Pair plasma relaxation time scales.
Aksenov, A G; Ruffini, R; Vereshchagin, G V
2010-04-01
By numerically solving the relativistic Boltzmann equations, we compute the time scale for relaxation to thermal equilibrium for an optically thick electron-positron plasma with baryon loading. We focus on the time scales of electromagnetic interactions. The collisional integrals are obtained directly from the corresponding QED matrix elements. Thermalization time scales are computed for a wide range of values of both the total-energy density (over 10 orders of magnitude) and of the baryonic loading parameter (over 6 orders of magnitude). This also allows us to study such interesting limiting cases as the almost purely electron-positron plasma or electron-proton plasma as well as intermediate cases. These results appear to be important both for laboratory experiments aimed at generating optically thick pair plasmas as well as for astrophysical models in which electron-positron pair plasmas play a relevant role.
Pair plasma in pulsar magnetospheres
International Nuclear Information System (INIS)
Asseo, Estelle
2003-01-01
The main features of radiation received from pulsars imply that they are neutron stars which contain an extremely intense magnetic field and emit coherently in the radio domain. Most recent studies attribute the origin of the coherence to plasma instabilities arising in pulsar magnetospheres; they mainly concern the linear, or the nonlinear, character of the involved unstable waves. We briefly introduce radio pulsars and specify physical conditions in pulsar emission regions: geometrical properties, magnetic field, pair creation processes and repartition of relativistic charged particles. We point to the main ingredients of the linear theory, extensively explored since the 1970s: (i) a dispersion relation specific to the pulsar case; (ii) the characteristics of the waves able to propagate in relativistic pulsar plasmas; (iii) the different ways in which a two-humped distribution of particles may arise in a pulsar magnetosphere and favour the development of a two-stream instability. We sum up recent improvements of the linear theory: (i) the determination of a 'coupling function' responsible for high values of the wave field components and electromagnetic energy available; (ii) the obtention of new dispersion relations for actually anisotropic pulsar plasmas with relativistic motions and temperatures; (iii) the interaction between a plasma and a beam, both with relativistic motions and temperatures; (iv) the interpretation of observed 'coral' and 'conal' features, associated with the presence of boundaries and curved magnetic field lines in the emission region; (v) the detailed topology of the magnetic field in the different parts of the emission region and its relation to models recently proposed to interpret drifting subpulses observed from PSR 0943+10, showing 20 sub-beams of emission. We relate the nonlinear evolution of the two-stream instability and development of strong turbulence in relativistic pulsar plasmas to the emergence of relativistic solitons, able
Indian Academy of Sciences (India)
ion plasma are discussed. It is shown that the temperature and/or mass difference of both species could produce drift wave in a pair-ion plasma. The results are discussed in the context of the fullerene pair-ion plasma experiment.
Pair creation and plasma oscillations
International Nuclear Information System (INIS)
Prozorkevich, A. V.; Vinnik, D. V.; Schmidt, S. M.; Hecht, M. B.; Roberts, C. D.
2000-01-01
We describe aspects of particle creation in strong fields using a quantum kinetic equation with a relaxation-time approximation to the collision term. The strong electric background field is determined by solving Maxwell's equation in tandem with the Vlasov equation. Plasma oscillations appear as a result of feedback between the background field and the field generated by the particles produced. The plasma frequency depends on the strength of the initial background fields and the collision frequency, and is sensitive to the necessary momentum-dependence of dressed-parton masses
Indian Academy of Sciences (India)
of charged particles in electromagnetic fields. The linear and nonlinear collective modes in electron-positron plasma have been investigated theoretically [3–6]. Recently, Oohara and Hatakeyama [7] have developed a novel method for generating a pair plasma con- sisting of only negative and positive ions with equal mass ...
Plasma analog of particle-pair production
International Nuclear Information System (INIS)
Tsidulko, Yu.A.; Berk, H.L.
1996-09-01
It is shown that the plasma axial shear flow instability satisfies the Klein-Gordon equation. The plasma instability is then shown to be analogous to spontaneous particle-pair production when a potential energy is present that is greater than twice the particle rest mass energy. Stability criteria can be inferred based on field theoretical conservation laws
(RN) pair production by photons in a hot Maxwellian plasma
International Nuclear Information System (INIS)
Haug, E.
2004-01-01
The production of electron-positron pairs by photons in the Coulomb Field of electrons and positrons (triplet production) in hot thermal plasmas is investigated. The pair production rate for this process is calculated as a function of the photon energy and compared with the rate of photon-nucleus pair production for semi-relativistic and relativistic plasma temperatures. (author)
Perpendicular relativistic shocks in magnetized pair plasma
Plotnikov, Illya; Grassi, Anna; Grech, Mickael
2018-04-01
Perpendicular relativistic (γ0 = 10) shocks in magnetized pair plasmas are investigated using two dimensional Particle-in-Cell simulations. A systematic survey, from unmagnetized to strongly magnetized shocks, is presented accurately capturing the transition from Weibel-mediated to magnetic-reflection-shaped shocks. This transition is found to occur for upstream flow magnetizations 10-3 10-2, it leaves place to a purely electromagnetic precursor following from the strong emission of electromagnetic waves at the shock front. Particle acceleration is found to be efficient in weakly magnetized perpendicular shocks in agreement with previous works, and is fully suppressed for σ > 10-2. Diffusive Shock Acceleration is observed only in weakly magnetized shocks, while a dominant contribution of Shock Drift Acceleration is evidenced at intermediate magnetizations. The spatial diffusion coefficients are extracted from the simulations allowing for a deeper insight into the self-consistent particle kinematics and scale with the square of the particle energy in weakly magnetized shocks. These results have implications for particle acceleration in the internal shocks of AGN jets and in the termination shocks of Pulsar Wind Nebulae.
Tearing modes with pressure gradient effect in pair plasmas
International Nuclear Information System (INIS)
Cai Huishan; Li Ding; Zheng Jian
2009-01-01
The general dispersion relation of tearing mode with pressure gradient effect in pair plasmas is derived analytically. If the pressure gradients of positron and electron are not identical in pair plasmas, the pressure gradient has significant influence at tearing mode in both collisionless and collisional regimes. In collisionless regime, the effects of pressure gradient depend on its magnitude. For small pressure gradient, the growth rate of tearing mode is enhanced by pressure gradient. For large pressure gradient, the growth rate is reduced by pressure gradient. The tearing mode can even be stabilized if pressure gradient is large enough. In collisional regime, the growth rate of tearing mode is reduced by the pressure gradient. While the positron and electron have equal pressure gradient, tearing mode is not affected by pressure gradient in pair plasmas.
En route to matter-antimatter pair plasmas
Energy Technology Data Exchange (ETDEWEB)
Stenson, Eve V.; Hergenhahn, Uwe; Paschkowski, Norbert; Saitoh, Haruhiko; Stanja, Juliane [Max Planck Institute for Plasma Physics, Greifswald and Garching (Germany); Niemann, Holger; Sunn Pedersen, Thomas [Max Planck Institute for Plasma Physics, Greifswald and Garching (Germany); Ernst Moritz Arndt University of Greifswald, Greifswald (Germany); Schweikhard, Lutz [Ernst Moritz Arndt University of Greifswald, Greifswald (Germany); Hugenschmidt, Christoph [Technische Universitaet Muenchen, Garching (Germany); Danielson, James R.; Surko, Clifford M. [University of California, San Diego, La Jolla (United States)
2015-05-01
The APEX and PAX projects have as their overarching goal the laboratory creation and confinement of the world's first positron-electron pair plasma. Plasmas of this type have been the subject of hundreds of theoretical investigations and are also believed to play a role in various astrophysical environments. In order to achieve this goal in an experimentally accessible volume (e.g., 10 liters), a record number (≥ 10{sup 10}) of cold (∝ 1 eV) positrons are to be accumulated and combined with a corresponding population of electrons. Notable requirements include a high-intensity positron beam (such as NEPOMUC), a suitable magnetic confinement device for the pair plasma (such as a levitated dipole), high-efficiency tools for bridging the two (i.e., means by which the positrons can be efficiently cooled, trapped, and injected across flux surfaces), and diagnostics not only for the pair plasma, but also for the positron beam and for intermediary non-neutral plasmas. This talk will summarize the project as a whole and recent work by the APEX/PAX team on its various elements.
On the rogue wave propagation in ion pair superthermal plasma
Energy Technology Data Exchange (ETDEWEB)
Abdelwahed, H. G., E-mail: hgomaa-eg@yahoo.com, E-mail: hgomaa-eg@mans.edu.eg; Zahran, M. A. [Physics Department, College of Sciences and Humanities Studies Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj (Saudi Arabia); Theoretical Physics Group, Physics Department, Faculty of Science, Mansoura University, Mansoura (Egypt); El-Shewy, E. K., E-mail: emadshewy@yahoo.com; Elwakil, S. A. [Theoretical Physics Group, Physics Department, Faculty of Science, Mansoura University, Mansoura (Egypt)
2016-02-15
Effects of superthermal electron on the features of nonlinear acoustic waves in unmagnetized collisionless ion pair plasma with superthermal electrons have been examined. The system equations are reduced in the form of the nonlinear Schrodinger equation. The rogue wave characteristics dependences on the ionic density ratio (ν = n{sub –0}/n{sub +0}), ionic mass ratio (Q = m{sub +}/m{sub −}), and superthermality index (κ) are investigated. It is worth mentioning that the results present in this work could be applicable in the Earth's ionosphere plasmas.
Acoustic nonlinear periodic waves in pair-ion plasmas
Mahmood, Shahzad; Kaladze, Tamaz; Ur-Rehman, Hafeez
2013-09-01
Electrostatic acoustic nonlinear periodic (cnoidal) waves and solitons are investigated in unmagnetized pair-ion plasmas consisting of same mass and oppositely charged ion species with different temperatures. Using reductive perturbation method and appropriate boundary conditions, the Korteweg-de Vries (KdV) equation is derived. The analytical solutions of both cnoidal wave and soliton solutions are discussed in detail. The phase plane plots of cnoidal and soliton structures are shown. It is found that both compressive and rarefactive cnoidal wave and soliton structures are formed depending on the temperature ratio of positive and negative ions in pair-ion plasmas. In the special case, it is revealed that the amplitude of soliton may become larger than it is allowed by the nonlinear stationary wave theory which is equal to the quantum tunneling by particle through a potential barrier effect. The serious flaws in the earlier published results by Yadav et al., [PRE 52, 3045 (1995)] and Chawla and Misra [Phys. Plasmas 17, 102315 (2010)] of studying ion acoustic nonlinear periodic waves are also pointed out.
Spontaneous hole-clump pair creation in weakly unstable plasmas
International Nuclear Information System (INIS)
Berk, H.L.; Breizman, B.N.; Petviashvili, N.V.
1997-03-01
A numerical simulation of a kinetic instability near threshold shows how a hole and clump spontaneously appear in the particle distribution function. The hole and clump support a pair of Bernstein, Greene, Kruskal (BGK) nonlinear waves that last much longer than the inverse linear damping rate while they are upshifting and downshifting in frequency. The frequency shifting allows a balance between the power nonlinearly extracted from the resonant particles and the power dissipated into the background plasma. These waves eventually decay due to phase space gradient smoothing caused by collisionality
Progress toward the creation of magnetically confined pair plasmas
Energy Technology Data Exchange (ETDEWEB)
Saitoh, Haruhiko [Max-Planck-Institut fuer Plasmaphysik (Germany); The University of Tokyo (Japan); Hergenhahn, Uwe; Paschkowski, Norbert; Stanja, Juliane; Stenson, Eve V. [Max-Planck-Institut fuer Plasmaphysik (Germany); Niemann, Holger; Sunn Pedersen, Thomas [Max-Planck-Institut fuer Plasmaphysik (Germany); Ernst-Moritz-Arndt-Universitaet Greifswald (Germany); Stoneking, Matthew R. [Max-Planck-Institut fuer Plasmaphysik (Germany); Lawrence University (United States); Hugenschmidt, Christoph; Piochacz, Christian; Vohburger, Sebastian [Technische Universitaet Muenchen (Germany); Schweikhard, Lutz [Ernst-Moritz-Arndt-Universitaet Greifswald (Germany); Danielson, James R.; Surko, Clifford M. [University of California, San Diego (United States)
2016-07-01
The PAX (Positron Accumulation eXperiment) and APEX (A Positron Electron eXperiment) projects aim to experimentally study the unique wave propagation and stability properties of pair plasmas. We plan to accumulate a large number of positrons in a multicell-type trap system (PAX) and to confine them with electrons in APEX, a levitated dipole or stellarator configuration, operated at the NEPOMUC facility, the world's most intense positron source. In this contribution, we report on recent results from PAX and APEX. We have conducted electron experiments with a 2.3 T Penning-Malmberg trap; confinement for more than 1 hour and observation of a collective mode were demonstrated. At NEPOMUC, we have characterized the positron beam for a wide energy range. In a prototype permanent-magnet dipole trap, efficient (38%) injection of the remoderated 5 eV positron beam was realized using E x B drifts. Based on these results, design studies on the confinement of pair-plasmas in a levitated dipole trap are ongoing.
Drift waves and counter rotating vortices in pair-ion plasmas
Energy Technology Data Exchange (ETDEWEB)
Haque, Q., E-mail: qamar_haque@hotmail.co [Theoretical Plasma Physics Division, PINSTECH P.O. Nilore, Islamabad (Pakistan)
2010-07-19
Linear dispersion relation has been found for drift and acoustic waves in pair-ion-electron plasmas. The stationary solution in the form of counter rotating vortices has been obtained in the presence of equilibrium potential profile. It is noticed that the speed of nonlinear structures is reduced with the increase of electrons concentration in pair-ion plasmas. Linear instability condition has also been found in the presence of shear flow. It is pointed out that the present results can be useful for future pair-ion plasma experiments.
Nonlinear electrostatic structures in homogeneous and inhomogeneous pair-ion plasmas
International Nuclear Information System (INIS)
Mahmood, S.; Ur-Rehman, H.; Shah, A.; Haque, Q.
2012-01-01
The nonlinear electrostatic structures such as solitons, shocks were studied in homogeneous, unmagnetized pair-ion plasma. The dissipation in the system was taken through kinematic viscosities of both pair-ion species. The one dimensional (Korteweg-de Vries-Burgers) KdVB equation was derived using reductive perturbation method. The analytical solution of KdVB equation was obtained using tanh method. It was found that solitons and monotonic shocks structures were formed in such type of plasmas depending on the value of dissipation in the system. Both compressive and refractive structures of solitons and monotonic shocks were obtained depending on the temperatures of negative and positive ions. The oscillatory shock structures in pair-ion plasmas were also obtained and its necessary conditions of formation were discussed. The acoustic solitons were also investigated in inhomogeneous unmagnetized pair-ion plasmas. The Korteweg-de Vries (KdV) like equation with an additional term due to density gradients was obtained by employing the reductive perturbation technique. It was found that amplitude of both compressive and refractive solitons was found to be enhanced as the density gradient parameter was increased. The Landau damping rates of electrostatic ion waves were studied for non-Maxwellian or Lorentzian pair-ion plasmas. The Val sov equation was solved analytically for weak damping effects in pair-ion plasma. It was found that Landau damping rate of ion plasma wave was increased in Lorentzian case in comparison with Maxwellian pair-ion plasmas. The numerical results were obtained by taking into account the parameters of pair-ion plasmas produced in laboratory experiments in Japan. (orig./A.B.)
Electron-positron pair production in a hot accretion plasma around a massive black hole
International Nuclear Information System (INIS)
Takahara, Fumio; Kusunose, Masaaki.
1985-01-01
We investigate the electron-positron pair production in a hot accretion plasma around a supermassive black hole in connection with active galactic nuclei. Assuming that an optically thin two-temperature plasma is produced in the vicinity of the central black hole, we examine the condition for the significant pair production by comparing relevant time scales. Since the pair production is dominated by collisions between hard photons, the conditions for significant pair production depend on the production rate of hard photons. We examine the case where the unsaturated Comptonization of soft photons produces hard photons as well as that of bremsstrahlung. We show that significant pair production occurs for a moderately high accretion rate with relatively slow accretion flow as compared to the free fall velocity in both cases. Possible consequences of pair production are briefly discussed. (author)
Structure functions and pair correlations of the quark-gluon plasma
International Nuclear Information System (INIS)
Thoma, Markus H.
2005-01-01
Recent experiments at RHIC and theoretical considerations indicate that the quark-gluon plasma, present in the fireball of relativistic heavy-ion collisions, might be in a liquid phase. The liquid state can be identified by characteristic correlation and structure functions. Here definitions of the structure functions and pair correlations of the quark-gluon plasma are presented as well as perturbative results. These definitions might be useful for verifying the quark-gluon-plasma liquid in QCD lattice calculations
Modulation instability of ion thermal waves in a pair-ion plasma containing charged dust impurities
International Nuclear Information System (INIS)
Sabry, R.
2008-01-01
Modulation instability of ion thermal waves (ITWs) is investigated in a plasma composed of positive and negative ions as well as a fraction of stationary charged (positive or negative) dust impurities. For this purpose, a linear dispersion relation and a nonlinear Schroedinger equation are derived. The latter admits localized envelope solitary wave solutions of bright (pulses) and dark (holes, voids) type. The envelope soliton depends on the intrinsic plasma parameters. It is found that modulation instability of ITWs is significantly affected by the presence of positively/negatively charged dust grains. The findings of this investigation should be useful in understanding the stable electrostatic wave packet acceleration mechanisms in pair-ion plasma, and also enhances our knowledge on the occurrence of instability associated to the existence of charged dust impurities in pair-ion plasmas. Our results should be of relevance for laboratory plasmas.
Interesting features of nonlinear shock equations in dissipative pair-ion-electron plasmas
International Nuclear Information System (INIS)
Masood, W.; Rizvi, H.
2011-01-01
Two dimensional nonlinear electrostatic waves are studied in unmagnetized, dissipative pair-ion-electron plasmas in the presence of weak transverse perturbation. The dissipation in the system is taken into account by incorporating the kinematic viscosity of both positive and negative ions. In the linear case, a biquadratic dispersion relation is obtained, which yields the fast and slow modes in a pair-ion-electron plasma. It is shown that the limiting cases of electron-ion and pair-ion can be retrieved from the general biquadratic dispersion relation, and the differences in the characters of the waves propagating in both the cases are also highlighted. Using the small amplitude approximation method, the nonlinear Kadomtsev Petviashvili Burgers as well as Burgers-Kadomtsev Petviashvili equations are derived and their applicability for pair-ion-electron plasma is explained in detail. The present study may have relevance to understand the formation of two dimensional electrostatic shocks in laboratory produced pair-ion-electron plasmas.
Erratum: A Simple, Analytical Model of Collisionless Magnetic Reconnection in a Pair Plasma
Hesse, Michael; Zenitani, Seiji; Kuznetsova, Masha; Klimas, Alex
2011-01-01
The following describes a list of errata in our paper, "A simple, analytical model of collisionless magnetic reconnection in a pair plasma." It supersedes an earlier erratum. We recently discovered an error in the derivation of the outflow-to-inflow density ratio.
Finite temperature QCD corrections to lepton-pair formation in a quark-gluon plasma
International Nuclear Information System (INIS)
Altherr, T.
1989-02-01
We discuss the O(α S ) corrections to lepton-pair production in a quark-gluon plasma in equilibrium. The corrections are found to be very small in the domain of interest for ultrarelativistic heavy ions collisions. Interesting effects, however, appear at the annihilation threshold of the thermalized quarks
The energy of a moving quark-antiquark pair in an Script N = 4 SYM plasma
Chernicoff, Mariano; García, J. Antonio; Güijosa, Alberto
2006-09-01
We make use of the AdS/CFT correspondence to determine the energy of an external quark-antiquark pair that moves through strongly-coupled thermal Script N = 4 super-Yang-Mills plasma, both in the rest frame of the plasma and in the rest frame of the pair. It is found that the pair feels no drag force, has an energy that reproduces the expected 1/L (or γ/L) behavior at small quark-antiquark separations, and becomes unbound beyond a certain screening length whose velocity-dependence we determine. We discuss the relation between the high-velocity limit of our results and the lightlike Wilson loop proposed recently as a definition of the jet-quenching parameter.
Kinetics of electron-positron pair plasmas using an adaptive Monte Carlo method
International Nuclear Information System (INIS)
Pilla, R.P.; Shaham, J.
1997-01-01
A new algorithm for implementing the adaptive Monte Carlo method is given. It is used to solve the Boltzmann equations that describe the time evolution of a nonequilibrium electron-positron pair plasma containing high-energy photons. These are coupled nonlinear integro-differential equations. The collision kernels for the photons as well as pairs are evaluated for Compton scattering, pair annihilation and creation, bremsstrahlung, and Coulomb collisions. They are given as multidimensional integrals which are valid for all energies. For an homogeneous and isotropic plasma with no particle escape, the equilibrium solution is expressed analytically in terms of the initial conditions. For two specific cases, for which the photon and the pair spectra are initially constant or have a power-law distribution within the given limits, the time evolution of the plasma is analyzed using the new method. The final spectra are found to be in a good agreement with the analytical solutions. The new algorithm is faster than the Monte Carlo scheme based on uniform sampling and more flexible than the numerical methods used in the past, which do not involve Monte Carlo sampling. It is also found to be very stable. Some astrophysical applications of this technique are discussed. copyright 1997 The American Astronomical Society
A new purely growing instability in a strongly magnetized nonuniform pair plasma
International Nuclear Information System (INIS)
Shukla, Nitin; Shukla, P.K.
2007-01-01
It is shown that a strongly magnetized nonuniform electron-positron (hereafter referred to as e-p or pair) plasma is unstable against low-frequency (in comparison with the electron gyrofrequency) electrostatic oscillations. For this purpose, a dispersion relation is derived by using the Poisson equation as well as the electron and positron continuity equations with the guiding center drifts for the electron and positron fluids. The dispersion relation admits a purely growing instability in the presence of the equilibrium density and magnetic field inhomogeneities. Physically, instability arises because of the inhomogeneous magnetic field induced differential electron and positron density fluctuations, which do not keep in phase with the electrostatic potential arising from the charge separation in our nonuniform pair plasmas
Ion acoustic waves in pair-ion plasma: Linear and nonlinear analyses
International Nuclear Information System (INIS)
Saeed, R.; Mushtaq, A.
2009-01-01
Linear and nonlinear properties of low frequency ion acoustic wave (IAW) in pair-ion plasma in the presence of electrons are investigated. The dispersion relation and Kadomtsev-Petviashvili equation for linear/nonlinear IAW are derived from sets of hydrodynamic equations where the ion pairs are inertial while electrons are Boltzmannian. The dispersion curves for various concentrations of electrons are discussed and compared with experimental results. The predicted linear IAW propagates at the same frequencies as those of the experimentally observed IAW if n e0 ∼10 4 cm -3 . It is found that nonlinear profile of the ion acoustic solitary waves is significantly affected by the percentage ratio of electron number density and temperature. It is also determined that rarefactive solitary waves can propagate in this system. It is hoped that the results presented in this study would be helpful in understanding the salient features of the finite amplitude localized ion acoustic solitary pulses in a laboratory fullerene plasma.
A simple, analytical model of collisionless magnetic reconnection in a pair plasma
International Nuclear Information System (INIS)
Hesse, Michael; Zenitani, Seiji; Kuznetsova, Masha; Klimas, Alex
2009-01-01
A set of conservation equations is utilized to derive balance equations in the reconnection diffusion region of a symmetric pair plasma. The reconnection electric field is assumed to have the function to maintain the current density in the diffusion region and to impart thermal energy to the plasma by means of quasiviscous dissipation. Using these assumptions it is possible to derive a simple set of equations for diffusion region parameters in dependence on inflow conditions and on plasma compressibility. These equations are solved by means of a simple, iterative procedure. The solutions show expected features such as dominance of enthalpy flux in the reconnection outflow, as well as combination of adiabatic and quasiviscous heating. Furthermore, the model predicts a maximum reconnection electric field of E * =0.4, normalized to the parameters at the inflow edge of the diffusion region.
A Simple, Analytical Model of Collisionless Magnetic Reconnection in a Pair Plasma
Hesse, Michael; Zenitani, Seiji; Kuznetova, Masha; Klimas, Alex
2011-01-01
A set of conservation equations is utilized to derive balance equations in the reconnection diffusion region of a symmetric pair plasma. The reconnection electric field is assumed to have the function to maintain the current density in the diffusion region, and to impart thermal energy to the plasma by means of quasi-viscous dissipation. Using these assumptions it is possible to derive a simple set of equations for diffusion region parameters in dependence on inflow conditions and on plasma compressibility. These equations are solved by means of a simple, iterative, procedure. The solutions show expected features such as dominance of enthalpy flux in the reconnection outflow, as well as combination of adiabatic and quasi-viscous heating. Furthermore, the model predicts a maximum reconnection electric field of E(sup *)=0.4, normalized to the parameters at the inflow edge of the diffusion region.
Ion Streaming Instabilities in Pair Ion Plasma and Localized Structure with Non-Thermal Electrons
Nasir Khattak, M.; Mushtaq, A.; Qamar, A.
2015-12-01
Pair ion plasma with a fraction of non-thermal electrons is considered. We investigate the effects of the streaming motion of ions on linear and nonlinear properties of unmagnetized, collisionless plasma by using the fluid model. A dispersion relation is derived, and the growth rate of streaming instabilities with effect of streaming motion of ions and non-thermal electrons is calculated. A qausi-potential approach is adopted to study the characteristics of ion acoustic solitons. An energy integral equation involving Sagdeev potential is derived during this process. The presence of the streaming term in the energy integral equation affects the structure of the solitary waves significantly along with non-thermal electrons. Possible application of the work to the space and laboratory plasmas are highlighted.
Ion streaming instabilities in pair ion plasma and localized structure with non-thermal electrons
Energy Technology Data Exchange (ETDEWEB)
Khattak, M. Nasir; Qamar, A., E-mail: mnnasirphysics@gmail.com [Department of Physics, University of Peshawar (Pakistan); Mushtaq, A. [Department of Physics, Abdul Wali Khan University Mardan, National Center for Physics, Mardan (Pakistan)
2015-12-15
Pair ion plasma with a fraction of non-thermal electrons is considered. We investigate the effects of the streaming motion of ions on linear and nonlinear properties of unmagnetized, collisionless plasma by using the fluid model. A dispersion relation is derived, and the growth rate of streaming instabilities with effect of streaming motion of ions and non-thermal electrons is calculated. A quasi-potential approach is adopted to study the characteristics of ion acoustic solitons. An energy integral equation involving Sagdeev potential is derived during this process. The presence of the streaming term in the energy integral equation affects the structure of the solitary waves significantly along with non-thermal electrons. Possible application of the work to the space and laboratory plasmas are highlighted. (author)
Therapeutic plasma exchange: a paired comparison of Fresenius AS104 vs. COBE Spectra.
Burgstaler, E A; Pineda, A A
2001-01-01
For therapeutic plasma exchange (TPE), continuous flow separators are known to be efficient as exemplified by Fresenius AS104 and COBE Spectra. The AS104 uses an interface monitoring system in the centrifuge during TPE, whereas Spectra uses computer algorithms to establish the plasma-cell interface. To determine the plasma collection efficiency (PLCE), anticoagulant (AC) volumes used, and platelets (PLT) lost of the AS104 and the Spectra, we performed a prospective paired comparison of 20 TPE (each machine). The study included 17 patients, 1.3 plasma volume exchanges (without AC), equal inlet rates, and AC ratio of 13:1. Processing times did not include reinfuse mode. Platelet loss was determined by sampling the collection bags. Inlet rates were between 60-110 ml/min. Diagnosis included peripheral neuropathies, TTP and cryoglobulinemia. The AS104 had significantly (P<0.0001) lower average whole blood processed (F:6,601 vs. S:8,584 ml), AC volume (F:532 vs. S:719 ml), and processing time (F:80 vs. S:102 minutes) than Spectra. The AS104 had significantly (P<0.0001) higher average plasma flow rates (F:53 vs. S:44 ml/minute), plasma collection efficiency (F:90 vs. S:69%), and platelet loss (F:2.0 vs. S:0.14 x 10(11) plt) than Spectra. Platelet loss correlated with inlet flow rate with the AS104 but not with the Spectra. The AS104 has a significantly higher collection efficiency than Spectra allowing it to remove the same amount of plasma in significantly less time, by processing significantly less blood, using significantly less AC, but removing significantly more platelets than Spectra. Copyright 2001 Wiley-Liss, Inc.
International Nuclear Information System (INIS)
Boehm, H.M.; Conti, S.; Tosi, M.P.
1995-11-01
Electron energy loss experiments have shown a rapid softening of the bulk plasmon dispersion across the series of the alkali metals. Motivated by these observations, we reconsider the evaluation of the dynamic, long-wavelength exchange-correlation potential f xc (ω) in the electron fluid, which is of interest for applications in time-dependent density functional theory. The value of Re[f xc (ω pl )] at the plasma frequency ω pl determines the exchange-correlation contribution to the leading plasmon dispersion coefficient in the homogeneous electron fluid. Whereas an interpolation scheme originally proposed by Gross and Kohn assumes a monotonic increase of Re[f xc (ω) - f xc (0)] across the plasma frequency, we examine the possibility of strongly non-monotonic behaviour arising from a resonance process between plasmons and two-pair excitations. This process is evaluated with the help of sum rules and selfconsistency requirements with a single-pole approximation of the dielectric function. The cases of a fermion plasma and of a boson plasma are treated in parallel and the reliability of the results for the fermion plasma at low coupling is tested by calculations within a random phase approximation for the dielectric function. In all cases it is found that the resonance process accumulates oscillator strength in the neighbourhood of 2ω pl , thus decreasing the value of Re[f xc (ω pl )] below the static value f xc (0) fixed by the compressibility sum rule. Although this lowering does not suffice to account by itself for the measured plasmon dispersion coefficient in the low-density alkali metals, our results provide useful input for combined band-structure and exchange-correlation calculations. (author). 40 refs, 9 figs, 2 tabs
A stability analysis of electron-positron pair equilibria of a two-temperature plasma cloud
Energy Technology Data Exchange (ETDEWEB)
Sikora, M [Colorado Univ., Boulder, CO (USA); Zbyszewska, M [Polska Akademia Nauk, Warsaw (Poland). Centrum Astronomiczne
1986-01-01
The stability of a two-temperature homogeneous static plasma cloud against pair density perturbations is examined. We assumed that the electrons and positrons, cooled via radiation process, are reheated via Coulomb interactions with much hotter protons. Pair equilibrium plasma states are shown to be unstable if deltan{sub e}/deltan{sub p}<0 and deltan{sub e}/deltaT{sub p}<0 on the equilibrium surface n{sub e}{sup eq}(n{sub p},T{sub p}), where n{sub e}=n{sub +}+n{sub -}, n{sub p} and T{sub p} denote electron plus positron density, proton density and proton temperature, respectively. The minimum proton temperature and maximum proton density for which unstable states can appear are: (kT{sub p}){sub min} approx few x m{sub e}c{sup 2} and (n{sub p}){sub max} approx few/Rsigma{sub T}, where R is the plasma cloud radius. We discuss our results in the context of an accreting black hole model assuming that the proton temperature is close to its virial value, kT{sub p}{sup vir} approx GMm{sub p}/R and that subsonic accretion flow is realized at R < tens Schwarzschild radii. The unstable states then correspond to the luminosity range 0.01 L{sub Edd}
International Nuclear Information System (INIS)
Shah, Asif; Mahmood, S.; Haque, Q.
2011-01-01
The quantity n p0 (0) is different from n p0 (x) and same is true for v p0 (0), v p0 (x). Taking these differences into account and considering the mathematical relation v p0 (x)= 1/n p0 (x), it can easily be shown that derivatives of these space dependent densities and velocities are linked through the relation ∂v p0 (x)/∂η=-1/n p0 2 (x)∂n p0 (x)/∂η. We show that constraint (1) of the comment can also be transformed to derivative transformation relation. This derivative transformation relation can be used in the derivation of the KdV like equation and our model is valid for inhomogenous pair ion plasma. We mathematically and physically prove that the objections in the comment are false and baseless.
Oblique non-neutral solitary Alfven modes in weakly nonlinear pair plasmas
International Nuclear Information System (INIS)
Verheest, Frank; Lakhina, G S
2005-01-01
The equal charge-to-mass ratio for both species in pair plasmas induces a decoupling of the linear eigenmodes between waves that are charge neutral or non-neutral, also at oblique propagation with respect to a static magnetic field. While the charge-neutral linear modes have been studied in greater detail, including their weakly and strongly nonlinear counterparts, the non-neutral mode has received less attention. Here the nonlinear evolution of a solitary non-neutral mode at oblique propagation is investigated in an electron-positron plasma. Employing the framework of reductive perturbation analysis, a modified Korteweg-de Vries equation (with cubic nonlinearity) for the lowest-order wave magnetic field is obtained. In the linear approximation, the non-neutral mode has its magnetic component orthogonal to the plane spanned by the directions of wave propagation and of the static magnetic field. The linear polarization is not maintained at higher orders. The results may be relevant to the microstructure in pulsar radiation or to the subpulses
Razzaq, Javaria; Haque, Q.; Khan, Majid; Bhatti, Adnan Mehmood; Kamran, M.; Mirza, Arshad M.
2018-02-01
Nonlinear structure formation in ion-temperature-gradient (ITG) driven waves is investigated in pair-ion plasma comprising ions and nonthermal electrons (kappa, Cairns). By using the transport equations of the Braginskii model, a new set of nonlinear equations are derived. A linear dispersion relation is obtained and discussed analytically as well as numerically. It is shown that the nonthermal population of electrons affects both the linear and nonlinear characteristics of the ITG mode in pair-ion plasma. This work will be useful in tokamaks and stellarators where non-Maxwellian population of electrons may exist due to resonant frequency heating, electron cyclotron heating, runaway electrons, etc.
Zhdankin, Vladimir; Uzdensky, Dmitri A.; Werner, Gregory R.; Begelman, Mitchell C.
2018-02-01
We describe results from particle-in-cell simulations of driven turbulence in collisionless, magnetized, relativistic pair plasma. This physical regime provides a simple setting for investigating the basic properties of kinetic turbulence and is relevant for high-energy astrophysical systems such as pulsar wind nebulae and astrophysical jets. In this paper, we investigate the statistics of turbulent fluctuations in simulations on lattices of up to 10243 cells and containing up to 2 × 1011 particles. Due to the absence of a cooling mechanism in our simulations, turbulent energy dissipation reduces the magnetization parameter to order unity within a few dynamical times, causing turbulent motions to become sub-relativistic. In the developed stage, our results agree with predictions from magnetohydrodynamic turbulence phenomenology at inertial-range scales, including a power-law magnetic energy spectrum with index near -5/3, scale-dependent anisotropy of fluctuations described by critical balance, lognormal distributions for particle density and internal energy density (related by a 4/3 adiabatic index, as predicted for an ultra-relativistic ideal gas), and the presence of intermittency. We also present possible signatures of a kinetic cascade by measuring power-law spectra for the magnetic, electric and density fluctuations at sub-Larmor scales.
International Nuclear Information System (INIS)
Sakai, J.I.; Haruki, T.; Kazimura, Y.
2000-01-01
It is shown by using a 2-D fully relativistic electromagnetic particle-in-cell (PIC) code that the tearing instability in a current sheet of pair plasmas is caused by Landau resonances of both electrons and positrons. Strong magnetic flux can be generated during coalescence of magnetic islands in the nonlinear phase of the tearing instability. The magnetic flux produced in an O-type magnetic island is caused from the counter-streaming instability found by Kazimura et al. (1998). It is also shown that charge separation with a quadrupole-like structure is generated from the localized strong magnetic flux. During the decay of the quadrupole-like charge structure as well as the magnetic flux, there appear wave emission with high-frequency electromagnetic waves and Alfven waves as well as Langmuir waves. We also show by using a 3-D PIC code that current filaments associated with the O-type magnetic islands become unstable against the kink instability during the coalescence of current filaments. (orig.)
Gyro-viscosity and linear dispersion relations in pair-ion magnetized plasmas
Energy Technology Data Exchange (ETDEWEB)
Kono, M. [Faculty of Policy Studies, Chuo University, Tokyo 192-0393 (Japan); Vranjes, J. [Instituto de Astrofisica de Canarias, Tenerife E38205 (Spain); Departamento de Astrofisica, Universidad de La Laguna, Tenerife E38205 (Spain)
2015-11-15
A fluid theory has been developed by taking account of gyro-viscosity to study wave propagation characteristics in a homogeneous pair-ion magnetized plasma with a cylindrical symmetry. The exact dispersion relations derived by the Hankel-Fourier transformation are shown comparable with those observed in the experiment by Oohara and co-workers. The gyro-viscosity is responsible for the change in propagation characteristics of the ion cyclotron wave from forward to backward by suppressing the effect of the thermal pressure which normally causes the forward nature of dispersion. Although the experiment has been already explained by a kinetic theory by the present authors, the kinetic derivations are so involved because of exact particle orbits in phase space, finite Lamor radius effects, and higher order ion cyclotron resonances. The present fluid theory provides a simple and transparent structure to the dispersion relations since the gyro-viscosity is renormalized into the ion cyclotron frequency which itself indicates the backward nature of dispersion. The usual disadvantage of a fluid theory, which treats only fundamental modes of eigen-waves excited in a system and is not able to describe higher harmonics that a kinetic theory does, is compensated by simple derivations and clear picture based on the renormalization of the gyro-viscosity.
International Nuclear Information System (INIS)
Schlickeiser, R.; Krakau, S.; Supsar, M.
2013-01-01
The interaction of TeV gamma-rays from distant blazars with the extragalactic background light produces relativistic electron-positron pair beams by the photon-photon annihilation process. Using the linear instability analysis in the kinetic limit, which properly accounts for the longitudinal and the small but finite perpendicular momentum spread in the pair momentum distribution function, the growth rate of parallel propagating electrostatic oscillations in the intergalactic medium is calculated. Contrary to the claims of Miniati and Elyiv, we find that neither the longitudinal nor the perpendicular spread in the relativistic pair distribution function significantly affect the electrostatic growth rates. The maximum kinetic growth rate for no perpendicular spread is even about an order of magnitude greater than the corresponding reactive maximum growth rate. The reduction factors in the maximum growth rate due to the finite perpendicular spread in the pair distribution function are tiny and always less than 10 –4 . We confirm earlier conclusions by Broderick et al. and our group that the created pair beam distribution function is quickly unstable in the unmagnetized intergalactic medium. Therefore, there is no need to require the existence of small intergalactic magnetic fields to scatter the produced pairs, so that the explanation (made by several authors) for the Fermi non-detection of the inverse Compton scattered GeV gamma-rays by a finite deflecting intergalactic magnetic field is not necessary. In particular, the various derived lower bounds for the intergalactic magnetic fields are invalid due to the pair beam instability argument
Nonthermal Particle Acceleration in 3D Relativistic Magnetic Reconnection in Pair Plasma
Energy Technology Data Exchange (ETDEWEB)
Werner, Gregory R.; Uzdensky, Dmitri A., E-mail: Greg.Werner@colorado.edu [Center for Integrated Plasma Studies, Physics Department, University of Colorado, 390 UCB, Boulder, CO 80309 (United States)
2017-07-10
As a fundamental process converting magnetic to plasma energy in high-energy astrophysical plasmas, relativistic magnetic reconnection is a leading explanation for the acceleration of particles to the ultrarelativistic energies that are necessary to power nonthermal emission (especially X-rays and gamma-rays) in pulsar magnetospheres and pulsar wind nebulae, coronae and jets of accreting black holes, and gamma-ray bursts. An important objective of plasma astrophysics is therefore the characterization of nonthermal particle acceleration (NTPA) effected by reconnection. Reconnection-powered NTPA has been demonstrated over a wide range of physical conditions using large 2D kinetic simulations. However, its robustness in realistic 3D reconnection—in particular, whether the 3D relativistic drift-kink instability (RDKI) disrupts NTPA—has not been systematically investigated, although pioneering 3D simulations have observed NTPA in isolated cases. Here, we present the first comprehensive study of NTPA in 3D relativistic reconnection in collisionless electron–positron plasmas, characterizing NTPA as the strength of 3D effects is varied systematically via the length in the third dimension and the strength of the guide magnetic field. We find that, while the RDKI prominently perturbs 3D reconnecting current sheets, it does not suppress particle acceleration, even for zero guide field; fully 3D reconnection robustly and efficiently produces nonthermal power-law particle spectra closely resembling those obtained in 2D. This finding provides strong support for reconnection as the key mechanism powering high-energy flares in various astrophysical systems. We also show that strong guide fields significantly inhibit NTPA, slowing reconnection and limiting the energy available for plasma energization, yielding steeper and shorter power-law spectra.
Kinetic theory for radiation interacting with sound waves in ultrarelativistic pair plasmas
International Nuclear Information System (INIS)
Marklund, Mattias; Shukla, Padma K.; Stenflo, Lennart
2006-01-01
A kinetic theory for radiation interacting with sound waves in an ultrarelativistic electron-positron plasma is developed. It is shown that the effect of a spatial spectral broadening of the electromagnetic pulse is to introduce a reduction of the growth rates for the decay and modulational instabilities. Such spectral broadening could be due to a finite pulse coherence length, or through the use of random phase filters, and would stabilize the propagation of electromagnetic pulses
First on-line positron experiments en route to pair-plasma creation
Energy Technology Data Exchange (ETDEWEB)
Stanja, Juliane; Hergenhahn, Uwe; Stenson, Eve V. [Max-Planck-Institut fuer Plasmaphysik (Germany); Niemann, Holger; Sunn Pedersen, Thomas [Max-Planck-Institut fuer Plasmaphysik (Germany); Ernst-Moritz-Arndt Universitaet Greifswald (Germany); Saitoh, Haruhiko [Max-Planck-Institut fuer Plasmaphysik (Germany); The University of Tokyo (Japan); Stoneking, Matthew R. [Lawrence University (United States); Hugenschmidt, Christoph; Piochacz, Christian [Technische Universitaet Muenchen (Germany); Schweikhard, Lutz [Ernst-Moritz-Arndt Universitaet Greifswald (Germany)
2016-07-01
Electron-positron plasmas are predicted to show a fundamentally different behavior from traditional ion-electron plasmas, because of the equal masses of the two species. Using up to 10{sup 9} positrons per second provided by the NEPOMUC (Neutron-Induced Positron Source Munich) facility, the APEX/PAX team aims to create the first such plasma confined in a toroidal magnetic trap. Positron beam parameters as well as efficient injection and confinement schemes for both species in toroidal geometries are fundamental to the project. In this contribution we present results from first on-line positron experiments. Besides characterizing the NEPOMUC beam we conducted positron injection experiments into a dipole magnetic field configuration. Using static electric fields, a 5-eV positron beam was transported across magnetic field lines into the confinement region. With this method, up to 38% of the incoming particles reach the confinement region and make at least a 180 revolution around the magnet. Under dedicated experimental conditions confinement on the order of 1 ms was realized.
Meng, Xuanshi; Long, Yuexiao; Wang, Jianlei; Liu, Feng; Luo, Shijun
2018-02-01
Detailed particle-image-velocimetry (PIV) and surface pressure measurements are presented to study the vortex flow behind a slender conical forebody at high angles of attack. The results confirm the existence of two randomly appearing mirror imaged asymmetric bi-stable states of the separation vortices, giving rise to large side force and moment. A pair of carefully designed dielectric barrier discharge plasma actuators mounted near the apex and on both sides of the conical body are used to manipulate the vortex flow and thus provide control of the side forces on the body without using flaps. By making use of a duty-cycle actuation scheme that alternately actuates the port and starboard plasma actuators and optimizing the duty-cycle frequency, the present work demonstrates the feasibility of achieving a nearly perfect linear proportional control of the side force and moment in response to the duty-cycle ratio. Phase-locked PIV and surface pressure measurements are used to study the unsteady dynamic evolution of the flow within one duty-cycle actuation to reveal the flow control mechanism. It is found that under the duty-cycle actuation with the optimized frequency, the vortex flow essentially follows the plasma actuation by alternating between the two bi-stable states controlled directly by the duty-cycle ratio.
Dust ion-acoustic shock waves in magnetized pair-ion plasma with kappa distributed electrons
Kaur, B.; Singh, M.; Saini, N. S.
2018-01-01
We have performed a theoretical and numerical analysis of the three dimensional dynamics of nonlinear dust ion-acoustic shock waves (DIASWs) in a magnetized plasma, consisting of positive and negative ion fluids, kappa distributed electrons, immobile dust particulates along with positive and negative ion kinematic viscosity. By employing the reductive perturbation technique, we have derived the nonlinear Zakharov-Kuznetsov-Burgers (ZKB) equation, in which the nonlinear forces are balanced by dissipative forces (associated with kinematic viscosity). It is observed that the characteristics of DIASWs are significantly affected by superthermality of electrons, magnetic field strength, direction cosines, dust concentration, positive to negative ions mass ratio and viscosity of positive and negative ions.
International Nuclear Information System (INIS)
Altherr, T.
1989-12-01
The main topic of this thesis is a perturbative study of Quantum Field Theory at Finite Temperature. The real-time formalism is used throughout this work. We show the cancellation of infrared and mass singularities in the case of the first order QCD corrections to lepton pair production from a quark-gluon plasma. Two methods of calculation are presented and give the same finite result in the limit of vanishing quark mass. These finite terms are analysed and give small corrections in the region of interest for ultra-relativistic heavy ions collisions, except for a threshold factor. Specific techniques for finite temperature calculations are explicited in the case of the fermionic self-energy in QED [fr
Three-dimensional relativistic pair plasma reconnection with radiative feedback in the Crab Nebula
Energy Technology Data Exchange (ETDEWEB)
Cerutti, B. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Werner, G. R.; Uzdensky, D. A. [Center for Integrated Plasma Studies, Physics Department, University of Colorado, UCB 390, Boulder, CO 80309-0390 (United States); Begelman, M. C., E-mail: bcerutti@astro.princeton.edu, E-mail: greg.werner@colorado.edu, E-mail: uzdensky@colorado.edu, E-mail: mitch@jila.colorado.edu [JILA, University of Colorado and National Institute of Standards and Technology, UCB 440, Boulder, CO 80309-0440 (United States)
2014-02-20
The discovery of rapid synchrotron gamma-ray flares above 100 MeV from the Crab Nebula has attracted new interest in alternative particle acceleration mechanisms in pulsar wind nebulae. Diffuse shock-acceleration fails to explain the flares because particle acceleration and emission occur during a single or even sub-Larmor timescale. In this regime, the synchrotron energy losses induce a drag force on the particle motion that balances the electric acceleration and prevents the emission of synchrotron radiation above 160 MeV. Previous analytical studies and two-dimensional (2D) particle-in-cell (PIC) simulations indicate that relativistic reconnection is a viable mechanism to circumvent the above difficulties. The reconnection electric field localized at X-points linearly accelerates particles with little radiative energy losses. In this paper, we check whether this mechanism survives in three dimension (3D), using a set of large PIC simulations with radiation reaction force and with a guide field. In agreement with earlier works, we find that the relativistic drift kink instability deforms and then disrupts the layer, resulting in significant plasma heating but few non-thermal particles. A moderate guide field stabilizes the layer and enables particle acceleration. We report that 3D magnetic reconnection can accelerate particles above the standard radiation reaction limit, although the effect is less pronounced than in 2D with no guide field. We confirm that the highest-energy particles form compact bunches within magnetic flux ropes, and a beam tightly confined within the reconnection layer, which could result in the observed Crab flares when, by chance, the beam crosses our line of sight.
Directory of Open Access Journals (Sweden)
Cristina Yubero
2017-10-01
Full Text Available The spectroscopic method for gas temperature determination in argon non-thermal plasmas sustained at atmospheric pressure proposed recently by Spectrochimica Acta Part B 129 14 (2017—based on collisional broadening measurements of selected pairs of argon atomic lines, has been applied to other pairs of argon atomic lines, and the discrepancies found in some of these results have been analyzed. For validation purposes, the values of the gas temperature obtained using the different pairs of lines have been compared with the rotational temperatures derived from the OH ro-vibrational bands, using the Boltzmann-plot technique.
DEFF Research Database (Denmark)
Frederiksen, Marie; Thomsen, Cathrine; Frøshaug, May
2010-01-01
determined in placental tissue from the same individuals, and the relationship with the external exposure from house dust from the participants' homes was explored. Samples of maternal and umbilical cord plasma from a cohort of 51 pregnant women from the Copenhagen area were collected. Paired maternal...... and umbilical cord plasma were analysed for BDE-28, 37, 47, 85, 99, 100, 119, 138, 153, 154, 183, 209 and the brominated biphenyl BB-153 using automated SPE extraction and GC-HRMS for the tri- to hepta-BDEs and GC-LRMS (ECNI) for BDE-209. PBDEs were detected in all maternal and umbilical cord plasma samples...
Energy Technology Data Exchange (ETDEWEB)
Guo, Ruilong; Xie, Lun; He, Jiansen [School of Earth and Space Sciences, Peking University, Beijing 100871 (China); Pu, Zuyin; Fu, Suiyan [School of Earth and Space Sciences, Peking University, Beijing 100871 (China); PKU/UCLA Joint Research Institute in Science and Engineering, Peking University, Beijing (China); Chen, Li-Jen [NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States); Wang, Xiaogang [Harbin Institute of Technology, Harbin 150001 (China); Dunlop, Malcolm [School of Astronautics, Beihang University, Beijing 100191 (China); RAL Space, Rutherford Appleton Laboratory, STFC, Didcot OX11 0QX (United Kingdom); Bogdanova, Yulia V. [RAL Space, Rutherford Appleton Laboratory, STFC, Didcot OX11 0QX (United Kingdom); Yao, Zhonghua; Fazakerley, Andrew N. [UCL Mullard Space Science Laboratory, Dorking RH5 6NT (United Kingdom); Xiao, Chijie [School of Physics, Peking University, Beijing 100871 (China)
2016-05-15
Signatures of secondary islands are frequently observed in the magnetic reconnection regions of magnetotail plasmas. In this paper, magnetic structures with the secondary-island signatures observed by Cluster are reassembled by a fitting-reconstruction method. The results show three-dimensionally that a secondary island event can manifest the flux rope formed with an A{sub s}-type null and a B{sub s}-type null paired via their spines. We call this A{sub s}-spine-B{sub s}-like configuration the helically wrapped spine model. The reconstructed field lines wrap around the spine to form the flux rope, and an O-type topology is therefore seen on the plane perpendicular to the spine. Magnetized electrons are found to rotate on and cross the fan surface, suggesting that both the torsional-spine and the spine-fan reconnection take place in the configuration. Furthermore, detailed analysis implies that the spiral nulls and flux ropes were locally generated nearby the spacecraft in the reconnection outflow region, indicating that secondary reconnection may occur in the exhaust away from the primary reconnection site.
International Nuclear Information System (INIS)
Guo, Ruilong; Xie, Lun; He, Jiansen; Pu, Zuyin; Fu, Suiyan; Chen, Li-Jen; Wang, Xiaogang; Dunlop, Malcolm; Bogdanova, Yulia V.; Yao, Zhonghua; Fazakerley, Andrew N.; Xiao, Chijie
2016-01-01
Signatures of secondary islands are frequently observed in the magnetic reconnection regions of magnetotail plasmas. In this paper, magnetic structures with the secondary-island signatures observed by Cluster are reassembled by a fitting-reconstruction method. The results show three-dimensionally that a secondary island event can manifest the flux rope formed with an A_s-type null and a B_s-type null paired via their spines. We call this A_s-spine-B_s-like configuration the helically wrapped spine model. The reconstructed field lines wrap around the spine to form the flux rope, and an O-type topology is therefore seen on the plane perpendicular to the spine. Magnetized electrons are found to rotate on and cross the fan surface, suggesting that both the torsional-spine and the spine-fan reconnection take place in the configuration. Furthermore, detailed analysis implies that the spiral nulls and flux ropes were locally generated nearby the spacecraft in the reconnection outflow region, indicating that secondary reconnection may occur in the exhaust away from the primary reconnection site.
Heydari, Rouhollah; Elyasi, Najmeh S
2014-10-01
A novel, simple, and effective ion-pair cloud-point extraction coupled with a gradient high-performance liquid chromatography method was developed for determination of thiamine (vitamin B1 ), niacinamide (vitamin B3 ), pyridoxine (vitamin B6 ), and riboflavin (vitamin B2 ) in plasma and urine samples. The extraction and separation of vitamins were achieved based on an ion-pair formation approach between these ionizable analytes and 1-heptanesulfonic acid sodium salt as an ion-pairing agent. Influential variables on the ion-pair cloud-point extraction efficiency, such as the ion-pairing agent concentration, ionic strength, pH, volume of Triton X-100, extraction temperature, and incubation time have been fully evaluated and optimized. Water-soluble vitamins were successfully extracted by 1-heptanesulfonic acid sodium salt (0.2% w/v) as ion-pairing agent with Triton X-100 (4% w/v) as surfactant phase at 50°C for 10 min. The calibration curves showed good linearity (r(2) > 0.9916) and precision in the concentration ranges of 1-50 μg/mL for thiamine and niacinamide, 5-100 μg/mL for pyridoxine, and 0.5-20 μg/mL for riboflavin. The recoveries were in the range of 78.0-88.0% with relative standard deviations ranging from 6.2 to 8.2%. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
International Nuclear Information System (INIS)
Lin Xiaodong
2000-01-01
Making use of a Fabry-Perot interferometer driven by a piezoelectric crystal and selecting the suitable separation of plates, the ion temperature is defined by measuring the superimposed profile of the spectral line pair of the same ionized state ions in Tokamak. The advantage of this method is to higher spectral resolution and wider spectral range select
Peters, S.; Kaal, E.; Horsting, I.; Janssen, H.-G.
2012-01-01
A new method is presented for the analysis of phenolic acids in plasma based on ion-pairing ‘Micro-extraction in packed sorbent’ (MEPS) coupled on-line to in-liner derivatisation-gas chromatography-mass spectrometry (GC-MS). The ion-pairing reagent served a dual purpose. It was used both to improve
Wang, Rui; Chu, Yanle; Li, Xiaotian; Wan, Baoluo; Yu, Tong; Wang, Linxi; Hao, Lianqi; Guo, Maowen
2013-12-01
A reversed-phase ion pair chromatography method with liquid-liquid extraction analytical method was developed and validated for the determination of antazoline hydrochloride in plasma and excreta of rat. The aim of our study was to characterize the preclinical pharmacokinetics and excretion profiles of antazoline hydrochloride in rats after intravenous injection at the dose of 10 mg/kg. Plasma and excreta samples were extracted with ethyl acetate, and phenacetin was used as the internal standard. The result showed that the method is suitable for the quantification of antazoline hydrochloride in plasma and excreta samples. Analysis of accuracy (90.89-112.33%), imprecision (82.5%) showed adequate values. After a single intravenous administration at 10 mg/kg to rats, plasma concentration profile showed a relative fast elimination proceeding with a terminal elimination half-life of 3.53 h. Approximately 61.8 and 14.2% of the administered dose were recovered in urine and bile after 72 and 24 h post-dosing respectively; 5.9% of the administered dose was recovered in feces after 72 h post-dosing. The above results show that the major elimination route is urinary excretion. Copyright © 2013 John Wiley & Sons, Ltd.
Sadi, Baki B M; Vonderheide, Anne P; Caruso, Joseph A
2004-09-24
A reversed phase ion-pairing high performance liquid chromatographic (RPIP-HPLC) method is developed for the separation of two phosphorus herbicides, Glufosinate and Glyphosate as well as Aminomethylphosphonic acid (AMPA), the major metabolite of Glyphosate. Tetrabutylammonium hydroxide is used as the ion-pairing reagent in conjunction with an ammonium acetate/acetic acid buffering system at pH 4.7. An inductively coupled plasma mass spectrometer (ICP-MS) is coupled to the chromatographic system to detect the herbicides at m/z = 31P. Historically, phosphorus has been recognized as one of the elements difficult to analyze in argon plasma. This is due to its relatively high ionization potential (10.5 eV) as well as the inherent presence of the polyatomic interferences 14N16O1H+ and 15N16O+ overlapping its only isotope at m/z = 31. An octapole reaction cell is utilized to minimize the isobaric polyatomic interferences and to obtain the highest signal-to-background ratio. Detection limits were found to be in the low ppt range (25-32 ng/l). The developed method is successfully applied to the analysis of water samples collected from the Ohio River and spiked with a standard compounds at a level of 20 microg/l.
Eap, C B; Souche, A; Koeb, L; Baumann, P
1991-07-01
The ring sulfoxidation of thioridazine (THD), a widely used neuroleptic agent, yields two diastereoisomeric pairs, fast- and slow-eluting (FE and SE) thioridazine 5-sulfoxide (THD 5-SO). Until now, studies in which concentrations of these metabolites were measured in THD-treated patients have revealed no significant differences in their concentrations. Preliminary experiments in our laboratory had shown that sunlight and, to a lesser extent, dim daylight led to racemization and probably also to photolysis of the diastereoisomeric pairs as measured by high-performance liquid chromatography. Similar results were also obtained with direct UV light (UV lamp). In appropriate light-protected conditions, THD, northioridazine, mesoridazine, sulforidazine, and FE and SE THD 5-SO were measured in 11 patients treated with various doses of THD for at least 1 week. Significantly higher concentrations of the FE stereoisomeric pair were found. The concentration ratios THD 5-SO (FE)/THD 5-SO (SE) ranged from 0.89 to 1.75 in plasma and from 1.15 to 2.05 in urine. Because it is known that the ring sulfoxide contributes to the cardiotoxicity of the drug even more potently than the parent compound does, these results justify further studies to determine whether there is stereoselectivity in the cardiotoxicity of THD 5-SO.
Alshishani, Anas; Makahleh, Ahmad; Yap, Hui Fang; Gubartallah, Elbaleeq Adam; Salhimi, Salizawati Muhamad; Saad, Bahruddin
2016-12-01
A new sample preparation method, ion-pair vortex assisted liquid-liquid microextraction (VALLME-BE), for the determination of a highly polar anti-diabetic drug (metformin) in plasma sample was developed. The VALLME-BE was performed by diluting the plasma in borate buffer and extracted to 150µL 1-octanol containing 0.2M di-(2-ethylhexyl)phosphoric acid as intermediate phase. The drug was next back-extracted into 20µL of 0.075M HCl solution. The effects of pH, ion-pair concentration, type of organic solvent, volume of extraction phases, ionic strength, vortexing and centrifugation times on the extraction efficiency were investigated. The optimum conditions were at pH 9.3, 60s vortexing and 2min centrifugation. The microextract, contained metformin and buformin (internal standard), was directly injected into a HPLC unit using C1 column (250mm×4.6mm×10µm) and detected at 235nm. The method was validated and calibration curve was linear with r 2 >0.99 over the range of 20-2000µgL -1 . The limits of detection and quantitation were 1.4 and 4.1µgL -1 , respectively. The accuracy was within 94.8-108% of the nominal concentration. The relative standard deviation for inter- and intra-day precision was less than 10.8%. The method was conveniently applied for the determination of metformin in plasma samples. Copyright © 2016 Elsevier B.V. All rights reserved.
Lohmayer, Regina; Reithmaier, Gloria Maria Susanne; Bura-Nakić, Elvira; Planer-Friedrich, Britta
2015-03-17
Molybdenum precipitates preferentially under reducing conditions; therefore, its occurrence in sediment records is used as an indicator of paleoredox conditions. Although thiomolybdates (MoO4-xSx(2-) with x = 1-4) supposedly are necessary intermediates in the process of molybdenum precipitation under anoxic conditions, there is no information about their abundance in natural environments, because of a lack of element-specific methods with sufficiently low detection limits. Here, we optimized ion-pair chromatographic separation for coupling to an inductively coupled plasma-mass spectrometry detector (IPC-ICP-MS). 2-Propanol (10%-25% gradient) replaced the previously used acetonitrile (25%-75%) as the solvent, to reduce the carbon load into the plasma. In synthetic solutions, formation of thiomolybdates was found to occur spontaneously in the presence of excess sulfide and the degree of thiolation was highest at pH 7. Excess hydroxyl led to a transformation of thiomolybdates to molybdate. Under acidic to neutral conditions, precipitation of molybdenum and hydrolysis of tetrathiomolybdate were observed. Flash-freezing was found to be suitable to stabilize tetrathiomolybdate, with 2 mM) negatively affected the detection of molybdate, which eluted mainly in the dead volume, but had no negative effect on higher thiolated molybdates. Detection limits were ∼10 nM. With the newly developed IPC-ICP-MS method, thiomolybdates were found to form spontaneously in euxinic marine waters after adding a molybdate spike and occur naturally in sulfidic geothermal waters.
Bytingsvik, Jenny; van Leeuwen, Stefan P J; Hamers, Timo; Swart, Kees; Aars, Jon; Lie, Elisabeth; Nilsen, Else Mari Espseth; Wiig, Oystein; Derocher, Andrew E; Jenssen, Bjørn M
2012-11-15
Perfluoroalkyl substances (PFASs) are protein-binding blood-accumulating contaminants that may have detrimental toxicological effects on the early phases of mammalian development. To enable an evaluation of the potential health risks of PFAS exposure for polar bears (Ursus maritimus), an exposure assessment was made by examining plasma levels of PFASs in polar bear mothers in relation to their suckling cubs-of-the-year (~4 months old). Samples were collected at Svalbard in 1998 and 2008, and we investigated the between-year differences in levels of PFASs. Seven perfluorinated carboxylic acids (∑₇PFCAs: PFHpA, PFOA, PFNA, PFDA, PFUnDA, PFDoDA, and PFTrDA) and two perfluorinated sulfonic acids (∑₂PFSAs: PFHxS and PFOS) were detected in the majority of the mothers and cubs from both years. In mothers and cubs, most PFCAs were detected in higher concentrations in 2008 than in 1998. On the contrary, levels of PFOS were lower in 2008 than in 1998, while levels of PFHxS did not differ between the two sampling years. PFOS was the dominating compound in mothers and cubs both in 1998 and in 2008. Concentration of PFHpA did not differ between mothers and cubs, while concentrations of PFOA, PFNA, PFDA, PFUnDA, PFDoDA, PFTrDA, PFHxS, and PFOS were higher in mothers than in their cubs. Except from PFHpA, all compounds correlated significantly between mothers and their cubs. The mean cub to mother ratios ranged from 0.15 for PFNA to 1.69 for PFHpA. On average (mean±standard error of mean), the levels of ∑₇PFCAs and ∑₂PFSAs in cubs were 0.24±0.01 and 0.22±0.01 times the levels in their mothers, respectively. Although maternal transfer appears to be a substantial source of exposure for the cubs, the low cub to mother ratios indicate that maternal transfer of PFASs in polar bears is relatively low in comparison with hydrophobic contaminants (e.g. PCBs). Because the level of several PFASs in mothers and cubs from both sampling years exceeded the levels associated
Cheng, Heyong; Chen, Xiaopan; Shen, Lihuan; Wang, Yuanchao; Xu, Zigang; Liu, Jinhua
2018-01-05
Most of analytical community is focused on reversed phase high performance liquid chromatography (RP-HPLC) for mercury speciation by employing mobile phases comprising of high salts and moderate amounts of organic solvents. This study aims at rapid mercury speciation analysis by ion-pairing RP-HPLC with inductively coupled plasma mass spectrometry (ICP-MS) detection only using low salts for the sake of green analytical chemistry. Two ion-pairing HPLC methods were developed on individual usage of positively and negatively charged ion-pairing reagents (tetrabutylammonium hydroxide -TBAH and sodium dodecylbenzene sulfonate -SDBS), where sodium 3-mercapto-1-propysulfonate (MPS) and l-cysteine (Cys) were individually added in mobile phases to transform mercury species into negative and positive Hg-complexes for good resolution. Addition of phenylalanine was also utilized for rapid baseline separation in combination of short C 18 guard columns. Optimum mobile phases of 2.0mM SDBS+2.0mM Cys+1.0mM Phe (pH 3.0) and 4.0mM TBAH+2.0mM MPS+2.0mM Phe (pH 6.0) both achieved baseline separation of inorganic mercury (Hg 2+ ), methylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg) on two consecutive 12.5-mm C 18 columns. The former mobile phase was selected for mercury speciation in freshwater fish because of short separation time (3.0min). Detection limits of 0.015 for Hg 2+ , 0.014 for MeHg, 0.028 for EtHg and 0.042μgL -1 for PhHg were obtained along with satisfactory precisions of peak height and area (1.0-2.8% for 5.0μgL -1 Hg-mixture standard). Good accordance of determined values of MeHg and total mercury in certified reference materials of fish tissue (GBW 10029) and tuna fish (BCR-463) with certified values as well as good recoveries (91-106%) proved good accuracy of the proposed method. An example application to freshwater fish indicated its potential in routine analysis, where MeHg was presented at 3.7-20.3μgkg -1 as the dominate species. Copyright © 2017
Fang, Yong; Pan, Yushi; Li, Peng; Xue, Mei; Pei, Fei; Yang, Wenjian; Ma, Ning; Hu, Qiuhui
2016-12-15
An analytical method using reversed phase chromatography-inductively coupled plasma mass spectrometry for arsenic and mercury speciation analysis was described. The effect of ion-pairing reagent on simultaneous separation of four arsenic (arsenite, arsenate, monomethlyarsonate and dimethylarsinate) and three mercury species (inorganic mercury (Hg(II)), methylmecury and ethylmercury) was investigated. Parameters including concentrations and pH of the mobile phase were optimized. The separation and re-equilibration time was attained within 20min. Meanwhile, a sequential extraction method for arsenic and mercury in rice was tested. Subsequently, 1% HNO3 microwave-assisted extraction was chosen. Calibration curves based on peak area measurements were linear with correlation coefficient greater than 0.9958 for each species in the range studied. The detection limits of the species were in the range of 0.84-2.41μg/L for arsenic and 0.01-0.04μg/L for mercury, respectively. The proposed method was then successfully applied for the simultaneous determination of arsenic and mercury species in rice flour standard material and two kinds of rice from local markets. Copyright © 2016 Elsevier Ltd. All rights reserved.
Li, Shujiao; Lin, Hang; Qu, Cheng; Tang, Yuping; Shen, Juan; Li, Weixia; Yue, Shijun; Kai, Jun; Shang, Guanxiong; Zhu, Zhenhua; Zhang, Changbin; Liu, Pei; Yan, Hui; Zhang, Li; Qian, Li; Qian, Dawei; Duan, Jin-ao
2015-07-21
The compatibility of Angelicae Sinensis Radix (Danggui) and Carthami Flos (Honghua), a famous herb pair Gui-Hong, can produce synergistic and complementary hematinic effects. Our previous studies have indicated that Gui-Hong has therapeutic potential treatment in hemolytic and aplastic anemia (HAA). The present study aimed to investigate the hematinic effects of Danggui, Honghua and Gui-Hong on HAA rats induced by acetyl phenylhydrazine (APH) and cyclophosphamide (CP) and to explore the underlying hematinic regulation mechanisms. Rats were divided into 5 groups, and drugs were administered by oral gavage one time each day for continuous 7 days from the experiment began. Urine and plasma were analyzed by ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS). Partial least-squares discriminate analysis (PLS-DA) models were built to evaluate the therapeutic effects of Danggui, Honghua and Gui-Hong. Pearson correlation matrix analysis method was used to discover the correlations between potential biomarkers and biochemical indicators of HAA rats. Seven potential biomarkers contribute to the separation of model group and control group were tentatively identified. The levels of l-kynurenine, phenylalanine, nicotinic acid and sphingosine increased significantly (Pmetabonomics method is a promising tool in the efficacy and mechanism research of traditional Chinese medicines. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
Miller, John D.; Rankin, Timothy M.; Hua, Natalie T.; Ontiveros, Tina; Giovinco, Nicholas A.; Mills, Joseph L.; Armstrong, David G.
2015-01-01
In the past decade, autologous platelet-rich plasma (PRP) therapy has seen increasingly widespread integration into medical specialties. PRP application is known to accelerate wound epithelialization rates, and may also reduce postoperative wound site pain. Recently, we observed an increase in patient satisfaction following PRP gel (Angel, Cytomedix, Rockville, MD) application to split-thickness skin graft (STSG) donor sites. We assessed all patients known to our university-based hospital service who underwent multiple STSGs up to the year 2014, with at least one treated with topical PRP. Based on these criteria, five patients aged 48.4±17.6 (80% male) were identified who could serve as their own control, with mean time of 4.4±5.1 years between operations. In both therapies, initial dressing changes occurred on postoperative day (POD) 7, with donor site pain measured by Likert visual pain scale. Paired t-tests compared the size and thickness of harvested skin graft and patient pain level, and STSG thickness and surface area were comparable between control and PRP interventions (p>0.05 for all). Donor site pain was reduced from an average of 7.2 (±2.6) to 3 (±3.7), an average reduction in pain of 4.2 (standard error 1.1, p=0.0098) following PRP use. Based on these results, the authors suggest PRP as a beneficial adjunct for reducing donor site pain following STSG harvest. PMID:25623477
Directory of Open Access Journals (Sweden)
John D. Miller
2015-01-01
Full Text Available In the past decade, autologous platelet-rich plasma (PRP therapy has seen increasingly widespread integration into medical specialties. PRP application is known to accelerate wound epithelialization rates, and may also reduce postoperative wound site pain. Recently, we observed an increase in patient satisfaction following PRP gel (Angel, Cytomedix, Rockville, MD application to split-thickness skin graft (STSG donor sites. We assessed all patients known to our university-based hospital service who underwent multiple STSGs up to the year 2014, with at least one treated with topical PRP. Based on these criteria, five patients aged 48.4±17.6 (80% male were identified who could serve as their own control, with mean time of 4.4±5.1 years between operations. In both therapies, initial dressing changes occurred on postoperative day (POD 7, with donor site pain measured by Likert visual pain scale. Paired t-tests compared the size and thickness of harvested skin graft and patient pain level, and STSG thickness and surface area were comparable between control and PRP interventions (p>0.05 for all. Donor site pain was reduced from an average of 7.2 (±2.6 to 3 (±3.7, an average reduction in pain of 4.2 (standard error 1.1, p=0.0098 following PRP use. Based on these results, the authors suggest PRP as a beneficial adjunct for reducing donor site pain following STSG harvest.
Sagan, Bruce E.; Savage, Carla D.
2012-01-01
We introduce the notion of a Mahonian pair. Consider the set, P^*, of all words having the positive integers as alphabet. Given finite subsets S,T of P^*, we say that (S,T) is a Mahonian pair if the distribution of the major index, maj, over S is the same as the distribution of the inversion number, inv, over T. So the well-known fact that maj and inv are equidistributed over the symmetric group, S_n, can be expressed by saying that (S_n,S_n) is a Mahonian pair. We investigate various Mahonia...
Waitt, Catriona; Olagunju, Adeniyi; Nakalema, Shadia; Kyohaire, Isabella; Owen, Andrew; Lamorde, Mohammed; Khoo, Saye
2018-01-01
Abstract Background Breast milk transfer of first-line ART from mother to infant is not fully understood. Objectives To determine the concentrations of lamivudine, emtricitabine and tenofovir in maternal blood, breast milk and infant blood from breastfeeding mother–infant pairs. Methods Intensive pharmacokinetic sampling of maternal dried blood spots (DBS), dried breast milk spots (DBMS) and infant DBS from 30 Ugandan and 29 Nigerian mothers receiving first-line ART and their infants was conducted. DBS and DBMS were collected pre-dose and at 5–6 timepoints up to 12 h following observed dosing. Infant DBS were sampled twice during this period. Lamivudine, emtricitabine and tenofovir were quantified using LC-MS/MS, with non-compartmental analysis to calculate key pharmacokinetic parameters. Results Peak concentrations in breast milk from women taking lamivudine and emtricitabine occurred later than in plasma (4–8 h compared with 2 h for lamivudine and 2–4 h for emtricitabine). Consequently, the milk-to-plasma (M:P) ratio of lamivudine taken once daily was 0.95 (0.82–1.15) for AUC0–12, whereas for AUC12–20 this was 3.04 (2.87–4.16). Lamivudine was detectable in 36% (14/39) of infants [median 17.7 (16.3–22.7) ng/mL]. For 200 mg of emtricitabine once daily, the median M:P ratio was 3.01 (2.06–3.38). Three infants (19%) had measurable emtricitabine [median 18.5 (17.6–20.8) ng/mL]. For 300 mg of tenofovir once daily, the median M:P ratio was 0.015 (0–0.03) and no infant had measurable tenofovir concentrations. Conclusions Emtricitabine and lamivudine accumulate in breast milk and were detected in breastfeeding infants. In contrast, tenofovir penetrates the breast milk to a small degree, but is undetectable in breastfeeding infants. PMID:29309634
Waitt, Catriona; Olagunju, Adeniyi; Nakalema, Shadia; Kyohaire, Isabella; Owen, Andrew; Lamorde, Mohammed; Khoo, Saye
2018-04-01
Breast milk transfer of first-line ART from mother to infant is not fully understood. To determine the concentrations of lamivudine, emtricitabine and tenofovir in maternal blood, breast milk and infant blood from breastfeeding mother-infant pairs. Intensive pharmacokinetic sampling of maternal dried blood spots (DBS), dried breast milk spots (DBMS) and infant DBS from 30 Ugandan and 29 Nigerian mothers receiving first-line ART and their infants was conducted. DBS and DBMS were collected pre-dose and at 5-6 timepoints up to 12 h following observed dosing. Infant DBS were sampled twice during this period. Lamivudine, emtricitabine and tenofovir were quantified using LC-MS/MS, with non-compartmental analysis to calculate key pharmacokinetic parameters. Peak concentrations in breast milk from women taking lamivudine and emtricitabine occurred later than in plasma (4-8 h compared with 2 h for lamivudine and 2-4 h for emtricitabine). Consequently, the milk-to-plasma (M:P) ratio of lamivudine taken once daily was 0.95 (0.82-1.15) for AUC0-12, whereas for AUC12-20 this was 3.04 (2.87-4.16). Lamivudine was detectable in 36% (14/39) of infants [median 17.7 (16.3-22.7) ng/mL]. For 200 mg of emtricitabine once daily, the median M:P ratio was 3.01 (2.06-3.38). Three infants (19%) had measurable emtricitabine [median 18.5 (17.6-20.8) ng/mL]. For 300 mg of tenofovir once daily, the median M:P ratio was 0.015 (0-0.03) and no infant had measurable tenofovir concentrations. Emtricitabine and lamivudine accumulate in breast milk and were detected in breastfeeding infants. In contrast, tenofovir penetrates the breast milk to a small degree, but is undetectable in breastfeeding infants.
Kenyon, Chris R; Osbak, Kara Krista; Van Esbroek, Marjan; Lynen, Lutgarde; Crucitti, Tania
2018-01-01
Repeat syphilis is playing an increasing role in syphilis transmission in several populations. The assessment of repeat syphilis and response to treatment depends on accurately measuring intraindividual changes in non-treponemal tests. For a 0- to 6-month delta rapid plasma reagin (RPR) to be determined by routine individual RPR testing, samples are tested 6 months apart with differences in reagent batches, environmental conditions, and observers all leading to measurement errors. We hypothesized that conducting paired RPR testing (simultaneous testing of acute and convalescent samples) would enable a more accurate determination of delta RPR compared with individual testing. A total of 120 study participants with a new diagnosis of syphilis were followed up at 0, 3, 6, 9, 12, 18, and 24 months, with RPR testing performed via individual testing at each study visit and at any suspected repeat syphilis. Rapid plasma reagin paired testing was performed on samples from 0 and 6 months and at any suspected repeat syphilis. The quantitative agreement ±1 dilution among paired and individual testing was 97.2%. There was no difference in the proportion with serofast status at 6 months: 21 (19.4%) and 19 (17.6%) according to paired and individual testing, respectively (P = 0.726). There was no statistically significant difference between 0- and 6-month delta RPR as determined by paired and individual testing in predicting seroresponse at 12 months (86.1% and 91.6% agreement with 12-month serofast/nonserofast classification, respectively; P = 0.262). In our setting, individual testing performed equally well compared with paired testing. Follow-up of syphilis will remain onerous for the patient and the health care provider until new tests that can more accurately assess the response to therapy and repeat syphilis/treatment failure are developed.
Houzé, P; de Reynies, A; Baud, F J; Benatar, M F; Pays, M
1992-02-14
A method was developed for the separation and measurement of chloroquine and three metabolites (desethylchloroquine, bisdesethylchloroquine and 4-amino-7-chloroquinoline) in biological samples by ion-pair high-performance liquid chromatography with UV detection. The method uses 2,3-diaminoaphthalene as an internal standard and provides a limit of detection between 1 and 2 ng/ml for chloroquine and its metabolites. The assay was linear in the range 12.5-250 ng/ml and the analytical recovery and reproducibility were sufficient. The assay was applied to the analysis of biological samples from a patient undergoing chloroquine chemoprophylaxis and a patient who had ingested chloroquine in a suicide attempt.
Bytingsvik, Jenny; Lie, Elisabeth; Aars, Jon; Derocher, Andrew E; Wiig, Øystein; Jenssen, Bjørn M
2012-02-15
The aim of this study was to examine the plasma concentrations and prevalence of polychlorinated biphenyls (PCBs) and hydroxylated PCB-metabolites (OH-PCBs) in polar bear (Ursus maritimus) mothers (n=26) and their 4 months old cubs-of-the-year (n=38) from Svalbard to gain insight into the mother-cub transfer, biotransformation and to evaluate the health risk associated with the exposure to these contaminants. As samplings were performed in 1997/1998 and 2008, we further investigated the differences in levels and pattern of PCBs between the two sampling years. The plasma concentrations of Σ(21)PCBs (1997/1998: 5710 ± 3090 ng/g lipid weight [lw], 2008: 2560 ± 1500 ng/g lw) and Σ(6)OH-PCBs (1997/1998: 228 ± 60 ng/g wet weight [ww], 2008: 80 ± 38 ng/g ww) in mothers were significantly lower in 2008 compared to in 1997/1998. In cubs, the plasma concentrations of Σ(21)PCBs (1997/1998: 14680 ± 5350 ng/g lw, 2008: 6070 ± 2590 ng/g lw) and Σ(6)OH-PCBs (1997/1998: 98 ± 23 ng/g ww, 2008: 49 ± 21 ng/g ww) were also significantly lower in 2008 than in 1997/1998. Σ(21)PCBs in cubs was 2.7 ± 0.7 times higher than in their mothers. This is due to a significant maternal transfer of these contaminants. In contrast, Σ(6)OH-PCBs in cubs were approximately 0.53 ± 0.16 times the concentration in their mothers. This indicates a lower maternal transfer of OH-PCBs compared to PCBs. The majority of the metabolite/precursor-ratios were lower in cubs compared to mothers. This may indicate that cubs have a lower endogenous capacity to biotransform PCBs to OH-PCBs than polar bear mothers. Exposure to PCBs and OH-PCBs is a potential health risk for polar bears, and the levels of PCBs and OH-PCBs in cubs from 2008 were still above levels associated with health effects in humans and wildlife. Copyright © 2012 Elsevier B.V. All rights reserved.
Wolf, R.E.; Morrison, J.M.; Goldhaber, M.B.
2007-01-01
A method for the simultaneous determination of Cr(iii) and Cr(vi) species in waters, soil leachates and synthetic bio-fluids is described. The method uses reversed-phase ion-pairing liquid chromatography to separate the chromium species and a dynamic reaction cell (DRC??) equipped ICP-MS for detection of chromium. Separation of the chromium species is carried out in less than 2 min. Cr(iii) is complexed with ethylenediaminetetraacetic acid (EDTA) prior to separation by mixing samples with the mobile phase containing 2.0 mM tetrabutylammonium hydroxide (TBAOH), 0.5 mM EDTA (dipotassium salt), and 5% (vol/vol) methanol, adjusted to pH 7.6. The interfering 40Ar 12C+ background peak at mass 52 was reduced by over four orders of magnitude to less than 200 cps by using 0.65 mL min-1 ammonia as a reaction gas and an RPq setting on the DRC of 0.75. Method detection limits (MDLs) of 0.09 ??g L-1 for Cr(iii) and 0.06 ??g L-1 for Cr(vi) were obtained based on peak areas at mass 52 for 50 ??L injections of low level spikes. Reproducibility at 2 ??g L-1 was 3% RSD for 5 replicate injections. The tolerance of the method to various levels of common cations and anions found in natural waters and to matrix constituents found in soil leachates and simulated gastric and lung fluids was tested by performing spike recovery calculations for a variety of samples. ?? The Royal Society of Chemistry.
Topics in the physics of accretion onto black holes
International Nuclear Information System (INIS)
Stoeger, W.R.
1977-06-01
The subject is covered in chapters, entitled: introduction and overview; boundary-condition modification of accretion-disk models; standard assumptions and nonkeplerian inner-disk models; the 'inner edge' of accretion disks and spiral orbits; a review of comptonization in accretion disks and a criterion for Lightman-Eardley stability; the thickening of accretion disks and flows; radial pressure gradients and low-angular-momentum accretion; accretion-disk scenarios for X-ray transient and burst sources; photon pair-creation processes in transrelativistic plasmas; and the astrophysical consequences of Rosen's bi-metric theory of gravity. (U.K.)
Pairing correlations in nuclei
International Nuclear Information System (INIS)
Baba, C.V.K.
1988-01-01
There are many similarities between the properties of nucleons in nuclei and electrons in metals. In addition to the properties explainable in terms of independent particle motion, there are many important co-operative effects suggesting correlated motion. Pairing correlation which leads to superconductivity in metals and several important properties in nuclei , is an exmple of such correlations. An attempt has been made to review the effects of pairing correlations in nuclei. Recent indications of reduction in pairing correlations at high angular momenta is discussed. A comparision between pairing correlations in the cases of nuclei and electrons in metals is attempted. (author). 20 refs., 10 figs
Secure pairing with biometrics
Buhan, I.R.; Boom, B.J.; Doumen, J.M.; Hartel, Pieter H.; Veldhuis, Raymond N.J.
Secure pairing enables two devices that share no prior context with each other to agree upon a security association, which they can use to protect their subsequent communication. Secure pairing offers guarantees of the association partner identity and it should be resistant to eavesdropping and to a
Acar, T.; Lauter, K.; Naehrig, M.; Shumow, D.
2011-01-01
Pairings on elliptic curves are being used in an increasing number of cryptographic applications on many different devices and platforms, but few performance numbers for cryptographic pairings have been reported on embedded and mobile devices. In this paper we give performance numbers for affine and
International Nuclear Information System (INIS)
Balantekin, A. B.; Pehlivan, Y.
2007-01-01
We give the exact solution of orbit dependent nuclear pairing problem between two nondegenerate energy levels using the Bethe ansatz technique. Our solution reduces to previously solved cases in the appropriate limits including Richardson's treatment of reduced pairing in terms of rational Gaudin algebra operators
International Nuclear Information System (INIS)
Shimizu, Yoshifumi
2009-01-01
Except for the closed shell nuclei, almost all nuclei are in the superconducting state at their ground states. This well-known pair correlation in nuclei causes various interesting phenomena. It is especially to be noted that the pair correlation becomes weak in the excited states of nuclei with high angular momentum, which leads to the pair phase transition to the normal state in the high spin limit. On the other hand, the pair correlation becomes stronger in the nuclei with lower nucleon density than in those with normal density. In the region of neutron halo or skin state of unstable nuclei, this phenomenon is expected to be further enhanced to be observed compared to the ground state of stable nuclei. An overview of those interesting aspects caused via the pair correlation is presented here in the sections titled 'pair correlations in ground states', pair correlations in high spin states' and 'pair correlations in unstable nuclei' focusing on the high spin state. (S. Funahashi)
International Nuclear Information System (INIS)
Valles, James
2008-01-01
Nearly 50 years elapsed between the discovery of superconductivity and the emergence of the microscopic theory describing this zero resistance state. The explanation required a novel phase of matter in which conduction electrons joined in weakly bound pairs and condensed with other pairs into a single quantum state. Surprisingly, this Cooper pair formation has also been invoked to account for recently uncovered high-resistance or insulating phases of matter. To address this possibility, we have used nanotechnology to create an insulating system that we can probe directly for Cooper pairs. I will present the evidence that Cooper pairs exist and dominate the electrical transport in these insulators and I will discuss how these findings provide new insight into superconductor to insulator quantum phase transitions.
DEFF Research Database (Denmark)
Dalgas, Karina Märcher
2015-01-01
pair-sending families in the Philippines, this dissertation examines the long-term trajectories of these young Filipinas. It shows how the au pairs’ local and transnational family relations develop over time and greatly influence their life trajectories. A focal point of the study is how au pairs...... that Filipina au pairs see their stay abroad as an avenue of personal development and social recognition, I examine how the au pairs re-position themselves within their families at home through migration, and how they navigate between the often conflicting expectations of participation in the sociality......Since 2000, thousands of young Filipino migrants have come to Denmark as au pairs. Officially, they are there to “broaden their cultural horizons” by living temporarily with a Danish host family, but they also conduct domestic labor in exchange for food and money, which allows them to send...
Collective neutrino-pair emission due to Cooper pairing of protons in superconducting neutron stars
International Nuclear Information System (INIS)
Leinson, L.B.
2001-01-01
The neutrino emission due to formation and breaking of Cooper pairs of protons in superconducting cores of neutron stars is considered with taking into account the electromagnetic coupling of protons to ambient electrons. It is shown that collective response of electrons to the proton quantum transition contributes coherently to the complete interaction with a neutrino field and enhances the neutrino-pair production. Our calculation shows that the contribution of the vector weak current to the ννbar emissivity of protons is much larger than that calculated by different authors without taking into account the plasma effects. Partial contribution of the pairing protons to the total neutrino radiation from the neutron star core is very sensitive to the critical temperatures for the proton and neutron pairing. We show domains of these parameters where the neutrino radiation, caused by a singlet-state pairing of protons is dominating
Mesoscopic pairing without superconductivity
Hofmann, Johannes
2017-12-01
We discuss pairing signatures in mesoscopic nanowires with a variable attractive pairing interaction. Depending on the wire length, density, and interaction strength, these systems realize a simultaneous bulk-to-mesoscopic and BCS-BEC crossover, which we describe in terms of the parity parameter that quantifies the odd-even energy difference and generalizes the bulk Cooper pair binding energy to mesoscopic systems. We show that the parity parameter can be extracted from recent measurements of conductance oscillations in SrTiO3 nanowires by Cheng et al. [Nature (London) 521, 196 (2015), 10.1038/nature14398], where it marks the critical magnetic field that separates pair and single-particle currents. Our results place the experiment in the fluctuation-dominated mesoscopic regime on the BCS side of the crossover.
Investigations into nuclear pairing
International Nuclear Information System (INIS)
Clark, R.M.
2006-01-01
This paper is divided in two main sections focusing on different aspects of collective nuclear behavior. In the first section, solutions are considered for the collective pairing Hamiltonian. In particular, an approximate solution at the critical point of the pairing transition from harmonic vibration (normal nuclear behavior) to deformed rotation (superconducting behavior) in gauge space is found by analytic solution of the Hamiltonian. The eigenvalues are expressed in terms of the zeros of Bessel functions of integer order. The results are compared to the pairing bands based on the Pb isotopes. The second section focuses on the experimental search for the Giant Pairing Vibration (GPV) in nuclei. After briefly describing the origin of the GPV, and the reasons that the state has remained unidentified, a novel idea for populating this state is presented. A recent experiment has been performed using the LIBERACE+STARS detector system at the 88-Inch Cyclotron of LBNL to test the idea. (Author)
[Paired kidneys in transplant].
Regueiro López, Juan C; Leva Vallejo, Manuel; Prieto Castro, Rafael; Anglada Curado, Francisco; Vela Jiménez, Francisco; Ruiz García, Jesús
2009-02-01
Many factors affect the graft and patient survival on the renal transplant outcome. These factors depend so much of the recipient and donor. We accomplished a study trying to circumvent factors that depend on the donor. We checked the paired kidneys originating of a same donor cadaver. We examined the risk factors in the evolution and follow-up in 278 couples of kidney transplant. We describe their differences, significance, the graft and patient survival, their functionality in 3 and 5 years and the risk factors implicated in their function. We study immunogenic and no immunogenic variables, trying to explain the inferior results in the grafts that are established secondly. We regroup the paired kidneys in those that they did not show paired initial function within the same couple. The results yield a discreet deterioration in the graft and patient survival for second group establish, superior creatinina concentration, without obtaining statistical significance. The Cox regression study establishes the early rejection (inferior to three months) and DR incompatibility values like risk factors. This model of paired kidneys would be able to get close to best-suited form for risk factors analysis in kidney transplant from cadaver donors, if more patients examine themselves in the same way. The paired kidneys originating from the same donor do not show the same function in spite of sharing the same conditions of the donor and perioperative management.
Junctionless Cooper pair transistor
Energy Technology Data Exchange (ETDEWEB)
Arutyunov, K. Yu., E-mail: konstantin.yu.arutyunov@jyu.fi [National Research University Higher School of Economics , Moscow Institute of Electronics and Mathematics, 101000 Moscow (Russian Federation); P.L. Kapitza Institute for Physical Problems RAS , Moscow 119334 (Russian Federation); Lehtinen, J.S. [VTT Technical Research Centre of Finland Ltd., Centre for Metrology MIKES, P.O. Box 1000, FI-02044 VTT (Finland)
2017-02-15
Highlights: • Junctionless Cooper pair box. • Quantum phase slips. • Coulomb blockade and gate modulation of the Coulomb gap. - Abstract: Quantum phase slip (QPS) is the topological singularity of the complex order parameter of a quasi-one-dimensional superconductor: momentary zeroing of the modulus and simultaneous 'slip' of the phase by ±2π. The QPS event(s) are the dynamic equivalent of tunneling through a conventional Josephson junction containing static in space and time weak link(s). Here we demonstrate the operation of a superconducting single electron transistor (Cooper pair transistor) without any tunnel junctions. Instead a pair of thin superconducting titanium wires in QPS regime was used. The current–voltage characteristics demonstrate the clear Coulomb blockade with magnitude of the Coulomb gap modulated by the gate potential. The Coulomb blockade disappears above the critical temperature, and at low temperatures can be suppressed by strong magnetic field.
ON THE POLAR CAP CASCADE PAIR MULTIPLICITY OF YOUNG PULSARS
Energy Technology Data Exchange (ETDEWEB)
Timokhin, A. N.; Harding, A. K., E-mail: andrey.timokhin@nasa.gov [Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
2015-09-10
We study the efficiency of pair production in polar caps of young pulsars under a variety of conditions to estimate the maximum possible multiplicity of pair plasma in pulsar magnetospheres. We develop a semi-analytic model for calculation of cascade multiplicity which allows efficient exploration of the parameter space and corroborate it with direct numerical simulations. Pair creation processes are considered separately from particle acceleration in order to assess different factors affecting cascade efficiency, with acceleration of primary particles described by recent self-consistent non-stationary model of pair cascades. We argue that the most efficient cascades operate in the curvature radiation/synchrotron regime, the maximum multiplicity of pair plasma in pulsar magnetospheres is ∼few × 10{sup 5}. The multiplicity of pair plasma in magnetospheres of young energetic pulsars weakly depends on the strength of the magnetic field and the radius of curvature of magnetic field lines and has a stronger dependence on pulsar inclination angle. This result questions assumptions about very high pair plasma multiplicity in theories of pulsar wind nebulae.
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 19; Issue 11. Frustrated Lewis Pairs : Enabling via inability. Sanjoy Mukherjee ... Author Affiliations. Sanjoy Mukherjee Pakkirisamy Thilagar1. Department of Inorgainic and Physical Chemistry Indian Institute of Science Bangalore 560 012, India.
DEFF Research Database (Denmark)
Rodríguez, J. Tinguaro; Franco de los Ríos, Camilo; Gómez, Daniel
2015-01-01
In this paper we want to stress the relevance of paired fuzzy sets, as already proposed in previous works of the authors, as a family of fuzzy sets that offers a unifying view for different models based upon the opposition of two fuzzy sets, simply allowing the existence of different types...
Acar, T.; Lauter, K.; Naehrig, M.; Shumow, D.; Abdalla, M.; Lange, T.
2013-01-01
We report on relative performance numbers for affine and projective pairings on a dual-core Cortex A9 ARM processor. Using a fast inversion in the base field and doing inversion in extension fields by using the norm map to reduce to inversions in smaller fields, we find a very low ratio of
Energy Technology Data Exchange (ETDEWEB)
Lopez-Arrietea, M. G.; Solis, M. A.; De Llano, M. [Universidad Nacional Autonoma de Mexico, Mexico, D.F (Mexico)
2001-02-01
Excited cooper pairs formed in a many-fermion system are those with nonzero total center-of mass momentum (CMM). They are normally neglected in the standard Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity for being too few compared with zero CMM pairs. However, a Bose-Einstein condensation picture requires both zero and nonzero CMM pairs. Assuming a BCS model interaction between fermions we determine the populations for all CMM values of Cooper pairs by actually calculating the number of nonzero-CMM pairs relative to that of zero-CMM ones in both 2D and 3D. Although this ratio decreases rapidly with CMM, the number of Cooper pairs for any specific CMM less than the maximum (or breakup of the pair) momentum turns out to be typically larger than about 95% of those with zero-CMM at zero temperature T. Even at T {approx}100 K this fraction en 2D is still as large as about 70% for typical quasi-2D cuprate superconductor parameters. [Spanish] Los pares de cooper excitados formados en un sistema de muchos electrones, son aquellos con momentos de centro de masa (CMM) diferente de cero. Normalmente estos no son tomados en cuenta en la teoria estandar de la superconductividad de Bardeen-Cooper-Schrieffer (BCS) al suponer que su numero es muy pequeno comparados con los pares de centro de masa igual a cero. Sin embargo, un esquema de condensacion Bose-Einstein requiere de ambos pares, con CMM cero y diferente de cero. Asumiendo una interaccion modelo BCS entre los fermiones, determinamos la poblacion de pares cooper con cada uno de todos los posibles valores del CMM calculando el numero de pares con momentos de centro de masa diferente de cero relativo a los pares de CMM igual a cero, en 2D y 3D. Aunque esta razon decrece rapidamente con el CMM, el numero de pares de cooper para cualquier CMM especifico menor que el momento maximo (o rompimiento de par) es tipicamente mas grande que el 95% de aquellos con CMM cero. Aun a T {approx}100 K esta fraccion en 2D es
Multi-pair states in electron–positron pair creation
Energy Technology Data Exchange (ETDEWEB)
Wöllert, Anton, E-mail: woellert@mpi-hd.mpg.de; Bauke, Heiko, E-mail: heiko.bauke@mpi-hd.mpg.de; Keitel, Christoph H.
2016-09-10
Ultra strong electromagnetic fields can lead to spontaneous creation of single or multiple electron–positron pairs. A quantum field theoretical treatment of the pair creation process combined with numerical methods provides a description of the fermionic quantum field state, from which all observables of the multiple electron–positron pairs can be inferred. This allows to study the complex multi-particle dynamics of electron–positron pair creation in-depth, including multi-pair statistics as well as momentum distributions and spin. To illustrate the potential benefit of this approach, it is applied to the intermediate regime of pair creation between nonperturbative Schwinger pair creation and perturbative multiphoton pair creation where the creation of multi-pair states becomes nonnegligible but cascades do not yet set in. Furthermore, it is demonstrated how spin and helicity of the created electrons and positrons are affected by the polarization of the counterpropagating laser fields, which induce the creation of electron–positron pairs.
Multi-pair states in electron–positron pair creation
International Nuclear Information System (INIS)
Wöllert, Anton; Bauke, Heiko; Keitel, Christoph H.
2016-01-01
Ultra strong electromagnetic fields can lead to spontaneous creation of single or multiple electron–positron pairs. A quantum field theoretical treatment of the pair creation process combined with numerical methods provides a description of the fermionic quantum field state, from which all observables of the multiple electron–positron pairs can be inferred. This allows to study the complex multi-particle dynamics of electron–positron pair creation in-depth, including multi-pair statistics as well as momentum distributions and spin. To illustrate the potential benefit of this approach, it is applied to the intermediate regime of pair creation between nonperturbative Schwinger pair creation and perturbative multiphoton pair creation where the creation of multi-pair states becomes nonnegligible but cascades do not yet set in. Furthermore, it is demonstrated how spin and helicity of the created electrons and positrons are affected by the polarization of the counterpropagating laser fields, which induce the creation of electron–positron pairs.
International Nuclear Information System (INIS)
Hrasko, P.; Foeldy, L.; Toth, A.
1986-07-01
Electron-positron pair production in strong Coulomb fields is outlined. It is shown that the singular behaviour of the adiabatic basis can be removed if solutions of the time dependent external field Dirac equation are used as a basis to expand the fermion field operator. This latter 'asymptotic basis' makes it possible to introduce Feynman-propagator. Applying the reduction technique, the computation of all of the basic quantities can be reduced to the solution of an integral equation. The positron spectrum for separable potential model with Lorentzian time dependence and for potential jump is analyzed in the pole approximation. (author)
Pairing correlations around scission
International Nuclear Information System (INIS)
Krappe, H.J.; Fadeev, S.
2001-01-01
To describe pairing correlations in a fissioning system one commonly projects the BCS wave function separately onto good particle numbers in each fragment in the exit channel, but only onto the total number of particles in the parent system. We propose to interpolate between these limiting situations by the generator-coordinate method with the particle-number difference between the nascent fragments as the generator coordinate. Model calculations are presented for the Hill-Wheeler-box potential with a δ-function diaphragm to mimic scission
DEFF Research Database (Denmark)
Dalgas, Karina Märcher
2016-01-01
Ethnographers are increasingly making use of Facebook to acquire access and general acquaintance with their field of study. However, little has been written on how Facebook is used methodologically in research that does not have social media sites as the main focus of interest. This article argues...... the au pairs resist and embrace such dominant representations, and on how such representations are ascribed different meanings in the transnational social fields of which the migrant are a part. The article is based on ethnographic fieldwork conducted between 2010 and 2014 in Denmark, the Philippines...
Assessing Intimacy: The Pair Inventory.
Schaefer, Mark T.; Olson, David H.
1981-01-01
Personal Assessment of Intimacy in Relationships (PAIR) provides systematic information in five types of intimacy: emotional, social, sexual, intellectual and recreational. PAIR can be used with couples in marital therapy and enrichment groups. (Author)
QSO Pairs across Active Galaxies
Indian Academy of Sciences (India)
2016-01-27
Jan 27, 2016 ... Several QSO pairs have been reported and their redshifts determined, where the two objects in each pair are located across an active galaxy. The usually accepted explanation of such occurrences is that the pair is ejected from the parent galaxy. Currently interpreted redshifted spectra for both the QSOs ...
International Nuclear Information System (INIS)
Chela-Flores, J.
1981-08-01
A many-body approach to hadron structure is presented, in which we consider two parton species: spin-0 (b-partons), and spin-1/2 (f-partons). We extend a boson and a fermion pairing scheme for the b-, and f-partons respectively, into a Yang-Mills gauge theory. The main feature of this theory is that the gauge field is not identified with the usual gluon field variable in QCD. We study the confinement problem of the hadron constituents, and obtain, for low temperatures, partons that are confined by energy gaps. As the critical temperatures for the corresponding phase transitions are approached, the energy gap gradually disappears, and confinement is lost. The theory goes beyond the non-relativistic harmonic oscillator quark model, in the sense of giving physical reasons why a non-relativistic approximation is adequate in describing the internal dynamics of hadron structure. (author)
International Nuclear Information System (INIS)
Greiter, M.
1992-01-01
This dissertation contains a collection of individual articles on various topics. Their significance in the corresponding field as well as connections between them are emphasized in a general and comprehensive introduction. In the first article, the author explores the consequences for macroscopic effective Lagrangians of assuming that the momentum density is proportional to the flow of conserved current. The universal corrections obtained for the macroscopic Lagrangian of a superconductor describe the London Hall effect, and provide a fully consistent derivation of it. In the second article, a heuristic principle is proposed for quantized Hall states: the existence and incompressibility of fractionally quantized Hall states is explained by an argument based on an adiabatic localization of magnetic flux, the process of trading uniform flux for an equal amount of fictitious flux attached to the particles. This principle is exactly implemented in the third article. For a certain class of model Hamiltonians, the author obtains Laughlin's Jastrow type wave functions explicitly from a filled Landau level, by smooth extrapolation in quantum statistics. The generalization of this analysis to the torus geometry shows that theorems restricting the possibilities of quantum statistics on closed surfaces are circumvented in the presence of a magnetic field. In the last article, the existence is proposed of a novel incompressible quantum liquid, a paired Hall state, at a half filled Landau level. This state arises adiabatically from free fermions in zero magnetic field, and reduces to a state previously proposed by Halperin in the limit of tightly bound pairs. It supports unusual excitations, including neutral fermions and charge e/4 anyons with statistical parameter θ = π/8
Multi-pair states in electron–positron pair creation
Directory of Open Access Journals (Sweden)
Anton Wöllert
2016-09-01
Full Text Available Ultra strong electromagnetic fields can lead to spontaneous creation of single or multiple electron–positron pairs. A quantum field theoretical treatment of the pair creation process combined with numerical methods provides a description of the fermionic quantum field state, from which all observables of the multiple electron–positron pairs can be inferred. This allows to study the complex multi-particle dynamics of electron–positron pair creation in-depth, including multi-pair statistics as well as momentum distributions and spin. To illustrate the potential benefit of this approach, it is applied to the intermediate regime of pair creation between nonperturbative Schwinger pair creation and perturbative multiphoton pair creation where the creation of multi-pair states becomes nonnegligible but cascades do not yet set in. Furthermore, it is demonstrated how spin and helicity of the created electrons and positrons are affected by the polarization of the counterpropagating laser fields, which induce the creation of electron–positron pairs.
Pair potentials in liquid metals
International Nuclear Information System (INIS)
Faber, T.E.
1980-01-01
The argument which justifies the use of a pair potential to describe the structure-dependent term in the energy of liquid metals is briefly reviewed. Because there is an additional term in the energy which depends upon volume rather than structure, and because the pair potential itself is volume-dependent, the relationship between pair potential and observable properties such as pressure, bulk modulus and pair distribution function is more complicated for liquid metals than it is for molecular liquids. Perhaps for this reason, the agreement between pair potentials inferred from observable properties and pair potentials calculated by means of pseudo-potential theory is still far from complete. The pair potential concept is applicable only to simple liquid metals, in which the electron-ion interaction is weak. No attempt is made to discuss liquid transition and rare-earth metals, which are not simple in this sense. (author)
Experimental many-pairs nonlocality
Poh, Hou Shun; Cerè, Alessandro; Bancal, Jean-Daniel; Cai, Yu; Sangouard, Nicolas; Scarani, Valerio; Kurtsiefer, Christian
2017-08-01
Collective measurements on large quantum systems together with a majority voting strategy can lead to a violation of the Clauser-Horne-Shimony-Holt Bell inequality. In the presence of many entangled pairs, this violation decreases quickly with the number of pairs and vanishes for some critical pair number that is a function of the noise present in the system. Here we show that a different binning strategy can lead to a more substantial Bell violation when the noise is sufficiently small. Given the relation between the critical pair number and the source noise, we then present an experiment where the critical pair number is used to quantify the quality of a high visibility photon pair source. Our results demonstrate nonlocal correlations using collective measurements operating on clusters of more than 40 photon pairs.
Kramers Pairs in configuration interaction
DEFF Research Database (Denmark)
Avery, John Scales; Avery, James Emil
2003-01-01
The theory of symmetry-preserving Kramers pair creation operators is reviewed and formulas for applying these operators to configuration interaction calculations are derived. A new and more general type of symmetry-preserving pair creation operator is proposed and shown to commute with the total ...
International Nuclear Information System (INIS)
Shirbisheh, Vahid
2012-01-01
As the first step towards developing noncommutative geometry over Hecke C ∗ -algebras, we study property (RD) (Rapid Decay) for Hecke pairs. When the subgroup H in a Hecke pair (G, H) is finite, we show that the Hecke pair (G, H) has (RD) if and only if G has (RD). This provides us with a family of examples of Hecke pairs with property (RD). We also adapt Paul Jolissant’s works in Jolissaint (J K-Theory 2:723–735, 1989; Trans Amer Math Soc 317(1):167–196, 1990) to the setting of Hecke C ∗ -algebras and show that when a Hecke pair (G, H) has property (RD), the algebra of rapidly decreasing functions on the set of double cosets is closed under holomorphic functional calculus of the associated (reduced) Hecke C ∗ -algebra. Hence they have the same K 0 -groups.
Instability of vortex pair leapfrogging
DEFF Research Database (Denmark)
Tophøj, Laust; Aref, Hassan
2013-01-01
Leapfrogging is a periodic solution of the four-vortex problem with two positive and two negative point vortices all of the same absolute circulation arranged as co-axial vortex pairs. The set of co-axial motions can be parameterized by the ratio 0 vortex pair sizes at the time when one...... pair passes through the other. Leapfrogging occurs for α > σ2, where is the silver ratio. The motion is known in full analytical detail since the 1877 thesis of Gröbli and a well known 1894 paper by Love. Acheson ["Instability of vortex leapfrogging," Eur. J. Phys.21, 269-273 (2000...... pairs fly off to infinity, and a "walkabout" mode, where the vortices depart from leapfrogging but still remain within a finite distance of one another. We show numerically that this transition is more gradual, a result that we relate to earlier investigations of chaotic scattering of vortex pairs [L...
RELATIVISTIC CYCLOTRON INSTABILITY IN ANISOTROPIC PLASMAS
Energy Technology Data Exchange (ETDEWEB)
López, Rodrigo A.; Moya, Pablo S.; Muñoz, Víctor; Valdivia, J. Alejandro [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Navarro, Roberto E.; Araneda, Jaime A. [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Viñas, Adolfo F., E-mail: rlopez186@gmail.com [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, MD 20771 (United States)
2016-11-20
A sufficiently large temperature anisotropy can sometimes drive various types of electromagnetic plasma micro-instabilities, which can play an important role in the dynamics of relativistic pair plasmas in space, astrophysics, and laboratory environments. Here, we provide a detailed description of the cyclotron instability of parallel propagating electromagnetic waves in relativistic pair plasmas on the basis of a relativistic anisotropic distribution function. Using plasma kinetic theory and particle-in-cell simulations, we study the influence of the relativistic temperature and the temperature anisotropy on the collective and noncollective modes of these plasmas. Growth rates and dispersion curves from the linear theory show a good agreement with simulations results.
Pairing induced superconductivity in holography
Bagrov, Andrey; Meszena, Balazs; Schalm, Koenraad
2014-09-01
We study pairing induced superconductivity in large N strongly coupled systems at finite density using holography. In the weakly coupled dual gravitational theory the mechanism is conventional BCS theory. An IR hard wall cut-off is included to ensure that we can controllably address the dynamics of a single confined Fermi surface. We address in detail the interplay between the scalar order parameter field and fermion pairing. Adding an explicitly dynamical scalar operator with the same quantum numbers as the fermion-pair, the theory experiences a BCS/BEC crossover controlled by the relative scaling dimensions. We find the novel result that this BCS/BEC crossover exposes resonances in the canonical expectation value of the scalar operator. This occurs not only when the scaling dimension is degenerate with the Cooper pair, but also with that of higher derivative paired operators. We speculate that a proper definition of the order parameter which takes mixing with these operators into account stays finite nevertheless.
Nuclear scissors mode with pairing
International Nuclear Information System (INIS)
Balbutsev, E. B.; Malov, L. A.; Schuck, P.; Urban, M.; Vinas, X.
2008-01-01
The coupled dynamics of the scissors mode and the isovector giant quadrupole resonance are studied using a generalized Wigner function moments method, taking into account pair correlations. Equations of motion for angular momentum, quadrupole moment, and other relevant collective variables are derived on the basis of the time-dependent Hartree-Fock-Bogolyubov equations. Analytical expressions for energy centroids and transition probabilities are found for the harmonic-oscillator model with the quadrupole-quadrupole residual interaction and monopole pairing force. Deformation dependences of energies and B(M1) values are correctly reproduced. The inclusion of pair correlations leads to a drastic improvement in the description of qualitative and quantitative characteristics of the scissors mode.
Pairing mechanism in oxide superconductors
International Nuclear Information System (INIS)
Hirsch, J.E.
1988-01-01
A useful way to learn about the pairing mechanism that is responsible for high T c superconductivity is to study properties of model Hamiltonians on small systems. The goal is to find the simplest model that can describe the essential physics of high T c superconductivity. The authors have used Monte Carlo simulation and exact diagonalization techniques to study properties of systems of up to 64 sites. Their results show that spin fluctuations and other spin related mechanisms induced by a Hubbard on-site repulsion U are not likely to give rise to pairing, neither in one nor in multiple band models. In contrast, charge fluctuations in a model with both strong U and V (repulsion between Cu and O) are shown to give rise to pairing and it is suggested that this model provides a plausible mechanism for high T c superconductivity
QCD pairing in primordial nuggets
Lugones, G.; Horvath, J. E.
2003-08-01
We analyze the problem of boiling and surface evaporation of quark nuggets in the cosmological quark-hadron transition. Recently, it has been shown that QCD pairing modifies the stability properties of strange quark matter. More specifically, strange quark matter in a color-flavor locked state was found to be absolutely stable for a much wider range of the parameters than ordinary unpaired strange quark matter (G. Lugones and J. E. Horvath, Phys. Rev. D, 66, 074017 (2002)). Assuming that primordial quark nuggets are actually formed we analyze the consequences of pairing on the rates of boiling and surface evaporation in order to determine whether they could have survived.
Exclusive electroproduction of pion pairs
International Nuclear Information System (INIS)
Warkentin, N.; Schaefer, A.; Diehl, M.; Ivanov, D. Yu.
2007-01-01
We investigate electroproduction of pion pairs on the nucleon in the framework of QCD factorization for hard exclusive processes. We extend previous analyses by taking the hard-scattering coefficients at next-to-leading order in α s . The dynamics of the produced pion pair is described by two-pion distribution amplitudes, for which we perform a detailed theoretical and phenomenological analysis. In particular, we obtain constraints on these quantities by comparing our results with measurements of angular observables that are sensitive to the interference between two-pion production in the isoscalar and isovector channels. (orig.)
Instantons in lepton pair production
International Nuclear Information System (INIS)
Brandenburg, A.; Ringwald, A.; Utermann, A.
2006-05-01
We consider QCD instanton-induced contributions to lepton pair production in hadron-hadron collisions. We relate these contributions to those known from deep inelastic scattering and demonstrate that they can be calculated reliably for sufficiently large momentum transfer. We observe that the instanton contribution to the angular distribution of the lepton pairs at finite momentum transfer strongly violates the Lam-Tung relation - a relation between coefficient functions of the angular distribution which is valid within the framework of ordinary perturbation theory. The drastic violation of this relation, as seen in experimental data, might be related to such instanton-induced effects. (Orig.)
RELAXATION OF BLAZAR-INDUCED PAIR BEAMS IN COSMIC VOIDS
Energy Technology Data Exchange (ETDEWEB)
Miniati, Francesco [Physics Department, Wolfgang-Pauli-Strasse 27, ETH-Zuerich, CH-8093 Zuerich (Switzerland); Elyiv, Andrii, E-mail: fm@phys.ethz.ch [Institut d' Astrophysique et de Geophysique, Universite de Liege, B-4000 Liege (Belgium)
2013-06-10
The stability properties of a low-density ultrarelativistic pair beam produced in the intergalactic medium (IGM) by multi-TeV gamma-ray photons from blazars are analyzed. The problem is relevant for probes of magnetic field in cosmic voids through gamma-ray observations. In addition, dissipation of such beams could considerably affect the thermal history of the IGM and structure formation. We use a Monte Carlo method to quantify the properties of the blazar-induced electromagnetic shower, in particular the bulk Lorentz factor and the angular spread of the pair beam generated by the shower, as a function of distance from the blazar itself. We then use linear and nonlinear kinetic theory to study the stability of the pair beam against the growth of electrostatic plasma waves, employing the Monte Carlo results for our quantitative estimates. We find that the fastest growing mode, like any perturbation mode with even a very modest component perpendicular to the beam direction, cannot be described in the reactive regime. Due to the effect of nonlinear Landau damping, which suppresses the growth of plasma oscillations, the beam relaxation timescale is found to be significantly longer than the inverse Compton loss time. Finally, density inhomogeneities associated with cosmic structure induce loss of resonance between the beam particles and plasma oscillations, strongly inhibiting their growth. We conclude that relativistic pair beams produced by blazars in the IGM are stable on timescales that are long compared with the electromagnetic cascades. There appears to be little or no effect of pair beams on the IGM.
PAIR PRODUCTION IN LOW-LUMINOSITY GALACTIC NUCLEI
International Nuclear Information System (INIS)
Moscibrodzka, M.; Gammie, C. F.; Dolence, J. C.; Shiokawa, H.
2011-01-01
Electron-positron pairs may be produced near accreting black holes by a variety of physical processes, and the resulting pair plasma may be accelerated and collimated into a relativistic jet. Here, we use a self-consistent dynamical and radiative model to investigate pair production by γγ collisions in weakly radiative accretion flows around a black hole of mass M and accretion rate M-dot . Our flow model is drawn from general relativistic magnetohydrodynamic simulations, and our radiation field is computed by a Monte Carlo transport scheme assuming the electron distribution function is thermal. We argue that the pair production rate scales as r -6 M -1 M-dot 6 . We confirm this numerically and calibrate the scaling relation. This relation is self-consistent in a wedge in M, M-dot parameter space. If M-dot is too low the implied pair density over the poles of the black hole is below the Goldreich-Julian density and γγ pair production is relatively unimportant; if M-dot is too high the models are radiatively efficient. We also argue that for a power-law spectrum the pair production rate should scale with the observables L X ≡ X-ray luminosity and M as L 2 X M -4 . We confirm this numerically and argue that this relation likely holds even for radiatively efficient flows. The pair production rates are sensitive to black hole spin and to the ion-electron temperature ratio which are fixed in this exploratory calculation. We finish with a brief discussion of the implications for Sgr A* and M87.
Guanidinium Pairing Facilitates Membrane Translocation
Czech Academy of Sciences Publication Activity Database
Allolio, Christoph; Baxová, Katarína; Vazdar, M.; Jungwirth, Pavel
2016-01-01
Roč. 120, č. 1 (2016), s. 143-153 ISSN 1520-6106 R&D Projects: GA ČR GA13-06181S Institutional support: RVO:61388963 Keywords : ab initio molecular dynamics * guanidinium * like charge pairing * membrane Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.177, year: 2016
Pairing Linguistic and Music Intelligences
DiEdwardo, MaryAnn Pasda
2005-01-01
This article describes how music in the language classroom setting can be a catalyst for developing reading, writing, and understanding skills. Studies suggest that pairing music and linguistic intelligences in the college classroom improves students' grades and abilities to compose theses statements for research papers in courses that emphasize…
Conjugal Pairing in Escherichia Coli
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 13; Issue 8. Conjugal Pairing in Escherichia Coli. Joshua Lederberg. Classics Volume 13 Issue 8 August 2008 pp 793-794. Fulltext. Click here to view fulltext PDF. Permanent link: https://www.ias.ac.in/article/fulltext/reso/013/08/0793-0794 ...
DEFF Research Database (Denmark)
Martinez Peñas, Umberto; Pellikaan, Ruud
2017-01-01
Error-correcting pairs were introduced as a general method of decoding linear codes with respect to the Hamming metric using coordinatewise products of vectors, and are used for many well-known families of codes. In this paper, we define new types of vector products, extending the coordinatewise ...
'Leonard pairs' in classical mechanics
International Nuclear Information System (INIS)
Zhedanov, Alexei; Korovnichenko, Alyona
2002-01-01
Leonard pairs (LP) are matrices with the property of mutual tri-diagonality. We introduce and study a classical analogue of LP. We show that corresponding classical 'Leonard' dynamical variables satisfy non-linear relations of the AW-type with respect to Poisson brackets. (author)
International Nuclear Information System (INIS)
Horton, W.
1998-07-01
The origin of plasma turbulence from currents and spatial gradients in plasmas is described and shown to lead to the dominant transport mechanism in many plasma regimes. A wide variety of turbulent transport mechanism exists in plasmas. In this survey the authors summarize some of the universally observed plasma transport rates
Statistical deprojection of galaxy pairs
Nottale, Laurent; Chamaraux, Pierre
2018-06-01
Aims: The purpose of the present paper is to provide methods of statistical analysis of the physical properties of galaxy pairs. We perform this study to apply it later to catalogs of isolated pairs of galaxies, especially two new catalogs we recently constructed that contain ≈1000 and ≈13 000 pairs, respectively. We are particularly interested by the dynamics of those pairs, including the determination of their masses. Methods: We could not compute the dynamical parameters directly since the necessary data are incomplete. Indeed, we only have at our disposal one component of the intervelocity between the members, namely along the line of sight, and two components of their interdistance, i.e., the projection on the sky-plane. Moreover, we know only one point of each galaxy orbit. Hence we need statistical methods to find the probability distribution of 3D interdistances and 3D intervelocities from their projections; we designed those methods under the term deprojection. Results: We proceed in two steps to determine and use the deprojection methods. First we derive the probability distributions expected for the various relevant projected quantities, namely intervelocity vz, interdistance rp, their ratio, and the product rp v_z^2, which is involved in mass determination. In a second step, we propose various methods of deprojection of those parameters based on the previous analysis. We start from a histogram of the projected data and we apply inversion formulae to obtain the deprojected distributions; lastly, we test the methods by numerical simulations, which also allow us to determine the uncertainties involved.
International Nuclear Information System (INIS)
Weitzner, H.
1990-06-01
This paper discusses the following topics: MHD plasma activity: equilibrium, stability and transport; statistical analysis; transport studies; edge physics studies; wave propagation analysis; basic plasma physics and fluid dynamics; space plasma; and numerical methods
International Nuclear Information System (INIS)
Bingham, R.; Angelis, U. de; Johnston, T.W.
1991-01-01
Recently attention has focused on charged particle acceleration in a plasma by a fast, large amplitude, longitudinal electron plasma wave. The plasma beat wave and plasma wakefield accelerators are two efficient ways of producing ultra-high accelerating gradients. Starting with the plasma beat wave accelerator (PBWA) and laser wakefield accelerator (LWFA) schemes and the plasma wakefield accelerator (PWFA) steady progress has been made in theory, simulations and experiments. Computations are presented for the study of LWFA. (author)
Measurements of Pair Production and Electron Capture from the Continuum in Heavy Particle Collisions
2002-01-01
% WA99 \\\\ \\\\ Large transient Coulomb fields, which are generated in collisions of high-Z systems at sufficiently high energies, lead to copious production of electron-positron pairs. It has been suggested that these lepton pairs might mask signals arising from plasma phase interaction. Pair-production cross-sections have been calculated by several authors with results that differ significantly from each other. For very heavy ions and high energies, multiple pairs are expected to be formed even in single peripheral collisions. Perturbative and nonperturbative treatments lead to various predictions for the fractions of multiple pair formation out of the total cross-sections. Some of the electrons produced will be captured into bound states of the ion, thereby, reducing its charge state by one unit. This process which has been termed $^{\\prime\\prime}$Electron Capture from Pair Production$^{\\prime\\prime}$, represents the only electron capture process which increases with energy, and as such, will dominate all oth...
Plasma-assisted catalytic ionization using porous nickel plate
International Nuclear Information System (INIS)
Oohara, W.; Maeda, T.; Higuchi, T.
2011-01-01
Hydrogen atomic pair ions, i.e., H + and H - ions, are produced by plasma-assisted catalytic ionization using a porous nickel plate. Positive ions in a hydrogen plasma generated by dc arc discharge are irradiated to the porous plate, and pair ions are produced from the back of the irradiation plane. It becomes clear that the production quantity of pair ions mainly depends on the irradiation current of positive ions and the irradiation energy affects the production efficiency of H - ions.
Charge Aspects of Composite Pair Superconductivity
Flint, Rebecca
2014-03-01
Conventional Cooper pairs form from well-defined electronic quasiparticles, making the internal structure of the pair irrelevant. However, in the 115 family of superconductors, the heavy electrons are forming as they pair and the internal pair structure becomes as important as the pairing mechanism. Conventional spin fluctuation mediated pairing cannot capture the direct transition from incoherent local moments to heavy fermion superconductivity, but the formation of composite pairs favored by the two channel Kondo effect can. These composite pairs are local d-wave pairs formed by two conduction electrons in orthogonal Kondo channels screening the same local moment. Composite pairing shares the same symmetries as magnetically mediated pairing, however, only composite pairing necessarily involves a redistribution of charge within the unit cell originating from the internal pair structure, both as a monopole (valence change) and a quadrupole effect. This redistribution will onset sharply at the superconducting transition temperature. A smoking gun test for composite pairing is therefore a sharp signature at Tc - for example, a cusp in the Mossbauer isomer shift in NpPd5Al2 or in the NQR shift in (Ce,Pu)CoIn5.
Kinetic equations with pairing correlations
International Nuclear Information System (INIS)
Fauser, R.
1995-12-01
The Gorkov equations are derived for a general non-equilibrium system. The Gorkov factorization is generalized by the cumulant expansion of the 2-particle correlation and by a generalized Wick theorem in the case of a perturbation expansion. A stationary solution for the Green functions in the Schwinger-Keldysh formalism is presented taking into account pairing correlations. Especially the effects of collisional broadening on the spectral functions and Green functions is discussed. Kinetic equations are derived in the quasi-particle approximation and in the case of particles with width. Explicit expressions for the self-energies are given. (orig.)
Endocrine factors of pair bonding.
Stárka, L
2007-01-01
Throughout literature--fiction and poetry, fine arts and music--falling in love and enjoying romantic love plays a central role. While several psychosocial conceptions of pair attachment consider the participation of hormones, human endocrinology has dealt with this theme only marginally. According to some authors in addictology, falling in love shows some signs of hormonal response to stressors with changes in dopamine and serotonin signalling and neurotrophin (transforming growth factor b) concentration. Endorphins, oxytocin and vasopressin may play a role during the later phases of love. However, proof of hormonal events associated with love in humans has, until recently, been lacking.
DEFF Research Database (Denmark)
Christensen, Ole; Goh, Say Song
2012-01-01
The time–frequency analysis of a signal is often performed via a series expansion arising from well-localized building blocks. Typically, the building blocks are based on frames having either Gabor or wavelet structure. In order to calculate the coefficients in the series expansion, a dual frame...... is needed. The purpose of the present paper is to provide constructions of dual pairs of frames in the setting of the Hilbert space of periodic functions L2(0,2π). The frames constructed are given explicitly as trigonometric polynomials, which allows for an efficient calculation of the coefficients...
DEFF Research Database (Denmark)
Dalgas, Karina Märcher
2016-01-01
Most Filipina au pairs in Denmark send remittances back home, and for many, au pairing forms part of longer-term migration trajectories. This article explores how Filipina au pairs try to carve out a future for themselves abroad. It shows that they navigate within tight webs of financial interdep......Most Filipina au pairs in Denmark send remittances back home, and for many, au pairing forms part of longer-term migration trajectories. This article explores how Filipina au pairs try to carve out a future for themselves abroad. It shows that they navigate within tight webs of financial...
International Nuclear Information System (INIS)
Thode, L.E.
1981-01-01
A method is described for electron beam heating of a high-density plasma to drive a fast liner. An annular or solid relativistic electron beam is used to heat a plasma to kilovolt temperatures through streaming instabilities in the plasma. Energy deposited in the plasma then converges on a fast liner to explosively or ablatively drive the liner to implosion. (U.K.)
International Nuclear Information System (INIS)
Kirchner, Barbara; Malberg, Friedrich; Firaha, Dzmitry S; Hollóczki, Oldamur
2015-01-01
In the present article we briefly review the extensive discussion in literature about the presence or absence of ion pair-like aggregates in ionic liquids. While some experimental studies point towards the presence of neutral subunits in ionic liquids, many other experiments cannot confirm or even contradict their existence. Ion pairs can be detected directly in the gas phase, but no direct method is available to observe such association behavior in the liquid, and the corresponding indirect experimental proofs are based on such assumptions as unity charges at the ions. However, we have shown by calculating ionic liquid clusters of different sizes that assuming unity charges for ILs is erroneous, because a substantial charge transfer is taking place between the ionic liquid ions that reduce their total charge. Considering these effects might establish a bridge between the contradicting experimental results on this matter. Beside these results, according to molecular dynamics simulations the lifetimes of ion–ion contacts and their joint motions are far too short to verify the existence of neutral units in these materials. (topical review)
Some advances in pairing theory
International Nuclear Information System (INIS)
Rowe, D.J.
2001-01-01
Two advances are reviewed in the application of pairing-force theory in the nuclear shell model. The first exploits a discovery that a wide range of two-nucleon interactions conserve seniority as a good quantum number. As a consequence, the eigenstates of a Hamiltonian with such an interaction belong to irreducible representations of a compact unitary-symplectic group. This makes it possible to extend the simply-solvable models with J=0 pairing forces to a much richer set of models and still obtain states uniquely classified by their seniority and angular momentum quantum numbers. Moreover, many of the low-lying energy levels of such models can be obtained algebraically; in technical terms, the models are in some cases completely solvable and in other cases partially solvable by algebraic methods. The second advance exploits the discovery that, in a coherent state representation, states of good nucleon number can be projected analytically from BCS vacuum and excited quasiparticle states. This makes it possible to perform calculations in a number-projected BCS basis without losing much of the advantage of working of the quasiparticle scheme. (Author)
Physical processes in relativistic plasmas
International Nuclear Information System (INIS)
Svensson, R.
1984-01-01
The continuum emission in many active galactic nuclei (AGNs) extend to 100 keV and beyond (e.g. Rothschild et al. 1983). In thermal models of the continuum emission this implies temperatures above 10 9 K or kT of order mc 2 . In such a plasma the electrons are at least mildly relativistic and furthermore the particles and the photons are energetic enough to produce electron-positron pairs. The physics of such hot plasmas has only recently been studied in any detail and here we review the results of those studies. Significant electron-positron pair production may also occur in non-thermal models of the continuum emission if the optical depth to photon-photon pair production is greater than unity. We review the few results obtained regarding this interesting but not very well studied possibility. First, however, we briefly discuss the processes taking place in relativistic plasmas and the standard models for the continuum emission from AGNs. We then summarize the effects pair production have on these models and the observational implications of the presence of electron-positron pairs. (orig./WL)
Dubin, D. H. E.
This chapter explores several aspects of the linear electrostatic normal modes of oscillation for a single-species non-neutral plasma in a Penning trap. Linearized fluid equations of motion are developed, assuming the plasma is cold but collisionless, which allow derivation of the cold plasma dielectric tensor and the electrostatic wave equation. Upper hybrid and magnetized plasma waves in an infinite uniform plasma are described. The effect of the plasma surface in a bounded plasma system is considered, and the properties of surface plasma waves are characterized. The normal modes of a cylindrical plasma column are discussed, and finally, modes of spheroidal plasmas, and finite temperature effects on the modes, are briefly described.
PandA : pairings and arithmetic
Chuengsatiansup, C.; Naehrig, M.; Ribarski, P.; Schwabe, P.; Cao, Z.; Zhang, F.
2014-01-01
This paper introduces PandA, a software framework for Pairings and Arithmetic. It is designed to bring together advances in the efficient computation of cryptographic pairings and the development and implementation of pairing-based protocols. The intention behind the PandA framework is to give
Dynamical pairing correlations in rotating nuclei
International Nuclear Information System (INIS)
Szymanski, Z.
1985-01-01
When the atomic nucleus rotates fast enough the static pair correlations may be destroyed. In this situation the pair-vibrations become an important manifestation of the short-range attractive pairing force. The influence of this effect on nuclear properties at high spin is discussed. (orig.)
Momentum dependence in pair production by an external field
Asakawa, M.
1992-08-01
The transverse and the longitudinal momentum dependences of the pair production under an adiabatically exerted uniform abelian external field are calculated with their importance in models for the production of quark-gluon plasma in ultrarelativistic heavy ion collisions in mind. The importance of the initial condition is revealed. We show that superposition of acceleration by the external field and barrier penetration is reflected in the longitudinal momentum dependence. The peculiar nature of the boost invariant system which is expected to be approximately realized in ultrarelativistic nuclear collisions is pointed out.
Momentum dependence in pair production by an external field
International Nuclear Information System (INIS)
Asakawa, M.
1992-01-01
The transverse and the longitudinal momentum dependences of the pair production under an adiabatically exerted uniform abelian external field are calculated with their importance in models for the production of quark-gluon plasma in ultrarelativistic heavy ion collisions in mind. The importance of the initial condition is revealed. We show that superposition of acceleration by the external field and barrier penetration is reflected in the longitudinal momentum dependence. The peculiar nature of the boost invariant system which is expected to be approximately realized in ultrarelativistic nuclear collisions is pointed out. (orig.)
International Nuclear Information System (INIS)
Karchevskij, A.I.; Potanin, E.P.
2000-01-01
The review of the most important studies on the isotope separation processes in the rotating plasma is presented. The device is described and the characteristics of operation of the pulse plasma centrifuges with weakly and strongly ionized plasma as well as the stationary plasma centrifuges with the medium weak ionization and devices, applying the stationary vacuum arc with the high ionization rate and the stationary beam-plasma discharge with complete ionization, are presented. The possible mechanisms of the isotope separation in plasma centrifuges are considered. The specific energy consumption for isotope separation in these devices is discussed [ru
Kaplan, S A; ter Haar, D
2013-01-01
Plasma Astrophysics is a translation from the Russian language; the topics discussed are based on lectures given by V.N. Tsytovich at several universities. The book describes the physics of the various phenomena and their mathematical formulation connected with plasma astrophysics. This book also explains the theory of the interaction of fast particles plasma, their radiation activities, as well as the plasma behavior when exposed to a very strong magnetic field. The text describes the nature of collective plasma processes and of plasma turbulence. One author explains the method of elementary
Swanson, DG
1989-01-01
Plasma Waves discusses the basic development and equations for the many aspects of plasma waves. The book is organized into two major parts, examining both linear and nonlinear plasma waves in the eight chapters it encompasses. After briefly discussing the properties and applications of plasma wave, the book goes on examining the wave types in a cold, magnetized plasma and the general forms of the dispersion relation that characterize the waves and label the various types of solutions. Chapters 3 and 4 analyze the acoustic phenomena through the fluid model of plasma and the kinetic effects. Th
X-ray flares from runaway pair production in active galactic nuclei
Kirk, J. G.; Mastichiadis, A.
1992-01-01
The hard X-ray spectrum of AGNs is nonthermal, probably arising from an electron-positron pair cascade, with some emission reflected off relatively cold matter. There has been interest in models on which protons are accelerated and create relativistic electrons on interaction with a local radiation field. It is shown here that a sufficient column density of protons can lead to runaway pair production: photons generated by the relativistic pairs are the targets for the protons to produce more pairs. This can produce X-ray fluxes with the characteristics observed in AGN. The model predicts the maximum ratio of luminosity to source size as well as their spectrum in the early phases. The same mechanism may also be able to create the knots of synchrotron-radiating pair plasma seen in sources such as 3C273.
Pair shell model description of collective motions
International Nuclear Information System (INIS)
Chen Hsitseng; Feng Dahsuan
1996-01-01
The shell model in the pair basis has been reviewed with a case study of four particles in a spherical single-j shell. By analyzing the wave functions according to their pair components, the novel concept of the optimum pairs was developed which led to the proposal of a generalized pair mean-field method to solve the many-body problem. The salient feature of the method is its ability to handle within the framework of the spherical shell model a rotational system where the usual strong configuration mixing complexity is so simplified that it is now possible to obtain analytically the band head energies and the moments of inertia. We have also examined the effects of pair truncation on rotation and found the slow convergence of adding higher spin pairs. Finally, we found that when the SDI and Q .Q interactions are of equal strengths, the optimum pair approximation is still valid. (orig.)
Stanislavsky, A.; Volvach, Ya.; Konovalenko, A.; Koval, A.
2017-08-01
In this paper a new sight on the study of solar bursts historically called drift pairs (DPs) is presented. Having a simple morphology on dynamic spectra of radio records (two short components separated in time, and often they are very similar) and discovered at the dawn of radio astronomy, their features remain unexplained totally up to now. Generally, the DPs are observed during the solar storms of type III bursts, but not every storm of type III bursts is linked with DPs. Detected by ground-based instruments at decameter and meter wavelengths, the DP bursts are limited in frequency bandwidth. They can drift from high frequencies to low ones and vice versa. Their frequency drift rate may be both lower and higher than typical rates of type III bursts at the same frequency range. The development of low-frequency radio telescopes and data processing provide additional possibilities in the research. In this context the fresh analysis of DPs, made from recent observations in the summer campaign of 2015, are just considered. Their study was implemented by updated tools of the UTR-2 radio telescope at 9-33 MHz. During 10-12 July of 2015, DPs forming the longest patterns on dynamic spectra are about 7% of the total number of recorded DPs. Their marvelous resemblance in frequency drift rates with the solar S-bursts is discussed.
Production of magnetic monopole pairs
International Nuclear Information System (INIS)
Maher, R.L.
1980-01-01
Using a covariant photon propagator (developed by W.B. Campbell) to represent a photon exchange between a magnetic monopole and an electric charge, the first order production amplitudes in a Feynman-Dyson perturbation expansion and the resulting differential cross-sections are calculated for monopole pair creation from: (i) electron positron annihilation, (ii) photon scattering in the presence of a nucleus, and (iii) electron scattering in the presence of a nucleus. This theory does not specify the spin character of magnetic monopoles, so all processes are calculated twice: for spin zero monopoles and for spin one-half monopoles. In the first and last processes the differential cross-sections have sufficiently different dependences on the production angles (associated with the monopoles momenta), so that near threshold experiments could distinguish between whether monopoles are either spin one-half or spin zero entities. For the t'Hooft monopole mass estimate (5-8 x 10 3 GeV) very high energy particle and photon beam sources would be required to achieve threshold for these production processes
International Nuclear Information System (INIS)
Thode, L.E.
1981-01-01
A method is described of providing electron beam heating of a high-density plasma to drive a fast liner to implode a structured microsphere. An annular relativistic electron beam is used to heat an annular plasma to kilovolt temperatures through streaming instabilities in the plasma. Energy deposited in the annular plasma then converges on a fast liner to explosively or ablatively drive the liner to convergence to implode the structured microsphere. (U.K.)
Report on Pairing-based Cryptography.
Moody, Dustin; Peralta, Rene; Perlner, Ray; Regenscheid, Andrew; Roginsky, Allen; Chen, Lily
2015-01-01
This report summarizes study results on pairing-based cryptography. The main purpose of the study is to form NIST's position on standardizing and recommending pairing-based cryptography schemes currently published in research literature and standardized in other standard bodies. The report reviews the mathematical background of pairings. This includes topics such as pairing-friendly elliptic curves and how to compute various pairings. It includes a brief introduction to existing identity-based encryption (IBE) schemes and other cryptographic schemes using pairing technology. The report provides a complete study of the current status of standard activities on pairing-based cryptographic schemes. It explores different application scenarios for pairing-based cryptography schemes. As an important aspect of adopting pairing-based schemes, the report also considers the challenges inherent in validation testing of cryptographic algorithms and modules. Based on the study, the report suggests an approach for including pairing-based cryptography schemes in the NIST cryptographic toolkit. The report also outlines several questions that will require further study if this approach is followed.
Counter-facing plasma guns for efficient extreme ultra-violet plasma light source
Kuroda, Yusuke; Yamamoto, Akiko; Kuwabara, Hajime; Nakajima, Mitsuo; Kawamura, Tohru; Horioka, Kazuhiko
2013-11-01
A plasma focus system composed of a pair of counter-facing coaxial guns was proposed as a long-pulse and/or repetitive high energy density plasma source. We applied Li as the source of plasma for improvement of the conversion efficiency, the spectral purity, and the repetition capability. For operation of the system with ideal counter-facing plasma focus mode, we changed the system from simple coaxial geometry to a multi-channel configuration. We applied a laser trigger to make synchronous multi-channel discharges with low jitter. The results indicated that the configuration is promising to make a high energy density plasma with high spectral efficiency.
Pairing from dynamically screened Coulomb repulsion in bismuth
Ruhman, Jonathan; Lee, Patrick A.
2017-12-01
Recently, Prakash et al. have discovered bulk superconductivity in single crystals of bismuth, which is a semimetal with extremely low carrier density. At such low density, we argue that conventional electron-phonon coupling is too weak to be responsible for the binding of electrons into Cooper pairs. We study a dynamically screened Coulomb interaction with effective attraction generated on the scale of the collective plasma modes. We model the electronic states in bismuth to include three Dirac pockets with high velocity and one hole pocket with a significantly smaller velocity. We find a weak-coupling instability, which is greatly enhanced by the presence of the hole pocket. Therefore we argue that bismuth is the first material to exhibit superconductivity driven by retardation effects of Coulomb repulsion alone. By using realistic parameters for bismuth we find that the acoustic plasma mode does not play the central role in pairing. We also discuss a matrix element effect, resulting from the Dirac nature of the conduction band, which may affect Tc in the s -wave channel without breaking time-reversal symmetry.
International Nuclear Information System (INIS)
Jones, M.E.; Winske, D.; Keinigs, R.; Lemons, D.
1996-01-01
This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project has been to develop a fundamental understanding of dusty plasmas at the Laboratory. While dusty plasmas are found in space in galactic clouds, planetary rings, and cometary tails, and as contaminants in plasma enhanced fabrication of microelectronics, many of their properties are only partially understood. Our work has involved both theoretical analysis and self-consistent plasma simulations to understand basic properties of dusty plasmas related to equilibrium, stability, and transport. Such an understanding can improve the control and elimination of plasma dust in industrial applications and may be important in the study of planetary rings and comet dust tails. We have applied our techniques to the study of charging, dynamics, and coagulation of contaminants in plasma processing reactors for industrial etching and deposition processes and to instabilities in planetary rings and other space plasma environments. The work performed in this project has application to plasma kinetics, transport, and other classical elementary processes in plasmas as well as to plasma waves, oscillations, and instabilities
International Nuclear Information System (INIS)
Anon.
1984-01-01
This book examines the fundamental theory and various applications of ion mobility spectroscopy. Plasma chromatography developed from research on the diffusion and mobility of ions. Topics considered include instrument design and description (e.g., performance, spectral interpretation, sample handling, mass spectrometry), the role of ion mobility in plasma chromatography (e.g., kinetic theory of ion transport), atmospheric pressure ionization (e.g., rate equations), the characterization of isomers by plasma chromatography (e.g., molecular ion characteristics, polynuclear aromatics), plasma chromatography as a gas chromatographic detection method (e.g., qualitative analysis, continuous mobility monitoring, quantitative analysis), the analysis of toxic vapors by plasma chromatography (e.g., plasma chromatograph calibration, instrument control and data processing), the analysis of semiconductor devices and microelectronic packages by plasma chromatography/mass spectroscopy (e.g., analysis of organic surface contaminants, analysis of water in sealed electronic packages), and instrument design and automation (hardware, software)
An Entropic Approach for Pair Trading
Directory of Open Access Journals (Sweden)
Daisuke Yoshikawa
2017-06-01
Full Text Available In this paper, we derive the optimal boundary for pair trading. This boundary defines the points of entry into or exit from the market for a given stock pair. However, if the assumed model contains uncertainty, the resulting boundary could result in large losses. To avoid this, we develop a more robust strategy by accounting for the model uncertainty. To incorporate the model uncertainty, we use the relative entropy as a penalty function in the expected profit from pair trading.
Magnetized pair Bose gas: relativistic superconductor
International Nuclear Information System (INIS)
Daicic, J.; Frankel, N.E.; Kowalenko, V.
1993-01-01
The magnetized Bose gas at temperatures above pair threshold is investigated. New magnetization laws are obtained for a wide range of field strengths, and the gas is shown to exhibit the Meissner effect. Some related results for the Fermi gas, a relativistic paramagnet, are also discussed. It is concluded that the pair gases, through the interplay between pair creation, temperature, field strength, statistics and/in the case of fermions/spin, have remarkable magnetic properties. 14 refs
A method for measuring plasma position in TJ-I Tokamak
International Nuclear Information System (INIS)
Quin, J.; TJ-I Team.
1993-01-01
A method using pairs of Mirnov coils to measure the plasma position in TJ-I is presented. The simple toroidal filament model which neglects the effect of plasma current density profile has proven to be acceptable within the experimental accuracy. The effect of plasma current density profile remains to be small, if the plasma current density profile has a quadratic form. (Author)
Variational study of the pair hopping model
International Nuclear Information System (INIS)
Fazekas, P.
1990-01-01
We study the ground state of a Hamiltonian introduced by Kolb and Penson for modelling situations in which small electron pairs are formed. The Hamiltonian consists of a tight binding band term, and a term describing the nearest neighbour hopping of electron pairs. We give a Gutzwiller-type variational treatment, first with a single-parameter Ansatz treated in the single site Gutzwiller approximation, and then with more complicated trial wave functions, and an improved Gutzwiller approximation. The calculation yields a transition from a partially paired normal state, in which the spin susceptibility has a diminished value, into a fully paired state. (author). 16 refs, 2 figs
Dual origin of pairing in nuclei
Energy Technology Data Exchange (ETDEWEB)
Idini, A. [University of Jyvaskyla, Department of Physics (Finland); Potel, G. [Michigan State University, National Superconducting Cyclotron Laboratory (United States); Barranco, F. [Escuela Superior de Ingenieros, Universidad de Sevilla, Departamento de Fìsica Aplicada III (Spain); Vigezzi, E., E-mail: enrico.vigezzi@mi.infn.it [INFN Sezione di Milano (Italy); Broglia, R. A. [Università di Milano, Dipartimento di Fisica (Italy)
2016-11-15
The pairing correlations of the nucleus {sup 120}Sn are calculated by solving the Nambu–Gor’kov equations, including medium polarization effects resulting from the interweaving of quasiparticles, spin and density vibrations, taking into account, within the framework of nuclear field theory (NFT), processes leading to self-energy and vertex corrections and to the induced pairing interaction. From these results one can not only demonstrate the inevitability of the dual origin of pairing in nuclei, but also extract information which can be used at profit to quantitatively disentangle the contributions to the pairing gap Δ arising from the bare and from the induced pairing interaction. The first is the strong {sup 1}S{sub 0} short-range NN potential resulting from meson exchange between nucleons moving in time reversal states within an energy range of hundreds of MeV from the Fermi energy. The second results from the exchange of vibrational modes between nucleons moving within few MeV from the Fermi energy. Short- (v{sub p}{sup bare}) and long-range (v{sub p}{sup ind}) pairing interactions contribute essentially equally to nuclear Cooper pair stability. That is to the breaking of gauge invariance in open-shell superfluid nuclei and thus to the order parameter, namely to the ground state expectation value of the pair creation operator. In other words, to the emergent property of generalized rigidity in gauge space, and associated rotational bands and Cooper pair tunneling between members of these bands.
Pair production in small angle Bhabha scattering
International Nuclear Information System (INIS)
Arbuzov, A.B.; Kuraev, Eh.A.; Merenkov, N.P.; Trentadue, L.
1995-01-01
The radiative corrections due to a pair production in the small angle high energy e + e - Bhabha scattering are considered. The corrections due to the production of virtual pairs as well as real soft and hard ones are calculated analytically. The collinear and semi-collinear kinematical regions of the hard pair production are taken into account. The results in the leading and next-to-leading logarithmic approximations provide the accuracy of Ο (0.1%). The results of numerical calculations show that the effects of pairs production are to be taken into account in the precise luminosity determination at LEP. 9 refs., 3 figs., 2 tabs
Heteroditopic receptors for ion-pair recognition.
McConnell, Anna J; Beer, Paul D
2012-05-21
Ion-pair recognition is a new field of research emerging from cation and anion coordination chemistry. Specific types of heteroditopic receptor designs for ion pairs and the complexity of ion-pair binding are discussed to illustrate key concepts such as cooperativity. The importance of this area of research is reflected by the wide variety of potential applications of ion-pair receptors, including applications as membrane transport and salt solubilization agents and sensors. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Dual origin of pairing in nuclei
Idini, A.; Potel, G.; Barranco, F.; Vigezzi, E.; Broglia, R. A.
2016-11-01
The pairing correlations of the nucleus 120Sn are calculated by solving the Nambu-Gor'kov equations, including medium polarization effects resulting from the interweaving of quasiparticles, spin and density vibrations, taking into account, within the framework of nuclear field theory (NFT), processes leading to self-energy and vertex corrections and to the induced pairing interaction. From these results one can not only demonstrate the inevitability of the dual origin of pairing in nuclei, but also extract information which can be used at profit to quantitatively disentangle the contributions to the pairing gap Δ arising from the bare and from the induced pairing interaction. The first is the strong 1 S 0 short-range NN potential resulting from meson exchange between nucleons moving in time reversal states within an energy range of hundreds of MeV from the Fermi energy. The second results from the exchange of vibrational modes between nucleons moving within few MeV from the Fermi energy. Short- ( v p bare) and long-range ( v p ind) pairing interactions contribute essentially equally to nuclear Cooper pair stability. That is to the breaking of gauge invariance in open-shell superfluid nuclei and thus to the order parameter, namely to the ground state expectation value of the pair creation operator. In other words, to the emergent property of generalized rigidity in gauge space, and associated rotational bands and Cooper pair tunneling between members of these bands.
Finding Maximal Pairs with Bounded Gap
DEFF Research Database (Denmark)
Brodal, Gerth Stølting; Lyngsø, Rune B.; Pedersen, Christian N. S.
1999-01-01
. In this paper we present methods for finding all maximal pairs under various constraints on the gap. In a string of length n we can find all maximal pairs with gap in an upper and lower bounded interval in time O(n log n+z) where z is the number of reported pairs. If the upper bound is removed the time reduces...... to O(n+z). Since a tandem repeat is a pair where the gap is zero, our methods can be seen as a generalization of finding tandem repeats. The running time of our methods equals the running time of well known methods for finding tandem repeats....
Handley, John C.; Babcock, Jason S.; Pelz, Jeff B.
2003-12-01
Image evaluation tasks are often conducted using paired comparisons or ranking. To elicit interval scales, both methods rely on Thurstone's Law of Comparative Judgment in which objects closer in psychological space are more often confused in preference comparisons by a putative discriminal random process. It is often debated whether paired comparisons and ranking yield the same interval scales. An experiment was conducted to assess scale production using paired comparisons and ranking. For this experiment a Pioneer Plasma Display and Apple Cinema Display were used for stimulus presentation. Observers performed rank order and paired comparisons tasks on both displays. For each of five scenes, six images were created by manipulating attributes such as lightness, chroma, and hue using six different settings. The intention was to simulate the variability from a set of digital cameras or scanners. Nineteen subjects, (5 females, 14 males) ranging from 19-51 years of age participated in this experiment. Using a paired comparison model and a ranking model, scales were estimated for each display and image combination yielding ten scale pairs, ostensibly measuring the same psychological scale. The Bradley-Terry model was used for the paired comparisons data and the Bradley-Terry-Mallows model was used for the ranking data. Each model was fit using maximum likelihood estimation and assessed using likelihood ratio tests. Approximate 95% confidence intervals were also constructed using likelihood ratios. Model fits for paired comparisons were satisfactory for all scales except those from two image/display pairs; the ranking model fit uniformly well on all data sets. Arguing from overlapping confidence intervals, we conclude that paired comparisons and ranking produce no conflicting decisions regarding ultimate ordering of treatment preferences, but paired comparisons yield greater precision at the expense of lack-of-fit.
Stereo Pair: Wellington, New Zealand
2000-01-01
Wellington, the capital city of New Zealand, is located on the shores of Port Nicholson, a natural harbor at the south end of North Island. The city was founded in 1840 by British emigrants and now has a regional population of more than 400,000 residents. As seen here, the natural terrain imposes strong control over the urban growth pattern (urban features generally appear gray or white in this view). Rugged hills generally rising to 300 meters (1,000 feet) help protect the city and harbor from strong winter windsNew Zealand is seismically active and faults are readily seen in the topography. The Wellington Fault forms the straight northwestern (left) shoreline of the harbor. Toward the southwest (down) the fault crosses through the city, then forms linear canyons in the hills before continuing offshore at the bottom. Toward the northeast (upper right) the fault forms the sharp mountain front along the northern edge of the heavily populated Hutt Valley.This stereoscopic image pair was generated using topographic data from the Shuttle Radar Topography Mission, combined with an enhanced true color Landsat7 satellite image. The topography data are used to create two differing perspectives of a single image, one perspective for each eye. In doing so, each point in the image is shifted slightly, depending on its elevation. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions.Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30 meter (99 foot) spatial resolution of most Landsat images and will provide a valuable complement for studying the historic and growing Landsat data archive. The Landsat 7 Thematic Mapper image used here was provided to the SRTM project by the United States Geological Survey, Earth Resources Observation Systems (EROS) data Center, Sioux Falls, South Dakota.Elevation data used in this image
SRTM Stereo Pair: Fiji Islands
2000-01-01
image pair and viewing them with a stereoscope. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions.This image was acquired by SRTM aboard the Space Shuttle Endeavour, launched on February 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (about 200 feet) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC.Size: 192 km (119 miles) x 142 km (88 miles) Location: 17.8 deg. South lat., 178.0 deg. East lon. Orientation: North at top Date Acquired: February 19, 2000 Image: NASA/JPL/NIMA
Hole pairing induced by antiferromagnetic spin fluctuations
International Nuclear Information System (INIS)
Su, Z.B.; Yu Lu; Dong, J.M.; Tosatti, E.
1987-08-01
The effective interaction induced by antiferromagnetic spin fluctuations is considered in the random phase approximation in the context of the recently discovered high T c oxide superconductors. This effective attraction favours a triplet pairing of holes. The implications of such pairing mechanism are discussed in connection with the current experimental observations. (author). 30 refs, 2 figs
Exploring Pair Programming Benefits for MIS Majors
Dongo, Tendai; Reed, April H.; O'Hara, Margaret
2016-01-01
Pair programming is a collaborative programming practice that places participants in dyads, working in tandem at one computer to complete programming assignments. Pair programming studies with Computer Science (CS) and Software Engineering (SE) majors have identified benefits such as technical productivity, program/design quality, academic…
Exclusive production of W pairs in CMS
INSPIRE-00002838
2014-01-01
We report the results on the search for exclusive production of $W$ pairs in the LHC with data collected by the Compact Muon Solenoid detector in proton-proton collisions at $\\sqrt{s}$~=~7~TeV. The analysis comprises the two-photon production of a $W$ pairs, ${pp\\to p\\,W^{+}W^{-}\\,p\\to p\\,\
Exclusive production of $W$ pairs in CMS
Da Silveira, Gustavo Gil; CMS
2014-01-01
We report the results on the search for exclusive production of $W$ pairs in the LHC with data collected by the Compact Muon Solenoid detector in proton-proton collisions at $\\sqrt{s}$~=~7~TeV. The analysis comprises the two-photon production of a $W$ pairs, ${pp\\to p\\,W^{+}W^{-}\\,p\\to p\\,\
Becoming independent through au pair migration
DEFF Research Database (Denmark)
Dalgas, Karina Märcher
2015-01-01
. This article argues that, despite this critique, au pairing does play an important formative role for young Filipinas because it opens up for experiences abroad that enable them to be recognised as independent adults in Philippine society. Rather than autonomy, however, au pairs define their independence...
A New Secure Pairing Protocol using Biometrics
Buhan, I.R.
2008-01-01
Secure Pairing enables two devices, which share no prior context with each other, to agree upon a security association that they can use to protect their subsequent communication. Secure pairing offers guarantees of the association partner identity and it should be resistant to eavesdropping or to a
Pair creation at large inherent angles
International Nuclear Information System (INIS)
Chen, P.; Tauchi, T.; Schroeder, D.V.
1992-01-01
In the next-generation linear colliders, the low-energy e + e - pairs created during the collision of high-energy e + e - beams would cause potential deleterious background problems to the detectors. At low collider energies, the pairs are made essentially by the incoherent process, where the pair is created by the interaction of beamstrahlung photons on the individual particles in the oncoming beam. This problem was first identified by Zolotarev, et al. At energies where the beamstrahlung parameter Υ lies approximately in the range 0.6 approx-lt Υ approx-lt 100, pair creation from the beamstrahlung photons is dominated by a coherent process, first noted by Chen. The seriousness of this pair creation problem lies in the transverse momenta that the pair particles carry when leaving the interaction point (IP) with large angles. Since the central issue is the transverse momentum for particles with large angles, the authors notice that there is another source for it. Namely, when the pair particles are created at low energies, the intrinsic angles of these pairs when produced may already be large. In this paper they reinvestigate the problem, following essentially the same equivalent photon approach, but with changes in specific details including the virtual photon spectrum. In addition, various assumptions are made more explicit. The formulas derived are then applied to the collider parameters designed by Palmer
Plasma Generator Using Spiral Conductors
Szatkowski, George N. (Inventor); Dudley, Kenneth L. (Inventor); Ticatch, Larry A. (Inventor); Smith, Laura J. (Inventor); Koppen, Sandra V. (Inventor); Nguyen, Truong X. (Inventor); Ely, Jay J. (Inventor)
2016-01-01
A plasma generator includes a pair of identical spiraled electrical conductors separated by dielectric material. Both spiraled conductors have inductance and capacitance wherein, in the presence of a time-varying electromagnetic field, the spiraled conductors resonate to generate a harmonic electromagnetic field response. The spiraled conductors lie in parallel planes and partially overlap one another in a direction perpendicular to the parallel planes. The geometric centers of the spiraled conductors define endpoints of a line that is non-perpendicular with respect to the parallel planes. A voltage source coupled across the spiraled conductors applies a voltage sufficient to generate a plasma in at least a portion of the dielectric material.
Drummond, James E
1961-01-01
A historic snapshot of the field of plasma physics, this fifty-year-old volume offers an edited collection of papers by pioneering experts in the field. In addition to assisting students in their understanding of the foundations of classical plasma physics, it provides a source of historic context for modern physicists. Highly successful upon its initial publication, this book was the standard text on plasma physics throughout the 1960s and 70s.Hailed by Science magazine as a ""well executed venture,"" the three-part treatment ranges from basic plasma theory to magnetohydrodynamics and microwa
International Nuclear Information System (INIS)
Omichi, Takeo; Yamanaka, Toshiyuki.
1976-01-01
Object: To recycle a coolant in a sealed hollow portion formed interiorly of a plasma limiter itself to thereby to cause direct contact between the coolant and the plasma limiter and increase of contact area therebetween to cool the plasma limiter. Structure: The heat resulting from plasma generated during operation and applied to the body of the plasma limiter is transmitted to the coolant, which recycles through an inlet and outlet pipe, an inlet and outlet nozzle and a hollow portion to hold the plasma limiter at a level less than a predetermined temperature. On the other hand, the heater wire is, at the time of emergency operation, energized to heat the plasma limiter, but this heat is transmitted to the limiter body to increase the temperature thereof. However, the coolant recycling the hollow portion comes into direct contact with the limiter body, and since the plasma limiter surround the hollow portion, the heat amount transmitted from the limiter body to the coolant increases to sufficiently cool the plasma limiter. (Yoshihara, H.)
Measurements of Pair Production and Electron Capture from the Continuum in Heavy Particle Collisions
2002-01-01
Large transient Coulomb fields, which are generated in collisions of high-Z systems at sufficiently high energies, lead to copious production of electron-positron pairs. It has been suggested that these lepton pairs might mask signals arising from plasma phase interaction. Pair-production cross sections have been calculated by several authors with results which differ significantly from each other. Some of the electrons produced may be captured into bound states of the ion, thereby, reducing its charge state by one unit. This process which has been termed ``Electron Capture from Pair Production``, represents the only electron capture pro which increases with energy, and as such, will dominate all others in the ultrarelativistic energy regime. Ions having undergone this process would be lost from storage-type accelerators. The absolute cross sections for capture have been calculated with results which differ by as much as an order of magnitude. If as large as some of the calculations predict, Relativistic Heav...
Rayleigh-Taylor instability in an equal mass plasma
Energy Technology Data Exchange (ETDEWEB)
Adak, Ashish, E-mail: ashish-adak@yahoo.com [Department of Instrumentation Science, Jadavpur University, Kolkata 700 032 (India); Ghosh, Samiran, E-mail: sran-g@yahoo.com [Department of Applied Mathematics, University of Calcutta 92, Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Chakrabarti, Nikhil, E-mail: nikhil.chakrabarti@saha.ac.in [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)
2014-09-15
The Rayleigh-Taylor (RT) instability in an inhomogeneous pair-ion plasma has been analyzed. Considering two fluid model for two species of ions (positive and negative), we obtain the possibility of the existence of RT instability. The growth rate of the RT instability as usual depends on gravity and density gradient scale length. The results are discussed in context of pair-ion plasma experiments.
Bridge between fusion plasma and plasma processing
International Nuclear Information System (INIS)
Ohno, Noriyasu; Takamura, Shuichi
2008-01-01
In the present review, relationship between fusion plasma and processing plasma is discussed. From boundary-plasma studies in fusion devices new applications such as high-density plasma sources, erosion of graphite in a hydrogen plasma, formation of helium bubbles in high-melting-point metals and the use of toroidal plasmas for plasma processing are emerging. The authors would like to discuss a possibility of knowledge transfer from fusion plasmas to processing plasmas. (T. Ikehata)
String pair production in non homogeneous backgrounds
Energy Technology Data Exchange (ETDEWEB)
Bolognesi, S. [Department of Physics “E. Fermi” University of Pisa, and INFN - Sezione di Pisa,Largo Pontecorvo, 3, Ed. C, 56127 Pisa (Italy); Rabinovici, E. [Racah Institute of Physics, The Hebrew University of Jerusalem,91904 Jerusalem (Israel); Tallarita, G. [Departamento de Ciencias, Facultad de Artes Liberales,Universidad Adolfo Ibáñez, Santiago 7941169 (Chile)
2016-04-28
We consider string pair production in non homogeneous electric backgrounds. We study several particular configurations which can be addressed with the Euclidean world-sheet instanton technique, the analogue of the world-line instanton for particles. In the first case the string is suspended between two D-branes in flat space-time, in the second case the string lives in AdS and terminates on one D-brane (this realizes the holographic Schwinger effect). In some regions of parameter space the result is well approximated by the known analytical formulas, either the particle pair production in non-homogeneous background or the string pair production in homogeneous background. In other cases we see effects which are intrinsically stringy and related to the non-homogeneity of the background. The pair production is enhanced already for particles in time dependent electric field backgrounds. The string nature enhances this even further. For spacial varying electrical background fields the string pair production is less suppressed than the rate of particle pair production. We discuss in some detail how the critical field is affected by the non-homogeneity, for both time and space dependent electric field backgrouds. We also comment on what could be an interesting new prediction for the small field limit. The third case we consider is pair production in holographic confining backgrounds with homogeneous and non-homogeneous fields.
Thermodynamics of pairing phase transition in nuclei
International Nuclear Information System (INIS)
Karim, Afaque; Ahmad, Shakeb
2014-01-01
The pairing gaps, pairing energy, heat capacity and entropy are calculated within BCS (Bardeen- Cooper-Schrieffer) based quasi particle approach, including thermal fluctuations on pairing field within pairing model for all nuclei (light, medium, heavy and super heavy nuclei). Quasi particles approach in BCS theory was introduced and reformulated to study various properties. For thermodynamic behavior of nuclei at finite temperatures, the anomalous averages of creation and annihilation operators are introduced. It is solved self consistently at finite temperatures to obtain BCS Hamiltonian. After doing unitary transformation, we obtained the Hamiltonian in the diagonal form. Thus, one gets temperature dependence gap parameter and pairing energy for nuclei. Moreover, the energy at finite temperatures is the sum of the condensation energy and the thermal energy of fermionic quasi particles. With the help of BCS Hamiltonian, specific heat, entropy and free energy are calculated for different nuclei. In this paper the gap parameter occupation number and pairing energy as a function of temperature which is important for all the light, medium, heavy and super heavy nuclei is calculated. Moreover, the various thermo dynamical quantities like specific heat, entropy and free energy is also obtained for different nuclei. Thus, the thermodynamics of pairing phase transition in nuclei is studied
Exploring Pair Programming Benefits for MIS Majors
Directory of Open Access Journals (Sweden)
April H. Reed
2016-12-01
Full Text Available Pair programming is a collaborative programming practice that places participants in dyads, working in tandem at one computer to complete programming assignments. Pair programming studies with Computer Science (CS and Software Engineering (SE majors have identified benefits such as technical productivity, program/design quality, academic performance, and increased satisfaction for their participants. In this paper, pair programming is studied with Management Information Systems (MIS majors, who (unlike CS and SE majors taking several programming courses typically take only one programming course and often struggle to develop advanced programming skills within that single course. The researchers conducted two pair programming experiments in an introductory software development course for MIS majors over three semesters to determine if pair programming could enhance learning for MIS students. The program results, researchers’ direct observations, and participants’ responses to a survey questionnaire were analyzed after each experiment. The results indicate that pair programming appears to be beneficial to MIS students’ technical productivity and program design quality, specifically the ability to create programs using high-level concepts. Additionally, results confirmed increased student satisfaction and reduced frustration, as the pairs worked collaboratively to produce a program while actively communicating and enjoying the process.
Effect of pairing on nuclear dynamics
International Nuclear Information System (INIS)
Scamps, Guillaume
2014-01-01
Pairing correlations is an essential component for the description of the atomic nuclei. The effects of pairing on static property of nuclei are now well known. In this thesis, the effect of pairing on nuclear dynamics is investigated. Theories that includes pairing are benchmarked in a model case. The TDHF+BCS theory turns out to be a good compromise between the physics taken into account and the numerical cost. This TDHF+BCS theory was retained for realistic calculations. Nevertheless, the application of pairing in the BCS approximation may induce new problems due to (1) the particle number symmetry breaking, (2) the non-conservation of the continuity equation. These difficulties are analysed in detail and solutions are proposed. In this thesis, a 3 dimensional TDHF+BCS code is developed to simulate the nuclear dynamic. Applications to giant resonances show that pairing modify only the low lying peaks. The high lying collective components are only affected by the initial conditions. An exhaustive study of the giant quadrupole resonances with the TDHF+BCS theory is performed on more than 700 spherical or deformed nuclei. Is is shown that the TDHF+BCS theory reproduces well the collective energy of the resonance. After validation on the small amplitude limit problem, the approach was applied to study nucleon transfer in heavy ion reactions. A new method to extract transfer probabilities is introduced. It is demonstrated that pairing significantly increases the two-nucleon transfer probability. (author) [fr
String pair production in non homogeneous backgrounds
International Nuclear Information System (INIS)
Bolognesi, S.; Rabinovici, E.; Tallarita, G.
2016-01-01
We consider string pair production in non homogeneous electric backgrounds. We study several particular configurations which can be addressed with the Euclidean world-sheet instanton technique, the analogue of the world-line instanton for particles. In the first case the string is suspended between two D-branes in flat space-time, in the second case the string lives in AdS and terminates on one D-brane (this realizes the holographic Schwinger effect). In some regions of parameter space the result is well approximated by the known analytical formulas, either the particle pair production in non-homogeneous background or the string pair production in homogeneous background. In other cases we see effects which are intrinsically stringy and related to the non-homogeneity of the background. The pair production is enhanced already for particles in time dependent electric field backgrounds. The string nature enhances this even further. For spacial varying electrical background fields the string pair production is less suppressed than the rate of particle pair production. We discuss in some detail how the critical field is affected by the non-homogeneity, for both time and space dependent electric field backgrouds. We also comment on what could be an interesting new prediction for the small field limit. The third case we consider is pair production in holographic confining backgrounds with homogeneous and non-homogeneous fields.
National Research Council Canada - National Science Library
Swanson, D. G
1989-01-01
... Swanson, D.G. (Donald Gary), D a t e - Plasma waves. Bibliography: p. Includes index. 1. Plasma waves. QC718.5.W3S43 1989 ISBN 0-12-678955-X I. Title. 530.4'4 88-34388 Printed in the United Sta...
International Nuclear Information System (INIS)
Weitzner, H.
1991-06-01
The Magneto-Fluid Dynamics Division continues to study a broad range of problems originating in plasma physics. Its principal focus is fusion plasma physics, and most particularly topics of particular significance for the world magnetic fusion program. During the calendar year 1990 we explored a wide range of topics including RF-induced transport as a plasma control mechanism, edge plasma modelling, further statistical analysis of L and H mode tokamak plasmas, antenna design, simulation of the edge of a tokamak plasma and the L-H transition, interpretation of the CCT experimental results at UCLA, turbulent transport, studies in chaos, the validity of moment approximations to kinetic equations and improved neoclassical modelling. In more basic studies we examined the statistical mechanisms of Coulomb systems and applied plasma ballooning mode theory to conventional fluids in order to obtain novel fluid dynamics stability results. In space plasma physics we examined the problem of reconnection, the effect of Alfven waves in space environments, and correct formulation of boundary conditions of the Earth for waves in the ionosphere
International Nuclear Information System (INIS)
Ebisawa, Katsuyuki.
1985-01-01
Purpose: To enable to easily detect that the thickness of material to be abraded is reduced to an allowable limit from the outerside of the plasma container even during usual operation in a plasma vessel for a thermonuclear device. Constitution: A labelled material is disposed to the inside or rear face of constituent members of a plasma container undergoing the irradiation of plasma particles. A limiter plate to be abraded in the plasma container is composed of an armour member and heat removing plate, in which the armour member is made of graphite and heat-removing plate is made of copper. If the armour member is continuously abraded under the effect of sputtering due to plasma particles, silicon nitride embedded so far in the graphite at last appears on the surface of the limiter plate to undergo the impact shocks of the plasma particles. Accordingly, abrasion of the limiter material can be detected by a detector comprising gas chromatography and it can easily be detected from the outside of the plasma content even during normal operation. (Horiuchi, T.)
Nonrandom network connectivity comes in pairs
Directory of Open Access Journals (Sweden)
Felix Z. Hoffmann
2017-02-01
Full Text Available Overrepresentation of bidirectional connections in local cortical networks has been repeatedly reported and is a focus of the ongoing discussion of nonrandom connectivity. Here we show in a brief mathematical analysis that in a network in which connection probabilities are symmetric in pairs, Pij = Pji, the occurrences of bidirectional connections and nonrandom structures are inherently linked; an overabundance of reciprocally connected pairs emerges necessarily when some pairs of neurons are more likely to be connected than others. Our numerical results imply that such overrepresentation can also be sustained when connection probabilities are only approximately symmetric.
Soliton pair creation at finite temperatures
International Nuclear Information System (INIS)
Grigoriev, D.Yu.; Rubakov, V.A.
1988-01-01
Creation of soliton-antisoliton pairs at finite temperature is considered within a (1+1)-dimensional model of a real scalar field. It is argued that at certain temperatures, the soliton pair creation in quantum theory can be investigated by studying classical field evolution in real time. The classical field equations are solved numerically, and the pair creation rate and average number of solitons are evaluated. No peculiar suppression of the rate is observed. Some results on the sphaleron transitions in (1+1)-dimensional abelian Higgs model are also presented. (orig.)
Pairing fluctuations in trapped Fermi gases
International Nuclear Information System (INIS)
Viverit, Luciano; Bruun, Georg M.; Minguzzi, Anna; Fazio, Rosario
2004-01-01
We examine the contribution of pairing fluctuations to the superfluid order parameter for harmonically trapped atomic Fermi gases in the BCS regime. In the limit of small systems we consider, both analytically and numerically, their space and temperature dependence. We predict a parity effect, i.e., that pairing fluctuations show a maximum or a minimum at the center of the trap, depending on the value of the last occupied shell being even or odd. We propose to detect pairing fluctuations by measuring the density-density correlation function after a ballistic expansion of the gas
AudioPairBank: Towards A Large-Scale Tag-Pair-Based Audio Content Analysis
Sager, Sebastian; Elizalde, Benjamin; Borth, Damian; Schulze, Christian; Raj, Bhiksha; Lane, Ian
2016-01-01
Recently, sound recognition has been used to identify sounds, such as car and river. However, sounds have nuances that may be better described by adjective-noun pairs such as slow car, and verb-noun pairs such as flying insects, which are under explored. Therefore, in this work we investigate the relation between audio content and both adjective-noun pairs and verb-noun pairs. Due to the lack of datasets with these kinds of annotations, we collected and processed the AudioPairBank corpus cons...
English for au pairs the au pair's guide to learning English
Curtis, Lucy
2014-01-01
English for Au Pairs has interlinked stories about a group of au pairs new to England. Marta, an 18-year-old from Poland arrives in the UK to work as an au pair. Throughout her year-long stay she has many different experiences - some bad, some good - but with the support of her host family she finds new friends and improves her English. English for Au Pairs offers insight into the joys and difficulties of being an au pair while at the same time reinforcing English language learning through grammar explanations and exercises.
Energy Technology Data Exchange (ETDEWEB)
Alfven, H [California Univ., San Diego, La Jolla (USA)
1981-01-01
The properties of space plasmas are analyzed, based on laboratory results and data obtained by in situ measurements in the magnetosphere (including the heliosphere). Attention is given to the question of how much knowledge can be gained by a systematic comparison of different regions of plasma, and plasmas are considered with linear dimensions varying from laboratory size up to the Hubble distance. The traditional magnetic field description of plasmas is supplemented by an electric current description and it is demonstrated that many problems are easier to understand with a dualistic approach. Using the general plasma properties obtained, the origin and evolution of the solar system is summarized and the evolution and present structure of the universe (cosmology) is discussed.
International Nuclear Information System (INIS)
Thode, L.E.
1981-01-01
A relativistic electron beam generator or accelerator produces a high-voltage electron beam which is modulated to initiate electron bunching within the beam which is then applied to a high-density target plasma which typically comprises DT, DD, or similar thermonuclear gas at a density of 10 17 to 10 20 electrons per cubic centimeter. As a result, relativistic streaming instabilities are initiated within the high-density target plasma causing the relativistic electron beam to efficiently deposit its energy into a small localized region of the high-density plasma target. The high-temperature plasma can be used to heat a high Z material to generate radiation. Alternatively, a tunable radiation source is produced by using a moderate Z gas or a mixture of high Z and low Z gas as the target plasma. (author)
International Nuclear Information System (INIS)
Ohnuma, Toshiro; Ohno, J.
1994-01-01
Superconducting (SC) plasmas are proposed and investigated. The SC plasmas are not yet familiar and have not yet been studied. However, the existence and the importance of SC plasmas are stressed in this report. The existence of SC plasmas are found as follows. There is a fundamental property of Meissner effect in superconductors, which shows a repulsive effect of magnetic fields. Even in that case, in a microscopic view, there is a region of magnetic penetration. The penetration length λ is well-known as London's penetration depth, which is expressed as δ = (m s /μ 0 n s q s 2 ) 1/2 where m s , n s , q s and μ o show the mass, the density, the charge of SC electron and the permeability in free space, respectively. Because this expression is very simple, no one had tried it into more simple and meaningful form. Recently, one of the authors (T.O.) has found that the length can be expressed into more simple and understandable fundamental form as λ = c/ω ps where c = (ε 0 μ 0 ) -1/2 and ω ps = (n s q s 2 /m s ε 0 ) 1/2 are the light velocity and the superconducting plasma frequency. From this simple expression, the penetration depth of the magnetic field to SC is found as a SC plasma skin depth, that is, the fundamental property of SC can be expressed by the SC plasmas. This discovery indicates an importance of the studies of superconducting plasmas. From these points, several properties (propagating modes et al) of SC plasmas, which consist of SC electrons, normal electrons and lattice ions, are investigated in this report. Observations of SC plasma frequency is also reported with a use of Terahertz electromagnet-optical waves
A twin study of the trough plasma steady-state concentration of metformin
DEFF Research Database (Denmark)
Stage, Tore B; Damkier, Per; Pedersen, Rasmus S
2015-01-01
OBJECTIVE: The aim of this study was to determine the intrapair similarity in trough steady-state plasma concentrations of metformin in monozygotic and dizygotic twin pairs. METHODS: We included 16 twin pairs (eight monozygotic and eight dizygotic twin pairs) for this study after contacting 524 t...
Effects of disorder on the electron pairing
International Nuclear Information System (INIS)
Oviedo-Roa, R.; Wang, C.; Navarro, O.
1996-01-01
The electron pairing in randomly disordered lattices is studied by using an attractive Hubbard model, and by mapping the many-body problem onto a tight-binding one in a higher dimensional space, where a diagonal disorder is considered within the coherent-potential approximation. The results show an enhancement of the pair-binding energy as the self-energy difference increases in a binary alloy A x B 1-x . This fact suggests that the pairing process is highly sensitive to the one-particle localization condition. A ground-state phase diagram for on-site interaction disorder shows regions where pairing is avoided for ordered diatomic systems but not for disordered case
Pairing properties of realistic effective interactions
Directory of Open Access Journals (Sweden)
Gargano A.
2016-01-01
Full Text Available We investigate the pairing properties of an effective shell-model interaction defined within a model space outside 132Sn and derived by means of perturbation theory from the CD-Bonn free nucleon-nucleon potential. It turns out that the neutron pairing component of the effective interaction is significantly weaker than the proton one, which accounts for the large pairing gap difference observed in the two-valence identical particle nuclei 134Sn and 134Te. The role of the contribution arising from one particle-one hole excitations in determining the pairing force is discussed and its microscopic structure is also analyzed in terms of the multipole decomposition.
Statistical mechanics of magnetized pair Fermi gas
International Nuclear Information System (INIS)
Daicic, J.; Frankel, N.E.; Kowalenko, V.
1993-01-01
Following previous work on the magnetized pair Bose gas this contribution presents the statistical mechanics of the charged relativistic Fermi gas with pair creation in d spatial dimensions. Initially, the gas in no external fields is studied. As a result, expansions for the various thermodynamic functions are obtained in both the μ/m→0 (neutrino) limit, and about the point μ/m =1, where μ is the chemical potential. The thermodynamics of a gas of quantum-number conserving massless fermions is also discussed. Then a complete study of the pair Fermi gas in a homogeneous magnetic field, is presented investigating the behavior of the magnetization over a wide range of field strengths. The inclusion of pairs leads to new results for the net magnetization due to the paramagnetic moment of the spins and the diamagnetic Landau orbits. 20 refs
Degenerated differential pair with controllable transconductance
Mensink, Clemens; Mensink, Clemens H.J.; Nauta, Bram
1998-01-01
A differential pair with input transistors and provided with a variable degeneration resistor. The degeneration resistor comprises a series arrangement of two branches of coupled resistors which are shunted in mutually corresponding points by respective control transistors whose gates are
Projected entangled pair states: status and prospects
Energy Technology Data Exchange (ETDEWEB)
Verstraete, Frank [Universitaet Wien (Austria)
2008-07-01
We report on the progress made to extend the density matrix renormalization group to higher dimensions, discuss the underlying theory of projected entangled pair states (PEPS) and illustrate its potential on the hand of a few examples.
Isovectorial pairing in solvable and algebraic models
International Nuclear Information System (INIS)
Lerma, Sergio; Vargas, Carlos E; Hirsch, Jorge G
2011-01-01
Schematic interactions are useful to gain some insight in the behavior of very complicated systems such as the atomic nuclei. Prototypical examples are, in this context, the pairing interaction and the quadrupole interaction of the Elliot model. In this contribution the interplay between isovectorial pairing, spin-orbit, and quadrupole terms in a harmonic oscillator shell (the so-called pairing-plus-quadrupole model) is studied by algebraic methods. The ability of this model to provide a realistic description of N = Z even-even nuclei in the fp-shell is illustrated with 44 Ti. Our calculations which derive from schematic and simple terms confirm earlier conclusions obtained by using realistic interactions: the SU(3) symmetry of the quadrupole term is broken mainly by the spin-orbit term, but the energies depends strongly on pairing.
Three mirror pairs of fermion families
International Nuclear Information System (INIS)
Montvay, I.
1988-01-01
A simple model with three mirror pairs of fermion families is considered which allows for a substantial mixing between the mirror fermion partners without conflicting with known phenomenology. (orig.)
QCD angular correlations for muon pair production
International Nuclear Information System (INIS)
Kajantie, K.; Raitio, R.; Lindfors, J.
1978-01-01
Angular distributions of muons are discussed in the framework of a QCD treatment of muon pair production in hadron-hadron collisions. The predicted angular effects are independent of the infrared behavior of QCD. Measuring them will permit one to determine whether the origin of the large transverse momentum of the pair is in the quark transverse momenta or in a constituent-constituent subprocess. (author)
Pairing interaction method in crystal field theory
International Nuclear Information System (INIS)
Dushin, R.B.
1989-01-01
Expressions, permitting to describe matrix elements of secular equation for metal-ligand pairs via parameters of the method of pairing interactions, genealogical coefficients and Clebsch-Gordan coefficients, are given. The expressions are applicable to any level or term of f n and d n configurations matrix elements for the terms of the maximum multiplicity of f n and d n configurations and also for the main levels of f n configurations are tabulated
Influence of quadrupole pairing on backbending
International Nuclear Information System (INIS)
Faessler, A.; Wakai, M.
1978-01-01
The backbending phenomenon is attributed to the Coriolis antipairing and the rotational alignment effects. We can consider both effects simultaneously by applying the cranked Hartree-Fock-Bogoliubov theory to the description of the rotational motion of nuclei. In usual treatments of the backbending, however, only the monopole pairing force is considered and pairing forces of other types are neglected. This may be the main reason for starting of the backbending at too small total angular momentum in theoretical results. (orig.) [de
Transverse Momentum Distributions for Heavy Quark Pairs
Berger, Edmond L.; Meng, Ruibin
1993-01-01
We study the transverse momentum distribution for a $pair$ of heavy quarks produced in hadron-hadron interactions. Predictions for the large transverse momentum region are based on exact order $\\alpha_s^3$ QCD perturbation theory. For the small transverse momentum region, we use techniques for all orders resummation of leading logarithmic contributions associated with initial state soft gluon radiation. The combination provides the transverse momentum distribution of heavy quark pairs for all...
International Nuclear Information System (INIS)
Alfven, H.
1986-04-01
Traditionally the views in our cosmic environment have been based on observations in the visual octave of the electromagnetic spectrum, during the last half-century supplemented by infrared and radio observations. Space research has opened the full spectrum. Of special importance are the X-ray-gamma-ray regions, in which a number of unexpected phenomena have been discovered. Radiations in these regions are likely to originate mainly from magnetised cosmic plasma. Such a medium may also emit synchrotron radiation which is observable in the radio region. If we try to base a model of the universe on the plasma phenomena mentioned we find that the plasma universe is drastically different from the traditional visual universe. Information about the plasma universe can also be obtained by extrapolation of laboratory experiments and magnetospheric in situ measurements of plasma. This approach is possible because it is likely that the basic properties of plasma are the same everywhere. In order to test the usefulness of the plasma universe model we apply it to cosmogony. Such an approach seems to be rather successful. For example, the complicated structure of the Saturnian C ring can be accounted for. It is possible to reconstruct certain phenomena 4-5 bilions years ago with an accuracy of better than 1 percent
Seniority zero pair coupled cluster doubles theory
International Nuclear Information System (INIS)
Stein, Tamar; Henderson, Thomas M.; Scuseria, Gustavo E.
2014-01-01
Coupled cluster theory with single and double excitations accurately describes weak electron correlation but is known to fail in cases of strong static correlation. Fascinatingly, however, pair coupled cluster doubles (p-CCD), a simplified version of the theory limited to pair excitations that preserve the seniority of the reference determinant (i.e., the number of unpaired electrons), has mean field computational cost and is an excellent approximation to the full configuration interaction (FCI) of the paired space provided that the orbital basis defining the pairing scheme is adequately optimized. In previous work, we have shown that optimization of the pairing scheme in the seniority zero FCI leads to a very accurate description of static correlation. The same conclusion extends to p-CCD if the orbitals are optimized to make the p-CCD energy stationary. We here demonstrate these results with numerous examples. We also explore the contributions of different seniority sectors to the coupled cluster doubles (CCD) correlation energy using different orbital bases. We consider both Hartree-Fock and Brueckner orbitals, and the role of orbital localization. We show how one can pair the orbitals so that the role of the Brueckner orbitals at the CCD level is retained at the p-CCD level. Moreover, we explore ways of extending CCD to accurately describe strongly correlated systems
International Nuclear Information System (INIS)
1979-01-01
This report contains the papers delivered at the AEB - Natal University summer school on plasma physics held in Durban during January 1979. The following topics were discussed: Tokamak devices; MHD stability; trapped particles in tori; Tokamak results and experiments; operating regime of the AEB Tokamak; Tokamak equilibrium; high beta Tokamak equilibria; ideal Tokamak stability; resistive MHD instabilities; Tokamak diagnostics; Tokamak control and data acquisition; feedback control of Tokamaks; heating and refuelling; neutral beam injection; radio frequency heating; nonlinear drift wave induced plasma transport; toroidal plasma boundary layers; microinstabilities and injected beams and quasilinear theory of the ion acoustic instability
International Nuclear Information System (INIS)
Ikehata, Takashi; Mase, Hiroshi
1998-01-01
The plasma centrifuge is one of statistical isotope separation processes which uses the centrifugal force of a J x B driven rotating plasma in a magnetic field to give rise to the mass-dependent radial transport of isotopic ions. The system has been developed as an alternative to the gas centrifuge because a much higher rotational velocity and separation factor have been achieved. In this review, the physical aspects of the plasma centrifuge followed by the recent experimental achievements are described, especially in comparison with the gas centrifuge. (author)
Micro-column plasma emission liquid chromatograph. [Patent application
Gay, D.D.
1982-08-12
In a direct current plasma emission spectrometer for use in combination with a microcolumn liquid chromatograph, an improved plasma source unit is claimed. The plasma source unit includes a quartz capillary tube having an inlet means, outlet off gas means and a pair of spaced electrodes defining a plasma region in the tube. The inlet means is connected to and adapted to receive eluant of the liquid chromatograph along with a stream of plasma-forming gas. There is an opening through the wall of the capillary tube penetrating into the plasma region. A soft glass capillary light pipe is disposed at the opening, is connected to the spectrometer, and is adapted to transmit light passing from the plasma region to the spectrometer. There is also a source of electromotive force connected to the electrodes sufficient to initiate and sustain a plasma in the plasma region of the tube.
Base pair probability estimates improve the prediction accuracy of RNA non-canonical base pairs.
Directory of Open Access Journals (Sweden)
Michael F Sloma
2017-11-01
Full Text Available Prediction of RNA tertiary structure from sequence is an important problem, but generating accurate structure models for even short sequences remains difficult. Predictions of RNA tertiary structure tend to be least accurate in loop regions, where non-canonical pairs are important for determining the details of structure. Non-canonical pairs can be predicted using a knowledge-based model of structure that scores nucleotide cyclic motifs, or NCMs. In this work, a partition function algorithm is introduced that allows the estimation of base pairing probabilities for both canonical and non-canonical interactions. Pairs that are predicted to be probable are more likely to be found in the true structure than pairs of lower probability. Pair probability estimates can be further improved by predicting the structure conserved across multiple homologous sequences using the TurboFold algorithm. These pairing probabilities, used in concert with prior knowledge of the canonical secondary structure, allow accurate inference of non-canonical pairs, an important step towards accurate prediction of the full tertiary structure. Software to predict non-canonical base pairs and pairing probabilities is now provided as part of the RNAstructure software package.
Base pair probability estimates improve the prediction accuracy of RNA non-canonical base pairs.
Sloma, Michael F; Mathews, David H
2017-11-01
Prediction of RNA tertiary structure from sequence is an important problem, but generating accurate structure models for even short sequences remains difficult. Predictions of RNA tertiary structure tend to be least accurate in loop regions, where non-canonical pairs are important for determining the details of structure. Non-canonical pairs can be predicted using a knowledge-based model of structure that scores nucleotide cyclic motifs, or NCMs. In this work, a partition function algorithm is introduced that allows the estimation of base pairing probabilities for both canonical and non-canonical interactions. Pairs that are predicted to be probable are more likely to be found in the true structure than pairs of lower probability. Pair probability estimates can be further improved by predicting the structure conserved across multiple homologous sequences using the TurboFold algorithm. These pairing probabilities, used in concert with prior knowledge of the canonical secondary structure, allow accurate inference of non-canonical pairs, an important step towards accurate prediction of the full tertiary structure. Software to predict non-canonical base pairs and pairing probabilities is now provided as part of the RNAstructure software package.
Hintze, Paul E.
2016-01-01
NASA's Kennedy Space Center has developed two solvent-free precision cleaning techniques: plasma cleaning and supercritical carbon dioxide (SCCO2), that has equal performance, cost parity, and no environmental liability, as compared to existing solvent cleaning methods.
Indian Academy of Sciences (India)
-focusing in a plasma ... Center for Energy Studies, Indian Institute of Technology, New Delhi 110 016, India; Tata Consultancy Services, Gurgaon, India; Ideal Institute of Technology, Ghaziabad, India; Center for Research in Cognitive, ...
Czech Academy of Sciences Publication Activity Database
Lunov, Oleg
2016-01-01
Roč. 174, č. 3 (2016), s. 486-487 ISSN 0007-0963 Institutional support: RVO:68378271 Keywords : plasma * ionized gas Subject RIV: BO - Biophysics OBOR OECD: Biophysics Impact factor: 4.706, year: 2016
International Nuclear Information System (INIS)
Drouet, M.G.
1984-03-01
IREQ was contracted by the Canadian Electrical Association to review plasma technology and assess the potential for application of this technology in Canada. A team of experts in the various aspects of this technology was assembled and each team member was asked to contribute to this report on the applications of plasma pertinent to his or her particular field of expertise. The following areas were examined in detail: iron, steel and strategic-metals production; surface treatment by spraying; welding and cutting; chemical processing; drying; and low-temperature treatment. A large market for the penetration of electricity has been identified. To build up confidence in the technology, support should be provided for selected R and D projects, plasma torch demonstrations at full power, and large-scale plasma process testing
International Nuclear Information System (INIS)
Crowther, J.M.
1997-09-01
Many methods are currently used for the production of thin metal films. However, all of these have drawbacks associated with them, for example the need for UHV conditions, high temperatures, exotic metal precursors, or the inability to coat complex shaped objects. Reduction of supported metal salts by non-isothermal plasma treatment does not suffer from these drawbacks. In order to produce and analyse metal films before they become contaminated, a plasma chamber which could be attached directly to a UHV chamber with XPS capability was designed and built. This allowed plasma treatment of supported metal salts and surface analysis by XPS to be performed without exposure of the metal film to the atmosphere. Non-equilibrium plasma treatment of Nylon 66 supported gold(lll) chloride using hydrogen as the feed gas resulted in a 95% pure gold film, the remaining 5% of the film being carbon. If argon or helium were used as the feed gases during plasma treatment the resultant gold films were 100% pure. Some degree of surface contamination of the films due to plasma treatment was observed but was easily removed by argon ion cleaning. Hydrogen plasma reduction of glass supported silver(l) nitrate and palladium(ll) acetate films reveals that this metallization technique is applicable to a wide variety of metal salts and supports, and has also shown the ability of plasma reduction to retain the complex 'fern-like' structures seen for spin coated silver(l) nitrate layers. Some metal salts are susceptible to decomposition by X-rays. The reduction of Nylon 66 supported gold(lll) chloride films by soft X-rays to produce nanoscopic gold particles has been studied. The spontaneous reduction of these X-ray irradiated support gold(lll) chloride films on exposure to the atmosphere to produce gold rich metallic films has also been reported. (author)
Hazeltine, R D
2003-01-01
Detailed and authoritative, this volume examines the essential physics underlying international research in magnetic confinement fusion. It offers readable, thorough accounts of the fundamental concepts behind methods of confining plasma at or near thermonuclear conditions. Designed for a one- or two-semester graduate-level course in plasma physics, it also represents a valuable reference for professional physicists in controlled fusion and related disciplines.
Energy Technology Data Exchange (ETDEWEB)
Zaveryaev, V [Kurchatov Institute, Moscow (Russian Federation); others, and
2012-09-15
The success in achieving peaceful fusion power depends on the ability to control a high temperature plasma, which is an object with unique properties, possibly the most complicated object created by humans. Over years of fusion research a new branch of science has been created, namely plasma diagnostics, which involves knowledge of almost all fields of physics, from electromagnetism to nuclear physics, and up-to-date progress in engineering and technology (materials, electronics, mathematical methods of data treatment). Historically, work on controlled fusion started with pulsed systems and accordingly the methods of plasma parameter measurement were first developed for short lived and dense plasmas. Magnetically confined hot plasmas require the creation of special experimental techniques for diagnostics. The diagnostic set is the most scientifically intensive part of a plasma device. During many years of research operation some scientific tasks have been solved while new ones arose. New tasks often require significant changes in the diagnostic system, which is thus a very flexible part of plasma machines. Diagnostic systems are designed to solve several tasks. As an example here are the diagnostic tasks for the International Thermonuclear Experimental Reactor - ITER: (1) Measurements for machine protection and basic control; (2) Measurements for advanced control; (3) Additional measurements for performance evaluation and physics. Every new plasma machine is a further step along the path to the main goal - controlled fusion - and nobody knows in advance what new phenomena will be met on the way. So in the planning of diagnostic construction we should keep in mind further system upgrading to meet possible new scientific and technical challenges. (author)
Generalized pairing strategies-a bridge from pairing strategies to colorings
Directory of Open Access Journals (Sweden)
Győrffy Lajos
2016-12-01
Full Text Available In this paper we define a bridge between pairings and colorings of the hypergraphs by introducing a generalization of pairs called t-cakes for t ∈ ℕ, t ≥ 2. For t = 2 the 2-cakes are the same as the well-known pairs of system of distinct representatives, that can be turned to pairing strategies in Maker-Breaker hypergraph games, see Hales and Jewett [12]. The two-colorings are the other extremity of t-cakes, in which the whole ground set of the hypergraph is one big cake that we divide into two parts (color classes. Starting from the pairings (2-cake placement and two-colorings we define the generalized t-cake placements where we pair p elements by q elements (p, q ∈ ℕ, 1 ≤ p, q < t, p + q = t.
Investigation of a staged plasma-focus apparatus
International Nuclear Information System (INIS)
Lee, J.H.; McFarland, D.R.; Harries, W.L.
1978-01-01
A new staged plasma-focus geometry combining two Mather-type plasma-focus guns has been constructed, and the current-sheet dynamics investigated. The production of simultaneous pairs of plasma foci has been achieved. The intensities of X-ray and fusion-neutron emission were measured and found to agree with the scaling law for a plasma focus. Advantages of this new geometry include the possibility of using plasma-focus type pinches in multiple arrays at power levels beyond the validity regime of the current scaling law for a single gun. (author)
Radical-pair based avian magnetoreception
Procopio, Maria; Ritz, Thorsten
2014-03-01
Behavioural experiments suggest that migratory birds possess a magnetic compass sensor able to detect the direction of the geomagnetic. One hypothesis for the basis of this remarkable sensory ability is that the coherent quantum spin dynamics of photoinduced radical pair reactions transduces directional magnetic information from the geomagnetic field into changes of reaction yields, possibly involving the photoreceptor cryptochrome in the birds retina. The suggested radical-pair based avian magnetoreception has attracted attention in the field of quantum biology as an example of a biological sensor which might exploit quantum coherences for its biological function. Investigations on such a spin-based sensor have focussed on uncovering the design features for the design of a biomimetic magnetic field sensor. We study the effects of slow fluctuations in the nuclear spin environment on the directional signal. We quantitatively evaluate the robustness of signals under fluctuations on a timescale longer than the lifetime of a radical pair, utilizing two models of radical pairs. Our results suggest design principles for building a radical-pair based compass sensor that is both robust and highly directional sensitive.
International Nuclear Information System (INIS)
Roberts, L.E.
1988-01-01
For colliding beams of several species of ions we compare thermal to perturbative quantum chromodynamic contributions for inclusive large mass muon pair production by using a hydrodynamic model to estimate the temperatures of the quark-gluon plasma produced by each species. The production of high energy dimuons with M ≅-4 GeV, will be favored energetically by the quark-gluon plasma. 10 refs., 4 figs., 2 tabs
A review of quantum collision dynamics in Debye plasmas
Janev, R. K.; Zhang, Song Bin; Wang, Jian Guo
2016-01-01
Hot, dense plasmas exhibit screened Coulomb interactions, resulting from the collective effects of correlated many-particle interactions. In the lowest particle correlation order (pair-wise correlations), the interaction between charged plasma particles reduces to the Debye-H\\"uckel (Yukawa-type) potential, characterized by the Debye screening length D. Due to the importance of Coulomb interaction screening in dense laboratory and astrophysical plasmas, hundreds of theoretical investigations ...
Isominkowskian theory of Cooper Pairs in superconductors
International Nuclear Information System (INIS)
Animalu, A.O.E.
1993-01-01
Via the use of Santilli's isominkowskian space, the author presents a relativistic extension of the author's recent treatment of the Cooper Pair in superconductivity based on the Lie-isotopic lifting of quantum mechanics known as Hadronic Mechanics. The isominkowskian treatment reduces the solution of the eiganvalue problem for the quasiparticle energy spectrum to a geometric problem of specifying the metric of the isominkowskian space inside the pair in various models of ordinary high T c superconductors. The use of an intriguing realization of the metric due to Dirac reduces the dimensionality of the interior space to two yielding a spin mutation from 1/2 to zero inside a Cooper pair in two-band BCS and Hubbard models. 12 refs
On pair-absorption in intrinsic vapours
International Nuclear Information System (INIS)
Hotop, R.; Niemax, K.; Schlueter, D.
1982-01-01
The bound-state pair-absorption bands Cs(6 2 S 1 sub(/) 2 ) + Cs(6 2 S 1 sub(/) 2 ) + hν → Cs(5 2 D 5 sub(/) 2 sub(,) 3 sub(/) 2 ) + Cs(6 2 P 1 sub(/) 2 ) and the K-K continuum-state pair-absorptions in the wavelength region 2.350 <= lambda <= 2.850 Angstroem have been investigated experimentally. In the case of the bound-state pair-absorption bands a theoretical approach for the absorption cross section at the band centre is given which is in good agreement with the experimental observation. Differences between our and the theoretical formulas given by the Stanford group are discussed. (orig.)
Pair production by a deep potential well
International Nuclear Information System (INIS)
Nikishov, A.I.
1987-01-01
Solutions are obtained for the Dirac and Klein-Gordon equations with a one-dimensional symmetric potential well, having a flat bottom and arbitrary depth, width and field strengths at the walls. Quasi-stationary solutions describing a pair production by the well and the inverse process are obtained. It is shown that if the pair production probability is small, it is expressed in terms of the pair production probability on one wall and the particle oscillation frequency in the well. If the well has a supercritical depth, the lower continuum contains positron resonance scattering states at energies close to the real part of the quasi-stationary level energy (Zeldovich's effect). The qualitative dependence of the positron penetration coefficient through the wall on its energy and the well depth is an evidence that the solution of the so called one-particle Dirac equation describes in fact a many-particle system with a charge of 0 or 1
The inverse problem for Schwinger pair production
Directory of Open Access Journals (Sweden)
F. Hebenstreit
2016-02-01
Full Text Available The production of electron–positron pairs in time-dependent electric fields (Schwinger mechanism depends non-linearly on the applied field profile. Accordingly, the resulting momentum spectrum is extremely sensitive to small variations of the field parameters. Owing to this non-linear dependence it is so far unpredictable how to choose a field configuration such that a predetermined momentum distribution is generated. We show that quantum kinetic theory along with optimal control theory can be used to approximately solve this inverse problem for Schwinger pair production. We exemplify this by studying the superposition of a small number of harmonic components resulting in predetermined signatures in the asymptotic momentum spectrum. In the long run, our results could facilitate the observation of this yet unobserved pair production mechanism in quantum electrodynamics by providing suggestions for tailored field configurations.
Hadronic production of massive lepton pairs
International Nuclear Information System (INIS)
Berger, E.L.
1982-12-01
A review is presented of recent experimental and theoretical progress in studies of the production of massive lepton pairs in hadronic collisions. I begin with the classical Drell-Yan annihilation model and its predictions. Subsequently, I discuss deviations from scaling, the status of the proofs of factorization in the parton model, higher-order terms in the perturbative QCD expansion, the discrepancy between measured and predicted yields (K factor), high-twist terms, soft gluon effects, transverse-momentum distributions, implications for weak vector boson (W +- and Z 0 ) yields and production properties, nuclear A dependence effects, correlations of the lepton pair with hadrons in the final state, and angular distributions in the lepton-pair rest frame
Charged topological black hole pair creation
International Nuclear Information System (INIS)
Mann, R.B.
1998-01-01
I examine the pair creation of black holes in space-times with a cosmological constant of either sign. I consider cosmological C-metrics and show that the conical singularities in this metric vanish only for three distinct classes of black hole metric, two of which have compact event horizons on each spatial slice. One class is a generalization of the Reissner-Nordstroem (anti-)de Sitter black holes in which the event horizons are the direct product of a null line with a 2-surface with topology of genus g. The other class consists of neutral black holes whose event horizons are the direct product of a null conoid with a circle. In the presence of a domain wall, black hole pairs of all possible types will be pair created for a wide range of mass and charge, including even negative mass black holes. I determine the relevant instantons and Euclidean actions for each case. (orig.)
Theory of antiferromagnetic pairing in cuprate superconductors
International Nuclear Information System (INIS)
Plakida, N.M.
2006-01-01
A review of the antiferromagnetic exchange and spin-fluctuation pairing theory in the cuprate superconductors is given. We briefly discuss a phenomenological approach and a theory in the limit of weak Coulomb correlations. A microscopic theory in the strong correlation limit is presented in more detail. In particular, results of our recently developed theory for the effective p-d Hubbard model and the reduced t-J model are given. We have proved that retardation effects for the antiferromagnetic exchange interaction are unimportant that results in pairing of all charge carriers in the conduction band and high Tc proportional to the Fermi energy. The spin-fluctuation interaction caused by kinematic interaction gives an additional contribution to the d-wave pairing. Dependence of Tc on the hole concentration and the lattice constant (or pressure) and an oxygen isotope shift are discussed
Holographic EPR pairs, wormholes and radiation
Chernicoff, Mariano; Güijosa, Alberto; Pedraza, Juan F.
2013-10-01
As evidence for the ER = EPR conjecture, it has recently been observed that the string that is holographically dual to an entangled quark-antiquark pair separating with (asymptotically) uniform acceleration has a wormhole on its worldsheet. We point out that a two-sided horizon and a wormhole actually appear for much more generic quark-antiquark trajectories, which is consistent with the fact that the members of an EPR pair need not be permanently out of causal contact. The feature that determines whether the causal structure of the string worldsheet is trivial or not turns out to be the emission of gluonic radiation by the dual quark and antiquark. In the strongly-coupled gauge theory, it is only when radiation is emitted that one obtains an unambiguous separation of the pair into entangled subsystems, and this is what is reflected on the gravity side by the existence of the worldsheet horizon.
Drell-Yan lepton pair photoproduction
International Nuclear Information System (INIS)
Badalyan, R.G.; Grabskij, V.O.; Matinyan, S.G.
1989-01-01
The study of photon structure functions by spectra of massive lepton pairs (M l + l - ≥ 2 GeV) in photon fragmentation region in γp-interactions at high energies is suggested. In calculations of Drell-Yan lepton pair inclusive spectra in γp-interactions for photon structure functions there are used results obtained within QCD, data on γγ-interactions in e + e - → e + e - X on colliders as well as results from the analysis of vector meson non-diffractive photoproduction at high energies. It is shown that there exists a sufficienly wide kinematic region over variables X l + l - and M l + l - , wherein photon structure functions can be studied by spectra of Grell-Yan lepton pairs in the processes of their photoproduction. 31 refs.; 6 figs.; 1 tab
International Nuclear Information System (INIS)
Buchs, Gilles; Krasheninnikov, Arkady V; Ruffieux, Pascal; Groening, Pierangelo; Foster, Adam S; Nieminen, Risto M; Groening, Oliver
2007-01-01
The specific, local modification of the electronic structure of carbon nanomaterials is as important for novel electronic device fabrication as the doping in the case of silicon-based electronics. Here, we report low temperature scanning tunneling microscopy and spectroscopy study of semiconducting carbon nanotubes subjected to hydrogen-plasma treatment. We show that plasma treatment mostly results in the creation of paired electronic states in the nanotube band gap. Combined with extensive first-principle simulations, our results provide direct evidence that these states originate from correlated chemisorption of hydrogen adatoms on the tube surface. The energy splitting of the paired states is governed by the adatom-adatom interaction, so that controlled hydrogenation can be used for engineering the local electronic structure of nanotubes and other sp 2 -bonded nanocarbon systems
Leveraging extreme laser-driven magnetic fields for gamma-ray generation and pair production
Jansen, O.; Wang, T.; Stark, D. J.; d’Humières, E.; Toncian, T.; Arefiev, A. V.
2018-05-01
The ability of an intense laser pulse to propagate in a classically over-critical plasma through the phenomenon of relativistic transparency is shown to facilitate the generation of strong plasma magnetic fields. Particle-in-cell simulations demonstrate that these fields significantly enhance the radiation rates of the laser-irradiated electrons, and furthermore they collimate the emission so that a directed and dense beam of multi-MeV gamma-rays is achievable. This capability can be exploited for electron–positron pair production via the linear Breit–Wheeler process by colliding two such dense beams. Presented simulations show that more than 103 pairs can be produced in such a setup, and the directionality of the positrons can be controlled by the angle of incidence between the beams.
Lax pairs: a novel type of separability
International Nuclear Information System (INIS)
Fokas, A S
2009-01-01
An attempt is made to place into historical context the fundamental concept of Lax pairs. For economy of presentation, emphasis is placed on the effectiveness of Lax pairs for the analysis of integrable nonlinear evolution PDEs. It is argued that Lax pairs provide a deeper type of separability than the classical separation of variables. Indeed, it is shown that: (a) the solution of the Cauchy problem of evolution equations is based on the derivation of a nonlinear Fourier transform pair, and this is achieved by employing the spectral analysis of one of the two eigenvalue equations forming a Lax pair; thus, although this methodology still follows the reverent philosophy of the classical separation of variables and transform methods, it can be applied to a class of nonlinear PDEs. (b) The solution of initial-boundary-value problems of evolution equations is based on the simultaneous spectral analysis of both equations forming a Lax pair and hence, in a sense, it employs the synthesis instead of the separation of variables; this methodology does not have a direct classical analogue, however, it can be considered as the nonlinearization of a method which combines Green's function classical integral representations with an analogue of the method of images, but which are now formulated in the spectral (Fourier) instead of the physical space. In addition to presenting a general methodology for analysing initial- and initial-boundary-value problems for nonlinear integrable evolution equations in one and two spatial variables, recent progress is reviewed for the derivation and the solution of integrable nonlinear evolution PDEs formulated in higher than two spatial dimensions. (topical review)
Top quark pair production in ATLAS
Moreno Llacer, M; The ATLAS collaboration
2010-01-01
Top-quark pairs are expected to be produced at the LHC, even at the lower beam energy and luminosity in the first years of running. Establishing the top-pair signal and measuring the production cross-section are important benchmarks for ATLAS, and will help understand the detector performance for events with high-pT leptons, high jet multiplicity, missing transverse energy. The prospects for early top physics measurements will be shown, with a particular emphasis on the progress achieved with data so far.
Mass resolution for lepton pairs at Isabelle
International Nuclear Information System (INIS)
Baltay, C.; Paige, F.E.
1978-01-01
Experiments measuring e + e - and μ + μ-pairs will be the principal way of searching at ISABELLE for the Z 0 and for vector mesons made from new heavy quark-antiquark (Q anti Q ) pairs. Although the best possible mass resolution is clearly of benefit in such experiments, excessive resolution would lead to an unnecessarily large detector. It is believed that a mass resolution of a few percent is appropriate in searching both for the Z 0 and for new Q anti Q states. However, there are some interesting experiments which would require much better mass resolution, of order 1/4% FWHM. 9 references
Ponderomotive effects in multiphoton pair production
Kohlfürst, Christian; Alkofer, Reinhard
2018-02-01
The Dirac-Heisenberg-Wigner formalism is employed to investigate electron-positron pair production in cylindrically symmetric but otherwise spatially inhomogeneous, oscillating electric fields. The oscillation frequencies are hereby tuned to obtain multiphoton pair production in the nonperturbative threshold regime. An effective mass, as well as a trajectory-based semiclassical analysis, is introduced in order to interpret the numerical results for the distribution functions as well as for the particle yields and spectra. The results, including the asymptotic particle spectra, display clear signatures of ponderomotive forces.
Holographic EPR Pairs, Wormholes and Radiation
Chernicoff, Mariano; Güijosa, Alberto; Pedraza, Juan F.
2013-01-01
As evidence for the ER=EPR conjecture, it has recently been observed that the string that is holographically dual to an entangled quark-antiquark pair separating with (asymptotically) uniform acceleration has a wormhole on its worldsheet. We point out that a two-sided horizon and a wormhole actually appear for much more generic quark-antiquark trajectories, which is consistent with the fact that the members of an EPR pair need not be permanently out of causal contact. The feature that determi...
Gluino-pair production at the Tevatron
International Nuclear Information System (INIS)
Beenakker, W.; Spira, M.; Zerwas, P.M.
1995-05-01
The next-to-leading order QCD corrections to the production of gluino pairs at the Tevatron are presented in this paper. Similar to the production of squark-antisquark pairs, the dependence of the cross section on the renormalization/factorization scale is reduced considerably by including the higher-order corrections. The cross section increases with respect to the lowest-order calculation which, in previous experimental analyses, had been evaluated at the scale of the invariant energy of the partonic subprocesses. (orig.)
Facial expressions and pair bonds in hylobatids.
Florkiewicz, Brittany; Skollar, Gabriella; Reichard, Ulrich H
2018-06-06
Facial expressions are an important component of primate communication that functions to transmit social information and modulate intentions and motivations. Chimpanzees and macaques, for example, produce a variety of facial expressions when communicating with conspecifics. Hylobatids also produce various facial expressions; however, the origin and function of these facial expressions are still largely unclear. It has been suggested that larger facial expression repertoires may have evolved in the context of social complexity, but this link has yet to be tested at a broader empirical basis. The social complexity hypothesis offers a possible explanation for the evolution of complex communicative signals such as facial expressions, because as the complexity of an individual's social environment increases so does the need for communicative signals. We used an intraspecies, pair-focused study design to test the link between facial expressions and sociality within hylobatids, specifically the strength of pair-bonds. The current study compared 206 hr of video and 103 hr of focal animal data for ten hylobatid pairs from three genera (Nomascus, Hoolock, and Hylobates) living at the Gibbon Conservation Center. Using video footage, we explored 5,969 facial expressions along three dimensions: repertoire use, repertoire breadth, and facial expression synchrony [FES]. We then used focal animal data to compare dimensions of facial expressiveness to pair bond strength and behavioral synchrony. Hylobatids in our study overlapped in only half of their facial expressions (50%) with the only other detailed, quantitative study of hylobatid facial expressions, while 27 facial expressions were uniquely observed in our study animals. Taken together, hylobatids have a large facial expression repertoire of at least 80 unique facial expressions. Contrary to our prediction, facial repertoire composition was not significantly correlated with pair bond strength, rates of territorial synchrony
Time resolved plasma characterization in a long conduction time planar plasma opening switch
International Nuclear Information System (INIS)
Adler, L.K.; Greenly, J.B.; Qi, N.; Hammer, D.A.
1989-01-01
The authors discuss additional experiments in which the plasma dynamics and properties will be monitored in detail before and during opening. Space and time resolved density, temperature and motion information about the plasma and neutrals is given by emission spectroscopy and streak photography and correlated to the current and voltage traces. Specifically, we will look for the effects of neutrals evolving off of surfaces, stagnation of the switch plasma, and rvec J x rvec B motion of the plasma downstream of the switch. Diagnostics include current and voltage monitors, a multi-aperture biased Faraday cup, emission spectroscopy and streak photography. Pairs of B dot loops are positioned in the stripline just upstream and downstream of the POS. Also, two single B loops were placed further downstream to look for bulk plasma motion. An inductive monitor gives the voltage at the upstream side of the POS and the Faraday cup monitors the gun plasma consistency from shot to shot
International Nuclear Information System (INIS)
Franz, G.
1990-01-01
This textbook discusses the following topics: Phenomenological description of a direct current glow discharge; the plasma (temperature distribution and measurement, potential variation, electron energy distribution function, charge neutralization, wall potentials, plasma oscillations); Production of charge carriers (ions, electrons, ionization in the cathode zone, negative glowing zone, Faraday dark space, positive column, anode zone, hollow cathode discharges); RF-discharges (charge carrier production, RF-Shields, scattering mechanisms); Sputtering (ion-surface interaction, kinetics, sputtering yield and energy distribution, systems and conditions, film formation and stresses, contamination, bias techniques, multicomponent film deposition, cohesion, magnetrons, triode systems, plasma enhanced chemical vapor deposition); Dry etching (sputter etching, reactive etching, topography, process control, quantitative investigations); Etching mechanisms (etching of Si and SiO 2 with CF 4 , of III/V-compound-semiconductors, combination of isotrope and anisotrope etching methods, surface cleaning); ion beam systems (applications, etching); Dyclotron-resonance-systems (electron cyclotron resonance systems, whistler-sources and 'resonant inductive plasma etching'); Appendix (electron energy distribution functions, Bohm's transition zone, plasma oscillations, scattering cross sections and mean free path, metastable states, Child-Langmuir-Schottky equation, loss mechanisms, charge carrier distribution in the positive column, breakdown at high frequencies, motion in a magnetic field, skin depth of an electric field for a HF-discharge, whistler waves, dispersion relations for plane wave propagation). (orig.) With 138 figs
International Nuclear Information System (INIS)
Wilhelm, R.
1989-01-01
Successful plasma heating is essential in present fusion experiments, for the demonstration of DpT burn in future devices and finally for the fusion reactor itself. This paper discusses the common heating systems with respect to their present performance and their applicability to future fusion devices. The comparative discussion is oriented to the various function of heating, which are: - plasma heating to fusion-relevant parameters and to ignition in future machines, -non-inductive, steady-pstate current drive, - plasma profile control, -neutral gas breakdown and plasma build-up. In view of these different functions, the potential of neutral beam injection (NBI) and the various schemes of wave heating (ECRH, LH, ICRH and Alven wave heating) is analyzed in more detail. The analysis includes assessments of the present physical and technical state of these heating methods, and makes suggestions for future developments and about outstanding problems. Specific attention is given to the still critical problem of efficient current drive, especially with respect to further extrapolation towards an economically operating tokamak reactor. Remarks on issues such as reliability, maintenance and economy conclude this comparative overview on plasma heating systems. (author). 43 refs.; 13 figs.; 3 tabs
Dislocation processes in quasicrystals-Kink-pair formation control or jog-pair formation control
International Nuclear Information System (INIS)
Takeuchi, Shin
2005-01-01
A computer simulation of dislocation in a model quasiperiodic lattice indicates that the dislocation feels a large Peierls potential when oriented in particular directions. For a dislocation with a high Peierls potential, the glide velocity and the climb velocity of the dislocation can be described almost in parallel in terms of the kink-pair formation followed by kink motion and the jog-pair formation followed by jog motion, respectively. The activation enthalpy of the kink-pair formation is the sum of the kink-pair formation enthalpy and the atomic jump activation enthalpy, while the activation enthalpy of the jog-pair formation involves the jog-pair enthalpy and the self-diffusion enthalpy. Since the kink-pair energy can be considerably larger than the jog-pair energy, the climb velocity can be faster than the glide velocity, so that the plastic deformation of quasicrystals can be brought not by dislocation glide but by dislocation climb at high temperatures
Quark pair creation in color electric fields and effects of magnetic fields
International Nuclear Information System (INIS)
Tanji, Noato
2010-01-01
The time evolution of a system where a uniform and classical SU(3) color electric field and quantum fields of quarks interact with each other is studied focusing on non-perturbative pair creation and its back reaction. We characterize a color direction of an electric field in a gauge invariant way, and investigate its dependence. Momentum distributions of created quarks show plasma oscillation as well as quantum effects such as the Pauli blocking and interference. Pressure of the system is also calculated, and we show that pair creation moderates degree of anisotropy of pressure. Furthermore, enhancement of pair creation and induction of chiral charge under a color magnetic field which is parallel to an electric field are discussed.
On the time scales of the pair production processes in astrophysics
International Nuclear Information System (INIS)
Zdziarski, A.A.
1982-01-01
The problem of the e + e - pair production by photo-photon, photon-particle, and particle-particle collisions in the black hole spherically symmetric accretion is considered. It is shown that these processes are much too slow to lead to any appreciable pair density in an optically thin accretion flow. The γγ process can play a role in an accretion flow of the optical thickness of a few. The rates of pair production in the binary particle collisions are calculated and it is shown that the ep → epe + e - process is by one order of magnitude slower than ee → eee + e - process. The maximum temperature of a stationary plasma with tau→0 is lower than that previously calculated by Bisnovatyi-Kogan, Zel'dvich and Sunyaev (1971). (orig.)
Gow, J.D.; Wilcox, J.M.
1961-12-26
A device is designed for producing and confining highenergy plasma from which neutrons are generated in copious quantities. A rotating sheath of electrons is established in a radial electric field and axial magnetic field produced within the device. The electron sheath serves as a strong ionizing medium to gas introdueed thereto and also functions as an extremely effective heating mechanism to the resulting plasma. In addition, improved confinement of the plasma is obtained by ring magnetic mirror fields produced at the ends of the device. Such ring mirror fields are defined by the magnetic field lines at the ends of the device diverging radially outward from the axis of the device and thereafter converging at spatial annular surfaces disposed concentrically thereabout. (AFC)
Pair- ${v}$ -SVR: A Novel and Efficient Pairing nu-Support Vector Regression Algorithm.
Hao, Pei-Yi
This paper proposes a novel and efficient pairing nu-support vector regression (pair--SVR) algorithm that combines successfully the superior advantages of twin support vector regression (TSVR) and classical -SVR algorithms. In spirit of TSVR, the proposed pair--SVR solves two quadratic programming problems (QPPs) of smaller size rather than a single larger QPP, and thus has faster learning speed than classical -SVR. The significant advantage of our pair--SVR over TSVR is the improvement in the prediction speed and generalization ability by introducing the concepts of the insensitive zone and the regularization term that embodies the essence of statistical learning theory. Moreover, pair--SVR has additional advantage of using parameter for controlling the bounds on fractions of SVs and errors. Furthermore, the upper bound and lower bound functions of the regression model estimated by pair--SVR capture well the characteristics of data distributions, thus facilitating automatic estimation of the conditional mean and predictive variance simultaneously. This may be useful in many cases, especially when the noise is heteroscedastic and depends strongly on the input values. The experimental results validate the superiority of our pair--SVR in both training/prediction speed and generalization ability.This paper proposes a novel and efficient pairing nu-support vector regression (pair--SVR) algorithm that combines successfully the superior advantages of twin support vector regression (TSVR) and classical -SVR algorithms. In spirit of TSVR, the proposed pair--SVR solves two quadratic programming problems (QPPs) of smaller size rather than a single larger QPP, and thus has faster learning speed than classical -SVR. The significant advantage of our pair--SVR over TSVR is the improvement in the prediction speed and generalization ability by introducing the concepts of the insensitive zone and the regularization term that embodies the essence of statistical learning theory
Direct extraction of negative lithium ions from a lithium plasma
International Nuclear Information System (INIS)
Wada, M.; Tsuda, H.; Sasao, M.
1990-01-01
Negative lithium ions (Li - ) were directly extracted from a lithium plasma in a multiline cusp plasma container. A pair of permanent magnets mounted near the extractor electrode created the filter magnetic field that separated the extraction region plasma from the main discharge plasma. The plasma electrode facing the extraction region plasma was biased with respect to the other parts of the chamber wall, which acted as discharge anodes. The larger filter magnetic field resulted larger Li - current. When the bias to the plasma electrode was several volts positive against the anode potential, extracted Li - current took the maximum for a fixed strength of the filter field. These dependences of Li - upon the filter magnetic field and the plasma electrode bias are similar to the ones of negative hydrogen ions
International Nuclear Information System (INIS)
Weitzner, H.
1989-08-01
A cursory examination of the research activities of the Magneto-Fluid Dynamics Division for the calendar year 1988 shows the effects of the gradual transformation of the group. Although our principal activity, fusion plasma physics research, is unchanged, the work shows closer ties to problems relevant to present experiments than previously. Most notable is the concentrated effort on tokamak equilibrium and transport. We are exploring the implication of turbulence induced transport, resistive MHD effects, neoclassical transport, and possible interpretations of transport based on classical phenomena. In addition, one of our members has chosen to focus on problems of enhanced statistical methods for interpretation of experiments. All of this activity preceded the Tokamak Transport Initiative and reflects our active involvement and concern with the world-wide tokamak program. Since equilibrium and transport are by no means the only theoretical plasma physics problems affecting fusion devices we continue substantial efforts in wave propagation and heating, particle simulation of plasmas, stability theory, enhancement of numerical algorithms, and general plasma physics. We are attempting to develop effective numerical schemes for the Boltzmann equation, adaptive grid methods for MHD, and particle simulation of boundary and antenna effects. Many of these topics reflect our continuing concern to maintain a modest effort in the development of theoretical models and tools for problems of real significance to fusion, but not necessarily of immediate highest priority. We select problems which we expect to become extremely important in the future. Our space plasma physics activities, funded by agencies other than DOE, transfers knowledge learned in fusion plasma physics to another area and conversely stimulates work also relevant to fusion problems
Electron plasma waves and plasma resonances
International Nuclear Information System (INIS)
Franklin, R N; Braithwaite, N St J
2009-01-01
In 1929 Tonks and Langmuir predicted of the existence of electron plasma waves in an infinite, uniform plasma. The more realistic laboratory environment of non-uniform and bounded plasmas frustrated early experiments. Meanwhile Landau predicted that electron plasma waves in a uniform collisionless plasma would appear to be damped. Subsequent experimental work verified this and revealed the curious phenomenon of plasma wave echoes. Electron plasma wave theory, extended to finite plasmas, has been confirmed by various experiments. Nonlinear phenomena, such as particle trapping, emerge at large amplitude. The use of electron plasma waves to determine electron density and electron temperature has not proved as convenient as other methods.
Multi-photon creation and single-photon annihilation of electron-positron pairs
Energy Technology Data Exchange (ETDEWEB)
Hu, Huayu
2011-04-27
In this thesis we study multi-photon e{sup +}e{sup -} pair production in a trident process, and singlephoton e{sup +}e{sup -} pair annihilation in a triple interaction. The pair production is considered in the collision of a relativistic electron with a strong laser beam, and calculated within the theory of laser-dressed quantum electrodynamics. A regularization method is developed systematically for the resonance problem arising in the multi-photon process. Total production rates, positron spectra, and relative contributions of different reaction channels are obtained in various interaction regimes. Our calculation shows good agreement with existing experimental data from SLAC, and adds further insights into the experimental findings. Besides, we study the process in a manifestly nonperturbative domain, whose accessibility to future all-optical experiments based on laser acceleration is shown. In the single-photon e{sup +}e{sup -} pair annihilation, the recoil momentum is absorbed by a spectator particle. Various kinematic configurations of the three incoming particles are examined. Under certain conditions, the emitted photon exhibits distinct angular and polarization distributions which could facilitate the detection of the process. Considering an equilibrium relativistic e{sup +}e{sup -} plasma, it is found that the single-photon process becomes the dominant annihilation channel for plasma temperatures above 3 MeV. Multi-particle correlation effects are therefore essential for the e{sup +}e{sup -} dynamics at very high density. (orig.)
Multi-photon creation and single-photon annihilation of electron-positron pairs
International Nuclear Information System (INIS)
Hu, Huayu
2011-01-01
In this thesis we study multi-photon e + e - pair production in a trident process, and singlephoton e + e - pair annihilation in a triple interaction. The pair production is considered in the collision of a relativistic electron with a strong laser beam, and calculated within the theory of laser-dressed quantum electrodynamics. A regularization method is developed systematically for the resonance problem arising in the multi-photon process. Total production rates, positron spectra, and relative contributions of different reaction channels are obtained in various interaction regimes. Our calculation shows good agreement with existing experimental data from SLAC, and adds further insights into the experimental findings. Besides, we study the process in a manifestly nonperturbative domain, whose accessibility to future all-optical experiments based on laser acceleration is shown. In the single-photon e + e - pair annihilation, the recoil momentum is absorbed by a spectator particle. Various kinematic configurations of the three incoming particles are examined. Under certain conditions, the emitted photon exhibits distinct angular and polarization distributions which could facilitate the detection of the process. Considering an equilibrium relativistic e + e - plasma, it is found that the single-photon process becomes the dominant annihilation channel for plasma temperatures above 3 MeV. Multi-particle correlation effects are therefore essential for the e + e - dynamics at very high density. (orig.)
International Nuclear Information System (INIS)
Tsytovich, V.N.; Bingham, R.; Angelis, U. de
1989-09-01
The field of ''dusty plasmas'' promises to be a very rewarding topic of research for the next decade or so, not only from the academic point of view where the emphasis is on developing the theory of the often complex collective and non-linear processes, but also from the point of view of applications in astrophysics, space physics, environmental and energy research. In this ''comment'' we should like to sketch the current development of this fast growing and potentially very important research area. We will discuss the new features of ''dusty'' plasmas in the most general terms and then briefly mention some successful applications and effects which have already been examined. (author)
Hannibal, Darcy L; Cassidy, Lauren C; Vandeleest, Jessica; Semple, Stuart; Barnard, Allison; Chun, Katie; Winkler, Sasha; McCowan, Brenda
2018-05-02
Laboratory rhesus macaques are often housed in pairs and may be temporarily or permanently separated for research, health, or management reasons. While both long-term social separations and introductions can stimulate a stress response that impacts inflammation and immune function, the effects of short-term overnight separations and whether qualities of the pair relationship mediate these effects are unknown. In this study, we investigated the effects of overnight separations on the urinary cortisol concentration of 20 differentially paired adult female rhesus macaques (Macaca mulatta) at the California National Primate Research Center. These females were initially kept in either continuous (no overnight separation) or intermittent (with overnight separation) pair-housing and then switched to the alternate pair-housing condition part way through the study. Each study subject was observed for 5 weeks, during which we collected measures of affiliative, aggressive, anxious, abnormal, and activity-state behaviors in both pair-housing conditions. Additionally, up to three urine samples were collected from each subject per week and assayed for urinary free cortisol and creatinine. Lastly, the behavioral observer scored each pair on four relationship quality attributes ("Anxious," "Tense," "Well-meshed," and "Friendly") using a seven-point scale. Data were analyzed using a generalized linear model with gamma distribution and an information theoretic approach to determine the best model set. An interaction between the intermittent pairing condition and tense pair adjective rating was in the top three models of the best model set. Dominance and rates of affiliation were also important for explaining urinary cortisol variation. Our results suggest that to prevent significant changes in HPA-axis activation in rhesus macaque females, which could have unintended effects on research outcomes, pairs with "Tense" relationships and overnight separations preventing tactile contact
Pair Negotiation When Developing English Speaking Tasks
Bohórquez Suárez, Ingrid Liliana; Gómez Sará, Mary Mily; Medina Mosquera, Sindy Lorena
2011-01-01
This study analyzes what characterizes the negotiations of seventh graders at a public school in Bogotá when working in pairs to develop speaking tasks in EFL classes. The inquiry is a descriptive case study that follows the qualitative paradigm. As a result of analyzing the data, we obtained four consecutive steps that characterize students'…
Klein tunneling phenomenon with pair creation process
Wu, G. Z.; Zhou, C. T.; Fu, L. B.
2018-01-01
In this paper, we study the Klein tunneling phenomenon with electron-positron pair creation process. Pairs can be created from the vacuum by a supercritical single-well potential (for electrons). In the time region, the time-dependent growth pattern of the created pairs can be characterized by four distinct regimes which can be considered as four different statuses of the single well. We find that if positrons penetrate the single well by Klein tunneling in different statuses, the total number of the tunneling positrons will be different. If Klein tunneling begins at the initial stage of the first status i.e. when the sing well is empty, the tunneling process and the total number of tunneling positrons are similar to the traditional Klein tunneling case without considering the pair creation process. As the tunneling begins later, the total tunneling positron number increases. The number will finally settle to an asymptotic value when the tunneling begins later than the settling-down time t s of the single well which has been defined in this paper.
Effective pair potentials for spherical nanoparticles
International Nuclear Information System (INIS)
Van Zon, Ramses
2009-01-01
An effective description for rigid spherical nanoparticles in a fluid of point particles is presented. The points inside the nanoparticles and the point particles are assumed to interact via spherically symmetric additive pair potentials, while the distribution of points inside the nanoparticles is taken to be spherically symmetric and smooth. The resulting effective pair interactions between a nanoparticle and a point particle, as well as between two nanoparticles, are then given by spherically symmetric potentials. If overlap between particles is allowed, as can occur for some forms of the pair potentials, the effective potential generally has non-analytic points. It is shown that for each effective potential the expressions for different overlapping cases can be written in terms of one analytic auxiliary potential. Even when only non-overlapping situations are possible, the auxiliary potentials facilitate the formulation of the effective potentials. Effective potentials for hollow nanoparticles (appropriate e.g. for buckyballs) are also considered and shown to be related to those for solid nanoparticles. For hollow nanoparticles overlap is more physical, since this covers the case of a smaller particle embedded in a larger, hollow nanoparticle. Finally, explicit expressions are given for the effective potentials derived from basic pair potentials of power law and exponential form, as well as from the commonly used London–van der Waals, Morse, Buckingham, and Lennard-Jones potentials. The applicability of the latter is demonstrated by comparison with an atomic description of nanoparticles with an internal face centered cubic structure
Odd-frequency pairing in superconducting heterostructures
Energy Technology Data Exchange (ETDEWEB)
Golubov, A A [Faculty of Science and Technology and MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede (Netherlands); Tanaka, Y [Department of Applied Physics, Nagoya University, Nagoya, 464-8603 (Japan); Asano, Y [Department of Applied Physics, Hokkaido University, Sapporo 060-8628 (Japan); Tanuma, Y [Institute of Physics, Kanagawa University, 3-7-1, Rokkakubashi, Kanagawa-ku, Yokohama 221-8686 (Japan)], E-mail: a.golubov@utwente.nl
2009-04-22
We review the theory of odd-frequency pairing in superconducting heterostructures, where an odd-frequency pairing component is induced near interfaces. A general description of the superconducting proximity effect in a normal metal or a ferromagnet attached to an unconventional superconductor (S) is given within quasiclassical kinetic theory for various types of symmetry state in S. Various possible symmetry classes in a superconductor are considered which are consistent with the Pauli principle: even-frequency spin-singlet even-parity (ESE) state, even-frequency spin-triplet odd-parity (ETO) state, odd-frequency spin-triplet even-parity (OTE) state and odd-frequency spin-singlet odd-parity (OSO) state. As an example, we consider a junction between a diffusive normal metal (DN) and a p-wave superconductor (even-frequency spin-triplet odd-parity symmetry), where the pairing amplitude in DN belongs to an odd-frequency spin-triplet even-parity symmetry class. We also discuss the manifestation of odd-frequency pairing in conventional superconductor/normal (S/N) proximity systems and its relation to the classical McMillan-Rowell oscillations.
Impact of Paired Tutoring and Mentoring.
Bruce, Jennifer E.; Trammell, Jack
2003-01-01
Discusses a study that examines the effects of paired tutoring and mentoring on academic achievement of college freshmen in a probationary program. Results show that students with mentoring and tutoring services by the same person show greater academic gains as measured by compliance and academic achievement than do those students who were…
Pair breaking and charge relaxation in superconductors
International Nuclear Information System (INIS)
Nielson, J.B.; Pethick, C.J.; Rammer, J.; Smith, H.
1982-01-01
We present a general formalism based on the quasiclassical Green's function for calculating charge imbalance in nonequilibrium superconductors. Our discussion is sufficiently general that it applies at arbitrary temperatures, and under conditions when the width of quasiparticle states are appreciable due to pair breaking processes, and when strong coupling effects are significant. As a first application we demonstrate in detail how in the limit of smallpair breaking and for a weak coupling superconductor the collision term in the formalism reduces to the one in the quasiparticle Boltzmann equation. We next treat the case of charge imbalance generated by tunnel injection, with pair breaking by phonons and magnetic impurities. Over the range of temperatures investigated exerimentally to date, the calculated charge imbalance is rather close to that evaluated using the Boltzmann equation, even if pair braeking is so strong as almost to destroy superconductivity. Finally we consider charge imbalance generated by the combined influence of a supercurrent and a temperature gradient. We give calculations for a dirty superconductor with scattering by phonons as the pair breaking mechanism, and the results give a reasonable account of the experimental data of Clarke, Fjordboge, and Lindelof. We carry out calculations for the case of impurity scattering along which are valid not only in the clean and dirty limits, but also for intermediate situations. These enable us to see how the large contribution to the charge imbalance found for energies close to the gap edge in the clean case is reduced with increasing impurity scattering
Pseudopotential transformation of correlated-pair equations
International Nuclear Information System (INIS)
Szasz, L.; Brown, L.
1975-01-01
A pseudopotential transformation for correlated-pair equations is derived that yields solutions that are pseudowavefunctions, i.e., they do not have to be orthogonal to the core functions. The approximate solutions for the transformation will be much simpler to compute, but they do not involve a loss of accuracy
Predictive labeling with dependency pairs using SAT
Koprowski, A.; Middeldorp, A.; Pfenning, F.
2007-01-01
This paper combines predictive labeling with dependency pairs and reports on its implementation. Our starting point is the method of proving termination of rewrite systems using semantic labeling with infinite models in combination with lexicographic path orders. We replace semantic labeling with
Multipole pair vibrations in superfluid 3He
International Nuclear Information System (INIS)
Baldo, M.; Giansiracusa, G.; Lombardo, U.; Pucci, R.; Petronio, G.
1978-01-01
Starting from a path integral formation of the 3 He superfluidity, the authors study the pair vibrations around the BCS solution. For both the BW and ABM states get a set of possible excitations. In particular it is shown that a new type of excitation is present for pure 1 = 2 spin singlet vibration. (Auth.)
Pion-pair production by two photons
International Nuclear Information System (INIS)
Terazawa, Hidezumi.
1994-07-01
The cross section for pion-pair production by two photons is calculated approximately by using the low energy theorem previously derived from partially-conserved-axial-vector-current hypothesis and current algebra, and found to agree very well with the experimental data recently obtained by the Mark II, TPC/Two-Gamma and CLEO Collaborations. (author)
Computing Hypercrossed Complex Pairings in Digital Images
Directory of Open Access Journals (Sweden)
Simge Öztunç
2013-01-01
Full Text Available We consider an additive group structure in digital images and introduce the commutator in digital images. Then we calculate the hypercrossed complex pairings which generates a normal subgroup in dimension 2 and in dimension 3 by using 8-adjacency and 26-adjacency.
Phenomena, dynamics and instabilities of vortex pairs
International Nuclear Information System (INIS)
Williamson, C H K; Asselin, D J; Leweke, T; Harris, D M
2014-01-01
Our motivation for studying the dynamics of vortex pairs stems initially from an interest in the trailing wake vortices from aircraft and the dynamics of longitudinal vortices close to a vehicle surface. However, our motivation also comes from the fact that vortex–vortex interactions and vortex–wall interactions are fundamental to many turbulent flows. The intent of the paper is to present an overview of some of our recent work concerning the formation and structure of counter-rotating vortex pairs. We are interested in the long-wave and short-wave three-dimensional instabilities that evolve for an isolated vortex pair, but also we would like to know how vortex pairs interact with a wall, including both two-dimensional interactions, and also the influence of the surface on the three-dimensional instabilities. The emphasis of this presentation is on physical mechanisms by which vortices interact with each other and with surfaces, principally from an experimental approach, but also coupled with analytical studies. (paper)
A Novel Approach for Collaborative Pair Programming
Goel, Sanjay; Kathuria, Vanshi
2010-01-01
The majority of an engineer's time in the software industry is spent working with other programmers. Agile methods of software development like eXtreme Programming strongly rely upon practices like daily meetings and pair programming. Hence, the need to learn the skill of working collaboratively is of primary importance for software developers.…
Pair production of intermediate vector bosons
International Nuclear Information System (INIS)
Mikaelian, K.O.
1979-01-01
The production of intermediate vector boson pairs W + W - , Z 0 Z 0 , W +- Z 0 and W +- γ in pp and p anti p collisions is discussed. The motivation is to detect the self-interactions among the four intermediate vector bosons
Pairing the Adult Learner and Boutique Wineries
Holyoke, Laura; Heath-Simpson, Delta
2013-01-01
This study explored connections between adult learners and their experiences in the context of small boutique wineries operating in the start-up phase of the organizational life cycle. The research objective was to gain insight regarding the pairing of adult learners with the entering of a specialty industry. Fourteen individuals from four…
Frustrated Lewis pairs: Design and reactivity
Indian Academy of Sciences (India)
for FLP systems and their unique reactivity are discussed here. Keywords. Lewis .... we will concentrate on the design principles of such. FLPs and the ... Designs of frustrated Lewis pairs ..... 64 and neutral titanium (III) complex [Cp2TiOC6.
Environmentally benign working pairs for adsorption refrigeration
International Nuclear Information System (INIS)
Cui Qun; Tao Gang; Chen Haijun; Guo Xinyue; Yao Huqing
2005-01-01
This paper begins from adsorption working pairs: water and ethanol were selected as refrigerants; 13x molecular sieve, silica gel, activated carbon, adsorbent NA and NB, proposed by authors, were selected as adsorbents, and the performance of adsorption working pairs in adsorption refrigeration cycle was studied. The adsorption isotherms of adsorbents (NA and NB) were obtained by high-vacuum gravimetric method. Desorption properties of adsorbents were analyzed and compared by thermal analysis method. The performance of adsorption refrigeration was studied on simulation device of adsorption refrigeration cycle. After presentation of adsorption isotherms, the thermodynamic performance for their use in adsorption refrigeration system was calculated. The results show: (1) the maximum adsorption capacity of water on adsorbent NA reaches 0.7 kg/kg, and the maximum adsorption capacity of ethanol on adsorbent NB is 0.68 kg/kg, which is three times that of ethanol on activated carbon, (2) the refrigeration capacity of NA-water working pair is 922 kJ/kg, the refrigeration capacity of NB-ethanol is 2.4 times that of activated carbon-methanol, (3) as environmental friendly and no public hazard adsorption working pair, NA-H 2 O and NB-ethanol can substitute activated carbon-methanol in adsorption refrigeration system using low-grade heat source
International Nuclear Information System (INIS)
Georgios, Anagnostou
2004-01-01
Combined measurements of the 4 LEP collaborations for the fermion pair processes e + e - →f anti f are presented. The results show no significant deviations when compared with the Standard Model predictions and are used to set limits on contact interactions, Z' gauge bosons and low scale gravity models with large extra dimensions. (orig.)
Frustrated Lewis pairs-assisted tritium labeling
Czech Academy of Sciences Publication Activity Database
Marek, Aleš; Široká, Sabina; Elbert, Tomáš
2016-01-01
Roč. 14, č. 5 (2016), s. 219 ISSN 2336-7202. [Sjezd českých a slovenských chemických společností /68./. 04.09.2016-07.09.2016, Praha] Institutional support: RVO:61388963 Keywords : frustrated Lewis pairs * one-pot synthesis * tritium -labeling Subject RIV: CC - Organic Chemistry
Angular assymetries in a shielded pair line
International Nuclear Information System (INIS)
Fanchiotti, H.; Garcia Canal, C.A.; Vucetich, H.
1979-01-01
The capacitance matrix and surface charge density distribution of an unbalanced pair line with both longitudinal and balanced excitations is presented. In particular the case in which the axes of the inner wires are not restricted to lie on a line through the axis of the shield is discussed
Binaries and triples among asteroid pairs
Pravec, Petr; Scheirich, Peter; Kušnirák, Peter; Hornoch, Kamil; Galád, Adrián
2015-08-01
Despite major achievements obtained during the past two decades, our knowledge of the population and properties of small binary and multiple asteroid systems is still far from advanced. There is a numerous indirect evidence for that most small asteroid systems were formed by rotational fission of cohesionless parent asteroids that were spun up to the critical frequency presumably by YORP, but details of the process are lacking. Furthermore, as we proceed with observations of more and more binary and paired asteroids, we reveal new facts that substantially refine and sometimes change our understanding of the asteroid systems. One significant new finding we have recently obtained is that primaries of many asteroid pairs are actually binary or triple systems. The first such case found is (3749) Balam (Vokrouhlický, ApJL 706, L37, 2009). We have found 9 more binary systems among asteroid pairs within our ongoing NEOSource photometric project since October 2012. They are (6369) 1983 UC, (8306) Shoko, (9783) Tensho-kan, (10123) Fideoja, (21436) Chaoyichi, (43008) 1999 UD31, (44620) 1999 RS43, (46829) 1998 OS14 and (80218) 1999 VO123. We will review their characteristics. These paired binaries as we call them are mostly similar to binaries in the general ("background") population (of unpaired asteroids), but there are a few trends. The paired binaries tend to have larger secondaries with D_2/D_1 = 0.3 to 0.5 and they also tend to be wider systems with 8 of the 10 having orbital periods between 30 and 81 hours, than average among binaries in the general population. There may be also a larger fraction of triples; (3749) Balam is a confirmed triple, having a larger close and a smaller distant satellite, and (8306) Shoko and (10123) Fideoja are suspect triples as they show additional rotational lightcurve components with periods of 61 and 38.8 h that differ from the orbital period of 36.2 and 56.5 h, respectively. The unbound secondaries tend to be of the same size or
Plasma physics and engineering
Fridman, Alexander
2011-01-01
Part I: Fundamentals of Plasma Physics and Plasma ChemistryPlasma in Nature, in the Laboratory, and in IndustryOccurrence of Plasma: Natural and Man MadeGas DischargesPlasma Applications, Plasmas in IndustryPlasma Applications for Environmental ControlPlasma Applications in Energy ConversionPlasma Application for Material ProcessingBreakthrough Plasma Applications in Modern TechnologyElementary Processes of Charged Species in PlasmaElementary Charged Particles in Plasma and Their Elastic and Inelastic CollisionsIonization ProcessesMechanisms of Electron Losses: The Electron-Ion RecombinationEl
Dusty-Plasma Particle Accelerator
Foster, John E.
2005-01-01
A dusty-plasma apparatus is being investigated as means of accelerating nanometer- and micrometer-sized particles. Applications for the dusty-plasma particle accelerators fall into two classes: Simulation of a variety of rapidly moving dust particles and micrometeoroids in outer-space environments that include micrometeoroid streams, comet tails, planetary rings, and nebulae and Deposition or implantation of nanoparticles on substrates for diverse industrial purposes that could include hardening, increasing thermal insulation, altering optical properties, and/or increasing permittivities of substrate materials. Relative to prior apparatuses used for similar applications, dusty-plasma particle accelerators offer such potential advantages as smaller size, lower cost, less complexity, and increased particle flux densities. A dusty-plasma particle accelerator exploits the fact that an isolated particle immersed in plasma acquires a net electric charge that depends on the relative mobilities of electrons and ions. Typically, a particle that is immersed in a low-temperature, partially ionized gas, wherein the average kinetic energy of electrons exceeds that of ions, causes the particle to become negatively charged. The particle can then be accelerated by applying an appropriate electric field. A dusty-plasma particle accelerator (see figure) includes a plasma source such as a radio-frequency induction discharge apparatus containing (1) a shallow cup with a biasable electrode to hold the particles to be accelerated and (2) a holder for the substrate on which the particles are to impinge. Depending on the specific design, a pair of electrostatic-acceleration grids between the substrate and discharge plasma can be used to both collimate and further accelerate particles exiting the particle holder. Once exposed to the discharge plasma, the particles in the cup quickly acquire a negative charge. Application of a negative voltage pulse to the biasable electrode results in the
DEFF Research Database (Denmark)
Goetze, Jens P; Hilsted, Linda M; Rehfeld, Jens F
2014-01-01
Cardiovascular risk assessment remains difficult in elderly patients. We examined whether chromogranin A (CgA) measurement in plasma may be valuable in assessing risk of death in elderly patients with symptoms of heart failure in a primary care setting. A total of 470 patients (mean age 73 years...
International Nuclear Information System (INIS)
Furth, H.P.; Goldston, R.J.; Zweben, S.J.
1990-10-01
The fraction of fusion-reaction energy that is released in energetic charged ions, such as the alpha particles of the D-T reaction, can be thermalized within the reacting plasma and used to maintain its temperature. This mechanism facilitates the achievement of very high energy-multiplication factors Q, but also raises a number of new issues of confinement physics. To ensure satisfactory reaction operation, three areas of energetic-ion interaction need to be addressed: single-ion transport in imperfectly symmetric magnetic fields or turbulent background plasmas; energetic-ion-driven (or stabilized) collective phenomena; and fusion-heat-driven collective phenomena. The first of these topics is already being explored in a number of tokamak experiments, and the second will begin to be addressed in the D-T-burning phase of TFTR and JET. Exploration of the third topic calls for high-Q operation, which is a goal of proposed next-generation plasma-burning projects. Planning for future experiments must take into consideration the full range of plasma-physics and engineering R ampersand D areas that need to be addressed on the way to a fusion power demonstration
Metal-mediated DNA base pairing: alternatives to hydrogen-bonded Watson-Crick base pairs.
Takezawa, Yusuke; Shionoya, Mitsuhiko
2012-12-18
With its capacity to store and transfer the genetic information within a sequence of monomers, DNA forms its central role in chemical evolution through replication and amplification. This elegant behavior is largely based on highly specific molecular recognition between nucleobases through the specific hydrogen bonds in the Watson-Crick base pairing system. While the native base pairs have been amazingly sophisticated through the long history of evolution, synthetic chemists have devoted considerable efforts to create alternative base pairing systems in recent decades. Most of these new systems were designed based on the shape complementarity of the pairs or the rearrangement of hydrogen-bonding patterns. We wondered whether metal coordination could serve as an alternative driving force for DNA base pairing and why hydrogen bonding was selected on Earth in the course of molecular evolution. Therefore, we envisioned an alternative design strategy: we replaced hydrogen bonding with another important scheme in biological systems, metal-coordination bonding. In this Account, we provide an overview of the chemistry of metal-mediated base pairing including basic concepts, molecular design, characteristic structures and properties, and possible applications of DNA-based molecular systems. We describe several examples of artificial metal-mediated base pairs, such as Cu(2+)-mediated hydroxypyridone base pair, H-Cu(2+)-H (where H denotes a hydroxypyridone-bearing nucleoside), developed by us and other researchers. To design the metallo-base pairs we carefully chose appropriate combinations of ligand-bearing nucleosides and metal ions. As expected from their stronger bonding through metal coordination, DNA duplexes possessing metallo-base pairs exhibited higher thermal stability than natural hydrogen-bonded DNAs. Furthermore, we could also use metal-mediated base pairs to construct or induce other high-order structures. These features could lead to metal-responsive functional
Schwinger pair creation of Kaluza-Klein particles: Pair creation without tunneling
International Nuclear Information System (INIS)
Friedmann, Tamar; Verlinde, Herman
2005-01-01
We study Schwinger pair creation of charged Kaluza-Klein (KK) particles from a static KK electric field. We find that the gravitational backreaction of the electric field on the geometry--which is incorporated via the electric KK-Melvin solution--prevents the electrostatic potential from overcoming the rest mass of the KK particles, thus impeding the tunneling mechanism which is often thought of as responsible for the pair creation. However, we find that pair creation still occurs with a finite rate formally similar to the classic Schwinger result, but via an apparently different mechanism, involving a combination of the Unruh effect and vacuum polarization due to the E-field
Neutron pair and proton pair transfer reactions between identical cores in the sulfur region
International Nuclear Information System (INIS)
Mermaz, M.C.
1995-12-01
Optical model and exact finite range distorted-wave Born approximation analyses were performed on neutron pair exchange between identical cores for 32 S and 34 S nuclei and on proton pair exchange between identical cores for 30 Si and 32 S. The extracted spectroscopic factors were compared with theoretical ones deduced from Hartree-Fock calculations on these pair of nuclei. The enhancement of the experimental cross sections with respect to the theoretical ones strongly suggests evidence for a nuclear Josephson effect. (author). 15 refs., 5 figs., 3 tabs
Magnetoresistive waves in plasmas
International Nuclear Information System (INIS)
Felber, F.S.; Hunter, R.O. Jr.; Pereira, N.R.; Tajima, T.
1982-01-01
The self-generated magnetic field of a current diffusing into a plasma between conductors can magnetically insulate the plasma. Propagation of magnetoresistive waves in plasmas is analyzed. Applications to plasma opening switches are discussed
Model for pairing phase transition in atomic nuclei
International Nuclear Information System (INIS)
Schiller, A.; Guttormsen, M.; Hjorth-Jensen, M.; Rekstad, J.; Siem, S.
2002-01-01
A model is developed which allows the investigation and classification of the pairing phase transition in atomic nuclei. The regions of the parameter space are discussed for which a pairing phase transition can be observed. The model parameters include number of particles, attenuation of pairing correlations with increasing seniority, single-particle level spacing, and pairing gap parameter
Paired peer learning through engineering education outreach
Fogg-Rogers, Laura; Lewis, Fay; Edmonds, Juliet
2017-01-01
Undergraduate education incorporating active learning and vicarious experience through education outreach presents a critical opportunity to influence future engineering teaching and practice capabilities. Engineering education outreach activities have been shown to have multiple benefits; increasing interest and engagement with science and engineering for school children, providing teachers with expert contributions to engineering subject knowledge, and developing professional generic skills for engineers such as communication and teamwork. This pilot intervention paired 10 pre-service teachers and 11 student engineers to enact engineering outreach in primary schools, reaching 269 children. A longitudinal mixed methods design was employed to measure change in attitudes and Education Outreach Self-Efficacy in student engineers; alongside attitudes, Teaching Engineering Self-Efficacy and Engineering Subject Knowledge Confidence in pre-service teachers. Highly significant improvements were noted in the pre-service teachers' confidence and self-efficacy, while both the teachers and engineers qualitatively described benefits arising from the paired peer mentor model.
Top quark pair production beyond NNLO
Energy Technology Data Exchange (ETDEWEB)
Muselli, Claudio [TIF Lab, Dipartimento di Fisica, Università di Milano, and INFN - Sezione di Milano,Via Celoria 16, I-20133 Milano (Italy); Bonvini, Marco [Rudolf Peierls Centre for Theoretical Physics, University of Oxford,1 Keble Road, OX1 3NP, Oxford (United Kingdom); Forte, Stefano [TIF Lab, Dipartimento di Fisica, Università di Milano, and INFN - Sezione di Milano,Via Celoria 16, I-20133 Milano (Italy); Marzani, Simone [Center for Theoretical Physics, Massachusetts Institute of Technology,77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Ridolfi, Giovanni [Dipartimento di Fisica, Università di Genova and INFN - Sezione di Genova,Via Dodecaneso 33, I-16146 Genova (Italy)
2015-08-17
We construct an approximate expression for the total cross section for the production of a heavy quark-antiquark pair in hadronic collisions at next-to-next-to-next-to-leading order (N{sup 3}LO) in α{sub s}. We use a technique which exploits the analyticity of the Mellin space cross section, and the information on its singularity structure coming from large N (soft gluon, Sudakov) and small N (high energy, BFKL) all order resummations, previously introduced and used in the case of Higgs production. We validate our method by comparing to available exact results up to NNLO. We find that N{sup 3}LO corrections increase the predicted top pair cross section at the LHC by about 4% over the NNLO.
Top quark pair production beyond NNLO
International Nuclear Information System (INIS)
Muselli, Claudio; Bonvini, Marco; Forte, Stefano; Marzani, Simone; Ridolfi, Giovanni
2015-01-01
We construct an approximate expression for the total cross section for the production of a heavy quark-antiquark pair in hadronic collisions at next-to-next-to-next-to-leading order (N 3 LO) in α s . We use a technique which exploits the analyticity of the Mellin space cross section, and the information on its singularity structure coming from large N (soft gluon, Sudakov) and small N (high energy, BFKL) all order resummations, previously introduced and used in the case of Higgs production. We validate our method by comparing to available exact results up to NNLO. We find that N 3 LO corrections increase the predicted top pair cross section at the LHC by about 4% over the NNLO.
Photoproduction of Drell-Yan lepton pairs
International Nuclear Information System (INIS)
Jones, L.M.; Sullivan, J.D.; Willen, D.E.; Wyld, H.W.
1979-01-01
We investigate the Drell-Yan reaction γp → (μ + μ - ) X with an eye to experimental determination of the photon structure functions. Contributions to the process from both the nonhadronic anomaly and the vector-dominance piece are estimated: we find that the cross section from the anomaly dominates the vector-dominance contribution at large Q 2 . The background from Bethe-Heitler pairs is also calculated; it is somewhat suppressed by going to y=0, and further suppressed relative to the Drell-Yan contribution for fixed Q 2 by looking at high center-of-mass energies and at small Q/sub perpendicular/ for the pair. Overall we find that the absolute Drell-Yan cross sections in the regions of interest are very small; experimental study of the process will be difficult
A search for resonant Z pair production
Energy Technology Data Exchange (ETDEWEB)
Boveia, Antonio [Univ. of California, Santa Barbara, CA (United States)
2008-12-01
I describe a search for anomalous production of Z pairs through a new massive resonance X in 2.5-2.9 fb^{-1} of p$\\bar{p}$ collisions at √s = 1.96 TeV using the CDFII Detector at the Fermilab Tevatron. I reconstruct Z pairs through their decays to electrons, muons, and quarks. To achieve perhaps the most efficient lepton reconstruction ever used at CDF, I apply a thorough understanding of the detector and new reconstruction software heavily revised for this purpose. In particular, I have designed and employ new general-purpose algorithms for tracking at large η in order to increase muon acceptance. Upon analyzing the unblinded signal samples, I observe no X → ZZ candidates and set upper limits on the production cross section using a Kaluza-Klein graviton-like acceptance.
Magnetically-enhanced open string pair production
Lu, J. X.
2017-12-01
We consider the stringy interaction between two parallel stacks of D3 branes placed at a separation. Each stack of D3 branes in a similar fashion carry an electric flux and a magnetic flux with the two sharing no common field strength index. The interaction amplitude has an imaginary part, giving rise to the Schwinger-like pair production of open strings. We find a significantly enhanced rate of this production when the two electric fluxes are almost identical and the brane separation is on the order of string scale. This enhancement will be largest if the two magnetic fluxes are opposite in direction. This novel enhancement results from the interplay of the non-perturbative Schwinger-type pair production due to the electric flux and the stringy tachyon due to the magnetic flux, and may have realistic physical applications.
Radiation- and pair-loaded shocks
Lyutikov, Maxim
2018-06-01
We consider the structure of mildly relativistic shocks in dense media, taking into account the radiation and pair loading, and diffusive radiation energy transfer within the flow. For increasing shock velocity (increasing post-shock temperature), the first important effect is the efficient energy redistribution by radiation within the shock that leads to the appearance of an isothermal jump, whereby the flow reaches the final state through a discontinuous isothermal transition. The isothermal jump, on scales much smaller than the photon diffusion length, consists of a weak shock and a quick relaxation to the isothermal conditions. Highly radiation-dominated shocks do not form isothermal jump. Pair production can mildly increase the overall shock compression ratio to ≈10 (4 for matter-dominated shocks and 7 of the radiation-dominated shocks).
Dynamics and Instabilities of Vortex Pairs
Leweke, Thomas; Le Dizès, Stéphane; Williamson, Charles H. K.
2016-01-01
This article reviews the characteristics and behavior of counter-rotating and corotating vortex pairs, which are seemingly simple flow configurations yet immensely rich in phenomena. Since the reviews in this journal by Widnall (1975) and Spalart (1998) , who studied the fundamental structure and dynamics of vortices and airplane trailing vortices, respectively, there have been many analytical, computational, and experimental studies of vortex pair flows. We discuss two-dimensional dynamics, including the merging of same-sign vortices and the interaction with the mutually induced strain, as well as three-dimensional displacement and core instabilities resulting from this interaction. Flows subject to combined instabilities are also considered, in particular the impingement of opposite-sign vortices on a ground plane. We emphasize the physical mechanisms responsible for the flow phenomena and clearly present the key results that are useful to the reader for predicting the dynamics and instabilities of parallel vortices.
Space-Efficient Re-Pair Compression
DEFF Research Database (Denmark)
Bille, Philip; Gørtz, Inge Li; Prezza, Nicola
2017-01-01
Re-Pair [5] is an effective grammar-based compression scheme achieving strong compression rates in practice. Let n, σ, and d be the text length, alphabet size, and dictionary size of the final grammar, respectively. In their original paper, the authors show how to compute the Re-Pair grammar...... in expected linear time and 5n + 4σ2 + 4d + √n words of working space on top of the text. In this work, we propose two algorithms improving on the space of their original solution. Our model assumes a memory word of [log2 n] bits and a re-writable input text composed by n such words. Our first algorithm runs...
Glass scintillator pair for compensation neutron logging
International Nuclear Information System (INIS)
Ji Changsong; Li Xuezhi; Yiu Guangduo
1985-01-01
Glass scintillator pair types ST 1604 and ST 1605 for compensation of neutron logging is developed. The neutron sensitive material used is multistick lithium glass scintillators 3 and 4 mm in diameter respectively. Thermoneutron detection efficiencies are 50-60% and 100% respectively. The detection efficiency for 60 Co γ ray is lower than 0.3%. The type ST 1604 and ST 1605 may also be used as high sensitive neutron detectors in an intensive γ ray field
On $ \\phi $ -amicable pairs (with appendix)
G.L. Cohen; H.J.J. te Riele (Herman)
1995-01-01
textabstractLet $\\phi(n)$ denote Euler's totient function, i.e., the number of positive integers~$
Signature scheme based on bilinear pairs
Tong, Rui Y.; Geng, Yong J.
2013-03-01
An identity-based signature scheme is proposed by using bilinear pairs technology. The scheme uses user's identity information as public key such as email address, IP address, telephone number so that it erases the cost of forming and managing public key infrastructure and avoids the problem of user private generating center generating forgery signature by using CL-PKC framework to generate user's private key.
Hadronic production of lepton pairs (experimental)
International Nuclear Information System (INIS)
Boucrot, J.
1980-12-01
Hadonic production of lepton pairs has become a good testground of Q.C.D. The large effects predicted in cross sections and in Psub(T) distributions are seen and may be one of the good indirect proofs of the existence of gluons. Detailed experimental results are available, and clearly it is necessary that higher order Q.C.D. corrections should be estimated
W+- pairs and neutral currents at ISABELLE
International Nuclear Information System (INIS)
Mikaelian, K.O.
1975-01-01
A report is presented on two different types of processes which may form part of the weak interactions program. The first is the production of pairs of charged weak bosons in the process pp → W + W - X; the second involves searching for neutral current effects in the rate for ordinary lepton production, without measuring any charge asymmetry or helicities using the reaction pp → l + l - X
Narrowband polarization entangled telecom photon pair source
Kaiser , Florian; Issautier , Amandine; Alibart , Olivier; Martin , Anthony; Tanzilli , Sébastien
2011-01-01
Contributed Talk; International audience; During the last decade, quantum entanglement has paved the way out to of the lab modern applications such as quantum computation and communication. Today, small scale quantum networks exist already, but they are limited to a few 100 km distance, due to intrinsic fiber transmission losses and non perfect detectors. These networks are typically established using photon pair sources based on spontaneous parametric down conversion (SPDC). Widely used enta...
Determination of the pairing-strength constants in the isovector plus isoscalar pairing case
Mokhtari, D.; Fellah, M.; Allal, N. H.
2016-05-01
A method for the determination of the pairing-strength constants, in the neutron-proton (n-p) isovector plus isoscalar pairing case, is proposed in the framework of the BCS theory. It is based on the fitting of these constants to reproduce the experimentally known pairing gap parameters as well as the root-mean-squared (r.m.s) charge radii values. The method is applied to some proton-rich even-even nuclei. The single-particle energies used are those of a deformed Woods-Saxon mean field. It is shown that the obtained value of the ratio GnpT=0/G npT=1 is of the same order as the ones, arbitrary chosen, of some previous works. The effect of the inclusion of the isoscalar n-p pairing in the r.m.s matter radii is then numerically studied for the same nuclei.
Neutrino signal from pair-instability supernovae
Wright, Warren P.; Gilmer, Matthew S.; Fröhlich, Carla; Kneller, James P.
2017-11-01
A very massive star with a carbon-oxygen core in the range of 64M ⊙Earth from two, one-dimensional pair-instability supernova simulations which bracket the mass range of stars which explode by this mechanism taking into account the full time and energy dependence of the neutrino emission and the flavor evolution through the outer layers of the star. We calculate the neutrino signals in five different detectors chosen to represent present or near future designs. We find the more massive progenitors explode as pair-instability supernova which can easily be detected in multiple different neutrino detectors at the "standard" supernova distance of 10 kpc producing several events in DUNE, JUNO, and Super-Kamiokande, while the lightest progenitors produce only a handful of events (if any) in the same detectors. The proposed Hyper-Kamiokande detector would detect neutrinos from a large pair-instability supernova as far as ˜50 kpc allowing it to reach the Megallanic Clouds and the several very high mass stars known to exist there.
Exclusive production of W pairs in CMS
Directory of Open Access Journals (Sweden)
Silveira Da
2014-04-01
Full Text Available We report the results on the search for exclusive production of W pairs in the LHC with data collected by the Compact Muon Solenoid detector in proton-proton collisions at √s = 7 TeV. The analysis comprises the two-photon production of a W pairs, pp → pW+ W− p → p νe± νµ∓ p. Two events are observed in data for pT(ℓ > 4 GeV, |η(ℓ| 20 GeV, in agreement with the standard model prediction of 2.2 ± 0.4 signal events with 0.84 ± 0.15 background events. Moreover, a study of the tail of the lepton pair transverse momentum distribution is performed to search for an evidence of anomalous quartic gauge couplings in the γγ → W+ W− vertex. As no events are observed in data, it results in a model-independent upper limits for the anomalous W quartic gauge couplings aW0,C/Λ2, which are of the order of 10−4.
Galactic Pairs in the Early Universe
Kohler, Susanna
2018-02-01
In the spirit of Valentines Day, today well be exploring apparent pairs of galaxies in the distant, early universe. How can we tell whether these duos are actually paired galaxies, as opposed to disguised singles?Real Pair, or Trick of the Light?In the schematic timeline of the universe, the epoch of reionization is when the first galaxies and quasars began to form and evolve. [NASA]The statistics of merging galaxies throughout the universe reveal not only direct information about how galaxies interact, but also cosmological information about the structure of the universe. While weve observed many merging galaxy pairs at low redshift, however, its much more challenging to identify these duos in the early universe.A merging pair of galaxies at high redshift appears to us as a pair of unresolved blobs that lie close to each other in the sky. But spotting such a set of objects doesnt necessarily mean were looking at a merger! There are three possible scenarios to explain an observed apparent duo:Its a pair of galaxies in a stage of merger.Its a projection coincidence; the two galaxies arent truly near each other.Its a single galaxy being gravitationally lensed by a foreground object. This strong lensing produces the appearance of multiple galaxies.Hubble photometry of one of the three galaxy groups identified at z 8, with the galaxies in the image labeled with their corresponding approximate photometric redshifts. [Adapted from Chaikin et al. 2018]Hunting for Distant DuosIn a recent study led by Evgenii Chaikin (Peter the Great St. Petersburg Polytechnic University, Russia), a team of scientists has explored the Hubble Ultra Deep Field in search ofhigh-redshift galaxies merging during the epoch of reionization, when the first galaxies formed and evolved.Using an approach called the dropout technique, which leverages the visibility of the galaxies in different wavelength filters, Chaikin and collaborators obtain approximate redshifts for an initial sample of 7
Pair formation by a deep potential well
International Nuclear Information System (INIS)
Nikishov, A.I.
1987-01-01
We obtain solutions of the Dirac and Klein-Gordon equations for a symmetric one-dimensional potential well with a flat bottom, and arbitrary depth, width, and field strength at the walls. Quasistationary solutions are found describing pair creation by the well, and the inverse process. It is shown that when the probability of pair creation by the well is small, it can be expressed in terms of the probability of pair creation at one of the walls and the oscillation frequency of the particle in the well. Among the states of the lower continuum, there are positron resonance scattering states for supercritical well depths. The energies of these states are close to the real part of the quasistationary energy level (the Zel'dovich effect). The qualitative dependence of the transmission coefficient of the positron through the well on its energy and the well width supports the idea that the solution of the so-called one-particle Dirac equation describes a many-particle system with charge 0 or 1
Pair creation by dynamic field configurations
International Nuclear Information System (INIS)
Aoyama, H.
1982-01-01
This thesis deals with the dynamics of the classical configuration of a quantum field unstable due to pair creation. The effective action method is developed first to treat such problems for a simple two-field model. Physical quantities such as pair creation probabilities are related to a complex function called the effective configuration, which is defined to minimize the effective action. Unitarity of the S-matrix is verified at the lowest order of the weak-field approximation. At the same order, the real valued vacuum expectation value of the quantum field, named the real configuration, is constructed in terms of the effective configuration. An integro-differential equation for the real configuration is given and is used to show that the real configuration is causal, while the effective configuration is not. Two practical applications of the effective action method are discussed. The first deals with pair creation in an anisotropic universe, and the real geometry is given in terms of the effective geometry in the samll anisotropy limit. The second deals with expanding vacuum bubbles. Corresponding to three possible situations, three kinds of field equations of each of the effective configuration and the real configuration are obtained. The behavior of the bubble is also studied by a semi-classical method, and one of the three situations is suggested to be plausible
Quantitative evaluation of pairs and RS steganalysis
Ker, Andrew D.
2004-06-01
We give initial results from a new project which performs statistically accurate evaluation of the reliability of image steganalysis algorithms. The focus here is on the Pairs and RS methods, for detection of simple LSB steganography in grayscale bitmaps, due to Fridrich et al. Using libraries totalling around 30,000 images we have measured the performance of these methods and suggest changes which lead to significant improvements. Particular results from the project presented here include notes on the distribution of the RS statistic, the relative merits of different "masks" used in the RS algorithm, the effect on reliability when previously compressed cover images are used, and the effect of repeating steganalysis on the transposed image. We also discuss improvements to the Pairs algorithm, restricting it to spatially close pairs of pixels, which leads to a substantial performance improvement, even to the extent of surpassing the RS statistic which was previously thought superior for grayscale images. We also describe some of the questions for a general methodology of evaluation of steganalysis, and potential pitfalls caused by the differences between uncompressed, compressed, and resampled cover images.
Pair-correlations in swimmer suspensions
Nambiar, Sankalp; Subramanian, Ganesh
2017-11-01
Suspensions of rear-actuated swimming microorganisms, such as E.coli, exhibit several interesting phenomena including spontaneous pattern formation above a critical concentration, novel rheological properties, shear-induced concentration banding etc. Explanations based on mean-field theory are only qualitative, since interactions between swimmers are important for typical experimental concentrations. We analytically characterize the hydrodynamic pair-interactions in a quiescent suspension of slender straight swimmers. The pair-correlation, calculated at leading order by integrating the swimmer velocity disturbances along straight trajectories, decays as 1/r2 for r >> L (L being the swimmer size). This allows us to characterize both polar and nematic correlations in an interacting swimmer suspension. In the absence of correlations, the velocity covariance asymptotes from a constant for r > L, the latter being characteristic of a suspension of non-interacting point force-dipoles. On including correlations, the slow decay of the pair-orientation correlation leads to an additional contribution to the velocity covariance that diverges logarithmically with system size.
Estimating Eulerian spectra from pairs of drifters
LaCasce, Joe
2017-04-01
GPS-tracked surface drifters offer the possibility of sampling energetic variations at the ocean surface on scales of only 10s of meters, much less than that resolved by satellite. Here we investigate whether velocity differences between pairs of drifters can be used to estimate kinetic energy spectra. Theoretical relations between the spectrum and the second-order longitudinal structure function for 2D non-divergent flow are derived. The structure function is a natural statistic for particle pairs and is easily calculated. However it integrates contributions across wavenumber, and this tends to obscure the spectral dependencies when turbulent inertial ranges are of finite extent. Nevertheless, the transform from spectrum to structure function is robust, as illustrated with Eulerian data collected from aircraft. The inverse transform, from structure function to spectrum, is much less robust, yielding poor results in particular at large wavenumbers. This occurs because the transform involves a filter function which magnifies contributions from large pair separations, which tend to be noisy. Fitting the structure function to a polynomial improves the spectral estimate, but not sufficiently to distinguish correct inertial range dependencies. Thus with Lagrangian data, it is appears preferable to focus on structure functions, despite their shortcomings.
Magnetic Pair Creation Transparency in Pulsars
Story, Sarah; Baring, M. G.
2013-04-01
The Fermi gamma-ray pulsar database now exceeds 115 sources and has defined an important part of Fermi's science legacy, providing rich information for the interpretation of young energetic pulsars and old millisecond pulsars. Among the well established population characteristics is the common occurrence of exponential turnovers in the 1-10 GeV range. These turnovers are too gradual to arise from magnetic pair creation in the strong magnetic fields of pulsar inner magnetospheres, so their energy can be used to provide lower bounds to the typical altitude of GeV band emission. We explore such constraints due to single-photon pair creation transparency below the turnover energy. We adopt a semi-analytic approach, spanning both domains when general relativistic influences are important and locales where flat spacetime photon propagation is modified by rotational aberration effects. Our work clearly demonstrates that including near-threshold physics in the pair creation rate is essential to deriving accurate attenuation lengths. The altitude bounds, typically in the range of 2-6 neutron star radii, provide key information on the emission altitude in radio quiet pulsars that do not possess double-peaked pulse profiles. For the Crab pulsar, which emits pulsed radiation up to energies of 120 GeV, we obtain a lower bound of around 15 neutron star radii to its emission altitude.
Paired and interacting galaxies: Conference summary
International Nuclear Information System (INIS)
Norman, C.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
Orthogonal expansions related to compact Gelfand pairs
DEFF Research Database (Denmark)
Berg, Christian; Peron, Ana P.; Porcu, Emilio
2017-01-01
. The functions of this class are the functions having a uniformly convergent expansion ∑ϕεZB(ϕ)(u)ϕ(x) for xεG,uεL, where the sum is over the space Z of positive definite spherical functions ϕ:G→C for the Gelfand pair, and (B(ϕ))ϕεZ is a family of continuous positive definite functions on L such that ∑ϕε......For a locally compact group G, let P(G) denote the set of continuous positive definite functions f:G→C. Given a compact Gelfand pair (G,K) and a locally compact group L, we characterize the class PK#(G,L) of functions fεP(G×L) which are bi-invariant in the G-variable with respect to K......(d)) and (U(q),U(q-1)) as well as for the product of these Gelfand pairs.The result generalizes recent theorems of Berg-Porcu (2016) and Guella-Menegatto (2016)....
Recent developments in quantum plasma physics
International Nuclear Information System (INIS)
Shukla, P K; Eliasson, B
2010-01-01
We present a review of recent developments in nonlinear quantum plasma physics involving quantum hydrodynamics and effective nonlinear Schroedinger equation formalisms, for describing collective phenomena in dense quantum plasmas with degenerate electrons. As examples, we discuss simulation studies of the formation and dynamics of dark solitons and quantum vortices, and of nonlinear interactions between intense circularly polarized electromagnetic (CPEM) waves and electron plasma oscillations (EPOs) in dense quantum-electron plasmas with immobile ions. The electron dynamics of dark solitons and quantum vortices is governed by a pair of equations comprising the nonlinear Schroedinger and Poisson system of equations. Both dark solitons and singly charged electron vortices are robust, and the latter tend to form pairs of oppositely charged vortices. The two-dimensional quantum-electron vortex pairs survive during collisions under the change of partners. The dynamics of the CPEM waves is governed by a nonlinear Schroedinger equation, which is nonlinearly coupled with the Schroedinger equation of the EPOs via the relativistic ponderomotive force, the relativistic electron mass increase in the CPEM field, and the electron density fluctuations. The present governing equations in one-spatial dimension admit stationary solutions in the form of dark solitons. The nonlinear equations also depict trapping of localized CPEM wave envelopes in the electron density holes that are associated with a positive potential profile.
Strong pairing approximation in comparison with the exact solutions to the pairing Hamiltonian
Directory of Open Access Journals (Sweden)
Lunyov A.V.
2016-01-01
Full Text Available Results of the Strong Pairing Approximation (SPA as a method with the exact particle number conservation are compared with those of the quasiparticle method (QM. It is shown that SPA comes to the same equations as QM for the gap parameter, chemical potential and one- and two-quasiparticle states. Calculations are performed for 14864Gd84 as an example, and compared with the exact solutions to the pairing Hamiltonian.
Detecting nonlocal Cooper pair entanglement by optical Bell inequality violation
Nigg, Simon E.; Tiwari, Rakesh P.; Walter, Stefan; Schmidt, Thomas L.
2014-01-01
Based on the Bardeen Cooper Schrieffer (BCS) theory of superconductivity, the coherent splitting of Cooper pairs from a superconductor to two spatially separated quantum dots has been predicted to generate nonlocal pairs of entangled electrons. In order to test this hypothesis, we propose a scheme to transfer the spin state of a split Cooper pair onto the polarization state of a pair of optical photons. We show that the produced photon pairs can be used to violate a Bell inequality, unambiguo...
The paired-domination and the upper paired-domination numbers of graphs
Directory of Open Access Journals (Sweden)
Włodzimierz Ulatowski
2015-01-01
Full Text Available In this paper we continue the study of paired-domination in graphs. A paired-dominating set, abbreviated PDS, of a graph \\(G\\ with no isolated vertex is a dominating set of vertices whose induced subgraph has a perfect matching. The paired-domination number of \\(G\\, denoted by \\(\\gamma_{p}(G\\, is the minimum cardinality of a PDS of \\(G\\. The upper paired-domination number of \\(G\\, denoted by \\(\\Gamma_{p}(G\\, is the maximum cardinality of a minimal PDS of \\(G\\. Let \\(G\\ be a connected graph of order \\(n\\geq 3\\. Haynes and Slater in [Paired-domination in graphs, Networks 32 (1998, 199-206], showed that \\(\\gamma_{p}(G\\leq n-1\\ and they determine the extremal graphs \\(G\\ achieving this bound. In this paper we obtain analogous results for \\(\\Gamma_{p}(G\\. Dorbec, Henning and McCoy in [Upper total domination versus upper paired-domination, Questiones Mathematicae 30 (2007, 1-12] determine \\(\\Gamma_{p}(P_n\\, instead in this paper we determine \\(\\Gamma_{p}(C_n\\. Moreover, we describe some families of graphs \\(G\\ for which the equality \\(\\gamma_{p}(G=\\Gamma_{p}(G\\ holds.
Cairns, R A
1985-01-01
This book is intended as an introduction to plasma physics at a level suitable for advanced undergraduates or beginning postgraduate students in physics, applied mathematics or astrophysics. The main prerequisite is a knowledge of electromagnetism and of the associated mathematics of vector calculus. SI units are used throughout. There is still a tendency amongst some plasma physics researchers to· cling to C.g.S. units, but it is the author's view that universal adoption of SI units, which have been the internationally agreed standard since 1960, is to be encouraged. After a short introductory chapter, the basic properties of a plasma con cerning particle orbits, fluid theory, Coulomb collisions and waves are set out in Chapters 2-5, with illustrations drawn from problems in nuclear fusion research and space physics. The emphasis is on the essential physics involved and (he theoretical and mathematical approach has been kept as simple and intuitive as possible. An attempt has been made to draw attention t...
An amplitude modulated radio frequency plasma generator
Lei, Fan; Li, Xiaoping; Liu, Yanming; Liu, Donglin; Yang, Min; Xie, Kai; Yao, Bo
2017-04-01
A glow discharge plasma generator and diagnostic system has been developed to study the effects of rapidly variable plasmas on electromagnetic wave propagation, mimicking the plasma sheath conditions encountered in space vehicle reentry. The plasma chamber is 400 mm in diameter and 240 mm in length, with a 300-mm-diameter unobstructed clear aperture. Electron densities produced are in the mid 1010 electrons/cm3. An 800 W radio frequency (RF) generator is capacitively coupled through an RF matcher to an internally cooled stainless steel electrode to form the plasma. The RF power is amplitude modulated by a waveform generator that operates at different frequencies. The resulting plasma contains electron density modulations caused by the varying power levels. A 10 GHz microwave horn antenna pair situated on opposite sides of the chamber serves as the source and detector of probe radiation. The microwave power feed to the source horn is split and one portion is sent directly to a high-speed recording oscilloscope. On mixing this with the signal from the pickup horn antenna, the plasma-induced phase shift between the two signals gives the path-integrated electron density with its complete time dependent variation. Care is taken to avoid microwave reflections and extensive shielding is in place to minimize electronic pickup. Data clearly show the low frequency modulation of the electron density as well as higher harmonics and plasma fluctuations.
International Nuclear Information System (INIS)
Hosogane, Nobuyuki; Nakayama, Takahide.
1985-01-01
Purpose: To prevent concentration of plasma currents to the plasma center upon plasma shutdown in a torus type thermonuclear device by the injection of fuels to the plasma center thereby prevent plasma disruption at the plasma center. Constitution: The plasma shutdown device comprises a plasma current measuring device that measures the current distribution of plasmas confined within a vacuum vessel and outputs a control signal for cooling the plasma center when the plasma currents concentrate to the plasma center and a fuel supply device that supplies fuels to the plasma center for cooling the center. The fuels are injected in the form of pellets into the plasmas. The direction and the velocity of the injection are set such that the pellets are ionized at the center of the plasmas. (Horiuchi, T.)
Counter-facing plasma guns for efficient extreme ultra-violet plasma light source
Directory of Open Access Journals (Sweden)
Kuroda Yusuke
2013-11-01
Full Text Available A plasma focus system composed of a pair of counter-facing coaxial guns was proposed as a long-pulse and/or repetitive high energy density plasma source. We applied Li as the source of plasma for improvement of the conversion efficiency, the spectral purity, and the repetition capability. For operation of the system with ideal counter-facing plasma focus mode, we changed the system from simple coaxial geometry to a multi-channel configuration. We applied a laser trigger to make synchronous multi-channel discharges with low jitter. The results indicated that the configuration is promising to make a high energy density plasma with high spectral efficiency.
A method for measuring plasma position in TJ-I Tokamak
International Nuclear Information System (INIS)
Quin, J.; TJ-I, Team
1993-01-01
A method using pairs of Mirnov coils to measure the plasma position in TJ-I is presented. The simple toroidal filament model which neglects the effect of plasma current density profile has proven to be acceptable within the experimental accuracy. The effect of plasma current density profile remains to be small, if the plasma current density profile has a quadratic form. (Author) 5 refs
A method for measuring plasma position in TJ-I Tokamak
Energy Technology Data Exchange (ETDEWEB)
Quin, J.; TJ-I, Team
1993-07-01
A method using pairs of Mirnov coils to measure the plasma position in TJ-I is presented. The simple toroidal filament model which neglects the effect of plasma current density profile has proven to be acceptable within the experimental accuracy. The effect of plasma current density profile remains to be small, if the plasma current density profile has a quadratic form. (Author) 5 refs.
Enhanced laser beam coupling to a plasma
International Nuclear Information System (INIS)
Steiger, A.D.; Woods, C.H.
1976-01-01
Density perturbations are induced in a heated plasma by means of a pair of oppositely directed, polarized laser beams of the same frequency. The wavelength of the density perturbations is equal to one half the wavelength of the laser beams. A third laser beam is linearly polarized and directed at the perturbed plasma along a line that is perpendicular to the direction of the two opposed beams. The electric field of the third beam is oriented to lie in the plane containing the three beams. The frequency of the third beam is chosen to cause it to interact resonantly with the plasma density perturbations, thereby efficiently coupling the energy of the third beam to the plasma. 10 claims, 2 figures
Top quark pair production at the LHC
Energy Technology Data Exchange (ETDEWEB)
Baernreuther, Peter
2012-06-28
One of the most interesting and manifold processes in the Standard Model of elementary particle physics is the top quark pair production. It enabled the discovery of the top quark at the Tevatron in 1995 and the determination of many of its properties. By means of a precise measurement and calculation of the cross section of top quark pair production it is possible to extract the top quark mass. Improvements in the gluon parton distribution functions (important for the Higgs boson production) or improvements in the prediction of the Higgs mass are also closely linked with the top quark pair production. Furthermore, the production process plays an important role in the discovery of new physics. On the one hand the top quark pair decays form the largest part of the background in many BSM models, on the other hand BSM physics can be detected directly in the decay process by investigating the charge symmetry or the invariant mass spectrum. At the LHC it will be possible for the first time to produce a large amount of top quarks; thereby the statistical errors of the observables will be strongly reduced. The enormous increase in the production rate has two reasons. On the one hand, the acceleration energy of the LHC (14 TeV and 7 TeV) is significantly greater than that of the Tevatron (1.96 Tev). This leads to an increase of the cross section by a factor of 100 ({proportional_to}7.3 pb at the Tevatron to {proportional_to}800 pb at 14 TeV LHC). On the other hand, the luminosity of the LHC outperforms the Tevatron by a factor of 10-100. The reduced experimental errors for the observables demand an improvement of the theoretical error. The experimental accuracy of the LHC and the great relevance of the process led to an intensive activity of different research groups in order to improve the calculation of the cross section of top quark pair production. This work presents for the first time a complete numerical result for the full NNLO correction for the top quark pair
Top quark pair production at the LHC
International Nuclear Information System (INIS)
Baernreuther, Peter
2012-01-01
One of the most interesting and manifold processes in the Standard Model of elementary particle physics is the top quark pair production. It enabled the discovery of the top quark at the Tevatron in 1995 and the determination of many of its properties. By means of a precise measurement and calculation of the cross section of top quark pair production it is possible to extract the top quark mass. Improvements in the gluon parton distribution functions (important for the Higgs boson production) or improvements in the prediction of the Higgs mass are also closely linked with the top quark pair production. Furthermore, the production process plays an important role in the discovery of new physics. On the one hand the top quark pair decays form the largest part of the background in many BSM models, on the other hand BSM physics can be detected directly in the decay process by investigating the charge symmetry or the invariant mass spectrum. At the LHC it will be possible for the first time to produce a large amount of top quarks; thereby the statistical errors of the observables will be strongly reduced. The enormous increase in the production rate has two reasons. On the one hand, the acceleration energy of the LHC (14 TeV and 7 TeV) is significantly greater than that of the Tevatron (1.96 Tev). This leads to an increase of the cross section by a factor of 100 (∝7.3 pb at the Tevatron to ∝800 pb at 14 TeV LHC). On the other hand, the luminosity of the LHC outperforms the Tevatron by a factor of 10-100. The reduced experimental errors for the observables demand an improvement of the theoretical error. The experimental accuracy of the LHC and the great relevance of the process led to an intensive activity of different research groups in order to improve the calculation of the cross section of top quark pair production. This work presents for the first time a complete numerical result for the full NNLO correction for the top quark pair production in quark anti
Older Galaxy Pair Has Surprisingly Youthful Glow
2007-01-01
[figure removed for brevity, see original site] Poster Version A pair of interacting galaxies might be experiencing the galactic equivalent of a mid-life crisis. For some reason, the pair, called Arp 82, didn't make their stars early on as is typical of most galaxies. Instead, they got a second wind later in life -- about 2 billion years ago -- and started pumping out waves of new stars as if they were young again. Arp 82 is an interacting pair of galaxies with a strong bridge and a long tail. NGC 2535 is the big galaxy and NGC 2536 is its smaller companion. The disk of the main galaxy looks like an eye, with a bright 'pupil' in the center and oval-shaped 'eyelids.' Dramatic 'beads on a string' features are visible as chains of evenly spaced star-formation complexes along the eyelids. These are presumably the result of large-scale gaseous shocks from a grazing encounter. The colors of this galaxy indicate that the observed stars are young to intermediate in age, around 2 million to 2 billion years old, much less than the age of the universe (13.7 billion years). The puzzle is: why didn't Arp 82 form many stars earlier, like most galaxies of that mass range? Scientifically, it is an oddball and provides a relatively nearby lab for studying the age of intermediate-mass galaxies. This picture is a composite captured by Spitzer's infrared array camera with light at wavelength 8 microns shown in red, NASA's Galaxy Evolution Explorer combined 1530 and 2310 Angstroms shown in blue, and the Southeastern Association for Research in Astronomy Observatory light at 6940 Angstroms shown in green.
Augmenting Think-Pair-Share with Simulations
Lee, Kevin M.; Siedell, C. M.; Prather, E. E.; CATS
2009-01-01
Computer simulations are valuable tools for the teaching and learning of introductory astronomy. They enable students to link together small pieces of information into mental models of complex physical systems that are far beyond their everyday experience. They can also be used to authentically test a student's conceptual understanding of a physical system by asking the student to make predictions regarding its behavior. Students receive formative feedback by testing their predictions in simulations. Think-Pair-Share - the posing of conceptual questions to students and having them vote on the answer before and after discussion with their peers - can benefit considerably from the incorporation of simulations. Simulations can be used for delivering content that precedes Think-Pair-Share, as the prompt the questions is based upon, or as a feedback tool to illustrate the answer to a question. These techniques are utilized in ClassAction - a collection of materials designed to enhance the metacognitive skills of Astro 101 students by promoting interactive engagement and providing rapid feedback. The main focus is dynamic conceptual questions largely based upon graphics that can be projected in the classroom. Many questions are available in a Flash computer database and instructors have the capability to recast these questions into alternate permutations based on their own preferences and student responses. Outlines, graphics, and simulations are included which instructors can use to provide feedback. This poster provides examples of simulation usage in Think-Pair-Share related to sky motions, lunar phases, and stellar properties. A multi-institutional classroom validation study of ClassAction is currently underway as a Collaboration of Astronomy Teaching Scholars (CATS) research project. All materials are publicly available at http://astro.unl.edu. We would like to thank the NSF for funding under Grant Nos. 0404988 and 0715517, a CCLI Phase III Grant for the
Paired structures and bipolar knowledge representation
DEFF Research Database (Denmark)
Montero, Javier; Bustince, Humberto; Franco, Camilo
In this strictly positional paper we propose a general approach to bipolar knowledge representation, where the meaning of concepts can be modelled by examining their decomposition into opposite and neutral categories. In particular, it is the semantic relationship between the opposite categories...... and at the same time the type of neutrality rising in between opposites. Based on this first level of bipolar knowledge representation, paired structures in fact offer the means to characterize a specific bipolar valuation scale depending on the meaning of the concept that has to be verified. In this sense...
Z Boson Pair-Production at LEP
Achard, P; Aguilar-Benítez, M; Alcaraz, J; Alemanni, G; Allaby, James V; Aloisio, A; Alviggi, M G; Anderhub, H; Andreev, V P; Anselmo, F; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Bajo, A; Baksay, G; Baksay, L; Baldew, S V; Banerjee, S; Banerjee, Sw; Barczyk, A; Barillère, R; Bartalini, P; Basile, M; Batalova, N; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Bellucci, L; Berbeco, R; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Biasini, M; Biglietti, M; Biland, A; Blaising, J J; Blyth, S C; Bobbink, Gerjan J; Böhm, A; Boldizsar, L; Borgia, B; Bottai, S; Bourilkov, D; Bourquin, Maurice; Braccini, S; Branson, J G; Brochu, F; Burger, J D; Burger, W J; Cai, X D; Capell, M; Cara Romeo, G; Carlino, G; Cartacci, A M; Casaus, J; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada, M; Chamizo-Llatas, M; Chang, Y H; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chiefari, G; Cifarelli, Luisa; Cindolo, F; Clare, I; Clare, R; Coignet, G; Colino, N; Costantini, S; de la Cruz, B; Cucciarelli, S; van Dalen, J A; De Asmundis, R; Déglon, P L; Debreczeni, J; Degré, A; Dehmelt, K; Deiters, K; Della Volpe, D; Delmeire, E; Denes, P; De Notaristefani, F; De Salvo, A; Diemoz, M; Dierckxsens, M; Dionisi, C; Dittmar, M; Doria, A; Dova, M T; Duchesneau, D; Duda, M; Echenard, B; Eline, A; El-Hage, A; El-Mamouni, H; Engler, A; Eppling, F J; Extermann, P; Falagán, M A; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, M; Ferguson, T; Fesefeldt, H S; Fiandrini, E; Field, J H; Filthaut, Frank; Fisher, P H; Fisher, W; Fisk, I; Forconi, G; Freudenreich, Klaus; Furetta, C; Galaktionov, Yu; Ganguli, S N; García-Abia, P; Gataullin, M; Gentile, S; Giagu, S; Gong, Z F; Grenier, G; Grimm, O; Grünewald, M W; Guida, M; van Gulik, R; Gupta, V K; Gurtu, A; Gutay, L J; Haas, D; Hatzifotiadou, D; Hebbeker, T; Hervé, A; Hirschfelder, J; Hofer, H; Hohlmann, M; Holzner, G; Hou, S R; Hu, Y; Jin, B N; Jones, L W; de Jong, P; Josa-Mutuberria, I; Käfer, D; Kaur, M; Kienzle-Focacci, M N; Kim, J K; Kirkby, Jasper; Kittel, E W; Klimentov, A; König, A C; Kopal, M; Koutsenko, V F; Kräber, M H; Krämer, R W; Krüger, A; Kunin, A; Ladrón de Guevara, P; Laktineh, I; Landi, G; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Le Goff, J M; Leiste, R; Levtchenko, M; Levchenko, P M; Li, C; Likhoded, S; Lin, C H; Lin, W T; Linde, Frank L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lü, Y S; Luci, C; Luminari, L; Lustermann, W; Ma Wen Gan; Malgeri, L; Malinin, A; Maña, C; Mans, J; Martin, J P; Marzano, F; Mazumdar, K; McNeil, R R; Mele, S; Merola, L; Meschini, M; Metzger, W J; Mihul, A; Milcent, H; Mirabelli, G; Mnich, J; Mohanty, G B; Muanza, G S; Muijs, A J M; Musicar, B; Musy, M; Nagy, S; Natale, S; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Nisati, A; Novák, T; Nowak, H; Ofierzynski, R A; Organtini, G; Pal, I; Palomares, C; Paolucci, P; Paramatti, R; Passaleva, G; Patricelli, S; Paul, T; Pauluzzi, M; Paus, C; Pauss, Felicitas; Pedace, M; Pensotti, S; Perret-Gallix, D; Petersen, B; Piccolo, D; Pierella, F; Pioppi, M; Piroué, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pozhidaev, V; Pothier, J; Prokofev, D; Prokofiev, D O; Quartieri, J; Rahal-Callot, G; Rahaman, M A; Raics, P; Raja, N; Ramelli, R; Rancoita, P G; Ranieri, R; Raspereza, A V; Razis, P A; Ren, D; Rescigno, M; Reucroft, S; Riemann, S; Riles, K; Roe, B P; Romero, L; Rosca, A; Rosier-Lees, S; Roth, S; Rosenbleck, C; Roux, B; Rubio, J A; Ruggiero, G; Rykaczewski, H; Sakharov, A; Saremi, S; Sarkar, S; Salicio, J; Sánchez, E; Schäfer, C; Shchegelskii, V; Schopper, Herwig Franz; Schotanus, D J; Sciacca, C; Servoli, L; Shevchenko, S; Shivarov, N; Shoutko, V; Shumilov, E; Shvorob, A V; Son, D; Souga, C; Spillantini, P; Steuer, M; Stickland, D P; Stoyanov, B; Strässner, A; Sudhakar, K; Sultanov, G G; Sun, L Z; Sushkov, S; Suter, H; Swain, J D; Szillási, Z; Tang, X W; Tarjan, P; Tauscher, Ludwig; Taylor, L; Tellili, B; Teyssier, D; Timmermans, C; Ting, Samuel C C; Ting, S M; Tonwar, S C; Tóth, J; Tully, C; Tung, K L; Ulbricht, J; Valente, E; Van de Walle, R T; Vásquez, R; Veszpremi, V; Vesztergombi, G; Vetlitskii, I; Vicinanza, D; Viertel, Gert M; Villa, S; Vivargent, M; Vlachos, S; Vodopyanov, I; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Wadhwa, M; Wang, Q; Wang, X L; Wang, Z M; Weber, M; Wienemann, P; Wilkens, H; Wynhoff, S; Xia, L; Xu, Z Z; Yamamoto, J; Yang, B Z; Yang, C G; Yang, H J; Yang, M; Yeh, S C; Zalite, A; Zalite, Yu; Zhang, Z P; Zhao, J; Zhu, G Y; Zhu, R Y; Zhuang, H L; Zichichi, A; Zimmermann, B; Zöller, M
2003-01-01
Events stemming from the pair-production of Z bosons in e^+e^- collisions are studied using 217.4 pb^-1 of data collected with the L3 detector at centre-of-mass energies from 200 GeV up to 209 GeV. The special case of events with b quarks is also investigated. Combining these events with those collected at lower centre-of-mass energies, the Standard Model predictions for the production mechanism are verified. In addition, limits are set on anomalous couplings of neutral gauge bosons and on effects of extra space dimensions.
Pair Negotiation When Developing English Speaking Tasks
Directory of Open Access Journals (Sweden)
Ingrid Liliana Bohórquez Suárez
2011-12-01
Full Text Available This study analyzes what characterizes the negotiations of seventh graders at a public school in Bogotá when working in pairs to develop speaking tasks in EFL classes. The inquiry is a descriptive case study that follows the qualitative paradigm. As a result of analyzing the data, we obtained four consecutive steps that characterize students’ negotiations: Establishing a connection with a partner to work with, proposing practical alternatives, refusing mates’ propositions, and making practical decisions. Moreover, we found that the constant performance of the process of negotiation provokes students to construct a sociolinguistic identity that allows agreements to emerge.
Production of supersymmetric pairs at antipp colliders
International Nuclear Information System (INIS)
Peschanski, R.
1985-02-01
Production and decay rates of squarks and gluinos at antipp colliders are shown to depend not only on the mass scale but on the ratio of squark to gluino mass. In the degenerate case which is shown to be natural in a large class of broken Supergravity models with minimal field content the predicted cross-sections are enhanced by a sizeable factor. This gives an improved bound on the squark mass (70 GeV) from the analysis of Cern monojets and indications for the search of squark decay modes of supersymmetric pairs at antipp colliders in the near future
Pairing correlations in a fissioning potential well
International Nuclear Information System (INIS)
Krappe, H.J.; Fadeev, S.
1999-01-01
To describe pairing correlations in a fissioning system one commonly projects the BCS wave function separately onto good particle numbers in each fragment in the exit channel, but only onto the total number of particles in the parent system. We propose to interpolate between these limiting situations by the generator-coordinate method with the particle-number difference between the nascent fragments as the generator coordinate. Model calculations are presented for the Hill-Wheeler box potential with a δ-function diaphragm to mimic scission
Hadroproduction of massive lepton pairs and QCD
International Nuclear Information System (INIS)
Berger, E.L.
1979-04-01
A survey is presented of some current issues of interest in attempts to describe the production of massive lepton pairs in hadronic collisions at high energies. I concentrate on the interpretation of data in terms of the parton model and on predictions derived from quantum-chromodynamics (QCD), their reliability and their confrontation with experiment. Among topics treated are the connection with deep-inelastic lepton scattering, universality of structure functions, and the behavior of cross-sections as a function of transverse momentum
Dimer pair correlations on the brick lattice
International Nuclear Information System (INIS)
Yokoi, C.S.O.; Nagle, J.F.; Sulinas, S.R.
1986-01-01
Using exact methods, pair-correlation functions are studied in the dimer model defined on a brick lattice. At long distances these functions exhibit strongly anisotropic algebraic decay and, near criticality, the length scales diverge differently in the two principal directions. The critical exponents are v /sub x/ =1/2 and v /sub y/ =1. These results are in agreement with deductions drawn from recent exact finite-size scaling calculations. We also interpret our results in the light of domain wall theories of commensurate-incommensurate transitions, and in particular we study the relation of the present model to the discrete version of the Pokrovsky-Talapov model introduced by Villain
Detecting nonlocal Cooper pair entanglement by optical Bell inequality violation
Energy Technology Data Exchange (ETDEWEB)
Nigg, Simon E.; Tiwari, Rakesh P.; Walter, Stefan; Schmidt, Thomas L. [Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland)
2015-07-01
Based on the Bardeen Cooper Schrieffer (BCS) theory of superconductivity, the coherent splitting of Cooper pairs from a superconductor to two spatially separated quantum dots has been predicted to generate nonlocal pairs of entangled electrons. In order to test this hypothesis, we propose a scheme to transfer the spin state of a split Cooper pair onto the polarization state of a pair of optical photons. We show that the produced photon pairs can be used to violate a Bell inequality, unambiguously demonstrating the entanglement of the split Cooper pairs.
Detecting nonlocal Cooper pair entanglement by optical Bell inequality violation
Nigg, Simon E.; Tiwari, Rakesh P.; Walter, Stefan; Schmidt, Thomas L.
2015-03-01
Based on the Bardeen-Cooper-Schrieffer theory of superconductivity, the coherent splitting of Cooper pairs from a superconductor to two spatially separated quantum dots has been predicted to generate nonlocal pairs of entangled electrons. In order to test this hypothesis, we propose a scheme to transfer the spin state of a split Cooper pair onto the polarization state of a pair of optical photons. We show that the photon pairs produced can be used to violate a Bell inequality, unambiguously demonstrating the entanglement of the split Cooper pairs.
Frequent Pairs in Data Streams: Exploiting Parallelism and Skew
DEFF Research Database (Denmark)
Campagna, Andrea; Kutzkow, Konstantin; Pagh, Rasmus
2011-01-01
We introduce the Pair Streaming Engine (PairSE) that detects frequent pairs in a data stream of transactions. Our algorithm finds the most frequent pairs with high probability, and gives tight bounds on their frequency. It is particularly space efficient for skewed distribution of pair supports...... items mining in data streams. We show how to efficiently scale these approaches to handle large transactions. We report experimental results showcasing precision and recall of our method. In particular, we find that often our method achieves excellent precision, returning identical upper and lower...... bounds on the supports of the most frequent pairs....
Pair Production Constraints on Superluminal Neutrinos Revisited
International Nuclear Information System (INIS)
Brodsky, Stanley
2012-01-01
We revisit the pair creation constraint on superluminal neutrinos considered by Cohen and Glashow in order to clarify which types of superluminal models are constrained. We show that a model in which the superluminal neutrino is effectively light-like can evade the Cohen-Glashow constraint. In summary, any model for which the CG pair production process operates is excluded because such timelike neutrinos would not be detected by OPERA or other experiments. However, a superluminal neutrino which is effectively lightlike with fixed p 2 can evade the Cohen-Glashow constraint because of energy-momentum conservation. The coincidence involved in explaining the SN1987A constraint certainly makes such a picture improbable - but it is still intrinsically possible. The lightlike model is appealing in that it does not violate Lorentz symmetry in particle interactions, although one would expect Hughes-Drever tests to turn up a violation eventually. Other evasions of the CG constraints are also possible; perhaps, e.g., the neutrino takes a 'short cut' through extra dimensions or suffers anomalous acceleration in matter. Irrespective of the OPERA result, Lorentz-violating interactions remain possible, and ongoing experimental investigation of such possibilities should continue.
Using Dictionary Pair Learning for Seizure Detection.
Ma, Xin; Yu, Nana; Zhou, Weidong
2018-02-13
Automatic seizure detection is extremely important in the monitoring and diagnosis of epilepsy. The paper presents a novel method based on dictionary pair learning (DPL) for seizure detection in the long-term intracranial electroencephalogram (EEG) recordings. First, for the EEG data, wavelet filtering and differential filtering are applied, and the kernel function is performed to make the signal linearly separable. In DPL, the synthesis dictionary and analysis dictionary are learned jointly from original training samples with alternating minimization method, and sparse coefficients are obtained by using of linear projection instead of costly [Formula: see text]-norm or [Formula: see text]-norm optimization. At last, the reconstructed residuals associated with seizure and nonseizure sub-dictionary pairs are calculated as the decision values, and the postprocessing is performed for improving the recognition rate and reducing the false detection rate of the system. A total of 530[Formula: see text]h from 20 patients with 81 seizures were used to evaluate the system. Our proposed method has achieved an average segment-based sensitivity of 93.39%, specificity of 98.51%, and event-based sensitivity of 96.36% with false detection rate of 0.236/h.
Generalized quantum interference of correlated photon pairs
Kim, Heonoh; Lee, Sang Min; Moon, Han Seb
2015-01-01
Superposition and indistinguishablility between probability amplitudes have played an essential role in observing quantum interference effects of correlated photons. The Hong-Ou-Mandel interference and interferences of the path-entangled photon number state are of special interest in the field of quantum information technologies. However, a fully generalized two-photon quantum interferometric scheme accounting for the Hong-Ou-Mandel scheme and path-entangled photon number states has not yet been proposed. Here we report the experimental demonstrations of the generalized two-photon interferometry with both the interferometric properties of the Hong-Ou-Mandel effect and the fully unfolded version of the path-entangled photon number state using photon-pair sources, which are independently generated by spontaneous parametric down-conversion. Our experimental scheme explains two-photon interference fringes revealing single- and two-photon coherence properties in a single interferometer setup. Using the proposed interferometric measurement, it is possible to directly estimate the joint spectral intensity of a photon pair source. PMID:25951143
Odd-frequency pairing in superconducting heterostructures .
Golubov, A. A.; Tanaka, Y.; Yokoyama, T.; Asano, Y.
2007-03-01
We present a general theory of the proximity effect in junctions between unconventional superconductors and diffusive normal metals (DN) or ferromagnets (DF). We consider all possible symmetry classes in a superconductor allowed by the Pauli principle: even-frequency spin-singlet even-parity state, even-frequency spin-triplet odd-parity state, odd-frequency spin-triplet even-parity state and odd-frequency spin-singlet odd-parity state. For each of the above states, symmetry and spectral properties of the induced pair amplitude in the DN (DF) are determined. The cases of junctions with spin-singlet s- and d-wave superconductors and spin-triplet p-wave superconductors are adressed in detail. We discuss the interplay between the proximity effect and midgap Andreev bound states arising at interfaces in unconventional (d- or p-wave) junctions. The most striking property is the odd-frequency symmetry of the pairing amplitude induced in DN (DF) in contacts with p-wave superconductors. This leads to zero-energy singularity in the density of states and to anomalous screening of an external magnetic field. Peculiarities of Josephson effect in d- or p-wave junctions are discussed. Experiments are suggested to detect an order parameter symmetry using heterostructures with unconventional superconductors.
The leptoquark hunter's guide: pair production
Diaz, Bastian; Schmaltz, Martin; Zhong, Yi-Ming
2017-10-01
Leptoquarks occur in many new physics scenarios and could be the next big discovery at the LHC. The purpose of this paper is to point out that a model-independent search strategy covering all possible leptoquarks is possible and has not yet been fully exploited. To be systematic we organize the possible leptoquark final states according to a leptoquark matrix with entries corresponding to nine experimentally distinguishable leptoquark decays: any of {light-jet, b-jet, top} with any of {neutrino, e/ μ, τ}. The 9 possibilities can be explored in a largely model-independent fashion with pair-production of leptoquarks at the LHC. We review the status of experimental searches for the 9 components of the leptoquark matrix, pointing out which 3 have not been adequately covered. We plead that experimenters publish bounds on leptoquark cross sections as functions of mass for as wide a range of leptoquark masses as possible. Such bounds are essential for reliable recasts to general leptoquark models. To demonstrate the utility of the leptoquark matrix approach we collect and summarize searches with the same final states as leptoquark pair production and use them to derive bounds on a complete set of Minimal Leptoquark models which span all possible flavor and gauge representations for scalar and vector leptoquarks.
Cooperative interactions between paired domain and homeodomain.
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.
Optimisation of a quantum pair space thruster
Directory of Open Access Journals (Sweden)
Valeriu DRAGAN
2012-06-01
Full Text Available The paper addresses the problem of propulsion for long term space missions. Traditionally a space propulsion unit has a propellant mass which is ejected trough a nozzle to generate thrust; this is also the case with inert gases energized by an on-board power unit. Unconventional methods for propulsion include high energy LASERs that rely on the momentum of photons to generate thrust. Anti-matter has also been proposed for energy storage. Although the momentum of ejected gas is significantly higher, the LASER propulsion offers the perspective of unlimited operational time – provided there is a power source. The paper will propose the use of the quantum pair formation for generating a working mass, this is different than conventional anti-matter thrusters since the material particles generated are used as propellant not as energy storage.Two methods will be compared: LASER and positron-electron, quantum pair formation. The latter will be shown to offer better momentum above certain energy levels.For the demonstrations an analytical solution is obtained and provided in the form of various coefficients. The implications are, for now, theoretical however the practicality of an optimized thruster using such particles is not to be neglected for long term space missions.
Understanding Fomalhaut as a Cooper pair
Feng, F.; Jones, H. R. A.
2018-03-01
Fomalhaut is a nearby stellar system and has been found to be a triple based on astrometric observations. With new radial velocity and astrometric data, we study the association between Fomalhaut A, B, and C in a Bayesian framework, finding that the system is gravitationally bound or at least associated. Based on simulations of the system, we find that Fomalhaut C can be easily destabilized through combined perturbations from the Galactic tide and stellar encounters. Considering that observing the disruption of a triple is probably rare in the solar neighbourhood, we conclude that Fomalhaut C is a so-called `gravitational pair' of Fomalhaut A and B. Like the Cooper pair mechanism in superconductors, this phenomenon only appears once the orbital energy of a component becomes comparable with the energy fluctuations caused by the environment. Based on our simulations, we find (1) an upper limit of 8 km s-1 velocity difference is appropriate when selecting binary candidates, and (2) an empirical formula for the escape radius, which is more appropriate than tidal radius when measuring the stability of wide binaries.
Leptoquark pair production in hadronic interactions
International Nuclear Information System (INIS)
Bluemlein, J.; Boos, E.; Moskovskij Gosudarstvennyj Univ., Moscow; Kryukov, A.; Moskovskij Gosudarstvennyj Univ., Moscow
1996-10-01
The scalar and vector leptoquark pair production cross sections in hadronic collisions are calculated. In a model independent analysis we consider the most general C and P conserving couplings of gluons to both scalar and vector leptoquarks described by an effective low-energy Lagangian which obeys SU(3) c invariance. Analytrical expressions are derived for the differential and integral scattering cross sections including the case of anomalous vector leptoquark couplings, κ G and λ G , to the gluon field. Numerical predictions are given for the kinematic range of the TEVATRON and LHC. The pair production cross sections are also calculated for the resolved photon contributions to ep → e anti ΦΦX at HERA and LEP x LHC, and for the process γγ → Φ anti ΦX at possible future e + e - linear colliders and γγ colliders. Estimates of the search potential for scalar and vector leptoquarks at present and future high energy colliders are given. (orig.)
Synergy between pair coupled cluster doubles and pair density functional theory
Energy Technology Data Exchange (ETDEWEB)
Garza, Alejandro J.; Bulik, Ireneusz W. [Department of Chemistry, Rice University, Houston, Texas 77251-1892 (United States); Henderson, Thomas M. [Department of Chemistry and Department of Physics and Astronomy, Rice University, Houston, Texas 77251-1892 (United States); Scuseria, Gustavo E. [Department of Chemistry and Department of Physics and Astronomy, Rice University, Houston, Texas 77251-1892 (United States); Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)
2015-01-28
Pair coupled cluster doubles (pCCD) has been recently studied as a method capable of accounting for static correlation with low polynomial cost. We present three combinations of pCCD with Kohn–Sham functionals of the density and on-top pair density (the probability of finding two electrons on top of each other) to add dynamic correlation to pCCD without double counting. With a negligible increase in computational cost, these pCCD+DFT blends greatly improve upon pCCD in the description of typical problems where static and dynamic correlations are both important. We argue that—as a black-box method with low scaling, size-extensivity, size-consistency, and a simple quasidiagonal two-particle density matrix—pCCD is an excellent match for pair density functionals in this type of fusion of multireference wavefunctions with DFT.
Treatment of pairing correlations based on the equations of motion for zero-coupled pair operators
International Nuclear Information System (INIS)
Andreozzi, F.; Covello, A.; Gargano, A.; Ye, L.J.; Porrino, A.
1985-01-01
The pairing problem is treated by means of the equations of motion for zero-coupled pair operators. Exact equations for the seniority-v states of N particles are derived. These equations can be solved by a step-by-step procedure which consists of progressively adding pairs of particles to a core. The theory can be applied at several levels of approximation depending on the number of core states which are taken into account. Some numerical applications to the treatment of v = 0, v = 1, and v = 2 states in the Ni isotopes are performed. The accuracy of various approximations is tested by comparison with exact results. For the seniority-one and seniority-two problems it turns out that the results obtained from the first-order theory are very accurate, while those of higher order calculations are practically exact. Concerning the seniority-zero problem, a fifth-order calculation reproduces quite well the three lowest states
Quantifying inbreeding avoidance through extra-pair reproduction.
Reid, Jane M; Arcese, Peter; Keller, Lukas F; Germain, Ryan R; Duthie, A Bradley; Losdat, Sylvain; Wolak, Matthew E; Nietlisbach, Pirmin
2015-01-01
Extra-pair reproduction is widely hypothesized to allow females to avoid inbreeding with related socially paired males. Consequently, numerous field studies have tested the key predictions that extra-pair offspring are less inbred than females' alternative within-pair offspring, and that the probability of extra-pair reproduction increases with a female's relatedness to her socially paired male. However, such studies rarely measure inbreeding or relatedness sufficiently precisely to detect subtle effects, or consider biases stemming from failure to observe inbred offspring that die during early development. Analyses of multigenerational song sparrow (Melospiza melodia) pedigree data showed that most females had opportunity to increase or decrease the coefficient of inbreeding of their offspring through extra-pair reproduction with neighboring males. In practice, observed extra-pair offspring had lower inbreeding coefficients than females' within-pair offspring on average, while the probability of extra-pair reproduction increased substantially with the coefficient of kinship between a female and her socially paired male. However, simulations showed that such effects could simply reflect bias stemming from inbreeding depression in early offspring survival. The null hypothesis that extra-pair reproduction is random with respect to kinship therefore cannot be definitively rejected in song sparrows, and existing general evidence that females avoid inbreeding through extra-pair reproduction requires reevaluation given such biases. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.
Particle Acceleration, Magnetic Field Generation, and Emission in Relativistic Pair Jets
Nishikawa, K.-I.; Ramirez-Ruiz, E.; Hardee, P.; Hededal, C.; Mizuno, Y.
2005-01-01
Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created by relativistic pair jets are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet propagating through an ambient plasma with and without initial magnetic fields. The growth rates of the Weibel instability depends on the distribution of pair jets. Simulations show that the Weibel instability created in the collisionless shock accelerates particles perpendicular and parallel to the jet propagation direction. The simulation results show that this instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.
Introduction to plasma physics and controlled fusion
Chen, Francis F
2016-01-01
The third edition of this classic text presents a complete introduction to plasma physics and controlled fusion, written by one of the pioneering scientists in this expanding field. It offers both a simple and intuitive discussion of the basic concepts of the subject matter and an insight into the challenging problems of current research. This outstanding text offers students a painless introduction to this important field; for teachers, a large collection of problems; and for researchers, a concise review of the fundamentals as well as original treatments of a number of topics never before explained so clearly. In a wholly lucid manner the second edition covered charged-particle motions, plasmas as fluids, kinetic theory, and nonlinear effects. For the third edition, two new chapters have been added to incorporate discussion of more recent advances in the field. The new chapter 9 on Special Plasmas covers non-neutral plasmas, pure electron plasmas, solid and ultra-cold plasmas, pair-ion plasmas, d...
International Nuclear Information System (INIS)
Ikuta, Kazunari.
1981-09-01
Instead of using linear accelerators, it is possible to breed fissile fuels with the help of high current plasma focus device. A mechanism of accelerating proton beam in plasma focus device to high energy would be a change of inductance in plasma column because of rapid growth of plasma instability. A possible scheme of plasma focus breeder is also proposed. (author)
Enhanced stability of bound pairs at nonzero lattice momenta
International Nuclear Information System (INIS)
Kornilovitch, Pavel
2004-01-01
A two-body problem on the square lattice is analyzed. The interaction potential consists of strong on-site repulsion and nearest-neighbor attraction. The exact pairing conditions are derived for s-, p-, and d-symmetric bound states. The pairing conditions are strong functions of the total pair momentum K. It is found that the stability of pairs increases with K. At weak attraction, the pairs do not form at the Γ point but stabilize at lattice momenta close to the Brillouin zone boundary. The phase boundaries in the momentum space, which separate stable and unstable pairs, are calculated. It is found that the pairs are formed easier along the (π,0) direction than along the (π,π) direction. This might lead to the appearance of 'hot pairing spots' on the K x and K y axes
Pair formation models for sexually transmitted infections : A primer
Kretzschmar, MEE; Heijne, Janneke C M
For modelling sexually transmitted infections, duration of partnerships can strongly influence the transmission dynamics of the infection. If partnerships are monogamous, pairs of susceptible individuals are protected from becoming infected, while pairs of infected individuals delay onward
Theoretical analysis of noncanonical base pairing interactions in ...
Indian Academy of Sciences (India)
PRAKASH KUMAR
Noncanonical base pairs in RNA have strong structural and functional implications but are currently not considered ..... Full optimizations of the systems were also carried out using ... of the individual bases in the base pair through the equation.
Quasi spin pairing and the structure of the Lipkin model
International Nuclear Information System (INIS)
Cambiaggio, M.C.; Plastino, A.
1978-01-01
By introducing the concepts of quasi-spin pairing and quasi-spin seniority, the Lipkin model is extended to a variable number of particles. The properties of quasi-spin pairing are seen to be quite similar to those of ordinary pairing. The quasi-spin seniority allows one to obtain a simple classification of excited multiplets. A 'pairing plus monopole' model is studied in connection with the Hartree-Fock theory. (orig.) [de
Extensions of Bessel sequences to dual pairs of frames
DEFF Research Database (Denmark)
Christensen, Ole; Kim, Hong Oh; Kim, Rae Young
2013-01-01
Tight frames in Hilbert spaces have been studied intensively for the past years. In this paper we demonstrate that it often is an advantage to use pairs of dual frames rather than tight frames. We show that in any separable Hilbert space, any pairs of Bessel sequences can be extended to a pair of...... be extended to a pair of dual frames. © 2012 Elsevier Inc. All rights reserved....
Muon pair study at LHC: ALICE experiment
International Nuclear Information System (INIS)
Chevallier, M.; Cheynis, B.; Grossiord, J.Y.; Guinet, D.; Guichard, A.; Lautesse, P.; Jacquin, M.; Nikulin, V.
1998-01-01
The nuclear matter at very high density, possibly as a quark gluon plasma, will be studied with ALICE at LHC, via the measurement of heavy quark resonances detected through their dimuon decay. The group is participating, since the end of 1996, in the development of the tracking chambers of the dimuon arm. These detectors are wire chambers with segmented cathodes and should measure the position of the tracks with a resolution of ≅ 100 μm in order to get a dimuon mass resolution better than 100 MeV. (authors)
Pair production by a superhard photon in a crystal
International Nuclear Information System (INIS)
Kalashnikov, N.P.; Kovalev, G.V.; Strikhanov, M.N.
1980-01-01
Electron-positron pair production by a hard photon moving almost parallelly to the crystallographic axis or monocrystal plane is considered. Calculation is conducted of the production differential by the energies of pair components and total cross section of pair production in the case when primary photon moved at a small angle THETA 0 m 2 /U [ru
Evolution of closely linked gene pairs in vertebrate genomes
Franck, E.; Hulsen, T.; Huynen, M.A.; Jong, de W.W.; Lunsen, N.H.; Madsen, O.
2008-01-01
The orientation of closely linked genes in mammalian genomes is not random: there are more head-to-head (h2h) gene pairs than expected. To understand the origin of this enrichment in h2h gene pairs, we have analyzed the phylogenetic distribution of gene pairs separated by less than 600 bp of
A Golub-Kahan-type reduction method for matrix pairs
Hochstenbach, M.E.; Reichel, L.; Yu, X.
2015-01-01
We describe a novel method for reducing a pair of large matrices {A;B} to a pair of small matrices {H;K}. The method is an extension of Golub-Kahan bidiagonalization to matrix pairs, and simplifies to the latter method when B is the identity matrix. Applications to Tikhonov regularization of large
A Golub-Kahan-type reduction method for matrix pairs
Hochstenbach, M.E.; Reichel, L.; Yu, X.
2015-01-01
We describe a novel method for reducing a pair of large matrices {A,B} to a pair of small matrices {H,K}. The method is an extension of Golub–Kahan bidiagonalization to matrix pairs, and simplifies to the latter method when B is the identity matrix. Applications to Tikhonov regularization of large
On extensions of wavelet systems to dual pairs of frames
DEFF Research Database (Denmark)
Christensen, Ole; Kim, Hong Oh; Kim, Rae Young
2015-01-01
It is an open problem whether any pair of Bessel sequences with wavelet structure can be extended to a pair of dual frames by adding a pair of singly generated wavelet systems. We consider the particular case where the given wavelet systems are generated by the multiscale setup with trigonometric...
QSO Pairs across Active Galaxies: Evidence of Blueshifts? D. Basu
Indian Academy of Sciences (India)
2006-12-04
Dec 4, 2006 ... Abstract. Several QSO pairs have been reported and their redshifts determined, where the two objects in each pair are located across an active galaxy. The usually accepted explanation of such occurrences is that the pair is ejected from the parent galaxy. Currently interpreted redshifted spec- tra for both ...
Sharp corners as sources of spiral pairs
International Nuclear Information System (INIS)
Biton, Y.; Rabinovitch, A.; Braunstein, D.; Friedman, M.; Aviram, I.
2010-01-01
It is demonstrated that using the FitzHugh-Nagumo model, stimulation of excitable media inside a region possessing sharp corners, can lead to the appearance of sources of spiral-pairs of sustained activity. The two conditions for such source creation are: The corners should be less than 120 deg. and the range of stimulating amplitudes should be small, occurring just above the threshold value and decreasing with the corner angle. The basic mechanisms driving the phenomenon are discussed. These include: A. If the corner angle is below 120 deg., the wave generated inside cannot emerge at the corner tip, resulting in the creation of two free edges which start spiraling towards each other. B. Spiraling must be strong enough; otherwise annihilation of the rotating arms would occur too soon to create a viable source. C. The intricacies of the different radii involved are elucidated. Possible applications in heart stimulation and in chemical reactions are considered.
Neutron area monitor with TLD pairs
International Nuclear Information System (INIS)
Guzman G, K. A.; Borja H, C. G.; Valero L, C.; Hernandez D, V. M.; Vega C, H. R.
2011-11-01
The response of a passive neutron area monitor with pairs of thermoluminescent dosimeters has been calculated using the Monte Carlo code MCNP5. The response was calculated for one TLD 600 located at the center of a polyethylene cylinder, as moderator. When neutrons collide with the moderator lose their energy reaching the TLD with thermal energies where the ambient dose equivalent is calculated. The response was calculated for 47 monoenergetic neutron sources ranging from 1E(-9) to 20 MeV. Response was calculated using two irradiation geometries, one with an upper source and another with a lateral source. For both irradiation schemes the response was calculated with the TLDs in two positions, one parallel to the source and another perpendicular to the source. The advantage of this passive neutron monitor area is that can be used in locations with intense, pulsed and mixed radiation fields. (Author)
Radiative corrections for the leptonic pair production
Energy Technology Data Exchange (ETDEWEB)
Elend, H H
1971-01-01
The one-photon bremsstrahlung correction for symmetrical lepton pair production is newly calculated. For this, from all the Feynman diagrams, the subset is picked out for this process which essentially contributes to the symmetrical case. The matrix element square value for the chosen sub-set is expressed by the Bethe-Heitler matrix element square value provided with certain kinematic factors (Huld relationship), where a) a development after the energy of the Bremsquantum, assumed to be small, is carried out and the series is cut off after the second term beyond the infrared section, b) a high-energy approximation is made. Furthermore, c) the structure of the target nucleus and of the recoil transfered to it is neglected, d) the integration on the phase space of the bremsquantitum is carried out with a peaking approximation. All these approximations are individually discussed, and the validity limits which they set for the bremsstrahlung in the result are accurately given.
One Monopole-Antimonopole Pair Solutions
International Nuclear Information System (INIS)
Teh, Rosy; Wong, K.-M.
2009-01-01
We present new classical generalized one monopole-antimonopole pair solutions of the SU(2) Yang-Mills-Higgs theory with the Higgs field in the adjoint representation. We show that in general the one monopole-antimonopole solution need not be solved by imposing mθ-winding number to be integer greater than one. We also show that this solution can be solved when m = 1 by transforming the large distance asymptotic solutions to general solutions that depend on a parameter p. Secondly we show that these large distance asymptotic solutions can be further generalized to the Jacobi elliptic functions. We focus our numerical calculation on the Jacobi elliptic functions solution when the nφ-winding number is one and show that this generalized Jacobi elliptic 1-MAP solution possesses lower energy. All these solutions are numerical finite energy non-BPS solutions of the Yang-Mills-Higgs field theory.
An advanced KB mirror pair for microfocusing
Ferme, J J
2001-01-01
A new range of micro-focusing mirrors based on KB pairs has been developed by SESO for Beamline Nanospectroscopy at the Elettra Storage Ring in Trieste, Italy. Both the focusing and the aspheric shape are adjustable with stepper motors. The goal of the beamline is to have a high photon density spot with a variable size in the experimental chamber over the whole soft X-ray range. The estimated dimension of the final spot should be smaller than 4 mu m sup 2 FWHM, with a photon density of the order of 10 sup 1 sup 3 photons/s mu m sup 2; this may be achieved only by accepting an angular divergence on these mirrors of between 5 and 10 mrad. This condition can be fulfilled only with elliptical (or plane elliptical) mirrors with very limited residual slope errors (below 1 mu rad RMS) that are able to correct even small focal distance errors.
Na Cl ion pair association in water-DMSO mixtures: Effect of ion pair ...
Indian Academy of Sciences (India)
The 12-6-1 potential model predicts running coordination numbers closest to experimental data. Keywords. ... value of interaction energy minimum between the Na. + and Cl. − ..... ion pair mostly remains as a CIP, a fair amount of SAIP is also ...
Asteroid clusters similar to asteroid pairs
Pravec, P.; Fatka, P.; Vokrouhlický, D.; Scheeres, D. J.; Kušnirák, P.; Hornoch, K.; Galád, A.; Vraštil, J.; Pray, D. P.; Krugly, Yu. N.; Gaftonyuk, N. M.; Inasaridze, R. Ya.; Ayvazian, V. R.; Kvaratskhelia, O. I.; Zhuzhunadze, V. T.; Husárik, M.; Cooney, W. R.; Gross, J.; Terrell, D.; Világi, J.; Kornoš, L.; Gajdoš, Š.; Burkhonov, O.; Ehgamberdiev, Sh. A.; Donchev, Z.; Borisov, G.; Bonev, T.; Rumyantsev, V. V.; Molotov, I. E.
2018-04-01
We studied the membership, size ratio and rotational properties of 13 asteroid clusters consisting of between 3 and 19 known members that are on similar heliocentric orbits. By backward integrations of their orbits, we confirmed their cluster membership and estimated times elapsed since separation of the secondaries (the smaller cluster members) from the primary (i.e., cluster age) that are between 105 and a few 106 years. We ran photometric observations for all the cluster primaries and a sample of secondaries and we derived their accurate absolute magnitudes and rotation periods. We found that 11 of the 13 clusters follow the same trend of primary rotation period vs mass ratio as asteroid pairs that was revealed by Pravec et al. (2010). We generalized the model of the post-fission system for asteroid pairs by Pravec et al. (2010) to a system of N components formed by rotational fission and we found excellent agreement between the data for the 11 asteroid clusters and the prediction from the theory of their formation by rotational fission. The two exceptions are the high-mass ratio (q > 0.7) clusters of (18777) Hobson and (22280) Mandragora for which a different formation mechanism is needed. Two candidate mechanisms for formation of more than one secondary by rotational fission were published: the secondary fission process proposed by Jacobson and Scheeres (2011) and a cratering collision event onto a nearly critically rotating primary proposed by Vokrouhlický et al. (2017). It will have to be revealed from future studies which of the clusters were formed by one or the other process. To that point, we found certain further interesting properties and features of the asteroid clusters that place constraints on the theories of their formation, among them the most intriguing being the possibility of a cascade disruption for some of the clusters.
Equation of state of strongly coupled plasma mixtures
International Nuclear Information System (INIS)
DeWitt, H.E.
1984-01-01
Thermodynamic properties of strongly coupled (high density) plasmas of mixtures of light elements have been obtained by Monte Carlo simulations. For an assumed uniform charge background the equation of state of ionic mixtures is a simple extension of the one-component plasma EOS. More realistic electron screening effects are treated in linear response theory and with an appropriate electron dielectric function. Results have been obtained for the ionic pair distribution functions, and for the electric microfield distribution
PAIR'14 / PAIR'15 STUDENT CONFERENCES ON PLANNING IN ARTIFICIAL INTELLIGENCE AND ROBOTICS
Directory of Open Access Journals (Sweden)
Editorial Foreword
2015-12-01
Full Text Available Dear Readerthe original idea of the student conference on “Planning in Artificial Intelligence and Robotics” (PAIR is to join young researchers from particular laboratories in Czech Republic, where planning problems are investigated from artificial intelligence (AI or robotics points of view. The first year of PAIR has been organized at the Dept. of Computer Science, Faculty Electrical Engineering, Czech Technical University in 2014.At PAIR 2014, laboratories from Prague and Brno were presented. In particular, students and researchers from Charles University, Czech Technical University in Prague, Brno University of Technology, and Central European Institute of Technology participated at the event. Beside an introduction of the particular research groups and their topics, students presented contributions on their current research results. Ten papers were presented on topics ranging from domain–independent planning, trajectory planning to applications for unmanned aerial and legged robots. This first event provides us an initial experience with the community of young researchers in Czech Republic that are working planning in robotic or AI. Based on the success of PAIR 2014, we decided to continue with our effort to establish a suitable fora for students that are geographically very close, but usually do not meet, because of participation on different Robotics and AI events.The second student conference on Planning in Artificial Intelligence and Robotics (PAIR 2015 successfully continues the tradition of the first year of the conference organized in Prague. This year, the conference was collocated with 10th anniversary of RoboTour contest in Písek. This format enable us to extend the impact of the PAIR conference and improve the visibility of the growing student community. The conference reached a good amount of interesting papers focused on image processing for mobile robots, swarm control, driving simulation, robot control, or domain
... Links Patient Resources For Health Professionals Subscribe Search Plasma Free Metanephrines Send Us Your Feedback Choose Topic ... Images View Sources Ask Us Also Known As Plasma Metanephrines Formal Name Fractionated Plasma Free Metanephrines (Metanephrine ...
Cheng, D. Y.
1971-01-01
Converging, coaxial accelerator electrode configuration operates in vacuum as plasma gun. Plasma forms by periodic injections of high pressure gas that is ionized by electrical discharges. Deflagration mode of discharge provides acceleration, and converging contours of plasma gun provide focusing.
ECR plasma photographs as a plasma diagnostic
Energy Technology Data Exchange (ETDEWEB)
Racz, R; Biri, S; Palinkas, J [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem ter 18/c (Hungary)
2011-04-15
Low, medium or highly charged ions delivered by electron cyclotron resonance (ECR) ion sources all are produced in the ECR plasma. In order to study such plasmas, high-resolution visible light plasma photographs were taken at the ATOMKI ECR ion source. An 8 megapixel digital camera was used to photograph plasmas made from He, methane, N, O, Ne, Ar, Kr, Xe gases and from their mixtures. The analysis of the photo series gave many qualitative and some valuable physical information on the nature of ECR plasmas. A comparison was made between the plasma photos and computer simulations, and conclusions were drawn regarding the cold electron component of the plasma. The warm electron component of similar simulation was compared with x-ray photos emitted by plasma ions. While the simulations are in good agreement with the photos, a significant difference was found between the spatial distribution of the cold and warm electrons.
Plasma physics and fusion plasma electrodynamics
Bers, Abraham
2016-01-01
Plasma is a ubiquitous state of matter at high temperatures. The electrodynamics of plasmas encompasses a large number of applications, from understanding plasmas in space and the stars, to their use in processing semiconductors, and their role in controlled energy generation by nuclear fusion. This book covers collective and single particle dynamics of plasmas for fully ionized as well as partially ionized plasmas. Many aspects of plasma physics in current fusion energy generation research are addressed both in magnetic and inertial confinement plasmas. Linear and nonlinear dynamics in hydrodynamic and kinetic descriptions are offered, making both simple and complex aspects of the subject available in nearly every chapter. The approach of dividing the basic aspects of plasma physics as "linear, hydrodynamic descriptions" to be covered first because they are "easier", and postponing the "nonlinear and kinetic descriptions" for later because they are "difficult" is abandoned in this book. For teaching purpose...
Plasma waves in an inhomogeneous cylindrical plasma
International Nuclear Information System (INIS)
Pesic, S.S.
1976-01-01
The complete dispersion equation governing small amplitude plasma waves propagating in an inhomogeneous cylindrical plasma confined by a helical magnetic field is solved numerically. The efficiency of the wave energy thermalization in the lower hybrid frequency range is studied
Adler, Adam S; Bedinger, Daniel; Adams, Matthew S; Asensio, Michael A; Edgar, Robert C; Leong, Renee; Leong, Jackson; Mizrahi, Rena A; Spindler, Matthew J; Bandi, Srinivasa Rao; Huang, Haichun; Tawde, Pallavi; Brams, Peter; Johnson, David S
2018-04-01
Deep sequencing and single-chain variable fragment (scFv) yeast display methods are becoming more popular for discovery of therapeutic antibody candidates in mouse B cell repertoires. In this study, we compare a deep sequencing and scFv display method that retains native heavy and light chain pairing with a related method that randomly pairs heavy and light chain. We performed the studies in a humanized mouse, using interleukin 21 receptor (IL-21R) as a test immunogen. We identified 44 high-affinity binder scFv with the native pairing method and 100 high-affinity binder scFv with the random pairing method. 30% of the natively paired scFv binders were also discovered with the randomly paired method, and 13% of the randomly paired binders were also discovered with the natively paired method. Additionally, 33% of the scFv binders discovered only in the randomly paired library were initially present in the natively paired pre-sort library. Thus, a significant proportion of "randomly paired" scFv were actually natively paired. We synthesized and produced 46 of the candidates as full-length antibodies and subjected them to a panel of binding assays to characterize their therapeutic potential. 87% of the antibodies were verified as binding IL-21R by at least one assay. We found that antibodies with native light chains were more likely to bind IL-21R than antibodies with non-native light chains, suggesting a higher false positive rate for antibodies from the randomly paired library. Additionally, the randomly paired method failed to identify nearly half of the true natively paired binders, suggesting a higher false negative rate. We conclude that natively paired libraries have critical advantages in sensitivity and specificity for antibody discovery programs.
Quiescent plasma machine for plasma investigation
International Nuclear Information System (INIS)
Ferreira, J.L.
1993-01-01
A large volume quiescent plasma device is being developed at INPE to study Langmuir waves and turbulence generated by electron beams (E b ≤ 500 e V) interacting with plasma. This new quiescent plasma machine was designed to allow the performance of several experiments specially those related with laboratory space plasma simulation experiments. Current-driven instabilities and related phenomena such as double-layers along magnetic field lines are some of the many experiments planned for this machine. (author)
Plasma basic concepts and nitrogen containing plasmas
Sanz Lluch, M. del Mar; Tanarro, Isabel
2007-01-01
Basic concepts related to plasmas are described as well as the typical characterization methods currently available. A brief overview about some plasma applications is given, but focusing on plasma used in material processing mainly devoted to the microelectronics industry. Finally, specific applications related to plasma-assisted MBE for nitrides and dilute nitrides are given, showing some interesting research works performed to that purpose, and giving the usual characterization techniques ...
Demographic mechanisms of inbreeding adjustment through extra-pair reproduction.
Reid, Jane M; Duthie, A Bradley; Wolak, Matthew E; Arcese, Peter
2015-07-01
One hypothesis explaining extra-pair reproduction is that socially monogamous females mate with extra-pair males to adjust the coefficient of inbreeding (f) of extra-pair offspring (EPO) relative to that of within-pair offspring (WPO) they would produce with their socially paired male. Such adjustment of offspring f requires non-random extra-pair reproduction with respect to relatedness, which is in turn often assumed to require some mechanism of explicit pre-copulatory or post-copulatory kin discrimination. We propose three demographic processes that could potentially cause mean f to differ between individual females' EPO and WPO given random extra-pair reproduction with available males without necessarily requiring explicit kin discrimination. Specifically, such a difference could arise if social pairings formed non-randomly with respect to relatedness or persisted non-randomly with respect to relatedness, or if the distribution of relatedness between females and their sets of potential mates changed during the period through which social pairings persisted. We used comprehensive pedigree and pairing data from free-living song sparrows (Melospiza melodia) to quantify these three processes and hence investigate how individual females could adjust mean offspring f through instantaneously random extra-pair reproduction. Female song sparrows tended to form social pairings with unrelated or distantly related males slightly less frequently than expected given random pairing within the defined set of available males. Furthermore, social pairings between more closely related mates tended to be more likely to persist across years than social pairings between less closely related mates. However, these effects were small and the mean relatedness between females and their sets of potential extra-pair males did not change substantially across the years through which social pairings persisted. Our framework and analyses illustrate how demographic and social structuring within
Lectures in plasma diagnostics
International Nuclear Information System (INIS)
Hutchinson, I.H.
1990-06-01
This paper discusses the following topics on plasma diagnostics: Electric probes in flowing and magnetized plasmas; Electron cyclotron emission absorption; Magnetic diagnostics; Spectroscopy; and Thomson Scattering
Plasma electron losses in a multidipole plasma
International Nuclear Information System (INIS)
Haworth, M.D.
1983-01-01
The magnitude of the plasma electron cusp losses in a multidipole plasma device is determined by using a plasma electron heating technique. This method consists of suddenly generating approximately monoenergetic test electrons inside the multidipole plasma, which is in a steady-state equilibrium prior to the introduction of the test electrons. The Coulomb collisions between the test electrons and the plasma electrons result in heating the plasma electrons. The experimentally measured time evolution of the plasma electron temperature is compared with that predicted by a kinetic-theory model which calculates the time evolution of the test electron and the plasma electron distribution functions. The analytical solution of the plasma electron heating rate when the test electrons are first introduced into the plasma predicts that there is no dependence on ion mass. Experimental results in helium, neon, argon, and krypton multidipole plasmas confirm this prediction. The time-evolved solution of the kinetic equations must be solved numerically, and these results (when coupled with the experimental heating results) show that the plasma electron cusp-loss width is on the order of an electron Larmor radius
Physics of plasma etching and plasma deposition
Schram, D.C.; Hoog, de F.J.; Bisschops, T.J.; Kroesen, G.M.W.; Howorka, F.; Lindinger, W.; Maerk, T.D.
1986-01-01
The kinetics and mechanism of the title processes are discussed on the basis of a model in which the plasma-surface system is subdivided into 5 regions: (I) plasma prodn., (II) plasma flow plus radicals, (III) gas adsorbed layer, (IV) modified surface, and (V) undisturbed solid (or liq.) state.
Non-linear collective phenomena in dusty plasmas
International Nuclear Information System (INIS)
Tsytovich, V N; Morfill, G E
2004-01-01
Dusty plasmas are unusual states of matter where the interactions between the dust grains can be collective and are not a sum of all pair particle interactions. This state of matter is appropriate to form non-linear dissipative collective self-organized structures. It is found that the potential around the grains can be over-screened leading to a new phenomenon-collective attraction of pairs of large charge grains of equal sign. The grain clouds can self-contract and their collapse is terminated at distances where the interaction becomes repulsive. The homogeneous dusty plasma distribution is universally unstable to form structures. The potential of the collective attraction is proportional to the square of the dimensionless parameter P = n d Z d /n i , where n d and n i are the average dust and ion densities, respectively, and Z d is the dust charge in units of electron charge. The collective attraction is determined by finite grain size and by the presence of absorption of plasma flux on grains. The physics of attraction is related to the space charge accumulation caused by collective flux disturbances. The collective attraction operates for systems with size larger than the mean free path for ion-dust absorption, the condition met in many existing low temperature dusty plasma experiments, in edge plasmas of fusion devices and in space dusty plasmas. The collective attraction exceeds the previously known non-collective attraction such as shadow attraction or wake attraction. The collective attraction can be responsible for pairing of dust grains (this process is completely classical in contrast to the known pairing in superconductivity) and can serve as the main process for the formation of more complicated dust complexes up to dust-plasma crystals. The equilibrium structures formed by collective attraction have universal properties and can exist in a limited domain of parameters (similar to the equilibrium balance known for stars). The balance conditions for
Pair production in a strong electric field with back-reaction
International Nuclear Information System (INIS)
Eisenberg, J.M.; Kluger, Y.; Svetitsky, B.
1992-01-01
We present a summary of the present status of efforts to solve the problem in which pairs are produced in a strong electric field, are accelerated by it, and then react back on it through the counter-field produced by their current. This picture has been used by Bialas and Czyz and others as a model for effects that may possibly arise in the study of the quark-gluon plasma. We here give a didactic review of recent developments in this back-reaction problem. We first present a simple version of the theory of pair tunneling from a fixed electric field, and then sketch how this has been applied to the quark-gluon plasma. Then we turn to a field formulation of the problem for charged bosons, which leads to the need to carry out a renormalization program, outlined again in simple terms. Numerical results for this program are presented for one spatial dimension, the corresponding physical behaviour of the system is discussed, and the implications for three spatial dimensions are considered. We exhibit a phenomenological transport equation embodying physics that is essentially identical to that of the field formulation, thus helping to tie the model of Bialas and Czyz for the quark-gluon plasma to a field-theory formulation. Last, we note the status of extensions to the problem with three space dimensions; the fermion case; the formulation in terms of boost-invariant variables (as desirable for the quark-gluon plasma); and transport equations derived in a fundamental and consistent fashion. 5 figs., 13 refs. (author)
Stacey, Weston M
2012-01-01
This revised and enlarged second edition of the popular textbook and reference contains comprehensive treatments of both the established foundations of magnetic fusion plasma physics and of the newly developing areas of active research. It concludes with a look ahead to fusion power reactors of the future. The well-established topics of fusion plasma physics -- basic plasma phenomena, Coulomb scattering, drifts of charged particles in magnetic and electric fields, plasma confinement by magnetic fields, kinetic and fluid collective plasma theories, plasma equilibria and flux surface geometry, plasma waves and instabilities, classical and neoclassical transport, plasma-materials interactions, radiation, etc. -- are fully developed from first principles through to the computational models employed in modern plasma physics. The new and emerging topics of fusion plasma physics research -- fluctuation-driven plasma transport and gyrokinetic/gyrofluid computational methodology, the physics of the divertor, neutral ...
Isolated galaxies, pairs, and groups of galaxies
International Nuclear Information System (INIS)
Kuneva, I.; Kalinkov, M.
1990-01-01
The authors searched for isolated galaxies, pairs and groups of galaxies in the CfA survey (Huchra et al. 1983). It was assumed that the distances to galaxies are given by R = V/H sub o, where H sub o = 100 km s(exp -1) Mpc(exp -1) and R greater than 6 Mpc. The searching procedure is close to those, applied to find superclusters of galaxies (Kalinkov and Kuneva 1985, 1986). A sphere with fixed radius r (asterisk) is described around each galaxy. The mean spatial density in the sphere is m. Let G 1 be any galaxy and G 2 be its nearest neighbor at a distance R 2 . If R sub 2 exceeds the 95 percent quintile in the distribution of the distances of the second neighbors, then G 1 is an isolated galaxy. Let the midpoint of G 1 and G 2 be O 2 and r 2 =R 2 2. For the volume V 2 , defined with the radius r 2 , the density D 2 less than k mu, the galaxy G 2 is a single one and the procedure for searching for pairs and groups, beginning with this object is over and we have to pass to another object. Here the authors present the groups - isolated and nonisolated - with n greater than 3, found in the CfA survey in the Northern galactic hemisphere. The parameters used are k = 10 and r (asterisk) = 5 Mpc. Table 1 contains: (1) the group number, (2) the galaxy, nearest to the multiplet center, (3) multiplicity n, (4) the brightest galaxy if it is not listed in (2); (5) and (6) are R.A. and Dec. (1950), (7) - mean distance D in Mpc. Further there are the mean density rho (8) of the multiplet (galaxies Mpc (exp -3)), (9) the density rho (asterisk) for r (asterisk) = 5 Mpc and (10) the density rho sub g for the group with its nearest neighbor. The parenthesized digits for densities in the last three columns are powers of ten
Oscillatory processes in plasma
International Nuclear Information System (INIS)
Gallin, E.
1980-01-01
The oscillatory process play an important part in plasma evolution, In hot plasma in particular, the interactions between the oscillation modes are preponderant in relation to the binary collisions between particles. The nonlineary interactions between collective plasma oscillations can generate, in this case, a non-balanced steady state of plasma (steady turbulence). The paper elucidates some aspects of the oscillatory phenomena which contribute to the plasma state evolution, especially of hot plasma. A major part of the paper is devoted to the study of parametric instabilities in plasma and their role in increasing the temperature of plasma components (electrons, ions). Both parametric instabilities in plasma in the vicinity of thermodynamic balance and parametric processes is steady turbulent plasma are analysed - in relation to additional heating of hot plasma. An important result of the thesis refers to the drowing-up of a non-lineary interaction model between the oscillation modes in turbulent plasma, being responsible for the electromagnetic radiation in hot plasma. On the basis of the model suggested in the paper the existence of a low frequency radiative mode in hot plasma in a turbulent state, can be demonstrated. Its frequency could be even lower than plasma frequency in the field of long waves be even lower than plasma frequency in the field of long waves. Such a radiative mode was detected experimentally in focussed plasma installations. (author)
Radiation-mediated Shocks in Gamma-Ray Bursts: Pair Creation
Lundman, Christoffer; Beloborodov, Andrei M.; Vurm, Indrek
2018-05-01
Relativistic sub-photospheric shocks are a possible mechanism for producing prompt gamma-ray burst (GRB) emission. Such shocks are mediated by scattering of radiation. We introduce a time-dependent, special relativistic code which dynamically couples Monte Carlo radiative transfer to the flow hydrodynamics. The code also self-consistently follows electron–positron pair production in photon–photon collisions. We use the code to simulate shocks with properties relevant to GRBs. We focus on plane-parallel solutions, which are accurate deep below the photosphere. The shock generates a power-law photon spectrum through the first-order Fermi mechanism, extending upward from the typical upstream photon energy. Strong (high Mach number) shocks produce rising νF ν spectra. We observe that in non-relativistic shocks the spectrum extends to {E}\\max ∼ {m}e{v}2, where v is the speed difference between the upstream and downstream. In relativistic shocks the spectrum extends to energies E> 0.1 {m}e{c}2 where its slope softens due to Klein–Nishina effects. Shocks with Lorentz factors γ > 1.5 are prolific producers of electron–positron pairs, yielding hundreds of pairs per proton. The main effect of pairs is to reduce the shock width by a factor of ∼ {Z}+/- -1. Most pairs annihilate far downstream of the shock, and the radiation spectrum relaxes to a Wien distribution, reaching equilibrium with the plasma at a temperature determined by the shock jump conditions and the photon number per proton. We discuss the implications of our results for observations of radiation generated by sub-photospheric shocks.
Investigation of tau pair production at PETRA
International Nuclear Information System (INIS)
Kuester, H.
1983-11-01
The reaction e + e - -> tau + tau - has been measured at center of mass energies around 34 GeV. The selection is sensitive to 93% of the tau pair decays, thus making possible a high identification efficiency of proportional 70% over a large solid angle. The total cross section has been measured to Rsub(tau) = sigmasub(tautau)/sigmasub(point) = .94 +- .06(stat.) +- .06(syst.). In the differential cross section a charge asymmetry of Asub(tau) = (-(9.0 +- 6.6)% was observed, corresponding to a tau axial vector coupling to the weak neutral current of asub(tau) = -.94 +- 0.69. Moreover, final states from the decays tau -> πν, tau -> eνν, and tau -> μνν have been isolated and branching ratios into these channels have been determined. From the inclusive momentum spectra of the observed decay products (including the channel tau -> rhoν) the forward backward asymmetry of tau polarization has been determined to Asub(p,tau) = -(1 +- 22)% which corresponds to vsub(tau) = -.1 +- 2.9. Tests on factorization are discussed. (orig.) [de
Development of pair distribution function analysis
International Nuclear Information System (INIS)
Vondreele, R.; Billinge, S.; Kwei, G.; Lawson, A.
1996-01-01
This is the final report of a 3-year LDRD project at LANL. It has become more and more evident that structural coherence in the CuO 2 planes of high-T c superconducting materials over some intermediate length scale (nm range) is important to superconductivity. In recent years, the pair distribution function (PDF) analysis of powder diffraction data has been developed for extracting structural information on these length scales. This project sought to expand and develop this technique, use it to analyze neutron powder diffraction data, and apply it to problems. In particular, interest is in the area of high-T c superconductors, although we planned to extend the study to the closely related perovskite ferroelectric materials andother materials where the local structure affects the properties where detailed knowledge of the local and intermediate range structure is important. In addition, we planned to carry out single crystal experiments to look for diffuse scattering. This information augments the information from the PDF
Erratum: Correction to: Soliton and shocks in pair ion plasma in presence of superthermal electron
Samanta, Utpal Kumar; Chatterjee, Prasanta; Nej, Monimala
2018-06-01
Correction to: Astrophys Space Sci (2013) 345:291-296 https://doi.org/10.1007/s10509-013-1403-8. There were typos in the last author's name in the original publication. The name is correctly shown here.
Efficient Implementation of the Pairing on Mobilephones Using BREW
Yoshitomi, Motoi; Takagi, Tsuyoshi; Kiyomoto, Shinsaku; Tanaka, Toshiaki
Pairing based cryptosystems can accomplish novel security applications such as ID-based cryptosystems, which have not been constructed efficiently without the pairing. The processing speed of the pairing based cryptosystems is relatively slow compared with the other conventional public key cryptosystems. However, several efficient algorithms for computing the pairing have been proposed, namely Duursma-Lee algorithm and its variant ηT pairing. In this paper, we present an efficient implementation of the pairing over some mobilephones. Moreover, we compare the processing speed of the pairing with that of the other standard public key cryptosystems, i. e. RSA cryptosystem and elliptic curve cryptosystem. Indeed the processing speed of our implementation in ARM9 processors on BREW achieves under 100 milliseconds using the supersingular curve over F397. In addition, the pairing is more efficient than the other public key cryptosystems, and the pairing can be achieved enough also on BREW mobilephones. It has become efficient enough to implement security applications, such as short signature, ID-based cryptosystems or broadcast encryption, using the pairing on BREW mobilephones.
Observing Pair-Work Task in an English Speaking Class
Directory of Open Access Journals (Sweden)
Diana Achmad
2014-01-01
Full Text Available This paper reports on students’ pair-work interactions to develop their speaking skills in an ELT classroom which consisted of international learners. A number of 16 learners of intermediate proficiency with IELTS score band 5.5 were observed. The teacher had paired those he considered among them to be the more competent ones (hereafter, stronger with the less competent ones (hereafter, weaker; therefore, eight pairs were observed during the lesson. The task given to the students was to express ‘Agree and Disagree’ in the context of giving opinions related to social life. Based on the observations, the task was successfully implemented by six pairs; thus, the two others faced some problems. From the first pair, it was seen that the stronger student had intimated the weaker one into speaking during the task. The other pair, who was both of the same native, did not converse in English as expected and mostly used their native language to speak with one another presumably due to respect from the stronger student towards the weaker one. In situations like this, when pair-work becomes unproductive, rotating pairs is recommended to strengthen information sharing and assigning roles to avoid a student from taking over the activity from his or her pair. In conclusion, pairing international learners with mixed speaking proficiency by teachers must be conducted as effectively as possible by initially identifying their ability and learning culture to profoundly expand the students’ language resources.
Topological Nodal Cooper Pairing in Doped Weyl Metals
Li, Yi; Haldane, F. D. M.
2018-02-01
We generalize the concept of Berry connection of the single-electron band structure to that of a two-particle Cooper pairing state between two Fermi surfaces with opposite Chern numbers. Because of underlying Fermi surface topology, the pairing Berry phase acquires nontrivial monopole structure. Consequently, pairing gap functions have topologically protected nodal structure as vortices in the momentum space with the total vorticity solely determined by the pair monopole charge qp. The nodes of gap function behave as the Weyl-Majorana points of the Bogoliubov-de Gennes pairing Hamiltonian. Their relation with the connection patterns of the surface modes from the Weyl band structure and the Majorana surface modes inside the pairing gap is also discussed. Under the approximation of spherical Fermi surfaces, the pairing symmetry are represented by monopole harmonic functions. The lowest possible pairing channel carries angular momentum number j =|qp|, and the corresponding gap functions are holomorphic or antiholomorphic functions on Fermi surfaces. After projected on the Fermi surfaces with nontrivial topology, all the partial-wave channels of pairing interactions acquire the monopole charge qp independent of concrete pairing mechanism.
Pulsar Pair Cascades in Magnetic Fields with Offset Polar Caps
Harding, Alice K.; Muslimov, Alex G.
2012-01-01
Neutron star magnetic fields may have polar caps (PC) that are offset from the dipole axis, through field-line sweepback near the light cylinder or non-symmetric currents within the star. The effects of such offsets on electron-positron pair cascades are investigated, using simple models of dipole magnetic fields with small distortions that shift the PCs by different amounts or directions. Using a Monte Carlo pair cascade simulation, we explore the changes in the pair spectrum, multiplicity and energy flux across the PC, as well as the trends in pair flux and pair energy flux with spin-down luminosity, L(sub sd). We also give an estimate of the distribution of heating flux from returning positrons on the PC for different offsets. We find that even modest offsets can produce significant increases in pair multiplicity, especially for pulsars that are near or beyond the pair death lines for centered PCs, primarily because of higher accelerating fields. Pair spectra cover several decades in energy, with the spectral range of millisecond pulsars (MSPs) two orders of magnitude higher than for normal pulsars, and PC offsets allow significant extension of all spectra to lower pair energies. We find that the total PC pair luminosity L(sub pair) is proportional to L(sub sd), with L(sub pair) approximates 10(exp -3) L(sub sd) for normal pulsars and L(sub pair) approximates 10(exp -2) L(sub sd) for MSPs. Remarkably, the total PC heating luminosity for even large offsets increases by less than a factor of two, even though the PC area increases by much larger factors, because most of the heating occurs near the magnetic axis.
International Nuclear Information System (INIS)
Rosenberg, Marelene
2005-01-01
Our theoretical research on dust-plasma interactions has concentrated on three main areas: (a)studies of grain charging and applications; (b) waves and instabilities in weakly correlated dusty plasma with applications to space and laboratory plasmas; (c) waves in strongly coupled dusty plasmas.
Communication through plasma sheaths
International Nuclear Information System (INIS)
Korotkevich, A. O.; Newell, A. C.; Zakharov, V. E.
2007-01-01
We wish to transmit messages to and from a hypersonic vehicle around which a plasma sheath has formed. For long distance transmission, the signal carrying these messages must be necessarily low frequency, typically 2 GHz, to which the plasma sheath is opaque. The idea is to use the plasma properties to make the plasma sheath appear transparent
Plasma blob generation due to cooperative elliptic instability.
Manz, P; Xu, M; Müller, S H; Fedorczak, N; Thakur, S C; Yu, J H; Tynan, G R
2011-11-04
Using fast-camera measurements the generation mechanism of plasma blobs is investigated in the linear device CSDX. During the ejection of plasma blobs the plasma is dominated by an m=1 mode, which is a counterrotating vortex pair. These flows are known to be subject to the cooperative elliptic instability, which is characterized by a cooperative disturbance of the vortex cores and results in a three-dimensional breakdown of two-dimensional flows. The first experimental evidence of a cooperative elliptic instability preceding the blob-ejection is provided in terms of the qualitative evolution of the vortex geometries and internal wave patterns.
A study of electron-positron pair equilibria in models of compact X- and gamma-ray sources
International Nuclear Information System (INIS)
Bjoernsson, G.
1990-01-01
Thermal electron-positron pair equilibria in two temperature models of compact x ray and gamma ray sources are studied. The pairs are assumed to be heated by Coulomb interaction with the much hotter protons and cooled by bremsstrahlung emission, Compton scattering, and annihilation. Two parameters, the proton optical depth and the compactness, characterize each equilibrium state. It is shown that a careful account of the energy balance is very important when the stability properties of the pair equilibria in a spherical plasma cloud are determined. The equilibria are found to be unstable in a very limited range of compactness and proton optical depth. This particular instability is unlikely to be the cause of the observed variability of the compact sources and implies that it is possible to build up high pair densities by a thermal mechanism in two temperature environments. The most important result considers the effects of pairs on the structure of geometrically and effectively optically thin accretion disks. A new approach for solving for the equilibrium structure of the disks is presented. In effect, the pair equilibrium states are projected into the space spanned by the disk structure parameters. This allows a direct visualization of all possible disk solutions at once. Each solution profile needs to be calculated only once and a complete disk solution is obtained by a simple radial coordinate transformation. The disk solutions are thus seen to be scale free in terms of the radial coordinate as well as in terms of the mass of the central object and the accretion rate. Two particular disk solutions are given. It is shown that including electron-positron pairs in the disk structure calculations leads to a breakdown of the thin disk assumptions and that more detailed disk modeling is required before electron-positron pairs can be self-consistently included
Magnetic Field Dependence and Q of the Josephson Plasma Resonance
DEFF Research Database (Denmark)
Pedersen, Niels Falsig; Finnegan, T. F.; Langenberg, D. N.
1972-01-01
of supercurrent density which is not observed in conventional measurements of the field-dependent critical current. The frequency and field dependence of the plasma-resonance linewidth are interpreted as evidence that the previously unobserved quasiparticle-pair-interference tunnel current predicted by Josephson...
Real time control of plasmas and ECRH systems on TCV
Paley, J.I.; Felici, F.; Berrino, J.; Coda, S.; Cruz, N.; Duval, B.P.; Goodman, T.P.; Martin, Y.; Moret, J.-M.; Piras, F.; Rodrigues, A.P.; Santos, B.; Varandas, C.A.F.
2008-01-01
Developments in the real time control hardware on TCV paired with the flexibility of plasma shaping and ECRH actuators are opening many opportunities to perform real time experiments and develop algorithms and methods for fusion applications. The ability to control MHD instabilities is particularly
Plasma Turbulence General Topics
Energy Technology Data Exchange (ETDEWEB)
Kadomtsev, B. B. [Nuclear Energy Institute, Academy of Sciences of the USSR, Moscow, USSR (Russian Federation)
1965-06-15
It is known that under experimental conditions plasma often shows chaotic motion. Such motion, when many degrees of freedom are excited to levels considerably above the thermal level, will be called turbulent. The properties of turbulent plasma in many respects differ from the properties of laminar plasma. It can be said that the appearance of various anomalies in plasma behaviour indicates the presence of turbulence in plasma. In order to verify directly the presence of turbulent motion in plasma we must, however, measure the fluctuation of some microscopic parameters in plasma.
Introduction to plasma dynamics
Morozov, A I
2013-01-01
As the twenty-first century progresses, plasma technology will play an increasing role in our lives, providing new sources of energy, ion-plasma processing of materials, wave electromagnetic radiation sources, space plasma thrusters, and more. Studies of the plasma state of matter not only accelerate technological developments but also improve the understanding of natural phenomena. Beginning with an introduction to the characteristics and types of plasmas, Introduction to Plasma Dynamics covers the basic models of classical diffuse plasmas used to describe such phenomena as linear and shock w
Trapped magnetic field in a (NdFeB)–(MgB{sub 2}) pair-type bulk magnet
Energy Technology Data Exchange (ETDEWEB)
Aldica, Gheorghe [National Institute of Materials Physics, Atomistilor 105bis, 077125 Magurele, Ilfov (Romania); Burdusel, Mihail [National Institute of Materials Physics, Atomistilor 105bis, 077125 Magurele, Ilfov (Romania); Faculty of Materials Science and Engineering, ‘‘Politehnica’’ University of Bucharest, Splaiul Independentei 316, 060042 Bucharest (Romania); Badica, Petre, E-mail: badica2003@yahoo.com [National Institute of Materials Physics, Atomistilor 105bis, 077125 Magurele, Ilfov (Romania)
2014-10-15
Highlights: • Dense MgB{sub 2} discs were obtained by ex-situ Spark Plasma Sintering. • A NdFeB–MgB{sub 2} pair-type bulk magnet was tested for different working conditions. • The polarity of the NdFeB permanent magnet influences macro flux jumps of MgB{sub 2}. • Trapped field of the pair was 2.45 T (20 K) and 3.3 T (12 K). - Abstract: Superconducting bulk discs, S, of 20 mm in diameter and 3.5 or 3.3 mm thickness of MgB{sub 2} (pristine or added with cubic BN, respectively) with density above 97% were prepared by Spark Plasma Sintering. Discs were combined in a pair-type sandwich-like arrangement with a permanent NdFeB axially magnetised magnet, PM (∼0.5 T). Measurement of the trapped field, B{sub tr}, with temperature, time, and the reduction rate of the applied magnetic field was performed using a Hall sensor positioned at the centre between the superconductor and the permanent magnet. It is shown that the permanent magnet with certain polarity favors higher trapped field of the superconductor owing to suppression of flux jumps specific for high density MgB{sub 2} samples. The B{sub tr} of the PM–S pair was 2.45 T (20 K) and 3.3 T (12 K)
Trapped magnetic field in a (NdFeB)–(MgB2) pair-type bulk magnet
International Nuclear Information System (INIS)
Aldica, Gheorghe; Burdusel, Mihail; Badica, Petre
2014-01-01
Highlights: • Dense MgB 2 discs were obtained by ex-situ Spark Plasma Sintering. • A NdFeB–MgB 2 pair-type bulk magnet was tested for different working conditions. • The polarity of the NdFeB permanent magnet influences macro flux jumps of MgB 2 . • Trapped field of the pair was 2.45 T (20 K) and 3.3 T (12 K). - Abstract: Superconducting bulk discs, S, of 20 mm in diameter and 3.5 or 3.3 mm thickness of MgB 2 (pristine or added with cubic BN, respectively) with density above 97% were prepared by Spark Plasma Sintering. Discs were combined in a pair-type sandwich-like arrangement with a permanent NdFeB axially magnetised magnet, PM (∼0.5 T). Measurement of the trapped field, B tr , with temperature, time, and the reduction rate of the applied magnetic field was performed using a Hall sensor positioned at the centre between the superconductor and the permanent magnet. It is shown that the permanent magnet with certain polarity favors higher trapped field of the superconductor owing to suppression of flux jumps specific for high density MgB 2 samples. The B tr of the PM–S pair was 2.45 T (20 K) and 3.3 T (12 K)
PLANNING IN ARTIFICIAL INTELLIGENCE AND ROBOTICS (PAIR
Directory of Open Access Journals (Sweden)
Editorial, Foreword
2016-11-01
Full Text Available September 18th, 2016Deggendorf, Germanyhttp://robotics.fel.cvut.cz/pair16/Organized by: Artificial Intelligence Center Department of Computer Science Faculty of Electrical Engineering Czech Technical University in PragueTechnicka 2, Prague 6, 166 27, Czech RepublicGuest editors:Jan Faigl (Artificial Intelligence Center, Department of Computer Science, Faculty of Electrical Engineering, Czech Technical University in PragueJiří Vokřínek (Artificial Intelligence Center, Department of Computer Science, Faculty of Electrical Engineering, Czech Technical University in PragueScientific comittee:D. Belter (Poznań University of Technology, PolandW. Dorner (Technische Hochschule Deggendorf, GermanyJ. Faigl (Czech Technical University in PragueT. Krajník (University of Lincoln, United KingdomA. Komenda (Czech Technical University in PragueG. Kupris (Technische Hochschule Deggendorf, GermanyM. Rollo (Czech Technical University in PragueM. Saska (Czech Technical University in PragueJ. Vokřínek (Czech Technical University in PragueV. Vonásek (Czech Technical University in PragueK. Walas (Poznań University of Technology, Poland Foreword:The third year of the student conference on “Planning in Artificial Intelligence and Robotics” (PAIR continues in joining young researchers and students interested in robotics and artificial intelligence. In 2016, we follow the schema of the last year as a joint event with the RoboTour competition in Deggendorf, Germany. Thanks to the great collaboration with Gerald Kupris and Wolfgang Donner from Technische Hochschule Deggendorf and support from Czech Technical University under project No. SVK 26/16/F3 and Bayerisches Staatsministerium der Finanzen, für Landesentwicklung und Heimat, we have been able to provide accommodations and travel support to participants and an invited speaker. Fourteen papers have accepted and listed in the conference program. The papers have been authored by students from Central Europe
Hidden Pair of Supermassive Black Holes
Kohler, Susanna
2015-08-01
Could a pair of supermassive black holes (SMBHs) be lurking at the center of the galaxy Mrk 231? A recent study finds that this may be the case and the unique spectrum of this galaxy could be the key to discovering more hidden binary SMBH systems.Where Are the Binary Supermassive Black Holes?Its believed that most, if not all, galaxies have an SMBH at their centers. As two galaxies merge, the two SMBHs should evolve into a closely-bound binary system before they eventually merge. Given the abundance of galaxy mergers, we would expect to see the kinematic and visual signatures of these binary SMBHs among observed active galactic nuclei yet such evidence for sub-parsec binary SMBH systems remains scarce and ambiguous. This has led researchers to wonder: is there another way that we might detect these elusive systems?A collaboration led by Chang-Shuo Yan (National Astronomical Observatories, Chinese Academy of Sciences) thinks that there is. The group suggests that these systems might have distinct signatures in their optical-to-UV spectra, and they identify a system that might be just such a candidate: Mrk 231.A Binary CandidateProposed model of Mrk 231. Two supermassive black holes, each with their own mini-disk, orbit each other in the center of a circumbinary disk. The secondary black hole has cleared gap in the circumbinary disk as a result of its orbit around the primary black hole. [Yan et al. 2015]Mrk 231 is a galaxy with a disturbed morphology and tidal tails strong clues that it might be in the final stages of a galactic merger. In addition to these signs, Mrk 231 also has an unusual spectrum for a quasar: its continuum emission displays an unexpected drop in the near-UV band.Yan and her collaborators propose that the odd behavior of Mrk 231s spectrum can be explained if the center of the galaxy houses a pair of SMBHs each with its own mini accretion disk surrounded by a circumbinary accretion disk. As the secondary SMBH orbits the primary SMBH (with a
Stereo Pair, Salt Lake City, Utah
2002-01-01
The 2002 Winter Olympics are hosted by Salt Lake City at several venues within the city, in nearby cities, and within the adjacent Wasatch Mountains. This image pair provides a stereoscopic map view of north central Utah that includes all of these Olympic sites. In the south, next to Utah Lake, Provo hosts the ice hockey competition. In the north, northeast of the Great Salt Lake, Ogden hosts curling and the nearby Snowbasin ski area hosts the downhill events. In between, southeast of the Great Salt Lake, Salt Lake City hosts the Olympic Village and the various skating events. Further east, across the Wasatch Mountains, the Park City ski resort hosts the bobsled, ski jumping, and snowboarding events. The Winter Olympics are always hosted in mountainous terrain. This view shows the dramatic landscape that makes the Salt Lake City region a world-class center for winter sports.This stereoscopic image was generated by draping a Landsat satellite image over a Shuttle Radar Topography Mission digital elevation model. Two differing perspectives were then calculated, one for each eye. They can be seen in 3-D by viewing the left image with the right eye and the right image with the left eye (cross-eyed viewing or by downloading and printing the image pair and viewing them with a stereoscope. When stereoscopically merged, the result is a vertically exaggerated view of Earth's surface in its full three dimensions.Landsat has been providing visible and infrared views of the Earth since 1972. SRTM elevation data matches the 30-meter (98-foot) resolution of most Landsat images and will substantially help in analyzing the large and growing Landsat image archive, managed by the U.S. Geological Survey (USGS).Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR
Paired Straight Hearth Furnace - Transformational Ironmaking Process
Energy Technology Data Exchange (ETDEWEB)
Lu, Wei-Kao [McMaster Univ., Hamilton, ON (Canada); Debski, Paul [Andritz Metals Inc.,Canonsburg, PA (United States)
2014-11-19
The U. S. steel industry has reduced its energy intensity per ton of steel shipped by 33% since 1990. However, further significant gains in energy efficiency will require the development of new, transformational iron and steelmaking processes. The Paired Straight Hearth Furnace (PSH) process is an emerging alternative high productivity, direct reduced iron (DRI) technology that may achieve very low fuel rates and has the potential to replace blast furnace ironmaking. The PSH furnace can operate independently or may be coupled with other melting technologies to produce liquid hot metal that is both similar to blast furnace iron and suitable as a feedstock for basic oxygen steelmaking furnaces. The PSH process uses non-metallurgical coal as a reductant to convert iron oxides such as iron ore and steelmaking by-product oxides to DRI pellets. In this process, a multi-layer, nominally 120mm tall bed of composite “green balls” made from oxide, coal and binder is built up and contained within a moving refractory hearth. The pellet bed absorbs radiant heat energy during exposure to the high temperature interior refractory surfaces of the PSH while generating a strongly reducing gas atmosphere in the bed that yields a highly metalized DRI product. The PSH concept has been well tested in static hearth experiments. A moving bed design is being developed. The process developers believe that if successful, the PSH process has the potential to replace blast furnaces and coke ovens at a fraction of the operating and capital cost while using about 30% less energy relative to current blast furnace technology. DRI output could also feed electric arc furnaces (EAFs) by displacing a portion of the scrap charge.
Top-quark pair production near threshold
International Nuclear Information System (INIS)
Sumino, Y.; Fujii, K.; Hagiwara, K.; Murayama, H.; Ng, C.
1993-01-01
We present a novel formalism to calculate the total and the differential cross sections for heavy unstable top-quark pair production near threshold. Within the context of the nonrelativistic quark model, we introduce the running toponium width Γ FTHETA (E,p) in the Schroedinger equation for the three-point Green's function that governs the t bar t contribution to the e + e- annihilation process. The effect of the running of the width is found to be significant in two aspects: (i) it takes account of the phase-space volume for the decay process t bar t→bW + bar bW- and provides a consistent framework for calculating the differential cross sections; and (ii) it reduces the widths of the low-lying resonances to considerably less than 2Γ t (m t 2 ). Furthermore, the running of the width causes the total cross section to decrease significantly at c.m. energies below the first ''resonance'' enhancement, whereas it makes the ''peak'' cross section more distinct than is obtained in the fixed toponium width approximation. We use the two-loop-improved QCD potential in our calculation, and the α s (m Z ) Mbar S dependences of the total and differential cross sections are studied quantitatively, where M bar S denotes the modified minimal subtraction scheme. We find that the correlations in the α s and m t measurements are opposite in the total and differential cross sections, and the simultaneous measurements would lead to an accurate determination of both parameters
Affected sib pair tests in inbred populations.
Liu, W; Weir, B S
2004-11-01
The affected-sib-pair (ASP) method for detecting linkage between a disease locus and marker loci was first established 50 years ago, and since then numerous modifications have been made. We modify two identity-by-state (IBS) test statistics of Lange (Lange, 1986a, 1986b) to allow for inbreeding in the population. We evaluate the power and false positive rates of the modified tests under three disease models, using simulated data. Before estimating false positive rates, we demonstrate that IBS tests are tests of both linkage and linkage disequilibrium between marker and disease loci. Therefore, the null hypothesis of IBS tests should be no linkage and no LD. When the population inbreeding coefficient is large, the false positive rates of Lange's tests become much larger than the nominal value, while those of our modified tests remain close to the nominal value. To estimate power with a controlled false positive rate, we choose the cutoff values based on simulated datasets under the null hypothesis, so that both Lange's tests and the modified tests generate same false positive rate. The powers of Lange's z-test and our modified z-test are very close and do not change much with increasing inbreeding. The power of the modified chi-square test also stays stable when the inbreeding coefficient increases. However, the power of Lange's chi-square test increases with increasing inbreeding, and is larger than that of our modified chi-square test for large inbreeding coefficients. The power is high under a recessive disease model for both Lange's tests and the modified tests, though the power is low for additive and dominant disease models. Allowing for inbreeding is therefore appropriate, at least for diseases known to be recessive.
Collisionless plasmas in astrophysics
Belmont, Gerard; Mottez, Fabrice; Pantellini, Filippo; Pelletier, Guy
2013-01-01
Collisionless Plasmas in Astrophysics examines the unique properties of media without collisions in plasma physics. Experts in this field, the authors present the first book to concentrate on collisionless conditions in plasmas, whether close or not to thermal equilibrium. Filling a void in scientific literature, Collisionless Plasmas in Astrophysics explains the possibilities of modeling such plasmas, using a fluid or a kinetic framework. It also addresses common misconceptions that even professionals may possess, on phenomena such as "collisionless (Landau) damping". Abundant illustrations
International Nuclear Information System (INIS)
Dreicer, H.; Banton, M.E.; Ingraham, J.C.; Wittman, F.; Wright, B.L.
1976-01-01
The Experimental Plasma Physics group's main efforts continue to be directed toward the understanding of the mechanisms of electromagnetic energy absorption in a plasma, and the resultant plasma heating and energy transport. The high-frequency spectrum of plasma waves parametrically excited by the microwave signal at high powers has been measured. The absorption of a small test microwave signal in a plasma made parametrically unstable by a separate high-power driver microwave signal was also studied
International Nuclear Information System (INIS)
Hanni, R.S.
1975-01-01
The concept of the plasma horizon, defined as the boundary of the region in which an infinitely thin plasma can be supported against Coulomb attraction by a magnetic field, shows that the argument of selective accretion does not rule out the existence of charged black holes embedded in a conducting plasma. A detailed account of the covariant definition of plasma horizon is given and some examples of plasma horizons are presented. 7 references
Adiabatic pair creation in heavy-ion and laser fields
International Nuclear Information System (INIS)
Pickl, P.; Durr, D.
2008-01-01
The planned generation of lasers and heavy-ion colliders renews the hope to see electron-positron pair creation in strong classical fields. This old prediction is usually referred to as spontaneous pair creation. We observe that both heavy-ion collisions and pair creation in strong laser fields, are instances of the theory of adiabatic pair creation. We shall present the theory, thereby correcting earlier results. We give the momentum distribution of created pairs in overcritical fields. We discuss carefully the proposed experimental verifications and conclude that pure laser-based experiments are highly questionable. We propose a new experiment, joining laser fields and heavy ions, which may be feasible with present-day technology and which may indeed verify the theoretical prediction of adiabatic pair creation. Our presentation relies on recent rigorous works in mathematical physics. (authors)
Pair production in a strong electric field with back-reaction
International Nuclear Information System (INIS)
Eisenberg, J.M.
1992-01-01
A summary is presented of the current status of efforts to solve the problem in which pairs are produced in a strong electric field, are accelerated by it, and then react back on it through the counter-field produced by their current. A review of recent developments in this back-reaction problem is given. A simple version of the theory of pair tunneling from a fixed electric field, is first presented and then a sketch is provided as to how this has been applied to the quark-gluon plasma. Then I turn to a field formulation of the problem for charged bosons, which leads to the need to carry out a renormalization program, outlined again in simple terms. Numerical results for this program are presented for one and for three spatial dimensions, and the corresponding physical behaviour of the system is discussed. I exhibit a phenomenological transport equation embodying physics that is essentially identical to that of the field formulation. Lastly, I present the extension to the fermion case and to the formulation in terms of boost-invariant variables (as required for the quark-gluon plasma). 6 figs., 17 refs. (author)
Nucleon-pair approximation to the nuclear shell model
Energy Technology Data Exchange (ETDEWEB)
Zhao, Y.M., E-mail: ymzhao@sjtu.edu.cn [Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Arima, A. [Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Musashi Gakuen, 1-26-1 Toyotamakami Nerima-ku, Tokyo 176-8533 (Japan)
2014-12-01
Atomic nuclei are complex systems of nucleons–protons and neutrons. Nucleons interact with each other via an attractive and short-range force. This feature of the interaction leads to a pattern of dominantly monopole and quadrupole correlations between like particles (i.e., proton–proton and neutron–neutron correlations) in low-lying states of atomic nuclei. As a consequence, among dozens or even hundreds of possible types of nucleon pairs, very few nucleon pairs such as proton and neutron pairs with spin zero, two (in some cases spin four), and occasionally isoscalar spin-aligned proton–neutron pairs, play important roles in low-energy nuclear structure. The nucleon-pair approximation therefore provides us with an efficient truncation scheme of the full shell model configurations which are otherwise too large to handle for medium and heavy nuclei in foreseeable future. Furthermore, the nucleon-pair approximation leads to simple pictures in physics, as the dimension of nucleon-pair subspace is always small. The present paper aims at a sound review of its history, formulation, validity, applications, as well as its link to previous approaches, with the focus on the new developments in the last two decades. The applicability of the nucleon-pair approximation and numerical calculations of low-lying states for realistic atomic nuclei are demonstrated with examples. Applications of pair approximations to other problems are also discussed.
Considerations on Velocities and Accelerations in Higher Pairs Mechanisms
Directory of Open Access Journals (Sweden)
Florina-Carmen Ciornei
2015-12-01
Full Text Available The paper proposes a method for finding the velocities and accelerations in the pairs from a mechanism with higher pairs in the case when the curvature radii of the curves achieving the higher pair are finite. There are obtained the characteristic equations of the motion in the higher pair for the case that one of the curves has zero curvature radius, condition characteristic to the knife edge follower. The relations are required to justify the difference between the particular cases of knife edge follower and flat face follower. The methodology is exemplified through an actual example.
Exotic Paired States with Anisotropic Spin-Dependent Fermi Surfaces
International Nuclear Information System (INIS)
Feiguin, Adrian E.; Fisher, Matthew P. A.
2009-01-01
We propose a model for realizing exotic paired states in cold Fermi gases by using a spin-dependent optical lattice to engineer mismatched Fermi surfaces for each hyperfine species. The BCS phase diagram shows a stable paired superfluid state with coexisting pockets of momentum space with gapless unpaired carriers, similar to the Sarma state in polarized mixtures, but in our case the system is unpolarized. We propose the possible existence of an exotic 'Cooper-pair Bose-metal' phase, which has a gap for single fermion excitations but gapless and uncondensed 'Cooper-pair' excitations residing on a 'Bose surface' in momentum space.
Alexander-equivalent Zariski pairs of irreducible sextics
DEFF Research Database (Denmark)
Eyral, Christophe; Oka, Mutsuo
2009-01-01
The existence of Alexander-equivalent Zariski pairs dealing with irreducible curves of degree 6 was proved by Degtyarev. However, no explicit example of such a pair is available (only the existence is known) in the literature. In this paper, we construct the first concrete example.......The existence of Alexander-equivalent Zariski pairs dealing with irreducible curves of degree 6 was proved by Degtyarev. However, no explicit example of such a pair is available (only the existence is known) in the literature. In this paper, we construct the first concrete example....
Pairing from strong repulsion in triangular lattice Hubbard model
Zhang, Shang-Shun; Zhu, Wei; Batista, Cristian D.
2018-04-01
We propose a pairing mechanism between holes in the dilute limit of doped frustrated Mott insulators. Hole pairing arises from a hole-hole-magnon three-body bound state. This pairing mechanism has its roots on single-hole kinetic energy frustration, which favors antiferromagnetic (AFM) correlations around the hole. We demonstrate that the AFM polaron (hole-magnon bound state) produced by a single hole propagating on a field-induced polarized background is strong enough to bind a second hole. The effective interaction between these three-body bound states is repulsive, implying that this pairing mechanism is relevant for superconductivity.
Butterflyfishes as a System for Investigating Pair Bonding
Nowicki, Jessica
2017-11-14
For many animals, affiliative relationships such as pair bonds form the foundation of society, and are highly adaptive. Animal systems amenable for comparatively studying pair bonding are important for identifying underlying biological mechanisms, but mostly exist in mammals. Better establishing fish systems will enable comparison of pair bonding mechanisms across taxonomically distant lineages that may reveal general underlying principles. We examined the utility of wild butterflyfishes (f: Chaetodontidae; g: Chaetodon) for comparatively studying pair bonding. Stochastic character mapping inferred that within the family, pairing is ancestral, with at least seven independent transitions to group formation and seven transition to solitary behavior from the late Miocene to recent. In six sympatric and wide-spread species representing a clade with one ancestrally reconstructed transition from paired to solitary grouping, we then verified social systems at Lizard Island, Australia. In situ observations confirmed that Chaetodon baronessa, C. lunulatus, and C. vagabundus are predominantly pair bonding, whereas C. rainfordi, C. plebeius, and C. trifascialis are predominantly solitary. Even in the predominantly pair bonding species, C. lunulatus, a proportion of adults (15 %) are solitary. Importantly, inter- and intra-specific differences in social systems do not co-vary with other previously established attributes (geographic occurrence, parental care, diet, or territoriality). Hence, the proposed butterflyfish populations are promising for comparative analyses of pair bonding and its mechanistic underpinnings. Avenues for further developing the system are proposed, including determining whether the utility of these species applies across their geographic disruptions.
Review of quantum collision dynamics in Debye plasmas
Directory of Open Access Journals (Sweden)
R.K. Janev
2016-09-01
Full Text Available Hot, dense plasmas exhibit screened Coulomb interactions, resulting from the collective effects of correlated many-particle interactions. In the lowest particle correlation order (pair-wise correlations, the interaction between charged plasma particles reduces to the Debye–Hückel (Yukawa-type potential, characterized by the Debye screening length. Due to the importance of Coulomb interaction screening in dense laboratory and astrophysical plasmas, hundreds of theoretical investigations have been carried out in the past few decades on the plasma screening effects on the electronic structure of atoms and their collision processes employing the Debye–Hückel screening model. The present article aims at providing a comprehensive review of the recent studies in atomic physics in Debye plasmas. Specifically, the work on atomic electronic structure, photon excitation and ionization, electron/positron impact excitation and ionization, and excitation, ionization and charge transfer of ion-atom/ion collisions will be reviewed.
Study of electron pair production in hadron and nuclear collisions at the CERN SPS
Liebold, H-P; Sako, H; Belaga, V; Bielcikova, J; Stachel, J
2002-01-01
The NA45/CERES experiment investigates primarily the production of electron-positron pairs and of direct photons in proton-nucleus and nucleus-nucleus collisions. For electron-positron pairs the experiment studies the continuum in the mass region of about 0.05 to 2 GeV/c$^2$ and the vector mesons $\\varrho ,~ \\omega$, and, $\\phi$. Since for electromagnetic probes final state interactions are practically negligible these observables are unique for studying the evolution and dynamics of ultrarelativistic heavy-ion collisions from the hot and dense early stage where a quark-gluon plasma is expected to be formed to the final freeze-out stage when hadrons decouple.\\\\ \\\\ The experiment also studies the spectral distributions of charged particles, their distribution relative to the reaction plane, and identified high momentum pions. Another topic of investigation are QED pairs produced in peripheral nuclear collisions.\\\\ \\\\ The first phase of the experiment, NA45, has been concluded with two main results: i) There is...
Study of Electron-Pair Spectroscopy in Pb-Pb Collisions at LHC
CERN. Geneva
1993-01-01
Among observables that have been proposed as signals of quark gluon plasma the lepton pairs from decays of vector bosons r, w, j, J/Y, U,... play important role. Effects such as the J/Y suppression, chiral symmetry restoration, strangeness enhancement and fast "clock" for the fireball lifetime are associated with possibilities of the lepton-pair spectroscopy in PbPb collisions at the LHC energies. In PbPb collisions the high particle density in central rapidity region is expected and therefore one has first of all to verify the feasibility of experiments aimed to measurement of cross sections, width and positions of vector resonances. For this purpose the programme LHCWPT has been developed which simulates production and two-and three-body decays of the Â¹Â¡, hÂ°, h, r, w, f, J/Y, U and Drell-Yan pairs in central rapidity region and also a detection of electrons and positrons in HEAVY ION DEDICATED EXPERIMENT.
AGT, Burge pairs and minimal models
International Nuclear Information System (INIS)
Bershtein, M.; Foda, O.
2014-01-01
We consider the AGT correspondence in the context of the conformal field theory M p,p ′ ⊗M H , where M p,p ′ is the minimal model based on the Virasoro algebra V p,p ′ labeled by two co-prime integers {p,p ′ }, 1
pairs {Y 1 ι ,Y 2 ι } that satisfy Y 2,σ ι,⊺ −Y 1,σ+r ι −1 ι,⊺ ≥1−s ι , and Y 1,σ ι,⊺ −Y 2,σ+p−r ι −1 ι,⊺ ≥1−p ′ +s ι , where Y i,σ ι,⊺ is the σ-column of Y i ι , i∈{1,2}, we obtain a well-defined expression that we identify with B n p,p ′ ,H . We check the correctness of this expression for 1. Any 1-point B 1 p,p ′ ,H on the torus, when the operator insertion is the identity, and 2. The 6-point B 3 3,4,H on the sphere that involves six Ising magnetic operators.
On the kinetic theory of the one-component plasma
International Nuclear Information System (INIS)
Cohen, J.S.
1984-01-01
In this thesis, kinetic theory is applied to transport phenomena of a one-component plasma. Existing kinetic equations, containing both dynamical screening effects and close binary collisions do not suffer from divergencies. Recently an approximation for the pair correlation function has been proposed that is valid for small values of the plasma collision parameter. Upon insertion of this expression into the general form of the collision integral, one obtains another convergent kinetic equation. This thesis shows that both kinetic equations yield the same coefficient of heat conductivity and viscosity; and that for a hot dilute plasma the arbitrary transport coefficient is rather insensitive to the pair correlation function. In the second part, the author studies the diffusion of a tagged particle in an external magnetic field. It is found that the longitudinal self-diffusion coefficient contra-varies monotonically with the magnetic field strength. (Auth.)
Wong, Chiow San
2016-01-01
This book presents some fundamental aspects of plasma technology that are important for beginners interested to start research in the area of plasma technology . These include the properties of plasma, methods of plasma generation and basic plasma diagnostic techniques. It also discusses several low cost plasma devices, including pulsed plasma sources such as plasma focus, pulsed capillary discharge, vacuum spark and exploding wire; as well as low temperature plasmas such as glow discharge and dielectric barrier discharge which the authors believe may have potential applications in industry. The treatments are experimental rather than theoretical, although some theoretical background is provided where appropriate. The principles of operation of these devices are also reviewed and discussed.
International Nuclear Information System (INIS)
Efthimion, P.; Hawryluk, R.J.; Hojsak, W.; Marsala, R.J.; Mueller, D.; Rauch, W.; Tait, G.D.; Taylor, G.; Thompson, M.
1985-01-01
The Tokamak Fusion Test Reactor employs feedback control systems for four plasma parameters, i.e. for plasma current, for plasma major radius, for plasma vertical position, and for plasma density. The plasma current is controlled by adjusting the rate of change of current in the Ohmic Heating (OH) coil system. Plasma current is continuously sensed by a Rogowski coil and its associated electronics; the error between it and a preprogrammed reference plasma current history is operated upon by a ''proportional-plusintegral-plus-derivative'' (PID) control algorithm and combined with various feedforward terms, to generate compensating commands to the phase-controlled thyristor rectifiers which drive current through the OH coils. The plasma position is controlled by adjusting the currents in Equilibrium Field and Horizontal Field coil systems, which respectively determine the vertical and radial external magnetic fields producing J X B forces on the plasma current. The plasma major radius position and vertical position, sensed by ''B /sub theta/ '' and ''B /sub rho/ '' magnetic flux pickup coils with their associated electronics, are controlled toward preprogrammed reference histories by allowing PID and feedforward control algorithms to generate commands to the EF and HF coil power supplies. Plasma density is controlled by adjusting the amount of gas injected into the vacuum vessel. Time-varying gains are used to combine lineaveraged plasma density measurements from a microwave interferometer plasma diagnostic system with vacuum vessel pressure measurements from ion gauges, with various other measurements, and with preprogrammed reference histories, to determine commands to piezoelectric gas injection valves
International conference on plasma physics
International Nuclear Information System (INIS)
Silin, V.P.; Sitenko, A.G.
1985-01-01
A brief report on the 6th International conference on plasma physics and on the 6th International Congress on plasma waves and plasma instabilities, which have taken place in summer 1984 in Losanne, is presented. Main items of the conference are enlightened, such as the general theory of a plasma, laboratory plasma, thermonuclear plasma, cosmic plasma and astrophysics
International Nuclear Information System (INIS)
Anon.
1986-01-01
Plasma and fluid physics includes the fields of fusion research and space investigation. This book discusses the most important advances in these areas over the past decade and recommends a stronger commitment to basic research in plasma and fluid physics. The book recommends that plasma and fluid physics be included in physics curriculums because of their increasing importance in energy and defense. The book also lists recent accomplishments in the fields of general plasma physics, fusion plasma confinement and heating, space and astrophysical plasmas, and fluid physics and lists research opportunities in these areas. A funding summary explains how research monies are allocated and suggests ways to improve their effectiveness
Wave propagation on a plasma media
International Nuclear Information System (INIS)
Torres-Silva, H.; Villarroel-Gonzalez, C.; Reggiani, N.; Sakanaka, P.H.
1995-01-01
Chiral-media and ferrite media have been studied over the last decade for many applications. Chiral-media have been examined as coating for reducing radar cross section, for antennas and arrays, for antenna radomes in waveguides and for microstrip substrate. Here, we examine a chiral-plasma medium, where the plasma part of the composite medium is non-reciprocal due to the external magnetic field, to find the general dispersion relation giving the ω against K behavior, vector phasor Helmholtz based equations are derived. We determine the modal eigenvalue properties in the chiral-plasma medium, which is doubly anisotropic. For the case of waves which propagate parallel to the magnetic field is a cold magnetized chiro-plasma. We compare our results with the typical results obtained for a cold plasma. Also we obtain the chiral-Faraday rotation which can be compared with the typical Faraday rotation for a pair of right-and left-handed circularly polarized waves. (author). 5 refs., 2 figs
Pavlovian autoshaping procedures increase plasma corticosterone levels in rats.
Tomie, Arthur; Silberman, Yuval; Williams, Kayon; Pohorecky, Larissa A
2002-06-01
Pavlovian autoshaping conditioned responses (CRs) are complex sequences of conditioned stimulus (CS)-directed skeletal-motor responses that are elicited by CS objects predictive of food unconditioned stimulus (US). Autoshaping CRs are observed under conditions known to be conducive to elevations in plasma corticosterone levels, as, for example, in response to the eating of food as well as in response to signals predictive of food. Two experiments investigated the relationships between Pavlovian autoshaping procedures, the performance of Pavlovian autoshaping CRs, and plasma corticosterone levels in male Long-Evans rats. In Experiment 1, rats in the CS-US paired group (n=30) were given 20 daily sessions of Pavlovian autoshaping training wherein the insertion of a retractable lever CS was followed by the response-independent presentation of the food US. Tail blood samples obtained after the 20th autoshaping session revealed higher plasma corticosterone levels in the CS-US paired group than in the CS-US random control group (n=10). In Experiment 2, rats (n=35) were assessed for basal plasma corticosterone levels 2 weeks prior to autoshaping training. Plasma samples obtained immediately following the first autoshaping session, and prior to the acquisition of lever-press autoshaping CR performance, revealed higher plasma corticosterone levels in the CS-US paired group (n=24) relative to basal levels. This effect was not observed in the CS-US random control group (n=11). Data suggest that corticosterone release is a physiological endocrine Pavlovian CR induced by lever CS-food US pairings during Pavlovian autoshaping procedures, rather than a by-product of autoshaping CR performance. Implications of the link between autoshaping procedures and corticosterone release are discussed.
AT Base Pair Anions vs. (9-methyl-A)(1-methyl-T) Base Pair Anions
International Nuclear Information System (INIS)
Radisic, Dunja; Bowen, Kit H.; Dabkowska, Iwona; Storoniak, Piotr; Rak, Janusz; Gutowski, Maciej S.
2005-01-01
The anionic base pairs of adenine and thymine, (AT)-, and 9-methyladenine and 1-methylthymine, (MAMT)-, have been investigated both theoretically and experimentally in a complementary, synergistic study. Calculations on (AT)- found that it had undergone a barrier-free proton transfer (BFPT) similar to that seen in other dimer anion systems and that its structural configuration that was neither Watson-Crick (WC) nor Hoogsteen (HS). The vertical detachment energy (VDE) of (AT)- was determined by anion photoelectron spectroscopy and found to be in agreement with the VDE value predicted by theory for the BFPT mechanism. An AT pair in DNA is structurally immobilized into the WC configuration, in part, by being bonded to the sugars of the double helix. This circumstance was mimicked by methylating the sites on both A and T where these sugars would have been tied, viz., 9-methyladenine and 1-methylthymine. Calculations found no BFPT in (MAMT)- and a resulting (MAMT)- configuration that wa s either HS or WC, with the configurations differing in stability by ca. 2 kcal/mol. The photoelectron spectrum of (MAMT)- occurred at a completely different electron binding energy than had (AT)-. Moreover, the VDE value of (MAMT)- was in agreement with that predicted by theory. The configuration of (MAMT)- and its lack of electron-induced proton transfer are inter-related. While there may be other pathways for electron-induced damage, BFPT in the WC/HS configurations of (AT)- is not feasible
AT base pair anions versus (9-methyl-A)(1-methyl-T) base pair anions.
Radisic, Dunja; Bowen, Kit H; Dabkowska, Iwona; Storoniak, Piotr; Rak, Janusz; Gutowski, Maciej
2005-05-04
The anionic base pairs of adenine and thymine, (AT)(-), and 9-methyladenine and 1-methylthymine, (MAMT)(-), have been investigated both theoretically and experimentally in a complementary, synergistic study. Calculations on (AT)(-) found that it had undergone a barrier-free proton transfer (BFPT) similar to that seen in other dimer anion systems and that its structural configuration was neither Watson-Crick (WC) nor Hoogsteen (HS). The vertical detachment energy (VDE) of (AT)(-) was determined by anion photoelectron spectroscopy and found to be in agreement with the VDE value predicted by theory for the BFPT mechanism. An AT pair in DNA is structurally immobilized into the WC configuration, in part, by being bonded to the sugars of the double helix. This circumstance was mimicked by methylating the sites on both A and T where these sugars would have been tied, viz., 9-methyladenine and 1-methylthymine. Calculations found no BFPT in (MAMT)(-) and a resulting (MAMT)(-) configuration that was either HS or WC, with the configurations differing in stability by ca. 2 kcal/mol. The photoelectron spectrum of (MAMT)(-) occurred at a completely different electron binding energy than had (AT)(-). Moreover, the VDE value of (MAMT)(-) was in agreement with that predicted by theory. The configuration of (MAMT)(-) and its lack of electron-induced proton transfer are inter-related. While there may be other pathways for electron-induced DNA alterations, BFPT in the WC/HS configurations of (AT)(-) is not feasible.
The Multipole Plasma Trap-PIC Modeling Results
Hicks, Nathaniel; Bowman, Amanda; Godden, Katarina
2017-10-01
A radio-frequency (RF) multipole structure is studied via particle-in-cell computer modeling, to assess the response of quasi-neutral plasma to the imposed RF fields. Several regimes, such as pair plasma, antimatter plasma, and conventional (ion-electron) plasma are considered. In the case of equal charge-to-mass ratio of plasma species, the effects of the multipole field are symmetric between positive and negative particles. In the case of a charge-to-mass disparity, the multipole RF parameters (frequency, voltage, structure size) may be chosen such that the light species (e.g. electrons) is strongly confined, while the heavy species (e.g. positive ions) does not respond to the RF field. In this case, the trapped negative space charge creates a potential well that then traps the positive species. 2D and 3D particle-in-cell simulations of this concept are presented, to assess plasma response and trapping dependences on multipole order, consequences of the formation of an RF plasma sheath, and the effects of an axial magnetic field. The scalings of trapped plasma parameters are explored in each of the mentioned regimes, to guide the design of prospective experiments investigating each. Supported by U.S. NSF/DOE Partnership in Basic Plasma Science and Engineering Grant PHY-1619615.
AGT, Burge pairs and minimal models
Energy Technology Data Exchange (ETDEWEB)
Bershtein, M. [Landau Institute for Theoretical Physics,Chernogolovka (Russian Federation); Institute for Information Transmission Problems,Moscow (Russian Federation); National Research University Higher School of Economics, International Laboratory of Representation Theory and Mathematical Physics, Independent University of Moscow, Moscow (Russian Federation); Foda, O. [Mathematics and Statistics, University of Melbourne,Parkville, VIC 3010 (Australia)
2014-06-30
We consider the AGT correspondence in the context of the conformal field theory M{sup p,p{sup ′}}⊗M{sup H}, where M{sup p,p{sup ′}} is the minimal model based on the Virasoro algebra V{sup p,p{sup ′}} labeled by two co-prime integers {p,p"′}, 1
pairs {Y_1"ι,Y_2"ι} that satisfy Y{sub 2,σ}{sup ι,⊺}−Y{sub 1,σ+r{sub ι−1}{sup ι,⊺}}≥1−s{sub ι}, and Y{sub 1,σ}{sup ι,⊺}−Y{sub 2,σ+p−r{sub ι−1}{sup ι,⊺}}≥1−p{sup ′}+s{sub ι}, where Y{sub i,σ}{sup ι,⊺} is the σ-column of Y{sub i}{sup ι}, i∈{1,2}, we obtain a well-defined expression that we identify with B{sub n}{sup p,p{sup ′,H}}. We check the correctness of this expression for 1. Any 1-point B{sub 1}{sup p,p{sup ′,H}} on the torus, when the operator insertion is the identity, and 2. The 6-point B{sub 3}{sup 3,4,H} on the sphere that involves six Ising magnetic operators.
Galaxy pairs as a probe for mergers at z ~ 2
DEFF Research Database (Denmark)
Man, A.W.S.; Zirm, Andrew Wasmuth; Toft, Sune
2011-01-01
In this work I investigate the redshift evolution of pair fraction of a sample of 196 massive galaxies from z = 0 to 3, selected from the COSMOS field. We find that on average a massive galaxy undergoes ~ 1.1 \\pm 0.5 major merger since z = 3. I will review the current limitations of using the pair...
Inflation of the screening length induced by Bjerrum pairs
Zwanikken, J.W.; van Roij, R.H.H.G.
2009-01-01
Within a modified Poisson–Boltzmann theory we study the effect of Bjerrum pairs on the typical length scale 1/¯κ over which electric fields are screened in electrolyte solutions, taking into account a simple association–dissociation equilibrium between free ions and Bjerrum pairs. At low densities
Theory of pairing symmetry in the vortex states
Yokoyama, Takehito; Ichioka, Yukio; Yanaka, Yukio; Golubov, Alexandre Avraamovitch
2010-01-01
We investigate pairing symmetry in an Abrikosov vortex and vortex lattice. It is shown that the Cooper pair wave function at the center of an Abrikosov vortex with vorticity m has a different parity with respect to frequency from that in the bulk if m is an odd number, while it has the same parity
Proton-neutron correlations in a broken-pair model
International Nuclear Information System (INIS)
Akkermans, J.N.L.
1981-01-01
In this thesis nuclear-structure calculations are reported which were performed with the broken-pair model. The model which is developed, is an extension of existing broken-pair models in so far that it includes both proton and neutron valence pairs. The relevant formalisms are presented. In contrast to the number-non-conserving model, a proton-neutron broken-pair model is well suited to study the correlations which are produced by the proton-neutron interaction. It is shown that the proton-neutron force has large matrix elements which mix the proton- with neutron broken-pair configurations. This occurs especially for Jsup(PI)=2 + and 3 - pairs. This property of the proton-neutron force is used to improve the spectra of single-closed shell nuclei, where particle-hole excitations of the closed shell are a special case of broken-pair configurations. Using Kr and Te isotopes it is demonstrated that the proton-neutron force gives rise to correlated pair structures, which remain remarkably constant with varying nucleon numbers. (Auth.)
Finding Question-Answer Pairs from Online Forums
DEFF Research Database (Denmark)
Cong, Gao; Wang, Long; Lin, Chin-Yew
2008-01-01
Online forums contain a huge amount of valuable user generated content. In this paper we address the problem of extracting question-answer pairs from forums. Question-answer pairs extracted from forums can be used to help Question Answering services (e.g. Yahoo! Answers) among other applications...
Observing Pair-Work Task in an English Speaking Class
Achmad, Diana; Yusuf, Yunisrina Qismullah
2014-01-01
This paper reports on students' pair-work interactions to develop their speaking skills in an ELT classroom which consisted of international learners. A number of 16 learners of intermediate proficiency with IELTS score band 5.5 were observed. The teacher had paired those he considered among them to be the more competent ones (hereafter, stronger)…
On e(+)e(-) pair production by colliding electromagnetic pulses
Narozhny, NB; Bulanov, SS; Mur, VD; Popov, VS
2004-01-01
Electron-positron pair production from vacuum in an electromagnetic field created by two counterpropagating focused laser pulses interacting with each other is analyzed. The dependence of the number of produced pairs on the intensity of a laser pulse and the focusing parameter is studied with a
Observation of charmonium pairs produced exclusively in pp collisions
Aaij, R.; Adeva, B.; Adinolfi, M.; Affolder, A.; Ajaltouni, Z.; Akar, S.; Albrecht, J.; Alessio, F.; Alexander, M.; Ali, S.; Alkhazov, G.; Cartelle, P. Alvarez; Alves, A. A.; Amato, S.; Amerio, S.; Amhis, Y.; An, L.; Anderlini, L.; Anderson, J.; Andreassen, R.; Andreotti, M.; Andrews, J. E.; Appleby, R. B.; Gutierrez, O. Aquines; Archilli, F.; Artamonov, A.; Artuso, M.; Aslanides, E.; Auriemma, G.; Baalouch, M.; Bachmann, S.; Back, J. J.; Badalov, A.; Baldini, W.; Barlow, R. J.; Barschel, C.; Barsuk, S.; Barter, W.; Batozskaya, V.; Battista, V.; Bay, A.; Beaucourt, L.; Beddow, J.; Bedeschi, F.; Bediaga, I.; Belogurov, S.; Belous, K.; Belyaev, I.; Onderwater, G.; Pellegrino, A.
A search is performed for the central exclusive production of pairs of charmonia produced in proton-proton collisions. Using data corresponding to an integrated luminosity of 3 fb(-1) collected at centre-of-mass energies of 7 and 8 TeV, J/psi J/psi and J/psi psi (2S) pairs are observed, which have
Teleportation of Quantum States through Mixed Entangled Pairs
Institute of Scientific and Technical Information of China (English)
ZHENG Shi-Biao
2006-01-01
@@ We describe a protocol for quantum state teleportation via mixed entangled pairs. With the help of an ancilla,near-perfect teleportation might be achieved. For pure entangled pairs, perfect teleportation might be achieved with a certain probability without using an ancilla. The protocol is generalized to teleportation of multiparticle states and quantum secret sharing.
minimal pairs of polytopes and their number of vertices
African Journals Online (AJOL)
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Using this operation we give a new algorithm to reduce and find a minimal pair of polytopes from the given ... Key words/phrases: Pairs of compact convex sets, Blaschke addition, Minkowski sum, mnimality ... product K(X)×K(X) by K2. (X).
Pairing renormalization and regularization within the local density approximation
International Nuclear Information System (INIS)
Borycki, P.J.; Dobaczewski, J.; Nazarewicz, W.; Stoitsov, M.V.
2006-01-01
We discuss methods used in mean-field theories to treat pairing correlations within the local density approximation. Pairing renormalization and regularization procedures are compared in spherical and deformed nuclei. Both prescriptions give fairly similar results, although the theoretical motivation, simplicity, and stability of the regularization procedure make it a method of choice for future applications
Solving the Airline Crew Pairing Problem using Subsequence Generation
DEFF Research Database (Denmark)
Rasmussen, Matias Sevel; Lusby, Richard Martin; Ryan, David M.
2010-01-01
Good and fast solutions to the airline crew pairing problem are highly interesting for the airline industry, as crew costs are the biggest expenditure after fuel for an airline. The crew pairing problem is typically modelled as a set partitioning problem and solved by column generation. However, ...
Solving the Airline Crew Pairing Problem using Subsequence Generation
DEFF Research Database (Denmark)
Rasmussen, Matias Sevel; Ryan, David; Lusby, Richard Martin
2009-01-01
Good and fast solutions to the airline crew pairing problem are highly interesting for the airline industry, as crew costs are the biggest expenditure after fuel for an airline. The crew pairing problem is typically modelled as a set partitioning problem and solved by column generation. However, ...
Intruder level and deformation in SD-pair shell model
International Nuclear Information System (INIS)
Luo Yan'an; Ning Pingzhi; Pan Feng
2004-01-01
The influence of intruder level on nuclear deformation is studied within the framework of the nucleon-pair shell model truncated to an SD-pair subspace. The results suggest that the intruder level has a tendency to reduce the deformation and plays an important role in determining the onset of rotational behavior. (authors)
Extending the Extensional Lambda Calculus with Surjective Pairing is Conservative
DEFF Research Database (Denmark)
Støvring, Kristian
2006-01-01
We answer Klop and de Vrijer's question whether adding surjective-pairing axioms to the extensional lambda calculus yields a conservative extension. The answer is positive. As a byproduct we obtain a "syntactic" proof that the extensional lambda calculus with surjective pairing is consistent....
Relativistic quasiparticle random phase approximation with a separable pairing force
International Nuclear Information System (INIS)
Tian Yuan; Ma Zhongyu; Ring Peter
2009-01-01
In our previous work, we introduced a separable pairing force for relativistic Hartree-Bogoliubov calculations. This force was adjusted to reproduce the pairing properties of the Gogny force in nuclear matter. By using the well known techniques of Talmi and Moshinsky it can be expanded in a series of separable terms and converges quickly after a few terms. It was found that the pairing properties can be depicted on almost the same footing as the original pairing interaction, not only in nuclear matter, but also in finite nuclei. In this study, we construct a relativistic quasiparticle random phase approximation (RQRPA) with this separable pairing interaction and calculate the excitation energies of the first excited 2 + states and reduced B(E2; 0 + →2 + ) transition rates for a chain of Sn isotopes in RQRPA. Compared with the results of the full Gogny force, we find that this simple separable pairing interaction can describe the pairing properties of the excited vibrational states as well as the original pairing interaction. (authors)
Pair production of arbitrary spin particles by electromagnetic fields
International Nuclear Information System (INIS)
Kruglov, S.I.
2006-01-01
The exact solutions of the wave equation for arbitrary spin particles in the field of the soliton-like electric impulse were obtained. The differential probability of pair production of particles by electromagnetic fields has been evaluated on the basis of the exact solutions. As a particular case, the particle pair production in the constant and uniform electric field were studied
Quantitative measures of entanglement in pair-coherent states
International Nuclear Information System (INIS)
Agarwal, G S; Biswas, Asoka
2005-01-01
The pair-coherent states for a two-mode radiation field are known to belong to a family of states with non-Gaussian wavefunction. The nature of quantum entanglement between the two modes and some features of non-classicality are studied for such states. The existing criterion for inseparability are examined in the context of pair-coherent states
The Electrostatic Instability for Realistic Pair Distributions in Blazar/EBL Cascades
Vafin, S.; Rafighi, I.; Pohl, M.; Niemiec, J.
2018-04-01
This work revisits the electrostatic instability for blazar-induced pair beams propagating through the intergalactic medium (IGM) using linear analysis and PIC simulations. We study the impact of the realistic distribution function of pairs resulting from the interaction of high-energy gamma-rays with the extragalactic background light. We present analytical and numerical calculations of the linear growth rate of the instability for the arbitrary orientation of wave vectors. Our results explicitly demonstrate that the finite angular spread of the beam dramatically affects the growth rate of the waves, leading to the fastest growth for wave vectors quasi-parallel to the beam direction and a growth rate at oblique directions that is only a factor of 2–4 smaller compared to the maximum. To study the nonlinear beam relaxation, we performed PIC simulations that take into account a realistic wide-energy distribution of beam particles. The parameters of the simulated beam-plasma system provide an adequate physical picture that can be extrapolated to realistic blazar-induced pairs. In our simulations, the beam looses only 1% of its energy, and we analytically estimate that the beam would lose its total energy over about 100 simulation times. An analytical scaling is then used to extrapolate the parameters of realistic blazar-induced pair beams. We find that they can dissipate their energy slightly faster by the electrostatic instability than through inverse-Compton scattering. The uncertainties arising from, e.g., details of the primary gamma-ray spectrum are too large to make firm statements for individual blazars, and an analysis based on their specific properties is required.
Pair Formation of Hard Core Bosons in Flat Band Systems
Mielke, Andreas
2018-05-01
Hard core bosons in a large class of one or two dimensional flat band systems have an upper critical density, below which the ground states can be described completely. At the critical density, the ground states are Wigner crystals. If one adds a particle to the system at the critical density, the ground state and the low lying multi particle states of the system can be described as a Wigner crystal with an additional pair of particles. The energy band for the pair is separated from the rest of the multi-particle spectrum. The proofs use a Gerschgorin type of argument for block diagonally dominant matrices. In certain one-dimensional or tree-like structures one can show that the pair is localised, for example in the chequerboard chain. For this one-dimensional system with periodic boundary condition the energy band for the pair is flat, the pair is localised.
Inflation of the screening length induced by Bjerrum pairs.
Zwanikken, Jos; van Roij, René
2009-10-21
Within a modified Poisson-Boltzmann theory we study the effect of Bjerrum pairs on the typical length scale [Formula: see text] over which electric fields are screened in electrolyte solutions, taking into account a simple association-dissociation equilibrium between free ions and Bjerrum pairs. At low densities of Bjerrum pairs, this length scale is well approximated by the Debye length [Formula: see text], with ρ(s) the free-ion density. At high densities of Bjerrum pairs, however, we find [Formula: see text], which is significantly larger than 1/κ due to the enhanced effective permittivity of the electrolyte, caused by the polarization of Bjerrum pairs. We argue that this mechanism may explain the recently observed anomalously large colloid-free zones between an oil-dispersed colloidal crystal and a colloidal monolayer at the oil-water interface.
An Intelligent Model for Pairs Trading Using Genetic Algorithms.
Huang, Chien-Feng; Hsu, Chi-Jen; Chen, Chi-Chung; Chang, Bao Rong; Li, Chen-An
2015-01-01
Pairs trading is an important and challenging research area in computational finance, in which pairs of stocks are bought and sold in pair combinations for arbitrage opportunities. Traditional methods that solve this set of problems mostly rely on statistical methods such as regression. In contrast to the statistical approaches, recent advances in computational intelligence (CI) are leading to promising opportunities for solving problems in the financial applications more effectively. In this paper, we present a novel methodology for pairs trading using genetic algorithms (GA). Our results showed that the GA-based models are able to significantly outperform the benchmark and our proposed method is capable of generating robust models to tackle the dynamic characteristics in the financial application studied. Based upon the promising results obtained, we expect this GA-based method to advance the research in computational intelligence for finance and provide an effective solution to pairs trading for investment in practice.
Pair truncation for rotational nuclei: j=17/2 model
International Nuclear Information System (INIS)
Halse, P.; Jaqua, L.; Barrett, B.R.
1989-01-01
The suitability of the pair condensate approach for rotational states is studied in a single j=17/2 shell of identical nucleons interacting through a quadrupole-quadrupole Hamiltonian. The ground band and a K=2 excited band are both studied in detail. A direct comparison of the exact states with those constituting the SD and SDG subspaces is used to identify the important degrees of freedom for these levels. The range of pairs necessary for a good description is found to be highly state dependent; S and D pairs are the major constituents of the low-spin ground-band levels, while G pairs are needed for those in the γ band. Energy spectra are obtained for each truncated subspace. SDG pairs allow accurate reproduction of the binding energy and K=2 excitation energy, but still give a moment of inertia which is about 30% too small even for the lowest levels
Overdensity of galaxies in the environment of quasar pairs
Sandrinelli, A.; Falomo, R.; Treves, A.; Scarpa, R.; Uslenghi, M.
2018-03-01
We report on a study of the galaxy environments of low redshift physical quasars pairs. We selected 20 pairs having projected separation Survey images, we evaluated the galaxy overdensity around these quasars in pairs and then compare it with that of a sample of isolated quasars with same redshift and luminosity. It is found that on average there is a systematic larger overdensity of galaxies around quasars in pairs with respect to that of isolated quasars. This may represent a significant link between nuclear activity and galaxy environment. However, at odds with that, the closest quasar pairs seem to inhabit poorer environments. Implications of present results and perspectives for future work are briefly discussed.
Special issue: Plasma Conversion
Nozaki, T.; Bogaerts, A.; Tu, X.; van de Sanden, M. C. M.
2017-01-01
With growing concern of energy and environmental issues, the combination of plasma and heterogeneous catalysts receives special attention in greenhouse gas conversion, nitrogen fixation and hydrocarbon chemistry. Plasma gas conversion driven by renewable electricity is particularly important for the
Neutrino beam plasma instability
Indian Academy of Sciences (India)
positron or electron–proton plasma in the context of early universe, stars and supernova ... proper. Of course, in their later work on kinetic theory (KT) [5] of neutrino plasma inter- .... for electron also with additional electric potential term.
International Nuclear Information System (INIS)
Elliott, J.A.
1993-01-01
Plasma kinetic theory is discussed and a comparison made with the kinetic theory of gases. The plasma is described by a modified set of fluid equations and it is shown how these fluid equations can be derived. (UK)
International Nuclear Information System (INIS)
Rubenchik, A.; Witkowski, S.
1991-01-01
This book provides a comprehensive review of laser fusion plasma physics and contains the most up-to-date information on high density plasma physics and radiation transport, useful for astrophysicists and high density physicists
Plasma heating in collisionless plasma at low plasma density
International Nuclear Information System (INIS)
Wulf, H.O.
1977-01-01
The high frequency heating of a collisionless, fully ionized low density plasma is investigated in the range: 2ωc 2 2 under pumping frequencies. A pulsed 1 MHz transmitter excites a fast standing, magneto-acoustical wave in the plasma, via the high frequency magnetic field of a Stix solenoid. The available modulation degrees are between 0.7 and 7.0%. As power consumption measurements show, there appears at all investigated pumping frequencies an effective energy transfer to the plasma that cannot be explained with the classical MHD models. Measurements with electrostatic probes and further with a miniature counter-field spectrometer yield an electron and ion temperature gain of two to three factors and 15-18, compared to the corresponding values in the initial plasma. (orig./HT) [de
Possible uses of the DLS dipoles in a search for the quark-gluon plasma at the AGS
International Nuclear Information System (INIS)
Kirk, P.N.
1985-01-01
The possible use of dipole magnets in an experiment to search for the quark-gluon plasma is discussed, specifically the two dipole magnets based on the lampshade concept that are currently being constructed for use at LBL. A major advantage of this design is that the efficiency of pair detectors is almost independent of pair mass and transverse momentum over the entire range of interest. The efficiency does depend highly on the pair rapidity and the target location, however
Obliquely propagating large amplitude solitary waves in charge neutral plasmas
Directory of Open Access Journals (Sweden)
F. Verheest
2007-01-01
Full Text Available This paper deals in a consistent way with the implications, for the existence of large amplitude stationary structures in general plasmas, of assuming strict charge neutrality between electrons and ions. With the limit of pair plasmas in mind, electron inertia is retained. Combining in a fluid dynamic treatment the conservation of mass, momentum and energy with strict charge neutrality has indicated that nonlinear solitary waves (as e.g. oscillitons cannot exist in electron-ion plasmas, at no angle of propagation with respect to the static magnetic field. Specifically for oblique propagation, the proof has turned out to be more involved than for parallel or perpendicular modes. The only exception is pair plasmas that are able to support large charge neutral solitons, owing to the high degree of symmetry naturally inherent in such plasmas. The nonexistence, in particular, of oscillitons is attributed to the breakdown of the plasma approximation in dealing with Poisson's law, rather than to relativistic effects. It is hoped that future space observations will allow to discriminate between oscillitons and large wave packets, by focusing on the time variability (or not of the phase, since the amplitude or envelope graphs look very similar.
Van Gog, Tamara; Kester, Liesbeth; Paas, Fred
2010-01-01
Van Gog, T., Kester, L., & Paas, F. (2010, August). Effects of worked examples, example-problem pairs, and problem-example pairs compared to problem solving. Paper presented at the Biannual EARLI SIG meeting of Instructional design and Learning and instruction with computers, Ulm, Germany.
On the combination of the Cooper pair and the Ogg pair in the high-Tc oxide superconductor
International Nuclear Information System (INIS)
Zhang Liyuan.
1991-08-01
In this paper it is argued that the superconductivity of the high-T c oxide superconductor (HTOS) can be explained by the combinating mechanism of the Cooper pair and the Ogg pair. The properties of the superconducting state of the HTOS have been calculated under this mechanism, and the theoretical results are overall consistent with the experiment. (author). 37 refs
Introduction to Plasma Physics
Gurnett, Donald A.; Bhattacharjee, Amitava
2017-03-01
Preface; 1. Introduction; 2. Characteristic parameters of a plasma; 3. Single particle motions; 4. Waves in a cold plasma; 5. Kinetic theory and the moment equations; 6. Magnetohydrodynamics; 7. MHD equilibria and stability; 8. Discontinuities and shock waves; 9. Electrostatic waves in a hot unmagnetized plasma; 10. Waves in a hot magnetized plasma; 11. Nonlinear effects; 12. Collisional processes; Appendix A. Symbols; Appendix B. Useful trigonometric identities; Appendix C. Vector differential operators; Appendix D. Vector calculus identities; Index.
International Nuclear Information System (INIS)
Reichle, R.
2004-01-01
This document gathers the 43 slides presented in the framework of the week long lecture 'hot plasmas 2004' and dedicated to plasma-wall interaction in a tokamak. This document is divided into 4 parts: 1) thermal load on the wall, power extraction and particle recovery, 2) basic edge plasma physics, 3) processes that drive the plasma-solid interaction, and 4) material conditioning (surface treatment...) for ITER
Plasma physics an introduction
Fitzpatrick, Richard
2014-01-01
Plasma Physics: An Introduction is based on a series of university course lectures by a leading name in the field, and thoroughly covers the physics of the fourth state of matter. This book looks at non-relativistic, fully ionized, nondegenerate, quasi-neutral, and weakly coupled plasma. Intended for the student market, the text provides a concise and cohesive introduction to plasma physics theory, and offers a solid foundation for students wishing to take higher level courses in plasma physics.
Application of plasma focus device to compression of toroidal plasma
International Nuclear Information System (INIS)
Ikuta, Kazunari
1980-01-01
A new concept of compressing a toroidal plasma using a plasma focus device is considered. Maximum compression ratio of toroidal plasma is determined merely by the initial density ratio of the toroidal plasma to a sheet plasma in a focus device because of the Rayleigh-Taylor instability. An initiation senario of plasma-linear is also proposed with a possible application of this concepts to the creation of a burning plasma in reversed field configurations, i.e., burning plasma vortex. (author)
Merging a Pair of Supermassive Black Holes
Kohler, Susanna
2016-10-01
hydrodynamically, simulating the final stages of the galaxy merger.When the separation of the two SMBHs is small enough, the authors extract a spherical region of 5 kpc from around the pair and evolve this as an N-body simulation.Finally, the separation of the SMBHs becomes so small (0.01 pc) that gravitational-wave emission is the dominant loss of energy driving the inspiral. The authors add post-Newtonian terms into the N-body simulation to account for this.Time evolution of the separation between the SMBHs, beginning with the hydrodynamical simulation (blue), then transitioning to the direct N-body calculation (red), and ending with the introduction of post-Newtonian terms (green) to account for gravitational-wave emission. [Adapted from Khan et al. 2016]Successful CoalescenceKhan and collaborators complex approach allows them to simulate the entire process of the merger and SMBH coalescence, resulting in several key determinations.First, they demonstrate that the SMBHs can coalesce on timescales of only tens of Myr, which is roughly two orders of magnitude smaller than what was typically estimated before. They find that gas dissipation before the merger is instrumental in creating the conditions that allow for this rapid orbital decay.The authors also demonstrate that the gravitational potential of the galaxy merger remnant is triaxial throughout the merger. Khan and collaborators simulations confirm that this non-spherical potential solves the final parsec problem by sending stars on plunging orbits around the SMBHs. These more distant stars cause the SMBHs to lose angular momentum through dynamical friction and continue their inspiral, even when the stars immediately surrounding the SMBHs have been depleted.This simulation isan important step toward a better understanding of SMBH mergers. Its outcomes are especially promising for future gravitational-wave campaigns, as the short SMBH coalescence timescales indicate that these mergers could indeed be observable
Electronic pairing mechanism due to band modification with increasing pair number
International Nuclear Information System (INIS)
Mizia, J.
1995-01-01
It is shown that a shift of an electron band with electron occupation number n, which is changing during the transition to the superconducting state, can lower the total energy of the system. In fact it will bring a negative contribution to the pairing potential, which is proportional to the product of the electron band shift with occupation number and the charge transfer during the transition to the superconducting state. The shift of the electron band comes from the change of stresses and the change of correlation effects in the CuO 2 plane with n, that in turn is caused by the changing oxygen concentration. This model explains the phenomenological success of Hirsch's model, which gives no explanation how the band shift in energy can give rise to superconductivity. (orig.)
Transport processes in multicomponent plasma
International Nuclear Information System (INIS)
Zissis, G.
2002-01-01
Full text: This book treats in detail, as indicated in the title, the transport phenomena in multicomponent plasmas. Here, the term 'transport' applies to the study of mass and energy transfer in plasmas due to the interactions between pairs of particles only. Radiation is legitimately omitted; anyway, radiative transfer is another field of study. As the author himself mentions in the introduction, 'the term multicomponent plasma implies a partially or fully ionized mixture of arbitrary number of species of neutral and charged particles satisfying the condition of quasi-neutrality'. In fact, this book treats a large variety of plasmas applying to different systems ranging from low-pressure systems which may be far from local thermodynamic equilibrium (LTE) conditions, to thermal plasmas in LTE or near-LTE states with special attention to two-temperature systems; partially ionized plasmas with low ionization degree for which electron-neutral interactions are predominant, to systems with higher ionization degrees in which charged particle interactions are no more negligible. In addition, for all the above stated situations, the author treats both plasmas which are subjected to an external electromagnetic field and those which are not (homogeneous and inhomogeneous cases). Furthermore, in the last chapters a special discussion concerning molecular plasmas is presented. Taking into account the evolution of plasma modelling in the last few years, the subject is of current interest and the reader will find in the book a large amount of information necessary for a good understanding of transport phenomena in plasmas: for a plasma simulation specialist, this book may be regarded as reference text, which includes all necessary mathematical relations for his work. However, it should not be considered a simple formulary; the reader will also find here an excellent description of the theoretical basis necessary for the derivation of all given expressions. To this point of view
DEFF Research Database (Denmark)
Palmgren, Michael Broberg; Bækgaard, Lone; Lopez Marques, Rosa Laura
2011-01-01
The plasma membrane separates the cellular contents from the surrounding environment. Nutrients must enter through the plasma membrane in order to reach the cell interior, and toxic metabolites and several ions leave the cell by traveling across the same barrier. Biological pumps in the plasma me...
Tipa, R.S.
2012-01-01
Plasmas, due to their electrical and chemical properties, release in the invironment a unique cocktail of charged species, energetic photons and active radicals. Plasmas have a miriad of applications. To mention just a few, plasmas are being used in the semiconductors industry, atomic layer
International Nuclear Information System (INIS)
Kulsrud, R.M.
1982-10-01
Two examples of plasma phenomena of importance to astrophysics are reviewed. These are examples where astrophysical understanding hinges on further progress in plasma physics understanding. The two examples are magnetic reconnection and the collisionless interaction between a population of energetic particles and a cooler gas or plasma, in particular the interaction between galactic cosmic rays and the interstellar medium
Plasma processing and chemistry
Schram, D.C.; Mullen, van der J.J.A.M.; Sanden, van de M.C.M.
1994-01-01
The growing field of applications of plasma as deposition, etching, surface modification and chemical conversion has stimulated a renewed interest in plasma science in the atomic physical chemistry regime. The necessity to optimize the various plasma processing techniques in terms of rates, and
Twin photon pairs in a high-Q silicon microresonator
Energy Technology Data Exchange (ETDEWEB)
Rogers, Steven; Lu, Xiyuan [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Jiang, Wei C. [Institute of Optics, University of Rochester, Rochester, New York 14627 (United States); Lin, Qiang, E-mail: qiang.lin@rochester.edu [Institute of Optics, University of Rochester, Rochester, New York 14627 (United States); Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627 (United States)
2015-07-27
We report the generation of high-purity twin photon pairs through cavity-enhanced non-degenerate four-wave mixing (FWM) in a high-Q silicon microdisk resonator. Twin photon pairs are created within the same cavity mode and are consequently expected to be identical in all degrees of freedom. The device is able to produce twin photons at telecommunication wavelengths with a pair generation rate as large as (3.96 ± 0.03) × 10{sup 5} pairs/s, within a narrow bandwidth of 0.72 GHz. A coincidence-to-accidental ratio of 660 ± 62 was measured, the highest value reported to date for twin photon pairs, at a pair generation rate of (2.47 ± 0.04) × 10{sup 4} pairs/s. Through careful engineering of the dispersion matching window, we have reduced the ratio of photons resulting from degenerate FWM to non-degenerate FWM to less than 0.15.
Parietal lesion effects on cued recall following pair associate learning.
Ben-Zvi, Shir; Soroker, Nachum; Levy, Daniel A
2015-07-01
We investigated the involvement of the posterior parietal cortex in episodic memory in a lesion-effects study of cued recall following pair-associate learning. Groups of patients who had experienced first-incident stroke, generally in middle cerebral artery territory, and exhibited damage that included lateral posterior parietal regions, were tested within an early post-stroke time window. In three experiments, patients and matched healthy comparison groups executed repeated study and cued recall test blocks of pairs of words (Experiment 1), pairs of object pictures (Experiment 2), or pairs of object pictures and environmental sounds (Experiment 3). Patients' brain CT scans were subjected to quantitative analysis of lesion volumes. Behavioral and lesion data were used to compute correlations between area lesion extent and memory deficits, and to conduct voxel-based lesion-symptom mapping. These analyses implicated lateral ventral parietal cortex, especially the angular gyrus, in cued recall deficits, most pronouncedly in the cross-modal picture-sound pairs task, though significant parietal lesion effects were also found in the unimodal word pairs and picture pairs tasks. In contrast to an earlier study in which comparable parietal lesions did not cause deficits in item recognition, these results indicate that lateral posterior parietal areas make a substantive contribution to demanding forms of recollective retrieval as represented by cued recall, especially for complex associative representations. Copyright © 2015 Elsevier Ltd. All rights reserved.
Pairing gaps from nuclear mean-field models
International Nuclear Information System (INIS)
Bender, M.; Rutz, K.; Maruhn, J.A.
2000-01-01
We discuss the pairing gap, a measure for nuclear pairing correlations, in chains of spherical, semi-magic nuclei in the framework of self-consistent nuclear mean-field models. The equations for the conventional BCS model and the approximate projection-before-variation Lipkin-Nogami method are formulated in terms of local density functionals for the effective interaction. We calculate the Lipkin-Nogami corrections of both the mean-field energy and the pairing energy. Various definitions of the pairing gap are discussed as three-point, four-point and five-point mass-difference formulae, averaged matrix elements of the pairing potential, and single-quasiparticle energies. Experimental values for the pairing gap are compared with calculations employing both a delta pairing force and a density-dependent delta interaction in the BCS and Lipkin-Nogami model. Odd-mass nuclei are calculated in the spherical blocking approximation which neglects part of the the core polarization in the odd nucleus. We find that the five-point mass difference formula gives a very robust description of the odd-even staggering, other approximations for the gap may differ from that up to 30% for certain nuclei. (orig.)
The coevolution of long-term pair bonds and cooperation.
Song, Z; Feldman, M W
2013-05-01
The evolution of social traits may not only depend on but also change the social structure of the population. In particular, the evolution of pairwise cooperation, such as biparental care, depends on the pair-matching distribution of the population, and the latter often emerges as a collective outcome of individual pair-bonding traits, which are also under selection. Here, we develop an analytical model and individual-based simulations to study the coevolution of long-term pair bonds and cooperation in parental care, where partners play a Snowdrift game in each breeding season. We illustrate that long-term pair bonds may coevolve with cooperation when bonding cost is below a threshold. As long-term pair bonds lead to assortative interactions through pair-matching dynamics, they may promote the prevalence of cooperation. In addition to the pay-off matrix of a single game, the evolutionarily stable equilibrium also depends on bonding cost and accidental divorce rate, and it is determined by a form of balancing selection because the benefit from pair-bond maintenance diminishes as the frequency of cooperators increases. Our findings highlight the importance of ecological factors affecting social bonding cost and stability in understanding the coevolution of social behaviour and social structures, which may lead to the diversity of biological social systems. © 2013 The Authors. Journal of Evolutionary Biology © 2013 European Society For Evolutionary Biology.
Separable pairing force for relativistic quasiparticle random-phase approximation
International Nuclear Information System (INIS)
Tian Yuan; Ma Zhongyu; Ring, Peter
2009-01-01
We have introduced a separable pairing force, which was adjusted to reproduce the pairing properties of the Gogny force in nuclear matter. This separable pairing force is able to describe in relativistic Hartree-Bogoliubov (RHB) calculations the pairing properties in the ground state of finite nuclei on almost the same footing as the original Gogny interaction. In this work we investigate excited states using the Relativistic Quasiparticle Random-Phase Approximation (RQRPA) with the same separable pairing force. For consistency the Goldstone modes and the convergence with various cutoff parameters in this version of RQRPA are studied. The first excited 2 + states for the chain of Sn isotopes with Z=50 and the chain of isotones with N=82 isotones are calculated in RQRPA together with the 3 - states of Sn isotopes. By comparing our results with experimental data and with the results of the original Gogny force we find that this simple separable pairing interaction is very successful in depicting the pairing properties of vibrational excitations.
High Level Rule Modeling Language for Airline Crew Pairing
Mutlu, Erdal; Birbil, Ş. Ilker; Bülbül, Kerem; Yenigün, Hüsnü
2011-09-01
The crew pairing problem is an airline optimization problem where a set of least costly pairings (consecutive flights to be flown by a single crew) that covers every flight in a given flight network is sought. A pairing is defined by using a very complex set of feasibility rules imposed by international and national regulatory agencies, and also by the airline itself. The cost of a pairing is also defined by using complicated rules. When an optimization engine generates a sequence of flights from a given flight network, it has to check all these feasibility rules to ensure whether the sequence forms a valid pairing. Likewise, the engine needs to calculate the cost of the pairing by using certain rules. However, the rules used for checking the feasibility and calculating the costs are usually not static. Furthermore, the airline companies carry out what-if-type analyses through testing several alternate scenarios in each planning period. Therefore, embedding the implementation of feasibility checking and cost calculation rules into the source code of the optimization engine is not a practical approach. In this work, a high level language called ARUS is introduced for describing the feasibility and cost calculation rules. A compiler for ARUS is also implemented in this work to generate a dynamic link library to be used by crew pairing optimization engines.
Some aspects of plasma thermodynamics
International Nuclear Information System (INIS)
Gorgoraki, V.I.
1986-01-01
The objective reasons which have inhibited the development of a plasma-thermodynamics theory are discussed and the authors formulate the fundamental principles which can be the basis of a common plasma-thermodynamics theory. Two kinds of thermodynamic equilibrium plasmas are discussed, an isothermal plasma and a nonisothermal plasma. An isothermal plasma is a high-temperature plasma; the Saha-Eggert equation describes its behavior. A nonisothermal plasma is a low-temperature plasma, and the reactions taking place therein are purely plasma-chemical. The ionization equilibrium and the composition of such a plasma can be found with the aid of the equations presented in this paper
Analysis of Food Pairing in Regional Cuisines of India.
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Anupam Jain
Full Text Available Any national cuisine is a sum total of its variety of regional cuisines, which are the cultural and historical identifiers of their respective regions. India is home to a number of regional cuisines that showcase its culinary diversity. Here, we study recipes from eight different regional cuisines of India spanning various geographies and climates. We investigate the phenomenon of food pairing which examines compatibility of two ingredients in a recipe in terms of their shared flavor compounds. Food pairing was enumerated at the level of cuisine, recipes as well as ingredient pairs by quantifying flavor sharing between pairs of ingredients. Our results indicate that each regional cuisine follows negative food pairing pattern; more the extent of flavor sharing between two ingredients, lesser their co-occurrence in that cuisine. We find that frequency of ingredient usage is central in rendering the characteristic food pairing in each of these cuisines. Spice and dairy emerged as the most significant ingredient classes responsible for the biased pattern of food pairing. Interestingly while individual spices contribute to negative food pairing, dairy products on the other hand tend to deviate food pairing towards positive side. Our data analytical study highlighting statistical properties of the regional cuisines, brings out their culinary fingerprints that could be used to design algorithms for generating novel recipes and recipe recommender systems. It forms a basis for exploring possible causal connection between diet and health as well as prospection of therapeutic molecules from food ingredients. Our study also provides insights as to how big data can change the way we look at food.
Analysis of Food Pairing in Regional Cuisines of India.
Jain, Anupam; N K, Rakhi; Bagler, Ganesh
2015-01-01
Any national cuisine is a sum total of its variety of regional cuisines, which are the cultural and historical identifiers of their respective regions. India is home to a number of regional cuisines that showcase its culinary diversity. Here, we study recipes from eight different regional cuisines of India spanning various geographies and climates. We investigate the phenomenon of food pairing which examines compatibility of two ingredients in a recipe in terms of their shared flavor compounds. Food pairing was enumerated at the level of cuisine, recipes as well as ingredient pairs by quantifying flavor sharing between pairs of ingredients. Our results indicate that each regional cuisine follows negative food pairing pattern; more the extent of flavor sharing between two ingredients, lesser their co-occurrence in that cuisine. We find that frequency of ingredient usage is central in rendering the characteristic food pairing in each of these cuisines. Spice and dairy emerged as the most significant ingredient classes responsible for the biased pattern of food pairing. Interestingly while individual spices contribute to negative food pairing, dairy products on the other hand tend to deviate food pairing towards positive side. Our data analytical study highlighting statistical properties of the regional cuisines, brings out their culinary fingerprints that could be used to design algorithms for generating novel recipes and recipe recommender systems. It forms a basis for exploring possible causal connection between diet and health as well as prospection of therapeutic molecules from food ingredients. Our study also provides insights as to how big data can change the way we look at food.
Analysis of Food Pairing in Regional Cuisines of India
Bagler, Ganesh
2015-01-01
Any national cuisine is a sum total of its variety of regional cuisines, which are the cultural and historical identifiers of their respective regions. India is home to a number of regional cuisines that showcase its culinary diversity. Here, we study recipes from eight different regional cuisines of India spanning various geographies and climates. We investigate the phenomenon of food pairing which examines compatibility of two ingredients in a recipe in terms of their shared flavor compounds. Food pairing was enumerated at the level of cuisine, recipes as well as ingredient pairs by quantifying flavor sharing between pairs of ingredients. Our results indicate that each regional cuisine follows negative food pairing pattern; more the extent of flavor sharing between two ingredients, lesser their co-occurrence in that cuisine. We find that frequency of ingredient usage is central in rendering the characteristic food pairing in each of these cuisines. Spice and dairy emerged as the most significant ingredient classes responsible for the biased pattern of food pairing. Interestingly while individual spices contribute to negative food pairing, dairy products on the other hand tend to deviate food pairing towards positive side. Our data analytical study highlighting statistical properties of the regional cuisines, brings out their culinary fingerprints that could be used to design algorithms for generating novel recipes and recipe recommender systems. It forms a basis for exploring possible causal connection between diet and health as well as prospection of therapeutic molecules from food ingredients. Our study also provides insights as to how big data can change the way we look at food. PMID:26430895
Preferred and avoided codon pairs in three domains of life
Directory of Open Access Journals (Sweden)
Tenson Tanel
2008-10-01
Full Text Available Abstract Background Alternative synonymous codons are not used with equal frequencies. In addition, the contexts of codons – neighboring nucleotides and neighboring codons – can have certain patterns. The codon context can influence both translational accuracy and elongation rates. However, it is not known how strong or conserved the codon context preferences in different organisms are. We analyzed 138 organisms (bacteria, archaea and eukaryotes to find conserved patterns of codon pairs. Results After removing the effects of single codon usage and dipeptide biases we discovered a set of neighboring codons for which avoidances or preferences were conserved in all three domains of life. Such biased codon pairs could be divided into subtypes on the basis of the nucleotide patterns that influence the bias. The most frequently avoided type of codon pair was nnUAnn. We discovered that 95.7% of avoided nnUAnn type patterns contain out-frame UAA or UAG triplets on the sense and/or antisense strand. On average, nnUAnn codon pairs are more frequently avoided in ORFeomes than in genomes. Thus we assume that translational selection plays a major role in the avoidance of these codon pairs. Among the preferred codon pairs, nnGCnn was the major type. Conclusion Translational selection shapes codon pair usage in protein coding sequences by rules that are common to all three domains of life. The most frequently avoided codon pairs contain the patterns nnUAnn, nnGGnn, nnGnnC, nnCGCn, GUCCnn, CUCCnn, nnCnnA or UUCGnn. The most frequently preferred codon pairs contain the patterns nnGCnn, nnCAnn or nnUnCn.
Amperean Pairing and the Pseudogap Phase of Cuprate Superconductors
Lee, Patrick A.
2014-07-01
The enigmatic pseudogap phase in underdoped cuprate high-Tc superconductors has long been recognized as a central puzzle of the Tc problem. Recent data show that the pseudogap is likely a distinct phase, characterized by a medium range and quasistatic charge ordering. However, the origin of the ordering wave vector and the mechanism of the charge order is unknown. At the same time, earlier data show that precursive superconducting fluctuations are also associated with this phase. We propose that the pseudogap phase is a novel pairing state where electrons on the same side of the Fermi surface are paired, in strong contrast with conventional Bardeen-Cooper-Schrieffer theory which pairs electrons on opposite sides of the Fermi surface. In this state the Cooper pair carries a net momentum and belongs to a general class called pair density wave. The microscopic pairing mechanism comes from a gauge theory formulation of the resonating valence bond (RVB) picture, where spinons traveling in the same direction feel an attractive force in analogy with Ampere's effects in electromagnetism. We call this Amperean pairing. Charge order automatically appears as a subsidiary order parameter even when long-range pair order is destroyed by phase fluctuations. Our theory gives a prediction of the ordering wave vector which is in good agreement with experiment. Furthermore, the quasiparticle spectrum from our model explains many of the unusual features reported in photoemission experiments. The Fermi arc, the unusual way the tip of the arc terminates, and the relation of the spanning vector of the arc tips to the charge ordering wave vector also come out naturally. Finally, we propose an experiment that can directly test the notion of Amperean pairing.
A nucleon-pair and boson coexistent description of nuclei
Dai, Lianrong; Pan, Feng; Draayer, J. P.
2017-07-01
We study a mixture of s-bosons and like-nucleon pairs with the standard pairing interaction outside an inert core. Competition between the nucleon-pairs and s-bosons is investigated in this scenario. The robustness of the BCS-BEC coexistence and crossover phenomena are examined through an analysis of pf-shell nuclei with realistic single-particle energies, in which two configurations with Pauli blocking of nucleon-pair orbits due to the formation of the s-bosons is taken into account. When the nucleon-pair orbits are considered to be independent of the s-bosons, the BCS-BEC crossover becomes smooth, with the number of the s-bosons noticeably more than that of the nucleon-pairs near the half-shell point, a feature that is demonstrated in the pf-shell for several values of the standard pairing interaction strength. As a further test of the robustness of the BCS-BEC coexistence and crossover phenomena in nuclei, results are given for values of even-even 102-130Sn with 100Sn taken as a core and valence neutron pairs confined within the 1d 5/2, 0g 7/2, 1d 3/2, 2s 1/2, 1h 11/2 orbits in the nucleon-pair orbit and the s-boson independent approximation. The results indicate that the B(E2) values are reproduced well. Supported by National Natural Science Foundation of China (11375080, 11675071), the U.S. National Science Foundation (OCI-0904874 and ACI-1516338), U. S. Department of Energy (DE-SC0005248), the Southeastern Universities Research Association, the China-U. S. Theory Institute for Physics with Exotic Nuclei (CUSTIPEN) (DE-SC0009971), and the LSU-LNNU joint research program (9961) is acknowledged
Hybrid TLC-pair meter for the Sphinx Project
Wada, T.; Yamamoto, I.; Takahashi, N.; Misaki, A.
1985-01-01
The chief aims in THE SPHINX PROJECT are research of super lepton physics and new detector experiments. At the second phase of THE SPHINX PROJECT, a hybrid TLC-PAIR METER was designed for measuring high energy neutrino sources (E upsilon * TeV), searching high energy muon sources (E mu TeV) and measuring muon group (E mu 1 TeV). The principle of PAIR METER has been already proposed. In this TLC-PAIR METER, electromagnetic shower induced by cosmic ray muons are detected using TL (Thermoluminescence) sheets with position counters.