Science.gov

Sample records for coupled channels calculation

  1. Four-body continuum-discretized coupled-channels calculations

    SciTech Connect

    Rodriguez-Gallardo, M.; Arias, J. M.; Moro, A. M.; Gomez-Camacho, J.; Thompson, I. J.; Tostevin, J. A.

    2009-11-15

    The development of a continuum-bin scheme of discretization for three-body projectiles is necessary for studies of reactions of Borromean nuclei such as {sup 6}He within the continuum-discretized coupled-channels approach. Such a procedure, for constructing bin states on selected continuum energy intervals, is formulated and applied for the first time to reactions of a three-body projectile. The continuum representation uses the eigenchannel expansion of the three-body S matrix. The method is applied to the challenging case of the {sup 6}He+{sup 208}Pb reaction at 22 MeV, where an accurate treatment of both the Coulomb and the nuclear interactions with the target is necessary.

  2. ATOMIC AND MOLECULAR PHYSICS: Coupled-Channels Optical Calculation for Electron Scattering from Metastable Helium

    NASA Astrophysics Data System (ADS)

    Wang, Yuan-Cheng; Zhou, Ya-Jun; Cheng, Yong-Jun; Ma, Jia

    2009-08-01

    Coupled-channels optical calculations for total and resonance excitation integral cross sections for electron scattering on the metastable level 21,3 S of helium are presented. The results are in agreement with other theoretical and experimental data.

  3. Calculation of nuclear reaction cross sections on excited nuclei with the coupled-channels method

    SciTech Connect

    Kawano, T.; Talou, P.; Lynn, J. E.; Chadwick, M. B.; Madland, D. G.

    2009-08-15

    We calculate nuclear cross sections on excited nuclei in the fast neutron energy range. We partition the whole process into two contributions: the direct reaction part and the compound nuclear reactions. A coupled-channels method is used for calculating the direct transition of the nucleus from the initial excited state, which is a member of the ground-state rotational band, to the final ground and excited low-lying levels. This process is strongly affected by the channel coupling. The compound nuclear reactions on the excited state are calculated with the statistical Hauser-Feshbach model, with the transmission coefficients obtained from the coupled-channels calculation. The calculations are performed for a strongly deformed nucleus {sup 169}Tm, and selected cross sections for the ground and first excited states are compared. The calculation is also made for actinides to investigate possible modification to the fission cross section when the target is excited. It is shown that both the level coupling for the entrance channel, and the different target spin, change the fission cross section.

  4. Present status of coupled-channels calculations for heavy-ion subbarrier fusion reactions

    NASA Astrophysics Data System (ADS)

    Hagino, K.; Yao, J. M.

    2016-05-01

    The coupled-channels method has been a standard tool in analyzing heavy-ion fusion reactions at energies around the Coulomb barrier. We investigate three simplifications usually adopted in the coupledchannels calculations. These are i) the exclusion of non-collective excitations, ii) the assumption of coordinate independent coupling strengths, and iii) the harmonic oscillator approximation for multiphonon excitations. In connection to the last point, we propose a novel microscopic method based on the beyond-mean-field approach in order to take into account the anharmonic effects of collective vibrations.

  5. Coupled-rearrangement-channels calculation of the three-body system under the absorbing boundary condition

    NASA Astrophysics Data System (ADS)

    Iwasaki, M.; Otani, R.; Ito, M.; Kamimura, M.

    2016-06-01

    We formulate the absorbing boundary condition (ABC) in the coupled rearrangement-channels variational method (CRCVM) for the three-body problem. The absorbing potential is introduced in the system of the identical three-bosons, on which the boson symmetry is explicitly imposed by considering the rearrangement channels. The resonance parameters and the strength of the monopole breakup are calculated by the CRCVM + ABC method, and the results are compared with the complex scaling method (CSM). We have found that the results of the ABC method are consistent with the CSM results. The effect of the boson symmetry, which is often neglected in the calculation of the triple α reactions, is also discussed.

  6. Analytical transformed harmonic oscillator basis for continuum discretized coupled channels calculations

    SciTech Connect

    Moro, A. M.; Arias, J. M.; Gomez-Camacho, J.; Perez-Bernal, F.

    2009-11-15

    A new method for continuum discretization in continuum-discretized coupled-channels calculations is proposed. The method is based on an analytic local-scale transformation of the harmonic-oscillator wave functions proposed for other purposes in a recent work [Karatagladis et al., Phys. Rev. C 71, 064601 (2005)]. The new approach is compared with the standard method of continuum discretization in terms of energy bins for the reactions d+{sup 58}Ni at 80 MeV, {sup 6}Li+{sup 40}Ca at 156 MeV, and {sup 6}He+{sup 208}Pb at 22 MeV and 240 MeV/nucleon. In all cases very good agreement between both approaches is found.

  7. Coupled-rearrangement-channels calculation of the three-body system under the absorbing boundary condition

    NASA Astrophysics Data System (ADS)

    Iwasaki, M.; Otani, R.; Ito, M.; Kamimura, M.

    2016-05-01

    We formulate the method of the absorbing boundary condition (ABC) in the coupled-rearrangement-channels variational method (CRCMV) for the three-body problem. In the present study, we handle the simple three-boson system, and the absorbing potential is introduced in the Jacobi coordinate in the individual rearrangement channels. The resonance parameters and the strength of the monopole breakup are compared with the complex scaling method (CSM). We have found that the CRCVM + ABC method nicely works in the threebody problem with the rearrangement channels.

  8. Hyperspherical coupled channel calculations of energy and structure of 4He-4He-Li+ and its isotopic combinations

    NASA Astrophysics Data System (ADS)

    Liu, Min-min; Wu, Meng-Shan; Han, Hui-li; Shi, Ting-yun

    2016-07-01

    The ground state vibrational energy and spatial features of 4He-4He-Li+ and its triatomic isotopic complexes are studied using the slow variable discretization (SVD) method in the hyperspherical coordinates for the zero total angular momentum. Our results show that the dominant structure of the system is an isosceles triangle with the shorter side associated with the two Li+-He distances using the sum-of-potential approximation. Corrections caused by the induced dipole-induced dipole interactions on the He atoms are also investigated. The effects are seen to be small and have a minor influence on the binding energy and the structure of present system. The results are also compared with the full ab initio calculations including all the three-body interactions and information of three-body corrections is obtained.

  9. Hyperspherical coupled channel calculations of energy and structure of (4)He-(4)He-Li(+) and its isotopic combinations.

    PubMed

    Liu, Min-Min; Wu, Meng-Shan; Han, Hui-Li; Shi, Ting-Yun

    2016-07-21

    The ground state vibrational energy and spatial features of (4)He-(4)He-Li(+) and its triatomic isotopic complexes are studied using the slow variable discretization (SVD) method in the hyperspherical coordinates for the zero total angular momentum. Our results show that the dominant structure of the system is an isosceles triangle with the shorter side associated with the two Li(+)-He distances using the sum-of-potential approximation. Corrections caused by the induced dipole-induced dipole interactions on the He atoms are also investigated. The effects are seen to be small and have a minor influence on the binding energy and the structure of present system. The results are also compared with the full ab initio calculations including all the three-body interactions and information of three-body corrections is obtained. PMID:27448884

  10. Four-body continuum-discretized coupled-channels calculations: Application to {sup 6}He+{sup 64}Zn at 13.6 MeV

    SciTech Connect

    Rodriguez-Gallardo, M.; Arias, J. M.; Moro, A. M.; Gomez-Camacho, J.; Thompson, I. J.; Tostevin, J. A.

    2010-04-26

    The recently developed four-body continuum-discretized coupled-channels (CDCC) method, making use of the binning procedure, is applied to the reaction {sup 6}He+{sup 64}Zn at 13.6 MeV (around the Coulomb barrier). Excellent agreement with available elastic data is found.

  11. Coupled channel calculations for electron-positron pair production in collisions of heavy ionsThis work is part of the doctoral thesis of Matthias Gail, Giessen (D26) 2001.

    NASA Astrophysics Data System (ADS)

    Gail, Matthias; Grün, Norbert; Scheid, Werner

    2003-04-01

    Coupled channel calculations are performed for electron-positron pair production in relativistic collisions of heavy ions. For this purpose the wavefunction is expanded into different types of basis sets consisting of atomic wavefunctions centred around the projectile ion only and around both of the colliding nuclei. The results are compared with experimental data from Belkacem et al (1997 Phys. Rev. A 56 2807). This work is part of the doctoral thesis of Matthias Gail, Giessen (D26) 2001.

  12. Nonadiabatic quantum dynamics of C(1D)+H2→CH+H: coupled-channel calculations including Renner-Teller and Coriolis terms.

    PubMed

    Defazio, Paolo; Bussery-Honvault, Béatrice; Honvault, Pascal; Petrongolo, Carlo

    2011-09-21

    The Renner-Teller (RT) coupled-channel dynamics for the C((1)D)+H(2)(X(1)Σ(g) (+))→CH(X(2)Π)+H((2)S) reaction has been investigated for the first time, considering the first two singlet states ã̃(1)A' and b(1)A'' of CH(2) dissociating into the products and RT couplings, evaluated through the ab initio matrix elements of the electronic angular momentum. We have obtained initial-state-resolved probabilities, cross sections and thermal rate constants via the real wavepacket method for both coupled electronic states. In contrast to the N((2)D)+H(2)(X(1)Σ(g)(+)) system, RT effects tend to reduce probabilities, cross sections, and rate constants in the low energy range compared to Born-Oppenheimer (BO) ones, due to the presence of a repulsive RT barrier in the effective potentials and to long-lived resonances. Furthermore, contrary to BO results, the rate constants have a positive temperature dependence in the 100-400 K range. The two-state RT rate constant at 300 K, lower than the BO one, remains inside the error bars of the experimental value.

  13. Coupled-channel scattering on a torus

    SciTech Connect

    Guo, Peng; Dudek, Jozef Jon; Edwards, Robert G.; Szczepaniak, Adam Pawel

    2013-07-01

    Based on the Hamiltonian formalism approach, a generalized Luscher's formula for two particle scattering in both the elastic and coupled-channel cases in moving frames is derived from a relativistic Lippmann-Schwinger equation. Some strategies for extracting scattering amplitudes for a coupled-channel system from the discrete finite-volume spectrum are discussed and illustrated with a toy model of two-channel resonant scattering. This formalism will, in the near future, be used to extract information about hadron scattering from lattice QCD computations.

  14. Beyond the Coherent Coupled Channels Description of Nuclear Fusion

    SciTech Connect

    Dasgupta, M.; Hinde, D. J.; Diaz-Torres, A.; Bouriquet, B.; Low, Catherine I.; Newton, J. O.; Milburn, G. J.

    2007-11-09

    New measurements of fusion cross sections at deep sub-barrier energies for the reactions {sup 16}O+{sup 204,208}Pb show a steep but almost saturated logarithmic slope, unlike {sup 64}Ni-induced reactions. Coupled channels calculations cannot simultaneously reproduce these new data and above-barrier cross-sections with the same Woods-Saxon nuclear potential. It is argued that this highlights an inadequacy of the coherent coupled channels approach. It is proposed that a new approach explicitly including gradual decoherence is needed to allow a consistent description of nuclear fusion.

  15. Integral dependent spin couplings in CI calculations

    NASA Technical Reports Server (NTRS)

    Iberle, K.; Davidson, E. R.

    1982-01-01

    Although the number of ways to combine Slater determinants to form spin eigenfunctions increases rapidly with the number of open shells, most of these spin couplings will make only a small contribution to a given state, provided the spin coupling is chosen judiciously. The technique of limiting calculations to the interacting subspace pioneered by Bunge (1970) was employed by Munch and Davidson (1975) to the vanadium atom. The use of an interacting space looses its advantage in more complex cases. However, the problem can always be reduced to only one interacting spin coupling by making the coefficients integral dependent. The present investigation is concerned with the performance of integral dependent interacting couplings, taking into account the results of three test calculations.

  16. Extracting Effective Higgs Couplings in the Golden Channel

    SciTech Connect

    Chen, Yi; Vega-Morales, Roberto

    2014-04-08

    Kinematic distributions in Higgs decays to four charged leptons, the so called ‘golden channel, are a powerful probe of the tensor structure of its couplings to neutral electroweak gauge bosons. In this study we construct the first part of a comprehensive analysis framework designed to maximize the information contained in this channel in order to perform direct extraction of the various possible Higgs couplings. We first complete an earlier analytic calculation of the leading order fully differential cross sections for the golden channel signal and background to include the 4e and 4μ final states with interference between identical final states. We also examine the relative fractions of the different possible combinations of scalar-tensor couplings by integrating the fully differential cross section over all kinematic variables as well as show various doubly differential spectra for both the signal and background. From these analytic expressions we then construct a ‘generator level’ analysis framework based on the maximum likelihood method. Then, we demonstrate the ability of our framework to perform multi-parameter extractions of all the possible effective couplings of a spin-0 scalar to pairs of neutral electroweak gauge bosons including any correlations. Furthermore, this framework provides a powerful method for study of these couplings and can be readily adapted to include the relevant detector and systematic effects which we demonstrate in an accompanying study to follow.

  17. Extracting Effective Higgs Couplings in the Golden Channel

    DOE PAGES

    Chen, Yi; Vega-Morales, Roberto

    2014-04-08

    Kinematic distributions in Higgs decays to four charged leptons, the so called ‘golden channel, are a powerful probe of the tensor structure of its couplings to neutral electroweak gauge bosons. In this study we construct the first part of a comprehensive analysis framework designed to maximize the information contained in this channel in order to perform direct extraction of the various possible Higgs couplings. We first complete an earlier analytic calculation of the leading order fully differential cross sections for the golden channel signal and background to include the 4e and 4μ final states with interference between identical final states.more » We also examine the relative fractions of the different possible combinations of scalar-tensor couplings by integrating the fully differential cross section over all kinematic variables as well as show various doubly differential spectra for both the signal and background. From these analytic expressions we then construct a ‘generator level’ analysis framework based on the maximum likelihood method. Then, we demonstrate the ability of our framework to perform multi-parameter extractions of all the possible effective couplings of a spin-0 scalar to pairs of neutral electroweak gauge bosons including any correlations. Furthermore, this framework provides a powerful method for study of these couplings and can be readily adapted to include the relevant detector and systematic effects which we demonstrate in an accompanying study to follow.« less

  18. Quantum Biological Channel Modeling and Capacity Calculation

    PubMed Central

    Djordjevic, Ivan B.

    2012-01-01

    Quantum mechanics has an important role in photosynthesis, magnetoreception, and evolution. There were many attempts in an effort to explain the structure of genetic code and transfer of information from DNA to protein by using the concepts of quantum mechanics. The existing biological quantum channel models are not sufficiently general to incorporate all relevant contributions responsible for imperfect protein synthesis. Moreover, the problem of determination of quantum biological channel capacity is still an open problem. To solve these problems, we construct the operator-sum representation of biological channel based on codon basekets (basis vectors), and determine the quantum channel model suitable for study of the quantum biological channel capacity and beyond. The transcription process, DNA point mutations, insertions, deletions, and translation are interpreted as the quantum noise processes. The various types of quantum errors are classified into several broad categories: (i) storage errors that occur in DNA itself as it represents an imperfect storage of genetic information, (ii) replication errors introduced during DNA replication process, (iii) transcription errors introduced during DNA to mRNA transcription, and (iv) translation errors introduced during the translation process. By using this model, we determine the biological quantum channel capacity and compare it against corresponding classical biological channel capacity. We demonstrate that the quantum biological channel capacity is higher than the classical one, for a coherent quantum channel model, suggesting that quantum effects have an important role in biological systems. The proposed model is of crucial importance towards future study of quantum DNA error correction, developing quantum mechanical model of aging, developing the quantum mechanical models for tumors/cancer, and study of intracellular dynamics in general. PMID:25371271

  19. Benchmarking Calculations of Excitonic Couplings between Bacteriochlorophylls.

    PubMed

    Kenny, Elise P; Kassal, Ivan

    2016-01-14

    Excitonic couplings between (bacterio)chlorophyll molecules are necessary for simulating energy transport in photosynthetic complexes. Many techniques for calculating the couplings are in use, from the simple (but inaccurate) point-dipole approximation to fully quantum-chemical methods. We compared several approximations to determine their range of applicability, noting that the propagation of experimental uncertainties poses a fundamental limit on the achievable accuracy. In particular, the uncertainty in crystallographic coordinates yields an uncertainty of about 20% in the calculated couplings. Because quantum-chemical corrections are smaller than 20% in most biologically relevant cases, their considerable computational cost is rarely justified. We therefore recommend the electrostatic TrEsp method across the entire range of molecular separations and orientations because its cost is minimal and it generally agrees with quantum-chemical calculations to better than the geometric uncertainty. Understanding these uncertainties can guard against striving for unrealistic precision; at the same time, detailed benchmarks can allow important qualitative questions-which do not depend on the precise values of the simulation parameters-to be addressed with greater confidence about the conclusions. PMID:26651217

  20. Coupled gating between cardiac calcium release channels (ryanodine receptors).

    PubMed

    Marx, S O; Gaburjakova, J; Gaburjakova, M; Henrikson, C; Ondrias, K; Marks, A R

    2001-06-01

    Excitation-contraction coupling in heart muscle requires the activation of Ca(2+)-release channels/type 2 ryanodine receptors (RyR2s) by Ca(2+) influx. RyR2s are arranged on the sarcoplasmic reticular membrane in closely packed arrays such that their large cytoplasmic domains contact one another. We now show that multiple RyR2s can be isolated under conditions such that they remain physically coupled to one another. When these coupled channels are examined in planar lipid bilayers, multiple channels exhibit simultaneous gating, termed "coupled gating." Removal of the regulatory subunit, the FK506 binding protein (FKBP12.6), functionally but not physically uncouples multiple RyR2 channels. Coupled gating between RyR2 channels may be an important regulatory mechanism in excitation-contraction coupling as well as in other signaling pathways involving intracellular Ca(2+) release. PMID:11397781

  1. Separable coupled-channels momentum space potentials for nuclear reactions

    NASA Astrophysics Data System (ADS)

    Hlophe, Linda; Eremenko, Vasily; Elster, Charlotte; Nunes, Filomena; Deltuva, Arbanas; Escher, Jutta; Thompson, Ian; Torus Collaboration

    2015-10-01

    Many nuclei are deformed and their properties may be described using a rotational model. This involves defining a deformed surface of the nucleus and constructing the nuclear interaction as a function of distance to the surface. The resulting potential has non-zero matrix elements between different rotational states which are characterized by the nuclear spin-parity Iπ, leading to channel couplings. Our goal is to utilize these coupled-channels potentials in momentum space Faddeev calculations which take into account core excitations. For this purpose their separable representation in momentum space is necessary. We accomplish this by employing the separable representation scheme developed by Ernst, Shakin, and Thaler (EST). Since the potentials are complex, the multichannel EST scheme is generalized to non-Hermitian potentials. In the case of proton-nucleus interactions the EST scheme is further extended to include charged particles. The multichannel EST scheme is applied to scattering off 10Be and 12C. For 10Be only couplings to the first excited state (Iπ =2+) were included while for 12C the first two excited states (Iπ =2+ ,4+) were taken into account. Research for this project was supported in part by the US Department of Energy, Office of Science of Nuclear Physics contact.

  2. Viscous flow calculations in turbomachinery channels

    NASA Astrophysics Data System (ADS)

    Martelli, F.; Michelassi, V.

    1993-02-01

    An implicit procedure based on the artificial compressibility formulation is presented for the numerical solution of the two-dimensional incompressible steady Navier-Stokes equations in the presence of large separated regions. Turbulence effects are accounted for by the Chien low Reynolds number form of the K - \\varepsilon turbulence model and the Baldwin-Lomax algebraic expression for turbulent viscosity. The governing equations are written in conservative form and irnplicitly solved in fully coupled form using the approximate factorization technique. Preliminary tests were carried out in a laminar flow regime to check the accuracy and stability of the method in two-dimensional and cylindrical axisymmetric flow configurations. After testing in laminar and turbulent flow regimes and comparing the two turbulence models, the code was successfully applied to an actual gas turbine diffuser at low Mach numbers.

  3. Calculated Coupling Efficiency Between an Elliptical-Core Optical Fiber and a Silicon Oxynitride Rib Waveguide [Corrected Copy

    NASA Technical Reports Server (NTRS)

    Tuma, Margaret L.; Beheim, Glenn

    1995-01-01

    The effective-index method and Marcatili's technique were utilized independently to calculate the electric field profile of a rib channel waveguide. Using the electric field profile calculated from each method, the theoretical coupling efficiency between a single-mode optical fiber and a rib waveguide was calculated using the overlap integral. Perfect alignment was assumed and the coupling efficiency calculated. The coupling efficiency calculation was then repeated for a range of transverse offsets.

  4. Renormalization group calculations with k∥ dependent couplings in a ladder

    NASA Astrophysics Data System (ADS)

    Abramovici, G.

    2006-05-01

    We investigate the phase diagram of a ladder system (two chains, with a Hubbard interaction U and an interband coupling t⊥). It is already known [M. Fabrizio, Phys. Rev. B 48 (1993) 15838] that backward interband scattering (gb) plays a particular role in this system. Moreover, some authors (for instance [ H.J. Schulz, Phys. Rev. B 53 (1996) R2959]) have early pointed out that, because of this coupling gb, parallel momentum (k∥) dependence could not be neglected. So we have introduced an original method to include k∥ dependence of couplings, in a RG calculation using the one particle irreducible (OPI) scheme. We calculate different susceptibilities, which are classified according to their symmetries. Our results depend on whether we include k∥ dependence or not. When we include this dependence, we observe a region with large antiferromagnetic fluctuations, in the vicinity of small t⊥, followed by a superconducting region with a simultaneous divergence of the spin density waves channel. The region with only spin density wave fluctuations disappears, when k∥ dependence is neglected. Altogether, our results prove that k∥ is an influential variable in the renormalization group flow, for a ladder.

  5. High-Fidelity Coupled Monte-Carlo/Thermal-Hydraulics Calculations

    NASA Astrophysics Data System (ADS)

    Ivanov, Aleksandar; Sanchez, Victor; Ivanov, Kostadin

    2014-06-01

    Monte Carlo methods have been used as reference reactor physics calculation tools worldwide. The advance in computer technology allows the calculation of detailed flux distributions in both space and energy. In most of the cases however, those calculations are done under the assumption of homogeneous material density and temperature distributions. The aim of this work is to develop a consistent methodology for providing realistic three-dimensional thermal-hydraulic distributions by coupling the in-house developed sub-channel code SUBCHANFLOW with the standard Monte-Carlo transport code MCNP. In addition to the innovative technique of on-the fly material definition, a flux-based weight-window technique has been introduced to improve both the magnitude and the distribution of the relative errors. Finally, a coupled code system for the simulation of steady-state reactor physics problems has been developed. Besides the problem of effective feedback data interchange between the codes, the treatment of temperature dependence of the continuous energy nuclear data has been investigated.

  6. An R-matrix package for coupled-channel problems in nuclear physics

    NASA Astrophysics Data System (ADS)

    Descouvemont, P.

    2016-03-01

    We present an R-matrix Fortran package to solve coupled-channel problems in nuclear physics. The basis functions are chosen as Lagrange functions, which permits simple calculations of the matrix elements. The main input is the coupling potentials at some nucleus-nucleus distances, specified by the program. The program provides the collision matrix and, optionally, the associated wave function. The present method deals with open and closed channels simultaneously, without numerical instability associated with closed channels. It can also solve coupled-channel problems for non-local potentials. Long-range potentials can be treated with propagation techniques, which significantly speed up the calculations. We first present an overview of the R-matrix theory, and of the Lagrange-mesh method. A description of the package and its installation on a UNIX machine is then provided. Finally, five typical examples are discussed.

  7. Quantum description of coupling to neutron-rearrangement channels in fusion reactions near the Coulomb barrier

    SciTech Connect

    Samarin, V. V.

    2015-10-15

    The fusion cross sections for the {sup 17,18}O+{sup 27}Al, {sup 18}O+{sup 58}Ni, and {sup 6}He+{sup 197}Au reactions were calculated by the coupled-channel method. The radial dependence of matrices that describe coupling to valence-neutron-rearrangement channels was determined with the aid of two-center wave functions. The coupling-strength parameters were evaluated on the basis of numerically solving the time-dependent Schrödinger equation. Satisfactory agreement with experimental data was obtained.

  8. Submicroscopic Ca2+ diffusion mediates inhibitory coupling between individual Ca2+ channels.

    PubMed

    Imredy, J P; Yue, D T

    1992-08-01

    Dihydropyridine-sensitive Ca2+ channels in heart demonstrate an important negative feedback property: they close, or inactivate, in response to prior Ca2+ entry. We now find that Ca2+ influx through one channel can selectively contribute to the inactivation of another adjacent channel, without a generalized elevation of bulk intracellular Ca2+ concentration. Intracellular application of the Ca2+ chelator BAPTA greatly diminishes such negative interactions within Ca2+ channel pairs. These findings demonstrate that Ca2+ currents are controlled not only by intrinsic channel properties, but also by local diffusive interactions among neighboring channels. Such inhibitory coupling among channels provides a concrete example of localized Ca2+ signaling, long proposed to exist on the basis of theoretical calculations. PMID:1323309

  9. Amplitude death of coupled hair bundles with stochastic channel noise

    NASA Astrophysics Data System (ADS)

    Kim, Kyung-Joong; Ahn, Kang-Hun

    2014-04-01

    Hair cells conduct auditory transduction in vertebrates. In lower vertebrates such as frogs and turtles, due to the active mechanism in hair cells, hair bundles (stereocilia) can be spontaneously oscillating or quiescent. Recently an amplitude death phenomenon has been proposed [K.-H. Ahn, J. R. Soc. Interface, 10, 20130525 (2013)] as a mechanism for auditory transduction in frog hair-cell bundles, where sudden cessation of the oscillations arises due to the coupling between nonidentical hair bundles. The gating of the ion channel is intrinsically stochastic due to the stochastic nature of the configuration change of the channel. The strength of the noise due to the channel gating can be comparable to the thermal Brownian noise of hair bundles. Thus, we perform stochastic simulations of the elastically coupled hair bundles. In spite of stray noisy fluctuations due to its stochastic dynamics, our simulation shows the transition from collective oscillation to amplitude death as interbundle coupling strength increases. In its stochastic dynamics, the formation of the amplitude death state of coupled hair bundles can be seen as a sudden suppression of the displacement fluctuation of the hair bundles as the coupling strength increases. The enhancement of the signal-to-noise ratio through the amplitude death phenomenon is clearly seen in the stochastic dynamics. Our numerical results demonstrate that the multiple number of transduction channels per hair bundle is an important factor to the amplitude death phenomenon, because the phenomenon may disappear for a small number of transduction channels due to strong gating noise.

  10. Dynamical Coupled-channels Effects on Pion Photoproduction

    SciTech Connect

    Julia-Diaz, B; Lee, T -S. H.; Matsuyama, A; Sato, T; Smith, L C

    2007-12-18

    The electromagnetic pion production reactions are investigated within the dynamical coupled-channels model developed in {\\bf Physics Reports, 439, 193 (2007)}. The meson-baryon channels included in this study are $\\gamma N$, $\\pi N$, $\\eta N$, and the $\\pi\\Delta$, $\\rho N$ and $\\sigma N$ resonant components of the $\\pi\\pi N$ channel. With the hadronic parameters of the model determined in a recent study of $\\pi N$ scattering, we show that the pion photoproduction data up to the second resonance region can be described to a very large extent by only adjusting the bare $\\gamma N \\rightarrow N^*$ helicity amplitudes, while the non-resonant electromagnetic couplings are taken from previous works. It is found that the coupled-channels effects can contribute about 10 - 20 $\\%$ of the production cross sections in the $\\Delta$ (1232) resonance region, and can drastically change the magnitude and shape of the cross sections in the second resonance region. The importance of the off-shell effects in a dynamical approach is also demonstrated. The meson cloud effects as well as the coupled-channels contributions to the $\\gamma N \\rightarrow N^*$ form factors are found to be mainly in the low $Q^2$ region. For the magnetic M1 $\\gamma N \\rightarrow \\Delta$ (1232) form factor, the results are close to that of the Sato-Lee Model. Necessary improvements to the model and future developments are discussed.

  11. Dynamical coupled-channels effects on pion photoproduction

    SciTech Connect

    Julia-Diaz, B.; Lee, T.-S. H.; Matsuyama, A.; Sato, T.; Smith, L. C.

    2008-04-15

    The electromagnetic pion production reactions are investigated within the dynamical coupled-channels model developed by Matsuyama, Sato, and Lee [Phys. Rep. 439, 193 (2007)]. The meson-baryon channels included in this study are {gamma}N,{pi}N,{eta}N, and the {pi}{delta},{rho}N, and {sigma}N resonant components of the {pi}{pi}N channel. With the hadronic parameters of the model determined in a recent study of {pi}N scattering, we show that the pion photoproduction data up to the second resonance region can be described to a very large extent by only adjusting the bare {gamma}N{yields}N* helicity amplitudes, while the nonresonant electromagnetic couplings are taken from previous works. It is found that the coupled-channels effects can contribute about 30-40 % of the production cross sections in the {delta} (1232) resonance region, and can drastically change the magnitude and shape of the cross sections in the second resonance region. The importance of the loop-integrations in a dynamical approach is also demonstrated. The meson cloud effects as well as the coupled-channels contributions to the {gamma}N{yields}N* form factors are found to be mainly in the low Q{sup 2} region. Necessary improvements to the model and future developments are discussed.

  12. Hindered magnetic dipole transitions between P-wave bottomonia and coupled-channel effects

    NASA Astrophysics Data System (ADS)

    Guo, Feng-Kun; Meißner, Ulf-G.; Yang, Zhi

    2016-09-01

    In the hindered magnetic dipole transitions of heavy quarkonia, the coupled-channel effects originating from the coupling of quarkonia to a pair of heavy and anti-heavy mesons can play a dominant role. Here, we study the hindered magnetic dipole transitions between two P-wave bottomonia, χb (nP) and hb (n‧ P), with n ≠n‧. In these processes the coupled-channel effects are expected to lead to partial widths much larger than the quark model predictions. We estimate these partial widths which, however, are very sensitive to unknown coupling constants related to the vertices χb0 (nP) B B bar . A measurement of the hindered M1 transitions can shed light on the coupled-channel dynamics in these transitions and hence on the size of the coupling constants. We also suggest to check the coupled-channel effects by comparing results from quenched and fully dynamical lattice QCD calculations.

  13. Progress on the Coupling Coil for the MICE Channel

    SciTech Connect

    Green, M.A.; Li, D.; Virostek, S.P.; Lau, W.; Witte, H.; Yang,S.Q.; Drumm, P.; Ivanyushenkov, Y.

    2005-05-08

    This report describes the progress on the coupling magnet for the international Muon Ionization Cooling Experiment (MICE). MICE consists of two cells of a SFOFO cooling channel that is similar to that studied in the level 2 study of a neutrino factory. The MICE RF coupling coil module (RFCC module) consists of a 1.56 m diameter superconducting solenoid, mounted around four cells of conventional 201.25 MHz closed RF cavities. This report discusses the progress that has been made on the superconducting coupling coil that is around the center of the RF coupling module. This report describes the process by which one would cool the coupling coil using a single small 4 K cooler. In addition, the coupling magnet power system and quench protection system are also described.

  14. Mechanism of Electromechanical Coupling in Voltage-Gated Potassium Channels

    PubMed Central

    Blunck, Rikard; Batulan, Zarah

    2012-01-01

    Voltage-gated ion channels play a central role in the generation of action potentials in the nervous system. They are selective for one type of ion – sodium, calcium, or potassium. Voltage-gated ion channels are composed of a central pore that allows ions to pass through the membrane and four peripheral voltage sensing domains that respond to changes in the membrane potential. Upon depolarization, voltage sensors in voltage-gated potassium channels (Kv) undergo conformational changes driven by positive charges in the S4 segment and aided by pairwise electrostatic interactions with the surrounding voltage sensor. Structure-function relations of Kv channels have been investigated in detail, and the resulting models on the movement of the voltage sensors now converge to a consensus; the S4 segment undergoes a combined movement of rotation, tilt, and vertical displacement in order to bring 3–4e+ each through the electric field focused in this region. Nevertheless, the mechanism by which the voltage sensor movement leads to pore opening, the electromechanical coupling, is still not fully understood. Thus, recently, electromechanical coupling in different Kv channels has been investigated with a multitude of techniques including electrophysiology, 3D crystal structures, fluorescence spectroscopy, and molecular dynamics simulations. Evidently, the S4–S5 linker, the covalent link between the voltage sensor and pore, plays a crucial role. The linker transfers the energy from the voltage sensor movement to the pore domain via an interaction with the S6 C-termini, which are pulled open during gating. In addition, other contact regions have been proposed. This review aims to provide (i) an in-depth comparison of the molecular mechanisms of electromechanical coupling in different Kv channels; (ii) insight as to how the voltage sensor and pore domain influence one another; and (iii) theoretical predictions on the movement of the cytosolic face of the Kv channels during

  15. Point kinetics calculations with fully coupled thermal fluids reactivity feedback

    SciTech Connect

    Zhang, H.; Zou, L.; Andrs, D.; Zhao, H.; Martineau, R.

    2013-07-01

    The point kinetics model has been widely used in the analysis of the transient behavior of a nuclear reactor. In the traditional nuclear reactor system safety analysis codes such as RELAP5, the reactivity feedback effects are calculated in a loosely coupled fashion through operator splitting approach. This paper discusses the point kinetics calculations with the fully coupled thermal fluids and fuel temperature feedback implemented into the RELAP-7 code currently being developed with the MOOSE framework. (authors)

  16. Regulation of heartbeat by G protein-coupled ion channels.

    PubMed

    Brown, A M

    1990-12-01

    The coupling of ion channels to receptors by G proteins is the subject of this American Physiological Society Walter B. Cannon Memorial "Physiology in Perspective" Lecture. This subject is particularly appropriate because it includes a molecular explanation of a homeostatic mechanism involving the autonomic nervous system and the latter subject preoccupied Dr. Cannon during most of his career. With the use of reconstitution methods, we and others have shown that heterotrimeric guanine nucleotide-binding (G) proteins couple receptors to ion channels by both membrane-delimited, direct pathways and cytoplasmic second messenger pathways. Furthermore, one set of receptors may be coupled to as many as three different sets of ion channels to form networks. Dual G protein pathways lead to the prediction of biphasic ion current responses in cell signaling, and this prediction was confirmed. In sinoatrial pacemaker cells, the pacemaking hyperpolarization-activated inward current (If) is directly regulated by the G proteins Gs and Go, and the two can act simultaneously. This could explain the classical observation that vagal inhibition of heart rate is greater during sympathetic stimulation. Because deactivation of the muscarinic response occurs much faster than the G protein alpha-subunit hydrolyzes guanosine 5'-triphosphate, we looked for accessory cellular factors. A surprising result was that the small monomeric ras G protein blocked the muscarinic pathway. The significance of this observation is unknown, but it appears that small and large G proteins may interact in ion channel signaling pathways.

  17. Regulation of heartbeat by G protein-coupled ion channels.

    PubMed

    Brown, A M

    1990-12-01

    The coupling of ion channels to receptors by G proteins is the subject of this American Physiological Society Walter B. Cannon Memorial "Physiology in Perspective" Lecture. This subject is particularly appropriate because it includes a molecular explanation of a homeostatic mechanism involving the autonomic nervous system and the latter subject preoccupied Dr. Cannon during most of his career. With the use of reconstitution methods, we and others have shown that heterotrimeric guanine nucleotide-binding (G) proteins couple receptors to ion channels by both membrane-delimited, direct pathways and cytoplasmic second messenger pathways. Furthermore, one set of receptors may be coupled to as many as three different sets of ion channels to form networks. Dual G protein pathways lead to the prediction of biphasic ion current responses in cell signaling, and this prediction was confirmed. In sinoatrial pacemaker cells, the pacemaking hyperpolarization-activated inward current (If) is directly regulated by the G proteins Gs and Go, and the two can act simultaneously. This could explain the classical observation that vagal inhibition of heart rate is greater during sympathetic stimulation. Because deactivation of the muscarinic response occurs much faster than the G protein alpha-subunit hydrolyzes guanosine 5'-triphosphate, we looked for accessory cellular factors. A surprising result was that the small monomeric ras G protein blocked the muscarinic pathway. The significance of this observation is unknown, but it appears that small and large G proteins may interact in ion channel signaling pathways. PMID:1701981

  18. Calculating electron beam properties in an ionized benzene channel

    SciTech Connect

    Goosman, D.R.

    1986-08-01

    We have derived formulas for the equilibrium-beam radius and other properties of an electron beam propagating in an ionized benzene channel. These formulas have been determined for two special cases. The first was for Gaussian spatial profiles for both the electron and laser beams. We obtained an analytical result for the equilibrium-beam radius, even though we included both KrF laser-induced and collisional sources of ionization of different sizes. The second case we considered was for laser and electron beams with flat radial profiles. These calculations were performed to determine if a laser-guided electron beam could reduce the focal size of an electron accelerator. We also developed a personal-computer spreadsheet program that receives 10 inputs and calculates 26 dependent quantities relating to the beam and ionization properties.

  19. Effects of weakly coupled channels on quasielastic barrier distributions

    SciTech Connect

    Piasecki, E.; Kisielinski, M.; Swiderski, L.; Keeley, N.; Rusek, K.; Strojek, I.; Gawlikowicz, W.; JastrzePbski, J.; Kordyasz, A.; Trzcinska, A.; Kliczewski, S.; Kowalczyk, M.; Khlebnikov, S.; Koshchiy, E.; Kozulin, E.; Loktev, T.; Smirnov, S.; Krogulski, T.; Mutterer, M.; Piasecki, K.

    2009-11-15

    Heavy-ion collisions often produce fusion barrier distributions with structures displaying a fingerprint of couplings to highly collective excitations. Similar distributions can be obtained from large-angle quasielastic scattering, although in this case, the role of the many weak direct-reaction channels is unclear. For {sup 20}Ne+{sup 90}Zr, we have observed the barrier structures expected for the highly deformed neon projectile; however, for {sup 20}Ne+{sup 92}Zr, we find significant extra absorption into a large number of noncollective inelastic channels. This leads to smearing of the barrier distribution and a consequent reduction in the ''resolving power'' of the quasielastic method.

  20. Flux, coupling, and selectivity in ionic channels of one conformation.

    PubMed Central

    Chen, D P; Eisenberg, R S

    1993-01-01

    Ions crossing biological membranes are described as a concentration of charge flowing through a selective open channel of one conformation and analyzed by a combination of Poisson and Nernst-Planck equations and boundary conditions, called the PNP theory for short. The ion fluxes in this theory interact much as ion fluxes interact in biological channels and mediated transporters, provided the theoretical channel contains permanent charge and has selectivity created by (electro-chemical) resistance at its ends. Interaction occurs because the flux of different ionic species depends on the same electric field. That electric field is a variable, changing with experimental conditions because the screening (i.e., shielding) of the permanent charge within the channel changes with experimental conditions. For example, the screening of charge and the shape of the electric field depend on the concentration of all ionic species on both sides of the channel. As experimental interventions vary the screening, the electric field varies, and thus the flux of each ionic species varies conjointly, and is, in that sense, coupled. Interdependence and interaction are the rule, independence is the exception, in this channel. PMID:7693003

  1. The continuum discretized coupled-channels method and its applications

    NASA Astrophysics Data System (ADS)

    Yahiro, Masanobu; Ogata, Kazuyuki; Matsumoto, Takuma; Minomo, Kosho

    2012-09-01

    This is a review of recent developments in the continuum discretized coupled-channels method (CDCC) and its applications to nuclear physics, cosmology and astrophysics, and nuclear engineering. The theoretical foundation of CDCC is shown, and a microscopic reaction theory for nucleus-nucleus scattering is constructed as an underlying theory of CDCC. CDCC is then extended to treat Coulomb breakup and four-body breakup. We also propose a new theory that makes CDCC applicable to inclusive reactions.

  2. Coupling Algorithms for Calculating Sensitivities of Population Balances

    SciTech Connect

    Man, P. L. W.; Kraft, M.; Norris, J. R.

    2008-09-01

    We introduce a new class of stochastic algorithms for calculating parametric derivatives of the solution of the space-homogeneous Smoluchowski's coagulation equation. Currently, it is very difficult to produce low variance estimates of these derivatives in reasonable amounts of computational time through the use of stochastic methods. These new algorithms consider a central difference estimator of the parametric derivative which is calculated by evaluating the coagulation equation at two different parameter values simultaneously, and causing variance reduction by maximising the covariance between these. The two different coupling strategies ('Single' and 'Double') have been compared to the case when there is no coupling ('Independent'). Both coupling algorithms converge and the Double coupling is the most 'efficient' algorithm. For the numerical example chosen we obtain a factor of about 100 in efficiency in the best case (small system evolution time and small parameter perturbation)

  3. Coupled-channels study of fine structure in the {alpha} decay of well deformed nuclei

    SciTech Connect

    Ni Dongdong; Ren Zhongzhou

    2011-06-15

    We formulate a theoretical model for the {alpha} decay of well-deformed even-even nuclei based on the coupled-channel Schroedinger equation. The {alpha}-decay half-lives and fine structures observed in {alpha} decay are well described by the five-channel microscopic calculations. Since the branching ratios to high-spin states are hard to understand in the traditional {alpha}-decay theories, this success could be important to interpret future observations of heavier nuclei. It is also found that the {alpha} transition to high-spin states is a powerful tool to probe the energy spectrum and deformation of daughter nuclei.

  4. Large eddy simulation of turbulent channel flow: ILLIAC 4 calculation

    NASA Technical Reports Server (NTRS)

    Kim, J.; Moin, P.

    1979-01-01

    The three-dimensional time dependent equations of motion were numerically integrated for fully-developed turbulent channel flow. A large scale flow field was obtained directly from the solution of these equations, and small scale field motions were simulated through an eddy viscosity model. The calculations were carried out on the ILLIAC 4 computer. The computed flow patterns show that the wall layer consists of coherent structures of low speed and high speed streaks alternating in the spanwise direction. These structures were absent in the regions away from the wall. Hot spots, small localized regions of very large turbulent shear stress, were frequently observed. The profiles of the pressure velocity-gradient correlations show a significant transfer of energy from the normal to the spanwise component of turbulent kinetic energy in the immediate neighborhood of the wall ('the splatting effect').

  5. Towards an optical potential for rare-earths through coupled channels

    NASA Astrophysics Data System (ADS)

    Nobre, G. P. A.; Dietrich, F. S.; Herman, M.; Palumbo, A.; Hoblit, S.; Brown, D.

    2014-11-01

    The coupled-channel theory is a natural way of treating nonelastic channels, in particular those arising from collective excitations, defined by nuclear deformations. Proper treatment of such excitations is often essential to the accurate description of reaction experimental data. Previous works have applied different models to specific nuclei with the purpose of determining angular-integrated cross sections. In this work, we present an extensive study of the effects of collective couplings and nuclear deformations on integrated cross sections as well as on angular distributions in a consistent manner for neutron-induced reactions on nuclei in the rare-earth region. This specific subset of the nuclide chart was chosen precisely because of a clear static deformation pattern. We analyze the convergence of the coupled-channel calculations regarding the number of states being explicitly coupled. Inspired by the work done by Dietrich et al., a model for deforming the spherical Koning-Delaroche optical potential as function of quadrupole and hexadecupole deformations is also proposed. We demonstrate that the obtained results of calculations for total, elastic and inelastic cross sections, as well as elastic and inelastic angular distributions correspond to a remarkably good agreement with experimental data for scattering energies above around a few MeV.

  6. Coupling of individual quantum emitters to channel plasmons

    PubMed Central

    Bermúdez-Ureña, Esteban; Gonzalez-Ballestero, Carlos; Geiselmann, Michael; Marty, Renaud; Radko, Ilya P.; Holmgaard, Tobias; Alaverdyan, Yury; Moreno, Esteban; García-Vidal, Francisco J.; Bozhevolnyi, Sergey I.; Quidant, Romain

    2015-01-01

    Efficient light-matter interaction lies at the heart of many emerging technologies that seek on-chip integration of solid-state photonic systems. Plasmonic waveguides, which guide the radiation in the form of strongly confined surface plasmon-polariton modes, represent a promising solution to manipulate single photons in coplanar architectures with unprecedented small footprints. Here we demonstrate coupling of the emission from a single quantum emitter to the channel plasmon polaritons supported by a V-groove plasmonic waveguide. Extensive theoretical simulations enable us to determine the position and orientation of the quantum emitter for optimum coupling. Concomitantly with these predictions, we demonstrate experimentally that 42% of a single nitrogen-vacancy centre emission efficiently couples into the supported modes of the V-groove. This work paves the way towards practical realization of efficient and long distance transfer of energy for integrated solid-state quantum systems. PMID:26249363

  7. Coupling of individual quantum emitters to channel plasmons

    NASA Astrophysics Data System (ADS)

    Bermúdez-Ureña, Esteban; Gonzalez-Ballestero, Carlos; Geiselmann, Michael; Marty, Renaud; Radko, Ilya P.; Holmgaard, Tobias; Alaverdyan, Yury; Moreno, Esteban; García-Vidal, Francisco J.; Bozhevolnyi, Sergey I.; Quidant, Romain

    2015-08-01

    Efficient light-matter interaction lies at the heart of many emerging technologies that seek on-chip integration of solid-state photonic systems. Plasmonic waveguides, which guide the radiation in the form of strongly confined surface plasmon-polariton modes, represent a promising solution to manipulate single photons in coplanar architectures with unprecedented small footprints. Here we demonstrate coupling of the emission from a single quantum emitter to the channel plasmon polaritons supported by a V-groove plasmonic waveguide. Extensive theoretical simulations enable us to determine the position and orientation of the quantum emitter for optimum coupling. Concomitantly with these predictions, we demonstrate experimentally that 42% of a single nitrogen-vacancy centre emission efficiently couples into the supported modes of the V-groove. This work paves the way towards practical realization of efficient and long distance transfer of energy for integrated solid-state quantum systems.

  8. Quench Protection for the MICE Cooling Channel Coupling Magnet

    SciTech Connect

    Guo, Xing Long; Xu, Feng Yu; Wang, Li; Green, Michael A.; Pan, Heng; Wu, Hong; Liu, X.K.; Jia, Lin Xiang; Amm, Kathleen

    2008-08-02

    This paper describes the passive quench protection system selected for the muon ionization cooling experiment (MICE) cooling channel coupling magnet. The MICE coupling magnet will employ two methods of quench protection simultaneously. The most important method of quench protection in the coupling magnet is the subdivision of the coil. Cold diodes and resistors are put across the subdivisions to reduce both the voltage to ground and the hot-spot temperature. The second method of quench protection is quench-back from the mandrel, which speeds up the spread of the normal region within the coils. Combining quench back with coil subdivision will reduce the hot spot temperature further. This paper explores the effect on the quench process of the number of coil sub-divisions, the quench propagation velocity within the magnet, and the shunt resistance.

  9. Coupled Neutron Transport and Thermal Fluids Calculations for the VHTR

    NASA Astrophysics Data System (ADS)

    Connolly, Kevin John; Huning, Alexander J.; Rahnema, Farzad; Garimella, Srinivas

    2014-06-01

    A new multiphysics method is presented for coupled neutronics and thermal fluids calculations in the VHTR. This new method combines the capabilities of two existing solvers: the COMET neutronics solver, and a thermal fluids module designed specifically for the gas-cooled reactor lattice design featured in this next-generation reactor. This paper provides the necessary background on the neutronics and thermal fluids aspects of the new solution strategy and explains the mode of coupling. A test problem is presented in order to prove the efficacy of the new coupled method. Results are given for a whole-core VHTR, including detailed temperature information at the fuel pin level, explicit power calculations of individual pins, and a thermal map of the bulk graphite and coolant temperatures throughout the core. Solutions are determined quickly when compared to other methods which offer the same level of detail and accuracy, and thus justify further research and development of this method in the near future.

  10. Towards a Coupled-channel Optical Potential for Rare-earth Nuclei

    NASA Astrophysics Data System (ADS)

    Nobre, G. P. A.; Palumbo, A.; Brown, D.; Herman, M.; Hoblit, S.; Dietrich, F. S.

    2014-04-01

    We present an outline of an extensive study of the effects of collective couplings and nuclear deformations on integrated cross sections as well as on angular distributions in a consistent manner for neutron-induced reactions on nuclei in the rare-earth region. This specific subset of the nuclide chart was chosen precisely because of a clear static deformation pattern. We analyze the convergence of the coupled-channel calculations regarding the number of states being explicitly coupled. A model for deforming the spherical Koning-Delaroche optical potential as function of quadrupole and hexadecupole deformations is also proposed, inspired by previous works. We demonstrate that the obtained results of calculations for total, elastic, inelastic, and capture cross sections, as well as elastic and inelastic angular distributions are in remarkably good agreement with experimental data for scattering energies around a few MeV.

  11. Expressions for Form Factors for Inelastic Scattering and Charge Exchange in Plane-Wave, Distorted-Wave, and Coupled-Channels Reaction Formalisms

    SciTech Connect

    Dietrich, F S

    2006-09-25

    This document is intended to facilitate calculation of inelastic scattering and charge-exchange cross sections in a variety of reaction models, including the plane-wave and distorted-wave approximations and the full coupled-channels treatments. Expressions are given for the coupling potentials between the relevant channels in both coordinate and momentum space. In particular, it is expected that the plane-wave calculations should be useful as a check on the correctness of coupled-channels calculations. The Fourier transform methods used to calculate the plane-wave approximation cross sections are also intended to be used to generate the transition potentials for coupled-channels codes, using a folding model with local effective interactions. Specific expressions are given for calculating transition densities for the folding model in the random phase approximation (RPA).

  12. Beam envelope calculations in general linear coupled lattices

    SciTech Connect

    Chung, Moses; Qin, Hong; Groening, Lars; Xiao, Chen; Davidson, Ronald C.

    2015-01-15

    The envelope equations and Twiss parameters (β and α) provide important bases for uncoupled linear beam dynamics. For sophisticated beam manipulations, however, coupling elements between two transverse planes are intentionally introduced. The recently developed generalized Courant-Snyder theory offers an effective way of describing the linear beam dynamics in such coupled systems with a remarkably similar mathematical structure to the original Courant-Snyder theory. In this work, we present numerical solutions to the symmetrized matrix envelope equation for β which removes the gauge freedom in the matrix envelope equation for w. Furthermore, we construct the transfer and beam matrices in terms of the generalized Twiss parameters, which enables calculation of the beam envelopes in arbitrary linear coupled systems.

  13. Beam envelope calculations in general linear coupled lattices

    NASA Astrophysics Data System (ADS)

    Chung, Moses; Qin, Hong; Groening, Lars; Davidson, Ronald C.; Xiao, Chen

    2015-01-01

    The envelope equations and Twiss parameters (β and α) provide important bases for uncoupled linear beam dynamics. For sophisticated beam manipulations, however, coupling elements between two transverse planes are intentionally introduced. The recently developed generalized Courant-Snyder theory offers an effective way of describing the linear beam dynamics in such coupled systems with a remarkably similar mathematical structure to the original Courant-Snyder theory. In this work, we present numerical solutions to the symmetrized matrix envelope equation for β which removes the gauge freedom in the matrix envelope equation for w. Furthermore, we construct the transfer and beam matrices in terms of the generalized Twiss parameters, which enables calculation of the beam envelopes in arbitrary linear coupled systems.

  14. Calculations on seismic coupling of underground explosions in salt

    SciTech Connect

    Heusinkveld, M.E.

    1981-01-20

    This report details the results of a theoretical study of seismic coupling and decoupling of underground explosions in a salt medium. A series of chemical and nuclear explosions was carried out years ago in salt domes for the Cowboy and the Dribble programs to provide experimental data on seismic coupling for both tamped explosions and explosions in cavities. The Cowboy program consisted of a series of chemical explosions, and the Dribble program consisted of the tamped nuclear Salmon event, the Sterling nuclear event in the Salmon cavity, and an associated site calibration effort. This report presents the results of extensive computer calculations, which are in satisfactory agreement with the experimental data. The calculations were extended to give general results on seismic coupling in salt. The measure of seismic coupling for most of this work was the residual reduced displacement potential (residual RDP). The decoupling associated with a shot in a cavity was expressed as the ratio of the resulting residual RDP to that of an equal-sized tamped shot.

  15. Coupled-channel effects for the bottomonium with realistic wave functions

    NASA Astrophysics Data System (ADS)

    Lu, Yu; Anwar, Muhammad Naeem; Zou, Bing-Song

    2016-08-01

    With Gaussian expansion method (GEM), realistic wave functions are used to calculate coupled-channel effects for the bottomonium under the framework of 3P0 model. The simplicity and accuracy of GEM are explained. We calculate the mass shifts, probabilities of the B meson continuum, S -D mixing angles, strong and dielectric decay widths. Our calculation shows that both S -D mixing and the B meson continuum can contribute to the suppression of the vector meson's dielectric decay width. We suggest more precise measurements on the radiative decays of ϒ (10580 ) and ϒ (11020 ) to distinguish these two effects. The above quantities are also calculated with simple harmonic oscillator (SHO) wave function approximation for comparison. The deviation between GEM and SHO indicates that it is essential to treat the wave functions accurately for near threshold states.

  16. The relationship between mean channel selection and the calculated coefficient of variation.

    PubMed

    Schuette, W H; Carducci, E; Marti, G E; Shackney, S E; Eden, M

    1985-09-01

    Calculated coefficients of variation (CV) taken from the quotient of the standard deviation (S.D.) and the mean value of measured distributions are often used as an indicator of system performance in linear flow cytometry (FCM). The ability of the calculated CV to estimate the true CV of the underlying experiment before grouping (channelization) is dependent on the relationship between the width of the data channels and the magnitude of the S.D. of the measured distribution. When the channel width is equal to the S.D. of a distribution, the calculated CV is approximately 20% larger than the true CV of an experiment. By the time the S.D. is only one-half of a channel width, the calculated CV is unreliable. When the distribution S.D. is narrower than a channel's width, small changes in the distribution mean value will cause large variations in the calculated CV. As the true CV decreases, the calculation must be made with higher mean channel values. This dependence of calculated CV accuracy upon the relationship between S.D. and channel width places limitations upon mean channel selection that must be considered when using CV calculations for evaluating system performance, especially when looking for small improvements during optical alignment procedures. When an instrument is assumed to have a constant CV and the data are collected linearly, it is possible to improve the CV estimation accuracy by placing distributions in higher-numbered channels.(ABSTRACT TRUNCATED AT 250 WORDS)

  17. Dynamical coupled-channels approach to hadronic and electromagnetic kaon-hyperon production on the proton

    SciTech Connect

    Julia-Diaz, B.; Saghai, B.; Tabakin, F.

    2006-05-15

    A dynamical coupled-channels formalism for processes {pi}N{yields}KY and {gamma}N{yields}KY is presented that provides a comprehensive investigation of recent data on the {gamma}p{yields}K{sup +}{lambda} reaction. The nonresonant interactions within the subspace KY+{pi}N are derived from effective Lagrangians, using a unitary transformation method. The calculations of photoproduction amplitudes are simplified by casting the coupled-channels equations into a form such that the empirical {gamma}N{yields}{pi}N amplitudes are input and only the parameters associated with the KY channel are determined by performing {chi}{sup 2} fits to all of the available data for {pi}{sup -}p{yields}K deg.{lambda},K deg.{sigma} deg., and {gamma}p{yields}K{sup +}{lambda}. Good agreement between our models and those data are obtained. In the fits to {pi}N{yields}KY channels, most of the parameters are constrained within {+-}20% of the values given by the Particle Data Group and/or quark model predictions, whereas for {gamma}p{yields}K{sup +}{lambda} parameters, ranges compatible with broken SU(6) x O(3) symmetry are imposed. The main reaction mechanisms in K{sup +}{lambda} photoproduction are singled out and issues related to newly suggested resonances S{sub 11},P{sub 13}, and D{sub 13} are studied. Results illustrating the importance of using a coupled-channels treatment are reported. Meson cloud effects on the {gamma}N{yields}N* transitions are also discussed.

  18. Strongly coupled turbulent gas-particle flows in vertical channels

    NASA Astrophysics Data System (ADS)

    Fox, Rodney O.; Capecelatro, Jesse; Desjardins, Olivier

    2015-11-01

    Eulerian-Lagrangian (EL) simulations of strongly coupled (high mass loading) gas-particle flows in vertical channels are performed with the purpose of exploring the fundamental physics of fully developed, wall-bounded multiphase turbulence. An adaptive spatial filter is developed that accurately decomposes the total granular energy of the particles into correlated and uncorrelated components at each location in the wall-normal direction of the flow. In this manner, Reynolds- and phase-averaged (PA) two-phase turbulence statistics up to second order are reported for both phases and for three values of the PA mean fluid velocity. As expected due to the high mass loading, in all cases the turbulence production due to mean drag dominates production due to mean shear. A multiphase LRR-IP Reynolds-stress turbulence model is developed to predict the turbulent flow statistics as a function of the wall-normal distance. Using a correlation for the vertical drift velocity developed from the EL data, the turbulence model predictions agree satisfactorily with all of one-point EL statistics for the vertical channel flows, as well as for the homogeneous cluster-induced turbulence (CIT) statistics reported previously. Funded by U.S. National Science Foundation (CBET-1437865).

  19. High-accuracy coupled cluster calculations of atomic properties

    SciTech Connect

    Borschevsky, A.; Yakobi, H.; Eliav, E.; Kaldor, U.

    2015-01-22

    The four-component Fock-space coupled cluster and intermediate Hamiltonian methods are implemented to evaluate atomic properties. The latter include the spectra of nobelium and lawrencium (elements 102 and 103) in the range 20000-30000 cm{sup −1}, the polarizabilities of elements 112-114 and 118, required for estimating their adsorption enthalpies on surfaces used to separate them in accelerators, and the nuclear quadrupole moments of some heavy atoms. The calculations on superheavy elements are supported by the very good agreement with experiment obtained for the lighter homologues.

  20. High-accuracy coupled cluster calculations of atomic properties

    NASA Astrophysics Data System (ADS)

    Borschevsky, A.; Yakobi, H.; Eliav, E.; Kaldor, U.

    2015-01-01

    The four-component Fock-space coupled cluster and intermediate Hamiltonian methods are implemented to evaluate atomic properties. The latter include the spectra of nobelium and lawrencium (elements 102 and 103) in the range 20000-30000 cm-1, the polarizabilities of elements 112-114 and 118, required for estimating their adsorption enthalpies on surfaces used to separate them in accelerators, and the nuclear quadrupole moments of some heavy atoms. The calculations on superheavy elements are supported by the very good agreement with experiment obtained for the lighter homologues.

  1. Coupled-Channels Approach for Dissipative Quantum Dynamics in Near-Barrier Collisions

    SciTech Connect

    Diaz-Torres, A.; Hinde, D. J.; Dasgupta, M.; Milburn, G. J.; Tostevin, J. A.

    2009-03-04

    A novel quantum dynamical model based on the dissipative quantum dynamics of open quantum systems is presented. It allows the treatment of both deep-inelastic processes and quantum tunneling (fusion) within a fully quantum mechanical coupled-channels approach. Model calculations show the transition from pure state (coherent) to mixed state (decoherent and dissipative) dynamics during a near-barrier nuclear collision. Energy dissipation, due to irreversible decay of giant-dipole excitations of the interacting nuclei, results in hindrance of quantum tunneling.

  2. Coupled cluster channels in the homogeneous electron gas

    SciTech Connect

    Shepherd, James J. E-mail: jamesjshepherd@gmail.com; Henderson, Thomas M.; Scuseria, Gustavo E.

    2014-03-28

    We discuss diagrammatic modifications to the coupled cluster doubles (CCD) equations, wherein different groups of terms out of rings, ladders, crossed-rings, and mosaics can be removed to form approximations to the coupled cluster method, of interest due to their similarity with various types of random phase approximations. The finite uniform electron gas (UEG) is benchmarked for 14- and 54-electron systems at the complete basis set limit over a wide density range and performance of different flavours of CCD is determined. These results confirm that rings generally overcorrelate and ladders generally undercorrelate; mosaics-only CCD yields a result surprisingly close to CCD. We use a recently developed numerical analysis [J. J. Shepherd and A. Grüneis, Phys. Rev. Lett. 110, 226401 (2013)] to study the behaviours of these methods in the thermodynamic limit. We determine that the mosaics, on forming the Brueckner one-body Hamiltonian, open a gap in the effective one-particle eigenvalues at the Fermi energy. Numerical evidence is presented which shows that methods based on this renormalisation have convergent energies in the thermodynamic limit including mosaic-only CCD, which is just a renormalised MP2. All other methods including only a single channel, namely, ladder-only CCD, ring-only CCD, and crossed-ring-only CCD, appear to yield divergent energies; incorporation of mosaic terms prevents this from happening.

  3. Efficient coupling of acoustic modes in microfluidic channel devices.

    PubMed

    Bora, M; Shusteff, M

    2015-08-01

    This work introduces a new numerical simulation approach to acoustic microfluidic chip design based on coupled-resonator theory. A simplified acoustofluidic device operating in the transverse elastic mode is investigated and optimized for maximal pressure standing wave amplitude. This design approach provides insights into the symmetry and frequency characteristics of acoustic chip resonances that cannot be obtained from analysis based on wave propagation arguments. The new approach reveals that optimal performance requires spatial symmetry-matching and frequency-matching of the full device's elastic resonance to the channel's acoustic resonance. Symmetry selection is demonstrated for a three terminal piezoelectric transducer actuation scheme showing suppression of opposite-symmetry and enhancement of same-symmetry acoustic modes. Excitation of ultrasonic waves exhibits the anti-crossing behaviour predicted by coupled mode theory with the acoustic mode splitting into two distinct branches. Increased efficiency of energy transfer from the transducer into the fluid, with its corresponding increase in pressure amplitude, suggests a potential path toward significant increases in acoustic separator performance. PMID:26118358

  4. Structural basis for the coupling between activation and inactivation gates in K+ channels

    PubMed Central

    Cuello, Luis G.; Jogini, Vishwanath; Cortes, D. Marien.; Pan, Albert C; Gagnon, Dominique G.; Dalmas, Olivier; Cordero-Morales, Julio F.; Chakrapani, Sudha; Roux, Benoit; Perozo, Eduardo

    2011-01-01

    The coupled interplay between activation and inactivation gating is a functional hallmark of K+ channels1,2. This coupling has been experimentally demonstrated from ion interaction effects3,4, cysteine accessibility1 and is associated with a well-defined boundary of energetically coupled residues2. The structure of KcsA in its fully open conformation, as well as four other partial openings, richly illustrates the structural basis of activation-inactivation gating5. Here, we have identified the mechanistic principles by which movements on the inner bundle gate trigger conformational changes at the selectivity filter, leading to the non-conductive C-type inactivated state. Analysis of a series of KcsA open structures suggests that as a consequence of the hinge bending and rotation of TM2, the aromatic ring of Phe103 tilts towards residues Thr74 and Thr75 in the pore helix as well as Ile100 in the neighboring subunit. This allows the network of hydrogen bonds among residues W67, E71, and D80 to destabilize the selectivity filter6,7, facilitating entry to its non-conductive conformation. Mutations at position 103, affect gating kinetics in a size-dependent way: small side chain substitutions F103A and F103C severely impair inactivation kinetics, while larger side chains (F103W) have more subtle effects. This suggests that the allosteric coupling between the inner helical bundle and the selectivity filter might rely on straightforward mechanical deformation propagated through a network of steric contacts. Average interactions calculated from molecular dynamics simulations show favourable open state interaction-energies between Phe103 and surrounding residues. Similar interactions were probed in the Shaker K-channel where inactivation was impaired in the mutant I470A. We propose that side chain rearrangements at position 103 mechanically couple activation and inactivation in KcsA and a variety of other K channels. PMID:20613845

  5. Parallelization strategy for large-scale vibronic coupling calculations.

    PubMed

    Rabidoux, Scott M; Eijkhout, Victor; Stanton, John F

    2014-12-26

    The vibronic coupling model of Köppel, Domcke, and Cederbaum is a powerful means to understand, predict, and analyze electronic spectra of molecules, especially those that exhibit phenomena that involve breakdown of the Born-Oppenheimer approximation. In this work, we describe a new parallel algorithm for carrying out such calculations. The algorithm is conceptually founded upon a "stencil" representation of the required computational steps, which motivates an efficient strategy for coarse-grained parallelization. The equations involved in the direct-CI type diagonalization of the model Hamiltonian are presented, the parallelization strategy is discussed in detail, and the method is illustrated by calculations involving direct-product basis sets with as many as 17 vibrational modes and 130 billion basis functions. PMID:25295469

  6. A ligand channel through the G protein coupled receptor opsin.

    PubMed

    Hildebrand, Peter W; Scheerer, Patrick; Park, Jung Hee; Choe, Hui-Woog; Piechnick, Ronny; Ernst, Oliver P; Hofmann, Klaus Peter; Heck, Martin

    2009-01-01

    The G protein coupled receptor rhodopsin contains a pocket within its seven-transmembrane helix (TM) structure, which bears the inactivating 11-cis-retinal bound by a protonated Schiff-base to Lys296 in TM7. Light-induced 11-cis-/all-trans-isomerization leads to the Schiff-base deprotonated active Meta II intermediate. With Meta II decay, the Schiff-base bond is hydrolyzed, all-trans-retinal is released from the pocket, and the apoprotein opsin reloaded with new 11-cis-retinal. The crystal structure of opsin in its active Ops* conformation provides the basis for computational modeling of retinal release and uptake. The ligand-free 7TM bundle of opsin opens into the hydrophobic membrane layer through openings A (between TM1 and 7), and B (between TM5 and 6), respectively. Using skeleton search and molecular docking, we find a continuous channel through the protein that connects these two openings and comprises in its central part the retinal binding pocket. The channel traverses the receptor over a distance of ca. 70 A and is between 11.6 and 3.2 A wide. Both openings are lined with aromatic residues, while the central part is highly polar. Four constrictions within the channel are so narrow that they must stretch to allow passage of the retinal beta-ionone-ring. Constrictions are at openings A and B, respectively, and at Trp265 and Lys296 within the retinal pocket. The lysine enforces a 90 degrees elbow-like kink in the channel which limits retinal passage. With a favorable Lys side chain conformation, 11-cis-retinal can take the turn, whereas passage of the all-trans isomer would require more global conformational changes. We discuss possible scenarios for the uptake of 11-cis- and release of all-trans-retinal. If the uptake gate of 11-cis-retinal is assigned to opening B, all-trans is likely to leave through the same gate. The unidirectional passage proposed previously requires uptake of 11-cis-retinal through A and release of photolyzed all-trans-retinal through

  7. Coupled cluster calculations on TiO2 nanoclusters

    SciTech Connect

    Berardo, Enrico; Hu, Hanshi; Kowalski, Karol; Zwijnenburg, Martijn A.

    2013-08-14

    The excitation energies of the four lowest-lying singlet excited states of the TiO2 Ti2O4 and Ti3O6 clusters are calculated by a variety of different Equation-of-Motion Coupled Cluster (EOM-CC) approaches in order to obtain benchmark values for the optical excitations of titanium dioxide clusters. More specifically we investigate what is the effect of the inclusion of triple excitations "triples" in the (EOM-)CC scheme on the calculated excited states of those clusters. While for the monomer and dimer the inclusion of triples causes only a rigid shift in the excitation energies, in the case of the trimer the crossing of the interested states is observed. Coupled cluster approaches where triples are treated perturbatively were found to offer no advantage over EOM-CCSD, whereas the active-space methods (EOM-CCSDt(II/I)) proved to yield results very close to the full EOM-CCSDT, but at a much lower computational cost.

  8. Two-center convergent close-coupling calculations for positron-lithium collisions

    SciTech Connect

    Lugovskoy, A. V.; Kadyrov, A. S.; Bray, I.; Stelbovics, A. T.

    2010-12-15

    We report on two-center convergent close-coupling calculations of positron-lithium collisions. The target is treated as one active electron interacting with an inert ion core. The positronium formation channels are taken into account explicitly utilizing both negative- and positive-energy Laguerre-based states. A large number of channels and high partial waves are used to ensure the convergence of the cross sections. We find the Ramsauer-Townsend minimum in total and elastic cross sections at an impact energy E of about 0.0016 eV. As found previously for H and He, the contributions to the breakup cross section from both the Li and the Ps centers become the same as the threshold is approached.

  9. Theoretical calculations of hyperfine coupling constants for muoniated butyl radicals.

    PubMed

    Chen, Ya Kun; Fleming, Donald G; Wang, Yan Alexander

    2011-04-01

    The hyperfine coupling constants (HFCCs) of all the butyl radicals that can be produced by muonium (Mu) addition to butene isomers (1- and 2-butene and isobutene) have been calculated, to compare with the experimental results for the muon and proton HFFCs for these radicals reported in paper II (Fleming, D. G.; et al. J. Phys. Chem. A 2011, 10.1021/jp109676b) that follows. The equilibrium geometries and HFCCs of these muoniated butyl radicals as well as their unsubstituted isotopomers were treated at both the spin-unrestricted MP2/EPR-III and B3LYP/EPR-III levels of theory. Comparisons with calculations carried out for the EPR-II basis set have also been made. All calculations were carried out in vacuo at 0 K only. A C-Mu bond elongation scheme that lengthens the equilibrium C-H bond by a factor of 1.076, on the basis of recent quantum calculations of the muon HFCCs of the ethyl radical, has been exploited to determine the vibrationally corrected muon HFCCs. The sensitivity of the results to small variations around this scale factor was also investigated. The computational methodology employed was "benchmarked" in comparisons with the ethyl radical, both with higher level calculations and with experiment. For the β-HFCCs of interest, compared to B3LYP, the MP2 calculations agree better with higher level theories and with experiment in the case of the eclipsed C-Mu bond and are generally deemed to be more reliable in predicting the equilibrium conformations and muon HFCCs near 0 K, in the absence of environmental effects. In some cases though, the experimental results in paper II demonstrate that environmental effects enhance the muon HFCC in the solid phase, where much better agreement with the experimental muon HFCCs near 0 K is found from B3LYP than from MP2. This seemingly better level of agreement is probably fortuitous, due to error cancellations in the DFT calculations, which appear to mimic these environmental effects. For the staggered proton HFCCs of the

  10. Quench Protection for the MICE Cooling Channel CouplingMagnet

    SciTech Connect

    Green, M.A.; Wang, L.; Guo, X.L.

    2007-11-20

    The MICE coupling coil is fabricated from Nb-Ti, which hashigh quench propagation velocities within the coil in all directionscompared to coils fabricated with other superconductors such as niobiumtin. The time for the MICE coupling coil to become fully normal throughnormal region propagation in the coil is shorter than the time needed fora safe quench (as defined by a hot-spot temperature that is less than 300K). A MICE coupling coil quench was simulated using a code written at theInstitute of Cryogenics and Superconductive Technology (ICST) at theHarbin Institute of Technology (HIT). This code simulates quench backfrom the mandrel as well as normal region propagation within the coil.The simulations included sub-division of the coil. Each sub-division hasa back to back diodes and resistor across the coil. Current flows in theresistor when there is enough voltage across the coil to cause current toflow through the diodes in the forward direction. The effects of thenumber of coil sub-divisions and the value of the resistor across thesub-division on the quench were calculated with and without quench back.Sub-division of the coupling coil reduces the peak voltage to ground, thelayer-to-layer voltage and the magnet hot-spot temperature. Quench backreduces the magnet hot-spot temperature, but the peak voltage to groundand layer-to-layer voltage are increased, because the magnet quenchesfaster. The resistance across the coil sub-division affects both thehot-spot temperature and the peak voltage to ground.

  11. Radial Moment Calculations of Coupled Electron-Photon Beams

    SciTech Connect

    FRANKE,BRIAN C.; LARSEN,EDWARD W.

    2000-07-19

    The authors consider the steady-state transport of normally incident pencil beams of radiation in slabs of material. A method has been developed for determining the exact radial moments of 3-D beams of radiation as a function of depth into the slab, by solving systems of 1-D transport equations. They implement these radial moment equations in the ONEBFP discrete ordinates code and simulate energy-dependent, coupled electron-photon beams using CEPXS-generated cross sections. Modified P{sub N} synthetic acceleration is employed to speed up the iterative convergence of the 1-D charged particle calculations. For high-energy photon beams, a hybrid Monte Carlo/discrete ordinates method is examined. They demonstrate the efficiency of the calculations and make comparisons with 3-D Monte Carlo calculations. Thus, by solving 1-D transport equations, they obtain realistic multidimensional information concerning the broadening of electron-photon beams. This information is relevant to fields such as industrial radiography, medical imaging, radiation oncology, particle accelerators, and lasers.

  12. A microscopic, coupled-channel theory of pion scattering

    SciTech Connect

    Kagarlis, M.A.; Johnson, M.B.; Fortune, H.T.

    1995-05-15

    The authors develop a new and comprehensive coordinate-space theory of pion-nucleus scattering to facilitate disentangling the conventional aspects of pion scattering from the non-conventional ones relevant to issues of hadron dynamics. They work in coordinate space in order to both unify and extend the relatively extensive and successful analyses of exclusive pion-nucleus reactions previously made within a similar framework. They construct the optical potential microscopically in shell-model framework by summing particle-hole pair configurations, leading naturally to a coupled-channel formulation. The theory includes a complete treatment of all spin-isospin components of the pion-nucleon scattering amplitude, and Fermi averaging is done explicitly. The authors present numerical results showing the significance of Fermi motion and spin dependence on charge-exchange angular distributions: Single and double spin flip are shown to play dominant and generally unappreciated roles in charge-exchange reactions, and corrections for Fermi motion are shown to be needed in order to quantitatively separate medium effects from conventional multiple scattering. 72 refs., 11 figs.

  13. RELATIVISTIC R-MATRIX CLOSE-COUPLING CALCULATIONS FOR PHOTOIONIZATION OF Si-LIKE Ni XV

    SciTech Connect

    Singh, Jagjit; Jha, A. K. S.; Mohan, Man

    2010-02-01

    We present relativistic close-coupling photoionization calculations of Ni XV using the Breit-Pauli R-matrix method to obtain photoionization cross section of Ni XV from the ground state 3s {sup 2}3p {sup 2}({sup 3} P {sub 0}) and the lowest four 3s {sup 2}3p {sup 2} ({sup 3} P {sub 1,2}, {sup 1} D {sub 2}, {sup 1} S {sub 0}) excited states. A multiconfiguration eigenfunction expansion of the core Ni XVI is employed with configurations 3s {sup 2}3p, 3s3p {sup 2}, 3s {sup 2}3d, 3p {sup 3}, 3s3p3d, 3p {sup 2}3d, 3s3d {sup 2}, 3p3d {sup 2}. We have included the lowest 40 target level states of Ni XVI in the photoionization calculations of Ni XV. Cross sections are determined by the Rydberg series of autoionizing resonances converging to several ionic states of Ni XVI. In our calculations, we have taken into account all the important physical effects such as exchange, channel coupling, and short-range correlation. Further, relativistic effects are incorporated by including mass correction, Darwin term, and spin-orbit interaction terms. The present calculations using the lowest 40 target levels of Ni XVI are presented for the first time and can be useful for modeling the ionization balance of Ni XV in laboratory and astrophysical plasmas.

  14. 3V: cavity, channel and cleft volume calculator and extractor

    PubMed Central

    Voss, Neil R.; Gerstein, Mark

    2010-01-01

    As larger macromolecular structures become available, there is a growing need to understand their ‘internal’ volumes—such as deep clefts, channels and cavities—as these often play critical roles in their function. The 3V web server can automatically extract and comprehensively analyze all the internal volumes from input RNA and protein structures. It rapidly finds internal volumes by taking the difference between two rolling-probe solvent-excluded surfaces, one with as large as possible a probe radius and the other with a solvent radius (typically 1.5 Å for water). The outputs are volumetric representations, both as images and downloadable files, which can be used for further analysis. The 3V server and source code are available from http://3vee.molmovdb.org. PMID:20478824

  15. Fade margin calculation for channels impaired by Rician fading

    NASA Technical Reports Server (NTRS)

    Davarian, F.

    1985-01-01

    Excess path loss due to multipath severely restricts the performance of power limited mobile networks such as those using satellite-aided links. To reduce multipath related losses, the higher elevation angle of the spacecraft can be exploited by utilizing mobile antennas which reduce the strength of the multipath reflections in favor of the line-of-sight signal. The presence of a strong and stable path in a fading link will change the envelope statistics of the received waveform from Rayleigh to a more favorable Rician distribution. It is determined that the excess path loss, or fade margin, of a Rician channel when coherent detection of binary phase shift keying (BPSK) or quaternary phase shift keying (QPSK) signals is considered. The results are presented parametrically such that they can be applied to a wide range of propagation characteristics from heavy fading to nonfading situations. Furthermore, similar results are also given for the case where only limited coverage is provided.

  16. High accuracy modeling for advanced nuclear reactor core designs using Monte Carlo based coupled calculations

    NASA Astrophysics Data System (ADS)

    Espel, Federico Puente

    The main objective of this PhD research is to develop a high accuracy modeling tool using a Monte Carlo based coupled system. The presented research comprises the development of models to include the thermal-hydraulic feedback to the Monte Carlo method and speed-up mechanisms to accelerate the Monte Carlo criticality calculation. Presently, deterministic codes based on the diffusion approximation of the Boltzmann transport equation, coupled with channel-based (or sub-channel based) thermal-hydraulic codes, carry out the three-dimensional (3-D) reactor core calculations of the Light Water Reactors (LWRs). These deterministic codes utilize nuclear homogenized data (normally over large spatial zones, consisting of fuel assembly or parts of fuel assembly, and in the best case, over small spatial zones, consisting of pin cell), which is functionalized in terms of thermal-hydraulic feedback parameters (in the form of off-line pre-generated cross-section libraries). High accuracy modeling is required for advanced nuclear reactor core designs that present increased geometry complexity and material heterogeneity. Such high-fidelity methods take advantage of the recent progress in computation technology and coupled neutron transport solutions with thermal-hydraulic feedback models on pin or even on sub-pin level (in terms of spatial scale). The continuous energy Monte Carlo method is well suited for solving such core environments with the detailed representation of the complicated 3-D problem. The major advantages of the Monte Carlo method over the deterministic methods are the continuous energy treatment and the exact 3-D geometry modeling. However, the Monte Carlo method involves vast computational time. The interest in Monte Carlo methods has increased thanks to the improvements of the capabilities of high performance computers. Coupled Monte-Carlo calculations can serve as reference solutions for verifying high-fidelity coupled deterministic neutron transport methods

  17. Static and dynamic polarizabilities of Na{sup -} within a variationally stable coupled-channel hyperspherical method

    SciTech Connect

    Masili, Mauro; Groote, J.J. de

    2004-11-01

    Using a model potential representation combined with a variationally stable method, we present a precise calculation of the electric dipole polarizabilities of the sodium negative ion (Na{sup -}). The effective two-electron eigensolutions for Na{sup -} are obtained from a hyperspherical coupled-channel calculation. This approach allows efficient error control and insight into the system's properties through one-dimensional potential curves. Our result of 1018.3 a.u. for the static dipole polarizability is in agreement with previous calculations and supports our results for the dynamic polarizability, which has scarcely been investigated hitherto.

  18. Coupled-cluster based basis sets for valence correlation calculations

    NASA Astrophysics Data System (ADS)

    Claudino, Daniel; Gargano, Ricardo; Bartlett, Rodney J.

    2016-03-01

    Novel basis sets are generated that target the description of valence correlation in atoms H through Ar. The new contraction coefficients are obtained according to the Atomic Natural Orbital (ANO) procedure from CCSD(T) (coupled-cluster singles and doubles with perturbative triples correction) density matrices starting from the primitive functions of Dunning et al. [J. Chem. Phys. 90, 1007 (1989); ibid. 98, 1358 (1993); ibid. 100, 2975 (1993)] (correlation consistent polarized valence X-tuple zeta, cc-pVXZ). The exponents of the primitive Gaussian functions are subject to uniform scaling in order to ensure satisfaction of the virial theorem for the corresponding atoms. These new sets, named ANO-VT-XZ (Atomic Natural Orbital Virial Theorem X-tuple Zeta), have the same number of contracted functions as their cc-pVXZ counterparts in each subshell. The performance of these basis sets is assessed by the evaluation of the contraction errors in four distinct computations: correlation energies in atoms, probing the density in different regions of space via (-3 ≤ n ≤ 3) in atoms, correlation energies in diatomic molecules, and the quality of fitting potential energy curves as measured by spectroscopic constants. All energy calculations with ANO-VT-QZ have contraction errors within "chemical accuracy" of 1 kcal/mol, which is not true for cc-pVQZ, suggesting some improvement compared to the correlation consistent series of Dunning and co-workers.

  19. Coupled-cluster based basis sets for valence correlation calculations.

    PubMed

    Claudino, Daniel; Gargano, Ricardo; Bartlett, Rodney J

    2016-03-14

    Novel basis sets are generated that target the description of valence correlation in atoms H through Ar. The new contraction coefficients are obtained according to the Atomic Natural Orbital (ANO) procedure from CCSD(T) (coupled-cluster singles and doubles with perturbative triples correction) density matrices starting from the primitive functions of Dunning et al. [J. Chem. Phys. 90, 1007 (1989); ibid. 98, 1358 (1993); ibid. 100, 2975 (1993)] (correlation consistent polarized valence X-tuple zeta, cc-pVXZ). The exponents of the primitive Gaussian functions are subject to uniform scaling in order to ensure satisfaction of the virial theorem for the corresponding atoms. These new sets, named ANO-VT-XZ (Atomic Natural Orbital Virial Theorem X-tuple Zeta), have the same number of contracted functions as their cc-pVXZ counterparts in each subshell. The performance of these basis sets is assessed by the evaluation of the contraction errors in four distinct computations: correlation energies in atoms, probing the density in different regions of space via ⟨r(n)⟩ (-3 ≤ n ≤ 3) in atoms, correlation energies in diatomic molecules, and the quality of fitting potential energy curves as measured by spectroscopic constants. All energy calculations with ANO-VT-QZ have contraction errors within "chemical accuracy" of 1 kcal/mol, which is not true for cc-pVQZ, suggesting some improvement compared to the correlation consistent series of Dunning and co-workers.

  20. Quantum Monte Carlo calculations of magnetic couplings in cuprates

    NASA Astrophysics Data System (ADS)

    Foyevtsova, Kateryna; Krogel, Jaron; Kim, Jeongnim; Reboredo, Fernando

    2014-03-01

    Spin excitations are generally believed to play a fundamental role in the mechanism of high temperature superconductivity in cuprates. However, accurate description of the cuprates' magnetic properties and, in particular, calculation of spin exchange couplings have been a long-standing challenge to the electronic structure theory. While the quantum-mechanically more rigorous cluster methods suffer from finite-size effects, the density functional theory approach, on the other hand, is ambiguous due to a rich variety of approximations to the exchange-correlation functional available which often give very different numbers for the spin exchange constants. For example, in some cuprates the theoretically predicted values of the nearest-neighbor superexchange range from 1 eV (local density approximation) to 0.05 eV (periodic unrestricted Hartree Fock) [C. de Graaf et al, PRB 63 014404 (2000)]. We compute spin exchange constants with the fixed-node diffusion Monte Carlo method (FN-DMC). In one-dimensional cuprates, we find that the FN-DMC computed nearest-neighbor spin superexchange is in an excellent agreement with experiment. This both demonstrates that FN-DMC is capable of describing properly the magnetism of strongly correlated oxides as well as positions this technique as the method of choice for theoretical parameterization of spin models. Research supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division.

  1. Coupled-cluster based basis sets for valence correlation calculations.

    PubMed

    Claudino, Daniel; Gargano, Ricardo; Bartlett, Rodney J

    2016-03-14

    Novel basis sets are generated that target the description of valence correlation in atoms H through Ar. The new contraction coefficients are obtained according to the Atomic Natural Orbital (ANO) procedure from CCSD(T) (coupled-cluster singles and doubles with perturbative triples correction) density matrices starting from the primitive functions of Dunning et al. [J. Chem. Phys. 90, 1007 (1989); ibid. 98, 1358 (1993); ibid. 100, 2975 (1993)] (correlation consistent polarized valence X-tuple zeta, cc-pVXZ). The exponents of the primitive Gaussian functions are subject to uniform scaling in order to ensure satisfaction of the virial theorem for the corresponding atoms. These new sets, named ANO-VT-XZ (Atomic Natural Orbital Virial Theorem X-tuple Zeta), have the same number of contracted functions as their cc-pVXZ counterparts in each subshell. The performance of these basis sets is assessed by the evaluation of the contraction errors in four distinct computations: correlation energies in atoms, probing the density in different regions of space via ⟨r(n)⟩ (-3 ≤ n ≤ 3) in atoms, correlation energies in diatomic molecules, and the quality of fitting potential energy curves as measured by spectroscopic constants. All energy calculations with ANO-VT-QZ have contraction errors within "chemical accuracy" of 1 kcal/mol, which is not true for cc-pVQZ, suggesting some improvement compared to the correlation consistent series of Dunning and co-workers. PMID:26979680

  2. Fully Coupled Channel Approach to Doubly Strange s-Shell Hypernuclei

    SciTech Connect

    Nemura, H.; Shinmura, S.; Akaishi, Y.; Myint, Khin Swe

    2005-05-27

    We describe ab initio calculations of doubly strange, S=-2, s-shell hypernuclei ({sub {lambda}}{sub {lambda}}{sup 4}H, {sub {lambda}}{sub {lambda}}{sup 5}H, {sub {lambda}}{sub {lambda}}{sup 5}He, and {sub {lambda}}{sub {lambda}}{sup 6}He) as a first attempt to explore the few-body problem of the full-coupled channel scheme for these systems. The wave function includes {lambda}{lambda}, {lambda}{sigma}, N{xi}, and {sigma}{sigma} channels. Minnesota NN, D2{sup '} YN, and simulated YY potentials based on the Nijmegen hard-core model are used. Bound-state solutions of these systems are obtained. We find that a set of phenomenological B{sub 8}B{sub 8} interactions among the octet baryons in S=0,-1, and -2 sectors, which is consistent with all of the available experimental binding energies of S=0,-1, and -2 s-shell (hyper)nuclei, can predict a particle stable bound state of {sub {lambda}}{sub {lambda}}{sup 4}H. For {sub {lambda}}{sub {lambda}}{sup 5}H and {sub {lambda}}{sub {lambda}}{sup 5}He, {lambda}N-{sigma}N and {xi}N-{lambda}{sigma} potentials significantly affect the net {lambda}{lambda}-N{xi} coupling, and a large {xi} probability is obtained even for a weaker {lambda}{lambda}-N{xi} potential.

  3. TRPV1 channels are functionally coupled with BK(mSlo1) channels in rat dorsal root ganglion (DRG) neurons.

    PubMed

    Wu, Ying; Liu, Yongfeng; Hou, Panpan; Yan, Zonghe; Kong, Wenjuan; Liu, Beiying; Li, Xia; Yao, Jing; Zhang, Yuexuan; Qin, Feng; Ding, Jiuping

    2013-01-01

    The transient receptor potential vanilloid receptor 1 (TRPV1) channel is a nonselective cation channel activated by a variety of exogenous and endogenous physical and chemical stimuli, such as temperature (≥42 °C), capsaicin, a pungent compound in hot chili peppers, and allyl isothiocyanate. Large-conductance calcium- and voltage-activated potassium (BK) channels regulate the electric activities and neurotransmitter releases in excitable cells, responding to changes in membrane potentials and elevation of cytosolic calcium ions (Ca(2+)). However, it is unknown whether the TRPV1 channels are coupled with the BK channels. Using patch-clamp recording combined with an infrared laser device, we found that BK channels could be activated at 0 mV by a Ca(2+) influx through TRPV1 channels not the intracellular calcium stores in submilliseconds. The local calcium concentration around BK is estimated over 10 μM. The crosstalk could be affected by 10 mM BAPTA, whereas 5 mM EGTA was ineffectual. Fluorescence and co-immunoprecipitation experiments also showed that BK and TRPV1 were able to form a TRPV1-BK complex. Furthermore, we demonstrated that the TRPV1-BK coupling also occurs in dosal root ganglion (DRG) cells, which plays a critical physiological role in regulating the "pain" signal transduction pathway in the peripheral nervous system. PMID:24147119

  4. Solving non-Markovian open quantum systems with multi-channel reservoir coupling

    SciTech Connect

    Broadbent, Curtis J.; Jing, Jun; Yu, Ting; Eberly, Joseph H.

    2012-08-15

    We extend the non-Markovian quantum state diffusion (QSD) equation to open quantum systems which exhibit multi-channel coupling to a harmonic oscillator reservoir. Open quantum systems which have multi-channel reservoir coupling are those in which canonical transformation of reservoir modes cannot reduce the number of reservoir operators appearing in the interaction Hamiltonian to one. We show that the non-Markovian QSD equation for multi-channel reservoir coupling can, in some cases, lead to an exact master equation which we derive. We then derive the exact master equation for the three-level system in a vee-type configuration which has multi-channel reservoir coupling and give the analytical solution. Finally, we examine the evolution of the three-level vee-type system with generalized Ornstein-Uhlenbeck reservoir correlations numerically. - Highlights: Black-Right-Pointing-Pointer The concept of multi-channel vs. single-channel reservoir coupling is rigorously defined. Black-Right-Pointing-Pointer The non-Markovian quantum state diffusion equation for arbitrary multi-channel reservoir coupling is derived. Black-Right-Pointing-Pointer An exact time-local master equation is derived under certain conditions. Black-Right-Pointing-Pointer The analytical solution to the three-level system in a vee-type configuration is found. Black-Right-Pointing-Pointer The evolution of the three-level system under generalized Ornstein-Uhlenbeck noise is plotted for many parameter regimes.

  5. Measurements and coupled reaction channels analysis of one- and two-proton transfer reactions for the 28Si + 90,94Zr systems

    NASA Astrophysics Data System (ADS)

    Kalkal, Sunil; Mandal, S.; Jhingan, A.; Gehlot, J.; Sugathan, P.; Golda, K. S.; Madhavan, N.; Garg, Ritika; Goyal, Savi; Mohanto, Gayatri; Sandal, Rohit; Chakraborty, Santosh; Verma, Shashi; Behera, Bivash; Eleonora, G.; Wollersheim, H. J.; Singh, R.

    2012-03-01

    Measurements of angular distributions for one- and two-proton stripping reactions for 28Si + 90,94Zr systems were performed at 120 MeV. The experiment was carried out with the 28Si beam at Inter University Accelerator Center, New Delhi. The theoretical calculations were performed using the quantum mechanical coupled reaction channels code fresco. The distorted wave Born approximation calculations reproduced the experimental angular distributions for the one-proton transfer channel for both the systems reasonably well but failed for the two-proton transfer channel. Coupled channels calculations including various intermediate states (involving target and projectile inelastic excitations before and/or after transfer) along with the sequential transfer were able to reproduce the two-proton transfer angular distributions for both the systems reasonably well. It seems that at an energy above the Coulomb barrier, there is significant contribution of the indirect multistep and sequential transfer to the two-proton stripping reaction.

  6. Dean flow-coupled inertial focusing in curved channels.

    PubMed

    Ramachandraiah, Harisha; Ardabili, Sahar; Faridi, Asim M; Gantelius, Jesper; Kowalewski, Jacob M; Mårtensson, Gustaf; Russom, Aman

    2014-05-01

    Passive particle focusing based on inertial microfluidics was recently introduced as a high-throughput alternative to active focusing methods that require an external force field to manipulate particles. In inertial microfluidics, dominant inertial forces cause particles to move across streamlines and occupy equilibrium positions along the faces of walls in flows through straight micro channels. In this study, we systematically analyzed the addition of secondary Dean forces by introducing curvature and show how randomly distributed particles entering a simple u-shaped curved channel are focused to a fixed lateral position exiting the curvature. We found the lateral particle focusing position to be fixed and largely independent of radius of curvature and whether particles entering the curvature are pre-focused (at equilibrium) or randomly distributed. Unlike focusing in straight channels, where focusing typically is limited to channel cross-sections in the range of particle size to create single focusing point, we report here particle focusing in a large cross-section area (channel aspect ratio 1:10). Furthermore, we describe a simple u-shaped curved channel, with single inlet and four outlets, for filtration applications. We demonstrate continuous focusing and filtration of 10 μm particles (with >90% filtration efficiency) from a suspension mixture at throughputs several orders of magnitude higher than flow through straight channels (volume flow rate of 4.25 ml/min). Finally, as an example of high throughput cell processing application, white blood cells were continuously processed with a filtration efficiency of 78% with maintained high viability. We expect the study will aid in the fundamental understanding of flow through curved channels and open the door for the development of a whole set of bio-analytical applications.

  7. LETTER TO THE EDITOR: Time-dependent close-coupling calculations for the double photoionization of He and H2

    NASA Astrophysics Data System (ADS)

    Colgan, J.; Pindzola, M. S.; Robicheaux, F.

    2004-12-01

    Photoionization cross sections for both atomic helium and molecular hydrogen are calculated using a time-dependent close-coupling method. The total electronic wavefunction for the two-electron system is expanded in six dimensions, where four dimensions are represented on a radial and angular lattice and a coupled channels expansion is used to represent the other two dimensions. Double photoionization cross sections are obtained for both He and H2 for a range of photon energies above the complete fragmentation threshold. Comparisons are made with absolute experimental measurements.

  8. Exact and truncated Coriolis coupling calculations for the S(1D)+HD reaction employing the ground adiabatic electronic state.

    PubMed

    Yang, Huan; Han, Keli; Schatz, George C; Smith, Sean C; Hankel, Marlies

    2010-10-21

    We present exact quantum differential cross sections and exact and estimated integral cross sections and branching ratios for the title reaction. We employ a time-dependent wavepacket method as implemented in the DIFFREALWAVE code including all Coriolis couplings and also an adapted DIFFREALWAVE code where the helicity quantum number and with this the Coriolis couplings have been truncated. Our exact differential cross sections at 0.453 eV total energy, one of the experimental energies, show good agreement with the experimental results for one of the product channels. While the truncated calculation present a significant reduction in the computational effort needed they overestimate the exact integral cross sections.

  9. Proton-Nucleus Total Cross Sections in Coupled-Channel Approach

    NASA Technical Reports Server (NTRS)

    Tripathi, R. K.; Wilson, John W.; Cucinotta, Francis A.

    2000-01-01

    Recently, nucleon-nucleon (N-N) cross sections in the medium have been extracted directly from experiment. The in-medium N-N cross sections form the basic ingredients of several heavy-ion scattering approaches including the coupled-channel approach developed at the Langley Research Center. In the present study the ratio of the real to the imaginary part of the two-body scattering amplitude in the medium was investigated. These ratios are used in combination with the in-medium N-N cross sections to calculate total proton-nucleus cross sections. The agreement is excellent with the available experimental data. These cross sections are needed for the radiation risk assessment of space missions.

  10. Multiscale modelling of coupled Ca2+ channels using coloured stochastic Petri nets.

    PubMed

    Liu, Fei; Heiner, Monika

    2013-08-01

    Stochastic modelling of coupled Ca2+ channels is a challenge, especially when the coupling of the channels, as determined by their spatial arrangement relative to each other, has to be considered at multiple spatial scales. In this study, the authors address this problem using coloured stochastic Petri nets (SPNc) as high-level description to generate continuous-time Markov chains. The authors develop several models with increasing complexity. They first apply SPNc to model single clusters of coupled Ca2+ channels arranged in a regular or irregular lattice, where they describe how to represent the geometrical arrangement of Ca2+ channels relative to each other using colours. They then apply this modelling idea to construct more complex models by modelling spatially arranged clusters of channels. The authors' models can be easily reproduced and adapted to different scenarios.

  11. Resonant coupling of Rayleigh waves through a narrow fluid channel causing extraordinary low acoustic transmission.

    PubMed

    Garcia-Chocano, Victor M; Nagaraj; Lòpez-Rios, Tomàs; Gumen, Lyudmila; Sànchez-Dehesa, Josè; Krokhin, Arkadii

    2012-10-01

    Coupling of Rayleigh waves propagating along two metal surfaces separated by a narrow fluid channel is predicted and experimentally observed. Although the coupling through a fluid (water) is weak, a strong synchronization in propagation of Rayleigh waves even for the metals with sufficiently high elastic contrast (brass and aluminum) is observed. Dispersion equation for two polarizations of the coupled Rayleigh waves is derived and experimentally confirmed. Excitation of coupled Rayleigh waves in a channel of finite length leads to anomalously low transmission of acoustic energy at discrete set of resonant frequencies. This effect may find useful applications in the design of acoustic metamaterial screens and reflectors.

  12. Dynamical coupled-channels study of meson production reactions from EBAC@Jlab

    SciTech Connect

    Hiroyuki Kamano

    2011-10-01

    We present the current status of a combined and simultaneous analysis of meson production reactions based on a dynamical coupled-channels (DCC) model, which is conducted at Excited Baryon Analysis Center (EBAC) of Jefferson Lab.

  13. Non-empirical calculations of NMR indirect carbon-carbon coupling constants. Part 6: propellanes.

    PubMed

    Krivdin, Leonid B

    2004-01-01

    A full set of carbon-carbon coupling constants have been calculated at the SOPPA level in the series of six most representative propellanes. Special attention was focused on spin-spin couplings involving both bridgehead carbons, and these data were rationalized in terms of the multipath coupling mechanism and hybridization effects. Many unknown couplings in the propellane frameworks were predicted with high reliability.

  14. Channel-Coupling Contribution to the Widths of Decay Nuclear States and to Their Wave Functions

    SciTech Connect

    Kadmensky, S.G.

    2004-12-01

    By using the formalism of the quantum theory of fission, the amplitudes of partial decay widths and the asymptotic behavior of the wave function for a decaying nucleus are found with allowance for open-decay-channel coupling not only for fission, but also for the binary decays of nuclei through protonic, alpha-particle, cluster, and other channels.

  15. G-protein-coupled inward rectifier potassium channels involved in corticostriatal presynaptic modulation.

    PubMed

    Meneses, David; Mateos, Verónica; Islas, Gustavo; Barral, Jaime

    2015-09-01

    Presynaptic modulation has been associated mainly with calcium channels but recent data suggests that inward rectifier potassium channels (K(IR)) also play a role. In this work we set to characterize the role of presynaptic K(IR) channels in corticostriatal synaptic transmission. We elicited synaptic potentials in striatum by stimulating cortical areas and then determined the synaptic responses of corticostriatal synapsis by using paired pulse ratio (PPR) in the presence and absence of several potassium channel blockers. Unspecific potassium channels blockers Ba(2+) and Cs(+) reduced the PPR, suggesting that these channels are presynaptically located. Further pharmacological characterization showed that application of tertiapin-Q, a specific K(IR)3 channel family blocker, also induced a reduction of PPR, suggesting that K(IR)3 channels are present at corticostriatal terminals. In contrast, exposure to Lq2, a specific K(IR)1.1 inward rectifier potassium channel, did not induce any change in PPR suggesting the absence of these channels in the presynaptic corticostriatal terminals. Our results indicate that K(IR)3 channels are functionally expressed at the corticostriatal synapses, since blockage of these channels result in PPR decrease. Our results also help to explain how synaptic activity may become sensitive to extracellular signals mediated by G-protein coupled receptors. A vast repertoire of receptors may influence neurotransmitter release in an indirect manner through regulation of K(IR)3 channels.

  16. Coupled-Channel Computation of Direct Neutron Capture on Non-Spherical Nuclei

    NASA Astrophysics Data System (ADS)

    Arbanas, Goran; Thompson, Ian; Escher, Jutta; Nunes, Filomena; Elster, Charlotte; Zhang, Shi-Sheng

    2014-09-01

    Models of direct neutron capture of neutrons have so far accounted for the effects of non-spherical nuclei either in the incoming wave functions (via non-spherical optical model potentials), or in the final bound states (via non-spherical real potential wells), but not in both. Since it is known that spherical optical potentials do not give a good reproduction of low energy neutron-scattering observables of deformed nuclei, we have performed calculations in which the initial and final states are both treated in a self-consistent, non-spherical-nucleus picture. We have done this in the coupled-channels model of nuclear reactions implemented in the FRESCO code by using the same deformation-length for the couplings to the rotational-band states in the incoming and the final state configurations. We compute direct capture using this method for even-mass calcium isotopes 40 , 42 , 44 , 46 , 48Ca to study the effect across the two closed neutron shells, for neutron-rich even-mass tin isotopes relevant to models of astrophysical nucleosynthesis, and for 56Fe that is an important structural material used in nuclear applications. Models of direct neutron capture of neutrons have so far accounted for the effects of non-spherical nuclei either in the incoming wave functions (via non-spherical optical model potentials), or in the final bound states (via non-spherical real potential wells), but not in both. Since it is known that spherical optical potentials do not give a good reproduction of low energy neutron-scattering observables of deformed nuclei, we have performed calculations in which the initial and final states are both treated in a self-consistent, non-spherical-nucleus picture. We have done this in the coupled-channels model of nuclear reactions implemented in the FRESCO code by using the same deformation-length for the couplings to the rotational-band states in the incoming and the final state configurations. We compute direct capture using this method for even

  17. Fusion and neutron transfer reactions with weakly bound nuclei within time-dependent and coupled channel approaches

    NASA Astrophysics Data System (ADS)

    Samarin, V. V.

    2016-05-01

    The time-dependent Schrödinger equation and the coupled channel approach based on the method of perturbed stationary two-center states are used to describe nucleon transfers and fusion in low-energy nuclear reactions. Results of the cross sections calculation for the formation of the 198Au and fusion in the 6He+197Au reaction and for the formation of the 65Zn in 6He+64Zn reaction agree satisfactorily with the experimental data near the barrier. The Feynman's continual integrals calculations for a few-body systems were used for the proposal of the new form of the shell model mean field for helium isotopes.

  18. Partitioning modes and rates of sediment flux derived from terrace-channel coupling

    NASA Astrophysics Data System (ADS)

    Higson, J. L.; Singer, M. B.

    2012-12-01

    Sediment supply to channels from failed banks/terraces is a geomorphic problem that has received scant treatment in the literature, especially with respect to the partitioning of such laterally eroded sediment into bedload v. suspended load and the resultant channel grain size distribution. Such coupling between terraces/banks and channels is an important component for understanding the exhaustion of the legacy sediments in disturbed watersheds, especially where terraces are contaminated by past mining activities. More than 4x106 kg of mercury (Hg) was lost during the 19th Century hydraulic mining process in the Sierra Nevada foothills of California and documented levels of total Hg concentration in legacy terraces all along the Yuba River are up to 3 orders of magnitude higher than background values. Thus, the ongoing erosion of legacy terraces from the mining period poses important risks to sensitive and ecologically productive lowlands downstream. The problem of bank/terrace erosion in river corridors is generally treated either using a channel centerline (toe cutting) approach or by infinite slope stability at a cross section, but the interaction of failed sediment with the channel is an important and missing component for fully assessing downstream risks of failing contaminated terraces. We have developed a new physically based model that can be used to quantify the extent and caliber of episodic erosion of legacy terrace sediments. The model combines analysis of bank/terrace failure in response to variable fluvial hydrology with a representation of local cross section evolution of grain size distribution and sediment routing. Terrace stability is calculated through an infinite slope stability model, driven by a Dupuit-Forchheimer groundwater model to assess soil moisture contributing to failure. The grain size distribution (GSD) in the channel bed is evolved based on calculation of sediment transport, which also yields net flux of fine material that is known

  19. Astrophysical S-factor for 6Li(ρ, γ)7Be in the coupled-channel Gamow shell model

    NASA Astrophysics Data System (ADS)

    Dong, G. X.; Fossez, K.; Michel, N.; Płoszajczak, M.

    2016-02-01

    We have applied the Gamow shell model (GSM) in the coupled-channel representation to study the astrophysical S-factor for the proton radiative capture reaction of 6Li. Reaction channels are built by coupling the proton wave function expanded in different partial waves with the GSM wave functions of the ground state (1+) and the excited states (31+, 01+ and 21+) of 6Li. All relevant E1, M1, and E2 transitions from the initial continuum states in 7Be to the final bound states (3/21- and 1/21-) are included. It is found that the calculated total astrophysical S factor for this reaction agrees well with the experimental data.

  20. Resonant excitation of coupled Rayleigh waves in a short and narrow fluid channel clad between two identical metal plates

    SciTech Connect

    García-Chocano, Victor M.; López-Rios, Tomás; Krokhin, Arkadii; Sanchez-Dehesa, Jose

    2011-12-23

    Transmission of ultrasonic waves through a slit between two water immersed brass plates is studied for sub-wavelength plate thicknesses and slit apertures. Extraordinary high absorption is observed at discrete frequencies corresponding to resonant excitation of Rayleigh waves on the both sides of the channel. The coupling of the Rayleigh waves occurs through the fluid and the corresponding contribution to the dispersion has been theoretically derived and also experimentally confirmed. Symmetric and anti-symmetric modes are predicted but only the symmetric mode resonances have been observed. It follows from the dispersion equation that the coupled Rayleigh waves cannot be excited in a channel with apertures less than the critical one. The calculated critical aperture is in a good agreement with the measured acoustic spectra. These findings could be applied to design a broadband absorptive metamaterial.

  1. Resonant excitation of coupled Rayleigh waves in a short and narrow fluid channel clad between two identical metal plates

    DOE PAGES

    García-Chocano, Victor M.; López-Rios, Tomás; Krokhin, Arkadii; Sanchez-Dehesa, Jose

    2011-12-23

    Transmission of ultrasonic waves through a slit between two water immersed brass plates is studied for sub-wavelength plate thicknesses and slit apertures. Extraordinary high absorption is observed at discrete frequencies corresponding to resonant excitation of Rayleigh waves on the both sides of the channel. The coupling of the Rayleigh waves occurs through the fluid and the corresponding contribution to the dispersion has been theoretically derived and also experimentally confirmed. Symmetric and anti-symmetric modes are predicted but only the symmetric mode resonances have been observed. It follows from the dispersion equation that the coupled Rayleigh waves cannot be excited in amore » channel with apertures less than the critical one. The calculated critical aperture is in a good agreement with the measured acoustic spectra. These findings could be applied to design a broadband absorptive metamaterial.« less

  2. Channel coupling in heavy quarkonia: Energy levels, mixing, widths, and new states

    SciTech Connect

    Danilkin, I. V.; Simonov, Yu. A.

    2010-04-01

    The mechanism of channel coupling via decay products is used to study energy shifts, level mixing as well as the possibility of new near-threshold resonances in cc, bb systems. The Weinberg eigenvalue method is formulated in the multichannel problems, which allows one to describe coupled-channel resonances and wave functions in a unitary way, and to predict new states due to channel coupling. Realistic wave functions for all single-channel states and decay matrix elements computed earlier are exploited, and no new fitting parameters are involved. Examples of level shifts, widths, and mixings are presented; the dynamical origin of X(3872) and the destiny of the single-channel 2{sup 3}P{sub 1}(cc) state are clarified. As a result a sharp and narrow peak in the state with quantum numbers J{sup PC}=1{sup ++} is found at 3.872 GeV, while the single-channel resonance originally around 3.940 GeV becomes increasingly broad and disappears with growing coupling to open channels.

  3. Dual Lattice Boltzmann method for electrokinetic coupling : behavior at high and low salinities in rough channels.

    NASA Astrophysics Data System (ADS)

    Fiorentino, Eve-Agnès; Toussaint, Renaud; Jouniaux, Laurence

    2014-05-01

    We study the coupling between hydraulic and electric flows in a porous medium at small scale using the Lattice Boltzmann method. This method is a computational fluid dynamics technique that is used for advection and diffusion modeling. We implement a coupled Lattice Boltzmann algorithm that solves both the mass transport and the electric field arising from charges displacements. The streaming potential and electroosmosis phenomena occur in a variety of situations and derive from this coupling. We focus on the streaming potential which is described using the ratio between the created potential difference and the applied pressure gradient. The streaming potential is assumed to be a linear function of the fluid conductivity, but experimental results highlight anomalous behaviors at low and high salinity. We try to account for them by setting extreme conditions that are likely to generate non-linearities. Several pore radii are tested so as to determine what is the effect of a radius that is comparable to the Debye length, the screening length of the electric potential, due to the ions in the electrolyte. The volumetric integral of the electrical current is calculated for comparison with the 2D simulations. High values of zeta potential are tested to verify if the discrepancy regarding the theoretical result is concentration-dependent. We try to include a surface conductivity term in the coefficient formulation. Some tests including a rugosity on the channel walls are performed. All of these attempts show a normal behaviour of the streaming potential at high salinity. We observe a decrease of the ratio at low conductivity, showing that this ratio is modified when the pore radius becomes negligible compared with the Debye length, which is physically meaningful in little pores at low concentrations. References : S. Pride. Governing equations for the coupled electromagnetics and acoustics of porous media. Physical Review B, 50 : 15678-15696, 1994. D. A. Wolf

  4. Principal pathway coupling agonist binding to channel gating in nicotinic receptors

    NASA Astrophysics Data System (ADS)

    Lee, Won Yong; Sine, Steven M.

    2005-11-01

    Synaptic receptors respond to neurotransmitters by opening an intrinsic ion channel in the final step in synaptic transmission. How binding of the neurotransmitter is conveyed over the long distance to the channel remains a central question in neurobiology. Here we delineate a principal pathway that links neurotransmitter binding to channel gating by using a structural model of the Torpedo acetylcholine receptor at 4-Å resolution, recordings of currents through single receptor channels and determinations of energetic coupling between pairs of residues. We show that a pair of invariant arginine and glutamate residues in each receptor α-subunit electrostatically links peripheral and inner β-sheets from the binding domain and positions them to engage with the channel. The key glutamate and flanking valine residues energetically couple to conserved proline and serine residues emerging from the top of the channel-forming α-helix, suggesting that this is the point at which the binding domain triggers opening of the channel. The series of interresidue couplings identified here constitutes a primary allosteric pathway that links neurotransmitter binding to channel gating.

  5. Unitary coupled-channels model for three-mesons decays of heavy mesons

    SciTech Connect

    Hiroyuki Kamano; Nakamura, Satoshi X.; Lee, Tsung-Shung H.; Sato, Toru

    2011-12-16

    In this study, a unitary coupled-channels model is presented for investigating the decays of heavy mesons and excited meson states into three light pseudoscalar mesons. The model accounts for the three-mesons final state interactions in the decay processes, as required by both the three-body and two-body unitarity conditions. In the absence of the Z-diagram mechanisms that are necessary consequences of the three-body unitarity, our decay amplitudes are reduced to a form similar to those used in the so-called isobar-model analysis. We apply our coupled-channels model to the three-pions decays of α1(1260), π2(1670), π2(2100), and D0 mesons, and show that the Z-diagram mechanisms can contribute to the calculated Dalitz plot distributions by as much as 30% in magnitudes in the regions where f0(600), ρ(770), and f2(1270) dominate the distributions. Also, by fitting to the same Dalitz plot distributions, we demonstrate that the decay amplitudes obtained with the unitary model and the isobar model can be rather different, particularly in the phase that plays a crucial role in extracting the CKM CP-violating phase from the data of B meson decays. Our results indicate that the commonly used isobar model analysis must be extended to account for the final state interactions required by the three-body unitarity to reanalyze the three-mesons decays of heavy mesons, thereby exploring hybrid or exotic mesons, and signatures of physics beyond the standard model.

  6. Unitary coupled-channels model for three-mesons decays of heavy mesons

    DOE PAGES

    Hiroyuki Kamano; Nakamura, Satoshi X.; Lee, Tsung-Shung H.; Sato, Toru

    2011-12-16

    In this study, a unitary coupled-channels model is presented for investigating the decays of heavy mesons and excited meson states into three light pseudoscalar mesons. The model accounts for the three-mesons final state interactions in the decay processes, as required by both the three-body and two-body unitarity conditions. In the absence of the Z-diagram mechanisms that are necessary consequences of the three-body unitarity, our decay amplitudes are reduced to a form similar to those used in the so-called isobar-model analysis. We apply our coupled-channels model to the three-pions decays of α1(1260), π2(1670), π2(2100), and D0 mesons, and show that themore » Z-diagram mechanisms can contribute to the calculated Dalitz plot distributions by as much as 30% in magnitudes in the regions where f0(600), ρ(770), and f2(1270) dominate the distributions. Also, by fitting to the same Dalitz plot distributions, we demonstrate that the decay amplitudes obtained with the unitary model and the isobar model can be rather different, particularly in the phase that plays a crucial role in extracting the CKM CP-violating phase from the data of B meson decays. Our results indicate that the commonly used isobar model analysis must be extended to account for the final state interactions required by the three-body unitarity to reanalyze the three-mesons decays of heavy mesons, thereby exploring hybrid or exotic mesons, and signatures of physics beyond the standard model.« less

  7. TRPV4 and KCa ion channels functionally couple as osmosensors in the paraventricular nucleus

    PubMed Central

    Feetham, C H; Nunn, N; Lewis, R; Dart, C; Barrett-Jolley, R

    2015-01-01

    Background and Purpose Transient receptor potential vanilloid type 4 (TRPV4) and calcium-activated potassium channels (KCa) mediate osmosensing in many tissues. Both TRPV4 and KCa channels are found in the paraventricular nucleus (PVN) of the hypothalamus, an area critical for sympathetic control of cardiovascular and renal function. Here, we have investigated whether TRPV4 channels functionally couple to KCa channels to mediate osmosensing in PVN parvocellular neurones and have characterized, pharmacologically, the subtype of KCa channel involved. Experimental Approach We investigated osmosensing roles for TRPV4 and KCa channels in parvocellular PVN neurones using cell-attached and whole-cell electrophysiology in mouse brain slices and rat isolated PVN neurons. Intracellular Ca2+ was recorded using Fura-2AM. The system was modelled in the NEURON simulation environment. Key Results Hypotonic saline reduced action current frequency in hypothalamic slices; a response mimicked by TRPV4 channel agonists 4αPDD (1 μM) and GSK1016790A (100 nM), and blocked by inhibitors of either TRPV4 channels (RN1734 (5 μM) and HC067047 (300 nM) or the low-conductance calcium-activated potassium (SK) channel (UCL-1684 30 nM); iberiotoxin and TRAM-34 had no effect. Our model was compatible with coupling between TRPV4 and KCa channels, predicting the presence of positive and negative feedback loops. These predictions were verified using isolated PVN neurons. Both hypotonic challenge and 4αPDD increased intracellular Ca2+ and UCL-1684 reduced the action of hypotonic challenge. Conclusions and Implications There was functional coupling between TRPV4 and SK channels in parvocellular neurones. This mechanism contributes to osmosensing in the PVN and may provide a novel pharmacological target for the cardiovascular or renal systems. PMID:25421636

  8. Exchange coupling in transition metal monoxides: Electronic structure calculations

    SciTech Connect

    Fischer, Guntram; Daene, Markus W; Ernst, Arthur; Bruno, Patrick; Lueders, Martin; Szotek, Zdzislawa; Temmerman, Walter M; Wolfam, Hergert

    2009-01-01

    An ab initio study of magnetic-exchange interactions in antiferromagnetic and strongly correlated 3d transition metal monoxides is presented. Their electronic structure is calculated using the local self-interaction correction approach, implemented within the Korringa-Kohn-Rostoker band-structure method, which is based on multiple scattering theory. The Heisenberg exchange constants are evaluated with the magnetic force theorem. Based on these the corresponding Neel temperatures TN and spin-wave dispersions are calculated. The Neel temperatures are obtained using mean-field approximation, random-phase approximation and Monte Carlo simulations. The pressure dependence of TN is investigated using exchange constants calculated for different lattice constants. All the calculated results are compared to experimental data.

  9. Role of protein dynamics in ion selectivity and allosteric coupling in the NaK channel

    PubMed Central

    Brettmann, Joshua B.; Urusova, Darya; Tonelli, Marco; Silva, Jonathan R.; Henzler-Wildman, Katherine A.

    2015-01-01

    Flux-dependent inactivation that arises from functional coupling between the inner gate and the selectivity filter is widespread in ion channels. The structural basis of this coupling has only been well characterized in KcsA. Here we present NMR data demonstrating structural and dynamic coupling between the selectivity filter and intracellular constriction point in the bacterial nonselective cation channel, NaK. This transmembrane allosteric communication must be structurally different from KcsA because the NaK selectivity filter does not collapse under low-cation conditions. Comparison of NMR spectra of the nonselective NaK and potassium-selective NaK2K indicates that the number of ion binding sites in the selectivity filter shifts the equilibrium distribution of structural states throughout the channel. This finding was unexpected given the nearly identical crystal structure of NaK and NaK2K outside the immediate vicinity of the selectivity filter. Our results highlight the tight structural and dynamic coupling between the selectivity filter and the channel scaffold, which has significant implications for channel function. NaK offers a distinct model to study the physiologically essential connection between ion conduction and channel gating. PMID:26621745

  10. Functional Coupling of Ca2+ Channels and Ryanodine Receptors in Cardiac Myocytes

    NASA Astrophysics Data System (ADS)

    Sham, James S. K.; Cleemann, Lars; Morad, Martin

    1995-01-01

    In skeletal muscle, dihydropyridine receptors are functionally coupled to ryanodine receptors of the sarcoplasmic reticulum in triadic or diadic junctional complexes. In cardiac muscle direct physical or functional couplings have not been demonstrated. We have tested the hypothesis of functional coupling of L-type Ca2+ channels and ryanodine receptors in rat cardiac myocytes by comparing the efficacies of Ca2+ in triggering Ca2+ release when the ion enters the cell via the Ca2+ channels or the Na^+/Ca2+ exchanger. Ca2+ transported through the Ca2+ channels was 20-160 times more effective than Ca2+ influx via the Na^+/Ca2+ exchanger in gating Ca2+ release from the sarcoplasmic reticulum, suggesting privileged communication between Ca2+ channels and ryanodine receptors. In support of this hypothesis we found that Ca2+ channels were inactivated by Ca2+ release from the sarcoplasmic reticulum, even though the myoplasmic Ca2+ concentrations were buffered with 10 mM EGTA. The data thus suggest privileged cross signaling between the dihydropyridine and ryanodine receptors such that Ca2+ flux through either the Ca2+ channel or the ryanodine receptor alters the gating kinetics of the other channel.

  11. Reprint of : Correlated voltage probe model of relaxation in two Coulomb-coupled edge channels

    NASA Astrophysics Data System (ADS)

    Nigg, Simon E.

    2016-08-01

    A phenomenological correlated voltage probe model is introduced to mimic the effects of inelastic scattering between particles in different conduction channels of a phase coherent conductor. As an illustration, the non-equilibrium distribution functions of two noisy co-propagating chiral edge channels of the integer quantum Hall effect are calculated and compared with recent experiments. The method is further applied to calculate the linear response current noise through an interacting Mach-Zehnder interferometer.

  12. The effects of dual-channel coupling on the transition from amplitude death to oscillation death

    NASA Astrophysics Data System (ADS)

    Chen, Jiangnan; Liu, Weiqing; Zhu, Yun; Xiao, Jinghua

    2016-07-01

    Oscillation quenching including amplitude death (AD) and oscillation death (OD) in addition to the transition processes between them have been hot topics in aspect of chaos control, physical and biological applications. The effects of dual-channel coupling on the AD and OD dynamics regimes, and their transition processes in coupled nonidentical oscillators are explored numerically and theoretically. Our results indicate that an additional repulsive coupling tends to shrink the AD domain while it enlarges the OD domain, however, an additional attractive coupling acts inversely. As a result, the transitions from AD to OD are replaced by transitions from oscillation state (OS) to AD or from OS to OD in the dual-channel coupled oscillators with different frequency mismatches. Our results are helpful to better understand the control of AD and OD and their transition processes.

  13. Quantum calculation of disordered length in fcc single crystals using channelling techniques

    NASA Astrophysics Data System (ADS)

    Abu-Assy, M. K.

    2006-04-01

    Lattices of face-centred cubic crystals (fcc), due to irradiation processes, may become disordered in stable configurations like the dumb-bell configuration (DBC) or body-centred interstitial (BCI). In this work, a quantum mechanical treatment for the calculation of transmission coefficients of channelled positrons from their bound states in the normal lattice regions into the allowed bound states in the disordered regions is given as a function of the length of the disordered regions. In order to obtain more reliable results, higher anharmonic terms in the planar channelling potential are considered in the calculations by using first-order perturbation theory where new bound states have been found. The calculations were executed in the energy range 10 200 MeV of the incident positron on a copper single crystal in the planar direction (100).

  14. Coupled Electron-Ion Monte Carlo calculations of atomic hydrogen

    NASA Astrophysics Data System (ADS)

    Holzmann, Markus; Pierleoni, Carlo; Ceperley, David M.

    2005-07-01

    We present a new Monte Carlo method which couples Path Integral for finite temperature protons with Quantum Monte Carlo for ground state electrons, and we apply it to metallic hydrogen for pressures beyond molecular dissociation. This method fills the gap between high temperature electron-proton Path Integral and ground state Diffusion Monte Carlo methods. Our data exhibit more structure and higher melting temperatures of the proton crystal than Car-Parrinello Molecular Dynamics results using LDA. We further discuss the quantum motion of the protons and the zero temperature limit.

  15. Combining molecular dynamics and an electrodiffusion model to calculate ion channel conductance.

    PubMed

    Wilson, Michael A; Nguyen, Thuy Hien; Pohorille, Andrew

    2014-12-14

    Establishing the relation between the structures and functions of protein ion channels, which are protein assemblies that facilitate transmembrane ion transport through water-filled pores, is at the forefront of biological and medical sciences. A reliable way to determine whether our understanding of this relation is satisfactory is to reproduce the measured ionic conductance over a broad range of applied voltages. This can be done in molecular dynamics simulations by way of applying an external electric field to the system and counting the number of ions that traverse the channel per unit time. Since this approach is computationally very expensive we develop a markedly more efficient alternative in which molecular dynamics is combined with an electrodiffusion equation. This alternative approach applies if steady-state ion transport through channels can be described with sufficient accuracy by the one-dimensional diffusion equation in the potential given by the free energy profile and applied voltage. The theory refers only to line densities of ions in the channel and, therefore, avoids ambiguities related to determining the surface area of the channel near its endpoints or other procedures connecting the line and bulk ion densities. We apply the theory to a simple, model system based on the trichotoxin channel. We test the assumptions of the electrodiffusion equation, and determine the precision and consistency of the calculated conductance. We demonstrate that it is possible to calculate current/voltage dependence and accurately reconstruct the underlying (equilibrium) free energy profile, all from molecular dynamics simulations at a single voltage. The approach developed here applies to other channels that satisfy the conditions of the electrodiffusion equation. PMID:25494790

  16. Light propagation in an array of rectilinear and curvilinear coupled channel waveguides

    SciTech Connect

    Goncharov, A A; Svidzinsky, K K; Sychugov, V A; Usievich, B A

    2003-04-30

    Light transmission through an array of tunnel-coupled channel waveguides is studied in detail. It is shown that a discrete structure of the light-transmitting medium leads to a modification of the law of light refraction. It is also shown that a new type of total internal reflection of light inside the structure manifests itself in an inhomogeneous array of coupled waveguides. The process of light propagation in an array of identical channel waveguides, which are arranged equidistantly along concentric circles, is investigated. It is established that such a waveguide array is equivalent to an inhomogeneous system of coupled waveguides. The mode excitation process in an array of ring channel waveguides located on cylindrical and conical surfaces is considered. (waveguides)

  17. A General approach for calculating coupling impedances of small discontinuities

    NASA Astrophysics Data System (ADS)

    Kurennoy, Sergei S.; Gluckstern, Robert L.; Stupakov, Gennady V.

    A general theory of the beam interaction with small discontinuities of the vacuum chamber is developed taking into account the reaction of radiated waves back on the discontinuity. The reactive impedance calculated earlier is reproduced as the first order, and the resistive one as the second order of a perturbation theory based on this general approach. The theory also gives, in a very natural way, the results for the trapped modes due to small discontinuities obtained earlier by a different method.

  18. Coupling of CFTR Cl- channel gating to an ATP hydrolysis cycle.

    PubMed

    Baukrowitz, T; Hwang, T C; Nairn, A C; Gadsby, D C

    1994-03-01

    For cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels to open, they must be phosphorylated by protein kinase A and then exposed to a hydrolyzable nucleoside triphosphate, such as ATP. To test whether channel opening is linked to ATP hydrolysis, we applied VO4 and BeF3 to CFTR channels in inside-out patches excised from cardiac myocytes. These inorganic phosphate analogs interrupt ATP hydrolysis cycles by binding tightly in place of the released hydrolysis product, inorganic phosphate. The analogs acted only on CFTR channels opened by ATP and locked them open, increasing their mean open time by 2-3 orders of magnitude. These findings establish that opening and closing of CFTR channels are coupled to an ATP hydrolysis cycle.

  19. Temperature and voltage coupling to channel opening in transient receptor potential melastatin 8 (TRPM8).

    PubMed

    Raddatz, Natalia; Castillo, Juan P; Gonzalez, Carlos; Alvarez, Osvaldo; Latorre, Ramon

    2014-12-19

    Expressed in somatosensory neurons of the dorsal root and trigeminal ganglion, the transient receptor potential melastatin 8 (TRPM8) channel is a Ca(2+)-permeable cation channel activated by cold, voltage, phosphatidylinositol 4,5-bisphosphate, and menthol. Although TRPM8 channel gating has been characterized at the single channel and macroscopic current levels, there is currently no consensus regarding the extent to which temperature and voltage sensors couple to the conduction gate. In this study, we extended the range of voltages where TRPM8-induced ionic currents were measured and made careful measurements of the maximum open probability the channel can attain at different temperatures by means of fluctuation analysis. The first direct measurements of TRPM8 channel temperature-driven conformational rearrangements provided here suggest that temperature alone is able to open the channel and that the opening reaction is voltage-independent. Voltage is a partial activator of TRPM8 channels, because absolute open probability values measured with fully activated voltage sensors are less than 1, and they decrease as temperature rises. By unveiling the fast temperature-dependent deactivation process, we show that TRPM8 channel deactivation is well described by a double exponential time course. The fast and slow deactivation processes are temperature-dependent with enthalpy changes of 27.2 and 30.8 kcal mol(-1). The overall Q10 for the closing reaction is about 33. A three-tiered allosteric model containing four voltage sensors and four temperature sensors can account for the complex deactivation kinetics and coupling between voltage and temperature sensor activation and channel opening. PMID:25352597

  20. Temperature and voltage coupling to channel opening in transient receptor potential melastatin 8 (TRPM8).

    PubMed

    Raddatz, Natalia; Castillo, Juan P; Gonzalez, Carlos; Alvarez, Osvaldo; Latorre, Ramon

    2014-12-19

    Expressed in somatosensory neurons of the dorsal root and trigeminal ganglion, the transient receptor potential melastatin 8 (TRPM8) channel is a Ca(2+)-permeable cation channel activated by cold, voltage, phosphatidylinositol 4,5-bisphosphate, and menthol. Although TRPM8 channel gating has been characterized at the single channel and macroscopic current levels, there is currently no consensus regarding the extent to which temperature and voltage sensors couple to the conduction gate. In this study, we extended the range of voltages where TRPM8-induced ionic currents were measured and made careful measurements of the maximum open probability the channel can attain at different temperatures by means of fluctuation analysis. The first direct measurements of TRPM8 channel temperature-driven conformational rearrangements provided here suggest that temperature alone is able to open the channel and that the opening reaction is voltage-independent. Voltage is a partial activator of TRPM8 channels, because absolute open probability values measured with fully activated voltage sensors are less than 1, and they decrease as temperature rises. By unveiling the fast temperature-dependent deactivation process, we show that TRPM8 channel deactivation is well described by a double exponential time course. The fast and slow deactivation processes are temperature-dependent with enthalpy changes of 27.2 and 30.8 kcal mol(-1). The overall Q10 for the closing reaction is about 33. A three-tiered allosteric model containing four voltage sensors and four temperature sensors can account for the complex deactivation kinetics and coupling between voltage and temperature sensor activation and channel opening.

  1. Temperature and Voltage Coupling to Channel Opening in Transient Receptor Potential Melastatin 8 (TRPM8)*♦

    PubMed Central

    Raddatz, Natalia; Castillo, Juan P.; Gonzalez, Carlos; Alvarez, Osvaldo; Latorre, Ramon

    2014-01-01

    Expressed in somatosensory neurons of the dorsal root and trigeminal ganglion, the transient receptor potential melastatin 8 (TRPM8) channel is a Ca2+-permeable cation channel activated by cold, voltage, phosphatidylinositol 4,5-bisphosphate, and menthol. Although TRPM8 channel gating has been characterized at the single channel and macroscopic current levels, there is currently no consensus regarding the extent to which temperature and voltage sensors couple to the conduction gate. In this study, we extended the range of voltages where TRPM8-induced ionic currents were measured and made careful measurements of the maximum open probability the channel can attain at different temperatures by means of fluctuation analysis. The first direct measurements of TRPM8 channel temperature-driven conformational rearrangements provided here suggest that temperature alone is able to open the channel and that the opening reaction is voltage-independent. Voltage is a partial activator of TRPM8 channels, because absolute open probability values measured with fully activated voltage sensors are less than 1, and they decrease as temperature rises. By unveiling the fast temperature-dependent deactivation process, we show that TRPM8 channel deactivation is well described by a double exponential time course. The fast and slow deactivation processes are temperature-dependent with enthalpy changes of 27.2 and 30.8 kcal mol−1. The overall Q10 for the closing reaction is about 33. A three-tiered allosteric model containing four voltage sensors and four temperature sensors can account for the complex deactivation kinetics and coupling between voltage and temperature sensor activation and channel opening. PMID:25352597

  2. Convergent close-coupling calculations of positron-magnesium scattering

    SciTech Connect

    Savage, Jeremy S.; Fursa, Dmitry V.; Bray, Igor

    2011-06-15

    The single-center convergent close-coupling method has been applied to positron-magnesium scattering at incident energies from 0.01 to 100 eV. Cross sections are presented for elastic scattering and excitation of 3 {sup 1}P, as well as for the total ionization and total scattering processes. We also provide an estimate of the positronium formation cross section. The results agree very well with the measurements of the total cross section by Stein et al. [Nucl. Instrum. Methods Phys. Res. Sect. B 143, 68 (1998)], and consistent with the positronium formation measurements of Surdutovich et al. [Phys. Rev. A 68, 022709 (2003)] for positron energies above the ionization threshold. For energies below the positronium formation threshold (0.8 eV) we find a large P-wave resonance at 0.17 eV. A similar resonance behavior was found by Mitroy and Bromley [Phys. Rev. Lett. 98, 173001 (2007)] at an energy of 0.1 eV.

  3. COUPLING

    DOEpatents

    Frisch, E.; Johnson, C.G.

    1962-05-15

    A detachable coupling arrangement is described which provides for varying the length of the handle of a tool used in relatively narrow channels. The arrangement consists of mating the key and keyhole formations in the cooperating handle sections. (AEC)

  4. Dynamical coupled-channels model for neutrino-induced meson productions in resonance region

    NASA Astrophysics Data System (ADS)

    Nakamura, S. X.; Kamano, H.; Sato, T.

    2015-10-01

    A dynamical coupled-channels (DCC) model for neutrino-nucleon reactions in the resonance region is developed. Starting from the DCC model that we have previously developed through an analysis of π N ,γ N →π N ,η N ,K Λ ,K Σ reaction data for W ≤2.1 GeV , we extend the model of the vector current to Q2≤3.0 (GeV /c )2 by analyzing electron-induced reaction data for both proton and neutron targets. We derive axial-current matrix elements that are related to the π N interactions of the DCC model through the partially conserved axial current (PCAC) relation. Consequently, the interference pattern between resonant and nonresonant amplitudes is uniquely determined. We calculate cross sections for neutrino-induced meson productions, and compare them with available data. Our result for the single-pion production reasonably agrees with the data. We also make a comparison with the double-pion production data. Our model is the first DCC model that can give the double-pion production cross sections in the resonance region. We also make comparison of our result with other existing models to reveal an importance of testing the models in the light of PCAC and electron reaction data. The DCC model developed here will be a useful input for constructing a neutrino-nucleus reaction model and a neutrino event generator for analyses of neutrino experiments.

  5. Regulation of channel function due to physical energetic coupling with a lipid bilayer

    SciTech Connect

    Ashrafuzzaman, Md.; Tseng, C.-Y.; Tuszynski, J.A.

    2014-03-07

    Highlights: • Lipid membrane regulation of membrane protein functions has been addressed. • Energetics behind ion channel-membrane coupling phenomena has been investigated. • Charge based interactions stabilize peptide–lipid complex. • Screened Coulomb interaction model explains the energetics. • Van der Waals and electrostatic forces drive peptides and lipids to close proximity. - Abstract: Regulation of membrane protein functions due to hydrophobic coupling with a lipid bilayer has been investigated. An energy formula describing interactions between lipid bilayer and integral ion channels with different structures, which is based on the screened Coulomb interaction approximation, has been developed. Here the interaction energy is represented as being due to charge-based interactions between channel and lipid bilayer. The hydrophobic bilayer thickness channel length mismatch is found to induce channel destabilization exponentially while negative lipid curvature linearly. Experimental parameters related to channel dynamics are consistent with theoretical predictions. To measure comparable energy parameters directly in the system and to elucidate the mechanism at an atomistic level we performed molecular dynamics (MD) simulations of the ion channel forming peptide–lipid complexes. MD simulations indicate that peptides and lipids experience electrostatic and van der Waals interactions for short period of time when found within each other’s proximity. The energies from these two interactions are found to be similar to the energies derived theoretically using the screened Coulomb and the van der Waals interactions between peptides (in ion channel) and lipids (in lipid bilayer) due to mainly their charge properties. The results of in silico MD studies taken together with experimental observable parameters and theoretical energetic predictions suggest that the peptides induce ion channels inside lipid membranes due to peptide–lipid physical interactions

  6. Onsager's cross coupling effects in gas flows confined to micro-channels

    NASA Astrophysics Data System (ADS)

    Wang, Ruijie; Xu, Xinpeng; Xu, Kun; Qian, Tiezheng

    2016-08-01

    In rarefied gases, mass and heat transport processes interfere with each other, leading to the mechano-caloric effect and thermo-osmotic effect, which are of interest to both theoretical study and practical applications. We employ the unified gas-kinetic scheme to investigate these cross coupling effects in gas flows in micro-channels. Our numerical simulations cover channels of planar surfaces and also channels of ratchet surfaces, with Onsager's reciprocal relation verified for both cases. For channels of planar surfaces, simulations are performed in a wide range of Knudsen number, and our numerical results show good agreement with the literature results. For channels of ratchet surfaces, simulations are performed for both the slip and transition regimes, and our numerical results not only confirm the theoretical prediction [Phys. Rev. Lett. 107, 164502 (2011), 10.1103/PhysRevLett.107.164502] for the Knudsen number in the slip regime but also show that the off-diagonal kinetic coefficients for cross coupling effects are maximized at a Knudsen number in the transition regime. Finally, a preliminary optimization study is carried out for the geometry of Knudsen pump based on channels of ratchet surfaces.

  7. Allosteric coupling of the inner activation gate to the outer pore of a potassium channel.

    PubMed

    Peters, Christian J; Fedida, David; Accili, Eric A

    2013-10-23

    In potassium channels, functional coupling of the inner and outer pore gates may result from energetic interactions between residues and conformational rearrangements that occur along a structural path between them. Here, we show that conservative mutations of a residue near the inner activation gate of the Shaker potassium channel (I470) modify the rate of C-type inactivation at the outer pore, pointing to this residue as part of a pathway that couples inner gate opening to changes in outer pore structure and reduction of ion flow. Because they remain equally sensitive to rises in extracellular potassium, altered inactivation rates of the mutant channels are not secondary to modified binding of potassium to the outer pore. Conservative mutations of I470 also influence the interaction of the Shaker N-terminus with the inner gate, which separately affects the outer pore.

  8. Functional coupling of TRPV4 channels and BK channels in regulating spontaneous contractions of the guinea pig urinary bladder.

    PubMed

    Isogai, Ayu; Lee, Ken; Mitsui, Retsu; Hashitani, Hikaru

    2016-09-01

    We investigated the role of TRPV4 channels (TRPV4) in regulating the contractility of detrusor smooth muscle (DSM) and muscularis mucosae (MM) of the urinary bladder. Distribution of TRPV4 in DSM and MM of guinea-pig bladders was examined by fluorescence immunohistochemistry. Changes in the contractility of DSM and MM bundles were measured using isometric tension recording. Intracellular Ca(2+) dynamics were visualized by Cal-520 fluorescent Ca(2+) imaging, while membrane potential changes were recorded using intracellular microelectrode technique. DSM and MM expressed TRPV4 immunoreactivity. GSK1016790A (GSK, 1 nM), a TRPV4 agonist, evoked a sustained contraction in both DSM and MM associated with a cessation of spontaneous phasic contractions in a manner sensitive to HC-067047 (10 μM), a TRPV4 antagonist. Iberiotoxin (100 nM) and paxilline (1 μM), large conductance Ca(2+)-activated K(+) (BK) channel blockers restored the spontaneous contractions in GSK. The sustained contractions in DSM and MM were reduced by nifedipine (10 μM), a blocker of L-type voltage-dependent Ca(2+) channels (LVDCCs) by about 40 % and by nominally Ca(2+)-free solution by some 90 %. GSK (1 nM) abolished spontaneous Ca(2+) transients, increased basal Ca(2+) levels and also prevented spontaneous action potential discharge associated with DSM membrane hyperpolarization. In conclusion, Ca(2+) influx through TRPV4 appears to activate BK channels to suppress spontaneous contractions and thus a functional coupling of TRPV4 with BK channels may act as a self-limiting mechanism for bladder contractility during its storage phase. Despite the membrane hyperpolarization in GSK, Ca(2+) entry mainly through TRPV4 develops the tonic contraction. PMID:27497848

  9. Unidirectional Photoreceptor-to-Müller Glia Coupling and Unique K+ Channel Expression in Caiman Retina

    PubMed Central

    Rivera, Yomarie; Benedikt, Jan; Ulbricht, Elke; Karl, Anett; Dávila, José; Savvinov, Alexey; Kucheryavykh, Yuriy; Inyushin, Mikhail; Cubano, Luis A.; Pannicke, Thomas; Veh, Rüdiger W.; Francke, Mike; Verkhratsky, Alexei; Eaton, Misty J.; Reichenbach, Andreas; Skatchkov, Serguei N.

    2014-01-01

    Background Müller cells, the principal glial cells of the vertebrate retina, are fundamental for the maintenance and function of neuronal cells. In most vertebrates, including humans, Müller cells abundantly express Kir4.1 inwardly rectifying potassium channels responsible for hyperpolarized membrane potential and for various vital functions such as potassium buffering and glutamate clearance; inter-species differences in Kir4.1 expression were, however, observed. Localization and function of potassium channels in Müller cells from the retina of crocodiles remain, hitherto, unknown. Methods We studied retinae of the Spectacled caiman (Caiman crocodilus fuscus), endowed with both diurnal and nocturnal vision, by (i) immunohistochemistry, (ii) whole-cell voltage-clamp, and (iii) fluorescent dye tracing to investigate K+ channel distribution and glia-to-neuron communications. Results Immunohistochemistry revealed that caiman Müller cells, similarly to other vertebrates, express vimentin, GFAP, S100β, and glutamine synthetase. In contrast, Kir4.1 channel protein was not found in Müller cells but was localized in photoreceptor cells. Instead, 2P-domain TASK-1 channels were expressed in Müller cells. Electrophysiological properties of enzymatically dissociated Müller cells without photoreceptors and isolated Müller cells with adhering photoreceptors were significantly different. This suggests ion coupling between Müller cells and photoreceptors in the caiman retina. Sulforhodamine-B injected into cones permeated to adhering Müller cells thus revealing a uni-directional dye coupling. Conclusion Our data indicate that caiman Müller glial cells are unique among vertebrates studied so far by predominantly expressing TASK-1 rather than Kir4.1 K+ channels and by bi-directional ion and uni-directional dye coupling to photoreceptor cells. This coupling may play an important role in specific glia-neuron signaling pathways and in a new type of K+ buffering. PMID

  10. Dynamical coupled-channels study of {pi}N{yields}{pi}{pi}N reactions

    SciTech Connect

    Kamano, H.; Julia-Diaz, B.; Lee, T.-S. H.; Matsuyama, A.; Sato, T.

    2009-02-15

    As a step toward performing a complete coupled-channels analysis of the world data of {pi}N,{gamma}*N{yields}{pi}N,{eta}N,{pi}{pi}N reactions, the {pi}N{yields}{pi}{pi}N reactions are investigated starting with the dynamical coupled-channels model developed in Phys. Rev. C 76, 065201 (2007). The channels included are {pi}N,{eta}N, and {pi}{pi}N which has {pi}{delta},{rho}N, and {sigma}N resonant components. The nonresonant amplitudes are generated from solving a set of coupled-channels equations with the meson-baryon potentials defined by effective Lagrangians. The resonant amplitudes are generated from 16 bare excited nucleon (N*) states that are dressed by the nonresonant interactions as constrained by the unitarity condition. The data of total cross sections and {pi}N and {pi}{pi} invariant mass distributions of {pi}{sup +}p{yields}{pi}{sup +}{pi}{sup +}n,{pi}{sup +}{pi}{sup 0}p and {pi}{sup -}p{yields}{pi}{sup +}{pi}{sup -}n,{pi}{sup -}{pi}{sup 0}p,{pi}{sup 0}{pi}{sup 0}n reactions from threshold to the invariant mass W=2 GeV can be described to a very large extent. We show the importance of the coupled-channels effects and the strong interference among the contributions from the {pi}{delta},{sigma}N, and {rho}N channels. The large interference between the resonant and nonresonant amplitudes is also demonstrated. Possible future developments are discussed.

  11. Electrical coupling between the human serotonin transporter and voltage-gated Ca(2+) channels.

    PubMed

    Ruchala, Iwona; Cabra, Vanessa; Solis, Ernesto; Glennon, Richard A; De Felice, Louis J; Eltit, Jose M

    2014-07-01

    Monoamine transporters have been implicated in dopamine or serotonin release in response to abused drugs such as methamphetamine or ecstasy (MDMA). In addition, monoamine transporters show substrate-induced inward currents that may modulate excitability and Ca(2+) mobilization, which could also contribute to neurotransmitter release. How monoamine transporters modulate Ca(2+) permeability is currently unknown. We investigate the functional interaction between the human serotonin transporter (hSERT) and voltage-gated Ca(2+) channels (CaV). We introduce an excitable expression system consisting of cultured muscle cells genetically engineered to express hSERT. Both 5HT and S(+)MDMA depolarize these cells and activate the excitation-contraction (EC)-coupling mechanism. However, hSERT substrates fail to activate EC-coupling in CaV1.1-null muscle cells, thus implicating Ca(2+) channels. CaV1.3 and CaV2.2 channels are natively expressed in neurons. When these channels are co-expressed with hSERT in HEK293T cells, only cells expressing the lower-threshold L-type CaV1.3 channel show Ca(2+) transients evoked by 5HT or S(+)MDMA. In addition, the electrical coupling between hSERT and CaV1.3 takes place at physiological 5HT concentrations. The electrical coupling between monoamine neurotransmitter transporters and Ca(2+) channels such as CaV1.3 is a novel mechanism by which endogenous substrates (neurotransmitters) or exogenous substrates (like ecstasy) could modulate Ca(2+)-driven signals in excitable cells. PMID:24854234

  12. Calculation of Coupling Efficiencies for Laser-Driven Photonic Bandgap Structures

    SciTech Connect

    England, R. J.; Ng, C.; Noble, R.; Spencer, J. E.

    2010-11-04

    We present a technique for calculating the power coupling efficiency for a laser-driven photonic bandgap structure using electromagnetic finite element simulations, and evaluate the efficiency of several coupling scenarios for the case of a hollow-core photonic bandgap fiber accelerator structure.

  13. Calculation, normalization, and perturbation of quasinormal modes in coupled cavity-waveguide systems.

    PubMed

    Kristensen, Philip Trøst; de Lasson, Jakob Rosenkrantz; Gregersen, Niels

    2014-11-15

    We show how one can use a nonlocal boundary condition, which is compatible with standard frequency domain methods, for numerical calculation of quasinormal modes in optical cavities coupled to waveguides. In addition, we extend the definition of the quasinormal mode norm by use of the theory of divergent series to provide a framework for modeling of optical phenomena in such coupled cavity-waveguide systems. As example applications, we calculate the Purcell factor and study perturbative changes in the complex resonance frequency of a photonic crystal cavity coupled to a defect waveguide.

  14. Calculation, normalization, and perturbation of quasinormal modes in coupled cavity-waveguide systems.

    PubMed

    Kristensen, Philip Trøst; de Lasson, Jakob Rosenkrantz; Gregersen, Niels

    2014-11-15

    We show how one can use a nonlocal boundary condition, which is compatible with standard frequency domain methods, for numerical calculation of quasinormal modes in optical cavities coupled to waveguides. In addition, we extend the definition of the quasinormal mode norm by use of the theory of divergent series to provide a framework for modeling of optical phenomena in such coupled cavity-waveguide systems. As example applications, we calculate the Purcell factor and study perturbative changes in the complex resonance frequency of a photonic crystal cavity coupled to a defect waveguide. PMID:25490468

  15. STIM1 dimers undergo unimolecular coupling to activate Orai1 channels

    PubMed Central

    Zhou, Yandong; Wang, Xizhuo; Wang, Xianming; Loktionova, Natalia A.; Cai, Xiangyu; Nwokonko, Robert M.; Vrana, Erin; Wang, Youjun; Rothberg, Brad S.; Gill, Donald L.

    2015-01-01

    The endoplasmic reticulum (ER) Ca2+ sensor, STIM1, becomes activated when ER-stored Ca2+ is depleted and translocates into ER–plasma membrane junctions where it tethers and activates Orai1 Ca2+ entry channels. The dimeric STIM1 protein contains a small STIM-Orai-activating region (SOAR)—the minimal sequence sufficient to activate Orai1 channels. Since SOAR itself is a dimer, we constructed SOAR concatemer–dimers and introduced mutations at F394, which is critical for Orai1 coupling and activation. The F394H mutation in both SOAR monomers completely blocks dimer function, but F394H introduced in only one of the dimeric SOAR monomers has no effect on Orai1 binding or activation. This reveals an unexpected unimolecular coupling between STIM1 and Orai1 and argues against recent evidence suggesting dimeric interaction between STIM1 and two adjacent Orai1 channel subunits. The model predicts that STIM1 dimers may be involved in crosslinking between Orai1 channels with implications for the kinetics and localization of Orai1 channel opening. PMID:26399906

  16. STIM1 dimers undergo unimolecular coupling to activate Orai1 channels

    NASA Astrophysics Data System (ADS)

    Zhou, Yandong; Wang, Xizhuo; Wang, Xianming; Loktionova, Natalia A.; Cai, Xiangyu; Nwokonko, Robert M.; Vrana, Erin; Wang, Youjun; Rothberg, Brad S.; Gill, Donald L.

    2015-09-01

    The endoplasmic reticulum (ER) Ca2+ sensor, STIM1, becomes activated when ER-stored Ca2+ is depleted and translocates into ER-plasma membrane junctions where it tethers and activates Orai1 Ca2+ entry channels. The dimeric STIM1 protein contains a small STIM-Orai-activating region (SOAR)--the minimal sequence sufficient to activate Orai1 channels. Since SOAR itself is a dimer, we constructed SOAR concatemer-dimers and introduced mutations at F394, which is critical for Orai1 coupling and activation. The F394H mutation in both SOAR monomers completely blocks dimer function, but F394H introduced in only one of the dimeric SOAR monomers has no effect on Orai1 binding or activation. This reveals an unexpected unimolecular coupling between STIM1 and Orai1 and argues against recent evidence suggesting dimeric interaction between STIM1 and two adjacent Orai1 channel subunits. The model predicts that STIM1 dimers may be involved in crosslinking between Orai1 channels with implications for the kinetics and localization of Orai1 channel opening.

  17. Electronic coupling calculations with transition charges, dipoles, and quadrupoles derived from electrostatic potential fitting

    SciTech Connect

    Fujimoto, Kazuhiro J.

    2014-12-07

    A transition charge, dipole, and quadrupole from electrostatic potential (TrESP-CDQ) method for electronic coupling calculations is proposed. The TrESP method is based on the classical description of electronic Coulomb interaction between transition densities for individual molecules. In the original TrESP method, only the transition charge interactions were considered as the electronic coupling. In the present study, the TrESP method is extended to include the contributions from the transition dipoles and quadrupoles as well as the transition charges. Hence, the self-consistent transition density is employed in the ESP fitting procedure. To check the accuracy of the present approach, several test calculations are performed to a helium dimer, a methane dimer, and an ethylene dimer. As a result, the TrESP-CDQ method gives a much improved description of the electronic coupling, compared with the original TrESP method. The calculated results also show that the self-consistent treatment to the transition densities contributes significantly to the accuracy of the electronic coupling calculations. Based on the successful description of the electronic coupling, the contributions to the electronic coupling are also analyzed. This analysis clearly shows a negligible contribution of the transition charge interaction to the electronic coupling. Hence, the distribution of the transition density is found to strongly influence the magnitudes of the transition charges, dipoles, and quadrupoles. The present approach is useful for analyzing and understanding the mechanism of excitation-energy transfer.

  18. [Magnetic field numerical calculation and analysis for magnetic coupling of centrifugal blood pump for extracorporeal circulation].

    PubMed

    Hu, Zhaoyan; Lu, Lijun; Zhang, Tianyi; Chen, Zhenglong; Zhang, Tao

    2013-12-01

    This paper mainly studies the driving system of centrifugal blood pump for extracorporeal circulation, with the core being disc magnetic coupling. Structure parameters of disc magnetic coupling are related to the ability of transferring magnetic torque. Therefore, it is necessary to carry out disc magnetic coupling permanent magnet pole number (n), air gap length (L(g)), permanent magnet thickness (L(m)), permanent magnet body inside diameter (R(i)) and outside diameter (R(o)), etc. thoroughly. This paper adopts the three-dimensional static magnetic field edge element method of Ansys for numerical calculation, and analyses the relations of magnetic coupling each parameter to transmission magnetic torque. It provides a good theory basis and calculation method for further optimization of the disc magnetic coupling.

  19. Convergent close-coupling calculations of positron scattering on metastable helium

    SciTech Connect

    Utamuratov, R.; Kadyrov, A. S.; Fursa, D. V.; Bray, I.; Stelbovics, A. T.

    2010-10-15

    The convergent close-coupling method has been applied to positron scattering on a helium atom in the 2 {sup 3}S metastable state. For this system the positronium (Ps) formation channel is open even at zero scattering energy making the inclusion of the Ps channels especially important. Spin algebra is presented for the general case of arbitrary spins. A proof is given of the often-used assumption about the relationship between the amplitudes for ortho-positronium and para-positronium formation. The cross sections for scattering from 2 {sup 3}S are shown to be significantly larger than those obtained for the ground state.

  20. SLO BK Potassium Channels Couple Gap Junctions to Inhibition of Calcium Signaling in Olfactory Neuron Diversification.

    PubMed

    Alqadah, Amel; Hsieh, Yi-Wen; Schumacher, Jennifer A; Wang, Xiaohong; Merrill, Sean A; Millington, Grethel; Bayne, Brittany; Jorgensen, Erik M; Chuang, Chiou-Fen

    2016-01-01

    The C. elegans AWC olfactory neuron pair communicates to specify asymmetric subtypes AWCOFF and AWCON in a stochastic manner. Intercellular communication between AWC and other neurons in a transient NSY-5 gap junction network antagonizes voltage-activated calcium channels, UNC-2 (CaV2) and EGL-19 (CaV1), in the AWCON cell, but how calcium signaling is downregulated by NSY-5 is only partly understood. Here, we show that voltage- and calcium-activated SLO BK potassium channels mediate gap junction signaling to inhibit calcium pathways for asymmetric AWC differentiation. Activation of vertebrate SLO-1 channels causes transient membrane hyperpolarization, which makes it an important negative feedback system for calcium entry through voltage-activated calcium channels. Consistent with the physiological roles of SLO-1, our genetic results suggest that slo-1 BK channels act downstream of NSY-5 gap junctions to inhibit calcium channel-mediated signaling in the specification of AWCON. We also show for the first time that slo-2 BK channels are important for AWC asymmetry and act redundantly with slo-1 to inhibit calcium signaling. In addition, nsy-5-dependent asymmetric expression of slo-1 and slo-2 in the AWCON neuron is necessary and sufficient for AWC asymmetry. SLO-1 and SLO-2 localize close to UNC-2 and EGL-19 in AWC, suggesting a role of possible functional coupling between SLO BK channels and voltage-activated calcium channels in AWC asymmetry. Furthermore, slo-1 and slo-2 regulate the localization of synaptic markers, UNC-2 and RAB-3, in AWC neurons to control AWC asymmetry. We also identify the requirement of bkip-1, which encodes a previously identified auxiliary subunit of SLO-1, for slo-1 and slo-2 function in AWC asymmetry. Together, these results provide an unprecedented molecular link between gap junctions and calcium pathways for terminal differentiation of olfactory neurons.

  1. SLO BK Potassium Channels Couple Gap Junctions to Inhibition of Calcium Signaling in Olfactory Neuron Diversification

    PubMed Central

    Schumacher, Jennifer A.; Wang, Xiaohong; Merrill, Sean A.; Millington, Grethel; Bayne, Brittany; Jorgensen, Erik M.; Chuang, Chiou-Fen

    2016-01-01

    The C. elegans AWC olfactory neuron pair communicates to specify asymmetric subtypes AWCOFF and AWCON in a stochastic manner. Intercellular communication between AWC and other neurons in a transient NSY-5 gap junction network antagonizes voltage-activated calcium channels, UNC-2 (CaV2) and EGL-19 (CaV1), in the AWCON cell, but how calcium signaling is downregulated by NSY-5 is only partly understood. Here, we show that voltage- and calcium-activated SLO BK potassium channels mediate gap junction signaling to inhibit calcium pathways for asymmetric AWC differentiation. Activation of vertebrate SLO-1 channels causes transient membrane hyperpolarization, which makes it an important negative feedback system for calcium entry through voltage-activated calcium channels. Consistent with the physiological roles of SLO-1, our genetic results suggest that slo-1 BK channels act downstream of NSY-5 gap junctions to inhibit calcium channel-mediated signaling in the specification of AWCON. We also show for the first time that slo-2 BK channels are important for AWC asymmetry and act redundantly with slo-1 to inhibit calcium signaling. In addition, nsy-5-dependent asymmetric expression of slo-1 and slo-2 in the AWCON neuron is necessary and sufficient for AWC asymmetry. SLO-1 and SLO-2 localize close to UNC-2 and EGL-19 in AWC, suggesting a role of possible functional coupling between SLO BK channels and voltage-activated calcium channels in AWC asymmetry. Furthermore, slo-1 and slo-2 regulate the localization of synaptic markers, UNC-2 and RAB-3, in AWC neurons to control AWC asymmetry. We also identify the requirement of bkip-1, which encodes a previously identified auxiliary subunit of SLO-1, for slo-1 and slo-2 function in AWC asymmetry. Together, these results provide an unprecedented molecular link between gap junctions and calcium pathways for terminal differentiation of olfactory neurons. PMID:26771544

  2. Coupled-channels study of fine structure in the {alpha} decay of platinum isotopes

    SciTech Connect

    Ni Dongdong; Ren Zhongzhou

    2011-09-15

    The fine structure observed in the {alpha} decay of deformed platinum isotopes is investigated using the recently developed five-channel formalism, based on the coupled-channel Schroedinger equation with outgoing wave boundary conditions. The internal effect of daughter states is taken into account in dealing with the interaction matrix and the {alpha}-cluster formation. The available experimental data concerning {alpha}-decay half-lives and fine structures are reproduced. Some predictions are made especially for the {alpha} decay of neutron-rich isotopes, which could guide future experiments.

  3. Communication: Finite size correction in periodic coupled cluster theory calculations of solids

    NASA Astrophysics Data System (ADS)

    Liao, Ke; Grüneis, Andreas

    2016-10-01

    We present a method to correct for finite size errors in coupled cluster theory calculations of solids. The outlined technique shares similarities with electronic structure factor interpolation methods used in quantum Monte Carlo calculations. However, our approach does not require the calculation of density matrices. Furthermore we show that the proposed finite size corrections achieve chemical accuracy in the convergence of second-order Møller-Plesset perturbation and coupled cluster singles and doubles correlation energies per atom for insulating solids with two atomic unit cells using 2 × 2 × 2 and 3 × 3 × 3 k-point meshes only.

  4. Regulation of Neurovascular Coupling in Autoimmunity to Water and Ion Channels

    PubMed Central

    Jukkola, Peter; Gu, Chen

    2014-01-01

    Much progress has been made in understanding autoimmune channelopathies, but the underlying pathogenic mechanisms are not always clear due to broad expression of some channel proteins. Recent studies show that autoimmune conditions that interfere with neurovascular coupling in the central nervous system (CNS) can lead to neurodegeneration. Cerebral blood flow that meets neuronal activity and metabolic demand is tightly regulated by local neural activity. This process of reciprocal regulation involves coordinated actions of a number of cell types, including neurons, glia, and vascular cells. In particular, astrocytic endfeet cover more than 90% of brain capillaries to assist blood-brain barrier (BBB) function, and wrap around synapses and nodes of Ranvier to communicate with neuronal activity. In this review, we highlight four types of channel proteins that are expressed in astrocytes, regarding their structures, biophysical properties, expression and distribution patterns, and related diseases including autoimmune disorders. Water channel aquaporin 4 (AQP4) and inwardly-rectifying potassium (Kir4.1) channels are concentrated in astrocytic endfeet, whereas some voltage-gated Ca2+ and two-pore-domain K+ channels are expressed throughout the cell body of reactive astrocytes. More channel proteins are found in astrocytes under normal and abnormal conditions. This research field will contribute to a better understanding of pathogenic mechanisms underlying autoimmune disorders. PMID:25462580

  5. Relativistic Density Functional Calculations of Hyperfine Coupling with Variational versus Perturbational Treatment of Spin-Orbit Coupling.

    PubMed

    Verma, Prakash; Autschbach, Jochen

    2013-04-01

    Different approaches are compared for relativistic density functional theory (DFT) and Hartree-Fock (HF) calculations of electron-nucleus hyperfine coupling (HFC) in molecules with light atoms, in transition metal complexes, and in selected actinide halide complexes with a formal metal 5f(1) configuration. The comparison includes hybrid density functionals with range-separated exchange. Within the variationally stable zeroth-order regular approximation (ZORA) relativistic framework, the HFC is obtained (i) with a linear response (LR) method where spin-orbit (SO) coupling is treated as a linear perturbation, (ii) with a spin-polarized approach closely related to a DFT method for calculating magnetic anisotropy (MA) previously devised by van Wüllen et al. where SO coupling is included variationally, (iii) with a quasi-restricted variational SO method previously devised by van Lenthe, van der Avoird, and Wormer (LWA). The MA and LWA approaches for HFC calculations were implemented in the open-source NWChem quantum chemistry package as part of this study. The methodology extends recent implementations for calculations of electronic g-factors (J. Chem. Theor. Comput.2013, 9, 1052). The impact of electron correlation (DFT vs HF) and DFT delocalization errors, the effects of spin-polarization, the importance of treating spin-orbit coupling beyond first-order, and the magnitude of finite-nucleus effects, are investigated. Similar to calculations of g-factors, the MA approach in conjunction with hybrid functionals performs reasonably well for theoretical predictions of HFC in a wide range of scenarios. PMID:26583544

  6. Calculated coupling efficiency between an elliptical-core optical fiber and an optical waveguide over temperature

    NASA Technical Reports Server (NTRS)

    Tuma, Margaret L.; Weisshaar, Andreas; Li, Jian; Beheim, Glenn

    1995-01-01

    To determine the feasibility of coupling the output of a single-mode optical fiber into a single-mode rib waveguide in a temperature varying environment, a theoretical calculation of the coupling efficiency between the two was investigated. Due to the complex geometry of the rib guide, there is no analytical solution to the wave equation for the guided modes, thus, approximation and/or numerical techniques must be utilized to determine the field patterns of the guide. In this study, three solution methods were used for both the fiber and guide fields; the effective-index method (EIM), Marcatili's approximation, and a Fourier method. These methods were utilized independently to calculate the electric field profile of each component at two temperatures, 20 C and 300 C, representing a nominal and high temperature. Using the electric field profile calculated from each method, the theoretical coupling efficiency between an elliptical-core optical fiber and a rib waveguide was calculated using the overlap integral and the results were compared. It was determined that a high coupling efficiency can be achieved when the two components are aligned. The coupling efficiency was more sensitive to alignment offsets in the y direction than the x, due to the elliptical modal field profile of both components. Changes in the coupling efficiency over temperature were found to be minimal.

  7. The human histamine H3 receptor couples to GIRK channels in Xenopus oocytes.

    PubMed

    Sahlholm, Kristoffer; Nilsson, Johanna; Marcellino, Daniel; Fuxe, Kjell; Arhem, Peter

    2007-07-19

    The histamine H(3) receptor mediates inhibitory responses in the nervous system. Here, we demonstrate the coupling of the human histamine H(3) receptor to G protein-coupled inward rectifier potassium (GIRK) channels in Xenopus oocytes, using voltage-clamp. The histamine H(3) receptor agonist (R)-alpha-methylhistamine increased GIRK currents with an EC(50) of 2.5 nM. The response to (R)-alpha-methylhistamine was inhibited by the specific antagonist/inverse agonist clobenpropit. GIRK channels represent a novel effector pathway for the histamine H(3) receptor, also suggesting the use of electrophysiology assays in histamine H(3) receptor drug screening, allowing for the resolution of G protein activation kinetics.

  8. Double and single pion photoproduction within a dynamical coupled-channels model

    SciTech Connect

    Kamano, H.; Julia-Diaz, B.; Lee, T.-S. H.; Matsuyama, A.; Sato, T.

    2009-12-15

    Within a dynamical coupled-channels model that has already been fixed by analyzing the data of the {pi}N{yields}{pi}N and {gamma}N{yields}{pi}N reactions, we present the predicted double pion photoproduction cross sections up to the second resonance region, W<1.7 GeV. The roles played by the different mechanisms within our model in determining both the single and double pion photoproduction reactions are analyzed, focusing on the effects attributable to the direct {gamma}N{yields}{pi}{pi}N mechanism, the interplay between the resonant and nonresonant amplitudes, and the coupled-channels effects. The model parameters that can be determined most effectively in the combined studies of both the single and double pion photoproduction data are identified for future studies.

  9. Double and single pion photoproduction within a dynamical coupled-channels model

    SciTech Connect

    Hiroyuki Kamano; Julia-Diaz, Bruno; Lee, T. -S. H.; Matsuyama, Akihiko; Sato, Toru

    2009-12-16

    Within a dynamical coupled-channels model which has already been fixed from analyzing the data of the πN → πN and γN → πN reactions, we present the predicted double pion photoproduction cross sections up to the second resonance region, W < 1.7 GeV. The roles played by the different mechanisms within our model in determining both the single and double pion photoproduction reactions are analyzed, focusing on the effects due to the direct γN → ππN mechanism, the interplay between the resonant and non-resonant amplitudes, and the coupled-channels effects. As a result, the model parameters which can be determined most effectively in the combined studies of both the single and double pion photoproduction data are identified for future studies.

  10. Double and single pion photoproduction within a dynamical coupled-channels model

    DOE PAGES

    Hiroyuki Kamano; Julia-Diaz, Bruno; Lee, T. -S. H.; Matsuyama, Akihiko; Sato, Toru

    2009-12-16

    Within a dynamical coupled-channels model which has already been fixed from analyzing the data of the πN → πN and γN → πN reactions, we present the predicted double pion photoproduction cross sections up to the second resonance region, W < 1.7 GeV. The roles played by the different mechanisms within our model in determining both the single and double pion photoproduction reactions are analyzed, focusing on the effects due to the direct γN → ππN mechanism, the interplay between the resonant and non-resonant amplitudes, and the coupled-channels effects. As a result, the model parameters which can be determined mostmore » effectively in the combined studies of both the single and double pion photoproduction data are identified for future studies.« less

  11. Operational calibration of the METEOSAT water vapor channel by calculated radiances.

    PubMed

    Schmetz, J

    1989-08-01

    A method is presented for calibrating the water vapor channel (5.7-7.1 microm) of the geostationary meteorological satellite METEOSAT by radiative transfer calculations. Radiances are calculated from the temperature and moisture profiles of conventional radiosondes and linearly related to collocated satellite measured digital counts. Collocations are considered only for areas with neither medium nor high level cloud. Radiosonde data are routinely received twice per day (1200 and 2400 UT). Radiosonde profiles from an 8-day period in May 1988, and simultaneous Meteosat-2 water vapor measurements are analyzed. The total of 340 collocations provides a calibration coefficient with a precision of 2% assuming a 95% confidence. A preliminary analysis of calibration coefficients of the recently launched METEOSAT-3 shows a significant increase of 6% over a period of 48 days in Sept./Oct. 1988. The calibrated water vapor radiances are operationally used to estimate the upper tropospheric humidity field and to correct the height assignment of semitransparent clouds.

  12. A method for calculating turbulent boundary layers and losses in the flow channels of turbomachines

    NASA Technical Reports Server (NTRS)

    Schumann, Lawrence F.

    1987-01-01

    An interactive inviscid core flow-boundary layer method is presented for the calculation of turbomachine channel flows. For this method, a one-dimensional inviscid core flow is assumed. The end-wall and blade surface boundary layers are calculated using an integral entrainment method. The boundary layers are assumed to be collateral and thus are two-dimensional. The boundary layer equations are written in a streamline coordinate system. The streamwise velocity profiles are approximated by power law profiles. Compressibility is accounted for in the streamwise direction but not in the normal direction. Equations are derived for the special cases of conical and two-dimensional rectangular diffusers. For these cases, the assumptions of a one-dimensional core flow and collateral boundary layers are valid. Results using the method are compared with experiment and good quantitative agreement is obtained.

  13. Effect of coupled channels on the energy dependence of phenomenological optical potential parameters

    NASA Astrophysics Data System (ADS)

    Al-Rayashi, W. S.; Jaghoub, M. I.

    2016-06-01

    The phenomenological optical potential parameters are known to vary with incident energy due to sources of nonlocalities in the nucleon-nucleus elastic scattering process. Here we investigate the effect of one source, which is coupling the ground-state elastic channel to collective inelastic excitations on the energy dependence of the optical potential parameters. For incident energies in the range 10-70 MeV, we considered elastic and inelastic nucleon scattering from light, medium, and heavy nuclei ranging from 6Li to 208Pb. The potential parameters were first determined by fitting the elastic angular distributions only. Then we included coupling to collective excitation channels and determined the potential parameters that reproduced the elastic and inelastic angular distribution data simultaneously. Our results show that coupling to inelastic excitations reduces the energy variations of the potential parameters compared to that of the elastic scattering case. In particular, the our best fit values for the real part of the spin-orbit term are highly stable as a function of energy. The values of the surface imaginary term are not only more stable but are also reduced compared to the elastic case. The reduction is a direct consequence of the channel coupling accounting explicitly for part of the flux removed from the elastic channel. In the fitting process we also searched for the best fit values of the deformation parameters. Our values compare well with the corresponding ones obtained in previous works. Finally, we used our best fit values for the potential and deformation parameters to theoretically predict the total elastic, total cross section, and polarization data. The predicted values are in very good agreement with the experimental data.

  14. Dynamical Coupled-Channel Model of Meson Production Reactions in the Nucleon Resonance Region

    SciTech Connect

    T.-S. H. Lee; A. Matsuyama; T. Sato

    2006-11-15

    A dynamical coupled-channel model is presented for investigating the nucleon resonances (N*) in the meson production reactions induced by pions and photons. Our objective is to extract the N* parameters and to investigate the meson production reaction mechanisms for mapping out the quark-gluon substructure of N* from the data. The model is based on an energy-independent Hamiltonian which is derived from a set of Lagrangians by using a unitary transformation method.

  15. Light-Quark Baryon Spectroscopy within ANL-Osaka Dynamical Coupled-Channels Approach

    NASA Astrophysics Data System (ADS)

    Kamano, Hiroyuki

    2016-10-01

    Recent results on the study of light-quark baryons with the ANL-Osaka dynamical coupled-channels (DCC) approach are presented, which contain the N^* and Δ ^* spectroscopy via the analysis of π N and γ N reactions and the Λ ^* and Σ ^* spectroscopy via the analysis of K^- p reactions. A recent application of our DCC approach to neutrino-nucleon reactions in the resonance region is also presented.

  16. Coupling between the voltage-sensing and pore domains in a voltage-gated potassium channel.

    PubMed

    Schow, Eric V; Freites, J Alfredo; Nizkorodov, Alex; White, Stephen H; Tobias, Douglas J

    2012-07-01

    Voltage-dependent potassium (Kv), sodium (Nav), and calcium channels open and close in response to changes in transmembrane (TM) potential, thus regulating cell excitability by controlling ion flow across the membrane. An outstanding question concerning voltage gating is how voltage-induced conformational changes of the channel voltage-sensing domains (VSDs) are coupled through the S4-S5 interfacial linking helices to the opening and closing of the pore domain (PD). To investigate the coupling between the VSDs and the PD, we generated a closed Kv channel configuration from Aeropyrum pernix (KvAP) using atomistic simulations with experiment-based restraints on the VSDs. Full closure of the channel required, in addition to the experimentally determined TM displacement, that the VSDs be displaced both inwardly and laterally around the PD. This twisting motion generates a tight hydrophobic interface between the S4-S5 linkers and the C-terminal ends of the pore domain S6 helices in agreement with available experimental evidence.

  17. Accurate collision-induced line-coupling parameters for the fundamental band of CO in He - Close coupling and coupled states scattering calculations

    NASA Technical Reports Server (NTRS)

    Green, Sheldon; Boissoles, J.; Boulet, C.

    1988-01-01

    The first accurate theoretical values for off-diagonal (i.e., line-coupling) pressure-broadening cross sections are presented. Calculations were done for CO perturbed by He at thermal collision energies using an accurate ab initio potential energy surface. Converged close coupling, i.e., numerically exact values, were obtained for coupling to the R(0) and R(2) lines. These were used to test the coupled states (CS) and infinite order sudden (IOS) approximate scattering methods. CS was found to be of quantitative accuracy (a few percent) and has been used to obtain coupling values for lines to R(10). IOS values are less accurate, but, owing to their simplicity, may nonetheless prove useful as has been recently demonstrated.

  18. Ferromagnetic spin coupling in the chromium dimer cation: Measurements by photodissociation spectroscopy combined with coupled-cluster calculations

    SciTech Connect

    Egashira, Kazuhiro; Yamada, Yurika; Kita, Yukiumi; Tachikawa, Masanori

    2015-02-07

    The magnetic coupling of the chromium dimer cation, Cr{sub 2}{sup +}, has been an outstanding problem for decades. An optical absorption spectrum of Cr{sub 2}{sup +} has been obtained by photodissociation spectroscopy in the photon-energy range from 2.0 to 5.0 eV. Besides, calculations have been performed by the equation-of-motion coupled-cluster singles and doubles method for vertical excitation of the species. Their coincidence supports our assignment that the ground electronic state exhibits a ferromagnetic spin coupling, which is contrary to those of neutral and negatively charged dimers, Cr{sub 2} and Cr{sub 2}{sup −}, in their lowest spin states.

  19. Calculation of correlation function of a spatially coupled spiking neural network

    NASA Astrophysics Data System (ADS)

    Qiu, Siwei; Chow, Carson

    The dynamics of a large but finite number of coupled spiking neurons is not well understood. We analyze finite size effects in a network of synaptically coupled theta neurons. We show how the system can be characterized by a functional integral from which finite size effects are calculated perturbatively. We discuss the implications of this technique for bump attractors. Thanks to support of the Intramural Research Program of the NIH, NIDDK.

  20. Calculation of nuclear spin-spin coupling constants using frozen density embedding

    SciTech Connect

    Götz, Andreas W.; Autschbach, Jochen; Visscher, Lucas

    2014-03-14

    We present a method for a subsystem-based calculation of indirect nuclear spin-spin coupling tensors within the framework of current-spin-density-functional theory. Our approach is based on the frozen-density embedding scheme within density-functional theory and extends a previously reported subsystem-based approach for the calculation of nuclear magnetic resonance shielding tensors to magnetic fields which couple not only to orbital but also spin degrees of freedom. This leads to a formulation in which the electron density, the induced paramagnetic current, and the induced spin-magnetization density are calculated separately for the individual subsystems. This is particularly useful for the inclusion of environmental effects in the calculation of nuclear spin-spin coupling constants. Neglecting the induced paramagnetic current and spin-magnetization density in the environment due to the magnetic moments of the coupled nuclei leads to a very efficient method in which the computationally expensive response calculation has to be performed only for the subsystem of interest. We show that this approach leads to very good results for the calculation of solvent-induced shifts of nuclear spin-spin coupling constants in hydrogen-bonded systems. Also for systems with stronger interactions, frozen-density embedding performs remarkably well, given the approximate nature of currently available functionals for the non-additive kinetic energy. As an example we show results for methylmercury halides which exhibit an exceptionally large shift of the one-bond coupling constants between {sup 199}Hg and {sup 13}C upon coordination of dimethylsulfoxide solvent molecules.

  1. Calculation of nuclear spin-spin coupling constants using frozen density embedding.

    PubMed

    Götz, Andreas W; Autschbach, Jochen; Visscher, Lucas

    2014-03-14

    We present a method for a subsystem-based calculation of indirect nuclear spin-spin coupling tensors within the framework of current-spin-density-functional theory. Our approach is based on the frozen-density embedding scheme within density-functional theory and extends a previously reported subsystem-based approach for the calculation of nuclear magnetic resonance shielding tensors to magnetic fields which couple not only to orbital but also spin degrees of freedom. This leads to a formulation in which the electron density, the induced paramagnetic current, and the induced spin-magnetization density are calculated separately for the individual subsystems. This is particularly useful for the inclusion of environmental effects in the calculation of nuclear spin-spin coupling constants. Neglecting the induced paramagnetic current and spin-magnetization density in the environment due to the magnetic moments of the coupled nuclei leads to a very efficient method in which the computationally expensive response calculation has to be performed only for the subsystem of interest. We show that this approach leads to very good results for the calculation of solvent-induced shifts of nuclear spin-spin coupling constants in hydrogen-bonded systems. Also for systems with stronger interactions, frozen-density embedding performs remarkably well, given the approximate nature of currently available functionals for the non-additive kinetic energy. As an example we show results for methylmercury halides which exhibit an exceptionally large shift of the one-bond coupling constants between (199)Hg and (13)C upon coordination of dimethylsulfoxide solvent molecules.

  2. Calculation Of The Interdiffusion Coefficient In The Cu-Zn Diffusion Couple

    NASA Astrophysics Data System (ADS)

    Hoxha, Adhurim; Oettel, Heinrich; Heger, Dietrich

    2010-01-01

    A quantitative analysis of multiphase diffusion in Cu-Zn diffusion couple is presented. The analysis is based in using the concentration profiles provided by electron micro-beam analyzer. From the dependence of the square of phase thickness from annealing time, the growth constant for each phase in each annealing temperature can be calculated. Knowing the growth constant of γ and ɛ phases one can calculate the activation energy and the diffusion coefficient of the above mentioned intermetallic phases.

  3. Coupled-channels density-matrix approach to low-energy nuclear collision dynamics: A technique for quantifying quantum decoherence effects on reaction observables

    SciTech Connect

    Diaz-Torres, Alexis

    2010-11-15

    The coupled-channels density-matrix technique for nuclear reaction dynamics, which is based on the Liouville-von Neumann equation with Lindblad dissipative terms, is developed with the inclusion of full angular momentum couplings. It allows a quantitative study of the role and importance of quantum decoherence in nuclear scattering. Formulas of asymptotic observables that can reveal effects of quantum decoherence are given. A method for extracting energy-resolved scattering information from the time-dependent density matrix is introduced. As an example, model calculations are carried out for the low-energy collision of the {sup 16}O projectile on the {sup 154}Sm target.

  4. The first-principle coupled calculations using TMCC and CFX for the pin-wise simulation of LWR

    SciTech Connect

    Li, L.; Wang, K.

    2012-07-01

    The coupling of neutronics and thermal-hydraulics plays an important role in the reactor safety, core design and operation of nuclear power facilities. This paper introduces the research on the coupling of Monte Carlo method and CFD method, specifically using TMCC and CFX. The methods of the coupling including the coupling approach, data transfer, mesh mapping and transient coupling scheme are studied firstly. The coupling of TMCC and CFX for the steady state calculations is studied and described for the single rod model and the 3 x 3 Rod Bundle model. The calculation results prove that the coupling method is feasible and the coupled calculation can be used for steady state calculations. However, the oscillation which occurs during the coupled calculation indicates that this method still needs to be improved for the accuracy. Then the coupling for the transient calculations is also studied and tested by two cases of the steady state and the lost of heat sink. The preliminary results of the transient coupled calculations indicates that the transient coupling with TMCC and CFX is able to simulate the transients but instabilities are occurring. It is also concluded that the transient coupling of TMCC and CFX needs to be improved due to the limitation of computational resource and the difference of time scales. (authors)

  5. Coupled-channel Treatment of Isobaric Analog Resonances in (p,p‧) Capture Processes

    NASA Astrophysics Data System (ADS)

    Thompson, I. J.; Arbanas, G.

    2014-04-01

    With the advent of nuclear reactions on unstable isotopes, there has been a renewed interest in using isobaric analogue resonances (IAR) as a tool for probing the nuclear structure. The position and width of isobaric analogue resonances in nucleon-nucleus scattering are accurate and detailed indicators of the positions of resonances and bound states with good single-particle characters. We report on implementation within our coupled-channels code FRESCO of the charge-exchange interaction term that transforms an incident proton into a neutron. Isobaric analog resonances are seen as peaks in γ-ray spectrum when the proton is transformed into a neutron at an energy near a neutron bound state. The Lane coupled-channels formalism was extended to follow the non-orthogonality of this neutron channel with that configuration of an inelastic outgoing proton, and the target being left in a particle-hole excited state. This is tested for 208Pb, for which good (p,p'γ) coincidence data exists.

  6. Coupled-channel treatment of Isobaric Analog Resonances in (p,p') Capture Processes

    SciTech Connect

    Thompson, I J; Arbanas, Goran

    2013-01-01

    With the advent of nuclear reactions on unstable isotopes, there has been a renewed interest in using isobaric analogue resonances (IAR) as a tool for probing the nuclear structure. The position and width of isobaric analogue resonances in nucleon-nucleus scattering are accurate and detailed indicators of the positions of resonances and bound states with good single-particle characters. We report on implementation within our coupled-channels code FRESCO of the charge-exchange interaction term that transforms an incident proton into a neutron. Isobaric analog resonances are seen as peaks in gamma-ray spectrum when the proton is transformed into a neutron at an energy near a neutron bound state. The Lane coupled-channels formalism was extended to follow the nonorthogonality of this neutron channel with that configuration of an inelastic outgoing proton, and the target being left in a particle-hole excited state. This is tested for 208Pb, for which good (p,p g)

  7. A generalized spin diffusion equation with four electrochemical potentials for channels with spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Sayed, Shehrin; Hong, Seokmin; Datta, Supriyo

    We will present a general semiclassical theory for an arbitrary channel with spin-orbit coupling (SOC), that uses four electrochemical potential (U + , D + , U - , and D -) depending on the sign of z-component of the spin (up (U) , down (D)) and the sign of the x-component of the group velocity (+ , -) . This can be considered as an extension of the standard spin diffusion equation that uses two electrochemical potentials for up and down spin states, allowing us to take into account the unique coupling between charge and spin degrees of freedom in channels with SOC. We will describe applications of this model to answer a number of interesting questions in this field such as: (1) whether topological insulators can switch magnets, (2) how the charge to spin conversion is influenced by the channel resistivity, and (3) how device structures can be designed to enhance spin injection. This work was supported by FAME, one of six centers of STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA.

  8. Spin Circuit Model for 2D Channels with Spin-Orbit Coupling

    NASA Astrophysics Data System (ADS)

    Hong, Seokmin; Sayed, Shehrin; Datta, Supriyo

    2016-03-01

    In this paper we present a general theory for an arbitrary 2D channel with “spin momentum locking” due to spin-orbit coupling. It is based on a semiclassical model that classifies all the channel electronic states into four groups based on the sign of the z-component of the spin (up (U), down (D)) and the sign of the x-component of the velocity (+, -). This could be viewed as an extension of the standard spin diffusion model which uses two separate electrochemical potentials for U and D states. Our model uses four: U+, D+, U-, and D-. We use this formulation to develop an equivalent spin circuit that is also benchmarked against a full non-equilibrium Green’s function (NEGF) model. The circuit representation can be used to interpret experiments and estimate important quantities of interest like the charge to spin conversion ratio or the maximum spin current that can be extracted. The model should be applicable to topological insulator surface states with parallel channels as well as to other layered structures with interfacial spin-orbit coupling.

  9. Spin Circuit Model for 2D Channels with Spin-Orbit Coupling.

    PubMed

    Hong, Seokmin; Sayed, Shehrin; Datta, Supriyo

    2016-01-01

    In this paper we present a general theory for an arbitrary 2D channel with "spin momentum locking" due to spin-orbit coupling. It is based on a semiclassical model that classifies all the channel electronic states into four groups based on the sign of the z-component of the spin (up (U), down (D)) and the sign of the x-component of the velocity (+, -). This could be viewed as an extension of the standard spin diffusion model which uses two separate electrochemical potentials for U and D states. Our model uses four: U+, D+, U-, and D-. We use this formulation to develop an equivalent spin circuit that is also benchmarked against a full non-equilibrium Green's function (NEGF) model. The circuit representation can be used to interpret experiments and estimate important quantities of interest like the charge to spin conversion ratio or the maximum spin current that can be extracted. The model should be applicable to topological insulator surface states with parallel channels as well as to other layered structures with interfacial spin-orbit coupling.

  10. Spin Circuit Model for 2D Channels with Spin-Orbit Coupling.

    PubMed

    Hong, Seokmin; Sayed, Shehrin; Datta, Supriyo

    2016-01-01

    In this paper we present a general theory for an arbitrary 2D channel with "spin momentum locking" due to spin-orbit coupling. It is based on a semiclassical model that classifies all the channel electronic states into four groups based on the sign of the z-component of the spin (up (U), down (D)) and the sign of the x-component of the velocity (+, -). This could be viewed as an extension of the standard spin diffusion model which uses two separate electrochemical potentials for U and D states. Our model uses four: U+, D+, U-, and D-. We use this formulation to develop an equivalent spin circuit that is also benchmarked against a full non-equilibrium Green's function (NEGF) model. The circuit representation can be used to interpret experiments and estimate important quantities of interest like the charge to spin conversion ratio or the maximum spin current that can be extracted. The model should be applicable to topological insulator surface states with parallel channels as well as to other layered structures with interfacial spin-orbit coupling. PMID:26932563

  11. A QCDSR calculation for the {phi}D{sub s}D{sub s} coupling constant

    SciTech Connect

    Rodrigues, B. O.; Chiapparini, M.; Bracco, M. E.

    2013-03-25

    In this work, we use the QCD Sum Rules (QCDSR) technique to obtain informations about the strong coupling constant of the three meson vertex {phi}D{sub s}D{sub s}. The calculation is done for the case where the {phi} meson is considered off-shell.

  12. Convergent close-coupling calculations of helium single ionization by antiproton impact

    SciTech Connect

    Abdurakhmanov, I. B.; Kadyrov, A. S.; Fursa, D. V.; Bray, I.; Stelbovics, A. T.

    2011-12-15

    We apply the fully quantum-mechanical convergent close-coupling method to the calculation of antiproton scattering on the ground state of helium. The helium target is treated as a three-body Coulomb system using frozen-core and multiconfiguration approximations. The electron-electron correlation of the target is fully treated in both cases. Though both calculations yield generally good agreement with experiment for the total ionization cross sections, the multiconfiguration results are substantially higher at the lower energies than the frozen-core ones. Calculated longitudinal ejected electron and recoil-ion momentum distributions for the single ionization of helium are in good agreement with the experiment.

  13. Heterologously expressed serotonin 1A receptors couple to muscarinic K+ channels in heart.

    PubMed Central

    Karschin, A; Ho, B Y; Labarca, C; Elroy-Stein, O; Moss, B; Davidson, N; Lester, H A

    1991-01-01

    In cardiac atrial cells, muscarinic acetylcholine receptors activate a K+ current directly via a guanine nucleotide-binding protein (G protein). Serotonin type 1A receptors may activate a similar pathway in hippocampal neurons. To develop a system in which receptor/G protein/K+ channel coupling can be experimentally manipulated, we have used a highly efficient recombinant vaccinia virus vector system to express human serotonin 1A receptors in primary cultures of rat atrial myocytes. The expressed 1A receptors activated the inwardly rectifying K+ conductance that is normally activated by the endogenous muscarinic acetylcholine receptors. Maximal responses to either agonist occluded further activation by the other agonist. The average activation time constants for serotonin were about 5 times slower than for acetylcholine. The data support suggestions that the intracellular signaling pathway from seven-helix receptors to G proteins and directly to ion channels is widespread in excitable cells. After a fraction of the G proteins are activated irreversibly by guanosine 5'-[gamma-thio]triphosphate, subsequent transduction proceeds more efficiently. One possible interpretation is that multiple G-protein molecules are required to activate each channel. Vaccinia virus expression vectors are thus useful for expressing seven-helix receptors in primary cultures of postmitotic cells and have provided a heterologous expression system for the signaling pathway from seven-helix receptors to G proteins and directly to ion channels. Images PMID:1905814

  14. Coupled-channel Dπ, Dη and {D}_soverline{K} scattering from lattice QCD

    NASA Astrophysics Data System (ADS)

    Moir, Graham; Peardon, Michael; Ryan, Sinéad M.; Thomas, Christopher E.; Wilson, David J.

    2016-10-01

    We present the first lattice QCD study of coupled-channel Dπ, Dη and {D}_soverline{K} scattering in isospin-1/2 in three partial waves. Using distillation, we compute matrices of correlation functions with bases of operators capable of resolving both meson and mesonmeson contributions to the spectrum. These correlation matrices are analysed using a variational approach to extract the finite-volume energy eigenstates. Utilising Lüscher's method and its extensions, we constrain scattering amplitudes in S, P and D-wave as a function of energy. By analytically continuing the scattering amplitudes to complex energies, we investigate the S-matrix singularities. Working at m π ≈ 391 MeV, we find a pole corresponding to a J P = 0+ near-threshold bound state with a large coupling to Dπ. We also find a deeply bound J P = 1- state, and evidence for a J P = 2+ narrow resonance coupled predominantly to Dπ. Elastic Dπ scattering in the isospin-3 /2 channel is studied and we find a weakly repulsive interaction in S-wave.

  15. Ab Initio Calculations of Spin-Orbit Coupling for Heavy-Metal Containing Radicals

    NASA Astrophysics Data System (ADS)

    Cheng, Lan

    2016-06-01

    The perturbative treatment of spin-orbit coupling (SOC) on top of scalar-relativistic calculations is a cost-effective alternative to rigorous fully relativistic calculations. In this work the applicability of the perturbative scheme in the framework of spin-free exact two-component theory is demonstrated with calculations of SO splittings and SOC contributions to molecular properties in small heavy-metal containing radicals, including AuO, AuS, and ThO^+. The equation of motion coupled cluster techniques have been used to accurately account for the electron-correlation effects in these radicals, and basis-set effects are carefully analyzed. The computed results are compared with experimental measurements for SO splittings and dipole moments when available.

  16. The photodissociation mechanisms of acrylonitrile: Ab initio calculations on reaction channels and surface intersections

    SciTech Connect

    Du Weina; Luo Cheng; Li Zesheng

    2008-11-07

    The dissociations of CH{sub 2}CHCN into CH{sub 2}CH+CN and CH{sub 2}C+HCN in the S{sub 0}, T{sub 1}, and {sup 1}{pi}{sub 2}{pi}{sub C{identical_to}}{sub N}* (definitions of {pi} orbitals can refer to computational details) states, have been explored at the complete active space self-consistent field level of theory employing the Dunning correlation consistent triple-zeta basis set. The lowest energy points of the surface crossing seams have been searched. Two conical intersections, from {sup 1}{pi}{sub C{identical_to}}{sub N}{pi}{sub 1}* to {sup 1}{pi}{sub 2}{pi}{sub 1}* (CI{sub 1}) and from {sup 1}{pi}{sub 2}{pi}{sub 1}* to S{sub 0} (CI{sub 2}), and one intersystem crossing point (T{sub 1}/S{sub 0}) have been located. The energies of all critical points have been recomputed with the multiconfigurational second-order perturbation method. At each conical intersection, derivative coupling and unscaled gradient difference vectors have been analyzed to determine the relaxation channels that the molecule may evolve in after nonradiative decay. Once the molecule is photoexcited to the {sup 1}{pi}{sub 2}{pi}{sub 1}* or {sup 1}{pi}{sub C{identical_to}}{sub N}{pi}{sub 1}* state, it would relax along the similar pathway: funneling through CI{sub 1} and then CI{sub 2}, and finally populate the ground state. Our results show that upon 193 nm photoexcitation, the most probable reaction channel is the ground-state HCN elimination following radiationless decays from excited states through surface crossings, which consists with experimental results J. Chem. Phys. 108, 5784 (1998). The investigated dissociation channels on the {sup 1}{pi}{sub 2}{pi}{sub C{identical_to}}{sub N}* surface, which are inaccessible upon 193 nm photoexcitation, may provide information for reactions induced by higher energy excitations.

  17. Operational calibration of the METEOSAT water vapor channel by calculated radiances.

    PubMed

    Schmetz, J

    1989-08-01

    A method is presented for calibrating the water vapor channel (5.7-7.1 microm) of the geostationary meteorological satellite METEOSAT by radiative transfer calculations. Radiances are calculated from the temperature and moisture profiles of conventional radiosondes and linearly related to collocated satellite measured digital counts. Collocations are considered only for areas with neither medium nor high level cloud. Radiosonde data are routinely received twice per day (1200 and 2400 UT). Radiosonde profiles from an 8-day period in May 1988, and simultaneous Meteosat-2 water vapor measurements are analyzed. The total of 340 collocations provides a calibration coefficient with a precision of 2% assuming a 95% confidence. A preliminary analysis of calibration coefficients of the recently launched METEOSAT-3 shows a significant increase of 6% over a period of 48 days in Sept./Oct. 1988. The calibrated water vapor radiances are operationally used to estimate the upper tropospheric humidity field and to correct the height assignment of semitransparent clouds. PMID:20555647

  18. CFD-CAA Coupled Calculations of a Tandem Cylinder Configuration to Assess Facility Installation Effects

    NASA Technical Reports Server (NTRS)

    Redonnet, Stephane; Lockard, David P.; Khorrami, Mehdi R.; Choudhari, Meelan M.

    2011-01-01

    This paper presents a numerical assessment of acoustic installation effects in the tandem cylinder (TC) experiments conducted in the NASA Langley Quiet Flow Facility (QFF), an open-jet, anechoic wind tunnel. Calculations that couple the Computational Fluid Dynamics (CFD) and Computational Aeroacoustics (CAA) of the TC configuration within the QFF are conducted using the CFD simulation results previously obtained at NASA LaRC. The coupled simulations enable the assessment of installation effects associated with several specific features in the QFF facility that may have impacted the measured acoustic signature during the experiment. The CFD-CAA coupling is based on CFD data along a suitably chosen surface, and employs a technique that was recently improved to account for installed configurations involving acoustic backscatter into the CFD domain. First, a CFD-CAA calculation is conducted for an isolated TC configuration to assess the coupling approach, as well as to generate a reference solution for subsequent assessments of QFF installation effects. Direct comparisons between the CFD-CAA calculations associated with the various installed configurations allow the assessment of the effects of each component (nozzle, collector, etc.) or feature (confined vs. free jet flow, etc.) characterizing the NASA LaRC QFF facility.

  19. On the pole content of coupled channels chiral approaches used for the K bar N system

    NASA Astrophysics Data System (ADS)

    Cieplý, A.; Mai, M.; Meißner, Ulf-G.; Smejkal, J.

    2016-10-01

    Several theoretical groups describe the antikaon-nucleon interaction at low energies within approaches based on the chiral SU(3) dynamics and including next-to-leading order contributions. We present a comparative analysis of the pertinent models and discuss in detail their pole contents. It is demonstrated that the approaches lead to very different predictions for the K- p amplitude extrapolated to subthreshold energies as well as for the K- n amplitude. The origin of the poles generated by the models is traced to the so-called zero coupling limit, in which the inter-channel couplings are switched off. This provides new insights into the pole contents of the various approaches. In particular, different concepts of forming the Λ (1405) resonance are revealed and constraints related to the appearance of such poles in a given approach are discussed.

  20. Control of Energy Density inside a Disordered Medium by Coupling to Open or Closed Channels.

    PubMed

    Sarma, Raktim; Yamilov, Alexey G; Petrenko, Sasha; Bromberg, Yaron; Cao, Hui

    2016-08-19

    We demonstrate experimentally the efficient control of light intensity distribution inside a random scattering system. The adaptive wave front shaping technique is applied to a silicon waveguide containing scattering nanostructures, and the on-chip coupling scheme enables access to all input spatial modes. By selectively coupling the incident light to the open or closed channels of the disordered system, we not only vary the total energy stored inside the system by a factor of 7.4, but also change the energy density distribution from an exponential decay to a linear decay and to a profile peaked near the center. This work provides an on-chip platform for controlling light-matter interactions in turbid media. PMID:27588875

  1. Control of Energy Density inside a Disordered Medium by Coupling to Open or Closed Channels

    NASA Astrophysics Data System (ADS)

    Sarma, Raktim; Yamilov, Alexey G.; Petrenko, Sasha; Bromberg, Yaron; Cao, Hui

    2016-08-01

    We demonstrate experimentally the efficient control of light intensity distribution inside a random scattering system. The adaptive wave front shaping technique is applied to a silicon waveguide containing scattering nanostructures, and the on-chip coupling scheme enables access to all input spatial modes. By selectively coupling the incident light to the open or closed channels of the disordered system, we not only vary the total energy stored inside the system by a factor of 7.4, but also change the energy density distribution from an exponential decay to a linear decay and to a profile peaked near the center. This work provides an on-chip platform for controlling light-matter interactions in turbid media.

  2. Non-empirical calculations of NMR indirect carbon-carbon coupling constants. Part 7--spiroalkanes.

    PubMed

    Krivdin, Leonid B

    2004-06-01

    Carbon-carbon spin-spin coupling constants were calculated at the SOPPA level for a series of seven classical spiroalkanes, spiro[2.2]pentane, spiro[2.3]hexane, spiro[2.4]heptane, spiro[2.5]octane, spiro[3.3]heptane, spiro[4.4]nonane and spiro[5.5]undecane, with special focus upon couplings involving and/or across spiro carbons. Many interesting structural trends were investigated originating in specific geometries and unusual bonding environments at the spiro carbon.

  3. Non–Ca2+-conducting Ca2+ channels in fish skeletal muscle excitation-contraction coupling

    PubMed Central

    Schredelseker, Johann; Shrivastav, Manisha; Dayal, Anamika; Grabner, Manfred

    2010-01-01

    During skeletal muscle excitation-contraction (EC) coupling, membrane depolarizations activate the sarcolemmal voltage-gated L-type Ca2+ channel (CaV1.1). CaV1.1 in turn triggers opening of the sarcoplasmic Ca2+ release channel (RyR1) via interchannel protein–protein interaction to release Ca2+ for myofibril contraction. Simultaneously to this EC coupling process, a small and slowly activating Ca2+ inward current through CaV1.1 is found in mammalian skeletal myotubes. The role of this Ca2+ influx, which is not immediately required for EC coupling, is still enigmatic. Interestingly, whole-cell patch clamp experiments on freshly dissociated skeletal muscle myotubes from zebrafish larvae revealed the lack of such Ca2+ currents. We identified two distinct isoforms of the pore-forming CaV1.1α1S subunit in zebrafish that are differentially expressed in superficial slow and deep fast musculature. Both do not conduct Ca2+ but merely act as voltage sensors to trigger opening of two likewise tissue-specific isoforms of RyR1. We further show that non-Ca2+ conductivity of both CaV1.1α1S isoforms is a common trait of all higher teleosts. This non-Ca2+ conductivity of CaV1.1 positions teleosts at the most-derived position of an evolutionary trajectory. Though EC coupling in early chordate muscles is activated by the influx of extracellular Ca2+, it evolved toward CaV1.1-RyR1 protein–protein interaction with a relatively small and slow influx of external Ca2+ in tetrapods. Finally, the CaV1.1 Ca2+ influx was completely eliminated in higher teleost fishes. PMID:20212109

  4. Dynamical coupled-channels model of {pi}N scattering in the W{<=}2 GeV nucleon resonance region

    SciTech Connect

    Julia-Diaz, B.; Lee, T.-S. H.; Matsuyama, A.; Sato, T.

    2007-12-15

    As a first step to analyze the electromagnetic meson production reactions in the nucleon resonance region, the parameters of the hadronic interactions of a dynamical coupled-channels model, developed in Physics Reports 439, 193 (2007), are determined by fitting the {pi}N-scattering data. The channels included in the calculations are {pi}N,{eta}N, and {pi}{pi}N, which has {pi}{delta},{rho}N, and {sigma}N resonant components. The nonresonant meson-baryon interactions of the model are derived from a set of Lagrangians by using a unitary transformation method. One or two bare excited nucleon states in each of S,P,D, and F partial waves are included to generate the resonant amplitudes in the fits. The parameters of the model are first determined by fitting as much as possible the empirical {pi}N elastic-scattering amplitudes of SAID up to 2 GeV. We then refine and confirm the resulting parameters by directly comparing the predicted differential cross section and target polarization asymmetry with the original data of the elastic {pi}{sup {+-}}p{yields}{pi}{sup {+-}}p and charge-exchange {pi}{sup -}p{yields}{pi}{sup 0}n processes. The predicted total cross sections of {pi}N reactions and {pi}N{yields}{eta}N reactions are also in good agreement with the data. Applications of the constructed model in analyzing the electromagnetic meson production data as well as the future developments are discussed.

  5. Dynamical Coupled-Channel Model of pi-N scattering in te W < 2 GeV Nucleon Resonane Region

    SciTech Connect

    Lee, T S.H.; Julia-diaz, B; Matsuyama, A; Sato, T

    2007-12-01

    As a first step to analyze the electromagnetic meson production reactions in the nucleon resonance region, the parameters of the hadronic interactions of a dynamical coupled-channel model, developed in {\\it Physics Reports 439, 193 (2007)}, are determined by fitting the empirical $\\pi N$ elastic scattering amplitudes of SAID up to 2 GeV. The channels included in the calculations are $\\pi N$, $\\eta N$ and $\\pi\\pi N$ which has $\\pi\\Delta$, $\\rho N$, and $\\sigma N$ resonant components. The non-resonant meson-baryon interactions of the model are derived from a set of Lagrangians by using a unitary transformation method. One or two bare excited nucleon states in each of $S$, $P$, $D$, and $F$ partial waves are included to generate the resonant amplitudes in the fits. The predicted total cross sections of $\\pi N$ reactions and $\\pi N\\rightarrow \\eta N$ reactions are in good agreement with the data. Applications of the constructed model in analyzing the electromagnetic meson production data as well as the future developments are discussed.

  6. Cell-Transistor Coupling: Investigation of Potassium Currents Recorded with p- and n-Channel FETs

    PubMed Central

    Wrobel, Günter; Seifert, Reinhard; Ingebrandt, Sven; Enderlein, Jörg; Ecken, Holger; Baumann, Arnd; Kaupp, U. Benjamin; Offenhäusser, Andreas

    2005-01-01

    Microelectronic-based biosensors that allow noninvasive measurement of cell activity are in the focus of current developments, however, the mechanisms underlying the cell-transistor coupling are not completely understood. In particular, characteristic properties of the extracellular voltage response such as the waveform and amplitude are not satisfactorily described by electrical circuit models. Here we examine the electrical coupling between a nonmetallized field-effect transistor (FET) and a cell line expressing a voltage-gated EAG K+ channel. The activation kinetics of this channel depends on the voltage pulse protocol and extracellular divalent cations. This feature allows testing, whether the extracellular voltage signal recorded with the FET faithfully tracks the current simultaneously recorded with the patch-clamp technique. We find that the FET signals contain different kinetic components that cannot be entirely explained by equivalent electrical-circuit models. Rather, we suggest that changes in ion concentration in the small cleft between cell and FET may change the surface potential of the FET. This study provides evidence that the electrochemical processes at the cell-transistor interface are complex and that at least two different mechanisms contribute to the shape and amplitude of transistor signals. PMID:16100284

  7. Postirradiation behavior of p-channel charge-coupled devices irradiated at 153 K

    NASA Astrophysics Data System (ADS)

    Gow, Jason P. D.; Wood, Daniel; Murray, Neil J.; Burt, David; Hall, David J.; Dryer, Ben; Holland, Andrew D.

    2016-04-01

    The displacement damage hardness that can be achieved using p-channel charge-coupled devices (CCD) was originally demonstrated in 1997, and since then a number of other studies have demonstrated an improved tolerance to radiation-induced charge transfer inefficiency when compared to n-channel CCDs. A number of recent studies have also shown that the temperature history of the device after the irradiation impacts the performance of the detector, linked to the mobility of defects at different temperatures. The initial results from an e2v technologies p-channel CCD204 irradiated at 153 K with 10-MeV equivalent proton fluences of 1.24×109 and 1.24×1011 protons cm-2 is described. The dark current, cosmetic quality, and the number of defects identified using trap pumping immediately were monitored after the irradiation for a period of 150 h with the device held at 153 K and then after different periods of time at room temperature. The device also exhibited a flatband voltage shift of around 30 mV/krad, determined by the reduction in full well capacity.

  8. Coupled-channels quantum theory of electronic flux density in electronically adiabatic processes: fundamentals.

    PubMed

    Diestler, D J

    2012-03-22

    The Born-Oppenheimer (BO) description of electronically adiabatic molecular processes predicts a vanishing electronic flux density (j(e)), =1/2∫dR[Δ(b) (x;R) - Δ(a) (x;R)] even though the electrons certainly move in response to the movement of the nuclei. This article, the first of a pair, proposes a quantum-mechanical "coupled-channels" (CC) theory that allows the approximate extraction of j(e) from the electronically adiabatic BO wave function . The CC theory is detailed for H(2)(+), in which case j(e) can be resolved into components associated with two channels α (=a,b), each of which corresponds to the "collision" of an "internal" atom α (proton a or b plus electron) with the other nucleus β (proton b or a). The dynamical role of the electron, which accommodates itself instantaneously to the motion of the nuclei, is submerged in effective electronic probability (population) densities, Δ(α), associated with each channel (α). The Δ(α) densities are determined by the (time-independent) BO electronic energy eigenfunction, which depends parametrically on the configuration of the nuclei, the motion of which is governed by the usual BO nuclear Schrödinger equation. Intuitively appealing formal expressions for the electronic flux density are derived for H(2)(+).

  9. Calculation of hyperfine coupling constant by symmetry adapted cluster expansion configuration interaction theory. II. Anisotropic constants

    NASA Astrophysics Data System (ADS)

    Momose, Takamasa; Yamaguchi, Makoto; Shida, Tadamasa

    1990-11-01

    Following the previous work on the isotropic hyperfine coupling constants (HFCCs) of polyatomic radicals the symmetry adapted cluster expansion-configuration interaction (SAC-CI) theory is applied to calculate anisotropic HFCCs also. The results are compared with available experimental data from diatomic to polyatomic radicals such as the vinoxy. For radicals consisting of only the first row atoms Dunning's double zeta (DZ) basis set is shown to be adequate, but for those containing the second row atoms inclusion of polarization functions is required. Compared with the isotropic HFCC the calculation of the anisotropic HFCC is less formidable. However, ignorance of electron correlation causes serious disagreements with experimental data.

  10. Viscosity calculated in simulations of strongly coupled dusty plasmas with gas friction

    SciTech Connect

    Feng Yan; Goree, J.; Liu Bin

    2011-05-15

    A two-dimensional strongly coupled dusty plasma is modeled using Langevin and frictionless molecular dynamical simulations. The static viscosity {eta} and the wave-number-dependent viscosity {eta}(k) are calculated from the microscopic shear in the random motion of particles. A recently developed method of calculating the wave-number-dependent viscosity {eta}(k) is validated by comparing the results of {eta}(k) from the two simulations. It is also verified that the Green-Kubo relation can still yield an accurate measure of the static viscosity {eta} in the presence of a modest level of friction as in dusty plasma experiments.

  11. A coupling model of the radiative transport equation for calculating photon migration in biological tissue

    NASA Astrophysics Data System (ADS)

    Fujii, Hiroyuki; Okawa, Shinpei; Yamada, Yukio; Hoshi, Yoko; Watanabe, Masao

    2015-12-01

    Development of a physically accurate and computationally efficient photon migration model for turbid media is crucial for optical computed tomography such as diffuse optical tomography. For the development, this paper constructs a space-time coupling model of the radiative transport equation with the photon diffusion equation. In the coupling model, a space-time regime of the photon migration is divided into the ballistic and diffusive regimes with the interaction between the both regimes to improve the accuracy of the results and the efficiency of computation. The coupling model provides an accurate description of the photon migration in various turbid media in a wide range of the optical properties, and reduces computational loads when compared with those of full calculation of the RTE.

  12. Distributed Multipolar Expansion Approach to Calculation of Excitation Energy Transfer Couplings.

    PubMed

    Błasiak, Bartosz; Maj, Michał; Cho, Minhaeng; Góra, Robert W

    2015-07-14

    We propose a new approach for estimating the electrostatic part of the excitation energy transfer (EET) coupling between electronically excited chromophores based on the transition density-derived cumulative atomic multipole moments (TrCAMM). In this approach, the transition potential of a chromophore is expressed in terms of truncated distributed multipolar expansion and analytical formulas for the TrCAMMs are derived. The accuracy and computational feasibility of the proposed approach is tested against the exact Coulombic couplings, and various multipole expansion truncation schemes are analyzed. The results of preliminary calculations show that the TrCAMM approach is capable of reproducing the exact Coulombic EET couplings accurately and efficiently and is superior to other widely used schemes: the transition charges from electrostatic potential (TrESP) and the transition density cube (TDC) method.

  13. Accurate calculation of Stokes drag for point-particle tracking in two-way coupled flows

    NASA Astrophysics Data System (ADS)

    Horwitz, J. A. K.; Mani, A.

    2016-08-01

    In this work, we propose and test a method for calculating Stokes drag applicable to particle-laden fluid flows where two-way momentum coupling is important. In the point-particle formulation, particle dynamics are coupled to fluid dynamics via a source term that appears in the respective momentum equations. When the particle Reynolds number is small and the particle diameter is smaller than the fluid scales, it is common to approximate the momentum coupling source term as the Stokes drag. The Stokes drag force depends on the difference between the undisturbed fluid velocity evaluated at the particle location, and the particle velocity. However, owing to two-way coupling, the fluid velocity is modified in the neighborhood of a particle, relative to its undisturbed value. This causes the computed Stokes drag force to be underestimated in two-way coupled point-particle simulations. We develop estimates for the drag force error as function of the particle size relative to the grid size. Because the disturbance field created by the particle contaminates the surrounding fluid, correctly calculating the drag force cannot be done solely by direct interpolation of the fluid velocity. Instead, we develop a correction method that calculates the undisturbed fluid velocity from the computed disturbed velocity field by adding an estimate of the velocity disturbance created by the particle. The correction scheme is tested for a particle settling in an otherwise quiescent fluid and is found to reduce the error in computed settling velocity by an order of magnitude compared with common interpolation schemes.

  14. Current status of a coupled-channel partial wave analysis using data from CLAS at Jefferson Lab

    SciTech Connect

    M. Bellis, Z. Krahn, M. McCracken, C. Meyer and M. Williams

    2009-04-01

    The non-strange baryon spectrum has been mapped out predominantly by studying N π elastic scattering with phase-shift analysis as the tool of choice. While there has been much success with these experimental techniques, the results have fueled debates in the community, most notably regarding the missing baryons problem. Theoretical solutions to this discrepancy appeal to a diquark-system within the baryons or a coupling to states other than N π. The CLAS detector at Jefferson Lab has turned out high-statistics, photoproduction datasets which are optimal for resolving these issues. However, new analytical techniques may be required to deal with this rich physics sector. The baryon resonances are photoproduced off liquid hydrogen and the CLAS detector allows us to measure a variety of final states. We will have access to nπ +, pπ 0, pπ + π −, pω,pη, pη′, ΛK + and ΣK + final states. A robust software package has been developed that allows for the fitting of these states individually and in a coupled-channel mode. We make use of flexible C++ based tools that allow fast and general calculations of amplitudes based on a covariant tensor formalism. New techniques have been applied to background subtraction which brings an added level of consistency to the analysis. Polarization information from other experiments is incorporated at fit time to help distinguish potentially ambiguous physics processes by using information outside of the CLAS datasets. Some of these channels have more mature analysis (pω,ΛK +) and the preliminary measuremen will be shown as well as an overview of the analysis tools.

  15. Calculations of spin-spin coupling constants in aromatic nitrogen heterocyclics

    NASA Astrophysics Data System (ADS)

    Long, S. A. T.; Memory, J. D.

    HH, CH, NH, CC, and NC spin-spin coupling constants were calculated using the FP-INDO method and the Fermi contact interaction for pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, quinoline, quinoxaline, phthalazine, isoquinoline, cinnoline, quinazoline, acridine, phenazine, benzo[ g]quinoxaline, and benzo[ b]-phenazine. The agreement between theory and experiment was comparable to that for polynuclear aromatic hydrocarbons reported earlier.

  16. Measurements and coupled reaction channels analysis of one and two proton transfer reactions for 28Si+90,94Zr systems

    NASA Astrophysics Data System (ADS)

    Kalkal, Sunil; Mandal, S.; Jhingan, A.; Gehlot, J.; Sugathan, P.; Golda, K. S.; Madhavan, N.; Garg, Ritika; Goyal, Savi; Mohanto, Gayatri; Verma, S.; Sandal, Rohit; Behera, Bivash; Eleonora, G.; Wollersheim, H. J.; Singh, R.

    2011-10-01

    Measurements of angular distributions for one and two proton stripping reactions for 28Si+90,94Zr systems were performed at lab energy 120 MeV with 28Si beam at Inter University Accelerator Center, New Delhi. Theoretical calculations performed using the quantum mechanical coupled reaction channels code FRESCO (including various intermediate states involving target and projectile excitations before and/or after transfer along with sequential transfer) were able to reproduce one and two proton transfer angular distributions for both the systems reasonably well. It was found that the DWBA calculations could describe the one proton transfer data well for both the systems but failed to reproduce the angular distributions for two proton transfer channels. The present measurements underline the importance of sequential transfer at energies much above the Coulomb barrier. We had also performed transfer reaction measurements for these systems in the sub- and near barrier region using recoil mass separator.

  17. Development of a coupling code for PWR reactor cavity radiation streaming calculation

    SciTech Connect

    Zheng, Z.; Wu, H.; Cao, L.; Zheng, Y.; Zhang, H.; Wang, M.

    2012-07-01

    PWR reactor cavity radiation streaming is important for the safe of the personnel and equipment, thus calculation has to be performed to evaluate the neutron flux distribution around the reactor. For this calculation, the deterministic codes have difficulties in fine geometrical modeling and need huge computer resource; and the Monte Carlo codes require very long sampling time to obtain results with acceptable precision. Therefore, a coupling method has been developed to eliminate the two problems mentioned above in each code. In this study, we develop a coupling code named DORT2MCNP to link the Sn code DORT and Monte Carlo code MCNP. DORT2MCNP is used to produce a combined surface source containing top, bottom and side surface simultaneously. Because SDEF card is unsuitable for the combined surface source, we modify the SOURCE subroutine of MCNP and compile MCNP for this application. Numerical results demonstrate the correctness of the coupling code DORT2MCNP and show reasonable agreement between the coupling method and the other two codes (DORT and MCNP). (authors)

  18. Interaction of Galphaq and Kir3, G protein-coupled inwardly rectifying potassium channels.

    PubMed

    Kawano, Takeharu; Zhao, Peng; Floreani, Christina V; Nakajima, Yasuko; Kozasa, Tohru; Nakajima, Shigehiro

    2007-04-01

    Activation of substance P receptors, which are coupled to Galpha(q), inhibits the Kir3.1/3.2 channels, resulting in neuronal excitation. We have shown previously that this channel inactivation is not caused by reduction of the phosphatidylinositol 4,5-bisphosphate level in membrane. Moreover, Galpha(q) immunoprecipitates with Kir3.2 (J Physiol 564:489-500, 2005), suggesting that Galpha(q) interacts with Kir3.2. Positive immunoprecipitation, however, does not necessarily indicate direct interaction between the two proteins. Here, the glutathione transferase pull-down assay was used to investigate interaction between Galpha(q) and the K(+) channels. We found that Galpha(q) interacted with N termini of Kir3.1, Kir3.2, and Kir3.4. However, Galpha(q) did not interact with the C terminus of any Kir3 or with the C or N terminus of Kir2.1. TRPC6 is regulated by the signal initiated by Galpha(q). Immunoprecipitation, however, showed that Galpha(q) did not interact with TRPC6. Thus, the interaction between Galpha(q) and the Kir3 N terminus is quite specific. This interaction occurred in the presence of GDP or GDP-AlF(-)(4). The Galpha(q) binding could take place somewhere between residues 51 to 90 of Kir3.2; perhaps the segment between 81 to 90 residues is crucial. Gbetagamma, which is known to bind to N terminus of Kir3, did not compete with Galpha(q) for the binding, suggesting that these two binding regions are different. These findings agree with the hypothesis (J Physiol 564:489-500, 2005) that the signal to inactivate the Kir3 channel could be mainly transmitted directly from Galpha(q) to Kir3. PMID:17296805

  19. Mechanical coupling of the multiple structural elements of the large-conductance mechanosensitive channel during expansion

    PubMed Central

    Li, Jie; Guo, Jianli; Ou, Xiaomin; Zhang, Mingfeng; Li, Yuezhou; Liu, Zhenfeng

    2015-01-01

    The prokaryotic mechanosensitive channel of large conductance (MscL) is a pressure-relief valve protecting the cell from lysing during acute osmotic downshock. When the membrane is stretched, MscL responds to the increase of membrane tension and opens a nonselective pore to about 30 Å wide, exhibiting a large unitary conductance of ∼3 nS. A fundamental step toward understanding the gating mechanism of MscL is to decipher the molecular details of the conformational changes accompanying channel opening. By applying fusion-protein strategy and controlling detergent composition, we have solved the structures of an archaeal MscL homolog from Methanosarcina acetivorans trapped in the closed and expanded intermediate states. The comparative analysis of these two new structures reveals significant conformational rearrangements in the different domains of MscL. The large changes observed in the tilt angles of the two transmembrane helices (TM1 and TM2) fit well with the helix-pivoting model derived from the earlier geometric analyses based on the previous structures. Meanwhile, the periplasmic loop region transforms from a folded structure, containing an ω-shaped loop and a short β-hairpin, to an extended and partly disordered conformation during channel expansion. Moreover, a significant rotating and sliding of the N-terminal helix (N-helix) is coupled to the tilting movements of TM1 and TM2. The dynamic relationships between the N-helix and TM1/TM2 suggest that the N-helix serves as a membrane-anchored stopper that limits the tilts of TM1 and TM2 in the gating process. These results provide direct mechanistic insights into the highly coordinated movement of the different domains of the MscL channel when it expands. PMID:26261325

  20. Terrestrial LiDAR monitoring of rock slope-channel coupling

    NASA Astrophysics Data System (ADS)

    Bell, R.; Blöthe, J. H.; Meyer, N. K.; Hoffmann, T.; Hoffert, H.; Kreiner, D.; Elverfeldt, K. V.

    2009-04-01

    In steep terrain, various types of landslides (e.g. rock falls, debris flows and slides) are important erosional processes which often have a major impact on fluvial systems. On the one hand, they may divert river channels to opposite slopes or even block entire river channels, leading to the formation of landslide-dammed lakes. On the other hand, rivers prepare or even trigger landslides by undercutting slopes, which again will have an impact on the river channel. Our focus is on two study areas. One of them, the Schlichem Valley, is located in the Swabian Alb (SW-Germany), a lower mountain range consisting of Jurassic sedimentary rocks forming a cuesta landscape. There, the focus is on a larger landslide complex which blocked the river Schlichem three times during the 18th century and which is still active. Recent activity, especially at the location where the landslide enters the fluvial system, is investigated using Terrestrial LiDAR monitoring. The second study area is located in the Gesaeuse National Park in the Austrian Alps. There, various geomorphic environments are investigated by Terrestrial LiDAR including a vertical rock face in Dachstein limestone, which talus slope is directly coupled to the river Enns. The talus slope is built up by rock fall deposits, eroded mainly through smaller debris flow events. Furthermore, the talus slope is undercut by flood events of the river Enns. In this study a concept and first results are presented. They suggest how rock slope processes and their interactions with river channels can be monitored.

  1. Renormalization effects on the MSSM from a calculable model of a strongly coupled hidden sector

    SciTech Connect

    Arai, Masato; Okada, Nobuchika

    2011-10-01

    We investigate possible renormalization effects on the low-energy mass spectrum of the minimal supersymmetric standard model (MSSM), using a calculable model of strongly coupled hidden sector. We model the hidden sector by N=2 supersymmetric quantum chromodynamics with gauge group SU(2)xU(1) and N{sub f}=2 matter hypermultiplets, perturbed by a Fayet-Iliopoulos term which breaks the supersymmetry down to N=0 on a metastable vacuum. In the hidden sector the Kaehler potential is renormalized. Upon identifying a hidden sector modulus with the renormalization scale, and extrapolating to the strongly coupled regime using the Seiberg-Witten solution, the contribution from the hidden sector to the MSSM renormalization group flows is computed. For concreteness, we consider a model in which the renormalization effects are communicated to the MSSM sector via gauge mediation. In contrast to the perturbative toy examples of hidden sector renormalization studied in the literature, we find that our strongly coupled model exhibits rather intricate effects on the MSSM soft scalar mass spectrum, depending on how the hidden sector fields are coupled to the messenger fields. This model provides a concrete example in which the low-energy spectrum of MSSM particles that are expected to be accessible in collider experiments is obtained using strongly coupled hidden sector dynamics.

  2. Functional coupling between sodium-activated potassium channels and voltage-dependent persistent sodium currents in cricket Kenyon cells

    PubMed Central

    Takahashi, Izumi

    2015-01-01

    In this study, we examined the functional coupling between Na+-activated potassium (KNa) channels and Na+ influx through voltage-dependent Na+ channels in Kenyon cells isolated from the mushroom body of the cricket Gryllus bimaculatus. Single-channel activity of KNa channels was recorded with the cell-attached patch configuration. The open probability (Po) of KNa channels increased with increasing Na+ concentration in a bath solution, whereas it decreased by the substitution of Na+ with an equimolar concentration of Li+. The Po of KNa channels was also found to be reduced by bath application of a high concentration of TTX (1 μM) and riluzole (100 μM), which inhibits both fast (INaf) and persistent (INaP) Na+ currents, whereas it was unaffected by a low concentration of TTX (10 nM), which selectively blocks INaf. Bath application of Cd2+ at a low concentration (50 μM), as an inhibitor of INaP, also decreased the Po of KNa channels. Conversely, bath application of the inorganic Ca2+-channel blockers Co2+ and Ni2+ at high concentrations (500 μM) had little effect on the Po of KNa channels, although Cd2+ (500 μM) reduced the Po of KNa channels. Perforated whole cell clamp analysis further indicated the presence of sustained outward currents for which amplitude was dependent on the amount of Na+ influx. Taken together, these results indicate that KNa channels could be activated by Na+ influx passing through voltage-dependent persistent Na+ channels. The functional significance of this coupling mechanism was discussed in relation to the membrane excitability of Kenyon cells and its possible role in the formation of long-term memory. PMID:26269549

  3. Spin-orbit couplings within the equation-of-motion coupled-cluster framework: Theory, implementation, and benchmark calculations.

    PubMed

    Epifanovsky, Evgeny; Klein, Kerstin; Stopkowicz, Stella; Gauss, Jürgen; Krylov, Anna I

    2015-08-14

    We present a formalism and an implementation for calculating spin-orbit couplings (SOCs) within the EOM-CCSD (equation-of-motion coupled-cluster with single and double substitutions) approach. The following variants of EOM-CCSD are considered: EOM-CCSD for excitation energies (EOM-EE-CCSD), EOM-CCSD with spin-flip (EOM-SF-CCSD), EOM-CCSD for ionization potentials (EOM-IP-CCSD) and electron attachment (EOM-EA-CCSD). We employ a perturbative approach in which the SOCs are computed as matrix elements of the respective part of the Breit-Pauli Hamiltonian using zeroth-order non-relativistic wave functions. We follow the expectation-value approach rather than the response-theory formulation for property calculations. Both the full two-electron treatment and the mean-field approximation (a partial account of the two-electron contributions) have been implemented and benchmarked using several small molecules containing elements up to the fourth row of the periodic table. The benchmark results show the excellent performance of the perturbative treatment and the mean-field approximation. When used with an appropriate basis set, the errors with respect to experiment are below 5% for the considered examples. The findings regarding basis-set requirements are in agreement with previous studies. The impact of different correlation treatment in zeroth-order wave functions is analyzed. Overall, the EOM-IP-CCSD, EOM-EA-CCSD, EOM-EE-CCSD, and EOM-SF-CCSD wave functions yield SOCs that agree well with each other (and with the experimental values when available). Using an EOM-CCSD approach that provides a more balanced description of the target states yields more accurate results. PMID:26277122

  4. Spin-orbit couplings within the equation-of-motion coupled-cluster framework: Theory, implementation, and benchmark calculations

    SciTech Connect

    Epifanovsky, Evgeny; Klein, Kerstin; Gauss, Jürgen; Stopkowicz, Stella; Krylov, Anna I.

    2015-08-14

    We present a formalism and an implementation for calculating spin-orbit couplings (SOCs) within the EOM-CCSD (equation-of-motion coupled-cluster with single and double substitutions) approach. The following variants of EOM-CCSD are considered: EOM-CCSD for excitation energies (EOM-EE-CCSD), EOM-CCSD with spin-flip (EOM-SF-CCSD), EOM-CCSD for ionization potentials (EOM-IP-CCSD) and electron attachment (EOM-EA-CCSD). We employ a perturbative approach in which the SOCs are computed as matrix elements of the respective part of the Breit-Pauli Hamiltonian using zeroth-order non-relativistic wave functions. We follow the expectation-value approach rather than the response-theory formulation for property calculations. Both the full two-electron treatment and the mean-field approximation (a partial account of the two-electron contributions) have been implemented and benchmarked using several small molecules containing elements up to the fourth row of the periodic table. The benchmark results show the excellent performance of the perturbative treatment and the mean-field approximation. When used with an appropriate basis set, the errors with respect to experiment are below 5% for the considered examples. The findings regarding basis-set requirements are in agreement with previous studies. The impact of different correlation treatment in zeroth-order wave functions is analyzed. Overall, the EOM-IP-CCSD, EOM-EA-CCSD, EOM-EE-CCSD, and EOM-SF-CCSD wave functions yield SOCs that agree well with each other (and with the experimental values when available). Using an EOM-CCSD approach that provides a more balanced description of the target states yields more accurate results.

  5. Spin-orbit couplings within the equation-of-motion coupled-cluster framework: Theory, implementation, and benchmark calculations

    NASA Astrophysics Data System (ADS)

    Epifanovsky, Evgeny; Klein, Kerstin; Stopkowicz, Stella; Gauss, Jürgen; Krylov, Anna I.

    2015-08-01

    We present a formalism and an implementation for calculating spin-orbit couplings (SOCs) within the EOM-CCSD (equation-of-motion coupled-cluster with single and double substitutions) approach. The following variants of EOM-CCSD are considered: EOM-CCSD for excitation energies (EOM-EE-CCSD), EOM-CCSD with spin-flip (EOM-SF-CCSD), EOM-CCSD for ionization potentials (EOM-IP-CCSD) and electron attachment (EOM-EA-CCSD). We employ a perturbative approach in which the SOCs are computed as matrix elements of the respective part of the Breit-Pauli Hamiltonian using zeroth-order non-relativistic wave functions. We follow the expectation-value approach rather than the response-theory formulation for property calculations. Both the full two-electron treatment and the mean-field approximation (a partial account of the two-electron contributions) have been implemented and benchmarked using several small molecules containing elements up to the fourth row of the periodic table. The benchmark results show the excellent performance of the perturbative treatment and the mean-field approximation. When used with an appropriate basis set, the errors with respect to experiment are below 5% for the considered examples. The findings regarding basis-set requirements are in agreement with previous studies. The impact of different correlation treatment in zeroth-order wave functions is analyzed. Overall, the EOM-IP-CCSD, EOM-EA-CCSD, EOM-EE-CCSD, and EOM-SF-CCSD wave functions yield SOCs that agree well with each other (and with the experimental values when available). Using an EOM-CCSD approach that provides a more balanced description of the target states yields more accurate results.

  6. Rod image: a new method for the calculation of pump efficiency in reflecting close-coupled cavities

    SciTech Connect

    Docchio, F.

    1985-11-15

    Reflecting close-coupling cavities for solid-state lasers often provide beams of better quality, although with a slightly lower efficiency compared with those of the usual ellipticl cavities. A new method for the calculation efficiency in reflecting close-coupled cavities is proposed. Examples of efficiency calculations are discussed.

  7. Efficient Calculations of Dispersion Energies for Nanoscale Systems from Coupled Density Response Functions.

    PubMed

    Podeszwa, Rafał; Cencek, Wojciech; Szalewicz, Krzysztof

    2012-06-12

    Dispersion energies computed from coupled Kohn-Sham (CKS) dynamic density-density response functions are known to be highly accurate. At the same time, the computational algorithm is of only modest complexity compared to other accurate methods of dispersion energy calculation. We present a new implementation of this algorithm that removes several computational barriers present in current implementations and enables calculations of dispersion energies for systems with more than 200 atoms using more than 5000 basis functions. The improvements were mainly achieved by reorganizing the algorithm to minimize memory and disk usage. We present applications to two systems: the buckycatcher complex with fullerene and the vancomycin complex with a diacetyl-Lys-d-Ala-d-Ala bacterial wall precursor, both calculations performed with triple-ζ-quality basis sets. Our implementation makes it possible to use ab initio computed dispersion energies in popular "density functional theory plus dispersion" approaches.

  8. Influence of channel base current and varying return stroke speed on the calculated fields of three important return stroke models

    NASA Technical Reports Server (NTRS)

    Thottappillil, Rajeev; Uman, Martin A.; Diendorfer, Gerhard

    1991-01-01

    Compared here are the calculated fields of the Traveling Current Source (TCS), Modified Transmission Line (MTL), and the Diendorfer-Uman (DU) models with a channel base current assumed in Nucci et al. on the one hand and with the channel base current assumed in Diendorfer and Uman on the other hand. The characteristics of the field wave shapes are shown to be very sensitive to the channel base current, especially the field zero crossing at 100 km for the TCS and DU models, and the magnetic hump after the initial peak at close range for the TCS models. Also, the DU model is theoretically extended to include any arbitrarily varying return stroke speed with height. A brief discussion is presented on the effects of an exponentially decreasing speed with height on the calculated fields for the TCS, MTL, and DU models.

  9. Effects on calculated half-widths and shifts from the line coupling for asymmetric-top molecules

    NASA Astrophysics Data System (ADS)

    Ma, Q.; Boulet, C.; Tipping, R. H.

    2014-06-01

    The refinement of the Robert-Bonamy formalism by considering the line coupling for linear molecules developed in our previous studies [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013); 140, 104304 (2014)] have been extended to asymmetric-top molecules. For H2O immersed in N2 bath, the line coupling selection rules applicable for the pure rotational band to determine whether two specified lines are coupled or not are established. Meanwhile, because the coupling strengths are determined by relative importance of off-diagonal matrix elements versus diagonal elements of the operator -iS1 - S2, quantitative tools are developed with which one is able to remove weakly coupled lines from consideration. By applying these tools, we have found that within reasonable tolerances, most of the H2O lines in the pure rotational band are not coupled. This reflects the fact that differences of energy levels of the H2O states are pretty large. But, there are several dozen strongly coupled lines and they can be categorized into different groups such that the line couplings occur only within the same groups. In practice, to identify those strongly coupled lines and to confine them into sub-linespaces are crucial steps in considering the line coupling. We have calculated half-widths and shifts for some groups, including the line coupling. Based on these calculations, one can conclude that for most of the H2O lines, it is unnecessary to consider the line coupling. However, for several dozens of lines, effects on the calculated half-widths from the line coupling are small, but remain noticeable and reductions of calculated half-widths due to including the line coupling could reach to 5%. Meanwhile, effects on the calculated shifts are very significant and variations of calculated shifts could be as large as 25%.

  10. Effects on Calculated Half-Widths and Shifts from the Line Coupling for Asymmetric-Top Molecules

    NASA Technical Reports Server (NTRS)

    Ma, Q.; Boulet, C.; Tipping, R. H.

    2014-01-01

    The refinement of the Robert-Bonamy formalism by considering the line coupling for linear molecules developed in our previous studies [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013); 140, 104304 (2014)] have been extended to asymmetric-top molecules. For H2O immersed in N2 bath, the line coupling selection rules applicable for the pure rotational band to determine whether two specified lines are coupled or not are established. Meanwhile, because the coupling strengths are determined by relative importance of off-diagonal matrix elements versus diagonal elements of the operator -iS1 -S2, quantitative tools are developed with which one is able to remove weakly coupled lines from consideration. By applying these tools, we have found that within reasonable tolerances, most of the H2O lines in the pure rotational band are not coupled. This reflects the fact that differences of energy levels of the H2O states are pretty large. But, there are several dozen strongly coupled lines and they can be categorized into different groups such that the line couplings occur only within the same groups. In practice, to identify those strongly coupled lines and to confine them into sub-linespaces are crucial steps in considering the line coupling. We have calculated half-widths and shifts for some groups, including the line coupling. Based on these calculations, one can conclude that for most of the H2O lines, it is unnecessary to consider the line coupling. However, for several dozens of lines, effects on the calculated half-widths from the line coupling are small, but remain noticeable and reductions of calculated half-widths due to including the line coupling could reach to 5%. Meanwhile, effects on the calculated shifts are very significant and variations of calculated shifts could be as large as 25%.

  11. Effects on calculated half-widths and shifts from the line coupling for asymmetric-top molecules

    SciTech Connect

    Ma, Q.; Tipping, R. H.

    2014-06-28

    The refinement of the Robert-Bonamy formalism by considering the line coupling for linear molecules developed in our previous studies [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013); 140, 104304 (2014)] have been extended to asymmetric-top molecules. For H{sub 2}O immersed in N{sub 2} bath, the line coupling selection rules applicable for the pure rotational band to determine whether two specified lines are coupled or not are established. Meanwhile, because the coupling strengths are determined by relative importance of off-diagonal matrix elements versus diagonal elements of the operator −iS{sub 1} − S{sub 2}, quantitative tools are developed with which one is able to remove weakly coupled lines from consideration. By applying these tools, we have found that within reasonable tolerances, most of the H{sub 2}O lines in the pure rotational band are not coupled. This reflects the fact that differences of energy levels of the H{sub 2}O states are pretty large. But, there are several dozen strongly coupled lines and they can be categorized into different groups such that the line couplings occur only within the same groups. In practice, to identify those strongly coupled lines and to confine them into sub-linespaces are crucial steps in considering the line coupling. We have calculated half-widths and shifts for some groups, including the line coupling. Based on these calculations, one can conclude that for most of the H{sub 2}O lines, it is unnecessary to consider the line coupling. However, for several dozens of lines, effects on the calculated half-widths from the line coupling are small, but remain noticeable and reductions of calculated half-widths due to including the line coupling could reach to 5%. Meanwhile, effects on the calculated shifts are very significant and variations of calculated shifts could be as large as 25%.

  12. Long-range correlation energy calculated from coupled atomic response functions

    SciTech Connect

    Ambrosetti, Alberto; Reilly, Anthony M.; Tkatchenko, Alexandre; DiStasio, Robert A.

    2014-05-14

    An accurate determination of the electron correlation energy is an essential prerequisite for describing the structure, stability, and function in a wide variety of systems. Therefore, the development of efficient approaches for the calculation of the correlation energy (and hence the dispersion energy as well) is essential and such methods can be coupled with many density-functional approximations, local methods for the electron correlation energy, and even interatomic force fields. In this work, we build upon the previously developed many-body dispersion (MBD) framework, which is intimately linked to the random-phase approximation for the correlation energy. We separate the correlation energy into short-range contributions that are modeled by semi-local functionals and long-range contributions that are calculated by mapping the complex all-electron problem onto a set of atomic response functions coupled in the dipole approximation. We propose an effective range-separation of the coupling between the atomic response functions that extends the already broad applicability of the MBD method to non-metallic materials with highly anisotropic responses, such as layered nanostructures. Application to a variety of high-quality benchmark datasets illustrates the accuracy and applicability of the improved MBD approach, which offers the prospect of first-principles modeling of large structurally complex systems with an accurate description of the long-range correlation energy.

  13. Coupled-Channel Models of Direct-Semidirect Capture via Giant-Dipole Resonances

    NASA Astrophysics Data System (ADS)

    Thompson, I. J.; Escher, J. E.; Arbanas, G.

    2014-04-01

    Semidirect capture, a two-step process that excites a giant-dipole resonance followed by its radiative de-excitation, is a dominant process near giant-dipole resonances, that is, for incoming neutron energies within 5-20 MeV. At lower energies such processes may affect neutron capture rates that are relevant to astrophysical nucleosynthesis models. We implement a semidirect capture model in the coupled-channel reaction code Fresco and validate it by comparing the cross section for direct-semidirect capture 208Pb(n,γ)209Pb to experimental data. We also investigate the effect of low-energy electric dipole strength in the pygmy resonance. We use a conventional single-particle direct-semidirect capture code Cupido for comparison. Furthermore, we present and discuss our results for direct-semidirect capture reaction 130Sn(n,γ)131Sn, the cross section of which is known to have a significant effect on nucleosynthesis models.

  14. Coupled-Channel Models of Direct-Semidirect Capture via Giant-Dipole Resonances

    SciTech Connect

    Thompson, I J; Escher, Jutta E; Arbanas, Goran

    2013-01-01

    Semidirect capture, a two-step process that excites a giant-dipole resonance followed by its radiative de-excitation, is a dominant process near giant-dipole resonances, that is, for incoming neutron energies within 5 20 MeV. At lower energies such processes may affect neutron capture rates that are relevant to astrophysical nucleosynthesis models. We implement a semidirect capture model in the coupled-channel reaction code Fresco and validate it by comparing the cross section for direct-semidirect capture 208Pb(n,g)209Pb to experimental data. We also investigate the effect of low-energy electric dipole strength in the pygmy resonance. We use a conventional single-particle direct-semidirect capture code Cupido for comparison. Furthermore, we present and discuss our results for direct-semidirect capture reaction 130Sn(n,g)131Sn, the cross section of which is known to have a significant effect on nucleosynthesis models.

  15. Discovery of functional monoclonal antibodies targeting G-protein-coupled receptors and ion channels.

    PubMed

    Wilkinson, Trevor C I

    2016-06-15

    The development of recombinant antibody therapeutics is a significant area of growth in the pharmaceutical industry with almost 50 approved monoclonal antibodies on the market in the US and Europe. Despite this growth, however, certain classes of important molecular targets have remained intractable to therapeutic antibodies due to complexity of the target molecules. These complex target molecules include G-protein-coupled receptors and ion channels which represent a large potential target class for therapeutic intervention with monoclonal antibodies. Although these targets have typically been addressed by small molecule approaches, the exquisite specificity of antibodies provides a significant opportunity to provide selective modulation of these target proteins. Given this opportunity, substantial effort has been applied to address the technical challenges of targeting these complex membrane proteins with monoclonal antibodies. In this review recent progress made in the strategies for discovery of functional monoclonal antibodies for these challenging membrane protein targets is addressed. PMID:27284048

  16. Isospin decomposition of γ N →N* transitions within a dynamical coupled-channels model

    NASA Astrophysics Data System (ADS)

    Kamano, H.; Nakamura, S. X.; Lee, T.-S. H.; Sato, T.

    2016-07-01

    By extending the dynamical coupled-channels analysis performed in our previous work [Phys. Rev. C 88, 035209 (2013)], 10.1103/PhysRevC.88.035209 to include the available data of photoproduction of π mesons off neutrons, the transition amplitudes for the photoexcitation of the neutron-to-nucleon resonances, γ n →N* , at the resonance pole positions are determined. The combined fits to the data for both the proton- and neutron-target reactions also revise our results for the resonance pole positions and the γ p →N* transition amplitudes. Our results allow an isospin decomposition of the γ N →N* transition amplitudes for the isospin I =1/2 N* resonances, which is necessary for testing hadron structure models and gives crucial inputs for constructing models of neutrino-induced reactions in the nucleon resonance region.

  17. Sensing pressure in the cardiovascular system: Gq-coupled mechanoreceptors and TRP channels.

    PubMed

    Sharif-Naeini, Reza; Folgering, Joost H A; Bichet, Delphine; Duprat, Fabrice; Delmas, Patrick; Patel, Amanda; Honoré, Eric

    2010-01-01

    Despite the central physiological importance of cardiovascular mechanotransduction, the molecular identities of the sensors and the signaling pathways have long remained elusive. Indeed, how pressure is transduced into cellular excitation has only recently started to emerge. In both arterial and cardiac myocytes, the diacylglycerol-sensitive canonical transient receptor potential (TRPC) subunits are proposed to underlie the stretch-activated depolarizing cation channels. An indirect mechanism of activation through a ligand-independent conformational switch of Gq-coupled receptors by mechanical stress is invoked. Such a mechanism involving the angiotensin type 1 receptor and TRPC6 is proposed to trigger the arterial myogenic response to intraluminal pressure. TRPC6 is also involved in load-induced cardiac hypertrophy. In this review, we will focus on the molecular basis of pressure sensing in the cardiovascular system and associated disease states.

  18. Complex analysis of scattering 1p-shell nuclei in the framework of coupled channel method

    NASA Astrophysics Data System (ADS)

    Nassurlla, M.; Burtebayev, N.; Duisebayev, A.; Burtebayeva, J.; Spitaleri, C.; Urkinbayev, A.; Rusek, K.; Piasecki, E.; Kliczewski, S.; Trzcinska, A.; Sakuta, S. B.; Boztosun, I.; Artemov, S. V.; Galanina, L. I.

    2016-04-01

    The scattering process on 1p-shell nuclei, having the cluster structure, can be seen in the anomaly increasing of cross sections for large angles. Most often, this increasing of cross sections is connected with mechanism of transfer of clusters or nucleons. The study of the α-cluster transfer mechanism in the elastic scattering of 20Ne ions on 16O nuclei is important for investigation burning process in evolution of the Universe immediately after the Big-Bang. Therefore new experiment on the heavy ion accelerator (Warsaw University) was carried out with a significant expansion of the range of angles up to 1700 in center mass system at E Lab =50.0 MeV. Data analysis of angular distribution was performed in framework of the optical model and coupled channel method. The optimal parameters of the optical potential were obtained and the spectroscopic factor was obtained 1 for 20Ne as α +16O.

  19. Stability of the Zagreb realization of the Carnegie-Mellon-Berkeley coupled-channels unitary model

    NASA Astrophysics Data System (ADS)

    Osmanović, H.; Ceci, S.; Švarc, A.; Hadžimehmedović, M.; Stahov, J.

    2011-09-01

    In Hadžimehmedović [Phys. Rev. CPRVCAN0556-281310.1103/PhysRevC.84.035204 84, 035204 (2011)] we have used the Zagreb realization of Carnegie-Melon-Berkeley coupled-channel, unitary model as a tool for extracting pole positions from the world collection of partial-wave data, with the aim of eliminating model dependence in pole-search procedures. In order that the method is sensible, we in this paper discuss the stability of the method with respect to the strong variation of different model ingredients. We show that the Zagreb CMB procedure is very stable with strong variation of the model assumptions and that it can reliably predict the pole positions of the fitted partial-wave amplitudes.

  20. Stability of the Zagreb realization of the Carnegie-Mellon-Berkeley coupled-channels unitary model

    SciTech Connect

    Osmanovic, H.; Hadzimehmedovic, M.; Stahov, J.; Ceci, S.; Svarc, A.

    2011-09-15

    In Hadzimehmedovicet al.[Phys. Rev. C 84, 035204 (2011)] we have used the Zagreb realization of Carnegie-Melon-Berkeley coupled-channel, unitary model as a tool for extracting pole positions from the world collection of partial-wave data, with the aim of eliminating model dependence in pole-search procedures. In order that the method is sensible, we in this paper discuss the stability of the method with respect to the strong variation of different model ingredients. We show that the Zagreb CMB procedure is very stable with strong variation of the model assumptions and that it can reliably predict the pole positions of the fitted partial-wave amplitudes.

  1. The Effect of Extending the Length of the Coupling Coils in a MuonIonization Cooling Channel

    SciTech Connect

    Green, Michael A.

    2007-11-10

    RF cavities are used to re-accelerate muons that have beencooled by absorbers that are in low beta regions of a muon ionizationcooling channel. A superconducting coupling magnet (or magnets) arearound or among the RF cavities of a muon ionization-cooling channel. Thefield from the magnet guides the muons so that they are kept within theiris of the RF cavities that are used to accelerate the muons. Thisreport compares the use of a single short coupling magnet with anextended coupling magnet that has one or more superconducting coils aspart of a muon-cooling channel of the same design as the muon ionizationcooling experiment (MICE). Whether the superconducting magnet is shortand thick or long and this affects the magnet stored energy and the peakfield in the winding. The magnetic field distribution also affects is themuon beam optics in the cooling cell of a muon coolingchannel.

  2. Evidence for L -dependence generated by channel coupling: 16O scattering from 12C at 115.9 MeV

    NASA Astrophysics Data System (ADS)

    Mackintosh, R. S.

    2016-09-01

    Background: In earlier work, inversion of S matrix for 330 MeV 16O on 12C resulted in highly undulatory potentials; the S matrix resulted from the inclusion of strong coupling to states of projectile and target nuclei. L -independent S -matrix equivalent potentials for other explicitly L -dependent potentials have been found to be undulatory. Purpose: To investigate the possible implications of the undulatory dynamic polarization potential for an underlying L dependence of the 16O on 12C optical potential. Methods: S matrix to potential, SL→V (r ) , inversion which yields local potentials that reproduce the elastic channel S matrix of coupled channel (CC) calculations, will be applied to the S matrix for 115.9 MeV 16O on 12C. Further, SL for explicitly L -dependent potentials are inverted and the resulting L -independent potentials are characterized and compared with the undulatory potentials found for 16O on 12C. Results: Some of the undulatory features exhibited by the potentials modified by channel coupling for 115.9 MeV 16O on 12C can be simulated by simple parameterized L -dependent potentials. Conclusions: The elastic scattering of 16O by 12C is a particularly favorable case for revealing the effective L dependence of the potential modified by channel coupling. Nevertheless, there is no reason to suppose that undularity is not a generic property leading in many cases to the choice: nucleus-nucleus potentials are (i) smooth and L -dependent, (ii) L -independent and undulatory, or (iii) both.

  3. Fast and accurate inductance and coupling calculation for a multi-layer Nb process

    NASA Astrophysics Data System (ADS)

    Fourie, Coenrad J.; Takahashi, Akitomo; Yoshikawa, Nobuyuki

    2015-03-01

    Currently, fabrication processes for superconductive integrated circuits are moving to multiple wiring and shielding layers, some of which are placed below the main ground plane (GP) and device layers. The Advanced Industrial Science and Technology advanced process (ADP2) was the first such multi-layer Nb process with planarized passive transmission line and GP layers below the junction layer, and is at the time of writing still the most developed. This process allows complex circuit designs, and accurate inductance extraction helps to push the boundaries of the layouts possible. We show that the position of ground connections between ground layers influences the inductance of structures for which these GPs act as return path, and that this needs to be accounted for in modelling. However, due to the number of wiring layers and GPs, full layout modelling of large cells causes long calculation times. In this paper we discuss methods with which to reduce model size, and calibrate InductEx calculations using these methods against measured results. We show that model reduction followed by calibration results in fast calculation times while good accuracy is maintained. We also show that InductEx correctly handles coupling between conductors in a multi-layer layout, and how to model layouts to gauge unwanted coupling between power lines and single flux quantum electronics.

  4. Lattice dynamics and electron-phonon coupling calculations using nondiagonal supercells

    NASA Astrophysics Data System (ADS)

    Lloyd-Williams, Jonathan H.; Monserrat, Bartomeu

    2015-11-01

    We study the direct calculation of total energy derivatives for lattice dynamics and electron-phonon coupling calculations using supercell matrices with nonzero off-diagonal elements. We show that it is possible to determine the response of a periodic system to a perturbation characterized by a wave vector with reduced fractional coordinates (m1/n1,m2/n2,m3/n3) using a supercell containing a number of primitive cells equal to the least common multiple of n1,n2, and n3. If only diagonal supercell matrices are used, a supercell containing n1n2n3 primitive cells is required. We demonstrate that the use of nondiagonal supercells significantly reduces the computational cost of obtaining converged zero-point energies and phonon dispersions for diamond and graphite. We also perform electron-phonon coupling calculations using the direct method to sample the vibrational Brillouin zone with grids of unprecedented size, which enables us to investigate the convergence of the zero-point renormalization to the thermal and optical band gaps of diamond.

  5. Structural Studies of Inositol 1,4,5-Trisphosphate Receptor COUPLING LIGAND BINDING TO CHANNEL GATING

    SciTech Connect

    Chan, Jenny; Yamazaki, Haruka; Ishiyama, Noboru; Seo, Min-Duk; Mal, Tapas K.; Michikawa, Takayuki; Mikoshiba, Katsuhiko; Ikura, Mitsuhiko

    2010-11-22

    The three isoforms of the inositol 1,4,5-trisphosphate receptor (IP{sub 3}R) exhibit distinct IP{sub 3} sensitivities and cooperativities in calcium (Ca{sup 2+}) channel function. The determinants underlying this isoform-specific channel gating mechanism have been localized to the N-terminal suppressor region of IP3R. We determined the 1.9 {angstrom} crystal structure of the suppressor domain from type 3 IP{sub 3}R (IP{sub 3}R3{sub SUP}, amino acids 1-224) and revealed structural features contributing to isoform-specific functionality of IP{sub 3}R by comparing it with our previously determined structure of the type 1 suppressor domain (IP{sub 3}R1{sub SUP}). The molecular surface known to associate with the ligand binding domain (amino acids 224-604) showed marked differences between IP{sub 3}R3{sub SUP} and IP{sub 3}R1{sub SUP}. Our NMR and biochemical studies showed that three spatially clustered residues (Glu-20, Tyr-167, and Ser-217 in IP{sub 3}R1 and Glu-19, Trp-168, and Ser-218 in IP{sub 3}R3) within the N-terminal suppressor domains of IP{sub 3}R1{sub SUP} and IP{sub 3}R3{sub SUP} interact directly with their respective C-terminal fragments. Together with the accompanying paper (Yamazaki, H., Chan, J., Ikura, M., Michikawa, T., and Mikoshiba, K. (2010) J. Biol. Chem. 285, 36081-36091), we demonstrate that the single aromatic residue in this region (Tyr-167 in IP{sub 3}R1 and Trp-168 in IP{sub 3}R3) plays a critical role in the coupling between ligand binding and channel gating.

  6. Uplink scheduling and adjacent-channel coupling loss analysis for TD-LTE deployment.

    PubMed

    Yeo, Woon-Young; Moon, Sung Ho; Kim, Jae-Hoon

    2014-01-01

    TD-LTE, one of the two duplexing modes in LTE, operates in unpaired spectrum and has the advantages of TDD-based technologies. It is expected that TD-LTE will be more rapidly deployed in near future and most of WiMax operators will upgrade their networks to TD-LTE gradually. Before completely upgrading to TD-LTE, WiMax may coexist with TD-LTE in an adjacent frequency band. In addition, multiple TD-LTE operators may deploy their networks in adjacent bands. When more than one TDD network operates in adjacent frequency bands, severe interference may happen due to adjacent channel interference (ACI) and unsynchronized operations. In this paper, coexistence issues between TD-LTE and other systems are analyzed and coexistence requirements are provided. This paper has three research objectives. First, frame synchronization between TD-LTE and WiMax is discussed by investigating possible combinations of TD-LTE and WiMax configurations. Second, an uplink scheduling algorithm is proposed to utilize a leakage pattern of ACI in synchronized operations. Third, minimum requirements for coexistence in unsynchronized operations are analyzed by introducing a concept of adjacent-channel coupling loss. From the analysis and simulation results, we can see that coexistence of TD-LTE with other TDD systems is feasible if the two networks are synchronized. For the unsynchronized case, some special cell-site engineering techniques may be required to reduce the ACI. PMID:24707214

  7. Uplink scheduling and adjacent-channel coupling loss analysis for TD-LTE deployment.

    PubMed

    Yeo, Woon-Young; Moon, Sung Ho; Kim, Jae-Hoon

    2014-01-01

    TD-LTE, one of the two duplexing modes in LTE, operates in unpaired spectrum and has the advantages of TDD-based technologies. It is expected that TD-LTE will be more rapidly deployed in near future and most of WiMax operators will upgrade their networks to TD-LTE gradually. Before completely upgrading to TD-LTE, WiMax may coexist with TD-LTE in an adjacent frequency band. In addition, multiple TD-LTE operators may deploy their networks in adjacent bands. When more than one TDD network operates in adjacent frequency bands, severe interference may happen due to adjacent channel interference (ACI) and unsynchronized operations. In this paper, coexistence issues between TD-LTE and other systems are analyzed and coexistence requirements are provided. This paper has three research objectives. First, frame synchronization between TD-LTE and WiMax is discussed by investigating possible combinations of TD-LTE and WiMax configurations. Second, an uplink scheduling algorithm is proposed to utilize a leakage pattern of ACI in synchronized operations. Third, minimum requirements for coexistence in unsynchronized operations are analyzed by introducing a concept of adjacent-channel coupling loss. From the analysis and simulation results, we can see that coexistence of TD-LTE with other TDD systems is feasible if the two networks are synchronized. For the unsynchronized case, some special cell-site engineering techniques may be required to reduce the ACI.

  8. Uplink Scheduling and Adjacent-Channel Coupling Loss Analysis for TD-LTE Deployment

    PubMed Central

    Yeo, Woon-Young; Moon, Sung Ho

    2014-01-01

    TD-LTE, one of the two duplexing modes in LTE, operates in unpaired spectrum and has the advantages of TDD-based technologies. It is expected that TD-LTE will be more rapidly deployed in near future and most of WiMax operators will upgrade their networks to TD-LTE gradually. Before completely upgrading to TD-LTE, WiMax may coexist with TD-LTE in an adjacent frequency band. In addition, multiple TD-LTE operators may deploy their networks in adjacent bands. When more than one TDD network operates in adjacent frequency bands, severe interference may happen due to adjacent channel interference (ACI) and unsynchronized operations. In this paper, coexistence issues between TD-LTE and other systems are analyzed and coexistence requirements are provided. This paper has three research objectives. First, frame synchronization between TD-LTE and WiMax is discussed by investigating possible combinations of TD-LTE and WiMax configurations. Second, an uplink scheduling algorithm is proposed to utilize a leakage pattern of ACI in synchronized operations. Third, minimum requirements for coexistence in unsynchronized operations are analyzed by introducing a concept of adjacent-channel coupling loss. From the analysis and simulation results, we can see that coexistence of TD-LTE with other TDD systems is feasible if the two networks are synchronized. For the unsynchronized case, some special cell-site engineering techniques may be required to reduce the ACI. PMID:24707214

  9. Using $$X(3823)\\to J/\\psi\\pi^+\\pi^-$$ to Identify Coupled-Channel Effects

    DOE PAGES

    Wang, Bo; Xu, Hao; Liu, Xiang; Chen, Dian-Yong; Coito, Susana; Eichten, Estia

    2016-03-17

    Very recently, a new charmonium-like state X(3823) was observed by the Belle and BESIII experiments, which is a good candidate of D-wave charmonium ψ(13D2). Since the X(3872) is just below the DD¯ * threshold, the decay X(3823) → J/ψπ+π - can be a golden channel to test the significance of coupled-channel effects. In this work, this decay is considered including both the hidden-charm dipion and the usual QCDME contributions. The partial decay width, the dipion invariant mass spectrum distribution dΓ[X(3823) → J/ψπ+π - ]/dmπ +π- , and the corresponding dΓ[X(3823) → J/ψπ+π- ]/d cos θ distribution are computed. Many parametersmore » are determined from existing experimental data, leaving the results mainly dependent on only one unknown phase between the QCDME and hidden-charm dipion amplitudes.« less

  10. Coupled-channels study of the {pi}{sup -}p{yields}{eta}n process

    SciTech Connect

    Durand, J.; Saghai, B.; Lee, T.-S. H.; Sato, T.

    2008-08-15

    The reaction {pi}{sup -}p{yields}{eta}n is investigated within a dynamical coupled-channels model of meson production reactions in the nucleon resonance region. The meson baryon channels included are {pi}N,{eta}N,{pi}{delta},{sigma}N, and {rho}N. The nonresonant meson-baryon interactions of the model are derived from a set of Lagrangians by using a unitary transformation method. One or two excited nucleon states in each of S,P,D, and F partial waves are included to generate the resonant amplitudes. Data of the {pi}{sup -}p{yields}{eta}n reaction from threshold up to a total center-of-mass energy of about 2 GeV are satisfactorily reproduced and the roles played by the following nine nucleon resonances are investigated: S{sub 11}(1535),S{sub 11}(1650),P{sub 11}(1440),P{sub 11}(1710),P{sub 13}(1720),D{sub 13}(1520),D{sub 13}(1700),D{sub 15} (1675), and F{sub 15}(1680). The reaction mechanism and the predicted {eta}N scattering length are discussed.

  11. Theoretical grounds of relativistic methods for calculation of spin-spin coupling constants in nuclear magnetic resonance spectra

    NASA Astrophysics Data System (ADS)

    Rusakova, I. L.; Rusakov, Yu Yu; Krivdin, L. B.

    2016-04-01

    The theoretical grounds of the modern relativistic methods for quantum chemical calculation of spin-spin coupling constants in nuclear magnetic resonance spectra are considered. Examples and prospects of application of relativistic calculations of these constants in the structural studies of organic and heteroorganic compounds are discussed. Practical recommendations on relativistic calculations of spin-spin coupling constants using the available software are given. The bibliography includes 622 references.

  12. Theoretical grounds of relativistic methods for calculation of spin–spin coupling constants in nuclear magnetic resonance spectra

    NASA Astrophysics Data System (ADS)

    Rusakova, I. L.; Rusakov, Yu Yu; Krivdin, L. B.

    2016-04-01

    The theoretical grounds of the modern relativistic methods for quantum chemical calculation of spin–spin coupling constants in nuclear magnetic resonance spectra are considered. Examples and prospects of application of relativistic calculations of these constants in the structural studies of organic and heteroorganic compounds are discussed. Practical recommendations on relativistic calculations of spin–spin coupling constants using the available software are given. The bibliography includes 622 references.

  13. Local scale analyses of hillslope-channel coupling in the cuesta landscape of the Swabian Alb, S-W Germany

    NASA Astrophysics Data System (ADS)

    Blöthe, J. H.; Hoffmann, T.; Bell, R.; Meyer, N. K.; Dix, A.; Röhrs, M.

    2009-04-01

    In upland fluvial systems hillslope and channel processes are often closely connected. While the influence of fluvial erosion on hillslope stability received much attention in the past, the influence of hillslope processes on the fluvial system has less comprehensively been investigated. Especially landslides can have a profound impact on the fluvial system, by either altering channel morphology, diverting the channel course or, in some cases, by blocking the entire valley resulting in a landslide dammed lake. The disturbance of a river system by landslides often causes a marked knickpoint in the channel's longitudinal profile. Adjustment of the longitudinal profile depends on sediment input and erosivity of the material delivered to the channel, but also on the human impact on the system. In case of erosive landslide material a fast adjustment to disturbance is assumed. The main aim of this study is to analyse the impact of landslides on channel morphology in the Fils and the Schlichem catchments. Both catchments are located in the Swabian Alb (SW Germany), a cuesta landscape where hillslope processes are dominated by landslide processes. Within these catchments, bank failures, small slump failures and valley cross-sections for local river reaches are mapped and taken as a proxy for the activity of the coupled area. River longitudinal profiles are calculated from high resolution digital elevation models. Additionally, the thickness of alluvial sediment upstream and downstream of the disturbed areas is determined in the field in order to identify the effects of landslides on the alluvial sedimentation. Besides the geomorphological evidence, historical sources on channel pattern changes and landslide impacts are analysed. Preliminary results show that the impact of landslides on the river longitudinal profile can be detected in the longitudinal profiles on a local scale. The higher frequency of small slump failures within the disturbed area compared to undisturbed

  14. Emergent properties of nuclei from ab initio coupled-cluster calculations

    NASA Astrophysics Data System (ADS)

    Hagen, G.; Hjorth-Jensen, M.; Jansen, G. R.; Papenbrock, T.

    2016-06-01

    Emergent properties such as nuclear saturation and deformation, and the effects on shell structure due to the proximity of the scattering continuum and particle decay channels are fascinating phenomena in atomic nuclei. In recent years, ab initio approaches to nuclei have taken the first steps towards tackling the computational challenge of describing these phenomena from Hamiltonians with microscopic degrees of freedom. This endeavor is now possible due to ideas from effective field theories, novel optimization strategies for nuclear interactions, ab initio methods exhibiting a soft scaling with mass number, and ever-increasing computational power. This paper reviews some of the recent accomplishments. We also present new results. The recently optimized chiral interaction NNLO{}{{sat}} is shown to provide an accurate description of both charge radii and binding energies in selected light- and medium-mass nuclei up to 56Ni. We derive an efficient scheme for including continuum effects in coupled-cluster computations of nuclei based on chiral nucleon-nucleon and three-nucleon forces, and present new results for unbound states in the neutron-rich isotopes of oxygen and calcium. The coupling to the continuum impacts the energies of the {J}π =1/{2}-,3/{2}-,7/{2}-,3/{2}+ states in {}{17,23,25}O, and—contrary to naive shell-model expectations—the level ordering of the {J}π =3/{2}+,5/{2}+,9/{2}+ states in {}{53,55,61}Ca. ).

  15. A modified coupled pair functional approach. [for dipole moment calculation of metal hydride ground states

    NASA Technical Reports Server (NTRS)

    Chong, D. P.; Langhoff, S. R.

    1986-01-01

    A modified coupled pair functional (CPF) method is presented for the configuration interaction problem that dramatically improves properties for cases where the Hartree-Fock reference configuration is not a good zeroth-order wave function description. It is shown that the tendency for CPF to overestimate the effect of higher excitations arises from the choice of the geometric mean for the partial normalization denominator. The modified method is demonstrated for ground state dipole moment calculations of the NiH, CuH, and ZnH transition metal hydrides, and compared to singles-plus-doubles configuration interaction and the Ahlrichs et al. (1984) CPF method.

  16. Coupled Electron-Ion Monte Carlo Calculations of Dense Metallic Hydrogen

    NASA Astrophysics Data System (ADS)

    Pierleoni, Carlo; Ceperley, David M.; Holzmann, Markus

    2004-09-01

    We present an efficient new Monte Carlo method which couples path integrals for finite temperature protons with quantum Monte Carlo calculations for ground state electrons, and we apply it to metallic hydrogen for pressures beyond molecular dissociation. We report data for the equation of state for temperatures across the melting of the proton crystal. Our data exhibit more structure and higher melting temperatures of the proton crystal than do Car-Parrinello molecular dynamics results. This method fills the gap between high temperature electron-proton path integral and ground state diffusion Monte Carlo methods and should have wide applicability.

  17. A conformational study of hydroxyflavones by vibrational spectroscopy coupled to DFT calculations

    NASA Astrophysics Data System (ADS)

    Machado, N. F. L.; Batista de Carvalho, L. A. E.; Otero, J. C.; Marques, M. P. M.

    2013-05-01

    The conformational preferences of a series of hydroxyflavones were studied by Raman and FTIR spectroscopies, coupled to Density Functional Theory calculations. Special attention was paid to the effect of hydroxyl substitution, due to its importance on the biological activity of these compounds. Their conformational preferences were found to be determined mainly by the orientation of the hydroxylic groups at C7 and within the catechol moiety, leading to the occurrence of distinct conformers in the solid state. A complete assignment of the experimental spectra was carried out for these molecules, in the light of their most stable conformers and the corresponding predicted vibrational pattern.

  18. Inner-shell correlations and Sturm expansions in coupled perturbation calculations of atomic systems

    SciTech Connect

    Sherstyuk, A.I.; Solov`eva, G.S.

    1995-04-01

    It is shown that virtual Hartree-Fock orbitals in Sturm-type expansions can be used to calculate the response of atomic systems to an external field within the framework of the coupled perturbation theory with allowance for correlation effects. The corrected electron-electron interaction in a system with field-distorted orbitals is considered by adding a nonlocal potential to a one-electron Hartree-Fock operator within each group of equivalent elections. The remaining correlation effects are calculated by solving a system of equations for corrections to the radial functions. The system is solved iteratively, with each subsequent iteration corresponding to a correction of an increasingly higher order in the electron--electron interaction. The explicit expression derived for the polarizability contains one-and two-particle radial integrals of the Sturm functions.

  19. Accurate near-field calculation in the rigorous coupled-wave analysis method

    NASA Astrophysics Data System (ADS)

    Weismann, Martin; Gallagher, Dominic F. G.; Panoiu, Nicolae C.

    2015-12-01

    The rigorous coupled-wave analysis (RCWA) is one of the most successful and widely used methods for modeling periodic optical structures. It yields fast convergence of the electromagnetic far-field and has been adapted to model various optical devices and wave configurations. In this article, we investigate the accuracy with which the electromagnetic near-field can be calculated by using RCWA and explain the observed slow convergence and numerical artifacts from which it suffers, namely unphysical oscillations at material boundaries due to the Gibbs phenomenon. In order to alleviate these shortcomings, we also introduce a mathematical formulation for accurate near-field calculation in RCWA, for one- and two-dimensional straight and slanted diffraction gratings. This accurate near-field computational approach is tested and evaluated for several representative test-structures and configurations in order to illustrate the advantages provided by the proposed modified formulation of the RCWA.

  20. Equation-of-motion coupled cluster method for high spin double electron attachment calculations

    SciTech Connect

    Musiał, Monika Lupa, Łukasz; Kucharski, Stanisław A.

    2014-03-21

    The new formulation of the equation-of-motion (EOM) coupled cluster (CC) approach applicable to the calculations of the double electron attachment (DEA) states for the high spin components is proposed. The new EOM equations are derived for the high spin triplet and quintet states. In both cases the new equations are easier to solve but the substantial simplification is observed in the case of quintets. Out of 21 diagrammatic terms contributing to the standard DEA-EOM-CCSDT equations for the R{sub 2} and R{sub 3} amplitudes only four terms survive contributing to the R{sub 3} part. The implemented method has been applied to the calculations of the excited states (singlets, triplets, and quintets) energies of the carbon and silicon atoms and potential energy curves for selected states of the Na{sub 2} (triplets) and B{sub 2} (quintets) molecules.

  1. Leptin-stimulated KATP channel trafficking: a new paradigm for β-cell stimulus-secretion coupling?

    PubMed

    Holz, George G; Chepurny, Oleg G; Leech, Colin A

    2013-01-01

    Insulin secretion from pancreatic β-cells is initiated by the closure of ATP-sensitive K+ channels (KATP) in response to high concentrations of glucose, and this action of glucose is counteracted by the hormone leptin, an adipokine that signals through the Ob-Rb receptor to increase KATP channel activity. Despite intensive investigations, the molecular basis for KATP channel regulation remains uncertain, particularly from the standpoint of whether fluctuations in plasma membrane KATP channel content underlie alterations of KATP channel activity in response to glucose or leptin. Surprisingly, newly published findings reveal that leptin stimulates AMP-activated protein kinase (AMPK) in order to promote trafficking of KATP channels from cytosolic vesicles to the plasma membrane of β-cells. This action of leptin is mimicked by low concentrations of glucose that also activate AMPK and that inhibit insulin secretion. Thus, a new paradigm for β-cell stimulus-secretion coupling is suggested in which leptin exerts a tonic inhibitory effect on β-cell excitability by virtue of its ability to increase plasma membrane KATP channel density and whole-cell KATP channel current. One important issue that remains unresolved is whether high concentrations of glucose suppress AMPK activity in order to shift the balance of membrane cycling so that KATP channel endocytosis predominates over vesicular KATP channel insertion into the plasma membrane. If so, high concentrations of glucose might transiently reduce KATP channel density/current, thereby favoring β-cell depolarization and insulin secretion. Such an AMPK-dependent action of glucose would complement its established ability to generate an increase of ATP/ADP concentration ratio that directly closes KATP channels in the plasma membrane.

  2. Potassium channels in the Cx43 gap junction perinexus modulate ephaptic coupling: an experimental and modeling study.

    PubMed

    Veeraraghavan, Rengasayee; Lin, Joyce; Keener, James P; Gourdie, Robert; Poelzing, Steven

    2016-10-01

    It was recently demonstrated that cardiac sodium channels (Nav1.5) localized at the perinexus, an intercalated disc (ID) nanodomain associated with gap junctions (GJ), may contribute to electrical coupling between cardiac myocytes via an ephaptic mechanism. Impairment of ephaptic coupling by acute interstitial edema (AIE)-induced swelling of the perinexus was associated with arrhythmogenic, anisotropic conduction slowing. Given that Kir2.1 has also recently been reported to localize at intercalated discs, we hypothesized that Kir2.1 channels may reside within the perinexus and that inhibiting them may mitigate arrhythmogenic conduction slowing observed during AIE. Using gated stimulated emission depletion (gSTED) and stochastic optical reconstruction microscopy (STORM) super-resolution microscopy, we indeed find that a significant proportion of Kir2.1 channels resides within the perinexus. Moreover, whereas Nav1.5 inhibition during AIE exacerbated arrhythmogenic conduction slowing, inhibiting Kir2.1 channels during AIE preferentially increased transverse conduction velocity-decreasing anisotropy and ameliorating arrhythmia risk compared to AIE alone. Comparison of our results with a nanodomain computer model identified enrichment of both Nav1.5 and Kir2.1 at intercalated discs as key factors underlying the experimental observations. We demonstrate that Kir2.1 channels are localized within the perinexus alongside Nav1.5 channels. Further, targeting Kir2.1 modulates intercellular coupling between cardiac myocytes, anisotropy of conduction, and arrhythmia propensity in a manner consistent with a role for ephaptic coupling in cardiac conduction. For over half a century, electrical excitation in the heart has been thought to occur exclusively via gap junction-mediated ionic current flow between cells. Further, excitation was thought to depend almost exclusively on sodium channels with potassium channels being involved mainly in returning the cell to rest. Here, we

  3. A Mathematica package for calculation of planar channeling radiation spectra of relativistic electrons channeled in a diamond-structure single crystal (quantum approach)

    NASA Astrophysics Data System (ADS)

    Azadegan, B.

    2013-03-01

    The presented Mathematica code is an efficient tool for simulation of planar channeling radiation spectra of relativistic electrons channeled along major crystallographic planes of a diamond-structure single crystal. The program is based on the quantum theory of channeling radiation which has been successfully applied to study planar channeling at electron energies between 10 and 100 MeV. Continuum potentials for different planes of diamond, silicon and germanium single crystals are calculated using the Doyle-Turner approximation to the atomic scattering factor and taking thermal vibrations of the crystal atoms into account. Numerical methods are applied to solve the one-dimensional Schrödinger equation. The code is designed to calculate the electron wave functions, transverse electron states in the planar continuum potential, transition energies, line widths of channeling radiation and depth dependencies of the population of quantum states. Finally the spectral distribution of spontaneously emitted channeling radiation is obtained. The simulation of radiation spectra considerably facilitates the interpretation of experimental data. Catalog identifier: AEOH_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEOH_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 446 No. of bytes in distributed program, including test data, etc.: 209805 Distribution format: tar.gz Programming language: Mathematica. Computer: Platforms on which Mathematica is available. Operating system: Operating systems on which Mathematica is available. RAM: 1 MB Classification: 7.10. Nature of problem: Planar channeling radiation is emitted by relativistic charged particles during traversing a single crystal in direction parallel to a crystallographic plane. Channeling is modeled as the motion

  4. Lattice dynamics and electron-phonon coupling calculations using nondiagonal supercells

    NASA Astrophysics Data System (ADS)

    Lloyd-Williams, Jonathan; Monserrat, Bartomeu

    Quantities derived from electron-phonon coupling matrix elements require a fine sampling of the vibrational Brillouin zone. Converged results are typically not obtainable using the direct method, in which a perturbation is frozen into the system and the total energy derivatives are calculated using a finite difference approach, because the size of simulation cell needed is prohibitively large. We show that it is possible to determine the response of a periodic system to a perturbation characterized by a wave vector with reduced fractional coordinates (m1 /n1 ,m2 /n2 ,m3 /n3) using a supercell containing a number of primitive cells equal to the least common multiple of n1, n2, and n3. This is accomplished by utilizing supercell matrices containing nonzero off-diagonal elements. We present the results of electron-phonon coupling calculations using the direct method to sample the vibrational Brillouin zone with grids of unprecedented size for a range of systems, including the canonical example of diamond. We also demonstrate that the use of nondiagonal supercells reduces by over an order of magnitude the computational cost of obtaining converged vibrational densities of states and phonon dispersion curves. J.L.-W. is supported by the Engineering and Physical Sciences Research Council (EPSRC). B.M. is supported by Robinson College, Cambridge, and the Cambridge Philosophical Society. This work was supported by EPSRC Grants EP/J017639/1 and EP/K013564/1.

  5. Nonrelativistic structure calculations of two-electron ions in a strongly coupled plasma environment

    SciTech Connect

    Bhattacharyya, S.; Saha, J. K.; Mukherjee, T. K.

    2015-04-01

    In this work, the controversy between the interpretations of recent measurements on dense aluminum plasma created with the Linac coherent light source (LCLS) x-ray free electron laser (FEL) and the Orion laser has been addressed. In both kinds of experiments, heliumlike and hydrogenlike spectral lines are used for plasma diagnostics. However, there exist no precise theoretical calculations for He-like ions within a dense plasma environment. The strong need for an accurate theoretical estimate for spectral properties of He-like ions in a strongly coupled plasma environment leads us to perform ab initio calculations in the framework of the Rayleigh-Ritz variation principle in Hylleraas coordinates where an ion-sphere potential is used. An approach to resolve the long-drawn problem of numerical instability for evaluating two-electron integrals with an extended basis inside a finite domain is presented here. The present values of electron densities corresponding to the disappearance of different spectral lines obtained within the framework of an ion-sphere potential show excellent agreement with Orion laser experiments in Al plasma and with recent theories. Moreover, this method is extended to predict the critical plasma densities at which the spectral lines of H-like and He-like carbon and argon ions disappear. Incidental degeneracy and level-crossing phenomena are being reported for two-electron ions embedded in strongly coupled plasma. Thermodynamic pressure experienced by the ions in their respective ground states inside the ion spheres is also reported.

  6. Calculating Hot Spring/Atmospheric Coupling Using the Coefficient of Convective Heat Transfer

    NASA Astrophysics Data System (ADS)

    Lindsey, C.; Price, A. N.; Fairley, J. P., Jr.; Larson, P. B.

    2015-12-01

    We calculated the correlation between discharge temperature and wind speed for multiple hydrothermal springs, both in the Alvord Basin of southeast Oregon and our primary field location in Yellowstone National Park, using spring temperatures, wind speeds, and air temperatures logged at three minute intervals for multiple days. We find that some hydrothermal springs exhibit strong coupling with wind speed and/or air temperatures. The three springs described in this work display this strong coupling, with correlations between wind speed and spring temperature as high as 70 percent; as a result, we can use the changes in spring temperature as a proxy for changes in the coefficient of convective heat transfer (h) between the springs and the atmosphere. The coefficient of convective heat transfer is a complex parameter to measure, but is a necessary input to many heat and mass flux analyses. The results of this study provide a way to estimate h for springs with strong atmospheric coupling, which is a critical component of a total energy balance for hydrothermal discharge areas.

  7. Ion-channel-coupled receptor-based platform for a real-time measurement of G-protein-coupled receptor activities.

    PubMed

    Lim, Jong Hyun; Oh, Eun Hae; Park, Juhun; Hong, Seunghun; Park, Tai Hyun

    2015-02-24

    A simple but efficient measurement platform based on ion-channel-coupled receptors and nanovesicles was developed for monitoring the real-time activity of G-protein-coupled receptors (GPCRs). In this work, an olfactory receptor (OR), the most common class A GPCR, was covalently fused with a Kir6.2 channel so that the GPCR action directly induced the opening of the ion channels and changes in the electrical membrane potential without complex cellular signaling processes. This strategy reduced the measurement errors caused by instability of various cellular components. In addition, rather than using whole cells, a cell-surface-derived nanovesicle was used to preserve the membrane-integrated structure of GPCRs and to exclude case-dependent cellular conditions. Another merit of using the nanovesicle is that nanovesicles can be easily combined with nanomaterial-based field-effect transistors (FETs) to build a sensitive and stable measurement platform to monitor GPCR activities with high sensitivity in real-time. Using a platform based on carbon nanotube FETs and nanovesicles carrying Kir6.2-channel-coupled ORs, we monitored the real-time response of ORs to their ligand molecules. Significantly, since this platform does not rely on rather unstable cell signaling pathways, our platform could be utilized for a rather long time period without losing its functionality. This system can be utilized extensively for simple and sensitive analysis of the activities of various GPCRs and should enable various academic and practical applications.

  8. Coupled-channels quantum theory of electronic flux density in electronically adiabatic processes: application to the hydrogen molecule ion.

    PubMed

    Diestler, D J; Kenfack, A; Manz, J; Paulus, B

    2012-03-22

    This article presents the results of the first quantum simulations of the electronic flux density (j(e)) by the "coupled-channels" (CC) theory, the fundamentals of which are presented in the previous article [Diestler, D. J. J. Phys. Chem. A 2012, DOI: 10.1021/jp207843z]. The principal advantage of the CC scheme is that it employs exclusively standard methods of quantum chemistry and quantum dynamics within the framework of the Born-Oppenheimer approximation (BOA). The CC theory goes beyond the BOA in that it yields a nonzero j(e) for electronically adiabatic processes, in contradistinction to the BOA itself, which always gives j(e) = 0. The CC is applied to oriented H(2)(+) vibrating in the electronic ground state ((2)Σ(g)(+)), for which the nuclear and electronic flux densities evolve on a common time scale of about 22 fs per vibrational period. The system is chosen as a touchstone for the CC theory, because it is the only one for which highly accurate flux densities have been calculated numerically without invoking the BOA [Barth et al, Chem. Phys. Lett. 2009, 481, 118]. Good agreement between CC and accurate results supports the CC approach, another advantage of which is that it allows a transparent interpretation of the temporal and spatial properties of j(e).

  9. Analysis of metal pollutants in the Houston Ship Channel by inductively coupled plasma/mass spectrometry.

    PubMed

    Saleh, M A; Wilson, B L

    1999-09-01

    Trace metal pollutants in the surface water of the Houston Ship Channel were determined using inductively coupled plasma/mass spectrometry (ICP/MS). Metal concentrations varied according to sampling sites. Barium, cobalt, chromium, molybdenum, silver, beryllium, antimony, lead, and mercury concentrations were relatively similar throughout the channel averaging 83.25, 0.55, 6. 31, 6.66, 0.02, 0.017, 3.61, 0.68, and 0.055 microg/L, respectively. Titanium, manganese, copper, zinc, nickel, and selenium concentrations were found to be higher at stations closer to the Galveston Bay (as the water is turning from relatively fresh water to sea water) with concentration ranges of 102.5-351.7, 0.3-25, 0. 3-25, 30-280, 16-77, 6.2-26.5, and 0.0-6.2 microg/L, respectively. Aluminum was found to be much higher at the Buffalo Bayou station (341 microg/L) followed by the San Jacinto station (104 microg/L) with an average of 42 microg/L in the other two stations. Vanadium was found to be unusually high at the Washburn Tunnel station (116 microg/L) and at much lower concentrations in the other three stations, averaging 6.5 microg/L. Iron was also higher at the Buffalo Bayou station (143 microg/L) but was absent at the Lynchburg Ferries station. Arsenic was not found at the Lynchburg and San Jacinto stations. However, arsenic had similar concentrations of 1. 983 and 1.835 microg/L at Buffalo Bayou and Washburn Tunnel, respectively. Cadmium was higher at the Lynchburg Ferries station (3. 3 microg/L) and ranged from 0.3 to 0.96 microg/L in the other locations. Thallium was not found in any of the stations.

  10. Calculation of light delay for coupled microrings by FDTD technique and Padé approximation.

    PubMed

    Huang, Yong-Zhen; Yang, Yue-De

    2009-11-01

    The Padé approximation with Baker's algorithm is compared with the least-squares Prony method and the generalized pencil-of-functions (GPOF) method for calculating mode frequencies and mode Q factors for coupled optical microdisks by FDTD technique. Comparisons of intensity spectra and the corresponding mode frequencies and Q factors show that the Padé approximation can yield more stable results than the Prony and the GPOF methods, especially the intensity spectrum. The results of the Prony method and the GPOF method are greatly influenced by the selected number of resonant modes, which need to be optimized during the data processing, in addition to the length of the time response signal. Furthermore, the Padé approximation is applied to calculate light delay for embedded microring resonators from complex transmission spectra obtained by the Padé approximation from a FDTD output. The Prony and the GPOF methods cannot be applied to calculate the transmission spectra, because the transmission signal obtained by the FDTD simulation cannot be expressed as a sum of damped complex exponentials.

  11. Calculation of the resonant contribution to {Z}_{{eff}}({k}_{0}) using close-coupled equations for positron–molecule scattering

    NASA Astrophysics Data System (ADS)

    Armour, E. A. G.; Plummer, M.

    2016-08-01

    In a previous paper (2010 Phys. Rev. A 82 042702; 2014 Phys. Rev. A 89 069901(E)), one of us (EAGA) calculated the resonant contribution to {Z}{eff}({k}0), the effective number of electrons available for annihilation by a positron with wave number k 0, in the scattering of a heavy positron by H2. The mass of the positron was increased just sufficiently for a bound state to occur. This calculation was carried out using the Kohn variational method. An alternative method is to use the close-coupled equations for the system under consideration. We compare our results with those obtained by Gribakin and Lee (2006 Phys. Rev. Lett. 97 193201). There is a resonant contribution to {Z}{eff}({k}0) from the vibrationally excited quasibound state which may be described by a Breit–Wigner resonance formula arising naturally from the close-coupling analysis if a certain additional assumption is made. There is also a separate resonant contribution to {Z}{eff}({k}0) from the open channel function influenced by the quasibound state, and a cross term. It is shown that the contribution from the quasibound state is very similar to the expression for the resonant contribution obtained by Gribakin and Lee. Comparison is made with other treatments, for example, the close-coupling calculation of Nishimura and Gianturco (2003 Phys. Rev. Lett. 90 183201).

  12. Calculation of mutual information for nonlinear communication channel at large signal-to-noise ratio

    NASA Astrophysics Data System (ADS)

    Terekhov, I. S.; Reznichenko, A. V.; Turitsyn, S. K.

    2016-10-01

    Using the path-integral technique we examine the mutual information for the communication channel modeled by the nonlinear Schrödinger equation with additive Gaussian noise. The nonlinear Schrödinger equation is one of the fundamental models in nonlinear physics, and it has a broad range of applications, including fiber optical communications—the backbone of the internet. At large signal-to-noise ratio we present the mutual information through the path-integral, which is convenient for the perturbative expansion in nonlinearity. In the limit of small noise and small nonlinearity we derive analytically the first nonzero nonlinear correction to the mutual information for the channel.

  13. Emergent properties of nuclei from ab initio coupled-cluster calculations

    DOE PAGES

    Hagen, G.; Hjorth-Jensen, M.; Jansen, G. R.; Papenbrock, T.

    2016-05-17

    Emergent properties such as nuclear saturation and deformation, and the effects on shell structure due to the proximity of the scattering continuum and particle decay channels are fascinating phenomena in atomic nuclei. In recent years, ab initio approaches to nuclei have taken the first steps towards tackling the computational challenge of describing these phenomena from Hamiltonians with microscopic degrees of freedom. Our endeavor is now possible due to ideas from effective field theories, novel optimization strategies for nuclear interactions, ab initio methods exhibiting a soft scaling with mass number, and ever-increasing computational power. We review some of the recent accomplishments. We also present new results. The recently optimized chiral interaction NNLOmore » $${}_{{\\rm{sat}}}$$ is shown to provide an accurate description of both charge radii and binding energies in selected light- and medium-mass nuclei up to 56Ni. We derive an efficient scheme for including continuum effects in coupled-cluster computations of nuclei based on chiral nucleon–nucleon and three-nucleon forces, and present new results for unbound states in the neutron-rich isotopes of oxygen and calcium. Finally, the coupling to the continuum impacts the energies of the $${J}^{\\pi }=1/{2}^{-},3/{2}^{-},7/{2}^{-},3/{2}^{+}$$ states in $${}^{\\mathrm{17,23,25}}$$O, and—contrary to naive shell-model expectations—the level ordering of the $${J}^{\\pi }=3/{2}^{+},5/{2}^{+},9/{2}^{+}$$ states in $${}^{\\mathrm{53,55,61}}$$Ca.« less

  14. Vibrationally Averaged Long-Range Molecule-Molecule Dispersion Coefficients from Coupled-Cluster Calculations

    NASA Astrophysics Data System (ADS)

    Schmidt, Matthew; Nooijen, Marcel

    2011-06-01

    Recent years have seen increasing interest in the structure and dynamics of molecular clusters formed when a chromophore molecule such as CO_2, OCS or N_2O is solvated by number of He atoms and/or para-H_2 molecules. A key experimental probe of their behaviour is the shift of a chromophore's vibrational transition frequency which occurs when the solvent species are attached to it. Such shifts are driven by the changes in the solvent-chromophore interaction potential upon vibrational excitation of the probe molecule. While `conventional' supermolecule calculations can often provide realistic predictions of such changes in the potential well and repulsive wall region, they become increasingly unreliable for describing the weak interactions at long range where most of the solvent species in a large cluster are located. It is therefore important to have accurate relative-orientation and monomer-stretching dependent long-range C_6, C_8 and C10 dispersion coefficients to incorporate into the models for the interaction potential and for its dependence on the chromophore's vibrational state. This paper describes how those coefficients can be obtained from calculated monomer dipole, quadrupole, and octupole polarizabilities for imaginary frequencies, and by making use of the Casimir-Polder relation and angular momentum coupling to extract orientation-dependent quantities. The calculations are performed using a modified version of the ACES2 program system which allows the calculation of dipole, quadrupole and octupole polarizabilities at the EOM-CCSD level, and of static multipole moments using CCSD(T) calculations and adequate basis sets. For each relevant level of the chromophore, vibrational averaging is performed by calculating the imaginary frequency polarizabilities at judiciously chosen geometries and performing a numerical integration using the free-molecule vibrational wavefunction. Subsequent work will involve merging this long-range part of the potential with a

  15. Coupled-channel effects in elastic scattering and near-barrier fusion induced by weakly bound nuclei and exotic halo nuclei

    SciTech Connect

    Beck, C.; Keeley, N.

    2007-05-15

    The influence on fusion of coupling to the breakup process is investigated for reactions where at least one of the colliding nuclei has a sufficiently low binding energy for breakup to become an important process. Elastic scattering, excitation functions for sub- and near-barrier fusion cross sections, and breakup yields are analyzed for {sup 6,7}Li+{sup 59}Co. Continuum-discretized coupled-channels (CDCC) calculations describe well the data at and above the barrier. Elastic scattering with {sup 6}Li (as compared to {sup 7}Li) indicates the significant role of breakup for weakly bound projectiles. A study of {sup 4,6}He induced fusion reactions with a three-body CDCC method for the {sup 6}He halo nucleus is presented. The relative importance of breakup and bound-state structure effects on total fusion is discussed.

  16. Pharmacological Characterization of 5-HT1A Autoreceptor-Coupled GIRK Channels in Rat Dorsal Raphe 5-HT Neurons

    PubMed Central

    Montalbano, Alberto; Corradetti, Renato; Mlinar, Boris

    2015-01-01

    G protein-activated inwardly rectifying potassium (GIRK) channels in 5-HT neurons are assumed to be principal effectors of 5-hydroxytryptamine 1A (5-HT1A) autoreceptors, but their pharmacology, subunit composition and the role in regulation of 5-HT neuron activity have not been fully elucidated. We sought for a pharmacological tool for assessing the functional role of GIRK channels in 5-HT neurons by characterizing the effects of drugs known to block GIRK channels in the submicromolar range of concentrations. Whole-cell voltage-clamp recording in brainstem slices were used to determine concentration-response relationships for the selected GIRK channel blockers on 5-HT1A autoreceptor-activated inwardly rectifying K+ conductance in rat dorsal raphe 5-HT neurons. 5-HT1A autoreceptor-activated GIRK conductance was completely blocked by the nonselective inwardly rectifying potassium channels blocker Ba2+ (EC50 = 9.4 μM, full block with 100 μM) and by SCH23390 (EC50 = 1.95 μM, full block with 30 μM). GIRK-specific blocker tertiapin-Q blocked 5-HT1A autoreceptor-activated GIRK conductance with high potency (EC50 = 33.6 nM), but incompletely, i.e. ~16% of total conductance resulted to be tertiapin-Q-resistant. U73343 and SCH28080, reported to block GIRK channels with submicromolar EC50s, were essentially ineffective in 5-HT neurons. Our data show that inwardly rectifying K+ channels coupled to 5-HT1A autoreceptors display pharmacological properties generally expected for neuronal GIRK channels, but different from GIRK1-GIRK2 heteromers, the predominant form of brain GIRK channels. Distinct pharmacological properties of GIRK channels in 5-HT neurons should be explored for the development of new therapeutic agents for mood disorders. PMID:26460748

  17. A collective coupled-channel model and mirror state energy displacements

    NASA Astrophysics Data System (ADS)

    Fraser, P. R.; Amos, K.; Canton, L.; Karataglidis, S.; van der Knijff, D.; Svenne, J. P.

    2015-09-01

    The spectra of nucleon-nucleus mirror systems allow examination of charge symmetry breaking in nucleon-nucleus interactions. To date, such examination has been performed with studies using microscopic models of structure. Herein we seek characterisation with a coupled-channel model in which the nucleon-nucleus interactions are described using a collective model prescription with the Pauli principle taken into account. The neutron-nucleus Hamiltonian is chosen to give the best match to the compound system spectrum, with emphasis on finding the correct ground state energy relative to the neutron-nucleus threshold. The Coulomb interactions for the proton-nucleus partner of a mirror pair are determined using charge distributions that match the root-mean-square charge radii of the nuclei in question. With the Coulomb interaction so defined modifying the neutron-nucleus Hamiltonian, we then predict a spectrum for the relevant proton-nucleus compound. Discrepancies in that resulting spectrum with measured values we tentatively ascribe to charge-symmetry breaking effects. We consider spectra obtained in this way for the mirror pairs 13C and 13N, 15C and 15F, and 15O and 15N, all to ˜ 10 MeV excitation.

  18. Nuclear Astrophysics Studies with the Method of Continuum-Discretized Coupled-Channels

    SciTech Connect

    Ogata, K.; Yahiro, M.; Hashimoto, S.; Iseri, Y.; Kan, M.; Kamimura, M.

    2010-05-12

    The method of continuum-discretized coupled-channels (CDCC) is applied to two nuclear astrophysics studies. One is the determination of the astrophysical factor S{sub 17}(0) for the {sup 7}Be(p,gamma){sup 8}B reaction from the analysis of {sup 8}B breakup by {sup 208}Pb at 52 A MeV. We obtain S{sub 17}(0) = 20.9{sub -1.9}{sup +2.0} eV b, which is significantly larger than the previous one, S{sub 17}(0) = 18.9+-1.8 eV b, determined from an analysis with the virtual photon theory. The difference between the two values is found to be due to the contributions from nuclear breakup and higher-order processes. The other application of CDCC is the re-evaluation of the triple-alpha reaction rate by directly solving the three-body Schroedinger equation. The resonant and nonresonant processes are treated on the same footing. An accurate description of the alpha-alpha nonresonant states significantly quenches the Coulomb barrier between the first two alpha-particles and the third alpha-particle. Consequently, the alpha-alpha nonresonant continuum states give a markedly larger contribution at low temperatures than that reported in previous studies. We find an increase in triple-alpha reaction rate by 26 orders of magnitude around 10{sup 7} K compared with the rate of NACRE.

  19. Extraction of Electromagnetic Transition Form Factors for Nucleon Resonances within a Dynamical Coupled-Channels Model

    SciTech Connect

    N. Suzuki, T. Sato, T.-S. H. Lee

    2010-10-01

    We explain the application of a recently developed analytic continuation method to extract the electromagnetic transition form factors for the nucleon resonances ($N^*$) within a dynamical coupled-channel model of meson-baryon reactions.Illustrative results of the obtained $N^*\\rightarrow \\gamma N$ transition form factors, defined at the resonance pole positions on the complex energy plane, for the well isolated $P_{33}$ and $D_{13}$, and the complicated $P_{11}$ resonances are presented. A formula has been developed to give an unified representation of the effects due to the first two $P_{11}$ poles, which are near the $\\pi\\Delta$ threshold, but are on different Riemann sheets. We also find that a simple formula, with its parameters determined in the Laurent expansions of $\\pi N \\rightarrow \\pi N$ and $\\gamma N \\rightarrow\\pi N$ amplitudes, can reproduce to a very large extent the exact solutions of the considered model at energies near the real parts of the extracted resonance positions. We indicate the differences between our results and those extracted from the approaches using the Breit-Wigner parametrization of resonant amplitudes to fit the data.

  20. [Plasma temperature calculation and coupling mechanism analysis of laser-double wire hybrid welding].

    PubMed

    Zheng, Kai; Li, Huan; Yang, Li-Jun; Gu, Xiao-Yan; Gao, Ying

    2013-04-01

    The plasma radiation of laser-double wire hybrid welding was collected by using fiber spectrometer, the coupling mechanism of arc with laser was studied through high-speed photography during welding process, and the temperature of hybrid plasma was calculated by using the method of Boltzmann plot. The results indicated that with laser hybrid, luminance was enhanced; radiation intensity became stronger; arc was attracted to the laser point; cross section contracted and arc was more stable. The laser power, welding current and arc-arc distance are important factors that have great influence on electron temperature. Increase in the laser power, amplification of welding current and reduction of arc-arc distance can all result in the rise of temperature. PMID:23841392

  1. Connected triple excitations in coupled-cluster calculations of hyperpolarizabilities: Neon

    NASA Technical Reports Server (NTRS)

    Rice, Julia E.; Scuseria, Gustavo E.; Lee, Timothy J.; Taylor, Peter R.; Almloef, Jan

    1992-01-01

    We have calculated the second hyperpolarizability gamma of neon using the CCSD(T) method. The accuracy of the CCSD(T) approach has been established by explicit comparison with the single, double and triple excitation coupled-cluster (CCSDT) method using extended basis sets that are known to be adequate for the description of gamma. Our best estimate for gamma(sub 0) of 110 +/- 3 a.u. is in good agreement with other recent theoretical values and with Shelton's recent experimental estimate of 108 +/- 2 a.u. Comparison of the MP2 and CCSD(T) hyperpolarizability values indicates that MP2 gives a very good description of the electron correlation contribution to gamma(sub 0). We have combined MP2 frequency-dependent corrections with the CCSD(T) gamma(sub 0) to yield values of gamma(-2 omega;omega,omega,0) and gamma(exp K)(-omega;omega,0,0).

  2. Coupled channel effect in elastic scattering and fusion for 6,7Li+28Si

    NASA Astrophysics Data System (ADS)

    Sinha, Mandira; Roy, Subinit; Basu, P.; Majumdar, H.; Santra, S.; Parkar, V. V.; Golda, K. S.; Kailas, S.

    2011-10-01

    The fusion excitation and elastic angular distribution were measured for 6,7Li+28Si from below to above Coulomb barrier (≤ 3Vb) energies. The barrier distribution derived from the fusion data was found to be broad and asymmetric at the sub-barrier region, compared to 1D BPM estimation. Effect of rotational coupling on fusion was found to be not so dominant. Phenomenological optical potential parameters, with surface and volume type imaginary potentials, were obtained from f tting of elastic scattering data and energy dependence of real and imaginary surface strengths were investigated around the barrier. CDCC calculations considering only breakup of projectile were performed for 6,7Li+28Si with the elastic scattering data, using the code FRESCO. The effects of breakup of projectile on elastic cross section do not agree with the energy dependence of real and imaginary strength with volume type imaginary potential around the barrier.

  3. Compact four-channel terahertz demultiplexer based on directional coupling photonic crystal

    NASA Astrophysics Data System (ADS)

    Jiu-Sheng, Li; Han, Liu; Le, Zhang

    2015-09-01

    Electromagnetic polarization conveys valuable information for signal processing. Manipulation of terahertz wavelength demultiplexer exhibits tremendous potential in developing application of terahertz science and technology. We propose an approach to separate efficiently four frequencies terahertz waves based on three cascaded directional coupling two-dimensional photonic crystal waveguides. Both plane wave expansion method and finite-difference time-domain method are used to calculate and analyze the characteristics of the proposed device. The simulation results show that the designed terahertz wavelength demultiplexer can split four different wavelengths of terahertz wave into different propagation directions with high transmittance and low crosstalk. The present device is very compact and the total size is 6.8×10.6 mm2. This enables the terahertz wavelength demultiplexer to be used in terahertz wave system and terahertz wave integrated circuit fields.

  4. Calculated coupling of electron and proton transfer in the photosynthetic reaction center of Rhodopseudomonas viridis.

    PubMed Central

    Lancaster, C R; Michel, H; Honig, B; Gunner, M R

    1996-01-01

    Based on new Rhodopseudomonas (Rp.) viridis reaction center (RC) coordinates with a reliable structure of the secondary acceptor quinone (QB) site, a continuum dielectric model and finite difference technique have been used to identify clusters of electrostatically interacting ionizable residues. Twenty-three residues within a distance of 25 A from QB (QB cluster) have been shown to be strongly electrostatically coupled to QB, either directly or indirectly. An analogous cluster of 24 residues is found to interact with QA (QA cluster). Both clusters extend to the cytoplasmic surface in at least two directions. However, the QB cluster differs from the QA cluster in that it has a surplus of acidic residues, more strong electrostatic interactions, is less solvated, and experiences a strong positive electrostatic field arising from the polypeptide backbone. Consequently, upon reduction of QA or QB, it is the QB cluster, and not the QA cluster, which is responsible for substoichiometric proton uptake at neutral pH. The bulk of the changes in the QB cluster are calculated to be due to the protonation of a tightly coupled cluster of the three Glu residues (L212, H177, and M234) within the QB cluster. If the lifetime of the doubly reduced state QB2- is long enough, Asp M43 and Ser L223 are predicted to also become protonated. The calculated complex titration behavior of the strongly interacting residues of the QB cluster and the resulting electrostatic response to electron transfer may be a common feature in proton-transferring membrane protein complexes. Images FIGURE 2 p2482-a FIGURE 6 FIGURE 8 FIGURE 10 PMID:8744288

  5. Closed state-coupled C-type inactivation in BK channels.

    PubMed

    Yan, Jiusheng; Li, Qin; Aldrich, Richard W

    2016-06-21

    Ion channels regulate ion flow by opening and closing their pore gates. K(+) channels commonly possess two pore gates, one at the intracellular end for fast channel activation/deactivation and the other at the selectivity filter for slow C-type inactivation/recovery. The large-conductance calcium-activated potassium (BK) channel lacks a classic intracellular bundle-crossing activation gate and normally show no C-type inactivation. We hypothesized that the BK channel's activation gate may spatially overlap or coexist with the C-type inactivation gate at or near the selectivity filter. We induced C-type inactivation in BK channels and studied the relationship between activation/deactivation and C-type inactivation/recovery. We observed prominent slow C-type inactivation/recovery in BK channels by an extreme low concentration of extracellular K(+) together with a Y294E/K/Q/S or Y279F mutation whose equivalent in Shaker channels (T449E/K/D/Q/S or W434F) caused a greatly accelerated rate of C-type inactivation or constitutive C-inactivation. C-type inactivation in most K(+) channels occurs upon sustained membrane depolarization or channel opening and then recovers during hyperpolarized membrane potentials or channel closure. However, we found that the BK channel C-type inactivation occurred during hyperpolarized membrane potentials or with decreased intracellular calcium ([Ca(2+)]i) and recovered with depolarized membrane potentials or elevated [Ca(2+)]i Constitutively open mutation prevented BK channels from C-type inactivation. We concluded that BK channel C-type inactivation is closed state-dependent and that its extents and rates inversely correlate with channel-open probability. Because C-type inactivation can involve multiple conformational changes at the selectivity filter, we propose that the BK channel's normal closing may represent an early conformational stage of C-type inactivation.

  6. Calculation of fully developed flow and heat transfer in streamwise-periodic dimpled channels

    NASA Astrophysics Data System (ADS)

    Choudhury, Dipankar; Karki, Kailash C.

    1991-01-01

    An analysis is presented for fluid flow and heat transfer in a parallel plate channel with periodically spaced dimples. The flow is assumed to be constant property, two dimensional and laminar, with uniform wall temperature thermal boundary condition in the periodic fully developed region. A control-volume finite-difference method based on generalized curvilinear coordinates with the capability to handle periodic boundary conditions has been developed in order to solve the problem. Computations have been carried out for a variety of geometric parameter, Reynolds number, and Prandtl number combinations. Local results presented for the periodic fully developed velocity and temperature fields provide a good physical understanding of the fluid flow and heat transfer phenomena. The average heat transfer and pressure drop results are presented for all the cases studied. Decrease in the channel width and the dimple spacing are both accompanied by increase in the heat transfer and pressure drop.

  7. Non-empirical calculations of NMR indirect carbon-carbon coupling constants. Part 9--Bicyclobutane-containing polycycloalkanes.

    PubMed

    Krivdin, Leonid B

    2004-10-01

    13C--(13)C spin-spin coupling constants characterizing the bicyclobutane moiety of seven well-known bicyclobutane-containing polycycloalkanes were calculated at the SOPPA level. Benchmark calculations on tricyclopentane and octabisvalene revealed an appropriate level of theory and sufficient quality of basis sets used to perform geometry searches and to calculate spin-spin coupling constants. Several experimental uncertainties were resolved and a number of interesting couplings were predicted. The most interesting trend observed in this series of polycycloalkanes is the marked increase (decrease in absolute value) of J(C,C) between bridgehead carbons with increase in the puckering angle of the bicyclobutane moiety. This predicts almost zero coupling between bridgehead carbons of tricyclopentane and explains the positive J(C,C) in tetrahedrane in contrast to the negative bridgehead-bridgehead J(C,C) in bicyclobutane.

  8. Estradiol activates epithelial sodium channels in rat alveolar cells through the G protein-coupled estrogen receptor

    PubMed Central

    Mitzelfelt, Jeremiah D.; Yu, Ling; Yue, Qiang; Duke, Billie Jeanne; Harrell, Constance S.; Neigh, Gretchen N.; Eaton, Douglas C.

    2013-01-01

    Female sex predisposes individuals to poorer outcomes during respiratory disorders like cystic fibrosis and influenza-associated pneumonia. A common link between these disorders is dysregulation of alveolar fluid clearance via disruption of epithelial sodium channel (ENaC) activity. Recent evidence suggests that female sex hormones directly regulate expression and activity of alveolar ENaC. In our study, we identified the mechanism by which estradiol (E2) or progesterone (P4) independently regulates alveolar ENaC. Using cell-attached patch clamp, we measured ENaC single-channel activity in a rat alveolar cell line (L2) in response to overnight exposure to either E2 or P4. In contrast to P4, E2 increased ENaC channel activity (NPo) through an increase in channel open probability (Po) and an increased number of patches with observable channel activity. Apical plasma membrane abundance of the ENaC α-subunit (αENaC) more than doubled in response to E2 as determined by cell surface biotinylation. αENaC membrane abundance was approximately threefold greater in lungs from female rats in proestrus, when serum E2 is greatest, compared with diestrus, when it is lowest. Our results also revealed a significant role for the G protein-coupled estrogen receptor (Gper) to mediate E2's effects on ENaC. Overall, our results demonstrate that E2 signaling through Gper selectively activates alveolar ENaC through an effect on channel gating and channel density, the latter via greater trafficking of channels to the plasma membrane. The results presented herein implicate E2-mediated regulation of alveolar sodium channels in the sex differences observed in the pathogenesis of several pulmonary diseases. PMID:24097558

  9. Estradiol activates epithelial sodium channels in rat alveolar cells through the G protein-coupled estrogen receptor.

    PubMed

    Greenlee, Megan M; Mitzelfelt, Jeremiah D; Yu, Ling; Yue, Qiang; Duke, Billie Jeanne; Harrell, Constance S; Neigh, Gretchen N; Eaton, Douglas C

    2013-12-01

    Female sex predisposes individuals to poorer outcomes during respiratory disorders like cystic fibrosis and influenza-associated pneumonia. A common link between these disorders is dysregulation of alveolar fluid clearance via disruption of epithelial sodium channel (ENaC) activity. Recent evidence suggests that female sex hormones directly regulate expression and activity of alveolar ENaC. In our study, we identified the mechanism by which estradiol (E2) or progesterone (P4) independently regulates alveolar ENaC. Using cell-attached patch clamp, we measured ENaC single-channel activity in a rat alveolar cell line (L2) in response to overnight exposure to either E2 or P4. In contrast to P4, E2 increased ENaC channel activity (NPo) through an increase in channel open probability (Po) and an increased number of patches with observable channel activity. Apical plasma membrane abundance of the ENaC α-subunit (αENaC) more than doubled in response to E2 as determined by cell surface biotinylation. αENaC membrane abundance was approximately threefold greater in lungs from female rats in proestrus, when serum E2 is greatest, compared with diestrus, when it is lowest. Our results also revealed a significant role for the G protein-coupled estrogen receptor (Gper) to mediate E2's effects on ENaC. Overall, our results demonstrate that E2 signaling through Gper selectively activates alveolar ENaC through an effect on channel gating and channel density, the latter via greater trafficking of channels to the plasma membrane. The results presented herein implicate E2-mediated regulation of alveolar sodium channels in the sex differences observed in the pathogenesis of several pulmonary diseases. PMID:24097558

  10. Electron collisions with phenol: Total, integral, differential, and momentum transfer cross sections and the role of multichannel coupling effects on the elastic channel

    NASA Astrophysics Data System (ADS)

    da Costa, Romarly F.; de Oliveira, Eliane M.; Bettega, Márcio H. F.; Varella, Márcio T. do N.; Jones, Darryl B.; Brunger, Michael J.; Blanco, Francisco; Colmenares, Rafael; Limão-Vieira, Paulo; García, Gustavo; Lima, Marco A. P.

    2015-03-01

    We report theoretical and experimental total cross sections for electron scattering by phenol (C6H5OH). The experimental data were obtained with an apparatus based in Madrid and the calculated cross sections with two different methodologies, the independent atom method with screening corrected additivity rule (IAM-SCAR), and the Schwinger multichannel method with pseudopotentials (SMCPP). The SMCPP method in the Nopen-channel coupling scheme, at the static-exchange-plus-polarization approximation, is employed to calculate the scattering amplitudes at impact energies ranging from 5.0 eV to 50 eV. We discuss the multichannel coupling effects in the calculated cross sections, in particular how the number of excited states included in the open-channel space impacts upon the convergence of the elastic cross sections at higher collision energies. The IAM-SCAR approach was also used to obtain the elastic differential cross sections (DCSs) and for correcting the experimental total cross sections for the so-called forward angle scattering effect. We found a very good agreement between our SMCPP theoretical differential, integral, and momentum transfer cross sections and experimental data for benzene (a molecule differing from phenol by replacing a hydrogen atom in benzene with a hydroxyl group). Although some discrepancies were found for lower energies, the agreement between the SMCPP data and the DCSs obtained with the IAM-SCAR method improves, as expected, as the impact energy increases. We also have a good agreement among the present SMCPP calculated total cross section (which includes elastic, 32 inelastic electronic excitation processes and ionization contributions, the latter estimated with the binary-encounter-Bethe model), the IAM-SCAR total cross section, and the experimental data when the latter is corrected for the forward angle scattering effect [Fuss et al., Phys. Rev. A 88, 042702 (2013)].

  11. Electron collisions with phenol: Total, integral, differential, and momentum transfer cross sections and the role of multichannel coupling effects on the elastic channel

    SciTech Connect

    Costa, Romarly F. da; Oliveira, Eliane M. de; Lima, Marco A. P.; Bettega, Márcio H. F.; Varella, Márcio T. do N.; Jones, Darryl B.; Brunger, Michael J.; Blanco, Francisco; Colmenares, Rafael; and others

    2015-03-14

    We report theoretical and experimental total cross sections for electron scattering by phenol (C{sub 6}H{sub 5}OH). The experimental data were obtained with an apparatus based in Madrid and the calculated cross sections with two different methodologies, the independent atom method with screening corrected additivity rule (IAM-SCAR), and the Schwinger multichannel method with pseudopotentials (SMCPP). The SMCPP method in the N{sub open}-channel coupling scheme, at the static-exchange-plus-polarization approximation, is employed to calculate the scattering amplitudes at impact energies ranging from 5.0 eV to 50 eV. We discuss the multichannel coupling effects in the calculated cross sections, in particular how the number of excited states included in the open-channel space impacts upon the convergence of the elastic cross sections at higher collision energies. The IAM-SCAR approach was also used to obtain the elastic differential cross sections (DCSs) and for correcting the experimental total cross sections for the so-called forward angle scattering effect. We found a very good agreement between our SMCPP theoretical differential, integral, and momentum transfer cross sections and experimental data for benzene (a molecule differing from phenol by replacing a hydrogen atom in benzene with a hydroxyl group). Although some discrepancies were found for lower energies, the agreement between the SMCPP data and the DCSs obtained with the IAM-SCAR method improves, as expected, as the impact energy increases. We also have a good agreement among the present SMCPP calculated total cross section (which includes elastic, 32 inelastic electronic excitation processes and ionization contributions, the latter estimated with the binary-encounter-Bethe model), the IAM-SCAR total cross section, and the experimental data when the latter is corrected for the forward angle scattering effect [Fuss et al., Phys. Rev. A 88, 042702 (2013)].

  12. Contribution of coupling between human myometrial beta2-adrenoreceptor and the BK(Ca) channel to uterine quiescence.

    PubMed

    Chanrachakul, Boonsri; Broughton Pipkin, Fiona; Khan, Raheela N

    2004-12-01

    The beta(2)-adrenergic receptor (beta(2)-AR) and the large-conductance Ca(2+)-activated K(+) (BK(Ca)) channel have been shown, separately, to be involved in mediating uterine relaxation. Our recent studies reveal that the levels of both beta(2)-AR and BK(Ca) channel proteins in pregnant human myometrium decrease by approximately 50% after the onset of labor. We present direct evidence in support of a structural and functional association between the beta(2)-AR and the BK(Ca) channel in pregnant human myometrium. Localization of both proteins is predominantly plasmalemmal, with 60% of beta(2)-AR colocalizing with the BK(Ca) channel. Coimmunoprecipitation studies indicate that BK(Ca) and beta(2)-AR are structurally linked by direct protein-protein interactions. Functional correlation was confirmed by experiments of human myometrial contractility in which the BK(Ca) channel blocker, paxilline, significantly antagonized the relaxant effect of the beta(2)-AR agonist ritodrine. These novel findings provide an insight into the coupling between the beta(2)-AR and BK(Ca) channel and may have utility in the application of this signaling cascade for therapeutic potential in the management of preterm labor.

  13. Extensive calculations on 12 Λ-S and 27 Ω states of PCl+ cation including spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Niu, Xianghong; Shi, Deheng; Sun, Jinfeng; Zhu, Zunlue

    2014-01-01

    The potential energy curves (PECs) of 27 Ω states generated from the 12 Λ-S states (X2Π, A2Π, 14Π, 24Π, 12Σ-, 22Σ-, 14Σ-, 24Σ-, 12Σ+, 14Σ+, 12Δ and 14Δ) of PCl+ cation are studied for the first time for internuclear separations from about 0.10 to 1.10 nm using an ab initio quantum chemical method. All the 12 Λ-S states correlate to the first dissociation channel of PCl+ cation. Of these Λ-S states, the 24Π is found to be the repulsive one. The 14Σ+, 12Δ and 14Δ are found to be the inverted ones. And the 12Δ is found to possess the double wells. The PECs are calculated by the complete active space self-consistent field method, which is followed by the internally contracted multireference configuration interaction approach with the Davidson correction in combination with the correlation-consistent basis sets, aug-cc-pV(n+d)Z. The effect of core-valence correlation and scalar relativistic corrections on the spectroscopic parameters is briefly discussed. Scalar relativistic corrections are included by the third-order Douglas-Kroll Hamiltonian approximation at the level of a cc-pV5Z basis set. Core-valence correlation corrections are included with a cc-pCVTZ basis set. The convergent behavior of present calculations is discussed with respect to the basis set and level of theory. The spin-orbit coupling is accounted for by the state interaction method with the Breit-Pauli Hamiltonian using the all-electron cc-pCVTZ basis set. All the PECs are extrapolated to the complete basis set limit. The spectroscopic parameters are evaluated for the 11 Λ-S bound states and for the 23 Ω bound states, and are compared with available experimental and other theoretical results. Fair agreement has been found between the present spectroscopic parameters and the measurements. The energy splitting in the X2Π Λ-S state is calculated to be 346.11 cm-1, close to the estimated measurements of 370 cm-1. It demonstrates that the spectroscopic parameters reported here can

  14. Density-Functional and Coupled-Cluster Singles-and-Doubles Calculations of the Nuclear Shielding and Indirect Nuclear Spin-Spin Coupling Constants of o-Benzyne.

    PubMed

    Helgaker, Trygve; Jaszuński, Michał

    2007-01-01

    Density-functional theory (DFT) and coupled-cluster singles-and-doubles (CCSD) theory are applied to compute the nuclear magnetic resonance (NMR) shielding and indirect nuclear spin-spin coupling constants of o-benzyne, whose biradical nature makes it difficult to study both experimentally and theoretically. Because of near-equilibrium triplet instabilities that follow from its biradical character, the calculated DFT NMR properties of o-benzyne are unusually sensitive to details of the exchange-correlation functional. However, this sensitivity is greatly reduced if these properties are calculated at the equilibrium of the chosen functional. A strong correlation is demonstrated between the quality of the calculated indirect spin-spin coupling constants and the quality of the calculated lowest triplet excitation energy in o-benzyne. Orbital-unrelaxed coupled-cluster theory should be less affected by such instabilities, and the CCSD NMR properties were only calculated at the experimental equilibrium geometry. For the shielding constants, the results in best agreement with experimental results are obtained with CCSD theory and with the Keal-Tozer KT1 and KT2 functionals. For the triply bonded carbon atoms, these models yield an isotropic shielding of 1.3, -3.3, and -1.2 ppm, respectively, compared with the experimentally observed shielding of 3.7 ppm for incarcerated o-benzyne. For the indirect spin-spin coupling constants, the CCSD model and the Perdew-Burke-Ernzerhof functional both yield reliable results; for the most interesting spin-spin coupling constant, (1)J (C⋮C), we obtain 210 and 209 Hz with these two models, respectively, somewhat above the recently reported experimental value of 177.9 ± 0.7 Hz for o-benzyne inside a molecular container, suggesting large incarceration effects.

  15. Free energy calculation of water addition coupled to reduction of aqueous RuO4-

    NASA Astrophysics Data System (ADS)

    Tateyama, Yoshitaka; Blumberger, Jochen; Ohno, Takahisa; Sprik, Michiel

    2007-05-01

    Free energy calculations were carried out for water addition coupled reduction of aqueous ruthenate, RuO4-+H2O +e-→[RuO3(OH)2]2-, using Car-Parrinello molecular dynamics simulations. The full reaction is divided into the reduction of the tetrahedral monoanion, RuO4-+e-→RuO42-, followed by water addition, RuO42-+H2O →[RuO3(OH)2]2-. The free energy of reduction is computed from the fluctuations of the vertical energy gap using the MnO4-+e -→MnO42- reaction as reference. The free energy for water addition is estimated using constrained molecular dynamics methods. While the description of this complex reaction, in principle, involves multiple reaction coordinates, we found that reversible transformation of the reactant into the product can be achieved by control of a single reaction coordinate consisting of a suitable linear combination of atomic distances. The free energy difference of the full reaction is computed to be -0.62eV relative to the normal hydrogen electrode. This is in good agreement with the experimental value of -0.59eV, lending further support to the hypothesis that, contrary to the ruthenate monoanion, the dianion is not tetrahedral but forms a trigonal-bipyramidal dihydroxo complex in aqueous solution. We construct an approximate two-dimensional free energy surface using the coupling parameter for reduction and the mechanical constraint for water addition as variables. Analyzing this surface we find that in the most favorable reaction pathway the reduction reaction precedes water addition. The latter takes place via the protonated complex [RuO3(OH)]- and subsequent transport of the created hydroxide ion to the fifth coordination site of Ru.

  16. Coupled cluster calculations of optical rotatory dispersion of (S)-methyloxirane

    NASA Astrophysics Data System (ADS)

    Tam, Mary C.; Russ, Nicholas J.; Crawford, T. Daniel

    2004-08-01

    Coupled cluster (CC) and density-functional theory (DFT) calculations of optical rotation, [α]λ, have been carried out for the difficult case of (S)-methyloxirane for comparison to recently published gas-phase cavity ringdown polarimetry data. Both theoretical methods are exquisitely sensitive to the choice of one-electron basis set, and diffuse functions have a particularly large impact on the computed values of [α]λ. Furthermore, both methods show a surprising sensitivity to the choice of optimized geometry, with [α]355 values varying by as much as 15 deg dm-1 (g/mL)-1 among molecular structures that differ only negligibly. Although at first glance the DFT/B3LYP values of [α]355 appear to be superior to those from CC theory, the success of DFT in this case appears to stem from a significant underestimation of the lowest (Rydberg) excitation energy in methyloxirane, resulting in a shift of the first-order pole in [α]λ (the Cotton effect) towards the experimentally chosen incident radiation lines. This leads to a fortuitous positive shift in the value of [α]355 towards the experimental result. The coupled cluster singles and doubles model, on the other hand, correctly predicts the position of the absorption pole (to within 0.05 eV of the experimental result), but fails to describe correctly the shape/curvature of the ORD region λ=355, resulting in an incorrect prediction of both the magnitude and the sign of the optical rotation.

  17. Channel

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03693 Channel

    This channel is located south of Iani Chaos.

    Image information: VIS instrument. Latitude -10.9N, Longitude 345.5E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  18. Overview of coupled-channels analyses of meson production reactions: The way to the N*s

    SciTech Connect

    Julia-Diaz, Bruno

    2011-10-24

    We provide a brief review of the main existing theoretical efforts to extract and interpret the properties of baryon resonances from the experimental data for hadro-, photo- and electro-production of mesons on the nucleon. The focus is set on the dynamical coupled-channels models. An effort is made to highlight the relevant aspects of the different approaches, within the space limitations of these proceedings.

  19. The foot structure from the type 1 ryanodine receptor is required for functional coupling to store-operated channels.

    PubMed

    Sampieri, Alicia; Diaz-Muñoz, Mauricio; Antaramian, Anaid; Vaca, Luis

    2005-07-01

    In the present study we have explored structural determinants of the functional interaction between skeletal muscle ryanodine receptor (RyR1) and transient receptor potential channel 1 (TRPC1) channels expressed in Chinese hamster ovary cells. We have illustrated a functional interaction between TRPC1 channels and RyR1 for the regulation of store-operated calcium entry (SOCE) initiated after releasing calcium from a caffeine-sensitive intracellular calcium pool. RNA interference experiments directed to reduce the amount of TRPC1 protein indicate that RyR1 associates to at least two different types of store-operated channels (SOCs), one dependent and one independent of TRPC1. In contrast, bradykinin-induced SOCE is completely dependent on the presence of TRPC1 protein, as we have previously illustrated. Removing the foot structure from RyR1 results in normal caffeine-induced release of calcium from internal stores but abolishes the activation of SOCE, indicating that this structure is require for functional coupling to SOCs. The footless RyR1 protein shows a different cellular localization when compared with wild type RyR1. The later protein shows a higher percentage of colocalization with FM-464, a marker of plasma membrane. The implications of the foot structure for the functional and physical coupling to TRPC and SOCs is discussed.

  20. Multi-reference approach to the calculation of photoelectron spectra including spin-orbit coupling

    SciTech Connect

    Grell, Gilbert; Bokarev, Sergey I. Kühn, Oliver; Winter, Bernd; Seidel, Robert; Aziz, Emad F.; Aziz, Saadullah G.

    2015-08-21

    X-ray photoelectron spectra provide a wealth of information on the electronic structure. The extraction of molecular details requires adequate theoretical methods, which in case of transition metal complexes has to account for effects due to the multi-configurational and spin-mixed nature of the many-electron wave function. Here, the restricted active space self-consistent field method including spin-orbit coupling is used to cope with this challenge and to calculate valence- and core-level photoelectron spectra. The intensities are estimated within the frameworks of the Dyson orbital formalism and the sudden approximation. Thereby, we utilize an efficient computational algorithm that is based on a biorthonormal basis transformation. The approach is applied to the valence photoionization of the gas phase water molecule and to the core ionization spectrum of the [Fe(H{sub 2}O){sub 6}]{sup 2+} complex. The results show good agreement with the experimental data obtained in this work, whereas the sudden approximation demonstrates distinct deviations from experiments.

  1. Multi-reference approach to the calculation of photoelectron spectra including spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Grell, Gilbert; Bokarev, Sergey I.; Winter, Bernd; Seidel, Robert; Aziz, Emad F.; Aziz, Saadullah G.; Kühn, Oliver

    2015-08-01

    X-ray photoelectron spectra provide a wealth of information on the electronic structure. The extraction of molecular details requires adequate theoretical methods, which in case of transition metal complexes has to account for effects due to the multi-configurational and spin-mixed nature of the many-electron wave function. Here, the restricted active space self-consistent field method including spin-orbit coupling is used to cope with this challenge and to calculate valence- and core-level photoelectron spectra. The intensities are estimated within the frameworks of the Dyson orbital formalism and the sudden approximation. Thereby, we utilize an efficient computational algorithm that is based on a biorthonormal basis transformation. The approach is applied to the valence photoionization of the gas phase water molecule and to the core ionization spectrum of the [Fe(H2O)6]2+ complex. The results show good agreement with the experimental data obtained in this work, whereas the sudden approximation demonstrates distinct deviations from experiments.

  2. Transonic Shock Oscillations and Wing Flutter Calculated with an Interactive Boundary Layer Coupling Method

    NASA Technical Reports Server (NTRS)

    Edwards, John W.

    1996-01-01

    A viscous-inviscid interactive coupling method is used for the computation of unsteady transonic flows involving separation and reattachment. A lag-entrainment integral boundary layer method is used with the transonic small disturbance potential equation in the CAP-TSDV (Computational Aeroelasticity Program - Transonic Small Disturbance) code. Efficient and robust computations of steady and unsteady separated flows, including steady separation bubbles and self-excited shock-induced oscillations are presented. The buffet onset boundary for the NACA 0012 airfoil is accurately predicted and shown computationally to be a Hopf bifurcation. Shock-induced oscillations are also presented for the 18 percent circular arc airfoil. The oscillation onset boundaries and frequencies are accurately predicted, as is the experimentally observed hysteresis of the oscillations with Mach number. This latter stability boundary is identified as a jump phenomenon. Transonic wing flutter boundaries are also shown for a thin swept wing and for a typical business jet wing, illustrating viscous effects on flutter and the effect of separation onset on the wing response at flutter. Calculations for both wings show limit cycle oscillations at transonic speeds in the vicinity of minimum flutter speed indices.

  3. Research on Structural Safety of the Stratospheric Airship Based on Multi-Physics Coupling Calculation

    NASA Astrophysics Data System (ADS)

    Ma, Z.; Hou, Z.; Zang, X.

    2015-09-01

    As a large-scale flexible inflatable structure by a huge inner lifting gas volume of several hundred thousand cubic meters, the stratospheric airship's thermal characteristic of inner gas plays an important role in its structural performance. During the floating flight, the day-night variation of the combined thermal condition leads to the fluctuation of the flow field inside the airship, which will remarkably affect the pressure acted on the skin and the structural safety of the stratospheric airship. According to the multi-physics coupling mechanism mentioned above, a numerical procedure of structural safety analysis of stratospheric airships is developed and the thermal model, CFD model, finite element code and criterion of structural strength are integrated. Based on the computation models, the distributions of the deformations and stresses of the skin are calculated with the variation of day-night time. The effects of loads conditions and structural configurations on the structural safety of stratospheric airships in the floating condition are evaluated. The numerical results can be referenced for the structural design of stratospheric airships.

  4. Rotational excitation of symmetric top molecules by collisions with atoms: Close coupling, coupled states, and effective potential calculations for NH3-He

    NASA Technical Reports Server (NTRS)

    Green, S.

    1976-01-01

    The formalism for describing rotational excitation in collisions between symmetric top rigid rotors and spherical atoms is presented both within the accurate quantum close coupling framework and also the coupled states approximation of McGuire and Kouri and the effective potential approximation of Rabitz. Calculations are reported for thermal energy NH3-He collisions, treating NH3 as a rigid rotor and employing a uniform electron gas (Gordon-Kim) approximation for the intermolecular potential. Coupled states are found to be in nearly quantitative agreement with close coupling results while the effective potential method is found to be at least qualitatively correct. Modifications necessary to treat the inversion motion in NH3 are discussed.

  5. Graded Ca2+/calmodulin-dependent coupling of voltage-gated CaV1.2 channels

    PubMed Central

    Dixon, Rose E; Moreno, Claudia M; Yuan, Can; Opitz-Araya, Ximena; Binder, Marc D; Navedo, Manuel F; Santana, Luis F

    2015-01-01

    In the heart, reliable activation of Ca2+ release from the sarcoplasmic reticulum during the plateau of the ventricular action potential requires synchronous opening of multiple CaV1.2 channels. Yet the mechanisms that coordinate this simultaneous opening during every heartbeat are unclear. Here, we demonstrate that CaV1.2 channels form clusters that undergo dynamic, reciprocal, allosteric interactions. This ‘functional coupling’ facilitates Ca2+ influx by increasing activation of adjoined channels and occurs through C-terminal-to-C-terminal interactions. These interactions are initiated by binding of incoming Ca2+ to calmodulin (CaM) and proceed through Ca2+/CaM binding to the CaV1.2 pre-IQ domain. Coupling fades as [Ca2+]i decreases, but persists longer than the current that evoked it, providing evidence for ‘molecular memory’. Our findings suggest a model for CaV1.2 channel gating and Ca2+-influx amplification that unifies diverse observations about Ca2+ signaling in the heart, and challenges the long-held view that voltage-gated channels open and close independently. DOI: http://dx.doi.org/10.7554/eLife.05608.001 PMID:25714924

  6. Use of Label-free Optical Biosensors to Detect Modulation of Potassium Channels by G-protein Coupled Receptors

    PubMed Central

    Fleming, Matthew R.; Shamah, Steven M.; Kaczmarek, Leonard K.

    2014-01-01

    Ion channels control the electrical properties of neurons and other excitable cell types by selectively allowing ions to flow through the plasma membrane1. To regulate neuronal excitability, the biophysical properties of ion channels are modified by signaling proteins and molecules, which often bind to the channels themselves to form a heteromeric channel complex2,3. Traditional assays examining the interaction between channels and regulatory proteins require exogenous labels that can potentially alter the protein's behavior and decrease the physiological relevance of the target, while providing little information on the time course of interactions in living cells. Optical biosensors, such as the X-BODY Biosciences BIND Scanner system, use a novel label-free technology, resonance wavelength grating (RWG) optical biosensors, to detect changes in resonant reflected light near the biosensor. This assay allows the detection of the relative change in mass within the bottom portion of living cells adherent to the biosensor surface resulting from ligand induced changes in cell adhesion and spreading, toxicity, proliferation, and changes in protein-protein interactions near the plasma membrane. RWG optical biosensors have been used to detect changes in mass near the plasma membrane of cells following activation of G protein-coupled receptors (GPCRs), receptor tyrosine kinases, and other cell surface receptors. Ligand-induced changes in ion channel-protein interactions can also be studied using this assay. In this paper, we will describe the experimental procedure used to detect the modulation of Slack-B sodium-activated potassium (KNa) channels by GPCRs. PMID:24562095

  7. Coupled Radiation Effects in Thermochemical Nonequilibrium Shock-Capturing Flowfield Calculations

    NASA Technical Reports Server (NTRS)

    Hartung, Lin C.; Mitcheltree, Robert A.; Gnoffo, Peter A.

    1993-01-01

    Lunar and Mars return conditions are examined using the LAURA flow field code and the LORAN radiation code to assess the effect of radiative coupling on axisymmetric thermochemical nonequilibrium flows. Coupling of the two codes is achieved iteratively. Special treatment required to couple radiation in a shock-capturing method is discussed. Results indicate that while coupling effects are generally the same as occur in equilibrium flows, under certain conditions radiation can modify the chemical kinetics of a nonequilibrium flow and thus alter relaxation processes. Coupling effects are found to be small for all cases considered, except for a five meter diameter aerobrake returning from Mars at 13.6 kilometers per second.

  8. Intracellular calcium level is an important factor influencing ion channel modulations by PLC-coupled metabotropic receptors in hippocampal neurons.

    PubMed

    Sugawara, Yuto; Echigo, Ryousuke; Kashima, Kousuke; Minami, Hanae; Watanabe, Megumi; Nishikawa, Yuiko; Muranishi, Miho; Yoneda, Mitsugu; Ohno-Shosaku, Takako

    2013-05-28

    Signaling pathways involving phospholipase C (PLC) are involved in various neural functions. Understanding how these pathways are regulated will lead to a better understanding of their roles in neural functions. Previous studies demonstrated that receptor-driven PLCβ activation depends on intracellular Ca(2+) concentration ([Ca(2+)]i), suggesting the possibility that PLCβ-dependent cellular responses are basically Ca(2+) dependent. To test this possibility, we examined whether modulations of ion channels driven by PLC-coupled metabotropic receptors are sensitive to [Ca(2+)]i using cultured hippocampal neurons. Muscarinic activation triggered an inward current at -100 mV (the equilibrium potential for K(+)) in a subpopulation of neurons. This current response was suppressed by pirenzepine (an M1-preferring antagonist), PLC inhibitor, non-selective cation channel blocker, and lowering [Ca(2+)]i. Using the neurons showing no response at -100 mV, effects of muscarinic activation on K(+) channels were examined at -40 mV. Muscarinic activation induced a transient decrease of the holding outward current. This current response was mimicked and occluded by XE991, an M-current K(+) channel blocker, suppressed by pirenzepine, PLC inhibitor and lowering [Ca(2+)]i, and enhanced by elevating [Ca(2+)]i. Similar results were obtained when group I metabotropic glutamate receptors were activated instead of muscarinic receptors. These results clearly show that ion channel modulations driven by PLC-coupled metabotropic receptors are dependent on [Ca(2+)]i, supporting the hypothesis that cellular responses induced by receptor-driven PLCβ activation are basically Ca(2+) dependent.

  9. ATP-sensitive K(+) channels (Kir6.1/SUR1) regulate gap junctional coupling in cochlear-supporting cells.

    PubMed

    Blödow, Alexander; Begandt, Daniela; Bader, Almke; Becker, Annegret; Burghard, Alice; Kühne, Daniela; Kral, Andrej; Ngezahayo, Anaclet

    2016-07-01

    Using the double whole-cell patch-clamp technique, we found that the absence of intracellular ATP led to gap junction uncoupling in cochlear-supporting Hensen cells. The uncoupling was observed as a progressive reduction of the gap junctional electrical conductance from a starting value of approximately 40 nS to less than 0.04 nS within 10-20 min. The conductance rundown was partly avoided by at least 3 mM ATP and completely suppressed by 5 mM ATP or 5'-adenylyl-imidodiphosphate (AMP-PNP), the non-hydrolysable ATP analog, in the pipette filling solution, suggesting that ATP was needed as ligand and not as a hydrolysable energy supplier or substrate for enzymatic reactions. The effect of intracellular ATP was mimicked by the external application of barium, a nonselective blocker of inwardly rectifying K(+) (Kir) channels, and glibenclamide, an inhibitor of the ATP-sensitive Kir channels (KATP). Moreover a Ba(2+)-sensitive whole-cell inward current was observed in absence of internal ATP. We propose that the internal ATP kept the KATP channels in a closed state, thereby maintaining the gap junction coupling of Hensen cells. The immunostaining of guinea pig cochlear tissue revealed for the first time the expression of the KATP channel subunits Kir6.1 and SUR1 in Hensen cells and supported the proposed hypothesis. The results suggest that KATP channels, as regulator of the gap junction coupling in Hensen cells, could be the physiological link between the metabolic state of the supporting cells and K(+) recycling in the organ of Corti. PMID:27030354

  10. ATP-sensitive K(+) channels (Kir6.1/SUR1) regulate gap junctional coupling in cochlear-supporting cells.

    PubMed

    Blödow, Alexander; Begandt, Daniela; Bader, Almke; Becker, Annegret; Burghard, Alice; Kühne, Daniela; Kral, Andrej; Ngezahayo, Anaclet

    2016-07-01

    Using the double whole-cell patch-clamp technique, we found that the absence of intracellular ATP led to gap junction uncoupling in cochlear-supporting Hensen cells. The uncoupling was observed as a progressive reduction of the gap junctional electrical conductance from a starting value of approximately 40 nS to less than 0.04 nS within 10-20 min. The conductance rundown was partly avoided by at least 3 mM ATP and completely suppressed by 5 mM ATP or 5'-adenylyl-imidodiphosphate (AMP-PNP), the non-hydrolysable ATP analog, in the pipette filling solution, suggesting that ATP was needed as ligand and not as a hydrolysable energy supplier or substrate for enzymatic reactions. The effect of intracellular ATP was mimicked by the external application of barium, a nonselective blocker of inwardly rectifying K(+) (Kir) channels, and glibenclamide, an inhibitor of the ATP-sensitive Kir channels (KATP). Moreover a Ba(2+)-sensitive whole-cell inward current was observed in absence of internal ATP. We propose that the internal ATP kept the KATP channels in a closed state, thereby maintaining the gap junction coupling of Hensen cells. The immunostaining of guinea pig cochlear tissue revealed for the first time the expression of the KATP channel subunits Kir6.1 and SUR1 in Hensen cells and supported the proposed hypothesis. The results suggest that KATP channels, as regulator of the gap junction coupling in Hensen cells, could be the physiological link between the metabolic state of the supporting cells and K(+) recycling in the organ of Corti.

  11. Electronic coupling matrix elements from charge constrained density functional theory calculations using a plane wave basis set

    NASA Astrophysics Data System (ADS)

    Oberhofer, Harald; Blumberger, Jochen

    2010-12-01

    We present a plane wave basis set implementation for the calculation of electronic coupling matrix elements of electron transfer reactions within the framework of constrained density functional theory (CDFT). Following the work of Wu and Van Voorhis [J. Chem. Phys. 125, 164105 (2006)], the diabatic wavefunctions are approximated by the Kohn-Sham determinants obtained from CDFT calculations, and the coupling matrix element calculated by an efficient integration scheme. Our results for intermolecular electron transfer in small systems agree very well with high-level ab initio calculations based on generalized Mulliken-Hush theory, and with previous local basis set CDFT calculations. The effect of thermal fluctuations on the coupling matrix element is demonstrated for intramolecular electron transfer in the tetrathiafulvalene-diquinone (Q-TTF-Q-) anion. Sampling the electronic coupling along density functional based molecular dynamics trajectories, we find that thermal fluctuations, in particular the slow bending motion of the molecule, can lead to changes in the instantaneous electron transfer rate by more than an order of magnitude. The thermal average, ( {< {| {H_ab } |^2 } > } )^{1/2} = 6.7 {mH}, is significantly higher than the value obtained for the minimum energy structure, | {H_ab } | = 3.8 {mH}. While CDFT in combination with generalized gradient approximation (GGA) functionals describes the intermolecular electron transfer in the studied systems well, exact exchange is required for Q-TTF-Q- in order to obtain coupling matrix elements in agreement with experiment (3.9 mH). The implementation presented opens up the possibility to compute electronic coupling matrix elements for extended systems where donor, acceptor, and the environment are treated at the quantum mechanical (QM) level.

  12. Coupled-cluster with active space selected higher amplitudes: performance of seminatural orbitals for ground and excited state calculations.

    PubMed

    Köhn, Andreas; Olsen, Jeppe

    2006-11-01

    The active space approach for coupled-cluster models is generalized using the general active space concept and implemented in a string-based general coupled-cluster code. Particular attention is devoted to the choice of orbitals on which the subspace division is based. Seminatural orbitals are proposed for that purpose. These orbitals are obtained by diagonalizing only the hole-hole and particle-particle block of the one-electron density of a lower-order method. The seminatural orbitals are shown to be a good replacement for complete active space self-consistent field orbitals and avoid the ambiguities with respect to the reference determinant introduced by the latter orbitals. The seminatural orbitals also perform well in excited state calculations, including excited states with strong double excitation contributions, which usually are difficult to describe with standard coupled-cluster methods. A set of vertical excitation energies is obtained and benchmarked against full configuration interaction calculations, and alternative hierarchies of active space coupled-cluster models are proposed. As a simple application the spectroscopic constants of the C(2) B (1)Delta(g) and B(') (1)Sigma(g) (+) states are calculated using active space coupled-cluster methods and basis sets up to quadruple-zeta quality in connection with extrapolation and additivity schemes. PMID:17100432

  13. Coupled-cluster with active space selected higher amplitudes: Performance of seminatural orbitals for ground and excited state calculations

    NASA Astrophysics Data System (ADS)

    Köhn, Andreas; Olsen, Jeppe

    2006-11-01

    The active space approach for coupled-cluster models is generalized using the general active space concept and implemented in a string-based general coupled-cluster code. Particular attention is devoted to the choice of orbitals on which the subspace division is based. Seminatural orbitals are proposed for that purpose. These orbitals are obtained by diagonalizing only the hole-hole and particle-particle block of the one-electron density of a lower-order method. The seminatural orbitals are shown to be a good replacement for complete active space self-consistent field orbitals and avoid the ambiguities with respect to the reference determinant introduced by the latter orbitals. The seminatural orbitals also perform well in excited state calculations, including excited states with strong double excitation contributions, which usually are difficult to describe with standard coupled-cluster methods. A set of vertical excitation energies is obtained and benchmarked against full configuration interaction calculations, and alternative hierarchies of active space coupled-cluster models are proposed. As a simple application the spectroscopic constants of the C2 BΔg1 and B'Σg+1 states are calculated using active space coupled-cluster methods and basis sets up to quadruple-zeta quality in connection with extrapolation and additivity schemes.

  14. Climate variability and predictability associated with the Indo-Pacific Oceanic Channel Dynamics in the CCSM4 Coupled System Model

    NASA Astrophysics Data System (ADS)

    Yuan, Dongliang; Xu, Peng; Xu, Tengfei

    2016-03-01

    An experiment using the Community Climate System Model (CCSM4), a participant of the Coupled Model Intercomparison Project phase-5 (CMIP5), is analyzed to assess the skills of this model in simulating and predicting the climate variabilities associated with the oceanic channel dynamics across the Indo-Pacific Oceans. The results of these analyses suggest that the model is able to reproduce the observed lag correlation between the oceanic anomalies in the southeastern tropical Indian Ocean and those in the cold tongue in the eastern equatorial Pacific Ocean at a time lag of 1 year. This success may be largely attributed to the successful simulation of the interannual variations of the Indonesian Throughflow, which carries the anomalies of the Indian Ocean Dipole (IOD) into the western equatorial Pacific Ocean to produce subsurface temperature anomalies, which in turn propagate to the eastern equatorial Pacific to generate ENSO. This connection is termed the "oceanic channel dynamics" and is shown to be consistent with the observational analyses. However, the model simulates a weaker connection between the IOD and the interannual variability of the Indonesian Throughflow transport than found in the observations. In addition, the model overestimates the westerly wind anomalies in the western-central equatorial Pacific in the year following the IOD, which forces unrealistic upwelling Rossby waves in the western equatorial Pacific and downwelling Kelvin waves in the east. This assessment suggests that the CCSM4 coupled climate system has underestimated the oceanic channel dynamics and overestimated the atmospheric bridge processes.

  15. Dynamical coupled-channels analysis of {sup 1}H(e,e{sup '}{pi})N reactions

    SciTech Connect

    Julia-Diaz, B.; Kamano, H.; Lee, T.-S. H.; Matsuyama, A.; Sato, T.; Suzuki, N.

    2009-08-15

    We have performed a dynamical coupled-channels analysis of available p(e,e{sup '}{pi})N data in the region of W{<=}1.6 GeV and Q{sup 2}{<=}1.45 (GeV/c){sup 2}. The channels included are {gamma}*N, {pi}N, {eta}N, and {pi}{pi}N that has {pi}{delta}, {rho}N, and {sigma}N components. With the hadronic parameters of the model determined in our previous investigations of {pi}N{yields}{pi}N, {pi}{pi}N reactions, we have found that the available data in the considered W{<=}1.6 GeV region can be fitted well by only adjusting the bare {gamma}*N{yields}N* helicity amplitudes for the lowest N* states in P{sub 33}, P{sub 11}, S{sub 11}, and D{sub 13} partial waves. The sensitivity of the resulting parameters to the amount of data included in the analysis is investigated. The importance of coupled-channels effect on the p(e,e{sup '}{pi})N cross sections is demonstrated. The meson cloud effect, as required by the unitarity conditions, on the {gamma}*N{yields}N* form factors are also examined. Necessary future developments, both experimentally and theoretically, are discussed.

  16. Quantum calculations on water in the KcsA channel cavity with permeant and non-permeant ions

    SciTech Connect

    Kariev, Alisher M.; Green, Michael E.

    2009-04-30

    Different ions in the pore of the KcsA channel behave differently, and we relate this to their solvation. We show that the selectivity is dependent, in part, on the solvation in the cavity (sometimes referred to as the vestibule, it is the region containing water molecules between the intracellular gate and the selectivity filter at the extracellular end of the pore). We have shown earlier that potassium is more dependent at the upper end of the cavity region on solvation by the threonines there, while sodium ion has more water molecules as ligands. In addition, sodium ion is placed asymmetrically, while potassium is nearly exactly symmetric with respect to the four-fold symmetry of the channel. We have now extended these calculations to rubidium and cesium ions, and find that rubidium solvation resembles that of potassium (and both are permeant ions), while cesium resembles sodium (and both are non-permeant), in terms of the geometry of up to eight hydrating, and four non-hydrating, water molecules. In each case, a maximum of 12 water molecules are relevant to the calculation. The placement of the water molecules in the two cases is essentially the same as found from the electron density in the X-ray structure of Zhou and MacKinnon. For Na+ and K+, we show that energy decreases from bulk to the cavity to the lowest position in the selectivity filter (accurate energy could not be calculated for the heavier ions). A separate calculation shows that fixing the Na+ ion at the position of the K+ minimum, followed by re-optimization produced a significantly modified system, not something that could be produced by thermal fluctuations. Moving the K+ into the Na+ position in the upper cavity led to a small increase in energy, ≈ 3 kBT, but was accompanied by large shifts in the positions of hydrating waters, which would create a major kinetic barrier. Therefore, thermal fluctuations could not invalidate the conclusions of the main calculations.

  17. Hydrodynamic Coupling in Microbially Mediated Fracture Mineralization: Formation of Self-Organized Groundwater Flow Channels

    NASA Astrophysics Data System (ADS)

    Lunn, R. J.; El Mountassir, G.; MacLachlan, E.; Moir, H.

    2013-12-01

    Evidence of fossilized microorganisms embedded within mineral veins and mineral-filled fractures has been observed in a wide range of geological environments. Microorganisms can act as sites for mineral nucleation and also contribute to mineral precipitation by inducing local geochemical changes. In this study, we explore fundamental controls on microbially induced mineralization in rock fractures. Specifically, we systematically investigate the influence of hydrodynamics (velocity, flow rate, aperture) on microbially mediated calcite precipitation. We use a case study of microbially induced calcite precipitation as a model biomineralization system to investigate potential feedback mechanisms between the temporally varying patterns of mineral precipitation within a fracture and the resulting variations in the local velocity field. Fractures are represented as a series of precision-etched parallel channels between a pair of sealed Perspex plates. Multiple channels are designed to maintain a constant flow rate, whilst independently adjusting channel aperture and width to explore the effects of aperture and fluid velocity on biomineral precipitation. Our experimental results demonstrate that a feedback mechanism exists between the gradual reduction in fracture aperture due to precipitation, and its effect on the local fluid velocity. This feedback results in mineral fill distributions that focus flow into a small number of self-organizing channels that remain open, ultimately controlling the final aperture profile that governs flow within the fracture. This feedback mechanism exists because precipitation on the fracture walls (as opposed to in solution) requires the bacteria to be transported to the fracture surface. Bacteria settle out of a quiescent solution at a velocity that is dependent on individual floc size and density. This settling velocity competes with the bed shear velocity, inhibiting deposition via entrainment. As precipitation progresses, the flow

  18. Channel representation in physically based models coupling groundwater and surface water: pitfalls and how to avoid them.

    PubMed

    Käser, Daniel; Graf, Tobias; Cochand, Fabien; McLaren, Rob; Therrien, René; Brunner, Philip

    2014-01-01

    Recent models that couple three-dimensional subsurface flow with two-dimensional overland flow are valuable tools for quantifying complex groundwater/stream interactions and for evaluating their influence on watershed processes. For the modeler who is used to defining streams as a boundary condition, the representation of channels in integrated models raises a number of conceptual and technical issues. These models are far more sensitive to channel topography than conventional groundwater models. On all spatial scales, both the topography of a channel and its connection with the floodplain are important. For example, the geometry of river banks influences bank storage and overbank flooding; the slope of the river is a primary control on the behavior of a catchment; and at the finer scale bedform characteristics affect hyporheic exchange. Accurate data on streambed topography, however, are seldom available, and the spatial resolution of digital elevation models is typically too coarse in river environments, resulting in unrealistic or undulating streambeds. Modelers therefore perform some kind of manual yet often cumbersome correction to the available topography. In this context, the paper identifies some common pitfalls, and provides guidance to overcome these. Both aspects of topographic representation and mesh discretization are addressed. Additionally, two tutorials are provided to illustrate: (1) the interpolation of channel cross-sectional data and (2) the refinement of a mesh along a stream in areas of high topographic variability.

  19. Screening determination of pharmaceutical pollutants in different water matrices using dual-channel capillary electrophoresis coupled with contactless conductivity detection.

    PubMed

    Le, Minh Duc; Duong, Hong Anh; Nguyen, Manh Huy; Sáiz, Jorge; Pham, Hung Viet; Mai, Thanh Duc

    2016-11-01

    In this study, the employment of purpose-made dual-channel compact capillary electrophoresis (CE) instrument with capacitively coupled contactless conductivity detection (C(4)D) as a simple and inexpensive solution for screening determination of various pharmaceutical pollutants frequently occurring in surface water and hospital wastewater in Hanoi, Vietnam is reported. Five negatively charged pharmaceutically active compounds, namely ibuprofen, diclofenac, bezafibrate, ketoprofen and mefenamic acid were determined using the first channel whereas three positively charged ones, namely diphenhydramine, metoprolol and atenolol were determined with the second channel of the CE-C(4)D instrument. Two different background electrolytes (BGEs) were used in these two CE channels independently. The best detection limits achieved were in the range of 0.2-0.8mg/L without sample pre-concentration. Enrichment factors up to 200 were obtainable with the inclusion of a solid phase extraction step. Good agreement between results obtained from CE-C(4)D and those with the standard confirmation method (HPLC-DAD) was achieved, with correlation coefficients higher than 0.98. PMID:27591645

  20. Electromechanical coupling and design considerations in single-layer MoS2 suspended-channel transistors and resonators

    NASA Astrophysics Data System (ADS)

    Yang, Rui; Islam, Arnob; Feng, Philip X.-L.

    2015-11-01

    We report on the analysis of electromechanical coupling effects in suspended doubly-clamped single-layer MoS2 structures, and the designs of suspended-channel field-effect transistors (FETs) and vibrating-channel nanoelectromechanical resonators. In DC gating scenario, signal transduction processes including electrostatic actuation, deflection, straining on bandgap, mobility, carrier density and their intricate cross-interactions, have been analyzed considering strain-enhanced mobility (by up to 4 times), to determine the transfer characteristics. In AC gating scenario and resonant operations (using 100 MHz and 1 GHz devices as relevant targets), we demonstrate that the vibrating-channel MoS2 devices can offer enhanced signals (than the zero-bandgap graphene counterparts), thanks to the resonant straining effects on electron transport of the semiconducting channel. We also show dependence of signal intensity and signal-to-background ratio (SBR) on device geometries and scaling effects, with SBR enhancement by a factor of ~8 for resonance signal, which provide guidelines toward designing future devices with desirable parameters.

  1. Subunit composition of G(o) proteins functionally coupling galanin receptors to voltage-gated calcium channels.

    PubMed Central

    Kalkbrenner, F; Degtiar, V E; Schenker, M; Brendel, S; Zobel, A; Heschler, J; Wittig, B; Schultz, G

    1995-01-01

    The neuropeptide galanin is widely expressed in the central nervous system and other tissues and induces different cellular reactions, e.g. hormone release from pituitary and inhibition of insulin release from pancreatic B cells. By microinjection of antisense oligonucleotides we studied the question as to which G proteins mediate the galanin-induced inhibition of voltage-gated Ca2+ channels in the rat pancreatic B-cell line RINm5F and in the rat pituitary cell line GH3. Injection of antisense oligonucleotides directed against alpha 01, beta 2, beta 3, gamma 2 and gamma 4 G protein subunits reduced the inhibition of Ca2+ channel current which was induced by galanin, whereas no change was seen after injection of cells with antisense oligonucleotides directed against alpha i, alpha q, alpha 11, alpha 14, alpha 15, beta 1, beta 4, gamma 1, gamma 3, gamma 5, or gamma 7 G protein subunits or with sense control oligonucleotides. In view of these data and of previous results, we conclude that the galanin receptors in GH3 and in RINm5F cells couple mainly to the G(0) protein consisting of alpha 01 beta 2 gamma 2 to inhibit Ca2+ channels and use alpha 01beta 3 gamma 4 less efficiently. The latter G protein composition was previously shown to be used by muscarinic M4 receptors to inhibit Ca2+ channels. Images PMID:7588602

  2. Analyzing and Interpreting NMR Spin-Spin Coupling Constants Using Molecular Orbital Calculations

    ERIC Educational Resources Information Center

    Autschbach, Jochen; Le Guennic, Boris

    2007-01-01

    Molecular orbital plots are used to analyze and interpret NMR spin-spin coupling constants, also known as J coupling constants. Students have accepted the concept of contributions to molecular properties from individual orbitals without the requirement to provide explicit equations.

  3. A Novel Field-Circuit FEM Modeling and Channel Gain Estimation for Galvanic Coupling Real IBC Measurements.

    PubMed

    Gao, Yue-Ming; Wu, Zhu-Mei; Pun, Sio-Hang; Mak, Peng-Un; Vai, Mang-I; Du, Min

    2016-01-01

    Existing research on human channel modeling of galvanic coupling intra-body communication (IBC) is primarily focused on the human body itself. Although galvanic coupling IBC is less disturbed by external influences during signal transmission, there are inevitable factors in real measurement scenarios such as the parasitic impedance of electrodes, impedance matching of the transceiver, etc. which might lead to deviations between the human model and the in vivo measurements. This paper proposes a field-circuit finite element method (FEM) model of galvanic coupling IBC in a real measurement environment to estimate the human channel gain. First an anisotropic concentric cylinder model of the electric field intra-body communication for human limbs was developed based on the galvanic method. Then the electric field model was combined with several impedance elements, which were equivalent in terms of parasitic impedance of the electrodes, input and output impedance of the transceiver, establishing a field-circuit FEM model. The results indicated that a circuit module equivalent to external factors can be added to the field-circuit model, which makes this model more complete, and the estimations based on the proposed field-circuit are in better agreement with the corresponding measurement results. PMID:27049386

  4. A Novel Field-Circuit FEM Modeling and Channel Gain Estimation for Galvanic Coupling Real IBC Measurements

    PubMed Central

    Gao, Yue-Ming; Wu, Zhu-Mei; Pun, Sio-Hang; Mak, Peng-Un; Vai, Mang-I; Du, Min

    2016-01-01

    Existing research on human channel modeling of galvanic coupling intra-body communication (IBC) is primarily focused on the human body itself. Although galvanic coupling IBC is less disturbed by external influences during signal transmission, there are inevitable factors in real measurement scenarios such as the parasitic impedance of electrodes, impedance matching of the transceiver, etc. which might lead to deviations between the human model and the in vivo measurements. This paper proposes a field-circuit finite element method (FEM) model of galvanic coupling IBC in a real measurement environment to estimate the human channel gain. First an anisotropic concentric cylinder model of the electric field intra-body communication for human limbs was developed based on the galvanic method. Then the electric field model was combined with several impedance elements, which were equivalent in terms of parasitic impedance of the electrodes, input and output impedance of the transceiver, establishing a field-circuit FEM model. The results indicated that a circuit module equivalent to external factors can be added to the field-circuit model, which makes this model more complete, and the estimations based on the proposed field-circuit are in better agreement with the corresponding measurement results. PMID:27049386

  5. A Novel Field-Circuit FEM Modeling and Channel Gain Estimation for Galvanic Coupling Real IBC Measurements.

    PubMed

    Gao, Yue-Ming; Wu, Zhu-Mei; Pun, Sio-Hang; Mak, Peng-Un; Vai, Mang-I; Du, Min

    2016-04-02

    Existing research on human channel modeling of galvanic coupling intra-body communication (IBC) is primarily focused on the human body itself. Although galvanic coupling IBC is less disturbed by external influences during signal transmission, there are inevitable factors in real measurement scenarios such as the parasitic impedance of electrodes, impedance matching of the transceiver, etc. which might lead to deviations between the human model and the in vivo measurements. This paper proposes a field-circuit finite element method (FEM) model of galvanic coupling IBC in a real measurement environment to estimate the human channel gain. First an anisotropic concentric cylinder model of the electric field intra-body communication for human limbs was developed based on the galvanic method. Then the electric field model was combined with several impedance elements, which were equivalent in terms of parasitic impedance of the electrodes, input and output impedance of the transceiver, establishing a field-circuit FEM model. The results indicated that a circuit module equivalent to external factors can be added to the field-circuit model, which makes this model more complete, and the estimations based on the proposed field-circuit are in better agreement with the corresponding measurement results.

  6. Numerical calculation of the transient behaviour of two pure cross-flow heat exchangers coupled by a circulating flow stream

    NASA Astrophysics Data System (ADS)

    Na Ranong, Chakkrit; Hapke, Jobst; Roetzel, Wilfried

    2010-11-01

    The transient thermal behaviour of a heat shifting system consisting of two pure cross-flow heat exchangers coupled by a circulating flow stream is studied theoretically. A suitable mathematical description of the system is based on the energy balance equation for general flow processes yielding a system of coupled hyperbolic partial differential equations in two dimensions. System responses to perturbations of inlet temperatures and mass flow rates are numerically calculated with an explicit finite difference method. A criterion for the generation of computational grids minimising effects of numerical dispersion and dissipation is applied to the system of coupled pure cross-flow heat exchangers which has not been considered up to now. Due to its internal circulation the coupled system shows a different behaviour compared to single cross-flow heat exchangers like inverse response and oscillatory behaviour to non-oscillating input signals.

  7. Line coupling effects in the isotropic Raman spectra of N{sub 2}: A quantum calculation at room temperature

    SciTech Connect

    Thibault, Franck; Boulet, Christian; Ma, Qiancheng

    2014-01-28

    We present quantum calculations of the relaxation matrix for the Q branch of N{sub 2} at room temperature using a recently proposed N{sub 2}-N{sub 2} rigid rotor potential. Close coupling calculations were complemented by coupled states studies at high energies and provide about 10 200 two-body state-to state cross sections from which the needed one-body cross-sections may be obtained. For such temperatures, convergence has to be thoroughly analyzed since such conditions are close to the limit of current computational feasibility. This has been done using complementary calculations based on the energy corrected sudden formalism. Agreement of these quantum predictions with experimental data is good, but the main goal of this work is to provide a benchmark relaxation matrix for testing more approximate methods which remain of a great utility for complex molecular systems at room (and higher) temperatures.

  8. Line Coupling Effects in the Isotropic Raman Spectra of N2: A Quantum Calculation at Room Temperature

    NASA Technical Reports Server (NTRS)

    Thibault, Franck; Boulet, Christian; Ma, Qiancheng

    2014-01-01

    We present quantum calculations of the relaxation matrix for the Q branch of N2 at room temperature using a recently proposed N2-N2 rigid rotor potential. Close coupling calculations were complemented by coupled states studies at high energies and provide about 10200 two-body state-to state cross sections from which the needed one-body cross-sections may be obtained. For such temperatures, convergence has to be thoroughly analyzed since such conditions are close to the limit of current computational feasibility. This has been done using complementary calculations based on the energy corrected sudden formalism. Agreement of these quantum predictions with experimental data is good, but the main goal of this work is to provide a benchmark relaxation matrix for testing more approximate methods which remain of a great utility for complex molecular systems at room (and higher) temperatures.

  9. Benchmark calculations on the nuclear quadrupole-coupling parameters for open-shell molecules using non-relativistic and scalar-relativistic coupled-cluster methods

    SciTech Connect

    Cheng, Lan

    2015-08-14

    Quantum-chemical computations of nuclear quadrupole-coupling parameters for 24 open-shell states of small molecules based on non-relativistic and spin-free exact two-component (SFX2C) relativistic equation-of-motion coupled-cluster (EOM-CC) as well as spin-orbital-based restricted open-shell Hartree-Fock coupled-cluster (ROHF-CC) methods are reported. Relativistic effects, the performance of the EOM-CC and ROHF-CC methods for treating electron correlation, as well as basis-set convergence have been carefully analyzed. Consideration of relativistic effects is necessary for accurate calculations on systems containing third-row (K-Kr) and heavier elements, as expected, and the SFX2C approach is shown to be a useful cost-effective option here. Further, it is demonstrated that the EOM-CC methods constitute flexible and accurate alternatives to the ROHF-CC methods in the calculations of nuclear quadrupole-coupling parameters for open-shell states.

  10. Calculation of the drag and heat transfer from a sphere in the gas flow in a cylindrical channel

    NASA Astrophysics Data System (ADS)

    Simakov, N. N.

    2016-09-01

    A numerical experiment on the simulation of heat transfer from a sphere to a gas flow in a cylindrical channel in the Stokes and transient flow regimes has been described. Radial and axial profiles of the gas temperature and the dependences of drag coefficient C d of the body and Nusselt number Nu on Reynolds number Re have been calculated and analyzed. The problem of the influence of the early drag crisis for a sphere on its heat transfer to the gas flow has been considered. The estimation of this phenomenon has shown that the early drag crisis of the sphere in a strongly turbulent flow causes a reduction in heat transfer from the sphere to the gas by three to six times (in approximately the same proportion as for its drag coefficient).

  11. Voltage dependence of cardiac excitation-contraction coupling: unitary Ca2+ current amplitude and open channel probability.

    PubMed

    Altamirano, Julio; Bers, Donald M

    2007-09-14

    Excitation-contraction coupling in cardiac myocytes occurs by Ca2+-induced Ca2+ release, where L-type Ca2+ current evokes a larger sarcoplasmic reticulum (SR) Ca2+ release. The Ca2+-induced Ca2+ release amplification factor or gain (SR Ca2+ release/I(Ca)) is usually assessed by the V(m) dependence of current and Ca2+ transients. Gain rises at negative V(m), as does single channel I(Ca) (i(Ca)), which has led to the suggestion that the increases of i(Ca) amplitude enhances gain at more negative V(m). However, I(Ca) = NP(o) x i(Ca) (where NP(o) is the number of open channels), and NP(o) and i(Ca) both depend on V(m). To assess how i(Ca) and NP(o) separately influence Ca2+-induced Ca2+ release, we measured I(Ca) and junctional SR Ca2+ release in voltage-clamped rat ventricular myocytes using "Ca2+ spikes" (confocal microscopy). To vary i(Ca) alone, we changed [Ca2+](o) rapidly at constant test V(m) (0 mV) or abruptly repolarized from +120 mV to different V(m) (at constant [Ca2+](o)). To vary NP(o) alone, we altered Ca2+ channel availability by varying holding V(m) (at constant test V(m)). Reducing either i(Ca) or NP(o) alone increased excitation-contraction coupling gain. Thus, increasing i(Ca) does not increase gain at progressively negative test V(m). Such enhanced gain depends on lower NP(o) and reduced redundant Ca2+ channel openings (per junction) and a consequently smaller denominator in the gain equation. Furthermore, modest i(Ca) (at V(m) = 0 mV) may still effectively trigger SR Ca2+ release, whereas at positive V(m) (and smaller i(Ca)), high and well-synchronized channel openings are required for efficient excitation-contraction coupling. At very positive V(m), reduced i(Ca) must explain reduced SR Ca2+ release.

  12. Weak-coupling calculations in the /sup 208/Pb core region

    SciTech Connect

    McGrory, J.B.

    1981-01-01

    The structure of Tl and Hg isotopes near the /sup 208/Pb core is discussed in terms of a weak-coupling model where low-lying proton-hole states are coupled to low-lying neutron-hole states. The even Pb isotopes are first discussed in terms of a generalized seniority-2 approximation which is shown to be very accurate. The weak-coupling results are not satisfactory, and it is suggested that the defeat may be in the n-p interaction.

  13. Second-law analysis for buoyancy-driven hydromagnetic couple stress fluid flow through a porous channel

    NASA Astrophysics Data System (ADS)

    Kareem, Semiu O.; Adesanya, Samuel O.; Vincent, Uchechukwu E.

    2016-08-01

    This paper examines the combined effects of the buoyancy force and of the magnetic field on the entropy generation rate in the flow of a couple stress fluid through a porous vertical channel. The flow's dynamical equations were non-dimensionalised and solved via the application of the Adomian decomposition method (ADM). Variations of some thermo-physical parameters were conducted and discussed, with regard to the physics of the fluid. Our result shows that the entropy generation rate increases as the buoyancy increases in the fluid. In addition, the irreversibility in the flow system results mainly from the fluid's viscosity, ohmic heating, and the buoyancy.

  14. Coupled Radon and Water Temperature Measurements to Characterize the Effects of Altered Stream Channel Planform

    NASA Astrophysics Data System (ADS)

    Amerson, B. E.; Poole, G. C.; O'Daniel, S. J.

    2013-12-01

    In summer 2011, a 2.6 km reach of Meacham Creek, Oregon, USA, was altered from a straight, steep wall-based channel to more a sinuous, low-gradient channel. Key objectives of this restoration project were to increase the rate and magnitude of hyporheic exchange. The overarching goal was to initiate increased buffering and lagging of water temperature in the subsurface to mitigate warm surface water temperature in Meacham Creek, an important spawning and rearing stream for depressed populations of Chinook salmon and summer steelhead. To evaluate progress toward project goals and objectives, stream temperature and groundwater temperature in 22 wells have been measured hourly at the restoration site since March 2011. In addition, the radioactive isotope 222Rn was measured in each well and in the surface water on two occasions. The relative residence time of down welling stream water measured in the wells can be determined by ranked amplitude depression and lagged phase of annual temperature signals in the wells relative to that of the open channel flow. Residence times predicted by annual temperature signal dynamics are corroborated by 222Rn concentrations in each well. The data collected to date provide a foundation for developing a groundwater thermal model to predict the effects of channel reconfiguration on ground-surface water exchange and associated temperature effects at the reach scale.

  15. Assessment of the CCSD and CCSD(T) Coupled-Cluster Methods in Calculating Heats of Formation for Zn Complexes

    NASA Astrophysics Data System (ADS)

    Weaver, Michael N.; Yang, Yue; Merz, Kenneth M.

    2009-08-01

    Heats of formation were calculated using coupled-cluster methods for a series of zinc complexes. The calculated values were evaluated against previously conducted computational studies using density functional methods as well as experimental values. Heats of formation for nine neutral ZnXn complexes [X = -Zn, -H, -O, -F2, -S, -Cl, -Cl2, -CH3, (-CH3)2] were determined at the CCSD and CCSD(T) levels using the 6-31G** and TZVP basis sets as well as the LANL2DZ-6-31G** (LACVP**) and LANL2DZ-TZVP hybrid basis sets. The CCSD(T)/6-31G** level of theory was found to predict the heat of formation for the nonalkyl Zn complexes most accurately. The alkyl Zn species were problematic in that none of the methods that were tested accurately predicted the heat of formation for these complexes. In instances where experimental geometric parameters were available, these were most accurately predicted by the CCSD/6-31G** level of theory; going to CCSD(T) did not improve agreement with the experimental values. Coupled-cluster methods did not offer a systemic improvement over DFT calculations for a given functional/basis set combination. With the exceptions of ZnH and ZnF2, there are multiple density functionals that outperform coupled-cluster calculations with the 6-31G** basis set.

  16. Spin orbit coupling for molecular ab initio density matrix renormalization group calculations: Application to g-tensors

    SciTech Connect

    Roemelt, Michael

    2015-07-28

    Spin Orbit Coupling (SOC) is introduced to molecular ab initio density matrix renormalization group (DMRG) calculations. In the presented scheme, one first approximates the electronic ground state and a number of excited states of the Born-Oppenheimer (BO) Hamiltonian with the aid of the DMRG algorithm. Owing to the spin-adaptation of the algorithm, the total spin S is a good quantum number for these states. After the non-relativistic DMRG calculation is finished, all magnetic sublevels of the calculated states are constructed explicitly, and the SOC operator is expanded in the resulting basis. To this end, spin orbit coupled energies and wavefunctions are obtained as eigenvalues and eigenfunctions of the full Hamiltonian matrix which is composed of the SOC operator matrix and the BO Hamiltonian matrix. This treatment corresponds to a quasi-degenerate perturbation theory approach and can be regarded as the molecular equivalent to atomic Russell-Saunders coupling. For the evaluation of SOC matrix elements, the full Breit-Pauli SOC Hamiltonian is approximated by the widely used spin-orbit mean field operator. This operator allows for an efficient use of the second quantized triplet replacement operators that are readily generated during the non-relativistic DMRG algorithm, together with the Wigner-Eckart theorem. With a set of spin-orbit coupled wavefunctions at hand, the molecular g-tensors are calculated following the scheme proposed by Gerloch and McMeeking. It interprets the effective molecular g-values as the slope of the energy difference between the lowest Kramers pair with respect to the strength of the applied magnetic field. Test calculations on a chemically relevant Mo complex demonstrate the capabilities of the presented method.

  17. Mechanically driven accumulation of microscale material at coupled solid-fluid interfaces in biological channels.

    PubMed

    Zohdi, T I

    2014-02-01

    The accumulation of microscale materials at solid-fluid interfaces in biological channels is often the initial stage of certain growth processes, which are present in some forms of atherosclerosis. The objective of this work is to develop a relatively simple model for such accumulation, which researchers can use to qualitatively guide their analyses. Specifically, the approach is to construct rate equations for the accumulation at the solid-fluid interface as a function of the intensity of the shear stress. The accumulation of material subsequently reduces the cross-sectional area of the channel until the fluid-induced shear stress at the solid-fluid interface reaches a critical value, which terminates the accumulation rate. Characteristics of the model are explored analytically and numerically.

  18. Channel calibration for digital array radar in the presence of amplitude-phase and mutual coupling errors

    NASA Astrophysics Data System (ADS)

    Li, Weixing; Zhang, Yue; Lin, Jianzhi; Chen, Zengping

    2015-10-01

    Amplitude-phase errors and mutual coupling errors among multi-channels in digital array radar (DAR) will seriously deteriorate the performance of signal processing such as digital beam-forming (DBF) and high resolution direction finding. In this paper, a combined algorithm for error calibration in DAR has been demonstrated. The algorithm firstly estimates the amplitude-phase errors of each channel using interior calibration sources with the help of the calibration network. Then the signals from far field are received and the amplitude-phase errors are compensated. According to the subspace theories, the relationship between the principle eigenvectors and distorted steering vectors is expressed, and the cost function containing the mutual coupling matrix (MCM) and incident directions is established. Making use of the properties of MCM of uniform linear array, Gauss-Newton method is implied to iteratively compute the MCM and the direction of arrival (DOA). Simulation results have shown the effectiveness and performance of proposed algorithm. Based on an 8-elements DAR test-bed, experiments are carried out in anechoic chamber. The results illustrate that the algorithm is feasible in actual systems.

  19. Neurotensinergic Excitation of Dentate Gyrus Granule Cells via Gαq-Coupled Inhibition of TASK-3 Channels.

    PubMed

    Zhang, Haopeng; Dong, Hailong; Cilz, Nicholas I; Kurada, Lalitha; Hu, Binqi; Wada, Etsuko; Bayliss, Douglas A; Porter, James E; Lei, Saobo

    2016-03-01

    Neurotensin (NT) is a 13-amino acid peptide and serves as a neuromodulator in the brain. Whereas NT has been implicated in learning and memory, the underlying cellular and molecular mechanisms are ill-defined. Because the dentate gyrus receives profound innervation of fibers containing NT and expresses high density of NT receptors, we examined the effects of NT on the excitability of dentate gyrus granule cells (GCs). Our results showed that NT concentration dependently increased action potential (AP) firing frequency of the GCs by the activation of NTS1 receptors resulting in the depolarization of the GCs. NT-induced enhancement of AP firing frequency was not caused indirectly by releasing glutamate, GABA, acetylcholine, or dopamine, but due to the inhibition of TASK-3 K(+) channels. NT-mediated excitation of the GCs was G protein dependent, but independent of phospholipase C, intracellular Ca(2+) release, and protein kinase C. Immunoprecipitation experiment demonstrates that the activation of NTS1 receptors induced the association of Gαq/11 and TASK-3 channels suggesting a direct coupling of Gαq/11 to TASK-3 channels. Endogenously released NT facilitated the excitability of the GCs contributing to the induction of long-term potentiation at the perforant path-GC synapses. Our results provide a cellular mechanism that helps to explain the roles of NT in learning and memory. PMID:25405940

  20. Ignition calculations using a reduced coupled-mode electron- ion energy exchange model*

    NASA Astrophysics Data System (ADS)

    Garbett, W. J.; Chapman, D. A.

    2016-03-01

    Coupled-mode models for electron-ion energy exchange can predict large deviations from standard binary collision models in some regimes. A recently developed reduced coupled-mode model for electron-ion energy exchange, which accurately reproduces full numerical results over a wide range of density and temperature space, has been implemented in the Nym hydrocode and used to assess the impact on ICF capsule fuel assembly and performance. Simulations show a lack of sensitivity to the model, consistent with results from a range of simpler alternative models. Since the coupled-mode model is conceptually distinct to models based on binary collision theory, this result provides increased confidence that uncertainty in electron-ion energy exchange will not impact ignition attempts.

  1. Active zone scaffolds differentially accumulate Unc13 isoforms to tune Ca(2+) channel-vesicle coupling.

    PubMed

    Böhme, Mathias A; Beis, Christina; Reddy-Alla, Suneel; Reynolds, Eric; Mampell, Malou M; Grasskamp, Andreas T; Lützkendorf, Janine; Bergeron, Dominique Dufour; Driller, Jan H; Babikir, Husam; Göttfert, Fabian; Robinson, Iain M; O'Kane, Cahir J; Hell, Stefan W; Wahl, Markus C; Stelzl, Ulrich; Loll, Bernhard; Walter, Alexander M; Sigrist, Stephan J

    2016-10-01

    Brain function relies on fast and precisely timed synaptic vesicle (SV) release at active zones (AZs). Efficacy of SV release depends on distance from SV to Ca(2+) channel, but molecular mechanisms controlling this are unknown. Here we found that distances can be defined by targeting two unc-13 (Unc13) isoforms to presynaptic AZ subdomains. Super-resolution and intravital imaging of developing Drosophila melanogaster glutamatergic synapses revealed that the Unc13B isoform was recruited to nascent AZs by the scaffolding proteins Syd-1 and Liprin-α, and Unc13A was positioned by Bruchpilot and Rim-binding protein complexes at maturing AZs. Unc13B localized 120 nm away from Ca(2+) channels, whereas Unc13A localized only 70 nm away and was responsible for docking SVs at this distance. Unc13A(null) mutants suffered from inefficient, delayed and EGTA-supersensitive release. Mathematical modeling suggested that synapses normally operate via two independent release pathways differentially positioned by either isoform. We identified isoform-specific Unc13-AZ scaffold interactions regulating SV-Ca(2+)-channel topology whose developmental tightening optimizes synaptic transmission.

  2. Reciprocal voltage sensor-to-pore coupling leads to potassium channel C-type inactivation

    PubMed Central

    Conti, Luca; Renhorn, Jakob; Gabrielsson, Anders; Turesson, Fredrik; Liin, Sara I; Lindahl, Erik; Elinder, Fredrik

    2016-01-01

    Voltage-gated potassium channels open at depolarized membrane voltages. A prolonged depolarization causes a rearrangement of the selectivity filter which terminates the conduction of ions – a process called slow or C-type inactivation. How structural rearrangements in the voltage-sensor domain (VSD) cause alteration in the selectivity filter, and vice versa, are not fully understood. We show that pulling the pore domain of the Shaker potassium channel towards the VSD by a Cd2+ bridge accelerates C-type inactivation. Molecular dynamics simulations show that such pulling widens the selectivity filter and disrupts the K+ coordination, a hallmark for C-type inactivation. An engineered Cd2+ bridge within the VSD also affect C-type inactivation. Conversely, a pore domain mutation affects VSD gating-charge movement. Finally, C-type inactivation is caused by the concerted action of distant amino acid residues in the pore domain. All together, these data suggest a reciprocal communication between the pore domain and the VSD in the extracellular portion of the channel. PMID:27278891

  3. Active zone scaffolds differentially accumulate Unc13 isoforms to tune Ca(2+) channel-vesicle coupling.

    PubMed

    Böhme, Mathias A; Beis, Christina; Reddy-Alla, Suneel; Reynolds, Eric; Mampell, Malou M; Grasskamp, Andreas T; Lützkendorf, Janine; Bergeron, Dominique Dufour; Driller, Jan H; Babikir, Husam; Göttfert, Fabian; Robinson, Iain M; O'Kane, Cahir J; Hell, Stefan W; Wahl, Markus C; Stelzl, Ulrich; Loll, Bernhard; Walter, Alexander M; Sigrist, Stephan J

    2016-10-01

    Brain function relies on fast and precisely timed synaptic vesicle (SV) release at active zones (AZs). Efficacy of SV release depends on distance from SV to Ca(2+) channel, but molecular mechanisms controlling this are unknown. Here we found that distances can be defined by targeting two unc-13 (Unc13) isoforms to presynaptic AZ subdomains. Super-resolution and intravital imaging of developing Drosophila melanogaster glutamatergic synapses revealed that the Unc13B isoform was recruited to nascent AZs by the scaffolding proteins Syd-1 and Liprin-α, and Unc13A was positioned by Bruchpilot and Rim-binding protein complexes at maturing AZs. Unc13B localized 120 nm away from Ca(2+) channels, whereas Unc13A localized only 70 nm away and was responsible for docking SVs at this distance. Unc13A(null) mutants suffered from inefficient, delayed and EGTA-supersensitive release. Mathematical modeling suggested that synapses normally operate via two independent release pathways differentially positioned by either isoform. We identified isoform-specific Unc13-AZ scaffold interactions regulating SV-Ca(2+)-channel topology whose developmental tightening optimizes synaptic transmission. PMID:27526206

  4. Reciprocal voltage sensor-to-pore coupling leads to potassium channel C-type inactivation

    NASA Astrophysics Data System (ADS)

    Conti, Luca; Renhorn, Jakob; Gabrielsson, Anders; Turesson, Fredrik; Liin, Sara I.; Lindahl, Erik; Elinder, Fredrik

    2016-06-01

    Voltage-gated potassium channels open at depolarized membrane voltages. A prolonged depolarization causes a rearrangement of the selectivity filter which terminates the conduction of ions - a process called slow or C-type inactivation. How structural rearrangements in the voltage-sensor domain (VSD) cause alteration in the selectivity filter, and vice versa, are not fully understood. We show that pulling the pore domain of the Shaker potassium channel towards the VSD by a Cd2+ bridge accelerates C-type inactivation. Molecular dynamics simulations show that such pulling widens the selectivity filter and disrupts the K+ coordination, a hallmark for C-type inactivation. An engineered Cd2+ bridge within the VSD also affect C-type inactivation. Conversely, a pore domain mutation affects VSD gating-charge movement. Finally, C-type inactivation is caused by the concerted action of distant amino acid residues in the pore domain. All together, these data suggest a reciprocal communication between the pore domain and the VSD in the extracellular portion of the channel.

  5. Reciprocal voltage sensor-to-pore coupling leads to potassium channel C-type inactivation

    NASA Astrophysics Data System (ADS)

    Conti, Luca; Renhorn, Jakob; Gabrielsson, Anders; Turesson, Fredrik; Liin, Sara I.; Lindahl, Erik; Elinder, Fredrik

    2016-06-01

    Voltage-gated potassium channels open at depolarized membrane voltages. A prolonged depolarization causes a rearrangement of the selectivity filter which terminates the conduction of ions – a process called slow or C-type inactivation. How structural rearrangements in the voltage-sensor domain (VSD) cause alteration in the selectivity filter, and vice versa, are not fully understood. We show that pulling the pore domain of the Shaker potassium channel towards the VSD by a Cd2+ bridge accelerates C-type inactivation. Molecular dynamics simulations show that such pulling widens the selectivity filter and disrupts the K+ coordination, a hallmark for C-type inactivation. An engineered Cd2+ bridge within the VSD also affect C-type inactivation. Conversely, a pore domain mutation affects VSD gating-charge movement. Finally, C-type inactivation is caused by the concerted action of distant amino acid residues in the pore domain. All together, these data suggest a reciprocal communication between the pore domain and the VSD in the extracellular portion of the channel.

  6. Reciprocal voltage sensor-to-pore coupling leads to potassium channel C-type inactivation.

    PubMed

    Conti, Luca; Renhorn, Jakob; Gabrielsson, Anders; Turesson, Fredrik; Liin, Sara I; Lindahl, Erik; Elinder, Fredrik

    2016-01-01

    Voltage-gated potassium channels open at depolarized membrane voltages. A prolonged depolarization causes a rearrangement of the selectivity filter which terminates the conduction of ions - a process called slow or C-type inactivation. How structural rearrangements in the voltage-sensor domain (VSD) cause alteration in the selectivity filter, and vice versa, are not fully understood. We show that pulling the pore domain of the Shaker potassium channel towards the VSD by a Cd(2+) bridge accelerates C-type inactivation. Molecular dynamics simulations show that such pulling widens the selectivity filter and disrupts the K(+) coordination, a hallmark for C-type inactivation. An engineered Cd(2+) bridge within the VSD also affect C-type inactivation. Conversely, a pore domain mutation affects VSD gating-charge movement. Finally, C-type inactivation is caused by the concerted action of distant amino acid residues in the pore domain. All together, these data suggest a reciprocal communication between the pore domain and the VSD in the extracellular portion of the channel. PMID:27278891

  7. Calculation of coupled secular oscillation frequencies and axial secular frequency in a nonlinear ion trap by a homotopy method.

    PubMed

    Doroudi, Alireza

    2009-11-01

    In this paper the homotopy perturbation method is used for calculation of the frequencies of the coupled secular oscillations and axial secular frequencies of a nonlinear ion trap. The motion of the ion in a rapidly oscillating field is transformed to the motion in an effective potential. The equations of ion motion in the effective potential are in the form of a Duffing-like equation. The homotopy perturbation method is used for solving the resulted system of coupled nonlinear differential equations and the resulted axial equation for obtaining the expressions for ion secular frequencies as a function of nonlinear field parameters and amplitudes of oscillations. The calculated axial secular frequencies are compared with the results of Lindstedt-Poincare method and the exact results. PMID:20365087

  8. Multiple Resonators as a Multi-Channel Bus for Coupling Josephson Junction Qubits

    NASA Astrophysics Data System (ADS)

    Thrailkill, Zechariah; Lambert, Joseph; Ramos, Roberto

    2010-03-01

    Josephson junction-based qubits have been shown to be promising components for a future quantum computer. A network of these superconducting qubits will require quantum information to be stored in and transferred among them. Resonators made of superconducting metal strips are useful elements for this purpose because they have long coherence times and can dispersively couple qubits. We explore the use of multiple resonators with different resonant frequencies to couple qubits. We find that an array of resonators with different frequencies can be individually addressed to store and retrieve information, while coupling qubits dispersively. We show that a control qubit can be used to effectively isolate an active qubit from an array of resonators so that it can function within the same frequency range used by the resonators.

  9. Multi-channel terahertz wavelength division demultiplexer with defects-coupled photonic crystal waveguide

    NASA Astrophysics Data System (ADS)

    Li, Shaopeng; Liu, Hongjun; Sun, Qibing; Huang, Nan

    2016-05-01

    Terahertz (THz) wavelength division demultiplexer based on a compact defects-coupled photonic crystal waveguide is proposed and demonstrated numerically. This device consists of an input waveguide that perpendicularly coupled with a series of defects cavities, each of which captures the resonance frequency from the input waveguide. Coupled-mode theory and finite element method are used to analyze the transmission properties of the structure. It is found that the transmission wavelength centered around 1 THz can be adjusted by changing the geometrical parameters of defects cavities, which equals to THz waves generated by optical methods such as difference frequency generation and optical rectification. Applications in this frequency range are urgently needed. Furthermore, the highest transmission efficiency of 0.94 can be achieved when a perfect wavelength-selective mirror is set in the output waveguide.

  10. Calculation of the heavy-hadron axial couplings g1, g2, and g3 using lattice QCD

    SciTech Connect

    Will Detmold, David Lin, Stefan Meinel

    2012-06-01

    In a recent paper [arXiv:1109.2480] we have reported on a lattice QCD calculation of the heavy-hadron axial couplings g{sub 1}, g{sub 2}, and g{sub 3}. These quantities are low-energy constants of heavy-hadron chiral perturbation theory (HH{chi}PT) and are related to the B*B{pi}, {Sigma}{sub b}*{Sigma}{sub b}{pi}, and {Sigma}{sub b}{sup (*)}{Lambda}{sub b}{pi} couplings. In the following, we discuss important details of the calculation and give further results. To determine the axial couplings, we explicitly match the matrix elements of the axial current in QCD with the corresponding matrix elements in HH{chi}PT. We construct the ratios of correlation functions used to calculate the matrix elements in lattice QCD, and study the contributions from excited states. We present the complete numerical results and discuss the data analysis in depth. In particular, we demonstrate the convergence of SU(4|2) HH{chi}PT for the axial current matrix elements at pion masses up to about 400 MeV and show the impact of the nonanalytic loop contributions. Finally, we present additional predictions for strong and radiative decay widths of charm and bottom baryons.

  11. Nonlinear dynamic fluid-structure interaction calculations with coupled finite element and finite volume programs

    SciTech Connect

    Lewis, M.W.; Kashiwa, B.A.; Meier, R.W.; Bishop, S.

    1994-08-01

    Two- and three-dimensional fluid-structure interaction computer programs for the simulation of nonlinear dynamics were developed and applied to a number of problems. The programs were created by coupling Arbitrary Lagrangian-Eulerian finite volume fluid dynamics programs with strictly Lagrangian finite element structural dynamics programs. The resulting coupled programs can use either fully explicit or implicit time integration. The implicit time integration is accomplished by iterations of the fluid dynamics pressure solver and the structural dynamics system solver. The coupled programs have been used to solve problems involving incompressible fluids, membrane and shell elements, compressible multiphase flows, explosions in both air and water, and large displacements. In this paper, we present the approach used for the coupling and describe test problems that verify the two-dimensional programs against an experiment and an analytical linear problem. The experiment involves an explosion underwater near an instrumented thin steel plate. The analytical linear problem is the vibration of an infinite cylinder surrounded by an incompressible fluid to a given radius.

  12. Nonlinear dynamic fluid-structure interaction calculations with coupled finite element and finite volume programs

    NASA Astrophysics Data System (ADS)

    Lewis, M. W.; Kashiwa, B. A.; Meier, R. W.; Bishop, S.

    1994-07-01

    Two- and three-dimensional fluid-structure interaction computer programs for the simulation of nonlinear dynamics were developed and applied to a number of problems. The programs were created by coupling Arbitrary Lagrangian-Eulerian finite volume fluid dynamics programs with strictly Lagrangian finite element structural dynamics programs. The resulting coupled programs can use either fully explicit or implicit time integration. The implicit time integration is accomplished by iterations of the fluid dynamics pressure solver and the structural dynamics system solver. The coupled programs have been used to solve problems involving incompressible fluids, membrane and shell elements, compressible multiphase flows, explosions in both air and water, and large displacements. In this paper, we present the approach used for the coupling and describe test problems that verify the two-dimensional programs against an experiment and an analytical linear problem. The experiment involves an explosion underwater near an instrumented thin steel plate. The analytical linear problem is the vibration of an infinite cylinder surrounded by an incompressible fluid to a given radius.

  13. Coupling electrodeposition with layer-by-layer assembly to address proteins within microfluidic channels.

    PubMed

    Wang, Yifeng; Liu, Yi; Cheng, Yi; Kim, Eunkyoung; Rubloff, Gary W; Bentley, William E; Payne, Gregory F

    2011-12-22

    Two thin-film assembly methods are coupled to address proteins. Electrodeposition confers programmability and generates a template for layer-by-layer (LbL) assembly. LbL enables precise control of film thickness and the incorporation of labile biological components. The capabilities are demonstrated using glucose oxidase (GOx) based electrochemical biosensing within a microfabricated fluidic device.

  14. Suprachiasmatic nucleus function and circadian entrainment are modulated by G protein-coupled inwardly rectifying (GIRK) channels

    PubMed Central

    Hablitz, L M; Molzof, H E; Paul, J R; Johnson, R L; Gamble, K L

    2014-01-01

    Abstract G protein signalling within the central circadian oscillator, the suprachiasmatic nucleus (SCN), is essential for conveying time-of-day information. We sought to determine whether G protein-coupled inwardly rectifying potassium channels (GIRKs) modulate SCN physiology and circadian behaviour. We show that GIRK current and GIRK2 protein expression are greater during the day. Pharmacological inhibition of GIRKs and genetic loss of GIRK2 depolarized the day-time resting membrane potential of SCN neurons compared to controls. Behaviourally, GIRK2 knockout (KO) mice failed to shorten free running period in response to wheel access in constant darkness and entrained more rapidly to a 6 h advance of a 12 h:12 h light–dark (LD) cycle than wild-type (WT) littermate controls. We next examined whether these effects were due to disrupted signalling of neuropeptide Y (NPY), which is known to mediate non-photic phase shifts, attenuate photic phase shifts and activate GIRKs. Indeed, GIRK2 KO SCN slices had significantly fewer silent cells in response to NPY, likely contributing to the absence of NPY-induced phase advances of PER2::LUC rhythms in organotypic SCN cultures from GIRK2 KO mice. Finally, GIRK channel activation is sufficient to cause a non-photic-like phase advance of PER2::LUC rhythms on a Per2Luc+/− background. These results suggest that rhythmic regulation of GIRK2 protein and channel function in the SCN contributes to day-time resting membrane potential, providing a mechanism for the fine tuning responses to non-photic and photic stimuli. Further investigation could provide insight into disorders with circadian disruption comorbidities such as epilepsy and addiction, in which GIRK channels have been implicated. PMID:25217379

  15. Strongly coupled fluid-particle flows in vertical channels. I. Reynolds-averaged two-phase turbulence statistics

    NASA Astrophysics Data System (ADS)

    Capecelatro, Jesse; Desjardins, Olivier; Fox, Rodney O.

    2016-03-01

    Simulations of strongly coupled (i.e., high-mass-loading) fluid-particle flows in vertical channels are performed with the purpose of understanding the fundamental physics of wall-bounded multiphase turbulence. The exact Reynolds-averaged (RA) equations for high-mass-loading suspensions are presented, and the unclosed terms that are retained in the context of fully developed channel flow are evaluated in an Eulerian-Lagrangian (EL) framework for the first time. A key distinction between the RA formulation presented in the current work and previous derivations of multiphase turbulence models is the partitioning of the particle velocity fluctuations into spatially correlated and uncorrelated components, used to define the components of the particle-phase turbulent kinetic energy (TKE) and granular temperature, respectively. The adaptive spatial filtering technique developed in our previous work for homogeneous flows [J. Capecelatro, O. Desjardins, and R. O. Fox, "Numerical study of collisional particle dynamics in cluster-induced turbulence," J. Fluid Mech. 747, R2 (2014)] is shown to accurately partition the particle velocity fluctuations at all distances from the wall. Strong segregation in the components of granular energy is observed, with the largest values of particle-phase TKE associated with clusters falling near the channel wall, while maximum granular temperature is observed at the center of the channel. The anisotropy of the Reynolds stresses both near the wall and far away is found to be a crucial component for understanding the distribution of the particle-phase volume fraction. In Part II of this paper, results from the EL simulations are used to validate a multiphase Reynolds-stress turbulence model that correctly predicts the wall-normal distribution of the two-phase turbulence statistics.

  16. 512-Channel and 13-Region Simultaneous Recordings Coupled with Optogenetic Manipulation in Freely Behaving Mice

    PubMed Central

    Xie, Kun; Fox, Grace E.; Liu, Jun; Tsien, Joe Z.

    2016-01-01

    The development of technologies capable of recording both single-unit activity and local field potentials (LFPs) over a wide range of brain circuits in freely behaving animals is the key to constructing brain activity maps. Although mice are the most popular mammalian genetic model, in vivo neural recording has been traditionally limited to smaller channel count and fewer brain structures because of the mouse’s small size and thin skull. Here, we describe a 512-channel tetrode system that allows us to record simultaneously over a dozen cortical and subcortical structures in behaving mice. This new technique offers two major advantages – namely, the ultra-low cost and the do-it-yourself flexibility for targeting any combination of many brain areas. We show the successful recordings of both single units and LFPs from 13 distinct neural circuits of the mouse brain, including subregions of the anterior cingulate cortices, retrosplenial cortices, somatosensory cortices, secondary auditory cortex, hippocampal CA1, dentate gyrus, subiculum, lateral entorhinal cortex, perirhinal cortex, and prelimbic cortex. This 512-channel system can also be combined with Cre-lox neurogenetics and optogenetics to further examine interactions between genes, cell types, and circuit dynamics across a wide range of brain structures. Finally, we demonstrate that complex stimuli – such as an earthquake and fear-inducing foot-shock – trigger firing changes in all of the 13 brain regions recorded, supporting the notion that neural code is highly distributed. In addition, we show that localized optogenetic manipulation in any given brain region could disrupt network oscillations and caused changes in single-unit firing patterns in a brain-wide manner, thereby raising the cautionary note of the interpretation of optogenetically manipulated behaviors. PMID:27378865

  17. 512-Channel and 13-Region Simultaneous Recordings Coupled with Optogenetic Manipulation in Freely Behaving Mice.

    PubMed

    Xie, Kun; Fox, Grace E; Liu, Jun; Tsien, Joe Z

    2016-01-01

    The development of technologies capable of recording both single-unit activity and local field potentials (LFPs) over a wide range of brain circuits in freely behaving animals is the key to constructing brain activity maps. Although mice are the most popular mammalian genetic model, in vivo neural recording has been traditionally limited to smaller channel count and fewer brain structures because of the mouse's small size and thin skull. Here, we describe a 512-channel tetrode system that allows us to record simultaneously over a dozen cortical and subcortical structures in behaving mice. This new technique offers two major advantages - namely, the ultra-low cost and the do-it-yourself flexibility for targeting any combination of many brain areas. We show the successful recordings of both single units and LFPs from 13 distinct neural circuits of the mouse brain, including subregions of the anterior cingulate cortices, retrosplenial cortices, somatosensory cortices, secondary auditory cortex, hippocampal CA1, dentate gyrus, subiculum, lateral entorhinal cortex, perirhinal cortex, and prelimbic cortex. This 512-channel system can also be combined with Cre-lox neurogenetics and optogenetics to further examine interactions between genes, cell types, and circuit dynamics across a wide range of brain structures. Finally, we demonstrate that complex stimuli - such as an earthquake and fear-inducing foot-shock - trigger firing changes in all of the 13 brain regions recorded, supporting the notion that neural code is highly distributed. In addition, we show that localized optogenetic manipulation in any given brain region could disrupt network oscillations and caused changes in single-unit firing patterns in a brain-wide manner, thereby raising the cautionary note of the interpretation of optogenetically manipulated behaviors. PMID:27378865

  18. Seasonal-scale abrasion and quarrying patterns from a two-dimensional ice-flow model coupled to distributed and channelized subglacial drainage

    NASA Astrophysics Data System (ADS)

    Beaud, Flavien; Flowers, Gwenn E.; Pimentel, Sam

    2014-08-01

    Field data and numerical modeling show that glaciations have the potential either to enhance relief or to dampen topography. We aim to model the effect of the subglacial hydraulic system on spatiotemporal patterns of glacial erosion by abrasion and quarrying on time scales commensurate with drainage system fluctuations (e.g., seasonal to annual). We use a numerical model that incorporates a dual-morphology subglacial drainage system coupled to a higher-order ice-flow model and process-specific erosion laws. The subglacial drainage system allows for a dynamic transition between two morphologies: the distributed system, characterized by an increase in basal water pressure with discharge, and the channelized system, which exhibits a decrease in equilibrium water pressure with increasing discharge. We apply the model to a simple synthetic glacier geometry, drive it with prescribed meltwater input variations, and compute sliding and erosion rates over a seasonal cycle. When both distributed and channelized systems are included, abrasion and sliding maxima migrate ~ 20% up-glacier compared to simulations with distributed drainage only. Power-law sliding generally yields to a broader response of abrasion to water pressure changes along the flowline compared to Coulomb-friction sliding. Multi-day variations in meltwater input elicit a stronger abrasion response than either diurnal- or seasonal variations alone for the same total input volume. An increase in water input volume leads to increased abrasion. We find that ice thickness commensurate with ice sheet outlet glaciers can hinder the up-glacier migration of abrasion. Quarrying patterns computed with a recently published law differ markedly from calculated abrasion patterns, with effective pressure being a stronger determinant than sliding speeds of quarrying rates. These variations in calculated patterns of instantaneous erosion as a function of hydrology-, sliding-, and erosion-model formulation, as well as model

  19. Functional assay for T4 lysozyme-engineered G Protein-Coupled Receptors with an ion channel reporter

    PubMed Central

    Niescierowicz, Katarzyna; Caro, Lydia; Cherezov, Vadim; Vivaudou, Michel; Moreau, Christophe J.

    2013-01-01

    Summary: Structural studies of G protein-coupled receptors (GPCRs) extensively use the insertion of globular soluble protein domains in order to facilitate their crystallization. However, when inserted in the third intracellular loop (i3 loop), the soluble protein domain disrupts their coupling to G proteins and impedes the GPCRs functional characterization by standard G protein-based assays. Therefore, activity tests of crystallization-optimized GPCRs are essentially limited to their ligand binding properties using radioligand binding assays. Functional characterization of additional thermostabilizing mutations requires the insertion of similar mutations in the wild-type receptor to allow G protein-activation tests. We demonstrate that Ion Channel-Coupled Receptor technology is a complementary approach for a comprehensive functional characterization of crystallization-optimized GPCRs and potentially of any engineered GPCR. Ligand-induced conformational changes of the GPCRs are translated into electrical signal and detected by simple current recordings, even though binding of G proteins is sterically blocked by the added soluble protein domain. PMID:24268646

  20. Transonic shock oscillations calculated with a new interactive boundary layer coupling method

    NASA Technical Reports Server (NTRS)

    Edwards, John W.

    1993-01-01

    A new viscous-inviscid interactive coupling method is described with the aim of allowing time-accurate computation of unsteady transonic flows involving separation and reattachment. A lag-entrainment integral boundary layer method is used in conjunction with a transonic small disturbance potential code. The solutions are coupled with a novel variable gain, integral control method for the boundary layer displacement thickness. Efficient and robust computations of steady and unsteady separated flows, including steady separation bubbles and self-excited shock-induced oscillations, are presented. The buffet onset boundary for the NACA 0012 airfoil is accurately predicted and shown computationally to be a Hopf bifurcation. Shock-induced oscillations are also presented for the 18 percent thick circular arc airfoil. The oscillation onset boundaries and frequencies are accurately predicted, as is the experimentally observed hysteresis of the oscillations with Mach number; this latter stability boundary is identified as a jump phenomenon.

  1. Calculating Derivative Couplings between Time-Dependent Hartree-Fock Excited States with Pseudo-Wavefunctions.

    PubMed

    Alguire, Ethan C; Ou, Qi; Subotnik, Joseph E

    2015-06-18

    A pseudo-wavefunction description of time-dependent Hartree-Fock (TDHF) states is proposed and used to develop an analytic expression for derivative couplings between TDHF excited states based on the Hellmann-Feynman theorem. The resulting expression includes Pulay terms associated with using an atom-centered basis as well as a correction to ensure translational invariance. We demonstrate that our formalism recovers the well-known Chernyak-Mukamel expression near a crossing and in the limit of a complete basis, and thus our approach is consistent with time-dependent response theory. In a companion paper (DOI 10.1021/jp5057682 ), we investigate these derivative couplings near conical intersections and show that they behave correctly. PMID:25148602

  2. The Immediately Releasable Pool of Mouse Chromaffin Cell Vesicles Is Coupled to P/Q-Type Calcium Channels via the Synaptic Protein Interaction Site

    PubMed Central

    Álvarez, Yanina D.; Belingheri, Ana Verónica; Perez Bay, Andrés E.; Javis, Scott E.; Tedford, H. William; Zamponi, Gerald; Marengo, Fernando D.

    2013-01-01

    It is generally accepted that the immediately releasable pool is a group of readily releasable vesicles that are closely associated with voltage dependent Ca2+ channels. We have previously shown that exocytosis of this pool is specifically coupled to P/Q Ca2+ current. Accordingly, in the present work we found that the Ca2+ current flowing through P/Q-type Ca2+ channels is 8 times more effective at inducing exocytosis in response to short stimuli than the current carried by L-type channels. To investigate the mechanism that underlies the coupling between the immediately releasable pool and P/Q-type channels we transiently expressed in mouse chromaffin cells peptides corresponding to the synaptic protein interaction site of Cav2.2 to competitively uncouple P/Q-type channels from the secretory vesicle release complex. This treatment reduced the efficiency of Ca2+ current to induce exocytosis to similar values as direct inhibition of P/Q-type channels via ω-agatoxin-IVA. In addition, the same treatment markedly reduced immediately releasable pool exocytosis, but did not affect the exocytosis provoked by sustained electric or high K+ stimulation. Together, our results indicate that the synaptic protein interaction site is a crucial factor for the establishment of the functional coupling between immediately releasable pool vesicles and P/Q-type Ca2+ channels. PMID:23382986

  3. A spreadsheet-coupled SOLGAS: A computerized thermodynamic equilibrium calculation tool. Revision 1

    SciTech Connect

    Trowbridge, L.D.; Leitnaker, J.M.

    1995-07-01

    SOLGAS, an early computer program for calculating equilibrium in a chemical system, has been made more user-friendly, and several ``bells and whistles`` have been added. The necessity to include elemental species has been eliminated. The input of large numbers of starting conditions has been automated. A revised spreadsheet-based format for entering data, including non-ideal binary and ternary mixtures, simplifies and reduces chances for error. Calculational errors by SOLGAS are flagged, and several programming errors are corrected. Auxiliary programs are available to assemble and partially automate plotting of large amounts of data. Thermodynamic input data can be changed on line. The program can be operated with or without a co-processor. Copies of the program, suitable for the IBM-PC or compatibles with at least 384 bytes of low RAM, are available from the authors. This user manual contains appendices with examples of the use of SOLGAS. These range from elementary examples, such as, the relationships among water, ice, and water vapor, to more complex systems: phase diagram calculation of UF{sub 4} and UF{sub 6} system; burning UF{sub 4} in fluorine; thermodynamic calculation of the Cl-F-O-H system; equilibria calculations in the CCl{sub 4}--CH{sub 3}OH system; and limitations applicable to aqueous solutions. An appendix also contains the source code.

  4. Coupled DEM-CFD Investigation of Granular Transport in a Fluid Channel

    NASA Astrophysics Data System (ADS)

    Zhao, T.; Dai, F.; Xu, N. W.

    2015-09-01

    This paper presents three dimensional numerical investigations of granular transport in fluids, analysed by the Discrete Element Method (DEM) coupled with Computational Fluid Mechanics (CFD). By employing this model, the relevance of flow velocity and granular depositional morphology has been clarified. The larger the flow velocity is, the further distance the grains can be transported to. In this process, the segregation of solid grains has been clearly identified. This research reveals that coarse grains normally accumulate near the grain source region, while the fine grains can be transported to the flow front. Regardless of the different flow velocities used in these simulations, the intensity of grains segregation remains almost unchanged. The results obtained from the DEM-CFD coupled simulations can reasonably explain the grain transport process occurred in natural environments, such as river scouring, evolution of river/ocean floor, deserts and submarine landslides.

  5. Calculating hyperfine couplings in large ionic crystals containing hundreds of QM atoms: subsystem DFT is the key.

    PubMed

    Kevorkyants, Ruslan; Wang, Xiqiao; Close, David M; Pavanello, Michele

    2013-11-14

    We present an application of the linear scaling frozen density embedding (FDE) formulation of subsystem DFT to the calculation of isotropic hyperfine coupling constants (hfcc's) of atoms belonging to a guanine radical cation embedded in a guanine hydrochloride monohydrate crystal. The model systems range from an isolated guanine to a 15,000 atom QM/MM cluster where the QM region is comprised of 36 protonated guanine cations, 36 chlorine anions, and 42 water molecules. Our calculations show that the embedding effects of the surrounding crystal cannot be reproduced by small model systems nor by a pure QM/MM procedure. Instead, a large QM region is needed to fully capture the complicated nature of the embedding effects in this system. The unprecedented system size for a relativistic all-electron isotropic hfcc calculation can be approached in this work because the local nature of the electronic structure of the organic crystals considered is fully captured by the FDE approach.

  6. Test of the coupled channels model for sub-barrier fusion reactions

    SciTech Connect

    Liu, Z.; Zhang, H.; Xu, J.; Xu, K.; Lu, J.; Ruan, M. )

    1990-12-01

    The mean-square angular momenta of the compound nucleus {sup 227}Pa becomes constant at and below the energy which shifted {ital F} MeV from barrier {ital V}{sub {ital b}} with respect to one-dimensional barrier penetration. This energy shift is borne out to be self-consistent with the total coupling strength extracted from the {l angle}{ital l}{sup 2}{r angle} value at the barrier.

  7. Ab initio calculation of electron-phonon coupling in monoclinic β-Ga2O3 crystal

    NASA Astrophysics Data System (ADS)

    Ghosh, Krishnendu; Singisetti, Uttam

    2016-08-01

    The interaction between electrons and vibrational modes in monoclinic β-Ga2O3 is theoretically investigated using ab-initio calculations. The large primitive cell of β-Ga2O3 gives rise to 30 phonon modes all of which are taken into account in transport calculation. The electron-phonon interaction is calculated under density functional perturbation theory and then interpolated using Wannier-Fourier interpolation. The long-range interaction elements between electrons and polar optical phonon (POP) modes are calculated separately using the Born effective charge tensor. The direction dependence of the long-range POP coupling in a monoclinic crystal is explored and is included in the transport calculations. Scattering rate calculations are done using the Fermi golden rule followed by solving the Boltzmann transport equation using the Rode's method to estimate low field mobility. A room temperature mobility of 115 cm2/V s is observed. Comparison with recent experimentally reported mobility is done for a wide range of temperatures (30 K-650 K). It is also found that the POP interaction dominates the electron mobility under low electric field conditions. The relative contribution of the different POP modes is analyzed and the mode 21 meV POP is found to have the highest impact on low field electron mobility at room temperature.

  8. Implementation and Validation of Fully Relativistic GW Calculations: Spin-Orbit Coupling in Molecules, Nanocrystals, and Solids.

    PubMed

    Scherpelz, Peter; Govoni, Marco; Hamada, Ikutaro; Galli, Giulia

    2016-08-01

    We present an implementation of G0W0 calculations including spin-orbit coupling (SOC) enabling investigations of large systems, with thousands of electrons, and we discuss results for molecules, solids, and nanocrystals. Using a newly developed set of molecules with heavy elements (called GW-SOC81), we find that, when based upon hybrid density functional calculations, fully relativistic (FR) and scalar-relativistic (SR) G0W0 calculations of vertical ionization potentials both yield excellent performance compared to experiment, with errors below 1.9%. We demonstrate that while SR calculations have higher random errors, FR calculations systematically underestimate the VIP by 0.1 to 0.2 eV. We further verify that SOC effects may be well approximated at the FR density functional level and then added to SR G0W0 results for a broad class of systems. We also address the use of different root-finding algorithms for the G0W0 quasiparticle equation and the significant influence of including d electrons in the valence partition of the pseudopotential for G0W0 calculations. Finally, we present statistical analyses of our data, highlighting the importance of separating definitive improvements from those that may occur by chance due to a limited number of samples. We suggest the statistical analyses used here will be useful in the assessment of the accuracy of a large variety of electronic structure methods. PMID:27331614

  9. H-H, C-H, and C-C NMR spin-spin coupling constants calculated by the FP-INDO method for aromatic hydrocarbons

    NASA Technical Reports Server (NTRS)

    Long, S. A. T.; Memory, J. D.

    1978-01-01

    The FP-INDO (finite perturbation-intermediate neglect of differential overlap) method is used to calculate the H-H, C-H, and C-C coupling constants in hertz for molecules of six different benzenoid hydrocarbons: benzene, naphthalene, biphenyl, anthracene, phenanthrene, and pyrene. The calculations are based on both the actual and the average molecular geometries. It is found that only the actual molecular geometries can always yield the correct relative order of values for the H-H coupling constants. For the calculated C-C coupling constants, as for the calculated C-H coupling constants, the signs are positive (negative) for an odd (even) number of bonds connecting the two nuclei. Agreements between the calculated and experimental values of the coupling constants for all six molecules are comparable to those reported previously for other molecules.

  10. Accurate spectroscopic calculations of the 17 Λ-S and 59 Ω states of the AsP molecule including the spin-orbit coupling effect

    NASA Astrophysics Data System (ADS)

    Shi, Deheng; Liu, Qionglan; Wang, Shuai; Sun, Jinfeng; Zhu, Zunlue

    2015-01-01

    The potential energy curves (PECs) of 59 Ω states generated from the 17 Λ-S states (X1Σ+, a3Σ+, 15Σ+, b3Δ, c3Π, 15Π, 25Σ+, 23Δ, 23Π, 33Σ+, A1Π, 23Σ+, 35Σ+, 17Σ+, 15Δ, 25Δ, and 25Π) of AsP molecule are studied for the first time for internuclear separations from about 0.10 to 1.10 nm. All the Λ-S states are contributed to the first three dissociation channels of AsP molecule except for the A1Π. The 23Σ+, 35Σ+, 17Σ+, 15Δ, 25Δ, and 25Π are found to be the repulsive states. The a3Σ+, 15Π, b3Δ, 17Σ+, 15Δ, 25Δ, and 25Π are found to be the inverted states. Each of the 33Σ+, c3Π, 23Π, 15Π, and 15Σ+ states has one potential barrier. The PECs are calculated by the CASSCF method, which is followed by the internally contracted MRCI approach with Davidson correction. Core-valence correlation and scalar relativistic corrections are included. The convergent behavior of present calculations is discussed with respect to the basis set and level of theory. The spin-orbit coupling effect is accounted for. All these PECs are extrapolated to the complete basis set limit. The spectroscopic parameters are evaluated for the bound states involved, and are compared with available measurements. Excellent agreement has been found between the present results and the measurements. It shows that the spectroscopic parameters reported in this paper can be expected to be reliably predicted ones. The conclusion is gained that the effect of spin-orbit coupling on the spectroscopic parameters is not obvious for all the Λ-S bound states except for few ones such as 15Σ+ and c3Π.

  11. Determining the Structure of Oxalate Anion Using Infrared and Raman Spectroscopy Coupled with Gaussian Calculations

    ERIC Educational Resources Information Center

    Peterson, Karen I.; Pullman, David P.

    2016-01-01

    A laboratory project for the upper-division physical chemistry laboratory is described, and it combines IR and Raman spectroscopies with Gaussian electronic structure calculations to determine the structure of the oxalate anion in solid alkali oxalates and in aqueous solution. The oxalate anion has two limiting structures whose vibrational spectra…

  12. Polarizabilities and first hyperpolarizabilities of HF, Ne, and BH from full configuration interaction and coupled cluster calculations

    NASA Astrophysics Data System (ADS)

    Larsen, Helena; Olsen, Jeppe; Hättig, Christof; Jørgensen, Poul; Christiansen, Ove; Gauss, Jürgen

    1999-08-01

    Static and frequency-dependent polarizabilities and first hyperpolarizabilities have been calculated for HF and Ne using full configuration interaction (FCI) and a hierarchy of coupled cluster models: coupled cluster singles (CCS), an approximate coupled cluster singles and doubles model (CC2), coupled cluster singles and doubles (CCSD), an approximate coupled cluster singles, doubles, and triples model (CC3), and coupled cluster singles, doubles, and triples (CCSDT). A previous study of BH concerning FCI benchmarking has been extended to include CC3 and static CCSDT values. Systematic improvements of the polarizabilities and the hyperpolarizabilities are found going from CCS to CCSD and from CCSD to CC3 or CCSDT. Little or no improvement of the polarizabilities and no improvement of the hyperpolarizabilities are seen when going from CCS to CC2. The CCSD results represent a significant improvement over CCS and CC2 but are again surpassed by the CC3 results which agree very well with the FCI values. The relative error for the static polarizability at the CC3 level is 0.11% for Ne and, respectively, 0.16% and 0.20% for αxx and αzz of HF. For βzzz and βzxx the errors are 0.50% and 1.7%, respectively. Only in the challenging case of BH does CCSDT improve the CC3 values. The dispersion for the polarizabilities and hyperpolarizabilities is predicted with increasing accuracy in the CCS-CC2-CCSD-CC3 sequence as expected from the increasing accuracy of the electronic excitation energies. For all molecules the effect of orbital relaxation has been investigated for the static properties. The inclusion of orbital relaxation gives results that are somewhat different from the unrelaxed results but are in general no improvement.

  13. Coupling between positronium formation and elastic positron-scattering channels in the rare gases

    SciTech Connect

    Jay, P. M.; Coleman, P. G.

    2010-07-15

    Measurements of elastic-scattering cross sections are presented for positron collisions with helium, neon, argon, krypton, and xenon around the threshold energy for positronium (Ps) formation. The elastic cross section falls slowly with increasing energy above the Ps formation threshold in helium and neon, whereas in argon, krypton, and xenon it exhibits an increase, which appears both more prominent and more sustained as the atomic number of the gas increases. It is proposed that this coupling is a result of an intermediate virtual Ps state that enhances branching into the (atom plus positron) final state.

  14. Calculation of coupling to slow and fast waves in the LHRF from phased waveguide arrays

    SciTech Connect

    Pinsker, R.I.; Duvall, R.E.; Fortgang, C.M.; Colestock, P.L.

    1986-04-01

    A previously reported algorithm for solving the problem of coupling electromagnetic energy in the LHRF from a phased array of identical rectangular waveguides to a plane-stratified, magnetized cold plasma is numerically implemented. The resulting computer codes are sufficiently general to allow for an arbitrary number of waveguides with finite dimensions in both poloidal and toroidal directions, and are thus capable of computing coupling to both slow and fast waves in the plasma. Some of the details of the implementation and the extension of the algorithm to allow study of the Fourier spectrum of slow and fast waves launched by the array are discussed. Good agreement is found with previously reported, less general work for the slow wave launching case. The effect of phasing multirow arrays in the poloidal direction is studied, and an asymmetry between phasing 'up' and 'down' is found that persists in the case where the plasma adjacent to the array is uniform. A 4 x 3 array designed to launch fast waves of high phase velocity is studied. By using the optimal poloidal phasing, low reflection coefficients (absolute value of R/sup 2/ less than or equal to 20%) are found under some not unrealistic edge plasma conditions, but most of the input power is trapped in the outermost layer of the plasma. Implications of our results for fast wave current drive experiments are discussed.

  15. Dynamical coupling of plasmons and molecular excitations by hybrid quantum/classical calculations: time-domain approach.

    PubMed

    Sakko, Arto; Rossi, Tuomas P; Nieminen, Risto M

    2014-08-01

    The presence of plasmonic material influences the optical properties of nearby molecules in untrivial ways due to the dynamical plasmon-molecule coupling. We combine quantum and classical calculation schemes to study this phenomenon in a hybrid system that consists of a Na(2) molecule located in the gap between two Au/Ag nanoparticles. The molecule is treated quantum-mechanically with time-dependent density-functional theory, and the nanoparticles with quasistatic classical electrodynamics. The nanoparticle dimer has a plasmon resonance in the visible part of the electromagnetic spectrum, and the Na(2) molecule has an electron-hole excitation in the same energy range. Due to the dynamical interaction of the two subsystems the plasmon and the molecular excitations couple, creating a hybridized molecular-plasmon excited state. This state has unique properties that yield e.g. enhanced photoabsorption compared to the freestanding Na(2) molecule. The computational approach used enables decoupling of the mutual plasmon-molecule interaction, and our analysis verifies that it is not legitimate to neglect the back coupling effect when describing the dynamical interaction between plasmonic material and nearby molecules. Time-resolved analysis shows nearly instantaneous formation of the coupled state, and provides an intuitive picture of the underlying physics. PMID:25028486

  16. Dynamical coupling of plasmons and molecular excitations by hybrid quantum/classical calculations: time-domain approach.

    PubMed

    Sakko, Arto; Rossi, Tuomas P; Nieminen, Risto M

    2014-08-01

    The presence of plasmonic material influences the optical properties of nearby molecules in untrivial ways due to the dynamical plasmon-molecule coupling. We combine quantum and classical calculation schemes to study this phenomenon in a hybrid system that consists of a Na(2) molecule located in the gap between two Au/Ag nanoparticles. The molecule is treated quantum-mechanically with time-dependent density-functional theory, and the nanoparticles with quasistatic classical electrodynamics. The nanoparticle dimer has a plasmon resonance in the visible part of the electromagnetic spectrum, and the Na(2) molecule has an electron-hole excitation in the same energy range. Due to the dynamical interaction of the two subsystems the plasmon and the molecular excitations couple, creating a hybridized molecular-plasmon excited state. This state has unique properties that yield e.g. enhanced photoabsorption compared to the freestanding Na(2) molecule. The computational approach used enables decoupling of the mutual plasmon-molecule interaction, and our analysis verifies that it is not legitimate to neglect the back coupling effect when describing the dynamical interaction between plasmonic material and nearby molecules. Time-resolved analysis shows nearly instantaneous formation of the coupled state, and provides an intuitive picture of the underlying physics.

  17. Intercellular Odontoblast Communication via ATP Mediated by Pannexin-1 Channel and Phospholipase C-coupled Receptor Activation

    PubMed Central

    Sato, Masaki; Furuya, Tadashi; Kimura, Maki; Kojima, Yuki; Tazaki, Masakazu; Sato, Toru; Shibukawa, Yoshiyuki

    2015-01-01

    Extracellular ATP released via pannexin-1 channels, in response to the activation of mechanosensitive-TRP channels during odontoblast mechanical stimulation, mediates intercellular communication among odontoblasts in dental pulp slice preparation dissected from rat incisor. Recently, odontoblast cell lines, such as mouse odontoblast lineage cells, have been widely used to investigate physiological/pathological cellular functions. To clarify whether the odontoblast cell lines also communicate with each other by diffusible chemical substance(s), we investigated the chemical intercellular communication among cells from mouse odontoblast cell lines following mechanical stimulation. A single cell was stimulated using a glass pipette filled with standard extracellular solution. We measured intracellular free Ca2+ concentration ([Ca2+]i) by fura-2 in stimulated cells, as well as in cells located nearby. Direct mechanical stimulation to a single odontoblast increased [Ca2+]i, which showed sensitivity to capsazepine. In addition, we observed increases in [Ca2+]i not only in the mechanically stimulated odontoblast, but also in nearby odontoblasts. We could observe mechanical stimulation-induced increase in [Ca2+]i in a stimulated human embryo kidney (HEK) 293 cell, but not in nearby HEK293 cells. The increase in [Ca2+]i in nearby odontoblasts, but not in the stimulated odontoblast, was inhibited by adenosine triphosphate (ATP) release channel (pannexin-1) inhibitor in a concentration- and spatial-dependent manner. Moreover, in the presence of phospholipase C (PLC) inhibitor, the increase in [Ca2+]i in nearby odontoblasts, following mechanical stimulation of a single odontoblast, was abolished. We could record some inward currents evoked from odontoblasts near the stimulated odontoblast, but the currents were observed in only 4.8% of the recorded odontoblasts. The results of this study showed that ATP is released via pannexin-1, from a mechanically stimulated odontoblast

  18. Soil Mixing Coupled to Soil Production and Transport on Hillslopes: Responses to Channel Incision, Feather River, California

    NASA Astrophysics Data System (ADS)

    Yoo, K.; Weinman, B. A.; Mudd, S. M.; Hurst, M. D.; Gabet, E. J.; Singhvi, A. K.; Maher, K.

    2012-12-01

    Soil mantled hillslopes arise from the combined processes of soil production from the underlying in-situ saprolite/bedrock and the subsequent lateral transport of the colluvial soil materials toward hillslope toes. Often these toes are bounded by channels and respond to channel aggradation or incision. Biological agents such as trees and burrowing animals are often observed to be responsible for soil production and transport. Thus morphologic evolution of hillslopes is primarily derived by the combined action of channel processes setting the hillslopes' boundary condition and biophysical perturbations mixing soils. However, little is known about how the soil perturbation is coupled to the production and transport of soils. Here we quantify soil-mixing rates using optically stimulated luminescence at two hillslopes with contrasting slope gradients and erosion rates being located above and below a migrating knickpoint. The knickpoint is within a tributary basin to the Middle Fork Feather River that incised into a Sierran granitic batholith over the past five million years creating ~1km relief between the river and the surrounding plateau. Vertical soil-mixing rates range from 5-19 cm/kyr and do not vary with slope gradients and physical erosion rate. The distributions of single grain OSL ages from the two hillslopes' soils are also undistinguishable. Furthermore, LiDAR-based tree heights and densities are not statistically different between the two Hillslopes. Therefore, soil perturbation with indistinguishable intensities results in large difference in sediment flux when subject to different slope gradients. Not only do the soils in the three transects have similar mixing rates, but they also feature similar soil thicknesses. These properties, given the transects' differing erosion rates, can only be explained by varying chemical weathering processes in saprolite.

  19. Electrophysiology-based analysis of human histamine H(4) receptor pharmacology using GIRK channel coupling in Xenopus oocytes.

    PubMed

    Sahlholm, Kristoffer; Nilsson, Johanna; Marcellino, Daniel; Fuxe, Kjell; Arhem, Peter

    2008-09-01

    The recently cloned histamine H(4) receptor is expressed predominantly in haematopoietic cells and has been found to modulate the function of mast cells, eosinophils, dendritic cells and T lymphocytes. It represents an attractive target for pharmacological interventions against a number of inflammatory and autoimmune disorders. In the present work we used two-electrode voltage-clamp to demonstrate histamine H(4) receptor modulation of G protein-coupled inward rectifier potassium (GIRK) channels heterologously expressed in Xenopus oocytes. In accordance with earlier findings in other effector systems, full agonism by histamine and (R)-alpha-methylhistamine, partial agonism by clobenpropit and inverse agonism by thioperamide were observed. Furthermore, in oocytes injected with low amounts of receptor cRNA, clobenpropit apparently acted as a neutral antagonist. We also used the high temporal resolution afforded by this system to study the differential time courses of response deactivation upon ligand washout for clobenpropit and (R)-alpha-methylhistamine. GIRK channels represent a novel effector system for histamine H(4) receptor modulation, which may be of physiological relevance and prove useful in the development of compounds targeting this receptor.

  20. Initial Measurement of Intrapixel Variations in Back-Illuminated, High-Resistivity, p-Channel, Charge Coupled Device

    NASA Astrophysics Data System (ADS)

    Puls, Jason; Oluseyi, Hakeem M.

    2008-05-01

    In 1929 Edwin Hubble discovered the universe's expansion. Seventy years later it was unexpectedly found that the rate of expansion is accelerating due to some vast cosmic energy. This cosmic energy, apparently gravitationally repulsive and spread homogeneously through the universe, has come to be known as dark energy. To better understand this universal force, scientists utilize Type Ia supernovae and weak gravitational lensing as cosmological probes. Lawrence Berkeley National Laboratory (LBNL) is developing the Supernova Acceleration Probe (SNAP), a proposed space-based telescope that will be used to identify and measure supernovae and measure weak gravitational lensing signals across fifteen square degrees of the sky. The SNAP telescope will incorporate an innovative camera that consists of back-illuminated, high-resistivity, p-channel charged coupled devices (CCDs) for visible to near-infrared light detection. Presented are results obtained from the measurement and analysis of a 10.5 μm pixel pitch, 1.4k by 1.4k format, p-channel CCD fabricated on high-resistivity silicon at LBNL. The fully depleted device is 300 μm thick and backside illuminated. We report on the first measurement of the intrapixel sensitivity and spatial variations of these CCDs. We also report measurements of electric field distortions near the edges of the CCD active area.

  1. Multi-channel purge and trap system coupled with ion chromatography for the determination of alkylamines in cosmetics.

    PubMed

    Zhong, Zhixiong; Li, Gongke; Luo, Zhibin; Zhu, Binghui

    2012-02-17

    A new multi-channel purge and trap system coupled with ion chromatography for the determination of six alkylamines in cosmetics was developed. The proposed method, based on purge and trap of the volatile alkylamines, involved in a miniaturization and multi-channel integration of classical steam distillation and a simple approach for routine labs. The procedure was rapidly achieved within 10 min and the matrix interferences could be effectively eliminated. Sample pretreatment frequency was higher than 40 h(-1). The linear ranges were 0.1-15 mg L(-1) and the detection limits varied from 0.023 to 0.038 mg L(-1). This method was successfully utilized to determine the amounts of alkylamines in cosmetics with recoveries ranging from 80.3 to 105.5% and the relative standard deviations (RSDs) ranging from 0.78 to 7.5%. It was proved to be accurate, time-saving, and suitable for the determination of large numbers of cosmetics in a short time. PMID:22244166

  2. IOS and ECS line coupling calculation for the CO-He system - Influence on the vibration-rotation band shapes

    NASA Astrophysics Data System (ADS)

    Boissoles, J.; Boulet, C.; Robert, D.; Green, S.

    1987-09-01

    Line coupling coefficients resulting from rotational excitation of CO perturbed by He are computed within the infinite order sudden approximation (IOSA) and within the energy corrected sudden approximation (ECSA). The influence of this line coupling on the 1-0 CO-He vibration-rotation band shape is then computed for the case of weakly overlapping lines in the 292-78 K temperature range. The IOS and ECS results differ only at 78 K by a weak amount at high frequencies. Comparison with an additive superposition of Lorentzian lines shows strong modifications in the troughs between the lines. These calculated modifications are in excellent quantitative agreement with recent experimental data for all the temperatures considered. The applicability of previous approaches to CO-He system, based on either the strong collision model or exponential energy gap law, is also discussed.

  3. IOS and ECS line coupling calculation for the CO-He system: Influence on the vibration-rotation band shapes

    NASA Astrophysics Data System (ADS)

    Boissoles, J.; Boulet, C.; Robert, D.; Green, S.

    1987-09-01

    Line coupling coefficients resulting from rotational excitation of CO perturbed by He are computed within the infinite order sudden approximation (IOSA) and within the energy corrected sudden approximation (ECSA). The influence of this line coupling on the 1-0 CO-He vibration-rotation band shape is then computed for the case of weakly overlapping lines in the 292-78 K temperature range. The IOS and ECS results differ only at 78 K by a weak amount at high frequencies. Comparison with an additive superposition of lorentzian lines shows strong modifications in the troughs between the lines. These calculated modifications are in excellent quantitative agreement with recent experimental data for all the temperatures considered. The applicability of previous approaches to CO-He system, based on either the strong collision model or exponential energy gap law, is also discussed.

  4. User's guide for the computer code COLTS for calculating the coupled laminar and turbulent flow over a Jovian entry probe

    NASA Technical Reports Server (NTRS)

    Kumar, A.; Graeves, R. A.

    1980-01-01

    A user's guide for a computer code 'COLTS' (Coupled Laminar and Turbulent Solutions) is provided which calculates the laminar and turbulent hypersonic flows with radiation and coupled ablation injection past a Jovian entry probe. Time-dependent viscous-shock-layer equations are used to describe the flow field. These equations are solved by an explicit, two-step, time-asymptotic finite-difference method. Eddy viscosity in the turbulent flow is approximated by a two-layer model. In all, 19 chemical species are used to describe the injection of carbon-phenolic ablator in the hydrogen-helium gas mixture. The equilibrium composition of the mixture is determined by a free-energy minimization technique. A detailed frequency dependence of the absorption coefficient for various species is considered to obtain the radiative flux. The code is written for a CDC-CYBER-203 computer and is capable of providing solutions for ablated probe shapes also.

  5. IOS and ECS line coupling calculation for the CO-He system - Influence on the vibration-rotation band shapes

    NASA Technical Reports Server (NTRS)

    Boissoles, J.; Boulet, C.; Robert, D.; Green, S.

    1987-01-01

    Line coupling coefficients resulting from rotational excitation of CO perturbed by He are computed within the infinite order sudden approximation (IOSA) and within the energy corrected sudden approximation (ECSA). The influence of this line coupling on the 1-0 CO-He vibration-rotation band shape is then computed for the case of weakly overlapping lines in the 292-78 K temperature range. The IOS and ECS results differ only at 78 K by a weak amount at high frequencies. Comparison with an additive superposition of Lorentzian lines shows strong modifications in the troughs between the lines. These calculated modifications are in excellent quantitative agreement with recent experimental data for all the temperatures considered. The applicability of previous approaches to CO-He system, based on either the strong collision model or exponential energy gap law, is also discussed.

  6. Convergent-close-coupling calculations for excitation and ionization processes of electron-hydrogen collisions in Debye plasmas

    SciTech Connect

    Zammit, Mark C.; Fursa, Dmitry V.; Bray, Igor

    2010-11-15

    Electron-hydrogen scattering in weakly coupled hot-dense plasmas has been investigated using the convergent-close-coupling method. The Yukawa-type Debye-Hueckel potential has been used to describe the plasma screening effects. The target structure, excitation dynamics, and ionization process change dramatically as the screening is increased. Excitation cross sections for the 1s{yields}2s,2p,3s,3p,3d and 2s{yields}2p,3s,3p,3d transitions and total and total ionization cross sections for the scattering from the 1s and 2s states are presented. Calculations cover the energy range from thresholds to high energies (250 eV) for various Debye lengths. We find that as the screening increases, the excitation and total cross sections decrease, while the total ionization cross sections increase.

  7. On-shell coupled-channel approach to proton-hydrogen collisions without partial-wave expansion

    SciTech Connect

    Kadyrov, A. S.; Bray, I.; Stelbovics, A. T.

    2006-01-15

    A fully quantal approach to proton collisions with hydrogen based on the atomic-orbital close-coupling method is presented. The method leads to a system of coupled three-dimensional momentum-space integral equations for the scattering amplitudes. These equations are reduced to two-dimensional ones using an on-shell approximation. Furthermore, by considering the symmetry of the problem, we demonstrate that these can be reduced to just one dimension. The resulting equations are solved without partial-wave expansion. Cross sections for electron transfer in proton collisions with the ground state of atomic hydrogen are calculated and shown to agree well with experiment over a wide energy range.

  8. Method for coupling two-dimensional to three-dimensional discrete ordinates calculations

    SciTech Connect

    Thompson, J.L.; Emmett, M.B.; Rhoades, W.A.; Dodds, H.L. Jr.

    1985-01-01

    A three-dimensional (3-D) discrete ordinates transport code, TORT, has been developed at the Oak Ridge National Laboratory for radiation penetration studies. It is not feasible to solve some 3-D penetration problems with TORT, such as a building located a large distance from a point source, because (1) the discretized 3-D problem is simply too big to fit on the computer or (2) the computing time (and corresponding cost) is prohibitive. Fortunately, such problems can be solved with a hybrid approach by coupling a two-dimensional (2-D) description of the point source, which is assumed to be azimuthally symmetric, to a 3-D description of the building, the region of interest. The purpose of this paper is to describe this hybrid methodology along with its implementation and evaluation in the DOTTOR (Discrete Ordinates to Three-dimensional Oak Ridge Transport) code.

  9. Coupled generator and combustor performance calculations for potential early commercial MHD power plants

    NASA Technical Reports Server (NTRS)

    Dellinger, T. C.; Hnat, J. G.; Marston, C. H.

    1979-01-01

    A parametric study of the performance of the MHD generator and combustor components of potential early commercial open-cycle MHD/steam power plants is presented. Consideration is given to the effects of air heater system concept, MHD combustor type, coal type, thermal input power, oxygen enrichment of the combustion, subsonic and supersonic generator flow and magnetic field strength on coupled generator and combustor performance. The best performance is found to be attained with a 3000 F, indirectly fired air heater, no oxygen enrichment, Illinois no. 6 coal, a two-stage cyclone combustor with 85% slag rejection, a subsonic generator, and a magnetic field configuration yielding a constant transverse electric field of 4 kV/m. Results indicate that optimum net MHD generator power is generally compressor-power-limited rather than electric-stress-limited, with optimum net power a relatively weak function of operating pressure.

  10. Monte Carlo calculations of the optical coupling between bismuth germanate crystals and photomultiplier tubes

    SciTech Connect

    Derenzo, S.E.; Riles, J.K.

    1981-10-01

    The high density and atomic number of bismuth germanate (Bi/sub 4/Ge/sub 3/O/sub 12/ or BGO) make it a very useful detector for positron emission tomography. Modern tomograph designs use large numbers of small, closely-packed crystals for high spatial resolution and high sensitivity. However, the low light output, the high refractive index (n=2.15), and the need for accurate timing make it important to optimize the transfer of light to the photomultiplier tube (PMT). We describe the results of a Monte Carlo computer program developed to study the effect of crystal shape, reflector type, and the refractive index of the PMT window on coupling efficiency. The program simulates total internal, external, and Fresnel reflection as well as internal absorption and scattering by bubbles.

  11. Magnetic coupling constants of self-assembled Cu(II) [3×3] grids: alternative spin model from theoretical calculations.

    PubMed

    Calzado, Carmen J; Ben Amor, Nadia; Maynau, Daniel

    2014-07-14

    This paper reports a theoretical analysis of the electronic structure and magnetic properties of a ferromagnetic Cu(II) [3×3] grid. A two-step strategy, combining calculations on the whole grid and on binuclear fragments, has been employed to evaluate all the magnetic interactions in the grid. The calculations confirm an S = 7/2 ground state, which is in accordance with the magnetisation versus field curve and the thermal dependence of the magnetic moment data. Only the first-neighbour coupling terms present non-negligible amplitudes, all of them in agreement with the structure and arrangement of the Cu 3d magnetic orbitals. The results indicate that the dominant interaction in the system is the antiferromagnetic coupling between the ring and the central Cu sites (J3 = J4 ≈ -31 cm(-1)). In the ring two different interactions can be distinguished, J1 = 4.6 cm(-1) and J2 = -0.1 cm(-1), in contrast to the single J model employed in the magnetic data fit. The calculated J values have been used to determine the energy level distribution of the Heisenberg magnetic states. The effective magnetic moment versus temperature plot resulting from this ab initio energy profile is in good agreement with the experimental curve and the fitting obtained with the simplified spin model, despite the differences between these two spin models. This study underlines the role that the theoretical evaluations of the coupling constants can play on the rationalisation of the magnetic properties of these complex polynuclear systems.

  12. Multi-Channel Hyperspectral Fluorescence Detection Excited by Coupled Plasmon-Waveguide Resonance

    PubMed Central

    Du, Chan; Liu, Le; Zhang, Lin; Guo, Jun; Guo, Jihua; Ma, Hui; He, Yonghong

    2013-01-01

    We propose in this paper a biosensor scheme based on coupled plasmon-waveguide resonance (CPWR) excited fluorescence spectroscopy. A symmetrical structure that offers higher surface electric field strengths, longer surface propagation lengths and depths is developed to support guided waveguide modes for the efficient excitation of fluorescence. The optimal parameters for the sensor films are theoretically and experimentally investigated, leading to a detection limit of 0.1 nM (for a Cy5 solution). Multiplex analysis possible with the fluorescence detection is further advanced by employing the hyperspectral fluorescence technique to record the full spectra for every pixel on the sample plane. We demonstrate experimentally that highly overlapping fluorescence (Cy5 and Dylight680) can be distinguished and ratios of different emission sources can be determined accurately. This biosensor shows great potential for multiplex detections of fluorescence analytes. PMID:24129023

  13. Complexes of an argon atom with the linear anions HCC - and HC 4-: results of coupled cluster calculations

    NASA Astrophysics Data System (ADS)

    Botschwina, P.; Oswald, R.

    2003-08-01

    Large-scale coupled cluster calculations have been carried out for the complexes of an argon atom with the linear anions HCC - and HC 4-. In both cases, almost T-shaped structures are energetically favoured. Their equilibrium dissociation energies ( De) are predicted to be 501(5) and 507(5) cm -1, respectively. In contrast to the isoelectronic neutral systems Ar + HCN and Ar + HC 3N, no energy minima are found for the 'hydrogen-bonded' configurations. While the complex Ar ⋯ HCC - is rather flexible, Ar ⋯ HC 4- appears to be fairly rigid, quite similar to isoelectronic Ar ⋯ HC 3N or Ar ⋯ HC 4H.

  14. Non-empirical calculations of NMR indirect carbon-carbon coupling constants. Part 10--carbocages.

    PubMed

    Krivdin, Leonid B

    2004-11-01

    A comprehensive theoretical study of nine classical caged polycycloalkanes (tetrahedrane, prismane, homoprismane, quadricyclane, cubane, pentaprismane, hexaprismane, adamantane and diamantane) was carried out with special focus on the structural behavior of their J(C,C) values calculated at the SOPPA level. The structural behavior of J(C,C) in small carbocages is dominated by steric strain whereas in medium-sized polycycloalkanes the J(C,C) values show no marked peculiarities and follow several well-defined structural trends typical of other alicyclic compounds.

  15. Simplified calculation of wave-coupling between lines in high-speed integrated circuits

    NASA Technical Reports Server (NTRS)

    Matthaei, George L.; Long, Stephen I.; Shu, Jeff C.-H.

    1990-01-01

    The construction of time-domain solutions by the superposition of modes is explained for the general case, which may not have any symmetry in the lines or terminations. This simplified method requires that the logic-gate terminal impedances be approximated by linear effective resistances that can be adequately determined by SPICE analysis of the actual logic gates. Several examples of results of crosstalk calculations made by the simplified method are presented and compared with corresponding results obtained using the SPICE transmission-line methods of Tripathi and Rettig (1985) along with full SPICE models of the logic gates. The simplified approach is shown to give satisfactory agreement for most purposes.

  16. Modeling coupled blast/structure interaction with Zapotec, benchmark calculations for the Conventional Weapon Effects Backfill (CONWEB) tests.

    SciTech Connect

    Bessette, Gregory Carl

    2004-09-01

    Modeling the response of buried reinforced concrete structures subjected to close-in detonations of conventional high explosives poses a challenge for a number of reasons. Foremost, there is the potential for coupled interaction between the blast and structure. Coupling enters the problem whenever the structure deformation affects the stress state in the neighboring soil, which in turn, affects the loading on the structure. Additional challenges for numerical modeling include handling disparate degrees of material deformation encountered in the structure and surrounding soil, modeling the structure details (e.g., modeling the concrete with embedded reinforcement, jointed connections, etc.), providing adequate mesh resolution, and characterizing the soil response under blast loading. There are numerous numerical approaches for modeling this class of problem (e.g., coupled finite element/smooth particle hydrodynamics, arbitrary Lagrange-Eulerian methods, etc.). The focus of this work will be the use of a coupled Euler-Lagrange (CEL) solution approach. In particular, the development and application of a CEL capability within the Zapotec code is described. Zapotec links two production codes, CTH and Pronto3D. CTH, an Eulerian shock physics code, performs the Eulerian portion of the calculation, while Pronto3D, an explicit finite element code, performs the Lagrangian portion. The two codes are run concurrently with the appropriate portions of a problem solved on their respective computational domains. Zapotec handles the coupling between the two domains. The application of the CEL methodology within Zapotec for modeling coupled blast/structure interaction will be investigated by a series of benchmark calculations. These benchmarks rely on data from the Conventional Weapons Effects Backfill (CONWEB) test series. In these tests, a 15.4-lb pipe-encased C-4 charge was detonated in soil at a 5-foot standoff from a buried test structure. The test structure was composed of a

  17. Two chaos synchronization schemes and public-channel message transmission in a mutually coupled semiconductor lasers system

    NASA Astrophysics Data System (ADS)

    Jiang, Ning; Pan, Wei; Yan, Lianshan; Luo, Bin; Yang, Lei; Xiang, Shuiying; Zheng, Di

    2009-06-01

    Chaos synchronization and message transmission of a mutually coupled system consisting of two semiconductor lasers (SLs) and a partially transparent mirror (PTM) in between are investigated theoretically. Analytical results show that two types of chaos synchronization schemes, named as isochronal synchronization (IS) and leader/laggard synchronization (LLS), can be achieved by adjusting the reflectivity and position of PTM. By establishing SIMULINK model, numerical simulations illustrate that as the PTM is positioned at the center of two lasers, IS is available when the reflectivity of PTM is moderate. The LLS is achieved when the reflectivity of PTM equals to 0.5, which means feedback strength equals to coupling strength. Its lag time is just determined by the difference of feedback delay time. The investigations of mutual chaos pass filtering (MCPF) effects and the secure chaotic communication simulations indicate that IS allows real-time bidirectional message transmission on a public-channel, while LLS can achieve higher security chaotic communication by using its lag time as cryptography key. The demonstrated system can be used as a rudiment of array chaos communications system.

  18. Piezoelectric coupling in a field-effect transistor with a nanohybrid channel of ZnO nanorods grown vertically on graphene.

    PubMed

    Quang Dang, Vinh; Kim, Do-Il; Thai Duy, Le; Kim, Bo-Yeong; Hwang, Byeong-Ung; Jang, Mi; Shin, Kyung-Sik; Kim, Sang-Woo; Lee, Nae-Eung

    2014-12-21

    Piezoelectric coupling phenomena in a graphene field-effect transistor (GFET) with a nano-hybrid channel of chemical-vapor-deposited Gr (CVD Gr) and vertically aligned ZnO nanorods (NRs) under mechanical pressurization were investigated. Transfer characteristics of the hybrid channel GFET clearly indicated that the piezoelectric effect of ZnO NRs under static or dynamic pressure modulated the channel conductivity (σ) and caused a positive shift of 0.25% per kPa in the Dirac point. However, the GFET without ZnO NRs showed no change in either σ or the Dirac point. Analysis of the Dirac point shifts indicated transfer of electrons from the CVD Gr to ZnO NRs due to modulation of their interfacial barrier height under pressure. High responsiveness of the hybrid channel device with fast response and recovery times was evident in the time-dependent behavior at a small gate bias. In addition, the hybrid channel FET could be gated by mechanical pressurization only. Therefore, a piezoelectric-coupled hybrid channel GFET can be used as a pressure-sensing device with low power consumption and a fast response time. Hybridization of piezoelectric 1D nanomaterials with a 2D semiconducting channel in FETs enables a new design for future nanodevices.

  19. A simplified spherical harmonic method for coupled electron-photon transport calculations

    SciTech Connect

    Josef, J.A.

    1997-12-01

    In this thesis the author has developed a simplified spherical harmonic method (SP{sub N} method) and associated efficient solution techniques for 2-D multigroup electron-photon transport calculations. The SP{sub N} method has never before been applied to charged-particle transport. He has performed a first time Fourier analysis of the source iteration scheme and the P{sub 1} diffusion synthetic acceleration (DSA) scheme applied to the 2-D SP{sub N} equations. The theoretical analyses indicate that the source iteration and P{sub 1} DSA schemes are as effective for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. In addition, he has applied an angular multigrid acceleration scheme, and computationally demonstrated that it performs as well as for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. It has previously been shown for 1-D S{sub N} calculations that this scheme is much more effective than the DSA scheme when scattering is highly forward-peaked. The author has investigated the applicability of the SP{sub N} approximation to two different physical classes of problems: satellite electronics shielding from geomagnetically trapped electrons, and electron beam problems.

  20. Communication: Quantum six-dimensional calculations of the coupled translation-rotation eigenstates of H2O@C60

    NASA Astrophysics Data System (ADS)

    Felker, Peter M.; Bačić, Zlatko

    2016-05-01

    We report rigorous quantum calculations of the translation-rotation (TR) eigenstates of para- and ortho-H2O@C60. They provide a comprehensive description of the dynamical behavior of H2O inside the fullerene having icosahedral (Ih) symmetry. The TR eigenstates are assigned in terms of the irreducible representations of the proper symmetry group of H2O@C60, as well as the appropriate translational and rotational quantum numbers. The coupling between the orbital and the rotational angular momenta of the caged H2O gives rise to the total angular momentum λ, which additionally labels each TR level. The calculated TR levels allow tentative assignments of a number of transitions in the recent experimental INS spectra of H2O@C60 that have not been assigned previously.

  1. A reinvestigation of singlet benzyne thermochemistry predicted by CASPT2, coupled-cluster and density functional calculations

    NASA Astrophysics Data System (ADS)

    Cramer, Christopher J.; Nash, John J.; Squires, Robert R.

    1997-10-01

    Recent CASPT2 calculations of the heats of formation of the isomeric benzynes by R. Lindh and M. Schütz[Chem. Phys. Lett. 258 (1996) 409] are re-examined. The unrealistically low value reported for p-benzene (132.7 kcal/mol) is shown to be an artifact of the use of incorrect CASSCF and CASPT2 energies for p-benzene, as well as a flawed isodesmic reaction analysis. Use of correct energies and an appropriate isodesmic reaction leads to excellent agreement between the calculated and measured heats of formation for p-benzene. The performance of coupled-cluster methods and density functional theory in predicting benzyne thermochemistry and singlet-triplet splittings is also evaluated.

  2. Communication: Quantum six-dimensional calculations of the coupled translation-rotation eigenstates of H2O@C60.

    PubMed

    Felker, Peter M; Bačić, Zlatko

    2016-05-28

    We report rigorous quantum calculations of the translation-rotation (TR) eigenstates of para- and ortho-H2O@C60. They provide a comprehensive description of the dynamical behavior of H2O inside the fullerene having icosahedral (Ih) symmetry. The TR eigenstates are assigned in terms of the irreducible representations of the proper symmetry group of H2O@C60, as well as the appropriate translational and rotational quantum numbers. The coupling between the orbital and the rotational angular momenta of the caged H2O gives rise to the total angular momentum λ, which additionally labels each TR level. The calculated TR levels allow tentative assignments of a number of transitions in the recent experimental INS spectra of H2O@C60 that have not been assigned previously.

  3. Calculations of hyperfine coupling constant of copper(II) in aqueous environment. Finite temperature molecular dynamics and relativistic effects.

    PubMed

    Malček, Michal; Bučinský, Lukáš; Valko, Marián; Biskupič, Stanislav

    2015-09-01

    The presented paper is focused on the calculation of hyperfine coupling constants (HFCC) of Cu (2+) ion in water environment. To simulate the conditions of the electron paramagnetic resonance (EPR) experiment in aqueous phase, molecular dynamics using the density functional theory (DFT) was employed. In total three different functionals (BLYP, B3LYP, M06) were employed for studying their suitability in describing coordination of Cu (2+) by water molecules. The system of our interest was composed of one Cu (2+) cation surrounded by a selected number (between thirty and fifty) of water molecules. Besides the non-relativistic HFCCs (Fermi contact terms) of Cu (2+) also the four-component relativistic HFCC calculations are presented. The importance of the proper evaluation of HFCCs, the inclusion of spin-orbit term, for Cu (2+) containing systems (Neese, J. Chem. Phys. 118, 3939 2003; Almeida et al., Chem. Phys. 332, 176 2007) is confirmed at the relativistic four-component level of theory.

  4. Source-Coupled, N-Channel, JFET-Based Digital Logic Gate Structure Using Resistive Level Shifters

    NASA Technical Reports Server (NTRS)

    Krasowski, Michael J.

    2011-01-01

    A circuit topography is used to create usable, digital logic gates using N (negatively doped) channel junction field effect transistors (JFETs), load resistors, level shifting resistors, and supply rails whose values are based on the DC parametric distributions of these JFETs. This method has direct application to the current state-of-the-art in high-temperature (300 to 500 C and higher) silicon carbide (SiC) device production, and defines an adaptation to the logic gate described in U.S. Patent 7,688,117 in that, by removing the level shifter from the output of the gate structure described in the patent (and applying it to the input of the same gate), a source-coupled gate topography is created. This structure allows for the construction AND/OR (sum of products) arrays that use far fewer transistors and resistors than the same array as constructed from the gates described in the aforementioned patent. This plays a central role when large multiplexer constructs are necessary; for example, as in the construction of memory. This innovation moves the resistive level shifter from the output of the basic gate structure to the front as if the input is now configured as what would be the output of the preceding gate, wherein the output is the two level shifting resistors. The output of this innovation can now be realized as the lone follower transistor with its source node as the gate output. Additionally, one may leave intact the resistive level shifter on the new gate topography. A source-coupled to direct-coupled logic translator will be the result.

  5. Calculation of Coupled Vibroacoustics Response Estimates from a Library of Available Uncoupled Transfer Function Sets

    NASA Technical Reports Server (NTRS)

    Smith, Andrew; LaVerde, Bruce; Hunt, Ron; Fulcher, Clay; Towner, Robert; McDonald, Emmett

    2012-01-01

    The design and theoretical basis of a new database tool that quickly generates vibroacoustic response estimates using a library of transfer functions (TFs) is discussed. During the early stages of a launch vehicle development program, these response estimates can be used to provide vibration environment specification to hardware vendors. The tool accesses TFs from a database, combines the TFs, and multiplies these by input excitations to estimate vibration responses. The database is populated with two sets of uncoupled TFs; the first set representing vibration response of a bare panel, designated as H(sup s), and the second set representing the response of the free-free component equipment by itself, designated as H(sup c). For a particular configuration undergoing analysis, the appropriate H(sup s) and H(sup c) are selected and coupled to generate an integrated TF, designated as H(sup s +c). This integrated TF is then used with the appropriate input excitations to estimate vibration responses. This simple yet powerful tool enables a user to estimate vibration responses without directly using finite element models, so long as suitable H(sup s) and H(sup c) sets are defined in the database libraries. The paper discusses the preparation of the database tool and provides the assumptions and methodologies necessary to combine H(sup s) and H(sup c) sets into an integrated H(sup s + c). An experimental validation of the approach is also presented.

  6. Experimental Measurements and Density Functional Theory Calculations of Continuum Lowering in Strongly Coupled Plasmas

    NASA Astrophysics Data System (ADS)

    Vinko, Sam

    2014-10-01

    An accurate description of the ionization potential depression (IPD) of ions in plasmas due to their interaction with the environment is a fundamental problem in plasma physics, playing a key role in determining the ionization balance, charge state distribution, opacity and plasma equation of state. Here I present the first experimental investigation of the IPD as a function of ionic charge state in a range of dense Mg, Al and Si plasmas, using the Linac Coherent Light Source X-ray free-electron laser. The measurements show significantly larger IPDs than are predicted by the most commonly used models, such as that of Stewart-Pyatt, or the ion-sphere model of Zimmerman-More. Instead, plasma simulations using finite-temperature density functional theory with excited-state projector augmented-wave potentials show excellent agreement with the experimental results and explain the stronger-than-expected continuum lowering through the electronic structure of the valence states in these strong-coupling conditions, which retain much of their atomic characteristics close to the ion core regions. These results have a profound impact on the understanding and modelling of plasmas over a wide range of warm- and hot-dense matter conditions.

  7. A new, coupled transport-diffusion method for radiative transfer calculations

    SciTech Connect

    Wollaber, A. B.; Warsa, J. S.

    2013-07-01

    We derive and present a new frequency- and angle-integrated low-order system of equations designed to enhance the accuracy of a coupled, high-order (transport) solution of the thermal radiative transfer equations. In particular, our new low-order system is designed to use intensity-weighted opacities and anisotropic diffusion coefficients generated by a solution of the Implicit Monte Carlo (IMC) equations in order to predict the spatial dependence of the material temperature and radiation energies in the ensuing time cycle. The predicted temperature solution can then be exploited to generate appropriately time-centered opacities, specific heats, and Planck emission spectra for the upcoming IMC solution. Additionally, the relatively inexpensive solution of the low-order system can be iteratively solved to recommend an adaptive time step size before the IMC solution is computed. A test implementation has been implemented using existing software available from the Jayenne and Capsaicin projects at Los Alamos National Laboratory. We present initial results from a new driver code that has integrated these stochastic and deterministic software packages. (authors)

  8. Coupled calculation of the airflow interaction with elastic rod of square cross section

    NASA Astrophysics Data System (ADS)

    Pogudalina, S. V.; Fedorova, N. N.; Valger, S. A.

    2016-10-01

    The paper presents the results of numerical modeling of vibration of an elastic rod mounted normal to external flow and fixed rigidly to a substrate. The simulation is performed with ANSYS software using the technology of bidirectional coupling (2FSI). The hydrodynamic, conjugate and modal analysis have been performed. The structure of the air flow in the vicinity of the model was analyzed. The oscillations of the elastic model were revealed and the stress - strain state was obtained. The natural frequencies of the rod and corresponding vibration shapes are found. To prevent undesired vibrations of elastic structures which can lead to their destruction, the interaction of structures with external air flow must the considered. Related physical processes in which movement of the air has an impact on the behavior of deformable objects (Fluid Structure Interaction, FSI) are a key element in many engineering problems of aviation and civil engineering. Aeroelasticity phenomenon must be considered when creating modern aircraft, designing high-rise and extended buildings.

  9. Dominant ferromagnetic coupling over antiferromagnetic in Ni doped ZnO: First-principles calculations

    NASA Astrophysics Data System (ADS)

    Haq, Bakhtiar Ul; Ahmed, Rashid; Abdellatif, Galila; Shaari, Amiruddin; Butt, Faheem K.; Kanoun, Mohammed Benali; Goumri-Said, Souraya

    2016-02-01

    The low magnetic moment (MM) in diluted magnetic semiconductors (DMS) at low impurity doping levels has triggered considerable research into condensed magnetic semiconductors (CMS).This work reports an ab-initio investigation of the electronic structures and magnetic properties of ZnO in a zinc-blende (ZB) structure doped with nickel ions. Ni-doped ZnO-based DMS and CMS exhibit a dominance of ferromagnetic coupling over antiferromagnetic. A robust increase in the magnetization has been observed as a function of Ni impurity levels. This material favors short-range magnetic interactions at the ground state, suggesting that the observed ferromagnetism is defined by the double exchange mechanism. The spin-polarized density of states (DOS) of Ni-doped ZnO characterizes it as half-metallic with a considerable energy gap for up-spin components and as metallic for-down spins. Half-metallic Ni:ZnO based magnetic semiconductors with high magnetization are expected to have potential applications in spintronics.

  10. Cis-trans isomerisation of azobenzenes studied by laser-coupled NMR spectroscopy and DFT calculations.

    PubMed

    Wazzan, Nuha A; Richardson, Patricia R; Jones, Anita C

    2010-07-30

    In a combined experimental and computational study of a group of para-substituted azobenzenes, the effects of substituents and solvent on the kinetics of thermal cis-to-trans isomerisation have been examined and the success of DFT calculations in predicting kinetic parameters assessed. Mono-substituted species are predicted to isomerise by inversion in both non-polar and polar solvent, whereas for push-pull azobenzenes the mechanism is predicted to change from inversion to rotation on going from non-polar to polar solvent. Computed free energies of activation qualitatively reproduce experimental trends but do not quantitatively predict the kinetics of cis-trans isomerisation. The polarisable continuum model of solvation fails to predict the experimentally observed influence of solvent on the entropy of activation.

  11. Close-coupling calculations of fine-structure excitation of Ne II due to H and electron collisions

    NASA Astrophysics Data System (ADS)

    Stancil, Phillip C.; Cumbee, Renata; Wang, Qianxia; Loch, Stuart; Pindzola, Michael; Schultz, David R.; Buenker, Robert; McLaughlin, Brendan; Ballance, Connor

    2016-06-01

    Fine-structure transitions within the ground term of ions and neutral atoms dominate the cooling in a variety of molecular regions and also provide important density and temperature diagnostics. While fine-structure rates due to electron collisions have been studied for many systems, data are generally sparse for elements larger than oxygen, at low temperatures, and for collisions due to heavy particles. We provide rate coefficients for H collisions for the first time. The calculations were performed using the quantum molecular-orbital close-coupling approach and the elastic approximation. The heavy-particle collisions use new potential energies for the lowest-lying NeH+ states computed with the MRDCI method. The focus of the electron-impact calculations is to provide fine-structure excitation rate coefficients down to 10 K. We compare with previous calculations at higher temperatures (Griffin et al. 2001), and use a range of calculations to provide an estimate of the uncertainty on our recommended rate coefficients. A brief discussion of astrophysical applications is also provided.Griffin, D.C., et al., 2001, J. Phys. B, 34, 4401This work partially supported by NASA grant No. NNX15AE47G.

  12. Determining the anisotropic exchange coupling of CrO2 via first-principles density functional theory calculations

    NASA Astrophysics Data System (ADS)

    Sims, H.; Oset, S. J.; Butler, W. H.; MacLaren, James M.; Marsman, Martijn

    2010-06-01

    We report a study of the anisotropic exchange interactions in bulk CrO2 calculated from first principles within density functional theory (DFT) [W. Kohn and L. J. Sham, Phys. Rev. 140, A1133 (1965)10.1103/PhysRev.140.A1133]. We determine the exchange coupling energies, using both the experimental lattice parameters and those obtained within DFT, within a modified Heisenberg model Hamiltonian in two ways. We employ a supercell method in which certain spins within a cell are rotated and the energy dependence is calculated and a spin-spiral method that modifies the periodic boundary conditions of the problem to allow for an overall rotation of the spins between unit cells. Using the results from each of these methods, we calculate the spin-wave stiffness constant D from the exchange energies using the magnon dispersion relation. We employ a Monte Carlo method to determine the DFT-predicted Curie temperature from these calculated energies and compare with accepted values. Finally, we offer an evaluation of the accuracy of the DFT-based methods and suggest implications of the competing ferromagnetic and antiferromagnetic interactions.

  13. Equation-Of Coupled-Cluster Calculations of Photodetachment Cross Sections for Atomic Negative Ions across the Periodic Table

    NASA Astrophysics Data System (ADS)

    Ichino, Takatoshi; Cheng, Lan; Stanton, John F.

    2016-06-01

    The innovative application of the ion-trap technique by Wester and coworkers has yielded definitive experimental values of photodetachment cross sections for the atomic oxygen radical anion (Obullet -) [Hlavenka et al., J. Chem. Phys. 130, 061105 (2009)]. In the present study, equation-of-motion coupled-cluster (EOM-CC) calculations have been performed to derive theoretical values of photodetachment cross sections for the negative ions of atoms in the first two periods of the periodic table as well as of those which belong to the alkali metal and halogen groups. Two methods have been employed to derive the cross sections. One involves the Dyson orbitals obtained from EOM-CC calculations and plane wave functions for the detached electron in the transition dipole moment integrals. The other method utilizes the moment theory following EOM-CC calculations of transition dipole moments for a large number of pseudo-states. The cross sections so evaluated for Obullet - match the experimental values very well. Generally good agreement has been found between the theoretical and experimental values of the cross sections for the atoms in the first two periods, while the present calculations cast some doubt on reported experimental values for some atoms beyond the second period. Substantial relativistic effects on the cross section have been observed for heavy elements in the alkali metal and halogen groups.

  14. Optimization of the Advanced Earth Observing Satellite II Global Imager channels by use of radiative transfer calculations.

    PubMed

    Nakajima, T Y; Nakajima, T; Nakajima, M; Fukushima, H; Kuji, M; Uchiyama, A; Kishino, M

    1998-05-20

    The channel specifications of the Global Imager onboard the Advanced Earth Observing Satellite II have been determined by extensive numerical experiments. The results show that there is an optimum feasible position for each ocean color channel. The bandwidth of the 0.763-microm channel should be less than 10 nm for good sensitivity to the cloud top height and geometric thickness of the cloud layer; a 40-nm bandwidth is suitable for the 1.38-microm channel to have the strongest contrast between cloudy and clear radiance with a sufficient radiant energy; and a 3.7-microm channel is better than a 3.95-microm channel for estimation of the sea surface temperature (SST) and determination of the cloud particle size when the bandwidth of the channel is 0.33 microm. A three-wavelength combination of 6.7, 7.3, and 7.5 microm is an optimized choice for water vapor profiling. The combination of 8.6, 10.8, and 12.0 microm is suitable for cloud microphysics and SST retrievals with the split-window technique.

  15. Accurate bond energies of biodiesel methyl esters from multireference averaged coupled-pair functional calculations.

    PubMed

    Oyeyemi, Victor B; Keith, John A; Carter, Emily A

    2014-09-01

    Accurate bond dissociation energies (BDEs) are important for characterizing combustion chemistry, particularly the initial stages of pyrolysis. Here we contribute to evaluating the thermochemistry of biodiesel methyl ester molecules using ab initio BDEs derived from a multireference averaged coupled-pair functional (MRACPF2)-based scheme. Having previously validated this approach for hydrocarbons and a variety of oxygenates, herein we provide further validation for bonds within carboxylic acids and methyl esters, finding our scheme predicts BDEs within chemical accuracy (i.e., within 1 kcal/mol) for these molecules. Insights into BDE trends with ester size are then analyzed for methyl formate through methyl crotonate. We find that the carbonyl group in the ester moiety has only a local effect on BDEs. C═C double bonds in ester alkyl chains are found to increase the strengths of bonds adjacent to the double bond. An important exception are bonds beta to C═C or C═O bonds, which produce allylic-like radicals upon dissociation. The observed trends arise from different degrees of geometric relaxation and resonance stabilization in the radicals produced. We also compute BDEs in various small alkanes and alkenes as models for the long hydrocarbon chain of actual biodiesel methyl esters. We again show that allylic bonds in the alkenes are much weaker than those in the small methyl esters, indicating that hydrogen abstractions are more likely at the allylic site and even more likely at bis-allylic sites of alkyl chains due to more electrons involved in π-resonance in the latter. Lastly, we use the BDEs in small surrogates to estimate heretofore unknown BDEs in large methyl esters of biodiesel fuels.

  16. Accurate bond energies of biodiesel methyl esters from multireference averaged coupled-pair functional calculations.

    PubMed

    Oyeyemi, Victor B; Keith, John A; Carter, Emily A

    2014-09-01

    Accurate bond dissociation energies (BDEs) are important for characterizing combustion chemistry, particularly the initial stages of pyrolysis. Here we contribute to evaluating the thermochemistry of biodiesel methyl ester molecules using ab initio BDEs derived from a multireference averaged coupled-pair functional (MRACPF2)-based scheme. Having previously validated this approach for hydrocarbons and a variety of oxygenates, herein we provide further validation for bonds within carboxylic acids and methyl esters, finding our scheme predicts BDEs within chemical accuracy (i.e., within 1 kcal/mol) for these molecules. Insights into BDE trends with ester size are then analyzed for methyl formate through methyl crotonate. We find that the carbonyl group in the ester moiety has only a local effect on BDEs. C═C double bonds in ester alkyl chains are found to increase the strengths of bonds adjacent to the double bond. An important exception are bonds beta to C═C or C═O bonds, which produce allylic-like radicals upon dissociation. The observed trends arise from different degrees of geometric relaxation and resonance stabilization in the radicals produced. We also compute BDEs in various small alkanes and alkenes as models for the long hydrocarbon chain of actual biodiesel methyl esters. We again show that allylic bonds in the alkenes are much weaker than those in the small methyl esters, indicating that hydrogen abstractions are more likely at the allylic site and even more likely at bis-allylic sites of alkyl chains due to more electrons involved in π-resonance in the latter. Lastly, we use the BDEs in small surrogates to estimate heretofore unknown BDEs in large methyl esters of biodiesel fuels. PMID:24621192

  17. Dynamical coupling of plasmons and molecular excitations by hybrid quantum/classical calculations: time-domain approach

    NASA Astrophysics Data System (ADS)

    Sakko, Arto; Rossi, Tuomas P.; Nieminen, Risto M.

    2014-08-01

    The presence of plasmonic material influences the optical properties of nearby molecules in untrivial ways due to the dynamical plasmon-molecule coupling. We combine quantum and classical calculation schemes to study this phenomenon in a hybrid system that consists of a Na2 molecule located in the gap between two Au/Ag nanoparticles. The molecule is treated quantum-mechanically with time-dependent density-functional theory, and the nanoparticles with quasistatic classical electrodynamics. The nanoparticle dimer has a plasmon resonance in the visible part of the electromagnetic spectrum, and the Na2 molecule has an electron-hole excitation in the same energy range. Due to the dynamical interaction of the two subsystems the plasmon and the molecular excitations couple, creating a hybridized molecular-plasmon excited state. This state has unique properties that yield e.g. enhanced photoabsorption compared to the freestanding Na2 molecule. The computational approach used enables decoupling of the mutual plasmon-molecule interaction, and our analysis verifies that it is not legitimate to neglect the backcoupling effect when describing the dynamical interaction between plasmonic material and nearby molecules. Time-resolved analysis shows nearly instantaneous formation of the coupled state, and provides an intuitive picture of the underlying physics.

  18. A simplified spherical harmonic method for coupled electron-photon transport calculations

    SciTech Connect

    Josef, J.A.

    1996-12-01

    In this thesis we have developed a simplified spherical harmonic method (SP{sub N} method) and associated efficient solution techniques for 2-D multigroup electron-photon transport calculations. The SP{sub N} method has never before been applied to charged-particle transport. We have performed a first time Fourier analysis of the source iteration scheme and the P{sub 1} diffusion synthetic acceleration (DSA) scheme applied to the 2-D SP{sub N} equations. Our theoretical analyses indicate that the source iteration and P{sub 1} DSA schemes are as effective for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. Previous analyses have indicated that the P{sub 1} DSA scheme is unstable (with sufficiently forward-peaked scattering and sufficiently small absorption) for the 2-D S{sub N} equations, yet is very effective for the 1-D S{sub N} equations. In addition, we have applied an angular multigrid acceleration scheme, and computationally demonstrated that it performs as well for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. It has previously been shown for 1-D S{sub N} calculations that this scheme is much more effective than the DSA scheme when scattering is highly forward-peaked. We have investigated the applicability of the SP{sub N} approximation to two different physical classes of problems: satellite electronics shielding from geomagnetically trapped electrons, and electron beam problems. In the space shielding study, the SP{sub N} method produced solutions that are accurate within 10% of the benchmark Monte Carlo solutions, and often orders of magnitude faster than Monte Carlo. We have successfully modeled quasi-void problems and have obtained excellent agreement with Monte Carlo. We have observed that the SP{sub N} method appears to be too diffusive an approximation for beam problems. This result, however, is in agreement with theoretical expectations.

  19. Comparison of the quantum and classical calculations of flux density of (220) channeled positrons in Si crystal

    NASA Astrophysics Data System (ADS)

    Korotchenko, K. B.; Tukhfatullin, TA; Pivovarov, Yu L.; Eikhorn, Yu L.

    2016-07-01

    Simulation of flux-peaking effect of the 255 MeV positrons channeled in (220) Si crystals is performed in the frame of classical and quantum mechanics. Comparison of the results obtained using both approaches shows relatively good agreement.

  20. Hillslope-channel coupling in a steep Hawaiian catchment accelerates erosion rates over 100-fold

    NASA Astrophysics Data System (ADS)

    Stock, J. D.; Hanshaw, M. N.; Rosener, M.; Schmidt, K. M.; Brooks, B. A.; Tribble, G.; Jacobi, J.

    2009-12-01

    In tropical watersheds, hillslope changes are producing increasing amounts of fine sediment that can be quickly carried to reefs by channels. Suspended sediment concentrations off the reefs of Molokai, Hawaii, chronically exceed a toxic level of 10 mg/L, threatening reef ecosystems. We hypothesize that historic conversion of watersheds from soil creep to overland flow erosion increased both magnitude and frequency of sediment flooding adjacent reefs. We combined surficial and ecological mapping, hillslope and stream gages, and novel sensors to locate, quantify and model the generation of fine sediments polluting the Molokai reef. Ecological and geomorphic mapping from LiDAR and multi-spectral imagery located a subset of overland flow areas with vegetation cover below a threshold value preventing erosion. Here, feral goat grazing exposed cohesive volcanic soils whose low matrix hydraulic conductivities (1-20 mm/hour) promote Horton overland flow erosion. We instrumented steep, barren hillslopes with soil moisture sensors, overland flow meters, Parshall flumes, ISCO sediment samplers, and a rain gage and conducted repeat Tripod LiDAR and infiltration tests. To characterize soil resistance here and elsewhere to overland flow erosion, we deployed a Cohesive Strength Meter (CSM) to simulate the stresses of flowing water. At the 13.5 km 2 watershed mouth we used a USGS stream gage and ISCO sediment sampler to estimate total load. Over 2 years, storms triggered overland flow during rainfall intensities above 10-15 mm/hr. Overland flow meters indicate such flows can be up to 3 cm deep, with a tendency to deepen downslope. CSM tests indicate that these depths are insufficient to erode soils where vegetation is dense, but far above threshold values of 2-3 mm depth for bare soil erosion. Sediment ratings curves for both hillslope and downstream catchment gages show strong clock-wise hysteresis during the first intense storms in the Fall, becoming linear later in the rainy

  1. Born-Oppenheimer and Renner-Teller coupled-channel quantum reaction dynamics of O((3)P) + H2(+)(X(2)Σg(+)) collisions.

    PubMed

    Gamallo, Pablo; Defazio, Paolo; González, Miguel; Paniagua, Miguel; Petrongolo, Carlo

    2015-09-28

    We present Born-Oppenheimer (BO) and Renner-Teller (RT) time dependent quantum dynamics studies of the reactions O((3)P) + H2(+)(X(2)Σg(+)) → OH(+)(X(3)Σ(-)) + H((2)S) and OH(X(2)Π) + H(+). We consider the OH2(+) X[combining tilde](2)A'' and Ã(2)A' electronic states that correlate with a linear (2)Π species. The electronic angular momenta operators L[combining circumflex] and L[combining circumflex](2) are considered in nonadiabatic coupled-channel calculations, where the associated RT effects are due to diagonal V(RT) potentials that add up to the PESs and to off-diagonal C(RT) couplings between the potential energy surfaces (PESs). Initial-state-resolved reaction probabilities PI, integral cross sections σI, and rate constants kI are obtained using recent ab initio PESs and couplings and the real wavepacket formalism. Because the PESs are strongly attractive, PI have no threshold energy and are large, σI decrease with collision energy, and kI depend little on the temperature. The X[combining tilde](2)A'' PES is up to three times more reactive than the Ã(2)A' PES and H2(+) rotational effects (j0 = 0, 1) are negligible. The diagonal V(RT) potentials are strongly repulsive at the collinearity and nearly halve all low-energy observables with respect to the BO ones. The off-diagonal C(RT) couplings are important at low partial waves, where they mix the X[combining tilde](2)A'' and Ã(2)A' states up to ∼20%. However, V(RT) effects predominate over the C(RT) ones that change at most by ∼19% the BO values of σI and kI. The reaction O((3)P) + H2(+)(X(2)Σg(+)) → OH(+)(X(3)Σ(-)) + H((2)S) is probably one of the most reactive atom + diatom collisions because its RT rate constant at room temperature is equal to 2.26 × 10(-10) cm(3) s(-1). Within the BO approximation, the present results agree rather well with recent quasiclassical and centrifugal-sudden data using the same PESs.

  2. Electronic couplings for molecular charge transfer: Benchmarking CDFT, FODFT, and FODFTB against high-level ab initio calculations

    SciTech Connect

    Kubas, Adam; Blumberger, Jochen; Hoffmann, Felix; Heck, Alexander; Elstner, Marcus; Oberhofer, Harald

    2014-03-14

    We introduce a database (HAB11) of electronic coupling matrix elements (H{sub ab}) for electron transfer in 11 π-conjugated organic homo-dimer cations. High-level ab inito calculations at the multireference configuration interaction MRCI+Q level of theory, n-electron valence state perturbation theory NEVPT2, and (spin-component scaled) approximate coupled cluster model (SCS)-CC2 are reported for this database to assess the performance of three DFT methods of decreasing computational cost, including constrained density functional theory (CDFT), fragment-orbital DFT (FODFT), and self-consistent charge density functional tight-binding (FODFTB). We find that the CDFT approach in combination with a modified PBE functional containing 50% Hartree-Fock exchange gives best results for absolute H{sub ab} values (mean relative unsigned error = 5.3%) and exponential distance decay constants β (4.3%). CDFT in combination with pure PBE overestimates couplings by 38.7% due to a too diffuse excess charge distribution, whereas the economic FODFT and highly cost-effective FODFTB methods underestimate couplings by 37.6% and 42.4%, respectively, due to neglect of interaction between donor and acceptor. The errors are systematic, however, and can be significantly reduced by applying a uniform scaling factor for each method. Applications to dimers outside the database, specifically rotated thiophene dimers and larger acenes up to pentacene, suggests that the same scaling procedure significantly improves the FODFT and FODFTB results for larger π-conjugated systems relevant to organic semiconductors and DNA.

  3. Coupling hydrodynamics and radiation calculations for star-jet interactions in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    de la Cita, V. M.; Bosch-Ramon, V.; Paredes-Fortuny, X.; Khangulyan, D.; Perucho, M.

    2016-06-01

    Context. Stars and their winds can contribute to the non-thermal emission in extragalactic jets. Because of the complexity of jet-star interactions, the properties of the resulting emission are closely linked to those of the emitting flows. Aims: We simulate the interaction between a stellar wind and a relativistic extragalactic jet and use the hydrodynamic results to compute the non-thermal emission under different conditions. Methods: We performed relativistic axisymmetric hydrodynamical simulations of a relativistic jet interacting with a supersonic, non-relativistic stellar wind. We computed the corresponding streamlines out of the simulation results and calculated the injection, evolution, and emission of non-thermal particles accelerated in the jet shock, focusing on electrons or e±-pairs. Several cases were explored, considering different jet-star interaction locations, magnetic fields, and observer lines of sight. The jet luminosity and star properties were fixed, but the results are easily scalable when these parameters are changed. Results: Individual jet-star interactions produce synchrotron and inverse Compton emission that peaks from X-rays to MeV energies (depending on the magnetic field), and at ~100-1000 GeV (depending on the stellar type), respectively. The radiation spectrum is hard in the scenarios explored here as a result of non-radiative cooling dominance, as low-energy electrons are efficiently advected even under relatively high magnetic fields. Interactions of jets with cold stars lead to an even harder inverse Compton spectrum because of the Klein-Nishina effect in the cross section. Doppler boosting has a strong effect on the observer luminosity. Conclusions: The emission levels for individual interactions found here are in the line of previous, more approximate, estimates, strengthening the hypothesis that collective jet-star interactions could significantly contribute at high energies under efficient particle acceleration.

  4. Channel capacities of an exactly solvable spin-star system

    NASA Astrophysics Data System (ADS)

    Arshed, Nigum; Toor, A. H.; Lidar, Daniel A.

    2010-06-01

    We calculate the entanglement-assisted and -unassisted channel capacities of an exactly solvable spin star system, which models the quantum dephasing channel. The capacities for this non-Markovian model exhibit a strong dependence on the coupling strengths of the bath spins with the system, the bath temperature, and the number of bath spins. For equal couplings and bath frequencies, the channel becomes periodically noiseless.

  5. Channel capacities of an exactly solvable spin-star system

    SciTech Connect

    Arshed, Nigum; Toor, A. H.; Lidar, Daniel A.

    2010-06-15

    We calculate the entanglement-assisted and -unassisted channel capacities of an exactly solvable spin star system, which models the quantum dephasing channel. The capacities for this non-Markovian model exhibit a strong dependence on the coupling strengths of the bath spins with the system, the bath temperature, and the number of bath spins. For equal couplings and bath frequencies, the channel becomes periodically noiseless.

  6. Comparison of Schroedinger and Dirac coupled-channels analyses of the sup 28 Si( p , p prime ) sup 28 Si reaction at 500 MeV

    SciTech Connect

    de Swiniarski, R.; Beatty, D.; Donoghue, E.; Fergerson, R.W.; Franey, M.; Gazzaly, M.; Glashausser, C.; Hintz, N.; Jones, K.W.; McClelland, J.B.; Nanda, S.; Plum, M. Serin Physics Laboratory, Rutgers University, Piscataway, NJ School of Physics and Astronomy, University of Minnesota, Minneapolis, MN Los Alamos Meson Physics Facility, Los Alamos National Laboratory, Los Alamos, NM )

    1990-09-01

    Analyzing powers have been measured for elastic and inelastic scattering of 500-MeV protons from {sup 28}Si. These data for the first 0{sup +}, 2{sup +}, and 4{sup +} states and the corresponding cross-section data have been analyzed with both Schroedinger and Dirac equation phenomenological coupled-channels methods. Good, qualitatively similar, results are achieved with the two methods.

  7. G-protein coupled receptor 18 (GPR18) in channel catfish: Expression analysis and efficacy as immunostimulant against Aeromonas hydrophila infection

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objectives of this study were: 1) to determine the transcriptional profiles of G-protein coupled receptor 18 (GPR18) in channel catfish after infection with A. hydrophila compared to that in healthy catfish; 2) to determine whether over-expression of GPR18 in catfish gill cells will offer protec...

  8. Four-way coupled simulations of small particles in turbulent channel flow: The effects of particle shape and Stokes number

    NASA Astrophysics Data System (ADS)

    Zhao, F.; George, W. K.; van Wachem, B. G. M.

    2015-08-01

    This paper investigates the effects of particle shape and Stokes number on the behaviour of non-spherical particles in turbulent channel flow. Although there are a number of studies concerning spherical particles in turbulent flows, most important applications occurring in process, energy, and pharmaceutical industries deal with non-spherical particles. The computation employs a unique and novel four-way coupling with the Lagrangian point-particle approach. The fluid phase at low Reynolds number (Reτ = 150) is modelled by direct numerical simulation, while particles are tracked individually. Inter-particle and particle-wall collisions are also taken into account. To explore the effects of particles on the flow turbulence, the statistics of the fluid flow such as the fluid velocity, the terms in the turbulence kinetic energy equation, the slip velocity between the two phases and velocity correlations are analysed considering ellipsoidal particles with different inertia and aspect ratio. The results of the simulations show that the turbulence is considerably attenuated, even in the very dilute regime. The reduction of the turbulence intensity is predominant near the turbulence kinetic energy peak in the near wall region, where particles preferentially accumulate. Moreover, the elongated shape of ellipsoids strengthens the turbulence attenuation. In simulations with ellipsoidal particles, the fluid-particle interactions strongly depend on the orientation of the ellipsoids. In the near wall region, ellipsoids tend to align predominantly within the streamwise (x) and wall-normal (y) planes and perpendicular to the span-wise direction, whereas no preferential orientation in the central region of the channel is observed. Important conclusions from this work include the effective viscosity of the flow is not affected, the direct dissipation by the particles is negligible, and the primary mechanism by which the particles affect the flow is by altering the turbulence

  9. Four-way coupled simulations of small particles in turbulent channel flow: The effects of particle shape and Stokes number

    SciTech Connect

    Zhao, F.; Wachem, B. G. M. van; George, W. K.

    2015-08-15

    This paper investigates the effects of particle shape and Stokes number on the behaviour of non-spherical particles in turbulent channel flow. Although there are a number of studies concerning spherical particles in turbulent flows, most important applications occurring in process, energy, and pharmaceutical industries deal with non-spherical particles. The computation employs a unique and novel four-way coupling with the Lagrangian point-particle approach. The fluid phase at low Reynolds number (Re{sub τ} = 150) is modelled by direct numerical simulation, while particles are tracked individually. Inter-particle and particle-wall collisions are also taken into account. To explore the effects of particles on the flow turbulence, the statistics of the fluid flow such as the fluid velocity, the terms in the turbulence kinetic energy equation, the slip velocity between the two phases and velocity correlations are analysed considering ellipsoidal particles with different inertia and aspect ratio. The results of the simulations show that the turbulence is considerably attenuated, even in the very dilute regime. The reduction of the turbulence intensity is predominant near the turbulence kinetic energy peak in the near wall region, where particles preferentially accumulate. Moreover, the elongated shape of ellipsoids strengthens the turbulence attenuation. In simulations with ellipsoidal particles, the fluid-particle interactions strongly depend on the orientation of the ellipsoids. In the near wall region, ellipsoids tend to align predominantly within the streamwise (x) and wall-normal (y) planes and perpendicular to the span-wise direction, whereas no preferential orientation in the central region of the channel is observed. Important conclusions from this work include the effective viscosity of the flow is not affected, the direct dissipation by the particles is negligible, and the primary mechanism by which the particles affect the flow is by altering the turbulence

  10. Expression of a Diverse Array of Ca2+-Activated K+ Channels (SK1/3, IK1, BK) that Functionally Couple to the Mechanosensitive TRPV4 Channel in the Collecting Duct System of Kidney

    PubMed Central

    Li, Yue; Hu, Hongxiang; Butterworth, Michael B.; Tian, Jin-Bin; Zhu, Michael X.; O’Neil, Roger G.

    2016-01-01

    The voltage- and Ca2+-activated, large conductance K+ channel (BK, maxi-K) is expressed in the collecting duct system of kidney where it underlies flow- and Ca2+-dependent K+ excretion. To determine if other Ca2+-activated K+ channels (KCa) may participate in this process, mouse kidney and the K+-secreting mouse cortical collecting duct (CCD) cell line, mCCDcl1, were assessed for TRPV4 and KCa channel expression and cross-talk. qPCR mRNA analysis and immunocytochemical staining demonstrated TRPV4 and KCa expression in mCCDcl1 cells and kidney connecting tubule (CNT) and CCD. Three subfamilies of KCa channels were revealed: the high Ca2+-binding affinity small-conductance SK channels, SK1and SK3, the intermediate conductance channel, IK1, and the low Ca2+-binding affinity, BK channel (BKα subunit). Apparent expression levels varied in CNT/CCD where analysis of CCD principal cells (PC) and intercalated cells (IC) demonstrated differential staining: SK1:PCIC, IK1:PC>IC, BKα:PC = IC, and TRPV4:PC>IC. Patch clamp analysis and fluorescence Ca2+ imaging of mCCDcl1 cells demonstrated potent TRPV4-mediated Ca2+ entry and strong functional cross-talk between TRPV4 and KCa channels. TRPV4-mediated Ca2+ influx activated each KCa channel, as evidenced by selective inhibition of KCa channels, with each active KCa channel enhancing Ca2+ entry (due to membrane hyperpolarization). Transepithelial electrical resistance (TEER) analysis of confluent mCCDcl1 cells grown on permeable supports further demonstrated this cross-talk where TRPV4 activation induce a decrease in TEER which was partially restored upon selective inhibition of each KCa channel. It is concluded that SK1/SK3 and IK1 are highly expressed along with BKα in CNT and CCD and are closely coupled to TRPV4 activation as observed in mCCDcl1 cells. The data support a model in CNT/CCD segments where strong cross talk between TRPV4-mediated Ca2+ influx and each KCa channel leads to enhance Ca2+ entry which

  11. KANTBP 2.0: New version of a program for computing energy levels, reaction matrix and radial wave functions in the coupled-channel hyperspherical adiabatic approach

    NASA Astrophysics Data System (ADS)

    Chuluunbaatar, O.; Gusev, A. A.; Vinitsky, S. I.; Abrashkevich, A. G.

    2008-11-01

    A FORTRAN 77 program for calculating energy values, reaction matrix and corresponding radial wave functions in a coupled-channel approximation of the hyperspherical adiabatic approach is presented. In this approach, a multi-dimensional Schrödinger equation is reduced to a system of the coupled second-order ordinary differential equations on a finite interval with homogeneous boundary conditions: (i) the Dirichlet, Neumann and third type at the left and right boundary points for continuous spectrum problem, (ii) the Dirichlet and Neumann type conditions at left boundary point and Dirichlet, Neumann and third type at the right boundary point for the discrete spectrum problem. The resulting system of radial equations containing the potential matrix elements and first-derivative coupling terms is solved using high-order accuracy approximations of the finite element method. As a test desk, the program is applied to the calculation of the reaction matrix and radial wave functions for 3D-model of a hydrogen-like atom in a homogeneous magnetic field. This version extends the previous version 1.0 of the KANTBP program [O. Chuluunbaatar, A.A. Gusev, A.G. Abrashkevich, A. Amaya-Tapia, M.S. Kaschiev, S.Y. Larsen, S.I. Vinitsky, Comput. Phys. Commun. 177 (2007) 649-675]. Program summaryProgram title: KANTBP Catalogue identifier: ADZH_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADZH_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 20 403 No. of bytes in distributed program, including test data, etc.: 147 563 Distribution format: tar.gz Programming language: FORTRAN 77 Computer: Intel Xeon EM64T, Alpha 21264A, AMD Athlon MP, Pentium IV Xeon, Opteron 248, Intel Pentium IV Operating system: OC Linux, Unix AIX 5.3, SunOS 5.8, Solaris, Windows XP RAM: This depends on the

  12. The role of the magnetic orbitals in the calculation of the magnetic coupling constants from multireference perturbation theory methods.

    PubMed

    Angeli, Celestino; Calzado, Carmen J

    2012-07-21

    The use of multireference perturbation theory (MRPT) for the calculation of the magnetic coupling in binuclear complexes has shown to give poor results if applied on a minimal active space complete active space self-consistent field (CASSCF) wavefunction. In this work, we identify the origin of this problem in the starting CASSCF orbitals, which are exceedingly localized on the metal atoms. Focusing on the case of antiferromagnetic systems, it is shown that the form of the active orbitals has a dramatic effect on the relative description of the neutral and ionic structures. Finally, a simple and computational inexpensive strategy is proposed for the calculation of a set of magnetic orbitals describing in a more balanced way the neutral and ionic structures. The use of these orbitals, instead the CASSCF ones, in minimal active space MRPT2 calculations leads to a marked improvement of the J values, which become in reasonable agreement with those obtained with the expensive high level difference dedicated configuration interaction approach and with the experimental values.

  13. Toward enabling large-scale open-shell equation-of-motion coupled cluster calculations: triplet states of β-carotene

    SciTech Connect

    Hu, Hanshi; Bhaskaran-Nair, Kiran; Apra, Edoardo; Govind, Niranjan; Kowalski, Karol

    2014-10-02

    In this paper we discuss the application of novel parallel implementation of the coupled cluster (CC) and equation-of-motion coupled cluster methods (EOMCC) in calculations of excitation energies of triplet states in beta-carotene. Calculated excitation energies are compared with experimental data, where available. We also provide a detailed description of the new parallel algorithms for iterative CC and EOMCC models involving single and doubles excitations.

  14. Calculated protein and proton motions coupled to electron transfer: electron transfer from QA- to QB in bacterial photosynthetic reaction centers.

    PubMed

    Alexov, E G; Gunner, M R

    1999-06-29

    Reaction centers from Rhodobacter sphaeroides were subjected to Monte Carlo sampling to determine the Boltzmann distribution of side-chain ionization states and positions and buried water orientation and site occupancy. Changing the oxidation states of the bacteriochlorophyll dimer electron donor (P) and primary (QA) and secondary (QB) quinone electron acceptors allows preparation of the ground (all neutral), P+QA-, P+QB-, P0QA-, and P0QB- states. The calculated proton binding going from ground to other oxidation states and the free energy of electron transfer from QA-QB to form QAQB- (DeltaGAB) compare well with experiment from pH 5 to pH 11. At pH 7 DeltaGAB is measured as -65 meV and calculated to be -80 meV. With fixed protein positions as in standard electrostatic calculations, DeltaGAB is +170 meV. At pH 7 approximately 0.2 H+/protein is bound on QA reduction. On electron transfer to QB there is little additional proton uptake, but shifts in side chain protonation and position occur throughout the protein. Waters in channels leading from QB to the surface change site occupancy and orientation. A cluster of acids (GluL212, AspL210, and L213) and SerL223 near QB play important roles. A simplified view shows this cluster with a single negative charge (on AspL213 with a hydrogen bond to SerL233) in the ground state. In the QB- state the cluster still has one negative charge, now on the more distant AspL210. AspL213 and SerL223 move so SerL223 can hydrogen bond to QB-. These rearrangements plus other changes throughout the protein make the reaction energetically favorable.

  15. Comparison of MCNP calculation and measurement of neutron fluence in a channel for short-time irradiation in the LVR-15 reactor

    SciTech Connect

    Lahodova, Z.; Flibor, S.; Klupak, V.; Kucera, J.; Marek, M.; Viererbl, L.

    2006-07-01

    The main purpose of this work was to evaluate the neutron energy distribution in a channel of the LVR-15 reactor used mostly for short-time neutron activation analysis. Twenty types of activation monitors were irradiated in this channel equipped with a pneumatic facility with a transport time of 3.5 s. The activities measured and the corresponding reaction rates were used to determinate the neutron spectrum. The reaction rates were compared with MCNP calculations to confirm the results. The second purpose of this work was to verify our nuclear data library used for the reaction rate calculations. The experiment results were also incorporated into our database system of neutron energy distribution at the reactor core. (authors)

  16. Coriolis coupling effects in the calculation of state-to-state integral and differential cross sections for the H+D2 reaction.

    PubMed

    Chu, Tian-Shu; Han, Ke-Li; Hankel, Marlies; Balint-Kurti, Gabriel G

    2007-06-01

    The quantum wavepacket parallel computational code DIFFREALWAVE is used to calculate state-to-state integral and differential cross sections for the title reaction on the BKMP2 surface in the total energy range of 0.4-1.2 eV with D2 initially in its ground vibrational-rotational state. The role of Coriolis couplings in the state-to-state quantum calculations is examined in detail. Comparison of the results from calculations including the full Coriolis coupling and those using the centrifugal sudden approximation demonstrates that both the energy dependence and the angular dependence of the calculated cross sections are extremely sensitive to the Coriolis coupling, thus emphasizing the importance of including it correctly in an accurate state-to-state calculation.

  17. KANTBP: A program for computing energy levels, reaction matrix and radial wave functions in the coupled-channel hyperspherical adiabatic approach

    NASA Astrophysics Data System (ADS)

    Chuluunbaatar, O.; Gusev, A. A.; Abrashkevich, A. G.; Amaya-Tapia, A.; Kaschiev, M. S.; Larsen, S. Y.; Vinitsky, S. I.

    2007-10-01

    A FORTRAN 77 program is presented which calculates energy values, reaction matrix and corresponding radial wave functions in a coupled-channel approximation of the hyperspherical adiabatic approach. In this approach, a multi-dimensional Schrödinger equation is reduced to a system of the coupled second-order ordinary differential equations on the finite interval with homogeneous boundary conditions of the third type. The resulting system of radial equations which contains the potential matrix elements and first-derivative coupling terms is solved using high-order accuracy approximations of the finite-element method. As a test desk, the program is applied to the calculation of the energy values and reaction matrix for an exactly solvable 2D-model of three identical particles on a line with pair zero-range potentials. Program summaryProgram title: KANTBP Catalogue identifier: ADZH_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADZH_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 4224 No. of bytes in distributed program, including test data, etc.: 31 232 Distribution format: tar.gz Programming language: FORTRAN 77 Computer: Intel Xeon EM64T, Alpha 21264A, AMD Athlon MP, Pentium IV Xeon, Opteron 248, Intel Pentium IV Operating system: OC Linux, Unix AIX 5.3, SunOS 5.8, Solaris, Windows XP RAM: depends on (a) the number of differential equations; (b) the number and order of finite-elements; (c) the number of hyperradial points; and (d) the number of eigensolutions required. Test run requires 30 MB Classification: 2.1, 2.4 External routines: GAULEG and GAUSSJ [W.H. Press, B.F. Flanery, S.A. Teukolsky, W.T. Vetterley, Numerical Recipes: The Art of Scientific Computing, Cambridge University Press, Cambridge, 1986] Nature of problem: In the hyperspherical adiabatic

  18. UV/visible Fourier transform spectroscopy using an inductively-coupled plasma: dual-channel noise cancellation

    NASA Astrophysics Data System (ADS)

    Travis, J. C.; Winchester, M. R.; Salit, M. L.; Wythoff, B. J.; Scheeline, A.

    1993-04-01

    Although technological advances have extended the range of Fourier transform spectroscopy (FTS) into the UV/visible spectral domain, its application to spectroscopic and spectrometric problems has been hampered-relative to such applications in the infrared domain-by noise considerations. Although the technique retains high resolution, accurate wavelength registration, and simultaneous broad band coverage, the multiplex advantage present in the IR is severely compromised in the UV/visible due to the relative insignificance of detector noise. In particular, signal-carried noise distributes widely through the spectrum, degrading the dynamic range needed for many spectroscopic and analytical applications. This study demonstrates the use of complementary optical output channels in a commercial FTS to achieve up to ten-fold noise reductions for spectra acquired from an analytical inductively-coupled plasma with conventional pneumatic sample aspiration. The study also demonstrates the advisability of increasing the sampling rate of future instruments to exceed the maximum noise frequency characteristic of droplet evaporation effects.

  19. Classical Electrodynamics Coupled to Quantum Mechanics for Calculation of Molecular Optical Properties: a RT-TDDFT/FDTD Approach

    SciTech Connect

    Chen, Hanning; McMahon, J. M.; Ratner, Mark A.; Schatz, George C.

    2010-09-02

    A new multiscale computational methodology was developed to effectively incorporate the scattered electric field of a plasmonic nanoparticle into a quantum mechanical (QM) optical property calculation for a nearby dye molecule. For a given location of the dye molecule with respect to the nanoparticle, a frequency-dependent scattering response function was first determined by the classical electrodynamics (ED) finite-difference time-domain (FDTD) approach. Subsequently, the time-dependent scattered electric field at the dye molecule was calculated using the FDTD scattering response function through a multidimensional Fourier transform to reflect the effect of polarization of the nanoparticle on the local field at the molecule. Finally, a real-time time-dependent density function theory (RT-TDDFT) approach was employed to obtain a desired optical property (such as absorption cross section) of the dye molecule in the presence of the nanoparticle’s scattered electric field. Our hybrid QM/ED methodology was demonstrated by investigating the absorption spectrum of the N3 dye molecule and the Raman spectrum of pyridine, both of which were shown to be significantly enhanced by a 20 nm diameter silver sphere. In contrast to traditional quantum mechanical optical calculations in which the field at the molecule is entirely determined by intensity and polarization direction of the incident light, in this work we show that the light propagation direction as well as polarization and intensity are important to nanoparticle-bound dye molecule response. At no additional computation cost compared to conventional ED and QM calculations, this method provides a reliable way to couple the response of the dye molecule’s individual electrons to the collective dielectric response of the nanoparticle.

  20. Density functional theory calculations of the redox potentials of actinide(VI)/actinide(V) couple in water.

    PubMed

    Steele, Helen M; Guillaumont, Dominique; Moisy, Philippe

    2013-05-30

    The measured redox potential of an actinide at an electrode surface involves the transfer of a single electron from the electrode surface on to the actinide center. Before electron transfer takes place, the complexing ligands and molecules of solvation need to become structurally arranged such that the electron transfer is at its most favorable. Following the electron transfer, there is further rearrangement to obtain the minimum energy structure for the reduced state. As such, there are three parts to the total energy cycle required to take the complex from its ground state oxidized form to its ground state reduced form. The first part of the energy comes from the structural rearrangement and solvation energies of the actinide species before the electron transfer or charge transfer process; the second part, the energy of the electron transfer; the third part, the energy required to reorganize the ligands and molecules of solvation around the reduced species. The time resolution of electrochemical techniques such as cyclic voltammetry is inadequate to determine to what extent bond and solvation rearrangement occurs before or after electron transfer; only for a couple to be classed as reversible is it fast in terms of the experimental time. Consequently, the partitioning of the energy theoretically is of importance to obtain good experimental agreement. Here we investigate the magnitude of the instantaneous charge transfer through calculating the fast one electron reduction energies of AnO2(H2O)n(2+), where An = U, Np, and Pu, for n = 4-6, in solution without inclusion of the structural optimization energy of the reduced form. These calculations have been performed using a number of DFT functionals, including the recently developed functionals of Zhao and Truhlar. The results obtained for calculated electron affinities in the aqueous phase for the AnO2(H2O)5(2+/+) couples are within 0.04 V of accepted experimental redox potentials, nearly an order of magnitude

  1. Flow-Noise Calculation Using the Mutual Coupling Between Vulcanized Rubber and the Flow Around in Water

    NASA Astrophysics Data System (ADS)

    Li, Xue-Gang; Yang, Kun-De; Ma, Yuan-Liang

    2012-06-01

    A vulcanized rubber layer is usually used on the head of an axisymmetric body to keep it streamlined and watertight. The elastic boundary condition is considered when the flow noise of an axisymmetric body is calculated, and we employ the mutual coupling method between the vulcanized rubber layer and the flow around to solve the flow-noise field for an axisymmetric body in water. The results show that the deformation of the vulcanized rubber layer is reduced with the increase in Young's modulus. The Young's modulus of the rubber material should be large enough to keep it streamlined, and the noise power levels in the peak of the axisymmetric body are smaller than the other positions, which provides us with important theoretical support for laying acoustic arrays on the head of the body.

  2. A comparison of density functional theory and coupled cluster methods for the calculation of electric dipole polarizability gradients of methane

    NASA Astrophysics Data System (ADS)

    Paidarová, Ivana; Sauer, Stephan P. A.

    2012-12-01

    We have compared the performance of density functional theory (DFT) using five different exchange-correlation functionals with four coupled cluster theory based wave function methods in the calculation of geometrical derivatives of the polarizability tensor of methane. The polarizability gradients of hydrocarbons are important ingredients in the simulation of their electron energy loss spectra and reliable but cost-effective methods for obtaining the gradients need to be found. In the present work we present results of a systematic investigation on methane as a prototype molecule with special focus on DFT methods. The KT3, B3LYP, CAM-B3LYP, B97-2 and PBE0 DFT exchange-correlation functionals and the highly correlated wave function methods SOPPA(CCSD), CCSD-LR, CCSD and CCSD(T) were employed in combination with a series of eleven basis sets. Comparison of the DFT results with CCSD(T)/daug-cc-pVQZ reference values reveals that none of the investigated DFT approaches reaches the accuracy of correlated wave function based methods and that the best DFT results are obtained with the PBE0 exchange-correlation functional and Sadlej's polarized valence triple zeta basis set. The SOPPA(CCSD) method, on the other hand, produces results in close agreement with the more expensive pure coupled cluster methods.

  3. The Effect of Approximating Some Molecular Integrals in Coupled-Cluster Calculations: Fundamental Frequencies and Rovibrational Spectroscopic Constants of Cyclopropenylidene

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Dateo, Christopher E.

    2005-01-01

    The singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations, denoted CCSD(T), has been used, in conjunction with approximate integral techniques, to compute highly accurate rovibrational spectroscopic constants of cyclopropenylidene, C3H2. The approximate integral technique was proposed in 1994 by Rendell and Lee in order to avoid disk storage and input/output bottlenecks, and today it will also significantly aid in the development of algorithms for distributed memory, massively parallel computer architectures. It is shown in this study that use of approximate integrals does not impact the accuracy of CCSD(T) calculations. In addition, the most accurate spectroscopic data yet for C3H2 is presented based on a CCSD(T)/cc-pVQZ quartic force field that is modified to include the effects of core-valence electron correlation. Cyclopropenylidene is of great astronomical and astrobiological interest because it is the smallest aromatic ringed compound to be positively identified in the interstellar medium, and is thus involved in the prebiotic processing of carbon and hydrogen. The singles and doubles coupled-cluster method that includes a perturbational estimate of

  4. Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP) and Endolysosomal Two-pore Channels Modulate Membrane Excitability and Stimulus-Secretion Coupling in Mouse Pancreatic β Cells.

    PubMed

    Arredouani, Abdelilah; Ruas, Margarida; Collins, Stephan C; Parkesh, Raman; Clough, Frederick; Pillinger, Toby; Coltart, George; Rietdorf, Katja; Royle, Andrew; Johnson, Paul; Braun, Matthias; Zhang, Quan; Sones, William; Shimomura, Kenju; Morgan, Anthony J; Lewis, Alexander M; Chuang, Kai-Ting; Tunn, Ruth; Gadea, Joaquin; Teboul, Lydia; Heister, Paula M; Tynan, Patricia W; Bellomo, Elisa A; Rutter, Guy A; Rorsman, Patrik; Churchill, Grant C; Parrington, John; Galione, Antony

    2015-08-28

    Pancreatic β cells are electrically excitable and respond to elevated glucose concentrations with bursts of Ca(2+) action potentials due to the activation of voltage-dependent Ca(2+) channels (VDCCs), which leads to the exocytosis of insulin granules. We have examined the possible role of nicotinic acid adenine dinucleotide phosphate (NAADP)-mediated Ca(2+) release from intracellular stores during stimulus-secretion coupling in primary mouse pancreatic β cells. NAADP-regulated Ca(2+) release channels, likely two-pore channels (TPCs), have recently been shown to be a major mechanism for mobilizing Ca(2+) from the endolysosomal system, resulting in localized Ca(2+) signals. We show here that NAADP-mediated Ca(2+) release from endolysosomal Ca(2+) stores activates inward membrane currents and depolarizes the β cell to the threshold for VDCC activation and thereby contributes to glucose-evoked depolarization of the membrane potential during stimulus-response coupling. Selective pharmacological inhibition of NAADP-evoked Ca(2+) release or genetic ablation of endolysosomal TPC1 or TPC2 channels attenuates glucose- and sulfonylurea-induced membrane currents, depolarization, cytoplasmic Ca(2+) signals, and insulin secretion. Our findings implicate NAADP-evoked Ca(2+) release from acidic Ca(2+) storage organelles in stimulus-secretion coupling in β cells. PMID:26152717

  5. Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP) and Endolysosomal Two-pore Channels Modulate Membrane Excitability and Stimulus-Secretion Coupling in Mouse Pancreatic β Cells.

    PubMed

    Arredouani, Abdelilah; Ruas, Margarida; Collins, Stephan C; Parkesh, Raman; Clough, Frederick; Pillinger, Toby; Coltart, George; Rietdorf, Katja; Royle, Andrew; Johnson, Paul; Braun, Matthias; Zhang, Quan; Sones, William; Shimomura, Kenju; Morgan, Anthony J; Lewis, Alexander M; Chuang, Kai-Ting; Tunn, Ruth; Gadea, Joaquin; Teboul, Lydia; Heister, Paula M; Tynan, Patricia W; Bellomo, Elisa A; Rutter, Guy A; Rorsman, Patrik; Churchill, Grant C; Parrington, John; Galione, Antony

    2015-08-28

    Pancreatic β cells are electrically excitable and respond to elevated glucose concentrations with bursts of Ca(2+) action potentials due to the activation of voltage-dependent Ca(2+) channels (VDCCs), which leads to the exocytosis of insulin granules. We have examined the possible role of nicotinic acid adenine dinucleotide phosphate (NAADP)-mediated Ca(2+) release from intracellular stores during stimulus-secretion coupling in primary mouse pancreatic β cells. NAADP-regulated Ca(2+) release channels, likely two-pore channels (TPCs), have recently been shown to be a major mechanism for mobilizing Ca(2+) from the endolysosomal system, resulting in localized Ca(2+) signals. We show here that NAADP-mediated Ca(2+) release from endolysosomal Ca(2+) stores activates inward membrane currents and depolarizes the β cell to the threshold for VDCC activation and thereby contributes to glucose-evoked depolarization of the membrane potential during stimulus-response coupling. Selective pharmacological inhibition of NAADP-evoked Ca(2+) release or genetic ablation of endolysosomal TPC1 or TPC2 channels attenuates glucose- and sulfonylurea-induced membrane currents, depolarization, cytoplasmic Ca(2+) signals, and insulin secretion. Our findings implicate NAADP-evoked Ca(2+) release from acidic Ca(2+) storage organelles in stimulus-secretion coupling in β cells.

  6. Adiabatic and coupled channels calculations for near barrier fusion of 16O +238U using realistic nucleon-nucleon interaction

    NASA Astrophysics Data System (ADS)

    Ismail, M.; Seif, W. M.; Botros, M. M.

    2016-04-01

    We investigate the fusion cross-section and the fusion barrier distribution of 16O +238U at near- and sub-barrier energies. We use an interaction potential generated by the semi-microscopic double folding model-based on density dependent (DD) form of the realistic Michigan-three-Yukawa (M3Y) Reid nucleon-nucleon (NN) interaction. We studied the role of both the static and dynamic deformations of the target nucleus on the fusion process. Rotational and vibrational degrees of freedom of 238U-nucleus are considered. We found that the deformation and the octupole vibrations in 238U enhance its sub-barrier fusion cross-section. The signature of the the octupole vibrational modes of 238U appears clearly in its fusion barrier distribution profile.

  7. Finite-Perturbation Intermediate - Neglect - of - Differential - Overlap Molecular Orbital Calculations of Nuclear Magnetic Resonance Spin-Spin Coupling Constants for Polycyclic Aromatic Hydrocarbons and Aromatic Nitrogen Heterocyclics

    NASA Astrophysics Data System (ADS)

    Long, Sheila Ann Thibeault

    The H-H, C-H, and C-C spin-spin coupling constants were calculated by the finite-perturbation, intermediate -neglect-of-differential-overlap method using the Fermi contact interaction for benzene, naphthalene, biphenyl, anthracene, phenanthrene, and pyrene. The calculations were made using both the actual and the average molecular geometries. For all six of these molecules, the agreements between the calculated and the experimental coupling constants were comparable to those previously reported for other, predominantly smaller, molecules. The actual molecular geometries always gave the correct relative order of values for the H-H coupling constants, whereas the average molecular geometries did not always do so. The magnitudes, but not the signs, of the calculated coupling constants were sensitive to small changes in molecular geometry. The results were the best (next best) for the H-H (C-H) coupling constants. In addition the H-H, C-H, N-H, C-C, and N-C spin -spin coupling constants were calculated in a similar manner for pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, quinoline, quinoxaline, phthalazine, benzo g quinoxaline, and benzo b phenazine. The agreements between the theoretical and the experimental values were comparable to those for the polycyclic aromatic hydrocarbons.

  8. An accurate and linear-scaling method for calculating charge-transfer excitation energies and diabatic couplings

    SciTech Connect

    Pavanello, Michele; Van Voorhis, Troy; Visscher, Lucas; Neugebauer, Johannes

    2013-02-07

    Quantum-mechanical methods that are both computationally fast and accurate are not yet available for electronic excitations having charge transfer character. In this work, we present a significant step forward towards this goal for those charge transfer excitations that take place between non-covalently bound molecules. In particular, we present a method that scales linearly with the number of non-covalently bound molecules in the system and is based on a two-pronged approach: The molecular electronic structure of broken-symmetry charge-localized states is obtained with the frozen density embedding formulation of subsystem density-functional theory; subsequently, in a post-SCF calculation, the full-electron Hamiltonian and overlap matrix elements among the charge-localized states are evaluated with an algorithm which takes full advantage of the subsystem DFT density partitioning technique. The method is benchmarked against coupled-cluster calculations and achieves chemical accuracy for the systems considered for intermolecular separations ranging from hydrogen-bond distances to tens of Angstroms. Numerical examples are provided for molecular clusters comprised of up to 56 non-covalently bound molecules.

  9. Analysis of BCC-HCP Reconstructive Transformation in Ti by Coupling Symmetry to First-Principles Calculations

    NASA Astrophysics Data System (ADS)

    Hatch, D. M.; Stokes, H. T.; Srinivasan, S. G.; Lookman, T.; Saxena, A.

    2002-03-01

    Many structural transformations involve no group-subgroup relationship and hence are beyond the purview of the classical Landau theory. We study a titanium martensitic transformation from a body-centered cubic (BCC) to a hexagonal close-packed (HCP) phase. We present a systematic and general methodology to describe this and related reconstructive transformations by coupling group-symmetry arguments to first-principles calculations. We describe (i) a symmetry-based four-step algorithm to enumerate transformation paths, (ii) evaluate the energy barriers along these transformation paths using all-electron first principles calculations, (iii) choose the path with the least energy barrier and deduce its full set of primary and secondary order parameters (OP's) to establish an appropriate Landau-Ginsburg free-energy functional,(iv) for the minimum energy path, identify a special point of the primary OP corresponding to the end product phase as a function of local distortions. Specifically, we find a generalization of the Burger's mechinism for this transformation. Our procedure is rigorous and general enough to be applicable to other reconstructive transitions such as BCC-FCC, HCP-OMEGA, BCC-OMEGA, etc.

  10. Coupling of Neutral-Beam-Driven Compressional Alfvén Eigenmodes to Kinetic Alfvén Waves in NSTX Tokamak and Energy Channeling.

    PubMed

    Belova, E V; Gorelenkov, N N; Fredrickson, E D; Tritz, K; Crocker, N A

    2015-07-01

    An energy-channeling mechanism is proposed to explain flattening of the electron temperature profiles at a high beam power in the beam-heated National Spherical Torus Experiment (NSTX). Results of self-consistent simulations of neutral-beam-driven compressional Alfvén eigenmodes (CAEs) in NSTX are presented that demonstrate strong coupling of CAEs to kinetic Alfvén waves at the Alfvén resonance location. It is suggested that CAEs can channel energy from the beam ions to the location of the resonant mode conversion at the edge of the beam density profile, modifying the energy deposition profile.

  11. Free-volume theory coupled with soft-SAFT for viscosity calculations: comparison with molecular simulation and experimental data.

    PubMed

    Llovell, F; Marcos, R M; Vega, L F

    2013-07-11

    The evaluation of phase equilibria and solubility properties through theoretical approaches is a well-known field, where a significant amount of models are able to describe them with a good degree of accuracy. However, the simultaneous calculation of transport properties together with thermodynamic phase properties still remains a challenge, due to the difficulties in describing the behavior of properties like the viscosity of fluids with the same approach. In this work, the free-volume theory (FVT) has been coupled with the soft-SAFT equation for the first time to extend the capabilities of the equation to the calculation of transport properties. The theory has been first tested using simulation data of the viscosity of the Lennard-Jones (LJ) fluid and LJ chains over a wide range of temperature and pressure. Good agreement has been found at all chain lengths, except for some deviations at near-zero density values. Several trends of the viscosity parameters with the length of the chain are identified, allowing the prediction of other chain fluids. Finally, the new equation has been applied to the n-alkanes family, where viscosity is a key property, and results are compared with experimental data. The three viscosity parameters were fitted to viscosity data of the pure fluid at several isotherms or isobars, whereas the density and pressure (or temperature) were taken from the soft-SAFT output. Again, the effect of these parameters on the viscosity has been investigated and compared with results obtained for the LJ chains and with previous work of other authors. The new equation performs very well in all cases, with a global average absolute deviation of 2.12% and shows predictive capabilities for heavier compounds. This empowers soft-SAFT with new capabilities, allowing the equation to calculate phase, interfacial, and transport properties with the same model and degree of accuracy.

  12. Decreasing Cx36 Gap Junction Coupling Compensates for Overactive KATP Channels to Restore Insulin Secretion and Prevent Hyperglycemia in a Mouse Model of Neonatal Diabetes

    PubMed Central

    Nguyen, Linda M.; Pozzoli, Marina; Hraha, Thomas H.; Benninger, Richard K.P.

    2014-01-01

    Mutations to the ATP-sensitive K+ channel (KATP channel) that reduce the sensitivity of ATP inhibition cause neonatal diabetes mellitus via suppression of β-cell glucose-stimulated free calcium activity ([Ca2+]i) and insulin secretion. Connexin-36 (Cx36) gap junctions also regulate islet electrical activity; upon knockout of Cx36, β-cells show [Ca2+]i elevations at basal glucose. We hypothesized that in the presence of overactive ATP-insensitive KATP channels, a reduction in Cx36 would allow elevations in glucose-stimulated [Ca2+]i and insulin secretion to improve glucose homeostasis. To test this, we introduced a genetic knockout of Cx36 into mice that express ATP-insensitive KATP channels and measured glucose homeostasis and islet metabolic, electrical, and insulin secretion responses. In the normal presence of Cx36, after expression of ATP-insensitive KATP channels, blood glucose levels rapidly rose to >500 mg/dL. Islets from these mice showed reduced glucose-stimulated [Ca2+]i and no insulin secretion. In mice lacking Cx36 after expression of ATP-insensitive KATP channels, normal glucose levels were maintained. Islets from these mice had near-normal glucose-stimulated [Ca2+]i and insulin secretion. We therefore demonstrate a novel mechanism by which islet function can be recovered in a monogenic model of diabetes. A reduction of gap junction coupling allows sufficient glucose-stimulated [Ca2+]i and insulin secretion to prevent the emergence of diabetes. PMID:24458355

  13. Dean-flow-coupled elasto-inertial three-dimensional particle focusing under viscoelastic flow in a straight channel with asymmetrical expansion-contraction cavity arrays.

    PubMed

    Yuan, D; Zhang, J; Yan, S; Pan, C; Alici, G; Nguyen, N T; Li, W H

    2015-07-01

    In this paper, 3D particle focusing in a straight channel with asymmetrical expansion-contraction cavity arrays (ECCA channel) is achieved by exploiting the dean-flow-coupled elasto-inertial effects. First, the mechanism of particle focusing in both Newtonian and non-Newtonian fluids was introduced. Then particle focusing was demonstrated experimentally in this channel with Newtonian and non-Newtonian fluids using three different sized particles (3.2 μm, 4.8 μm, and 13 μm), respectively. Also, the effects of dean flow (or secondary flow) induced by expansion-contraction cavity arrays were highlighted by comparing the particle distributions in a single straight rectangular channel with that in the ECCA channel. Finally, the influences of flow rates and distances from the inlet on focusing performance in the ECCA channel were studied. The results show that in the ECCA channel particles are focused on the cavity side in Newtonian fluid due to the synthesis effects of inertial and dean-drag force, whereas the particles are focused on the opposite cavity side in non-Newtonian fluid due to the addition of viscoelastic force. Compared with the focusing performance in Newtonian fluid, the particles are more easily and better focused in non-Newtonian fluid. Besides, the Dean flow in visco-elastic fluid in the ECCA channel improves the particle focusing performance compared with that in a straight channel. A further advantage is three-dimensional (3D) particle focusing that in non-Newtonian fluid is realized according to the lateral side view of the channel while only two-dimensional (2D) particle focusing can be achieved in Newtonian fluid. Conclusively, this novel Dean-flow-coupled elasto-inertial microfluidic device could offer a continuous, sheathless, and high throughput (>10 000 s(-1)) 3D focusing performance, which may be valuable in various applications from high speed flow cytometry to cell counting, sorting, and analysis.

  14. Dean-flow-coupled elasto-inertial three-dimensional particle focusing under viscoelastic flow in a straight channel with asymmetrical expansion–contraction cavity arrays

    PubMed Central

    Yuan, D.; Zhang, J.; Yan, S.; Pan, C.; Alici, G.; Nguyen, N. T.; Li, W. H.

    2015-01-01

    In this paper, 3D particle focusing in a straight channel with asymmetrical expansion–contraction cavity arrays (ECCA channel) is achieved by exploiting the dean-flow-coupled elasto-inertial effects. First, the mechanism of particle focusing in both Newtonian and non-Newtonian fluids was introduced. Then particle focusing was demonstrated experimentally in this channel with Newtonian and non-Newtonian fluids using three different sized particles (3.2 μm, 4.8 μm, and 13 μm), respectively. Also, the effects of dean flow (or secondary flow) induced by expansion–contraction cavity arrays were highlighted by comparing the particle distributions in a single straight rectangular channel with that in the ECCA channel. Finally, the influences of flow rates and distances from the inlet on focusing performance in the ECCA channel were studied. The results show that in the ECCA channel particles are focused on the cavity side in Newtonian fluid due to the synthesis effects of inertial and dean-drag force, whereas the particles are focused on the opposite cavity side in non-Newtonian fluid due to the addition of viscoelastic force. Compared with the focusing performance in Newtonian fluid, the particles are more easily and better focused in non-Newtonian fluid. Besides, the Dean flow in visco-elastic fluid in the ECCA channel improves the particle focusing performance compared with that in a straight channel. A further advantage is three-dimensional (3D) particle focusing that in non-Newtonian fluid is realized according to the lateral side view of the channel while only two-dimensional (2D) particle focusing can be achieved in Newtonian fluid. Conclusively, this novel Dean-flow-coupled elasto-inertial microfluidic device could offer a continuous, sheathless, and high throughput (>10 000 s−1) 3D focusing performance, which may be valuable in various applications from high speed flow cytometry to cell counting, sorting, and analysis. PMID:26339309

  15. Dean-flow-coupled elasto-inertial three-dimensional particle focusing under viscoelastic flow in a straight channel with asymmetrical expansion-contraction cavity arrays.

    PubMed

    Yuan, D; Zhang, J; Yan, S; Pan, C; Alici, G; Nguyen, N T; Li, W H

    2015-07-01

    In this paper, 3D particle focusing in a straight channel with asymmetrical expansion-contraction cavity arrays (ECCA channel) is achieved by exploiting the dean-flow-coupled elasto-inertial effects. First, the mechanism of particle focusing in both Newtonian and non-Newtonian fluids was introduced. Then particle focusing was demonstrated experimentally in this channel with Newtonian and non-Newtonian fluids using three different sized particles (3.2 μm, 4.8 μm, and 13 μm), respectively. Also, the effects of dean flow (or secondary flow) induced by expansion-contraction cavity arrays were highlighted by comparing the particle distributions in a single straight rectangular channel with that in the ECCA channel. Finally, the influences of flow rates and distances from the inlet on focusing performance in the ECCA channel were studied. The results show that in the ECCA channel particles are focused on the cavity side in Newtonian fluid due to the synthesis effects of inertial and dean-drag force, whereas the particles are focused on the opposite cavity side in non-Newtonian fluid due to the addition of viscoelastic force. Compared with the focusing performance in Newtonian fluid, the particles are more easily and better focused in non-Newtonian fluid. Besides, the Dean flow in visco-elastic fluid in the ECCA channel improves the particle focusing performance compared with that in a straight channel. A further advantage is three-dimensional (3D) particle focusing that in non-Newtonian fluid is realized according to the lateral side view of the channel while only two-dimensional (2D) particle focusing can be achieved in Newtonian fluid. Conclusively, this novel Dean-flow-coupled elasto-inertial microfluidic device could offer a continuous, sheathless, and high throughput (>10 000 s(-1)) 3D focusing performance, which may be valuable in various applications from high speed flow cytometry to cell counting, sorting, and analysis. PMID:26339309

  16. A simple analytical model of coupled single flow channel over porous electrode in vanadium redox flow battery with serpentine flow channel

    NASA Astrophysics Data System (ADS)

    Ke, Xinyou; Alexander, J. Iwan D.; Prahl, Joseph M.; Savinell, Robert F.

    2015-08-01

    A simple analytical model of a layered system comprised of a single passage of a serpentine flow channel and a parallel underlying porous electrode (or porous layer) is proposed. This analytical model is derived from Navier-Stokes motion in the flow channel and Darcy-Brinkman model in the porous layer. The continuities of flow velocity and normal stress are applied at the interface between the flow channel and the porous layer. The effects of the inlet volumetric flow rate, thickness of the flow channel and thickness of a typical carbon fiber paper porous layer on the volumetric flow rate within this porous layer are studied. The maximum current density based on the electrolyte volumetric flow rate is predicted, and found to be consistent with reported numerical simulation. It is found that, for a mean inlet flow velocity of 33.3 cm s-1, the analytical maximum current density is estimated to be 377 mA cm-2, which compares favorably with experimental result reported by others of ∼400 mA cm-2.

  17. Activation of T84 cell chloride channels by carbachol involves a phosphoinositide-coupled muscarinic M3 receptor.

    PubMed

    Dickinson, K E; Frizzell, R A; Sekar, M C

    1992-04-10

    Muscarinic agonists stimulate Cl- secretion across monolayers of the colon tumor epithelial cell line, T84. The muscarinic receptor has been characterized in T84 cell homogenates by radioligand binding using [3H]N-methylscopolamine ([3H]NMS). [3H]NMS bound to a single population of sites at 25 degrees C in 100 mM NaCl, 20 mM HEPES, 10 mM MgCl2, pH 7.4 buffer, with calculated Kd = 278 (+/- 44) pM and Bmax = 40 (+/- 6) fmol/mg protein (n = 4). Binding was reversible (diss. t1/2 = 18 +/- 3 min) and stereoselective (dexetimide Ki = 0.3 nM) much greater than levetimide (Ki = 8300 nM). Antagonists exhibited the following rank order of potencies and Ki values (nM): atropine (0.54) greater than 4-diphenylacetoxy-N-methylpiperidine methobromide (4-DAMP) (0.84) greater than dicyclomine (14) = hexahydrosiladifenidol (18) greater than pirenzepine (136) greater than AF-DX 116 (3610). The same sequence was observed for inhibition of carbachol-induced 125I efflux from T84 monolayers. This is indicative of an M3 'glandular' muscarinic receptor. Coupling to second messenger systems was examined by labelling monolayers with [14C]arachidonic acid (AA) or [3H]inositol. Carbachol (0.3 mM) did not release [14C]AA from labelled lipids, but ionomycin produced a dose-dependent increase in media [14C]AA. Carbachol (0.3 mM) elevated inositol monophosphate 14-fold. The results suggest that muscarinic agonists stimulate Cl- secretion by interacting with an M3 receptor coupled to inositide lipid hydrolysis. PMID:1379932

  18. Simultaneous observation of collagen and elastin based on the combined nonlinear optical imaging technique coupled with two-channel synchronized detection method

    NASA Astrophysics Data System (ADS)

    Chen, Jianxin; Zhuo, Shuangmu; Luo, Tianshu; Liu, Dingzhong; Zhao, Jingjun

    2008-08-01

    Collagen and elastin are the most important proteins of the connective tissues in higher vertebrates. In this paper, we present a combined nonlinear optical imaging technique of second-harmonic generation and two-photon excited fluorescence to simultaneously observe the collagen and elastic fiber of dermis in a freshly excised human skin and rabbit aorta using a two-channel synchronized detection method. The obtained two-channel overlay image in the backward direction can clearly distinguish the morphological structure and distribution of collagen and elastic fibers. Tissue spectrum further confirms the obtained structural information. These results suggest that the combined nonlinear optical imaging technique coupled with two-channel synchronized detection method can be an effective tool for detecting collage and elastic fibers without any invasive tissue procedure of slicing, embedding, fixation and staining when two structural proteins are simultaneously present in the biological tissue.

  19. Development of two-channel prototype ITER vacuum ultraviolet spectrometer with back-illuminated charge-coupled device and microchannel plate detectors

    SciTech Connect

    Seon, C. R.; Choi, S. H.; Cheon, M. S.; Pak, S.; Lee, H. G.; Biel, W.; Barnsley, R.

    2010-10-15

    A vacuum ultraviolet (VUV) spectrometer of a five-channel spectral system is designed for ITER main plasma impurity measurement. To develop and verify the system design, a two-channel prototype system is fabricated with No. 3 (14.4-31.8 nm) and No. 4 (29.0-60.0 nm) among the five channels. The optical system consists of a collimating mirror to collect the light from source to slit, two holographic diffraction gratings with toroidal geometry, and two different electronic detectors. For the test of the prototype system, a hollow cathode lamp is used as a light source. To find the appropriate detector for ITER VUV system, two kinds of detectors of the back-illuminated charge-coupled device and the microchannel plate electron multiplier are tested, and their performance has been investigated.

  20. Development of two-channel prototype ITER vacuum ultraviolet spectrometer with back-illuminated charge-coupled device and microchannel plate detectors.

    PubMed

    Seon, C R; Choi, S H; Cheon, M S; Pak, S; Lee, H G; Biel, W; Barnsley, R

    2010-10-01

    A vacuum ultraviolet (VUV) spectrometer of a five-channel spectral system is designed for ITER main plasma impurity measurement. To develop and verify the system design, a two-channel prototype system is fabricated with No. 3 (14.4-31.8 nm) and No. 4 (29.0-60.0 nm) among the five channels. The optical system consists of a collimating mirror to collect the light from source to slit, two holographic diffraction gratings with toroidal geometry, and two different electronic detectors. For the test of the prototype system, a hollow cathode lamp is used as a light source. To find the appropriate detector for ITER VUV system, two kinds of detectors of the back-illuminated charge-coupled device and the microchannel plate electron multiplier are tested, and their performance has been investigated.

  1. Distinct Ca2+ sources in dendritic spines of hippocampal CA1 neurons couple to SK and Kv4 channels

    PubMed Central

    Wang, Kang; Lin, Mike T.; Adelman, John P.; Maylie, James

    2013-01-01

    SUMMARY Ca2+-activated SK channels and voltage-gated A-type Kv4 channels shape dendritic excitatory postsynaptic potentials (EPSPs) in hippocampal CA1 pyramidal neurons. Synaptically evoked Ca2+ influx through N-methyl-D-aspartate receptors (NMDARs) activates spine SK channels, reducing EPSPs and the associated spine head Ca2+ transient. However, results using glutamate uncaging implicated Ca2+ influx through SNX-482 (SNX) sensitive Cav2.3 (R-type) Ca2+ channels as the Ca2+ source for SK channel activation. The present findings show that using Schaffer collateral stimulation the effects of SNX and apamin are not mutually exclusive and SNX increases EPSPs independent of SK channel activity. Dialysis with 1,2-bis(o-aminophenoxy)ethane-N’N’N’-tetraacetic acid (BAPTA), application of 4-Aminopyridine (4-AP), expression of a Kv4.2 dominant negative subunit, and dialysis with a KChIPs antibody occluded the SNX-induced increase of EPSPs. The results suggest two distinct Ca2+ signaling pathways within dendritic spines, that links Ca2+ influx through NMDARs to SK channels and Ca2+ influx through R-type Ca2+ channels to Kv4.2-containing channels. PMID:24462100

  2. G protein-coupled receptor signaling via Src kinase induces endogenous human transient receptor potential vanilloid type 6 (TRPV6) channel activation.

    PubMed

    Spehr, Jennifer; Gelis, Lian; Osterloh, Markus; Oberland, Sonja; Hatt, Hanns; Spehr, Marc; Neuhaus, Eva M

    2011-04-15

    Ca(2+) homeostasis plays a critical role in a variety of cellular processes. We showed previously that stimulation of the prostate-specific G protein-coupled receptor (PSGR) enhances cytosolic Ca(2+) and inhibits proliferation of prostate cells. Here, we analyzed the signaling mechanisms underlying the PSGR-mediated Ca(2+) increase. Using complementary molecular, biochemical, electrophysiological, and live-cell imaging techniques, we found that endogenous Ca(2+)-selective transient receptor potential vanilloid type 6 (TRPV6) channels are critically involved in the PSGR-induced Ca(2+) signal. Biophysical characterization of the current activated by PSGR stimulation revealed characteristic properties of TRPV6. The molecular identity of the involved channel was confirmed using RNA interference targeting TrpV6. TRPV6-mediated Ca(2+) influx depended on Src kinase activity. Src kinase activation occurred independently of G protein activation, presumably by direct interaction with PSGR. Taken together, we report that endogenous TRPV6 channels are activated downstream of a G protein-coupled receptor and present the first physiological characterization of these channels in situ. PMID:21349844

  3. Electronic structures in coupled two quantum dots by 3D-mesh Hartree-Fock-Kohn-Sham calculation

    NASA Astrophysics Data System (ADS)

    Matsuse, T.; Hama, T.; Kaihatsu, H.; Toyoda, N.; Takizawa, T.

    To study the electronic structures of quantum dots in the framework of self-interaction-free including three dimensional effects, we adopt the theory of nonlocal effective potential introduced by Kohn and Sham [#!ks65!#]. For utilizing the advantageous point of the real space (3D) mesh method to solve the original nonlinear and nonlocal Hartree-Fock-Kohn-Sham (HFKS)-equation, we introduce a linearization of the equation in the local form by introducing the local Coulomb potentials which depend on explicitly the two single particle states. In practice, for solving the local form HFKS-equation, we use the Car-Parrinello-like relaxation method and the Coulomb potentials are obtained by solving the Poisson equation under proper boundary conditions. Firstly the observed energy gap between triplet- and singlet-states of N = 4 in DBS [#!tarucha96!#] is discussed to reproduce the addition energies and chemical potentials depending the magnetic field. Next the coupling between two-quantum dots in TBS [#!aht97!#] is studied by adding the square barrier between two dots. The spin-degeneracy [#!aht97!#] measured in gate-voltage depending on magnetic field is well reproduced in the limit of small mismatch. Finally, the electronic states in the ring structure are calculated and discussed how the ring size and magnetic field affect to the structures.

  4. A novel DNA sequence similarity calculation based on simplified pulse-coupled neural network and Huffman coding

    NASA Astrophysics Data System (ADS)

    Jin, Xin; Nie, Rencan; Zhou, Dongming; Yao, Shaowen; Chen, Yanyan; Yu, Jiefu; Wang, Quan

    2016-11-01

    A novel method for the calculation of DNA sequence similarity is proposed based on simplified pulse-coupled neural network (S-PCNN) and Huffman coding. In this study, we propose a coding method based on Huffman coding, where the triplet code was used as a code bit to transform DNA sequence into numerical sequence. The proposed method uses the firing characters of S-PCNN neurons in DNA sequence to extract features. Besides, the proposed method can deal with different lengths of DNA sequences. First, according to the characteristics of S-PCNN and the DNA primary sequence, the latter is encoded using Huffman coding method, and then using the former, the oscillation time sequence (OTS) of the encoded DNA sequence is extracted. Simultaneously, relevant features are obtained, and finally the similarities or dissimilarities of the DNA sequences are determined by Euclidean distance. In order to verify the accuracy of this method, different data sets were used for testing. The experimental results show that the proposed method is effective.

  5. Calculation of BER in multi-channel silicon optical interconnects: comparative analysis of strip and photonic crystal waveguides

    NASA Astrophysics Data System (ADS)

    You, Jie; Lavdas, Spyros; Panoiu, Nicolae C.

    2016-05-01

    We present an effective approach to evaluate the performance of multi-channel silicon (Si) photonic systems. The system is composed of strip Si photonic waveguides (Si-PhWs) with uniform cross-section or photonic-crystal (PhC) Si waveguides (Si-PhCWs), combined with a set of direct-detection receivers. Moreover, the optical field in each channel is the superposition of a continuous-wave nonreturn-to-zero ON-OFF keying modulated signal and a white Gaussian noise. In order to characterize the optical signal propagation in the waveguides, an accurate mathematical model describing all relevant linear and nonlinear optical effects and its linearized version is employed. In addition, two semi-analytical methods, time- and frequency-domain Karhunen-Loève series expansion, are used to assess the system bit-error-rate (BER). Our analysis reveals that Si-PhCWs provide similar performance as Si-PhWs, but for 100× shorter length. Importantly, much worse BER is achieved in Si-PhCWs when one operates in slow-light regime, due to the enhanced linear and nonlinear effects.

  6. On the calculation of nuclear spin-spin coupling constants. The bond length dependence of the Fermi contact term in H 2 and HD

    NASA Astrophysics Data System (ADS)

    Bacskay, George B.

    1995-08-01

    A theoretical study of the Fermi contact contribution to the HH and HD spin-spin coupling constant is reported, with special emphasis on its calculation using quantum chemical techniques over a wide range of internuclear distances, that has necessitated an extension of the existing methodology so the effects of near-degeneracy are properly treated. A detailed configuration interaction calculation on H 2 shows that as the molecule is stretched the coupling constant displays a sharp increase before decaying to zero as the molecule dissociates. Such distance dependence is reflected in the calculated vibrational averages of the coupling constant for HD that show a rapid increase with vibrational excitation.

  7. The performance of hybrid density functional theory for the calculation of indirect nuclear spin-spin coupling constants in substituted hydrocarbons.

    PubMed

    Lutnaes, Ola B; Ruden, Torgeir A; Helgaker, Trygve

    2004-10-01

    Density functional theory, in particular, with the Becke-3-parameter-Lee-Yang-Parr (B3LYP) hybrid functional, has been shown to be a promising method for the calculation of indirect nuclear spin-spin coupling constants. However, no systematic investigation has so far been undertaken to evaluate the capability of B3LYP to calculate these coupling constants accurately, taking properly into account the vibrational contributions. In this work, vibrationally corrected indirect spin-spin coupling constants were calculated using the B3LYP functional for 10 rigid unsubstituted and substituted hydrocarbons: ethyne, ethene, allene, cyclopropene, cyclopropane, cyclobutene, pyrrole, furan, thiophene and benzene. The resulting spin-spin constants were compared with the available experimental values. The basis sets in these calculations give indirect nuclear spin-spin coupling constants of ethyne that are almost converged to the basis-set limit, making the intrinsic error of the computational method and the error in equilibrium geometry the main sources of error. On average, the B3LYP functional overestimates the indirect nuclear spin-spin coupling constants in hydrocarbons by 10%.

  8. Calculations of 21 Λ-S and 42 Ω states of BC molecule: Potential energy curves, spectroscopic parameters and spin-orbit coupling effect.

    PubMed

    Xing, Wei; Shi, Deheng; Sun, Jinfeng; Zhu, Zunlue

    2016-01-15

    The potential energy curves (PECs) were calculated for the 42 Ω states generated from the 21 Λ-S states (X(4)Σ(-), A(4)Π, B(4)Σ(-), a(2)Π, b(2)Σ(-), c(2)Δ, d(2)Σ(+), e(2)Π, 3(2)Π, 4(2)Π, 5(2)Π, 2(2)Σ(-), 3(2)Σ(-), 2(2)Σ(+), 3(2)Σ(+), 2(2)Δ, 3(2)Δ, 1(4)Σ(+), 2(4)Π, 1(4)Δ and 1(2)Φ), which originated from the lowest two dissociation channels, B((2)Pu)+C((3)Pg) and B((2)Pu)+C((1)Dg), of the BC molecule. The PECs were calculated for internuclear separations from 0.08 to 1.10 nm using the CASSCF method, which was followed by the icMRCI approach with the aug-cc-pV6Z basis set. Of these 21 Λ-S states, the e(2)Π, 2(2)Δ, 2(2)Σ(-), 4(2)Π, 1(2)Φ and 3(2)Δ possess the double wells. The A(4)Π, a(2)Π, c(2)Δ, 2(4)Π, 4(2)Π, 5(2)Π, 1(4)Δ and 1(2)Φ states are inverted with the spin-orbit coupling (SOC) effect taken into account. The first well of e(2)Π state and the second well of 4(2)Π and 2(2)Δ states do not have any vibrational states whether with or without the SOC effect included. All the Λ-S and Ω states involved in this paper are bound states. Scalar relativistic correction was included by the third-order Douglas-Kroll Hamiltonian approximation at the level of an aug-cc-pV5Z basis set. Core-valence correlation correction was included at the level of an aug-cc-pCV5Z basis set. The SOC effect was accounted for by the state interaction method with the Breit-Pauli Hamiltonian and the all-electron cc-pCV5Z basis set. The PECs of all the states were extrapolated to the complete basis set limit. The spectroscopic parameters were obtained. The vibrational properties of several Λ-S and Ω states with the relatively shallow wells were evaluated. The SOC effect on the spectroscopic parameters is not obvious for almost all the states. The spectroscopic properties reported in this paper can be expected to be reliably predicted ones.

  9. Calculations of 21 Λ-S and 42 Ω states of BC molecule: Potential energy curves, spectroscopic parameters and spin-orbit coupling effect

    NASA Astrophysics Data System (ADS)

    Xing, Wei; Shi, Deheng; Sun, Jinfeng; Zhu, Zunlue

    2016-01-01

    The potential energy curves (PECs) were calculated for the 42 Ω states generated from the 21 Λ-S states (X4Σ-, A4Π, B4Σ-, a2Π, b2Σ-, c2Δ, d2Σ+, e2Π, 32Π, 42Π, 52Π, 22Σ-, 32Σ-, 22Σ+, 32Σ+, 22Δ, 32Δ, 14Σ+, 24Π, 14Δ and 12Φ), which originated from the lowest two dissociation channels, B(2Pu) + C(3Pg) and B(2Pu) + C(1Dg), of the BC molecule. The PECs were calculated for internuclear separations from 0.08 to 1.10 nm using the CASSCF method, which was followed by the icMRCI approach with the aug-cc-pV6Z basis set. Of these 21 Λ-S states, the e2Π, 22Δ, 22Σ-, 42Π, 12Φ and 32Δ possess the double wells. The A4Π, a2Π, c2Δ, 24Π, 42Π, 52Π, 14Δ and 12Φ states are inverted with the spin-orbit coupling (SOC) effect taken into account. The first well of e2Π state and the second well of 42Π and 22Δ states do not have any vibrational states whether with or without the SOC effect included. All the Λ-S and Ω states involved in this paper are bound states. Scalar relativistic correction was included by the third-order Douglas-Kroll Hamiltonian approximation at the level of an aug-cc-pV5Z basis set. Core-valence correlation correction was included at the level of an aug-cc-pCV5Z basis set. The SOC effect was accounted for by the state interaction method with the Breit-Pauli Hamiltonian and the all-electron cc-pCV5Z basis set. The PECs of all the states were extrapolated to the complete basis set limit. The spectroscopic parameters were obtained. The vibrational properties of several Λ-S and Ω states with the relatively shallow wells were evaluated. The SOC effect on the spectroscopic parameters is not obvious for almost all the states. The spectroscopic properties reported in this paper can be expected to be reliably predicted ones.

  10. Perturbation Theory with Convergent Series for Large Values of Coupling Constant:. a Calculation of β-FUNCTION in φ4 Model

    NASA Astrophysics Data System (ADS)

    Belokurov, V. V.; Shavgulidze, E. T.; Solov'yov, Yu. P.; Yudin, I. L.

    2001-04-01

    A new perturbation theory with convergent series is used to calculate quantities given by a finite number of terms of the traditional perturbation theory. As examples of such a problem, the zero-dimensional analog of a functional integral and β-function in gφ4 model in four-dimensional space-time are considered. The results obtained demonstrate high accuracy of the calculation in a wide region of coupling constant values.

  11. Indirect spin-spin coupling constants in CH 4, SiH 4 and GeH 4 - Gas-phase NMR experiment and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Antušek, Andrej; Keḑziera, Dariusz; Jackowski, Karol; Jaszuński, Michał; Makulski, Włodzimierz

    2008-09-01

    New values of the indirect spin-spin coupling constants in CH 4, SiH 4 and GeH 4, derived from experiment and ab initio calculations, are reported. The new experimental values of 1J(CH), 1J(SiH) and 1J(GeH) are obtained from gas-phase NMR spectra. The dependence of the measured one-bond coupling constants on the density is analysed and the results are extrapolated to zero-density point to eliminate the effects due to intermolecular forces. In the calculation of the coupling constants, at the nonrelativistic level coupled cluster singles and doubles (CCSD) perturbation theory is used and the basis set convergence of the results is discussed. The relativistic corrections are estimated from Dirac-Hartree-Fock (DHF) calculations. The final theoretical values are obtained adding available estimates of the vibrational and temperature corrections. The agreement of the calculated and experimental 1J(XH), X = C, Si, Ge, constants is very satisfying, the differences are approximately 1-3%.

  12. Recruitment of Gβγ controls the basal activity of G-protein coupled inwardly rectifying potassium (GIRK) channels: crucial role of distal C terminus of GIRK1.

    PubMed

    Kahanovitch, Uri; Tsemakhovich, Vladimir; Berlin, Shai; Rubinstein, Moran; Styr, Boaz; Castel, Ruth; Peleg, Sagit; Tabak, Galit; Dessauer, Carmen W; Ivanina, Tatiana; Dascal, Nathan

    2014-12-15

    The G-protein coupled inwardly rectifying potassium (GIRK, or Kir3) channels are important mediators of inhibitory neurotransmission via activation of G-protein coupled receptors (GPCRs). GIRK channels are tetramers comprising combinations of subunits (GIRK1-4), activated by direct binding of the Gβγ subunit of Gi/o proteins. Heterologously expressed GIRK1/2 exhibit high, Gβγ-dependent basal currents (Ibasal) and a modest activation by GPCR or coexpressed Gβγ. Inversely, the GIRK2 homotetramers exhibit low Ibasal and strong activation by Gβγ. The high Ibasal of GIRK1 seems to be associated with its unique distal C terminus (G1-dCT), which is not present in the other subunits. We investigated the role of G1-dCT using electrophysiological and fluorescence assays in Xenopus laevis oocytes and protein interaction assays. We show that expression of GIRK1/2 increases the plasma membrane level of coexpressed Gβγ (a phenomenon we term 'Gβγ recruitment') but not of coexpressed Gαi3. All GIRK1-containing channels, but not GIRK2 homomers, recruited Gβγ to the plasma membrane. In biochemical assays, truncation of G1-dCT reduces the binding between the cytosolic parts of GIRK1 and Gβγ, but not Gαi3. Nevertheless, the truncation of G1-dCT does not impair activation by Gβγ. In fluorescently labelled homotetrameric GIRK1 channels and in the heterotetrameric GIRK1/2 channel, the truncation of G1-dCT abolishes Gβγ recruitment and decreases Ibasal. Thus, we conclude that G1-dCT carries an essential role in Gβγ recruitment by GIRK1 and, consequently, in determining its high basal activity. Our results indicate that G1-dCT is a crucial part of a Gβγ anchoring site of GIRK1-containing channels, spatially and functionally distinct from the site of channel activation by Gβγ.

  13. Recruitment of Gβγ controls the basal activity of G-protein coupled inwardly rectifying potassium (GIRK) channels: crucial role of distal C terminus of GIRK1

    PubMed Central

    Kahanovitch, Uri; Tsemakhovich, Vladimir; Berlin, Shai; Rubinstein, Moran; Styr, Boaz; Castel, Ruth; Peleg, Sagit; Tabak, Galit; Dessauer, Carmen W; Ivanina, Tatiana; Dascal, Nathan

    2014-01-01

    The G-protein coupled inwardly rectifying potassium (GIRK, or Kir3) channels are important mediators of inhibitory neurotransmission via activation of G-protein coupled receptors (GPCRs). GIRK channels are tetramers comprising combinations of subunits (GIRK1–4), activated by direct binding of the Gβγ subunit of Gi/o proteins. Heterologously expressed GIRK1/2 exhibit high, Gβγ-dependent basal currents (Ibasal) and a modest activation by GPCR or coexpressed Gβγ. Inversely, the GIRK2 homotetramers exhibit low Ibasal and strong activation by Gβγ. The high Ibasal of GIRK1 seems to be associated with its unique distal C terminus (G1-dCT), which is not present in the other subunits. We investigated the role of G1-dCT using electrophysiological and fluorescence assays in Xenopus laevis oocytes and protein interaction assays. We show that expression of GIRK1/2 increases the plasma membrane level of coexpressed Gβγ (a phenomenon we term ‘Gβγ recruitment’) but not of coexpressed Gαi3. All GIRK1-containing channels, but not GIRK2 homomers, recruited Gβγ to the plasma membrane. In biochemical assays, truncation of G1-dCT reduces the binding between the cytosolic parts of GIRK1 and Gβγ, but not Gαi3. Nevertheless, the truncation of G1-dCT does not impair activation by Gβγ. In fluorescently labelled homotetrameric GIRK1 channels and in the heterotetrameric GIRK1/2 channel, the truncation of G1-dCT abolishes Gβγ recruitment and decreases Ibasal. Thus, we conclude that G1-dCT carries an essential role in Gβγ recruitment by GIRK1 and, consequently, in determining its high basal activity. Our results indicate that G1-dCT is a crucial part of a Gβγ anchoring site of GIRK1-containing channels, spatially and functionally distinct from the site of channel activation by Gβγ. PMID:25384780

  14. Analysis of light propagation for a crossing of thin silicon wires using vertical tunnelling coupling with a thick optical channel waveguide

    SciTech Connect

    Tsarev, A V; Kolosovskii, E A

    2013-08-31

    Using silicon photonic wires in a silicon-on-insulator structure as an example, we examine the problem of crossings of thin, high-index-contrast channel waveguides. To ensure high optical wave transmission efficiency at as low a level of parasitic scattering as possible, we propose using a structure with vertical coupling between a thin tapered silicon waveguide and a thick polymer waveguide, separated by a thin buffer oxide layer. Numerical simulation is used to find conditions under which such a structure (3 × 90 μm in dimensions) ensures 98 % and 99 % transmission efficiency at ∼1.55 μm in 35- and 26-nm spectral ranges, respectively, for direct propagation and 99.99 % transmission in the transverse direction. The optical element in question is proposed for use in optical microchips with multiple channel waveguide crossings. (integrated optical waveguides)

  15. Mode couplings in a two-stream free-electron laser with a helical wiggler and an ion-channel guiding

    SciTech Connect

    Mohsenpour, Taghi Alirezaee, Hajar

    2014-08-15

    In this study, the method of perturbation has been applied to obtain the dispersion relation (DR) of a two-stream free-electron laser (FEL) with a helical wiggler and an ion-channel with all relativistic effects on waves. This DR has been solved numerically to find the unstable modes and their growth rate. Numerical solutions of DR show that the growth rate is considerably enhanced in comparison with single-stream free-electron laser. In group II orbits, with relatively large wiggler induced velocities, new couplings are found. The effect of the velocity difference of the two electron beams on the instabilities has also been investigated in this study. Moreover, the effect of the ion-channel density on the maximum growth rate of FEL resonance has been analyzed.

  16. Sub-Barrier Fusion Calculations for the {sup 9}Li+{sup 70}Zn System

    SciTech Connect

    Balantekin, A. B.; Kocak, G.

    2008-11-11

    Sub-barrier fusion cross sections for the {sup 9}Li+{sup 70}Zn system are analyzed within the framework of the coupled channels model. We find that inclusion of the inelastic and one-neutron transfer channels in the coupled-channels calculations fails to reproduce the data. We find that possible formation of a molecular bond accompanied by two-neutron transfer may account for the observed behavior.

  17. Evidence for Hysteretic Substrate Channeling in the Proline Dehydrogenase and Δ1-Pyrroline-5-carboxylate Dehydrogenase Coupled Reaction of Proline Utilization A (PutA)*

    PubMed Central

    Moxley, Michael A.; Sanyal, Nikhilesh; Krishnan, Navasona; Tanner, John J.; Becker, Donald F.

    2014-01-01

    PutA (proline utilization A) is a large bifunctional flavoenzyme with proline dehydrogenase (PRODH) and Δ1-pyrroline-5-carboxylate dehydrogenase (P5CDH) domains that catalyze the oxidation of l-proline to l-glutamate in two successive reactions. In the PRODH active site, proline undergoes a two-electron oxidation to Δ1-pyrroline-5-carboxlylate, and the FAD cofactor is reduced. In the P5CDH active site, l-glutamate-γ-semialdehyde (the hydrolyzed form of Δ1-pyrroline-5-carboxylate) undergoes a two-electron oxidation in which a hydride is transferred to NAD+-producing NADH and glutamate. Here we report the first kinetic model for the overall PRODH-P5CDH reaction of a PutA enzyme. Global analysis of steady-state and transient kinetic data for the PRODH, P5CDH, and coupled PRODH-P5CDH reactions was used to test various models describing the conversion of proline to glutamate by Escherichia coli PutA. The coupled PRODH-P5CDH activity of PutA is best described by a mechanism in which the intermediate is not released into the bulk medium, i.e., substrate channeling. Unexpectedly, single-turnover kinetic experiments of the coupled PRODH-P5CDH reaction revealed that the rate of NADH formation is 20-fold slower than the steady-state turnover number for the overall reaction, implying that catalytic cycling speeds up throughput. We show that the limiting rate constant observed for NADH formation in the first turnover increases by almost 40-fold after multiple turnovers, achieving half of the steady-state value after 15 turnovers. These results suggest that EcPutA achieves an activated channeling state during the approach to steady state and is thus a new example of a hysteretic enzyme. Potential underlying causes of activation of channeling are discussed. PMID:24352662

  18. The K⁻N→KΞ reaction in coupled channel chiral models up to next-to-leading order

    SciTech Connect

    Magas, V. K.; Ramos, A.; Feijoo, A.

    2009-01-01

    We study the meson-baryon interaction in S-wave in the strangeness S=-1 sector using a chiral unitary approach based on a next-to-leading order chiral SU(3) Lagrangian. We fit our model to the large set of experimental data in different two-body channels. We pay particular attention to the K⁻N→KΞ reaction, where the effect of the next-to-leading order terms in the Lagrangian are sufficiently large to be observed, since at tree level the cross section of this reaction is zero. For these channels we improve our approach by phenomenologically taking into account effects of the high spin hyperonic resonances.

  19. Description of nucleon-transfer and fusion reactions within time-dependent approaches and coupled-channel method

    SciTech Connect

    Samarin, V. V.

    2015-01-15

    The time-dependent Schrödinger equation and the method of perturbed stationary states that is based on the expansion of the total wave function for the system of two nuclear cores and a nucleon in a set of nucleon two-center functions are used to describe nucleon transfers and fusion in low-energy nuclear reactions. A set of multichannel equations that couple the relative motion of nuclei to the motion of the nucleon is obtained. The kinetic-energy coupling matrix is similar to the coupling matrix for collective excitations of nuclei.

  20. 5-HT3 receptor-channels coupled with Na+ influx in human T cells: role in T cell activation.

    PubMed

    Khan, N A; Poisson, J P

    1999-09-01

    The study was conducted on a human (Jurkat) T cell line, loaded with a Na+ fluorescent probe, SBFI/AM. Serotonin and an agonist of 5-HT3 receptor-channels, 2-methyl-5HT, evoked Na+ influx, whereas the agonists of other serotonergic receptor subtypes, i.e., 5-HT1A and 5-HT1B receptors, failed to induce Na+ influx in these cells. By using 3H-BRL43694, an agonist of 5-HT3 receptor-channels, we characterized 5-HT3 lymphocyte receptors which exhibited a density (Bmax) of 300 +/- 20 fmol/10(6) cells and a Kd of 30 nM in Jurkat T cells. The T-cell 5-HT3 receptor-channel is not regulated either by the protein kinase C or by the free intracellular calcium concentrations as the agents known to activate the PKC and to induce increases in intracellular free calcium concentrations failed to influence the free intracellular Na+ concentrations, [Na+]i, in these cells. Furthermore, an increase in [Na+]i, induced by 2-methyl-5HT, via 5-HT3 receptor-channels seems to stimulate T-cell activation by facilitating the progression of T cells from S to G2/M phase of the cell cycle.

  1. GIS-based channel flow and sediment transport simulation using CCHE1D coupled with AnnAGNPS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    CCHE1D (Center for Computational Hydroscience and Engineering 1-Dimensional model) simulates unsteady free-surface flows with nonequilibrium, nonuniform sediment transport in dendritic channel networks. Since early 1990’s, the model and its software packages have been developed and continuously main...

  2. Pumiliotoxin B binds to a site on the voltage-dependent sodium channel that is allosterically coupled to other binding sites.

    PubMed Central

    Gusovsky, F; Rossignol, D P; McNeal, E T; Daly, J W

    1988-01-01

    Pumiliotoxin B (PTX-B), an alkaloid that has cardiotonic and myotonic activity, increases sodium influx in guinea pig cerebral cortical synaptoneurosomes. In the presence of scorpion venom (Leiurus) or purified alpha-scorpion toxin, the PTX-B-induced sodium influx is enhanced severalfold. PTX-B alone has no effect on sodium flux in N18 neuroblastoma cells but, in the presence of alpha-scorpion toxin, stimulation of sodium influx by PTX-B reaches levels comparable to that attained with the sodium channel activator veratridine. In neuroblastoma LV9 cells, a variant mutant that lacks sodium channels, neither veratridine nor PTX-B induces sodium fluxes in either the presence or absence of alpha-scorpion toxin. In synaptoneurosomes and in N18 cells, the sodium influx induced by the combination of PTX-B and alpha-scorpion toxin is inhibited by tetrodotoxin and local anesthetics. PTX-B does not interact with two of the known toxin sites on the sodium channel, as evidenced by a lack of effect on binding of [3H]saxitoxin or [3H]batrachotoxinin A benzoate to brain synaptoneurosomes. Synergistic effects on sodium influx with alpha-scorpion toxin, beta-scorpion toxin, and brevetoxin indicate that PTX-B does not interact directly with three other toxin sites on the sodium channel. Thus, PTX-B appears to activate sodium influx by interacting with yet another site on the voltage-dependent sodium channel, a site that is coupled allosterically to sites for alpha-scorpion toxin, beta-scorpion toxin, and brevetoxin. PMID:2448797

  3. G-protein coupled receptor 18 (GPR18) in channel catfish: expression analysis and efficacy as immunostimulant against Aeromonas hydrophila infection.

    PubMed

    Pridgeon, Julia W; Klesius, Phillip H

    2013-10-01

    The objectives of this study were: 1) to determine the transcriptional profiles of G-protein coupled receptor 18 (GPR18) in channel catfish after infection with Aeromonas hydrophila compared to that in healthy catfish; 2) to determine whether over-expression of GPR18 in catfish gill cells will offer protection against infection of A. hydrophila; 3) to determine whether recombinant pcDNA-GPR18 could be used as an immunostimulant to protect channel catfish against A. hydrophila infection. Quantitative PCR revealed that the transcription levels of GPR18 in all tissues of infected catfish were significantly (P < 0.05) induced except in the intestine. When pcDNA3.2-vectored recombinant GPR18 was transfected in catfish gill cells G1B, the over-expression of pcDNA-GPR18 offered significant (P < 0.05) protection to G1B cells against A. hydrophila infection. When channel catfish were intraperitoneally injected with QCDCR adjuvant formulated pcDNA-GPR18 and challenged with a highly virulent A. hydrophila strain at 1-, 2-, 14-, and 28-days post treatment, pcDNA-GPR18 offered 50%, 100%, 57%, and 55% protection to channel catfish, respectively. Macrophages of fish treated with pcDNA-GPR18 produced significantly (P < 0.05) higher amounts of reactive oxygen species and nitric oxide than that of fish treated with pcDNA vector alone. In addition, serum lysozyme activity of catfish injected with pcDNA-GPR18 was significantly (P < 0.08) increased. Taken together, our results suggest that pcDNA-GPR18 could be used as a novel immunostimulant to provide immediate protection to channel catfish against A. hydrophila infection.

  4. Time-domain calculations of the 1D and 2D spectra of resonantly-coupled vibrations in liquids and proteins

    NASA Astrophysics Data System (ADS)

    Torii, Hajime

    2012-12-01

    A time-domain computational method for calculating 1D and 2D spectra of resonantly-coupled vibrations in condensed-phase systems is presented. This method simultaneously takes into account the diagonal frequency modulations, the off-diagonal vibrational couplings, and the dynamics of the system, and is applicable to systems of wide interest, e.g., the O-H stretching modes of water and alcohols, and the amide I modes of proteins. The case of the amide I mode of (Ala-d)4 in D2O solution is shown as an example.

  5. Allosteric coupling between proximal C-terminus and selectivity filter is facilitated by the movement of transmembrane segment 4 in TREK-2 channel

    PubMed Central

    Zhuo, Ren-Gong; Peng, Peng; Liu, Xiao-Yan; Yan, Hai-Tao; Xu, Jiang-Ping; Zheng, Jian-Quan; Wei, Xiao-Li; Ma, Xiao-Yun

    2016-01-01

    TREK-2, a member of two-pore-domain potassium channel family, regulates cellular excitability in response to diverse stimuli. However, how such stimuli control channel function remains unclear. Here, by characterizing the responses of cytosolic proximal C-terminus deletant (ΔpCt) and transmembrane segment 4 (M4)-glycine hinge mutant (G312A) to 2-Aminoethoxydiphenyl borate (2-APB), an activator of TREK-2, we show that the transduction initiated from pCt domain is allosterically coupled with the conformation of selectivity filter (SF) via the movements of M4, without depending on the original status of SF. Moreover, ΔpCt and G312A also exhibited blunted responses to extracellular alkalization, a model to induce SF conformational transition. These results suggest that the coupling between pCt domain and SF is bidirectional, and M4 movements are involved in both processes. Further mechanistic exploration reveals that the function of Phe316, a residue close to the C-terminus of M4, is associated with such communications. However, unlike TREK-2, M4-hinge of TREK-1 only controls the transmission from pCt to SF, rather than SF conformational changes triggered by pHo changes. Together, our findings uncover the unique gating properties of TREK-2, and elucidate the mechanisms for how the extracellular and intracellular stimuli harness the pore gating allosterically. PMID:26879043

  6. Data pattern sensitivity in tracking performance of an AC coupled Costas loop with hard-limited in-phase channel

    NASA Technical Reports Server (NTRS)

    Park, Y. H.

    1979-01-01

    This paper is concerned with data pattern sensitivity in carrier tracking performance of an AC coupled Costas loop with a suppressed BPSK signal. The signal amplitude suppression factor is derived as a function of data 'asymmetry ratio' - the ratio of '1's to the total number of bits in a period of a periodic signal. For an asymmetric pattern, the effect of AC coupling is noticeable whereas there is almost no effect for symmetric square wave. The tracking performance with an asymmetric pattern is worse than that with a symmetric pattern. However, it is also shown that as expected, the tracking performance of a DC coupled loop with an asymmetric pattern is better than that with a symmetric pattern.

  7. Electron-impact excitation of Fe{sup 2+}: A comparison of intermediate coupling frame transformation, Breit-Pauli and Dirac R-matrix calculations

    SciTech Connect

    Badnell, N. R.; Ballance, C. P.

    2014-04-20

    Modeling the spectral emission of low-charge iron group ions enables the diagnostic determination of the local physical conditions of many cool plasma environments such as those found in H II regions, planetary nebulae, active galactic nuclei, etc. Electron-impact excitation drives the population of the emitting levels and, hence, their emissivities. By carrying-out Breit-Pauli and intermediate coupling frame transformation (ICFT) R-matrix calculations for the electron-impact excitation of Fe{sup 2+}, which both use the exact same atomic structure and the same close-coupling expansion, we demonstrate the validity of the application of the powerful ICFT method to low-charge iron group ions. This is in contradiction to the finding of Bautista et al., who carried-out ICFT and Dirac R-matrix calculations for the same ion. We discuss possible reasons.

  8. Ab Initio and Improved Empirical Potentials for the Calculation of the Anharmonic Vibrational States and Intramolecular Mode Coupling of N-Methylacetamide

    NASA Technical Reports Server (NTRS)

    Gregurick, Susan K.; Chaban, Galina M.; Gerber, R. Benny; Kwak, Dochou (Technical Monitor)

    2001-01-01

    The second-order Moller-Plesset ab initio electronic structure method is used to compute points for the anharmonic mode-coupled potential energy surface of N-methylacetamide (NMA) in the trans(sub ct) configuration, including all degrees of freedom. The vibrational states and the spectroscopy are directly computed from this potential surface using the Correlation Corrected Vibrational Self-Consistent Field (CC-VSCF) method. The results are compared with CC-VSCF calculations using both the standard and improved empirical Amber-like force fields and available low temperature experimental matrix data. Analysis of our calculated spectroscopic results show that: (1) The excellent agreement between the ab initio CC-VSCF calculated frequencies and the experimental data suggest that the computed anharmonic potentials for N-methylacetamide are of a very high quality; (2) For most transitions, the vibrational frequencies obtained from the ab initio CC-VSCF method are superior to those obtained using the empirical CC-VSCF methods, when compared with experimental data. However, the improved empirical force field yields better agreement with the experimental frequencies as compared with a standard AMBER-type force field; (3) The empirical force field in particular overestimates anharmonic couplings for the amide-2 mode, the methyl asymmetric bending modes, the out-of-plane methyl bending modes, and the methyl distortions; (4) Disagreement between the ab initio and empirical anharmonic couplings is greater than the disagreement between the frequencies, and thus the anharmonic part of the empirical potential seems to be less accurate than the harmonic contribution;and (5) Both the empirical and ab initio CC-VSCF calculations predict a negligible anharmonic coupling between the amide-1 and other internal modes. The implication of this is that the intramolecular energy flow between the amide-1 and the other internal modes may be smaller than anticipated. These results may have

  9. Coupled calculation of vibrational frequencies and intensities. Part VI. IR and Raman spectra of crotonaldehyde, methacrolein and methyl-vinylketone

    NASA Astrophysics Data System (ADS)

    Oelichmann, H.-J.; Bougeard, D.; Schrader, B.

    1981-12-01

    The vibrational spectra of trans-crotonaldehyde, methacrolein and methylvinylketone have been reinvestigated and the bands assigned. Normal coordinate analyses of these molecules based on the given assignments have been carried out in the valence force field approximation. A transferable force field for α, β-unsaturated aldehydes and ketones was obtained leading to good agreement between observed and calculated frequencies. The relative cartesian displacements of the atoms given in the L matrices were used to compute the IR and Raman intensities of each mode by a modified CNDO/2 procedure. The intensity calculations confirm the assignments and support the calculated force constants.

  10. Rotational-vibrational Description of Nucleon Scattering on Actinide Nuclei Using a Dispersive Coupled-channel Optical Model

    NASA Astrophysics Data System (ADS)

    Quesada, J. M.; Capote, R.; Soukhovitskiı˜, E. Sh.; Chiba, S.

    2014-04-01

    Tamura's coupling formalism has been extended to consider low-lying rotational bands built on vibrational (single-particle) band heads in well-deformed even-even (odd) actinides. These additional excitations are introduced as a perturbation to the underlying rigid rotor structure that is known to describe well the ground state rotational band of major actinides. Coupling matrix elements needed in extended Tamura's formalism are derived for both even-even and odd actinides. Employed dispersive optical model (DCCOMP) replaces the incident proton energy Ep (for proton induced reactions) by the equivalent Coulomb subtracted energy in all potential terms including both the imaginary and real potentials with the corresponding dispersive corrections. Therefore, the optical potential becomes fully symmetric for protons and neutrons. This potential is used to fit simultaneously all the available optical experimental databases (including neutron strength functions) for nucleon scattering on 238U and 232Th (even even) nuclei. Quasi-elastic (p,n) scattering data to the isobaric analogue states of the target nuclei are also used to constrain the isovector part of the optical potential. Derived Lane-consistent DCCOMP is based on coupling of almost all levels below 1 MeV of excitation energy. The ground state, octupole, beta, gamma and non-axial rotational bands are considered for even nuclei, and rotational bands built on single-particle levels - for odd nuclei. Application of derived potential to odd targets based on a new coupling scheme is foreseen.

  11. 'She's usually quicker than the calculator': financial management and decision-making in couples living with dementia.

    PubMed

    Boyle, Geraldine

    2013-09-01

    This article explores how married couples managed their finances and made financial decisions when one spouse had dementia, drawing comparisons with the approaches used prior to the illness. More specifically, the article examines the role of social factors in influencing the involvement of people with dementia in financial management and decision-making, particularly whether a gender dynamic adopted earlier in a marriage similarly influenced a gendered approach following dementia. The research formed part of a larger study of everyday decision-making by couples living with dementia which explored the role of non-cognitive factors in influencing whether people with dementia were involved in decision-making processes. Twenty-one married couples living at home took part; the recently-diagnosed were excluded. Qualitative methods -including participant observation and interviews - were used to examine the couples' fiscal management and decision-making-processes, the perceptions of people with dementia and their spouses about their current financial abilities and whether any support provided by spouse-carers influenced their partners' financial capacity. The fieldwork was undertaken in the North of England between June 2010 and May 2011. Thematic analysis of the data showed that social factors influenced the perceived capacity of people with dementia and the financial practices adopted by the couples. In particular, gender influenced whether people with dementia were involved in financial decisions. The research demonstrated that non-cognitive factors need to be taken into account when assessing and facilitating the capacity of people with dementia. In addition, as people with dementia were somewhat marginalised in decisions about designating financial authority (Lasting Power of Attorney), spouse-carers may need guidance on how to undertake advance care planning and how to support their relatives with dementia in major decision-making, particularly when there are

  12. Variational versus Perturbational Treatment of Spin-Orbit Coupling in Relativistic Density Functional Calculations of Electronic g Factors: Effects from Spin-Polarization and Exact Exchange.

    PubMed

    Verma, Prakash; Autschbach, Jochen

    2013-02-12

    Different approaches are compared for relativistic calculations of electronic g factors of molecules with light atoms, transition metal complexes, and selected complexes with actinides, using density functional theory (DFT) and Hartree-Fock (HF) theory. The comparison includes functionals with range-separated exchange. Within the variationally stable zeroth-order regular approximation (ZORA) relativistic framework, g factors are obtained with a linear response (LR) method where spin-orbit (SO) coupling is treated as a linear perturbation, a spin-polarized approach based on magnetic anisotropy (MA) that includes SO coupling variationally, and a quasi-restricted variational SO method previously devised by van Lenthe, van der Avoird, and Wormer (LWA). The MA and LWA approaches were implemented in the open-source NWChem quantum chemistry package. We address the importance of electron correlation (DFT vs HF), the importance of including spin polarization in the g tensor methodology, the question of whether the use of nonrelativistic spin density functionals is adequate for such calculations, and the importance of treating spin-orbit coupling beyond first-order. For selected systems, the extent of the DFT delocalization error is explicitly investigated via calculations of the energy as a function of fractional electron numbers. For a test set of small molecules with light main group atoms, all levels of calculation perform adequately as long as there is no energetic near-degeneracy among occupied and unoccupied orbitals. The interplay between different factors determining the accuracy of calculated g factors becomes more complex for systems with heavy elements such as third row transition metals and actinides. The MA approach is shown to perform acceptably well for a wide range of scenarios. PMID:26588748

  13. A computational study of barium blockades in the KcsA potassium channel based on multi-ion potential of mean force calculations and free energy perturbation.

    PubMed

    Rowley, Christopher N; Roux, Benoît

    2013-10-01

    Electrophysiological studies have established that the permeation of Ba(2+) ions through the KcsA K(+)-channel is impeded by the presence of K(+) ions in the external solution, while no effect is observed for external Na(+) ions. This Ba(2+) "lock-in" effect suggests that at least one of the external binding sites of the KcsA channel is thermodynamically selective for K(+). We used molecular dynamics simulations to interpret these lock-in experiments in the context of the crystallographic structure of KcsA. Assuming that the Ba(2+) is bound in site S(2) in the dominant blocked state, we examine the conditions that could impede its translocation and cause the observed "lock-in" effect. Although the binding of a K(+) ion to site S(1) when site S(2) is occupied by Ba(2+) is prohibitively high in energy (>10 kcal/mol), binding to site S0 appears to be more plausible (ΔG > 4 kcal/mol). The 2D potential of mean force (PMF) for the simultaneous translocation of Ba(2+) from site S(2) to site S(1) and of a K(+) ion on the extracellular side shows a barrier that is consistent with the concept of external lock-in. The barrier opposing the movement of Ba(2+) is very high when a cation is in site S(0), and considerably smaller when the site is unoccupied. Furthermore, free energy perturbation calculations show that site S(0) is selective for K(+) by 1.8 kcal/mol when S(2) is occupied by Ba(2+). However, the same site S(0) is nonselective when site S(2) is occupied by K(+), which shows that the presence of Ba(2+) affects the selectivity of the pore. A theoretical framework within classical rate theory is presented to incorporate the concentration dependence of the external ions on the lock-in effect.

  14. A computational study of barium blockades in the KcsA potassium channel based on multi-ion potential of mean force calculations and free energy perturbation

    PubMed Central

    Rowley, Christopher N.

    2013-01-01

    Electrophysiological studies have established that the permeation of Ba2+ ions through the KcsA K+-channel is impeded by the presence of K+ ions in the external solution, while no effect is observed for external Na+ ions. This Ba2+ “lock-in” effect suggests that at least one of the external binding sites of the KcsA channel is thermodynamically selective for K+. We used molecular dynamics simulations to interpret these lock-in experiments in the context of the crystallographic structure of KcsA. Assuming that the Ba2+ is bound in site S2 in the dominant blocked state, we examine the conditions that could impede its translocation and cause the observed “lock-in” effect. Although the binding of a K+ ion to site S1 when site S2 is occupied by Ba2+ is prohibitively high in energy (>10 kcal/mol), binding to site S0 appears to be more plausible (ΔG > 4 kcal/mol). The 2D potential of mean force (PMF) for the simultaneous translocation of Ba2+ from site S2 to site S1 and of a K+ ion on the extracellular side shows a barrier that is consistent with the concept of external lock-in. The barrier opposing the movement of Ba2+ is very high when a cation is in site S0, and considerably smaller when the site is unoccupied. Furthermore, free energy perturbation calculations show that site S0 is selective for K+ by 1.8 kcal/mol when S2 is occupied by Ba2+. However, the same site S0 is nonselective when site S2 is occupied by K+, which shows that the presence of Ba2+ affects the selectivity of the pore. A theoretical framework within classical rate theory is presented to incorporate the concentration dependence of the external ions on the lock-in effect. PMID:24043859

  15. A linearization of quantum channels

    NASA Astrophysics Data System (ADS)

    Crowder, Tanner

    2015-06-01

    Because the quantum channels form a compact, convex set, we can express any quantum channel as a convex combination of extremal channels. We give a Euclidean representation for the channels whose inverses are also valid channels; these are a subset of the extreme points. They form a compact, connected Lie group, and we calculate its Lie algebra. Lastly, we calculate a maximal torus for the group and provide a constructive approach to decomposing any invertible channel into a product of elementary channels.

  16. Calculations of non-gray gas radiative heat transfer by coupling the discrete ordinates method with the Leckner model in 3D rectangular enclosures

    NASA Astrophysics Data System (ADS)

    Fathi Azarkhavarani, M. E.; Hosseini Abardeh, R.; Rahmani, M.

    2016-11-01

    In this study a new approach for radiation heat flux calculations by coupling the discrete ordinates method with the Leckner global model is introduced. The aim is to analyze the radiative heat transfer problem within a three-dimensional enclosure filled with non-gray gas mixture of {H}2{O} and {C}{O}2. A computer code developed by this approach is applied to radiative calculations in three groups of well-known test cases published previously; considering homogeneous and inhomogeneous isothermal and non-isothermal participating media. All results are compared with well-known calculations based on statistical narrow band model. Also a new series of predictions for a medium with non-black walls and various mixture of {H}2{O} and {C}{O}2 is performed to demonstrate the applicability of the Leckner model. The effect of different compositions of {H}2{O} and {C}{O}2 on the radiative transfer within modern combustors is also examined. Based on the results obtained, it is believed that the discrete ordinates method coupled with the Leckner global model despite of its inherent simplicity and low computational cost is sufficiently accurate. For its convenient use, this method is suitable for a wide range of engineering calculations of participating media as well as for its link to previously written computational fluid dynamics codes.

  17. Calculations of non-gray gas radiative heat transfer by coupling the discrete ordinates method with the Leckner model in 3D rectangular enclosures

    NASA Astrophysics Data System (ADS)

    Fathi Azarkhavarani, M. E.; Hosseini Abardeh, R.; Rahmani, M.

    2015-12-01

    In this study a new approach for radiation heat flux calculations by coupling the discrete ordinates method with the Leckner global model is introduced. The aim is to analyze the radiative heat transfer problem within a three-dimensional enclosure filled with non-gray gas mixture of H2O and CO2 . A computer code developed by this approach is applied to radiative calculations in three groups of well-known test cases published previously; considering homogeneous and inhomogeneous isothermal and non-isothermal participating media. All results are compared with well-known calculations based on statistical narrow band model. Also a new series of predictions for a medium with non-black walls and various mixture of H2O and CO2 is performed to demonstrate the applicability of the Leckner model. The effect of different compositions of H2O and CO2 on the radiative transfer within modern combustors is also examined. Based on the results obtained, it is believed that the discrete ordinates method coupled with the Leckner global model despite of its inherent simplicity and low computational cost is sufficiently accurate. For its convenient use, this method is suitable for a wide range of engineering calculations of participating media as well as for its link to previously written computational fluid dynamics codes.

  18. DRC2: A code with specialized applications for coupling localized Monte Carlo adjoint calculations with fluences from two-dimensional R-Z discrete ordinates air-over-ground calculations

    SciTech Connect

    Slater, C.O.

    1992-01-01

    The DRC2 code, which couples MASH or MASHX adjoint leakages with DORT 2-D discrete ordinates forward directional fluences, is described. The forward fluences are allowed to vary both axially and radially over the coupling surface, as opposed to the strictly axial variation allowed by the predecessor DRC code. Input instructions are presented along with descriptions and results from several sample problems. Results from the sample problems are used to compare DRC2 with DRC, DRC2 with DORT, and DRC2 with itself for the case of x-y dependence versus no x-y dependence of the forward fluence. The test problems demonstrate that for small systems DRC and DRC2 give essentially the same results. Some significant differences are noted for larger systems. Additionally, DRC2 results with no x-y dependence of the forward directional fluences are practically the same as those calculated by DRC.

  19. Calculation of P,T-odd interaction constant of PbF using Z-vector method in the relativistic coupled-cluster framework.

    PubMed

    Sasmal, Sudip; Pathak, Himadri; Nayak, Malaya K; Vaval, Nayana; Pal, Sourav

    2015-08-28

    The effective electric field experienced by the unpaired electron in the ground state of PbF, which is a potential candidate in the search of electron electric dipole moment due to some special characteristics, is calculated using Z-vector method in the coupled cluster single- and double- excitation approximation with four component Dirac spinor. This is an important quantity to set the upper bound limit of the electron electric dipole moment. Further, we have calculated molecular dipole moment and parallel magnetic hyperfine structure constant (A‖) of (207)Pb in PbF to test the accuracy of the wavefunction obtained in the Z-vector method. The outcome of our calculations clearly suggests that the core electrons have significant contribution to the "atom in compound" properties. PMID:26328830

  20. Review. The mammalian proton-coupled peptide cotransporter PepT1: sitting on the transporter-channel fence?

    PubMed

    Meredith, David

    2009-01-27

    The proton-coupled di- and tripeptide transporter PepT1 (SLC15a1) is the major route by which dietary nitrogen is taken up from the small intestine, as well as being the route of entry for important therapeutic (pro)drugs such as the beta-lactam antibiotics, angiotensin-converting enzyme inhibitors and antiviral and anti-cancer agents. PepT1 is a member of the major facilitator superfamily of 12 transmembrane domain transporter proteins. Expression studies in Xenopus laevis on rabbit PepT1 that had undergone site-directed mutagenesis of a conserved arginine residue (arginine282 in transmembrane domain 7) to a glutamate revealed that this residue played a role in the coupling of proton and peptide transport and prevented the movement of non-coupled ions during the transporter cycle. Mutations of arginine282 to other non-positive residues did not uncouple proton-peptide cotransport, but did allow additional ion movements when substrate was added. By contrast, mutations to positive residues appeared to function the same as wild-type. These findings are discussed in relation to the functional role that arginine282 may play in the way PepT1 operates, together with structural information from the homology model of PepT1 based on the Escherichia coli lactose permease crystal structure.

  1. Raman spectrum of MoS2 /WS2 heterostructure from first-principles calculation of phonon electron coupling

    NASA Astrophysics Data System (ADS)

    Jiang, Jun; Zhang, Xiaoguang; Liang, Liangbo; Barmparis, Georgios D.; Puzyrev, Yevgeniy S.; Pantelides, Sokrates T.

    We present a first-principles method to calculate Raman spectrum of MoS2/WS2 heterostructure due to electron excitation. The first step is to calculate the ground state phonon modes and the displacements of the atoms from the ground state to the excited states. In the next step, Inelastic multi-phonon relaxation for the excited electron is considered to produce the Raman spectrum quantitatively. The relative Raman intensity, peak width and shape are obtained directly from a sum over trillions of configurations of multiple phonon modes using a Monte Carlo scheme. Alternatively, we also calculate the overlap between the ground state phonon mode eigenvectors and the excited state atomic displacements, which provides a quick and qualitative description for the Raman shifting due to electron excitation. This work is supported by NSF Grant 1508898.

  2. Method of averaged energy differences of coupled states and other approaches for calculation line broadening parameters of HD16O transitions

    NASA Astrophysics Data System (ADS)

    Dudaryonok, A. S.; Voronin, B. A.; Lavrentieva, N. N.; Lugovskoy, A. A.; Starikov, V. I.

    2012-11-01

    Air-broadening coefficients of the water isotopologue HD16O up to J = 50 for P, Q and R branches calculated using different methods are presented. For partially labeled lines ("good" quantum numbers: J, symmetry and level number) we combined three methods for calculating half-widths: J-dependence and JJ'-dependence up to J=15 and averaging coefficients calculated using a previously developed semi-empirical method for high J (15-50). For lines with full assignments based on normal modes v1, v2, v3, Ka, Kc we used: (a) an analytical model (approximation) which depends on use of rotational quantum numbers J and Ka for both the upper and lower levels; and (b) a method based on the estimate of the averaged energy differences between coupled states. The comparison of calculated data with broadening coefficients from HITRAN-2008 and available experimental data is presented. The resulting broadening coefficients can be used to calculate spectra of water vapor with hundreds millions of weak lines with reasonable accuracy. The line list VTT [Voronin, Tennyson, Tolchenov, MNRAS, 2010], supporting programs, files for calculations of spectra HD16O and estimation of broadening coefficient are made freely available also in electronic form via http://www.exomol.com.

  3. Hillslope-channel coupling in the Nepal Himalayas and threat to man-made structures: The middle Kali Gandaki valley

    NASA Astrophysics Data System (ADS)

    Fort, M.; Cossart, E.; Arnaud-Fassetta, G.

    2010-12-01

    In mountain areas, the confinement of valleys favours landslide interaction with rivers, causing channel changes or short-lived dams and lakes that may threaten trails, roads and human settlements. Their impacts may occur successively in space and time, and they affect randomly the functioning of the sediment fluxes. The present study focuses on the interaction patterns between unstable mountain slopes and the Kali Gandaki River, in the Nepal Himalayas. In this valley, the deepest on earth, a road linking the Myagdi and Mustang districts has been under construction for the past 5 years, either cutting into the bedrock or crossing areas affected episodically by debris slides, earth flows, debris flows and rock slides. On the basis of the geomorphic evolution observed over the last three decades, we assess the potential threats that now arise following completion of the road. We mapped three areas of recurrent mass wasting features characteristic of the most frequent situations encountered in this valley. We analyzed the combination of the hydro-geomorphic processes involved. With the use of a DEM, we assessed the volume and spatial impact of temporary river dams on infrastructure located along the valley floor. We estimated hydraulic parameters to document the geomorphic efficiency of river flooding after dam breaching. We reconstructed the spatial extent of (1) areas threatened by backwater flooding upstream of the dams and (2) areas threatened by the collapse of the dams. We describe the current geomorphic and sedimentary adjustments still at work along the valley sides. Our findings confirm that in the High Himalaya, medium scale landslides (10 5-6 m 3) play a major role in the overall process of denudation and sediment transfer. They highly influence the transient nature of bedload transport in the channel. In reducing the residence time of sediments in temporary, spatially limited traps of the valley bottom, they enhance the vulnerability of land and people

  4. Registration of infrared single photons by a two-channel receiver based on fiber-coupled superconducting single-photon detectors

    NASA Astrophysics Data System (ADS)

    Okunev, O.; Chulkova, G.; Milostnaya, I.; Antipov, A.; Smirnov, K.; Morozov, D.; Korneev, A.; Voronov, B.; Gol'tsman, G.; Slysz, W.; Wegrzecki, M.; Bar, J.; Grabiec, P.; Górska, M.; Pearlman, A.; Cross, A.; Kitaygorsky, J.; Sobolewski, Roman

    2008-03-01

    Single-photon detectors (SPDs) are the foundation of all quantum communications (QC) protocols. Among different classes of SPDs currently studied, NbN superconducting SPDs (SSPDs) are established as the best devices for ultrafast counting of single photons in the infrared (IR) wavelength range. The SSPDs are nanostructured, 100 μm2 in total area, superconducting meanders, patterned by electron lithography in ultra-thin NbN films. Their operation has been explained within a phenomenological hot-electron photoresponse model. We present the design and performance of a novel, two-channel SPD receiver, based on two fiber-coupled NbN SSPDs. The receivers have been developed for fiber-based QC systems, operational at 1.3 μm and 1.55 μm telecommunication wavelengths. They operate in the temperature range from 4.2 K to 2 K, in which the NbN SSPDs exhibit their best performance. The receiver unit has been designed as a cryostat insert, placed inside a standard liquid-heliumstorage dewar. The input of the receiver consists of a pair of single-mode optical fibers, equipped with the standard FC connectors and kept at room temperature. Coupling between the SSPD and the fiber is achieved using a specially designed, precise micromechanical holder that places the fiber directly on top of the SSPD nanostructure. Our receivers achieve the quantum efficiency of up to 7% for near-IR photons, with the coupling efficiency of about 30%. The response time was measured to be < 1.5 ns and it was limited by our read-out electronics. The jitter of fiber-coupled SSPDs is < 35 ps and their dark-count rate is below 1s-1. The presented performance parameters show that our single-photon receivers are fully applicable for quantum correlation-type QC systems, including practical quantum cryptography.

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

    NASA Astrophysics Data System (ADS)

    Zarycz, M. Natalia C.; Provasi, Patricio F.; Sauer, Stephan P. A.

    2015-12-01

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

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

    SciTech Connect

    Zarycz, M. Natalia C. Provasi, Patricio F.; Sauer, Stephan P. A.

    2015-12-28

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

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

    PubMed

    Zarycz, M Natalia C; Provasi, Patricio F; Sauer, Stephan P A

    2015-12-28

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

  8. Coupled cluster calculations of mean excitation energies of the noble gas atoms He, Ne and Ar and of the H2 molecule

    NASA Astrophysics Data System (ADS)

    Sauer, Stephan P. A.; Haq, Inam Ul; Sabin, John R.; Oddershede, Jens; Christiansen, Ove; Coriani, Sonia

    2014-03-01

    Using an asymmetric Lanczos chain algorithm for the calculation of the coupled cluster linear response functions at the coupled cluster singles and doubles (CCSD) and coupled cluster singles and approximate iterative doubles (CC2) levels of approximation, we have calculated the mean excitation energies of the noble gases He, Ne and Ar, and of the hydrogen molecule (H2). Convergence with respect to the one-electron basis set was investigated in detail for families of correlation-consistent basis sets including both augmentation and core-valence functions. We find that the electron correlation effects at the CCSD level change the mean excitation energies obtained at the uncorrelated Hartree-Fock level by about 1%. For the two-electron systems He and H2, our CCSD results (for a Lanczos chain length equal to the full excitation space), I0 = 42.28 eV (helium) and I0 = 19.62 eV (H2), correspond to full configuration interaction results and are therefore the exact, non-relativistic theoretical values for the mean excitation energy of these two systems within the Bethe theory for the chosen basis set and, in the case of H2, at the experimental equilibrium geometry.

  9. Malignant hyperthermia susceptibility arising from altered resting coupling between the skeletal muscle L-type Ca2+ channel and the type 1 ryanodine receptor

    PubMed Central

    Eltit, Jose Miguel; Bannister, Roger A.; Moua, Ong; Altamirano, Francisco; Hopkins, Philip M.; Pessah, Isaac N.; Molinski, Tadeusz F.; López, Jose R.; Beam, Kurt G.; Allen, Paul D.

    2012-01-01

    Malignant hyperthermia (MH) susceptibility is a dominantly inherited disorder in which volatile anesthetics trigger aberrant Ca2+ release in skeletal muscle and a potentially fatal rise in perioperative body temperature. Mutations causing MH susceptibility have been identified in two proteins critical for excitation–contraction (EC) coupling, the type 1 ryanodine receptor (RyR1) and CaV1.1, the principal subunit of the L-type Ca2+ channel. All of the mutations that have been characterized previously augment EC coupling and/or increase the rate of L-type Ca2+ entry. The CaV1.1 mutation R174W associated with MH susceptibility occurs at the innermost basic residue of the IS4 voltage-sensing helix, a residue conserved among all CaV channels [Carpenter D, et al. (2009) BMC Med Genet 10:104–115.]. To define the functional consequences of this mutation, we expressed it in dysgenic (CaV1.1 null) myotubes. Unlike previously described MH-linked mutations in CaV1.1, R174W ablated the L-type current and had no effect on EC coupling. Nonetheless, R174W increased sensitivity of Ca2+ release to caffeine (used for MH diagnostic in vitro testing) and to volatile anesthetics. Moreover, in CaV1.1 R174W-expressing myotubes, resting myoplasmic Ca2+ levels were elevated, and sarcoplasmic reticulum (SR) stores were partially depleted, compared with myotubes expressing wild-type CaV1.1. Our results indicate that CaV1.1 functions not only to activate RyR1 during EC coupling, but also to suppress resting RyR1-mediated Ca2+ leak from the SR, and that perturbation of CaV1.1 negative regulation of RyR1 leak identifies a unique mechanism that can sensitize muscle cells to MH triggers. PMID:22547813

  10. Malignant hyperthermia susceptibility arising from altered resting coupling between the skeletal muscle L-type Ca2+ channel and the type 1 ryanodine receptor.

    PubMed

    Eltit, Jose Miguel; Bannister, Roger A; Moua, Ong; Altamirano, Francisco; Hopkins, Philip M; Pessah, Isaac N; Molinski, Tadeusz F; López, Jose R; Beam, Kurt G; Allen, Paul D

    2012-05-15

    Malignant hyperthermia (MH) susceptibility is a dominantly inherited disorder in which volatile anesthetics trigger aberrant Ca(2+) release in skeletal muscle and a potentially fatal rise in perioperative body temperature. Mutations causing MH susceptibility have been identified in two proteins critical for excitation-contraction (EC) coupling, the type 1 ryanodine receptor (RyR1) and Ca(V)1.1, the principal subunit of the L-type Ca(2+) channel. All of the mutations that have been characterized previously augment EC coupling and/or increase the rate of L-type Ca(2+) entry. The Ca(V)1.1 mutation R174W associated with MH susceptibility occurs at the innermost basic residue of the IS4 voltage-sensing helix, a residue conserved among all Ca(V) channels [Carpenter D, et al. (2009) BMC Med Genet 10:104-115.]. To define the functional consequences of this mutation, we expressed it in dysgenic (Ca(V)1.1 null) myotubes. Unlike previously described MH-linked mutations in Ca(V)1.1, R174W ablated the L-type current and had no effect on EC coupling. Nonetheless, R174W increased sensitivity of Ca(2+) release to caffeine (used for MH diagnostic in vitro testing) and to volatile anesthetics. Moreover, in Ca(V)1.1 R174W-expressing myotubes, resting myoplasmic Ca(2+) levels were elevated, and sarcoplasmic reticulum (SR) stores were partially depleted, compared with myotubes expressing wild-type Ca(V)1.1. Our results indicate that Ca(V)1.1 functions not only to activate RyR1 during EC coupling, but also to suppress resting RyR1-mediated Ca(2+) leak from the SR, and that perturbation of Ca(V)1.1 negative regulation of RyR1 leak identifies a unique mechanism that can sensitize muscle cells to MH triggers. PMID:22547813

  11. Weak antilocalization and electron-electron interaction in coupled multiple-channel transport in a Bi2Se3 thin film

    NASA Astrophysics Data System (ADS)

    Jing, Yumei; Huang, Shaoyun; Zhang, Kai; Wu, Jinxiong; Guo, Yunfan; Peng, Hailin; Liu, Zhongfan; Xu, H. Q.

    2016-01-01

    The electron transport properties of a topological insulator Bi2Se3 thin film are studied in Hall-bar geometry. The film with a thickness of 10 nm is grown by van der Waals epitaxy on fluorophlogopite mica and Hall-bar devices are fabricated from the as-grown film directly on the mica substrate. Weak antilocalization and electron-electron interaction effects are observed and analyzed at low temperatures. The phase-coherence length extracted from the measured weak antilocalization characteristics shows a strong power-law increase with decreasing temperature and the transport in the film is shown to occur via coupled multiple (topological surface and bulk states) channels. The conductivity of the film shows a logarithmical decrease with decreasing temperature and thus the electron-electron interaction plays a dominant role in quantum corrections to the conductivity of the film at low temperatures.

  12. Weak antilocalization and electron-electron interaction in coupled multiple-channel transport in a Bi2Se3 thin film.

    PubMed

    Jing, Yumei; Huang, Shaoyun; Zhang, Kai; Wu, Jinxiong; Guo, Yunfan; Peng, Hailin; Liu, Zhongfan; Xu, H Q

    2016-01-28

    The electron transport properties of a topological insulator Bi2Se3 thin film are studied in Hall-bar geometry. The film with a thickness of 10 nm is grown by van der Waals epitaxy on fluorophlogopite mica and Hall-bar devices are fabricated from the as-grown film directly on the mica substrate. Weak antilocalization and electron-electron interaction effects are observed and analyzed at low temperatures. The phase-coherence length extracted from the measured weak antilocalization characteristics shows a strong power-law increase with decreasing temperature and the transport in the film is shown to occur via coupled multiple (topological surface and bulk states) channels. The conductivity of the film shows a logarithmical decrease with decreasing temperature and thus the electron-electron interaction plays a dominant role in quantum corrections to the conductivity of the film at low temperatures.

  13. A highly energetic process couples calcium influx through L-type calcium channels to insulin secretion in pancreatic β-cells

    PubMed Central

    Jung, Seung-Ryoung; Reed, Benjamin J.; Sweet, Ian R.

    2009-01-01

    Calcium (Ca2+) influx is required for the sustained secretion of insulin and is accompanied by a large rate of energy usage. We hypothesize that the energy usage reflects a process [Ca2+/metabolic coupling process (CMCP)] that couples Ca2+ to insulin secretion by pancreatic islets. The aim of the study was to test this hypothesis by testing the effect of inhibiting candidate Ca2+-sensitive proteins proposed to play a critical role in the CMCP. The effects of the inhibitors on oxygen consumption rate (OCR), a reflection of ATP usage, and insulin secretion rate (ISR) were compared with those seen when L-type Ca2+ channels were blocked with nimodipine. We reasoned that if a downstream Ca2+-regulated site was responsible for the OCR associated with the CMCP, then its inhibition should mimic the effect of nimodipine. Consistent with previous findings, nimodipine decreased glucose-stimulated OCR by 36% and cytosolic Ca2+ by 46% and completely suppressed ISR in rat pancreatic islets. Inhibitors of three calmodulin-sensitive proteins (myosin light-chain kinase, calcineurin, and Ca2+/calmodulin-dependent protein kinase II) did not meet the criteria. In contrast, KN-62 severed the connection between Ca2+ influx, OCR, and ISR without interfering with Ca2+ influx. In the presence of nimodipine or KN-62, potentiators of ISR, acetylcholine, GLP-1, and arginine had little effect on insulin secretion, suggesting that the CMCP is also essential for the amplification of ISR. In conclusion, a KN-62-sensitive process directly mediates the effects of Ca2+ influx via L-type Ca2+ channels on OCR and ISR, supporting the essential role of the CMCP in mediating ISR. PMID:19584201

  14. Relativistic four-component calculations of indirect nuclear spin-spin couplings with efficient evaluation of the exchange-correlation response kernel

    SciTech Connect

    Křístková, Anežka; Malkin, Vladimir G.; Komorovsky, Stanislav; Repisky, Michal; Malkina, Olga L.

    2015-03-21

    In this work, we report on the development and implementation of a new scheme for efficient calculation of indirect nuclear spin-spin couplings in the framework of four-component matrix Dirac-Kohn-Sham approach termed matrix Dirac-Kohn-Sham restricted magnetic balance resolution of identity for J and K, which takes advantage of the previous restricted magnetic balance formalism and the density fitting approach for the rapid evaluation of density functional theory exchange-correlation response kernels. The new approach is aimed to speedup the bottleneck in the solution of the coupled perturbed equations: evaluation of the matrix elements of the kernel of the exchange-correlation potential. The performance of the new scheme has been tested on a representative set of indirect nuclear spin-spin couplings. The obtained results have been compared with the corresponding results of the reference method with traditional evaluation of the exchange-correlation kernel, i.e., without employing the fitted electron densities. Overall good agreement between both methods was observed, though the new approach tends to give values by about 4%-5% higher than the reference method. On the average, the solution of the coupled perturbed equations with the new scheme is about 8.5 times faster compared to the reference method.

  15. The calculation of accurate 17O hyperfine coupling constants in the hydroxyl radical: A difficult problem for current quantum chemical methods

    NASA Astrophysics Data System (ADS)

    Wetmore, Stacey D.; Eriksson, Leif A.; Boyd, Russell J.

    1998-12-01

    The hyperfine coupling constants (HFCCs) in the hydroxyl radical are investigated through comparison of results obtained from a variety of quantum chemical methods. The couplings obtained from the multi-reference configuration interaction (MRCI) wave function, built upon the restricted open-shell Hartree-Fock (ROHF) reference determinant, are investigated in terms of the basis set, the configuration selection energy threshold, and the size of the reference space. Overall results which converge to the experimental couplings are obtained for hydrogen, but not for oxygen. In particular, the MRCI method shows no improvement over density functional theory (the B3LYP functional), for the calculation of Aiso(17O). On the other hand, results in excellent agreement with experiment are obtained through the use of the quadratic configuration interaction (QCISD) method based on the unrestricted HF (UHF) reference determinant with the identical basis sets. Examination of UHF and ROHF based coupled-cluster methods, CCSD and CCSD(T), indicates that once a high enough level of electron correlation is included, the oxygen HFCC is independent of the form of the reference determinant. Unlike the ROHF-CCSD method, which yields reliable results once the effects of triple excitations have been taken into account, the MRCI wave function cannot easily be adjusted to account for the inadequacies of the ROHF reference determinant in order to accurately predict 17O HFCCs.

  16. Vibronic coupling in molecular crystals: A Franck-Condon Herzberg-Teller model of H-aggregate fluorescence based on quantum chemical cluster calculations

    SciTech Connect

    Wykes, M. Parambil, R.; Gierschner, J.; Beljonne, D.

    2015-09-21

    Here, we present a general approach to treating vibronic coupling in molecular crystals based on atomistic simulations of large clusters. Such clusters comprise model aggregates treated at the quantum chemical level embedded within a realistic environment treated at the molecular mechanics level. As we calculate ground and excited state equilibrium geometries and vibrational modes of model aggregates, our approach is able to capture effects arising from coupling to intermolecular degrees of freedom, absent from existing models relying on geometries and normal modes of single molecules. Using the geometries and vibrational modes of clusters, we are able to simulate the fluorescence spectra of aggregates for which the lowest excited state bears negligible oscillator strength (as is the case, e.g., ideal H-aggregates) by including both Franck-Condon (FC) and Herzberg-Teller (HT) vibronic transitions. The latter terms allow the adiabatic excited state of the cluster to couple with vibrations in a perturbative fashion via derivatives of the transition dipole moment along nuclear coordinates. While vibronic coupling simulations employing FC and HT terms are well established for single-molecules, to our knowledge this is the first time they are applied to molecular aggregates. Here, we apply this approach to the simulation of the low-temperature fluorescence spectrum of para-distyrylbenzene single-crystal H-aggregates and draw comparisons with coarse-grained Frenkel-Holstein approaches previously extensively applied to such systems.

  17. Analysis of the KROTOS KFC test by coupling X-Ray image analysis and MC3D calculations

    SciTech Connect

    Brayer, C.; Charton, A.; Grishchenko, D.; Fouquart, P.; Bullado, Y.; Compagnon, F.; Correggio, P.; Cassiaut-Louis, N.; Piluso, P.

    2012-07-01

    During a hypothetical severe accident sequence in a Pressurized Water Reactor (PWR), the hot molten materials (corium) issuing from the degraded reactor core may generate a steam explosion if they come in contact with water and may damage the structures and threaten the reactor integrity. The SERENA program is an international OECD project that aims at helping the understanding of this phenomenon also called Fuel Coolant Interaction (FCI) by providing data. CEA takes part in this program by performing tests in its KROTOS facility where steam explosions using prototypic corium can be triggered. Data about the different phases in the premixing are extracted from the KROTOS X-Ray radioscopy images by using KIWI software (KROTOS Image analysis of Water-corium Interaction) currently developed by CEA. The MC3D code, developed by IRSN, is a thermal-hydraulic multiphase code mainly dedicated to FCI studies. It is composed of two applications: premixing and explosion. An overall FCI calculation with MC3D requires a premixing calculation followed by an explosion calculation. The present paper proposes an alternative approach in which all the features of the premixing are extracted from the X-Ray pictures using the KIWI software and transferred to an MC3D dataset for a direct simulation of the explosion. The main hypothesis are discussed as well as the first explosion results obtained with MC3D for the KROTOS KFC test. These results are rather encouraging and are analyzed on the basis of comparisons with the experimental data. (authors)

  18. The S4-S5 linker directly couples voltage sensor movement to the activation gate in the human ether-a'-go-go-related gene (hERG) K+ channel.

    PubMed

    Ferrer, Tania; Rupp, Jason; Piper, David R; Tristani-Firouzi, Martin

    2006-05-01

    A key unresolved question regarding the basic function of voltage-gated ion channels is how movement of the voltage sensor is coupled to channel opening. We previously proposed that the S4-S5 linker couples voltage sensor movement to the S6 domain in the human ether-a'-go-go-related gene (hERG) K+ channel. The recently solved crystal structure of the voltage-gated Kv1.2 channel reveals that the S4-S5 linker is the structural link between the voltage sensing and pore domains. In this study, we used chimeras constructed from hERG and ether-a'-go-go (EAG) channels to identify interactions between residues in the S4-S5 linker and S6 domain that were critical for stabilizing the channel in a closed state. To verify the spatial proximity of these regions, we introduced cysteines in the S4-S5 linker and at the C-terminal end of the S6 domain and then probed for the effect of oxidation. The D540C-L666C channel current decreased in an oxidizing environment in a state-dependent manner consistent with formation of a disulfide bond that locked the channel in a closed state. Disulfide bond formation also restricted movement of the voltage sensor, as measured by gating currents. Taken together, these data confirm that the S4-S5 linker directly couples voltage sensor movement to the activation gate. Moreover, rather than functioning simply as a mechanical lever, these findings imply that specific interactions between the S4-S5 linker and the activation gate stabilize the closed channel conformation.

  19. Analytic energy derivatives for the calculation of the first-order molecular properties using the domain-based local pair-natural orbital coupled-cluster theory

    NASA Astrophysics Data System (ADS)

    Datta, Dipayan; Kossmann, Simone; Neese, Frank

    2016-09-01

    The domain-based local pair-natural orbital coupled-cluster (DLPNO-CC) theory has recently emerged as an efficient and powerful quantum-chemical method for the calculation of energies of molecules comprised of several hundred atoms. It has been demonstrated that the DLPNO-CC approach attains the accuracy of a standard canonical coupled-cluster calculation to about 99.9% of the basis set correlation energy while realizing linear scaling of the computational cost with respect to system size. This is achieved by combining (a) localized occupied orbitals, (b) large virtual orbital correlation domains spanned by the projected atomic orbitals (PAOs), and (c) compaction of the virtual space through a truncated pair natural orbital (PNO) basis. In this paper, we report on the implementation of an analytic scheme for the calculation of the first derivatives of the DLPNO-CC energy for basis set independent perturbations within the singles and doubles approximation (DLPNO-CCSD) for closed-shell molecules. Perturbation-independent one-particle density matrices have been implemented in order to account for the response of the CC wave function to the external perturbation. Orbital-relaxation effects due to external perturbation are not taken into account in the current implementation. We investigate in detail the dependence of the computed first-order electrical properties (e.g., dipole moment) on the three major truncation parameters used in a DLPNO-CC calculation, namely, the natural orbital occupation number cutoff used for the construction of the PNOs, the weak electron-pair cutoff, and the domain size cutoff. No additional truncation parameter has been introduced for property calculation. We present benchmark calculations on dipole moments for a set of 10 molecules consisting of 20-40 atoms. We demonstrate that 98%-99% accuracy relative to the canonical CCSD results can be consistently achieved in these calculations. However, this comes with the price of tightening the

  20. Nonlinear channelizer.

    PubMed

    In, Visarath; Longhini, Patrick; Kho, Andy; Neff, Joseph D; Leung, Daniel; Liu, Norman; Meadows, Brian K; Gordon, Frank; Bulsara, Adi R; Palacios, Antonio

    2012-12-01

    The nonlinear channelizer is an integrated circuit made up of large parallel arrays of analog nonlinear oscillators, which, collectively, serve as a broad-spectrum analyzer with the ability to receive complex signals containing multiple frequencies and instantaneously lock-on or respond to a received signal in a few oscillation cycles. The concept is based on the generation of internal oscillations in coupled nonlinear systems that do not normally oscillate in the absence of coupling. In particular, the system consists of unidirectionally coupled bistable nonlinear elements, where the frequency and other dynamical characteristics of the emergent oscillations depend on the system's internal parameters and the received signal. These properties and characteristics are being employed to develop a system capable of locking onto any arbitrary input radio frequency signal. The system is efficient by eliminating the need for high-speed, high-accuracy analog-to-digital converters, and compact by making use of nonlinear coupled systems to act as a channelizer (frequency binning and channeling), a low noise amplifier, and a frequency down-converter in a single step which, in turn, will reduce the size, weight, power, and cost of the entire communication system. This paper covers the theory, numerical simulations, and some engineering details that validate the concept at the frequency band of 1-4 GHz.