrotron data. The cell parameters and displacement parameters are also studied and compared with the reported values.

  18. Zn-phthalocyanine-functionalized nanometal and nanometal-TiO₂ hybrids: aggregation behavior and excited-state dynamics.

    Science.gov (United States)

    Ashokkumar, R; Kathiravan, A; Ramamurthy, P

    2014-07-21

    Dithiol-substituted Zn-phthalocyanine derivatives (TAZnPc1, TAZnPc2 and TAZnPc3) were synthesized and functionalized on nanometals (Au and Ag) and nanometal-TiO2 hybrids were harnessed to cover the visible region of the absorption spectrum. Photophysical studies reveal that both H- and J-aggregation were present in the ZnPc-functionalized nanometal, and the extent of J-aggregation is superior on the surface of Ag nanoparticles. On the other hand, no H-aggregation was observed in the nanometal-TiO2 hybrid film, despite the fact that the tetra-anchoring derivative (TAZnPc3) shows lesser J-aggregation on the nanometal-TiO2 hybrid film than that of other two mono-anchoring derivatives (TAZnPc1 and TAZnPc2). Further, the electron injection and recombination processes were investigated by time-resolved fluorescence and absorption spectroscopy. All the derivatives furnish biexponential decay on the nanometal surface. The shorter component is due to electron injection of ZnPc-nanometal particles and the longer component is due to free ZnPc. The rate of electron injection is faster for ZnPc-gold nanoparticles than that of silver nanoparticles, predominantly in TAZnPc1. This is due to the greater aggregation tendency of ZnPc derivatives on Ag nanoparticles than Au nanoparticles. After electron injection, the electron-transfer product (i.e. the radical cation of ZnPc) was observed at 600 nm. Moreover, the fluorescence of ZnPc derivatives on nanometal-TiO2 films was completely quenched due to the shuttling of electrons from ZnPc to TiO2 efficiently by metal nanoparticles. PMID:24902514

  19. Adsorption and dissociation of H{sub 2}O on Al(1 1 1) surface by density functional theory calculation

    Energy Technology Data Exchange (ETDEWEB)

    Guo, F.Y. [Institute of Automobile and Mechanical Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114 (China); Key Laboratory of Manufacture and Test Techniques for Automobile Parts (Chongqing University of Technology), Ministry of Education, Chongqing 400054 (China); Key Laboratory of Lightweight and Reliability Technology for Engineering Vehicle, College of Hunan Province, Changsha, Hunan 410114 (China); Long, C.G., E-mail: 416014737@qq.com [Institute of Automobile and Mechanical Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114 (China); Key Laboratory of Manufacture and Test Techniques for Automobile Parts (Chongqing University of Technology), Ministry of Education, Chongqing 400054 (China); Key Laboratory of Lightweight and Reliability Technology for Engineering Vehicle, College of Hunan Province, Changsha, Hunan 410114 (China); Zhang, J.; Zhang, Z. [Institute of Automobile and Mechanical Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114 (China); Key Laboratory of Manufacture and Test Techniques for Automobile Parts (Chongqing University of Technology), Ministry of Education, Chongqing 400054 (China); Key Laboratory of Lightweight and Reliability Technology for Engineering Vehicle, College of Hunan Province, Changsha, Hunan 410114 (China); Liu, C.H. [Institute of Automobile and Mechanical Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114 (China); Yu, K. [Department of Materials Science and Engineering, Central South University, Changsha, Hunan 410083 (China)

    2015-01-01

    Highlights: • O{sub 2} on Al(1 1 1) surface can spontaneously dissociate, but H{sub 2}O can not. • H{sub 2}O, OH and H on top sites are favorable on Al(1 1 1) surface. • O on the hollow (fcc) site is preferred. • O which plays a key role in the dissociate reaction of H{sub 2}O. - Abstract: Using the first-principles calculations method based on the density functional theory, we systematically study the adsorption behavior of a single molecular H{sub 2}O on a clean and a pre-adsorbed O atom Al(1 1 1) surface, and also its corresponding dissociation reactions. The equilibrium configuration on top, bridge, and hollow (fcc and hcp) site were determined by relaxation of the system relaxation. The adsorptions of H{sub 2}O, OH and H on top sites are favorable on the Al(1 1 1) surface, while that of O on the hollow (fcc) site is preferred. The results show that the hydrogen atom dissociating from H{sub 2}O needs a 248.32 kJ/mol of energy on clean Al(1 1 1) surface, while the dissociating energy decreases to 128.53 kJ/mol with the aid of the O absorption. On the other hand, these phenomena indicate that the dehydrogenated reaction energy barrier of the pre-adsorbed O on metal surface is lower than that of on a clean one, because O can promote the dehydrogenation of H{sub 2}O.

  20. Synthesis of functionally graded nano Al2O3–Ni composite coating by pulse electrodeposition

    International Nuclear Information System (INIS)

    The main goal of this research is the synthesis of functionally graded nickel–nano Al2O3 composite coatings by using pulse deposition in which the amount of the embedded nano alumina particles changes in the cross section of the composite. For producing functionally graded nanocomposite coatings by pulse electrodeposition under ultrasonic agitation, frequency and duty cycle changes can be applied and in this research, the influence of both parameters has been studied. Microstructure of these coatings investigated by SEM, EBSD and XRD methods. By changing the duty cycle from 90% to 10% at different frequency, the microstructure of the coatings did not change significantly. These coatings showed ductile structure with {0 0 1} texture at primary layers and small randomly oriented grains at final layers. The most important factor affecting the microstructure of the nickel matrix was the average current density and incorporation of nano alumina particles does not have significant effect on the microstructure. The optimum condition for production of functionally graded nano Al2O3–Ni coating was changing of the duty cycle from 90% to 10% at fixed frequency of 10 Hz.

  1. Tunable Excited-State Properties and Dynamics as a Function of Pt–Pt Distance in Pyrazolate-Bridged Pt(II) Dimers

    Energy Technology Data Exchange (ETDEWEB)

    Brown-Xu, Samantha E.; Kelley, Matthew S. J.; Fransted, Kelly A.; Chakraborty, Arnab; Schatz, George C.; Castellano, Felix N.; Chen, Lin X.

    2016-02-04

    The influence of molecular structure on excited state properties and dynamics of a series of cyclometalated platinum dimers was investigated through a combined experimental and theoretical approach using femtosecond transient absorption (fs TA) spectroscopy and density functional theory (DFT) calculations. The molecules have the general formula [Pt(ppy)(µ-R2pz)]2 where ppy = 2-phenylpyridine, pz = pyrazolate and R = H, Me, Ph, or tBu, and are strongly photoluminescent at room temperature. The distance between the platinum centers in this A frame geometry can be varied depending on the steric bulk of the bridging pyrazolate ligands that exert structural constraints and compress the Pt-Pt distance. At large Pt-Pt distances there is little interaction between the subunits and the chromophore behaves similar to a monomer with excited states described as mixtures of ligand-centered and metal-to-ligand charge transfer (LC/MLCT) transitions. When the Pt(II) centers are brought closer together with bulky bridging ligands, they interact through their orbitals and the S1 and T1 states are best characterized as metal metal to ligand charge transfer (MMLCT) in character. The results of the fs TA experiments reveal that intersystem crossing (ISC) occurs on ultrafast timescales (τS1 < 200 fs) while there are two relaxation processes occurring within the triplet manifold, τ1 = 0.5 – 3.2 ps and τ2 = 20 – 70 ps; the longer time constants correspond to the presence of bulkier bridging ligands. DFT calculations illustrate that the Pt-Pt distances further contract in the T1 3MMLCT states, therefore slower relaxation may be related to a larger structural reorganization. Subsequent investigations using faster time resolution are planned to measure the ISC process as well as to identify any potential coherent interaction(s) between the platinum centers that may occur.

  2. Electronic structure, lattice constant, optical and mechanical properties for NaCl-structured Ti-Al-N by density functional theory

    International Nuclear Information System (INIS)

    The electronic structure, lattice constant, optical and mechanical properties of NaCl-structured Ti-Al-N compounds were studied by density functional theory with the plane wave pseudopotential method. The calculation results indicated that in a NaCl-structured TiN containing dilute solvent Al, the calculated forming energy of the paired defects of substitute Al for Ti+N vacancy is -1.7325 eV per pair of defects, while that of the paired defects of substitute Al for N+Ti vacancy is -10.62 eV per pair of defects. In other words, the energetically preferred occupation sites of Al atoms are Ti sites. In relation to the reference system of TiN, the substitute Al atoms for Ti increased the charge transfer to N atoms, while Al for N decreased it. On the other hand, the substitute Al for Ti exhibits cationic while those for N exhibit anionic. The addition of Al into the cubic TiN resulted in much universe feature of the refractory index in the visible light regime. The calculated reflectivity indicates that TiN is colorful while (Ti3Al)N4 is gray. The smaller lattice constant, lower elastic properties (the elastic tensor, bulk modulus and Young modulus) and higher hardness of NaCl-structure (Ti3Al)N4, than those of TiN, were discussed in terms of effects of the substitute Al for Ti on its electronic structure

  3. Absence of magnetic dipolar phase transition and evolution of low-energy excitations in PrNb2Al20 with crystal electric field Γ3 ground state. Evidence from 93Nb-NQR studies

    International Nuclear Information System (INIS)

    We report measurements of bulk magnetic susceptibility and 93Nb nuclear quadrupole resonance (NQR) in the Pr-based caged compound PrNb2Al20. By analyzing the magnetic susceptibility and magnetization, the crystal electric field (CEF) level scheme of PrNb2Al20 is determined to be Γ3(0 K)–Γ4(21.32 K)–Γ5(43.98 K)–Γ1(51.16 K) within the framework of the localized 4f electron picture. The 93Nb-NQR spectra exhibit neither spectral broadening nor spectral shift upon cooling down to 75 mK. The 93Nb-NQR spin–lattice relaxation rate 1/T1 at 5 K depends on the frequency and remains almost constant below 5 K. The frequency dependence of 1/T1 is attributed to the magnetic fluctuation due to the hyperfine-enhanced 141Pr nuclear moment inherent in the nonmagnetic Γ3 CEF ground state. The present NQR results provide evidence that no symmetry-breaking magnetic dipole order occurs down to 75 mK. Also, considering an invariant form of the quadrupole and octupole couplings between a 93Nb nucleus and Pr 4f electrons, Pr 4f quadrupoles and an octupole can couple with a 93Nb nuclear quadrupole moment and nuclear spin, respectively. Together with the results of bulk measurements, the present NQR results suggest that the possibility of a static quadrupole or octupole ordering can be excluded down to 100 mK. At low temperatures below 500 mK, however, the nuclear spin-echo decay rate gradually increases and the decay curve changes from Gaussian decay to Lorentzian decay, suggesting the evolution of a low-energy excitation. (author)

  4. SYNTHESIS OF FUNCTIONAL MACROMOLECULE INTERMEDIATE THROUGH ACYLATION CATALYZED BY [Emim]Cl-AlCl3 IONIC LIQUID

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Acylation reaction of anthracene with oxalyl chloride in the presence of [Emim]C1-A1C13 ionic liquid has been investigated. Pure 1,2-aceanthryenedione, which is used as intermediate of functional aromatic polymer material, was obtained by recrystalling the reaction mixture with aether and was determined by GC/MS, 1HNMR and FTIR analysis. The influences of various parameters, such as the contents of AlCl3 in [Emim]C1-A1C13, the amount of acylation agent, amount of [Emim]C1-A1C13, reaction temperature and reaction time were investigated. The optimum conditions were as follows: the molar fraction of A1C13 in ionic liquid [x(AlCl3)] being 0.67 , molar ratio of ionic liquid to anthracene being 2:1 , molar ratio of oxalyl chloride to anthracene being 2:1, reaction temperature being 40℃ and reaction time being 6h. Under above conditions, the yield and selectivity of 1,2-aceanthrylenedione can reach 91.5% and 98.3% respectively. Further more, [Emim]C1-A1C13 ionic liquid, compared with metal halides such as AlCl3, was found to catalyze the reaction as a novel environmental friendly catalyst and solvent and can be reused.

  5. Structural and electronic properties of SrAl2O4:Eu2+ from density functional theory calculations

    International Nuclear Information System (INIS)

    Highlights: •Persistent phosphor SrAl2O4:Eu2+ was synthesized and studied. •Ab initio calculations of its electronic properties were performed. •Lowest position of the Eu 4f states in the band gap was determined. •Position of the Eu 4f states agrees with the charge transfer transition. -- Abstract: A stoichiometric micro-sized powder SrAl2O4:Eu2+ was synthesized by traditional solid state reaction at 1250 °C. Low-temperature spectroscopic measurements revealed two luminescence bands at 450 nm and 512 nm; their origin was discussed. Theoretical calculations of the structural and optical properties of SrAl2O4:Eu2+ in the framework of the density functional theory (DFT) were carried out; the obtained results were compared with the corresponding experimental data. For the first time, the position of the lowest 4f states of Eu in the host’s band gap was calculated for both available Sr positions to be at about 4.5–5 eV above the top of the valence band. Reliability of this result is confirmed by good agreement with the experimental value of the O(2p)–Eu(4f) charge transfer energy, which is equal to about 4.9 eV

  6. Electronic states of thiophene/phenylene co-oligomers: Extreme-ultra violet excited photoelectron spectroscopy observations and density functional theory calculations

    International Nuclear Information System (INIS)

    We have investigated electronic states in the valence electron bands for the thin films of three thiophene/phenylene co-oligomer (TPCO) compounds, 2,5-bis(4-biphenylyl)thiophene (BP1T), 1,4-bis(5-phenylthiophen-2-yl)benzene (AC5), and 1,4-bis{5-[4-(trifluoromethyl)phenyl]thiophen-2-yl}benzene (AC5-CF3), by using extreme-UV excited photoelectron spectroscopy (EUPS). By comparing both EUPS spectra and secondary electron spectra between AC5 and AC5-CF3, we confirm that CF3 substitution to AC5 deepens valence states by 2 eV, and increases the ionization energy by 3 eV. From the cut-off positions of secondary electron spectra, the work functions of AC5, AC5-CF3, and BP1T are evaluated to be 3.8 eV, 4.8 eV, and 4.0 eV, respectively. We calculate molecular orbital (MO) energy levels by the density functional theory and compare results of calculations with those of experiments. Densities of states obtained by broadening MO levels well explain the overall features of experimental EUPS spectra of three TPCOs.

  7. Electronic states of thiophene/phenylene co-oligomers: Extreme-ultra violet excited photoelectron spectroscopy observations and density functional theory calculations

    Science.gov (United States)

    Kawaguchi, Yoshizo; Sasaki, Fumio; Mochizuki, Hiroyuki; Ishitsuka, Tomoaki; Tomie, Toshihisa; Ootsuka, Teruhisa; Watanabe, Shuji; Shimoi, Yukihiro; Yamao, Takeshi; Hotta, Shu

    2013-02-01

    We have investigated electronic states in the valence electron bands for the thin films of three thiophene/phenylene co-oligomer (TPCO) compounds, 2,5-bis(4-biphenylyl)thiophene (BP1T), 1,4-bis(5-phenylthiophen-2-yl)benzene (AC5), and 1,4-bis{5-[4-(trifluoromethyl)phenyl]thiophen-2-yl}benzene (AC5-CF3), by using extreme-UV excited photoelectron spectroscopy (EUPS). By comparing both EUPS spectra and secondary electron spectra between AC5 and AC5-CF3, we confirm that CF3 substitution to AC5 deepens valence states by 2 eV, and increases the ionization energy by 3 eV. From the cut-off positions of secondary electron spectra, the work functions of AC5, AC5-CF3, and BP1T are evaluated to be 3.8 eV, 4.8 eV, and 4.0 eV, respectively. We calculate molecular orbital (MO) energy levels by the density functional theory and compare results of calculations with those of experiments. Densities of states obtained by broadening MO levels well explain the overall features of experimental EUPS spectra of three TPCOs.

  8. X-ray tomographic imaging of Al/SiCp functionally graded composites fabricated by centrifugal casting

    International Nuclear Information System (INIS)

    The present work refers to an X-ray microtomography experiment aiming at the elucidation of some aspects regarding particle distribution in SiC-particle-reinforced functionally graded aluminium composites. Precursor composites were produced by rheocasting. These were then molten and centrifugally cast to obtain the functionally graded composites. From these, cylindrical samples, around 1 mm in diameter, were extracted, which were then irradiated with a X-ray beam produced at the European Synchrotron Radiation Facility. The 3-D images were obtained in edge-detection mode. A segmentation procedure has been adapted in order to separate the pores and SiC particles from the Al matrix. Preliminary results on the particle and pore distributions are presented

  9. Modulation transfer function characteristic of uniform-doping transmission-mode GaAs/GaAlAs photocathode

    Institute of Scientific and Technical Information of China (English)

    Ren Ling; Chang Ben-Kang

    2011-01-01

    The resolution characteristic can be obtained by the modulation transfer function(MTF)of a GaAs/GaAlAs photocathode.After establishing the theoretical model of GaAs(100)-oriented atomic configuration and the formula for the ionized impurity scattering of the non-equilibrium carriers,this paper calculates the trajectories of photoelectrons in a photocathode.Thus the distribution of photoelectron spots on the emit-face is obtained,which is namely the point spread function.The MTF is obtained by Fourier transfer of the line spread function obtained from the point spread function.The MTF obtained from these calculations is shown to depend heavily on the electron diffusion length,and enhanced considerably by decreasing the electron diffusion length and increasing the doping concentration.Furthermore,the resolution is enhanced considerably by increasing the active-layer thickness,especially at high spatial frequencies.The best spatial resolution is 860 lp/mm,for the GaAs photocathode of doping concentration 1×1019cm-3,electron diffusion length 3.6 μm and the active-layer thickness 2 μm,under the 633-nm light irradiated. This research will contribute to the future improvement of the cathode's resolution for preparing a high performance GaAs photocathode,and improve the resolution of a low light level image intensifier.

  10. Excitation function for the production of 262Bh (Z = 107) in theodd-Z projectile reaction 208Pb(55Mn, n)

    Energy Technology Data Exchange (ETDEWEB)

    Folden III, C.M.; Nelson, S.L.; Dullmann, Ch.E.; Schwantes, J.M.; Sudowe, R.; Zielinski, P.M.; Gregorich, K.E.; Nitsche, H.; Hoffman, D.C.

    2005-05-16

    The excitation function for production of 262Bh in the odd-Z-projectile reaction 208Pb(55Mn,n) has been measured at three projectile energies using the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. In total, 33 decay chains originating from 262Bh and 2 decay chains originating from 261Bh were observed. The measured decay properties are in good agreement with previous reports. The maximum cross section of 540 +180 - 150 pb is observed at a lab-frame center-of-target energy of 264.0 MeV and is more than fives times larger than that expected based on previously reported results for production of 262Bh in the analogous even-Z-projectile reaction 209Bi(54Cr,n). Our results indicate that the optimum beam energy in one-neutron-out heavy-ion fusion reactions can be estimated simply using the ''Optimum Energy Rule'' proposed by Swiatecki, Siwek-Wilczynska, and Wilczynski.

  11. Nuclear model analysis of excitation functions of proton induced reactions on 86Sr, 88Sr and natZr: Evaluation of production routes of 86Y

    International Nuclear Information System (INIS)

    The proton induced nuclear reactions on 86Sr, 88Sr and natZr were investigated for the production of 86Y. The literature data were compared with the results of nuclear model calculations using the codes ALICE-IPPE, TALYS 1.6 and EMPIRE 3.2. The thick target yields of 86Y were calculated from the recommended excitation functions. Analysis of radioyttrium impurities was also performed. A comparison of the various production routes showed that for medical applications of 86Y, the reaction 86Sr(p,n)86Y is the method of choice, which gives efficient yield with minimum impurities. - Highlights: • Nuclear model calculations on protons on 86Sr, 88Sr and natZr using the codes ALICE-IPPE, TALYS-1.6 and EMPIRE 3.2 and evaluation of the 86Sr(p,n)86Y and 88Sr(p,3n)86Y reactions for 86Y production. • Calculation of thick target yields of 86Y and comparison with the calculated and experimental yield data given in literature. • Analysis of radionuclidic impurities in the production of 86Y. • Comparison of production routes of 86Y for medical application

  12. The structure of the hydrated electron. Part 2. A mixed quantum classical molecular dynamics - embedded cluster density functional theory: single-excitation configuration interaction study

    CERN Document Server

    Shkrob, I A; Larsen, R E; Schwartz, B J; Glover, William J.; Larsen, Ross E.; Schwartz, Benjamin J.; Shkrob, Ilya A.

    2006-01-01

    Adiabatic mixed quantum/classical molecular dynamics simulations were used to generate snapshots of the hydrated electron (e-) in liquid water at 300 K. Water cluster anions that include two complete solvation shells centered on the e- were extracted from these simulations and embedded in a matrix of fractional point charges designed to represent the rest of the solvent. Density functional theory and single-excitation configuration interaction methods were then applied to these embedded clusters. The salient feature of these hybrid calculations is significant transfer (ca. 0.18) of the excess electron's charge density into the O 2p orbitals in OH groups forming the solvation cavity. We used the results of these calculations to examine the structure of the molecular orbitals, the density of states, the absorption spectra in the visible and ultraviolet, the hyperfine coupling (hfc) tensors, and the IR and Raman spectra of the e-. The calculated hfc tensors were used to compute the EPR and ESEEM spectra for the ...

  13. Excitation function for the production of 262Bh (Z=107) in the odd-Z-projectile reaction 208Pb(55Mn, n)

    International Nuclear Information System (INIS)

    The excitation function for production of 262Bh in the odd-Z-projectile reaction 208Pb(55Mn, n) has been measured at three projectile energies using the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. In total, 33 decay chains originating from 262Bh and 2 decay chains originating from 261Bh were observed. The measured decay properties are in good agreement with previous reports. The maximum cross section of 540-150+180 pb is observed at a lab-frame center-of-target energy of 264.0 MeV and is more than five times larger than that expected based on previously reported results for production of 262Bh in the analogous even-Z-projectile reaction 209Bi(54Cr, n). Our results indicate that the optimum beam energy in one-neutron-out heavy-ion fusion reactions can be estimated simply using the optimum energy rule proposed by SwiaPtecki, Siwek-Wilczynska, and Wilczynski

  14. "Theory of mind and executive function in Chinese preschool children": Correction to Duh et al. (2016).

    Science.gov (United States)

    2016-04-01

    Reports an error in "Theory of Mind and Executive Function in Chinese Preschool Children" by Shinchieh Duh, Jae H. Paik, Patricia H. Miller, Stephanie C. Gluck, Hui Li and Igor Himelfarb (Developmental Psychology, Advanced Online Publication, Feb 4, 2016, np). In the article, there were two errors in Table 6. The coefficient between WM and Age was incorrectly set as .46; it should have been .46. Further, the coefficient between WM and Gender should be .00 instead of .00. The correct version is provided. (The following abstract of the original article appeared in record 2016-05744-001.) Cross-cultural research on children's theory of mind (ToM) understanding has raised questions about its developmental sequence and relationship with executive function (EF). The current study examined how ToM develops (using the tasks from Wellman & Liu, 2004) in relation to 2 EF skills (conflict inhibition, working memory) in 997 Chinese preschoolers (ages 3, 4, 5) in Chengdu, China. Compared with prior research with other Chinese and non-Chinese children, some general patterns in development were replicated in this sample. However, the children showed culture-specific reversals in the developmental sequence of ToM. For example, Chengdu children performed differently on the 2 false-belief tasks that were thought to be equivalent. Furthermore, conflict inhibition as well as working memory uniquely predicted ToM performance. We discuss the issues of ToM development as they relate to test items and cross-cultural-and subcultural-differences. (PsycINFO Database Record PMID:27010231

  15. The Relationship between Language Functions and Character Types in Noon val-Ghalam by Jalal Al Ahmad

    Directory of Open Access Journals (Sweden)

    Sayyed Ahmad Parsa

    2013-11-01

    Full Text Available Abstract Making harmony among language functions of story characters with their character types is one of the characteristics and advantages of modern and successful story writing. In traditional fictional literature in Iran (prose and verse, this point is not considered important and story characters, generally, speak in the voice of narrator or writer since there is the narrators statement on their speech, they are not the representative of their class and character type. Not paying attention to this subject, causes disorder in either making supposition of reality or personifying, which are both important principals of story telling. This study views from this point the story of Noon val-Ghalam of Jalal Al Ahmad who is a contemporary writer. The methodology is qualitative, and data collection is based on content–analysis and document- analysis. As Al Ahmad was one of the Iranian contemporary writers and was familiar with western and Iranian writers, it is expected that the language and way of describing story characters he made, be based on their social classes. But this study, by stating different proofs, shows that this writer ignores the relationship necessary for language functions and character type among characters in the story and because of the imposition of his knowledge, statement and political and social view, the independence of the protagonists in his story is not well-considered.  The inflection of political and social thoughts of each writer among his works, is not a shortfall by itself, but representing of speeches in protagonists, in the way which is not in harmony with their characters, underestimates them as an instrument for specific social and political representatives. This not only displays the character like a personified ideas, but also distructs processing of fictional dialogue as an important element in storytelling . Since in each language people from different social groups, use almost the same vocabularies that

  16. Preparation and characterization of Al2O3-Ti3SiC2 composites and its functionally graded materials

    International Nuclear Information System (INIS)

    Alumina/titanium silicon carbide (Al2O3-Ti3SiC2) composites and its functionally graded materials (FGMs) were fabricated by a powder metallurgy processes and their microstructure and properties were investigated, respectively. The experimental results showed that the Vickers hardness of composites decreased with increasing Ti3SiC2 content while the fracture toughness and strength exhibited the opposite trend. Minimum Vickers hardness (4 GPa), maximum strength (598 MPa) and maximum toughness (11.24 MPa m1/2) were reached in the pure Ti3SiC2 material. Strength and hardness of FGMs were evaluated. Observation using an scanning electron microscope (SEM) indicated that the presence of Ti3SiC2 of FGMs inhibited the growth of alumina grains through a pinning mechanism. The study shows that the combination of the layered Ti3SiC2 structure and the fine alumina grains can result in a Al2O3-Ti3SiC2 composites possessing a high toughness and low Vickers hardness without a sacrifice in the strength

  17. Fabrication of Al{sub 2}O{sub 3}-W Functionally Graded Materials by Slipcasting Method

    Energy Technology Data Exchange (ETDEWEB)

    Katayama, Tomoyuki; Sukenaga, Sohei; Saito, Noritaka; Nakashima, Kunihiko [Department of Materials Science and Engineering, Kyushu University, 744, Motooka, Nishiku, Fukuoka 819-0395 (Japan); Kagata, Hajime, E-mail: saito@zaiko.kyushu-u.ac.jp [Advanced Ceramic Section, TOTO Ltd., 2-1-1, Nakashima, Kokura, Kitakyushu, Fukuoka 802-8601 (Japan)

    2011-10-29

    We have successfully fabricated a functionally graded material (FGM) from tungsten and alumina powders by a slip-casting method. This FGM has applications as a sealing and conducting component for high-intensity discharge lamps (HiDLs) that have a translucent alumina envelope. Two types of W powder, with different oxidizing properties, were used as the raw powders for the Al{sub 2}O{sub 3}-W FGM. 'Oxidized W' was prepared by heat-treatment at 200 deg. C for 180 min in air. Alumina and each of the W powders were mixed in ultrapure water by ultrasonic stirring. The slurry was then cast into a cylindrical acrylic mold, which had a base of porous alumina, under controlled pressure. The green compacts were subsequently dried, and then sintered using a vacuum furnace at 1600 deg. C for a fixed time. The microstructures of the FGMs were observed by scanning electron microscopy (SEM) of the polished section. The Al{sub 2}O{sub 3}-W FGM with the 'oxidized W' powder resulted in a microscopic compositional gradient. However, the FGM with 'as-received W' showed no compositional gradient. This result was mainly attributed to the difference between the {zeta}-potentials of the W powders with the different oxidizing conditions; basically 'oxidized W' powder tends to disperse because of the larger {zeta}-potential of the oxide layer coated on the W powder core.

  18. New Au–Cu–Al thin film shape memory alloys with tunable functional properties and high thermal stability

    International Nuclear Information System (INIS)

    An Au–Cu–Al thin film materials library prepared by combinatorial sputter-deposition was characterized by high-throughput experimentation in order to identify and assess new shape memory alloys (SMAs) in this alloy system. Automated resistance measurements during thermal cycling between −20 and 250 °C revealed a wide composition range that undergoes reversible phase transformations with martensite transformation start temperatures, reverse transformation finish temperatures and transformation hysteresis ranging from −15 to 149 °C, 5 to 185 °C and 8 to 60 K, respectively. High-throughput X-ray diffraction analysis of the materials library confirmed that the phase-transforming compositions can be attributed to the existence of the β-AuCuAl parent phase and its martensite product. The formation of large amount of phases based on face-centered cubic (Au–Cu), Al–Cu and Al–Au is responsible for limiting the range of phase-transforming compositions. Selected alloys in this system show excellent thermal cyclic stability of the phase transformation. The functional properties of these alloys, combined with the inherent properties of Au-based alloys, i.e. aesthetic value, oxidation and corrosion resistance, makes them attractive as smart materials for a wide range of applications, including applications as SMAs for elevated temperatures in harsh environment

  19. Structures and autocorrelation functions of liquid Al and Mg modelled via Lennard-Jones potential from molecular dynamics simulation

    Indian Academy of Sciences (India)

    G A Adebayo; O Akinlade; L A Hussain

    2005-02-01

    The structures and autocorrelation functions of Al and Mg in the liquid state are investigated through the pair distribution function (), the diffusion coefficients as well as the shear viscosity via the Green{Kubo and Einstein relations. From the structure and the Enskog relation we determined the frequency of collisions of atoms in the first shell of () in the systems. We also discovered that the packing fraction of Lennard-Jones liquids should be approximately half the reduced density value. This approximation is accurate to within 99%. The temperature dependence of the pair distribution function and the atomic mean square displacement are investigated by performing simulations at various experimental temperatures and corresponding densities. The structures of the systems are affected by temperature via movements of atoms in the first minimum of (). The Lennard-Jones model shows that density dependence of the shear viscosity is in agreement with what is expected of simple liquids in the range of investigated temperatures and densities. In the gas limit, the Stoke-Einstein relation = B/2 is grossly overestimated by Lennard-Jones model. This could not be attributed to defficiencies in the model, as other investigators using first principle method could not obtain the gas limit of the Stoke-Einstein relation.

  20. Validation of the German version of the extended ALS functional rating scale as a patient-reported outcome measure.

    Science.gov (United States)

    Abdulla, Susanne; Vielhaber, Stefan; Körner, Sonja; Machts, Judith; Heinze, Hans-Jochen; Dengler, Reinhard; Petri, Susanne

    2013-09-01

    The revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) is a well-established rating instrument to assess the functional status of ALS patients. A recent innovation was the addition of three further items designed to improve its sensitivity at lower levels of physical function (ALSFRS-Extension, ALSFRS-EX). Neither the ALSFRS-R nor the ALSFRS-EX has been validated in German yet. The aim of the present study was the validation of the German version of a self-administered form of the ALSFRS-EX. Seventy-six patients participated in the study. Psychometric analysis included reliability assessment and factorial analysis. To evaluate convergent validity, correlations between ALSFRS-EX items and the MRC score, spasticity, tongue movement, pulmonary function, ALSAQ-40 and Borg dyspnoea scales (upright and supine) were performed. Internal consistency as measured by Cronbach's alpha (total scale 0.868, subscales 0.690-0.938) and corrected item to total correlations (all above 0.50) was high. Test-retest reliability assessed by Spearman's rho (0.882-0.972) and Cohen's Kappa (0.63-0.92) was also high. Principal component analysis with varimax rotation yielded a four-factor solution accounting for approximately 79% of the variance. Clinical parameters were strongly correlated with respective items and subscores of the ALSFRS-EX (muscle strength 0.568-0.833 p < 0.01; spasticity -0.236 to -0.376 p < 0.05; tongue movement 0.437-0.818 p < 0.01; pulmonary function 0.485-0.577 p < 0.01). ALSAQ-40 and Borg score correlated highly with the corresponding ALSFRS-EX items. The German self-report version of the ALSFRS-EX possesses very good psychometric properties similar to the original scale including high internal consistency and test-retest reliability as well as excellent convergent validity. PMID:23736973

  1. Fission-evaporation competition in excited uranium and fermium nuclei

    International Nuclear Information System (INIS)

    The production cross sections and excitation functions for the 223-226U neutron deficient isotopes have been measured in the 20Ne+208Pb and 22Ne+208Pb reactions for (4,5)n and (4-7)n evaporation channels of the de-excitation of the compound nuclei 228U* and 230U*, respectively. The present study considers in addition the de-excitation via the (5,6)n evaporation channels of the 224U* compound nucleus formed in the 27Al+197Au reaction. The production cross sections of 247g,246Fm formed after evaporation of (5,6)n and (7,8)n from the 252Fm* and 254Fm* compound nuclei produced in the 20Ne+232Th and 22Ne+232Th reactions were also measured respectively. The evaporation residues emerging from the target were separated in-flight from the projectiles and background reaction products by the electrostatic recoil separator VASSILISSA [1]. The investigation regards the U and Fm compound nuclei in the 40-80 MeV excitation energy range. For the analysis of the (Hl, xn) evaporation cross sections the advanced statistical model [2] calculations were used. The angular momentum dependence of the shell correction to the fission barrier, and the effects of the nuclear viscosity and dynamical deformation for these fissile excited nuclei are considered. The n/Γt> values at the initial steps of the de-excitation cascade for the U and Fm compound nuclei were derived from the measured excitation functions and discussed from the point of view of the consequences for the fission process dynamics

  2. Nonlinear excitations in biomolecules

    International Nuclear Information System (INIS)

    The aim of the workshop entitled ''Nonlinear Excitations in Biomolecules'' is to attempt to bridge the gap between the physicists and biologists communities which is mainly due to language and cultural barriers. The progress of nonlinear science in the last few decades which have shown that the combination of nonlinearity, which characterize most biological phenomena, and cooperative effects in a system having a large number of degrees of freedom, can give rise to coherent excitations with remarkable properties. New concepts, such as solitons nd nonlinear energy localisation have become familiar to physicists and applied mathematicians. It is thus tempting to make an analogy between these coherent excitations and the exceptional stability of some biological processes, such as for instance DNA transcription, which require the coordination of many events in the ever changing environment of a cell. Physicists are now invoking nonlinear excitations to describe and explain many bio-molecular processes while biologists often doubt that the seemingly infinite variety of phenomena that they are attempting to classify can be reduced to such simple concepts. A large part of the meeting is devoted to tutorial lectures rather than to latest research results. The book provides a pedagogical introduction to the two topics forming the backbone of the meeting: the theory of nonlinear excitations and solitons, and their application in biology; and the structure and function of biomolecules, as well as energy and charge transport in biophysics. In order to emphasize the link between physics and biology, the volume is not divided along these two topics but according to biological subjects. Each chapter starts with a short introduction attempting to help the reader to find his way among the contributions and point out the connection between them. 23 lectures over the 32 presented have been selected and refers to quantum properties of macro-molecules. (J.S.)

  3. Perspectives on double-excitations in TDDFT

    CERN Document Server

    Elliott, Peter; Canahui, Chris; Maitra, Neepa T

    2011-01-01

    The adiabatic approximation in time-dependent density functional theory (TDDFT) yields reliable excitation spectra with great efficiency in many cases, but fundamentally fails for states of double excitation character. We discuss how double-excitations are at the root of some of the most challenging problems for TDDFT today. We then present new results for (i) the calculation of autoionizing resonances in the helium atom, (ii) understanding the nature of the double excitations appearing in the quadratic response function, and (iii) retrieving double-excitations through a real-time semiclassical approach to correlation in a model quantum dot.

  4. Functional applications of Al·Al2O3 nanowires : laser assisted α-Al2O3 synthesis and fabrication of micro-/nanostructured surfaces for cell compatibility studies

    OpenAIRE

    Aktas, Oral Cenk

    2009-01-01

    Recently, one-dimensional (1D) nanostructures have attracted considerable interest of nanoscience studies as well as nanotechnology applications. Especially 1D hetero-structural nanowires with a combination of two different materials, for instance metal/metal oxide composites, hold a great potential for various photonic and electronic applications. Thus, Al·Al2O3 core-shell nanowires, which were firstly reported by Veith et al., form an interesting class of such hetero-nanostructures. This...

  5. Nuclear excitation in muonic gold

    CERN Document Server

    Robert Tissot, B; Debrunner, P; Engfer, R; Link, R; Schellenberg, L; Schneuwly, H; Walter, H K

    1973-01-01

    Energies and intensities of muonic X-rays in gold were measured at the CERN muon channel with an experimental set-up as described by Backe et al. (1972). The 2p-1s and 3d-2p transitions could only be analysed taking into account beside the static quadrupole interaction a dynamical hyperfine interaction of the 2p states, which leads to an excitation of the first four nuclear levels. The dynamical hyperfine interaction was calculated using the core excitation model (de Shalit, (1961)). (0 refs).

  6. Electronic structure and optical properties of CdS{sub x}Se{sub 1−x} solid solution nanostructures from X-ray absorption near edge structure, X-ray excited optical luminescence, and density functional theory investigations

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, M. W. [DESY (Deutsches Elektronen-Synchrotron), FS-PEX, Notkestrasse 85, 22607 Hamburg (Germany); Yiu, Y. M., E-mail: yyiu@uwo.ca; Sham, T. K. [Department of Chemistry, University of Western Ontario, London, ON N6A5B7 (Canada); Ward, M. J. [Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, NY 14853 (United States); Liu, L. [Institute of Functional Nano and Soft Materials (FUNSOM) and Soochow University-Western University Center for Synchrotron Radiation Research, Soochow University, Suzhou, Jiangsu, 215123 (China); Hu, Y. [Canadian Light Source, University of Saskatchewan, Saskatoon, SK S7N2V3 (Canada); Zapien, J. A. [Center Of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR (China); Liu, Yingkai [Institute of Physics and Electronic Information, Yunnan Normal University, Kunming, Yunnan, 650500 (China)

    2014-11-21

    The electronic structure and optical properties of a series of iso-electronic and iso-structural CdS{sub x}Se{sub 1−x} solid solution nanostructures have been investigated using X-ray absorption near edge structure, extended X-ray absorption fine structure, and X-ray excited optical luminescence at various absorption edges of Cd, S, and Se. It is found that the system exhibits compositions, with variable local structure in-between that of CdS and CdSe accompanied by tunable optical band gap between that of CdS and CdSe. Theoretical calculation using density functional theory has been carried out to elucidate the observations. It is also found that luminescence induced by X-ray excitation shows new optical channels not observed previously with laser excitation. The implications of these observations are discussed.

  7. Hydrogen bonding and coordination bonding in the electronically excited states of the MOF Cu2 (L)2 (L=5-(4-pyridyl)tetrazole) CH2Cl2: A time-dependent density functional theory study

    International Nuclear Information System (INIS)

    The solvent-dependent luminescent metal-organic framework (MOF), Cu2(L)2·CH2Cl2 (L=5-(4-pyridyl)tetrazole), in the electronically excited states was studied using time-dependent density functional theory (TDDFT) method. Based on the analysis of the frontier molecular orbitals and electronic configuration, it revealed that the emission is attributed to a ligand-to-metal charge transfer (LMCT). Besides, we investigated the behavior of the hydrogen bonding and coordination bonding in the excited state S1 of Cu2(L)2·CH2Cl2. The results indicated that the strength of the hydrogen bonding N5⋯H39-C2 between the dichloromethane molecule and the tetrazole ligand was decreased in the S1 state, while the coordination bond Cu2-N8 was strengthened in the excited state. Moreover, we further demonstrated that the hydrogen bonding weakening and coordination bonding strengthening should be beneficial to the luminescent process of the MOF. Highlights: ► Solvent-dependent luminescent MOF was studied by TDDFT. ► Emission mechanism was a ligand to metal charge transition (LMCT). ► 1H NMR and binding energies indicate H-bond weakening in excited states. ► The coordination bonds become stronger in the excited states

  8. Gain and loss of function of ALS-related mutations of TARDBP (TDP-43) cause motor deficits in vivo.

    Science.gov (United States)

    Kabashi, Edor; Lin, Li; Tradewell, Miranda L; Dion, Patrick A; Bercier, Valérie; Bourgouin, Patrick; Rochefort, Daniel; Bel Hadj, Samar; Durham, Heather D; Vande Velde, Christine; Rouleau, Guy A; Drapeau, Pierre

    2010-02-15

    TDP-43 has been found in inclusion bodies of multiple neurological disorders, including amyotrophic lateral sclerosis, frontotemporal dementia, Parkinson's disease and Alzheimer's disease. Mutations in the TDP-43 encoding gene, TARDBP, have been subsequently reported in sporadic and familial ALS patients. In order to investigate the pathogenic nature of these mutants, the effects of three consistently reported TARDBP mutations (A315T, G348C and A382T) were tested in cell lines, primary cultured motor neurons and living zebrafish embryos. Each of the three mutants and wild-type (WT) human TDP-43 localized to nuclei when expressed in COS1 and Neuro2A cells by transient transfection. However, when expressed in motor neurons from dissociated spinal cord cultures these mutant TARDBP alleles, but less so for WT TARDBP, were neurotoxic, concomitant with perinuclear localization and aggregation of TDP-43. Finally, overexpression of mutant, but less so of WT, human TARDBP caused a motor phenotype in zebrafish (Danio rerio) embryos consisting of shorter motor neuronal axons, premature and excessive branching as well as swimming deficits. Interestingly, knock-down of zebrafisfh tardbp led to a similar phenotype, which was rescued by co-expressing WT but not mutant human TARDBP. Together these approaches showed that TARDBP mutations cause motor neuron defects and toxicity, suggesting that both a toxic gain of function as well as a novel loss of function may be involved in the molecular mechanism by which mutant TDP-43 contributes to disease pathogenesis. PMID:19959528

  9. Non-equilibrium Green's function calculation of AlGaAs-well-based and GaSb-based terahertz quantum cascade laser structures

    Energy Technology Data Exchange (ETDEWEB)

    Yasuda, H., E-mail: yasuda@nict.go.jp; Hosako, I. [National Institute of Information and Communications Technology, 4-2-1 Nukui-Kitamachi, Koganei, Tokyo 184-8795 (Japan)

    2015-03-16

    We investigate the performance of terahertz quantum cascade lasers (THz-QCLs) based on Al{sub x}Ga{sub 1−x}As/Al{sub y}Ga{sub 1−y}As and GaSb/AlGaSb material systems to realize higher-temperature operation. Calculations with the non-equilibrium Green's function method reveal that the AlGaAs-well-based THz-QCLs do not show improved performance, mainly because of alloy scattering in the ternary compound semiconductor. The GaSb-based THz-QCLs offer clear advantages over GaAs-based THz-QCLs. Weaker longitudinal optical phonon–electron interaction in GaSb produces higher peaks in the spectral functions of the lasing levels, which enables more electrons to be accumulated in the upper lasing level.

  10. Excitation functions of (p,2n) and (p,pn) reactions and differential and integral yields of 123I in proton induced nuclear reactions on highly enriched 124Xe

    International Nuclear Information System (INIS)

    Excitation functions were measured for (p,2n) and (p,pn) reactions on 99.9% enriched 124Xe from threshold up to 44 MeV. The (p,2n) reactions is much stronger than the (p,pn) channel; above 36 MeV, however, the two processes have almost equal cross sections. Differential yields of 123I were measured experimentally as a function of proton energy and were also calculated from the excitation functions. Our experimental and theoretical yield data are consistent within 15%, but lower by a factor of 2 than the literature experimental values. Our studies show that the optimum energy range for the production of 123I is Ep = 29 → 23 MeV. The theoretically expected thick target yield of 123I at 6.6 h after EOB is 11.2 mCi/μAh, and is in agreement with the high-current experimental production yields. (author)

  11. Theoretical research relating to excitation spectrum of furan. Application of integral direct coupled cluster linear response (direct CCLR) method; Furan no reiki supekutoru ni kansuru ronriteki kenkyu. Integral-direct Coupled Cluster Linear Response (direct CCLR) ho no tekiyo

    Energy Technology Data Exchange (ETDEWEB)

    Shigemitsu, Yasuhiro. [Nagasaki Industrial Technology Center, Nagasaki (Japan)

    1999-07-01

    heoretical researches relating to excitation spectrum of furan have been carried out for many years, and they reveal the problems that should be solved in order to predict highly reliable excitation energy. In general, it is difficult to uniformly obtain highly reliable calculation results for all excitation states since different excitation states show different electronic correlative effects. Means for obtaining the electron states in ground state and excited state and calculating the energy difference thereof is the mainstream of the theoretical calculation of the excitation energy. CASSCF/CASPT 2 developed by Roos et al. is a typical method excellent in quantitative description. Recently, the comparison between direct CCLR and CASSCF/CASPT 2 as examples for calculating the excitation spectrum of furan was carried out by using the same ground function. For Rydberg excitation, CC3, CAS, CASPT 2 show good agreement with each other. (NEDO)

  12. Microstructure and Resisting Thermal Shock Behaviors of TiC-Al2O3/Fe Functionally Graded MaterialsPrepared by SHS/PHIP

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The microstructure and composition of TiC-Al2O3/Fe functionally graded materials (FGM) prepared by self-propagating high temperature synthesis and pseudo-hot isostatic pressing (SHS/PHIP) were studied, and the resisting thermal shock behaviors were analyzed. The results show that TiC-Al2O3/Fe FGM has graded composition distribution. No cross-section crack through the layers was found in the tests of thermal shock and fatigue.

  13. New insights into structure-function relationship of the DHPR beta1a subunit in skeletal muscle excitation-contraction coupling using zebrafish 'relaxed' as an expression system

    International Nuclear Information System (INIS)

    The paralyzed zebrafish strain relaxed carries a null mutation for the skeletal muscle dihydropyridine receptor (DHPR) [beta]1a subunit. The lack of [beta]1a not only impedes functional [alpha]1S membrane expression but also precludes the skeletal muscle-specific ultrastructural arrangement of DHPRs into tetrads opposite ryanodine receptor (RyR1), coherent with the absence of skeletal muscle excitation-contraction (EC) coupling. With the plethora of experimental approaches feasible with zebrafish model organism and importantly with the [beta]1-null mutation having a monogenetic inheritance and because of the survival of the relaxed larvae for some days, we were able to establish the zebrafish relaxed as an expression system. Linking in vitro to in vivo observations, a clear differentiation between the major functional roles of [beta] subunits in EC coupling was feasible. The skeletal muscle [beta]1a subunit was able to restore all parameters of EC coupling upon expression in relaxed myotubes and larvae. Expression of the phylogenetically closest isoform to [beta]1a, the cardiac/neuronal [beta]2a subunit or the most distant neuronal [beta]M from the housefly in relaxed myotubes and larvae was likewise able to fully restore [alpha]1S triad targeting and facilitate charge movement. However, efficient tetrad formation and thus intact DHPR-RyR1 coupling was exclusively promoted by the [beta]1a isoform. Consequently, we postulated a model according to which [beta]1a acts as a unique allosteric modifier of [alpha]1S conformation crucial for skeletal muscle EC coupling. Therefore, unique structural elements in [beta]1a must be present which endow it with this exclusive property. Earlier, a unique hydrophobic heptad repeat motif (LVV) in the [beta]1a C-terminus was postulated by others to be essential for skeletal muscle EC coupling. We wanted to address the question if the proposed [beta]1a heptad repeat motif could be an active element of the DHPR-RyR1 signal transduction

  14. Harmonically excited orbital variations

    International Nuclear Information System (INIS)

    Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In this formulation the equations of motion adopt the form of a damped harmonic oscillator when torques are applied to the orbit in a variationally prescribed manner. The frequencies of the oscillator equation are in some ways unexpected but can nonetheless be exploited through resonant forcing functions to achieve large secular variations in the orbital elements. Two cases are discussed using a circular orbit as the control case: (1) large changes in orbital inclination achieved by harmonic excitation rather than one impulsive velocity change, and (2) periodic and secular changes to the longitude of the ascending node using both stable and unstable excitation strategies. The implications of these equations are also discussed for both artificial satellites and natural satellites. For the former, two utilitarian orbits are suggested, each exploiting a form of harmonic excitation. 5 refs

  15. The Influence of Al2O3 Powder Morphology on the Properties of Cu-Al2O3 Composites Designed for Functionally Graded Materials (FGM)

    Science.gov (United States)

    Strojny-Nędza, Agata; Pietrzak, Katarzyna; Węglewski, Witold

    2016-07-01

    In order to meet the requirements of an increased efficiency applying to modern devices and in more general terms science and technology, it is necessary to develop new materials. Combining various types of materials (such as metals and ceramics) and developing composite materials seem to be suitable solutions. One of the most interesting materials includes Cu-Al2O3 composite and gradient materials (FGMs). Due to their potential properties, copper-alumina composites could be used in aerospace industry as rocket thrusters and components in aircraft engines. The main challenge posed by copper matrix composites reinforced by aluminum oxide particles is obtaining the uniform structure with no residual porosity (existing within the area of the ceramic phase). In the present paper, Cu-Al2O3 composites (also in a gradient form) with 1, 3, and 5 vol.% of aluminum oxide were fabricated by the hot pressing and spark plasma sintering methods. Two forms of aluminum oxide (αAl2O3 powder and electrocorundum) were used as a reinforcement. Microstructural investigations revealed that near fully dense materials with low porosity and a clear interface between the metal matrix and ceramics were obtained in the case of the SPS method. In this paper, the properties (mechanical, thermal, and tribological) of composite materials were also collected and compared. Technological tests were preceded by finite element method analyses of thermal stresses generated in the gradient structure, and additionally, the role of porosity in the formation process of composite properties was modeled. Based on the said modeling, technological conditions for obtaining FGMs were proposed.

  16. Centrifugal casting processes of manufacturing in situ functionally gradient composite materials of Al-19Si-5Mg alloy

    Institute of Scientific and Technical Information of China (English)

    XIE Yong; LIU Changming; ZHAI Yanbo; WANG Kai; LING Xuedong

    2009-01-01

    Cylindrical components of in situ functionally gradient composite materials of Al-19Si-5Mg alloy were manufactured by centrifugal casting. Microstructure characteristics of the manufactured components were observed and the effects of the used process factors on these character-istics were analyzed. The results of observations shows that, in thickness, the components possess microstructures accumulating lots of Mg2Si particles and a portion of primary silicon particles in the inner layer, a little Mg2Si and primary silicon particles in the outer layer, and without any Mg2Si and primary silicon particle in the middle layer. The results of the analysis indicate that the rotation rate of centrifugal casting, mould temperature, and melt pouring temperature have evidently affected the accumulation of the second phase particles. Also, the higher the centrifugal rotation rate, mould temperature, and melt pouring temperature are, the more evident in the inner layer the degree of accumulation of Mg2Si and primary silicon particles is.

  17. Structural and functional properties of Al:ZnO thin films grown by Pulsed Laser Deposition at room temperature

    International Nuclear Information System (INIS)

    Current research on transparent conductive oxides (TCOs) is focusing on indium-free TCOs, such as Al-doped ZnO (AZO), as an alternative to indium–tin oxide. In this work, AZO thin films were grown by Pulsed Laser Deposition at room temperature in oxygen atmosphere. The O2 pressure was varied from 0.01 Pa to 10 Pa, highlighting the effects of defect formation and oxygen vacancies on the film properties. Structural properties were characterized by X-ray diffraction and Scanning Electron Microscopy, while functional properties were characterized by measurement of electrical conductivity, Hall mobility, carrier density and optical transmission. At an optimal deposition pressure of 2 Pa, optical transparency in the visible range and minimum resistivity (4.5 ∙ 10−4 Ω cm) were found, comparable to state-of-the-art TCOs. Mean value of visible transparency was shown to increase with increasing pressure, up to 88% at a deposition pressure of 10 Pa.

  18. A Density Functional Theory Study of Codoping Characteristics of Sulfur with Alkaline Earth in Delafossite CuAlO2

    Science.gov (United States)

    Qi-Jun, Liu; Han, Qin; Zheng-Tang, Liu

    2016-04-01

    The structural, electronic properties and formation energies of sulfur and alkaline earth codoped delafossite CuAlO2 have been investigated using the first-principles density functional theory calculations. Our results reveal that the volume of codoping systems increases with the increasing atomic radius of metal atoms. The formation energies under different growth conditions have been calculated, showing that the codoping systems are formed easily under O-rich growth conditions. Electronic band structures and density of states have been obtained. The decreased bandgaps, enhanced covalence and appearance of electron acceptors after codoping are all good for p-type conductivity. Supported by the National Natural Science Foundation of China under Grant Nos. 11347199, 51402244, and 11547311, the Specialized Research Fund for Doctoral Program of Higher Education of China under Grant No. 20130184120028, the Fundamental Research Fund for the Central Universities, China under Grant Nos. 2682014CX084, 2682014ZT30, and 2682014ZT31, and the fund of the State Key Laboratory of Solidification Processing in NWPU under Grant No. SKLSP201511

  19. Excitation function of sup 1 sup 2 sup 2 Te(d, n) sup 1 sup 2 sup 3 I nuclear reaction: production of sup 1 sup 2 sup 3 I at a low energy cyclotron

    CERN Document Server

    Takács, S; Szelecsenyi, F; Kovács, Z; Tarkanyi, F; Sonck, M; Hermanne, A

    1999-01-01

    The excitation function of the sup 1 sup 2 sup 2 Te(d, n) sup 1 sup 2 sup 3 I nuclear reaction has been measured from threshold up to 21 MeV by the stacked foil irradiation technique. Good agreement was obtained with the results of the recent model calculations but an energy shift of 2 MeV to lower energy can be seen when comparing with cross section measured earlier. Integral yields have been deduced from the measured excitation function and have been compared with experimental thick target yields found in the literature. A comparison of the yields of the proton and deuteron induced reactions for production of sup 1 sup 2 sup 3 I is given.

  20. Electron impact excitation cross sections for carbon

    Science.gov (United States)

    Ganas, P. S.

    1981-04-01

    A realistic analytic atomic independent particle model is used to generate wave functions for the valence and excited states of carbon. Using these wave functions in conjunction with the Born approximation and the Russell-Saunders LS-coupling scheme, we calculate generalized oscillator strengths and integrated cross sections for various excitations from the 2p 2( 3P O) valence state.

  1. Electron impact excitation cross sections for carbon

    International Nuclear Information System (INIS)

    A realistic analytic atomic independent particle model is used to generate wave functions for the valence and excited states of carbon. Using these wave functions in conjunction with the Born approximation and the Russell-Saunders LS-coupling scheme, we calculate generalized oscillator strengths and integrated cross sections for various excitations from the 2p2(3P0) valence state. (orig.)

  2. Double electron excitation of helium by charged particle impact

    International Nuclear Information System (INIS)

    Complete text of publication follows. A four-body classical trajectory Monte Carlo method is applied in the study of double electron excitation of helium by charged particle impact. The calculations are based on the independent particle model. As projectiles we consider protons and antiprotons with energies between 0.25 and 5 MeV. The state selective total cross sections as a function of the impact energy are calculated and compared with experimental and theoretical data. Fig. 1. shows the double excitation cross sections of helium to the (2s2)1S (Fig. 1a), (2s2p)1P (Fig. 1b) and (2p2)1D (Fig. 1c) states as a function of the impact energy. The errors of our calculated data are smaller or comparable with the size of the symbols. Our recent cross sections are compared with the experimental data of Giese et al. and Moretto-Capelle et al. and with the previous calculations of Bodea et al. Instead of the antiproton impact, the experiments in ref. were carried out with electron impact. These cross sections are shown at the energy where the electron velocity is equal that of the antiproton velocity. In all cases the cross sections for antiprotons exceeds the cross section for protons. The largest difference is obtained for the excitation of the (2s2)1S state (Fig. 1a). According to our expectation, with increasing projectile energies the cross sections for proton and antiproton impact approaching each other. This tendency is valid for the previous calculations of Bodea et al. except for the (2p2)1D (Fig. 1c). The calculated cross sections generally agree with the experimental values. (author)

  3. Circadian regulation of human cortical excitability.

    Science.gov (United States)

    Ly, Julien Q M; Gaggioni, Giulia; Chellappa, Sarah L; Papachilleos, Soterios; Brzozowski, Alexandre; Borsu, Chloé; Rosanova, Mario; Sarasso, Simone; Middleton, Benita; Luxen, André; Archer, Simon N; Phillips, Christophe; Dijk, Derk-Jan; Maquet, Pierre; Massimini, Marcello; Vandewalle, Gilles

    2016-01-01

    Prolonged wakefulness alters cortical excitability, which is essential for proper brain function and cognition. However, besides prior wakefulness, brain function and cognition are also affected by circadian rhythmicity. Whether the regulation of cognition involves a circadian impact on cortical excitability is unknown. Here, we assessed cortical excitability from scalp electroencephalography (EEG) responses to transcranial magnetic stimulation in 22 participants during 29 h of wakefulness under constant conditions. Data reveal robust circadian dynamics of cortical excitability that are strongest in those individuals with highest endocrine markers of circadian amplitude. In addition, the time course of cortical excitability correlates with changes in EEG synchronization and cognitive performance. These results demonstrate that the crucial factor for cortical excitability, and basic brain function in general, is the balance between circadian rhythmicity and sleep need, rather than sleep homoeostasis alone. These findings have implications for clinical applications such as non-invasive brain stimulation in neurorehabilitation. PMID:27339884

  4. Density functional study of the structural and magnetic properties of Al12X(X=Sc, Ti, V, Gr, Mn, Fe, Co, Ni, Cu, Zn) clusters

    International Nuclear Information System (INIS)

    Started from the four types 13-atom high-symmetric (Ih, Oh , D5h, D3h) close-packed structures and by replacing a 3d group atom in the unequivalent position, the structural and magnetic properties of the doped Al12X (X=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) clusters are systematically studied by u- sing the density-functional theory. Our results show that: except Al12Cr and Al12Fe, all the other Al12X clusters prefer to the Ih-replacing geometry as the ground-state structure, and with replacing surface atom for the early 3d elements (X=Sc, Ti, V, Mn) but the central atom for the late 3d elements (X=Co, Ni, Cu, Zn); Al12Cr and Al12Fe prefer to the Oh structure with replacing a surface atom as the ground- state; The energy-closed isomers can be found clearly for the doped clusters for most 3d elements (X= Ti, V, Cr, Fe, Co, Zn); Magnetism enhancement effect can be found in general for all these doped clusters as comparing with the pure Al13 cluster. (authors)

  5. Muon sites in Ce(Ru,Rh)2Al10 investigated by using Density Functional Theory from the view point of electronic potential

    International Nuclear Information System (INIS)

    Numerical investigations on muon sites in Ce-based Kondo semiconductors, Ce(Ru,Rh)2Al10 were carried out by using the Density Functional Theory. From the view point of simple electrostatic potential calculations, we found all the previously reported muon sites, suggested by different groups (Kambe S et al. 2010 J. Phys. Soc. Jpn. 79 053708 and Khalyavin D D et al., 2010 Phys. Rev. B 82 100405(R)), can be possibly chosen as muon stopping sites. We also investigated the changes in the potential of the Rh-doped case. We discovered that the electronic potential around the nearest Ru atom to the substituted Rh atom is affected and the potential becomes asymmetric around the nearest Ru ion. Although big changes in hyperfine fields at muon sites have been reported (Guo H et al. 2013 Phys. Rev. B 88 115206), the muon positions estimated from the potential calculations do not change much

  6. Proton induced reactions on Ti, V, Mn, Fe, Co and Ni. Measurement and hybrid model analysis of integral excitation functions and their application in model calculation for the production of cosmogenic nuclides

    International Nuclear Information System (INIS)

    By means of the stacked foil technique 67 excitation functions of p induced reactions on the target elements Ti, V, Mn, Fe, Co, and Ni were measured in the energy range between 45 and 200 MeV. For residual nuclei with 42 <= A <= 60 and half-lives between 12 hours and 5.26 years cross sections could be determined whereby reactions of the type (p, n) to (p, 8p9n) contributed. On the base of the cross sections determined in this theses (together with the data of selected other authors) at set of cosmochemically relevant excitation functions for the description of the interaction of galactic protons with matter was established up to the GeV region, and model calculations for the production of cosmogenic nuclides in meteorites and cosmic dust were performed. For this depth dependent fluxes of galactic protons in meteorites were calculated, and production rates of radionuclides were determined from theses fluxes and the new excitation functions. (orig./HSI)

  7. Effects of aerobic exercise therapy and cognitive behavioural therapy on functioning and quality of life in amyotrophic lateral sclerosis: protocol of the FACTS-2-ALS trial

    Directory of Open Access Journals (Sweden)

    van de Weerd Margreet GH

    2011-06-01

    Full Text Available Abstract Background Amyotrophic lateral sclerosis (ALS is a fatal progressive neurodegenerative disorder affecting motor neurons in the spinal cord, brainstem and motor cortex, leading to muscle weakness. Muscle weakness may result in the avoidance of physical activity, which exacerbates disuse weakness and cardiovascular deconditioning. The impact of the grave prognosis may result in depressive symptoms and hopelessness. Since there is no cure for ALS, optimal treatment is based on symptom management and preservation of quality of life (QoL, provided in a multidisciplinary setting. Two distinctly different therapeutic interventions may be effective to improve or preserve daily functioning and QoL at the highest achievable level: aerobic exercise therapy (AET to maintain or enhance functional capacity and cognitive behavioural therapy (CBT to improve coping style and cognitions in patients with ALS. However, evidence to support either approach is still insufficient, and the underlying mechanisms of the approaches remain poorly understood. The primary aim of the FACTS-2-ALS trial is to study the effects of AET and CBT, in addition to usual care, compared to usual care alone, on functioning and QoL in patients with ALS. Methods / Design A multicentre, single-blinded, randomized controlled trial with a postponed information model will be conducted. A sample of 120 patients with ALS (1 month post diagnosis will be recruited from 3 university hospitals and 1 rehabilitation centre. Patients will be randomized to one of three groups i.e. (1 AET + usual care, (2 CBT + usual care, (3 Usual care. AET consists of a 16-week aerobic exercise programme, on 3 days a week. CBT consists of individual psychological support of patients in 5 to 10 sessions over a 16-week period. QoL, functioning and secondary outcome measures will be assessed at baseline, immediately post intervention and at 3- and 6-months follow-up. Discussion The FACTS-2-ALS study is the first

  8. Molecular properties of excited electronic state: Formalism, implementation, and applications of analytical second energy derivatives within the framework of the time-dependent density functional theory/molecular mechanics

    International Nuclear Information System (INIS)

    This work extends our previous works [J. Liu and W. Z. Liang, J. Chem. Phys. 135, 014113 (2011); J. Liu and W. Z. Liang, J. Chem. Phys. 135, 184111 (2011)] on analytical excited-state energy Hessian within the framework of time-dependent density functional theory (TDDFT) to couple with molecular mechanics (MM). The formalism, implementation, and applications of analytical first and second energy derivatives of TDDFT/MM excited state with respect to the nuclear and electric perturbations are presented. Their performances are demonstrated by the calculations of adiabatic excitation energies, and excited-state geometries, harmonic vibrational frequencies, and infrared intensities for a number of benchmark systems. The consistent results with the full quantum mechanical method and other hybrid theoretical methods indicate the reliability of the current numerical implementation of developed algorithms. The computational accuracy and efficiency of the current analytical approach are also checked and the computational efficient strategies are suggested to speed up the calculations of complex systems with many MM degrees of freedom. Finally, we apply the current analytical approach in TDDFT/MM to a realistic system, a red fluorescent protein chromophore together with part of its nearby protein matrix. The calculated results indicate that the rearrangement of the hydrogen bond interactions between the chromophore and the protein matrix is responsible for the large Stokes shift

  9. Reply to Frewer et al. Comments on Janocha et al. Lie Symmetry Analysis of the Hopf Functional-Differential Equation. Symmetry 2015, 7, 1536–1566

    Directory of Open Access Journals (Sweden)

    Marta Wacławczyk

    2016-04-01

    Full Text Available We reply to the comment by Frewer and Khujadze regarding our contribution “Lie Symmetry Analysis of the Hopf Functional-Differential Equation” (Symmetry 2015, 7(3, 1536. The method developed by the present authors considered the Lie group analysis of the Hopf equations with functional derivatives in the equation, not the integro-differential equations in general. It was based on previous contributions (Oberlack and Wacławczyk, Arch. Mech. 2006, 58; Wacławczyk and Oberlack, J. Math. Phys. 2013, 54. In fact, three of the symmetries calculated in (Symmetry 2015, 7(3, 1536 break due to internal consistency constrains and conditions imposed on test functions, the same concerns the corresponding symmetries derived by Frewer and Khujadze and another, spurious symmetry, which was not discussed by Frewer and Khujadze. As a result, the same set of symmetries is obtained with both approaches.

  10. Thermoluminescence excitation spectroscopy: A versatile technique to study persistent luminescence phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Bos, Adrie J.J., E-mail: a.j.j.bos@tudelft.n [Delft University of Technology, Faculty of Applied Sciences, Mekelweg 15, 2629 JB Delft (Netherlands); Duijvenvoorde, Ronald M. van; Kolk, Erik van der [Delft University of Technology, Faculty of Applied Sciences, Mekelweg 15, 2629 JB Delft (Netherlands); Drozdowski, Winicjusz [Nicholas Copernicus University, Institute of Physics, Grudziadzka 5, PL-87100 Torun (Poland); Dorenbos, Pieter [Delft University of Technology, Faculty of Applied Sciences, Mekelweg 15, 2629 JB Delft (Netherlands)

    2011-07-15

    A versatile new facility to study photoionization processes in impurity doped compounds is presented. In this new facility monochromatic light is coupled to a thermoluminescence reader, enabling a fully automated recording of glow curves as a function of photon excitation wavelength. It provides detailed information on the mechanism of trap filling preceding persistent luminescence. The technique is first demonstrated with a study on Lu{sub 2}SiO{sub 5}:Ce{sup 3+} and then applied to commercial modern day double lanthanide doped SrAl{sub 2}O{sub 4}:Eu{sup 2+},Dy{sup 3+}, Sr{sub 4}Al{sub 14}O{sub 25}:Eu{sup 2+},Dy{sup 3+}, CaAl{sub 2}O{sub 4}:Eu{sup 2+},Nd{sup 3+}; and to the classical ZnS:Cu{sup +} persistent luminescence phosphors. The presented data provide new insight into the mechanism of persistent luminescence. - Highlights: {yields} New set-up for measuring glow curves as a function of photon excitation wavelength. {yields} TL excitation spectra for Eu{sup 2+} doped persistent luminescence phosphors are shown. {yields} Eu{sup 2+} is the source of electrons liberated during daylight excitation.

  11. Free electrons and ionic liquids: study of excited states by means of electron-energy loss spectroscopy and the density functional theory multireference configuration interaction method

    OpenAIRE

    Regeta, Khrystyna; Bannwarth, Christoph; Grimme, Stefan; Allan, Michael

    2015-01-01

    The technique of low energy (0–30 eV) electron impact spectroscopy, originally developed for gas phase molecules, is applied to room temperature ionic liquids (IL). Electron energy loss (EEL) spectra recorded near threshold, by collecting 0–2 eV electrons, are largely continuous, assigned to excitation of a quasi-continuum of high overtones and combination vibrations of low-frequency modes. EEL spectra recorded by collecting 10 eV electrons show predominantly discrete vibrational and electron...

  12. The first quadrupole excitations in spherical nuclei and nuclear pairing

    Directory of Open Access Journals (Sweden)

    Saperstein E. E.

    2012-12-01

    Full Text Available Excitation energies and transition probabilities of the first 2+ excitations in even lead, tin and nickel isotopes are calculated within the self-consistent Theory of Finite Fermi Systems based on the Energy Density Functional by Fayans et al. A reasonable agreement with available experimental data is obtained. The effect of the density dependence of the effective pairing interaction is analyzed in detail by comparing results obtained with volume and surface pairing. The effect is found to be noticeable, especially for the 2+-energies which are systematically higher at 200–300 keV for the volume paring as compared with the surface pairing case, the latterbeing in a better agreement with the data.

  13. Si-doped AlGaAs/GaAs(6 3 1)A heterostructures grown by MBE as a function of the As-pressure

    Science.gov (United States)

    Méndez-García, Víctor-Hugo; Shimomura, S.; Gorbatchev, A. Yu.; Cruz-Hernández, E.; Vázquez-Cortés, D.

    2015-09-01

    The effects of doping with silicon (Si) AlGaAs layers grown by molecular beam epitaxy on GaAs (6 3 1)-oriented substrates as a function of the arsenic pressure (PAs) is presented and compared with layers grown on (1 0 0) oriented substrates. The surface texture of the AlGaAs (6 3 1) films is composed by nanogrooves, whose dimensions depend on PAs. On the contrary, the MBE growth on the (1 0 0) plane resulted on rough surfaces, without evidence of formation of terraces. Mobility and carrier density of AlGaAs:Si layers grown on substrates (6 3 1) were studied as a function of PAs. The doping type conversion from p-type to n-type as a function of the As pressure is corroborated for high index samples. All the films grown on (1 0 0) exhibited silicon n-type doping. These observations were related with the amphotericity of Si, where it acts as a donor impurity occupying Al or Ga-sites or as an acceptor when it takes an As-site, depending on the competition that the Si atoms encounters with As for any of these sites. The acceptor and donor lines close to the AlGaAs transition observed by photoluminescence spectroscopy (PL) were affected by the incorporation of Si. When increasing PAs the energy of the main PL peak is redshifted for n-type AlGaAs layers, but it is shifted back towards high energy once the conduction type conversion takes place. X-ray diffraction patterns revealed high crystalline quality for samples grown at the highest PAs.

  14. Atomic to Nanoscale Investigation of Functionalities of an Al2O3 Coating Layer on a Cathode for Enhanced Battery Performance

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Pengfei; Zheng, Jianming; Zhang, Xiaofeng; Xu, Rui; Amine, Khalil; Xiao, J; Zhang, Ji-Guang; Wang, Chong-Min

    2016-02-09

    Surface coating has been identified as an effective approach for enhancing the capacity retention of layered structure cathode. However, the underlying operating mechanism of such a thin coating layer, in terms of surface chemical functionality and capacity retention, remains unclear. In this work, we use aberration-corrected scanning transmission electron microscopy and high-efficiency spectroscopy to probe the delicate functioning mechanism of an Al2O3 coating layer on a Li1.2Ni0.2Mn0.6O2 cathode. We discovered that in terms of surface chemical function, the Al2O3 coating suppresses the side reaction between the cathode and the electrolyte during battery cycling. At the same time, the Al2O3 coating layer also eliminates the chemical reduction of Mn from the cathode particle surface, therefore preventing the dissolution of the reduced Mn into the electrolyte. In terms of structural stability, we found that the Al2O3 coating layer can mitigate the layer to spinel phase transformation, which otherwise will be initiated from the particle surface and propagate toward the interior of the particle with the progression of battery cycling. The atomic to nanoscale effects of the coating layer observed here provide insight into the optimized design of a coating layer on a cathode to enhance the battery properties.

  15. Equilibrium structure and Ti-catalyzed H2 desorption in NaAlH4 nano-particles from density functional theory

    DEFF Research Database (Denmark)

    Vegge, T.

    2006-01-01

    kinetics significantly, the physical understanding remains elusive. Density functional theory is used to calculate the energy of the potential low energy surfaces of NaAlH4 to establish the equilibrium particle shape, and furthermore to determine the deposition energy of Ti/TiH2 and the substitutional...... energy for Ti@Al and Ti@Na-sites on the exposed facets. The substitutional processes are energetically preferred and the Na-vacancy formation energy is found to be strongly reduced in the presence of Ti. The barrier for H2 desorption is found to depend significantly on surface morphology and in...

  16. Modeling the collective excitations in a full Heusler Co{sub 2} FeAl{sub 0.5} Si{sub 0.5} (CFAS) spin valve magnetic nanopillar in the electromagnetic field

    Energy Technology Data Exchange (ETDEWEB)

    David, Cherine; Arumugam, Brinda; Rajamani, Amuda, E-mail: amuvenkat@gmail.com; Natarajan, Kanimozhi

    2014-12-15

    This paper describes the physics of collective excitations that are caused by spin-transfer torques in CFAS magnetic multilayer. When the magnetizations of the pinned and free layers are not collinear with each other, the spin-polarized currents transfer angular momentum to the magnetizations near the interfaces, giving rise to spin-transfer torques. The currents in magnetic multilayer are spin polarised and can carry enough angular momentum. When an electron spin carried by the current interacts with a magnetic layer, the exchange interaction leads to torque between the spin and the magnetization vector of the free layer. This is Spin Transfer Torque (STT) and it excites the magnetization when it is large enough. The Spin Transfer Torque induced collective excitations for the CFAS spin valve pillar have been extensively studied in this paper. - Highlights: • We have modeled LLGS equation for CFAS multilayer array. • The dynamics of collective excitation induced by STT is investigated. • The interactions exhibit solitonic behaviour at both limiting modes of polarization. • The spin components of the solitons are graphically represented.

  17. Metal-insulator transition at the LaAlO3/SrTiO3 interface revisited: A hybrid functional study

    KAUST Repository

    Cossu, F.

    2013-07-17

    We investigate the electronic properties of the LaAlO3/SrTiO3 interface using density functional theory. In contrast to previous studies, which relied on (semi-)local functionals and the GGA+U method, we here use a recently developed hybrid functional to determine the electronic structure. This approach offers the distinct advantage of accessing both the metallic and insulating multilayers on a parameter-free equal footing. As compared to calculations based on semilocal GGA functionals, our hybrid functional calculations lead to a considerably increased band gap for the insulating systems. The details of the electronic structure show substantial deviations from those obtained by GGA calculations. This casts severe doubts on all previous results based on semilocal functionals. In particular, corrections using rigid band shifts (“scissors operator”) cannot lead to valid results.

  18. Valence excitation energies of alkenes, carbonyl compounds, and azabenzenes by time-dependent density functional theory: Linear response of the ground state compared to collinear and noncollinear spin-flip TDDFT with the Tamm-Dancoff approximation

    Science.gov (United States)

    Isegawa, Miho; Truhlar, Donald G.

    2013-04-01

    Time-dependent density functional theory (TDDFT) holds great promise for studying photochemistry because of its affordable cost for large systems and for repeated calculations as required for direct dynamics. The chief obstacle is uncertain accuracy. There have been many validation studies, but there are also many formulations, and there have been few studies where several formulations were applied systematically to the same problems. Another issue, when TDDFT is applied with only a single exchange-correlation functional, is that errors in the functional may mask successes or failures of the formulation. Here, to try to sort out some of the issues, we apply eight formulations of adiabatic TDDFT to the first valence excitations of ten molecules with 18 density functionals of diverse types. The formulations examined are linear response from the ground state (LR-TDDFT), linear response from the ground state with the Tamm-Dancoff approximation (TDDFT-TDA), the original collinear spin-flip approximation with the Tamm-Dancoff (TD) approximation (SF1-TDDFT-TDA), the original noncollinear spin-flip approximation with the TDA approximation (SF1-NC-TDDFT-TDA), combined self-consistent-field (SCF) and collinear spin-flip calculations in the original spin-projected form (SF2-TDDFT-TDA) or non-spin-projected (NSF2-TDDFT-TDA), and combined SCF and noncollinear spin-flip calculations (SF2-NC-TDDFT-TDA and NSF2-NC-TDDFT-TDA). Comparing LR-TDDFT to TDDFT-TDA, we observed that the excitation energy is raised by the TDA; this brings the excitation energies underestimated by full linear response closer to experiment, but sometimes it makes the results worse. For ethylene and butadiene, the excitation energies are underestimated by LR-TDDFT, and the error becomes smaller making the TDA. Neither SF1-TDDFT-TDA nor SF2-TDDFT-TDA provides a lower mean unsigned error than LR-TDDFT or TDDFT-TDA. The comparison between collinear and noncollinear kernels shows that the noncollinear kernel

  19. GAMA/WiggleZ: The 1.4GHz radio luminosity functions of high- and low-excitation radio galaxies and their redshift evolution to z=0.75

    CERN Document Server

    Pracy, Michael; Sadler, Elaine; Croom, Scott; Baldry, Ivan; Bland-Hawthorn, Joss; Brough, Sarah; Brown, Michael; Couch, Warrick; Davis, Tamara; Drinkwater, Michael; Hopkins, Andrew; Jarvis, Matt; Jelliffe, Ben; Jurek, Russell; Loveday, Jon; Pimbblet, Kevin; Prescott, Matt; Wisniosk, Emily; Woods, David

    2016-01-01

    We present radio Active Galactic Nuclei (AGN) luminosity functions over the redshift range 0.005 < z < 0.75. The sample from which the luminosity functions are constructed is an optical spectroscopic survey of radio galaxies, identified from matched Faint Images of the Radio Sky at Twenty-cm survey (FIRST) sources and Sloan Digital Sky Survey (SDSS) images.The radio AGN are separated into Low Excitation Radio Galaxies (LERGs) and High Excitation Radio Galaxies (HERGs) using the optical spectra. We derive radio luminosity functions for LERGs and HERGs separately in the three redshift bins (0.005 < z < 0.3, 0.3 < z < 0.5 and 0.5 < z <0.75). The radio luminosity functions can be well described by a double power-law. Assuming this double power-law shape the LERG population displays little or no evolution over this redshift range evolving as ~$(1+z)^{0.06}$ assuming pure density evolution or ~ $(1+z)^{0.46}$ assuming pure luminosity evolution. In contrast, the HERG population evolves more r...

  20. Boson and fermion many-body assemblies: Fingerprints of excitations in the ground-state wave functions, with examples of superfluid 4He and the homogeneous correlated electron liquid

    International Nuclear Information System (INIS)

    After a brief summary of some basic properties of ideal gases of bosons and of fermions, two many-body Hamiltonians are cited for which ground-state wave functions allow the generation of excited states. But because of the complexity of ground-state many-body wave functions, we then consider properties of reduced density matrices, and in particular, the diagonal element of the second-order density matrix. For both the homogeneous correlated electron liquid and for an assembly of charged bosons, the ground-state pair correlation function g(r) has fingerprints of the zero-point energy of the plasmon modes. These affect crucially the static structure factor S(k), in the long wavelength limit. This is best understood by means of the Ornstein-Zernike direct correlation function c(r), which plays an important role throughout this article. Turning from such charged liquids, both boson and fermion, to superfluid 4He, the elevated temperature (T) structure factor S(k, T) is related, albeit approximately, to its zero-temperature counterpart, via the velocity of sound, reflecting the collective phonon excitations, and the superfluid density. Finally some future directions are pointed. (author)

  1. Ultrasensitive detection of Hg{sup 2+} using oligonucleotide-functionalized AlGaN/GaN high electron mobility transistor

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Junjie [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Division of Nanobiomedicine, Key Laboratory for Nano-Bio Interface Research, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Li, Jiadong; Miao, Bin; Wu, Dongmin, E-mail: dmwu2008@sinano.ac.cn [i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215125 (China); Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Wang, Jine; Pei, Renjun, E-mail: rjpei2011@sinano.ac.cn [Division of Nanobiomedicine, Key Laboratory for Nano-Bio Interface Research, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Wu, Zhengyan, E-mail: zywu@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China)

    2014-08-25

    An oligonucleotide-functionalized ion sensitive AlGaN/GaN high electron mobility transistor (HEMT) was fabricated to detect trace amounts of Hg{sup 2+}. The advantages of ion sensitive AlGaN/GaN HEMT and highly specific binding interaction between Hg{sup 2+} and thymines were combined. The current response of this Hg{sup 2+} ultrasensitive transistor was characterized. The current increased due to the accumulation of Hg{sup 2+} ions on the surface by the highly specific thymine-Hg{sup 2+}-thymine recognition. The dynamic linear range for Hg{sup 2+} detection has been determined in the concentrations from 10{sup −14} to 10{sup −8} M and a detection limit below 10{sup −14} M level was estimated, which is the best result of AlGaN/GaN HEMT biosensors for Hg{sup 2+} detection till now.

  2. Oxidation of MCrAlY bonding layers of thermal insulation coatings as a function of production parameters and alloy composition

    International Nuclear Information System (INIS)

    The oxidation behaviour of intermediate or bonding layers on a given gas turbine material (IN 100) is reported. The layers were brought onto the base material by plasma arc spraying in free air or controlled atmosphere, and consisted of spray powders of different aluminium content (Co-31 Ni-21Cr8Al0.5Y; Co-33Ni-21Cr-16Al0.5Y; composite powder with a Ni-19 Cr alloy core and 6% Al cladding). These bonding layers received a ceramic cover (ZrO2 + 7% of Y2O3) to serve as a thermal insulation coating. The oxidation behaviour of the bonding layers were analysed as a function of different spray powders, spraying techniques, surface roughness of bonding layer, and thickness of insulation coating or bonding layer. (MM)

  3. Novel joining of dissimilar ceramics in the Si{sub 3}N{sub 4}-Al{sub 2}O{sub 3} system using polytypoid functional gradients

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Caroline S.; Zhang, Xiao Feng; Thomas, Gareth

    2001-05-01

    A unique approach to crack-free joining of heterogeneous ceramics is demonstrated by the use of sialon polytypoids as Functionally Graded Materials (FGM) as defined by the phase diagram in the system, Si3N4-Al2O3. Polytypoids in the Al2O3-Si3N4 system offer a path to compatibility for heterogeneous ceramics. This paper describes successful hot press sintering of multilayered FGM's with 20 layers of thickness 500 mm each. Transmission Electron Microscopy was used to identify the polytypoids at the interfaces of different areas of the joint. It has been found that the 15R polytypoid was formed in the Al2O3-contained layers and the 12H polytypoid was formed in the Si3N4-contained layers.

  4. A microscale multi-functional metal-organic framework as a fluorescence chemosensor for Fe(III), Al(III) and 2-hydroxy-1-naphthaldehyde.

    Science.gov (United States)

    Kang, Yang; Zheng, Xiang-Jun; Jin, Lin-Pei

    2016-06-01

    A microscale metal-organic framework [Eu(atpt)1.5(phen)(H2O)]n (H2atpt=2-aminoterephthalic acid, phen=1,10-phenanthroline) (Eu-MOF) was synthesized and characterized by elemental analysis, luminescence spectrum, powder X-ray diffraction, dynamic light scattering and scanning electron microscope. The fluorescence response of Eu-MOF to metal ions and aldehydes showed that Eu-MOF is highly selective to Fe(III), Al(III) and 2-hydroxy-1-naphthaldehyde (2-OH-NA). Eu-MOF could be utilized as a multi-functional fluorescence chemosensor for Fe(III), Al(III) and 2-hydroxy-1-naphthaldehyde (2-OH-NA). The detection limit of Fe(III), Al(III) and 2-OH-NA was 45, 10 and 36μM, respectively. The corresponding sensing mechanisms were explored. PMID:26967663

  5. New Modes of Nuclear Excitations

    OpenAIRE

    Tsoneva Nadia; Lenske Horst

    2013-01-01

    We present a theoretical approach based on density functional theory supplemented by a microscopic multi-phonon model which is applied for investigations of pygmy resonances and other excitations of different multipolarities in stable and exotic nuclei. The possible relation of low-energy modes to the properties of neutron or proton skins is systematically studied in isotonic and isotopic chains. The fine structure of nuclear electric and magnetic response functions is analyzed and compared t...

  6. Ultra-sensitive film sensor based on Al2O3-Au nanoparticles supported on PDDA-functionalized graphene for the determination of acetaminophen.

    Science.gov (United States)

    Li, Jianbo; Sun, Weiyan; Wang, Xiaojiao; Duan, Huimin; Wang, Yanhui; Sun, Yuanling; Ding, Chaofan; Luo, Chuannan

    2016-08-01

    An electrochemical sensor of acetaminophen based on poly(diallyldimethylammonium chloride) (PDDA)-functionalized reduced graphene-loaded Al2O3-Au nanoparticles coated onto glassy carbon electrode (Al2O3-Au/PDDA/reduced graphene oxide (rGO)/glass carbon electrode (GCE)) were prepared by layer self-assembly technique. The as-prepared electrode-modified materials were characterized by scanning electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. The electrocatalytic performances of Al2O3-Au/PDDA/rGO-modified glassy carbon electrode toward the acetaminophen were investigated by cyclic voltammetry and differential pulse voltammetry. The modified electrodes of graphene oxide (GO)/GCE, PDDA/rGO/GCE, and Al2O3-Au/PDDA/rGO/GCE were constructed for comparison and learning the catalytic mechanism. The research showed Al2O3-Au/PDDA/rGO/GCE having good electrochemical performance, attributing to the synergetic effect that comes from the special nanocomposite structure and physicochemical properties of Al2O3-Au nanoparticles and graphene. A low detection limit of 6 nM (S/N = 3) and a wide linear detection range from 0.02 to 200 μM (R (2) = 0.9970) was obtained. The preparation of sensor was successfully applied for the detection of acetaminophen in commercial pharmaceutical pills. Graphical abstract Schematic diagram of synthesis of Al2O3-Au/PDDA/rGO/GCE. PMID:27255103

  7. Predicting lattice parameter as a function of cation disorder in MgAl2O4 spinel

    International Nuclear Information System (INIS)

    In the perfect magnesium aluminate spinel structure all the tetrahedral sites are occupied by Mg2+ ions, while Al3+ ions occupy all the octahedral sites. Real MgAl2O4, however, exhibits cation disorder (inversion), so that some Mg2+ ions reside in octahedral sites with an equal number of Al3+ ions in tetrahedral sites. Atomistic simulation was used to correlate the degree of inversion with changes in lattice parameter. Results from several approaches, including a combined energy minimization-Monte Carlo technique (CEMMC), are compared with available experimental data. These show that the mean field method is not useful, while the defect volume approach can yield predictions that are useful in interpreting the CEMMC results, which agree most closely with experiment

  8. Feeding and Distribution of Porosity in Cast Al-Si Alloys as Function of Alloy Composition and Modification

    DEFF Research Database (Denmark)

    Tiedje, Niels Skat; Taylor, John A.; Easton, Mark A.

    2012-01-01

    Unmodified, Na-modified, and Sr-modified castings of Al-7 pct Si and Al-12.5 pct Si alloys were cast in molds in which it was possible to create different cooling conditions. It is shown how solidification influences the distribution of porosity at the surface and the center of the castings as a...... casting, while Sr-modified castings solidify in a mushy manner that creates a more homogeneous distribution of porosity in the casting. The amount of porosity was highest in the Sr-modified alloys, lower in the Na-modified alloys, and lowest in the unmodified alloys. The size of the porosity-free layer...

  9. An Investigation of Stylistic Features of Kashf al-Mahjoub on the Basis of Halliday Functional Grammar

    OpenAIRE

    fatemeh majidi; hadi yavari; zohre ghodosi feyz abadi

    2015-01-01

    In order to grasp the attitude of the writer and discover the semantic system of his mind as well as the dominant ideology of the text, this paper aims to investigate the stylistic features of Kashf al-Mahjoub based on the ideational and interpersonal metafunctions (in the Halliday grammar). The most important results of this study are as following: the center of attention in the discourse of Kashf al-Mahjoub is the God. He is present in a place to be defined as one of the issues of Sufism an...

  10. Microstructural Evolution and Functional Properties of Fe-Mn-Al-Ni Shape Memory Alloy Processed by Selective Laser Melting

    Science.gov (United States)

    Niendorf, Thomas; Brenne, Florian; Krooß, Philipp; Vollmer, Malte; Günther, Johannes; Schwarze, Dieter; Biermann, Horst

    2016-03-01

    In the current study, a Fe-Mn-Al-Ni shape memory alloy is processed by additive manufacturing for the first time. Microstructural evolution upon processing is strongly affected by thermal gradients and solidification velocity and, thus, by processing parameters and the actual specimen geometry. By single-step solutionizing heat treatment pronounced grain growth is initiated leading to microstructures showing good reversibility. The compressive stress-strain response revealed maximum reversible pseudo-elastic strain of about 7.5 pct. Critical steps toward further optimization of additively manufactured Fe-Mn-Al-Ni shape memory alloys are discussed.

  11. Microstructural Evolution and Functional Properties of Fe-Mn-Al-Ni Shape Memory Alloy Processed by Selective Laser Melting

    Science.gov (United States)

    Niendorf, Thomas; Brenne, Florian; Krooß, Philipp; Vollmer, Malte; Günther, Johannes; Schwarze, Dieter; Biermann, Horst

    2016-06-01

    In the current study, a Fe-Mn-Al-Ni shape memory alloy is processed by additive manufacturing for the first time. Microstructural evolution upon processing is strongly affected by thermal gradients and solidification velocity and, thus, by processing parameters and the actual specimen geometry. By single-step solutionizing heat treatment pronounced grain growth is initiated leading to microstructures showing good reversibility. The compressive stress-strain response revealed maximum reversible pseudo-elastic strain of about 7.5 pct. Critical steps toward further optimization of additively manufactured Fe-Mn-Al-Ni shape memory alloys are discussed.

  12. Lifetime of electronic excitations in metal nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Quijada, M; Diez Muino, R; Echenique, P M [Centro de Fisica de Materiales CFM-Materials Physics Center MPC, Centro Mixto CSIC-UPV/EHU, Edificio Korta, Avenida de Tolosa 72, 20018 San Sebastian (Spain); Borisov, A G; Alonso, J A, E-mail: rdm@ehu.e [Donostia International Physics Center DIPC, P Manuel de Lardizabal 4, 20018 San Sebastian (Spain)

    2010-05-15

    Electronic excitations in metal particles with sizes up to a few nanometers are shown to have a one-electron character when a laser pulse is applied off the plasmon resonance. The calculated lifetimes of these excitations are in the femtosecond timescale but their values are substantially different from those in bulk. This deviation can be explained from the large weight of the excitation wave function in the nanoparticle surface region, where dynamic screening is significantly reduced. The well-known quadratic dependence of the lifetime with the excitation energy in bulk breaks down in these finite-size systems.

  13. Study of the 27Al(n,2,)26Al reaction via accelerator mass spectrometry

    International Nuclear Information System (INIS)

    The excitation function for the 27Al(n,2n)26Al reaction is expected to show a strongly non-linear behavior in the neutron-energy region around 14 MeV, the neutron energy in D-T plasmas; thus the production rate of 26Al (t1/2=7.2*105 a) in D-T fusion environments can in principle be used to measure the temperature of such plasmas. Existing measurements, however, are strongly discordant. Therefore, a new accurate measurement of the 27Al(n,2n)26Al cross sections in the near threshold region (En=13.5-14.8 MeV) was performed with the goal to achieve relative cross sections with the highest accuracy possible. In addition, the measurements were also designed to provide good absolute cross-section values, as absolute cross sections are important for radioactive waste predictions. Samples of Al metal were irradiated with neutrons in the energy range near threshold (Eth=13.55 MeV) at the Radiuminstitutes of both Vienna and St. Petersburg, and in Tokai-mura, Japan. In Tuebingen irradiations with neutrons of higher energies (17 and 19 MeV) were performed. The amount of 26Al produced during the irradiations was measured via accelerator mass spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA). This work represents the first 26Al measurements for this new facility. With this system, a background as low as 3*10-15 for 26Al/27Al isotope ratios was obtained, corresponding to a (n,2n) cross section of 0.04 mb. Utilizing AMS, cross sections with much higher precision and considerably closer to the threshold than in previous investigations could be measured. The prerequisite for its application as a temperature monitor, namely a very well known shape of the excitation function was met. A quantitative prediction of the sensitivity of this method for monitoring the temperature in a D-T fusion plasma was therefore possible. For thermal plasmas temperature changes in the order of 5 to 15 % should be detectable. An even higher sensitivity was found for non

  14. Band alignment and chemical bonding at the GaAs/Al{sub 2}O{sub 3} interface: A hybrid functional study

    Energy Technology Data Exchange (ETDEWEB)

    Colleoni, Davide, E-mail: davide.colleoni@epfl.ch; Miceli, Giacomo; Pasquarello, Alfredo [Chaire de Simulation à l' Echelle Atomique (CSEA), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2015-11-23

    The band alignment at the interface between GaAs and amorphous Al{sub 2}O{sub 3} is studied through the use of hybrid functionals. For the oxide component, a disordered model is generated through density-functional molecular dynamics. The achieved structure shows good agreement with the experimental characterization. The potential line-up across the interface is obtained for two atomistic GaAs/Al{sub 2}O{sub 3} interface models, which differ by the GaAs substrate termination. The calculated valence band offset amounts to 3.9 eV for an interface characterized by the occurrence of Ga–O bonds as dominant chemical bonding, favoring the high-energy side in the range of experimental values (2.6–3.8 eV). The effect of As antisite and As–As dimer defects on the band alignment is shown to be negligible.

  15. Measurement of the excitation function of {sup 65}Cu({sup 3}He,2n){sup 66}Ga; Medida da funcao excitacao da reacao {sup 65} Cu({sup 3} He,2n) {sup 66} Ga

    Energy Technology Data Exchange (ETDEWEB)

    Bastos, M.A.V.; Vinagre Filho, U.M.; Costa, V.L. da [Instituto de Engenharia Nuclear (IEN), Rio de Janeiro, RJ (Brazil)

    1996-07-01

    The excitation function of the {sup 65} Cu({sup 3} He,2n) {sup 66} Ga reaction was measured. It was performed by irradiation of several stacks of two copper foils with {sup 3} He until 36 MeV from the cyclotron CV-28 of IEN. The initial energy of {sup 3} He beam was measured by spectrometry of charged particles with Si (au) detector, placed at 90 deg C respecting to the incident beam. The activities was measured by gamma rays spectrometry using HPGe detector. The results are compared with others found in the literature. (author)

  16. Design, fabrication, and calibration of curved integral coils for measuring transfer function, uniformity, and effective length of LBL ALS [Lawrence Berkeley Laboratory Advanced Light Source] Booster Dipole Magnets

    International Nuclear Information System (INIS)

    A matched pair of curved integral coils has been designed, fabricated and calibrated at Lawrence Berkeley Laboratory for measuring Advanced Light Source (ALS) Booster Dipole Magnets. Distinctive fabrication and calibration techniques are described. The use of multifilar magnet wire in fabrication integral search coils is described. Procedures used and results of AC and DC measurements of transfer function, effective length and uniformity of the prototype booster dipole magnet are presented in companion papers. 8 refs

  17. Doubly excited triplet states of highly stripped ions

    International Nuclear Information System (INIS)

    Transition energies, Coulomb repulsions and effective quantum numbers have been calculated for the doubly excited Nsnp: 3P0 (for N=2, n=N,..,5); Nsnd: 3De (for N=2, n=N+1,..,5) and Npnd: 3F0 (for N=2, n=N+1,..,5) states for the highly stripped ions Na9+,Mg10+,Al11+,Si12+,P13+ and S14+. Time-dependent perturbation theory has been applied to calculate such transitions properties. A time-dependent harmonic perturbation causes simultaneous excitation of both the electrons with a change of spin state. The doubly excited energy levels and the analytic representation of their wave functions are obtained by identifying the poles of an appropriately constructed linearized variational functional with respect to driving frequency. Most of the results are new. The transition energies and effective quantum numbers of 2s2p: 3P0 states of all the ions agree well with the only available experimental data. (orig.)

  18. Excited atoms. Vozbuzhdennye atomy

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, B.M.

    1982-01-01

    An examination is made of the properties of excited atoms and molecules, the processes of their formation in a gas and plasma, and the diffusion of excited atoms in a gas. A presentation is made of the processes in which excited and metastable atoms and molecules in a gas are destroyed upon collision with electrons, atoms, and molecules. A study is made of the relaxation of excited states during collisions - excitation transfer, depolarization, transitions between fine structure states, etc. Information is given on ionization that includes the participation of excited atoms - the Penning process, associative ionization. An examination is made of highly excited states of atoms and the processes that take place during their participation. The book is intended for personnel in the area of physics and chemistry of plasma, atomic and molecular physics, chemical physics as well as in allied areas of physics. 1280 references, 52 figures, 76 tables.

  19. Functionally graded ZrO2-NiCrAlY coatings prepared by plasma spraying using pre-mixed, spheroidized powders

    International Nuclear Information System (INIS)

    Functionally graded ZrO2-NiCrAlY coatings were prepared by plasma spraying. Pre-mixed, plasma spheroidized powders were used as the feedstock. The advantage of using pre-mixed, spheroidized powders was to ensure chemical homogeneity and promote uniform density along the graded layers, and these pre-mixed powders are used to form the different interlayers of functionally graded coatings in the present study. The microstructure, density and microhardness changed gradiently in the ZrO2-NiCrAlY FGM (functionally graded materials) coatings. The bond strength of ZrO2-NiCrAlY FGM coatings with different graded layers was measured. Results showed that for as-sprayed coatings with the same thickness, the bond strength increased with the number of graded layers. The bond strength of the FGM coatings with five graded layers was about twice as high as that of the duplex coatings because of the significant reduction of the residual stress in the coatings. Experimental results also showed that the bond strength of as-sprayed FGM coating increased significantly after hot isostatic press (HIP) treatment and the reason can be attributed to the densification of the microstructure, the decrease of defects in the coatings, interdiffusion between layers and reduction in the residual thermal stresses. (orig.)

  20. Lower motor neuron dysfunction in ALS.

    Science.gov (United States)

    de Carvalho, Mamede; Swash, Michael

    2016-07-01

    In the motor system there is a complex interplay between cortical structures and spinal cord lower motor neurons (LMN). In this system both inhibitory and excitatory neurons have relevant roles. LMN loss is a marker of motor neuron disease/amyotrophic lateral sclerosis (MND/ALS). Conventional needle electromyography (EMG) does not allow LMN loss to be quantified. Measurement of compound muscle action potential (CMAP) amplitude or area, and the neurophysiological index, provide a surrogate estimate of the number of functional motor units. Increased motor neuronal excitability is a neurophysiological marker of ALS in the context of a suspected clinical and electrophysiological diagnosis. In the LMN system, fasciculation potentials (FPs) are the earliest changes observed in affected muscles, a feature of LMN hyperexcitability. Reinnervation is best investigated by needle EMG although other methods can be explored. Moreover needle EMG give information about the temporal profile of the reinnervation process, important ancillary data. Quantitative motor unit potential analysis is a valuable method of evaluating reinnervation. The importance of FPs has been recognized in the Awaji criteria for the electrodiagnosis of ALS, criteria that are a sensitive adjunct to the revised El Escorial criteria. Finally, functionality of LMN's, and perhaps excitability studies in motor nerves, aids understanding of the disease process, allowing measurement of potential treatment effects in clinical trials. Other investigational techniques, such as electrical impedance myography, muscle and nerve ultrasound, and spinal cord imaging methods may prove useful in future. PMID:27117334

  1. Self-excitation of single nanomechanical pillars

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyun S; Qin Hua; Blick, Robert H [Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706-1691 (United States)], E-mail: blick@engr.wisc.edu

    2010-03-15

    Self-excitation is a mechanism that is ubiquitous for electromechanical power devices such as electrical generators. This is conventionally achieved by making use of the magnetic field component in electrical generators (Nedic and Lipo 2000 IEEE/IAS Conf. Records (Rome, Italy) vol 1 pp 51-6), a good and widely visible example of which is the wind turbine farm (Muljadi et al 2005 J. Sol. Energy Eng. 127 581-7). In other words, a static force, such as the wind acting on rotor blades, can generate a resonant excitation at a certain mechanical frequency. For nanomechanical systems (Craighead 2000 Science 290 1532-5; Roukes 2001 Phys. World 14 25-31; Cleland 2003 Foundations of Nanomechanics (Berlin: Springer); Ayari et al 2007 Nano Lett. 7 2252-7; Koenig et al 2008 Nat. Nanotechnol. 3 482-4) such a self-excitation (SE) mechanism is also highly desirable, because it can generate mechanical oscillations at radio frequencies by simply applying a dc bias voltage. This is of great importance for low-power signal communication devices and detectors, as well as for mechanical computing elements. For a particular nanomechanical system-the single electron shuttle-this effect was predicted some time ago by Gorelik et al (Phys. Rev. Lett. 80 4526-9). Here, we use a nanoelectromechanical single electron transistor (NEMSET) to demonstrate self-excitation for both the soft and hard regimes, respectively. The ability to use self-excitation in nanomechanical systems may enable the detection of quantum mechanical backaction effects (Naik et al 2006 Nature 443 193-6) in direct tunneling, macroscopic quantum tunneling (Savelev et al 2006 New J. Phys. 8 105-15) and rectification (Pistolesi and Fazio 2005 Phys. Rev. Lett. 94 036806-4). All these effects have so far been overshadowed by the large driving voltages that had to be applied.

  2. Vacuum ultraviolet excitation of 1S0 and 3P0 emission of Pr3+ in Sr0.7La0.3Al11.7Mg0.3O19 and SrB4O7

    International Nuclear Information System (INIS)

    The emission and excitation properties of a SrB4O7:1% Pr3+ powder sample and a Sr0.7La0.3Al11.7Mg0.3O19:3.5% Pr3+ single crystal were investigated using x-ray and synchrotron radiation. The 4f5d states of Pr3+ in these host lattices are at a higher energy than the 4f2[1S0] state. In the hexa-aluminate this results in the successive emission of two photons. 1S0→1I6 emission is followed by emission from the 3P0 state. The quantum efficiency of the total 3P0 emission is 25%. In the tetra-borate the 3P0 emission is quenched by multiphonon relaxation to the 1D2 state from which only weak emission is observed. In the hexa-aluminate as in the tetra-borate, host lattice excitation does not result in efficient emission from the 1S0 state. In the hexa-aluminate the excitation energy is transferred from the host lattice preferentially to the lower-energy 3PJ and 1I6 states, resulting in 3P0 emission only. (author)

  3. Molecular excitation energies to high-lying bound states from time-dependent density-functional response theory: Characterization and correction of the time-dependent local density approximation ionization threshold

    Science.gov (United States)

    Casida, Mark E.; Jamorski, Christine; Casida, Kim C.; Salahub, Dennis R.

    1998-03-01

    This paper presents an evaluation of the performance of time-dependent density-functional response theory (TD-DFRT) for the calculation of high-lying bound electronic excitation energies of molecules. TD-DFRT excitation energies are reported for a large number of states for each of four molecules: N2, CO, CH2O, and C2H4. In contrast to the good results obtained for low-lying states within the time-dependent local density approximation (TDLDA), there is a marked deterioration of the results for high-lying bound states. This is manifested as a collapse of the states above the TDLDA ionization threshold, which is at -ɛHOMOLDA (the negative of the highest occupied molecular orbital energy in the LDA). The -ɛHOMOLDA is much lower than the true ionization potential because the LDA exchange-correlation potential has the wrong asymptotic behavior. For this reason, the excitation energies were also calculated using the asymptotically correct potential of van Leeuwen and Baerends (LB94) in the self-consistent field step. This was found to correct the collapse of the high-lying states that was observed with the LDA. Nevertheless, further improvement of the functional is desirable. For low-lying states the asymptotic behavior of the exchange-correlation potential is not critical and the LDA potential does remarkably well. We propose criteria delineating for which states the TDLDA can be expected to be used without serious impact from the incorrect asymptotic behavior of the LDA potential.

  4. Biomimetic Hydroxyapatite Growth on Functionalized Surfaces of Ti-6Al-4V and Ti-Zr-Nb Alloys

    Science.gov (United States)

    Pylypchuk, Ie V.; Petranovskaya, A. L.; Gorbyk, P. P.; Korduban, A. M.; Markovsky, P. E.; Ivasishin, O. M.

    2015-08-01

    A biomimetic approach for coating titanium-containing alloys with hydroxyapatite (HA) is reported in the article. Two types of Ti-containing alloys were chosen as an object for coating: Ti-6Al-4V (recommended for orthopedic application) and a novel highly biocompatible Ti-Zr-Nb alloy, with good mechanical compatibility due to a modulus that is more close to that of human bones (E ≈ 50 GPa instead of 110 GPa in Ti-6Al-4V). Coating process was carried out in a 10×-concentrated simulated body fluid (SBF)—synthetic analog of human body plasma. The effect of oxidized and carboxylated alloy surface on formation of biomimetic hydroxyapatite has been studied. By XRD, we found influence of thermal conditions on HA crystal formation and size. SEM images and Fourier transform infrared confirmed that hydroxyapatite with different morphology, crystallinity, and Ca/P ratio formed on metallic surfaces. X-ray photoelectron spectroscopy showed that in the Ti-6AL-4V sample the observed Ca/P ratio reach 0.97, whereas in the Ti-Zr-Nb sample the observed Ca/P ratio reach 1.15.

  5. Ionization and excitation of lithium atoms by fast charged particle impact: identification of mechanisms for double K-shell vacancy production as a function of the projectile charge and velocity

    International Nuclear Information System (INIS)

    Ionization and excitation of lithium atoms by fast charged particle impact: identification of mechanisms for double K-shell vacancy production as a function of projectile charge and velocity. Auger electron spectroscopy is used for an experimental investigation of ionization and excitation of lithium atoms by ions (Kr34+ and Ar18+) and electrons at high impact velocities (from 6 to 60 a.u.). In particular, relative contributions of the mechanisms responsible for lithium K-shell ionization-excitation are determined for various projectile charges Zp and velocities vp. A large range of perturbation parameters |Zp|/vp is explored (|Zp|/vp = 0,05 - 0,7 a.u.). From single K-shell excitation results, it appears that the projectile-electron interaction gives mainly rise to a dipole-like transition 1s -> np Concerning K-shell ionization-excitation, the separation of the TS2 (two independent projectile-electron interactions) and TS1 (one projectile-electron interaction) mechanisms responsible for the formation of the 2snp 1,3P and 2sns 1,3S lithium states is performed. In TS1 process, the projectile-electron interaction can be followed by an electron-electron interaction (dielectronic process) or by an internal rearrangement of the residual target after a sudden potential change (shake process). From Born theory, ab initio calculations are performed. The good agreement between theoretical and experimental results confirms the mechanism identification. For the production of P states, TS1 is found to be strongly dominant for small |Zp|/vp values and TS2 is found to be most important for large |Zp|/vp values. Since P states cannot be formed significantly via a shake process, the TS1 and TS2 separation provides a direct signature of the dielectronic process. On the other hand, the TS1 process is shown to be the unique process for producing the S states. At the moment, only the shake aspect of the TS1 process can explain the fact that the 2s3s configuration is preferentially

  6. Evaluation of thermal resistance constitution for packaged AlGaN/GaN high electron mobility transistors by structure function method

    International Nuclear Information System (INIS)

    The evaluation of thermal resistance constitution for packaged AlGaN/GaN high electron mobility transistor (HEMT) by structure function method is proposed in this paper. The evaluation is based on the transient heating measurement of the AlGaN/GaN HEMT by pulsed electrical temperature sensitive parameter method. The extracted chip-level and package-level thermal resistances of the packaged multi-finger AlGaN/GaN HEMT with 400-μm SiC substrate are 22.5 K/W and 7.2 K/W respectively, which provides a non-invasive method to evaluate the chip-level thermal resistance of packaged AlGaN/GaN HEMTs. It is also experimentally proved that the extraction of the chip-level thermal resistance by this proposed method is not influenced by package form of the tested device and temperature boundary condition of measurement stage. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  7. Recursive design of nonlinear H∞ excitation controller

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This work is concerned with the problem of L2 gain disturbance attenuation for nonlinear systems and nonlinear robust control for power systems. In terms of the recurrence design approach proposed, the nonnegative solution of dissipative inequality and the storage function of nonlinear H∞ control for a generator excitation system are acquired. From this storage function, the excitation controller is constructed. Moreover, simulation results manifest the effectiveness of this design method.

  8. Conceptualizing the relations between metacognition and executive functions in Amyotrophic Lateral Sclerosis (ALS) patients’ caregivers. A preliminary study

    OpenAIRE

    Stefania La Foresta; Sonia Messina; Cristina Faraone; Giovanna Pistorino; Giuseppe Vita; Christian Lunetta; Maria Catena Quattropani

    2015-01-01

    Executive Functions are goal-directed neurocognitive processes that allow the management of cognition and behavior. Executive Functions are essential to allow people to set goals, self-monitor, inhibit inappropriate responses, and generally engage in well-planned, flexible, future-oriented behavior. Metacognitive processes, in close alliance with executive functions, are viewed as integral components of awareness and emotional regulation. The influence of metacognition on planning, monitoring...

  9. Green functions and Langevin equations for nonlinear diffusion equations: A comment on ‘Markov processes, Hurst exponents, and nonlinear diffusion equations’ by Bassler et al.

    Science.gov (United States)

    Frank, T. D.

    2008-02-01

    We discuss two central claims made in the study by Bassler et al. [K.E. Bassler, G.H. Gunaratne, J.L. McCauley, Physica A 369 (2006) 343]. Bassler et al. claimed that Green functions and Langevin equations cannot be defined for nonlinear diffusion equations. In addition, they claimed that nonlinear diffusion equations are linear partial differential equations disguised as nonlinear ones. We review bottom-up and top-down approaches that have been used in the literature to derive Green functions for nonlinear diffusion equations and, in doing so, show that the first claim needs to be revised. We show that the second claim as well needs to be revised. To this end, we point out similarities and differences between non-autonomous linear Fokker-Planck equations and autonomous nonlinear Fokker-Planck equations. In this context, we raise the question whether Bassler et al.’s approach to financial markets is physically plausible because it necessitates the introduction of external traders and causes. Such external entities can easily be eliminated when taking self-organization principles and concepts of nonextensive thermostatistics into account and modeling financial processes by means of nonlinear Fokker-Planck equations.

  10. New modes of nuclear excitations

    International Nuclear Information System (INIS)

    We present a theoretical approach based on density functional theory supplemented by a microscopic multi-phonon model which is applied for investigations of pygmy resonances and other excitations of different multipolarities in stable and exotic nuclei. The possible relation of low-energy modes to the properties of neutron or proton skins is systematically studied in isotonic and isotopic chains. Calculations have been performed for the following N=50 isotones: 88Sr, 90Zr, 92Mo and 86Kr up to 10 MeV. The fine structure of nuclear electric and magnetic response functions is analyzed and compared to experimental data. The agreement between data and calculations confirms the predictive power of our theoretical approach for the exploratory investigations of new modes of excitation

  11. Excited states v.6

    CERN Document Server

    Lim, Edward C

    2013-01-01

    Excited States, Volume 6 is a collection of papers that discusses the excited states of molecules. The first paper discusses the linear polyene electronic structure and potential surfaces, considering both the theoretical and experimental approaches in such electronic states. This paper also reviews the theory of electronic structure and cites some experimental techniques on polyene excitations, polyene spectroscopic phenomenology, and those involving higher states of polyenes and their triplet states. Examples of these experimental studies of excited states involve the high-resolution one-pho

  12. Excited states 2

    CERN Document Server

    Lim, Edward C

    2013-01-01

    Excited States, Volume 2 is a collection of papers that deals with molecules in the excited states. The book describes the geometries of molecules in the excited electronic states. One paper describes the geometries of a diatomic molecule and of polyatomic molecules; it also discusses the determination of the many excited state geometries of molecules with two, three, or four atoms by techniques similar to diatomic spectroscopy. Another paper introduces an ordered theory related to excitons in pure and mixed molecular crystals. This paper also presents some experimental data such as those invo

  13. Coefficient Estimates for New Subclasses of Analytic and Bi-Univalent Functions Defined by Al-Oboudi Differential Operator

    Directory of Open Access Journals (Sweden)

    Serap Bulut

    2013-01-01

    Full Text Available We introduce and investigate two new subclasses and of analytic and bi-univalent functions in the open unit disk For functions belonging to these classes, we obtain estimates on the first two Taylor-Maclaurin coefficients and

  14. Evaluation of the drain—source voltage effect on AlGaAs/InGaAs PHEMTs thermal resistance by the structure function method

    International Nuclear Information System (INIS)

    The effect of drain—source voltage on AlGaAs/InGaAs PHEMTs thermal resistance is studied by experimental measuring and simulation. The result shows that AlGaAs/InGaAs PHEMTs thermal resistance presents a downward trend under the same power dissipation when the drain—source voltage (VDS) is decreased. Moreover, the relatively low VDS and large drain—source current (IDS) result in a lower thermal resistance. The chip-level and package-level thermal resistance have been extracted by the structure function method. The simulation result indicated that the high electric field occurs at the gate contact where the temperature rise occurs. A relatively low VDS leads to a relatively low electric field, which leads to the decline of the thermal resistance. (semiconductor devices)

  15. X-ray microtomography of fatigue crack closure as a function of applied load in Al-Li 2090 T8E41 samples

    Energy Technology Data Exchange (ETDEWEB)

    Morano, R.; Stock, S.R.; Davis, G.R.; Elliott, J.C.

    2000-07-01

    Crack closure is held to be responsible for very low fatigue crack growth rates in many alloys such as Al-Li 2090 T8E41, and early crack face contact during unloading or prolonged contact during loading seems to reduce the driving force for crack extension. High resolution x-ray computed tomography (i.e., microtomography) allows one to image the entire volumes of samples and to quantify opening as a function of applied load over the entire crack surface. Crack closure results are reported for a fatigue crack grown under load ratio R = 0.1 in a compact tension sample of Al-Li 2090 T8E41; the crack was free to choose its path unconstrained by side-grooves which are normally used to suppress crack deflection. The inter-relationship between crack path, crack face contact and applied load level are discussed.

  16. Effect of Sn and Sb element on the magnetism and functional properties of Ni-Mn-Al ferromagnetic shape memory alloys

    Science.gov (United States)

    Agarwal, Sandeep; Mukhopadhyay, P. K.

    2016-03-01

    We have replaced Al partially with Sb and Sn in Ni-Mn-Al systems and investigated its effect on magnetism, entropy change and magnetoresistance in the vicinity of martensitic transformation. Both the samples had identical lattice parameters and Mn contents, which are mostly responsible for magnetism in these systems, yet there were marked changes in magnetic and functional properties of these systems. It was found that the magnetization increased in Sb alloy, while entropy change and magnetoresistance decreased as compared to Sn alloy. These changes are attributed to the change in antiferromagnetic interaction as a result of variation in the Ni d-Mn d hybridization arising due to presence of different sp elements.

  17. Radial Basis Function Network-based prediction of global solar radiation data: Application for sizing of a stand-alone photovoltaic system at Al-Madinah, Saudi Arabia

    International Nuclear Information System (INIS)

    In this paper, Radial Basis Function network (RBF) is used for modelling and predicting the daily global solar radiation data using other meteorological data such as air temperature, sunshine duration, and relative humidity. These data were recorded in the period 1998-2002 at Al-Madinah (Saudi Arabia) by the National Renewable Energy Laboratory. Four RBF-models have been developed for predicting the daily global solar radiation. It was found that the RBF-model which uses the sunshine duration and air temperature as input parameters, gives accurate results as the correlation coefficient in this case is 98.80%. A comparative study between developed RBF, Multilayer perceptron and conventional regression models are presented and discussed in this paper, In addition, an application for estimating the sizing of a stand-alone PV system at Al-Maidinah is presented in order to show the effectiveness of the developed RBF-model.

  18. Influences of S, Se, Te and Po substitutions on structural, electronic and optical properties of hexagonal CuAlO2 using GGA and B3LYP functionals.

    Science.gov (United States)

    Liu, Qi-Jun; Jiao, Zhen; Liu, Fu-Sheng; Liu, Zheng-Tang

    2016-06-01

    The effects of X-doping (X = S, Se, Te and Po) on the structural, electronic and optical properties of hexagonal CuAlO2 were studied using first-principles density functional theory. The calculated results showed the obtained lattice constants to increase with increasing atomic number, and the X-doping to be energetically more favorable under Al-rich conditions. The calculated electronic properties showed decreased bandgaps with increasing atomic number, which was due to the better covalent hybridizations after sulfuration doping. The enhanced covalency was further confirmed by calculating the Mulliken atomic populations and bond populations. The density of states indicated the increase of the contribution to antibonding from the X-p states to be a benefit for p-type conductivity. Moreover, the X-doping induced a red shift of the absorption edge. PMID:27168530

  19. Relative excitation of the seismic shear waves Sn and Lg as a function of source depth and their propagation from Melanesia and Banda arcs to Australia

    Directory of Open Access Journals (Sweden)

    J. OLIVER

    1977-06-01

    Full Text Available SUMMARY. - Seismic activity associated with the collision of the continental
    part of the Australian plate with the oceanic Melanesian arcs along Papua New
    Guinea and the Banda arc provides an unusual opportunity to study the relative
    excitation of the seismic shear waves Sn and Lg. These waves are produced by
    earthquakes located along the arcs in the upper 200 km of the earth and are
    recorded by the Australian WWSSN Stations at Charters Towers (CTA and Alice
    Springs (ASP. The paths to these stations are predominantly continental. The data
    clearly show that for events located at crustal depths, Lg is the predominant phase
    on the records and Sn is either absent or very weak. For events deeper than about
    50-70 km, Sn becomes the predominant phase on the records. These observations
    arc in qualitative agreement with the explanations of Sn and Lg as higher
    modes of surface waves, for the particle displacement amplitudes are maximum
    within the crust for Lg and maximum within the lid of the lithospheric mantle
    for Sn. The data suggest that either the crustal wave guide for Lg is more
    efficient than that for Sn, or that Lg is more easily excited than Sn. No clear
    Lg is observed from shallow earthquakes when the length of the segment of the
    path crossing oceanic structure is greater than about 200 km. Also, widespread
    Quaternary volcanism within the « stable » area of central Papua New Guinea
    to the south of the mobile belt does not seem to affect the efficient transmission
    of high-frequency (1 Hz shear energy.
    The paths from events located along the New Hebrides, Solomon, and New
    Britain arcs to Australia traverse oceanic structure, and no Lg is observed from
    these paths. The inefficient propagation of Sn along these paths from both
    shallow and intermediate-depth events can be explained as follows: 1 For
    the New Hebrides case, the

  20. An Investigation of Stylistic Features of Kashf al-Mahjoub on the Basis of Halliday Functional Grammar

    Directory of Open Access Journals (Sweden)

    fatemeh majidi

    2015-03-01

    Full Text Available In order to grasp the attitude of the writer and discover the semantic system of his mind as well as the dominant ideology of the text, this paper aims to investigate the stylistic features of Kashf al-Mahjoub based on the ideational and interpersonal metafunctions (in the Halliday grammar. The most important results of this study are as following: the center of attention in the discourse of Kashf al-Mahjoub is the God. He is present in a place to be defined as one of the issues of Sufism and, by defining him, the worlds, man and other things are also defined. Regarding the ideational metafunction, the text is mainly abstract. Such a kind of thinking and the relative discourse are congruent with Sufism system of evaluation and beliefs as wells as the doctrine of spiritualism. The text is more persuasive than imperative. Even in the expression of norms, high and absolute commanding is not used. To persuade the reader, the author employs argumentative, descriptive and explaining devices as well as declarative and interrogative moods. He uses subjunctive mood instead of imperative and draws on the Quran and hadith as evidence for fixing the discourse of Sufism. Benedictive mood dominates the text and one of the characteristics of this text is arousing of emotions. To facilitate and expedite the process of persuasion, the writer uses emotive moods. Dubitative has the lowest frequency whereas the certainty mood has notable frequency. Declarative mood has the highest frequency.