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Sample records for pair coulomb interaction

  1. Coulomb interactions and fermion condensation

    SciTech Connect

    Capstick, S.; Cutkosky, R.E.; Joensen, M.A. ); Wang, K.C. )

    1990-08-15

    The influence of the Coulomb interaction in states containing massless and flavorless fermion-antifermion pairs is studied, using a continuum formulation within the finite volume {ital S}{sup 3}. Several different forms for the Coulomb interaction are examined, including confining potentials as well as nonconfining potentials. The calculations show that if the interaction is strong enough, the Coulomb interaction leads to condensation of pairs, and that this condensation has a chiral character. The condensation does not depend on whether the interaction is confining. It is found that simplified variational approximations are not accurate enough for an adequate description of the states.

  2. 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.

  3. 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.

  4. Supercurrent Drag via the Coulomb Interaction

    NASA Astrophysics Data System (ADS)

    Duan, Ji-Min; Yip, Sungkit

    1996-03-01

    We predict a supercurrent drag effect due to the Coulomb interaction between two parallel superconducting wires/layers. In contrast to previously explored frictional drag effect between two semiconducting quantum wells, our nondissipative drag mechanism ( J.-M. Duan and S. K. Yip, Phys. Rev. Lett.70), 3647 (1993). is based on considerations of the free energy of collective charge fluctuations. Our prediction has been confirmed experimentally ( X. Huang et al.), Phys. Rev. Lett.74, 4051 (1995). This mechanism generally exists in other nondissipative systems, such as double-layer quantum Hall syatems ( J.-M. Duan, Europhys. Lett.29), 489 (1995)., or between the two edge channels of a Hall bar, and between one-dimensional Luttinger Liquids.

  5. Electron-pair excitations and the molecular Coulomb continuum

    SciTech Connect

    Colgan, James

    2009-01-01

    Electron-pair excitations in the molecular hydrogen continuum are described by quantizing rotations of the momentum plane of the electron pair about by the pair's relative momentum. A helium-like description of the molecular pi.Joto double ionization is thus extended to higher angular momenta of the electron pair. A simple three-state superposition is found to account surprisingly well for recent observations of noncoplanar electron-pair, molecular-axis angular distributions.

  6. Dynamical interactions of galaxy pairs

    NASA Technical Reports Server (NTRS)

    Athanassoula, E.

    1990-01-01

    Here the author briefly reviews the dynamics of sinking satellites and the effect of companions on elliptical galaxies. The author then discusses recent work on interacting disk systems, and finally focuses on a favorite interacting pair, NGC 5194/5195.

  7. Long-range Coulomb interaction in nodal-ring semimetals

    NASA Astrophysics Data System (ADS)

    Huh, Yejin; Moon, Eun-Gook; Kim, Yong Baek

    2016-01-01

    Recently there have been several proposals of materials predicted to be nodal-ring semimetals, where zero energy excitations are characterized by a nodal ring in the momentum space. This class of materials falls between the Dirac-like semimetals and the more conventional Fermi-surface systems. As a step towards understanding this unconventional system, we explore the effects of the long-range Coulomb interaction. Due to the vanishing density of states at the Fermi level, Coulomb interaction is only partially screened and remains long-ranged. Through renormalization group and large-Nf computations, we have identified a nontrivial interacting fixed point. The screened Coulomb interaction at the interacting fixed point is an irrelevant perturbation, allowing controlled perturbative evaluations of physical properties of quasiparticles. We discuss unique experimental consequences of such quasiparticles: acoustic wave propagation, anisotropic dc conductivity, and renormalized phonon dispersion as well as energy dependence of quasiparticle lifetime.

  8. Ion PairInteractions.

    PubMed

    Fujisawa, Kaori; Humbert-Droz, Marie; Letrun, Romain; Vauthey, Eric; Wesolowski, Tomasz A; Sakai, Naomi; Matile, Stefan

    2015-09-01

    We report that anion-π and cation-π interactions can occur on the same aromatic surface. Interactions of this type are referred to as ion pairinteractions. Their existence, nature, and significance are elaborated in the context of spectral tuning, ion binding in solution, and activation of cell-penetrating peptides. The origin of spectral tuning by ion pairinteractions is unraveled with energy-minimized excited-state structures: The solvent- and pH-independent red shift of absorption and emission of push-pull fluorophores originates from antiparallel ion pair-π attraction to their polarized excited state. In contrast, the complementary parallel ion pair-π repulsion is spectroscopically irrelevant, in part because of charge neutralization by intriguing proton and electron transfers on excited push-pull surfaces. With time-resolved fluorescence measurements, very important differences between antiparallel and parallel ion pairinteractions are identified and quantitatively dissected from interference by aggregation and ion pair dissociation. Contributions from hydrogen bonding, proton transfer, π-π interactions, chromophore twisting, ion pairing, and self-assembly are systematically addressed and eliminated by concise structural modifications. Ion-exchange studies in solution, activation of cell-penetrating peptides in vesicles, and computational analysis all imply that the situation in the ground state is complementary to spectral tuning in the excited state; i.e., parallel rather than antiparallel ion pairinteractions are preferred, despite repulsion from the push-pull dipole. The overall quite complete picture of ion pairinteractions provided by these remarkably coherent yet complex results is expected to attract attention throughout the multiple disciplines of chemistry involved. PMID:26291550

  9. 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.

  10. 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…

  11. Interplay of Coulomb interaction and spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Bünemann, Jörg; Linneweber, Thorben; Löw, Ute; Anders, Frithjof B.; Gebhard, Florian

    2016-07-01

    We employ the Gutzwiller variational approach to investigate the interplay of Coulomb interaction and spin-orbit coupling in a three-orbital Hubbard model. Already in the paramagnetic phase we find a substantial renormalization of the spin-orbit coupling that enters the effective single-particle Hamiltonian for the quasiparticles. Only close to half band-filling and for sizable Coulomb interaction do we observe clear signatures of Hund's atomic rules for spin, orbital, and total angular momentum. For a finite local Hund's rule exchange interaction we find a ferromagnetically ordered state. The spin-orbit coupling considerably reduces the size of the ordered moment, it generates a small ordered orbital moment, and it induces a magnetic anisotropy. To investigate the magnetic anisotropy energy, we use an external magnetic field that tilts the magnetic moment away from the easy axis (1 ,1 ,1 ) .

  12. 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).

  13. Stationary entanglement between two nanomechanical oscillators induced by Coulomb interaction

    NASA Astrophysics Data System (ADS)

    Qin, Wu; Yin, Xiao; Zhi-Ming, Zhang

    2016-01-01

    We propose a scheme for entangling two nanomechanical oscillators by Coulomb interaction in an optomechanical system. We find that the steady-state entanglement of two charged nanomechanical oscillators can be obtained when the coupling between them is stronger than a critical value which relies on the detuning. Remarkably, the degree of entanglement can be controlled by the Coulomb interaction and the frequencies of the two charged oscillators. Project supported by the Major Research Plan of the National Natural Science Foundation of China (Grant No. 91121023), the National Natural Science Foundation of China (Grant Nos. 61378012, 60978009, and 11574092), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20124407110009), the National Basic Research Program of China (Grant Nos. 2011CBA00200 and 2013CB921804), and the Program for Changjiang Scholar and Innovative Research Team in University, China (Grant No. IRT1243).

  14. Cooling of cryogenic electron bilayers via the Coulomb interaction

    NASA Astrophysics Data System (ADS)

    Gamble, John King; Friesen, Mark; Joynt, Robert; Coppersmith, S. N.

    2011-09-01

    Heat dissipation in current-carrying cryogenic nanostructures is problematic because the phonon density of states decreases strongly as energy decreases. We show that the Coulomb interaction can prove a valuable resource for carrier cooling via coupling to a nearby cold electron reservoir. Specifically, we consider the geometry of an electron bilayer in a silicon-based heterostructure and analyze the power transfer. We show that, across a range of temperatures, separations, and sheet densities, the electron-electron interaction dominates the phonon heat-dissipation modes as the main cooling mechanism. Coulomb cooling is most effective at low densities, when phonon cooling is least effective in silicon, making it especially relevant for experiments attempting to perform coherent manipulations of single spins.

  15. Coulomb interaction from the interplay between confinement and screening

    NASA Astrophysics Data System (ADS)

    Gaete, P.; Guendelman, E. I.

    2004-07-01

    It has been noticed that confinement effects can be described by the addition of a -FμνaFaμν term in the Lagrangian density. We now study the combined effect of such "confinement term" and that of a mass term. The surprising result is that the interplay between these two terms gives rise to a Coulomb interaction. Our picture has a certain correspondence with the quasiconfinement picture described by Giles, Jaffe and de Rujula for QCD with symmetry breaking.

  16. Coulomb blockade and incoherent tunneling of Cooper pairs in ultrasmall junctions affected by strong quantum fluctuations

    NASA Astrophysics Data System (ADS)

    Kuzmin, L. S.; Nazarov, Yu. V.; Haviland, D. B.; Delsing, P.; Claeson, T.

    1991-08-01

    We have fabricated and investigated submicron-size (0.01 and 0.04 μm2) Pb-alloy single Josephson junctions attached to high-resistance thin-film NiCr or Cr leads which provide the necessary conditions for a strong charging effect. When the Josephson coupling energy is less than the charging energy, we find a novel shape of the current-voltage curves, with a Coulomb gap at small voltages, and a current peak at larger voltages. A theory based on the concept of incoherent Cooper-pair tunneling has explained the data well.

  17. Simulation of Coulomb interaction effects in electron sources

    NASA Astrophysics Data System (ADS)

    Rouse, John; Zhu, Xieqing; Liu, Haoning; Munro, Eric

    2011-07-01

    Over many years, we have developed electron source simulation software that has been used widely in the electron optics community to aid the development of rotationally symmetric electron and ion guns. The simulation includes the modelling of cathode emission and the effects of volumetric space charge. In the present paper we describe the existing software and explain how we have extended this software to include the effects of discrete Coulomb interactions between the electrons as they travel from the cathode surface to the exit of the gun. In the paper, we will describe the numerical models we have employed, the techniques we have used to maximize the speed of the Coulomb force computation and present several illustrative examples of cases analyzed using the new software, including thermal field emitters, LaB 6 guns and flat dispenser-type cathodes.

  18. 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.

  19. Coulomb-interaction effects on the electronic structure of radially polarized excitons in nanorings

    NASA Astrophysics Data System (ADS)

    Barticevic, Z.; Pacheco, M.; Simonin, J.; Proetto, C. R.

    2006-04-01

    The electronic structure of radially polarized excitons in structured nanorings is analyzed, with emphasis in the ground-state properties and their dependence under applied magnetic fields perpendicular to the ring plane. The electron-hole Coulomb attraction has been treated rigorously, through numerical diagonalization of the full exciton Hamiltonian in the noninteracting electron-hole pairs basis. Depending on the relative weight of the kinetic energy and Coulomb contributions, the ground-state of polarized excitons has “extended” or “localized” features. In the first case, corresponding to small rings dominated by the kinetic energy, the ground-state shows Aharonov-Bohm (AB) oscillations due to the individual orbits of the building particles of the exciton. In the localized regime, corresponding to large rings dominated by the Coulomb interaction, the only remaining AB oscillations are due to the magnetic flux trapped between the electron and hole orbits. This dependence of the exciton, a neutral excitation, on the flux difference confirms this feature as a signature of Coulomb dominated polarized excitons. Analytical approximations are provided in both regimes, which accurately reproduce the numerical results.

  20. 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. PMID:24722427

  1. Attractive Coulomb interaction of two-dimensional Rydberg excitons

    NASA Astrophysics Data System (ADS)

    Shahnazaryan, V.; Shelykh, I. A.; Kyriienko, O.

    2016-06-01

    We analyze theoretically the Coulomb scattering processes of highly excited excitons in the direct-band-gap semiconductor quantum wells. We find that contrary to the interaction of ground-state excitons, the electron and hole exchange interaction between excited excitons has an attractive character both for s - and p -type two-dimensional (2D) excitons. Moreover, we show that similar to the three-dimensional highly excited excitons, the direct interaction of 2D Rydberg excitons exhibits van der Waals-type long-range interaction. The results predict the linear growth of the absolute value of exchange interaction strength with an exciton principal quantum number and point the way towards enhancement of optical nonlinearity in 2D excitonic systems.

  2. Challenges in calculating molecular systems with Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Kirnosov, Nikita; Sharkey, Keeper; Adamowicz, Ludwik

    2014-03-01

    The highly accurate quantum mechanical calculations are not only crucial for high-resolution experimental data verification, but may also serve as a guide in the field of exotic systems exploration. Including all non-relativistic effects in a single-step variational approach and rigorously separating out the center of mass motion allows us to build a reliable model for calculating bound states of molecular systems with Coulomb interactions. In these calculations the wave function of the system is expanded in terms of explicitly correlated Gaussian (ECG) basis functions. Examples of calculations of energies and other properties of some molecular systems will be presented.

  3. A convergent multipole expansion for 1,3 and 1,4 Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Rafat, M.; Popelier, P. L. A.

    2006-04-01

    Traditionally force fields express 1,3 and 1,4 interactions as bonded terms via potentials that involve valence and torsion angles, respectively. These interactions are not modeled by point charge terms, which are confined to electrostatic interactions between more distant atoms (1,n where n >4). Here we show that both 1,3 and 1,4 interactions can be described on the same footing as 1,n (n>4) interactions by a convergent multipole expansion of the Coulomb energy of the participating atom pairs. The atomic multipole moments are generated by the theory of quantum chemical topology. The procedure to make the multipole expansion convergent is based on a "shift procedure" described in earlier work [L. Joubert and P. L. A. Popelier, Molec. Phys. 100, 3357 (2002)].

  4. Mechanical model of the Lorentz force and Coulomb interaction

    NASA Astrophysics Data System (ADS)

    Dmitriyev, Valery

    2008-09-01

    The centripetal and Coriolis accelerations experienced by a cart traveling over a rotating turntable are usually calculated proceeding from the known kinematics of the problem. Respective forces can be regarded as due to the entrainment of the cart in the moving solid environs. We extend the approach to the general case of a particle entrained in the flow of the surrounding medium. The expression for the driving force on the particle obtained from the kinematics of the entrainment prescribed appears to be isomorphic to the Lorentz and Coulomb force on a positive electric charge. The inverse direction of the electromagnetic force on a negative charge implies that a growing applied flow induces the upstream motion of the particle. A possible microscopic mechanism for it may be the Magnus force dynamics of a kink in a vortex tangle. The loop on a straight vortex filament can be taken as a model of the electron, the loop with a cavitation models the positron. The Lorentz force is concerned with the Coriolis acceleration. The Coulomb interaction is due to the centripetal or centrifugal force that arises in the turbophoresis of the kink in the perturbation field generated in the medium by the center of pressure.

  5. 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.

  6. Pair interactions in red-faced warblers

    USGS Publications Warehouse

    Barber, P.M.; Martin, T.E.; Smith, Kimberly G.

    1998-01-01

    Forty pairs of breeding Red-faced Warblers (Cardellina rubrifrons) were observed in 1992 and 1993 on the Mogollon Rim, Arizona. Intrusions by extra-pair males, interactions between pair members, and other pair interaction behaviors were recorded. The majority of intrusions occurred during the building stage of the nesting cycle. Males responded to intrusions during nest building by decreasing intra-pair distance. Males maintained shorter intra-pair distances by following the female when she initiated movements and by not initiating pair movements themselves. Intra-pair distances were as short or shorter during the incubation period as during nest building, and were shorter during incubation than during egg laying. Males continued to follow females beyond the expected fertile period. Possible explanations for continued mate following include: males guard their mates against predators, males guard their paternity for future nesting attempts, and males respond to extra-pair male intrusions, which continue during incubation.

  7. 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

  8. The generalized Coulomb interactions for relativistic scalar bosons

    NASA Astrophysics Data System (ADS)

    Zarrinkamar, S.; Panahi, H.; Rezaei, M.

    2016-07-01

    Approximate analytical solutions of Duffin-Kemmer-Petiau (DKP) equation are obtained for the truncated Coulomb, generalized Cornell, Richardson and Song-Lin potentials via the quasi-exact analytical ansatz approach.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.

  11. Exploring Coulomb interaction in piezoelectric materials for assisting the laser cooling of solids

    NASA Astrophysics Data System (ADS)

    Hassani Nia, Iman; Mohseni, Hooman

    2014-02-01

    Realization of anti-Stokes cooling requires high enough photon extraction efficiency as well as quantum efficiency, making the implementation of this technique extremely difficult for semiconductors. Here, for the first time, we demonstrate that the Coulomb interaction between photogenerated electron-hole pairs in strong piezoelectric materials such as GaN/InGaN quantum wells could assist laser cooling. By comparing to the cavity back-action mechanism, we also explain how this process depends upon laser detuning with respect to bandgap. To demonstrate the advantage of this method even further, we present simulations by using experimentally reported parameters of GaN and In0.15Ga0.85N, in order to conclude that the net cooling is indeed possible even with current III-nitride growth technology.

  12. Calculation of proton-deuteron breakup reactions including the Coulomb interaction between the two protons.

    PubMed

    Deltuva, A; Fonseca, A C; Sauer, P U

    2005-08-26

    The Coulomb interaction between the two protons is fully included in the calculation of proton-deuteron breakup with realistic interactions for the first time. The hadron dynamics is based on the purely nucleonic charge-dependent (CD) Bonn potential and its realistic extension CD Bonn +Delta to a coupled-channel two-baryon potential, allowing for single virtual Delta-isobar excitation. Calculations are done using integral equations in momentum space. The screening and renormalization approach is employed for including the Coulomb interaction. The Coulomb effect on breakup observables is seen at all energies in particular kinematic regimes. PMID:16197210

  13. Fermi Surface of Sr_{2}RuO_{4}: Spin-Orbit and Anisotropic Coulomb Interaction Effects.

    PubMed

    Zhang, Guoren; Gorelov, Evgeny; Sarvestani, Esmaeel; Pavarini, Eva

    2016-03-11

    The topology of the Fermi surface of Sr_{2}RuO_{4} is well described by local-density approximation calculations with spin-orbit interaction, but the relative size of its different sheets is not. By accounting for many-body effects via dynamical mean-field theory, we show that the standard isotropic Coulomb interaction alone worsens or does not correct this discrepancy. In order to reproduce experiments, it is essential to account for the Coulomb anisotropy. The latter is small but has strong effects; it competes with the Coulomb-enhanced spin-orbit coupling and the isotropic Coulomb term in determining the Fermi surface shape. Its effects are likely sizable in other correlated multiorbital systems. In addition, we find that the low-energy self-energy matrix-responsible for the reshaping of the Fermi surface-sizably differs from the static Hartree-Fock limit. Finally, we find a strong spin-orbital entanglement; this supports the view that the conventional description of Cooper pairs via factorized spin and orbital part might not apply to Sr_{2}RuO_{4}. PMID:27015496

  14. Study of ultrasonic attenuation in f-electron systems in the paramagnetic limit of Coulomb interaction

    SciTech Connect

    Shadangi, Asit Ku.; Rout, G. C.

    2015-05-15

    We report here a microscopic model study of ultrasonic attenuation in f-electron systems based on Periodic Anderson Model in which Coulomb interaction is considered within a mean-field approximation for a weak interaction. The Phonon is coupled to the conduction band and f-electrons. The phonon Green's function is calculated by Zubarev's technique of the Green's function method. The temperature dependent ultrasonic attenuation co-efficient is calculated from the imaginary part of the phonon self-energy in the dynamic and long wave length limit. The f-electron occupation number is calculated self-consistently in paramagnetic limit of Coulomb interaction. The effect of the Coulomb interaction on ultrasonic attenuation is studied by varying the phonon coupling parameters to the conduction and f-electrons, hybridization strength, the position of f-level and the Coulomb interaction Strength. Results are discussed on the basis of experimental results.

  15. Weak interaction rate Coulomb corrections in big bang nucleosynthesis

    SciTech Connect

    Smith, Christel J.; Fuller, George M.

    2010-03-15

    We have applied a fully relativistic Coulomb wave correction to the weak reactions in the full Kawano/Wagoner big bang nucleosynthesis (BBN) code. We have also added the zero-temperature radiative correction. We find that using this higher accuracy Coulomb correction results in good agreement with previous work, giving only a modest {approx}0.04% increase in helium mass fraction over correction prescriptions applied previously in BBN calculations. We have calculated the effect of these corrections on other light element abundance yields in BBN, and we have studied these yields as functions of electron neutrino lepton number. This has allowed insights into the role of the weak neutron-proton interconversion processes in the setting of the neutron-to-proton ratio during the BBN epoch. We find that the lepton capture processes' contributions to this ratio are only second order in the Coulomb correction.

  16. Collective modes in charge-density waves and long-range Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Virosztek, Attila; Maki, Kazumi

    1993-07-01

    We study theoretically the collective modes in charge-density waves in the presence of long-range Coulomb interaction. We find that earlier works by Takada and his collaborators are inadequate since they introduced inconsistent approximations in evaluating a variety of correlation functions. The amplitude mode is unaffected by the Coulomb interaction, while the phase mode splits into the phason with linear dispersion (i.e., acoustic mode) and the optical mode with an energy gap in the presence of the Coulomb interaction. In particular, we establish the temperature dependence of the phason velocity vφ. A comparison with recent neutron-scattering data on the phason velocity in the charge-density wave of a single crystal of blue bronze K0.3MoO3 indicates that mean-field theory which includes the long-range Coulomb interaction gives an excellent description of the observed phason velocity.

  17. On-site screened Coulomb interactions for localized electrons in transition metal oxides and defect systems

    NASA Astrophysics Data System (ADS)

    Shih, Bi-Ching; Zhang, Peihong; Department of Physics Team

    2011-03-01

    Electronic and structural properties of strongly correlated material systems are largely determined by the strength of the on-site Coulomb interaction. Theoretical models devised to capture the physics of strongly correlated materials usually involve screened Coulomb interactions as adjustable parameters. We present first-principles results for the screened on-site Coulomb and exchange energy for transition metal oxides. The dielectric screening is calculated within the random phase approximation and the localized electrons are represented by maximally localized Wannier functions. We further extend our study to calculate on-site Coulomb interactions for localized defect states in semiconductors. We acknowledge the computational support provided by the Center for Computational Research at the University at Buffalo, SUNY. This work is supported by the National Science Foundation under Grant No. DMR-0946404 and by the Department of Energy under Grant No. DE-SC0002623.

  18. 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.

  19. 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.

  20. Induced Pairing Interaction in Neutron Star Matter

    NASA Astrophysics Data System (ADS)

    Lombardo, U.; Schulze, H.-J.; Zuo, W.

    2013-01-01

    The three superfluid phases supposed to occur in neutron stars are reviewed in the framework of the generalized BCS theory with the induced interaction. The structure of neutron stars characterized by beta-stable asymmetric nuclear matter in equilibrium with the gravitational force discloses new aspects of the pairing mechanism. Some of them are discussed in this report, in particular the formation in dense matter of Cooper pairs in the presence of three-body forces and the interplay between repulsive and attractive polarization effects on isospin T = 1 Cooper pairs embedded into the neutron and proton environment. Quantitative estimates of the energy gaps are reported and their sensitivity to the medium effects, i.e., interaction and polarization, is explored.

  1. 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…

  2. 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.

  3. 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.

  4. Pairing interaction effects in exciton level densities

    SciTech Connect

    Fu, C.Y.

    1989-01-01

    Recent progress in pairing corrections for exciton state-density formulas used in pre-compound nuclear reaction theories is reviewed. These correction factors are, strictly speaking, dependent on the nuclear excitation energy U and the exciton number n. A simple formula for (U,n)-dependent pairing corrections has been derived, based on the BCS pairing equations for constant single-particle spacing, for the exciton state-density formula for one kind of Fermion. It has been shown that the constant-pairing-energy correction used in standard state-density formulas, such U{sub 0} in Gilbert and Cameron, is a limiting case of the general (U,n)-dependent results. Spin cutoff factors with pairing effects were also obtained using the same theory and parameterized into an explicit (U,n)-dependent function, thereby defining a simple exciton level-density formula for applications in quantum mechanical precompound theories. Preliminary results from extending such simple pairing-interaction representations to level-density formulas for two kinds of Fermions are summarized. The results show that the ratios in the exciton level densities in the one-Fermion and two-Fermion approaches vary with both U and n, thus likely leading to differences in calculated compound to precompound ratios. However, the differences in the spin cutoff factors in the two cases are found to be rather small. 12 refs., 3 figs.

  5. Comment on ``Pairing interaction and Galilei invariance''

    NASA Astrophysics Data System (ADS)

    Arias, J. M.; Gallardo, M.; Gómez-Camacho, J.

    1999-05-01

    A recent article by Dussel, Sofia, and Tonina studies the relation between Galilei invariance and dipole energy weighted sum rule (EWSR). The authors find that the pairing interaction, which is neither Galilei nor Lorentz invariant, produces big changes in the EWSR and in effective masses of the nucleons. They argue that these effects of the pairing force could be realistic. In this Comment we stress the validity of Galilei invariance to a very good approximation in this context of low-energy nuclear physics and show that the effective masses and the observed change in the EWSR for the electric dipole operator relative to its classical value are compatible with this symmetry.

  6. Effect of Coulomb interactions on the disorder-driven superconductor-insulator transition

    NASA Astrophysics Data System (ADS)

    Sherman, Daniel; Gorshunov, Boris; Poran, Shachaf; Trivedi, Nandini; Farber, Eli; Dressel, Martin; Frydman, Aviad

    2014-01-01

    We have studied the evolution of the superconducting energy gap of indium oxide through the disorder-driven superconductor-to-insulator transition (SIT) using two distinct experimental methods that allow us to test the influence of metallic screening: tunneling spectroscopy in which a metallic electrode is adjacent to the studied sample, thus screening Coulomb interactions, and contactless terahertz spectroscopy which probes the unperturbed sample. The tunneling measurements reveal a similar superconducting gap on both sides of the SIT and at temperatures above and below Tc. Terahertz measurements detect the superconducting gap below but not above the critical temperature nor in the insulating state. This difference between the two spectroscopy methods is attributed to the effect of Coulomb interactions which are screened in the tunneling experiments. Our study reveals the importance of Coulomb interactions on the energy gap of disordered superconductors.

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

    PubMed

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

    2016-01-01

    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. PMID:26892805

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

    PubMed Central

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

    2016-01-01

    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. PMID:26892805

  9. 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.

  10. Coulomb Interaction Effects In Semiconductor Heterostructures With Spin-Orbit Interaction

    NASA Astrophysics Data System (ADS)

    Capps, Jeremy Patrick

    In this thesis we analyze two different situations where the interplay between the spin-orbit coupling (SOI) of the Rashba and Dresselhaus type, linear in the electron momentum, and the Coulomb interaction generates a specific macroscopic phenomenology that can be experimentally observed. In the first problem, we investigate the Friedel oscillations that can be sustained in the presence of the Coulomb repulsion in a two-dimensional lateral superlattice with SOI and analyze the dependence on several system parameters. Then, we are concerned with the properties of a single quantum well in the special regime where the coupling strengths of the Rashba and Dresselhaus interactions are equal. Starting from general total-energy considerations, we demonstrate that the SU(2) spin-rotation symmetry and the resulting persistent helical state (PHS) predicted to occur are not in fact realized; the actual spin order being that of an itinerant antiferromagnet (IAF). We obtain numerical results that describe the temperature evolution of the order parameter in the IAF state and determine the critical temperature of the transition to the paramagnetic order. Transport in this state is modeled by using the solutions of a Boltzmann equation obtained within the relaxation time approximation. Numerical estimates performed for realistic GaAs and InAs samples indicate that at low temperatures, the amplitude of the spin-Seebeck coefficient can be increased by scattering on magnetic impurities.

  11. 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.

  12. Wannier function approach to realistic Coulomb interactions in layered materials and heterostructures

    NASA Astrophysics Data System (ADS)

    Rösner, M.; Şaşıoǧlu, E.; Friedrich, C.; Blügel, S.; Wehling, T. O.

    2015-08-01

    We introduce an approach to derive realistic Coulomb interaction terms in freestanding layered materials and vertical heterostructures from ab initio modeling of the corresponding bulk materials. To this end, we establish a combination of calculations within the framework of the constrained random-phase approximation, Wannier function representation of Coulomb matrix elements within some low-energy Hilbert space, and continuum medium electrostatics, which we call Wannier function continuum electrostatics (WFCE). For monolayer and bilayer graphene we reproduce full ab initio calculations of the Coulomb matrix elements within an accuracy of 0.3 eV or better. We show that realistic Coulomb interactions in bilayer graphene can be manipulated on the eV scale by different dielectric and metallic environments. A comparison to electronic phase diagrams derived in M. M. Scherer et al. [Phys. Rev. B 85, 235408 (2012), 10.1103/PhysRevB.85.235408] suggests that the electronic ground state of bilayer graphene is a layered antiferromagnet and remains surprisingly unaffected by these strong changes in the Coulomb interaction.

  13. Nonlocal quantum state engineering with the Cooper pair splitter beyond the Coulomb blockade regime

    NASA Astrophysics Data System (ADS)

    Amitai, Ehud; Tiwari, Rakesh P.; Walter, Stefan; Schmidt, Thomas L.; Nigg, Simon E.

    2016-02-01

    A Cooper pair splitter consists of two quantum dots side-coupled to a conventional superconductor. Usually, the quantum dots are assumed to have a large charging energy compared to the superconducting gap, in order to suppress processes other than the coherent splitting of Cooper pairs. In this work, in contrast, we investigate the limit in which the charging energy is smaller than the superconducting gap. This allows us, in particular, to study the effect of a Zeeman field comparable to the charging energy. We find analytically that in this parameter regime the superconductor mediates an interdot tunneling term with a spin symmetry determined by the Zeeman field. Together with electrostatically tunable quantum dots, we show that this makes it possible to engineer a spin triplet state shared between the quantum dots. Compared to previous works, we thus extend the capabilities of the Cooper pair splitter to create entangled nonlocal electron pairs.

  14. Hydrodynamics of pairs of interacting cytoskeletal filaments

    NASA Astrophysics Data System (ADS)

    Shinar, Tamar; Shelley, Michael

    2011-11-01

    Pairwise filament interactions underlie the dynamics of complex cytoskeletal networks in cells. These networks in turn play a crucial role in many cellular processes such as formation of the mitotic spindle and cell cleavage in cytokinesis. We model interactions of pairs of filaments immersed in a viscous, fluidic environment. The filaments are modeled using a slender body approximation, capturing their indirect interactions mediated by the immersing fluid. Direct filament interactions via molecular motors complexes induce alignment and parallel or anti-parallel sliding. The motor proteins are modeled as simple spring-like structures that walk directionally toward one end of the filament. We examine the resulting stresses in the fluid to better understand how the microscopic interactions lead to bulk behavior of cytoskeletal networks.

  15. Bond alternation in the infinite polyene: effect of long range Coulomb interactions

    SciTech Connect

    Mazumdar, S.; Campbell, D.K.

    1985-01-01

    We investigate the effects of long-range Coulomb interactions on bond and site dimerizations in a one-dimensional half-filled band. It is shown that the ground state broken symmetry is determined by two sharp inequalities involving the Coulomb parameters. Broken symmetry with periodicity 2k/sub F/ is guaranteed only if the first inequality (downward convexity of the intersite potential) is obeyed, while the second inequality gives the phase boundary between the bond-dimerized and site-dimerized phases. Application of these inequalities to the Pariser-Parr-Pople model for linear polyenes shows that the infinite polyene has enhanced bond alternation for both Ohno and Mataga-Nishimoto parametrizations of the intersite Coulomb terms. The possible role of distant neighbor interactions in photogeneration experiments is discussed. 26 refs., 3 figs.

  16. Initial-state Coulomb interaction in the dd{yields}{alpha}{pi}{sup 0} reaction

    SciTech Connect

    Laehde, Timo A.; Miller, Gerald A.

    2007-05-15

    The effects of initial-state Coulomb interactions in the charge-symmetry-breaking reaction dd{yields}{alpha}{pi}{sup 0} are investigated within a previously published formalism. This is a leading order effect in which the Coulomb interaction between the two initial state protons leads to the breakup of the two deuterons into a continuum state that is well connected to the final {alpha}{pi}{sup 0} state by the strong emission of a pion. As a first step, we use a simplified set of d and {alpha} wave functions and a plane-wave approximation for the initial dd state. This Coulomb mechanism, by itself, yields cross sections that are much larger than the experimental ones, and which are comparable in size to the contributions from other mechanisms. Inclusion of this mechanism is therefore necessary in a realistic calculation.

  17. Nonlocal topological magnetoelectric effect by Coulomb interaction at a topological insulator-ferromagnet interface

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    The interface between a topological insulator and a ferromagnetic insulator exhibits an interesting interplay of topological Dirac electrons and magnetism. As has been shown recently, the breaking of time-reversal invariance by magnetic order generates a Chern-Simons term in the action, that in turn leads to a Berry phase and a magnetoelectric effect of topological origin. Here, we consider the system in the presence of a long-range Coulomb interaction between the Dirac electrons, and find that the magnetoelectric effect of the fluctuating electric field becomes nonlocal. We derive a Landau-Lifshitz equation for the fluctuation-induced magnetization dynamics and the Euler-Lagrange equation of the Coulomb field by explicit one-loop calculations. Via the Coulomb interaction, divergences in the in-plane magnetization affect the magnetization dynamics over large distances in a topologically protected way.

  18. Correlated Cooper pair transport and microwave photon emission in the dynamical Coulomb blockade

    NASA Astrophysics Data System (ADS)

    Leppäkangas, Juha; Fogelström, Mikael; Marthaler, Michael; Johansson, Göran

    2016-01-01

    We study theoretically electromagnetic radiation emitted by inelastic Cooper-pair tunneling. We consider a dc-voltage-biased superconducting transmission line terminated by a Josephson junction. We show that the generated continuous-mode electromagnetic field can be expressed as a function of the time-dependent current across the Josephson junction. The leading-order expansion in the tunneling coupling, similar to the P (E ) theory, has previously been used to investigate the photon emission statistics in the limit of sequential (independent) Cooper-pair tunneling. By explicitly evaluating the system characteristics up to the fourth order in the tunneling coupling, we account for dynamics between consecutively tunneling Cooper pairs. Within this approach we investigate how temporal correlations in the charge transport can be seen in the first- and second-order coherences of the emitted microwave radiation.

  19. Effects of Coulomb interactions on the superconducting gaps in iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Leong, Zhidong; Phillips, Philip

    2016-04-01

    Recent angle-resolved photoemission spectroscopy measurements of Co-doped LiFeAs report a large and robust superconducting gap on the Γ -centered hole band that lies 8 meV below the Fermi level. We show that, unlike a conventional superconductor described by BCS theory, a multiband system with strong interband Coulomb interactions can explain these observations. We model LiFeAs with a five-band model in which the shallow hole band is coupled with the other bands by only Coulomb interactions. Using Eliashberg theory, we find reasonable interaction parameters that reproduce the Tc and all five gaps of LiFeAs. The energy independence of the Coulomb interactions then ensures the robustness of the gap induced on the shallow band. Furthermore, due to the repulsive nature of the Coulomb interactions, the gap changes sign between the shallow band and the other hole pockets, corresponding to an unconventional s± gap symmetry. Unlike other families of iron-based superconductors, the gap symmetry of LiFeAs has not been ascertained experimentally. The experimental implications of this sign-changing state are discussed.

  20. Zero bias maximum of differential conductance in coupled quantum dots: The effect of interdot Coulomb interaction

    NASA Astrophysics Data System (ADS)

    Rajput, Gagan; Chand, S.; Ahluwalia, P. K.; Sharma, K. C.

    2010-10-01

    In this paper, we present a theoretical study of correlated electronic transport through coupled double quantum dot (DQD) system attached to normal leads, using a generalised two impurity Anderson Hamiltonian in the presence of intra- and inter-dot Coulomb interactions. A generic formulation from which different structures, i.e. series, symmetric as well as asymmetric parallel and T-shape, can be obtained easily, is developed using Keldysh non-equilibrium Green functions method. The occupation numbers and correlators appearing in the formulation have been calculated in a self-consistent manner. A special attention is paid to investigate the ZBM in the differential conductance, which appears, develops and disappears over a particular range of interdot Coulomb interaction, in the configuration of interest. The ZBM is found to result from the renormalization of energy levels induced by the interdot Coulomb interaction and therefore an attempt has been made to understand it within the framework of local density of states. The interdot tunneling is found to enhance the effect of the interdot Coulomb interaction in inducing the ZBM in all the three configurations. Calculations for the T-shape configuration reveal that non-zero value of the interdot tunneling is an essential condition for the appearance of the ZBM in the differential conductance.

  1. Testing refined shell-model interactions in the s d shell: Coulomb excitation of 26Na

    NASA Astrophysics Data System (ADS)

    Siebeck, B.; Seidlitz, M.; Blazhev, A.; Reiter, P.; Altenkirch, R.; Bauer, C.; Butler, P. A.; de Witte, H.; Elseviers, J.; Gaffney, L. P.; Hess, H.; Huyse, M.; Kröll, T.; Lutter, R.; Pakarinen, J.; Pietralla, N.; Radeck, F.; Scheck, M.; Schneiders, D.; Sotty, C.; van Duppen, P.; Vermeulen, M.; Voulot, D.; Warr, N.; Wenander, F.; Miniball Collaboration; Rex-Isolde Collaboration

    2015-01-01

    Background: Shell-model calculations crucially depend on the residual interaction used to approximate the nucleon-nucleon interaction. Recent improvements to the empirical universal s d interaction (USD) describing nuclei within the s d shell yielded two new interactions—USDA and USDB—causing changes in the theoretical description of these nuclei. Purpose: Transition matrix elements between excited states provide an excellent probe to examine the underlying shell structure. These observables provide a stringent test for the newly derived interactions. The nucleus 26Na with 7 valence neutrons and 3 valence protons outside the doubly-magic 16O core is used as a test case. Method: A radioactive beam experiment with 26Na (T1 /2=1 ,07 s ) was performed at the REX-ISOLDE facility (CERN) using Coulomb excitation at safe energies below the Coulomb barrier. Scattered particles were detected with an annular Si detector in coincidence with γ rays observed by the segmented MINIBALL array. Coulomb excitation cross sections of the beam have been obtained by normalization to the well known Coulomb excitation cross sections of the 104Pd target. Results: The observation of three γ -ray transitions in 26Na together with available spectroscopic data allows us to determine E 2 - and M 1 -transitional matrix elements. Results are compared to theoretical predictions. Conclusion: The improved theoretical description of 26Na could be validated. Remaining discrepancies between experimental data and theoretical predictions indicate the need for future experiments and possibly further theoretical improvements.

  2. Charge avalanches and depinning in the Coulomb glass: The role of long-range interactions

    NASA Astrophysics Data System (ADS)

    Andresen, Juan Carlos; Pramudya, Yohanes; Katzgraber, Helmut G.; Thomas, Creighton K.; Zimanyi, Gergely T.; Dobrosavljević, V.

    2016-03-01

    We explore the stability of far-from-equilibrium metastable states of a three-dimensional Coulomb glass at zero temperature by studying charge avalanches triggered by a slowly varying external electric field. Surprisingly, we identify a sharply defined dynamical ("depinning") phase transition from stationary to nonstationary charge displacement at a critical value of the external electric field. Using particle-conserving dynamics, scale-free system-spanning avalanches are observed only at the critical field. We show that the qualitative features of this depinning transition are completely different for an equivalent short-range model, highlighting the key importance of long-range interactions for nonequilibrium dynamics of Coulomb glasses.

  3. Contact Pairing Interaction for the Hartree-Fock-Bogoliubov Calculations

    SciTech Connect

    Dobaczewski, J.

    2001-10-18

    Properties of density-dependent contact pairing interactions in nuclei are discussed. It is shown that the pairing interaction that is intermediate between surface and volume pairing forces gives the pairing gaps that are compatible with the experimental odd-even mass staggering. Results of the deformed Hartree-Fock-Bogoliubov calculations for this ''mixed'' pairing interaction, and using the transformed harmonic oscillator basis, are presented.

  4. Interaction of a skewed Rankine vortex pair

    NASA Astrophysics Data System (ADS)

    Jayavel, S.; Patil, Pratish P.; Tiwari, Shaligram

    2008-08-01

    An analytical investigation is carried out to study the kinematics of a fluid particle in an interacting field of a skewed pair of fixed Rankine vortices. A general formulation governing the kinematics of a fluid particle has been presented based on the superposition of the velocity field due to each vortex in the pair. The kinematics of a Lagrangian fluid particle is found to be governed by a nonlinear dynamical system. The fixed or stationary points of the dynamical system have been identified analytically and their existence is confirmed by the nature of particle paths in the neighborhood of fixed points. The nature of the particle path and velocity signal is reported for general as well as special configurations of the vortex pair in the presence and absence of an external uniform flow. As a specific application of the proposed problem, superimposition of the translational velocity on a semi-infinite field of longitudinal vortices generated by vortex generators mounted on fin plates of heat exchangers has also been studied.

  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. 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. PMID:26677107

  7. Simbuca, using a graphics card to simulate Coulomb interactions in a penning trap

    NASA Astrophysics Data System (ADS)

    Van Gorp, S.; Beck, M.; Breitenfeldt, M.; De Leebeeck, V.; Friedag, P.; Herlert, A.; Iitaka, T.; Mader, J.; Kozlov, V.; Roccia, S.; Soti, G.; Tandecki, M.; Traykov, E.; Wauters, F.; Weinheimer, Ch.; Zákoucký, D.; Severijns, N.

    2011-05-01

    In almost all cases, N-body simulations are limited by the computation time available. Coulomb interaction calculations scale with O(N2) with N the number of particles. Approximation methods exist already to reduce the computation time to O(NlogN), although calculating the interaction still dominates the total simulation time. We present Simbuca, a simulation package for thousands of ions moving in a Penning trap which will be applied for the WITCH experiment. Simbuca uses the output of the Cunbody-1 library, which calculates the gravitational interaction between entities on a graphics card, and adapts it for Coulomb calculations. Furthermore the program incorporates three realistic buffer gas models, the possibility of importing realistic electric and magnetic fieldmaps and different order integrators with adaptive step size and error control. The software is released under the GNU General Public License and free for use.

  8. 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. PMID:8787739

  9. 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.

  10. 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.

  11. Coulomb Interaction between InAs/GaAs Quantum Dots and Adjacent Impurities

    SciTech Connect

    Engstroem, O.; Kaniewska, M.; Kaczmarczyk, M.

    2011-12-23

    Defects positioned close to a plane of quantum dots (QDs) are shown to be influenced by coulomb interaction effect when the quantum dots are charged by electrons. Signals from deep level transient spectroscopy (DLTS) measurement give rise to a mirror effect in the spectrum depending on movement of the defect energy level in relation to the Fermi-level as a result of the electron traffic at the QDs.

  12. Spectral broadening due to long-range Coulomb interactions in the molecular metal TTF-TCNQ

    NASA Astrophysics Data System (ADS)

    Cano-Cortés, L.; Dolfen, A.; Merino, J.; Behler, J.; Delley, B.; Reuter, K.; Koch, E.

    2007-04-01

    We employ density-functional theory to calculate realistic parameters for an extended Hubbard model of the molecular metal TTF-TCNQ. Considering both intra- and intermolecular screening in the crystal, we confirm the importance of the suspected longer-range Coulomb interactions along the molecular stacks, as well as inter-stack coupling. Contrary to past belief, these terms do not lead to the formation of a Wigner lattice, but simply broaden the spectral function.

  13. Coulomb interaction of acceptors in Cd1-xMnxTe/CdTe quantum dot

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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 Cd1-xMnxTe/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.

  14. Physical interrelation between Fokker-Planck and random walk models with application to Coulomb interactions.

    NASA Technical Reports Server (NTRS)

    Englert, G. W.

    1971-01-01

    A model of the random walk is formulated to allow a simple computing procedure to replace the difficult problem of solution of the Fokker-Planck equation. The step sizes and probabilities of taking steps in the various directions are expressed in terms of Fokker-Planck coefficients. Application is made to many particle systems with Coulomb interactions. The relaxation of a highly peaked velocity distribution of particles to equilibrium conditions is illustrated.

  15. 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.

  16. 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.

  17. The effects of Coulomb interactions on the superconducting gaps in iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Leong, Zhidong; Phillips, Philip

    2015-03-01

    Recent ARPES measurements on Co-doped LiFeAs report a large and robust superconducting gap on a band below the chemical potential. We will show that, unlike a conventional BCS theory, a multiband system with strong interband Coulomb interactions can explain the observations. We use a two-band model consisting of a superconducting electron band and a hole band that is below the chemical potential. The two bands are coupled via interband Coulomb interactions. Using Eliashberg theory, we found that superconductivity in the electron band induces a large superconducting gap in the hole band. Furthermore, the repulsive nature of the Coulomb interactions gives the induced gap an opposite sign, corresponding to an s+/- gap symmetry. Unlike other families of iron pnictides, the gap symmetry of LiFeAs has not been ascertained experimentally. The implications for the superconducting mechanism in iron pnictides will be discussed. Z. Leong is supported by a scholarship from the Agency of Science, Technology and Research. P. Phillips is supported by the Center for Emergent Superconductivity, a DOE Energy Frontier Research Center, Grant No. DE-AC0298CH1088.

  18. 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.

  19. Independent pair parton interactions model of hadron interactions

    NASA Astrophysics Data System (ADS)

    Dremin, I. M.; Nechitailo, V. A.

    2004-08-01

    A model of independent pair parton interactions is proposed, according to which hadron interactions are represented by a set of independent binary parton collisions. The final multiplicity distribution is described by a convolution of the negative binomial distributions in each of the partonic collisions. As a result, it is given by a weighted sum of negative binomial distributions with parameters multiplied by the number of active pairs. Its shape and moments are considered. Experimental data on multiplicity distributions in high energy pp¯ processes are well fitted by these distributions. Predictions for the CERN Large Hadron Collider and higher energies are presented. The difference between e+e- and pp¯ processes is discussed.

  20. Atomic Regime in Which the Magnetic Interaction Dominates the Coulomb Interaction for Highly Excited States of Hydrogen

    PubMed Central

    Mueller, Ronald O.; Hughes, Vernon W.

    1974-01-01

    The atomic regime in which the interaction of the electron with an external magnetic field dominates the Coulomb interaction with the nucleus, relevant to pulsars, can be realized at laboratory magnetic fields for discrete autoionized states of hydrogen, at energies above the ionization limit. Approximate wave functions, energy levels, and electric dipole transition probabilities are presented for hydrogen, and an atomic beam absorption spectroscopy experiment at 50 kG is proposed to study this new regime. PMID:16578723

  1. 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.

  2. 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.

  3. Charge separation in organic solar cells: Effects of Coulomb interaction, recombination and hole propagation

    NASA Astrophysics Data System (ADS)

    Nemati Aram, Tahereh; Asgari, Asghar; Mayou, Didier

    2016-07-01

    Bulk heterojunction (BHJ) organic photovoltaic cells are analysed within a simple efficient model that includes the important physical properties of such photovoltaic systems. In this model, in contrast with most of the previous studies, we take into account the motion of both the electron and the hole in the separation process at the donor-acceptor interface. We theoretically examine the exciton dissociation yield under the influences of charge Coulomb interaction and non-radiative recombination. We find that the electron-hole local Coulomb attraction and charge carriers' coupling parameters play an important role in the system performance and in the optimal energy conversion efficiency of the BHJ photocell. We show that the fixed-hole models tend to underestimate the yield.

  4. Doubly excited {sup 1,3}P{sup e} resonance states of helium and the hydrogen negative ion interacting with Coulomb and screened Coulomb potentials

    SciTech Connect

    Kar, Sabyasachi; Ho, Y. K.

    2011-04-15

    We have investigated the doubly excited {sup 1,3}P{sup e} resonance states of helium and the hydrogen negative ion interacting with Coulomb and screened Coulomb potentials using exponential correlated wave functions. In the pure Coulomb case, calculations have been carried out by using the complex-coordinate rotation and the stabilization method. The {sup 1}P{sup e} resonance states of He below the N= 3, 4, and 5 thresholds of He{sup +}, and the {sup 3}P{sup e} resonance states of He below the N= 3 thresholds of He{sup +}, are reported. The 5p{sup 2} {sup 3}P{sup e} state, which has attracted recent interest, is also reported and discussed. In the screened Coulomb case, we have used the stabilization method to obtain two different series (3pnp and 3dnd) of resonance states below the N= 3 He{sup +} threshold as a function of the screening parameters. Resonance widths for the 3dnd series show some interesting behaviors. The resonance parameters (position and width) for helium and the hydrogen negation ion as functions of the screening parameters are reported.

  5. 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

  6. 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

  7. Understanding the influence of Coulomb and dispersion interactions on the wetting behavior of ionic liquids.

    PubMed

    Rane, Kaustubh S; Errington, Jeffrey R

    2014-11-01

    We study the role of dispersion and electrostatic interactions in the wetting behavior of ionic liquids on non-ionic solid substrates. We consider a simple model of an ionic liquid consisting of spherical ions that interact via Lennard-Jones and Coulomb potentials. Bulk and interfacial properties are computed for five fluids distinguished by the strength of the electrostatic interaction relative to the dispersion interaction. We employ Monte Carlo simulations and an interface-potential-based approach to calculate the liquid-vapor and substrate-fluid interfacial properties. Surface tensions for each fluid are evaluated over a range of temperatures that spans from a reduced temperature of approximately 0.6 to the critical point. Contact angles are calculated at select temperatures over a range of substrate-fluid interaction strengths that spans from the near-drying regime to the wetting regime. We observe that an increase in the relative strength of Coulombic interactions between ions leads to increasing deviation from Guggenheim's corresponding states theory. We show how this deviation is related to lower values of liquid-vapor excess entropies observed for strongly ionic fluids. Our results show that the qualitative nature of wetting behavior is significantly influenced by the competition between dispersion and electrostatic interactions. We discuss the influence of electrostatic interactions on the nature of wetting and drying transitions and corresponding states like behavior observed for contact angles. For all of the fluids studied, we observe a relatively narrow range of substrate-fluid interaction strengths wherein the contact angle is nearly independent of temperature. The influence of the ionic nature of the fluid on the temperature dependence of contact angle is also discussed. PMID:25381536

  8. 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.

  9. Theory of intervalley Coulomb interactions in monolayer transition-metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Dery, Hanan

    2016-08-01

    Exciton optical transitions in transition-metal dichalcogenides offer unique opportunities to study rich many-body physics. Recent experiments in monolayer WSe2 and WS2 have shown that, while the low-temperature photoluminescence from neutral excitons and three-body complexes is suppressed in the presence of elevated electron densities or strong photoexcitation, new dominant peaks emerge in the low-energy side of the spectrum. I present a theory that elucidates the nature of these optical transitions showing the role of the intervalley Coulomb interaction. After deriving a compact dynamical form for the Coulomb potential, I calculate the self-energy of electrons due to their interaction with this potential. For electrons in the upper valleys of the spin-split conduction band, the self-energy includes a moderate redshift due to exchange and, most importantly, a correlation-induced virtual state in the band gap. The latter sheds light on the origin of the luminescence in monolayer WSe2 and WS2 in the presence of pronounced many-body interactions.

  10. Coulomb-induced pairing in a quarter-filled band model for κ-(BEDT-TTF)2X

    NASA Astrophysics Data System (ADS)

    de Silva, W. Wasanthi; Gomes, Niladri; Mazumdar, Sumit; Clay, R. Torsten

    κ -(BEDT-TTF)2X is a two dimensional organic charge transfer solid superconductor with a hole density of one half per (BEDT-TTF) molecule. With one hole per dimer of molecules, the material is frequently described using an effective 1 / 2 -filled band Hubbard model on an anisotropic triangular lattice. Within this effective model a metal to antiferromagnetic (AFM) semiconductor phase transition is found. Calculations beyond the mean field level, however, have shown absence of superconductivity within the model. We present the results of correlated-electron calculations on the κ-lattice for up to 64 BEDT-TTF molecules using the Constrained Path Monte Carlo (CPMC) and Path Integral Renormalization Group (PIRG) methods over a wide range of carrier density. We show that superconducting pair-pair correlations in this model are enhanced by electron-electron (e-e) interactions for d-wave pairing symmetry uniquely for hole density close to quarter-filling. Our results indicate that this enhancement of superconductivity is not related to the presence of AFM order, but to the strong tendency to spin-singlet formation in the quarter-filled band. Supported by DOE Grant DE-FG02-06ER46315 and NSF-CHE-151475.

  11. Coulomb drag

    NASA Astrophysics Data System (ADS)

    Narozhny, B. N.; Levchenko, A.

    2016-04-01

    Coulomb drag is a transport phenomenon whereby long-range Coulomb interaction between charge carriers in two closely spaced but electrically isolated conductors induces a voltage (or, in a closed circuit, a current) in one of the conductors when an electrical current is passed through the other. The magnitude of the effect depends on the exact nature of the charge carriers and the microscopic, many-body structure of the electronic systems in the two conductors. Drag measurements have become part of the standard toolbox in condensed matter physics that can be used to study fundamental properties of diverse physical systems including semiconductor heterostructures, graphene, quantum wires, quantum dots, and optical cavities.

  12. 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.

  13. 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. PMID:27035318

  14. Relativistic symmetries with the trigonometric Pöschl—Teller potential plus Coulomb-like tensor interaction

    NASA Astrophysics Data System (ADS)

    Babatunde, J. Falaye; Sameer, M. Ikhdair

    2013-06-01

    The Dirac equation is solved to obtain its approximate bound states for a spin-1/2 particle in the presence of trigonometric Pöschl—Teller (tPT) potential including a Coulomb-like tensor interaction with arbitrary spin—orbit quantum number κ using an approximation scheme to substitute the centrifugal terms κ(κ ± 1)r-2. In view of spin and pseudo-spin (p-spin) symmetries, the relativistic energy eigenvalues and the corresponding two-component wave functions of a particle moving in the field of attractive and repulsive tPT potentials are obtained using the asymptotic iteration method (AIM). We present numerical results in the absence and presence of tensor coupling A and for various values of spin and p-spin constants and quantum numbers n and κ. The non-relativistic limit is also obtained.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Hartree-Fock ground-state energy of anyons with no Coulomb interaction in the zero effective field

    NASA Astrophysics Data System (ADS)

    Sitko, Piotr

    1994-05-01

    We find, in the Hartree-Fock approximation, the ground-state energy of anyons with no Coulomb interaction in the case when the external magnetic field precisely cancels the average statistical field. From the point of view of the fractional quantum Hall effect it is shown that statistics transmutations to superfermions at filling fractions v = {1}/{2 p} are not energetically favourable.

  3. Charge and spin order in one dimensional systems with long range Coulomb interaction

    NASA Astrophysics Data System (ADS)

    Belen Valenzuela, M.; Fratini, Simone; Baeriswyl, Dionys

    2004-03-01

    In this talk I present our results of studying a system of electrons on a one-dimensional lattice, interacting through long range Coulomb forces, by means of a variational technique which is the strong coupling analog of the Gutzwiller approach. For quarter filling we find that the effects of commensurability together with the strength of the interaction give rise to charge ordering as the ground state. When we add the spin degrees of freedom it is found that they are coupled by an antiferromagnetic kinetic exchange J, which turn out to be much smaller than the energy scale governing the charge degrees of freedom. Our results shed new light on the insulating phases of organic quasi-1D compounds where charge ordering sets in at high temperatures and coexists with spin ordering at low temperatures. We also present a phase diagram of interaction versus fillings where we identify three phases: weak charge density waves, Wigner crystal and Generalized Wigner crystal (solution of the Wigner crystal problem with the additional constraint for the electrons of living in the host lattice of the ions). Refs: B. Valenzuela et al. Phys. Rev. B, 68 (2003) 045112, S. Fratini et al. Contribution to the Michael J. Rice Special Issue of "Synthetic Metals" 2003, (cond-mat/0309450).

  4. Glucose-Nucleobase Pseudo Base Pairs: Biomolecular Interactions within DNA.

    PubMed

    Vengut-Climent, Empar; Gómez-Pinto, Irene; Lucas, Ricardo; Peñalver, Pablo; Aviñó, Anna; Fonseca Guerra, Célia; Bickelhaupt, F Matthias; Eritja, Ramón; González, Carlos; Morales, Juan C

    2016-07-18

    Noncovalent forces rule the interactions between biomolecules. Inspired by a biomolecular interaction found in aminoglycoside-RNA recognition, glucose-nucleobase pairs have been examined. Deoxyoligonucleotides with a 6-deoxyglucose insertion are able to hybridize with their complementary strand, thus exhibiting a preference for purine nucleobases. Although the resulting double helices are less stable than natural ones, they present only minor local distortions. 6-Deoxyglucose stays fully integrated in the double helix and its OH groups form two hydrogen bonds with the opposing guanine. This 6-deoxyglucose-guanine pair closely resembles a purine-pyrimidine geometry. Quantum chemical calculations indicate that glucose-purine pairs are as stable as a natural T-A pair. PMID:27328804

  5. 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.

  6. Systematic Detection of Epistatic Interactions Based on Allele Pair Frequencies

    PubMed Central

    Ackermann, Marit; Beyer, Andreas

    2012-01-01

    Epistatic genetic interactions are key for understanding the genetic contribution to complex traits. Epistasis is always defined with respect to some trait such as growth rate or fitness. Whereas most existing epistasis screens explicitly test for a trait, it is also possible to implicitly test for fitness traits by searching for the over- or under-representation of allele pairs in a given population. Such analysis of imbalanced allele pair frequencies of distant loci has not been exploited yet on a genome-wide scale, mostly due to statistical difficulties such as the multiple testing problem. We propose a new approach called Imbalanced Allele Pair frequencies (ImAP) for inferring epistatic interactions that is exclusively based on DNA sequence information. Our approach is based on genome-wide SNP data sampled from a population with known family structure. We make use of genotype information of parent-child trios and inspect 3×3 contingency tables for detecting pairs of alleles from different genomic positions that are over- or under-represented in the population. We also developed a simulation setup which mimics the pedigree structure by simultaneously assuming independence of the markers. When applied to mouse SNP data, our method detected 168 imbalanced allele pairs, which is substantially more than in simulations assuming no interactions. We could validate a significant number of the interactions with external data, and we found that interacting loci are enriched for genes involved in developmental processes. PMID:22346757

  7. Importance of anisotropic Coulomb interaction in LaMnO3

    NASA Astrophysics Data System (ADS)

    Mellan, Thomas A.; Corà, Furio; Grau-Crespo, Ricardo; Ismail-Beigi, Sohrab

    2015-08-01

    In low-temperature antiferromagnetic LaMnO3, strong and localized electronic interactions among Mn 3 d electrons prevent a satisfactory description from standard local density and generalized gradient approximations in density functional theory calculations. Here, we show that the strong on-site electronic interactions are described well only by using direct and exchange corrections to the intraorbital Coulomb potential. Only DFT + U calculations with explicit exchange corrections produce a balanced picture of electronic, magnetic, and structural observables in agreement with experiment. To understand the reason, a rewriting of the functional form of the + U corrections is presented that leads to a more physical and transparent understanding of the effect of these correction terms. The approach highlights the importance of Hund's coupling (intraorbital exchange) in providing anisotropy across the occupation and energy eigenvalues of the Mn d states. This intraorbital exchange is the key to fully activating the Jahn-Teller distortion, reproducing the experimental band gap and stabilizing the correct magnetic ground state in LaMnO3. The best parameter values for LaMnO3 within the DFT (PBEsol) + U framework are determined to be U =8 eV and J =1.9 eV.

  8. The Coulomb interaction in Helium-3: Interplay of strong short-range and weak long-range potentials

    NASA Astrophysics Data System (ADS)

    Kirscher, J.; Gazit, D.

    2016-04-01

    Quantum chromodynamics and the electroweak theory at low energies are prominent instances of the combination of a short-range and a long-range interaction. For the description of light nuclei, the large nucleon-nucleon scattering lengths produced by the strong interaction, and the reduction of the weak interaction to the Coulomb potential, play a crucial role. Helium-3 is the first bound nucleus comprised of more than one proton in which this combination of forces can be studied. We demonstrate a proper renormalization of Helium-3 using the pionless effective field theory as the formal representation of the nuclear regime as strongly interacting fermions. The theory is found consistent at leading and next-to-leading order without isospin-symmetry-breaking 3-nucleon interactions and a non-perturbative treatment of the Coulomb interaction. The conclusion highlights the significance of the regularization method since a comparison to previous work is contradictory if the difference in those methods is not considered. With a perturbative Coulomb interaction, as suggested by dimensional analysis, we find the Helium-3 system properly renormalized, too. For both treatments, renormalization-scheme independence of the effective field theory is demonstrated by regulating the potential and a variation of the associated cutoff.

  9. Pair interaction energy for a 12-electron 2D square Quantum Dot.

    NASA Astrophysics Data System (ADS)

    Nissenbaum, Daniel; Barbiellini, Bernardo; Bansil, Arun

    2004-03-01

    We have investigated a system of 12 electrons enclosed in a 2D square well representing a quantum dot. We employ a Jastrow-type wavefunction with Slater determinants and optimize the Jastrow parameter using the variational Monte Carlo method. We use the Metropolis algorithm to select a large distribution of configuration points and to perform a relatively noiseless calculation of the radial distribution function and to obtain insight into the contrast between the Fermi hole for the same-spin electrons and the Coulomb hole for the opposite-spin electrons. The calculated pair interaction energy provides a handle for constructing a model Hamiltonian useful for the study of spontaneous spin magnetization of the system. Work supported in part by the USDOE.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. Fast Multipole Method for Coulomb Interaction Based on Traceless Totally Symmetric Tensor

    NASA Astrophysics Data System (ADS)

    Huang, He; Li, Rui; Chen, Jie; Luo, Li-Shi; Zhang, He

    2015-04-01

    The fast multipole method (FMM) is widely used to calculate the Coulomb interaction between a huge amount of charged particles. The efficiency of FMM scales with O(N) for N particles with any arbitrary distribution. Hence it is apposite for problems with complicated charge distribution or geometry. Under the same FMM framework, there are different approaches, such as using spherical harmonic functions or Maxwell Cartesian tensors. Here we will present a version using traceless totally symmetric Maxwell Cartesian tensor. The previous Maxwell Cartesian tensor based FMM uses totally symmetric tensor. There are (n + 1)(n + 2) / 2 independent elements in a rank n totally symmetric tensor. However, there are only 2 n + 1 independent elements in a rank n traceless totally symmetric tensor, due to which the efficiency of the traceless version is highly improved compared with the old version, especially when high accuracy is needed and high rank tensors are used. Work supported by the Department of Energy, Laboratory Directed Research and Development Funding, under Contract No. DE-AC05-06OR23177.

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

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

    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.

  16. 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

  17. 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.

  18. Anisotropy of the Coulomb Interaction between Folded Proteins: Consequences for Mesoscopic Aggregation of Lysozyme

    PubMed Central

    Chan, Ho Yin; Lankevich, Vladimir; Vekilov, Peter G.; Lubchenko, Vassiliy

    2012-01-01

    Toward quantitative description of protein aggregation, we develop a computationally efficient method to evaluate the potential of mean force between two folded protein molecules that allows for complete sampling of their mutual orientation. Our model is valid at moderate ionic strengths and accounts for the actual charge distribution on the surface of the molecules, the dielectric discontinuity at the protein-solvent interface, and the possibility of protonation or deprotonation of surface residues induced by the electric field due to the other protein molecule. We apply the model to the protein lysozyme, whose solutions exhibit both mesoscopic clusters of protein-rich liquid and liquid-liquid separation; the former requires that protein form complexes with typical lifetimes of approximately milliseconds. We find the electrostatic repulsion is typically lower than the prediction of the Derjaguin-Landau-Verwey-Overbeek theory. The Coulomb interaction in the lowest-energy docking configuration is nonrepulsive, despite the high positive charge on the molecules. Typical docking configurations barely involve protonation or deprotonation of surface residues. The obtained potential of mean force between folded lysozyme molecules is consistent with the location of the liquid-liquid coexistence, but produces dimers that are too short-lived for clusters to exist, suggesting lysozyme undergoes conformational changes during cluster formation. PMID:22768950

  19. 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''.

  20. 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.

  1. 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.

  2. Pseudopotential theory of interacting roton pairs in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Bedell, K.; Pines, D.; Zawadowski, A.

    1984-01-01

    A configuration-space pseudopotential, which is closely related to that used by Aldrich and Pines to describe the effective interaction between background particles in 3He and 4He, is constructed and used to calculate the roton-roton scattering amplitude. From that amplitude we obtain a theory that is completely congruent with the roton-liquid theory of Bedell, Pines, and Fomin. We calculate two-roton bound states, roton-liquid parameters, and roton lifetimes, as well as information about the hybridization of the two-roton bound state with excitations of higher and lower energy. Excellent agreement between theory and experiment is obtained for the l=2 bound state at zero pair momentum, the roton lifetime, the roton contribution to the normal-fluid viscosity and the normal-fluid density, and the temperature variation of the roton energy. The effective roton-roton coupling parameters at large pair momentum are found to be an order of magnitude larger than those for small or vanishing pair momentum. At SVP we find that a substantial number of two-roton bound states of varying symmetry exist for pair momentum up to ~ 3 Å -1; at standard pressure, however the roton-roton interaction for momenta ~ 1 Å -1 is found to become repulsive, so that both the l=2 bound state at zero pair momentum and bound states at intermediate momenta are predicted to disappear under pressure.

  3. Interaction effects on the tunneling of electron-hole pairs in coupled quantum dots

    NASA Astrophysics Data System (ADS)

    Guerrero, Hector M.; Cocoletzi, Gregorio H.; Ulloa, Sergio E.

    2001-03-01

    The transit time of carriers is beginning to be an important parameter in the physical operation of semiconductor quantum dot `devices'. In the present work, we study the coherent propagation of electron-hole pairs in coupled self-assembled quantum dots in close proximity. These systems, achieved experimentally in a number of different geometries, have been recently implemented as a novel storage of optical information that may give rise to smart pixel technology in the near future [1]. Here, we apply an effective mass hamiltonian approach and solve numerically the time dependent Schroedinger equation of a system of photo-created electron-hole pairs in the dots. Our approach takes into account both Coulomb interactions and confinement effects. The time evolution is investigated in terms of the structural parameters for typical InAs-GaAs dots. Different initial conditions are considered, reflecting the basic processes that would take place in these experiments. We study the probabilities of finding the electron and hole in either the same or adjacent quantum dot, and study carefully the role of interactions in this behavior. [1] T. Lundstrom, W. Schoenfeld, H. Lee, and P. M. Petroff, Science 286, 2312 (1999).

  4. Interactional Competence across Proficiency Levels: How Do Learners Manage Interaction in Paired Speaking Tests?

    ERIC Educational Resources Information Center

    Galaczi, Evelina D.

    2014-01-01

    Paired speaking tasks are now commonly used in both pedagogic and assessment contexts, as they elicit a wide range of interactional skills. The current study aims to offer an investigation of the interaction co-constructed by learners at different proficiency levels who are engaged in a paired speaking test, and to provide insights into the…

  5. A flexible algorithm for calculating pair interactions on SIMD architectures

    NASA Astrophysics Data System (ADS)

    Páll, Szilárd; Hess, Berk

    2013-12-01

    Calculating interactions or correlations between pairs of particles is typically the most time-consuming task in particle simulation or correlation analysis. Straightforward implementations using a double loop over particle pairs have traditionally worked well, especially since compilers usually do a good job of unrolling the inner loop. In order to reach high performance on modern CPU and accelerator architectures, single-instruction multiple-data (SIMD) parallelization has become essential. Avoiding memory bottlenecks is also increasingly important and requires reducing the ratio of memory to arithmetic operations. Moreover, when pairs only interact within a certain cut-off distance, good SIMD utilization can only be achieved by reordering input and output data, which quickly becomes a limiting factor. Here we present an algorithm for SIMD parallelization based on grouping a fixed number of particles, e.g. 2, 4, or 8, into spatial clusters. Calculating all interactions between particles in a pair of such clusters improves data reuse compared to the traditional scheme and results in a more efficient SIMD parallelization. Adjusting the cluster size allows the algorithm to map to SIMD units of various widths. This flexibility not only enables fast and efficient implementation on current CPUs and accelerator architectures like GPUs or Intel MIC, but it also makes the algorithm future-proof. We present the algorithm with an application to molecular dynamics simulations, where we can also make use of the effective buffering the method introduces.

  6. Interatomic Coulomb interaction and electron nematic bond order in FeSe

    NASA Astrophysics Data System (ADS)

    Jiang, Kun; Hu, Jiangping; Ding, Hong; Wang, Ziqiang

    2016-03-01

    Despite having the simplest atomic structure, bulk FeSe has an observed electronic structure with the largest deviation from the band theory predictions among all Fe-based superconductors and exhibits a low-temperature nematic electronic state without intervening magnetic order. We show that the Fe-Fe interatomic Coulomb repulsion V offers a natural explanation for the puzzling electron correlation effects in FeSe superconductors. It produces a strongly renormalized low-energy band structure where the van Hove singularity sits remarkably close to Fermi level in the high-temperature electron liquid phase as observed experimentally. This proximity enables the quantum fluctuations in V to induce a rotational symmetry breaking electronic bond order in the d -wave channel. We argue that this emergent low-temperature d -wave bond nematic state, different from the commonly discussed ferro-orbital order and spin nematicity, has been observed recently by several angle-resolved photoemission experiments detecting the lifting of the band degeneracies at high-symmetry points in the Brillouin zone. We present a symmetry analysis of the space group and identify the hidden antiunitary T symmetry that protects the band degeneracy and the electronic order/interaction that can break the symmetry and lift the degeneracy. We show that the d -wave nematic bond order, together with the spin-orbit coupling, provide a unique explanation of the temperature dependence, momentum space anisotropy, and domain effects observed experimentally. We discuss the implications of our findings on the structural transition, the absence of magnetic order, and the intricate competition between nematicity and superconductivity in FeSe superconductors.

  7. Pair interaction of catalytically active colloids: from assembly to escape

    NASA Astrophysics Data System (ADS)

    Sharifi-Mood, Nima; Mozaffari, Ali; Córdova-Figueroa, Ubaldo M.

    2016-07-01

    The dynamics and pair trajectory of two self-propelled colloids are reported. The autonomous motions of the colloids are due to a catalytic chemical reaction taking place asymmetrically on their surfaces that generates a concentration gradient of interactive solutes around the particles and actuate particle propulsion. We consider two spherical particles with symmetric catalytic caps extending over the local polar angles $\\theta^1_{cap}$ and $\\theta^2_{cap}$ from the centers of active sectors in an otherwise quiescent fluid. A combined analytical-numerical technique was developed to solve the coupled mass transfer equation and the hydrodynamics in the Stokes flow regime. The ensuing pair trajectory of the colloids is controlled by the reacting coverages $\\theta^j_{cap}$ and their initial relative orientation with respect to each other. Our analysis indicates two possible scenarios for pair trajectories of catalytic self-propelled particles: either the particles approach, come into contact and assemble or they interact and move away from each other (escape). For arbitrary motions of the colloids, it is found that the direction of particle rotations is the key factor in determining the escape or assembly scenario. Based on the analysis, a phase diagram is sketched for the pair trajectory of the catalytically active particles as a function of active coverages and their initial relative orientations. We believe this study has important implications in elucidation of collective behaviors of auotophoretically self-propelled colloids.

  8. 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

  9. Alignment of H(2p) in collisions of protons and antiprotons with hydrogen atoms with screened Coulomb interaction

    NASA Astrophysics Data System (ADS)

    Jakimovski, Dragan; Janev, Ratko K.

    2016-07-01

    The effects of screened Coulomb interaction on the alignment of H(2p) state produced in collisions of hydrogen atoms with protons and antiprotons are investigated in the energy range 1-200 keV by using the two-center atomic orbital close-coupling (TC-AOCC) method. It is shown that the decrease of the binding energy of hydrogen nl-states and the reduction of the number of bound states with increasing the strength of the screening affect significantly the alignment degree and its energy dependence. In the case of antiproton-H collision the difference between the alignments with screened and unscreened Coulomb potential increases with increasing the strength of the screening in the entire energy range above 2 keV/u, while in the case of proton-H collision it does so only in the energy range 5-25 keV/u.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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 C3 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.

  11. 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.

  12. 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.

  13. 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. PMID:27284655

  14. 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. PMID:21867316

  15. Non-separable pairing interaction kernels applied to superconducting cuprates

    NASA Astrophysics Data System (ADS)

    Haley, Stephen B.; Fink, Herman J.

    2014-05-01

    A pairing Hamiltonian H(Γ) with a non-separable interaction kernel Γ produces HTS for relatively weak interactions. The doping and temperature dependence of Γ(x,T) and the chemical potential μ(x) is determined by a probabilistic filling of the electronic states in the cuprate unit cell. A diverse set of HTS and normal state properties is examined, including the SC phase transition boundary TC(x), SC gap Δ(x,T), entropy S(x,T), specific heat C(x,T), and spin susceptibility χs(x,T). Detailed x,T agreement with cuprate experiment is obtained for all properties.

  16. 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.

  17. Ordered phases in the Holstein-Hubbard model: Interplay of strong Coulomb interaction and electron-phonon coupling

    NASA Astrophysics Data System (ADS)

    Murakami, Yuta; Werner, Philipp; Tsuji, Naoto; Aoki, Hideo

    2013-09-01

    We study the Holstein-Hubbard model at half filling to explore ordered phases including superconductivity (SC), antiferromagnetism (AF), and charge order (CO) in situations where the electron-electron and electron-phonon interactions are strong (comparable to the electronic bandwidth). The model is solved in the dynamical mean-field approximation with a continuous-time quantum Monte Carlo impurity solver. We determine the superconducting transition temperature Tc and the SC order parameter and show that the phonon-induced retardation or the strong Coulomb interaction leads to a significant reduction and shift of the Tc dome against the effective electron-electron interaction Ueff given by the Hubbard U reduced by the phonon-mediated attraction in the static limit. This behavior is analyzed by comparison to an effective static model in the polaron representation with a renormalized bandwidth. In addition, we discuss the superconducting gap Δ and 2Δ/Tc to reveal the effect of the retardation and the Coulomb interaction. We also determine the finite-temperature phase diagram including AF and CO. In the moderate-coupling regime, there is a hysteretic region of AF and CO around Ueff=0, while the two phases are separated by a paramagnetic metal in the weak-coupling regime and a paramagnetic insulator in the strong-coupling regime.

  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. 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.

  20. Screened Coulomb interactions in metallic alloys. II. Screening beyond the single-site and atomic-sphere approximations

    NASA Astrophysics Data System (ADS)

    Ruban, A. V.; Simak, S. I.; Korzhavyi, P. A.; Skriver, H. L.

    2002-06-01

    A quantitative description of the configurational part of the total energy of metallic alloys with substantial atomic size difference cannot be achieved in the atomic-sphere approximation: It needs to be corrected at least for the multipole-moment interactions in the Madelung part of the one-electron potential and energy. In the case of a random alloy such interactions can be accounted for only by lifting the atomic-sphere and single-site approximations, in order to include the polarization due to local environment effects. Nevertheless, a simple parametrization of the screened Coulomb interactions for the ordinary single-site methods, including the generalized perturbation method, is still possible. We obtained such a parametrization for bulk and surface NiPt alloys, which allows one to obtain quantitatively accurate effective interactions in this system.

  1. Interaction-induced pair hyperpolarizabilities by spherical irreducible tensors

    NASA Astrophysics Data System (ADS)

    Bancewicz, Tadeusz

    1999-10-01

    Starting from the electrostatic part of the intermolecular multipole interaction energy we derived irreducible spherical tensor formulas for the first-order long-range, interaction-induced first and second pair hyperpolarizabilities ΔβLM and ΔγLM for arbitrary shape monomers. For atoms a general relation is obtained for the dipolei-2k-pole hyperpolarizability tensor Z(i+k) of arbitrary order, between its irreducible spherical components Z00[((((11)a11)a2…)ai-21)kk] and the Cartesian counterpart Zzz…z(i+k). For isotropic systems the expressions for Δβzzz and Δγzzzz are in full agreement with the Cartesian tensor results of Buckingham, Concannon and Hands [J. Phys. Chem. 98, 10455 (1994)] and Li et al. [J. Chem. Phys. 105, 10954 (1996)]. Our irreducible spherical tensor results for ΔβLM and ΔγLM are very desirable when dealing with molecular rotations, e.g., in spectral line shape calculations of interaction-induced hyper-Rayleigh and/or hyper-Raman light scattering. Finally we show how our spherical tensor formula for ΔβLM can be used for calculation of, one molecule forbidden, hyper-Rayleigh and hyper-Raman (A1 vibration) pair hyperpolarizability Δβzzz for molecules of octahedral symmetry Oh.

  2. 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.

  3. Spin-orbit interaction in bremsstrahlung and its effect on the electron motion in a strong Coulomb field

    NASA Astrophysics Data System (ADS)

    Kovtun, Oleksiy; Tioukine, Valeri; Surzhykov, Andrey; Yerokhin, Vladimir A.; Cederwall, Bo; Tashenov, Stanislav

    2015-12-01

    Linear polarization of bremsstrahlung x rays produced in collisions of longitudinally polarized 2.1-MeV electrons with gold atoms was studied using the Compton scattering technique. We observed that the angle of x-ray polarization is strongly correlated with the incoming electron polarization. This correlation reveals the dominance of the spin-orbit interaction in bremsstrahlung and indicates a striking effect of the electron spin on the electron motion in a strong Coulomb field. The results confirm the validity of the theoretical predictions in a computationally challenging energy regime.

  4. Spatial Patterns in Rydberg Excitations from Logarithmic Pair Interactions.

    PubMed

    Lechner, Wolfgang; Zoller, Peter

    2015-09-18

    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. PMID:26430998

  5. 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. PMID:26434352

  6. 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

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

    NASA Astrophysics Data System (ADS)

    Zimbovskaya, Natalya A.

    2015-06-01

    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.

  8. 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.

  9. Effect of Coulomb interaction on time of flight of cold antiprotons launched from an ion trap

    NASA Technical Reports Server (NTRS)

    Camp, J. B.; Witteborn, F. C.

    1993-01-01

    Time-of-flight spectra for Maxwell-Boltzman (MB) distributions of antiprotons initially held in an ion trap and detected after being launched through a 50-cm-long shielding drift tube have been calculated. The distributions used are of temperature 0.4-40 K, cubic length 0.003-3.0 cm, and number 10-100 particles. The mutual Coulomb repulsion of the particles causes a reduction in the number of late arrival particles expected from the MB velocity distribution. The Coulomb energy is not equally divided among the particles during the expansion. The energy is transferred preferentially to the outer particles so that the reduction in the number of slow particles is not necessarily large. The reduction factor is found to be greater than unity when the potential energy of the trapped ions is greater than about 5 percent of the ions' kinetic energy and is about 2 for the launch parameters of the Los Alamos antiproton gravity experiment.

  10. Repulsive interactions in quantum Hall systems as a pairing problem

    NASA Astrophysics Data System (ADS)

    Ortiz, G.; Nussinov, Z.; Dukelsky, J.; Seidel, A.

    2013-10-01

    A subtle relation between quantum Hall physics and the phenomenon of pairing is unveiled. By use of second quantization, we establish a connection between (i) a broad class of rotationally symmetric two-body interactions within the lowest Landau level and (ii) integrable hyperbolic Richardson-Gaudin-type Hamiltonians that arise in (px+ipy) superconductivity. Specifically, we show that general Haldane pseudopotentials (and their sums) can be expressed as a sum of repulsive noncommuting (px+ipy)-type pairing Hamiltonians. The determination of the spectrum and individual null spaces of each of these noncommuting Richardson-Gaudin-type Hamiltonians is nontrivial yet is Bethe ansatz solvable. For the Laughlin sequence, it is observed that this problem is frustration free and zero-energy ground states lie in the common null space of all of these noncommuting Hamiltonians. This property allows for the use of a new truncated basis of pairing configurations in which to express Laughlin states at general filling factors. We prove separability of arbitrary Haldane pseudopotentials, providing explicit expressions for their second quantized forms, and further show by explicit construction how to exploit the topological equivalence between different geometries (disk, cylinder, and sphere) sharing the same topological genus number, in the second quantized formalism, through similarity transformations. As an application of the second quantized approach, we establish a “squeezing principle” that applies to the zero modes of a general class of Hamiltonians, which includes but is not limited to Haldane pseudopotentials. We also show how one may establish (bounds on) “incompressible filling factors” for those Hamiltonians. By invoking properties of symmetric polynomials, we provide explicit second quantized quasihole generators; the generators that we find directly relate to bosonic chiral edge modes and further make aspects of dimensional reduction in the quantum Hall systems

  11. 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.

  12. 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.

  13. Dynamics and thermodynamics of a pair of interacting magnetic dipoles

    NASA Astrophysics Data System (ADS)

    Schmidt, Heinz-Jürgen; Schröder, Christian; Hägele, Eva; Luban, Marshall

    2015-05-01

    We consider the dynamics and thermodynamics of a pair of magnetic dipoles interacting via their magnetic fields. We consider only the ‘spin’ degrees of freedom; the dipoles are fixed in space. With this restriction it is possible to provide the general solution of the equations of motion in analytical form. Thermodynamic quantities, such as the specific heat and the zero field susceptibility are calculated analytically or by combining low temperature asymptotic series and a complete high temperature expansion. The thermal expectation value of the autocorrelation function is determined for the low temperature regime and short times including terms linear in T. Furthermore, we have performed Monte Carlo simulations for the system under consideration and compared our analytical results with these.

  14. 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.

  15. Charge transport in charge-ordered layered crystals θ-(BEDT-TTF)2MZn(SCN)4 (M=Cs,Rb) : Effects of long-range Coulomb interaction and the Pauli exclusion principle

    NASA Astrophysics Data System (ADS)

    Takahide, Yamaguchi; Kimata, Motoi; Hazama, Kaori; Terashima, Taichi; Uji, Shinya; Konoike, Takako; Yamamoto, Hiroshi M.

    2010-06-01

    We have measured the current-voltage (I-V) characteristics, dielectric properties, and magnetoresistances of insulating layered organic crystals θ-(BEDT-TTF)2MZn(SCN)4 (M=Cs,Rb) , in which electron-electron Coulomb interactions are considered to induce charge ordering. The in-plane I-V characteristics follow the power law with a large exponent that exceeds 10 in the low-temperature limit. The nonlinear I-V characteristics are attributed to electric field induced unbinding of pairs of an electron and a hole that are thermally excited and attracted to each other due to two-dimensional long-range Coulomb interaction. The temperature and frequency dependences of the in-plane dielectric constant for M=Cs are explained by the polarization of the electron-hole bound pairs, consistently with the I-V characteristics. The large dielectric anisotropy ( ≈100 at 0.6 K) observed for M=Cs suggests two-dimensional long-range Coulomb interaction, which is also consistent with the explanation of the nonlinear I-V curves. The organic crystals have a large positive magnetoresistance ratio, e.g., ≈10000% for M=Cs in a magnetic field of 10 T at 0.1 K. The magnetoresistance is nearly independent of the magnetic field orientation despite the highly two-dimensional charge transport, indicating that it is electron-spin related. The magnetoresistance may be caused by magnetic field induced parallel alignment of spins of mobile and localized electrons, both in the highest occupied molecular orbital of a BEDT-TTF molecule, and by the resulting suppression of conduction due to the Pauli exclusion principle.

  16. Modeling the initial conditions of interacting galaxy pairs using Identikit

    NASA Astrophysics Data System (ADS)

    Mortazavi, S. Alireza; Lotz, Jennifer M.; Barnes, Joshua E.; Snyder, Gregory F.

    2016-01-01

    We develop and test an automated technique to model the dynamics of interacting galaxy pairs. We use Identikit as a tool for modelling and matching the morphology and kinematics of the interacting pairs of equal-mass galaxies. In order to reduce the effect of subjective human judgement, 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-fitting model. In this work, we use an independent set of GADGET SPH simulations as input data to determine the systematic bias in the measured encounter parameters based on the known initial conditions of these simulations. We test both cold gas and young stellar components in the GADGET simulations to explore the effect of choosing H I versus H α as the line-of-sight velocity tracer. We find that we can group the results into tests with good, fair, and poor convergence based on the distribution of parameters of models close to the best-fitting model. For tests with good and fair convergence, we rule out large fractions of parameter space and recover merger stage, eccentricity, pericentric distance, viewing angle, and initial disc orientations within 3σ of the correct value. All of tests on prograde-prograde systems have either good or fair convergence. The results of tests on edge-on discs are less biased than face-on tests. Retrograde and polar systems do not converge and may require constraints from regions other than the tidal tails and bridges.

  17. Thermoelectric transport through a zigzag like chain: Influence of the chain length, the interdot tunneling and the intradot Coulomb interaction

    NASA Astrophysics Data System (ADS)

    Li, Rui-Xue; Ni, Yun; Li, Hai-Dong; Tian, Xing-Ling; Yao, Kai-Lun; Fu, Hua-Hua

    2016-07-01

    We have studied the thermoelectric transport through a zigzaglike chain in the linear response regime using the non-equilibrium Green's function method. This model consists of the main zigzaglike chain and the side radicals coupled with the main chain at the next-near-neighbor sites. The finite-scale effect on the thermoelectric properties has been studied, our results show that thermoelectric efficiency can be enhanced by increasing the chain length. The thermopower and the figure of merit can be enhanced by strengthening the interdot tunneling coupling between the main chain and the side radicals. However, increase of the interdot tunneling coupling in the main chain can weaken the thermoelectric efficiency. Moreover, the thermoelectric efficiency is also strongly dependent on the intradot Coulomb interaction. These results can provide a guidance for the synthesis of thermal devices with high thermoelectric efficiency.

  18. 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)

  19. 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…

  20. A comparison of Coulombic interaction methods in non-equilibrium studies of heat transfer in water

    NASA Astrophysics Data System (ADS)

    Muscatello, Jordan; Bresme, Fernando

    2011-12-01

    We investigate the impact of the treatment of electrostatic interactions on the heat conduction of liquid water. With this purpose, we report a series of non-equilibrium molecular dynamics computer simulations of the Modified Central Force Model of water. We consider both the Ewald summation approach, which includes the full range of the electrostatic interactions, and the Wolf method, which uses a cutoff to truncate the long range contributions. It is shown that the relaxation of the temperature profiles towards the stationary state solution and the equation of state of the liquid are not affected by the treatment of the electrostatic interactions. However, the truncation of the interactions results in lower internal energy fluxes as well as lower thermal conductivities. We also find that the anomalous increase of the thermal conductivity of water with temperature is reproduced by the different methods considered in this work, showing that this physical behavior is independent of the treatment of the long range electrostatic interactions.

  1. 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…

  2. 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.

  3. 3d-4f magnetic interaction with density functional theory plus u approach: local Coulomb correlation and exchange pathways.

    PubMed

    Zhang, Yachao; Yang, Yang; Jiang, Hong

    2013-12-12

    The 3d-4f exchange interaction plays an important role in many lanthanide based molecular magnetic materials such as single-molecule magnets and magnetic refrigerants. In this work, we study the 3d-4f magnetic exchange interactions in a series of Cu(II)-Gd(III) (3d(9)-4f(7)) dinuclear complexes based on the numerical atomic basis-norm-conserving pseudopotential method and density functional theory plus the Hubbard U correction approach (DFT+U). We obtain improved description of the 4f electrons by including the semicore 5s5p states in the valence part of the Gd-pseudopotential. The Hubbard U correction is employed to treat the strongly correlated Cu-3d and Gd-4f electrons, which significantly improve the agreement of the predicted exchange constants, J, with experiment, indicating the importance of accurate description of the local Coulomb correlation. The high efficiency of the DFT+U approach enables us to perform calculations with molecular crystals, which in general improve the agreement between theory and experiment, achieving a mean absolute error smaller than 2 cm(-1). In addition, through analyzing the physical effects of U, we identify two magnetic exchange pathways. One is ferromagnetic and involves an interaction between the Cu-3d, O-2p (bridge ligand), and the majority-spin Gd-5d orbitals. The other one is antiferromagnetic and involves Cu-3d, O-2p, and the empty minority-spin Gd-4f orbitals, which is suppressed by the planar Cu-O-O-Gd structure. This study demonstrates the accuracy of the DFT+U method for evaluating the 3d-4f exchange interactions, provides a better understanding of the exchange mechanism in the Cu(II)-Gd(III) complexes, and paves the way for exploiting the magnetic properties of the 3d-4f compounds containing lanthanides other than Gd. PMID:24274078

  4. Competition between disorder and Coulomb interaction in a two-dimensional plaquette Hubbard model

    NASA Astrophysics Data System (ADS)

    Lee, Hunpyo; Jeschke, Harald O.; Valentí, Roser

    2016-06-01

    We have studied a disordered Nc×Nc plaquette Hubbard model on a two-dimensional square lattice at half-filling using a coherent potential approximation (CPA) in combination with a single-site dynamical mean field theory (DMFT) approach with a paramagnetic bath. Such a model conveniently interpolates between the ionic Hubbard model at Nc=√{2 } and the Anderson model at Nc=∞ and enables the analysis of the various limiting properties. We confirmed that within the CPA approach a band insulator behavior appears for noninteracting strongly disordered systems with a small plaquette size Nc=4 , while the paramagnetic Anderson insulator with nearly gapless density of states is present for large plaquette sizes Nc=48 . When the interaction U is turned on in the strongly fluctuating random potential regions, the electrons on the low energy states push each other into high energy states in DMFT in a paramagnetic bath and correlated metallic states with a quasiparticle peak and Hubbard bands emerge, though a larger critical interaction U is needed to obtain this state from the paramagnetic Anderson insulator (Nc=48 ) than from the band insulator (Nc=4 ). Finally, we observe a Mott insulator behavior in the strong interaction U regions for both Nc=4 and Nc=48 independent of the disorder strength. We discuss the application of this model to real materials.

  5. 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…

  6. Phase stability of Fe and Mn within density-functional theory plus on-site Coulomb interaction approaches

    NASA Astrophysics Data System (ADS)

    Stojić, N. L.; Binggeli, N. L.

    Approaches based on the density-functional theory and including the on-site Coulomb interaction U have been extensively used to describe strongly correlated systems. Moreover, it has been shown that even in the case of moderate correlations, present for example in some of the 3d transition metals, this and similar methods can improve upon the local-density and generalized-gradient approximation (LDA and GGA) results. We investigate, by means of the LDA+U and GGA+U approaches, the phase stability of Fe and Mn, for which it is known that the LDA predicts a wrong ground state. In particular, we compare two different double-counting corrections, the so called "fully-localized limit" (FLL) and "around mean-field" (AMF). We find that the LDA and the LDA+UAMF do not yield the correct ground state, while the LDA+UFLL, GGA+UAMF and GGA+UFLL for specific ranges of effective U values, typically around 1 eV, give the correct phase stability, and in general, an improved description of the equilibrium volume and magnetic moment, compared to the GGA values.

  7. Effective on-site Coulomb interaction and electron configurations in transition-metal complexes from constraint density functional theory

    NASA Astrophysics Data System (ADS)

    Nawa, Kenji; Nakamura, Kohji; Akiyama, Toru; Ito, Tomonori; Weinert, Michael

    Effective on-site Coulomb interactions (Ueff) and electron configurations in the localized d and f orbitals of metal complexes in transition-metal oxides and organometallic molecules, play a key role in the first-principles search for the true ground-state. However, wide ranges of values in the Ueff parameter of a material, even in the same ionic state, are often reported. Here, we revisit this issue from constraint density functional theory (DFT) by using the full-potential linearized augmented plane wave method. The Ueff parameters for prototypical transition-metal oxides, TMO (TM =Mn, Fe, Co, Ni), were calculated by the second derivative of the total energy functional with respect to the d occupation numbers inside the muffin-tin (MT) spheres as a function of the sphere radius. We find that the calculated Ueff values depend significantly on the MT radius, with a variation of more than 3 eV when the MT radius changes from 2.0 to 2.7 a.u., but importantly an identical valence band structure can be produced in all the cases, with an approximate scaling of Ueff. This indicates that a simple transferability of the Ueff value among different calculation methods is not allowed. We further extend the constraint DFT to treat various electron configurations of the localized d-orbitals in organometallic molecules, TMCp2 (TM =Cr, Mn, Fe, Co, Ni), and find that the calculated Ueff values can reproduce the experimentally determined ground-state electron configurations.

  8. Heterogeneous dynamics and stretched exponential decay of spatio-temporal correlations for Coulomb-interacting particles in confined geometries

    NASA Astrophysics Data System (ADS)

    Ghosal, Amit; Ash, Biswarup; Chakrabarti, Jaydeb

    2015-03-01

    We investigate the dynamics of Coulomb-interacting confined particles over a range of temperatures capturing the crossover from a Wigner molecule to a liquid-like phase. Dynamical signatures, derived from the Van-Hove correlations, develop pivotal understanding of the phases as well as the intervening crossover, which are inaccessible from the study of static correlations alone. The motion of the particles shows frustrations, produces heterogeneities depending on the observation time-scales and temperatures and results into a non-Gaussian behavior. The extent and nature of the departure of the behavior of spatio-temporal correlations from the conventional wisdom depends crucially on the symmetry of the confinements. In particular, we find that the decay of correlations follow a stretched-exponential form in traps that lack any symmetry. Our data offers a broad support to a theoretical model that integrates the non-Gaussian behavior arising from the convolution of Gaussian fluctuations weighted by appropriate diffusivities, consistent with local dynamics. The richness of information from the dynamic correlation will be shown to improve the understanding of melting in confined systems in a powerful manner.

  9. On the limit of existence of Borromean binding in three-particle systems with screened Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Pawlak, Mariusz; Bylicki, Mirosław; Mukherjee, Prasanta K.

    2014-05-01

    Molecular-type systems, (m1)±(m2)±(m3)∓, consisting of three particles of masses mi and of unit electric charges with the Coulomb interactions weakened by the Debye screening are considered. Existence and range of Borromean binding in symmetric systems (of masses m1 = m2) is investigated with respect to the masses of their constituents. It is shown that such systems can exist in Borromean ground states if the mass ratio q = m3/m1 is less or equal to 1.668. This improves considerably the lower bound to the limit of existence of the Borromean binding of symmetric systems suggested by Pont and Serra (2009 Phys. Rev. A 79 032508) as q ⩽ 1. Qualitative meaning of the improvement is that the Borromean binding occurs not only for systems where two identical particles are heavier than the third one but it is also possible for systems of the opposite mass relation. The range of screening parameter in which a system is Borromean known as a Borromean window is also determined for μ+μ+e-, π+π+μ-, π+μ-μ- and e+e-e-.

  10. Dirac Hamiltonian and Reissner-Nordström metric: Coulomb interaction in curved space-time

    NASA Astrophysics Data System (ADS)

    Noble, J. H.; Jentschura, U. D.

    2016-03-01

    We investigate the spin-1 /2 relativistic quantum dynamics in the curved space-time generated by a central massive charged object (black hole). This necessitates a study of the coupling of a Dirac particle to the Reissner-Nordström space-time geometry and the simultaneous covariant coupling to the central electrostatic field. The relativistic Dirac Hamiltonian for the Reissner-Nordström geometry is derived. A Foldy-Wouthuysen transformation reveals the presence of gravitational and electrogravitational spin-orbit coupling terms which generalize the Fokker precession terms found for the Dirac-Schwarzschild Hamiltonian, and other electrogravitational correction terms to the potential proportional to αnG , where α is the fine-structure constant and G is the gravitational coupling constant. The particle-antiparticle symmetry found for the Dirac-Schwarzschild geometry (and for other geometries which do not include electromagnetic interactions) is shown to be explicitly broken due to the electrostatic coupling. The resulting spectrum of radially symmetric, electrostatically bound systems (with gravitational corrections) is evaluated for example cases.

  11. An entropic understanding of Coulomb force

    NASA Astrophysics Data System (ADS)

    Cho, Jin-Ho; Kim, Hyosung

    2012-02-01

    Exploiting Verlinde's proposal on the entropic understanding of Newton's law, we show that Coulomb force could also be understood as an entropically emergent force (rather than as a fundamental force). We apply Kaluza-Klein idea to Verlinde's formalism to obtain Coulomb interaction in the lower dimensions. The kinematics concerning the Kaluza-Klein momenta separates the interaction due to the momentum flow from the gravitational interaction. The momentum-charge conversion relation results in the precise form of Coulomb interaction.

  12. 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}.

  13. Interactions between pairs of bacteriocins from lactic bacteria.

    PubMed

    Mulet-Powell, N; Lacoste-Armynot, A M; Viñas, M; Simeon de Buochberg, M

    1998-09-01

    Activity of pairs of crude extracts of lactic acid bacteria (LAB) containing different bacteriocins (nisin, pediocin AcH, lacticin 481, lactacin F, and lactacin B) was measured against 10 different indicator strains. Experiments were carried out both in liquid and on solid media. Both synergisms and antagonisms were observed. Lacticin 481 produced mainly antagonistic effects whereas pediocin AcH produced mainly synergistic effects. The use of more than one LAB bacteriocin as a combination biopreservative might be envisaged. PMID:9766080

  14. 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.

  15. A Monte Carlo simulation of Coulomb collisions and wave-particle interactions in space plasma at high latitudes

    NASA Astrophysics Data System (ADS)

    Barghouthi, Imad Ahmad

    In study 1, a Monte Carlo simulation was used to investigate the behavior of O(+) ions that are E x B-drifting through a background of neutral O, with the effect of O(+) (Coulomb) self-collisions included. Wide ranges of the ion-to-neutral density ratio n(sub i)/n(sub n) and electrostatic field E were considered in order to investigate the change of ion behavior with respect to the solar cycle and altitude. For low altitudes and/or solar minimum (n(sub i)/n(sub n) less than or equal to 10(exp -5)), the effect of self-collisions is negligible. For higher values of n(sub i)/n(sub n), the effect of self-collisions becomes significant and, hence, the non-Maxwellian features of the O(+) distributions are reduced. In study 2, the steady-state flow of the polar wind protons through a background of O(+) ions was studied. The Fokker-Planck expression was used to represent H(+)-0(+) Coulomb collisions. The transition layer between the collision-dominated and the collisionless regions plays a pivotal role in the behavior of the H(+) flow. In the transition region, the shape of H(+) distribution changes in a complicated manner from Maxwellian to 'kidney bean.' The flow also changes from subsonic to supersonic within the transition region. The heat fluxes of parallel and perpendicular energies change rapidly from their maximum (positive) to their minimum (negative) values within the same transition region. In study 3, a Monte Carlo simulation was developed in order to study the effect of the wave-particle interactions (WPI) on O(+) and H(+) ions outflow in the polar wind. The simulation also considered the other mechanisms included in the classical polar wind studies such as gravity, polarization electrostatic field, and divergence of geomagnetic field lines. Also, an altitude dependent wave spectral density was adopted. The main conclusions are (1) the O(+) velocity distribution develops conic features at high altitudes; (2) the O(+) ions are preferentially energized; (3) the

  16. a Monte Carlo Simulation of Coulomb Collisions and Wave-Particle Interactions in Space Plasma at High Latitudes

    NASA Astrophysics Data System (ADS)

    Barghouthi, Imad Ahmad

    In study I, a Monte Carlo simulation was used to investigate the behavior of O^+ ions that are E x B-drifting through a background of neutral O, with the effect of O^+(Coulomb) self-collisions included. Wide ranges of the ion-to-neutral density ratio n_{i}/n _{n} and electrostatic field E were considered in order to investigate the change of ion behavior with respect to the solar cycle and altitude. For low altitudes and/or solar minimum (n_{i }/n_{n} <= 10 ^{-5}), the effect of self-collisions is negligible. For higher values of n_ {i}/n_{n}, the effect of self-collisions becomes significant and, hence, the non-Maxwellian features of the O^+ distributions are reduced. In study II, the steady-state flow of the polar wind protons through a background of O^+ ions was studied. The Fokker-Planck expression was used to represent H^+-O ^+ Coulomb collisions. The transition layer between the collision-dominated and the collisionless regions plays a pivotal role in the behavior of the H^+ flow. In the transition region, the shape of H ^+ distribution changes in a complicated manner from Maxwellian to "kidney bean". The flow also changes from subsonic to supersonic within the transition region. The heat fluxes of parallel and perpendicular energies change rapidly from their maximum (positive) to their minimum (negative) values within the same transition region. In study III, a Monte Carlo simulation was developed in order to study the effect of the wave-particle interactions (WPI) on O^+ and H^+ ions outflow in the polar wind. The simulation also considered the other mechanisms included in the classical polar wind studies such as gravity, polarization electrostatic field, and divergence of geomagnetic field lines. Also, an altitude dependent wave spectral density was adopted. The main conclusions are (1) the O^+ velocity distribution develops conic features at high altitudes; (2) the O^+ ions are preferentially energized; (3) the escape flux of O^+ increased by a factor of

  17. Beyond Gaussian pair fluctuation theory for strongly interacting Fermi gases

    NASA Astrophysics Data System (ADS)

    Mulkerin, Brendan C.; Liu, Xia-Ji; Hu, Hui

    2016-07-01

    Interacting Fermi systems in the strongly correlated regime play a fundamental role in many areas of physics and are of particular interest to the condensed matter community. Though weakly interacting fermions are understood, strongly correlated fermions are difficult to describe theoretically as there is no small interaction parameter to expand about. Existing strong-coupling theories rely heavily on the so-called many-body T -matrix approximation that sums ladder-type Feynman diagrams. Here, by acknowledging the fact that the effective interparticle interaction (i.e., the vertex function) becomes smaller above three dimensions, we propose an alternative way to reorganize Feynman diagrams and develop a theoretical framework for interacting Fermi gases beyond the ladder approximation. As an application, we solve the equation of state for three- and two-dimensional strongly interacting fermions and find excellent agreement with experimental [M. J. H. Ku et al., Science 335, 563 (2012), 10.1126/science.1214987] and other theoretical results above temperatures of 0.5 TF .

  18. 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.

  19. Theory of strongly correlated electron systems. I. Intersite Coulomb interaction and the approximation of renormalized fermions in total energy calculations

    NASA Astrophysics Data System (ADS)

    Sandalov, I.; Lundin, U.; Eriksson, O.

    The diagrammatic strong-coupling perturbation theory (SCPT) for correlated electron systems is developed for intersite Coulomb interaction and for a nonorthogonal basis set. The construction is based on iterations of exact closed equations for many-electron Green functions (GFs) for Hubbard operators in terms of functional derivatives with respect to external sources. The graphs, which do not contain the contributions from the fluctuations of the local population numbers of the ion states, play a special role: a one-to-one correspondence is found between the subset of such graphs for the many-electron GFs and the complete set of Feynman graphs of weak-coupling perturbation theory (WCPT) for single-electron GFs. This fact is used for formulation of the approximation of renormalized Fermions (ARF) in which the many-electron quasi-particles behave analogously to normal Fermions. Then, by analyzing: (a) Sham's equation, which connects the self-energy and the exchange-correlation potential in density functional theory (DFT); and (b) the Galitskii and Migdal expressions for the total energy, written within WCPT and within ARF SCPT, a way we suggest a method to improve the description of the systems with correlated electrons within the local density approximation (LDA) to DFT. The formulation, in terms of renormalized Fermions LDA (RF LDA), is obtained by introducing the spectral weights of the many-electron GFs into the definitions of the charge density, the overlap matrices, effective mixing and hopping matrix elements, into existing electronic structure codes, whereas the weights themselves have to be found from an additional set of equations. Compared with LDA+U and self-interaction correction (SIC) methods, RF LDA has the advantage of taking into account the transfer of spectral weights, and, when formulated in terms of GFs, also allows for consideration of excitations and nonzero temperature. Going beyond the ARF SCPT, as well as RF LDA, and taking into account the

  20. Quasi-stationary states and a classification of the range of pair interactions

    SciTech Connect

    Gabrielli, A.; Joyce, M.; Marcos, B.

    2011-03-24

    Systems of long-range interacting particles present typically 'quasi-stationary' states (QSS). Investigating their lifetime for a generic pair interaction V(r{yields}{infinity}){approx}1/r{sup {gamma}} we give a classification of the range of the interactions according to the dynamical properties of the system.

  1. 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.

  2. 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.

  3. 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.

  4. Modeling growth paths of interacting crack pairs in elastic media.

    PubMed

    Ghelichi, Ramin; Kamrin, Ken

    2015-10-28

    The problem of predicting the growth of a system of cracks, each crack influencing the growth of the others, arises in multiple fields. We develop an analytical framework toward this aim, which we apply to the 'En-Passant' family of crack growth problems, in which a pair of initially parallel, offset cracks propagate nontrivially toward each other under far-field opening stress. We utilize boundary integral and perturbation methods of linear elasticity, linear elastic fracture mechanics, and common crack opening criteria to calculate the first analytical model for curved En-Passant crack paths. The integral system is reduced under a hierarchy of approximations, producing three methods of increasing simplicity for computing crack paths. The last such method is a major highlight of this work, using an asymptotic matching argument to predict crack paths based on superposition of simple, single-crack fields. Within the corresponding limits of the three methods, all three are shown to agree with each other. We provide comparisons to exact results and existing experimental data to verify certain approximation steps. PMID:26330342

  5. 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. PMID:26059822

  6. Effective pairing interaction in semi-infinite nuclear matter in the Brueckner approach: Model {delta}-shaped NN interaction

    SciTech Connect

    Baldo, M.; Lombardo, U.; Saperstein, E.E.; Zverev, M.V.

    1995-09-01

    The problem of pairing in semi-infinite nuclear matter is considered in the Brueckner approach. Equations for effective pairing interaction in semi-infinite matter are derived for the case of the separable representation of realistic NN interaction. The propagator of two noninteracting particles in a semi-infinite potential well is calculated numerically. The equation for effective interaction is solved for a model 8-shaped NN interaction, which correctly reproduces NN scattering in the low-energy limit. 15 refs., 10 figs.

  7. 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. PMID:26948095

  8. Higher angular momentum pairing from transverse gauge interactions

    NASA Astrophysics Data System (ADS)

    Chung, Suk Bum; Mandal, Ipsita; Raghu, Srinivas; Chakravarty, Sudip

    2013-07-01

    In this paper, we study the superconductivity of nonrelativistic fermions at finite-density coupled to a transverse U(1) gauge field, with the effective interaction including the Landau-damping. This model, first studied by Holstein, Norton, and Pincus [Phys. Rev. B1098-012110.1103/PhysRevB.8.2649 8, 2649 (1973)] has been known as an example of a non-Fermi liquid, i.e., a metallic state in which the decay rate of a quasiparticle is large compared to the characteristic quasiparticle energy; other examples of the non-Fermi liquid includes the two dimensional (2d) electron gas in a magnetic field at ν=1/2 and the normal state of optimally doped cuprate superconductors. Our study thus addresses the question of whether or not non-Fermi liquids, like Fermi liquids, are unstable towards the formation of superconductivity. The results are (i) the non-Fermi liquid is stable against superconductivity below a critical gauge coupling, (ii) above this critical coupling, the ground state is an unconventional superconductor with angular momentum ℓ≥2. Our results are obtained from a solution of the Dyson-Nambu equation. Note that in this problem there is a quantum critical point between a non-Fermi liquid state and the superconducting state, as the critical coupling is nonzero. This is in contrast to a weakly coupled metal, which exhibits superconductivity for infinitesimally weak interaction regardless of its sign.

  9. 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.

  10. Effect of spin-orbit and on-site Coulomb interactions on the electronic structure and lattice dynamics of uranium monocarbide

    NASA Astrophysics Data System (ADS)

    Wdowik, U. D.; Piekarz, P.; Legut, D.; Jagło, G.

    2016-08-01

    Uranium monocarbide, a potential fuel material for the generation IV reactors, is investigated within density functional theory. Its electronic, magnetic, elastic, and phonon properties are analyzed and discussed in terms of spin-orbit interaction and localized versus itinerant behavior of the 5 f electrons. The localization of the 5 f states is tuned by varying the local Coulomb repulsion interaction parameter. We demonstrate that the theoretical electronic structure, elastic constants, phonon dispersions, and their densities of states can reproduce accurately the results of x-ray photoemission and bremsstrahlung isochromat measurements as well as inelastic neutron scattering experiments only when the 5 f states experience the spin-orbit interaction and simultaneously remain partially localized. The partial localization of the 5 f electrons could be represented by a moderate value of the on-site Coulomb interaction parameter of about 2 eV. The results of the present studies indicate that both strong electron correlations and spin-orbit effects are crucial for realistic theoretical description of the ground-state properties of uranium carbide.

  11. 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.

  12. 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. PMID:19072764

  13. The estimations of electron-positron pair's production at the high-intensity laser interactions with matter

    SciTech Connect

    Gryaznykh, D. A.; Kandiev, Y. Z.; Lykov, V. A.

    1997-04-15

    The processes of electron-positron pairs generation induced by laser radiation of 10{sup 18}-10{sup 20} W/cm{sup 2} are studied. The results of pairs production in Coulomb field of nucleus by relativistic electrons are presented. The estimations of positrons generation and yield from targets considering production from electrons and bremsstrahlung photons are made. The PRIZMA-code simulations performed using Monte-Carlo method confirm the estimations. The positrons yield of 10{sup 8}-10{sup 10} from high-Z targets irradiated by picosecond lasers of power 10{sup 2}-10{sup 3} TW is found to be possible.

  14. 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

    2013-04-24

    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.

  15. 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.

  16. Collective Modes and f-Wave Pairing Interactions in Superfluid {sup 3}He

    SciTech Connect

    Davis, J. P.; Choi, H.; Pollanen, J.; Halperin, W. P.

    2006-09-15

    Precision measurements of collective mode frequencies in superfluid {sup 3}He-B are sensitive to quasiparticle and f-wave pairing interactions. Measurements were performed at various pressures using interference of transverse sound in an acoustic cavity. We fit the measured collective mode frequencies, which depend on the strength of f-wave pairing and the Fermi liquid parameter F{sub 2}{sup s}, to theoretical predictions and discuss what implications these values have for observing new order parameter collective modes.

  17. Quantifying Electrical Interactions between Cardiomyocytes and Other Cells in Micropatterned Cell Pairs

    PubMed Central

    Nguyen, Hung; Badie, Nima; McSpadden, Luke; Pedrotty, Dawn; Bursac, Nenad

    2014-01-01

    Micropatterning is a powerful technique to control cell shape and position on a culture substrate. In this chapter, we describe the method to reproducibly create large numbers of micropatterned heterotypic cell pairs with defined size, shape, and length of cell–cell contact. These cell pairs can be utilized in patch clamp recordings to quantify electrical interactions between cardiomyocytes and non-cardiomyocytes. PMID:25070342

  18. Photon emission and pair production in the interaction of ultra-intense lasers with electrons

    NASA Astrophysics Data System (ADS)

    Jirka, Martin; Klimo, Ondrej; Bulanov, Sergei; Weber, Stefan

    2015-11-01

    With the advent of 10 PW laser facilities, new regimes of laser-matter interaction are opening since QED effects come into play. Due to the radiation reaction which takes place in ultra-intense laser-matter interactions, charged particles lose their energy by emitting high-energy photons. These photons can in the strong laser field create electron-positron pairs via Breit-Wheeler process. One possible interaction scenario leading to efficient generation of pairs is the interaction of two colliding laser pulses with an electron target lying in the common focal spot. In our PIC simulations, gamma-ray photon emission and pair production are studied for different laser wavelengths, intensities and both laser polarization. According to our results, linearly polarized laser pulses seem to be more convenient for efficient pair creation. The role of ions contained in the target and its density are also assessed. Results are compared with the different interaction configuration when the energetic electron bunch interacts with one counter-propagating laser pulse. This research has been partially supported by the Czech Science Foundation (Project No. 15-02964S).

  19. 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.

  20. 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.

  1. 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.

  2. Study of atomic dipole-dipole interactions via measurement of atom-pair kinetics

    NASA Astrophysics Data System (ADS)

    Thaicharoen, Nithiwadee; Gonçalves, Luís Felipe; Raithel, Georg

    2016-05-01

    We observe atom-pair kinetics due to binary dipolar forces by direct imaging of the center-of-mass positions of the individual Rydberg atoms and pair-correlation analysis. To prepare a highly dipolar quantum state, Rydberg-atom ensembles are switched from a weakly- into a strongly-interacting regime via adiabatic state transformation. The transformed atoms exhibit a large permanent electric dipole moment that is locked to the direction of an applied electric field. The resultant electric dipole-dipole forces reveal dumbbell-shaped pair correlation images that demonstrate the anisotropy of the binary dipolar force. The dipole-dipole interaction coefficient C3, derived from the time dependence of the images, agrees with the value calculated from the known permanent electric-dipole moment of the atoms. The observations also show the dynamics reminiscent of disorder-induced heating in strongly coupled particle systems.

  3. The Role of CH···O Coulombic Interactions in Determining Rotameric Conformations of Phenyl Substituted 1,3-Dioxanes and Tetrahydropyrans.

    PubMed

    Wiberg, Kenneth B; Lambert, Kyle M; Bailey, William F

    2015-08-21

    The rotameric conformations of the phenyl ring in both the axial and the equatorial conformers of phenyl substituted 1,3-dioxanes and tetrahydropyrans are compared with those of the corresponding phenylcyclohexanes at the MP2/6-311+G* level. The compounds with an axial phenyl commonly adopt a conformation in which the plane of the aromatic ring is perpendicular to the benzylic C-H bond. However, axial 5-phenyl-1,3-dioxane adopts a "parallel" conformation that allows an ortho hydrogen to be proximate to the two ring oxygens, leading to attractive CH···O interactions. Stabilizing Coulombic interactions of this sort are found with many of the oxygen-containing six-membered rings that were investigated. PMID:26182246

  4. 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. PMID:25240347

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

    NASA Astrophysics Data System (ADS)

    Shimazaki, Tomomi; Nakajima, Takahito

    2014-09-01

    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.

  6. 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…

  7. The Quantity and Quality of Language Practice in Typical Interactive Pair/Group Tasks

    ERIC Educational Resources Information Center

    Collins, Laura; White, Joanna

    2014-01-01

    This article reports on a study examining the language practice opportunities that occurred during a range of paired and small group interactive tasks in an intensive English as a Second Language (ESL) class of francophone Grade 6 students. The analysis focussed on the opportunities the tasks provided for the use of two complex and challenging…

  8. Spin and pseudospin symmetric Dirac particles in the field of Tietz—Hua potential including Coulomb tensor interaction

    NASA Astrophysics Data System (ADS)

    Sameer, M. Ikhdair; Majid, Hamzavi

    2013-09-01

    Approximate analytical solutions of the Dirac equation for Tietz—Hua (TH) potential including Coulomb-like tensor (CLT) potential with arbitrary spin—orbit quantum number κ are obtained within the Pekeris approximation scheme to deal with the spin—orbit coupling terms κ(κ ± 1)r-2. Under the exact spin and pseudospin symmetric limitation, bound state energy eigenvalues and associated unnormalized two-component wave functions of the Dirac particle in the field of both attractive and repulsive TH potential with tensor potential are found using the parametric Nikiforov—Uvarov (NU) method. The cases of the Morse oscillator with tensor potential, the generalized Morse oscillator with tensor potential, and the non-relativistic limits have been investigated.

  9. Stereoscopic Investigations of 3D Coulomb Balls

    SciTech Connect

    Kaeding, Sebastian; Melzer, Andre; Arp, Oliver; Block, Dietmar; Piel, Alexander

    2005-10-31

    In dusty plasmas particles are arranged due to the influence of external forces and the Coulomb interaction. Recently Arp et al. were able to generate 3D spherical dust clouds, so-called Coulomb balls. Here, we present measurements that reveal the full 3D particle trajectories from stereoscopic imaging.

  10. 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

  11. Computation of the high temperature Coulomb density matrix in periodic boundary conditions

    NASA Astrophysics Data System (ADS)

    Militzer, B.

    2016-07-01

    The high temperature many-body density matrix is fundamental to path integral computation. The pair approximation, where the interaction part is written as a product of pair density matrices, is commonly used and is accurate to order τ2, where τ is the step size in the imaginary time. Here we present a method for systems with Coulomb interactions in periodic boundary conditions that consistently treats the all interactions with the same level of accuracy. It is shown that this leads to a more accurate high temperature solution of the Bloch equation. The method is applied to many-body simulation and tests for the isolated hydrogen atom and molecule are presented.

  12. Evidence for Phonon Mediated Pairing Interaction in the Halo of the Nucleus {sup 11}Li

    SciTech Connect

    Potel, G.; Barranco, F.; Vigezzi, E.; Broglia, R. A.

    2010-10-22

    With the help of a unified nuclear-structure-direct-reaction theory we analyze the reaction {sup 1}H({sup 11}Li,{sup 9}Li){sup 3}H. The two halo neutrons are correlated through the bare and the induced (medium polarization) pairing interaction. By considering all dominant reaction channels leading to the population of the 1/2{sup -} (2.69 MeV) first excited state of {sup 9}Li, namely, multistep transfer (successive, simultaneous, and nonorthogonality), breakup, and inelastic channels, it is possible to show that the experiment provides direct evidence of phonon mediated pairing.

  13. 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

  14. 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.

  15. 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. PMID:25460685

  16. Coulomb attraction in optical spectra of quantum discs

    NASA Astrophysics Data System (ADS)

    Adolph, B.; Glutsch, S.; Bechstedt, F.

    1994-06-01

    We present a theory which describes the influence of the Coulomb interaction on the optical spectra of quantum discs within the envelope function formalism. Starting from a non-local Elliott formula luminescence is traced back to two-particle wave functions and energies. They are solutions of the corresponding Schrödinger equation for an electron-hole pair under the influence of the Coulomb attraction and confinement potentials determined by the spatial variation of the band edges of the considered microstructure. We present a complete numerical solution of the two-particle problem for flat quantum dots, i.e. discs for which the size quantization in growth direction is much stronger than that in the xy-plane. We discuss two different situations, single discs with infinite and finite confinement potentials. Resulting theoretical lineshapes are compared with luminescence spectra obtained recently for quantum discs fabricated by laser-induced thermal cation interdiffusion in quantum-well structures.

  17. Studies of Coulomb Gauge QCD

    SciTech Connect

    Adam P. Szczepaniak; Eric S. Swanson

    2000-12-12

    Here we will discuss how the nonabelian Coulomb kernel exhibits confinement already at the mean field level. In the heavy quark limit residual interactions between heavy quarks and transverse gluons are spin dependent i.e., relativistic and can be calculated using the Foldy-Wouthuysen transformation. This makes the Coulomb gauge suitable for studying the nonrelativistic limit. Finally it is possible to use standard mean field techniques to define quasiparticle excitations, which, as we discuss below, have similar properties to what is usually assumed about constituent quarks in the light quark sector.

  18. Influence of Constitution and Charge on Radical Pairing Interactions in Tris-radical Tricationic Complexes.

    PubMed

    Cheng, Chuyang; Cheng, Tao; Xiao, Hai; Krzyaniak, Matthew D; Wang, Yuping; McGonigal, Paul R; Frasconi, Marco; Barnes, Jonathan C; Fahrenbach, Albert C; Wasielewski, Michael R; Goddard, William A; Stoddart, J Fraser

    2016-07-01

    The results of a systematic investigation of trisradical tricationic complexes formed between cyclobis(paraquat-p-phenylene) bisradical dicationic (CBPQT(2(•+))) 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 CBPQT(4+) ring and the dumbbells containing BIPY(2+) 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 charges 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 CBPQT(2(•+)) 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 CBPQT(2(•+)) 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

  19. 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).

  20. New nucleotide pairs for stable DNA triplexes stabilized by stacking interaction.

    PubMed

    Mizuta, Masahiro; Banba, Jun-ichi; Kanamori, Takashi; Tawarada, Ryuya; Ohkubo, Akihiro; Sekine, Mitsuo; Seio, Kohji

    2008-07-30

    New nucleotide pairs applicable to formation of DNA triplexes were developed. We designed oligonucleotides incorporating 5-aryl deoxycytidine derivatives (dC5Ars) and cyclic deoxycytidine derivatives, dCPPP and dCPPI, having an expanded aromatic area, as the second strand. As pairing partners, two types of abasic residues (C3: propylene linker, phi: abasic base) were chosen. It was concluded that, when the 5-aryl-modified cytosine bases paired with the abasic sites in TFOs in a space-fitting manner, the stability of the resulting triplexes significantly increased. The recognition of C3 toward dC5Ars was selective because of the stacking interactions between their aromatic part and the nucleobases flanking the abasic site. These results indicate the potential utility of new nucleotide triplets for DNA triplex formation, which might expand the variety of structures and sequences and might be useful for biorelated fields such as DNA nanotechnologies. PMID:18611007

  1. Generation of periodic ultrashort electron bunches and strongly asymmetric ion Coulomb explosion in nanometer foils interacting with ultra-intense laser pulse

    SciTech Connect

    Tian Youwei; Yu Wei; Xu Han; Lei Anle; Shen Baifei; Wang Xin; Lu Peixiang; Senecha, Vinod

    2008-05-15

    The interaction of a linearly polarized intense laser pulse with an ultrathin nanometer plasma layer is investigated to understand the physics of the ion acceleration. It is shown by the computer simulation that the plasma response to the laser pulse comprises two steps. First, due to the vxB effect, electrons in the plasma layer are extracted and periodic ultrashort relativistic electron bunches are generated every half of a laser period. Second, strongly asymmetric Coulomb explosion of ions in the foil occurs due to the strong electrostatic charge separation, once the foil is burnt through. Followed by the laser accelerated electron bunch, the ion expansion in the forward direction occurs along the laser beam that is much stronger as compared to the backward direction.

  2. Density-functional calculation of effective Coulomb interactions in nonmetallic systems: Application to Mn in CdTe, CdS, and ZnO

    NASA Astrophysics Data System (ADS)

    Gunnarsson, O.; Postnikov, A. V.; Andersen, O. K.

    1989-11-01

    The effective Coulomb interaction U between the 3d electrons of Mn impurities in CdTe, CdS, and ZnO is calculated. The influence of the host on the renormalization of U is studied. It is shown that the screening due to charge transfer to the Mn atom is very efficient for Mn in CdTe, less efficient for Mn in CdS, and rather inefficient for ZnO. This is related to the increasing ionic character, which makes charge transfer to Mn increasingly difficult. The total effect of all charge-transfer processes, including charge transfer to the ligand atoms, is nevertheless substantial even for Mn in ZnO.

  3. Development of the Physical Activity Interactive Recall (PAIR) for Aboriginal children.

    PubMed

    Lévesque, Lucie; Cargo, Margaret; Salsberg, Jon

    2004-03-29

    BACKGROUND: Aboriginal children in Canada are at increased risk for type 2 diabetes. Given that physical inactivity is an important modifiable risk factor for type 2 diabetes, prevention efforts targeting Aboriginal children include interventions to enhance physical activity involvement. These types of interventions require adequate assessment of physical activity patterns to identify determinants, detect trends, and evaluate progress towards intervention goals. The purpose of this study was to develop a culturally appropriate interactive computer program to self-report physical activity for Kanien'kehá:ka (Mohawk) children that could be administered in a group setting. This was an ancillary study of the ongoing Kahnawake Schools Diabetes Prevention Project (KSDPP). METHODS: During Phase I, focus groups were conducted to understand how children describe and graphically depict type, intensity and duration of physical activity. Sixty-six students (40 girls, 26 boys, mean age = 8.8 years, SD = 1.8) from four elementary schools in three eastern Canadian Kanien'kehá:ka communities participated in 15 focus groups. Children were asked to discuss and draw about physical activity. Content analysis of focus groups informed the development of a school-day and non-school-day version of the physical activity interactive recall (PAIR). In Phase II, pilot-tests were conducted in two waves with 17 and 28 children respectively to assess the content validity of PAIR. Observation, videotaping, and interviews were conducted to obtain children's feedback on PAIR content and format. RESULTS: Children's representations of activity type and activity intensity were used to compile a total of 30 different physical activity and 14 non-physical activity response choices with accompanying intensity options. Findings from the pilot tests revealed that Kanien'kehá:ka children between nine and 13 years old could answer PAIR without assistance. Content validity of PAIR was judged to be adequate

  4. Development of the Physical Activity Interactive Recall (PAIR) for Aboriginal children

    PubMed Central

    Lévesque, Lucie; Cargo, Margaret; Salsberg, Jon

    2004-01-01

    Background Aboriginal children in Canada are at increased risk for type 2 diabetes. Given that physical inactivity is an important modifiable risk factor for type 2 diabetes, prevention efforts targeting Aboriginal children include interventions to enhance physical activity involvement. These types of interventions require adequate assessment of physical activity patterns to identify determinants, detect trends, and evaluate progress towards intervention goals. The purpose of this study was to develop a culturally appropriate interactive computer program to self-report physical activity for Kanien'kehá:ka (Mohawk) children that could be administered in a group setting. This was an ancillary study of the ongoing Kahnawake Schools Diabetes Prevention Project (KSDPP). Methods During Phase I, focus groups were conducted to understand how children describe and graphically depict type, intensity and duration of physical activity. Sixty-six students (40 girls, 26 boys, mean age = 8.8 years, SD = 1.8) from four elementary schools in three eastern Canadian Kanien'kehá:ka communities participated in 15 focus groups. Children were asked to discuss and draw about physical activity. Content analysis of focus groups informed the development of a school-day and non-school-day version of the physical activity interactive recall (PAIR). In Phase II, pilot-tests were conducted in two waves with 17 and 28 children respectively to assess the content validity of PAIR. Observation, videotaping, and interviews were conducted to obtain children's feedback on PAIR content and format. Results Children's representations of activity type and activity intensity were used to compile a total of 30 different physical activity and 14 non-physical activity response choices with accompanying intensity options. Findings from the pilot tests revealed that Kanien'kehá:ka children between nine and 13 years old could answer PAIR without assistance. Content validity of PAIR was judged to be adequate

  5. Exploring the separability of the three-body Coulomb problem in hyperspherical elliptic coordinates

    NASA Astrophysics Data System (ADS)

    Tolstikhin, Oleg I.; Matsuzawa, Michio

    2001-06-01

    An approximate symmetry of the three-body Coulomb problem which reveals itself via approximate separability of the hyperspherical adiabatic (HSA) eigenvalue problem in hyperspherical elliptic (HSE) coordinates (η,ξ) and thus is intimately related to the HSA approximation is discussed. The additional integral of motion responsible for this separability is specific to the Coulomb interaction and generalizes the Laplace-Runge-Lentz vector known from the two-body Coulomb problem and the integral of separation constant of the two-center Coulomb problem. In the zeroth approximation, this symmetry leads to a completely separable representation of the three-body wave function, where each state is labeled by a pair of HSE quantum numbers (nη,nξ) that generalize the spheroidal quantum numbers for diatomic molecules, on the one hand, and the Herrick-Lin quantum numbers for two-electron atoms, on the other. This approximation is illustrated by calculations for a number of three-body Coulomb systems for states with zero total angular momentum. Taking into account the nonadiabatic couplings as well as the nonseparable part of the Coulomb potential by mixing a few separable states permits one to obtain accurate results for systems with arbitrary masses and charges of particles and for a wide spectrum below the three-body breakup threshold.

  6. 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. PMID:26945102

  7. 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

  8. 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

  9. Molecular Interactions in 1-Ethyl-3-methylimidazolium Acetate Ion Pair: A Density Functional Study

    NASA Astrophysics Data System (ADS)

    Dhumal, Nilesh R.; Kim, Hyung J.; Kiefer, Johannes

    2009-08-01

    The density functional method is used to obtain the molecular structure, electron density topography, and vibrational frequencies of the ion pair 1-ethyl-3-methylimidazolium acetate. Different conformers are simulated on the basis of molecular interactions between the 1-ethyl-3-methylimidazolium cation and acetate anion. The lowest energy conformers exhibit strong C-H···O interionic interactions compared with other conformers. Characteristic vibrational frequencies of the ion pair and their shifts with respect to free ions are analyzed via the natural bond orbitals and difference electron density maps coupled with molecular electron density topology. Theoretically scaled vibrational frequencies are also compared with the spontaneous Raman scattering and attenuated total reflection infrared absorption measurements.

  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. Formation of chain structures in systems of charged grains interacting via isotropic pair potentials

    SciTech Connect

    Vaulina, O. S.; Lisina, I. I.; Koss, K. G.

    2013-05-15

    Conditions for the formation of chain structures of charged grains confined in the gravitational field by external electric fields are studied analytically and numerically. The relationships between the parameters of the pair interaction potential, the number of grains, and the electric field gradient in the trap are found. A criterion for the violation of stable equilibrium in a quasi-one-dimensional chain of grains and the formation of a new configuration in the system is proposed.

  12. Finite-N corrections to Vlasov dynamics and the range of pair interactions

    NASA Astrophysics Data System (ADS)

    Gabrielli, Andrea; Joyce, Michael; Morand, Jules

    2014-12-01

    We explore the conditions on a pair interaction for the validity of the Vlasov equation to describe the dynamics of an interacting N -particle system in the large N limit. Using a coarse graining in phase space of the exact Klimontovich equation for the N -particle system, we evaluate, neglecting correlations of density fluctuations, the scalings with N of the terms describing the corrections to the Vlasov equation for the coarse-grained one-particle phase space density. Considering a generic interaction with radial pair force F (r ) , with F (r ) ˜1 /rγ at large scales, and regulated to a bounded behavior below a "softening" scale ɛ , we find that there is an essential qualitative difference between the cases γ d , i.e., depending on the the integrability at large distances of the pair force. In the former case, the corrections to the Vlasov dynamics for a given coarse-grained scale are essentially insensitive to the softening parameter ɛ , while for γ >d the amplitude of these terms is directly regulated by ɛ , and thus by the small scale properties of the interaction. This corresponds to a simple physical criterion for a basic distinction between long-range (γ ≤d ) and short-range (γ >d ) interactions, different from the canonical one (γ ≤d +1 or γ >d +1 ) based on thermodynamic analysis. This alternative classification, based on purely dynamical considerations, is relevant notably to understanding the conditions for the existence of so-called quasistationary states in long-range interacting systems.

  13. 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

  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. 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.

  16. Longitudinal multiparameter assay of lymphocyte interactions from onset by microfluidic cell pairing and culture.

    PubMed

    Dura, Burak; Servos, Mariah M; Barry, Rachel M; Ploegh, Hidde L; Dougan, Stephanie K; Voldman, Joel

    2016-06-28

    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

  17. 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.

  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. 1D Coulomb drag between coupled nanowires formed at oxide interfaces

    NASA Astrophysics Data System (ADS)

    Tang, Yuhe; Tomczyk, Michelle; Huang, Mengchen; Lee, Hyungwoo; Eom, Chang-Beom; Irvin, Patrick; Levy, Jeremy

    ``Coulomb drag'' is a transport phenomenon where Coulomb interaction between two close but electrically isolated conductors induces voltage in one conductor when an electric current is injected in the other conductor. It is a powerful approach to probe electronic correlations. Here we examine 1D electronic correlations in a proximally coupled nanowire system where two parallel nanowires are created with conductive atomic force microscopy at the LaAlO3/SrTiO3 interface. Coulomb drag measurements are made by injecting current into one wire (drive wire) and measuring the induced voltage in the other wire (drag wire). This geometry offers experimental insights into the interplay of electron pairing and superconductivity in reduced dimensions. We gratefully acknowledge financial support from DOE DE-SC0014417 (JL).

  20. Pairing interaction near a nematic quantum critical point of a three-band CuO2 model

    DOE PAGESBeta

    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.

  1. 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.

  2. Emission of correlated electron pairs from solid surfaces

    NASA Astrophysics Data System (ADS)

    Gollisch, H.; Schwartzenberg, N. V.; Feder, R.

    2006-08-01

    Low-energy electron pairs, which are emitted from solid surfaces upon impact of a photon [ (γ,2e) process] or an electron [ (e,2e) process] carry information on the exchange and screened Coulomb interaction between the two electrons inside the solid. We present a method for calculating such correlated two-electron states as antisymmetrized products of two one-electron states coupled by a “correlation factor,” which depends upon the one-electron quantum numbers and the relative spatial coordinate. The resulting pair correlation functions are illustrated for the cases of two plane-wave electrons interacting via a bare and a screened Coulomb potential. Low-energy electron diffraction-type one-electron states are then coupled in this manner and employed as final pair states in calculations of (e,2e) and (γ,2e) reaction cross sections from the Cu(111) surface. For (e,2e) , the angular distributions calculated without and with Coulomb interaction U exhibit, for antiparallel spins, a distinct correlation hole. For parallel spins, a large hole, which is already present without U , is enhanced. The (γ,2e) distributions, which originate from the screened U inside the solid, have a large central region of enhanced intensity for antiparallel spins, out of which the exchange interaction carves a sizable hole. In all cases, the bare Coulomb repulsion on the way from the surface to the detectors reduces the intensity to zero for equal momenta of the two electrons.

  3. Pairing gaps in the Hartree-Fock-Bogoliubov theory with the Gogny D1S interaction

    NASA Astrophysics Data System (ADS)

    Robledo, L. M.; Bernard, R.; Bertsch, G. F.

    2012-12-01

    As part of a program to study odd-A nuclei in the Hartree-Fock-Bogoliubov (HFB) theory, we have developed a new calculational tool to find the HFB minima of odd-A nuclei based on the gradient method and using interactions of Gogny's form. The HFB minimization includes both time-even and time-odd fields in the energy functional, avoiding the commonly used “filling approximation”. Here we apply the method to calculate neutron pairing gaps in some representative isotope chains of spherical and deformed nuclei, namely the Z=8,50, and 82 spherical chains and the Z=62 and 92 deformed chains. We find that the gradient method is quite robust, permitting us to carry out systematic surveys involving many nuclei. We find that the time-odd field does not have large effect on the pairing gaps calculated with the Gogny D1S interaction. Typically, adding the T-odd field as a perturbation increases the pairing gap by 100 keV, but the re-minimization brings the gap back down. This outcome is very similar to results reported for the Skyrme family of nuclear energy density functionals. Comparing the calculated gaps with the experimental ones, we find that the theoretical errors have both signs implying that the D1S interaction has a reasonable overall strength. However, we find some systematic deficiencies comparing spherical and deformed chains and comparing the lighter chains with the heavier ones. The gaps for heavy spherical nuclei are too high, while those for deformed nuclei tend to be too low. The calculated gaps of spherical nuclei show hardly any A dependence, contrary to the data. Inclusion of the T-odd component of the interaction does not change these qualitative findings.

  4. 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. PMID:27254134

  5. 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. PMID:27411074

  6. DBBP: database of binding pairs in protein-nucleic acid interactions

    PubMed Central

    2014-01-01

    Background Interaction of proteins with other molecules plays an important role in many biological activities. As many structures of protein-DNA complexes and protein-RNA complexes have been determined in the past years, several databases have been constructed to provide structure data of the complexes. However, the information on the binding sites between proteins and nucleic acids is not readily available from the structure data since the data consists mostly of the three-dimensional coordinates of the atoms in the complexes. Results We analyzed the huge amount of structure data for the hydrogen bonding interactions between proteins and nucleic acids and developed a database called DBBP (DataBase of Binding Pairs in protein-nucleic acid interactions, http://bclab.inha.ac.kr/dbbp). DBBP contains 44,955 hydrogen bonds (H-bonds) of protein-DNA interactions and 77,947 H-bonds of protein-RNA interactions. Conclusions Analysis of the huge amount of structure data of protein-nucleic acid complexes is labor-intensive, yet provides useful information for studying protein-nucleic acid interactions. DBBP provides the detailed information of hydrogen-bonding interactions between proteins and nucleic acids at various levels from the atomic level to the residue level. The binding information can be used as a valuable resource for developing a computational method aiming at predicting new binding sites in proteins or nucleic acids. PMID:25474259

  7. 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.

  8. 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.

  9. 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.

  10. Kinetics and fracture resistance of lithiated silicon nanostructure pairs controlled by their mechanical interaction

    PubMed Central

    Lee, Seok Woo; Lee, Hyun-Wook; Ryu, Ill; Nix, William D.; Gao, Huajian; Cui, Yi

    2015-01-01

    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. PMID:26112834

  11. Entropic Corrections to Coulomb's Law

    NASA Astrophysics Data System (ADS)

    Hendi, S. H.; Sheykhi, A.

    2012-04-01

    Two well-known quantum corrections to the area law have been introduced in the literatures, namely, logarithmic and power-law corrections. Logarithmic corrections, arises from loop quantum gravity due to thermal equilibrium fluctuations and quantum fluctuations, while, power-law correction appears in dealing with the entanglement of quantum fields in and out the horizon. Inspired by Verlinde's argument on the entropic force, and assuming the quantum corrected relation for the entropy, we propose the entropic origin for the Coulomb's law in this note. Also we investigate the Uehling potential as a radiative correction to Coulomb potential in 1-loop order and show that for some value of distance the entropic corrections of the Coulomb's law is compatible with the vacuum-polarization correction in QED. So, we derive modified Coulomb's law as well as the entropy corrected Poisson's equation which governing the evolution of the scalar potential ϕ. Our study further supports the unification of gravity and electromagnetic interactions based on the holographic principle.

  12. 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.

  13. 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. PMID:26388114

  14. GGIP: Structure and sequence-based GPCR-GPCR interaction pair predictor.

    PubMed

    Nemoto, Wataru; Yamanishi, Yoshihiro; Limviphuvadh, Vachiranee; Saito, Akira; Toh, Hiroyuki

    2016-09-01

    G Protein-Coupled Receptors (GPCRs) are important pharmaceutical targets. More than 30% of currently marketed pharmaceutical medicines target GPCRs. Numerous studies have reported that GPCRs function not only as monomers but also as homo- or hetero-dimers or higher-order molecular complexes. Many GPCRs exert a wide variety of molecular functions by forming specific combinations of GPCR subtypes. In addition, some GPCRs are reportedly associated with diseases. GPCR oligomerization is now recognized as an important event in various biological phenomena, and many researchers are investigating this subject. We have developed a support vector machine (SVM)-based method to predict interacting pairs for GPCR oligomerization, by integrating the structure and sequence information of GPCRs. The performance of our method was evaluated by the Receiver Operating Characteristic (ROC) curve. The corresponding area under the curve was 0.938. As far as we know, this is the only prediction method for interacting pairs among GPCRs. Our method could accelerate the analyses of these interactions, and contribute to the elucidation of the global structures of the GPCR networks in membranes. Proteins 2016; 84:1224-1233. © 2016 Wiley Periodicals, Inc. PMID:27191053

  15. Synchrotron radiation, pair production, and longitudinal electron motion during 10-100 PW laser solid interactions

    SciTech Connect

    Brady, C. S.; Arber, T. D.; Ridgers, C. P.; York Plasma Institute, University of York, York, Yorkshire YO10 5DD ; Bell, A. R.

    2014-03-15

    At laser intensities above 10{sup 23} W/cm{sup 2}, the interaction of a laser with a plasma is qualitatively different to the interactions at lower intensities. In this intensity regime, solid targets start to become relativistically underdense, gamma-ray production by synchrotron emission starts to become an important feature of the dynamics and, at even higher intensities, electron-positron pair production by the non-linear Breit-Wheeler process starts to occur. In this paper, an analysis is presented of the effects of target density, laser intensity, target preplasma properties, and other parameters on the conversion efficiency, spectrum, and angular distribution of gamma-rays by synchrotron emission. An analysis of the importance of Breit-Wheeler pair production is also presented. Target electron densities between 10{sup 22} cm{sup −3} and 5 × 10{sup 24} cm{sup −3} and laser intensities covering the range between 10{sup 21} W/cm{sup 2} (available with current generation laser facilities) and 10{sup 24} W/cm{sup 2} (upper intensity range expected from the ELI facility are considered. Results are explained in terms of the behaviour of the head of the laser pulse as it interacts with the target.

  16. 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. PMID:26973872

  17. 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

  18. Inferring Active and Prognostic Ligand-Receptor Pairs with Interactions in Survival Regression Models

    PubMed Central

    Ruggeri, Christina; Eng, Kevin H

    2014-01-01

    Modeling signal transduction in cancer cells has implications for targeting new therapies and inferring the mechanisms that improve or threaten a patient’s treatment response. For transcriptome-wide studies, it has been proposed that simple correlation between a ligand and receptor pair implies a relationship to the disease process. Statistically, a differential correlation (DC) analysis across groups stratified by prognosis can link the pair to clinical outcomes. While the prognostic effect and the apparent change in correlation are both biological consequences of activation of the signaling mechanism, a correlation-driven analysis does not clearly capture this assumption and makes inefficient use of continuous survival phenotypes. To augment the correlation hypothesis, we propose that a regression framework assuming a patient-specific, latent level of signaling activation exists and generates both prognosis and correlation. Data from these systems can be inferred via interaction terms in survival regression models allowing signal transduction models beyond one pair at a time and adjusting for other factors. We illustrate the use of this model on ovarian cancer data from the Cancer Genome Atlas (TCGA) and discuss how the finding may be used to develop markers to guide targeted molecular therapies. PMID:25657571

  19. Resonantly enhanced electron-positron pair production in ultra-intense laser-matter interaction

    NASA Astrophysics Data System (ADS)

    Fillion-Gourdeai, Francois; Lorin, Emmanuel; Bandrauk, Andre

    2013-05-01

    A new mechanism for pair production from the interaction of a laser with two nuclei is presented. The latter takes advantage of the Stark effect in diatomic molecules and the presence of molecular resonances in the negative and positive energy continua. Both move in the complex energy plane as the interatomic distance and the electric field strength are varied. We demonstrate that there is an enhancement of pair production at the crossing of these resonances. This mechanism is studied in a very simple one-dimensional model where the nuclei are modelled by delta function potential wells and the laser by a constant electric field. The position of resonances is evaluated by using the Weyl-Titchmarch-Kodaira theory, which allows to treat singular boundary value problems and to compute the spectral density. The rate of producing pairs is also computed. It is shown that this process yields a positron production rate which is approximately an order of magnitude higher than in the single nucleus case and a few orders of magnitudes higher than Schwinger's tunnelling result in a static field.

  20. 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)

  1. Coulomb interaction energy including overlap effects for the ground states of LiNa and Na 2

    NASA Astrophysics Data System (ADS)

    Bussery, B.; Achkar, Y.; Aubert-Frécon, M.

    1989-01-01

    A recently proposed method to calculate first-order electrostatic as well as second-order induction and dispersion energies including charge-overlap effects for the interaction between two atoms each with one active electron is applied to the systems Li(2s) + Na(3s) and Na(3s) + Na(3s), giving the induction energy for both systems. The variation with R of the relative contribution of the overlapping and non-overlapping configuration space regions is discussed for the largest dispersion and induction terms.

  2. Spectroscopic and computational analysis of the molecular interactions in the ionic liquid ion pair [BMP]{sup +}[TFSI]{sup -}

    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.

  3. 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.

  4. Dynamical DMRG study of non-linear optical response in one-dimensional dimerized Hubbard model with nearest neighbor Coulomb interaction and alternating on-site potential

    NASA Astrophysics Data System (ADS)

    Sota, Shigetoshi; Tohyama, Takami; Brazovskii, Serguei

    2012-02-01

    The optical response of organic compounds has been attracting much attention. The one of the reasons is the huge non-linear and ultrafast optical response [K. Yamamoto et. al., J. Phys. Soc. Jpn. 77, 074709(2008)]. In order to investigate such optical properties, we carry out dynamical DMRG calculations to obtain optical responses in the 1/4-filled one-dimensional Hubbard model including the nearest neighbor Coulomb interaction and the alternating electron hopping. The charge gap [S. Nishimoto, M. Takahashi, and Y. Ohta, J. Phys. Soc. Jpn. 69, 1594(2000)] and the bound state [H. Benthien and E. Jeckelmann, Eur. Phys. J. B 44, 287(2005)] in this model have been discussed based on DMRG calculations. In the present study, we introduce an alternating on-site potential giving the polarization in the system into the dimerized Hubbard model, which breaks the reflection symmetry of the system. In this talk, we discuss the obtained linear and the 2nd order non-linear optical susceptibility in order to make a prediction for non-linear optical experiments in the future.

  5. 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.

  6. 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.

  7. 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. PMID:24484310

  8. 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.

  9. 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.

  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.; 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

  11. Deformation and Interaction of Droplet Pairs in a Microchannel Under ac Electric Fields

    NASA Astrophysics Data System (ADS)

    Chen, Xiaodong; Song, Yongxin; Li, Dongqing; Hu, Guoqing

    2015-08-01

    The deformation and interaction of a droplet pair in an electric field determine the success of droplet coalescence. Electric intensity and initial droplet separation are crucial parameters in this process. In this work, a combined theoretical and numerical analysis is performed to study the electrohydrodynamics of confined droplet pairs in a rectangular microchannel under ac electric fields. We develop a theoretical model to predict the relationship between critical electric intensity and droplet separation. A geometrical model relating the initial droplet separation to the cone angle is also established to determine the critical separation for partial coalescence. These models are validated by comparisons with existing experimental observations. According to the initial separation and electric intensity, five regimes of droplet interactions are classified by direct numerical simulations, namely noncoalescence, coalescence, partial coalescence, ejection after coalescence, and ejection with partial coalescence. According to their controlling mechanisms, the five regimes are distinguished by three well-defined boundaries. The detailed dynamics of the partial coalescence phenomenon is resolved when the droplet separation exceeds the critical value. A dynamic liquid bridge between the droplets is sustained by the competition between surface tension and electric stress. The dynamics of ejected microjets at the exterior ends are also addressed to show their responses to the oscillating electric field. The full understanding of the droplet dynamics under electric fields can be used to predict the droplet fusion behaviors and thus to facilitate the design of droplet-based microfluidic devices.

  12. Search for Pair Production of Strongly Interacting Particles Decaying to Pairs of Jets in pp̄ Collisions at √s=1.96 TeV

    DOE PAGESBeta

    Aaltonen, T.; Albin, E.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A.; Antos, J.; Apollinari, G.; Appel, J. A.; Arisawa, T.; et al

    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

  13. 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.

    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.

  14. Search for pair production of strongly interacting particles decaying to pairs of jets in pp collisions at √s=1.96 TeV.

    PubMed

    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; St Denis, R; 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

    2013-07-19

    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(pp[over ¯]→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. PMID:23909308

  15. Microscopic calculation and local approximation of the spatial dependence of the pairing field with bare and induced interactions

    SciTech Connect

    Pastore, A.; Barranco, F.; Vigezzi, E.

    2008-08-15

    The bare nucleon-nucleon interaction is essential for the production of pair correlations in nuclei, but an important contribution also arises from the induced interaction resulting from the exchange of collective vibrations between nucleons moving in time reversal states close to the Fermi energy. The pairing field resulting from the summed interaction is strongly peaked at the nuclear surface. It is possible to reproduce the detailed spatial dependence of this field by using either a local approximation, which fully takes into account finite size effects, or a contact interaction, with parameters that are quite different from those commonly used in more phenomenological approaches.

  16. Probing the role of interlayer coupling and coulomb interactions on electronic structure in few-layer MoSe₂ nanostructures.

    PubMed

    Bradley, Aaron J; Ugeda, Miguel M; da Jornada, Felipe H; Qiu, Diana Y; Ruan, Wei; Zhang, Yi; Wickenburg, Sebastian; Riss, Alexander; Lu, Jiong; Mo, Sung-Kwan; Hussain, Zahid; Shen, Zhi-Xun; Louie, Steven G; Crommie, Michael F

    2015-04-01

    Despite the weak nature of interlayer forces in transition metal dichalcogenide (TMD) materials, their properties are highly dependent on the number of layers in the few-layer two-dimensional (2D) limit. Here, we present a combined scanning tunneling microscopy/spectroscopy and GW theoretical study of the electronic structure of high quality single- and few-layer MoSe2 grown on bilayer graphene. We find that the electronic (quasiparticle) bandgap, a fundamental parameter for transport and optical phenomena, decreases by nearly one electronvolt when going from one layer to three due to interlayer coupling and screening effects. Our results paint a clear picture of the evolution of the electronic wave function hybridization in the valleys of both the valence and conduction bands as the number of layers is changed. This demonstrates the importance of layer number and electron-electron interactions on van der Waals heterostructures and helps to clarify how their electronic properties might be tuned in future 2D nanodevices. PMID:25775022

  17. 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

  18. Liquid and glass polymorphism in a monatomic system with isotropic, smooth pair interactions.

    PubMed

    Abraham, Joel Y; Buldyrev, Sergey V; Giovambattista, Nicolas

    2011-12-01

    Systems of particles with interactions given by the Jagla core-softened pair potential are known to exhibit water-like thermodynamic anomalies and a liquid-liquid phase transition. The drawback of the Jagla potential is that it is characterized by discontinuous forces acting between particles and thus is not suitable for standard molecular dynamics (MD) simulations. Here we introduce a smooth version of the Jagla potential based on two Fermi distributions and study the properties of a system of particles interacting via this new "Fermi-Jagla" pair potential by using standard MD simulations. We find that the liquid based on the Fermi-Jagla potential retains most of the properties of the liquid based on the original Jagla potential. Namely, it exhibits the following water-like anomalies: (i) decrease of density, (ii) increase of compressibility, κ(T)(T,P), and (iii) increase of isobaric specific heat, C(P)(T,P), upon isobaric cooling, and (iv) increase of diffusivity upon isothermal compression. The Fermi-Jagla potential also exhibits (i') density minima, (ii') compressibility minima, (iii') isobaric specific heat minima upon isobaric cooling, and (iv') diffusivity minima upon isothermal compression. As in the Jagla model case, we find a liquid-liquid phase transition (LLPT) and a liquid-liquid critical point in the equilibrium liquid. Contrary to the case of the original Jagla model liquid, the LLPT line for the Fermi-Jagla potential has a negative slope in the P-T plane that extends well above the crystallization temperature. This feature makes the Fermi-Jagla potential a better candidate to reproduce the behavior of tetrahedral liquids including water, for which the LLPT line observed in simulations has also negative slope. In the glass state, the Fermi-Jagla pair potential results in reversible polyamorphism between low- and high-density amorphous solids (LDA and HDA, respectively). We also find that HDA results from pressure-induced amorphization of the model

  19. OncoBinder facilitates interpretation of proteomic interaction data by capturing coactivation pairs in cancer.

    PubMed

    Van Coillie, Samya; Liang, Lunxi; Zhang, Yao; Wang, Huanbin; Fang, Jing-Yuan; Xu, Jie

    2016-04-01

    High-throughput methods such as co-immunoprecipitationmass spectrometry (coIP-MS) and yeast 2 hybridization (Y2H) have suggested a broad range of unannotated protein-protein interactions (PPIs), and interpretation of these PPIs remains a challenging task. The advancements in cancer genomic researches allow for the inference of "coactivation pairs" in cancer, which may facilitate the identification of PPIs involved in cancer. Here we present OncoBinder as a tool for the assessment of proteomic interaction data based on the functional synergy of oncoproteins in cancer. This decision tree-based method combines gene mutation, copy number and mRNA expression information to infer the functional status of protein-coding genes. We applied OncoBinder to evaluate the potential binders of EGFR and ERK2 proteins based on the gastric cancer dataset of The Cancer Genome Atlas (TCGA). As a result, OncoBinder identified high confidence interactions (annotated by Kyoto Encyclopedia of Genes and Genomes (KEGG) or validated by low-throughput assays) more efficiently than co-expression based method. Taken together, our results suggest that evaluation of gene functional synergy in cancer may facilitate the interpretation of proteomic interaction data. The OncoBinder toolbox for Matlab is freely accessible online. PMID:26872056

  20. 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.

  1. Application of the pair torque interaction potential to simulate the elastic behavior of SLMoS2

    NASA Astrophysics Data System (ADS)

    Berinskii, I. E.; Panchenko, A. Yu; Podolskaya, E. A.

    2016-05-01

    This paper is devoted to the application of the pair torque interaction potential for the simulation of the elastic behavior of a promising two-dimensional material: single layer molybdenium disulphide (SLMoS2). It is demonstrated that both Mo-Mo and S-S interactions can be regarded as pair force interactions with sufficient accuracy. Using both experimental and calculated numerically elastic moduli, and also the phonon spectrum available in the literature, the parameters of the Morse potential are determined for Mo-Mo and S-S bonds, and the parameters of the pair torque potential are obtained for the Mo-S bond. As a result, a combination of force and torque pair potentials is proposed, which allows for the correct modelling of SLMoS2 mechanical behavior.

  2. In silico studies toward understanding the interactions of DNA base pairs with protonated linear/cyclic diamines.

    PubMed

    Sen, Anik; Sahu, Debashis; Ganguly, Bishwajit

    2013-08-29

    Protonated amino groups are ubiquitous in nature and important in the fields of chemistry and biology. In search of efficient polyamine analogues, we have performed DFT calculations on the interactions of some simple cyclic and constrained protonated diamines with the DNA base pairs and compared the results with those obtained for the corresponding interactions involving linear diamines, which mimic biogenic polyamines such as spermine. The interactions are mainly governed by the strong hydrogen bonding between the ligand and the DNA base pairs. The DFT calculations suggest that the major-groove N7 interaction (GC base pair) with linear diamine is energetically more favored than other possible interactions, as reported with spermine. The cyclic diamines exhibited better interactions with the N7 site of the AT and GC base pairs of DNA than the linear diamines. The net atomic charges calculated for the protonated amine hydrogens were higher for the cyclic systems than for the linear diamines, inducing better binding affinity with the DNA base pairs. The stable conformers of cyclic diamines were predicted using the MP2/aug-cc-pVDZ level of theory. The positions of the protonated diamine groups in these cyclic systems are crucial for effective binding with the DNA base pairs. The DFT-calculated results show that diequatorial (ee) 1,2-cyclohexadiamine (CHDA) is a promising candidate as a polyamine analogue for biogenic polyamines. Molecular dynamics simulations were performed using explicit water molecules for the interaction of representative ligands with the DNA base pairs to examine the influence of solvent molecules on such interactions. PMID:23909683

  3. Aun (n = 1,11) Clusters Interacting With Lone-Pair Ligands.

    PubMed

    Rajský, Tomáš; Urban, Miroslav

    2016-06-01

    We analyze the pattern of binding energies (BEs) of small Aun clusters (n = 1-7, 11) with lone-pair ligands (L = H2O, SH2, NH3, PH3, PF3, PCl3, and PMe3) employing the density functional theory. We use PBE0 functional with the dispersion correction and scalar relativistic effective core potential. This approach provides correct BEs when compared with benchmark CCSD(T) calculations for Au-L and Au2-L complexes. The pattern of BEs of Aun-L complexes is irregular with BE for Au3 ≈ Au4 > Au2 > Au7 > Au5 > Au11 > Au6 > Au1. Electron affinities (EAs) of Aun clusters exhibit oscillatory pattern with the cluster size. Binding energies of Aun-L complexes are oscillatory as well following EAs of Aun clusters. BEs of odd and even Aun-L complexes were analyzed separately. The bonding mechanism in odd Aun-L complexes is dominated by the lone pair → metal electron donation to the singly occupied valence Aun orbital accompanied by the back-donation. Even Aun clusters create covalent Aun-L bonds with BEs higher than those in odd Aun-L complexes. The BEs pattern and optimized geometries of Aun-L complexes correspond to the picture of creating the gold-ligand bond through the lone pair of a ligand interacting with the singly occupied molecular orbital in odd clusters or lowest unoccupied molecular orbital in even clusters of Aun. Ligands in both odd and even Aun-L complexes form three groups with binding energies that correlate with their ionization energies. The lowest BE is calculated for H2O as a ligand, followed by SH2 and NH3. PX3 ligands exhibit highest BEs. PMID:27187633

  4. Coulomb Glass: a Mean Field Study

    NASA Astrophysics Data System (ADS)

    Mandra, Salvatore; Palassini, Matteo

    2012-02-01

    We study the Coulomb glass model of disordered localized electrons with long-range Coulomb interaction, which describes systems such as disordered insulators, granular metals, amorphous semiconductors, or doped crystalline semiconductors. Long ago Efros and Shklovskii showed that the long-range repulsion induces a soft Coulomb gap in the single particle density of states at low temperatures. Recent works suggested that this gap is associated to a transition to a glass phase, similar to the Almeida-Thouless transition in spin glasses. In this work, we use a mean field approach to characterize several physical properties of the Coulomb glass. In particular, following a seminal work of Bray and Moore, we show that the Edward-Anderson parameter qEA and the spin glass susceptibility χSG are directly related to spectrum distribution of the Hessian matrix around free energy minima. Using this result, we show that no glass transition is associated to the gap formation.

  5. Successive interaction of pairs of soluble organics with nanosilica in aqueous media.

    PubMed

    Gun'ko, V M; Zarko, V I; Voronin, E F; Goncharuk, E V; Andriyko, L S; Guzenko, N V; Nosach, L V; Janusz, W

    2006-08-01

    Successive interaction of different pairs of water-soluble polymers (poly(ethylene glycol) (PEG), poly(vinyl pyrrolidone) (PVP), poly(vinyl alcohol) (PVA)), proteins (bovine serum albumin (BSA), ovalbumin, gelatin, and ossein), and smaller organics such as lecithin (1-stearoyl-2-oleoyl phosphatidylcholine, SOPC) and Aethonium (1,2-ethylene-bis(N-dimethyl carbodecyl oxymethyl) ammonium dichloride) with nanosilicas A-300 (S(BET)=232 and 297 m(2) g(-1)) and A-50 (S(BET)=52 m(2)g(-1)) was studied using dynamic light scattering, adsorption, and infrared (FTIR) spectroscopy methods. Time-dependent rearrangement of particle size distributions (PSDs) depicts appearance of both smaller and larger aggregates for silica/PEG(I-first adsorbate)/BSA(II-second adsorbate) and silica/PVP(I)/BSA(II) (i.e., BSA adsorbs onto PEG/silica or PVP/silica) than that for silica/organic compound I. However, in the cases of PVA(I)-BSA(II) and PVA(I)-SOPC(II) a similar effect is not observed because only increased aggregation occurs. The successive equilibrium adsorption of similar pairs shows a diminution of the adsorption of the second compound (gelatin, ovalbumin) with increasing amount of the first adsorbed polymer (PEG or PVP). PMID:16643935

  6. 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

  7. 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. PMID:27049933

  8. 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.

  9. Modeling intermolecular interactions of physisorbed organic molecules using pair potential calculations

    SciTech Connect

    Kroeger, Ingo; Stadtmueller, Benjamin; Wagner, Christian; Weiss, Christian; Temirov, Ruslan; Tautz, F. Stefan; Kumpf, Christian

    2011-12-21

    The understanding and control of epitaxial growth of organic thin films is of crucial importance in order to optimize the performance of future electronic devices. In particular, the start of the submonolayer growth plays an important role since it often determines the structure of the first layer and subsequently of the entire molecular film. We have investigated the structure formation of 3,4,9,10-perylene-tetracarboxylic dianhydride and copper-phthalocyanine molecules on Au(111) using pair-potential calculations based on van der Waals and electrostatic intermolecular interactions. The results are compared with the fundamental lateral structures known from experiment and an excellent agreement was found for these weakly interacting systems. Furthermore, the calculations are even suitable for chemisorptive adsorption as demonstrated for copper-phthalocyanine/Cu(111), if the influence of charge transfer between substrate and molecules is known and the corresponding charge redistribution in the molecules can be estimated. The calculations are of general applicability for molecular adsorbate systems which are dominated by electrostatic and van der Waals interaction.

  10. Protein:protein interactions and the pairing of boundary elements in vivo

    PubMed Central

    Blanton, Jason; Gaszner, Miklos; Schedl, Paul

    2003-01-01

    Although it is now well-established that boundary elements/insulators function to subdivide eukaryotic chromosomes into autonomous regulatory domains, the underlying mechanisms remain elusive. One idea is that boundaries act as barriers, preventing the processive spreading of “active” or “silenced” chromatin between domains. Another is that the partitioning into autonomous functional units is a consequence of an underlying structural subdivision of the chromosome into higher order “looped” domains. In this view, boundaries are thought to delimit structural domains by interacting with each other or with some other nuclear structure. The studies reported here provide support for the looped domain model. We show that the Drosophila scs and scs‘ boundary proteins, Zw5 and BEAF, respectively, interact with each other in vitro and in vivo. Moreover, consistent with idea that this protein:protein interaction might facilitate pairing of boundary elements, we find that that scs and scs‘ are in close proximity to each other in Drosophila nuclei. PMID:12629048

  11. Probing new physics of cubic Higgs boson interaction via Higgs pair production at hadron colliders

    NASA Astrophysics Data System (ADS)

    He, Hong-Jian; Ren, Jing; Yao, Weiming

    2016-01-01

    Despite the discovery of a Higgs boson h (125 GeV) at the LHC run 1, its self-interaction has fully evaded direct experimental probe so far. Such self-interaction is vital for electroweak symmetry breaking, vacuum stability, and electroweak phase transition. It is a most likely place to encode new physics beyond the standard model. We parametrize such new physics by model-independent dimension-six effective operators and study their tests via Higgs pair production at hadron colliders. We analyze three major di-Higgs production channels at the parton level and compare the parameter dependence of total cross sections and kinematic distributions at the LHC (14 TeV) and p p (100 TeV) hadron collider. We further perform full simulations for the di-Higgs production channel g g →h h →b b ¯γ γ and its backgrounds at the p p (100 TeV) hadron collider. We construct four kinds of benchmark points and study the sensitivities to probing different regions of the parameter space of cubic Higgs interactions. We find that for a one-parameter analysis and with a 3 ab-1 (30 ab-1 ) integrated luminosity, the g g →h h →b b ¯γ γ channel can measure the SM cubic Higgs coupling and the derivative cubic Higgs coupling to an accuracy of about 13% (4.2%) and 5% (1.6%), respectively.

  12. Kinetics and fracture resistance of lithiated silicon nanostructure pairs controlled by their mechanical interaction

    DOE PAGESBeta

    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 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

  13. Quantum simulation of pairing Hamiltonians with nearest-neighbor-interacting qubits

    NASA Astrophysics Data System (ADS)

    Wang, Zhixin; Gu, Xiu; Wu, Lian-Ao; Liu, Yu-xi

    2016-06-01

    Although a universal quantum computer is still far from reach, the tremendous advances in controllable quantum devices, in particular with solid-state systems, make it possible to physically implement "quantum simulators." Quantum simulators are physical setups able to simulate other quantum systems efficiently that are intractable on classical computers. Based on solid-state qubit systems with various types of nearest-neighbor interactions, we propose a complete set of algorithms for simulating pairing Hamiltonians. The fidelity of the target states corresponding to each algorithm is numerically studied. We also compare algorithms designed for different types of experimentally available Hamiltonians and analyze their complexity. Furthermore, we design a measurement scheme to extract energy spectra from the simulators. Our simulation algorithms might be feasible with state-of-the-art technology in solid-state quantum devices.

  14. 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.

  15. 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.

  16. 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.

  17. Irreversible adiabatic decoherence of dipole-interacting nuclear-spin pairs coupled with a phonon bath

    NASA Astrophysics Data System (ADS)

    Domínguez, F. D.; González, C. E.; Segnorile, H. H.; Zamar, R. C.

    2016-02-01

    We study the quantum adiabatic decoherence of a multispin array, coupled with an environment of harmonic phonons, in the framework of the theory of open quantum systems. We follow the basic formal guidelines of the well-known spin-boson model, since in this framework it is possible to derive the time dependence of the reduced density matrix in the adiabatic time scale, without resorting to coarse-graining procedures. However, instead of considering a set of uncoupled spins interacting individually with the boson field, the observed system in our model is a network of weakly interacting spin pairs; the bath corresponds to lattice phonons, and the system-environment interaction is generated by the variation of the dipole-dipole energy due to correlated shifts of the spin positions, produced by the phonons. We discuss the conditions that the model must meet in order to fit within the adiabatic regime. By identifying the coupling of the dipole-dipole spin interaction with the low-frequency acoustic modes as the source of decoherence, we calculate the decoherence function of the reduced spin density matrix in closed way, and estimate the decoherence rate of a typical element of the reduced density matrix in one- and three-dimensional models of the spin array. Using realistic values for the various parameters of the model we conclude that the dipole-phonon mechanism can be particularly efficient to degrade multispin coherences, when the number of active spins involved in a given coherence is high. The model provides insight into the microscopic irreversible spin dynamics involved in the buildup of quasiequilibrium states and in the coherence leakage during refocusing experiments in nuclear magnetic resonance of crystalline solids.

  18. 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.

  19. 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. PMID:26102481

  20. 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.

  1. An Instructional Method for Mixed Medical Sociology Classes: Paired Observations of Practitioner-Patient Interactions.

    ERIC Educational Resources Information Center

    Selig, Suzanne M.; Perlstadt, Harry

    1985-01-01

    In a medical sociology course composed of health care students with little sociology background and sociology students with no health care background, a paired observation exercise was given. Health care and sociology students were paired, and each pair observed the same medical encounter and reviewed each other's papers. (Author/RM)

  2. Interaction effects on galaxy pairs with Gemini/GMOS - II: oxygen abundance gradients

    NASA Astrophysics Data System (ADS)

    Rosa, D. A.; Dors, O. L.; Krabbe, A. C.; Hägele, G. F.; Cardaci, M. V.; Pastoriza, M. G.; Rodrigues, I.; Winge, C.

    2014-11-01

    In this paper, we derive oxygen abundance gradients from H II regions located in 11 galaxies in eight systems of close pairs. Long-slit spectra in the range 4400-7300 Å were obtained with the Gemini Multi-Object Spectrograph at Gemini South (GMOS-S). Spatial profiles of oxygen abundance in the gaseous phase along galaxy discs were obtained using calibrations based on strong emission lines (N2 and O3N2). We found oxygen gradients to be significantly flatter for all the studied galaxies than those in typical isolated spiral galaxies. Four objects in our sample, AM 1219A, AM 1256B, AM 2030A and AM 2030B, show a clear break in the oxygen abundance at galactocentric radius R/R25 between 0.2 and 0.5. For AM 1219A and AM 1256B, we found negative slopes for the inner gradients, and for AM 2030B, we found a positive slope. All three cases show a flatter behaviour to the outskirts of the galaxies. For AM 2030A, we found a positive slope for the outer gradient, while the inner gradient is almost compatible with a flat behaviour. We found a decrease of star formation efficiency in the zone that corresponds to the oxygen abundance gradient break for AM 1219A and AM 2030B. For the former, a minimum in the estimated metallicities was found very close to the break zone, which could be associated with a corotation radius. However, AM 1256B and AM 2030A, present a star formation rate maximum but not an extreme oxygen abundance value. All four interacting systems that show oxygen gradient breaks have extreme SFR values located very close to break zones.The H II regions located in close pairs of galaxies follow the same relation between the ionization parameter and the oxygen abundance as those regions in isolated galaxies.

  3. Demonstration of facilitatory I wave interaction in the human motor cortex by paired transcranial magnetic stimulation

    PubMed Central

    Ziemann, Ulf; Tergau, Frithjof; Wassermann, Eric M; Wischer, Stephan; Hildebrandt, Jörg; Paulus, Walter

    1998-01-01

    Transcranial magnetic stimulation (TMS) of the human motor cortex results in multiple discharges (D and I waves) in the corticospinal tract. We tested whether these volleys can be explored non-invasively with paired TMS. The intensity of the first stimulus (S1) was set to produce a motor-evoked potential (MEP) of 1 mV in the resting contralateral abductor digiti minimi (ADM) muscle; the second stimulus (S2) was set to 90 % of the resting motor threshold. At interstimulus intervals of 1·1-1·5, 2·3-2·9 and 4·1-4·4 ms the MEP elicited by S1 plus S2 was larger than that produced by S1 alone.Varying the S1 intensity between 70 and 130 % resting motor threshold with S2 held constant at 90 % resting motor threshold showed that the threshold for the first MEP peak was <= 70 % resting motor threshold. The second and third MEP peaks appeared only at higher S1 intensities. The latency of all peaks decreased with increasing S1 intensity.Varying the S2 intensity with S1 held constant to produce a MEP of 1 mV on its own showed that the amplitude of all MEP peaks increased with S2 intensity, but that their timing remained unchanged.Paired TMS in the active ADM (S1 clearly suprathreshold, S2 just above threshold; interstimulus interval, 1 ms) produced strong MEP facilitation. The onset of this facilitation occurred later by about 1·5 ms than the onset of the MEP evoked by S2 alone. No MEP facilitation was seen if the magnetic S2 was replaced by anodal or cathodal transcranial electrical stimulation.It is concluded that the MEP facilitation after paired TMS, at least for the first MEP peak, is due to facilitatory interaction between I waves, and takes place in the motor cortex at or upstream from the corticospinal neurone. PMID:9679173

  4. Relationship between pairing symmetries and interaction parameters in iron-based superconductors from functional renormalization group calculations

    NASA Astrophysics Data System (ADS)

    Yuan, Jing; Hu, Jiangping

    2016-03-01

    Pairing symmetries of iron-based superconductors are investigated systematically in a five-orbital model within the different regions of interaction parameters by functional renormalization group (FRG). Even for a fixed Fermi surface with both hole and electron pockets, it is found that depending on interaction parameters, a variety of pairing symmetries, including two types of d-wave and two types of s-wave pairing symmetries, can emerge. Only the dx^2-y^2 - and the s±-waves are robustly supported by the nearest-neighbor (NN) intra-orbital J 1 and the next-nearest-neighbor (NNN) intra-orbital J 2 antiferromagnetic (AFM) exchange couplings, respectively. This study suggests that the accurate initial input of the interaction parameters is essential to make FRG a useful method to determine the leading channel of superconducting instability.

  5. 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.

  6. New mechanism for the generation of electron-positron pairs in Laser-Matter Interaction: Resonantly Enhanced Pair Production in a molecular system

    NASA Astrophysics Data System (ADS)

    Fillion-Gourdeau, François; Lorin, Emmanuel; Bandrauk, André D.

    2013-02-01

    A new mechanism for pair production from the interaction of a laser with two nuclei is presented. The latter takes advantage of the Stark effect in diatomic molecules and the presence of molecular resonances in the negative and positive energy continua. Both move in the complex energy plane as the interatomic distance and the electric field strength are varied. We demonstrate that there is an enhancement of pair production at the crossing of these resonances. This mechanism is studied in a very simple one-dimensional model where the nuclei are modeled by delta function potential wells and the laser by a constant electric field. The position of resonances is evaluated by using the Weyl-Titchmarch-Kodaira theory, which allows to treat singular boundary value problems and to compute the spectral density. The rate of producing pairs is also computed. It is shown that this process yields a positron production rate which is approximately an order of magnitude higher than in the single nucleus case and a few orders of magnitudes higher than Schwinger's tunneling result in a static field.

  7. Hybrid simulation approach incorporating microscopic interaction along with rigid body degrees of freedom for stacking between base pairs.

    PubMed

    Mondal, Manas; Halder, Sukanya; Chakrabarti, Jaydeb; Bhattacharyya, Dhananjay

    2016-04-01

    Stacking interaction between the aromatic heterocyclic bases plays an important role in the double helical structures of nucleic acids. Considering the base as rigid body, there are total of 18 degrees of freedom of a dinucleotide step. Some of these parameters show sequence preferences, indicating that the detailed atomic interactions are important in the stacking. Large variants of non-canonical base pairs have been seen in the crystallographic structures of RNA. However, their stacking preferences are not thoroughly deciphered yet from experimental results. The current theoretical approaches use either the rigid body degrees of freedom where the atomic information are lost or computationally expensive all atom simulations. We have used a hybrid simulation approach incorporating Monte-Carlo Metropolis sampling in the hyperspace of 18 stacking parameters where the interaction energies using AMBER-parm99bsc0 and CHARMM-36 force-fields were calculated from atomic positions. We have also performed stacking energy calculations for structures from Monte-Carlo ensemble by Dispersion corrected density functional theory. The available experimental data with Watson-Crick base pairs are compared to establish the validity of the method. Stacking interaction involving A:U and G:C base pairs with non-canonical G:U base pairs also were calculated and showed that these structures were also sequence dependent. This approach could be useful to generate multiscale modeling of nucleic acids in terms of coarse-grained parameters where the atomic interactions are preserved. This method would also be useful to predict structure and dynamics of different base pair steps containing non Watson-Crick base pairs, as found often in the non-coding RNA structures. © 2015 Wiley Periodicals, Inc. Biopolymers 105: 212-226, 2016. PMID:26600167

  8. Giant Coulomb blockade magnetoresistance

    SciTech Connect

    Zhang, Xiaoguang; Wen, Z. C.; Wei, H. X.; Han, Prof. X. F.

    2010-01-01

    We show that the Coulomb blockade voltage can be made to depend strongly on the electron spin in a thin magnetic granular layer inserted in the middle of an insulating layer of a tunnel junction. This strong spin dependence is predicted from the spin-dependent inter-granular conductance through any of the following effects within the granular layer, giant magnetoresistance (GMR), tunneling magnetoresistance (TMR), colossal magnetoresistance (CMR), or GMR through a polymer spacer. The resulting Coulomb blockade magnetoresistance (CBMR) ratio can exceed the magnetoresistance ratio of the granular layer itself by orders of magnitude. Unlike other magenetoresistance effects, the CBMR effect does not require magnetic electrodes.

  9. Confinement of Coulomb balls

    SciTech Connect

    Arp, O.; Block, D.; Klindworth, M.; Piel, A.

    2005-12-15

    A model for the confinement of the recently discovered Coulomb balls is proposed. These spherical three-dimensional plasma crystals are trapped inside a rf discharge under gravity conditions and show an unusual structural order in complex plasmas. Measurements of the thermophoretic force acting on the trapped dust particles and simulations of the plasma properties of the discharge are presented. The proposed model of confinement considers thermophoretic, ion-drag, and electric field forces, and shows excellent agreement with the observations. The findings suggest that self-confinement does not significantly contribute to the structural properties of Coulomb balls.

  10. 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%.

  11. 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.

  12. Observations of energetic particles between a pair of corotating interaction regions

    SciTech Connect

    Wu, Z.; Chen, Y.; Tang, C. L.; Li, G.; Zhao, L. L.; Ebert, R. W.; Desai, M. I.; Mason, G. M.; Lavraud, B.; Sauvaud, J.; Zhao, L.; Landi, E.; Liu, Y. C.-M.; Guo, F.

    2014-01-20

    We report observations of the acceleration and trapping of energetic ions and electrons between a pair of corotating interaction regions (CIRs). The event occurred in Carrington Rotation 2060. Observed by the STEREO-B spacecraft, the two CIRs were separated by less than 5 days. In contrast to other CIR events, the fluxes of the energetic ions and electrons in this event reached their maxima between the trailing edge of the first CIR and the leading edge of the second CIR. The radial magnetic field (B{sub r} ) reversed its sense and the anisotropy of the flux also changed from Sunward to anti-Sunward between the two CIRs. Furthermore, there was an extended period of counterstreaming suprathermal electrons between the two CIRs. Similar observations for this event were also obtained with the Advanced Composition Explorer and STEREO-A. We conjecture that these observations were due to a U-shaped, large-scale magnetic field topology connecting the reverse shock of the first CIR and the forward shock of the second CIR. Such a disconnected U-shaped magnetic field topology may have formed due to magnetic reconnection in the upper corona.

  13. Cotunneling Drag Effect in Coulomb-Coupled Quantum Dots.

    PubMed

    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. PMID:27541473

  14. 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.

  15. 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.

  16. Lone-pair interactions in the photoelectron spectra of dicarboxylic acids: malonic acid and its α-alkyl derivatives

    NASA Astrophysics Data System (ADS)

    Ajò, D.; Ciliberto, E.; Fragalà, I.; Granozzi, G.

    1980-02-01

    Photoelectron spectra of malonic, methylmalonic and diethylmalonic acids are reported. The energy splitting of photoelectron bands representing carbonyl oxygen lone pairs is due to a "through-bond" interaction mechanism. The magnitude of the splitting depends upon the α-alkyl substitution because of conformational effects.

  17. Rotational Study of Dimethyl Ether-Chlorotrifluoroethylene: Lone Pair···π Interaction Links the Two Subunits.

    PubMed

    Spada, Lorenzo; Gou, Qian; Geboes, Yannick; Herrebout, Wouter A; Melandri, Sonia; Caminati, Walther

    2016-07-14

    The rotational spectra of two isotopologues of chlorotrifluoroethylene-dimethyl ether show that the two constituent molecules are held together by a lone pair···π interaction. The ether oxygen is linked to the (CF2) carbon atom, with a C-O distance of 2.908 Å. PMID:26812179

  18. 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.

  19. Coulomb Breakup Problem

    SciTech Connect

    Kadyrov, A. S.; Bray, I.; Stelbovics, A. T.; Mukhamedzhanov, A. M.

    2008-12-05

    We formulate scattering theory in the framework of a surface-integral approach utilizing analytically known asymptotic forms of the three-body wave functions. This formulation is valid for both short-range and Coulombic potentials. The post and prior forms of the breakup amplitude are derived without any reference to renormalization procedures.

  20. Interactive Effects of Age and Familiarization in Paired-Associate Learning

    ERIC Educational Resources Information Center

    Baumeister, Alfred A.; Maisto, Albert A.

    1974-01-01

    Presents a study of paired-associative learning involving a total of 80 preschool and second grade children. Four familiarization categories of pretraining were utilized; results are discussed in terms of the effects of pretraining conditions and age on paired-associative learning and their consistency with some developmental hypotheses and phase…

  1. Argon Interaction with Gold Surfaces: Ab Initio-Assisted Determination of Pair Ar-Au Potentials for Molecular Dynamics Simulations.

    PubMed

    Grenier, Romain; To, Quy-Dong; de Lara-Castells, María Pilar; Léonard, Céline

    2015-07-01

    Global potentials for the interaction between the Ar atom and gold surfaces are investigated and Ar-Au pair potentials suitable for molecular dynamics simulations are derived. Using a periodic plane-wave representation of the electronic wave function, the nonlocal van-der-Waals vdW-DF2 and vdW-OptB86 approaches have been proved to describe better the interaction. These global interaction potentials have been decomposed to produce pair potentials. Then, the pair potentials have been compared with those derived by combining the dispersionless density functional dlDF for the repulsive part with an effective pairwise dispersion interaction. These repulsive potentials have been obtained from the decomposition of the repulsive interaction between the Ar atom and the Au2 and Au4 clusters and the dispersion coefficients have been evaluated by means of ab initio calculations on the Ar+Au2 complex using symmetry adapted perturbation theory. The pair potentials agree very well with those evaluated through periodic vdW-DF2 calculations. For benchmarking purposes, CCSD(T) calculations have also been performed for the ArAu and Ar+Au2 systems using large basis sets and extrapolations to the complete basis set limit. This work highlights that ab initio calculations using very small surface clusters can be used either as an independent cross-check to compare the performance of state-of-the-art vdW-corrected periodic DFT approaches or, directly, to calculate the pair potentials necessary in further molecular dynamics calculations. PMID:26046588

  2. Dependence of the Rate of LiF Ion-Pairing on the Description of Molecular Interaction.

    PubMed

    Pluhařová, Eva; Baer, Marcel D; Schenter, Gregory K; Jungwirth, Pavel; Mundy, Christopher J

    2016-03-01

    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 generalized 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 parametrization. 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 straightforward application of variational transition state theory 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. PMID:26501355

  3. Coulomb problem for vector bosons

    SciTech Connect

    Kuchiev, M.Yu.; Flambaum, V.V.

    2006-05-01

    The Coulomb problem for vector bosons W{sup {+-}} incorporates a well-known difficulty; the charge of the boson localized in a close vicinity of the attractive Coulomb center proves to be infinite. The paradox is shown to be resolved by the QED vacuum polarization, which brings in a strong effective repulsion that eradicates the infinite charge of the boson on the Coulomb center. This property allows one to define the Coulomb problem for vector bosons properly.

  4. 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.

  5. Iron-free hexagonal pnictide superconductor SrPtAs: pairing interaction from electron-phonon coupling and possible d + id pairing?

    NASA Astrophysics Data System (ADS)

    Rhim, Sonny; Agterberg, Daniel F.; Weinert, Michael; Freeman, A. J.

    2014-03-01

    The iron-free hexagonal pnictide superconductor, SrPtAs, exhibits a prime example of staggered non-centrosymmetricity with non-negligible spin-orbit coupling, where locally broken inversion symmetry, despite the presence of global inversion, results in non-trivial consequences- an enhancement of the spin susceptibility and the paramagnetic limiting field.[2] Earlier calculations revealed that SrPtAs has three bands with quasi-two-dimensional features, where corresponding Fermi surfaces have two sheets around the zone center and one around the zone corner. We extended our first-principels calculations to include phonon dispersions. From this, the electron-phonon interaction is investigted in the framework of Eliashberg theory. Phonons near the K point contribute mostly to the pairing via both inter- and intra-band scattering. Further, the possibility of pairing symmetry with chiral d + id is discussed, which has been suggested when EF moves to a van Hove singularity either by n- or p-type doping.[3] DOE (DE-FG02-05ER45372).

  6. Redistribution of the density of states due to Coulomb interactions in La{sub 2-2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7}.

    SciTech Connect

    Mazur, D.; Gray, K. E.; Zasadzinski, J. F.; Ozyuzer, L.; Beloborodov, I. S.; Zheng, H.; Mitchell, J. F.; Materials Science Division; IIT; Izmir Inst. Tech.; Univ. of Chicago

    2007-01-01

    Tunneling data on La{sub 1.28}Sr{sub 1.72}Mn{sub 2}O{sub 7} crystals confirm Coulomb interaction effects through the {radical}{bar E} dependence of the density of states. Importantly, the data and analysis at high energy E show a pileup of states: most of the states removed from near the Fermi level are found between {approx}40 and 130 meV, from which we infer the possibility of universal behavior. The agreement of our tunneling data with recent photoemission results further confirms our analysis.

  7. Thermalization of pair plasma with proton loading

    SciTech Connect

    Aksenov, A. G.

    2009-05-03

    We study kinetic evolution of nonequilibrium optically thick electron-positron plasma towards thermal equilibrium solving numerically relativistic Boltzmann equations with energy per particle ranging from 0.1 to 10 MeV. We generalize our results presented in [1], considering proton loading of the pair plasma. Proton loading introduces new characteristic timescales essentially due to proton-proton and proton-electron Coulomb collisions. Taking into account not only binary but also triple direct and inverse interactions between electrons, positrons, photons and protons we show that thermal equilibrium is reached on a timescale t{sub th}{approx_equal}10{sup -11} sec.

  8. Role of interaction energy in the specificity of transcription. I-The Watson Crick G-C base pair template.

    PubMed Central

    Sanyal, N K; Kumar, U; Roychoudhury, M

    1980-01-01

    The purpose of this work is to show that the selectivity of the nucleotide bases in RNA transcription c an be inferred, in principle, from the DNA base pair - RNA base interaction. The catalytic role of enzymes in this process is, therefore, only to form the sugar - phosphate backbone. A systematic study for the evaluation of the interaction energy of the DNA base pair with the enterant RNA bases have been undertaken to elucidate the aforesaid mechanism. Electrostatic hard sphere approximation of Nash and Bradley 1 has been employed. Non bonded induced dipole and London dispersion forces are not taken into account. The present communication gives the results of computations of the interaction energy of the four RNA bases. The results have been discussed with reference to Stent's and Zubay's schemes of RNA transcription. PMID:7443519

  9. Experimental study of the hydrodynamic interaction between a pair of bubbles ascending in a non-Newtonian liquid

    NASA Astrophysics Data System (ADS)

    Samano, Diego; Velez, Rodrigo; Zenit, Roberto

    2009-11-01

    We present some experimental results about the interaction of a pair of bubbles ascending in non-Newtonian fluids. A high speed camera was used to follow in-line and off-line rising motion of two bubbles in a Newtonian fluid (a glycerin-water solution), a Boger fluid (aqueous polyacrylamide solution), and a shear-thinning fluid (aqueous xanthan solution). For the case of shear-thinning fluids, the power index, n, affects the tendency of the bubble pair to aggregate. Therefore, in addition to bubble separation, orientation and Reynolds number, the hydrodynamic force depends strongly on the shear-thinning nature of the fluid. Several examples will be shown. For elastic fluids, the Deborah number affects the hydrodynamic interaction. We found that the appearance of the negative wake changes the nature of the interaction substantially. Some examples and comparisons with numerical results will be presented.

  10. Coulomb attraction in the optical spectra of quantum disks

    NASA Astrophysics Data System (ADS)

    Adolph, B.; Glutsch, S.; Bechstedt, F.

    1993-11-01

    In this paper we present a theory that describes the influence of the Coulomb interaction between electrons and holes on the optical spectra of flat quantum dots within the envelope-function formalism. Starting from a nonlocal Elliott-like formula, absorption and luminescence characteristics are traced back to properties of two-particle wave functions and energies, which are solutions of the corresponding Schrödinger equation for an electron-hole pair under the influence of the Coulomb attraction and confinement potentials, determined by the spatial variation of the band edges of the considered microstructure. We present a complete numerical solution of the two-particle problem for flat quantum dots, i.e., disks for which the size quantization in the growth direction is much stronger than that in the perpendicular plane. The resulting theoretical line shapes are compared with luminescence spectra obtained recently for quantum dots fabricated by laser-induced thermal cation interdiffusion in quantum-well structures.

  11. 1/f Noise in a Coulomb Glass.

    NASA Astrophysics Data System (ADS)

    Yu, Clare C.; Shtengel, Kirill

    2002-03-01

    Low frequency 1/f noise is found in Coulomb glasses, among other systems with slow relaxation. It has been recently studied in detail in Si:B in the experimental work of Massey and Lee [1]. They concluded that their findings were inconsistent with the single-particle mechanisms proposed earlier. We show that the observed noise can be produced by charge fluctuations due to electrons hopping between isolated sites and a percolating network at low temperatures [2]. Coulomb interactions are included through the Coulomb gap in the density of states. The low frequency noise spectrum goes as ω^-α with α slightly larger than 1. This result, together with the temperature dependence of α and the noise amplitude are in good agreement with the experiments of Massey and Lee. [1] J. G. Massey and Mark Lee, Phys. Rev. Lett. 79, 3986 (1997). [2] Kirill Shtengel and Clare C. Yu (2001), cond-mat/0111302.

  12. 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.

  13. Hydrodynamic interactions between pairs of capsules and drops in a simple shear: Effects of viscosity ratio and heterogeneous collision

    NASA Astrophysics Data System (ADS)

    Singh, Rajesh Kumar; Sarkar, Kausik

    2015-12-01

    Hydrodynamic interactions between a pair of capsules in simple shear are numerically investigated using a front-tracking finite difference method. The membrane of the capsule is modeled using different hyperelastic constitutive relations. We also compare the pair interactions between drops to those between capsules. An increased viscosity ratio leads to a reduced net cross-stream separation between capsules as well as drops after collision. At low viscosity ratios, for the same capillary number drop-pairs show higher cross-stream separation than those for capsule-pairs, while substantially large viscosity ratios result in almost the same value for both cases. We investigate pair-collisions between two heterogeneous capsules C1 and C2 with two different capillary numbers. The maximum deformation of C1 was seen to increase with increasing stiffness (decreasing capillary number) of C2, even though the stiffness of C1 was kept fixed. The findings are similar for a drop-pair, however, with a smaller maximum deformation for the same combinations of capillary numbers. The final cross-stream drift of the trajectory of C1 decreases with the increasing stiffness of C2, but the relative trajectory between the capsules remains unchanged. The maximum deformation and the cross-stream drift of the trajectory of C1 are shown to approximately vary with power-law functions of the ratio of the capillary numbers of C1 and C2. An analytical explanation of the dependence on the two capillary numbers is offered. Different membrane constitutive laws result in similar deformation and drift in trajectory.

  14. Pax-3-DNA interaction: flexibility in the DNA binding and induction of DNA conformational changes by paired domains.

    PubMed Central

    Chalepakis, G; Wijnholds, J; Gruss, P

    1994-01-01

    The mouse Pax-3 gene encodes a protein that is a member of the Pax family of DNA binding proteins. Pax-3 contains two DNA binding domains: a paired domain (PD) and a paired type homeodomain (HD). Both domains are separated by 53 amino acids and interact synergistically with a sequence harboring an ATTA motif (binding to the HD) and a GTTCC site (binding to the PD) separated by 5 base pairs. Here we show that the interaction of Pax-3 with these two binding sites is independent of their angular orientation. In addition, the protein spacer region between the HD and the PD can be shortened without changing the spatial flexibility of the two DNA binding domains which interact with DNA. Furthermore, by using circular permutation analysis we determined that binding of Pax-3 to a DNA fragment containing a specific binding site causes conformational changes in the DNA, as indicated by the different mobilities of the Pax-3-DNA complexes. The ability to change the conformation of the DNA was found to be an intrinsic property of the Pax-3 PD and of all Pax proteins that we tested so far. These in vitro studies suggest that interaction of Pax proteins with their specific sequences in vivo may result in an altered DNA conformation. Images PMID:8065927

  15. 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.

  16. Interaction of a two-layer vortex pair with a submerged cylindrical obstacle in a two layer rotating fluid

    NASA Astrophysics Data System (ADS)

    Ryzhov, Eugene A.; Sokolovskiy, Mikhail A.

    2016-05-01

    We consider the dynamics of a two-layer compensated vortex pair (heton) interacting with a submerged cylindrical obstacle of small height located in the lower layer of a two-layer fluid in the f-plane. The pair consists of two counter-rotating vortices of equal strengths each located in different layers of the two-layer rotating fluid. We make use of two approaches. The first one considers a model of point vortices, and the second one assumes the vortices as finite-core vorticity patches analyzed by means of contour dynamics techniques. The point vortex model features two regimes of the pair's motion: an unbounded motion as the pair advances to infinity after being deflected by the cylindrical obstacle and an oscillatory motion inside a bounded region near the cylindrical obstacle. The oscillations, in turn, are of two types. The first corresponds to a finite yet unpredictable number of vortex revolutions near the cylinder, and the second results in an infinite number of revolutions. By exploiting contour dynamics techniques, we obtain very similar unbounded dynamics of a distributed vorticity heton given relatively strong stratification. An important feature of this dynamics is that the contours associated with the pair hold almost unperturbed signifying sufficient stability. By decreasing stratification, we observe complicated dynamics involving vorticity redistribution and vortex splitting.

  17. 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

  18. σ-Hole···π and lone pair···π interactions in benzylic halides.

    PubMed

    Montoro, Teresa; Tardajos, Gloria; Guerrero, Andrés; Torres, María del Rosario; Salgado, Cástor; Fernández, Israel; Osío Barcina, José

    2015-06-14

    Intermolecular and intramolecular halogen···π interactions in benzylic halides (Ph-CR2-X; X = F, Cl, Br and I) derived from 7-phenylnorbornane were investigated. The imposed geometry of the 7-arylnorbornane moiety prevents the participation of intramolecular attractive interactions between the σ-hole region of the halogen atom and the π electrons of the aromatic ring. Crystallographic data show intermolecular halogen bonds in iodide 1 and bromide 2 in the solid state. On the other hand, both UV-Vis and D-NMR data suggest the occurrence of intramolecular interactions between the halogen atoms and the phenyl rings in these compounds in solution. To provide more insight into the nature of the observed stabilizing interactions, density functional calculations were also carried out. These computations confirm the presence of genuine lone pairπ intramolecular interactions which strongly affect the stability and the electronic structure of these species. PMID:25960103

  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

    2014-05-01

    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. PMID:24811636

  20. 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.

  1. 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.

  2. 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.

  3. 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…

  4. 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

  5. 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.

  6. 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.

  7. Ion Coulomb crystals

    NASA Astrophysics Data System (ADS)

    Drewsen, Michael

    2015-03-01

    The following text will give a brief introduction to the physics of the spatially ordered structures, so-called Coulomb crystals, that appear when confined ions are cooled to sufficiently low temperatures. It will as well briefly comment on the very diverse scientific applications of such crystals, which have emerged the past two decades. While this document lacks figures, it includes a substantial number of references in which more detailed information can be found. It is the hope that the text will stimulate the reader to dig deeper into one or more of the discussed subjects and inspire her/him to think about new potential applications.

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. 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.

  13. Modelling gamma-ray photon emission and pair production in high-intensity laser–matter interactions

    SciTech Connect

    Ridgers, C.P.; Central Laser Facility, STFC Rutherford-Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX ; Kirk, J.G.; Duclous, R.; Blackburn, T.G.; Brady, C.S.; Bennett, K.; Arber, T.D.; Bell, A.R.; Central Laser Facility, STFC Rutherford-Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX

    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.

  14. 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

  15. Systematic mapping of WNT-FZD protein interactions reveals functional selectivity by distinct WNT-FZD pairs.

    PubMed

    Dijksterhuis, Jacomijn P; Baljinnyam, Bolormaa; Stanger, Karen; Sercan, Hakki O; Ji, Yun; Andres, Osler; Rubin, Jeffrey S; Hannoush, Rami N; Schulte, Gunnar

    2015-03-13

    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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. Development of a Model Protein Interaction Pair as a Benchmarking Tool for the Quantitative Analysis of 2-Site Protein-Protein Interactions.

    PubMed

    Yamniuk, Aaron P; Newitt, John A; Doyle, Michael L; Arisaka, Fumio; Giannetti, Anthony M; Hensley, Preston; Myszka, David G; Schwarz, Fred P; Thomson, James A; Eisenstein, Edward

    2015-12-01

    A significant challenge in the molecular interaction field is to accurately determine the stoichiometry and stepwise binding affinity constants for macromolecules having >1 binding site. The mission of the Molecular Interactions Research Group (MIRG) of the Association of Biomolecular Resource Facilities (ABRF) is to show how biophysical technologies are used to quantitatively characterize molecular interactions, and to educate the ABRF members and scientific community on the utility and limitations of core technologies [such as biosensor, microcalorimetry, or analytic ultracentrifugation (AUC)]. In the present work, the MIRG has developed a robust model protein interaction pair consisting of a bivalent variant of the Bacillus amyloliquefaciens extracellular RNase barnase and a variant of its natural monovalent intracellular inhibitor protein barstar. It is demonstrated that this system can serve as a benchmarking tool for the quantitative analysis of 2-site protein-protein interactions. The protein interaction pair enables determination of precise binding constants for the barstar protein binding to 2 distinct sites on the bivalent barnase binding partner (termed binase), where the 2 binding sites were engineered to possess affinities that differed by 2 orders of magnitude. Multiple MIRG laboratories characterized the interaction using isothermal titration calorimetry (ITC), AUC, and surface plasmon resonance (SPR) methods to evaluate the feasibility of the system as a benchmarking model. Although general agreement was seen for the binding constants measured using solution-based ITC and AUC approaches, weaker affinity was seen for surface-based method SPR, with protein immobilization likely affecting affinity. An analysis of the results from multiple MIRG laboratories suggests that the bivalent barnase-barstar system is a suitable model for benchmarking new approaches for the quantitative characterization of complex biomolecular interactions. PMID:26543437

  3. Communication: Fine discretization of pair interactions and an approximate analytical strategy for predicting equilibrium behavior of complex fluids.

    PubMed

    Hollingshead, Kyle B; Jain, Avni; Truskett, Thomas M

    2013-10-28

    We study whether fine discretization (i.e., terracing) of continuous pair interactions, when used in combination with first-order mean-spherical approximation theory, can lead to a simple and general analytical strategy for predicting the equilibrium structure and thermodynamics of complex fluids. Specifically, we implement a version of this approach to predict how screened electrostatic repulsions, solute-mediated depletion attractions, or ramp-shaped repulsions modify the radial distribution function and the potential energy of reference hard-sphere fluids, and we compare the predictions to exact results from molecular simulations. PMID:24181996

  4. N lone-pair···π interaction: a rotational study of chlorotrifluoroethylene···ammonia.

    PubMed

    Gou, Qian; Spada, Lorenzo; Geboes, Yannick; Herrebout, Wouter A; Melandri, Sonia; Caminati, Walther

    2015-03-28

    The rotational spectra of four isotopologues of the adduct C2F3Cl-NH3 show that NH3 is bound to the partner molecule through a (N)lone-pair···π interaction. Ammonia is located in proximity to the C2 atom (the one linked to two fluorine atoms), with the C2···N distance = 2.987(2) Å. The nuclear hyperfine structure due to the quadrupole coupling effects of (35)Cl/(37)Cl and (14)N nuclei has been fully resolved. The (14)N quadrupole coupling constants allow estimating the effective orientation of NH3 in the complex. PMID:25484247

  5. Pair interactions in polyelectrolyte-nanoparticle systems: Influence of dielectric inhomogeneities and the partial dissociation of polymers and nanoparticles

    SciTech Connect

    Pryamitsyn, Victor; Ganesan, Venkat

    2015-10-28

    We study the effective pair interactions between two charged spherical particles in polyelectrolyte solutions using polymer self-consistent field theory. In a recent study [V. Pryamitsyn and V. Ganesan, Macromolecules 47, 6095 (2015)], we considered a model in which the particles possess fixed charge density, the polymers contain a prespecified amount of dissociated charges and, the dielectric constant of the solution was assumed to be homogeneous in space and independent of the polymer concentration. In this article, we present results extending our earlier model to study situations in which either or both the particle and the polymers possess partially dissociable groups. Additionally, we also consider the case when the dielectric constant of the solution depends on the local concentration of the polymers and when the particle’s dielectric constant is lower than that of the solvent. For each case, we quantify the polymer-mediated interactions between the particles as a function of the polymer concentrations and the degree of dissociation of the polymer and particles. Consistent with the results of our previous study, we observe that the polymer-mediated interparticle interactions consist of a short-range attraction and a long-range repulsion. The partial dissociablity of the polymer and particles was seen to have a strong influence on the strength of the repulsive portion of the interactions. Rendering the dielectric permittivity to be inhomogeneous has an even stronger effect on the repulsive interactions and results in changes to the qualitative nature of interactions in some parametric ranges.

  6. Structural features of bicomponent dust Coulomb balls formed by the superposition of fields of different origin in plasma

    SciTech Connect

    Psakhie, S. G.; Zolnikov, K. P.; Kryzhevich, D. S.; Abdrashitov, A. V.

    2008-05-15

    A binary mixture of dust particles in plasma which are in an external electrostatic harmonic confining field as well as in the field consisting of gravitational, thermophoretic, and electrostatic force is simulated. The interparticle interaction is described by the Yukawa isotropic pair potential. The structural properties of the binary mixture of particles depending on composition are investigated. The segregation features of a system of particles of two species under the conditions of recent experiments on Coulomb ball formation are studied. It is shown that particles form a shell structure in which every shell contains only its own species of particles; in so doing, smaller-sized particles make up outer shells with respect to larger-sized particles. When the size difference between the particles becomes more and more pronounced, they are spatially separated up to the formation of two independent Coulomb balls.

  7. Geometrically-frustrated pseudogap phase of Coulomb liquids

    NASA Astrophysics Data System (ADS)

    Pramudya, Y.; Terletska, H.; Pankov, S.; Manousakis, E.; Dobrosavljević, V.

    2012-06-01

    We study a class of models with long-range repulsive interactions of the generalized Coulomb form V(r)∼1/rα. We show that decreasing the interaction exponent in the regime αinteractions. A nearly frozen Coulomb liquid then survives in a broad pseudogap phase found at T>Tc, which is characterized by an unusual temperature dependence of all quantities. In contrast, the leading critical behavior very close to the charge-ordering temperature remains identical as in models with short-range interactions.

  8. NaFe_{0.56}Cu_{0.44}As: A Pnictide Insulating Phase Induced by On-Site Coulomb Interaction.

    PubMed

    Matt, C E; Xu, N; Lv, Baiqing; Ma, Junzhang; Bisti, F; Park, J; Shang, T; Cao, Chongde; Song, Yu; Nevidomskyy, Andriy H; Dai, Pengcheng; Patthey, L; Plumb, N C; Radovic, M; Mesot, J; Shi, M

    2016-08-26

    In the studies of iron pnictides, a key question is whether their bad-metal state from which the superconductivity emerges lies in close proximity with a magnetically ordered insulating phase. Recently, it was found that at low temperatures, the heavily Cu-doped NaFe_{1-x}Cu_{x}As (x>0.3) iron pnictide is an insulator with long-range antiferromagnetic order, similar to the parent compound of cuprates but distinct from all other iron pnictides. Using angle-resolved photoemission spectroscopy, we determined the momentum-resolved electronic structure of NaFe_{1-x}Cu_{x}As (x=0.44) and identified that its ground state is a narrow-gap insulator. Combining the experimental results with density functional theory (DFT) and DFT+U calculations, our analysis reveals that the on-site Coulombic (Hubbard) and Hund's coupling energies play crucial roles in the formation of the band gap about the chemical potential. We propose that at finite temperatures, charge carriers are thermally excited from the Cu-As-like valence band into the conduction band, which is of Fe 3d-like character. With increasing temperature, the number of electrons in the conduction band becomes larger and the hopping energy between Fe sites increases, and finally the long-range antiferromagnetic order is destroyed at T>T_{N}. Our study provides a basis for investigating the evolution of the electronic structure of a Mott insulator transforming into a bad metallic phase and eventually forming a superconducting state in iron pnictides. PMID:27610876

  9. Derivation of Pitzer Interaction Parameters for an Aqueous Species Pair of FeCitrate- and Mg2+

    NASA Astrophysics Data System (ADS)

    Jang, J.; Olivas, T.; Nemer, M.

    2013-12-01

    The Waste Isolation Pilot Plant (WIPP) is a deep underground repository for the disposal of transuranic (TRU) radioactive waste developed by the U.S. Department of Energy (DOE). The WIPP is located within the bedded salts of the Permian Salado Formation, which consists of interbedded halite and anhydrite layers overlaying the Castile Formation. The waste includes, but is not limited to, the salts of citric acid and iron. To calculate the solution chemistry for brines of WIPP-relevance, WIPP Performance Assessment (PA) employs the Pitzer formulation to determine the activity coefficients of aqueous species in brine. The current WIPP thermodynamic database, however, does not include iron species and their Pitzer parameters, in spite of the fact that there will be a large amount of iron in the WIPP. Iron would be emplaced as part of the waste, as well as the containers for the waste. The objective of this analysis is to derive the Pitzer binary interaction parameters for the pair of Mg2+ and FeCitrate-. Briefly, an aqueous model for dissolution of Fe(OH)2(s) in MgNa2Citrate solution was fitted to the experimentally measured solubility data. The aqueous model consists of several chemical reactions and related Pitzer interaction parameters. Specifically, Pitzer binary interaction parameters for the Mg2+ and FeCitrate- pair (β(0), β(1), and Cφ) were fitted to the experimental data. Anoxic gloveboxes were used to keep the oxygen level low (less than 6 ppm) throughout the experiments. Aging time was more than 800 days to ensure equilibrium. EQ3NR packaged in EQ3/6 v.8.0a calculates the aqueous speciation and saturation index using an aqueous model addressed in EQ3/6's database. The saturation index indicates how far the system is from equilibrium with respect to the solid of interest. Thus, the smaller the sum of squared saturation indices that the aqueous model calculates for the given number of experiments, the more closely the model attributes equilibrium to each

  10. Pairing and unpairing electron densities in organic systems: Two-electron three center through space and through bonds interactions

    SciTech Connect

    Lobayan, Rosana M.; Bochicchio, Roberto C.

    2014-05-07

    Two-electron three-center bonding interactions in organic ions like methonium (CH{sub 5}{sup +}), ethonium (C{sub 2}H{sub 7}{sup +}), and protonated alkanes n−C{sub 4}H{sub 11}{sup +} 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.

  11. Retired A Stars and Their Companions. VI. A Pair of Interacting Exoplanet Pairs Around the Subgiants 24 Sextanis and HD 200964

    NASA Astrophysics Data System (ADS)

    Johnson, John Asher; Payne, Matthew; Howard, Andrew W.; Clubb, Kelsey I.; Ford, Eric B.; Bowler, Brendan P.; Henry, Gregory W.; Fischer, Debra A.; Marcy, Geoffrey W.; Brewer, John M.; Schwab, Christian; Reffert, Sabine; Lowe, Thomas B.

    2011-01-01

    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 Jup and 0.86 M Jup, assuming a stellar mass M sstarf= 1.54 M ⊙. 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 Jup and 0.90 M Jup, assuming M sstarf= 1.44 M ⊙. 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. Based on observations obtained at the Lick Observatory, which is operated by the University of California, and W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology.

  12. Methods for detecting interactions between imprinted genes and environmental exposures using birth cohort designs with mother-offspring pairs.

    PubMed

    Wang, Shuang; Yu, Zhaoxia; Miller, Rachel L; Tang, Deliang; Perera, Frederica P

    2011-01-01

    Genomic imprinting is a form of epigenetic regulation in mammals in which the same allele of a gene is expressed differently depending on the parental origin of the allele. Traditionally, the detection of imprinted genes that affect complex diseases has been focused on linkage designs with pedigrees or case-parent designs with case-parent trios. In the past two decades, the birth cohort design with mother-offspring pairs has been applied to understand better the effect of environmental influences during pregnancy and beginning of life on the growth and development of children. No work has been done on the detection of imprinted genes using birth cohort designs. Moreover, although the importance of imprinting has been well recognized, no study has looked at how environmental exposures modify the effects of imprinted genes. In this study, we show that the proposed imprinting test using the birth cohort design with mother-offspring pairs is an efficient test for testing the interactions between imprinted genes and environmental exposures. Through extensive simulation studies and a real data application, the proposed imprinting test has demonstrated much improved power in detecting gene-environment interactions than that of a test assuming the Mendelian dominant model when the true underlying genetic model is imprinting. PMID:21778739

  13. Using full configuration interaction quantum Monte Carlo in a seniority zero space to investigate the correlation energy equivalence of pair coupled cluster doubles and doubly occupied configuration interaction.

    PubMed

    Shepherd, James J; Henderson, Thomas M; Scuseria, Gustavo E

    2016-03-01

    Over the past few years, pair coupled cluster doubles (pCCD) has shown promise for the description of strong correlation. This promise is related to its apparent ability to match results from doubly occupied configuration interaction (DOCI), even though the latter method has exponential computational cost. Here, by modifying the full configuration interaction quantum Monte Carlo algorithm to sample only the seniority zero sector of Hilbert space, we show that the DOCI and pCCD energies are in agreement for a variety of 2D Hubbard models, including for systems well out of reach for conventional configuration interaction algorithms. Our calculations are aided by the sign problem being much reduced in the seniority zero space compared with the full space. We present evidence for this and then discuss the sign problem in terms of the wave function of the system which appears to have a simplified sign structure. PMID:26957162

  14. Using full configuration interaction quantum Monte Carlo in a seniority zero space to investigate the correlation energy equivalence of pair coupled cluster doubles and doubly occupied configuration interaction

    NASA Astrophysics Data System (ADS)

    Shepherd, James J.; Henderson, Thomas M.; Scuseria, Gustavo E.

    2016-03-01

    Over the past few years, pair coupled cluster doubles (pCCD) has shown promise for the description of strong correlation. This promise is related to its apparent ability to match results from doubly occupied configuration interaction (DOCI), even though the latter method has exponential computational cost. Here, by modifying the full configuration interaction quantum Monte Carlo algorithm to sample only the seniority zero sector of Hilbert space, we show that the DOCI and pCCD energies are in agreement for a variety of 2D Hubbard models, including for systems well out of reach for conventional configuration interaction algorithms. Our calculations are aided by the sign problem being much reduced in the seniority zero space compared with the full space. We present evidence for this and then discuss the sign problem in terms of the wave function of the system which appears to have a simplified sign structure.

  15. OncoBinder facilitates interpretation of proteomic interaction data by capturing coactivation pairs in cancer

    PubMed Central

    Zhang, Yao; Wang, Huanbin; Fang, Jing-Yuan; Xu, Jie

    2016-01-01

    High-throughput methods such as co-immunoprecipitationmass spectrometry (coIP-MS) and yeast 2 hybridization (Y2H) have suggested a broad range of unannotated protein-protein interactions (PPIs), and interpretation of these PPIs remains a challenging task. The advancements in cancer genomic researches allow for the inference of “coactivation pairs” in cancer, which may facilitate the identification of PPIs involved in cancer. Here we present OncoBinder as a tool for the assessment of proteomic interaction data based on the functional synergy of oncoproteins in cancer. This decision tree-based method combines gene mutation, copy number and mRNA expression information to infer the functional status of protein-coding genes. We applied OncoBinder to evaluate the potential binders of EGFR and ERK2 proteins based on the gastric cancer dataset of The Cancer Genome Atlas (TCGA). As a result, OncoBinder identified high confidence interactions (annotated by Kyoto Encyclopedia of Genes and Genomes (KEGG) or validated by low-throughput assays) more efficiently than co-expression based method. Taken together, our results suggest that evaluation of gene functional synergy in cancer may facilitate the interpretation of proteomic interaction data. The OncoBinder toolbox for Matlab is freely accessible online. PMID:26872056

  16. Young Foreign Language Learners' Interactions during Task-Based Paired Assessments

    ERIC Educational Resources Information Center

    Butler, Yuko Goto; Zeng, Wei

    2014-01-01

    Despite the popularity of task-based language teaching (TBLT) in foreign language (FL) education at elementary school, it remains unclear how young learners' FL abilities can best be evaluated with tasks. The present study seeks to understand developmental differences in interactions among elementary-school students during task-based language…

  17. The Influence of Context-Specific and Dispositional Achievement Goals on Children's Paired Collaborative Interaction

    ERIC Educational Resources Information Center

    Harris, Amanda; Yuill, Nicola; Luckin, Rosemary

    2008-01-01

    Background: Research has demonstrated that working collaboratively can have positive effects on children's learning. While key factors have been identified which influence the quality of these interactions, little research has addressed the influence of children's achievement goals on collaborative behaviour. Aims: This paper investigates the…

  18. Coulomb crystallization of highly charged ions

    NASA Astrophysics Data System (ADS)

    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

    2015-03-01

    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 40Ar13+) 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 Ar13+ 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.

  19. Coulomb drag in topological insulator films

    NASA Astrophysics Data System (ADS)

    Liu, Hong; Liu, Weizhe Edward; Culcer, Dimitrie

    2016-05-01

    We study Coulomb drag between the top and bottom surfaces of topological insulator films. We derive a kinetic equation for the thin-film spin density matrix containing the full spin structure of the two-layer system, and analyze the electron-electron interaction in detail in order to recover all terms responsible for Coulomb drag. Focusing on typical topological insulator systems, with a film thicknesses d up to 6 nm, we obtain numerical and approximate analytical results for the drag resistivity ρD and find that ρD is proportional to T2d-4 na-3/2 np-3/2 at low temperature T and low electron density na,p, with a denoting the active layer and p the passive layer. In addition, we compare ρD with graphene, identifying qualitative and quantitative differences, and we discuss the multi-valley case, ultra thin films and electron-hole layers.

  20. Open-shell pair interaction energy decomposition analysis (PIEDA): Formulation and application to the hydrogen abstraction in tripeptides

    NASA Astrophysics Data System (ADS)

    Green, Mandy C.; Fedorov, Dmitri G.; Kitaura, Kazuo; Francisco, Joseph S.; Slipchenko, Lyudmila V.

    2013-02-01

    An open-shell extension of the pair interaction energy decomposition analysis (PIEDA) within the framework of the fragment molecular orbital (FMO) method is developed. The open-shell PIEDA method allows the analysis of inter- and intramolecular interactions in terms of electrostatic, exchange-repulsion, charge-transfer, dispersion, and optional polarization energies for molecular systems with a radical or high-spin fragment. Taking into account the low computational cost and scalability of the FMO and PIEDA methods, the new scheme provides a means to characterize the stabilization of radical and open-shell sites in biologically relevant species. The open-shell PIEDA is applied to the characterization of intramolecular interactions in capped trialanine upon hydrogen abstraction (HA) at various sites on the peptide. Hydrogen abstraction reaction is the first step in the oxidative pathway initiated by reactive oxygen or nitrogen species, associated with oxidative stress. It is found that HA results in significant geometrical reorganization of the trialanine peptide. Depending on the HA site, terminal interactions in the radical fold conformers may become weaker or stronger compared to the parent molecule, and often change the character of the non-covalent bonding from amide stacking to hydrogen bonding.

  1. Monitoring Flower Visitation Networks and Interactions between Pairs of Bumble Bees in a Large Outdoor Flight Cage

    PubMed Central

    Lihoreau, Mathieu; Chittka, Lars; Raine, Nigel E.

    2016-01-01

    Pollinators, such as bees, often develop multi-location routes (traplines) to exploit subsets of flower patches within larger plant populations. How individuals establish such foraging areas in the presence of other foragers is poorly explored. Here we investigated the foraging patterns of pairs of bumble bees (Bombus terrestris) released sequentially into an 880m2 outdoor flight cage containing 10 feeding stations (artificial flowers). Using motion-sensitive video cameras mounted on flowers, we mapped the flower visitation networks of both foragers, quantified their interactions and compared their foraging success over an entire day. Overall, bees that were released first (residents) travelled 37% faster and collected 77% more nectar, thereby reaching a net energy intake rate 64% higher than bees released second (newcomers). However, this prior-experience advantage decreased as newcomers became familiar with the spatial configuration of the flower array. When both bees visited the same flower simultaneously, the most frequent outcome was for the resident to evict the newcomer. On the rare occasions when newcomers evicted residents, the two bees increased their frequency of return visits to that flower. These competitive interactions led to a significant (if only partial) spatial overlap between the foraging patterns of pairs of bees. While newcomers may initially use social cues (such as olfactory footprints) to exploit flowers used by residents, either because such cues indicate higher rewards and/or safety from predation, residents may attempt to preserve their monopoly over familiar resources through exploitation and interference. We discuss how these interactions may favour spatial partitioning, thereby maximising the foraging efficiency of individuals and colonies. PMID:26982030

  2. Monitoring Flower Visitation Networks and Interactions between Pairs of Bumble Bees in a Large Outdoor Flight Cage.

    PubMed

    Lihoreau, Mathieu; Chittka, Lars; Raine, Nigel E

    2016-01-01

    Pollinators, such as bees, often develop multi-location routes (traplines) to exploit subsets of flower patches within larger plant populations. How individuals establish such foraging areas in the presence of other foragers is poorly explored. Here we investigated the foraging patterns of pairs of bumble bees (Bombus terrestris) released sequentially into an 880m2 outdoor flight cage containing 10 feeding stations (artificial flowers). Using motion-sensitive video cameras mounted on flowers, we mapped the flower visitation networks of both foragers, quantified their interactions and compared their foraging success over an entire day. Overall, bees that were released first (residents) travelled 37% faster and collected 77% more nectar, thereby reaching a net energy intake rate 64% higher than bees released second (newcomers). However, this prior-experience advantage decreased as newcomers became familiar with the spatial configuration of the flower array. When both bees visited the same flower simultaneously, the most frequent outcome was for the resident to evict the newcomer. On the rare occasions when newcomers evicted residents, the two bees increased their frequency of return visits to that flower. These competitive interactions led to a significant (if only partial) spatial overlap between the foraging patterns of pairs of bees. While newcomers may initially use social cues (such as olfactory footprints) to exploit flowers used by residents, either because such cues indicate higher rewards and/or safety from predation, residents may attempt to preserve their monopoly over familiar resources through exploitation and interference. We discuss how these interactions may favour spatial partitioning, thereby maximising the foraging efficiency of individuals and colonies. PMID:26982030

  3. Coulomb Mediated Hybridization of Excitons in Coupled Quantum Dots

    NASA Astrophysics Data System (ADS)

    Ardelt, P.-L.; Gawarecki, K.; Müller, K.; Waeber, A. M.; Bechtold, A.; Oberhofer, K.; Daniels, J. M.; Klotz, F.; Bichler, M.; Kuhn, T.; Krenner, H. J.; Machnikowski, P.; Finley, J. J.

    2016-02-01

    We report Coulomb mediated hybridization of excitonic states in optically active InGaAs quantum dot molecules. By probing the optical response of an individual quantum dot molecule as a function of the static electric field applied along the molecular axis, we observe unexpected avoided level crossings that do not arise from the dominant single-particle tunnel coupling. We identify a new few-particle coupling mechanism stemming from Coulomb interactions between different neutral exciton states. Such Coulomb resonances hybridize the exciton wave function over four different electron and hole single-particle orbitals. Comparisons of experimental observations with microscopic eight-band k .p calculations taking into account a realistic quantum dot geometry show good agreement and reveal that the Coulomb resonances arise from broken symmetry in the artificial semiconductor molecule.

  4. A model study on a pair of trapped particles interacting with an arbitrary effective range

    NASA Astrophysics Data System (ADS)

    Goswami, Partha; Deb, Bimalendu

    2016-08-01

    We study the effects of the effective range of interaction on the eigenvalues and eigenstates of two particles confined in a three-dimensional (3D) isotropic as well as one- or quasi-one dimensional harmonic (1D) traps. For this we employ model potentials which mimic finite-range s-wave interactions over a wide range of s-wave scattering length a s including the unitarity limits {a}s\\to +/- ∞ . Our results show that when the range is larger than the 3D or 1D harmonic oscillator length scale, the eigenvalues and eigenstates are nearly similar to those of noninteracting two particles in the 3D or 1D trap, respectively. In case of 3D, we find that when the range goes to zero, the results of contact potential as derived by Busch et al (1998 Foundations of Physics 28 549) are reproduced. However, in the case of 1D, such reproducibility does not occur as the range goes to zero. We have calculated the eigenvalues and eigenstates in a 1D harmonic trap taking one dimensional finite-range model potential. We have also calculated the bound state properties of two particles confined in a highly anisotropic quasi-1D trap taking three-dimensional finite-range model potential, and examined whether these quasi-1D results approach towards 1D ones as the aspect ratio η of the radial to axial frequency of the trap increases. We find that if the range is very small compared to the axial size of the trap, then one can reach 1D regime for η ≥slant 10000. However, for a large range, one can almost get 1D results for smaller values of η. This study will be important for the exploration of two-body or many body physics of trapped ultracold atoms interacting with narrow Feshbach resonance for which the effective range can be large.

  5. Evolutionarily conserved paired immunoglobulin-like receptor α (PILRα) domain mediates its interaction with diverse sialylated ligands.

    PubMed

    Sun, Yonglian; Senger, Kate; Baginski, Tomasz K; Mazloom, Anita; Chinn, Yvonne; Pantua, Homer; Hamidzadeh, Kajal; Ramani, Sree Ranjani; Luis, Elizabeth; Tom, Irene; Sebrell, Andrew; Quinones, Gabriel; Ma, Yan; Mukhyala, Kiran; Sai, Tao; Ding, Jiabing; Haley, Benjamin; Shadnia, Hooman; Kapadia, Sharookh B; Gonzalez, Lino C; Hass, Philip E; Zarrin, Ali A

    2012-05-01

    Paired immunoglobulin-like receptor (PILR) α is an inhibitory receptor that recognizes several ligands, including mouse CD99, PILR-associating neural protein, and Herpes simplex virus-1 glycoprotein B. The physiological function(s) of interactions between PILRα and its cellular ligands are not well understood, as are the molecular determinants of PILRα/ligand interactions. To address these uncertainties, we sought to identify additional PILRα ligands and further define the molecular basis for PILRα/ligand interactions. Here, we identify two novel PILRα binding partners, neuronal differentiation and proliferation factor-1 (NPDC1), and collectin-12 (COLEC12). We find that sialylated O-glycans on these novel PILRα ligands, and on known PILRα ligands, are compulsory for PILRα binding. Sialylation-dependent ligand recognition is also a property of SIGLEC1, a member of the sialic acid-binding Ig-like lectins. SIGLEC1 Ig domain shares ∼22% sequence identity with PILRα, an identity that includes a conserved arginine localized to position 97 in mouse and human SIGLEC1, position 133 in mouse PILRα and position 126 in human PILRα. We observe that PILRα/ligand interactions require conserved PILRα Arg-133 (mouse) and Arg-126 (human), in correspondence with a previously reported requirement for SIGLEC1 Arg-197 in SIGLEC1/ligand interactions. Homology modeling identifies striking similarities between PILRα and SIGLEC1 ligand binding pockets as well as at least one set of distinctive interactions in the galactoxyl-binding site. Binding studies suggest that PILRα recognizes a complex ligand domain involving both sialic acid and protein motif(s). Thus, PILRα is evolved to engage multiple ligands with common molecular determinants to modulate myeloid cell functions in anatomical settings where PILRα ligands are expressed. PMID:22396535

  6. Evolutionarily Conserved Paired Immunoglobulin-like Receptor α (PILRα) Domain Mediates Its Interaction with Diverse Sialylated Ligands

    PubMed Central

    Sun, Yonglian; Senger, Kate; Baginski, Tomasz K.; Mazloom, Anita; Chinn, Yvonne; Pantua, Homer; Hamidzadeh, Kajal; Ramani, Sree Ranjani; Luis, Elizabeth; Tom, Irene; Sebrell, Andrew; Quinones, Gabriel; Ma, Yan; Mukhyala, Kiran; Sai, Tao; Ding, Jiabing; Haley, Benjamin; Shadnia, Hooman; Kapadia, Sharookh B.; Gonzalez, Lino C.; Hass, Philip E.; Zarrin, Ali A.

    2012-01-01

    Paired immunoglobulin-like receptor (PILR) α is an inhibitory receptor that recognizes several ligands, including mouse CD99, PILR-associating neural protein, and Herpes simplex virus-1 glycoprotein B. The physiological function(s) of interactions between PILRα and its cellular ligands are not well understood, as are the molecular determinants of PILRα/ligand interactions. To address these uncertainties, we sought to identify additional PILRα ligands and further define the molecular basis for PILRα/ligand interactions. Here, we identify two novel PILRα binding partners, neuronal differentiation and proliferation factor-1 (NPDC1), and collectin-12 (COLEC12). We find that sialylated O-glycans on these novel PILRα ligands, and on known PILRα ligands, are compulsory for PILRα binding. Sialylation-dependent ligand recognition is also a property of SIGLEC1, a member of the sialic acid-binding Ig-like lectins. SIGLEC1 Ig domain shares ∼22% sequence identity with PILRα, an identity that includes a conserved arginine localized to position 97 in mouse and human SIGLEC1, position 133 in mouse PILRα and position 126 in human PILRα. We observe that PILRα/ligand interactions require conserved PILRα Arg-133 (mouse) and Arg-126 (human), in correspondence with a previously reported requirement for SIGLEC1 Arg-197 in SIGLEC1/ligand interactions. Homology modeling identifies striking similarities between PILRα and SIGLEC1 ligand binding pockets as well as at least one set of distinctive interactions in the galactoxyl-binding site. Binding studies suggest that PILRα recognizes a complex ligand domain involving both sialic acid and protein motif(s). Thus, PILRα is evolved to engage multiple ligands with common molecular determinants to modulate myeloid cell functions in anatomical settings where PILRα ligands are expressed. PMID:22396535

  7. Superconductor-insulator transition in the presence of Coulomb disorder

    NASA Astrophysics Data System (ADS)

    Shklovskii, B. I.

    2007-12-01

    Superconductor-insulator transition driven by the decreasing concentration of electrons n is studied in the case of the disorder potential created by randomly positioned charged impurities. Electrons and Cooper pairs (formed by a non-Coulomb attraction) nonlinearly screen the random potential of impurities. Both electrons and Cooper pairs can be delocalized or localized in the resulting self-consistent potential. The border separating the superconductor and insulator phases in the plane of the concentration of electrons and the length of the Cooper pair is found. For a strong disorder, the central segment of this border follows the Bose-Einstein-Condensation-BCS crossover line defined for a clean sample.

  8. Species-specific long range interactions between receptor/ligand pairs.

    PubMed Central

    Liebert, R B; Prieve, D C

    1995-01-01

    Total internal reflection microscopy (TIRM) monitors Brownian fluctuations in elevation as small as 1 nm by measuring the scattering of a single sphere illuminated by an evanescent wave when the sphere is levitated by colloidal forces such as electrostatic double-layer repulsion. From the Boltzmann distribution of elevations sampled by the sphere over time, the potential energy profile can be determined with a resolution of approximately 0.1 of the thermal energy kT. Thus, the interaction between a receptor-coated (goat, horse, or rabbit immunoglobulin G (IgG)) latex sphere and a protein A (SpA)-coated glass microscope slide was studied. A typical TIRM potential energy profile measured between a bare sphere and a bare glass plate, where the sphere fluctuates around the secondary potential energy minimum formed between double-layer repulsion and gravitational attraction, agrees well with DLVO theory. The interactions measured between IgG-coated spheres and SpA-coated slides, on the other hand, displayed a weaker repulsion compared with that observed between bare surfaces under the same conditions. Analysis of the results obtained between the coated surfaces suggests an additional attractive force. The decay length of this attraction correlates with the known dissociation constants for the binding of IgG with SpA in free solution. Images FIGURE 1 PMID:7669911

  9. Electronic structure of an anticancer drug DC81 and its interaction with DNA base pairs

    NASA Astrophysics Data System (ADS)

    Tiwari, Gargi; Sharma, Dipendra; Dwivedi, K. K.; Dwivedi, M. K.

    2016-05-01

    The drug, 8-Hydroxy-7-methoxy-pyrrolo-[2,1-c][1,4] benzodiazepine-5-one, commonly christened as DC81 belongs to the pyrrolo-[2,1-c][1,4]benzodiazepine (PBDs) family. It is a member of the group of naturally occurring antitumour antibiotics produced by various Streptomyces species. The antitumour activity of DC81 is attributed to its sequence specific interaction with G-C rich DNA region in particular, for Pu-G-Pu motifs. In the present paper, physico-chemical properties DC81 have been carried out using an ab-initio method, HF/6-31G(d,p) with GAMESS program. MEP, HOMO and LUMO surfaces have been scanned. Ionization potential, electron affinity, electronegativity, global hardness and softness of the drug have been calculated. Further, drug-DNA interactions have been examined using modified second order perturbation theory along with multicentred-multipole expansion technique. Results have been discussed in the light of other theoretical and experimental observations. Efforts have been made to elucidate the binding patterns and thereby biological properties of the drug.

  10. Four distances between pairs of amino acids provide a precise description of their interaction.

    PubMed

    Cohen, Mati; Potapov, Vladimir; Schreiber, Gideon

    2009-08-01

    The three-dimensional structures of proteins are stabilized by the interactions between amino acid residues. Here we report a method where four distances are calculated between any two side chains to provide an exact spatial definition of their bonds. The data were binned into a four-dimensional grid and compared to a random model, from which the preference for specific four-distances was calculated. A clear relation between the quality of the experimental data and the tightness of the distance distribution was observed, with crystal structure data providing far tighter distance distributions than NMR data. Since the four-distance data have higher information content than classical bond descriptions, we were able to identify many unique inter-residue features not found previously in proteins. For example, we found that the side chains of Arg, Glu, Val and Leu are not symmetrical in respect to the interactions of their head groups. The described method may be developed into a function, which computationally models accurately protein structures. PMID:19680437

  11. Interaction of the main components from the traditional Chinese drug pair Chaihu-Shaoyao based on rat intestinal absorption.

    PubMed

    Chen, Yan; Wang, Jinyan; Yuan, Ling; Zhou, Lei; Jia, Xiaobin; Tan, Xiaobin

    2011-01-01

    The Chaihu-Shaoyao drug pair (Bupleuri Radix and Paeoniae Radix Alba) which is a traditional Chinese drug pair, has been widely used for anti-inflammatory purposes. Saikosaponin a (SSA), saikosaponin d (SSD) and paeoniflorin are identified as the main components in the pair. The present study focused on the interaction of the main components based on investigating their intestinal absorption using a four-site perfused rat intestinal model in order to clarify the mechanism of the compatibility of Chaihu-Shaoyao. The concentrations of SSA, SSD and paeoniflorin in the intestinal perfusate were determined by LC/MS or UPLC (Ultra Performance Liquid Chromatography) methods, followed by P*(eff) (effective permeability) and 10% ABS (the percent absorption of 10 cm of intestine) calculations. The results showed that all of the three main components displayed very low permeabilities (P*(eff) < 0.4), which implied their poor absorption in the rat intestine. The absorption levels of SSA and SSD were similar in intestine and higher in ileum than those in other intestinal regions in the decreasing order: colon, jejunum and duodenum. However, there is no significant difference in the absorption of paeoniflorin in the four segments (P < 0.05). The P*(eff) values of paeoniflorin exhibited an almost 2.11-fold or 1.90-fold increase in ileum when it was co-administrated with SSA and SSD, as well as 2.42-, 2.18-fold increase in colon, respectively, whereas the absorptions of SSA and SSD were not influenced by paeoniflorin. In conclusion, SSA and SSD could promote the absorption of paeoniflorin. To some extent this might explain the nature of the compatibility mechanisms of composite formulae in TCMs. PMID:22095024

  12. Rashba Splitting of Cooper Pairs

    NASA Astrophysics Data System (ADS)

    Shekhter, R. I.; Entin-Wohlman, O.; Jonson, M.; Aharony, A.

    2016-05-01

    We investigate theoretically the properties of a weak link between two superconducting leads, which has the form of a nonsuperconducting nanowire with a strong Rashba spin-orbit coupling caused by an electric field. In the Coulomb-blockade regime of single-electron tunneling, we find that such a weak link acts as a "spin splitter" of the spin states of Cooper pairs tunneling through the link, to an extent that depends on the direction of the electric field. We show that the Josephson current is sensitive to interference between the resulting two transmission channels, one where the spins of both members of a Cooper pair are preserved and one where they are both flipped. As a result, the current is a periodic function of the strength of the spin-orbit interaction and of the bending angle of the nanowire (when mechanically bent); an identical effect appears due to strain-induced spin-orbit coupling. In contrast, no spin-orbit induced interference effect can influence the current through a single weak link connecting two normal metals.

  13. Rashba Splitting of Cooper Pairs.

    PubMed

    Shekhter, R I; Entin-Wohlman, O; Jonson, M; Aharony, A

    2016-05-27

    We investigate theoretically the properties of a weak link between two superconducting leads, which has the form of a nonsuperconducting nanowire with a strong Rashba spin-orbit coupling caused by an electric field. In the Coulomb-blockade regime of single-electron tunneling, we find that such a weak link acts as a "spin splitter" of the spin states of Cooper pairs tunneling through the link, to an extent that depends on the direction of the electric field. We show that the Josephson current is sensitive to interference between the resulting two transmission channels, one where the spins of both members of a Cooper pair are preserved and one where they are both flipped. As a result, the current is a periodic function of the strength of the spin-orbit interaction and of the bending angle of the nanowire (when mechanically bent); an identical effect appears due to strain-induced spin-orbit coupling. In contrast, no spin-orbit induced interference effect can influence the current through a single weak link connecting two normal metals. PMID:27284669

  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. PMID:27443742

  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. Light-emitting self-assembled peptide nucleic acids exhibit both stacking interactions and Watson-Crick base pairing

    NASA Astrophysics Data System (ADS)

    Berger, Or; Adler-Abramovich, Lihi; Levy-Sakin, Michal; Grunwald, Assaf; Liebes-Peer, Yael; Bachar, Mor; Buzhansky, Ludmila; Mossou, Estelle; Forsyth, V. Trevor; Schwartz, Tal; Ebenstein, Yuval; Frolow, Felix; Shimon, Linda J. W.; Patolsky, Fernando; Gazit, Ehud

    2015-05-01

    The two main branches of bionanotechnology involve the self-assembly of either peptides or DNA. Peptide scaffolds offer chemical versatility, architectural flexibility and structural complexity, but they lack the precise base pairing and molecular recognition available with nucleic acid assemblies. Here, inspired by the ability of aromatic dipeptides to form ordered nanostructures with unique physical properties, we explore the assembly of peptide nucleic acids (PNAs), which are short DNA mimics that have an amide backbone. All 16 combinations of the very short di-PNA building blocks were synthesized and assayed for their ability to self-associate. Only three guanine-containing di-PNAs—CG, GC and GG—could form ordered assemblies, as observed by electron microscopy, and these di-PNAs efficiently assembled into discrete architectures within a few minutes. The X-ray crystal structure of the GC di-PNA showed the occurrence of both stacking interactions and Watson-Crick base pairing. The assemblies were also found to exhibit optical properties including voltage-dependent electroluminescence and wide-range excitation-dependent fluorescence in the visible region.

  17. Systematic study of real photon and Drell-Yan pair production in p+A (d+A) interactions

    NASA Astrophysics Data System (ADS)

    Krelina, M.; Basso, E.; Goncalves, V. P.; Nemchik, J.; Pasechnik, R.

    2016-07-01

    We study nuclear effects in production of Drell-Yan pairs and direct photons in proton-nucleus collisions. For the first time, these effects are studied within the color dipole approach using the Green function formalism which naturally incorporates the color transparency and quantum coherence effects. The corresponding numerical results for the nuclear modification factor are compared with available data. Besides, we present a variety of predictions for the nuclear suppression as a function of transverse momentum pT, Feynman variable xF and invariant mass M of the lepton pair which can be verified by experiments at RHIC and LHC. We found that the nuclear suppression is caused predominantly by effects of quantum coherence (shadowing corrections) and by the effective energy loss induced by multiple initial state interactions. Whereas the former dominate at small Bjorken x2 in the target, the latter turns out to be significant at large x1 in the projectile beam and is universal at different energies and transverse momenta.

  18. Interaction between magnetic vortex cores in a pair of nonidentical nanodisks

    SciTech Connect

    Sinnecker, J. P.; Vigo-Cotrina, H.; Garcia, F.; Novais, E. R. P.; Guimarães, A. P.

    2014-05-28

    The coupling of two nonidentical magnetic nanodisks, i.e., with different vortex gyrotropic frequencies, is studied. From the analytical approach, the interactions between the nanodisks along x and y directions (the coupling integrals) were obtained as a function of distance. From the numerical solution of Thiele's equation, we derived the eigenfrequencies of the vortex cores as a function of distance. The motion of the two vortex cores and, consequently, the time dependence of the total magnetization M(t) were derived both using Thiele's equation and by micromagnetic simulation. From M(t), a recently developed method, the magnetic vortex echoes, analogous to the Nuclear Magnetic Resonance spin echoes, was used to compute the distance dependence of the magnetic coupling strength. The results of the two approaches differ by approximately 10%; using one single term, a dependence with distance found is broadly in agreement with studies employing other techniques.

  19. Changes in flexibility upon binding: Application of the self-consistent pair contact probability method to protein-protein interactions

    NASA Astrophysics Data System (ADS)

    Canino, Lawrence S.; Shen, Tongye; McCammon, J. Andrew

    2002-12-01

    We extend the self-consistent pair contact probability method to the evaluation of the partition function for a protein complex at thermodynamic equilibrium. Specifically, we adapt the method for multichain models and introduce a parametrization for amino acid-specific pairwise interactions. This method is similar to the Gaussian network model but allows for the adjusting of the strengths of native state contacts. The method is first validated on a high resolution x-ray crystal structure of bovine Pancreatic Phospholipase A2 by comparing calculated B-factors with reported values. We then examine binding-induced changes in flexibility in protein-protein complexes, comparing computed results with those obtained from x-ray crystal structures and molecular dynamics simulations. In particular, we focus on the mouse acetylcholinesterase:fasciculin II and the human α-thrombin:thrombomodulin complexes.

  20. Probing long-range carrier-pair spin-spin interactions in a conjugated polymer by detuning of electrically detected spin beating

    NASA Astrophysics Data System (ADS)

    van Schooten, Kipp J.; Baird, Douglas L.; Limes, Mark E.; Lupton, John M.; Boehme, Christoph

    2015-04-01

    Weakly coupled electron spin pairs that experience weak spin-orbit interaction can control electronic transitions in molecular and solid-state systems. Known to determine radical pair reactions, they have been invoked to explain phenomena ranging from avian magnetoreception to spin-dependent charge-carrier recombination and transport. Spin pairs exhibit persistent spin coherence, allowing minute magnetic fields to perturb spin precession and thus recombination rates and photoreaction yields, giving rise to a range of magneto-optoelectronic effects in devices. Little is known, however, about interparticle magnetic interactions within such pairs. Here we present pulsed electrically detected electron spin resonance experiments on poly(styrene-sulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) devices, which show how interparticle spin-spin interactions (magnetic-dipolar and spin-exchange) between charge-carrier spin pairs can be probed through the detuning of spin-Rabi oscillations. The deviation from uncoupled precession frequencies quantifies both the exchange (<30 neV) and dipolar (23.5+/-1.5 neV) interaction energies responsible for the pair's zero-field splitting, implying quantum mechanical entanglement of charge-carrier spins over distances of 2.1+/-0.1 nm.

  1. Probing long-range carrier-pair spin–spin interactions in a conjugated polymer by detuning of electrically detected spin beating

    PubMed Central

    van Schooten, Kipp J.; Baird, Douglas L.; Limes, Mark E.; Lupton, John M.; Boehme, Christoph

    2015-01-01

    Weakly coupled electron spin pairs that experience weak spin–orbit interaction can control electronic transitions in molecular and solid-state systems. Known to determine radical pair reactions, they have been invoked to explain phenomena ranging from avian magnetoreception to spin-dependent charge-carrier recombination and transport. Spin pairs exhibit persistent spin coherence, allowing minute magnetic fields to perturb spin precession and thus recombination rates and photoreaction yields, giving rise to a range of magneto-optoelectronic effects in devices. Little is known, however, about interparticle magnetic interactions within such pairs. Here we present pulsed electrically detected electron spin resonance experiments on poly(styrene-sulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) devices, which show how interparticle spin–spin interactions (magnetic-dipolar and spin-exchange) between charge-carrier spin pairs can be probed through the detuning of spin-Rabi oscillations. The deviation from uncoupled precession frequencies quantifies both the exchange (<30 neV) and dipolar (23.5±1.5 neV) interaction energies responsible for the pair's zero-field splitting, implying quantum mechanical entanglement of charge-carrier spins over distances of 2.1±0.1 nm. PMID:25868686

  2. On the internal d-wave structure of s+/- pairs in Iron-based Superconductors

    NASA Astrophysics Data System (ADS)

    Ong, Tze Tzen; Coleman, Piers

    2014-03-01

    A key issue in understanding the high temperature iron-based superconductors concerns the mechanism by which the paired electrons minimize their strong mutual Coulomb repulsion. Whereas electronically paired superconductors generally avoid the Coulomb interaction through the formation of higher angular momentum pairs, iron based superconductors involve s-wave (s+/-) pairs with zero angular momentum. By taking account of the orbital degrees of freedom of the iron atoms, here we show that the s+/- pairs in these materials possess hidden d-wave symmetry, forming orbital triplets in which the the d-wave angular momentum of the pairs is compensated by the internal angular momentum of the orbitals. The recent observation of a gap with octahedral structure in KFe2As2 materials can be understood as a transition to a ``high spin'' configuration of the d-wave orbital triplets, through the alignment of the two angular momentum components of the pair. We acknowledge funding from DOE grant DE-FG02-99ER45790.

  3. Toward ab initio DFT: Pairing and Optimized Effective Potential

    NASA Astrophysics Data System (ADS)

    Drut, Joaquin

    2010-11-01

    The quest for a universal nuclear energy density functional has stimulated research in many different areas of quantum many-body physics. Advances in the last decade have enabled quantum chemists to explicitly construct energy density functionals for the Coulomb interaction from first principles. This task was accomplished by extending the notion of density-dependent functionals to include explicit dependence on the Kohn-Sham orbitals. The resulting approach is usually called the Optimized Effective Potential (OEP). Are these developments useful in the nuclear case? Can one extend the OEP to include pairing? In this contribution we present some first answers to these and other related questions.

  4. 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.

  5. Unravelling the interaction dynamics of a carbonatite-silicate magmatic pair: A numerical approach based on Korteweg Stress theory

    NASA Astrophysics Data System (ADS)

    Valentini, L.; Moore, K. R.; Chazot, G.

    2009-04-01

    Most of the worldwide carbonatites occur in spatial association with silicate rocks. Even when unquestionable evidence for the associated carbonatite and silicate rocks to represent contemporaneous liquids exists, the modes of interaction between the two liquids can be difficult to infer. In general, the retrieval of information about the mechanisms of interaction between magmas can be complicated by the intrinsic dynamical nature of such systems. The development of new physico-chemical equilibria (e.g. hybridization) can erase any information about the previous stages of interaction. However, the occurrence of magmatic heterogeneities, such as enclaves and flow bands, as well as mineral disequilibrium textures, may serve as dynamic markers for the underlying interaction processes. Small-scale heterogeneities, in the form of micron to millimetre sized globules, characterized by more or less smooth interfaces, are frequently observed in carbonatite-silicate pairs. Textural observation, as well as the lack of suitable mechanisms for the dispersion of a discrete magmatic liquid in the form of a small-scale emulsion, have lead many petrologists to advocate immiscible separation as the process capable of forming such textures. However, the geochemical criteria for liquid immiscibility are not always met, and when not coupled with geochemical and dynamical arguments, textural observation may lead to ambiguous conclusions. In this study we adopted an integrated approach in order to infer the details of magmatic interaction of a carbonatite-silicate pair from Massif Central (France). The studied samples display emulsion-like textures, formed by micro-scale dolomitic globules dispersed in a trachytic glassy matrix. Our approach is based on a novel numerical method, coupled with textural observation and geochemical analyses. The novelty of our numerical model consists in the inclusion, in the adopted advection-diffusion equations, of a term that takes into account the effect

  6. Efros-Shklovskii variable range hopping conductivity without Coulomb gap

    NASA Astrophysics Data System (ADS)

    Chen, Tianran; Skinner, Brian

    In doped semiconductors and Coulomb glasses, in the limit of weak coupling, the electron conductivity primarily proceeds by phonon-assisted tunneling or hopping between different sites through the insulating gaps that separate them. Electron conduction can occur both through nearest-neighbor hopping and through cotunneling of electrons between distant sites via a chain of intermediate virtual states. In the presence of some disorder, the latter mechanism dominates at low temperatures, where the length of the hops grows to optimize the conductivity. This transport mechanism was introduced by Mott, and is called variable range hopping. When the Coulomb interaction between localized electrons is taken into account, it can be shown that at a sufficiently low temperature, variable range hopping conductivity obeys the Efros-Shklovskii (ES) law, which has been observed in a number of amorphous semiconductors and granular metal systems at low temperatures. ES conductivity has been long understood as the result of a soft, Coulomb gap at the Fermi level. However, such a theory overlooks the presence of spatial correlations between site energies and their possible effects on electrical conductivity. In this talk, we show both analytically and numerically that in systems where spatial correlations must be taken into account, ES conductivity may persist far outside the Coulomb gap, in contrast to conventional transport theory for doped semiconductors and Coulomb glasses where ES conductivity only occurs within the Coulomb gap.

  7. Fast and accurate Coulomb calculation with Gaussian functions.

    PubMed

    Füsti-Molnár, László; Kong, Jing

    2005-02-15

    Coulomb interaction is one of the major time-consuming components in a density functional theory (DFT) calculation. In the last decade, dramatic progresses have been made to improve the efficiency of Coulomb calculation, including continuous fast multipole method (CFMM) and J-engine method, all developed first inside Q-Chem. The most recent development is the advent of Fourier transform Coulomb method developed by Fusti-Molnar and Pulay, and an improved version of the method has been recently implemented in Q-Chem. It replaces the least efficient part of the previous Coulomb methods with an accurate numerical integration scheme that scales in O(N2) instead of O(N4) with the basis size. The result is a much smaller slope in the linear scaling with respect to the molecular size and we will demonstrate through a series of benchmark calculations that it speeds up the calculation of Coulomb energy by several folds over the efficient existing code, i.e., the combination of CFMM and J-engine, without loss of accuracy. Furthermore, we will show that it is complementary to the latter and together the three methods offer the best performance for Coulomb part of DFT calculations, making the DFT calculations affordable for very large systems involving thousands of basis functions. PMID:15743222

  8. Bound free electron-positron pair production accompanied by giant dipole resonances

    SciTech Connect

    Senguel, M. Y.; Gueclue, M. C.

    2011-01-15

    At the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), for example, virtual photons produce many particles. At small impact parameters where the colliding nuclei make peripheral collisions, photon fluxes are very large and these are responsible for the multiple photonuclear interactions. Free pair productions, bound free pair productions, and nuclear Coulomb excitations are important examples of such interactions, and these processes play important roles in the beam luminosity at RHIC and LHC. Here we obtained the impact parameter dependence of bound free pair production cross sections and by using this probability we obtained bound free electron-positron pair production with nuclear breakup for heavy ion collisions at RHIC and LHC. We also compared our results to the other calculations.

  9. Pairing Strengths for a Two Orbital Model of the Fe-pnictides

    SciTech Connect

    Qi, Xiao-Liang; Raghu, S.; Liu, Chao-Xing; Scalapino, D.J.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-25

    Using an RPA approximation, we have calculated the strengths of the singlet and triplet pairing interactions which arise from the exchange of spin and orbital fluctuations for a 2-orbital model of the Fe-pnictide superconductors. When the system is doped with F, the electron pockets become dominant and we find that the strongest pairing occurs in the singlet d-wave pairing and the triplet p-wave pairing channels, which compete closely. The pairing structure in the singlet d-wave channel corresponds to a superposition of near neighbor intra-orbital singlets with a minus sign phase difference between the d{sub xz} and d{sub yz} pairs. The leading pairing configuration in the triplet channel also involves a nearest neighbor intra-orbital pairing. We find that the strengths of both the singlet and triplet pairing grow, with the singlet pairing growing faster, as the onsite Coulomb interaction approaches the value where the S = 1 particle-hole susceptibility diverges.

  10. Nonlinear interaction between a pair of oblique modes in a supersonic mixing layer: Long-wave limit

    NASA Technical Reports Server (NTRS)

    Balsa, Thomas F.; Gartside, James

    1995-01-01

    The nonlinear interaction between a pair of symmetric, oblique, and spatial instability modes is studied in the long-wave limit using asymptotic methods. The base flow is taken to be a supersonic mixing layer whose Mach number is such that the corresponding vortex sheet is marginally stable according to Miles' criterion. It is shown that the amplitude of the mode obeys a nonlinear integro-differential equation. Numerical solutions of this equation show that, when the obliqueness angle is less than pi/4, the effect of the nonlinearity is to enhance the growth rate of the instability. The solution terminates in a singularity at a finite streamwise location. This result is reminiscent of that obtained in the vicinity of the neutral point by other authors in several different types of flows. On the other hand, when the obliqueness angle is more than pi/4, the streamwise development of the amplitude is characterized by a series of modulations. This arises from the fact that the nonlinear term in the amplitude equation may be either stabilizing or destabilizing, depending on the value of the streamwise coordinate. However, even in this case the amplitude of the disturbance increases, though not as rapidly as in the case for which the angle is less than pi/4. Quite generally then, the nonlinear interaction between two oblique modes in a supersonic mixing layer enhances the growth of the disturbance.

  11. C-terminal domains of a histone demethylase interact with a pair of transcription factors and mediate specific chromatin association

    PubMed Central

    Zhang, Shuaibin; Zhou, Bing; Kang, Yanyuan; Cui, Xia; Liu, Ao; Deleris, Angelique; Greenberg, Maxim V. C.; Cui, Xiekui; Qiu, Qi; Lu, Falong; Wohlschlegel, James A.; Jacobsen, Steven E.; Cao, Xiaofeng

    2015-01-01

    JmjC domain containing protein 14 (JMJ14) is an H3K4-specific histone demethylase that plays important roles in RNA-mediated gene silencing and flowering time regulation in Arabidopsis. However, how JMJ14 is recruited to its target genes remains unclear. Here, we show that the C-terminal FYRN and FYRC domains of JMJ14 are required for RNA silencing and flowering time regulation. Chromatin binding of JMJ14 is lost upon deletion of its FYRN and FYRC domains, and H3K4me3 is increased. FYRN and FYRC domains interact with a pair of NAC domain containing transcription factors, NAC050 and NAC052. Genome-wide ChIP analysis revealed that JMJ14 and NAC050/052 share a set of common target genes with CTTGNNNNNCAAG consensus sequences. Mutations in either NAC052 or NAC050 impair RNA-mediated gene silencing. Together, our findings demonstrate an important role of FYRN and FYRC domains in targeting JMJ14 through direct interaction with NAC050/052 proteins, which reveals a novel mechanism of histone demethylase recruitment. PMID:26617990

  12. Spatio-temporal correlations in Coulomb clusters

    NASA Astrophysics Data System (ADS)

    Ash, Biswarup; Chakrabarti, J.; Ghosal, Amit

    2016-05-01

    The dynamical responses of Coulomb-interacting particles in two-dimensional nanoclusters are analyzed at different temperatures characterizing their solid- and liquid-like behavior. Depending on the trap symmetry, spatial correlations undergo slow, stretched exponential relaxations at long times, arising from spatially correlated motion in string-like paths. Such results stem from the combined effects of confinement and long-range repulsion, making the systems inherently heterogeneous. While particles in a “solid” flow produce dynamic heterogeneities, motion in “liquid” yields an unusually long tail in the distribution of particle displacements. A phenomenological model captures much of the subtleties of our numerical simulations.

  13. Coulomb sum rule for {sup 4}He

    SciTech Connect

    J. Carlson; J. Jourdan; R. Schiavilla; I. Sick

    2002-10-01

    We determine the Coulomb sum for {sup 4}He using world data on {sup 4}He(e, e') and compare the results to calculations based on realistic interactions and including two-body components in the nuclear charge operator. We find good agreement between theory and experiment using free-nucleon form factors. The apparent reduction of the in-medium G{sub ep} implied by IA-interpretation of the L/T-ratios measured in {sup 4}He(e,e'p) and {sup 4}He([vec]e, e'p) is not confirmed.

  14. Investigation of Coulomb dipole polarization effects on reactions involving exotic nuclei

    NASA Astrophysics Data System (ADS)

    Fernández-García, J. P.; Alvarez, M. A. G.; Chamon, L. C.

    2015-07-01

    We have analyzed elastic scattering angular distributions and total reaction cross sections of the exotic nuclei 11,9Li on 208Pb, at energies below and above the Coulomb barrier. For this purpose, we have used an optical potential with no adjustable parameters, composed by the nuclear São Paulo potential, derived from the nonlocal nature of the interaction, and the Coulomb dipole polarization potential, derived from the semiclassical theory of Coulomb excitation. Within this formalism, we identified an unusual long-range absorption for the +208Pb 11Li system, which is dominated by the Coulomb interaction. We compare it to the absorption mechanisms observed for +208Pb6He which, unlike those of +208Pb11Li, take place at small interacting distances, where both Coulomb and nuclear interactions are important. The proposed approach shows to be a fundamental basis to study reactions involving exotic nuclei.

  15. Fast HPLC method using ion-pair and hydrophilic interaction liquid chromatography for determination of phenylephrine in pharmaceutical formulations.

    PubMed

    Dousa, Michal; Gibala, Petr

    2010-01-01

    A rapid procedure based on a direct extraction and HPLC determination with fluorescence detection of phenylephrine in pharmaceutical sachets that include a large excess of paracetamol (65 + 1, w/w), ascorbic acid (5 + 1, w/w), and other excipients (aspartame and sucrose) was developed and validated. The final optimized chromatographic method for ion-pair chromatography used an XTerra RP18 column, 3 microm particle size, 50 x 3.0 mm id. The mobile phase consisted of a mixture of acetonitrile and buffer (10 mM sodium octane-1-sulfonate, adjusted with H3PO4 to pH 2.2; 200 + 800, v/v), with a constant flow rate of 0.3 mL/min. The separation was carried out at 30 degrees C, and the injection volume was 3 microL. Fluorescence detection was performed at excitation and emission wavelengths of 275 and 310 nm, respectively. The mobile phase parameters, such as the organic solvent fraction (acetonitrile) in mobile phase as an organic modifier, the concentration of sodium octane-1-sulfonate as a counter-ion, temperature, and pH of mobile phase, were studied. As an alternative to ion-pair chromatography, hydrophilic interaction liquid chromatography (HILIC) was investigated using a Luna HILIC column, 3 microm, 100 x 4.6 mm id. The mobile phase consisted of acetonitrile and buffer (5 mM potassium dihydrogen phosphate, adjusted with H3PO4 to pH 2.5; 750 + 250, v/v) at a flow rate of 0.8 mL/min. The separation was carried out at 25 degrees C, and the injection volume was 5 microL. The proposed method has an advantage of a very simple sample pretreatment, and is much faster than the currently utilized HPLC methods using gradient elution and UV detection. Commercial samples of sachets were successfully analyzed by the proposed HPLC method. PMID:21140654

  16. Density Matrix Renormalization Group Study of a One Dimensional Three-Orbital Hubbard Model: The role of pair hopping and spin-flip interactions

    NASA Astrophysics Data System (ADS)

    Kaushal, Nitin; Liu, Guangkun; Bishop, Chris; Liang, Shuhua; Li, Shaozhi; Johnston, Steve; Dagotto, Elbio

    Using the Density Matrix Renormalization Group technique, we extensively study a three-orbital Hubbard model in one dimension without pair hopping and spin-flip Hund interactions. The phase diagram varying the electronic density n and Hubbard U is constructed and compared against previous results obtained using the full interaction Hamiltonian. Our results suggest that spin-flip and pair hopping terms are not crucially important to address the orbital-selective Mott phase. This analysis paves the way to study multiorbital Hubbard models using techniques such as the Constrained-Path Quantum Monte Carlo (CPQMC) and Determinant Quantum Monte Carlo (DQMC) methods since they perform better, reducing for instance the severity of the ``sign problem'', in the absence of pair hopping and spin flip terms in the interaction.

  17. Isovector spin-singlet (T = 1, S = 0) and isoscalar spin-triplet (T = 0, S = 1) pairing interactions and spin-isospin response

    NASA Astrophysics Data System (ADS)

    Sagawa, H.; Bai, C. L.; Colò, G.

    2016-08-01

    We review several experimental and theoretical advances that emphasize common aspects of the study of spin-singlet, T = 1, and spin-triplet, T = 0, pairing correlations in nuclei. We first discuss various empirical evidence of the special role played by the T = 1 pairing interaction. In particular, we show the peculiar features of the nuclear pairing interaction in the low-density regime, and possible outcomes such as the BCS–BEC crossover in nuclear matter and, in an analogous way, in loosely bound nuclei. We then move to the competition between T = 1 and T = 0 pairing correlations. The effect of such competition on the low-lying spectra is studied in N = Z odd-odd nuclei by using a three-body model; in this case, it is shown that the inversion of the {J}π ={0}+ and {J}π ={1}+ states near the ground state, and the strong magnetic dipole transitions between them, can be considered as a clear manifestation of strong T = 0 pairing correlations in these nuclei. The effect of T = 0 pairing correlations is also quite evident if one studies charge-changing transitions. The Gamow–Teller (GT) states in N=Z+2 nuclei are studied here by using self-consistent Hartree–Fock–Bogoliubov (HFB) plus quasiparticle random-phase approximation calculations in which the T = 0 pairing interaction is taken into account. Strong GT states are found, near the ground state of daughter nuclei; these are compared with available experimental data from charge-exchange reactions, and such comparison can pinpoint the value of the strength of the T = 0 interaction. Pair transfer reactions are eventually discussed. While two-neutron transfer has long been proposed as a tool to measure the T = 1 superfluidity in the nuclear ground states, the study of deuteron transfer is still in its infancy, despite its potential interest for revealing effects coming from both T = 1 and T = 0 interactions. We also point out that the reaction mechanism may mask the strong pair transfer amplitudes predicted

  18. Derivation of Pitzer Interaction Parameters for an Aqueous Species Pair of Sodium and Iron(II)-Citrate Complex

    NASA Astrophysics Data System (ADS)

    Jang, J. H.; Nemer, M.

    2015-12-01

    The U.S. DOE Waste Isolation Pilot Plant (WIPP) is a deep underground repository for the permanent disposal of transuranic (TRU) radioactive waste. The WIPP is located in the Permian Delaware Basin near Carlsbad, New Mexico, U.S.A. The TRU waste includes, but is not limited to, iron-based alloys and the complexing agent, citric acid. Iron is also present from the steel used in the waste containers. The objective of this analysis is to derive the Pitzer activity coefficients for the pair of Na+ and FeCit- complex to expand current WIPP thermodynamic database. An aqueous model for the dissolution of Fe(OH)2(s) in a Na3Cit solution was fitted to the experimentally measured solubility data. The aqueous model consists of several chemical reactions and related Pitzer interaction parameters. Specifically, Pitzer interaction parameters for the Na+ and FeCit- pair (β(0), β(1), and Cφ) plus the stability constant for species of FeCit- were fitted to the experimental data. Anoxic gloveboxes were used to keep the oxygen level low (<1 ppm) throughout the experiments due to redox sensitivity. EQ3NR, a computer program for geochemical aqueous speciation-solubility calculations, packaged in EQ3/6 v.8.0a, calculates the aqueous speciation and saturation index using an aqueous model addressed in EQ3/6's database. The saturation index indicates how far the system is from equilibrium with respect to the solid of interest. Thus, the smaller the sum of squared saturation indices that the aqueous model calculates for the given number of experiments, the more closely the model attributes equilibrium to each individual experiment with respect to the solid of interest. The calculation of aqueous speciation and saturation indices was repeated by adjusting stability constant of FeCit-, β(0), β(1), and Cφ in the database until the values are found that make the sum of squared saturation indices the smallest for the given number of experiments. Results will be presented at the time of

  19. Probing the Role of Interlayer Coupling and Coulomb Interactions on Electronic Structure in Few-Layer MoSe2Nanostructures

    NASA Astrophysics Data System (ADS)

    Bradley, Aaron J.; M. Ugeda, Miguel; da Jornada, Felipe H.; Qiu, Diana Y.; Ruan, Wei; Zhang, Yi; Wickenburg, Sebastian; Riss, Alexander; Lu, Jiong; Mo, Sung-Kwan; Hussain, Zahid; Shen, Zhi-Xun; Louie, Steven G.; Crommie, Michael F.

    2015-04-01

    Despite the weak nature of interlayer forces in transition metal dichalcogenide (TMD) materials, their properties are highly dependent on the number of layers in the few-layer two-dimensional (2D) limit. Here, we present a combined scanning tunneling microscopy/spectroscopy and GW theoretical study of the electronic structure of high quality single- and few-layer MoSe2 grown on bilayer graphene. We find that the electronic (quasiparticle) bandgap, a fundamental parameter for transport and optical phenomena, decreases by nearly one electronvolt when going from one layer to three due to interlayer coupling and screening effects. Our results paint a clear picture of the evolution of the electronic wave function hybridization in the valleys of both the valence and conduction bands as the number of layers is changed. This demonstrates the importance of layer number and electron-electron interactions on van der Waals heterostructures, and helps to clarify how their electronic properties might be tuned in future 2D nanodevices.

  20. Probing the Role of Interlayer Coupling and Coulomb Interactions on Electronic Structure in Few-Layer MoSe2 Nanostructures

    PubMed Central

    2015-01-01

    Despite the weak nature of interlayer forces in transition metal dichalcogenide (TMD) materials, their properties are highly dependent on the number of layers in the few-layer two-dimensional (2D) limit. Here, we present a combined scanning tunneling microscopy/spectroscopy and GW theoretical study of the electronic structure of high quality single- and few-layer MoSe2 grown on bilayer graphene. We find that the electronic (quasiparticle) bandgap, a fundamental parameter for transport and optical phenomena, decreases by nearly one electronvolt when going from one layer to three due to interlayer coupling and screening effects. Our results paint a clear picture of the evolution of the electronic wave function hybridization in the valleys of both the valence and conduction bands as the number of layers is changed. This demonstrates the importance of layer number and electron–electron interactions on van der Waals heterostructures and helps to clarify how their electronic properties might be tuned in future 2D nanodevices. PMID:25775022

  1. Probing the Role of Interlayer Coupling and Coulomb Interactions on Electronic Structure in Few-Layer MoSe 2 Nanostructures

    DOE PAGESBeta

    Bradley, Aaron J.; M. Ugeda, Miguel; da Jornada, Felipe H.; Qiu, Diana Y.; Ruan, Wei; Zhang, Yi; Wickenburg, Sebastian; Riss, Alexander; Lu, Jiong; Mo, Sung-Kwan; et al

    2015-03-16

    Despite the weak nature of interlayer forces in transition metal dichalcogenide (TMD) materials, their properties are highly dependent on the number of layers in the few-layer two-dimensional (2D) limit. Here, we present a combined scanning tunneling microscopy/spectroscopy and GW theoretical study of the electronic structure of high quality single- and few-layer MoSe2 grown on bilayer graphene. We find that the electronic (quasiparticle) bandgap, a fundamental parameter for transport and optical phenomena, decreases by nearly one electronvolt when going from one layer to three due to interlayer coupling and screening effects. Our results paint a clear picture of the evolution ofmore » the electronic wave function hybridization in the valleys of both the valence and conduction bands as the number of layers is changed. This demonstrates the importance of layer number and electron-electron interactions on van der Waals heterostructures and helps to clarify how their electronic properties might be tuned in future 2D nanodevices.« less

  2. Probing the Role of Interlayer Coupling and Coulomb Interactions on Electronic Structure in Few-Layer MoSe 2 Nanostructures

    SciTech Connect

    Bradley, Aaron J.; M. Ugeda, Miguel; da Jornada, Felipe H.; Qiu, Diana Y.; Ruan, Wei; Zhang, Yi; Wickenburg, Sebastian; Riss, Alexander; Lu, Jiong; Mo, Sung-Kwan; Hussain, Zahid; Shen, Zhi-Xun; Louie, Steven G.; Crommie, Michael F.

    2015-03-16

    Despite the weak nature of interlayer forces in transition metal dichalcogenide (TMD) materials, their properties are highly dependent on the number of layers in the few-layer two-dimensional (2D) limit. Here, we present a combined scanning tunneling microscopy/spectroscopy and GW theoretical study of the electronic structure of high quality single- and few-layer MoSe2 grown on bilayer graphene. We find that the electronic (quasiparticle) bandgap, a fundamental parameter for transport and optical phenomena, decreases by nearly one electronvolt when going from one layer to three due to interlayer coupling and screening effects. Our results paint a clear picture of the evolution of the electronic wave function hybridization in the valleys of both the valence and conduction bands as the number of layers is changed. This demonstrates the importance of layer number and electron-electron interactions on van der Waals heterostructures and helps to clarify how their electronic properties might be tuned in future 2D nanodevices.

  3. A semi-analytical calculation of the electrostatic pair interaction between nonuniformly charged colloidal spheres at an air-water interface

    NASA Astrophysics Data System (ADS)

    Lian, Zengju

    2016-07-01

    We study the electrostatic pair interaction between two nonuniformly like-charged colloidal spheres trapped in an air-water interface. Under the linear Poisson-Boltzmann approximation, a general form of the electrostatic potential for the system is shown in terms of multipole expansions. After combining the translation-rotation transform of the coordinates with the numerical multipoint collection, we give a semi-analytical result of the electrostatic pair interaction between the colloids. The pair interaction changes quantitatively or even qualitatively with different distributions of the surface charges on the particles. Because of the anisotropic distribution of the surface charge and the asymmetric dielectric medium, the dipole moment of the ion cloud associating with the particle orients diagonally to the air-water interface with an angle α. When the angle is large, the colloids interact repulsively, while they attract each other when the angle is small. The attractive colloids may be "Janus-like" charged and be arranged with some specific configurations. Whatever the repulsions or the attractions, they all decay asymptotically ∝1/d3 (d is the center-center distance of the particles) which is consistent with our general acknowledge. The calculation results also provide an insight of the effect of the ion concentration, particle size, and the total charge of the particle on the pair interaction between the particles.

  4. A semi-analytical calculation of the electrostatic pair interaction between nonuniformly charged colloidal spheres at an air-water interface.

    PubMed

    Lian, Zengju

    2016-07-01

    We study the electrostatic pair interaction between two nonuniformly like-charged colloidal spheres trapped in an air-water interface. Under the linear Poisson-Boltzmann approximation, a general form of the electrostatic potential for the system is shown in terms of multipole expansions. After combining the translation-rotation transform of the coordinates with the numerical multipoint collection, we give a semi-analytical result of the electrostatic pair interaction between the colloids. The pair interaction changes quantitatively or even qualitatively with different distributions of the surface charges on the particles. Because of the anisotropic distribution of the surface charge and the asymmetric dielectric medium, the dipole moment of the ion cloud associating with the particle orients diagonally to the air-water interface with an angle α. When the angle is large, the colloids interact repulsively, while they attract each other when the angle is small. The attractive colloids may be "Janus-like" charged and be arranged with some specific configurations. Whatever the repulsions or the attractions, they all decay asymptotically ∝1/d(3) (d is the center-center distance of the particles) which is consistent with our general acknowledge. The calculation results also provide an insight of the effect of the ion concentration, particle size, and the total charge of the particle on the pair interaction between the particles. PMID:27394119

  5. Pair approximation for polarization interaction and adiabatic nuclear and electronic sampling method for fluids with dipole polarizability

    NASA Astrophysics Data System (ADS)

    Predota, Milan; Cummings, Peter T.; Chialvo, Ariel A.

    The adiabatic nuclear and electronic sampling method (ANES), originally formulated as an efficient Monte Carlo algorithm for systems with fluctuating charges, is applied to the simulation of a polarizable water model with induced dipole moments. Structural, thermodynamic and dipolar properties obtained by ANES and a newer algorithm, the pair approximation for polarization interaction (PAPI), are compared with full iteration. With the best parameters, the inaccuracy of both approximate methods was found to be comparable with the uncertainty of the full iteration. The PAPI method with iteration radius equal to the second minimum of the oxygen-oxygen correlation function is, depending on the convergence tolerance, 10-15 times faster than the full iteration for 256 molecules, and yields very accurate structure and thermodynamics with deviation about 0.3%. When the iteration radius is increased to the cutoff distance, exact results are recovered at the cost of decreased efficiency. The ANES method with small nuclear displacements proved to inefficiently sample the configurational space. Simulations at low electronic temperatures with large nuclear displacements are inaccurate for up to 100 electronic moves, and increasing this number would make the simulations as slow as the full iteration. The most accurate and efficient adiabatic ANES simulations are those with infinite electronic temperature, large nuclear displacements and 1-10 electronic moves. The extra freedom of induced dipoles in the ANES method at high electronic temperatures modifies the observed dipolar properties; however, the question of whether the dielectric constant is also modified needs further consideration.

  6. Luminescent blooming of dendronic carbon nanotubes through ion-pairing interactions with an Eu(III) complex.

    PubMed

    Maggini, Laura; Toma, Francesca Maria; Feruglio, Luigi; Malicka, Joanna M; Da Ros, Tatiana; Armaroli, Nicola; Prato, Maurizio; Bonifazi, Davide

    2012-05-01

    A multiwalled carbon nanotube (MWCNT) scaffold was covalently functionalized with a second-generation polyamidoamine (PAMAM) dendron, presenting four terminal amino groups per grafted aryl moiety. These reactive functions were alkylated to obtain a positively charged polycationic dendron/carbon nanotube system (d-MWCNTs⋅Cl), which eventually underwent anion exchange reaction with a negatively charged and highly luminescent Eu(III) complex ([EuL(4)]⋅NEt(4), in which L = (2-naphtoyltrifluoroacetonate)). This process afforded the target material d-MWCNTs⋅[EuL(4)], in which MWCNTs are combined with red-emitting Eu(III) centers through electrostatic interactions with the dendronic branches. Characterization of the novel MWCNT materials was accomplished by means of TGA and TEM, whereas d-MWCNTs⋅Cl and d-MWCNTs⋅ [EuL(4)] further underwent XPS, SEM and Raman analyses. These studies demonstrate the integrity of the luminescent [EuL(4)](-) center in the luminescent hybrid, the massive load of the cationic binding sites, and the virtually complete anion-exchange into the final hybrid material. The occurrence of the ion-pairing interaction with MWCNTs was unambiguously demonstrated through DOSY NMR diffusion studies. Photophysical investigations show that MWCNTs⋅[EuL(4)] is a highly soluble and brightly luminescent red hybrid material in which MWCNTs act as photochemically inert scaffolds with negligible UV/Vis absorption, compared with the grafted Eu complex, and with no quenching activity. The high dispersibility of MWCNTs⋅[EuL(4)] in a polymer matrix makes it a promising luminophore for applications in material science. PMID:22488679

  7. Renormalization in Coulomb gauge QCD

    NASA Astrophysics Data System (ADS)

    Andraši, A.; Taylor, John C.

    2011-04-01

    In the Coulomb gauge of QCD, the Hamiltonian contains a non-linear Christ-Lee term, which may alternatively be derived from a careful treatment of ambiguous Feynman integrals at 2-loop order. We investigate how and if UV divergences from higher order graphs can be consistently absorbed by renormalization of the Christ-Lee term. We find that they cannot.

  8. Nucleon-nucleon correlations in heavy ion transfer reactions: Recent investigations at energies far below the Coulomb barrier

    SciTech Connect

    Corradi, Lorenzo

    2015-10-15

    Excitation functions of one- and two-neutron transfer channels have been measured for the {sup 96}Zr+{sup 40}Ca and {sup 116}Sn+{sup 60}Ni systems at bombarding energies ranging from the Coulomb barrier to ∼25% below. Target-like recoils have been identified in A, Z and velocity with the large solid angle magnetic spectrometer PRISMA. The experimental transfer probabilities have been compared, in absolute values and in slope, with semiclassical microscopic calculations which incorporate nucleon-nucleon pairing correlations. For the first time in a heavy ion collision, one was able to provide a consistent description of one and two neutron transfer reactions by incorporating, in the reaction mechanism, all known structure information of entrance and exit channels nuclei. In particular, there is no need to introduce any enhancement factor for the description of two neutron transfer, of course very important are the correlations induced by the pairing interaction.

  9. Young Learners' Interactional Development in Task-Based Paired-Assessment in Their First and Foreign Languages: A Case of English Learners in China

    ERIC Educational Resources Information Center

    Butler, Yuko Goto; Zeng, Wei

    2015-01-01

    In response to the growing interest in evaluating young learners' foreign language (FL) performance, this study aims to deepen our understanding of young learners' developmental differences in interaction during task-based paired-language assessments. To examine age effects separately from the effect of general language proficiency, we analysed…

  10. Implementation of Pair Work and Group Work for Creation of Interaction Opportunities for Learners in Large Classes: The Viability of the Two Strategies

    ERIC Educational Resources Information Center

    Otienoh, Ruth O.

    2015-01-01

    This paper is based on an action research carried out in two Kenyan Primary schools in Nairobi. The purpose was to implement group work and pair work to improve teaching and learning in large classes by creating interaction opportunities for learners. This was a mixed method study of dominant/less dominant design where interviews and structured…

  11. Coulomb problem for vector particles : Energy spectrum.

    SciTech Connect

    Kuchiev, M. Yu.; Flambaum, V. V.; Physics; Univ. of South Wales

    2006-05-31

    The Coulomb problem for vector bosons W{+-} incorporates a well-known difficulty; the charge of the boson localized in a close vicinity of the attractive Coulomb center proves to be infinite. The paradox is shown to be resolved by the QED vacuum polarization, which brings in a strong effective repulsion that eradicates the infinite charge of the boson on the Coulomb center. This property allows one to define the Coulomb problem for vector bosons properly.

  12. Coulomb gauge approach for charmonium meson and hybrid radiative transitions

    NASA Astrophysics Data System (ADS)

    Gou, Peng; Yépez-Martínez, Tochtli; Szczepaniak, Adam P.

    2015-01-01

    We consider the lowest order interaction of the Foldy-Wouthuysen QED and QCD Hamiltonian in the Coulomb gauge approach, to describe radiative transitions between conventional and hybrids charmonium mesons. The results are compared to potential quark models and lattices calculations.

  13. Coulomb gauge approach for charmonium meson and hybrid radiative transitions

    DOE PAGESBeta

    Gou, Peng; Yepez-Martínez, Tochtli; Szczepaniak, Adam P.

    2015-01-22

    We consider the lowest order interaction of the Foldy-Wouthuysen QED and QCD Hamiltonian in the Coulomb gauge approach, to describe radiative transitions between conventional and hybrids charmonium mesons. The results are compared to potential quark models and lattices calculations.

  14. Hydrodynamic Coulomb drag of strongly correlated electron liquids

    NASA Astrophysics Data System (ADS)

    Apostolov, S. S.; Levchenko, A.; Andreev, A. V.

    2014-03-01

    We develop a theory of Coulomb drag in ultraclean double layers with strongly correlated carriers. In the regime where the equilibration length of the electron liquid is shorter than the interlayer spacing the main contribution to the Coulomb drag arises from hydrodynamic density fluctuations. The latter consist of plasmons driven by fluctuating longitudinal stresses, and diffusive modes caused by temperature fluctuations and thermal expansion of the electron liquid. We express the drag resistivity in terms of the kinetic coefficients of the electron fluid. Our results are nonperturbative in interaction strength and do not assume Fermi-liquid behavior of the electron liquid.

  15. Strong Coulomb effects in hole-doped Heisenberg chains

    NASA Astrophysics Data System (ADS)

    Schnack, J.

    2005-06-01

    Substances such as the “telephone number compound” Sr14Cu24O41 are intrinsically hole-doped. The involved interplay of spin and charge dynamics is a challenge for theory. In this article we propose to describe hole-doped Heisenberg spin rings by means of complete numerical diagonalization of a Heisenberg Hamiltonian that depends parametrically on hole positions and includes the screened Coulomb interaction among the holes. It is demonstrated that key observables like magnetic susceptibility, specific heat, and inelastic neutron scattering cross section depend sensitively on the dielectric constant of the screened Coulomb potential.

  16. Microwave ac Conductivity Spectrum of a Coulomb Glass

    SciTech Connect

    Lee, Mark; Stutzmann, M. L.

    2001-07-30

    We report the first observation of the transition between interacting and noninteracting behavior in the ac conductivity spectrum {sigma}({omega}) of a doped semiconductor in its Coulomb glass state near T=0 K . The transition manifests itself as a crossover from approximately linear frequency dependence below {approx}10 GHz , to quadratic dependence above {approx}15 GHz . The sharpness of the transition and the magnitude of the crossover frequency strongly suggest that the transition is driven by photon-induced excitations across the Coulomb gap, in contrast to existing theoretical descriptions.

  17. Pairing forces in nuclei

    SciTech Connect

    Chasman, R.R.

    1996-12-31

    In this contribution, the author mentions some features of pairing forces that are unique to nuclei and cover some areas of major interest in nuclear structure research, that involve pairing. At the level of most nuclear structure studies, nuclei are treated as consisting of two kinds of fermions (protons and neutrons) in a valence space with rather few levels. These features give rise to unique aspects of pairing forces in nuclei: (1) n-p pairing in T = 0 as well as the usual T = 1 pairing that is characteristic of like fermions; (2) a need to correct pairing calculations for the (1/N) effects that can typically be neglected in superconducting solids. An issue of current concern is the nature of the pairing interaction: several recent studies suggest a need for a density dependent form of the pairing interaction. There is a good deal of feedback between the questions of accurate calculations of pairing interactions and the form and magnitude of the pairing interaction. Finally, the authors discuss some many-body wave functions that are a generalization of the BCS wave function form, and apply them to a calculation of energy level spacings in superdeformed rotational bands.

  18. Nonstationary multistate Coulomb and multistate exponential models for nonadiabatic transitions

    SciTech Connect

    Ostrovsky, V. N.

    2003-07-01

    The nonstationary Schroedinger equation is considered in a finite basis of states. The model Hamiltonian matrix corresponds to a single diabatic potential curve with a Coulombic {approx}1/t time dependence. An arbitrary number of other diabatic potential curves are flat, i.e., time independent and have arbitrary energies. Related states are coupled by constant interactions with the Coulomb state. The resulting nonstationary Schroedinger equation is solved by the method of contour integral. Probabilities of transitions to any other state are obtained as t{yields}{infinity} in a simple analytical form for the case when the Coulomb state is populated initially (at instant of time t{yields}+0). The formulas apply both to the cases when a horizontal diabatic potential curve is crossed by the Coulomb one and to a noncrossing situation. In the limit of weak coupling, the transition probabilities are interpreted in terms of a sequence of pairwise Landau-Zener-type transitions. Mapping of the Coulomb model onto an exactly solvable exponential multistate model is established. For the special two-state case, the well-known Nikitin model is recovered.

  19. Coulomb dissociation of N,2120

    NASA Astrophysics Data System (ADS)

    Röder, Marko; Adachi, Tatsuya; Aksyutina, Yulia; Alcantara, Juan; Altstadt, Sebastian; Alvarez-Pol, Hector; Ashwood, Nicholas; Atar, Leyla; Aumann, Thomas; Avdeichikov, Vladimir; Barr, M.; Beceiro, Saul; Bemmerer, Daniel; Benlliure, Jose; Bertulani, Carlos; Boretzky, Konstanze; Borge, Maria J. G.; Burgunder, G.; Caamaño, Manuel; Caesar, Christoph; Casarejos, Enrique; Catford, Wilton; Cederkäll, Joakim; Chakraborty, S.; Chartier, Marielle; Chulkov, Leonid; Cortina-Gil, Dolores; Crespo, Raquel; Datta Pramanik, Ushasi; Diaz-Fernandez, Paloma; Dillmann, Iris; Elekes, Zoltan; Enders, Joachim; Ershova, Olga; Estrade, A.; Farinon, F.; Fraile, Luis M.; Freer, Martin; Freudenberger, M.; Fynbo, Hans; Galaviz, Daniel; Geissel, Hans; Gernhäuser, Roman; Göbel, Kathrin; Golubev, Pavel; Gonzalez Diaz, D.; Hagdahl, Julius; Heftrich, Tanja; Heil, Michael; Heine, Marcel; Heinz, Andreas; Henriques, Ana; Holl, Matthias; Ickert, G.; Ignatov, Alexander; Jakobsson, Bo; Johansson, Hâkan; Jonson, Björn; Kalantar-Nayestanaki, Nasser; Kanungo, Rituparna; Kelic-Heil, Aleksandra; Knöbel, Ronja; Kröll, Thorsten; Krücken, Reiner; Kurcewicz, J.; Kurz, Nikolaus; Labiche, Marc; Langer, Christoph; Le Bleis, Tudi; Lemmon, Roy; Lepyoshkina, Olga; Lindberg, Simon; Machado, Jorge; Marganiec, Justyna; Mostazo Caro, Magdalena; Movsesyan, Alina; Najafi, Mohammad Ali; Nilsson, Thomas; Nociforo, Chiara; Panin, Valerii; Paschalis, Stefanos; Perea, Angel; Petri, Marina; Pietri, S.; Plag, Ralf; Prochazka, A.; Rahaman, Md. Anisur; Rastrepina, Ganna; Reifarth, Rene; Ribeiro, Guillermo; Ricciardi, M. Valentina; Rigollet, Catherine; Riisager, Karsten; Rossi, Dominic; Sanchez del Rio Saez, Jose; Savran, Deniz; Scheit, Heiko; Simon, Haik; Sorlin, Olivier; Stoica, V.; Streicher, Branislav; Taylor, Jon; Tengblad, Olof; Terashima, Satoru; Thies, Ronja; Togano, Yasuhiro; Uberseder, Ethan; Van de Walle, J.; Velho, Paulo; Volkov, Vasily; Wagner, Andreas; Wamers, Felix; Weick, Helmut; Weigand, Mario; Wheldon, Carl; Wilson, G.; Wimmer, Christine; Winfield, J. S.; Woods, Philip; Yakorev, Dmitry; Zhukov, Mikhail; Zilges, Andreas; Zuber, Kai; R3B Collaboration

    2016-06-01

    Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N,2120 are reported. Relativistic N,2120 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the 19N (n ,γ )20N and 20N (n ,γ ) 21N excitation functions and thermonuclear reaction rates have been determined. The 19 (n ,γ )20N rate is up to a factor of 5 higher at T <1 GK with respect to previous theoretical calculations, leading to a 10% decrease in the predicted fluorine abundance.

  20. Coulomb Energies in ^18Ne

    NASA Astrophysics Data System (ADS)

    Sherr, R.; Fortune, H. T.

    1998-10-01

    Coulomb energies of the ^18Ne mirrors of the levels of ^18O vary considerably from state to state, an effect understood as arising from their different configurations. All the low-lying positive-parity states in these nuclei can be described in terms of two nucleons coupled to an ^16O core plus a collective component (most probably four-particle two-hole (4p-2h)). We have computed Coulomb energies using one such formulation(Lawson, Serduke and Fortune, Phys. Rev. C 14), 1245 (1976).. Two-particle energies arise from coupling a neutron to single-particle states of ^17O, and a proton to the mirror states of ^17F. For the 4p-2h component, we use the ^14O-^14C mass difference, plus a ph Coulomb term(Sherr and Bertsch, Phys. Rev. C 12), 1671 (1975).. Agreement is perhaps slightly better than another such attempt(Nero, Adelberger and Dietrich, Phys. Rev. C 24), 1864 (1981). using wave functions from Benson and Flowers.

  1. Conductance through a proximitized nanowire in the Coulomb blockade regime

    NASA Astrophysics Data System (ADS)

    van Heck, Bernard; Lutchyn, Roman; Glazman, Leonid

    Motivated by recent experiments of the Copenhagen group on InAs nanowires with epitaxial Al, we investigate the two-terminal conductance of a strongly proximitized nanowire in the Coulomb blockade regime. We identify the leading electron transport processes at zero applied magnetic field B as well as at finite fields, suppressing the induced gap Δind (B) . In the conventional superconducting phase, the conductance is controlled by the sequential Cooper pair tunneling if Δind (B) exceeds the charging energy Ec, and by the elastic single-electron processes if Δind (B) Coulomb blockade peaks, which explains the experimental finding in Ref.. We also develop a quantitative theory for the differential conductance and examine its evolution across the topological transition point.

  2. Energy relaxation and separation of a hot electron-hole pair in organic aggregates from a time-dependent wavepacket diffusion method

    SciTech Connect

    Han, Lu; Liang, WanZhen; Zhao, Yi; Zhong, Xinxin

    2014-06-07

    The time-dependent wavepacket diffusive method [X. Zhong and Y. Zhao, J. Chem. Phys. 138, 014111 (2013)] is extended to investigate the energy relaxation and separation of a hot electron-hole pair in organic aggregates with incorporation of Coulomb interaction and electron-phonon coupling. The pair initial condition generated by laser pulse is represented by a Gaussian wavepacket with a central momentum. The results reveal that the hot electron energy relaxation is very well described by two rate processes with the fast rate much larger than the slow one, consistent with experimental observations, and an efficient electron-hole separation is accomplished accompanying the fast energy relaxation. Furthermore, although the extra energy indeed helps the separation by overcoming the Coulomb interaction, the width of initial wavepacket is much sensitive to the separation efficiency and the narrower wavepacket generates the more separated charges. This behavior may be useful to understand the experimental controversy of the hot carrier effect on charge separation.

  3. Lone pair⋯π interactions involving carbonyl π-systems: Experimental and theoretical study of the complexes of COF2 and COFCl with dimethyl ether

    NASA Astrophysics Data System (ADS)

    Geboes, Yannick; De Proft, Frank; Herrebout, Wouter A.

    2016-09-01

    In this theoretical and experimental study, the ability of carbonyl fluoride (COF2) and carbonyl chloride fluoride (COFCl) to form noncovalent interactions with the Lewis base dimethyl ether (DME) is assessed. From ab initio calculations, two stable complexes are found for COF2·DME, both formed through a lone pair⋯π interaction. FTIR measurements on liquefied noble gas solutions, supported by ab initio calculations, statistical thermodynamical calculations and Monte Carle Free Energy Perturbation calculations, show that a 1:1 lone pair⋯π bonded complex is found in solution, with an experimental complexation enthalpy of -14.5(3) kJ mol-1. For COFCl·DME three lone pair⋯π complexes, as well as a Cl⋯O halogen bonded complex, are found from ab initio calculations. Experimentally, clear complex bands for 1:1 lone pair⋯π complexes are observed, with an experimental complexation enthalpy of -11.4(2) kJ mol-1. Furthermore, indications of the presence of a small amount of the halogen bonded complex are also observed.

  4. New Theoretical Insight into the Interactions and Properties of Formic Acid: Development of a Quantum-Based Pair Potential for Formic Acid.

    SciTech Connect

    Roszak, S; Gee, R; Balasubramanian, K; Fried, L

    2005-08-08

    We performed ab initio quantum chemical studies for the development of intra and intermolecular interaction potentials for formic acid for use in molecular dynamics simulations of formic acid molecular crystal. The formic acid structures considered in the ab initio studies include both the cis and trans monomers which are the conformers that have been postulated as part of chains constituting liquid and crystal phases under extreme conditions. Although the cis to trans transformation is not energetically favored, the trans isomer was found as a component of stable gas-phase species. Our decomposition scheme for the interaction energy indicates that the hydrogen bonded complexes are dominated by the Hartree-Fock forces while parallel clusters are stabilized by the electron correlation energy. The calculated three-body and higher interactions are found to be negligible, thus rationalizing the development of an atom-atom pair potential for formic acid based on high-level ab initio calculations of small formic acid clusters. Here we present an atom-atom pair potential that includes both intra- and inter-molecular degrees of freedom for formic acid. The newly developed pair potential is used to examine formic acid in the condensed phase via molecular dynamics simulations. The isothermal compression under hydrostatic pressure obtained from molecular dynamics simulations is in good agreement with experiment. Further, the calculated equilibrium melting temperature is found to be in good agreement with experiment.

  5. New theoretical insight into the interactions and properties of formic acid: development of a quantum-based pair potential for formic acid.

    PubMed

    Roszak, Szczepan; Gee, Richard H; Balasubramanian, Krishnan; Fried, Laurence E

    2005-10-01

    We performed ab initio quantum-chemical studies for the development of intra- and intermolecular interaction potentials for formic acid for use in molecular-dynamics simulations of formic acid molecular crystal. The formic acid structures considered in the ab initio studies include both the cis and trans monomers which are the conformers that have been postulated as part of chains constituting liquid and crystal phases under extreme conditions. Although the cis to trans transformation is not energetically favored, the trans isomer was found as a component of stable gas-phase species. Our decomposition scheme for the interaction energy indicates that the hydrogen-bonded complexes are dominated by the Hartree-Fock forces while parallel clusters are stabilized by the electron correlation energy. The calculated three-body and higher interactions are found to be negligible, thus rationalizing the development of an atom-atom pair potential for formic acid based on high-level ab initio calculations of small formic acid clusters. Here we present an atom-atom pair potential that includes both intra- and inter molecular degrees of freedom for formic acid. The newly developed pair potential is used to examine formic acid in the condensed phase via molecular-dynamics simulations. The isothermal compression under hydrostatic pressure obtained from molecular-dynamics simulations is in good agreement with experiment. Further, the calculated equilibrium melting temperature is found to be in good agreement with experiment. PMID:16238411

  6. Early annihilation and diffuse backgrounds in models of weakly interacting massive particles in which the cross section for pair annihilation is enhanced by 1/upsilon.

    PubMed

    Kamionkowski, Marc; Profumo, Stefano

    2008-12-31

    Recent studies have considered modifications to the standard weakly interacting massive particle scenario in which the pair annihilation cross section (times relative velocity v) is enhanced by a factor 1/upsilon to approximately 10(-3) in the Galaxy, enough to explain several puzzling Galactic radiation signals. We show that in these scenarios a burst of weakly interacting massive particle annihilation occurs in the first collapsed dark-matter halos. We show that severe constraints to the annihilation cross section derive from measurements of the diffuse extragalactic radiation and from ionization and heating of the intergalactic medium. PMID:19437633

  7. Coulomb Collision Algorithms for Particle Codes

    NASA Astrophysics Data System (ADS)

    Cohen, Bruce

    2006-04-01

    This paper surveys some of the particle code algorithms used to model Coulomb collisions in fully ionized plasmas, e.g., pair-wise operators such as the Takizuka-Abe^1 scheme and extensions^2, Langevin equation collision operators^3,4, and partially linearized gyrokinetic collisions operators for strongly magnetized plasmas.^5,6,7 Some recent experience is reported.^8 Issues such as physics completeness, accuracy, and comparative algorithm performance are highlighted. 1. T. Takizuka and H. Abe, J. Comput. Phys. 25, 205 (1977). 2. K. Nanbu, Phys. Rev. E 55, 4642 (1997). 3. M.E. Jones, et al., J. Comp. Phys. 123, 169 (1996). 4. W.M. Manheimer, M. Lampe, and G. Joyce, et al., J. Comp. Phys. 138, 565 (1997). 5. X.Q. Xu and M.N. Rosenbluth, Phys. Fluids B 3, 627 (1991). 6. A.M. Dimits and B.I. Cohen, Phys. Rev. E 49, 709 (1994). 7. Z. Lin, W. M. Tang, and W. W. Lee, Phys.Plasmas 2, 2975 (August 1995). 8. B.I. Cohen, et al., ``Effects of ion-ion collisions and inhomogeneity in two-dimensional kinetic ion simulations of stimulated Brillouin backscattering,'' accepted for publication in Phys. Plasmas (2006).

  8. Bose-Einstein Condensation of Nonideal Cooper Pairs in the Hartree-Fock-Popov Theory

    NASA Astrophysics Data System (ADS)

    Cheng, Ze

    2016-08-01

    The Hartree-Fock-Popov theory of interacting Bose particles is generalized to the Cooper-pair system with a screened Coulomb repulsive interaction in high-temperature superconductors. At zero temperature, it is found that the condensate density n_c(0) of Cooper pairs is of the order n_c(0)˜eq 10^{18} cm^{-3}, consistently with the fact that a small fraction of the total p holes participate in pairing. We find that the phonon velocity c(0) at zero temperature is of the order c(0)˜eq 10 km s^{-1}. The computation shows that the transition temperature T_c is a dome-shaped function of the p hole concentration δ , which is consistent with experiments. At finite temperature, we find that the condensate fraction n_c(T)/n decreases continuously from n_c(0)/n to zero as the temperature increases from zero to the transition temperature T_c. For higher temperatures, we find that the repulsive interaction between Cooper pairs drives more Cooper pairs into the condensate. The computation reveals that the phonon velocity c( T) decreases continuously from c(0) to zero as the temperature increases from zero to the transition temperature T_c. The Cooper-pair system undergoes a first-order phase transition from the normal state to the BEC state.

  9. Coulomb Dissociation of 27P

    NASA Astrophysics Data System (ADS)

    Beceiro Novo, S.; Sümmerer, K.; Cortina-Gil, D.; Wimmer, C.; Plag, R.; Alvarez-Pol, H.; Aumann, T.; Behr, K.; Boretzky, K.; Casarejos, E.; Chatillon, A.; Datta-Pramanik, U.; Elekes, Z.; Fulop, Z.; Galaviz, D.; Geissel, H.; Giron, S.; Greife, U.; Hammache, F.; Heil, M.; Hoffman, J.; Johansson, H.; Karagiannis, C.; Kiselev, O.; Kurz, N.; Larsson, K.; Le Bleis, T.; Litvinov, Y.; Mahata, K.; Muentz, C.; Nociforo, C.; Ott, W.; Paschalis, S.; Prokopowicz, W.; Rodriguez-Tajes, C.; Rossi, D.; Simon, H.; Stanoiu, M.; Stroth, J.; Typel, S.; Wagner, A.; Wamers, F.; Weick, H.

    2012-09-01

    In this work the astrophysical 26Si(p,γ)27P reaction is studied using the Coulomb dissociation technique. We performed a 27P Coulomb Dissociation experiment at GSI, Darmstadt (28 May-5 June 2007) using the ALADIN-LAND setup which allows complete-kinematic studies. A secondary 27P beam at 498 AMeV impinging a 515mg/cm2 Pb target was used. The relative energy of the outgoing system (26Si+p) is measured obtaining the resonant states of the 27P. Preliminary results show four resonant states measured at 0.36±0.07, 0.88±0.09, 1.5±0.2, 2.3±0.3 MeV and evidence of a higher state at around 3.1 MeV. The preliminary total cross section obtained for relative energies between 0 and 3 MeV has been measured and yields 55±7 mb.

  10. Communication: Oscillating charge migration between lone pairs persists without significant interaction with nuclear motion in the glycine and Gly-Gly-NH-CH{sub 3} radical cations

    SciTech Connect

    Vacher, Morgane; Bearpark, Michael J.; Robb, Michael A.

    2014-05-28

    Coupled electron-nuclear dynamics has been studied, using the Ehrenfest method, for four conformations of the glycine molecule and a single conformation of Gly-Gly-NH-CH{sub 3}. The initial electronic wavepacket was a superposition of eigenstates corresponding to ionization from the σ lone pairs associated with the carbonyl oxygens and the amine nitrogen. For glycine, oscillating charge migration (when the nuclei were frozen) was observed for the 4 conformers studied with periods ranging from 2 to 5 fs, depending on the energy gap between the lone pair cationic states. When coupled nuclear motion was allowed (which was mainly NH{sub 2} partial inversion), the oscillations hardly changed. For Gly-Gly-NH-CH{sub 3}, charge migration between the carbonyl oxygens and the NH{sub 2} lone pair can be observed with a period similar to glycine itself, also without interaction with nuclear motion. These simulations suggest that charge migration between lone pairs can occur independently of the nuclear motion.

  11. Heavy quarks, gluons and the confinement potential in Coulomb gauge

    NASA Astrophysics Data System (ADS)

    Popovici, Carina; Watson, Peter; Reinhardt, Hugo

    2011-05-01

    We consider the heavy quark limit of Coulomb gauge QCD, with the truncation of the Yang-Mills sector to include only (dressed) two-point functions. We find that the rainbow-ladder approximation to the gap and Bethe-Salpeter equations is nonperturbatively exact and moreover, we provide a direct connection between the temporal gluon propagator and the quark confinement potential. Further, we show that only bound states of color singlet quark-antiquark (meson) and quark-quark (SU(2) baryon) pairs are physically allowed.

  12. Heavy quarks, gluons and the confinement potential in Coulomb gauge

    SciTech Connect

    Popovici, Carina; Watson, Peter; Reinhardt, Hugo

    2011-05-23

    We consider the heavy quark limit of Coulomb gauge QCD, with the truncation of the Yang-Mills sector to include only (dressed) two-point functions. We find that the rainbow-ladder approximation to the gap and Bethe-Salpeter equations is nonperturbatively exact and moreover, we provide a direct connection between the temporal gluon propagator and the quark confinement potential. Further, we show that only bound states of color singlet quark-antiquark (meson) and quark-quark (SU(2) baryon) pairs are physically allowed.

  13. J-pairing interaction, number of states, and nine-j sum rules of four identical particles

    SciTech Connect

    Zhao, Y.M.; Arima, A.

    2005-11-01

    We study the J-pairing Hamiltonian and find that the sum of eigenvalues of spin-I states equals the sum of the norm matrix elements within the pair basis for four identical particles such as four fermions in a single-j shell or four bosons with spin l. We relate the number of states to sum rules of nine-j coefficients. We obtained sum rules for nine-j coefficients <(jj)J,(jj)K:I|(jj)J,(jj)K:I> and <(ll)J,(ll)K:I|(ll)J,(ll)K:I> summing over (1) even J and even K, (2) even J and odd K, (3) odd J and odd K, and (4) both even and odd values for J and K, where j is a half integer and l is an integer.

  14. The interaction energies and polarizabilities of sodium fluoride, sodium chloride, and some alkali and halide ions pairs

    NASA Astrophysics Data System (ADS)

    Bounds, David G.; Hinchliffe, Alan

    1982-02-01

    Ab initio SCF pair potentials and polarizabilities for NaF, NaCl, F 2-2, Na 2-2, K 2-2, FCl 2-, LiNa 2+, LiK 2+, presented. Together with results reported previously, these values form a complete and consistent set of energy and polarizability data on the fluorides and chlorides of lithium, sodium and potassium.

  15. Enantiomeric pair of copper(II) polypyridyl-alanine complexes: Effect of chirality on their interaction with biomolecules.

    PubMed

    Ng, Chew Hee; Chan, Cheang Wei; Lai, Jing Wei; Ooi, Ing Hong; Chong, Kok Vei; Maah, Mohd Jamil; Seng, Hoi Ling

    2016-07-01

    Like chiral organic drugs, the chemical and biological properties of metal complexes can be dependent on chirality. Two pairs of [Cu(phen)(ala)(H2O)]X·xH2O (phen=1.10-phenanthroline: X=NO3(-); ala: l-alanine (l-ala), 1 and d-alanine (d-ala) 2; and (X=Cl(-); ala: l-ala, 3 and d-ala, 4) complex salts (x=number of lattice water molecules) have been synthesized and characterized. The crystal structure of 3 has been determined. The same pair of enantiomeric species, viz. [Cu(phen)(l-ala)(H2O)](+) and [Cu(phen)(d-ala)(H2O)](+), have been identified to be present in the aqueous solutions of both 1 and 3, and in those of both 2 and 4 respectively. Both 3 and 4 bind more strongly to ds(AT)6 than ds(CG)6. There is no or insignificant effect of the chirality of 3 and 4 on the production of hydroxyl radicals, binding to deoxyribonucleic acid from calf thymus (CT-DNA), ds(CG)6, G-quadruplex and 17-base pair duplex, and inhibition of both topoisomerase I and proteasome. Among the three proteasome proteolytic sites, the trypsin-like site is inhibited most strongly by these complexes. However, the chirality of 3 and 4 does affect the number of restriction enzymes inhibited, and their binding constants towards ds(AT)6 and serum albumin. PMID:27105312

  16. Higher-order structure of nucleic acids in the gas phase: top-down analysis of base-pairing interactions

    PubMed Central

    Fabris, D.; Kellersberger, K.A.; Wilhide, J.A.

    2012-01-01

    Non-ergodic as well as ergodic activation methods are capable of maintaining the integrity of base pairs during the top-down analysis of nucleic acids. Here, we investigate the significance of this characteristic in the investigation of higher-order structures of increasing complexity. We show that cognate fragments produced by typical backbone cleavages may not be always detected as separate sequence ions, but rather as individual products that remain associated through mutual pairing contacts. This effect translates into unintended masking of cleavage events that take place in double-stranded regions, thus leading to the preferential detection of fragments originating from unpaired regions. Such effect is determined by the stability of the weak non-covalent association between complementary stretches, which is affected by base composition, length of the double-stranded structure, and charge of the precursor ion selected for analysis. Although such effect may prevent the achievement of full sequence coverage for primary structure determination, it may provide the key to correctly differentiate double- versus single-stranded regions, in what could be defined as gas-phase footprinting experiments. In light of the critical role played by base pairs in defining the higher-order structure of nucleic acids, these approaches will be expected to support an increased utilization of mass spectrometry for the investigation of nucleic acid structure and dynamics. PMID:24027423

  17. Infrared spectrum of the Ag(+)-(pyridine)2 ionic complex: probing interactions in artificial metal-mediated base pairing.

    PubMed

    Chakraborty, Shamik; Dopfer, Otto

    2011-07-11

    The isolated pyridine-Ag(+)-pyridine unit (Py-Ag(+)-Py) is employed as a model system to characterize the recently observed Ag(+)-mediated base pairing in DNA oligonucleotides at the molecular level. The structure and infrared (IR) spectrum of the Ag(+)-Py(2) cationic complex are investigated in the gas phase by IR multiple-photon dissociation (IRMPD) spectroscopy and quantum chemical calculations to determine the preferred metal-ion binding site and other salient properties of the potential-energy surface. The IRMPD spectrum has been obtained in the 840-1720 cm(-1) fingerprint region by coupling the IR free electron laser at the Centre Laser Infrarouge d'Orsay (CLIO) with a Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer equipped with an electrospray ionization source. The spectroscopic results are interpreted with quantum chemical calculations conducted at the B3LYP/aug-cc-pVDZ level. The analysis of the IRMPD spectrum is consistent with a σ complex, in which the Ag(+) ion binds to the nitrogen lone pairs of the two Py ligands in a linear configuration. The binding motif of Py-Ag(+)-Py in the gas phase is the same as that observed in Ag(+)-mediated base pairing in solution. Ag(+) bonding to the π-electron system of the aromatic ring is predicted to be a substantially less-favorable binding motif. PMID:21442717

  18. Electronic cooling via interlayer Coulomb coupling in multilayer epitaxial graphene

    PubMed Central

    Mihnev, Momchil T.; Tolsma, John R.; Divin, Charles J.; Sun, Dong; Asgari, Reza; Polini, Marco; Berger, Claire; de Heer, Walt A.; MacDonald, Allan H.; Norris, Theodore B.

    2015-01-01

    In van der Waals bonded or rotationally disordered multilayer stacks of two-dimensional (2D) materials, the electronic states remain tightly confined within individual 2D layers. As a result, electron–phonon interactions occur primarily within layers and interlayer electrical conductivities are low. In addition, strong covalent in-plane intralayer bonding combined with weak van der Waals interlayer bonding results in weak phonon-mediated thermal coupling between the layers. We demonstrate here, however, that Coulomb interactions between electrons in different layers of multilayer epitaxial graphene provide an important mechanism for interlayer thermal transport, even though all electronic states are strongly confined within individual 2D layers. This effect is manifested in the relaxation dynamics of hot carriers in ultrafast time-resolved terahertz spectroscopy. We develop a theory of interlayer Coulomb coupling containing no free parameters that accounts for the experimentally observed trends in hot-carrier dynamics as temperature and the number of layers is varied. PMID:26399955

  19. Effect of Coulomb screening length on nuclear "pasta" simulations

    NASA Astrophysics Data System (ADS)

    Alcain, P. N.; Giménez Molinelli, P. A.; Nichols, J. I.; Dorso, C. O.

    2014-05-01

    We study the role of the effective Coulomb interaction strength and length on the dynamics of nucleons in conditions according to those in a neutron star's crust. Calculations were made with a semiclassical molecular dynamics model, studying isospin symmetric matter at subsaturation densities and low temperatures. The electrostatic interaction between protons is included as a screened Coulomb potential in the spirit of the Thomas-Fermi approximation, but the screening length is artificially varied to explore its effect on the formation of the nonhomogeneous nuclear structures known as "nuclear pasta." As the screening length increases, we can see a transition from a one-per-cell pasta regime (due exclusively to finite-size effects) to a more appealing multiple pasta per simulation box. This qualitative difference in the structure of neutron star matter at low temperatures shows that special caution should be taken when the screening length is estimated for numerical simulations.

  20. Coulomb field scattering in Born-Infeld electrodynamics

    SciTech Connect

    Tennant, Daniel

    2011-02-15

    In the context of Born-Infeld electrodynamics, the electromagnetic fields interact with each other via their nonlinear couplings. A calculation will be performed where an incoming electromagnetic plane wave scatters off a Coulomb field in the geometrical optics approximation. In addition to finding the first-order angle of deflection, exact solutions for the trajectory will also be found. The possibility of electromagnetic bound states will be discussed.

  1. Coulombic contribution and fat center vortex model

    SciTech Connect

    Rafibakhsh, Shahnoosh; Deldar, Sedigheh

    2007-02-27

    The fat (thick) center vortex model is one of the phenomenological models which is fairly successful to interpret the linear potential between static sources. However, the Coulombic part of the potential has not been investigated by the model yet. In an attempt to get the Coulombic contribution and to remove the concavity of the potentials, we are studying different vortex profiles and vortex sizes.

  2. Plane Wave and Coulomb Asymptotics

    NASA Astrophysics Data System (ADS)

    Mulligan, P. G.; Crothers, D. S. F.

    2004-01-01

    A simple plane wave solution of the Schrödinger Helmholtz equation is a quantum eigenfunction obeying both energy and linear momentum correspondence principles. Inclusion of the outgoing wave with scattering amplitude f obeys unitarity and the optical theorem. By closely considering the standard asymptotic development of the plane wave, we show that there is a problem with angular momentum when we consider forward scattering at the point of closest approach and at large impact parameter given semiclassically by (l + 1/2)/k where l is the azimuthal quantum number and may be large (J Leech et al, Phys. Rev. Lett. 88 257901 (2002)). The problem is resolved via non-uniform, non-standard analysis involving the Heaviside step function, unifying classical, semiclassical and quantum mechanics, and the treatment is extended to the case of pure Coulomb scattering.

  3. Coulomb blockade with neutral modes.

    PubMed

    Kamenev, Alex; Gefen, Yuval

    2015-04-17

    We study transport through a quantum dot in the fractional quantum Hall regime with filling factors ν=2/3 and ν=5/2, weakly coupled to the leads. We account for both injection of electrons to or from the leads, and quasiparticle rearrangement processes between the edge and the bulk of the quantum dot. The presence of neutral modes introduces topological constraints that modify qualitatively the features of the Coulomb blockade (CB). The periodicity of CB peak spacings doubles and the ratio of spacing between adjacent peaks approaches (in the low temperature and large dot limit) a universal value: 2∶1 for ν=2/3 and 3∶1 for ν=5/2. The corresponding CB diamonds alternate their width in the direction of the bias voltage and allow for the determination of the neutral mode velocity, and of the topological numbers associated with it. PMID:25933323

  4. Extended Kepler-Coulomb quantum superintegrable systems in three dimensions

    NASA Astrophysics Data System (ADS)

    Kalnins, E. G.; Kress, J. M.; Miller, W., Jr.

    2013-03-01

    The quantum Kepler-Coulomb system in three dimensions is well known to be second order superintegrable, with a symmetry algebra that closes polynomially under commutators. This polynomial closure is also typical for second order superintegrable systems in 2D and for second order systems in 3D with nondegenerate (four-parameter) potentials. However, the degenerate three-parameter potential for the 3D Kepler-Coulomb system (also second order superintegrable) is an exception, as its symmetry algebra does not close polynomially. The 3D four-parameter potential for the extended Kepler-Coulomb system is not even second order superintegrable, but Verrier and Evans (2008 J. Math. Phys. 49 022902) showed it was fourth order superintegrable, and Tanoudis and Daskaloyannis (2011 arXiv:11020397v1) showed that, if a second fourth order symmetry is added to the generators, the symmetry algebra closes polynomially. Here, based on the Tremblay, Turbiner and Winternitz construction, we consider an infinite class of quantum extended Kepler-Coulomb three- and four-parameter systems indexed by a pair of rational numbers (k1, k2) and reducing to the usual systems when k1 = k2 = 1. We show these systems to be superintegrable of arbitrarily high order and determine the structure of their symmetry algebras. We demonstrate that the symmetry algebras close algebraically; only for systems admitting extra discrete symmetries is polynomial closure achieved. Underlying the structure theory is the existence of raising and lowering operators, not themselves symmetry operators or even defined independent of basis, that can be employed to construct the symmetry operators and their structure relations.

  5. A bioinspired redox relay that mimics radical interactions of the Tyr-His pairs of photosystem II

    NASA Astrophysics Data System (ADS)

    Megiatto, Jackson D., Jr.; Méndez-Hernández, Dalvin D.; Tejeda-Ferrari, Marely E.; Teillout, Anne-Lucie; Llansola-Portolés, Manuel J.; Kodis, Gerdenis; Poluektov, Oleg G.; Rajh, Tijana; Mujica, Vladimiro; Groy, Thomas L.; Gust, Devens; Moore, Thomas A.; Moore, Ana L.

    2014-05-01

    In water-oxidizing photosynthetic organisms, light absorption generates a powerfully oxidizing chlorophyll complex (P680•+) in the photosystem II reaction centre. This is reduced via an electron transfer pathway from the manganese-containing water-oxidizing catalyst, which includes an electron transfer relay comprising a tyrosine (Tyr)-histidine (His) pair that features a hydrogen bond between a phenol group and an imidazole group. By rapidly reducing P680•+, the relay is thought to mitigate recombination reactions, thereby ensuring a high quantum yield of water oxidation. Here, we show that an artificial reaction centre that features a benzimidazole-phenol model of the Tyr-His pair mimics both the short-internal hydrogen bond in photosystem II and, using electron paramagnetic resonance spectroscopy, the thermal relaxation that accompanies proton-coupled electron transfer. Although this artificial system is much less complex than the natural one, theory suggests that it captures the essential features that are important in the function of the relay.

  6. Optimized Unlike-Pair Interactions for Water-Carbon Dioxide Mixtures described by the SPC/E and EPM2 Models

    SciTech Connect

    Vlcek, Lukas; Chialvo, Ariel A; Cole, David; Cole, David R

    2011-01-01

    The unlike- pair interaction parameters for the SPC/E- EPM2 models have been optimized to reproduce the mutual solubility of water and carbon dioxide at the conditions of liquid- supercritical fluid phase equilibria. An efficient global optimization of the parameters is achieved through an implementation of the coupling parameter approach, adapted to phase equilibria calculations in the Gibbs ensemble, that explicitly corrects for the over- polarization of the SPC/E water molecule in the non- polar CO2 environments. The resulting H2O- CO2 force field reproduces accurately the available experimental solubilities at the two fluid phases in equilibria as well as the corresponding species tracer diffusion coefficients.

  7. Shell-Structure and Pairing Interaction in Superheavy Nuclei: Rotational Properties of the Z=104 Nucleus Rf256

    NASA Astrophysics Data System (ADS)

    Greenlees, P. T.; Rubert, J.; Piot, J.; Gall, B. J. P.; Andersson, L. L.; Asai, M.; Asfari, Z.; Cox, D. M.; Dechery, F.; Dorvaux, O.; Grahn, T.; Hauschild, K.; Henning, G.; Herzan, A.; Herzberg, R.-D.; Heßberger, F. P.; Jakobsson, U.; Jones, P.; Julin, R.; Juutinen, S.; Ketelhut, S.; Khoo, T.-L.; Leino, M.; Ljungvall, J.; Lopez-Martens, A.; Lozeva, R.; Nieminen, P.; Pakarinen, J.; Papadakis, P.; Parr, E.; Peura, P.; Rahkila, P.; Rinta-Antila, S.; Ruotsalainen, P.; Sandzelius, M.; Sarén, J.; Scholey, C.; Seweryniak, D.; Sorri, J.; Sulignano, B.; Theisen, Ch.; Uusitalo, J.; Venhart, M.

    2012-07-01

    The rotational band structure of the Z=104 nucleus Rf256 has been observed up to a tentative spin of 20ℏ using state-of-the-art γ-ray spectroscopic techniques. This represents the first such measurement in a superheavy nucleus whose stability is entirely derived from the shell-correction energy. The observed rotational properties are compared to those of neighboring nuclei and it is shown that the kinematic and dynamic moments of inertia are sensitive to the underlying single-particle shell structure and the specific location of high-j orbitals. The moments of inertia therefore provide a sensitive test of shell structure and pairing in superheavy nuclei which is essential to ensure the validity of contemporary nuclear models in this mass region. The data obtained show that there is no deformed shell gap at Z=104, which is predicted in a number of current self-consistent mean-field models.

  8. Shell-structure and pairing interaction in superheavy nuclei: rotational properties of the z=104 nucleus (256)rf.

    PubMed

    Greenlees, P T; Rubert, J; Piot, J; Gall, B J P; Andersson, L L; Asai, M; Asfari, Z; Cox, D M; Dechery, F; Dorvaux, O; Grahn, T; Hauschild, K; Henning, G; Herzan, A; Herzberg, R-D; Heßberger, F P; Jakobsson, U; Jones, P; Julin, R; Juutinen, S; Ketelhut, S; Khoo, T-L; Leino, M; Ljungvall, J; Lopez-Martens, A; Lozeva, R; Nieminen, P; Pakarinen, J; Papadakis, P; Parr, E; Peura, P; Rahkila, P; Rinta-Antila, S; Ruotsalainen, P; Sandzelius, M; Sarén, J; Scholey, C; Seweryniak, D; Sorri, J; Sulignano, B; Theisen, Ch; Uusitalo, J; Venhart, M

    2012-07-01

    The rotational band structure of the Z=104 nucleus (256)Rf has been observed up to a tentative spin of 20ℏ using state-of-the-art γ-ray spectroscopic techniques. This represents the first such measurement in a superheavy nucleus whose stability is entirely derived from the shell-correction energy. The observed rotational properties are compared to those of neighboring nuclei and it is shown that the kinematic and dynamic moments of inertia are sensitive to the underlying single-particle shell structure and the specific location of high-j orbitals. The moments of inertia therefore provide a sensitive test of shell structure and pairing in superheavy nuclei which is essential to ensure the validity of contemporary nuclear models in this mass region. The data obtained show that there is no deformed shell gap at Z=104, which is predicted in a number of current self-consistent mean-field models. PMID:23031099

  9. Poisson Green's function method for increased computational efficiency in numerical calculations of Coulomb coupling elements

    NASA Astrophysics Data System (ADS)

    Zimmermann, Anke; Kuhn, Sandra; Richter, Marten

    2016-01-01

    Often, the calculation of Coulomb coupling elements for quantum dynamical treatments, e.g., in cluster or correlation expansion schemes, requires the evaluation of a six dimensional spatial integral. Therefore, it represents a significant limiting factor in quantum mechanical calculations. If the size or the complexity of the investigated system increases, many coupling elements need to be determined. The resulting computational constraints require an efficient method for a fast numerical calculation of the Coulomb coupling. We present a computational method to reduce the numerical complexity by decreasing the number of spatial integrals for arbitrary geometries. We use a Green's function formulation of the Coulomb coupling and introduce a generalized scalar potential as solution of a generalized Poisson equation with a generalized charge density as the inhomogeneity. That enables a fast calculation of Coulomb coupling elements and, additionally, a straightforward inclusion of boundary conditions and arbitrarily spatially dependent dielectrics through the Coulomb Green's function. Particularly, if many coupling elements are included, the presented method, which is not restricted to specific symmetries of the model, presents a promising approach for increasing the efficiency of numerical calculations of the Coulomb interaction. To demonstrate the wide range of applications, we calculate internanostructure couplings, such as the Förster coupling, and illustrate the inclusion of symmetry considerations in the method for the Coulomb coupling between bound quantum dot states and unbound continuum states.

  10. Pick a Pair. Pancake Pairs

    ERIC Educational Resources Information Center

    Miller, Pat

    2005-01-01

    Cold February weather and pancakes are a traditional pairing. Pancake Day began as a way to eat up the foods that were abstained from in Lent--traditionally meat, fat, eggs and dairy products. The best-known pancake event is The Pancake Day Race in Buckinghamshire, England, which has been run since 1445. This column describes pairs of books that…

  11. Pair interactions among ternary DPPC/POPC/cholesterol mixtures in liquid-ordered and liquid-disordered phases.

    PubMed

    Yang, Jing; Martí, Jordi; Calero, Carles

    2016-05-18

    Saturated phospholipids, unsaturated phospholipids, and cholesterol are essential components of cell membranes, making the understanding of their mutual interactions of great significance. We have performed microsecond molecular dynamics simulations on the ternary mixtures of DPPC/POPC/cholesterol to systematically examine lipid-lipid and cholesterol-lipid interactions in the liquid-ordered and the liquid-disordered phases. The results show that there exists a competition between the tighter packing of cholesterol-lipid and the looser packing of lipid-lipid as the membrane changes from the liquid-disordered phase to the liquid-ordered phase. Depending on the lipid saturation, the favor of lipid-lipid interactions is in the order of saturated-saturated > monounsaturated-monounsaturated > saturated-monounsaturated. Cholesterol-saturated lipid interactions are more favorable than cholesterol-monounsaturated lipid ones. The results are consistent with the push-pull forces derived from experiments and give general insights into the interactions among membrane components. PMID:27103534

  12. Identification of Genes Important for the Physical Interaction between Protein Pairs through Reverse PCA (rPCA).

    PubMed

    Lev, Ifat; Volpe, Marina; Ben-Aroya, Shay

    2014-01-01

    Cells contain many important protein complexes involved in performing and regulating structural, metabolic, and signaling functions. Understanding physical and functional interactions between proteins in living systems is of vital importance in biology. The importance of protein-protein interactions (PPIs) has led to the development of several powerful methodologies and techniques to detect them. All of this information has enabled the creation of large protein-interaction networks. One important challenge in biology is to understand how protein complexes respond to genetic perturbations. Here we describe a systematic genetic assay termed "reverse PCA," which allows the identification of genes whose products are required for modulating the physical interaction between two given proteins. Our assay starts with a yeast strain in which the PPI of interest can be detected by resistance to the drug methotrexate, in the context of the protein-fragment complementation assay (PCA). By combining the synthetic genetic array (SGA) technology, we can systematically screen mutant libraries of the yeast Saccharomyces cerevisiae to identify trans-acting mutations that disrupt the physical interaction of interest. The identification of such mutants is valuable for unraveling important regulatory mechanisms, and for defining the response of the protein interactome to specific perturbations. PMID:25181300

  13. Conductance of a proximitized nanowire in the Coulomb blockade regime

    NASA Astrophysics Data System (ADS)

    van Heck, B.; Lutchyn, R. M.; Glazman, L. I.

    2016-06-01

    We identify the leading processes of electron transport across finite-length segments of proximitized nanowires and build a quantitative theory of their two-terminal conductance. In the presence of spin-orbit interaction, a nanowire can be tuned across the topological transition point by an applied magnetic field. Due to a finite segment length, electron transport is controlled by the Coulomb blockade. Upon increasing of the field, the shape and magnitude of the Coulomb blockade peaks in the linear conductance are defined, respectively, by Andreev reflection, single-electron tunneling, and resonant tunneling through the Majorana modes emerging after the topological transition. Our theory provides the framework for the analysis of experiments with proximitized nanowires [such as reported in S. M. Albrecht et al., Nature (London) 531, 206 (2016), 10.1038/nature17162] and identifies the signatures of the topological transition in the two-terminal conductance.

  14. Coulomb effects in low-energy nuclear fragmentation

    NASA Technical Reports Server (NTRS)

    Wilson, John W.; Chun, Sang Y.; Badavi, Francis F.; John, Sarah

    1993-01-01

    Early versions of the Langley nuclear fragmentation code NUCFRAG (and a publicly released version called HZEFRG1) assumed straight-line trajectories throughout the interaction. As a consequence, NUCFRAG and HZEFRG1 give unrealistic cross sections for large mass removal from the projectile and target at low energies. A correction for the distortion of the trajectory by the nuclear Coulomb fields is used to derive fragmentation cross sections. A simple energy-loss term is applied to estimate the energy downshifts that greatly alter the Coulomb trajectory at low energy. The results, which are far more realistic than prior versions of the code, should provide the data base for future transport calculations. The systematic behavior of charge-removal cross sections compares favorably with results from low-energy experiments.

  15. Reexamination of an anomaly in near-threshold pair production

    SciTech Connect

    De Braeckeleer, L.; Adelberger, E.G.; Garcia, A. )

    1992-11-01

    We investigated a reported anomaly in near-threshold pair production, using radioactive sources to measure the {gamma}+Ge{r arrow}{ital e}{sup +}+{ital e}{sup {minus}}+Ge cross-section at {ital E}{sub {gamma}}=1063, 1086, 1112, 1173, 1213, 1299, 1332, and 1408 keV. Although the data agree with the theory (numerical calculations based on an exact partial-wave formulation for a screened central potential) at the higher energies, the data lie above the theory at 1063, 1082, and 1112 keV. The discrepancy is reduced by including the final-state Coulomb interaction between the {ital e}{sup +} and {ital e}{sup {minus}}.

  16. Numerical approach to Coulomb gauge QCD

    SciTech Connect

    Matevosyan, Hrayr H.; Szczepaniak, Adam P.; Bowman, Patrick O.

    2008-07-01

    We calculate the ghost two-point function in Coulomb gauge QCD with a simple model vacuum gluon wave function using Monte Carlo integration. This approach extends the previous analytic studies of the ghost propagator with this ansatz, where a ladder-rainbow expansion was unavoidable for calculating the path integral over gluon field configurations. The new approach allows us to study the possible critical behavior of the coupling constant, as well as the Coulomb potential derived from the ghost dressing function. We demonstrate that IR enhancement of the ghost correlator or Coulomb form factor fails to quantitatively reproduce confinement using Gaussian vacuum wave functional.

  17. Examining the Role of Communication on Sibling Relationship Quality and Interaction for Sibling Pairs with and without a Developmental Disability

    ERIC Educational Resources Information Center

    Smith, Ashlyn L.; Romski, MaryAnn; Sevcik, Rose A.

    2013-01-01

    This study examined communication interaction patterns when one sibling had a developmental disability as well as the role of communication skills in sibling relationship quality. Thirty sibling dyads were categorized into one of three communication status groups: emerging, context-dependent, and independent communicators. Independent…

  18. The Nature of Negotiations in Face-to-Face versus Computer-Mediated Communication in Pair Interactions

    ERIC Educational Resources Information Center

    Rouhshad, Amir; Wigglesworth, Gillian; Storch, Neomy

    2016-01-01

    The Interaction Approach argues that negotiation for meaning and form is conducive to second language development. To date, most of the research on negotiations has been either in face-to-face (FTF) or text-based synchronous computer-mediated communication (SCMC) modes. Very few studies have compared the nature of negotiations across the modes.…

  19. Novel base-pairing interactions at the tRNA wobble position crucial for accurate reading of the genetic code

    NASA Astrophysics Data System (ADS)

    Rozov, Alexey; Demeshkina, Natalia; Khusainov, Iskander; Westhof, Eric; Yusupov, Marat; Yusupova, Gulnara

    2016-01-01

    Posttranscriptional modifications at the wobble position of transfer RNAs play a substantial role in deciphering the degenerate genetic code on the ribosome. The number and variety of modifications suggest different mechanisms of action during messenger RNA decoding, of which only a few were described so far. Here, on the basis of several 70S ribosome complex X-ray structures, we demonstrate how Escherichia coli tRNALysUUU with hypermodified 5-methylaminomethyl-2-thiouridine (mnm5s2U) at the wobble position discriminates between cognate codons AAA and AAG, and near-cognate stop codon UAA or isoleucine codon AUA, with which it forms pyrimidine-pyrimidine mismatches. We show that mnm5s2U forms an unusual pair with guanosine at the wobble position that expands general knowledge on the degeneracy of the genetic code and specifies a powerful role of tRNA modifications in translation. Our models consolidate the translational fidelity mechanism proposed previously where the steric complementarity and shape acceptance dominate the decoding mechanism.

  20. Novel base-pairing interactions at the tRNA wobble position crucial for accurate reading of the genetic code.

    PubMed

    Rozov, Alexey; Demeshkina, Natalia; Khusainov, Iskander; Westhof, Eric; Yusupov, Marat; Yusupova, Gulnara

    2016-01-01

    Posttranscriptional modifications at the wobble position of transfer RNAs play a substantial role in deciphering the degenerate genetic code on the ribosome. The number and variety of modifications suggest different mechanisms of action during messenger RNA decoding, of which only a few were described so far. Here, on the basis of several 70S ribosome complex X-ray structures, we demonstrate how Escherichia coli tRNA(Lys)(UUU) with hypermodified 5-methylaminomethyl-2-thiouridine (mnm(5)s(2)U) at the wobble position discriminates between cognate codons AAA and AAG, and near-cognate stop codon UAA or isoleucine codon AUA, with which it forms pyrimidine-pyrimidine mismatches. We show that mnm(5)s(2)U forms an unusual pair with guanosine at the wobble position that expands general knowledge on the degeneracy of the genetic code and specifies a powerful role of tRNA modifications in translation. Our models consolidate the translational fidelity mechanism proposed previously where the steric complementarity and shape acceptance dominate the decoding mechanism. PMID:26791911

  1. Novel base-pairing interactions at the tRNA wobble position crucial for accurate reading of the genetic code

    PubMed Central

    Rozov, Alexey; Demeshkina, Natalia; Khusainov, Iskander; Westhof, Eric; Yusupov, Marat; Yusupova, Gulnara

    2016-01-01

    Posttranscriptional modifications at the wobble position of transfer RNAs play a substantial role in deciphering the degenerate genetic code on the ribosome. The number and variety of modifications suggest different mechanisms of action during messenger RNA decoding, of which only a few were described so far. Here, on the basis of several 70S ribosome complex X-ray structures, we demonstrate how Escherichia coli tRNALysUUU with hypermodified 5-methylaminomethyl-2-thiouridine (mnm5s2U) at the wobble position discriminates between cognate codons AAA and AAG, and near-cognate stop codon UAA or isoleucine codon AUA, with which it forms pyrimidine–pyrimidine mismatches. We show that mnm5s2U forms an unusual pair with guanosine at the wobble position that expands general knowledge on the degeneracy of the genetic code and specifies a powerful role of tRNA modifications in translation. Our models consolidate the translational fidelity mechanism proposed previously where the steric complementarity and shape acceptance dominate the decoding mechanism. PMID:26791911

  2. An Unusual Genomic Position Effect on Drosophila White Gene Expression: Pairing Dependence, Interactions with Zeste, and Molecular Analysis of Revertants

    PubMed Central

    Hazelrigg, T.; Petersen, S.

    1992-01-01

    The white gene in the A(R)4-24 P[white,rosy] insertion on chromosome 2 has a novel expression pattern, in which it is repressed in the dorsal half of the eye. X-ray mutagenesis led to the isolation of six revertants mapping to chromosome 2, which are wild type in a zeste(+) background, and three extreme derivatives, in which white gene expression is repressed in ventral regions of the eye as well. By Southern blot analyses the breakpoints of five of the revertants and one of the extreme derivatives were mapped in the flanking DNA bordering each side of the A(R)4-24 insertion. The revertants show some dorsal repression of white in the presence of z(1), and by this criterion each is only a partial revertant. The extreme derivatives act not only in cis, but also in trans to repress expression of A(R)4-24 and its various derivatives. We provide evidence that these trans effects are proximity-dependent effects, possibly mediated by pairing of gene copies, as they do not extend to copies of the white gene located elsewhere in the genome. We show that one extreme derivative, E1, is a small deletion spanning the insertion site at the 5' end of the white gene, and propose that the distance between a negative regulatory element in the 5' flanking DNA and the white promoter influences the degree of the repression. PMID:1732157

  3. Spatio-temporal correlations in Coulomb clusters

    NASA Astrophysics Data System (ADS)

    Ghosal, Amit; Ash, Biswarup; Chakrabarti, Jaydeb

    Dynamical response of Coulomb-particles in nanoclusters are investigated at different temperatures characterizing their solid-like (Wigner molecule) and liquid-like behavior. The density correlations probe spatio-temporal relaxation, uncovering distinct behavior at multiple time scales in these systems. They show a stretched-Gaussian or stretched-exponential spatial decay at long times in circular and irregular traps. Interplay of confinement and long-range nature of interactions yields spatially correlated motion of the particles in string-like paths, leaving the system heterogeneous even at long times. While particles in a `solid' flow producing dynamic heterogeneities, their random motion in `liquid' defies central limit theorem. Distinguishing the two confinements, temperature dependent motional signatures serve as a criterion for the crossover between `solid' and `liquid'. The irregular Wigner molecule turns into a nearly homogeneous liquid over a much wider temperature window compared to the circular case. The temperature dependence of different relaxation time scales builds crucial insights. A phenomenological model, relating the unusual dynamics to the heterogeneous nature of the diffusivities in the system, captures much of the subtleties of our numerical simulations.

  4. Examining the role of communication on sibling relationship quality and interaction for sibling pairs with and without a developmental disability.

    PubMed

    Smith, Ashlyn L; Romski, Maryann; Sevcik, Rose A

    2013-09-01

    This study examined communication interaction patterns when one sibling had a developmental disability as well as the role of communication skills in sibling relationship quality. Thirty sibling dyads were categorized into one of three communication status groups: emerging, context-dependent, and independent communicators. Independent communicators and their siblings did not differ in terms of syntactic complexity but typically developing siblings dominated the interaction and exhibited greater lexical diversity regardless of communication status. Communication status did not impact the warmth/closeness, rivalry, or conflict in the sibling relationship, but siblings of independent communicators engaged in the greatest amount of helping and managing behaviors. These results represent a first step in understanding the role of communication skills in the sibling relationship for families of children with disabilities. PMID:24245732

  5. Crystallization in two-component Coulomb systems.

    PubMed

    Bonitz, M; Filinov, V S; Fortov, V E; Levashov, P R; Fehske, H

    2005-12-01

    The analysis of Coulomb crystallization is extended from one-component to two-component plasmas. Critical parameters for the existence of Coulomb crystals are derived for both classical and quantum crystals. In the latter case, a critical mass ratio of the two charged components is found, which is of the order of 80. Thus, holes in semiconductors with sufficiently flat valence bands are predicted to spontaneously order into a regular lattice. Such hole crystals are intimately related to ion Coulomb crystals in white dwarf and neutron stars as well as to ion crystals produced in the laboratory. A unified phase diagram of two-component Coulomb crystals is presented and is verified by first-principles computer simulations. PMID:16384315

  6. Pair potentials for protein folding: choice of reference states and sensitivity of predicted native states to variations in the interaction schemes.

    PubMed Central

    Betancourt, M. R.; Thirumalai, D.

    1999-01-01

    We examine the similarities and differences between two widely used knowledge-based potentials, which are expressed as contact matrices (consisting of 210 elements) that gives a scale for interaction energies between the naturally occurring amino acid residues. These are the Miyazawa-Jernigan contact interaction matrix M and the potential matrix S derived by Skolnick J et al., 1997, Protein Sci 6:676-688. Although the correlation between the two matrices is good, there is a relatively large dispersion between the elements. We show that when Thr is chosen as a reference solvent within the Miyazawa and Jernigan scheme, the dispersion between the M and S matrices is reduced. The resulting interaction matrix B gives hydrophobicities that are in very good agreement with experiment. The small dispersion between the S and B matrices, which arises due to differing reference states, is shown to have dramatic effect on the predicted native states of lattice models of proteins. These findings and other arguments are used to suggest that for reliable predictions of protein structures, pairwise additive potentials are not sufficient. We also establish that optimized protein sequences can tolerate relatively large random errors in the pair potentials. We conjecture that three body interaction may be needed to predict the folds of proteins in a reliable manner. PMID:10048329

  7. Interaction energy in pairs of phthalazinium dibenzoylmethylid (PDBM)-protic solvent molecules estimated in the limits of the cell ternary solution model, by spectral means

    NASA Astrophysics Data System (ADS)

    Nicoleta, Melniciuc-Puica; Mihaela, Avadanei; Maria, Caprosu; Dana Ortansa, Dorohoi

    2012-10-01

    The dipolar compound Phthalazinium-dibenzoylmethylid (PDBM) was used as spectrally active molecule in order to analyze the molecular interactions in ternary solutions containing at least one protic solvent. In PDBM + protic solvent (1) + aprotic solvent (2) ternary solutions, PDBM can be involved both in universal and specific interactions reflected in solvatochromic effects. The protic solvent (or the solvent with the higher electric permittivity) was considered as being active from the interactions point of view. The content of the first solvation sphere of the studied ylid has been established on the basis of the statistical cell model of ternary solutions. The active solvent molecules are dominant in the first solvation sphere of the PDBM molecules. The difference between the interaction energies in the PDBM-active solvent (1) and PDBM-inactive solvent (2) molecular pairs has been determined for three binary solvents water + ethanol (W + E), propionic acid + chloroform (PA + C) and octanol + 1,2 dichloroethane (O + DCE). The hydrogen bond formation energy of the PDBM-protic solvent complex has been estimated in the binary solvents PA + C and O + DCE containing one protic (PA and O, respectively) and one aprotic solvent with close electro-optical parameters refractive index and electric permittivity of the components.

  8. The analysis of historical earthquakes of the North Anatolian Fault in the Marmara Region, Turkey for the last 15 centuries based on intensity and continuous Coulomb scenarios: Implications for the fault geometry and the interaction of individual earthqua

    NASA Astrophysics Data System (ADS)

    Yaltırak, Cenk; Şahin, Murat

    2016-04-01

    In this study we evaluated the historical earthquakes of the Marmara Region totally in three-stages. In first stage, historical earthquakes were compiled from the available catalogues and classified according to their spatial distribution, whereas only the ones, related with the active northern branch of the North Anatolian Fault (NAF) were selected. Then, the next phase of classification was made to relate historical data to the ancient and historical settlements, for which a kind of shake map was produced for each event. In the second stage, three different fault models, suggested for the geometry of the NAF in the Marmara Region, were integrated into a GIS database. Mw magnitudes were calculated for each fault segment by using lengths, seismogenic depths, and slip-rates of fault segments. In the third stage, the revised digital geological map of the Marmara Region were compiled based on 1:500k conventional maps and were used to estimate the Vs30 distribution within a grid of 750x750 m. Modified Mercalli Intensity (MMI) maps were produced for each earthquake scenario, depending on the geometry of different fault models, calculated model magnitudes and intensity distributions. Moreover, we tested the surface ruptures of each earthquake scenarios by using the Coulomb stress change model for historical data covering a time era between AD 478 and 2016 in assumption with a constant horizontal slip rate of 19 mma-1 for all fault segments. As conclusion, the horsetail-fault geometry (Yaltırak, 2002) among all 3 fault models yielded the best fit to the distribution of intensities and coulomb models.

  9. Coulomb Distortion in the Inelastic Regime

    SciTech Connect

    Patricia Solvignon, Dave Gaskell, John Arrington

    2009-09-01

    The Coulomb distortion effects have been for a long time neglected in deep inelastic scattering for the good reason that the incident energies were very high. But for energies in the range of earlier data from SLAC or at JLab, the Coulomb distortion could have the potential consequence of affecting the A-dependence of the EMC effect and of the longitudinal to transverse virtual photon absorption cross section ratio $R(x,Q^2)$.

  10. On the modelling of Coulomb friction

    NASA Astrophysics Data System (ADS)

    Cull, S. J.; Tucker, R. W.

    1999-03-01

    This paper analyses two different representations of Coulomb friction in the context of a dynamic simulation of the torsional vibrations of a driven drill-string. A simple model is used to compare the relative merits of a piecewise analytic approach using a discontinuous friction profile to a numerical integration using a smooth nonlinear representation of the Coulomb friction. In both cases the effects of viscous damping on the excitation of torsional relaxation oscillations are exhibited.

  11. Modelling Coulomb Collisions in Anisotropic Plasmas

    NASA Astrophysics Data System (ADS)

    Hellinger, P.; Travnicek, P. M.

    2009-12-01

    Collisional transport in anisotropic plasmas is investigated comparing the theoretical transport coefficients (Hellinger and Travnicek, 2009) for anisotropic particles with the results of the corresponding Langevin equation, obtained as a generalization of Manheimer et al. (1997). References: Hellinger, P., and P. M. Travnicek (2009), On Coulomb collisions in bi-Maxwellian plasmas, Phys. Plasmas, 16, 054501. Manheimer, W. M., M. Lampe and G. Joyce (1997), Langevin representation of Coulomb collisions in PIC simulations, J. Comput. Phys., 138, 563-584.

  12. Structural and thermodynamic consequences of burial of an artificial ion pair in the hydrophobic interior of a protein

    PubMed Central

    Robinson, Aaron C.; Castañeda, Carlos A.; Schlessman, Jamie L.; García-Moreno E., Bertrand

    2014-01-01

    An artificial charge pair buried in the hydrophobic core of staphylococcal nuclease was engineered by making the V23E and L36K substitutions. Buried individually, Glu-23 and Lys-36 both titrate with pKa values near 7. When buried together their pKa values appear to be normal. The ionizable moieties of the buried Glu–Lys pair are 2.6 Å apart. The interaction between them at pH 7 is worth 5 kcal/mol. Despite this strong interaction, the buried Glu–Lys pair destabilizes the protein significantly because the apparent Coulomb interaction is sufficient to offset the dehydration of only one of the two buried charges. Save for minor reorganization of dipoles and water penetration consistent with the relatively high dielectric constant reported by the buried ion pair, there is no evidence that the presence of two charges in the hydrophobic interior of the protein induces any significant structural reorganization. The successful engineering of an artificial ion pair in a highly hydrophobic environment suggests that buried Glu–Lys pairs in dehydrated environments can be charged and that it is possible to engineer charge clusters that loosely resemble catalytic sites in a scaffold protein with high thermodynamic stability, without the need for specialized structural adaptations. PMID:25074910

  13. Structural and thermodynamic consequences of burial of an artificial ion pair in the hydrophobic interior of a protein.

    PubMed

    Robinson, Aaron C; Castañeda, Carlos A; Schlessman, Jamie L; García-Moreno, E Bertrand

    2014-08-12

    An artificial charge pair buried in the hydrophobic core of staphylococcal nuclease was engineered by making the V23E and L36K substitutions. Buried individually, Glu-23 and Lys-36 both titrate with pKa values near 7. When buried together their pKa values appear to be normal. The ionizable moieties of the buried Glu-Lys pair are 2.6 Å apart. The interaction between them at pH 7 is worth 5 kcal/mol. Despite this strong interaction, the buried Glu-Lys pair destabilizes the protein significantly because the apparent Coulomb interaction is sufficient to offset the dehydration of only one of the two buried charges. Save for minor reorganization of dipoles and water penetration consistent with the relatively high dielectric constant reported by the buried ion pair, there is no evidence that the presence of two charges in the hydrophobic interior of the protein induces any significant structural reorganization. The successful engineering of an artificial ion pair in a highly hydrophobic environment suggests that buried Glu-Lys pairs in dehydrated environments can be charged and that it is possible to engineer charge clusters that loosely resemble catalytic sites in a scaffold protein with high thermodynamic stability, without the need for specialized structural adaptations. PMID:25074910

  14. CHARGE-IMBALANCE RELAXATION IN THE PRESENCE OF A PAIR-BREAKING INTERACTION IN SUPERCONDUCTING AlEr FILMS

    SciTech Connect

    Lemberger, T.R.; Clarke, J.

    1980-07-01

    The charge-imbalance relaxation rate, 1/F*{sub T{sub Q*}}, has been measured in dirty superconducting AlEr films in which Er is a pair-breaking magnetic impurity that induces charge relaxation through elastic exchange scattering. Measurements were made in the range 0.1 {approx}< {Delta}(T)/k{sub B}T{sub c} {approx}< 1.4 for Er concentrations varying from 21 to 1660 at. ppm that produced estimated exchange scattering rates, {tau}{sub S}{sup -1}, from about 10{sup 9} sec{sup -1} to 5 x 10{sup 10} sec{sup -1}. Measured values of 1/F*{sub T{sub Q*}} were in good agreement with the Schmid-Schoen expression, 1/F*{sub T{sub Q*}}=({pi}{Delta}/4k{sub B}T{sub c}{tau}{sub E}) x (1+2{tau}{sub E}/{tau}{sub S}){sup 1/2}, for {Delta}/k{sub B}T{sub c} {approx}< 0.8, where {tau}{sub E}{sup -1} is the electron-phonon scattering rate estimated from the measured transition temperature. For larger values of {Delta}/k{sub B}T{sub c}, the relaxation rate increased less rapidly with {Delta}. The appropriate Boltzmann equation was solved on a computer to obtain values for 1/F*{sub T{sub Q*}} in the range 0.5 {approx}< T/T{sub c} {approx}< 0.999999. The computed values of 1/F*{sub T{sub Q*}} agreed with several analytic expressions valid for {Delta}/k{sub B}T{sub c} << 1, but not with the experimental data: The computed curves increased more rapidly than linearly with {Delta}/k{sub B}T{sub c} near T{sub c}, and the shape of the 1/F*{sub T{sub Q*}} vs {Delta}/k{sub B}T{sub c} curves was qualitatively different. This discrepancy suggests that either the generally accepted expression for exchange charge relaxation is incorrect, or that the Boltzmann equation is inappropriate for these calculations.

  15. Strong Coulomb effects on pions produced in heavy ion collisons

    NASA Astrophysics Data System (ADS)

    Sullivan, J. P.; Bistirlich, J. A.; Bowman, H. R.; Bossingham, R.; Buttke, T.; Crowe, K. M.; Frankel, K. A.; Martoff, C. J.; Miller, J.; Murphy, D. L.; Rasmussen, J. O.; Zajc, W. A.; Hashimoto, O.; Koike, M.; Péter, J.; Benenson, W.; Crawley, G. M.; Kashy, E.; Nolen, J. A.

    1982-03-01

    Doubly differential cross sections for the production of π+ and π- near the velocity of the incident beam for pion laboratory angles from 0 to 20 degrees are presented. Beams of 20Ne with EA=280, 380, and 480 MeV and 40Ar with EA=535 MeV incident on C, NaF, KCl, Cu, and U targets were used. A sharp peak in the π- spectrum and a depression in the π+ spectrum is observed at 0° near the incident projectile velocity. The effect is explained in terms of Coulomb interactions between pions and fragments of the incident beam. Least squares fits to the data using the Coulomb correction formulas of Gyulassy and Kauffmann and an effective projectile fragment charge are made. The relationship between these data and previously measured projectile fragmentation data is discussed and a simple parametrization of projectile mass, target mass, and beam energy dependence of the differential cross sections is given. NUCLEAR REACTIONS C, NaF, Cu, U (20Ne,π+/-)X, EA=280-480 MeV; C, KCl (40Ar,π+/-)X, EA=535 MeV; measured σ(Eπ,θπ), θπ=0°-20°, π velocity near beam velocity; deduced projectile fragment charges, Coulomb effects.

  16. Photoelectron wave function in photoionization: plane wave or Coulomb wave?

    PubMed

    Gozem, Samer; Gunina, Anastasia O; Ichino, Takatoshi; Osborn, David L; Stanton, John F; Krylov, Anna I

    2015-11-19

    The calculation of absolute total cross sections requires accurate wave functions of the photoelectron and of the initial and final states of the system. The essential information contained in the latter two can be condensed into a Dyson orbital. We employ correlated Dyson orbitals and test approximate treatments of the photoelectron wave function, that is, plane and Coulomb waves, by comparing computed and experimental photoionization and photodetachment spectra. We find that in anions, a plane wave treatment of the photoelectron provides a good description of photodetachment spectra. For photoionization of neutral atoms or molecules with one heavy atom, the photoelectron wave function must be treated as a Coulomb wave to account for the interaction of the photoelectron with the +1 charge of the ionized core. For larger molecules, the best agreement with experiment is often achieved by using a Coulomb wave with a partial (effective) charge smaller than unity. This likely derives from the fact that the effective charge at the centroid of the Dyson orbital, which serves as the origin of the spherical wave expansion, is smaller than the total charge of a polyatomic cation. The results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion. PMID:26509428

  17. Quasi-exactly solvable relativistic soft-core Coulomb models

    SciTech Connect

    Agboola, Davids Zhang, Yao-Zhong

    2012-09-15

    By considering a unified treatment, we present quasi exact polynomial solutions to both the Klein-Gordon and Dirac equations with the family of soft-core Coulomb potentials V{sub q}(r)=-Z/(r{sup q}+{beta}{sup q}){sup 1/q}, Z>0, {beta}>0, q{>=}1. We consider cases q=1 and q=2 and show that both cases are reducible to the same basic ordinary differential equation. A systematic and closed form solution to the basic equation is obtained using the Bethe ansatz method. For each case, the expressions for the energies and the allowed parameters are obtained analytically and the wavefunctions are derived in terms of the roots of a set of Bethe ansatz equations. - Highlights: Black-Right-Pointing-Pointer The relativistic bound-state solutions of the soft-core Coulomb models. Black-Right-Pointing-Pointer Quasi-exact treatments of the Dirac and Klein-Gordon equations for the soft-core Coulomb models. Black-Right-Pointing-Pointer Solutions obtained in terms of the roots to the Bethe ansatz equations. Black-Right-Pointing-Pointer The hidden Lie algebraic structure discussed for the models. Black-Right-Pointing-Pointer Results useful in describing mesonic atoms and interaction of intense laser fields with atom.

  18. Electron pairing without superconductivity.

    PubMed

    Cheng, Guanglei; Tomczyk, Michelle; Lu, Shicheng; Veazey, Joshua P; Huang, Mengchen; Irvin, Patrick; Ryu, Sangwoo; Lee, Hyungwoo; Eom, Chang-Beom; Hellberg, C Stephen; Levy, Jeremy

    2015-05-14

    Strontium titanate (SrTiO3) is the first and best known superconducting semiconductor. It exhibits an extremely low carrier density threshold for superconductivity, and possesses a phase diagram similar to that of high-temperature superconductors--two factors that suggest an unconventional pairing mechanism. Despite sustained interest for 50 years, direct experimental insight into the nature of electron pairing in SrTiO3 has remained elusive. Here we perform transport experiments with nanowire-based single-electron transistors at the interface between SrTiO3 and a thin layer of lanthanum aluminate, LaAlO3. Electrostatic gating reveals a series of two-electron conductance resonances-paired electron states--that bifurcate above a critical pairing field Bp of about 1-4 tesla, an order of magnitude larger than the superconducting critical magnetic field. For magnetic fields below Bp, these resonances are insensitive to the applied magnetic field; for fields in excess of Bp, the resonances exhibit a linear Zeeman-like energy splitting. Electron pairing is stable at temperatures as high as 900 millikelvin, well above the superconducting transition temperature (about 300 millikelvin). These experiments demonstrate the existence of a robust electronic phase in which electrons pair without forming a superconducting state. Key experimental signatures are captured by a model involving an attractive Hubbard interaction that describes real-space electron pairing as a precursor to superconductivity. PMID:25971511

  19. Electron pairing without superconductivity

    NASA Astrophysics Data System (ADS)

    Cheng, Guanglei; Tomczyk, Michelle; Lu, Shicheng; Veazey, Joshua P.; Huang, Mengchen; Irvin, Patrick; Ryu, Sangwoo; Lee, Hyungwoo; Eom, Chang-Beom; Hellberg, C. Stephen; Levy, Jeremy

    2015-05-01

    Strontium titanate (SrTiO3) is the first and best known superconducting semiconductor. It exhibits an extremely low carrier density threshold for superconductivity, and possesses a phase diagram similar to that of high-temperature superconductors--two factors that suggest an unconventional pairing mechanism. Despite sustained interest for 50 years, direct experimental insight into the nature of electron pairing in SrTiO3 has remained elusive. Here we perform transport experiments with nanowire-based single-electron transistors at the interface between SrTiO3 and a thin layer of lanthanum aluminate, LaAlO3. Electrostatic gating reveals a series of two-electron conductance resonances--paired electron states--that bifurcate above a critical pairing field Bp of about 1-4 tesla, an order of magnitude larger than the superconducting critical magnetic field. For magnetic fields below Bp, these resonances are insensitive to the applied magnetic field; for fields in excess of Bp, the resonances exhibit a linear Zeeman-like energy splitting. Electron pairing is stable at temperatures as high as 900 millikelvin, well above the superconducting transition temperature (about 300 millikelvin). These experiments demonstrate the existence of a robust electronic phase in which electrons pair without forming a superconducting state. Key experimental signatures are captured by a model involving an attractive Hubbard interaction that describes real-space electron pairing as a precursor to superconductivity.

  20. Electron pairing without superconductivity

    NASA Astrophysics Data System (ADS)

    Levy, Jeremy

    Strontium titanate (SrTiO3) is the first and best known superconducting semiconductor. It exhibits an extremely low carrier density threshold for superconductivity, and possesses a phase diagram similar to that of high-temperature superconductors--two factors that suggest an unconventional pairing mechanism. Despite sustained interest for 50 years, direct experimental insight into the nature of electron pairing in SrTiO3 has remained elusive. Here we perform transport experiments with nanowire-based single-electron transistors at the interface between SrTiO3 and a thin layer of lanthanum aluminate, LaAlO3. Electrostatic gating reveals a series of two-electron conductance resonances--paired electron states--that bifurcate above a critical pairing field Bp of about 1-4 tesla, an order of magnitude larger than the superconducting critical magnetic field. For magnetic fields below Bp, these resonances are insensitive to the applied magnetic field; for fields in excess of Bp, the resonances exhibit a linear Zeeman-like energy splitting. Electron pairing is stable at temperatures as high as 900 millikelvin, well above the superconducting transition temperature (about 300 millikelvin). These experiments demonstrate the existence of a robust electronic phase in which electrons pair without forming a superconducting state. Key experimental signatures are captured by a model involving an attractive Hubbard interaction that describes real-space electron pairing as a precursor to superconductivity. Support from AFOSR, ONR, ARO, NSF, DOE and NSSEFF is gratefully acknowledged.