Particle-hole optical model and strength functions for high-energy giant resonances
Urin, M. H.
2010-08-15
A formulation of the particle-hole optical model is proposed for describing the contribution of the fragmentation effect to the formation of strength functions for high-energy giant resonances. The model is based on the Bethe-Goldstone equation for the energy-averaged particle-hole Green's function. In this equation, the particle-hole interaction that is induced by a virtual excitation of multiquasiparticle configurations and in which, upon averaging over energy, an imaginary part is contained is taken into account. An analogy with the single-quasiparticle optical model is discussed.
Charge-changing particle-hole excitation of 16N and 16F nuclei
NASA Astrophysics Data System (ADS)
Taqi Al-Bayati, Ali H.; Darwesh, Sarah S.
2013-12-01
The nuclear structure of 16N (closed shell + ν - π) and 16F (closed shell + π - ν) nuclei is studied using particle-hole proton-neutron Tamm-Dancoff Approximation pn TDA and particle-hole proton-neutron Random Phase Approximation pn RPA. The particle-hole Hamiltonian of PSD model space is to be diagonalized in the presence of the PSDMWKPN interaction: for P-space the Cohen-Kurath interaction, for SD-space the Wildenthal Interaction, for the coupling matrix elements between P- and SD-spaces the Millener-Kurath interaction is used, spurious components were eliminated with CM contribution. The results containing energy level schemes and electromagnetic transition strength are compared with the available experimental data.
Charge-changing particle-hole excitation of {sup 16}N and {sup 16}F nuclei
Taqi Al-Bayati, Ali H.; Darwesh, Sarah S.
2013-12-16
The nuclear structure of {sup 16}N (closed shell + ν − π) and {sup 16}F (closed shell + π − ν) nuclei is studied using particle-hole proton-neutron Tamm-Dancoff Approximation pn TDA and particle-hole proton-neutron Random Phase Approximation pn RPA. The particle-hole Hamiltonian of PSD model space is to be diagonalized in the presence of the PSDMWKPN interaction: for P-space the Cohen-Kurath interaction, for SD-space the Wildenthal Interaction, for the coupling matrix elements between P- and SD-spaces the Millener-Kurath interaction is used, spurious components were eliminated with CM contribution. The results containing energy level schemes and electromagnetic transition strength are compared with the available experimental data.
The Particle-Hole Map: A Computational Tool To Visualize Electronic Excitations.
Li, Yonghui; Ullrich, Carsten A
2015-12-08
We introduce the particle-hole map (PHM), which is a visualization tool to analyze electronic excitations in molecules in the time or frequency domain, to be used in conjunction with time-dependent density-functional theory (TDDFT) or other ab initio methods. The purpose of the PHM is to give detailed insight into electronic excitation processes that is not obtainable from local visualization methods, such as transition densities, density differences, or natural transition orbitals. The PHM is defined as a nonlocal function of two spatial variables and provides information about the origins, destinations, and connections of charge fluctuations during an excitation process; it is particularly valuable to analyze charge-transfer excitonic processes. In contrast with the transition density matrix, the PHM has a statistical interpretation involving joint probabilities of individual states and their transitions; it satisfies several sum rules and exact conditions, and it is easier to read and interpret. We discuss and illustrate the properties of the PHM and give several examples and applications to excitations in one-dimensional model systems, in a hydrogen chain, and in a benzothiadiazole (BT)-based molecule.
Particle-hole states in Sn 120
NASA Technical Reports Server (NTRS)
Leonard, R. F.
1972-01-01
The 45 MeV deuteron beam from the Berkeley 88-inch cyclotron was used to study the particle-hole states in Sn-120. The present work resolved a number of individual levels and compared their strength and excitation energy with that observed in the Sn-120(d, He-3) reaction, which was also remeasured. A schematic diagram of the scattering system is given along with a description.
Spin-projected generalized Hartree-Fock method as a polynomial of particle-hole excitations
NASA Astrophysics Data System (ADS)
Henderson, Thomas M.; Scuseria, Gustavo E.
2017-08-01
The past several years have seen renewed interest in the use of symmetry-projected Hartree-Fock for the description of strong correlations. Unfortunately, these symmetry-projected mean-field methods do not adequately account for dynamic correlation. Presumably, this shortcoming could be addressed if one could combine symmetry-projected Hartree-Fock with a many-body method such as coupled-cluster theory, but this is by no means straightforward because the two techniques are formulated in very different ways. However, we have recently shown that the singlet S2-projected unrestricted Hartree-Fock wave function can in fact be written in a coupled-cluster-like wave function. That is, the spin-projected unrestricted Hartree-Fock wave function can be written as a polynomial of a double-excitation operator acting on some closed-shell reference determinant. Here, we extend this result and show that the spin-projected generalized Hartree-Fock wave function (which has both S2 and Sz projection) is likewise a polynomial of low-order excitation operators acting on a closed-shell determinant and provide a closed-form expression for the resulting polynomial coefficients. The spin projection of the generalized Hartree-Fock wave function introduces connected triple and quadruple excitations which are absent when spin-projecting an unrestricted Hartree-Fock determinant. We include a few preliminary applications of the combination of this spin-projected Hartree-Fock and coupled-cluster theory to the Hubbard Hamiltonian and comment on generalizations of the methodology. Results here are not for production level, but a similarity-transformed theory that combines the two offers the promise of being accurate for both weak and strong correlation, and may offer significant improvements in the intermediate correlation regime where neither projected Hartree-Fock nor coupled cluster is particularly accurate.
Particle-hole states in nuclear matter
Matyas, C.A.
1985-01-01
This work deals with the collective excitations in nuclear matter, from the point of view of the TDA approximation. Our calculations involved the construction of a Hamiltonian, expressed as a matrix in the space of particle-hole excitations with a given momentum transfer. We used in this Hamiltonian an average single nucleon potential, and (in some cases) an effective interaction obtained for the potential HEA in the relativistic Brueckner-Hartree Fock theory. The eigenvectors of the TDA-Hamiltonian were used to compute the strength of the collective response of nuclear matter to external probes. Our results, succinctly described in the last section, are summarized in a set of figures at the end of this monograph. The specific form of the TDA equations that we used, and the procedure to calculate the degree of collectivity of the solutions, is studied in detail in the fifth chapter. A derivation of the TDA equations, and a discussion of the solutions for a separable potential, is given in the fourth chapter. The structure of a non-relativistic potential for a system of two nucleons is examined in the third chapter, in several representations. On the other hand, the particle-hole states relevant to our discussions on the TDA equations are introduced in the first two chapters.
NASA Astrophysics Data System (ADS)
Feldman, Joel; Knörrer, Horst; Trubowitz, Eugene
A self contained analysis demonstrates that the sum of all particle-hole ladder contributions for a two dimensional, weakly coupled fermion gas with a strictly convex Fermi curve at temperature zero is bounded. This is used in our construction of two dimensional Fermi liquids. This article contains the statements of the main results. The proofs are contained in the full, electronic, article. Electronic Supplementary Material: Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00220-004-1038-2.
Chen, Qijin
2016-01-01
BCS–Bose-Einstein condensation (BEC) crossover is effected by increasing pairing strength between fermions from weak to strong in the particle-particle channel, and has attracted a lot of attention since the experimental realization of quantum degenerate atomic Fermi gases. Here we study the effect of the (often dropped) particle-hole channel on the zero T gap Δ(0), superfluid transition temperature Tc, the pseudogap at Tc, and the mean-field ratio 2Δ(0)/, from BCS through BEC regimes, using a pairing fluctuation theory which includes self-consistently the contributions of finite-momentum pairs and features a pseudogap in single particle excitation spectrum. Summing over the infinite particle-hole ladder diagrams, we find a complex dynamical structure for the particle-hole susceptibility χph, and conclude that neglecting the self-energy feedback causes a serious over-estimate of χph. While our result in the BCS limit agrees with Gor’kov et al., the particle-hole channel effect becomes more complex and pronounced in the crossover regime, where χph is reduced by both a smaller Fermi surface and a big (pseudo)gap. Deep in the BEC regime, the particle-hole channel contributions drop to zero. We predict a density dependence of the magnetic field at the Feshbach resonance, which can be used to quantify χph and test different theories. PMID:27183875
NASA Astrophysics Data System (ADS)
Chen, Qijin
2016-05-01
BCS-Bose-Einstein condensation (BEC) crossover is effected by increasing pairing strength between fermions from weak to strong in the particle-particle channel, and has attracted a lot of attention since the experimental realization of quantum degenerate atomic Fermi gases. Here we study the effect of the (often dropped) particle-hole channel on the zero T gap Δ(0), superfluid transition temperature Tc, the pseudogap at Tc, and the mean-field ratio 2Δ(0)/, from BCS through BEC regimes, using a pairing fluctuation theory which includes self-consistently the contributions of finite-momentum pairs and features a pseudogap in single particle excitation spectrum. Summing over the infinite particle-hole ladder diagrams, we find a complex dynamical structure for the particle-hole susceptibility χph, and conclude that neglecting the self-energy feedback causes a serious over-estimate of χph. While our result in the BCS limit agrees with Gor’kov et al., the particle-hole channel effect becomes more complex and pronounced in the crossover regime, where χph is reduced by both a smaller Fermi surface and a big (pseudo)gap. Deep in the BEC regime, the particle-hole channel contributions drop to zero. We predict a density dependence of the magnetic field at the Feshbach resonance, which can be used to quantify χph and test different theories.
Chen, Qijin
2016-05-17
BCS-Bose-Einstein condensation (BEC) crossover is effected by increasing pairing strength between fermions from weak to strong in the particle-particle channel, and has attracted a lot of attention since the experimental realization of quantum degenerate atomic Fermi gases. Here we study the effect of the (often dropped) particle-hole channel on the zero T gap Δ(0), superfluid transition temperature Tc, the pseudogap at Tc, and the mean-field ratio 2Δ(0)/, from BCS through BEC regimes, using a pairing fluctuation theory which includes self-consistently the contributions of finite-momentum pairs and features a pseudogap in single particle excitation spectrum. Summing over the infinite particle-hole ladder diagrams, we find a complex dynamical structure for the particle-hole susceptibility χph, and conclude that neglecting the self-energy feedback causes a serious over-estimate of χph. While our result in the BCS limit agrees with Gor'kov et al., the particle-hole channel effect becomes more complex and pronounced in the crossover regime, where χph is reduced by both a smaller Fermi surface and a big (pseudo)gap. Deep in the BEC regime, the particle-hole channel contributions drop to zero. We predict a density dependence of the magnetic field at the Feshbach resonance, which can be used to quantify χph and test different theories.
The particle-hole map: Formal derivation and numerical implementation.
Li, Yonghui; Ullrich, Carsten A
2016-10-28
The particle-hole map (PHM) is a tool to visualize electronic excitations, based on representations in a canonical orbital transition space. Introduced as an alternative to the transition density matrix, the PHM has a simple probabilistic interpretation, indicating the origins and destinations of electrons and holes and, hence, the roles of different functional units of molecules during an excitation. We present a formal derivation of the PHM, starting from the particle-hole transition density matrix and projecting onto a set of single-particle orbitals. We implement the PHM using atom-centered localized basis sets and discuss the example of the molecular charge-transfer complex C2H4-C2F4.
Friction and particle-hole pairs. [in dissipative quantum phenomena
NASA Technical Reports Server (NTRS)
Guinea, F.
1984-01-01
The effect induced by dissipation on quantum phenomena has recently been considered, taking into account as a starting point a phenomenological Hamiltonian in which the environment is simulated by an appropriately chosen set of harmonic oscillators. It is found that this approach should be adequate to describe the low-energy behavior of a wide class of environments. The present investigation is concerned with an analysis of the case in which the environment is a gas (or liquid) of fermions, and the relevant low-energy excitations are particle-hole pairs. A study is conducted regarding the extent to which the quantum results obtained for harmonic oscillators are also valid in the considered situation. Linear-response theory is used to derive an effective action which describes the motion of an external particle coupled to a normal Fermi fluid.
Friction and particle-hole pairs. [in dissipative quantum phenomena
NASA Technical Reports Server (NTRS)
Guinea, F.
1984-01-01
The effect induced by dissipation on quantum phenomena has recently been considered, taking into account as a starting point a phenomenological Hamiltonian in which the environment is simulated by an appropriately chosen set of harmonic oscillators. It is found that this approach should be adequate to describe the low-energy behavior of a wide class of environments. The present investigation is concerned with an analysis of the case in which the environment is a gas (or liquid) of fermions, and the relevant low-energy excitations are particle-hole pairs. A study is conducted regarding the extent to which the quantum results obtained for harmonic oscillators are also valid in the considered situation. Linear-response theory is used to derive an effective action which describes the motion of an external particle coupled to a normal Fermi fluid.
Generalized oscillator strength and Coulomb excitation
NASA Astrophysics Data System (ADS)
Chidichimo, Marita C.; Thorsley, Michael D.
2003-02-01
Coulomb interaction is characterized by two nondimensional fundamental quantities: the Sommerfeld parameter η and the adiabaticity parameter ξ=ηf-ηi. In this different approach, we choose these variables to describe the behavior of the generalized oscillator strength (GOS). The expression we obtain is valid for scattering of electrons, positrons, and nuclei by arbitrary targets. We present asymptotic expansions, in the quantal and semiclassical approximation, of the electric dipole GOS.
Measurement of Atomic Oscillator Strength Distribution from the Excited States
Hussain, Shahid; Saleem, M.; Baig, M. A.
2008-10-22
Saturation technique has been employed to measure the oscillator strength distribution in spectra of helium lithium using an electrical discharge cell a thermionic diode ion detector respectively. The photoabsorption cross sections in the discrete or bound region (commonly known as f-values) have been determined form the Rydberg series accessed from a particular excited state calibrating it with the absolute value of the photoionization cross section measured at the ionization threshold. The extracted discrete f-values merge into the oscillator strength densities, estimated from the measured photoionization cross sections at different photon energies above the first ionization threshold. The experimental data on helium and lithium show continuity between the discrete and the continuous oscillator strengths across the ionization threshold.
A particle-hole calculation for pion production in relativistic heavy-ion collisions
NASA Technical Reports Server (NTRS)
Norbury, J. W.; Deutchman, P. A.; Townsend, L. W.
1985-01-01
A differential cross section for pi-meson production in peripheral heavy-ion collisions is formulated within the context of a particle-hole model in the Tamm-Dancoff approximation. This is the first attempt at a fully quantum-mechanical particle-hole calculation for pion production in relativistic heavy-ion collisions. The particular reaction studied is an O-16 projectile colliding with a C-12 target at rest. In the projectile a linear combination of isobar-hole states is formed, with the possibility of a coherent isobar giant resonance. The target can be excited to its giant M1 resonance (J-pi = 1(+), T = 1) at 15.11 MeV, or to its isobar analog neighbors, B-12 at 13.4 MeV and N-12 at 17.5 MeV. The theory is compared to recent experimental results.
A particle-hole calculation for pion production in relativistic heavy-ion collisions
NASA Astrophysics Data System (ADS)
Norbury, J. W.; Deutchman, P. A.; Townsend, L. W.
1985-02-01
A differential cross section for pi-meson production in peripheral heavy-ion collisions is formulated within the context of a particle-hole model in the Tamm-Dancoff approximation. This is the first attempt at a fully quantum-mechanical particle-hole calculation for pion production in relativistic heavy-ion collisions. The particular reaction studied is an O-16 projectile colliding with a C-12 target at rest. In the projectile a linear combination of isobar-hole states is formed, with the possibility of a coherent isobar giant resonance. The target can be excited to its giant M1 resonance (J-pi = 1(+), T = 1) at 15.11 MeV, or to its isobar analog neighbors, B-12 at 13.4 MeV and N-12 at 17.5 MeV. The theory is compared to recent experimental results.
A particle-hole calculation for pion production in relativistic heavy-ion collisions
NASA Technical Reports Server (NTRS)
Norbury, J. W.; Deutchman, P. A.; Townsend, L. W.
1985-01-01
A differential cross section for pi-meson production in peripheral heavy-ion collisions is formulated within the context of a particle-hole model in the Tamm-Dancoff approximation. This is the first attempt at a fully quantum-mechanical particle-hole calculation for pion production in relativistic heavy-ion collisions. The particular reaction studied is an O-16 projectile colliding with a C-12 target at rest. In the projectile a linear combination of isobar-hole states is formed, with the possibility of a coherent isobar giant resonance. The target can be excited to its giant M1 resonance (J-pi = 1(+), T = 1) at 15.11 MeV, or to its isobar analog neighbors, B-12 at 13.4 MeV and N-12 at 17.5 MeV. The theory is compared to recent experimental results.
Anisotropic Particle-Hole Excitations in Black Phosphorus
NASA Astrophysics Data System (ADS)
Schuster, R.; Trinckauf, J.; Habenicht, C.; Knupfer, M.; Büchner, B.
2015-07-01
We report on the energy- and momentum-resolved optical response of black phosphorus (BP) in its bulk form. Along the armchair direction of the puckered layers, we find a highly dispersive mode that is strongly suppressed in the perpendicular (zigzag) direction. This mode emerges out of the single-particle continuum for finite values of momentum and is therefore interpreted as an exciton. We argue that this exciton, which has already been predicted theoretically for phosphorene—the monolayer form of BP—can be detected by conventional optical spectroscopy in the two-dimensional case and might pave the way for optoelectronic applications of this emerging material.
The Linear Response of OXYGEN-16 in a Relativistic Particle-Hole Model
NASA Astrophysics Data System (ADS)
Price, Michael William
The nuclear structure of excited states in ('16)O is studied using the particle-hole (p-h) model in a Dirac -Hartree single-particle basis. The excited-states are assumed to be produced by an exter- nal perturbation which acts in first order and can be expressed as a sum of single -nucleon operators (linear response). In this thesis, the excited nuclear states are viewed as a linear combination of p-h states which are mixed by a Lorentz invariant finite -range p-h interaction. The particle- and hole-states are described by the self-consistently determined Dirac-Hartree spinor wave functions of Horowitz and Serot.* The linearized equations of motion are solved for the excited state energies and the corresponding p-h admixture amplitudes in the Tamm -Dancoff and random-phase approximations. In this model, the p-h basis is at first restricted to p-h states allowed from 1-(H/2PI)(omega) transitions (in the language of an oscillator model) and then extended to include particle states that lie at higher energies in the Dirac-Hartree continuum. The p-h interaction is writ- ten as a sum of five Lorentz invariant terms (scalar, vector, pseudo-scalar or pseudo-vector, axial-vector and tensor) and is allowed to assume various parameterizations (strengths and ranges) including (a) those suggested by relativistic mean field theories based on (sigma) and (omega), and (sigma), (omega), (rho) and (pi) meson exchange, and (b) those obtained by means of chi-squared RPA fits to selected experimental energy levels in ('16)O. Throughout this work, the validity of the predicted excited state energy levels arising from the various treatments of the p-h basis and interaction is tested by comparing with experimental energy levels in ('16)O. The calculated admixture amplitudes are used in conjunction with relativistic transition operators to predict transition rates for selected electro-weak processes. It is found that the agreement between these relativistic predictions and experimental
Line strengths, collision strengths and excitation rates for multiply-charged silicon ions
NASA Technical Reports Server (NTRS)
Davis, J.; Kepple, P. C.; Blaha, M.
1977-01-01
In the present paper, the line strengths, collision strengths, and rate coefficients are calculated for a variety of transitions in multiply charged silicon ions from Si(VI) to Si(XIV). The line strengths are obtained by using Clementi wave functions for the ground-state configuration, and excited-state wave functions generated by a semiempirical method. The collision strengths are calculated in an LS coupling scheme in the distorted-wave approximation, neglecting exchange except for the helium-like transitions. These results are then integrated over a Maxwellian velocity distribution function to yield rate coefficients. The rates are presented graphically and also in terms of a two-parameter fit.
Line strengths, collision strengths and excitation rates for multiply-charged silicon ions
NASA Technical Reports Server (NTRS)
Davis, J.; Kepple, P. C.; Blaha, M.
1977-01-01
In the present paper, the line strengths, collision strengths, and rate coefficients are calculated for a variety of transitions in multiply charged silicon ions from Si(VI) to Si(XIV). The line strengths are obtained by using Clementi wave functions for the ground-state configuration, and excited-state wave functions generated by a semiempirical method. The collision strengths are calculated in an LS coupling scheme in the distorted-wave approximation, neglecting exchange except for the helium-like transitions. These results are then integrated over a Maxwellian velocity distribution function to yield rate coefficients. The rates are presented graphically and also in terms of a two-parameter fit.
Collision Strengths for Electron Collisional Excitation of S II
NASA Technical Reports Server (NTRS)
Tayal, S. S.
1997-01-01
Electron collisional excitation strengths for inelastic transitions in S II are calculated using the R-matrix method in a 19-state (3s(sup 2)3p(sup 3)(sup 4)S(sup o), (sup 2)D(sup o), (sup 2)p(sup o), 3s3p(sup 4)(sup 4)P, (sup 2)D, (sup 2)S, 3S(sup 2)3p(sup 2)3d(sup 2)P, (sup 4)F, (sup 4)D, (sup 2)F, (sup 4)P, 3s(sup 2)3p(sup 2)4s(sup 4)P, (sup 2)P, 3s(sup 2)3p(sup 2)4p(sup 2)S(s o), (sup 4)D(sup o), (sup 4)P(sup o), (sup 2)D(sup o), (sup 4)S(sup o), (sup 2)P(sup o)) close-coupling approximation. These target states are represented by extensive configuration-interaction wave functions that give excitation energies and oscillator strengths that are usually in good agreement with the experimental values and the available accurate calculations. The present results for collision strengths are in very good agreement with the recent merged beams energy loss measurement of Liao et al. and agree reasonably well with the 18-state R-matrix calculation of Ramsbottom, Bell, & Stafford, but show significant differences from the 12-state R-matrix calculation of Cai & Pradhan.
Particle-hole symmetry, many-body localization, and topological edge modes
NASA Astrophysics Data System (ADS)
Vasseur, Romain; Friedman, Aaron J.; Parameswaran, S. A.; Potter, Andrew C.
We study the excited states of interacting fermions in one dimension with particle-hole symmetric disorder (equivalently, random-bond XXZ chains) using a combination of renormalization group methods and exact diagonalization. Absent interactions, the entire many-body spectrum exhibits infinite-randomness quantum critical behavior with highly degenerate excited states. We show that though interactions are an irrelevant perturbation in the ground state, they drastically affect the structure of excited states: even arbitrarily weak interactions split the degeneracies in favor of thermalization (weak disorder) or spontaneously broken particle-hole symmetry, driving the system into a many-body localized spin glass phase (strong disorder). In both cases, the quantum critical properties of the non-interacting model are destroyed, either by thermal decoherence or spontaneous symmetry breaking. This system then has the interesting and counterintuitive property that edges of the many-body spectrum are less localized than the center of the spectrum. We argue that our results rule out the existence of certain excited state symmetry-protected topological orders. Supported by the Gordon and Betty Moore Foundation's EPiQS Initiative (Grant GBMF4307 (ACP), the Quantum Materials Program at LBNL (RV), NSF Grant DMR-1455366 and UCOP Research Catalyst Award No. CA-15-327861 (SAP).
Balatsky, A.
2010-05-04
Superconducting excitations - Bogoliubov quasiparticles - are the quantum mechanical mixture of negatively charged electron (-e) and positively charged hole (+e). We propose a new observable for Angular Resolved Photoemission Spectroscopy (ARPES) studies that is the manifestation of the particle-hole entanglement of the superconducting quasiparticles. We call this observable a Bogoliubov angle. This angle measures the relative weight of particle and hole amplitude in the superconducting (Bogoliubov) quasiparticle. We show how this quantity can be measured by comparing the ratio of spectral intensities at positive and negative energies.
Breit-Pauli oscillator strengths and electron excitation collision strengths for Si VIII
NASA Astrophysics Data System (ADS)
Tayal, S. S.
2012-05-01
Aims: Oscillator strengths and electron impact excitation collision strengths for transitions between the 68 fine-structure levels of the 2s22p3, 2s2p4, 2p5, 2s22p23s, 2s22p23p, 2s22p23d and 2s2p33s configurations in Si VIII are calculated. Thermally averaged collision strengths are presented as a function of electron temperature for application to solar and other astrophysical plasmas. Methods: The collision strengths have been calculated using the B-splineBreit-Pauli R-matrixmethod for allowed and forbidden transitions in Si VIII. The relativistic effects have been incorporated through mass, Darwin and spin-orbit one-body operators in the Breit-Pauli Hamiltonian in the scattering calculation, while in the calculation of oscillator strengths the one-body and two-body relativistic operators are included. Flexible non-orthogonal sets of spectroscopic and correlation radial functions are used to obtain accurate description of Si VIII levels and to represent the scattering functions. The 68 fine-structure levels of the 2s22p3, 2s2p4, 2p5, 2s22p23s, 2s22p23p, 2s22p23d and 2s2p33s configurations have been considered in both the radiative and scattering calculations. The present scattering calculations are more extensive than previous ones, leading to a total 2278 transitions between fine-structure levels. Results: The calculated excitation energies are in excellent agreement with experiment and represent an improvement over the previous calculations. The present collision strengths show reasonable agreement with the previously available R-matrix and distorted-wave calculations. The oscillator strengths for E1 transitions normally compare very well with previous calculations. The effective collision strengths are obtained by integrating total resonant and non-resonant collision strengths over a Maxwellian distribution of electron energies and these are presented over a wide temperature range from 104 to 4.0 × 106 K. Tables 1-4 are only available in electronic form at
Transport and particle-hole asymmetry in graphene on boron nitride
NASA Astrophysics Data System (ADS)
DaSilva, Ashley M.; Jung, Jeil; Adam, Shaffique; MacDonald, Allan H.
2015-06-01
All local electronic properties of graphene on a hexagonal boron nitride (hBN) substrate exhibit spatial moiré patterns related to lattice constant and orientation differences between shared triangular Bravais lattices. We apply a previously derived effective Hamiltonian for the π bands of graphene on hBN to address the carrier dependence of transport properties, concentrating on the conductivity features at four electrons and four holes per unit cell. These transport features measure the strength of Bragg scattering of π electrons off the moiré pattern, and they exhibit a striking particle-hole asymmetry that we trace to specific features of the effective Hamiltonian that we interpret physically.
Properties of high-energy isoscalar monopole excitations in medium-heavy mass spherical nuclei
Gorelik, M. L. Shlomo, Sh. Tulupov, B. A. Urin, M. H.
2015-07-15
The recently developed particle-hole dispersive optical model is applied to describe properties of high-energy isoscalar monopole excitations in medium-heavy mass spherical nuclei. In particular, the double transition density averaged over the energy of the isoscalar monopole excitations is considered for {sup 208}Pb in a wide energy interval, which includes the isoscalar giant monopole resonance and its overtone. The energy-averaged strength functions of these resonances are also analyzed.
Experimental Observations of Particle-hole Asymmetry for Composite Fermions
NASA Astrophysics Data System (ADS)
Liu, Yang
In this talk, I will present our experimental study of the breaking of particle-hole symmetry for composite fermions (CFs), quasi-particles formed by attaching two flux quanta to each electron at large perpendicular magnetic fields. We measure the Fermi contour of the spin-polarized CFs near ν = 1 / 2 via commensurability oscillations, and find an asymmetry of the Fermi wave vector for ν < 1 / 2 and > 1 / 2 . In particular, we find that the deduced wave vector is smaller for ν > 1 / 2 compared to ν < 1 / 2 , and on both sides consistent with the density of minority carriers in the lowest Landau level. We also study the spin-polarization transitions of fractional quantum Hall states near ν = 3 / 2 and 1/2; these states are particle-hole conjugates of each other and are expected to have the same polarization energies. Our systematic results clearly show the transition energies are about three times larger for states near ν = 3 / 2 compared to those near ν = 1 / 2 . Work done in collaboration with D. Kamburov, M. A. Mueed, S. Hasdemir, A. Wojs, J.K. Jain, L.N. Pfeiffer, K.W. West, K.W. Baldwin, and M. Shayegan. We acknowledge support from the DOE, NSF, the Gordon and Betty Moore Foundation and the Keck Foundation. The experiments were partly performed at the National High Magnetic Field Laboratory.
Lan, Zhihao; Minář, Jiří; Levi, Emanuele; Li, Weibin; Lesanovsky, Igor
2015-11-13
The devil's staircase is a fractal structure that characterizes the ground state of one-dimensional classical lattice gases with long-range repulsive convex interactions. Its plateaus mark regions of stability for specific filling fractions which are controlled by a chemical potential. Typically, such a staircase has an explicit particle-hole symmetry; i.e., the staircase at more than half filling can be trivially extracted from the one at less than half filling by exchanging the roles of holes and particles. Here, we introduce a quantum spin chain with competing short-range attractive and long-range repulsive interactions, i.e., a nonconvex potential. In the classical limit the ground state features generalized Wigner crystals that--depending on the filling fraction--are composed of either dimer particles or dimer holes, which results in an emergent complete devil's staircase without explicit particle-hole symmetry of the underlying microscopic model. In our system the particle-hole symmetry is lifted due to the fact that the staircase is controlled through a two-body interaction rather than a one-body chemical potential. The introduction of quantum fluctuations through a transverse field melts the staircase and ultimately makes the system enter a paramagnetic phase. For intermediate transverse field strengths, however, we identify a region where the density-density correlations suggest the emergence of quasi-long-range order. We discuss how this physics can be explored with Rydberg-dressed atoms held in a lattice.
NASA Astrophysics Data System (ADS)
Lan, Zhihao; Minář, Jiří; Levi, Emanuele; Li, Weibin; Lesanovsky, Igor
2015-11-01
The devil's staircase is a fractal structure that characterizes the ground state of one-dimensional classical lattice gases with long-range repulsive convex interactions. Its plateaus mark regions of stability for specific filling fractions which are controlled by a chemical potential. Typically, such a staircase has an explicit particle-hole symmetry; i.e., the staircase at more than half filling can be trivially extracted from the one at less than half filling by exchanging the roles of holes and particles. Here, we introduce a quantum spin chain with competing short-range attractive and long-range repulsive interactions, i.e., a nonconvex potential. In the classical limit the ground state features generalized Wigner crystals that—depending on the filling fraction—are composed of either dimer particles or dimer holes, which results in an emergent complete devil's staircase without explicit particle-hole symmetry of the underlying microscopic model. In our system the particle-hole symmetry is lifted due to the fact that the staircase is controlled through a two-body interaction rather than a one-body chemical potential. The introduction of quantum fluctuations through a transverse field melts the staircase and ultimately makes the system enter a paramagnetic phase. For intermediate transverse field strengths, however, we identify a region where the density-density correlations suggest the emergence of quasi-long-range order. We discuss how this physics can be explored with Rydberg-dressed atoms held in a lattice.
Core excitation effects on oscillator strengths for transitions in four electron atomic systems
NASA Astrophysics Data System (ADS)
Chang, T. N.; Luo, Yuxiang
2007-06-01
By including explicitly the electronic configurations with two and three simultaneously excited electronic orbital, we have extended the BSCI (B-spline based configuration interaction) method [1] to estimate directly the effect of inner shell core excitation to oscillator strengths for transitions in four-electron atomic systems. We will present explicitly the change in oscillator strengths due to core excitations, especially for transitions involving doubly excited states and those with very small oscillator strengths. The length and velocity results are typically in agreement better than 1% or less. [1] Tu-nan Chang, in Many-body Theory of Atomic Structure and Photoionization, edited by T. N. Chang (World Scientific, Singapore, 1993), p. 213-47; and T. N. Chang and T. K. Fang, Elsevier Radiation Physics and Chemistry 70, 173-190 (2004).
Particle-Hole Duality in the Lowest Landau Level
NASA Astrophysics Data System (ADS)
Nguyen, Dung Xuan; Can, Tankut; Gromov, Andrey
2017-05-01
We derive a number of exact relations between response functions of holomorphic, chiral fractional quantum Hall states and their particle-hole (PH) conjugates. These exact relations allow one to calculate the Hall conductivity, Hall viscosity, various Berry phases, and the static structure factor of PH conjugate states from the corresponding properties of the original states. These relations establish a precise duality between chiral quantum Hall states and their PH conjugates. The key ingredient in the proof of the relations is a generalization of Girvin's construction of PH-conjugate states to inhomogeneous magnetic field and curvature. Finally, we make several nontrivial checks of the relations, including for the Jain states and their PH conjugates.
Particle-hole asymmetry in gapped topological insulator surface states
NASA Astrophysics Data System (ADS)
Tabert, C. J.; Carbotte, J. P.
2015-06-01
We consider the combined effect of a gap and the Zeeman interaction on the helical Dirac fermions that exist on the surface of a topological insulator. Magneto-optical properties, the magnetization, Hall effect, and the density of states are considered with emphasis on the particle-hole asymmetry, which arises when a subdominant Schrödinger piece is included along with the dominant Dirac part of the Hamiltonian. When appropriate, we compare our results with those of a single-valley gapped graphene system for which Zeeman splitting behaves differently. We provide a derivation of the phase offset in the magnetic oscillations brought about by the combined effect of the gap and Schrödinger term without requiring the semiclassical Onsager quantization condition. Our results agree with previous discussions based on semiclassical arguments.
Particle-hole symmetry and the composite Fermi liquid
NASA Astrophysics Data System (ADS)
Barkeshli, Maissam; Mulligan, Michael; Fisher, Matthew P. A.
2015-10-01
The half-filled Landau level is widely believed to be described by the Halperin-Lee-Read theory of the composite Fermi liquid (CFL). In this paper, we develop a theory for the particle-hole conjugate of the CFL, the anti-CFL, which we argue to be a distinct phase of matter as compared with the CFL. The anti-CFL provides a possible explanation of a recent experiment [D. Kamburov et al., Phys. Rev. Lett. 113, 196801 (2014), 10.1103/PhysRevLett.113.196801] demonstrating that the density of composite fermions in GaAs quantum wells corresponds to the electron density when the filling fraction ν <1/2 and to the hole density when ν >1/2 . We introduce a local field theory for the CFL and anti-CFL in the presence of a boundary, which we use to study CFL-insulator-CFL junctions, and the interface between the anti-CFL and CFL. We show that the CFL-anti-CFL interface allows partially fused boundary phases in which "composite electrons" can directly tunnel into "composite holes," providing a nontrivial example of transmutation between topologically distinct quasiparticles. We discuss several observable consequences of the anti-CFL, including a predicted resistivity jump at a first-order transition between uniform CFL and anti-CFL phases. We also present a theory of a continuous quantum phase transition between the CFL and anti-CFL. We conclude that particle-hole symmetry requires a modified view of the half-filled Landau level, in the presence of strong electron-electron interactions and weak disorder, as a critical point between the CFL and the anti-CFL.
NASA Astrophysics Data System (ADS)
Grieve, M. F. R.; Ramsbottom, C. A.
2012-08-01
Accurate fine-structure atomic data for the Fe-peak elements are essential for interpreting astronomical spectra. There is a severe paucity of data available for Sc II, highlighted by the fact that no collision strengths are readily available for this ion. We present electron-impact excitation collision strengths and Maxwellian averaged effective collision strengths for Sc II. The collision strengths were calculated for all 3916 transitions amongst 89 jj levels (arising from the 3d4s, 3d2, 4s2, 3d4p, 4s4p, 3d5s, 3d4d, 3d5p, 4p2 and 3d4f configurations), resulting in a 944 coupled channel problem. The R-matrix package RMATRXII was utilized, along with the transformation code FINE and the external region code PSTGF, to calculate the collision strengths for a range of incident electron energies in the 0 to 8.3 Rydberg region. Maxwellian averaged effective collision strengths were then produced for 27 temperatures lying within the astrophysically significant range of 30 to 105 K. The collision strengths and effective collision strengths were produced for two different target models. The purpose was to systematically examine the effect of including open 3p correlation terms into the configuration interaction expansion for the wavefunction. The first model consisted of all 36 CI terms that could be generated with the 3p core closed. The second model incorporated an additional six configurations which allowed for single-electron excitations from within the 3p core. Comparisons are made between the two models and the results of Bautista et al., obtained by private communication. It is concluded that the first model produced the most reliable set of collision and effective collision strengths for use in astrophysical and plasma applications.
Klein, A.; Une, T.
1988-10-01
In an accompanying paper, we have described a new approach to the computation of ground-state energies and of correlated particle-hole excitations in terms of a phenomenological pseudo-Hamiltonian containing two- and more-body smooth effective potentials which sum the results of short-range correlations and of density fluctuation amplitudes which describe long-range correlations. In this paper we study the problem of relating the pseudopotentials to a (possibly singular) microscopic interaction with the aid of tools developed within the framework of the coupled cluster theory of Kuemmel and his collaborators, the results containing both familiar and unfamiliar elements. For example, the formulas derived, which depend on Bethe-Goldstone and Bethe-Faddeev amplitudes, include new definitions of particle-hole scattering matrix elements. An important consistency check is satisfied, in that the problem of defining the phenomenological potentials in terms of the microscopic ones must yield two separate but equivalent solutions, once within the framework of the theory of the ground-state energy and a second time within the framework of the theory of excitations. The entire package is studied with the aid of a modified version of coupled cluster theory, and shown to form a self-consistent entity. Among the desirable features of the formalism is that the large gap in the single-particle energy spectrum often utilized in existing formalisms is naturally absent from the current one.
Electron impact excitation collision strengths for extreme ultraviolet lines of Fe VII
Tayal, S. S.; Zatsarinny, O. E-mail: oleg.zatsarinny@drake.edu
2014-06-10
Extensive calculations have been performed for electron impact excitation collision strengths and oscillator strengths for the Fe VII extreme ultraviolet lines of astrophysical importance. The collision strengths for fine-structure transitions are calculated in the B-spline Breit-Pauli R-matrix approach. The target wavefunctions have been calculated in the multiconfiguration Hartree-Fock method with term-dependent non-orthogonal orbitals. The close-coupling expansion includes 189 fine-structure levels of Fe VII belonging to terms of the ground 3p {sup 6}3d {sup 2} and excited 3p {sup 5}3d {sup 3}, 3p {sup 6}3d4l, 3p {sup 6}3d5s, and 3p {sup 6}3d5p configurations. The effective collision strengths are determined from the electron excitation collision strengths by integration over a Maxwellian distribution of electron velocities. The effective collision strengths are provided for 17766 fine-structure transitions at electron temperatures from 10{sup 4} to 10{sup 7} K. Our results normally agree with the previous R-matrix frame-transformation calculations by Witthoeft and Badnell. However, there are important differences for some transitions with the previous calculations. The corrections to the previous results are mainly due to more extensive expansions for the Fe VII target states.
Electron Impact Excitation Collision Strengths for Extreme Ultraviolet Lines of Fe VII
NASA Astrophysics Data System (ADS)
Tayal, S. S.; Zatsarinny, O.
2014-06-01
Extensive calculations have been performed for electron impact excitation collision strengths and oscillator strengths for the Fe VII extreme ultraviolet lines of astrophysical importance. The collision strengths for fine-structure transitions are calculated in the B-spline Breit-Pauli R-matrix approach. The target wavefunctions have been calculated in the multiconfiguration Hartree-Fock method with term-dependent non-orthogonal orbitals. The close-coupling expansion includes 189 fine-structure levels of Fe VII belonging to terms of the ground 3p 63d 2 and excited 3p 53d 3, 3p 63d4l, 3p 63d5s, and 3p 63d5p configurations. The effective collision strengths are determined from the electron excitation collision strengths by integration over a Maxwellian distribution of electron velocities. The effective collision strengths are provided for 17766 fine-structure transitions at electron temperatures from 104 to 107 K. Our results normally agree with the previous R-matrix frame-transformation calculations by Witthoeft & Badnell. However, there are important differences for some transitions with the previous calculations. The corrections to the previous results are mainly due to more extensive expansions for the Fe VII target states.
Particle-hole duality, integrability, and Russian doll BCS model
NASA Astrophysics Data System (ADS)
Bork, L. V.; Pogosov, W. V.
2015-08-01
We address a generalized Richardson model (Russian doll BCS model), which is characterized by the breaking of time-reversal symmetry. This model is known to be exactly solvable and integrable. We point out that the Russian doll BCS model, on the level of Hamiltonian, is also particle-hole symmetric. This implies that the same state can be expressed both in the particle and hole representations with two different sets of Bethe roots. We then derive exact relations between Bethe roots in the two representations, which can hardly be obtained staying on the level of Bethe equations. In a quasi-classical limit, similar identities for usual Richardson model, known from literature, are recovered from our results. We also show that these relations for Richardson roots take a remarkably simple form at half-filling and for a symmetric with respect to the middle of the interaction band distribution of one-body energy levels, since, in this special case, the rapidities in the particle and hole representations up to the translation satisfy the same system of equations.
CC2 oscillator strengths within the local framework for calculating excitation energies (LoFEx)
NASA Astrophysics Data System (ADS)
Baudin, Pablo; Kjærgaard, Thomas; Kristensen, Kasper
2017-04-01
In a recent work [P. Baudin and K. Kristensen, J. Chem. Phys. 144, 224106 (2016)], we introduced a local framework for calculating excitation energies (LoFEx), based on second-order approximated coupled cluster (CC2) linear-response theory. LoFEx is a black-box method in which a reduced excitation orbital space (XOS) is optimized to provide coupled cluster (CC) excitation energies at a reduced computational cost. In this article, we present an extension of the LoFEx algorithm to the calculation of CC2 oscillator strengths. Two different strategies are suggested, in which the size of the XOS is determined based on the excitation energy or the oscillator strength of the targeted transitions. The two strategies are applied to a set of medium-sized organic molecules in order to assess both the accuracy and the computational cost of the methods. The results show that CC2 excitation energies and oscillator strengths can be calculated at a reduced computational cost, provided that the targeted transitions are local compared to the size of the molecule. To illustrate the potential of LoFEx for large molecules, both strategies have been successfully applied to the lowest transition of the bivalirudin molecule (4255 basis functions) and compared with time-dependent density functional theory.
Particle-hole symmetry without particle-hole symmetry in the quantum Hall effect at ν = 5 / 2
NASA Astrophysics Data System (ADS)
Feldman, Dmitri; Zucker, Philip
Numerical results suggest that the quantum Hall effect at ν = 5 / 2 is described by the Pfaffian or anti-Pfaffian state in the absence of disorder and Landau level mixing. In realistic samples both disorder and Landau level mixing are strong on the 5 / 2 plateau. The experimental observation of the upstream neutral mode on the sample edge is incompatible with the Pfaffian state. Tunneling experiments give an upper bound on the universal exponent g in the zero bias conductance G ~T 2 g - 2 . That bound is inconsistent with the anti-Pfaffian state. We show that a recent proposal of the PH-Pfaffian topological order by Son is compatible with the tunneling experiments and the observation of the upstream mode. The quasiparticle statistics of the PH-Pfaffian state is similar to the statistics in the Pfaffian and anti-Pfaffian states and its interferometric signatures are also similar to those of the Pfaffian and anti-Pfaffian topological orders. The absence of the particle-hole symmetry at ν = 5 / 2 is not an obstacle to the existence of the PH-Pfaffian order since the order is robust to symmetry breaking. We acknowledge support by the NSF under Grant No. DMR-1205715.
OSCILLATOR STRENGTHS OF VIBRIONIC EXCITATIONS OF NITROGEN DETERMINED BY THE DIPOLE (γ, γ) METHOD
Liu, Ya-Wei; Kang, Xu; Xu, Long-Quan; Ni, Dong-Dong; Zhu, Lin-Fan; Yang, Ke; Hiraoka, Nozomu; Tsuei, Ku-Ding E-mail: yangke@sinap.ac.cn
2016-03-10
The oscillator strengths of the valence-shell excitations of molecular nitrogen have significant applicational values in studies of the Earth's atmosphere and interstellar gases. In this work, the absolute oscillator strengths of the valence-shell excitations of molecular nitrogen in 12.3–13.4 eV were measured by the novel dipole (γ, γ) method, in which the high-resolution inelastic X-ray scattering is operated at a negligibly small momentum transfer and can simulate the photoabsorption process. Because the experimental technique used in the present work is distinctly different from those used previously, the present experimental results give an independent cross-check to previous experimental and theoretical data. The excellent coincidence of the present results with the dipole (e, e) and those that were extrapolated indicates that the present oscillator strengths can serve as benchmark data.
Ziminski, Joseph J; Hessler, Sabine; Margetts-Smith, Gabriella; Sieburg, Meike C; Crombag, Hans S; Koya, Eisuke
2017-03-22
Cues that predict the availability of food rewards influence motivational states and elicit food-seeking behaviors. If a cue no longer predicts food availability, then animals may adapt accordingly by inhibiting food-seeking responses. Sparsely activated sets of neurons, coined "neuronal ensembles," have been shown to encode the strength of reward-cue associations. Although alterations in intrinsic excitability have been shown to underlie many learning and memory processes, little is known about these properties specifically on cue-activated neuronal ensembles. We examined the activation patterns of cue-activated orbitofrontal cortex (OFC) and nucleus accumbens (NAc) shell ensembles using wild-type and Fos-GFP mice, which express green fluorescent protein (GFP) in activated neurons, after appetitive conditioning with sucrose and extinction learning. We also investigated the neuronal excitability of recently activated, GFP+ neurons in these brain areas using whole-cell electrophysiology in brain slices. Exposure to a sucrose cue elicited activation of neurons in both the NAc shell and OFC. In the NAc shell, but not the OFC, these activated GFP+ neurons were more excitable than surrounding GFP- neurons. After extinction, the number of neurons activated in both areas was reduced and activated ensembles in neither area exhibited altered excitability. These data suggest that learning-induced alterations in the intrinsic excitability of neuronal ensembles is regulated dynamically across different brain areas. Furthermore, we show that changes in associative strength modulate the excitability profile of activated ensembles in the NAc shell.SIGNIFICANCE STATEMENT Sparsely distributed sets of neurons called "neuronal ensembles" encode learned associations about food and cues predictive of its availability. Widespread changes in neuronal excitability have been observed in limbic brain areas after associative learning, but little is known about the excitability changes that
Intermediate-energy Coulomb excitation of 104Sn: Moderate E 2 strength decrease approaching 100Sn
NASA Astrophysics Data System (ADS)
Doornenbal, P.; Takeuchi, S.; Aoi, N.; Matsushita, M.; Obertelli, A.; Steppenbeck, D.; Wang, H.; Audirac, L.; Baba, H.; Bednarczyk, P.; Boissinot, S.; Ciemala, M.; Corsi, A.; Furumoto, T.; Isobe, T.; Jungclaus, A.; Lapoux, V.; Lee, J.; Matsui, K.; Motobayashi, T.; Nishimura, D.; Ota, S.; Pollacco, E. C.; Sakurai, H.; Santamaria, C.; Shiga, Y.; Sohler, D.; Taniuchi, R.
2014-12-01
The reduced transition probability B (E 2 )↑ of the first excited 2+ state in the nucleus 104Sn was measured via Coulomb excitation in inverse kinematics at intermediate energies. A value of 0.173(28) e2b 2 was extracted from the absolute cross section on a Pb target. Feeding contributions in 104Sn from higher lying states were estimated by a reference measurement of the stable 112Sn. Corresponding only to a moderate decrease of excitation strength relative to the almost constant values observed in the proton-rich, even-A Sn-114106 isotopes, present state-of-the-art shell-model predictions, which include proton and neutron excitations across the N =Z =50 shell closures as well as standard polarization charges, underestimate the experimental findings.
NASA Astrophysics Data System (ADS)
Zucker, P. T.; Feldman, D. E.
2016-08-01
Numerical results suggest that the quantum Hall effect at ν =5 /2 is described by the Pfaffian or anti-Pfaffian state in the absence of disorder and Landau-level mixing. Those states are incompatible with the observed transport properties of GaAs heterostructures, where disorder and Landau-level mixing are strong. We show that the recent proposal of a particle-hole (PH)-Pfaffian topological order by Son is consistent with all experiments. The absence of particle-hole symmetry at ν =5 /2 is not an obstacle to the existence of the PH-Pfaffian order since the order is robust to symmetry breaking.
Surprising robustness of particle-hole symmetry for composite-fermion liquids
NASA Astrophysics Data System (ADS)
Sreejith, G. J.; Zhang, Yuhe; Jain, J. K.
2017-09-01
We report on fixed phase diffusion Monte Carlo calculations that show that, even for a large amount of Landau level mixing, the energies of the Pfaffian and anti-Pfaffian phases remain very nearly the same, as also do the excitation gaps at 1 /3 and 2 /3 . These results, combined with previous theoretical and experimental investigations, indicate that particle hole (PH) symmetry for fully spin polarized composite fermion states is much more robust than a priori expected, emerging even in models that explicitly break PH symmetry. We provide insight into this fact by showing that the low energy physics of a generic repulsive 3-body interaction is captured, to a large extent and over a range of filling factors, by a mean field approximation that maps it into a PH symmetric 2-body interaction. This explains why Landau level mixing, which effectively generates such a generic 3-body interaction, is inefficient in breaking PH symmetry. As a byproduct, our results provide a systematic construction of a 2-body interaction which produces, to a good approximation, the Pfaffian wave function as its ground state.
B(E1) Strengths from Coulomb excitation of 11Be
Summers, N C; Pain, S D; Orr, N A; Catford, W N; Angelique, J C; Ashwood, N I; Bouchat, V; Clarke, N M; Curtis, N; Freer, M; Fulton, B R; Hanappe, F; Labiche, M; Loucey, J L; Lemmon, R C; Mahboub, D; Ninane, A; Normand, G; Nunes, F M; Soic, N; Stuttge, L; Timis, C N; Thompson, I; Winfield, J S; Ziman, V
2007-03-06
The B(E1;1/2{sup +}{yields} 1/2{sup -}) strength for {sup 11}Be has been extracted from intermediate energy Coulomb excitation measurements, over a range of beam energies using a new reaction model, the extended continuum discretized coupled channels (XCDCC) method. In addition, a measurement of the excitation cross section for {sup 11}Be+{sup 208}Pb at 38.6 MeV/nucleon is reported. The B(E1) strength of 0.105(12) e{sup 2}fm{sup 2} derived from this measurement is consistent with those made previously at 60 and 64 MeV/nucleon, in contrast to an anomalously low result obtained at 43 MeV/nucleon. By coupling a multi-configuration description of the projectile structure with realistic reaction theory, the XCDCC model provides for the first time a fully quantum mechanical description of Coulomb excitation. The XCDCC calculations reveal that the excitation process involves significant contributions from nuclear, continuum, and higher-order effects. An analysis of the present and two earlier intermediate energy measurements yields a combined B(E1) strength of 0.105(7) e{sup 2}fm{sup 2}. This value is in good agreement with the value deduced independently from the lifetime of the 1/2{sup -} state in {sup 11}Be, and has a comparable precision.
High-energy electron-impact excitation process: The generalized oscillator strengths of helium
NASA Astrophysics Data System (ADS)
Han, Xiao-Ying; Li, Jia-Ming
2006-12-01
The high-energy electron impact excitation cross sections are directly proportional to the generalized oscillator strengths (GOSs) of the target (an atom or molecule). In the present work, the GOSs of helium from the ground state to nS1 , nP1 , nD1 (n→∞) and adjacent continuum excited states are calculated by a modified R -matrix code within the first Born approximation. In order to treat the bound-bound and bound-continuum transitions in a unified manner, the GOS density (GOSD) is defined based on the quantum defect theory. The GOSD surfaces of S1 , P1 , and D1 channels are calculated and tested stringently by the recent experiments. With the recommended GOSD surfaces with sufficient accuracy, the GOSDs (i.e., GOSs) from the ground state into all nS1 , nP1 , and nD1 excited states of helium can be obtained by interpolation. Thus, the high-energy electron impact excitation cross sections of all these excited states can be readily obtained. In addition to the high-energy electron impact excitation cross sections, a scheme to calculate the cross sections in the entire incident energy range is discussed.
NASA Astrophysics Data System (ADS)
Wang, Chong; Cooper, Nigel R.; Halperin, Bertrand I.; Stern, Ady
2017-07-01
It is well known that there is a particle-hole symmetry for spin-polarized electrons with two-body interactions in a partially filled Landau level, which becomes exact in the limit where the cyclotron energy is large compared to the interaction strength; thus, one can ignore mixing between Landau levels. This symmetry is explicit in the description of a half-filled Landau level recently introduced by Son, using Dirac fermions, but it was thought to be absent in the older fermion-Chern-Simons approach, developed by Halperin, Lee, and Read (HLR) and subsequent authors. We show here, however, that when properly evaluated, the HLR theory gives results for long-wavelength low-energy physical properties—including the Hall conductance in the presence of impurities and the positions of minima in the magnetoroton spectra for fractional quantized Hall states close to half-filling—that are identical to predictions of the Dirac formulation. In fact, the HLR theory predicts an emergent particle-hole symmetry near half-filling, even when the cyclotron energy is finite.
NASA Astrophysics Data System (ADS)
Blaow, M. M.; Shaw, B. A.
2015-03-01
The sensitivity of magnetic Barkhausen noise (MBN) profile to changes in the excitation field strength has been investigated in case carburized EN36 steel. In general, the 0.5 mm case depth EN 36 steel specimen induces a double peak profile indicative of inhomogeneity through the detected depth in the magnetized landscape. Various excitation field amplitudes have been applied to the electromagnet to generate various excitation fields on the specimen surface. Excitation field at the lowest level induced an MBN emission of two peaks of equivalent heights at low current value. The first peak occurs at lower field than the second peak in each half magnetization cycle. As the excitation field increases, the height of both peaks increased but the second peak, at higher field, increases in a higher rate than that of the first peak at lower field. Beyond certain magnetizing voltage, both peaks heights began to saturate and no further increase in the MBN intensity has been noticed. The results are discussed on the basis of the available theories on MBN.
Effective Collision Strengths for Electron Impact Excitation of Inelastic Transitions in S III
NASA Technical Reports Server (NTRS)
Tayal, S. S.
1997-01-01
We have calculated electron collisional excitation strengths for all electric dipole forbidden, semi-forbidden, and allowed transitions among the lowest 17 LS states 3s(exp 2)3p(exp 2) P-3, D-1, S-1, 3s3p(exp 3)S-5(exp 0), D-3(exp 0), P-3(exp 0), P-1(exp 0), S-3(exp 0), D-1(exp 0), 3S(exp 2)3p3d D-1(exp 0), F-3(exp 0), P-3(exp 0), D-3(exp 0), F-3(exp 0), P-1(exp 0), and 3S(exp 2)3p4S P-3(exp 0), P-l(exp 0) of S III using the R-matrix method. These S m states are represented by fairly extensive configuration-interaction wave functions that yield excited state energies in close agreement with recent laboratory measurements. Rydberg series of resonances converging to the excited state thresholds are explicitly included in the scattering calculation. The effective collision strengths are determined assuming Maxwellian distribution of electron energies. These are listed over a wide temperature range ([0.5-10] x 10(exp 4) K) and compared, where possible, with other available calculations. Subject headings: atomic data - atomic processes
Emergent particle-hole symmetry in spinful bosonic quantum Hall systems
NASA Astrophysics Data System (ADS)
Geraedts, S. D.; Repellin, C.; Wang, Chong; Mong, Roger S. K.; Senthil, T.; Regnault, N.
2017-08-01
When a fermionic quantum Hall system is projected into the lowest Landau level, there is an exact particle-hole symmetry between filling fractions ν and 1 -ν . We investigate whether a similar symmetry can emerge in bosonic quantum Hall states, where it would connect states at filling fractions ν and 2 -ν . We begin by showing that the particle-hole conjugate to a composite fermion "Jain state" is another Jain state, obtained by reverse flux attachment. We show how information such as the shift and the edge theory can be obtained for states which are particle-hole conjugates. Using the techniques of exact diagonalization and infinite density matrix renormalization group, we study a system of two-component (i.e., spinful) bosons, interacting via a δ -function potential. We first obtain real-space entanglement spectra for the bosonic integer quantum Hall effect at ν =2 , which plays the role of a filled Landau level for the bosonic system. We then show that at ν =4 /3 the system is described by a Jain state which is the particle-hole conjugate of the Halperin (221) state at ν =2 /3 . We show a similar relationship between nonsinglet states at ν =1 /2 and 3 /2 . We also study the case of ν =1 , providing unambiguous evidence that the ground state is a composite Fermi liquid. Taken together our results demonstrate that there is indeed an emergent particle-hole symmetry in bosonic quantum Hall systems.
Particle-Hole Asymmetry in the Cuprate Pseudogap Measured with Time-Resolved Spectroscopy
NASA Astrophysics Data System (ADS)
Miller, Tristan L.; Zhang, Wentao; Eisaki, Hiroshi; Lanzara, Alessandra
2017-03-01
One of the most puzzling features of high-temperature cuprate superconductors is the pseudogap state, which appears above the temperature at which superconductivity is destroyed. There remain fundamental questions regarding its nature and its relation to superconductivity. But to address these questions, we must first determine whether the pseudogap and superconducting states share a common property: particle-hole symmetry. We introduce a new technique to test particle-hole symmetry by using laser pulses to manipulate and measure the chemical potential on picosecond time scales. The results strongly suggest that the asymmetry in the density of states is inverted in the pseudogap state, implying a particle-hole asymmetric gap. Independent of interpretation, these results can test theoretical predictions of the density of states in cuprates.
Optical oscillator strengths for valence-shell and Br-3d inner-shell excitations of HCl and HBr.
Li, Wen-Bin; Zhu, Lin-Fan; Yuan, Zhen-Sheng; Liu, Xiao-Jing; Xu, Ke-Zun
2006-10-21
Absolute optical oscillator strength density spectra for valence-shell excitations of HCl and HBr, as well as for Br-3d inner-shell excitations of HBr, have been determined by high-resolution electron-energy-loss-spectroscopy method in the dipole limit. Absolute optical oscillator strengths for the discrete transitions of HCl and HBr are reported and compared with the previous results determined by the photoabsorption method.
Atomic mean excitation energies for stopping powers from local plasma oscillator strengths
NASA Technical Reports Server (NTRS)
Wilson, J. W.; Xu, Y. J.; Chang, C. K.; Kamaratos, E.
1984-01-01
The stopping of a charged particle by isolated atoms is investigated theoretically using an 'atomic plasma' model in which atomic oscillator strengths are replaced by the plasma frequency spectrum. The plasma-frequency correction factor for individual electron motion proposed by Pines (1953) is incorporated, and atomic mean excitation energies are calculated for atoms through Sr. The results are compared in a graph with those obtained theoretically by Inokuti et al. (1978, 1981) and Dehmer et al. (1975) and with the experimental values compiled by Seltzer and Berger (1982): good agreement is shown.
Rajchert, Joanna; Winiewski, Mikołaj
2017-01-01
This study explored how the Pavlovian temperamental traits strength of excitation (SE) and strength of inhibition (SI) were related to rejection and aggression. We predicted that rejection would increase aggression, but that higher SE and SI would mitigate this effect. Participants (n = 117) completed Strelau and Zawadzki’s (1998) Pavlovian Temperament Survey. A week later they were told that a peer wanted (acceptance) or did not want (rejection) to work with them and they were given a chance to react aggressively by damaging that person’s chance of getting a job. We found that only high SE was negatively related to rejected individuals’ aggression. The results are related to the diathesis-stress and catalyst models’ accounts of the role of temperament in shaping experience of social stress. PMID:28293212
Rajchert, Joanna; Winiewski, Mikołaj
2017-01-01
This study explored how the Pavlovian temperamental traits strength of excitation (SE) and strength of inhibition (SI) were related to rejection and aggression. We predicted that rejection would increase aggression, but that higher SE and SI would mitigate this effect. Participants (n = 117) completed Strelau and Zawadzki's (1998) Pavlovian Temperament Survey. A week later they were told that a peer wanted (acceptance) or did not want (rejection) to work with them and they were given a chance to react aggressively by damaging that person's chance of getting a job. We found that only high SE was negatively related to rejected individuals' aggression. The results are related to the diathesis-stress and catalyst models' accounts of the role of temperament in shaping experience of social stress.
Scaling of collision strengths for highly-excited states of ions of the H- and He-like sequences
NASA Astrophysics Data System (ADS)
Fernández-Menchero, L.; Del Zanna, G.; Badnell, N. R.
2016-08-01
Emission lines from highly-excited states (n ≥ 5) of H- and He-like ions have been detected in astrophysical sources and fusion plasmas. For such excited states, R-matrix or distorted wave calculations for electron-impact excitation are very limited, due to the large size of the atomic basis set needed to describe them. Calculations for n ≥ 6 are also not generally available. We study the behaviour of the electron-impact excitation collision strengths and effective collision strengths for the most important transitions used to model electron collision dominated astrophysical plasmas, solar, for example. We investigate the dependence on the relevant parameters: the principal quantum number n or the nuclear charge Z. We also estimate the importance of coupling to highly-excited states and the continuum by comparing the results of different sized calculations. We provide analytic formulae to calculate the electron-impact excitation collision strengths and effective collision strengths to highly-excited states (n ≥ 8) of H- and He-like ions. These extrapolated effective collision strengths can be used to interpret astrophysical and fusion plasma via collisional-radiative modelling. Tables of atomic data for Si xiii and S xv are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/592/A135
TRANSITION PROBABILITIES AND COLLISION STRENGTHS FOR ELECTRON-IMPACT EXCITATION OF Cl III
Sossah, A. M.; Tayal, S. S.
2012-10-15
We report transition probabilities and effective collision strengths for electron-impact excitation of the astrophysically important Cl III ion. The collision strengths are calculated in the close-coupling approximation using the B-spline Breit-Pauli R-matrix method. The multiconfiguration Hartree-Fock method with term-dependent non-orthogonal orbitals is employed for an accurate description of the target wave functions. The 68 fine-structure levels belonging to the 32 LS states of 3s {sup 2}3p{sup 3}, 3s3p{sup 4}, 3s {sup 2}3p {sup 2}3d, 3s {sup 2}3p {sup 2}4s, and 3s {sup 2}3p {sup 2}4p configurations are included in the close-coupling expansion. The effective collision strengths are obtained by averaging the electron collision strengths over a Maxwellian distribution of velocities, and those are tabulated for all 2278 possible fine-structure transitions at electron temperatures in the range from 5000 to 1,000,000 K. Our results are compared with previous theoretical results and available experimental data. Overall, we reached a good agreement with the 23 state calculation of Ramsbottom et al., but some discrepancies are seen for some transitions.
NASA Astrophysics Data System (ADS)
Gorelik, M. L.; Shlomo, S.; Tulupov, B. A.; Urin, M. H.
2016-11-01
The particle-hole dispersive optical model, developed recently, is applied to study properties of high-energy isoscalar monopole excitations in medium-heavy mass spherical nuclei. The energy-averaged strength functions of the isoscalar giant monopole resonance and its overtone in 208Pb are analyzed. In particular, we analyze the energy-averaged isoscalar monopole double transition density, the key quantity in the description of the hadron-nucleus inelastic scattering, and studied the validity of the factorization approximation using semi classical and microscopic one body transition densities, respectively, in calculating the cross sections for the excitation of isoscalar giant resonances by inelastic alpha scattering.
NASA Astrophysics Data System (ADS)
Cha, D.
1983-05-01
The στ+ strength function is studied with the quasiparticle random phase approximation. The residual interaction modifies the pairing theory strength function in two ways. The particle-hole interaction reduces the overall strength by about a factor of 2, without shifting strength between different levels. The particle-particle interaction does not affect the overall strength, but shifts part of the strength from the lowest excitation to a higher excitation energy region. By comparing the theory with the observed (ft) values of the β+ decay in medium heavy nuclei, we find that an additional quenching is required for the στ+ mode, similar in magnitude to the additional quenching present in other isovector spin-flip transitions. Finally, we predict that there is a large concentration of the στ+ strength at higher excitation energy which cannot be observed by the β+ decay. NUCLEAR STRUCTURE στ+ states in odd-odd mass nuclei between A=100-150. QP-RPA calculation with zero-range interaction. Calculated (ft).
Motor cortex excitability is not differentially modulated following skill and strength training.
Leung, M; Rantalainen, T; Teo, W-P; Kidgell, D
2015-10-01
A single session of skill or strength training can modulate the primary motor cortex (M1), which manifests as increased corticospinal excitability (CSE) and decreased short-latency intra-cortical inhibition (SICI). We tested the hypothesis that both skill and strength training can propagate the neural mechanisms mediating cross-transfer and modulate the ipsilateral M1 (iM1). Transcranial magnetic stimulation (TMS) measured baseline CSE and SICI in the contralateral motor cortex (cM1) and iM1. Participants completed 4 sets of unilateral training with their dominant arm, either visuomotor tracking, metronome-paced strength training (MPST), self-paced strength training (SPST) or control. Immediately post training, TMS was repeated in both M1s. Motor-evoked potentials (MEPs) increased and inhibition was reduced for skill and MPST training from baseline in both M1s. Self-paced strength training and control did not produce changes in CSE and SICI when compared to baseline in both M1s. After training, skill and MPST increased CSE and decreased SICI in cM1 compared to SPST and control. Skill and MPST training decreased SICI in iM1 compared to SPST and control post intervention; however, CSE in iM1 was not different across groups post training. Both skill training and MPST facilitated an increase in CSE and released SICI in iM1 and cM1 compared to baseline. Our results suggest that synchronizing to an auditory or a visual cue promotes neural adaptations within the iM1, which is thought to mediate cross transfer. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.
Non-extensive quantum statistics with particle-hole symmetry
NASA Astrophysics Data System (ADS)
Biró, T. S.; Shen, K. M.; Zhang, B. W.
2015-06-01
Based on Tsallis entropy (1988) and the corresponding deformed exponential function, generalized distribution functions for bosons and fermions have been used since a while Teweldeberhan et al. (2003) and Silva et al. (2010). However, aiming at a non-extensive quantum statistics further requirements arise from the symmetric handling of particles and holes (excitations above and below the Fermi level). Naive replacements of the exponential function or "cut and paste" solutions fail to satisfy this symmetry and to be smooth at the Fermi level at the same time. We solve this problem by a general ansatz dividing the deformed exponential to odd and even terms and demonstrate that how earlier suggestions, like the κ- and q-exponential behave in this respect.
Amusia, M.Y.; Baltenkov, A.S.; Zhuravleva, G.I.
1995-08-01
It is demonstrated that the oscillator strength of resonant inner-shell excitation in a noble gas atom is considerably smaller than that in its alkali neighbor because in the latter case the effective charge acting upon excited electron is much bigger. With increase of the excitation`s principal quantum number the difference between line intensities in noble gases and their alkali neighbors rapidly disappears. The calculations are performed in the Hartree-Fock approximation and with inclusion of rearrangement effects due to inner vacancy creation and its Auger decay. A paper has been submitted for publication.
Emergent particle-hole symmetry in the half-filled Landau level
NASA Astrophysics Data System (ADS)
Mulligan, Michael; Raghu, S.; Fisher, Matthew P. A.
2016-08-01
We provide an effective description of a particle-hole symmetric state of electrons in a half-filled Landau level, starting from the traditional approach pioneered by Halperin, Lee, and Read [Phys. Rev. B 47, 7312 (1993), 10.1103/PhysRevB.47.7312]. Specifically, we study a system consisting of alternating quasi-one-dimensional strips of composite Fermi liquid (CFL) and composite hole liquid (CHL), both of which break particle-hole symmetry. When the CFL and CHL strips are identical in size, the resulting state is manifestly invariant under the combined action of a particle-hole transformation with respect to a single Landau level (which interchanges the CFL and CHL) and translation by one unit, equal to the strip width, in the direction transverse to the strips. At distances long compared to the strip width, we demonstrate that the system is described by a Dirac fermion coupled to an emergent gauge field, with an antiunitary particle-hole symmetry, as recently proposed by Son [Phys. Rev. X 5, 031027 (2015), 10.1103/PhysRevX.5.031027].
Collision Strengths for Electron Impact Excitation of Inelastic Transitions in Ar II
NASA Technical Reports Server (NTRS)
Tayal, S. S.; Henry, Ronald J. W.
1996-01-01
We have calculated collision strengths for electron impact excitation of inelastic transitions in Ar II using the R-matrix method in two independent nine- and 19-state close-coupling approximations. In the nine-state calculation the 3s(sup 2)3p(sup 5)2p(sup 0), 3S(sup 3)p(sup 6)S-2, 3p(sup 4)(P-3)4s(sup 2)P, 3p(sup 4)(P-3)3d(sup 2)P, 3p(sup 4)(D-1)4s(sup 2)D, 3p(sup 4)(P-3)3d(sup 2)D, 3p(sup 4)(S-1)4s(sup 2)S, 3p(sup 4)(D-1)3d(sup 2)S and 3p(sup 4)(D-1)4d(sup 2)S states are included, while in the 19-state calculation these states plus an additional ten states 3p(sup 4)(P-3)3d(sup 2)F, 3p(sup 4)(P-3)4p(sup 2)D(sup 0), 2p(sup 0), 2S(sup 0), 3p(sup 4)(D-1)4p(sup 2)P(sup 0), 2D(sup O), 2F(sup 0), 3p(sup 4)(D-1)3d(sup 2)D, p-2 and 3p(sup 4)(S-1)4p(sup 2)P(sup 0) are considered. These target states are represented by fairly extensive configuration-interaction wavefunctions which yield excitation energies and oscillator strengths that are generally in good agreement with the available most accurate calculations and the experimental values. Rydberg series of resonances converging to the excited state thresholds are included in the calculation. The effective collision strengths are obtained assuming a Maxwellian distribution of electron energies which are tabulated over the temperature range (0.5-20) x 10(exp 4) K.
Collision Strengths for Electron Impact Excitation of Inelastic Transitions in Ar II
NASA Technical Reports Server (NTRS)
Tayal, S. S.; Henry, Ronald J. W.
1996-01-01
We have calculated collision strengths for electron impact excitation of inelastic transitions in Ar II using the R-matrix method in two independent nine- and 19-state close-coupling approximations. In the nine-state calculation the 3s(sup 2)3p(sup 5)2p(sup 0), 3S(sup 3)p(sup 6)S-2, 3p(sup 4)(P-3)4s(sup 2)P, 3p(sup 4)(P-3)3d(sup 2)P, 3p(sup 4)(D-1)4s(sup 2)D, 3p(sup 4)(P-3)3d(sup 2)D, 3p(sup 4)(S-1)4s(sup 2)S, 3p(sup 4)(D-1)3d(sup 2)S and 3p(sup 4)(D-1)4d(sup 2)S states are included, while in the 19-state calculation these states plus an additional ten states 3p(sup 4)(P-3)3d(sup 2)F, 3p(sup 4)(P-3)4p(sup 2)D(sup 0), 2p(sup 0), 2S(sup 0), 3p(sup 4)(D-1)4p(sup 2)P(sup 0), 2D(sup O), 2F(sup 0), 3p(sup 4)(D-1)3d(sup 2)D, p-2 and 3p(sup 4)(S-1)4p(sup 2)P(sup 0) are considered. These target states are represented by fairly extensive configuration-interaction wavefunctions which yield excitation energies and oscillator strengths that are generally in good agreement with the available most accurate calculations and the experimental values. Rydberg series of resonances converging to the excited state thresholds are included in the calculation. The effective collision strengths are obtained assuming a Maxwellian distribution of electron energies which are tabulated over the temperature range (0.5-20) x 10(exp 4) K.
Ding, X D; Wang, Y Z; Xiong, X M; Du, X S; Zhang, J X
2012-04-01
An experimental observation of force interactions in scanning tunneling microscopy (STM) is presented. A technique for measuring force interactions between a conventional STM probe and a sample by spectra analysis of its thermal fluctuations from tunneling current in STM is developed theoretically and experimentally. Thermally excited fluctuation of the STM probe is exactly discerned in air and then force gradient is determined from its corresponding eigen-frequency with a formula similar to that for a small-amplitude atomic force microscopy (AFM). The observed force interactions are consistent with forces in dynamic AFM. Shear strength of 7 GPa for highly oriented pyrolytic graphite (HOPG) under compressive stress is obtained from the experiment and using the elastic theory. We believe that this technique is of scientific significance as it enables accurate measurement of short-range force interactions at atomic scale under true STM conditions.
Strength failure of spatial reticulated structures under multi-support excitation
NASA Astrophysics Data System (ADS)
Ye, Jihong; Zhang, Zhiqiang; Chu, Ye
2011-03-01
Under strong earthquakes, long-span spatial latticed structures may collapse due to dynamic instability or strength failure. The elasto-plastic dynamic behaviors of three spatial latticed structures, including two double-layer cylindrical shells and one spherical shell constructed for the 2008 Olympic Games in Beijing, were quantitatively examined under multi-support excitation (MSE) and uniform support excitation (USE). In the numerical analyses, several important parameters were investigated such as the peak acceleration and displacement responses at key joints, the number and distribution of plastic members, and the deformation of the shell at the moment of collapse. Analysis results reveal the features and the failure mechanism of the spatial latticed structures under MSE and USE. In both scenarios, the double-layer reticulated shell collapses in the "overflow" mode, and the collapse is governed by the number of invalid plastic members rather than the total number of plastic members, beginning with damage to some of the local regions near the supports. By comparing the numbers and distributions of the plastic members under MSE to those under USE, it was observed that the plastic members spread more sufficiently and the internal forces are more uniform under MSE, especially in cases of lower apparent velocities in soils. Due to the effects of pseudo-static displacement, the stresses in the members near the supports under MSE are higher than those under USE.
Bunno, Yoshibumi; Suzuki, Toshiaki; Iwatsuki, Hiroyasu
2015-12-01
[Purpose] The aim of this study was to investigate the changes in spinal motor neuron excitability and autonomic nervous system activity during motor imagery of isometric thenar muscle activity at 10% and 50% maximal voluntary contraction (MVC). [Methods] The F-waves and low frequency/high frequency (LF/HF) ratio were recorded at rest, during motor imagery, and post-trial. For motor imagery trials, subjects were instructed to imagine thenar muscle activity at 10% and 50% MVC while holding the sensor of a pinch meter for 5 min. [Results] The F-waves and LF/HF ratio during motor imagery at 50% MVC were significantly increased compared with those at rest, whereas those during motor imagery at 10% MVC were not significantly different from those at rest. The relative values of the F/M amplitude ratio during motor imagery at 50% MVC were significantly higher than those at 10% MVC. The relative values of persistence and the LF/HF ratio during motor imagery were similar during motor imagery at the two muscle contraction strengths. [Conclusion] Motor imagery can increase the spinal motor neuron excitability and cardiac sympathetic nerve activity. Motor imagery at 50% MVC may be more effective than motor imagery at 10% MVC.
Proton particle-hole states in 208Pb
NASA Astrophysics Data System (ADS)
Grabmayr, P.; Mairle, G.; Schmidt-Rohr, U.; Berg, G. P. A.; Meissburger, J.; von Rossen, P.; Tain, J. L.
1987-07-01
Differential cross sections for the 209Bi(d, 3He) 208Pb transitions to the proton particle-proton hole states in 208Pb were obtained with the 45 MeV analyzed deuteron beam from the JULIC cyclotron and the high resolution spectrograph BIG KARL. 72 states up to 6.6 MeV were studied with an overall resolution of 12 to 15keV. Spectroscopic factors were extracted relative to the simultaneously measured calibration reaction 208Pb(d, 3He) 207Tl. For 26 states new parity assignments were possible on the basis of the measured angular distributions. The deduced inclusion into one of the four multiplets put limits on the possible spins of the states in question. With the help of sum rule arguments the spins of 12 states were assigned. The comparison with shell model calculations give only rough agreement as they predict the energies of the respective states about 300 keV too high. The magnetic dipole state at 5.846 MeV was observed with a Spectroscopic factor C2S = 0.17. From this, together with the transition probability B(M1↑) = (1.6 ± 0.5) μN2 from a ( overlineγ, γ') experiment we derived size and relative sign of the dominant neutron and proton spin-flip amplitudes. The result gives clear evidence for the isoscalar character of this state in accordance wtih TDA and RPA predictions. The matrix elements of the two-body residual interaction were derived unambiguously for the h{9}/{2} ∗ s{1}/{2}and h{9}/{2} ∗ d{3}/{2} multiplets. For the h{9}/{2}∗ h{11}/{2} and h{9}/{2} ∗ d{5}/{2} multiplets uncertainties are larger because of assumptions of some of the spins for the states of high excitation energy. The four monopole terms are found close to the average of -308 keV. They are dominated by the Coulomb contributions of ≈ - 216 keV. The deduced J-dependence of the matrix elements differs from those found in other systematic investigations indicating more complicated underlying nuclear forces must contribute.
NASA Astrophysics Data System (ADS)
Safronova, U. I.; Johnson, W. R.
2004-05-01
Energies of n s1/2 ( n=6-9 ) , n pj ( n=6-8 ) , n dj ( n=6-7 ) , and 5 fj states in neutral Au and Au-like ions with nuclear charges Z=80 83 are calculated using relativistic many-body perturbation theory. Reduced matrix elements, oscillator strengths, transition rates and lifetimes are determined for the 30 possible n lj - n' l 'j' electric-dipole transitions. Results for a limited number states n s1/2 , n pj ( n=6 7 ) and 6 dj are obtained in the relativistic single-double (SD) approximation, where single and double excitations of Dirac-Fock wave functions are included to all orders in perturbation theory. Using SD wave functions, accurate values are obtained for energies of the eight lowest states and for the fourteen possible electric-dipole matrix elements between these states. With the aid of the SD wave functions, we also determine transition rates and oscillator strengths for the fourteen transitions together with lifetimes of 6 pj , 7 pj , and 6 dj levels. We investigate the hyperfine structure in Hg II and Tl III . The hyperfine A values are determined for 6 s1/2 and 6 pj states in 199 Hg+ , 201 Hg+ , and 205 Tl2+ isotopes. These calculations provide a theoretical benchmark for comparison with experiment and theory.
Radiative capture studies of the electromagnetic decays of highly excited states
Snover, K.A.
1980-01-01
Selected examples of interesting E1, M1, and E2 resonance studies in (p,..gamma..) and (..cap alpha..,..gamma..) reactions are discussed. These include a unique determination of E1 amplitudes in the /sup 12/C(P,..gamma../sub 0/)/sup 13/N reaction, E2 strength in light nuclei, M1 decays to the ground states and to the excited O/sup +/ states of the doubly magic /sup 16/O and /sup 40/Ca nuclei, second harmonic E1 resonances in (p,..gamma..), and M1 ..gamma..-decay of stretched particle-hole states in /sup 16/O and /sup 28/Si.
NASA Astrophysics Data System (ADS)
Catapano, Marilena; Romeo, Francesco; Citro, Roberta; Giubileo, Filippo
2015-12-01
We extend the Blonder-Tinkham-Klapwijk treatment including particle-hole mixing boundary conditions in the Bogoliubov-de Gennes scattering problem to describe anomalous conductance features often reported in normal-metal/superconductor junctions. We calculate the differential conductance spectra and show that conductance dips, not expected in the standard formulation, can be explained in terms of a phase π-shift between the bulk and the interface order parameter. A tight-binding model is also introduced to give a quantitative description of the phase-shift in terms of the transparency and polarization of the interface. We characterize the physics arising from particle-hole mixing boundary conditions at the interface and its effects on the conductance anomalies in superconductor-normal heterostructures.
Particle-hole symmetry and electromagnetic response of a half-filled Landau level
NASA Astrophysics Data System (ADS)
Levin, Michael; Son, Dam Thanh
2017-03-01
We derive exact physical consequences of particle-hole symmetry of the ν =1 /2 state of electrons in a strong magnetic field. We show that if the symmetry is not spontaneously broken, the Hall conductivity and the susceptibility satisfy an exact relationship, valid at any wave number and frequencies much below the cyclotron frequency. The relationship holds for clean systems and also for systems with statistically particle-hole symmetric disorder. We work out the constraints this relationship imposes on the theory of the Dirac composite fermion. We also argue that that the exact relationship is violated in the Halperin-Lee-Read (HLR) field theory and present an explicit calculation within a Galilean invariant mean-field approximation to the HLR theory to illustrate the breakdown.
PARTICLE-HOLE NATURE OF THE LIGHT HIGH-SPIN TOROIDAL ISOMERS
Staszczak, A.; Wong, Cheuk-Yin
2015-01-01
Nuclei under non-collective rotation with a large angular momentum above some threshold can assume a toroidal shape. In our previous work, we showed by using cranked Skyrme Hartree Fock approach that even even, N = Z, high-K, toroidal isomeric states may have general occurrences for light nuclei with 28 < A < 52. We present here some additional results and systematics on the particle-hole nature of these high-spin toroidal isomers.
Particle-Hole Symmetry Breaking in the Pseudogap State of Bi2201
Hashimoto, M.; He, R.-H.; Tanaka, K.; Testaud, J.P.; Meevasana1, W.; Moore, R.G.; Lu, D.H.; Yao, H.; Yoshida, Y.; Eisaki, H.; Devereaux, T.P.; Hussain, Z.; Shen, Z.-X.; /SIMES, Stanford /Stanford U., Geballe Lab.
2011-08-19
In conventional superconductors, a gap exists in the energy absorption spectrum only below the transition temperature (T{sub c}), corresponding to the energy price to pay for breaking a Cooper pair of electrons. In high-T{sub c} cuprate superconductors above T{sub c}, an energy gap called the pseudogap exists, and is controversially attributed either to pre-formed superconducting pairs, which would exhibit particle-hole symmetry, or to competing phases which would typically break it. Scanning tunnelling microscopy (STM) studies suggest that the pseudogap stems from lattice translational symmetry breaking and is associated with a different characteristic spectrum for adding or removing electrons (particle-hole asymmetry). However, no signature of either spatial or energy symmetry breaking of the pseudogap has previously been observed by angle-resolved photoemission spectroscopy (ARPES). Here we report ARPES data from Bi2201 which reveals both particle-hole symmetry breaking and dramatic spectral broadening indicative of spatial symmetry breaking without long range order, upon crossing through T* into the pseudogap state. This symmetry breaking is found in the dominant region of the momentum space for the pseudogap, around the so-called anti-node near the Brillouin zone boundary. Our finding supports the STM conclusion that the pseudogap state is a broken-symmetry state that is distinct from homogeneous superconductivity.
Weiss oscillations and particle-hole symmetry at the half-filled Landau level
Cheung, Alfred K. C.; Raghu, S.; Mulligan, Michael
2017-06-15
Particle-hole symmetry in the lowest Landau level of the two-dimensional electron gas requires the electrical Hall conductivity to equal ± e2/2h at half filling. Here, we study the consequences of weakly broken particle-hole symmetry for magnetoresistance oscillations about half filling in the presence of an applied periodic one-dimensional electrostatic potential using the Dirac composite fermion theory proposed by Son [Son, Phys. Rev. X 5, 031027 (2015)]. At fixed electron density, the oscillation minima are asymmetrically biased towards higher magnetic fields, while at fixed magnetic field the oscillations occur symmetrically as the electron density is varied about half filling. We findmore » an approximate “sum rule” obeyed for all pairs of oscillation minima that can be tested in experiment. The locations of the magnetoresistance oscillation minima for the composite fermion theory of Halperin, Lee, and Read (HLR) and its particle-hole conjugate agree exactly. Within the current experimental resolution, the locations of the oscillation minima produced by the Dirac composite fermion coincide with those of HLR. These results may indicate that all three composite fermion theories describe the same long-wavelength physics.« less
Pairing of particle-hole symmetric composite fermions in half-filled Landau level
NASA Astrophysics Data System (ADS)
Wang, Zhiqiang; Chakravarty, Sudip
2016-10-01
In a recent proposal of the half-filled Landau level, the composite fermions are taken to be Dirac particles and particle-hole symmetric. Cooper pairing of these composite fermions in different angular momentum channels, ℓ , can give rise to different kinds of Pfaffian states. In addition to the well-known Moore-Read Pfaffian and anti-Pfaffian states, a new putative particle-hole symmetric Pfaffian state, corresponding to the s -wave pairing channel, was also proposed. However, the possible underlying pairing mechanism is not clear at all. In this work we provide a specific pairing mechanism for realizing some of these Pfaffian states. We show that there can be nonzero pairing in angular momentum channels |ℓ |≥1 depending on the magnitude of a coupling constant. There is a quantum phase transition from the Dirac composite Fermi-liquid state to Cooper pairing states in angular momentum channels |ℓ |≥1 as the coupling constant is tuned across its critical point value. Surprisingly the particle-hole symmetric ℓ =0 channel pairing turns out to be impossible irrespective of the size of the coupling constant.
Weiss oscillations and particle-hole symmetry at the half-filled Landau level
NASA Astrophysics Data System (ADS)
Cheung, Alfred K. C.; Raghu, S.; Mulligan, Michael
2017-06-01
Particle-hole symmetry in the lowest Landau level of the two-dimensional electron gas requires the electrical Hall conductivity to equal ±e2/2 h at half filling. We study the consequences of weakly broken particle-hole symmetry for magnetoresistance oscillations about half filling in the presence of an applied periodic one-dimensional electrostatic potential using the Dirac composite fermion theory proposed by Son [Son, Phys. Rev. X 5, 031027 (2015), 10.1103/PhysRevX.5.031027]. At fixed electron density, the oscillation minima are asymmetrically biased towards higher magnetic fields, while at fixed magnetic field the oscillations occur symmetrically as the electron density is varied about half filling. We find an approximate "sum rule" obeyed for all pairs of oscillation minima that can be tested in experiment. The locations of the magnetoresistance oscillation minima for the composite fermion theory of Halperin, Lee, and Read (HLR) and its particle-hole conjugate agree exactly. Within the current experimental resolution, the locations of the oscillation minima produced by the Dirac composite fermion coincide with those of HLR. These results may indicate that all three composite fermion theories describe the same long-wavelength physics.
Excitation energies, oscillator strengths and lifetimes in Mg-like vanadium
NASA Astrophysics Data System (ADS)
Gupta, G. P.; Msezane, A. Z.
2013-08-01
Excitation energies from the ground state for 86 fine-structure levels as well as oscillator strengths and radiative decay rates for all fine-structure transitions among the levels of the terms (1s22s22p6)3s2(1S), 3s3p(1,3Po), 3s3d(1,3D), 3s4s(1,3S), 3s4p(1,3Po), 3s4d(1,3D), 3s4f(1,3Fo), 3p2(1S, 3P, 1D), 3p3d(1,3Po, 1,3Do, 1,3Fo), 3p4s(1,3Po), 3p4p(1,3S, 1,3P, 1,3D), 3p4d(1,3Po, 1,3Do, 1,3Fo), 3p4f(1,3D, 1,3F, 1,3G) and 3d2(1S, 3P, 1D,3F,1G) of V XII are calculated using extensive configuration-interaction wave functions obtained with the configuration-interaction version 3 computer code of Hibbert. The important relativistic effects in intermediate coupling are included through the Breit-Pauli approximation. In order to keep our calculated energy splittings as close as possible to the corresponding experimental values, we have made small adjustments to the diagonal elements of the Hamiltonian matrices. The mixing among several fine-structure levels is found to be very strong. Our fine-tuned excitation energies, including their ordering, are in excellent agreement (better than 0.25%) with the available experimental results. From our calculated radiative decay rates, we have also calculated the radiative lifetimes of fine-structure levels. Generally, our calculated data for the excitation energies and radiative decay rates are found to agree reasonably well with other available calculations. However, significant differences between our calculated lifetimes and those from the calculation of Froese Fischer et al (2006 At. Data Nucl. Data Tables 92 607) for a few fine-structure levels, mainly those belonging to the 3p4d configuration, are noted and discussed. Also, our calculated lifetime for the longer-lived level 3s3p(3P1) is found to be in excellent agreement with the corresponding value of Curtis (1991 Phys. Scr. 43 137). ) for all 1108 transitions in V XII are available with the first author (
Safronova, U.I.; Johnson, W.R.
2004-05-01
Energies of ns{sub 1/2}(n=6-9), np{sub j}(n=6-8), nd{sub j}(n=6-7), and 5f{sub j} states in neutral Au and Au-like ions with nuclear charges Z=80-83 are calculated using relativistic many-body perturbation theory. Reduced matrix elements, oscillator strengths, transition rates and lifetimes are determined for the 30 possible nl{sub j}-n{sup '}l{sub j{sup '}}{sup '} electric-dipole transitions. Results for a limited number states, ns{sub 1/2}, np{sub j}(n=6-7) and 6d{sub j} are obtained in the relativistic single-double (SD) approximation, where single and double excitations of Dirac-Fock wave functions are included to all orders in perturbation theory. Using SD wave functions, accurate values are obtained for energies of the eight lowest states and for the fourteen possible electric-dipole matrix elements between these states. With the aid of the SD wave functions, we also determine transition rates and oscillator strengths for the fourteen transitions together with lifetimes of 6p{sub j}, 7p{sub j}, and 6d{sub j} levels. We investigate the hyperfine structure in Hg II and Tl III. The hyperfine A values are determined for 6s{sub 1/2} and 6p{sub j} states in {sup 199}Hg{sup +}, {sup 201}Hg{sup +}, and {sup 205}Tl{sup 2+} isotopes. These calculations provide a theoretical benchmark for comparison with experiment and theory.
Collective magnetic excitations of C4-symmetric magnetic states in iron-based superconductors
NASA Astrophysics Data System (ADS)
Scherer, Daniel D.; Eremin, Ilya; Andersen, Brian M.
2016-11-01
We study the collective magnetic excitations of the recently discovered C4-symmetric spin-density-wave states of iron-based superconductors with particular emphasis on their orbital character based on an itinerant multiorbital approach. This is important since the C4-symmetric spin-density-wave states exist only at moderate interaction strengths where damping effects from a coupling to the continuum of particle-hole excitations strongly modify the shape of the excitation spectra compared to predictions based on a local moment picture. We uncover a distinct orbital polarization inherent to magnetic excitations in C4-symmetric states, which provide a route to identify the different commensurate magnetic states appearing in the continuously updated phase diagram of the iron-pnictide family.
NASA Astrophysics Data System (ADS)
Grieve, M. F. R.; Ramsbottom, C. A.; Hudson, C. E.; Keenan, F. P.
2014-01-01
We present Maxwellian-averaged effective collision strengths for the electron-impact excitation of S III over a wide range of electron temperatures of astrophysical importance, log Te (K) = 3.0-6.0. The calculation incorporates 53 fine-structure levels arising from the six configurations—3s 23p 2, 3s3p 3, 3s 23p3d, 3s 23p4s, 3s 23p4p, and 3s 23p4d—giving rise to 1378 individual lines and is undertaken using the recently developed RMATRX II plus FINE95 suite of codes. A detailed comparison is made with a previous R-matrix calculation and significant differences are found for some transitions. The atomic data are subsequently incorporated into the modeling code CLOUDY to generate line intensities for a range of plasma parameters, with emphasis on allowed ultraviolet extreme-ultraviolet emission lines detected from the Io plasma torus. Electron density-sensitive line ratios are calculated with the present atomic data and compared with those from CHIANTI v7.1, as well as with Io plasma torus spectra obtained by Far-Ultraviolet Spectroscopic Explorer and Extreme-Ultraviolet Explorer. The present line intensities are found to agree well with the observational results and provide a noticeable improvement on the values predicted by CHIANTI.
Grieve, M. F. R.; Ramsbottom, C. A.; Hudson, C. E.; Keenan, F. P.
2014-01-01
We present Maxwellian-averaged effective collision strengths for the electron-impact excitation of S III over a wide range of electron temperatures of astrophysical importance, log T{sub e} (K) = 3.0-6.0. The calculation incorporates 53 fine-structure levels arising from the six configurations—3s {sup 2}3p {sup 2}, 3s3p {sup 3}, 3s {sup 2}3p3d, 3s {sup 2}3p4s, 3s {sup 2}3p4p, and 3s {sup 2}3p4d—giving rise to 1378 individual lines and is undertaken using the recently developed RMATRX II plus FINE95 suite of codes. A detailed comparison is made with a previous R-matrix calculation and significant differences are found for some transitions. The atomic data are subsequently incorporated into the modeling code CLOUDY to generate line intensities for a range of plasma parameters, with emphasis on allowed ultraviolet extreme-ultraviolet emission lines detected from the Io plasma torus. Electron density-sensitive line ratios are calculated with the present atomic data and compared with those from CHIANTI v7.1, as well as with Io plasma torus spectra obtained by Far-Ultraviolet Spectroscopic Explorer and Extreme-Ultraviolet Explorer. The present line intensities are found to agree well with the observational results and provide a noticeable improvement on the values predicted by CHIANTI.
Oscillator strengths for high-excitation Ti II from laboratory measurements and calculations
NASA Astrophysics Data System (ADS)
Lundberg, H.; Hartman, H.; Engström, L.; Nilsson, H.; Persson, A.; Palmeri, P.; Quinet, P.; Fivet, V.; Malcheva, G.; Blagoev, K.
2016-07-01
This work reports new experimental radiative lifetimes of six 3d2(3F)5s levels in singly ionized titanium, with an energy around 63 000 cm-1 and four 3d2(3F)4p odd parity levels where we confirm previous investigations. Combining the new 5s lifetimes with branching fractions measured previously by Pickering et al., we report 57 experimental log gf values for transitions from the 5s levels. The lifetime measurements are performed using time-resolved laser-induced fluorescence on ions produced by laser ablation. One- and two-step photon excitation is employed to reach the 4p and 5s levels, respectively. Theoretical calculations of the radiative lifetimes of the measured levels as well as of oscillator strengths for 3336 transitions from these levels are reported. The calculations are carried out by a pseudo-relativistic Hartree-Fock method taking into account core-polarization effects. The theoretical results are in a good agreement with the experiments and are needed for accurate abundance determinations in astronomical objects.
Collective excitations in the continuum
Dussel, G. G.; Betan, R. Id; Liotta, R. J.; Vertse, T.
2009-12-15
Pairing (particle-particle) giant resonances are analyzed within a shell-model formalism in the complex energy plane with the aim of understanding why they have not been observed so far. A comparison is made with the equivalent particle-hole mode by applying the formalism to the analysis of the well-understood particle-hole giant resonance. It is found that because of the proper treatment of the continuum intrinsic to the formalism, giant pairing resonances lie much higher than previously predicted and that some of them may be too wide to be observed, whereas others are meaningful excitations. For these, new experimental searches are proposed.
NASA Astrophysics Data System (ADS)
Chen, Qijin
2013-03-01
Feshbach resonances have been the key to achieve tunable effective pairing interaction strength in atomic Fermi gases. Most important experiments, as well as their theoretical explanations, rely on precise determination of the locations of these resonances. For the extensively studied 6Li and 40K Fermi gases, the positions of the widely used s-wave Feshbach resonances have been regarded as being measured with high precision. In this talk, we show that due to inevitable particle-hole fluctuations, there is a significant density effect on the resonance locations. For a 6Li gas with a realistic TF = 1 μK, the shift in location in terms of magnetic field can be as high as 8G at low temperature T, and this effect does not necessarily go away at high T. This will cause important consequences as to whether and how the scattering length taken from the literature need to be re-calibrated for the concrete parameters specific to a given experiment. Supported by NSF, MOE and MOST of China.
NASA Astrophysics Data System (ADS)
Cassidy, C. M.; Ramsbottom, C. A.; Scott, M. P.; Burke, P. G.
2010-04-01
Context. Considerable demand exists for electron excitation data for ion{Ni}{ii}, since lines from this abundant ion are observed in a wide variety of laboratory and astrophysical spectra. The accurate theoretical determination of these data can present a significant challenge however, due to complications arising from the presence of an open 3d-shell in the description of the target ion. Aims: In this work we present collision strengths and Maxwellian averaged effective collision strengths for the electron-impact excitation of ion{Ni}{ii}. Attention is concentrated on the 153 forbidden fine-structure transitions between the energetically lowest 18 levels of ion{Ni}{ii}. Effective collision strengths have been evaluated at 27 individual electron temperatures ranging from 30-100 000 K. To our knowledge this is the most extensive theoretical collisional study carried out on this ion to date. Methods: The parallel R-matrix package RMATRX II has recently been extended to allow for the inclusion of relativistic effects. This suite of codes has been utilised in the present work in conjunction with PSTGF to evaluate collision strengths and effective collision strengths for all of the low-lying forbidden fine-structure transitions. The following basis configurations were included in the target model - 3d9, 3d84s, 3d84p, 3d74s2 and 3d74s4p - giving rise to a sophisticated 295 jj-level, 1930 coupled channel scattering problem. Results: Comprehensive comparisons are made between the present collisional data and those obtained from earlier theoretical evaluations. While the effective collision strengths agree well for some transitions, significant discrepancies exist for others. Table 2 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/513/A55
Multi-pair excitations in an electron liquid
NASA Astrophysics Data System (ADS)
Bachlechner, M. E.; Holas, A.; Böhm, H. M.; Schinner, A.
1996-07-01
Single (particle-hole)-pair excitations, as described in the well-known Lindhard function, are restricted to a strip in the ( q, ω) plane — the so-called particle-hole continuum. We present a perturbational analysis of the dynamic dielectric function allowing a generalization of this property for n-pair contributions. Consequences for the electron energy-loss function and related quantities are discussed.
Mason, Joel; Frazer, Ashlyn; Horvath, Deanna M; Pearce, Alan J; Avela, Janne; Howatson, Glyn; Kidgell, Dawson
2017-07-01
We used transcranial magnetic stimulation (TMS) to determine the corticospinal responses from an agonist and synergist muscle following strength training of the right elbow flexors. Motor-evoked potentials were recorded from the biceps brachii and flexor carpi radialis during a submaximal contraction from 20 individuals (10 women, 10 men, aged 18-35 years; training group; n = 10 and control group; n = 10) before and after 3 weeks of strength training at 80% of 1-repetition maximum (1-RM). To characterise the input-output properties of the corticospinal tract, stimulus-response curves for corticospinal excitability and inhibition of the right biceps brachii and flexor carpi radialis were constructed and assessed by examining the area under the recruitment curve (AURC). Strength training resulted in a 29% (P < 0.001) increase in 1-RM biceps brachii strength and this was accompanied by a 19% increase in isometric strength of the wrist flexors (P = 0.001). TMS revealed an increase in corticospinal excitability AURC and a decrease in silent period duration AURC for the biceps brachii and flexor carpi radialis following strength training (all P < 0.05). However, the changes in corticospinal function were not associated with increased muscle strength. These findings show that the corticospinal responses to strength training of a proximal upper limb muscle are not spatially restricted, but rather, results in a change in connectivity, among an agonist and a synergistic muscle relevant to force production.
NASA Astrophysics Data System (ADS)
Hayes, A. B.; Cline, D.; Moody, K. J.; Ragnarsson, I.; Wu, C. Y.; Becker, J. A.; Carpenter, M. P.; Carroll, J. J.; Gohlke, D.; Greene, J. P.; Hecht, A. A.; Janssens, R. V. F.; Karamian, S. A.; Lauritsen, T.; Lister, C. J.; Macri, R. A.; Propri, R.; Seweryniak, D.; Wang, X.; Wheeler, R.; Zhu, S.
2010-10-01
A 98% pure 242mAm (K=5-, t1/2=141 years) isomeric target was Coulomb excited with a 170.5-MeV Ar40 beam. The selectivity of Coulomb excitation, coupled with the sensitivity of Gammasphere plus CHICO, was sufficient to identify 46 new states up to spin 18ℏ in at least four rotational bands; 11 of these new states lie in the isomer band, 13 in a previously unknown yrast Kπ=6- rotational band, and 13 in a band tentatively identified as the predicted yrast Kπ=5+ band. The rotational bands based on the Kπ=5- isomer and the 6- bandhead were populated by Coulomb excitation with unexpectedly equal cross sections. The γ-ray yields are reproduced by Coulomb excitation calculations using a two-particle plus rotor model (PRM), implying nearly complete ΔK=1 mixing of the two almost-degenerate rotational bands, but recovering the Alaga rule for the unperturbed states. The degeneracy of the 5- and 6- bands allows for precise determination of the mixing interaction strength V, which approaches the strong-mixing limit; this agrees with the 50% attenuation of the Coriolis matrix element assumed in the model calculations. The fractional admixture of the IKπ=66- state in the nominal 65- isomer band state is measured within the PRM as 45.6-1.1+0.3%. The E2 and M1 strengths coupling the 5- and 6- bands are enhanced significantly by the mixing, while E1 and E2 couplings to other low-K bands are not measurably enhanced. The yields of the 5+ band are reproduced by an E3 strength of ≈15 W.u., competitive with the interband E2 strength. Alignments of the identified two-particle Nilsson states in Am242 are compared with the single-particle alignments in Am241.
NASA Astrophysics Data System (ADS)
Chakraborty, Shiladitya; Galanakis, Dimitrios; Phillips, Philip
2010-12-01
High-temperature copper oxide superconductors (cuprates) display unconventional physics when they are lightly doped whereas the standard theory of metals prevails in the opposite regime. For example, the thermoelectric power, that is the voltage that develops across a sample in response to a temperature gradient, changes sign abruptly near optimal doping in a wide class of cuprates, a stark departure from the standard theory of metals in which the thermopower vanishes only when one electron exists per site. We show that this effect arises from proximity to a state in which particle-hole symmetry is dynamically generated. The operative mechanism is dynamical spectral weight transfer from states that lie at least 2 eV away from the chemical potential. We show that the sign change is reproduced quantitatively within the Hubbard model for moderate values of the on-site repulsion, U . For sufficiently large values of on-site repulsion, for example, U=20t ( t the hopping matrix element), dynamical spectral weight transfer attenuates and our calculated results for the thermopower are in prefect agreement with exact atomic limit. The emergent particle-hole symmetry close to optimal doping points to pairing in the cuprates being driven by high-energy electronic states.
Spontaneous particle-hole symmetry breaking of correlated fermions on the Lieb lattice
NASA Astrophysics Data System (ADS)
Bercx, Martin; Hofmann, Johannes S.; Assaad, Fakher F.; Lang, Thomas C.
2017-01-01
We study spinless fermions with nearest-neighbor repulsive interactions (t -V model) on the two-dimensional three-band Lieb lattice. At half-filling, the free electronic band structure consists of a flat band at zero energy and a single cone with linear dispersion. The flat band is expected to be unstable upon inclusion of electronic correlations, and a natural channel is charge order. However, due to the three-orbital unit cell, commensurate charge order implies an imbalance of electron and hole densities and therefore doping away from half-filling. Our numerical results show that below a finite-temperature Ising transition a charge density wave with one electron and two holes per unit cell and its partner under particle-hole transformation are spontaneously generated. Our calculations are based on recent advances in auxiliary-field and continuous-time quantum Monte Carlo simulations that allow sign-free simulations of spinless fermions at half-filling. It is argued that particle-hole symmetry breaking provides a route to access levels of finite doping, without introducing a sign problem.
Civitarese, O.; Dumrauf, A.G.; Reboiro, M. )
1990-04-01
Finite temperature bosonic contributions to the nuclear level density parameter are calculated. The adopted formalism is based on the random-phase approximation treatment of particle-particle, hole-hole, and particle-hole channels of an isospin-independent {delta} force. The particle-particle (hole-hole) channels are renormalized and they are treated together with the particle-hole channels. Random-phase approximation contributions to the level density parameter are found to display low-temperature features which are similar to the ones that are due to the collapse of pairing correlations.
NASA Astrophysics Data System (ADS)
Bayne, Michael G.; Uchida, Yuki; Eller, Joshua; Daniels, Carena; Chakraborty, Arindam
2016-11-01
theory (GP-MP2) giving similar results to the GP-CI method in terms of reduction of the double excitation space and accuracy to the ground-state energy. This work also extends the analytical derivation of the geminal-projected particle-hole creation operators that were used for the construction of the CI wave function to coupled-cluster theory (GP-CCSD). This general derivation can also be applied to other many-electron theories and multideterminant quantum Monte Carlo calculations.
Quenching of the Giant Dipole Resonance Strength at High Excitation Energy
NASA Astrophysics Data System (ADS)
Santonocito, D.; Blumenfeld, Y.; Agodi, C.; Alba, R.; Bellia, G.; Coniglione, R.; Delaunay, F.; Del Zoppo, A.; Finocchiaro, P.; Frascaria, N.; Hongmei, F.; Lima, V.; Maiolino, C.; Migneco, E.; Piattelli, P.; Sapienza, P.; Scarpaci, J. A.
2007-05-01
The evolution with excitation energy of the Giant Dipole Resonance features in nuclei of mass A≈108-136 is reviewed. We first discuss the results of the experiments performed with MEDEA studying the GDR gamma decay from hot nuclei populated at excitation energies above 300 MeV. The focus of the paper is on the excitation energy region between 160 and 290 MeV. This region has been investigated through the study of the reactions 116Sn + 12C at 17 and 23 A MeV, and 116Sn + 24Mg at 17 A MeV. Gamma-rays were detected using MEDEA in coincidence with evaporation residues detected in MACISTE. The analysis of the gamma-ray spectra and their comparison with statistical calculations are presented. The comparison with γ-ray spectra from the reaction 36Ar + 98Mo at higher excitation energies shows a coherent scenario where a progressive reduction of γ multiplicity relative to predictions for 100% of the Energy Weighted Sum Rule is observed above 200 MeV excitation energy. Finally, the existence of a link between disappearance of collective motion and the liquid-gas phase transitions is discussed.
Lee, Chaohong
2004-09-17
We investigate the Bose-Einstein condensation (BEC, superfluidity) of particle-hole pairs in ultracold fermionic atoms with repulsive interactions and arbitrary polarization, which are trapped within optical lattices. In the strongly repulsive limit, the dynamics of particle-hole pairs can be described by a hard-core Bose-Hubbard model. The insulator-superfluid and charge-density-wave- (CDW) superfluid phase transitions can be induced by decreasing and increasing the potential depths with controlling the trapping laser intensity, respectively. The parameter and polarization dependence of the critical temperatures for the ordered states (BEC and/or CDW) are discussed simultaneously.
NASA Astrophysics Data System (ADS)
Jia, L. Y.
2016-06-01
The particle-hole symmetry (equivalence) of the full shell-model Hilbert space is straightforward and routinely used in practical calculations. In this work I show that this symmetry is preserved in the subspace truncated up to a certain generalized seniority and give the explicit transformation between the states in the two types (particle and hole) of representations. Based on the results, I study particle-hole symmetry in popular theories that could be regarded as further truncations on top of the generalized seniority, including the microscopic interacting boson (fermion) model, the nucleon-pair approximation, and other models.
NASA Astrophysics Data System (ADS)
Maruyama, T.; Kurasawa, H.; Suzuki, T.
2005-02-01
The role of the Landau-Migdal parameters with the pseudovector ga and the tensor coupling gt is examined for the giant Gamow-Teller (GT) states in the relativistic random phase approximation (RPA). The excitation energy is dominated by both ga and gt in a similar way, while the GT strength is independent of ga and gt in the RPA of the nucleon space, and is quenched, compared with that in non-relativistic one. The coupling of the particle-hole states with nucleon-antinucleon states requires the renormalization of the divergence.
NASA Astrophysics Data System (ADS)
Cassidy, C. M.; Ramsbottom, C. A.; Scott, M. P.
2011-09-01
In this paper, we present collision strengths and Maxwellian averaged effective collision strengths for the electron-impact excitation of Ni II. Attention is expressly concentrated on the optically allowed fine-structure transitions between the 3d 9, 3d 84s, and 3d 74s 2 even parity levels and the 3d 84p and 3d 74s 4p odd parity levels. The parallel RMATRXII R-matrix package has been recently extended to allow for the inclusion of relativistic fine-structure effects. This suite of codes has been utilized in conjunction with the parallel PSTGF and PSTGICF programs in order to compute converged total collision strengths for the allowed transitions with which this study is concerned. All 113 LS terms identified with the 3d 9, 3d 84s, 3d 74s 2, 3d 84p, and 3d 74s 4p basis configurations were included in the target wavefunction representation, giving rise to a sophisticated 295 jj-level, 1930 coupled channel scattering complex. Maxwellian averaged effective collision strengths have been computed at 30 individual electron temperatures ranging from 30 to 1,000,000 K. This range comfortably encompasses all temperatures significant to astrophysical and plasma applications. The convergence of the collision strengths is exhaustively investigated and comparisons are made with previous theoretical works, where significant discrepancies exist for the majority of transitions. We conclude that intrinsic in achieving converged collision strengths and thus effective collision strengths for the allowed transitions is the combined inclusion of contributions from the (N + 1) partial waves extending to a total angular momentum value of L = 50 and further contributions from even higher partial waves accomplished by employing a "top-up" procedure.
Huang, Edwin W.; Scalapino, Douglas J.; Maier, Thomas A.; ...
2017-07-17
Evidence for the presence of high-energy magnetic excitations in overdoped La2–xSrxCuO4 (LSCO) has raised questions regarding the role of spin fluctuations in the pairing mechanism. If they remain present in overdoped LSCO, why does Tc decrease in this doping regime? Here, using results for the dynamic spin susceptibility Imχ(q,ω) obtained from a determinantal quantum Monte Carlo calculation for the Hubbard model, we address this question. We find that while high-energy magnetic excitations persist in the overdoped regime, they lack the momentum to scatter pairs between the antinodal regions. Finally, it is the decrease in the spectral weight at large momentummore » transfer, not observed by resonant inelastic x-ray scattering, which leads to a reduction in the d-wave spin-fluctuation pairing strength.« less
NASA Astrophysics Data System (ADS)
Huang, Edwin W.; Scalapino, Douglas J.; Maier, Thomas A.; Moritz, Brian; Devereaux, Thomas P.
2017-07-01
Evidence for the presence of high-energy magnetic excitations in overdoped La2 -xSrxCuO4 (LSCO) has raised questions regarding the role of spin fluctuations in the pairing mechanism. If they remain present in overdoped LSCO, why does Tc decrease in this doping regime? Here, using results for the dynamic spin susceptibility Im χ (q ,ω ) obtained from a determinantal quantum Monte Carlo calculation for the Hubbard model, we address this question. We find that while high-energy magnetic excitations persist in the overdoped regime, they lack the momentum to scatter pairs between the antinodal regions. It is the decrease in the spectral weight at large momentum transfer, not observed by resonant inelastic x-ray scattering, which leads to a reduction in the d -wave spin-fluctuation pairing strength.
Particle-hole symmetry in algebraic Bethe Ansatz for the XXX model
NASA Astrophysics Data System (ADS)
Stagraczynski, R.; Lulek, T.
2010-03-01
It is well known that the space of all quantum states of the XXX model for a magnetic ring of N nodes, each with the spin 1/2, decomposes into sectors with r spin deviations, r = 0,1, 2,..., N [1, 2, 3, 4]. The sectors r and N - r are related mutually by the particle-hole transformation which exchanges the signs + and - on each node. We discuss here effects of this transformation on the formalism of algebraic Bethe Ansatz, in particular on the form of the monodromy matrix, the main tool of this formalism. We derive explicitly appropriate transformation rules for CN- orbits of magnetic configurations and the corresponding Fourier transformations within the bases of wavelets. In particular, we point out some important phase relations between orbits on both sides of the equator.
Chang, Zhiwei; Li, Jiguang; Dong, Chenzhong
2010-12-30
Multiconfiguration Dirac-Fock (MCDF) method was employed to calculate the first five ionization potentials, electron affinities, resonance excitation energies, oscillator strengths, and radii for the element Uus and its homologue At. Main valence correlation effects were taken into account. The Breit interaction and QED effects were also estimated. The uncertainties of calculated IPs, EAs, and IR for Uus and At were reduced through an extrapolation procedure. The good consistency with available experimental and other theoretical values demonstrates the validity of the present results. These theoretical data therefore can be used to predict some unknown physicochemical properties of element Uus, Astatine, and their compounds.
Collective excitations and the nature of Mott transition in undoped gapped graphene.
Jafari, S A
2012-08-01
The particle-hole continuum (PHC) for massive Dirac fermions provides an unprecedented opportunity for the formation of two collective split-off states, one in the singlet and the other in the triplet (spin-1) channel, when the short-range interactions are added to the undoped system. Both states are close in energy and are separated from the continuum of free particle-hole excitations by an energy scale of the order of the gap parameter Δ. They both disperse linearly with two different velocities, reminiscent of spin-charge separation in Luttinger liquids. When the strength of Hubbard interactions is stronger than a critical value, the velocity of singlet excitation, which we interpret as a charge composite boson, becomes zero and renders the system a Mott insulator. Beyond this critical point the low-energy sector is left with a linearly dispersing triplet mode-a characteristic of a Mott insulator. The velocity of the triplet mode at the Mott criticality is twice the velocity of the underlying Dirac fermions. The phase transition line in the space of U and Δ is in qualitative agreement with our previous dynamical mean field theory calculations.
Electronic excitations in long polyenes revisited.
Schmidt, Maximilian; Tavan, Paul
2012-03-28
We apply the valence shell model OM2 [W. Weber and W. Thiel, Theor. Chem. Acc. 103, 495, (2000)] combined with multireference configuration interaction (MRCI) to compute the vertical excitation energies and transition dipole moments of the low-energy singlet excitations in the polyenes with 4 ≤ N ≤ 22π-electrons. We find that the OM2/MRCI descriptions closely resemble those of Pariser-Parr-Pople (PPP) π-electron models [P. Tavan and K. Schulten, Phys. Rev. B 36, 4337, (1987)], if equivalent MRCI procedures and regularly alternating model geometries are used. OM2/MRCI optimized geometries are shown to entail improved descriptions particularly for smaller polyenes (N ≤ 12), for which sizeable deviations from the regular model geometries are found. With configuration interaction active spaces covering also the σ- in addition to the π-electrons, OM2/MRCI excitation energies turn out to become smaller by at most 0.35 eV for the ionic and 0.15 eV for the covalent excitations. The particle-hole (ph) symmetry, which in Pariser-Parr-Pople models arises from the zero-differential overlap approximation, is demonstrated to be only weakly broken in OM2 such that the oscillator strengths of the covalent 1B(u)(-) states, which artificially vanish in ph-symmetric models, are predicted to be very small. According to OM2/MRCI and experimental data the 1B(u)(-) state is the third excited singlet state for N < 12 and becomes the second for N ≥ 14. By comparisons with results of other theoretical approaches and experimental evidence we argue that deficiencies of the particular MRCI method employed by us, which show up in a poor size consistency of the covalent excitations for N > 12, are caused by its restriction to at most doubly excited references.
Electronic excitations in long polyenes revisited
NASA Astrophysics Data System (ADS)
Schmidt, Maximilian; Tavan, Paul
2012-03-01
We apply the valence shell model OM2 [W. Weber and W. Thiel, Theor. Chem. Acc. 103, 495, (2000), 10.1007/s002149900083] combined with multireference configuration interaction (MRCI) to compute the vertical excitation energies and transition dipole moments of the low-energy singlet excitations in the polyenes with 4 ⩽ N ⩽ 22π-electrons. We find that the OM2/MRCI descriptions closely resemble those of Pariser-Parr-Pople (PPP) π-electron models [P. Tavan and K. Schulten, Phys. Rev. B 36, 4337, (1987)], if equivalent MRCI procedures and regularly alternating model geometries are used. OM2/MRCI optimized geometries are shown to entail improved descriptions particularly for smaller polyenes (N ⩽ 12), for which sizeable deviations from the regular model geometries are found. With configuration interaction active spaces covering also the σ- in addition to the π-electrons, OM2/MRCI excitation energies turn out to become smaller by at most 0.35 eV for the ionic and 0.15 eV for the covalent excitations. The particle-hole (ph) symmetry, which in Pariser-Parr-Pople models arises from the zero-differential overlap approximation, is demonstrated to be only weakly broken in OM2 such that the oscillator strengths of the covalent 1B_u^- states, which artificially vanish in ph-symmetric models, are predicted to be very small. According to OM2/MRCI and experimental data the 1B_u^- state is the third excited singlet state for N < 12 and becomes the second for N ⩾ 14. By comparisons with results of other theoretical approaches and experimental evidence we argue that deficiencies of the particular MRCI method employed by us, which show up in a poor size consistency of the covalent excitations for N > 12, are caused by its restriction to at most doubly excited references.
Effective collision strengths for electron impact excitations in S II. [plasma torus of Io
NASA Technical Reports Server (NTRS)
Tayal, S. S.; Henry, Ronald J. W.; Nakazaki, S.
1987-01-01
Electron impact collision strengths for forbidden, semiforbidden, and allowed transitions in S II calculated using the R-matrix method are presented. Configuration interaction wave functions are used to represent the six target states included in the calculation. At low impact energies the collision strengths are dominated by resonances for several transitions. The contribution from higher partial waves is obtained in the close-coupling approximation with exchange terms omitted. Results are presented for the effective collision strengths over a wide temperature range (5000-150,000 K) of astrophysical interest. The present results for the 4S(0) yields 2P(0) transition are 20-30 percent lower than previous calculations, while for the 4S(0) yields 2D(0) transition they are in good agreement. The results are approximately 30 percent higher than those of Ho and Henry (1983) for the 4S(0) yields 2P(0) transition at 80,000 K, and the difference between the two results increases with decreasing temperatures (under 80,000 K).
NASA Technical Reports Server (NTRS)
Wilson, J. W.; Xu, Y. J.; Kamaratos, E.; Chang, C. K.
1984-01-01
The basic model of Lindhard and Scharff, known as the local plasma model, is used to study the effects on stopping power of the chemical and physical state of the medium. Unlike previous work with the local plasma model, in which individual electron shifts in the plasma frequency were estimated empirically, he Pines correction derived for a degenerate Fermi gas is shown herein to provide a reasonable estimate, even on the atomic scale. Thus, the model is moved to a complete theoretical base requiring no empirical adjustments, as characteristic of past applications. The principal remaining error is in the overestimation of the low-energy absorption properties that are characteristic of the plasma model in the region of the atomic discrete spectrum, although higher-energy phenomena are accurately represented, and even excitation-to-ionization ratios are given to fair accuracy. Mean excitation energies for covalent-bonded gases and solids, for ionic gases and crystals, and for metals are calculated using first-order models of the bonded states.
Tallent, Jamie; Goodall, Stuart; Gibbon, Karl C; Hortobágyi, Tibor; Howatson, Glyn
2017-01-01
There is a limited understanding of the neurological adaptations responsible for changes in strength following shortening and lengthening resistance training and subsequent detraining. The aim of the study was to investigate differences in corticospinal and spinal responses to resistance training of the tibialis anterior muscle between shortening or lengthening muscle contractions for 4 weeks and after 2 weeks of detraining. Thirty-one untrained individuals were assigned to either shortening or lengthening isokinetic resistance training (4 weeks, 3 days/weeks) or a non-training control group. Transcranial magnetic stimulation and peripheral nerve stimulation (PNS) were used to assess corticospinal and spinal changes, respectively, at pre-, mid-, post-resistance training and post detraining. Greater increases changes (P < 0.01) in MVC were found from the respective muscle contraction training. Motor evoked potentials (expressed relative to background EMG) significantly increased in lengthening resistance training group under contraction intensities ranging from 25 to 80% of the shortening and lengthening contraction intensity (P < 0.01). In the shortening resistance training group increases were only seen at 50 and 80% of both contraction type. Volitional drive (V-wave) showed a greater increase following lengthening resistance training (57%) during maximal lengthening contractions compared to maximal shortening contractions following shortening resistance training (23%; P < 0.001). During the detraining period MVC and V-wave did not change (P > 0.05), although MEP amplitude decreased during the detraining period (P < 0.01). No changes in H-reflex were found pre to post resistance training or post detraining. Modulation in V-wave appeared to be contraction specific, whereby greatest increases occurred following lengthening resistance training. Strength and volitional drive is maintained following 2 weeks detraining, however corticospinal excitability appears to
Tallent, Jamie; Goodall, Stuart; Gibbon, Karl C.; Hortobágyi, Tibor; Howatson, Glyn
2017-01-01
There is a limited understanding of the neurological adaptations responsible for changes in strength following shortening and lengthening resistance training and subsequent detraining. The aim of the study was to investigate differences in corticospinal and spinal responses to resistance training of the tibialis anterior muscle between shortening or lengthening muscle contractions for 4 weeks and after 2 weeks of detraining. Thirty-one untrained individuals were assigned to either shortening or lengthening isokinetic resistance training (4 weeks, 3 days/weeks) or a non-training control group. Transcranial magnetic stimulation and peripheral nerve stimulation (PNS) were used to assess corticospinal and spinal changes, respectively, at pre-, mid-, post-resistance training and post detraining. Greater increases changes (P < 0.01) in MVC were found from the respective muscle contraction training. Motor evoked potentials (expressed relative to background EMG) significantly increased in lengthening resistance training group under contraction intensities ranging from 25 to 80% of the shortening and lengthening contraction intensity (P < 0.01). In the shortening resistance training group increases were only seen at 50 and 80% of both contraction type. Volitional drive (V-wave) showed a greater increase following lengthening resistance training (57%) during maximal lengthening contractions compared to maximal shortening contractions following shortening resistance training (23%; P < 0.001). During the detraining period MVC and V-wave did not change (P > 0.05), although MEP amplitude decreased during the detraining period (P < 0.01). No changes in H-reflex were found pre to post resistance training or post detraining. Modulation in V-wave appeared to be contraction specific, whereby greatest increases occurred following lengthening resistance training. Strength and volitional drive is maintained following 2 weeks detraining, however corticospinal excitability appears to
Zhang, Yuhe; Wójs, A; Jain, J K
2016-09-09
The spin transitions in the fractional quantum Hall effect provide a direct measure of the tiny energy differences between differently spin-polarized states and thereby serve as an extremely sensitive test of the quantitative accuracy of the theory of the fractional quantum Hall effect, and, in particular, of the role of Landau-level mixing in lifting the particle-hole symmetry. We report on an accurate quantitative study of this physics, evaluating the effect of Landau-level mixing in a nonperturbative manner using a fixed-phase diffusion Monte Carlo method. We find excellent agreement between our calculated critical Zeeman energies and the experimentally measured values. In particular, we find, as also do experiments, that the critical Zeeman energies for fractional quantum Hall states at filling factors ν=2-n/(2n±1) are significantly higher than those for ν=n/(2n±1), a quantitative signature of the lifting of particle-hole symmetry due to Landau-level mixing.
NASA Astrophysics Data System (ADS)
Zhang, Yuhe; Wójs, A.; Jain, J. K.
2016-09-01
The spin transitions in the fractional quantum Hall effect provide a direct measure of the tiny energy differences between differently spin-polarized states and thereby serve as an extremely sensitive test of the quantitative accuracy of the theory of the fractional quantum Hall effect, and, in particular, of the role of Landau-level mixing in lifting the particle-hole symmetry. We report on an accurate quantitative study of this physics, evaluating the effect of Landau-level mixing in a nonperturbative manner using a fixed-phase diffusion Monte Carlo method. We find excellent agreement between our calculated critical Zeeman energies and the experimentally measured values. In particular, we find, as also do experiments, that the critical Zeeman energies for fractional quantum Hall states at filling factors ν =2 -n /(2 n ±1 ) are significantly higher than those for ν =n /(2 n ±1 ), a quantitative signature of the lifting of particle-hole symmetry due to Landau-level mixing.
NASA Astrophysics Data System (ADS)
Fursa, T. V.; Surzhikov, A. P.; Petrov, M. V.
2016-02-01
The paper presents the research results by the improvement of the non-destructive testing method of concrete strength by the parameters of the electric response to impact excitation. The electric response parameters from the set of identical concrete samples sized of 100×100×100 mm were studied. It is shown that the use of linear filtering procedure reduces the variance of diagnostic electric parameter for concrete strength determination and is in a good agreement with the elastic characteristics of the material.
On the particle excitations in the XXZ spin chain
NASA Astrophysics Data System (ADS)
Ovchinnikov, A. A.
2013-12-01
We continue to study the excited states for the XXZ spin chain corresponding to the complex roots of the Bethe Ansatz equations with the imaginary part equal to π/2. We propose the particle-hole symmetry which relates the eigenstates build up from the two different pseudovacuum states. We find the XXX spin chain limit for the eigenstates with the complex roots. We also comment on the low-energy excited states for the XXZ spin chain.
Czerwonko, J.
1988-04-01
Since nonlinear effects are of the same importance as the particle-hole asymmetry (PHA) effects for normal Fermi liquids, at least for some physical situations, a formalism is presented taking both into account. Moreover, because the nonlinearity or PHA is easiest to induce by strong magnetic fields, weak polarization effects are also included. The kinetic equations for the weakly coupled density and magnetization modes are obtained under these circumstances. They lead to an additional effective mass equation in comparison to the Landau formula, joining the suitable angular average of the effective interaction of triples of quasiparticles with gradient of the two-quasiparticle interaction with PHA effects included. The equations are investigated in detail for ac magnetic field much smaller than the dc field in two cases: (1) at almost equilibrium magnetization of the sample and (2) at almost equilibrium (in the length) magnetization precessing around a dc field tipped to it by an angle Theta not equal to O.
Breznay, Nicholas P.; Kapitulnik, Aharon
2017-09-15
Electrons confined to two dimensions display an unexpected diversity of behaviors as they are cooled to absolute zero. Noninteracting electrons are predicted to eventually “localize” into an insulating ground state, and it has long been supposed that electron correlations stabilize only one other phase: superconductivity. However, many two-dimensional (2D) superconducting materials have shown surprising evidence for metallic behavior, where the electrical resistivity saturates in the zero-temperature limit; the nature of this unexpected metallic state remains under intense scrutiny. We report electrical transport properties for two disordered 2D superconductors, indium oxide and tantalum nitride, and observe a magnetic field–tuned transition frommore » a true superconductor to a metallic phase with saturated resistivity. Lastly, this metallic phase is characterized by a vanishing Hall resistivity, suggesting that it retains particle-hole symmetry from the disrupted superconducting state.« less
Collective and single-particle excitations in two-dimensional dipolar Bose gases
NASA Astrophysics Data System (ADS)
Filinov, A.; Bonitz, M.
2012-10-01
The Berezinskii-Kosterlitz-Thouless transition in two-dimensional dipolar systems has been studied recently by path integral Monte Carlo simulations [A. Filinov , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.070401 105, 070401 (2010)]. Here, we complement this analysis and study temperature-coupling strength dependence of the density (particle-hole) and single-particle (SP) excitation spectra both in superfluid and normal phases. The dynamic structure factor, S(q,ω), of the longitudinal excitations is rigorously reconstructed with full information on damping. The SP spectral function, A(q,ω), is worked out from the one-particle Matsubara Green's function. A stochastic optimization method is applied for reconstruction from imaginary times. In the superfluid regime sharp energy resonances are observed in both the density and SP excitations. The involved hybridization of both spectra is discussed. In contrast, in the normal phase, when there is no coupling, the density modes, beyond acoustic phonons, are significantly damped. Our results generalize previous zero-temperature analyses based on variational many-body wave functions [F. Mazzanti , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.102.110405 102, 110405 (2009); D. Hufnagl , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.107.065303 107, 065303 (2011)], where the underlying physics of the excitation spectrum and the role of the condensate has not been addressed.
NASA Astrophysics Data System (ADS)
Peng, Degao; Yang, Yang; Zhang, Peng; Yang, Weitao
2014-12-01
In this article, we develop systematically second random phase approximations (RPA) and Tamm-Dancoff approximations (TDA) of particle-hole and particle-particle channels for calculating molecular excitation energies. The second particle-hole RPA/TDA can capture double excitations missed by the particle-hole RPA/TDA and time-dependent density-functional theory (TDDFT), while the second particle-particle RPA/TDA recovers non-highest-occupied-molecular-orbital excitations missed by the particle-particle RPA/TDA. With proper orbital restrictions, these restricted second RPAs and TDAs have a formal scaling of only O(N4). The restricted versions of second RPAs and TDAs are tested with various small molecules to show some positive results. Data suggest that the restricted second particle-hole TDA (r2ph-TDA) has the best overall performance with a correlation coefficient similar to TDDFT, but with a larger negative bias. The negative bias of the r2ph-TDA may be induced by the unaccounted ground state correlation energy to be investigated further. Overall, the r2ph-TDA is recommended to study systems with both single and some low-lying double excitations with a moderate accuracy. Some expressions on excited state property evaluations, such as < hat{S}2rangle are also developed and tested.
Peng, Degao; Yang, Yang; Zhang, Peng; Yang, Weitao
2014-12-07
In this article, we develop systematically second random phase approximations (RPA) and Tamm-Dancoff approximations (TDA) of particle-hole and particle-particle channels for calculating molecular excitation energies. The second particle-hole RPA/TDA can capture double excitations missed by the particle-hole RPA/TDA and time-dependent density-functional theory (TDDFT), while the second particle-particle RPA/TDA recovers non-highest-occupied-molecular-orbital excitations missed by the particle-particle RPA/TDA. With proper orbital restrictions, these restricted second RPAs and TDAs have a formal scaling of only O(N(4)). The restricted versions of second RPAs and TDAs are tested with various small molecules to show some positive results. Data suggest that the restricted second particle-hole TDA (r2ph-TDA) has the best overall performance with a correlation coefficient similar to TDDFT, but with a larger negative bias. The negative bias of the r2ph-TDA may be induced by the unaccounted ground state correlation energy to be investigated further. Overall, the r2ph-TDA is recommended to study systems with both single and some low-lying double excitations with a moderate accuracy. Some expressions on excited state property evaluations, such as ⟨Ŝ(2)⟩ are also developed and tested.
Peng, Degao; Yang, Yang; Zhang, Peng; Yang, Weitao
2014-12-07
In this article, we develop systematically second random phase approximations (RPA) and Tamm-Dancoff approximations (TDA) of particle-hole and particle-particle channels for calculating molecular excitation energies. The second particle-hole RPA/TDA can capture double excitations missed by the particle-hole RPA/TDA and time-dependent density-functional theory (TDDFT), while the second particle-particle RPA/TDA recovers non-highest-occupied-molecular-orbital excitations missed by the particle-particle RPA/TDA. With proper orbital restrictions, these restricted second RPAs and TDAs have a formal scaling of only O(N{sup 4}). The restricted versions of second RPAs and TDAs are tested with various small molecules to show some positive results. Data suggest that the restricted second particle-hole TDA (r2ph-TDA) has the best overall performance with a correlation coefficient similar to TDDFT, but with a larger negative bias. The negative bias of the r2ph-TDA may be induced by the unaccounted ground state correlation energy to be investigated further. Overall, the r2ph-TDA is recommended to study systems with both single and some low-lying double excitations with a moderate accuracy. Some expressions on excited state property evaluations, such as 〈S{sup ^2}〉 are also developed and tested.
NASA Astrophysics Data System (ADS)
Palmeri, P.; Quinet, P.; Lundberg, H.; Engström, L.; Nilsson, H.; Hartman, H.
2017-10-01
We report new time-resolved laser-induced fluorescence lifetime measurements for 22 highly excited even-parity levels in singly ionized yttrium (Y ii). To populate these levels belonging to the configurations 4d6s, 5s6s 4d5d, 5p2, 4d7s and 4d6d, a two-step laser excitation technique was used. Our previous pseudo-relativistic Hartree-Fock model (Biémont et al. 2011) was improved by extending the configuration interaction up to n = 10 to reproduce the new experimental lifetimes. A set of semi-empirical oscillator strengths extended to transitions falling in the spectral range λλ194-3995 nm, depopulating these 22 even-parity levels in Y ii, is presented and compared to the values found in the Kurucz's data base (Kurucz 2011).
Third-order particle-hole ring diagrams with contact-interactions and one-pion exchange
NASA Astrophysics Data System (ADS)
Kaiser, N.
2017-05-01
The third-order particle-hole ring diagrams are evaluated for a NN-contact interaction of the Skyrme type. The pertinent four-loop coefficients in the energy per particle \\bar{E}(kf) ˜ kf^{5+2n} are reduced to double integrals over cubic expressions in Euclidean polarization functions. Dimensional regularization of divergent integrals is performed by subtracting power divergences and the validity of this method is checked against the known analytical results at second order. The complete \\mathcal{O}(p2) NN-contact interaction is obtained by adding two tensor terms and their third-order ring contributions are also calculated in detail. The third-order ring energy arising from long-range 1π -exchange is computed and it is found that direct and exchange contributions are all attractive. The very large size of the three-ring energy due to point-like 1π-exchange, \\bar{E}(k_{f0}) ˜eq -92 MeV at saturation density, is however in no way representative for that of realistic chiral NN-potentials. Moreover, the third-order (particle-particle and hole-hole) ladder diagrams are evaluated with the full \\mathcal{O}(p2) contact interaction, and the simplest three-ring contributions to the isospin-asymmetry energy A(kf)˜ kf5 are studied.
NASA Astrophysics Data System (ADS)
Cabrera-Trujillo, R.; Méndez-Fragoso, R.; Cruz, S. A.
2017-07-01
We study the electronic properties of a hydrogen atom under cylindrical confinement as obtained by a numerical solution to the Schrödinger equation by means of a finite-differences approach. In particular we calculate the dipole oscillator strength, static and dynamic dipole polarizabilities, as well as the mean excitation energy as a function of the position of the hydrogen impurity along the symmetry axis for the case of a ‘standard’ cylindrical confinement cavity and several confinement conditions. The effect of the displacement on the electronic properties is reflected in the change of the wave-function as the impurity approaches the cylinder potential lid produced by the surrounding confinement environment. We find that the intensity of the main dipole transition, {f}1sσ \\to 2pσ , is reduced as the atom is displaced off-center along the symmetry axis, reaching a minimum half-way between the center of the cylinder and the lid and then increasing when at the cylinder lid. In the process some other transition lines become more intense with a maximum also at half-way between the center and the cylinder lid. We find that the label assignment on the excitation transitions changes as the impurity is displaced along the symmetry axis due to the polarizability of the impurity electronic cloud. Results for the static and dynamic polarizability for the confined impurity as well as the mean excitation energy for the cases of penetrable and impenetrable confinement are presented. We find that the static polarizability increases as the impurity approaches the cylinder lid meanwhile the mean excitation energy is reduced.
Yu, Y J; Dong, C Z; Li, J G; Fricke, B
2008-03-28
Multiconfiguration Dirac-Fock method is employed to calculate the excitation energies, ionization potentials, oscillator strengths, and radii for all neutral and up to four times ionized species of element Uuq, as well as the homolog elements Ge, Sn, and Pb. Using an extrapolative scheme, improved ionization potentials of Uuq were obtained with an uncertainty of less than 2000 cm(-1). Two relatively stronger resonance transitions are predicted for the element Uuq. In particular, the strongest line in Uuq, corresponding to the [6d(10)7s(2)7p(3/2)8s(1/2)](1)-->[6d(10)7s(2)7p(3/2)(2)](2) transition at 22 343 cm(-1), just lies in the prime energy region of experimental measurement.
NASA Astrophysics Data System (ADS)
Grieve, M. F. R.; Ramsbottom, C. A.; Keenan, F. P.
2013-08-01
Context. Mg viii emission lines are observed in a range of astronomical objects such as the Sun, other cool stars and in the coronal line region of Seyfert galaxies. Under coronal conditions Mg viii emits strongly in the extreme ultraviolet (EUV) and soft X-ray spectral regions which makes it an ideal ion for plasma diagnostics. Aims: Two theoretical atomic models, consisting of 125 fine structure levels, are developed for the Mg viii ion. The 125 levels arise from the 2s22p, 2s2p2, 2p3, 2s23s, 2s23p, 2s23d, 2s2p3s, 2s2p3p, 2s2p3d, 2p23s, 2p23p and 2p23d configurations. Electron impact excitation collision strengths and radiative transition probabilities are calculated for both Mg viii models, compared with existing data, and the best model selected to generate a set of theoretical emission line intensities. The EUV lines, covering 312-790 Å, are compared with existing solar spectra (SERTS-89 and SUMER), while the soft X-ray transitions (69-97 Å) are examined for potential density diagnostic line ratios and also compared with the limited available solar and stellar observational data. Methods: The R-matrix codes Breit-Pauli RMATRXI and RMATRXII are utilised, along with the PSTGF code, to calculate the collision strengths for two Mg viii models. Collision strengths are averaged over a Maxwellian distribution to produce the corresponding effective collision strengths for use in astrophysical applications. Transition probabilities are also calculated using the CIV3 atomic structure code. The best data are then incorporated into the modelling code CLOUDY and line intensities generated for a range of electron temperatures and densities appropriate to solar and stellar coronal plasmas. Results: The present effective collision strengths are compared with two previous calculations. Good levels of agreement are found with the most recent, but there are large differences with the other for forbidden transitions. The resulting line intensities compare favourably with the
Talpalar, Thomas I.; Talpalar, Adolfo E.
2016-01-01
Hyperbaric environments induce the high pressure neurological syndrome (HPNS) characterized by hyperexcitability of the central nervous system (CNS) and memory impairment. Human divers and other animals experience the HPNS at pressures beyond 1.1 MPa. High pressure depresses synaptic transmission and alters its dynamics in various animal models. Medial perforant path (MPP) synapses connecting the medial entorhinal cortex with the hippocampal formation are suppressed by 50% at 10.1MPa. Reduction of synaptic inputs is paradoxically associated with enhanced ability of dentate gyrus (DG)’ granule cells (GCs) to generate spikes at high pressure. This mechanism allows MPP inputs to elicit standard GC outputs at 0.1–25 Hz frequencies under hyperbaric conditions. An increased postsynaptic gain of MPP inputs probably allows diving animals to perform in hyperbaric environments, but makes them vulnerable to high intensity/frequency stimuli producing hyperexcitability. Increasing extracellular Ca2+ ([Ca2+]o) partially reverted pressure-mediated depression of MPP inputs and increased MPP’s low-pass filter properties. We postulated that raising [Ca2+]o in addition to increase synaptic inputs may reduce network excitability in the DG potentially improving its function and reducing sensitivity to high intensity and pathologic stimuli. For this matter, we activated the MPP with single and 50 Hz frequency stimuli that simulated physiologic and deleterious conditions, while assessing the GC’s output under various conditions of pressure and [Ca2+]o. Our results reveal that the pressure and [Ca2+]o produce an inverse modulation on synaptic input strength and network excitability. These coincident phenomena suggest a potential general mechanism of networks that adjusts gain as an inverse function of synaptic inputs’ strength. Such mechanism may serve for adaptation to variable pressure and other physiological and pathological conditions and may explain the increased
Talpalar, Thomas I; Talpalar, Adolfo E
2016-01-01
Hyperbaric environments induce the high pressure neurological syndrome (HPNS) characterized by hyperexcitability of the central nervous system (CNS) and memory impairment. Human divers and other animals experience the HPNS at pressures beyond 1.1 MPa. High pressure depresses synaptic transmission and alters its dynamics in various animal models. Medial perforant path (MPP) synapses connecting the medial entorhinal cortex with the hippocampal formation are suppressed by 50% at 10.1MPa. Reduction of synaptic inputs is paradoxically associated with enhanced ability of dentate gyrus (DG)' granule cells (GCs) to generate spikes at high pressure. This mechanism allows MPP inputs to elicit standard GC outputs at 0.1-25 Hz frequencies under hyperbaric conditions. An increased postsynaptic gain of MPP inputs probably allows diving animals to perform in hyperbaric environments, but makes them vulnerable to high intensity/frequency stimuli producing hyperexcitability. Increasing extracellular Ca(2+) ([Ca(2+)]o) partially reverted pressure-mediated depression of MPP inputs and increased MPP's low-pass filter properties. We postulated that raising [Ca(2+)]o in addition to increase synaptic inputs may reduce network excitability in the DG potentially improving its function and reducing sensitivity to high intensity and pathologic stimuli. For this matter, we activated the MPP with single and 50 Hz frequency stimuli that simulated physiologic and deleterious conditions, while assessing the GC's output under various conditions of pressure and [Ca(2+)]o. Our results reveal that the pressure and [Ca(2+)]o produce an inverse modulation on synaptic input strength and network excitability. These coincident phenomena suggest a potential general mechanism of networks that adjusts gain as an inverse function of synaptic inputs' strength. Such mechanism may serve for adaptation to variable pressure and other physiological and pathological conditions and may explain the increased
NASA Astrophysics Data System (ADS)
Calixto, M.; Pérez-Romero, E.
2014-08-01
We revise the unireps. of U(2, 2) describing conformal particles with continuous mass spectrum from a many-body perspective, which shows massive conformal particles as compounds of two correlated massless particles. The statistics of the compound (boson/fermion) depends on the helicity h of the massless components (integer/half-integer). Coherent states (CS) of particle-hole pairs ("excitons") are also explicitly constructed as the exponential action of exciton (non-canonical) creation operators on the ground state of unpaired particles. These CS are labeled by points Z (2 × 2 complex matrices) on the Cartan-Bergman domain {D}_4=U(2,2)/U(2)^2, and constitute a generalized (matrix) version of Perelomov U(1, 1) coherent states labeled by points z on the unit disk {D}_1=U(1,1)/U(1)^2. First, we follow a geometric approach to the construction of CS, orthonormal basis, U(2, 2) generators and their matrix elements and symbols in the reproducing kernel Hilbert space H_λ ({D}_4) of analytic square-integrable holomorphic functions on {D}_4, which carries a unitary irreducible representation of U(2, 2) with index λ in {N} (the conformal or scale dimension). Then we introduce a many-body representation of the previous construction through an oscillator realization of the U(2, 2) Lie algebra generators in terms of eight boson operators with constraints. This particle picture allows us for a physical interpretation of our abstract mathematical construction in the many-body jargon. In particular, the index λ is related to the number 2(λ - 2) of unpaired quanta and to the helicity h = (λ - 2)/2 of each massless particle forming the massive compound.
Calixto, M. Pérez-Romero, E.
2014-08-01
We revise the unireps. of U(2, 2) describing conformal particles with continuous mass spectrum from a many-body perspective, which shows massive conformal particles as compounds of two correlated massless particles. The statistics of the compound (boson/fermion) depends on the helicity h of the massless components (integer/half-integer). Coherent states (CS) of particle-hole pairs (“excitons”) are also explicitly constructed as the exponential action of exciton (non-canonical) creation operators on the ground state of unpaired particles. These CS are labeled by points Z (2×2 complex matrices) on the Cartan-Bergman domain D₄=U(2,2)/U(2)², and constitute a generalized (matrix) version of Perelomov U(1, 1) coherent states labeled by points z on the unit disk D₁=U(1,1)/U(1)². First, we follow a geometric approach to the construction of CS, orthonormal basis, U(2, 2) generators and their matrix elements and symbols in the reproducing kernel Hilbert space H{sub λ}(D₄) of analytic square-integrable holomorphic functions on D₄, which carries a unitary irreducible representation of U(2, 2) with index λϵN (the conformal or scale dimension). Then we introduce a many-body representation of the previous construction through an oscillator realization of the U(2, 2) Lie algebra generators in terms of eight boson operators with constraints. This particle picture allows us for a physical interpretation of our abstract mathematical construction in the many-body jargon. In particular, the index λ is related to the number 2(λ – 2) of unpaired quanta and to the helicity h = (λ – 2)/2 of each massless particle forming the massive compound.
Cao, Xiao-Jie
2010-01-01
Auditory nerve fibers are the major source of excitation to the three groups of principal cells of the ventral cochlear nucleus (VCN), bushy, T stellate, and octopus cells. Shock-evoked excitatory postsynaptic currents (eEPSCs) in slices from mice showed systematic differences between groups of principal cells, indicating that target cells contribute to determining pre- and postsynaptic properties of synapses from spiral ganglion cells. Bushy cells likely to be small spherical bushy cells receive no more than three, most often two, excitatory inputs; those likely to be globular bushy cells receive at least four, most likely five, inputs. T stellate cells receive 6.5 inputs. Octopus cells receive >60 inputs. The N-methyl-d-aspartate (NMDA) components of eEPSCs were largest in T stellate, smaller in bushy, and smallest in octopus cells, and they were larger in neurons from younger than older mice. The average AMPA conductance of a unitary input is 22 ± 15 nS in both groups of bushy cells, <1.5 nS in octopus cells, and 4.6 ± 3 nS in T stellate cells. Sensitivity to philanthotoxin (PhTX) and rectification in the intracellular presence of spermine indicate that AMPA receptors that mediate eEPSCs in T stellate cells contain more GluR2 subunits than those in bushy and octopus cells. The AMPA components of eEPSCs were briefer in bushy (0.5 ms half-width) than in T stellate and octopus cells (0.8–0.9 ms half-width). Widening of eEPSCs in the presence of cyclothiazide (CTZ) indicates that desensitization shortens eEPSCs. CTZ-insensitive synaptic depression of the AMPA components was greater in bushy and octopus than in T stellate cells. PMID:20739600
Cao, Xiao-Jie; Oertel, Donata
2010-11-01
Auditory nerve fibers are the major source of excitation to the three groups of principal cells of the ventral cochlear nucleus (VCN), bushy, T stellate, and octopus cells. Shock-evoked excitatory postsynaptic currents (eEPSCs) in slices from mice showed systematic differences between groups of principal cells, indicating that target cells contribute to determining pre- and postsynaptic properties of synapses from spiral ganglion cells. Bushy cells likely to be small spherical bushy cells receive no more than three, most often two, excitatory inputs; those likely to be globular bushy cells receive at least four, most likely five, inputs. T stellate cells receive 6.5 inputs. Octopus cells receive >60 inputs. The N-methyl-d-aspartate (NMDA) components of eEPSCs were largest in T stellate, smaller in bushy, and smallest in octopus cells, and they were larger in neurons from younger than older mice. The average AMPA conductance of a unitary input is 22 ± 15 nS in both groups of bushy cells, <1.5 nS in octopus cells, and 4.6 ± 3 nS in T stellate cells. Sensitivity to philanthotoxin (PhTX) and rectification in the intracellular presence of spermine indicate that AMPA receptors that mediate eEPSCs in T stellate cells contain more GluR2 subunits than those in bushy and octopus cells. The AMPA components of eEPSCs were briefer in bushy (0.5 ms half-width) than in T stellate and octopus cells (0.8-0.9 ms half-width). Widening of eEPSCs in the presence of cyclothiazide (CTZ) indicates that desensitization shortens eEPSCs. CTZ-insensitive synaptic depression of the AMPA components was greater in bushy and octopus than in T stellate cells.
Information Content of the Low-Energy Electric Dipole Strength: Correlation Analysis
Reinhard, P.-G.; Nazarewicz, Witold
2013-01-01
Background: Recent experiments on the electric dipole (E1) polarizability in heavy nuclei have stimulated theoretical interest in the low-energy electric dipole strength, both isovector and isoscalar. Purpose: We study the information content carried by the electric dipole strength with respect to isovector and isoscalar indicators characterizing bulk nuclear matter and finite nuclei. To separate isoscalar and isovector modes, and low-energy strength and giant resonances, we analyze the E1 strength as a function of the excitation energy E and momentum transfer q. Methods: We use the self-consistent nuclear density functional theory with Skyrme energy density functionals, augmented by the random phase approximation, to compute the E1 strength and covariance analysis to assess correlations between observables. Calculations are performed for the spherical, doubly magic nuclei 208Pb and 132Sn. Results: We demonstrate that E1 transition densities in the low-energy region below the giant dipole resonance exhibit appreciable state dependence and multinodal structures, which are fingerprints of weak collectivity. The correlation between the accumulated low-energy strength and the symmetry energy is weak, and dramatically depends on the energy cutoff assumed. On the other hand, a strong correlation is predicted between isovector indicators and the accumulated isovector strength at E around 20 MeV and momentum transfer q 0.65 fm 1. Conclusions: Momentum- and coordinate-space patterns of the low-energy dipole modes indicate a strong fragmentation into individual particle-hole excitations. The global measure of low-energy dipole strength correlates poorly with the nuclear symmetry energy and other isovector characteristics. Consequently, our results do not support the suggestion that there exists a collective pygmy dipole resonance, which is a strong indicator of nuclear isovector properties. By considering nonzero values of momentum transfer, one can isolate individual
NASA Astrophysics Data System (ADS)
Qiu, Yiheng; Henderson, Thomas M.; Scuseria, Gustavo E.
2016-09-01
Spin-projected Hartree-Fock is written as a particle-hole excitation ansatz over a symmetry-adapted reference determinant. Remarkably, this expansion has an analytic expression that we were able to decipher. While the form of the polynomial expansion is universal, the excitation amplitudes need to be optimized. This is equivalent to the optimization of orbitals in the conventional projected Hartree-Fock framework of non-orthogonal determinants. Using the inverse of the particle-hole expansion, we similarity transform the Hamiltonian in a coupled-cluster style theory. The left eigenvector of the non-Hermitian Hamiltonian is constructed in a similar particle-hole expansion fashion, and we show that to numerically reproduce variational projected Hartree-Fock results, one needs as many pair excitations in the bra as the number of strongly correlated entangled pairs in the system. This single-excitation polynomial similarity transformation theory is an alternative to our recently presented double excitation theory, but supports projected Hartree-Fock and coupled cluster simultaneously rather than interpolating between them.
NASA Astrophysics Data System (ADS)
Qiu, Yiheng; Henderson, Thomas M.; Scuseria, Gustavo E.
2017-05-01
Projected Hartree-Fock theory provides an accurate description of many kinds of strong correlations but does not properly describe weakly correlated systems. Coupled cluster theory, in contrast, does the opposite. It therefore seems natural to combine the two so as to describe both strong and weak correlations with high accuracy in a relatively black-box manner. Combining the two approaches, however, is made more difficult by the fact that the two techniques are formulated very differently. In earlier work, we showed how to write spin-projected Hartree-Fock in a coupled-cluster-like language. Here, we fill in the gaps in that earlier work. Further, we combine projected Hartree-Fock and coupled cluster theory in a variational formulation and show how the combination performs for the description of the Hubbard Hamiltonian and for several small molecular systems.
NASA Astrophysics Data System (ADS)
Tkachov, Grigory; Hentschel, Martina
2009-05-01
Extended defects in graphene, such as linear edges, break the translational invariance and can also have an impact on the symmetries specific to massless Dirac-type quasiparticles in this material. The paper examines the consequences of a broken Dirac fermion parity in the framework of the effective boundary conditions varying from the Berry-Mondragon mass confinement to a zigzag edge. The parity breaking reflects the structural sublattice asymmetry of zigzag-type edges and is closely related to the previously predicted time-reversal symmetric edge states. We calculate the local and global densities of the edge states and show that they carry a specific polarization resembling to some extent that of spin-polarized materials. The lack of the parity leads to a non-analytical particle-hole asymmetry in the edge-state properties. We use our findings to interpret recently observed tunneling spectra in zigzag-terminated graphene. We also propose a graphene-based tunneling device where the particle-hole asymmetric edge states result in strongly nonlinear conductance-voltage characteristics, which could be used to manipulate the tunneling transport.
NASA Astrophysics Data System (ADS)
Heyde, K.; de Coster, C.; Decroix, B.; Wood, J. L.
2001-11-01
We discuss the recent observation of low-lying collective bands built on 0+ intruder states in the neutron-deficient Pb region. Next to an interpretation making use of a deformed mean-field, we also discuss thes excitations within the context of 2p-2h and 4p-4h proton excitations across the Z = 82 proton shell closure. Possibilities to embed this shell-model description within the context of interacting particle and hole pairs, or within an extended Interacting Boson Model (EIBM), is put forward. We also indicate the presence of symmetries within this EIBM.
Latella, Christopher; Hendy, Ashlee M; Pearce, Alan J; VanderWesthuizen, Dan; Teo, Wei-Peng
2016-01-01
Objective: The current understanding of acute neurophysiological responses to resistance training remains unclear. Therefore, we aimed to compare the time-course of acute corticospinal responses following a single-session heavy strength training (HST) of the biceps brachii (BB) muscle and provide quantifiable evidence based on the super-compensation model in an applied setting. Methods: Fourteen participants completed a counter-balanced, cross-over study that consisted of a single HST session (5 sets × 3 repetition maximum [RM]) of the BB and a control session (CON). Single- and paired-pulse transcranial magnetic stimulation (TMS) was used to measure changes in motor-evoked potential (MEP) amplitude, intra-cortical facilitation (ICF), short-interval intra-cortical inhibition (SICI) and long-interval intra-cortical inhibition (LICI). Additionally, maximal muscle compound wave (MMAX) and maximal voluntary isometric contraction (MVIC) of the BB were taken. All measures were taken at baseline, immediately post and at 10, 20, 30 min and 1, 2, 6, 24, 48 and 72 h post-training. Results: A significant reduction in MEP amplitude was observed immediately post training (P = 0.001), while MVIC (P < 0.001) and MMAX (P = 0.047) were reduced for up to 30 min post-training. An increase in MVIC (p < 0.001) and MMAX (p = 0.047) was observed at 6 h, while an increase in MEP amplitude (p = 0.014) was only observed at 48 and 72 h. No changes in SICI, ICF and LICI were observed. Conclusion: Our results suggest that: (1) acute changes in corticospinal measures returned to baseline in a shorter timeframe than the current super-compensation model (24-48 h) and (2) changes in corticospinal excitability post-HST may be modulated "downstream" of the primary motor cortex (M1).
Latella, Christopher; Hendy, Ashlee M.; Pearce, Alan J.; VanderWesthuizen, Dan; Teo, Wei-Peng
2016-01-01
Objective: The current understanding of acute neurophysiological responses to resistance training remains unclear. Therefore, we aimed to compare the time-course of acute corticospinal responses following a single-session heavy strength training (HST) of the biceps brachii (BB) muscle and provide quantifiable evidence based on the super-compensation model in an applied setting. Methods: Fourteen participants completed a counter-balanced, cross-over study that consisted of a single HST session (5 sets × 3 repetition maximum [RM]) of the BB and a control session (CON). Single- and paired-pulse transcranial magnetic stimulation (TMS) was used to measure changes in motor-evoked potential (MEP) amplitude, intra-cortical facilitation (ICF), short-interval intra-cortical inhibition (SICI) and long-interval intra-cortical inhibition (LICI). Additionally, maximal muscle compound wave (MMAX) and maximal voluntary isometric contraction (MVIC) of the BB were taken. All measures were taken at baseline, immediately post and at 10, 20, 30 min and 1, 2, 6, 24, 48 and 72 h post-training. Results: A significant reduction in MEP amplitude was observed immediately post training (P = 0.001), while MVIC (P < 0.001) and MMAX (P = 0.047) were reduced for up to 30 min post-training. An increase in MVIC (p < 0.001) and MMAX (p = 0.047) was observed at 6 h, while an increase in MEP amplitude (p = 0.014) was only observed at 48 and 72 h. No changes in SICI, ICF and LICI were observed. Conclusion: Our results suggest that: (1) acute changes in corticospinal measures returned to baseline in a shorter timeframe than the current super-compensation model (24–48 h) and (2) changes in corticospinal excitability post-HST may be modulated “downstream” of the primary motor cortex (M1). PMID:27990108
NASA Astrophysics Data System (ADS)
Volin, Dmytro
2012-10-01
This paper is devoted to integrable {{{g}{l} ({n} | {m})}} spin chains, which allow for formulation of the string hypothesis. Considering the thermodynamic limit of such spin chains, we derive linear functional equations that symmetrically treat holes and particles. The functional equations naturally organize different types of excitations into a pattern equivalent to the one of Y-system, and, not surprisingly, the Y-system can be easily derived from the functional equations. The Y-system is known to contain most of the information about the symmetry of the model, therefore we map the symmetry knowledge directly to the description of string excitations. Our analysis is applicable for highest weight representations which for some choice of the Kac-Dynkin diagram have only one nonzero Dynkin label. This generalizes known results for the AdS/CFT spectral problem and for the Hubbard model.
Few-valence-particle excitations around doubly magic {sup 132}Sn
Daly, P.J.; Zhang, C.T.; Bhattacharyya, P.
1996-11-01
Prompt {gamma}-ray cascades in neutron-rich nuclei around doubly-magic {sup 132}Sn have been studied using a {sup 248}Cm fission source. Yrast states located in the N = 82 isotones {sup 134}Te and {sup 135}I are interpreted as valence proton and neutron particle-hole core excitations with the help of shell model calculations employing empirical nucleon-nucleon interactions from both {sup 132}Sn and {sup 208}Pb regions.
Role of nuclear couplings in the inelastic excitation of weakly-bound neutron-rich nuclei
Dasso, C.H.; Lenzi, S.M.; Vitturi, A.
1996-12-31
Much effort is presently devoted to the study of nuclear systems far from the stability line. Particular emphasis has been placed in light systems such as {sup 11}Li, {sup 8}B and others, where the very small binding energy of the last particles causes their density distribution to extend considerably outside of the remaining nuclear core. Some of the properties associated with this feature are expected to characterize also heavier systems in the vicinity of the proton or neutron drip lines. It is by now well established that low-lying concentrations of multipole strength arise from pure configurations in which a peculiar matching between the wavelength of the continuum wavefunction of the particles and the range of the weakly-bound hole states occurs. To this end the authors consider the break-up of a weakly-bound system in a heavy-ion collision and focus attention in the inelastic excitation of the low-lying part of the continuum. They make use of the fact that previous investigations have shown that the multipole response in this region is not of a collective nature and describe their excited states as pure particle-hole configurations. Since the relevant parameter determining the strength distributions is the binding energy of the last bound orbital they find it most convenient to use single-particle wavefunctions generated by a sperical square-well potential with characteristic nuclear dimensions and whose depth has been adjusted to give rise to a situation in which the last occupied neutron orbital is loosely-bound. Spin-orbit couplings are, for the present purpose, ignored. The results of this investigation clearly indicate that nuclear couplings have the predominant role in causing projectile dissociation in many circumstances, even at bombarding energies remarkably below the Coulomb barrier.
NASA Astrophysics Data System (ADS)
Hu, Xiao-Dong
1997-11-01
The reactions 12C(n,p)12B,/ 14C(n,p)14B,/ 16O(n,p)16N,/ 26Mg(n,p)26Na and 30Si(n,p)30Al were studied at a neutron energy of 278 MeV using the charge-exchange facility at the TRIUMF accelerator laboratory in Vancouver, Canada. Excitation-energy spectra and differential cross sections for the observed excitations in these reactions were extracted over the momentum-transfer range from 1.2 to 2.5 fm-1 (θlab in 19o,/ 23o,/ 27o,/ 31o and 35o). The primary goal of this work was the study of T = 2 'stretched' particle-hole states, more specifically (/nu d5/2,/ /pi p3/2-1)/ 4/sp- states excited in 14B,/ (/nu f7/2,/pi d5/2-1)/ 6/sp- states excited in 26Na, and (/nu f7/2,/ /pi d5/2-1)/ 6/sp- states excited in 30Al. The identification of these states was based on: (1) comparison of the experimental cross section angular distribution with theoretical differential cross sections calculated with the distorted-wave-impulse approximation (DWIA); (2) comparison of the measured excitation energies with excitation energies of analog stretched states; and (3) comparison of the spectroscopic strength for these (n,p) reactions to (p,n) and (e,e') spectroscopic strengths. The T = 1 (/nu d5/2,/ /pi p3/2-1)/ 4/sp- 'stretched' states excited in 12B and 16N were also studied. For the 12C(n,p)12B reaction (on targets of CH2 and graphite), 4/sp- T = 1 strength at Ex = 4.25 MeV was observed and found to be consistent with previous measurements; this state was used for calibrating excitation-energy scales for the other targets and as a consistency check among the different experimental runs for this project.
Zhang, Bei; Sodickson, Daniel K; Lattanzi, Riccardo; Duan, Qi; Stoeckel, Bernd; Wiggins, Graham C
2012-04-01
In 7 T traveling wave imaging, waveguide modes supported by the scanner radiofrequency shield are used to excite an MR signal in samples or tissue which may be several meters away from the antenna used to drive radiofrequency power into the system. To explore the potential merits of traveling wave excitation for whole-body imaging at 7 T, we compare numerical simulations of traveling wave and TEM systems, and juxtapose full-wave electrodynamic simulations using a human body model with in vivo human traveling wave imaging at multiple stations covering the entire body. The simulated and in vivo traveling wave results correspond well, with strong signal at the periphery of the body and weak signal deep in the torso. These numerical results also illustrate the complicated wave behavior that emerges when a body is present. The TEM resonator simulation allowed comparison of traveling wave excitation with standard quadrature excitation, showing that while the traveling wave B +1 per unit drive voltage is much less than that of the TEM system, the square of the average B +1 compared to peak specific absorption rate (SAR) values can be comparable in certain imaging planes. Both systems produce highly inhomogeneous excitation of MR signal in the torso, suggesting that B(1) shimming or other parallel transmission methods are necessary for 7 T whole body imaging. Copyright © 2011 Wiley-Liss, Inc.
Sohn, Woon Yong; Brenner, Valérie; Gloaguen, Eric; Mons, Michel
2016-11-02
Conformer-selective IR gas phase spectroscopy and high level quantum chemistry methods have been used to characterise the diversity of local NH-π interactions between the π ring of a phenylalanine aromatic residue and the nearby main chain amide groups. The study of model systems shows how the amide NH stretch vibrational features, in the 3410-3460 cm(-1) frequency range, can be used to monitor the strength of these local π H-bonds, which is found to depend on both the backbone conformation and the aromatic side chain orientation. This is rationalized in terms of partial electron transfer between the π cloud and the main chain NH bonds, with the help of analysis tools based on Natural Bonding Orbitals and Non-Covalent Interactions plots. The experimental study, extended to the NH-π interactions when the Phe residue is excited in its first ππ* electronic state, also demonstrates the principle of the ππ* labelling technique, i.e. a selective labelling of those NH bonds in a peptide molecule that are in close contact with an aromatic ring, as an elegant tool for IR spectroscopic assignments. The validation of theoretical predictions against experimental data (frequency change upon excitation) eventually qualifies the use of the CC2 method for the description of the ππ* excited states of systems having a phenyl ring, both in terms of structure, vibrational modes and nature of excited states.
Zhang, Hong Lin; Sampson, D. H.
1989-02-01
Relativistic distorted wave collision strengths are given for the 88 possible transitions between the ground level and the excited levels with n = 3 and n = 4 in the 71 neon-like ions with nuclear charge number Z in the range 22 less than or equal to Z less than or equal to 92. The calculations are made for the six final, or scattered, electron energies E' = 0.008, 0.04, 0.10, 0.21, 0.41 and 0.75, where E' is in units of Z/sub eff//sup 2/ Rydbergs with Z/sub eff/ = Z /minus/ 7.5. In addition, the transition energies and electric dipole oscillator strengths are given. 10 refs., 4 tabs.
NASA Astrophysics Data System (ADS)
Zhao, J.; Wijayaratne, K.; Butler, A.; Yang, J.; Malliakas, C. D.; Chung, D. Y.; Louca, D.; Kanatzidis, M. G.; van Wezel, J.; Chatterjee, U.
2017-09-01
We report an in-depth angle-resolved photoemission spectroscopy study on 2 H -TaS2 , a canonical incommensurate charge density wave (CDW) system. This study demonstrates that just as in related incommensurate CDW systems, 2 H -TaSe2 and 2 H -NbSe2 , the energy gap (ΔCDW) of 2 H -TaS2 is localized along the K -centered Fermi surface barrels and is particle-hole asymmetric. The persistence of ΔCDW even at temperatures higher than the CDW transition temperature TCDW in 2 H -TaS2 , reflects the similar pseudogap behavior observed previously in 2 H -TaSe2 and 2 H -NbSe2 . However, in sharp contrast to 2 H -NbSe2 , where ΔCDW is nonzero only in the vicinity of a few "hot spots" on the inner K -centered Fermi surface barrels, ΔCDW in 2 H -TaS2 is nonzero along the entirety of both K -centered Fermi surface barrels. Based on a tight-binding model, we attribute this dichotomy in the momentum dependence and the Fermi surface specificity of ΔCDW between otherwise similar CDW compounds to the different orbital orientations of their electronic states that participate in the CDW pairing. Our results suggest that the orbital selectivity plays a critical role in the description of incommensurate CDW materials.
a Theoretical Study of Projectile Delta Excitations in
NASA Astrophysics Data System (ADS)
Jo, Yung
1995-01-01
An approach is proposed for the investigation of the projectile Delta excitations induced by charge exchange reactions in the intermediate energy region. The nuclear structure part of the formalism is based on the particle-hole model and the nuclear reaction part is treated within the plane-wave impulse approximation (PWIA). In the nuclear structure part, all important nuclear medium effects are included. We take into account the nucleon knock-out mode and the related nucleon particle -nucleon hole (NN^{-1}) correlations. In order to perform the calculations, we first set up coupled-channel (CC) equations for the excited nucleons. The Lanczos method is adopted to solve this CC equations. In this dissertation we study the contribution of the projectile delta excitation process to (p, n) reaction spectra from a nuclear target. The spin observables are also calculated and discussed.
Train to develop your upper and lower body strength in your muscles and bones by performing body-weight squats and push-ups.The Train Like an Astronaut project uses the excitement of exploration to...
NASA Astrophysics Data System (ADS)
Idini, A.; Potel, G.; Barranco, F.; Vigezzi, E.; Broglia, R. A.
2015-09-01
A complete characterization of the structure of nuclei can be obtained by combining information arising from inelastic scattering, Coulomb excitation, and γ -decay, together with one- and two-particle transfer reactions. In this way it is possible to probe both the single-particle and collective components of the nuclear many-body wave function resulting from the coupling of these modes and, as a result, diagonalizing the low-energy Hamiltonian. We address the question of how accurately such a description can account for experimental observations in the case of superfluid nuclei. Our treatment goes beyond the traditional approach, in which these properties are calculated separately, and most often for systems near closed shells, based on perturbative approximations (weak coupling). It is concluded that renormalizing empirically and on equal footing bare single-particle and collective motion of open-shell nuclei in terms of self-energy (mass) and vertex corrections (screening), as well as particle-hole and pairing interactions through particle-vibration coupling (PVC), leads to a detailed, quantitative account of the data, constraining the possible values of the k mass, of the 1S0 bare N N interaction, and of the PVC strengths within a rather narrow window.
Morgan, M Thomas; Bagchi, Pritha; Fahrni, Christoph J
2013-03-07
Cu(I)-responsive fluorescent probes based on a photoinduced electron transfer (PET) mechanism generally show incomplete fluorescence recovery relative to the intrinsic quantum yield of the fluorescence reporter. Previous studies on probes with an N-aryl thiazacrown Cu(I)-receptor revealed that the recovery is compromised by incomplete Cu(I)-N coordination and resultant ternary complex formation with solvent molecules. Building upon a strategy that successfully increased the fluorescence contrast and quantum yield of Cu(I) probes in methanol, we integrated the arylamine PET donor into the backbone of a hydrophilic thiazacrown ligand with a sulfonated triarylpyrazoline as a water-soluble fluorescence reporter. This approach was not only expected to disfavor ternary complex formation in aqueous solution but also to maximize PET switching through a synergistic Cu(I)-induced conformational change. The resulting water-soluble probe 1 gave a strong 57-fold fluorescence enhancement upon saturation with Cu(I) with high selectivity over other cations, including Cu(II), Hg(II), and Cd(II); however, the recovery quantum yield did not improve over probes with the original N-aryl thiazacrown design. Concluding from detailed photophysical data, including responses to acidification, solvent isotope effects, quantum yields, and time-resolved fluorescence decay profiles, the fluorescence contrast of 1 is compromised by inadequate coordination of Cu(I) to the weakly basic arylamine nitrogen of the PET donor and by fluorescence quenching via two distinct excited state proton transfer pathways operating under neutral and acidic conditions.
The interplay between nucleonic and nuclear spin-isospin excitations
NASA Astrophysics Data System (ADS)
Weise, W.
Following a brief review of pion-nucleon coupling in relativistic quark models and the introduction of the Δ(1232) at the quark level, we develop the nuclear spin-isospin response function in a framework of nucleons and Δ‧s interacting through exchange of mesons. The spin-isospin dependent particle-hole interaction will be elaborated and various different aspects of the Landau-Migdal parameter g‧ for nucleons and Δ‧s will be discussed. We summarize the evidence for broad Δ-hole states at high excitation energies (200-400 MeV). Then the impact of the existence of such Δ-hole excitations on the quenching of Gamow-Teller and magnetic isovector spin transitions at low energy is discussed in combination with conventional nuclear mechanisms like core polarization and ground state correlations.
Morgan, M. Thomas; Bagchi, Pritha; Fahrni, Christoph J.
2012-01-01
Cu(I)-responsive fluorescent probes based on a photoinduced electron transfer (PET) mechanism generally show incomplete fluorescence recovery relative to the intrinsic quantum yield of the fluorescence reporter. Previous studies on probes with an N-aryl thiazacrown Cu(I)-receptor revealed that the recovery is compromised by incomplete Cu(I)-N coordination and resultant ternary complex formation with solvent molecules. Building upon a strategy that successfully increased the fluorescence contrast and quantum yield of Cu(I) probes in methanol, we integrated the arylamine PET donor into the backbone of a hydrophilic thiazacrown ligand with a sulfonated triarylpyrazoline as a water-soluble fluorescence reporter. This approach was not only expected to disfavor ternary complex formation in aqueous solution but also to maximize PET switching through a synergistic Cu(I)-induced conformational change. The resulting water-soluble probe 1 gave a strong 57-fold fluorescence enhancement upon saturation with Cu(I) with high selectivity over other cations, including Cu(II), Hg(II), and Cd(II); however, the recovery quantum yield did not improve over probes with the original N-aryl thiazacrown design. Concluding from detailed photophysical data, including responses to acidification, solvent isotope effects, quantum yields, and time-resolved fluorescence decay profiles, the fluorescence contrast of 1 is compromised by inadequate coordination of Cu(I) to the weakly basic arylamine nitrogen of the PET donor and by fluorescence quenching via two distinct excited state proton transfer pathways operating under neutral and acidic conditions. PMID:23169532
NASA Astrophysics Data System (ADS)
Pradhan, Anil; Nahar, Sultana; Palay, Ethan; Eissner, Werner
2011-05-01
The aims of the Iron Project and the Rmax Project are detailed study of radiative and collisional processes of astrophysically abundant atoms and ions, mainly iron and iron-peak elements, over a wide energy range, from infra-red to X-rays. We will illustrate the dominance of high energy photoexciation-of-core (PEC) resonances in photoionization of Fe XVII due to strong coupling effects on dipole transition arrays 2p5 --> 2p4 (3 s , 3 d) in the core and examine PEC and non-PEC resonance strengths for their expanded role to incorporate inner-shell excitations for improved opacities. Comparisons show that the currently available cross sections from the Opacity Project are considerably underestimated. For Fe XIV, we present preliminary results from a large scale computation where 747 fine structure levels with n <= 10, l <= 9, and 0.5 <= J <= 9.5, and 71,407 electric dipole allowed fine structure transitions have been obtained. We will also demonstrate the fine structure effects on the collision strengths and in very low energy photoionzation for in nebular oxygen abundance. Partial Supports: NSF, DOE
NASA Astrophysics Data System (ADS)
Kaneshita, Eiji; Tohyama, Takami
2011-03-01
We investigate the spin wave excitation in the metallic antiferromagnetic phase of iron pnictide superconductors based on calculated neutron scattering spectra by mean-field calculations with a random phase approximation in a five-band itinerant model [E.K. & T.T., RPB 82, 094441 (2010)]. The calculated excitation spectra reproduce well spin-wave dispersions observed in inelastic neutron scattering, with a realistic magnetic moment for CaFe 2 As 2 . A particle-hole gap is found to be crucial to obtain consistent results; we predict the spin wave in LaFeAsO disappears at a lower energy than in CaFe 2 As 2 .
Bray, James William [Niskayuna, NY; Garces, Luis Jose [Niskayuna, NY
2012-03-13
The disclosed technology is a cryogenic static exciter. The cryogenic static exciter is connected to a synchronous electric machine that has a field winding. The synchronous electric machine is cooled via a refrigerator or cryogen like liquid nitrogen. The static exciter is in communication with the field winding and is operating at ambient temperature. The static exciter receives cooling from a refrigerator or cryogen source, which may also service the synchronous machine, to selected areas of the static exciter and the cooling selectively reduces the operating temperature of the selected areas of the static exciter.
Itinerant Magnetic Excitations in Antiferromagnetic CaFe2As2
Diallo, S.; Antropov, V.; Perring, T.; Broholm, C.; Pulikkotil, J.; Ni, N.; Bud'ko, S.; Canfield, P.; Kreyssig, A.; Goldman, A.; McQueeney, R.
2009-05-07
Neutron scattering measurements of the magnetic excitations in single crystals of antiferromagnetic CaFe{sub 2}As{sub 2} reveal steeply dispersive and well-defined spin waves up to an energy of {approx}100 meV. Magnetic excitations above 100 meV and up to the maximum energy of 200 meV are however broader in energy and momentum than the experimental resolution. While the low energy modes can be fit to a Heisenberg model, the total spectrum cannot be described as arising from excitations of a local moment system. Ab initio calculations of the dynamic magnetic susceptibility suggest that the high energy behavior is dominated by the damping of spin waves by particle-hole excitations.
NASA Astrophysics Data System (ADS)
Minola, M.; Dellea, G.; Gretarsson, H.; Peng, Y. Y.; Lu, Y.; Porras, J.; Loew, T.; Yakhou, F.; Brookes, N. B.; Huang, Y. B.; Pelliciari, J.; Schmitt, T.; Ghiringhelli, G.; Keimer, B.; Braicovich, L.; Le Tacon, M.
2015-05-01
We used resonant inelastic x-ray scattering (RIXS) with and without analysis of the scattered photon polarization, to study dispersive spin excitations in the high temperature superconductor YBa2Cu3O6 +x over a wide range of doping levels (0.1 ≤x ≤1 ). The excitation profiles were carefully monitored as the incident photon energy was detuned from the resonant condition, and the spin excitation energy was found to be independent of detuning for all x . These findings demonstrate that the largest fraction of the spin-flip RIXS profiles in doped cuprates arises from magnetic collective modes, rather than from incoherent particle-hole excitations as recently suggested theoretically [Benjamin et al. Phys. Rev. Lett. 112, 247002 (2014)]. Implications for the theoretical description of the electron system in the cuprates are discussed.
NASA Astrophysics Data System (ADS)
Khaneja, Navin
2017-09-01
The paper describes the design of broadband chirp excitation pulses. We first develop a three stage model for understanding chirp excitation in NMR. We then show how a chirp π pulse can be used to refocus the phase of the chirp excitation pulse. The resulting magnetization still has some phase dispersion in it. We show how a combination of two chirp π pulses instead of one can be used to eliminate this dispersion, leaving behind a small residual phase dispersion. The excitation pulse sequence presented here allows exciting arbitrary large bandwidths without increasing the peak rf-amplitude. Experimental excitation profiles for the residual HDO signal in a sample of 99.5 % D2O are displayed as a function of resonance offset. Although methods presented in this paper have appeared elsewhere, we present complete analytical treatment that elucidates the working of these methods.
NASA Technical Reports Server (NTRS)
Mcpeak, W. L.
1975-01-01
A new exciter switch assembly has been installed at the three DSN 64-m deep space stations. This assembly provides for switching Block III and Block IV exciters to either the high-power or 20-kW transmitters in either dual-carrier or single-carrier mode. In the dual-carrier mode, it provides for balancing the two drive signals from a single control panel located in the transmitter local control and remote control consoles. In addition to the improved switching capabilities, extensive monitoring of both the exciter switch assembly and Transmitter Subsystem is provided by the exciter switch monitor and display assemblies.
ERIC Educational Resources Information Center
Wright, Bradford L.
1975-01-01
Advocates the creation of swimming pool oscillations as part of a general investigation of mechanical oscillations. Presents the equations, procedure for deriving the slosh modes, and methods of period estimation for exciting swimming pool oscillations. (GS)
NASA Astrophysics Data System (ADS)
Panas, Itai
2011-01-01
Two Bi2201 model systems are employed to demonstrate how, beside the Cu-O σ band, a second band of purely O 2pπ character can be made to cross the Fermi level due to its sensitivity to the local crystal field. This result is employed to explain the particle-hole symmetry breaking across the pseudogap recently reported by Shen and co-workers [see M. Hashimoto , Nature Phys.10.1038/nphys1632 6, 414 (2010).]. Support for a two-bands-on-a-checkerboard candidate mechanism for high-Tc superconductivity is claimed. Analysis based on band structures, partial density of states, and sum over states densities scanning-tunneling-microscopy-type images is provided.
NASA Astrophysics Data System (ADS)
Szybisz, Leszek
1996-03-01
Elementary excitations in rather thick symmetric films of liquid 4He at T=0 K are investigated. They are characterized by a momentum ħq parallel to the surface and may be described by bound or continuum states, which are obtained by solving a Bogoliubov-type equation formulated within the framework of the paired-phonon analysis and the hypernetted-chain approximation. Films of coverages nc=0.3 and 0.4 Å-2 confined by simple Gaussian potentials are studied. The excitation spectrum is numerically evaluated by discretizing the associated eigenvalue problem in a finite box. The evolution of the energy levels as a function of the box size is explored. Examples of the calculated energies and wave functions are displayed in a series of figures. Two differing sorts of continuum states may be distinguished. Depending on the behavior of their excitation energies as a function of the box size on the one hand, and the spatial distribution of their wave functions inside the film and in the asymptotic region far apart from the interface layer on the other, the continuum solutions can be separated into two classes of excitations: (a) the ``regular'' continuum states and (b) the ``resonant modes.'' The matrix elements of the particle-hole potential and the penetration factors of the most important states are examined. The lowest-lying branch of states is always bound and for qexcitations of the system. Our results support the occurrence of the repulsion between ``bulk'' and ripplon excitations proposed by Pitaevskii and Stringari. The strength of contributions originated from different normal modes to the liquid structure function is evaluated. While for very small values of momenta (q<=0.2 A
Takeuchi, Asia; Ahern, Terence L.; Henderson, Sean O.
2011-01-01
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. PMID:21691475
2004-12-01
for purposes of vocoding in high noise environments: Task 1: Estimation of voiced excitation functions using skin surface vibration...High Noise Environments. The work on “ Voiced Excitations” shows that the surface vibrations of neck skin, during voicing , carry a great deal of...5 in this report). For field use, it may be better to obtain data from another location on the neck or face. A pressure function of voiced speech is
Mukhopadhyay, N.C.
1986-01-01
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. (LEW)
Stoller, R J
1976-08-01
Sexual excitement depends on a scenario the person to be aroused has been writing since childhood. The story is an adventure, an autobiography disguised as fiction, in which the hero/heroine hides crucial intrapsychic conflicts, mysteries, screen memories of actual traumatic events and the resolution of these elements into a happy ending, best celebrated by orgasm. The function of the fantasy is to take these painful experiences and convert them to pleasure-triumph. In order to sharpen excitement-the vibration between the fear of original traumas repeating and the hope of a pleasurable conclusion this time-one introduces into the story elements of risk (approximations of the trauma) meant to prevent boredom and safety factors (sub-limnal signals to the storyteller that the risk are not truly dangerous). Sexual fantasy can be studied by means of a person's daydreams (including those chosen in magazines, books, plays, television, movies, and outright pornography), masturbatory behavior, object choice, foreplay, techniques of intercourse, or postcoital behavior.
ERIC Educational Resources Information Center
Londeree, Ben R.
1981-01-01
Postural deviations resulting from strength and flexibility imbalances include swayback, scoliosis, and rounded shoulders. Screening tests are one method for identifying strength problems. Tests for the evaluation of postural problems are described, and exercises are presented for the strengthening of muscles. (JN)
ERIC Educational Resources Information Center
Londeree, Ben R.
1981-01-01
Postural deviations resulting from strength and flexibility imbalances include swayback, scoliosis, and rounded shoulders. Screening tests are one method for identifying strength problems. Tests for the evaluation of postural problems are described, and exercises are presented for the strengthening of muscles. (JN)
Contribution of excited states to stellar weak-interaction rates in odd-A nuclei
NASA Astrophysics Data System (ADS)
Sarriguren, P.
2016-05-01
Weak-interaction rates, including β decay and electron capture, are studied in several odd-A nuclei in the p f -shell region at various densities and temperatures of astrophysical interest. Special attention is paid to the relative contribution to these rates of thermally populated excited states in the decaying nucleus. The nuclear structure involved in the weak processes is studied within a quasiparticle random-phase approximation with residual interactions in both particle-hole and particle-particle channels on top of a deformed Skyrme Hartree-Fock mean field with pairing correlations. In the range of densities and temperatures considered, it is found that the total rates do not differ much from the rates of the ground state fully populated. In any case, the changes are not larger than the uncertainties due to the nuclear-model dependence of the rates.
Recurrent Excitation in Neocortical Circuits
NASA Astrophysics Data System (ADS)
Douglas, Rodney J.; Koch, Christof; Mahowald, Misha; Martin, Kevan A. C.; Suarez, Humbert H.
1995-08-01
The majority of synapses in the mammalian cortex originate from cortical neurons. Indeed, the largest input to cortical cells comes from neighboring excitatory cells. However, most models of cortical development and processing do not reflect the anatomy and physiology of feedback excitation and are restricted to serial feedforward excitation. This report describes how populations of neurons in cat visual cortex can use excitatory feedback, characterized as an effective "network conductance," to amplify their feedforward input signals and demonstrates how neuronal discharge can be kept proportional to stimulus strength despite strong, recurrent connections that threaten to cause runaway excitation. These principles are incorporated into models of cortical direction and orientation selectivity that emphasize the basic design principles of cortical architectures.
... strengthens your heart and lungs. When you strength train with weights, you're using your muscles to ... see there are lots of different ways to train with weights. Try a few good basic routines ...
Anisotropic softening of magnetic excitations along the nodal direction in superconducting cuprates.
Guarise, M; Dalla Piazza, B; Berger, H; Giannini, E; Schmitt, T; Rønnow, H M; Sawatzky, G A; van den Brink, J; Altenfeld, D; Eremin, I; Grioni, M
2014-12-18
The high-Tc cuprate superconductors are close to antiferromagnetic order. Recent measurements of magnetic excitations have reported an intriguing similarity to the spin waves--magnons--of the antiferromagnetic insulating parent compounds, suggesting that magnons may survive in damped, broadened form throughout the phase diagram. Here we show by resonant inelastic X-ray scattering on Bi(2)Sr(2)CaCu(2)O(8+δ) (Bi-2212) that the analogy with spin waves is only partial. The magnon-like features collapse along the nodal direction in momentum space and exhibit a photon energy dependence markedly different from the Mott-insulating case. These observations can be naturally described by the continuum of charge and spin excitations of correlated electrons. The persistence of damped magnons could favour scenarios for superconductivity built from quasiparticles coupled to spin fluctuations. However, excitation spectra composed of particle-hole excitations suggest that superconductivity emerges from a coherent treatment of electronic spin and charge in the form of quasiparticles with very strong magnetic correlations.
N=50 core excited states studied in the 4696Pd50 nucleus
NASA Astrophysics Data System (ADS)
Palacz, M.; Nyberg, J.; Grawe, H.; Sieja, K.; de Angelis, G.; Bednarczyk, P.; Blazhev, A.; Curien, D.; Dombradi, Z.; Dorvaux, O.; Ekman, J.; Gałkowski, J.; Górska, M.; Iwanicki, J.; Jaworski, G.; Kownacki, J.; Ljungvall, J.; Moszyński, M.; Nowacki, F.; Rudolph, D.; Sohler, D.; Wolski, D.; Ziębliński, M.
2012-07-01
The four-proton hole 96Pd neighbor of the doubly-magic 100Sn nucleus was studied in-beam, using a fusion-evaporation reaction of a 58Ni beam on a 45Sc target. States of 96Pd were established up to an excitation energy of 9707 keV. A core-excited odd-parity isomer with T1/2=37.7(1.1) ns was identified. Shell model calculations were performed in four different model spaces. Even-parity states of 96Pd are very well reproduced in large-scale shell model (LSSM) calculations in which excitations are allowed of up to five g9/2 protons and neutrons across the N=Z=50 gap, to the g7/2, d5/2, d3/2, and s1/2 orbitals. The odd-parity isomer can be only qualitatively interpreted though, employing calculation in the full fpg shell model space, with just one particle-hole core excitation.
Damped spin-wave excitations in the itinerant antiferromagnet γ -Fe0.7Mn0.3
NASA Astrophysics Data System (ADS)
Ibuka, S.; Itoh, S.; Yokoo, T.; Endoh, Y.
2017-06-01
The collective spin-wave excitations in the antiferromagnetic state of γ -Fe0.7Mn0.3 were investigated using the inelastic neutron-scattering technique. The spin excitations remain isotropic up to high excitation energy, ℏ ω =78 meV. The excitations gradually become broad and damped above 40 meV. The damping parameter γ reaches 110(16) meV at ℏ ω =78 meV, which is much larger than that for other metallic compounds, e.g., CaFe2As2 (24 meV), La2 -2 xSr1 +2 xMn2O7 (52-72 meV), and Mn90Cu10 (88 meV). In addition, the spin-wave dispersion shows a deviation from the relation (ℏω ) 2=c2q2+Δ2 above 40 meV. The group velocity above this energy increases to 470(40) meVÅ, which is higher than that at the low energies, c =226 (5 ) meVÅ. These results could suggest that the spin-wave excitations merge with the continuum of the individual particle-hole excitations at 40 meV.
Oscillator strengths and collision strengths for S v
NASA Technical Reports Server (NTRS)
Van Wyngaarden, W. L.; Henry, R. J. W.
1981-01-01
Observations of the optical extreme-ultraviolet spectrum of the Jupiter planetary system during the Voyager space mission revealed bright emission lines of some sulfur ions. The spectra of the torus at the orbit of Io are likely to contain S V lines. The described investigation provides oscillator strengths and collision strengths for the first four UV lines. The collision strengths from the ground state to four other excited states are also obtained. Use is made of a two-state calculation which is checked for convergence for some transitions by employing a three-state or a four-state approximation. Target wave functions for S V are calculated so that the oscillator strengths calculated in dipole length and dipole velocity approximations agree within 5%.
NASA Astrophysics Data System (ADS)
Gurgi, L. A.; Regan, P. H.; Daniel, T.; Podolyák, Zs.; Bruce, A. M.; Mason, P. J. R.; Mǎrginean, N.; Mǎrginean, R.; Werner, V.; Alharbi, T.; Alkhomashi, N.; Bajoga, A. D.; Britton, R.; Cǎta-Danil, I.; Carroll, R. J.; Deleanu, D.; Bucurescu, D.; Florea, N.; Gheorghe, I.; Ghita, D. G.; Glodariu, T.; Lice, R.; Mihai, C.; Mulholland, K. F.; Negret, A.; Olacel, A.; Roberts, O. J.; Sava, T.; Söderström, P.-A.; Stroe, L.; Suvaila, R.; Toma, S.; Wilson, E.; Wood, R. T.
2017-08-01
This paper presents precision measurements of electromagnetic decay probabilities associated with electric dipole transitions in the prolate-deformed nucleus 183Re. The nucleus of interest was formed using the fusion evaporation reaction 180Hf(7Li,4n)183Re at a beam energy of 30 MeV at the tandem accelerator at the HH-IFIN Institute, Bucharest Romania. Coincident decay gamma rays from near-yrast cascades were detected using the combined HPGe-LaBr3 detector array ROSPHERE. The time differences between cascade gamma rays were measured using the LaBr3 detectors to determine the half-lives of the two lowest lying spin-parity 9/2- states at excitation energies of 496 and 617 keV to be 5.65(5) and 2.08(3) ns respectively. The deduced E1 transition rates from these two states are discussed in terms of the K-hindrance between the low-lying structures in this prolate-deformed nucleus.
RESONANT CAVITY EXCITATION SYSTEM
Baker, W.R.; Kerns, Q.A.; Riedel, J.
1959-01-13
An apparatus is presented for exciting a cavity resonator with a minimum of difficulty and, more specifically describes a sub-exciter and an amplifier type pre-exciter for the high-frequency cxcitation of large cavities. Instead of applying full voltage to the main oscillator, a sub-excitation voltage is initially used to establish a base level of oscillation in the cavity. A portion of the cavity encrgy is coupled to the input of the pre-exciter where it is amplified and fed back into the cavity when the pre-exciter is energized. After the voltage in the cavity resonator has reached maximum value under excitation by the pre-exciter, full voltage is applied to the oscillator and the pre-exciter is tunned off. The cavity is then excited to the maximum high voltage value of radio frequency by the oscillator.
Crossover from spin waves to diffusive spin excitations in underdoped Ba(Fe1-xCox)2 As2
Tucker, G S; Fernandes, R M; Pratt, D K; Thaler, A; Ni, N; Marty, K; Christianson, A D; Lumsden, M D; Sales, B C; Sefat, A S; Bud'ko, S L; Canfield, P C; Kreyssig, A; Goldman, A I; McQueeney, R J
2014-05-01
Using inelastic neutron scattering, we show that the onset of superconductivity in underdoped Ba(Fe1-xCox)2As2 coincides with a crossover from well-defined spin waves to overdamped and diffusive spin excitations. This crossover occurs despite the presence of long-range stripe antiferromagnetic order for samples in a compositional range from x=0.04 to 0.055, and is a consequence of the shrinking spin-density wave gap and a corresponding increase in the particle-hole (Landau) damping. The latter effect is captured by a simple itinerant model relating Co doping to changes in the hot spots of the Fermi surface. We argue that the overdamped spin fluctuations provide a pairing mechanism for superconductivity in these materials.
Howe, Lauren C; Krosnick, Jon A
2017-01-03
Attitude strength has been the focus of a huge volume of research in psychology and related sciences for decades. The insights offered by this literature have tremendous value for understanding attitude functioning and structure and for the effective application of the attitude concept in applied settings. This is the first Annual Review of Psychology article on the topic, and it offers a review of theory and evidence regarding one of the most researched strength-related attitude features: attitude importance. Personal importance is attached to an attitude when the attitude is perceived to be relevant to self-interest, social identification with reference groups or reference individuals, and values. Attaching personal importance to an attitude causes crystallizing of attitudes (via enhanced resistance to change), effortful gathering and processing of relevant information, accumulation of a large store of well-organized relevant information in long-term memory, enhanced attitude extremity and accessibility, enhanced attitude impact on the regulation of interpersonal attraction, energizing of emotional reactions, and enhanced impact of attitudes on behavioral intentions and action. Thus, important attitudes are real and consequential psychological forces, and their study offers opportunities for addressing behavioral change.
NASA Technical Reports Server (NTRS)
Beecher, L. C.; Williams, F. T.
1970-01-01
Gas-driven vibration exciter produces a sinusoidal excitation function controllable in frequency and in amplitude. It allows direct vibration testing of components under normal loads, removing the possibility of component damage due to high static pressure.
Butler, J.N.; Shukla, S.
1995-05-01
The experimental status of excited charmed mesons is reviewed and is compared to theoretical expectations. Six states have been observed and their properties are consistent with those predicted for excited charmed states with orbital angular momentum equal to one.
Pearce, A J; Hendy, A; Bowen, W A; Kidgell, D J
2013-12-01
Cross-education strength training has being shown to retain strength and muscle thickness in the immobilized contralateral limb. Corticospinal mechanisms have been proposed to underpin this phenomenon; however, no transcranial magnetic stimulation (TMS) data has yet been presented. This study used TMS to measure corticospinal responses following 3 weeks of unilateral arm training on the contralateral, immobilize arm. Participants (n = 28) were randomly divided into either immobilized strength training (Immob + train) immobilized no training (Immob) or control. Participants in the immobilized groups had their nondominant arm rested in a sling, 15 h/day for 3 weeks. The Immob + train group completed unilateral arm curl strength training, while the Immob and control groups did not undertake training. All participants were tested for corticospinal excitability, strength, and muscle thickness of both arms. Immobilization resulted in a group x time significant reduction in strength, muscle thickness and corticospinal excitability for the untrained limb of the Immob group. Conversely, no significant change in strength, muscle thickness, or corticospinal excitability occurred in the untrained limb of the Immob + train group. These results provide the first evidence of corticospinal mechanisms, assessed by TMS, underpinning the use of unilateral strength training to retain strength and muscle thickness following immobilization of the contralateral limb.
Broadband single-molecule excitation spectroscopy
Piatkowski, Lukasz; Gellings, Esther; van Hulst, Niek F.
2016-01-01
Over the past 25 years, single-molecule spectroscopy has developed into a widely used tool in multiple disciplines of science. The diversity of routinely recorded emission spectra does underpin the strength of the single-molecule approach in resolving the heterogeneity and dynamics, otherwise hidden in the ensemble. In early cryogenic studies single molecules were identified by their distinct excitation spectra, yet measuring excitation spectra at room temperature remains challenging. Here we present a broadband Fourier approach that allows rapid recording of excitation spectra of individual molecules under ambient conditions and that is robust against blinking and bleaching. Applying the method we show that the excitation spectra of individual molecules exhibit an extreme distribution of solvatochromic shifts and distinct spectral shapes. Importantly, we demonstrate that the sensitivity and speed of the broadband technique is comparable to that of emission spectroscopy putting both techniques side-by-side in single-molecule spectroscopy. PMID:26794035
Acoustically excited heated jets. 1: Internal excitation
NASA Technical Reports Server (NTRS)
Lepicovsky, J.; Ahuja, K. K.; Brown, W. H.; Salikuddin, M.; Morris, P. J.
1988-01-01
The effects of relatively strong upstream acoustic excitation on the mixing of heated jets with the surrounding air are investigated. To determine the extent of the available information on experiments and theories dealing with acoustically excited heated jets, an extensive literature survey was carried out. The experimental program consisted of flow visualization and flowfield velocity and temperature measurements for a broad range of jet operating and flow excitation conditions. A 50.8-mm-diam nozzle was used for this purpose. Parallel to the experimental study, an existing theoretical model of excited jets was refined to include the region downstream of the jet potential core. Excellent agreement was found between theory and experiment in moderately heated jets. However, the theory has not yet been confirmed for highly heated jets. It was found that the sensitivity of heated jets to upstream acoustic excitation varies strongly with the jet operating conditions and that the threshold excitation level increases with increasing jet temperature. Furthermore, the preferential Strouhal number is found not to change significantly with a change of the jet operating conditions. Finally, the effects of the nozzle exit boundary layer thickness appear to be similar for both heated and unheated jets at low Mach numbers.
Resonant plasmon-axion excitations induced by charge density wave order in a Weyl semimetal
NASA Astrophysics Data System (ADS)
Redell, Matthew D.; Mukherjee, Shantanu; Lee, Wei-Cheng
2016-06-01
We investigate the charge excitations of a Weyl semimetal in the axionic charge density wave (axionic CDW) state. While it has been shown that the topological response (anomalous Hall conductivity) is protected against the CDW state, we find that the long-wavelength plasmon excitation is radically influenced by the dynamics of the CDW order parameter. In the normal state, we show that an undamped collective mode should exist at q ⃗≈Q⃗CDW if there is an attractive interaction favoring the formation of the CDW state. The undamped nature of this collective mode is attributed to a gaplike feature in the particle-hole continuum at q ⃗≈Q⃗CDW due to the chirality of the Weyl nodes, which is not seen in other materials with CDW instability. In the CDW state, the long-wavelength plasmon excitations become more dispersive due to the additional interband scattering not allowed in the normal state. Moreover, because the translational symmetry is spontaneously broken, umklapp scattering, the process conserving the total momentum only up to n Q⃗CDW , with n an integer and Q⃗CDW the ordering wave vector, emerges in the CDW state. We find that the plasmon excitation couples to the phonon mode of the CDW order via the umklapp scattering, leading to two branches of resonant collective modes observable in the density-density correlation function at q ⃗≈0 and q ⃗≈Q⃗CDW . Based on our analysis, we propose that measuring these resonant plasmon-axion excitations around q ⃗≈0 and q ⃗≈Q⃗CDW by momentum-resolved electron energy loss spectroscopy could serve as a reliable way to detect the axionic CDW state in Weyl semimetals.
Excitation of interstellar hydrogen chloride
NASA Technical Reports Server (NTRS)
Neufild, David A.; Green, Sheldon
1994-01-01
We have computed new rate coefficients for the collisional excitation of HCl by He, in the close-coupled formalism and using an interaction potential determined recently by Willey, Choong, & DeLucia. Results have been obtained for temperatures between 10 K and 300 K. With the use of the infinite order sudden approximation, we have derived approximate expressions of general applicability which may be used to estimate how the rate constant for a transition (J to J prime) is apportioned among the various hyperfine states F prime of the final state J prime. Using these new rate coefficients, we have obtained predictions for the HCl rotational line strengths expected from a dense clump of interstellar gas, as a function of the HCl fractional abundance. Over a wide range of HCl abundances, we have found that the line luminosities are proportional to abundance(exp 2/3), a general result which can be explained using a simple analytical approximation. Our model for the excitation of HCl within a dense molecular cloud core indicates that the J = 1 goes to 0 line strengths measured by Blake, Keene, & Phillips toward the Orion Molecular Cloud (OMC-1) imply a fractional abundance n(HCl)/n(H2) approximately 2 x 10(exp -9), a value which amounts to only approximately 0.3% of the cosmic abundance of chlorine nuclei. Given a fractional abundance of 2 x 10(exp -9), the contribution of HCl emission to the total radiative cooling of a dense clump is small. For Orion, we predict a flux approximately 10(exp -19) W/sq cm for the HCl J = 3 goes to 2 line near 159.8 micrometers, suggesting that the strength of this line could be measured using the Infrared Space Observatory.
NASA Astrophysics Data System (ADS)
Ullrich, C. A.; Vignale, G.
1998-09-01
It is well known that high-frequency collective excitations in electronic systems are not Landau damped, i.e., they cannot decay effectively into single particle-hole pairs. The leading damping mechanism in this regime is instead provided by dynamical exchange and correlation effects, such as multipair production. These effects are not captured by the widely used adiabatic local-density approximation (ALDA), which accounts for Landau damping only. In the recently developed time-dependent current density-functional formalism [G. Vignale, C. A. Ullrich, and S. Conti, Phys. Rev. Lett. 79, 4878 (1997)], exchange and correlation enter as viscoelastic stresses in the electron fluid, causing an additional damping that is not contained in the ALDA. We use this theory to derive an explicit formula for the linewidth of collective electronic excitations that are not Landau damped. The formula is then applied to calculate the linewidth of collective modes in two-dimensional (2D) quantum strips. In comparison with the corresponding modes in the homogeneous 2D electron gas, we find an order-of-magnitude enhancement of the linewidth due to the nonuniformity of the system.
Kidgell, D J; Frazer, A K; Daly, R M; Rantalainen, T; Ruotsalainen, I; Ahtiainen, J; Avela, J; Howatson, G
2015-08-06
Strength training of one limb results in a substantial increase in the strength of the untrained limb, however, it remains unknown what the corticospinal responses are following either eccentric or concentric strength training and how this relates to the cross-education of strength. The aim of this study was to determine if eccentric or concentric unilateral strength training differentially modulates corticospinal excitability, inhibition and the cross-transfer of strength. Changes in contralateral (left limb) concentric strength, eccentric strength, motor-evoked potentials, short-interval intracortical inhibition and silent period durations were analyzed in groups of young adults who exercised the right wrist flexors with either eccentric (N=9) or concentric (N=9) contractions for 12 sessions over 4weeks. Control subjects (N=9) did not train. Following training, both groups exhibited a significant strength gain in the trained limb (concentric group increased concentric strength by 64% and eccentric group increased eccentric strength by 62%) and the extent of the cross-transfer of strength was 28% and 47% for the concentric and eccentric group, respectively, which was different between groups (P=0.031). Transcranial magnetic stimulation revealed that eccentric training reduced intracortical inhibition (37%), silent period duration (15-27%) and increased corticospinal excitability (51%) compared to concentric training for the untrained limb (P=0.033). There was no change in the control group. The results show that eccentric training uniquely modulates corticospinal excitability and inhibition of the untrained limb to a greater extent than concentric training. These findings suggest that unilateral eccentric contractions provide a greater stimulus in cross-education paradigms and should be an integral part of the rehabilitative process following unilateral injury to maximize the response. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.
Stretched-State Excitations with the
NASA Astrophysics Data System (ADS)
Garcia, Luis Alberto Casimiro
Neutron time-of-fight spectra were obtained for the ^{14}C(p,n) ^{14}N, ^{18 }O(p,n)^{18}F, and ^{30}Si(p,n) ^{30}P reactions at 135 MeV with the beam-swinger system at the Indiana University Cyclotron Facility. Excitation-energy spectra and the differential cross sections for the observed excitations in these reactions were extracted over the momentum transfer range from 0 to 2.7 fm^{-1}. The primary goal of this work was to obtain the strengths and distributions for the "stretched" states. The identification of these states was based on comparisons of the theoretical differential cross sections, performed in a DWIA formalism, with the experimental cross sections. Isospin assignments were based primarily on comparisons of the measured (p,n) and (e,e^') spectroscopic strengths. Candidate (pid_ {5/2},nu{rm p}_sp {3/2}{-1}), J^ pi = 4 ^- T = 0, 1 and 2, 1 hbaromega states, were identified at E_{x} = 8.5, 13.8, 19.5, and 26.7 MeV in the ^{14}C(p,n) ^{14}N reaction, and the corresponding isovector strengths were extracted. The observed 4^--state excitation energies and the strengths are in good agreement with the analog T = 1 and 2, 4^--states observed in the (e,e^') reaction. Large -basis shell-model calculations were found to predict reasonably well the excitation energies; however, these calculations overpredict the strength by a factor of 2, for the T = 1 and 2 components. In the ^{18}O(p,n) ^{18}F reaction at 135 MeV, (pi d_{5/2},nu {rm d}_sp{5/2}{-1 }) 5^+ T = 0 0hbaromega strength was observed, concentrated in a single state, at E_{x} = 1.1 MeV, with 75% of the extreme-single-particle-model (ESPM) strength, in good agreement with a shell-model calculation. No 6^- 1hbaromega strength was observed in this reaction. Candidate (pi {rm d}_{5/2},nu p _sp{3/2}{-1}) J ^pi = 4^- T = 0, 1 and 2, 1hbaromega states, were identified at E_{x} = 3.9, 9.4, 10.2, 11.4, 12.0, 14.4, 15.3, 17.3, 18.0, 19.7, 21.4, and 23.4 MeV. The observed 4^- T = 2 state excitation energies and
RESONANT CAVITY EXCITATION SYSTEM
Baker, W.R.
1959-08-01
A cavity excitation circuit is described for rapidly building up and maintaining high-level oscillations in a resonant cavity. The circuit overcomes oscillation buildup slowing effects such as ion locking in the cavity by providing for the selective application of an amplified accelerating drive signal to the main cavity exciting oscillator during oscillation buildup and a direct drive signal to the oscillator thereafter.
Octupole strength in the neutron-rich calcium isotopes
NASA Astrophysics Data System (ADS)
Riley, L. A.; McPherson, D. M.; Agiorgousis, M. L.; Baugher, T. R.; Bazin, D.; Bowry, M.; Cottle, P. D.; DeVone, F. G.; Gade, A.; Glowacki, M. T.; Gregory, S. D.; Haldeman, E. B.; Kemper, K. W.; Lunderberg, E.; Noji, S.; Recchia, F.; Sadler, B. V.; Scott, M.; Weisshaar, D.; Zegers, R. G. T.
2016-04-01
Low-lying excited states of the neutron-rich calcium isotopes Ca-5248 have been studied via γ -ray spectroscopy following inverse-kinematics proton scattering on a liquid hydrogen target using the GRETINA γ -ray tracking array. The energies and strengths of the octupole states in these isotopes are remarkably constant, indicating that these states are dominated by proton excitations.
Application of Strength Diagnosis.
ERIC Educational Resources Information Center
Newton, Robert U.; Dugan, Eric
2002-01-01
Discusses the various strength qualities (maximum strength, high- and low-load speed strength, reactive strength, rate of force development, and skill performance), noting why a training program design based on strength diagnosis can lead to greater efficacy and better performance gains for the athlete. Examples of tests used to assess strength…
8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER ...
8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER No. 2., AND GENERATOR UNITS BEHIND EXCITER No. 2 IN BACKGROUND. EXCITER No. 1 GENERATOR HAS A COVER OVER TOP HALF OF COMMUTATOR ELEMENT. VIEW TO NORTHWEST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA
Transitional γ strength in Cd isotopes
NASA Astrophysics Data System (ADS)
Larsen, A. C.; Ruud, I. E.; Bürger, A.; Goriely, S.; Guttormsen, M.; Görgen, A.; Hagen, T. W.; Harissopulos, S.; Nyhus, H. T.; Renstrøm, T.; Schiller, A.; Siem, S.; Tveten, G. M.; Voinov, A.; Wiedeking, M.
2013-01-01
The level densities and γ-ray strength functions of 105,106,111,112Cd have been extracted from particle-γ coincidence data using the Oslo method. The level densities are in very good agreement with known levels at low excitation energy. The γ-ray strength functions display no strong enhancement for low γ energies. However, more low-energy strength is apparent for 105,106Cd than for 111,112Cd. For γ energies above ≈4 MeV, there is evidence for some extra strength, similar to what has been previously observed for the Sn isotopes. The origin of this extra strength is unclear; it might be due to E1 and M1 transitions originating from neutron skin oscillations or the spin-flip resonance, respectively.
Excitation of atomic nitrogen by electron impact
NASA Technical Reports Server (NTRS)
Stone, E. J.; Zipf, E. C.
1972-01-01
Absolute cross sections were measured for the excitation of the N I(1134, 1164, 1168, 1200, 1243, and 1743 A) multiplets by electron impact on atomic nitrogen. The presence of vibrationally excited molecular nitrogen in the discharged gas was confirmed, and its effect on the measurements is discussed. The ratio of the oscillator strengths of the 1200 and 1134 A resonance transitions is presented, as well as the branching ratio for the N I(1311/1164 A) multiplets. Striking differences in the distribution of intensity between the spectra of atomic nitrogen and molecular nitrogen excited by energetic electrons suggest an optical method for measuring the density of atomic nitrogen in the upper atmosphere.
Nanoscale control of phonon excitations in graphene
Kim, Hyo Won; Ko, Wonhee; Ku, JiYeon; Jeon, Insu; Kim, Donggyu; Kwon, Hyeokshin; Oh, Youngtek; Ryu, Seunghwa; Kuk, Young; Hwang, Sung Woo; Suh, Hwansoo
2015-01-01
Phonons, which are collective excitations in a lattice of atoms or molecules, play a major role in determining various physical properties of condensed matter, such as thermal and electrical conductivities. In particular, phonons in graphene interact strongly with electrons; however, unlike in usual metals, these interactions between phonons and massless Dirac fermions appear to mirror the rather complicated physics of those between light and relativistic electrons. Therefore, a fundamental understanding of the underlying physics through systematic studies of phonon interactions and excitations in graphene is crucial for realising graphene-based devices. In this study, we demonstrate that the local phonon properties of graphene can be controlled at the nanoscale by tuning the interaction strength between graphene and an underlying Pt substrate. Using scanning probe methods, we determine that the reduced interaction due to embedded Ar atoms facilitates electron–phonon excitations, further influencing phonon-assisted inelastic electron tunnelling. PMID:26109454
Self-energy of an impurity in an ideal Fermi gas to second order in the interaction strength
NASA Astrophysics Data System (ADS)
Trefzger, Christian; Castin, Yvan
2014-09-01
We study in three dimensions the problem of a spatially homogeneous zero-temperature ideal Fermi gas of spin-polarized particles of mass m perturbed by the presence of a single distinguishable impurity of mass M. The interaction between the impurity and the fermions involves only the partial s wave through the scattering length a and has negligible range b compared to the inverse Fermi wave number 1/kF of the gas. Through the interactions with the Fermi gas the impurity gives birth to a quasiparticle, which will be here a Fermi polaron (or more precisely a monomeron). We consider the general case of an impurity moving with wave vector K ≠0: Then the quasiparticle acquires a finite lifetime in its initial momentum channel because it can radiate particle-hole pairs in the Fermi sea. A description of the system using a variational approach, based on a finite number of particle-hole excitations of the Fermi sea, then becomes inappropriate around K =0. We rely thus upon perturbation theory, where the small and negative parameter kFa→0- excludes any branches other than the monomeronic one in the ground state (as, e.g., the dimeronic one), and allows us a systematic study of the system. We calculate the impurity self-energy Σ(2)(K,ω) up to second order included in a. Remarkably, we obtain an analytical explicit expression for Σ(2)(K,ω), allowing us to study its derivatives in the plane (K,ω). These present interesting singularities, which in general appear in the third-order derivatives ∂3Σ(2)(K,ω). In the special case of equal masses, M =m, singularities appear already in the physically more accessible second-order derivatives ∂2Σ(2)(K,ω); using a self-consistent heuristic approach based on Σ(2) we then regularize the divergence of the second-order derivative ∂K2ΔE(K) of the complex energy of the quasiparticle found in Trefzger and Castin [Europhys. Lett. 104, 50005 (2013), 10.1209/0295-5075/104/50005] at K =kF, and we predict an interesting scaling
Excitability dependent pattern formation
NASA Astrophysics Data System (ADS)
Prabhakara, Kaumudi; Gholami, Azam; Bodenschatz, Eberhard
2014-03-01
On starvation, the amoebae Dictyostelium discoideum emit the chemo-attractant cyclic adenosine monophosphate (cAMP) at specific frequencies. The neighboring amoebae sense cAMP through membrane receptors and produce their own cAMP. Soon the cells synchronize and move via chemotaxis along the gradient of cAMP. The response of the amoebae to the emission of cAMP is seen as spiral waves or target patterns under a dark field microscope. The causal reasons for the selection of one or the other patterns are still unclear. Here we present a possible explanation based on excitability. The excitability of the amoebae depends on the starvation time because the gene expression changes with starvation. Cells starved for longer times are more excitable. In this work, we mix cells of different excitabilities to study the dependence of the emergent patterns on the excitability. Preliminary results show a transition from spirals to target patterns for specific excitabilities. A phase map of the patterns for different combinations of excitability and number densities is obtained. We compare our findings with numerical simulations of existing theoretical models.
15. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 WITH EXCITER No. ...
15. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 WITH EXCITER No. 1 BEHIND. OVERHEAD CRANE DANGLES AT TOP OF PHOTO. VIEW TO NORTHEAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA
Geomagnetic excitation of nutation
NASA Astrophysics Data System (ADS)
Ron, C.; Vondrák, J.
2015-08-01
We tested the hypothesis of Malkin (2013), who demonstrated that the observed changes of Free Core Nutation parameters (phase, amplitude) occur near the epochs of geomagnetic jerks. We found that if the numerical integration of Brzeziński broad-band Liouville equations of atmospheric/oceanic excitations is re-initialized at the epochs of geomagnetic jerks, the agreement between the integrated and observed celestial pole offsets is improved (Vondrák & Ron, 2014). Nevertheless, this approach assumes that the influence of geomagnetic jerks leads to a stepwise change in the position of celestial pole, which is physically not acceptable. Therefore we introduce a simple continuous excitation function that hypothetically describes the influence of geomagnetic jerks, and leads to rapid but continuous changes of pole position. The results of numerical integration of atmospheric/oceanic excitations and this newly introduced excitation are then compared with the observed celestial pole offsets, and prove that the agreement is improved significantly.
NASA Technical Reports Server (NTRS)
Tammadge, C. E.
1975-01-01
Standard methods of excitation are not always practical when a single mode of known frequency requires investigation. This form of investigation is often required on a modified aircraft. A new method of excitation was developed and proved in flight, which consists of firing small rocket charges attached to the aircraft structure. Damping values at gradually increasing airspeeds are obtained, as in Stick Jerk tests, and flutter speeds predicted.
Nuclear Excitation via Auger Transitions (NEAT)
NASA Astrophysics Data System (ADS)
Ward, Thomas; Emery, Guy; Rasmussen, John; Karwowski, Hugon; Castaneda, Carlos
2008-10-01
Triggering (prompt de-excitation) of isomeric states produced in a process of coupling nuclear excitations to atomic shells via Auger transitions (NEAT) is studied. In this resonant process the nuclear transition energy between the two states must be less than the Auger transition energy. This requires the emitted Auger electron energy and the exact on-resonance nuclear excitation share the Auger transition energy. NEAT is compared to other proposed processes of nuclear excitation produced by x-rays (NEET), by electron capture (NEEC) and bound internal conversion (BIC), all of which suffer from off-resonance nuclear excitation except in those accidental cases where the energies may coincide. Estimates of the total resonance strength will be given for the case of ^182mHf which has been extensively studied theoretically. A second case, ^189Os, where NEAT processes may contribute to the nuclear resonance fluorescence (NRF) of the ground state to the 5.8hr isomeric state will also be examined as a good case for experimental verification of the NEAT process.
Nondestructive Determination of Bond Strength
NASA Technical Reports Server (NTRS)
2000-01-01
Although many nondestructive techniques have been applied to detect disbonds in adhesive joints, no absolutely reliable nondestructive method has been developed to detect poor adhesion and evaluate the strength of bonded joints prior to the present work which used nonlinear ultrasonic methods to investigate adhesive bond cure conditions. Previously, a variety of linear and nonlinear ultrasonic methods with water coupling had been used to study aluminum-adhesive-aluminum laminates, prepared under different adhesive curing conditions, for possible bond strength determination. Therefore, in the course of this research effort, a variety of finite-amplitude experimental methods which could possibly differentiate various cure conditions were investigated, including normal and oblique incidence approaches based on nonlinear harmonic generation as well as several non-collinear two-wave interaction approaches. Test samples were mechanically scanned in various ways with respect to the focus of a transmitting transducer operated at several variable excitation frequencies and excitation levels. Even when powerful sample-related resonances were exploited by means of a frequency scanning approach, it was very difficult to isolate the nonlinear characteristics of adhesive bonds. However, a multi-frequency multi-power approach was quite successful and reliable. Ultrasonic tone burst signals at increasing power levels, over a wide frequency range, were transmitted through each bond specimen to determine its excitation dependent nonlinear harmonic resonance behavior. Relative amplitude changes were observed particularly in the higher harmonic spectral data and analyzed using a local displacement and strain analysis in the linear approximation. Two analysis approaches of the excitation-dependent data at specific resonances were found to be quite promising. One of these approaches may represent a very robust algorithm for classifying an adhesive bond as being properly cured or not
Electron Impact Excitation of Ti XVIII
NASA Astrophysics Data System (ADS)
Zhong, Jia Yong; Zeng, Jiao Long; Zhao, Gang; Bari, Muhanmmud Abbas; Zhang, Jie
2005-10-01
Two different methods were used to calculate the collision strengths of boron-like titanium. One was a close-coupling way using the Dirac Atomic R-matrix Code (DARC) of P. H. Norrington and I. P. Grant (private communication), and the other was based on a relativistic distorted-wave (RDW) approximation with a Flexible Atomic Code (FAC) by Gu (2003). For DARC, the lowest 125 fine-structure levels belonging to the (1s2) 2s22p, 2s2p2, 2p3, 2s23l, 2s2p3l, and 2p23l (l=s, p, and d) configurations were included in the calculations. The target model space encompassed the lowest 15 levels, and all 105Δn=0 transitions together with 40 partial waves were included in calculations of the collision strengths. For FAC, the configuration interactions included in the calculations of atomic structure and excitation were among the same configurations of DARC. The collision strengths for all 125 levels were calculated at 10 scattered electron energies (10-10000eV). The effective collision strengths, obtained after integrating the collision strengths of two codes over a Maxwellian distribution of electron energies, were also calculated for the electron temperatures in the range (50-500eV). For application to spectral modeling or diagnostics, we report a complete set of data for the energy levels, radiative rates, and effective collision strengths (only FAC) for all transitions.
Electromagnetic Transition Strengths in 27Ne
NASA Astrophysics Data System (ADS)
Loelius, Charles; Iwasaki, Hironori; Whitmore, Kenneth; Grinder, Mara; Elder, Robert; Lunderberg, Eric; Elman, Brandon; Longfellow, Brenden; Gade, Alexandra; Bazin, Daniel; Weisshaar, Dirk; Bender, Peter; Belarge, Joe; Kobayashi, Nobu; Petri, Marina; Heil, Sebastian; Mathy, Michael; Syndikus, Ina; Hufnagel, Alexander
2016-09-01
Previous measurements have established that halo nuclei are well characterized by their electromagnetic properties, with the E1 transition strengths reflecting a large neutron radius, and M1 transition strengths characterizing the dominant s wave strength. The 1/2+ excited state of 27Ne is close to the neutron separation energy and is expected to have a single valence neutron in the s orbital, and therefore has the potential to exhibit halo effects. Furthermore, neighboring isotopes 26Ne, 28Ne demonstrate substantial deformation, so that 27Ne should serve as an excellent benchmark for investigating the interplay between halo and deformation effects. We present here results of a new measurement of the lifetime of the 27Ne 1/2+ excited state, performed at the NSCL using the Recoil Distance Method with the TRIPLEX Plunger in conjunction with GRETINA. In addition, a Coulomb-excitation measurement of 27Ne has been performed using a novel application of the TRIPLEX plunger. The resulting transition strengths have been extracted and their implications are discussed.
Systematics of the στ- strength in nuclei
NASA Astrophysics Data System (ADS)
Bertsch, G.; Cha, D.; Toki, H.
1981-08-01
The structure of the στ- strength function is studied with a zero range interaction. The systematics of the giant Gamow-Teller state requires an interaction strength for Vστ of about 200-240 MeV fm3. While most of the strength goes to a state at high excitation, we find that ~20-30% of the strength remains at low excitation energy. The L=1 states show considerable J splitting, with a major peak at ≅20 MeV excitation. This peak contains components of J=0,1, and 2. Comparison with the experimental L=1 energy shows that the momentum dependence of the στ interaction is small. [NUCLEAR STRUCTURE. Gamow-Teller states and L=1 states in adjacent odd-odd mass nuclei of double closed shells. TDA and RPA calculation with zero range interaction.
NASA Astrophysics Data System (ADS)
Schwerdtfeger, Christine A.; Mazziotti, David A.
2012-12-01
Treatment of two-electron excitations is a fundamental but computationally expensive part of ab initio calculations of many-electron correlation. In this paper we develop a low-rank spectral expansion of two-electron excitations for accelerated electronic-structure calculations. The spectral expansion differs from previous approaches by relying upon both (i) a sum of three expansions to increase the rank reduction of the tensor and (ii) a factorization of the tensor into geminal (rank-two) tensors rather than orbital (rank-one) tensors. We combine three spectral expansions from the three distinct forms of the two-electron reduced density matrix (2-RDM), (i) the two-particle 2D, (ii) the two-hole 2Q, and the (iii) particle-hole 2G matrices, to produce a single spectral expansion with significantly accelerated convergence. While the resulting expansion is applicable to any quantum-chemistry calculation with two-particle excitation amplitudes, it is employed here in the parametric 2-RDM method [D. A. Mazziotti, Phys. Rev. Lett. 101, 253002 (2008)], 10.1103/PhysRevLett.101.253002. The low-rank parametric 2-RDM method scales quartically with the basis-set size, but like its full-rank version it can capture multi-reference correlation effects that are difficult to treat efficiently by traditional single-reference wavefunction methods. Applications are made to computing potential energy curves of HF and triplet OH+, equilibrium bond distances and frequencies, the HCN-HNC isomerization, and the energies of hydrocarbon chains. Computed 2-RDMs nearly satisfy necessary N-representability conditions. The low-rank spectral expansion has the potential to expand the applicability of the parametric 2-RDM method as well as other ab initio methods to large-scale molecular systems that are often only treatable by mean-field or density functional theories.
Collective excitations in a superfluid of color-flavor locked quark matter
Fukushima, Kenji; Iida, Kei
2005-04-01
We investigate collective excitations coupled with baryon density in a system of massless three-flavor quarks in the collisionless regime. By using the Nambu-Jona-Lasinio (NJL) model in the mean-field approximation, we field-theoretically derive the spectra both for the normal and color-flavor locked (CFL) superfluid phases at zero temperature. In the normal phase, we obtain usual zero sound as a low-lying collective mode in the particle-hole (vector) channel. In the CFL phase, the nature of collective excitations varies in a way dependent on whether the excitation energy, {omega}, is larger or smaller than the threshold given by twice the pairing gap {delta}, at which pair excitations with nonzero total momentum become allowed to break up into two quasiparticles. For {omega}<<2{delta}, a phonon corresponding to fluctuations in the U(1) phase of {delta} appears as a sharp peak in the particle-particle ('H') channel. We reproduce the property known from low-energy effective theories that this mode propagates at a velocity of v{sub H}=1/{radical}(3) in the low momentum regime; the decay constant f{sub H} obtained in the NJL model is identical with the QCD result obtained in the mean-field approximation. We also find that, as the momentum of the phonon increases, the excitation energy goes up and asymptotically approaches {omega}=2{delta}. Above the threshold for pair excitations ({omega}>2{delta}), zero sound manifests itself in the vector channel. By locating the zero sound pole of the vector propagator in the complex energy plane, we investigate the attenuation and energy dispersion relation of zero sound. In the long wavelength limit, the phonon mode, the only low-lying excitation, has its spectral weight in the H channel alone, while the spectral function vanishes in the vector channel. This is due to nontrivial mixing between the H and vector channels in the superfluid medium. We finally extend our study to the case of nonzero temperature. We demonstrate how
Charge-Density-Excitation Spectrum in the t-t'-J-V Model
NASA Astrophysics Data System (ADS)
Greco, Andrés; Yamase, Hiroyuki; Bejas, Matías
2017-03-01
We study the density-density correlation function in a large-N scheme of the t-t'-J-V model. When the nearest-neighbor Coulomb interaction V is zero, our model exhibits phase separation in a wide doping region and we obtain large spectral weight near momentum q = (0,0) at low energy, which originates from the proximity to phase separation. These features are much stronger for electron doping than for hole doping. However, once phase separation is suppressed by including a finite V, the low-energy spectral weight around q = (0,0) is substantially suppressed. Instead a sharp zero-sound mode is stabilized above the particle-hole continuum. We discuss that the presence of a moderate value of V, which is frequently neglected in the t-J model, is important to understand low-energy charge excitations especially close to q = (0,0) for electron doping. This insight should be taken into account in a future study of x-ray scattering measurements.
Plasmon Excitations of Multi-layer Graphene on a Conducting Substrate
Gumbs, Godfrey; Iurov, Andrii; Wu, Jhao-Ying; Lin, M. F.; Fekete, Paula
2016-01-01
We predict the existence of low-frequency nonlocal plasmons at the vacuum-surface interface of a superlattice of N graphene layers interacting with conducting substrate. We derive a dispersion function that incorporates the polarization function of both the graphene monolayers and the semi-infinite electron liquid at whose surface the electrons scatter specularly. We find a surface plasmon-polariton that is not damped by particle-hole excitations or the bulk modes and which separates below the continuum mini-band of bulk plasmon modes. The surface plasmon frequency of the hybrid structure always lies below , the surface plasmon frequency of the conducting substrate. The intensity of this mode depends on the distance of the graphene layers from the conductor’s surface, the energy band gap between valence and conduction bands of graphene monolayer and, most importantly, on the number of two-dimensional layers. For a sufficiently large number of layers the hybrid structure has no surface plasmon. The existence of plasmons with different dispersion relations indicates that quasiparticles with different group velocity may coexist for various ranges of wavelengths determined by the number of layers in the superlattice. PMID:26883086
NASA Astrophysics Data System (ADS)
Baker, Joshua A.; Kelley, David F.; Kelley, Anne Myers
2013-07-01
Resonance Raman excitation profiles for the longitudinal optical (LO) phonon fundamental and its first overtone have been measured for organic ligand capped, wurtzite form CdSe nanocrystals of ˜3.2 nm diameter dissolved in chloroform. The absolute differential Raman cross-section for the fundamental is much larger when excited at 532 or 543 nm, on the high-frequency side of the lowest-wavelength absorption maximum, than for excitation in the 458-476 nm range although the absorbance is higher at the shorter wavelengths. That is, the quantum yield for resonance Raman scattering is reduced for higher-energy excitation. In contrast, the photoluminescence quantum yield is relatively constant with wavelength. The optical absorption spectrum and the resonance Raman excitation profiles and depolarization dispersion curves are reproduced with a model for the energies, oscillator strengths, electron-phonon couplings, and dephasing rates of the multiple low-lying electronic excitations. The Huang-Rhys factor for LO phonon in the lowest excitonic transition is found to lie in the range S = 0.04-0.14. The strong, broad absorption feature about 0.5 eV above the lowest excitonic peak, typically labeled as the 1P3/21Pe transition, is shown to consist of at least two significant components that vary greatly in the magnitude of their electron-phonon coupling.
NASA Astrophysics Data System (ADS)
Minola, M.; Lu, Y.; Peng, Y. Y.; Dellea, G.; Gretarsson, H.; Haverkort, M. W.; Ding, Y.; Sun, X.; Zhou, X. J.; Peets, D. C.; Chauviere, L.; Dosanjh, P.; Bonn, D. A.; Liang, R.; Damascelli, A.; Dantz, M.; Lu, X.; Schmitt, T.; Braicovich, L.; Ghiringhelli, G.; Keimer, B.; Le Tacon, M.
2017-09-01
Spin excitations in the overdoped high temperature superconductors Tl2 Ba2 CuO6 +δ and (Bi ,Pb )2(Sr ,La )2CuO6 +δ were investigated by resonant inelastic x-ray scattering (RIXS) as functions of doping and detuning of the incoming photon energy above the Cu -L3 absorption peak. The RIXS spectra at optimal doping are dominated by a paramagnon feature with peak energy independent of photon energy, similar to prior results on underdoped cuprates. Beyond optimal doping, the RIXS data indicate a sharp crossover to a regime with a strong contribution from incoherent particle-hole excitations whose maximum shows a fluorescencelike shift upon detuning. The spectra of both compound families are closely similar, and their salient features are reproduced by exact-diagonalization calculations of the single-band Hubbard model on a finite cluster. The results are discussed in the light of recent transport experiments indicating a quantum phase transition near optimal doping.
Electron-impact excitation of Ne4+
NASA Astrophysics Data System (ADS)
Griffin, D. C.; Badnell, N. R.
2000-10-01
We present the results of extensive close-coupling calculations of electron-impact excitation of the C-like ion, Ne4+. We first compare effective collision strengths determined from a 20-level Breit-Pauli R-matrix calculation with those obtained from a 20-level intermediate-coupling frame transformation (ICFT) R-matrix calculation. The ICFT method was also employed to perform two much larger calculations; we compare the effective collision strengths determined from these calculations with each other and with those obtained from the 20-level calculations in order to assess the effects of increasing both the size of the configuration-interaction expansion of the target and the size of the close-coupling expansion. Our final calculation, with 130 terms and 261 levels in the configuration-interaction expansion of the target and 66 terms and 138 levels in the close-coupling expansion, provides improved data for excitation between the levels of the 2s22p2, 2s2p3 and 2p4 configurations and the first close-coupling results for excitation to the levels of the 2s22p3ℓ configurations in Ne4+.
Imaging of cardiac electrical excitation conduction.
Zhou, D F; Jiang, S Q; Zhu, J C; Zhao, C; Yan, Y R; Gronemeyer, D; Van Leeuwen, P
2015-08-01
We present a multiple time windows beamformer (MTWB) method of solving the inverse problem of magnetic field and non-invasively imaging the cardiac electrical excitation conduction using the magnetocardiac signals acquired by a 61-channel superconducting quantum interference device (SQUID). The MTWB constructs spatial filters for each location in source space, one for each component of the source moment based on the distributed source model, and estimates the cardiac equivalent current sources. The output of spatial filters is the source strength estimated in three-dimensional space and the weight matrix calculated with magnetocardiac signals in multiple time windows. A signal subspace projection technique is used to suppress noise. Then, the characteristics of cardiac electrical excitation conduction among two healthy subjects and two coronary vessel stenosis (CVS) patients are extracted from reconstructed current sources with maximum strength at each instant during QRS complex and ST-T segment, and a series of two-dimensional cardiac electrical excitation conduction maps (EECM) are obtained. It is demonstrated that two healthy subjects are of similar and the stronger electrical activities than those of two CVS patients. This technique can be used as an effective tool for the diagnosis of heart diseases.
Excitation Methods for Bridge Structures
Farrar, C.R.; Duffy, T.A.; Cornwell, P.J.; Doebling, S.W.
1999-02-08
This paper summarizes the various methods that have been used to excited bridge structures during dynamic testing. The excitation methods fall into the general categories of ambient excitation methods and measured-input excitation methods. During ambient excitation the input to the bridge is not directly measured. In contrast, as the category label implies, measured-input excitations are usually applied at a single location where the force input to the structure can be monitored. Issues associated with using these various types of measurements are discussed along with a general description of the various excitation methods.
Fluorescent resonant excitation energy transfer in linear polyenes.
Das, Mousumi; Ramasesha, S
2010-03-28
We have studied the dynamics of excitation transfer between two conjugated polyene molecules whose intermolecular separation is comparable to the molecular dimensions. We have employed a correlated electron model that includes both the charge-charge, charge-bond, and bond-bond intermolecular electron repulsion integrals. We have shown that the excitation transfer rate varies as inverse square of donor-acceptor separation R(-2) rather than as R(-6), suggested by the Forster type of dipolar approximation. Our time-evolution study also shows that the orientational dependence on excitation transfer at a fixed short donor-acceptor separation cannot be explained by Forster type of dipolar approximation beyond a certain orientational angle of rotation of an acceptor polyene with respect to the donor polyene. The actual excitation transfer rate beyond a certain orientational angle is faster than the Forster type of dipolar approximation rate. We have also studied the excitation transfer process in a pair of push-pull polyenes for different push-pull strengths. We have seen that, depending on the push-pull strength, excitation transfer could occur to other dipole coupled states. Our study also allows for the excitation energy transfer to optically dark states which are excluded by Forster theory since the one-photon transition intensity to these states (from the ground state) is zero.
Fluorescent resonant excitation energy transfer in linear polyenes
NASA Astrophysics Data System (ADS)
Das, Mousumi; Ramasesha, S.
2010-03-01
We have studied the dynamics of excitation transfer between two conjugated polyene molecules whose intermolecular separation is comparable to the molecular dimensions. We have employed a correlated electron model that includes both the charge-charge, charge-bond, and bond-bond intermolecular electron repulsion integrals. We have shown that the excitation transfer rate varies as inverse square of donor-acceptor separation R-2 rather than as R-6, suggested by the Förster type of dipolar approximation. Our time-evolution study also shows that the orientational dependence on excitation transfer at a fixed short donor-acceptor separation cannot be explained by Förster type of dipolar approximation beyond a certain orientational angle of rotation of an acceptor polyene with respect to the donor polyene. The actual excitation transfer rate beyond a certain orientational angle is faster than the Förster type of dipolar approximation rate. We have also studied the excitation transfer process in a pair of push-pull polyenes for different push-pull strengths. We have seen that, depending on the push-pull strength, excitation transfer could occur to other dipole coupled states. Our study also allows for the excitation energy transfer to optically dark states which are excluded by Förster theory since the one-photon transition intensity to these states (from the ground state) is zero.
Isoscalar [ital M]1 strength in lead
Alarcon, R.; Choi, S. ); Laszewski, R.M.; Dale, D.S. )
1993-09-01
Highly polarized tagged photons were used to measure the distribution of [ital M]1 transition strength in [sup 206]Pb at excitations between 5.5 and 6.9 MeV. The total [ital M]1 strength found in this energy range is consistent with that reported in [sup 208]Pb. For the isoscalar state at 5.8 MeV in [sup 206]Pb, [ital B]([ital M]1[up arrow])=(0.72[plus minus]0.15)[mu][sub [ital N
NASA Astrophysics Data System (ADS)
Egidi, Franco; Segado, Mireia; Koch, Henrik; Cappelli, Chiara; Barone, Vincenzo
2014-12-01
In this work, we report a comparative study of computed excitation energies, oscillator strengths, and excited-state energy gradients of (S)-nicotine, chosen as a test case, using multireference methods, coupled cluster singles and doubles, and methods based on time-dependent density functional theory. This system was chosen because its apparent simplicity hides a complex electronic structure, as several different types of valence excitations are possible, including n-π*, π-π*, and charge-transfer states, and in order to simulate its spectrum it is necessary to describe all of them consistently well by the chosen method.
Egidi, Franco Segado, Mireia; Barone, Vincenzo; Koch, Henrik; Cappelli, Chiara
2014-12-14
In this work, we report a comparative study of computed excitation energies, oscillator strengths, and excited-state energy gradients of (S)-nicotine, chosen as a test case, using multireference methods, coupled cluster singles and doubles, and methods based on time-dependent density functional theory. This system was chosen because its apparent simplicity hides a complex electronic structure, as several different types of valence excitations are possible, including n-π{sup *}, π-π{sup *}, and charge-transfer states, and in order to simulate its spectrum it is necessary to describe all of them consistently well by the chosen method.
Spin waves and magnetic excitations
Borovik-Romanov, A.S.; Sinha, S.K.
1988-01-01
This book describes both simple spin waves (magnons) and complicated excitations in magnetic systems. The following subjects are covered: - various methods of magnetic excitation investigations such as neutron scattering on magnetic excitations, spin-wave excitation by radio-frequency, power light scattering on magnons and magnetic excitation observation within the light-absorption spectrum; - oscillations of magnetic electron systems coupled with phonons, nuclear spin systems and localized impurity modes: - low-dimensional magnetics, amorphous magnetics and spin glasses.
Neutron-spectroscopic strength in Ru isotopes
Duarte, J.L.M.; Borello-Lewin, T.; Horodynski-Matsushigue, L.B. )
1994-08-01
A systematic, high resolution (6--8 keV) study of ([ital d],[ital t]) reactions on [sup 100,102,104]Ru is reported. Spectroscopic factors were extracted by comparison of experimental angular distributions with distorted wave Born approximation predictions. All of the information for [sup 99]Ru and, for excitation energies above 0.9 MeV, for [sup 103]Ru is new. Most of the strength expected for the 50--82 neutron shell was found. The strength distributions are discussed, also in comparison with the corresponding stripping reactions. Special attention is focused on extremely low and relatively intense [ital l]=3 excitations and on the [ital l]=4 transfer pattern observed.
NASA Technical Reports Server (NTRS)
Parcell, L. A.; Mceachran, R. P.; Stauffer, A. D.
1990-01-01
The differential and total cross section for the excitation of the 3s1P10 and 3p1P1 states of neon by positron impact were calculated using a distorted-wave approximation. The results agree well with experimental conclusions.
Proteins of Excitable Membranes
Nachmansohn, David
1969-01-01
Excitable membranes have the special ability of changing rapidly and reversibly their permeability to ions, thereby controlling the ion movements that carry the electric currents propagating nerve impulses. Acetylcholine (ACh) is the specific signal which is released by excitation and is recognized by a specific protein, the ACh-receptor; it induces a conformational change, triggering off a sequence of reactions resulting in increased permeability. The hydrolysis of ACh by ACh-esterase restores the barrier to ions. The enzymes hydrolyzing and forming ACh and the receptor protein are present in the various types of excitable membranes. Properties of the two proteins directly associated with electrical activity, receptor and esterase, will be described in this and subsequent lectures. ACh-esterase has been shown to be located within the excitable membranes. Potent enzyme inhibitors block electrical activity demonstrating the essential role in this function. The enzyme has been recently crystallized and some protein properties will be described. The monocellular electroplax preparation offers a uniquely favorable material for analyzing the properties of the ACh-receptor and its relation to function. The essential role of the receptor in electrical activity has been demonstrated with specific receptor inhibitors. Recent data show the basically similar role of ACh in the axonal and junctional membranes; the differences of electrical events and pharmacological actions are due to variations of shape, structural organization, and environment. PMID:19873642
Cross Sections for Electron Impact Excitation of Ions Relevant to Planetary Atmospheres Observation
NASA Technical Reports Server (NTRS)
Tayal, Swaraj S.
1998-01-01
The goal of this research grant was to calculate accurate oscillator strengths and electron collisional excitation strengths for inelastic transitions in atomic species of relevance to Planetary Atmospheres. Large scale configuration-interaction atomic structure calculations have been performed to obtain oscillator strengths and transition probabilities for transitions among the fine-structure levels and R-matrix method has been used in the calculations of electron-ion collision cross sections of C II, S I, S II, S III, and Ar II. A number of strong features due to ions of sulfur have been detected in the spectra of Jupiter satellite Io. The electron excitation cross sections for the C II and S II transitions are studied in collaboration with the experimental atomic physics group at the Jet Propulsion Laboratory. There is excellent agreement between experiment and theory which provide an accurate and broad-base test of the ability of theoretical methods used in the calculation of atomic processes. Specifically, research problems have been investigated for: electron impact excitation cross sections of C II: electron impact excitation cross sections of S III; energy levels and oscillator strengths for transitions in S III; collision strengths for electron collisional excitation of S II; electron impact excitation of inelastic transitions in Ar II; oscillator strengths of fine-structure transitions in neutral sulfur; cross sections for inelastic scattering of electrons from atomic nitrogen; and excitation of atomic ions by electron impact.
Synthesis of laughter by modifying excitation characteristics.
Thati, Sathya Adithya; Kumar K, Sudheer; Yegnanarayana, B
2013-05-01
In this paper, a method to synthesize laughter by modifying the excitation source information is presented. The excitation source information is derived by extracting epoch locations and instantaneous fundamental frequency using zero frequency filtering approach. The zero frequency filtering approach is modified to capture the rapidly varying instantaneous fundamental frequency in natural laugh signals. The nature of variation of excitation features in natural laughter is examined to determine the features to be incorporated in the synthesis of a laugh signal. Features such as pitch period and strength of excitation are modified in the utterance of vowel /a/ or /i/ to generate the laughter signal. Frication is also incorporated wherever appropriate. Laugh signal is generated by varying parameters at both call level and bout level. Experiments are conducted to determine the significance of different features in the perception of laughter. Subjective evaluation is performed to determine the level of acceptance and quality of synthesis of the synthesized laughter signal for different choices of parameter values and for different input types.
Flexibility and Muscular Strength.
ERIC Educational Resources Information Center
Liemohn, Wendell
1988-01-01
This definition of flexibility and muscular strength also explores their roles in overall physical fitness and focuses on how increased flexibility and muscular strength can help decrease or eliminate lower back pain. (CB)
Flexibility and Muscular Strength.
ERIC Educational Resources Information Center
Liemohn, Wendell
1988-01-01
This definition of flexibility and muscular strength also explores their roles in overall physical fitness and focuses on how increased flexibility and muscular strength can help decrease or eliminate lower back pain. (CB)
Excitation of millimeter and submillimeter water masers
NASA Technical Reports Server (NTRS)
Neufeld, David A.; Melnick, Gary J.
1991-01-01
The excitation of maser emission in millimeter and submillimeter transitions of interstellar and circumstellar water is considered. An escape probability method is used to determine the equilibrium populations in 349 rotational states of both ortho- and para-water under varying conditions of gas temperature, density, water abundance, and radiation field. It is shown that, under those conditions believed to prevail around late-type stars and within star-forming regions, strong millimeter and submillimeter water maser emission can be generated by collisional excitations by H2. Several maser transitions can have strengths close to that of the 22 GHz line. The water maser line which can be observed from mountaintop facilities and those which will require air- or space-borne platforms are indicated. The exact portion of parameter space in which each maser transition exhibits peak emission is shown.
Excitation of millimeter and submillimeter water masers
NASA Technical Reports Server (NTRS)
Neufeld, David A.; Melnick, Gary J.
1991-01-01
The excitation of maser emission in millimeter and submillimeter transitions of interstellar and circumstellar water is considered. An escape probability method is used to determine the equilibrium populations in 349 rotational states of both ortho- and para-water under varying conditions of gas temperature, density, water abundance, and radiation field. It is shown that, under those conditions believed to prevail around late-type stars and within star-forming regions, strong millimeter and submillimeter water maser emission can be generated by collisional excitations by H2. Several maser transitions can have strengths close to that of the 22 GHz line. The water maser line which can be observed from mountaintop facilities and those which will require air- or space-borne platforms are indicated. The exact portion of parameter space in which each maser transition exhibits peak emission is shown.
ERIC Educational Resources Information Center
Connaughton, Daniel; Connaughton, Angela; Poor, Linda
2001-01-01
Strength training can be fun, safe, and appropriate for young girls and women and is an important component of any fitness program when combined with appropriate cardiovascular and flexibility activities. Concerns and misconceptions regarding girls' strength training are discussed, presenting general principles of strength training for children…
ERIC Educational Resources Information Center
Connaughton, Daniel; Connaughton, Angela; Poor, Linda
2001-01-01
Strength training can be fun, safe, and appropriate for young girls and women and is an important component of any fitness program when combined with appropriate cardiovascular and flexibility activities. Concerns and misconceptions regarding girls' strength training are discussed, presenting general principles of strength training for children…
Tamii, A.; Adachi, T.; Hatanaka, K.; Hashimoto, H.; Kaneda, T.; Matsubara, H.; Okamura, H.; Sakemi, Y.; Shimizu, Y.; Tameshige, Y.; Yosoi, M.; Carter, J.; Dozono, M.; Fujita, H.; Fujita, Y.; Itoh, M.; Kawabata, T.; Nakanishi, K.; Sasamoto, Y.; Neumann-Cosel, P. von
2007-06-13
Experimental technique for measuring proton inelastic scattering with high-resolution at 295 MeV and at forward angles including zero degrees is described. The method is useful for extracting spin part of the M1 strength via nuclear excitation as well as E1 strength via Coulomb excitation. An excitation energy resolution of 20 keV, good scattering angle resolution, and low background condition have been achieved. The experimental technique was applied for several sd and pf shell nuclei.
Nature of low-lying electric dipole resonance excitations in 74Ge
NASA Astrophysics Data System (ADS)
Negi, D.; Wiedeking, M.; Lanza, E. G.; Litvinova, E.; Vitturi, A.; Bark, R. A.; Bernstein, L. A.; Bleuel, D. L.; Bvumbi, S.; Bucher, T. D.; Daub, B. H.; Dinoko, T. S.; Easton, J. L.; Görgen, A.; Guttormsen, M.; Jones, P.; Kheswa, B. V.; Khumalo, N. A.; Larsen, A. C.; Lawrie, E. A.; Lawrie, J. J.; Majola, S. N. T.; Masiteng, L. P.; Nchodu, M. R.; Ndayishimye, J.; Newman, R. T.; Noncolela, S. P.; Orce, J. N.; Papka, P.; Pellegri, L.; Renstrøm, T.; Roux, D. G.; Schwengner, R.; Shirinda, O.; Siem, S.
2016-08-01
Isospin properties of dipole excitations in 74Ge are investigated using the (α ,α'γ ) reaction and compared to (γ ,γ' ) data. The results indicate that the dipole excitations in the energy region of 6 to 9 MeV adhere to the scenario of the recently found splitting of the region of dipole excitations into two separated parts: one at low energy, being populated by both isoscalar and isovector probes, and the other at high energy, excited only by the electromagnetic probe. Relativistic quasiparticle time blocking approximation (RQTBA) calculations show a reduction in the isoscalar E 1 strength with an increase in excitation energy, which is consistent with the measurement.
Excited bands in even-even rare-earth nuclei
Vargas, Carlos E.; Hirsch, Jorge G.
2004-09-13
The energetics of states belonging to normal parity bands in even-even dysprosium isotopes, and their B(E2) transition strengths, are studied using an extended pseudo-SU(3) shell model. States with pseudospin 1 are added to the standard pseudospin 0 space, allowing for a proper description of known excited normal parity bands.
Experiments on excitation waves
NASA Astrophysics Data System (ADS)
Müller, S. C.
Recent trends in the experimentation on chemical and biochemical excitation waves are presented. In the Belousov-Zhabotinsky reaction, which is the most suitable chemical laboratory system for the study of wave propagation in excitable medium, the efficient control of wave dynamics by electrical fields and by light illumination is illustrated. In particular, the effects of a feedback control are shown. Further new experiments in this system are concerned with three-dimensional topologies and boundary effects. Important biological applications are found in the aggregation of slime mould amoebae, in proton waves during oscillatory glycolysis, and in waves of spreading depression in neuronal tissue as studied by experiments in chicken retina. Numerical simulations with appropriate reaction-diffusion models complement a large number of these experimental findings.
Magnetostrictive resonance excitation
Schwarz, Ricardo B.; Kuokkala, Veli-Tapani
1992-01-01
The resonance frequency spectrum of a magnetostrictive sample is remotely determined by exciting the magnetostrictive property with an oscillating magnetic field. The permeability of a magnetostrictive material and concomitant coupling with a detection coil varies with the strain in the material whereby resonance responses of the sample can be readily detected. A suitable sample may be a magnetostrictive material or some other material having at least one side coated with a magnetostrictive material. When the sample is a suitable shape, i.e., a cube, rectangular parallelepiped, solid sphere or spherical shell, the elastic moduli or the material can be analytically determined from the measured resonance frequency spectrum. No mechanical transducers are required and the sample excitation is obtained without contact with the sample, leading to highly reproducible results and a measurement capability over a wide temperature range, e.g. from liquid nitrogen temperature to the Curie temperature of the magnetostrictive material.
NASA Technical Reports Server (NTRS)
Badler, N. I.; Lee, P.; Wong, S.
1985-01-01
Strength modeling is a complex and multi-dimensional issue. There are numerous parameters to the problem of characterizing human strength, most notably: (1) position and orientation of body joints; (2) isometric versus dynamic strength; (3) effector force versus joint torque; (4) instantaneous versus steady force; (5) active force versus reactive force; (6) presence or absence of gravity; (7) body somatotype and composition; (8) body (segment) masses; (9) muscle group envolvement; (10) muscle size; (11) fatigue; and (12) practice (training) or familiarity. In surveying the available literature on strength measurement and modeling an attempt was made to examine as many of these parameters as possible. The conclusions reached at this point toward the feasibility of implementing computationally reasonable human strength models. The assessment of accuracy of any model against a specific individual, however, will probably not be possible on any realistic scale. Taken statistically, strength modeling may be an effective tool for general questions of task feasibility and strength requirements.
NASA Astrophysics Data System (ADS)
Copelli, M.; Campos, P. R. A.
2007-04-01
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 observe that the dynamic range is maximum when the coupling among the elements is critical, corroborating a general reasoning recently proposed. Although the maximum dynamic range yielded by general SF networks is slightly worse than that of random networks, for special SF networks which lack loops the enhancement of the dynamic range can be dramatic, reaching nearly five decades. In order to understand the role of loops on the transfer function we propose a simple model in which the density of loops in the network can be gradually increased, and show that this is accompanied by a gradual decrease of dynamic range.
Harmonically excited orbital variations
Morgan, T.
1985-08-06
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.
An Improved Multidimensional MPA Procedure for Bidirectional Earthquake Excitations
Wang, Feng; Sun, Jian-Gang; Zhang, Ning
2014-01-01
Presently, the modal pushover analysis procedure is extended to multidimensional analysis of structures subjected to multidimensional earthquake excitations. an improved multidimensional modal pushover analysis (IMMPA) method is presented in the paper in order to estimate the response demands of structures subjected to bidirectional earthquake excitations, in which the unidirectional earthquake excitation applied on equivalent SDOF system is replaced by the direct superposition of two components earthquake excitations, and independent analysis in each direction is not required and the application of simplified superposition formulas is avoided. The strength reduction factor spectra based on superposition of earthquake excitations are discussed and compared with the traditional strength reduction factor spectra. The step-by-step procedure is proposed to estimate seismic demands of structures. Two examples are implemented to verify the accuracy of the method, and the results of the examples show that (1) the IMMPA method can be used to estimate the responses of structure subjected to bidirectional earthquake excitations. (2) Along with increase of peak of earthquake acceleration, structural response deviation estimated with the IMMPA method may also increase. (3) Along with increase of the number of total floors of structures, structural response deviation estimated with the IMMPA method may also increase. PMID:25140333
An improved multidimensional MPA procedure for bidirectional earthquake excitations.
Wang, Feng; Sun, Jian-Gang; Zhang, Ning
2014-01-01
Presently, the modal pushover analysis procedure is extended to multidimensional analysis of structures subjected to multidimensional earthquake excitations. an improved multidimensional modal pushover analysis (IMMPA) method is presented in the paper in order to estimate the response demands of structures subjected to bidirectional earthquake excitations, in which the unidirectional earthquake excitation applied on equivalent SDOF system is replaced by the direct superposition of two components earthquake excitations, and independent analysis in each direction is not required and the application of simplified superposition formulas is avoided. The strength reduction factor spectra based on superposition of earthquake excitations are discussed and compared with the traditional strength reduction factor spectra. The step-by-step procedure is proposed to estimate seismic demands of structures. Two examples are implemented to verify the accuracy of the method, and the results of the examples show that (1) the IMMPA method can be used to estimate the responses of structure subjected to bidirectional earthquake excitations. (2) Along with increase of peak of earthquake acceleration, structural response deviation estimated with the IMMPA method may also increase. (3) Along with increase of the number of total floors of structures, structural response deviation estimated with the IMMPA method may also increase.
Pulse excitation of bolometer bridges
NASA Technical Reports Server (NTRS)
Rusk, S. J.
1972-01-01
Driving bolometer bridge by appropriately phased excitation pulses increases signal-to-noise ratio of bolometer sensor which operates on a chopped light beam. Method allows higher applied voltage than is possible by conventional ac or dc excitation.
Apparatus for photon excited catalysis
NASA Technical Reports Server (NTRS)
Saffren, M. M. (Inventor)
1977-01-01
An apparatus is described for increasing the yield of photonically excited gas phase reactions by extracting excess energy from unstable, excited species by contacting the species with the surface of a finely divided solid.
Observation of low- and high-energy Gamow-Teller phonon excitations in nuclei.
Fujita, Y; Fujita, H; Adachi, T; Bai, C L; Algora, A; Berg, G P A; von Brentano, P; Colò, G; Csatlós, M; Deaven, J M; Estevez-Aguado, E; Fransen, C; De Frenne, D; Fujita, K; Ganioğlu, E; Guess, C J; Gulyás, J; Hatanaka, K; Hirota, K; Honma, M; Ishikawa, D; Jacobs, E; Krasznahorkay, A; Matsubara, H; Matsuyanagi, K; Meharchand, R; Molina, F; Muto, K; Nakanishi, K; Negret, A; Okamura, H; Ong, H J; Otsuka, T; Pietralla, N; Perdikakis, G; Popescu, L; Rubio, B; Sagawa, H; Sarriguren, P; Scholl, C; Shimbara, Y; Shimizu, Y; Susoy, G; Suzuki, T; Tameshige, Y; Tamii, A; Thies, J H; Uchida, M; Wakasa, T; Yosoi, M; Zegers, R G T; Zell, K O; Zenihiro, J
2014-03-21
Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A = 42, 46, 50, and 54 "f-shell" nuclei in ((3)He, t) charge-exchange reactions. In the (42)Ca → (42)Sc reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the (54)Fe → (54)Co reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.
Plasmonic hybrid nanostructure with controlled interaction strength
NASA Astrophysics Data System (ADS)
Grzelak, Justyna K.; Krajnik, Bartosz; Thoreson, Mark D.; Nyga, Piotr; Shalaev, Vladimir M.; Mackowski, Sebastian
2014-03-01
In this report we discuss the influence of plasmon excitations in a silver island film on the fluorescence of photosynthetic complex, peridinin-chlorophyll-protein (PCP). Control of the separation between these two components is obtained by fabricating a wedge layer of silica across the substrate, with a thickness from 0 to 46 nm. Continuous variation of the silica thickness allows for gradual change of interaction strength between plasmon excitations in the metallic film and the excited states of pigments comprising photosynthetic complexes. While the largest separation between the silver film and photosynthetic complexes results in fluorescence featuring a mono-exponential decay and relatively narrow distribution of intensities, the PCP complexes placed on thinner silica spacers show biexponential fluorescence decay and significantly broader distribution of total fluorescence intensities. This broad distribution is a signature of stronger sensitivity of fluorescence enhancement upon actual parameters of a hybrid nanostructure. By gradual change of the silica spacer thickness we are able to reproduce classical distance dependence of fluorescence intensity in plasmonic hybrid nanostructures on ensemble level. Experiments carried out for different excitation wavelengths indicate that the interaction is stronger for excitations resonant with plasmon absorption in the metallic layer.
Strength function under the absorbing boundary condition
NASA Astrophysics Data System (ADS)
Iwasaki, M.; Otani, R.; Ito, M.
2014-12-01
The strength function of the linear response by the external field is calculated in the formalism of the absorbing boundary condition (ABC). The dipole excitation of a schematic two-body system is treated in the present study. The extended completeness relation, which is assumed on the analogy of the formulation in the complex scaling method (CSM), is applied to the calculation of the strength function. The calculation of the strength function is successful in the present formalism and hence, the extended completeness relation seems to work well in the ABC formalism. The contributions from the resonance and the non-resonant continuum is also analyzed according to the decomposition of the energy levels in the extended completeness relation.
Get excited: reappraising pre-performance anxiety as excitement.
Brooks, Alison Wood
2014-06-01
Individuals often feel anxious in anticipation of tasks such as speaking in public or meeting with a boss. I find that an overwhelming majority of people believe trying to calm down is the best way to cope with pre-performance anxiety. However, across several studies involving karaoke singing, public speaking, and math performance, I investigate an alternative strategy: reappraising anxiety as excitement. Compared with those who attempt to calm down, individuals who reappraise their anxious arousal as excitement feel more excited and perform better. Individuals can reappraise anxiety as excitement using minimal strategies such as self-talk (e.g., saying "I am excited" out loud) or simple messages (e.g., "get excited"), which lead them to feel more excited, adopt an opportunity mind-set (as opposed to a threat mind-set), and improve their subsequent performance. These findings suggest the importance of arousal congruency during the emotional reappraisal process.
Xiao, Jing-Lin
2009-03-01
In an asymmetry quantum dot, the properties of the electron, which is strongly coupled with phonon, were investigated. The variational relations of the first internal excited state energy, the excitation energy and the frequency of transition spectral line between the first internal excited state and the ground state of the electron which is strongly coupled with phonon in an asymmetry quantum dot with the transverse and longituainal effective confinement length of quantum dot and the electron-phonon coupling strength were studied by using a linear combination operator and the unitary transformation methods. Numerical calculations for the variational relations of the first internal excited state energy, the excitation energy and the frequency of transition spectral line between the first internal excited state and the ground state of the electron which is strongly coupled with phonon in an asymmetry quantum dot with the transverse and longituainal effective confinement length of quantum dot and the electron-phonon coupling strength were performed and the results show that the first internal excited state energy, the excitation energy and the frequency of transition spectral line between the first internal excited state and the ground state of the electron which is strongly coupled with phonon in an asymmetry quantum dot will strongly increase with decreasing the transverse and longitudinal effective confinement length. The first internal excited state energy of the electron which is strongly coupled with phonon in an asymmetry quantum dot will decrease with increasing the electron-phonon coupling strength. The excitation energy and the frequency of transition spectral line between the first internal excited state and the ground state of the electron which is strongly coupled with phonon in an asymmetry quantum dot will increase with increasing the electron-phonon coupling strength.
Alumina fiber strength improvement
NASA Technical Reports Server (NTRS)
Pepper, R. T.; Nelson, D. C.
1982-01-01
The effective fiber strength of alumina fibers in an aluminum composite was increased to 173,000 psi. A high temperature heat treatment, combined with a glassy carbon surface coating, was used to prevent degradation and improve fiber tensile strength. Attempts to achieve chemical strengthening of the alumina fiber by chromium oxide and boron oxide coatings proved unsuccessful. A major problem encountered on the program was the low and inconsistent strength of the Dupont Fiber FP used for the investigation.
Search for Gluonic Excitations
Eugenio, Paul
2007-10-26
Studies of meson spectra via strong decays provide insight regarding QCD at the confinement scale. These studies have led to phenomenological models for QCD such as the constituent quark model. However, QCD allows for a much richer spectrum of meson states which include extra states such as exotics, hybrids, multi-quarks, and glueballs. First discussion of the status of exotic meson searches is given followed by a discussion of plans at Jefferson Lab to double the energy of the machine to 12 GeV, which will allow us to access photoproduction of mesons in search for gluonic excited states.
Search for Gluonic Excitations
Paul Eugenio
2007-10-01
Studies of meson spectra via strong decays provide insight regarding QCD at the confinement scale. These studies have led to phenomenological models for QCD such as the constituent quark model. However, QCD allows for a much richer spectrum of meson states which include extra states such as exotics, hybrids, multi-quarks, and glueballs. First discussion of the status of exotic meson searches is given followed by a discussion of plans at Jefferson Lab to double the energy of the machine to 12 GeV, which will allow us to access photoproduction of mesons in search for gluonic excited states.
Metastable Interactions: Dissociative Excitation.
1985-05-01
participate. The mercuric halide compounds HgBr2 , HgCl 2 , and HgI2 are of recent interest because of laser output achieved on the B2 E - X2 E transition in...the * respective mercuric halide radicals in the range of 400-600 nm. Population inversion has been obtained by photodissociation and electron impact...excitation in mixtures o the mercuric - halide compounds and the rare gases. Chang and -* Burnham (3) have noted Improved laser efficiency and improved
Creveling, R.
1957-12-17
S> A shock-excited quartz crystal oscillator is described. The circuit was specifically designed for application in micro-time measuring work to provide an oscillator which immediately goes into oscillation upon receipt of a trigger pulse and abruptly ceases oscillation when a second pulse is received. To achieve the instant action, the crystal has a prestressing voltage applied across it. A monostable multivibrator receives the on and off trigger pulses and discharges a pulse through the crystal to initiate or terminate oscillation instantly.
Strength Training and Your Child
... Old Feeding Your 1- to 2-Year-Old Strength Training and Your Child KidsHealth > For Parents > Strength ... help prevent injuries and speed up recovery. About Strength Training Strength training is the practice of using ...
Excitability in Dictyostelium development
NASA Astrophysics Data System (ADS)
Schwab, David
2013-03-01
Discovering how populations of cells reliably develop into complex multi-cellular structures is a key challenge in modern developmental biology. This requires an understanding of how networks at the single-cell level, when combined with intercellular signaling and environmental cues, give rise to the collective behaviors observed in cellular populations. I will present work in collaboration with the Gregor lab, showing that the signal-relay response of starved cells of the amoebae Dictyostelium discoideum can be well modeled as an excitable system. This is in contrast to existing models of the network that postulate a feed-forward cascade. I then extend the signal-relay model to describe how spatial gradient sensing may be achieved via excitability. One potential advantage of relying on feedback for gradient sensing is in preventing ``cheaters'' that do not produce signals from taking over the population. I then combine these models of single-cell signaling and chemotaxis to perform large-scale agent-based simulations of aggregating populations. This allows direct study of how variations in single-cell dynamics modify population behavior. In order to further test this model, I use the results of a screen for mutant cell lines that exhibit altered collective patterns. Finally, I use an existing FRET movie database of starved cell populations at varying cell densities and dilution rates to study heterogeneity in repeated spatio-temporal activity patterns.
NASA Astrophysics Data System (ADS)
Maucher, Fabian; Sutcliffe, Paul
2017-07-01
In this paper, we present extensive numerical simulations of an excitable medium to study the long-term dynamics of knotted vortex strings for all torus knots up to crossing number 11. We demonstrate that FitzHugh-Nagumo evolution preserves the knot topology for all the examples presented, thereby providing a field theory approach to the study of knots. Furthermore, the evolution yields a well-defined minimal length for each knot that is comparable to the ropelength of ideal knots. We highlight the role of the medium boundary in stabilizing the length of the knot and discuss the implications beyond torus knots. We also show that there is not a unique attractor within a given knot topology.
CINE: Comet INfrared Excitation
NASA Astrophysics Data System (ADS)
de Val-Borro, Miguel; Cordiner, Martin A.; Milam, Stefanie N.; Charnley, Steven B.
2017-08-01
CINE calculates infrared pumping efficiencies that can be applied to the most common molecules found in cometary comae such as water, hydrogen cyanide or methanol. One of the main mechanisms for molecular excitation in comets is the fluorescence by the solar radiation followed by radiative decay to the ground vibrational state. This command-line tool calculates the effective pumping rates for rotational levels in the ground vibrational state scaled by the heliocentric distance of the comet. Fluorescence coefficients are useful for modeling rotational emission lines observed in cometary spectra at sub-millimeter wavelengths. Combined with computational methods to solve the radiative transfer equations based, e.g., on the Monte Carlo algorithm, this model can retrieve production rates and rotational temperatures from the observed emission spectrum.
Electron Impact Excitation Of Ti XIX
NASA Astrophysics Data System (ADS)
Aggarwal, Kanti M.; Keenan, F. P.
2012-05-01
Emission lines of Ti XIX are important for the modeling and diagnostics of lasing, fusion and astrophysical plasmas, for which atomic data are required for a variety of parameters, such as energy levels, radiative rates (A- values), and excitation rates or equivalently the effective collision strengths (Υ), which are obtained from the electron impact collision strengths (Ω). Experimentally, energy levels are available for Ti XIX on the NIST website, but there is paucity for accurate collisional atomic data. Therefore, here we report a complete set of results (namely energy levels, radiative rates, and effective collision strengths) for all transitions among the lowest 98 levels of Ti XIX. These levels belong to the (1s2) 2s2, 2s2p, 2p2, 2s3l, 2p3l, 2s4l, and 2p4l configurations. Finally, we also report the A- values for four types of transitions, namely electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1), and magnetic quadrupole (M2), because these are also required for plasma modeling. For our calculations of wavefunctions, we have adopted the fully relativistic GRASP code, and for the calculations of Ω, the Dirac atomic R-matrix code (DARC) of PH Norrington and IP Grant. Additionally, parallel calculations have also been performed with the Flexible Atomic Code (FAC) of Gu, so that all atomic parameters can be rigorously assessed for accuracy.
Front interaction induces excitable behavior
NASA Astrophysics Data System (ADS)
Parra-Rivas, P.; Matías, M. A.; Colet, P.; Gelens, L.; Walgraef, D.; Gomila, D.
2017-02-01
Spatially extended systems can support local transient excitations in which just a part of the system is excited. The mechanisms reported so far are local excitability and excitation of a localized structure. Here we introduce an alternative mechanism based on the coexistence of two homogeneous stable states and spatial coupling. We show the existence of a threshold for perturbations of the homogeneous state. Subthreshold perturbations decay exponentially. Superthreshold perturbations induce the emergence of a long-lived structure formed by two back to back fronts that join the two homogeneous states. While in typical excitability the trajectory follows the remnants of a limit cycle, here reinjection is provided by front interaction, such that fronts slowly approach each other until eventually annihilating. This front-mediated mechanism shows that extended systems with no oscillatory regimes can display excitability.
Electron impact excitation of highly charged sodium-like ions
NASA Technical Reports Server (NTRS)
Blaha, M.; Davis, J.
1978-01-01
Optical transition probabilities and electron collision strengths for Ca X, Fe XVI, Zn XX, Kr XXVI and Mo XXXII are calculated for transitions between n equal to 3 and n equal to 4 levels. The calculations neglect relativistic effects on the radial functions. A semi-empirical approach provides wave functions of the excited states; a distorted wave function without exchange is employed to obtain the excitation cross sections. The density dependence of the relative intensities of certain emission lines in the sodium isoelectronic sequence is also discussed.
Static Dielectric Breakdown Strength of Condensed Heterogeneous High Explosives
1987-06-01
3-1 TRIPLE JUNCTION . . .. . . . . . . . . . . . . . . . * * * .3-2 SURFACE FLASHOVER ...enhancement at dielectric interfaces, surface flashover , humidity, surrounding atmosphere, temperature, pressure, and excitation time), which are...discussed in Chapter 3. To obtain meaningful critical field strengths, it is necessary to suppress surface flashover around the insulator sides and
Optically excited states in positronium
NASA Technical Reports Server (NTRS)
Howell, R. H.; Ziock, Klaus P.; Magnotta, F.; Dermer, Charles D.; Failor, R. A.; Jones, K. M.
1990-01-01
Optical excitation are reported of the 1 3S-2 3P transition in positronium, and a second excitation from n=2 to higher n states. The experiment used light from two pulsed dye lasers. Changes in the positronium annihilation rate during and after the laser pulse were used to deduce the excited state populations. The n=2 level was found to be saturable and excitable to a substantial fraction of n=2 positronium to higher levels. Preliminary spectroscopic measurements were performed on n=14 and n=15 positronium.
Fission fragment excited laser system
McArthur, David A.; Tollefsrud, Philip B.
1976-01-01
A laser system and method for exciting lasing action in a molecular gas lasing medium which includes cooling the lasing medium to a temperature below about 150 K and injecting fission fragments through the lasing medium so as to preferentially excite low lying vibrational levels of the medium and to cause population inversions therein. The cooled gas lasing medium should have a mass areal density of about 5 .times. 10.sup.-.sup.3 grams/square centimeter, relaxation times of greater than 50 microseconds, and a broad range of excitable vibrational levels which are excitable by molecular collisions.
NASA Astrophysics Data System (ADS)
Sonnenschein, Bernard; Peron, Thomas K. DM.; Rodrigues, Francisco A.; Kurths, Jürgen; Schimansky-Geier, Lutz
2014-08-01
We study the collective dynamics of noise-driven excitable elements, so-called active rotators. Crucially here, the natural frequencies and the individual coupling strengths are drawn from some joint probability distribution. Combining a mean-field treatment with a Gaussian approximation allows us to find examples where the infinite-dimensional system is reduced to a few ordinary differential equations. Our focus lies in the cooperative behavior in a population consisting of two parts, where one is composed of excitable elements, while the other one contains only self-oscillatory units. Surprisingly, excitable behavior in the whole system sets in only if the excitable elements have a smaller coupling strength than the self-oscillating units. In this way positive local correlations between natural frequencies and couplings shape the global behavior of mixed populations of excitable and oscillatory elements.
Strength and Balance Exercises
... Venous Thromboembolism Aortic Aneurysm More Strength and Balance Exercises Updated:Sep 8,2016 If you have medical ... if you have been inactive and want to exercise vigorously, check with your doctor before beginning a ...
NASA Technical Reports Server (NTRS)
Bingham, Cindy
1990-01-01
Viewgraphs on reduction of bone strength are presented. WEHI 231 B growth rates, experimental chambers used to apply the electric field to the cell cultures, and a mouse suspended by rotating cuff in electromagnetic field are shown.
NASA Technical Reports Server (NTRS)
Tcheng, Ping; Elliot, Joe
1987-01-01
Special grip-strength meter designed for accurate, reproducible measurement of hand rehabilitation. Four strain gauges connected in Wheatstone bridge to measure deflection caused by gripping hand. Compressive force exerted by hand transmitted to measuring beams. Beams therefore deflected or strained, and mechanical strain sensed by strain gauges and converted into electrical signal. After amplification and conditioning, signal displayed on LED as measure of gripping strength of hand.
Syn, C
2009-12-22
Strength of the apple parts has been noticed to decrease, especially those installed by the new induction heating system since the LEP campaign started. Fig. 1 shows the ultimate tensile strength (UTS), yield strength (YS), and elongation of the installed or installation-simulated apples on various systems. One can clearly see the mean values of UTS and YS of the post-LEP parts decreased by about 8 ksi and 6 ksi respectively from those of the pre-LEP parts. The slight increase in elongation seen in Fig.1 can be understood from the weak inverse relationship between the strength and elongation in metals. Fig.2 shows the weak correlation between the YS and elongation of the parts listed in Fig. 1. Strength data listed in Figure 1 were re-plotted as histograms in Figs. 3 and 4. Figs. 3a and 4a show histograms of all UTS and YS data. Figs. 3b and 4b shows histograms of pre-LEP data and Figs. 3c and 4c of post-LEP data. Data on statistical scatter of tensile strengths have been rarely published by material suppliers. Instead, only the minimum 'guaranteed' strength data are typically presented. An example of strength distribution of aluminum 7075-T6 sheet material, listed in Fig. 5, show that its scatter width of both UTS and YS for a single sheet can be about 6 ksi and for multi-lot scatter can be as large as 11 ksi even though the sheets have been produced through well-controlled manufacturing process. By approximating the histograms shown in Figs. 3 and 4 by a Gaussian or similar type of distribution curves, one can plausibly see the strength reductions in the later or more recent apples. The pre-LEP data in Figs. 3b and 4b show wider scatter than the post-LEP data in Figs. 3c and 4c and seem to follow the binomial distribution of strength indicating that the apples might have been made from two different lots of material, either from two different vendors or from two different melts of perhaps slightly different chemical composition by a single vendor. The post
Exotic modes of excitation in deformed neutron-rich nuclei
Yoshida, Kenichi
2011-05-06
Low-lying dipole excitation mode in neutron-rich Mg isotopes close to the drip line is investigated in the framework of the Hartree-Fock-Bogoliubov and the quasiparticle random-phase approximation employing the Skyrme and the pairing energy-density functionals. It is found that the low-lying dipole-strength distribution splits into the K{sup {pi}} = 0{sup -} and 1{sup -} components due to the nuclear deformation. The low-lying dipole strength increases as the neutron drip-line is approached.
Offner, Franklin F.
1972-01-01
The model of the excitable membrane assumes common channels for Na+ and K+; the two ion species interact within the pores through their electrostatic forces. The electric field varies across the membrane and with time, as a result of ionic redistribution. Ionic flow is primarily controlled by energy barriers at the two interfaces and by Ca++ adsorption at the external interface. When the membrane is polarized, the high electric field at the external interface acting on the membrane fixed charge keeps the effective channel diameter small, so that only dihydrated ions can cross the interface. The higher energy required to partially dehydrate Na+ accounts for its lower permeability when polarized. Depolarized, the channel entrance can expand, permitting quadrihydrated ions to pass; the large initial Na+ flow is the result of the large concentration ratio across the interface. The effect at the internal interface is symmetric; Na+ crosses with greater difficulty when the membrane is depolarized. Na+ inactivation occurs when the ion distribution within the membrane has assumed its new steady-state value. Calculations based on parameters consistent with physicochemical data agree generally with a wide range of experiments. The model does not obey the two fundamental Hodgkin-Huxley (HH) postulates (independence principle, ion flow proportional to thermodynamic potential). In several instances the model predicts experimental results which are not predicted by the HH equations. ImagesFIGURE 12 PMID:4655662
Double excitations in finite systems.
Romaniello, P; Sangalli, D; Berger, J A; Sottile, F; Molinari, L G; Reining, L; Onida, G
2009-01-28
Time-dependent density-functional theory (TDDFT) is widely used in the study of linear response properties of finite systems. However, there are difficulties in properly describing excited states, which have double- and higher-excitation characters, which are particularly important in molecules with an open-shell ground state. These states would be described if the exact TDDFT kernel were used; however, within the adiabatic approximation to the exchange-correlation (xc) kernel, the calculated excitation energies have a strict single-excitation character and are fewer than the real ones. A frequency-dependent xc kernel could create extra poles in the response function, which would describe states with a multiple-excitation character. We introduce a frequency-dependent xc kernel, which can reproduce, within TDDFT, double excitations in finite systems. In order to achieve this, we use the Bethe-Salpeter equation with a dynamically screened Coulomb interaction W(omega), which can describe these excitations, and from this we obtain the xc kernel. Using a two-electron model system, we show that the frequency dependence of W does indeed introduce the double excitations that are instead absent in any static approximation of the electron-hole screening.
Bulk Properties of Nuclear Matter From Excitations of Nuclei
Shlomo, Shalom
2007-10-26
We consider the predictive power of Hartree-Fock (HF) approximation in determining properties of finite nuclei and thereby in extracting bulk properties of infinite nuclear matter (NM) by extrapolation. In particular, we review the current status of determining the value of NM incompressibility coefficient K, considering the most sensitive method of analyzing the recent accurate experimental data on excitation strengths of compression modes of nuclei within microscopic relativistic and non-relativistic theoretical models. We discuss the consequences of common violations of self-consistency in HF based random-phase-approximation calculations of strength functions and present results of highly accurate calculations of centroid energies and excitation cross sections of giant resonances. Explanations (resolutions) of long standing discrepancies in the value of K are presented.
Probing the neutron skin thickness in collective modes of excitation
NASA Astrophysics Data System (ADS)
Paar, N.; Horvat, A.
2014-03-01
Nuclear collective motion provides valuable constraint on the size of neutron-skin thickness and the properties of nuclear matter symmetry energy. By employing relativistic nuclear energy density functional (RNEDF) and covariance analysis related to χ2 fitting of the model parameters, relevant observables are identified for dipole excitations, which strongly correlate with the neutron-skin thickness (rnp), symmetry energy at saturation density (J) and slope of the symmetry energy (L). Using the RNEDF framework and experimental data on pygmy dipole strength (68Ni, 132Sn, 208Pb) and dipole polarizability (208Pb), it is shown how the values of J, and L, and rnp are constrained. The isotopic dependence of moments associated to dipole excitations in 116-136Sn shows that the low-energy dipole strength and polarizability in neutron-rich nuclei display strong sensitivity to the symmetry energy parameter J, more pronounced than in isotopes with moderate neutron-to-proton number ratios.
NASA Technical Reports Server (NTRS)
Bechert, D. W.
1982-01-01
The generation of instability waves in free shear layers is investigated. The model assumes an infinitesimally thin shear layer shed from a semi-infinite plate which is exposed to sound excitation. The acoustical shear layer excitation by a source further away from the plate edge in the downstream direction is very weak while upstream from the plate edge the excitation is relatively efficient. A special solution is given for the source at the plate edge. The theory is then extended to two streams on both sides of the shear layer having different velocities and densities. Furthermore, the excitation of a shear layer in a channel is calculated. A reference quantity is found for the magnitude of the excited instability waves. For a comparison with measurements, numerical computations of the velocity field outside the shear layer were carried out.
Vibrational excitation induces double reaction.
Huang, Kai; Leung, Lydie; Lim, Tingbin; Ning, Zhanyu; Polanyi, John C
2014-12-23
Electron-induced reaction at metal surfaces is currently the subject of extensive study. Here, we broaden the range of experimentation to a comparison of vibrational excitation with electronic excitation, for reaction of the same molecule at the same clean metal surface. In a previous study of electron-induced reaction by scanning tunneling microscopy (STM), we examined the dynamics of the concurrent breaking of the two C-I bonds of ortho-diiodobenzene physisorbed on Cu(110). The energy of the incident electron was near the electronic excitation threshold of E0=1.0 eV required to induce this single-electron process. STM has been employed in the present work to study the reaction dynamics at the substantially lower incident electron energies of 0.3 eV, well below the electronic excitation threshold. The observed increase in reaction rate with current was found to be fourth-order, indicative of multistep reagent vibrational excitation, in contrast to the first-order rate dependence found earlier for electronic excitation. The change in mode of excitation was accompanied by altered reaction dynamics, evidenced by a different pattern of binding of the chemisorbed products to the copper surface. We have modeled these altered reaction dynamics by exciting normal modes of vibration that distort the C-I bonds of the physisorbed reagent. Using the same ab initio ground potential-energy surface as in the prior work on electronic excitation, but with only vibrational excitation of the physisorbed reagent in the asymmetric stretch mode of C-I bonds, we obtained the observed alteration in reaction dynamics.
Relativistic Coulomb excitation of 88Kr
NASA Astrophysics Data System (ADS)
Moschner, K.; Blazhev, A.; Jolie, J.; Warr, N.; Boutachkov, P.; Bednarczyk, P.; Sieja, K.; Algora, A.; Ameil, F.; Bentley, M. A.; Brambilla, S.; Braun, N.; Camera, F.; Cederkäll, J.; Corsi, A.; Danchev, M.; DiJulio, D.; Fahlander, C.; Gerl, J.; Giaz, A.; Golubev, P.; Górska, M.; Grebosz, J.; Habermann, T.; Hackstein, M.; Hoischen, R.; Kojouharov, I.; Kurz, N.; Mǎrginean, N.; Merchán, E.; Möller, T.; Naqvi, F.; Nara Singh, B. S.; Nociforo, C.; Pietralla, N.; Pietri, S.; Podolyák, Zs.; Prochazka, A.; Reese, M.; Reiter, P.; Rudigier, M.; Rudolph, D.; Sava, T.; Schaffner, H.; Scruton, L.; Taprogge, J.; Thomas, T.; Weick, H.; Wendt, A.; Wieland, O.; Wollersheim, H.-J.
2016-11-01
To investigate the systematics of mixed-symmetry states in N =52 isotones, a relativistic Coulomb excitation experiment was performed during the PreSPEC campaign at the GSI Helmholtzzentrum für Schwerionenforschung to determine E 2 transition strengths to 2+ states of the radioactive nucleus 88Kr. Absolute transition rates could be measured towards the first and third 2+ states. For the latter a mixed-symmetry character is suggested on the basis of the indication for a strong M 1 transition to the fully symmetric 21+ state, extending the knowledge of the N =52 isotones below Z =40 . A comparison with the proton-neutron interacting boson model and shell-model predictions is made and supports the assignment.
Peterson, Carrie L; Rogers, Lynn M; Bednar, Michael S; Bryden, Anne M; Keith, Michael W; Perreault, Eric J; Murray, Wendy M
2017-04-01
Following biceps transfer to enable elbow extension in individuals with tetraplegia, motor re-education may be facilitated by greater corticomotor excitability. Arm posture modulates corticomotor excitability of the nonimpaired biceps. If arm posture also modulates excitability of the transferred biceps, posture may aid in motor re-education. Our objective was to determine whether multi-joint arm posture affects corticomotor excitability of the transferred biceps similar to the nonimpaired biceps. We also aimed to determine whether corticomotor excitability of the transferred biceps is related to elbow extension strength and muscle length. Corticomotor excitability was assessed in 7 arms of individuals with tetraplegia and biceps transfer using transcranial magnetic stimulation and compared to biceps excitability of nonimpaired individuals. Single-pulse transcranial magnetic stimulation was delivered to the motor cortex with the arm in functional postures at rest. Motor-evoked potential amplitude was recorded via surface electromyography. Elbow moment was recorded during maximum isometric extension trials, and muscle length was estimated using a biomechanical model. Arm posture modulated corticomotor excitability of the transferred biceps differently than the nonimpaired biceps. Elbow extension strength was positively related and muscle length was unrelated, respectively, to motor-evoked potential amplitude across the arms with biceps transfer. Corticomotor excitability of the transferred biceps is modulated by arm posture and may contribute to strength outcomes after tendon transfer. Future work should determine whether modulating corticomotor excitability via posture promotes motor re-education during the rehabilitative period following surgery.
Coulomb Excitation of the N = 50 nucleus 80Zn
NASA Astrophysics Data System (ADS)
van de Walle, J.; Aksouh, F.; Ames, F.; Behrens, T.; Bildstein, V.; Blazhev, A.; Cederkäll, J.; Clément, E.; Cocolios, T. E.; Davinson, T.; Delahaye, P.; Eberth, J.; Ekström, A.; Fedorov, D. V.; Fedosseev, V. N.; Fraile, L. M.; Franchoo, S.; Gernhauser, R.; Georgiev, G.; Habs, D.; Heyde, K.; Huber, G.; Huyse, M.; Ibrahim, F.; Ivanov, O.; Iwanicki, J.; Jolie, J.; Kester, O.; Köster, U.; Kröll, T.; Krücken, R.; Lauer, M.; Lisetskiy, A. F.; Lutter, R.; Marsh, B. A.; Mayet, P.; Niedermaier, O.; Nilsson, T.; Pantea, M.; Perru, O.; Raabe, R.; Reiter, P.; Sawicka, M.; Scheit, H.; Schrieder, G.; Schwalm, D.; Seliverstov, M. D.; Sieber, T.; Sletten, G.; Smirnova, N.; Stanoiu, M.; Stefanescu, I.; Thomas, J.-C.; Valiente-Dobón, J. J.; van Duppen, P.; Verney, D.; Voulot, D.; Warr, N.; Weisshaar, D.; Wenander, F.; Wolf, B. H.; Zielińska, M.
2008-05-01
Neutron rich Zinc isotopes, including the N = 50 nucleus 80Zn, were produced and post-accelerated at the Radioactive Ion Beam (RIB) facility REX-ISOLDE (CERN). Low-energy Coulomb excitation was induced on these isotopes after post-acceleration, yielding B(E2) strengths to the first excited 2+ states. For the first time, an excited state in 80Zn was observed and the 21+ state in 78Zn was established. The measured B(E2,21+-->01+) values are compared to two sets of large scale shell model calculations. Both calculations reproduce the observed B(E2) systematics for the full Zinc isotopic chain. The results for N = 50 isotones indicate a good N = 50 shell closure and a strong Z = 28 proton core polarization. The new results serve as benchmarks to establish theoretical models, predicting the nuclear properties of the doubly magic nucleus 78Ni.
Theoretical study of K-shell excitations in formaldehyde
NASA Astrophysics Data System (ADS)
Trofimov, A. B.; Moskovskaya, T. E.; Gromov, E. V.; Köppel, H.; Schirmer, J.
2001-08-01
The C 1s and O 1s excitation of formaldehyde (H2CO) has been studied within an ab initio framework. The second-order algebraic-diagrammatic construction [ADC(2)] polarization propagator method has been used to calculate energies and oscillator strengths of the electronic transitions. For selected C 1s excited states also multireference configuration-interaction (MRCI) calculations were performed. The vibrational excitations accompanying the electronic transitions have been studied using a linear vibronic coupling model. The theoretical C 1s and O 1s spectra are in excellent qualitative agreement with high-resolution K-shell photoabsorption measurements. The present results support the previous assignments of the C 1s spectrum, while they revise the interpretation of the O 1s spectrum above 537 eV. In contrast to the C 1s case, the main photoabsorption intensity in the O 1s spectrum is due to nd rather than to np Rydberg excitations. For the two lowest singlet excited states, that is, the 1B1(C 1s-->π*) single excitation and the 1B2(C 1s,n-->π*2) double excitation, we find vibronic interaction with the 1A1(C 1s-->3s) and 1A2(C 1s-->3d) Rydberg states via the ν4 out-of-plane bending mode. In addition, the 1B2(C 1s,n-->π*2) and the 1A1(C 1s-->3s) states interact via the ν5 mode. The vibronic coupling leads to a complex spectral pattern in the low-energy part of the C 1s excitation spectrum, allowing one to interpret the finer details of the experiment.
Collision rates for electron excitation of Mg V lines
NASA Astrophysics Data System (ADS)
Tayal, S. S.; Sossah, A. M.
2015-02-01
Aims: Transition probabilities and electron impact excitation collision strengths and rates for astrophysically important lines in Mg V are reported. The 86 fine-structure levels of the 2s22p4, 2s2p5, 2p6, 2s22p33s, 2s22p33p and 2s22p33d configurations are included in our calculations. The effective collision strengths are presented as a function of electron temperature for solar and other astrophysical applications. Methods: The collision strengths have been calculated using the B-splineBreit-Pauli R-matrixmethod for all fine-structure transitions among the 86 levels. The one-body mass, Darwin and spin-orbit relativistic effects are included in the Breit-Pauli Hamiltonian in the scattering calculations. The one-body and two-body relativistic operators are included in the multiconfiguration Hartree-Fock calculations of transition probabilities. Several sets of non-orthogonal spectroscopic and correlation radial orbitals are used to obtain accurate description of Mg V 86 levels and to represent the scattering functions. Results: The calculated excitation energies are in very good agreement with experiment and represents an improvement over the previous calculations. The present collision strengths show good agreement with the previously available R-matrix and distorted-wave calculations. The oscillator strengths for E1 transitions normally compare very well with previous calculations. The thermally averaged collision strengths are obtained by integrating total resonant and non-resonant collision strengths over a Maxwellian distribution of electron energies and these are presented over the temperature range log 10Te = 3.2-6.0 K. Tables 1-4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/574/A87
Suppressing self-excited vibrations of mechanical systems by impulsive force excitation
NASA Astrophysics Data System (ADS)
Pumhössel, Thomas
2016-09-01
In this contribution, self-excited mechanical systems subjected to force excitation of impulsive type are investigated. It is shown that applying force impulses which are equally spaced in time, but whose impulsive strength depends in a certain manner on the state-variables of the mechanical system, results in a periodic energy exchange between lower and higher modes of vibration. Moreover, in the theoretical case of Dirac delta impulses, it is possible that no energy crosses the system boundary while energy is transferred across modes, i.e. neither external energy is fed to the mechanical system, nor energy is extracted from the mechanical system. Shifting energy to higher modes of vibration, whose natural damping is larger compared to lower ones, results in a faster dissipation of energy. An analytical stability investigation is presented using the assumption of impulsive forcing of Dirac delta type, which allows deciding easily about the stability by evaluating the eigenvalues of the coefficient matrix of a corresponding set of difference equations. It is shown that the developed impulsive forcing concept is capable to suppress self-excited vibrations of mechanical systems. Some numerical results of a simple mechanical system with two degrees of freedom underline the presented approach.
Gupta, Sakshi; Ahmad, Azeem; Mehta, Dalip S.; Gambhir, Vijayeta; Reddy, Martha N.
2015-08-31
In a typical Raman based sensor, a single laser beam is used for exciting the sample and the backscattered or forward scattered light is collected using collection optics and is analyzed by a spectrometer. We have investigated that by means of exciting the sample with multiple beams, i.e., by dividing the same input power of the single beam into two or three or more beams and exciting the sample from different angles, the Raman signal enhances significantly. Due to the presence of multiple beams passing through the same volume of the sample, an interference pattern is formed and the volume of interaction of excitation beams with the sample increases. By means of this geometry, the enhancement in the Raman signal is observed and it was found that the signal strength increases linearly with the increase in number of excitation beams. Experimental results of this scheme for excitation of the samples are reported for explosive detection at a standoff distance.
Dynamic Characteristics of Excited Atomic Systems
NASA Astrophysics Data System (ADS)
Bezuglov, N. N.; Dimitrijevic, M. S.; Klyucharev, A. N.; Mihajlov, A. A.
2014-12-01
The dynamics of excited atom interactions with other atoms, which often lead to associative ionization, is largely governed by stochastic diffusion of the valence electron through Rydberg states prior to the ionization. Such processes are associated with random changes of the energy state of the highly excited electron, and they are likely to influence the nuclear dynamics, especially at subthermal collision energies. Possibilities of manipulation of the chaotic dynamics of Rydberg states require a detailed exploration. For an electron in a given Rydberg state moving in a microwave field, which can be generated via interaction with another atom or molecule, there exists critical field strength, above which motion of the electron in the energy space is chaotic. Recently a way to block the dynamic chaos regime was shown, if a given Rydberg state is located somewhat above the middle between the two other states with the orbital quantum number differing by one, whereby level shifts can be controlled by employing Stark/Zeeman shifts in external DC electric/magnetic fields. The stochastic effects in collisions involving Rydberg particles, in which the initial and final reaction channels are connected via intermediate highly excited collision complexes with multiple crossings of energy levels, can be treated using the dynamic chaos approach (Chirikov criterion, Standard and Keppler mapping of time evolution of the Rydberg electron, solution of the Fokker-Plank- and Langevin-type of equations, etc.). Such approach to obtaining dynamics characteristics is a natural choice, since the treatment of Rydberg electron dynamics as a kind of diffusion process allowing one to bypass the multi-level-crossing problem, which can hardly be solved by conventional quantum chemistry methods.
NASA Technical Reports Server (NTRS)
Omidvar, K.
1971-01-01
Expressions for the excitation cross section of the highly excited states of the hydrogenlike atoms by fast charged particles have been derived in the dipole approximation of the semiclassical impact parameter and the Born approximations, making use of a formula for the asymptotic expansion of the oscillator strength of the hydrogenlike atoms given by Menzel. When only the leading term in the asymptotic expansion is retained, the expression for the cross section becomes identical to the expression obtained by the method of the classical collision and correspondence principle given by Percival and Richards. Comparisons are made between the Bethe coefficients obtained here and the Bethe coefficients of the Born approximation for transitions where the Born calculation is available. Satisfactory agreement is obtained only for n yields n + 1 transitions, with n the principal quantum number of the excited state.
Kurkjian, C.R.
1985-01-01
This book presents information on the following topics: a look at the history of glass strength; atomistic theory of fracture; surface chemistry in relation to the strength and fracture of silicate glasses; high-speed photographic investigations of the dynamic localized loading of some oxide glasses; a correction for measurements of contact area using Newton's rings; envionmentally enhanced crack growth; fatigue in glass; behavior of flaws in fused silica fibers; fracture toughness of chalcogenide glasses and glass-ceramics; fracture analysis of glass surfaces; and fracture mechanics parameters for glasses - a compilation and correlation.
Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX
2010-08-31
High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.
Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub
2012-06-05
High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.
Spin Resonance Strength Calculations
NASA Astrophysics Data System (ADS)
Courant, E. D.
2009-08-01
In calculating the strengths of depolarizing resonances it may be convenient to reformulate the equations of spin motion in a coordinate system based on the actual trajectory of the particle, as introduced by Kondratenko, rather than the conventional one based on a reference orbit. It is shown that resonance strengths calculated by the conventional and the revised formalisms are identical. Resonances induced by radiofrequency dipoles or solenoids are also treated; with rf dipoles it is essential to consider not only the direct effect of the dipole but also the contribution from oscillations induced by it.
Magnetic dipole strength in 128Xe and 134Xe in the spin-flip resonance region
NASA Astrophysics Data System (ADS)
Massarczyk, R.; Rusev, G.; Schwengner, R.; Dönau, F.; Bhatia, C.; Gooden, M. Â. E.; Kelley, J. Â. H.; Tonchev, A. Â. P.; Tornow, W.
2014-11-01
The magnetic dipole strength in the energy region of the spin-flip resonance is investigated in 128Xe and 134Xe using quasimonoenergetic and linearly polarized γ -ray beams at the High-Intensity γ -Ray Source facility in Durham, North Carolina, USA. Absorption cross sections were deduced for the magnetic and electric and dipole strength distributions separately for various intervals of excitation energy, including the strength of states in the unresolved quasicontinuum. The magnetic dipole strength distributions show structures resembling a resonance in the spin-flip region around an excitation energy of 8 MeV. The electric dipole strength distributions obtained from the present experiments are in agreement with the ones deduced from an earlier experiment using broad-band bremsstrahlung instead of a quasimonoenergetic beam. The experimental magnetic and electric dipole strength distributions are compared with phenomenological approximations and with predictions of a quasiparticle random phase approximation in a deformed basis.
Pygmy Dipole Strength and Neutron Skins in Exotic Nuclei
NASA Astrophysics Data System (ADS)
Klimkiewicz, A.; Paar, N.; Adrich, P.; Fallot, M.; Boretzky, K.; Aumann, T.; Cortina-Gil, D.; Pramanik, U. Datta; Elze, Th. W.; Emling, H.; Geissel, H.; Hellström, M.; Jones, K. L.; Kratz, J. V.; Kulessa, R.; Nociforo, C.; Palit, R.; Simon, H.; Surówka, G.; Sümmerer, K.; Vretenar, D.; Waluś, W.
2008-05-01
Dipole strength distributions were determined for the neutron-rich nuclei 129-132Sn and 133,134Sb from electromagnetic excitation in an experiment using the FRS-LAND setup. For all nuclei, a sizeable fraction of ``pygmy'' dipole strength at excitation energies well below the giant dipole resonance was observed. The integrated low-lying dipole strength of the nuclei with low neutron separation energies can be compared to results for stable nuclei (e.g. N = 82 isotopes) determined for the energy regime of 5-9 MeV. A clear increase of the dipole strength with increasing asymmetry of the nuclei is observed. Comparing the ratio of the low-lying dipole over the giant dipole strength to recent relativistic mean field calculations, values for the parameters a4 and p0 of the symmetry energy and for the neutron skin thickness are derived. Averaged over 130Sn and 132Sn we extract a4 = 31.8+/-1.3 MeV and p0 = 2.2+/-0.5 MeV/fm3. The neutron skin sizes are determined to Rn-Rp = 0.23+/-0.03 fm and 0.24+/-0.03 fm for 130Sn and 132Sn, respectively. For 208Pb a neutron skin thickness of Rn-Rp = 0.18+/-0.035 fm follows, when applying the same method and using earlier published experimental findings on the dipole strength.
Neural adaptations to electrical stimulation strength training.
Hortobágyi, Tibor; Maffiuletti, Nicola A
2011-10-01
This review provides evidence for the hypothesis that electrostimulation strength training (EST) increases the force of a maximal voluntary contraction (MVC) through neural adaptations in healthy skeletal muscle. Although electrical stimulation and voluntary effort activate muscle differently, there is substantial evidence to suggest that EST modifies the excitability of specific neural paths and such adaptations contribute to the increases in MVC force. Similar to strength training with voluntary contractions, EST increases MVC force after only a few sessions with some changes in muscle biochemistry but without overt muscle hypertrophy. There is some mixed evidence for spinal neural adaptations in the form of an increase in the amplitude of the interpolated twitch and in the amplitude of the volitional wave, with less evidence for changes in spinal excitability. Cross-sectional and exercise studies also suggest that the barrage of sensory and nociceptive inputs acts at the cortical level and can modify the motor cortical output and interhemispheric paths. The data suggest that neural adaptations mediate initial increases in MVC force after short-term EST.
Exponential processes in human auditory excitation and adaptation.
Formby, C; Rutledge, J C; Sherlock, L P
2002-02-01
Peripheral auditory adaptation has been studied extensively in animal models, and multiple exponential components have been identified. This study explores the feasibility of estimating these component processes for human listeners with a peripheral model of adaptation. The processes were estimated from off-frequency masked detection data that probed temporal masking responses to a gated narrowband masker. The resulting response patterns reflected step-like onset and offset features with characteristically little evidence of confounding backward and forward masking. The model was implemented with linear combinations of exponential functions to represent the unadapted excitation response to gating the masker on and then off and the opposing effects of adaptation in each instance. The onset and offset of the temporal masking response were assumed to be approximately inverse operations and were modeled independently in this scheme. The unadapted excitation response at masker onset and the reversed excitation response at masker offset were each represented in the model by a single exponential function. The adaptation processes were modeled by three independent exponential functions, which were reversed at masker offset. Each adaptation component was subtractive and partially negated the unadapted excitation response to the dynamic masker. This scheme allowed for quantification of the response amplitude, action latency, and time constant for the unadapted excitation component and for each adaptation component. The results reveal that (1) the amplitudes of the unadapted excitation and reversed excitation components grow nonlinearly with masker level and mirror the 'compressive' input-output velocity response of the basilar membrane; (2) the time constants for the unadapted excitation and reversed excitation components are related inversely to masker intensity, which is compatible with neural synchrony increasing at masker onset (or offset) with increasing masker strength
Dirac R-matrix collision strengths and effective collision strengths for transitions of Ni xvii
NASA Astrophysics Data System (ADS)
Hudson, C. E.; Norrington, P. H.; Ramsbottom, C. A.; Scott, M. P.
2012-01-01
Context. Electron impact excitation collision strengths are required for the analysis and interpretation of stellar observations. Aims: This calculation aims to provide fine structure effective collision strengths for the Ni xvii ion using a method which includes contributions from resonances. Methods: A fully relativistic R-matrix calculation has been performed using the DARC code. In the structure part of our calculation 141 fine-structure levels are employed and 37 of these are used in the scattering calculation. Results: Collision strengths have been determined for 666 fine-structure transitions arising from the 37 lowest j-levels involving configurations 3s2, 3p2, 3d2, 3s3p, 3s3d, 3p3d and 3s4s. The effective collision strengths for these transitions have been calculated for electron temperatures (Te) in the range log 10Te(K) = 4.5 - 8.0. Effective collision strengths are tabulated for transitions between the first ten fine structure levels, arising from the 3s2, 3s3p and 3p2 configurations. The remaining transitions are available at the CDS as well as via the author's website. Tables 2 and 5 are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/537/A12
NASA Technical Reports Server (NTRS)
Whitney, J. M.
1983-01-01
The notch strength of composites is discussed. The point stress and average stress criteria relate the notched strength of a laminate to the average strength of a relatively long tensile coupon. Tests of notched specimens in which microstrain gages have been placed at or near the edges of the holes have measured strains much larger that those measured in an unnotched tensile coupon. Orthotropic stress concentration analyses of failed notched laminates have also indicated that failure occurred at strains much larger than those experienced on tensile coupons with normal gage lengths. This suggests that the high strains at the edge of a hole can be related to the very short length of fiber subjected to these strains. Lockheed has attempted to correlate a series of tests of several laminates with holes ranging from 0.19 to 0.50 in. Although the average stress criterion correlated well with test results for hole sizes equal to or greater than 0.50 in., it over-estimated the laminate strength in the range of hole sizes from 0.19 to 0.38 in. It thus appears that a theory is needed that is based on the mechanics of failure and is more generally applicable to the range of hole sizes and the varieties of laminates found in aircraft construction.
Gender Differences in Strength.
ERIC Educational Resources Information Center
Heyward, Vivian H.; And Others
1986-01-01
This investigation examined gender differences of 103 physically active men and women in upper and lower body strength as a function of lean body weight and the distribution of muscle and subcutaneous fat in the upper and lower limbs. Results are discussed. (Author/MT)
High strength composites evaluation
Marten, S.M.
1992-02-01
A high-strength, thick-section, graphite/epoxy composite was identified. The purpose of this development effort was to evaluate candidate materials and provide LANL with engineering properties. Eight candidate materials (Samples 1000, 1100, 1200, 1300, 1400, 1500, 1600, and 1700) were chosen for evaluation. The Sample 1700 thermoplastic material was the strongest overall.
Coulomb excitations of monolayer germanene
NASA Astrophysics Data System (ADS)
Shih, Po-Hsin; Chiu, Yu-Huang; Wu, Jhao-Ying; Shyu, Feng-Lin; Lin, Ming-Fa
2017-01-01
The feature-rich electronic excitations of monolayer germanene lie in the significant spin-orbit coupling and the buckled structure. The collective and single-particle excitations are diversified by the magnitude and direction of transferred momentum, the Fermi energy and the gate voltage. There are four kinds of plasmon modes, according to the unique frequency- and momentum-dependent phase diagrams. They behave as two-dimensional acoustic modes at long wavelength. However, for the larger momenta, they might change into another kind of undamped plasmons, become the seriously suppressed modes in the heavy intraband e–h excitations, keep the same undamped plasmons, or decline and then vanish in the strong interband e–h excitations. Germanene, silicene and graphene are quite different from one another in the main features of the diverse plasmon modes.
Coulomb excitations of monolayer germanene
Shih, Po-Hsin; Chiu, Yu-Huang; Wu, Jhao-Ying; Shyu, Feng-Lin; Lin, Ming-Fa
2017-01-01
The feature-rich electronic excitations of monolayer germanene lie in the significant spin-orbit coupling and the buckled structure. The collective and single-particle excitations are diversified by the magnitude and direction of transferred momentum, the Fermi energy and the gate voltage. There are four kinds of plasmon modes, according to the unique frequency- and momentum-dependent phase diagrams. They behave as two-dimensional acoustic modes at long wavelength. However, for the larger momenta, they might change into another kind of undamped plasmons, become the seriously suppressed modes in the heavy intraband e–h excitations, keep the same undamped plasmons, or decline and then vanish in the strong interband e–h excitations. Germanene, silicene and graphene are quite different from one another in the main features of the diverse plasmon modes. PMID:28091555
Strength Training: For Overall Fitness
Healthy Lifestyle Fitness Strength training is an important part of an overall fitness program. Here's what strength training can do for you — and how to ... lean muscle mass and burn calories more efficiently? Strength training to the rescue! Strength training is a ...
Excitations of strange bottom baryons
NASA Astrophysics Data System (ADS)
Woloshyn, R. M.
2016-09-01
The ground-state and first-excited-state masses of Ωb and Ω_{bb} baryons are calculated in lattice QCD using dynamical 2 + 1 flavour gauge fields. A set of baryon operators employing different combinations of smeared quark fields was used in the framework of the variational method. Results for radial excitation energies were confirmed by carrying out a supplementary multiexponential fitting analysis. Comparison is made with quark model calculations.
Collisional excitation of interstellar formaldehyde
NASA Technical Reports Server (NTRS)
Green, S.; Garrison, B. J.; Lester, W. A., Jr.; Miller, W. H.
1978-01-01
Previous calculations for rates of excitation of ortho-H2CO by collisions with He have been extended to higher rotational levels and kinetic temperatures to 80 K. Rates for para-H2CO have also been computed. Pressure-broadening widths for several spectral lines have been obtained from these calculations and are found to agree with recent data within the experimental uncertainty of 10%. Excitation of formaldehyde by collisions with H2 molecules is also discussed.
Code of Federal Regulations, 2012 CFR
2012-10-01
... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...
Code of Federal Regulations, 2010 CFR
2010-10-01
... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...
Code of Federal Regulations, 2011 CFR
2011-10-01
... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...
Code of Federal Regulations, 2014 CFR
2014-10-01
... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...
Code of Federal Regulations, 2013 CFR
2013-10-01
... REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet... generator unless it is provided with a permanent magnet or a residual-magnetism-type exciter that has the...
Weier, Ashleigh T; Kidgell, Dawson J
2012-01-01
Paired-pulse transcranial magnetic stimulation (TMS) was used to investigate 4 wks of leg strength training with and without whole body vibration (WBV) on corticospinal excitability and short-latency intracortical inhibition (SICI). Participants (n = 12) were randomly allocated to either a control or experimental (WBV) group. All participants completed 12 squat training sessions either with (WBV group) or without (control group) exposure to WBV (f = 35 Hz, A = 2.5 mm). There were significant (P < 0.05) increases in squat strength and corticospinal excitability and significant (P < 0.05) reductions in SICI for both groups following the 4 wk intervention. There were no differences detected between groups for any dependant variable (P > 0.05). It appears that WBV training does not augment the increase in strength or corticospinal excitability induced by strength training alone.
Weier, Ashleigh T.; Kidgell, Dawson J.
2012-01-01
Paired-pulse transcranial magnetic stimulation (TMS) was used to investigate 4 wks of leg strength training with and without whole body vibration (WBV) on corticospinal excitability and short-latency intracortical inhibition (SICI). Participants (n = 12) were randomly allocated to either a control or experimental (WBV) group. All participants completed 12 squat training sessions either with (WBV group) or without (control group) exposure to WBV (f = 35 Hz, A = 2.5 mm). There were significant (P < 0.05) increases in squat strength and corticospinal excitability and significant (P < 0.05) reductions in SICI for both groups following the 4 wk intervention. There were no differences detected between groups for any dependant variable (P > 0.05). It appears that WBV training does not augment the increase in strength or corticospinal excitability induced by strength training alone. PMID:22654645
Redox Control of Cardiac Excitability
Aggarwal, Nitin T.
2013-01-01
Abstract Reactive oxygen species (ROS) have been associated with various human diseases, and considerable attention has been paid to investigate their physiological effects. Various ROS are synthesized in the mitochondria and accumulate in the cytoplasm if the cellular antioxidant defense mechanism fails. The critical balance of this ROS synthesis and antioxidant defense systems is termed the redox system of the cell. Various cardiovascular diseases have also been affected by redox to different degrees. ROS have been indicated as both detrimental and protective, via different cellular pathways, for cardiac myocyte functions, electrophysiology, and pharmacology. Mostly, the ROS functions depend on the type and amount of ROS synthesized. While the literature clearly indicates ROS effects on cardiac contractility, their effects on cardiac excitability are relatively under appreciated. Cardiac excitability depends on the functions of various cardiac sarcolemal or mitochondrial ion channels carrying various depolarizing or repolarizing currents that also maintain cellular ionic homeostasis. ROS alter the functions of these ion channels to various degrees to determine excitability by affecting the cellular resting potential and the morphology of the cardiac action potential. Thus, redox balance regulates cardiac excitability, and under pathological regulation, may alter action potential propagation to cause arrhythmia. Understanding how redox affects cellular excitability may lead to potential prophylaxis or treatment for various arrhythmias. This review will focus on the studies of redox and cardiac excitation. Antioxid. Redox Signal. 18, 432–468. PMID:22897788
Electron-excited molecule interactions
Christophorou, L.G. Tennessee Univ., Knoxville, TN . Dept. of Physics)
1991-01-01
In this paper the limited but significant knowledge to date on electron scattering from vibrationally/rotationally excited molecules and electron scattering from and electron impact ionization of electronically excited molecules is briefly summarized and discussed. The profound effects of the internal energy content of a molecule on its electron attachment properties are highlighted focusing in particular on electron attachment to vibrationally/rotationally and to electronically excited molecules. The limited knowledge to date on electron-excited molecule interactions clearly shows that the cross sections for certain electron-molecule collision processes can be very different from those involving ground state molecules. For example, optically enhanced electron attachment studies have shown that electron attachment to electronically excited molecules can occur with cross sections 10{sup 6} to 10{sup 7} times larger compared to ground state molecules. The study of electron-excited molecule interactions offers many experimental and theoretical challenges and opportunities and is both of fundamental and technological significance. 54 refs., 15 figs.
Electrostatic Tuning of Cellular Excitability
Börjesson, Sara I.; Parkkari, Teija; Hammarström, Sven; Elinder, Fredrik
2010-01-01
Abstract Voltage-gated ion channels regulate the electric activity of excitable tissues, such as the heart and brain. Therefore, treatment for conditions of disturbed excitability is often based on drugs that target ion channels. In this study of a voltage-gated K channel, we propose what we believe to be a novel pharmacological mechanism for how to regulate channel activity. Charged lipophilic substances can tune channel opening, and consequently excitability, by an electrostatic interaction with the channel's voltage sensors. The direction of the effect depends on the charge of the substance. This was shown by three compounds sharing an arachidonyl backbone but bearing different charge: arachidonic acid, methyl arachidonate, and arachidonyl amine. Computer simulations of membrane excitability showed that small changes in the voltage dependence of Na and K channels have prominent impact on excitability and the tendency for repetitive firing. For instance, a shift in the voltage dependence of a K channel with −5 or +5 mV corresponds to a threefold increase or decrease in K channel density, respectively. We suggest that electrostatic tuning of ion channel activity constitutes a novel and powerful pharmacological approach with which to affect cellular excitability. PMID:20141752
Evolution of the giant dipole resonance properties with excitation energy
NASA Astrophysics Data System (ADS)
Santonocito, D.; Blumenfeld, Y.
2006-10-01
The studies of the evolution of the hot Giant Dipole Resonance (GDR) properties as a function of excitation energy are reviewed. The discussion will mainly focus on the A ˜ 100-120 mass region where a large amount of data concerning the width and the strength evolution with excitation energy are available. Models proposed to interpret the main features and trends of the experimental results will be presented and compared to the available data in order to extract a coherent scenario on the limits of the development of the collective motion in nuclei at high excitation energy. Experimental results on the GDR built in hot nuclei in the mass region A ˜ 60-70 will be also shown, allowing to investigate the mass dependence of the main GDR features. The comparison between limiting excitation energies for the collective motion and critical excitation energies extracted from caloric curve studies will suggest a possible link between the disappearance of collective motion and the liquid-gas phase transition.
Cross-education of muscular strength is facilitated by homeostatic plasticity.
Frazer, Ashlyn K; Williams, Jacqueline; Spittle, Michael; Kidgell, Dawson J
2017-04-01
We examined the effect of priming the ipsilateral motor cortex (M1) using anodal transcranial direct current stimulation (tDCS) prior to a single bout of strength training on the cross-transfer of strength and corticospinal excitability and inhibition of the ipsilateral M1. In a randomized double-blinded cross-over design, changes in strength and indices of corticospinal plasticity were analysed in 13 adults who were exposed to 20 min of ipsilateral anodal and sham tDCS (applied to the ipsilateral M1 to the training arm) followed by a single strength training session of the right Biceps Brachii only. The induction of homeostatic plasticity via anodal tDCS priming, significantly increased strength of the untrained left Biceps Brachii (12%) compared to sham tDCS (2%), increased corticospinal excitability (12-33%) and cross-activation (25%) when ipsilateral anodal tDCS was applied to the right M1 prior to a single session of strength training. Interestingly, ipsilateral sham tDCS and strength training resulted in an average increase in MEP amplitude of 2-32%. The novel findings of this study include: priming the ipsilateral M1 via anodal tDCS prior to a single bout of strength training augments the cross-transfer of strength which is manifested by an increase in corticospinal excitability and cross-activation. These findings provide insight into how priming methods that induce homeostatic plasticity may be used to enhance the cross-education phenomenon.
Savukov, I. M.; Filin, D. V.
2014-12-29
Many applications are in need of accurate photoionization cross sections, especially in the case of complex atoms. Configuration-interaction relativistic-many-body-perturbation theory (CI-RMBPT) has been successful in predicting atomic energies, matrix elements between discrete states, and other properties, which is quite promising, but it has not been applied to photoionization problems owing to extra complications arising from continuum states. In this paper a method that will allow the conversion of discrete CI-(R)MPBT oscillator strengths (OS) to photoionization cross sections with minimal modifications of the codes is introduced and CI-RMBPT cross sections of Ne, Ar, Kr, and Xe are calculated. A consistent agreement with experiment is found. RMBPT corrections are particularly significant for Ar, Kr, and Xe and improve agreement with experimental results compared to the particle-hole CI method. As a result, the demonstrated conversion method can be applied to CI-RMBPT photoionization calculations for a large number of multivalence atoms and ions.
Savukov, I. M.; Filin, D. V.
2014-12-29
Many applications are in need of accurate photoionization cross sections, especially in the case of complex atoms. Configuration-interaction relativistic-many-body-perturbation theory (CI-RMBPT) has been successful in predicting atomic energies, matrix elements between discrete states, and other properties, which is quite promising, but it has not been applied to photoionization problems owing to extra complications arising from continuum states. In this paper a method that will allow the conversion of discrete CI-(R)MPBT oscillator strengths (OS) to photoionization cross sections with minimal modifications of the codes is introduced and CI-RMBPT cross sections of Ne, Ar, Kr, and Xe are calculated. A consistent agreementmore » with experiment is found. RMBPT corrections are particularly significant for Ar, Kr, and Xe and improve agreement with experimental results compared to the particle-hole CI method. As a result, the demonstrated conversion method can be applied to CI-RMBPT photoionization calculations for a large number of multivalence atoms and ions.« less
Collective excitation of a trapped Bose-Einstein condensate with spin-orbit coupling
NASA Astrophysics Data System (ADS)
Chen, Li; Pu, Han; Yu, Zeng-Qiang; Zhang, Yunbo
2017-03-01
We investigate the collective excitations of a Raman-induced spin-orbit coupled Bose-Einstein condensate confined in a quasi-one-dimensional harmonic trap using the Bogoliubov method. By tuning the Raman coupling strength, three phases of the system can be identified. By calculating the transition strength, we are able to classify various excitation modes that are experimentally relevant. We show that the three quantum phases possess distinct features in their collective excitation properties. In particular, the spin dipole and the spin breathing modes can be used to clearly map out the phase boundaries. We confirm these predictions by direct numerical simulations of the quench dynamics that excites the relevant collective modes.
Long-Range Quantum Ising Spin Glasses at T=0: Gapless Collective Excitations and Universality
NASA Astrophysics Data System (ADS)
Andreanov, A.; Müller, M.
2012-10-01
We solve the Sherrington-Kirkpatrick model in a transverse field Γ deep in its quantum glass phase at zero temperature. We show that the glass phase is critical everywhere, exhibiting collective excitations with a gapless Ohmic spectral function. Using an effective potential approach, we interpret the latter as arising from disordered collective excitations behaving like weakly coupled, underdamped oscillators. For a small transverse field Γ, the low-frequency spectrum takes a form independent of the fluctuation strength Γ.
Long-range quantum Ising spin glasses at t=0: gapless collective excitations and universality.
Andreanov, A; Müller, M
2012-10-26
We solve the Sherrington-Kirkpatrick model in a transverse field Γ deep in its quantum glass phase at zero temperature. We show that the glass phase is critical everywhere, exhibiting collective excitations with a gapless Ohmic spectral function. Using an effective potential approach, we interpret the latter as arising from disordered collective excitations behaving like weakly coupled, underdamped oscillators. For a small transverse field Γ, the low-frequency spectrum takes a form independent of the fluctuation strength Γ.
Performance seeking control excitation mode
NASA Technical Reports Server (NTRS)
Schkolnik, Gerard
1995-01-01
Flight testing of the performance seeking control (PSC) excitation mode was successfully completed at NASA Dryden on the F-15 highly integrated digital electronic control (HIDEC) aircraft. Although the excitation mode was not one of the original objectives of the PSC program, it was rapidly prototyped and implemented into the architecture of the PSC algorithm, allowing valuable and timely research data to be gathered. The primary flight test objective was to investigate the feasibility of a future measurement-based performance optimization algorithm. This future algorithm, called AdAPT, which stands for adaptive aircraft performance technology, generates and applies excitation inputs to selected control effectors. Fourier transformations are used to convert measured response and control effector data into frequency domain models which are mapped into state space models using multiterm frequency matching. Formal optimization principles are applied to produce an integrated, performance optimal effector suite. The key technical challenge of the measurement-based approach is the identification of the gradient of the performance index to the selected control effector. This concern was addressed by the excitation mode flight test. The AdAPT feasibility study utilized the PSC excitation mode to apply separate sinusoidal excitation trims to the controls - one aircraft, inlet first ramp (cowl), and one engine, throat area. Aircraft control and response data were recorded using on-board instrumentation and analyzed post-flight. Sensor noise characteristics, axial acceleration performance gradients, and repeatability were determined. Results were compared to pilot comments to assess the ride quality. Flight test results indicate that performance gradients were identified at all flight conditions, sensor noise levels were acceptable at the frequencies of interest, and excitations were generally not sensed by the pilot.
Corium crust strength measurements.
Lomperski, S.; Nuclear Engineering Division
2009-11-01
Corium strength is of interest in the context of a severe reactor accident in which molten core material melts through the reactor vessel and collects on the containment basemat. Some accident management strategies involve pouring water over the melt to solidify it and halt corium/concrete interactions. The effectiveness of this method could be influenced by the strength of the corium crust at the interface between the melt and coolant. A strong, coherent crust anchored to the containment walls could allow the yet-molten corium to fall away from the crust as it erodes the basemat, thereby thermally decoupling the melt from the coolant and sharply reducing the cooling rate. This paper presents a diverse collection of measurements of the mechanical strength of corium. The data is based on load tests of corium samples in three different contexts: (1) small blocks cut from the debris of the large-scale MACE experiments, (2) 30 cm-diameter, 75 kg ingots produced by SSWICS quench tests, and (3) high temperature crusts loaded during large-scale corium/concrete interaction (CCI) tests. In every case the corium consisted of varying proportions of UO{sub 2}, ZrO{sub 2}, and the constituents of concrete to represent a LWR melt at different stages of a molten core/concrete interaction. The collection of data was used to assess the strength and stability of an anchored, plant-scale crust. The results indicate that such a crust is likely to be too weak to support itself above the melt. It is therefore improbable that an anchored crust configuration could persist and the melt become thermally decoupled from the water layer to restrict cooling and prolong an attack of the reactor cavity concrete.
Excitation with quantum light. I. Exciting a harmonic oscillator
NASA Astrophysics Data System (ADS)
Carreño, J. C. López; Laussy, F. P.
2016-12-01
We present a two-part study of the excitation of an optical target by quantum light. In this first part, we introduce the problematic and address the first case of interest, that of exciting the quantum harmonic oscillator, corresponding to, e.g., a single-mode passive cavity or a noninteracting bosonic field. We introduce a mapping of the Hilbert space that allows to chart usefully the accessible regions. We then consider the quantum excitation from single-photon sources in the form of a two-level system under various regimes of (classical) pumping: incoherent, coherent, and in the Mollow triplet regime. We close this first part with an overview of the material to be covered in the subsequent work.
Sadomasochism, sexual excitement, and perversion.
Kernberg, O F
1991-01-01
Sadomasochism, an ingredient of infantile sexuality, is an essential part of normal sexual functioning and love relations, and of the very nature of sexual excitement. Sadomasochistic elements are also present in all sexual perversions. Sadomasochism starts out as the potential for erotic masochism in both sexes, and represents a very early capacity to link aggression with the libidinal elements of sexual excitement. Sexual excitement may be considered a basic affect that overcomes primitive splitting of love and hatred. Erotic desire is a more mature form of sexual excitement. Psychoanalytic exploration makes it possible to uncover the unconscious components of sexual excitement: wishes for symbiotic fusion and for aggressive penetration and intermingling; bisexual identifications; the desire to transgress oedipal prohibitions and the secretiveness of the primal scene, and to violate the boundaries of a teasing and withholding object. The relation between these wishes and the development of erotic idealization processes in both sexes is explored in the context of a critical review of the pertinent psychoanalytic literature.
Strengths only or strengths and relative weaknesses? A preliminary study.
Rust, Teri; Diessner, Rhett; Reade, Lindsay
2009-10-01
Does working on developing character strengths and relative character weaknesses cause lower life satisfaction than working on developing character strengths only? The present study provides a preliminary answer. After 76 college students completed the Values in Action Inventory of Strengths (C. Peterson & M. E. P. Seligman, 2004), the authors randomly assigned them to work on 2 character strengths or on 1 character strength and 1 relative weakness. Combined, these groups showed significant gains on the Satisfaction With Life Scale (E. Diener, R. A. Emmons, R. J. Larsen, & S. Griffin, 1985), compared with a 32-student no-treatment group. However, there was no significant difference in gain scores between the 2-strengths group and the 1-character-strength-and-1-relative-character-weakness group. The authors discuss how focusing on relative character weaknesses (along with strengths) does not diminish-and may assist in increasing-life satisfaction.
Properties of Shell-Model Wavefunctions at High Excitation Energies
NASA Astrophysics Data System (ADS)
Frazier, Njema Jioni
Within the framework of the nuclear shell model with a realistic residual hamiltonian one can obtain the exact solution of the many-body problem. This makes it possible to study the interrelation between regular and chaotic features of dynamics in a generic many-body system with strong interaction. As an important application, we analyse the fragmentation of simple configurations as a function of excitation energy and interaction strength and examine the transition strengths induced by simple operators as a function of excitation energy. The analysis is performed for two systems; that of 12 valence particles in the sd-shell, or 28Si, and that of 8 valence particles in the sd-shell, or 24Mg. For the system of 12 valence particles in the sd-shell, we examine the fragmentation of shell-model basis states. For the system of 8 valence nucleons in the sd-shell, we examine the fragmentation associated with single-nucleon transfer and Gamow-Teller transitions. For the fragmentation of basis states, we use our statistics to establish the generic shape of the strength function distribution in the region of strong mixing. For the realistic interaction, the strength function distribution is close to Gaussian in the central part of the energy spectra. The width of the distribution is larger than predicted by Fermi's golden rule (4). We then take this one step further and examine the strength distributions associated with the one-nucleon transfer operator, aλ†, and the Gamow-Teller (GT) operator, Σλλ'(σμ τ±) λλ'aλ†a λ'. The spectroscopic factor, which is proportional to the square of the matrix element for the aλ† operator, is the simplest quantity used in predicting experimental observables. In our discussion of Gamow-Teller transitions, we examine both the GT strength function distribution and the values of total strength B(GT). For all the cases we examine, we take advantage of the reliability of our model for low-lying levels and our statistics to explore
Observation of isoscalar and isovector dipole excitations in neutron-rich 20O
NASA Astrophysics Data System (ADS)
Nakatsuka, N.; Baba, H.; Aumann, T.; Avigo, R.; Banerjee, S. R.; Bracco, A.; Caesar, C.; Camera, F.; Ceruti, S.; Chen, S.; Derya, V.; Doornenbal, P.; Giaz, A.; Horvat, A.; Ieki, K.; Inakura, T.; Imai, N.; Kawabata, T.; Kobayashi, N.; Kondo, Y.; Koyama, S.; Kurata-Nishimura, M.; Masuoka, S.; Matsushita, M.; Michimasa, S.; Million, B.; Motobayashi, T.; Murakami, T.; Nakamura, T.; Ohnishi, T.; Ong, H. J.; Ota, S.; Otsu, H.; Ozaki, T.; Saito, A.; Sakurai, H.; Scheit, H.; Schindler, F.; Schrock, P.; Shiga, Y.; Shikata, M.; Shimoura, S.; Steppenbeck, D.; Sumikama, T.; Syndikus, I.; Takeda, H.; Takeuchi, S.; Tamii, A.; Taniuchi, R.; Togano, Y.; Tscheuschner, J.; Tsubota, J.; Wang, H.; Wieland, O.; Wimmer, K.; Yamaguchi, Y.; Yoneda, K.; Zenihiro, J.
2017-05-01
The isospin characters of low-energy dipole excitations in neutron-rich unstable nucleus 20O were investigated, for the first time in unstable nuclei. Two spectra obtained from a dominant isovector probe (20O + Au) and a dominant isoscalar probe (20O + α) were compared and analyzed by the distorted-wave Born approximation to extract independently the isovector and isoscalar dipole strengths. Two known 1- states with large isovector dipole strengths at energies of 5.36(5) MeV (11-) and 6.84(7) MeV (12-) were also excited by the isoscalar probe. These two states were found to have different isoscalar dipole strengths, 2.70(32)% (11-) and 0.67(12)% (12-), respectively, in exhaustion of the isoscalar dipole-energy-weighted sum rule. The difference in isoscalar strength indicated that they have different underlying structures.
Modeling excitable systems: Reentrant tachycardia
NASA Astrophysics Data System (ADS)
Lancaster, Jarrett L.; Hellen, Edward H.; Leise, Esther M.
2010-01-01
Excitable membranes are an important type of nonlinear dynamical system, and their study can be used to provide a connection between physical and biological circuits. We discuss two models of excitable membranes important in cardiac and neural tissues. One model is based on the Fitzhugh-Nagumo equations, and the other is based on a three-transistor excitable circuit. We construct a circuit that simulates reentrant tachycardia and its treatment by surgical ablation. This project is appropriate for advanced undergraduates as a laboratory capstone project or as a senior thesis or honors project and can also be a collaborative project, with one student responsible for the computational predictions and another for the circuit construction and measurements.
Indirect excitation of ultrafast demagnetization
Vodungbo, Boris; Tudu, Bahrati; Perron, Jonathan; ...
2016-01-06
Does the excitation of ultrafast magnetization require direct interaction between the photons of the optical pump pulse and the magnetic layer? Here, we demonstrate unambiguously that this is not the case. For this we have studied the magnetization dynamics of a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon excitation with an intense femtosecond-short IR laser pulse, the film exhibits the classical ultrafast demagnetization phenomenon although only a negligible number of IR photons penetrate the aluminum layer. In comparison with an uncapped cobalt/palladium reference film, the initial demagnetization of the capped film occurs with a delayed onset andmore » at a slower rate. Both observations are qualitatively in line with energy transport from the aluminum layer into the underlying magnetic film by the excited, hot electrons of the aluminum film. As a result, our data thus confirm recent theoretical predictions.« less
Indirect excitation of ultrafast demagnetization
Vodungbo, Boris; Tudu, Bahrati; Perron, Jonathan; Delaunay, Renaud; Müller, Leonard; Berntsen, Magnus H.; Grübel, Gerhard; Malinowski, Grégory; Weier, Christian; Gautier, Julien; Lambert, Guillaume; Zeitoun, Philippe; Gutt, Christian; Jal, Emmanuelle; Reid, Alexander H.; Granitzka, Patrick W.; Jaouen, Nicolas; Dakovski, Georgi L.; Moeller, Stefan; Minitti, Michael P.; Mitra, Ankush; Carron, Sebastian; Pfau, Bastian; von Korff Schmising, Clemens; Schneider, Michael; Eisebitt, Stefan; Lüning, Jan
2016-01-01
Does the excitation of ultrafast magnetization require direct interaction between the photons of the optical pump pulse and the magnetic layer? Here, we demonstrate unambiguously that this is not the case. For this we have studied the magnetization dynamics of a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon excitation with an intense femtosecond-short IR laser pulse, the film exhibits the classical ultrafast demagnetization phenomenon although only a negligible number of IR photons penetrate the aluminum layer. In comparison with an uncapped cobalt/palladium reference film, the initial demagnetization of the capped film occurs with a delayed onset and at a slower rate. Both observations are qualitatively in line with energy transport from the aluminum layer into the underlying magnetic film by the excited, hot electrons of the aluminum film. Our data thus confirm recent theoretical predictions. PMID:26733106
Indirect excitation of ultrafast demagnetization
Vodungbo, Boris; Tudu, Bahrati; Perron, Jonathan; Delaunay, Renaud; Müller, Leonard; Berntsen, Magnus H.; Grübel, Gerhard; Malinowski, Grégory; Weier, Christian; Gautier, Julien; Lambert, Guillaume; Zeitoun, Philippe; Gutt, Christian; Jal, Emmanuelle; Reid, Alexander H.; Granitzka, Patrick W.; Jaouen, Nicolas; Dakovski, Georgi L.; Moeller, Stefan; Minitti, Michael P.; Mitra, Ankush; Carron, Sebastian; Pfau, Bastian; von Korff Schmising, Clemens; Schneider, Michael; Eisebitt, Stefan; Lüning, Jan
2016-01-06
Does the excitation of ultrafast magnetization require direct interaction between the photons of the optical pump pulse and the magnetic layer? Here, we demonstrate unambiguously that this is not the case. For this we have studied the magnetization dynamics of a ferromagnetic cobalt/palladium multilayer capped by an IR-opaque aluminum layer. Upon excitation with an intense femtosecond-short IR laser pulse, the film exhibits the classical ultrafast demagnetization phenomenon although only a negligible number of IR photons penetrate the aluminum layer. In comparison with an uncapped cobalt/palladium reference film, the initial demagnetization of the capped film occurs with a delayed onset and at a slower rate. Both observations are qualitatively in line with energy transport from the aluminum layer into the underlying magnetic film by the excited, hot electrons of the aluminum film. As a result, our data thus confirm recent theoretical predictions.
Stochastic excitation of stellar oscillations
NASA Astrophysics Data System (ADS)
Samadi, Reza
2001-05-01
Since more than about thirty years, solar oscillations are thought to be excited stochastically by the turbulent motions in the solar convective zone. It is currently believed that oscillations of stars lower than 2 solar masses - which possess an upper convective zone - are excited stochastically by turbulent convection in their outer layers. Providing that accurate measurements of the oscillation amplitudes and damping rates are available it is possible to evaluate the power injected into the modes and thus - by comparison with the observations - to constrain current theories. A recent theoretical work (Samadi & Goupil, 2001; Samadi et al., 2001) supplements and reinforces the theory of stochastic excitation of star vibrations. This process was generalized to a global description of the turbulent state of their convective zone. The comparison between observation and theory, thus generalized, will allow to better know the turbulent spectrum of stars, and this in particular thanks to the COROT mission.
Excitation optimization for damage detection
Bement, Matthew T; Bewley, Thomas R
2009-01-01
A technique is developed to answer the important question: 'Given limited system response measurements and ever-present physical limits on the level of excitation, what excitation should be provided to a system to make damage most detectable?' Specifically, a method is presented for optimizing excitations that maximize the sensitivity of output measurements to perturbations in damage-related parameters estimated with an extended Kalman filter. This optimization is carried out in a computationally efficient manner using adjoint-based optimization and causes the innovations term in the extended Kalman filter to be larger in the presence of estimation errors, which leads to a better estimate of the damage-related parameters in question. The technique is demonstrated numerically on a nonlinear 2 DOF system, where a significant improvement in the damage-related parameter estimation is observed.
Effect of interchain coupling on the excited polaron in conjugated polymers
NASA Astrophysics Data System (ADS)
Li, Xiao-xue; Chen, Gang
2017-02-01
Based on the one-dimensional extended Su-Schrieffer-Heeger model, we theoretically investigate the effect of interchain coupling on the formation and polarization of the single-excited state of polaron in conjugated polymers. It is found that there exists a turnover value of the coupling strength, over which the excited polaron could not be formed in either of the two coupled chains. Instead, a polaron-like particle is localized at the center of each chain. In addition, we also find that the reverse polarization of the excited polaron could be enhanced for some cases in polymer when the interchain coupling becomes strong until it exceeds the critical value.
On the interplay between allowed Gamow-Teller and Isovector Spin Monopole (IVSM) excitations
Bes, D. R.; Civitarese, O.; Suhonen, J.
2011-12-16
The excitation of Gamow-Teller (GT) and Isovector Spin Monopole (IVSM) modes in {sup 116}In by (p,n) and (n,p)) charge-exchange reactions is studied within the framework of the Quasiparticle Random-phase Approximation. It is shown that the admixture of the IVSM and Gamow-Teller (GT) excitations is negligible, and that the contribution to the strength above 20 MeV excitation energy, in {sup 116}In, is, most likely, due to the IVSM ({sigma}r{sup 2}{tau}{sup {+-}}) mode.
Switching the vibrational excitation of a polyatomic ion in multi-photon strong field ionization
NASA Astrophysics Data System (ADS)
Liu, Yuzhu; Gerber, Thomas; Radi, Peter; Sych, Yaroslav; Knopp, Gregor
2014-08-01
The multiphoton ionization (MPI) of CH3I has been investigated by angular resolved photoelectron spectroscopy as a function of femtosecond laser excitation intensity. A sudden change in the electron kinetic energy is observed above a specific field strength. The multiphoton excitation at a fixed wavelength of 800 nm becomes vibronically resonant due to Stark shifting of intermediate Rydberg state levels. The present letter gives an experimental evidence for ultrafast optical control of the vibrational excitation in a polyatomic ion by adjusting the intensity of a femtosecond laser pulse.
Experimental studies of excitations in a BEC in light-induced gauge fields
NASA Astrophysics Data System (ADS)
Li, Chuan-Hsun; Blasing, David; Olson, Abraham; Niffenegger, Robert; Chen, Yong P.
2014-05-01
We present our experimental studies of various excitation processes in a 87Rb Bose-Einstein condensate (BEC) in the presence of Raman light-induced gauge fields. We have systematically studied controllable inter-band excitations by modulating the strength of the Raman coupling, and probed the resultant decay from the upper dressed bands and heating of the BEC. We also present preliminary results probing the effects of synthetic spin-orbit coupling and gauge fields on collective excitations as well as photoassociation processes in the BEC.
Calculation of molecular excitation rates
NASA Technical Reports Server (NTRS)
Flynn, George
1993-01-01
State-to-state collisional excitation rates for interstellar molecules observed by radio astronomers continue to be required to interpret observed line intensities in terms of local temperatures and densities. A problem of particular interest is collisional excitation of water which is important for modeling the observed interstellar masers. In earlier work supported by a different NASA Grant, excitation of water in collisions with He atoms was studied; after many years of successively more refined calculations that problem now seems to be well understood, and discrepancies with earlier experimental data for related (pressure broadening) phenomena are believed to reflect experimental errors. Because of interstellar abundances, excitation by H2, the dominant interstellar species, is much more important than excitation by He, although it has been argued that rates for excitation by these are similar. Under the current grant theoretical study of this problem has begun which is greatly complicated by the additional degrees of freedom which must be included both in determining the interaction potential and also in the molecular scattering calculation. We have now computed the interaction forces for nearly a thousand molecular geometries and are close to having an acceptable global fit to these points which is necessary for the molecular dynamics calculations. Also, extensive modifications have been made to the molecular scattering code, MOLSCAT. These included coding the rotational basis sets and coupling matrix elements required for collisions of an asymmetric top with a linear rotor. A new method for numerical solution of the coupled equations has been incorporated. Because of the long-ranged nature of the water-hydrogen interaction it is necessary to integrate the equations to rather large intermolecular separations, and the integration methods previously available in MOLSCAT are not ideal for such cases. However, the method used by Alexander in his HIBRIDON code is
Differences in excitability between median and superficial radial sensory axons.
Fujimaki, Yumi; Kanai, Kazuaki; Misawa, Sonoko; Shibuya, Kazumoto; Isose, Sagiri; Nasu, Saiko; Sekiguchi, Yukari; Ohmori, Shigeki; Noto, Yu-ichi; Kugio, Yumiko; Shimizu, Toshio; Matsubara, Shiro; Lin, Cindy S Y; Kuwabara, Satoshi
2012-07-01
The aim of this study was to investigate differences in excitability properties of human median and superficial radial sensory axons (e.g., axons innervating the glabrous and hairy skin in the hand). Previous studies have shown that excitability properties differ between motor and sensory axons, and even among sensory axons between median and sural sensory axons. In 21 healthy subjects, threshold tracking was used to examine excitability indices such as strength-duration time constant, threshold electrotonus, supernormality, and threshold change at the 0.2 ms inter-stimulus interval in latent addition. In addition, threshold changes induced by ischemia for 10 min were compared between median and superficial radial sensory axons. Compared with radial sensory axons, median axons showed shorter strength-duration time constant, greater threshold changes in threshold electrotonus (fanning-out), greater supernormality, and smaller threshold changes in latent addition. Threshold changes in both during and after ischemia were greater for median axons. These findings suggest that membrane potential in human median sensory axons is more negative than in superficial radial axons, possibly due to greater activity of electrogenic Na(+)/K(+) pump. These results may reflect adaptation to impulses load carried by median axons that would be far greater with a higher frequency. Biophysical properties are not identical in different human sensory axons, and therefore their responses to disease may differ. Copyright © 2011 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
Resonant parametric excitations driven by lower-hybrid fields
NASA Astrophysics Data System (ADS)
Villalon, E.
1980-11-01
Three-wave parametric excitation in inhomogeneous plasmas is examined in a two-dimensional geometry relevant to supplementary rf heating of tokamaks. The stabilization of resonant parametric excitation due to a linear mismatch in wavenumbers and to the Landau-damping rates of the decay waves is analyzed, assuming that the magnitude of the pump field is constant in time and in the spatial region where the resonant interaction takes place. Both types of temporally growing modes and spatially amplified instabilities are studied, using a WKB analysis. It is shown that by increasing the strength of the mismatch K prime or the width of the pump L, the growth rate of the fastest growing normal mode will decrease. The amount of spatial amplification is also reduced by the mismatch in wavenumbers and by the damping rates of the excited waves. Because of the finite spatial extent of the pump electric field, the amplification length is smaller than or equal to L, depending on the strength of the mismatch and damping rates.
Excited-to-excited-state scattering using weak measurements
NASA Astrophysics Data System (ADS)
U, Satya Sainadh; Narayanan, Andal
2015-11-01
Weak measurements are a subset of measurement processes in quantum mechanics wherein the system, which is being measured, interacts very weakly with the measuring apparatus. Measurement values of observables undergoing a weak interaction and their amplification are concepts that have sharpened our understanding of interaction processes in quantum mechanics. Recent experiments show that naturally occurring processes such as resonance fluorescence from excited states of an atom can exhibit weak value amplification effect. In this paper we theoretically analyze the process of elastic resonance fluorescence from a V -type three-level atomic system, using the well-known Weiskopff-Wigner (WW) theory of spontaneous emission. Within this theory we show that a weak interaction regime can be identified and for suitable choices of initial and final excited states the mean scattering time between these states show an amplification effect during interaction with the vacuum bath modes of the electromagnetic field. We thus show that a system-bath interaction can show weak value amplification. Using our theory we reproduce the published experimental results carried out in such a system. More importantly, our theory can calculate scattering time scales in elastic resonance scattering between multiple excited states of a single atom or between common excited state configurations of interacting multiatom systems.
Autoresonant Excitation of Antiproton Plasmas
NASA Astrophysics Data System (ADS)
Andresen, G. B.; Ashkezari, M. D.; Baquero-Ruiz, M.; Bertsche, W.; Bowe, P. D.; Butler, E.; Carpenter, P. T.; Cesar, C. L.; Chapman, S.; Charlton, M.; Fajans, J.; Friesen, T.; Fujiwara, M. C.; Gill, D. R.; Hangst, J. S.; Hardy, W. N.; Hayden, M. E.; Humphries, A. J.; Hurt, J. L.; Hydomako, R.; Jonsell, S.; Madsen, N.; Menary, S.; Nolan, P.; Olchanski, K.; Olin, A.; Povilus, A.; Pusa, P.; Robicheaux, F.; Sarid, E.; Silveira, D. M.; So, C.; Storey, J. W.; Thompson, R. I.; van der Werf, D. P.; Wurtele, J. S.; Yamazaki, Y.
2011-01-01
We demonstrate controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense, and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination.
Directional excitation without breaking reciprocity
NASA Astrophysics Data System (ADS)
Ramezani, Hamidreza; Dubois, Marc; Wang, Yuan; Shen, Y. Ron; Zhang, Xiang
2016-09-01
We propose a mechanism for directional excitation without breaking reciprocity. This is achieved by embedding an impedance matched parity-time symmetric potential in a three-port system. The amplitude distribution within the gain and loss regions is strongly influenced by the direction of the incoming field. Consequently, the excitation of the third port is contingent on the direction of incidence while transmission in the main channel is immune. Our design improves the four-port directional coupler scheme, as there is no need to implement an anechoic termination to one of the ports.
Decentralized nonlinear optimal excitation control
Lu, Q.; Sun, Y.; Xu, Z.; Mochizuki, T.
1996-11-01
A design method to lay emphasis on differential geometric approach for decentralized nonlinear optimal excitation control of multimachine systems is suggested in this paper. The control law achieved is implemented via purely local measurements. Moreover, it is independent of the parameters of power networks. Simulations are performed on a six-machine system. It has been demonstrated that the nonlinear optimal excitation control could adapt to the conditions under large disturbances. Besides, this paper has verified that the optimal control in the sense of LQR principle for the linearized system is equivalent to an optimal control in the sense of a quasi-quadratic performance index for the primitive nonlinear control system.
Parametric excitation and squeezing in a many-body spinor condensate
Hoang, T. M.; Anquez, M.; Robbins, B. A.; Yang, X. Y.; Land, B. J.; Hamley, C. D.; Chapman, M. S.
2016-01-01
Atomic spins are usually manipulated using radio frequency or microwave fields to excite Rabi oscillations between different spin states. These are single-particle quantum control techniques that perform ideally with individual particles or non-interacting ensembles. In many-body systems, inter-particle interactions are unavoidable; however, interactions can be used to realize new control schemes unique to interacting systems. Here we demonstrate a many-body control scheme to coherently excite and control the quantum spin states of an atomic Bose gas that realizes parametric excitation of many-body collective spin states by time varying the relative strength of the Zeeman and spin-dependent collisional interaction energies at multiples of the natural frequency of the system. Although parametric excitation of a classical system is ineffective from the ground state, we show that in our experiment, parametric excitation from the quantum ground state leads to the generation of quantum squeezed states. PMID:27044675
Parametric excitation and squeezing in a many-body spinor condensate
NASA Astrophysics Data System (ADS)
Hoang, T. M.; Anquez, M.; Robbins, B. A.; Yang, X. Y.; Land, B. J.; Hamley, C. D.; Chapman, M. S.
2016-04-01
Atomic spins are usually manipulated using radio frequency or microwave fields to excite Rabi oscillations between different spin states. These are single-particle quantum control techniques that perform ideally with individual particles or non-interacting ensembles. In many-body systems, inter-particle interactions are unavoidable; however, interactions can be used to realize new control schemes unique to interacting systems. Here we demonstrate a many-body control scheme to coherently excite and control the quantum spin states of an atomic Bose gas that realizes parametric excitation of many-body collective spin states by time varying the relative strength of the Zeeman and spin-dependent collisional interaction energies at multiples of the natural frequency of the system. Although parametric excitation of a classical system is ineffective from the ground state, we show that in our experiment, parametric excitation from the quantum ground state leads to the generation of quantum squeezed states.
Optimization of the excitation light sheet in selective plane illumination microscopy
Gao, Liang
2015-01-01
Selective plane illumination microscopy (SPIM) allows rapid 3D live fluorescence imaging on biological specimens with high 3D spatial resolution, good optical sectioning capability and minimal photobleaching and phototoxic effect. SPIM gains its advantage by confining the excitation light near the detection focal plane, and its performance is determined by the ability to create a thin, large and uniform excitation light sheet. Several methods have been developed to create such an excitation light sheet for SPIM. However, each method has its own strengths and weaknesses, and tradeoffs must be made among different aspects in SPIM imaging. In this work, we present a strategy to select the excitation light sheet among the latest SPIM techniques, and to optimize its geometry based on spatial resolution, field of view, optical sectioning capability, and the sample to be imaged. Besides the light sheets discussed in this work, the proposed strategy is also applicable to estimate the SPIM performance using other excitation light sheets. PMID:25798312
Nitsche, M A; Paulus, W
2000-01-01
In this paper we demonstrate in the intact human the possibility of a non-invasive modulation of motor cortex excitability by the application of weak direct current through the scalp.Excitability changes of up to 40 %, revealed by transcranial magnetic stimulation, were accomplished and lasted for several minutes after the end of current stimulation.Excitation could be achieved selectively by anodal stimulation, and inhibition by cathodal stimulation.By varying the current intensity and duration, the strength and duration of the after-effects could be controlled.The effects were probably induced by modification of membrane polarisation. Functional alterations related to post-tetanic potentiation, short-term potentiation and processes similar to postexcitatory central inhibition are the likely candidates for the excitability changes after the end of stimulation. Transcranial electrical stimulation using weak current may thus be a promising tool to modulate cerebral excitability in a non-invasive, painless, reversible, selective and focal way. PMID:10990547
Nature of the lowest excited states of neutral polyenyl radicals and polyene radical cations
NASA Astrophysics Data System (ADS)
Starcke, Jan Hendrik; Wormit, Michael; Dreuw, Andreas
2009-10-01
Due to the close relation of the polyenyl radicals C2n+1H2n+3• and polyene radical cations C2nH2n+2•+ to the neutral linear polyenes, one may suspect their excited states to possess substantial double excitation character, similar to the famous S1 state of neutral polyenes and thus to be equally problematic for simple excited state theories. Using the recently developed unrestricted algebraic-diagrammatic construction scheme of second order perturbation theory and the equation-of-motion coupled-cluster method, the vertical excitation energies, their corresponding oscillator strengths, and the nature of the wave functions of the lowest excited electronic states of the radicals are calculated and analyzed in detail. For the polyenyl radicals two one-photon allowed states are found as D1 and D4 states, with two symmetry-forbidden D2 and D3 states in between, while in the polyene radical cations D1 and D2 are allowed and D3 is forbidden. The order of the states is conserved with increasing chain length. It is found that all low-lying excited states exhibit a significant but similar amount of doubly excited configuration in their wave functions of 15%-20%. Using extrapolation, predictions for the excitation energies of the five lowest excited states of the polyene radical cations are made for longer chain lengths.
Strength of ~20-Hz Rebound and Motor Recovery After Stroke.
Parkkonen, Eeva; Laaksonen, Kristina; Piitulainen, Harri; Pekkola, Johanna; Parkkonen, Lauri; Tatlisumak, Turgut; Forss, Nina
2017-05-01
Stroke is a major cause of disability worldwide, and effective rehabilitation is crucial to regain skills for independent living. Recently, novel therapeutic approaches manipulating the excitatory-inhibitory balance of the motor cortex have been introduced to boost recovery after stroke. However, stroke-induced neurophysiological changes of the motor cortex may vary despite of similar clinical symptoms. Therefore, better understanding of excitability changes after stroke is essential when developing and targeting novel therapeutic approaches. We identified recovery-related alterations in motor cortex excitability after stroke using magnetoencephalography. Dynamics (suppression and rebound) of the ~20-Hz motor cortex rhythm were monitored during passive movement of the index finger in 23 stroke patients with upper limb paresis at acute phase, 1 month, and 1 year after stroke. After stroke, the strength of the ~20-Hz rebound to stimulation of both impaired and healthy hand was decreased with respect to the controls in the affected (AH) and unaffected (UH) hemispheres, and increased during recovery. Importantly, the rebound strength was lower than that of the controls in the AH and UH also to healthy-hand stimulation despite of intact afferent input. In the AH, the rebound strength to impaired-hand stimulation correlated with hand motor recovery. Motor cortex excitability is increased bilaterally after stroke and decreases concomitantly with recovery. Motor cortex excitability changes are related to both alterations in local excitatory-inhibitory circuits and changes in afferent input. Fluent sensorimotor integration, which is closely coupled with excitability changes, seems to be a key factor for motor recovery.
M1 excitation in Sm isotopes and the proton-neutron sdg interacting boson model
NASA Astrophysics Data System (ADS)
Mizusaki, Takahiro; Otsuka, Takaharu; Sugita, Michiaki
1991-10-01
The magnetic-dipole scissors mode in spherical to deformed Sm isotopes is studied in terms of the proton-neutron sdg interacting boson model, providing a good agreement with recent experiment by Ziegler et al. The present calculation correctly reproduces the increase of M1 excitation strength in going from spherical to deformed nuclei. It is suggested that there may be 1+ states which do not correspond to the scissors mode but absorb certain M1 strength from the ground state.
Oscillator strength distribution in the alkaline-earth elements
NASA Astrophysics Data System (ADS)
Barrientos, Carmen; Martin, Inmaculada
1988-01-01
The oscillator strength distribution between the discrete and continuous regions of the spectra of Mg, Ca, Sr, and Ba has been obtained. Computations have been carried out through the Quantum Defect Orbital (QDO) method, with explicit introduction of the two-electron transitions that lead to resonances in the spectra of the last three elements. Interference effects between excitations to autoionizing levels and to the continuum hve been ignored.
Lifetimes and electromagnetic transition strengths in 157Dy
NASA Astrophysics Data System (ADS)
Gladnishki, K. A.; Petkov, P.; Möller, O.; Dewald, A.; Jolie, J.; Tonev, D.; Trichkova, M.; Heinze, S.; von Brentano, P.; Bazzacco, D.; Ur, C. A.; Farnea, E.; Axiotis, M.; Lunardi, S.; de Angelis, G.; Napoli, D. R.; Marginean, N.; Martinez, T.; Caprio, M. A.; Rainovski, G.
2017-08-01
Lifetimes of excited states of 157Dy were measured by recoil distance Doppler-shift (RDDS) and Doppler-shift attenuation (DSAM) methods. The γ -ray coincidence data were analyzed by the differential decay curve method. The level scheme and the newly deduced transition strengths were simultaneously described in the framework of the particle plus triaxial rotor model (PTRM) and the rigid-rotor model.
Prepubescent Strength Training. Some Considerations.
ERIC Educational Resources Information Center
Priest, Joe W.; Holshouser, Richard S.
1987-01-01
Under the careful supervision of a trained fitness professional, the benefits of prepubescent strength training (improved strength, power, muscular endurance, bone density) outweigh the risks (acute and chronic musculoskeletal injuries). (CB)
NASA Astrophysics Data System (ADS)
Pietralla, N.; Beck, O.; Besserer, J.; von Brentano, P.; Eckert, T.; Fischer, R.; Fransen, C.; Herzberg, R.-D.; Jäger, D.; Jolos, R. V.; Kneissl, U.; Krischok, B.; Margraf, J.; Maser, H.; Nord, A.; Pitz, H. H.; Rittner, M.; Schiller, A.; Zilges, A.
1997-02-01
Photon scattering experiments have been performed on the heavy deformed nuclei 178,180Hf using an Eγ < 4 MeV bremsstrahlung beam as a continuous energy photon source. Numerous dipole excitations have been identified from the spectra of high-resolution Ge γ detectors. Spins, K quantum numbers, dipole excitation strengths, and level widths, have been extracted from the scattering cross sections. From the measured level widths lifetimes of 67 levels can be deduced. The excitation strength of the scissors mode is discussed and extends the systematics from the neighboring rare earth nuclei. Besides the ΔK = 1 excitations other dipole excitations have been observed that are distinguished from the scissors mode states by their different decay behavior.
Crossover from skin mode to proton-neutron mode in E1 excitations of neutron-rich nuclei
NASA Astrophysics Data System (ADS)
Nakada, H.; Inakura, T.; Sawai, H.
2013-03-01
The character of the low-energy E1 excitations is investigated by analyzing transition densities obtained from the RPA calculations in the doubly magic nuclei. We propose a decomposition method of the E1 excitations into the pn mode (i.e., oscillation between protons and neutrons) and the skin mode (i.e., oscillation of the neutron skin against the inner core) via the transition densities, by which their mixing is handled in a straightforward manner. Crossover behavior of the E1 excitations is found, from the skin mode at low energy to the pn mode at higher energy. The ratio of the skin-mode strength to the full strength turns out to be insensitive to the nuclides and to the effective interactions in the energy region of the crossover. Depending on the excitation energy, the observed low-energy E1 excitations are not necessarily dominated by the skin mode, as exemplified for 90Zr.
Homeostatic Scaling of Excitability in Recurrent Neural Networks
Remme, Michiel W. H.; Wadman, Wytse J.
2012-01-01
Neurons adjust their intrinsic excitability when experiencing a persistent change in synaptic drive. This process can prevent neural activity from moving into either a quiescent state or a saturated state in the face of ongoing plasticity, and is thought to promote stability of the network in which neurons reside. However, most neurons are embedded in recurrent networks, which require a delicate balance between excitation and inhibition to maintain network stability. This balance could be disrupted when neurons independently adjust their intrinsic excitability. Here, we study the functioning of activity-dependent homeostatic scaling of intrinsic excitability (HSE) in a recurrent neural network. Using both simulations of a recurrent network consisting of excitatory and inhibitory neurons that implement HSE, and a mean-field description of adapting excitatory and inhibitory populations, we show that the stability of such adapting networks critically depends on the relationship between the adaptation time scales of both neuron populations. In a stable adapting network, HSE can keep all neurons functioning within their dynamic range, while the network is undergoing several (patho)physiologically relevant types of plasticity, such as persistent changes in external drive, changes in connection strengths, or the loss of inhibitory cells from the network. However, HSE cannot prevent the unstable network dynamics that result when, due to such plasticity, recurrent excitation in the network becomes too strong compared to feedback inhibition. This suggests that keeping a neural network in a stable and functional state requires the coordination of distinct homeostatic mechanisms that operate not only by adjusting neural excitability, but also by controlling network connectivity. PMID:22570604
Strength Development for Young Adolescents
ERIC Educational Resources Information Center
McDaniel, Larry W.; Jackson, Allen; Gaudet, Laura
2009-01-01
Participation in strength training is important for older children or young adolescences who wish to improve fitness or participate in sports. When designing strength training programs for our youth this age group is immature anatomically, physiologically, and psychologically. For the younger or inexperienced group the strength training activities…
Strength Training and Children's Health.
ERIC Educational Resources Information Center
Faigenbaum, Avery D.
2001-01-01
Provides an overview of the potential health benefits of strength training for children, discussing the role of strength training in preventing sports-related injuries and highlighting design considerations for such programs. The focus is on musculoskeletal adaptations to strength training that are observable in healthy children. Guidelines for…
Strength Training and Children's Health.
ERIC Educational Resources Information Center
Faigenbaum, Avery D.
2001-01-01
Provides an overview of the potential health benefits of strength training for children, discussing the role of strength training in preventing sports-related injuries and highlighting design considerations for such programs. The focus is on musculoskeletal adaptations to strength training that are observable in healthy children. Guidelines for…
Strength of Rewelded Inconel 718
NASA Technical Reports Server (NTRS)
Bayless, E.; Lovoy, C. V.; Mcllwain, M. C.; Munafo, P.
1982-01-01
Inconel 718, nickel-based alloy used extensively for high-temperature structural service, welded repeatedly without detriment to its strength. According to NASA report, tests show 12 repairs on same weld joint do not adversely affect ultimate tensile strenth, yield strength, fatigue strength, metallurgical grain structures, or ability of weld joint to respond to post weld heat treatments.
NASA Astrophysics Data System (ADS)
Schilders, S. P.; Gu, M.
2000-03-01
The effect of multiple scattering in a turbid medium on single-photon and two-photon fluorescence microscopy is experimentally investigated for different scattering characteristics including scattering anisotrophy and optical thickness of a turbid medium. It is demonstrated that two-photon excitation can provide significant improvement in penetration depth through turbid media, due to reduced scattering experienced by the excitation beam. It is also shown that the limiting factor in obtaining high-quality images under singlephoton excitation is the fast degradation of image resolution caused by multiple scattering, while for twophoton excitation it is limited by the degradation of image contrast due to the reduction in fluorescence strength.
The fracture strength and frictional strength of Weber Sandstone
Byerlee, J.D.
1975-01-01
The fracture strength and frictional strength of Weber Sandstone have been measured as a function of confining pressure and pore pressure. Both the fracture strength and the frictional strength obey the law of effective stress, that is, the strength is determined not by the confining pressure alone but by the difference between the confining pressure and the pore pressure. The fracture strength of the rock varies by as much as 20 per cent depending on the cement between the grains, but the frictional strength is independent of lithology. Over the range 0 2 kb, ??=0??5 + 0??6??n. This relationship also holds for other rocks such as gabbro, dunite, serpentinite, granite and limestone. ?? 1975.
Launch Excitement with Water Rockets
ERIC Educational Resources Information Center
Sanchez, Juan Carlos; Penick, John
2007-01-01
Explosions and fires--these are what many students are waiting for in science classes. And when they do occur, students pay attention. While we can't entertain our students with continual mayhem, we can catch their attention and cater to their desires for excitement by saying, "Let's make rockets." In this activity, students make simple, reusable…
Elementary Excitations in Quantum Liquids.
ERIC Educational Resources Information Center
Pines, David
1981-01-01
Discusses elementary excitations and their role in condensed matter physics, focusing on quantum plasma, helium liquids, and superconductors. Considers research primarily conducted in the 1950s and concludes with a brief survey of some closely related further developments. (Author/JN)
Pseudorandom selective excitation in NMR
NASA Astrophysics Data System (ADS)
Walls, Jamie D.; Coomes, Alexandra
2011-09-01
In this work, average Hamiltonian theory is used to study selective excitation under a series of small flip-angle θ-pulses θ ≪ {π}/{3} applied either periodically [corresponding to the DANTE pulse sequence] or aperiodically to a spin-1/2 system. First, an average Hamiltonian description of the DANTE pulse sequence is developed that is valid for frequencies either at or very far from integer multiples of {1}/{τ}, where τ is the interpulse delay. For aperiodic excitation, a single resonance, νsel, can be selectively excited if the θ-pulse phases are modulated in concert with the interpulse delays. The conditions where average Hamiltonian theory can be accurately applied to describe the dynamics under aperiodic selective pulses, which are referred to as pseudorandom-DANTE or p-DANTE sequences, are similar to those found for the DANTE sequence. Signal averaging over different p-DANTE sequences improves the apparent selectivity at νsel by reducing the excitations at other frequencies. Experimental demonstrations of p-DANTE sequences and comparisons with the theory are presented.
Exciting cytoskeleton-membrane waves
NASA Astrophysics Data System (ADS)
Shlomovitz, R.; Gov, N. S.
2008-10-01
Propagating waves on the surface of cells, over many micrometers, involve active forces. We investigate here the mechanical excitation of such waves when the membrane is perturbed by an external oscillatory force. The external perturbation may trigger the propagation of such waves away from the force application. This scheme is then suggested as a method to probe the properties of the excitable medium of the cell, and learn about the mechanisms that drive the wave propagation. We then apply these ideas to a specific model of active cellular membrane waves, demonstrating how the response of the system to the external perturbation depends on the properties of the model. The most outstanding feature that we find is that the excited waves exhibit a resonance phenomenon at the frequency corresponding to the tendency of the system to develop a linear instability. Mechanical excitation of membrane waves in cells at different frequencies can therefore be used to characterize the properties of the mechanism underlying the existence of these waves.
Communicating the Excitement of Science
Michael Turner
2016-07-12
In this talk (which will include some exciting science) I will discuss some lessons I have learned about communicating science to scientists (in my own field and others), students, the public, the press, and policy makers in giving 500+ colloquia and seminars, 300+ public lectures and many informal presentations (including cocktail parties).
Predictions for Excited Strange Baryons
Fernando, Ishara P.; Goity, Jose L.
2016-04-01
An assessment is made of predictions for excited hyperon masses which follow from flavor symmetry and consistency with a 1/N c expansion of QCD. Such predictions are based on presently established baryonic resonances. Low lying hyperon resonances which do not seem to fit into the proposed scheme are discussed.
Pattern Formation in Excitable Media
NASA Astrophysics Data System (ADS)
Mikhailov, Alexander S.
1997-03-01
In this talk I give a short review of the history and the current state of theoretical research on spiral wave patterns in excitable media. I start with the theoretical model of wave propagation in excitable media proposed in 1946 by Wiener and Rosenblueth(N. Wiener and A. Rosenblueth, The mathematical formulation of the problem of conduction of impulses in a network of connected excitable elements, specifically in cardiac muscle, Arch. Inst. Cardiol. Mexico 16 (1946) 205). This model describes spiral waves rotating around obstacles. I show how, by taking additionally into account curvature effects and gradual recovery of the medium after passage of an excitation wave, the model is generalized to describe freely rotating spiral waves and the breakup which produces spirals. In the context of this kinematic model, complex dynamics of spiral waves, i.e. their meandering, drift and resonance, is discussed. Instabilities of spiral waves in confined geometries, i.e. inside a circular region and on a sphere, are analyzed. At the end, I show how spiral waves in such systems can be efficiently controlled by application of a delayed global feedback. The talk is based on the review paper(A. S. Mikhailov, V. A. Davydov, and V. S. Zykov, Complex dynamics of spiral waves and motion of curves, Physica D 70 (1994) 1) and the monograph(A. S. Mikhailov, Foundations of Synergetics I, 2nd revised edition (Springer, Berlin, 1994)).
Elementary Excitations in Quantum Liquids.
ERIC Educational Resources Information Center
Pines, David
1981-01-01
Discusses elementary excitations and their role in condensed matter physics, focusing on quantum plasma, helium liquids, and superconductors. Considers research primarily conducted in the 1950s and concludes with a brief survey of some closely related further developments. (Author/JN)
Launch Excitement with Water Rockets
ERIC Educational Resources Information Center
Sanchez, Juan Carlos; Penick, John
2007-01-01
Explosions and fires--these are what many students are waiting for in science classes. And when they do occur, students pay attention. While we can't entertain our students with continual mayhem, we can catch their attention and cater to their desires for excitement by saying, "Let's make rockets." In this activity, students make simple, reusable…
Excitation processes in cometary comae
NASA Astrophysics Data System (ADS)
Singh, P. D.
The excitation of cometary NH and S2 molecules is discussed. Particular attention is given to emission bands due to a specific S2 transition in the range of 2829-3058 A observed in the UV spectra of comet IRAS Araki-Alcock (1983). It is suggested that photodissociation and dissociative electron recombination processes may be sources of metastable nitrogen atoms in comets.
Perceptual Load Alters Visual Excitability
ERIC Educational Resources Information Center
Carmel, David; Thorne, Jeremy D.; Rees, Geraint; Lavie, Nilli
2011-01-01
Increasing perceptual load reduces the processing of visual stimuli outside the focus of attention, but the mechanism underlying these effects remains unclear. Here we tested an account attributing the effects of perceptual load to modulations of visual cortex excitability. In contrast to stimulus competition accounts, which propose that load…
NASA Technical Reports Server (NTRS)
Peeters, E.; Martin-Hernandez, N. L.; Rodriguez-Fernandez, N. J.; Tielens, A. G. G. M.
2004-01-01
An overview is given of ISO results on regions of high excitation ISM and gas, i.e. HII regions, the Galactic Centre and Supernovae Remnants. IR emission due to fine-structure lines, molecular hydrogen, silicates, polycyclic aromatic hydrocarbons and dust are summarized, their diagnostic capabilities illustrated and their implications highlighted.
Dynamics of excited molecular states
NASA Astrophysics Data System (ADS)
Meyer, Hans-Dieter
2005-01-01
The photo-excitation or photo-ionization of a polyatomic molecule is typically accompanied by a strong excitation of the vibrational modes. In particular when a conical intersection of the electronic potential energy surfaces involved lies within or close to the Frank-Condon zone, the nuclear motion becomes very complicated, often chaotic, and the spectra become irregular and dense. An accurate simulation of the dynamics of such excited molecules requires firstly that the multi-dimensional and multi-state potential energy surface - or a reliable model thereof - can be determined. Secondly, the multi-dimensional quantum dynamics have to be solved. This is a very difficult task, because of the high dimensionality of the problem (6 to 30 degrees of freedom, say). The multi-configuration time-dependent Hartree (MCTDH) method has proven to be very useful for the study of such problems. In fact, an accurate treatment of the quantal dynamics of molecules like the allene cation (C3 H+4, 15D), the butatriene cation (C4 H+4, 18D), or the pyrazine molecule (C4N2H4, 24D) in their full dimensionality, is - up to date - only possible with MCTDH. (The acronym n D denotes the dimensionality.) The construction of the vibronic model Hamiltonian and the MCTDH method will be briefly discussed. After this, the excited state dynamics of the butatriene and pyrazine molecules will be discussed.
Fast excitation variable period wiggler
van Steenbergen, A.; Gallardo, J.; Romano, T.; Woodle, M.
1991-01-01
The design of an easily stackable, variable period length, fast excitation driven wiggler, making use of geometrically alternating substacks of Vanadium Permandur ferromagnetic laminations, interspaced with conductive, non magnetic, laminations which act as eddy current induced field reflectors,'' is discussed and experimental results obtained with short wiggler models are presented.
Fast excitation variable period wiggler
van Steenbergen, A.; Gallardo, J.; Romano, T.; Woodle, M.
1991-12-31
The design of an easily stackable, variable period length, fast excitation driven wiggler, making use of geometrically alternating substacks of Vanadium Permandur ferromagnetic laminations, interspaced with conductive, non magnetic, laminations which act as eddy current induced ``field reflectors,`` is discussed and experimental results obtained with short wiggler models are presented.
Communicating the Excitement of Science
Michael Turner
2009-06-05
In this talk (which will include some exciting science) I will discuss some lessons I have learned about communicating science to scientists (in my own field and others), students, the public, the press, and policy makers in giving 500+ colloquia and seminars, 300+ public lectures and many informal presentations (including cocktail parties).
Oscillator strengths and collision strengths for some ions of oxygen and sulphur
NASA Technical Reports Server (NTRS)
Ho, Y. K.; Henry, R. J. W.
1982-01-01
Collision strengths for electron impact excitation of the O II, O III, S II and S III for some transitions in the ultraviolet of the type ns(sup 2) np(sup q) yields ns np(sup q +1), ns(sup 2) np(sup q) yields ns(sup 2) np(sup q-1) (n+1)s and 3s2 3p(sup q) yields 352 3p(sup q -1) 3d are calculated in a close coupling approximation for an energy rate up to one million K. Configuration interaction target wave functions which give oscillator strengths accurate to 10% for O II and O III, and 20-30% for S II and S III, are used in the expansion. Accurate knowledge of the electron impact excitation cross sections is particularly significant for a proper interpretation of the combined ultraviolet observations of the Voyager UVS and IUE results on properties of the Io plasma torus.
Systematics of strength function sum rules
Johnson, Calvin W.
2015-08-28
Sum rules provide useful insights into transition strength functions and are often expressed as expectation values of an operator. In this letter I demonstrate that non-energy-weighted transition sum rules have strong secular dependences on the energy of the initial state. Such non-trivial systematics have consequences: the simplification suggested by the generalized Brink–Axel hypothesis, for example, does not hold for most cases, though it weakly holds in at least some cases for electric dipole transitions. Furthermore, I show the systematics can be understood through spectral distribution theory, calculated via traces of operators and of products of operators. Seen through this lens,more » violation of the generalized Brink–Axel hypothesis is unsurprising: one expectssum rules to evolve with excitation energy. Moreover, to lowest order the slope of the secular evolution can be traced to a component of the Hamiltonian being positive (repulsive) or negative (attractive).« less
Systematics of strength function sum rules
Johnson, Calvin W.
2015-08-28
Sum rules provide useful insights into transition strength functions and are often expressed as expectation values of an operator. In this letter I demonstrate that non-energy-weighted transition sum rules have strong secular dependences on the energy of the initial state. Such non-trivial systematics have consequences: the simplification suggested by the generalized Brink–Axel hypothesis, for example, does not hold for most cases, though it weakly holds in at least some cases for electric dipole transitions. Furthermore, I show the systematics can be understood through spectral distribution theory, calculated via traces of operators and of products of operators. Seen through this lens, violation of the generalized Brink–Axel hypothesis is unsurprising: one expectssum rules to evolve with excitation energy. Moreover, to lowest order the slope of the secular evolution can be traced to a component of the Hamiltonian being positive (repulsive) or negative (attractive).
Systematics of strength function sum rules
NASA Astrophysics Data System (ADS)
Johnson, Calvin W.
2015-11-01
Sum rules provide useful insights into transition strength functions and are often expressed as expectation values of an operator. In this letter I demonstrate that non-energy-weighted transition sum rules have strong secular dependences on the energy of the initial state. Such non-trivial systematics have consequences: the simplification suggested by the generalized Brink-Axel hypothesis, for example, does not hold for most cases, though it weakly holds in at least some cases for electric dipole transitions. Furthermore, I show the systematics can be understood through spectral distribution theory, calculated via traces of operators and of products of operators. Seen through this lens, violation of the generalized Brink-Axel hypothesis is unsurprising: one expects sum rules to evolve with excitation energy. Furthermore, to lowest order the slope of the secular evolution can be traced to a component of the Hamiltonian being positive (repulsive) or negative (attractive).
Mixing of molecular excitation in a uniaxial liquid crystal
Aver`yanov, E.M.
1995-07-01
The influence of the mixing of molecular excitations due to local-field effects on the dielectric and spectral properties of uniaxial liquid crystals is investigated. The general properties of the spectrum of transverse optical excitations of the medium, viz, the sum rules for the oscillator strengths, frequencies, and damping constants of the dielectric function resonances, are established. The restricted applicability of the idea of a back ground polarizability (dielectric function) in the analysis of the mixing of molecular excitations is demonstrated. Mixing is taken into account in deriving new dispersion formulas for the imaginary and real parts of the dielectric tensor, which differ significantly from those used in the literature. A range of applicability has been established for the latter. Qualitative and quantitative interpretations of controversial experimental data for an extensive list of objects are given. The occurrence of mixing of dipole-active molecular vibrations, whose intensity has been found to be strongest for polyphilic objects that form nonchiral ferroelectric phases, has been demonstrated for molecular liquids and uniaxial liquid crystals from various chemical classes for the first time. The mixing of molecular excitations is considered as a possible mechanism for {open_quotes}polarization catastrophe{close_quotes} in liquid crystals having a soft mode in hthespectrum of transverse optical modes of vibration for the high-temperature phase. 53 refs., 1 fig.
Neutron star structure and collective excitations of finite nuclei
NASA Astrophysics Data System (ADS)
Paar, N.; Moustakidis, Ch. C.; Marketin, T.; Vretenar, D.; Lalazissis, G. A.
2014-07-01
A method is introduced that establishes relations between properties of collective excitations in finite nuclei and the phase transition density nt and pressure Pt at the inner edge separating the liquid core and the solid crust of a neutron star. A theoretical framework that includes the thermodynamic method, relativistic nuclear energy density functionals, and the quasiparticle random-phase approximation is employed in a self-consistent calculation of (nt,Pt) and collective excitations in nuclei. Covariance analysis shows that properties of charge-exchange dipole transitions, isovector giant dipole and quadrupole resonances, and pygmy dipole transitions are correlated with the core-crust transition density and pressure. A set of relativistic nuclear energy density functionals, characterized by systematic variation of the density dependence of the symmetry energy of nuclear matter, is used to constrain possible values for (nt,Pt). By comparing the calculated excitation energies of giant resonances, energy-weighted pygmy dipole strength, and dipole polarizability with available data, we obtain the weighted average values: nt=0.0955±0.0007 fm-3 and Pt=0.59±0.05 MeV fm-3. This approach crucially depends on experimental results for collective excitations in nuclei and, therefore, accurate measurements are necessary to further constrain the structure of the crust of neutron stars.
Failure strength of icy lithospheres
NASA Technical Reports Server (NTRS)
Golombek, M. P.; Banerdt, W. B.
1987-01-01
Lithospheric strengths derived from friction on pre-existing fractures and ductile flow laws show that the tensile strength of intact ice under applicable conditions is actually an order of magnitude stronger than widely assumed. It is demonstrated that this strength is everywhere greater than that required to initiate frictional sliding on pre-existing fractures and faults. Because the tensile strength of intact ice increases markedly with confining pressure, it actually exceeds the frictional strength at all depths. Thus, icy lithospheres will fail by frictional slip along pre-existing fractures at yeild stresses greater than previously assumed rather than opening tensile cracks in intact ice.
Oxygen K-shell excitation spectroscopy of hydrogen peroxide
NASA Astrophysics Data System (ADS)
Rühl, E.; Hitchcock, A. P.
1991-07-01
The absolute oscillator strength spectrum for oxygen K-shell excitation of hydrogen peroxide has been derived from electron energy loss spectra recorded under electric dipole scattering conditions. The spectrum is dominated by an intense low-lying excitation to the {O 1s -1, σ* (OO)} state at 533.0 eV. The spectrum is compared to the O 1 s spectra of bis (trifluoromethyl) peroxide and bis( t-butyl)peroxide. The spectra of all three peroxides exhibit a strong transition around 533 eV which involves O 1s promotions to an orbital of largely σ* (OO) character. The bond length-σ* resonance energy correlation and its relation to near-edge X-ray absorption fine structure (NEXAFS) determinations of the geometry of O 2 adsorbed on various metal surfaces is explored.
Mass spectrum and decay constants of radially excited vector mesons
NASA Astrophysics Data System (ADS)
Mojica, Fredy F.; Vera, Carlos E.; Rojas, Eduardo; El-Bennich, Bruno
2017-07-01
We calculate the masses and weak decay constants of flavorless and flavored ground and radially excited JP=1- mesons within a Poincaré covariant continuum framework based on the Bethe-Salpeter equation. We use in both the quark's gap equation and the meson bound-state equation an infrared massive and finite interaction in the leading symmetry-preserving truncation. While our numerical results are in rather good agreement with experimental values where they are available, no single parametrization of the QCD inspired interaction reproduces simultaneously the ground and excited mass spectrum, which confirms earlier work on pseudoscalar mesons. This feature being a consequence of the lowest truncation, we pin down the range and strength of the interaction in both cases to identify common qualitative features that may help to tune future interaction models beyond the rainbow-ladder approximation.
Excited-state absorption measurements of Tm3+-doped crystals
NASA Astrophysics Data System (ADS)
Szela, J. W.; Mackenzie, J. I.
2012-06-01
High resolution, absolute excited-state absorption (ESA) spectra, at room temperature, from the long-lived 3F4 energy level of several crystals doped with trivalent thulium (Tm3+) ions have been measured employing high-brightness narrowband (FWHM <30 nm) light emitting diodes (LEDs) as a probe wavelength. The aim of this investigation was to determine the strength of ESA channels at wavelengths addressable by commercially available semiconductor laser diodes operating around 630-680 nm. The favourable lifetime of the 3F4 manifold and negligible ground-state absorption (GSA) for the red-wavelength second-step excitation, ensures a direct and efficient route for a dual-wavelength pumping scheme of the thulium ion, which will enable blue-green laser emission from its 1G4 upper-laser level.
Clustered chimera states in systems of type-I excitability
NASA Astrophysics Data System (ADS)
Vüllings, Andrea; Hizanidis, Johanne; Omelchenko, Iryna; Hövel, Philipp
2014-12-01
The chimera state is a fascinating phenomenon of coexisting synchronized and desynchronized behaviour that was discovered in networks of nonlocally coupled identical phase oscillators over ten years ago. Since then, chimeras have been found in numerous theoretical and experimental studies and more recently in models of neuronal dynamics as well. In this work, we consider a generic model for a saddle-node bifurcation on a limit cycle representative of neural excitability type I. We obtain chimera states with multiple coherent regions (clustered chimeras/multi-chimeras) depending on the distance from the excitability threshold, the range of nonlocal coupling and the coupling strength. A detailed stability diagram for these chimera states and other interesting coexisting patterns (like traveling waves) is presented.
Excitation waves on a minimal small-world model
NASA Astrophysics Data System (ADS)
Isele, Thomas; Hartung, Benedikt; Hövel, Philipp; Schöll, Eckehard
2015-04-01
We examine traveling-wave solutions on a regular ring network with one additional long-range link that spans a distance d. The nodes obey the FitzHugh-Nagumo kinetics in the excitable regime. The additional shortcut induces a plethora of spatio-temporal behavior that is not present without it. We describe the underlying mechanisms for different types of patterns: propagation failure, period decreasing, bistability, shortcut blocking and period multiplication. For this purpose, we investigate the dependence on d, the network size, the coupling range in the original ring and the global coupling strength and present a phase diagram summarizing the different scenarios. Furthermore, we discuss the scaling behavior of the critical distance by analytical means and address the connection to spatially continuous excitable media.
Production of Excited Atomic Hydrogen and Deuterium from HD Photodissociation
NASA Astrophysics Data System (ADS)
Machacek, J. R.; Bozek, J. D.; Furst, J. E.; Gay, T. J.; Gould, H.; Kilcoyne, A. L. D.; McLaughlin, K. W.
2008-05-01
We have measured the production of Lyα, Hα, and Hβ fluorescence from atomic H and D for the photodissociation of HD by linearly-polarized photons with energies between 20 and 66 eV. In this energy range, excited photofragments result primarily from the production of doubly-excited molecular species which promptly autoionize or dissociate into two neutrals. Theoretical calculation are not yet available for HD, but comparison between the relative cross sections for H2, D2 and HD targets and the available theory for H2 and D2 [1] allow for an estimate of the relative strength of each dissociation channel in this energy range. [1] J. D. Bozek et al., J. Phys. B 39, 4871 (2006). Support provided by the NSF (Grant PHY-0653379), DOE (LBNL/ALS) and ANSTO (Access to Major Research Facilities Programme).
Fibonacci anyon excitations of one-dimensional dipolar lattice bosons
NASA Astrophysics Data System (ADS)
Äńurić, Tanja; Biedroń, Krzysztof; Zakrzewski, Jakub
2017-02-01
We study a system of dipolar bosons in a one-dimensional optical lattice using exact diagonalization and density matrix renormalization group methods. In particular, we analyze low energy properties of the system at an average filling of 3/2 atoms per lattice site. We identify the region of the parameter space where the system has non-Abelian Fibonacci anyon excitations that correspond to fractional domain walls between different charge-density waves. When such one-dimensional systems are combined into a two-dimensional network, braiding of Fibonacci anyon excitations has potential application for fault tolerant, universal, topological quantum computation. Contrary to previous calculations, our results also demonstrate that super-solid phases are not present in the phase diagram for the discussed 3/2 average filling. Instead, decreasing the value of the nearest-neighbor tunneling strength leads to a direct, Berezinskii-Kosterlitz-Thouless, superfluid to charge-density-wave quantum phase transition.
Band Excitation Kelvin probe force microscopy utilizing photothermal excitation
Collins, Liam; Jesse, Stephen; Balke, Nina; ...
2015-03-13
A multifrequency open loop Kelvin probe force microscopy (KPFM) approach utilizing photothermal as opposed to electrical excitation is developed. Photothermal band excitation (PthBE)-KPFM is implemented here in a grid mode on a model test sample comprising a metal-insulator junction with local charge-patterned regions. Unlike the previously described open loop BE-KPFM, which relies on capacitive actuation of the cantilever, photothermal actuation is shown to be highly sensitive to the electrostatic force gradient even at biases close to the contact potential difference (CPD). PthBE-KPFM is further shown to provide a more localized measurement of true CPD in comparison to the gold standardmore » ambient KPFM approach, amplitude modulated KPFM. In conclusion, PthBE-KPFM data contain information relating to local dielectric properties and electronic dissipation between tip and sample unattainable using conventional single frequency KPFM approaches.« less
Band Excitation Kelvin probe force microscopy utilizing photothermal excitation
Collins, Liam; Jesse, Stephen; Balke, Nina; Rodriguez, Brian J.; Kalinin, Sergei; Li, Qian
2015-03-13
A multifrequency open loop Kelvin probe force microscopy (KPFM) approach utilizing photothermal as opposed to electrical excitation is developed. Photothermal band excitation (PthBE)-KPFM is implemented here in a grid mode on a model test sample comprising a metal-insulator junction with local charge-patterned regions. Unlike the previously described open loop BE-KPFM, which relies on capacitive actuation of the cantilever, photothermal actuation is shown to be highly sensitive to the electrostatic force gradient even at biases close to the contact potential difference (CPD). PthBE-KPFM is further shown to provide a more localized measurement of true CPD in comparison to the gold standard ambient KPFM approach, amplitude modulated KPFM. In conclusion, PthBE-KPFM data contain information relating to local dielectric properties and electronic dissipation between tip and sample unattainable using conventional single frequency KPFM approaches.
Lakkis, S
1999-03-01
A case study showing the attitudes and actions reinforcing discrimination against women's rights in Lebanon is presented. The study illustrates the way in which the public¿s views and the interests of families and local dignitaries can manipulate opinions. Organizations aimed at protecting women's rights have found strength in working together. The Lebanese League, an organization comprised of 17 women's and human rights associations, has established a center and a telephone hotline to encourage abused women to disclose and discuss their situation. The center provides support in the form of legal, psychological and medical assistance. Another organization working with the Lebanese League towards the same vision is the Lebanese Physically Handicapped Union. Efforts to lobby around a Lebanese legislation discriminating against women so far had no success, but all organizations involved are aware of the need to work through a range of interventions, and to take a long-term view, before they can count on any success.
Hagel, William C.; Smidt, Frederick A.; Korenko, Michael K.
1977-01-01
A high-strength ferritic alloy useful for fast reactor duct and cladding applications where an iron base contains from about 9% to about 13% by weight chromium, from about 4% to about 8% by weight molybdenum, from about 0.2% to about 0.8% by weight niobium, from about 0.1% to about 0.3% by weight vanadium, from about 0.2% to about 0.8% by weight silicon, from about 0.2% to about 0.8% by weight manganese, a maximum of about 0.05% by weight nitrogen, a maximum of about 0.02% by weight sulfur, a maximum of about 0.02% by weight phosphorous, and from about 0.04% to about 0.12% by weight carbon.
Effects of Frequency-Dependent Membrane Capacitance on Neural Excitability
Grill, Warren M.
2015-01-01
Objective Models of excitable cells consider the membrane specific capacitance as a ubiquitous and constant parameter. However, experimental measurements show that the membrane capacitance declines with increasing frequency, i.e., exhibits dispersion. We quantified the effects of frequency-dependent membrane capacitance, c(f), on the excitability of cells and nerve fibers across the frequency range from dc to hundreds of kilohertz. Approach We implemented a model of c(f) using linear circuit elements, and incorporated it into several models of neurons with different channel kinetics: the Hodgkin-Huxley (HH) model of an unmyelinated axon, the McIntyre-Richardson-Grill (MRG) of a mammalian myelinated axon, and a model of a cortical neuron from prefrontal cortex. We calculated thresholds for excitation and kHz frequency conduction block, the conduction velocity, recovery cycle, strength-distance relationship and firing rate. Main results The impact of c(f) on activation thresholds depended on the stimulation waveform and channel kinetics. We observed no effect using rectangular pulse stimulation, and a reduction for frequencies of 10 kHz and above using sinusoidal signals only for the MRG model. c(f) had minimal impact on the recovery cycle and the strength-distance relationship, whereas the conduction velocity increased by up to 7.9% and 1.7% for myelinated and unmyelinated fibers, respectively. Block thresholds declined moderately when incorporating c(f), the effect was greater at higher frequencies, and the maximum reduction was 11.5%. Finally, c(f) marginally altered the firing pattern of a model of a prefrontal cortex cell, reducing the median interspike interval by less than 2%. Significance This is the first comprehensive analysis of the effects of dispersive capacitance on neural excitability, and as the interest on stimulation with kHz signals gains more attention, it defines the regions over which frequency-dependent membrane capacitance, c(f), should be
Excitation rates for transitions in Ca XV
NASA Astrophysics Data System (ADS)
Aggarwal, K. M.; Keenan, F. P.
2003-08-01
Collision strengths for transitions among the energetically lowest 46 fine-structure levels belonging to the (1s2) 2s22p2, 2s2p3, 2p4, and 2s22p3l configurations of Ca XV are computed, over a wide electron energy range below 300 Ryd, using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant (\\cite{Norrington03}). Resonances in the threshold region have been resolved in a fine energy mesh, and excitation rates are determined over a wide electron temperature range below 107 K. The results are compared with those available in the literature, and the accuracy of the data is assessed. Table \\ref{tab3} is also (and Table 4 only) available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/407/769
Mean excitation energies for molecular ions
NASA Astrophysics Data System (ADS)
Jensen, Phillip W. K.; Sauer, Stephan P. A.; Oddershede, Jens; Sabin, John R.
2017-03-01
The essential material constant that determines the bulk of the stopping power of high energy projectiles, the mean excitation energy, is calculated for a range of smaller molecular ions using the RPA method. It is demonstrated that the mean excitation energy of both molecules and atoms increase with ionic charge. However, while the mean excitation energies of atoms also increase with atomic number, the opposite is the case for mean excitation energies for molecules and molecular ions. The origin of these effects is explained by considering the spectral representation of the excited state contributing to the mean excitation energy.
High-j neutron excitations outside 136Xe
NASA Astrophysics Data System (ADS)
Talwar, R.; Kay, B. P.; Mitchell, A. J.; Adachi, S.; Entwisle, J. P.; Fujita, Y.; Gey, G.; Noji, S.; Ong, H. J.; Schiffer, J. P.; Tamii, A.
2017-08-01
The ν 0 h9 /2 and ν 0 i13 /2 strength at 137Xe, a single neutron outside the N =82 shell closure, has been determined using the 136Xe(α ,3He)137Xe reaction carried out at 100 MeV. We confirm the recent observation of the second 13 /2+ state and reassess previous data on the 9 /2- states, obtaining spectroscopic factors. These new data provide additional constraints on predictions of the same single-neutron excitations at 133Sn.
Excitation-energy dependence of the giant dipole resonance width
NASA Astrophysics Data System (ADS)
Enders, G.; Berg, F. D.; Hagel, K.; Kühn, W.; Metag, V.; Novotny, R.; Pfeiffer, M.; Schwalb, O.; Charity, R. J.; Gobbi, A.; Freifelder, R.; Henning, W.; Hildenbrand, K. D.; Holzmann, R.; Mayer, R. S.; Simon, R. S.; Wessels, J. P.; Casini, G.; Olmi, A.; Stefanini, A. A.
1992-07-01
High-energy γ rays have been measured in coincidence with heavy fragents in deeply inelastic reactions of 136Xe+48Ti at 18.5 MeV/nucleon. The giant dipole resonance (GDR) strength function is deduced from an analysis of the photon spectra within the statistical model. The GDR width Γ is studied as a function of the fragment excitation energy E*. A saturation at about Γ=10 MeV is observed for E*/A>=1.0 MeV/nucleon.
Plasma undulator based on laser excitation of wakefields in a plasma channel.
Rykovanov, S G; Schroeder, C B; Esarey, E; Geddes, C G R; Leemans, W P
2015-04-10
An undulator is proposed based on the plasma wakefields excited by a laser pulse in a plasma channel. Generation of the undulator fields is achieved by inducing centroid oscillations of the laser pulse in the channel. The period of such an undulator is proportional to the Rayleigh length of the laser pulse and can be submillimeter, while preserving high undulator strength. The electron trajectories in the undulator are examined, expressions for the undulator strength are presented, and the spontaneous radiation is calculated. Multimode and multicolor laser pulses are considered for greater tunability of the undulator period and strength.
Impact strength and indentation hardness of high-strength ceramics
Grady, D.E.
1993-08-01
Hugoniot elastic limit and indentation hardness data are provided for selected high-strength ceramics AlN, Al{sub 2}O{sub 3}, B{sub 4}C, SiC, TiB, Zr{sub 2}. Degree of correlation of the strength data by the two test methods is examined. Influence of reformation mechanism on strength measurement, including rate sensitivity, size scale and confining pressure, is discussed.
Electric Monopole Transition Strengths in Stable Nickel Isotopes
NASA Astrophysics Data System (ADS)
Evitts, Lee; Garnsworthy, Adam; Kibedi, Tibor; Super-e Collaboration
2016-09-01
Electric monopole (E 0) transition strengths are a sensitive probe for investigating nuclear structure and shape coexistence. There is a need for E 0 transition strengths in closed shell nuclei in order to develop our understanding of the mechanisms responsible for the generation of electric monopole strength. Simultaneous detections of γ rays and internal conversion electrons must be measured in order to determine an E 0 transition strength. A series of measurements in the stable nickel isotopes were performed at the Australian National University. Excited states in 58 , 60 , 62Ni were populated via inelastic proton scattering. The CAESAR array of Compton-suppressed HPGe detectors was used to measure the (E 2 / M 1) mixing ratio of transitions from angular distributions of γ rays. The Super-e spectrometer was used to measure electron-gamma branching ratios in order to extract E 0 transition strengths for a number of Jπ ->Jπ transitions. An overview of the experiments will be presented, along with preliminary results for E 0 transition strengths between Jπ ≠ 0 states in the semi-magic nuclei, 58 , 60 , 62Ni. A comparison with the matrix elements obtained from a new microscopic model for E 0 transitions will be made. This work was supported in part by the Natural Sciences and Engineering Research Council of Canada (NSERC).
Receiver-exciter controller design
NASA Technical Reports Server (NTRS)
Jansma, P. A.
1982-01-01
A description of the general design of both the block 3 and block 4 receiver-exciter controllers for the Deep Space Network (DSN) Mark IV-A System is presented along with the design approach. The controllers are designed to enable the receiver-exciter subsystem (RCV) to be configured, calibrated, initialized and operated from a central location via high level instructions. The RECs are designed to be operated under the control of the DMC subsystem. The instructions are in the form of standard subsystem blocks (SSBs) received via the local area network (LAN). The centralized control provided by RECs and other DSCC controllers in Mark IV-A is intended to reduce DSN operations costs from the Mark III era.
Light baryons and their excitations
NASA Astrophysics Data System (ADS)
Eichmann, Gernot; Fischer, Christian S.; Sanchis-Alepuz, Hèlios
2016-11-01
We study ground states and excitations of light octet and decuplet baryons within the framework of Dyson-Schwinger and Faddeev equations. We improve upon similar approaches by explicitly taking into account the momentum-dependent dynamics of the quark-gluon interaction that leads to dynamical chiral symmetry breaking. We perform calculations in both the three-body Faddeev framework and the quark-diquark approximation in order to assess the impact of the latter on the spectrum. Our results indicate that both approaches agree well with each other. The resulting spectra furthermore agree one-to-one with experiment, provided well-known deficiencies of the rainbow-ladder approximation are compensated for. We also discuss the mass evolution of the Roper and the excited Δ with varying pion mass and analyze the internal structure in terms of their partial wave decompositions.
Study of gamma-ray strength functions
Gardner, D.G.; Gardner, M.A.; Dietrich, F.S.
1980-08-07
The use of gamma-ray strength function systematics to calculate neutron capture cross sections and capture gamma-ray spectra is discussed. The ratio of the average capture width, GAMMA/sub ..gamma../-bar, to the average level spacing, D/sub obs/, both at the neutron separation energy, can be derived from such systematics with much less uncertainty than from separate systematics for values of GAMMA/sub ..gamma../-bar and D/sub obs/. In particular, the E1 gamma-ray strength function is defined in terms of the giant dipole resonance (GDR). The GDR line shape is modeled with the usual Lorentzian function and also with a new energy-dependent, Breit-Wigner (EDBW) function. This latter form is further parameterized in terms of two overlapping resonances, even for nuclei where photonuclear measurements do not resolve two peaks. In the mass ranges studied, such modeling is successful for all nuclei away from the N = 50 closed neutron shell. Near the N = 50 shell, a one-peak EDBW appears to be more appropriate. Examples of calculated neutron capture excitation functions and capture gamma-ray spectra using the EDBW form are given for target nuclei in the mass-90 region and also in the Ta-Au mass region. 20 figures.
Electron impact excitation of Hg/+/
NASA Technical Reports Server (NTRS)
Crandall, D. H.; Phaneuf, R. A.; Dunn, G. H.
1974-01-01
A crossed charged beam technique was employed in the investigation reported. The ion beam was crossed at right angles by a magnetically confined electron beam. Cross sections were determined as a function of electron impact energy. Considerable structure in the excitation cross section appears immediately above the threshold. It is pointed out that a primary application of cross sections is related to the calculation of plasma rate coefficients.
Self-excited multifractal dynamics
NASA Astrophysics Data System (ADS)
Filimonov, V.; Sornette, D.
2011-05-01
We introduce the self-excited multifractal (SEMF) model, defined such that the amplitudes of the increments of the process are expressed as exponentials of a long memory of past increments. The principal novel feature of the model lies in the self-excitation mechanism combined with exponential nonlinearity, i.e. the explicit dependence of future values of the process on past ones. The self-excitation captures the microscopic origin of the emergent endogenous self-organization properties, such as the energy cascade in turbulent flows, the triggering of aftershocks by previous earthquakes and the "reflexive" interactions of financial markets. The SEMF process has all the standard stylized facts found in financial time series, which are robust to the specification of the parameters and the shape of the memory kernel: multifractality, heavy tails of the distribution of increments with intermediate asymptotics, zero correlation of the signed increments and long-range correlation of the squared increments, the asymmetry (called "leverage" effect) of the correlation between increments and absolute value of the increments and statistical asymmetry under time reversal.
Entanglement entropy of electronic excitations
NASA Astrophysics Data System (ADS)
Plasser, Felix
2016-05-01
A new perspective into correlation effects in electronically excited states is provided through quantum information theory. The entanglement between the electron and hole quasiparticles is examined, and it is shown that the related entanglement entropy can be computed from the eigenvalue spectrum of the well-known natural transition orbital (NTO) decomposition. Non-vanishing entanglement is obtained whenever more than one NTO pair is involved, i.e., in the case of a multiconfigurational or collective excitation. An important implication is that in the case of entanglement it is not possible to gain a complete description of the state character from the orbitals alone, but more specific analysis methods are required to decode the mutual information between the electron and hole. Moreover, the newly introduced number of entangled states is an important property by itself giving information about excitonic structure. The utility of the formalism is illustrated in the cases of the excited states of two interacting ethylene molecules, the conjugated polymer para-phenylene vinylene, and the naphthalene molecule.
Synaptic Control of Motoneuronal Excitability
Rekling, Jens C.; Funk, Gregory D.; Bayliss, Douglas A.; Dong, Xiao-Wei; Feldman, Jack L.
2016-01-01
Movement, the fundamental component of behavior and the principal extrinsic action of the brain, is produced when skeletal muscles contract and relax in response to patterns of action potentials generated by motoneurons. The processes that determine the firing behavior of motoneurons are therefore important in understanding the transformation of neural activity to motor behavior. Here, we review recent studies on the control of motoneuronal excitability, focusing on synaptic and cellular properties. We first present a background description of motoneurons: their development, anatomical organization, and membrane properties, both passive and active. We then describe the general anatomical organization of synaptic input to motoneurons, followed by a description of the major transmitter systems that affect motoneuronal excitability, including ligands, receptor distribution, pre- and postsynaptic actions, signal transduction, and functional role. Glutamate is the main excitatory, and GABA and glycine are the main inhibitory transmitters acting through ionotropic receptors. These amino acids signal the principal motor commands from peripheral, spinal, and supraspinal structures. Amines, such as serotonin and norepinephrine, and neuropeptides, as well as the glutamate and GABA acting at metabotropic receptors, modulate motoneuronal excitability through pre- and postsynaptic actions. Acting principally via second messenger systems, their actions converge on common effectors, e.g., leak K+ current, cationic inward current, hyperpolarization-activated inward current, Ca2+ channels, or presynaptic release processes. Together, these numerous inputs mediate and modify incoming motor commands, ultimately generating the coordinated firing patterns that underlie muscle contractions during motor behavior. PMID:10747207
Channelopathies of skeletal muscle excitability
Cannon, Stephen C.
2016-01-01
Familial disorders of skeletal muscle excitability were initially described early in the last century and are now known to be caused by mutations of voltage-gated ion channels. The clinical manifestations are often striking, with an inability to relax after voluntary contraction (myotonia) or transient attacks of severe weakness (periodic paralysis). An essential feature of these disorders is fluctuation of symptoms that are strongly impacted by environmental triggers such as exercise, temperature, or serum K+ levels. These phenomena have intrigued physiologists for decades, and in the past 25 years the molecular lesions underlying these disorders have been identified and mechanistic studies are providing insights for therapeutic strategies of disease modification. These familial disorders of muscle fiber excitability are “channelopathies” caused by mutations of a chloride channel (ClC-1), sodium channel (NaV1.4), calcium channel (CaV1.1) and several potassium channels (Kir2.1, Kir2.6, Kir3.4). This review provides a synthesis of the mechanistic connections between functional defects of mutant ion channels, their impact on muscle excitability, how these changes cause clinical phenotypes, and approaches toward therapeutics. PMID:25880512
Wedding ring shaped excitation coil
MacLennan, Donald A.; Tsai, Peter
2001-01-01
A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and/or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency.
Fault Roughness Records Strength
NASA Astrophysics Data System (ADS)
Brodsky, E. E.; Candela, T.; Kirkpatrick, J. D.
2014-12-01
Fault roughness is commonly ~0.1-1% at the outcrop exposure scale. More mature faults are smoother than less mature ones, but the overall range of roughness is surprisingly limited which suggests dynamic control. In addition, the power spectra of many exposed fault surfaces follow a single power law over scales from millimeters to 10's of meters. This is another surprising observation as distinct structures such as slickenlines and mullions are clearly visible on the same surfaces at well-defined scales. We can reconcile both observations by suggesting that the roughness of fault surfaces is controlled by the maximum strain that can be supported elastically in the wallrock. If the fault surface topography requires more than 0.1-1% strain, it fails. Invoking wallrock strength explains two additional observations on the Corona Heights fault for which we have extensive roughness data. Firstly, the surface is isotropic below a scale of 30 microns and has grooves at larger scales. Samples from at least three other faults (Dixie Valley, Mount St. Helens and San Andreas) also are isotropic at scales below 10's of microns. If grooves can only persist when the walls of the grooves have a sufficiently low slope to maintain the shape, this scale of isotropy can be predicted based on the measured slip perpendicular roughness data. The observed 30 micron scale at Corona Heights is consistent with an elastic strain of 0.01 estimated from the observed slip perpendicular roughness with a Hurst exponent of 0.8. The second observation at Corona Heights is that slickenlines are not deflected around meter-scale mullions. Yielding of these mullions at centimeter to meter scale is predicted from the slip parallel roughness as measured here. The success of the strain criterion for Corona Heights supports it as the appropriate control on fault roughness. Micromechanically, the criterion implies that failure of the fault surface is a continual process during slip. Macroscopically, the
Wheelchair armrest strength testing.
Cooper, R A; Rentschler, A J; O'Connor, T J; Ster, J F
2000-01-01
There are about 1.4 million manual wheelchair users, 100,000 electric-powered wheelchair users, and 60,000 electric-powered scooter users. The current study was undertaken to determine if the fasteners of a clamp-type armrest receiver were prone to failure. The first test was used to examine the potential misalignment of the armrest receiver components that attach it to the frame. The second test was to evaluate the entire armrest using the American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society of North America armrest static strength standard. Finally, we conducted three fatigue tests. The first fatigue test was performed by repeating the static stability tests multiple times. The last two tests were a modified version of the double-drum wheelchair fatigue test used to apply repeated loading and vibration simultaneously. A paired t-test showed that there is no statistically significant difference (p = 0.08), with a confidence of 95%, between critical alignment measurements. The armrest including the receiver passed the standard requirement of a force of 760 N being applied outward at 15 degrees. During fatigue testing, we found that armrests did not exhibit any visible or functional damage. Upon completion of the tests, the armrests and receivers functioned properly. At about 100,289 cycles on a double-drum test machine, three bolts failed on each armrest receiver when the screws were loosened to have only five threads engaged prior to commencing the test. The design of the armrest tested was in compliance with existing national and international standards. Currently, both International Standards Organization and American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society committees are developing standards for seating systems that will include static, impact, and fatigue strength testing of devices like lateral torso supports, lateral hip support, etc. Methods similar to those
Dirac R-matrix calculation for electron-impact excitation of S xiii
NASA Astrophysics Data System (ADS)
Li, F.; Liang, G. Y.; Bari, M. A.; Zhao, G.
2013-08-01
Context. Sulfur emission lines in the soft X-ray and extreme-ultraviolet regions are observed in a variety of laboratory and astrophysical spectra. But accurate electron impact excitation data for S xiii for state-of-the-art NLTE spectral models are scarce. Aims: We calculated electron-impact excitation collision strengths and effective collision strengths of S xiii for transitions among the lowest-lying 98 fine-structure states 1s22lnl' corresponding to principal quantum numbers n = 2,3,4. The effective collision strengths for these transitions were computed over a wide temperature range (log 10Te (K) = 4.53-7.53) for various astrophysical plasma conditions. Methods: We used the fully-relativistic parallel Dirac R-matrix code to calculate collision strengths. To generate target wavefunctions and energy levels for scattering calculations, we employed the GRASP0 multi-configuration Dirac-Fock code for states up to n = 5. Results: The wavefunctions are generated from 27 configurations - 1s22lnl'(n = 2,3,4,5) - giving rise to 166 jj energy levels. The collision and effective collision strengths among the lowest 98 fine-structure levels are compared with the previous theoretical calculations. The collision strengths for most transitions agree well at higher incident electron energies. Conclusions: The resonant contributions to effective collision strengths are most dominant at lower temperatures.
NASA Technical Reports Server (NTRS)
Christian, Jerry D.
1973-01-01
Students are not generally made aware of the extraordinary magnitude of the strengths of chemical bonds in terms of the forces required to pull them apart. Molecular bonds are usually considered in terms of the energies required to break them, and we are not astonished at the values encountered. For example, the Cl2 bond energy, 57.00 kcal/mole, amounts to only 9.46 x 10(sup -20) cal/molecule, a very small amount of energy, indeed, and impossible to measure directly. However, the forces involved in realizing the energy when breaking the bond operate over a very small distance, only 2.94 A, and, thus, f(sub ave) approx. equals De/(r - r(sub e)) must be very large. The forces involved in dissociating the molecule are discussed in the following. In consideration of average forces, the molecule shall be assumed arbitrarily to be dissociated when the atoms are far enough separated so that the potential, relative to that of the infinitely separated atoms, is reduced by 99.5% from the potential of the molecule at the equilibrium bond length (r(sub e)) for Cl2 of 1.988 A this occurs at 4.928 A.
Airborne field strength monitoring
NASA Astrophysics Data System (ADS)
Bredemeyer, J.; Kleine-Ostmann, T.; Schrader, T.; Münter, K.; Ritter, J.
2007-06-01
In civil and military aviation, ground based navigation aids (NAVAIDS) are still crucial for flight guidance even though the acceptance of satellite based systems (GNSS) increases. Part of the calibration process for NAVAIDS (ILS, DME, VOR) is to perform a flight inspection according to specified methods as stated in a document (DOC8071, 2000) by the International Civil Aviation Organization (ICAO). One major task is to determine the coverage, or, in other words, the true signal-in-space field strength of a ground transmitter. This has always been a challenge to flight inspection up to now, since, especially in the L-band (DME, 1GHz), the antenna installed performance was known with an uncertainty of 10 dB or even more. In order to meet ICAO's required accuracy of ±3 dB it is necessary to have a precise 3-D antenna factor of the receiving antenna operating on the airborne platform including all losses and impedance mismatching. Introducing precise, effective antenna factors to flight inspection to achieve the required accuracy is new and not published in relevant papers yet. The authors try to establish a new balanced procedure between simulation and validation by airborne and ground measurements. This involves the interpretation of measured scattering parameters gained both on the ground and airborne in comparison with numerical results obtained by the multilevel fast multipole algorithm (MLFMA) accelerated method of moments (MoM) using a complex geometric model of the aircraft. First results will be presented in this paper.
Improving Interlaminar Shear Strength
NASA Technical Reports Server (NTRS)
Jackson, Justin
2015-01-01
To achieve NASA's mission of space exploration, innovative manufacturing processes are being applied to the fabrication of complex propulsion elements.1 Use of fiber-reinforced, polymeric composite tanks are known to reduce weight while increasing performance of propulsion vehicles. Maximizing the performance of these materials is needed to reduce the hardware weight to result in increased performance in support of NASA's missions. NASA has partnered with the Mississippi State University (MSU) to utilize a unique scalable approach of locally improving the critical properties needed for composite structures. MSU is responsible for the primary development of the concept with material and engineering support provided by NASA. The all-composite tank shown in figure 1 is fabricated using a prepreg system of IM7 carbon fiber/CYCOM 5320-1 epoxy resin. This is a resin system developed for out-of-autoclave applications. This new technology is needed to support the fabrication of large, all composite structures and is currently being evaluated on a joint project with Boeing for the Space Launch System (SLS) program. In initial efforts to form an all composite pressure vessel using this prepreg system, a 60% decrease in properties was observed in scarf joint regions. Inspection of these areas identified interlaminar failure in the adjacent laminated structure as the main failure mechanism. This project seeks to improve the interlaminar shear strength (ILSS) within the prepreg layup by locally modifying the interply region shown in figure 2.2
Adult neurogenesis modifies excitability of the dentate gyrus
Ikrar, Taruna; Guo, Nannan; He, Kaiwen; Besnard, Antoine; Levinson, Sally; Hill, Alexis; Lee, Hey-Kyoung; Hen, Rene; Xu, Xiangmin; Sahay, Amar
2013-01-01
Adult-born dentate granule neurons contribute to memory encoding functions of the dentate gyrus (DG) such as pattern separation. However, local circuit-mechanisms by which adult-born neurons partake in this process are poorly understood. Computational, neuroanatomical and electrophysiological studies suggest that sparseness of activation in the granule cell layer (GCL) is conducive for pattern separation. A sparse coding scheme is thought to facilitate the distribution of similar entorhinal inputs across the GCL to decorrelate overlapping representations and minimize interference. Here we used fast voltage-sensitive dye (VSD) imaging combined with laser photostimulation and electrical stimulation to examine how selectively increasing adult DG neurogenesis influences local circuit activity and excitability. We show that DG of mice with more adult-born neurons exhibits decreased strength of neuronal activation and more restricted excitation spread in GCL while maintaining effective output to CA3c. Conversely, blockade of adult hippocampal neurogenesis changed excitability of the DG in the opposite direction. Analysis of GABAergic inhibition onto mature dentate granule neurons in the DG of mice with more adult-born neurons shows a modest readjustment of perisomatic inhibitory synaptic gain without changes in overall inhibitory tone, presynaptic properties or GABAergic innervation pattern. Retroviral labeling of connectivity in mice with more adult-born neurons showed increased number of excitatory synaptic contacts of adult-born neurons onto hilar interneurons. Together, these studies demonstrate that adult hippocampal neurogenesis modifies excitability of mature dentate granule neurons and that this non-cell autonomous effect may be mediated by local circuit mechanisms such as excitatory drive onto hilar interneurons. Modulation of DG excitability by adult-born dentate granule neurons may enhance sparse coding in the GCL to influence pattern separation. PMID:24421758
Role of momentum transfer in the quenching of the Gamow-Teller strength
Marketin, T.; Martinez-Pinedo, G.; Paar, N.; Vretenar, D.
2012-10-20
A recent analysis of (p,n) and (n,p) reaction data from {sup 90}Zr was performed recently, where a significant amount of Gamow-Teller strength was found above the resonance, an energy region previously unreachable by experimental setups. The extracted strengths in the {beta}{sub -} and the {beta}{sub +} channel indicate that approximately 10% of the total strength necessary to satisfy the model independent Ikeda sum rule is missing. One possible source of this discrepancy is the treatment of the isovector spin monopole (IVSM) mode of excitation which has been found to occurr at high excitation energies. Employing the relativistic Hartree-Bogoliubov (RHB) model and the protonneutron relativistic quasiparticle random phase approximation (pn-RQRPA) to calculate the nuclear response, we explore the contribution of the IVSM mode to the total L= 0 strength and apply our results to the available data.
Role of momentum transfer in the quenching of the Gamow-Teller strength
NASA Astrophysics Data System (ADS)
Marketin, T.; Martínez-Pinedo, G.; Paar, N.; Vretenar, D.
2012-10-01
A recent analysis of (p,n) and (n,p) reaction data from 90Zr was performed recently, where a significant amount of Gamow-Teller strength was found above the resonance, an energy region previously unreachable by experimental setups. The extracted strengths in the β- and the β+ channel indicate that approximately 10% of the total strength necessary to satisfy the model independent Ikeda sum rule is missing. One possible source of this discrepancy is the treatment of the isovector spin monopole (IVSM) mode of excitation which has been found to occurr at high excitation energies. Employing the relativistic Hartree-Bogoliubov (RHB) model and the protonneutron relativistic quasiparticle random phase approximation (pn-RQRPA) to calculate the nuclear response, we explore the contribution of the IVSM mode to the total L = 0 strength and apply our results to the available data.
Electron impact excitation of Si II and Fe XIV
NASA Astrophysics Data System (ADS)
Aggarwal, K. M.; Keenan, F. P.
2015-01-01
Energy levels, radiative rates, lifetimes, collision strengths and effective collision strengths are calculated for two important Al-like ions, namely Si II and Fe XIV. For Si II, the lowest 56 levels of the 3s23p, 3s3p2 3p3 3s23d, 3s3p3d, 3s24l and 3s25l configurations are included, whereas for Fe XIV additional 80 levels of 3p23d, 3s3d2 and 3p3d2 are considered, but not of 3s2 5l. For the determination of atomic structure GRASP has been adopted and radiative rates are calculated for all E1, E2, Ml and M2 transitions. Electron impact excitation collision strengths are calculated with the DARC code, over a wide energy range, and resonances are resolved in a fine energy mesh to determine effective collision strengths over a wide range of temperatures. Extensive comparisons are made for all atomic parameters with available theoretical and experimental data, and the accuracy of the present results is assessed. Energy levels are estimated to be accurate to ~1% and all other parameters to be better than 20%.
Wisitsorasak, Apiwat; Wolynes, Peter G.
2012-01-01
The remarkable strength of glasses is examined using the random first order transition theory of the glass transition. The theory predicts that strength depends on elastic modulus but also on the configurational energy frozen in when the glass is prepared. The stress catalysis of cooperative rearrangements of the type responsible for the supercooled liquid’s high viscosity account quantitatively for the measured strength of a range of metallic glasses, silica, and a polymer glass. PMID:22988070
NASA Astrophysics Data System (ADS)
Adamatzky, Andrew
2012-11-01
Excitable cellular automata with dynamical excitation interval exhibit a wide range of space-time dynamics based on an interplay between propagating excitation patterns which modify excitability of the automaton cells. Such interactions leads to formation of standing domains of excitation, stationary waves and localized excitations. We analyzed morphological and generative diversities of the functions studied and characterized the functions with highest values of the diversities. Amongst other intriguing discoveries we found that upper boundary of excitation interval more significantly affects morphological diversity of configurations generated than lower boundary of the interval does and there is no match between functions which produce configurations of excitation with highest morphological diversity and configurations of interval boundaries with highest morphological diversity. Potential directions of future studies of excitable media with dynamically changing excitability may focus on relations of the automaton model with living excitable media, e.g. neural tissue and muscles, novel materials with memristive properties and networks of conductive polymers.
Newman, D G; Pearn, J; Barnes, A; Young, C M; Kehoe, M; Newman, J
1984-01-01
Norms for hand grip strength of healthy children are presented. Sex and age specific centiles for age 5 to 18 years have been determined using a portable strain gauge dynamometer with an accuracy of 0.5 N. The test group comprised 1417 healthy, urban school children from a middle class suburb of Brisbane. Mean maximum grip strength (of four tests, two with each hand) and mean peak grip strength (best of four tests) were recorded. Mean values of peak grip strength were 10 to 15% higher than the average maximum grip in all age groups. At all ages girls had a reduced grip strength compared with boys and although boys manifested a continual, approximately linear increase in grip strength through all age groups, girls manifested an approximately linear increase up to 13 years after which mean hand grip usually remained constant. By the age of 18 years boys had a mean grip strength some 60% higher than girls. Correlations with height and weight are also presented. "Handedness' influenced grip strength and was most noticeable in children aged over 10 years. The clinical use of hand grip strength centiles for the early indication of neurological and muscular disorders and for following the natural history of neuromuscular disease is discussed. Images Fig. 1 PMID:6732276
Neutrino-pair emission from nuclear de-excitation in core-collapse supernova simulations
NASA Astrophysics Data System (ADS)
Fischer, T.; Langanke, K.; Martínez-Pinedo, G.
2013-12-01
We study the impact of neutrino-pair production from the de-excitation of highly excited heavy nuclei on core-collapse supernova simulations, following the evolution up to several 100 ms after core bounce. Our study is based on the agile-boltztransupernova code, which features general relativistic radiation hydrodynamics and accurate three-flavor Boltzmann neutrino transport in spherical symmetry. In our simulations the nuclear de-excitation process is described in two different ways. At first we follow the approach proposed by Fuller and Meyer [Astrophys. J.AJLEEY0004-637X10.1086/170317 376, 701 (1991)], which is based on strength functions derived in the framework of the nuclear Fermi-gas model of noninteracting nucleons. Second, we parametrize the allowed and forbidden strength distributions in accordance with measurements for selected nuclear ground states. We determine the de-excitation strength by applying the Brink hypothesis and detailed balance. For both approaches, we find that nuclear de-excitation has no effect on the supernova dynamics. However, we find that nuclear de-excitation is the leading source for the production of electron antineutrinos as well as heavy-lepton-flavor (anti)neutrinos during the collapse phase. At sufficiently high densities, the associated neutrino spectra are influenced by interactions with the surrounding matter, making proper simulations of neutrino transport important for the determination of the neutrino-energy loss rate. We find that, even including nuclear de-excitations, the energy loss during the collapse phase is overwhelmingly dominated by electron neutrinos produced by electron capture.
Physiological Effects of Strength Training and Various Strength Training Devices.
ERIC Educational Resources Information Center
Wilmore, Jack H.
Current knowledge in the area of muscle physiology is a basis for a discussion on strength training programs. It is now recognized that the expression of strength is related to, but not dependent upon, the size of the muscle and is probably more related to the ability to recruit more muscle fibers in the contraction, or to better synchronize their…
Physiological Effects of Strength Training and Various Strength Training Devices.
ERIC Educational Resources Information Center
Wilmore, Jack H.
Current knowledge in the area of muscle physiology is a basis for a discussion on strength training programs. It is now recognized that the expression of strength is related to, but not dependent upon, the size of the muscle and is probably more related to the ability to recruit more muscle fibers in the contraction, or to better synchronize their…
Control of excitation in the fluorescence microscope.
Lea, D J; Ward, D J
1979-01-01
In fluorescence microscopy image brightness and contrast and the rate of fading depend upon the intensity of illumination of the specimen. An iris diaphragm or neutral density filters may be used to reduce fluorescence excitation. Also the excitation bandwidth may be varied by using a broad band exciter filter with a set of interchangeable yellow glass filters at the lamphouse.
Resource Paper: Molecular Excited State Relaxation Processes.
ERIC Educational Resources Information Center
Rhodes, William
1979-01-01
Develops the concept of oscillatory v dissipative limits as it applies to electronic excited state processes in molecular systems. Main emphasis is placed on the radiative and nonradiative dynamics of the excited state of a molecule prepared by interaction with light or some other excitation source. (BT)
Collective excitations of the hybrid atomic-molecular Bose-Einstein condensates
Gupta, Moumita; Dastidar, Krishna Rai
2010-06-15
We investigate the low-energy excitations of the spherically and axially trapped atomic Bose-Einstein condensate coupled to a molecular Bose gas by coherent Raman transitions. We apply the sum-rule approach of many-body response theory to derive the low-lying collective excitation frequencies of the hybrid atom-molecular system. The atomic and molecular ground-state densities obtained in Gross-Pitaevskii and modified Gross-Pitaevskii (including the higher order Lee-Huang-Yang term in interatomic interaction) approaches are used to find out the individual energy components and hence the excitation frequencies. We obtain different excitation energies for different angular momenta and study their characteristic dependence on the effective Raman detuning, the scattering length for atom-atom interaction, and the intensities of the coupling lasers. We show that the inclusion of the higher-order nonlinear interatomic interaction in modified Gross-Pitaevskii approach introduces significant corrections to the ground-state properties and the excitation frequencies both for axially and spherically trapped coupled {sup 87}Rb condensate system with the increase in the s-wave scattering length (for peak gas-parameter {>=}10{sup -3}). It has been shown that the excitation frequencies decrease with the increase in the effective Raman detuning as well as the s-wave scattering length, whereas excitation frequencies increase with the increase in the atom-molecular coupling strength. The frequencies in modified Gross-Pitaevskii approximation exhibit an upward trend after a certain value of scattering length and also largely deviate from the Gross-Pitaevskii results with the increase in s-wave scattering length. The strong dependence of excitation frequencies on the laser intensities used for Raman transitions manifests the role of atom-molecular coupling strength on the control of collective excitations. The collective excitation frequencies for the hybrid atom-molecular BEC differ
Effect of adhesive layers on microshear bond strength of nanocomposite resin to dentin
Ebrahim, Mohamed I.
2017-01-01
Background Bond strength of adhesive layer can absorb unwanted stresses of polymerization shrinkage in composite resin restorations; increased microshear bond strength can prevent failure of restoration materials, the purpose of this study was to evaluate the effect of adhesive layers on microshear bond strength of nanocomposite resin to dentin. Material and Methods Two different types of adhesive systems: universal adhesive (ExciTE) and newly developed adhesive (Nano-Bond), and one type of light-cured resin restorative material (Nanocomposite resin) were used in this study. The occlusal surfaces of extracted human molar teeth were ground perpendicular to the long axis of each tooth to expose a flat dentin surface. The adhesives were applied on dentin surfaces (single application or double application). Nanocomposite resin was then placed and light cured for 40 seconds. After 24 hours of immersion in water at 37°C, then subjected to thermocycling before testing, a microshear bond test was carried out. The data were analyzed by a two-way ANOVA. For comparison between groups, Tukey’s post-hoc test was used. Results The mean bond strengths of ExciTE and Nano-Bond adhesives with a single application were 8.8 and 16.6 MPa, respectively. The mean bond strengths of ExciTE and Nano-Bond adhesives with double application were 13.2 and 21.8MPa, respectively. There were no statistically significant differences in microshear bond strengths between the single application of Nano-Bond and the double application of ExciTE adhesives. Conclusions Microshear bond strength increased significantly as the applied adhesive layer was doubled. Key words:Adhesive, microshear, bond, strength, nanocomposite. PMID:28210433
Nonlinear mode coupling and resonant excitations in two-component Bose-Einstein condensates.
Xue, Ju-Kui; Li, Guan-Qiang; Zhang, Ai-Xia; Peng, Ping
2008-01-01
Nonlinear excitations in two-component Bose-Einstein condensates (BECs) described by two coupled Gross-Pitaevskii equations are investigated analytically and numerically. The beating phenomenon, the higher-harmonic generation, and the mixing of the excited modes are revealed by both variational approximation and numerical method. The strong excitations induced by the parametric resonance are also studied by time-periodic modulation for the intercomponent interaction. The resonance conditions in terms of the modulation frequency and the strength of intercomponent interaction are obtained analytically, which are confirmed by numerical method. Direct numerical simulations show that, when the resonance takes place, periodic phase separation and multisoliton configurations (including soliton trains, soliton pairs, and multidomain walls) can be excited. In particular, we demonstrate a method for formation of multisoliton configurations through parametric resonance in two-component BECs.
Net force on an asymmetrically excited two-atom system from vacuum fluctuations
NASA Astrophysics Data System (ADS)
Donaire, M.
2016-12-01
A net force on a system of two dissimilar atoms, one of which is excited, is shown to result from their van der Waals interaction. It is accompanied by a net transfer of linear momentum to the quantum fluctuations of the electromagnetic field. This momentum results from the asymmetric interference of the virtual photons scattered off each atom along the interatomic direction, which is in itself a manifestation of the optical theorem. Ultimately, the virtual photons' momentum, of equal strength and opposite direction to the momentum gained by the two-atom system while excited, is released through directional spontaneous emission, which allows for an indirect measure, a posteriori, of the total force on the excited system. A quantitative prediction is made in a two-alkali atom system. It is conjectured that a net force and hence a nonzero momentum of quantum fluctuations take place in any asymmetrically excited system.
Duque, H. V.; Do, T. P. T.; Konovalov, D. A.; White, R. D.; Brunger, M. J. E-mail: darryl.jones@flinders.edu.au; Jones, D. B. E-mail: darryl.jones@flinders.edu.au
2015-03-28
In this paper, we report newly derived integral cross sections (ICSs) for electron impact vibrational excitation of tetrahydrofuran (THF) at intermediate impact energies. These cross sections extend the currently available data from 20 to 50 eV. Further, they indicate that the previously recommended THF ICS set [Garland et al., Phys. Rev. A 88, 062712 (2013)] underestimated the strength of the electron-impact vibrational excitation processes. Thus, that recommended vibrational cross section set is revised to address those deficiencies. Electron swarm transport properties were calculated with the amended vibrational cross section set, to quantify the role of electron-driven vibrational excitation in describing the macroscopic swarm phenomena. Here, significant differences of up to 17% in the transport coefficients were observed between the calculations performed using the original and revised cross section sets for vibrational excitation.
Excitation of Love waves in a thin film layer by a line source.
NASA Technical Reports Server (NTRS)
Tuan, H.-S.; Ponamgi, S. R.
1972-01-01
The excitation of a Love surface wave guided by a thin film layer deposited on a semiinfinite substrate is studied in this paper. Both the thin film and the substrate are considered to be elastically isotropic. Amplitudes of the surface wave in the thin film region and the substrate are found in terms of the strength of a line source vibrating in a direction transverse to the propagating wave. In addition to the surface wave, the bulk shear wave excited by the source is also studied. Analytical expressions for the bulk wave amplitude as a function of the direction of propagation, the acoustic powers transported by the surface and bulk waves, and the efficiency of surface wave excitation are obtained. A numerical example is given to show how the bulk wave radiation pattern depends upon the source frequency, the film thickness and other important parameters of the problem. The efficiency of surface wave excitation is also calculated for various parameter values.
The structure of triply excited, negative-ion resonances in the autoionizing region of helium
NASA Astrophysics Data System (ADS)
Trantham, K. W.; Jacka, M.; Rau, A. R. P.; Buckman, S. J.
1999-02-01
The formation and decay of the two lowest-lying, triply excited 0953-4075/32/3/021/img7 resonances in the autoionizing region of the helium spectrum (57-60 eV) have been studied by measuring electron-impact excitation functions for the n = 2 singly excited states of helium as a function of electron scattering angle. These results offer unambiguous confirmation of the classification of these states as 0953-4075/32/3/021/img8 and 0953-4075/32/3/021/img9, respectively. Furthermore, the observation of the relative strengths of the decay of these features into the various final states enables some speculation as to the structure of the three excited electrons.
Turbulent swirling jets with excitation
NASA Technical Reports Server (NTRS)
Taghavi, Rahmat; Farokhi, Saeed
1988-01-01
An existing cold-jet facility at NASA Lewis Research Center was modified to produce swirling flows with controllable initial tangential velocity distribution. Two extreme swirl profiles, i.e., one with solid-body rotation and the other predominated by a free-vortex distribution, were produced at identical swirl number of 0.48. Mean centerline velocity decay characteristics of the solid-body rotation jet flow exhibited classical decay features of a swirling jet with S - 0.48 reported in the literature. However, the predominantly free-vortex distribution case was on the verge of vortex breakdown, a phenomenon associated with the rotating flows of significantly higher swirl numbers, i.e., S sub crit greater than or equal to 0.06. This remarkable result leads to the conclusion that the integrated swirl effect, reflected in the swirl number, is inadequate in describing the mean swirling jet behavior in the near field. The relative size (i.e., diameter) of the vortex core emerging from the nozzle and the corresponding tangential velocity distribution are also controlling factors. Excitability of swirling jets is also investigated by exciting a flow with a swirl number of 0.35 by plane acoustic waves at a constant sound pressure level and at various frequencies. It is observed that the cold swirling jet is excitable by plane waves, and that the instability waves grow about 50 percent less in peak r.m.s. amplitude and saturate further upstream compared to corresponding waves in a jet without swirl having the same axial mass flux. The preferred Strouhal number based on the mass-averaged axial velocity and nozzle exit diameter for both swirling and nonswirling flows is 0.4.
Peculiarities of collisional excitation transfer with excited screened energy levels of atoms
Gerasimov, V. A.; Gerasimov, V. V.; Pavlinskiy, A. V.
2007-09-15
We report an experimental discovery of deviations from the known regularities in collisional excitation transfer processes for metal atoms. The collisional excitation transfer with excited screened energy levels of thulium and dysprosium atoms is studied. The selecting role of the screening 6s shell in collisional excitation transfer is shown.
Volumetric Light-Field Excitation
Schedl, David C.; Bimber, Oliver
2016-01-01
We explain how to concentrate light simultaneously at multiple selected volumetric positions by means of a 4D illumination light field. First, to select target objects, a 4D imaging light field is captured. A light field mask is then computed automatically for this selection to avoid illumination of the remaining areas. With one-photon illumination, simultaneous generation of complex volumetric light patterns becomes possible. As a full light-field can be captured and projected simultaneously at the desired exposure and excitation times, short readout and lighting durations are supported. PMID:27363565
NASA Astrophysics Data System (ADS)
Deleanu, D.; Balabanski, D. L.; Venkova, Ts.; Bucurescu, D.; Mărginean, N.; Ganioǧlu, E.; Căta-Danil, Gh.; Atanasova, L.; Căta-Danil, I.; Detistov, P.; Filipescu, D.; Ghiţă, D.; Glodariu, T.; Ivaşcu, M.; Mărginean, R.; Mihai, C.; Negret, A.; Pascu, S.; Sava, T.; Stroe, L.; Suliman, G.; Zamfir, N. V.
2013-01-01
Excited states in 129I were populated with the 124Sn(7Li,2n) reaction at 23 MeV. In-beam measurements of γ-ray coincidences were performed with an array of eight HPGe detectors and five LaBr3(Ce) scintillation detectors. Based on the γγ coincidence data, a positive parity band structure built on the 7/2+ ground state was established and the πg7/2 configuration at oblate deformation was assigned to it. The results are compared to interacting Boson-Fermion model (IBFM) and total Routhian surface (TRS) calculations.
[Neurosteroids. Neuromodulators of cerebral excitability].
Calixto González, E; Brailowsky, S
1998-01-01
Steroids which are produced by the brain are called neurosteroids, and they are able to modulate neurotransmissions: GABAergic; glutamatergic; glycinergic, and cholinergic (nicotine receptor). These effects are of short latency and duration, and do not implicate the cellular genome. The interaction of these neurosteroids with membrane receptors contribute to the regulation of neuronal excitability, and their study has allowed a better understanding of cognitive, hormonal, and epileptic phenomena as well as the development of new drugs with anxiolytic, antidepressive, anesthetic and anti-epileptic effects.
Multiarmed Spirals in Excitable Media
NASA Astrophysics Data System (ADS)
Vasiev, Bakthier; Siegert, Florian; Weijer, Cornelis
1997-03-01
Numerical studies of the properties of multiarmed spirals show that they can form spontaneously in low excitability media. The maximum number of arms in a multiarmed spiral is proportional to the ratio of the single spiral period to the refractoriness of the medium. Multiarmed spirals are formed due to attraction of single spirals if these spirals rotate in the same direction and their tips are less than one wavelength apart, i.e., a spiral broken not far from its tip can evolve into a 2-armed spiral. We propose this mechanism to be responsible for the formation of multiarmed spirals in mounds of the slime mold Dictyostelium discoideum.
Multi-Band Excitation Vocoder.
1987-03-01
to random. Vocoder Clean speechb 715 Noe Uncoded WA 0. eiard: 2400 bps 36.5 71.4 B elgard: Noise Excitation 36.4 66.3 I Ta~ble 1.1: DI ? Bem I Another...estimation. Chapter 4 dis - cumes methods for synthesizing speech from these model parameters. In Chapter 5, we apply the MBE Model to the problem of bit-rate...expensive problem. However, we note that for a given pitch period, the best spectral envelope parameters can be easily estimated. To show this, we di - I
High Frequency Chandler Wobble Excitation
NASA Astrophysics Data System (ADS)
Seitz, F.; Stuck, J.; Thomas, M.
2003-04-01
Variations of Earth rotation on sub-daily to secular timescales are caused by mass redistributions in the Earth system as a consequence of geophysical processes and gravitational influences. Forced oscillations of polar motion are superposed by free oscillations of the Earth, i.e. the Chandler wobble and the free core nutation. In order to study the interactions between externally induced polar motion and the Earth's free oscillations, a non-linear gyroscopic model has been developed. In most of the former investigations on polar motion, the Chandler wobble is introduced as a damped oscillation with predetermined frequency and amplitude. However, as the effect of rotational deformation is a backcoupling mechanism of polar motion on the Earth's rotational dynamics, both period and amplitude of the Chandler wobble are time-dependent when regarding additional excitations from, e.g., atmospheric or oceanic mass redistributions. The gyroscopic model is free of any explicit information concerning amplitude, phase, and period of free oscillations. The characteristics of the Earth's free oscillation is reproduced by the model from rheological and geometrical parameters and rotational deformation is taken into account. This enables to study the time variable Chandler oscillation when the gyro is forced with atmospheric and oceanic angular momentum from the global atmospheric ECHAM3-T21 general circulation model together with the ocean model for circulation and tides OMCT driven by ECHAM including surface pressure. Besides, mass redistributions in the Earth's body due to gravitational and loading deformations are regarded and external torques exerted by Moon and Sun are considered. The numerical results of the gyro are significantly related with the geodetically observed time series of polar motion published by the IERS. It is shown that the consistent excitation is capable to counteract the damping and thus to maintain the Chandler amplitude. Spectral analyses of the ECHAM
Theoretical studies of electronically excited states
Besley, Nicholas A.
2014-10-06
Time-dependent density functional theory is the most widely used quantum chemical method for studying molecules in electronically excited states. However, excited states can also be computed within Kohn-Sham density functional theory by exploiting methods that converge the self-consistent field equations to give excited state solutions. The usefulness of single reference self-consistent field based approaches for studying excited states is demonstrated by considering the calculation of several types of spectroscopy including the infrared spectroscopy of molecules in an electronically excited state, the rovibrational spectrum of the NO-Ar complex, core electron binding energies and the emission spectroscopy of BODIPY in water.
Gene circuit designs for noisy excitable dynamics.
Rué, Pau; Garcia-Ojalvo, Jordi
2011-05-01
Certain cellular processes take the form of activity pulses that can be interpreted in terms of noise-driven excitable dynamics. Here we present an overview of different gene circuit architectures that exhibit excitable pulses of protein expression, when subject to molecular noise. Different types of excitable dynamics can occur depending on the bifurcation structure leading to the specific excitable phase-space topology. The bifurcation structure is not, however, linked to a particular circuit architecture. Thus a given gene circuit design can sustain different classes of excitable dynamics depending on the system parameters.
Spin excitations in /sup 48/Ca and /sup 90/Zr with 319 MeV protons
Nanda, S.K.
1985-05-01
Cross sections, analyzing powers, and spin-flip probabilities have been measured in the low momentum transfer region in the /sup 90/Zr(p vector, p' vector) /sup 90/Zr* reaction at 319 MeV. A rich fine structure is observed for the first time in inelastic proton scattering in the previously proposed M1 giant resonance region. Angular distribution of most of these states are consistent with M1 excitation. The excitation energies of the fine structure states are in good agreement with similar structure seen in electron scattering; however, discrepancies in spin assignments remain. The measured cross section for the entire bump is about 37 +- 10% of the Distorted Wave Impulse Approximation (DWIA) prediction for the M1 strength in /sup 90/Zr with simple wave functions. However, an analysis of the fine structure states reveals about 15% of the strength in the M1 region to be due to narrow El states; another 8% is attributed to M2 strength. The spin-flip measurements for /sup 90/Zr reveal a large spin-flip probability value for the M1 region; good agreement is obtained with DWIA calculations. However, a large cross section for spin excitations distributed uniformly over the excitation energy region from about 7 to 25 MeV is observed for the first time. The spin excitation strength in this giant resonance continuum is found to about 0.80 mb/sr/MeV. Angular distributions for the spin-flip cross sections from 7 to 18 MeV in steps of 2 MeV have been analyzed with low multipole spin excitation calculations in the DWIA framework; the observed spin-flip strength in this region is found to be consistent with spin excitation involving angular momentum transfer of up to two. Finally, cross section, analyzing power, and spin-flip probability data have also been obtained for the 10.23 MeV M1 transition in the /sup 48/Ca(p vector, p' vector)/sup 48/Ca* reaction at 319 MeV. The quenching of M1 strength in /sup 48/Ca relative to theoretical predictions is found to be consistent with
Measurement of tune spread in the Tevatron versus octupole strength
Marriner, John; Martens, Mike; /Fermilab
1996-08-01
An experiment was performed in the Tevatron to measure the tune spread versus octupole strength. The experiment is sensitive to the relationship between octupole strength and current in the T:OZF circuit and to the octupole (and other non-linear focusing fields) in the Tevatron. The major motivation for the experiment was to determine the value of octupole excitation that minimizes the tune spread: this value is an estimate of the value required to obtain ''zero'' total octupole excitation in the extraction process. The experiment was performed using the strip-line kickers at A17 and the resonant Schottky pickups. The horizontal proton kicker was excited with a sine-wave from a vector signal analyzer (HP-89440A) and the horizontal proton signal was received. The gating circuitry normally used to select proton or antiproton bunches was by-passed. The response function was measured and recorded on a floppy disk. Measurements were initially made with a 200 Hz span (0.250 Hz frequency bins) and later with a 100 Hz span (0.125 Hz frequency bins).
Strength Training for Young Athletes.
ERIC Educational Resources Information Center
Kraemer, William J.; Fleck, Steven J.
This guide is designed to serve as a resource for developing strength training programs for children. Chapter 1 uses research findings to explain why strength training is appropriate for children. Chapter 2 explains some of the important physiological concepts involved in children's growth and development as they apply to developing strength…
Strength Training for Young Athletes.
ERIC Educational Resources Information Center
Kraemer, William J.; Fleck, Steven J.
This guide is designed to serve as a resource for developing strength training programs for children. Chapter 1 uses research findings to explain why strength training is appropriate for children. Chapter 2 explains some of the important physiological concepts involved in children's growth and development as they apply to developing strength…
Aluminum alloys with improved strength
NASA Technical Reports Server (NTRS)
Deiasi, R.; Adler, P.
1975-01-01
Mechanical strength and stress corrosion of new BAR and 7050 alloys that include Zn instead of Cr have been studied and compared with those of 7075 aluminum alloy. Added mechanical strength of new alloys is attributed to finer grain size of 5 to 8 micrometers, however, susceptibility to stress corrosion attack is increased.
Collective excitations and retarded interactions
NASA Astrophysics Data System (ADS)
Choi, M. Y.; Huberman, B. A.
1985-03-01
We study the dynamics of many-body systems with retarded interactions and show how their non-Markovian character can lead to nonergodic behavior. This nonergodicity is characterized by the appearance of long periods or chaotic wanderings in phase space. We construct the phase diagrams for Ising-type systems with delayed interactions, and show the emergence of non-Gibbsian measures as a function of both interaction strengths and delays.
Strength properties of fly ash based controlled low strength materials.
Türkel, S
2007-08-25
Controlled low strength material (CLSM) is a flowable mixture that can be used as a backfill material in place of compacted soils. Flowable fill requires no tamping or compaction to achieve its strength and typically has a load carrying capacity much higher than compacted soils, but it can still be excavated easily. The selection of CLSM type should be based on technical and economical considerations for specific applications. In this study, a mixture of high volume fly ash (FA), crushed limestone powder (filler) and a low percentage of pozzolana cement have been tried in different compositions. The amount of pozzolana cement was kept constant for all mixes as, 5% of fly ash weight. The amount of mixing water was chosen in order to provide optimum pumpability by determining the spreading ratio of CLSM mixtures using flow table method. The shear strength of the material is a measure of the materials ability to support imposed stresses on the material. The shear strength properties of CLSM mixtures have been investigated by a series of laboratory tests. The direct shear test procedure was applied for determining the strength parameters Phi (angle of shearing resistance) and C(h) (cohesion intercept) of the material. The test results indicated that CLSM mixtures have superior shear strength properties compared to compacted soils. Shear strength, cohesion intercept and angle of shearing resistance values of CLSM mixtures exceeded conventional soil materials' similar properties at 7 days. These parameters proved that CLSM mixtures are suitable materials for backfill applications.
Three-photon excitation in fluorescence microscopy
NASA Astrophysics Data System (ADS)
Hell, Stefan W.; Bahlmann, Karsten; Schrader, Martin; Soini, Aleksi; Malak, Henryk; Gryczynski, Ignacy; Lakowicz, Joseph R.
1996-01-01
We show experiments proving the feasibility of scanning fluorescence microscopy by three-photon excitation. Three-photon excitation fluorescence axial images are shown of polystyrene beads stained with the fluorophore 2,5- bis(4-biphenyl)oxazole (BBO). Three-photon excitation is performed at an excitation wavelength of 900 nm and with pulses of 130 fs duration provided by a mode-locked titanium-sapphire laser. Fluorescence is collected between 350 and 450 nm. The fluorescence image signal features a third-order dependence on the excitation power, also providing intrinsic 3-D imaging. The resolution of a three-photon excitation microscope is increased over that of a comparable two-photon excitation microscope.
Inner-shell excitation of acetylene by electron impact
Michelin, S.E.; Pessoa, O.; Oliveira, H.L.; Veiteinheimer, E.; Santos, A.M.S.; Fujimoto, M.M.; Iga, I.; Lee, M.-T.
2005-08-15
The distorted-wave approximation (DWA) is applied to study K-shell excitation in C{sub 2}H{sub 2} by electron impact. More specifically, calculated differential and integral cross sections for the X {sup 1}{sigma}{sub g}{sup +}{yields}{sup 1,3}{pi}{sub g}(1s{sigma}{sub g}{yields}1p{pi}{sub g}) and X {sup 1}{sigma}{sub g}{sup +}{yields}{sup 1,3}{pi}{sub u}(1s{sigma}{sub u}{yields}1p{pi}{sub g}) transitions in this target in the 300-800 eV incident energy range are reported. The triplet-to-singlet ratios of respective integral cross sections, namely, RI(3:1), calculated by dividing the integral cross sections for transitions leading to the triplet core-excited states by those leading to the corresponding singlet states, are also reported as a function of incident energies. In general, our calculated sums of the generalized oscillator strength for transitions leading to the {sup 1}{pi}{sub g} and {sup 1}{pi}{sub u} excited states are in good agreement with the available experimental data. On the other hand, the present calculated integral cross sections and the corresponding data for its isoelectronic species CO are significantly different. Possible physical origins for this difference are discussed.
Orbital excitation blockade and algorithmic cooling in quantum gases.
Bakr, Waseem S; Preiss, Philipp M; Tai, M Eric; Ma, Ruichao; Simon, Jonathan; Greiner, Markus
2011-12-21
Interaction blockade occurs when strong interactions in a confined, few-body system prevent a particle from occupying an otherwise accessible quantum state. Blockade phenomena reveal the underlying granular nature of quantum systems and allow for the detection and manipulation of the constituent particles, be they electrons, spins, atoms or photons. Applications include single-electron transistors based on electronic Coulomb blockade and quantum logic gates in Rydberg atoms. Here we report a form of interaction blockade that occurs when transferring ultracold atoms between orbitals in an optical lattice. We call this orbital excitation blockade (OEB). In this system, atoms at the same lattice site undergo coherent collisions described by a contact interaction whose strength depends strongly on the orbital wavefunctions of the atoms. We induce coherent orbital excitations by modulating the lattice depth, and observe staircase-like excitation behaviour as we cross the interaction-split resonances by tuning the modulation frequency. As an application of OEB, we demonstrate algorithmic cooling of quantum gases: a sequence of reversible OEB-based quantum operations isolates the entropy in one part of the system and then an irreversible step removes the entropy from the gas. This technique may make it possible to cool quantum gases to have the ultralow entropies required for quantum simulation of strongly correlated electron systems. In addition, the close analogy between OEB and dipole blockade in Rydberg atoms provides a plan for the implementation of two-quantum-bit gates in a quantum computing architecture with natural scalability.
Effect of Low Sodium, Tetrodotoxin, and Temperature Variation upon Excitation
Guttman, Rita
1968-01-01
The lowering of external sodium raised both the constant quantity threshold, Qo, and the rheobase, Io, in both real space-clamped squid axons and the theoretical axon as computed on the basis of the standard Hodgkin-Huxley equations. In both real and theoretical axons the minimum intensity for excitability for short pulses, which occurs at about 15°C, was still present when low sodium replaced seawater. Low sodium did not affect the temperature dependence of the strength-duration relationship in the range, 5° to 25°C. The excitability of tetrodotoxin-treated real axons was found to be more temperature-dependent than that of normal real axons. Also the data on dosage-response to TTX of real axons fit the dose-response relationship of a hypothetical system in which one TTX ion binds reversibly to its receptor to produce a fraction of the inhibitory effect, the curve being identical to a simple adsorption isotherm. The Hodgkin-Huxley equations describe the broad outline of events occurring during excitation quite well. PMID:5654403
Femtosecond stimulated Raman spectroscopy of flavin after optical excitation.
Weigel, A; Dobryakov, A; Klaumünzer, B; Sajadi, M; Saalfrank, P; Ernsting, N P
2011-04-07
In blue-light photoreceptors using flavin (BLUF), the signaling state is formed already within several 100 ps after illumination, with only small changes of the absorption spectrum. The accompanying structural evolution can, in principle, be monitored by femtosecond stimulated Raman spectroscopy (FSRS). The method is used here to characterize the excited-state properties of riboflavin and flavin adenine dinucleotide in polar solvents. Raman modes are observed in the range 90-1800 cm(-1) for the electronic ground state S(0) and upon excitation to the S(1) state, and modes >1000 cm(-1) of both states are assigned with the help of quantum-chemical calculations. Line shapes are shown to depend sensitively on resonance conditions. They are affected by wavepacket motion in any of the participating electronic states, resulting in complex amplitude modulation of the stimulated Raman spectra. Wavepackets in S(1) can be marked, and thus isolated, by stimulated-emission pumping with the picosecond Raman pulses. Excited-state absorption spectra are obtained from a quantitative comparison of broadband transient fluorescence and absorption. In this way, the resonance conditions for FSRS are determined. Early differences of the emission spectrum depend on excess vibrational energy, and solvation is seen as dynamic Stokes shift of the emission band. The nπ* state is evidenced only through changes of emission oscillator strength during solvation. S(1) quenching by adenine is seen with all methods in terms of dynamics, not by spectral intermediates.
The Relationship Between Maximal Strength and Reactive Strength.
Beattie, Kris; Carson, Brian P; Lyons, Mark; Kenny, Ian C
2017-04-01
Maximum- and reactive-strength qualities both have important roles in athletic movements and sporting performance. Very little research has investigated the relationship between maximum strength and reactive strength. The aim of this study was to investigate the relationship between maximum-strength (isometric midthigh-pull peak force [IMTP PF]) and reactive-strength (drop-jump reactive-strength index [DJ-RSI]) variables at 0.3-m, 0.4-m, 0.5-m, and 0.6-m box heights. A secondary aim was to investigate the between- and within-group differences in reactive-strength characteristics between relatively stronger athletes (n = 11) and weaker athletes (n = 11). Forty-five college athletes across various sports were recruited to participate in the study (age, 23.7 ± 4.0 y; mass, 87.5 ± 16.1 kg; height, 1.80 ± 0.08 m). Pearson correlation results showed that there was a moderate association (r = .302-.431) between maximum-strength variables (absolute, relative, and allometric scaled PF) and RSI at 0.3, 0.4, 0.5 and 0.6 m (P ≤ .05). In addition, 2-tailed independent-samples t tests showed that the RSIs for relatively stronger athletes (49.59 ± 2.57 N/kg) were significantly larger than those of weaker athletes (33.06 ± 2.76 N/kg) at 0.4 m (Cohen d = 1.02), 0.5 m (d = 1.21), and 0.6 m (d = 1.39) (P ≤ .05). Weaker athletes also demonstrated significant decrements in RSI as eccentric stretch loads increased at 0.3-m through 0.6-m box heights, whereas stronger athletes were able to maintain their reactive-strength ability. This research highlights that in specific sporting scenarios, when there are high eccentric stretch loads and fast stretch-shortening-cycle demands, athletes' reactive-strength ability may be dictated by their relative maximal strength, specifically eccentric strength.
On the Excitation and Formation of Circumstellar Fullerenes
NASA Astrophysics Data System (ADS)
Bernard-Salas, Jeronimo; Cami, J.; Peeters, E.; Jones, A. P.; Micelotta, E.; Groenewegen, M. A.
2013-01-01
Recently, we reported the first detection of fullerenes (C60, C70) in space, specifically in Tc1, a young planetary nebulae (PNe). Once injected into the ISM, these stable species survive and are thus probably widespread in the Galaxy where they contribute to interstellar extinction, heating processes, and complex chemical reactions. Following our discovery, fullerenes have now been detected in a wide range of sources (post-AGBs, PNe, reflection nebula, HII regions, H-poor stars, and YSOs), showing that when conditions are favorable, fullerenes are formed in large quantities. The challenge resides now in determining its excitation mechanisms (fluorescence vs. thermal), as this sets their diagnostic value. To this end we have analyzed the mid-IR spectrum of three fullerene-rich PNe Tc1, SMP SMC 16, and SMP LMC 56 and compared them with thermal and fluorescence models. The strength of the fullerene bands in the three planetary nebulae is very similar, while the strength of the radiation field, is markedly different. Additionally, the spatial profile of different dust components in Tc1 indicates that the fullerene emission (C60) peaks far away from the central source. All this is hard to reconcile with a thermal origin for the fullerene excitation, and thus favors fluorescence as the excitation mechanism. In addition, the spectra in the three PNe show a strong broad plateau with substructure in the 6-9um range, and which is likely related to the fullerene formation mechanism. We present model spectra for 3 nm radius HAC particles and show that these can reproduce the 6-9um plateau, which may imply that fullerenes are formed by photo-chemical processing of hydrogenated amorphous carbon (HAC) nano-particles.
Excitation of seismic waves by a tornado
NASA Astrophysics Data System (ADS)
Valovcin, A.; Tanimoto, T.; Twardzik, C.
2016-12-01
Tornadoes are among the most common natural disasters to occur in the United States. Various methods are currently used in tornado forecasting, including surface weather stations, weather balloons and satellite and Doppler radar. These methods work for detecting possible locations of tornadoes and funnel clouds, but knowing when a tornado has touched down still strongly relies on reports from spotters. Studying tornadoes seismically offers an opportunity to know when a tornado has touched down without requiring an eyewitness report. With the installation of Earthscope's Transportable Array (TA), there have been an increased number of tornadoes that have come within close range of seismometers. We have identified seismic signals corresponding to three tornadoes that occurred in 2011 in the central US. These signals were recorded by the TA station closest to each of the tornado tracks. For each tornado, the amplitudes of the seismic signals increase when the storm is in contact with the ground, and continue until the tornado lifts off some time later. This occurs at both high and low frequencies. In this study we will model the seismic signal generated by a tornado at low frequencies (below 0.1 Hz). We will begin by modeling the signal from the Joplin tornado, an EF5 rated tornado which occurred in Missouri on May 22, 2011. By approximating the tornado as a vertical force, we model the generated signal as the tornado moves along its track and changes in strength. By modeling the seismic waveform generated by a tornado, we can better understand the seismic-excitation process. It could also provide a way to quantitatively compare tornadoes. Additional tornadoes to model include the Calumet-El Reno-Piedmont-Guthrie (CEPG) and Chickasa-Blanchard-Newcastle (CBN) tornadoes, both of which occurred on May 24, 2011 in Oklahoma.
Strength deterioration of high strength concrete in sulfate environment
Park, Y.S.; Suh, J.K.; Lee, J.H.; Shin, Y.S.
1999-09-01
Sulfate in soil and groundwater may cause damage to the concrete in underground structures. In this paper, laboratory tests were performed to assess the damage of chemical attack by magnesium sulfate and sodium sulfate on normal and high strength concretes. The selected solutions were pure water and 10% sulfate solutions (sodium and magnesium), which were determined by consideration of the soil environment in Korea. The parameters in experimental programs were water-binder ratio, silica fume content, and the compressive strength of concrete. Observed differences in the characteristics between normal and high strength concretes are discussed, and a scheme for maximizing the resistance of high strength concrete against various kinds of sulfates is suggested.
NASA Astrophysics Data System (ADS)
Jungclaus, A.; Gargano, A.; Grawe, H.; Taprogge, J.; Nishimura, S.; Doornenbal, P.; Lorusso, G.; Shimizu, Y.; Simpson, G. S.; Söderström, P.-A.; Sumikama, T.; Xu, Z. Y.; Baba, H.; Browne, F.; Fukuda, N.; Gernhäuser, R.; Gey, G.; Inabe, N.; Isobe, T.; Jung, H. S.; Kameda, D.; Kim, G. D.; Kim, Y.-K.; Kojouharov, I.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Li, Z.; Sakurai, H.; Schaffner, H.; Steiger, K.; Suzuki, H.; Takeda, H.; Vajta, Zs.; Watanabe, H.; Wu, J.; Yagi, A.; Yoshinaga, K.; Bönig, S.; Coraggio, L.; Daugas, J.-M.; Drouet, F.; Gadea, A.; Ilieva, S.; Itaco, N.; Kröll, T.; Montaner-Pizá, A.; Moschner, K.; Mücher, D.; Nishibata, H.; Odahara, A.; Orlandi, R.; Wendt, A.
2016-04-01
For the first time, the γ decay of excited states has been observed in a nucleus situated in the quadrant south-east of doubly magic 132Sn, a region in which experimental information so far is limited to ground-state properties. Six γ rays with energies of 50, 86, 103, 227, 357, and 602 keV were observed following the β -delayed neutron emission from Cd13385, populated in the projectile fission of a 238U beam at the Radioactive Isotope Beam Factory at RIKEN within the EURICA project. The new experimental information is compared to the results of a modern realistic shell-model calculation, the first one in this region very far from stability, focusing in particular on the π 0 g9/2 -1⊗ν 1 f7 /2 particle-hole multiplet in In13283. In addition, theoretical estimates based on a scaling of the two-body matrix elements for the π h11/2 -1⊗ν g9 /2 analog multiplet in Tl208127, one major proton and one major neutron shell above, are presented.
NASA Technical Reports Server (NTRS)
Feibelman, Walter A.; Bruhweiler, Frederick C.; Johansson, Sveneric
1991-01-01
Archival high-dispersion spectra from the IUE are used in a search for Bowen emission lines of Fe II excited by the stronger transition of the O VI resonance doublet. The possibility of using these Fe II emission lines as a diagnostic of the strength of the far-ultraviolet emission of O VI at 1032 A is explored. It is found that the Fe II emission lines are quite common and strong in symbiotic stars, particularly those of the type known as 'symbiotic novae', as well as in normal novae. The lines are observed in central stars of some planetary nebulae of the O VI sequence besides a few central stars of type WR. High density, high excitation, and high temperature are suggested to be requirements for the excitation of the Fe II fluorescence lines. It is pointed out that while these lines were observed in PG 1159-035 and K1-16, they were not observed in AGNs.
Multiphoton excitation of fluorescent DNA base analogs.
Katilius, Evaldas; Woodbury, Neal W
2006-01-01
Multiphoton excitation was used to investigate properties of the fluorescent DNA base analogs, 2-aminopurine (2AP) and 6-methylisoxanthopterin (6MI). 2-aminopurine, a fluorescent analog of adenine, was excited by three-photon absorption. Fluorescence correlation measurements were attempted to evaluate the feasibility of using three-photon excitation of 2AP for DNA-protein interaction studies. However, high excitation power and long integration times needed to acquire high signal-to-noise fluorescence correlation curves render three-photon excitation FCS of 2AP not very useful for studying DNA base dynamics. The fluorescence properties of 6-methylisoxanthopterin, a guanine analog, were investigated using two-photon excitation. The two-photon absorption cross-section of 6MI was estimated to be about 2.5 x 10(-50) cm(4)s (2.5 GM units) at 700 nm. The two-photon excitation spectrum was measured in the spectral region from 700 to 780 nm; in this region the shape of the two-photon excitation spectrum is very similar to the shape of single-photon excitation spectrum in the near-UV spectral region. Two-photon excitation of 6MI is suitable for fluorescence correlation measurements. Such measurements can be used to study DNA base dynamics and DNA-protein interactions over a broad range of time scales.
Electric quadrupole transition probabilities and line strengths of Ti{sup 11+}
Gökçe, Yasin; Çelik, Gültekin; Yıldız, Murat
2014-07-15
Electric quadrupole transition probabilities and line strengths have been calculated using the weakest bound electron potential model for sodium-like titanium, considering many transition arrays. We employed numerical Coulomb approximation and non-relativistic Hartree–Fock wavefunctions for the expectation values of radii in determination of parameters of the model. The necessary energy values have been taken from experimental data in the literature. The calculated electric quadrupole line strengths have been compared with available data in the literature and good agreement has been obtained. Moreover, some electric quadrupole transition probability and line strength values not existing in the literature for some highly excited levels have been obtained using this method.
The Pavlovian "principle of strength".
Windholz, G
1995-01-01
The Pavlovian principle of strength assumed that the magnitude of the conditional response is a linear function of the intensity of the external conditional stimulus. But experiments failed to provide evidence for the universality of the principle. The Pavlovians tried to identify conditions that distorted the linearity of this relationship. Some of the disturbing conditions were external and some were internal intervening variables. It is possible that the relation between the strength of the conditional stimulus and the magnitude of the conditional response is not linear but logarithmic. Pavlov acknowledged the lack of experimental evidence to support the principle of strength in its original form.
Isoscalar monopole and dipole excitations of cluster states and giant resonances in 12C
NASA Astrophysics Data System (ADS)
Kanada-En'yo, Yoshiko
2016-05-01
The isoscalar monopole (ISM) and dipole (ISD) excitations in 12C are investigated theoretically with the shifted antisymmetrized molecular dynamics (AMD) plus 3 α -cluster generator coordinate method (GCM). The small-amplitude vibration modes are described by coherent one-particle one-hole excitations expressed by a small shift of single-nucleon Gaussian wave functions within the AMD framework, whereas the large-amplitude cluster modes are incorporated by superposing 3 α -cluster wave functions in the GCM. The coupling of the excitations in the intrinsic frame with the rotation and parity transformation is taken into account microscopically by the angular-momentum and parity projections. The present a calculation that describes the ISM and ISD excitations over a wide energy region covering cluster modes in the low-energy region and the giant resonances in the high-energy region, although the quantitative description of the high-energy part is not satisfactory. The low-energy ISM and ISD strengths of the cluster modes are enhanced by the distance motion between α clusters, and they split into a couple of states because of the angular motion of α clusters. The low-energy ISM strengths exhaust 26% of the energy-weighted sum rule, which is consistent with the experimental data for the 12C(02+; 7.65 MeV) and 12C(03+; 10.3 MeV) measured by (e ,e') ,(α ,α') , and (6Li,6Li' ) scatterings. In the calculated low-energy ISD strengths, two 1- states (the 11- and 12- states) with the significant strengths are obtained over E =10 -15 MeV. The results indicate that the ISD excitations can be a good probe to experimentally search for new cluster states such as the 12C(12-) obtained in the present calculation.
A rat in vitro model for the measurement of multiple excitability properties of cutaneous axons.
Maurer, Konrad; Bostock, Hugh; Koltzenburg, Martin
2007-11-01
To establish an in vitro model for measurement of the excitability properties of cutaneous sensory axons. We used a saphenous skin-nerve preparation from adult rat in combination with computerized threshold tracking. We measured strength-duration time constant, the recovery of excitability after a supramaximal stimulus and the accommodation to conditioning subthreshold polarizing stimuli (threshold electrotonus, current-threshold relationship) and compared these with previously published recordings from sensory axons in human median nerve. Threshold electrotonus and the amplitude of superexcitability were indistinguishable between human median nerve in vivo and rat saphenous nerve in vitro, but several excitability parameters were significantly different in the rat: strength-duration time constant was significantly shorter (0.19+/-0.01 vs. 0.53+/-0.02 ms); the refractory period was shorter (1.9+/-1.1 ms vs. 3.5+/-1.0 ms) and late subexcitability was smaller (6.3+/-0.3% vs. 11.3+/-0.5%); thirdly, during recording of current-threshold relationship, rat nerves displayed more inward rectification to strong hyperpolarizing currents. Parameters were stable over more than 3h. Excitability changes of sensory Abeta-fibres can be reliably studied in the rat in vitro and are qualitatively similar to humans. This rat model will facilitate pharmacological studies of nerve excitability and work on models of neuropathy.
Cross Sections for Electron Impact Excitation of Astrophysically Abundant Atoms and Ions
NASA Technical Reports Server (NTRS)
Tayal, S. S.
2006-01-01
Electron collisional excitation rates and transition probabilities are important for computing electron temperatures and densities, ionization equilibria, and for deriving elemental abundances from emission lines formed in the collisional and photoionized astrophysical plasmas. Accurate representation of target wave functions that properly account for the important correlation and relaxation effects and inclusion of coupling effects including coupling to the continuum are essential components of a reliable collision calculation. Non-orthogonal orbitals technique in multiconfiguration Hartree-Fock approach is used to calculate oscillator strengths and transition probabilities. The effect of coupling to the continuum spectrum is included through the use of pseudostates which are chosen to account for most of the dipole polarizabilities of target states. The B-spline basis is used in the R-matrix approach to calculate electron excitation collision strengths and rates. Results for oscillator strengths and electron excitation collision strengths for transitions in N I, O I, O II, O IV, S X and Fe XIV have been produced
Excited Baryons in Holographic QCD
de Teramond, Guy F.; Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins
2011-11-08
The light-front holographic QCD approach is used to describe baryon spectroscopy and the systematics of nucleon transition form factors. Baryon spectroscopy and the excitation dynamics of nucleon resonances encoded in the nucleon transition form factors can provide fundamental insight into the strong-coupling dynamics of QCD. The transition from the hard-scattering perturbative domain to the non-perturbative region is sensitive to the detailed dynamics of confined quarks and gluons. Computations of such phenomena from first principles in QCD are clearly very challenging. The most successful theoretical approach thus far has been to quantize QCD on discrete lattices in Euclidean space-time; however, dynamical observables in Minkowski space-time, such as the time-like hadronic form factors are not amenable to Euclidean numerical lattice computations.
Microwave Excitation In ECRIS plasmas
Ciavola, G.; Celona, L.; Consoli, F.; Gammino, S.; Maimone, F.; Barbarino, S.; Catalano, R. S.; Mascali, D.; Tumino, L.
2007-09-28
A number of phenomena related to the electron cyclotron resonance ion sources (ECRIS) has been better understood recently by means of the improvement of comprehension of the coupling mechanism between microwave generators and ECR plasma. In particular, the two frequency heating and the frequency tuning effect, that permit a remarkable increase of the current for the highest charge states ions, can be explained in terms of modes excitation in the cylindrical cavity of the plasma chamber. Calculations based on this theoretical approach have been performed, and the major results will be presented. It will be shown that the electric field pattern completely changes for a few MHz frequency variations and the changes in ECRIS performances can be correlated to the efficiency of the power transfer between electromagnetic field and plasma.
Propagation failure in excitable media
Hagberg, A.; Meron, E.
1998-01-01
We study a mechanism of pulse propagation failure in excitable media where stable traveling pulse solutions appear via a subcritical pitchfork bifurcation. The bifurcation plays a key role in that mechanism. Small perturbations, externally applied or from internal instabilities, may cause pulse propagation failure (wave breakup) provided the system is close enough to the bifurcation point. We derive relations showing how the pitchfork bifurcation is unfolded by weak curvature or advective field perturbations and use them to demonstrate wave breakup. We suggest that the recent observations of wave breakup in the Belousov-Zhabotinsky reaction induced by either an electric field [J.J. Taboada {ital et al.}. Chaos {bold 4}, 519 (1994)] or a transverse instability [M. Markus, G. Kloss, and I. Kusch, Nature (London) {bold 371}, 402 (1994)] are manifestations of this mechanism. {copyright} {ital 1998} {ital The American Physical Society}
Statistical dynamo theory: Mode excitation.
Hoyng, P
2009-04-01
We compute statistical properties of the lowest-order multipole coefficients of the magnetic field generated by a dynamo of arbitrary shape. To this end we expand the field in a complete biorthogonal set of base functions, viz. B= summation operator_{k}a;{k}(t)b;{k}(r) . The properties of these biorthogonal function sets are treated in detail. We consider a linear problem and the statistical properties of the fluid flow are supposed to be given. The turbulent convection may have an arbitrary distribution of spatial scales. The time evolution of the expansion coefficients a;{k} is governed by a stochastic differential equation from which we infer their averages a;{k} , autocorrelation functions a;{k}(t)a;{k *}(t+tau) , and an equation for the cross correlations a;{k}a;{l *} . The eigenfunctions of the dynamo equation (with eigenvalues lambda_{k} ) turn out to be a preferred set in terms of which our results assume their simplest form. The magnetic field of the dynamo is shown to consist of transiently excited eigenmodes whose frequency and coherence time is given by Ilambda_{k} and -1/Rlambda_{k} , respectively. The relative rms excitation level of the eigenmodes, and hence the distribution of magnetic energy over spatial scales, is determined by linear theory. An expression is derived for |a;{k}|;{2}/|a;{0}|;{2} in case the fundamental mode b;{0} has a dominant amplitude, and we outline how this expression may be evaluated. It is estimated that |a;{k}|;{2}/|a;{0}|;{2} approximately 1/N , where N is the number of convective cells in the dynamo. We show that the old problem of a short correlation time (or first-order smoothing approximation) has been partially eliminated. Finally we prove that for a simple statistically steady dynamo with finite resistivity all eigenvalues obey Rlambda_{k}<0 .
Strength Training and Your Child
... considering strength-training programs: An instructor-to-child ratio of no more than 1 to 10. The ... major muscle groups of the upper and lower body and core. Kids should start with no load ( ...
Circadian regulation of human cortical excitability
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
Kolesov, Roman
2006-04-15
Sharp resonances in optical excitation of ruby by laser pulses are observed as Zeeman sublevels anticross in an external magnetic field. For the R{sub 1} optical line of ruby (694.3 nm) excitation drops when the external magnetic field strength approaches 4.14 kG while for the R{sub 2} line (692.9 nm) it increases in 4.14 and 2.07 kG fields. A simple theoretical description of the observed effects on the basis of level mixing explains both situations.
A search for excited fermions in electron-proton collisions at HERA
NASA Astrophysics Data System (ADS)
Derrick, M.; Krakauer, D.; Magill, S.; Musgrave, B.; Repond, J.; Schlereth, J.; Stanek, R.; Talaga, R. L.; Thron, J.; Arzarello, F.; Ayad, R.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Bruni, P.; Romeo, G. Cara; Castellini, G.; Chiarini, M.; Cifarelli, L.; Cindolo, F.; Ciralli, F.; Contin, A.; D'Auria, S.; Frasconi, F.; Gialas, I.; Giusti, P.; Iacobucci, G.; Laurenti, G.; Levi, G.; Margotti, A.; Massam, T.; Nania, R.; Nemoz, C.; Palmonari, F.; Polini, A.; Sartorelli, G.; Timellini, R.; Garcia, Y. Zamora; Zichichi, A.; Bargende, A.; Crittenden, J.; Desch, K.; Diekmann, B.; Doeker, T.; Eckart, M.; Feld, L.; Frey, A.; Geerts, M.; Geitz, G.; Grothe, M.; Hartmann, H.; Haun, D.; Heinloth, K.; Hilger, E.; Jakob, H.-P.; Katz, U. F.; Mari, S. M.; Mass, A.; Mengel, S.; Mollen, J.; Paul, E.; Rembser, Ch.; Schattevoy, R.; Schneider, J.-L.; Schramm, D.; Stamm, J.; Wedemeyer, R.; Campbell-Robson, S.; Cassidy, A.; Dyce, N.; Foster, B.; George, S.; Gilmore, R.; Heath, G. P.; Heath, H. F.; Llewellyn, T. J.; Morgado, C. J. S.; Norman, D. J. P.; O'Mara, J. A.; Tapper, R. J.; Wilson, S. S.; Yoshida, R.; Rau, R. R.; Arneodo, M.; Iannotti, L.; Schioppa, M.; Susinno, G.; Bernstein, A.; Caldwell, A.; Parsons, J. A.; Ritz, S.; Sciulli, F.; Straub, P. B.; Wai, L.; Yang, S.; Borzemski, P.; Chwastowski, J.; Eskreys, A.; Piotrzkowski, K.; Zachara, M.; Zawiejski, L.; Adamczyk, L.; Bednarek, B.; Eskreys, K.; Jeleń, K.; Kisielewska, D.; Kowalski, T.; Rulikowska-Zarebska, E.; Suszycki, L.; Zajac, J.; Kedzierski, T.; Kotański, A.; Przybycień, M.; Bauerdick, L. A. T.; Behrens, U.; Bienlein, J. K.; Böttcher, S.; Coldewey, C.; Drews, G.; Flasiński, M.; Gilkinson, D. J.; Göttlicher, P.; Gutjahr, B.; Haas, T.; Hain, W.; Hasell, D.; Heßling, H.; Hultschig, H.; Iga, Y.; Joos, P.; Kasemann, M.; Klanner, R.; Koch, W.; Köpke, L.; Kötz, U.; Kowalski, H.; Kroger, W.; Krüger, J.; Labs, J.; Ladage, A.; Löhr, B.; Löwe, M.; Lüke, D.; Mańczak, O.; Ng, J. S. T.; Nickel, S.; Notz, D.; Ohrenberg, K.; Roco, M.; Rohde, M.; Roldán, J.; Schneekloth, U.; Schulz, W.; Selonke, F.; Stiliaris, E.; Voß, T.; Westphal, D.; Wolf, G.; Youngman, C.; Grabosch, H. J.; Leich, A.; Meyer, A.; Rethfeldt, C.; Schlenstedt, S.; Barbagli, G.; Pelfer, P.; Anzivino, G.; Maccarrone, G.; de Pasquale, S.; Qian, S.; Votano, L.; Bamberger, A.; Freidhof, A.; Poser, T.; Söldner-Rembold, S.; Schroeder, J.; Theisen, G.; Trefzger, T.; Brook, N. H.; Bussey, P. J.; Doyle, A. T.; Fleck, I.; Jamieson, V. A.; Saxon, D. H.; Utley, M. L.; Wilson, A. S.; Dannemann, A.; Holm, U.; Horstmann, D.; Kammerlocher, H.; Krebs, B.; Neumann, T.; Sinkus, R.; Wick, K.; Badura, E.; Burow, B. D.; Fürtjes, A.; Hagge, L.; Lohrmann, E.; Mainusch, J.; Milewski, J.; Nakahata, M.; Pavel, N.; Poelz, G.; Schott, W.; Terron, J.; Zetsche, F.; Bacon, T. C.; Beuselinck, R.; Butterworth, I.; Gallo, E.; Harris, V. L.; Hung, B. H.; Long, K. R.; Miller, D. B.; Morawitz, P. P. O.; Prinias, A.; Sedgbeer, J. K.; Whitfield, A. F.; Mallik, U.; McCliment, E.; Wang, M. Z.; Wang, S. M.; Wu, J. T.; Zhang, Y.; Cloth, P.; Filges, D.; An, S. H.; Hong, S. M.; Nam, S. W.; Park, S. K.; Suh, M. H.; Yon, S. H.; Imlay, R.; Kartik, S.; Kim, H.-J.; McNeil, R. R.; Metcalf, W.; Nadendla, V. K.; Barreiro, F.; Cases, G.; Graciani, R.; Hernández, J. M.; Hervás, L.; Labarga, L.; Del Peso, J.; Puga, J.; de Trocóniz, J. F.; Ikraiam, F.; Mayer, J. K.; Smith, G. R.; Corriveau, F.; Hanna, D. S.; Hartmann, J.; Hung, L. W.; Lim, J. N.; Matthews, C. G.; Patel, P. M.; Sinclair, L. E.; Stairs, D. G.; St. Laurent, M.; Ullmann, R.; Zacek, G.; Bashkirov, V.; Dolgoshein, B. A.; Stifutkin, A.; Bashindzhagyan, G. L.; Ermolov, P. F.; Gladilin, L. K.; Golubkov, Y. A.; Kobrin, V. D.; Kuzmin, V. A.; Proskuryakov, A. S.; Savin, A. A.; Shcheglova, L. M.; Solomin, A. N.; Zotov, N. P.; Bentvelsen, S.; Botje, M.; Chlebana, F.; Dake, A.; Engelen, J.; de Jong, P.; de Kamps, M.; Kooijman, P.; Kruse, A.; O'Dell, V.; Tenner, A.; Tiecke, H.; Verkerke, W.; Vreeswijk, M.; Wiggers, L.; de Wolf, E.; van Woudenberg, R.; Acosta, D.; Bylsma, B.; Durkin, L. S.; Honscheid, K.; Li, C.; Ling, T. Y.; McLean, K. W.; Murray, W. N.; Park, I. H.; Romanowski, T. A.; Seidlein, R.; Bailey, D. S.; Blair, G. A.; Byrne, A.; Cashmore, R. J.; Cooper-Sarkar, A. M.; Daniels, D.; Devenish, R. C. E.; Harnew, N.; Lancaster, M.; Luffman, P. E.; Lindemann, L.; McFall, J.; Nath, C.; Quadt, A.; Uijterwaal, H.; Walczak, R.; Wilson, F. F.; Yip, T.; Abbiendi, G.; Bertolin, A.; Brugnera, R.; Carlin, R.; Dal Corso, F.; de Giorgi, M.; Dosselli, U.; Limentani, S.; Morandin, M.; Posocco, M.; Stanco, L.; Stroili, R.; Voci, C.; Bulmahn, J.; Butterworth, J. M.; Feild, R. G.; Oh, B. Y.; Whitmore, J. J.; D'Agostini, G.; Iori, M.; Marini, G.; Mattioli, M.; Nigro, A.; Tassi, E.; Hart, J. C.; McCubbin, N. A.; Prytz, K.; Shah, T. P.; Short, T. L.; Barberis, E.; Cartiglia, N.; Dubbs, T.; Heusch, C.; van Hook, M.; Hubbard, B.; Lockman, W.; Rahn, J. T.; Sadrozinski, H. F.-W.; Seiden, A.; Biltzinger, J.; Seifert, R. J.; Walenta, A. H.; Zech, G.; Abramowicz, H.; Briskin, G.; Dagan, S.; Levy, A.; Hasegawa, T.; Hazumi, M.; Ishii, T.; Kuze, M.; Mine, S.; Nagasawa, Y.; Nagira, T.; Nakao, M.; Suzuki, I.; Tokushuku, K.; Yamada, S.; Yamazaki, Y.; Chiba, M.; Hamatsu, R.; Hirose, T.; Homma, K.; Kitamura, S.; Nagayama, S.; Nakamitsu, Y.; Cirio, R.; Costa, M.; Ferrero, M. I.; Lamberti, L.; Maselli, S.; Peroni, C.; Sacchi, R.; Solano, A.; Staiano, A.; Dardo, M.; Bailey, D. C.; Bandyopadhyay, D.; Benard, F.; Brkic, M.; Crombie, M. B.; Gingrich, D. M.; Hartner, G. F.; Joo, K. K.; Levman, G. M.; Martin, J. F.; Orr, R. S.; Sampson, C. R.; Teuscher, R. J.; Catterall, C. D.; Jones, T. W.; Kaziewicz, P. B.; Lane, J. B.; Saunders, R. L.; Shulman, J.; Blankenship, K.; Kochocki, J.; Lu, B.; Mo, L. W.; Bogusz, W.; Charchula, K.; Ciborowski, J.; Gajewski, J.; Grzelak, G.; Kasprazak, M.; Krzyżanowski, M.; Muchorowski, K.; Nowak, R. J.; Pawlak, J. M.; Tymieniecka, T.; Wróblewski, A. K.; Zakrzewski, J. A.; Żarnecki, A. F.; Adamus, M.; Eisenberg, Y.; Glasman, C.; Karshon, U.; Revel, D.; Shapira, A.; Ali, I.; Behrens, B.; Dasu, S.; Fordham, C.; Foudas, C.; Goussiou, A.; Loveless, R. J.; Reeder, D. D.; Silverstein, S.; Smith, W. H.; Tsurugai, T.; Bhadra, S.; Frisken, W. R.; Furutani, K. M.
1995-12-01
A search for excited states of the standard model fermions was performed using the ZEUS detector at the HERA electron-proton collider, operating at a centre of mass energy of 296 GeV. In a sample corresponding to an integrated luminosity of 0.55 pb-1, no evidence was found for any resonant state decaying into final states composed of a fermion and a gauge boson. Limits on the coupling strength times branching ratio of excited fermions are presented for masses between 50 GeV and 250 GeV, extending previous search regions significantly.
Nakai, Hiromi; Yoshikawa, Takeshi; Nonaka, Yutaro
2017-01-05
This study presents an efficient algorithm to search for the poles of dynamic polarizability to obtain excited states of large systems with nonlocal excitation nature. The present algorithm adopts a homogeneous search with a constant frequency interval and a bisection search to achieve high accuracy. Furthermore, the subtraction process of the information about the detected poles from the total dynamic polarizability is used to extract the undetected pole contributions. Numerical assessments confirmed the accuracy and efficiency of the present algorithm in obtaining the excitation energies and oscillator strengths of all dipole-allowed excited states. A combination of the present pole-search algorithm and divide-and-conquer-based dynamic polarizability calculations was found to be promising to treat nonlocal excitations of large systems. © 2016 Wiley Periodicals, Inc.
Machine Gun Liner Bond Strength
2007-08-01
investigation does not constitute a complete analysis of liner failures in the M2 machine gun. The fact that two different liner-failure modes were...An order-of-magnitude estimate can be made of the bond strength in this case using a standard elastic analysis and some reasonable assumptions... analysis of the forces on the machine gun bullet, it was found that the measured bond strength was adequate to resist the reaction forces produced when
Collisional energy transfer from excited nitrogen dioxide
Patten, K.O.
1991-05-01
The radiative lifetimes of gaseous nitrogen dioxide excited by pulsed, tunable dye laser radiation are determined for excitation wavelengths ranging from 400 to 750 nm. When the data are expressed in the form of zero-pressure radiative rate constants (k{sub 0}/s{sup {minus}1}), they fit a linear equation with respect to excitation energy. This fit predicts a radiative lifetime of 64 {mu}s for 400 nm excitation and 102 {mu}s at 750 nm. The effects of pressure, observation delay time, and wavelength range of the fluorescence detection apparatus are determined for both radiative lifetime and quenching constant. Dispersed fluorescence spectra from excited nitrogen dioxide are analyzed into three-parameter functions that approximate the corresponding excited state population distributions. Energy transfer from nitrogen dioxide excited at 532 nm and colliding with thirteen buffer gases is studied by this population deconvolution method. The energy removal rate constants increase in the order Ne < Ar < Kr < Xe < He < CO < N{sub 2} < O{sub 2} < NO < NO{sub 2} < CO{sub 2} < SF{sub 6} < SO{sub 2}. The energy transfer rate constant is strongly correlated with the number of degrees of freedom of the buffer molecule and with low vibrational frequencies of the buffer molecule. Population deconvolution from excited nitrogen dioxide fluorescence spectra is again employed to find energy removal rate constants for the NO {sub 2}{sup *}-NO{sub 2} collisions, excited by dye laser at 475.34, 435.04, and 400.00 nm. The energy transfer rate constant increases with decreasing excitation wavelength. The energy removal rate constant between 400 and 532 nm excitation increases as the (3.6 {plus minus} 0.4) power of the excitation photon energy. 76 refs., 67 figs., 16 tabs.
Excitement in shame: the price we pay.
Aledort, Stewart L
2014-01-01
This paper explores the role of excitement in shame, extending the theoretical underpinnings of my work (Aledort, 2002, 2003, 2008, 2009) on narcissism and the omnipotent child syndrome. Shame, excitement, and early narcissistic self-states are complexly intermingled, each influencing the other. Empathy alone is insufficient; the passion connected to shame can be easily hidden. Detailed case studies describe a model for working with the excitement in shame, how it functions, and how it gets resolved.
NASA Astrophysics Data System (ADS)
Kumar, Ashok; Thakkar, Ajit J.
2011-11-01
Experimental photoabsorption cross-sections combined with constraints provided by the Kuhn-Reiche-Thomas sum rule and the high-energy behavior of the dipole-oscillator-strength density are used to construct dipole oscillator strength distributions for buckminsterfullerene (C60). The distributions are used to predict dipole sum rules Sk, mean excitation energies Ik, the frequency dependent polarizability, and C6 coefficients for the long-range dipole-dipole interactions of C60 with a variety of atoms and molecules.
Collision strengths for nebular [O III] optical and infrared lines
NASA Astrophysics Data System (ADS)
Storey, P. J.; Sochi, Taha; Badnell, N. R.
2014-07-01
We present electron collision strengths and their thermally averaged values for the nebular forbidden lines of the astronomically abundant doubly ionized oxygen ion, O2+, in an intermediate coupling scheme using the Breit-Pauli relativistic terms as implemented in an R-matrix atomic scattering code. We use several atomic targets for the R-matrix scattering calculations including one with 72 atomic terms. We also compare with new results obtained using the intermediate coupling frame transformation method. We find spectroscopically significant differences against a recent Breit-Pauli calculation for the excitation of the [O III] λ4363 transition but confirm the results of earlier calculations.
Dipole Excitation of Soft and Giant Resonances in 132Sn and neighboring unstable nuclei
NASA Astrophysics Data System (ADS)
Boretzky, Konstanze
2006-04-01
The evolution of dipole-strength distributions above the one-neutron threshold was investigated for exotic neutron-rich nuclei in a series of experiments using the electromagnetic projectile excitation at beam energies around 500 MeV/u. For halo nuclei, the large observed dipole strength (shown here for 11Be) is explained within the direct-breakup model to be of non-collective character. For neutron-rich oxygen isotopes, the origin of the observed low-lying strength is concluded to be due to single-particle transitions on theoretical grounds. The dipole strength spectra for 130,132Sn exhibit resonance-like structures observed at energies around 10 MeV exhausting a few percent of the Thomas-Reiche-Kuhn (TRK) sum rule, separated clearly from the dominant Giant Dipole Resonance (GDR). The data agree with predictions for a new dipole mode related to the oscillation of excess neutrons versus the core nucleons ("pygmy resonance").
Spatially encoded multiple-quantum excitation.
Ridge, Clark D; Borvayeh, Leila; Walls, Jamie D
2013-05-28
In this work, we present a simple method to spatially encode the transition frequencies of nuclear spin transitions and to read out these frequencies within a single scan. The experiment works by combining pulsed field gradients with an excitation sequence that selectively excites spin transitions within certain sample regions. After the initial excitation, imaging the resulting ẑ-magnetization is used to determine the locations where the excitations occurred, from which the corresponding transition frequencies are determined. Simple experimental demonstrations of this technique on one- and two-spin systems are presented.
Laser Excited Fluorescence Studies Of Black Liquor
NASA Astrophysics Data System (ADS)
Horvath, J. J.; Semerjian, H. G.
1986-10-01
Laser excited fluorescence of black liquor was investigated as a possible monitoring technique for pulping processes. A nitrogen pumped dye laser was used to examine the fluorescence spectrum of black liquor solutions. Various excitation wavelengths were used between 290 and 403 nm. Black liquor fluorescence spectra were found to vary with both excitation wavelength and black liquor concentration. Laser excited fluorescence was found to be a sensitive technique for measurement of black liquor with good detection limits and linear response over a large dynamic range.
Single determinant calculations of excited state polarizabilities
NASA Astrophysics Data System (ADS)
Jonsson, Dan; Norman, Patrick; Ågren, Hans
1997-12-01
We apply response theory to simulate excited state polarizabilities emphasizing the possibility to do so by means of optimization of a ground state single determinant only. The excited state polarizabilities are given by the double residues of the cubic response functions. A set of molecules with varying ground state configurations and properties have been considered: water, ozone, formaldehyde, ethylene, butadiene, cyclobutadiene, pyridine, pyrazine and s-tetrazine. The results have been compared to excited state experiments where available and with linear response calculations of the multi-determinant optimized excited state. It is shown that calculations of excited state polarizabilities based on a ground state optimized single determinant work well for most of the cases investigated. This contention is exemplified by the fact the gas phase value from an electrochromism experiment for the polarizability of the 1 1B2 excited state of formaldehyde is better reproduced by ground state cubic response theory than by the corresponding separate state linear response function calculation, and by that the calculations call for an experimental reinvestigation of the excited state polarizabilities of s-tetrazine. A few prerequisites are given: The excited state should be isolated in energy, the ordering of the main contributing states should be reproduced, and the geometric conformation of the excited state in question should not be very different from the ground state geometry. The computational and formal advantages of the approach are discussed.
Quasiparticle excitations in superdeformed [sup 192]Hg
Fallon, P. ); Lauritsen, T.; Ahmad, I.; Carpenter, M.P. ); Cederwall, B.; Clark, R.M. ); Crowell, B. ); Deleplanque, M.A.; Diamond, R.M. ); Gall, B.; Hannachi, F. ); Henry, R.G.; Janssens, R.V.F.; Khoo, T.L. ); Korichi, A. ); Lee, I.Y.; Macchiavelli, A.O. (Nuclear Science Division, Lawrence
1995-04-01
For the first time, two excited superdeformed (SD) bands have been observed in the double closed shell superdeformed nucleus [sup 192]Hg. One of the SD bands exhibits a pronounced peak in the dynamic moment of inertia which is interpreted as a crossing between two excited SD configurations involving the [ital N]=7 intruder and the [512]5/2 orbitals. This is only the second occurrence of such a crossing in a SD nucleus around [ital A]=190. The second excited SD band has near identical transition energies to an excited SD band in [sup 191]Hg.
Low energy dipole strength from large scale shell model calculations
NASA Astrophysics Data System (ADS)
Sieja, Kamila
2017-09-01
Low energy enhancement of radiative strength functions has been deduced from experiments in several mass regions of nuclei. Such an enhancement is believed to impact the calculated neutron capture rates which are crucial input for reaction rates of astrophysical interest. Recently, shell model calculations have been performed to explain the upbend of the γ-strength as due to the M1 transitions between close-lying states in the quasi-continuum in Fe and Mo nuclei. Beyond mean-↓eld calculations in Mo suggested, however, a non-negligible role of electric dipole in the low energy enhancement. So far, no calculations of both dipole components within the same theoretical framework have been presented in this context. In this work we present newly developed large scale shell model appraoch that allows to treat on the same footing natural and non-natural parity states. The calculations are performed in a large sd - pf - gds model space, allowing for 1p{1h excitations on the top of the full pf-shell con↓guration mixing. We restrict the discussion to the magnetic part of the dipole strength, however, we calculate for the ↓rst time the magnetic dipole strength between states built of excitations going beyond the classical shell model spaces. Our results corroborate previous ↓ndings for the M1 enhancement for the natural parity states while we observe no enhancement for the 1p{1h contributions. We also discuss in more detail the e↑ects of con↓guration mixing limitations on the enhancement coming out from shell model calculations.
Acute Strength Training Increases Responses to Stimulation of Corticospinal Axons.
Nuzzo, James L; Barry, Benjamin K; Gandevia, Simon C; Taylor, Janet L
2016-01-01
Acute strength training of forearm muscles increases resting twitch forces from motor cortex stimulation. It is unclear if such effects are spinal in origin and if they also occur with training of larger muscles. With the use of subcortical stimulation of corticospinal axons, the current study examined if one session of strength training of the elbow flexor muscles leads to spinal cord changes and if the type of training is important. In experiment 1, 10 subjects completed ballistic isometric training, ballistic concentric training, and no training (control) on separate days. In experiment 2, 13 subjects completed ballistic isometric training and slow-ramp isometric training. Before and after training, transcranial magnetic stimulation over the contralateral motor cortex elicited motor-evoked potentials (MEPs) in the resting biceps brachii, and electrical stimulation of corticospinal tract axons at the cervicomedullary junction elicited cervicomedullary motor-evoked potentials (CMEPs). Motor-evoked potential and CMEP twitch forces were also measured. In experiment 1, CMEPs and CMEP twitch forces were significantly facilitated after ballistic isometric training compared to control. In experiment 2, MEPs, MEP twitch forces, CMEPs, and CMEP twitch forces increased for 15 to 25 min after ballistic and slow-ramp isometric training. Via processes within the spinal cord, one session of strength training of the elbow flexors increases net output from motoneurons projecting to the trained muscles. Likely mechanisms include increased efficacy of corticospinal-motoneuronal synapses or increased motoneuron excitability. However, the rate of force generation during training is not important for inducing these changes. A concomitant increase in motor cortical excitability is likely. These short-term changes may represent initial neural adaptations to strength training.
Photon strength functions from photon scattering
NASA Astrophysics Data System (ADS)
Schwengner, Ronald
2015-10-01
We present photon-scattering experiments using bremsstrahlung at the γELBE facility of Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and using quasi-monoenergetic, polarized γ rays at the HI γS facility of the Triangle Universities Nuclear Laboratory (TUNL) in Durham. In the analysis of the spectra measured by using bremsstrahlung at γELBE, we include intensity in the quasi-continuum and perform simulations of statistical γ-ray cascades using the code γDEX to estimate intensities of inelastic transitions to low-lying excited states. Simulated average branching ratios are compared with model-independent branching ratios obtained from spectra measured by using monoenergetic γ beams at HI γS. Photoabsorption cross sections deduced in this way are presented for selected nuclides. Strength in the energy region of the so-called pygmy dipole resonance (PDR) is considered in nuclei around mass 80 and in xenon isotopes. In collaboration with Ralph Massarczyk, Los Alamos National Laboratory.
Muscular strength and physical function.
Brill, P A; Macera, C A; Davis, D R; Blair, S N; Gordon, N
2000-02-01
The purpose of this study was to evaluate the potential association of muscular strength and endurance at baseline with the prevalence of functional limitations at follow-up. Study participants were 3,069 men and 589 women (30-82 yr) who received a clinical examination including a strength evaluation at the Cooper Clinic between 1980 and 1989 and responded to a 1990 mail-back survey. Participants also had to achieve at least 85% of their age-predicted maximal heart rate on a maximal exercise treadmill test and have no history of heart attack, stroke, diabetes, high blood pressure, cancer, or arthritis at their first visit. A strength index composite score (0-6) was calculated using age- and sex-specific tertiles from bench press, leg press, and sit-up tests. Those scoring 5 or 6 were categorized in the high strength group. Functional health status was assessed by responses to questions about the participant's ability to perform light, moderate, and strenuous recreational, household, daily living, and personal care tasks. After an average follow-up of 5 yr, 7% of men and 12% of women reported at least one functional limitation. A logistic regression model including age, aerobic fitness, body mass index, and new health problems at follow-up found that, relative to those with lower levels of strength, the odds of reporting functional limitations at follow-up in men and women categorized as having higher levels of strength were 0.56 (95%CI = 0.34, 0.93) and 0.54 (95%CI = 0.21, 1.39), respectively. These findings, if replicated in other populations, suggest that maintenance of strength throughout the lifespan may reduce the prevalence of functional limitations.
Mason, Joel; Frazer, Ashlyn K; Horvath, Deanna M; Pearce, Alan J; Avela, Janne; Howatson, Glyn; Kidgell, Dawson J
2017-08-22
Cross-education of strength occurs when strength-training one limb increases the strength of the untrained limb and is restricted to the untrained homologous muscle. Cortical circuits located ipsilateral to the trained limb might be involved. We used transcranial magnetic stimulation (TMS) to determine the corticomotor responses from the untrained homologous (biceps brachii) and non-homologous (flexor carpi radialis) muscle following strength-training of the right elbow flexors. Motor evoked potentials were recorded from the untrained left biceps brachii and flexor carpi radialis during a submaximal contraction from 20 individuals (10 women, 10 men, aged 18-35 years; training group; n = 10 and control group; n = 10) before and after 3-weeks of strength-training the right biceps brachii at 80% of 1-repetition maximum (1-RM). Recruitment-curves for corticomotor excitability and inhibition of the untrained homologous and non-homologous muscle were constructed and assessed by examining the area under the recruitment curve (AURC). Strength-training increased strength of the trained elbow flexors (29%), resulting in a 18% increase in contralateral strength of the untrained elbow flexors (P <0.0001). The trained wrist flexors increased by 19%, resulting in a 12% increase in strength of the untrained wrist flexors (P = 0.005). TMS showed increased corticomotor excitability and decreased corticomotor inhibition for the untrained homologous muscle (P < 0.05); however, there were no changes in the untrained non-homologous muscle (P > 0.05). These findings show that the cross-education of muscular strength is spatially distributed; however, the neural adaptations are confined to the motor pathway ipsilateral to the untrained homologous agonist.