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Sample records for pair coulomb interaction

  1. Coulomb scattering in a 2D interacting electron gas and production of EPR pairs.

    PubMed

    Saraga, D S; Altshuler, B L; Loss, Daniel; Westervelt, R M

    2004-06-18

    We propose a setup to generate nonlocal spin Einstein-Podolsky-Rosen pairs via pair collisions in a 2D interacting electron gas, based on constructive two-particle interference in the spin-singlet channel at the pi/2 scattering angle. We calculate the scattering amplitude via the Bethe-Salpeter equation in the ladder approximation and small r(s) limit and find that the Fermi sea leads to a substantial renormalization of the bare scattering process. From the scattering length, we estimate the current of spin-entangled electrons and show that it is within experimental reach.

  2. Coulomb interactions in particle beams

    SciTech Connect

    Jansen, G.H. )

    1990-01-01

    This book develops analytical and computer models for beams in which Coulomb interactions are important. The research into the different phenomena of Coulomb interactions in particle beams is stimulated by developments in the field of electron beam lithography for VLSI electronics. The standard theory of charged particle optics breaks down for intense beams in which interactions between particles are significant. This monograph is devoted to the theory of these intense beams, which are not only used in VLSI electronics but also in scanning electron microscopes. The theory is also applicable to focused ion beams, which are used in VLSI mask repair.

  3. Universal properties of high-temperature superconductors from real-space pairing: Role of correlated hopping and intersite Coulomb interaction within the t -J -U model

    NASA Astrophysics Data System (ADS)

    Zegrodnik, Michał; Spałek, Józef

    2017-08-01

    We study the effect of the correlated hopping term and the intersite Coulomb interaction term on principal features of the d -wave superconducting (SC) state, in both the electron- and hole-doped regimes within the t -J -U model. In our analysis, we use the approach based on the diagrammatic expansion of the Gutzwiller wave function (DE-GWF), which allows us to go beyond the renormalized mean-field theory (RMFT). We show that the correlated hopping term enhances the pairing at the electron-doped side of the phase diagram. Moreover, the so-called non-BCS regime (which manifests itself by the negative kinetic energy gain at the transition to the SC phase) is narrowed down with the increasing magnitude of the correlated hopping ˜K . Also, the doping dependencies of the nodal Fermi velocity and Fermi momentum, as well as the average number of double occupancies, are analyzed with reference to the experimental data for selected values of the parameter K . For the sake of completeness, the influence of the intersite Coulomb repulsion on the obtained results is provided. Additionally, selected results concerning the Hubbard-model case are also presented. A complete model with all two-site interactions is briefly discussed in Appendix for reference.

  4. Coulomb bound states of strongly interacting photons

    SciTech Connect

    Maghrebi, M. F.; Choi, S.; Martin, I.; Firstenberg, O.; Lukin, M. D.; Büchler, H. P.; Gorshkov, A. V.

    2015-09-16

    We show that two photons coupled to Rydberg states via electromagnetically induced transparency (EIT) can interact via an effective Coulomb potential. The interaction then gives rise to a continuum of two-body bound states. Within the continuum, metastable bound states are distinguished in analogy with quasi-bound states tunneling through a potential barrier. We find multiple branches of metastable bound states whose energy spectrum is governed by the Coulomb problem, thus obtaining a photonic analogue of the hydrogen atom. These states propagate with a negative group velocity in the medium, which allows for a simple preparation and detection scheme, before they slowly decay to pairs of bound Rydberg atoms. As a result, we verify the metastability and backward propagation of these Coulomb bound states with exact numerical simulations.

  5. Coulomb bound states of strongly interacting photons

    DOE PAGES

    Maghrebi, M. F.; Gullans, Michael J.; Bienias, P.; ...

    2015-09-16

    We show that two photons coupled to Rydberg states via electromagnetically induced transparency (EIT) can interact via an effective Coulomb potential. The interaction then gives rise to a continuum of two-body bound states. Within the continuum, metastable bound states are distinguished in analogy with quasi-bound states tunneling through a potential barrier. We find multiple branches of metastable bound states whose energy spectrum is governed by the Coulomb problem, thus obtaining a photonic analogue of the hydrogen atom. These states propagate with a negative group velocity in the medium, which allows for a simple preparation and detection scheme, before they slowlymore » decay to pairs of bound Rydberg atoms. As a result, we verify the metastability and backward propagation of these Coulomb bound states with exact numerical simulations.« less

  6. Coulomb Bound States of Strongly Interacting Photons

    NASA Astrophysics Data System (ADS)

    Maghrebi, M. F.; Gullans, M. J.; Bienias, P.; Choi, S.; Martin, I.; Firstenberg, O.; Lukin, M. D.; Büchler, H. P.; Gorshkov, A. V.

    2015-09-01

    We show that two photons coupled to Rydberg states via electromagnetically induced transparency can interact via an effective Coulomb potential. This interaction gives rise to a continuum of two-body bound states. Within the continuum, metastable bound states are distinguished in analogy with quasibound states tunneling through a potential barrier. We find multiple branches of metastable bound states whose energy spectrum is governed by the Coulomb potential, thus obtaining a photonic analogue of the hydrogen atom. Under certain conditions, the wave function resembles that of a diatomic molecule in which the two polaritons are separated by a finite "bond length." These states propagate with a negative group velocity in the medium, allowing for a simple preparation and detection scheme, before they slowly decay to pairs of bound Rydberg atoms.

  7. Coulomb interaction in multiple scattering theory

    NASA Astrophysics Data System (ADS)

    Ray, L.; Hoffmann, G. W.; Thaler, R. M.

    1980-10-01

    The treatment of the Coulomb interaction in the multiple scattering theories of Kerman-McManus-Thaler and Watson is examined in detail. By neglecting virtual Coulomb excitations, the lowest order Coulomb term in the Watson optical potential is shown to be a convolution of the point Coulomb interaction with the distributed nuclear charge, while the equivalent Kerman-McManus-Thaler Coulomb potential is obtained from an averaged, single-particle Coulombic T matrix. The Kerman-McManus-Thaler Coulomb potential is expressed as the Watson Coulomb term plus additional Coulomb-nuclear and Coulomb-Coulomb cross terms, and the omission of the extra terms in usual Kerman-McManus-Thaler applications leads to negative infinite total reaction cross section predictions and incorrect pure Coulomb scattering limits. Approximations are presented which eliminate these anomalies. Using the two-potential formula, the full projectile-nucleus T matrix is separated into two terms, one resulting from the distributed nuclear charge and the other being a Coulomb distorted nuclear T matrix. It is shown that the error resulting from the omission of the Kerman-McManus-Thaler Coulomb terms is effectively removed when the pure Coulomb T matrix in Kerman-McManus-Thaler is replaced by the analogous quantity in the Watson approach. Using the various approximations, theoretical angular distributions are obtained for 800 MeV p+208Pb elastic scattering and compared with experimental data. NUCLEAR REACTIONS 208Pb(p, p), E=0.8 GeV, Kerman, McManus, and Thaler, and Watson multiple scattering theories, Coulomb correction terms, high momentum transfer.

  8. Coulomb interactions in particle beams

    NASA Astrophysics Data System (ADS)

    Jansen, Gerrit Hermanus

    The theory of particle interactions in low and medium density, nonrelativistic, time-independent beams of identical particles, in probe forming instruments is discussed. Low and medium density and nonrelativistic refer to beam currents typically much smaller than 1 mA and beam voltages typically between 1 and 100 keV. Time-independent implies that the flow of particles is assumed to be constant. The theory is developed for electron-beam lithography pattern generators and scanning electron microscopes. It should be applicable to focused ion beam tools as well. The analytical models used are based on the ideas of Van Leeuwen and Jansen (1983). This work is extended and confronted with other theories and the results of numerical Monte Carlo simulation. The impact of particle interactions on beams in drift space is stressed. Results of an analysis to extend the model to beams in an external uniform acceleration field are presented.

  9. Existence and consequences of Coulomb pairing of electrons in a solid

    SciTech Connect

    Mahajan, S.M.; Thyagaraja, A.

    1996-11-01

    It is shown from first principles that, in the periodic potential of a crystalline solid, short-range (i.e., screened) binary Coulomb interactions can lead to a two-electron bound state. It is further suggested that these composite bosonic states (charge -2e, and typically spin zero) could mediate an effectively attractive interaction between pairs of conduction electrons close to the Fermi level. This necessarily short range attractive interaction, which is crucially dependent on the band structure of the solid, and is complementary to the phonon-mediated one, may provide a source for the existence and properties of short correlation-length electron pairs (analogous to but distinct from Cooper pairs) needed to understand high temperature superconductivity. Several distinctive and observable characteristics of the proposed pairing scheme are discussed.

  10. Nanoplasmonic renormalization and enhancement of Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Durach, Maxim; Rusina, Anastasia; Klimov, Victor I.; Stockman, Mark I.

    2008-08-01

    In this paper we propose a general and powerful theory of the plasmonic enhancement of the many-body phenomena resulting in a closed expression for the surface plasmon-dressed Coulomb interaction. We illustrate this theory by computing dressed interaction explicitly for an important example of metal-dielectric nanoshells which exhibits a rich resonant behavior in magnitude and phase. This interaction is used to describe the nanoplasmonic-enhanced F¨orster resonant energy transfer (FRET) between nanocrystal quantum dots near a nanoshell.

  11. Nanoplasmonic renormalization and enhancement of Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Durach, M.; Rusina, A.; Klimov, V. I.; Stockman, M. I.

    2008-10-01

    In this paper, we propose a general and powerful theory of the plasmonic enhancement of the many-body phenomena resulting in a closed expression for the surface plasmon-dressed Coulomb interaction. We illustrate this theory by computing the dressed interaction explicitly for an important example of metal-dielectric nanoshells which exhibits a rich resonant behavior in magnitude and phase. This interaction is used to describe the nanoplasmonic-enhanced Förster resonant energy transfer (FRET) between nanocrystal quantum dots near a nanoshell.

  12. Coulomb interaction driven instabilities of sliding Luttinger liquids

    NASA Astrophysics Data System (ADS)

    Sur, Shouvik; Yang, Kun

    2017-08-01

    We study systems made of periodic arrays of one-dimensional quantum wires coupled by Coulomb interaction. Using bosonization an interacting metallic fixed point is obtained, which is shown to be a higher-dimensional analog of the Tomonaga-Luttinger liquid, or a sliding Luttinger liquid. This non-Fermi liquid metallic state, however, is unstable in the presence of weak interwire backscatterings, which favor charge density wave states and suppress pairing. Depending on the effective strength of the Coulomb repulsion and the size of interwire spacing, various charge density wave states are stabilized, including Wigner crystal states. Our method allows for the determination of the specific ordering patterns and corresponding energy and temperature scales.

  13. Off-shell Jost solutions for Coulomb and Coulomb-like interactions in all partial waves

    SciTech Connect

    Laha, U.; Bhoi, J.

    2013-01-15

    By exploiting the theory of ordinary differential equations, with judicious use of boundary conditions, interacting Green's functions and their integral transforms together with certain properties of higher transcendental functions, useful analytical expressions for the off-shell Jost solutions for motion in Coulomb and Coulomb-nuclear potentials are derived in maximal reduced form through different approaches to the problem in the representation space. The exact analytical expressions for the off-shell Jost solutions for Coulomb and Coulomb-like potentials are believed to be useful for the description of the charged particle scattering/reaction processes.

  14. Effect of Coulomb interaction on multi-electronwave packet dynamics

    SciTech Connect

    Shiokawa, T.; Takada, Y.; Konabe, S.; Hatsugai, Y.; Muraguchi, M.; Endoh, T.; Shiraishi, K.

    2013-12-04

    We have investigated the effect of Coulomb interaction on electron transport in a one-dimensional nanoscale structure using a multi-electron wave packet approach. To study the time evolution, we numerically solve the time-dependent Hartree-Fock equation, finding that the electron wave packet dynamics strongly depends on the Coulomb interaction strength. When the Coulomb interaction is large, each electron wave packet moves separately in the presence of an electric field. With weak Coulomb interaction, however, the electron wave packets overlap, forming and moving as one collective wave packet.

  15. Stability of the d-wave pairing with respect to the intersite Coulomb repulsion in cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Val'kov, V. V.; Dzebisashvili, D. M.; Korovushkin, M. M.; Barabanov, A. F.

    2017-10-01

    Within the spin-fermion model for cuprate superconductors, the influence of the intersite Coulomb interactions V2 and V‧2 between holes located at the next-nearest-neighbor oxygen ions of CuO2 plane on the implementation of the dx2-y2-wave pairing is studied. It is shown that d-wave pairing can be suppressed only for unphysically large values of V2 and V‧2.

  16. Screened Coulomb interactions with non-uniform surface charge

    NASA Astrophysics Data System (ADS)

    Ghosal, Sandip; Sherwood, John D.

    2017-03-01

    The screened Coulomb interaction between a pair of infinite parallel planes with spatially varying surface charge is considered in the limit of small electrical potentials for arbitrary Debye lengths. A simple expression for the disjoining pressure is derived in terms of a two-dimensional integral in Fourier space. The integral is evaluated for periodic and random charge distributions and the disjoining pressure is expressed as a sum over Fourier-Bloch reciprocal lattice vectors or in terms of an integral involving the autocorrelation function, respectively. The force between planes with a finite area of uniform charge, a model for the DLVO interaction between finite surfaces, is also calculated. It is shown that the overspill of the charge cloud beyond the region immediately between the charged areas results in a reduction of the disjoining pressure, as reported by us recently in the long Debye length limit for planes of finite width.

  17. Anyon pairing via phonon-mediated interaction

    NASA Astrophysics Data System (ADS)

    Kandemir, B. S.

    2006-08-01

    In this paper, we study the pairing of anyons subjected to an external uniform magnetic field and confined in a two-dimensional parabolic quantum dot within the framework of Fröhlich large bipolaron theory, motivated by the Wilczek’s prescription that treats anyons as composites having both charges and fictitious flux tubes. In this model, electrons bound to Aharanov-Bohm type flux tubes and surrounded by a cloud of virtual LO phonons interact with each other through the long range Coulomb and statistical potentials. In order to discuss the effects of both spatial confinement potential and external uniform magnetic field on the boundaries of the stability region of such a pairing in real space, we perform a self-consistent treatment of the ground-state energies of both an interacting anyon pair and two noninteracting anyons. Our results suggest that two interacting anyons can be bound into a condensate anyon pair through a phonon-mediated interaction.

  18. Electronic structure of a deformable trimer with a coulomb interaction and a variable number of electrons

    SciTech Connect

    Aplesnin, S. S.; Piskunova, N. I.

    2011-01-15

    The electronic spectrum of a trimer with a variable number of electrons has been calculated in the Hubbard model by exact diagonalization. The dependences of the chemical potential shift, magnetic moment, and energy level splitting near the chemical potential on the magnetic field, Coulomb interaction between the electrons located at the vertices of the triangle, trimer deformation, and three-center interaction have been established. The removal of magnetic degeneracy in the trimer when the intersite Coulomb and three-center interactions are taken into account and the formation of a singlet pair of electrons under trimer deformation have been detected.

  19. Exchange Coulomb interaction in nanotubes: Dispersion of Langmuir waves

    SciTech Connect

    Andreev, P. A. Ivanov, A. Yu.

    2015-07-15

    The microscopic derivation of the Coulomb exchange interaction for electrons located on the nanotubes is presented. The derivation is based on the many-particle quantum hydrodynamic method. We demonstrate the effect of curvature of the nanocylinders on the force of exchange interaction. We calculate corresponding dispersion dependencies for electron oscillations on the nanotubes.

  20. Coulomb Interactions in Hanbury Brown-Twiss Experiments with Electrons

    ERIC Educational Resources Information Center

    Shen, Kan

    2009-01-01

    This dissertation examines the effect of Coulomb interactions in Hanbury Brown-Twiss (HBT) type experiments with electrons. HBT experiments deal with intensity interference, which is related to the second-order correlation function of the particle field. This is an extension of the usual amplitude interference experiment, such as Young's…

  1. Limits to Electron Beam Emittance from Stochastic Coulomb Interactions

    SciTech Connect

    Coleman-Smith, Christopher; Padmore, Howard A.; Wan, Weishi

    2008-08-22

    Dense electron beams can now be generated on an ultrafast timescale using laser driven photo-cathodes and these are used for a range of applications from ultrafast electron defraction to free electron lasers. Here we determine a lower bound to the emittance of an electron beam limited by fundamental stochastic Coulomb interactions.

  2. Coulomb Interactions in Hanbury Brown-Twiss Experiments with Electrons

    ERIC Educational Resources Information Center

    Shen, Kan

    2009-01-01

    This dissertation examines the effect of Coulomb interactions in Hanbury Brown-Twiss (HBT) type experiments with electrons. HBT experiments deal with intensity interference, which is related to the second-order correlation function of the particle field. This is an extension of the usual amplitude interference experiment, such as Young's…

  3. Evidence for the importance of extended Coulomb interactions and forward scattering in cuprate superconductors.

    PubMed

    Johnston, S; Vishik, I M; Lee, W S; Schmitt, F; Uchida, S; Fujita, K; Ishida, S; Nagaosa, N; Shen, Z X; Devereaux, T P

    2012-04-20

    The prevalent view of the high-temperature superconducting cuprates is that their essential low-energy physics is captured by local Coulomb interactions. However, this view been challenged recently by studies indicating the importance of longer-range components. Motivated by this, we demonstrate the importance of these components by examining the electron-phonon (e-ph) interaction with acoustic phonons in connection with the recently discovered renormalization in the near-nodal low-energy (~8-15 meV) dispersion of Bi(2)Sr(2)CaCu(2)O(8+δ). By studying its nontrivial momentum and doping dependence we conclude a predominance of forward scattering arising from the direct interplay between the e-ph and extended Coulomb interactions. Our results thus demonstrate how the low-energy renormalization can provide a pathway to new insights into how these interactions interplay with one another and influence pairing and dynamics in the cuprates.

  4. Electron interactions in graphene through an effective Coulomb potential

    NASA Astrophysics Data System (ADS)

    Rodrigues, Joao N. B.; Adam, Shaffique

    A recent numerical work [H.-K. Tang et al, PRL 115, 186602 (2015)] considering graphene's π-electrons interacting through an effective Coulomb potential that is finite at short-distances, stressed the importance of the sp2 -electrons in determining the semimetal to Mott insulator phase transition in graphene. Some years ago, I. F. Herbut [PRL 97, 146401 (2006)] studied such a transition by mapping graphene's π-electrons into a Gross-Neveu model. From a different perspective, D. T. Son [PRB 75, 235423 (2007)] put the emphasis on the long-range interactions by modelling graphene as Dirac fermions interacting through a bare Coulomb potential. Here we build on these works and explore the phase diagram of Dirac fermions interacting through an effective Coulomb-like potential screened at short-distances. The interaction potential used allows for analytic results that controllably switch between the two perspectives above. This work was supported by the Singapore National Research Foundation (NRF-NRFF2012-01 and CA2DM medium-sized centre program) and by the Singapore Ministry of Education and Yale-NUS College (R-607-265-01312).

  5. Coulomb displacement energies as a probe for nucleon pairing in the f7/2 shell

    NASA Astrophysics Data System (ADS)

    Kankainen, A.; Eronen, T.; Gorelov, D.; Hakala, J.; Jokinen, A.; Kolhinen, V. S.; Reponen, M.; Rissanen, J.; Saastamoinen, A.; Sonnenschein, V.; ńystö, J.

    2014-05-01

    Coulomb displacement energies of T =1/2 mirror nuclei have been studied via a series of high-precision QEC-value measurements with the double Penning trap mass spectrometer JYFLTRAP. Most recently, the QEC values of the f7/2-shell mirror nuclei V45 (QEC=7123.82(22) keV) and Mn49 (QEC=7712.42(24) keV) have been measured with unprecedented precision. The data reveal a 16-keV (1.6σ) offset in the adopted Atomic Mass Evaluation 2012 value of Mn49, suggesting the need for further measurements to verify whether there is a breakdown of the quadratic form of the isobaric multiplet mass equation in the fp shell. Precisely measured QEC values confirm that the pairing effect in the Coulomb energies is quenched when entering the f7/2 shell and reaches a minimum in the midshell.

  6. Stability of Dirac Liquids with Strong Coulomb Interaction

    NASA Astrophysics Data System (ADS)

    Tupitsyn, Igor S.; Prokof'ev, Nikolay V.

    2017-01-01

    We develop and apply the diagrammatic Monte Carlo technique to address the problem of the stability of the Dirac liquid state (in a graphene-type system) against the strong long-range part of the Coulomb interaction. So far, all attempts to deal with this problem in the field-theoretical framework were limited either to perturbative or random phase approximation and functional renormalization group treatments, with diametrically opposite conclusions. Our calculations aim at the approximation-free solution with controlled accuracy by computing vertex corrections from higher-order skeleton diagrams and establishing the renormalization group flow of the effective Coulomb coupling constant. We unambiguously show that with increasing the system size L (up to ln (L )˜40 ), the coupling constant always flows towards zero; i.e., the two-dimensional Dirac liquid is an asymptotically free T =0 state with divergent Fermi velocity.

  7. Coulomb and electron-phonon interactions in metals

    NASA Astrophysics Data System (ADS)

    Tupitsyn, Igor S.; Mishchenko, Andrey S.; Nagaosa, Naoto; Prokof'ev, Nikolay

    2016-10-01

    An accurate and consistent theory of phonons in metals requires that all long-range Coulomb interactions between charged particles (electrons and ions) be treated on equal footing. So far, all attempts to deal with this nonperturbative system were relying on uncontrolled approximations in the absence of small parameters. In this paper, we develop the diagrammatic Monte Carlo approach for a two-component Coulomb system that obtains the solution to this fundamental problem in an approximation-free way by computing vertex corrections from higher-order skeleton graphs. The feasibility of the method is demonstrated by calculating the spectrum of longitudinal acoustic phonons in a simple cubic lattice, determining their sound velocity, and obtaining the phonon spectral densities by analytic continuation of the Matsubara-Green's functions. Final results are checked against the lowest-order fully self-consistent G W approximation in both adiabatic and nonadiabatic regimes.

  8. A nonlinear Bloch model for Coulomb interaction in quantum dots

    SciTech Connect

    Bidegaray-Fesquet, Brigitte Keita, Kole

    2014-02-15

    In this paper, we first derive a Coulomb Hamiltonian for electron–electron interaction in quantum dots in the Heisenberg picture. Then we use this Hamiltonian to enhance a Bloch model, which happens to be nonlinear in the density matrix. The coupling with Maxwell equations in case of interaction with an electromagnetic field is also considered from the Cauchy problem point of view. The study is completed by numerical results and a discussion about the advisability of neglecting intra-band coherences, as is done in part of the literature.

  9. Photodetachment of hydrogen negative ions with screened Coulomb interaction

    SciTech Connect

    Zhang, Song Bin; Chen, Xiang Jun; Wang, Jian Guo; Janev, R. K.; Qu, Yi Zhi

    2010-06-15

    The effects of Coulomb interaction screening on photodetachment cross sections of hydrogen negative ions below the n =2 excitation threshold is investigated by using the R-matrix method with pseudostates. The contributions of Feshbach and shape resonances to H{sup -} photodetachment cross section are presented when screening length (D) varies from D = {infinity} to D = 4.6 a.u. It is found that the interaction screening has dramatic effects on the photodetachment cross sections of hydrogen negative ions in the photoelectron energy region around the n = 2 excitation threshold by strongly affecting the evolution of near-threshold resonances.

  10. Comparison of hard-cylinder and screened Coulomb interactions in the modeling of supercoiled DNAs.

    PubMed

    Delrow, J J; Gebe, J A; Schurr, J M

    1997-10-05

    A 1000 base pair (bp) model supercoiled DNA is simulated using spherical screened Coulomb interactions between subunits on one hand and equivalent hard-cylinder interactions on the other. The amplitudes, or effective charges, of the spherical screened Coulomb electrostatic potentials are chosen so that the electrostatic potential surrounding the middle of a linear array of 2001 subunits (31.8 A diameter) closely matches the solution of the nonlinear Poisson-Boltzmann equation for a cylinder with 12 A radius and the full linear charge density of DNA at all distances beyond the 24 A hard-core diameter. This superposition of spherical screened Coulomb potentials is practically identical to the particular solution of the cylindrical linearized Poisson-Boltzmann equation that matches the solution of the nonlinear Poisson-Boltzmann equation at large distances. The interaction energy between subunits is reckoned from the effective charges according to the standard DLVO expression. The equivalent hard-cylinder diameter is chosen following Stigter's protocol for matching second virial coefficients, but for the full linear charge density of DNA. The electrostatic persistence length of the model with screened Coulomb interactions is extremely sensitive to the (arbitrarily) chosen subunit length at the higher salt concentrations. The persistence length of the hard-cylinder model is adjusted to match that of the screened Coulomb model for each ionic condition. Simulations for a superhelix density sigma = -0.05 using a spherical screened Coulomb interaction plus a 24 A hard-cylinder core (SCPHC) potential indicate that the radius of gyration of this 1000 bp DNA actually undergoes a slight increase as the NaCl concentration is raised from 0.01 to 1.0M. Thus, merely softening the potential from hard-cylinder to screened Coulomb form does not produce a large decrease in radius of gyration with increasing NaCl concentration for DNAs of this size. Radii of gyration, static structure

  11. Super-Coulombic atom-atom interactions in hyperbolic media

    NASA Astrophysics Data System (ADS)

    Cortes, Cristian L.; Jacob, Zubin

    2017-01-01

    Dipole-dipole interactions, which govern phenomena such as cooperative Lamb shifts, superradiant decay rates, Van der Waals forces and resonance energy transfer rates, are conventionally limited to the Coulombic near-field. Here we reveal a class of real-photon and virtual-photon long-range quantum electrodynamic interactions that have a singularity in media with hyperbolic dispersion. The singularity in the dipole-dipole coupling, referred to as a super-Coulombic interaction, is a result of an effective interaction distance that goes to zero in the ideal limit irrespective of the physical distance. We investigate the entire landscape of atom-atom interactions in hyperbolic media confirming the giant long-range enhancement. We also propose multiple experimental platforms to verify our predicted effect with phonon-polaritonic hexagonal boron nitride, plasmonic super-lattices and hyperbolic meta-surfaces as well. Our work paves the way for the control of cold atoms above hyperbolic meta-surfaces and the study of many-body physics with hyperbolic media.

  12. Super-Coulombic atom-atom interactions in hyperbolic media.

    PubMed

    Cortes, Cristian L; Jacob, Zubin

    2017-01-25

    Dipole-dipole interactions, which govern phenomena such as cooperative Lamb shifts, superradiant decay rates, Van der Waals forces and resonance energy transfer rates, are conventionally limited to the Coulombic near-field. Here we reveal a class of real-photon and virtual-photon long-range quantum electrodynamic interactions that have a singularity in media with hyperbolic dispersion. The singularity in the dipole-dipole coupling, referred to as a super-Coulombic interaction, is a result of an effective interaction distance that goes to zero in the ideal limit irrespective of the physical distance. We investigate the entire landscape of atom-atom interactions in hyperbolic media confirming the giant long-range enhancement. We also propose multiple experimental platforms to verify our predicted effect with phonon-polaritonic hexagonal boron nitride, plasmonic super-lattices and hyperbolic meta-surfaces as well. Our work paves the way for the control of cold atoms above hyperbolic meta-surfaces and the study of many-body physics with hyperbolic media.

  13. Coulomb interaction effects on the Majorana states in quantum wires.

    PubMed

    Manolescu, A; Marinescu, D C; Stanescu, T D

    2014-04-30

    The stability of the Majorana modes in the presence of a repulsive interaction is studied in the standard semiconductor wire-metallic superconductor configuration. The effects of short-range Coulomb interaction, which is incorporated using a purely repulsive δ-function to model the strong screening effect due to the presence of the superconductor, are determined within a Hartree-Fock approximation of the effective Bogoliubov-De Gennes Hamiltonian that describes the low-energy physics of the wire. Through a numerical diagonalization procedure we obtain interaction corrections to the single particle eigenstates and calculate the extended topological phase diagram in terms of the chemical potential and the Zeeman energy. We find that, for a fixed Zeeman energy, the interaction shifts the phase boundaries to a higher chemical potential, whereas for a fixed chemical potential this shift can occur either at lower or higher Zeeman energies. These effects can be interpreted as a renormalization of the g-factor due to the interaction. The minimum Zeeman energy needed to realize Majorana fermions decreases with the increasing strength of the Coulomb repulsion. Furthermore, we find that in wires with multi-band occupancy this effect can be enhanced by increasing the chemical potential, i.e. by occupying higher energy bands.

  14. Super-Coulombic atom–atom interactions in hyperbolic media

    PubMed Central

    Cortes, Cristian L.; Jacob, Zubin

    2017-01-01

    Dipole–dipole interactions, which govern phenomena such as cooperative Lamb shifts, superradiant decay rates, Van der Waals forces and resonance energy transfer rates, are conventionally limited to the Coulombic near-field. Here we reveal a class of real-photon and virtual-photon long-range quantum electrodynamic interactions that have a singularity in media with hyperbolic dispersion. The singularity in the dipole–dipole coupling, referred to as a super-Coulombic interaction, is a result of an effective interaction distance that goes to zero in the ideal limit irrespective of the physical distance. We investigate the entire landscape of atom–atom interactions in hyperbolic media confirming the giant long-range enhancement. We also propose multiple experimental platforms to verify our predicted effect with phonon–polaritonic hexagonal boron nitride, plasmonic super-lattices and hyperbolic meta-surfaces as well. Our work paves the way for the control of cold atoms above hyperbolic meta-surfaces and the study of many-body physics with hyperbolic media. PMID:28120826

  15. Dynamic screening of the three-body coulomb interactions

    NASA Astrophysics Data System (ADS)

    Zhang-jin, Chen

    1998-03-01

    The BBK approach is modified by the introduction of effective Sommerfeld parameters for both symmetric and asymmetric geometries, according to the fact that the strength of any particular two-body Coulomb interaction is affected by the presence of the third particle. The triple differential cross sections for electron impact ionization of atomic helium at incident energies of 40 and 50 eV in asymmetric geometry are calculated. Results of this approach are found to be in good agreement with the absolute measurements and the only existing theoretical results of the convergent close-coupling method.

  16. Mean Field Evolution of Fermions with Coulomb Interaction

    NASA Astrophysics Data System (ADS)

    Porta, Marcello; Rademacher, Simone; Saffirio, Chiara; Schlein, Benjamin

    2017-03-01

    We study the many body Schrödinger evolution of weakly coupled fermions interacting through a Coulomb potential. We are interested in a joint mean field and semiclassical scaling, that emerges naturally for initially confined particles. For initial data describing approximate Slater determinants, we prove convergence of the many-body evolution towards Hartree-Fock dynamics. Our result holds under a condition on the solution of the Hartree-Fock equation, that we can only show in a very special situation (translation invariant data, whose Hartree-Fock evolution is trivial), but that we expect to hold more generally.

  17. Slave rotor approach to dynamically screened Coulomb interactions in solids

    NASA Astrophysics Data System (ADS)

    Krivenko, I. S.; Biermann, S.

    2015-04-01

    Recent studies of dynamical screening of the electronic Coulomb interactions in solids have revived interest in lattice models of correlated fermions coupled to bosonic degrees of freedom (Hubbard-Holstein-type models). We propose a new dynamical mean-field-based approach to dynamically screened Coulomb interactions. In the effective Anderson-Holstein model, a transformation to slave rotors [S. Florens and A. Georges, Phys. Rev. B 66, 165111 (2002), 10.1103/PhysRevB.66.165111] is performed to decouple the dynamical part of the interaction. This transformation allows for a systematic derivation and analysis of recently introduced approximate schemes for the solution of dynamical impurity problems, in particular, the Bose factor ansatz within the dynamic atomic limit approximation (DALA) with and without Lang-Firsov correction. More importantly still, it suggests an optimized choice for a Bose factor in the sense of the variational principle of Feynman and Peierls. We demonstrate the accuracy of our scheme and present a comparison to calculations within the DALA.

  18. Inter-ion coulomb interactions in a magneto-optical trap ion source

    NASA Astrophysics Data System (ADS)

    Steele, A. V.; Knuffman, B.; McClelland, J. J.

    2011-05-01

    We have investigated the role played by inter-ion Coulomb interactions in a magneto-optical trap ion source (MOTIS). Using a Monte Carlo simulation accounting for all pair-wise ion-ion Coulomb interactions in the source, we have calculated the broadening of the transverse spatial and velocity distributions as well as the increase in emittance over a range of beam currents and extraction electric fields. Using a 7Li MOTIS, we have experimentally studied the broadening of the spatial distribution as a function of total beam current and extraction electric field by measuring the fraction of the beam current that passes through a 20 μm diameter aperture. The Monte Carlo simulations agree well with the experimental results, indicating that such simulations capture the essential physics of the source. Our results show that while Coulomb interactions can cause a significant increase in emittance in some situations, it is possible to keep the effects to an acceptable level by suitable choice of extraction field and beam current. These considerations are essential to the process of optimizing MOTIS geometry and operating conditions for use in high-resolution focused ion beam applications.

  19. Local molecular field theory for effective attractions between like charged objects in systems with strong Coulomb interactions.

    PubMed

    Chen, Yng-Gwei; Weeks, John D

    2006-05-16

    Strong, short-ranged positional correlations involving counterions can induce a net attractive force between negatively charged strands of DNA and lead to the formation of ion pairs in dilute ionic solutions. However, the long range of the Coulomb interactions impedes the development of a simple local picture. We address this general problem by mapping the properties of a nonuniform system with Coulomb interactions onto those of a simpler system with short-ranged intermolecular interactions in an effective external field that accounts for the averaged effects of appropriately chosen long-ranged and slowly varying components of the Coulomb interactions. The remaining short-ranged components combine with the other molecular core interactions and strongly affect pair correlations in dense or strongly coupled systems. We show that pair correlation functions in the effective short-ranged system closely resemble those in the uniform primitive model of ionic solutions and illustrate the formation of ion pairs and clusters at low densities. The theory accurately describes detailed features of the effective attraction between two equally charged walls at strong coupling and intermediate separations of the walls. Analytical results for the minimal coupling strength needed to get any attraction and for the separation at which the attractive force is a maximum are presented.

  20. Coulomb interaction effect in tilted Weyl fermion in two dimensions

    NASA Astrophysics Data System (ADS)

    Isobe, Hiroki; Nagaosa, Naoto

    Weyl fermions with tilted linear dispersions characterized by several different velocities appear in some systems including the quasi-two-dimensional organic semiconductor α-(BEDT-TTF)2I3 and three-dimensional WTe2. The Coulomb interaction between electrons modifies the velocities in an essential way in the low energy limit, where the logarithmic corrections dominate. Taking into account the coupling to both the transverse and longitudinal electromagnetic fields, we derive the renormalization group equations for the velocities of the tilted Weyl fermions in two dimensions, and found that they increase as the energy decreases and eventually hit the velocity of light c to result in the Cherenkov radiation. Especially, the system restores the isotropic Weyl cone even when the bare Weyl cone is strongly tilted and the velocity of electrons becomes negative in certain directions.

  1. Effects of Coulomb Interactions on Disordered Two-Dimensional Systems.

    NASA Astrophysics Data System (ADS)

    Green, Mark Christopher

    This dissertation is divided into two parts. Part I examines the effects of screening by a metallic electrode on the Coulomb gap, and related properties. The computer model restricts electrons to the lattice points of a two -dimensional square lattice. Disorder results from a random potential energy assigned to each lattice site. Screening is by image charges resulting from a simulated metal plate placed at a distance h/2 from the electron surface, with image charges a distance h from the electrons. The results show the single-particle density of states and the single-particle density of excitations as a function of the distance h. Part II relates to recent experiments on mesoscopic metal-oxide semiconductor field effect transistors ^* (MOSFETs). The experimental results show sharp peaks in the source-drain current as a function of the gate voltage. The peaks are believed to be due to coherent tunneling between the source and drain electrodes, via a localized state near the center. The structure of such peaks at low temperatures is expected to be Lorentzian, but the observed peaks had a non-Lorentzian character, and also exhibited resolvable secondary peaks on the shoulders of the main peak. These features were interpreted as due to Coulomb interactions between the tunneling site and electrons which may enter or exit the localized states during the experiment and excitations internal to the system. We have performed computer simulations based upon the above model. The results, while not entirely conclusive, seemed to verify the approach taken. ftn^dag Supported in part by the San Diego Supercomputer Center. ^SSupported in part by TRW, Space and Defense Sector. *A. B. Fowler, G. L. Timp, J. J. Wainer and R. A. Webb, Phys. Rev. Lett. 57, 138 (1986).

  2. Amorphous silica modeled with truncated and screened Coulomb interactions: A molecular dynamics simulation study

    NASA Astrophysics Data System (ADS)

    Carré, Antoine; Berthier, Ludovic; Horbach, Jürgen; Ispas, Simona; Kob, Walter

    2007-09-01

    We show that finite-range alternatives to the standard long-range pair potential for silica by van Beest et al. [Phys. Rev. Lett. 64, 1955 (1990)] might be used in molecular dynamics simulations. We study two such models that can be efficiently simulated since no Ewald summation is required. We first consider the Wolf method, where the Coulomb interactions are truncated at a cutoff distance rc such that the requirement of charge neutrality holds. Various static and dynamic quantities are computed and compared to results from simulations using Ewald summations. We find very good agreement for rc≈10Å. For lower values of rc, the long-range structure is affected which is accompanied by a slight acceleration of dynamic properties. In a second approach, the Coulomb interaction is replaced by an effective Yukawa interaction with two new parameters determined by a force fitting procedure. The same trend as for the Wolf method is seen. However, slightly larger cutoffs have to be used in order to obtain the same accuracy with respect to static and dynamic quantities as for the Wolf method.

  3. Distance dependence and salt sensitivity of pairwise, coulombic interactions in a protein

    PubMed Central

    Lee, Kelly K.; Fitch, Carolyn A.; García-Moreno E., Bertrand

    2002-01-01

    Histidine pKa values were measured in charge-reversal (K78E, K97E, K127E, and K97E/K127E) and charge-neutralization (E10A, E101A, and R35A) mutants of staphylococcal nuclease (SNase) by 1H-NMR spectroscopy. Energies of interaction between pairs of charges (ΔGij) were obtained from the shifts in pKa values relative to wild-type values. The data describe the distance dependence and salt sensitivity of pairwise coulombic interactions. Calculations with a continuum electrostatics method captured the experimental ΔGij when static structures were used and when the protein interior was treated empirically with a dielectric constant of 20. The ΔGij when rij ≤ 10 Å were exaggerated slightly in the calculations. Coulomb's law with a dielectric constant near 80 and a Debye-Hückel term to account for screening by the ionic strength reproduced the salt sensitivity and distance dependence of ΔGij as well as the structure-based method. In their interactions with each other, surface charges behave as if immersed in water; the Debye length describes realistically the distance where interactions become negligible at a given ionic strength. On average, charges separated by distances (rij) ≈5 Å interacted with ΔGij ≈ 0.6 kcal/mole in 0.01 M KCl, but ΔGij decayed to ≤0.10 kcal/mole when rij = 20 Å. In 0.10 M KCl, ΔGij ≈ 0.10 kcal/mole when rij = 10 Å. In 1.5 M KCl, only short-range interactions with rij ≤ 5 Å persisted. Although at physiological ionic strengths the interactions between charges separated by more than 10 Å are extremely weak, in situations where charge imbalance exists many weak interactions can cumulatively produce substantial effects. PMID:11967358

  4. Resonance tuning due to Coulomb interaction in strong near-field coupled metamaterials

    SciTech Connect

    Roy Chowdhury, Dibakar; Xu, Ningning; Zhang, Weili; Singh, Ranjan

    2015-07-14

    Coulomb's law is one of the most fundamental laws of physics that describes the electrostatic interaction between two like or unlike point charges. Here, we experimentally observe a strong effect of Coulomb interaction in tightly coupled terahertz metamaterials where the split-ring resonator dimers in a unit cell are coupled through their near fields across the capacitive split gaps. Using a simple analytical model, we evaluated the Coulomb parameter that switched its sign from negative to positive values indicating the transition in the nature of Coulomb force from being repulsive to attractive depending upon the near field coupling between the split ring resonators. Apart from showing interesting effects in the strong coupling regime between meta-atoms, Coulomb interaction also allows an additional degree of freedom to achieve frequency tunable dynamic metamaterials.

  5. Phase Competition and Superconductivity in κ-(BEDT-TTF)2X: Importance of Intermolecular Coulomb Interactions

    NASA Astrophysics Data System (ADS)

    Watanabe, Hiroshi; Seo, Hitoshi; Yunoki, Seiji

    2017-03-01

    We theoretically study the competition among different electronic phases in molecular conductors κ-(BEDT-TTF)2X. The ground-state properties of a 3/4-filled extended Hubbard model with the κ-type geometry are investigated by a variational Monte Carlo method. We find various competing phases: dimer-Mott insulator, polar charge-ordered insulator, 3-fold charge-ordered metal, and superconductivity, whose pairing symmetry is an "extended-s + dx2 - y2"-wave type. Our results show that the superconducting phase is stabilized not on the verge of the Mott metal-insulator transition but near charge order instabilities, clearly indicating the importance of the intradimer charge degree of freedom and the intermolecular Coulomb interactions, beyond the simple description of the half-filled Hubbard model.

  6. Separable wave equation for three Coulomb interacting particles

    NASA Astrophysics Data System (ADS)

    Colavecchia, F. D.; Gasaneo, G.; Garibotti, C. R.

    1998-02-01

    We consider a separable approximation to the Schrödinger equation for the three-body Coulomb problem and found its exact solution above the ionization threshold. This wave function accounts for different possible asymptotic behaviors and reduces to the well-known product of three two-body Coulomb waves (C3) for scattering conditions. The momenta and position-dependent modifications recently proposed for the Sommerfeld parameters, as an improvement to the C3 model, are analyzed. We show how these changes can be included in our model as a suitable physically based variations in the separable approximation for the wave equation.

  7. High-T C superconductivity in Cs3C60 compounds governed by local Cs-C60 Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Harshman, Dale R.; Fiory, Anthony T.

    2017-04-01

    Unique among alkali-doped A 3C60 fullerene compounds, the A15 and fcc forms of Cs3C60 exhibit superconducting states varying under hydrostatic pressure with highest transition temperatures at T\\text{C}\\text{meas}   =  38.3 and 35.2 K, respectively. Herein it is argued that these two compounds under pressure represent the optimal materials of the A 3C60 family, and that the C60-associated superconductivity is mediated through Coulombic interactions with charges on the alkalis. A derivation of the interlayer Coulombic pairing model of high-T C superconductivity employing non-planar geometry is introduced, generalizing the picture of two interacting layers to an interaction between charge reservoirs located on the C60 and alkali ions. The optimal transition temperature follows the algebraic expression, T C0  =  (12.474 nm2 K)/ℓζ, where ℓ relates to the mean spacing between interacting surface charges on the C60 and ζ is the average radial distance between the C60 surface and the neighboring Cs ions. Values of T C0 for the measured cation stoichiometries of Cs3-x C60 with x  ≈  0 are found to be 38.19 and 36.88 K for the A15 and fcc forms, respectively, with the dichotomy in transition temperature reflecting the larger ζ and structural disorder in the fcc form. In the A15 form, modeled interacting charges and Coulomb potential e2/ζ are shown to agree quantitatively with findings from nuclear-spin relaxation and mid-infrared optical conductivity. In the fcc form, suppression of T\\text{C}\\text{meas} below T C0 is ascribed to native structural disorder. Phononic effects in conjunction with Coulombic pairing are discussed.

  8. High-T C superconductivity in Cs3C60 compounds governed by local Cs-C60 Coulomb interactions.

    PubMed

    Harshman, Dale R; Fiory, Anthony T

    2017-04-12

    Unique among alkali-doped A 3C60 fullerene compounds, the A15 and fcc forms of Cs3C60 exhibit superconducting states varying under hydrostatic pressure with highest transition temperatures at [Formula: see text]  =  38.3 and 35.2 K, respectively. Herein it is argued that these two compounds under pressure represent the optimal materials of the A 3C60 family, and that the C60-associated superconductivity is mediated through Coulombic interactions with charges on the alkalis. A derivation of the interlayer Coulombic pairing model of high-T C superconductivity employing non-planar geometry is introduced, generalizing the picture of two interacting layers to an interaction between charge reservoirs located on the C60 and alkali ions. The optimal transition temperature follows the algebraic expression, T C0  =  (12.474 nm(2) K)/ℓζ, where ℓ relates to the mean spacing between interacting surface charges on the C60 and ζ is the average radial distance between the C60 surface and the neighboring Cs ions. Values of T C0 for the measured cation stoichiometries of Cs3-x C60 with x  ≈  0 are found to be 38.19 and 36.88 K for the A15 and fcc forms, respectively, with the dichotomy in transition temperature reflecting the larger ζ and structural disorder in the fcc form. In the A15 form, modeled interacting charges and Coulomb potential e(2)/ζ are shown to agree quantitatively with findings from nuclear-spin relaxation and mid-infrared optical conductivity. In the fcc form, suppression of [Formula: see text] below T C0 is ascribed to native structural disorder. Phononic effects in conjunction with Coulombic pairing are discussed.

  9. Coulomb-tail effect of electron-electron interaction on nonsequential double ionization

    NASA Astrophysics Data System (ADS)

    Zhou, Yueming; Huang, Cheng; Lu, Peixiang

    2011-08-01

    With the classical ensemble model, we investigate the manifestations of the Coulomb tail of electron-electron interaction in nonsequential double ionization by comparing the results from the short-range electron-electron interaction with those from the Coulombic electron-electron interaction. At the intensity below the recollision threshold, the two-electron momentum distributions in the direction parallel to the laser polarization show an anticorrelated behavior for the Coulombic electron-electron interaction while a correlated behavior for the short-range interaction, which indicates the responsibility of the Coulomb tail of the electron-electron interaction for the experimentally observed anticorrelated emission [Y. Liu, S. Tschuch, A. Rudenko, M. Durr, M. Siegel, U. Morgner, R. Moshammer, and J. Ullrich, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.101.053001 101, 053001 (2008)]. In the transverse direction, for the Coulombic electron-electron interaction, the two electrons exhibit no effect of repulsion at an intensity below the recollision threshold while a strong repulsion effect at an intensity above the threshold, which becomes weaker as the laser intensity further increases. Back analysis shows that the role of the Coulomb tail of electron-electron interaction leads asymmetric energy sharing (AES) to be prevalent at recollision. This AES results in the two electrons leaving the ion at different times or with different initial momenta, which is responsible for the anticorrelated behavior in the parallel direction and the intensity-dependent repulsion effect in the transverse direction.

  10. Coulomb-tail effect of electron-electron interaction on nonsequential double ionization

    SciTech Connect

    Zhou Yueming; Huang Cheng; Lu Peixiang

    2011-08-15

    With the classical ensemble model, we investigate the manifestations of the Coulomb tail of electron-electron interaction in nonsequential double ionization by comparing the results from the short-range electron-electron interaction with those from the Coulombic electron-electron interaction. At the intensity below the recollision threshold, the two-electron momentum distributions in the direction parallel to the laser polarization show an anticorrelated behavior for the Coulombic electron-electron interaction while a correlated behavior for the short-range interaction, which indicates the responsibility of the Coulomb tail of the electron-electron interaction for the experimentally observed anticorrelated emission [Y. Liu, S. Tschuch, A. Rudenko, M. Durr, M. Siegel, U. Morgner, R. Moshammer, and J. Ullrich, Phys. Rev. Lett. 101, 053001 (2008)]. In the transverse direction, for the Coulombic electron-electron interaction, the two electrons exhibit no effect of repulsion at an intensity below the recollision threshold while a strong repulsion effect at an intensity above the threshold, which becomes weaker as the laser intensity further increases. Back analysis shows that the role of the Coulomb tail of electron-electron interaction leads asymmetric energy sharing (AES) to be prevalent at recollision. This AES results in the two electrons leaving the ion at different times or with different initial momenta, which is responsible for the anticorrelated behavior in the parallel direction and the intensity-dependent repulsion effect in the transverse direction.

  11. Effective pairing interactions with isospin density dependence

    SciTech Connect

    Margueron, J.; Sagawa, H.; Hagino, K.

    2008-05-15

    We perform Hartree-Fock-Bogoliubov (HFB) calculations for semi-magic calcium, nickel, tin, and lead isotopes and N=20,28,50, and 82 isotones using density-dependent pairing interactions recently derived from a microscopic nucleon-nucleon interaction. These interactions have an isovector component so that the pairing gaps in symmetric and neutron matter are reproduced. Our calculations well account for the experimental data for the neutron number dependence of binding energy, two-neutron separation energy, and odd-even mass staggering of these isotopes. This result suggests that by introducing the isovector term in the pairing interaction, one can construct a global effective pairing interaction that is applicable to nuclei in a wide range of the nuclear chart. It is also shown with the local density approximation that the pairing field deduced from the pairing gaps in infinite matter reproduces qualitatively well the pairing field for finite nuclei obtained with the HFB method.

  12. Isospin effect of Coulomb interaction on the dissipation and fragmentation in intermediate energy heavy ion collisions

    SciTech Connect

    Liu Jianye; Guo Wenjun; Gao Yuanyi; Xing Yongzhong; Li Xiguo

    2004-09-01

    We investigate separately the isospin effects of Coulomb interaction and symmetry potential on the dissipation and fragmentation in the intermediate energy heavy ion collisions by using isospin-dependent quantum molecular dynamics model. The calculated results show that the Coulomb interaction induces the reductions of both isospin fractionation ratio and nuclear stopping (momentum dissipation). However, the Coulomb interaction not only does not change obviously the strong isospin effect of the symmetry potential on the isospin fractionation ratio but also does not change obviously that of in-medium two-body collision on the nuclear stopping. On the contrary, the symmetry potential induces the enhancement of the isospin fractionation ratio but it is insensitive to the nuclear stopping. Finally, the competition between the Coulomb interaction and symmetry potential induces the reductions of both isospin fractionation ratio and nuclear stopping for two forms of symmetry potentials in this paper.

  13. Coulomb-interaction-dependent effect of high-order sideband generation in an optomechanical system

    NASA Astrophysics Data System (ADS)

    Kong, Cui; Xiong, Hao; Wu, Ying

    2017-03-01

    High-order sideband generation in an optomechanical system coupled to a charged object is discussed, and the features of Coulomb-interaction-dependent effect are identified. We show that the Coulomb-interaction-dependent effect of high-order sideband generation exhibits essential difference between the case of weak control field and strong control field. In the weak control field case, the output spectra are in the perturbative regime and there is hardly any Coulomb-interaction-dependent effect in an optomechanical system coupling to an object with a small amount of charge. In the strong control field case, the output spectra are in the nonperturbative regime and robust Coulomb-interaction-dependent effect arises even if there are few charges. The amplitudes of specific sidebands are also discussed, and it is shown that Coulomb interaction plays an important role in achieving optomechanical control. Due to the extremely sensitive charge number, the Coulomb-interaction-dependent effect of high-order sideband generation is remarkable in many aspects and may be used to precision measurement of electrical charges beyond the linearized optomechanical interaction.

  14. The effect of Coulomb interactions on thermoelectric properties of quantum dots

    NASA Astrophysics Data System (ADS)

    Zimbovskaya, Natalya; Kuzmin, Valery

    2014-03-01

    Thermoelectric effects in a quantum dot coupled to the source and drain charge reservoirs are explored using a nonequilibrium Green's functions formalism beyond the Hartree-Fock approxomation. We concentrate on theoretical analysis of the influence of Coulomb interactions on thermopower and the figure of merit ZT . Obtained results show that Coulomb interactions between charge carriers on the dot significantly contribute to its thermoelectric properties. In the present work, we trace the transition from the Coulomb blockade regime to Kondo regime in the thermoelectric properties of the quantum dot which occurs when we gradually strengthen the coupling of the dot to the charge reservoirs. We show that within the Coulomb blockade regime (when the coupling of the dot to the leads is weak compared to the characteristic strength of the charge carriers interactions) thermoelectric characteristics of the dot display distinct features caused by Coulomb interactions. These features indicate possibilities of enhancement of thermoelectric efficiency of the considered systems. Within the Kondo regime, when the couplings of the dot to the leads became stronger, the influence of Coulomb interactions declines bringing a decrease in the the thermoelectric efficiency.

  15. Effects of coulomb repulsion on conductivity of heterojunction carbon nanotube quantum dots with spin-orbital coupling and interacting leads

    NASA Astrophysics Data System (ADS)

    Ogloblya, O. V.; Kuznietsova, H. M.; Strzhemechny, Y. M.

    2017-01-01

    We performed numerical studies for the conductance of a heterojunction carbon nanotube quantum dot (QD) with an extra spin orbital quantum number and a conventional QD in which the electron state is determined only by the spin quantum number. Our computational approach took into account the spin-orbit interaction and the Coulomb repulsion both between electrons on a QD as well as between the QD electron and the contacts. We utilized an approach based on the Keldysh non-equilibrium Green's function formalism as well as the equation of motion technique. We focused on the case of a finite Coulombic on-site repulsion and considered two possible cases of applied voltage: spin bias and conventional bias. For the system of interest we obtained bias spectroscopy diagrams, i.e. contour charts showing dependence of conductivity on two variables - voltage and the energy level position in a QD - which can be controlled by the plunger gate voltage. The finite Coulombic repulsion splits the density of states into two distinct maxima with the energy separation between them controlled by that parameter. It was also shown that an increase of either the value of the on-site Coulomb repulsion in a QD or the parameter of the Coulomb repulsion between the electrons in the QD and the contacts leads to an overall shift of the density of electronic states dependence toward higher energy values. Presence of the QD-lead interaction yields formation of a new pair of peaks in the differential conductance dependence. We also show that existence of four quantum states in a QD leads to abrupt changes in the density of states. These results could be beneficial for potential applications in nanotube-based amperometric sensors.

  16. Interplay between on-site electron-phonon interaction and inter-site Coulomb repulsion

    SciTech Connect

    Nath, S.; Mondal, N. S.; Roy, K.; Ghosh, N. K.

    2016-05-23

    We present a numerical study on the interplay between on-site electron-phonon (EP) interaction and inter-site Coulomb repulsion in the U/t =0.0 limit on a small cluster. Results show the formation of only S0 bipolarons. However, two polarons or bipolarons can be present at distances |i-j|=2. It is observed that inter-site Coulomb repulsion may favor formation of S0 bipolarons.

  17. Wave operator in few-body quantum scattering with Coulomb-like interactions

    SciTech Connect

    Kroeger, H.

    1985-01-01

    Functional analytical methods like strong approximation of operator-valued functions and Dunfords' calculus are applied to yield a contour integral representation with a finite contour of wave operators for nonrelativistic potential scattering with Coulomb and short-range interactions, which avoids high singularities of Coulomb-like Green's functions of stationary scattering theory. The Green's function is the unique solution of the resolvent equation, which has an A-proper kernel allowing projector methods for its solution.

  18. Investigation of coulomb and pairing effects using new developed empirical formulas for proton-induced reaction cross sections

    SciTech Connect

    Tel, E. Aydin, E. G.; Aydin, A.; Kaplan, A.; Boeluekdemir, M. H.; Okuducu, S.

    2010-03-15

    We have investigated Coulomb and pairing effects by using new empirical formulas including the new coefficients for (p, {alpha}) at 17.9 MeV, (p, np) at 22.3 MeV, and (p, n{alpha}) at 24.8 and 28.5 MeV energies. A new formula is obtained by adjusting Levkovskii's original asymmetry parameter formula and also Tel et al. formula for proton-induced reactions. The new coefficients by using least-squares fitting method for the reactions are determined. In addition, the findings of the present study are compared with the available experimental data.

  19. Solution of two-body relativistic bound state equations with confining plus Coulomb interactions

    NASA Technical Reports Server (NTRS)

    Maung, Khin Maung; Kahana, David E.; Norbury, John W.

    1992-01-01

    Studies of meson spectroscopy have often employed a nonrelativistic Coulomb plus Linear Confining potential in position space. However, because the quarks in mesons move at an appreciable fraction of the speed of light, it is necessary to use a relativistic treatment of the bound state problem. Such a treatment is most easily carried out in momentum space. However, the position space Linear and Coulomb potentials lead to singular kernels in momentum space. Using a subtraction procedure we show how to remove these singularities exactly and thereby solve the Schroedinger equation in momentum space for all partial waves. Furthermore, we generalize the Linear and Coulomb potentials to relativistic kernels in four dimensional momentum space. Again we use a subtraction procedure to remove the relativistic singularities exactly for all partial waves. This enables us to solve three dimensional reductions of the Bethe-Salpeter equation. We solve six such equations for Coulomb plus Confining interactions for all partial waves.

  20. Interplay between short-range correlated disorder and Coulomb interaction in nodal-line semimetals

    NASA Astrophysics Data System (ADS)

    Wang, Yuxuan; Nandkishore, Rahul M.

    2017-09-01

    In nodal-line semimetals, Coulomb interactions and short-range correlated disorder are both marginal perturbations to the clean noninteracting Hamiltonian. We analyze their interplay using a weak-coupling renormalization group approach. In the clean case, the Coulomb interaction has been found to be marginally irrelevant, leading to Fermi liquid behavior. We extend the analysis to incorporate the effects of disorder. The nodal line structure gives rise to kinematical constraints similar to that for a two-dimensional Fermi surface, which plays a crucial role in the one-loop renormalization of the disorder couplings. For a twofold degenerate nodal loop (Weyl loop), we show that disorder flows to strong coupling along a unique fixed trajectory in the space of symmetry inequivalent disorder couplings. Along this fixed trajectory, all symmetry inequivalent disorder strengths become equal. For a fourfold degenerate nodal loop (Dirac loop), disorder also flows to strong coupling, however, the strengths of symmetry inequivalent disorder couplings remain different. We show that feedback from disorder reverses the sign of the beta function for the Coulomb interaction, causing the Coulomb interaction to flow to strong coupling as well. However, the Coulomb interaction flows to strong coupling asymptotically more slowly than disorder. Extrapolating our results to strong coupling, we conjecture that at low energies nodal line semimetals should be described by a noninteracting nonlinear sigma model. We discuss the relation of our results with possible many-body localization at zero temperatures in such materials.

  1. Influence of the Coulomb interaction on the exchange coupling in granular magnets

    NASA Astrophysics Data System (ADS)

    Udalov, O. G.; Beloborodov, I. S.

    2017-04-01

    We develop a theory of the exchange interaction between ferromagnetic (FM) metallic grains embedded into insulating matrix by taking into account the Coulomb blockade effects. For bulk ferromagnets separated by the insulating layer the exchange interaction strongly depends on the height and thickness of the tunneling barrier created by the insulator. We show that for FM grains embedded into insulating matrix the exchange coupling additionally depends on the dielectric properties of this matrix due to the Coulomb blockade effects. In particular, the FM coupling decreases with decreasing the dielectric permittivity of insulating matrix. We find that the change in the exchange interaction due to the Coulomb blockade effects can be a few tens of percent. Also, we study dependence of the intergrain exchange interaction on the grain size and other parameters of the system.

  2. Coexistence and competition of on-site and intersite Coulomb interactions in Mott-molecular-dimers

    NASA Astrophysics Data System (ADS)

    Juliano, R. C.; de Arruda, A. S.; Craco, L.

    2016-02-01

    We reveal the interplay between on-site (U) and intersite (V) Coulomb interactions in the extended two-site Hubbard model. Due to its atomic-like form quantum correlations intrinsic to Mott-molecular-dimers are exactly computed. Our results for physical quantities such as double occupancy and specific heat are consistent with those obtained for the one-band Hubbard model, suggesting that a two-site dimer model is able to capture the essential thermodynamic properties of strongly interacting electron systems. It is noted that intersite Coulomb interactions promote the formation of doublons, which compete with the spin-singlet state induced by the on-site Coulomb repulsion. Our results are expected to be relevant for understanding electronic and thermodynamical properties of interacting electrons in systems with strongly coupled magnetic atoms.

  3. Influence of the Coulomb interaction on the exchange coupling in granular magnets.

    PubMed

    Udalov, O G; Beloborodov, I S

    2017-04-20

    We develop a theory of the exchange interaction between ferromagnetic (FM) metallic grains embedded into insulating matrix by taking into account the Coulomb blockade effects. For bulk ferromagnets separated by the insulating layer the exchange interaction strongly depends on the height and thickness of the tunneling barrier created by the insulator. We show that for FM grains embedded into insulating matrix the exchange coupling additionally depends on the dielectric properties of this matrix due to the Coulomb blockade effects. In particular, the FM coupling decreases with decreasing the dielectric permittivity of insulating matrix. We find that the change in the exchange interaction due to the Coulomb blockade effects can be a few tens of percent. Also, we study dependence of the intergrain exchange interaction on the grain size and other parameters of the system.

  4. Production of low kinetic energy electrons and energetic ion pairs by Intermolecular Coulombic Decay.

    PubMed

    Hergenhahn, Uwe

    2012-12-01

    The paper gives an introduction into Interatomic and Intermolecular Coulombic Decay (ICD). ICD is an autoionization process, which contrary to Auger decay involves neighbouring sites of the initial vacancy as an integral part of the decay transition. As a result of ICD, slow electrons are produced which generally are known to be active in radiation damage. The author summarizes the properties of ICD and reviews a number of important experiments performed in recent years. Intermolecular Coulombic Decay can generally take place in weakly bonded aggregates in the presence of ionizing particles or ionizing radiation. Examples collected here mostly use soft X-rays produced by synchrotron radiation to ionize, and use rare-gas clusters, water clusters or solutes in a liquid jet to observe ICD after irradiation. Intermolecular Coulombic Decay is initiated by single ionization into an excited state. The subsequent relaxation proceeds via an ultra-fast energy transfer to a neighbouring site, where a second ionization occurs. Secondary electrons from ICD have clearly been identified in numerous systems. ICD can take place after primary ionization, as the second step of a decay cascade which also involves Auger decay, or after resonant excitation with an energy which exceeds the ionization potential of the system. ICD is expected to play a role whenever particles or radiation with photon energies above the ionization energies for inner valence electrons are present in weakly bonded matter, e.g., biological tissue. The process produces at the same time a slow electron and two charged atomic or molecular fragments, which will lead to structural changes around the ionized site.

  5. Coulomb interactions and the metal-insulator transition in p-SiGe

    NASA Astrophysics Data System (ADS)

    Coleridge, P. T.; Lapointe, J.; Williams, R. L.; Zawadzki, P.

    2001-10-01

    Magnetoresistance data in p-SiGe samples is analysed using the Renormalisation Group theories of Finkel'stein and Castellani et al. The interaction parameter, γ2 is found to be of order one or larger than one, sufficient to explain the metallic behaviour in terms of delocalising Coulomb interaction corrections.

  6. Theoretical study of interplay between coulomb interaction and electron occupancy in graphene in ferromagnetic state

    NASA Astrophysics Data System (ADS)

    Swain, Rashmirekha; Sahu, Sivabrata; Rout, G. C.

    2017-05-01

    We report here a microscopic tight binding theoretical model study of ferromagnetism in graphene taking into account of substrate effect and Coulomb interaction in both the sub-lattices of the honeycomb lattice. The Coulomb interaction is treated here within mean-field approximation giving rise to the ferromagnetic magnetization under different electron occupancies of graphene. The temperature dependent ferromagnetic magnetization is calculated from the electron co-relations obtained from the electron Green's functions. It is observed that ferromagnetic gap displaces sudden change for different electron occupancies separating paramagnetic from the ferromagnetic phase. The effect of on-site Coulomb interaction energy, electron occupancy and temperature on ferromagnetic gap is investigated and is reported in this communication.

  7. Probing interband coulomb interactions in semiconductor nanostructures with 2D double-quantum coherence spectroscopy.

    PubMed

    Velizhanin, Kirill A; Piryatinski, Andrei

    2011-05-12

    Employing the interband exciton scattering model, we have derived a closed set of equations determining the 2D double-quantum coherence signal sensitive to the interband Coulomb interactions (i.e., many-body Coulomb interactions leading to the couplings between exciton and biexciton bands) in semiconductor nanostructures such as nanocrystals, quantum wires, wells, and carbon nanotubes. Our general analysis of 2D double-quantum coherence resonances has demonstrated that the interband Coulomb interactions lead to new cross-peaks whose appearance can be interpreted as a result of exciton and biexciton state mixing. The presence of the strongly coupled resonant states and weakly coupled background of off-resonant states can significantly simplify cross-peak analysis by eliminating the congested background spectrum. Our simulations of the 2D double-quantum coherence signal in PbSe NCs have validated this approach.

  8. Limits on Lorentz Invariance Violation from Coulomb Interactions in Nuclei and Atoms.

    PubMed

    Flambaum, V V; Romalis, M V

    2017-04-07

    Anisotropy in the speed of light that has been constrained by Michelson-Morley-type experiments also generates anisotropy in the Coulomb interactions. This anisotropy can manifest itself as an energy anisotropy in nuclear and atomic experiments. Here the experimental limits on Lorentz violation in _{10}^{21}Ne are used to improve the limits on Lorentz symmetry violations in the photon sector, namely, the anisotropy of the speed of light and the Coulomb interactions, by 7 orders of magnitude in comparison with previous experiments: the speed of light is isotropic to a part in 10^{28}.

  9. Effects of the Lorentz Invariance Violation on Coulomb Interactions in Nuclei and Atoms

    NASA Astrophysics Data System (ADS)

    Flambaum, V. V.; Romalis, M. V.

    2017-04-01

    Anisotropy in the speed of light that has been constrained by Michelson-Morley-type experiments also generates anisotropy in the Coulomb interactions. This anisotropy can manifest itself as an energy anisotropy in nuclear and atomic experiments. Here the experimental limits on Lorentz violation in Ne2110 are used to improve the limits on Lorentz symmetry violations in the photon sector, namely, the anisotropy of the speed of light and the Coulomb interactions, by 7 orders of magnitude in comparison with previous experiments: the speed of light is isotropic to a part in 10-28.

  10. Effect of interedge Coulomb interactions on the transport between quantum Hall edge states

    NASA Astrophysics Data System (ADS)

    Moon, K.; Girvin, S. M.

    1996-08-01

    In a recent experiment, Milliken et al. demonstrated possible evidence for a Luttinger liquid through measurements of the tunneling conductance between edge states in the ν=1/3 quantum Hall plateau. However, at low temperatures, a discrepancy exists between the theoretical predictions based on Luttinger liquid theory and experiment. We consider the possibility that this is due to long-range Coulomb interactions, which become dominant at low temperatures. Using renormalization-group methods, we calculate the crossover behavior from Luttinger liquid to the Coulomb interaction dominated regime. The crossover behavior thus obtained seems to resolve one of the discrepancies, yielding good agreement with experiment.

  11. Nonconventional screening of the Coulomb interaction in FexOy clusters: An ab initio study

    NASA Astrophysics Data System (ADS)

    Peters, L.; Şaşıoǧlu, E.; Rossen, S.; Friedrich, C.; Blügel, S.; Katsnelson, M. I.

    2017-04-01

    From microscopic point-dipole model calculations of the screening of the Coulomb interaction in nonpolar systems by polarizable atoms, it is known that screening strongly depends on dimensionality. For example, in one-dimensional systems, the short-range interaction is screened, while the long-range interaction is antiscreened. This antiscreening is also observed in some zero-dimensional structures, i.e., molecular systems. By means of ab initio calculations in conjunction with the random-phase approximation (RPA) within the FLAPW method, we study screening of the Coulomb interaction in FexOy clusters. For completeness, these results are compared with their bulk counterpart magnetite. It appears that the on-site Coulomb interaction is very well screened both in the clusters and bulk. On the other hand, for the intersite Coulomb interaction, the important observation is made that it is almost constant throughout the clusters, while for the bulk it is almost completely screened. More precisely and interestingly, in the clusters antiscreening is observed by means of ab initio calculations.

  12. Hydrodynamic interactions between pairs of colloidal spheres

    NASA Astrophysics Data System (ADS)

    Parmley, Samantha J.; Ou-Yang, H. Daniel

    1998-03-01

    The use of optical tweezers is becoming a standard technique for probing the colloidal environment and much recent work has been focused on colloidal interactions. We report on a novel method for studying the pair interaction between colloidal particles. We currently use phase lock-in methods to make dynamic measurements of a microsphere held and oscillated by laser tweezers. By using a second tweezers to fix a particle near the oscillating particle one can measure the pair interaction by observing the change in the dynamics. In this presentation we will demonstrate the capability of this method by measurement of the hydrodynamic interaction between pairs of polystyrene microspheres as a function of interparticle spacing. We expect to extend this technique to measure general colloidal interactions.

  13. Optimal Hubbard models for materials with nonlocal Coulomb interactions: graphene, silicene, and benzene.

    PubMed

    Schüler, M; Rösner, M; Wehling, T O; Lichtenstein, A I; Katsnelson, M I

    2013-07-19

    To understand how nonlocal Coulomb interactions affect the phase diagram of correlated electron materials, we report on a method to approximate a correlated lattice model with nonlocal interactions by an effective Hubbard model with on-site interactions U(*) only. The effective model is defined by the Peierls-Feynman-Bogoliubov variational principle. We find that the local part of the interaction U is reduced according to U(*)=U-V[over ¯], where V[over ¯] is a weighted average of nonlocal interactions. For graphene, silicene, and benzene we show that the nonlocal Coulomb interaction can decrease the effective local interaction by more than a factor of 2 in a wide doping range.

  14. A critical phase induced by interplay of spin-orbit coupling and Coulomb interaction

    NASA Astrophysics Data System (ADS)

    Moon, Eun-Gook; Xu, Cenke; Kim, Yong Baek; Balents, Leon

    2013-03-01

    We study long range Coulomb interaction effect on the Luttinger Hamiltonian in three spatial dimensions, which describes strong spin orbit coupling intrinsically. The Hamiltonian has energy spectrum of inverted band gap semiconductors as in well-known HgTe; only one quadratic band touching point exists at the gamma point in Brillouin zone protected by the cubic and time reversal symmetries. Using controlled renormalization group techniques, we find that long-range Coulomb interaction converts the quadratic band touching state into a non-Fermi liquid (NFL) state, in some ways analogous to the Luttinger liquid state in one dimension. Consequently, all physical quantities become scale invariant and show deviations from non-interacting electrons' properties. Temperature and field dependence of various thermodynamic functions are obtained. Moreover, our ground state can be viewed as a parent state of topological insulators, magnetic metals, and Weyl semi-metals by breaking either cubic symmetry or time-reversal symmetry. The strong Coulomb interaction changes phase boundaries qualitatively and phase diagrams with the Coulomb interaction are provided. Applications to iridium-oxides materials are also discussed.

  15. Influence of the coulomb interaction on the liquid-gas phase transition and nuclear multifragmentation.

    PubMed

    Gulminelli, F; Chomaz, Ph; Raduta, Al H; Raduta, Ad R

    2003-11-14

    The liquid-gas phase transition is analyzed from the topologic properties of the event distribution in the observables space. A multicanonical formalism allows one to directly relate the standard phase transition with neutral particles to the case where the nonsaturating Coulomb interaction is present, and to interpret the Coulomb effect as a deformation of the probability distributions and a rotation of the order parameter. This formalism is applied to a statistical multifragmentation model and consequences for the nuclear multifragmentation phase transitions are drawn.

  16. Probing the tides in interacting galaxy pairs

    NASA Technical Reports Server (NTRS)

    Borne, Kirk D.

    1990-01-01

    Detailed spectroscopic and imaging observations of colliding elliptical galaxies revealed unmistakable diagnostic signatures of the tidal interactions. It is possible to compare both the distorted luminosity distributions and the disturbed internal rotation profiles with numerical simulations in order to model the strength of the tidal gravitational field acting within a given pair of galaxies. Using the best-fit numerical model, one can then measure directly the mass of a specific interacting binary system. This technique applies to individual pairs and therefore complements the classical methods of measuring the masses of galaxy pairs in well-defined statistical samples. The 'personalized' modeling of galaxy pairs also permits the derivation of each binary's orbit, spatial orientation, and interaction timescale. Similarly, one can probe the tides in less-detailed observations of disturbed galaxies in order to estimate some of the physical parameters for larger samples of interacting galaxy pairs. These parameters are useful inputs to the more universal problems of (1) the galaxy merger rate, (2) the strength and duration of the driving forces behind tidally stimulated phenomena (e.g., starbursts and maybe quasi steller objects), and (3) the identification of long-lived signatures of interaction/merger events.

  17. Effect of long-range repulsive Coulomb interactions on packing structure of adhesive particles.

    PubMed

    Chen, Sheng; Li, Shuiqing; Liu, Wenwei; Makse, Hernán A

    2016-02-14

    The packing of charged micron-sized particles is investigated using discrete element simulations based on adhesive contact dynamic model. The formation process and the final obtained structures of ballistic packings are studied to show the effect of interparticle Coulomb force. It is found that increasing the charge on particles causes a remarkable decrease of the packing volume fraction ϕ and the average coordination number 〈Z〉, indicating a looser and chainlike structure. Force-scaling analysis shows that the long-range Coulomb interaction changes packing structures through its influence on particle inertia before they are bonded into the force networks. Once contact networks are formed, the expansion effect caused by repulsive Coulomb forces are dominated by short-range adhesion. Based on abundant results from simulations, a dimensionless adhesion parameter Ad*, which combines the effects of the particle inertia, the short-range adhesion and the long-range Coulomb interaction, is proposed and successfully scales the packing results for micron-sized particles within the latest derived adhesive loose packing (ALP) regime. The structural properties of our packings follow well the recent theoretical prediction which is described by an ensemble approach based on a coarse-grained volume function, indicating some kind of universality in the low packing density regime of the phase diagram regardless of adhesion or particle charge. Based on the comprehensive consideration of the complicated inter-particle interactions, our findings provide insight into the roles of short-range adhesion and repulsive Coulomb force during packing formation and should be useful for further design of packings.

  18. Assessing Paired Orals: Raters' Orientation to Interaction

    ERIC Educational Resources Information Center

    Ducasse, Ana Maria; Brown, Annie

    2009-01-01

    Speaking tasks involving peer-to-peer candidate interaction are increasingly being incorporated into language proficiency assessments, in both large-scale international testing contexts, and in smaller-scale, for example course-related, ones. This growth in the popularity and use of paired and group orals has stimulated research, particularly into…

  19. Many-body effects of Coulomb interaction on Landau levels in graphene

    NASA Astrophysics Data System (ADS)

    Sokolik, A. A.; Zabolotskiy, A. D.; Lozovik, Yu. E.

    2017-03-01

    In strong magnetic fields, massless electrons in graphene populate relativistic Landau levels with the square-root dependence of each level energy on its number and magnetic field. Interaction-induced deviations from this single-particle picture were observed in recent experiments on cyclotron resonance and magneto-Raman scattering. Previous attempts to calculate such deviations theoretically using the unscreened Coulomb interaction resulted in overestimated many-body effects. This work presents many-body calculations of cyclotron and magneto-Raman transitions in single-layer graphene in the presence of Coulomb interaction, which is statically screened in the random-phase approximation. We take into account self-energy and excitonic effects as well as Landau level mixing, and achieve good agreement of our results with the experimental data for graphene on different substrates. The important role of a self-consistent treatment of the screening is found.

  20. Electron-phonon interaction and pairing mechanism in superconducting Ca-intercalated bilayer graphene

    NASA Astrophysics Data System (ADS)

    Margine, E. R.; Lambert, Henry; Giustino, Feliciano

    2016-02-01

    Using the ab initio anisotropic Eliashberg theory including Coulomb interactions, we investigate the electron-phonon interaction and the pairing mechanism in the recently-reported superconducting Ca-intercalated bilayer graphene. We find that C6CaC6 can support phonon-mediated superconductivity with a critical temperature Tc = 6.8-8.1 K, in good agreement with experimental data. Our calculations indicate that the low-energy Caxy vibrations are critical to the pairing, and that it should be possible to resolve two distinct superconducting gaps on the electron and hole Fermi surface pockets.

  1. Simple interpretation of nuclear orientation for Coulomb barrier distributions derived from a realistic effective interaction

    SciTech Connect

    Ismail, M.; Seif, W. M.

    2010-03-15

    A simple straightforward method has been presented to predict the dependence of barrier distributions at arbitrary orientations on different deformations. The proposed interpretation is developed independently of the complicated numerical calculations. It is related to the change of half-density radius of the deformed nucleus, in the direction of the separation vector. The microscopic calculations of Coulomb barrier are carried out by using a realistic density dependent nucleon-nucleon (NN) interaction, BDM3Y, for the interaction between spherical, {sup 48}Ca, and deformed, {sup 244}Pu, nuclei, as an example. To do so, the double-folding model for the interaction of spherical-deformed nuclei is put in a suitable computational form for the calculation of the potential at several separation distances and orientation angles using the density dependent NN force without consuming computational time. We found that the orientation distributions of the Coulomb barrier parameters show similar patterns to those of the interacting deformed nucleus radius. It is found that the orientation distribution of the Coulomb barrier radius follows the same variation of the deformed nucleus radius while the barrier height distribution follows it inversely. This correlation (anticorrelation) allows a simple evaluation of the orientation barrier distribution which would be very helpful to estimate when the barrier parameters will increase or decrease and at which orientations they will be independent of the deformation. This also allows us to estimate the compact and elongated configurations of the interacting nuclei which lead to hot and cold fusion, respectively.

  2. Simple interpretation of nuclear orientation for Coulomb barrier distributions derived from a realistic effective interaction

    NASA Astrophysics Data System (ADS)

    Ismail, M.; Seif, W. M.

    2010-03-01

    A simple straightforward method has been presented to predict the dependence of barrier distributions at arbitrary orientations on different deformations. The proposed interpretation is developed independently of the complicated numerical calculations. It is related to the change of half-density radius of the deformed nucleus, in the direction of the separation vector. The microscopic calculations of Coulomb barrier are carried out by using a realistic density dependent nucleon-nucleon (NN) interaction, BDM3Y, for the interaction between spherical, Ca48, and deformed, Pu244, nuclei, as an example. To do so, the double-folding model for the interaction of spherical-deformed nuclei is put in a suitable computational form for the calculation of the potential at several separation distances and orientation angles using the density dependent NN force without consuming computational time. We found that the orientation distributions of the Coulomb barrier parameters show similar patterns to those of the interacting deformed nucleus radius. It is found that the orientation distribution of the Coulomb barrier radius follows the same variation of the deformed nucleus radius while the barrier height distribution follows it inversely. This correlation (anticorrelation) allows a simple evaluation of the orientation barrier distribution which would be very helpful to estimate when the barrier parameters will increase or decrease and at which orientations they will be independent of the deformation. This also allows us to estimate the compact and elongated configurations of the interacting nuclei which lead to hot and cold fusion, respectively.

  3. Coexistence and competition of on-site and intersite Coulomb interactions in Mott-molecular-dimers

    NASA Astrophysics Data System (ADS)

    Arruda, Alberto; Juliano, Raffael; Werlang, Thiago; Craco, Luis

    2015-03-01

    Recent findings of Mott-Hubbard physics in ultracold atoms trapped in periodic potentials have reinvigorated the search for quantum simulators of fermionic and bosonic Hubbard-like models. With this in mind, we performed a systematic study of a two-site realization of the Hubbard model, i.e, in a regime where this model can exactly treated. Particularly, we reveal the interplay between on-site (U) and intersite (V) Coulomb interactions in the extended two-site Hubbard model. Due to its atomic-like form quantum correlations intrinsic to Mott-molecular-dimers are exactly computed. Our results for physical quantities such as double occupancy and specific heat are consistent with those obtained for the one-band Hubbard model, suggesting that a two-site dimer model is able to capture the essential thermodynamic properties of strongly interacting electron systems. It is shown that intersite Coulomb interactions promotes the formation of doublons, which compete with the spin-singlet state induced by the on-site Coulomb repulsion. Our results are expected to be relevant for understanding electronic and thermodynamical properties of interacting electrons in strongly coupled magnetic atoms.

  4. Quasiparticle weight and renormalized Fermi velocity of graphene with long-range Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Tang, Ho-Kin; Leaw, Jia Ning; Rodrigues, J. N. B.; Sengupta, P.; Assaad, F. F.; Adam, S.

    In this work, we study the effects of realistic Coulomb interactions in graphene using a projective quantum Monte Carlo simulation of electrons at half-filing on a honeycomb lattice. We compute the quasiparticle residue, the renormalized Fermi velocity and the antiferromagnetic order parameter as a function of both the long-range and short-range components of the Coulomb potential. We find that the Mott insulator transition is determined mostly by the short-range interaction and is consistent with the Gross-Neveu-Yukawa critical theory. Far from the critical point and in the semi-metallic regime, we find that the Fermi-velocity and quasiparticle residue are influenced by the long-range tail of the Coulomb potential, and for very small interaction strength are consistent with predictions of first order perturbation theory. For experimentally relevant and stronger values of the long-range interaction, our numerical data contradicts prediction from both perturbation theory and the renormalization group approaches. This work was supported by Singapore National Research Foundation (NRF-NRFF2012-01 and CA2DM mid-size Centre), Singapore Ministry of Education(Yale-NUS College R-607-265-01312 and MOE2014-T2-2-112), and DFG Grant No. AS120/9-1.

  5. Paired and interacting galaxies: Conference summary

    NASA Technical Reports Server (NTRS)

    Norman, Colin A.

    1990-01-01

    The author gives a summary of the conference proceedings. The conference began with the presentation of the basic data sets on pairs, groups, and interacting galaxies with the latter being further discussed with respect to both global properties and properties of the galactic nuclei. Then followed the theory, modelling and interpretation using analytic techniques, simulations and general modelling for spirals and ellipticals, starbursts and active galactic nuclei. Before the conference the author wrote down the three questions concerning pairs, groups and interacting galaxies that he hoped would be answered at the meeting: (1) How do they form, including the role of initial conditions, the importance of subclustering, the evolution of groups to compact groups, and the fate of compact groups; (2) How do they evolve, including issues such as relevant timescales, the role of halos and the problem of overmerging, the triggering and enhancement of star formation and activity in the galactic nuclei, and the relative importance of dwarf versus giant encounters; and (3) Are they important, including the frequency of pairs and interactions, whether merging and interactions are very important aspects of the life of a normal galaxy at formation, during its evolution, in forming bars, shells, rings, bulges, etc., and in the formation and evolution of active galaxies? Where possible he focuses on these three central issues in the summary.

  6. Calculation of the matrix elements of the Coulomb interaction involving relativistic hydrogenic wave functions

    NASA Astrophysics Data System (ADS)

    Sarkadi, L.

    2017-03-01

    The program MTRDCOUL [1] calculates the matrix elements of the Coulomb interaction between a charged particle and an atomic electron, ∫ ψf∗ (r) ∣ R - r∣-1ψi(r) d r. Bound-free transitions are considered, and relativistic hydrogenic wave functions are used. In this revised version a bug discovered in the F3Y CPC Program Library subprogram [2] is fixed.

  7. Correlated wave functions for three-particle systems with Coulomb interaction - The muonic helium atom

    NASA Technical Reports Server (NTRS)

    Huang, K.-N.

    1977-01-01

    A computational procedure for calculating correlated wave functions is proposed for three-particle systems interacting through Coulomb forces. Calculations are carried out for the muonic helium atom. Variational wave functions which explicitly contain interparticle coordinates are presented for the ground and excited states. General Hylleraas-type trial functions are used as the basis for the correlated wave functions. Excited-state energies of the muonic helium atom computed from 1- and 35-term wave functions are listed for four states.

  8. Towards a First-Principles Determination of Effective Coulomb Interactions in Correlated Electron Materials: Role of Intershell Interactions

    NASA Astrophysics Data System (ADS)

    Seth, Priyanka; Hansmann, Philipp; van Roekeghem, Ambroise; Vaugier, Loig; Biermann, Silke

    2017-08-01

    The determination of the effective Coulomb interactions to be used in low-energy Hamiltonians for materials with strong electronic correlations remains one of the bottlenecks for parameter-free electronic structure calculations. We propose and benchmark a scheme for determining the effective local Coulomb interactions for charge-transfer oxides and related compounds. Intershell interactions between electrons in the correlated shell and ligand orbitals are taken into account in an effective manner, leading to a reduction of the effective local interactions on the correlated shell. Our scheme resolves inconsistencies in the determination of effective interactions as obtained by standard methods for a wide range of materials, and allows for a conceptual understanding of the relation of cluster model and dynamical mean field-based electronic structure calculations.

  9. Current correlations in an interacting Cooper-pair beam splitter

    NASA Astrophysics Data System (ADS)

    Rech, J.; Chevallier, D.; Jonckheere, T.; Martin, T.

    2012-01-01

    We propose an approach allowing the computation of currents and their correlations in interacting multiterminal mesoscopic systems involving quantum dots coupled to normal and/or superconducting leads. The formalism relies on the expression of branching currents and noise crossed correlations in terms of one- and two-particle Green's functions for the dots electrons, which are then evaluated self-consistently within a conserving approximation. We then apply this to the Cooper-pair beam-splitter setup recently proposed [L. Hofstetter , Nature (London)NATUAS0028-083610.1038/nature08432 461, 960 (2009); Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.107.136801 107, 136801 (2011); L. G. Herrmann , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.026801 104, 026801 (2010)], which we model as a double quantum dot with weak interactions, connected to a superconducting lead and two normal ones. Our method not only enables us to take into account a local repulsive interaction on the dots, but also to study its competition with the direct tunneling between dots. Our results suggest that even a weak Coulomb repulsion tends to favor positive current cross correlations in the antisymmetric regime (where the dots have opposite energies with respect to the superconducting chemical potential).

  10. Self-Consistent Monte Carlo Study of the Coulomb Interaction under Nano-Scale Device Structures

    NASA Astrophysics Data System (ADS)

    Sano, Nobuyuki

    2011-03-01

    It has been pointed that the Coulomb interaction between the electrons is expected to be of crucial importance to predict reliable device characteristics. In particular, the device performance is greatly degraded due to the plasmon excitation represented by dynamical potential fluctuations in high-doped source and drain regions by the channel electrons. We employ the self-consistent 3D Monte Carlo (MC) simulations, which could reproduce both the correct mobility under various electron concentrations and the collective plasma waves, to study the physical impact of dynamical potential fluctuations on device performance under the Double-gate MOSFETs. The average force experienced by an electron due to the Coulomb interaction inside the device is evaluated by performing the self-consistent MC simulations and the fixed-potential MC simulations without the Coulomb interaction. Also, the band-tailing associated with the local potential fluctuations in high-doped source region is quantitatively evaluated and it is found that the band-tailing becomes strongly dependent of position in real space even inside the uniform source region. This work was partially supported by Grants-in-Aid for Scientific Research B (No. 2160160) from the Ministry of Education, Culture, Sports, Science and Technology in Japan.

  11. Transport properties of an Aharonov-Bohm ring with strong interdot Coulomb interaction.

    PubMed

    Liu, Yu-Shen; Chen, Hao; Yang, Xi-Feng

    2007-06-20

    Based on the Keldysh Green's function technique and the equation-of-motion method, we investigate theoretically the electronic transport properties of an Aharonov-Bohm ring with embedded coupled double quantum dots connected to two electrodes in a symmetrical parallel configuration in the presence of strong interdot Coulomb interaction. Special attention is paid to the effects of the interdot Coulomb interaction on the transport properties. It has been shown numerically that the interdot Coulomb interaction gives rise to four electronic states in the ring. The quantum interferences between two strongly coupled electronic states and two weakly coupled ones lead to two Breit-Wigner and two Fano resonances in the linear conductance spectrum with the magnetic flux switched on or the imbalance between the energy levels of two quantum dots. The positions and shapes of the four resonances can be controlled by adjusting the magnetic flux through the device or energy levels of the two quantum dots. When the Fermi energy levels in the leads sweep across the weakly coupled electronic states, the negative differential conductance (NDC) is developed in the current-voltage characteristics for the non-equilibrium case.

  12. Magnetic field effect on the Coulomb interaction of acceptors in semimagnetic quantum dot

    SciTech Connect

    Kalpana, P.; Merwyn, A.; Nithiananthi, P.; Jayakumar, K.; Reuben, Jasper D.

    2015-06-24

    The Coulomb interaction of holes in a Semimagnetic Cd{sub 1-x}Mn{sub x}Te / CdTe Spherical and Cubical Quantum Dot (SMQD) in a magnetic field is studied using variational approach in the effective mass approximation. Since these holes in QD show a pronounced collective behavior, while distinct single particle phenomena is suppressed, their interaction in confined potential becomes very significant. It has been observed that acceptor-acceptor interaction is more in cubical QD than in spherical QD which can be controlled by the magnetic field. The results are presented and discussed.

  13. Influence of long-range Coulomb interaction in velocity map imaging

    NASA Astrophysics Data System (ADS)

    Barillot, T.; Brédy, R.; Celep, G.; Cohen, S.; Compagnon, I.; Concina, B.; Constant, E.; Danakas, S.; Kalaitzis, P.; Karras, G.; Lépine, F.; Loriot, V.; Marciniak, A.; Predelus-Renois, G.; Schindler, B.; Bordas, C.

    2017-07-01

    The standard velocity-map imaging (VMI) analysis relies on the simple approximation that the residual Coulomb field experienced by the photoelectron ejected from a neutral or ion system may be neglected. Under this almost universal approximation, the photoelectrons follow ballistic (parabolic) trajectories in the externally applied electric field, and the recorded image may be considered as a 2D projection of the initial photoelectron velocity distribution. There are, however, several circumstances where this approximation is not justified and the influence of long-range forces must absolutely be taken into account for the interpretation and analysis of the recorded images. The aim of this paper is to illustrate this influence by discussing two different situations involving isolated atoms or molecules where the analysis of experimental images cannot be performed without considering long-range Coulomb interactions. The first situation occurs when slow (meV) photoelectrons are photoionized from a neutral system and strongly interact with the attractive Coulomb potential of the residual ion. The result of this interaction is the formation of a more complex structure in the image, as well as the appearance of an intense glory at the center of the image. The second situation, observed also at low energy, occurs in the photodetachment from a multiply charged anion and it is characterized by the presence of a long-range repulsive potential. Then, while the standard VMI approximation is still valid, the very specific features exhibited by the recorded images can be explained only by taking into consideration tunnel detachment through the repulsive Coulomb barrier.

  14. Probing molecular interaction in ionic liquids by low frequency spectroscopy: Coulomb energy, hydrogen bonding and dispersion forces.

    PubMed

    Fumino, Koichi; Reimann, Sebastian; Ludwig, Ralf

    2014-10-28

    Ionic liquids are defined as salts composed solely of ions with melting points below 100 °C. These remarkable liquids have unique and fascinating properties and offer new opportunities for science and technology. New combinations of ions provide changing physical properties and thus novel potential applications for this class of liquid materials. To a large extent, the structure and properties of ionic liquids are determined by the intermolecular interaction between anions and cations. In this perspective we show that far infrared and terahertz spectroscopy are suitable methods for studying the cation-anion interaction in these Coulomb fluids. The interpretation of the measured low frequency spectra is supported by density functional theory calculations and molecular dynamics simulations. We present results for selected aprotic and protic ionic liquids and their mixtures with molecular solvents. In particular, we focus on the strength and type of intermolecular interaction and how both parameters are influenced by the character of the ions and their combinations. We show that the total interaction between cations and anions is a result of a subtle balance between Coulomb forces, hydrogen bonds and dispersion forces. For protic ionic liquids we could measure distinct vibrational modes in the low frequency spectra indicating clearly the cation-anion interaction characterized by linear and medium to strong hydrogen bonds. Using isotopic substitution we have been able to dissect frequency shifts related to pure interaction strength between cations and anions and to different reduced masses only. In this context we also show how these different types of interaction may influence the physical properties of ionic liquids such as the melting point, viscosity or enthalpy of vaporization. Furthermore we demonstrate that low frequency spectroscopy can also be used for studying ion speciation. Low vibrational features can be assigned to contact ion pairs and solvent separated

  15. Effects of anisotropy and Coulomb interactions on quantum transport in a quadruple quantum-dot structure

    NASA Astrophysics Data System (ADS)

    Kagan, M. Yu.; Val'kov, V. V.; Aksenov, S. V.

    2017-01-01

    We present an analytical and numerical investigation of the spectral and transport properties of a quadruple quantum-dot (QQD) structure which is one of the popular low-dimensional systems in the context of fundamental quantum physics study, future electronic applications, and quantum calculations. The density of states, occupation numbers, and conductance of the structure were analyzed using the nonequilibrium Green's functions in the tight-binding approach and the equation-of-motion method. In particular the anisotropy of hopping integrals and on-site electron energies as well as the effects of the finite intra- and interdot Coulomb interactions were investigated. It was found out that the anisotropy of the kinetic processes in the system leads to the Fano-Feshbach asymmetrical peak. We demonstrated that the conductance of the QQD device has a wide insulating band with steep edges separating triple-peak structures if the intradot Coulomb interactions are taken into account. The interdot Coulomb correlations between the central QDs result in the broadening of this band and the occurrence of an additional band with low conductance due to the Fano antiresonances. It was shown that in this case the conductance of the anisotropic QQD device can be dramatically changed by tuning the anisotropy of on-site electron energies.

  16. The role of Coulomb interaction in thermoelectric effects of an Aharonov-Bohm interferometer.

    PubMed

    Liu, Yu-Shen; Zhang, De-Bao; Yang, Xi-Feng; Feng, Jin-Fu

    2011-06-03

    We investigate the thermoelectric effects of an Aharonov-Bohm (AB) interferometer with a quantum dot (QD) embedded in each of its arms, where the intra-dot Coulomb interaction between electrons in each QD is taken into account. Using Green's function methods and the equation of motion (EOM) technique, we find that the Seebeck coefficient and Lorenz number can be strongly enhanced when the chemical potential sweeps the molecular states associated with the Fano line-shapes in the transmission spectra, due to quantum interference effects between the bonding and antibonding molecular states. It is found that enhancement of the thermoelectric effects occurs between the two groups of conductance peaks in the presence of strong intra-dot Coulomb interaction-the reason being that a transmission node is developed in the Coulomb blockade regime. In this case, the maximum value of the Lorenz number approaches 10π(2)k(B)(2)/(3e(2)). Its thermoelectric conversion efficiency in the absence of phonon thermal conductance, described by the figure of merit ZT, approaches 2 at room temperature. Therefore, it may be used as a high-efficiency solid-state thermoelectric conversion device under certain circumstances.

  17. Transport coefficients of graphene: Interplay of impurity scattering, Coulomb interaction, and optical phonons

    NASA Astrophysics Data System (ADS)

    Xie, Hong-Yi; Foster, Matthew S.

    2016-05-01

    We study the electric and thermal transport of the Dirac carriers in monolayer graphene using the Boltzmann-equation approach. Motivated by recent thermopower measurements [F. Ghahari, H.-Y. Xie, T. Taniguchi, K. Watanabe, M. S. Foster, and P. Kim, Phys. Rev. Lett. 116, 136802 (2016), 10.1103/PhysRevLett.116.136802], we consider the effects of quenched disorder, Coulomb interactions, and electron-optical-phonon scattering. Via an unbiased numerical solution to the Boltzmann equation we calculate the electrical conductivity, thermopower, and electronic component of the thermal conductivity, and discuss the validity of Mott's formula and of the Wiedemann-Franz law. An analytical solution for the disorder-only case shows that screened Coulomb impurity scattering, although elastic, violates the Wiedemann-Franz law even at low temperature. For the combination of carrier-carrier Coulomb and short-ranged impurity scattering, we observe the crossover from the interaction-limited (hydrodynamic) regime to the disorder-limited (Fermi-liquid) regime. In the former, the thermopower and the thermal conductivity follow the results anticipated by the relativistic hydrodynamic theory. On the other hand, we find that optical phonons become non-negligible at relatively low temperatures and that the induced electron thermopower violates Mott's formula. Combining all of these scattering mechanisms, we obtain the thermopower that quantitatively coincides with the experimental data.

  18. Impacts of coulomb interactions on the magnetic responses of excitonic complexes in single semiconductor nanostructures.

    PubMed

    Chang, Wen-Hao; Lin, Chia-Hsien; Fu, Ying-Jhe; Lin, Ta-Chun; Lin, Hsuan; Cheng, Shuen-Jen; Lin, Sheng-Di; Lee, Chien-Ping

    2010-01-21

    We report on the diamagnetic responses of different exciton complexes in single InAs/GaAs self-assembled quantum dots (QDs) and quantum rings (QRs). For QDs, the imbalanced magnetic responses of inter-particle Coulomb interactions play a crucial role in the diamagnetic shifts of excitons (X), biexcitons (XX), and positive trions (X-). For negative trions (X-) in QDs, anomalous magnetic responses are observed, which cannot be described by the conventional quadratic energy shift with the magnetic field. The anomalous behavior is attributed to the apparent change in the electron wave function extent after photon emission due to the strong Coulomb attraction by the hole in its initial state. In QRs, the diamagnetic responses of X and XX also show different behaviors. Unlike QDs, the diamagnetic shift of XX in QRs is considerably larger than that of X. The inherent structural asymmetry combined with the inter-particle Coulomb interactions makes the wave function distribution of XX very different from that of X in QRs. Our results suggest that the phase coherence of XX in QRs may survive from the wave function localization due to the structural asymmetry or imperfections.

  19. Coulomb interactions-induced perfect spin-filtering effect in a quadruple quantum-dot cell

    NASA Astrophysics Data System (ADS)

    Kagan, M. Yu.; Val'kov, V. V.; Aksenov, S. V.

    2017-10-01

    A quadruple quantum-dot (QQD) cell is proposed as a spin filter. The transport properties of the QQD cell were studied in linear response regime on the basis of the equations of motion for retarded Green's functions. The developed approach allowed us to take into account the influence of both intra- and interdot Coulomb interactions on charge carriers' spin polarization. It was shown that the presence of the insulating bands in the conductance due to the Coulomb correlations results in the emergence of spin-polarized windows (SPWs) in magnetic field leading to the high spin polarization. We demonstrated that the SPWs can be effectively manipulated by gate fields and considering the hopping between central dots in both isotropic and anisotropic regimes.

  20. New calculations and measurements of the Coulomb cross-section for the production of direct electron pairs by high energy nuclei

    NASA Technical Reports Server (NTRS)

    Derrickson, J. H.; Dake, S.; Dong, B. L.; Eby, P. B.; Fountain, W. F.; Fuki, M.; Gregory, J. C.; Hayashi, T.; Iyono, A.; King, D. T.

    1989-01-01

    Recently, new calculations were made of the direct Coulomb pair cross section that rely less in arbitrary parameters. More accurate calculations of the cross section down to low pair energies were made. New measurements of the total direct electron pair yield, and the energy and angular distribution of the electron pairs in emulsion were made for O-16 at 60 and 200 GeV/amu at S-32 at 200 GeV/amu which give satisfactory agreement with the new calculations. These calculations and measurements are presented along with previous accelerator measurements made of this effect during the last 40 years. The microscope scanning criteria used to identify the direct electron pairs is described. Prospects for application of the pair method to cosmic ray energy measurements in the region 10 (exp 13) to 10 (exp 15) eV/amu are discussed.

  1. Residue Coulomb Interaction Among Isobars and Its Influence in Symmetry Energy of Neutron-Rich Fragment

    NASA Astrophysics Data System (ADS)

    Ma, Chun-Wang; Wang, Shan-Shan; Zhang, Yan-Li; Zhao, Yi-Long; Wei, Hui-Ling

    2015-09-01

    The residue Coulomb interaction (RCI), which affects the result of symmetry-energy coefficient of neutron-rich nucleus in isobaric yield ratio (IYR) method, is difficult to be determined. Four RCI approximations are investigated: (i) The M1-RCI adopting the ac/T (the ratio of Coulomb energy coefficient to temperature) determined from the IYR of mirror-nucleus fragments; (ii) The M2-RCI by fitting the difference between IYRs; (iii) The M3-RCI adopting the standard Coulomb energy at a temperature T = 2 MeV; and (iv) Neglecting the RCI among isobars. The M1-, M2- and M3-RCI are no larger than 0.4. In particular, the M2-RCI is very close to zero. The effects of RCI in asym/T of fragment are also studied. The M1- and M4-asym/T are found to be the lower and upper limitations of asym/T, respectively. The M2-asym/T overlaps the M4-asym/T, which indicates that the M2-RCI is negligible in the IYR method, and the RCI among the three isobars can be neglected. The relative consistent low values of M3-asym/T (7.5 ± 2.5) are found in very neutron-rich isobars. Supported by the Program for Science & Technology Innovation Talents in Universities of Henan Province (13HASTIT046), and Young Teacher Project in Henan Normal University (HNU), China

  2. Effective single-band models for the high-Tc cuprates. I. Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Feiner, L. F.; Jefferson, J. H.; Raimondi, R.

    1996-04-01

    Starting with the three-band extended Hubbard model (or d-p model) widely used to represent the CuO2 planes in the high-Tc cuprates, we make a systematic reduction to an effective single-band model using a previously developed cell-perturbation method. The range of parameters for which this mapping is a good approximation is explored in the full Zaanen-Sawatzky-Allen diagram (copper Coulomb repulsion Ud versus charge-transfer energy ɛ), together with an investigation of the validity of a further mapping to an effective charge-spin (t-J-V) model. The variation of the effective single-band parameters with the parameters of the underlying multi-band model is investigated in detail, and the parameter regime where the model represents the high-Tc cuprates is examined for specific features that might distinguish it from the general case. In particular, we consider the effect of Coulomb repulsions on oxygen (Up) and between copper and oxygen (Vpd). We find that the reduction to an effective single-band model is generally valid for describing the low-energy physics, and that Vpd and Up (unless unrealistically large) actually slightly improve the convergence of the cell-perturbation method. Unlike in the usual single-band Hubbard model, the effective intercell hopping and Coulomb interactions are different for electrons and holes. We find that this asymmetry, which vanishes in the extreme Mott-Hubbard regime (Ud<<ɛ), is quite appreciable in the charge-transfer regime (Ud>~ɛ), particularly for the effective Coulomb interactions. We show that for doped holes (forming Zhang-Rice singlets) on neighboring cells the interaction induced by Vpd can even be attractive due to locally enhanced pd hybridization, while this cannot occur for electrons. The Coulomb interaction induced by Up is always repulsive; in addition Up gives rise to a ferromagnetic spin-spin interaction which opposes antiferromagnetic superexchange. We show that for hole-doped systems this leads to a subtle

  3. Coulomb enhancement of superconducting pair-pair correlations in a 3/4 -filled model for κ -(BEDT-TTF)2X

    NASA Astrophysics Data System (ADS)

    De Silva, W. Wasanthi; Gomes, N.; Mazumdar, S.; Clay, R. T.

    2016-05-01

    We present the results of precise correlated-electron calculations on the monomer lattices of the organic charge-transfer solids κ -(BEDT-TTF) 2X for 32 and 64 molecular sites. Our calculations are for band parameters corresponding to X =Cu[N (CN) 2]Cl and Cu2(CN) 3, which are semiconducting antiferromagnetic and quantum spin liquid, respectively, at ambient pressure. We have performed our calculations for variable electron densities ρ per BEDT-TTF molecule, with ρ ranging from 1 to 2. We find that d -wave superconducting pair-pair correlations are enhanced by electron-electron interactions only for a narrow carrier concentration about ρ =1.5 , which is precisely the carrier concentration where superconductivity in the charge-transfer solids occurs. Our results indicate that the enhancement in pair-pair correlations is not related to antiferromagnetic order, but to a proximate hidden spin-singlet state that manifests itself as a charge-ordered state in other charge-transfer solids. Long-range superconducting order does not appear to be present in the purely electronic model, suggesting that electron-phonon interactions also must play a role in a complete theory of superconductivity.

  4. Coulomb-like interaction in nematic emulsions induced by external torques exerted on the colloids.

    PubMed

    Pergamenshchik, V M; Uzunova, V O

    2007-07-01

    An external mechanical torque on colloids immersed in a nematic liquid crystal can induce a Coulomb-like 1/r interaction between them [Lev and Tomchuk, Phys. Rev. E 59, 591 (1999); Lev, ibid. 65, 021709 (2002)]. In this paper we show that the director-mediated Coulomb-like interaction of two colloids is determined by the vectors Gamma perpendicular (1) and Gamma perpendicular (2) of the transverse external torques exerted upon these colloids. We derive the 1/r potential in which the scalar product -(Gamma perpendicular (1) x Gamma perpendicular (2)) of the two torques plays the role of the product of two electrostatic charges. The 1/r interaction is attractive for (Gamma perpendicular (1) x Gamma perpendicular (2))>0 and repulsive for (Gamma perpendicular (1) x Gamma perpendicular (2))<0 ("parallel torques" attract whereas "antiparallel torques" repel each other). The vector of transverse torque determines the two-component "elastic charge" (dyad), which is illustrated by the 1/r2 and 1/r3 terms in the elastic energy (the elastic analogs of the monopole-dipole and dipole-dipole interactions). The general status of the pairwise approach to nematic emulsions is considered in terms of the elastic charge density.

  5. Odd frequency pairing of interacting Majorana fermions

    NASA Astrophysics Data System (ADS)

    Huang, Zhoushen; Woelfle, Peter; Balatsky, Alexandar

    Majorana fermions are rising as a promising key component in quantum computation. While the prevalent approach is to use a quadratic (i.e. non-interacting) Majorana Hamiltonian, when expressed in terms of Dirac fermions, generically the Hamiltonian involves interaction terms. Here we focus on the possible pair correlations in a simple model system. We study a model of Majorana fermions coupled to a boson mode and show that the anomalous correlator between different Majorana fermions, located at opposite ends of a topological wire, exhibits odd frequency behavior. It is stabilized when the coupling strength g is above a critical value gc. We use both, conventional diagrammatic theory and a functional integral approach, to derive the gap equation, the critical temperature, the gap function, the critical coupling, and a Ginzburg-Landau theory allowing to discuss a possible subleading admixture of even-frequency pairing. Work supported by USDOE DE-AC52-06NA25396 E304, Knut and Alice Wallenberg Foundation, and ERC DM-321031.

  6. A Fortran program to calculate the matrix elements of the Coulomb interaction involving hydrogenic wave functions

    NASA Astrophysics Data System (ADS)

    Sarkadi, L.

    2017-03-01

    The program MTRXCOUL [1] calculates the matrix elements of the Coulomb interaction between a charged particle and an atomic electron, ∫ψf∗ (r) | R - r | - 1ψi(r) d r. Bound-free transitions are considered, and non-relativistic hydrogenic wave functions are used. In this revised version a bug discovered in the F3Y CPC Program Library (PL) subprogram [2] is fixed. Furthermore, the COULCC CPC PL subprogram [3] applied for the calculations of the radial wave functions of the free states and the Bessel functions is replaced by the CPC PL subprogram DCOUL [4].

  7. Quantum Simulator for the Hubbard Model with Long-Range Coulomb Interactions Using Surface Acoustic Waves

    NASA Astrophysics Data System (ADS)

    Byrnes, Tim; Recher, Patrik; Kim, Na Young; Utsunomiya, Shoko; Yamamoto, Yoshihisa

    2007-07-01

    An experimental scheme for a quantum simulator of strongly correlated electrons is proposed. Our scheme employs electrons confined in a two-dimensional electron gas in a GaAs/AlGaAs heterojunction. Two surface acoustic waves are then induced in the substrate, creating a two-dimensional “egg-carton” potential. The dynamics of the electrons in this potential are described by a Hubbard model with long-range Coulomb interactions. Estimates of the Hubbard parameters suggest that observations of quantum phase transition phenomena are within experimental reach.

  8. Coulomb static stress interactions between simulated M>7 earthquakes and major faults in Southern California

    NASA Astrophysics Data System (ADS)

    Rollins, J. C.; Ely, G. P.; Jordan, T. H.

    2010-12-01

    We calculate the Coulomb stress changes imparted to major Southern California faults by thirteen simulated worst-case-scenario earthquakes for the region, including the “Big Ten” scenarios (Ely et al, in progress). The source models for the earthquakes are variable-slip simulations from the SCEC CyberShake project (Graves et al, 2010). We find strong stress interactions between the San Andreas and subparallel right-lateral faults, thrust faults under the Los Angeles basin, and the left-lateral Garlock Fault. M>7 earthquakes rupturing sections of the southern San Andreas generally decrease Coulomb stress on the San Jacinto and Elsinore faults and impart localized stress increases and decreases to the Garlock, San Cayetano, Puente Hills and Sierra Madre faults. A M=7.55 quake rupturing the San Andreas between Lake Hughes and San Gorgonio Pass increases Coulomb stress on the eastern San Cayetano fault, consistent with Deng and Sykes (1996). M>7 earthquakes rupturing the San Jacinto, Elsinore, Newport-Inglewood and Palos Verdes faults decrease stress on parallel right-lateral faults. A M=7.35 quake on the San Cayetano Fault decreases stress on the Garlock and imparts localized stress increases and decreases to the San Andreas. A M=7.15 quake on the Puente Hills Fault increases stress on the San Andreas and San Jacinto faults, decreases stress on the Sierra Madre Fault and imparts localized stress increases and decreases to the Newport-Inglewood and Palos Verdes faults. A M=7.25 shock on the Sierra Madre Fault increases stress on the San Andreas and decreases stress on the Puente Hills Fault. These findings may be useful for hazard assessment, paleoseismology, and comparison with dynamic stress interactions featuring the same set of earthquakes.

  9. The MV model of the color glass condensate for a finite number of sources including Coulomb interactions

    DOE PAGES

    McLerran, Larry; Skokov, Vladimir V.

    2016-09-19

    We modify the McLerran–Venugopalan model to include only a finite number of sources of color charge. In the effective action for such a system of a finite number of sources, there is a point-like interaction and a Coulombic interaction. The point interaction generates the standard fluctuation term in the McLerran–Venugopalan model. The Coulomb interaction generates the charge screening originating from well known evolution in x. Such a model may be useful for computing angular harmonics of flow measured in high energy hadron collisions for small systems. In this study we provide a basic formulation of the problem on a lattice.

  10. The MV model of the color glass condensate for a finite number of sources including Coulomb interactions

    NASA Astrophysics Data System (ADS)

    McLerran, Larry; Skokov, Vladimir V.

    2017-01-01

    We modify the McLerran-Venugopalan model to include only a finite number of sources of color charge. In the effective action for such a system of a finite number of sources, there is a point-like interaction and a Coulombic interaction. The point interaction generates the standard fluctuation term in the McLerran-Venugopalan model. The Coulomb interaction generates the charge screening originating from well known evolution in x. Such a model may be useful for computing angular harmonics of flow measured in high energy hadron collisions for small systems. In this paper we provide a basic formulation of the problem on a lattice.

  11. The MV model of the color glass condensate for a finite number of sources including Coulomb interactions

    SciTech Connect

    McLerran, Larry; Skokov, Vladimir V.

    2016-09-19

    We modify the McLerran–Venugopalan model to include only a finite number of sources of color charge. In the effective action for such a system of a finite number of sources, there is a point-like interaction and a Coulombic interaction. The point interaction generates the standard fluctuation term in the McLerran–Venugopalan model. The Coulomb interaction generates the charge screening originating from well known evolution in x. Such a model may be useful for computing angular harmonics of flow measured in high energy hadron collisions for small systems. In this study we provide a basic formulation of the problem on a lattice.

  12. Convective Polymer Depletion on Pair Particle Interactions

    NASA Astrophysics Data System (ADS)

    Fan, Tai-Hsi; Taniguchi, Takashi; Tuinier, Remco

    2011-11-01

    Understanding transport, reaction, aggregation, and viscoelastic properties of colloid-polymer mixture is of great importance in food, biomedical, and pharmaceutical sciences. In non-adsorbing polymer solutions, colloidal particles tend to aggregate due to the depletion-induced osmotic or entropic force. Our early development for the relative mobility of pair particles assumed that polymer reorganization around the particles is much faster than particle's diffusive time, so that the coupling of diffusive and convective effects can be neglected. Here we present a nonequilibrium two-fluid (polymer and solvent) model to resolve the convective depletion effect. The theoretical framework is based on ground state approximation and accounts for the coupling of fluid flow and polymer transport to better describe pair particle interactions. The momentum and polymer transport, chemical potential, and local viscosity and osmotic pressure are simultaneously solved by numerical approximation. This investigation is essential for predicting the demixing kinetics in the pairwise regime for colloid-polymer mixtures. This work is supported by NSF CMMI 0952646.

  13. Cooperative interactions between paired domain and homeodomain.

    PubMed

    Jun, S; Desplan, C

    1996-09-01

    The Pax proteins are a family of transcriptional regulators involved in many developmental processes in all higher eukaryotes. They are characterized by the presence of a paired domain (PD), a bipartite DNA binding domain composed of two helix-turn-helix (HTH) motifs,the PAI and RED domains. The PD is also often associated with a homeodomain (HD) which is itself able to form homo- and hetero-dimers on DNA. Many of these proteins therefore contain three HTH motifs each able to recognize DNA. However, all PDs recognize highly related DNA sequences, and most HDs also recognize almost identical sites. We show here that different Pax proteins use multiple combinations of their HTHs to recognize several types of target sites. For instance, the Drosophila Paired protein can bind, in vitro, exclusively through its PAI domain, or through a dimer of its HD, or through cooperative interaction between PAI domain and HD. However, prd function in vivo requires the synergistic action of both the PAI domain and the HD. Pax proteins with only a PD appear to require both PAI and RED domains, while a Pax-6 isoform and a new Pax protein, Lune, may rely on the RED domain and HD. We propose a model by which Pax proteins recognize different target genes in vivo through various combinations of their DNA binding domains, thus expanding their recognition repertoire.

  14. Interaction effects in superconductor/quantum spin Hall devices: Universal transport signatures and fractional Coulomb blockade

    NASA Astrophysics Data System (ADS)

    Aasen, David; Lee, Shu-Ping; Karzig, Torsten; Alicea, Jason

    2016-10-01

    Interfacing s -wave superconductors and quantum spin Hall edges produces time-reversal-invariant topological superconductivity of a type that can not arise in strictly one-dimensional systems. With the aim of establishing sharp fingerprints of this phase, we use renormalization-group methods to extract universal transport characteristics of superconductor/quantum spin Hall heterostructures where the native edge states serve as leads. We determine scaling forms for the conductance through a grounded superconductor and show that the results depend sensitively on the interaction strength in the leads, the size of the superconducting region, and the presence or absence of time-reversal-breaking perturbations. We also study transport across a floating superconducting island isolated by magnetic barriers. Here, we predict e -periodic Coulomb-blockade peaks, as recently observed in nanowire devices [S. M. Albrecht et al., Nature (London) 531, 206 (2016), 10.1038/nature17162], with the added feature that the island can support fractional charge tunable via the relative orientation of the barrier magnetizations. As an interesting corollary, when the magnetic barriers arise from strong interactions at the edge that spontaneously break time-reversal symmetry, the Coulomb-blockade periodicity changes from e to e /2 . These findings suggest several future experiments that probe unique characteristics of topological superconductivity at the quantum spin Hall edge.

  15. Coulomb interaction parameters in bcc iron: an LDA+DMFT study.

    PubMed

    Belozerov, A S; Anisimov, V I

    2014-09-17

    We study the influence of Coulomb interaction parameters on electronic structure and magnetic properties of paramagnetic bcc Fe by means of the local density approximation plus dynamical mean-field theory approach. We consider the local Coulomb interaction in the density-density form as well as in the form with spin rotational invariance approximated by averaging over all directions of the quantization axis. Our results indicate that the magnetic properties of bcc Fe are mainly affected by the Hund's rule coupling J rather than by the Hubbard U. By employing the constrained density functional theory approach in the basis of Wannier functions of spd character, we obtain U = 4 eV and J = 0.9 eV. In spite of the widespread belief that U = 4 eV is too large for bcc Fe, our calculations with the obtained values of U and J result in a satisfactory agreement with the experiment. The correlation effects caused by U are found to be weak even for large U = 6 eV. The agreement between the calculated and experimental Curie temperatures is further improved if J is reduced to 0.8 eV. However, with the decrease of J, the effective local magnetic moment moves further away from the experimental value.

  16. Hartree corrections in a mean-field limit for fermions with Coulomb interaction

    NASA Astrophysics Data System (ADS)

    Petrat, Sören

    2017-06-01

    We consider the many-body dynamics of fermions with Coulomb interaction in a mean-field scaling limit where the kinetic and potential energy are of the same order for large particle numbers. In the considered limit the spatial variation of the mean-field is small. We prove two results about this scaling limit. First, due to the small variation, i.e., small forces, we show that the many-body dynamics can be approximated by the free dynamics with an appropriate phase factor with the conjectured optimal error term. Second, we show that the Hartree dynamics gives a better approximation with a smaller error term. In this sense, assuming that the error term in the first result is optimal, we derive the Hartree equations from the many-body dynamics with Coulomb interaction in a mean-field scaling limit. , which features invited work from the best early-career researchers working within the scope of J. Phys. A. This project is part of the Journal of Physics series’ 50th anniversary celebrations in 2017. Sören Petrat was selected by the Editorial Board of J. Phys. A as an emerging talent.

  17. Coulombic interactions during advection-dominated transport of ions in porous media

    NASA Astrophysics Data System (ADS)

    Muniruzzaman, Muhammad; Stolze, Lucien; Rolle, Massimo

    2017-04-01

    Solute transport of charged species in porous media is significantly affected by the electrochemical migration term resulting from the charge-induced interactions among dissolved ions and with solid surfaces. Therefore, the characterization of such Coulombic interactions and their effect on multicomponent ionic transport is of critical importance for assessing the fate of charged solutes in porous media. In this work we present a detailed investigation of the electrochemical effects during conservative multicomponent ionic transport in homogeneous and heterogeneous domains by means of laboratory bench-scale experiments and numerical simulations. The investigation aims at quantifying the key role of small-scale electrostatic interactions in flow-through systems, especially when advection is the dominant mass-transfer process. Considering dilute solutions of strong electrolytes (e.g., MgCl2 and NaBr) we report results showing the important role of Coulombic interactions in the lateral displacement of the different ionic species for steady-state transport scenarios in which the solutions are continuously injected through different portions of the flow-through chamber [1, 2]. Successively, we focus our attention on transient transport and pulse injection of the electrolytes. In these experiments high-resolution spatial and temporal monitoring of the ions' concentrations (600 samples; 1800 concentration measurements), at closely spaced outlet ports (5 mm), allowed us resolving the effects of charge interactions on the temporal breakthrough and spatial profiles of the cations and anions [3]. The interpretation of the experimental results requires a multicomponent modeling approach with an accurate description of local hydrodynamic dispersion, as well as the explicit quantification of the dispersive fluxes' cross-coupling due to the Coulombic interactions between the charged species. A new 2-D simulator [4], coupling the solution of the multicomponent ionic transport

  18. Extraordinary waves in two dimensional electron gas with separate spin evolution and Coulomb exchange interaction

    NASA Astrophysics Data System (ADS)

    Andreev, Pavel A.

    2017-02-01

    The hydrodynamics analysis of waves in a two-dimensional degenerate electron gas with a separate spin evolution is presented. The transverse electric field is included along with the longitudinal electric field. The Coulomb exchange interaction is included in the analysis. In contrast with the three-dimensional plasma-like media, the contribution of the transverse electric field is rather small, but it decreases the frequency of the extraordinary wave at small wave vectors. We show the decrease in the frequency of both the extraordinary (Langmuir) wave and the spin-electron acoustic wave due to the exchange interaction. Moreover, spin-electron acoustic waves have negative dispersion at the relatively large spin-polarization. The corresponding dispersion dependencies are presented and analyzed.

  19. Fragmentation and Coulomb explosion of deuterium clusters by the interaction with intense laser pulses

    SciTech Connect

    Isla, M.; Alonso, J.A.

    2005-08-15

    Experiments of Zweiback et al. [Phys. Rev. Lett. 84, 2634 (2000)] on the interaction of intense femtosecond laser pulses with a dense molecular beam of large deuterium clusters have shown that these clusters can lose most of their electrons and explode, in a process known as Coulomb explosion. The collisions between the fast deuterium (D) nuclei give rise to D-D fusion. This has motivated us to carry out computer simulations based on the time-dependent density-functional theory in order to understand the ultrafast processes occurring under these high excitations. In particular we have studied the laser irradiation of the singly charged cluster D{sub 13}{sup +}. The simulations show the occurrence of two different cluster fragmentation behaviors, depending on the intensity of the laser pulse: For not too large intensities, the cluster becomes disassembled in a slow way, whereas for large laser intensities substantial ionization takes place and a violent explosion occurs due to the electrostatic repulsion between the nuclei following the loss of the electrons by the cluster. The fast fragmentation mode fits well into the idea of the Coulomb explosion.

  20. The interacting pair MKN 305/306

    NASA Astrophysics Data System (ADS)

    Dietrich, Matthias

    1990-11-01

    Direct images and spectra at different slit positions of the interacting system Mkn 305/306 are discussed. Both galaxies show starburst properties due to tidal interaction. The morphology and velocity structure of Mkn 306 reveals the strongest warp of a stellar disk so far known. The galaxies Mkn 305 and Mkn 306 form a double system with 30 arcsec separation and having a common envelope at mB greater than or equal to 24.5. Furthermore a small tidal tail west of Mkn 305A, an isophote twist of Mkn 305 and the near identical redshifts of the two galaxies prove that this is a physical pair. Mkn 306 itself was classified as a double nucleus galaxy (Petrosyan et al., 1978). The optical morphology of Mkn 306 has the form of an integral sign which is similar to the radio morphology of strongly warped galaxies (Bottema et al., 1987). But in the optical the warp of the stellar component is normally far weaker than in the radio for the HI-gas. Therefore the authors investigate whether the double nucleus structure of Mkn 306 is real or an artifact due to an extreme warp in the optical. The origin for the warp phenomenon is not clear yet. Direct images of the galaxy system were taken with the Calar Alto 2.2m telescope in the B-band and at La Silla in the r-band using the 2.2m telescope; low dispersion spectra (240 A/mm) as well as high dispersion spectra (56 A/mm) for studying the velocity field were taken with the Calar Alto 3.5m telescope at different position angles. Also a spectrum of Mkn 305 was taken at Calar Alto with the 3.5m telescope covering the whole spectral range (240 A/mm).

  1. Fermi surface versus Fermi sea contributions to intrinsic anomalous and spin Hall effects of multiorbital metals in the presence of Coulomb interaction and spin-Coulomb drag

    NASA Astrophysics Data System (ADS)

    Arakawa, Naoya

    2016-06-01

    Anomalous Hall effect (AHE) and spin Hall effect (SHE) are fundamental phenomena, and their potential for application is great. However, we understand the interaction effects unsatisfactorily, and should have clarified issues about the roles of the Fermi sea term and Fermi surface term of the conductivity of the intrinsic AHE or SHE of an interacting multiorbital metal and about the effects of spin-Coulomb drag on the intrinsic SHE. Here, we resolve the first issue and provide the first step about the second issue by developing a general formalism in the linear response theory with appropriate approximations and using analytic arguments. The most striking result is that even without impurities, the Fermi surface term, a non-Berry-curvature term, plays dominant roles at high or slightly low temperatures. In particular, this Fermi surface term causes the temperature dependence of the dc anomalous Hall or spin Hall conductivity due to the interaction-induced quasiparticle damping and the correction of the dc spin Hall conductivity due to the spin-Coulomb drag. Those results revise our understanding of the intrinsic AHE and SHE. We also find that the differences between the dc anomalous Hall and longitudinal conductivities arise from the difference in the dominant multiband excitations. This not only explains why the Fermi sea term such as the Berry-curvature term becomes important in clean and low-temperature case only for interband transports, but also provides the useful principles on treating the electron-electron interaction in an interacting multiorbital metal for general formalism of transport coefficients. Several correspondences between our results and experiments are finally discussed.

  2. Borromean Windows for Three-Particle Systems under Screened Coulomb Interactions

    NASA Astrophysics Data System (ADS)

    Jiang, Zi-Shi; Song, Xiu-Dan; Zhou, Lin; Kar, Sabyasachi

    2017-05-01

    We have carried out calculations to search Borromean windows (BWs) for 11 different three-body systems interacting with screened Coulomb (Yukawa-type) potentials using Hylleraas-type wave functions within the framework of a variational approach. The critical values of the screening parameters for the ground states of the systems under consideration are reported for which the three-body systems are stable, while all the possible fragments are unbound; that is, it shows windows for Borromean binding. Supported by the National Natural Science Foundation of China under Grant No. 11304086, the University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province of China under Grant No. UNPYSCT-2015019, and the Natural Science Foundation for Distinguished Young Scholars in Heilongjiang University under Grant No. JCL201503

  3. Coulomb interactions in a low-voltage focussed ion beam system

    NASA Astrophysics Data System (ADS)

    Marianowski, K.; Ohnweiler, T.; Plies, E.

    2011-07-01

    To be able to further optimise a low-voltage focussed ion beam system with immersion lenses and booster principle it is necessary to investigate the influence of Coulomb interactions in such a system in more detail. Therefore, Monte Carlo simulations have been done for an example system consisting of two immersion lenses separated by a drift space set to high potential (booster voltage) using both the commercial software package IMAGE by Mebs Ltd. and the programme MONTEC developed by G.H. Jansen. Parameters varied here are the total column length, the working distance as well as the internal operating mode of the objective lens. Results will be presented for landing energies of 3, 2 and 1 keV.

  4. Simple correlation-corrected theory of systems described by screened coulomb interactions.

    PubMed

    Forsman, Jan

    2007-05-08

    We present a simple correlation-corrected density functional treatment of dispersions containing macroions, where these are assumed to interact via screened Coulomb potentials, as given by Debye-Hückel theory. A straightforward mean-field description even fails to qualitatively capture important correlation effects displayed by such systems. However, if an effective, correlation-corrected potential is adopted at short range, then the predictions are in qualitative and semiquantitative agreement with simulated results. The correlation corrections are evaluated in a manner that is completely analogous to those recently presented in correlation-corrected Poisson-Boltzmann theory (Forsman, J. J. Phys. Chem. B 2004, 108, 9236). The accuracy of the theory is evaluated by comparison with simulation data on systems displaying correlation-generated packing effects and stratification forces.

  5. Strength of the effective Coulomb interaction at metal and insulator surfaces.

    PubMed

    Şaşıoğlu, Ersoy; Friedrich, Christoph; Blügel, Stefan

    2012-10-05

    The effective on-site Coulomb interaction (Hubbard U) between localized electrons at crystal surfaces is expected to be enhanced due to the reduced coordination number and reduced subsequent screening. By means of first principles calculations employing the constrained random-phase approximation we show that this is indeed the case for simple metals and insulators but not necessarily for transition metals and insulators that exhibit pronounced surface states. In the latter case, the screening contribution from surface states as well as the influence of the band narrowing increases the electron polarization to such an extent as to overcompensate the decrease resulting from the reduced effective screening volume. The Hubbard U parameter is thus substantially reduced in some cases, e.g., by around 30% for the (100) surface of bcc Cr.

  6. Effective single-band Hubbard model for the cuprates: Coulomb interactions and apical oxygen

    NASA Astrophysics Data System (ADS)

    Feiner, L. F.; Jefferson, J. H.; Raimondi, R.

    1995-02-01

    Starting with the three-band d-p model representing the high- Tc cuprates, we make a systematic reduction to an effective single-band model using a previously developed cell-perturbation method. In particular, we consider the effect of Coulomb repulsions on oxygen ( Up) and between copper and oxygen ( Vpd), and show that the resulting net Coloumb interaction between doped holes on neighbouring cells can be attractive due to locally enhanced pd hybridization, while this cannot occur for electrons. Extending to a five-band model, by including d 3 z2- r2 and apex p z orbitals, we show that there is, in addition to the usual Zhang-Rice singlet, a two-hole cell state which can be low in energy (depending on the proximity of the apicals), and may lead to a breakdown of the effective single-band model.

  7. Relativistic effects in the photoionization of hydrogen-like ions with screened Coulomb interaction

    SciTech Connect

    Xie, L. Y.; Wang, J. G.; Janev, R. K.

    2014-06-15

    The relativistic effects in the photoionization of hydrogen-like ion with screened Coulomb interaction of Yukawa type are studied for a broad range of screening lengths and photoelectron energies. The bound and continuum wave functions have been determined by solving the Dirac equation. The study is focused on the relativistic effects manifested in the characteristic features of photoionization cross section for electric dipole nl→ε,l±1 transitions: shape resonances, Cooper minima and cross section enhancements due to near-zero-energy states. It is shown that the main source of relativistic effects in these cross section features is the fine-structure splitting of bound state energy levels. The relativistic effects are studied in the photoionization of Fe{sup 25+} ion, as an example.

  8. Coulomb Interaction Effect in Weyl Fermions with Tilted Energy Dispersion in Two Dimensions.

    PubMed

    Isobe, Hiroki; Nagaosa, Naoto

    2016-03-18

    Weyl fermions with tilted linear dispersions characterized by several different velocities appear in some systems including the quasi-two-dimensional organic semiconductor α-(BEDT-TTF)_{2}I_{3} and three-dimensional WTe_{2}. The Coulomb interaction between electrons modifies the velocities in an essential way in the low-energy limit, where the logarithmic corrections dominate. Taking into account the coupling to both the transverse and longitudinal electromagnetic fields, we derive the renormalization group equations for the velocities of the tilted Weyl fermions in two dimensions, and found that they increase as the energy decreases and eventually hit the speed of light c to result in the Cherenkov radiation. Especially, the system restores the isotropic Weyl cone even when the bare Weyl cone is strongly tilted and the velocity of electrons becomes negative in certain directions.

  9. Coulomb Interaction Effect in Weyl Fermions with Tilted Energy Dispersion in Two Dimensions

    NASA Astrophysics Data System (ADS)

    Isobe, Hiroki; Nagaosa, Naoto

    2016-03-01

    Weyl fermions with tilted linear dispersions characterized by several different velocities appear in some systems including the quasi-two-dimensional organic semiconductor α -(BEDT -TTF )2I3 and three-dimensional WTe2 . The Coulomb interaction between electrons modifies the velocities in an essential way in the low-energy limit, where the logarithmic corrections dominate. Taking into account the coupling to both the transverse and longitudinal electromagnetic fields, we derive the renormalization group equations for the velocities of the tilted Weyl fermions in two dimensions, and found that they increase as the energy decreases and eventually hit the speed of light c to result in the Cherenkov radiation. Especially, the system restores the isotropic Weyl cone even when the bare Weyl cone is strongly tilted and the velocity of electrons becomes negative in certain directions.

  10. Strength of effective Coulomb interactions and origin of ferromagnetism in hydrogenated graphene

    NASA Astrophysics Data System (ADS)

    Şaşıoǧlu, E.; Hadipour, H.; Friedrich, C.; Blügel, S.; Mertig, I.

    2017-02-01

    Hydrogenation provides a novel way to tune the electronic properties of graphene. Recent scanning tunneling microscopy experiments have demonstrated that local graphene magnetism can be selectively switched on and off by hydrogen (H) dimers. Employing first-principles calculations in conjunction with the constrained random-phase approximation we determine the strength of the effective Coulomb interaction U in hydrogenated graphene. We find that the calculated U parameters are smaller than the ones in graphene and depend on the H concentration. Moreover, the U parameters are very sensitive to the position of H atoms adsorbed on the graphene lattice. We discuss the instability of the paramagnetic state of the hydrogenated graphene towards the ferromagnetic one on the basis of calculated U parameters within the Stoner model. Spin-polarized calculations reveal that the itinerant ferromagnetism in hydrogenated graphene can be well accounted for by the Stoner model.

  11. Quasi-particle spectrum in trilayer graphene: Role of onsite coulomb interaction and interlayer coupling

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjay; Ajay

    2015-01-01

    Stacking dependent quasi-particle spectrum and density of states (DOS) in trilayer (ABC-, ABA- and AAA-stacked) graphene are analyzed using mean-field Green's function equations of motion method. Interlayer coupling (t1) is found to be responsible for the splitting of quasi-particle peaks in each stacking order. Coulomb interaction suppresses the trilayer splitting and generates a finite gap at Fermi level in ABC- while a tiny gap in ABA-stacked trilayer graphene. Influence of t⊥ is prominent for AAA-stacking as compared to ABC- and ABA-stacking orders. The theoretically obtained quasi-particle energies and DOS has been viewed in terms of recent angle resolved photoemission spectroscopic (ARPES) and scanning tunneling microscopic (STM) data available on these systems.

  12. The equation-transform model for Dirac–Morse problem including Coulomb tensor interaction

    SciTech Connect

    Ortakaya, Sami

    2013-11-15

    The approximate solutions of Dirac equation with Morse potential in the presence of Coulomb-like tensor potential are obtained by using Laplace transform (LT) approach. The energy eigenvalue equation of the Dirac particles is found and some numerical results are obtained. By using convolution integral, the corresponding radial wave functions are presented in terms of confluent hypergeometric functions. -- Highlights: •The Dirac equation with tensor interaction is solved by using Laplace transform. •For solving this equation, we introduce the equation-transform model. •Numerical results and plots for pseudospin and spin symmetric solutions are given. •The obtained numerical results by using transform method are compared with orthogonal polynomial method.

  13. Coulomb-interaction induced coupling of Landau levels in intrinsic and modulation-doped quantum wells

    NASA Astrophysics Data System (ADS)

    Paul, J.; Stevens, C. E.; Zhang, H.; Dey, P.; McGinty, D.; McGill, S. A.; Smith, R. P.; Reno, J. L.; Turkowski, V.; Perakis, I. E.; Hilton, D. J.; Karaiskaj, D.

    2017-06-01

    We have performed two-dimensional Fourier transform spectroscopy on intrinsic and modulation doped quantum wells in external magnetic fields up to 10 T. In the undoped sample, the strong Coulomb interactions and the increasing separations of the electron and hole charge distributions with increasing magnetic fields lead to a nontrivial in-plane dispersion of the magneto-excitons. Thus, the discrete and degenerate Landau levels are coupled to a continuum. The signature of this continuum is the emergence of elongated spectral line shapes at the Landau level energies, which are exposed by the multidimensional nature of our technique. Surprisingly, the elongation of the peaks is completely absent in the lowest Landau level spectra obtained from the modulation doped quantum well at high fields.

  14. Coulomb Interactions between Cytoplasmic Electric Fields and Phosphorylated Messenger Proteins Optimize Information Flow in Cells

    PubMed Central

    Gatenby, Robert A.; Frieden, B. Roy

    2010-01-01

    Background Normal cell function requires timely and accurate transmission of information from receptors on the cell membrane (CM) to the nucleus. Movement of messenger proteins in the cytoplasm is thought to be dependent on random walk. However, Brownian motion will disperse messenger proteins throughout the cytosol resulting in slow and highly variable transit times. We propose that a critical component of information transfer is an intracellular electric field generated by distribution of charge on the nuclear membrane (NM). While the latter has been demonstrated experimentally for decades, the role of the consequent electric field has been assumed to be minimal due to a Debye length of about 1 nanometer that results from screening by intracellular Cl− and K+. We propose inclusion of these inorganic ions in the Debye-Huckel equation is incorrect because nuclear pores allow transit through the membrane at a rate far faster than the time to thermodynamic equilibrium. In our model, only the charged, mobile messenger proteins contribute to the Debye length. Findings Using this revised model and published data, we estimate the NM possesses a Debye-Huckel length of a few microns and find this is consistent with recent measurement using intracellular nano-voltmeters. We demonstrate the field will accelerate isolated messenger proteins toward the nucleus through Coulomb interactions with negative charges added by phosphorylation. We calculate transit times as short as 0.01 sec. When large numbers of phosphorylated messenger proteins are generated by increasing concentrations of extracellular ligands, we demonstrate they generate a self-screening environment that regionally attenuates the cytoplasmic field, slowing movement but permitting greater cross talk among pathways. Preliminary experimental results with phosphorylated RAF are consistent with model predictions. Conclusion This work demonstrates that previously unrecognized Coulomb interactions between

  15. Gas-liquid phase coexistence and crossover behavior of binary ionic fluids with screened Coulomb interactions.

    PubMed

    Patsahan, O

    2014-06-01

    We study the effects of an interaction range on the gas-liquid phase diagram and the crossover behavior of a simple model of ionic fluids: an equimolar binary mixture of equisized hard spheres interacting through screened Coulomb potentials which are repulsive between particles of the same species and attractive between particles of different species. Using the collective variables theory, we find explicit expressions for the relevant coefficients of the effective φ{4} Ginzburg-Landau Hamiltonian in a one-loop approximation. Within the framework of this approximation, we calculate the critical parameters and gas-liquid phase diagrams for varying inverse screening length z. Both the critical temperature scaled by the Yukawa potential contact value and the critical density rapidly decrease with an increase of the interaction range (a decrease of z) and then for z<0.05 they slowly approach the values found for a restricted primitive model (RPM). We find that gas-liquid coexistence region reduces with an increase of z and completely vanishes at z≃2.78. Our results clearly show that an increase in the interaction range leads to a decrease of the crossover temperature. For z≃0.01, the crossover temperature is the same as for the RPM.

  16. Superconducting pairing of interacting electrons: implications from the two-impurity Anderson model

    NASA Astrophysics Data System (ADS)

    Zhu, Lijun; Zhu, Jian-Xin

    2011-03-01

    We study the non-local superconducting pairing of two interacting Anderson impurities, which has an instability near the quantum critical point from the competition between the Kondo effect and an antiferromagnetic inter-impurity spin exchange interaction. As revealed by the dynamics over the whole energy range, the superconducting pairing fluctuations acquire considerable strength from an energy scale much higher than the characteristic spin fluctuation scale while the low energy behaviors follow those of the staggered spin susceptibility. We argue that the superconducting pairing might not need the spin fluctuations as the glue, but rather originated from the effective Coulomb interaction. On the other hand, critical spin fluctuations in the vicinity of quantum criticality are also crucial to a superconducting pairing instability, by preventing a Fermi liquid fixed point being reached to keep the superconducting pairing fluctuations finite at low energies. A superconducting order, to reduce the accumulated entropy carried by the critical degrees of freedom, may arise favorably from this instability. This work is supported by the U.S. DOE through the LANL/LDRD program.

  17. Measurements and calculations of the Coulomb cross section for the production of direct electron pairs by energetic heavy nuclei in nuclear track emulsion

    NASA Technical Reports Server (NTRS)

    Derrickson, J. H.; Eby, P. B.; Fountain, W. F.; Parnell, T. A.; Dong, B. L.; Gregory, J. C.; Takahashi, Y.; King, D. T.

    1988-01-01

    Measurements and theoretical predictions of the Coulomb cross section for the production of direct electron pairs by heavy ions in emulsion have been performed. Nuclear track emulsions were exposed to the 1.8 GeV/amu Fe-56 beam at the Lawrence Berkeley Laboratory bevalac and to the 60 and 200 GeV/amu O-16 and the 200 GeV/amu S-32 beam at the European Center for Nuclear Research Super Proton Synchrotron modified to accelerate heavy ions. The calculations combine the Weizsacker-Williams virtual quanta method applicable to the low-energy transfers and the Kelner-Kotov relativistic treatment for the high-energy transfers. Comparison of the measured total electron pair yield, the energy transfer distribution, and the emission angle distribution with theoretical predictions revealed a discrepancy in the frequency of occurrence of the low-energy pairs (less than or = 10 MeV). The microscope scanning criteria used to identify the direct electron pairs is described and efforts to improve the calculation of the cross section for pair production are also discussed.

  18. Isospin Dependent Pairing Interactions and BCS-BEC crossover

    SciTech Connect

    Sagawa, H.; Margueron, J.; Hagino, K.

    2008-11-11

    We propose new types of density dependent contact pairing interaction which reproduce the pairing gaps in symmetric and neutron matters obtained by a microscopic treatment based on the realistic nucleon-nucleon interaction. The BCS-BEC crossover of neutrons pairs in symmetric and asymmetric nuclear matters is studied by using these contact interactions. It is shown that the bare and screened pairing interactions lead to different features of the BCS-BEC crossover in symmetric nuclear matter. We perform Hartree-Fock-Bogoliubov (HFB) calculations for semi-magic Calcium, Nickel, Tin and Lead isotopes and N = 20, 28, 50 and 82 isotones using these density-dependent pairing interactions. Our calculations well account for the experimental data for the neutron number dependence of binding energy, two neutrons separation energy, and odd-even mass staggering of these isotopes. Especially the interaction IS+IV Bare without the medium polarization effect gives satisfactory results for all the isotopes.

  19. Heat-capacity changes in host-guest complexation by Coulomb interactions in aqueous solution.

    PubMed

    Kano, Koji; Ishida, Yoshiyuki; Kitagawa, Kohei; Yasuda, Mayuko; Watanabe, Maki

    2007-10-01

    Heat-capacity changes (deltaC(p)0) were determined for the complexation of 1-alkanecarboxylates with protonated hexakis(6-amino-6-deoxy)-alpha-cyclodextrin (per-NH3(+)-alpha-CD) and heptakis(6-amino-6-deoxy)-beta-cyclodextrin (per-NH3(+)-beta-CD). DeltaC(p)0 decreased with an increase in the binding constant (K) and plateaued at K = 4000 M(-1). The complexes of 1-pentanoate, 1-hexanoate, and 1-heptanoate with per-NH3(+)-alpha-CD are classified as the host-guest system in which the size of the guest fits the CD cavity well. In such a system, van der Waals interaction is the major force for complexation, leading to a negative deltaH0 value. Simultaneously, the water molecules around the hydrophobic alkyl chain of the guest and inside the CD cavity are released to the aqueous bulk phase, leading to a positive deltaS0 value. The negative deltaC(p)0 value in such complexation is ascribed to dehydration of the hydrophobic alkyl chain of the guest and extrusion of the water molecules inside the CD cavity. Meanwhile, the complexes that show positive deltaC(p)0 values are characterized by complexation in which the guest molecules are significantly smaller than the CD cavities. In such a case, the complexation is endothermic and driven by the entropy gain. When the guest is much smaller than the CD cavity, the main binding force should be Coulomb interaction. To form an ionic bond, dehydration of the charged groups must occur. This process is endothermic and leads to positive deltaH0 and deltaS0 values. As the top of the CD cavity is capped by a small but hydrophobic alkyl chain, the water molecules inside the CD cavity may form the iceberg structure. This process must be accompanied by a positive deltaC(p)0 value. Hence, the complexation of a small guest with the CD with a large cavity through Coulomb interactions shows positive and large deltaC(p)0 values. These conclusions were applied to the electrostatic binding of proteins with an anionic ligand.

  20. FMM-Yukawa: An adaptive fast multipole method for screened Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Huang, Jingfang; Jia, Jun; Zhang, Bo

    2009-11-01

    A Fortran program package is introduced for the rapid evaluation of the screened Coulomb interactions of N particles in three dimensions. The method utilizes an adaptive oct-tree structure, and is based on the new version of fast multipole method in which the exponential expansions are used to diagonalize the multipole-to-local translations. The program and its full description, as well as several closely related packages are also available at http://www.fastmultipole.org/. This paper is a brief review of the program and its performance. Catalogue identifier: AEEQ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEQ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GPL 2.0 No. of lines in distributed program, including test data, etc.: 12 385 No. of bytes in distributed program, including test data, etc.: 79 222 Distribution format: tar.gz Programming language: Fortran77 and Fortran90 Computer: Any Operating system: Any RAM: Depends on the number of particles, their distribution, and the adaptive tree structure Classification: 4.8, 4.12 Nature of problem: To evaluate the screened Coulomb potential and force field of N charged particles, and to evaluate a convolution type integral where the Green's function is the fundamental solution of the modified Helmholtz equation. Solution method: An adaptive oct-tree is generated, and a new version of fast multipole method is applied in which the "multipole-to-local" translation operator is diagonalized. Restrictions: Only three and six significant digits accuracy options are provided in this version. Unusual features: Most of the codes are written in

  1. Interacting preformed Cooper pairs in resonant Fermi gases

    SciTech Connect

    Gubbels, K. B.; Stoof, H. T. C.

    2011-07-15

    We consider the normal phase of a strongly interacting Fermi gas, which can have either an equal or an unequal number of atoms in its two accessible spin states. Due to the unitarity-limited attractive interaction between particles with different spin, noncondensed Cooper pairs are formed. The starting point in treating preformed pairs is the Nozieres-Schmitt-Rink (NSR) theory, which approximates the pairs as being noninteracting. Here, we consider the effects of the interactions between the Cooper pairs in a Wilsonian renormalization-group scheme. Starting from the exact bosonic action for the pairs, we calculate the Cooper-pair self-energy by combining the NSR formalism with the Wilsonian approach. We compare our findings with the recent experiments by Harikoshi et al. [Science 327, 442 (2010)] and Nascimbene et al. [Nature (London) 463, 1057 (2010)], and find very good agreement. We also make predictions for the population-imbalanced case, which can be tested in experiments.

  2. IMPORTANCE OF FULL COULOMB INTERACTIONS FOR UNDERSTANDING THE ELECTRONIC STRUCTURE OF DELTA-Pu

    SciTech Connect

    Gorelov, E; Kolorenc, J; Wehling, T; Hafermann, H; Lichtenstein, A I; Shick, A B; Rubtsov, A N; Katsnelson, M I; Landa, A; McMahan, A K

    2010-04-01

    The solid-state properties of most elements are now well understood on the basis of quantum physics - with few exceptions, notably the element number 94, plutonium. Plutonium has six crystalline phases at ambient pressure, some of which are separated by unusual phase transitions with large discontinuities in volume, exhibit negative thermal expansion coefficients, or form exotic low-symmetry structures. The main challenge to explain these anomalous properties is that the characteristic ingredient of actinides, the 5f electronic states, are in the cross-over regime between the localized and delocalized (itinerant) behaviour in Pu. The early part of the actinide series with the 5f states being itinerant, i.e. part of the metallic bond, culminates with Pu; starting with Am (Z = 95), the 5f states are localized, nonbonding, and resemble the 4f states in lanthanides. Both itinerant and localized regimes are well covered by existing theories, but they cannot be simply interpolated due to the importance of dynamical electron-electron correlations. Here we present accurate quantum Monte Carlo calculations achieving previously inaccessible resolution. Obtained results demonstrate that interplay of the full Coulomb interaction vertex with spin-orbital coupling is crucial for understanding the experimentally observed spectral properties of plutonium near the Fermi level.

  3. Interatomic Coulombic Decay Effects in Theoretical DNA Recombination Systems Involving Protein Interaction Sites

    NASA Astrophysics Data System (ADS)

    Vargas, E. L.; Rivas, D. A.; Duot, A. C.; Hovey, R. T.; Andrianarijaona, V. M.

    2015-03-01

    DNA replication is the basis for all biological reproduction. A strand of DNA will ``unzip'' and bind with a complimentary strand, creating two identical strands. In this study, we are considering how this process is affected by Interatomic Coulombic Decay (ICD), specifically how ICD affects the individual coding proteins' ability to hold together. ICD mainly deals with how the electron returns to its original state after excitation and how this affects its immediate atomic environment, sometimes affecting the connectivity between interaction sites on proteins involved in the DNA coding process. Biological heredity is fundamentally controlled by DNA and its replication therefore it affects every living thing. The small nature of the proteins (within the range of nanometers) makes it a good candidate for research of this scale. Understanding how ICD affects DNA molecules can give us invaluable insight into the human genetic code and the processes behind cell mutations that can lead to cancer. Authors wish to give special thanks to Pacific Union College Student Senate in Angwin, California, for their financial support.

  4. Protein Solvation from Theory and Simulation: Exact Treatment of Coulomb Interactions in Three-Dimensional Theories

    SciTech Connect

    Perkyns, John S.; Lynch, Gillian C.; Howard, Jesse J.; Pettitt, Bernard M.

    2010-02-14

    Solvation forces dominate protein structure and dynamics. Integral equation theories allow a rapid and accurate evaluation of the effect of solvent around a complex solute, without the sampling issues associated with simulations of explicit solvent molecules. Advances in integral equation theories make it possible to calculate the angle dependent average solvent structure around an irregular molecular solution. We consider two methodological problems here: the treatment of long-ranged forces without the use of artificial periodicity or truncations and the effect of closures. We derive a method for calculating the long-ranged Coulomb interaction contributions to three-dimensional distribution functions involving only a rewriting of the system of integral equations and introducing no new formal approximations. We show the comparison of the exact forms with those implied by the supercell method. The supercell method is shown to be a good approximation for neutral solutes whereas the new method does not exhibit the known problems of the supercell method for charged solutes. Our method appears more numerically stable with respect to thermodynamic starting state. We also compare closures including the Kovalenko–Hirata closure, the hypernetted-chain _HNC_ and an approximate three-dimensional bridge fu nction combined with the HNC closure. Comparisons to molecular dynamics results are made for water as well as for the protein solute bovine pancreatic trypsin inhibitor. The proposed equations have less severe approximations and often provide results which compare favorably to molecular dynamics simulation where other methods fail.

  5. Non-local magnetoelectric effects via Coulomb interaction in TI-FMI heterostructures

    NASA Astrophysics Data System (ADS)

    Rex, Stefan; Nogueira, Flavio S.; Sudbø, Asle

    Magnetic order on the surface of a 3 D topological insulator (TI) has been predicted to evoke a topological magnetoelectric effect (TME) by the breaking of time-reversal invariance. In the TME, an electric field leads to a magnetic polarization in the same direction as the field and vice versa. Here, we consider heterostructures of TI and ferromagnetic insulator (FMI) layers. We show that in the presence of long-range Coulomb interactions the magnetization couples non-locally to the fluctuating electric field (non-local TME) by performing a field-theoretic calculation of the vacuum polarization. In addition, we obtain a Landau-Lifshitz equation for the magnetization dynamics, and find that charged magnetic textures lead to a net magnetization even at a large distance. Such textures can be induced by an external electric field with nonzero in-plane divergence. We apply this effect to a FMI-TI-FMI trilayer heterostructure with two parallel interfaces being well-separated by the bulk TI, where we propose to non-locally control the magnetic texture at one interface by proper gating of the other interface. A preprint can be found at arXiv:1510.04285 Supported by the Norwegian Research Council, Grants 205591/V20 and 216700/F20, and the Collaborative Research Center SFB 1143 ''Correlated Magnetism: From Frustration to Topology''.

  6. Protein solvation from theory and simulation: Exact treatment of Coulomb interactions in three-dimensional theories

    PubMed Central

    Perkyns, John S.; Lynch, Gillian C.; Howard, Jesse J.; Pettitt, B. Montgomery

    2010-01-01

    Solvation forces dominate protein structure and dynamics. Integral equation theories allow a rapid and accurate evaluation of the effect of solvent around a complex solute, without the sampling issues associated with simulations of explicit solvent molecules. Advances in integral equation theories make it possible to calculate the angle dependent average solvent structure around an irregular molecular solution. We consider two methodological problems here: the treatment of long-ranged forces without the use of artificial periodicity or truncations and the effect of closures. We derive a method for calculating the long-ranged Coulomb interaction contributions to three-dimensional distribution functions involving only a rewriting of the system of integral equations and introducing no new formal approximations. We show the comparison of the exact forms with those implied by the supercell method. The supercell method is shown to be a good approximation for neutral solutes whereas the new method does not exhibit the known problems of the supercell method for charged solutes. Our method appears more numerically stable with respect to thermodynamic starting state. We also compare closures including the Kovalenko–Hirata closure, the hypernetted-chain (HNC) and an approximate three-dimensional bridge function combined with the HNC closure. Comparisons to molecular dynamics results are made for water as well as for the protein solute bovine pancreatic trypsin inhibitor. The proposed equations have less severe approximations and often provide results which compare favorably to molecular dynamics simulation where other methods fail. PMID:20151732

  7. Protein solvation from theory and simulation: Exact treatment of Coulomb interactions in three-dimensional theories.

    PubMed

    Perkyns, John S; Lynch, Gillian C; Howard, Jesse J; Pettitt, B Montgomery

    2010-02-14

    Solvation forces dominate protein structure and dynamics. Integral equation theories allow a rapid and accurate evaluation of the effect of solvent around a complex solute, without the sampling issues associated with simulations of explicit solvent molecules. Advances in integral equation theories make it possible to calculate the angle dependent average solvent structure around an irregular molecular solution. We consider two methodological problems here: the treatment of long-ranged forces without the use of artificial periodicity or truncations and the effect of closures. We derive a method for calculating the long-ranged Coulomb interaction contributions to three-dimensional distribution functions involving only a rewriting of the system of integral equations and introducing no new formal approximations. We show the comparison of the exact forms with those implied by the supercell method. The supercell method is shown to be a good approximation for neutral solutes whereas the new method does not exhibit the known problems of the supercell method for charged solutes. Our method appears more numerically stable with respect to thermodynamic starting state. We also compare closures including the Kovalenko-Hirata closure, the hypernetted-chain (HNC) and an approximate three-dimensional bridge function combined with the HNC closure. Comparisons to molecular dynamics results are made for water as well as for the protein solute bovine pancreatic trypsin inhibitor. The proposed equations have less severe approximations and often provide results which compare favorably to molecular dynamics simulation where other methods fail.

  8. Crossover of Feshbach Resonances to Shape-Type Resonances in Electron-Hydrogen Atom Excitation with a Screened Coulomb Interaction

    SciTech Connect

    Zhang Songbin; Wang Jianguo; Janev, R. K.

    2010-01-15

    The effects of Coulomb interaction screening on electron-hydrogen atom excitation in the n=2 threshold region are investigated by using the R-matrix method with pseudostates. The interaction screening lifts the l degeneracy of n=2 Coulomb energy level, producing two distinct thresholds for 2s and 2p states. The phenomenon of transformation of {sup 1,3}P and {sup 1}D Feshbach resonances into shape-type resonances is observed when they pass across the 2s and 2p threshold, respectively, as the interaction screening increases. It is shown that this resonance transformation leads to dramatic effects in the 1s->2s and 1s->2p excitation collision strengths in the n=2 threshold collision energy region.

  9. Familiar Interacting Object Pairs Are Perceptually Grouped

    ERIC Educational Resources Information Center

    Green, Collin; Hummel, John E.

    2006-01-01

    Identification of objects in a scene may be influenced by functional relations among those objects. In this study, observers indicated whether a target object matched a label. Each target was presented with a distractor object, and these were sometimes arranged to interact (as if being used together) and sometimes not to interact. When the…

  10. Monte Carlo study of charge transport in organic sandwich-type single-carrier devices: Effects of Coulomb interactions

    NASA Astrophysics Data System (ADS)

    van der Holst, J. J. M.; van Oost, F. W. A.; Coehoorn, R.; Bobbert, P. A.

    2011-02-01

    We present the results of Monte Carlo simulations of transport of charge carriers of a single type in devices consisting of a disordered organic semiconductor sandwiched in between two electrodes. The simulations are based on hopping of carriers between sites with a Gaussian energetic distribution, which is either spatially uncorrelated or has a correlation based on interactions with randomly oriented dipoles. Coulomb interactions between the carriers are taken into account explicitly. For not too small injection barriers between the electrodes and the organic semiconductor, we find that the current obtained from the simulations can be described quite well by a one-dimensional drift-diffusion continuum model, which takes into account the long-range contributions of Coulomb interactions through the space-charge potential. For devices with low injection barriers, however, the simulations yield a considerably lower current than the continuum model. The reduction of the current for uncorrelated disorder is larger than for correlated disorder. By performing simulations in which the short-range contributions of the Coulomb interactions between the carriers are omitted, we demonstrate that the difference is caused by these short-range contributions. We can rationalize our results by analyzing the three-dimensional current distributions and the in-plane radial distribution function of the carriers resulting from the simulations for different injection barriers with and without taking into account these short-range contributions.

  11. Coulomb interaction-induced jitter amplification in RF-compressed high-brightness electron source ultrafast electron diffraction

    NASA Astrophysics Data System (ADS)

    Qi, Yingpeng; Pei, Minjie; Qi, Dalong; Li, Jing; Yang, Yan; Jia, Tianqing; Zhang, Shian; Sun, Zhenrong

    2017-02-01

    We have theoretically and experimentally demonstrated an RF compression-based jitter-amplification effect in high-brightness electron source ultrafast electron diffraction (UED), which degrades the temporal resolution significantly. A detailed analysis and simulations reveal the crucial role of the longitudinal and transverse Coulomb interaction for this jitter-amplification effect, which accord very well with experimental results. An optimized compact UED structure for full compression has been proposed, which can suppress the jitter by half and improve the temporal resolution to sub-100 fs. This Coulomb interaction-induced jitter amplification exists in nearly the whole ultrafast physics field where laser-electron synchronization is required. Moreover, it cannot be suppressed completely. The quantified explanation for the mechanism and optimization provides important guidance for photocathode accelerators and other compression-based ultrashort electron pulse generation and precise control.

  12. Diffusion in Coulomb crystals.

    PubMed

    Hughto, J; Schneider, A S; Horowitz, C J; Berry, D K

    2011-07-01

    Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter Γ=175 to Coulomb parameters up to Γ=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

  13. Diffusion in Coulomb crystals

    SciTech Connect

    Hughto, J.; Schneider, A. S.; Horowitz, C. J.; Berry, D. K.

    2011-07-15

    Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions ''hop'' in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter {Gamma}=175 to Coulomb parameters up to {Gamma}=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

  14. Reducing interaction in simultaneous paired stimulation with CI.

    PubMed

    Vellinga, Dirk; Bruijn, Saskia; Briaire, Jeroen J; Kalkman, Randy K; Frijns, Johan H M

    2017-01-01

    In this study simultaneous paired stimulation of electrodes in cochlear implants is investigated by psychophysical experiments in 8 post-lingually deaf subjects (and one extra subject who only participated in part of the experiments). Simultaneous and sequential monopolar stimulation modes are used as references and are compared to channel interaction compensation, partial tripolar stimulation and a novel sequential stimulation strategy named phased array compensation. Psychophysical experiments are performed to investigate both the loudness integration during paired stimulation at the main electrodes as well as the interaction with the electrode contact located halfway between the stimulating pair. The study shows that simultaneous monopolar stimulation has more loudness integration on the main electrodes and more interaction in between the electrodes than sequential stimulation. Channel interaction compensation works to reduce the loudness integration at the main electrodes, but does not reduce the interaction in between the electrodes caused by paired stimulation. Partial tripolar stimulation uses much more current to reach the needed loudness, but shows the same interaction in between the electrodes as sequential monopolar stimulation. In phased array compensation we have used the individual impedance matrix of each subject to calculate the current needed on each electrode to exactly match the stimulation voltage along the array to that of sequential stimulation. The results show that the interaction in between the electrodes is the same as monopolar stimulation. The strategy uses less current than partial tripolar stimulation, but more than monopolar stimulation. In conclusion, the paper shows that paired stimulation is possible if the interaction is compensated.

  15. From Coulomb Fluid to Self-Generated Charge Glass due to Long-Range Interactions and Geometric Frustration

    NASA Astrophysics Data System (ADS)

    Mahmoudian, Samiyeh; Rademaker, Louk; Ralko, Arnaud; Fratini, Simone; Dobrosavljević, Vladimir

    2015-03-01

    We show that introducing long-range Coulomb interactions immediately lifts the massive ground state degeneracy induced by geometric frustration for electrons on quarter-filled triangular lattices in the semi-classical regime. This produces not only a stripe-ordered (global) crystalline ground state, but also very many low-lying metastable states with amorphous ``stripe-glass'' spatial structure. At intermediate temperatures, such a frustrated Coulomb liquid shows remarkably slow (viscous) dynamics, with very long relaxation times growing in Arrhenius fashion upon cooling, as typical of ``strong glass formers.'' On shorter time scales, the system falls out of equilibrium and displays the ``aging'' phenomena characteristic of supercooled liquids around the glass transition. Our results, which are obtained using mean field theory, classical Monte Carlo simulations and exact diagonalization, show remarkable similarity with the recent observations of charge-glass behavior in ultra-clean triangular organic materials θ-RbZn and θ-CsZn.

  16. Revision of FMM-Yukawa: An adaptive fast multipole method for screened Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Huang, Jingfang; Pitsianis, Nikos P.; Sun, Xiaobai

    2010-12-01

    FMM-YUKAWA is a mathematical software package primarily for rapid evaluation of the screened Coulomb interactions of N particles in three dimensional space. Since its release, we have revised and re-organized the data structure, software architecture, and user interface, for the purpose of enabling more flexible, broader and easier use of the package. The package and its documentation are available at http://www.fastmultipole.org/, along with a few other closely related mathematical software packages. New version program summaryProgram title: FMM-Yukawa Catalogue identifier: AEEQ_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEQ_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU GPL 2.0 No. of lines in distributed program, including test data, etc.: 78 704 No. of bytes in distributed program, including test data, etc.: 854 265 Distribution format: tar.gz Programming language: FORTRAN 77, FORTRAN 90, and C. Requires gcc and gfortran version 4.4.3 or later Computer: All Operating system: Any Classification: 4.8, 4.12 Catalogue identifier of previous version: AEEQ_v1_0 Journal reference of previous version: Comput. Phys. Comm. 180 (2009) 2331 Does the new version supersede the previous version?: Yes Nature of problem: To evaluate the screened Coulomb potential and force field of N charged particles, and to evaluate a convolution type integral where the Green's function is the fundamental solution of the modified Helmholtz equation. Solution method: The new version of fast multipole method (FMM) that diagonalizes the multipole-to-local translation operator is applied with the tree structure adaptive to sample particle locations. Reasons for new version: To handle much larger particle ensembles, to enable the iterative use of the subroutines in a solver, and to remove potential contention in assignments for parallelization. Summary of revisions: The software package FMM-Yukawa has been

  17. Unlike-pair interactions at high pressure and high temperature

    SciTech Connect

    Ree, F.H.; van Thiel, M.

    1993-07-01

    Although there are more unlike-pairs than like-pairs in detonation products, information on unlike-pair interactions is scarce at present. We describe how unlike pair-interactions involving dissociation products of CO and CO{sub 2} can be derived by means of an accurate statistical mechanical theory of mixtures and recent shock wave data of CO and CO{sub 2}. We then extend this complex study further by interpreting shock data of liquid NO and N{sub 2} + O{sub 2} mixture. It was done by constraining the resulting potentials to agree with all available Hugoniot data of chemical species occurring in detonation products in a self-consistent manner.

  18. The effect of Coulomb interactions on thermoelectric properties of quantum dots

    SciTech Connect

    Zimbovskaya, Natalya A.

    2014-03-14

    Thermoelectric effects in a quantum dot coupled to the source and drain charge reservoirs are explored using a nonequilibrium Green's functions formalism beyond the Hartree-Fock approximation. Thermal transport is analyzed within a linear response regime. A transition from Coulomb blockade regime to Kondo regime in thermoelectric transport through a single-level quantum dot is traced using unified approximations for the relevant Green's functions.

  19. Coulomb static stress interactions between M>5 earthquakes and major active faults in Northern California

    NASA Astrophysics Data System (ADS)

    Segou, M.; Parsons, T.; Kalkan, E.

    2011-12-01

    We have calculated Coulomb stress changes between 1980-2006 in Northern California from fourteen events as well as from the major historic ruptures of 1865, 1868 and 1906. The seismic and fault geometry parameters are taken from the Working Group on California Earthquake Probabilities report (2008). We assess the static Coulomb stress hypothesis as a triggering mechanism for the aftershock sequences of these events using the high accuracy earthquake catalog of Waldhauser and Schaff (2008), which is based on waveform cross-correlation and double-difference methods. We examined the sensitivity of static Coulomb stress changes due to source parametrization by considering different rupture models and aftershock fault orientations for each event. To quantify the variability due to slip distribution, we used both a uniform and variable slip model. Source fault geometry corresponds to: (1) a fault plane suggested by the Global Centroid Moment Tensor (GCMT) and (2) the related mapped fault. In order to analyze the impact of the receiving fault geometry, we used: (1) geometry similar to the source and (2) optimally oriented fault planes for failure (King et al., 1994), taking into account the regional stress field derived in Hardebeck and Michael (2004) from focal mechanism analysis. The sensitivity of the calculations to different focal depths and apparent coefficients of friction (0.1-0.8) has been also investigated.

  20. Coulomb and spin-orbit interaction matrix elements in the ? configuration

    NASA Astrophysics Data System (ADS)

    Lo, Edwin

    1998-11-01

    The 0953-4075/31/21/006/img2 configuration is analysed in group-theoretical terms. Starting from the table given by Condon and Odabasi for the configuration 0953-4075/31/21/006/img2, we determine a set of convenient group-theoretical basis states, and rewrite the Coulomb matrix elements in terms of this new basis. Linear combinations from the different parts of the Coulomb operators are formed such that they have simple group transformation properties in our scheme. The sequence of groups that we use is 0953-4075/31/21/006/img4, where T denotes the isospin of Simonis et al, in which electrons with the same angular momentum l but different principal quantum numbers n are accommodated by introducing the eigenvalue 0953-4075/31/21/006/img5 of 0953-4075/31/21/006/img6. Using the Wigner-Eckart theorem and selection rules on the higher symmetry groups, the tables of the Coulomb and spin-orbit matrix elements for the reconstituted operators (with simple group transformation properties) are much simplified in terms of these basis states.

  1. Reducing interaction in simultaneous paired stimulation with CI

    PubMed Central

    Vellinga, Dirk; Briaire, Jeroen J.; Kalkman, Randy K.; Frijns, Johan H. M.

    2017-01-01

    In this study simultaneous paired stimulation of electrodes in cochlear implants is investigated by psychophysical experiments in 8 post-lingually deaf subjects (and one extra subject who only participated in part of the experiments). Simultaneous and sequential monopolar stimulation modes are used as references and are compared to channel interaction compensation, partial tripolar stimulation and a novel sequential stimulation strategy named phased array compensation. Psychophysical experiments are performed to investigate both the loudness integration during paired stimulation at the main electrodes as well as the interaction with the electrode contact located halfway between the stimulating pair. The study shows that simultaneous monopolar stimulation has more loudness integration on the main electrodes and more interaction in between the electrodes than sequential stimulation. Channel interaction compensation works to reduce the loudness integration at the main electrodes, but does not reduce the interaction in between the electrodes caused by paired stimulation. Partial tripolar stimulation uses much more current to reach the needed loudness, but shows the same interaction in between the electrodes as sequential monopolar stimulation. In phased array compensation we have used the individual impedance matrix of each subject to calculate the current needed on each electrode to exactly match the stimulation voltage along the array to that of sequential stimulation. The results show that the interaction in between the electrodes is the same as monopolar stimulation. The strategy uses less current than partial tripolar stimulation, but more than monopolar stimulation. In conclusion, the paper shows that paired stimulation is possible if the interaction is compensated. PMID:28182685

  2. Metacognitive decision making and social interactions during paired problem solving

    NASA Astrophysics Data System (ADS)

    Goos, Merrilyn

    1994-12-01

    The study described in this paper investigated the metacognitive strategies used by a pair of senior secondary school students while working together on mechanics problems. Verbal protocols from think-aloud paired problem-solving sessions were analysed in order to examine the monitoring contributions of each individual student, and the significance of student-student interactions. Although the students were generally successful in coordinating their different, yet complementary, problem-solving roles, their metacognitive decision making was sometimes adversely affected by the social interaction between them. The findings suggest some potential benefits and pitfalls of using small group work for problem solving.

  3. Electrohydrodynamic deformation and interaction of a pair of emulsion drops

    NASA Technical Reports Server (NTRS)

    Baygents, James C.

    1994-01-01

    The response of a pair of emulsion drops to the imposition of a uniform electric field is examined. The case studied is that of equal-sized drops whose line of centers is parallel to the axis of the applied field. A new boundary integral solution to the governing equations of the leaky dielectric model is developed; the formulation accounts for the electrostatic and hydrodynamic interactions between the drops, as well as their deformations. Numerical calculations show that, after an initial transient during which the drops primarily deform, the pair drift slowly together due to their electrostatic interactions.

  4. Bound states for a Coulomb-type potential induced by the interaction between a moving electric quadrupole moment and a magnetic field

    SciTech Connect

    Bakke, K.

    2014-02-15

    We discuss the arising of bound states solutions of the Schrödinger equation due to the presence of a Coulomb-type potential induced by the interaction between a moving electric quadrupole moment and a magnetic field. Furthermore, we study the influence of the Coulomb-type potential on the harmonic oscillator by showing a quantum effect characterized by the dependence of the angular frequency on the quantum numbers of the system, whose meaning is that not all values of the angular frequency are allowed. -- Highlights: • Interaction between a moving electric quadrupole moment and a magnetic field. • Arising of bound states solutions due to the presence of a Coulomb-type potential. • Influence of the Coulomb-type potential on the harmonic oscillator. • Dependence of the angular frequency on the quantum numbers of the system.

  5. Non-additivity of pair interactions in charged colloids

    NASA Astrophysics Data System (ADS)

    Finlayson, Samuel D.; Bartlett, Paul

    2016-07-01

    It is general wisdom that the pair potential of charged colloids in a liquid may be closely approximated by a Yukawa interaction, as predicted by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. We experimentally determine the effective forces in a binary mixture of like-charged particles, of species 1 and 2, with blinking optical tweezers. The measured forces are consistent with a Yukawa pair potential but the (12) cross-interaction is not equal to the geometric mean of the (11) and (22) like-interactions, as expected from DLVO. The deviation is a function of the electrostatic screening length and the size ratio, with the cross-interaction measured being consistently weaker than DLVO predictions. The corresponding non-additivity parameter is negative and grows in magnitude with increased size asymmetry.

  6. Paired and Interacting Galaxies: International Astronomical Union Colloquium No. 124

    NASA Technical Reports Server (NTRS)

    Sulentic, Jack W. (Editor); Keel, William C. (Editor); Telesco, C. M. (Editor)

    1990-01-01

    The proceedings of the International Astronomical Union Colloquium No. 124, held at the University of Alabama at Tuscaloosa, on December 4 to 7, are given. The purpose of the conference was to describe the current state of theoretical and observational knowledge of interacting galaxies, with particular emphasis on galaxies in pairs.

  7. Spin-isospin and pairing properties of modified Skyrme interactions

    NASA Astrophysics Data System (ADS)

    Van Giai, Nguyen; Sagawa, H.

    1981-11-01

    New sets of parameters for Skyrme interactions have been determined. In addition to the ground-state properties, they give satisfactory values for the compression modulus, spin and spin-isospin Landau parameters, and pairing matrix elements. Gamow-Teller states are calculated and compared with experimental data.

  8. Quantifying the FIR interaction enhancement in paired galaxies

    NASA Technical Reports Server (NTRS)

    Xu, Cong; Sulentic, Jack W.

    1990-01-01

    The Catalog of Isolated Pairs of Galaxies in the Northern Hemisphere, by Karachentsev (1972), was studied and a well-matched comparison sample taken from the Catalog of Isolated Galaxies, by Karachentseva (1973), in order to quantify the enhanced FIR emission properties of interacting galaxies.

  9. Molecular electrostatics for probing lone pairinteractions.

    PubMed

    Mohan, Neetha; Suresh, Cherumuttathu H; Kumar, Anmol; Gadre, Shridhar R

    2013-11-14

    An electrostatics-based approach has been proposed for probing the weak interactions between lone pair containing molecules and π deficient molecular systems. For electron-rich molecules, the negative minima in molecular electrostatic potential (MESP) topography give the location of electron localization and the MESP value at the minimum (Vmin) quantifies the electron-rich character of that region. Interactive behavior of a lone pair bearing molecule with electron deficient π-systems, such as hexafluorobenzene, 1,3,5-trinitrobenzene, 2,4,6-trifluoro-1,3,5-triazine and 1,2,4,5-tetracyanobenzene explored within DFT brings out good correlation of the lone pairinteraction energy (E(int)) with the Vmin value of the electron-rich system. Such interaction is found to be portrayed well with the Electrostatic Potential for Intermolecular Complexation (EPIC) model. On the basis of the precise location of MESP minimum, a prediction for the orientation of a lone pair bearing molecule with an electron deficient π-system is possible in the majority of the cases studied.

  10. The effect of Coulomb interactions on nonlinear thermovoltage and thermocurrent in quantum dots

    SciTech Connect

    Zimbovskaya, Natalya A.

    2015-06-28

    In the present work, we theoretically study the nonlinear regime of charge transport through a quantum dot coupled to the source and drain reservoirs. The investigation is carried out using a nonequilibrium Green’s function formalism beyond the Hartree-Fock approximation. Employed approximations for the relevant Green’s functions allow to trace a transition from Coulomb blockade regime to Kondo regime in the thermoelectric transport. Effects arising when electrons move in response to thermal gradient applied across the system are discussed, including experimentally observed thermovoltage zeros.

  11. Exact long-wavelength plasmon dispersion on a ring with soft Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Grasselli, Federico; Bertoni, Andrea; Goldoni, Guido

    2017-09-01

    We obtain the analytical dispersion of 1D plasmonic modes on a ring from the exact solution of the hydrodynamical model with soft Coulomb potential. We compare our results with the exact plasmon dispersion in straight 1D systems and find a set of formal correspondences between the two. In light of our results, we discuss recent experiments (Schmidt et al 2014 Nat. Commun. 5 3604) where ring-confined modes in nanodiscs are found to almost coincide with plasmonic excitations in 1D metallic nanostructures. We trace the similarity to the scaling properties of the plasmonic dispersion.

  12. An effective screened Coulomb interaction in a quasi-one-dimensional system

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Miao, Wen-Dan; Zhai, Li-Xue

    2014-01-01

    In this paper, we derive an analytical expression for the screened Coulomb potential between charge carriers in quasi-one-dimensional (Q1D) semiconductor structures. As an application, this potential has been used to investigate the screening effect on the binding energy of a neutral donor (D0) in quantum wires (QWRs). It is found that the screening effect decreases the neutral donor binding energy, and the screening effects are more obvious in wide QWRs than that in narrow ones. Dependence of screening length on temperature and carrier concentration has also been discussed.

  13. Electronic transport through a Majorana bound state coupled to a T-shaped quantum-dot system with Coulomb interaction

    NASA Astrophysics Data System (ADS)

    Huo, Dong-Ming

    2016-07-01

    Using the Green's function technique, we respectively investigate the electron transport properties of two spin components through the system of a T-shaped double quantum dot structure coupled to a Majorana bound state, in which only one quantum dot is connected with two metallic leads. We explore the interplay between the Fano effect and the MBSs for different dot-MBS coupling strength λ, dot-dot coupling strength t, and MBS-MBS coupling strength ɛM in the noninteracting case. Then the Coulomb interaction and magnetic field effect on the conductance spectra are investigated. Our results indicate that G↓(ω) is not affected by the Majorana bound states, but a "0.5" conductance signature occurs in the vicinities of Fermi level of G↑(ω). This robust property persists for a wide range of dot-dot coupling strength and dot-MBS coupling strength, but it can be destroyed by Coulomb interaction in quantum dots. By adjusting the size and direction of magnetic field around the quantum dots, the "0.5" conductance signature damaged by U can be restored. At last, the spin magnetic moments of two dots by applying external magnetic field are also predicted.

  14. The Interacting Galaxy Pair KPG 390: Hα Kinematics

    NASA Astrophysics Data System (ADS)

    Repetto, P.; Rosado, M.; Gabbasov, R.; Fuentes-Carrera, I.

    2010-04-01

    In this work, we present scanning Fabry-Perot (FP) Hα observations of the isolated interacting galaxy pair NGC 5278/79 obtained with the PUMA FP interferometer. We derived velocity fields and rotation curves for both galaxies. For NGC 5278 we also obtained the residual velocity map to investigate the non-circular motions, and estimated its mass by fitting the rotation curve with disk+halo components. We test three different types of halos (pseudo-isothermal, Hernquist, and Navarro-Frenk-White) and obtain satisfactory fits to the rotation curve for all profiles. The amount of dark matter required by the pseudo-isothermal profile is about 10 times smaller than that for the other two halo distributions. Finally, our kinematical results together with the analysis of dust lane distribution and of surface brightness profiles along the minor axis allowed us to determine univocally that both components of the interacting pair are trailing spirals.

  15. THE INTERACTING GALAXY PAIR KPG 390: H{alpha} KINEMATICS

    SciTech Connect

    Repetto, P.; Rosado, M.; Gabbasov, R.; Fuentes-Carrera, I.

    2010-04-15

    In this work, we present scanning Fabry-Perot (FP) H{alpha} observations of the isolated interacting galaxy pair NGC 5278/79 obtained with the PUMA FP interferometer. We derived velocity fields and rotation curves for both galaxies. For NGC 5278 we also obtained the residual velocity map to investigate the non-circular motions, and estimated its mass by fitting the rotation curve with disk+halo components. We test three different types of halos (pseudo-isothermal, Hernquist, and Navarro-Frenk-White) and obtain satisfactory fits to the rotation curve for all profiles. The amount of dark matter required by the pseudo-isothermal profile is about 10 times smaller than that for the other two halo distributions. Finally, our kinematical results together with the analysis of dust lane distribution and of surface brightness profiles along the minor axis allowed us to determine univocally that both components of the interacting pair are trailing spirals.

  16. Atom-Pair Kinetics with Strong Electric-Dipole Interactions.

    PubMed

    Thaicharoen, N; Gonçalves, L F; Raithel, G

    2016-05-27

    Rydberg-atom ensembles are switched from a weakly to a strongly interacting regime via adiabatic transformation of the atoms from an approximately nonpolar into a highly dipolar quantum state. The resultant electric dipole-dipole forces are probed using a device akin to a field ion microscope. Ion imaging and pair-correlation analysis reveal the kinetics of the interacting atoms. Dumbbell-shaped pair-correlation images demonstrate the anisotropy of the binary dipolar force. The dipolar C_{3} coefficient, derived from the time dependence of the images, agrees with the value calculated from the permanent electric-dipole moment of the atoms. The results indicate many-body dynamics akin to disorder-induced heating in strongly coupled particle systems.

  17. Effect of the Long-Range Coulomb Interaction on the Phase Diagram of the Kohn-Luttinger Superconducting State in Idealized Graphene

    NASA Astrophysics Data System (ADS)

    Kagan, M. Yu.; Mitskan, V. A.; Korovushkin, M. M.

    2016-12-01

    The effect of the long-range Coulomb interaction on the formation of the Kohn-Luttinger superconductivity in monolayer doped graphene is studied disregarding the Van der Waals potential of the substrate and both magnetic and non-magnetic impurities. It is shown that the allowance for the Kohn-Luttinger renormalizations up to the second order in perturbation theory in the on-site Hubbard interaction inclusively, as well as in the intersite Coulomb interaction, significantly affects the interplay between the superconducting phases with the f-wave, p+ip-wave, and d + id-wave symmetries of the order parameter. It is demonstrated that taking Coulomb repulsion of electrons located at the next-nearest neighboring atoms in such a system into account changes qualitatively the phase diagram and enhances the critical temperature of the transition to the superconducting phase.

  18. Intermolecular magnetic interactions in stacked DNA base pairs.

    PubMed

    Martínez, Fernando A; Aucar, Gustavo A

    2017-10-09

    The influence of pi-stacking on the magnetic properties of atoms that belong to adenine-thymine and guanine-cytosine pairs in sequences of three and five layers of DNA base pairs was analysed. As probes we used NMR spectroscopic parameters, which are among the most useful tools to learn about the transmission of magnetic interactions in molecules. Four DFT functionals were employed: B3LYP, BHANDLYP, KT2 and KT3, together with the SOPPA method. Besides, given that the number of non-hydrogen atoms of the supramolecular systems studied here is larger than 50 we applied a locally dense basis set scheme. Our results show that the piling up of a few Watson-Crick base pairs above and below a given pair modifies its NMR spectroscopic parameters by an amount that may be measurable and the percentage of variation does not depend on dispersion. We found that magnetic shieldings are more sensitive than J-couplings, and also that some atoms are more sensitive than others. Stacking affects the shielding of non-hydrogen atoms like nitrogens, that are donors in hydrogen bonds, HBs, and the carbons bonded to them. The amount of variation of these shieldings was found to be from 2% to 5% when the pairs are considered first as isolated, and then, placed in the middle of a sequence of three layers of base pairs. Such a variation becomes vanishingly small when the sequence contains more than three layers, showing that the stacking effect on NMR spectroscopic parameters has a local nature. We have also found a pattern for shieldings. First, equivalent atoms of similar monomers (thymine and adenine, or guanine and cytosine) have similar values of absolute shieldings in isolated pairs, and the amount of variation from isolated pairs to aggregates of a few pairs is also similar, meaning that equivalent atoms are affected in a similar manner by pi-stacking. Second, the hydrogen atoms which belong to hydrogen bonds are more sensitive to the piling up than the non-hydrogen atoms.

  19. Pressure dependence of dynamically screened Coulomb interactions in NiO: Effective Hubbard, Hund, intershell, and intersite components

    NASA Astrophysics Data System (ADS)

    Panda, S. K.; Jiang, H.; Biermann, S.

    2017-07-01

    In this work, we report the pressure dependence of the effective Coulomb interaction parameters (Hubbard U ) in paramagnetic NiO within the constrained random phase approximation (cRPA). We consider five different low-energy models starting from the most expensive one that treats both Ni-d and O-p states as correlated orbitals (d p -d p model) to the smallest possible two-orbital model comprising the eg states only (eg-eg model). We find that in all the considered models, the bare interactions are not very sensitive to the compression. However, the partially screened interaction parameters show an almost linear increment as a function of compression, resulting from the substantial weakening of screening effects upon compression. This counterintuitive trend is explained from the specific characteristic changes of the basic electronic structure of this system. We further calculate the nearest-neighbor intersite d -d interaction terms, which also show substantial enhancement due to compression. The computed interaction parameters for antiferromagnetic NiO are almost identical to their paramagnetic counterparts. Results for other prototypical 3 d transition metal monoxides, FeO, CoO, and CuO, further demonstrate that the monotonic increase of the partially screened interaction parameters under the application of pressure is a generic characteristic of transition metal monoxides. Finally, the effective parameters of 3 d states grow as a function of the atomic number of the transition metal ion.

  20. Color-Flavor Locked Strangelets in a New Quark Model with Linear Confinement and Coulomb-Type Interactions

    NASA Astrophysics Data System (ADS)

    Chen, Shi-Wu; Peng, Guang-Xiong

    2012-06-01

    The color-flavor locked (CFL) strangelets have been investigated in a new quark model with linear confinement and one-gluon-exchange interactions. Considering Coulomb energy, we have studied the properties of three kinds of CFL strangelets, namely, positively charged, negatively charged and nearly neutral CFL strangelets. It is found that the one-gluon-exchange effect lowers the energy of a strangelet considerably and thus makes it much more stable than without considering the effect. The charge of a positive strangelet is larger than 0.15A2/3 with A being the baryon number, but smaller than that in bag model. The charge of a negatively charged or nearly neutral CFL strangelet is nearly proportional to A1/3.

  1. Coulomb explosion as a probe to understand the mechanism of electron stripping from ions interacting with crystalline solids

    SciTech Connect

    Martin y Marero, David; Gordillo, Nuria; Gonzalez-Arrabal, Raquel

    2009-04-15

    When an ion impinges on a solid, it rapidly undergoes a process in which its electrons are stripped away provided the velocity of the orbiting electrons is smaller than the projectile speed. Electron stripping determines any posterior behavior of the ions in the solid, and it is assumed that it takes place on the surface of the solid, but no information is available on the details of the process. Here we show, using the Coulomb explosion of C{sub 2}{sup +} ions moving in Si as a tool, that electron stripping takes place in an orderly manner and that the number of electrons stripped, before charge equilibration, depends on a characteristic length. We also propose a relation capable of quantifying this dependence. We foresee these results as a starting point to a more general understanding of ion-solid interaction, with important consequences on ion beam analysis and modification techniques, and special significance in silicon technology.

  2. Examining the dynamic interactions on volatilities of paired stock markets

    NASA Astrophysics Data System (ADS)

    Lee, Jun Shean; Sek, Siok Kun

    2015-02-01

    We conduct empirical analyses to investigate the interaction between volatilities of paired stock markets. The main objective of this study is to reveal possibility of spillover effects among stock markets which can determine the performances of stock returns and trade volumes of stocks. In particular, we seek to investigate if there exist two-way causal relationships on the volatilities in two stock markets in two groups of countries, i.e. between emerging markets of ASEAN-5 and between emerging and advanced countries. Our study is focused in Malaysia stock market and the paired relationship with its neighbouring countries (ASEAN5) and advanced countries (Japan and U.S.) respectively. The multivariate GARCH(1,1) model is applied in studying the interactions on the volatilities of paired stock markets. The results are compared between neighbouring countries and with that of advanced countries. The results are expected to reveal linkages between volatilities of stock markets and the dynamic relationships across markets. The results provide useful information in studying the performances of stock markets and predicting the stock movements by incorporating the external impacts from foreign stock markets.

  3. Incoherent pair generation in a beam-beam interaction simulation

    NASA Astrophysics Data System (ADS)

    Rimbault, C.; Bambade, P.; Mönig, K.; Schulte, D.

    2006-03-01

    This paper deals with two topics: the generation of incoherent pairs in two beam-beam simulation programs, GUINEA-PIG and CAIN, and the influence of the International Linear Collider (ILC) beam parameter choices on the background in the micro vertex detector (VD) induced by direct hits. One of the processes involved in incoherent pair creation (IPC) is equivalent to a four fermions interaction and its cross section can be calculated exactly with a dedicated generator, BDK. A comparison of GUINEA-PIG and CAIN results with BDK allows to identify and quantify the uncertainties on IPC background predictions and to benchmark the GUINEA-PIG calculation. Based on this simulation and different VD designs, the five currently suggested ILC beam parameter sets have been compared regarding IPC background induced in the VD by direct IPC hits. We emphasize that the high luminosity set, as it is currently defined, would constrain both the choices of magnetic field and VD inner layer radius.

  4. Odd-frequency pairing of interacting Majorana fermions

    DOE PAGES

    Huang, Zhoushen; Wolfle, P.; Balatsky, Alexander V.

    2015-09-14

    In this study, Majorana fermions are rising as a promising key component in quantum computation. Although the prevalent approach is to use a quadratic (i.e., noninteracting) Majorana Hamiltonian, when expressed in terms of Dirac fermions, generically the Hamiltonian involves interaction terms. Here we focus on the possible pair correlations in a simple model system. We study a model of Majorana fermions coupled to a boson mode and show that the anomalous correlator between different Majorana fermions, located at opposite ends of a topological wire, exhibits odd-frequency behavior. It is stabilized when the coupling strength g is above a critical valuemore » gc. We use both, conventional diagrammatic theory and a functional integral approach, to derive the gap equation, the critical temperature, the gap function, the critical coupling, and a Ginzburg-Landau theory that allows discussing a possible subleading admixture of even-frequency pairing.« less

  5. Odd-frequency pairing of interacting Majorana fermions

    SciTech Connect

    Huang, Zhoushen; Wolfle, P.; Balatsky, Alexander V.

    2015-09-14

    In this study, Majorana fermions are rising as a promising key component in quantum computation. Although the prevalent approach is to use a quadratic (i.e., noninteracting) Majorana Hamiltonian, when expressed in terms of Dirac fermions, generically the Hamiltonian involves interaction terms. Here we focus on the possible pair correlations in a simple model system. We study a model of Majorana fermions coupled to a boson mode and show that the anomalous correlator between different Majorana fermions, located at opposite ends of a topological wire, exhibits odd-frequency behavior. It is stabilized when the coupling strength g is above a critical value gc. We use both, conventional diagrammatic theory and a functional integral approach, to derive the gap equation, the critical temperature, the gap function, the critical coupling, and a Ginzburg-Landau theory that allows discussing a possible subleading admixture of even-frequency pairing.

  6. Odd-frequency pairing of interacting Majorana fermions

    NASA Astrophysics Data System (ADS)

    Huang, Zhoushen; Wölfle, P.; Balatsky, A. V.

    2015-09-01

    Majorana fermions are rising as a promising key component in quantum computation. Although the prevalent approach is to use a quadratic (i.e., noninteracting) Majorana Hamiltonian, when expressed in terms of Dirac fermions, generically the Hamiltonian involves interaction terms. Here we focus on the possible pair correlations in a simple model system. We study a model of Majorana fermions coupled to a boson mode and show that the anomalous correlator between different Majorana fermions, located at opposite ends of a topological wire, exhibits odd-frequency behavior. It is stabilized when the coupling strength g is above a critical value gc. We use both, conventional diagrammatic theory and a functional integral approach, to derive the gap equation, the critical temperature, the gap function, the critical coupling, and a Ginzburg-Landau theory that allows discussing a possible subleading admixture of even-frequency pairing.

  7. Coulomb Damping

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2012-01-01

    Viscous damping is commonly discussed in beginning differential equations and physics texts but dry friction or Coulomb friction is not despite dry friction being encountered in many physical applications. One reason for avoiding this topic is that the equations involve a jump discontinuity in the damping term. In this article, we adopt an energy…

  8. Coulomb Damping

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2012-01-01

    Viscous damping is commonly discussed in beginning differential equations and physics texts but dry friction or Coulomb friction is not despite dry friction being encountered in many physical applications. One reason for avoiding this topic is that the equations involve a jump discontinuity in the damping term. In this article, we adopt an energy…

  9. Interaction between graphene and metamaterials: split rings vs. wire pairs

    SciTech Connect

    Zou, Yanhong; Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas

    2012-05-14

    We have recently shown that graphene is unsuitable to replace metals in the current-carrying elements of metamaterials. At the other hand, experiments have demonstrated that a layer of graphene can modify the optical response of a metal-based metamaterial. Here we study this electromagnetic interaction between metamaterials and graphene. We show that the weak optical response of graphene can be modified dramatically by coupling to the strong resonant fields in metallic structures. A crucial element determining the interaction strength is the orientation of the resonant fields. If the resonant electric field is predominantly parallel to the graphene sheet (e.g., in a complementary split-ring metamaterial), the metamaterial’s resonance can be strongly damped. If the resonant field is predominantly perpendicular to the graphene sheet (e.g., in a wire-pair metamaterial), no significant interaction exists.

  10. Interaction between graphene and metamaterials: split rings vs. wire pairs.

    PubMed

    Zou, Yanhong; Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas M

    2012-05-21

    We have recently shown that graphene is unsuitable to replace metals in the current-carrying elements of metamaterials. At the other hand, experiments have demonstrated that a layer of graphene can modify the optical response of a metal-based metamaterial. Here we study this electromagnetic interaction between metamaterials and graphene. We show that the weak optical response of graphene can be modified dramatically by coupling to the strong resonant fields in metallic structures. A crucial element determining the interaction strength is the orientation of the resonant fields. If the resonant electric field is predominantly parallel to the graphene sheet (e.g., in a complementary split-ring metamaterial), the metamaterial's resonance can be strongly damped. If the resonant field is predominantly perpendicular to the graphene sheet (e.g., in a wire-pair metamaterial), no significant interaction exists.

  11. Liquid-gas phase transitions in a multicomponent nuclear system with Coulomb and surface effects

    SciTech Connect

    Lee, S. J.; Mekjian, A. Z.

    2001-04-01

    The liquid-gas phase transition is studied in a multicomponent nuclear system using a local Skyrme interaction with Coulomb and surface effects. Some features are qualitatively the same as the results of Mu''ller and Serot where a relativistic mean field was used without Coulomb and surface effects. Surface tension brings the coexistence binodal surface to lower pressure. The Coulomb interaction makes the binodal surface smaller and causes another pair of binodal points at low pressure and large proton fraction with fewer protons in the liquid phase and more protons in the gas phase.

  12. The Coulombic Lattice Potential of Ionic Compounds: The Cubic Perovskites.

    ERIC Educational Resources Information Center

    Francisco, E.; And Others

    1988-01-01

    Presents coulombic models representing the particles of a system by point charges interacting through Coulomb's law to explain coulombic lattice potential. Uses rubidium manganese trifluoride as an example of cubic perovskite structure. Discusses the effects on cluster properties. (CW)

  13. The Coulombic Lattice Potential of Ionic Compounds: The Cubic Perovskites.

    ERIC Educational Resources Information Center

    Francisco, E.; And Others

    1988-01-01

    Presents coulombic models representing the particles of a system by point charges interacting through Coulomb's law to explain coulombic lattice potential. Uses rubidium manganese trifluoride as an example of cubic perovskite structure. Discusses the effects on cluster properties. (CW)

  14. Coulomb stress evolution along Xianshuihe-Xiaojiang Fault System since 1713 and its interaction with Wenchuan earthquake, May 12, 2008

    NASA Astrophysics Data System (ADS)

    Shan, Bin; Xiong, Xiong; Wang, Rongjiang; Zheng, Yong; Yang, Song

    2013-09-01

    The curved left-lateral strike-slip Xianshuihe-Xiaojiang Fault System (XXFS) in southwestern China extends at least 1400 km in the eastern margin of the Tibetan Plateau. Fieldworks confirm that the XXFS is one of the longest and most seismically active faults in China. The strain released by the slip motion on the XXFS is related to the convergence between the Indian and Eurasian plates. The entire fault system has experienced at least 35 earthquakes of M>6 in the recent 300 years and almost all segments of the system have been the locus of major historical earthquakes. Since the XXFS region is heavily populated (over 50 million people), understanding the migration of the large earthquakes in space and time is of crucial importance for the seismic hazard assessment in this region. We analyze a sequence of 25 earthquakes (M⩾6.5) that occurred along the XXFS since 1713, and investigate their influence on the 2008 Mw7.9 Wenchuan earthquake occurred on the adjacent Longmenshan fault. In our analysis, the relevant parameters for the earth crust are constrained by seismic studies. The locations and geometries of the earthquake faults as well as the rupture distributions are taken from field observations and seismological studies. Results from the Coulomb failure stress modeling indicate significant interactions among the earthquakes. After the 1713 earthquake, 19 out of 24 earthquakes occurred in the positive stress zone of the preceding earthquakes. The other 5 earthquakes located in the area without significant stress changes induced by the preceding events. In particular, we can identify 4 visible earthquake gaps with increasing seismic hazard along the XXFS, consistent with the findings from the paleo-seismological studies. The seismic activity and tectonic motion on the XXFS reduced the Coulomb stress accumulation at the hypocenter of 2008 Mw7.9 Wenchuan earthquake, implying that the Wenchuan earthquake might not be triggered directly by the seismic activities on

  15. Spatial Patterns in Rydberg Excitations from Logarithmic Pair Interactions

    NASA Astrophysics Data System (ADS)

    Lechner, Wolfgang; Zoller, Peter

    2015-09-01

    The collective excitations in ensembles of dissipative, laser driven ultracold atoms exhibit crystal-like patterns, a many-body effect of the Rydberg blockade mechanism. These crystalline structures are revealed in an experiment from a postselection of configurations with fixed numbers of excitations. Here, we show that these subensembles can be well represented by ensembles of effective particles that interact via logarithmic pair potentials. This allows one to study the emergent patterns with a small number of effective particles to determine the phases of Rydberg crystals and to systematically study contributions from N -body terms.

  16. Interplay of long-range and short-range Coulomb interactions in an Anderson-Mott insulator

    NASA Astrophysics Data System (ADS)

    Baćani, Mirko; Novak, Mario; Orbanić, Filip; Prša, Krunoslav; Kokanović, Ivan; Babić, Dinko

    2017-07-01

    In this paper, we tackle the complexity of coexisting disorder and Coulomb electron-electron interactions (CEEIs) in solids by addressing a strongly disordered system with intricate CEEIs and a screening that changes both with charge carrier doping level Q and temperature T . We report on an experimental comparative study of the T dependencies of the electrical conductivity σ and magnetic susceptibility χ of polyaniline pellets doped with dodecylbenzenesulfonic acid over a wide range. This material is special within the class of doped polyaniline by exhibiting in the electronic transport a crossover between a low-T variable range hopping (VRH) and a high-T nearest-neighbor hopping (NNH) well below room temperature. Moreover, there is evidence of a soft Coulomb gap ΔC in the disorder band, which implies the existence of a long-range CEEI. Simultaneously, there is an onsite CEEI manifested as a Hubbard gap U and originating in the electronic structure of doped polyaniline, which consists of localized electron states with dynamically varying occupancy. Therefore, our samples represent an Anderson-Mott insulator in which long-range and short-range CEEIs coexist. The main result of the study is the presence of a crossover between low- and high-T regimes not only in σ (T ) but also in χ (T ) , the crossover temperature T* being essentially the same for both observables over the entire doping range. The relatively large electron localization length along the polymer chains results in U being small, between 12 and 20 meV for the high and low Q , respectively. Therefore, the thermal energy at T* is sufficiently large to lead to an effective closing of the Hubbard gap and the consequent appearance of NNH in the electronic transport within the disorder band. ΔC is considerably larger than U , decreasing from 190 to 30 meV as Q increases, and plays the role of an activation energy in the NNH.

  17. Equilibrium cluster fluids: pair interactions via inverse design.

    PubMed

    Jadrich, R B; Bollinger, J A; Lindquist, B A; Truskett, T M

    2015-12-28

    Inverse methods of statistical mechanics are becoming productive tools in the design of materials with specific microstructures or properties. While initial studies have focused on solid-state design targets (e.g., assembly of colloidal superlattices), one can alternatively design fluid states with desired morphologies. This work addresses the latter and demonstrates how a simple iterative Boltzmann inversion strategy can be used to determine the isotropic pair potential that reproduces the radial distribution function of a fluid of amorphous clusters with prescribed size. The inverse designed pair potential of this "ideal" cluster fluid, with its broad attractive well and narrow repulsive barrier at larger separations, is qualitatively different from the so-called SALR form most commonly associated with equilibrium cluster formation in colloids, which features short-range attractive (SA) and long-range repulsive (LR) contributions. These differences reflect alternative mechanisms for promoting cluster formation with an isotropic pair potential, and they in turn produce structured fluids with qualitatively different static and dynamic properties. Specifically, equilibrium simulations show that the amorphous clusters resulting from the inverse designed potentials display more uniformity in size and shape, and they also show greater spatial and temporal resolution than those resulting from SALR interactions.

  18. Coulomb interactions and screening effects in few-layer black phosphorus: a tight-binding consideration beyond the long-wavelength limit

    NASA Astrophysics Data System (ADS)

    Prishchenko, D. A.; Mazurenko, V. G.; Katsnelson, M. I.; Rudenko, A. N.

    2017-06-01

    Coulomb interaction and its screening play an important role in many physical phenomena of materials ranging from optical properties to many-body effects including superconductivity. Here, we report on a systematic study of dielectric screening in few-layer black phosphorus (BP), a two-dimensional material with promising electronic and optical characteristics. We use a combination of a tight-binding model and rigorously determined bare Coulomb interactions, which allows us to consider relevant microscopic effects beyond the long-wavelength limit. We calculate the dielectric function of few-layer BP in the random phase approximation and show that it exhibits strongly anisotropic behavior even in the static limit. We also estimate the strength of effective local and non-local Coulomb interactions and determine their doping dependence. We find that the p z states responsible for low-energy excitations in BP provide a moderate contribution to the screening, weakening the on-site Coulomb interaction by less that a factor of two. Finally, we calculate the full plasmon spectrum of few-layer BP and discuss the effects beyond long-wavelengths.

  19. Strong Interactions of Photon Pairs in Cavity QED

    NASA Astrophysics Data System (ADS)

    Kimble, H. J.

    2008-05-01

    The charge and spin degrees of freedom of massive particles have relatively large long-range interactions, which enable nonlinear coupling between pairs of atoms, ions, electrons, and diverse quasi-particles. By contrast, photons have vanishingly small cross-sections for direct coupling. Instead, photon interactions must be mediated by a material system. Even then,typical materials produce photon-photon couplings that are orders of magnitude too small for nontrivial dynamics with individual photon pairs. The leading exception to this state of affairs is cavity quantum electrodynamics (cQED), where strong interactions between light and matter at the single-photon level have enabled a wide set of scientific advances [1]. My presentation will describe two experiments in the Caltech Quantum Optics Group where strong interactions of photon pairs have been observed. The work in Ref. [2] provided the initial realization of photon blockade for an atomic system by using a Fabry-Perot cavity containing one atom strongly coupled to the cavity field. The underlying blockade mechanism was the quantum anharmonicity of the ladder of energy levels for the composite atom-cavity system. Beyond this structural effect, a new % dynamical mechanism was identified in Ref. [3] for which photon transport is regulated by the conditional state of one intracavity atom, leading to an efficient mechanism that is insensitive to many experimental imperfections and which achieves high efficiency for single-photon transport. The experiment utilized the interaction of an atom with the fields of a microtoroidal resonator [4]. Regulation was achieved by way of an interference effect involving the directly transmitted optical field, the intracavity field in the absence of the atom, and the polarization field radiated by the atom, with the requisite nonlinearity provided by the quantum character of the emission from one atom.[1] R. Miller, T. E. Northup, K. M. Birnbaum, A. Boca, A. D. Boozer, and H. J

  20. Measuring pair-wise molecular interactions in a complex mixture

    NASA Astrophysics Data System (ADS)

    Chakraborty, Krishnendu; Varma, Manoj M.; Venkatapathi, Murugesan

    2016-03-01

    Complex biological samples such as serum contain thousands of proteins and other molecules spanning up to 13 orders of magnitude in concentration. Present measurement techniques do not permit the analysis of all pair-wise interactions between the components of such a complex mixture to a given target molecule. In this work we explore the use of nanoparticle tags which encode the identity of the molecule to obtain the statistical distribution of pair-wise interactions using their Localized Surface Plasmon Resonance (LSPR) signals. The nanoparticle tags are chosen such that the binding between two molecules conjugated to the respective nanoparticle tags can be recognized by the coupling of their LSPR signals. This numerical simulation is done by DDA to investigate this approach using a reduced system consisting of three nanoparticles (a gold ellipsoid with aspect ratio 2.5 and short axis 16 nm, and two silver ellipsoids with aspect ratios 3 and 2 and short axes 8 nm and 10 nm respectively) and the set of all possible dimers formed between them. Incident light was circularly polarized and all possible particle and dimer orientations were considered. We observed that minimum peak separation between two spectra is 5 nm while maximum is 184nm.

  1. Electron-hydrogen-atom elastic and inelastic scattering with screened Coulomb interaction around the n=2 excitation threshold

    SciTech Connect

    Zhang Songbin; Wang Jianguo; Janev, R. K.

    2010-03-15

    The effects of Coulomb interaction screening on electron-hydrogen-atom elastic and excitation scattering around the n=2 threshold have been investigated by using the R-matrix method with pseudostates. The elastic and excitation collision strengths show dramatic changes when the interaction screening length D varies from {infinity} to 3.8 a.u., as a result of the convergence of {sup 1,3}S Feshbach resonances to the varying 2s threshold and of the transformation of {sup 1,3}P and {sup 1}D Feshbach resonances into shape-type resonances when they pass across the 2s and 2p threshold at certain critical value of D, respectively [S. B. Zhang et al., Phys. Rev. Lett. 104, 023203 (2010)]. The resonance parameters for a large number of D in the range D={infinity}-3.8 a.u. are presented. It is observed that the {sup 1,3}P and {sup 1}D resonance contributions to the elastic and excitation collision strengths decrease rapidly with decreasing D after the resonance passes the critical D value. The contribution of a {sup 1}S{sup e} Feshbach resonance to the elastic or excitation collision strength changes into a cusp after the resonance merges into its parent 2s state and immerses into the background with the further decrease of D.

  2. Stabilization of the surface CDW order parameter by long-range Coulomb interaction

    NASA Astrophysics Data System (ADS)

    Aseev, P. P.; Artemenko, S. N.

    2012-06-01

    We study theoretically formation of two-dimensional (2D) charge density wave (CDW) in a system of conducting chains at the surface of an insulator due to interaction of quasi-1D surface electrons with phonons. We show that the unscreened long-range Coloumb interaction between the charges induced by fluctuations of the CDW phase stabilizes the finite order parameter value at finite temperatures, and thus the long-range order (LRO) exists. In the case of screened Coloumb interaction the phase fluctuations suppress the phase transition, but decay of the order parameter is rather slow, it obeys a power-law <Δ*(r)Δ(0)>∝r with small exponent γ.

  3. Switching between attractive and repulsive Coulomb-interaction-mediated drag in an ambipolar GaAs/AlGaAs bilayer device

    SciTech Connect

    Zheng, B.; Croxall, A. F.; Waldie, J. Sfigakis, F.; Farrer, I.; Beere, H. E.; Ritchie, D. A.; Das Gupta, K.

    2016-02-08

    We present measurements of Coulomb drag in an ambipolar GaAs/AlGaAs double quantum well structure that can be configured as both an electron-hole bilayer and a hole-hole bilayer, with an insulating barrier of only 10 nm between the two quantum wells. Coulomb drag resistivity is a direct measure of the strength of interlayer particle-particle interactions. We explore the strongly interacting regime of low carrier densities (2D interaction parameter r{sub s} up to 14). Our ambipolar device design allows a comparison between the effects of the attractive electron-hole and repulsive hole-hole interactions and also shows the effects of the different effective masses of electrons and holes in GaAs.

  4. Enhanced superconducting pairing interaction in indium-doped tin telluride

    SciTech Connect

    Erickson, A.S.

    2010-05-03

    The ferroelectric degenerate semiconductor Sn{sub 1-{delta}}Te exhibits superconductivity with critical temperatures, T{sub c}, of up to 0.3 K for hole densities of order 10{sup 21} cm{sup -3}. When doped on the tin site with greater than x{sub c} = 1.7(3)% indium atoms, however, superconductivity is observed up to 2 K, though the carrier density does not change significantly. We present specific heat data showing that a stronger pairing interaction is present for x > x{sub c} than for x < x{sub c}. By examining the effect of In dopant atoms on both T{sub c} and the temperature of the ferroelectric structural phase transition, T{sub SPT}, we show that phonon modes related to this transition are not responsible for this T{sub c} enhancement, and discuss a plausible candidate based on the unique properties of the indium impurities.

  5. Enhanced superconducting pairing interaction in indium-doped tin telluride

    SciTech Connect

    Erickson, A.S.; Chu, J.-H.; Toney, M.F.; Geballe, T.H.; Fisher, I.R.; /SLAC, SSRL /Stanford U., Appl. Phys. Dept. /Stanford U., Geballe Lab.

    2010-02-15

    The ferroelectric degenerate semiconductor Sn{sub 1-{delta}}Te exhibits superconductivity with critical temperatures, T{sub c}, of up to 0.3 K for hole densities of order 10{sup 21} cm{sup -3}. When doped on the tin site with greater than x{sub c} = 1.7(3)% indium atoms, however, superconductivity is observed up to 2 K, though the carrier density does not change significantly. We present specific heat data showing that a stronger pairing interaction is present for x > x{sub c} than for x < x{sub c}. By examining the effect of In dopant atoms on both T{sub c} and the temperature of the ferroelectric structural phase transition, T{sub SPT}, we show that phonon modes related to this transition are not responsible for this T{sub c} enhancement, and discuss a plausible candidate based on the unique properties of the indium impurities.

  6. Lone-pair interactions and photodissociation of compressed nitrogen trifluoride.

    PubMed

    Kurzydłowski, D; Wang, H B; Troyan, I A; Eremets, M I

    2014-08-14

    High-pressure behavior of nitrogen trifluoride (NF3) was investigated by Raman and IR spectroscopy at pressures up to 55 GPa and room temperature, as well as by periodic calculations up to 100 GPa. Experimentally, we find three solid-solid phase transitions at 9, 18, and 39.5 GPa. Vibrational spectroscopy indicates that in all observed phases NF3 remains in the molecular form, in contrast to the behavior of compressed ammonia. This finding is confirmed by density functional theory calculations, which also indicate that the phase transitions of compressed NF3 are governed by the interplay between lone‑pair interactions and efficient molecule packing. Although nitrogen trifluoride is molecular in the whole pressure range studied, we show that it can be photodissociated by mid-IR laser radiation. This finding paves the way for the use of NF3 as an oxidizing and fluorinating agent in high-pressure reactions.

  7. Lone-pair interactions and photodissociation of compressed nitrogen trifluoride

    NASA Astrophysics Data System (ADS)

    Kurzydłowski, D.; Wang, H. B.; Troyan, I. A.; Eremets, M. I.

    2014-08-01

    High-pressure behavior of nitrogen trifluoride (NF3) was investigated by Raman and IR spectroscopy at pressures up to 55 GPa and room temperature, as well as by periodic calculations up to 100 GPa. Experimentally, we find three solid-solid phase transitions at 9, 18, and 39.5 GPa. Vibrational spectroscopy indicates that in all observed phases NF3 remains in the molecular form, in contrast to the behavior of compressed ammonia. This finding is confirmed by density functional theory calculations, which also indicate that the phase transitions of compressed NF3 are governed by the interplay between lone-pair interactions and efficient molecule packing. Although nitrogen trifluoride is molecular in the whole pressure range studied, we show that it can be photodissociated by mid-IR laser radiation. This finding paves the way for the use of NF3 as an oxidizing and fluorinating agent in high-pressure reactions.

  8. Lone-pair interactions and photodissociation of compressed nitrogen trifluoride

    SciTech Connect

    Kurzydłowski, D.; Wang, H. B.; Eremets, M. I.; Troyan, I. A.

    2014-08-14

    High-pressure behavior of nitrogen trifluoride (NF{sub 3}) was investigated by Raman and IR spectroscopy at pressures up to 55 GPa and room temperature, as well as by periodic calculations up to 100 GPa. Experimentally, we find three solid-solid phase transitions at 9, 18, and 39.5 GPa. Vibrational spectroscopy indicates that in all observed phases NF{sub 3} remains in the molecular form, in contrast to the behavior of compressed ammonia. This finding is confirmed by density functional theory calculations, which also indicate that the phase transitions of compressed NF{sub 3} are governed by the interplay between lone‑pair interactions and efficient molecule packing. Although nitrogen trifluoride is molecular in the whole pressure range studied, we show that it can be photodissociated by mid-IR laser radiation. This finding paves the way for the use of NF{sub 3} as an oxidizing and fluorinating agent in high-pressure reactions.

  9. Competing hydrophobic and screened-coulomb interactions in hepatitis B virus capsid assembly.

    PubMed

    Kegel, Willem K; Schoot Pv, Paul van der

    2004-06-01

    Recent experiments show that, in the range from approximately 15 to 45 degrees C, an increase in the temperature promotes the spontaneous assembly into capsids of the Escherichia coli-expressed coat proteins of hepatitis B virus. Within that temperature interval, an increase in ionic strength up to five times that of standard physiological conditions also acts to promote capsid assembly. To explain both observations we propose an interaction of mean force between the protein subunits that is the sum of an attractive hydrophobic interaction, driving the self-assembly, and a repulsive electrostatic interaction, opposing the self-assembly. We find that the binding strength of the capsid subunits increases with temperature virtually independently of the ionic strength, and that, at fixed temperature, the binding strength increases with the square root of ionic strength. Both predictions are in quantitative agreement with experiment. We point out the similarities of capsid assembly in general and the micellization of surfactants. Finally we make plausible that electrostatic repulsion between the native core subunits of a large class of virus suppresses the formation in vivo of empty virus capsids, that is, without the presence of the charge-neutralizing nucleic acid.

  10. Influence of multiorbital and anisotropic Coulomb interactions on isotope effect coefficient in doped Fe-based superconductors

    NASA Astrophysics Data System (ADS)

    Rani, Luxmi; Ajay

    2017-06-01

    The present work describes the theoretical analysis of isotope effect coefficient as a function of transition temperature in two orbital per site model Hamiltonian in iron based superconducting system. The expression of isotope effect coefficient has been computed numerically and self-consistently by employing Green's function technique within the BCS- mean-field approximation. It is observed that the isotope effect coefficient increases with the increase of the hybridization while with the increase in Coulomb interaction it starts decreasing. On increasing the carrier density per site in two orbital per site iron pnictide system, isotope effect coefficient (α) exhibits large values (much higher than BCS limit) at lower temperatures. While in the underdoped case, isotope effect coefficient shows minimum value in superconducting states of the iron based systems. Furthermore, it has been found that the large value of the isotope effect coefficient is the indication of the fact that the contribution of phonon alone is inadequate as the origin of superconductivity in these systems. Finally, the obtained theoretical results have been compared with experimental and existing theoretical observations in iron based superconductors.

  11. The effect of Coulomb interaction on spasing conditions in small nanoparticles (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Pustovit, Vitaliy N.; Shahbazyan, Tigran V.; Chipouline, Arkadi; Urbas, Augustine M.

    2016-09-01

    The prediction of plasmonic laser (spaser) and its experimental realization in various systems have been among the highlights in the rapidly developing field of plasmonics during the past decade. First observed in gold nanoparticles (NP) coated by dye-doped dielectric shells spasing action was reported in hybrid plasmonic waveguides, semiconductor quantum dots on metal film, plasmonic nanocavities and nanocavity arrays, metallic NP and nanorods, and recently was studied in graphene-based structures. The small spaser size well below the diffraction limit gives rise to numerous promising applications, e.g., in sensing or medical diagnostics. However, most experimental realizations of spaser-based nanolasers were carried in relatively large systems, while only a handful of experiments reported spasing action in small systems with overall size below 50 nm. In this work, we perform a numerical study of the role of quenching and direct interactions between gain molecules in reaching the lasing threshold for small spherical NP with metal core and dye-doped dielectric shell. We use a semiclassical approach that combines Maxwell-Bloch equations with the Green function formalism to derive the threshold condition in terms of exact system eigenstates, which we find numerically. We show that for a large number of gain molecules needed to satisfy loss compensation condition, the coupling to nonresonant modes plays no significant role. In contrast, the direct dipole-dipole interactions, by causing random shifts in gain molecules' excitation energies, can hinder reaching the lasing threshold in small NP-based spasers.

  12. The impact of coulombic interactions among polar molecules and metal substrates on flow and lubrication properties

    NASA Astrophysics Data System (ADS)

    Gkagkas, K.; Ponnuchamy, V.

    2017-09-01

    In the current work we present an extensive study on the impact of short- and long-range interactions between solids and liquids on the hydrodynamic and lubrication behaviour of a tribological system. We have implemented a coarse grain molecular dynamics description of two ionic liquids (ILs) as lubricants which are confined by two infinitely long flat iron solids and which are subjected to a shearing flow. The impact of surface polarizability and molecule geometry on the ion arrangement under shearing has been studied in detail. The results have revealed two regimes of lubrication, with a liquid phase being present under low normal loads, while solidification of the ILs, accompanied by a steep rise of normal forces and significant wall slip is observed at small plate-to-plate distances.

  13. Texture segmentation via nonlinear interactions among Gabor feature pairs

    NASA Astrophysics Data System (ADS)

    Tang, Hak W.; Srinivasan, Venugopal; Ong, Sim-Heng

    1995-01-01

    Segmentation of an image based on texture can be performed by a set of N Gabor filters that uniformly covers the spatial frequency domain. The filter outputs that characterize the frequency and orientation content of the intensity distribution in the vicinity of a pixel constitute an N-element feature vector. As an alternative to the computationally intensive procedure of segmentation based on the N-element vectors generated at each pixel, we propose an algorithm for selecting a pair of filters that provides maximum discrimination between two textures constituting the object and its surroundings in an image. Images filtered by the selected filters are nonlinearity transformed to produce two feature maps. The feature maps are smoothed by an intercompetitive and intracooperative interaction process between them. These interactions have proven to be much superior to simple Gaussian filtering in reducing the effects of spatial variability of feature maps. A segmented binary image is then generated by a pixel-by-pixel comparison of the two maps. Results of experiments involving several texture combinations show that this procedure is capable of producing clean segmentation.

  14. Interplay between Coulomb interaction and quantum-confined Stark-effect in polar and nonpolar wurtzite InN/GaN quantum dots

    NASA Astrophysics Data System (ADS)

    Barthel, Stefan; Schuh, Kolja; Marquardt, Oliver; Hickel, Tilmann; Neugebauer, Jörg; Jahnke, Frank; Czycholl, Gerd

    2013-11-01

    In this paper we systematically analyze the electronic structures of polar and nonpolar wurtzite-InN/GaN quantum dots and their modification due to the quantum-confined Stark effect caused by intrinsic fields. This is achieved by combining continuum elasticity theory with an effective-bond orbital model to describe the elastic and single-particle electronic properties in these nitride systems. Based on these results, a many-body treatment is used to determine optical absorption spectra. The efficiency of optical transitions depends on the interplay between the Coulomb interaction and the quantum-confined Stark effect. We introduce an effective confinement potential which represents the electronic structure under the influence of the intrinsic polarization fields and calculate the needed strength of Coulomb interaction to diminish the separation of electrons and holes.

  15. Coulomb interaction of acceptors in Cd{sub 1−x}Mn{sub x}Te/CdTe quantum dot

    SciTech Connect

    Kalpana, P.; Nithiananthi, P. Jayakumar, K.; Reuben, A. Merwyn Jasper D.

    2014-04-24

    The investigation on the effect of confining potential like isotropic harmonic oscillator type potential on the binding and the Coulomb interaction energy of the double acceptors in the presence of magnetic field in a Cd{sub 1−x}Mn{sub x}Te/CdTe Spherical Quantum Dot has been made for the Mn ion composition x=0.3 and compared with the results obtained from the square well type potential using variational procedure in the effective mass approximation.

  16. Stretching single-stranded DNA: interplay of electrostatic, base-pairing, and base-pair stacking interactions.

    PubMed Central

    Zhang, Y; Zhou, H; Ou-Yang, Z C

    2001-01-01

    Recent single-macromolecule observations revealed that the force/extension characteristics of single-stranded DNA (ssDNA) are closely related to solution ionic concentration and DNA sequence composition. To understand this, we studied the elastic property of ssDNA through the Monte Carlo implementation of a modified freely jointed chain (FJC), with electrostatic, base-pairing, and base-pair stacking interactions all incorporated. The simulated force-extension profiles for both random and designed sequences have attained quantitative agreements with the experimental data. In low-salt solution, electrostatic interaction dominates, and at low forces, the molecule can be more easily aligned than an unmodified FJC. In high-salt solution, secondary hairpin structure appears in ssDNA by the formation of base pairs between complementary bases, and external stretching causes a hairpin-coil structural transition, which is continuous for ssDNA made of random sequences. In designed sequences such as poly(dA-dT) and poly(dG-dC), the stacking potential between base pairs encourages the aggregation of base pairs into bulk hairpins and makes the hairpin-coil transition a discontinuous (first-order) process. The sensitivity of elongation to the base-pairing rule is also investigated. The comparison of modeling calculations and the experimental data suggests that the base pairing of single-stranded polynucleotide molecules tends to form a nested and independent planar hairpin structure rather than a random intersecting pattern. PMID:11463654

  17. Weak interaction corrections to hadronic top quark pair production

    SciTech Connect

    Bernreuther, Werner; Fuecker, Michael; Si Zongguo

    2006-12-01

    We determine the weak interaction corrections of order {alpha}{sub s}{sup 2}{alpha} to hadronic top-quark pair production. First we compute the one-loop weak corrections to tt production due to gluon fusion and the order {alpha}{sub s}{sup 2}{alpha} corrections to tt production due to (anti)quark-gluon scattering in the standard model. With our previous result [W. Bernreuther, M. Fuecker, and Z. G. Si, Phys. Lett. B 633, 54 (2006).] this yields the complete corrections of order {alpha}{sub s}{sup 2}{alpha} to gg, qq, qg, and qg induced hadronic tt production with t and t polarizations and spin correlations fully taken into account. For the Tevatron and the LHC we determine the weak contributions to the transverse top momentum and to the tt invariant-mass distributions. At the LHC these corrections can be of the order of 10% compared with the leading-order results, for large p{sub T} and M{sub tt}, respectively. Apart from parity-even tt spin correlations we analyze also parity-violating double- and single-spin asymmetries and show how they are related if CP invariance holds. For t (and t) quarks which decay semileptonically, we compute a resulting charged-lepton forward-backward asymmetry A{sub PV} with respect to the t (t) direction, which is of the order of 1% at the LHC for suitable invariant-mass cuts.

  18. Shock interaction behind a pair of cylindrical obstacles

    NASA Astrophysics Data System (ADS)

    Liu, Heng; Mazumdar, Raoul; Eliasson, Veronica

    2014-11-01

    The body of work focuses on two-dimensional numerical simulations of shock interaction with a pair of cylindrical obstacles, varying the obstacle separation and incident shock strength. With the shock waves propagating parallel to the center-line between the two cylindrical obstacles, the shock strengths simulated vary from a Mach of 1.4 to a Mach of 2.4, against a wide range of obstacle separation distance to their diameters. These cases are simulated via a software package called Overture, which is used to solve the inviscid Euler equations of gas dynamics on overlapping grids with adaptive mesh refinement. The goal of these cases is to find a so-called ``safe'' region for obstacle spacing and varying shock Mach numbers, such that the pressure in the ``safe'' region is reduced downstream of the obstacles. The benefits apply to both building and armor design for the purpose of shock wave mitigation to keep humans and equipment safe. The results obtained from the simulations confirm that the length of the ``safe'' region and the degree of shock wave attenuation depend on the ratio of obstacle separation distance to obstacle diameter. The influence of various Mach number is also discussed.

  19. Pair structure and the pairing interaction in a bilayer Hubbard model for unconventional superconductivity

    SciTech Connect

    Maier, Thomas A

    2011-01-01

    The bilayer Hubbard model with an intralayer hopping t and an interlayer hopping t{sub {lambda}} provides an interesting testing ground for several aspects of what has been called unconventional superconductivity. One can study the type of pair structures which arise when there are multiple Fermi surfaces. One can also examine the pairing for a system in which the structure of the spin-fluctuation spectral weight can be changed. Using a dynamic cluster quantum Monte Carlo approximation, we find that near half filling, if the splitting between the bonding and antibonding bands t{sub {lambda}}/t is small, the gap has B{sub 1g} (d{sub x{sup 2}-y{sup 2}}-wave) symmetry, but when the splitting becomes larger, A{sub 1g} (s{sup {+-}}-wave) pairing is favored. We also find that in the s{sup {+-}} pairing region, the pairing is driven by interlayer spin fluctuations and that T{sub c} is enhanced.

  20. Comparing Pair and Small Group Interactions on Oral Tasks

    ERIC Educational Resources Information Center

    Lasito,; Storch, Neomy

    2013-01-01

    Although pair and small group activities are commonly used in second language (L2) classrooms, there are very few studies which can inform teachers about whether it is best to have students work in pairs or in small groups. In this study, conducted in a junior high school in Indonesia with learners of English as a Foreign Language (EFL), we…

  1. Pairing interaction and superconductivity in oxides and hydrides

    NASA Astrophysics Data System (ADS)

    Kulik, I. O.

    1990-05-01

    The existence of a universal mechanism of pairing between holes in electronegative metals is demonstrated. The pairing force arises as a consequence of orbital size dependence upon its filling and is characteristic for electronegative metals with moderate overlap between hole orbitals. This mechanism will not operate at very strong or very weak overlap regimes.

  2. Comparing Pair and Small Group Interactions on Oral Tasks

    ERIC Educational Resources Information Center

    Lasito,; Storch, Neomy

    2013-01-01

    Although pair and small group activities are commonly used in second language (L2) classrooms, there are very few studies which can inform teachers about whether it is best to have students work in pairs or in small groups. In this study, conducted in a junior high school in Indonesia with learners of English as a Foreign Language (EFL), we…

  3. Coulomb stress interactions among M≥5.9 earthquakes in the Gorda deformation zone and on the Mendocino Fracture Zone, Cascadia megathrust, and northern San Andreas fault

    USGS Publications Warehouse

    Rollins, John C.; Stein, Ross S.

    2010-01-01

    The Gorda deformation zone, a 50,000 km2 area of diffuse shear and rotation offshore northernmost California, has been the site of 20 M ≥ 5.9 earthquakes on four different fault orientations since 1976, including four M ≥ 7 shocks. This is the highest rate of large earthquakes in the contiguous United States. We calculate that the source faults of six recent M ≥ 5.9 earthquakes had experienced ≥0.6 bar Coulomb stress increases imparted by earthquakes that struck less than 9 months beforehand. Control tests indicate that ≥0.6 bar Coulomb stress interactions between M ≥ 5.9 earthquakes separated by Mw = 7.3 Trinidad earthquake are consistent with the locations of M ≥ 5.9 earthquakes in the Gorda zone until at least 1995, as well as earthquakes on the Mendocino Fault Zone in 1994 and 2000. Coulomb stress changes imparted by the 1980 earthquake are also consistent with its distinct elbow-shaped aftershock pattern. From these observations, we derive generalized static stress interactions among right-lateral, left-lateral and thrust faults near triple junctions.

  4. Interacting in Pairs in a Test of Oral Proficiency: Co-Constructing a Better Performance

    ERIC Educational Resources Information Center

    Brooks, Lindsay

    2009-01-01

    This study, framed within sociocultural theory, examines the interaction of adult ESL test-takers in two tests of oral proficiency: one in which they interacted with an examiner (the individual format) and one in which they interacted with another student (the paired format). The data for the eight pairs in this study were drawn from a larger…

  5. Spin-Triplet Pairing Induced by Spin-Singlet Interactions in Noncentrosymmetric Superconductors

    NASA Astrophysics Data System (ADS)

    Matsuzaki, Tomoaki; Shimahara, Hiroshi

    2017-02-01

    In noncentrosymmetric superconductors, we examine the effect of the difference between the intraband and interband interactions, which becomes more important when the band splitting increases. We define the difference ΔVμ between their coupling constants, i.e., that between the intraband and interband hopping energies of intraband Cooper pairs. Here, the subscript μ of ΔVμ indicates that the interactions scatter the spin-singlet and spin-triplet pairs when μ = 0 and μ = 1,2,3, respectively. It is shown that the strong antisymmetric spin-orbit interaction reverses the target spin parity of the interaction: it converts the spin-singlet and spin-triplet interactions represented by ΔV0 and ΔVμ>0 into effective spin-triplet and spin-singlet pairing interactions, respectively. Hence, for example, triplet pairing can be induced solely by the singlet interaction ΔV0. We name the pairing symmetry of the system after that of the intraband Cooper pair wave function, but with an odd-parity phase factor excluded. The pairing symmetry must then be even, even for the triplet component, and the following results are obtained. When ΔVμ is small, the spin-triplet p-wave interactions induce spin-triplet s-wave and spin-triplet d-wave pairings in the regions where the repulsive singlet s-wave interaction is weak and strong, respectively. When ΔV0 is large, a repulsive interband spin-singlet interaction can stabilize spin-triplet pairing. When the Rashba interaction is adopted for the spin-orbit interaction, the spin-triplet pairing interactions mediated by transverse magnetic fluctuations do not contribute to triplet pairing.

  6. Calculation of the Coulomb Fission Cross Sections for Pb-Pb and Bi-Pb Interactions at 158 A GeV

    NASA Technical Reports Server (NTRS)

    Poyser, William J.; Ahern, Sean C.; Norbury, John W.; Tripathi, R. K.

    2002-01-01

    The Weizsacker-Williams (WW) method of virtual quanta is used to make approximate cross section calculations for peripheral relativistic heavy-ion collisions. We calculated the Coulomb fission cross sections for projectile ions of Pb-208 and Bi-209 with energies of 158 A GeV interacting with a Pb-208 target. We also calculated the electromagnetic absorption cross section for Pb-208 ion interacting as described. For comparison we use both the full WW method and a standard approximate WW method. The approximate WW method in larger cross sections compared to the more accurate full WW method.

  7. Role of long range Coulomb interaction near the disorder driven metal-insulator transition in Ga1-xMnxAs

    NASA Astrophysics Data System (ADS)

    Mahmoudian, S.; Miranda, E.; Dobrosavljevic, V.

    2013-03-01

    Surprising signatures of interaction effects on disorder-driven localization have recently been observed by scanning tunneling microscopy of Ga1-xMnxAs, where visualizing the electronic wave function near the metal-insulator transition revealed[1] a pronounced suppression of the local tunneling density of states (LDOS) and enhanced localization only near the Fermi energy. These features highlight the limitation of the non-interacting picture, and point to the crucial importance of the long-range Coulomb interaction. Here, we implement a theoretical approach based on the recently developed Typical-Medium Theory,[2] the conceptually simplest approach to interaction-localization. We show that the presence of long-range Coulomb interaction leads to the simultaneous opening of a soft pseudogap in both the typical (geometrically averaged) and the average (algebraically averaged) LDOS, as the transition is approached. This result is consistent with the experimentally observed features of the STM spectra, suggesting new experiments that should be performed to fully characterize the quantum critical behavior at the metal-insulator transition

  8. INTERACTION OF LASER RADIATION WITH MATTER: Coulomb explosion of deuterium clusters in a magnetic trap and generation of neutrons

    NASA Astrophysics Data System (ADS)

    Zaretsky, D. F.

    2004-07-01

    A new method is proposed for injecting hot ions into a magnetic trap, which is based on the Coulomb explosion of clusters ionised by radiation from a high-power femtosecond laser. The parameters of the trap required for the confinement of the hot plasma produced after the explosion of deuterium clusters are estimated. It is shown that the neutron yield in the d — d reaction in the trap can substantially exceed this yield directly in the laser beam focus.

  9. The Importance of Discourse Style in Pairing Students for Interactive Communicative Tasks.

    ERIC Educational Resources Information Center

    Spelman, Mary

    A study analyzed the discourse of four pairs of students participating in dyadic interactive communicative tasks (ICTs) to discover if and how their discourse styles influenced the dynamics of interaction. Students were paired according to their teacher's evaluation of their discourse style as active or non-active, and were designated sender or…

  10. The influence of the interband Coulomb interaction and the f-electron hopping on excitonic correlations in the extended Falicov-Kimball model

    NASA Astrophysics Data System (ADS)

    Farkašovský, Pavol

    2015-05-01

    The density matrix renormalization group (DMRG) method is used to examine the effects of the interband Coulomb interaction U between f and d electrons as well as the f-electron hopping on the stability of the excitonic phase in the one-dimensional Falicov-Kimball model (FKM) with local hybridization V. It is found that the interband Coulomb interaction significantly enhances the excitonic Pdf=< d^+f > average and that this effect is especially strong in the limit of small hybridization, where the interacting Pdf(U) excitonic value is enhanced several hundred times in comparison to its non-interacting Pdf(U=0) value. The further increase in P df is observed due to the non-zero f-electron hopping, but these changes are considerable only if the d and f bands have opposite parity. In addition, the examination of the interplay between the excitonic effects and the charge density wave (CDW) instability showed that the CDW and excitonic phase coexist up to relatively large values of local hybridization (V ∼ 0.13) . The ground-state phase diagram of the model in the V\\text-U plane is discussed.

  11. Inferring homologous protein-protein interactions through pair position specific scoring matrix

    PubMed Central

    2013-01-01

    Background The protein-protein interaction (PPI) is one of the most important features to understand biological processes. For a PPI, the physical domain-domain interaction (DDI) plays the key role for biology functions. In the post-genomic era, to rapidly identify homologous PPIs for analyzing the contact residue pairs of their interfaces within DDIs on a genomic scale is essential to determine PPI networks and the PPI interface evolution across multiple species. Results In this study, we proposed "pair Position Specific Scoring Matrix (pairPSSM)" to identify homologous PPIs. The pairPSSM can successfully distinguish the true protein complexes from unreasonable protein pairs with about 90% accuracy. For the test set including 1,122 representative heterodimers and 2,708,746 non-interacting protein pairs, the mean average precision and mean false positive rate of pairPSSM were 0.42 and 0.31, respectively. Moreover, we applied pairPSSM to identify ~450,000 homologous PPIs with their interacting domains and residues in seven common organisms (e.g. Homo sapiens, Mus musculus, Saccharomyces cerevisiae and Escherichia coli). Conclusions Our pairPSSM is able to provide statistical significance of residue pairs using evolutionary profiles and a scoring system for inferring homologous PPIs. According to our best knowledge, the pairPSSM is the first method for searching homologous PPIs across multiple species using pair position specific scoring matrix and a 3D dimer as the template to map interacting domain pairs of these PPIs. We believe that pairPSSM is able to provide valuable insights for the PPI evolution and networks across multiple species. PMID:23367879

  12. Determination of the fermion pair size in a resonantly interacting superfluid.

    PubMed

    Schunck, Christian H; Shin, Yong-Il; Schirotzek, André; Ketterle, Wolfgang

    2008-08-07

    Fermionic superfluidity requires the formation of particle pairs, the size of which varies from the femtometre scale in neutron stars and nuclei to the micrometre scale in conventional superconductors. Many properties of the superfluid depend on the pair size relative to the interparticle spacing. This is expressed in 'BCS-BEC crossover' theories, describing the crossover from a Bardeen-Cooper-Schrieffer (BCS)-type superfluid of loosely bound, large Cooper pairs to Bose-Einstein condensates (BECs) of tightly bound molecules. Such a crossover superfluid has been realized in ultracold atomic gases where high-temperature superfluidity has been observed. The microscopic properties of the fermion pairs can be probed using radio-frequency spectroscopy. However, previous work was difficult to interpret owing to strong final-state interactions that were not well understood. Here we realize a superfluid spin mixture in which such interactions have negligible influence and present fermion pair dissociation spectra that reveal the underlying pairing correlations. This allows us to determine that the spectroscopic pair size in the resonantly interacting gas is 20 per cent smaller than the interparticle spacing. These are the smallest pairs so far observed in fermionic superfluids, highlighting the importance of small fermion pairs for superfluidity at high critical temperatures. We have also identified transitions from fermion pairs to bound molecular states and to many-body bound states in the case of strong final-state interactions.

  13. Electronic properties of single-layer antimony: Tight-binding model, spin-orbit coupling, and the strength of effective Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Rudenko, A. N.; Katsnelson, M. I.; Roldán, R.

    2017-02-01

    The electronic properties of single-layer antimony are studied by a combination of first-principles and tight-binding methods. The band structure obtained from relativistic density functional theory is used to derive an analytic tight-binding model that offers an efficient and accurate description of single-particle electronic states in a wide spectral region up to the mid-UV. The strong (λ =0.34 eV) intra-atomic spin-orbit interaction plays a fundamental role in the band structure, leading to splitting of the valence band edge and to a significant reduction of the effective mass of the hole carriers. To obtain an effective many-body model of two-dimensional Sb we calculate the screened Coulomb interaction and provide numerical values for the on-site V¯00 (Hubbard) and intersite V¯i j interactions. We find that the screening effects originate predominantly from the 5 p states, and are thus fully captured within the proposed tight-binding model. The leading kinetic and Coulomb energies are shown to be comparable in magnitude, | t01|/ (V¯00-V¯01) ˜1.6 , which suggests a strongly correlated character of 5 p electrons in Sb. The results presented here provide an essential step toward the understanding and rational description of a variety of electronic properties of this two-dimensional material.

  14. Dynamics of atoms in strong laser fields I: A quasi analytical model in momentum space based on a Sturmian expansion of the interacting nonlocal Coulomb potential

    NASA Astrophysics Data System (ADS)

    Ongonwou, F.; Tetchou Nganso, H. M.; Ekogo, T. B.; Kwato Njock, M. G.

    2016-12-01

    In this study we present a model that we have formulated in the momentum space to describe atoms interacting with intense laser fields. As a further step, it follows our recent theoretical approach in which the kernel of the reciprocal-space time-dependent Schrödinger equation (TDSE) is replaced by a finite sum of separable potentials, each of them supporting one bound state of atomic hydrogen (Tetchou Nganso et al. 2013). The key point of the model is that the nonlocal interacting Coulomb potential is expanded in a Coulomb Sturmian basis set derived itself from a Sturmian representation of Bessel functions of the first kind in the position space. As a result, this decomposition allows a simple spectral treatment of the TDSE in the momentum space. In order to illustrate the credibility of the model, we have considered the test case of atomic hydrogen driven by a linearly polarized laser pulse, and have evaluated analytically matrix elements of the atomic Hamiltonian and dipole coupling interaction. For various regimes of the laser parameters used in computations our results are in very good agreement with data obtained from other time-dependent calculations.

  15. Dynamics of atoms in strong laser fields I: A quasi analytical model in momentum space based on a Sturmian expansion of the interacting nonlocal Coulomb potential

    SciTech Connect

    Ongonwou, F.; Tetchou Nganso, H.M.; Ekogo, T.B.; Kwato Njock, M.G.

    2016-12-15

    In this study we present a model that we have formulated in the momentum space to describe atoms interacting with intense laser fields. As a further step, it follows our recent theoretical approach in which the kernel of the reciprocal-space time-dependent Schrödinger equation (TDSE) is replaced by a finite sum of separable potentials, each of them supporting one bound state of atomic hydrogen (Tetchou Nganso et al. 2013). The key point of the model is that the nonlocal interacting Coulomb potential is expanded in a Coulomb Sturmian basis set derived itself from a Sturmian representation of Bessel functions of the first kind in the position space. As a result, this decomposition allows a simple spectral treatment of the TDSE in the momentum space. In order to illustrate the credibility of the model, we have considered the test case of atomic hydrogen driven by a linearly polarized laser pulse, and have evaluated analytically matrix elements of the atomic Hamiltonian and dipole coupling interaction. For various regimes of the laser parameters used in computations our results are in very good agreement with data obtained from other time-dependent calculations.

  16. An Application of the Direct Coulomb Electron Pair Production Process to the Energy Measurement of the "VH-Group" in the "Knee" Region of the "All-Particle" Energy Spectrum

    NASA Technical Reports Server (NTRS)

    Derrickson, J. H.; Wu, J.; Christl, M. J.; Fountain, W. F.; Parnell, T. A.

    1999-01-01

    The "all-particle" cosmic ray energy spectrum appears to be exhibiting a significant change in the spectral index just above approximately 3000 TeV. This could indicate (1) a change in the propagation of the cosmic rays in the galactic medium, and/or (2) the upper limit of the supernova shock wave acceleration mechanism, and/or (3) a new source of high-energy cosmic rays. Air shower and JACEE data indicate the spectral change is associated with a composition change to a heavier element mixture whereas DICE does not indicate this. A detector concept will be presented that utilizes the energy dependence of the production of direct Coulomb electron-positron pairs by energetic heavy ions. Monte Carlo simulations of a direct electron pair detector consisting of Pb target foils interleaved with planes of 1-mm square scintillating optical fibers will be discussed. The goal is to design a large area, non-saturating instrument to measure the energy spectrum of the individual cosmic ray elements in the "VH-group" for energies greater than 10 TeV/nucleon.

  17. An Application of the Direct Coulomb Electron Pair Production Process to the Energy Measurement of the "VH-Group" in the "Knee" Region of the "All-Particle" Energy Spectrum

    NASA Technical Reports Server (NTRS)

    Derrickson, J. H.; Wu, J.; Christl, M. J.; Fountain, W. F.; Parnell, T. A.

    1999-01-01

    The "all-particle" cosmic ray energy spectrum appears to be exhibiting a significant change in the spectral index just above approximately 3000 TeV. This could indicate (1) a change in the propagation of the cosmic rays in the galactic medium, and/or (2) the upper limit of the supernova shock wave acceleration mechanism, and/or (3) a new source of high-energy cosmic rays. Air shower and JACEE data indicate the spectral change is associated with a composition change to a heavier element mixture whereas DICE does not indicate this. A detector concept will be presented that utilizes the energy dependence of the production of direct Coulomb electron-positron pairs by energetic heavy ions. Monte Carlo simulations of a direct electron pair detector consisting of Pb target foils interleaved with planes of 1-mm square scintillating optical fibers will be discussed. The goal is to design a large area, non-saturating instrument to measure the energy spectrum of the individual cosmic ray elements in the "VH-group" for energies greater than 10 TeV/nucleon.

  18. A number-projected model with generalized pairing interaction in application to rotating nuclei

    SciTech Connect

    Satula, W. |||; Wyss, R.

    1996-12-31

    A cranked mean-field model that takes into account both T=1 and T=0 pairing interactions is presented. The like-particle pairing interaction is described by means of a standard seniority force. The neutron-proton channel includes simultaneously correlations among particles moving in time reversed orbits (T=1) and identical orbits (T=0). The coupling between different pairing channels and nuclear rotation is taken into account selfconsistently. Approximate number-projection is included by means of the Lipkin-Nogami method. The transitions between different pairing phases are discussed as a function of neutron/proton excess, T{sub z}, and rotational frequency, {Dirac_h}{omega}.

  19. Non-additive interactions involving two distinct elements mediate sloppy-paired regulation by pair-rule transcription factors

    PubMed Central

    Prazak, Lisa; Fujioka, Miki; Gergen, J. Peter

    2010-01-01

    The relatively simple combinatorial rules responsible for establishing the initial metameric expression of sloppy-paired-1 (slp1) in the Drosophila blastoderm embryo make this system an attractive model for investigating the mechanism of regulation by pair rule transcription factors. This investigation of slp1 cis-regulatory architecture identifies two distinct elements, a proximal early stripe element (PESE) and a distal early stripe element (DESE) located from −3.1 kb to −2.5 kb and from −8.1 kb to −7.1 kb upstream of the slp1 promoter, respectively, that mediate this early regulation. The proximal element expresses only even-numbered stripes and mediates repression by Even-skipped (Eve) as well as by the combination of Runt and Fushi-tarazu (Ftz). A 272 basepair sub-element of PESE retains Eve-dependent repression, but is expressed throughout the even-numbered parasegments due to the loss of repression by Runt and Ftz. In contrast, the distal element expresses both odd and even-numbered stripes and also drives inappropriate expression in the anterior half of the odd-numbered parasegments due to an inability to respond to repression by Eve. Importantly, a composite reporter gene containing both early stripe elements recapitulates pair-rule gene-dependent regulation in a manner beyond what is expected from combining their individual patterns. These results indicate interactions involving distinct cis-elements contribute to the proper integration of pair-rule regulatory information. A model fully accounting for these results proposes that metameric slp1 expression is achieved through the Runt-dependent regulation of interactions between these two pair-rule response elements and the slp1 promoter. PMID:20435028

  20. Complex-Scaling Treatment for Doubly Excited Inter-Shell Resonances in H- Interacting with Screened Coulomb (Yukawa) Potentials

    NASA Astrophysics Data System (ADS)

    Ho, Y. K.; Kar, S.

    2012-10-01

    The doubly-excited inter-shell resonance states of the hydrogen negative ion with screened Coulomb potentials are investigated in the framework of complex-scaling method. Highly correlated wave functions with terms up to 1078 in Hylleraas coordinates are used. The resonance parameters for the 2 s3 s 1 S e associated with the H ( N = 2) threshold and the 3 s4 s 1 S e state associated with the H ( N = 3) threshold for various screening strengths are reported. Comparisons are made with other available data in the literature.

  1. Unusual Base-Pairing Interactions in Monomer–Template Complexes

    PubMed Central

    2016-01-01

    Many high-resolution crystal structures have contributed to our understanding of the reaction pathway for catalysis by DNA and RNA polymerases, but the structural basis of nonenzymatic template-directed RNA replication has not been studied in comparable detail. Here we present crystallographic studies of the binding of ribonucleotide monomers to RNA primer–template complexes, with the goal of improving our understanding of the mechanism of nonenzymatic RNA copying, and of catalysis by polymerases. To explore how activated ribonucleotides recognize and bind to RNA templates, we synthesized an unreactive phosphonate-linked pyrazole analogue of guanosine 5′-phosphoro-2-methylimidazolide (2-MeImpG), a highly activated nucleotide that has been used extensively to study nonenzymatic primer extension. We cocrystallized this analogue with structurally rigidified RNA primer–template complexes carrying single or multiple monomer binding sites, and obtained high-resolution X-ray structures of these complexes. In addition to Watson–Crick base pairing, we repeatedly observed noncanonical guanine:cytidine base pairs in our crystal structures. In most structures, the phosphate and leaving group moieties of the monomers were highly disordered, while in others the distance from O3′ of the primer to the phosphorus of the incoming monomer was too great to allow for reaction. We suggest that these effects significantly influence the rate and fidelity of nonenzymatic RNA replication, and that even primitive ribozyme polymerases could enhance RNA replication by enforcing Watson–Crick base pairing between monomers and primer–template complexes, and by bringing the reactive functional groups into closer proximity. PMID:28058281

  2. Interaction Effects on Combustion of Alcohol Droplet Pairs

    NASA Astrophysics Data System (ADS)

    Okai, Keiichi; Ono, Yutaka; Moriue, Osamu; Shiba, Seiji; Araki, Mikiya; Nomura, Hiroshi; Shiga, Seiichi; Tsue, Mitsuhiro; Kono, Michikata

    Experimental investigation was conducted on two droplet-array combustion of methanol and methanol/dodecanol mixture fuels in microgravity. For methanol, effects of ambient pressure and droplet spacing were examined. Results show that the droplet lifetime decreases with increasing spacing at relatively low pressure and the droplet lifetime becomes independent of spacing at higher-subcritical and supercritical pressures. For methanol/dodecanol mixture, effects of pressure, fuel composition were investigated in terms of occurrence of disruption. Disruption of droplet during combustion was demonstrated both for single droplet and droplet pairs.

  3. Binding and Release between Polymeric Carrier and Protein Drug: pH Mediated Interplay of Coulomb forces, Hydrogen Bonding, van der Waals Interactions and Entropy.

    PubMed

    De Luca, Sergio; Chen, Fan; Seal, Prasenjit; Stenzel, Martina H; Smith, Sean C

    2017-09-07

    The accelerating search for new types of drugs and delivery strategies poses the challenge to understand the mechanism of delivery. To this end, a detailed atomistic picture of binding between the drug and the carrier is quintessential. While many studies focus on the electrostatics of drug-vector interactions, it has also been pointed out that entropic factors relating to water and counter ions can play an important role. By carrying out extensive molecular dynamics simulations and subsequently validating with experiment, we shed light herein on the binding in aqueous solution between a protein drug and a polymeric carrier. We examined the complexation between the polymer, poly (ethylene glycol) methyl ether acrylate-b-poly(carboxyethyl acrylate (PEGMEA-b-PCEA) and the protein, egg white lysozyme, a system that acts as a model for polymer-vector / protein-drug delivery systems. The complexation has been visualized and characterized using contact maps and hydrogen bonding analyses for five independent simulations of the complex, each running over 100 ns. Binding at physiological pH is, as expected, mediated by coulombic attraction between the positively charged protein and negatively charged carboxylate groups on the polymer. However, we find that consideration of electrostatics alone is insufficient to explain the complexation behaviour at low pH. Intra-complex hydrogen bonds, van der Waals interactions also water-water interactions dictate that the polymer does not release the protein at pH 4.8 or indeed at pH 3.2, even though the Coulombic attractions are largely removed as carboxylate groups on the polymer become titrated. Experiments in aqueous solution carried out at pH = 7.0, 4.5, and 3.0 confirm the veracity of the computed binding behaviour. Overall, these combined simulation and experimental results illustrate that coulomb interactions need to be complemented with consideration of other entropic forces, mediated by van der Waals interactions and hydrogen

  4. Shot noise for resonant Cooper pair tunneling.

    PubMed

    Choi, M S; Plastina, F; Fazio, R

    2001-09-10

    We study intrinsic noise of current in a superconducting single-electron transistor, taking into account both coherence effects and Coulomb interaction near a Cooper pair resonance. Because of this interplay, the statistics of tunneling events deviates from the Poisson distribution and, more important, it shows even-odd asymmetry in the transmitted charge. The zero-frequency noise is suppressed significantly when the quasiparticle tunneling rates are comparable to the coherent oscillation frequency of Cooper pairs.

  5. Effect of Pair Interactions on Transition Probabilities between Inactive and Active States — Achieving Collective Behaviour via Pair Interactions in Social Insects —

    NASA Astrophysics Data System (ADS)

    Hayashi, Yoshikatsu; Yuki, Mai; Kikuchi, Tomonori; Tsuji, Kazuki; Sugawara, Ken

    2015-10-01

    To understand the evolution of well-organized social behaviour, we must first understand the mechanism by which collective behaviour is established. In this study, the mechanisms of collective behaviour in a colony of social insects were studied in terms of the transition probability between active and inactive states, which is linked to mutual interactions. The active and inactive states of the social insects were statistically extracted from the velocity profiles. From the duration distributions of the two states, we found that (1) the durations of active and inactive states follow an exponential law, and (2) pair interactions increase the transition probability from inactive to active states. The regulation of the transition probability by pair interactions suggests that such interactions control the populations of active and inactive workers in the colony.

  6. Interactive imagery and colour in paired-associate learning.

    PubMed

    Wilton, Richard N

    2006-01-01

    In four experiments participants were instructed to imagine scenes that described either an animal interacting with a coloured object or scenes in which the animal and coloured object were independent of each other. Participants were then given the name of the animal and required to select the name of the object and its colour. The results showed that the classic interactive imagery effect was greater for the selection of the name of the object than it was for colour. In Experiments 2, 3, and 4, additional measures were taken which suggest that the effect for colour is dependent upon the retrieval of other features of the object (e.g., its form). Thus it is argued that there is no primary interactive imagery effect for colour. The results were predicted by a version of the shared information hypothesis. The implications of the results for alternative theories are also considered.

  7. The Fulde-Ferrell-Larkin-Ovchinnikov phase in the presence of pair hopping interaction.

    PubMed

    Ptok, Andrzej; Maśka, Maciej M; Mierzejewski, Marcin

    2009-07-22

    The recent experimental support for the presence of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase in CeCoIn(5) directed attention towards the mechanisms responsible for this type of superconductivity. We investigate the FFLO state in a model where on-site/inter-site pairing coexists with the repulsive pair hopping interaction. The latter interaction is interesting in that it leads to pairing with non-zero momentum of the Cooper pairs even in the absence of the external magnetic field (the so-called η pairing). It turns out that, depending on the strength of the pair hopping interaction, the magnetic field can induce one of two types of the FFLO phase with different spatial modulations of the order parameter. It is argued that the properties of the FFLO phase may give information about the magnitude of the pair hopping interaction. We also show that η pairing and d-wave superconductivity may coexist in the FFLO state. It holds true also for superconductors which, in the absence of magnetic field, are of pure d-wave type.

  8. The interacting galaxy pair NGC 4485 and NGC 4490 - Star formation and the interstellar medium

    NASA Technical Reports Server (NTRS)

    Thronson, Harley A., Jr.; Hunter, Deidre A.; Casey, Sean; Harper, D. A.; Latter, William B.

    1989-01-01

    The 100- and 160-micron continuum emission from cool dust in the interacting gas-rich pair of galaxies, NGC 4490 and NGC 4485, was mapped. Visual continuum and H-alpha images of the pair were obtained. The state of the interstellar medium and the rate and efficiency of star formation are investigated.

  9. Pair Interactions and Mode of Communication: Comparing Face-to-Face and Computer Mediated Communication

    ERIC Educational Resources Information Center

    Tan, Lan Liana; Wigglesworth, Gillian; Storch, Neomy

    2010-01-01

    In today's second language classrooms, students are often asked to work in pairs or small groups. Such collaboration can take place face-to-face, but now more often via computer mediated communication. This paper reports on a study which investigated the effect of the medium of communication on the nature of pair interaction. The study involved…

  10. Small-Group Discussion in Physics: Peer Interaction Modes in Pairs and Fours.

    ERIC Educational Resources Information Center

    Alexopoulou, Evinella; Driver, Rosalind

    1996-01-01

    Investigates how Greek secondary school students interacted in pairs and fours while discussing and attempting to explain physical phenomena. Results indicate that students progressed significantly more in their physics reasoning after participation in fours than in pairs. Discourse analysis in different groupings suggests that differences were…

  11. Aboveground growth interactions of paired conifer seedlings in close proximity

    Treesearch

    Warren D. Devine; Timothy B. Harrington

    2011-01-01

    Where belowground resources are relatively abundant, naturally established trees sometimes occur in very close proximity to one another. We conducted a two-year study to assess the aboveground interactions between Douglas-fir (Pseudotsuga menziesii), grand fir (Abies grandis) and noble fir (Abies procera)...

  12. A dynamical proximity analysis of interacting galaxy pairs

    NASA Technical Reports Server (NTRS)

    Chatterjee, Tapan K.

    1990-01-01

    Using the impulsive approximation to study the velocity changes of stars during disk-sphere collisions and a method due to Bottlinger to study the post collision orbits of stars, the formation of various types of interacting galaxies is studied as a function of the distance of closest approach between the two galaxies.

  13. Dielectric-dependent screened Hartree-Fock exchange potential and Slater-formula with Coulomb-hole interaction for energy band structure calculations.

    PubMed

    Shimazaki, Tomomi; Nakajima, Takahito

    2014-09-21

    We previously reported a screened Hartree-Fock (HF) exchange potential for energy band structure calculations [T. Shimazaki and Y. Asai, J. Chem. Phys. 130, 164702 (2009); T. Shimazaki and Y. Asai, J. Chem. Phys. 132, 224105 (2010)]. In this paper, we discuss the Coulomb-hole (COH) interaction and screened Slater-formula and determine the energy band diagrams of several semiconductors, such as diamond, silicon, AlAs, AlP, GaAs, GaP, and InP, based on the screened HF exchange potential and Slater-formula with COH interaction, to demonstrate the adequacy of those theoretical concepts. The screened HF exchange potential and Slater-formula are derived from a simplified dielectric function and, therefore, include the dielectric constant in their expressions. We also present a self-consistent calculation technique to automatically determine the dielectric constant, which is incorporated into each self-consistent field step.

  14. Direct interaction of ligand–receptor pairs specifying stomatal patterning

    PubMed Central

    Lee, Jin Suk; Kuroha, Takeshi; Hnilova, Marketa; Khatayevich, Dmitriy; Kanaoka, Masahiro M.; McAbee, Jessica M.; Sarikaya, Mehmet; Tamerler, Candan; Torii, Keiko U.

    2012-01-01

    Valves on the plant epidermis called stomata develop according to positional cues, which likely involve putative ligands (EPIDERMAL PATTERNING FACTORS [EPFs]) and putative receptors (ERECTA family receptor kinases and TOO MANY MOUTHS [TMM]) in Arabidopsis. Here we report the direct, robust, and saturable binding of bioactive EPF peptides to the ERECTA family. In contrast, TMM exhibits negligible binding to EPF1 but binding to EPF2. The ERECTA family forms receptor homomers in vivo. On the other hand, TMM associates with the ERECTA family but not with itself. While ERECTA family receptor kinases exhibit complex redundancy, blocking ERECTA and ERECTA-LIKE1 (ERL1) signaling confers specific insensitivity to EPF2 and EPF1, respectively. Our results place the ERECTA family as the primary receptors for EPFs with TMM as a signal modulator and establish EPF2–ERECTA and EPF1–ERL1 as ligand–receptor pairs specifying two steps of stomatal development: initiation and spacing divisions. PMID:22241782

  15. Pair Creation in QED-Strong Pulsed Laser Fields Interacting with Electron Beams

    SciTech Connect

    Sokolov, Igor V.; Naumova, Natalia M.; Nees, John A.; Mourou, Gerard A.

    2010-11-05

    QED effects are known to occur in a strong laser pulse interaction with a counterpropagating electron beam, among these effects being electron-positron pair creation. We discuss the range of laser pulse intensities of J{>=}5x10{sup 22} W/cm{sup 2} combined with electron beam energies of tens of GeV. In this regime multiple pairs may be generated from a single beam electron, some of the newborn particles being capable of further pair production. Radiation backreaction prevents avalanche development and limits pair creation. The system of integro-differential kinetic equations for electrons, positrons and {gamma} photons is derived and solved numerically.

  16. Pair creation in QED-strong pulsed laser fields interacting with electron beams.

    PubMed

    Sokolov, Igor V; Naumova, Natalia M; Nees, John A; Mourou, Gérard A

    2010-11-05

    QED effects are known to occur in a strong laser pulse interaction with a counterpropagating electron beam, among these effects being electron-positron pair creation. We discuss the range of laser pulse intensities of J≥5×10(22) W/cm2 combined with electron beam energies of tens of GeV. In this regime multiple pairs may be generated from a single beam electron, some of the newborn particles being capable of further pair production. Radiation backreaction prevents avalanche development and limits pair creation. The system of integro-differential kinetic equations for electrons, positrons and γ photons is derived and solved numerically.

  17. Supramolecular architectures based on As(lone pair)···π(aryl) interactions.

    PubMed

    Zukerman-Schpector, Julio; Otero-de-la-Roza, Alberto; Luaña, Víctor; Tiekink, Edward R T

    2011-07-21

    As(lone pair)···π interactions provide stability to their crystal structures often leading to supramolecular chains and prevailing over As···X secondary contacts. The interaction (ca 8 kJ mol(-1)) arises from polarisation induced in the aryl ring by the As-lone pair plus the weak sharing of these electrons with the ring-C atoms.

  18. Non-covalent interactions in ionic liquid ion pairs and ion pair dimers: a quantum chemical calculation analysis.

    PubMed

    Marekha, Bogdan A; Kalugin, Oleg N; Idrissi, Abdenacer

    2015-07-14

    Ionic liquids (ILs) being composed of bulky multiatomic ions reveal a plethora of non-covalent interactions which determine their microscopic structure. In order to establish the main peculiarities of these interactions in an IL-environment, we have performed quantum chemical calculations for a set of representative model molecular clusters. These calculations were coupled with advanced methods of analysis of the electron density distribution, namely, the quantum theory of atoms in molecules (QTAIM) and the non-covalent interaction (NCI; J. Am. Chem. Soc., 2010, 132, 6499) approaches. The former allows for profound quantitative characterization of non-covalent interactions between atoms while the latter gives an overview of spatial extent, delocalization, and relative strength of such interactions. The studied systems consist of 1-butyl-3-methylimidazolium (Bmim(+)) cations and different perfluorinated anions: tetrafluoroborate (BF4(-)), hexafluorophosphate (PF6(-)), trifluoromethanesulfonate (TfO(-)), and bis(trifluoromethanesulfonyl)imide (TFSI(-)). IL ion pairs and ion pair dimers were considered as model structures for the neat ILs and large aggregates. Weak electrostatic hydrogen bonding was found between the anions and the imidazolium ring hydrogen atoms of cations. Weaker but still appreciable hydrogen bonding was also noted for hydrogen atoms adjacent to the imidazolium ring alkyl groups of Bmim(+). The relative strength of the hydrogen bonding is higher in BmimTfO and BmimBF4 ILs than in BmimPF6 and BmimTFSI, whereas BmimTfO and BmimTFSI reveal higher sensitivity of hydrogen bonding at the different hydrogen atoms of the imidazolium ring.

  19. Maximizing Impact: Pairing interactive web visualizations with traditional print media

    NASA Astrophysics Data System (ADS)

    Read, E. K.; Appling, A.; Carr, L.; De Cicco, L.; Read, J. S.; Walker, J. I.; Winslow, L. A.

    2016-12-01

    Our Nation's rapidly growing store of environmental data makes new demands on researchers: to take on increasingly broad-scale, societally relevant analyses and to rapidly communicate findings to the public. Interactive web-based data visualizations now commonly supplement or comprise journalism, and science journalism has followed suit. To maximize the impact of US Geological Survey (USGS) science, the USGS Office of Water Information Data Science team builds tools and products that combine traditional static research products (e.g., print journal articles) with web-based, interactive data visualizations that target non-scientific audiences. We developed a lightweight, open-source framework for web visualizations to reduce time to production. The framework provides templates for a data visualization workflow and the packaging of text, interactive figures, and images into an appealing web interface with standardized look and feel, usage tracking, and responsiveness. By partnering with subject matter experts to focus on timely, societally relevant issues, we use these tools to produce appealing visual stories targeting specific audiences, including managers, the general public, and scientists, on diverse topics including drought, microplastic pollution, and fisheries response to climate change. We will describe the collaborative and technical methodologies used; describe some examples of how it's worked; and challenges and opportunities for the future.

  20. Extremely strong bipolar optical interactions in paired graphene nanoribbons.

    PubMed

    Lu, Wanli; Chen, Huajin; Liu, Shiyang; Zi, Jian; Lin, Zhifang

    2016-03-28

    Graphene is an excellent multi-functional platform for electrons, photons, and phonons due to exceptional electronic, photonic, and thermal properties. When combining its extraordinary mechanical characteristics with optical properties, graphene-based nanostructures can serve as an appealing platform for optomechanical applications at the nanoscale. Here, we demonstrate, using full-wave simulations, the emergence of extremely strong bipolar optical forces, or, optical binding and anti-binding, between a pair of coupled graphene nanoribbons, due to the remarkable confinement and enhancement of optical fields arising from the large effective mode indices. In particular, the binding and anti-binding forces, which are about two orders of magnitude stronger than that in metamaterials and high-Q resonators, can be tailored by selective excitation of either the even or the odd optical modes, achievable by tuning the relative phase of the lightwaves propagating along the two ribbons. Based on the coupled mode theory, we derive analytical formulae for the bipolar optical forces, which agree well with the numerical results. The attractive optical binding force F(y)(b) and the repulsive anti-binding force F(y)(a) exhibit a remarkably different dependence on the gap distance g between the nanoribbons and the Fermi energy E(F), in the forms of F(y)(b) ∝ 1/√(g³E(F)) and F(y)(a) ∝ 1/E(F)(2). With E(F) dynamically tunable by bias voltage, the bipolar forces may provide a flexible handle for active control of the nanoscale optomechanical effects, and also, might be significant for optoelectronic and optothermal applications as well.

  1. Interplay between the pairing and quadrupole interactions in the algebraic realization of the microscopic shell model

    NASA Astrophysics Data System (ADS)

    Drumev, Kalin; Georgieva, Ana

    2015-04-01

    We explore the algebraic realization of the Pairing-Plus-Quadrupole Model/PQM/ in the framework of the Elliott‘s SU(3) Model with the aim to obtain the complementary and competing features of the two interactions through the relation between the pairing and the SU(3) bases. First, we establish a correspondence between the SO(8) pairing basis and the Elliott's SU(3) basis. It is derived from their complementarity to the same LST coupling chain of the shell-model number-conserving algebra. The probability distribution of the SU(3) basis states within the SO(8) pairing states is also obtained and allows the investigation of the interplay between the pairing and quadrupole interactions in the Hamiltonian of the PQM, containing both of them as limiting cases. The description of some realistic N∼Z nuclear systems is investigated in a SU(3)-symmetry-adapted basis within a model space of one and two oscillator shells.

  2. Superconductivity in repulsively interacting fermions on a diamond chain: Flat-band-induced pairing

    NASA Astrophysics Data System (ADS)

    Kobayashi, Keita; Okumura, Masahiko; Yamada, Susumu; Machida, Masahiko; Aoki, Hideo

    2016-12-01

    To explore whether a flat-band system can accommodate superconductivity, we consider repulsively interacting fermions on the diamond chain, a simplest possible quasi-one-dimensional system that contains a flat band. Exact diagonalization and the density-matrix renormalization group are used to show that we have a significant binding energy of a Cooper pair with a long-tailed pair-pair correlation in real space when the total band filling is slightly below 1/3, where a filled dispersive band interacts with the flat band that is empty but close to EF. Pairs selectively formed across the outer sites of the diamond chain are responsible for the pairing correlation. At exactly 1/3-filling an insulating phase emerges, where the entanglement spectrum indicates the particles on the outer sites are highly entangled and topological. These come from a peculiarity of the flat band in which "Wannier orbits" are not orthogonalizable.

  3. Investigation of the Gravitational Interaction between the Components of the Galaxy Pairs CPG 165

    NASA Astrophysics Data System (ADS)

    Tawfeek, Amira A.; Ali, Gamal B.; Amin, Magdy Y.

    2014-04-01

    In this paper the effect of interaction between the components of the galaxy pair CPG 165 on the symmetry of their morphologies and structures is studied by applying the technique of surface photometry. For each component of the pair we present the isophotal contours, profiles of surface brightness (SB), major-axis position angle (PA), and isophotal center-shift. The present analysis is done using the r- and i-band images from the Sloan Digital Sky Survey (SDSS) observation. It is found that the position angle and the isophotal center shift are strongly affected by the state of interaction between the components of the pair CPG 165.

  4. A mathematical model of stress generation in microtubule pair interactions

    NASA Astrophysics Data System (ADS)

    Fang, Fang; Betterton, Meredith; Shelley, Michael

    2014-11-01

    Microtubules and motor proteins are basic ingredients in many cellular structures and of new biosynthetic ``active'' suspensions. The interaction of microtubules with their surrounding fluid medium depends fundamentally upon the force generation afforded them through cross-linking motile motor proteins. Here we develop a simple mathematical model, based on the statistical mechanics, motor proteins binding and unbinding, to study the generation of active fluid stresses. We study the role and contributions of ``polarity sorting'' and ``tether'' relaxation on the generation of intrinsic, destabilizing stresses.

  5. Spectroscopic and ab initio investigation of 2,6-difluorophenylacetylene-amine complexes: coexistence of C-H···N and lone-pair···π complexes and intermolecular coulombic decay.

    PubMed

    Mondal, Sohidul Islam; Dey, Arghya; Sen, Saumik; Patwari, G Naresh; Ghosh, Debashree

    2015-01-07

    Binary complexes of 2,6-difluorophenylacetylene with methylamine, dimethylamine, trimethylamine and triethylamine were investigated using one colour resonant two photon ionization and infrared-optical double resonance spectroscopic techniques combined with high level ab initio calculations. All four amines form CAc-H···N hydrogen-bonded complexes. Additionally trimethylamine and triethylamine form complexes characterized by Lp···π interactions, due to the electron deficient nature of the phenyl ring of 2,6-difluorophenylacetylene. The Lp···π interacting structure of the 2,6-difluorophenylacetylene-trimethylamine complex is about 1.5 kJ mol(-1) higher in energy than the CAc-H···N hydrogen-bonded structure, which is the global minimum. Energy decomposition analysis indicates that the electrostatics and dispersion interactions favour the formation of CAc-H···N and Lp···π complexes, respectively. Interestingly the CAc-H···N hydrogen-bonded complex of 2,6-difluorophenylacetylene-triethylamine showed a smaller shift in the acetylenic C-H stretching frequency than the 2,6-difluorophenylacetylene-trimethylamine complex. The observed fragmentation of the binary complexes of 2,6-difluorophenylacetylene with the four amines following resonant two-photon ionization can be explained on the basis of the intermolecular coulombic decay process.

  6. Improved Shell models for screened Coulomb balls

    NASA Astrophysics Data System (ADS)

    Bonitz, M.; Kaehlert, H.; Henning, C.; Baumgartner, H.; Filinov, A.

    2006-10-01

    Spherical Coulomb crystals in dusty plasmas [1] are well described by an isotropic Yukawa-type pair interaction and an external parabolic confinement as was shown by extensive molecular dynamics simulations [2]. A much simpler description is possible with analytical shell models which have been derived for Yukawas plasmas in [3,4]. Here we analyze improved Yukawa shell models which include correlations along the lines proposed for Coulomb crystals in [5]. The shell configurations are efficiently evaluated using a Monte Carlo procedure. [1] O. Arp, A. Piel and A. Melzer, Phys. Rev. Lett. 93, 165004 (2004). [2] M. Bonitz, D. Block, O. Arp, V. Golunychiy, H. Baumgartner, P. Ludwig, A. Piel and A. Filinov, Phys. Rev. Lett. 96, 075001 (2006). [3] H. Totsuji, C. Totsuji, T. Ogawa, and K. Tsuruta, Phys. Rev. E 71, 045401 (2005). [4] C. Henning, M. Bonitz, A. Piel, P. Ludwig, H. Baumgartner, V. Golubnichiy, and D. Block, submitted to Phys. Rev. E [5] W.D. Kraeft and M. Bonitz, J. Phys. Conf. Ser. 35, 94 (2006).

  7. Isolated Galaxies versus Interacting Pairs with MaNGA

    NASA Astrophysics Data System (ADS)

    Fernández, María; Yuan, Fangting; Shen, Shiyin; Yin, Jun; Chang, Ruixiang; Feng, Shuai

    2015-10-01

    We present preliminary results of the spectral analysis on the radial distributions of the star formation history in both, a galaxy merger and a spiral isolated galaxy observed with MaNGA. We find that the central part of the isolated galaxy is composed by older stellar population ($\\sim$2 Gyr) than in the outskirts ($\\sim$7 Gyr). Also, the time-scale is gradually larger from 1 Gyr in the inner part to 3 Gyr in the outer regions of the galaxy. In the case of the merger, the stellar population in the central region is older than in the tails, presenting a longer time-scale in comparison to central part in the isolated galaxy. Our results are in agreement with a scenario where spiral galaxies are built from inside-out. In the case of the merger, we find evidence that interactions enhance star formation in the central part of the galaxy.

  8. Efficient table lookup without inverse square roots for calculation of pair wise atomic interactions in classical simulations.

    PubMed

    Nilsson, Lennart

    2009-07-15

    A major bottleneck in classical atomistic simulations of biomolecular systems is the calculation of the pair wise nonbonded (Coulomb, van der Waals) interactions. This remains an issue even when methods are used (e.g., lattice summation or spherical cutoffs) in which the number of interactions is reduced from O(N(2)) to O(NlogN) or O(N). The interaction forces and energies can either be calculated directly each time they are needed or retrieved using precomputed values in a lookup table; the choice between direct calculation and table lookup methods depends on the characteristics of the system studied (total number of particles and the number of particle kinds) as well as the hardware used (CPU speed, size and speed of cache, and main memory). A recently developed lookup table code, implemented in portable and easily maintained FORTRAN 95 in the CHARMM program (www.charmm.org), achieves a 1.5- to 2-fold speedup compared with standard calculations using highly optimized FORTRAN code in real molecular dynamics simulations for a wide range of molecular system sizes. No approximations other than the finite resolution of the tables are introduced, and linear interpolation in a table with the relatively modest density of 100 points/A(2) yields the same accuracy as the standard double precision calculations. For proteins in explicit water a less dense table (10 points/A(2)) is 10-20% faster than using the larger table, and only slightly less accurate. The lookup table is even faster than hand coded assembler routines in most cases, mainly due to a significantly smaller operation count inside the inner loop. (c) 2008 Wiley Periodicals, Inc.

  9. Comparative drug pair screening across multiple glioblastoma cell lines reveals novel drug-drug interactions

    PubMed Central

    Schmidt, Linnéa; Kling, Teresia; Monsefi, Naser; Olsson, Maja; Hansson, Caroline; Baskaran, Sathishkumar; Lundgren, Bo; Martens, Ulf; Häggblad, Maria; Westermark, Bengt; Forsberg Nilsson, Karin; Uhrbom, Lene; Karlsson-Lindahl, Linda; Gerlee, Philip; Nelander, Sven

    2013-01-01

    Background Glioblastoma multiforme (GBM) is the most aggressive brain tumor in adults, and despite state-of-the-art treatment, survival remains poor and novel therapeutics are sorely needed. The aim of the present study was to identify new synergistic drug pairs for GBM. In addition, we aimed to explore differences in drug-drug interactions across multiple GBM-derived cell cultures and predict such differences by use of transcriptional biomarkers. Methods We performed a screen in which we quantified drug-drug interactions for 465 drug pairs in each of the 5 GBM cell lines U87MG, U343MG, U373MG, A172, and T98G. Selected interactions were further tested using isobole-based analysis and validated in 5 glioma-initiating cell cultures. Furthermore, drug interactions were predicted using microarray-based transcriptional profiling in combination with statistical modeling. Results Of the 5 × 465 drug pairs, we could define a subset of drug pairs with strong interaction in both standard cell lines and glioma-initiating cell cultures. In particular, a subset of pairs involving the pharmaceutical compounds rimcazole, sertraline, pterostilbene, and gefitinib showed a strong interaction in a majority of the cell cultures tested. Statistical modeling of microarray and interaction data using sparse canonical correlation analysis revealed several predictive biomarkers, which we propose could be of importance in regulating drug pair responses. Conclusion We identify novel candidate drug pairs for GBM and suggest possibilities to prospectively use transcriptional biomarkers to predict drug interactions in individual cases. PMID:24101737

  10. Conceptual quantum chemical analysis of bonding and noncovalent interactions in the formation of frustrated Lewis pairs.

    PubMed

    Skara, Gabriella; Pinter, Balazs; Top, Jens; Geerlings, Paul; De Proft, Frank; De Vleeschouwer, Freija

    2015-03-27

    The contributions of covalent and noncovalent interactions to the formation of classical adducts of bulky Lewis acids and bases and frustrated Lewis pairs (FLPs) were scrutinized by using various conceptual quantum chemical techniques. Significantly negative complexation energies were calculated for fourteen investigated Lewis pairs containing bases and acids with substituents of various sizes. A Ziegler-Rauk-type energy decomposition analysis confirmed that two types of Lewis pairs can be distinguished on the basis of the nature of the primary interactions between reactants; dative-bond formation and concomitant charge transfer from the Lewis base to the acid is the dominant and most stabilizing factor in the formation of Lewis acid-base adducts, whereas weak interactions are the main thermodynamic driving force (>50 %) for FLPs. Moreover, the ease and extent of structural deformation of the monomers appears to be a key component in the formation of the former type of Lewis pairs. A Natural Orbital for Chemical Valence (NOCV) analysis, which was used to visualize and quantify the charge transfer between the base and the acid, clearly showed the importance and lack of this type of interaction for adducts and FLPs, respectively. The Noncovalent Interaction (NCI) method revealed several kinds of weak interactions between the acid and base components, such as dispersion, π-π stacking, C-H⋅⋅⋅π interaction, weak hydrogen bonding, halogen bonding, and weak acid-base interactions, whereas the Quantum Theory of Atoms in Molecules (QTAIM) provided further conceptual insight into strong acid-base interactions.

  11. Effect of Coulomb interactions and Hartree-Fock exchange on structural, elastic, optoelectronic and magnetic properties of Co2MnSi Heusler: A comparative study

    NASA Astrophysics Data System (ADS)

    Lantri, T.; Bentata, S.; Bouadjemi, B.; Benstaali, W.; Bouhafs, B.; Abbad, A.; Zitouni, A.

    2016-12-01

    Using the first-principle calculations, we have investigated the structural, elastic, optoelectronic and magnetic properties of Co2MnSi Heusler alloy. Based on the density functional theory (DFT) and hiring the full-potential linearized augmented plane wave (FP-LAPW) method, we have used five approaches: the Hybrid on-site exact exchange, the Local Spin Density Approximation (LSDA), the LSDA+U, the Generalized Gradient Approximation GGA and GGA+U; where the Hubbard on-site Coulomb interaction correction U is calculated by constraint local density approximation for Co and Mn atoms. Our results show that the highly-ordered Co2MnSi alloy is a ductile, stiff and anisotropic material. It has a half-metallic ferromagnetic character with an integer magnetic moment of 5 μB which is in good agreement with the Slater-Pauling rule.

  12. Correction for dispersion and Coulombic interactions in molecular clusters with density functional derived methods: application to polycyclic aromatic hydrocarbon clusters.

    PubMed

    Rapacioli, Mathias; Spiegelman, Fernand; Talbi, Dahbia; Mineva, Tzonka; Goursot, Annick; Heine, Thomas; Seifert, Gotthard

    2009-06-28

    The density functional based tight binding (DFTB) is a semiempirical method derived from the density functional theory (DFT). It inherits therefore its problems in treating van der Waals clusters. A major error comes from dispersion forces, which are poorly described by commonly used DFT functionals, but which can be accounted for by an a posteriori treatment DFT-D. This correction is used for DFTB. The self-consistent charge (SCC) DFTB is built on Mulliken charges which are known to give a poor representation of Coulombic intermolecular potential. We propose to calculate this potential using the class IV/charge model 3 definition of atomic charges. The self-consistent calculation of these charges is introduced in the SCC procedure and corresponding nuclear forces are derived. Benzene dimer is then studied as a benchmark system with this corrected DFTB (c-DFTB-D) method, but also, for comparison, with the DFT-D. Both methods give similar results and are in agreement with references calculations (CCSD(T) and symmetry adapted perturbation theory) calculations. As a first application, pyrene dimer is studied with the c-DFTB-D and DFT-D methods. For coronene clusters, only the c-DFTB-D approach is used, which finds the sandwich configurations to be more stable than the T-shaped ones.

  13. Protein-protein interaction interface residue pair prediction based on deep learning architecture.

    PubMed

    Zhao, Zhenni; Gong, Xinqi

    2017-05-19

    Proteins usually fulfill their biological functions by interacting with other proteins. Although some methods have been developed to predict the binding sites of a monomer protein, these are not sufficient for prediction of the interaction between two monomer proteins. The correct prediction of interface residue pairs from two monomer proteins is still an open question and has great significance for practical experimental applications in the life sciences. We hope to build a method for the prediction of interface residue pairs that is suitable for those applications. Here, we developed a novel deep network architecture called the multi-layered Long-Short Term Memory networks (LSTMs) approach for the prediction of protein interface residue pairs. Firstly, we created three new descriptions and used other six worked characterizations to describe an amino acid, then we employed these features to discriminate between interface residue pairs and non-interface residue pairs. Secondly, we used two thresholds to select residue pairs that are more likely to be interface residue pairs. Furthermore, this step increases the proportion of interface residue pairs and reduces the influence of imbalanced data. Thirdly, we built deep network architectures based on Long-Short Term Memory networks algorithm to organize and refine the prediction of interface residue pairs by employing features mentioned above. We trained the deep networks on dimers in the unbound state in the international Protein-protein Docking Benchmark version 3.0. The updated data sets in the versions 4.0 and 5.0 were used as the validation set and test set respectively. For our best model, the accuracy rate was over 62% when we chose the top 0.2% pairs of every dimer in the test set as predictions, which will be very helpful for the understanding of protein-protein interaction mechanisms and for guidance in biological experiments.

  14. Cotunneling Drag Effect in Coulomb-Coupled Quantum Dots

    NASA Astrophysics Data System (ADS)

    Keller, A. J.; Lim, J. S.; Sánchez, David; López, Rosa; Amasha, S.; Katine, J. A.; Shtrikman, Hadas; Goldhaber-Gordon, D.

    2016-08-01

    In Coulomb drag, a current flowing in one conductor can induce a voltage across an adjacent conductor via the Coulomb interaction. The mechanisms yielding drag effects are not always understood, even though drag effects are sufficiently general to be seen in many low-dimensional systems. In this Letter, we observe Coulomb drag in a Coulomb-coupled double quantum dot and, through both experimental and theoretical arguments, identify cotunneling as essential to obtaining a correct qualitative understanding of the drag behavior.

  15. The role of close pair interactions in triggering stellar bars and rings

    NASA Astrophysics Data System (ADS)

    Nair, Preethi; Ellison, Sara; Patton, David

    2015-03-01

    Recent works which have looked at bars in clusters versus the field have found no significant difference in bar fraction. However, other works (Nair & Abraham 2010, Lee et al. 2012) have found that bar fractions depend sensitively on the mass, morphology and color of the galaxy. In addition, simulations suggest that bar formation may depend on the merger ratio of close pair interactions as well as on the separation between the pairs. In this work, we analyze the bar fractions in a complete sample of ~23,000 close pairs derived from the Sloan Digital Sky Survey Data Release 7. We will present results illustrating the dependence of bar and ring fractions as a function of merger mass ratio, pair separation, galaxy morphology, and stellar mass. I will further compare the role of bars and close pairs in triggering central star formation and AGN.

  16. Interrelations between the pairing and quadrupole interactions in the microscopic Shell Model

    NASA Astrophysics Data System (ADS)

    Drumev, K. P.; Georgieva, A. I.

    2016-01-01

    We explore the dynamical symmetries of the shell model number conserving algebra, which define three types of pairing and quadrupole phases, with the aim to obtain the prevailing phase or phase transition for the real nuclear systems in a single shell. This is achieved by establishing a correspondence between each of the pairing bases with the Elliott's SU(3) basis that describes collective rotation of nuclear systems. This allows for a complete classification of the basis states of different number of particles in all the limiting cases. The probability distribution of the SU(3) basis states within theirs corresponding pairing states is also obtained. The relative strengths of dynamically symmetric quadrupole-quadrupole interaction in respect to the isoscalar, isovector and total pairing interactions define a control parameter, which estimates the importance of each term of the Hamiltonian in the correct reproduction of the experimental data for the considered nuclei.

  17. Interactions in 1-ethyl-3-methyl imidazolium tetracyanoborate ion pair: Spectroscopic and density functional study

    SciTech Connect

    Mao, James X.; Lee, Anita S.; Kitchin, John R.; Nulwala, Hunaid B.; Luebke, David R.; Damodaran, Krishnan

    2013-01-25

    Density Functional Theory is used to investigate a weakly coordinating room-temperature ionic liquid, 1-ethyl-3-methyl imidazolium tetracyanoborate ([Emim]{sup +}[TCB]{sup -}). Four locally stable conformers of the ion pair were located. Atoms-in-molecules (AIM) and electron density analysis indicated the existence of several hydrogen bonds. Further investigation through the Natural Bond Orbital (NBO) and Natural Energy Decomposition Analysis (NEDA) calculations provided insight into the origin of interactions in the [Emim]{sup +}[TCB]{sup -} ion pair. Strength of molecular interactions in the ionic liquid was correlated with frequency shifts of the characteristic vibrations of the ion pair. Harmonic vibrations of the ion pair were also compared with the experimental Raman and Infrared spectra. Vibrational frequencies were assigned by visualizing displacements of atoms around their equilibrium positions and through Potential Energy Distribution (PED) analysis.

  18. Interactions in 1-ethyl-3-methyl imidazolium tetracyanoborate ion pair: Spectroscopic and density functional study

    NASA Astrophysics Data System (ADS)

    Mao, James X.; Lee, Anita S.; Kitchin, John R.; Nulwala, Hunaid B.; Luebke, David R.; Damodaran, Krishnan

    2013-04-01

    Density Functional Theory is used to investigate a weakly coordinating room-temperature ionic liquid, 1-ethyl-3-methyl imidazolium tetracyanoborate ([Emim]+[TCB]-). Four locally stable conformers of the ion pair were located. Atoms-in-molecules (AIMs) and electron density analysis indicated the existence of several hydrogen bonds. Further investigation through the Natural Bond Orbital (NBO) and Natural Energy Decomposition Analysis (NEDA) calculations provided insight into the origin of interactions in the [Emim]+[TCB]- ion pair. Strength of molecular interactions in the ionic liquid was correlated with frequency shifts of the characteristic vibrations of the ion pair. Harmonic vibrations of the ion pair were also compared with the experimental Raman and Infrared spectra. Vibrational frequencies were assigned by visualizing displacements of atoms around their equilibrium positions and through Potential Energy Distribution (PED) analysis.

  19. Coulomb crystallization in classical and quantum systems

    NASA Astrophysics Data System (ADS)

    Bonitz, Michael

    2007-11-01

    Coulomb crystallization occurs in one-component plasmas when the average interaction energy exceeds the kinetic energy by about two orders of magnitude. A simple road to reach such strong coupling consists in using external confinement potentials the strength of which controls the density. This has been succsessfully realized with ions in traps and storage rings and also in dusty plasma. Recently a three-dimensional spherical confinement could be created [1] which allows to produce spherical dust crystals containing concentric shells. I will give an overview on our recent results for these ``Yukawa balls'' and compare them to experiments. The shell structure of these systems can be very well explained by using an isotropic statically screened pair interaction. Further, the thermodynamic properties of these systems, such as the radial density distribution are discussed based on an analytical theory [3]. I then will discuss Coulomb crystallization in trapped quantum systems, such as mesoscopic electron and electron hole plasmas in coupled layers [4,5]. These systems show a very rich correlation behavior, including liquid and solid like states and bound states (excitons, biexcitons) and their crystals. On the other hand, also collective quantum and spin effects are observed, including Bose-Einstein condensation and superfluidity of bound electron-hole pairs [4]. Finally, I consider Coulomb crystallization in two-component neutral plasmas in three dimensions. I discuss the necessary conditions for crystals of heavy charges to exist in the presence of a light component which typically is in the Fermi gas or liquid state. It can be shown that their exists a critical ratio of the masses of the species of the order of 80 [5] which is confirmed by Quantum Monte Carlo simulations [6]. Familiar examples are crystals of nuclei in the core of White dwarf stars, but the results also suggest the existence of other crystals, including proton or α-particle crystals in dense matter

  20. Coulomb flux tube on the lattice

    NASA Astrophysics Data System (ADS)

    Chung, Kristian; Greensite, Jeff

    2017-08-01

    In Coulomb gauge a longitudinal electric field is generated instantaneously with the creation of a static quark-antiquark pair. The field due to the quarks is a sum of two contributions, one from the quark and one from the antiquark, and there is no obvious reason that this sum should fall off exponentially with distance from the sources. We show here, however, from numerical simulations in pure SU(2) lattice gauge theory, that the color Coulomb electric field does in fact fall off exponentially with transverse distance away from a line joining static quark-antiquark sources, indicating the existence of a color Coulomb flux tube, and the absence of long-range Coulomb dipole fields.

  1. What is the most important for a nanoscale structure formations in HTSC?, spin, phonon or third way in Coulomb interaction and correlations?

    NASA Astrophysics Data System (ADS)

    Kusmartsev, F. V.; Saarela, M.

    2008-03-01

    We show that nanoscale superstructures observed in STM experiments in high temperature superconductor (HTSC) such as cuprates in superconducting state [1] are well described by a model of two-dimensional charged boson gas(2DBG). The bosons are located on top of a uniform, structureless, jellium neutralizing background. This model is the most fundamental and clean quantum system where different properties of the formation of the superconducting and insulating states mcan be studied by changing only one parameter -the boson density n0. At high densities the ground state is always superconducting, that is associated with the Bose-Einstein condensation of the charged bosons which form a superfluid state. Whereas at very low densities bosons localize into a Wigner crystal. Here we show that a dilute amount of impurities with opposite charge to bosons alter dramatically the properties of the system. Any charged impurity induces density oscillations, similar to Friedel oscillations in Fermi liquids. When the density decreases the amplitude of these charge density wave(CDW) oscillations increases. At some critical density there arises the CDW instability. As the result around each impurity a Coulomb bubble(CB) is formed. At such a CB there arises an orthogonality catastrophe associated with the formation of localized states inside CB orthogonal to the fluid of free bosons. The creation of localized states may be accompanied by a formation of local lattice distortions. The phenomenon is very similar to the conventional self-trapping or a formation of electronic strings[2]. The CDW instability arises due to over-screening of the Coulomb interaction. The phenomenon of CB formation is very general. They can be created and become localized around any potential induced by phonons or by individual impurities or both. As the result the quantum system separates into two phases: localized CBs distributed randomly and superfluid bosons forming a homogeneous state. When the density

  2. Application of Parallel Hybrid Algorithm in Massively Parallel GPGPU—The Improved Effective and Efficient Method for Calculating Coulombic Interactions in Simulations of Many Ions with SIMION

    NASA Astrophysics Data System (ADS)

    Saito, Kenichiro; Koizumi, Eiko; Koizumi, Hideya

    2012-09-01

    In our previous study, we introduced a new hybrid approach to effectively approximate the total force on each ion during a trajectory calculation in mass spectrometry device simulations, and the algorithm worked successfully with SIMION. We took one step further and applied the method in massively parallel general-purpose computing with GPU (GPGPU) to test its performance in simulations with thousands to over a million ions. We took extra care to minimize the barrier synchronization and data transfer between the host (CPU) and the device (GPU) memory, and took full advantage of the latency hiding. Parallel codes were written in CUDA C++ and implemented to SIMION via the user-defined Lua program. In this study, we tested the parallel hybrid algorithm with a couple of basic models and analyzed the performance by comparing it to that of the original, fully-explicit method written in serial code. The Coulomb explosion simulation with 128,000 ions was completed in 309 s, over 700 times faster than the 63 h taken by the original explicit method in which we evaluated two-body Coulomb interactions explicitly on one ion with each of all the other ions. The simulation of 1,024,000 ions was completed in 2650 s. In another example, we applied the hybrid method on a simulation of ions in a simple quadrupole ion storage model with 100,000 ions, and it only took less than 10 d. Based on our estimate, the same simulation is expected to take 5-7 y by the explicit method in serial code.

  3. Galaxy pairs in the Sloan Digital Sky Survey - II. The effect of environment on interactions

    NASA Astrophysics Data System (ADS)

    Ellison, Sara L.; Patton, David R.; Simard, Luc; McConnachie, Alan W.; Baldry, Ivan K.; Mendel, J. Trevor

    2010-09-01

    We use a sample of close galaxy pairs selected from the Sloan Digital Sky Survey Data Release 4 (SDSS DR4) to investigate in what environments galaxy mergers occur and how the results of these mergers depend on differences in local galaxy density. The galaxies are quantified morphologically using two-dimensional bulge-plus-disc decompositions and compared to a control sample matched in stellar mass, redshift and local projected density. Lower density environments have fractionally more galaxy pairs with small projected separations (rp) and relative velocities (Δv), but even high-density environments contain significant populations of pairs with parameters that should be conducive to interactions. The connection between environment and Δv also implies that the velocity selection of a pairs sample affects (biases) the environment from which the pairs are selected. Metrics of asymmetry and colour are used to identify merger activity and triggered star formation. The location of star formation is inferred by distinguishing bulge and disc colours and calculating bulge fractions from the SDSS images. Galaxies in the lowest density environments show the largest changes in star formation rate, asymmetry and bulge-to-total fractions at small separations, accompanied by bluer bulge colours. At the highest local densities, the only galaxy property to show an enhancement in the closest pairs is asymmetry. We interpret these results as evidence that whilst interactions (leading to tidal distortions) occur at all densities, triggered star formation is seen only in low-to-intermediate density environments. We suggest that this is likely due to the typically higher gas fractions of galaxies in low-density environments. Finally, by cross-correlating our sample of galaxy pairs with a cluster catalogue, we investigate the dependence of interactions on clustercentric distance. It is found that for close pairs the fraction of asymmetric galaxies is highest in the cluster centres.

  4. Investigating Coulomb's Law.

    ERIC Educational Resources Information Center

    Noll, Ellis; Koehlinger, Mervin; Kowalski, Ludwik; Swackhamer, Gregg

    1998-01-01

    Describes the use of a computer-linked camera to demonstrate Coulomb's law. Suggests a way of reducing the difficulties in presenting Coulomb's law by teaching the inverse square law of gravity and the inverse square law of electricity in the same unit. (AIM)

  5. On the non-classical contribution in lone-pairinteraction: IQA perspective.

    PubMed

    Badri, Zahra; Foroutan-Nejad, Cina; Kozelka, Jiri; Marek, Radek

    2015-10-21

    In the present work the nature of lone-pairinteractions between water molecules and a number of π-rings with different substituents/hetero-atoms in the light of quantum chemical topology approaches is studied. The Quantum Theory of Atoms in Molecules (QTAIM) and Interacting Quantum Atoms (IQA) were employed for distinguishing the role of heteroatoms and electron withdrawing substituents in the complex formation between water and π-rings. Our IQA study identified three classes of water-π complexes on the basis of the relative role of electrostatics (classical) and exchange-correlation (non-classical) factors in the interaction energy between the oxygen of water (the lone-pair donor) and the sp(2) atoms of the π-ring, i.e. the primary lp-π interaction. Considering both the primary and secondary (the rest of interatomic interactions except Owater-π-ring atoms) interactions demonstrates that the exchange-correlation is the dominant contributor to the binding energy. This proves a non-negligible contribution of non-classical factors in the stabilization of the lone-pair-π complexes. However, in spite of a relatively large contribution of the exchange-correlation, this part of the interaction energy is virtually counterbalanced by the deformation energy, i.e. the increase in atomic kinetic energy upon complexation. This finding clarifies why water-π interactions can be modelled by simple electrostatics without the need to invoke quantum effects.

  6. Theoretical Studies on the Intermolecular Interactions of Potentially Primordial Base-Pair Analogues

    SciTech Connect

    Leszczynski, Jerzy; Sponer, Judit; Sponer, Jiri; Sumpter, Bobby G; Fuentes-Cabrera, Miguel A; Vazquez-Mayagoitia, Alvaro

    2010-01-01

    Recent experimental studies on the Watson Crick type base pairing of triazine and aminopyrimidine derivatives suggest that acid/base properties of the constituent bases might be related to the duplex stabilities measured in solution. Herein we use high-level quantum chemical calculations and molecular dynamics simulations to evaluate the base pairing and stacking interactions of seven selected base pairs, which are common in that they are stabilized by two NH O hydrogen bonds separated by one NH N hydrogen bond. We show that neither the base pairing nor the base stacking interaction energies correlate with the reported pKa data of the bases and the melting points of the duplexes. This suggests that the experimentally observed correlation between the melting point data of the duplexes and the pKa values of the constituent bases is not rooted in the intrinsic base pairing and stacking properties. The physical chemistry origin of the observed experimental correlation thus remains unexplained and requires further investigations. In addition, since our calculations are carried out with extrapolation to the complete basis set of atomic orbitals and with inclusion of higher electron correlation effects, they provide reference data for stacking and base pairing energies of non-natural bases.

  7. Coulomb blockade in graphene nanoribbons.

    PubMed

    Sols, F; Guinea, F; Neto, A H

    2007-10-19

    We propose that recent transport experiments revealing the existence of an energy gap in graphene nanoribbons may be understood in terms of Coulomb blockade. Electron interactions play a decisive role at the quantum dots which form due to the presence of necks arising from the roughness of the graphene edge. With the average transmission as the only fitting parameter, our theory shows good agreement with the experimental data.

  8. Nucleon-pair states of even-even Sn isotopes based on realistic effective interactions

    NASA Astrophysics Data System (ADS)

    Cheng, Y. Y.; Qi, C.; Zhao, Y. M.; Arima, A.

    2016-08-01

    In this paper we study yrast states of 128,126,124Sn and 104,106,108Sn by using the monopole-optimized realistic interactions in terms of both the shell model (SM) and the nucleon-pair approximation (NPA). For yrast states of 128,126Sn and 104,106Sn, we calculate the overlaps between the wave functions obtained in the full SM space and those obtained in the truncated NPA space, and find that most of these overlaps are very close to 1. Very interestingly, for most of these states with positive parity and even spin or with negative parity and odd spin, the SM wave function is found to be well represented by one nucleon-pair basis state, viz., a simple picture of "nucleon-pair states" (nucleon-pair configuration without mixings) emerges. In 128,126Sn, the positive-parity (or negative-parity) yrast states with spin J >10 (or J >7 ) are found to be well described by breaking one or two S pairs in the 101+ (or 71-) state, i.e., the yrast state of seniority-two, spin-maximum, and positive-parity (or negative-parity), into non-S pair(s). Similar regularity is also pointed out for 104,106Sn. The evolution of E 2 transition rates between low-lying states in 128,126,124Sn is discussed in terms of the seniority scheme.

  9. Hydrodynamic interaction of a pair of bubbles rising in a quiescent liquid.

    NASA Astrophysics Data System (ADS)

    Sanada, Toshiyuki

    2005-11-01

    Interaction effects on the motions of a pair of bubbles, which either rose in vertical line or side by side, in silicon oil pool were experimentally studied. A pair of bubbles rising in vertical line was generated by releasing bubbles successively from a single nozzle, while one rising side by side was generated, by releasing bubble simultaneously from a pair of horizontally placed orifices. Bubble diameter and liquid kinematic viscosity were taken as the experimental parameters. The motions of bubbles were recorded by a high-speed camera with 2000 fps. We observed that Reynolds number significantly affected the motions of a pair of bubbles rising both in vertical line and side by side. When a pair of bubbles rose in vertical line, the trailing bubble was attracted by the leading bubble wake, and then it collided with leading bubble, in the case of low Re, while a pair of bubbles kept a mutual equilibrium distance due to the balance between the leading bubble wake attractive force and potential repulsive force, in the case of intermediate Re. As Re further increased, the trailing bubble oscillated and then escaped from the vertical line. When a pair of bubbles rose side by side, they separated from each other as they rose in the case of low Re, while they attracted each other and then collided if the initial bubble horizontal distance was smaller than a critical value, in the case of large Re.

  10. Probing the Pairing Interaction and Multiple Bardasis-Schrieffer Modes Using Raman Spectroscopy

    SciTech Connect

    Maiti, S.; Maier, T. A.; Böhm, T.; Hackl, R.; Hirschfeld, P. J.

    2016-12-15

    In unconventional superconductors, understanding the form of the pairing interaction is the primary goal. In this regard, Raman spectroscopy is a very useful tool, as it identifies the ground state and also the subleading pairing channels by probing collective modes. We propose a general theory for a multiband Raman response and identify new features in the spectrum that can provide a robust test for a pairing theory. We also identify multiple Bardasis-Schrieffer type collective modes and connect the weights of these modes to the subleading gap structures within a microscopic pairing theory. Furthermore, while our conclusions are completely general, we apply our approach to interpret the specific case of B 1 g Raman scattering in hole-doped BaFe 2 As 2 .

  11. Probing the Pairing Interaction and Multiple Bardasis-Schrieffer Modes Using Raman Spectroscopy

    DOE PAGES

    Maiti, S.; Maier, T. A.; Böhm, T.; ...

    2016-12-15

    In unconventional superconductors, understanding the form of the pairing interaction is the primary goal. In this regard, Raman spectroscopy is a very useful tool, as it identifies the ground state and also the subleading pairing channels by probing collective modes. We propose a general theory for a multiband Raman response and identify new features in the spectrum that can provide a robust test for a pairing theory. We also identify multiple Bardasis-Schrieffer type collective modes and connect the weights of these modes to the subleading gap structures within a microscopic pairing theory. Furthermore, while our conclusions are completely general, wemore » apply our approach to interpret the specific case of B 1 g Raman scattering in hole-doped BaFe 2 As 2 .« less

  12. Probing the Pairing Interaction and Multiple Bardasis-Schrieffer Modes Using Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Maiti, S.; Maier, T. A.; Böhm, T.; Hackl, R.; Hirschfeld, P. J.

    2016-12-01

    In unconventional superconductors, understanding the form of the pairing interaction is the primary goal. In this regard, Raman spectroscopy is a very useful tool, as it identifies the ground state and also the subleading pairing channels by probing collective modes. Here, we propose a general theory for a multiband Raman response and identify new features in the spectrum that can provide a robust test for a pairing theory. We identify multiple Bardasis-Schrieffer type collective modes and connect the weights of these modes to the subleading gap structures within a microscopic pairing theory. While our conclusions are completely general, we apply our approach to interpret the specific case of B1 g Raman scattering in hole-doped BaFe2 As2 .

  13. Pairing in spherical nuclei: Quasiparticle random-phase approximation calculations with the Gogny interaction

    NASA Astrophysics Data System (ADS)

    De Donno, V.; Co', G.; Anguiano, M.; Lallena, A. M.

    2017-05-01

    We investigate the effects of the pairing in spherical nuclei. We use the same finite-range interaction of Gogny type in the three steps of our approach, Hartree-Fock, Bardeen, Cooper, and Schrieffer, and quasiparticle random-phase-approximation calculations. We study electric- and magnetic-dipole and quadrupole and octupole excitations in oxygen and calcium isotopes and also in isotones with 20 neutrons. We investigate the pairing effects on single-particle energies and occupation probabilities, on the excitation energies, B values, and collectivity of low-lying states including the isoscalar electric-dipole and magnetic-dipole excitations, and also the giant resonances. The inclusion of the pairing increases the values of the excitation energies in all the cases that we have studied. In general, the effects of the pairing are too small to noticeably improve the agreement with the available experimental data.

  14. Equation of state of a dense plasma: Analytical results on the basis of quantum pair interaction potentials in the random phase approximation

    NASA Astrophysics Data System (ADS)

    Moldabekov, Zh A.; Ramazanov, T. S.; Gabdullin, M. T.

    2016-11-01

    In this work, using recently obtained expansion of the dielectric function in the long wave length limit by Moldabekov et al (2015 Phys. Plasmas 22 102104), we extended previously obtained formulas for the equation of state of the semiclassical dense plasma from Ramazanov et al (2015 Phys. Rev. E 92 023104) to the quantum case. Inner energy and contribution to the pressure due to plasma non-ideality derived for both Coulomb pair interaction and quantum pair interaction potentials. Obtained analytical result for the equation of state reproduces the Montroll-Ward contribution, which corresponds to the quantum ring sum. It was shown that the obtained results are consistent with the Thomas-Fermi approximation with the first order gradient correction. Additionally, the generalization of the quantum Deutsch potential to the case of the degenerate electrons is discussed. Obtained results will be useful for understanding of the physics of dense plasmas as well as for further development of the dense plasma simulation on the basis of the quantum potentials.

  15. On the classical description of the recombination of dark matter particles with a Coulomb-like interaction

    NASA Astrophysics Data System (ADS)

    Belotsky, K. M.; Esipova, E. A.; Kirillov, A. A.

    2016-10-01

    Cold dark matter (DM) scenario may be cured of several problems by involving self-interaction of dark matter. Viability of the models of long-range interacting DM crucially depends on the effectiveness of recombination of the DM particles, making thereby their interaction short-range. Usually in numeric calculations, recombination is described by cross section obtained on a feasible quantum level. However in a wide range of parameter values, a classical treatment, where the particles are bound due to dipole radiation, is applicable. The cross sections, obtained in both approaches, are very different and lead to diverse consequences. Classical cross section has a steeper dependence on relative velocity, what leads to the fact that, after decoupling of DM particles from thermal background of "dark photons" (carriers of DM long-range interaction), recombination process does not "freeze out", diminishing gradually density of unbound DM particles. Our simplified estimates show, that at the taken parameter values (the mass of DM particle is 100 GeV, interaction constant is 100-1, and quite natural assumptions on initial conditions, from which the result is very weakly dependent) the difference in residual density reaches about 5 orders of magnitude on pre-galactic stage. This estimate takes into account thermal effects induced by dipole radiation and recombination, which resulted in the increase of both temperature and density of DM particles by a half order of magnitude.

  16. Verbal play as a discourse resource in the social interactions of older and younger communication pairs.

    PubMed

    Shune, Samantha; Duff, Melissa Collins

    2014-01-01

    Verbal play, or the playful manipulation of elements of language, is a pervasive component of social interaction, serving important interpersonal functions. We analyzed verbal play in the interactional discourse of ten healthy younger pairs and ten healthy older pairs as they completed a collaborative referencing task. A total of 1,893 verbal play episodes were coded. While there were no group differences in verbal play frequency, age-related differences in the quality and function of these episodes emerged. While older participants engaged in more complex, extended, and reciprocal episodes that supported the social nature of communicative interactions (e.g., teasing), younger participants were more likely to engage in verbal play episodes for the purpose of successful task completion. Despite these age-related variations in the deployment of verbal play, verbal play is a robust interactional discourse resource in healthy aging, highlighting an element of human cognition that does not appear to decline with age.

  17. Verbal play as a discourse resource in the social interactions of older and younger communication pairs

    PubMed Central

    Shune, Samantha; Duff, Melissa Collins

    2014-01-01

    Verbal play, or the playful manipulation of elements of language, is a pervasive component of social interaction, serving important interpersonal functions. We analyzed verbal play in the interactional discourse of ten healthy younger pairs and ten healthy older pairs as they completed a collaborative referencing task. A total of 1,893 verbal play episodes were coded. While there were no group differences in verbal play frequency, age-related differences in the quality and function of these episodes emerged. While older participants engaged in more complex, extended, and reciprocal episodes that supported the social nature of communicative interactions (e.g., teasing), younger participants were more likely to engage in verbal play episodes for the purpose of successful task completion. Despite these age-related variations in the deployment of verbal play, verbal play is a robust interactional discourse resource in healthy aging, highlighting an element of human cognition that does not appear to decline with age. PMID:25485072

  18. 2. QUANTUM HALL EFFECT: The problem of Coulomb interactions in the theory of the quantum Hall effect

    NASA Astrophysics Data System (ADS)

    Baranov, M. A.; Pruisken, A. M. M.; Škoric, B.

    2001-10-01

    We summarize the main ingredients of a unifying theory for abelian quantum Hall states. This theory combines the Finkel'stein approach to localization and interaction effects with the topological concept of an instanton vacuum as well as Chern-Simons gauge theory. We elaborate on the meaning of a new symmetry (Script F invariance) for systems with an infinitely ranged interaction potential. We address the renormalization of the theory and present the main results in terms of a scaling diagram of the conductances.

  19. Microcomputer Interactive vs. Traditional Associative Learning in a Paired-Associative Recall Task.

    ERIC Educational Resources Information Center

    Newhouse, Barbara S.

    Differences between interactive microcomputer and traditional verbal learning groups in a paired-associate learning task were examined in this study. The 88 subjects, who were undergraduate education students, were randomly assigned to four groups. Each group was given one of two lists of ten high frequency words matched with either high or low…

  20. Effects of the osmolyte TMAO (Trimethylamine-N-oxide) on aqueous hydrophobic contact-pair interactions.

    PubMed

    Macdonald, Ryan D; Khajehpour, Mazdak

    2013-12-31

    Osmolytes are small, soluble organic molecules produced by living organisms for maintaining cell volume. These molecules have also been shown to have significant effects on the stability of proteins. Perhaps one of the most studied osmolytes is Trimethylamine-N-oxide (TMAO). Thermodynamic studies of the effects of TMAO on proteins have shown that this molecule is a strong stabilizer of the protein folded state, thus being able to counteract the effects of protein denaturants such as urea and guanidine hydrochloride. Most studies of TMAO effects on bio-molecular stability have until now been focused on how the osmolyte reduces the solubility of polypeptide backbones, while the effects of TMAO on hydrophobic interactions are still not well understood. In fact, there are few experimental data measuring the effect of TMAO on hydrophobic interactions. This work studies phenyl and alkyl contact pairs as model hydrophobic contact pairs. The formation of these contact pairs is monitored using fluorescence, i.e., through the quenching of phenol fluorescence by carboxylate ions; and a methodology is developed to isolate hydrophobic contributions from other interactions. The data demonstrate that the addition of TMAO to the aqueous solvent destabilizes hydrophobic contact pairs formed between alkyl and phenyl moieties. In other words, TMAO acts as a "denaturant" for hydrophobic interactions.

  1. Microcomputer Interactive vs. Traditional Associative Learning in a Paired-Associative Recall Task.

    ERIC Educational Resources Information Center

    Newhouse, Barbara S.

    Differences between interactive microcomputer and traditional verbal learning groups in a paired-associate learning task were examined in this study. The 88 subjects, who were undergraduate education students, were randomly assigned to four groups. Each group was given one of two lists of ten high frequency words matched with either high or low…

  2. Cooperative Interactions in Peer Tutoring: Patterns and Sequences in Paired Writing

    ERIC Educational Resources Information Center

    Duran, David

    2010-01-01

    The research analyzes the interaction of 24 students (12 pairs) of secondary students when using peer tutoring techniques to learn Catalan. Students worked together in a program to produce an authentic writing experience. Significant increases were observed in pre- and posttest Catalan attainment scores of students. An analysis of the…

  3. The Relationship between Ability-Paired Interactions and the Development of Fifth Graders' Concepts of Balance.

    ERIC Educational Resources Information Center

    Carter, Glenda; Jones, M. Gail

    This study describes the effects of ability-paired student interactions on achievement as fifth graders (ten-year-olds) worked on laboratory activities relating to balance. Achievement gains were assessed (n=83) by analysis of pre/posttest differences on the Lever Concept Test. Audio recordings and field notes (n=30) were analyzed for the…

  4. Influence of constitution and charge on radical pairing interactions in tris-radical tricationic complexes

    DOE PAGES

    Cheng, Chuyang; Cheng, Tao; Xiao, Hai; ...

    2016-07-06

    The results of a systematic investigation of trisradical tricationic complexes formed between cyclobis-(paraquat-p-phenylene) bisradical dicationic (CBPQT2(•+)) rings and a series of 18 dumbbells, containing centrally located 4,4'-bipyridinium radical cationic (BIPY•+) units within oligomethylene chains terminated for the most part by charged 3,5-dimethylpyridinium (PY+) and/or neutral 3,5- dimethylphenyl (PH) groups, are reported. The complexes were obtained by treating equimolar amounts of the CBPQT4+ ring and the dumbbells containing BIPY2+ units with zinc dust in acetonitrile solutions. Whereas UV–Vis–NIR spectra revealed absorption bands centered on ca. 1100 nm with quite different intensities for the 1:1 complexes depending on the constitutions and chargesmore » on the dumbbells, titration experiments showed that the association constants (Ka) for complex formation vary over a wide range, from 800 M–1 for the weakest to 180 000 M–1 for the strongest. While Coulombic repulsions emanating from PY+ groups located at the ends of some of the dumbbells undoubtedly contribute to the destabilization of the trisradical tricationic complexes, solid-state superstructures support the contention that those dumbbells with neutral PH groups at the ends of flexible and appropriately constituted links to the BIPY•+ units stand to gain some additional stabilization from C–H···π interactions between the CBPQT2(•+) rings and the PH termini on the dumbbells. The findings reported in this Article demonstrate how structural changes implemented remotely from the BIPY•+ units influence their non-covalent bonding interactions with CBPQT2(•+) rings. Different secondary effects (Coulombic repulsions versus C–H···π interactions) are uncovered, and their contributions to both binding strengths associated with trisradical interactions and the kinetics of associations and dissociations are discussed at some length, supported by extensive DFT calculations at

  5. Antiferromagnetic Ising spin glass competing with BCS pairing interaction in a transverse field

    NASA Astrophysics Data System (ADS)

    Magalhães, S. G.; Zimmer, F. M.; Kipper, C. J.; Calegari, E. J.

    2006-07-01

    The competition among spin glass (SG), antiferromagnetism (AF) and local pairing superconductivity (PAIR) is studied in a two-sublattice fermionic Ising spin glass model with a local BCS pairing interaction in the presence of an applied magnetic transverse field Γ. In the present approach, spins in different sublattices interact with a Gaussian random coupling with an antiferromagnetic mean J0 and standard deviation J. The problem is formulated in the path integral formalism in which spin operators are represented by bilinear combinations of Grassmann variables. The saddle-point Grand Canonical potential is obtained within the static approximation and the replica symmetric ansatz. The results are analysed in phase diagrams in which the AF and the SG phases can occur for small g (g is the strength of the local superconductor coupling written in units of J), while the PAIR phase appears as unique solution for large g. However, there is a complex line transition separating the PAIR phase from the others. It is second order at high temperature that ends in a tricritical point. The quantum fluctuations affect deeply the transition lines and the tricritical point due to the presence of Γ.

  6. Dopamine and opioid systems interact within the nucleus accumbens to maintain monogamous pair bonds

    PubMed Central

    Resendez, Shanna L; Keyes, Piper C; Day, Jeremy J; Hambro, Caely; Austin, Curtis J; Maina, Francis K; Eidson, Lori N; Porter-Stransky, Kirsten A; Nevárez, Natalie; McLean, J William; Kuhnmuench, Morgan A; Murphy, Anne Z; Mathews, Tiffany A; Aragona, Brandon J

    2016-01-01

    Prairie vole breeder pairs form monogamous pair bonds, which are maintained through the expression of selective aggression toward novel conspecifics. Here, we utilize behavioral and anatomical techniques to extend the current understanding of neural mechanisms that mediate pair bond maintenance. For both sexes, we show that pair bonding up-regulates mRNA expression for genes encoding D1-like dopamine (DA) receptors and dynorphin as well as enhances stimulated DA release within the nucleus accumbens (NAc). We next show that D1-like receptor regulation of selective aggression is mediated through downstream activation of kappa-opioid receptors (KORs) and that activation of these receptors mediates social avoidance. Finally, we also identified sex-specific alterations in KOR binding density within the NAc shell of paired males and demonstrate that this alteration contributes to the neuroprotective effect of pair bonding against drug reward. Together, these findings suggest motivational and valence processing systems interact to mediate the maintenance of social bonds. DOI: http://dx.doi.org/10.7554/eLife.15325.001 PMID:27371827

  7. Spatiotemporal interactions in the visual cortex following paired electrical stimulation of the retina.

    PubMed

    Cicione, Rosemary; Fallon, James B; Rathbone, Graeme D; Williams, Chris E; Shivdasani, Mohit N

    2014-11-04

    Retinal prostheses use spatiotemporal patterns of electrical stimulation across multiple electrodes to provide visual percepts to blind patients. It is generally assumed that percepts produced by individual electrodes are independent of one another, which may not be the case. In this study, we aimed to quantify interactions between pairs of electrical stimuli delivered to the retina. Normally sighted cats were implanted with a suprachoroidal electrode array. The retina was stimulated with a paired-pulse paradigm that consisted of a conditioning stimulus followed by a test stimulus, while recording multiunit activity in the visual cortex. Conditioning current, and spatial and temporal separation between the conditioning and test stimuli were varied. Cortical interactions were quantified by changes in multiunit activity elicited by stimulation with the paired-pulse paradigm, compared to stimulation of the test stimulus alone (control). Interactions varied as a function of conditioning current and temporal separation between the two stimulating pulses. Cortical activity increased compared to the control condition at an interstimulus delay of 1.025 ms and was significantly suppressed for delays between 20 and 90 ms, returning to near control levels for longer delays. The level of interactions increased when the conditioning current was increased. Interactions were found to be similar for electrode separations up to 3 mm. Interactions between sequential stimulation of pairs of electrodes in a suprachoroidal retinal prosthesis occur for delays up to 100 ms and electrode separations of several millimeters. Knowledge of these spatiotemporal interactions is essential for developing effective patterns of stimulation for retinal prostheses. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  8. Coupling strength in Coulomb and Yukawa one-component plasmas

    SciTech Connect

    Ott, T.; Bonitz, M.; Stanton, L. G.; Murillo, M. S.

    2014-11-15

    In a non-ideal classical Coulomb one-component plasma (OCP), all thermodynamic properties are known to depend only on a single parameter—the coupling parameter Γ. In contrast, if the pair interaction is screened by background charges (Yukawa OCP) the thermodynamic state depends, in addition, on the range of the interaction via the screening parameter κ. How to determine in this case an effective coupling parameter has been a matter of intensive debate. Here we propose a consistent approach for defining and measuring the coupling strength in Coulomb and Yukawa OCPs based on a fundamental structural quantity, the radial pair distribution function (RPDF). The RPDF is often accessible in experiments by direct observation or indirectly through the static structure factor. Alternatively, it is directly computed in theoretical models or simulations. Our approach is based on the observation that the build-up of correlation from a weakly coupled system proceeds in two steps: First, a monotonically increasing volume around each particle becomes devoid of other particles (correlation hole), and second (upon further increase of the coupling), a shell structure emerges around each particle giving rise to growing peaks of the RPDF. Using molecular dynamics simulation, we present a systematic study for the dependence of these features of the RPDF on Γ and κ and derive a simple expression for the effective coupling parameter.

  9. Role of ion-pair interactions on asphaltene stabilization by alkylbenzenesulfonic acids.

    PubMed

    Goual, Lamia; Sedghi, Mohammad

    2015-02-15

    The dispersion of asphaltenes by dodecylbenzenesulfonic acid (DBSA) has been the subject of several studies in the past. However, it is unclear how these interactions affect the structure of asphaltenes and why asphaltene aggregates are larger in the presence of ionic DBSA. The main goal of this study was to address these points using a combination of high-resolution transmission electron microscopy (HRTEM) and molecular dynamics (MD) simulations. Another objective was to compare ionic DBSA (i.e., dodecylbenzenesulfonate or DBS(-)) to nonionic amphiphiles such as alkylphenols. A striking similarity between dodecylbenzenesulfonate and alkylphenols was that both favored the formation of filamentary rather than globular asphaltene flocculates. However the mechanism by which those filaments formed was very different. Two strong electrostatic interactions between DBSA and asphaltenes were found: (i) those between protonated asphaltenes (i.e., AH(+)) and DBS(-) molecules, which were fifteen times stronger than asphaltene-alkylphenol interactions, and (ii) those between two asphaltene-dispersant pairs (i.e., AH(+)-DBS(-) ion pairs), which did not exist with alkylphenols. These interactions promoted the formation of large and compact asphaltene flocculates, as compared to small and loose ones formed without DBSA. Flocculates with DBSA could further bind to each other through ion-pair interactions. The binding occurred in series (generating long filaments) or in parallel (generating lateral ramifications). However the series configuration was energetically favored due to less steric effects generated by the side aliphatic chains of asphaltenes and DBSA.

  10. Finite-Range Separable Pairing Interaction Within New N3LO DFT Approach

    NASA Astrophysics Data System (ADS)

    Veselý, P.; Dobaczewski, J.; Michel, N.; Toivanen, J.

    2011-10-01

    For over four decades, the Skyrme functional within various parametrizations has been used to calculate nuclear properties. In the last few years there was a number of attempts to improve its performance and introduce generalized forms. In particular, the most general phenomenologi-cal quasi-local energy density functional, which contains all combinations of density, spin-density, and their derivatives up to the sixth order (N3LO), was proposed in reference [1]. Since in the phe-nomenological functional approaches the particle-particle (pp) interaction channel is treated independently from the particle-hole (ph) channel, there remains a question of what pairing interaction is suitable to use within the N3LO energy functional. In our study, we use the separable, finite-range, translationally invariant form given in [2], which we generalize to the arbitrary angular momentum channel. We discuss the application of this pairing interaction within the N3LO energy functional.

  11. Effects of the plasma profiles on photon and pair production in ultrahigh intensity laser solid interaction

    SciTech Connect

    Tian, Y. X.; Jin, X. L. Yan, W. Z.; Li, J. Q.; Li, B.; Yu, J. Q.

    2015-12-15

    The model of photon and pair production in strong field quantum electrodynamics is implemented into our 1D3V particle-in-cell code with Monte Carlo algorithm. Using this code, the evolution of the particles in ultrahigh intensity laser (∼10{sup 23} W/cm{sup 2}) interaction with aluminum foil target is observed. Four different initial plasma profiles are considered in the simulations. The effects of initial plasma profiles on photon and pair production, energy spectra, and energy evolution are analyzed. The results imply that one can set an optimal initial plasma profile to obtain the desired photon distributions.

  12. Non-invasive determination of external forces in vortex-pair-cylinder interactions

    NASA Astrophysics Data System (ADS)

    Hartmann, D.; Schröder, W.; Shashikanth, B. N.

    2012-06-01

    Expressions for the conserved linear and angular momenta of a dynamically coupled fluid + solid system are derived. Based on the knowledge of the flow velocity field, these expressions allow the determination of the external forces exerted on a body moving in the fluid such as, e.g., swimming fish. The verification of the derived conserved quantities is done numerically. The interaction of a vortex pair with a circular cylinder in various configurations of motions representing a generic test case for a dynamically coupled fluid + solid system is investigated in a weakly compressible Navier-Stokes setting using a Cartesian cut-cell method, i.e., the moving circular cylinder is represented by cut cells on a moving mesh. The objectives of this study are twofold. The first objective is to show the robustness of the derived expressions for the conserved linear and angular momenta with respect to bounded and discrete data sets. The second objective is to study the coupled dynamics of the vortex pair and a neutrally buoyant cylinder free to move in response to the fluid stresses exerted on its surface. A comparison of the vortex-body interaction with the case of a fixed circular cylinder evidences significant differences in the vortex dynamics. When the cylinder is fixed strong secondary vorticity is generated resulting in a repeating process between the primary vortex pair and the cylinder. In the neutrally buoyant cylinder case, a stable structure consisting of the primary vortex pair and secondary vorticity shear layers stays attached to the moving cylinder. In addition to these fundamental cases, the vortex-pair-cylinder interaction is studied for locomotion at constant speed and locomotion at constant thrust. It is shown that a similar vortex structure like in the neutrally buoyant cylinder case is obtained when the cylinder moves away from the approaching vortex pair at a constant speed smaller than the vortex pair translational velocity. Finally, the idealized

  13. Computationally simple, analytic, closed form solution of the Coulomb self-interaction problem in Kohn Sham density functional theory

    SciTech Connect

    Gonis, Antonios; Daene, Markus W; Nicholson, Don M; Stocks, George Malcolm

    2012-01-01

    We have developed and tested in terms of atomic calculations an exact, analytic and computationally simple procedure for determining the functional derivative of the exchange energy with respect to the density in the implementation of the Kohn Sham formulation of density functional theory (KS-DFT), providing an analytic, closed-form solution of the self-interaction problem in KS-DFT. We demonstrate the efficacy of our method through ground-state calculations of the exchange potential and energy for atomic He and Be atoms, and comparisons with experiment and the results obtained within the optimized effective potential (OEP) method.

  14. A Study of the Crystallizations Possible on the Surface of a Spherical Droplet Using Coulomb Interactions Between Point Charges

    DTIC Science & Technology

    1990-01-01

    This report may not be cited for purposes of advertisement. Reproduction of this document in whole or in part is prohibited except with permission of...at least part of a hemisphere. Examples of this are shown for N 26 and N - 99 in Figure 7. We have come across several cases where there are two or...expanding in theta we find 41 - 2/N!/2 The interaction energy which is to be subtracted is then U2 - 2TT* Integrall 0 (Phi*Sigma d&) where Phi is the

  15. ChIA-PET tool for comprehensive chromatin interaction analysis with paired-end tag sequencing.

    PubMed

    Li, Guoliang; Fullwood, Melissa J; Xu, Han; Mulawadi, Fabianus Hendriyan; Velkov, Stoyan; Vega, Vinsensius; Ariyaratne, Pramila Nuwantha; Mohamed, Yusoff Bin; Ooi, Hong-Sain; Tennakoon, Chandana; Wei, Chia-Lin; Ruan, Yijun; Sung, Wing-Kin

    2010-01-01

    Chromatin interaction analysis with paired-end tag sequencing (ChIA-PET) is a new technology to study genome-wide long-range chromatin interactions bound by protein factors. Here we present ChIA-PET Tool, a software package for automatic processing of ChIA-PET sequence data, including linker filtering, mapping tags to reference genomes, identifying protein binding sites and chromatin interactions, and displaying the results on a graphical genome browser. ChIA-PET Tool is fast, accurate, comprehensive, user-friendly, and open source (available at http://chiapet.gis.a-star.edu.sg).

  16. Fluid-dynamical scheme for equilibrium properties of two trapped fermion species with pairing interactions

    NASA Astrophysics Data System (ADS)

    Capuzzi, P.; Hernández, E. S.; Szybisz, L.

    2008-10-01

    We present a generalization of the fluid-dynamical scheme developed for nuclear physics to the case of two trapped fermion species with pairing interactions. To establish a macroscopic description of the mass and momentum conservation laws, we adopt a generalization of the usual Thomas-Fermi approach that includes the pairing energy. We analyze the equilibrium density and gap profiles for an equal population mixture of harmonically trapped Li6 atoms for different choices of the local equation of state. We examine slight departures from equilibrium within our formulation, finding that density oscillations can propagate as first sound coupled to pairing vibrations, that in a homogeneous fermion system exhibit a Bogoliubov-like quasiparticle spectrum. In this case, the dispersion relation for the coupled modes displays a rich scenario of stable, unstable, and damped regimes.

  17. Interactions between impurities and breather-pairs in a nonlinear lattice

    NASA Astrophysics Data System (ADS)

    Lin, Han; Chen, Weizhong; Lu, Lei; Wei, Rongjue

    2003-09-01

    Based on the Frenkel-Kontorova (FK) model with a δ-impurity, this Letter investigates the interactions between impurities and breather-pairs in a nonlinear pendulum chain driven by a vertical vibration. The numerical results show that a long impurity in pendulum length can absorb more energy into the chain and upgrade the energy level of the breather-pair, when the driving frequency is slight lower than that of parametric resonance of the perfect pendulums, while a short one plays a counteractive role. As the chain is driven at a higher frequency, the effect of impurities turns reverse, which shows a clear symmetry and equivalency between long and short impurities. The main results including the effect and the symmetry of impurities generalize the conclusion on the single breather to the breather-pair.

  18. An exchange-Coulomb model potential energy surface for the Ne-CO interaction. I. Calculation of Ne-CO van der Waals spectra.

    PubMed

    Dham, Ashok K; McCourt, Frederick R W; Meath, William J

    2009-06-28

    Exchange-Coulomb model potential energy surfaces have been developed for the Ne-CO interaction. The initial model is a three-dimensional potential energy surface based upon computed Heitler-London interaction energies and literature results for the long-range induction and dispersion energies, all as functions of interspecies distance, the orientation of CO relative to the interspecies axis, and the bond length of the CO molecule. Both a rigid-rotor model potential energy surface, obtained by setting the CO bond length equal to its experimental spectroscopic equilibrium value, and a vibrationally averaged model potential energy surface, obtained by averaging the stretching dependence over the ground vibrational motion of the CO molecule, have been constructed from the full data set. Adjustable parameters in each model potential energy surface have been determined through fitting a selected subset of pure rotational transition frequencies calculated for the (20)Ne-(12)C(12)O isotopolog to precisely known experimental values. Both potential energy surfaces provide calculated results for a wide range of available experimental microwave, millimeter-wave, and midinfrared Ne-CO transition frequencies that are generally far superior to those obtained using the best current literature potential energy surfaces. The vibrationally averaged CO ground state potential energy surface, employed together with a potential energy surface obtained from it by replacing the ground vibrational state average of the CO stretching dependence of the potential energy surface by an average over the first excited CO vibrational state, has been found to be particularly useful for computing and/or interpreting mid-IR transition frequencies in the Ne-CO dimer.

  19. Study on the impact of pair production interaction on D-T controllable neutron density logging.

    PubMed

    Yu, Huawei; Zhang, Li; Hou, Boran

    2016-05-01

    This paper considers the effect of pair production on the precision of D-T controllable neutron source density logging. Firstly, the principle of the traditional density logging and pulsed neutron density logging are analyzed and then gamma ray cross sections as a function of energy for various minerals are compared. In addition, the advantageous areas of Compton scattering and pair production interactions on high-energy gamma ray pulse height spectrum and the errors of a controllable source density measurement are studied using a Monte Carlo simulation method. The results indicate that density logging mainly utilizes the Compton scattering of gamma rays, while the attenuation of neutron induced gamma rays and the precision of neutron gamma density measurements are affected by pair production interactions, particularly in the gamma rays with energy higher than 2MeV. By selecting 0.2-2MeV energy range and performing proper lithology correction, the effect of pair production can be eliminated effectively and the density measurement error can be rendered close to the precision of chemical source density logging.

  20. An exchange-Coulomb model potential energy surface for the Ne-CO interaction. II. Molecular beam scattering and bulk gas phenomena in Ne-CO mixtures.

    PubMed

    Dham, Ashok K; McBane, George C; McCourt, Frederick R W; Meath, William J

    2010-01-14

    Four potential energy surfaces are of current interest for the Ne-CO interaction. Two are high-level fully ab initio surfaces obtained a decade ago using symmetry-adapted perturbation theory and supermolecule coupled-cluster methods. The other two are very recent exchange-Coulomb (XC) model potential energy surfaces constructed by using ab initio Heitler-London interaction energies and literature long range dispersion and induction energies, followed by the determination of a small number of adjustable parameters to reproduce a selected subset of pure rotational transition frequencies for the (20)Ne-(12)C(16)O van der Waals cluster. Testing of the four potential energy surfaces against a wide range of available experimental microwave, millimeter-wave, and mid-infrared Ne-CO transition frequencies indicated that the XC potential energy surfaces gave results that were generally far superior to the earlier fully ab initio surfaces. In this paper, two XC model surfaces and the two fully ab initio surfaces are tested for their abilities to reproduce experiment for a wide range of nonspectroscopic Ne-CO gas mixture properties. The properties considered here are relative integral cross sections and the angle dependence of rotational state-to-state differential cross sections, rotational relaxation rate constants for CO(v=2) in Ne-CO mixtures at T=296 K, pressure broadening of two pure rotational lines and of the rovibrational lines in the CO fundamental and first overtone transitions at 300 K, and the temperature and, where appropriate, mole fraction dependencies of the interaction second virial coefficient, the binary diffusion coefficient, the interaction viscosity, the mixture shear viscosity and thermal conductivity coefficients, and the thermal diffusion factor. The XC model potential energy surfaces give results that lie within or very nearly within the experimental uncertainties for all properties considered, while the coupled-cluster ab initio surface gives

  1. Embodied social interaction constitutes social cognition in pairs of humans: A minimalist virtual reality experiment

    PubMed Central

    Froese, Tom; Iizuka, Hiroyuki; Ikegami, Takashi

    2014-01-01

    Scientists have traditionally limited the mechanisms of social cognition to one brain, but recent approaches claim that interaction also realizes cognitive work. Experiments under constrained virtual settings revealed that interaction dynamics implicitly guide social cognition. Here we show that embodied social interaction can be constitutive of agency detection and of experiencing another's presence. Pairs of participants moved their “avatars” along an invisible virtual line and could make haptic contact with three identical objects, two of which embodied the other's motions, but only one, the other's avatar, also embodied the other's contact sensor and thereby enabled responsive interaction. Co-regulated interactions were significantly correlated with identifications of the other's avatar and reports of the clearest awareness of the other's presence. These results challenge folk psychological notions about the boundaries of mind, but make sense from evolutionary and developmental perspectives: an extendible mind can offload cognitive work into its environment. PMID:24419102

  2. Embodied social interaction constitutes social cognition in pairs of humans: a minimalist virtual reality experiment.

    PubMed

    Froese, Tom; Iizuka, Hiroyuki; Ikegami, Takashi

    2014-01-14

    Scientists have traditionally limited the mechanisms of social cognition to one brain, but recent approaches claim that interaction also realizes cognitive work. Experiments under constrained virtual settings revealed that interaction dynamics implicitly guide social cognition. Here we show that embodied social interaction can be constitutive of agency detection and of experiencing another's presence. Pairs of participants moved their "avatars" along an invisible virtual line and could make haptic contact with three identical objects, two of which embodied the other's motions, but only one, the other's avatar, also embodied the other's contact sensor and thereby enabled responsive interaction. Co-regulated interactions were significantly correlated with identifications of the other's avatar and reports of the clearest awareness of the other's presence. These results challenge folk psychological notions about the boundaries of mind, but make sense from evolutionary and developmental perspectives: an extendible mind can offload cognitive work into its environment.

  3. Interactions in ion pairs of protic ionic liquids: comparison with aprotic ionic liquids.

    PubMed

    Tsuzuki, Seiji; Shinoda, Wataru; Miran, Md Shah; Kinoshita, Hiroshi; Yasuda, Tomohiro; Watanabe, Masayoshi

    2013-11-07

    The stabilization energies for the formation (E(form)) of 11 ion pairs of protic and aprotic ionic liquids were studied by MP2/6-311G** level ab initio calculations to elucidate the difference between the interactions of ions in protic ionic liquids and those in aprotic ionic liquids. The interactions in the ion pairs of protic ionic liquids (diethylmethylammonium [dema] and dimethylpropylammonium [dmpa] based ionic liquids) are stronger than those of aprotic ionic liquids (ethyltrimethylammonium [etma] based ionic liquids). The E(form) for the [dema][CF3SO3] and [dmpa][CF3SO3] complexes (-95.6 and -96.4 kcal/mol, respectively) are significantly larger (more negative) than that for the [etma][CF3SO3] complex (-81.0 kcal/mol). The same trend was observed for the calculations of ion pairs of the three cations with the Cl(-), BF4(-), TFSA(-) anions. The anion has contact with the N-H bond of the dema(+) or dmpa(+) cations in the most stable geometries of the dema(+) and dmpa(+) complexes. The optimized geometries, in which the anions locate on the counter side of the cations, are 11.0-18.0 kcal/mol less stable, which shows that the interactions in the ions pairs of protic ionic liquids have strong directionality. The E(form) for the less stable geometries for the dema(+) and dmpa(+) complexes are close to those for the most stable etma(+) complexes. The electrostatic interaction, which is the major source of the attraction in the ion pairs, is responsible for the directionality of the interactions and determining the magnitude of the interaction energy. Molecular dynamic simulations of the [dema][TFSA] and [dmpa][TFSA] ionic liquids show that the N-H bonds of the cations have contact with the negatively charged (oxygen and nitrogen) atoms of TFSA(-) anion, while the strong directionality of the interactions was not suggested from the simulation of the [etma][CF3SO3] ionic liquid.

  4. Interactions in ion pairs of protic ionic liquids: Comparison with aprotic ionic liquids

    SciTech Connect

    Tsuzuki, Seiji; Shinoda, Wataru; Miran, Md. Shah; Kinoshita, Hiroshi; Yasuda, Tomohiro; Watanabe, Masayoshi

    2013-11-07

    The stabilization energies for the formation (E{sub form}) of 11 ion pairs of protic and aprotic ionic liquids were studied by MP2/6-311G{sup **} level ab initio calculations to elucidate the difference between the interactions of ions in protic ionic liquids and those in aprotic ionic liquids. The interactions in the ion pairs of protic ionic liquids (diethylmethylammonium [dema] and dimethylpropylammonium [dmpa] based ionic liquids) are stronger than those of aprotic ionic liquids (ethyltrimethylammonium [etma] based ionic liquids). The E{sub form} for the [dema][CF{sub 3}SO{sub 3}] and [dmpa][CF{sub 3}SO{sub 3}] complexes (−95.6 and −96.4 kcal/mol, respectively) are significantly larger (more negative) than that for the [etma][CF{sub 3}SO{sub 3}] complex (−81.0 kcal/mol). The same trend was observed for the calculations of ion pairs of the three cations with the Cl{sup −}, BF{sub 4}{sup −}, TFSA{sup −} anions. The anion has contact with the N–H bond of the dema{sup +} or dmpa{sup +} cations in the most stable geometries of the dema{sup +} and dmpa{sup +} complexes. The optimized geometries, in which the anions locate on the counter side of the cations, are 11.0–18.0 kcal/mol less stable, which shows that the interactions in the ions pairs of protic ionic liquids have strong directionality. The E{sub form} for the less stable geometries for the dema{sup +} and dmpa{sup +} complexes are close to those for the most stable etma{sup +} complexes. The electrostatic interaction, which is the major source of the attraction in the ion pairs, is responsible for the directionality of the interactions and determining the magnitude of the interaction energy. Molecular dynamic simulations of the [dema][TFSA] and [dmpa][TFSA] ionic liquids show that the N–H bonds of the cations have contact with the negatively charged (oxygen and nitrogen) atoms of TFSA{sup −} anion, while the strong directionality of the interactions was not suggested from the simulation

  5. The Interparticle Interaction Between a Vertically Aligned Dust Particle Pair in a Complex Plasma

    NASA Astrophysics Data System (ADS)

    Qiao, Ke; Ding, Zhiyue; Kong, Jie; Matthews, Lorin; Hyde, Truell

    2016-10-01

    The interaction between dust particles is a fundamental topic in complex plasma. In experiments on earth, the interparticle interaction in the horizontal direction (i.e., perpendicular to the gravitational force) is generally recognized to be a Yukawa potential. However, the interaction in the vertical direction is much more complicated, primarily due to the ion flow in the plasma sheath. In this research, we introduce a non-intrusive method to study the interaction between a vertically aligned dust particle pair confined in a glass box placed on the lower powered electrode within a GEC reference cell. This system is investigated for varying rf powers to obtain the trend of the interparticle interaction strength, which is contrasted with theoretical results. Using spontaneous thermal fluctuations of the neutral gas as the only driving force, we obtain the normal mode spectra of the dust pair, revealing not only the oscillation frequencies, but also the vibration amplitudes of the normal modes. The interaction strength between the upper and lower particle is obtained quantitatively from these mode spectra, showing strong nonreciprocity in both the vertical and horizontal directions. It will also be shown that the resulting horizontal attractive force of the upper particle on the lower particle can be larger than the horizontal confinement produced by the glass box alone. NSF / DOE funding is gratefully acknowledged - PHY1414523 & PHY1262031.

  6. Effects of the protein denaturant guanidinium chloride on aqueous hydrophobic contact-pair interactions.

    PubMed

    Macdonald, Ryan D; Khajehpour, Mazdak

    2015-01-01

    Guanidinium chloride (GdmCl) is one of the most common protein denaturants. Although GdmCl is well known in the field of protein folding, the mechanism by which it denatures proteins is not well understood. In fact, there are few studies looking at its effects on hydrophobic interactions. In this work the effect of GdmCl on hydrophobic interactions has been studied by observing how the denaturant influences model systems of phenyl and alkyl hydrophobic contact pairs. Contact pair formation is monitored through the use of fluorescence spectroscopy, i.e., measuring the intrinsic phenol fluorescence being quenched by carboxylate ions. Hydrophobic interactions are isolated from other interactions through a previously developed methodology. The results show that GdmCl does not significantly affect hydrophobic interactions between small moieties such as methyl groups and phenol; while on the other hand, the interaction of larger hydrophobes such as hexyl and heptyl groups with phenol is significantly destabilized. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Molecular Balances Based on Aliphatic CH-π and Lone-PairInteractions.

    PubMed

    Nijamudheen, A; Jose, Deepthi; Shine, A; Datta, Ayan

    2012-06-07

    CH···π and lone-pair···π interactions are estimated for a series of conformationally dynamic bicyclic N-aryliimides. On the basis of their strengths and mutual synergy/competition, the molecules prefer a folded/unfolded conformation. Calculations suggest strategies to selectively isolate the folded form by increasing the strength of the attractive CH···π interaction or removing the lone-pair···π repulsion. While the barrier for the folded ⇄ unfolded transformation is too large to conformationally lock the molecules in either of the conformers, the dynamics for hopping of the alkyl group across rings and tumbling over the rings are found to be facile in the folded conformation.

  8. Counterintuitive Coulomb hole around the bond midplane.

    PubMed

    Wang, Jian; Kim, Kwang S; Baerends, Evert Jan

    2010-05-28

    The Coulomb hole does not have its largest depth around an electron in or near the bond midplane. It splits into two parts, localized on both nuclear sites forming the bond. Even counterintuitive positive values of the "hole" around such a position may be observed. This happens when the Fermi hole is deeper than the total exchange-correlation hole at the reference electron position. This Coulomb "heap" is shown to arise from correlation effects on the one-electron density rather than correlation effects in the pair density. Left-right correlation tends to enhance the effect of the nuclear attraction, contracting the electron density around the nuclear positions and depleting the bond center region. Possible alternative definitions of the Coulomb hole are discussed, including one based on the exact Kohn-Sham exchange hole. Approximate density functional theory methods (generalized gradient approximation) are not accurate enough to realize the advantages of this definition.

  9. Galaxy pairs in the Sloan Digital Sky Survey - IV. Interactions trigger active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Ellison, Sara L.; Patton, David R.; Mendel, J. Trevor; Scudder, Jillian M.

    2011-12-01

    Galaxy-galaxy interactions are predicted to cause gas inflows leading to enhanced nuclear star formation. This prediction is borne out observationally, and is also supported by the gas-phase metallicity dilution in the inner regions of galaxies in close pairs. In this paper we test the further prediction that the gas inflows lead to enhanced accretion on to the central supermassive black hole, triggering activity in the nucleus. Based on a sample of 11 060 Sloan Digital Sky Survey galaxies with a close companion (rp < 80 h-170 kpc, ΔV < 200 km s-1), we classify active galactic nuclei (AGN) based either on emission line ratios or on spectral classification as a quasar. The AGN fraction in the close pairs sample is compared to a control sample of 110 600 mass- and redshift-matched control galaxies with no nearby companion. We find a clear increase in the AGN fraction in close pairs of galaxies with projected separations < 40 h-170 kpc by up to a factor of 2.5 relative to the control sample [although the enhancement depends on the chosen signal-to-noise ratio (S/N) cut of the sample]. The increase in AGN fraction is strongest in equal-mass galaxy pairings, and weakest in the lower mass component of an unequal-mass pairing. The increased AGN fraction at small separations is accompanied by an enhancement in the number of 'composite' galaxies whose spectra are the result of photoionization by both AGN and stars. Our results indicate that AGN activity occurs (at least in some cases) well before final coalescence and concurrently with ongoing star formation. Finally, we find a marked increase at small projected separations of the fraction of pairs in which both galaxies harbour AGN. We demonstrate that the fraction of double AGN exceeds the expected random fraction, indicating that some pairs undergo correlated nuclear activity. We discuss some of the factors that have led to conflicting results in previous studies of AGN in close pairs. Taken together with complementary

  10. The Isolated Interacting Galaxy Pair NGC 5426/27 (Arp 271)

    NASA Astrophysics Data System (ADS)

    Fuentes-Carrera, I.; Rosado, M.; Amram, P.; Dultzin-Hacyan, D.; Bernal, A.; Salo, H.; Laurikainen, E.; Cruz-González, I.; Le Coarer, E.

    2001-03-01

    The isolated interacting galaxy pair NGC 5426/27 (Arp 271) was observed using the scanning Fabry-Perot interferometer PUMA. The velocity field, various kinematical parameters and rotation curve for each galaxy were derived. We found a small bar-like structure in NGC 5426 and a severely distorted velocity field for NGC 5427. A range of possible masses was computed for each galaxy.

  11. Nonstandard interactions in plasmon decay to a neutrino pair in a strongly magnetized medium

    SciTech Connect

    Borisov, A. V.; Sizin, P. E.

    2016-05-15

    The neutrino luminosity of a stellar medium because of plasmon decay to a neutrino pair via nonstandard tensor interaction in a degenerate electron gas subjected to the effect of a magnetic field such strong that the electrons of the gas are in the lowest Landau level is calculated. Relative limits on nonstandard coupling constants are obtained from a comparison of the results of this calculation with the neutrino luminosity generated in the respective standard process proceeding under the same conditions.

  12. Excessive production of electron pairs by soft photons in low multiplicity ion interactions

    NASA Technical Reports Server (NTRS)

    Burnett, T. H.; Dake, S.; Fuki, M.; Gregory, J. C.; Hayashi, T.; Holynski, R.; Iwai, J.; Jones, W. V.; Jurak, A.; Lord, J. J.

    1985-01-01

    Three multiply charged primary cosmic ray interactions with carbon nuclei are reported, in which the number of materialized electron pairs within a distance of about 0.3 conversion length is larger than predicted from isospin considerations. These are the most energetic (sigma E gamma 4 TeV) of the low multiplicity ( 15 tracks) events observed in the Japanese-American Cooperative Experiment (JACEE-2) emulsion chamber.

  13. Assessment of the importance of the pairing interaction in the continuum

    SciTech Connect

    Id Betan, R.; Dussel, G. G.; Liotta, R. J.

    2008-10-15

    A pairing interaction fitted to be applied in nuclei with active particles moving close to the continuum threshold or even immersed in the continuum itself is introduced. It is found that the effects of the nonresonant continuum upon physically meaningful quantities is unimportant. We applied the theory to heavy tin isotopes and good agreement between theory and the very few available experimental data is found.

  14. Controlled exchange interaction between pairs of neutral atoms in an optical lattice.

    PubMed

    Anderlini, Marco; Lee, Patricia J; Brown, Benjamin L; Sebby-Strabley, Jennifer; Phillips, William D; Porto, J V

    2007-07-26

    Ultracold atoms trapped by light offer robust quantum coherence and controllability, providing an attractive system for quantum information processing and for the simulation of complex problems in condensed matter physics. Many quantum information processing schemes require the manipulation and deterministic entanglement of individual qubits; this would typically be accomplished using controlled, state-dependent, coherent interactions among qubits. Recent experiments have made progress towards this goal by demonstrating entanglement among an ensemble of atoms confined in an optical lattice. Until now, however, there has been no demonstration of a key operation: controlled entanglement between atoms in isolated pairs. Here we use an optical lattice of double-well potentials to isolate and manipulate arrays of paired (87)Rb atoms, inducing controlled entangling interactions within each pair. Our experiment realizes proposals to use controlled exchange coupling in a system of neutral atoms. Although 87Rb atoms have nearly state-independent interactions, when we force two atoms into the same physical location, the wavefunction exchange symmetry of these identical bosons leads to state-dependent dynamics. We observe repeated interchange of spin between atoms occupying different vibrational levels, with a coherence time of more than ten milliseconds. This observation demonstrates the essential component of a neutral atom quantum SWAP gate (which interchanges the state of two qubits). Its 'half-implementation', the root SWAP gate, is entangling, and together with single-qubit rotations it forms a set of universal gates for quantum computation.

  15. Effect of Inter-particle Interactions on Pair Correlations of One-Dimensional Anyon Gases

    NASA Astrophysics Data System (ADS)

    Li, Yan; He, Zhi

    2015-10-01

    The pair correlation function of the one-dimensional interacting anyonic system in its ground state is investigated based on the exact Bethe ansatz solution for arbitrary coupling constant () and statistics parameter (). We discuss the effects of the inter-particle interactions and the fractional statistics on the pair correlations in both position and momentum spaces. The pair correlations of anyons with coupling constant c and statistical parameter in position space are identical to that of the Lieb-Liniger Bose model with effective coupling constant . Besides the effect of renormalized coupling, the correlations in momentum space reveal more effects induced by the statistics parameter. The anyonic statistics results in the nonsymmetric correlation when the statistics parameter deviates from 0 (Bose statistics) and (Fermi statistics) for any coupling constant c. The correlations display peaks and dips, representing the bunching and antibunching of atoms, respectively. The correlations show crossover from bunching behavior of bosons to antibunching behavior of fermions as varies from 0 to for arbitrary coupling constant. Besides the fractional effect, we also observe the effects induced by the inter-particle interactions in the momentum correlations. With the increase of the coupling constant, the bunching effect between particles weakens and the antibunching points in the correlations shift.

  16. Nonnatural protein–protein interaction-pair design by key residues grafting

    PubMed Central

    Liu, Sen; Liu, Shiyong; Zhu, Xiaolei; Liang, Huanhuan; Cao, Aoneng; Chang, Zhijie; Lai, Luhua

    2007-01-01

    Protein–protein interface design is one of the most exciting fields in protein science; however, designing nonnatural protein–protein interaction pairs remains difficult. In this article we report a de novo design of a nonnatural protein–protein interaction pair by scanning the Protein Data Bank for suitable scaffold proteins that can be used for grafting key interaction residues and can form stable complexes with the target protein after additional mutations. Using our design algorithm, an unrelated protein, rat PLCδ1-PH (pleckstrin homology domain of phospholipase C-δ1), was successfully designed to bind the human erythropoietin receptor (EPOR) after grafting the key interaction residues of human erythropoietin binding to EPOR. The designed mutants of rat PLCδ1-PH were expressed and purified to test their binding affinities with EPOR. A designed triple mutation of PLCδ1-PH (ERPH1) was found to bind EPOR with high affinity (KD of 24 nM and an IC50 of 5.7 μM) both in vitro and in a cell-based assay, respectively, although the WT PLCδ1-PH did not show any detectable binding under the assay conditions. The in vitro binding affinities of the PLCδ1-PH mutants correlate qualitatively to the computational binding affinities, validating the design and the protein–protein interaction model. The successful practice of finding a proper protein scaffold and making it bind with EPOR demonstrates a prospective application in protein engineering targeting protein–protein interfaces. PMID:17372228

  17. Longitudinal multiparameter assay of lymphocyte interactions from onset by microfluidic cell pairing and culture

    PubMed Central

    Dura, Burak; Servos, Mariah M.; Barry, Rachel M.; Ploegh, Hidde L.; Dougan, Stephanie K.; Voldman, Joel

    2016-01-01

    Resolving how the early signaling events initiated by cell–cell interactions are transduced into diverse functional outcomes necessitates correlated measurements at various stages. Typical approaches that rely on bulk cocultures and population-wide correlations, however, only reveal these relationships broadly at the population level, not within each individual cell. Here, we present a microfluidics-based cell–cell interaction assay that enables longitudinal investigation of lymphocyte interactions at the single-cell level through microfluidic cell pairing, on-chip culture, and multiparameter assays, and allows recovery of desired cell pairs by micromanipulation for off-chip culture and analyses. Well-defined initiation of interactions enables probing cellular responses from the very onset, permitting single-cell correlation analyses between early signaling dynamics and later-stage functional outcomes within same cells. We demonstrate the utility of this microfluidic assay with natural killer cells interacting with tumor cells, and our findings suggest a possible role for the strength of early calcium signaling in selective coordination of subsequent cytotoxicity and IFN-gamma production. Collectively, our experiments demonstrate that this new approach is well-suited for resolving the relationships between complex immune responses within each individual cell. PMID:27303033

  18. An interaction scenario of the galaxy pair NGC 3893/96 (KPG 302): A single passage?

    SciTech Connect

    Gabbasov, R. F.; Rosado, M.; Klapp, J.

    2014-05-20

    Using the data obtained previously from Fabry-Perot interferometry, we study the orbital characteristics of the interacting pair of galaxies KPG 302 with the aim to estimate a possible interaction history, the conditions necessary for the spiral arm formation, and initial satellite mass. We found by performing N-body/smoothed particle hydrodynamics simulations of the interaction that a single passage can produce a grand design spiral pattern in less than 1 Gyr. Although we reproduce most of the features with the single passage, the required satellite to host mass ratio should be ∼1:5, which is not confirmed by the dynamical mass estimate made from the measured rotation curve. We conclude that a more realistic interaction scenario would require several passages in order to explain the mass ratio discrepancy.

  19. A Survey of Aspartate Phenylalanine and Glutamate Phenylalanine Interactions in the Protein Data Bank: Searching for Anion Pairs

    SciTech Connect

    Philip, Vivek M; Harris, Jason B; Adams, Rachel M; Nguyen, Don; Spires, Jeremy; Howell, Elizabeth E.; Hinde, Robert J

    2011-01-01

    Protein structures are stabilized using noncovalent interactions. In addition to the traditional noncovalent interactions, newer types of interactions are thought to be present in proteins. One such interaction, an anion pair, in which the positively charged edge of an aromatic ring interacts with an anion, forming a favorable anion quadrupole interaction, has been previously proposed [Jackson, M. R., et al. (2007) J. Phys. Chem. B111, 8242 8249]. To study the role of anion interactions in stabilizing protein structure, we analyzed pairwise interactions between phenylalanine (Phe) and the anionic amino acids, aspartate (Asp) and glutamate (Glu). Particular emphasis was focused on identification of Phe Asp or Glu pairs separated by less than 7 in the high-resolution, nonredundant Protein Data Bank. Simplifying Phe to benzene and Asp or Glu to formate molecules facilitated in silico analysis of the pairs. Kitaura Morokuma energy calculations were performed on roughly 19000 benzene formate pairs and the resulting energies analyzed as a function of distance and angle. Edgewise interactions typically produced strongly stabilizing interaction energies (2 to 7.3 kcal/mol), while interactions involving the ring face resulted in weakly stabilizing to repulsive interaction energies. The strongest, most stabilizing interactions were identified as preferentially occurring in buried residues. Anion pairs are found throughout protein structures, in helices as well as strands. Numerous pairs also had nearby cation interactions as well as potential stacking. While more than 1000 structures did not contain an anion pair, the 3134 remaining structures contained approximately 2.6 anion pairs per protein, suggesting it is a reasonably common motif that could contribute to the overall structural stability of a protein.

  20. Relationship between ability-paired interactions and the development of fifth graders' concepts of balance

    NASA Astrophysics Data System (ADS)

    Carter, Glenda; Jones, M. Gail

    This study describes the effects of ability-paired student interactions on achievement as fifth graders (10-year-olds) worked on laboratory activities relating to balance. Achievement gains were assessed (n = 83) by analysis of pretest-posttest differences on the lever concept test. Audio recordings and field notes (n = 30) were analyzed for the following laboratory behaviors: number of words spoken, tinkering, block moving, turns speaking, incidence of helping and distracting behavior. Results revealed that: (1) low-ability student achievement is greater when students are paired with high-ability partners; (2) low-ability students speak more words, exhibit less distracting behavior, and move blocks on the lever less when they are paired with a partner of high ability; (3) high-ability students speak more words, take more turns speaking, and exhibit more helping behaviors when they are paired with low-ability students rather than with other high ability students; and (4) there are no achievement differences for high-ability students regardless of the ability level of their partner. These findings suggest that heterogeneous grouping of students in science can be beneficial to low-ability students partnered with high-ability students, without being detrimental to the high-ability partners.

  1. Exact solutions for a type of electron pairing model with spin-orbit interactions and Zeeman coupling.

    PubMed

    Liu, Jia; Han, Qiang; Shao, L B; Wang, Z D

    2011-07-08

    A type of electron pairing model with spin-orbit interactions or Zeeman coupling is solved exactly in the framework of the Richardson ansatz. Based on the exact solutions for the case with spin-orbit interactions, it is shown rigorously that the pairing symmetry is of the p + ip wave and the ground state possesses time-reversal symmetry, regardless of the strength of the pairing interaction. Intriguingly, how Majorana fermions can emerge in the system is also elaborated. Exact results are illustrated for two systems, respectively, with spin-orbit interactions and Zeeman coupling.

  2. Compact Collision Kernels for Hard Sphere and Coulomb Cross Sections; Fokker-Planck Coefficients

    SciTech Connect

    Chang Yongbin; Shizgal, Bernie D.

    2008-12-31

    A compact collision kernel is derived for both hard sphere and Coulomb cross sections. The difference between hard sphere interaction and Coulomb interaction is characterized by a parameter {eta}. With this compact collision kernel, the calculation of Fokker-Planck coefficients can be done for both the Coulomb and hard sphere interactions. The results for arbitrary order Fokker-Planck coefficients are greatly simplified. An alternate form for the Coulomb logarithm is derived with concern to the temperature relaxation in a binary plasma.

  3. Effect of three-body Coulomb interactions on the breakup of light nuclei in the field of a heavy ion: An asymptotic estimate

    SciTech Connect

    Alt, E.O.; Irgaziev, B.F.; Muminov, A.T.

    1995-11-01

    The quasielastic breakup of light nuclei into two charged fragments in the Coulomb field of a heavy multiply charged ion are studied. For fragments diverging with extremely low energies an asymptotic estimate is obtained for the ratio of the differential cross section in which three-body Coulomb effects are taken into account to that in which these effects are disregarded. It is shown that effects due to the acceleration of breakup fragments in the field of the heavy ion are significant. 13 refs., 2 figs.

  4. Ecology of dark matter haloes -II. Effects of interactions on the alignment of halo pairs

    NASA Astrophysics Data System (ADS)

    L'Huillier, Benjamin; Park, Changbom; Kim, Juhan

    2017-01-01

    We use the Horizon Run 4 cosmological N-body simulation to study the effects of distant and close interactions on the alignments of the shapes, spins, and orbits of targets haloes with their neighbours, and their dependence on the local density environment and neighbour separation. Interacting targets have a significantly lower spin and higher sphericity and oblateness than all targets. Interacting pairs initially have anti-parallel spins, but the spins develop parallel alignment as time goes on. Neighbours tend to evolve in the plane of rotation of the target, and in the direction of the major axis of prolate haloes. Moreover, interactions are preferentially radial, while pairs with non-radial orbits are preferentially prograde. The alignment signals are stronger at high-mass and for close separations, and independent on the large-scale density. Positive alignment signals are found at redshifts up to 4, and increase with decreasing redshifts. Moreover, the orbits tend to become prograde at low redshift, while no alignment is found at high redshift (z = 4).

  5. Role of Exchange and Dipolar Interactions in the Radical Pair Model of the Avian Magnetic Compass☆

    PubMed Central

    Efimova, Olga; Hore, P.J.

    2008-01-01

    It is not yet understood how migratory birds sense the Earth's magnetic field as a source of compass information. One suggestion is that the magnetoreceptor involves a photochemical reaction whose product yields are sensitive to external magnetic fields. Specifically, a flavin-tryptophan radical pair is supposedly formed by photoinduced sequential electron transfer along a chain of three tryptophan residues in a cryptochrome flavoprotein immobilized in the retina. The electron Zeeman interaction with the Earth's magnetic field (∼50 μT), modulated by anisotropic magnetic interactions within the radicals, causes the product yields to depend on the orientation of the receptor. According to well-established theory, the radicals would need to be separated by >3.5 nm in order that interradical spin-spin interactions are weak enough to permit a ∼50 μT field to have a significant effect. Using quantum mechanical simulations, it is shown here that substantial changes in product yields can nevertheless be expected at the much smaller separation of 2.0 ± 0.2 nm where the effects of exchange and dipolar interactions partially cancel. The terminal flavin-tryptophan radical pair in cryptochrome has a separation of ∼1.9 nm and is thus ideally placed to act as a magnetoreceptor for the compass mechanism. PMID:17981903

  6. Role of exchange and dipolar interactions in the radical pair model of the avian magnetic compass.

    PubMed

    Efimova, Olga; Hore, P J

    2008-03-01

    It is not yet understood how migratory birds sense the Earth's magnetic field as a source of compass information. One suggestion is that the magnetoreceptor involves a photochemical reaction whose product yields are sensitive to external magnetic fields. Specifically, a flavin-tryptophan radical pair is supposedly formed by photoinduced sequential electron transfer along a chain of three tryptophan residues in a cryptochrome flavoprotein immobilized in the retina. The electron Zeeman interaction with the Earth's magnetic field ( approximately 50 microT), modulated by anisotropic magnetic interactions within the radicals, causes the product yields to depend on the orientation of the receptor. According to well-established theory, the radicals would need to be separated by >3.5 nm in order that interradical spin-spin interactions are weak enough to permit a approximately 50 microT field to have a significant effect. Using quantum mechanical simulations, it is shown here that substantial changes in product yields can nevertheless be expected at the much smaller separation of 2.0 +/- 0.2 nm where the effects of exchange and dipolar interactions partially cancel. The terminal flavin-tryptophan radical pair in cryptochrome has a separation of approximately 1.9 nm and is thus ideally placed to act as a magnetoreceptor for the compass mechanism.

  7. Ecology of dark matter haloes - II. Effects of interactions on the alignment of halo pairs

    NASA Astrophysics Data System (ADS)

    L'Huillier, Benjamin; Park, Changbom; Kim, Juhan

    2017-04-01

    We use the Horizon Run 4 cosmological N-body simulation to study the effects of distant and close interactions on the alignments of the shapes, spins and orbits of targets haloes with their neighbours, and their dependence on the local density environment and neighbour separation. Interacting targets have a significantly lower spin and higher sphericity and oblateness than all targets. Interacting pairs initially have antiparallel spins, but the spins develop parallel alignment as time goes on. Neighbours tend to evolve in the plane of rotation of the target, and in the direction of the major axis of prolate haloes. Moreover, interactions are preferentially radial, while pairs with non-radial orbits are preferentially prograde. The alignment signals are stronger at high mass and for close separations, and independent of the large-scale density. Positive alignment signals are found at redshifts up to 4, and increase with decreasing redshifts. Moreover, the orbits tend to become prograde at low redshift, while no alignment is found at high redshift (z = 4).

  8. Pairing interaction near a nematic quantum critical point of a three-band CuO2 model

    DOE PAGES

    Maier, Thomas A.; Scalapino, Douglas J.

    2014-11-21

    In this paper, we calculate the pairing interaction and the k dependence of the gap function associated with the nematic charge fluctuations of a CuO2 model.We find that the nematic pairing interaction is attractive for small momentum transfer and that it gives rise to d-wave pairing. Finally, as the doping p approaches a quantum critical point, the strength of this pairing increases and higher d-wave harmonics contribute to the k dependence of the superconducting gap function, reflecting the longer range nature of the nematic fluctuations.

  9. Pairing interaction near a nematic quantum critical point of a three-band CuO2 model

    SciTech Connect

    Maier, Thomas A.; Scalapino, Douglas J.

    2014-11-21

    In this paper, we calculate the pairing interaction and the k dependence of the gap function associated with the nematic charge fluctuations of a CuO2 model.We find that the nematic pairing interaction is attractive for small momentum transfer and that it gives rise to d-wave pairing. Finally, as the doping p approaches a quantum critical point, the strength of this pairing increases and higher d-wave harmonics contribute to the k dependence of the superconducting gap function, reflecting the longer range nature of the nematic fluctuations.

  10. Interactions of the Watson-Crick nucleic acid base pairs with carbon nanotubes and graphene: DFT and MP2 study

    NASA Astrophysics Data System (ADS)

    Stepanian, S. G.; Karachevtsev, M. V.; Karachevtsev, V. A.; Adamowicz, L.

    2014-08-01

    Structures and interaction energies of complexes formed by Watson-Crick base pairs and carbon surfaces (nanotubes and graphene) are investigated using the DFT M05-2X and MP2 quantum chemical computational methods. High structural flexibility of the complexes is demonstrated. Structures with approximately parallel and perpendicular orientations of the base pairs and the nanotube main axis are revealed. The complexes formed by the GC base pair and large-diameter zigzag nanotubes with the perpendicular orientation of the two systems are found to be the lowest energy configurations. Decomposition of the interaction energies into two-body contributions is applied to explain the nature of the interaction. The question of how the interaction between a base pair and a carbon surface affects the H-bonding between the nucleobases in the pair is elucidated.

  11. End of Frustration: Catalytic Precision Polymerization with Highly Interacting Lewis Pairs.

    PubMed

    Knaus, Maximilian G M; Giuman, Marco M; Pöthig, Alexander; Rieger, Bernhard

    2016-06-22

    Herein we report on the catalytic polymerization of diverse Michael-type monomers with high precision by using simple but highly active combinations of phosphorus-containing Lewis bases and organoaluminum compounds. The interacting Lewis pair catalysts enable the control of molecular weight and microstructure of the produced polymers. The reactions show a linear Mn vs consumption plot thus proving a living type polymerization. The initiation has been investigated by end-group analysis with ESI mass spectrometric analysis. With these main-group element Lewis acid base pairs, it is not only possible to polymerize sterically demanding, functionalized as well as heteroatom containing monomers but also, for the first time, to catalytically polymerize extended Michael systems, like 4-vinylpyridine.

  12. Lone-pairinteractions: analysis of the physical origin and biological implications.

    PubMed

    Novotný, Jan; Bazzi, Sophia; Marek, Radek; Kozelka, Jiří

    2016-07-28

    Lone-pair-π (lp-π) interactions have been suggested to stabilize DNA and protein structures, and to participate in the formation of DNA-protein complexes. To elucidate their physical origin, we have carried out a theoretical multi-approach analysis of two biologically relevant model systems, water-indole and water-uracil complexes, which we compared with the structurally similar chloride-tetracyanobenzene (TCB) complex previously shown to contain a strong charge-transfer (CT) binding component. We demonstrate that the CT component in lp-π interactions between water and indole/uracil is significantly smaller than that stabilizing the Cl(-)-TCB reference system. The strong lp(Cl(-))-π(TCB) orbital interaction is characterized by a small energy gap and an efficient lp-π* overlap. In contrast, in lp-π interactions between water and indole or uracil, the corresponding energy gap is larger and the overlap less efficient. As a result, water-uracil and water-indole interactions are weak forces composed by smaller contributions from all energy components: electrostatics, polarization, dispersion, and charge transfer. In addition, indole exhibits a negative electrostatic potential at its π-face, making lp-π interactions less favorable than O-Hπ hydrogen bonding. Consequently, some of the water-tryptophan contacts observed in X-ray structures of proteins and previously interpreted as lp-π interactions [Luisi, et al., Proteins, 2004, 57, 1-8], might in fact arise from O-Hπ hydrogen bonding.

  13. The influence of arene-ring size on stacking interaction with canonical base pairs

    NASA Astrophysics Data System (ADS)

    Formánek, Martin; Burda, Jaroslav V.

    2014-04-01

    Stacking interactions between aromatic molecules (benzene, p-cymene, biphenyl, and di- and tetra-hydrogen anthracene) and G.C and A.T canonical Watson-Crick (WC) base pairs are explored. Two functionals with dispersion corrections: ω-B97XD and B3LYP-D3 are used. For a comparison also the MP2 and B3LYP-D3/PCM methods were used for the most stable p-cymene…WC geometries. It was found that the stacking interaction increases with the size of π-conjugation system. Its extent is in agreement with experimental finding on anticancer activity of Ru(II) piano-stool complexes where intercalation of these aromatic molecules should play an important role. The explored structures are considered as ternary system so that decomposition of the interaction energy to pairwise and non-additivity contributions is also examined.

  14. Intriguing radical-radical interactions among double-electron oxidized adenine-thymine base pairs

    NASA Astrophysics Data System (ADS)

    Wang, Mei; Zhao, Jing; Zhang, Laibin; Su, Xiyu; Su, Hanlei; Bu, Yuxiang

    2015-01-01

    We present a theoretical investigation of the structural and electronic properties of double-electron oxidized adenine-thymine base pair as well as its deprotonated Watson-Crick derivatives. Double-electron oxidation can destabilize the AT unit, leading to a barrier-hindered metastable A+T+ state with a dissociation channel featuring negative dissociation energy. This unusual energetic phenomenon originates from the competition of electrostatic repulsion and attractively hydrogen-bonding interaction co-existing between Arad + and Trad +. The associated double-proton-transfer process is also explored, suggesting a possible two-step mechanism. Magnetic coupling interactions of various diradical structures are controlled by both intra- and inter-molecular interactions.

  15. Kinetics and fracture resistance of lithiated silicon nanostructure pairs controlled by their mechanical interaction

    SciTech Connect

    Lee, Seok Woo; Lee, Hyun -Wook; Ryu, Ill; Nix, William D.; Gao, Huajian; Cui, Yi

    2015-06-26

    Following an explosion of studies of silicon as a negative electrode for Li-ion batteries, the anomalous volumetric changes and fracture of lithiated single Si particles have attracted significant attention in various fields, including mechanics. However, in real batteries, lithiation occurs simultaneously in clusters of Si in a confined medium. Hence, understanding how the individual Si structures interact during lithiation in a closed space is necessary. Here, we demonstrate physical and mechanical interactions of swelling Si structures during lithiation using well-defined Si nanopillar pairs. Ex situ SEM and in situ TEM studies reveal that compressive stresses change the reaction kinetics so that preferential lithiation occurs at free surfaces when the pillars are mechanically clamped. Such mechanical interactions enhance the fracture resistance of lithiated Si by lessening the tensile stress concentrations in Si structures. Lastly, this study will contribute to improved design of Si structures at the electrode level for high-performance Li-ion batteries.

  16. Photoassociation of a cold-atom-molecule pair: Long-range quadrupole-quadrupole interactions

    SciTech Connect

    Lepers, M.; Dulieu, O.; Kokoouline, V.

    2010-10-15

    The general formalism of the multipolar expansion of electrostatic interactions is applied to the calculation of the potential energy between an excited atom (without fine structure) and a ground-state diatomic molecule at large mutual separations. Both partners exhibit a permanent quadrupole moment so that their mutual long-range interaction is dominated by a quadrupole-quadrupole term, which is attractive enough to bind trimers. Numerical results are given for an excited Cs(6{sup 2}P) atom and a ground-state Cs{sub 2} molecule. The prospects for achieving photoassociation of a cold-atom-dimer pair are thus discussed and found promising. The formalism can be generalized to the long-range interaction between molecules to investigate the formation of cold tetramers.

  17. Kinetics and fracture resistance of lithiated silicon nanostructure pairs controlled by their mechanical interaction

    NASA Astrophysics Data System (ADS)

    Lee, Seok Woo; Lee, Hyun-Wook; Ryu, Ill; Nix, William D.; Gao, Huajian; Cui, Yi

    2015-06-01

    Following an explosion of studies of silicon as a negative electrode for Li-ion batteries, the anomalous volumetric changes and fracture of lithiated single Si particles have attracted significant attention in various fields, including mechanics. However, in real batteries, lithiation occurs simultaneously in clusters of Si in a confined medium. Hence, understanding how the individual Si structures interact during lithiation in a closed space is necessary. Here, we demonstrate physical and mechanical interactions of swelling Si structures during lithiation using well-defined Si nanopillar pairs. Ex situ SEM and in situ TEM studies reveal that compressive stresses change the reaction kinetics so that preferential lithiation occurs at free surfaces when the pillars are mechanically clamped. Such mechanical interactions enhance the fracture resistance of lithiated Si by lessening the tensile stress concentrations in Si structures. This study will contribute to improved design of Si structures at the electrode level for high-performance Li-ion batteries.

  18. New approach to folding with the Coulomb wave function

    SciTech Connect

    Blokhintsev, L. D.; Savin, D. A.; Kadyrov, A. S.; Mukhamedzhanov, A. M.

    2015-05-15

    Due to the long-range character of the Coulomb interaction theoretical description of low-energy nuclear reactions with charged particles still remains a formidable task. One way of dealing with the problem in an integral-equation approach is to employ a screened Coulomb potential. A general approach without screening requires folding of kernels of the integral equations with the Coulomb wave. A new method of folding a function with the Coulomb partial waves is presented. The partial-wave Coulomb function both in the configuration and momentum representations is written in the form of separable series. Each term of the series is represented as a product of a factor depending only on the Coulomb parameter and a function depending on the spatial variable in the configuration space and the momentum variable if the momentum representation is used. Using a trial function, the method is demonstrated to be efficient and reliable.

  19. The impact of lone pairinteractions on photochromic properties in 1-D naphthalene diimide coordination networks.

    PubMed

    Liu, Jian-Jun; Guan, Ying-Fang; Chen, Yong; Lin, Mei-Jin; Huang, Chang-Cang; Dai, Wen-Xin

    2015-10-21

    Lone pairinteraction is an important but less studied binding force. Generally, it is too weak to influence the physical properties of supramolecular systems. Herein we reported the first example exhibiting the impact of lone pairinteractions on photochromic properties of naphthalene diimide based coordination networks. In three isostructural 1-D networks, [(DPNDI)ZnX2] (DPNDI = N,N-di(4-pyridyl)-1,4,5,8-naphthalene diimide, X = Cl for 1, X = Br for 2 and X = I for 3), they exhibit different electron-transfer photochromic behaviors due to different lone pairinteractions between the capped halogen atoms and electron-deficient DPNDI moieties. Specifically, 1 and 2 but not 3 are photochromic, which is attributed to a stronger lone pairinteraction in 3 than those in 1 and 2. This study anticipates breaking a new path for designing novel photochromic materials through such unnoticeable supramolecular interactions.

  20. Quantitative determination of pairing interactions for high-temperature superconductivity in cuprates

    PubMed Central

    Bok, Jin Mo; Bae, Jong Ju; Choi, Han-Yong; Varma, Chandra M.; Zhang, Wentao; He, Junfeng; Zhang, Yuxiao; Yu, Li; Zhou, X. J.

    2016-01-01

    A profound problem in modern condensed matter physics is discovering and understanding the nature of fluctuations and their coupling to fermions in cuprates, which lead to high-temperature superconductivity and the invariably associated strange metal state. We report the quantitative determination of normal and pairing self-energies, made possible by laser-based angle-resolved photoemission measurements of unprecedented accuracy and stability. Through a precise inversion procedure, both the effective interactions in the attractive d-wave symmetry and the repulsive part in the full symmetry are determined. The latter is nearly angle-independent. Near Tc, both interactions are nearly independent of frequency and have almost the same magnitude over the complete energy range of up to about 0.4 eV, except for a low-energy feature at around 50 meV that is present only in the repulsive part, which has less than 10% of the total spectral weight. Well below Tc, they both change similarly, with superconductivity-induced features at low energies. Besides finding the pairing self-energy and the attractive interactions for the first time, these results expose the central paradox of the problem of high Tc: how the same frequency-independent fluctuations can dominantly scatter at angles ±π/2 in the attractive channel to give d-wave pairing and lead to angle-independent repulsive scattering. The experimental results are compared with available theoretical calculations based on antiferromagnetic fluctuations, the Hubbard model, and quantum-critical fluctuations of the loop-current order. PMID:26973872

  1. Quantitative determination of pairing interactions for high-temperature superconductivity in cuprates.

    PubMed

    Bok, Jin Mo; Bae, Jong Ju; Choi, Han-Yong; Varma, Chandra M; Zhang, Wentao; He, Junfeng; Zhang, Yuxiao; Yu, Li; Zhou, X J

    2016-03-01

    A profound problem in modern condensed matter physics is discovering and understanding the nature of fluctuations and their coupling to fermions in cuprates, which lead to high-temperature superconductivity and the invariably associated strange metal state. We report the quantitative determination of normal and pairing self-energies, made possible by laser-based angle-resolved photoemission measurements of unprecedented accuracy and stability. Through a precise inversion procedure, both the effective interactions in the attractive d-wave symmetry and the repulsive part in the full symmetry are determined. The latter is nearly angle-independent. Near T c, both interactions are nearly independent of frequency and have almost the same magnitude over the complete energy range of up to about 0.4 eV, except for a low-energy feature at around 50 meV that is present only in the repulsive part, which has less than 10% of the total spectral weight. Well below T c, they both change similarly, with superconductivity-induced features at low energies. Besides finding the pairing self-energy and the attractive interactions for the first time, these results expose the central paradox of the problem of high T c: how the same frequency-independent fluctuations can dominantly scatter at angles ±π/2 in the attractive channel to give d-wave pairing and lead to angle-independent repulsive scattering. The experimental results are compared with available theoretical calculations based on antiferromagnetic fluctuations, the Hubbard model, and quantum-critical fluctuations of the loop-current order.

  2. Approximate arbitrary κ-state solutions of Dirac equation with Schiöberg and Manning-Rosen potentials within the coulomb-like Yukawa-like and generalized tensor interactions

    NASA Astrophysics Data System (ADS)

    Ikot, Akpan N.; Hassanabadi, Hassan; Obong, Hillary Patrick; Mehraban, H.; Yazarloo, Bentol Hoda

    2015-07-01

    The effects of Coulomb-like tensor (CLT), Yukawa-like tensor (YLT) and generalized tensor (GLT) interactions are investigated in the Dirac theory with Schiöberg and Manning-Rosen potentials within the framework of spin and pseudospin symmetries using the Nikiforov-Uvarov method. The bound state energy spectra and the radial wave functions have been approximately obtained in the case of spin and pseudospin symmetries. We have also reported some numerical results and figures to show the effects these tensor interactions.

  3. An integrable case of the p + ip pairing Hamiltonian interacting with its environment

    NASA Astrophysics Data System (ADS)

    Lukyanenko, Inna; Isaac, Phillip S.; Links, Jon

    2016-02-01

    We consider a generalization of the p + ip pairing Hamiltonian, with external interaction terms of a particular form. These terms allow for the exchange of particles between the system and its environment. As a result the {u}(1) symmetry associated with conservation of particle number, present in the p + ip Hamiltonian, is broken. Nonetheless the generalized model is integrable. We establish integrability using the boundary quantum inverse scattering method, with one of the reflection matrices chosen to be non-diagonal. We also derive the corresponding Bethe ansatz equations, the roots of which parametrize the exact solution for the energy spectrum.

  4. Luminosities of H alpha emitting regions in a pair of interacting galaxies in the Bootes void

    NASA Technical Reports Server (NTRS)

    Weistrop, D.; Hintzen, P.; Kennicutt, R.; Liu, C.; Lowenthal, J.; Cheng, K.-P.; Oliversen, R.; Woodgate, B.

    1993-01-01

    Luminosities of H alpha emission from a pair of interacting galaxies in the low density environment of the Bootes void are presented. CG 692 (IRAS 1519+5050) has an H alpha luminosity of 2 x 10(exp 42) ergs s(exp -1), indicating a star formation rate of 18.4 solar mass yr(exp -1). Individual extranuclear H alpha regions have luminosities of approximately 10(exp 40) ergs s(exp -1). These luminosities are similar to those found for H II regions in bright, late-type galaxies in more densely populated parts of the Universe.

  5. Linear response theory for a pair of coupled one-dimensional condensates of interacting atoms

    SciTech Connect

    Gritsev, Vladimir; Demler, Eugene; Polkovnikov, Anatoli

    2007-05-01

    We use the quantum sine-Gordon model to describe the low-energy dynamics of a pair of coupled one-dimensional condensates of interacting atoms. We show that the nontrivial excitation spectrum of the quantum sine-Gordon model, which includes soliton and breather excitations, can be observed in experiments with time-dependent modulation of the tunneling amplitude, potential difference between condensates, or phase of tunneling amplitude. We use the form-factor approach to compute structure factors corresponding to all three types of perturbations.

  6. Degenerated ground-states in a spin chain with pair interactions: a characterization by symbolic dynamics

    NASA Astrophysics Data System (ADS)

    Corona, L. A.; Salgado-García, R.

    2016-12-01

    In this paper we study a class of one-dimensional spin chain having a highly degenerated set of ground-state configurations. The model consists of spin chain having infinite-range pair interactions with a given structure. We show that the set of ground-state configurations of such a model can be fully characterized by means of symbolic dynamics. Particularly we found that the set ground-state configurations define what in symbolic dynamics is called sofic shift space. Finally we prove that this system has a non-vanishing residual entropy (the topological entropy of the shift space), which can be exactly calculated.

  7. Exploring new physics through contact interactions in lepton pair production at a linear collider

    SciTech Connect

    Perelstein, Maxim; Pasztor, Gabriella

    2001-12-04

    If a contact interaction type correction to a Standard Model process is observed, studying its detailed properties can provide information on the fundamental physics responsible for it. Assuming that such a correction has been observed in lepton pair production at a 500 GeV-1 TeV linear collider, we consider a few possible models that could explain it, such as theories with large and TeV-scale extra dimensions and models with lepton compositeness. We show that using the measured cross-sections and angular distributions, these models can be distinguished with a high degree of confidence.

  8. Self-consistent evaluation of effective Coulomb interaction U and its utilization to understand the degree of localization of electrons in vanadium spinels

    NASA Astrophysics Data System (ADS)

    Lal, Sohan; Pandey, Sudhir K.

    2017-07-01

    In present work, we try to understand the degree of localization of electrons in AV2O4 (A = Zn, Cd and Mg) compounds by using self-consistent calculated effective Coulomb interaction (Ueff) between localized electrons of V atom. The suitable values of d-linearization energy (Ed) of impurity V atom for calculating the Ueff for these compounds are found to be ≥ 44 eV above the Fermi level. Corresponding to these values of Ed, the self-consistently calculated values of effective ULSDA (UPBEsol) for ZnV2O4, MgV2O4 and CdV2O4 are ∼5.7 (∼5.9), ∼6.0 (∼6.2) and ∼5.6 (∼5.7) eV, respectively. The calculated values of t/Ueff (t is the transfer integral between neighboring sites) increases with decreasing V-V distance from CdV2O4 to MgV2O4 to ZnV2O4, which are consistent with the experimentally reported band gap. The t/Ueff for ZnV2O4, MgV2O4 and CdV2O4 are found to be ∼0.023, ∼0.02 and ∼0.018, respectively, which indicates that the degree of localization of electrons is largest for CdV2O4 and smallest for ZnV2O4 as compared to MgV2O4. The calculated values of lattice parameters aLSDA (aPBEsol) are found to be ∼ 1.7% (∼ 0.6%), ∼ 2.0% (∼ 0.7%) and ∼ 2.4% (∼ 0.7%) smaller than aexp for CdV2O4, MgV2O4 and ZnV2O4, respectively, which indicates that the PBEsol functional predicts the lattice parameters in good agreement with the experimental data. The present study shows the importance of Ueff in understanding the degree of localization of electrons in these compounds.

  9. Dependence of the rate of LiF ion pairing on the description of molecular interaction

    SciTech Connect

    Pluharova, Eva; Baer, Marcel D.; Schenter, Gregory K.; Jungwirth, Pavel; Mundy, Christopher J.

    2016-03-03

    We present an analysis of the dynamics of ion-pairing of Lithium Fluoride (LiF) in aqueous solvent using both detailed molecular simulation as well as reduced models within a Gener- alized Langevin Equation (GLE) framework. We explored the sensitivity of the ion-pairing phenomena to the details of descriptions of molecular interaction, comparing two empirical potentials to explicit quantum based density functional theory. We find quantitative differences in the potentials of mean force for ion-pairing as well as time dependent frictions that lead to variations in the rate constant and reactive flux correlation functions. These details reflect differences in solvent response to ion-pairing between different representations of molecular interaction and influence anharmonicity of the dynamic response. We find that the short time anharmonic response is recovered with a GLE parameterization. Recovery of the details of long time response may require extensions to the reduced model. We show that the utility of using a reduced model leads to a straight forward application of variational transition state the- ory concepts to the condensed phase system. The significance of this is reflected in the analysis of committor distributions and the variation of planar hypersurfaces, leading to an improved understanding of factors that determine the rate of LiF ion-pairing. CJM and GKS are supported by the U.S. Department of Energy‘s (DOE) Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. Pacific Northwest Na- tional Laboratory (PNNL) is operated for the Department of Energy by Battelle. MDB is grateful for the support of Laboratory Directed Research and Development funding under the auspices of PNNL’s Laboratory Initiative Materials Synthesis and Simulation across Scales (MS3). Additional computing resources were generously allocated by PNNL’s Institutional Computing program. EP acknowledges support from PNNL’s Alternate Sponsored

  10. Orientational ortho-H 2 pair interactions in the microporous framework MOF-5

    NASA Astrophysics Data System (ADS)

    FitzGerald, Stephen A.; Eckdahl, Christopher T.; McDonald, Cooper S.; Nelson, Jocienne N.; Shinbrough, Kai; Lai, Holden W. H.; Rowsell, Jesse L. C.

    2015-10-01

    Infrared spectroscopy is used to observe the orientational fine structure arising from ortho-H2 adsorbed at the primary site of the microporous framework MOF-5. The Q1(1 ) vibrational transition shows at least two symmetrically spaced fine structure bands on either side of the main band. These grow in relative intensity with increasing H2 concentration indicative of interacting H2 pairs. This interpretation is strongly supported by D2 addition experiments, which cause a large increase in intensity of the fine structure bands with only minimal change in the main band. The spectra are analyzed in terms of H2-H2 electric quadrupole-quadrupole interactions. Consistent with this approach we observe no fine structure bands for the Q1(0 ) vibrational transition arising from para-H2, which does not possess a quadrupole moment.

  11. Experimental Evidence of Lone Pairs - π System Interaction: the Rotational Spectrum of Chlorotrifluoroethylene - Water Complex

    NASA Astrophysics Data System (ADS)

    Evangelisti, L.; Gou, Q.; Feng, G.; Caminati, W.

    2013-06-01

    Chemists have always been interested in labeling the interactions between the molecules, i.e. from covalent to ionic bond or van der Waals force. Certainly the most important non-covalent bond is the hydrogen bond, also of fundamental importance in biology. More recently also weak Hbond, sometimes in competion with halogen bonding, have been investigated because they have assumed a fundamental importance. Here, we show the lone pairs - π interaction prevails on the latter ones. We measured the molecular beam Fourier transform microwave spectra of five isotopologues of the 1:1 adduct of chlorotrifluoroethylene with water. Besides the rotational constants, the quadrupole coupling constants of the chlorine atom have been determined. Quantum chemistry calculations, at the MP2/6-311++G(d,p) level, have been carried out in order to obtain information about the structure and relative stability of the conformers under study.

  12. Interaction and dynamics of homologous pairing protein 2 (HOP2) and DNA studied by MD simulation

    NASA Astrophysics Data System (ADS)

    Moktan, Hem; Pezza, Roberto; Zhou, Donghua

    2015-03-01

    The homologous pairing protein 2 (Hop2) plays an important role in meiosis and DNA repair. Together with protein Mnd1, Hop2 enhances the strand invasion activity of recombinase Dmc1 by over 30 times, facilitating proper synapsis of homologous chromosomes. We recently determined the NMR structure of the N-terminal domain of Hop2 and proposed a model of Protein-DNA complex based on NMR chemical shift perturbations and mutagenesis studies (Moktan, J Biol Chem 2014 10.1074/jbc.M114.548180). However structure and dynamics of the complex have not been studied at the atomic level yet. Here, we used classical MD simulations to study the interactions between the N-terminal HOP2 and DNA. The simulated results indicate that helix3 (H3) interacts with DNA in major groove and wing1 (W1) interacts mostly in minor groove mainly via direct hydrogen bonds. Also it is found that binding leads to reduced fluctuations in both protein and DNA. Several water bridge interactions have been identified. The residue-wise contributions to the interaction energy were evaluated. Also the functional motion of the protein is analyzed using principal component analysis. The results confirmed the importance of H3 and W1 for the stability of the complex, which is consistent with our previous experimental studies.

  13. Human interaction as environmental enrichment for pair-housed wolves and wolf-dog crosses.

    PubMed

    Mehrkam, Lindsay R; Verdi, Nicolle T; Wynne, Clive D L

    2014-01-01

    Private nonhuman animal sanctuaries are often financially limited in their ability to implement traditional environmental enrichment strategies. One possible solution may be to provide socialized animals with human interaction sessions. However, the merit of human interaction as enrichment has received little empirical attention to date. The present study aimed to evaluate whether human interaction could be enriching for socialized, pair-housed wolves and wolf-dog crosses at a private sanctuary. Observations of each subject were conducted in a reversal design to measure species-typical affiliation, activity levels, and aberrant behaviors when caretakers were both present and absent. The results demonstrate significantly higher levels of conspecific-directed affiliation and activity levels and reduced aberrant behavior when human interaction was available. Social play also increased when caregivers were present, supporting the hypothesis that play among conspecifics may be maintained by positive changes in an animal's environment. The potential for human interaction to be established as a scientifically validated, cost-effective enrichment strategy is supported by these findings.

  14. Coulomb gauge ghost propagator and the Coulomb form factor

    NASA Astrophysics Data System (ADS)

    Quandt, M.; Burgio, G.; Chimchinda, S.; Reinhardt, H.

    The ghost propagator and the Coulomb potential are evaluated in Coulomb gauge on the lattice, using an improved gauge fixing scheme which includes the residual symmetry. This setting has been shown to be essential in order to explain the scaling violations in the instantaneous gluon propagator. We find that both the ghost propagator and the Coulomb potential are insensitive to the Gribov problem or the details of the residual gauge fixing, even if the Coulomb potential is evaluated from the A0 -propagator instead of the Coulomb kernel. In particular, no signs of scaling violations could be found in either quantity, at least to well below the numerical accuracy where these violations were visible for the gluon propagator. The Coulomb potential from the A0 -propagator is shown to be in qualitative agreement with the (formally equivalent) expression evaluated from the Coulomb kernel.

  15. Interaction effects on galaxy pairs with Gemini/GMOS- III: stellar population synthesis

    NASA Astrophysics Data System (ADS)

    Krabbe, A. C.; Rosa, D. A.; Pastoriza, M. G.; Hägele, G. F.; Cardaci, M. V.; Dors, O. L., Jr.; Winge, C.

    2017-05-01

    We present an observational study of the impacts of interactions on the stellar population in a sample of galaxy pairs. Long-slit spectra in the wavelength range 3440-7300 Å obtained with the Gemini Multi-Object Spectrograph (GMOS) at Gemini South for 15 galaxies in nine close pairs were used. The spatial distributions of the stellar population contributions were obtained using the stellar population synthesis code starlight. Taking into account the different contributions to the emitted light, we found that most of the galaxies in our sample are dominated by young/intermediate stellar populations. This result differs from the one derived for isolated galaxies, where the old stellar population dominates the disc surface brightness. We interpreted such different behaviour as being due to the effect of gas inflows along the discs of interacting galaxies on the star formation over a time-scale of the order of about 2 Gyr. We also found that, in general, the secondary galaxy of a pair has a higher contribution from the young stellar population than the primary one. We compared the estimated values of stellar and nebular extinction derived from the synthesis method and the Hα/Hβ emission-line ratio, finding that nebular extinctions are systematically higher than stellar ones by about a factor of 2. We did not find any correlation between nebular and stellar metallicities. Neither did we find a correlation between stellar metallicities and ages, while a positive correlation between nebular metallicities and stellar ages was obtained, with older regions being the most metal-rich.

  16. Spectroscopic and computational analysis of the molecular interactions in the ionic liquid ion pair [BMP]+[TFSI]-

    SciTech Connect

    Mao, James X.; Nulwala, Hunaid B.; Luebke, David R.; Damodaran, Krishnan

    2012-11-01

    1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP]{sup +}[TFSI]{sup -}) ion pairs were studied using DFT at the B3LYP/6-31 + G(d) level. Nine locally stable conformations of the ion pair were located. In the most stable conformation, [TFSI]{sup -} takes a cis conformation and lies below the pyrrolidinium ring. Atoms-in-molecules (AIM) and electron density analysis indicated the existence of nine hydrogen bonds. Interaction energies were recalculated at the Second-order Møller–Plesset (MP2) level to show the importance of dispersion interaction. Further investigation through natural bond orbital (NBO) analysis provided insight into the importance of charge transfer interactions in the ion pair. Harmonic vibrations of the ion pair were calculated and compared with vibrations of the free ions as well as the experimental infrared spectrum. Assignments and frequency shifts are discussed in light of the inter-ionic interactions.

  17. Mapping IR Enhancements in Closely Interacting Spiral-Spiral Pairs: I. ISO CAM and ISO SWS Observations

    NASA Technical Reports Server (NTRS)

    Xu, C.; Gao, Y.; Mazzarella, J.; Lu, N.; Sulentic, J.; Domingue, D.

    2000-01-01

    Mid-infrared (MIR) imaging and spectroscopic observations are presented for a well defined sample of eight closely interacting (CLO) pairs of spiral galaxies that have overlapping disks and show enhanced far-infrared (FIR) emission.

  18. Mapping IR Enhancements in Closely Interacting Spiral-Spiral Pairs: I. ISO CAM and ISO SWS Observations

    NASA Technical Reports Server (NTRS)

    Xu, C.; Gao, Y.; Mazzarella, J.; Lu, N.; Sulentic, J.; Domingue, D.

    2000-01-01

    Mid-infrared (MIR) imaging and spectroscopic observations are presented for a well defined sample of eight closely interacting (CLO) pairs of spiral galaxies that have overlapping disks and show enhanced far-infrared (FIR) emission.

  19. The isolated interacting galaxy pair NGC 5426/27 (Arp 271)

    NASA Astrophysics Data System (ADS)

    Fuentes-Carrera, I.; Rosado, M.; Amram, P.; Dultzin-Hacyan, D.; Cruz-González, I.; Salo, H.; Laurikainen, E.; Bernal, A.; Ambrocio-Cruz, P.; Le Coarer, E.

    2004-02-01

    We present Hα observations of the isolated interacting galaxy pair NGC 5426/27 using the scanning Fabry-Perot interferometer PUMA. The velocity field, various kinematical parameters and rotation curve for each galaxy were derived. The FWHM map and the residual velocities map were also computed to study the role of non-circular motions of the gas. Most of these motions can be associated with the presence of spiral arms and structure such as central bars. We found a small bar-like structure in NGC 5426, a distorted velocity field for NGC 5427 and a bridge-like feature between both galaxies which seems to be associated with NGC 5426. Using the observed rotation curves, a range of possible masses was computed for each galaxy. These were compared with the orbital mass of the pair derived from the relative motion of the participants. The rotation curve of each galaxy was also used to fit different mass distribution models considering the most common theoretical dark halo models. An analysis of the interaction process is presented and a possible 3D scenario for this encounter is also suggested. Table 1 is only available in electronic form at http://www.edpsciences.org

  20. Pulsational Pair-instability Model for Superluminous Supernova PTF12dam: Interaction and Radioactive Decay

    NASA Astrophysics Data System (ADS)

    Tolstov, Alexey; Nomoto, Ken’ichi; Blinnikov, Sergei; Sorokina, Elena; Quimby, Robert; Baklanov, Petr

    2017-02-01

    Being a superluminous supernova, PTF12dam can be explained by a 56Ni-powered model, a magnetar-powered model, or an interaction model. We propose that PTF12dam is a pulsational pair-instability supernova, where the outer envelope of a progenitor is ejected during the pulsations. Thus, it is powered by a double energy source: radioactive decay of 56Ni and a radiative shock in a dense circumstellar medium. To describe multicolor light curves and spectra, we use radiation-hydrodynamics calculations of the STELLA code. We found that light curves are well described in the model with 40 M⊙ ejecta and 20–40 M⊙ circumstellar medium. The ejected 56Ni mass is about 6 M⊙, which results from explosive nucleosynthesis with large explosion energy (2–3) × 1052 erg. In comparison with alternative scenarios of pair-instability supernova and magnetar-powered supernova, in the interaction model, all the observed main photometric characteristics are well reproduced: multicolor light curves, color temperatures, and photospheric velocities.

  1. Fluctuation-driven anisotropy in effective pair interactions between nanoparticles: Thiolated gold nanoparticles in ethane

    NASA Astrophysics Data System (ADS)

    Jabes, B. Shadrack; Yadav, Hari O. S.; Kumar, Sanat K.; Chakravarty, Charusita

    2014-10-01

    Fluctuations within the ligand shell of a nanoparticle give rise to a significant degree of anisotropy in effective pair interactions for low grafting densities [B. Bozorgui, D. Meng, S. K. Kumar, C. Chakravarty, and A. Cacciuto, Nano Lett. 13, 2732 (2013)]. Here, we examine the corresponding fluctuation-driven anisotropy for gold nanocrystals densely passivated with short ligands. In particular, we consider gold nanocrystals capped by alkylthiols, both in vacuum and in ethane solvent at high density. As in the preceding study, we show that the anisotropy in the nanoparticle pair potential can be quantified by an angle-dependent correction term to the isotropic potential of mean force (PMF). We find that the anisotropy of the ligand shells is distance dependent, and strongly influenced by ligand interdigitation effects as well as expulsion of ligand chains from the interparticle region at short distances. Such fluctuation-driven anisotropy can be significant for alkylthiol-coated gold nanoparticles, specially for longer chain lengths, under good solvent conditions. The consequences of such anisotropy for self-assembly, specially as a function of grafting density, solvent quality and at interfaces, should provide some interesting insights in future work. Our results clearly show that an isotropic two-body PMF cannot adequately describe the thermodynamics and assembly behavior of nanoparticles in this dense grafting regime and inclusion of anisotropic effects, as well as possibly many-body interactions, is necessary. Extensions of this approach to other passivated nanoparticle systems and implications for self-assembly are considered.

  2. Fluctuation-driven anisotropy in effective pair interactions between nanoparticles: Thiolated gold nanoparticles in ethane

    SciTech Connect

    Jabes, B. Shadrack; Yadav, Hari O. S.; Chakravarty, Charusita; Kumar, Sanat K.

    2014-10-21

    Fluctuations within the ligand shell of a nanoparticle give rise to a significant degree of anisotropy in effective pair interactions for low grafting densities [B. Bozorgui, D. Meng, S. K. Kumar, C. Chakravarty, and A. Cacciuto, Nano Lett. 13, 2732 (2013)]. Here, we examine the corresponding fluctuation-driven anisotropy for gold nanocrystals densely passivated with short ligands. In particular, we consider gold nanocrystals capped by alkylthiols, both in vacuum and in ethane solvent at high density. As in the preceding study, we show that the anisotropy in the nanoparticle pair potential can be quantified by an angle-dependent correction term to the isotropic potential of mean force (PMF). We find that the anisotropy of the ligand shells is distance dependent, and strongly influenced by ligand interdigitation effects as well as expulsion of ligand chains from the interparticle region at short distances. Such fluctuation-driven anisotropy can be significant for alkylthiol-coated gold nanoparticles, specially for longer chain lengths, under good solvent conditions. The consequences of such anisotropy for self-assembly, specially as a function of grafting density, solvent quality and at interfaces, should provide some interesting insights in future work. Our results clearly show that an isotropic two-body PMF cannot adequately describe the thermodynamics and assembly behavior of nanoparticles in this dense grafting regime and inclusion of anisotropic effects, as well as possibly many-body interactions, is necessary. Extensions of this approach to other passivated nanoparticle systems and implications for self-assembly are considered.

  3. Three-body Coulomb continuum problem

    NASA Astrophysics Data System (ADS)

    Berakdar, J.; Briggs, J. S.

    1994-06-01

    A symmetric representation of the three-body Coulomb continuum wave function as a product of three two-body Coulomb wave functions is modified to allow for three-body effects whereby the Sommerfeld parameter describing the strength of interaction of any two particles is affected by the presence of the third particle. This approach gives excellent agreement with near-threshold absolute (e,2e) ionization cross sections. In particular a recently observed deep minimum in noncoplanar geometry is reproduced for the first time.

  4. Suppression of the Coulomb Interaction in the Off-Energy-Shell p-p Scattering from the p+d{yields}p+p+n Reaction

    SciTech Connect

    Tumino, A.; Spitaleri, C.; Rapisarda, G. G.; Cherubini, S.; Crucilla, V.; Gulino, M.; La Cognata, M.; Lamia, L.; Mudo, F.; Pizzone, R. G.; Romano, S.; Sergi, M. L.; Mukhamedzhanov, A.; Elekes, Z.; Fueloep, Z.; Gyuerky, G.; Kiss, G.; Somorjai, E.

    2007-06-22

    Off-energy-shell effects in p-p scattering have been investigated at p-p relative energies from 600 down to 80 keV applying the Trojan horse method (THM) to the p+d{yields}p+p+n reaction at 5 MeV. In contrast with the on-energy-shell case, no Coulomb-nuclear interference minimum has been found in the extracted THM p-p cross section, due to the suppression of the Coulomb amplitude as predicted by the half-off-energy shell calculations. This hypothesis is strengthened by the agreement between THM p-p data and calculated on-energy-shell n+n, n+p and nuclear p+p cross sections.

  5. Search for Pair Production of Strongly Interacting Particles Decaying to Pairs of Jets in pp̄ Collisions at √s=1.96 TeV

    DOE PAGES

    Aaltonen, T.; Albin, E.; Amerio, S.; ...

    2013-07-18

    We present a search for the pair production of a narrow nonstandard-model strongly interacting particle that decays to a pair of quarks or gluons, leading to a final state with four hadronic jets. We consider both nonresonant production via an intermediate gluon as well as resonant production via a distinct nonstandard-model intermediate strongly interacting particle. We use data collected by the CDF experiment in proton-antiproton collisions at √s=1.96 TeV corresponding to an integrated luminosity of 6.6 fb⁻¹. We find the data to be consistent with nonresonant production. We report limits on σ(pp̄→jjjj) as a function of the masses of themore » hypothetical intermediate particles. Upper limits on the production cross sections for nonstandard-model particles in several resonant and nonresonant processes are also derived.« less

  6. Search for Pair Production of Strongly Interacting Particles Decaying to Pairs of Jets in pp̄ Collisions at √s=1.96 TeV

    SciTech Connect

    Aaltonen, T.; Albin, E.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A.; Antos, J.; Apollinari, G.; Appel, J. A.; Arisawa, T.; Artikov, A.; Asaadi, J.; Ashmanskas, W.; Auerbach, B.; Aurisano, A.; Azfar, F.; Badgett, W.; Bae, T.; Barbaro-Galtieri, A.; Barnes, V. E.; Barnett, B. A.; Barria, P.; Bartos, P.; Bauce, M.; Bedeschi, F.; Behari, S.; Bellettini, G.; Bellinger, J.; Benjamin, D.; Beretvas, A.; Bhatti, A.; Bland, K. R.; Blumenfeld, B.; Bocci, A.; Bodek, A.; Bortoletto, D.; Boudreau, J.; Boveia, A.; Brigliadori, L.; Bromberg, C.; Brucken, E.; Budagov, J.; Budd, H. S.; Burkett, K.; Busetto, G.; Bussey, P.; Butti, P.; Buzatu, A.; Calamba, A.; Camarda, S.; Campanelli, M.; Canelli, F.; Carls, B.; Carlsmith, D.; Carosi, R.; Carrillo, S.; Casal, B.; Casarsa, M.; Castro, A.; Catastini, P.; Cauz, D.; Cavaliere, V.; Cavalli-Sforza, M.; Cerri, A.; Cerrito, L.; Chen, Y. C.; Chertok, M.; Chiarelli, G.; Chlachidze, G.; Cho, K.; Chokheli, D.; Ciocci, M. A.; Clark, A.; Clarke, C.; Convery, M. E.; Conway, J.; Corbo, M.; Cordelli, M.; Cox, C. A.; Cox, D. J.; Cremonesi, M.; Cruz, D.; Cuevas, J.; Culbertson, R.; d’Ascenzo, N.; Datta, M.; De Barbaro, P.; Demortier, L.; Deninno, M.; Devoto, F.; d’Errico, M.; Di Canto, A.; Di Ruzza, B.; Dittmann, J. R.; D’Onofrio, M.; Donati, S.; Dorigo, M.; Driutti, A.; Ebina, K.; Edgar, R.; Elagin, A.; Erbacher, R.; Errede, S.; Esham, B.; Eusebi, R.; Farrington, S.; Fernández Ramos, J. P.; Field, R.; Flanagan, G.; Forrest, R.; Franklin, M.; Freeman, J. C.; Frisch, H.; Funakoshi, Y.; Garfinkel, A. F.; Garosi, P.; Gerberich, H.; Gerchtein, E.; Giagu, S.; Giakoumopoulou, V.; Gibson, K.; Ginsburg, C. M.; Giokaris, N.; Giromini, P.; Giurgiu, G.; Glagolev, V.; Glenzinski, D.; Gold, M.; Goldin, D.; Golossanov, A.; Gomez, G.; Gomez-Ceballos, G.; Goncharov, M.; González López, O.; Gorelov, I.; Goshaw, A. T.; Goulianos, K.; Gramellini, E.; Grinstein, S.; Grosso-Pilcher, C.; Group, R. C.; Guimaraes da Costa, J.; Hahn, S. R.; Han, J. Y.; Happacher, F.; Hara, K.; Hare, M.; Harr, R. F.; Harrington-Taber, T.; Hatakeyama, K.; Hays, C.; Heinrich, J.; Herndon, M.; Hocker, A.; Hong, Z.; Hopkins, W.; Hou, S.; Hughes, R. E.; Husemann, U.; Hussein, M.; Huston, J.; Introzzi, G.; Iori, M.; Ivanov, A.; James, E.; Jang, D.; Jayatilaka, B.; Jeon, E. J.; Jindariani, S.; Jones, M.; Joo, K. K.; Jun, S. Y.; Junk, T. R.; Kambeitz, M.; Kamon, T.; Karchin, P. E.; Kasmi, A.; Kato, Y.; Ketchum, W.; Keung, J.; Kilminster, B.; Kim, D. H.; Kim, H. S.; Kim, J. E.; Kim, M. J.; Kim, S. B.; Kim, S. H.; Kim, Y. K.; Kim, Y. J.; Kimura, N.; Kirby, M.; Knoepfel, K.; Kondo, K.; Kong, D. J.; Konigsberg, J.; Kotwal, A. V.; Kreps, M.; Kroll, J.; Kruse, M.; Kuhr, T.; Kurata, M.; Laasanen, A. T.; Lammel, S.; Lancaster, M.; Lannon, K.; Latino, G.; Lee, H. S.; Lee, J. S.; Leo, S.; Leone, S.; Lewis, J. D.; Limosani, A.; Lipeles, E.; Liu, H.; Liu, Q.; Liu, T.; Lockwitz, S.; Loginov, A.; Lucchesi, D.; Lueck, J.; Lujan, P.; Lukens, P.; Lungu, G.; Lys, J.; Lysak, R.; Madrak, R.; Maestro, P.; Malik, S.; Manca, G.; Manousakis-Katsikakis, A.; Margaroli, F.; Marino, P.; Martínez, M.; Matera, K.; Mattson, M. E.; Mazzacane, A.; Mazzanti, P.; McNulty, R.; Mehta, A.; Mehtala, P.; Mesropian, C.; Miao, T.; Mietlicki, D.; Mitra, A.; Miyake, H.; Moed, S.; Moggi, N.; Moon, C. S.; Moore, R.; Morello, M. J.; Mukherjee, A.; Muller, Th.; Murat, P.; Mussini, M.; Nachtman, J.; Nagai, Y.; Naganoma, J.; Nakano, I.; Napier, A.; Nett, J.; Neu, C.; Nigmanov, T.; Nodulman, L.; Noh, S. Y.; Norniella, O.; Oakes, L.; Oh, S. H.; Oh, Y. D.; Oksuzian, I.; Okusawa, T.; Orava, R.; Ortolan, L.; Pagliarone, C.; Palencia, E.; Palni, P.; Papadimitriou, V.; Parker, W.; Pauletta, G.; Paulini, M.; Paus, C.; Phillips, T. J.; Piacentino, G.; Pianori, E.; Pilot, J.; Pitts, K.; Plager, C.; Pondrom, L.; Poprocki, S.; Potamianos, K.; Prokoshin, F.; Pranko, A.; Ptohos, F.; Punzi, G.; Ranjan, N.; Redondo Fernández, I.; Renton, P.; Rescigno, M.; Riddick, T.; Rimondi, F.; Ristori, L.; Robson, A.; Rodriguez, T.; Rolli, S.; Ronzani, M.; Roser, R.; Rosner, J. L.; Ruffini, F.; Ruiz, A.; Russ, J.; Rusu, V.; Safonov, A.; Sakumoto, W. K.; Sakurai, Y.; Santi, L.; Sato, K.; Saveliev, V.; Savoy-Navarro, A.; Schlabach, P.; Schmidt, E. E.; Schwarz, T.; Scodellaro, L.; Scuri, F.; Seidel, S.; Seiya, Y.; Semenov, A.; Sforza, F.; Shalhout, S. Z.; Shears, T.; Shepard, P. F.; Shimojima, M.; Shochet, M.; Shreyber-Tecker, I.; Simonenko, A.; Sinervo, P.; Sliwa, K.; Smith, J. R.; Snider, F. D.; Sorin, V.; Song, H.; Stancari, M.; Denis, R. St.; Stelzer, B.; Stelzer-Chilton, O.; Stentz, D.; Strologas, J.; Sudo, Y.; Sukhanov, A.; Suslov, I.; Takemasa, K.; Takeuchi, Y.; Tang, J.; Tecchio, M.; Teng, P. K.; Thom, J.; Thomson, E.; Thukral, V.; Toback, D.; Tokar, S.; Tollefson, K.; Tomura, T.; Tonelli, D.; Torre, S.; Torretta, D.; Totaro, P.; Trovato, M.; Ukegawa, F.; Uozumi, S.; Vázquez, F.; Velev, G.; Vellidis, C.; Vernieri, C.; Vidal, M.; Vilar, R.; Vizán, J.; Vogel, M.; Volpi, G.; Wagner, P.; Wallny, R.; Wang, S. M.; Warburton, A.; Waters, D.; Wester, W. C.; Whiteson, D.; Wicklund, A. B.; Wilbur, S.; Williams, H. H.; Wilson, J. S.; Wilson, P.; Winer, B. L.; Wittich, P.; Wolbers, S.; Wolfe, H.; Wright, T.; Wu, X.; Wu, Z.; Yamamoto, K.; Yamato, D.; Yang, T.; Yang, U. K.; Yang, Y. C.; Yao, W.-M.; Yeh, G. P.; Yi, K.; Yoh, J.; Yorita, K.; Yoshida, T.; Yu, G. B.; Yu, I.; Zanetti, A. M.; Zeng, Y.; Zhou, C.; Zucchelli, S.

    2013-07-18

    We present a search for the pair production of a narrow nonstandard-model strongly interacting particle that decays to a pair of quarks or gluons, leading to a final state with four hadronic jets. We consider both nonresonant production via an intermediate gluon as well as resonant production via a distinct nonstandard-model intermediate strongly interacting particle. We use data collected by the CDF experiment in proton-antiproton collisions at √s=1.96 TeV corresponding to an integrated luminosity of 6.6 fb⁻¹. We find the data to be consistent with nonresonant production. We report limits on σ(pp̄→jjjj) as a function of the masses of the hypothetical intermediate particles. Upper limits on the production cross sections for nonstandard-model particles in several resonant and nonresonant processes are also derived.

  7. Investigation of the gravitational interaction between the components of the galaxy pairs Arp 242, CPG 165, and CPG 410

    NASA Astrophysics Data System (ADS)

    Ali, Gamal B.; Tawfeek, Amira A.; Amin, Magdy Y.

    2015-12-01

    In this paper the effect of interaction between the components of the galaxy pairs Arp 242, CPG 165, and CPG 410 on the symmetry of their morphologies and structures is studied by applying the technique of surface photometry. For each component of each pair we present the isophotal contours, profiles of surface brightness (SB), major-axis position angle (PA), and isophotal center-shift. The present analysis is done using the r- and i-band images from the Sloan Digital Sky Survey (SDSS) observation. It is found that the position angle and the isophotal center shift are strongly affected by the state of interaction between the components of the pairs.

  8. On the decoupling between classical Coulomb matter and radiation

    NASA Astrophysics Data System (ADS)

    Alastuey, Angel; Appel, Walter

    2000-02-01

    We consider a model of matter coupled to radiation at equilibrium. Matter is described by a one-component plasma of classical point charges with Coulomb interactions, while radiation is represented by the classical transverse potential vector in Coulomb gauge. Using a straightforward generalization of the Bohr-van Leeuwen theorem, we show that the equilibrium properties of classical Coulomb matter remain unaffected by the presence of the classical radiation. As far as the real world is concerned, this decoupling does survive at large distances where both matter and radiation can be treated classically. This invalidates all the large-distances predictions, for the charge correlations, of the so-called Darwin models which incorporate retarded electromagnetic interactions beyond the instantaneous Coulomb potential. A second related important consequence is that the first relativistic corrections to the Coulomb thermodynamical quantities must be evaluated within the theory of quantum electrodynamics at finite temperature, even in a weakly relativistic and almost classical regime for matter.

  9. Modeling the Dynamics of Interacting Galaxy Pairs - Testing Identikit Using GADGET SPH Simulations

    NASA Astrophysics Data System (ADS)

    Mortazavi, S. Alireza; Lotz, Jennifer; Barnes, Joshua E.

    2015-01-01

    We develop and test an automated technique to model the dynamics of interacting galaxy pairs. We use Identikit (Barnes & Hibbard 2009; Barnes 2011) as a tool for modeling and matching the morphology and kinematics of the interacting pairs of similar-size galaxies. In order to reduce the effect of subjective human interference, we automate the selection of phase-space regions used to match simulations to data, and we explore how selection of these regions affects the random uncertainties of parameters in the best-fit model. In this work, we used an independent set of GADGET SPH simulations as input data, so we determined the systematic bias in the measured encounter parameters based on the known initial conditions of these simulations. We tested both cold gas and young stellar components in the GADGET simulations to explore the effect of choosing HI vs. Hα as the line of sight velocity tracer. We found that we can group the results into tests with good, fair, and poor convergence based on the distribution of parameters of models close enough to the best-fit model. For tests with good and fair convergence, we ruled out large fractions of parameter space and recovered merger stage, eccentricity, viewing angle, and pericentric distance within 2σ of the correct value. All of tests on gaseous component of prograde systems had either good or fair convergence. Retrograde systems and most of tests on young stars had poor convergence and may require constraints from regions other than the tidal tails. In this work we also present WIYN SparsePak IFU data for a few interacting galaxies, and we show the result of applying our method on this data set.

  10. Coulomb drag between helical Luttinger liquids

    NASA Astrophysics Data System (ADS)

    Kainaris, N.; Gornyi, I. V.; Levchenko, A.; Polyakov, D. G.

    2017-01-01

    We theoretically study Coulomb drag between two helical edges with broken spin-rotational symmetry, such as would occur in two capacitively coupled quantum spin Hall insulators. For the helical edges, Coulomb drag is particularly interesting because it specifically probes the inelastic interactions that break the conductance quantization for a single edge. Using the kinetic equation formalism, supplemented by bosonization, we find that the drag resistivity ρD exhibits a nonmonotonic dependence on the temperature T . In the limit of low T ,ρD vanishes with decreasing T as a power law if intraedge interactions are not too strong. This is in stark contrast to Coulomb drag in conventional quantum wires, where ρD diverges at T →0 irrespective of the strength of repulsive interactions. Another unusual property of Coulomb drag between the helical edges concerns higher T for which, unlike in the Luttinger liquid model, drag is mediated by plasmons. The special type of plasmon-mediated drag can be viewed as a distinguishing feature of the helical liquid—because it requires peculiar umklapp scattering only available in the presence of a Dirac point in the electron spectrum.

  11. Temperature-Dependent Ellipsometry Measurements of Partial Coulomb Energy in Superconducting Cuprates

    DOE PAGES

    Levallois, J.; Tran, M. K.; Pouliot, D.; ...

    2016-08-24

    Here we performed an experimental study of the temperature and doping dependence of the energy-loss function of the bilayer and trilayer bismuth cuprates family. The primary aim is to obtain information on the energy stored in the Coulomb interaction between the conduction electrons, on the temperature dependence thereof, and on the change of Coulomb interaction when Cooper pairs are formed. We performed temperature-dependent ellipsometry measurements on several Bi2Sr2CaCu2O8₋x single crystals: underdoped with Tc=60, 70, and 83 K; optimally doped with Tc=91 K; overdoped with Tc=84, 81, 70, and 58 K; as well as optimally doped Bi2Sr2Ca2Cu3O10+x with Tc=110 K. Ourmore » first observation is that, as the temperature drops through Tc, the loss function in the range up to 2 eV displays a change of temperature dependence as compared to the temperature dependence in the normal state. This effect at—or close to—Tc depends strongly on doping, with a sign change for weak overdoping. The size of the observed change in Coulomb energy, using an extrapolation with reasonable assumptions about its q dependence, is about the same size as the condensation energy that has been measured in these compounds. Our results therefore lend support to the notion that the Coulomb energy is an important factor for stabilizing the superconducting phase. Lastly, because of the restriction to small momentum, our observations do not exclude a possible significant contribution to the condensation energy of the Coulomb energy associated with the region of q around (π,π).« less

  12. Temperature-Dependent Ellipsometry Measurements of Partial Coulomb Energy in Superconducting Cuprates

    NASA Astrophysics Data System (ADS)

    Levallois, J.; Tran, M. K.; Pouliot, D.; Presura, C. N.; Greene, L. H.; Eckstein, J. N.; Uccelli, J.; Giannini, E.; Gu, G. D.; Leggett, A. J.; van der Marel, D.

    2016-07-01

    We performed an experimental study of the temperature and doping dependence of the energy-loss function of the bilayer and trilayer bismuth cuprates family. The primary aim is to obtain information on the energy stored in the Coulomb interaction between the conduction electrons, on the temperature dependence thereof, and on the change of Coulomb interaction when Cooper pairs are formed. We performed temperature-dependent ellipsometry measurements on several Bi2 Sr2 CaCu2 O8 -x single crystals: underdoped with Tc=60 , 70, and 83 K; optimally doped with Tc=91 K ; overdoped with Tc=84 , 81, 70, and 58 K; as well as optimally doped Bi2 Sr2 Ca2 Cu3 O10 +x with Tc=110 K . Our first observation is that, as the temperature drops through Tc, the loss function in the range up to 2 eV displays a change of temperature dependence as compared to the temperature dependence in the normal state. This effect at—or close to—Tc depends strongly on doping, with a sign change for weak overdoping. The size of the observed change in Coulomb energy, using an extrapolation with reasonable assumptions about its q dependence, is about the same size as the condensation energy that has been measured in these compounds. Our results therefore lend support to the notion that the Coulomb energy is an important factor for stabilizing the superconducting phase. Because of the restriction to small momentum, our observations do not exclude a possible significant contribution to the condensation energy of the Coulomb energy associated with the region of q around (π ,π ).

  13. DNA base dimers are stabilized by hydrogen-bonding interactions including non-Watson-Crick pairing near graphite surfaces.

    PubMed

    Shankar, Akshaya; Jagota, Anand; Mittal, Jeetain

    2012-10-11

    Single- and double-stranded DNA are increasingly being paired with surfaces and nanoparticles for numerous applications, such as sensing, imaging, and drug delivery. Unlike the majority of DNA structures in bulk that are stabilized by canonical Watson-Crick pairing between Ade-Thy and Gua-Cyt, those adsorbed on surfaces are often stabilized by noncanonical base pairing, quartet formation, and base-surface stacking. Not much is known about these kinds of interactions. To build an understanding of the role of non-Watson-Crick pairing on DNA behavior near surfaces, one requires basic information on DNA base pair stacking and hydrogen-bonding interactions. All-atom molecular simulations of DNA bases in two cases--in bulk water and strongly adsorbed on a graphite surface--are conducted to study the relative strengths of stacking and hydrogen bond interactions for each of the 10 possible combinations of base pairs. The key information obtained from these simulations is the free energy as a function of distance between two bases in a pair. We find that stacking interactions exert the dominant influence on the stability of DNA base pairs in bulk water as expected. The strength of stability for these stacking interactions is found to decrease in the order Gua-Gua > Ade-Gua > Ade-Ade > Gua-Thy > Gua-Cyt > Ade-Thy > Ade-Cyt > Thy-Thy > Cyt-Thy > Cyt-Cyt. On the other hand, mutual interactions of surface-adsorbed base pairs are stabilized mostly by hydrogen-bonding interactions in the order Gua-Cyt > Ade-Gua > Ade-Thy > Ade-Ade > Cyt-Thy > Gua-Gua > Cyt-Cyt > Ade-Cyt > Thy-Thy > Gua-Thy. Interestingly, several non-Watson-Crick base pairings, which are commonly ignored, have similar stabilization free energies due to interbase hydrogen bonding as Watson-Crick pairs. This clearly highlights the importance of non-Watson-Crick base pairing in the development of secondary structures of oligonucleotides near surfaces.

  14. Ultranarrow resonance in Coulomb drag between quantum wires at coinciding densities

    NASA Astrophysics Data System (ADS)

    Dmitriev, A. P.; Gornyi, I. V.; Polyakov, D. G.

    2016-08-01

    We investigate the influence of the chemical potential mismatch Δ (different electron densities) on Coulomb drag between two parallel ballistic quantum wires. For pair collisions, the drag resistivity ρD(Δ ) shows a peculiar anomaly at Δ =0 with ρD being finite at Δ =0 and vanishing at any nonzero Δ . The "bodyless" resonance in ρD(Δ ) at zero Δ is only broadened by processes of multiparticle scattering. We analyze Coulomb drag for finite Δ in the presence of both two- and three-particle scattering within the kinetic equation framework, focusing on a Fokker-Planck picture of the interaction-induced diffusion in momentum space of the double-wire system. We describe the dependence of ρD on Δ for both weak and strong intrawire equilibration due to three-particle scattering.

  15. Enthalpy of interaction between coaggregating and non-coaggregating oral bacterial pairs--a microcalorimetric study.

    PubMed

    Postollec, Florence; Norde, Willem; van der Mei, Henny C; Busscher, Henk J

    2003-10-01

    Bacterial adhesion and coaggregation are involved in the development of oral biofilms, called dental plaque. Although various techniques have already been used to study different aspects of these bacterial interactions, microcalorimetry has not yet been applied. This paper describes how isothermal reaction calorimetry can be employed to determine the enthalpy of coaggregation between two oral bacterial pairs. For most biological processes, the enthalpy tends to reach a minimum value, reflecting the most stable state, which is directly related to the heat content of the system. The calorimeter consists of four measuring units where reaction ampoules are filled with 1.5 ml of an Actinomyces naeslundii 147 suspension, while reference ampoules are filled with buffer only. After equilibration at 25 degrees C, 80 microl of a streptococcal suspension was titrated into the reaction ampoules. To study possible saturation of the binding sites on the actinomyces surface, three consecutive injections with streptococcal suspensions were done. Following each injection, a 20-microl aliquot was taken from the ampoule kept outside the calorimeter and the number of free (S(f)) and bound (S(b)) streptococci was determined microscopically. Experiments were carried out with a coaggregating streptococcal strain (Streptococcus oralis J22) and a non-coaggregating strain (Streptococcus sanguis PK1889), serving as a control. The coaggregation enthalpy was exothermic, that is, heat was released in the reaction ampoule upon coaggregation and the heat released by the coaggregating pair minus the heat released by the non-coaggregating pair yielded a coaggregation enthalpy of -0.015 x 10(-6) mJ/bound streptococcus for the first injection. Upon consecutive injections, the coaggregation enthalpy decreased to -0.0004 x 10(-6) mJ/bound streptococcus. Comparison with enthalpy changes reported for lectin-carbohydrate binding suggests that a huge number of binding sites are involved in the formation of

  16. PREFACE: Strongly Coupled Coulomb Systems Strongly Coupled Coulomb Systems

    NASA Astrophysics Data System (ADS)

    Neilson, David; Senatore, Gaetano

    2009-05-01

    This special issue contains papers presented at the International Conference on Strongly Coupled Coulomb Systems (SCCS), held from 29 July-2 August 2008 at the University of Camerino. Camerino is an ancient hill-top town located in the Apennine mountains of Italy, 200 kilometres northeast of Rome, with a university dating back to 1336. The Camerino conference was the 11th in a series which started in 1977: 1977: Orleans-la-Source, France, as a NATO Advanced Study Institute on Strongly Coupled Plasmas (hosted by Marc Feix and Gabor J Kalman) 1982: Les Houches, France (hosted by Marc Baus and Jean-Pierre Hansen) 1986: Santa Cruz, California, USA (hosted by Forrest J Rogers and Hugh E DeWitt) 1989: Tokyo, Japan (hosted by Setsuo Ichimaru) 1992: Rochester, New York, USA (hosted by Hugh M Van Horn and Setsuo Ichimaru) 1995: Binz, Germany (hosted by Wolf Dietrich Kraeft and Manfred Schlanges) 1997: Boston, Massachusetts, USA (hosted by Gabor J Kalman) 1999: St Malo, France (hosted by Claude Deutsch and Bernard Jancovici) 2002: Santa Fe, New Mexico, USA (hosted by John F Benage and Michael S Murillo) 2005: Moscow, Russia (hosted by Vladimir E Fortov and Vladimir Vorob'ev). The name of the series was changed in 1996 from Strongly Coupled Plasmas to Strongly Coupled Coulomb Systems to reflect a wider range of topics. 'Strongly Coupled Coulomb Systems' encompasses diverse many-body systems and physical conditions. The purpose of the conferences is to provide a regular international forum for the presentation and discussion of research achievements and ideas relating to a variety of plasma, liquid and condensed matter systems that are dominated by strong Coulomb interactions between their constituents. Each meeting has seen an evolution of topics and emphases that have followed new discoveries and new techniques. The field has continued to see new experimental tools and access to new strongly coupled conditions, most recently in the areas of warm matter, dusty plasmas

  17. Combinatorial transcriptional interaction within the Cardiac Neural Crest: a pair of HANDs in heart formation

    PubMed Central

    Firulli, Anthony B.; Conway, Simon J.

    2008-01-01

    The cardiac neural crest migrate from rostral dorsal neural folds and populate the branchial arches, which directly contribute to cardiac-outflow structures. Although neural crest cell specification is associated with a number of morphogenic factors, little is understood about the mechanisms by which transcription factors actually implement the transcriptional programs that dictate cell migration and later the differentiation into the proper cell types within the heart. It is clear from genetic evidence that members of the paired box family and basic helix-loop-helix (bHLH) transcription factors from the twist family of proteins are expressed in and play an important function in cardiac neural crest specification and differentiation. Interestingly, both paired box and bHLH factors can function as dimers and in the case of twist family bHLH factors partner choice can clearly dictate a change in transcriptional program. The focus of this review is to consider the role that the protein-protein interactions of these transcription factors may play determining cardiac neural crest specification and differentiation and how genetic alteration of transcription factor stoichiometry within the cell may reflect more than a simple null event. PMID:15269889

  18. Complete switchgrass genetic maps reveal subgenome collinearity, preferential pairing and multilocus interactions.

    PubMed

    Okada, Miki; Lanzatella, Christina; Saha, Malay C; Bouton, Joe; Wu, Rongling; Tobias, Christian M

    2010-07-01

    Polyploidy is an important aspect of the evolution of flowering plants. The potential of gene copies to diverge and evolve new functions is influenced by meiotic behavior of chromosomes leading to segregation as a single locus or duplicated loci. Switchgrass (Panicum virgatum) linkage maps were constructed using a full-sib population of 238 plants and SSR and STS markers to access the degree of preferential pairing and the structure of the tetraploid genome and as a step toward identification of loci underlying biomass feedstock quality and yield. The male and female framework map lengths were 1645 and 1376 cM with 97% of the genome estimated to be within 10 cM of a mapped marker in both maps. Each map coalesced into 18 linkage groups arranged into nine homeologous pairs. Comparative analysis of each homology group to the diploid sorghum genome identified clear syntenic relationships and collinear tracts. The number of markers with PCR amplicons that mapped across subgenomes was significantly fewer than expected, suggesting substantial subgenome divergence, while both the ratio of coupling to repulsion phase linkages and pattern of marker segregation indicated complete or near complete disomic inheritance. The proportion of transmission ratio distorted markers was relatively low, but the male map was more extensively affected by distorted transmission ratios and multilocus interactions, associated with spurious linkages.

  19. Density functional theory studies of interactions of ruthenium-arene complexes with base pair steps.

    PubMed

    Mutter, Shaun T; Platts, James A

    2011-10-20

    Density functional theory (DFT) calculations have been performed to determine the strength and geometry of intermolecular interactions of "piano-stool" ruthenium arene complexes, which show potential as anticancer treatments. Model complexes with methane and benzene indicate that the coordinated arene has C-H···π acceptor ability similar to that of free benzene, whereas this arene acts as a much stronger C-H donor or partner in π-stacking than free benzene. The source of these enhanced interactions is identified as a combination of electrostatic and dispersion effects. Complexes of Ru-arene complexes with base-pair step fragments of DNA, in which the arene has the potential to act as an intercalator, have also been investigated. Binding energies are found to be sensitive to the size and nature of the arene, with larger and more flexible arenes having stronger binding. π-stacking and C-H···π interactions between arene and DNA bases and hydrogen bonds from coordinated N-H to DNA oxygen atoms, as well as covalent Ru-N bonding, contribute to the overall binding. The effect of complexation on DNA structure is also examined, with larger rise and more negative slide values than canonical B-DNA observed in all cases.

  20. Kinetics and fracture resistance of lithiated silicon nanostructure pairs controlled by their mechanical interaction

    SciTech Connect

    Lee, Seok Woo; Lee, Hyun-Wook; Ryu, Ill; Nix, William D.; Gao, Huajian; Cui, Yi; /Stanford U., Materials Sci. Dept. /SLAC

    2015-06-01

    Following an explosion of studies of silicon as a negative electrode for Li-ion batteries, the anomalous volumetric changes and fracture of lithiated single Si particles have attracted significant attention in various fields, including mechanics. However, in real batteries, lithiation occurs simultaneously in clusters of Si in a confined medium. Hence, understanding how the individual Si structures interact during lithiation in a closed space is necessary. Herein, we demonstrate physical/mechanical interactions of swelling Si structures during lithiation using well-defined Si nanopillar pairs. Ex situ SEM and in situ TEM studies reveal that compressive stresses change the reaction kinetics so that preferential lithiation occurs at free surfaces when the pillars are mechanically clamped. Such mechanical interactions enhance the fracture resistance of This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under Contract No. DE-AC02-76SF00515. SLAC-PUB-16300 2 lithiated Si by lessening the tensile stress concentrations in Si structures. This study will contribute to improved design of Si structures at the electrode level for high performance Li-ion batteries.

  1. Kinetics and fracture resistance of lithiated silicon nanostructure pairs controlled by their mechanical interaction

    DOE PAGES

    Lee, Seok Woo; Lee, Hyun -Wook; Ryu, Ill; ...

    2015-06-26

    Following an explosion of studies of silicon as a negative electrode for Li-ion batteries, the anomalous volumetric changes and fracture of lithiated single Si particles have attracted significant attention in various fields, including mechanics. However, in real batteries, lithiation occurs simultaneously in clusters of Si in a confined medium. Hence, understanding how the individual Si structures interact during lithiation in a closed space is necessary. Here, we demonstrate physical and mechanical interactions of swelling Si structures during lithiation using well-defined Si nanopillar pairs. Ex situ SEM and in situ TEM studies reveal that compressive stresses change the reaction kinetics somore » that preferential lithiation occurs at free surfaces when the pillars are mechanically clamped. Such mechanical interactions enhance the fracture resistance of lithiated Si by lessening the tensile stress concentrations in Si structures. Lastly, this study will contribute to improved design of Si structures at the electrode level for high-performance Li-ion batteries.« less

  2. Molecular hydrogen "pairing" interaction in a metal organic framework system with unsaturated metal centers (MOF-74).

    PubMed

    Nijem, Nour; Veyan, Jean-François; Kong, Lingzhu; Wu, Haohan; Zhao, Yonggang; Li, Jing; Langreth, David C; Chabal, Yves J

    2010-10-27

    Infrared (IR) absorption spectroscopy measurements of molecular hydrogen in MOF-74-M (M = metal center) are performed as a function of temperature and pressure [to 45 kTorr (60 bar) at 300 K, and at lower pressures in the 20-200 K range] to investigate the nature of H(2) interactions with the unsaturated metal centers. A small shift (∼ -30 cm(-1) with respect to the unperturbed H(2) molecule) is observed for the internal stretch frequency of H(2) molecules adsorbed on the metal site at low loading. This finding is in contrast to much larger shifts (∼ -70 cm(-1)) observed in previous studies of MOFs with unsaturated metal centers (including MOF-74) and the general assumption that H(2) stretch shifts depend on adsorption energies (FitzGerald et al., Phys. Rev. B 2010, 81, 104305). We show that larger shifts (∼ -70 cm(-1)) do occur, but only when the next available site ("oxygen" site) is occupied. This larger shift originates from H(2)-H(2) interactions on neighboring sites of the same pore, consistent with the short distance between H(2) in these two sites ∼2.6 Å derived from an analysis of neutron diffraction experiments of D(2)-D(2) at 4 K (Liu et al., Langmuir 2008, 24, 4772-4777). Our results at 77 K and low loading can be explained by a diffusion barrier against pair disruption, which should be enhanced by this interaction. Calculations indicate that the vibrational shifts do not correlate with binding energies and are instead very sensitive to the environment (interaction potential and H(2)-H(2) interactions), which complicates the use of variable temperature IR methods to calculate adsorption energies of specific adsorption sites.

  3. Repetition and pair-interaction of string-like hopping motions in glassy polymers

    NASA Astrophysics Data System (ADS)

    Lam, Chi-Hang

    2017-06-01

    The dynamics of many glassy systems are known to exhibit string-like hopping motions each consisting of a line of particles displacing one another. By using the molecular dynamics simulations of glassy polymers, we show that these motions become highly repetitive back-and-forth motions as temperature decreases and do not necessarily contribute to net displacements. Particle hops which constitute string-like motions are reversed with a high probability, reaching 73% and beyond at low temperature. The structural relaxation rate is then dictated not by a simple particle hopping rate but instead by the rate at which particles break away from hopping repetitions. We propose that disruption of string repetitions and hence also structural relaxations are brought about by pair-interactions between strings.

  4. Delayed response of a fermion pair condensate to a modulation of the interaction strength

    NASA Astrophysics Data System (ADS)

    Plata, J.

    2009-09-01

    The effect of a sinusoidal modulation of the interaction strength on a fermion pair condensate is analytically studied. The system is described by a generalization of the coupled fermion-boson model that incorporates a time-dependent intermode coupling induced via a magnetic Feshbach resonance. Nontrivial effects are shown to emerge depending on the relative magnitude of the modulation period and the relaxation time of the condensate. Specifically, a nonadiabatic modulation drives the system out of thermal equilibrium: the external field induces a variation of the quasiparticle energies, and, in turn, a disequilibrium of the associated populations. The subsequent relaxation process is studied and an analytical description of the gap dynamics is obtained. Recent experimental findings are explained: the delay observed in the response to the applied field is understood as a temperature effect linked to the condensate relaxation time.

  5. The influence of intramolecular sulfur-lone pair interactions on small-molecule drug design and receptor binding.

    PubMed

    Hudson, B M; Nguyen, E; Tantillo, D J

    2016-04-28

    Sulfur-lone pair interactions are important conformational control elements in sulfur-containing heterocycles that abound in pharmaceuticals, natural products, agrochemicals, polymers and other important classes of organic molecules. Nonetheless, the role of intramolecular sulfur-lone pair interactions in the binding of small molecules to receptors is often overlooked. Here we analyze the magnitudes and origins of these interactions for a variety of biologically relevant small molecules using quantum chemical and automated docking calculations. In most cases examined in this study, the lowest energy conformation of the small molecule displays a sulfur-lone pair close contact. However, docking studies, both published and new, often predict that conformations without sulfur-lone pair contacts have the best binding affinity for their respective receptors. This is a serious problem. Since many of these predicted bound conformations are not actually energetically accessible, pursuing design (e.g., drug design) around these binding modes necessarily will lead, serendipity aside, to dead end designs. Our results constitute a caution that one best not neglect these interactions when predicting the binding affinities of potential ligands (drugs or not) for hosts (enzymes, receptors, DNA, RNA, synthetic hosts). Moreover, a better understanding and awareness of sulfur-lone pair interactions should facilitate the rational modulation of host-guest interactions involving sulfur-containing molecules.

  6. Pair-correlation properties and momentum distribution of finite number of interacting trapped bosons in three dimensions

    SciTech Connect

    Biswas, Anindya; Das, Tapan Kumar; Chakrabarti, Barnali

    2010-09-14

    We study the ground state pair-correlation properties of a weakly interacting trapped Bose gas in three dimensions by using a correlated many-body method. The use of the van der Waals interaction potential and an external trapping potential shows realistic features. We also test the validity of shape-independent approximation in the calculation of correlation properties.

  7. Photofragmentation, state interaction, and energetics of Rydberg and ion-pair states: Resonance enhanced multiphoton ionization of HI

    SciTech Connect

    Hróðmarsson, Helgi Rafn; Wang, Huasheng; Kvaran, Ágúst

    2014-06-28

    Mass resolved resonance enhanced multiphoton ionization data for hydrogen iodide (HI), for two-photon resonance excitation to Rydberg and ion-pair states in the 69 600–72 400 cm{sup −1} region were recorded and analyzed. Spectral perturbations due to homogeneous and heterogeneous interactions between Rydberg and ion-pair states, showing as deformations in line-positions, line-intensities, and line-widths, were focused on. Parameters relevant to photodissociation processes, state interaction strengths and spectroscopic parameters for deperturbed states were derived. Overall interaction and dynamical schemes to describe the observations are proposed.

  8. Junctionless Cooper pair transistor

    NASA Astrophysics Data System (ADS)

    Arutyunov, K. Yu.; Lehtinen, J. S.

    2017-02-01

    Quantum phase slip (QPS) is the topological singularity of the complex order parameter of a quasi-one-dimensional superconductor: momentary zeroing of the modulus and simultaneous 'slip' of the phase by ±2π. The QPS event(s) are the dynamic equivalent of tunneling through a conventional Josephson junction containing static in space and time weak link(s). Here we demonstrate the operation of a superconducting single electron transistor (Cooper pair transistor) without any tunnel junctions. Instead a pair of thin superconducting titanium wires in QPS regime was used. The current-voltage characteristics demonstrate the clear Coulomb blockade with magnitude of the Coulomb gap modulated by the gate potential. The Coulomb blockade disappears above the critical temperature, and at low temperatures can be suppressed by strong magnetic field.

  9. Semiclassical Coulomb field

    SciTech Connect

    Polonyi, J.

    2008-06-15

    The contribution of different modes of the Coulomb field to decoherence and to the dynamical breakdown of the time reversal invariance is calculated in the one-loop approximation for nonrelativistic electron gas. The dominant contribution was found to come from the usual collective modes in the plasma, namely, the zero-sound and the plasmon oscillations. The length scale of the quantum-classical transition is found to be close to the Thomas-Fermi screening length. It is argued that the extension of these modes to the whole Fock space yields optimal pointer states.

  10. Repulsive bound-atom pairs in an optical lattice with two-body interaction of nearest neighbors

    SciTech Connect

    Wang, Y.-M.; Liang, J.-Q.

    2010-04-15

    Repulsively interacting particles in a periodic potential can form bound composite objects with long lifetimes, as has been observed experimentally [Winkler et al., Nature (London) 441, 853 (2006)]. In this paper, a complete two-particle solution of one-dimensional periodical potential was derived in a strong interaction regime, where the on-site approximation of a two-body interaction in the Bose-Hubbard model (BHM) is extended to include the interaction of nearest neighbors, which results in atom-pair hopping. The energy spectrum of the bound pair is drastically reshaped due to the pair-hopping term, and complex eigenenergy corresponding to metastable states is also found that has not been discovered in the usual BHM. When the absolute value of a center-of-mass quasimomentum wave vector is greater than a critical value (|K|>K{sub c}), two bound-pair solutions are found. Furthermore, the spatial and momentum distributions of the bound pair displays a crossover from dark to bright soliton-like solutions in the extended BHM. Our results reduce to that of the usual BHM in the weak interaction case.

  11. Antiferromagnetism, charge density wave, and d-wave superconductivity in the extended t-J-U model: role of intersite Coulomb interaction and a critical overview of renormalized mean field theory.

    PubMed

    Abram, M; Zegrodnik, M; Spałek, J

    2017-09-13

    In the first part of the paper, we study the stability of antiferromagnetic (AF), charge density wave (CDW), and superconducting (SC) states within the t-J-U-V model of strongly correlated electrons by using the statistically consistent Gutzwiller approximation (SGA). We concentrate on the role of the intersite Coulomb interaction term V in stabilizing the CDW phase. In particular, we show that the charge ordering appears only above a critical value of V in a limited hole-doping range δ. The effect of the V term on SC and AF phases is that a strong interaction suppresses SC, whereas the AF order is not significantly influenced by its presence. In the second part, separate calculations for the case of a pure SC phase have been carried out within an extended approach (the diagrammatic expansion for the Gutzwiller wave function, DE-GWF) in order to analyze the influence of the intersite Coulomb repulsion on the SC phase with the higher-order corrections included beyond the SGA method. The upper concentration for the SC disappearance decreases with increasing V, bringing the results closer to experiment. In appendices A and B we discuss the ambiguity connected with the choice of the Gutzwiller renormalization factors within the renormalized mean filed theory when either AF or CDW orders are considered. At the end, we overview briefly the possible extensions of the current models to put descriptions of the SC, AF, and CDW states on equal footing.

  12. Role of electronic correlation in high-low temperature phase transition of hexagonal nickel sulfide: a comparative density functional theory study with and without correction for on-site Coulomb interaction.

    PubMed

    Zhang, Wei-Bing; Li, Jie; Tang, Bi-Yu

    2013-06-28

    The structural, electronic, magnetic, and elastic properties of hexagonal nickel sulfide (NiS) have been investigated comparatively by Density Functional theory (DFT) and DFT plus correction for on-site Coulomb interaction (DFT+U), in which two different exchange correlation functionals local density approximations (LDA) and general gradient approximations (GGA) in the form of Perdew-Burke-Ernzerhof (PBE) are used. Our results indicate LDA and PBE methods predict hexagonal NiS to be a paramagnetic metal whereas LDA(PBE)+U calculations with reasonable on-site Coulomb interaction energy give the antiferromagnetic insulating state of low temperature hexagonal NiS successfully. Meanwhile, compared with LDA(PBE) results, LDA(PBE)+U methods give larger lattice parameters, crystal volume, and shear constant c44, consistent with the experimental picture during high-low temperature phase transition of hexagonal NiS, in which an increase of the shear constant c44 and lattice parameters were found in the low-temperature antiferromagnetic phase. The present DFT and DFT+U calculations provide a reasonable description for the properties of high temperature and low temperature hexagonal NiS respectively, which indicates that electronic correlation is responsible for this high-low temperature phase transition.

  13. Antiferromagnetism, charge density wave, and d-wave superconductivity in the extended t-J-U model: role of intersite Coulomb interaction and a critical overview of renormalized mean field theory

    NASA Astrophysics Data System (ADS)

    Abram, M.; Zegrodnik, M.; Spałek, J.

    2017-09-01

    In the first part of the paper, we study the stability of antiferromagnetic (AF), charge density wave (CDW), and superconducting (SC) states within the t-J-U-V model of strongly correlated electrons by using the statistically consistent Gutzwiller approximation (SGA). We concentrate on the role of the intersite Coulomb interaction term V in stabilizing the CDW phase. In particular, we show that the charge ordering appears only above a critical value of V in a limited hole-doping range δ. The effect of the V term on SC and AF phases is that a strong interaction suppresses SC, whereas the AF order is not significantly influenced by its presence. In the second part, separate calculations for the case of a pure SC phase have been carried out within an extended approach (the diagrammatic expansion for the Gutzwiller wave function, DE-GWF) in order to analyze the influence of the intersite Coulomb repulsion on the SC phase with the higher-order corrections included beyond the SGA method. The upper concentration for the SC disappearance decreases with increasing V, bringing the results closer to experiment. In appendices A and B we discuss the ambiguity connected with the choice of the Gutzwiller renormalization factors within the renormalized mean filed theory when either AF or CDW orders are considered. At the end, we overview briefly the possible extensions of the current models to put descriptions of the SC, AF, and CDW states on equal footing.

  14. Interactive locomotion: Investigation and modeling of physically-paired humans while walking

    PubMed Central

    Le Goff, Camille G.; Ijspeert, Auke Jan

    2017-01-01

    In spite of extensive studies on human walking, less research has been conducted on human walking gait adaptation during interaction with another human. In this paper, we study a particular case of interactive locomotion where two humans carry a rigid object together. Experimental data from two persons walking together, one in front of the other, while carrying a stretcher-like object is presented, and the adaptation of their walking gaits and coordination of the foot-fall patterns are analyzed. It is observed that in more than 70% of the experiments the subjects synchronize their walking gaits; it is shown that these walking gaits can be associated to quadrupedal gaits. Moreover, in order to understand the extent by which the passive dynamics can explain this synchronization behaviour, a simple 2D model, made of two-coupled spring-loaded inverted pendulums, is developed, and a comparison between the experiments and simulations with this model is presented, showing that with this simple model we are able to reproduce some aspects of human walking behaviour when paired with another human. PMID:28877161

  15. The ChIP-exo Method: Identifying Protein-DNA Interactions with Near Base Pair Precision.

    PubMed

    Perreault, Andrea A; Venters, Bryan J

    2016-12-23

    Chromatin immunoprecipitation (ChIP) is an indispensable tool in the fields of epigenetics and gene regulation that isolates specific protein-DNA interactions. ChIP coupled to high throughput sequencing (ChIP-seq) is commonly used to determine the genomic location of proteins that interact with chromatin. However, ChIP-seq is hampered by relatively low mapping resolution of several hundred base pairs and high background signal. The ChIP-exo method is a refined version of ChIP-seq that substantially improves upon both resolution and noise. The key distinction of the ChIP-exo methodology is the incorporation of lambda exonuclease digestion in the library preparation workflow to effectively footprint the left and right 5' DNA borders of the protein-DNA crosslink site. The ChIP-exo libraries are then subjected to high throughput sequencing. The resulting data can be leveraged to provide unique and ultra-high resolution insights into the functional organization of the genome. Here, we describe the ChIP-exo method that we have optimized and streamlined for mammalian systems and next-generation sequencing-by-synthesis platform.

  16. Analyses of interactions among pair-rule genes and the gap gene Krüppel in Bombyx segmentation.

    PubMed

    Nakao, Hajime

    2015-09-01

    In the short-germ insect Tribolium, a pair-rule gene circuit consisting of the Tribolium homologs of even-skipped, runt, and odd-skipped (Tc-eve, Tc-run and Tc-odd, respectively) has been implicated in segment formation. To examine the application of the model to other taxa, I studied the expression and function of pair-rule genes in Bombyx mori, together with a Bombyx homolog of Krüppel (Bm-Kr), a known gap gene. Knockdown embryos of Bombyx homologs of eve, run and odd (Bm-eve, Bm-run and Bm-odd) exhibited asegmental phenotypes similar to those of Tribolium knockdowns. However, pair-rule gene interactions were similar to those of both Tribolium and Drosophila, which, different from Tribolium, shows a hierarchical segmentation mode. Additionally, the Bm-odd expression pattern shares characteristics with those of Drosophila pair-rule genes that receive upstream regulatory input. On the other hand, Bm-Kr knockdowns exhibited a large posterior segment deletion as observed in short-germ insects. However, a detailed analysis of these embryos indicated that Bm-Kr modulates expression of pair-rule genes like in Drosophila, although the mechanisms appear to be different. This suggested hierarchical interactions between Bm-Kr and pair-rule genes. Based on these results, I concluded that the pair-rule gene circuit model that describes Tribolium development is not applicable to Bombyx.

  17. Crystalline structures of particles interacting through the harmonic-repulsive pair potential

    NASA Astrophysics Data System (ADS)

    Levashov, V. A.

    2017-09-01

    The behavior of identical particles interacting through the harmonic-repulsive pair potential has been studied in 3D using molecular dynamics simulations at a number of different densities. We found that at many densities, as the temperature of the systems decreases, the particles crystallize into complex structures whose formation has not been anticipated in previous studies on the harmonic-repulsive pair potential. In particular, at certain densities, crystallization into the structure I a 3 ¯ d (space group #230) with 16 particles in the unit cell occupying Wyckoff special positions (16b) was observed. This crystal structure has not been observed previously in experiments or in computer simulations of single component atomic or soft matter systems. At another density, we observed a liquid which is rather stable against crystallization. Yet, we observed crystallization of this liquid into the monoclinic C2/c (space group #15) structure with 32 particles in the unit cell occupying four different non-special Wyckoff (8f) sites. In this structure particles located at different Wyckoff sites have different energies. From the perspective of the local atomic environment, the organization of particles in this structure resembles the structure of some columnar quasicrystals. At a different value of the density, we did not observe crystallization at all despite rather long molecular dynamics runs. At two other densities, we observed the formation of the β S n distorted diamond structures instead of the expected diamond structure. Possibly, we also observed the formation of the R 3 ¯ c hexagonal lattice with 24 particles per unit cell occupying non-equivalent positions.

  18. Crystalline structures of particles interacting through the harmonic-repulsive pair potential.

    PubMed

    Levashov, V A

    2017-09-21

    The behavior of identical particles interacting through the harmonic-repulsive pair potential has been studied in 3D using molecular dynamics simulations at a number of different densities. We found that at many densities, as the temperature of the systems decreases, the particles crystallize into complex structures whose formation has not been anticipated in previous studies on the harmonic-repulsive pair potential. In particular, at certain densities, crystallization into the structure Ia3¯d (space group #230) with 16 particles in the unit cell occupying Wyckoff special positions (16b) was observed. This crystal structure has not been observed previously in experiments or in computer simulations of single component atomic or soft matter systems. At another density, we observed a liquid which is rather stable against crystallization. Yet, we observed crystallization of this liquid into the monoclinic C2/c (space group #15) structure with 32 particles in the unit cell occupying four different non-special Wyckoff (8f) sites. In this structure particles located at different Wyckoff sites have different energies. From the perspective of the local atomic environment, the organization of particles in this structure resembles the structure of some columnar quasicrystals. At a different value of the density, we did not observe crystallization at all despite rather long molecular dynamics runs. At two other densities, we observed the formation of the βSn distorted diamond structures instead of the expected diamond structure. Possibly, we also observed the formation of the R3¯c hexagonal lattice with 24 particles per unit cell occupying non-equivalent positions.

  19. Remote Spacecraft Attitude Control by Coulomb Charging

    NASA Astrophysics Data System (ADS)

    Stevenson, Daan

    The possibility of inter-spacecraft collisions is a serious concern at Geosynchronous altitudes, where many high-value assets operate in proximity to countless debris objects whose orbits experience no natural means of decay. The ability to rendezvous with these derelict satellites would enable active debris removal by servicing or repositioning missions, but docking procedures are generally inhibited by the large rotational momenta of uncontrolled satellites. Therefore, a contactless means of reducing the rotation rate of objects in the space environment is desired. This dissertation investigates the viability of Coulomb charging to achieve such remote spacecraft attitude control. If a servicing craft imposes absolute electric potentials on a nearby nonspherical debris object, it will impart electrostatic torques that can be used to gradually arrest the object's rotation. In order to simulate the relative motion of charged spacecraft with complex geometries, accurate but rapid knowledge of the Coulomb interactions is required. To this end, a new electrostatic force model called the Multi-Sphere Method (MSM) is developed. All aspects of the Coulomb de-spin concept are extensively analyzed and simulated using a system with simplified geometries and one dimensional rotation. First, appropriate control algorithms are developed to ensure that the nonlinear Coulomb torques arrest the rotation with guaranteed stability. Moreover, the complex interaction of the spacecraft with the plasma environment and charge control beams is modeled to determine what hardware requirements are necessary to achieve the desired electric potential levels. Lastly, the attitude dynamics and feedback control development is validated experimentally using a scaled down terrestrial testbed. High voltage power supplies control the potential on two nearby conductors, a stationary sphere and a freely rotating cylinder. The nonlinear feedback control algorithms developed above are implemented to

  20. Excitonic pairing and insulating transition in two-dimensional semi-Dirac semimetals

    NASA Astrophysics Data System (ADS)

    Wang, Jing-Rong; Liu, Guo-Zhu; Zhang, Chang-Jin

    2017-02-01

    A sufficiently strong long-range Coulomb interaction can induce excitonic pairing in gapless Dirac semimetals, which generates a finite gap and drives the semimetal-insulator quantum phase transition. This phenomenon is in close analogy to dynamical chiral symmetry breaking in high-energy physics. In most realistic Dirac semimetals, including suspended graphene, the Coulomb interaction is too weak to open an excitonic gap. The Coulomb interaction plays a more important role at low energies in a two-dimensional semi-Dirac semimetal, in which the fermion spectrum is linear in one component of momenta and quadratic in the other, than a Dirac semimetal, and indeed leads to breakdown of Fermi liquid theory. We study dynamical excitonic gap generation in a two-dimensional semi-Dirac semimetal by solving the Dyson-Schwinger equation, and show that a moderately strong Coulomb interaction suffices to induce excitonic pairing. Additional short-range four-fermion coupling tends to promote excitonic pairing. Among the available semi-Dirac semimetals, we find that the TiO2/VO2 nanostructure provides a promising candidate for the realization of an excitonic insulator. We also apply the renormalization group method to analyze the strong coupling between the massless semi-Dirac fermions and the quantum critical fluctuation of the excitonic order parameter at the semimetal-insulator quantum critical point, and reveal non-Fermi liquid behaviors of semi-Dirac fermions.

  1. Coarse-graining strategy for molecular pair interactions: A reaction coordinate study for two- and three-dimensional systems

    NASA Astrophysics Data System (ADS)

    Heinemann, Thomas; Klapp, Sabine H. L.

    2017-04-01

    We investigate and provide optimal sets of reaction coordinates for mixed pairs of molecules displaying polar, uniaxial, or spherical symmetry in two and three dimensions. These coordinates are non-redundant, i.e., they implicitly involve the molecules' symmetries. By tabulating pair interactions in these coordinates, resulting tables are thus minimal in length and require a minimal memory space. The intended fields of application are computer simulations of large ensembles of molecules or colloids with rather complex interactions in a fluid or liquid crystalline phase at low densities. Using effective interactions directly in the form of tables can help bridging the time and length scales without introducing errors stemming from any modeling procedure. Finally, we outline an exemplary computational methodology for gaining an effective pair potential in these coordinates, based on the Boltzmann inversion principle, by providing a step-by-step recipe.

  2. Molecular Dynamics Simulations of Coulomb Explosion

    SciTech Connect

    Bringa, E M

    2002-05-17

    A swift ion creates a track of electronic excitations in the target material. A net repulsion inside the track can cause a ''Coulomb Explosion'', which can lead to damage and sputtering of the material. Here we report results from molecular-dynamics (MD) simulations of Coulomb explosion for a cylindrical track as a function of charge density and neutralization/quenching time, {tau}. Screening by the free electrons is accounted for using a screened Coulomb potential for the interaction among charges. The yield exhibits a prompt component from the track core and a component, which dominates at higher excitation density, from the heated region produced. For the cases studied, the number of atoms ejected per incident ion, i.e. the sputtering yield Y, is quadratic with charge density along the track as suggested by simple models. Y({tau} = 0.2 Debye periods) is nearly 20% of the yield when there is no neutralization ({tau} {yields} {infinity}). The connections between ''Coulomb explosions'', thermal spikes and measurements of electronic sputtering are discussed.

  3. Local Structure of Ion Pair Interaction in Lapatinib Amorphous Dispersions characterized by Synchrotron X-Ray diffraction and Pair Distribution Function Analysis

    NASA Astrophysics Data System (ADS)

    de Araujo, Gabriel L. B.; Benmore, Chris J.; Byrn, Stephen R.

    2017-04-01

    For many years, the idea of analyzing atom-atom contacts in amorphous drug-polymer systems has been of major interest, because this method has always had the potential to differentiate between amorphous systems with domains and amorphous systems which are molecular mixtures. In this study, local structure of ionic and noninonic interactions were studied by High-Energy X-ray Diffraction and Pair Distribution Function (PDF) analysis in amorphous solid dispersions of lapatinib in hypromellose phthalate (HPMCP) and hypromellose (HPMC-E3). The strategy of extracting lapatinib intermolecular drug interactions from the total PDF x-ray pattern was successfully applied allowing the detection of distinct nearest neighbor contacts for the HPMC-E3 rich preparations showing that lapatinib molecules do not cluster in the same way as observed in HPMC-P, where ionic interactions are present. Orientational correlations up to nearest neighbor molecules at about 4.3 Å were observed for polymer rich samples; both observations showed strong correlation to the stability of the systems. Finally, the superior physical stability of 1:3 LP:HPMCP was consistent with the absence of significant intermolecular interactions in (∆) in the range of 3.0 to 6.0 Å, which are attributed to C-C, C-N and C-O nearest neighbor contacts present in drug-drug interactions.

  4. Local structure of ion pair interaction in lapatinib amorphous dispersions characterized by synchrotron x-ray diffraction and pair distribution function analysis

    DOE PAGES

    de Araujo, Gabriel L. B.; Benmore, Chris J.; Byrn, Stephen R.

    2017-04-11

    For many years, the idea of analyzing atom-atom contacts in amorphous drug-polymer systems has been of major interest, because this method has always had the potential to differentiate between amorphous systems with domains and amorphous systems which are molecular mixtures. In this study, local structure of ionic and noninonic interactions were studied by High-Energy X-ray Diffraction and Pair Distribution Function (PDF) analysis in amorphous solid dispersions of lapatinib in hypromellose phthalate (HPMCP) and hypromellose (HPMC-E3). The strategy of extracting lapatinib intermolecular drug interactions from the total PDF x-ray pattern was successfully applied allowing the detection of distinct nearest neighbor contactsmore » for the HPMC-E3 rich preparations showing that lapatinib molecules do not cluster in the same way as observed in HPMC-P, where ionic interactions are present. Orientational correlations up to nearest neighbor molecules at about 4.3 Å were observed for polymer rich samples; both observations showed strong correlation to the stability of the systems. Lasty, the superior physical stability of 1:3 LP:HPMCP was consistent with the absence of significant intermolecular interactions in (ΔDinterLP(r)) in the range of 3.0 to 6.0 Å, which are attributed to C-C, C-N and C-O nearest neighbor contacts present in drug-drug interactions.« less

  5. Traceable Coulomb blockade thermometry

    NASA Astrophysics Data System (ADS)

    Hahtela, O.; Mykkänen, E.; Kemppinen, A.; Meschke, M.; Prunnila, M.; Gunnarsson, D.; Roschier, L.; Penttilä, J.; Pekola, J.

    2017-02-01

    We present a measurement and analysis scheme for determining traceable thermodynamic temperature at cryogenic temperatures using Coulomb blockade thermometry. The uncertainty of the electrical measurement is improved by utilizing two sampling digital voltmeters instead of the traditional lock-in technique. The remaining uncertainty is dominated by that of the numerical analysis of the measurement data. Two analysis methods are demonstrated: numerical fitting of the full conductance curve and measuring the height of the conductance dip. The complete uncertainty analysis shows that using either analysis method the relative combined standard uncertainty (k  =  1) in determining the thermodynamic temperature in the temperature range from 20 mK to 200 mK is below 0.5%. In this temperature range, both analysis methods produced temperature estimates that deviated from 0.39% to 0.67% from the reference temperatures provided by a superconducting reference point device calibrated against the Provisional Low Temperature Scale of 2000.

  6. Energies of Screened Coulomb Potentials.

    ERIC Educational Resources Information Center

    Lai, C. S.

    1979-01-01

    This article shows that, by applying the Hellman-Feynman theorem alone to screened Coulomb potentials, the first four coefficients in the energy series in powers of the perturbation parameter can be obtained from the unperturbed Coulomb system. (Author/HM)

  7. Systematic mutation and thermodynamic analysis of central tyrosine pairs in polyspecific NKG2D receptor interactions

    PubMed Central

    Culpepper, David J.; Maddox, Michael K.; Caldwell, Andrew B.; McFarland, Benjamin J.

    2010-01-01

    The homodimeric, activating natural killer cell receptor NKG2D interacts with multiple monomeric ligands polyspecifically, yet without central conformational flexibility. Crystal structures of multiple NKG2D-ligand interactions have identified the NKG2D tyrosine pair Tyr 152 and Tyr 199 as forming multiple specific but diverse interactions with MICA and related proteins. Here we systematically altered each tyrosine to tryptophan, phenylalanine, isoleucine, leucine, valine, serine, and alanine to measure the effect of mutation on affinity and thermodynamics for binding a range of similar ligands: MICA, the higher-affinity ligand MICB, and MICdesign, a high-affinity version of MICA that shares all NKG2D contact residues with MICA. Affinity and residue size were related: tryptophan could often substitute for tyrosine without loss of affinity; loss of the tyrosine hydroxyl through mutation to phenylalanine was tolerated more at position 152 than 199; and the smallest residues coincide with lowest affinities in general. NKG2D mutant van’t Hoff binding thermodynamics generally show that substitution of other residues for tyrosine causes a moderate positive or flat van’t Hoff slope consistent with moderate loss of binding enthalpy. One set of NKG2D mutations caused MICA to adopt a positive van’t Hoff slope corresponding to absorption of heat, and another set caused MICB to adopt a negative slope of greater heat release than wild-type. MICdesign shared one example of the first set with MICA and one of the second set with MICB. When the NKG2D mutation affinities were arranged according to change in nonpolar surface area and compared to results from specific antibody-antigen and protein-peptide interactions, it was found that hydrophobic surface loss in NKG2D reduced binding affinity less than reported in the other contexts. The hydrophobic effect at the center of the NKG2D binding appears more similar to that at the periphery of an antibody-antigen binding site than

  8. Pair interaction lattice gas simulations: Flow past obstacles in two and three dimensions

    SciTech Connect

    Vogeler, A.; Wolf-Gladrow, D.A. )

    1993-04-01

    Apart from the FCHC (face-centered hypercube), Nasilowski's pair interaction lattice gas (PI) is the only known lattice gas automaton for three-dimensional hydrodynamic simulations. Unfortunately, the viscosity of PI is not isotropic. In order to determine the degree anisotropy, the authors derive fluid dynamic equations for the regime of compressible viscid flow. From relaxation measurements of waves propagating in various directions they compute the physically relevant dissipation coefficients and compare their results with theoretical predictions. Although PI shows a high degree of anisotropy, they define the mean value of the dissipation tensor as effective shear viscosity. Using this value of v[sub eff][sup 2D] = 0.35, two-dimensional simulations of flow past a cylinder yield drag coefficients in quantitative agreement with wind tunnel measurements over a range of Reynolds numbers of 5-50. Three-dimensional simulations of flow past a sphere yield qualitative agreement with various references. A fit of the results to a semi-empirical curve provides an effective value of v[sub eff][sup 2D] = 0.21 for a range of Reynolds numbers from 0.19 to 40. In order to check for finite-size effects, the authors measured the mean free path [lambda] and computed the Knudsen numbers. They obtained [lambda] [approx]1 lattice unit, corresponding to Kn = 0.01 (2D) and Kn = 0.1 (3D). They found no significant finite-size effects. 44 refs., 10 figs.

  9. Phase transitions of boron carbide: Pair interaction model of high carbon limit

    NASA Astrophysics Data System (ADS)

    Yao, Sanxi; Huhn, W. P.; Widom, M.

    2015-09-01

    Boron Carbide exhibits a broad composition range, implying a degree of intrinsic substitutional disorder. While the observed phase has rhombohedral symmetry (space group R 3 bar m), the enthalpy minimizing structure has lower, monoclinic, symmetry (space group Cm). The crystallographic primitive cell consists of a 12-atom icosahedron placed at the vertex of a rhombohedral lattice, together with a 3-atom chain along the 3-fold axis. In the limit of high carbon content, approaching 20% carbon, the icosahedra are usually of type B11 Cp, where the p indicates the carbon resides on a polar site, while the chains are of type C-B-C. We establish an atomic interaction model for this composition limit, fit to density functional theory total energies, that allows us to investigate the substitutional disorder using Monte Carlo simulations augmented by multiple histogram analysis. We find that the low temperature monoclinic Cm structure disorders through a pair of phase transitions, first via a 3-state Potts-like transition to space group R3m, then via an Ising-like transition to the experimentally observed R 3 bar m symmetry. The R3m and Cm phases are electrically polarized, while the high temperature R 3 bar m phase is nonpolar.

  10. Interaction Energies and Dynamics of Acid–Base Pairs Isolated in Cavitands

    PubMed Central

    Purse, Byron W.; Butterfield, Sara M.; Ballester, Pablo; Shivanyuk, Alexander; Rebek, Julius

    2009-01-01

    The use of capsules and cavitands in physical organic chemistry is briefly reviewed, and their application to the study of salt bridges is introduced. Carboxylate/ammonium ion pairs are generated within an environment that more or less surrounds the functional groups within a synthetic fixed introverted solvent sphere. This is provided by cavitands that fold around amines and present them with a carboxylic acid function. Both organic and water-soluble versions were prepared, and their equilibrium affinities with quinuclidine bases were determined by NMR methods. The association constants range from approximately 103 M−1 in water to more than 105 M−1 in organic solvents. Studies of nitrogen inversion and tumbling of [2.2.2]-diazabicyclooctane within the introverted acids also illustrate the strength of the acid–base interactions. The barriers to in–out exchange of several amine guests were determined to be in the range from 15 to 24 kcal mol−1. Some parallels with enzymes are drawn: the receptor folds around the guest species; presents them with inwardly directed functionality; and provides a generally hydrophobic environment and a periphery of secondary amide bonds. PMID:18672933

  11. Spin Correlations of Strongly Interacting Massive Fermion Pairs as a Test of Bell's Inequality

    SciTech Connect

    Sakai, H.; Saito, T.; Kuboki, H.; Sasano, M.; Yako, K.; Ikeda, T.; Itoh, K.; Kawabata, T.; Maeda, Y.; Suda, K.; Uesaka, T.; Matsui, N.; Satou, Y.; Rangacharyulu, C.; Sekiguchi, K.; Tamii, A.

    2006-10-13

    We report the results of the first-time test of the local hidden variable theories (Bell-Clauser-Horne-Shimony-Holt) involving strongly interacting pairs of massive spin 1/2 hadrons from the decay of short-lived ({tau}<10{sup -21}sec) {sup 2}He spin-singlet state, populated in the nuclear reaction {sup 2}H+{sup 1}H{yields}{sup 2}He+n. The novel features of this experiment are (a) the use of an 'event body' detector of nearly 100% efficiency to prepare an unbiased sample and (b) a focal-plane polarimeter of full 2{pi} sr acceptance with a random 'post selection' of the reference axes. The spin-correlation function is deduced to be S{sub exp}({pi}/4)=2.83{+-}0.24{sub stat}{+-}0.07{sub sys}. This result is in agreement with nonlocal quantum mechanical prediction and it violates the Bell-CHSH inequality of vertical bar S vertical bar{<=}2 at a confidence level of 99.3%.

  12. PREFACE: Strongly Coupled Coulomb Systems

    NASA Astrophysics Data System (ADS)

    Fortov, Vladimir E.; Golden, Kenneth I.; Norman, Genri E.

    2006-04-01

    This special issue contains papers presented at the International Conference on Strongly Coupled Coulomb Systems (SCCS) which was held during the week of 20 24 June 2005 in Moscow, Russia. The Moscow conference was the tenth in a series of conferences. The previous conferences were organized as follows. 1977: Orleans-la-Source, France, as a NATO Advanced Study Institute on Strongly Coupled Plasmas (organized by Marc Feix and Gabor J Kalman) 1982: Les Houches, France (organized by Marc Baus and Jean-Pierre Hansen) 1986: Santa Cruz, California, USA (hosted by Forrest J Rogers and Hugh E DeWitt) 1989: Tokyo, Japan (hosted by Setsuo Ichimaru) 1992: Rochester, NY, USA (hosted by Hugh M Van Horn and Setsuo Ichimaru) 1995: Binz, Germany (hosted by Wolf Dietrich Kraeft and Manfred Schlanges) 1997: Boston, Massachusetts, USA (hosted by Gabor J Kalman) 1999: St Malo, France (hosted by Claude Deutsch and Bernard Jancovici) 2002: Santa Fe, New Mexico, USA (hosted by John F Benage and Michael S Murillo) After 1995 the name of the series was changed from `Strongly Coupled Plasmas' to the present name in order to extend the topics of the conferences. The planned frequency for the future is once every three years. The purpose of these conferences is to provide an international forum for the presentation and discussion of research accomplishments and ideas relating to a variety of plasma liquid and condensed matter systems, dominated by strong Coulomb interactions between their constituents. Strongly coupled Coulomb systems encompass diverse many-body systems and physical conditions. Each meeting has seen an evolution of topics and emphasis as new discoveries and new methods appear. This year, sessions were organized for invited presentations and posters on dense plasmas and warm matter, astrophysics and dense hydrogen, non-neutral and ultracold plasmas, dusty plasmas, condensed matter 2D and layered charged-particle systems, Coulomb liquids, and statistical theory of SCCS. Within

  13. Generalized oscillator strength and Coulomb excitation

    NASA Astrophysics Data System (ADS)

    Chidichimo, Marita C.; Thorsley, Michael D.

    2003-02-01

    Coulomb interaction is characterized by two nondimensional fundamental quantities: the Sommerfeld parameter η and the adiabaticity parameter ξ=ηf-ηi. In this different approach, we choose these variables to describe the behavior of the generalized oscillator strength (GOS). The expression we obtain is valid for scattering of electrons, positrons, and nuclei by arbitrary targets. We present asymptotic expansions, in the quantal and semiclassical approximation, of the electric dipole GOS.

  14. Coulomb blockade and Coulomb staircase behavior observed at room temperature

    NASA Astrophysics Data System (ADS)

    Uky Vivitasari, Pipit; Azuma, Yasuo; Sakamoto, Masanori; Teranishi, Toshiharu; Majima, Yutaka

    2017-02-01

    A single-electron transistor (SET) consists of source, drain, Coulomb island, and gate to modulate the number of electrons and control the current. For practical applications, it is important to operate a SET at room temperature. One proposal towards the ability to operate at room temperature is to decrease Coulomb island size down to a few nanometres. We investigate a SET using Sn-porphyrin (Sn-por) protected gold nanoparticles (AuNPs) with 1.4 nm in core diameter as a Coulomb island. The fabrication method of nanogap electrodes uses the combination of a top-down technique by electron beam lithography (EBL) and a bottom-up process through electroless gold plating (ELGP) as our group have described before. The electrical measurement was conducted at room temperature (300 K). From current-voltage (I d-V d) characteristics, we obtained clear Coulomb blockade phenomena together with a Coulomb staircase due to a Sn-por protected gold NP as a Coulomb island. Experimental results of I d-V d characteristics agree with a theoretical curve based on using the orthodox model. Clear dI d/dV d peaks are observed in the Coulomb staircase at 9 K which suggest the electron transports through excited energy levels of Au NPs. These results are a big step for obtaining SETs that can operate at room temperature.

  15. Analytic Coulomb approximations for dynamic multipole polarizabilities and dispersion forces

    NASA Astrophysics Data System (ADS)

    Lamm, Gene; Szabo, Attila

    1980-03-01

    ECA allows a wide variety of dispersion force coefficients to be easily calculated. Extensive, but not exhaustive, tabulations of C6, C8, C10, and D9 (three-body) coefficients are given. C6 coefficients involving the He 11S, 21S, 23S systems are compared with the accurate results of GW and, except for interactions of He 12S, excellent agreement is obtained. The discrepancies for He 11S are removed by a simple scaling procedure utilizing the static polarizability. To facilitate scaling of dispersion coefficients, normalized dispersion coefficients are defined. Normalized dipole and quadrupole dispersion coefficients are given for all alkaline earth-alkaline earth pairs. Accurate results for C6 and C8 coefficients are presented for all alkali-alkali pairs and C6 coefficients for alkali-alkaline earth interactions given. Sample C10 and D9 coefficients are listed for the alkalis and hydrogen. Coupling the ECA dynamic dipole polarizability to available discrete oscillator strength distribution data allows C6 coefficients to be obtained for the interaction of alkali, alkaline earth, and metastable helium atoms with the following systems: He, Ne, Ar, Kr, Xe, N, O, H2, N2, O2, NO, N2O, H2O, NH3, and CH4. Finally, C8 coefficients for He-alkali interactions are presented. A significant number of the dispersion coefficients obtained here are not available in the literature. Based on the success of ECA static multipole polarizability predictions, we feel the results presented here are generally the most reliable to date.

  16. Momentum-space treatment of Coulomb distortions in a multiple-scattering expansion

    NASA Astrophysics Data System (ADS)

    Chinn, C. R.; Elster, Ch.; Thaler, R. M.

    1991-10-01

    The momentum-space treatment of the Coulomb interaction within the framework of the Watson multiple-scattering expansion is derived and tested numerically. By neglecting virtual Coulomb excitations and higher-order terms, the lowest-order optical potential for proton-nucleus scattering is shown to be the sum of the convolutions of a two-body nucleon-nucleon t matrix with the nuclear density and the point Coulomb interaction with the nuclear charge density. The calculation of the optical potential, as well as the treatment of the Coulomb interaction, is performed entirely in momentum space in an exact and numerically stable procedure. Elastic-scattering observables are presented for 16O, 40Ca, and 208Pb at energies up to 500 MeV. Comparisons are made with approximate treatments of the Coulomb interaction. The interference of nonlocality effects in the nuclear optical potential with different treatments of the Coulomb interaction is investigated.

  17. A Chandra observation of the interacting pair of galaxies NGC 4485/4490

    NASA Astrophysics Data System (ADS)

    Roberts, T. P.; Warwick, R. S.; Ward, M. J.; Murray, S. S.

    2002-12-01

    We report the results of a 20-ks Chandra ACIS-S observation of the galaxy pair NGC 4485/4490. This is an interacting system containing a late-type spiral with an enhanced star formation rate (NGC 4490), and an irregular companion that possesses a disturbed morphology. A total of 29 discrete X-ray sources are found coincident with NGC 4490, but only one is found within NGC 4485. The sources range in observed X-ray luminosity from ~2 × 1037 to 4 × 1039 erg s-1. The more luminous sources appear, on average, to be spectrally harder than the fainter sources, an effect that is attributable to increased absorption in their spectra. Extensive diffuse X-ray emission is detected coincident with the disc of NGC 4490, and in the tidal tail of NGC 4485, which appears to be thermal in nature and hence the signature of a hot interstellar medium in both galaxies. However, the diffuse component accounts for only ~10 per cent of the total X-ray luminosity of the system (2 × 1040 erg s-1, 0.5-8 keV), which arises predominantly in a handful of the brightest discrete sources. This diffuse emission fraction is unusually low for a galaxy pair which has many characteristics that would lead it to be classified as a starburst system, possibly as a consequence of the small gravitational potential well of the system. The discrete source population, on the other hand, is similar to that observed in other starburst systems, possessing a flat luminosity function slope of ~-0.6 and a total of six ultraluminous X-ray sources (ULX). Five of the ULX are identified as probable black hole X-ray binary systems, and the sixth (which is coincident with a radio continuum source) is identified as an X-ray luminous supernova remnant. The ULX all lie in star formation regions, providing further evidence of the link between the ULX phenomenon and active star formation. Importantly, this shows that even in star-forming regions, the ULX population is dominated by accreting systems. We discuss the

  18. Dark Coulomb binding of heavy neutrinos of fourth family

    NASA Astrophysics Data System (ADS)

    Belotsky, K. M.; Esipova, E. A.; Khlopov, M. Yu.; Laletin, M. N.

    2015-11-01

    Direct dark matter searches put severe constraints on the weakly interacting massive particles (WIMPs). These constraints cause serious troubles for the model of stable neutrino of fourth generation with mass around 50GeV. Though the calculations of primordial abundance of these particles make them in the charge symmetric case a sparse subdominant component of the modern dark matter, their presence in the universe would exceed the current upper limits by several orders of the magnitude. However, if quarks and leptons of fourth generation possess their own Coulomb-like y-interaction, recombination of pairs of heavy neutrinos and antineutrinos and their annihilation in the “neutrinium” atoms can play important role in their cosmological evolution, reducing their modern abundance far below the experimental upper limits. The model of stable fourth generation assumes that the dominant part of dark matter is explained by excessive Ū antiquarks, forming (ŪŪŪ)-- charged clusters, bound with primordial helium in nuclear-interacting O-helium (OHe) dark atoms. The y charge conservation implies generation of the same excess of fourth generation neutrinos, potentially dangerous WIMP component of this scenario. We show that due to y-interaction recombination of fourth neutrinos with OHe hides these WIMPs from direct WIMP searches, leaving the negligible fraction of free neutrinos, what makes their existence compatible with the experimental constraints.

  19. Double quantum dot Cooper-pair splitter at finite couplings

    NASA Astrophysics Data System (ADS)

    Hussein, Robert; Jaurigue, Lina; Governale, Michele; Braggio, Alessandro

    2016-12-01

    We consider the subgap physics of a hybrid double-quantum dot Cooper-pair splitter with large single-level spacings, in the presence of tunneling between the dots and finite Coulomb intra- and interdot Coulomb repulsion. In the limit of a large superconducting gap, we treat the coupling of the dots to the superconductor exactly. We employ a generalized master-equation method, which easily yields currents, noise, and cross-correlators. In particular, for finite inter- and intradot Coulomb interaction, we investigate how the transport properties are determined by the interplay between local and nonlocal tunneling processes between the superconductor and the dots. We examine the effect of interdot tunneling on the particle-hole symmetry of the currents with and without spin-orbit interaction. We show that spin-orbit interaction in combination with finite Coulomb energy opens the possibility to control the nonlocal entanglement and its symmetry (singlet/triplet). We demonstrate that the generation of nonlocal entanglement can be achieved even without any direct nonlocal coupling to the superconducting lead.

  20. The Effects of Thinking Aloud Pair Problem Solving on High School Students' Chemistry Problem-Solving Performance and Verbal Interactions

    ERIC Educational Resources Information Center

    Jeon, Kyungmoon; Huffman, Douglas; Noh, Taehee

    2005-01-01

    A problem solving strategy, Thinking Aloud Pair Problem Solving (TAPPS), developed by Arthur Whimbey to help students monitor and understand their own thought process is presented. The TAPPS strategy encouraged the students interact verbally with each other to solve chemistry problems and improve the achievements in chemistry.

  1. Canonical Watson-Crick base pair interactions in π* type triplet states

    NASA Astrophysics Data System (ADS)

    Noguera, M.; Blancafort, L.; Sodupe, M.; Bertran, J.

    2006-03-01

    Ground state and triplet π → π* states of canonical Watson-Crick base pairs have been studied at the B3LYP level of theory. Excited states were found to be localized at either of the monomers forming the base pair (guanine, cytosine, adenine and thymine), geometry relaxation of the excited base pair being similar to that occurring in the isolated nucleobase. For thymine and cytosine, triplet π → π* excitation produces a significant elongation of the C5-C6 bond whereas for guanine and adenine there is a significant increase of the N3-C2 bond and pyramidalization of the NH2 group. Adenine-thymine energy pairing remains almost unaffected by triplet excitation. However, for guanine-cytosine, with excitation localized at the guanine moiety, base pairing energy decreases about 5 kcal/mol due to pyramidalization of the amino group of guanine.

  2. Galaxy pairs in the Sloan Digital Sky Survey - VI. The orbital extent of enhanced star formation in interacting galaxies

    NASA Astrophysics Data System (ADS)

    Patton, David R.; Torrey, Paul; Ellison, Sara L.; Mendel, J. Trevor; Scudder, Jillian M.

    2013-06-01

    We use pair and environmental classifications of ˜211 000 star-forming galaxies from the Sloan Digital Sky Survey, along with a suite of merger simulations, to investigate the enhancement of star formation as a function of separation in galaxy pairs. Using a new technique for distinguishing between the influence of nearby neighbours and larger scale environment, we find a clear enhancement in star formation out to projected separations of ˜150 kpc, beyond which there is no net enhancement. We find the strongest enhancements at the smallest separations (especially <20 kpc), consistent with earlier work. Similar trends are seen in the simulations, which indicate that the strongest enhancements are produced in highly disturbed systems approaching final coalescence, whereas the more modest enhancements seen at wider separations are the result of starburst activity triggered at first pericentre passage, which persists as the galaxies move to larger separations. The absence of any net enhancement beyond 150 kpc provides reassurance that the detected enhancements are due to galaxy-galaxy interactions, rather than larger scale environmental effects or potential pair selection biases. A rough census indicates that 66 per cent of the enhanced star formation in our pair sample occurs at separations >30 kpc. We conclude that significant interaction-induced star formation is not restricted to merger remnants or galaxies with close companions; instead, a larger population of wider separation pairs exhibit enhanced star formation due to recent close encounters.

  3. Kin recognition, not competitive interactions, predicts root allocation in young Cakile edentula seedling pairs.

    PubMed

    Bhatt, Mudra V; Khandelwal, Aditi; Dudley, Susan A

    2011-03-01

    • Recent studies have demonstrated sibling vs stranger differences in group root allocation in plants, suggesting that plants have the potential for kin discrimination in competition. However, morphology differences could potentially be generated by competition-based mechanisms. Here, we tested these hypotheses for the sibling vs stranger differences in root allocation in Cakile edentula. • Seeds were planted in pairs of either kin (siblings) or strangers, from all combinations of eight families, to give eight kin (sibling) and 28 stranger pair identities. Because the species has a seed dimorphism, the 10 replicates of each pair identity included both seed types. Root allocation, size inequality between seedlings in a pair, and competitive ability were derived from measures of biomass and height. • Cakile edentula seedlings demonstrated the same kin recognition response previously observed in juvenile plants, with lower root allocation in kin pairs than stranger pairs. The seed dimorphism was not associated with root allocation. • The two competitive mechanisms, genetic differences in competitive ability and increased size inequality in stranger groups, did not explain the root allocation differences in these seedlings. Kin recognition offered the most probable explanation for the differences in root allocation between sibling and stranger pairs. © 2010 The Authors. New Phytologist © 2010 New Phytologist Trust.

  4. Electronic and thermoelectric properties of Ce{sub 3}Te{sub 4} and La{sub 3}Te{sub 4} computed with density functional theory with on-site Coulomb interaction correction

    SciTech Connect

    Vo, Trinh; Allmen, Paul von; Huang, Chen-Kuo; Ma, James; Bux, Sabah; Fleurial, Jean-Pierre

    2014-10-07

    The electronic properties and Seebeck coefficients of Ce{sub 3}Te{sub 4} and La{sub 3}Te{sub 4} are computed using Density Functional Theory with on-site Coulomb interaction correction. We found that the Seebeck coefficients of Ce{sub 3}Te{sub 4} and La{sub 3}Te{sub 4} are almost equal at temperatures larger than the Curie temperature of Ce{sub 3}Te{sub 4}, and in good agreement with the measurements reported by May et al. [Phys. Rev. B 86, 035135 (2012)]. At temperatures below the Curie temperature, the Seebeck coefficient of Ce{sub 3}Te{sub 4} increases due to the ferromagnetic ordering, which leads the f-electron of Ce to contribute to the Seebeck coefficient in the relevant range of electron concentration.

  5. Target transverse size and laser polarization effects on pair production during ultra-relativistic-intense laser interaction with solid targets

    NASA Astrophysics Data System (ADS)

    Yuan, T.; Chen, M.; Yu, J. Y.; Liu, W. Y.; Luo, W.; Weng, S. M.; Sheng, Z. M.

    2017-06-01

    Pair production from the Breit-Wheeler process in ultra-intense laser pulse interactions with solid targets are studied by particle-in-cell simulations using the EPOCH code including the quantum electrodynamics module. We find that the pair yield depends on both the target transverse size and the laser pulse duration. For a short laser pulse, the highest pair yield is achieved with a target as wide as the laser spot size. For a long laser pulse, however, the optimal target size for the pair production increases with the pulse duration due to a self-generated cone by the hole-boring process. The effect of laser polarization upon the pair production is also studied. It is found that a circularly polarized laser pulse is more efficient in the ion acceleration rather than in the pair production. With the same laser energy, we find that a linearly polarized laser pulse can generate two times more positrons than the circularly polarized laser pulse does. These findings may benefit the future researches on the laser plasma based electron-positron production.

  6. Coulomb crystallization of highly charged ions.

    PubMed

    Schmöger, L; Versolato, O O; Schwarz, M; Kohnen, M; Windberger, A; Piest, B; Feuchtenbeiner, S; Pedregosa-Gutierrez, J; Leopold, T; Micke, P; Hansen, A K; Baumann, T M; Drewsen, M; Ullrich, J; Schmidt, P O; López-Urrutia, J R Crespo

    2015-03-13

    Control over the motional degrees of freedom of atoms, ions, and molecules in a field-free environment enables unrivalled measurement accuracies but has yet to be applied to highly charged ions (HCIs), which are of particular interest to future atomic clock designs and searches for physics beyond the Standard Model. Here, we report on the Coulomb crystallization of HCIs (specifically (40)Ar(13+)) produced in an electron beam ion trap and retrapped in a cryogenic linear radiofrequency trap by means of sympathetic motional cooling through Coulomb interaction with a directly laser-cooled ensemble of Be(+) ions. We also demonstrate cooling of a single Ar(13+) ion by a single Be(+) ion-the prerequisite for quantum logic spectroscopy with a potential 10(-19) accuracy level. Achieving a seven-orders-of-magnitude decrease in HCI temperature starting at megakelvin down to the millikelvin range removes the major obstacle for HCI investigation with high-precision laser spectroscopy.

  7. Coulomb edge effects in graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Jaskolski, W.; Ayuela, A.

    2014-10-01

    Coulomb effects in graphene nanoribbons with arbitrary edges are investigated with the use of a mean-field Hubbard model. It was recently shown that chiral ribbons with minimal edges, characterized by the translation vector (n,m), have a similar structure of bands localized around the Fermi energy as pure zigzag ribbons (n-m,0). Here we show that these flat bands in both ribbon cases differ in detail due to the perturbation induced by armchair edge nodes. For chiral ribbons the edge bands split at the zone boundary, where the corresponding bands of (n-m,0) zigzag ribbons are degenerate. Coulomb interactions enhance strongly this splitting and at the same time they bring spin into play. We modify each edge keeping global sublattice balance to find that spin degeneracy can be partially lifted. The breaking of spin-degeneracy depends on the asymmetry between the edges and in some cases leads to spin-polarized currents.

  8. General impossibility to 'prescribe' diffusion for a geminate pair in a central force field and peculiarities of geminate in ionic liquids.

    SciTech Connect

    Shkrob, I. A.

    2011-05-12

    Given the difficulty of obtaining analytical solutions for the diffusion of interacting geminate pairs of (ion) radicals in liquids, it is common, following the original treatment of Mozumder, to 'prescribe' this diffusion. A demonstration is given that such a prescription is impossible for any interaction potential other than the Coulomb potential. This demonstration suggests the inadequacy of this common approach to modeling geminate pair and spur dynamics in the largest emerging class of organic solvents: room-temperature ionic liquids.

  9. Fission barrier of actinides and superheavy nuclei: effect of pairing interaction

    NASA Astrophysics Data System (ADS)

    Abusara, H.

    2017-06-01

    Systematic calculations of fission barriers for axial deformation are performed for even-even nuclei in actinides region of the nuclear chart and superheavy nuclei. These calculations were performed using relativistic Hartree-Bogoliubov (RHB) formalism with separable pairing.

  10. Character of the pair interaction in solid and gaseous H2

    NASA Technical Reports Server (NTRS)

    England, W.; Etters, R.; Raich, J.; Danilowicz, R.

    1974-01-01

    Existing theoretical H2 pair potentials are investigated. We develop a spherically symmetric potential applicable to solid H2. It yields a ground-state energy of -98.7 K (experimental values range from -93.5 to -101 K). Pressure-volume data are also in excellent agreement with experiment between 0 and 25 kbar. Second virial coefficients using this potential are consistently too low. When an anisotropic pair potential is used, agreement becomes very good.

  11. Galaxy pairs in the Sloan Digital Sky Survey - X. Does gas content alter star formation rate enhancement in galaxy interactions?

    NASA Astrophysics Data System (ADS)

    Scudder, Jillian M.; Ellison, Sara L.; Momjian, Emmanuel; Rosenberg, Jessica L.; Torrey, Paul; Patton, David R.; Fertig, Derek; Mendel, J. Trevor

    2015-06-01

    New spectral line observations, obtained with the Jansky Very Large Array (VLA), of a sample of 34 galaxies in 17 close pairs are presented in this paper. The sample of galaxy pairs is selected to contain galaxies in close, major interactions (i.e. projected separations <30 h_{70}^{-1} kpc, and mass ratios less extreme than 4:1), while still having a sufficiently large angular separation that the VLA can spatially resolve both galaxies in the pair. Of the 34 galaxies, 17 are detected at >3σ. We compare the H I gas fraction of the galaxies with the triggered star formation present in that galaxy. When compared to the star formation rates (SFRs) of non-pair galaxies matched in mass, redshift, and local environment, we find that the star formation enhancement is weakly positively correlated (˜2.5σ) with H I gas fraction. In order to help understand the physical mechanisms driving this weak correlation, we also present results from a small suite of binary galaxy merger simulations with varying gas fractions. The simulated galaxies indicate that larger initial gas fractions are associated with lower levels of interaction-triggered star formation (relative to an identical galaxy in isolation), but also show that high gas fraction galaxies have higher absolute SFRs prior to an interaction. We show that when interaction-driven SFR enhancements are calculated relative to a galaxy with an average gas fraction for its stellar mass, the relationship between SFR and initial gas fraction dominates over the SFR enhancements driven by the interaction. Simulated galaxy interactions that are matched in stellar mass but not in gas fraction, like our VLA sample, yield the same general positive correlation between SFR enhancement and gas fraction that we observe.

  12. Origin of dz2 orbital suppression of d-wave superconductive pairs in cuprate

    NASA Astrophysics Data System (ADS)

    Tang, Huai Bao; Li, Guang; Zhang, Hai Jun; Zuo, Xue Qin; Meng, Fan Ming; Liu, Da Yong

    2015-07-01

    Compared to Hg-cuprate, the origin that the dz2 orbital suppresses the d-wave superconductive (SC) pairs in La-cuprate is studied based on an effective two-orbital t-J-U model by using the Kotliar-Ruckenstein (KR) slave-boson technique. By analyzing the orbital-dependent electron distribution, it is elaborated that the double occupancy of dx2-y2 orbital, caused by the dz2 orbital mixture, should be responsible for the suppression of the d-wave SC pairs in La-cuprate. When the Coulomb interaction U increases, the ground state hosting the large double occupancy of dx2-y2 orbital in La-cuprate is stabilized by the localization of the carriers due to the Coulomb-blocking instead of reducing the double occupancy by the way of lowering of Coulomb potential energy. Therefore, it could be concluded that the mechanism that the double occupancy destructs against d-wave SC pairs is robust even if the strong Coulomb interaction exists in the La-based compounds.

  13. Pair plasma formation in the interaction of a thin plasma with ultra-intense counter-propagating lasers

    NASA Astrophysics Data System (ADS)

    Slade-Lowther, Cody

    2016-10-01

    Next-generation lasers (e.g. ELI) expect to reach peak intensities of 1023 Wcm-2. At such intensities, the electromagnetic field strength is sufficient for non-linear Quantum Electrodynamics effects to become important. The processes of non-linear Compton scattering and Breit-Wheeler Pair production become likely at intensities >=1023 Wcm-2, and have been predicted to lead to prolific pair and γ-ray production via electromagnetic cascades. We present results for the case of two counter-propagating circularly- polarized lasers of intensity I ∈ [1023 ,1025 ] Wcm24 interacting with a plasma of initial density n0 ∈ [1025 ,1035 ] via the Monte-Carlo- particle-in-cell code EPOCH. We show the maximum pair plasma density in I vs n0 space. We further discuss the variation within this space on the plasma characteristics, including laser absorption and field-particle energy distribution.

  14. Long-read ChIA-PET for base-pair-resolution mapping of haplotype-specific chromatin interactions.

    PubMed

    Li, Xingwang; Luo, Oscar Junhong; Wang, Ping; Zheng, Meizhen; Wang, Danjuan; Piecuch, Emaly; Zhu, Jacqueline Jufen; Tian, Simon Zhongyuan; Tang, Zhonghui; Li, Guoliang; Ruan, Yijun

    2017-05-01

    Chromatin interaction analysis by paired-end tag sequencing (ChIA-PET) is a robust method for capturing genome-wide chromatin interactions. Unlike other 3C-based methods, it includes a chromatin immunoprecipitation (ChIP) step that enriches for interactions mediated by specific target proteins. This unique feature allows ChIA-PET to provide the functional specificity and higher resolution needed to detect chromatin interactions, which chromosome conformation capture (3C)/Hi-C approaches have not achieved. The original ChIA-PET protocol generates short paired-end tags (2 × 20 base pairs (bp)) to detect two genomic loci that are far apart on linear chromosomes but are in spatial proximity in the folded genome. We have improved the original approach by developing long-read ChIA-PET, in which the length of the paired-end tags is increased (up to 2 × 250 bp). The longer PET reads not only improve the tag-mapping efficiency but also increase the probability of covering phased single-nucleotide polymorphisms (SNPs), which allows haplotype-specific chromatin interactions to be identified. Here, we provide the detailed protocol for long-read ChIA-PET that includes cell fixation and lysis, chromatin fragmentation by sonication, ChIP, proximity ligation with a bridge linker, Tn5 tagmentation, PCR amplification and high-throughput sequencing. For a well-trained molecular biologist, it typically takes 6 d from cell harvesting to the completion of library construction, up to a further 36 h for DNA sequencing and <20 h for processing of raw sequencing reads.

  15. Mathematical analysis of endothelial sibling pair cell-cell interactions using time-lapse cinematography data.

    PubMed

    Brown, L M; Ryan, U S; Absher, M; Olazabal, B M

    1982-01-01

    The sibling pairs from two different endothelial cell cultures were analysed by time-lapse cinematography. It was shown that wounded and regular (low density seeded) cultures differed in the behaviour patterns of their siblings. The cultures differed most significantly in the minimum interdivision time (IDT) which was 27% lower for the wounded culture. In the wounded culture there was a greater correlation of IDT values between sibling pairs. IDT values recorded both for paired and for unpaired cells were shorter for the wounded than for the regular culture. The mean IDT for unpaired cells was longer than the mean IDT for paired cells in the regular culture. Thus paired cells in the regular culture, had shorter IDTs, but not as short as in the wounded culture. It was significant that in the wounded culture the first generation of siblings were very close (less than 150 microns apart) at division. Overall the behaviour differences between the two cultures resulted in a higher rate of increase in cell numbers, and thus faster repair, of the wounded monolayer.

  16. Ship and satellite observations of chlorophyll stocks in interacting cyclone-anticyclone eddy pairs in the western Gulf of Mexico

    NASA Technical Reports Server (NTRS)

    Biggs, Douglas, C.; Mueller-Karger, Frank E.

    1994-01-01

    When anticyclonic eddies shed by the Loop Current of the Gulf of Mexico reach the western margin of the gulf, they influence the surface circulation over the continental slope and rise. Of particular interest is the generation of cyclone (cold-core)-anticyclone (warm-core) pairs when aging Loop Current eddies interact with the continental margin. In this paper we describe the physical and biological characteristics of these cyclone-anticyclone pairs. Our objective was to determine how eddy pairs affect the distribution of phytoplankton in the region and how satellite ocean color measurements are applicable to tracing of the eddies. We present shipboard data collected between 1980 and 1982 on the hydrography, chlorophyll stocks, and nutrient concentrations of eddy pairs in the western Gulf of Mexico and compare these data with coastal zone color scanner (CZCS) images collected during the time frame of the cruises. Surface pigment concentrations followed a seasonal cycle, with low concentrations (0.05-0.1 mg m(exp -3)) found within cyclones and anticyclones from April through early November and higher concentrations (greater than 0.1 mg(exp -3)) found in the winter. CZCS pigment concentrations were locally high in the flow confluence of cyclone-anticyclone pairs. The CZCS imagery shows that some cyclone-anticyclone geometries transport high-chlorophyll shelf water seaward at least 100-200 km off-shelf.

  17. Ship and satellite observations of chlorophyll stocks in interacting cyclone-anticyclone eddy pairs in the western Gulf of Mexico

    NASA Technical Reports Server (NTRS)

    Biggs, Douglas, C.; Mueller-Karger, Frank E.

    1994-01-01

    When anticyclonic eddies shed by the Loop Current of the Gulf of Mexico reach the western margin of the gulf, they influence the surface circulation over the continental slope and rise. Of particular interest is the generation of cyclone (cold-core)-anticyclone (warm-core) pairs when aging Loop Current eddies interact with the continental margin. In this paper we describe the physical and biological characteristics of these cyclone-anticyclone pairs. Our objective was to determine how eddy pairs affect the distribution of phytoplankton in the region and how satellite ocean color measurements are applicable to tracing of the eddies. We present shipboard data collected between 1980 and 1982 on the hydrography, chlorophyll stocks, and nutrient concentrations of eddy pairs in the western Gulf of Mexico and compare these data with coastal zone color scanner (CZCS) images collected during the time frame of the cruises. Surface pigment concentrations followed a seasonal cycle, with low concentrations (0.05-0.1 mg m(exp -3)) found within cyclones and anticyclones from April through early November and higher concentrations (greater than 0.1 mg(exp -3)) found in the winter. CZCS pigment concentrations were locally high in the flow confluence of cyclone-anticyclone pairs. The CZCS imagery shows that some cyclone-anticyclone geometries transport high-chlorophyll shelf water seaward at least 100-200 km off-shelf.

  18. Ship and satellite observations of chlorophyl stocks in interacting cyclone-anticyclone eddy pairs in the western Gulf of Mexico

    SciTech Connect

    Biggs, D.C.; Mueller-Karger, F.E.

    1994-04-15

    When anticyclonic eddies shed by the Loop Current of the Gulf of Mexico reach the western margin of the gulf, they influence the surface circulation over the continental slope and rise. Of particular interest is the generation of cyclone (cold-core)- anticyclone (warm-core) pairs when aging Loop Current eddies interact with the continental margin. In this paper the authors describe the physical and biological characteristics of these cyclone-anticyclone pairs. Their objective was to determine how eddy pairs affect the distribution of phytoplankton in the region and how satellite ocean color measurements are applicable to tracing of the eddies. They present shipboard data collected between 1980 and 1982 on the hydrography, chlorophyll stocks, and nutrient concentrations of eddy pairs in the western Gulf of Mexico and compare these data with coastal zone color scanner (CZCS) images collected during the time frame of the cruises. Surface pigment concentrations followed a seasonal cycle, with low concentrations (0.05-0.1 mg m{sup {minus}3}) found within cyclones and anticyclones from April through early November and higher concentrations (>0.1 mg m{sup {minus}3}) found in the winter. CZCS pigment concentrations were locally high in the flow confluence of cyclone-anticyclone pairs. The CZCS imagery shows that some cyclone-anticyclone geometries transport high-chlorophyll shelf water seaward at least 100-200 km off-shelf. 46 figs., 9 figs., 3 tabs.

  19. Pairing and unpairing electron densities in organic systems: two-electron three center through space and through bonds interactions.

    PubMed

    Lobayan, Rosana M; Bochicchio, Roberto C

    2014-05-07

    Two-electron three-center bonding interactions in organic ions like methonium (CH5(+)), ethonium (C2H7(+)), and protonated alkanes n - C4H11(+) isomers (butonium cations) are described and characterized within the theoretical framework of the topological analysis of the electron density decomposition into its effectively paired and unpaired contributions. These interactions manifest in some of this type of systems as a concentration of unpaired electron cloud around the bond paths, in contrast to the well known paradigmatic boron hydrids in which it is not only concentrated close to the atomic nucleus and the bond paths but out of them and over the region defined by the involved atoms as a whole. This result permits to propose an attempt of classification for these interactions based in such manifestations. In the first type, it is called as interactions through bonds and in the second type as interactions through space type.

  20. Thermoelectrics with Coulomb-coupled quantum dots

    NASA Astrophysics Data System (ADS)

    Thierschmann, Holger; Sánchez, Rafael; Sothmann, Björn; Buhmann, Hartmut; Molenkamp, Laurens W.

    2016-12-01

    In this article we review the thermoelectric properties of three terminal devices with Coulomb-coupled quantum dots (QDs) as observed in recent experiments [1,2]. The system we consider consists of two Coulomb-blockade QDs, one of which can exchange electrons with only a single reservoir (heat reservoir), while the other dot is tunnel coupled with two reservoirs at a lower temperature (conductor). The heat reservoir and the conductor interact only via the Coulomb coupling of the quantum dots. It has been found that two regimes have to be considered. In the first one, the heat flow between the two systems is small. In this regime, thermally driven occupation fluctuations of the hot QD modify the transport properties of the conductor system. This leads to an effect called thermal gating. Experiments have shown how this can be used to control charge flow in the conductor by means of temperature in a remote reservoir. We further substantiate the observations with model calculations, and implications for the realisation of an all-thermal transistor are discussed. In the second regime, the heat flow between the two systems is relevant. Here the system works as a nanoscale heat engine, as proposed recently (Sánchez and Büttiker [3]). We review the conceptual idea, its experimental realisation and the novel features arising in this new kind of thermoelectric device such as decoupling of heat and charge flow.

  1. A general test for gene-environment interaction in sib pair-based association analysis of quantitative traits.

    PubMed

    van der Sluis, Sophie; Dolan, Conor V; Neale, Michael C; Posthuma, Danielle

    2008-07-01

    Several association studies support the hypothesis that genetic variants can modify the influence of environmental factors on behavioral outcomes, i.e., G x E interaction. The case-control design used in these studies is powerful, but population stratification with respect to allele frequencies can give rise to false positive or false negative associations. Stratification with respect to the environmental factors can lead to false positives or false negatives with respect to environmental main effects and G x E interaction effects as well. Here we present a model based on Fulker et al. (1999) and Purcell (2002) for the study of G x E interaction in family-based association designs, in which the effects of stratification can be controlled. Simulations illustrate the power to detect genetic and environmental main effects, and G x E interaction effects for the sib pair design. The power to detect interaction was studied in eight different situations, both with and without the presence of population stratification, and for categorical and continuous environmental factors. Results show that the power to detect genetic and environmental main effects, and G x E interaction effects, depends on the allele frequencies and the distribution of the environmental moderator. Admixture effects of realistic effect size lead only to very small stratification effects in the G x E component, so impractically large numbers of sib pairs are required to detect such stratification.

  2. Importance of the ion-pair interactions in the OPEP coarse-grained force field: parametrization and validation.

    PubMed

    Sterpone, Fabio; Nguyen, Phuong H; Kalimeri, Maria; Derreumaux, Philippe

    2013-10-08

    We have derived new effective interactions that improve the description of ion-pairs in the OPEP coarse-grained force field without introducing explicit electrostatic terms. The iterative Boltzmann inversion method was used to extract these potentials from all atom simulations by targeting the radial distribution function of the distance between the center of mass of the side-chains. The new potentials have been tested on several systems that differ in structural properties, thermodynamic stabilities and number of ion-pairs. Our modeling, by refining the packing of the charged amino-acids, impacts the stability of secondary structure motifs and the population of intermediate states during temperature folding/unfolding; it also improves the aggregation propensity of peptides. The new version of the OPEP force field has the potentiality to describe more realistically a large spectrum of situations where salt-bridges are key interactions.

  3. Importance of the ion-pair interactions in the OPEP coarse-grained force field: parametrization and validation

    PubMed Central

    Sterpone, Fabio; Nguyen, Phuong H.; Kalimeri, Maria; Derreumaux, Philippe

    2014-01-01

    We have derived new effective interactions that improve the description of ion-pairs in the OPEP coarse-grained force field without introducing explicit electrostatic terms. The iterative Boltzmann inversion method was used to extract these potentials from all atom simulations by targeting the radial distribution function of the distance between the center of mass of the side-chains. The new potentials have been tested on several systems that differ in structural properties, thermodynamic stabilities and number of ion-pairs. Our modeling, by refining the packing of the charged amino-acids, impacts the stability of secondary structure motifs and the population of intermediate states during temperature folding/unfolding; it also improves the aggregation propensity of peptides. The new version of the OPEP force field has the potentiality to describe more realistically a large spectrum of situations where salt-bridges are key interactions. PMID:25419192

  4. Effects of interlayer Sn-Sn lone pair interaction on the band gap of bulk and nanosheet SnO

    NASA Astrophysics Data System (ADS)

    Umezawa, Naoto; Zhou, Wei

    2015-03-01

    Effects of interlayer lone-pair interactions on the electronic structure of SnO are firstly explored by the density-functional theory. Our comprehensive study reveals that the band gap of SnO opens as increase in the interlayer Sn-Sn distance. The effect is rationalized by the character of band edges which consists of bonding and anti-bonding states from interlayer lone pair interactions. The band edges for several nanosheets and strained double-layer SnO are estimated. We conclude that the double-layer SnO is a promising material for visible-light driven photocatalyst for hydrogen evolution. This work is supported by the Japan Science and Technology Agency (JST) Precursory Research for Embryonic Science and Technology (PRESTO) program.

  5. Influence of electron-electron interactions on pair tunneling through a mesoscopic N-S tunnel junction.

    NASA Astrophysics Data System (ADS)

    Huck, A. K.; Hekking, F. W. J.

    1997-03-01

    At low temperatures and voltages, smaller than the superconducting gap, transport through a normal metal - superconductor (N-S) tunnel barrier is due to tunneling of electrons in pairs. For a mesoscopic N-S tunnel junction, this process is very sensitive to quantum interference effects: pair tunneling is determined by particle-particle diffusion (Cooperon propagation) near the junction (F.W.J. Hekking, Yu.V. Nazarov, Phys. Rev. Lett. 70, 1625 (1993)). On the other hand it is well-known that electron-electron interactions in a disordered metal lead to significant corrections to particle-particle diffusion (Yu.N. Ovchinnikov, Sov. Phys. JETP 37, 366 (1973)). We explore the effect of the interplay between disorder and interactions on the subgap conductivity of a mesoscopic N-S tunnel junction.

  6. Cooper-pair splitter: towards an efficient source of spin-entangled EPR pairs

    NASA Astrophysics Data System (ADS)

    Schonenberger, Christian

    2011-03-01

    In quantum mechanics the properties of two and more particles can be entangled. In basic science pairs of entangled particles, so called Einstein-Podolsky-Rosen (EPR) pairs, play a special role as toy objects for fundamental studies. They provide such things as ``spooky interaction at distance,'' but they also enable secure encoding and teleportation and are thus important for applications in quantum information technology. Whereas EPR pairs of photons can be generated by parametric down conversion (PDC) in a crystal, a similar source for EPR pairs of electrons does not exists yet. In several theory papers, it has been suggested to use a superconductor for this purpose. The superconducting ground state is formed by a condensate of Cooper-pairs which are electron pairs in a spin-singlet state. Since there are many Cooper pairs in a metallic superconductor like Al, the main tasks are to extract Cooper pairs one by one and to split them into different arms. A controlled and efficient splitting is possible if one makes use of Coulomb interaction. This has recently be demonstrated by two groups [2-4] using hybrid quantum-dot devices with both superconducting and normal metal contacts. In the present talk, I will discuss the Cooper-pair splitter results from the Basel-Budapest-Copenhagen team and compare with the other experiments. As an outlook we discuss approaches that aim at entanglement detection. The Cooper pair splitter holds great promises because very large splitting efficiencies approaching 100% and large pair current rates appear feasible. This work has been done by L. Hofstetter, S. Csonka, A. Geresdi, M. Aagesen, J. Nygard and C. Schönenberger

  7. A computational analysis of protein interactions in metabolic networks reveals novel enzyme pairs potentially involved in metabolic channeling.

    PubMed

    Huthmacher, Carola; Gille, Christoph; Holzhütter, Hermann-Georg

    2008-06-07

    Protein-protein interactions are operative at almost every level of cell structure and function as, for example, formation of sub-cellular organelles, packaging of chromatin, muscle contraction, signal transduction, and regulation of gene expression. Public databases of reported protein-protein interactions comprise hundreds of thousands interactions, and this number is steadily growing. Elucidating the implications of protein-protein interactions for the regulation of the underlying cellular or extra-cellular reaction network remains a great challenge for computational biochemistry. In this work, we have undertaken a systematic and comprehensive computational analysis of reported enzyme-enzyme interactions in the metabolic networks of the model organisms Escherichia coli and Saccharomyces cerevisiae. We grouped all enzyme pairs according to the topological distance that the catalyzed reactions have in the metabolic network and performed a statistical analysis of reported enzyme-enzyme interactions within these groups. We found a higher frequency of reported enzyme-enzyme interactions within the group of enzymes catalyzing reactions that are adjacent in the network, i.e. sharing at least one metabolite. As some of these interacting enzymes have already been implicated in metabolic channeling our analysis may provide a useful screening for candidates of this phenomenon. To check for a possible regulatory role of interactions between enzymes catalyzing non-neighboring reactions, we determined potentially regulatory enzymes using connectivity in the network and absolute change of Gibbs free energy. Indeed a higher portion of reported interactions pertain to such potentially regulatory enzymes.

  8. Controlling the transmitted information of a multi-photon interacting with a single-Cooper pair box

    SciTech Connect

    Kadry, Heba Abdel-Aty, Abdel-Haleem Zakaria, Nordin; Cheong, Lee Yen

    2014-10-24

    We study a model of a multi-photon interaction of a single Cooper pair box with a cavity field. The exchange of the information using this system is studied. We quantify the fidelity of the transmitted information. The effect of the system parameters (detuning parameter, field photons, state density and mean photon number) in the fidelity of the transmitted information is investigated. We found that the fidelity of the transmitted information can be controlled using the system parameters.

  9. Simulation of FREE→FREE Absorption Spectra and the Calculation of Interaction Potentials for Alkali-Rare Gas Atom Pairs

    NASA Astrophysics Data System (ADS)

    Hewitt, J. Darby; Spinka, Thomas M.; Readle, Jason. D.; Eden, J. Gary

    2013-06-01

    We have simulated free→free (X^2Σ^+_{1/2}→B^2Σ^+_{1/2}) absorption spectra for alkali-rare gas pairs. By comparing simulation results with experimental data, we have been able to iteratively determine the form for the B^2Σ^+_{1/2} interaction potential for the system for a range in internuclear separation of 1.5-20 Å. Simulation methods will be presented, as will our results pertaining to Cs-Ar.

  10. Tracing the Optical Imprints of AN Intermediate-Mass Black Hole Candidate in AN Interacting Galaxy Pair

    NASA Astrophysics Data System (ADS)

    Fuentes-Carrera, I.; Rosado, M.; Flores, H.; Borissova, J.

    We present observations of the extended optical counterpart of the bright, elongated ULX in the interacting galaxy pair NGC 5953/54 using the FLAMES-ARGUS integral field spectrograph on the VLT. We describe spectroscopic and spatial information of the ionized surroundings of this ULX in order to distinguish between two possible scenarios: a stellar-mass black hole binary or an intermediate-mass ( 50 solar masses) black hole.

  11. Interaction of formaldehyde with a water-tolerant frustrated Lewis pair.

    PubMed

    Ghattas, Ghazi; Bizzarri, Claudia; Hölscher, Markus; Langanke, Jens; Gürtler, Christoph; Leitner, Walter; Subhani, Muhammad Afzal

    2017-03-02

    A facile complexation of formaldehyde with the water-tolerant frustrated Lewis pair (FLP) B(C6F5)3/PtBu3 and its Al-analog under ambient conditions is reported. Unprecedented formaldehyde adducts 1, 2 and 4 have been identified and crystallographically characterized.

  12. Attention to Form in Collaborative Writing Tasks: Comparing Pair and Small Group Interaction

    ERIC Educational Resources Information Center

    Dobao, Ana Fernández

    2014-01-01

    This study examines the opportunities that a collaborative writing task completed in pairs and in small groups offers for attention to form. Previous research suggests that collaborative writing activities encourage learners to focus their attention on language and to collaborate in the resolution of their language-related problems in ways that…

  13. Attention to Form in Collaborative Writing Tasks: Comparing Pair and Small Group Interaction

    ERIC Educational Resources Information Center

    Dobao, Ana Fernández

    2014-01-01

    This study examines the opportunities that a collaborative writing task completed in pairs and in small groups offers for attention to form. Previous research suggests that collaborative writing activities encourage learners to focus their attention on language and to collaborate in the resolution of their language-related problems in ways that…

  14. Electron attraction mediated by Coulomb repulsion.

    PubMed

    Hamo, A; Benyamini, A; Shapir, I; Khivrich, I; Waissman, J; Kaasbjerg, K; Oreg, Y; von Oppen, F; Ilani, S

    2016-07-21

    One of the defining properties of electrons is their mutual Coulomb repulsion. However, in solids this basic property may change; for example, in superconductors, the coupling of electrons to lattice vibrations makes the electrons attract one another, leading to the formation of bound pairs. Fifty years ago it was proposed that electrons can be made attractive even when all of the degrees of freedom in the solid are electronic, by exploiting their repulsion from other electrons. This attraction mechanism, termed 'excitonic', promised to achieve stronger and more exotic superconductivity. Yet, despite an extensive search, experimental evidence for excitonic attraction has yet to be found. Here we demonstrate this attraction by constructing, from the bottom up, the fundamental building block of the excitonic mechanism. Our experiments are based on quantum devices made from pristine carbon nanotubes, combined with cryogenic precision manipulation. Using this platform, we demonstrate that two electrons can be made to attract each other using an independent electronic system as the 'glue' that mediates attraction. Owing to its tunability, our system offers insights into the underlying physics, such as the dependence of the emergent attraction on the underlying repulsion, and the origin of the pairing energy. We also demonstrate transport signatures of excitonic pairing. This experimental demonstration of excitonic pairing paves the way for the design of exotic states of matter.

  15. Electron attraction mediated by Coulomb repulsion

    NASA Astrophysics Data System (ADS)

    Hamo, A.; Benyamini, A.; Shapir, I.; Khivrich, I.; Waissman, J.; Kaasbjerg, K.; Oreg, Y.; von Oppen, F.; Ilani, S.

    2016-07-01

    One of the defining properties of electrons is their mutual Coulomb repulsion. However, in solids this basic property may change; for example, in superconductors, the coupling of electrons to lattice vibrations makes the electrons attract one another, leading to the formation of bound pairs. Fifty years ago it was proposed that electrons can be made attractive even when all of the degrees of freedom in the solid are electronic, by exploiting their repulsion from other electrons. This attraction mechanism, termed ‘excitonic’, promised to achieve stronger and more exotic superconductivity. Yet, despite an extensive search, experimental evidence for excitonic attraction has yet to be found. Here we demonstrate this attraction by constructing, from the bottom up, the fundamental building block of the excitonic mechanism. Our experiments are based on quantum devices made from pristine carbon nanotubes, combined with cryogenic precision manipulation. Using this platform, we demonstrate that two electrons can be made to attract each other using an independent electronic system as the ‘glue’ that mediates attraction. Owing to its tunability, our system offers insights into the underlying physics, such as the dependence of the emergent attraction on the underlying repulsion, and the origin of the pairing energy. We also demonstrate transport signatures of excitonic pairing. This experimental demonstration of excitonic pairing paves the way for the design of exotic states of matter.

  16. Self-Induced Oscillation for Electron-Hole Pair Confined in Quantum Dot

    SciTech Connect

    Tagawa, Tomoki; Tsubaki, Atsushi; Ishizuki, Masamu; Takeda, Kyozaburo

    2011-12-23

    We study the time-dependent (TD) phenomena of the electron-hole or electron-electron pair confined in the square quantum dot (SQD) system by computationally solving TD Schroedinger equation under the unrestricted Hartree-Fock (UHF) approach. A typical vacillation is found both in the electron and hole when the charged pair is strongly confined in the SQD while the charged particles have initially the same orbital symmetry. The FFT analysis elucidates that the transition matrix element due to the coulomb interaction involves the eigen frequency {omega} being equal to the excitation energy when the resonative vacillation appears. Thus, Coulomb potential has a potential to cause the self-induced ''Rabi'' oscillation when the charged-particle pair is confined only in the QD.

  17. Resonance energy transfer (RET)-Induced intermolecular pairing force: a tunable weak interaction and its application in SWNT separation.

    PubMed

    Pan, Xiaoyong; Chen, Hui; Wang, Wei Zhi; Ng, Siu Choon; Chan-Park, Mary B

    2011-07-21

    This paper explores evidence of an optically mediated interaction that is active in the separation mechanism of certain selective agents through consideration of the contrasting selective behaviors of two conjugated polymers with distinct optical properties. The involvement of a RET-induced intermolecular pairing force is implied by the different illumination response behaviors. The magnitude of this interaction scales with the external stimulus parameter, the illumination irradiance (I), and thus is tunable. This suggests a facile technique to modify the selectivity of polymers toward specific SWNT species by altering the polymer structure to adjust the corresponding intermolecular interaction. This is the first experimental verification and application of a RET-induced intermolecular pairing force to SWNT separation. With this kind of interaction taken into account, reasonable interpretation of some conflicting data, especially PLE maps, can be easily made. The above conclusion can be applied to other substances as long as they are electrically neutral and there is photon-induced RET between them. The significant magnitude of this interaction makes direct manipulation of molecules/particles possible and is expected to have applications in molecular engineering.

  18. Fano effect dominance over Coulomb blockade in transport properties of parallel coupled quantum dot system

    SciTech Connect

    Brogi, Bharat Bhushan Ahluwalia, P. K.; Chand, Shyam

    2015-06-24

    Theoretical study of the Coulomb blockade effect on transport properties (Transmission Probability and I-V characteristics) for varied configuration of coupled quantum dot system has been studied by using Non Equilibrium Green Function(NEGF) formalism and Equation of Motion(EOM) method in the presence of magnetic flux. The self consistent approach and intra-dot Coulomb interaction is being taken into account. As the key parameters of the coupled quantum dot system such as dot-lead coupling, inter-dot tunneling and magnetic flux threading through the system can be tuned, the effect of asymmetry parameter and magnetic flux on this tuning is being explored in Coulomb blockade regime. The presence of the Coulomb blockade due to on-dot Coulomb interaction decreases the width of transmission peak at energy level ε + U and by adjusting the magnetic flux the swapping effect in the Fano peaks in asymmetric and symmetric parallel configuration sustains despite strong Coulomb blockade effect.

  19. Fano effect dominance over Coulomb blockade in transport properties of parallel coupled quantum dot system

    NASA Astrophysics Data System (ADS)

    Brogi, Bharat Bhushan; Chand, Shyam; Ahluwalia, P. K.

    2015-06-01

    Theoretical study of the Coulomb blockade effect on transport properties (Transmission Probability and I-V characteristics) for varied configuration of coupled quantum dot system has been studied by using Non Equilibrium Green Function(NEGF) formalism and Equation of Motion(EOM) method in the presence of magnetic flux. The self consistent approach and intra-dot Coulomb interaction is being taken into account. As the key parameters of the coupled quantum dot system such as dot-lead coupling, inter-dot tunneling and magnetic flux threading through the system can be tuned, the effect of asymmetry parameter and magnetic flux on this tuning is being explored in Coulomb blockade regime. The presence of the Coulomb blockade due to on-dot Coulomb interaction decreases the width of transmission peak at energy level ɛ + U and by adjusting the magnetic flux the swapping effect in the Fano peaks in asymmetric and symmetric parallel configuration sustains despite strong Coulomb blockade effect.

  20. A Survey of Aspartate-Phenylalanine and Glutamate-Phenylalanine Interactions in the Protein Data Bank: Searching for Anion-pi Pairs

    SciTech Connect

    Philip, Vivek M; Harris, Jason B; Adams, Rachel M; Nguyen, Don; Spiers, Jeremy D; Baudry, Jerome Y; Howell, Elizabeth E; Hinde, Robert J

    2011-01-01

    Protein structures are stabilized using noncovalent interactions. In addition to the traditional noncovalent interactions, newer types of interactions are thought to be present in proteins. One such interaction, an anion-{pi} pair, in which the positively charged edge of an aromatic ring interacts with an anion, forming a favorable anion-quadrupole interaction, has been previously proposed [Jackson, M. R., et al. (2007) J. Phys. Chem. B111, 8242-8249]. To study the role of anion-{pi} interactions in stabilizing protein structure, we analyzed pairwise interactions between phenylalanine (Phe) and the anionic amino acids, aspartate (Asp) and glutamate (Glu). Particular emphasis was focused on identification of Phe-Asp or -Glu pairs separated by less than 7 {angstrom} in the high-resolution, nonredundant Protein Data Bank. Simplifying Phe to benzene and Asp or Glu to formate molecules facilitated in silico analysis of the pairs. Kitaura-Morokuma energy calculations were performed on roughly 19000 benzene-formate pairs and the resulting energies analyzed as a function of distance and angle. Edgewise interactions typically produced strongly stabilizing interaction energies (-2 to -7.3 kcal/mol), while interactions involving the ring face resulted in weakly stabilizing to repulsive interaction energies. The strongest, most stabilizing interactions were identified as preferentially occurring in buried residues. Anion-{pi} pairs are found throughout protein structures, in helices as well as {beta} strands. Numerous pairs also had nearby cation-{pi} interactions as well as potential {pi}-{pi} stacking. While more than 1000 structures did not contain an anion-{pi} pair, the 3134 remaining structures contained approximately 2.6 anion-{pi} pairs per protein, suggesting it is a reasonably common motif that could contribute to the overall structural stability of a protein.

  1. Extended Fluid-Dynamics and Collective Motion of Two Trapped Fermion Species with Pairing Interactions

    NASA Astrophysics Data System (ADS)

    Hernández, E. S.; Capuzzi, P.; Szybisz, L.

    2011-02-01

    We extend our earlier fluid-dynamical description of fermion superfluids incorporating the particle energy flow together with the equation of motion for the internal kinetic energy of the pairs. The formal scheme combines a set of equations similar to those of classical hydrodynamics with the equations of motion for the anomalous density and for its related momentum density and kinetic energy density. This dynamical frame represents a second order truncation of an infinite hierarchy of equations of motion isomorphic to the full time dependent Hartree-Fock-Bogoliubov equations in coordinate representation. We analyze the equilibrium solutions and fluctuations for a homogeneous, unpolarized fermion system of two species, and show that the collective spectrum presents the well-known Anderson-Bogoliubov low energy mode of homogeneous superfluids and a pairing vibration near the gap energy.

  2. Discovering Pair-Wise Genetic Interactions: An Information Theory-Based Approach

    PubMed Central

    Ignac, Tomasz M.; Skupin, Alexander; Sakhanenko, Nikita A.; Galas, David J.

    2014-01-01

    Phenotypic variation, including that which underlies health and disease in humans, results in part from multiple interactions among both genetic variation and environmental factors. While diseases or phenotypes caused by single gene variants can be identified by established association methods and family-based approaches, complex phenotypic traits resulting from multi-gene interactions remain very difficult to characterize. Here we describe a new method based on information theory, and demonstrate how it improves on previous approaches to identifying genetic interactions, including both synthetic and modifier kinds of interactions. We apply our measure, called interaction distance, to previously analyzed data sets of yeast sporulation efficiency, lipid related mouse data and several human disease models to characterize the method. We show how the interaction distance can reveal novel gene interaction candidates in experimental and simulated data sets, and outperforms other measures in several circumstances. The method also allows us to optimize case/control sample composition for clinical studies. PMID:24670935

  3. Electron-hydrogen atom-impact 1s{yields}2s and 1s{yields}2p excitation with screened Coulomb interaction between the n=2 and n=3 excitation thresholds

    SciTech Connect

    Zhang Songbin; Chen Xiangjun; Wang Jianguo; Janev, R. K.

    2011-03-15

    The effects of Coulomb interaction screening on electron-hydrogen atom 1S {yields} 2S and 1S {yields} 2p excitation scattering between the n = 2 and n = 3 excitation thresholds have been investigated by using the R-matrix method with pseudostates. The excitation collision strengths show dramatic changes when the interaction screening length D varies from {infinity} to 9 a.u., as a result of the convergence of S-type and some p- and D-type Feshbach resonances to the varying 3S or 3p thresholds, and due to the crossover of some other p-, D- and all F-type Feshbach resonances into shape-type resonances when they pass across the 3S or 3p threshold at certain critical values of D. The noncrossover of some p- and D-type Feshbach resonances into shape-type resonances at the 3S (or 3p for those of D-type) threshold is at variance with the behavior of these types of resonances at the 2S (2p for those of D-type) threshold, which results from the threefold splitting of the n = 3 hydrogenic level and, consequently, the more complex nature of the configuration mixing in the n = 3 threshold region. The evolution of the total 1S {yields} 2S, 1S {yields} 2p, and 2S {yields} 2p excitation collision strengths, when the screening strength varies, is presented and discussed.

  4. Superconducting transition temperatures and coherence length in non-s-wave pairing materials correlated with spin-fluctuation mediated interaction

    NASA Astrophysics Data System (ADS)

    Angilella, G. G.; March, N. H.; Pucci, R.

    2002-03-01

    Following earlier work on electron or hole liquids flowing through assemblies with magnetic fluctuations, we have recently exposed a marked correlation of the superconducting temperature Tc, for non-s-wave pairing materials, with coherence length ξ and effective mass m*. The very recent study of Abanov et al. [Europhys. Lett. 54, 488 (2001)] and the prior investigation of Monthoux and Lonzarich [Phys. Rev. B 59, 14 598 (1999)] have each focused on the concept of a spin-fluctuation temperature Tsf, which again is intimately related to Tc. For the d-wave pairing via antiferromagnetic spin fluctuations in the cuprates, these studies are brought into close contact with our own work, and the result is that kBTsf~ħ2/m*ξ2. This demonstrates that ξ is also determined by such antiferromagnetic spin-fluctuation mediated pair interaction. The coherence length in units of the lattice spacing is then essentially given in the cuprates as the square root of the ratio of two characteristic energies, namely, the kinetic energy of localization of a charge carrier of mass m* in a specified magnetic correlation length to the hopping energy. The quasi-two-dimensional ruthenate Sr2RuO4, with Tc~1.3 K, has p-wave spin-triplet pairing and so is also briefly discussed here.

  5. Radiative capture versus Coulomb dissociation.

    SciTech Connect

    Esbensen, H.; Physics

    2006-01-01

    Measurements of the Coulomb dissociation of {sup 8}B have been used to infer the rate of the inverse radiative proton capture on {sup 7}Be. The analysis is usually based on the assumptions that the two processes are related by detailed balance and described by E1 transitions. However, there are corrections to this relation. The Coulomb form factors for the two processes, for example, are not identical. There are also E2 transitions and higher-order effects in the Coulomb dissociation, and the nuclear induced breakup cannot always be ignored. While adding first-order E2 transitions enhances the decay energy spectrum, the other mechanisms cause a suppression at low relative energies. The net result may accidentally be close to the conventional first-order E1 calculation, but there are differences which cannot be ignored if accuracies of 10% or better are needed.

  6. Bound eigenstates for two truncated Coulomb potentials

    NASA Astrophysics Data System (ADS)

    Singh, David; Varshni, Y. P.; Dutt, Ranabir

    1985-07-01

    The eigenvalue problem for two particles interacting through the attractive truncated Coulomb potential, V(r)=-Ze2/(rp+βp)1/p, for p=1 and 2 is solved numerically. Energy eigenvalues accurate to within eight to six significant figures for the states 1s to 4f are calculated as a function of the truncation parameter β. It is found that the level ordering satisfies Enl>Enl' for l

  7. Molecular-Level Thermodynamic Switch Controls Chemical Equilibrium in Sequence-Specific Hydrophobic Interaction of 35 Dipeptide Pairs

    PubMed Central

    Chun, Paul W.

    2003-01-01

    Applying the Planck-Benzinger methodology, the sequence-specific hydrophobic interactions of 35 dipeptide pairs were examined over a temperature range of 273–333 K, based on data reported by Nemethy and Scheraga in 1962. The hydrophobic interaction in these sequence-specific dipeptide pairs is highly similar in its thermodynamic behavior to that of other biological systems. The results imply that the negative Gibbs free energy change minimum at a well-defined stable temperature, 〈Ts〉, where the bound unavailable energy, TΔSo = 0, has its origin in the sequence-specific hydrophobic interactions, are highly dependent on details of molecular structure. Each case confirms the existence of a thermodynamic molecular switch wherein a change of sign in ΔCpo(T)reaction (change in specific heat capacity of reaction at constant pressure) leads to true negative minimum in the Gibbs free energy change of reaction, ΔGo(T)reaction, and hence a maximum in the related equilibrium constant, Keq. Indeed, all interacting biological systems examined to date by Chun using the Planck-Benzinger methodology have shown such a thermodynamic switch at the molecular level, suggesting its existence may be universal. PMID:12547816

  8. Condensates of p-wave pairs are exact solutions for rotating two-component Bose gases.

    PubMed

    Papenbrock, T; Reimann, S M; Kavoulakis, G M

    2012-02-17

    We derive exact analytical results for the wave functions and energies of harmonically trapped two-component Bose-Einstein condensates with weakly repulsive interactions under rotation. The isospin symmetric wave functions are universal and do not depend on the matrix elements of the two-body interaction. The comparison with the results from numerical diagonalization shows that the ground state and low-lying excitations consist of condensates of p-wave pairs for repulsive contact interactions, Coulomb interactions, and the repulsive interactions between aligned dipoles.

  9. Condensates of p-Wave Pairs Are Exact Solutions for Rotating Two-Component Bose Gases

    SciTech Connect

    Papenbrock, T; Kavoulakis, G. M.

    2012-01-01

    We derive exact analytical results for the wave functions and energies of harmonically trapped two-component Bose-Einstein condensates with weakly repulsive interactions under rotation. The isospin symmetric wave functions are universal and do not depend on the matrix elements of the two-body interaction. The comparison with the results from numerical diagonalization shows that the ground state and low-lying excitations consist of condensates of p-wave pairs for repulsive contact interactions, Coulomb interactions, and the repulsive interactions between aligned dipoles.

  10. Structural variability and the nature of intermolecular interactions in Watson-Crick B-DNA base pairs.

    PubMed

    Czyznikowska, Z; Góra, R W; Zaleśny, R; Lipkowski, P; Jarzembska, K N; Dominiak, P M; Leszczynski, J

    2010-07-29

    A set of nearly 100 crystallographic structures was analyzed using ab initio methods in order to verify the effect of the conformational variability of Watson-Crick guanine-cytosine and adenine-thymine base pairs on the intermolecular interaction energy and its components. Furthermore, for the representative structures, a potential energy scan of the structural parameters describing mutual orientation of the base pairs was carried out. The results were obtained using the hybrid variational-perturbational interaction energy decomposition scheme. The electron correlation effects were estimated by means of the second-order Møller-Plesset perturbation theory and coupled clusters with singles and doubles method adopting AUG-cc-pVDZ basis set. Moreover, the characteristics of hydrogen bonds in complexes, mimicking those appearing in B-DNA, were evaluated using topological analysis of the electron density. Although the first-order electrostatic energy is usually the largest stabilizing component, it is canceled out by the associated exchange repulsion in majority of the studied crystallographic structures. Therefore, the analyzed complexes of the nucleic acid bases appeared to be stabilized mainly by the delocalization component of the intermolecular interaction energy which, in terms of symmetry adapted perturbation theory, encompasses the second- and higher-order induction and exchange-induction terms. Furthermore, it was found that the dispersion contribution, albeit much smaller in terms of magnitude, is also a vital stabilizing factor. It was also revealed that the intermolecular interaction energy and its components are strongly influenced by four (out of six) structural parameters describing mutual orientation of bases in Watson-Crick pairs, namely shear, stagger, stretch, and opening. Finally, as a part of a model study, much of the effort was devoted to an extensive testing of the UBDB databank. It was shown that the databank quite successfully reproduces the

  11. Modelling gamma-ray photon emission and pair production in high-intensity laser–matter interactions

    SciTech Connect

    Ridgers, C.P.; Kirk, J.G.; Duclous, R.; Blackburn, T.G.; Brady, C.S.; Bennett, K.; Arber, T.D.; Bell, A.R.

    2014-03-01

    In high-intensity (>10{sup 21} Wcm{sup −2}) laser–matter interactions gamma-ray photon emission by the electrons can strongly affect the electron's dynamics and copious numbers of electron–positron pairs can be produced by the emitted photons. We show how these processes can be included in simulations by coupling a Monte Carlo algorithm describing the emission to a particle-in-cell code. The Monte Carlo algorithm includes quantum corrections to the photon emission, which we show must be included if the pair production rate is to be correctly determined. The accuracy, convergence and energy conservation properties of the Monte Carlo algorithm are analysed in simple test problems.

  12. Momentum correlations of charmed pairs produced in π--Cu interactions at 230 GeV/c

    NASA Astrophysics Data System (ADS)

    Rybicki, K.; Ryłko, R.

    1995-02-01

    We study the production characteristics of 557 pairs of charmed hadrons produced in π--Cu interactions at 230 GeV/c using a momentum estimator for charmed hadrons with missing decay products. We find: the mean value of the transverse momentum squared of the charmed pairs is < pT, sum 2> = (1.98 ± 0.11 ± 0.09) GeV 2/c 2, the mean rapidity difference is < | ydiff| > = 0.54 ± 0.02 ± 0.24, and the mean effective mass is < Meff> = (4.45 ± 0.03 ± 0.13) GeV/c 2. Comparing these results with the next-to-leading order QCD predictions we find an agreement for ydiff and Meff, whilst the measured mean value of pT, sum 2 is significantly larger than the predicted value.

  13. Cold Fermions with Pairing Interactions: New Results Based on Fluiddynamical Descriptions

    NASA Astrophysics Data System (ADS)

    Capuzzi, P.; Hernández, E. S.; Szybisz, L.

    2012-03-01

    We present a rigorous derivation of the moment hierarchy of the density and pair density matrices of a two species fermion superfluid in coordinate representation. We discuss the tools to truncate at any desired level and present the derivation of the Extended Superfluid Thomas-Fermi (ESTF) fluiddynamical scheme. In order to establish the equation of state in equilibrium to be incorporated in the truncation, we extend the method of Papenbrock and Bertsch. We examine the dynamics of fluctuations in homogeneous fermion matter and show that it is consistent with the ordinary Random-Phase-approximation. We discuss some numerical results for equilibrium profiles and collective fluctuations of trapped cold gases.

  14. Systematic Mapping of WNT-FZD Protein Interactions Reveals Functional Selectivity by Distinct WNT-FZD Pairs*

    PubMed Central

    Dijksterhuis, Jacomijn P.; Baljinnyam, Bolormaa; Stanger, Karen; Sercan, Hakki O.; Ji, Yun; Andres, Osler; Rubin, Jeffrey S.; Hannoush, Rami N.; Schulte, Gunnar

    2015-01-01

    The seven-transmembrane-spanning receptors of the FZD1–10 class are bound and activated by the WNT family of lipoglycoproteins, thereby inducing a complex network of signaling pathways. However, the specificity of the interaction between mammalian WNT and FZD proteins and the subsequent signaling cascade downstream of the different WNT-FZD pairs have not been systematically addressed to date. In this study, we determined the binding affinities of various WNTs for different members of the FZD family by using bio-layer interferometry and characterized their functional selectivity in a cell system. Using purified WNTs, we show that different FZD cysteine-rich domains prefer to bind to distinct WNTs with fast on-rates and slow off-rates. In a 32D cell-based system engineered to overexpress FZD2, FZD4, or FZD5, we found that WNT-3A (but not WNT-4, -5A, or -9B) activated the WNT-β-catenin pathway through FZD2/4/5 as measured by phosphorylation of LRP6 and β-catenin stabilization. Surprisingly, different WNT-FZD pairs showed differential effects on phosphorylation of DVL2 and DVL3, revealing a previously unappreciated DVL isoform selectivity by different WNT-FZD pairs in 32D cells. In summary, we present extensive mapping of WNT-FZD cysteine-rich domain interactions complemented by analysis of WNT-FZD pair functionality in a unique cell system expressing individual FZD isoforms. Differential WNT-FZD binding and selective functional readouts suggest that endogenous WNT ligands evolved with an intrinsic natural bias toward different downstream signaling pathways, a phenomenon that could be of great importance in the design of FZD-targeting drugs. PMID:25605717

  15. Chromatin Interaction Analysis with Paired-End Tag Sequencing (ChIA-PET) for Mapping Chromatin Interactions and Understanding Transcription Regulation

    PubMed Central

    Poh, Huay Mei; Peh, Su Qin; Ong, Chin Thing; Zhang, Jingyao; Ruan, Xiaoan; Ruan, Yijun

    2012-01-01

    Genomes are organized into three-dimensional structures, adopting higher-order conformations inside the micron-sized nuclear spaces 7, 2, 12. Such architectures are not random and involve interactions between gene promoters and regulatory elements 13. The binding of transcription factors to specific regulatory sequences brings about a network of transcription regulation and coordination 1, 14. Chromatin Interaction Analysis by Paired-End Tag Sequencing (ChIA-PET) was developed to identify these higher-order chromatin structures 5,6. Cells are fixed and interacting loci are captured by covalent DNA-protein cross-links. To minimize non-specific noise and reduce complexity, as well as to increase the specificity of the chromatin interaction analysis, chromatin immunoprecipitation (ChIP) is used against specific protein factors to enrich chromatin fragments of interest before proximity ligation. Ligation involving half-linkers subsequently forms covalent links between pairs of DNA fragments tethered together within individual chromatin complexes. The flanking MmeI restriction enzyme sites in the half-linkers allow extraction of paired end tag-linker-tag constructs (PETs) upon MmeI digestion. As the half-linkers are biotinylated, these PET constructs are purified using streptavidin-magnetic beads. The purified PETs are ligated with next-generation sequencing adaptors and a catalog of interacting fragments is generated via next-generation sequencers such as the Illumina Genome Analyzer. Mapping and bioinformatics analysis is then performed to identify ChIP-enriched binding sites and ChIP-enriched chromatin interactions 8. We have produced a video to demonstrate critical aspects of the ChIA-PET protocol, especially the preparation of ChIP as the quality of ChIP plays a major role in the outcome of a ChIA-PET library. As the protocols are very long, only the critical steps are shown in the video. PMID:22564980

  16. Aromatic N versus aromatic F: bioisosterism discovered in RNA base pairing interactions leads to a novel class of universal base analogs.

    PubMed

    Koller, Alrun N; Bozilovic, Jelena; Engels, Joachim W; Gohlke, Holger

    2010-05-01

    The thermodynamics of base pairing is of fundamental importance. Fluorinated base analogs are valuable tools for investigating pairing interactions. To understand the influence of direct base-base interactions in relation to the role of water, pairing free energies between natural nucleobases and fluorinated analogs are estimated by potential of mean force calculations. Compared to pairing of AU and GC, pairing involving fluorinated analogs is unfavorable by 0.5-1.0 kcal mol(-1). Decomposing the pairing free energies into enthalpic and entropic contributions reveals fundamental differences for Watson-Crick pairs compared to pairs involving fluorinated analogs. These differences originate from direct base-base interactions and contributions of water. Pairing free energies of fluorinated base analogs with natural bases are less unfavorable by 0.5-1.0 kcal mol(-1) compared to non-fluorinated analogs. This is attributed to stabilizing C-F(...)H-N dipolar interactions and stronger N(...)H-C hydrogen bonds, demonstrating direct and indirect influences of fluorine. 7-methyl-7H-purine and its 9-deaza analog (Z) have been suggested as members of a new class of non-fluorinated base analogs. Z is found to be the least destabilizing universal base in the context of RNA known to date. This is the first experimental evidence for nitrogen-containing heterocylces as bioisosteres of aromatic rings bearing fluorine atoms.

  17. Enthalpy pair coefficients of interaction for DL-valine in aqueous solutions of polyatomic alcohols at 298 K

    NASA Astrophysics Data System (ADS)

    Mezhevoi, I. N.; Badelin, V. G.

    2013-12-01

    Integral enthalpies of dissolution Δsol H m of DL-valine are measured via calorimetry of dissolution in aqueous solutions of glycerol, ethylene glycol, and 1,2-propylene glycol. Standard values of the enthalpies of dissolution (Δsol H ○) and transfer (Δtr H ○) of amino acid from water to mixed solvent are calculated from the resulting experimental data. The enthalpy coefficients for pair interactions hxy of amino acid with polyatomic alcohol molecules are calculated using the McMillan-Meyer theory and have positive values. The obtained results are discussed in light of the theory of the predomination of various types of interactions in mixed solutions and the effect of structural features of interacting biomolecules on the thermochemical parameters of the dissolution of amino acids.

  18. RETIRED A STARS AND THEIR COMPANIONS. VI. A PAIR OF INTERACTING EXOPLANET PAIRS AROUND THE SUBGIANTS 24 SEXTANIS AND HD 200964

    SciTech Connect

    Johnson, John Asher; Payne, Matthew; Ford, Eric B.; Howard, Andrew W.; Marcy, Geoffrey W.; Clubb, Kelsey I.; Bowler, Brendan P.; Henry, Gregory W.; Fischer, Debra A.; Brewer, John M.; Schwab, Christian; Reffert, Sabine; Lowe, Thomas B.

    2011-01-15

    We report radial velocity (RV) measurements of the G-type subgiants 24 Sextanis (= HD 90043) and HD 200964. Both are massive, evolved stars that exhibit periodic variations due to the presence of a pair of Jovian planets. Photometric monitoring with the T12 0.80 m APT at Fairborn Observatory demonstrates both stars to be constant in brightness to {<=}0.002 mag, thus strengthening the planetary interpretation of the RV variations. Based on our dynamical analysis of the RV time series, 24 Sex b, c have orbital periods of 452.8 days and 883.0 days, corresponding to semimajor axes 1.333 AU and 2.08 AU, and minimum masses 1.99 M{sub Jup} and 0.86 M{sub Jup}, assuming a stellar mass M{sub *}= 1.54 M{sub sun}. HD 200964 b, c have orbital periods of 613.8 days and 825.0 days, corresponding to semimajor axes 1.601 AU and 1.95 AU, and minimum masses 1.99 M{sub Jup} and 0.90 M{sub Jup}, assuming M{sub *}= 1.44 M{sub sun}. We also carry out dynamical simulations to properly account for gravitational interactions between the planets. Most, if not all, of the dynamically stable solutions include crossing orbits, suggesting that each system is locked in a mean-motion resonance that prevents close encounters and provides long-term stability. The planets in the 24 Sex system likely have a period ratio near 2:1, while the HD 200964 system is even more tightly packed with a period ratio close to 4:3. However, we caution that further RV observations and more detailed dynamical modeling will be required to provide definitive and unique orbital solutions for both cases, and to determine whether the two systems are truly resonant.

  19. Density functional theory investigation of interaction of zigzag (7,0) single-walled carbon nanotube with Watson-Crick DNA base pairs

    NASA Astrophysics Data System (ADS)

    Shukla, Manoj K.; Dubey, Madan; Zakar, Eugene; Namburu, Raju; Leszczynski, Jerzy

    2010-08-01

    A first-principles investigation of interaction of DNA base pairs on the outer surface of zigzag (7,0) single-walled carbon nanotube (CNT) was carried out at the M05-2X/6-31G(d) level of geometry optimization and BSSE corrected interaction energy calculation using the same theoretical level and the 6-311G(d,p), cc-pVDZ and cc-pVTZ basis sets. Study revealed that CNT forms complexes of similar strength with both base pairs. Electron density maps suggest that complexes are characterized by stacking interaction through coupling of π-charge clouds of base pairs and CNT. BSSE corrected interaction energies and density of states calculations indicated the weak nature of interaction between base pairs and CNT.

  20. Long-range Coulomb interactions in surface systems: a first-principles description within self-consistently combined GW and dynamical mean-field theory.

    PubMed

    Hansmann, P; Ayral, T; Vaugier, L; Werner, P; Biermann, S

    2013-04-19

    Systems of adatoms on semiconductor surfaces display competing ground states and exotic spectral properties typical of two-dimensional correlated electron materials which are dominated by a complex interplay of spin and charge degrees of freedom. We report a fully ab initio derivation of low-energy Hamiltonians for the adatom systems Si(111):X, with X=Sn, Si, C, Pb, that we solve within self-consistently combined GW and dynamical mean-field theory. Calculated photoemission spectra are in agreement with available experimental data. We rationalize experimentally observed trends from Mott physics toward charge ordering along the series as resulting from substantial long-range interactions.