Dynamical coupled channel calculation of pion and omega meson production
Paris, Mark
2009-01-01
A dynamical coupled channel approach is used to study $\\pi$ and $\\omega$--meson production induced by pions and photons scattering from the proton. Six-channels are used to fit unpolarized and polarized scattering data including $\\pi N$, $\\eta N$, $\\pi\\Delta$, $\\sigma N$, $\\rho N$, $\\omega N$. Bare parameters in an effective hadronic Lagrangian are fixed in $\\chi^2$-fits to data from $\\pi N \\to \\pi N$, $\\gamma N \\to \\pi N$, $\\pi^- p \\to \\omega n$, and $\\gamma p \\to \\omega p$ reactions at center-of-mass energies from threshold to $E < 2.0$ GeV. The $T$ matrix determined in these fits is used to calculate the photon beam asymmetry for $\\omega$-meson production and the $\\omega N \\to \\omega N$ total cross section and scattering lengths.
Dynamical coupled channels calculation of pion and omega meson production
Paris, Mark W.
2009-02-15
The dynamical coupled-channels approach developed at the Excited Baryon Analysis Center is extended to include the {omega}N channel to study {pi}- and {omega}-meson production induced by scattering pions and photons from the proton. Six intermediate channels, including {pi}N, {eta}N, {pi}{delta}, {sigma}N, {rho}N, and {omega}N, are employed to describe unpolarized and polarized data. Bare parameters in an effective hadronic Lagrangian are determined in a fit to the data for {pi}N{yields}{pi}N, {gamma}N{yields}{pi}N, {pi}{sup -}p{yields}{omega}n, and {gamma}p{yields}{omega}p reactions at center-of-mass energies from threshold to W<2.0 GeV. The T matrix determined in these fits is used to calculate the photon beam asymmetry for {omega}-meson production and the {omega}N{yields}{omega}N total cross section and {omega}N-scattering lengths. The calculated beam asymmetry is in good agreement with the observed in the range of energies near threshold to W < or approx. 2.0 GeV.
Coupled channels calculation of a piLAMBDAN quasibound state
Garcilazo, H.; Gal, A.
2010-05-15
We extend the study of a J{sup P}=2{sup +},I=3/2, piLAMBDAN quasibound state [Phys. Rev. D 78, 014013 (2008)] by solving nonrelativistic Faddeev equations, using {sup 3}S{sub 1}-{sup 3}D{sub 1}, LAMBDAN-SIGMAN coupled channels chiral quark model local interactions, and piN and coupled piLAMBDA-piSIGMA separable interactions fitted to the position and decay parameters of the DELTA(1232) and SIGMA(1385) resonances, respectively. The results exhibit a strong sensitivity to the p-wave pion-hyperon interaction, with a piLAMBDAN quasibound state persisting over a wide range of acceptable parametrizations.
Calculation of nuclear reaction cross sections on excited nuclei with the coupled-channels method
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.
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.
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.
Analytic coupled channel calculation of ultracold three-body collision rates
NASA Astrophysics Data System (ADS)
Meyer, Edmund; Esry, B. D.
2012-06-01
We analyze three-body recombination for positive two-body s-wave scattering lengths. Using the adiabatic hyperspherical representation as a starting point, we introduce coupling between the three-body continuum and the weakly bound diatom plus atom channel in the vicinity of R˜a---the location where rigorous calculations have shown the coupling to peak [1]. In order to model loss to deeply bound diatom channels, we introduce a complex short-range K-matrix. Analytic expressions for the loss rates are derived and we recover the behavior found previously [2], including the overall a^4 scaling for identical bosons as well as the log-periodic modulation due to Efimov physics. Our formulation permits straightforward extensions to other symmetries and higher energies. [4pt] [1] J. P. D'Incao and B. D. Esry, Phys. Rev. A 72, 032710 (2005) [2] B. D. Esry, C. H. Greene, and J. P. Burke, Jr., Phys. Rev. Lett. 83, 1751 (1999).
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.
Study of 18O by the Microscopic (α + 14C) + (5He + 13C) Coupled-Channel Calculation
NASA Astrophysics Data System (ADS)
Ito, Makoto
The generalized two-center cluster model (GTCM), which can treat covalent, ionic and atomic configurations in general systems with two inert cores plus valence nucleons, is applied to the coupled channel problem of 18O = (α + 14C) + (5He + 13C). The energy levels of the 0+ state are calculated by GTCM, and we especially focus on the formation mechanism of three 0+ states, which are predicted by the AMD calculation. The pair formation of the 02 + and 03 + can be understood in terms of the weak coupling of the covalent MO and the dinucelar state of α + 14C. The level scheme of 18O is summarized in connection to the respective lighter system, 10Be.
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
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.
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.
Coupled-channel scattering on a torus
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.
Dynamical coupled-channel analysis at EBAC.
Lee, T.-S. H.; Physics
2008-01-01
In this contribution, the author reports on the dynamical coupled-channels analysis being pursued at the Excited Baryon Analysis Center (EBAC) of Jefferson Laboratory. EBAC was established in January 2006. Its objective is to extract the parameters associated with the excited states (N*) of the nucleon from the world data of meson production reactions, and to also develop theoretical interpretations of the extracted N* parameters.
Integral dependent spin couplings in CI calculations
NASA Astrophysics Data System (ADS)
Iberle, K.; Davidson, E. R.
1982-06-01
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.
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.
Extracting Effective Higgs Couplings in the Golden Channel
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.
Extracting Effective Higgs Couplings in the Golden Channel
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
Photoionization of few electron systems: a hybrid coupled channels approach
NASA Astrophysics Data System (ADS)
Pramod Majety, Vinay; Zielinski, Alejandro; Scrinzi, Armin
2015-06-01
We present the hybrid anti-symmetrized coupled channels method for the calculation of fully differential photo-electron spectra of multi-electron atoms and small molecules interacting with strong laser fields. The method unites quantum chemical few-body electronic structure with strong-field dynamics by solving the time dependent Schrödinger equation in a fully anti-symmetrized basis composed of multi-electron states from quantum chemistry and a one-electron numerical basis. Photoelectron spectra are obtained via the time dependent surface flux (tSURFF) method. Performance and accuracy of the approach are demonstrated for spectra from the helium and beryllium atoms and the hydrogen molecule in linearly polarized laser fields at wavelengths from 21 to 400 nm. At long wavelengths, helium and the hydrogen molecule at equilibrium inter-nuclear distance can be approximated as single channel systems whereas beryllium needs a multi-channel description.
Channel coupling in A(e-->,e'N-->)B reactions
NASA Astrophysics Data System (ADS)
Kelly, James J.
1999-06-01
The sensitivity of momentum distributions, recoil polarization observables, and response functions for nucleon knockout by polarized electron scattering to channel coupling in final-state interactions is investigated using a model in which both the distorting and the coupling potentials are constructed by folding density-dependent nucleon-nucleon effective interactions with nuclear transition densities. Elastic reorientation, inelastic scattering, and charge exchange are included for all possible couplings within the model space. Calculations for 16O are presented for 200 and 433 MeV ejectile energies, corresponding to proposed experiments at MAMI and TJNAF, and for 12C at 70 and 270 MeV, corresponding to experiments at NIKHEF and MIT-Bates. The relative importance of charge exchange decreases as the ejectile energy increases, but remains significant for 200 MeV. Both proton and neutron knockout cross sections for large recoil momenta, pm>300 MeV/c, are substantially affected by inelastic couplings even at 433 MeV. Significant effects on the cross section for neutron knockout are also predicted at smaller recoil momenta, especially for low energies. Many of the response functions and polarization observables for nucleon knockout are quite sensitive to the coupling scheme, especially those which vanish in the absence of final-state interactions. Polarization transfer for proton knockout is insensitive to channel coupling, even for fairly low ejectile energies, but polarization transfer for neutron knockout retains non-negligible sensitivity to channel coupling for energies up to about 200 MeV. The present results suggest that possible medium modifications of neutron and proton electromagnetic form factors for Q2>~0.5 (GeV/c)2 can be studied using recoil polarization with relatively little uncertainty due to final-state interactions.
The LOX calculator for fasted channel catfish
Technology Transfer Automated Retrieval System (TEKTRAN)
Channel catfish (Ictalurus punctatus) are typically harvested by seining, and are then transferred to a grading net, where the catch is held overnight. Respiratory demands of a large, confined channel catfish biomass can exceed available dissolved oxygen, so supplemental aeration is necessary. In 20...
Quantum Biological Channel Modeling and Capacity Calculation
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
Coupled-cluster calculations of nucleonic matter
NASA Astrophysics Data System (ADS)
Hagen, G.; Papenbrock, T.; Ekström, A.; Wendt, K. A.; Baardsen, G.; Gandolfi, S.; Hjorth-Jensen, M.; Horowitz, C. J.
2014-01-01
Background: The equation of state (EoS) of nucleonic matter is central for the understanding of bulk nuclear properties, the physics of neutron star crusts, and the energy release in supernova explosions. Because nuclear matter exhibits a finely tuned saturation point, its EoS also constrains nuclear interactions. Purpose: This work presents coupled-cluster calculations of infinite nucleonic matter using modern interactions from chiral effective field theory (EFT). It assesses the role of correlations beyond particle-particle and hole-hole ladders, and the role of three-nucleon forces (3NFs) in nuclear matter calculations with chiral interactions. Methods: This work employs the optimized nucleon-nucleon (NN) potential NNLOopt at next-to-next-to leading order, and presents coupled-cluster computations of the EoS for symmetric nuclear matter and neutron matter. The coupled-cluster method employs up to selected triples clusters and the single-particle space consists of a momentum-space lattice. We compare our results with benchmark calculations and control finite-size effects and shell oscillations via twist-averaged boundary conditions. Results: We provide several benchmarks to validate the formalism and show that our results exhibit a good convergence toward the thermodynamic limit. Our calculations agree well with recent coupled-cluster results based on a partial wave expansion and particle-particle and hole-hole ladders. For neutron matter at low densities, and for simple potential models, our calculations agree with results from quantum Monte Carlo computations. While neutron matter with interactions from chiral EFT is perturbative, symmetric nuclear matter requires nonperturbative approaches. Correlations beyond the standard particle-particle ladder approximation yield non-negligible contributions. The saturation point of symmetric nuclear matter is sensitive to the employed 3NFs and the employed regularization scheme. 3NFs with nonlocal cutoffs exhibit a
Benchmarking Calculations of Excitonic Couplings between Bacteriochlorophylls.
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
Mutual Coupling for each Channel of Cluster Radioactivity
NASA Astrophysics Data System (ADS)
Huang, Yin; Zhang, Hong Fei
2013-11-01
Every kinds of cluster radioactivities have different radioactive features depending on their emitted clusters and daughters nuclei. Thus each decay process can be treated as a radioactive channel, and the channels can be coupled to each other. Therefore some channels are abated or strengthen due to the coupling effects. Here we attempt to find out a way to evaluate the influence of each channel, and then introduce a physical quantity Mi to express this effect.
A liquid oxygen calculator for fasted channel catfish
Technology Transfer Automated Retrieval System (TEKTRAN)
An interactive liquid oxygen (LOX) calculator for fasted channel catfish confined in grading nets or in live haul tanks has been developed, using Microsoft Visual Studio 2005©. The calculator is based on results of scientific experiments on channel catfish metabolism, and estimates oxygen consumptio...
Fully converged iterative method for coupled channel problems
NASA Astrophysics Data System (ADS)
Shu, Di; Simbotin, I.; Côté, R.
2016-05-01
We implemented a numerical method using a distorted-wave perturbative approach for coupled-channel scattering problems. Our new method provides a way to avoid costly computations for the propagation of the full solutions in coupled-channel problems to large distances for slowly vanishing couplings. Thus, instead of dealing with large matrices, all computations are performed in a channel by channel fashion. The distorted wavefunction for each channel is initialized with the appropriate solution (which includes the diagonal element of the coupling potential matrix). We then solve single-channel inhomogeneous radial equations which contain the (off-diagonal) couplings as a perturbation, and we iterate until desired accuracy is achieved. We tested for stability by continuing to iterate even after convergence has been achieved, e.g., for a total of 75 iterations. Partial support from the US Army Research Office (ARO-MURI W911NF-14-1-0378), and from NSF (Grant No. PHY-1415560).
Coupled gating between cardiac calcium release channels (ryanodine receptors).
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
Optimized coordinates in vibrational coupled cluster calculations
Thomsen, Bo; Christiansen, Ove; Yagi, Kiyoshi
2014-04-21
The use of variationally optimized coordinates, which minimize the vibrational self-consistent field (VSCF) ground state energy with respect to orthogonal transformations of the coordinates, has recently been shown to improve the convergence of vibrational configuration interaction (VCI) towards the exact full VCI [K. Yagi, M. Keçeli, and S. Hirata, J. Chem. Phys. 137, 204118 (2012)]. The present paper proposes an incorporation of optimized coordinates into the vibrational coupled cluster (VCC), which has in the past been shown to outperform VCI in approximate calculations where similar restricted state spaces are employed in VCI and VCC. An embarrassingly parallel algorithm for variational optimization of coordinates for VSCF is implemented and the resulting coordinates and potentials are introduced into a VCC program. The performance of VCC in optimized coordinates (denoted oc-VCC) is examined through pilot applications to water, formaldehyde, and a series of water clusters (dimer, trimer, and hexamer) by comparing the calculated vibrational energy levels with those of the conventional VCC in normal coordinates and VCI in optimized coordinates. For water clusters, in particular, oc-VCC is found to gain orders of magnitude improvement in the accuracy, exemplifying that the combination of optimized coordinates localized to each monomer with the size-extensive VCC wave function provides a supreme description of systems consisting of weakly interacting sub-systems.
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.
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.
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.
Coupled channel approach to the structure of the X(3872)
Ortega, P. G.; Segovia, J.; Entem, D. R.; Fernandez, F.
2010-03-01
We have performed a coupled channel calculation of the 1{sup ++} cc sector including qq and DD* molecular configurations. The calculation was done within a constituent quark model which successfully describes the meson spectrum, in particular, the cc 1{sup --} sector. Two and four-quark configurations are coupled using the {sup 3}P{sub 0} model. The elusive X(3872) meson appears as a new state with a high probability for the DD* molecular component. When the mass difference between neutral and charged states is included, a large D{sup 0}D*{sup 0} component is found which dominates for large distances and breaks isospin symmetry in the physical state. The original cc(2{sup 3}P{sub 1}) state acquires a sizable DD* component and can be identified with the X(3940). We study the B{yields}K{pi}{sup +{pi}-}J/{psi} and B{yields}KD{sup 0}D*{sup 0} decays, finding a good agreement with Belle and BABAR experimental data.
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.
Surface potentials and the calculated selectivity of ion channels.
Miedema, Henk
2002-01-01
Ion channels catalyze the transport of ions across biological membranes. A proper understanding of ion-channel functioning is essential to our knowledge of cell physiology, and, in this context, ion-channel selectivity is a key concept. The extent to which a channel permeates two ion species, a and b, is expressed by the permeability ratio, P(a)/P(b). This paper addresses a complication in the calculation of P(a)/P(b) that is related to the existence of surface potentials (psi) and that so far has not been fully appreciated. This paper shows the rather surprising effect of psi on the calculated P(a)/P(b) of a channel that is permeable to two ion species of different valence. If we ignore psi, we conclude, for instance, P(a) > P(b). If we implement psi in the calculation of P(a)/P(b), we may, however, conclude exactly the reverse, i.e., P(a) < P(b). Because electrostatic potentials arise at the surface of essentially all biological membranes, this paper argues for a more critical evaluation of ion channel selectivity measurements. PMID:11751304
Hydrophobic Coupling of Lipid Bilayer Energetics to Channel Function
Goforth, Robyn L.; Chi, Aung K.; Greathouse, Denise V.; Providence, Lyndon L.; Koeppe, Roger E.; Andersen, Olaf S.
2003-01-01
The hydrophobic coupling between membrane-spanning proteins and the lipid bilayer core causes the bilayer thickness to vary locally as proteins and other “defects” are embedded in the bilayer. These bilayer deformations incur an energetic cost that, in principle, could couple membrane proteins to each other, causing them to associate in the plane of the membrane and thereby coupling them functionally. We demonstrate the existence of such bilayer-mediated coupling at the single-molecule level using single-barreled as well as double-barreled gramicidin channels in which two gramicidin subunits are covalently linked by a water-soluble, flexible linker. When a covalently attached pair of gramicidin subunits associates with a second attached pair to form a double-barreled channel, the lifetime of both channels in the assembly increases from hundreds of milliseconds to a hundred seconds—and the conductance of each channel in the side-by-side pair is almost 10% higher than the conductance of the corresponding single-barreled channels. The double-barreled channels are stabilized some 100,000-fold relative to their single-barreled counterparts. This stabilization arises from: first, the local increase in monomer concentration around a single-barreled channel formed by two covalently linked gramicidins, which increases the rate of double-barreled channel formation; and second, from the increased lifetime of the double-barreled channels. The latter result suggests that the two barrels of the construct associate laterally. The underlying cause for this lateral association most likely is the bilayer deformation energy associated with channel formation. More generally, the results suggest that the mechanical properties of the host bilayer may cause the kinetics of membrane protein conformational transitions to depend on the conformational states of the neighboring proteins. PMID:12719487
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.
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.
Mechanism of Electromechanical Coupling in Voltage-Gated Potassium Channels
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
Regulation of heartbeat by G protein-coupled ion channels.
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
Point kinetics calculations with fully coupled thermal fluids reactivity feedback
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)
Effects of weakly coupled channels on quasielastic barrier distributions
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.
Flux, coupling, and selectivity in ionic channels of one conformation.
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
Improving the calculation of magnetic coupling constants in MRPT methods.
Spivak, Mariano; Angeli, Celestino; Calzado, Carmen J; de Graaf, Coen
2014-09-01
The magnetic coupling in transition metal compounds with more than one unpaired electron per magnetic center has been studied with multiconfigurational perturbation theory. The usual shortcomings of these methodologies (severe underestimation of the magnetic coupling) have been overcome by describing the Slater determinants with a set of molecular orbitals that maximally resemble the natural orbitals of a high-level multiconfigurational reference configuration interaction calculation. These orbitals have significant delocalization tails onto the bridging ligands and largely increase the coupling strengths in the perturbative calculation. PMID:24992654
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.
Eikonal solutions to optical model coupled-channel equations
NASA Technical Reports Server (NTRS)
Cucinotta, Francis A.; Khandelwal, Govind S.; Maung, Khin M.; Townsend, Lawrence W.; Wilson, John W.
1988-01-01
Methods of solution are presented for the Eikonal form of the nucleus-nucleus coupled-channel scattering amplitudes. Analytic solutions are obtained for the second-order optical potential for elastic scattering. A numerical comparison is made between the first and second order optical model solutions for elastic and inelastic scattering of H-1 and He-4 on C-12. The effects of bound-state excitations on total and reaction cross sections are also estimated.
Coupled-channel and screening effects in charmonium spectrum
Li Baiqing; Meng Ce; Chao Kuangta
2009-07-01
Using the same quenched limit as input, we compare the charmonium spectra predicted by two different models, i.e., the coupled-channel model and the screened potential model in the mass region below 4 GeV, in which the contributions from decay channels involving P-wave (as well as even higher excited) D mesons can be neglected. We find that the two models have similar global features in describing the charmonium spectrum since they approximately embody the same effect of the vacuum polarization of dynamical light quark pairs. Adopting these models will be helpful to clarify the nature of the newly discovered charmonium or charmoniumlike states; and the coupled-channel model is more adept in investigating the influences of open-charm thresholds on the charmonium spectrum. In particular, we show the S-wave decay coupling effect on lowering the {chi}{sub c1}(2P) mass toward the DD* threshold, in support of the assignment of the X(3872) as a {chi}{sub c1}(2P)-dominated charmonium state.
Mutual coupling, channel model, and BER for curvilinear antenna arrays
NASA Astrophysics Data System (ADS)
Huang, Zhiyong
This dissertation introduces a wireless communications system with an adaptive beam-former and investigates its performance with different antenna arrays. Mutual coupling, real antenna elements and channel models are included to examine the system performance. In a beamforming system, mutual coupling (MC) among the elements can significantly degrade the system performance. However, MC effects can be compensated if an accurate model of mutual coupling is available. A mutual coupling matrix model is utilized to compensate mutual coupling in the beamforming of a uniform circular array (UCA). Its performance is compared with other models in uplink and downlink beamforming scenarios. In addition, the predictions are compared with measurements and verified with results from full-wave simulations. In order to accurately investigate the minimum mean-square-error (MSE) of an adaptive array in MC, two different noise models, the environmental and the receiver noise, are modeled. The minimum MSEs with and without data domain MC compensation are analytically compared. The influence of mutual coupling on the convergence is also examined. In addition, the weight compensation method is proposed to attain the desired array pattern. Adaptive arrays with different geometries are implemented with the minimum MSE algorithm in the wireless communications system to combat interference at the same frequency. The bit-error-rate (BER) of systems with UCA, uniform rectangular array (URA) and UCA with center element are investigated in additive white Gaussian noise plus well-separated signals or random direction signals scenarios. The output SINR of an adaptive array with multiple interferers is analytically examined. The influence of the adaptive algorithm convergence on the BER is investigated. The UCA is then investigated in a narrowband Rician fading channel. The channel model is built and the space correlations are examined. The influence of the number of signal paths, number of the
Coupled-channels study of fine structure in the {alpha} decay of well deformed nuclei
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.
Understanding the effect of channel coupling on fusion of 6Li+64Ni
NASA Astrophysics Data System (ADS)
Moin Shaikh, Md.; Roy, Subinit
2016-07-01
The effect of inelastic excitation and single particle transfer reactions on fusion have been investigated for the system 6Li+64Ni at near barrier energies. The calculations show that a simultaneous coupling to the inelastic excitation of projectile and target along with positive Q-value 1n- and 1p-stripping channels, describes the experimental CF cross sections reasonably well in the below barrier region.
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.
Coupling of individual quantum emitters to channel plasmons
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
Coupling of individual quantum emitters to channel plasmons.
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
Quench Protection for the MICE Cooling Channel Coupling Magnet
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.
Towards an optical potential for rare-earths through coupled channels
Nobre, G. P. A.; Herman, M.; Palumbo, A.; Hoblit, S.; Brown, D.; Dietrich, F. S.
2014-11-11
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.
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.
Coupling Algorithms for Calculating Sensitivities of Population Balances
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)
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').
Isovector channel of quark-meson-coupling model and its effect on symmetry energy
NASA Astrophysics Data System (ADS)
Wang, X. B.; Qi, C.; Xu, F. R.
2011-08-01
The non-relativistic approximation of the quark-meson-coupling model has been discussed and compared with the Skyrme-Hartree-Fock model which includes spin exchanges. Calculations show that the spin-exchange interaction has important effect on the descriptions of finite nuclei and nuclear matter through the Fock exchange. Also in the quark-meson-coupling model, it is the Fock exchange that leads to a nonlinear density-dependent isovector channel and changes the density-dependent behavior of the symmetry energy.
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.
NASA Astrophysics Data System (ADS)
Karpov, A. V.; Rachkov, V. A.; Samarin, V. V.
2015-12-01
Background: Significant enhancement of sub-barrier fusion cross sections owing to neutron transfer with positive Q values was observed in many combinations of colliding nuclei. This degree of freedom has not yet been included into the rigorous quantum coupled-channels (QCC) approach. However, the empirical coupled-channels model with neutron rearrangement [Zagrebaev, Phys. Rev. C 67, 061601 (2003), 10.1103/PhysRevC.67.061601] has already been successfully used in several papers to reproduce and predict cross sections for sub-barrier fusion reactions of stable nuclei. Purpose: The objective of this study is to combine the QCC approach and the empirical model to account for additional channels of neutron rearrangement. Method: Coupling of relative motion to collective degrees of freedom (rotation of nuclei and/or their surface vibrations) are taken into account within the QCC approach. The probability of transfer of x neutrons with a given Q value is estimated semiclassically. Results: The proposed new model was successfully tested on a few combinations of fusing nuclei 40Ca+90,96Zr, 32S+96,90, and 60,64Ni+100Mo. The calculated fusion cross sections and barrier distribution functions agree well with experimental data. Conclusions: The model developed in this work confirms all the conclusions previously made within the empirical coupled-channels model with neutron rearrangement [see Rachkov et al., Phys. Rev. C 90, 014614 (2014), 10.1103/PhysRevC.90.014614]. Moreover, it has an advantage of a more reliable microscopic account for the coupling between relative motion and the collective degrees of freedom. The proposed model can also be used to reproduce the structure of the barrier distribution function. This is a step forward to a complete solution of the long-term problem of accounting for neutron transfer channels in the QCC model.
Sato, Tohru; Tokunaga, Ken; Tanaka, Kazuyoshi
2006-01-14
A method of calculation of vibronic or electron-phonon coupling constant is presented for a Jahn-Teller molecule, cyclopentadienyl radical. It is pointed out that symmetry breaking at degenerate point and violation of Hellmann-Feynman theorem occur in the calculations based on a single Slater determinant. In order to overcome these difficulties, the electronic wave functions are calculated using generalized restricted Hartree-Fock and complete active space self-consistent-field method and the couplings are computed as matrix elements of the electronic operator of the vibronic coupling. Our result agrees well with the experimental and theoretical values. A concept of vibronic coupling density is proposed in order to explain the order of magnitude of the coupling constant from view of the electronic and vibrational structures. It illustrates the local properties of the coupling and enables us to control the interaction. It could open a way to the engineering of vibronic interactions. PMID:16422590
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).
Coupled channel analysis of molecule picture of Pc(4380 )
NASA Astrophysics Data System (ADS)
Shimizu, Yuki; Suenaga, Daiki; Harada, Masayasu
2016-06-01
We construct a potential obtained by one-pion exchange for the coupled channel Σc*D ¯ -ΣcD¯ * and solve the coupled Schrödinger equations to determine the binding energy. We find that there exists one or two bound states with the binding energy of several MeV below the threshold of Σc* and D ¯, dominantly made from a Σc* baryon and a D ¯ meson, with the size of about 1.5 fm for a wide parameter region. We also study the pentaquark states including a b quark and/or an anti-b quark. We show that there exist pentaquarks including c b ¯, b c ¯ , and b b ¯, all of which lie at about 10 MeV below the corresponding threshold and have size of about 1.5 fm.
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.
Calculation of anharmonic couplings and THz linewidths in crystalline PETN.
Pereverzev, Andrey; Sewell, Thomas D; Thompson, Donald L
2014-03-14
We have developed a method for calculating the cubic anharmonic couplings in molecular crystals for normal modes with the zero wave vector in the framework of classical mechanics, and have applied it, combined with perturbation theory, to obtain the linewidths of all infrared absorption lines of crystalline pentaerythritol tetranitrate in the terahertz region (<100 cm(-1)). Contributions of the up- and down-conversion processes to the total linewidth were calculated. The computed linewidths are in qualitative agreement with experimental data and the results of molecular dynamics simulations. Quantum corrections to the linewidths in the terahertz region are shown to be negligible. PMID:24628183
Calculation of anharmonic couplings and THz linewidths in crystalline PETN
Pereverzev, Andrey Sewell, Thomas D. Thompson, Donald L.
2014-03-14
We have developed a method for calculating the cubic anharmonic couplings in molecular crystals for normal modes with the zero wave vector in the framework of classical mechanics, and have applied it, combined with perturbation theory, to obtain the linewidths of all infrared absorption lines of crystalline pentaerythritol tetranitrate in the terahertz region (<100 cm{sup −1}). Contributions of the up- and down-conversion processes to the total linewidth were calculated. The computed linewidths are in qualitative agreement with experimental data and the results of molecular dynamics simulations. Quantum corrections to the linewidths in the terahertz region are shown to be negligible.
First Calculation of Hyperon Axial Couplings from Lattice QCD
Huey-Wen Lin; Konstantinos Orginos
2007-12-06
In this work, we report the first lattice calculation of the hyperon axial couplings, using the 2+1-flavor MILC configurations and domain-wall fermion valence quarks. Both the $\\Sigma$ and $\\Xi$ axial couplings are for the first time done in lattice QCD, and we find the numbers with greater precision than previous chiral perturbation theory and large-$N_c$ theory estimate: $g_{\\Sigma\\Sigma} = 0.450(21)_{\\rm stat}(22)_{\\rm syst}$ and $g_{\\Xi\\Xi} = -0.277(15)_{\\rm stat}(16)_{\\rm syst}$. As a side product, we also determine the low-energy chiral parameters $D$ and $F$ extracted from these coupling constants: $D=0.715(6)_{\\rm stat}(6)_{\\rm syst}$ and $F=0.453(5)_{\\rm stat}(5)_{\\rm syst}$.
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.
Beam envelope calculations in general linear coupled lattices
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.
Finite difference time domain calculations of antenna mutual coupling
NASA Technical Reports Server (NTRS)
Luebbers, Raymond J.; Kunz, Karl S.
1991-01-01
The Finite Difference Time Domain (FDTD) technique was applied to a wide variety of electromagnetic analysis problems, including shielding and scattering. However, the method has not been exclusively applied to antennas. Here, calculations of self and mutual admittances between wire antennas are made using FDTD and compared with results obtained during the method of moments. The agreement is quite good, indicating the possibilities for FDTD application to antenna impedance and coupling.
Finite difference time domain calculations of antenna mutual coupling
NASA Technical Reports Server (NTRS)
Luebbers, Raymond J.; Kunz, Karl S.
1991-01-01
The Finite Difference Time Domain (FDTD) technique has been applied to a wide variety of electromagnetic analysis problems, including shielding and scattering. However, the method has not been extensively applied to antennas. In this short paper calculations of self and mutual admittances between wire antennas are made using FDTD and compared with results obtained using the Method of Moments. The agreement is quite good, indicating the possibilities for FDTD application to antenna impedance and coupling.
A liquid oxygen calculator for fasted channel catfish
Technology Transfer Automated Retrieval System (TEKTRAN)
A review of scientific literature concerning channel catfish Ictalurus punctatus respiration resulted in development of a Microsoft Excel© spreadsheet for estimating the volume of oxygen consumed by a given fasted channel catfish biomass. Entry of ten variables into the spreadsheet provides estimate...
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).
Transmembrane allosteric coupling of the gates in a potassium channel
Wylie, Benjamin J.; Bhate, Manasi P.; McDermott, Ann E.
2014-01-01
It has been hypothesized that transmembrane allostery is the basis for inactivation of the potassium channel KcsA: opening the intracellular gate is spontaneously followed by ion expulsion at the extracellular selectivity filter. This suggests a corollary: following ion expulsion at neutral pH, a spontaneous global conformation change of the transmembrane helices, similar to the motion involved in opening, is expected. Consequently, both the low potassium state and the low pH state of the system could provide useful models for the inactivated state. Unique NMR studies of full-length KcsA in hydrated bilayers provide strong evidence for such a mutual coupling across the bilayer: namely, upon removing ambient potassium ions, changes are seen in the NMR shifts of carboxylates E118 and E120 in the pH gate in the hinges of the inner transmembrane helix (98–103), and in the selectivity filter, all of which resemble changes seen upon acid-induced opening and inhibition and suggest that ion release can trigger channel helix opening. PMID:24344306
High-accuracy coupled cluster calculations of atomic properties
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.
Black hole thermodynamics from calculations in strongly coupled gauge theory.
Kabat, D; Lifschytz, G; Lowe, D A
2001-02-19
We develop an approximation scheme for the quantum mechanics of N D0-branes at finite temperature in the 't Hooft large- N limit. The entropy of the quantum mechanics calculated using this approximation agrees well with the Bekenstein-Hawking entropy of a ten-dimensional nonextremal black hole with 0-brane charge. This result is in accordance with the duality conjectured by Itzhaki, Maldacena, Sonnenschein, and Yankielowicz [Phys. Rev. D 58, 046004 (1998)]. Our approximation scheme provides a model for the density matrix which describes a black hole in the strongly coupled quantum mechanics. PMID:11290159
Parallelization strategy for large-scale vibronic coupling calculations.
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
Quench Protection for the MICE Cooling Channel CouplingMagnet
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.
Two-center convergent close-coupling calculations for positron-lithium collisions
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.
Coupled cluster calculations on TiO2 nanoclusters
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.
Coupled-channel analysis of K{lambda} production in the nucleon resonance region
Shklyar, V.; Lenske, H.; Mosel, U.
2005-07-01
A unitary coupled-channel effective Lagrangian model is applied to the combined analysis of the ({pi},{gamma})N{yields}K{lambda} reactions in the energy region up to 2 GeV. To constrain the resonance couplings to the K{lambda} final state the recent photoproduction data obtained by the SAPHIR, Spring-8, and CLAS groups are included in the calculations. The main resonance contributions to the process stem from the S{sub 11}(1650),P{sub 13}(1720), and P{sub 13}(1900) states. The second peak at 1.9 GeV seen in the photoproduction cross-section data is described as a coherent sum of the resonance and background contributions. The prediction for the beam polarization observable is presented.
A microscopic, coupled-channel theory of pion scattering
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.
2 π production in the Giessen coupled-channels model
NASA Astrophysics Data System (ADS)
Shklyar, V.; Lenske, H.; Mosel, U.
2016-04-01
The coupled-channels Lagrangian approach underlying the Giessen model (GiM) is extended to describe the π N →π N ,2 π N scattering in the resonance energy region. As a feasibility study we investigate single- and double-pion production up to the second resonance region. The 2 π N production has been significantly improved by using the isobar approximation with σ N and π Δ (1232 ) in the intermediate state. The three-body unitarity is maintained up to an interference pattern between the isobar subchannels. The scattering amplitudes are obtained as a solution of the Bethe-Salpeter equation in the K -matrix approximation. As a first application we perform a partial-wave analysis of the π N →π N ,π0π0N reactions in the Roper resonance region. We obtain Rσ N(1440 ) =27-9+4% and Rπ Δ(1440 ) =12-3+5% for the σ N and π Δ (1232 ) decay branching ratios of N*(1440 ) , respectively. The extracted π N inelasticities and reaction amplitudes are consistent with the results from other groups.
A coupled channel study of HN2 unimolecular decay based on a global ab initio potential surface
NASA Technical Reports Server (NTRS)
Koizumi, Hiroyasu; Schatz, George C.; Walch, Stephen P.
1991-01-01
The unimolecular decay lifetimes of several vibrational states of HN2 are determined on the basis of an accurate coupled channel dynamics study using a global analytical potential surface. The surface reproduces the ab initio points with an rms error of 0.08 kcal/mol for energies below 20 kcal/mol. Modifications to the potential that describe the effect of improving the basis set in the ab initio calculations are provided. Converged coupled channel calculations are performed for the ground rotational state of HN2 to determine the lifetimes of the lowest ten vibrational states. Only the ground vibrational state (000) and first excited bend (001) are found to have lifetimes longer than 1 ps. The lifetimes of these states are estimated at 3 x 10 to the -9th and 2 x 10 to the -10th s, respectively. Variation of these results with quality of the ab initio calculations is not more than a factor of 5.
Radial Moment Calculations of Coupled Electron-Photon Beams
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.
The effect of pinning on drag in coupled one-dimensional channels of particles
NASA Astrophysics Data System (ADS)
Bairnsfather, C.; Olson Reichhardt, C. J.; Reichhardt, C.
2011-04-01
We consider a simple model for examining the effects of quenched disorder on drag consisting of particles interacting via a Yukawa potential that are placed in two coupled one-dimensional channels. The particles in one channel are driven and experience a drag from the undriven particles in the second channel. In the absence of pinning, for a finite driving force there is no pinned phase; instead, there are two dynamical regimes of completely coupled or locked flow and partially coupled flow. When pinning is added to one or both channels, we find that a remarkably rich variety of dynamical phases and drag effects arise that can be clearly identified by features in the velocity force curves. The presence of quenched disorder in only the undriven channel can induce a pinned phase in both channels. Above the depinning transition, the drag on the driven particles decreases with increasing pinning strength, and for high enough pinning strength, the particles in the undriven channel reach a reentrant pinned phase which produces a complete decoupling of the channels. We map out the dynamic phase diagrams as a function of pinning strength and the density of pinning in each channel. Our results may be relevant for understanding drag coupling in 1D Wigner crystal phases, and the effects we observe could also be explored using colloids in coupled channels produced with optical arrays, vortices in nanostructured superconductors, or other layered systems where drag effects arise.
RELATIVISTIC R-MATRIX CLOSE-COUPLING CALCULATIONS FOR PHOTOIONIZATION OF Si-LIKE Ni XV
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.
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.
Autocorrelation function of channel matrix in few-mode fibers with strong mode coupling.
Hu, Qian; Shieh, William
2013-09-23
Channel matrix plays a critical role in receiver design and ultimate channel performance. To fully describe the channel matrix of a few-mode fiber (FMF), we choose the generalized high-dimensional Gell-Mann matrices, an equivalent of the 2-dimensional Pauli matrices used for a single-mode fiber (SMF), as the basis for the channel matrix decomposition. The frequency dependence of channel matrix can be studied in terms of the autocorrelation function (ACF), showing how fast channel changes in frequency domain. In this paper, we derive a canonical stochastic differential equation (SDE) for the FMF channel matrix in the regime of strong coupling. With the SDE, we develop an analytical form for the ACF of FMF channel matrix, from which the channel correlation bandwidth is obtained. PMID:24104107
Fully Coupled Channel Approach to Doubly Strange s-Shell Hypernuclei
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.
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
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
Solving non-Markovian open quantum systems with multi-channel reservoir coupling
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.
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
Coupled-cluster based basis sets for valence correlation calculations.
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
Dean flow-coupled inertial focusing in curved channels
Ramachandraiah, Harisha; Ardabili, Sahar; Faridi, Asim M.; Gantelius, Jesper; Kowalewski, Jacob M.; Mårtensson, Gustaf; Russom, Aman
2014-01-01
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. PMID:25379077
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.
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.
Dynamical coupled-channels study of meson production reactions from EBAC@Jlab
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.
Dynamical coupled-channels study of meson production reactions from EBACatJLab
Kamano, Hiroyuki
2011-10-24
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.
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
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.
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
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.
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.
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
Cut-off rate calculations for the outer channel in a concatenated cooling system
NASA Technical Reports Server (NTRS)
Herro, M. A.; Costello, D. J., Jr.; Hu, L.
1984-01-01
Concatenated codes were long used as a practical means of achieving long block or constraint lengths for combating errors on very noisy channels. The inner and outer encoders are normally separated by an interleaver, so that decoded error bursts coming from the inner decoder are randomized before entering the outer decoder. The effectiveness of this interleaver is examined by calculating the cut-off rate of the outer channel seen by the outer decoder with and without interleaving. Interleaving never hurts the performance of a concatenated code, and when the inner code rate is near the cut-off rate of the inner channel, interleaving significantly improves code performance.
Calculation of coupling coefficients for equations of multipoint kinetics
NASA Astrophysics Data System (ADS)
Ioannisian, M. V.
2013-12-01
The multipoint kinetics equations for fission reaction rate are developed. The algorithm for computation of coupling coefficients is implemented within the MCU-5 code. Results from approbation of the method using the model problem and experimental data are presented.
NASA Astrophysics Data System (ADS)
Medvedev, A. E.; Fomin, V. M.
1998-05-01
An approximate analytical model for calculation of the parameters of a steady gas flow inside a plane constricting channel formed by two symmetrically positioned wedges is suggested. A Mach configuration of shock waves (triple point) is formed in the channel when the wedge angles are larger than some critical value. The flow calculation in a constricting channel reduces to the solution of the iterative problem for a system of nonlinear algebraic equations. The configurations of shock waves, the slipstream, and the sonic line are described by the proposed model of a gas flow. A comparison of the results obtained using this model allows a fairly accurate calculation of the Mach stem and the length of the subsonic-flow region.
Radially excited axial mesons and the enigmatic Zc and Zb in a coupled-channel model
NASA Astrophysics Data System (ADS)
Coito, Susana
2016-07-01
The enigmatic charged states Zc(3900 ), Zc(4020 ), Zc(4050 ), Zb(10610 ), and Zb(10650 ) are studied within a coupled-channel Schrödinger model, where radially excited quark-antiquark pairs, with the same angular momenta and isospin as the a1(1260 ) and b1(1235 ), are strongly coupled to their Okubo-Zweig-Iizuka-allowed decay channels D D¯*+D ¯D* and D*D¯*, or B B¯*+B ¯B* and B*B¯*, in S and D waves. Poles, matching the experimental mass and width of the above states, are found by varying only two free parameters. From the wave-function analysis of each resonance, the probability of each of the components contributing to the coupled system is estimated, and predictions can be made for the relative decay fractions among the coupled open-charm or open-bottom decay channels.
Unitary coupled-channels model for three-mesons decays of heavy mesons
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 α_{1}(1260), π_{2}(1670), π_{2}(2100), and D^{0} 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 f_{0}(600), ρ(770), and f_{2}(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.
Unitary coupled-channels model for three-mesons decays of heavy mesons
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
External iterative coupling strategy for surface-subsurface flow calculations in surface irrigation
Technology Transfer Automated Retrieval System (TEKTRAN)
Coupling the unsteady open-channel flow equations of surface irrigation with the equation of variably saturated porous media flow is a computationally complex problem, because of the dependence of infiltration on flow depths. Several models of this coupled process have been developed, all of which ...
TRPV4 and KCa ion channels functionally couple as osmosensors in the paraventricular nucleus
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
Dynamical coupled-channels study of {pi}N {right arrow} {pi pi}N reactions.
Kamano, H.; Julia-Diaz, B.; Lee, T.-S. H.; Matsuyama, A.; Sato, T.; Physics; Jefferson Lab.; Univ. of Barcelona; Shizuoka Univ.; Osaka Univ.
2009-02-24
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} + p {yields} {pi} + {pi} + n, {pi} + {pi}0p and {pi} - p {yields} {pi} + {pi} - n, {pi} - {pi}0p,{pi}0{pi}0n 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.
Role of protein dynamics in ion selectivity and allosteric coupling in the NaK channel
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
Proton-coupled protein transport through the anthrax toxin channel
Finkelstein, Alan
2008-01-01
Anthrax toxin consists of three proteins (approx. 90 kDa each): lethal factor (LF); oedema factor (OF); and protective antigen (PA). The former two are enzymes that act when they reach the cytosol of a targeted cell. To enter the cytosol, however, which they do after being endocytosed into an acidic vesicle compartment, they require the third component, PA. PA (or rather its proteolytically generated fragment PA63) forms at low pH a heptameric β-barrel channel, (PA63)7, through which LF and OF are transported—a phenomenon we have demonstrated in planar phospholipid bilayers. It might appear that (PA63)7 simply forms a large hole through which LF and OF diffuse. However, LF and OF are folded proteins, much too large to fit through the approximately 15 Å diameter (PA63)7 β-barrel. This paper discusses how the (PA63)7 channel both participates in the unfolding of LF and OF and functions in their translocation as a proton–protein symporter. PMID:18957378
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.
Correlated voltage probe model of relaxation in two Coulomb-coupled edge channels
NASA Astrophysics Data System (ADS)
Nigg, Simon E.
2016-01-01
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.
Exchange coupling in transition metal monoxides: Electronic structure calculations
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.
Hillslope-Channel Coupling at the Edge of a Relict Landscape
NASA Astrophysics Data System (ADS)
Berlin, M. M.; Anderson, R. S.
2008-12-01
Knickpoints on fluvial channels are often thought to separate a relict landscape upstream from an active, incising landscape downstream. However, immediately upstream of some knickpoints, we may find the channel has steepened due to its downstream boundary condition. Channel narrowing and an increase in the hillslope angle immediately uphill from the channel may also accompany this channel steepening. The edge of a relict landscape can therefore serve as a natural laboratory in which coupled channel and hillslope processes are strongly influenced by the transient process of knickpoint retreat. We use the topography of the Roan Plateau in western Colorado, revealed by Airborne Laser Swath Mapping, to guide the development of a numerical model in which channel and hillslope processes are coupled. We model knickpoint retreat along an upstream-dipping caprock that results in an effective base level fall for the upstream channel. This base level fall increases channel erosion within a reach hundreds of meters upstream from the waterfall; this erosion is further enhanced due to flow acceleration near the free overfall. We develop a physically-based model for self-formed bedrock channels to assess how much of the base level fall is accommodated by channel narrowing and how much by channel steepening. This steepening will in turn lower the basal boundary condition controlling adjacent hillslopes. By substituting space for time, we use the Roan Plateau to explore two time scales predicted by our model. The first is the channel response time, evaluated via the length scale over which oversteepening occurs. This will be influenced by the degree of channel narrowing, and requires that we capture adequately the dynamics of channel response to base level fall. The second time scale is reflected by the uphill extent and degree of hillslope steepening, which will depend on both the channel steepening (as a necessary trigger) and processes and rates of regolith production and
Single- and coupled-channel radial inverse scattering with supersymmetric transformations
NASA Astrophysics Data System (ADS)
Baye, Daniel; Sparenberg, Jean-Marc; Pupasov-Maksimov, Andrey M.; Samsonov, Boris F.
2014-06-01
The present status of the three-dimensional inverse-scattering method with supersymmetric transformations is reviewed for the coupled-channel case. We first revisit in a pedagogical way the single-channel case, where the supersymmetric approach is shown to provide a complete, efficient and elegant solution to the inverse-scattering problem for the radial Schrödinger equation with short-range interactions. A special emphasis is put on the differences between conservative and non-conservative transformations, i.e. transformations that do or do not conserve the behaviour of solutions of the radial Schrödinger equation at the origin. In particular, we show that for the zero initial potential, a non-conservative transformation is always equivalent to a pair of conservative transformations. These single-channel results are illustrated on the inversion of the neutron-proton triplet eigenphase shifts for the S- and D-waves. We then summarize and extend our previous works on the coupled-channel case, i.e. on systems of coupled radial Schrödinger equations, and stress remaining difficulties and open questions of this problem by putting it in perspective with the single-channel case. We mostly concentrate on two-channel examples to illustrate general principles while keeping mathematics as simple as possible. In particular, we discuss the important difference between the equal-threshold and different-threshold problems. For equal thresholds, conservative transformations can provide non-diagonal Jost and scattering matrices. Iterations of such transformations in the two-channel case are studied and shown to lead to practical algorithms for inversion. A convenient particular technique where the mixing parameter can be fitted without modifying the eigenphases is developed with iterations of pairs of conjugate transformations. This technique is applied to the neutron-proton triplet S-D scattering matrix, for which exactly-solvable matrix potential models are constructed. For
Hiroyuki Kamano
2012-04-01
We review a global analysis of meson production reactions off the nucleons by a collaboration at Excited Baryon Analysis Center of Jefferson Lab. The analysis is pursued with a dynamical coupled-channels approach, within which the dynamics of multi-channel reaction processes are taken into account in a fully consistent way with the two-body as well as three-body unitarity of the S-matrix. With this approach, new features of nucleon excitations are revealed as resonant particles originating from the non-trivial multi-channel reaction dynamics, which cannot be addressed by static hadron models where the nucleon excitations are treated as stable particles.
Coupling of CFTR Cl- channel gating to an ATP hydrolysis cycle.
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. PMID:7512348
NASA Astrophysics Data System (ADS)
Zimmermann, Anke; Kuhn, Sandra; Richter, Marten
2016-01-01
Often, the calculation of Coulomb coupling elements for quantum dynamical treatments, e.g., in cluster or correlation expansion schemes, requires the evaluation of a six dimensional spatial integral. Therefore, it represents a significant limiting factor in quantum mechanical calculations. If the size or the complexity of the investigated system increases, many coupling elements need to be determined. The resulting computational constraints require an efficient method for a fast numerical calculation of the Coulomb coupling. We present a computational method to reduce the numerical complexity by decreasing the number of spatial integrals for arbitrary geometries. We use a Green's function formulation of the Coulomb coupling and introduce a generalized scalar potential as solution of a generalized Poisson equation with a generalized charge density as the inhomogeneity. That enables a fast calculation of Coulomb coupling elements and, additionally, a straightforward inclusion of boundary conditions and arbitrarily spatially dependent dielectrics through the Coulomb Green's function. Particularly, if many coupling elements are included, the presented method, which is not restricted to specific symmetries of the model, presents a promising approach for increasing the efficiency of numerical calculations of the Coulomb interaction. To demonstrate the wide range of applications, we calculate internanostructure couplings, such as the Förster coupling, and illustrate the inclusion of symmetry considerations in the method for the Coulomb coupling between bound quantum dot states and unbound continuum states.
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).
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
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
Combining molecular dynamics and an electrodiffusion model to calculate ion channel conductance
NASA Astrophysics Data System (ADS)
Wilson, Michael A.; Nguyen, Thuy Hien; Pohorille, Andrew
2014-12-01
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.
Combining molecular dynamics and an electrodiffusion model to calculate ion channel conductance.
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
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)
Regulation of channel function due to physical energetic coupling with a lipid bilayer
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
Convergent close-coupling calculations of positron-magnesium scattering
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.
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
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
Dynamical coupled-channels study of {pi}N{yields}{pi}{pi}N reactions
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.
Barry, Joshua; Gu, Chen
2013-04-01
Proper localization of various ion channels is fundamental to neuronal functions, including postsynaptic potential plasticity, dendritic integration, action potential initiation and propagation, and neurotransmitter release. Microtubule-based forward transport mediated by kinesin motors plays a key role in placing ion channel proteins to correct subcellular compartments. PDZ- and coiled-coil-domain proteins function as adaptor proteins linking ionotropic glutamate and GABA receptors to various kinesin motors, respectively. Recent studies show that several voltage-gated ion channel/transporter proteins directly bind to kinesins during forward transport. Three major regulatory mechanisms underlying intracellular transport of ion channels are also revealed. These studies contribute to understanding how mechanical forces are coupled to electrical signaling and illuminating pathogenic mechanisms in neurodegenerative diseases. PMID:22910031
Barry, Joshua; Gu, Chen
2013-01-01
Proper localization of various ion channels is fundamental to neuronal functions, including postsynaptic potential plasticity, dendritic integration, action potential initiation and propagation, and neurotransmitter release. Microtubule-based forward transport mediated by kinesin motors plays a key role in placing ion channel proteins to correct subcellular compartments. PDZ- and coiled-coil-domain proteins function as adaptor proteins linking ionotropic glutamate and GABA receptors to various kinesin motors, respectively. Recent studies show that several voltage-gated ion channel/transporter proteins directly bind to kinesins during forward transport. Three major regulatory mechanisms underlying intracellular transport of ion channels are also revealed. These studies contribute to understanding how mechanical forces are coupled to electrical signaling and illuminating pathogenic mechanisms in neurodegenerative diseases. PMID:22910031
Dynamical coupled-channels study of pi N --> pi pi N reactions
Kamano, Hiroyuki; Julia Diaz, Bruno; Lee, Tsung-Shung; Matsuyama, Akihiko; Sato, Toru
2009-01-01
As a step toward performing a complete coupled-channels analysis of the world data of pi N, gamma^* N --> pi N, eta N, pi pi N reactions, the pi N --> pi pi N reactions are investigated starting with the dynamical coupled-channels model developed in Phys. Rev. C76, 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 non-resonant 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 which are dressed by the non-resonant interactions as constrained by the unitarity condition. The available total cross section data of pi^+ p --> pi^+ pi^+ n, pi^+ pi^0 and pi^- p --> pi^+ pi^- n, pi^- pi^0 n, pi^0 pi^0 n can be reproduced to a very large extent both in magnitudes and energy-dependence. Possible improvements of the model are investigated, in p
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.
Calculation of Coupling Efficiencies for Laser-Driven Photonic Bandgap Structures
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.
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
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. PMID:26771544
Coupled-channels study of fine structure in the {alpha} decay of platinum isotopes
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.
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
Fujimoto, Kazuhiro J
2014-12-01
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. PMID:25481127
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.
Convergent close-coupling calculations of positron scattering on metastable helium
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.
Double and single pion photoproduction within a dynamical coupled-channels model
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
Dynamical Coupled-Channel Model of Meson Production Reactions in the Nucleon Resonance Region
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.
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.
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
NASA Technical Reports Server (NTRS)
Kim, S.-W.
1989-01-01
Numerical calculations of turbulent reattaching shear layers in a divergent channel are presented. The turbulence is described by a multiple-time-scale turbulence model. The turbulent flow equations are solved by a control-volume based finite difference method. The computational results are compared with those obtained using k-epsilon turbulence models and algebraic Reynolds stress turbulence models. It is shown that the multiple-time-scale turbulence model yields significantly improved computational results than the other turbulence models in the region where the turbulence is in a strongly inequilibrium state.
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.
Diacylglycerol mediates regulation of TASK potassium channels by Gq-coupled receptors.
Wilke, Bettina U; Lindner, Moritz; Greifenberg, Lea; Albus, Alexandra; Kronimus, Yannick; Bünemann, Moritz; Leitner, Michael G; Oliver, Dominik
2014-01-01
The two-pore domain potassium (K2P) channels TASK-1 (KCNK3) and TASK-3 (KCNK9) are important determinants of background K(+) conductance and membrane potential. TASK-1/3 activity is regulated by hormones and transmitters that act through G protein-coupled receptors (GPCR) signalling via G proteins of the Gαq/11 subclass. How the receptors inhibit channel activity has remained unclear. Here, we show that TASK-1 and -3 channels are gated by diacylglycerol (DAG). Receptor-initiated inhibition of TASK required the activity of phospholipase C, but neither depletion of the PLC substrate PI(4,5)P2 nor release of the downstream messengers IP3 and Ca(2+). Attenuation of cellular DAG transients by DAG kinase or lipase suppressed receptor-dependent inhibition, showing that the increase in cellular DAG-but not in downstream lipid metabolites-mediates channel inhibition. The findings identify DAG as the signal regulating TASK channels downstream of GPCRs and define a novel role for DAG that directly links cellular DAG dynamics to excitability. PMID:25420509
Critical analysis of fragment-orbital DFT schemes for the calculation of electronic coupling values
NASA Astrophysics Data System (ADS)
Schober, Christoph; Reuter, Karsten; Oberhofer, Harald
2016-02-01
We present a critical analysis of the popular fragment-orbital density-functional theory (FO-DFT) scheme for the calculation of electronic coupling values. We discuss the characteristics of different possible formulations or "flavors" of the scheme which differ by the number of electrons in the calculation of the fragments and the construction of the Hamiltonian. In addition to two previously described variants based on neutral fragments, we present a third version taking a different route to the approximate diabatic state by explicitly considering charged fragments. In applying these FO-DFT flavors to the two molecular test sets HAB7 (electron transfer) and HAB11 (hole transfer), we find that our new scheme gives improved electronic couplings for HAB7 (-6.2% decrease in mean relative signed error) and greatly improved electronic couplings for HAB11 (-15.3% decrease in mean relative signed error). A systematic investigation of the influence of exact exchange on the electronic coupling values shows that the use of hybrid functionals in FO-DFT calculations improves the electronic couplings, giving values close to or even better than more sophisticated constrained DFT calculations. Comparing the accuracy and computational cost of each variant, we devise simple rules to choose the best possible flavor depending on the task. For accuracy, our new scheme with charged-fragment calculations performs best, while numerically more efficient at reasonable accuracy is the variant with neutral fragments.
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.
Quantum Mechanical Calculations of Charge Effects on gating the KcsA channel
Kariev, Alisher M.; Znamenskiy, Vasiliy S.; Green, Michael E.
2007-02-06
The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. A series of ab initio (density functional) calculations were carried out on side chains of a set of amino acids, plus water, from the (intracellular) gating region of the KcsA K+ channel. Their atomic coordinates, except hydrogen, are known from X-ray structures [D.A. Doyle, J.M. Cabral, R.A. Pfuetzner, A. Kuo, J.M. Gulbis, S.L. Cohen, B.T. Chait, R. MacKinnon, The structure of the potassium channel: molecular basis of K+ conduction and selectivity, Science 280 (1998) 69–77; R. MacKinnon, S.L. Cohen, A. Kuo, A. Lee, B.T. Chait, Structural conservation in prokaryotic and eukaryotic potassium channels, Science 280 (1998) 106–109; Y. Jiang, A. Lee, J. Chen, M. Cadene, B.T. Chait, R. MacKinnon, The open pore conformation of potassium channels. Nature 417 (2001) 523–526], as are the coordinates of some water oxygen atoms. The 1k4c structure is used for the starting coordinates. Quantum mechanical optimization, in spite of the starting configuration, places the atoms in positions much closer to the 1j95, more tightly closed, configuration. This state shows four water molecules forming a “basket” under the Q119 side chains, blocking the channel. When a hydrated K+ approaches this “basket”, the optimized system shows a strong set of hydrogen bonds with the K+ at defined positions, preventing further approach of the K+ to the basket. This optimized structure with hydrated K+ added shows an ice-like 12 molecule nanocrystal of water. If the water molecules exchange, unless they do it as a group, the channel will remain blocked. The “basket” itself appears to be very stable, although it is possible that the K+ with its hydrating water molecules may be more mobile, capable
A coupled RELAPS-3D/CFD methodology with a proof-of-principle calculation
Aumiller, D.L.; Tomlinson, E.T.; Bauer, R.C.
2000-01-01
The RELAP5-3D computer code was modified to make the explicit coupling capability in the code fully functional. As a test of the modified code, a coupled RELAP5/RELAP5 analysis of the Edwards-O'Brien blowdown problem was performed which showed no significant deviations from the standard RELAP5-3D predictions. In addition, a multiphase Computational Fluid Dynamics (CFD) code was modified to permit explicit coupling to RELAP5-3D. Several calculations were performed with this code. The first analysis used the experimental pressure history from a point just upstream of the break as a boundary condition. This analysis showed that a multiphase CFD code could calculate the thermodynamic and hydrodynamic conditions during a rapid blowdown transient. Finally, a coupled RELAP5/CFD analysis was performed. The results are presented in this paper.
Yang, Huaiyu; Gao, Zhaobing; Li, Ping; Yu, Kunqian; Yu, Ye; Xu, Tian-Le; Li, Min; Jiang, Hualiang
2012-01-01
Voltage sensing confers conversion of a change in membrane potential to signaling activities underlying the physiological processes. For an ion channel, voltage sensitivity is usually experimentally measured by fitting electrophysiological data to Boltzmann distributions. In our study, a two-state model of the ion channel and equilibrium statistical mechanics principle were used to test the hypothesis of empirically calculating the overall voltage sensitivity of an ion channel on the basis of its closed and open conformations, and determine the contribution of individual residues to the voltage sensing. We examined the theoretical paradigm by performing experimental measurements with Kv1.2 channel and a series of mutants. The correlation between the calculated values and the experimental values is at respective level, R2 = 0.73. Our report therefore provides in silico prediction of key conformations and has identified additional residues critical for voltage sensing. PMID:22768937
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.
Calculation of nuclear spin-spin coupling constants using frozen density embedding
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.
Spin Circuit Model for 2D Channels with Spin-Orbit Coupling
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
Coupled-channel treatment of Isobaric Analog Resonances in (p,p') Capture Processes
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)
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.
Spin Circuit Model for 2D Channels with Spin-Orbit Coupling.
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
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.
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.
First principles calculations of interlayer exchange coupling in bcc Fe/Cu/Fe structures
Kowalewski, M.; Heninrich, B.; Schulthess, T.C.; Butler, W.H.
1998-01-01
The authors report on theoretical calculations of interlayer exchange coupling between two Fe layers separated by a modified Cu spacer. These calculations were motivated by experimental investigations of similar structures by the SFU group. The multilayer structures of interest have the general form: Fe/Cu(k)/Fe and Fe/Cu(m)/X(1)/Cu(n)/Fe where X indicates one AL (atomic layer) of foreign atoms X (Cr, Ag, or Fe) and k, m, n represent the number of atomic layers of Cu. The purpose of the experimental and theoretical work was to determine the effect of modifying the pure Cu spacer by replacing the central Cu atomic layer with the atomic layer of foreign atoms X. The first principles calculation were performed using the Layer Korringa-Kohn-Rostoker (LKKR) method. The theoretical thickness dependence of the exchange coupling between two semi-infinite Fe layers was calculated for pure Cu spacer thicknesses in the range of 0 < k < 16. The effect of the foreign atoms X on the exchange coupling was investigated using the structure with 9 AL Cu spacer as a reference sample. The calculated changes in the exchange coupling are in qualitative agreement with experiment.
NASA Astrophysics Data System (ADS)
Rascher, Eric; Sass, Oliver
2015-04-01
Understanding the evolution and functions of a river system and interpreting the morphology and the dynamics of the channel is a key factor in fluvial geomorphology. For this purpose it is essential to analyse the processes of sediment input and output within and between river reaches and to detect the various forms of storage types on hillslopes and in the channel network. From these processes catchment scale sediment fluxes are derived and result in sediment budgets showing the amount and motion of sediment through the system. Sediment connectivity is a highly important characteristic of catchments when sediment transfer processes are studied. In this context, connectivity controls the sediment fluxes throughout the landscape which means the transfer of sediment from sediment sources to sinks and particularly the potential of a particle to move through the system. This study focuses on slope to channel coupling in the Johnsbach Valley, a typical, non-glaciated alpine catchment in the eastern Austrian Alps. The valley covers an area of 65 km² with altitudes ranging from 584 m a.s.l. at the outlet to 2369 m a.s.l. (Hochtor). The valley is drained by the Johnsbach River which originates in a crystalline bedrock dominated part of the catchment. After approximately 10 km of the distance downstream the lithology changes to calcareous bedrock. In this part of the Johnsbach Valley most of the sediment contributing areas are situated. To detect slope to channel coupling surface changes were measured and mass balances were quantified by terrestrial laser scanning using a RIEGL LMS-Z620. Four field sites were chosen were side channels are directly connected to the main fluvial system. Additionally two field sites show sediment movement in between the side channels. Field campaigns were carried out in September and October of 2013 as well as in April, July, August and October of 2014. First results show that sediment contribution from the side channels and erosion of
Using X(3823)→ J/ ψπ + π - to identify coupled-channel effects
NASA Astrophysics Data System (ADS)
Wang, Bo; Xu, Hao; Liu, Xiang; Chen, Dian-Yong; Coito, Susana; Eichten, Estia
2016-06-01
Very recently, the Belle and BESIII experiments observed a new charmonium-like state X(3823), which is a good candidate for the D-wave charmonium ψ(13 D 2). Because the X(3823) is just near the D bar D* 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 quantum chromodynamics multipole expansion (QCDME) contributions. The partial decay width, the dipion invariant mass spectrum distribution d Γ[ X(3823) → J/ ψπ + π -]/d m π+ π-, and the corresponding d Γ[ X(3823) → J/ ψπ + π -]/dcos θ distribution are computed. Many parameters are determined from existing experimental data, so the results depend mainly only on one unknown phase between the QCDME and hidden-charm dipion amplitudes.
TORT/MCNP coupling method for the calculation of neutron flux around a core of BWR.
Kurosawa, Masahiko
2005-01-01
For the analysis of BWR neutronics performance, accurate data are required for neutron flux distribution over the In-Reactor Pressure Vessel equipments taking into account the detailed geometrical arrangement. The TORT code can calculate neutron flux around a core of BWR in a three-dimensional geometry model, but has difficulties in fine geometrical modelling and lacks huge computer resource. On the other hand, the MCNP code enables the calculation of the neutron flux with a detailed geometry model, but requires very long sampling time to give enough number of particles. Therefore, a TORT/MCNP coupling method has been developed to eliminate the two problems mentioned above in each code. In this method, the TORT code calculates angular flux distribution on the core surface and the MCNP code calculates neutron spectrum at the points of interest using the flux distribution. The coupling method will be used as the DOT-DOMINO-MORSE code system. This TORT/MCNP coupling method was applied to calculate the neutron flux at points where induced radioactivity data were measured for 54Mn and 60Co and the radioactivity calculations based on the neutron flux obtained from the above method were compared with the measured data. PMID:16604689
Papenkort, S; Voigtmann, Th
2015-11-28
We present a hybrid-lattice Boltzmann (LB) algorithm for calculating the flow of glass-forming fluids that are governed by integral constitutive equations with pronounced nonlinear, non-Markovian dependence of the stresses on the flow history. The LB simulation for the macroscopic flow fields is combined with the mode-coupling theory (MCT) of the glass transition as a microscopic theory, in the framework of the integration-through transients formalism. Using the combined LB-MCT algorithm, pressure-driven planar channel flow is studied for a schematic MCT model neglecting spatial correlations in the microscopic dynamics. The cessation dynamics after removal of the driving pressure gradient shows strong signatures of oscillatory flow both in the macroscopic fields and the microscopic correlation functions. PMID:26627963
Clarke, D.B.; Harben, P.E.; Rock, D.W.; White, J.W.; Piacsek, A.
1997-07-01
In support of the Comprehensive Test Ban, research is under way on the long range propagation of signals from nuclear explosions in deep underwater sound (SOFAR) channel. Initially our work at LLNL on signals in the source region considered explosions in or above deep ocean. We studied the variation of wave properties and source region energy coupling as a function of height or depth of burst. Initial calculations on the CALE hydrodynamics code were linked at a few hundred milliseconds to a version of NRL`s weak code, NPE, which solves the nonlinear progressive wave equation. The simulation of the wave propagation was carried down to 5000 m depth and out to 10,000 m range. We have completed ten such simulations at a variety of heights and depths below the ocean surface.
NASA Astrophysics Data System (ADS)
Yi, Guang-Yu; Wang, Xiao-Qi; Gong, Wei-Jiang; Wu, Hai-Na; Chen, Xiao-Hui
2016-03-01
We investigate the Josephson effect in a triple-quantum-dot ring in which only one dot is coupled to the superconductors, by performing the numerical renormalization group calculations. As a result, two kinds of Josephson phase transitions arise. One is the phase transition accompanied by the sharp change of the current direction, whereas the other phase transition is only accompanied by the smooth change of the current direction. Our analysis shows that in this structure, the phase transitions are determined by the variation of interdot spin correlations. The geometry of triple-dot ring induces various spin-correlation modes, leading to the complicate phase transitions. What's notable is that a spin singlet can form between the two lateral dots, which is decoupled from the main channel of this structure. It is certain that such a structure provides an alternative proposal to manipulate the spin correlation between the lateral dots.
The first-principle coupled calculations using TMCC and CFX for the pin-wise simulation of LWR
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)
Empirically Based Conversion Factors for Calculating Couple-Years of Protection.
ERIC Educational Resources Information Center
Stover, John; Bertrand, Jane T.; Shelton, James D.
2000-01-01
Presents conversion factors to be used to translate the quality of the respective contraception methods distributed to a single measure of protection for calculating couple-years of protection in family planning studies. Discusses the implications for the evaluation of family planning programs. (SLD)
A QCDSR calculation for the {phi}D{sub s}D{sub s} coupling constant
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.
Convergent close-coupling calculations of helium single ionization by antiproton impact
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.
Application of coupled-channel Complex Scaling Method to {Lambda}(1405)
Dote, Akinobu; Myo, Takayuki
2011-10-21
We have applied the coupled-channel Complex Scaling Method (ccCSM) to the excited baryon {Lambda}(1405) which is the important building block of kaonic nuclei. {Lambda}(1405) is treated as a resonant state of the meson-baryon coupled system, K-barN and {pi}{Sigma}. In this article, it is reported that the ccCSM works well even with an energy-dependent K-barN potential such as a chiral SU(3)-based potential. We have tested two cases: the self-consistency condition is imposed on I) real energy and II) complex energy. Then, the self-consistent solutions are obtained in both cases in the framework of the ccCSM.
Control of Energy Density inside a Disordered Medium by Coupling to Open or Closed Channels.
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
NASA Astrophysics Data System (ADS)
Sicilia, E.; de Luca, G.; Chiodo, S.; Russo, N.; Calaminici, P.; Koster, A. M.; Jug, K.
Density functional calculations of the electric field gradient tensor at the nitrogen nucleus in 13 test molecules, containing 14 nitrogen sites, have been performed using the linear combination of Gaussian-type orbital Kohn-Sham density functional theory (LCGTO-KSDFT) approach. Local and gradient corrected functionals were used for all-electron calculations. All the molecular structures were optimized at their respective levels of theory with extended basis sets. Calibrated 14N nuclear quadrupole moments were obtained through a fitting procedure between calculated electric field gradients and experimental nuclear quadrupole coupling constants of the test set of molecules for each basis set and functional considered. With these calibrated 14N nuclear quadrupole moments, the nuclear quadrupole coupling constants of the following selected systems were determined: fluoromethylisonitrile, pyridine, pyrrole, imadazole, pyrazole, 1,8-bis(dimethyl-amino)naphthalene, cyclotetramethylenetetranitramine, cocaine and heroin.
Dynamical Coupled-Channel Model of pi-N scattering in te W < 2 GeV Nucleon Resonane Region
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.
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.
Coupled-Channels Density-Matrix Approach to Low-Energy Nuclear Reaction Dynamics
Diaz-Torres, Alexis
2011-10-28
Atomic nuclei are complex, quantum many-body systems whose structure manifests itself through intrinsic quantum states associated with different excitation modes or degrees of freedom. Collective modes (vibration and/or rotation) dominate at low energy (near the ground-state). The associated states are usually employed, within a truncated model space, as a basis in (coherent) coupled channels approaches to low-energy reaction dynamics. However, excluded states can be essential, and their effects on the open (nuclear) system dynamics are usually treated through complex potentials. Is this a complete description of open system dynamics? Does it include effects of quantum decoherence? Can decoherence be manifested in reaction observables? In this contribution, I discuss these issues and the main ideas of a coupled-channels density-matrix approach that makes it possible to quantify the role and importance of quantum decoherence in low-energy nuclear reaction dynamics. Topical applications, which refer to understanding the astrophysically important collision {sup 12}C+{sup 12}C and achieving a unified quantum dynamical description of relevant reaction processes of weakly-bound nuclei, are highlighted.
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.
Operational calibration of the METEOSAT water vapor channel by calculated radiances.
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
Operational calibration of the METEOSAT water vapor channel by calculated radiance
Schmetz, J.
1989-08-01
A method is presented for calibrating the water vapor channel (5.7--7.1 /mu/m) 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.
Electro-optical channel drop switching in a photonic crystal waveguide-cavity side-coupling system
NASA Astrophysics Data System (ADS)
Chang, Kao-Der; Liu, Cheng-Yang
2014-04-01
The electro-optical channel drop switching in a photonic crystal waveguide-cavity side-coupling system is reported. The line waveguide is formed by removing a single row of dielectric cylinders. The twin optical microcavities side coupled between linear waveguides is studied by solving Maxwell's equations. We determine the general characteristics of the coupling element required to achieve channel drop tunneling. By modulating the conductance of the twin microcavities, the electrical tunability of the resonant modes is observed in the transmission spectrum. The spectral characteristics suggest a potential application for this switching device as an efficient multichannel optical switch in the photonic integrated circuits.
Diestler, D J
2012-03-22
The Born-Oppenheimer (BO) description of electronically adiabatic molecular processes predicts a vanishing electronic flux density (j(e)),
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.
NASA Astrophysics Data System (ADS)
Sun, Shufeng; Wu, Yuyuan; Zhao, Rongyi
2001-04-01
According to a separated phase flow model for vertical annular two-phase flow in an annular channel, the liquid film thickness, distributions of velocities and temperatures in the liquid layer are predicted in the range of heat fluxes: 6000-12000 W/m 2, mass flux: 500-1100 kg/m2 s. The pressure drop along the flow channel and heat transfer coefficient are also calculated. The liquid film thickness is in the order of micrometers and heat transfer coefficient is 2800-7800 W/m2 K of liquid nitrogen boiling in narrow annular channels. The measured heat transfer coefficient is 29% higher than the calculated values. With the mass flux increasing and the gap of the annular channel decreasing, pressure drop and heat transfer coefficient increase.
Bennie, Simon J; van der Kamp, Marc W; Pennifold, Robert C R; Stella, Martina; Manby, Frederick R; Mulholland, Adrian J
2016-06-14
Projector-based embedding has recently emerged as a robust multiscale method for the calculation of various electronic molecular properties. We present the coupling of projector embedding with quantum mechanics/molecular mechanics modeling and apply it for the first time to an enzyme-catalyzed reaction. Using projector-based embedding, we combine coupled-cluster theory, density-functional theory (DFT), and molecular mechanics to compute energies for the proton abstraction from acetyl-coenzyme A by citrate synthase. By embedding correlated ab initio methods in DFT we eliminate functional sensitivity and obtain high-accuracy profiles in a procedure that is straightforward to apply. PMID:27159381
Current status of a coupled-channel partial wave analysis using data from CLAS at Jefferson Lab
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.
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.
Sakuta, S. B.; Burtebaev, N.; Artemov, S. V.; Yarmukhamedov, R.
2012-07-15
Existing experimental data on elastic and inelastic deuteron scattering on {sup 6}Li nuclei in the energy range from 8 to 50 MeV were analyzed within the approach of coupled reaction channels. The coupling of elastic scattering and inelastic scattering accompanied by the transition to the 3{sup +} state at E{sub x} 2.186 MeV and the mechanism involving the exchange of an alpha-particle cluster were taken into account in respective calculations. The phenomenological potentials obtained from the present analysis describe well experimental angular distributions at all energies and in full angular ranges. The depths of the real and imaginary parts of the potentials in question depend smoothly on energy at fixed values of the remaining parameters. The energy dependence of relevant volume integrals agrees well with similar data for the p + {sup 6}Li, {alpha} + {sup 6}Li, and {sup 12}C + {sup 12}C systems and with the predictions of a microscopic theory.
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
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.
Li, Jie; Guo, Jianli; Ou, Xiaomin; Zhang, Mingfeng; Li, Yuezhou; Liu, Zhenfeng
2015-08-25
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
A modified CAS-CI approach for an efficient calculation of magnetic exchange coupling constants
NASA Astrophysics Data System (ADS)
Fink, Karin; Staemmler, Volker
2013-09-01
A modification of the conventional wavefunction-based CAS-CI method for the calculation of magnetic exchange coupling constants J in small molecules and transition metal complexes is presented. In general, CAS-CI approaches yield much too small values for J since the energies of the important charge transfer configurations are calculated with the ground state orbitals and are therefore much too high. In the present approach we improve these energies by accounting for the relaxation of the orbitals in the charge transfer configurations. The necessary relaxation energies R can be obtained in separate calculations using mononuclear or binuclear model systems. The method is applied to a few examples, small molecules, binuclear transition metal complexes, and bulk NiO. It allows to obtaining fairly reliable estimates for J at costs that are not higher than those of conventional CAS-CI calculations. Therefore, extended and very time-consuming perturbation theory (PT2), configuration interaction (CI), or coupled cluster (CC) schemes on top of the CAS-CI calculation can be avoided and the modified CAS-CI (MCAS-CI) approach can be applied to rather large systems.
Viscosity calculated in simulations of strongly coupled dusty plasmas with gas friction
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.
Calculations of HOMs and coupled bunch instabilities due to the RHIC rf cavities
Rose, J.
1994-09-01
The cavities for the two RHIC rf systems have been defined, a 26.7 MHz cavity developed by the RHIC rf group and the well documented CERN SPS 200 MHz cavity tuned to 196.1 MHz for operation in RHIC. Calculations of the shunt impedances and Q`s of the higher order modes (HOMs) are summarized along with beadpull measurements of R/Q of selected modes. Estimates of coupled bunch instability growth rates are calculated with both analytical techniques and using the code ZAP and used to make projections of mode damping requirements.
Vibrational Spectrum of (CO)2 on Cu(100): Quantum Calculations with 18 Coupled Mode
NASA Technical Reports Server (NTRS)
Dzegilenko, Fedor; Bowman, Joel M.; Carter, Stuart; Saini, Subhash (Technical Monitor)
1998-01-01
We report calculations of the vibrational frequencies of CO dimer on Cu(100) using recently developed vibrational self-consistent field code. Eighteen modes are treated explicitly within three modes coupling representation. Nine symmetry distinct doublets are observed and the corresponding frequencies are computed. The thermally broadened spectrum of the CO-stretch fundamental is calculated at various temperatures. Both the temperature and coverage dependence of both the average CO-stretch frequency and the corresponding line-width are consistent with experimentally observed trends. The document contains no classified information International clearance is needed.
NASA Astrophysics Data System (ADS)
Wu, Zhe-Ying; Qi, Chong; Wyss, Ramon; Liu, Hong-Liang
2015-08-01
Background: The deviation between different model calculations that may occur when one goes toward regions where the masses are unknown is getting increased attention. This is related to the uncertainties of the different models which may have not been fully understood. Purpose: To explore in detail the effect of the isospin dependence of the spin-orbital force in the Woods-Saxon potential on global binding energy and deformation calculations. Method: The microscopic energies and nuclear deformations of about 1850 even-even nuclei are calculated systematically within the macroscopic-microscopic framework using three Woods-Saxon parametrizations, with different isospin dependencies, which were constructed mainly for nuclear spectroscopy calculations. Calculations are performed in the deformation space (β2,γ ,β4) . Both the monopole and doubly stretched quadrupole interactions are considered for the pairing channel. Results: The ground-state deformations obtained by the three calculations are quite similar to each other. Large differences are seen mainly in neutron-rich nuclei and in superheavy nuclei. Systematic calculations on the shape-coexisting second minima are also presented. As for the microscopic energies of the ground states, the results are also very close to each other. Only in a few cases the difference is larger than 2 MeV. The total binding energy is estimated by adding the macroscopic energy provided by the usual liquid drop model with its parameters fitted through the least square root and minimax criteria. Calculations are also compared with the results of other macroscopic-microscopic mass models. Conclusions: All the three calculations give similar values for the deformations, microscopic energies, and binding energies of most nuclei. One may expect to have a better understanding of the isospin dependence of the spin-orbital force with more data on proton- and neutron-rich nuclei.
Fluid-orbit coupling calculation for flight analysis of impulsively driven laser vehicle
NASA Astrophysics Data System (ADS)
Takahashi, Masayuki; Ohnishi, Naofumi
2013-08-01
Using a fluid-orbit coupling simulator, we numerically solve the three-dimensional Navier-Stokes equations with exchanging information of six-degree-of-freedom reactions for predicting impulsive flight motions of a laser propulsion vehicle driven by blast waves. By feedback of angular and translational velocities into the flowfield, pressure and viscous drags induced by the unsteady vehicle motion are introduced to provide precise motion analysis. In the impulsive-motion estimation of the laser-boosted vehicle, restoring forces and moments are underestimated if the vehicle motion effect is modeled using aerodynamic coefficients of steady flow. Also, a simple model using impulse data examined by experiments for predicting the impulsive motion is compared with our coupling approach which can reproduce instantaneous acceleration resulting from the interaction between the vehicle and the blast wave. Velocity overshoot is generated by evaluating sharp thrust through the coupling calculation, and the flight height becomes 6% larger than conventional prediction using the impulse data.
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.
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.
Development of a coupling code for PWR reactor cavity radiation streaming calculation
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)
Chemical trend of exchange coupling in diluted magnetic II-VI semiconductors: Ab initio calculations
NASA Astrophysics Data System (ADS)
Chanier, T.; Virot, F.; Hayn, R.
2009-05-01
We have calculated the chemical trend of magnetic exchange parameters ( Jdd , Nα , and Nβ ) of Zn-based II-VI semiconductors ZnA ( A=O , S, Se, and Te) doped with Co or Mn. We show that a proper treatment of electron correlations by the local spin-density approximation (LSDA)+U method leads to good agreement between experimental and theoretical values of the nearest-neighbor exchange coupling Jdd between localized 3d spins in contrast to the LSDA method. The exchange couplings between localized spins and doped electrons in the conduction band Nα are in good agreement with experiment as well. But the values for Nβ (coupling to doped holes in the valence band) indicate a crossover from weak coupling (for A=Te and Se) to strong coupling (for A=O ) and a localized hole state in ZnO:Mn. This hole localization explains the apparent discrepancy between photoemission and magneto-optical data for ZnO:Mn.
Renormalization effects on the MSSM from a calculable model of a strongly coupled hidden sector
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.
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.
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
Stability of the Zagreb realization of the Carnegie-Mellon-Berkeley coupled-channels unitary model
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.
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.
Coupled-Channel Models of Direct-Semidirect Capture via Giant-Dipole Resonances
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.
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.
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.
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
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.
Billeter, Salomon R; Egli, Daniel
2006-12-14
This paper generalizes the recently proposed approaches for calculating the derivative couplings between adiabatic states in density-functional theory (DFT) based on a Slater transition-state density to transitions such as singlet-singlet excitations, where a single-determinant ansatz is insufficient. The proposed approach is based on restricted open-shell Frank et al. [J. Chem. Phys. 108, 4060 (1998)] theory used to describe a spin-adapted Slater transition state. To treat the dependence of electron-electron interactions on the nuclear positions, variational linear-response density-functional perturbation theory is generalized to reference states with an orbital-dependent Kohn-Sham Hamiltonian and nontrivial occupation patterns. The methods proposed in this paper are not limited to the calculation of derivative coupling vectors, but can also be used for the calculation of other transition matrix elements. Moreover, they can be used to calculate the linear response of open-shell systems to arbitrary external perturbations in DFT. PMID:17176130
Sakuta, S. B.; Artemov, S.V.; Burtebaev, N.; Kerimkulov, Zh.; Novatsky, B. G.; Stepanov, D.N.; Yarmukhamedov, R.
2009-12-15
A unified description of existing experimental data on alpha-particle scattering by {sup 6}Li over the broad energy range from 18 to 166 MeV was obtained with allowance for channel-coupling effects and mechanisms involving the exchange of a deuteron cluster. Angular distributions were analyzed on the basis of the optical model and the coupled reaction channels method. It was shown that the inclusion of channel coupling and the contributions from one- and two-step exchangemechanismsmakes it possible to describe special features of the behavior of differential cross sections for both elastic and inelastic scattering in a full energy range. Optimum values found for the parameters of optical potentials agree with the parameters of the global potential proposed previously for nuclei in the mass region A > 12.
The Effect of Extending the Length of the Coupling Coils in a MuonIonization Cooling Channel
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.
NASA Astrophysics Data System (ADS)
Ramesh, K.; Devakar, M.
2015-11-01
In the present paper, the effects of magnetic field and heat transfer on the peristaltic flow of an incompressible couple stress fluid through porous medium in an inclined asymmetric channel have been studied under the long wavelength approximation. The exact solutions of the resultant governing equations have been obtained for the stream function, pressure gradient, temperature and heat transfer coefficients. The pressure difference and frictional forces have been computed numerically. The effects of Hartmann number, Darcy number, Grashof number, couple stress parameter, heat generation parameter and inclination angle on the heat characteristics, velocity characteristics, pumping characteristics and trapping phenomena are discussed in detail. It is found that the pressure gradient increases from horizontal channel to vertical channel. The best pumping can be seen at higher Hartmann number. The size of trapped bolus decreases with the increase of couple stress parameter and the strength of the magnetic flied. Increase of heat generation parameter increases the pressure gradient, temperature and the size of the bolus.
Mokelke, E A; Hu, Q; Song, M; Toro, L; Reddy, H K; Sturek, M
2003-09-01
Chronic hyperglycemia and hypercholesterolemia have been shown to alter ionic currents in vascular smooth muscle. We tested the hypothesis that the combined effect of hyperglycemia and hyperlipidemia (diabetic dyslipidemia) would increase the Ca2+-sensitive K+ (KCa) current as a compensatory response to an increase in intracellular Ca2+ concentration. We also hypothesized that exercise training would prevent this elevation in KCa current. Miniature Yucatan swine were randomly assigned to five groups: control, standard pig chow (C, n = 6); hyperlipidemic, high-fat pig chow (H, n = 5); diabetic, standard pig chow (D, n = 7); diabetic, high-fat pig chow ("diabetic dyslipidemic," DD, n = 12); and exercise-trained DD (DDX, n = 9). High-fat chow consisted of standard minipig chow supplemented with cholesterol (2%) and coconut oil. Increased coronary vasoconstriction assessed in vivo and in vitro in DD was prevented by exercise. Patch-clamp experiments performed on right coronary artery smooth muscle cells resulted in greater K+ current densities in the H, D, and DD groups vs. the DDX group between -10 and 40 mV. In fura 2-loaded cells, current activated by caffeine-induced Ca2+ release was greater in H, D, and DD compared with C and DDX (P < 0.05), whereas intracellular Ca2+ concentration was not different across groups. Finally, there were no differences in the KCa or Kv channel protein content between groups. These data indicate that hyperglycemia, hyperlipidemia, and diabetic dyslipidemia lead to elevated whole cell K+ current and increased functional coupling of KCa and Ca2+ release. Endurance exercise prevented increased coupling of Ca2+ release to KCa channel activation in diabetic dyslipidemia. PMID:12777409
Coupled movement of permeant and blocking ions in the CFTR chloride channel pore
Gong, Xiandi; Linsdell, Paul
2003-01-01
The cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel pore is blocked in a voltage-dependent manner by a broad range of anionic substances added to the cytoplasmic side of the membrane. Here we investigate the origin of the voltage dependence of block by intracellular Au(CN)2−, a highly permeant lyotropic anion which also acts as a high-affinity blocker of Cl− permeation. Not only the affinity, but also the voltage dependence of block by intracellular Au(CN)2− ions is strongly dependent on extracellular Cl− concentration; following replacement of most extracellular Cl− by glucose or by impermeant anions, block by Au(CN)2− shows greatly weakened voltage dependence. This suggests that coupled movement of Au(CN)2− and Cl− ions within the pore contributes to the voltage dependence of block. This explanation requires that interactions between different anions take place within the pore, implying simultaneous binding of multiple anions to intrapore sites. Other anions are able to substitute for extracellular Cl− and interact with intracellular Au(CN)2− ions. Analysis of the effects of different extracellular anions on the apparent affinity and voltage dependence of block by intracellular Au(CN)2− ions suggests that extracellular anions do not need to permeate through the channel in order to destabilize Au(CN)2− binding within the pore, implying that this destabilizing effect results from binding to an externally accessible site in the permeation pathway. We propose that multiple anions can bind simultaneously within the CFTR channel pore, and that repulsive interactions between bound anions speeds anion exit from the pore. PMID:12679371
Coupled movement of permeant and blocking ions in the CFTR chloride channel pore.
Gong, Xiandi; Linsdell, Paul
2003-06-01
The cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel pore is blocked in a voltage-dependent manner by a broad range of anionic substances added to the cytoplasmic side of the membrane. Here we investigate the origin of the voltage dependence of block by intracellular Au(CN)2-, a highly permeant lyotropic anion which also acts as a high-affinity blocker of Cl- permeation. Not only the affinity, but also the voltage dependence of block by intracellular Au(CN)2- ions is strongly dependent on extracellular Cl- concentration; following replacement of most extracellular Cl- by glucose or by impermeant anions, block by Au(CN)2- shows greatly weakened voltage dependence. This suggests that coupled movement of Au(CN)2- and Cl- ions within the pore contributes to the voltage dependence of block. This explanation requires that interactions between different anions take place within the pore, implying simultaneous binding of multiple anions to intrapore sites. Other anions are able to substitute for extracellular Cl- and interact with intracellular Au(CN)2- ions. Analysis of the effects of different extracellular anions on the apparent affinity and voltage dependence of block by intracellular Au(CN)2- ions suggests that extracellular anions do not need to permeate through the channel in order to destabilize Au(CN)2- binding within the pore, implying that this destabilizing effect results from binding to an externally accessible site in the permeation pathway. We propose that multiple anions can bind simultaneously within the CFTR channel pore, and that repulsive interactions between bound anions speeds anion exit from the pore. PMID:12679371
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.
Using $X(3823)\\to J/\\psi\\pi^+\\pi^-$ to Identify Coupled-Channel Effects
Wang, Bo; Xu, Hao; Liu, Xiang; Chen, Dian-Yong; Coito, Susana; Eichten, Estia
2015-07-28
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 parameters are determined from existing experimental data, leaving the results mainly dependent on only one unknown phase between the QCDME and hidden-charm dipion amplitudes.
Using $$X(3823)\\to J/\\psi\\pi^+\\pi^-$$ to Identify Coupled-Channel Effects
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
Chen, Jianchun; Ding, Shaojie; Li, Hui; He, Guolong; Zhang, Xuejuan
2014-09-01
This paper studies the combined effect of transmission delay and channel fluctuations on population behaviors of an excitatory Erdös-Rényi neuronal network. First, it is found that the network reaches a perfect spatial temporal coherence at a suitable membrane size. Such a coherence resonance is stimulus-free and is array-enhanced. Second, the presence of transmission delay can induce intermittent changes of the population dynamics. Besides, two resonant peaks of the population firing rate are observed as delay changes: one is at τd≈7ms for all membrane areas, which reflects the resonance between the delayed interaction and the intrinsic period of channel kinetics; the other occurs when the transmission delay equals to the mean inter-spike intervals of the population firings in the absence of delay, which reflects the resonance between the delayed interaction and the firing period of the non-delayed system. Third, concerning the impact of network topology and population size, it is found that decreasing the connection probability does not change the range of transmission delay but broadens the range of synaptic coupling that supports population neurons to generate action potentials synchronously and temporally coherently. Furthermore, there exists a critical connection probability that distinguishes the population dynamics into an asynchronous and synchronous state. All the results we obtained are based on networks of size N = 500, which are shown to be robust to further increasing the population size. PMID:25273211
IUPHAR-DB: the IUPHAR database of G protein-coupled receptors and ion channels.
Harmar, Anthony J; Hills, Rebecca A; Rosser, Edward M; Jones, Martin; Buneman, O Peter; Dunbar, Donald R; Greenhill, Stuart D; Hale, Valerie A; Sharman, Joanna L; Bonner, Tom I; Catterall, William A; Davenport, Anthony P; Delagrange, Philippe; Dollery, Colin T; Foord, Steven M; Gutman, George A; Laudet, Vincent; Neubig, Richard R; Ohlstein, Eliot H; Olsen, Richard W; Peters, John; Pin, Jean-Philippe; Ruffolo, Robert R; Searls, David B; Wright, Mathew W; Spedding, Michael
2009-01-01
The IUPHAR database (IUPHAR-DB) integrates peer-reviewed pharmacological, chemical, genetic, functional and anatomical information on the 354 nonsensory G protein-coupled receptors (GPCRs), 71 ligand-gated ion channel subunits and 141 voltage-gated-like ion channel subunits encoded by the human, rat and mouse genomes. These genes represent the targets of approximately one-third of currently approved drugs and are a major focus of drug discovery and development programs in the pharmaceutical industry. IUPHAR-DB provides a comprehensive description of the genes and their functions, with information on protein structure and interactions, ligands, expression patterns, signaling mechanisms, functional assays and biologically important receptor variants (e.g. single nucleotide polymorphisms and splice variants). In addition, the phenotypes resulting from altered gene expression (e.g. in genetically altered animals or in human genetic disorders) are described. The content of the database is peer reviewed by members of the International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification (NC-IUPHAR); the data are provided through manual curation of the primary literature by a network of over 60 subcommittees of NC-IUPHAR. Links to other bioinformatics resources, such as NCBI, Uniprot, HGNC and the rat and mouse genome databases are provided. IUPHAR-DB is freely available at http://www.iuphar-db.org. PMID:18948278
Uplink Scheduling and Adjacent-Channel Coupling Loss Analysis for TD-LTE Deployment
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
Uplink scheduling and adjacent-channel coupling loss analysis for TD-LTE deployment.
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
NASA Astrophysics Data System (ADS)
Noffsinger, Jesse; Giustino, Feliciano; Malone, Brad D.; Park, Cheol-Hwan; Louie, Steven G.; Cohen, Marvin L.
2010-12-01
EPW ( Electron- Phonon coupling using Wannier functions) is a program written in Fortran90 for calculating the electron-phonon coupling in periodic systems using density-functional perturbation theory and maximally localized Wannier functions. EPW can calculate electron-phonon interaction self-energies, electron-phonon spectral functions, and total as well as mode-resolved electron-phonon coupling strengths. The calculation of the electron-phonon coupling requires a very accurate sampling of electron-phonon scattering processes throughout the Brillouin zone, hence reliable calculations can be prohibitively time-consuming. EPW combines the Kohn-Sham electronic eigenstates and the vibrational eigenmodes provided by the Quantum ESPRESSO package (see Giannozzi et al., 2009 [1]) with the maximally localized Wannier functions provided by the wannier90 package (see Mostofi et al., 2008 [2]) in order to generate electron-phonon matrix elements on arbitrarily dense Brillouin zone grids using a generalized Fourier interpolation. This feature of EPW leads to fast and accurate calculations of the electron-phonon coupling, and enables the study of the electron-phonon coupling in large and complex systems. Program summaryProgram title: EPW Catalogue identifier: AEHA_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHA_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU Public License No. of lines in distributed program, including test data, etc.: 304 443 No. of bytes in distributed program, including test data, etc.: 1 487 466 Distribution format: tar.gz Programming language: Fortran 90 Computer: Any architecture with a Fortran 90 compiler Operating system: Any environment with a Fortran 90 compiler Has the code been vectorized or parallelized?: Yes, optimized for 1 to 64 processors RAM: Heavily system dependent, as small as a few MB Supplementary material: A copy of the "EPW/examples" directory
Relativistic DFT Calculation of (119)Sn Chemical Shifts and Coupling Constants in Tin Compounds.
Bagno, Alessandro; Casella, Girolamo; Saielli, Giacomo
2006-01-01
The nuclear shielding and spin-spin coupling constants of (119)Sn in stannane, tetramethylstannane, methyltin halides Me4-nSnXn (X = Cl, Br, I; n = 1-3), tin halides, and some stannyl cations have been investigated computationally by DFT methods and Slater all-electron basis sets, including relativistic effects by means of the zeroth order regular approximation (ZORA) method up to spin-orbit coupling. Calculated (119)Sn chemical shifts generally correlate well with experimental values, except when several heavy halogen atoms, especially iodine, are bound to tin. In such cases, calculated chemical shifts are almost constant at the scalar (spin-free) ZORA level; only at the spin-orbit level is a good correlation, which holds for all compounds examined, attained. A remarkable "heavy-atom effect", analogous to that observed for analogous alkyl halides, is evident. The chemical shift of the putative stannyl cation (SnH3(+)) has also been examined, and it is concluded that the spectrum of the species obtained in superacids is inconsistent with a simple SnH3(+) structure; strong coordination to even weak nucleophiles such as FSO3H leads to a very satisfactory agreement. On the contrary, the calculated (119)Sn chemical shift of the trimesitylstannyl cation is in very good agreement with the experimental value. Coupling constants between (119)Sn and halogen nuclei are also well-modeled in general (taking into account the large uncertainties in the experimental values); relativistic spin-orbit effects are again quite evident. Couplings to (13)C and (1)H also fall, on the average, on the same correlation line, but individual values show a significant deviation from the expected unit slope. PMID:26626377
Kannt, A; Lancaster, C R; Michel, H
1998-01-01
We have calculated the electrostatic potential and interaction energies of ionizable groups and analyzed the response of the protein environment to redox changes in Paracoccus denitrificans cytochrome c oxidase by using a continuum dielectric model and finite difference technique. Subsequent Monte Carlo sampling of protonation states enabled us to calculate the titration curves of all protonatable groups in the enzyme complex. Inclusion of a model membrane allowed us to restrict the calculations to the functionally essential subunits I and II. Some residues were calculated to have complex titration curves, as a result of strong electrostatic coupling, desolvation, and dipolar interactions. Around the heme a3-CuB binuclear center, we have identified a cluster of 18 strongly interacting residues that account for most of the proton uptake linked to electron transfer. This was calculated to be between 0.7 and 1.1 H+ per electron, depending on the redox transition considered. A hydroxide ion bound to CuB was determined to become protonated to form water upon transfer of the first electron to the binuclear site. The bulk of the protonation changes linked to further reduction of the heme a3-CuB center was calculated to be due to proton uptake by the interacting cluster and Glu(II-78). Upon formation of the three-electron reduced state (P1), His325, modeled in an alternative orientation away from CuB, was determined to become protonated. The agreement of these results with experiment and their relevance in the light of possible mechanisms of redox-coupled proton transfer are discussed. PMID:9533684
Kannt, A; Lancaster, C R; Michel, H
1998-02-01
We have calculated the electrostatic potential and interaction energies of ionizable groups and analyzed the response of the protein environment to redox changes in Paracoccus denitrificans cytochrome c oxidase by using a continuum dielectric model and finite difference technique. Subsequent Monte Carlo sampling of protonation states enabled us to calculate the titration curves of all protonatable groups in the enzyme complex. Inclusion of a model membrane allowed us to restrict the calculations to the functionally essential subunits I and II. Some residues were calculated to have complex titration curves, as a result of strong electrostatic coupling, desolvation, and dipolar interactions. Around the heme a3-CuB binuclear center, we have identified a cluster of 18 strongly interacting residues that account for most of the proton uptake linked to electron transfer. This was calculated to be between 0.7 and 1.1 H+ per electron, depending on the redox transition considered. A hydroxide ion bound to CuB was determined to become protonated to form water upon transfer of the first electron to the binuclear site. The bulk of the protonation changes linked to further reduction of the heme a3-CuB center was calculated to be due to proton uptake by the interacting cluster and Glu(II-78). Upon formation of the three-electron reduced state (P1), His325, modeled in an alternative orientation away from CuB, was determined to become protonated. The agreement of these results with experiment and their relevance in the light of possible mechanisms of redox-coupled proton transfer are discussed. PMID:9533684
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.
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%.
Effects on calculated half-widths and shifts from the line coupling for asymmetric-top molecules
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%.
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
Long-range correlation energy calculated from coupled atomic response functions
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.
NASA Astrophysics Data System (ADS)
Tantawi, Reda S.
2003-03-01
The influence of the electric charge of both the projectile and the target nucleus on the cross section of the inelastic collision of protons and antiprotons with atoms is investigated at energies ranging from 1 to 2500 KeV. The impact parameter method is used to analyse the cross sections of the excitation of the n = 3 states of H atom and He+, Li2+ ions being initially in the excited 2s states. The calculated cross sections for hydrogen atoms are compared with the other theoretical results based on coupled-channels methods.
Marcantoni, Andrea; Vandael, David H F; Mahapatra, Satyajit; Carabelli, Valentina; Sinnegger-Brauns, Martina J; Striessnig, Joerg; Carbone, Emilio
2010-01-13
We studied wild-type (WT) and Cav1.3(-/-) mouse chromaffin cells (MCCs) with the aim to determine the isoform of L-type Ca(2+) channel (LTCC) and BK channels that underlie the pacemaker current controlling spontaneous firing. Most WT-MCCs (80%) were spontaneously active (1.5 Hz) and highly sensitive to nifedipine and BayK-8644 (1,4-dihydro-2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)phenyl]-3-pyridinecarboxylic acid, methyl ester). Nifedipine blocked the firing, whereas BayK-8644 increased threefold the firing rate. The two dihydropyridines and the BK channel blocker paxilline altered the shape of action potentials (APs), suggesting close coupling of LTCCs to BK channels. WT-MCCs expressed equal fractions of functionally active Cav1.2 and Cav1.3 channels. Cav1.3 channel deficiency decreased the number of normally firing MCCs (30%; 2.0 Hz), suggesting a critical role of these channels on firing, which derived from their slow inactivation rate, sizeable activation at subthreshold potentials, and close coupling to fast inactivating BK channels as determined by using EGTA and BAPTA Ca(2+) buffering. By means of the action potential clamp, in TTX-treated WT-MCCs, we found that the interpulse pacemaker current was always net inward and dominated by LTCCs. Fast inactivating and non-inactivating BK currents sustained mainly the afterhyperpolarization of the short APs (2-3 ms) and only partially the pacemaker current during the long interspike (300-500 ms). Deletion of Cav1.3 channels reduced drastically the inward Ca(2+) current and the corresponding Ca(2+)-activated BK current during spikes. Our data highlight the role of Cav1.3, and to a minor degree of Cav1.2, as subthreshold pacemaker channels in MCCs and open new interesting features about their role in the control of firing and catecholamine secretion at rest and during sustained stimulations matching acute stress. PMID:20071512
NASA Astrophysics Data System (ADS)
Laute, Katja; Beylich, Achim A.
2010-05-01
Hillslopes occupy large areas of the earth surface. Studying the characteristics, development and interaction of hillslopes as components of the geomorphic hillslope-channel coupling process-response system will improve the understanding of the complex response of mountain landscape formation. The rates of hillslope processes are exceptionally varied and affected by many influences of varying intensity. Hillslope-channel coupling and sediment storage within slopes are important factors that influence sediment delivery through catchments, especially in steep environments. Within sediment transfers from sources to sinks in drainage basins, hillslopes function as a key element concerning sediment storage, both for short term periods as between rainstorms as well as for longer periods in colluvial deposits. This PhD project is part of the NFR funded SedyMONT-Norway project within the ESF TOPO-EUROPE SedyMONT (Timescales of sediment dynamics, climate and topographic change in mountain landscapes) programme. The focus of this study is on geomorphic hillslope-channel coupling or de-coupling and sediment transport within four distinct headwater areas of the Erdalen and Bødalen catchments in the Nordfjord valley-fjord system (inner Nordfjord, Western Norway). Both catchments can be described as steep, U-shaped and glacier-fed, subarctic tributary valleys. Approximately 14% of the 49 km2 large headwater area of Erdalen is occupied by hillslope deposits; in Bødalen hillslope deposits occupy 12% of the 42 km2 large headwater area. The main aims of the study are to present preliminary findings on (i) the identification of possible sediment sources and delivery pathways within the headwater areas of the catchments, (ii) to analyze the development of hillslope-channel coupling / de-coupling from postglacial to contemporary timescales as well as (iii) to investigate the current degree of geomorphic hillslope-channel coupling within the different headwater catchments and (iv) to
Leptin-stimulated KATP channel trafficking: a new paradigm for β-cell stimulus-secretion coupling?
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. PMID:24213304
Multicrossing Landau-Zener and close-coupling calculations of electron transfer in ? collisions
NASA Astrophysics Data System (ADS)
Lundsgaard, M. F. V.; Nielsen, S. E.; Rudolph, H.; Hansen, J. P.
1998-07-01
Cross sections for electron capture from Li(2s,2p) by proton impact have been calculated for energies in the range 10 eV-10 keV within the atomic orbital close-coupling (AO-CC) and the multicrossing Landau-Zener (MLZ) one-electron models. For the excited Li(2p) target the long-range mixing of the magnetic sublevels has been included in the MLZ calculations by means of a locking-radius model. The MLZ approximation to the AO-CC calculations is found to be appropriate at energies of about 10 eV. When diagonalizing the effective electronic Hamiltonian within the close-coupling basis a non-physical potential curve is disclosed. The cross section for 0953-4075/31/14/018/img7 capture from Li(2s) in particular is shown to be sensitive to this curve for energies below 50 eV. It is demonstrated how this problem is eliminated by including a pseudo-Li(1s) state in the AO-CC basis set.
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.
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.