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1

Thermoelectric effect in Aharonov–Bohm structures  

NASA Astrophysics Data System (ADS)

The thermoelectric effects of a single Aharonov–Bohm (SAB) ring and coupled double Aharonov–Bohm (DAB) rings have been investigated on a theoretical basis, taking into account the contributions of both electrons and phonons to the transport process by using the nonequilibrium Green's function technique. The thermoelectric figure of merit of the coupled DAB rings cannot be predicted directly by combining the values of two SAB ring systems due to the contribution of electron–phonon interaction to coupling between the two sites connecting the rings. We find that thermoelectric efficiency can be optimized by modulating the phases of the magnetic flux threading the two rings.

Lu, Xin; Wang, Jian-Sheng; Morrel, William G.; Ni, Xiaoxi; Wu, Chang-Qin; Li, Baowen

2015-01-01

2

Aharonov-Bohm ring with fluctuating flux  

NASA Astrophysics Data System (ADS)

We consider a noninteracting system of electrons on a clean one-channel Aharonov-Bohm ring that is threaded by a fluctuating magnetic flux. The flux derives from a Caldeira-Leggett bath of harmonic oscillators. We address the influence of the bath on the following properties: one- and two-particle Green's functions, dephasing, persistent current, and visibility of the Aharonov-Bohm effect in cotunneling transport through the ring. For the bath spectra considered here (including Nyquist noise of an external coil), we find no dephasing in the linear transport regime at zero temperature.

Marquardt, Florian; Bruder, C.

2002-03-01

3

The electric Aharonov-Bohm effect  

SciTech Connect

The seminal paper of Aharonov and Bohm [Phys. Rev. 115, 485 (1959)] is at the origin of a very extensive literature in some of the more fundamental issues in physics. They claimed that electromagnetic fields can act at a distance on charged particles even if they are identically zero in the region of space where the particles propagate, that the fundamental electromagnetic quantities in quantum physics are not only the electromagnetic fields but also the circulations of the electromagnetic potentials; what gives them a real physical significance. They proposed two experiments to verify their theoretical conclusions. The magnetic Aharonov-Bohm effect, where an electron is influenced by a magnetic field that is zero in the region of space accessible to the electron, and the electric Aharonov-Bohm effect where an electron is affected by a time-dependent electric potential that is constant in the region where the electron is propagating, i.e., such that the electric field vanishes along its trajectory. The Aharonov-Bohm effects imply such a strong departure from the physical intuition coming from classical physics that it is no wonder that they remain a highly controversial issue after more than fifty years, in spite of the fact that they are discussed in most of the text books in quantum mechanics. The magnetic case has been studied extensively. The experimental issues were settled by the remarkable experiments of Tonomura et al. [Phys. Rev. Lett. 48, 1443 (1982); Phys. Rev. Lett. 56, 792 (1986)] with toroidal magnets, that gave a strong evidence of the existence of the effect, and by the recent experiment of Caprez et al. [Phys. Rev. Lett. 99, 210401 (2007)] that shows that the results of the Tonomura et al. experiments cannot be explained by the action of a force. The theoretical issues were settled by Ballesteros and Weder [Commun. Math. Phys. 285, 345 (2009); J. Math. Phys. 50, 122108 (2009); Commun. Math. Phys. 303, 175 (2011)] who rigorously proved that quantum mechanics predicts the experimental results of Tonomura et al. and of Caprez et al. The electric Aharonov-Bohm effect has been much less studied. Actually, its existence, that has not been confirmed experimentally, is a very controversial issue. In their 1959 paper Aharonov and Bohm proposed an ansatz for the solution to the Schroedinger equation in regions where there is a time-dependent electric potential that is constant in space. It consists in multiplying the free evolution by a phase given by the integral in time of the potential. The validity of this ansatz predicts interference fringes between parts of a coherent electron beam that are subjected to different potentials. In this paper we prove that the exact solution to the Schroedinger equation is given by the Aharonov-Bohm ansatz up to an error bound in norm that is uniform in time and that decays as a constant divided by the velocity. Our results give, for the first time, a rigorous proof that quantum mechanics predicts the existence of the electric Aharonov-Bohm effect, under conditions that we provide. We hope that our results will stimulate the experimental research on the electric Aharonov-Bohm effect.

Weder, Ricardo [Departamento de Metodos Matematicos y Numericos, Instituto de Investigaciones en Matematicas Aplicadas y en Sistemas, Universidad Nacional Autonoma de Mexico, Apartado Postal 20-726, Mexico DF 01000 (Mexico)

2011-05-15

4

Dirac Electron in Aharonov-Bohm and Planar Coulomb Potentials  

Microsoft Academic Search

Exact analytic solutions are found to the Dirac equation in (2+1) dimensions for a combination of Aharonov-Bohm and Lorentz 3-vector Coulomb potentials. By means of solutions obtained the relativistic Aharonov-Bohm effect is studied for free and bound electron states.

V. R. Khalilov

2004-01-01

5

Propagator for an Aharonov-Bohm-Coulomb system  

E-print Network

The propagator of three-dimensional Aharonov-Bohm-Coulomb system is calculated by following the Duru-Kleinert method. It is shown that the system is reduced to two independent two dimensional Aharonov-Bohm plus harmonic oscillator systems through dimensional extension and Kustaanheimo-Stiefel transformation. The energy spectrum is deduced.

D. K. Park; Sahng-Kyoon Yoo; Soo-Young Lee; Jae-Rok Kahng; Chang Soo Park; Eui-Soon Yim; C. H. Lee

1997-07-02

6

Force and impulse from an Aharonov-Bohm flux line (Aharonov-Bohm force and impulse)  

Microsoft Academic Search

We calculate the force operator for a charged particle in the field of an Aharonov-Bohm flux line. Formally this is the Lorentz force, with the magnetic field operator modified to include quantum corrections due to anomolous commutation relations. For stationary states, the magnitude of the force is proportional to the product of the wavenumber k with the amplitudes of the

JM Robbins

2000-01-01

7

Aharonov-Bohm radiation of fermions  

SciTech Connect

We analyze Aharonov-Bohm radiation of charged fermions from oscillating solenoids and cosmic strings. We find that the angular pattern of the radiation has features that differ significantly from that for bosons. For example, fermionic radiation in the lowest harmonic is approximately isotropically distributed around an oscillating solenoid, whereas for bosons the radiation is dipolar. We also investigate the spin polarization of the emitted fermion-antifermion pair. Fermionic radiation from kinks and cusps on cosmic strings is shown to depend linearly on the ultraviolet cutoff, suggesting strong emission at an energy scale comparable to the string energy scale.

Chu Yizen; Mathur, Harsh [CERCA, Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106-7079 (United States); Vachaspati, Tanmay [CERCA, Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106-7079 (United States); Institute for Advanced Study, Princeton, New Jersey 08540 (United States)

2010-09-15

8

Deflating the Aharonov-Bohm Effect  

E-print Network

I argue that the metaphysical import of the Aharonov-Bohm effect has been overstated: correctly understood, it does not require either rejection of gauge invariance or any novel form of nonlocality. The conclusion that it does require one or the other follows from a failure to keep track, in the analysis, of the complex scalar field to which the magnetic vector potential is coupled. Once this is recognised, the way is clear to a local account of the ontology of electrodynamics (or at least, to an account no more nonlocal than quantum theory in general requires); I sketch a possible such account.

David Wallace

2014-07-18

9

Quantum chaos in Aharonov-Bohm oscillations  

SciTech Connect

Aharonov-Bohm oscillations in a mesoscopic ballistic ring are considered under the influence of a resonant magnetic field with one and two frequencies. The authors investigate the oscillations of the time-averaged electron energy at zero temperature in the regime of an isolated quantum nonlinear resonance and at the transition to quantum chaos, when two quantum nonlinear resonances overlap. It is shown that the time-averaged energy exhibits resonant behavior as a function of the magnetic flux, and has a ``staircase`` dependence on the amplitude of the external field. The delocalization of the quasi-energy eigenfunctions is analyzed.

Berman, G.P. [Los Alamos National Lab., NM (United States). Theoretical Div.; Campbell, D.K. [Univ. of Illinois, Urbana, IL (United States). Dept. of Physics; Bulgakov, E.N. [Kirensky Inst. of Physics, Krasnoyarsk (Russian Federation); Krive, I.V. [Ukrainian Academy of Sciences, Kharkov (Ukraine). Inst. for Low Temperature Physics and Engineering

1995-10-01

10

Locality of the Aharonov-Bohm-Casher effect  

E-print Network

We address the question of the locality versus nonlocality in the Aharonov-Bohm and the Aharonov-Casher effects. For this purpose, we investigate all possible configurations of ideal shielding of the overlap between the electromagnetic fields generated by a charge and by a magnetic flux, and analyze their consequences on the Aharonov-Bohm-Casher interference. In a classical treatment of shielding, the Aharonov-Bohm-Casher effect vanishes regardless of the geometry of shielding, when the local overlap of electromagnetic fields is completely eliminated. On the other hand, the result depends on the configuration of shielding if the charge quantization in the superconducting shield is taken into account. It is shown that our results are fully understood in terms of the fluctuating local-field interaction. Our analysis strongly supports the alternative view on the Aharonov-Bohm-Casher interference that the effects originate from the local action of electromagnetic fields.

Kicheon Kang

2014-08-04

11

Classical Electrodynamics without Fields and the Aharonov-Bohm effect  

Microsoft Academic Search

The Darwin-Breit Hamiltonian is applied to the Aharonov-Bohm experiment. In agreement with the standard Maxwell-Lorentz theory, the force acting on electrons from infinite solenoids or ferromagnetic rods vanishes. However, the interaction energies and phase factors of the electron wave packets are non-zero. This allows us to explain the Aharonov-Bohm effect without involvement of electromagnetic potentials, fields, and topological properties of

Eugene V. Stefanovich

2008-01-01

12

Relativistic Aharonov--Bohm effect in the presence of two-dimensional Coulomb potential  

E-print Network

We obtain exact solutions to the Dirac equation and the relevant binding energies in the combined Aharonov--Bohm--Coulomb potential in 2+1 dimensions. By means of solutions obtained the quantum Aharonov--Bohm effect is studied for free and bound electron states. We show that the total scattering amplitude in the combined Aharonov--Bohm--Coulomb potential is a sum of the Aharonov--Bohm and the Coulomb scattering amplitudes. This modifies expression for the standard Aharonov--Bohm cross section due to the interference these two amplitudes with each other.

Khalilov, V

2004-01-01

13

Aharonov-Bohm magnetism and Landau diamagnetism in semimetals  

E-print Network

We compute the magnetic response of hollow semimetal cylinders and rings to the presence of an axial Aharonov-Bohm magnetic flux, in the absence of interactions. We predict nullification of the Aharonov-Bohm effect for a class of dispersion laws that includes "non-relativistic" dispersion and demonstrate that at zero flux the ground-state of a very short "armchair" graphene tube will exhibit a ferromagnetic broken symmetry. We also compute the diamagnetic response of bulk semimetals to the presence of a uniform magnetic field, specifically predicting that the susceptibility has a logarithmic dependence on the size of the sample.

Eugene B. Kolomeisky; Joseph P. Straley

2011-12-29

14

Aharonov-Bohm magnetism and Landau diamagnetism in semimetals  

E-print Network

We compute the magnetic response of hollow semimetal cylinders and rings to the presence of an axial Aharonov-Bohm magnetic flux, in the absence of interactions. We predict nullification of the Aharonov-Bohm effect for a class of dispersion laws that includes "non-relativistic" dispersion and demonstrate that at zero flux the ground-state of a very short "armchair" graphene tube will exhibit a ferromagnetic broken symmetry. We also compute the diamagnetic response of bulk semimetals to the presence of a uniform magnetic field, specifically predicting that the susceptibility has a logarithmic dependence on the size of the sample.

Kolomeisky, Eugene B

2011-01-01

15

Symmetry-protected many-body Aharonov-Bohm effect  

E-print Network

It is known as a purely quantum effect that a magnetic flux affects the real physics of a particle, such as the energy spectrum, even if the flux does not interfere with the particle's path—the Aharonov-Bohm effect. Here ...

Santos, Luiz H.

16

Force and impulse from an Aharonov-Bohm flux line  

Microsoft Academic Search

We calculate the force operator for a charged particle in the field of an Aharonov-Bohm flux line. Formally this is the Lorentz force, with the magnetic field operator modified to include quantum corrections due to anomalous commutation relations. For stationary states, the magnitude of the force is proportional to the product of the wavenumber k with the amplitudes of the

J. P. Keating; J. M. Robbins

2001-01-01

17

Spectroscopic version of the Aharonov-Bohm effect  

E-print Network

An experiment is proposed in which the Aharonov-Bohm effect can be veryfied through a spectroscopic measurement. The apparatus consists of gaseous hydrochloric acid (HCl) immersed in the constant vector potential ${\\bf A}=A_0{\\bf z}$ present in the interior of a toroidal coil. Changes due to ${\\bf A}$ in the absorption spectrum of the gas are investigated.

C. Laganá

2014-03-21

18

The Aharonov–Bohm effect in scattering theory  

SciTech Connect

The Aharonov–Bohm effect is considered as a scattering event with nonrelativistic charged particles of the wavelength which is less than the transverse size of an impenetrable magnetic vortex. The quasiclassical WKB method is shown to be efficient in solving this scattering problem. We find that the scattering cross section consists of two terms, one describing the classical phenomenon of elastic reflection and another one describing the quantum phenomenon of diffraction; the Aharonov–Bohm effect is manifested as a fringe shift in the diffraction pattern. Both the classical and the quantum phenomena are independent of the choice of a boundary condition at the vortex edge, providing that probability is conserved. We show that a propagation of charged particles can be controlled by altering the flux of a magnetic vortex placed on their way. -- Highlights: •Aharonov–Bohm effect as a scattering event. •Impenetrable magnetic vortex of nonzero transverse size. •Scattering cross section is independent of a self-adjoint extension employed. •Classical phenomenon of elastic reflection and quantum phenomenon of diffraction. •Aharonov–Bohm effect as a fringe shift in the diffraction pattern.

Sitenko, Yu.A., E-mail: yusitenko@bitp.kiev.ua [Bogolyubov Institute for Theoretical Physics, National Academy of Sciences, 14-b Metrologichna Str., Kyiv, 03680 (Ukraine); Vlasii, N.D. [Physics Department, Taras Shevchenko National University of Kyiv, 64 Volodymyrska str., Kyiv, 01601 (Ukraine)] [Physics Department, Taras Shevchenko National University of Kyiv, 64 Volodymyrska str., Kyiv, 01601 (Ukraine)

2013-12-15

19

Relativistic Aharonov--Bohm effect in the presence of two-dimensional Coulomb potential  

Microsoft Academic Search

We obtain exact solutions to the Dirac equation and the relevant binding\\u000aenergies in the combined Aharonov--Bohm--Coulomb potential in 2+1 dimensions.\\u000aBy means of solutions obtained the quantum Aharonov--Bohm effect is studied for\\u000afree and bound electron states. We show that the total scattering amplitude in\\u000athe combined Aharonov--Bohm--Coulomb potential is a sum of the Aharonov--Bohm\\u000aand the Coulomb scattering

Vladislav Khalilov

2004-01-01

20

Planar massless fermions in Coulomb and Aharonov-Bohm potentials  

E-print Network

Solutions to the Dirac equation are constructed for a massless charged fermion in Coulomb and Aharonov--Bohm potentials in 2+1 dimensions. The Dirac Hamiltonian on this background is singular and needs a one-parameter self-adjoint extension, which can be given in terms of self-adjoint boundary conditions. We show that the virtual (quasistationary) bound states emerge in the presence of an attractive Coulomb potential when the so-called effective charges become overcritical and discuss a restructuring of the vacuum of the quantum electrodynamics when the virtual bound states emerge. We derive equations, which determine the energies and lifetimes of virtual bound states, find solutions of obtained equations for some values of parameters as well as analyze the local density of states as a function of energy in the presence of Coulomb and Aharonov--Bohm potentials.

Khalilov, V R

2013-01-01

21

Diffraction and quasiclassical limit of the Aharonov--Bohm effect  

E-print Network

Since the Aharonov-Bohm effect is the purely quantum effect that has no analogues in classical physics, its persistence in the quasiclassical limit seems to be hardly possible. Nevertheless, we show that the scattering Aharonov-Bohm effect does persist in the quasiclassical limit owing to the diffraction, i.e. the Fraunhofer diffraction in the case when space outside the enclosed magnetic flux is Euclidean, and the Fresnel diffraction in the case when the outer space is conical. Hence, the enclosed magnetic flux can serve as a gate for the propagation of short-wavelength, almost classical, particles. In the case of conical space, this quasiclassical effect which is in principle detectable depends on the particle spin.

Yu. A. Sitenko; N. D. Vlasii

2010-05-26

22

Observation of Aharonov-Bohm Effect by Electron Holography  

Microsoft Academic Search

In this experiment, an electron- and optical-holographic technique is employed with small toroidal ferromagnets each forming a magnetic-flux closure. The holographic interferometry proves that a phase difference between two electron beams having passed through the field-free regions agrees well with the fundamental relation known as the Aharonov-Bohm effect. It is also confirmed from the same hologram that flux leakage from

Akira Tonomura; Tsuyoshi Matsuda; Ryo Suzuki; Akira Fukuhara; Nobuyuki Osakabe; Hiroshi Umezaki; Junji Endo; Kohsei Shinagawa; Yutaka Sugita; Hideo Fujiwara

1982-01-01

23

Magnetotransport in Aharonov-Bohm interferometers: Exact numerical simulations  

NASA Astrophysics Data System (ADS)

The linear conductance of a two-terminal Aharonov-Bohm interferometer is an even function of the applied magnetic flux, as dictated by the Onsager-Casimir symmetry. Away from linear response this symmetry may be broken when many-body interactions are in effect. Using a numerically exact simulation tool, we study the dynamics and the steady-state behavior of the out-of-equilibrium double-dot Aharonov-Bohm interferometer, while considering different types of interactions: Model I includes a closed interferometer with an interdot electron-electron repulsion energy. In model II the interferometer is interacting with a dissipative environment, possibly driven away from equilibrium. In both cases we show that depending on the (horizontal, vertical) mirror symmetries of the setup, nonlinear transport coefficients obey certain magnetosymmetries. We compare numerically exact simulations to phenomenological approaches and special limits: The behavior of model I is compared to self-consistent mean-field calculations and master equation results in the Coulomb blockade regime. Model II, allowing heat dissipation to a thermal bath, is mimicked by an Aharonov-Bohm junction with a voltage probe. In both cases we find that phenomenological treatments capture the relevant transport symmetries, yet significant deviations in magnitude may show up.

Bedkihal, Salil; Segal, Dvira

2014-12-01

24

Aharonov-Bohm Effect: a Quantum Variation and Classical Analogy  

E-print Network

In this work we consider a quantum variation of the usual Aharonov-Bohm effect with two solenoids sufficiently close one to the other so that (external) electron cannot propagate between two solenoids but only around both solenoids. Here magnetic field (or classical vector potential of the electromagnetic field) acting at quantum propagating (external) electron represents the quantum mechanical average value or statistical mixture. It is obtained by wave function of single (internal, quantum propagating within some solenoid wire) electron (or homogeneous ensemble of such (internal) electrons) representing a quantum superposition with two practically non-interfering terms. All this implies that phase difference and interference shape translation of the quantum propagating (external) electron represent the quantum mechanical average value or statistical mixture. On the other hand we consider a classical analogy and variation of the usual Aharonov-Bohm effect in which Aharonov-Bohm solenoid is used for the primary coil inside secondary large coil in the remarkable classical Faraday experiment of the electromagnetic induction.

Vladan Pankovic; Darko Kapor; Stevica Djurovic; Milan Pantic

2014-04-23

25

AHARONOV-BOHM-TYPE EFFECTS IN ANTIDOT ARRAYS AND THEIR DECOHERENCE  

E-print Network

on the low field behavior in this paper. Various aspects of the AB-type oscillation effect in the quantumAHARONOV-BOHM-TYPE EFFECTS IN ANTIDOT ARRAYS AND THEIR DECOHERENCE MASANORI KATO, HIROYASU TANAKAAs/AlGaAs heterostructure. Keywords: Aharonov-Bohm oscillation, two-dimensional electron system, antidot array; vortex glass

Iye, Yasuhiro

26

Inelastic transport through Aharonov-Bohm interferometer in Kondo regime  

SciTech Connect

We formulate elastic and inelastic parts of linear conductance through an Aharonov-Bohm (AB) ring with an embedded quantum dot in the Kondo regime. The inelastic part G{sub inel} is proportional to T{sup 2} when the temperature T is much smaller than the Kondo temperature T{sub K}, whereas it is negligibly small compared with elastic part G{sub el} when T ? T{sub K}. G{sub inel} weakly depends on the magnetic flux penetrating the AB ring, which disturbs the precise detection of G{sub el}/(G{sub el}+G{sub inel}) by the visibility of AB oscillation.

Yoshii, Ryosuke; Eto, Mikio [Faculty of Science and Technology, Keio University, Yokohama 223-8522 (Japan); Sakano, Rui [Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581 (Japan); Affleck, Ian [Department of Physics and Astronomy, University of British Columbia, Vancouver (Canada)

2013-12-04

27

Optically induced Aharonov-Bohm effect in mesoscopic rings  

NASA Astrophysics Data System (ADS)

We show theoretically that strong electron coupling to circularly polarized photons in non-singly-connected nanostructures results in the appearance of an artificial gauge field that changes the electron phase. The effect arises from the breaking of time-reversal symmetry and is analogous to the well-known Aharonov-Bohm phase effect. It can manifest itself in the oscillations of conductance as a function of the intensity and frequency of the illumination. The theory of the effect is elaborated for mesoscopic rings in both ballistic and diffusive regimes.

Sigurdsson, H.; Kibis, O. V.; Shelykh, I. A.

2014-12-01

28

Detection of Majorana fermions in an Aharonov—Bohm interferometer  

NASA Astrophysics Data System (ADS)

By using the non-equilibrium Green's function technique, we investigate the electronic transport properties in an Aharonov—Bohm interferometer coupling with Majorana fermions. We find a fixed unit conductance peak which is independent of the other factors when the topological superconductor is grounded. Especially, an additional phase appears when the topological superconductor is in the strong Coulomb regime, which induces a new conductance resonant peak compared with the structure of replacing the topological superconductor by a quantum dot, and the conductance oscillation with the magnetic flux reveals a 2? phase shift by raising (lowering) a charge on the capacitor.

Shang, En-Ming; Pan, Yi-Ming; Shao, Lu-Bing; Wang, Bai-Gen

2014-05-01

29

Relativistic Aharonov-Bohm effect in the presence of planar Coulomb potentials  

NASA Astrophysics Data System (ADS)

Exact analytic solutions are found to the Dirac equation in 2+1 dimensions for a combination of an Aharonov-Bohm potential and the Lorentz three-vector and scalar Coulomb potentials. By means of the solutions obtained the relativistic quantum Aharonov-Bohm effect is studied for the free (in the presence of a Lorentz three-vector Coulomb potential) and bound fermion states. We obtain the total scattering amplitude in a combination of the Aharonov-Bohm and Lorentz three-vector Coulomb potentials as a sum of two scattering amplitudes. This modifies the expression for the standard Aharonov-Bohm cross section due to the interference of these two amplitudes with each other. We discuss that the observable quantities can be the phases of electron wave functions or the energies of bound states.

Khalilov, V. R.

2005-01-01

30

Fermion bound states in the Aharonov-Bohm field in 2+1 dimensions  

Microsoft Academic Search

We find exact solutions of the Dirac equation that describe fermion bound states in the Aharonov-Bohm potential in 2+1 dimensions with the particle spin taken into account. For this, we construct self-adjoint extensions of the Hamiltonian of the Dirac equation in the Aharonov-Bohm potential in 2+1 dimensions. The self-adjoint extensions depend on a single parameter. We select the range of

V. R. Khalilov

2010-01-01

31

Relativistic Aharonov-Bohm effect in the presence of planar Coulomb potentials  

Microsoft Academic Search

Exact analytic solutions are found to the Dirac equation in 2+1 dimensions for a combination of an Aharonov-Bohm potential and the Lorentz three-vector and scalar Coulomb potentials. By means of the solutions obtained the relativistic quantum Aharonov-Bohm effect is studied for the free (in the presence of a Lorentz three-vector Coulomb potential) and bound fermion states. We obtain the total

V. R. Khalilov

2005-01-01

32

Fermion bound states in the Aharonov-Bohm field in 2+1 dimensions  

Microsoft Academic Search

We find exact solutions of the Dirac equation that describe fermion bound states in the Aharonov-Bohm potential in 2+1 dimensions with the particle spin taken into account. For this, we construct self-adjoint extensions of the Hamiltonian of\\u000a the Dirac equation in the Aharonov-Bohm potential in 2+1 dimensions. The self-adjoint extensions depend on a single parameter. We select the range of

V. R. Khalilov

2010-01-01

33

Planar Massless Fermions in Coulomb and Aharonov-Bohm Potentials  

NASA Astrophysics Data System (ADS)

Solutions to the Dirac equation are constructed for a massless charged fermion in Coulomb and Aharonov-Bohm (AB) potentials in 2+1 dimensions. The Dirac Hamiltonian on this background is singular and needs a one-parameter self-adjoint extension, which can be given in terms of self-adjoint boundary conditions. We show that the virtual (quasistationary) bound states emerge in the presence of an attractive Coulomb potential when the so-called effective charges become overcritical and discuss a restructuring of the vacuum of the quantum electrodynamics when the virtual bound states emerge. We derive equations, which determine the energies and lifetimes of virtual bound states, find solutions of obtained equations for some values of parameters as well as analyze the local density of states (LDOS) as a function of energy in the presence of Coulomb and AB potentials.

Khalilov, V. R.; Lee, K. E.

2012-11-01

34

Dirac fermion in planar Coulomb and Aharonov--Bohm potentials  

E-print Network

Exact analytic solutions and the eigenenergies are found for the Dirac equation in 2+1 dimensions for a spin-one-half particle in a combination of the Lorentz 3-vector and scalar Coulomb as well as Aharonov--Bohm potentials. We employ the two-component Dirac equation which contains a new parameter introduced by Hagen to describe the spin of the spin-1/2 particle. We derive a transcendental equations that implicitly determine the energy spectrum of an electron near the negative-energy continuum boundary and the critical charges for some electron states. Fermion pair production from a vacuum by a strong Coulomb field in the presence of the magnetic flux tube of zero radius is considered. It is shown that the presence of the Ahanorov--Bohm flux tends to stabilize the system.

Khalilov, V R

2007-01-01

35

Fizeau`s experiment and the Aharonov--Bohm effect  

SciTech Connect

The electromagnetic wave equations in a moving medium may be approximated by a form similar to that of the Schroedinger equation for a particle in an electromagnetic field, with the velocity {bold v} of the medium and the vorticity {del}{times}{bold v} playing the roles of the vector potential and magnetic field, re- spectively. A purely classical optical analogue of the Aharonov--Bohm effect follows by consider- ation of the interference pattern produced by two beams, each of which propagates in a region with zero vorticity, but such that the flux of the vorticity through the closed loop defined by the optical paths does not vanish. Fizeau`s experiment (1851) on the velocity of light in moving media may be regarded as an example of such a situation. {copyright} {ital 1995} {ital American} {ital Association} {ital of} {ital Physics} {ital Teachers}.

Cook, R.J. [Department of Physics, United States Air Force Academy, Colorado Springs, Colorado 80840 (United States); Fearn, H.; Milonni, P.W. [Theoretical Division (T-4), Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1995-08-01

36

An Aharonov-Bohm interferometer for determining Bloch band topology.  

PubMed

The geometric structure of a single-particle energy band in a solid is fundamental for a wide range of many-body phenomena and is uniquely characterized by the distribution of Berry curvature over the Brillouin zone. We realize an atomic interferometer to measure Berry flux in momentum space, in analogy to an Aharonov-Bohm interferometer that measures magnetic flux in real space. We demonstrate the interferometer for a graphene-type hexagonal optical lattice loaded with bosonic atoms. By detecting the singular ? Berry flux localized at each Dirac point, we establish the high momentum resolution of this interferometric technique. Our work forms the basis for a general framework to fully characterize topological band structures. PMID:25525160

Duca, L; Li, T; Reitter, M; Bloch, I; Schleier-Smith, M; Schneider, U

2015-01-16

37

Magnetic edge states in Aharonov-Bohm graphene quantum rings  

SciTech Connect

The effect of electron-electron interaction on the electronic structure of Aharonov-Bohm (AB) graphene quantum rings (GQRs) is explored theoretically using the single-band tight-binding Hamiltonian and the mean-field Hubbard model. The electronic states and magnetic properties of hexagonal, triangular, and circular GQRs with different sizes and zigzag edge terminations are studied. The results show that, although the AB oscillations in the all types of nanoring are affected by the interaction, the spin splitting in the AB oscillations strongly depends on the geometry and the size of graphene nanorings. We found that the total spin of hexagonal and circular rings is zero and therefore, no spin splitting can be observed in the AB oscillations. However, the non-zero magnetization of the triangular rings breaks the degeneracy between spin-up and spin-down electrons, which produces spin-polarized AB oscillations.

Farghadan, R., E-mail: rfarghadan@kashanu.ac.ir; Heidari Semiromi, E. [Department of Physics, University of Kashan, Kashan (Iran, Islamic Republic of); Saffarzadeh, A. [Department of Physics, Payame Noor University, P.O. Box 19395-3697 Tehran (Iran, Islamic Republic of); Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada)

2013-12-07

38

Size effects in Aharonov-Bohm graphene rings  

NASA Astrophysics Data System (ADS)

Aharonov-Bohm (AB) effects in mesoscopic metal rings have been extensively studied. In this paper, we investigate these effects on the persistent currents (PCs) in a closed graphene ring with broken time-reversal symmetry. A hard boundary condition is introduced to describe the Dirac electrons moving along such a ring-shaped configuration, and then the induced persistent currents are numerically calculated. Differing from the properties of PCs revealed in the metal AB rings, we show that the present PCs neither show the regular saw-tooth-like features nor present the odd-even symmetry of the electron number. More interestingly, we show that the energy difference between the two valleys and the amplitude of the oscillating PCs increase with the decrease (increase) of the radius (width) of the graphene ring. Our results imply that the AB effect and size-dependent PCs in ring-shaped microstructures could be tested at room temperature.

Yan, Cong-Hua; Wei, Lian-Fu

2010-07-01

39

Electron in the Aharonov-Bohm potential and in the Coulomb field in 2+1 dimensions  

Microsoft Academic Search

We obtain exact solutions of the Dirac equation in 2+1 dimensions and the electron energy spectrum in the superposition of\\u000a the Aharonov-Bohm and Coulomb potentials, which are used to study the Aharonov-Bohm effect for states with continuous and\\u000a discrete energy spectra. We represent the total scattering amplitude as the sum of amplitudes of scattering by the Aharonov-Bohm\\u000a and Coulomb potentials.

V. R. Khalilov

2006-01-01

40

Electron in the Aharonov-Bohm potential and in the Coulomb field in 2+1 dimensions  

Microsoft Academic Search

We obtain exact solutions of the Dirac equation in 2+1 dimensions and the electron energy spectrum in the superposition of the Aharonov-Bohm and Coulomb potentials, which are used to study the Aharonov-Bohm effect for states with continuous and discrete energy spectra. We represent the total scattering amplitude as the sum of amplitudes of scattering by the Aharonov-Bohm and Coulomb potentials.

V. R. Khalilov

2006-01-01

41

Aharonov-Bohm interference in topological insulator nanoribbons.  

PubMed

Topological insulators represent unusual phases of quantum matter with an insulating bulk gap and gapless edges or surface states. The two-dimensional topological insulator phase was predicted in HgTe quantum wells and confirmed by transport measurements. Recently, Bi(2)Se(3) and related materials have been proposed as three-dimensional topological insulators with a single Dirac cone on the surface, protected by time-reversal symmetry. The topological surface states have been observed by angle-resolved photoemission spectroscopy experiments. However, few transport measurements in this context have been reported, presumably owing to the predominance of bulk carriers from crystal defects or thermal excitations. Here we show unambiguous transport evidence of topological surface states through periodic quantum interference effects in layered single-crystalline Bi(2)Se(3) nanoribbons, which have larger surface-to-volume ratios than bulk materials and can therefore manifest surface effects. Pronounced Aharonov-Bohm oscillations in the magnetoresistance clearly demonstrate the coherent propagation of two-dimensional electrons around the perimeter of the nanoribbon surface, as expected from the topological nature of the surface states. The dominance of the primary h/e oscillation, where h is Planck's constant and e is the electron charge, and its temperature dependence demonstrate the robustness of these states. Our results suggest that topological insulator nanoribbons afford promising materials for future spintronic devices at room temperature. PMID:20010826

Peng, Hailin; Lai, Keji; Kong, Desheng; Meister, Stefan; Chen, Yulin; Qi, Xiao-Liang; Zhang, Shou-Cheng; Shen, Zhi-Xun; Cui, Yi

2010-03-01

42

Fermion bound states in the Aharonov-Bohm field in 2+1 dimensions  

NASA Astrophysics Data System (ADS)

We find exact solutions of the Dirac equation that describe fermion bound states in the Aharonov-Bohm potential in 2+1 dimensions with the particle spin taken into account. For this, we construct self-adjoint extensions of the Hamiltonian of the Dirac equation in the Aharonov-Bohm potential in 2+1 dimensions. The self-adjoint extensions depend on a single parameter. We select the range of this parameter in which quantum fermion states are bound. We demonstrate that the energy levels of particles and antiparticles intersect. Because solutions of the Dirac equation in the Aharonov-Bohm potential in 2+1 dimensions describe the behavior of relativistic fermions in the field of the cosmic string in 3+1 dimensions, our results can presumably be used to describe fermions in the cosmic string field.

Khalilov, V. R.

2010-04-01

43

Tunable spin Seebeck effect in a double Rashba molecule embedded in an Aharonov-Bohm interferometer  

NASA Astrophysics Data System (ADS)

We study the spin-dependent thermoelectric properties of a Rashba quantum dot-molecule embedded in an Aharonov-Bohm interferometer. We show that by tuning conveniently both the Aharonov-Bohm and the Rashba spin orbit-induced phases, the different components of spin can have Seebeck coefficients of equal magnitude and different signs, so that the charge Seebeck coefficient vanishes while the spin Seebeck coefficient is finite. This means that a temperature gradient can produce in this system a spin voltage at the time that the charge voltage is zero, occurring an equivalent to the spin Seebeck effect observed in ferromagnets.

Gómez-Silva, G.; Ávalos-Ovando, O.; Ladrón de Guevara, M. L.; Orellana, P. A.

2014-09-01

44

Solutions of relativistic wave equations in superpositions of Aharonov-Bohm, magnetic, and electric fields  

E-print Network

We present new exact solutions (in 3+1 and 2+1 dimensions) of relativistic wave equations (Klein-Gordon and Dirac) in external electromagnetic fields of special form. These fields are combinations of Aharonov-Bohm solenoid field and some additional electric and magnetic fields. In particular, as such additional fields, we consider longitudinal electric and magnetic fields, some crossed fields, and some special non-uniform fields. The solutions obtained can be useful to study Aharonov-Bohm effect in the corresponding electromagnetic fields.

Bagrov, V G; Tlyachev, V B

2001-01-01

45

Solutions of relativistic wave equations in superpositions of Aharonov-Bohm, magnetic, and electric fields  

NASA Astrophysics Data System (ADS)

We present new exact solutions (in 3+1 and 2+1 dimensions) of relativistic wave equations (Klein-Gordon and Dirac) in external electromagnetic fields of special form. These fields are combinations of Aharonov-Bohm solenoid field and some additional electric and magnetic fields. In particular, as such additional fields, we consider longitudinal electric and magnetic fields, some crossed fields, and some special nonuniform fields. The solutions obtained can be useful to study the Aharonov-Bohm effect in the corresponding electromagnetic fields.

Bagrov, V. G.; Gitman, D. M.; Tlyachev, V. B.

2001-05-01

46

Photon mass and quantum effects of the Aharonov-Bohm type  

SciTech Connect

The magnetic field due to the photon rest mass m{sub ph} modifies the standard results of the Aharonov-Bohm effect for electrons, and of other recent quantum effects. For the effect involving a coherent superposition of beams of particles with opposite electromagnetic properties, by means of a tabletop experiment, the limit m{sub ph}{approx_equal}10{sup -51} g is achievable, improving by 6 orders of magnitude that derived by Boulware and Deser for the Aharonov-Bohm effect.

Spavieri, G. [Centro de Fisica Fundamental, Facultad de Ciencias, Universidad de Los Andes, Merida, 5101-Venezuela (Venezuela); Rodriguez, M. [Departamento de Fisica, FACYT, Universidad de Carabobo, Valencia, 2001-Venezuela (Venezuela)

2007-05-15

47

Cloaking of matter waves under the global Aharonov-Bohm effect  

SciTech Connect

We discuss the Aharonov-Bohm effect of a magnetic flux for its influence on a two-dimensional quantum cloak. It is shown that the matter wave of a charged particle under the global influence of the Aharonov-Bohm effect can still be perfectly cloaked and guided by the quantum cloak. Since the presence of the global influence of a magnetic flux on charged particles is universal, the perfect cloaking and guiding nature not only provides an ideal setup to cloak an object from matter waves but also provides an ideal setup to test the global physics of charged matter waves in the presence of a bare magnetic flux.

Lin, D.-H. [Department of Physics, National Sun Yat-sen University, Kaohsiung 804, Taiwan (China); Luan, P.-G. [Department of Optics and Photonics, National Central University, Jhongli 320, Taiwan (China)

2009-05-15

48

A Simple Proof of Magnetic and Electric Aharonov-Bohm Effects  

E-print Network

Magnetic Aharonov-Bohm effect (AB effect) was studied in hundreds of papers starting with the seminal paper of Aharonov and Bohm [AB] published in 1959. We give a new proof of the magnetic Aharonov-Bohm effect without using the scattering theory and the theory of inverse boundary value problems. We consider separately the cases of one and several obstacles. The electric AB effect was studied much less. We give the first proof of the electric AB effect in domains with moving boundaries. When the boundary does not move with the time the electric AB effect is absent.

Gregory Eskin

2014-07-20

49

Aharonov-Bohm signature for neutral polarized excitons in type-II quantum dot ensembles.  

PubMed

The Aharonov-Bohm effect is commonly believed to be a typical feature of the motion of a charged particle interacting with the electromagnetic vector potential. Here we present a magnetophotoluminescence study of type-II InP/GaAs self-assembled quantum dots, revealing the Aharonov-Bohm-type oscillations for neutral excitons when the hole ground state changes its angular momentum from l(h)=0 to l(h)=1, 2, and 3. The hole-ring parameters derived from a simple model are in excellent agreement with the structural parameters for this system. PMID:15089692

Ribeiro, E; Govorov, A O; Carvalho, W; Medeiros-Ribeiro, G

2004-03-26

50

Stokes' theorem, gauge symmetry and the time-dependent Aharonov-Bohm effect  

SciTech Connect

Stokes' theorem is investigated in the context of the time-dependent Aharonov-Bohm effect—the two-slit quantum interference experiment with a time varying solenoid between the slits. The time varying solenoid produces an electric field which leads to an additional phase shift which is found to exactly cancel the time-dependent part of the usual magnetic Aharonov-Bohm phase shift. This electric field arises from a combination of a non-single valued scalar potential and/or a 3-vector potential. The gauge transformation which leads to the scalar and 3-vector potentials for the electric field is non-single valued. This feature is connected with the non-simply connected topology of the Aharonov-Bohm set-up. The non-single valued nature of the gauge transformation function has interesting consequences for the 4-dimensional Stokes' theorem for the time-dependent Aharonov-Bohm effect. An experimental test of these conclusions is proposed.

Macdougall, James, E-mail: jbm34@mail.fresnostate.edu; Singleton, Douglas, E-mail: dougs@csufresno.edu [Department of Physics, California State University Fresno, Fresno, California 93740-8031 (United States)] [Department of Physics, California State University Fresno, Fresno, California 93740-8031 (United States)

2014-04-15

51

Electron in the Aharonov-Bohm potential and in the Coulomb field in 2+1 dimensions  

NASA Astrophysics Data System (ADS)

We obtain exact solutions of the Dirac equation in 2+1 dimensions and the electron energy spectrum in the superposition of the Aharonov-Bohm and Coulomb potentials, which are used to study the Aharonov-Bohm effect for states with continuous and discrete energy spectra. We represent the total scattering amplitude as the sum of amplitudes of scattering by the Aharonov-Bohm and Coulomb potentials. We show that the gauge-invariant phase of the wave function or the energy of the electron bound state can be observed. We obtain a formula for the scattering cross section of spin-polarized electrons scattered by the Aharonov-Bohm potential. We discuss the problem of the appearance of a bound state if the interaction between the electron spin and the magnetic field is taken into account in the form of the two-dimensional Dirac delta function.

Khalilov, V. R.

2006-12-01

52

Scattering of spin 1\\/2 particles by the 2+1 dimensional noncommutative Aharonov-Bohm potential  

Microsoft Academic Search

In this work we study modifications in the Aharonov-Bohm effect for relativistic spin 1\\/2 particles due to the noncommutativity of spacetime in 2+1 dimensions. The noncommutativity gives rise to a correction to the Aharonov-Bohm potential which is highly singular at the origin, producing divergences in a perturbative expansion around the usual solution of the free Dirac equation. This problem is

A. F. Ferrari; M. Gomes; C. A. Stechhahn

2007-01-01

53

Scattering of spin 1\\/2 particles by the 2+1 dimensional noncommutative Aharonov-Bohm potential  

Microsoft Academic Search

In this work we study modifications in the Aharonov-Bohm effect for\\u000arelativistic spin 1\\/2 particles due to the noncommutativity of spacetime in $2\\u000a+ 1$ dimensions. The noncommutativity gives rise to a correction to the\\u000aAharonov-Bohm potential which is highly singular at the origin, producing\\u000adivergences in a perturbative expansion around the usual solution of the free\\u000aDirac equation. This

A. F. Ferrari; M. Gomes; C. A. Stechhahn

2007-01-01

54

Decoherence of Kondo singlet caused by phase-sensitive detection of Aharonov-Bohm interferometer  

NASA Astrophysics Data System (ADS)

To investigate the decoherence of Kondo singlet, we once again check a model, an Aharonov-Bohm interferometer with a quantum dot coupling to left-right electrodes, which is designed by Yacoby to measure phase-sensitive of a quantum dot. By employing the cluster expansion, the equations of motion of Green's functions are transformed into the corresponding equations of connected Green's functions, which contain the correlation of two conducting electrons. With the method, we show that the Kondo singlet is suppressed by phase-sensitive detection of Aharonov-Bohm interferometer. Our numerical results have provided a qualitative explanation with the anomalous features observed in an experiment by Avinun-Kalish et al. [Phys. Rev. Lett.92 (2004) 156801].

Chen, Ming-Lun; Wang, Shun-Jin

2014-05-01

55

Fermion pair production in planar Coulomb and Aharonov--Bohm potentials  

Microsoft Academic Search

Exact analytic solutions are found for the Dirac equation in 2+1 dimensions for a spin-one-half particle in a combination of the Lorentz 3-vector and scalar Coulomb as well as Aharonov--Bohm potentials. We employ the two-component Dirac equation which contains a new parameter introduced by Hagen to describe the spin of the spin-1\\/2 particle. We derive a transcendental equations that implicitly

V. R. Khalilov; Choon-Lin Ho

2007-01-01

56

Time-dependent Pauli equation in the presence of the Aharonov-Bohm effect  

SciTech Connect

We use the Lewis-Riesenfeld theory to determine the exact form of the wavefunctions of a two-dimensional Pauli equation of a charged spin 1/2 particle with time-dependent mass and frequency in the presence of the Aharonov-Bohm effect and a two-dimensional time-dependent harmonic oscillator. We find that the irregular solution at the origin as well as the regular one contributes to the phase of the wavefunction.

Bouguerra, Y. [Laboratoire de Physique Theorique, Faculte des Sciences, Universite de Jijel, BP 98, Ouled Aissa, Jijel 18000 (Algeria); Bounames, A. [Laboratoire de Physique Theorique, Faculte des Sciences, Universite de Jijel, BP 98, Ouled Aissa, Jijel 18000 (Algeria); Frankfurt Institute of Advanced Studies, Johann Wolfgang Goethe University, Ruth-Moufang-Str. 1, 60438 Frankfurt am Main (Germany); Maamache, M.; Saadi, Y. [Laboratoire de Physique Quantique et Systemes Dynamiques, Faculte des Sciences, Universite Ferhat Abbas de Setif, Setif 19000 (Algeria)

2008-04-15

57

Aharonov-Bohm interferometry with quantum dots: scattering approach versus tunneling picture  

Microsoft Academic Search

We address the question of how to model electron transport through closed Aharonov-Bohm interferometers which contain quantum dots. By explicitly studying interferometers with one and two quantum dots, we establish the connection between a tunneling-Hamiltonian formulation on the one hand and a scattering-matrix approach on the other hand. We prove that, under certain circumstances, both approaches are equivalent, i.e., both

Björn Kubala; Jürgen König

2003-01-01

58

Fractal feature of localized electronic states in Fibonacci arrays of Aharonov-Bohm rings  

Microsoft Academic Search

The property of electronic transport in the Fibonacci array of ideal one-dimensional Aharonov-Bohm rings is studied utilizing the Landauer formalism and by analyzing the quantity called ``the Fibonacci invariant,'' which is derived from renormalization-group ideas. In contrast to previous studies, our invariant is not independent of the Fibonacci generation number j in a limited sense despite its expression having the

Atsushi Nomata; Shinkichi Horie

2007-01-01

59

Quantum nonlinear resonance and quantum chaos in Aharonov-Bohm oscillations in mesoscopic semiconductor rings  

Microsoft Academic Search

We consider Aharonov-Bohm oscillations in a mesoscopic semiconductor ring threaded by both a constant magnetic flux and a time-dependent, resonant magnetic field with one or two frequencies. Working in the ballistic regime, we establish that the theory of ``quantum nonlinear resonance'' applies, and thus that this system represents a possible solid-state realization of ``quantum nonlinear resonance'' and ``quantum chaos.'' In

Gennady P. Berman; Evgeny N. Bulgakov; David K. Campbell; Ilya V. Krive

1997-01-01

60

The Aharonov-Bohm effect: the role of tunneling and associated forces  

E-print Network

Through tunneling, small wavefunction tails can enter a finitely shielded cylinder with a magnetic field inside. When the shielding increases to infinity the Lorentz force goes to zero together with these tails. However, it is shown, by considering the radial derivative of the wavefunction on the cylinder surface, that a flux dependent force remains. This force explains in a natural way the Aharonov-Bohm effect in the idealized case of infinite shielding.

Hegerfeldt, G C

2008-01-01

61

The Aharonov-Bohm effect: the role of tunneling and associated forces  

E-print Network

Through tunneling, or barrier penetration, small wavefunction tails can enter a finitely shielded cylinder with a magnetic field inside. When the shielding increases to infinity the Lorentz force goes to zero together with these tails. However, it is shown, by considering the radial derivative of the wavefunction on the cylinder surface, that a flux dependent force remains. This force explains in a natural way the Aharonov-Bohm effect in the idealized case of infinite shielding.

G. C. Hegerfeldt; J. T. Neumann

2008-02-27

62

Scattering of spin 1/2 particles by the 2+1 dimensional noncommutative Aharonov-Bohm potential  

E-print Network

In this work we study modifications in the Aharonov-Bohm effect for relativistic spin 1/2 particles due to the noncommutativity of spacetime in $2 + 1$ dimensions. The noncommutativity gives rise to a correction to the Aharonov-Bohm potential which is highly singular at the origin, producing divergences in a perturbative expansion around the usual solution of the free Dirac equation. This problem is surmounted by using a perturbative expansion around the exact solution of the \\textit{commutative} Aharonov-Bohm problem. We calculate, in this setting, the scattering amplitude and the corrections to the differential and total cross sections for a spin 1/2 particle, in the small-flux limit.

Ferrari, A F; Stechhahn, C A

2007-01-01

63

Scattering of spin 1/2 particles by the 2+1 dimensional noncommutative Aharonov-Bohm potential  

NASA Astrophysics Data System (ADS)

In this work we study modifications in the Aharonov-Bohm effect for relativistic spin 1/2 particles due to the noncommutativity of spacetime in 2+1 dimensions. The noncommutativity gives rise to a correction to the Aharonov-Bohm potential which is highly singular at the origin, producing divergences in a perturbative expansion around the usual solution of the free Dirac equation. This problem is surmounted by using a perturbative expansion around the exact solution of the commutative Aharonov-Bohm problem. We calculate, in this setting, the scattering amplitude and the corrections to the differential and total cross sections for a spin 1/2 particle, in the small-flux limit.

Ferrari, A. F.; Gomes, M.; Stechhahn, C. A.

2007-10-01

64

Scattering of spin 1/2 particles by the 2+1 dimensional noncommutative Aharonov-Bohm potential  

SciTech Connect

In this work we study modifications in the Aharonov-Bohm effect for relativistic spin 1/2 particles due to the noncommutativity of spacetime in 2+1 dimensions. The noncommutativity gives rise to a correction to the Aharonov-Bohm potential which is highly singular at the origin, producing divergences in a perturbative expansion around the usual solution of the free Dirac equation. This problem is surmounted by using a perturbative expansion around the exact solution of the commutative Aharonov-Bohm problem. We calculate, in this setting, the scattering amplitude and the corrections to the differential and total cross sections for a spin 1/2 particle, in the small-flux limit.

Ferrari, A. F.; Gomes, M.; Stechhahn, C. A. [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318, 05315-970, Sao Paulo, SP (Brazil)

2007-10-15

65

A charged particle in a homogeneous magnetic field accelerated by a time-periodic Aharonov-Bohm flux  

SciTech Connect

We consider a nonrelativistic quantum charged particle moving on a plane under the influence of a uniform magnetic field and driven by a periodically time-dependent Aharonov-Bohm flux. We observe an acceleration effect in the case when the Aharonov-Bohm flux depends on time as a sinusoidal function whose frequency is in resonance with the cyclotron frequency. In particular, the energy of the particle increases linearly for large times. An explicit formula for the acceleration rate is derived with the aid of the quantum averaging method, and then it is checked against a numerical solution and a very good agreement is found. - Highlights: > A nonrelativistic quantum charged particle on a plane. > A homogeneous magnetic field and a periodically time-dependent Aharonov-Bohm flux. > The quantum averaging method applied to a time-dependent system. > A resonance of the AB flux with the cyclotron frequency. > An acceleration with linearly increasing energy; a formula for the acceleration rate.

Kalvoda, T. [Department of Theoretical Computer Science, Faculty of Information Technology, Czech Technical University in Prague, Kolejni 2, 160 00 Praha (Czech Republic); Stovicek, P., E-mail: stovicek@kmlinux.fjfi.cvut.cz [Department of Mathematics, Faculty of Nuclear Science, Czech Technical University in Prague, Trojanova 13, 120 00 Praha (Czech Republic)

2011-10-15

66

A charged particle in a homogeneous magnetic field accelerated by a time periodic Aharonov-Bohm flux  

E-print Network

We consider a nonrelativistic quantum charged particle moving on a plane under the influence of a uniform magnetic field and driven by a periodically time-dependent Aharonov-Bohm flux. We observe an acceleration effect in the case when the Aharonov-Bohm flux depends on time as a sinusoidal function whose frequency is in resonance with the cyclotron frequency. In particular, the energy of the particle increases linearly for large times. An explicit formula for the acceleration rate is derived with the aid of the quantum averaging method, and then it is checked against a numerical solution with a very good agreement.

T. Kalvoda; P. Stovicek

2011-07-14

67

Anyonic Strings and Membranes in Anti de Sitter Space and Dual Aharonov-Bohm Effects  

NASA Astrophysics Data System (ADS)

It is observed that strings in AdS5×S5 and membranes in AdS7×S4 exhibit long range phase interactions. Two well separated membranes dragged around one another in anti de Sitter space (AdS) acquire phases of 2?/N. The same phases are acquired by a well separated F and D string dragged around one another. The phases are shown to correspond to both the standard and a novel type of Aharonov-Bohm effect in the dual field theory.

Hartnoll, Sean A.

2007-03-01

68

Force-free gravitational redshift: proposed gravitational Aharonov-Bohm experiment.  

PubMed

We propose a feasible laboratory interferometry experiment with matter waves in a gravitational potential caused by a pair of artificial field-generating masses. It will demonstrate that the presence of these masses (and, for moving atoms, time dilation) induces a phase shift, even if it does not cause any classical force. The phase shift is identical to that produced by the gravitational redshift (or time dilation) of clocks ticking at the atom's Compton frequency. In analogy to the Aharonov-Bohm effect in electromagnetism, the quantum mechanical phase is a function of the gravitational potential and not the classical forces. PMID:23003927

Hohensee, Michael A; Estey, Brian; Hamilton, Paul; Zeilinger, Anton; Müller, Holger

2012-06-01

69

Quantum nonlinear resonance and quantum chaos in Aharonov-Bohm oscillations in mesoscopic semiconductor rings  

Microsoft Academic Search

We consider Aharonov-Bohm oscillations in a mesoscopic semiconductor ring threaded by both a constant magnetic flux and a time-dependent, resonant magnetic field with one or two frequencies. Working in the ballistic regime, we establish that the theory of {open_quotes}quantum nonlinear resonance{close_quotes} applies, and thus that this system represents a possible solid-state realization of {open_quotes}quantum nonlinear resonance{close_quotes} and {open_quotes}quantum chaos.{close_quotes} In

Gennady Berman; Evgeny Bulgakov; David Campbell; Ilya Krive

1997-01-01

70

Influence of Induced Charges in the Electric Aharonov-Bohm Effect  

E-print Network

This paper states that the induced charge should not be neglected in the electric Aharonov-Bohm effect. If the induced charge is taken into account, the interference pattern of the moving charge will not change with the potential difference between the two metal tubes. It means that the scale potential itself can not affect the phase of the moving charge, and the true factor affecting the phase of the moving charge is the energy of the system including the moving charge and the induced charge.

Rui-Feng Wang

2014-09-24

71

Fermions in scalar Coulomb and Aharonov-Bohm potentials in 2+1 dimensions  

NASA Astrophysics Data System (ADS)

The quantum-mechanical problem of constructing the self-adjoint Hamiltonians is physically rigorously solved for a Dirac Hamiltonian with a Coulomb scalar potential and an Aharonov-Bohm potential in 2+1 dimensions by taking into account a fermion spin. It is found that the Dirac Hamiltonian on this background requires the additional specification of a one-parameter self-adjoint extension, which can be given in terms of the physically acceptable boundary conditions. We derive equations that determine the spectra of the self-adjoint radial Dirac Hamiltonians for various parameter values. We discuss the role of a particle spin as the physical reason of the existence of bound fermion states in a pure Aharonov-Bohm potential and show that the particle and antiparticle states with zero energy exist only owing to the interaction of the fermion spin magnetic moment with the magnetic field. The energy levels of particles and antiparticles are intersected what may signal on the instability of a quantum system.

Khalilov, V. R.; Lee, K. E.

2011-05-01

72

Excitonic Aharonov-Bohm effect in a two-dimensional quantum ring  

SciTech Connect

We study theoretically the optical properties of an exciton in a two-dimensional ring threaded by a magnetic flux. We model the quantum ring by a confining potential that can be continuously tuned from strictly one-dimensional to truly two-dimensional with finite radius-to-width ratio. We present an analytic solution of the problem when the electron-hole interaction is short ranged. The oscillatory dependence of the oscillator strength as a function of the magnetic flux is attributed to the Aharonov-Bohm effect. The amplitude of the oscillations changes upon increasing the width of the quantum ring. We find that the Aharonov-Bohm oscillations of the ground state of the exciton decrease with increasing the width, but, remarkably, the amplitude remains finite down to radius-to-width ratios less than unity. We attribute this resilience of the excitonic oscillations to the nonsimple connectedness of our chosen confinement potential with its centrifugal core at the origin.

Gonzalez-Santander, C.; Dominguez-Adame, F. [Departamento de Fisica de Materiales, Universidad Complutense de Madrid, ES-28040 (Spain); Roemer, R. A. [Department of Physics and Centre for Scientific Computing, University of Warwick, Coventry, CV4 7AL (United Kingdom)

2011-12-15

73

Spin filtering in a Rashba-Dresselhaus-Aharonov-Bohm double-dot interferometer  

NASA Astrophysics Data System (ADS)

We study the spin-dependent transport of spin-1/2 electrons through an interferometer made of two elongated quantum dots or quantum nanowires, which are subject to both an Aharonov-Bohm flux and (Rashba and Dresselhaus) spin-orbit interactions. Similar to the diamond interferometer proposed in our previous papers (Aharony et al 2011 Phys. Rev. B 84 035323; Matityahu et al 2013 Phys. Rev. B 87 205438), we show that the double-dot interferometer can serve as a perfect spin filter due to a spin interference effect. By appropriately tuning the external electric and magnetic fields which determine the Aharonov-Casher and Aharonov-Bohm phases, and with some relations between the various hopping amplitudes and site energies, the interferometer blocks electrons with a specific spin polarization, independent of their energy. The blocked polarization and the polarization of the outgoing electrons is controlled solely by the external electric and magnetic fields and do not depend on the energy of the electrons. Furthermore, the spin filtering conditions become simpler in the linear-response regime, in which the electrons have a fixed energy. Unlike the diamond interferometer, spin filtering in the double-dot interferometer does not require high symmetry between the hopping amplitudes and site energies of the two branches of the interferometer and thus may be more appealing from an experimental point of view.

Matityahu, Shlomi; Aharony, Amnon; Entin-Wohlman, Ora; Tarucha, Seigo

2013-12-01

74

Spontaneous fermion creation in the coulomb field and Aharonov-Bohm potential in 2+1 dimensions  

Microsoft Academic Search

We find exact solutions of the Dirac equation and the fermion energy spectrum in the Coulomb ( vector and scalar) potential and Aharonov-Bohm potential in 2+1 dimensions taking the particle spin into account. We describe the fermion spin using the two-component Dirac equation with the additional ( spin) parameter introduced by Hagen. We consider the effect of creation of fermion

V. R. Khalilov

2009-01-01

75

On the spin- 1/2 Aharonov–Bohm problem in conical space: Bound states, scattering and helicity nonconservation  

SciTech Connect

In this work the bound state and scattering problems for a spin- 1/2 particle undergone to an Aharonov–Bohm potential in a conical space in the nonrelativistic limit are considered. The presence of a ?-function singularity, which comes from the Zeeman spin interaction with the magnetic flux tube, is addressed by the self-adjoint extension method. One of the advantages of the present approach is the determination of the self-adjoint extension parameter in terms of physics of the problem. Expressions for the energy bound states, phase-shift and S matrix are determined in terms of the self-adjoint extension parameter, which is explicitly determined in terms of the parameters of the problem. The relation between the bound state and zero modes and the failure of helicity conservation in the scattering problem and its relation with the gyromagnetic ratio g are discussed. Also, as an application, we consider the spin- 1/2 Aharonov–Bohm problem in conical space plus a two-dimensional isotropic harmonic oscillator. -- Highlights: •Planar dynamics of a spin- 1/2 neutral particle. •Bound state for Aharonov–Bohm systems. •Aharonov–Bohm scattering. •Helicity nonconservation. •Determination of the self-adjoint extension parameter.

Andrade, F.M., E-mail: fmandrade@uepg.br [Departamento de Matemática e Estatística, Universidade Estadual de Ponta Grossa, 84030-900 Ponta Grossa-PR (Brazil); Silva, E.O., E-mail: edilbertoo@gmail.com [Departamento de Física, Universidade Federal do Maranhão, Campus Universitário do Bacanga, 65085-580 São Luís-MA (Brazil); Pereira, M., E-mail: marciano@uepg.br [Departamento de Matemática e Estatística, Universidade Estadual de Ponta Grossa, 84030-900 Ponta Grossa-PR (Brazil)

2013-12-15

76

Aharonov-Bohm Superperiod in a Laughlin Quasiparticle Interferometer F. E. Camino, Wei Zhou, and V. J. Goldman  

E-print Network

Aharonov-Bohm Superperiod in a Laughlin Quasiparticle Interferometer F. E. Camino, Wei Zhou, and V flux quanta (5h=e) observed in a Laughlin quasiparticle interferometer, where an edge channel of the 1. The superperiod is accordingly understood as imposed by the anyonic statistical interaction of Laughlin

Goldman, Vladimir J.

77

The manifestly covariant Aharonov-Bohm effect in terms of the 4D fields  

E-print Network

In this paper it is presented a manifestly covariant formulation of the Aharonov-Bohm (AB) phase difference for the magnetic AB effect . This covariant AB phase is written in terms of the Faraday 2-form F and using the decomposition of F in terms of the electric and magnetic fields as four-dimensional (4D) geometric quantities. It is shown that there is a static electric field outside a stationary solenoid with resistive conductor carrying steady current, which causes that the AB phase difference in the magnetic AB effect may be determined by the electric part of the covariant expression, i.e. by the local influence of the 4D electric field and not, as generally accepted,in terms of nonzero vector potential.

Tomislav Ivezic

2014-07-14

78

Gaussian curvature and global effects: Gravitational Aharonov-Bohm effect revisited  

NASA Astrophysics Data System (ADS)

By using the Gauss-Bonnet formula, the integral of the Gaussian curvature over a 2-surface enclosed by a curve in the asymptotically flat region of a static spacetime was found to be a measure of a gravitational analogue of the Aharonov-Bohm effect by Ford and Vilenkin in the linearized regime. Employing the 1+3 formulation of spacetime decomposition, we study the same effect in the context of the full Einstein field equations for stationary spacetimes. Applying our approach to static tubelike and cylindrical distributions of dust, not only do we recover their result but we also obtain an extra term which is interpreted to be representing the classical version of the Colella-Overhauser-Werner effect (the Colella-Overhauser-Werner experiment).

Nouri-Zonoz, M.; Parvizi, A.

2013-07-01

79

Zero-mass fermions in Coulomb and Aharonov-Bohm potentials in 2+1 dimensions  

NASA Astrophysics Data System (ADS)

We consider the motion of a relativistic charged zero-mass fermion in Coulomb and Aharonov-Bohm potentials in 2+1 dimensions. With these singular external potentials, we construct one-parameter self-adjoint Dirac Hamiltonians classified by self-adjoint boundary conditions. We show that if the so-called effective charge becomes overcritical, then virtual (quasistationary) bound states occur. The wave functions corresponding to these states have large amplitudes near the Coulomb center, and their energy spectrum is quasidiscrete and consists of a number of broadened levels of a width related to the inverse lifetime of the quasistationary state. We derive equations for the quasidiscrete spectra and quasistationary state lifetimes and solve these equations in physically interesting cases. We study the so-called local densities of state, which can be assessed in physical experiments, as functions of the energy and the problem parameters, investigating these densities both analytically and graphically.

Khalilov, V. R.

2013-05-01

80

Effects of quantum deformation on the spin-1/2 Aharonov-Bohm problem  

NASA Astrophysics Data System (ADS)

In this Letter we study the Aharonov-Bohm problem for a spin-1/2 particle in the quantum deformed framework generated by the ?-Poincaré-Hopf algebra. We consider the nonrelativistic limit of the ?-deformed Dirac equation and use the spin-dependent term to impose an upper bound on the magnitude of the deformation parameter ?. By using the self-adjoint extension approach, we examine the scattering and bound state scenarios. After obtaining the scattering phase shift and the S-matrix, the bound states energies are obtained by analyzing the pole structure of the latter. Using a recently developed general regularization prescription [Phys. Rev. D. 85 (2012) 041701(R)], the self-adjoint extension parameter is determined in terms of the physics of the problem. For last, we analyze the problem of helicity conservation.

Andrade, F. M.; Silva, E. O.

2013-02-01

81

Thermoelectric effect in an Aharonov-Bohm ring with an embedded quantum dot  

PubMed Central

Thermoelectric effect is studied in an Aharonov-Bohm interferometer with an embedded quantum dot (QD) in the Coulomb blockade regime. The electrical conductance, electron thermal conductance, thermopower, and thermoelectric figure-of-merit are calculated by using the Keldysh Green's function method. It is found that the figure-of-merit ZT of the QD ring may be quite high due to the Fano effect originated from the quantum interference effect. Moreover, the thermoelectric efficiency is sensitive to the magnitude of the dot-lead and inter-lead coupling strengthes. The effect of intradot Coulomb repulsion on ZT is significant in the weak-coupling regime, and then large ZT values can be obtained at rather high temperature. PMID:22369454

2012-01-01

82

Chaotic Aharonov-Bohm scattering on surfaces of constant negative curvature  

NASA Astrophysics Data System (ADS)

A topological model of the Aharonov-Bohm scattering is presented, where the usual set-up is modelled by a genus-one Riemann surface with two cusps, i.e. leaks infinitely far away. This constant negative-curvature surface is uniformized by the Hecke congruence subgroup ?0(11) of the modular group. The fluxes through the holes are described by the even Dirichlet character for ?0(11). The scattering matrix having only off-diagonal elements (no reflection) is calculated. The fluctuating part of the off-diagonal entries shows a non-trivial dependence on the fluxes as well. The scattering resonances are related to the non-trivial zeros of a Dirichlet L-function. The chaotic nature of the scattering is related to the distribution of primes in arithmetical progressions.

Lévay, Péter

2000-06-01

83

Levinson's theorem and higher degree traces for Aharonov-Bohm operators  

SciTech Connect

We study Levinson-type theorems for the family of Aharonov-Bohm models from different perspectives. The first one is purely analytical involving the explicit calculation of the wave-operators and allowing to determine precisely the various contributions to the left hand side of Levinson's theorem, namely, those due to the scattering operator, the terms at 0-energy and at energy +{infinity}. The second one is based on non-commutative topology revealing the topological nature of Levinson's theorem. We then include the parameters of the family into the topological description obtaining a new type of Levinson's theorem, a higher degree Levinson's theorem. In this context, the Chern number of a bundle defined by a family of projections on bound states is explicitly computed and related to the result of a 3-trace applied on the scattering part of the model.

Kellendonk, Johannes [Universite de Lyon, Universite Lyon I, CNRS UMR5208, Institut Camille Jordan, 43 blvd du 11 novembre 1918, 69622 Villeurbanne Cedex (France); Pankrashkin, Konstantin [Laboratoire de Mathematiques d'Orsay, CNRS UMR 8628, Universite Paris-Sud XI, Batiment 425, 91405 Orsay Cedex (France); Richard, Serge [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571 (Japan)

2011-05-15

84

Interference effects in an Aharonov Bohm ring with random quantum dots  

NASA Astrophysics Data System (ADS)

We investigate electron transport through quantum dots embedded in an Aharonov Bohm ring. One or both of the dots are chaotic and are treated by random matrix theory. The conductance and conductance fluctuations are calculated as a function of the ratio of the level broadening to the average level spacing in the random dots using random scattering matrix theory with a Poisson kernel. Several interference mechanisms in the ring are examined. When one random dot and a single resonance level coexist and the multiple reflection between them is taken into account, the conductance is suppressed as the Fermi level of the leads approaches resonance in the large level broadening regime. For coupled random dot systems, characterized by two different ratios, the conductance is sensitive to the difference between the ratios when the multiple scattering inside the ring is disregarded, while it does not depend on the difference when the scattering is effective.

Aono, Tomosuke; Takahashi, Kazutaka

2007-05-01

85

Multiple-path Quantum Interference Effects in a Double-Aharonov-Bohm Interferometer.  

PubMed

We investigate quantum interference effects in a double-Aharonov-Bohm (AB) interferometer consisting of five quantum dots sandwiched between two metallic electrodes in the case of symmetric dot-electrode couplings by the use of the Green's function equation of motion method. The analytical expression for the linear conductance at zero temperature is derived to interpret numerical results. A three-peak structure in the linear conductance spectrum may evolve into a double-peak structure, and two Fano dips (zero conductance points) may appear in the quantum system when the energy levels of quantum dots in arms are not aligned with one another. The AB oscillation for the magnetic flux threading the double-AB interferometer is also investigated in this paper. Our results show the period of AB oscillation can be converted from 2? to ? by controlling the difference of the magnetic fluxes threading the two quantum rings. PMID:20596314

Yang, Xf; Liu, Ys

2010-01-01

86

Classical light analogue of the non-local Aharonov-Bohm effect  

NASA Astrophysics Data System (ADS)

We demonstrate the existence of a non-local geometric phase in the intensity-intensity correlations of classical incoherent light, that is not seen in the lower-order correlations. This two-photon Pancharatnam phase was observed and modulated in a Mach-Zehnder interferometer. Using acousto-optic interaction, independent phase noise was introduced to light in the two arms of the interferometer to create two independent incoherent classical sources from laser light. The experiment is the classical optical analogue of the multi-particle Aharonov-Bohm effect. As the trajectory of light over the Poincaré sphere introduces a phase shift observable only in the intensity-intensity correlation, it provides a means of deflecting the two-photon wavefront, while having no effect on single photons.

Satapathy, Nandan; Pandey, Deepak; Mehta, Poonam; Sinha, Supurna; Samuel, Joseph; Ramachandran, Hema

2012-03-01

87

Topological phases reviewed: The Aharonov Bohm, Aharonov Casher, and He McKellar Wilkens phases  

SciTech Connect

There are three topological phases related to electromagnetic interactions in quantum mechanics: 1. The Aharonov Bohm phase acquired when a charged particle encircles a magnetic field but travels through a field free region. 2. The Aharonov Casher phase acquired when a magnetic dipole encircles electric charges but travels through a charge free region. 3. The He McKellar Wilkens phase acquired when an electric dipole encircles magnetic charges but travels through a charge free region. We review the conditions under which these phases are indeed topological and their experimental realisation. Because the He McKellar Wilkens phase has been recently observed we pay particular attention to how the basic concept of 'an electric dipole encircles magnetic charges' was realised experimentally, and discuss possible future experimental realisations.

McKellar, B. H. J. [ARC Centre of Excellence for Particle Physics at the Terrascale, School of Physics, University of Melbourne (Australia); He, X-G. [Department of Physics, National Taiwan University, Taipei, Taiwan (China); Klein, A. G. [School of Physics, University of Melbourne (Australia)

2014-03-05

88

Wave-packet rectification in nonlinear electronic systems: A tunable Aharonov-Bohm diode  

PubMed Central

Rectification of electron wave-packets propagating along a quasi-one dimensional chain is commonly achieved via the simultaneous action of nonlinearity and longitudinal asymmetry, both confined to a limited portion of the chain termed wave diode. However, it is conceivable that, in the presence of an external magnetic field, spatial asymmetry perpendicular to the direction of propagation suffices to ensure rectification. This is the case of a nonlinear ring-shaped lattice with different upper and lower halves (diode), which is attached to two elastic chains (leads). The resulting device is mirror symmetric with respect to the ring vertical axis, but mirror asymmetric with respect to the chain direction. Wave propagation along the two diode paths can be modeled for simplicity by a discrete Schrödinger equation with cubic nonlinearities. Numerical simulations demonstrate that, thanks to the Aharonov-Bohm effect, such a diode can be operated by tuning the magnetic flux across the ring. PMID:24691462

Li, Yunyun; Zhou, Jun; Marchesoni, Fabio; Li, Baowen

2014-01-01

89

Analytical expression of Kondo temperature in quantum dot embedded in Aharonov-Bohm ring  

PubMed Central

We theoretically study the Kondo effect in a quantum dot embedded in an Aharonov-Bohm ring, using the "poor man's" scaling method. Analytical expressions of the Kondo temperature TK are given as a function of magnetic flux ? penetrating the ring. In this Kondo problem, there are two characteristic lengths, Lc=?vF?|?˜0| and LK = ?vF = TK, where vF is the Fermi velocity and ?˜0 is the renormalized energy level in the quantum dot. The former is the screening length of the charge fluctuation and the latter is that of the spin fluctuation, i.e., size of Kondo screening cloud. We obtain diferent expressions of TK(?) for (i) Lc ? LK ? L, (ii) Lc ? L ? LK, and (iii) L ? Lc ? LK, where L is the size of the ring. TK is remarkably modulated by ? in cases (ii) and (iii), whereas it hardly depends on ? in case (i). PACS numbers: PMID:22112300

2011-01-01

90

Electromagnetism, Local Covariance, the Aharonov-Bohm Effect and Gauss' Law  

NASA Astrophysics Data System (ADS)

We quantise the massless vector potential A of electromagnetism in the presence of a classical electromagnetic (background) current, j, in a generally covariant way on arbitrary globally hyperbolic spacetimes M. By carefully following general principles and procedures we clarify a number of topological issues. First we combine the interpretation of A as a connection on a principal U(1)-bundle with the perspective of general covariance to deduce a physical gauge equivalence relation, which is intimately related to the Aharonov-Bohm effect. By Peierls' method we subsequently find a Poisson bracket on the space of local, affine observables of the theory. This Poisson bracket is in general degenerate, leading to a quantum theory with non-local behaviour. We show that this non-local behaviour can be fully explained in terms of Gauss' law. Thus our analysis establishes a relationship, via the Poisson bracket, between the Aharonov-Bohm effect and Gauss' law - a relationship which seems to have gone unnoticed so far. Furthermore, we find a formula for the space of electric monopole charges in terms of the topology of the underlying spacetime. Because it costs little extra effort, we emphasise the cohomological perspective and derive our results for general p-form fields A ( p < dim( M)), modulo exact fields, for the Lagrangian density . In conclusion we note that the theory is not locally covariant, in the sense of Brunetti-Fredenhagen-Verch. It is not possible to obtain such a theory by dividing out the centre of the algebras, nor is it physically desirable to do so. Instead we argue that electromagnetism forces us to weaken the axioms of the framework of local covariance, because the failure of locality is physically well-understood and should be accommodated.

Sanders, Ko; Dappiaggi, Claudio; Hack, Thomas-Paul

2014-06-01

91

Spontaneous fermion creation in the coulomb field and Aharonov-Bohm potential in 2+1 dimensions  

NASA Astrophysics Data System (ADS)

We find exact solutions of the Dirac equation and the fermion energy spectrum in the Coulomb ( vector and scalar) potential and Aharonov-Bohm potential in 2+1 dimensions taking the particle spin into account. We describe the fermion spin using the two-component Dirac equation with the additional ( spin) parameter introduced by Hagen. We consider the effect of creation of fermion pairs from the vacuum by a strong Coulomb field in the Aharonov-Bohm potential in 2+1 dimensions. We obtain transcendental equations implicitly determining the electron energy spectrum near the boundary of the lower energy continuum and the critical charge. We numerically solve the equation for the critical charge. We show that for relatively weak magnetic flows, the critical charge decreases ( compared with the case with no magnetic field) if the energy of interaction of the electron spin magnetic moment with the magnetic field is negative and increases if this energy is positive.

Khalilov, V. R.

2009-02-01

92

Spontaneous fermion creation in the coulomb field and Aharonov-Bohm potential in 2+1 dimensions  

Microsoft Academic Search

We find exact solutions of the Dirac equation and the fermion energy spectrum in the Coulomb (vector and scalar) potential and Aharonov-Bohm potential in 2+1 dimensions taking the particle spin into account. We describe the fermion spin using the two-component Dirac equation with\\u000a the additional (spin) parameter introduced by Hagen. We consider the effect of creation of fermion pairs from

V. R. Khalilov

2009-01-01

93

Zero-energy states of fermions in the field of Aharonov--Bohm type in 2+1 dimensions  

Microsoft Academic Search

The quantum-mechanical problem of constructing a self-adjoint Hamiltonian for the Dirac equation in an Aharonov--Bohm field in 2+1 dimensions is solved with taking into account the fermion spin. The one-parameter family of self-adjoint extensions is found for the above Dirac Hamiltonian with particle spin. The correct domain of the self-adjoint Hamiltonian extension selecting by means of acceptable boundary conditions can

V. R. Khalilov

2010-01-01

94

Classical Electromagnetic Interaction of a Point Charge and a Magnetic Moment: Considerations Related to the Aharonov-Bohm Phase Shift  

Microsoft Academic Search

A fundamentally new understanding of the classical electromagetic interaction\\u000aof a point charge and a magnetic moment through order second order in 1\\/c is\\u000asuggested. This relativistic analysis connects together hidden momentum in\\u000amagnets, Solem's strange polarization of the classical hydrogen atom, and the\\u000aAharonov-Bohm Phase shift. We use a relativistic magnetic moment model\\u000aconsisting of many superimposed classical hydrogen

Timothy H. Boyer

2001-01-01

95

Classical Electromagnetic Interaction of a Point Charge and a Magnetic Moment: Considerations Related to the Aharonov–Bohm Phase Shift  

Microsoft Academic Search

A fundamentally new understanding of the classical electromagnetic interaction of a point charge and a magnetic dipole moment through order v\\u000a2\\u000a\\/c\\u000a2\\u000a is suggested. This relativistic analysis connects together hidden momentum in magnets, Solem's strange polarization of the classical hydrogen atom, and the Aharonov–Bohm phase shift. First we review the predictions following from the traditional particle-on-a-frictionless-rigid-ring model for

Timothy H. Boyer

2002-01-01

96

Beating of Aharonov-Bohm oscillations in a closed-loop interferometer  

SciTech Connect

One of the points at issue with closed-loop-type interferometers is beating in the Aharonov-Bohm (AB) oscillations. Recent observations suggest the possibility that the beating results from the Berry-phase pickup by the conducting electrons in materials with the strong spin-orbit interaction (SOI). In this study, we also observed beats in the AB oscillations in a gate-defined closed-loop interferometer fabricated on a GaAs/Al{sub 0.3}Ga{sub 0.7}As two-dimensional electron-gas heterostructure. Since this heterostructure has very small SOI, the picture of the Berry-phase pickup is ruled out. The observation of beats in this study, with the controllability of forming a single transverse subband mode in both arms of our gate-defined interferometer, also rules out the often-claimed multiple transverse subband effect. It is observed that nodes of the beats with an h/2e period exhibit a parabolic distribution for varying the side gate. These results are shown to be well interpreted, without resorting to the SOI effect, by the existence of two-dimensional multiple longitudinal modes in a single transverse subband. The Fourier spectrum of measured conductance, despite showing multiple h/e peaks with the magnetic-field dependence that are very similar to that from strong-SOI materials, can also be interpreted as the two-dimensional multiple-longitudinal-modes effect.

Jo, Sanghyun; Chang, Dong-In; Lee, Hu-Jong [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); National Center for Nanomaterials Technology, Pohang 790-784 (Korea, Republic of); Khym, Gyong Luck; Kang, Kicheon [Department of Physics and Institute for Condensed Matter Theory, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Chung, Yunchul [Department of Physics, Pusan National University, Busan 609-735 (Korea, Republic of); Mahalu, Diana; Umansky, Vladimir [Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100 (Israel)

2007-07-15

97

Creation of planar charged fermions in Coulomb and Aharonov-Bohm potentials  

E-print Network

The creation of charged fermions from the vacuum by a Coulomb field in the presence of an Aharonov--Bohm (AB) potential are studied in 2+1 dimensions. The process is governed by a (singular) Dirac Hamiltonian that requires the supplementary definition in order for it to be treated as a self-adjoint quantum-mechanical operator. By constructing a one-parameter self-adjoint extension of the Dirac Hamiltonian, specified by boundary conditions, we describe the (virtual bound) quasistationary states with "complex energy" emerging in an attractive Coulomb potential, derive for the first time, complex equations (depending upon the electron spin and the extension parameter) for the quasistationary state "complex energy". The constructed self-adjoint Dirac Hamiltonians in Coulomb and AB potentials are applied to provide a correct description to the low-energy electron excitations, as well as the creation of charged quasiparticles from the vacuum in graphene by the Coulomb impurity in the presence of AB potential. It is...

Khalilov, V R

2013-01-01

98

Creation of planar charged fermions in Coulomb and Aharonov-Bohm potentials  

NASA Astrophysics Data System (ADS)

The creation of charged fermions from the vacuum by a Coulomb field in the presence of an Aharonov-Bohm (AB) potential are studied in 2+1 dimensions. The process is governed by a (singular) Dirac Hamiltonian that requires the supplementary definition in order for it to be treated as a self-adjoint quantum-mechanical operator. By constructing a one-parameter self-adjoint extension of the Dirac Hamiltonian, specified by boundary conditions, we describe the (virtual bound) quasistationary states with "complex energy" emerging in an attractive Coulomb potential, derive for the first time, complex equations (depending upon the electron spin and the extension parameter) for the quasistationary state "complex energy". The constructed self-adjoint Dirac Hamiltonians in Coulomb and AB potentials are applied to provide a correct description to the low-energy electron excitations, as well as the creation of charged quasiparticles from the vacuum in graphene by the Coulomb impurity in the presence of AB potential. It is shown that the strong Coulomb field can create charged fermions for some range of the extension parameter.

Khalilov, V. R.

2013-08-01

99

Aharonov–Bohm Effect in the Photodetachment Microscopy of Hydrogen Negative Ions in an Electric Field  

NASA Astrophysics Data System (ADS)

The Aharonov–Bohm (AB) effect in the photodetachment microscopy of the H? ions in an electric field has been studied on the basis of the semiclassical theory. After the H? ion is irradiated by a laser light, they provide a coherent electron source. When the detached electron is accelerated by a uniform electric field, two trajectories of a detached electron which run from the source to the same point on the detector, will interfere with each other and lead to an interference pattern in the photodetachment microscopy. After the solenoid is electrified beside the H? ion, even though no Lorentz force acts on the electron outside the solenoid, the photodetachment microscopy interference pattern on the detector is changed with the variation in the magnetic flux enclosed by the solenoid. This is caused by the AB effect. Under certain conditions, the interference pattern reaches the macroscopic dimensions and could be observed in a direct AB effect experiment. Our study can provide some predictions for the future experimental study of the AB effect in the photodetachment microscopy of negative ions.

Wang, Dehua

2014-09-01

100

A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms  

NASA Astrophysics Data System (ADS)

Cold neutral atoms provide a versatile and controllable platform for emulating various quantum systems. Despite efforts to develop artificial gauge fields in these systems, realizing a unique ideal-solenoid-shaped magnetic field within the quantum domain in any real-world physical system remains elusive. Here we propose a scheme to generate a ``hairline'' solenoid with an extremely small size around 1 micrometer which is smaller than the typical coherence length in cold atoms. Correspondingly, interference effects will play a role in transport. Despite the small size, the magnetic flux imposed on the atoms is very large thanks to the very strong field generated inside the solenoid. By arranging different sets of Laguerre-Gauss (LG) lasers, the generation of Abelian and non-Abelian SU(2) lattice gauge fields is proposed for neutral atoms in ring- and square-shaped optical lattices. As an application, interference patterns of the magnetic type-I Aharonov-Bohm (AB) effect are obtained by evolving atoms along a circle over several tens of lattice cells. During the evolution, the quantum coherence is maintained and the atoms are exposed to a large magnetic flux. The scheme requires only standard optical access, and is robust to weak particle interactions.

Huo, Ming-Xia; Nie, Wei; Hutchinson, David A. W.; Kwek, Leong Chuan

2014-08-01

101

An asymptotic formula for energy eigenvalues in the bound-state Aharonov-Bohm effect  

NASA Astrophysics Data System (ADS)

An asymptotic formula for the energy eigenvalues of a charged particle contained in a cylindrical shell is derived. The formula is used to estimate the eigenvalues when there is a cylindrically symmetric static magnetic-induction field present and the system exhibits the bound-state Aharonov-Bohm effect. It is shown that the errors involved form an 0305-4470/31/47/014/img1 sequence with terms labelled by the radial quantum number. Numerical approximations obtained from the asymptotic formula are compared to those obtained from analytical solutions of Schrödinger's equation in the following two cases. (i) There is no magnetic-induction field in the shell itself but there is a field inside the inner cylinder. (ii) There is a constant magnetic-induction field in the shell as well as a (possibly different) field inside the inner cylinder. In these cases, the radial eigenfunctions are expressible in terms of Bessel functions and confluent hypergeometric functions, respectively. The numerical results are consistent with the asymptotic character of the formula for the energy eigenvalues.

Samandra, R. A.; Healy, W. P.

1998-11-01

102

Interference between two independent electrons: observation of two-particle Aharonov-Bohm interference  

E-print Network

Very much like the ubiquitous quantum interference of a single particle with itself, quantum interference of two independent, but indistinguishable, particles is also possible. This interference is a direct result of quantum exchange statistics, however, it is observed only in the joint probability to find the particles in two separated detectors. Here we report the first observation of such interference fringes between two independent and non-interacting electrons in an interferometer proposed by Yurke et al. and Samuelsson et al. Our experiment resembles the "Hanbury Brown and Twiss" (HBT) experiment, which was performed with classical waves. In the experiment, two independent and mutually incoherent electron beams were each partitioned into two trajectories. The combined four trajectories enclosed an Aharonov-Bohm (AB) flux (but not the two trajectories of a single electron). While individual currents were found to be independent of the AB flux, as expected, the cross-correlation between current fluctuations in two opposite points across the device exhibited strong AB oscillations. This is a direct signature of orbital entanglement between two electrons even though they never interact with each other.

I. Neder; N. Ofek; Y. Chung; M. Heiblum; D. Mahalu; V. Umansky

2007-05-01

103

Effect of vacuum polarization of charged massive fermions in an Aharonov--Bohm field  

E-print Network

The effect of vacuum polarization of charged massive fermions in an Aharonov-Bohm (AB) potential in 2+1 dimensions is investigated. The causal Green's function of the Dirac equation with the AB potential is represented via the regular and irregular solutions of the two-dimensional radial Dirac equation. It is shown that the vacuum current density contains the contribution from free filled states of the negative energy continuum as well as that from a bound unfilled state, which can emerge in the above background due to the interaction of the fermion spin magnetic moment with the AB magnetic field while the induced charge density contains only the contribution from the bound state. The expressions for the vacuum charge and induced current densities are obtained (recovered for massless fermions) for the graphene in the field of infinitesimally thin solenoid perpendicular to the plane of a sample. We also find the bound state energy as a function of magnetic flux, fermion spin and the radius of solenoid as well as discuss the role of the so-called self-adjoint extension parameter and determine it in terms of the physics of the problem.

V. R. Khalilov

2014-07-04

104

Fractal feature of localized electronic states in Fibonacci arrays of Aharonov-Bohm rings  

NASA Astrophysics Data System (ADS)

The property of electronic transport in the Fibonacci array of ideal one-dimensional Aharonov-Bohm rings is studied utilizing the Landauer formalism and by analyzing the quantity called “the Fibonacci invariant,” which is derived from renormalization-group ideas. In contrast to previous studies, our invariant is not independent of the Fibonacci generation number j in a limited sense despite its expression having the same form as the previous ones. Even so, this “ I -function,” which is a j -dependent invariant, is shown to preserve its importance in the study of the transport properties of a quasiperiodic system. The line shape of the I -function at j?15 exhibits a fractal-like behavior within the transmission rift (i.e., fine transmission gap). This fractal-like behavior of the line shape of the I -function is characterized by a scaling law. Self-similarity appears in the trace of the transmission probability, when the scaling index is in good agreement with the scaling index at another j .

Nomata, Atsushi; Horie, Shinkichi

2007-03-01

105

Aharonov-Bohm effect in the spin-incoherent regime of strongly correlated 1D electrons  

NASA Astrophysics Data System (ADS)

Recently the spin-incoherent regime of the interacting one-dimensional electron gas has received much attention. In this regime the exchange coupling of nearest neighbor spins is so small that it is completely disrupted by the thermal motion. This regime is generic to low density 1D systems. It is not captured by the standard Luttinger liquid theory and it is expected to exhibit a number of anomalous properties. One of its unusual features is an anomalous conductance suppression reminiscent of conductance reductions observed in quantum wires and point contacts. Despite its great theoretical interest spin incoherence has not yet been demonstrated conclusively in experiments and specific probes of the regime are needed. In this talk I will discuss various tunneling and Aharonov-Bohm interference geometries [1] that can serve this purpose. Spin incoherence will be shown to have a number of distinctive signatures in such experiments such as magnetic field dependent tunneling exponents [2], a strong magnetic field dependence of the interference contrast, and an anomalous scaling of this contrast with the applied voltage [1]. In collaboration with P.W. Brouwer and A.J. Millis. [1] M. Kindermann, P. W. Brouwer, and A. J. Millis, Phys. Rev. Lett. 97, 036809 (2006). [2] M. Kindermann and P. W. Brouwer, Phys. Rev. B 74, 115121 (2006).

Kindermann, Markus

2007-03-01

106

Aharonov-Bohm effect in relativistic and nonrelativistic two-dimensional electron gases: A comparative study  

NASA Astrophysics Data System (ADS)

We carry out a comparative study of electronic properties of two-dimensional electron gas (2DEG) in a magnetic field of an infinitesimally thin solenoid with relativistic dispersion as in graphene and quadratic dispersion as in semiconducting heterostructures. The problem of ambiguity of the zero-mode solutions of the Dirac equation is treated by considering of a finite radius flux tube which allows to select unique solutions associated with each K point of graphene’s Brillouin zone. Then this radius is allowed to go to zero. On the base of the obtained in this case analytical solutions in the Aharonov-Bohm potential the local density of states (LDOS) and total density of states are calculated. It is shown that in the case of graphene there is an excess of LDOS near the vortex while in 2DEG the LDOS is depleted. This results in excess of the induced by the vortex DOS in graphene and in its depletion in 2DEG. We discuss the application of the results for the local density of states for the scanning tunneling spectroscopy done on graphene.

Slobodeniuk, A. O.; Sharapov, S. G.; Loktev, V. M.

2010-08-01

107

Dephasing in an Aharonov-Bohm interferometer containing a lateral double quantum dot induced by coupling with a quantum dot charge sensor  

E-print Network

We theoretically investigated the dephasing in an Aharonov-Bohm interferometer containing a lateral double quantum dot induced by coupling with a quantum dot charge sensor. We employed the interpolative 2nd-order perturbation theory to include the charge sensing Coulomb interaction. It is shown that the visibility of the Aharonov-Bohm oscillation of the linear conductance decreases monotonically as the sensing Coulomb interaction increases. In particular, for a weak sensing interaction regime, the visibility decreases parabolically, and it behaves linearly for a strong sensing interaction regime.

T. Kubo; Y. Tokura; S. Tarucha

2010-05-12

108

Tracking electron pathways with magnetic field: Aperiodic Aharonov-Bohm oscillations in coherent transport through a periodic array of quantum dots  

NASA Astrophysics Data System (ADS)

We study resonant tunneling through a periodic square array of quantum dots sandwiched between modulation-doped quantum wells. If a magnetic field is applied parallel to the quantum dot plane, the tunneling current exhibits a highly complex Aharonov-Bohm oscillation pattern due to the interference of multiple pathways traversed by a tunneling electron. Individual pathways associated with conductance beats can be enumerated by sweeping the magnetic field at various tilt angles. Remarkably, Aharonov-Bohm oscillations are aperiodic unless the magnetic field slope relative to the quantum dot lattice axes is a rational number.

Petrosyan, L. S.; Shahbazyan, T. V.

2015-01-01

109

Zero-energy states of fermions in the field of Aharonov--Bohm type in 2+1 dimensions  

Microsoft Academic Search

The quantum-mechanical problem of constructing a self-adjoint Hamiltonian for\\u000athe Dirac equation in an Aharonov--Bohm field in 2+1 dimensions is solved with\\u000ataking into account the fermion spin. The one-parameter family of self-adjoint\\u000aextensions is found for the above Dirac Hamiltonian with particle spin. The\\u000acorrect domain of the self-adjoint Hamiltonian extension selecting by means of\\u000aacceptable boundary conditions can

V. R. Khalilov

2010-01-01

110

Aharonov-Bohm effect on AdS{sub 2} and nonlinear supersymmetry of reflectionless Poeschl-Teller system  

SciTech Connect

We explain the origin and the nature of a special nonlinear supersymmetry of a reflectionless Poeschl-Teller system by the Aharonov-Bohm effect for a non-relativistic particle on the AdS{sub 2}. A key role in the supersymmetric structure appearing after reduction by a compact generator of the AdS{sub 2} isometry is shown to be played by the discrete symmetries related to the space and time reflections in the ambient Minkowski space. We also observe that a correspondence between the two quantum non-relativistic systems is somewhat of the AdS/CFT holography nature.

Correa, Francisco [Departamento de Fisica, Universidad de Santiago de Chile, Casilla 307, Santiago 2 (Chile)], E-mail: fco.correa.s@gmail.com; Jakubsky, Vit [Departamento de Fisica, Universidad de Santiago de Chile, Casilla 307, Santiago 2 (Chile)], E-mail: v.jakubsky@gmail.com; Plyushchay, Mikhail S. [Departamento de Fisica, Universidad de Santiago de Chile, Casilla 307, Santiago 2 (Chile)], E-mail: mplyushc@lauca.usach.cl

2009-05-15

111

Zero-energy states of fermions in the field of Aharonov--Bohm type in 2+1 dimensions  

E-print Network

The quantum-mechanical problem of constructing a self-adjoint Hamiltonian for the Dirac equation in an Aharonov--Bohm field in 2+1 dimensions is solved with taking into account the fermion spin. The one-parameter family of self-adjoint extensions is found for the above Dirac Hamiltonian with particle spin. The correct domain of the self-adjoint Hamiltonian extension selecting by means of acceptable boundary conditions can contain regular and singular (at the point ${\\bf r}=0$) square-integrable functions on the half-line with measure $rdr$. We argue that the physical reason of the existence of singular solutions is the additional attractive potential, which appear due to the interaction between the spin magnetic moment of fermion and Aharonov--Bohm magnetic field. For some range of parameters there are bound fermionic states. It is shown that fermion (particle and antiparticle) states with zero energy are intersected what signals on the instability of quantum system and the possibility of a fermion-antifermio...

Khalilov, V R

2010-01-01

112

Mesoscopic photovoltaic effect in GaAs/Ga1-xAlxAs Aharonov-Bohm rings L. Angers, A. Chepelianskii, R. Deblock, B. Reulet, and H. Bouchiat  

E-print Network

Mesoscopic photovoltaic effect in GaAs/Ga1-xAlxAs Aharonov-Bohm rings L. Angers, A. Chepelianskii specific dc voltage. We have investigated this photovoltaic PV effect on GaAs/Ga1-xAlxAs Aharonov is generally done by measuring the dc induced signal sometimes called photovoltaic effect which has also given

Shepelyansky, Dima

113

Magnetoresistance of nanoscale molecular devices based on Aharonov-Bohm interferometry This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

Magnetoresistance of nanoscale molecular devices based on Aharonov-Bohm interferometry This article (2008) 383201 (32pp) doi:10.1088/0953-8984/20/38/383201 TOPICAL REVIEW Magnetoresistance of nanoscale necessary for the construction of nanometer-scale magnetoresistance devices based on an Aharonov

Hod, Oded

114

Role of spin-orbit interaction and Berry's phase in Aharonov-Bohm oscillations  

NASA Astrophysics Data System (ADS)

In this thesis we report the results of study on the role of spin-orbit (SO) interaction in Aharonov-Bohm (A-B) oscillations measured in (311)A GaAs two-dimensional (2D) holes, and the observed novel structures in the Fourier transform (FT) spectra of the A-B oscillations, which we interpret as manifestation of Berry's phase and interference of spin states. In the FT spectra of A-B oscillations measured in GaAs 2D holes, we observed novel structures, which are more complex than what is observed in the A-B measurements done in other materials (e.g., normal-metals and GaAs 2D electrons). To interpret the experimental data, we develop a simple model which considers A-B effect in a system with strong SO interaction. Using parameters such as spin-splitting energy (DeltaE), splitting of the Fermi wavevector (Deltak), and the effective magnetic field ( Beff), which characterize spin-related properties in GaAs 2D holes, we are able to obtain a qualitatively good agreement between simulations based on this model and experimental results. In addition, through further analysis of experimental data and careful comparison with simulated results, we demonstrate that observation of these novel features in GaAs 2D hole rings is indeed evidence for Berry's phase. Furthermore, it suggests that GaAs 2D hole is an excellent candidate for studying phenomena caused by spins. Moreover, the simple model mentioned above suggests a periodic evolution of A-B oscillations with Deltak, which can be tuned by changing the front gate voltage VFG. In the magnetoresistance of the ring, as VFG is tuned, we observe changes in the FT spectra. These changes can be systematically tracked in terms of simplicity and complexity in the FT structures as a function of V FG. Finally, to study the phase coherence of hole transport in our mesoscopic ring, we measured the temperature dependence of the A-B oscillations. We found that the average oscillation amplitude exhibits a temperature dependence of exp[-L/L?(T)], which represents the dephasing related to the phase coherence length L ? with L?(T) ˜ 1.5 T-1 mum.

Yau, Jeng-Bang

115

Aharonov-Bohm oscillations, quantum decoherence and amplitude modulation in mesoscopic InGaAs/InAlAs rings.  

PubMed

Low-temperature Aharonov-Bohm oscillations in the magnetoresistance of mesoscopic interferometric rings patterned on an InGaAs/InAlAs heterostructure are investigated for their dependence on excitation current and temperature. The rings have an average radius of 650 nm, and a lithographic arm width of 300 nm, yielding pronounced interference oscillations over a wide range of magnetic fields. Apart from a current and temperature dependence, the oscillation amplitude also shows a quasi-periodic modulation with applied magnetic field. The phase coherence length is extracted by analysis of the fundamental and higher Fourier components of the oscillations, and by direct analysis of the amplitude and its dependence on parameters. It is concluded that the Thouless energy forms the measure of excitation energies for quantum decoherence. The amplitude modulation finds an explanation in the effect of the magnetic flux threading the finite width of the interferometer arms. PMID:24096892

Ren, S L; Heremans, J J; Gaspe, C K; Vijeyaragunathan, S; Mishima, T D; Santos, M B

2013-10-30

116

Spin accumulation in a double-quantum-dot Aharonov-Bohm interferometer induced by Fano-Rashba effect  

NASA Astrophysics Data System (ADS)

Motivated by the results in the previous work (Phys. Rev. B 73, 235301), we investigate the nonequilibrium spin accumulation in a double-quantum-dot Aharonov-Bohm interferometer, by considering a local Rashba interaction in this structure. It is found that the spin accumulation is determined by the nonresonant transmission and Rashba interaction. Namely, the Fano-Rashba effect is a necessary condition to achieve the spin accumulation in the quantum dot of the resonant channel. Furthermore, the spin accumulation can be adjusted by the shift of the level of the nonresonant-channel quantum dot. When the intradot Coulomb interactions are taken into account within the Hubbard-I approximation, the spin accumulation is fully manipulated.

Wu, Haina; Han, Yu; Wang, Yan; Gong, Wei-Jiang

2013-06-01

117

Reduction by symmetries in singular quantum-mechanical problems: general scheme and application to Aharonov-Bohm model  

E-print Network

We develop a general technique for finding self-adjoint extensions of a symmetric operator that respect a given set of its symmetries. Problems of this type naturally arise when considering two- and three-dimensional Schr\\"odinger operators with singular potentials. The approach is based on constructing a unitary transformation diagonalizing the symmetries and reducing the initial operator to the direct integral of a suitable family of partial operators. We prove that symmetry preserving self-adjoint extensions of the initial operator are in a one-to-one correspondence with measurable families of self-adjoint extensions of partial operators obtained by reduction. The general scheme is applied to the three-dimensional Aharonov-Bohm Hamiltonian describing the electron in the magnetic field of an infinitely thin solenoid. We construct all self-adjoint extensions of this Hamiltonian, invariant under translations along the solenoid and rotations around it, and explicitly find their eigenfunction expansions.

A. G. Smirnov

2014-12-15

118

Distinguishability of stacks in ZnTe/ZnSe quantum dots via spectral analysis of Aharonov-Bohm oscillations  

NASA Astrophysics Data System (ADS)

A spectral analysis of the Aharonov-Bohm (AB) oscillations in photoluminescence intensity was performed for stacked type-II ZnTe/ZnSe quantum dots (QDs) fabricated within multilayered Zn-Se-Te system with sub-monolayer insertions of Te. Robust AB oscillations allowed for fine probing of distinguishable QDs stacks within the ensemble of QDs. The AB transition magnetic field, B AB , changed from the lower energy side to the higher energy side of the PL spectra revealing the presence of different sets of QDs stacks. The change occurs within the spectral range, where the contributing green and blue bands of the spectra overlapped. "Bundling" in lifetime measurements is seen at transition spectral regions confirming the results.

Roy, Bidisha; Ji, Haojie; Dhomkar, Siddharth; Cadieu, Fred J.; Peng, Le; Moug, Richard; Tamargo, Maria C.; Kuskovsky, Igor L.

2013-02-01

119

Single-Slit Electron Diffraction with Aharonov-Bohm Phase: Feynman's Thought Experiment with Quantum Point Contacts  

NASA Astrophysics Data System (ADS)

In a "thought experiment," now a classic in physics pedagogy, Feynman visualizes Young's double-slit interference experiment with electrons in magnetic field. He shows that the addition of an Aharonov-Bohm phase is equivalent to shifting the zero-field wave interference pattern by an angle expected from the Lorentz force calculation for classical particles. We have performed this experiment with one slit, instead of two, where ballistic electrons within two-dimensional electron gas diffract through a small orifice formed by a quantum point contact (QPC). As the QPC width is comparable to the electron wavelength, the observed intensity profile is further modulated by the transverse waveguide modes present at the injector QPC. Our experiments open the way to realizing diffraction-based ideas in mesoscopic physics.

Khatua, Pradip; Bansal, Bhavtosh; Shahar, Dan

2014-01-01

120

Spin-dependent quantum interference in Aharonov-Bohm ring embedded with two double-quantum-dot molecules.  

PubMed

The spin polarized transport properties through an Aharonov-Bohm ring embedded with a double quantum dot-molecule in each arm with Rashba spin-orbit (RSO) interaction is theoretically studied in the framework of the equation of motion of Green's function. Based on molecular state representation, the anti-resonance phenomenon in the conductance spectrum is readily explained. We found that the position of antiresonant peaks in conductance spectrum is determined by the interdot coupling strengths. Moreover, the magnitude of conductance of each spin component can be manipulated by the Rashba spin orbit interaction strength. Especially only one spin component electron can be allowed to transport through this structure by modulating the strength of RSO interaction properly. PMID:24745284

Wang, Xiaofei; Liu, Xiaojie; Zhao, Xueyang; Yin, Haitao; Wan, Weilong; Feng, Li

2014-03-01

121

Effective Beam Separation Schemes for the Measurement of the Electric Aharonov-Bohm Effect in an Ion Interferometer  

E-print Network

We propose an experiment for the first proof of the type I electric Aharonov-Bohm effect in an ion interferometer for hydrogen. The performances of three different beam separation schemes are simulated and compared. The coherent ion beam is generated by a single atom tip (SAT) source and separated by either two biprisms with a quadrupole lens, two biprisms with an einzel-lens or three biprisms. The beam path separation is necessary to introduce two metal tubes that can be pulsed with different electric potentials. The high time resolution of a delay line detector allows to work with a continuous ion beam and circumvents the pulsed beam operation as originally suggested by Aharonov and Bohm. We demonstrate, that the higher mass and therefore lower velocity of ions compared to electrons combined with the high expected SAT ion emission puts the direct proof of this quantum effect for the first time into reach of current technical possibilities. Thereby a high coherent ion detection rate is crucial to avoid long integration times that allow the influence of dephasing noise from the environment. We can determine the period of the expected matter wave interference pattern and the signal on the detector by determining the superposition angle of the coherent partial beams. Our simulations were tested with an electron interferometer setup and agree with the experimental results. We determine the separation scheme with three biprisms to be most efficient and predict a total signal acquisition time of only 80 s to measure a phase shift from 0 to 2$\\pi$ due to the electric Aharonov-Bohm effect.

Georg Schütz; Alexander Rembold; Andreas Pooch; Henrike Prochel; Alexander Stibor

2014-12-19

122

Measurement of the second-order Zeeman effect on the sodium clock transition in the weak-magnetic-field region using the scalar Aharonov-Bohm phase  

SciTech Connect

The second-order Zeeman effect of the sodium clock transition in a weak magnetic field of less than 50 {mu}T was measured as the scalar Aharonov-Bohm phase by two-photon stimulated Raman atom interferometry. The ac Stark effect of the Raman pulse was canceled out by adopting an appropriate intensity ratio of two photons in the Raman pulse. The Ramsey fringes for the pulse separation of 7 ms were obtained with a phase uncertainty of {pi}/200 rad. The nondispersive feature of the scalar Aharonov-Bohm phase was clearly demonstrated through 18 fringes with constant amplitude. The Breit-Rabi formula of the sodium clock transition was verified to be {Delta}{nu}=(0.222{+-}0.003)x10{sup 12}xB{sup 1.998{+-}0.004} in a magnetic field of less than 50 {mu}T.

Numazaki, Kazuya; Imai, Hiromitsu; Morinaga, Atsuo [Department of Physics, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510 (Japan)

2010-03-15

123

Quantum interference of surface states in bismuth nanowires probed by the Aharonov-Bohm oscillatory behavior of the magnetoresistance  

NASA Astrophysics Data System (ADS)

We report the observation of an oscillatory dependence of the low-temperature resistance of individual single-crystal bismuth nanowires on the Aharonov-Bohm phase of the magnetic flux threading the wire. 55 and 75nm wires were investigated in magnetic fields of up to 14T . For 55nm nanowires, longitudinal magnetoresistance periods of 0.8 and 1.6T that were observed at magnetic fields over 4T are assigned to h/2e to h/e magnetic flux modulation. The same modes of oscillation were observed in 75nm wires. The observed effects are consistent with models of the Bi surface where surface states give rise to a significant population of charge carriers of high effective mass that form a highly conducting tube around the nanowire. In the 55nm wires, the Fermi energy of the surface band is estimated to be 18meV . An interpretation of the magnetoresistance oscillations in terms of a subband structure in the surface state band caused by quantum interference in the tube is presented.

Nikolaeva, A.; Gitsu, D.; Konopko, L.; Graf, M. J.; Huber, T. E.

2008-02-01

124

Spectral dependence of the Aharonov Bohm effect in the magneto-photoluminescence of layered ZnTe-ZnSe structures  

NASA Astrophysics Data System (ADS)

Aharonov-Bohm (AB) oscillations in the mangeto-photoluminescence (PL) intensity of multilayered ZnTe/ZnSe structures grown via migration enhanced epitaxy (MEE) using three submonolayer deposition cycles of Zn-Te-Zn sandwiched between ZnSe barriers confirmed the presence of type-II ZnTe-based QDs. These co-exist with isoelectronic centers (ICs) as evident from the PL spectra. The spectral dependence of the transition magnetic field and the magnitude of the AB oscillation in intensity are investigated. A qualitative probing of distribution in the ensemble of QDs and ICs was done. The transition magnetic field changed from a lower value at the lower energy side of the PL emission to a higher value at the higher energy side which confirmed the lateral QD size distribution. AB oscillations at spectral positions dominated by emission from ICs were also observed suggesting that the presence of QDs also affects the ICs although the magnitude of the oscillation in the AB peak decreases at such spectral positions.

Roy, Bidisha; Ji, Haojie; Dhomkar, Siddharth; Peng, Le; Moug, Richard; Manna, Uttam; Tamargo, Maria; Cadieu, Fred; Kuskovsky, Igor

2012-02-01

125

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Nonlocal Andreev reflection and spin current in a three-terminal Aharonov-Bohm interferometer  

NASA Astrophysics Data System (ADS)

This paper theoretically reports the nonlocal Andreev reflection and spin current in a normal metal-ferromagnetic metal-superconducting Aharonov-Bohm interferometer. It is found that the electronic current and spin current are sensitive to systematic parameters, such as the gate voltage of quantum dots and the external magnetic flux. The electronic current in the normal metal lead results from two competing processes: quasiparticle transmission and nonlocal Andreev reflection. The appearance of zero spin-up electronic current (or spin-down electronic current) signals the existence of nonlocal Andreev reflection, and the presence of zero electronic current results in the appearance of pure spin current.

Peng, Ju; Yu, Hua-Ling; Wang, Zhi-Guo

2009-12-01

126

VOLUME 87, NUMBER 15 P H Y S I C A L R E V I E W L E T T E R S 8 OCTOBER 2001 Kondo Correlations and the Fano Effect in Closed Aharonov-Bohm Interferometers  

E-print Network

and the Fano Effect in Closed Aharonov-Bohm Interferometers Walter Hofstetter,1 Jürgen König,2,3 and Herbert of the lin- ear conductance G w , which shows a frequency doubling and a maximum at w p 2. Here, F

127

Real-time dynamics of spin-dependent transport through a double-quantum-dot Aharonov-Bohm interferometer with spin-orbit interaction  

NASA Astrophysics Data System (ADS)

The spin-resolved nonequilibrium real-time electron transport through a double-quantum-dot (DQD) Aharonov-Bohm (AB) interferometer with spin-orbit interaction (SOI) is explored. The SOI and AB interference in the real-time dynamics of spin transport is expressed by effective magnetic fluxes. Analytical formulas for the time-dependent currents, for initially unpolarized spins, are presented. In many cases, there appear spin currents in the electrodes, for which the spins in each electrode are polarized along characteristic directions, predetermined by the SOI parameters and by the geometry of the system. Special choices of the system parameters yield steady-state currents in which the spins are fully polarized along these characteristic directions. The time required to reach this steady state depends on the couplings of the DQD to the leads. The magnitudes of the currents depend strongly on the SOI-induced effective fluxes. Without the magnetic flux, the spin-polarized current cannot be sustained to the steady states, due to the phase rigidity for this system. For a nondegenerate DQD, transient spin transport can be produced by the sole effects of SOI. We also show that one can extract the spin-resolved currents from measurements of the total charge current.

Tu, Matisse Wei-Yuan; Aharony, Amnon; Zhang, Wei-Min; Entin-Wohlman, Ora

2014-10-01

128

Real-time dynamics of spin-dependent transport through a double-quantum-dot Aharonov-Bohm interferometer with spin-orbit interaction  

E-print Network

The spin-resolved non-equilibrium real-time electron transport through a double-quantum-dot (DQD) Aharonov-Bohm (AB) interferometer with spin-orbit interaction (SOI) is explored. The SOI and AB interference in the real-time dynamics of spin transport is expressed by effective magnetic fluxes. Analytical formulae for the time-dependent currents, for initially unpolarized spins, are presented. In many cases, there appear spin currents in the electrodes, for which the spins in each electrode are polarized along characteristic directions, pre-determined by the SOI parameters and by the geometry of the system. Special choices of the system parameters yield steady-state currents in which the spins are fully polarized along these characteristic directions. The time required to reach this steady state depends on the couplings of the DQD to the leads. The magnitudes of the currents depend strongly on the SOI-induced effective fluxes. Without the magnetic flux, the spin-polarized current cannot be sustained to the steady states, due to the phase rigidity for this system. For a non-degenerate DQD, transient spin transport can be produced by the sole effects of SOI. We also show that one can extract the spin-resolved currents from measurements of the total charge current.

Matisse Wei-Yuan Tu; Amnon Aharony; Wei-Min Zhang; Ora Entin-Wohlman

2014-10-02

129

Tunable spin-dependent Andreev reflection in a four-terminal Aharonov-Bohm interferometer with coherent indirect coupling and Rashba spin-orbit interaction  

PubMed Central

Using the nonequilibrium Green’s function method, we theoretically study the Andreev reflection(AR) in a four-terminal Aharonov-Bohm interferometer containing a coupled double quantum dot with the Rashba spin-orbit interaction (RSOI) and the coherent indirect coupling via two ferromagnetic leads. When two ferromagnetic electrodes are in the parallel configuration, the spin-up conductance is equal to the spin-down conductance due to the absence of the RSOI. However, for the antiparallel alignment, the spin-polarized AR occurs resulting from the crossed AR (CAR) and the RSOI. The effects of the coherent indirect coupling, RSOI, and magnetic flux on the Andreev-reflected tunneling magnetoresistance are analyzed at length. The spin-related current is calculated, and a distinct swap effect emerges. Furthermore, the pure spin current can be generated due to the CAR when two ferromagnets become two half metals. It is found that the strong RSOI and the large indirect coupling are in favor of the CAR and the production of the strong spin current. The properties of the spin-related current are tunable in terms of the external parameters. Our results offer new ways to manipulate the spin-dependent transport. PMID:23228047

2012-01-01

130

Tunable spin-dependent Andreev reflection in a four-terminal Aharonov-Bohm interferometer with coherent indirect coupling and Rashba spin-orbit interaction.  

PubMed

: Using the nonequilibrium Green's function method, we theoretically study the Andreev reflection(AR) in a four-terminal Aharonov-Bohm interferometer containing a coupled double quantum dot with the Rashba spin-orbit interaction (RSOI) and the coherent indirect coupling via two ferromagnetic leads. When two ferromagnetic electrodes are in the parallel configuration, the spin-up conductance is equal to the spin-down conductance due to the absence of the RSOI. However, for the antiparallel alignment, the spin-polarized AR occurs resulting from the crossed AR (CAR) and the RSOI. The effects of the coherent indirect coupling, RSOI, and magnetic flux on the Andreev-reflected tunneling magnetoresistance are analyzed at length. The spin-related current is calculated, and a distinct swap effect emerges. Furthermore, the pure spin current can be generated due to the CAR when two ferromagnets become two half metals. It is found that the strong RSOI and the large indirect coupling are in favor of the CAR and the production of the strong spin current. The properties of the spin-related current are tunable in terms of the external parameters. Our results offer new ways to manipulate the spin-dependent transport. PMID:23228047

Bai, Long; Zhang, Rong; Duan, Chen-Long

2012-01-01

131

Novel Aharonov-Bohm-like effect: Detectability of the vector potential in a solenoidal configuration with a ferromagnetic core covered by superconducting lead, and surrounded by a thin cylindrical shell of aluminum  

E-print Network

The flux as measured by the Josephson effect in a SQUID-like configuration with a ferromagnetic core inserted into its center, is shown to be sensitive to the vector potential arising from the central ferromagnetic core, even when the core is covered with a superconducting material that prevents any magnetic field lines from ever reaching the perimeter of the SQUID-like configuration. This leads to a macroscopic, Aharonov-Bohm-like effect that is observable in an asymmetric hysteresis loop in the response of the SQUID-like configuration to an externally applied magnetic field.

R. Y. Chiao

2012-06-23

132

Hysteretic method for measuring the flux trapped within the core of a superconducting lead-coated ferromagnetic torus by a linked superconducting tin ring, in a novel Aharonov-Bohm-like effect based on the Feynman path-integral principle  

E-print Network

A novel kind of nonlocal, macroscopic Aharonov-Bohm effect involving two topologically linked superconducting rings made out of two different materials, namely, lead and tin, is suggested for experimental observation, in which the lead ring is a torus containing a core composed of permanently magnetized ferromagnetic material. It is predicted that the remnant fields in a hysteresis loop induced by the application of a magnetic field imposed by a large external pair of Helmholtz coils upon the tin ring, will be asymmetric with respect to the origin of the loop. An appendix based on Feynman's path-integral principle is the basis for these predictions.

Raymond Chiao

2012-05-28

133

Darwin-Lagrangian Analysis for the Interaction of a Point Charge and a Magnet: Considerations Related to the Controversy Regarding the Aharonov-Bohm and Aharonov-Casher Phase Shifts  

E-print Network

The classical electromagnetic interaction of a point charge and a magnet is discussed by first calculating the interaction of point charge with a simple model magnetic moment and then suggesting a multiparticle limit. The Darwin Lagrangian is used to analyze the electromagnetic behavior of the model magnetic moment (composed of two oppositely charged particles of different mass in an initially circular orbit) interacting with a passing point charge. The changing mangetic moment is found to put a force back on a passing charge; this force is of order 1/c^2 and depends upon the magnitude of the magnetic moment. It is suggested that in the limit of a multiparticle magnetic toroid, the electric fields of the passing charge are screened out of the body of the magnet while the magnetic fields penetrate into the magnet. This is consistent with our understanding of the penetration of electromagnetic velocity fields into ohmic conductors. Conservation laws are discussed. The work corresponds to a classical electromagnetic analysis of the interaction which is basic to understanding the controversy over the Aharonov-Bohm and Aharonov-Casher phase shifts and represents a refutation of the suggestions of Aharonov, Pearle, and Vaidman.

Timothy H. Boyer

2005-06-23

134

The Aharonov Bohm effect unrevealed by  

E-print Network

and the experimental setup - Theory The Zone Foldoing model for carbon nanotubes - Ab-initio approach and results Zone to carbon nanotubes Band structure from -* orbitals Curvature of the tubes not considered in the model,0) r=10.36 Bohr r=5.94 Bohr 2 metallic tubes (8,8) (5,5) r=10.22 Bohr r=6.41 Bohr 1 Double walled (5

Marini, Andrea

135

Comment on Macroscopic Test of the Aharonov-Bohm Effect  

E-print Network

In this Comment it is shown that it cannot be argued that in the magnetic AB effect there is no force acting on the particle, i.e., that the observed phase shift is entirely due to nonzero vector potential. In stationary resistive conductors carrying constant currents there are quasistatic surface charges, which generate not only the electric field inside the wire driving the current, but also a static electric field outside it. These external static electric fields have nothing to do with Boyer's force picture and with his result for the existence of a time delay.

Tomislav Ivezic

2014-06-04

136

Fizeau`s experiment and the Aharonov--Bohm effect  

Microsoft Academic Search

The electromagnetic wave equations in a moving medium may be approximated by a form similar to that of the Schroedinger equation for a particle in an electromagnetic field, with the velocity {bold v} of the medium and the vorticity âÃ{bold v} playing the roles of the vector potential and magnetic field, re- spectively. A purely classical optical analogue of the

Richard J. Cook; H. Fearn; P. W. Milonni

1995-01-01

137

Induced current and Aharonov-Bohm effect in graphene  

NASA Astrophysics Data System (ADS)

The effect of vacuum polarization in the field of an infinitesimally thin solenoid at distances much larger than the radius of solenoid is investigated. The induced charge density and induced current are calculated. Though the induced charge density turned out to be zero, the induced current is a finite periodical function of the magnetic flux ? . The expression for this function is found exactly in a value of the flux. The induced current is equal to zero at the integer values of ?/?0 as well as at half-integer values of this ratio, where ?0=2??c/e is the elementary magnetic flux. The latter is a consequence of the Furry theorem and periodicity of the induced current with respect to magnetic flux. As an example we consider the graphene in the field of solenoid perpendicular to the plane of a sample.

Jackiw, R.; Milstein, A. I.; Pi, S.-Y.; Terekhov, I. S.

2009-07-01

138

The time-dependent, electromagnetic Aharonov-Bohm effect  

Microsoft Academic Search

Numerical, time-dependent solutions to the relativistic Dirac equation coupled with an external electromagnetic field are obtained using the staggered leap-frog method on a spatial lattice in two dimentions. The numerical stability of the method is evaluated and ensured by appropriate choices of the lattice constant and the time step. The action of the magnetic or electrostatic potentials in the region

Zachary Kertzman; Athanasios Petridis

2008-01-01

139

The time-dependent, electromagnetic Aharonov-Bohm effect  

NASA Astrophysics Data System (ADS)

Numerical, time-dependent solutions to the relativistic Dirac equation coupled with an external electromagnetic field are obtained using the staggered leap-frog method on a spatial lattice in two dimentions. The numerical stability of the method is evaluated and ensured by appropriate choices of the lattice constant and the time step. The action of the magnetic or electrostatic potentials in the region of zero electromagnetic fields is evaluated by means of the produced diffraction patterns. The time-dependent intereference as the spinor is guided around a quantum ring centered about an infinitely-long solenoid magnet is also studied.

Kertzman, Zachary; Petridis, Athanasios

2008-04-01

140

Induced current and Aharonov-Bohm effect in graphene  

E-print Network

The effect of vacuum polarization in the field of an infinitesimally thin solenoid at distances much larger than the radius of solenoid is investigated. The induced charge density and induced current are calculated. Though ...

Jackiw, Roman

141

Detecting Noncommutative Phase Space by Aharonov-Bohm Effect  

E-print Network

Noncommutative phase space plays an essential role in particle physics and quantum gravity at the Planck scale. However, direct experimental evidence or observation to demonstrate the existence of noncommutative phase space is still lacking.We study a quantum ring in noncommutative phase space based on the Seiberg-Witten map and give the effective magnetic potential and field coming from the noncommutative phase space, which induces the persistent current in the ring. We introduce two variables as two signatures to detect the noncommutative phase space and propose an experimental scheme to detect the noncommutative phase space as long as we measure the persistent current and the external magnetic flux.

Shi-Dong Liang; Haoqi Li; Guang-Yao Huang

2015-02-02

142

The Dynamical Mechanism of the Aharonov-Bohm Effect  

E-print Network

In this paper, it is emphasized that the dynamical cause for the A-B effect is the superimposed energy between the magnetic field produced by the moving charges and that in the solenoid, instead of the existence of the vector potential. If such a superposition between the magnetic fields can be eliminated, the A-B effect should not be observed any more. To verify this viewpoint, a new experimental method using a SQUID is suggested in this paper.

R. F. Wang

2007-05-28

143

THE CONTRIBUTION OF AZO DYES TO THE MUTAGENIC ACTIVITY OF THE CRISTAIS RIVER  

EPA Science Inventory

To verify if compounds within the discharge of a dye processing plant were contributing to the mutagenicity repeatedly found in the Cristais River, Sao Paulo, Brazil, we chemically characterized the treated industrial effluent, raw and treated water, and the sludge produced by a ...

144

AZO DYES ARE MAJOR CONTRIBUTORS TO THE MUTAGENIC ACTIVITY DETECTED IN THE CRISTAIS RIVER WATERS  

EPA Science Inventory

To determine if compounds from a dye processing plant were contributing to the mutagenicity repeatedly found in the Cristais River, Sao Paulo, Brazil, we chemically characterized the treated industrial effluent, raw and treated water, and the sludge produced by a Drinking Water T...

145

THE CASE FOR THE CONTRIBUTION OF CRISTAIS RIVER NITRO-AMINOBENZENE DYES TO THE MUTAGENICITY OF AMBIENT SAMPLES  

EPA Science Inventory

In order to verify if dyestuffs within an effluent of a textile industry was contributing to the systematic mutagenicity detected in the Cristais River, within the metropolitan region of Sao Paulo, mutagenic samples of the industrial effluent, crude water, and treated silt of the...

146

Resistance Fluctuations and AharonovBohm-Type Oscillations in Antidot Arrays in the Quantum Hall Regime  

E-print Network

in the quantum Hall regime are studied. Magnetoresistance of finite antidot array systems in the quantum HallResistance Fluctuations and Aharonov­Bohm-Type Oscillations in Antidot Arrays in the Quantum Hall in the present case. KEYWORDS: GaAs/AlGaAs, two-dimensional electron system, quantum Hall effect, antidot array

Iye, Yasuhiro

147

Transport, Aharonov-Bohm, and Topological Effects in Graphene Molecular Junctions and Graphene Nanorings  

E-print Network

The unique ultra-relativistic, massless, nature of electron states in two-dimensional extended graphene sheets, brought about by the honeycomb lattice arrangement of carbon atoms in two-dimensions, provides ingress to explorations of fundamental physical phenomena in graphene nanostructures. Here we explore the emergence of new behavior of electrons in atomically precise segmented graphene nanoribbons (GNRs) and graphene rings with the use of tight-binding calculations, non-equilibrium Green's function transport theory, and a newly developed Dirac continuum model that absorbs the valence-to-conductance energy gaps as position-dependent masses, including topological-in-origin mass-barriers at the contacts between segments. Through transport investigations in variable-width segmented GNRs with armchair, zigzag, and mixed edge terminations we uncover development of new Fabry-Perot-like interference patterns in segmented GNRs, a crossover from the ultra-relativistic massless regime, characteristic of extended gra...

Yannouleas, Constantine; Landman, Uzi

2015-01-01

148

Exciton storage in type-II quantum dots using the optical Aharonov-Bohm effect  

SciTech Connect

We investigate the bright-to-dark exciton conversion efficiency in type-II quantum dots subject to a perpendicular magnetic field. To this end, we take the exciton storage protocol recently proposed by Simonin and co-workers [Phys. Rev. B 89, 075304 (2014)] and simulate its coherent dynamics. We confirm the storage is efficient in perfectly circular structures subject to weak external electric fields, where adiabatic evolution is dominant. In practice, however, the efficiency rapidly degrades with symmetry lowering. Besides, the use of excited states is likely unfeasible owing to the fast decay rates. We then propose an adaptation of the protocol which does not suffer from these limitations.

Climente, Juan I.; Planelles, Josep, E-mail: josep.planelles@uji.es [Departament de Química Física i Analítica, Universitat Jaume I, E-12080 Castelló (Spain)

2014-05-12

149

Comment on "On the Electric Charge Quantization from the Aharonov-Bohm Potential"  

E-print Network

In the paper quant-ph/0503212, Barone and Halayel-Neto (BH) claim that charge quantization in quantum mechanics can be proven without the need for the existence of magnetic monopoles. In this paper it is argued that their claim is untrue.

R. MacKenzie; H. Paquette; J. Pinel; P. -L. Roussel

2005-04-07

150

Pauli Approximations to the Self-Adjoint Extensions of the Aharonov-Bohm Hamiltonian  

E-print Network

-parameter subfamilies. In these two cases we can choose the gyromagnetic ratio in the approximating Pauli Hamiltonian that the gyromagnetic ratio has to be chosen in a particular way. They do this by by matching the bound states the gyromagnetic ratio

151

Aharonov-Bohm Exciton Splittings in Carbon Nanotubes in Ultra-High Magnetic Fields  

NASA Astrophysics Data System (ADS)

The Ajiki-Ando (A-A) splitting of single-walled carbon nanotubes was observed by the magneto-absorption measurements conducted up to a very high magnetic field, 78 T for PFO-samples. The well-resolved absorption spectra from the E11 transitions in the PFO-samples showed a clear A-A splitting. The electro-magnetic flux compression method was used for generation of the field up to 360 T, where the absorption spectra of the E22 transition of the HiPco samples were measured by the streak spectroscopy. Parameters for the A-A splitting were determined for different chiralty of each case.

Takeyama, S.; Suzuki, H.; Otsubo, Y.; Yokoi, H.; Murakami, Y.; Maruyama, S.

2011-12-01

152

Anyonic strings and membranes in AdS space and dual Aharonov-Bohm effects  

Microsoft Academic Search

It is observed that strings in AdS_5 x S^5 and membranes in AdS_7 x S^4\\u000aexhibit long range phase interactions. Two well separated membranes dragged\\u000aaround one another in AdS acquire phases of 2\\\\pi\\/N. The same phases are\\u000aacquired by a well separated F and D string dragged around one another. The\\u000aphases are shown to correspond to both the

Sean A. Hartnoll

2006-01-01

153

The Dirac equation in Aharonov-Bohm background and regularization-renormalization process of its conformal limit  

Microsoft Academic Search

A thorough analysis is presented of the (2+1) space-time Dirac equation coupled to a confined magnetic field (B0) in both the bound-state sector and the scattering sector of the interacting theory. Contrary to earlier approaches to this problem, we start by keeping all the characteristic physical parameters arbitrary. We present and compare two nonequivalent descriptions: (i) the framework in which

Carlos O. Gorrichategui III

2004-01-01

154

Coherent and semiclassical states in a magnetic field in the presence of the Aharonov-Bohm solenoid  

NASA Astrophysics Data System (ADS)

A new approach to constructing coherent states (CS) and semiclassical states (SS) in a magnetic-solenoid field is proposed. The main idea is based on the fact that the AB solenoid breaks the translational symmetry in the xy-plane; this has a topological effect such that there appear two types of trajectories which embrace and do not embrace the solenoid. Due to this fact, one has to construct two different kinds of CS/SS which correspond to such trajectories in the semiclassical limit. Following this idea, we construct CS in two steps, first the instantaneous CS (ICS) and then the time-dependent CS/SS as an evolution of the ICS. The construction is realized for nonrelativistic and relativistic spinning particles both in (2 + 1) and (3 + 1) dimensions and gives a non-trivial example of SS/CS for systems with a nonquadratic Hamiltonian. It is stressed that CS depending on their parameters (quantum numbers) describe both pure quantum and semiclassical states. An analysis is represented that classifies parameters of the CS in such respect. Such a classification is used for the semiclassical decompositions of various physical quantities.

Bagrov, V. G.; Gavrilov, S. P.; Gitman, D. M.; Meira Filho, D. P.

2011-02-01

155

Mapeamento de Áreas Cafeeiras em imagens de Sensores Orbitais: estudo de caso em Aguanil, Boa Esperança, Campo Belo e Cristais-MG como suporte a estudos regionais  

Microsoft Academic Search

Coffee crop, an important economic and social activity to Brazil, is an agrobusiness segment that has not updated information about the productive profile. The present work comes to add in the sense to develop and\\/or adequate fundamental methods in geotechnologies that may significantly contribute to the study of the coffee crop in Minas Gerais State, allowing to diagnose the geographic

Marco Aurélio Barros

156

J. Phys. III Yance 7 (1997) 1515-1520 JULY 1997, PAGE 1515 Aharonov-Bohm Interference of Holes at Dislocations in  

E-print Network

interference of holes in macroscopic semiconductor sample containing an array of straight-line dislocations interference ill, is now widely observed as magnetoresistance oscillations in metallic or doped in a macroscopic sample, that is in a piece of semiconductor crystal containing an array of parallel dislocations

Boyer, Edmond

157

On the origin of the minimal coupling rule, and on the possiblity of observing a classical, "Aharonov-Bohm-like" angular momentum  

E-print Network

The minimal coupling rule is "derived" starting from Landau's relativistically invariant classical action for a charge in the presence of classical electromagnetic fields. Experiments are then proposed to see the resulting electromagnetic angular momentum of a classical, "lumpy" charged ring enclosing a solenoid. These classical, macroscopic experiments are similar in spirit to those proposed by Aharonov and Bohm at the quantum level.

Raymond Chiao

2011-04-22

158

Challenges for first-principles methods in theoretical and computational physics: multiple excitations in many-electrons systems and the Aharonov-Bohm effect in carbon nanotubes  

NASA Astrophysics Data System (ADS)

The objective of this research is to understand the temperature variation in dielectric materials of different geometry. The work is divided into three major segments. The Thermal Wave model has been taken into consideration as the classical Fourier law of heat conduction breaks down when a dielectric material of sub-micron geometry is heated rapidly. The first part of the work discusses primarily about the temperature distribution in a semi-infinite dielectric material, followed by the temperature profile in a finite body (plate) and finally mathematical formulation is presented for a two-layered body. The thermal wave equation is used because in dielectric materials the lag time due to temperature (taut) is much less than the lag time due to heat flux (tauq), ( taut <

Sarkar, Daipayan

159

The Electromagnetic Duality Formulation of Geometric Phases  

NASA Astrophysics Data System (ADS)

This paper focuses on the electromagnetic(EM) duality formulation of geometric phases of Aharonov-Bohm(A-B) effect and Aharonov-Casher(A-C) effect. Through the two four-vector potential formulation of electromagnetic theory, we construct a EM duality formulation for both A-B effect and A-C effect. The He-McKellar-Wilkens(HMW) effect is included as a EM duality counterpart of the A-C effect, and also the EM duality counterpart of the A-B effect is also predicted.

Zhang, Yuchao; Li, Kang

2014-11-01

160

Optical analog of the Iordanskii force in a Bose-Einstein condensate  

SciTech Connect

A vortex in a Bose-Einstein condensate generates the optical analog of the Aharonov-Bohm effect when illuminated with slow light. In contrast to the original Aharonov-Bohm effect the vortex will exchange forces with the light that leads to a measurable motion of the vortex.

Leonhardt, U.; Oehberg, P. [School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, Scotland (United Kingdom)

2003-05-01

161

Topology, Holes and Sources  

NASA Astrophysics Data System (ADS)

The Aharonov-Bohm effect is often called "topological." But it seems no more topological than magnetostatics, electrostatics or Newton-Poisson gravity (or just about any radiation, propagation from a source). I distinguish between two senses of "topological."

Afriat, Alexander

2013-03-01

162

Gauge invariance and the detection of gravitational radiation  

E-print Network

The detection of gravitational radiation raises some subtle issues having to do with the coordinate invariance of general relativity. This paper explains these issues and their resolution by using an analogy with the Aharonov-Bohm effect of quantum mechanics.

David Garfinkle

2005-11-16

163

VOLUME 87, NUMBER 25 P H Y S I C A L R E V I E W L E T T E R S 17 DECEMBER 2001 Coherent Coupling of Two Quantum Dots Embedded in an Aharonov-Bohm Interferometer  

E-print Network

is fabricated from a negative resist (calixarene) [10] with a dielectric constant of ecax 7.1 [11]. Hereby, the areas of the 2DEG which are below the calixarene are significantly less depleted by voltages which

Ludwig-Maximilians-Universität, München

164

Semiclassical Analysis for Spectral Shift Functions in Magnetic Scattering by Two Solenoidal Fields  

NASA Astrophysics Data System (ADS)

We study the Aharonov-Bohm effect through the semiclassical analysis for the spectral shift function and its derivative in magnetic scattering by two solenoidal fields in two dimensions, assuming that the total magnetic flux vanishes. The corresponding classical system has a trajectory oscillating between the centers of two solenoidal fields. The emphasis is placed on analyzing how the trapping effect is reflected in the semiclassical asymptotic formula. We also make a comment on the case of scattering by a finite number of solenoidal fields and discuss the relation between the Aharonov-Bohm effect from quantum mechanics and the trapping effect from classical mechanics.

Tamura, Hideo

165

Local geometric phase and quantum-state tomography for a superconducting qubit threaded by a magnetic flux  

NASA Astrophysics Data System (ADS)

We investigate the local geometric phase induced by Faraday's law of induction in a superconducting charge qubit threaded by an Aharonov-Bohm flux. A quantum-state reconstruction scheme, which is based on measurement of three complementary quantities, that is, the extra charge and two local currents, is introduced. We find that, while the variation of the local phase with magnetic field is determined by Faraday's law, incorporation of the time-reversal symmetry enables complete determination of the local phase. This procedure clearly demonstrates that the local geometric phase is a physical quantity (aside from a global phase factor), in contrast to the standard description of the Aharonov-Bohm effect.

Kang, Kicheon

2014-02-01

166

Interferometry through a Quantum Dot Coupled to Majorana Fermions  

NASA Astrophysics Data System (ADS)

We investigate transport properties of an Aharonov-Bohm interferometer with an embedded quantum dot with Majorana bound states at the end of the topological superconductor. The differential conductance is calculated by the Keldysh Green function formalism. The Fano resonance of the symmetric shape with the maximum value of 2e2/h emerges as a function of the bias voltage. We find that when the energy of the quantum dot is fixed to the energy of the Majorana bound state, the conductance shows ? periodicity as a function of the Aharonov-Bohm phase induced by the magnetic flux penetrating the interferometer which differs from the case of the superconducting lead.

Ueda, Akiko; Yokoyama, Takehito

167

EM International. Volume 1  

SciTech Connect

It is the intent of EM International to describe the Office of Environmental Restoration and Waste Management`s (EM`s) various roles and responsibilities within the international community. Cooperative agreements and programs, descriptions of projects and technologies, and synopses of visits to international sites are all highlighted in this semiannual journal. Focus on EM programs in this issue is on international collaboration in vitrification projects. Technology highlights covers: in situ sealing for contaminated sites; and remote sensors for toxic pollutants. Section on profiles of countries includes: Arctic contamination by the former Soviet Union, and EM activities with Germany--cooperative arrangements.

Not Available

1993-07-01

168

Random Matrix Theory for Closed Quantum Dots with Weak Spin-Orbit Coupling K. Held,* E. Eisenberg, and B. L. Altshuler  

E-print Network

Random Matrix Theory for Closed Quantum Dots with Weak Spin-Orbit Coupling K. Held,* E. Eisenberg) To lowest order in the coupling strength, the spin-orbit coupling in quantum dots results in a spin- dependent Aharonov-Bohm flux. This flux decouples the spin-up and spin-down random matrix theory ensembles

Eisenberg, Eli

169

Observing Altshuler--Aronov--Spivak Oscillation in a Hexagonal Antidot Array of Monolayer Graphene  

NASA Astrophysics Data System (ADS)

We show that hexagonal antidot lattices of monolayer graphene exhibited the Altshuler--Aronov--Spivak (AAS) effect in low field magnetoresistance. In higher magnetic fields, Aharonov--Bohm-type oscillations were visible. The phase of AAS oscillation indicated that the chirality effect of graphene is suppressed because of inter-valley scattering due to boundary scatterings.

Yagi, Ryuta; Shimomura, Midori; Tahara, Fumiya; Kobara, Hiroaki; Fukada, Seiya

2012-06-01

170

Quantum Phenomena Observed Using Electrons  

SciTech Connect

Electron phase microscopy based on the Aharonov-Bohm (AB) effect principle has been used to illuminate fundamental phenomena concerning magnetism and superconductivity by visualizing quantitative magnetic lines of force. This paper deals with confirmation experiments on the AB effect, the magnetization process of tiny magnetic heads for perpendicular recording, and vortex behaviors in high-Tc superconductors.

Tonomura, Akira [Okinawa Institute of Science and Technology, Onna-son, Okinawa 904-0412 (Japan); Advanced Research Laboratory, Hitachi, Ltd., Hatoyama, Saitama, 350-0395 (Japan); Advanced Science Institute, RIKEN, Wako, Saitama, 351-0198 (Japan)

2011-05-06

171

Nontrivial systems and the necessity of the scalar quantum mechanics axioms  

SciTech Connect

We discuss the necessity of the axioms of scalar quantum mechanics introduced by Paschke and clearly demonstrate their geometric and/or physical meaning. We show that reasonable nonrelativistic quantum mechanics is exactly specified by the axioms. A system describing the electric Aharonov-Bohm effect is presented. It illustrates the topological obstructions for the existence of a Hamiltonian.

Kotulek, Jan [Mathematical Institute, Silesian University at Opava, Na Rybnicku 1, 746 01 Opava (Czech Republic)

2009-06-15

172

Carbon nanotubes in confined magnetic fields: gap oscillations and  

E-print Network

Carbon nanotubes in confined magnetic fields: gap oscillations and persistent currents from a new;OutlineOutline Aharonov-Bohm oscillations in Carbon nanotubes Curvature effects Persistent currents #12 as a change in the interference pattern #12;The AB effect in carbon nano-tubes (CNTs) (I) A. Bachtold et al

Marini, Andrea

173

Remarks about Hardy inequalities on metric trees  

E-print Network

We find sharp conditions on the growth of a rooted regular metric tree such that the Neumann Laplacian on the tree satisfies a Hardy inequality. In particular, we consider homogeneous metric trees. Moreover, we show that a non-trivial Aharonov-Bohm magnetic field leads to a Hardy inequality on a loop graph.

Tomas Ekholm; Rupert L. Frank; Hynek Kovarik

2007-11-13

174

Interferometry in Higher Symmetry Forms of Electrodynamics and Physical Optics  

Microsoft Academic Search

It is shown that higher symmetry (O(3)) electrodynamical considerations lead to a straightforward explanation of the Sagnac effect in terms of the topological phase and Aharonov Bohm effect. The method is extended to interferometry and physical optics in general, using the Sagnac, Michelson and Young interferometers as examples.

Petar K. Anastasovski; T. E. Bearden; C. Ciubotariu; W. T. Coffey; L. B. Crowell; G. J. Evans; M. W. Evans; R. Flower; S. Jeffers; A. Labounsky; B. Lehnert; M. Meszaros; P. Molnar; E. Recami; D. Roscoe

2000-01-01

175

Environmental Media Services (EMS)  

NSDL National Science Digital Library

Environmental Media Services (EMS) is a nonprofit communications clearinghouse committed to the expansion of media coverage on critical environmental and public health issues. True to their mission, EMS staff "build relationships with top scientists, physicians, and other experts to bring journalists the latest and most credible information." EMS's modest homepage is free of clutter but full of content. While several sections are under construction and updates (currently) appear irregular, a series of available articles provides useful summaries of important environmental news issues over the past six months. Current articles include "The impacts of global warming on the oceans" and "Cool companies," among others.

176

OPTIMIZAC ~ AO EM REDES  

E-print Network

OPTIMIZAC¸ ~ AO EM REDES UMA VIS ~ AO GLOBAL Deolinda Dias Rasteiro, Jose Luis Santos, Marta Braz; Optimiza¸c~ao em Redes ­ Uma Vis~ao Global N = fv 1 ; : : : ; v n g j f1; : : : ; ng ­ conjunto de n'os (v est~ao associados parâ??ametros Exemplo: `j 'i 1 `j 'i 2 `j 'i 3 `j 'i 4 \\Gamma \\Gamma \\Gamma \\Gamma

Pascoal, Marta Margarida Braz

177

*Bacharel em Turismo.  

E-print Network

algumas questões que ainda fazem parte das discussões sobre as necessárias reformas estatais originadas no período da transição democrática e que se estendem até os dias atuais. Discussões essas que incluem também as transformações ocorridas na sociedade e que colocam as propostas de reformas para além da estrutura do Estado. É neste período que se pronuncia o esgotamento do planejamento centralizado como instrumento de condução política, não só em função dos problemas intrínsecos à estrutura estatal, mas principalmente por este não conseguir planejar a sociedade em virtude da nova complexidade social. Aliás, complexidade é a noção predominante nesse contexto em que se abrem novas propostas de planejamento, definidas através da co-responsabilidade entre os representantes do Estado e da

Ana Valéria Endres; Palavras-chave Turismo; Estado Planejamento; Planejamento Turístico

178

EM Radiation Program  

NSDL National Science Digital Library

The EM Radiation program displays the electric field vectors (in the x-y plane) and magnetic field contours (for the field in the z direction) calculated from the Lienard-Wiechert potentials for a charged particle. The default scenario shows the resulting radiation from a charged particle in simple harmonic motion. Additional particle trajectories can be specified using the Display | Switch GUI menu item. EM Radiation is an Open Source Physics program written for the teaching of electromagnetism. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the em_radiation.jar file will run the program if Java is installed. Other electromagnetism programs are also available. They can be found by searching ComPADRE for Open Source Physics, OSP, or electromagnetism.

Christian, Wolfgang

2008-05-20

179

The EM Earthquake Precursor  

NASA Astrophysics Data System (ADS)

Many attempts have been made to determine a sound forecasting method regarding earthquakes and warn the public in turn. Presently, the animal kingdom leads the precursor list alluding to a transmission related source. By applying the animal-based model to an electromagnetic (EM) wave model, various hypotheses were formed, but the most interesting one required the use of a magnetometer with a differing design and geometry. To date, numerous, high-end magnetometers have been in use in close proximity to fault zones for potential earthquake forecasting; however, something is still amiss. The problem still resides with what exactly is forecastable and the investigating direction of EM. After the 1989 Loma Prieta Earthquake, American earthquake investigators predetermined magnetometer use and a minimum earthquake magnitude necessary for EM detection. This action was set in motion, due to the extensive damage incurred and public outrage concerning earthquake forecasting; however, the magnetometers employed, grounded or buried, are completely subject to static and electric fields and have yet to correlate to an identifiable precursor. Secondly, there is neither a networked array for finding any epicentral locations, nor have there been any attempts to find even one. This methodology needs dismissal, because it is overly complicated, subject to continuous change, and provides no response time. As for the minimum magnitude threshold, which was set at M5, this is simply higher than what modern technological advances have gained. Detection can now be achieved at approximately M1, which greatly improves forecasting chances. A propagating precursor has now been detected in both the field and laboratory. Field antenna testing conducted outside the NE Texas town of Timpson in February, 2013, detected three strong EM sources along with numerous weaker signals. The antenna had mobility, and observations were noted for recurrence, duration, and frequency response. Next, two directional techniques were employed, resulting in three mapped, potential epicenters. The remaining, weaker signals presented similar directionality results to more epicentral locations. In addition, the directional results of the Timpson field tests lead to the design and construction of a third prototype antenna. In a laboratory setting, experiments were created to fail igneous rock types within a custom-designed Faraday Cage. An antenna emplaced within the cage detected EM emissions, which were both reproducible and distinct, and the laboratory results paralleled field results. With a viable system and continuous monitoring, a fracture cycle could be established and observed in real-time. Sequentially, field data would be reviewed quickly for assessment; thus, leading to a much improved earthquake forecasting capability. The EM precursor determined by this method may surpass all prior precursor claims, and the general public will finally receive long overdue forecasting.

Jones, K. B., II; Saxton, P. T.

2013-12-01

180

Some transport properties of the two-channel Kondo impurity  

NASA Astrophysics Data System (ADS)

We consider conduction electrons moving along a ring in two different orbital channels interacting with a spin-1/2 impurity via isotropic spin exchange. The exchange is the same for both channels, but a crystalline field breaks the orbital symmetry. The tower structure of the finite size corrections to the ground state energy is derived from the Bethe ansatz equations and used to discuss the Aharonov-Bohm-Casher interference pattern in the persistent current and the magnetoresistivity.

Schlottmann, P.; Zvyagin, A. A.

1997-04-01

181

Self-adjoint extensions of the Dirac Hamiltonian in the magnetic-solenoid field and related exact solutions  

Microsoft Academic Search

We study solutions of Dirac equation in the field of Aharonov-Bohm solenoid and a collinear uniform magnetic field. On this base we construct self-adjoint extensions of the Dirac Hamiltonian using von Neumann's theory of deficiency indices. We reduce (3+1)-dimensional problem to (2+1)-dimensional one by a proper choice of spin operator. Then we study the problem doing a finite radius regularization

S. P. Gavrilov; D. M. Gitman; A. A. Smirnov

2003-01-01

182

Green functions of the Dirac equation with magnetic-solenoid field  

Microsoft Academic Search

Various Green functions of the Dirac equation with a magnetic-solenoid field (the superposition of the Aharonov-Bohm field and a collinear uniform magnetic field) are constructed and studied. The problem is considered in 2+1 and 3+1 dimensions for the natural extension of the Dirac operator (the extension obtained from the solenoid regularization). Representations of the Green functions as proper time integrals

S. P. Gavrilov; D. M. Gitman; A. A. Smirnov

2004-01-01

183

Green functions of the Dirac equation with magnetic-solenoid field  

Microsoft Academic Search

Various Green functions of the Dirac equation with a magnetic-solenoid field (the superposition of the Aharonov–Bohm field and a collinear uniform magnetic field) are constructed and studied. The problem is considered in 2+1 and 3+1 dimensions for the natural extension of the Dirac operator (the extension obtained from the solenoid regularization). Representations of the Green functions as proper time integrals

S. P. Gavrilov; D. M. Gitman; A. A. Smirnov

2004-01-01

184

Using Time-Reversal Symmetry for Sensitive Incoherent Matter-Wave Sagnac Interferometry  

SciTech Connect

We present a theory of the transmission of guided matter-waves through Sagnac interferometers. Interferometer configurations with only one input and one output port have a property similar to the phase rigidity observed in the transmission through Aharonov-Bohm interferometers in coherent mesoscopic electronics. This property enables their operation with incoherent matter-wave sources. High rotation sensitivity is predicted for high finesse configurations.

Japha, Y.; Arzouan, O.; Avishai, Y.; Folman, R. [Department of Physics, Ben-Gurion University, Be'er-Sheva 84105 (Israel)

2007-08-10

185

Dynamical Electroweak Symmetry Breaking in $SO(5) \\\\times U(1)$ Gauge-Higgs Unification in the Randall-Sundrum Warped Space  

Microsoft Academic Search

In the gauge-Higgs unification scenario the Higgs field is unified with gauge fields in higher dimensional gauge theory. The 4D Higgs field $H(x)$ corresponds to 4D fluctuations of the Aharonov-Bohm phase (Wilson line phase) $\\\\theta_H$ in the extra-dimension. An $SO(5)\\\\times U(1)$ gauge-Higgs unification model in the Randall-Sundrum warped spacetime with top and bottom quarks is presented. Gauge couplings of the

Yutaka Hosotani

2009-01-01

186

Real-time Observation of Vortices in Superconductors by Lorentz Microscopy  

Microsoft Academic Search

The dynamics of individual quantized vortices in superconducting thin films became observable using coherent Lorentz microscopy with our field-emission transmission electron microscopes (1). The observation principle is based on the Aharonov-Bohm effect (2) Since a phase shift of 2pi is produced between two electron beams enclosing a magnetic flux of h\\/e, a vortex having magnetic flux of h\\/(2e) is a

Akira Tonomura

2005-01-01

187

Berry's phase for coherent states of Landau levels  

E-print Network

The Berry phases for coherent states and squeezed coherent states of Landau levels are calculated. Coherent states of Landau levels are interpreted as a result of a magnetic flux moved adiabatically from infinity to a finite place on the plane. The Abelian Berry phase for coherent states of Landau levels is an analog of the Aharonov- Bohm effect. Moreover, the non-Abelian Berry phase is calculated for the adiabatic evolution of the magnetic field B.

Wen-Long Yang; Jing-Ling Chen

2007-06-14

188

Thermal Dephasing in the Laughlin Quasiparticle Interferometer: Chiral Luttinger Liquid Behavior  

Microsoft Academic Search

We report experimental temperature dependence of the amplitude of\\u000aAharonov-Bohm oscillations in the Laughlin quasiparticle interferometer. The\\u000aresults fit very well the thermal dephasing dependence predicted for a g = 1\\/3\\u000achiral Luttinger liquid interferometer, and are clearly distinct from the\\u000aactivated behavior observed in single-particle resonant tunneling and Coulomb\\u000ablockade devices. The small deviation from the zero-bias theory seen

F. E. Camino; W. Zhou; V. J. Goldman

2005-01-01

189

Thermal Dephasing in the Laughlin Quasiparticle Interferometer: Chiral Luttinger Liquid Behavior  

Microsoft Academic Search

We report experimental temperature dependence of the amplitude of Aharonov-Bohm oscillations in the Laughlin quasiparticle interferometer. The results fit very well the thermal dephasing dependence predicted for a g = 1\\/3 chiral Luttinger liquid interferometer, and are clearly distinct from the activated behavior observed in single-particle resonant tunneling and Coulomb blockade devices. The small deviation from the zero-bias theory seen

F. E. Camino; W. Zhou; V. J. Goldman

2005-01-01

190

Thermal Dephasing in the Laughlin Quasiparticle Interferometer  

Microsoft Academic Search

We report experiments on thermal dephasing of the Aharonov-Bohm oscillations in the novel Laughlin quasiparticle (LQP) interferometer, [1] where quasiparticles of the 1\\/3 FQH fluid execute a closed path around an island of the 2\\/5 fluid. In the 10.2 <=T <=141 mK temperature range, qualitatively, the experimental results follow a thermal dephasing dependence expected for an electron interferometer, and show

F. E. Camino; Wei Zhou; V. J. Goldman

2006-01-01

191

EPA LABORATORIES IMPLEMENT EMS PROGRAM  

EPA Science Inventory

This paper highlights the breadth and magnitude of carrying out an effective Environmental Management System (EMS) program at the U.S. EPA's research and development laboratories. Federal research laboratories have unique operating challenges compared to more centralized industr...

192

Angus Robichaud's Reel G Em D A Bm D7  

E-print Network

Angus Robichaud's Reel 4 4 D G A D D G A D 3 3 G Em D A Bm D7 3 3 G Em D A D Animas Reel Bernie Waugh 4 4 3 3 G D G Bm Em C Am C D G D G Bm Em C Am D G The Arkansas Traveler 4 2 D G A D Em A 3D G A D Em G A D D G D A Bm Em A D G D A Em G A D #12;Asher Rodney Miller 4 4 D Em F#m G A D Em G A D A D1 2

Doyle, Peter

193

Angus Robichaud's Reel G Em D A Bm D7  

E-print Network

Angus Robichaud's Reel 4 4 D G A D D G A D 3 3 G Em D A Bm D7 3 3 G Em D A D Animas Reel Bernie Waugh 4 4 3 3 G D G Bm Em C Am C D G D G Bm Em C Am D G The Arkansas Traveler 4 2 D G A D Em A 3 D G A D Em G A D D G D A Bm Em A D G D A Em G A D #12; Asher Rodney Miller 4 4 D Em F#m G A D Em G A D A D 1

Doyle, Peter

194

Correlation of the NBME Advanced Clinical Examination in EM and the National EM M4 exams  

PubMed Central

Introduction Since 2011 two online, validated exams for fourth-year emergency medicine (EM) students have been available (National EM M4 Exams). In 2013 the National Board of Medical Examiners offered the Advanced Clinical Examination in Emergency Medicine (EM-ACE). All of these exams are now in widespread use; however, there are no data on how they correlate. This study evaluated the correlation between the EM-ACE exam and the National EM M4 Exams. Methods From May 2013 to April 2014 the EM-ACE and one version of the EM M4 exam were administered sequentially to fourth-year EM students at five U.S. medical schools. Data collected included institution, gross and scaled scores and version of the EM M4 exam. We performed Pearson’s correlation and random effects linear regression. Results 303 students took the EM-ACE and versions 1 (V1) or 2 (V2) of the EM M4 exams (279 and 24, respectively). The mean percent correct for the exams were as follows: EM-ACE 74.8 (SD-8.83), V1 83.0 (SD-6.41), V2 78.5 (SD-7.70). Pearson’s correlation coefficient for the V1/EM-ACE was 0.51 (0.42 scaled) and for the V2/EM-ACE was 0.59 (0.41 scaled). The coefficient of determination for V1/EM-ACE was 0.72 and for V2/EM-ACE = 0.71 (0.86 and 0.49 for scaled scores). The R-squared values were 0.25 and 0.30 (0.18 and 0.13, scaled), respectively. There was significant cluster effect by institution. Conclusion There was moderate positive correlation of student scores on the EM-ACE exam and the National EM M4 Exams.

Hiller, Katherine; Miller, Emily S.; Lawson, Luan; Wald, David; Beeson, Michael; Heitz, Corey; Morrissey, Thomas; House, Joseph; Poznanski, Stacey

2015-01-01

195

Lecture 12: EM Radiation (EMR)  

E-print Network

#12;James Clerk Maxwell You! 5 Finally, the pinnacle of EM... E · dA = qencl 0 B · dA = 0 E · dl = E = - dB dt{ Maxwell'sEquations F = q(E + v � B)Lorentz Force Law: Gauss's Law Gauss's Law for Mag. Faraday's Law Ampère's LawB · dl = µ0(Ireal + 0 dE dt ) 6 Must be cool 7 Maxwell's last two equations... B

Tobar, Michael

196

ISSN 0103-9741 Monografias em Cincia da Computao  

E-print Network

abordagem por reflexão computacional baseada em lógica Dárlinton Barbosa Feres Carvalho Edward Hermann Lucena Dezembro, 2010 Análise de Riscos em Projetos: uma abordagem por reexão computacional baseada em em um projeto, é proposto neste trabalho um modelo para reexão computacional baseado em lógica

Endler, Markus

197

School Budget Hold'em Facilitator's Guide  

ERIC Educational Resources Information Center

"School Budget Hold'em" is a game designed to help school districts rethink their budgeting process. It evolved out of Education Resource Strategies' (ERS) experience working with large urban districts around the country. "School Budget Hold'em" offers a completely new approach--one that can turn the budgeting process into a long-term visioning…

Education Resource Strategies, 2012

2012-01-01

198

Fully distributed EM for very large datasets  

Microsoft Academic Search

In EM and related algorithms, E-step compu- tations distribute easily, because data items are independent given parameters. For very large data sets, however, even storing all of the parameters in a single node for the M- step can be impractical. We present a frame- work that fully distributes the entire EM pro- cedure. Each node interacts only with pa- rameters

Jason Wolfe; Aria Haghighi; Dan Klein

2008-01-01

199

LANSIM and its applications to distributed EMS  

SciTech Connect

Distributed energy management systems (EMS) open up a host of alternative design options. Simulation plays an important role in evaluating performance and in comparing alternative designs. Currently all the proposed distributed EMSs are local area network (LAN)-based. To illustrate the application of LANSIM, comparisons are made with different distributed EMS configurations, different LAN technologies (Ethernet and FDDI), and different Ethernet implementations.

Lun, S.M.; Lo, T.; Wu, F.; Murphy, L. [Univ. of California, Berkeley, CA (United States). Dept. of Electrical Engineering and Computer Sciences; Sen, A. [ABB Systems Control, Santa Clara, CA (USD)

1996-08-01

200

Em que medida devem ser privados, em que medida devem ser pblicos o conhecimento e a informao?  

E-print Network

Em que medida devem ser privados, em que medida devem ser públicos o conhecimento e a informação? 1 Transparências com licença Creative Commons Em que medida devem ser privados, em que medida devem ser públicos o as alternativas? codexKonstanz #12;Em que medida devem ser privados, em que medida devem ser públicos o

Kuhlen, Rainer

201

EM International, July 1994, Volume 2  

SciTech Connect

The Office of Environmental Management (EM) at the Department of Energy (DOE) is seeking out and leveraging foreign technology, data, and resources in keeping with EM`s mandate to protect public health and the environment through the safe and cost-effective remediation of the Department`s nuclear weapons sites. EM works closely with foreign governments, industry, and universities to obtain innovative environmental technologies, scientific and engineering expertise, and operations experience that will support EM`s objectives. Where appropriate, these international resources are used to manage the more urgent risks at our sites, secure a safe workplace, help build consensus on critical issues, and strengthen our technology development program. Through international agreements EM engages in cooperative exchange of information, technology, and individuals. Currently, we are managing agreements with a dozen countries in Europe, Latin America, and Asia. These agreements focus on environmental restoration, waste management, transportation of radioactive wastes, and decontamination and decommissioning. This publication contains the following articles: in situ remediation integrated program; in-situ characterization and inspection of tanks; multimedia environmental pollutant assessment system (MEPAS); LLNL wet oxidation -- AEA technology. Besides these articles, this publication covers: EU activities with Russia; technology transfer activities; and international organization activities.

Not Available

1994-10-01

202

Žem?s ?kio gamybos (ekologin?s ir ?prastin?s) ?taka dirvožemio savyb?ms ir žiemini? kvie?i? gr?d? kokybei.  

E-print Network

??Tyrimai atlikti 2008–2009 m. Lietuvos žem?s ?kio universiteto Agroekologijos centro ekologin?s gamybos ir mokomajame (chemizuota gamyba) ?kiuose. Darbo tikslas - ?vertinti ekologin?s žem?s ?kio gamybos… (more)

Užpurvis,; Edgaras

2010-01-01

203

EMS offshore. A new horizon for paramedics.  

PubMed

The difficulty in getting medical aid to offshore drilling platforms can be a source of life-threatening delays. Recently, some companies have charted new waters by actually stationing EMS crews on their rigs. PMID:10116023

Mallard, A S

1991-10-01

204

EMS Division Potential Benefits of Selected  

E-print Network

Engineers Journal, January 1998, p 107 2 D. Kuhlmann-Wilsdorf, "Metal Fiber Brushes", in Electrical Contacts coils are stationary; there are no rotating cold seals #12;EMS Division Advanced Homopolar Motor Concept

205

Revisão sistemática sobre obesidade em adolescentes brasileiros  

Microsoft Academic Search

Resumo - O propósito deste estudo foi revisar, de forma sistemática, a literatura nacional sobre a prevalência e fatores associados à obesidade em adolescentes. A busca foi realizada nas bases de dados Pubmed e Bireme, através dos descritores: \\

Rafael Miranda Tassitano; Maria Cecília Marinho Tenório; Pedro C Hallal

206

M em ory for Item s and M em ory for R elations in the Procedural/D eclarative M em ory Fram ew ork  

E-print Network

ever, as we hope to m ake clear here, progress on this front M E M O R Y , 1 99 7, 5 (1 /2 ), 1 31 ±17M em ory for Item s and M em ory for R elations in the Procedural/D eclarative M em ory Fram ew ork ard Eichenbaum Boston U niversity, U SA A m ajor area of research in m em ory and am nesia concerns

Poldrack, Russ

207

Quantum Transport in Semiconductor Nanostructures  

Microsoft Academic Search

I. Introduction (Preface, Nanostructures in Si Inversion Layers,\\u000aNanostructures in GaAs-AlGaAs Heterostructures, Basic Properties).\\u000a II. Diffusive and Quasi-Ballistic Transport (Classical Size Effects, Weak\\u000aLocalization, Conductance Fluctuations, Aharonov-Bohm Effect, Electron-Electron\\u000aInteractions, Quantum Size Effects, Periodic Potential).\\u000a III. Ballistic Transport (Conduction as a Transmission Problem, Quantum Point\\u000aContacts, Coherent Electron Focusing, Collimation, Junction Scattering,\\u000aTunneling).\\u000a IV. Adiabatic Transport (Edge Channels and the

C. W. J. Beenakker; H. van Houten

2004-01-01

208

Cold Atoms in Non-Abelian Gauge Potentials: From the Hofstadter Moth to Lattice Gauge Theory  

SciTech Connect

We demonstrate how to create artificial external non-Abelian gauge potentials acting on cold atoms in optical lattices. The method employs atoms with k internal states, and laser assisted state sensitive tunneling, described by unitary kxk matrices. The single-particle dynamics in the case of intense U(2) vector potentials lead to a generalized Hofstadter butterfly spectrum which shows a complex mothlike structure. We discuss the possibility to realize non-Abelian interferometry (Aharonov-Bohm effect) and to study many-body dynamics of ultracold matter in external lattice gauge fields.

Osterloh, K. [Institut fuer Theoretische Physik, Universitaet Hannover, D-30167 Hannover (Germany); Baig, M. [IFAE, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain); Santos, L. [Institut fuer Theoretische Physik III, Universitaet Stuttgart, D-70550 Stuttgart (Germany); Zoller, P. [Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria); Lewenstein, M. [Institut fuer Theoretische Physik, Universitaet Hannover, D-30167 Hannover (Germany); ICFO-Institut de Ciencies Fotoniques, 08034 Barcelona (Spain)

2005-07-01

209

A general method for deriving vector potentials produced by knotted solenoids  

NASA Astrophysics Data System (ADS)

A general method for deriving exact expressions for vector potentials produced by arbitrarily knotted solenoids is presented. It consists of using simple physics ideas from magnetostatics to evaluate the magnetic field in a surrogate problem. The latter is obtained by modeling the knot with wire segments carrying steady currents on a cubical lattice. The expressions for a 31 (trefoil) and a 41 (figure-eight) knot are explicitly worked out. The results are of some importance in the study of the Aharonov-Bohm effect generalized to a situation in which charged particles moving through force-free regions are scattered by fluxes confined to the interior of knotted impenetrable tubes.

Sreedhar, V. V.

2014-10-01

210

Dirac fermions in a magnetic-solenoid field  

Microsoft Academic Search

We consider the Dirac equation with a magnetic-solenoid field (the\\u000asuperposition of the Aharonov--Bohm solenoid field and a collinear uniform\\u000amagnetic field). Using von Neumann's theory of the self-adjoint extensions of\\u000asymmetric operators, we construct a one-parameter family and a two-parameter\\u000afamily of self-adjoint Dirac Hamiltonians in the respective 2+1 and 3+1\\u000adimensions. Each Hamiltonian is specified by certain asymptotic

S. P. Gavrilov; D. M. Gitman; A. A. Smirnov; B. L. Voronov

2003-01-01

211

Green functions of the Dirac equation with magnetic-solenoid field  

NASA Astrophysics Data System (ADS)

Various Green functions of the Dirac equation with a magnetic-solenoid field (the superposition of the Aharonov-Bohm field and a collinear uniform magnetic field) are constructed and studied. The problem is considered in 2+1 and 3+1 dimensions for the natural extension of the Dirac operator (the extension obtained from the solenoid regularization). Representations of the Green functions as proper time integrals are derived. The nonrelativistic limit is considered. For the sake of completeness the Green functions of the Klein-Gordon particles are constructed as well.

Gavrilov, S. P.; Gitman, D. M.; Smirnov, A. A.

2004-05-01

212

Experimental constraints and a possible quantum Hall state at ? =5 /2  

NASA Astrophysics Data System (ADS)

Several topological orders have been proposed to explain the quantum Hall plateau at ? =5 /2 . The observation of an upstream neutral mode on the sample edge supports the non-Abelian anti-Pfaffian state. On the other hand, tunneling experiments favor the Halperin 331 state which exhibits no upstream modes. No proposed ground states agree with both types of experiments. We find a topological order, compatible with the results of both experiments. That order allows both finite and zero spin polarizations. It is Abelian but its signatures in Aharonov-Bohm interferometry can be similar to those of the Pfaffian and anti-Pfaffian states.

Yang, Guang; Feldman, D. E.

2014-10-01

213

Thévenin equivalence in disorderless quantum networks  

NASA Astrophysics Data System (ADS)

We outline the procedure of extending the Thévenin equivalence principle for classical electric circuits to reducing Aharonov-Bohm-based quantum networks into equivalent models. With examples, we show from first principles how the requirements are related to the electron band structure's Fermi level and the lattice spacing of the network. Quantum networks of varying degrees of coupling strength from four basic classifications of single and double entangled loops sharing symmetry and highly correlated band structures are used to demonstrate the concept. We show the limitations of how the principle may be applied. Several classes of examples are given and their equivalent forms are shown.

Cain, C. A.; Wu, C. H.

2015-01-01

214

Double-donor complex in vertically coupled quantum dots in a threading magnetic field  

PubMed Central

We consider a model of hydrogen-like artificial molecule formed by two vertically coupled quantum dots in the shape of axially symmetrical thin layers with on-axis single donor impurity in each of them and with the magnetic field directed along the symmetry axis. We present numerical results for energies of some low-lying levels as functions of the magnetic field applied along the symmetry axis for different quantum dot heights, radii, and separations between them. The evolution of the Aharonov-Bohm oscillations of the energy levels with the increase of the separation between dots is analyzed. PMID:23013550

2012-01-01

215

A Note on the Sagnac Effect for Matter Beams  

E-print Network

We study the Sagnac effect for matter beams, in order to estimate the kinematic corrections to the basic formula, deriving from the position and the extension of the interferometer, and discuss the analogy with the Aharonov-Bohm effect. We show that the formula for the Sagnac time delay is the same for matter and light beams in arbitrary stationary space-times, provided that a suitable condition on the speed of the beams is fulfilled. Hence, the same results obtained for light beams apply to matter beams.

Matteo Luca Ruggiero; Angelo Tartaglia

2014-11-01

216

Dirac oscillator interacting with a topological defect  

SciTech Connect

In this work we study the interaction problem of a Dirac oscillator with gravitational fields produced by topological defects. The energy levels of the relativistic oscillator in the cosmic string and in the cosmic dislocation space-times are sensible to curvature and torsion associated to these defects and are important evidence of the influence of the topology on this system. In the presence of a localized magnetic field the energy levels acquire a term associated with the Aharonov-Bohm effect. We obtain the eigenfunctions and eigenvalues and see that in the nonrelativistic limit some results known in standard quantum mechanics are reached.

Carvalho, J.; Furtado, C.; Moraes, F. [Unidade Academica de Tecnologia de Alimentos, CCTA, Universidade Federal de Campina Grande, Pereiros, 58840-000, Pombal, Paraiba (Brazil); Departamento de Fisica, CCEN, Universidade Federal da Paraiba, Cidade Universitaria, 58051-970 Joao Pessoa, Paraiba (Brazil)

2011-09-15

217

Excited exciton and biexciton localised states in a single quantum ring  

NASA Astrophysics Data System (ADS)

We observe excited exciton and biexciton states of localised excitons in an anisotropic quantum ring, where large polarisation asymmetry supports the presence of a crescent-like localised structure. We also find that saturation of the localised ground state exciton with increasing excitation can be attributed to relatively fast dissociation of biexcitons (˜430 ps) compared to slow relaxation from the excited state to the ground state (˜1000 ps). As no significant excitonic Aharonov-Bohm oscillations occur up to 14 T, we conclude that phase coherence around the rim is inhibited as a consequence of height anisotropy in the quantum ring.

Kim, H. D.; Kyhm, K.; Taylor, R. A.; Nicolet, A. A. L.; Potemski, M.; Nogues, G.; Je, K. C.; Lee, E. H.; Song, J. D.

2013-10-01

218

Spin transistor action from Onsager reciprocity and SU(2) gauge theory  

NASA Astrophysics Data System (ADS)

We construct a local gauge transformation to show how a generic, nonhomogeneous SU(2) spin-orbit Hamiltonian reduces to two U(1) Hamiltonians for spinless fermions at opposite magnetic fields, to leading order in the spin-orbit strength. Using an Onsager reciprocity relation, we show how the resulting spin conductance vanishes in a two-terminal setup, and how it is turned on by either weakly breaking time-reversal symmetry by applied magnetic fields or opening additional transport terminals. We numerically illustrate our theory for diffusive conductors, ballistic mesoscopic cavities as well as Aharonov-Bohm rings.

Adagideli, Inanc

2012-02-01

219

Pure phase decoherence in a ring geometry  

SciTech Connect

We study the dynamics of pure phase decoherence for a particle hopping around an N-site ring, coupled both to a spin bath and to an Aharonov-Bohm flux which threads the ring. Analytic results are found for the dynamics of the influence functional and of the reduced density matrix of the particle, both for initial single wave-packet states, and for states split initially into two separate wave packets moving at different velocities. We also give results for the dynamics of the current as a function of time.

Zhu, Z. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia, V6T 1Z1 (Canada); Aharony, A.; Entin-Wohlman, O. [Department of Physics and the Ilse Katz Center for Meso- and Nano-Scale Science and Technology, Ben Gurion University, Beer Sheva 84105 (Israel); Pacific Institute of Theoretical Physics, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia, V6T 1Z1 (Canada); Stamp, P. C. E. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia, V6T 1Z1 (Canada); Pacific Institute of Theoretical Physics, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia, V6T 1Z1 (Canada)

2010-06-15

220

Quasiballistic Transport of Dirac Fermions in a Bi2Se3 Nanowire  

NASA Astrophysics Data System (ADS)

Quantum coherent transport of surface states in a mesoscopic nanowire of the three-dimensional topological insulator Bi2Se3 is studied in the weak-disorder limit. At very low temperatures, many harmonics are evidenced in the Fourier transform of Aharonov-Bohm oscillations, revealing the long phase coherence length of spin-chiral Dirac fermions. Remarkably, from their exponential temperature dependence, we infer an unusual 1/T power law for the phase coherence length L?(T). This decoherence is typical for quasiballistic fermions weakly coupled to their environment.

Dufouleur, J.; Veyrat, L.; Teichgräber, A.; Neuhaus, S.; Nowka, C.; Hampel, S.; Cayssol, J.; Schumann, J.; Eichler, B.; Schmidt, O. G.; Büchner, B.; Giraud, R.

2013-05-01

221

Surface state dominated transport in topological insulator Bi2Te3 nanowires  

NASA Astrophysics Data System (ADS)

We report on low temperature magnetoresistance measurements on single-crystalline Bi2Te3 nanowires synthesized via catalytic growth and post-annealing in a Te-rich atmosphere. The observation of Aharonov-Bohm oscillations indicates the presence of topological surface states. Analyses of Subnikov-de Haas oscillations in perpendicular magnetoresistance yield extremely low two-dimensional carrier concentrations and effective electron masses, and very high carrier mobilities. All our findings are in excellent agreement with theoretical predictions of massless Dirac fermions at the surfaces of topological insulators.

Hamdou, Bacel; Gooth, Johannes; Dorn, August; Pippel, Eckhard; Nielsch, Kornelius

2013-11-01

222

Nonlocal Pancharatnam phase in two-photon interferometry  

NASA Astrophysics Data System (ADS)

We propose a polarized intensity interferometry experiment, which measures the nonlocal Pancharatnam phase acquired by a pair of Hanbury-Brown-Twiss photons. The setup involves two polarized thermal sources illuminating two polarized detectors. Varying the relative polarization angle of the detectors introduces a two-photon geometric phase. Local measurements at either detector do not reveal the effects of the phase, which is an optical analog of the multiparticle Aharonov-Bohm effect. The geometric phase sheds light on the three-slit experiment and suggests ways of tuning entanglement.

Mehta, Poonam; Samuel, Joseph; Sinha, Supurna

2010-09-01

223

Variational Monte Carlo Study of Anderson Localization in the Hubbard Model  

NASA Astrophysics Data System (ADS)

We have studied the effects of interactions on persistent currents in half-filled and quarter-filled Hubbard models with weak and intermediate strength disorder. Calculations are performed using a variational Gutzwiller ansatz that describes short range correlations near the Mott transition. A persistent current is induced with an Aharonov-Bohm flux, and the Anderson localization length is extracted from the scaling of the current with system size. We find that, at half filling, the localization length grows monotonically with interaction strength, even though the current itself is suppressed by strong correlations. This supports earlier dynamical mean field theory predictions that the elastic scattering rate is reduced near the Mott transition.

Atkinson, William; Farhoodfar, Avid; Gooding, Robert J.

2012-02-01

224

Surface state dominated transport in topological insulator Bi{sub 2}Te{sub 3} nanowires  

SciTech Connect

We report on low temperature magnetoresistance measurements on single-crystalline Bi{sub 2}Te{sub 3} nanowires synthesized via catalytic growth and post-annealing in a Te-rich atmosphere. The observation of Aharonov-Bohm oscillations indicates the presence of topological surface states. Analyses of Subnikov-de Haas oscillations in perpendicular magnetoresistance yield extremely low two-dimensional carrier concentrations and effective electron masses, and very high carrier mobilities. All our findings are in excellent agreement with theoretical predictions of massless Dirac fermions at the surfaces of topological insulators.

Hamdou, Bacel, E-mail: bhamdou@physnet.uni-hamburg.de; Gooth, Johannes; Dorn, August; Nielsch, Kornelius, E-mail: knielsch@physnet.uni-hamburg.de [Institute of Applied Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany)] [Institute of Applied Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany); Pippel, Eckhard [Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Germany)] [Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Germany)

2013-11-04

225

Topological phase shift in a cold-atom interferometer  

NASA Astrophysics Data System (ADS)

Matter-wave interferences in a four-pulse version of a Ramsey-Bordé atom interferometer have been utilized to study phase shifts. A topological phase shift analogous to the scalar Aharonov-Bohm effect proposed for charged-particle interferences in the presence of a pulsed electrostatic potential has been investigated. The time-dependent potential has been generated by the interaction of a laser field with an induced atomic dipole without spatial variation along the interferometer arms. The atom interferometer has been run with laser-cooled magnesium atoms stored in a magneto-optical trap.

Müller, J. H.; Bettermann, D.; Rieger, V.; Sengstock, K.; Sterr, U.; Ertmer, W.

1995-02-01

226

Magnetic Flux Effect on a Kondo-Induced Electric Polarization in a Triangular Triple Quantum Dot  

NASA Astrophysics Data System (ADS)

A magnetic flux effect is studied theoretically on an electric polarization induced by the Kondo effect in a triangular triple-quantum-dot system, where one of the three dots is connected to a metallic lead. This electric polarization exhibits an Aharonov–Bohm oscillation as a function of the magnetic flux penetrating through the triangular loop. The numerical renormalization group analysis reveals how the oscillation pattern depends on the Kondo coupling of a local spin with lead electrons, which is sensitive to the point contact with the lead. It provides an experimental implication that the Kondo effect is the origin of the emergent electric polarization.

Koga, Mikito; Matsumoto, Masashige; Kusunose, Hiroaki

2014-08-01

227

Generation of uniform synthetic magnetic fields by split driving of an optical lattice  

NASA Astrophysics Data System (ADS)

We describe a method to generate a synthetic gauge potential for ultracold atoms held in an optical lattice. Our approach uses a time-periodic driving potential based on quickly alternating two Hamiltonians to engineer the appropriate Aharonov-Bohm phases, and permits the simulation of a uniform tunable magnetic field. We explicitly demonstrate that our split-driving scheme reproduces the behavior of a charged quantum particle in a magnetic field over the complete range of field strengths, and obtain the Hofstadter butterfly band structure for the Floquet quasienergies.

Creffield, C. E.; Sols, F.

2014-08-01

228

Homotopy and Path Integrals  

E-print Network

This is an introductory review of the connection between homotopy theory and path integrals, mainly focus on works done by Schulman [23] that he compared path integral on SO(3) and its universal covering space SU(2), DeWitt and Laidlaw [15] that they proved the theorem to the case of path integrals on the multiply-connected topological spaces. Also, we discuss the application of the theorem in Aharonov-Bohm effect given by [20,24]. An informal introduction to homotopy theory is provided for readers who are not familiar with the theory.

Fumika Suzuki

2011-08-31

229

Dark strings and their couplings to the standard model  

NASA Astrophysics Data System (ADS)

We consider the standard model extended by a hidden sector U(1)X symmetry that is spontaneously broken at the TeV scale by the vacuum expectation value of an additional scalar field. We study "dark string" solutions in this model and their properties due to the Higgs portal and gauge kinetic mixing operators. We find that dark strings effectively interact with Higgs and Z bosons by linear couplings, and with leptons and baryons via Aharonov-Bohm couplings, thus possibly leading to new cosmological constraints on dark matter models with spontaneously broken extra U(1) symmetry factors.

Hyde, Jeffrey M.; Long, Andrew J.; Vachaspati, Tanmay

2014-03-01

230

Charge, from EM fields only  

E-print Network

Consider the electric field E about an electron. Its source has been thought a substance called charge, enclosed within a small volume that defines the size of the electron. Scattering experiments find no size at all. Charge is useful, but mysterious. This study concludes that charge is not real. Useful, but not real. Absent real charge, the electric field must look to a different source. We know another electric field, vxB, not sourced by charge. A simple model of the electron, using EM fields only, has been found that generates an electric field vxB very like E. Gauss' law finds the model contains charge, but div vxB cannot find the charge density. The model contains a permanent magnetic flux quantum, configured as a dipole. The dipolar B fields spin around the symmetry axis, accounting for angular momentum. Spin stabilizes the magnetic flux quantum, and creates the vxB electric field. Stability in this model is dynamic. Energy is exchanged between the dipolar magnetic moment and an encircling toroidal displacement current, at the Compton frequency, mc^2/h = 1.24x10^20 Hz. The electric field undulates at this rate, instead of being static like E associated with charge. Absent any real charge, we have to abandon the notion that size of a charged particle is that of a small sack full of charge. The only electric field is vxB, and its source is not charge. What is the size of an electron? Coulomb scattering finds it point-like, but its spinning B fields extend to infinity.

R. L. Collins

2007-03-04

231

EMS adaptation for climate change  

NASA Astrophysics Data System (ADS)

The purpose of this study was to find an appropriate scenario of pre-hospital transportation of an emergency medical service (EMS) system for burdensome casualties resulting from extreme climate events. A case of natural catastrophic events in Taiwan, 88 wind-caused disasters, was reviewed and analyzed. A sequential-conveyance method was designed to shorten the casualty transportation time and to promote the efficiency of ambulance services. A proposed mobile emergency medical center was first constructed in a safe area, but nearby the disaster area. The Center consists of professional medical personnel who process the triage of incoming patients and take care of casualties with minor injuries. Ambulances in the Center were ready to sequentially convey the casualties with severer conditions to an assigned hospital that is distant from the disaster area for further treatment. The study suggests that if we could construct a spacious and well-equipped mobile emergency medical center, only a small portion of casualties would need to be transferred to distant hospitals. This would reduce the over-crowding problem in hospital ERs. First-line ambulances only reciprocated between the mobile emergency medical center and the disaster area, saving time and shortening the working distances. Second-line ambulances were highly regulated between the mobile emergency medical center and requested hospitals. The ambulance service of the sequential-conveyance method was found to be more efficient than the conventional method and was concluded to be more profitable and reasonable on paper in adapting to climate change. Therefore, additional practical work should be launched to collect more precise quantitative data.

Pan, C.; Chang, Y.; Wen, J.; Tsai, M.

2010-12-01

232

Tour of the Electromagnetic Spectrum (EMS) Videos  

NSDL National Science Digital Library

These videos introduce middle- and high school-age learners to the electromagnetic spectrum. The product consists of 8 animations including an introduction to electromagnetic waves and one animation for each wavelength of the EM spectrum (Radio, Microwave, Infrared, Visible, Ultraviolet, X-Rays and Gamma Rays). Each wavelength of the EM spectrum offers a construct to illustrate and teach about NASA sensors, missions, and science. Emphasis is placed on relevant science, such as lunar exploration, and hot science topics, such as climate change. The examples and narrative for each wavelength animation build on the learners’ prior knowledge then introduces examples from NASA missions. These examples explore the use of spectral analysis and visualizations that help scientists make discoveries about the world around us using EM waves.

Troy Benesch

2009-01-01

233

EM-ONE : an architecture for reflective commonsense thinking  

E-print Network

This thesis describes EM-ONE, an architecture for commonsense thinking capable of reflective reasoning about situations involving physical, social, and mental dimensions. EM-ONE uses as its knowledge base a library of ...

Singh, Pushpinder, 1972-2006.

2005-01-01

234

ECE 341: Electromagnetic Fields I EM devices and systems  

E-print Network

in material media - Electromagnetic induction - Inductance - Magnetic energy Applications: - ElectronicsECE 341: Electromagnetic Fields I EM devices and systems - Can compute and analyze potentials compositions - Can evaluate capacitance, inductance, resistance, and conductance of EM structures - Understands

Schumacher, Russ

235

EM2: A Scalable Shared-Memory Multicore Architecture  

E-print Network

We introduce the Execution Migration Machine (EM2), a novel, scalable shared-memory architecture for large-scale multicores constrained by off-chip memory bandwidth. EM2 reduces cache miss rates, and consequently off-chip ...

Khan, Omer

2010-06-12

236

A emissão em 8mm e as bandas de Merrill-Sanford em estrelas carbonadas  

NASA Astrophysics Data System (ADS)

Estrelas carbonadas possuem bandas moleculares em absorção no visível e, no infravermelho (IR) as principais características espectrais se devem a emissão de grãos. Recentemente foi detectada a presença de bandas de SiC2 (Merrill-Sanford, MS) em emissão sendo atribuída à presença de um disco rico em poeira. Neste trabalho analisamos uma amostra de 14 estrelas carbonadas, observadas no telescópio de 1.52 m do ESO em 4 regiões espectrais diferentes, a fim de detectar as bandas de MS em emissão. Nossa amostra é composta de estrelas que apresentam além da emissão em 11.3 mm, outra em 8 mm. Esta última emissão, não usual nestes objetos, tem sido atribuída ou a moléculas de C2H2, ou a um composto sólido ainda indefinido. A detecção de emissões de MS e aquelas no IR, simultaneamente, revelaria um cenário mais complexo que o habitualmente esperado para os ventos destes objetos. No entanto como primeiro resultado, verificamos que as bandas de Merrill-Sanford encontram-se em absorção, não revelando nenhuma conexão com a emissão a 8 mm. Assim, temos duas hipóteses: (a) a emissão a 8 mm se deve à molécula C2H2 ou (b) essa emissão é resultado da emissão térmica de grãos. Testamos a segunda hipótese modelando a amostra com grãos não-homogêneos de SiC e quartzo, o qual emite em aproximadamente 8mm. Este grão seria produzido em uma fase evolutiva anterior a das carbonadas (estrelas S) e por terem uma estrutura cristalina são destruídos apenas na presença de campos de radiação ultravioleta muito intensos. Os modelos para os envoltórios utilizam o método de Monte Carlo para descrever o problema do transporte da radiação. As conclusões deste trabalho são: (1) as bandas de Merrill-Sanford se encontram em absorção, sugerindo um cenário usual para os ventos das estrelas da amostra; (2) neste cenário, a emissão em 8 mm seria resultado de grãos de quartzo com mantos de SiC, indicando que o quartzo poderia sobreviver a fase evolutiva S.

de Mello, A. B.; Lorenz-Martins, S.

2003-08-01

237

7 CFR 759.6 - EM to be made available.  

... 2014-01-01 2014-01-01 false EM to be made available. 759.6 Section 759...DESIGNATIONS AND NOTIFICATIONS § 759.6 EM to be made available. (a) For purposes of the EM Program under part 764, subpart I, of...

2014-01-01

238

7 CFR 759.6 - EM to be made available.  

Code of Federal Regulations, 2013 CFR

... 2013-01-01 2013-01-01 false EM to be made available. 759.6 Section 759...DESIGNATIONS AND NOTIFICATIONS § 759.6 EM to be made available. (a) For purposes of the EM Program under part 764, subpart I, of...

2013-01-01

239

7 CFR 1945.35 - Special EM loan training.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2009-01-01 true Special EM loan training. 1945.35 Section 1945...Assistance-General § 1945.35 Special EM loan training. (a) General...completed they will be well qualified to process EM loans without undue delay. The...

2011-01-01

240

7 CFR 1945.35 - Special EM loan training.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2009-01-01 true Special EM loan training. 1945.35 Section 1945...Assistance-General § 1945.35 Special EM loan training. (a) General...completed they will be well qualified to process EM loans without undue delay. The...

2010-01-01

241

7 CFR 1945.35 - Special EM loan training.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Special EM loan training. 1945.35 Section 1945...Assistance-General § 1945.35 Special EM loan training. (a) General...completed they will be well qualified to process EM loans without undue delay. The...

2012-01-01

242

Bayesian Gaussian Process Classification with the EM-EP Algorithm  

E-print Network

Bayesian Gaussian Process Classification with the EM-EP Algorithm Hyun-Chul Kim and Zoubin of hyperparameters to determine various aspects of the function. Recently, the expectation propagation (EP) approach an approximate EM algorithm, the EM-EP algorithm, to learn both the latent function and the hyperparameters

Ghahramani, Zoubin

243

On Convergence Properties of the EM Algorithm for Gaussian Mixtures  

Microsoft Academic Search

We build up the mathematical connection between the Expectation-Maximization (EM) algorithm and gradient-based approaches for maximum likelihood learning of finite gaussian mixtures. We show that the EM step in parameter space is obtained from the gradient via a projection matrix P, and we provide an explicit expression for the matrix. We then analyze the convergence of EM in terms of

Lei Xu; Michael I. Jordan

1996-01-01

244

A Structural EM Algorithm for Phylogenetic Inference  

Microsoft Academic Search

A central task in the study of molecular evolution is the reconstruction of a phylogenetic tree from sequences of current-day taxa. The most established approach to tree reconstruction is maximum likelihood (ML) analysis. Unfortunately, searching for the maximum likelihood phylogenetic tree is computationally prohibitive for large data sets. In this paper, we describe a new algorithm that uses Structural EM

Nir Friedman; Matan Ninio; Itsik Pe'er; Tal Pupko

2002-01-01

245

Network Emulation with NetEm  

Microsoft Academic Search

Many protocols and applications perform poorly when exposed to real life networks with delay and packet loss. Often, it is costly and dicult to reproduce Internet behavior in a controlled environment. There are tools avail- able for testing, but they are either expen- sive hardware solutions, proprietary software, or limited research projects. NetEm is a recent enhancement of the trac

Stephen Hemminger

246

Bolseiros em protesto. "Para a banca milhes,  

E-print Network

segunda vez a candida- tura a bolsa de doutoramento. Em 179 candidatos entraram 12. Ele era o 14.° e acha para os animais já houve dificuldades", diz. David Gomes e Ana Silva, de 23 e 24 anos, estão a começar

Instituto de Sistemas e Robotica

247

Mercury pollution in the Ems estuary  

NASA Astrophysics Data System (ADS)

From approximately 1960 to 1975 the Ems estuary received several tons of mercury per year from a chlor-alkali plant, a pesticide factory and some minor sources. The discharge has been reduced drastically from 1976 onwards. In 1975 and 1976 measurements were made on the distribution of mercury in the sediment. The horizontal distribution revealed a strong local enrichment of the sediment near the point of discharge. The vertical distribution was found to be in accordance with the local deposition rates. In the water phase no significant change in mercury content from 1975 to 1978/79 could be demonstrated. In 1978/79 a difference between Ems estuary and Dutch Wadden Sea was not significant. In 1978 mercury contents of eelpout Zoarces viviparus in the Ems estuary were about twice as high as in the Wadden Sea. In the Ems estuary a decrease of these contents was found between 1974/75 and 1978. A similar decline in the Wadden Sea may be related to a decreased mercury discharge by the River Rhine.

Essink, K.

1980-03-01

248

de Ps-Graduao em Enfermagem  

E-print Network

/data expedição CPF Nome da mãe/pai Estado civil E-mail Endereço residencial #12;Programa de Pós-Graduação em Dirigir-se ao Banco do Brasil e fazer um depósito para a Agência: 14532 Conta �nica do Tesouro Nacional

Floeter, Sergio Ricardo

249

Efficient Scanning for EM Based Target Localization  

E-print Network

of the time. 1 Introduction Focused Ion Beam Scanning Electron Microscopes (FIB-SEM) and their ability Image Fig. 1. FIB-SEM Scanning Process. The microscope repeatedly scans the surface of a sample blockEfficient Scanning for EM Based Target Localization Raphael Sznitman, Aurelien Lucchi, Natasa

Fua, Pascal

250

EM-dissertations completed in 2007  

E-print Network

theme: Computational and Experimental Mechanics Sensing, Monitoring and Control of Laser Based Welding-90-9022179-3 EM research theme: Computational and Experimental Mechanics Thermomechanical fatigue failure;Sensor-guided robotic laser welding Graaf, M.W. de Advisor: Prof.dr.ir. J. Meijer; prof.dr.ir. J

Franssen, Michael

251

College of Engineering EM Engineering Mechanics  

E-print Network

College of Engineering EM Engineering Mechanics KEY: # = new course * = course changed = course; bending of beams; combined loading of members; buckling of columns. Prereq: Registration in the College.Kinematics:cartesianandpolarcoordinatesystems;normalandtangentialcomponents;translatingand rotating reference frames. Kinetics of particles and rigid bodies: laws of motion; work and energy; impulse

MacAdam, Keith

252

ESPÉCIES DO GÊNERO Eimeria (APICOMPLEXA: EIMERIIDAE) EM TAMANDUÁS-BANDEIRA (Myrmecophaga tridactyla LINNAEUS, 1758) EM CATIVEIRO  

Microsoft Academic Search

1 ABSTRACT:- FREITAS, F.L. DA C.; ALMEIDA, K. DE S.; ZANETTI, A.S.; NASCIMENTO, A.A. DO; MACHADO, C. R.; MACHADO, R.Z. (Species of the genus Eimeria (Apicomplexa: Eimeriidae) in giant anteaters (Myrmecophaga tridactyla Linnaeus, 1758) in captivity). Espécies do gênero Eimeria (Apicomplexa: Eimeriidae) em Tamanduás-bandeira (Myrmecophaga tridactyla Linnaeus, 1758) em cativeiro. Revista Brasileira de Parasitologia Veterinária, v. 15, n. 1, p.

FAGNER LUIZ DA C. FREITAS; ANDRÉ S. ZANETTI; CÉLIO R. MACHADO; ROSANGELA Z. MACHADO

253

BUSCA LOCAL PARA POS-PROCESSAMENTO EM RESULTADOS DE OTIMIZAC~AO MULTI-OBJETIVO EM REDES DE FILAS  

E-print Network

BUSCA LOCAL PARA P´OS-PROCESSAMENTO EM RESULTADOS DE OTIMIZA¸C~AO MULTI-OBJETIVO EM REDES DE FILAS otimiza¸c~ao de redes de filas finitas, a capacidade total do sistema em ´areas de espera deve ser a menor algoritmo simulated annealing foi desenvolvido, especialmente para redes de filas finitas, produzindo solu

Cruz, Frederico

254

Frmions ultra-frios em redes ticas  

E-print Network

Férmions ultra-frios em redes óticas Thereza C de L Paiva Colóquio Interinstitucional CBPF - IMPA - UFF - UFRJ 18 de abril de 2012 #12;Átomos ultrafrios armadilhados Bósons e férmions Redes óticas;Redes óticasRedes óticas #12;Redes óticas Potencial confinante + Potencial periódico + #12;Dimensão 3D

Liu, I-Shih

255

Transportes em Revista.com Pas: Portugal  

E-print Network

Comentar artigo Imprimir PDF Enviar a um amigo 09 -10 -2012 Toyota aposta no hidrogénio para ve ículos Plug-in em Paris 21 -08 -2012 Toyota lan ça novo Auris com motoriza ção híbrida 20 -08 -2012 MAN Toyota Veículos híbridos Estatísticas deste artigo Passageiros & Mobilidade voltar Os utilizadores

Instituto de Sistemas e Robotica

256

TandEM: Titan and Enceladus mission  

Microsoft Academic Search

TandEM was proposed as an L-class (large) mission in response to ESA’s Cosmic Vision 2015–2025 Call, and accepted for further\\u000a studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds\\u000a tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini–Huygens\\u000a mission. These

A. Coustenis; S. K. Atreya; T. Balint; R. H. Brown; M. K. Dougherty; F. Ferri; M. Fulchignoni; D. Gautier; R. A. Gowen; C. A. Griffith; L. I. Gurvits; R. Jaumann; Y. Langevin; M. R. Leese; J. I. Lunine; C. P. McKay; X. Moussas; I. Müller-Wodarg; F. Neubauer; T. C. Owen; F. Raulin; E. C. Sittler; F. Sohl; C. Sotin; G. Tobie; T. Tokano; E. P. Turtle; J.-E. Wahlund; J. H. Waite; K. H. Baines; J. Blamont; A. J. Coates; I. Dandouras; T. Krimigis; E. Lellouch; R. D. Lorenz; A. Morse; C. C. Porco; M. Hirtzig; J. Saur; T. Spilker; J. C. Zarnecki; E. Choi; N. Achilleos; R. Amils; P. Annan; D. H. Atkinson; Y. Bénilan; C. Bertucci; B. Bézard; G. L. Bjoraker; M. Blanc; L. Boireau; J. Bouman; M. T. Capria; E. Chassefière; P. Coll; M. Combes; J. F. Cooper; A. Coradini; F. Crary; T. Cravens; I. A. Daglis; E. de Angelis; C. de Bergh; I. de Pater; C. Dunford; G. Durry; O. Dutuit; D. Fairbrother; F. M. Flasar; A. D. Fortes; R. Frampton; M. Fujimoto; M. Galand; O. Grasset; M. Grott; T. Haltigin; A. Herique; F. Hersant; H. Hussmann; W. Ip; R. Johnson; E. Kallio; S. Kempf; M. Knapmeyer; W. Kofman; R. Koop; T. Kostiuk; N. Krupp; M. Küppers; H. Lammer; L.-M. Lara; P. Lavvas; S. Le Mouélic; S. Lebonnois; S. Ledvina; J. Li; T. A. Livengood; R. M. Lopes; J.-J. Lopez-Moreno; D. Luz; P. R. Mahaffy; U. Mall; J. Martinez-Frias; B. Marty; T. McCord; C. Menor Salvan; A. Milillo; D. G. Mitchell; R. Modolo; O. Mousis; M. Nakamura; C. D. Neish; C. A. Nixon; D. Nna Mvondo; G. Orton; M. Paetzold; J. Pitman; S. Pogrebenko; W. Pollard; O. Prieto-Ballesteros; P. Rannou; K. Reh; L. Richter; F. T. Robb; R. Rodrigo; S. Rodriguez; P. Romani; M. Ruiz Bermejo; E. T. Sarris; P. Schenk; B. Schmitt; N. Schmitz; D. Schulze-Makuch; K. Schwingenschuh; A. Selig; B. Sicardy; L. Soderblom; L. J. Spilker; D. Stam; A. Steele; K. Stephan; D. F. Strobel; K. Szego; C. Szopa; R. Thissen; M. G. Tomasko; D. Toublanc; H. Vali; I. Vardavas; V. Vuitton; R. A. West; R. Yelle; E. F. Young

2009-01-01

257

Dirac fermions in a magnetic-solenoid field  

E-print Network

We consider the Dirac equation with a magnetic-solenoid field (the superposition of a solenoid field and a collinear uniform magnetic field). Using von Neumann's theory of the selfadjoint extensions of symmetric operators, we construct selfadjoint Dirac Hamiltonians for the case of the Aharonov-Bohm solenoid in 2+1 and 3+1 dimensions. Each extension of the family is specified by certain asymptotic boundary conditions at the AB solenoid. We find the spectrum and eigenfunctions for each value of the extension parameter. We also consider the regularized case of a finite-radius solenoid and study the dependence of the eigenfunctions on the behavior of the magnetic field inside the solenoid. In addition, we consider the regularization problem in the spinless case as well. The zero-radius limit yields a concrete selfadjoint Hamiltonian for the case of the magnetic-solenoid field with the Aharonov-Bohm solenoid. In addition, by the example of the radial Dirac Hamiltonian with the magnetic-solenoid field, we present ...

Gavrilov, S P; Smirnov, A A; Voronov, B L

2003-01-01

258

TandEM: Titan and Enceladus mission  

USGS Publications Warehouse

TandEM was proposed as an L-class (large) mission in response to ESA's Cosmic Vision 2015-2025 Call, and accepted for further studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini-Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TandEM is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini-Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time). In the current mission architecture, TandEM proposes to deliver two medium-sized spacecraft to the Saturnian system. One spacecraft would be an orbiter with a large host of instruments which would perform several Enceladus flybys and deliver penetrators to its surface before going into a dedicated orbit around Titan alone, while the other spacecraft would carry the Titan in situ investigation components, i.e. a hot-air balloon (Montgolfi??re) and possibly several landing probes to be delivered through the atmosphere. ?? Springer Science + Business Media B.V. 2008.

Coustenis, A.; Atreya, S.K.; Balint, T.; Brown, R.H.; Dougherty, M.K.; Ferri, F.; Fulchignoni, M.; Gautier, D.; Gowen, R.A.; Griffith, C.A.; Gurvits, L.I.; Jaumann, R.; Langevin, Y.; Leese, M.R.; Lunine, J.I.; McKay, C.P.; Moussas, X.; Muller-Wodarg, I.; Neubauer, F.; Owen, T.C.; Raulin, F.; Sittler, E.C.; Sohl, F.; Sotin, C.; Tobie, G.; Tokano, T.; Turtle, E.P.; Wahlund, J.-E.; Waite, J.H.; Baines, K.H.; Blamont, J.; Coates, A.J.; Dandouras, I.; Krimigis, T.; Lellouch, E.; Lorenz, R.D.; Morse, A.; Porco, C.C.; Hirtzig, M.; Saur, J.; Spilker, T.; Zarnecki, J.C.; Choi, E.; Achilleos, N.; Amils, R.; Annan, P.; Atkinson, D.H.; Benilan, Y.; Bertucci, C.; Bezard, B.; Bjoraker, G.L.; Blanc, M.; Boireau, L.; Bouman, J.; Cabane, M.; Capria, M.T.; Chassefiere, E.; Coll, P.; Combes, M.; Cooper, J.F.; Coradini, A.; Crary, F.; Cravens, T.; Daglis, I.A.; de Angelis, E.; De Bergh, C.; de Pater, I.; Dunford, C.; Durry, G.; Dutuit, O.; Fairbrother, D.; Flasar, F.M.; Fortes, A.D.; Frampton, R.; Fujimoto, M.; Galand, M.; Grasset, O.; Grott, M.; Haltigin, T.; Herique, A.; Hersant, F.; Hussmann, H.; Ip, W.; Johnson, R.; Kallio, E.; Kempf, S.; Knapmeyer, M.; Kofman, W.; Koop, R.; Kostiuk, T.; Krupp, N.; Kuppers, M.; Lammer, H.; Lara, L.-M.; Lavvas, P.; Le, Mouelic S.; Lebonnois, S.; Ledvina, S.; Li, J.; Livengood, T.A.; Lopes, R.M.; Lopez-Moreno, J. -J.; Luz, D.; Mahaffy, P.R.; Mall, U.; Martinez-Frias, J.; Marty, B.; McCord, T.; Salvan, C.M.; Milillo, A.; Mitchell, D.G.; Modolo, R.; Mousis, O.; Nakamura, M.; Neish, C.D.; Nixon, C.A.; Mvondo, D.N.; Orton, G.; Paetzold, M.; Pitman, J.; Pogrebenko, S.; Pollard, W.; Prieto-Ballesteros, O.; Rannou, P.; Reh, K.; Richter, L.; Robb, F.T.; Rodrigo, R.; Rodriguez, S.; Romani, P.; Bermejo, M.R.; Sarris, E.T.; Schenk, P.; Schmitt, B.; Schmitz, N.; Schulze-Makuch, D.; Schwingenschuh, K.; Selig, A.; Sicardy, B.; Soderblom, L.; Spilker, L.J.; Stam, D.; Steele, A.; Stephan, K.; Strobel, D.F.; Szego, K.; Szopa

2009-01-01

259

TandEM: Titan and Enceladus mission  

NASA Astrophysics Data System (ADS)

TandEM was proposed as an L-class (large) mission in response to ESA’s Cosmic Vision 2015-2025 Call, and accepted for further studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini-Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TandEM is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini-Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time). In the current mission architecture, TandEM proposes to deliver two medium-sized spacecraft to the Saturnian system. One spacecraft would be an orbiter with a large host of instruments which would perform several Enceladus flybys and deliver penetrators to its surface before going into a dedicated orbit around Titan alone, while the other spacecraft would carry the Titan in situ investigation components, i.e. a hot-air balloon (Montgolfière) and possibly several landing probes to be delivered through the atmosphere.

Coustenis, A.; Atreya, S. K.; Balint, T.; Brown, R. H.; Dougherty, M. K.; Ferri, F.; Fulchignoni, M.; Gautier, D.; Gowen, R. A.; Griffith, C. A.; Gurvits, L. I.; Jaumann, R.; Langevin, Y.; Leese, M. R.; Lunine, J. I.; McKay, C. P.; Moussas, X.; Müller-Wodarg, I.; Neubauer, F.; Owen, T. C.; Raulin, F.; Sittler, E. C.; Sohl, F.; Sotin, C.; Tobie, G.; Tokano, T.; Turtle, E. P.; Wahlund, J.-E.; Waite, J. H.; Baines, K. H.; Blamont, J.; Coates, A. J.; Dandouras, I.; Krimigis, T.; Lellouch, E.; Lorenz, R. D.; Morse, A.; Porco, C. C.; Hirtzig, M.; Saur, J.; Spilker, T.; Zarnecki, J. C.; Choi, E.; Achilleos, N.; Amils, R.; Annan, P.; Atkinson, D. H.; Bénilan, Y.; Bertucci, C.; Bézard, B.; Bjoraker, G. L.; Blanc, M.; Boireau, L.; Bouman, J.; Cabane, M.; Capria, M. T.; Chassefière, E.; Coll, P.; Combes, M.; Cooper, J. F.; Coradini, A.; Crary, F.; Cravens, T.; Daglis, I. A.; de Angelis, E.; de Bergh, C.; de Pater, I.; Dunford, C.; Durry, G.; Dutuit, O.; Fairbrother, D.; Flasar, F. M.; Fortes, A. D.; Frampton, R.; Fujimoto, M.; Galand, M.; Grasset, O.; Grott, M.; Haltigin, T.; Herique, A.; Hersant, F.; Hussmann, H.; Ip, W.; Johnson, R.; Kallio, E.; Kempf, S.; Knapmeyer, M.; Kofman, W.; Koop, R.; Kostiuk, T.; Krupp, N.; Küppers, M.; Lammer, H.; Lara, L.-M.; Lavvas, P.; Le Mouélic, S.; Lebonnois, S.; Ledvina, S.; Li, J.; Livengood, T. A.; Lopes, R. M.; Lopez-Moreno, J.-J.; Luz, D.; Mahaffy, P. R.; Mall, U.; Martinez-Frias, J.; Marty, B.; McCord, T.; Menor Salvan, C.; Milillo, A.; Mitchell, D. G.; Modolo, R.; Mousis, O.; Nakamura, M.; Neish, C. D.; Nixon, C. A.; Nna Mvondo, D.; Orton, G.; Paetzold, M.; Pitman, J.; Pogrebenko, S.; Pollard, W.; Prieto-Ballesteros, O.; Rannou, P.; Reh, K.; Richter, L.; Robb, F. T.; Rodrigo, R.; Rodriguez, S.; Romani, P.; Ruiz Bermejo, M.; Sarris, E. T.; Schenk, P.; Schmitt, B.; Schmitz, N.; Schulze-Makuch, D.; Schwingenschuh, K.; Selig, A.; Sicardy, B.; Soderblom, L.; Spilker, L. J.; Stam, D.; Steele, A.; Stephan, K.; Strobel, D. F.; Szego, K.; Szopa, C.; Thissen, R.; Tomasko, M. G.; Toublanc, D.; Vali, H.; Vardavas, I.; Vuitton, V.; West, R. A.; Yelle, R.; Young, E. F.

2009-03-01

260

Complete-data spaces and generalized EM algorithms  

Microsoft Academic Search

Expectation-maximization (EM) algorithms have been applied extensively for computing maximum-likelihood and penalized-likelihood parameter estimates in signal processing applications. Intrinsic to each EM algorithm is a complete-data space (CDS)-a hypothetical set of random variables that is related to the parameters more naturally than the measurements are. The authors describe two generalizations of the EM paradigm: (i) allowing the relationship between the

J. A. Fessler; A. O. Hero

1993-01-01

261

Em18 and Em16, new serologic marker epitopes for alveolar echinococcosis in western blot analysis, are the only two epitopes recognized by commercially available weak positive (cut off) sera for Em2plus-ELISA.  

PubMed

The assay system for antibody responses against Em2, the most specific antigen for serodiagnosis of alveolar echinococcosis (AE), has been established by enzyme-linked immunosorbent assay (ELISA) but not by Western blot assay, since Em2 antigen is not protein but carbohydrate in nature. Recently we reported that previously undescribed protein epitopes, designated Em18 and Em16 due to their molecular weights, were good serologic markers for AE by Western blot analysis. It has been shown that Em18 and Em16 are the only two epitopes recognized by commercially available weak positive (cut off) sera for the Em2plus-ELISA. PMID:8583132

Ito, A; Osawa, Y; Nakao, M; Horii, T; Okamoto, M; Itoh, M; Yamashita, T

1995-12-01

262

2. HI PAR (ACQUISITION RADAR) TOWER AND ENLISTED MEN (EM) ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. HI PAR (ACQUISITION RADAR) TOWER AND ENLISTED MEN (EM) BARRACKS WITH RADAR ATTACHED. - Nike Hercules Missile Battery Summit Site, Battery Control Administration & Barracks Building, Anchorage, Anchorage, AK

263

Test beam performance of CDF plug upgrade EM calorimeter  

SciTech Connect

CDF Plug Upgrade(tile-fiber) EM Calorimeter performed resolution of 15%/{radical}E{circle_plus}0.7% with non-linearity less than 1% in a energy range of 5-180 GeV at Fermilab Test Beam. Transverse uniformity of inside-tower-response of the EM Calorimeter was 2.2% with 56 GeV positron, which was reduced to 1.0% with response map correction. We observed 300 photo electron/GeV in the EM Calorimeter. Ratios of EM Calorimeter response to positron beam to that to {sup 137}Cs Source was stable within 1% in the period of 8 months.

Fukui, Y. [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan); CDF Upgrade Group

1998-01-01

264

You did what? Clinical errors in EMS.  

PubMed

It was late and you were exhausted. You ran a call that didn't go the way you would have liked. Errors occurred. What actions do you take when your partner is making mistakes? When do you step in? Do you step in? What if there's more to the errors than you realize? This article provides guidelines for EMS personnel to consider when dealing with a scenario that contains clinical errors. Although not an all-inclusive list, the examples and solutions may be beneficial to providers, including rookies and veterans. PMID:11501273

Linder, G; Murphy, P; Streger, M R

2001-08-01

265

EM threat analysis for wireless systems.  

SciTech Connect

Modern digital radio systems are complex and must be carefully designed, especially when expected to operate in harsh propagation environments. The ability to accurately predict the effects of propagation on wireless radio performance could lead to more efficient radio designs as well as the ability to perform vulnerability analyses before and after system deployment. In this report, the authors--experts in electromagnetic (EM) modeling and wireless communication theory--describe the construction of a simulation environment that is capable of quantifying the effects of wireless propagation on the performance of digital communication.

Burkholder, R. J. (Ohio State University Electroscience Laboratory); Mariano, Robert J.; Schniter, P. (Ohio State University Electroscience Laboratory); Gupta, I. J. (Ohio State University Electroscience Laboratory)

2006-06-01

266

Aquisição de Estreptococos Mutans e Desenvolvimento de Cárie Dental em Primogênitos  

PubMed Central

Objetivo Avaliar o momento de aquisição de estreptococos mutans (EM), desenvolvimento de cárie dental e as variáveis a eles associadas no decorrer de 23 meses, em primogênitos de famílias de baixo nível socioeconômico, desde os sete meses de idade. Método A amostra foi selecionada com base em mães densamente colonizadas por EM, incluindo todos os membros de 14 famílias que conviviam na mesma casa. Foram envolvidos no estudo 14 mães, pais e primogênitos e 8 parentes, na maioria avós. Exames clínicos e radiográficos iniciais determinaram os índices de cárie e condição periodontal dos adultos. Contagens de EM foram feitas em todos os adultos nas duas primeiras visitas. Nas crianças foram avaliados os níveis de EM, o número de dentes e de cáries, em quatro visitas. Resultados A prevalência de EM nos adultos foi alta, estando ausente em apenas um dos pais. EM foram detectados em 1, 2, 3 e 10 crianças, respectivamente nas visitas #1, 2, 3 e 4. A cárie dental foi detectada em apenas três crianças na última visita (aos 30 meses de idade), as quais apresentaram escores de EM significantemente maiores que as crianças sem cárie, na mesma visita. Conclusão Exclusivamente a condição social de baixa renda e mães densamente colonizadas por EM não são sinônimo de colonização precoce e alta atividade de cárie em crianças cuidadas em casa. O desenvolvimento de cárie está significantemente associado a escores elevados de EM nas crianças. PMID:22022218

NOCE, Erica; RUBIRA, Cassia Maria Fischer; da Silva ROSA, Odila Pereira; da SILVA, Salete Moura Bonifácio; BRETZ, Walter Antonio

2011-01-01

267

Rito Funerário entre os Florianopolitanos: corpos em diálogo  

Microsoft Academic Search

Abertura Quando os espanhóis encontraram-se com os ameríndios, o que os livros de história teimam em chamar de descobrimento, cosmologias diferentes foram postas em contato, num processo vigoroso de estranhamento do outro. Cada qual a sua maneira tratou de descobrir quem era este \\

Fernando Gonçalves Bitencourt

268

Nonlinear Cyclotron-Resonance Accelerations by a Generalized EM Wave  

E-print Network

). Unlike the usual transit-time accelerations e 00 v 1 this acceleration mechanism is independentNonlinear Cyclotron-Resonance Accelerations by a Generalized EM Wave AKIMOTO, Kazuhiro and HOJO accelerations by a 1D, EM, dispersive pulse in an external magnetic field are investigated. It is found

Boyer, Edmond

269

CURSO DE PS-GRADUAO EM COMPUTAO APLICADA  

E-print Network

Sistemas Complexos Física Matemática Fundamentos da Teoria de Conjuntos Nebulosos e da Teoria de Possibilidades Inteligência Artificial Inteligência Computacional e Aplicações Introdução à Teoria de Sistemas Teoria do Controle Inteligente Testes de Software Baseado em Modelo Tópicos Especiais em Computação

270

Dirio Econmico -Universidades Como ser investigador em Portugal  

E-print Network

Diário Económico - Universidades Como é ser investigador em Portugal Autor: N.D. Editora: ST e SF - Universidades Como é ser investigador em Portugal Autor: N.D. Editora: ST e SF Id: 1646658 Data Publicação: 19

Instituto de Sistemas e Robotica

271

Stochastic EM-based TFBS motif discovery with MITSU  

PubMed Central

Motivation: The Expectation–Maximization (EM) algorithm has been successfully applied to the problem of transcription factor binding site (TFBS) motif discovery and underlies the most widely used motif discovery algorithms. In the wider field of probabilistic modelling, the stochastic EM (sEM) algorithm has been used to overcome some of the limitations of the EM algorithm; however, the application of sEM to motif discovery has not been fully explored. Results: We present MITSU (Motif discovery by ITerative Sampling and Updating), a novel algorithm for motif discovery, which combines sEM with an improved approximation to the likelihood function, which is unconstrained with regard to the distribution of motif occurrences within the input dataset. The algorithm is evaluated quantitatively on realistic synthetic data and several collections of characterized prokaryotic TFBS motifs and shown to outperform EM and an alternative sEM-based algorithm, particularly in terms of site-level positive predictive value. Availability and implementation: Java executable available for download at http://www.sourceforge.net/p/mitsu-motif/, supported on Linux/OS X. Contact: a.m.kilpatrick@sms.ed.ac.uk PMID:24931999

Kilpatrick, Alastair M.; Ward, Bruce; Aitken, Stuart

2014-01-01

272

10 CFR Appendixes E-M to Part 52 - [Reserved  

Code of Federal Regulations, 2010 CFR

10 Energy 2 2010-01-01 2010-01-01 false [Reserved] E Appendixes E-M to Part 52 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS Appendixes E-M to Part 52...

2010-01-01

273

Notas para uma Avaliação do Discurso Marxista em Douglass North  

Microsoft Academic Search

A partir da publicação do livro Institutions, Institutional Change and Economic Performance em 1990 e da obtenção do Nobel em 1993, as contribuições de Douglass North parecem ter entrado definitivamente no debate sobre a questão do desenvolvimento das economias no longo prazo. Muito se discute atualmente sobre a natureza da obra de North, mais especificamente sobre o grau de neoclassicismo

Gabriel Galípolo; Paulo Gala; Danilo Araujo Fernandes

2008-01-01

274

Tuning of EM performance for streamlined aircraft radomes  

Microsoft Academic Search

Aircraft radomes are often streamlined and highly prone to EM performance degradation due to fabrication uncertainties and the non-uniformity of the constituent radome materials. A novel patching scheme is employed for the enhancement of the EM performance. Besides tuning the performance, this patching scheme can also be employed to determine the potential of the radome for any further improvements.

R. U. Nair; R. M. Jha

2004-01-01

275

BENJAMIN FRANKLIN E A HISTÓRIA DA ELETRICIDADE EM LIVROS DIDÁTICOS  

Microsoft Academic Search

Introdução Nos últimos anos, a história da ciência vem sendo introduzida em materiais didáticos utilizados em sala de aula. Uma das razões para isso é a pressão de órgãos governamentais, tais como a Secretaria de Educação Básica, responsável pela avaliação destes livros dentro do Programa Nacional de Livros Didáticos para o ens ino fundamental e médio. Os editais destes programas

Cibelle Celestino Silva; Ana Carolina Pimentel

276

Esparsidade, Estrutura, Escalamento e Estabilidade em Algebra Linear Computacional  

E-print Network

Sparsity, Structure, Scaling and Stability in Computational Linear Algebra - Textbook from the IX School of Computer Science, held on July 24-31 of 1994 at Recife, Brazil. Esparsidade, Estrutura, Escalamento e Estabilidade em Algebra Linear Computacional - Livro texto da IX Escola de Computacao, realizada nos dias 24 a 31 de Julho de 1994 em Recife, Brasil. This textbook is written in Portuguese Language.

Stern, Julio M

2011-01-01

277

Accuracy of EMS Trauma Transport Destination Plans in North Carolina.  

PubMed

Abstract Objective. Planning for time-sensitive injury may allow emergency medical services (EMS) systems to more accurately triage patients meeting accepted criteria to facilities most capable of providing life-saving treatment. In 2010, North Carolina (NC) implemented statewide Trauma Triage and Destination Plans (TTDPs) in all 100 of North Carolina's county-defined EMS systems. Each system was responsible for identifying the specific destination hospitals with appropriate resources to treat trauma patients. We sought to characterize the accuracy of their hospital designations. Methods. In this cross-sectional study, we collected TTDPs for each county-defined EMS system, including their assigned hospital capabilities (i.e., trauma center or community hospital). We conducted a survey with each EMS system to determine how their TTDP was constructed and maintained, as well as with each TTDP-designated hospital to verify their capabilities. We determined the accuracy of the EMS assigned hospital designations by comparing them to the hospital's reported capabilities. Results. The 100 NC EMS systems provided 380 designations for 112 hospitals. TTDPs were created by EMS administrators and medical directors, with only 55% of EMS systems engaging a hospital representative in the plan creation. Compared to the actual hospital capabilities, 97% of the EMS TTDP designations were correct. Twelve hospital designations were incorrect and the majority (10) overestimated hospital capabilities. Of the 100 EMS systems, 7 misclassified hospitals in their TTDP. EMS systems that did not verify their local hospitals' capabilities during TTDP development were more likely to incorrectly categorize a hospital's capabilities (p = 0.001). Conclusions. A small number of EMS systems misclassified hospitals in their TTDP, but most plans accurately reflected hospital capabilities. Misclassification occurred more often in systems that did not consult local hospitals prior to developing their TTDP. The potential of the TTDP to improve communication between EMS agencies and the facilities with which they work has not been fully realized. EMS agencies or systems should verify local hospital capabilities when engaging in destination planning efforts. PMID:24878396

Moss, Chailee; Cowden, Christopher S; Atterton, Laurie Meyer; Arasaratnam, Meredith H; Fernandez, Antonio R; Evarts, Jeff S; Barrier, Brian; Lerner, E Brooke; Mann, N Clay; Lohmeier, Chad; Shofer, Frances S; Brice, Jane H

2015-01-01

278

Acceleration of MAP-EM algorithm via over-relaxation.  

PubMed

To improve the convergence rate of the effective maximum a posteriori expectation-maximization (MAP-EM) algorithm in tomographic reconstructions, this study proposes a modified MAP-EM which uses an over-relaxation factor to accelerate image reconstruction. The proposed method, called MAP-AEM, is evaluated and compared with the results for MAP-EM and for an ordered-subset algorithm, in terms of the convergence rate and noise properties. The results show that the proposed method converges numerically much faster than MAP-EM and with a speed that is comparable to that for an ordered-subset type method. The proposed method is effective in accelerating MAP-EM tomographic reconstruction. PMID:25465068

Tsai, Yu-Jung; Huang, Hsuan-Ming; Fang, Yu-Hua Dean; Chang, Shi-Ing; Hsiao, Ing-Tsung

2014-11-15

279

Dor em membros em um serviço de reumatologia pediátrica Limb pain in a pediatric rheumatology outpatient clinic  

Microsoft Academic Search

Objetivo: Avaliar clínica e laboratorialmente crianças e adolescentes com dor em membros e sua possível associação com fibromialgia e hipermobilidade articular. Método: Estudo transversal realizado no período de janeiro de 2001 a dezembro de 2002, que incluiu 103 crianças e ado- lescentes atendidos no Ambulatório de Reumatologia Pediá- trica, com queixa de dor em membros. Além do exame físico geral,

Cássia Maria; P. L. Barbosa; Luciana Hangai; Maria Teresa Terreri; Cláudio Arnaldo Len; Maria Odete; E. Hilário

280

Estudo comparativo dos parâmetros angulares da marcha humana em ambiente aquático e terrestre em indivíduos hígidos adultos jovens  

Microsoft Academic Search

RESUMO Há um grande interesse em estudar o movimento humano den- tro da água, uma vez que o meio já é utilizado para treinamento e reabilitação devido às diferentes propriedades mecânicas que ofe- rece. No entanto, há uma carência de estudos sobre as caracterís- ticas biomecânicas do andar em ambiente aquático. O presente estudo teve como objetivo determinar as variáveis

Danieli Isabel Romanovitch Ribas; Vera Lúcia Israel; Elisângela Ferretti Manfra; Camila Costa de Araújo

2007-01-01

281

The Post-LBV Supernova 2001em  

NASA Astrophysics Data System (ADS)

The supernova (SN) 2001em in UGC 11794 was classified early as Type Ib/c, i.e., as one arising from a hydrogen-stripped star. As part of a radio survey with the Very Large Array of SNe Ib/c at late times (Stockdale et al. 2003, BAAS, 35, 1346), SN 2001em was detected as a highly luminous radio source ˜2 years after explosion. The SN was also subsequently discovered with Chandra to be a very luminous X-ray source. The properties of both the radio and X-ray emission are more characteristic of the Type II-narrow (IIn) SNe, where the SN shock is interacting with dense, massive circumstellar matter, resulting in bright radio synchrotron emission and thermal bremsstrahlung from the interaction region. In fact, SN 2001em has shown to have spectroscopically transformed to a SN IIn. The premise that this might indicate an off-axis gamma-ray burst has been presented (Granot & Ramirez-Ruiz 2004, ApJ, 609, L9) and later, rather convincingly, refuted (e.g., Schinzel et al. 2009, ApJ, 691, 1380). Chugai & Chevalier (2006, ApJ, 641, 1051) have interpreted the spectral transformation and radio/X-ray emission as the SN shock overtaking the detached hydrogen envelope of the progenitor star, which was shed in a superwind episode many years prior to explosion. Chevalier (2007, RMxAC, 30, 41) has further pointed to the required mass-loss rate in the event being equivalent to what would occur in the eruption of a luminous blue variable (LBV). The optical (ground-based and HST) and radio/X-ray data, together with mid-infrared Spitzer observations, tend to support this scenario of a very massive star that experienced a powerful LBV outburst prior to explosion. Such an event may not be unique, with possible parallels in the cases of SNe 2005bf and 2006jc, and may provide valuable new information about massive stellar evolution.

Van Dyk, Schuyler D.; Chornock, R.; Filippenko, A. V.; Foley, R. J.; Lewin, W. H. G.; Li, W.; Panagia, N.; Pooley, D.; Stockdale, C. J.; Weiler, K. W.

2009-12-01

282

Electromagnetic optimization of EMS-MAGLEV systems  

SciTech Connect

In EMS-MAGLEV high-speed transport systems, devices for propulsion, levitation and contactless on-board electric power transfer are combined in a single electromagnetic structure. The strong coupling among the windings affects the performance of each device and requires the utilization of numerical codes. The paper describes an overall optimization procedure, based on a suitable mathematical model of the system, which takes into account several items of the system performance. The parameters of the model are calculated by an automated sequence of FEM analyses of the configuration. Both the linear generator output characteristics and the propulsion force ripple are improved applying the procedure to a reference configuration. The results are compared with the results obtained by a sequence of partial optimizations operating separately on two different subsets of the geometric parameters.

Andriollo, M.; Martinelli, G.; Morini, A.; Tortella, A. [Univ. of Padova (Italy). Dept. of Electrical Engineering] [Univ. of Padova (Italy). Dept. of Electrical Engineering

1998-07-01

283

DOE EM industry programs robotics development  

SciTech Connect

The Office of Science and Technology (OST) manages an aggressive program for RD&D, as well as testing and evaluation for the U.S. Department of Energy`s (DOE) Environmental Management (EM) organization. The goal is to develop new and improved environmental restoration and waste management technologies to clean up the inventory of the DOE weapons complex faster, safer, and cheaper than is possible with currently available technologies. OST has organized technology management activities along focus teams for each major problem area. There are currently five focus areas: decontamination and decommissioning, tanks, subsurface contaminants, mixed waste, and plutonium. In addition, OST is pursuing research and development (R&D) that cuts across these focus areas by having applications in two or more focus areas. Currently, there are three cross-cutting programs: the robotics technology development; characterization, monitoring, and sensor technologies; and efficient separations and processing.

Staubly, R.; Kothari, V. [Dept. of Energy, Morgantown, WV (United States)

1997-12-01

284

Elevated ethyl methanesulfonate (EMS) in nelfinavir mesylate (Viracept, Roche): overview.  

PubMed

Roche's protease inhibitor nelfinavir mesylate (Viracept) produced between March 2007-June 2007 was found to contain elevated levels of ethyl methanesulfonate (EMS), a known mutagen (alkylator) - leading to a global recall of the drug. EMS levels in a daily dose (2,500 mg Viracept/day) were predicted not to exceed a dose of approximately 2.75 mg/day (approximately 0.055 mg/kg/day based on 50 kg patient). As existing toxicology data on EMS did not permit an adequate patient risk assessment, a comprehensive animal toxicology evaluation of EMS was conducted. General toxicity of EMS was investigated in rats over 28 days. Two studies for DNA damage were performed in mice; chromosomal damage was assessed using a micronucleus assay and gene mutations were detected using the MutaMouse transgenic model. In addition, experiments designed to extrapolate animal exposure to humans were undertaken. A general toxicity study showed that the toxicity of EMS occurred only at doses >or= 60 mg/kg/day, which is far above that received by patients. Studies for chromosomal damage and mutations in mice demonstrated a clear threshold effect with EMS at 25 mg/kg/day, under chronic dosing conditions. Exposure analysis (Cmax) demonstrated that approximately 370-fold higher levels of EMS than that ingested by patients, are needed to saturate known, highly conserved, error-free, mammalian DNA repair mechanisms for alkylation. In summary, animal studies suggested that patients who took nelfinavir mesylate with elevated levels of EMS are at no increased risk for carcinogenicity or teratogenicity over their background risk, since mutations are prerequisites for such downstream events. These findings are potentially relevant to >40 marketed drugs that are mesylate salts. PMID:19660105

Pozniak, Anton; Müller, Lutz; Salgo, Miklos; Jones, Judith K; Larson, Peter; Tweats, David

2009-01-01

285

Queda dos homicídios em São Paulo, Brasil: uma análise descritiva  

PubMed Central

Objetivo Descrever a evolução da mortalidade por homicídios no Município de São Paulo segundo tipo de arma, sexo, raça ou cor, idade e áreas de exclusão/inclusão social entre 1996 e 2008. Métodos Estudo ecológico de série temporal. Os dados sobre óbitos ocorridos no Município foram coletados da base de dados do Programa de Aprimoramento das Informações sobre Mortalidade, seguindo a Classificação Internacional de Doenças, Décima Revisão (CID-10). Foram calculadas as taxas de mortalidade por homicídio (TMH) para a população total, por sexo, raça ou cor, faixa etária, tipo de arma e área de exclusão/inclusão social. As TMH foram padronizadas por idade pelo método direto. Foram calculados os percentuais de variação no período estudado. Para as áreas de exclusão/inclusão social foram calculados os riscos relativos de morte por homicídio. Resultados As TMH apresentaram queda de 73,7% entre 2001 e 2008. Foi observada redução da TMH em todos os grupos analisados, mais pronunciada em homens (?74,5%), jovens de 15 a 24 anos (?78,0%) e moradores de áreas de exclusão social extrema (?79,3%). A redução ocorreu, sobretudo, nos homicídios cometidos com armas de fogo (?74,1%). O risco relativo de morte por homicídio nas áreas de exclusão extrema (tendo como referência áreas com algum grau de exclusão social) foi de 2,77 em 1996, 3,9 em 2001 e 2,13 em 2008. Nas áreas de alta exclusão social, o risco relativo foi de 2,07 em 1996 e 1,96 em 2008. Conclusões Para compreender a redução dos homicídios no Município, é importante considerar macrodeterminantes que atingem todo o Município e todos os subgrupos populacionais e microdeterminantes que atuam localmente, influenciando de forma diferenciada os homicídios com armas de fogo e os homicídios na população jovem, no sexo masculino e em residentes em áreas de alta exclusão social. PMID:21390415

Peres, Maria Fernanda Tourinho; Vicentin, Diego; Nery, Marcelo Batista; de Lima, Renato Sérgio; de Souza, Edinilsa Ramos; Cerda, Magdalena; Cardia, Nancy; Adorno, e Sérgio

2012-01-01

286

Evaluation of Fracture Azimuth by EM Wave and Elastic Wave  

NASA Astrophysics Data System (ADS)

Fracture system plays an important role in the development of underground energy, for example enhanced geothermal system (EGS), oil shale and shale gas, etc. Therefore, it becomes more and more important to detect and evaluate the fracture system. Geophysical prospecting is an useful method to evaluate the characteristics of the subsurface fractures. Currently, micro-seismology, multi-wave seismic exploration, and electromagnetic (EM) survey are reported to be used for the purpose. We are studying a method using both elastic wave and EM wave to detect and evaluate the fracture azimuth in laboratory. First, we build a 3D horizontal transverse isotropy (HTI) model, shown in the figure 1, by dry parallel fractures system, which was constructed by plexiglass plates and papers. Then, we used the ultrasonic system to obtain reflected S-wave data. Depending on the shear wave splitting, we evaluated the fracture azimuth by the algorithm of Pearson correlation coefficient. In addition, we used the full Polarimetric ultra wide band electromagnetic (FP-UWB-EM) wave System, shown in the figure 2, to obtain full polarimetric reflected EM-wave data. Depending on the rotation of the EM wave polarimetry, we evaluated the fracture azimuth by the the ration between maximum amplitude of co-polarimetric EM wave and maximum amplitude of cross-polarimetric EM wave. Finally, we used both EM-wave data and S-wave data to evaluate the fracture azimuth by the method of cross plot and statistical mathematics. To sum up, we found that FP-UWB-EM wave can be used to evaluated the fracture azimuth and is more accurate than ultrasound wave. Also joint evaluation using both data could improve the precision.

Feng, X.; Wang, Q.; Liu, C.; Lu, Q.; Zeng, Z.; Liang, W.; Yu, Y.; Ren, Q.

2013-12-01

287

Theory of EM monitoring of sea bottom geothermal areas  

NASA Astrophysics Data System (ADS)

Monitoring of geophysical conditions of marine sedimentary basins is necessary for predicting seismic events and for adaptation of geothermal technologies for seismically active (as a rule) sea bottom geothermal areas. These conditions are characterized by seismo-hydro-electromagnetic (EM) geophysical field interaction in the presence of gravity. Based on the main physical principles, geophysical and petrophysical data, we formulate a mathematical model of seismo-hydro-EM interaction in a basin of a marginal sea and calculate the transformation of a seismic excitation in the upper mantle under the central part of the sea of Japan into the low-frequency (0.1 to 10 Hz) EM signals at the top of the sea bottom sedimentary layer, at the sea surface and in the atmosphere up to the lower boundary of the ionosphere. Physics of the EM generation and propagation process is shown including: generation of EM waves in the upper mantle layer M by a seismic wave from under M, spatial modulation of diffusive EM waves by a seismic wave, stopping of the EM wave arrived (before the seismic P wave) from the upper mantle at the top of the sediments because of the high electric conductivity of seawater (3.5 S/m), immediate penetration of the EM wave through the seawater thickness after the delayed seismic P wave shock into the sea bottom, and EM emission from the sea surface into the atmosphere. Let us note that the EM signal in the sea bottom sediments is the first measurable signal of a seismic activation of geological structures beneath the seafloor and this signal is protected by seawater from the influence ionosphere disturbances. Amplitude of the computed magnetic signals (300, 200, 50, and 30 pT at the ocean-atmosphere interface and at the height of 10, 30 and 50 km, respectively), their predominant frequency (0.25 Hz), the delay of the seismic P wave in regard to the magnetic signal for the receivers at the shore (20 s), the amplitude of temperature disturbances in sediments (up to 0.02 K), the parameters of the long (150 km) tsunami wave of a small (up to 20 cm) amplitude far from the shore and other values that characterize the seismo-hydro-EM process are of the orders observed. Recommendations for the EM monitoring of dynamic processes beneath seafloor geothermal areas are given.

Ershov, Sergey; Mikhaylovskaya, Irina; Novik, Oleg

2006-04-01

288

UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM COMUNICAO  

E-print Network

Experiência profissional em comunicação 5 Produção científica na área de comunicação (artigos, livros e capítulos) 10 Produção científica em outras áreas de conhecimento (artigos, livros e capítulos) 5 (artigos, livros e 10 #12;3 capítulos) Produção científica em outras áreas de conhecimento (artigos, livros

Maier, Rudolf Richard

289

Environmental Education and Development Division (EM-522). Annual report, Fiscal year 1993  

SciTech Connect

The Environmental Education and Development Division (EM-522) is one of three divisions within the Office of Technology Integration and Environmental Education and Development (EM-52) in Environmental Restoration and Waste Management`s (EM`s) Office of Technology Development (EM-50). The primary design criterion for EM-522 education activities is directly related to meeting EM`s goal of environmental compliance on an accelerated basis and cleanup of the 1989 inventory of inactive sites and facilities by the year 2019. Therefore, EM-522`s efforts are directed specifically toward stimulating knowledge and capabilities to achieve the goals of EM while contributing to DOE`s overall goal of increasing scientific, mathematical, and technical literacy and competency. This report discusses fiscal year 1993 activities.

Not Available

1993-12-31

290

Truncated and constrained helical analogs of antimicrobial esculentin-2EM.  

PubMed

Esculentin-2EM is a 37-residue, cationic, amphipathic, ?-helical antimicrobial peptide isolated from a Korean frog, Glandirama emeljanovi. Many studies revealed that truncation of this peptide results in substantial decreases in its antimicrobial activity. Lee and his colleagues have recently reported that a 23-residue esculentin-2EM analog containing a tryptophanyl substitution at position 16 showed a significant recovery of the antimicrobial activity of the parent peptide. Here we report a new series of 15-residue esculentin-2EM analogs which are constrained into an ?-helical conformation via an oct-4-enyl cross-link. The resulting 'stapled' derivatives displayed remarkable increases not only in antimicrobial activity but also in helical content and protease resistance compared to Lee's original 23-residue esculentin-2EM analog. The preliminary data obtained in this work strongly supports the potential of our strategy for the development of a new class of peptide antibiotics. PMID:24211019

Pham, Thanh Kim; Kim, Do-Hee; Lee, Bong-Jin; Kim, Young-Woo

2013-12-15

291

Genética de populações e relações de parentesco em Ciconiiformes (Aves).  

E-print Network

??Estudos de genética de populações e de parentesco genético foram desenvolvidos em colhereiro (Platalea ajaja), cabeça-seca (Mycteria americana) e garça-branca-grande (Ardea alba egretta), de colônias… (more)

Carolina Isabel Miño

2010-01-01

292

Structure of Matter, Forces, EM Waves, Spectroscopy, Doppler Effect  

NSDL National Science Digital Library

These supplemental class notes cover the basic properties of matter, the nature of forces, the electromagnetic spectrum, and how astronomers exploit the properties of the EM spectrum to deduce the physical nature of distant objects.

O'Connell, Robert

2005-06-28

293

E.M. and Hadronic Shower Simulation with FLUKA  

SciTech Connect

A description of the main features of e.m. and hadronic shower simulation models used in the FLUKA code is summarized and some recent applications are discussed. The general status of the FLUKA project is also reported.

Battistoni, G.; Fasso, A.; Ferrari, A.; Ranft, J.; Rubbia, A.; Sala, P.R.; /INFN, Milan /SLAC /CERN /Siegen U. /Zurich, ETH

2005-10-03

294

NASA EM Followup of LIGO-Virgo Candidate Events  

NASA Technical Reports Server (NTRS)

We present a strategy for a follow-up of LIGO-Virgo candidate events using offline survey data from several NASA high-energy photon instruments aboard RXTE, Swift, and Fermi. Time and sky-location information provided by the GW trigger allows for a targeted search for prompt and afterglow EM signals. In doing so, we expect to be sensitive to signals which are too weak to be publicly reported as astrophysical EM events.

Blackburn, Lindy L.

2011-01-01

295

EM Telemetry Tool for Deep Well Drilling Applications  

SciTech Connect

This final report discusses the successful development and testing of a deep operational electromagnetic (EM) telemetry system, produced under a cooperative agreement with the United States Department of Energy's National Energy Technology Laboratory. This new electromagnetic telemetry system provides a wireless communication link between sensors deployed deep within oil and gas wells and data acquisition equipment located on the earth's surface. EM based wireless telemetry is a highly appropriate technology for oil and gas exploration in that it avoids the need for thousands of feet of wired connections. In order to achieve the project performance objectives, significant improvements over existing EM telemetry systems were made. These improvements included the development of new technologies that have improved the reliability of the communications link while extending operational depth. A key element of the new design is the incorporation of a data-fusion methodology which enhances the communication receiver's ability to extract very weak signals from large amounts of ambient environmental noise. This innovative data-fusion receiver based system adapts advanced technologies, not normally associated with low-frequency communications, and makes them work within the harsh drilling environments associated with the energy exploration market. Every element of a traditional EM telemetry system design, from power efficiency to reliability, has been addressed. The data fusion based EM telemetry system developed during this project is anticipated to provide an EM tool capability that will impact both onshore and offshore oil and gas exploration operations, for conventional and underbalanced drilling applications.

Jeffrey M. Gabelmann

2005-11-15

296

Evaluation of Use of Recombinant Em18 and Affinity-Purified Em18 for Serological Differentiation of Alveolar Echinococcosis from Cystic Echinococcosis and Other Parasitic Infections  

Microsoft Academic Search

To further evaluate recombinant Em18 antigen (rEm18) for immunodiagnosis of human alveolar echino- coccosis, 208 serum samples were examined by enzyme-linked immunosorbent assay (ELISA). To compara- tively assess the results of rEm18-ELISA, ELISA and immunoblot analysis with two affinity-purified native antigens were also performed with 45 selected serum samples. The results indicate that rEm18 is highly useful for serodiagnosis.

Ning Xiao; Wulamu Mamuti; Hiroshi Yamasaki; Yasuhito Sako; Minoru Nakao; Kazuhiro Nakaya; Bruno Gottstein; Peter M. Schantz; Marshall W. Lightowlers; Philip S. Craig; Akira Ito

2003-01-01

297

Isolamento de Salmonella spp. em pombos (Columba livia) no Distrito Federal : aspecto de relevância ao sistema de vigilância em saúde.  

E-print Network

??Dissertação (mestrado)—Universidade de Brasília, Faculdade de Agronomia e Medicina Veterinária, Programa de Pós-Graduação em Saúde Animal, 2014. A domesticação de pombos da espécie Columba livia,… (more)

Santos, Ivanildo de Oliveira Correia

2014-01-01

298

DOE EM industry programs robotics development  

SciTech Connect

The Office of Science and Technology (OST) manages an aggressive program for RD and D, as well as testing and evaluation for the Department of Energy`s (DOE`s) Environmental Management (EM) organization. The goal is to develop new and improved environmental restoration and waste management technologies to clean up the inventory of the DOE weapons complex faster, safer, and cheaper than is possible with currently available technologies. Robotic systems reduce worker exposure to the absolute minimum, while providing proven, cost-effective, and, for some applications, the only acceptable technique for addressing challenging problems. Development of robotic systems for remote operations occurs in three main categories: tank waste characterization and retrieval; decontamination and dismantlement; and characterization, mapping, and inspection systems. In addition, the Federal Energy Technology Center (FETC) has some other projects which fall under the heading of supporting R and D. The central objective of all FETC robotic projects is to make robotic systems more attractive by reducing costs and health risks associated with the deployment of robotic technologies in the cleanup of the nuclear weapons complex. This will be accomplished through development of robots that are cheaper, faster, safer, and more reliable, as well as more straightforward to modify/adapt and more intuitive to operate with autonomous capabilities and intelligent controls that prevent accidents and optimize task execution.

Staubly, R.; Kothari, V.

1998-12-31

299

Image segmentation by EM-based adaptive pulse coupled neural networks in brain magnetic resonance imaging.  

PubMed

We propose an automatic hybrid image segmentation model that integrates the statistical expectation maximization (EM) model and the spatial pulse coupled neural network (PCNN) for brain magnetic resonance imaging (MRI) segmentation. In addition, an adaptive mechanism is developed to fine tune the PCNN parameters. The EM model serves two functions: evaluation of the PCNN image segmentation and adaptive adjustment of the PCNN parameters for optimal segmentation. To evaluate the performance of the adaptive EM-PCNN, we use it to segment MR brain image into gray matter (GM), white matter (WM) and cerebrospinal fluid (CSF). The performance of the adaptive EM-PCNN is compared with that of the non-adaptive EM-PCNN, EM, and Bias Corrected Fuzzy C-Means (BCFCM) algorithms. The result is four sets of boundaries for the GM and the brain parenchyma (GM+WM), the two regions of most interest in medical research and clinical applications. Each set of boundaries is compared with the golden standard to evaluate the segmentation performance. The adaptive EM-PCNN significantly outperforms the non-adaptive EM-PCNN, EM, and BCFCM algorithms in gray mater segmentation. In brain parenchyma segmentation, the adaptive EM-PCNN significantly outperforms the BCFCM only. However, the adaptive EM-PCNN is better than the non-adaptive EM-PCNN and EM on average. We conclude that of the three approaches, the adaptive EM-PCNN yields the best results for gray matter and brain parenchyma segmentation. PMID:20042313

Fu, J C; Chen, C C; Chai, J W; Wong, S T C; Li, I C

2010-06-01

300

FitEM2EM--tools for low resolution study of macromolecular assembly and dynamics.  

PubMed

Studies of the structure and dynamics of macromolecular assemblies often involve comparison of low resolution models obtained using different techniques such as electron microscopy or atomic force microscopy. We present new computational tools for comparing (matching) and docking of low resolution structures, based on shape complementarity. The matched or docked objects are represented by three dimensional grids where the value of each grid point depends on its position with regard to the interior, surface or exterior of the object. The grids are correlated using fast Fourier transformations producing either matches of related objects or docking models depending on the details of the grid representations. The procedures incorporate thickening and smoothing of the surfaces of the objects which effectively compensates for differences in the resolution of the matched/docked objects, circumventing the need for resolution modification. The presented matching tool FitEM2EMin successfully fitted electron microscopy structures obtained at different resolutions, different conformers of the same structure and partial structures, ranking correct matches at the top in every case. The differences between the grid representations of the matched objects can be used to study conformation differences or to characterize the size and shape of substructures. The presented low-to-low docking tool FitEM2EMout ranked the expected models at the top. PMID:18974836

Frankenstein, Ziv; Sperling, Joseph; Sperling, Ruth; Eisenstein, Miriam

2008-01-01

301

Degradation of Benzodiazepines after 120 Days of EMS Deployment  

PubMed Central

Introduction EMS treatment of status epilepticus improves outcomes, but the benzodiazepine best suited for EMS use is unclear, given potential high environmental temperature exposures. Objective To describe the degradation of diazepam, lorazepam, and midazolam as a function of temperature exposure and time over 120 days of storage on active EMS units. Methods Study boxes containing vials of diazepam, lorazepam, and midazolam were distributed to 4 active EMS units in each of 2 EMS systems in the southwestern United States during May–August 2011. The boxes logged temperature every minute and were stored in EMS units per local agency policy. Two vials of each drug were removed from each box at 30-day intervals and underwent high-performance liquid chromatography to determine drug concentration. Concentration was analyzed as mean (and 95%CI) percent of initial labeled concentration as a function of time and mean kinetic temperature (MKT). Results 192 samples were collected (2 samples of each drug from each of 4 units per city at 4 time-points). After 120 days, the mean relative concentration (95%CI) of diazepam was 97.0% (95.7–98.2%) and of midazolam was 99.0% (97.7–100.2%). Lorazepam experienced modest degradation by 60 days (95.6% [91.6–99.5%]) and substantial degradation at 90 days (90.3% [85.2-95.4%]) and 120 days (86.5% [80.7–92.3%]). Mean MKT was 31.6°C (95%CI 27.1–36.1). Increasing MKT was associated with greater degradation of lorazepam, but not midazolam or diazepam. Conclusions Midazolam and diazepam experienced minimal degradation throughout 120 days of EMS deployment in high-heat environments. Lorazepam experienced significant degradation over 120 days and appeared especially sensitive to higher MKT exposure. PMID:24548058

McMullan, Jason T.; Jones, Elizabeth; Barnhart, Bruce; Denninghoff, Kurt; Spaite, Daniel; Zaleski, Erin; Silbergleit, Robert

2014-01-01

302

Learning when to Hold'em and When to Fold'em: ERS's Budget Hold'em Game Facilitates the Budget Development Process in Memphis  

ERIC Educational Resources Information Center

If your school district is facing a budget issue, it might surprise you to learn that the solution might very well lie in a game of cards. That certainly was the case earlier this year for the city schools of Memphis, Tennessee. The game is called Budget Hold'em, and it was developed by Education Resource Strategies (ERS) of Watertown,…

Education Resource Strategies, 2010

2010-01-01

303

EMS Stretcher "Misadventures" in a Large, Urban EMS System: A Descriptive Analysis of Contributing Factors and Resultant Injuries.  

PubMed

Purpose. There is a paucity of data regarding EMS stretcher-operation-related injuries. This study describes and analyzes characteristics associated with undesirable stretcher operations, with or without resultant injury in a large, urban EMS agency. Methods. In the study agency, all stretcher-related "misadventures" are required to be documented, regardless of whether injury results. All stretcher-related reports between July 1, 2009 and June 30, 2010 were queried in retrospective analysis, avoiding Hawthorne effect in stretcher operations. Results. During the year studied, 129,110 patients were transported. 23 stretcher incidents were reported (0.16 per 1,000 transports). No patient injury occurred. Four EMS providers sustained minor injuries. Among contributing aspects, the most common involved operations surrounding the stretcher-ambulance safety latch, 14/23 (60.9%). From a personnel injury prevention perspective, there exists a significant relationship between combative patients and crew injury related to stretcher operation, Fisher's exact test 0.048. Conclusions. In this large, urban EMS system, the incidence of injury related to stretcher operations in the one-year study period is markedly low, with few personnel injuries and no patient injuries incurred. Safety for EMS personnel and patients could be advanced by educational initiatives that highlight specific events and conditions contributing to stretcher-related adverse events. PMID:22606379

Goodloe, Jeffrey M; Crowder, Christopher J; Arthur, Annette O; Thomas, Stephen H

2012-01-01

304

EMS Stretcher “Misadventures” in a Large, Urban EMS System: A Descriptive Analysis of Contributing Factors and Resultant Injuries  

PubMed Central

Purpose. There is a paucity of data regarding EMS stretcher-operation-related injuries. This study describes and analyzes characteristics associated with undesirable stretcher operations, with or without resultant injury in a large, urban EMS agency. Methods. In the study agency, all stretcher-related “misadventures” are required to be documented, regardless of whether injury results. All stretcher-related reports between July 1, 2009 and June 30, 2010 were queried in retrospective analysis, avoiding Hawthorne effect in stretcher operations. Results. During the year studied, 129,110 patients were transported. 23 stretcher incidents were reported (0.16 per 1,000 transports). No patient injury occurred. Four EMS providers sustained minor injuries. Among contributing aspects, the most common involved operations surrounding the stretcher-ambulance safety latch, 14/23 (60.9%). From a personnel injury prevention perspective, there exists a significant relationship between combative patients and crew injury related to stretcher operation, Fisher's exact test 0.048. Conclusions. In this large, urban EMS system, the incidence of injury related to stretcher operations in the one-year study period is markedly low, with few personnel injuries and no patient injuries incurred. Safety for EMS personnel and patients could be advanced by educational initiatives that highlight specific events and conditions contributing to stretcher-related adverse events. PMID:22606379

Goodloe, Jeffrey M.; Crowder, Christopher J.; Arthur, Annette O.; Thomas, Stephen H.

2012-01-01

305

Analyses of Subnanometer Resolution Cryo-EM Density Maps  

PubMed Central

Today, electron cryomicroscopy (cryo-EM) can routinely achieve subnanometer resolutions of complex macromolecular assemblies. From a density map, one can extract key structural and functional information using a variety of computational analysis tools. At subnanometer resolution, these tools make it possible to isolate individual subunits, identify secondary structures, and accurately fit atomic models. With several cryo-EM studies achieving resolutions beyond 5 Å, computational modeling and feature recognition tools have been employed to construct backbone and atomic models of the protein components directly from a density map. In this chapter, we describe several common classes of computational tools that can be used to analyze and model subnanometer resolution reconstructions from cryo-EM. A general protocol for analyzing subnanometer resolution density maps is presented along with a full description of steps used in analyzing the 4.3 Å resolution structure of Mm-cpn. PMID:20888467

Baker, Matthew L.; Baker, Mariah R.; Hryc, Corey F.; DiMaio, Frank

2011-01-01

306

Residual Symmetries in the Presence of an EM Background  

E-print Network

The symmetry algebra of a QFT in the presence of an external EM background (named "residual symmetry") is investigated within a Lie-algebraic, model independent scheme. Some results previously encountered in the literature are here extended. In particular we compute the symmetry algebra for a constant EM background in D=3 and D=4 dimensions. In D= 3 dimensions the residual symmetry algebra is isomorphic to $u(1)\\oplus {\\cal P}_c(2)$, with ${\\cal P}_c(2)$ the centrally extended 2-dimensional Poincar\\'e algebra. In D=4 dimension the generic residual symmetry algebra is given by a seven-dimensional solvable Lie algebra which is explicitly computed. Residual symmetry algebras are also computed for specific non-constant EM backgrounds.

H. L. Carrion; M. Rojas; F. Toppan

2002-05-23

307

Convergence Results for the EM Approach to Mixtures of Experts Architectures  

E-print Network

The Expectation-Maximization (EM) algorithm is an iterative approach to maximum likelihood parameter estimation. Jordan and Jacobs (1993) recently proposed an EM algorithm for the mixture of experts architecture of ...

Jordan, Michael I.

1993-11-01

308

Estudo de apomixia em diferentes níveis de ploidia no Manihot spp.  

E-print Network

??Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Botânica, Programa de Pós-Graduação em Botânica, 2011. A apomixia em Manihot vem sendo estudada pelo… (more)

Ferreira, Adalgisa Maria Chaib

2011-01-01

309

EM-31 Alternative and Enhanced Chemical Cleaning Program  

SciTech Connect

King's introduction to his presentation made 5 important points: 1) Numerous SRS tanks scheduled for closure (contract commitments); 2) Cannot remove all sludge by mechanical means due to obstructions; 3) Chemical removal technology needed (likely oxalic acid); 4) Post - dissolution neutralization required prior to transfer to compliant tanks; 5) Sodium oxalate salts precipitate on neutralization and have negative downstream impacts. There were three SRS chemical cleaning programs in 2010: Baseline: 8wt percent OA batch contact, ECC: 1-3 wt. percent OA with oxalate destruction, and the Alternative/Enhanced Chemical Cleaning (EM-31). This talk is on the EM-31 program.

King, Bill (SRNL) [SRNL

2010-11-01

310

ARTIGO INTERNET Jogos Srios em debate no IST  

E-print Network

ARTIGO INTERNET «Jogos Sérios» em debate no IST in http://sol.sapo.pt/ Data: 2011-9-15 Link: http://sol.sapo.pt/inicio/Tecn ... «Jogos Sérios» em debate no IST O Instituto Superior Técnico (IST) vai ser o palco da II Conferência Internacional sobre aplicações e desenvolvimento de «Jogos Sérios» A conferência terá lugar nos dias 19 e 20 de

Instituto de Sistemas e Robotica

311

MESTRADO EM MICROBIOLOGIA EPIDEMIOLOGIA DE DOENAS TRANSMISSVEIS Faculdade de Cincias  

E-print Network

transmissíveis (DTs) e agentes etiológicos. História natural da infecção no hospedeiro. Noção de R0. Imunidade de grupo. Construção de modelos matemáticos para DTs: em equações às diferenças. Principais parâmetros dos modelos de DTs e sua estimação. Modelos para DTs formalizados em equações diferenciais. Padrões dinâmicos

Instituto de Sistemas e Robotica

312

Erros comuns de ingls em artigos cientficos escritos por pessoas de lngua portuguesa  

E-print Network

Erros comuns de inglês em artigos científicos escritos por pessoas de língua portuguesa Siang Wun comuns de inglês em artigos científicos escritos por pessoa #12;Introdução Baseado em experiência acumulada ao longo dos anos, ao revisar artigos escritos em inglês principalmente por pessoas de língua

Song, Siang Wun

313

Study on the Temperature Limitation of the Injecting Power to a Pyramidal EM-Wave Absorber  

Microsoft Academic Search

In this paper, first the temperature distribution of the pyramidal EM-wave absorber is calculated in the coupled method. Next, the injected power to the EM-wave absorber is changed to estimate the maximum power density that the EM-wave absorber can resist. As a result, the limitation of the injecting power density to a pyramidal EM-wave absorber is achievable.

Tetsuhiro Sasagawa; Shinya Watanabe; Osamu Hashimoto; Toshifumi Saito; Hiroshi Kurihara

2009-01-01

314

Quasi-Monte Carlo Sampling to improve the Efficiency of Monte Carlo EM  

E-print Network

Quasi-Monte Carlo Sampling to improve the Efficiency of Monte Carlo EM Wolfgang Jank Department@rhsmith.umd.edu November 17, 2003 Abstract In this paper we investigate an efficient implementation of the Monte Carlo EM al- gorithm based on Quasi-Monte Carlo sampling. The Monte Carlo EM algorithm is a stochastic version

Jank, Wolfgang

315

EMS Mutagenesis 101 From: Methods in Molecular Biology, vol. 323: Arabidopsis Protocols, Second Edition  

E-print Network

-genomic era, the use of reverse genetic approaches to understanding the role of genes in growth of EMS mutagenesis for the molecular genetic model plant Arabidopsis thaliana. Key Words: EMS; chemical produces T/A to G/C transversion and A/T to G/C transitions (1,3,4). At a low frequency, EMS generates G

Schumaker, Karen

316

Reliable prediction of EM radiation from a PCB at the design stage of electronic equipment  

Microsoft Academic Search

This paper presents a composite computer-aided design (CCAD) package for prediction of electromagnetic (EM) radiation from a printed circuit board (PCB) at the design stage of equipment. Such a CCAD package has been developed by combining an EM computation tool such as numerical electromagnetic code (NEC)-2, with other circuit design packages (CDPs). The method of prediction of EM radiation using

P. K. Saha; Jim Dowling

1998-01-01

317

Sensibilidade antimicrobiana de bactérias aeróbicas isoladas de úlceras leishmanióticas, em Corte de Pedra, BA  

Microsoft Academic Search

RESUMO Um estudo prospectivo, sobre a sensibilidade antimicrobiana da flora bacteriana em úlceras cutâneas leishmanióticas, foi realizado em pacientes portadores de leishmaniose tegumentar, em Corte de Pedra, Bahia. Foram estudados 84 pacientes, principalmente adolescentes e adultos dedicados à lavoura, apresentando lesão cutânea única. Staphylococcus aureus predominou (83%) nas culturas, sendo sensível à maioria dos antibióticos testados. Flora bacteriana mista esteve

Luis Angel Vera; Jefferson Lessa Soares de Macedo; Isolina Allen Ciuffo; Conceição Guerra Santos; João Barberino Santos

2006-01-01

318

Convergence results for the EM approach to mixtures of experts architectures  

Microsoft Academic Search

The Expectation-Maximization (EM) algorithm is an iterative approach to maximum likelihood parameter estimation. Jordan and Jacobs recently proposed an EM algorithm for the mixture of experts architecture of Jacobs, Jordan, Nowlan and Hinton (1991) and the hierarchical mixture of experts architecture of Jordan and Jacobs (1992). They showed empirically that the EM algorithm for these architectures yields significantly faster convergence

Michael I. Jordan; Lei Xu

1995-01-01

319

Airborne EM for geothermal and hydrogeological mapping  

NASA Astrophysics Data System (ADS)

Within the "VIGOR" project, aimed at assessing the geothermal potential of four regions in southern Italy, Airborne EM data have been acquired, modeled and interpreted. The system deployed was SkyTEM, a time-domain helicopter electromagnetic system designed for hydrogeophysical, environmental and mineral investigations. The AEM data provide, after data acquisition, analysis, processing, and modeling, a distribution volume of electrical resistivity, spanning an investigation depth from ground surface of few hundred meters, depending on resistivity condition. Resistivity is an important physical parameter for geothermal investigation, since it proved to be very effective in mapping anomalies due to hydrothermal fluid circulation, which usually has high salt content and produces clayey alteration minerals. Since the project required, among other issues, to define geothermal resources at shallow level, it was decided to perform a test with an airborne electromagnetic geophysical survey, to verify the advantages offered by the system in covering large areas in a short time. The geophysical survey was carried out in Sicily, Italy, in late 2011, over two test sites named "Termini" and "Western Sicily". The two areas were chosen on different basis. "Termini" area is covered by extensive geological surveys, and was going to be investigated also by means of electrical tomography in its northern part. Since geological condition of Sicily, even at shallow depth, is very complex, this area provided a good place for defining the resistivity values of the main geological units outcropping in the region. "Termini" survey has been also an occasion to define relations between resistivity distribution, lithological units and thermal conductivity. The "Western Sicily" area cover the main thermal manifestations of western Sicily, and the research target was to establish whether they are characterized by common hydrogeological or tectonic features that could be mapped by resistivity. SkyTEM data have been acquired in a series of flight lines and were then processed and inverted. In the "Termini" area the flight line spacing had 150 m separation. In the "Western Sicily" area two different line spacing were used: the 1 km spacing was used for the regional mapping, whereas for infill areas, around the main hydrothermal springs, the flight lines had 100 m spacing. The total number of flight line was 4580 km, and the explored surface was in excess of 2000 km2. After acquisition, data were processed to eliminate coupling with infrastructures, and noise. Inversions was then carried out using the quasi 3-D Spatially Constrained Inversion. The obtained resistivity volume has then been the base for a detailed lithological and geothermal interpretation. Lithological and geological maps were used to constrain surface condition and to understand the resistivity ranges of the different lithological units. On the base of resistivity values, lithological units were combined to establish the main litho-resistive units, then modeled at depth, down to achievable investigation depth. This detailed interpretative modeling was also the occasion of recognizing resistivity anomalies within carbonate units, which may possibly represent hydrogeological or hydrothermal bodies. The litho-resitive 3D model is now under investigation to verify how it can represent a viable way to image thermal conductivity variations at depth.

Menghini, A.; Manzella, A.; Viezzoli, A.; Montanari, D.; Maggi, S.

2012-12-01

320

UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM INFORMTICA  

E-print Network

Computação: 16, sendo 2 para candidatos com residência no exterior. 2.3.2 Linha de Pesquisa em Fundamentos e, Algoritmos e Métodos Formais (3 vagas), Processamento de Imagens e Sinais (7 vagas), Redes e Comunicação sem

Lucero, Jorge Carlos

321

UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM INFORMTICA  

E-print Network

no exterior. 2.3.2 Linha de Pesquisa em Fundamentos e Métodos de Computação: 15 (quinze), sendo quatro para imagens e sinais (9 vagas), robótica (2 vagas), redes e comunicação sem fio (2 vagas), hardware e sistemas

Maier, Rudolf Richard

322

Sonar-Based Mapping With Mobile Robots Using EM  

Microsoft Academic Search

This paper presents an algorithms for learn- ing occupancy grid maps with mobile robots equipped with range finders, such as sonar sen- sors. Our approach employs the EM algorithm to solve the concurrent mapping and localization problem. To accommodate the spatial nature of range data, it relies on a two-layered representa- tion of maps, where global maps are composed from

Wolfram Burgard; Dieter Fox; Hauke Jans; Christian Matenar; Sebastian Thrun

323

ISSN 0103-9741 Monografias em Cincia da Computao  

E-print Network

&P) activities, such as 3D geomodelling, seismic interpretation, real-time drilling follow-up and correction, offshore structures' design, static and dynamic simulations of these offshore structures, oil pipelines perfuração em tempo real, projeto de estruturas offshore, simulações estáticas e dinâmicas destas estruturas

Barbosa, Alberto

324

Minimum-Distortion Isometric Shape Correspondence Using EM Algorithm  

E-print Network

Minimum-Distortion Isometric Shape Correspondence Using EM Algorithm Yusuf Sahillioglu and Yu¨cel Yemez Abstract--We present a purely isometric method that establishes 3D correspondence between two (nearly) isometric shapes. Our method evenly samples high-curvature vertices from the given mesh

Yemez, Yücel

325

ISSN 0103-9741 Monografias em Cincia da Computao  

E-print Network

into cells from all three germinal layers while multipotent stem cells can generate only closely relatedISSN 0103-9741 Monografias em Ciência da Computação n° 04/09 Automatic Embryonic Stem Cells de Lucena February, 2009 Automatic Embryonic Stem Cells Detection and Counting in Fluorescence

Endler, Markus

326

PS-GRADUAO EM BIOLOGIA DE FUNGOS, ALGAS E PLANTAS  

E-print Network

identificação, sendo Carteira de identidade e CPF (original e fotocópia, ou fotocópia autenticada em cartório de Botânica Campus Universitário ­ Trindade - Florianópolis-SC-Brasil Cx. Postal 476 - CEP 88040

Floeter, Sergio Ricardo

327

A Generalized Partial Credit Model: Application of an EM Algorithm  

Microsoft Academic Search

The partial credit model (PCM) with a varying slope parameter is developed and called the generalized partial credit model (GPCM). The item step parameter of this model is decomposed to a location and a threshold parameter, following Andrich's (1978) rating scale formulation. The EM algorithm for estimating the model parameters is derived. The performance of this generalized model is compared

Eiji Muraki

1992-01-01

328

7 CFR 1945.20 - Making EM loans available.  

Code of Federal Regulations, 2010 CFR

...1945.20 Making EM loans...the actions required by § 1945...and other factors which are...Secretary in making determinations...Secretary in making a decision on the requested...consider other factors in accordance...the actions required in...

2010-01-01

329

EM Ground-Wave Propagation over the Curved Lunar Surface  

Microsoft Academic Search

VLF and LF electromagnetic (EM) ground-wave propagation between points on the surface of a smooth lunar sphere which is surrounded by free space or a cold isotropic plasma is investigated. Following Ward's analysis of recent lunar geophysical data, two mathematical models which are most likely to actually exist were chosen as either a cold homogeneous moon or a hot wet

Se Hyun Cho; Ray King

1972-01-01

330

INOVAÇÃO E TEORIAS DA FIRMA EM TRÊS PARADIGMAS  

Microsoft Academic Search

1. INTRODUÇÃO Desde os tempos de Alfred Marshall, a teoria econômica procura criar mo- delos que capturem a lógica do comportamento das firmas e dos merca- dos. Os resultados destes esforços não resultaram em um quadro analítico convergente, já que persistem controvérsias importantes acerca do papel das diferentes forças que influenciam o crescimento e os objetivos da firma. Winter (1993),

Paulo Bastos Tigre

331

A MORE COHERENT TOPIC SEQUENCE FOR E&M  

Microsoft Academic Search

The traditional sequence of topics in the E&M portion of the calculus-based introductory physics poses serious conceptual problems for the student. New concepts are introduced extremely rapidly; abstractions are layered on top of abstractions; complex mathematical formalisms are introduced rapidly; and the student is expected to assimilate all of this quickly. To many students it is not even clear what

Ruth Chabay; Bruce Sherwood

332

An EM algorithm for wavelet-based image restoration  

Microsoft Academic Search

Abstract: This paper introduces an expectation--maximization(EM) algorithm for image restoration (deconvolution) based on apenalized likelihood formulated in the wavelet domain. Regularizationis achieved by promoting a reconstruction with low-complexity,expressed in the wavelet coefficients, taking advantage ofthe well known sparsity of wavelet representations. Previous workshave investigated wavelet-based restoration but, except for certainspecial cases, the resulting criteria are solved...

Mário A. T. Figueiredo; Robert D. Nowak

2003-01-01

333

CONTINUIDADES E DESCONTINUIDADES HISTÓRICAS EM ANÁLISE DO DISCURSO  

Microsoft Academic Search

RESUMO: Este artigo apresenta e reflete sobre a trajetória da disciplina lingüística Análise do Discurso, tomando por base para essa reflexão os conceitos de paradigma e de continuidade vs. descontinuidade históricas, postulados por Khun. Embora a Análise do Discurso tenha sido fundada na França na década de 60, com um propósito definido, seu contato com outros povos possibilitou alteração em

Eli Gomes Castanho; Jarbas Vargas Nascimento

334

NUMBER: EM 1.00 (NEW) SECTION: Emergency Management  

E-print Network

NUMBER: EM 1.00 (NEW) SECTION: Emergency Management SUBJECT: Emergency Notification System Policy and taking into account the safety of the community, activate the notification system, unless issuing the Carolina Alert system. a. Emergency Management Coordinator, University of South Carolina Division of Law

Almor, Amit

335

The EM Algorithm for Mixtures of Factor Analyzers Zoubin Ghahramani  

E-print Network

). The algorithm used by these authors for dimensionality reduction is principal components analysis (PCA). 1 #12;z components analyzers to a mixture of factor analyzers. Their learning algorithm consisted of an outer loop of approximate EM to t the mixture components, combined with an inner loop of gradient descent to t each

Ghahramani, Zoubin

336

Cost-Effectiveness Analysis of Helicopter EMS for Trauma Patients  

Microsoft Academic Search

Study objective: To evaluate the cost-effectiveness of helicopter EMS for trauma patients. Methods: We applied a cost-effectiveness analysis from the service provider's perspective to cost and effectiveness estimates. The cost estimates comprise direct operating costs and additional survivors' hospital costs. The effectiveness estimates were calculated with the TRISS methodology from literature sources and data from a cohort of patients transported

Peter A Gearhart; Richard Wuerz; A. Russell Localio

1997-01-01

337

MESTRADO EM MICROBIOLOGIA FBRICAS CELULARES MICROBIANAS Instituto Superior Tcnico  

E-print Network

MESTRADO EM MICROBIOLOGIA FÁBRICAS CELULARES MICROBIANAS ­ Instituto Superior Técnico Objectivos: O microbiologia celular e molecular com as novas abordagens da engenharia metabólica à escala do genoma procariotas e eucariotas: - Estruturas celulares e compartimentalização; - Sistemas de transporte; - Fluxo de

Instituto de Sistemas e Robotica

338

Da Causalidade à Indecidibilidade em Ciências da Terra  

Microsoft Academic Search

As Ciências da Terra estudam a historia da Terra mas também os processos que aí ocorrem. São simultaneamente Ciências Históricas e Dinâmicas. O principio das causas actuais, enunciado por Lyell no século XIX, procurava explicar o passado a partir do presente e levou ao uniformismo, que suplantou o catastrofismo ainda no século XIX. Mas a observação dos processos em profundidade

A. Ribeiro

339

Hierarchical mixtures of experts and the EM algorithm  

Microsoft Academic Search

We present a tree-structured architecture for supervised learning. The statistical model underlying the architecture is a hierarchical mixture model in which both the mixture coefficients and the mixture components are generalized linear models (GLIMs). Learning is treated as a maximum likelihood problem; in particular, we present an expectation-maximization (EM) algorithm for adjusting the parameters of the architecture. We also develop

Michael I. Jordan; Robert A. Jacobs

1993-01-01

340

Hierarchical Mixtures of Experts and the EM Algorithm  

Microsoft Academic Search

We present a tree-structured architecture for supervised learning. The statistical model underlying the architecture is a hierarchical mixture model in which both the mixture coefficients and the mixture components are generalized linear models (GLIM's). Learning is treated as a maximum likelihood problem; in particular, we present an Expectation-Maximization (EM) algorithm for adjusting the parameters of the architecture. We also develop

Michael I. Jordan; Robert A. Jacobs

1994-01-01

341

ISSN 0103-9741 Monografias em Cincia da Computao  

E-print Network

, jogos para telefones celulares podem ser sé- rios candidatos a se tornarem uma forma importante de entretenimento em um futuro próximo. Entretanto, a maioria dos jogos (para computadores, consoles e dispositivos tipo de entretenimento. Embora jogos para telefones celulares pu- dessem atender a muitos usuários com

Endler, Markus

342

COMBINATION OF EM AND DC MEASUREMENTS FOR UPPER CRUSTAL STUDIES  

E-print Network

COMBINATION OF EM AND DC MEASUREMENTS FOR UPPER CRUSTAL STUDIES T. HARINARAYANA National method alone, could possibly be identified by a combination of methods. Further, distortion or error. This review covers the main results of the combination of these methods, giving more emphasis to case

Harinarayana, T.

343

População estelar nuclear e extranuclear em galáxias Seyfert 2  

NASA Astrophysics Data System (ADS)

A luz das estrelas foi, historicamente, vista por observadores de AGNs como uma poluição inconveniente. Conseqüentemente, a informação contida nas características estelares foi, durante muito tempo, largamente omitida. Nos primeiros estudos, o método empregado para remover esta contaminação estelar foi representá-la por um template de galáxia elíptica e subtraí-la do espectro observado, restando o puro AGN como um resíduo. Hoje sabemos que não é tão simples representar essa população. Vários estudos têm mostrado a presença de formação estelar recente próxima a região nuclear de galáxias Seyfert. Neste trabalho foi revisada a abordagem tradicional, tendo-se focalizado a análise na luz estelar. Espectros óticos de fenda longa, com alta razão sinal/ruído, foram usados para estudar a variação radial das larguras equivalentes de linhas de absorção e cores do contínuo. Utilizando o método de síntese espectral de populações estelares, foram estimadas as contribuições de populações estelares de diferentes idades (e de um contínuo tipo lei de potência) para a luz integrada das galáxias, em 4020A. As principais conclusões deste trabalho são: na região nuclear, mais da metade das galáxias Seyfert 2 da amostra (57%) apresenta contribuições das populações com 100 milhões de anos ou mais jovens superior a 20% do fluxo em 4020A, enquanto que em cerca de 40% delas a componente de 3 milhões de anos (e/ou luz que provem de um núcleo ativo) tem contribuição significativa (maior do que 10%). Estas contribuições em geral decrescem quando se vai para regiões mais distantes do centro das galáxias, respectivamente 53% e 30% a 1kpc, 40% e 15% a 3kpc do centro das galáxias. Estes resultados foram comparados com aqueles obtidos para uma amostra de galáxias não ativas de mesmo tipo de Hubble das Seyfert. Em uma análise inicial nota-se que em geral as galáxias Seyfert apresentam contribuições das populações de 100 milhões de anos maiores do que aquelas encontradas nas galáxias não ativas, sugerindo uma ligação entre a formação estelar e a atividade em galáxias.

Raimann, D. I.; Storchi-Bergmann, T.; Cid Fernandes, R., Jr.; Delgado, R. M. G.; Schmitt, H.; Heckman, T.; Leitherer, C.

2003-08-01

344

A non-qubit quantum adder as one-dimensional cellular automaton  

NASA Astrophysics Data System (ADS)

A complete quantum addition machine is presented and compared with methods employing unitary transformations first. A quantum half-adder circuit shown earlier can be implemented into each cell of a 1D cellular automaton. An electric Aharonov-Bohm effect version of the quantum circuit is used to illustrate this implementation. Whatever a quantum Turing machine can achieve is realized in the cellular automata architecture we propose here. The coherence requirement is limited to one cell area. The magnetic flux needed is 0.1?0, corresponding to 0.414 mT for a ring area of 1 square micron or an electric potential of 0.414 mV at 1 ps with an energy dissipation of 0.041 eV per iteration.

Wu, C. H.; Cain, C. A.

2014-05-01

345

Finite-size effects in a metallic multichannel ring with Kondo impurity: Persistent currents and magnetoresistance  

NASA Astrophysics Data System (ADS)

We consider a spin-1/2 impurity interacting with conduction electrons in two different orbital channels via an isotropic spin exchange. The exchange is the same for both channels, but a crystalline field breaks the symmetry between the orbital channels. This corresponds to a splitting of the conduction electron ?8 into two doublets in the quadrupolar Kondo effect, or to the electron-assisted tunneling of an atom in a double-well potential in an external magnetic field. Another possible realization could be a quantum dot coupled to two equal rings of the same length subject to an electrostatic potential difference. We consider the Bethe ansatz equations for this model and derive the tower structure of the finite-size corrections to the ground-state energy. These results are used to discuss the Aharonov-Bohm-Casher interference pattern in the persistent charge and spin currents, and the magnetoresistivity due to the scattering of electrons off the impurity.

Zvyagin, A. A.; Schlottmann, P.

1996-12-01

346

An Experimental Proposal to Test Dynamic Quantum Non-locality with Single-Atom Interferometry  

E-print Network

Quantum non-locality based on the well-known Bell inequality is of kinematic nature. A different type of quantum non-locality, the non-locality of the quantum equation of motion, is recently put forward with connection to the Aharonov-Bohm effect [Nature Phys. 6, 151 (2010)]. Evolution of the displacement operator provides an example to manifest such dynamic quantum non-locality. We propose an experiment using single-atom interferometry to test such dynamic quantum non-locality. We show how to measure evolution of the displacement operator with clod atoms in a spin-dependent optical lattice potential and discuss signature to identify dynamic quantum non-locality under a realistic experimental setting.

Shi-Liang Zhu; Zheng-Yuan Xue; Dan-Wei Zhang; Lu-Ming Duan

2010-09-14

347

Low-dimensional nanostructures and a semiclassical approach for teaching Feynman's sum-over-paths quantum theory  

NASA Astrophysics Data System (ADS)

An introduction to quantum mechanics based on the sum-over-paths (SOP) method originated by Richard P Feynman and developed by E F Taylor and coworkers is presented. The Einstein-Brillouin-Keller (EBK) semiclassical quantization rules are obtained following the SOP approach for bounded systems, and a general approach to the calculation of propagation amplitude is discussed for unbounded systems. These semiclassical results are obtained when the SOP is limited to the trajectories classically allowed. EBK semiclassical quantization and the topological Maslov index are used to deduce the correct quantum mechanical results for systems which live in a two-dimensional world as quantum dots and quantum rings. In the latter systems, the semiclassical propagation amplitude is used to discuss the Aharonov-Bohm effect. The development involves only elementary calculus and also provides a theoretical introduction to the quantum nature of low-dimensional nanostructures.

Onorato, P.

2011-03-01

348

Engineering massive quantum memories by topologically time-modulated spin rings  

E-print Network

We introduce a general scheme to realize perfect storage of quantum information in systems of interacting qubits. This novel approach is based on {\\it global} external controls of the Hamiltonian, that yield time-periodic inversions in the dynamical evolution, allowing a perfect periodic quantum state recontruction. We illustrate the method in the particularly interesting and simple case of spin systems affected by XY residual interactions with or without static imperfections. The global control is achieved by step time-inversions of an overall topological phase of the Aharonov-Bohm type. Such a scheme holds both at finite size and in the thermodynamic limit, thus enabling the massive storage of arbitrarily large numbers of local states, and is stable against several realistic sources of noise and imperfections.

S. M. Giampaolo; F. Illuminati; A. Di Lisi; S. De Siena

2006-01-24

349

Is Quantum Mechanics Incompatible with Newton's First Law?  

NASA Astrophysics Data System (ADS)

Quantum mechanics (QM) clearly violates Newton’s First Law of Motion (NFLM) in the quantum domain for one of the simplest problems, yielding an effect in a force-free region much like the Aharonov-Bohm effect. In addition, there is an incompatibility between the predictions of QM in the classical limit, and that of classical mechanics (CM) with respect to NFLM. A general argument is made that such a disparity may be found commonly for a wide variety of quantum predictions in the classical limit. Alternatives to the Schrödinger equation are considered that might avoid this problem. The meaning of the classical limit is examined. Critical views regarding QM by Schrödinger, Bohm, Bell, Clauser, and others are presented to provide a more complete perspective.

Rabinowitz, Mario

2008-04-01

350

Biprism electron interferometry with a single atom tip source.  

PubMed

Experiments with electron or ion matter waves require a coherent, monochromatic and long-term stable source with high brightness. These requirements are best fulfilled by single atom tip (SAT) field emitters. The performance of an iridium covered W(111) SAT is demonstrated and analyzed for electrons in a biprism interferometer. Furthermore we characterize the emission of the SAT in a separate field electron and field ion microscope and compare it with other emitter types. A new method is presented to fabricate the electrostatic charged biprism wire that separates and combines the matter wave. In contrast to other biprism interferometers the source and the biprism size are well defined within a few nanometers. The setup has direct applications in ion interferometry and Aharonov-Bohm physics. PMID:24704604

Schütz, G; Rembold, A; Pooch, A; Meier, S; Schneeweiss, P; Rauschenbeutel, A; Günther, A; Chang, W T; Hwang, I S; Stibor, A

2014-06-01

351

Control of tripod-scheme cold-atom wavepackets by manipulating a non-Abelian vector potential  

SciTech Connect

Tripod-scheme cold atoms interacting with laser beams have attracted considerable interest for their role in synthesizing effective non-Abelian vector potentials. Such effective vector potentials can be exploited to realize an all-optical imprinting of geometric phases onto matter waves. By working on carefully designed extensions of our previous work, we show that coherent lattice structure of cold-atom sub-wavepackets can be formed and that the non-Abelian Aharonov-Bohm effect can be easily manifested via the translational motion of cold atoms. We also show that by changing the frame of reference, effects due to a non-Abelian vector potential may be connected with a simple dynamical phase effect, and that under certain conditions it can be understood as an Abelian geometric phase in a different frame of reference. Results should help design better schemes for the control of cold-atom matter waves.

Zhang Qi, E-mail: cqtzq@nus.edu.s [Centre of Quantum Technologies and Department of Physics, National University of Singapore, 117543 (Singapore); Gong Jiangbin, E-mail: phygj@nus.edu.s [Department of Physics and Centre for Computational Science and Engineering, National University of Singapore, 117542 (Singapore); NUS Graduate School for Integrative Sciences and Engineering, Singapore 117597 (Singapore); Oh, C.H., E-mail: phyohch@nus.edu.s [Centre of Quantum Technologies and Department of Physics, National University of Singapore, 117543 (Singapore); Institute of Advanced Studies, Nanyang Technological University, Singapore 639798 (Singapore)

2010-06-15

352

Beyond the constant-mass Dirac physics: Solitons, charge fractionization, and the emergence of topological insulators in graphene rings  

E-print Network

The doubly-connected polygonal geometry of planar graphene rings is found to bring forth topological configurations for accessing nontrivial relativistic quantum field (RQF) theory models that carry beyond the constant-mass Dirac-fermion theory. These include generation of sign-alternating masses, solitonic excitations, and charge fractionization. The work integrates a RQF Lagrangian formulation with numerical tight-binding Aharonov-Bohm electronic spectra and the generalized position-dependent-mass Dirac equation. In contrast to armchair graphene rings (aGRGs) with pure metallic arms, certain classes of aGRGs with semiconducting arms, as well as with mixed metallic-semiconducting ones, are shown to exhibit properties of one-dimensional nontrivial topological insulators. This further reveals an alternative direction for realizing a graphene-based nontrivial topological insulator through the manipulation of the honeycomb lattice geometry, without a spin-orbit contribution.

Constantine Yannouleas; Igor Romanovsky; Uzi Landman

2014-01-22

353

Harnessing synthetic gauge fields for maximally entangled state generation  

E-print Network

We study the generation of entanglement between two species of neutral cold atoms living on an optical ring lattice, where each group of particles can be described by a $d$-dimensional Hilbert space (qu$d$it). Synthetic magnetic fields are exploited to create an entangled state between the pair of qu$d$its. Maximally entangled eigenstates are found for well defined values of the Aharonov-Bohm phase, which are zero energy eigenstates of both the kinetic and interacting parts of the Bose-Hubbard Hamiltonian, making them quite exceptional and robust against certain non-perturbative fluctuations of the Hamiltonian. We propose a protocol to reach the maximally entangled state (MES) by starting from an initially prepared ground state. Also, an indirect method to detect the MES by measuring the current of the particles is proposed.

Sebastian A. Reyes; Luis Morales-Molina; Miguel Orszag; Dominique Spehner

2014-01-21

354

Comparison of Tunneling Rates of Fractional Charges and Electrons across a Quantum Hall Strip  

NASA Astrophysics Data System (ADS)

The fundamental mechanism of current dissipation in a Hall strip is investigated by searching for the fastest process of charge relaxation between the edges. The tunneling rate of the fractional charge across a ? = 1/3 Laughlin state of width Y on the cylinder is found to fit t1/3~exp[-?Y2/12?2], where ? is the Landau length, and ?~=1.0. This rate is exponentially larger than the electron tunneling rate, and can be interpreted by analogy to the tunneling of a vortex through a superfluid. Fractional charge tunneling dominates current relaxation. It determines the Aharonov-Bohm oscillation period, and the magnitude of quantum shot-noise.

Auerbach, Assa

1998-01-01

355

Three attempts at two axioms for quantum mechanics  

E-print Network

The axioms of nonrelativistic quantum mechanics lack clear physical meaning. In particular, they say nothing about nonlocality. Yet quantum mechanics is not only nonlocal, it is twice nonlocal: there are nonlocal quantum correlations, and there is the Aharonov-Bohm effect, which implies that an electric or magnetic field h e r e may act on an electron t h e r e. Can we invert the logical hierarchy? That is, can we adopt nonlocality as an axiom for quantum mechanics and derive quantum mechanics from this axiom and an additional axiom of causality? Three versions of these two axioms lead to three different theories, characterized by "maximal nonlocal correlations", "jamming" and "modular energy". Where is quantum mechanics in these theories?

Daniel Rohrlich

2010-11-24

356

Essential properties of a D2+ molecular complex confined in ring-like nanostructures under external probes: Magnetic field and hydrostatic pressure  

NASA Astrophysics Data System (ADS)

A rigorous adiabatic approximation is used to investigate the energy states of the singly ionized double-donors D2+ complex formed by the coupling of a conduction band electron and two donor centers in a quantum ring with rectangular cross-section. The effects of changing the relative position between the Coulombic centers and the quantum ring geometry parameters, as well as the influence of external probes such as applied magnetic fields and hydrostatic pressure, are particularly studied, highlighting the important contribution of the repulsive inter-center interaction. The suppression of the Aharonov-Bohm ground state oscillations associated with the localization of the electron by the fixed donors is discussed. Comparison between the essential properties of an actual hydrogen ion H2+ and those of the D2+ complex trapped within a quantum ring shows that the strong electron confinement substantially increases the D2+ stability effects.

R-Fulla, M.; Marín, J. H.; Gutiérrez, W.; Mora-Ramos, M. E.; Duque, C. A.

2014-03-01

357

Transport of Massless Dirac Fermions in Non-topological Type Edge States  

PubMed Central

There are two types of intrinsic surface states in solids. The first type is formed on the surface of topological insulators. Recently, transport of massless Dirac fermions in the band of “topological” states has been demonstrated. States of the second type were predicted by Tamm and Shockley long ago. They do not have a topological background and are therefore strongly dependent on the properties of the surface. We study the problem of the conductivity of Tamm-Shockley edge states through direct transport experiments. Aharonov-Bohm magneto-oscillations of resistance are found on graphene samples that contain a single nanohole. The effect is explained by the conductivity of the massless Dirac fermions in the edge states cycling around the nanohole. The results demonstrate the deep connection between topological and non-topological edge states in 2D systems of massless Dirac fermions. PMID:25524881

Latyshev, Yu I.; Orlov, A. P.; Volkov, V. A.; Enaldiev, V. V.; Zagorodnev, I. V.; Vyvenko, O. F.; Petrov, Yu V.; Monceau, P.

2014-01-01

358

Dark matter in the SO(5) × U(1) gauge-Higgs unification  

NASA Astrophysics Data System (ADS)

In the SO(5){× }U(1) gauge-Higgs unification, the lightest neutral component of n_F SO(5)-spinor fermions (dark fermions), which are relevant as they have the observed unstable Higgs boson, becomes the dark matter of the universe. We show that the relic abundance of the dark matter determined by WMAP and Planck data is reproduced, below the bound placed by the direct-detection experiment by LUX, by a model with one light and three heavier (n_F=4) dark fermions with the lightest one with a mass from 2.3 TeV to 3.1 TeV. The corresponding Aharonov-Bohm phase ? _H in the fifth dimension ranges from 0.097 to 0.074. The case of n_F=3 (n_F = 5, 6) dark fermions yields a relic abundance smaller (larger) than the observed limit.

Funatsu, Shuichiro; Hatanaka, Hisaki; Hosotani, Yutaka; Orikasa, Yuta; Shimotani, Takuya

2014-11-01

359

Colloquium: Artificial gauge potentials for neutral atoms  

SciTech Connect

When a neutral atom moves in a properly designed laser field, its center-of-mass motion may mimic the dynamics of a charged particle in a magnetic field, with the emergence of a Lorentz-like force. In this Colloquium the physical principles at the basis of this artificial (synthetic) magnetism are presented. The corresponding Aharonov-Bohm phase is related to the Berry's phase that emerges when the atom adiabatically follows one of the dressed states of the atom-laser interaction. Some manifestations of artificial magnetism for a cold quantum gas, in particular, in terms of vortex nucleation are discussed. The analysis is then generalized to the simulation of non-Abelian gauge potentials and some striking consequences are presented, such as the emergence of an effective spin-orbit coupling. Both the cases of bulk gases and discrete systems, where atoms are trapped in an optical lattice, are addressed.

Dalibard, Jean; Gerbier, Fabrice; Juzeliunas, Gediminas; Oehberg, Patrik [Laboratoire Kastler Brossel, CNRS, UPMC, Ecole normale superieure, 24 rue Lhomond, 75005, Paris (France); Institute of Theoretical Physics and Astronomy, Vilnius University, A. Gostauto 12, Vilnius 01108 (Lithuania); SUPA, Department of Physics, Heriot-Watt University, Edinburgh, EH14 4AS (United Kingdom)

2011-10-01

360

Creation of two-dimensional coulomb crystals of ions in oblate Paul traps for quantum simulations  

E-print Network

We develop the theory to describe the equilibrium ion positions and phonon modes for a trapped ion quantum simulator in an oblate Paul trap that creates two-dimensional Coulomb crystals in a triangular lattice. By coupling the internal states of the ions to laser beams propagating along the symmetry axis, we study the effective Ising spin-spin interactions that are mediated via the axial phonons and are less sensitive to ion micromotion. We find that the axial mode frequencies permit the programming of Ising interactions with inverse power law spin-spin couplings that can be tuned from uniform to $r^{-3}$ with DC voltages. Such a trap could allow for interesting new geometrical configurations for quantum simulations on moderately sized systems including frustrated magnetism on triangular lattices or Aharonov-Bohm effects on ion tunneling. The trap also incorporates periodic boundary conditions around loops which could be employed to examine time crystals.

Bryce Yoshimura; Marybeth Stork; Danilo Dadic; W. C. Campbell; J. K. Freericks

2014-06-20

361

Creation of two-dimensional coulomb crystals of ions in oblate Paul traps for quantum simulations  

E-print Network

We develop the theory to describe the equilibrium ion positions and phonon modes for a trapped ion quantum simulator in an oblate Paul trap that creates two-dimensional Coulomb crystals in a triangular lattice. By coupling the internal states of the ions to laser beams propagating along the symmetry axis, we study the effective Ising spin-spin interactions that are mediated via the axial phonons and are less sensitive to ion micromotion. We find that the axial mode frequencies permit the programming of Ising interactions with inverse power law spin-spin couplings that can be tuned from uniform to $r^{-3}$ with DC voltages. Such a trap could allow for interesting new geometrical configurations for quantum simulations on moderately sized systems including frustrated magnetism on triangular lattices or Aharonov-Bohm effects on ion tunneling. The trap also incorporates periodic boundary conditions around loops which could be employed to examine time crystals.

Yoshimura, Bryce; Dadic, Danilo; Campbell, W C; Freericks, J K

2014-01-01

362

Transport properties of two finite armchair graphene nanoribbons  

PubMed Central

In this work, we present a theoretical study of the transport properties of two finite and parallel armchair graphene nanoribbons connected to two semi-infinite leads of the same material. Using a single ?-band tight binding Hamiltonian and based on Green’s function formalisms within a real space renormalization techniques, we have calculated the density of states and the conductance of these systems considering the effects of the geometric confinement and the presence of a uniform magnetic field applied perpendicularly to the heterostructure. Our results exhibit a resonant tunneling behaviour and periodic modulations of the transport properties as a function of the geometry of the considered conductors and as a function of the magnetic flux that crosses the heterostructure. We have observed Aharonov-Bohm type of interference representing by periodic metal-semiconductor transitions in the DOS and conductance curves of the nanostructures. PMID:23279756

2013-01-01

363

Symmetric, gated, ballistic rings as tunable electron interferometers  

NASA Astrophysics Data System (ADS)

In the present work we investigate the coherent electron transport in a symmetrically designed ballistic ring uniformly covered by a top metal gate. We find that as the Fermi energy is varied, the phase of Aharonov-Bohm (AB) oscillations near zero magnetic field switches between 0 and ?. It seems unlikely that this behaviour can be explained by some accidental asymmetry in the structures. We give a qualitative explanation of our results using a model where the ring is considered to be weakly coupled to the leads and the conductance is calculated on the basis of an exact energy spectrum of an ideal ring. This model predicts that a variation of the phase of AB oscillations with gate voltage may be observed in a symmetrical ring.

Olshanetsky, E. B.; Cassé, M.; Kvon, Z. D.; Gusev, G. M.; Litvin, L. V.; Plotnikov, A. V.; Maude, D. K.; Portal, J. C.

2000-02-01

364

Geometrically induced electric polarization in conical topological insulators  

E-print Network

We study the topological magnetoelectric effect on a conical topological insulator when a point charge $q$ is near the cone apex. The Hall current induced on the cone surface and the image charge configuration are determined. We also study a kind of gravitational Aharonov-Bohm effect in this geometry and realize a phase diference betwen the components of the wavefunctions (spinors) upon closed parallel transport around the (singular) cone tip. Concretely, a net current flowing towards cone apex (or botton) shows up, yielding electric polarization of the conical topological insulator. Such an effect may be detected, for instance, by means of the net accumulated Hall charge near the apex. Once it depends only on the geometry of the material (essetially, the cone apperture angle) this may be faced as a microscopic scale realization of (2+1)-dimensional Einstein gravity.

Jakson M. Fonseca; Winder A. Moura-Melo; Afranio R. Pereira

2011-11-29

365

Experimental study of surface waves scattering by a single vortex and a vortex dipole  

NASA Astrophysics Data System (ADS)

Surface waves interacting with filamentary vortex offer an interesting tool to characterize static and dynamics of surface vorticity. An experimental study of the scattered wave by a single vortex as well as by a vortex dipole is reported. On a plane wave front, the vortex circulation introduces a spatial phase shift that gives rise to dislocated waves. Dislocations can be explained by the effect of the differential advection due to the vortex flow, on the propagating wave front. Both the Burgers vector of dislocations and the scattering cross section are measured in the deep water regime. The analogy between the wave-vortex interaction and the Aharonov-Bohm effect in quantum mechanics is explored by contrasting the Burgers vectors of dislocations as well as the form of the scattered wave in both cases. For the case of the hard core vortex, spiral waves are observed in agreement with theoretical works on both the Aharanov-Bohm effect and classical surface wave mechanics.

Vivanco, Francisco; Melo, Francisco

2004-02-01

366

Electron interference in mesoscopic devices in the presence of nonclassical electromagnetic fields  

E-print Network

The interaction of mesoscopic interference devices with nonclassical electromagnetic fields is studied. The external quantum fields induce a phase factor on the electric charges. This phase factor, which is a generalization of the standard Aharonov-Bohm phase factor, is in the case of nonclassical electromagnetic fields a quantum mechanical operator. Its expectation value depends on the density matrix describing the nonclassical photons and determines the interference. Several examples are discussed, which show that the quantum noise of the nonclassical photons destroys slightly the electron interference fringes. An interesting application arises in the context of distant electron interference devices, irradiated with entangled photons. In this case the interfering electrons in the two devices become entangled. The same ideas are applied in the context of SQUID rings irradiated with nonclassical electromagnetic fields. It is shown that the statistics of the Cooper pairs tunneling through the Josephson junction depend on the statistics of the photons.

D. I. Tsomokos; C. C. Chong; A. Vourdas

2005-02-18

367

Mach-Zehnder interferometry with periodic voltage pulses  

NASA Astrophysics Data System (ADS)

We investigate theoretically a Mach-Zehnder interferometer driven by a time-dependent voltage. Motivated by recent experiments, we focus on a train of Lorentzian voltage pulses which we compare to a sinusoidal and a constant voltage. We discuss the visibilities of Aharonov-Bohm oscillations in the current and in the noise. For the current, we find a strikingly different behavior in the driven as compared to the static case for voltage pulses containing multiple charges. For pulses containing fractional charges, we find a universality at path-length differences equal to multiples of the spacing between the voltage pulses. These observations can be explained by the electronic energy distribution of the driven contact. In the noise oscillations, we find additional features which are characteristic to time-dependent transport. Finite electronic temperatures are found to have a qualitatively different influence on the current and the noise.

Hofer, Patrick P.; Flindt, Christian

2014-12-01

368

Black holes with quantum massive spin-2 hair  

SciTech Connect

We show that black holes can posses a long range quantum-mechanical hair associated with a massive spin-2 field, which can be detected by a stringy generalization of the Aharovon-Bohm effect, in which a string loop lassoes the black hole. The long distance effect persist for arbitrarily high mass of the spin-2 field. An analogous effect is exhibited by a massive antisymmetric two-form field. We make a close parallel between the two and the ordinary Aharonov-Bohm phenomenon, and also show that in the latter case the effect can be experienced even by the electrically-neutral particles, provided some boundary terms are added to the action.

Dvali, Gia [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, New York 10003 (United States)

2006-08-15

369

Black Holes with Quantum Massive Spin-2 Hair  

E-print Network

We show that black holes can posses a long range quantum mechanical hair associated with a massive spin-2 field, which can be detected by a stringy generalization of the Aharovon-Bohm effect, in which a string loop lassoes the black hole. The long distance effect persist for arbitrarily high mass of the spin-2 field. An analogous effect is exhibited by a massive antisymmetric two-form field. We make a close parallel between the two and the ordinary Aharonov-Bohm phenomenon, and also show that in the latter case the effect can be experienced even by the electrically-neutral particles, provided some boundary terms are added to the action.

Gia Dvali

2006-05-31

370

Optical conductivity of curved graphene  

E-print Network

We compute the optical conductivity for an out-of-plane deformation in graphene using an approach based on solutions of the Dirac equation in curved space. Different examples of periodic deformations along one direction translates into an enhancement of the optical conductivity peaks in the region of the far and mid infrared frequencies for periodicities $\\sim100\\,$nm. The width and position of the peaks can be changed by dialling the parameters of the deformation profiles. The enhancement of the optical conductivity is due to intraband transitions and the translational invariance breaking in the geometrically deformed background. Furthemore, we derive an analytical solution of the Dirac equation in a curved space for a general deformation along one spatial direction. For this class of geometries, it is shown that curvature induces an extra phase in the electron wave function, which can also be explored to produce interference devices of the Aharonov-Bohm type.

A. J. Chaves; T. Frederico; O. Oliveira; W. de Paula; M. C. Santos

2014-05-01

371

Spin Transistor Action from Hidden Onsager Reciprocity  

NASA Astrophysics Data System (ADS)

We investigate generic Hamiltonians for confined electrons with weak inhomogeneous spin-orbit coupling [1]. Using a local gauge transformation we show how the SU(2) Hamiltonian structure reduces to a U(1) x U(1) structure for spinless fermions in a fictitious orbital magnetic field, to leading order in the spin-orbit strength. Using an Onsager relation, we further show how the resulting spin conductance vanishes in a two-terminal setup, and how it is turned on by either weakly breaking time-reversal symmetry or opening additional transport terminals, thus allowing one to switch the generated spin current on or off. We numerically check our theory for mesoscopic cavities as well as Aharonov-Bohm rings.[4pt] [1] Adagideli et al., Phys. Rev. Lett. 108, 236601 (2012)

Adagideli, I.; Lutsker, V.; Scheid, M.; Jacquod, Ph.; Richter, K.

2013-03-01

372

Spin transistor action from hidden Onsager reciprocity.  

PubMed

We investigate generic Hamiltonians for confined electrons with weak inhomogeneous spin-orbit coupling. Using a local gauge transformation we show how the SU(2) Hamiltonian structure reduces to a U(1)×U(1) structure for spinless fermions in a fictitious orbital magnetic field, to leading order in the spin-orbit strength. Using an Onsager relation, we further show how the resulting spin conductance vanishes in a two-terminal setup, and how it is turned on by either weakly breaking time-reversal symmetry or opening additional transport terminals, thus allowing one to switch the generated spin current on or off. We numerically check our theory for mesoscopic cavities as well as Aharonov-Bohm rings. PMID:23003980

Adagideli, ?; Lutsker, V; Scheid, M; Jacquod, Ph; Richter, K

2012-06-01

373

Spin Transistor Action from Hidden Onsager Reciprocity  

NASA Astrophysics Data System (ADS)

We investigate generic Hamiltonians for confined electrons with weak inhomogeneous spin-orbit coupling. Using a local gauge transformation we show how the SU(2) Hamiltonian structure reduces to a U(1)×U(1) structure for spinless fermions in a fictitious orbital magnetic field, to leading order in the spin-orbit strength. Using an Onsager relation, we further show how the resulting spin conductance vanishes in a two-terminal setup, and how it is turned on by either weakly breaking time-reversal symmetry or opening additional transport terminals, thus allowing one to switch the generated spin current on or off. We numerically check our theory for mesoscopic cavities as well as Aharonov-Bohm rings.

Adagideli, ?.; Lutsker, V.; Scheid, M.; Jacquod, Ph.; Richter, K.

2012-06-01

374

The Physical Interpretation of the Lanczos Tensor  

E-print Network

The field equations of general relativity can be written as first order differential equations in the Weyl tensor, the Weyl tensor in turn can be written as a first order differential equation in a three index tensor called the Lanczos tensor. The Lanczos tensor plays a similar role in general relativity to that of the vector potential in electro-magnetic theory. The Aharonov-Bohm effect shows that when quantum mechanics is applied to electro-magnetic theory the vector potential is dynamically significant, even when the electro-magnetic field tensor $F_{ab}$ vanishes. Here it is assumed that in the quantum realm the Lanczos tensor is dynamically significant, and this leads to an attempt to quantize the gravitational field by pursuing the analogy between the vector field and the Lanczos tensor.

Mark D. Roberts

1999-04-04

375

Asymmetric coherent transmission for single particle diode and gyroscope  

E-print Network

We study the single particle scattering process in a coherent multi-site system consisting of a tight-binding ring threaded by an Aharonov-Bohm flux and several attaching leads. The asymmetric behavior of scattering matrix is discovered analytically in the framework of both Bethe Ansatz and Green's function formalism. It is found that, under certain conditions, a three-site electronic system can behave analogous to a perfect semiconductor diode where current flows only in one direction. The general result is also valid for a neutral particle system since the effective magnetic flux may be implemented by a globe rotation. This observation means that the three-site system can serve as an orientation measuring gyroscope due to the approximate linear dependence of the current difference of two output leads on the rotational angular velocity.

S. Yang; Z. Song; C. P. Sun

2009-12-02

376

Topologically protected excitons in porphyrin thin films  

NASA Astrophysics Data System (ADS)

The control of exciton transport in organic materials is of fundamental importance for the development of efficient light-harvesting systems. This transport is easily deteriorated by traps in the disordered energy landscape. Here, we propose and analyse a system that supports topological Frenkel exciton edge states. Backscattering of these chiral Frenkel excitons is prohibited by symmetry, ensuring that the transport properties of such a system are robust against disorder. To implement our idea, we propose a two-dimensional periodic array of tilted porphyrins interacting with a homogeneous magnetic field. This field serves to break time-reversal symmetry and results in lattice fluxes that mimic the Aharonov–Bohm phase acquired by electrons. Our proposal is the first blueprint for realizing topological phases of matter in molecular aggregates and suggests a paradigm for engineering novel excitonic materials.

Yuen-Zhou, Joel; Saikin, Semion K.; Yao, Norman Y.; Aspuru-Guzik, Alán

2014-11-01

377

Effect of donor impurity dislocation in elliptical quantum rings  

NASA Astrophysics Data System (ADS)

We investigate the effect of an off-center donor impurity on the electronic properties of a two-dimensional quantum ring with a deformed geometrical structure in the form of an ellipse. It is shown that the dislocation of impurity from the center of elliptical quantum ring opens sizable gaps in the energy spectrum and largely deforms the eigenenergies near the ground state. As a result, the Aharonov-Bohm oscillations are quenched and the persistent electron current decreases intensely. Moreover, we show that the ground state energy exhibits a local extremum when the donor impurity is located on semi-minor (or -major) axis of the elliptic ring. The effects of the eccentricity of elliptical ring on the energy spectra and persistent current are also studied.

Khajeh Salehani, Hojjatollah; Shakouri, Khosrow; Esmaeilzadeh, Mahdi

2015-02-01

378

Topologically protected excitons in porphyrin thin films  

E-print Network

The control of exciton transport in organic materials is of fundamental importance for the development of efficient light-harvesting systems. This transport is easily deteriorated by traps in the disordered energy landscape. Here, we propose and analyze a system that supports topological Frenkel exciton edge states. Backscattering of these chiral Frenkel excitons is prohibited by symmetry, ensuring that the transport properties of such a system are robust against disorder. To implement our idea, we propose a two-dimensional periodic array of tilted porphyrins interacting with a homogenous magnetic field. This field serves to break time-reversal symmetry and results in lattice fluxes that that mimic the Aharonov-Bohm phase acquired by electrons. Our proposal is the first blueprint for realizing topological phases of matter in molecular aggregates and suggests a paradigm for engineering novel excitonic materials.

Joel Yuen-Zhou; Semion S. Saikin; Norman Y. Yao; Alán Aspuru-Guzik

2014-06-05

379

Electric field geometries dominate quantum transport coupling in silicon nanoring  

SciTech Connect

Investigations on the relation between the geometries of silicon nanodevices and the quantum phenomenon they exhibit, such as the Aharonov–Bohm (AB) effect and the Coulomb blockade, were conducted. An arsenic doped silicon nanoring coupled with a nanowire by electron beam lithography was fabricated. At 1.47?K, Coulomb blockade oscillations were observed under modulation from the top gate voltage, and a periodic AB oscillation of ?B?=?0.178?T was estimated for a ring radius of 86?nm under a high sweeping magnetic field. Modulating the flat top gate and the pointed side gate was performed to cluster and separate the many electron quantum dots, which demonstrated that quantum confinement and interference effects coexisted in the doped silicon nanoring.

Lee, Tsung-Han, E-mail: askaleeg@gmail.com, E-mail: sfhu.hu@gmail.com; Hu, Shu-Fen, E-mail: askaleeg@gmail.com, E-mail: sfhu.hu@gmail.com [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China)

2014-03-28

380

Topological model for domain walls in (super-)Yang-Mills theories  

NASA Astrophysics Data System (ADS)

We derive a topological action that describes the confining phase of (super-)Yang-Mills theories with gauge group S U (N ) , similar to the work recently carried out by Seiberg and collaborators. It encodes all the Aharonov-Bohm phases of the possible nonlocal operators and phases generated by the intersection of flux tubes. Within this topological framework we show that the world volume theory of domain walls contains a Chern-Simons term at level N also seen in string theory constructions. The discussion can also illuminate dynamical differences of domain walls in the supersymmetric and nonsupersymmetric framework. Two further analogies, to string theory and the fractional quantum Hall effect, might lead to additional possibilities to investigate the dynamics.

Dierigl, Markus; Pritzel, Alexander

2014-11-01

381

Quantizations on the circle and coherent states  

E-print Network

We present a possible construction of coherent states on the unit circle as configuration space. Our approach is based on Borel quantizations on S^1 including the Aharonov-Bohm type quantum description. The coherent states are constructed by Perelomov's method as group related coherent states generated by Weyl operators on the quantum phase space Z x S^1. Because of the duality of canonical coordinates and momenta, i.e. the angular variable and the integers, this formulation can also be interpreted as coherent states over an infinite periodic chain. For the construction we use the analogy with our quantization and coherent states over a finite periodic chain where the quantum phase space was Z_M x Z_M. The coherent states constructed in this work are shown to satisfy the resolution of unity. To compare them with canonical coherent states, also some of their further properties are studied demonstrating similarities as well as substantial differences.

G. Chadzitaskos; P. Luft; J. Tolar

2012-01-18

382

Two-electron volcano-shaped quantum dot  

NASA Astrophysics Data System (ADS)

We propose a simple model of non-uniform volcano-shaped quantum dot that reflects the confinement details of the morphology of really fabricated GaAs/InAs nanorings and whose profile geometry, on the one hand, is described by means of simple analytical functions and, on the other hand, allows us to find exact one-particle wave functions. By using them as a basis function we calculate two-electron lower energies as functions of the external magnetic field applied along the growth axis. We show that the ring morphology and electron-electron interaction have great influence on the energy spectrum structure of nanoring and the Aharonov-Bohm oscillations.

Garcia, L. F.; Gutiérrez, W.; Mikhailov, I. D.

2014-12-01

383

Geometric phase in Bohmian mechanics  

SciTech Connect

Using the quantum kinematic approach of Mukunda and Simon, we propose a geometric phase in Bohmian mechanics. A reparametrization and gauge invariant geometric phase is derived along an arbitrary path in configuration space. The single valuedness of the wave function implies that the geometric phase along a path must be equal to an integer multiple of 2{pi}. The nonzero geometric phase indicates that we go through the branch cut of the action function from one Riemann sheet to another when we locally travel along the path. For stationary states, quantum vortices exhibiting the quantized circulation integral can be regarded as a manifestation of the geometric phase. The bound-state Aharonov-Bohm effect demonstrates that the geometric phase along a closed path contains not only the circulation integral term but also an additional term associated with the magnetic flux. In addition, it is shown that the geometric phase proposed previously from the ensemble theory is not gauge invariant.

Chou, Chia-Chun, E-mail: chiachun@mail.utexas.ed [Institute for Theoretical Chemistry and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Wyatt, Robert E., E-mail: wyattre@mail.utexas.ed [Institute for Theoretical Chemistry and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States)

2010-10-15

384

Electronic and Transport Properties of DNA-based Nanowires  

NASA Astrophysics Data System (ADS)

We study theoretically the transport properties through the quasi-one-dimensional (Q1D) one-channel DNA model and two-dimensional (2D) four-channel DNA model. We use a tight-binding (TB) technique to investigate the transmission, current-voltage characteristics, the differential conductance, and localization length as a function of incoming electron energy and magnetic flux. We find that the behavior of the transmission coefficients varies depending on the parameters of the backbone onsite energy, hopping integral from bases to backbone, and hydrogen bonds. Further, the fluctuations in the twisting angle from the temperature effects and the Aharonov-Bohm (AB) magnetic flux effect cause suppression and oscillations in the transmission.

Joe, Yong S.; Lee, Sun H.; Hedin, Eric R.

2011-12-01

385

Exciton Distribution between the Bright and Dark States in Single Carbon Nanotubes Studied by Magneto-Photoluminescence Spectroscopy  

NASA Astrophysics Data System (ADS)

We have performed micro-photoluminescence (PL) spectroscopy for single carbon nanotubes under magnetic fields at various temperatures. Sharp PL spectra of single carbon nanotubes allow us to directly observe the dark exciton PL peak a few meV below the bright exciton PL peak due to the Aharonov-Bohm effect [1]. From the PL intensity ratio of the dark to the bright excitons under magnetic fields, we found that the non-equilibrium (non-Boltzmann) distribution occurs between the bright and dark states, because phonons cannot scatter excitons between the two states with different parities [2]. Furthermore, we discuss the diameter dependence of the exciton population of the bright and dark states in single carbon nanotubes. [1] R. Matsunaga, K. Matsuda, and Y. Kanemitsu, Phys. Rev. Lett. 101, 147404 (2008). [2] V. Perebeinos, J. Tersoff, and Ph. Avouris, Nano Lett. 5, 2495 (2005).

Matsunaga, Ryusuke; Matsuda, Kazunari; Kanemitsu, Yoshihiko

2009-03-01

386

Quantum ring in a rotating frame in the presence of a topological defect  

NASA Astrophysics Data System (ADS)

In this contribution, we study the effects caused by rotation of an electron/hole in the presence of a screw dislocation confined in a quantum ring potential, within a quantum dynamics. The Tan-Inkson potential is used to model the confinement of the particle in two-dimensional quantum ring. We suppose that the quantum ring is placed in the presence of an external uniform magnetic field and an Aharonov-Bohm flux in the center of the system, and that the frame rotates around the z-axis. The Schrödinger equation is solved and the eigenfunctions and energy eigenvalues are exactly obtained for this configuration. The influence of the dislocation and the rotation on both the persistent current and magnetization is also studied.

Dantas, L.; Furtado, C.; Silva Netto, A. L.

2015-01-01

387

Cosmic strings in hidden sectors: 1. Radiation of standard model particles  

NASA Astrophysics Data System (ADS)

In hidden sector models with an extra U(1) gauge group, new fields can interact with the Standard Model only through gauge kinetic mixing and the Higgs portal. After the U(1) is spontaneously broken, these interactions couple the resultant cosmic strings to Standard Model particles. We calculate the spectrum of radiation emitted by these ``dark strings'' in the form of Higgs bosons, Z bosons, and Standard Model fermions assuming that string tension is above the TeV scale. We also calculate the scattering cross sections of Standard Model fermions on dark strings due to the Aharonov-Bohm interaction. These radiation and scattering calculations will be applied in a subsequent paper to study the cosmological evolution and observational signatures of dark strings.

Long, Andrew J.; Hyde, Jeffrey M.; Vachaspati, Tanmay

2014-09-01

388

Signatures of a noise-induced quantum phase transition in a mesoscopic metal ring.  

PubMed

We study a mesoscopic ring with an inline quantum dot threaded by an Aharonov-Bohm flux. Zero-point fluctuations of the electromagnetic environment capacitively coupled to the ring, with omega(s) spectral density, can suppress tunneling through the dot, resulting in a quantum phase transition from an unpolarized to a polarized phase. We show that robust signatures of such a transition can be found in the response of the persistent current in the ring to the external flux as well as to the bias between the dot and the arm. Particular attention is paid to the experimentally relevant cases of Ohmic (s = 1) and sub-Ohmic (s = 1/2) noise. PMID:16907395

Tong, Ning-Hua; Vojta, Matthias

2006-07-01

389

Complex States of Simple Molecular Systems  

E-print Network

A review is given of phase properties in molecular wave functions, composed of a number of (and, at least, two) electronic states that become degenerate at some nearby values of the nuclear configuration. Apart from discussing phases and interference in classical (non-quantal) systems, including light-waves, the review looks at the constructability of complex wave functions from observable quantities ("the phase problem"), at the controversy regarding quantum mechanical phase-operators, at the modes of observability of phase and at the role of phases in some non-demolition measurements. Advances in experimental and (especially) theoretical aspects of Aharonov-Bohm and topological (Berry) phases are described, including those involving two-electron and relativistic systems. Several works in the phase control and revivals of molecular wave-packets are cited as developments and applications of complex-function theory. Further topics that this review touches on are: coherent states, semiclassical approximations a...

Englman, R

2004-01-01

390

Resonances on hedgehog manifolds  

E-print Network

We discuss resonances for a nonrelativistic and spinless quantum particle confined to a two- or three-dimensional Riemannian manifold to which a finite number of semiinfinite leads is attached. Resolvent and scattering resonances are shown to coincide in this situation. Next we consider the resonances together with embedded eigenvalues and ask about the high-energy asymptotics of such a family. For the case when all the halflines are attached at a single point we prove that all resonances are in the momentum plane confined to a strip parallel to the real axis, in contrast to the analogous asymptotics in some metric quantum graphs; we illustrate it on several simple examples. On the other hand, the resonance behaviour can be influenced by a magnetic field. We provide an example of such a `hedgehog' manifold at which a suitable Aharonov-Bohm flux leads to absence of any true resonance, i.e. that corresponding to a pole outside the real axis.

Pavel Exner; Jiri Lipovsky

2013-02-21

391

Effective Teaching of Photonics E&M Theory Using COMSOL  

NSDL National Science Digital Library

Photonics and optical communications, after the exuberant growth and subsequent down turn in late 1990s and early 2000s, have entered a more mature and stable growth phase. As the technology of choice for long distance, high data rate, and high performance communication systems underlying the now ubiquitous Internet communications, photonics and optical communication professionals are and will continue to be in high demand. Because electromagnetic (E&M) theory is the foundation of photonics and optical communications, mastery of E&M theory is essential for those electrical engineering (EE) students who want to develop a career in this field. Traditionally, rigorous analytic skills in advanced mathematics especially in subjects such as partial differential equations (PDE) and linear algebra are a must to the understanding and applications of E&M theory, as well as photonic device and waveguide designs. However, as practical designs grow in complexity, even the most sophisticated and advanced analytic techniques in these mathematical subject areas can quickly fall short of being a suitable practical design tool. Standard industry practices utilize comprehensive software simulation packages to address these design needs. It is therefore appropriate and advantageous for EE students to learn and more importantly visualize the E&M theory by combining the basic mathematical principles, e.g., the Maxwell equations and wave equations, with practical software tools that they are more likely to use in their professional life. This paper discusses the introduction of COMSOL, a predominant industry PDE solver, to senior EE undergraduates as a learning tool of fundamental concepts in photonics such as transverse electrical (TE) modes and transverse magnetic (TM) modes in planar waveguide designs. This teaching method improves teaching effectiveness of E&M field and wave theory by helping the students better understand mathematical complexities through this readily available and reliable software tool. In addition to the theory, the students also gain the design capability using these industry standard software packages, and therefore bridging the gap between theory and practice.

2009-10-08

392

ATTRACT-EM: A New Method for the Computational Assembly of Large Molecular Machines Using Cryo-EM Maps  

PubMed Central

Many of the most important functions in the cell are carried out by proteins organized in large molecular machines. Cryo-electron microscopy (cryo-EM) is increasingly being used to obtain low resolution density maps of these large assemblies. A new method, ATTRACT-EM, for the computational assembly of molecular assemblies from their components has been developed. Based on concepts from the protein-protein docking field, it utilizes cryo-EM density maps to assemble molecular subunits at near atomic detail, starting from millions of initial subunit configurations. The search efficiency was further enhanced by recombining partial solutions, the inclusion of symmetry information, and refinement using a molecular force field. The approach was tested on the GroES-GroEL system, using an experimental cryo-EM map at 23.5 Å resolution, and on several smaller complexes. Inclusion of experimental information on the symmetry of the systems and the application of a new gradient vector matching algorithm allowed the efficient identification of docked assemblies in close agreement with experiment. Application to the GroES-GroEL complex resulted in a top ranked model with a deviation of 4.6 Å (and a 2.8 Å model within the top 10) from the GroES-GroEL crystal structure, a significant improvement over existing methods. PMID:23251350

de Vries, Sjoerd J.; Zacharias, Martin

2012-01-01

393

Application of Electromagnetic (EM) Separation Technology to Metal Refining Processes: A Review  

NASA Astrophysics Data System (ADS)

Application of electromagnetic (EM) force to metal processing has been considered as an emerging technology for the production of clean metals and other advanced materials. In the current paper, the principle of EM separation was introduced and several schemes of imposing EM field, such as DC electric field with a crossed steady magnetic field, AC electric field, AC magnetic field, and traveling magnetic field were reviewed. The force around a single particle or multi-particles and their trajectories in the conductive liquid under EM field were discussed. Applications of EM technique to the purification of different liquid metals such as aluminum, zinc, magnesium, silicon, copper, and steel were summarized. Effects of EM processing parameters, such as the frequency of imposed field, imposed magnetic flux density, processing time, particle size, and the EM unit size on the EM purification efficiency were discussed. Experimental and theoretical investigations have showed that the separation efficiency of inclusions from the molten aluminum using EM purification could as high as over 90 pct. Meanwhile, the EM purification was also applied to separate intermetallic compounds from metal melt, such as ?-AlFeMnSi-phase from the molten aluminum. And then the potential industrial application of EM technique was proposed.

Zhang, Lifeng; Wang, Shengqian; Dong, Anping; Gao, Jianwei; Damoah, Lucas Nana Wiredu

2014-12-01

394

Magneto-optical studies of quantum dots  

NASA Astrophysics Data System (ADS)

Significant effort in condensed matter physics has recently been devoted to the field of "spintronics" which seeks to utilize the spin degree of freedom of electrons. Unlike conventional electronics that rely on the electron charge, devices exploiting their spin have the potential to yield new and novel technological applications, including spin transistors, spin filters, and spin-based memory devices. Any such application has the following essential requirements: 1) Efficient electrical injection of spin-polarized carriers; 2) Long spin lifetimes; 3) Ability to control and manipulate electron spins; 4) Effective detection of spin-polarized carriers. Recent work has demonstrated efficient electrical injection from ferromagnetic contacts such as Fe and MnAs, utilizing a spin-Light Emitting Diode (spin-LED) as a method of detection. Semiconductor quantum dots (QDs) are attractive candidates for satisfying requirements 2 and 3 as their zero dimensionality significantly suppresses many spin-flip mechanisms leading to long spin coherence times, as well as enabling the localization and manipulation of a controlled number of electrons and holes. This thesis is composed of three projects that are all based on the optical properties of QD structures including: I) Intershell exchange between spin-polarized electrons occupying adjacent shells in InAs QDs; II) Spin-polarized multiexitons in InAs QDs in the presence of spin-orbit interactions; III) The optical Aharonov-Bohm effect in AlxGa1-xAs/AlyGa1-yAs quantum wells (QWs). In the following we introduce some of the basic optical properties of quantum dots, describe the main tool (spin-LED) employed in this thesis to inject and detect spins in these QDs, and conclude with the optical Aharonov-Bohm effect (OAB) in type-II QDs.

Russ, Andreas Hans

395

Phase diagram of the Bose-Hubbard model with T{sub 3} symmetry  

SciTech Connect

We study the quantum phase transition between the insulating and the globally coherent superfluid phases in the Bose-Hubbard model with T{sub 3} structure, the 'dice lattice'. Even in the absence of any frustration the superfluid phase is characterized by modulation of the order parameter on the different sublattices of the T{sub 3} structure. The zero-temperature critical point as a function of magnetic field shows the characteristic 'butterfly' form. At full frustration the superfluid region is strongly suppressed. In addition, due to the existence of the Aharonov-Bohm cages at f=1/2, we find some evidence for the existence of an intermediate insulating phase characterized by a zero superfluid stiffness but finite compressibility. In this intermediate phase bosons are localized due to the external frustration and the topology of the T{sub 3} lattice. We name this new phase the Aharonov-Bohm insulator. In the presence of charge frustration the phase diagram acquires the typical lobe structure. The form and hierarchy of the Mott insulating states with fractional fillings are dictated by the particular topology of the T{sub 3} lattice. The results presented were obtained by a variety of analytical methods: mean-field and variational techniques to approach the phase boundary from the superconducting side and a strongly coupled expansion appropriate for the Mott insulating region. In addition we performed quantum Monte Carlo simulations of the corresponding (2+1)-dimensional XY model to corroborate the analytical calculations with a more accurate quantitative analysis. We finally discuss experimental realization of the T{sub 3} lattice both with optical lattices and with Josephson junction arrays.

Rizzi, Matteo; Fazio, Rosario [NEST CNR-INFM and Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Cataudella, Vittorio [COHERENTIA CNR-INFM and Dipartimento di Fisica, Universita Federico II, 80126 Naples (Italy)

2006-04-01

396

Magnetic field effects on endcap EM calorimetry in SDC  

SciTech Connect

The SDC calorimeter will be immersed in a strong magnetic field in the endcap region because of the solenoid which supplies the SDC tracking field. This flux must be returned through the endcap region of the electromagnetic (EM) and hadronic (HAD) calorimeters. Since magnetic fields are known to induce changes in the light output of plastic scintillator, the endcap will need to be recalibrated once the solenoid is energized. In addition, gradients in the field will create nonuniformities in the calorimetric response. The induced constant term'' in the EM and HAD calorimeters due to the inhomogeneities induced by the magnetic field are here evaluated in order to see that SDC performance specifications are not compromised.

Green, D.

1993-01-25

397

Magnetic field effects on endcap EM calorimetry in SDC  

SciTech Connect

The SDC calorimeter will be immersed in a strong magnetic field in the endcap region because of the solenoid which supplies the SDC tracking field. This flux must be returned through the endcap region of the electromagnetic (EM) and hadronic (HAD) calorimeters. Since magnetic fields are known to induce changes in the light output of plastic scintillator, the endcap will need to be recalibrated once the solenoid is energized. In addition, gradients in the field will create nonuniformities in the calorimetric response. The ``induced constant term`` in the EM and HAD calorimeters due to the inhomogeneities induced by the magnetic field are here evaluated in order to see that SDC performance specifications are not compromised.

Green, D.

1993-01-25

398

Da universidade para o mercado de trabalho em onze pases  

E-print Network

Universia está a ser lançado em várias instituições de ensino superior portuguesas. Rede ibero-americana regista por mês 195 mil ofertas ANA BELA FERREIRA Desde quinta-feira que os 23 mil alunos da Universidade a pró-rei- tora, Ana Nunes de Almeida. Ao aderir a esta plataforma, que con- centra não só ofertas

Instituto de Sistemas e Robotica

399

DustEM: Dust extinction and emission modelling  

NASA Astrophysics Data System (ADS)

DustEM computes the extinction and the emission of interstellar dust grains heated by photons. It is written in Fortran 95 and is jointly developed by IAS and CESR. The dust emission is calculated in the optically thin limit (no radiative transfer) and the default spectral range is 40 to 108 nm. The code is designed so dust properties can easily be changed and mixed and to allow for the inclusion of new grain physics.

Compiègne, M.; Verstraete, L.; Jones, A.; Bernard, J.-P.; Boulanger, F.; Flagey, N.; Le Bourlot, J.; Paradis, D.; Ysard, N.

2013-07-01

400

MESTRADO EM MICROBIOLOGIA MICROBIOLOGIA DOS ALIMENTOS Faculdade de Medicina Veterinria  

E-print Network

MESTRADO EM MICROBIOLOGIA MICROBIOLOGIA DOS ALIMENTOS ­ Faculdade de Medicina Veterinária Objectivos: Esta UC visa ministrar formação geral e específica no domínio da Microbiologia dos Alimentos e que interfiram com a segurança sanitária dos alimentos ou promovam a respectiva fermentação, cura ou

Instituto de Sistemas e Robotica

401

UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM COMUNICAO  

E-print Network

candidatos residentes no Brasil. 3.4 Poderão inscrever-se no processo seletivo candidatos em fase de e Cópia do CPF. 3.5.7 Comprovante original do recolhimento da taxa de inscrição no valor de R$ 100,00 (cem reais) no Banco do Brasil (001), Agência 1607-1, conta 170500-8 (Conta �nica do Tesouro), código

Maier, Rudolf Richard

402

EMS mutagenesis in the pea aphid Acyrthosiphon pisum.  

PubMed

In aphids, clonal individuals can show distinct morphologic traits in response to environmental cues. Such phenotypic plasticity cannot be studied with classical genetic model organisms such as Caenorhabditis elegans or Drosophila melanogaster. The genetic basis of this biological process remain unknown, as mutations affecting this process are not available in aphids. Here, we describe a protocol to treat third-stage larvae with an alkylating mutagen, ethyl methanesulfonate (EMS), to generate random mutations within the Acyrthosiphon pisum genome. We found that even low concentrations of EMS were toxic for two genotypes of A. pisum. Mutagenesis efficiency was nevertheless assessed by estimating the occurrence of mutational events on the X chromosome. Indeed, any lethal mutation on the X-chromosome would kill males that are haploid on the X so that we used the proportion of males as an estimation of mutagenesis efficacy. We could assess a putative mutation rate of 0.4 per X-chromosome at 10 mM of EMS. We then applied this protocol to perform a small-scale mutagenesis on parthenogenetic individuals, which were screened for defects in their ability to produce sexual individuals in response to photoperiod shortening. We found one mutant line showing a reproducible altered photoperiodic response with a reduced production of males and the appearance of aberrant winged males (wing atrophy, alteration of legs morphology). This mutation appeared to be stable because it could be transmitted over several generations of parthenogenetic individuals. To our knowledge, this study represents the first example of an EMS-generated aphid mutant. PMID:24531730

Tagu, Denis; Le Trionnaire, Gaël; Tanguy, Sylvie; Gauthier, Jean-Pierre; Huynh, Jean-René

2014-04-01

403

Agentes e Emoes em Histrias Interativas Cesar Tadeu Pozzer  

E-print Network

foco da construção de elementos autônomos, semelhantes a personagens inteligentes de jogos eletrônicos entretenimento digital. Jogos de computador, que a cada dia estão mais avançados e que diariamente causam espanto). Diversas técnicas de IA são usadas em jogos para dar aos personagens características de aprendizado, tomada

Endler, Markus

404

A Biblioteca do IB em nmeros 2013 Acervo Total (publicaes)  

E-print Network

Total atual Livros * 347 33.796 Teses 259 3.483 Títulos de Periódicos 2.132 Correntes ** 256 Não livros e teses) Biblioteca fornecedora 262 Biblioteca solicitante 100 Nº de cópias fornecidas 3 a Biblioteca comprou 156 livros e recebeu em doação 36. ** 256 por compra, 65 por doação e 78 por permuta. #12;

Morandini, Andre C.

405

Plant's EMS yields 11-month payback in fuel savings  

SciTech Connect

A Johnson Controls 85 energy-management system (EMS) saved the King-Seeley Thermos Co. $70,000 in fuel costs and paid for itself within a year. The system controls 141 points in the 420,000-square-foot plant. Although the Johnson system was the low bidder, its software package with English language programming was the deciding factor. A summary of the JC 85 system describes its functions and performance. (DCK)

Galvin, C.

1982-05-24

406

CURSO DE PS-GRADUAO EM COMPUTAO APLICADA  

E-print Network

. Disciplinas do Núcleo obrigatório de Matemática Aplicada Matemática Computacional I Matemática Computacional Análise Wavelet I Análise Wavelet II Aprendizado Computacional e Reconhecimento de Padrões Banco de Dados Computacional e Aplicações Introdução à Teoria de Sistemas Dinâmicos Matemática Computacional III Métodos em

407

A Bayesian View on Cryo-EM Structure Determination  

PubMed Central

Three-dimensional (3D) structure determination by single-particle analysis of cryo-electron microscopy (cryo-EM) images requires many parameters to be determined from extremely noisy data. This makes the method prone to overfitting, that is, when structures describe noise rather than signal, in particular near their resolution limit where noise levels are highest. Cryo-EM structures are typically filtered using ad hoc procedures to prevent overfitting, but the tuning of arbitrary parameters may lead to subjectivity in the results. I describe a Bayesian interpretation of cryo-EM structure determination, where smoothness in the reconstructed density is imposed through a Gaussian prior in the Fourier domain. The statistical framework dictates how data and prior knowledge should be combined, so that the optimal 3D linear filter is obtained without the need for arbitrariness and objective resolution estimates may be obtained. Application to experimental data indicates that the statistical approach yields more reliable structures than existing methods and is capable of detecting smaller classes in data sets that contain multiple different structures. PMID:22100448

Scheres, Sjors H.W.

2012-01-01

408

A study on characteristics of EM radiation from stripline structure  

NASA Astrophysics Data System (ADS)

In recent years, effective methods for predicting and suppressing electromagnetic interference over a broad band are required. In this paper, we focus on the prediction of electromagnetic (EM) radiation from a stripline structure with a ground thin wire by an equivalent circuit model. First, frequency responses of common-mode (CM) current on the printed circuit board and EM radiation are studied with finite difference time domain modeling. Secondly, an equivalent circuit model for predicting CM current is proposed. The equivalent circuit model for prediction is based on the concepts of CM antenna impedance, distributed constant circuit, and electric coupling between the power plane and the thin ground wire. Good agreement between the predicted and full-wave analysis results indicates the validity of the proposed equivalent circuit model. The frequency response of EM radiation from the stripline structure can be identified using our proposed model. In addition, the equivalent circuit model provides enough flexibility for different geometric parameters and can be used to develop physical insights and design guidelines.

Kayano, Yoshiki; Inoue, Hiroshi

2011-10-01

409

The US DOE-EM International Program - 13004  

SciTech Connect

The U.S. Department of Energy (DOE) Office of Environmental Management (EM) conducts international collaboration activities in support of U.S. policies and objectives regarding the accelerated risk reduction and remediation of environmental legacy of the nations' nuclear weapons program and government sponsored nuclear energy research. The EM International Program supported out of the EM Office of the Associate Principal Deputy Assistant Secretary pursues collaborations with foreign government organizations, educational institutions and private industry to assist in identifying technologies and promote international collaborations that leverage resources and link international experience and expertise. In fiscal year (FY) 2012, the International Program awarded eight international collaborative projects for work scope spanning waste processing, groundwater and soil remediation, deactivation and decommissioning (D and D) and nuclear materials disposition initiatives to seven foreign organizations. Additionally, the International Program's scope and collaboration opportunities were expanded to include technical as well as non-technical areas. This paper will present an overview of the on-going tasks awarded in FY 2012 and an update of upcoming international activities and opportunities for expansion into FY 2013 and beyond. (authors)

Elmetti, Rosa R.; Han, Ana M.; Williams, Alice C. [Department of Energy, Office of Environmental Management, 1000 Independence Ave. SW, Washington, DC 20585 (United States)] [Department of Energy, Office of Environmental Management, 1000 Independence Ave. SW, Washington, DC 20585 (United States)

2013-07-01

410

Covariance Matrix Estimation for the Cryo-EM Heterogeneity Problem  

E-print Network

In cryo-electron microscopy (cryo-EM), a microscope generates a top view of a sample of randomly-oriented copies of a molecule. The cryo-EM problem is to use the resulting set of noisy 2D projection images taken at unknown directions to reconstruct the 3D structure of the molecule. In some situations, the molecule under examination exhibits structural variability, which poses a fundamental challenge in cryo-EM. The heterogeneity problem is the task of mapping the space of conformational states of a molecule. It has been previously shown that the leading eigenvectors of the covariance matrix of the 3D molecules can be used to solve the heterogeneity problem. Estimating the covariance matrix is however challenging, since only projections of the molecules are observed, but not the molecules themselves. In this paper, we derive an estimator for the covariance matrix as a solution to a certain linear system. The linear operator to be inverted, which we term the tomographic covariance transform, is an important obj...

Katsevich, Gene; Singer, Amit

2013-01-01

411

ANÁLISE DA INSERÇÃO DOS TEMAS DE HUMANIDADES E ÉTICA, COM METODOLOGIA DE APRENDIZAGEM BASEADA EM PROBLEMAS, EM CURRICULO MÉDICO INTEGRADO EM ESCOLA PÚBLICA NO DISTRITO FEDERAL, BRASIL  

PubMed Central

Objetivo Realizar uma análise da inserção da ética e humanidades no currículo do Curso de Medicina da Escola Superior em Ciências da Saúde - ESCS, escola pública do Distrito Federal, Brasil, de forma a contribuir com o processo de gestão curricular. Metodologia O Estudo é de coorte e documental. Foram pesquisados 37 termos relacionados à ética e 36 referentes à humanização nos objetivos educacionais e conteúdo dos módulos temáticos, habilidades e atitudes e interação ensino-serviço-comunidade, de 1a a 4a série e no programa do internato no currículo (ano 2006) e no projeto pedagógico do Curso de Medicina (2001). Resultados Maior inserção da humanização, ética e bioética na 1a e 2a série, quando comparado à inserção na 3a e 4a série e no internato, (IC95%-?=0,034, pvalue=0,007). Unidade de habilidades e atitudes: freqüência das 3 temáticas no currículo da 1a a 4a séries (IC95%-?=0,026, pvalue=0,013). Quando comparada a inserção entre o internato e as quatro primeiras séries, observa-se que nestas a inserção da temática humanização é superior (IC95%-?=0,042, pvalue=0,029). Conclusão O currículo desenvolvido no ano de 2006 na ESCS apresentou correlação com o projeto pedagógico do curso e contemplou a temática de forma abrangente, em todas as séries e internato. PMID:20396594

Novaes, Maria Rita Carvalho Garbi; Novaes, Luiz Carlos Garcez; Guilhem, Dirce; Lolas, Fernando; Silveira, Carla; Guiotti, Murilo

2009-01-01

412

EMS-STARS: Emergency Medical Services "Superuser" Transport Associations: An Adult Retrospective Study.  

PubMed

Abstract Objective. Emergency medical services (EMS) "superusers" -those who use EMS services at extremely high rates -have not been well characterized. Recent interest in the small group of individuals who account for a disproportionate share of health-care expenditures has led to research on frequent users of emergency departments and other health services, but little research has been done regarding those who use EMS services. To inform policy and intervention implementation, we undertook a descriptive analysis of EMS superusers in a large urban community. In this paper we compare EMS superusers to low, moderate, and high users to characterize factors contributing to EMS use. We also estimate the financial impact of EMS superusers. Methods. We conducted a retrospective cross-sectional study based on 1 year of data from an urban EMS system. Data for all EMS encounters with patients age ?18 years were extracted from electronic records generated on scene by paramedics. We identified demographic and clinical variables associated with levels of EMS use. EMS users were characterized by the annual number of EMS encounters: low (1), moderate (2-4), high (5-14), and superusers (?15). In addition, we performed a financial analysis using San Francisco Fire Department (SFFD) 2009 charge and reimbursement data. Results. A total of 31,462 adults generated 43,559 EMS ambulance encounters, which resulted in 39,107 transports (a 90% transport rate). Encounters for general medical reasons were common among moderate and high users and less frequent among superusers and low users, while alcohol use was exponentially correlated with encounter frequency. Superusers were significantly younger than moderate EMS users, and more likely to be male. The superuser group created a significantly higher financial burden/person than any other group, comprising 0.3% of the study population, but over 6% of annual EMS charges and reimbursements. Conclusions. In this retrospective study, adult EMS "superusers" emerged as a distinct, predominantly male population and their EMS encounters were associated with alcohol use. Continued analysis of this unique, high-cost, and frequently transported population will likely illuminate specific intervention strategies. PMID:25093273

Hall, M Kennedy; Raven, Maria C; Hall, Jane; Yeh, Clement; Allen, Elaine; Rodriguez, Robert M; Tangherlini, Niels L; Sporer, Karl A; Brown, John F

2015-01-01

413

Programa de Ps-Graduao em Cincia dos Alimentos CAL/CCA/UFSC Regimento Interno  

E-print Network

1 Programa de Pós-Graduação em Ciência dos Alimentos CAL/CCA/UFSC Regimento Interno UNIVERSIDADE FEDERAL DE SANTA CATARINA CENTRO DE CI�NCIAS AGRÁRIAS PROGRAMA DE P�S-GRADUA��O EM CI�NCIA DOS ALIMENTOS REGIMENTO DO PROGRAMA TÍTULO I DO OBJETIVO Art. 1. O Programa de Pós-Graduação em Ciência dos Alimentos

Floeter, Sergio Ricardo

414

iGrace modle informatique d'motions du robot compagnon EmI  

E-print Network

1 iGrace ­ modèle informatique d'émotions du robot compagnon EmI iGrace ­ emotional computational model for EmI companion robot Sébastien SAINT-AIM�, Brigitte LE-P�V�DIC, Dominique DUHAUT Valoria of EmI, as well as improvements to be made for its third version. Keywords. Emotions, computational

Paris-Sud XI, Université de

415

Quantificação de nitrofurazona e de nitrofurantoína em medicamentos por espectrofotometria de refletância difusa e de transmissão.  

E-print Network

??A nitrofurazona e a nitrofurantoína são substâncias derivadas dos nitrofuranos e comercializadas em preparações farmacêuticas com ação bactericida, antifúngica e antimicrobiana com um amplo espectro… (more)

Marcio das Neves Palumbo

2011-01-01

416

Avaliação da infecção por morbilivírus em cetáceos arrojados na costa portuguesa.  

E-print Network

??Dissertação de Mestrado Integrado em Medicina Veterinária O Dolphin morbilivírus (DMV) e o Porpoise morbillivirus (PMV) são membros da subfamília Paramyxovirinae, família Paramyxoviridae. Estes vírus… (more)

Bento, Maria Carolina Rocha de Medeiros

2012-01-01

417

Modeling of MHD edge containment in strip casting with ELEKTRA and CaPS-EM codes  

SciTech Connect

This paper presents modeling studies of magnetohydrodynamics analysis in twin-roll casting. Argonne National Laboratory (ANL) and ISPAT Inland Inc. (Inland), formerly Inland Steel Co., have worked together to develop a three-dimensional (3-D) computer model that can predict eddy currents, fluid flows, and liquid metal containment of an electromagnetic (EM) edge containment device. The model was verified by comparing predictions with experimental results of liquid metal containment and fluid flow in EM edge dams (EMDs) that were designed at Inland for twin-roll casting. This mathematical model can significantly shorten casting research on the use of EM fields for liquid metal containment and control. The model can optimize the EMD design so it is suitable for application, and minimize expensive time-consuming full-scale testing. Numerical simulation was performed by coupling a 3-D finite-element EM code (ELEKTRA) and a 3-D finite-difference fluids code (CaPS-EM) to solve heat transfer, fluid flow, and turbulence transport in a casting process that involves EM fields. ELEKTRA can predict the eddy-current distribution and the EM forces in complex geometries. CaPS-EM can model fluid flows with free surfaces. The computed 3-D magnetic fields and induced eddy currents in ELEKTRA are used as input to temperature- and flow-field computations in CaPS-EM. Results of the numerical simulation compared well with measurements obtained from both static and dynamic tests.

Chang, F. C.

2000-01-12

418

Iniciativas de Transição e Permacultura, como reestruturação e capacitação de comunidades em Portugal.  

E-print Network

??Mestrado em Gestão e Estratégia Industrial Este trabalho visa abordar o movimento de Iniciativas de Transição, analisando as suas motivações, baseadas fundamentalmente na insustentabilidade da… (more)

Soares, Pedro David Almeida Rebelo

2012-01-01

419

Covariance Matrix Estimation for the Cryo-EM Heterogeneity Problem*  

PubMed Central

In cryo-electron microscopy (cryo-EM), a microscope generates a top view of a sample of randomly oriented copies of a molecule. The problem of single particle reconstruction (SPR) from cryo-EM is to use the resulting set of noisy two-dimensional projection images taken at unknown directions to reconstruct the three-dimensional (3D) structure of the molecule. In some situations, the molecule under examination exhibits structural variability, which poses a fundamental challenge in SPR. The heterogeneity problem is the task of mapping the space of conformational states of a molecule. It has been previously suggested that the leading eigenvectors of the covariance matrix of the 3D molecules can be used to solve the heterogeneity problem. Estimating the covariance matrix is challenging, since only projections of the molecules are observed, but not the molecules themselves. In this paper, we formulate a general problem of covariance estimation from noisy projections of samples. This problem has intimate connections with matrix completion problems and high-dimensional principal component analysis. We propose an estimator and prove its consistency. When there are finitely many heterogeneity classes, the spectrum of the estimated covariance matrix reveals the number of classes. The estimator can be found as the solution to a certain linear system. In the cryo-EM case, the linear operator to be inverted, which we term the projection covariance transform, is an important object in covariance estimation for tomographic problems involving structural variation. Inverting it involves applying a filter akin to the ramp filter in tomography. We design a basis in which this linear operator is sparse and thus can be tractably inverted despite its large size. We demonstrate via numerical experiments on synthetic datasets the robustness of our algorithm to high levels of noise.

Katsevich, E.; Katsevich, A.; Singer, A.

2015-01-01

420

UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM FILOSOFIA  

E-print Network

Filosofia: 0,5 (um) ponto (até 1 pontos) 2.3. Livro de Filosofia: 1 (dois) pontos (até 2 pontos) 2.4. Resumo evento de Filosofia: 0,5 (um) ponto (até 1 pontos)" Leia-se "2.2. Capítulo de livro de Filosofia: 0,5 (meio) ponto (até 1 pontos) 2.3. Livro de Filosofia: 1 (um) ponto (até 2 pontos) 2.4. Resumo em anais de

Lucero, Jorge Carlos

421

PROGRAMA DE PS-GRADUAO EM EDUCAO MANUAL DO CANDIDATO  

E-print Network

.ppge.ufsc.br a partir de 12 de março de 2013); b) Cópia da Carteira de Identidade e do CPF; c) Cópia do DIPLOMA e do (apenas o CPF identificará o candidato), contendo `folha de rosto' (disponível a partir de 12 de março na, 1993. v. 2. p. 193-274. GONDRA, J. G. (Org.). Pesquisa em história da educação no Brasil. Rio de

Floeter, Sergio Ricardo

422

State of the Art in EM Field Computation  

SciTech Connect

This paper presents the advances in electromagnetic (EM) field computation that have been enabled by the US DOE SciDAC Accelerator Science and Technology project which supports the development and application of a suite of electromagnetic codes based on the higher-order finite element method. Implemented on distributed memory supercomputers, this state of the art simulation capability has produced results which are of great interest to accelerator designers and with realism previously not possible with standard codes. Examples from work on the International Linear Collider (ILC) project are described.

Ng, C.; Akcelik, V.; Candel, A.; Chen, S.; Folwell, N.; Ge, L.; Guetz, A.; Jiang, H.; Kabel, A.; Lee, L.-Q.; Li, Z.; Prudencio, E.; Schussman, G.; Uplenchwar, R.; Xiao,; Ko, K.; /SLAC

2006-09-25

423

An Effective EMS Hardware and Software Interface- The Trained Operator  

E-print Network

print out a specific alarm message if a piece of equipment fails to operate properly. This knowledge merely enables the operator to list capabilities, it does not imply understanding of how to react to, alter or cause those events. Knowledge alone... to be productive and the owner can begin to realize EMS benefits. ANALYSIS ,..... The three skill levels achieved so far, should be regarded as the minimum necessary for acceptable system opera tion. The next two training levels rep resent "money in the bank...

Cherry, C. L.

424

SEI: Junior E&M I Course Materials - Electrodynamics  

NSDL National Science Digital Library

This is a collection of resources for teaching electrodynamics. Included are homework questions, concept tests, student tutorials, and information about common student difficulties in the topic and ways to address these difficulties. This material was developed as part of a education research-based course transformation for junior level E&M. All of the resources developed for this course are available, sorted by individual topic and type, at http://www.compadre.org/psrc/items/Relations.cfm?ID=7891. Because this topic is not typically taught in depth in the courses used in developing these course materials, these materials are less complete than the other sections.

Pollock, Steven J.; Chasteen, Stephanie V.

2010-09-24

425

9/7/2004 Penumadu, Prashant, and Frost. EM-2004 1 A VIRTUAL TRIAXIAL COMPRESSION  

E-print Network

9/7/2004 Penumadu, Prashant, and Frost. EM-2004 1 A VIRTUAL TRIAXIAL COMPRESSION TEST SIMULATOR, Knoxville, TN, USA David J. Frost: Department of Civil and Environmental Engineering, Georgia Institute. #12;9/7/2004 Penumadu, Prashant, and Frost. EM-2004 2 Presentation Outline Concept of Virtual

Prashant, Amit

426

Global Convergence of the EM Algorithm for Unconstrained Latent Variable Models with Categorical Indicators  

ERIC Educational Resources Information Center

Convergence of the expectation-maximization (EM) algorithm to a global optimum of the marginal log likelihood function for unconstrained latent variable models with categorical indicators is presented. The sufficient conditions under which global convergence of the EM algorithm is attainable are provided in an information-theoretic context by…

Weissman, Alexander

2013-01-01

427

DIAGNÓSTICO DE FALHAS EM MÁQUINAS ROTATIVAS ATRAVÉS DA ANÁLISE DA VIBRAÇÃO TORCIONAL  

Microsoft Academic Search

RESUMO Os eixos, quando transmitem torque, agem como molas torcionais, além da flexão. Quando há variação cíclica no torque transmitido podem aparecer vibrações torcionais forçadas, que dependendo das freqüências naturais do sistema poderão causar ressonância, caso em que o eixo poderá oscilar em amplitudes suficientemente elevadas para produzir falhas. O presente trabalho apresenta técnicas de medição e análise de vibração

Evaldo Khater

428

Comportamento de Pantala flavescens (Odonata, Anisoptera, Libellulidae) e perda do investimento reprodutivo em áreas antropizadas  

Microsoft Academic Search

RESUMO: Pantala flavescens é uma libélula exofítica, territorialista e migratória. Devido ao comportamento migratório, a ocorrência desta espécie em áreas não alagadas é comum. No entanto, a presença de P. flavescens em áreas de estacionamento de veículos e o registro de eventos de oviposição sobre as latarias de automóveis não é bem entendida. O presente trabalho apresenta dados comportamentais de

Antonia Figueira Van de Koken

2007-01-01

429

Effectiveness of electromagnetic wave absorbers to improve 5.8 GHz DSRC EM environment inside tunnel  

Microsoft Academic Search

Electromagnetic (EM) wave absorbers have been used to improve the EM environment of an electronic toll collection (ETC) system on an express highway or a wireless local area network (LAN) system in an indoor environment. In this paper, an efficient multi-ray propagation model, which uses a combination of image technique and grid approach to trace multiple signal rays from transmitter

Ramesh K. POKHAREL; Hirotomo ICHINOSE; Osamu HASHIMOTO; Makoto TOYOTA; Itoji SAMEDA; Kouji WADA

2005-01-01

430

Developing State and National Evaluation Infrastructures- Guidance for the Challenges and Opportunities of EM&V  

SciTech Connect

Evaluating the impacts and effectiveness of energy efficiency programs is likely to become increasingly important for state policymakers and program administrators given legislative mandates and regulatory goals and increasing reliance on energy efficiency as a resource. In this paper, we summarize three activities that the authors have conducted that highlight the expanded role of evaluation, measurement and verification (EM&V): a study that identified and analyzed challenges in improving and scaling up EM&V activities; a scoping study that identified issues involved in developing a national efficiency EM&V standard; and lessons learned from providing technical assistance on EM&V issues to states that are ramping up energy efficiency programs. The lessons learned are summarized in 13 EM&V issues that policy makers should address in each jurisdiction and which are listed and briefly described. The paper also discusses how improving the effectiveness and reliability of EM&V will require additional capacity building, better access to existing EM&V resources, new methods to address emerging issues and technologies, and perhaps foundational documents and approaches to improving the credibility and cross jurisdictional comparability of efficiency investments. Two of the potential foundational documents discussed are a national EM&V standard or resource guide and regional deemed savings and algorithm databases.

Schiller, Steven R.; Goldman, Charles A.

2011-06-24

431

COLOR IMAGE SEGMENTATION USING A SELF-INITIALIZING EM Dana Elena Ilea and Paul F. Whelan  

E-print Network

COLOR IMAGE SEGMENTATION USING A SELF-INITIALIZING EM ALGORITHM Dana Elena Ilea and Paul F. Whelan-Maximization (EM) algorithm that we apply for color image segmentation. Since this algorithm partitions the data included in the development of an adaptive image segmentation scheme that has been applied to a large

Whelan, Paul F.

432

Adaptac~ao ao Contexto em Sistemas de Comunicac~ao Heterogeneos  

E-print Network

. Considerem-se por exemplo aplicac¸ ~oes cooperativas multi-utilizador tais como os jogos em rede ou aplicac¸~oes cooperativas multi-utilizador (tais como os jogos on-line). Embora a maioria das concretizac¸~oes actuais destes jogos se baseiem em arquitecturas cliente-servidor, foram j´a de- Este trabalho foi

Rodrigues, Luís E.T.

433

Uma Estratégia para a Visualização do Céu e seus Elementos em Jogos  

Microsoft Academic Search

Resumo Uma visualização convincente do céu e seus elementos (nuvens, sol, lua, estrelas) é fundamental para agregar realismo aos jogos que usam cenários em ambientes externos. Como uma simulação precisa desses efeitos pode ser computacionalmente muito cara, muitos jogos empregam artifícios, visualizando o céu como texturas mapeadas em esferas e caixas envolventes. Neste trabalho, apresentamos uma estratégia simples para simular

MARCIO PEREIRA DE ARAUJO; WALDEMAR CELES

434

Method for evaluating compatibility of commercial electromagnetic (EM) microsensor tracking systems with surgical and imaging tables  

NASA Astrophysics Data System (ADS)

Electromagnetic (EM) tracking systems have been successfully used for Surgical Navigation in ENT, cranial, and spine applications for several years. Catheter sized micro EM sensors have also been used in tightly controlled cardiac mapping and pulmonary applications. EM systems have the benefit over optical navigation systems of not requiring a line-of-sight between devices. Ferrous metals or conductive materials that are transient within the EM working volume may impact tracking performance. Effective methods for detecting and reporting EM field distortions are generally well known. Distortion compensation can be achieved for objects that have a static spatial relationship to a tracking sensor. New commercially available micro EM tracking systems offer opportunities for expanded image-guided navigation procedures. It is important to know and understand how well these systems perform with different surgical tables and ancillary equipment. By their design and intended use, micro EM sensors will be located at the distal tip of tracked devices and therefore be in closer proximity to the tables. Our goal was to define a simple and portable process that could be used to estimate the EM tracker accuracy, and to vet a large number of popular general surgery and imaging tables that are used in the United States and abroad.

Nafis, Christopher; Jensen, Vern; von Jako, Ron

2008-03-01

435

Chapter 19: HVAC Controls (DDC/EMS/BAS) Evaluation Protocol  

SciTech Connect

The HVAC Controls Evaluation Protocol is designed to address evaluation issues for direct digital controls/energy management systems/building automation systems (DDC/EMS/BAS) that are installed to control heating, ventilation, and air-conditioning (HVAC) equipment in commercial and institutional buildings. (This chapter refers to the DDC/EMS/BAS measure as HVAC controls.) This protocol may also be applicable to industrial facilities such as clean rooms and labs, which have either significant HVAC equipment or spaces requiring special environmental conditions. This protocol addresses only HVAC-related equipment and the energy savings estimation methods associated with installing such control systems as an energy efficiency measure. The affected equipment includes: Air-side equipment (air handlers, direct expansion systems, furnaces, other heating- and cooling-related devices, terminal air distribution equipment, and fans); Central plant equipment (chillers, cooling towers, boilers, and pumps). These controls may also operate or affect other end uses, such as lighting, domestic hot water, irrigation systems, and life safety systems such as fire alarms and other security systems. Considerable nonenergy benefits, such as maintenance scheduling, system component troubleshooting, equipment failure alarms, and increased equipment lifetime, may also be associated with these systems. When connected to building utility meters, these systems can also be valuable demand-limiting control tools. However, this protocol does not evaluate any of these additional capabilities and benefits.

Romberger, J.

2014-11-01

436

Children recognize emotions of EmI companion robot Sebastien Saint-Aime and Brigitte Le Pevedic and Dominique Duhaut  

E-print Network

Children recognize emotions of EmI companion robot S´ebastien Saint-Aim´e and Brigitte Le P´ev´edic and Dominique Duhaut Abstract-- This article presents the evaluation of the emotio- nal expressiveness of EmI and implementation of EmI, and experimentation to evaluate the expressiveness of EmI with 52 school children aged 7

Paris-Sud XI, Université de

437

Prevalence of Depression and Cognitive Impairment in Older Adult EMS Patients  

PubMed Central

Objectives To characterize the proportion of older adult ED patients with depression or cognitive impairment. To compare the prevalence of depression or cognitive impairment among ED patients arriving via EMS, as compared to other modes. Methods Community-dwelling older adults (age?60) presenting to an academic medical center ED were interviewed. Participants provided demographic and clinical information, and were evaluated for depression and cognitive impairment. Subjects arriving via EMS were compared to those arriving via other modes using the chi-square test, t-test, and the Wilcoxon rank sum test, where appropriate. Results Consent was obtained from 1342 eligible older adults; 695 (52%) arrived via EMS. The median age for those arriving via EMS was 74 (IQR 65, 82), 52% were female, 81% white. 15% of EMS patients had moderate or greater depression, as compared to 14% of patients arriving via other modes (p=0.52). 13% of EMS patients had cognitive impairment, as compared to 8% arriving via other modes (p<0.01). Depressed EMS patients frequently reported a history of depression (47%) and taking antidepressants (51%). Cognitively impaired EMS patients infrequently reported a history of dementia (16%) or taking medications for dementia (14%). Conclusions In this cohort of community-dwelling older adult ED patients depression and cognitive impairment were common. As compared to ED patients arriving by other transport means, patients arriving via EMS had similar prevalence of depression but an increased prevalence of cognitive impairment. Screening for depression and cognitive impairment by EMS providers may have value, but needs further investigation. PMID:20977363

Shah, Manish N.; Jones, Courtney M. C.; Richardson, Thomas M.; Conwell, Yeates; Katz, Paul; Schneider, Sandra M.

2010-01-01

438

The EM SSAB Annual Work Plan Process: Focusing Board Efforts and Resources - 13667  

SciTech Connect

One of the most daunting tasks for any new member of a local board of the Environmental Management Site Specific Advisory Board (EM SSAB) is to try to understand the scope of the clean-up activities going on at the site. In most cases, there are at least two or three major cleanup activities in progress as well as monitoring of past projects. When planning for future projects is added to the mix, the list of projects can be long. With the clean-up activities involving all major environmental media - air, water, soils, and groundwater, new EM SSAB members can find themselves totally overwhelmed and ineffective. Helping new members get over this initial hurdle is a major objective of EM and all local boards of the EM SSAB. Even as members start to understand the size and scope of the projects at a site, they can still be frustrated at the length of time it takes to see results and get projects completed. Many project and clean-up timelines for most of the sites go beyond 10 years, so it's not unusual for an EM SSAB member to see the completion of only 1 or 2 projects over the course of their 6-year term on the board. This paper explores the annual work planning process of the EM SSAB local boards, one tool that can be used to educate EM SSAB members into seeing the broader picture for the site. EM SSAB local work plans divide the site into projects focused on a specific environmental issue or media such as groundwater and/or waste disposal options. Projects are further broken down into smaller segments by highlighting major milestones. Using these metrics, local boards of the EM SSAB can start to quantify the effectiveness of the project in achieving the ultimate goal of site clean-up. These metrics can also trigger board advice and recommendations for EM. At the beginning of each fiscal year, the EM SSAB work plan provides a road map with quantifiable checkpoints for activities throughout the year. When the work plans are integrated with site-specific, enforceable regulatory milestones, they can provide a comprehensive work plan for not only the board, but also regulators, site contractors, and DOE. Because the work plans are reviewed and approved by DOE, they carry some weight in holding local boards of the EM SSAB accountable. This structure provides the basis for local boards to achieve their primary function, to provide DOE with information, advice, and recommendations concerning issues affecting the EM program at the site. (authors)

Young, Ralph [Paducah Citizens Advisory Board (United States)] [Paducah Citizens Advisory Board (United States)

2013-07-01

439

Capturing RNA-dependent pathways for cryo-EM analysis  

PubMed Central

Cryo-Electron Microscopy (EM) is a powerful technique to visualize biological processes at nanometer resolution. Structural studies of macromolecular assemblies are typically performed on individual complexes that are biochemically isolated from their cellular context. Here we present a molecular imaging platform to capture and view multiple components of cellular pathways within a functionally relevant framework. We utilized the bacterial protein synthesis machinery as a model system to develop our approach. By using modified Affinity Grid surfaces, we were able to recruit multiple protein assemblies bound to nascent strands of mRNA. The combined use of Affinity Capture technology and single particle electron microscopy provide the basis for visualizing RNA-dependent pathways in a remarkable new way. PMID:24688633

Tanner, Justin R.; Degen, Katherine; Gilmore, Brian L.; Kelly, Deborah F.

2012-01-01

440

High-dimensional cluster analysis with the Masked EM Algorithm  

PubMed Central

Cluster analysis faces two problems in high dimensions: first, the “curse of dimensionality” that can lead to overfitting and poor generalization performance; and second, the sheer time taken for conventional algorithms to process large amounts of high-dimensional data. We describe a solution to these problems, designed for the application of “spike sorting” for next-generation high channel-count neural probes. In this problem, only a small subset of features provide information about the cluster member-ship of any one data vector, but this informative feature subset is not the same for all data points, rendering classical feature selection ineffective. We introduce a “Masked EM” algorithm that allows accurate and time-efficient clustering of up to millions of points in thousands of dimensions. We demonstrate its applicability to synthetic data, and to real-world high-channel-count spike sorting data. PMID:25149694

Kadir, Shabnam N.; Goodman, Dan F. M.; Harris, Kenneth D.

2014-01-01

441

SEI: Junior E&M I Course Materials - Homework  

NSDL National Science Digital Library

This homework question collection was constructed over the course of four semesters of a transformed junior-level Electricity and Magnetism course on electro- and magneto-statics. Many questions are related to textbook problems, but with added elements of explanation, sense-making, estimation or approximation, real-world connections, and multiple-representations. Not all these homework questions were used in the course design project. Some problems used include detailed instructor notes, including statistics on student performance on each homework problem assigned. The homework solutions are only available to instructors by writing the authors, Steven.Pollock@colorado.edu This material was developed as part of a education research-based course transformation for junior level E&M. All of the resources developed for this course are available, sorted by individual topic and type, at http://www.compadre.org/psrc/items/Relations.cfm?ID=7891.

Pollock, Steven J.; Chasteen, Stephanie V.

2010-06-10

442

EM Properties of Magnetic Minerals at RADAR Frequencies  

NASA Technical Reports Server (NTRS)

Previous missions to Mars have revealed that Mars surface is magnetic at DC frequency. Does this highly magnetic surface layer attenuate RADAR energy as it does in certain locations on Earth? It has been suggested that the active magnetic mineral on Mars is titanomaghemite and/or titanomagnetite. When titanium is incorporated into a maghemite or magnetite crystal, the Curie temperature can be significantly reduced. Mars has a wide range of daily temperature fluctuations (303K - 143K), which could allow for daily passes through the Curie temperature. Hence, the global dust layer on Mars could experience widely varying magnetic properties as a function of temperature, more specifically being ferromagnetic at night and paramagnetic during the day. Measurements of EM properties of magnetic minerals were made versus frequency and temperature (300K- 180K). Magnetic minerals and Martian analog samples were gathered from a number of different locations on Earth.

Stillman, D. E.; Olhoeft, G. R.

2005-01-01

443

In-house labor saves University 50% of EMS cost  

SciTech Connect

By designing and installing its own energy-management system (EMS), the staff at Oklahoma State University hopes to reduce the cost of a Staefa EMA II system in half. However, the school has held up payment in accordance with its contract until some equipment problems are solved and the system is operating for 30 consecutive days at 95% of performance specifications. Faulty field multiplexers and inadequate voice-intercom equipment failed the first two acceptance tests. The 750-point system that will control 10 buildings should have a three-year payback. In-house crews are reducing installation costs because they are familiar with the buildings and can work around class schedules. Two separate bids were required because most bids failed to meet equipment specifications. (DCK)

Crawford, E.

1982-03-15

444

SEI: Junior E&M I Course Materials - Tutorials  

NSDL National Science Digital Library

This collection of tutorials and tutorial pre-tests was constructed for a transformed junior-level Electricity and Magnetism course. These tutorials are weekly student sessions, modeled after research-validated curricula developed at the University of Washington. Using these materials in study/recitation sections, students work in small groups with the instructor as a learning coach. The materials are designed to target known student difficulties, to elicit and develop conceptual understanding and math/physics connections. They also help faculty listen to student reasoning, get a clearer sense of student ideas, and determine where they are struggling. This material was developed as part of a education research-based course transformation for junior level E&M. All of the resources developed for this course are available, sorted by individual topic and type, at http://www.compadre.org/psrc/items/Relations.cfm?ID=7891.

Pollock, Steven J.; Chasteen, Stephanie V.; Kinney, Edward; Dubson, Michael

2010-06-10

445

Integrated EM & Thermal Simulations with Upgraded VORPAL Software  

SciTech Connect

Nuclear physics accelerators are powered by microwaves which must travel in waveguides between room-temperature sources and the cryogenic accelerator structures. The ohmic heat load from the microwaves is affected by the temperature-dependent surface resistance and in turn affects the cryogenic thermal conduction problem. Integrated EM & thermal analysis of this difficult non-linear problem is now possible with the VORPAL finite-difference time-domain simulation tool. We highlight thermal benchmarking work with a complex HOM feed-through geometry, done in collaboration with researchers at the Thomas Jefferson National Accelerator Laboratory, and discuss upcoming design studies with this emerging tool. This work is part of an effort to generalize the VORPAL framework to include generalized PDE capabilities, for wider multi-physics capabilities in the accelerator, vacuum electronics, plasma processing and fusion R&D fields, and we will also discuss user interface and algorithmic upgrades which facilitate this emerging multiphysics capability.

D.N. Smithe, D. Karipides, P. Stoltz, G. Cheng, H. Wang

2011-03-01

446

EMS mutant spectra generated by multi-parameter flow cytometry.  

PubMed

The CHO A(L) cell line contains a single copy of human chromosome 11 that encodes several cell surface proteins including glycosyl phosphatidylinositol (GPI) linked CD59 and CD90, as well as CD98, CD44 and CD151 which are not GPI-linked. The flow cytometry mutation assay (FCMA) measures mutations of the CD59 gene by the absence of fluorescence when stained with antibodies against the CD59 cell surface protein. We have measured simultaneous mutations in CD59, CD44, CD90, CD98 and CD151 to generate a mutant spectrum for ionizing radiation. After treatment with ethyl methanesulfonate (EMS) many cells have an intermediate level of CD59 staining. Single cells were sorted from CD59(-) regions with varying levels of fluorescence and the resulting clonal populations had a stable phenotype for CD59 expression. Mutant spectra were generated by flow cytometry using the isolated clones and nearly all clones were mutated in CD59 only. Interestingly, about 60% of the CD59 negative clones were actually GPI mutants determined by staining with the GPI specific fluorescently labeled bacterial toxin aerolysin (FLAER). The GPI negative cells are most likely caused by mutations in the X-linked pigA gene important in GPI biosynthesis. Small mutations of pigA and CD59 were expected for the alkylating agent EMS and the resulting spectra are significantly different than the large deletions found when analyzing radiation mutants. After analyzing the CD59(-) clonal populations we have adjusted the FCMA mutant regions from 1% to 10% of the mean of the CD59 positive peak to include the majority of CD59 mutants. PMID:19463836

Keysar, Stephen B; Fox, Michael H

2009-12-01

447

Effects of integrated use of organic and inorganic nutrient sources with effective microorganisms (EM) on seed cotton yield in Pakistan.  

PubMed

A field experiment was conducted to determine the effects of integrated use of organic and inorganic nutrient sources with effective microorganisms on growth and yield of cotton. Treatments included: control; organic materials (OM); effective microorganisms (EM); OM+EM; mineral NPK (170:85:60 kg); 1/2 mineral NPK+EM; 1/2 mineral NPK+OM+EM and mineral NPK+OM+EM. OM and EM alone did not increase the yield and yield attributing components significantly but integrated use of both resulted in a 44% increase over control. Application of NPK in combination with OM and EM resulted in the highest seed cotton yield (2470 kg ha-1). Integrated use of OM+EM with 1/2 mineral NPK yielded 2091 kg ha-1, similar to the yield (2165 kg ha-1) obtained from full recommended NPK, indicating that this combination can substitute for 85 kg N ha-1. Combination of both N sources with EM also increased the concentrations of NPK in plants. Economic analysis suggested the use of 1/2 mineral NPK with EM+OM saves the mineral N fertilizer by almost 50% compared to a system with only mineral NPK application. This study indicated that application of EM increased the efficiency of both organic and mineral nutrient sources but alone was ineffective in increasing yield. PMID:16023343

Khaliq, Abdul; Abbasi, M Kaleem; Hussain, Tahir

2006-05-01

448

Effects of caffeine or EDTA post-treatment on EMS mutagenesis in soybean  

Microsoft Academic Search

Seeds of soybean cultivar LD4 were mutagenically treated with EMS (0.3, 0.5, 0.6, 0.9, 0.5 and 1.8%) for 3 h only or plus caffeine (50 mM) or EDTA (1 mM) post-treatment for 5 h. The experimental results indicated that: (1) of the different concentrations of EMS treatment, the M2 mutation frequency induced with 0.6% EMS was the highest (9.7%). When

Zhu Baoge; Gu Aiqiu; Deng Xiangdong; Deng Yuxuan; Lu Zixian

1995-01-01

449

Um Framework para Proviso de QoS em Redes Mveis Sem Fio1  

E-print Network

Um Framework para Provisão de QoS em Redes Móveis Sem Fio1 Luciana dos Santos Lima, Antônio Tadeu A provisão de QoS em redes móveis sem fio integrando soluções isoladas encontradas na literatura. Esses descrita através de um cenário simulado em que serviços integrados são oferecidos sobre uma rede IP Móvel

Colcher, Sérgio

450

Centro de Cincias Agrrias Coordenao do Curso de Graduao em Cincia e Tecnologia de Alimentos  

E-print Network

Centro de Ciências Agrárias Coordenação do Curso de Graduação em Ciência e Tecnologia de Alimentos-2728 Regimento Interno do Curso de Graduação em Ciência e Tecnologia de alimentos Capítulo I ­ Das disposições iniciais Art. 1º - O Curso de Graduação em Ciência e Tecnologia de Alimentos, instituído pela Resolução 005

Floeter, Sergio Ricardo

451

User's guide for the PWR LOCA analysis capability of the WRAP-EM system  

SciTech Connect

The Water Reactor Analysis Package (WRAP) has been expanded to provide the capability to analyze loss-of-coolant accidents (LOCAs) in both pressurized water reactors (PWRs) and boiling water reactors (BWRs) by using evaluation models (EMs). The input specifications for modules in the WRAP-EM system are presented in this document along with the JOSHUA input templates. This document, along with the WRAP user's guide, provides a step-by-step procedure for setting up a PWR data base for the WRAP-EM system. 12 refs.

Beranek, F; Gregory, M V

1980-02-01

452

UFF/PROGEPE/CASQ/DPVS Diviso de Promoo e Vigilncia em Sade-DPVS  

E-print Network

considerado uma das principais causas de morte evitável. No mundo, cerca de 1,3 bilhões de pessoas são considerado como a terceira maior causa de morte evitável aumentando a morbidade em crianças por doenças respiratórias e em cinco vezes o risco de morte súbita em bebês. A atual Portaria Nº 3 de 25 de março de 2013 da

Souza, Max O.

453

Investigating the source of contaminated plumes downstream of the Alborz Sharghi coal washing plant using EM34 conductivity data, VLF-EM and DC-resistivity geophysical methods  

NASA Astrophysics Data System (ADS)

Coal washing factories may create serious environmental problems due to pyrite oxidation and acid mine drainage generation from coal waste piles on nearby land. Infiltration of pyrite oxidation products through the porous materials of the coal waste pile by rainwater cause changes in the conductivity of underground materials and groundwater downstream of the pile. Electromagnetic and electrical methods are effective for investigation and monitoring of the contaminated plumes caused by coal waste piles and tailings impoundments. In order to investigate the environmental impact from a coal waste pile at the Alborz Sharghi coal washing plant, an EM34 ground conductivity meter was used on seven parallel lines in an E-W direction, downstream of the waste pile. Two-dimensional resistivity models obtained by the inversion of EM34 conductivity data identified conductive leachate plumes. In addition, quasi-3D inversion of EM34 data has confirmed the decreasing resistivity at depth due to the contaminated plumes. Comparison between EM34, VLF and DC-resistivity datasets, which were acquired for similar survey lines, agree well in identifying changes in the resistivity trend. The EM34 and DC-resistivity sections have greater similarity and better smoothness rather than those of the VLF model. Two-dimensional inversion models of these methods have shown some contaminated plumes with low resistivity.

Shiraz, Farzin Amirkhani; Ardejani, Faramarz Doulati; Moradzadeh, Ali; Arab-Amiri, Ali Reza

2013-01-01

454

Mars' Magnetic Atmosphere: Ionospheric Currents, Lightning (or not), E&M; Subsurface Sounding, and Future Missions  

NASA Astrophysics Data System (ADS)

Mars' ionosphere has no obvious magnetic signs of large-scale, dust-produced lightning. However, there are numerous interesting ionospheric currents (some associated with crustal magnetic fields) which would allow for E&M; subsurface sounding.

Espley, J. R.; Connerney, J. E. P.

2014-07-01

455

Cryo-EM of macromolecular assemblies at near-atomic resolution.  

PubMed

With single-particle electron cryomicroscopy (cryo-EM), it is possible to visualize large, macromolecular assemblies in near-native states. Although subnanometer resolutions have been routinely achieved for many specimens, state of the art cryo-EM has pushed to near-atomic (3.3-4.6 Å) resolutions. At these resolutions, it is now possible to construct reliable atomic models directly from the cryo-EM density map. In this study, we describe our recently developed protocols for performing the three-dimensional reconstruction and modeling of Mm-cpn, a group II chaperonin, determined to 4.3 Å resolution. This protocol, utilizing the software tools EMAN, Gorgon and Coot, can be adapted for use with nearly all specimens imaged with cryo-EM that target beyond 5 Å resolution. Additionally, the feature recognition and computational modeling tools can be applied to any near-atomic resolution density maps, including those from X-ray crystallography. PMID:20885381

Baker, Matthew L; Zhang, Junjie; Ludtke, Steven J; Chiu, Wah

2010-09-01

456

Analysis of the electrochemistry of hemes with Ems spanning 800 mV  

PubMed Central

The free energy of heme reduction in different proteins is found to vary over more than 18 kcal/mol. It is a challenge to determine how proteins manage to achieve this enormous range of Ems with a single type of redox cofactor. Proteins containing 141 unique hemes of a-, b-, and c-type, with bis-His, His-Met, and aquo-His ligation were calculated using Multi-Conformation Continuum Electrostatics (MCCE). The experimental Ems range over 800 mV from ?350 mV in cytochrome c3 to 450 mV in cytochrome c peroxidase (vs. SHE). The quantitative analysis of the factors that modulate heme electrochemistry includes the interactions of the heme with its ligands, the solvent, the protein backbone, and sidechains. MCCE calculated Ems are in good agreement with measured values. Using no free parameters the slope of the line comparing calculated and experimental Ems is 0.73 (R2 = 0.90), showing the method accounts for 73% of the observed Em range. Adding a +160 mV correction to the His-Met c-type hemes yields a slope of 0.97 (R2 = 0.93). With the correction 65% of the hemes have an absolute error smaller than 60 mV and 92% are within 120 mV. The overview of heme proteins with known structures and Ems shows both the lowest and highest potential hemes are c-type, whereas the b-type hemes are found in the middle Em range. In solution, bis-His ligation lowers the Em by ?205 mV relative to hemes with His-Met ligands. The bis-His, aquo-His, and His-Met ligated b-type hemes all cluster about Ems which are ?200 mV more positive in protein than in water. In contrast, the low potential bis-His c-type hemes are shifted little from in solution, whereas the high potential His-Met c-type hemes are raised by ?300 mV from solution. The analysis shows that no single type of interaction can be identified as the most important in setting heme electrochemistry in proteins. For example, the loss of solvation (reaction field) energy, which raises the Em, has been suggested to be a major factor in tuning in situ Ems. However, the calculated solvation energy vs. experimental Em shows a slope of 0.2 and R2 of 0.5 thus correlates weakly with Ems. All other individual interactions show even less correlation with Em. However the sum of these terms does reproduce the range of observed Ems. Therefore, different proteins use different aspects of their structures to modulate the in situ heme electrochemistry. This study also shows that the calculated Ems are relatively insensitive to different heme partial charges and to the protein dielectric constant used in the simulation. PMID:19003997

Zheng, Zhong; Gunner, M. R.

2009-01-01

457

METODOLOGIAS LIMPAS PARA DETERMINAO DE ACARES TOTAIS EM CAF CRU EMPREGANDO ALGORITMOS GENTICOS  

E-print Network

Instituto de Tecnologia de Alimentos, 6 Faculdade de Engenharia de Alimentos - UNICAMP, 7 Instituto de a quantificação dos teores de lipídios em alimentos. FAPERGS, EMBRAPA, PROGRUPE-UNISC e FUNDAP-UNISC #12;

Ferreira, Márcia M. C.

458

Histórico demográfico e filogeografia em populações brasileiras de Ardea alba egretta.  

E-print Network

??Foram estudadas populações de Ardea alba egretta (garça-branca-grande) da família Ardeidae (Aves), amostradas em quatro regiões brasileiras, com latitudes diferentes (Rio Grande do Sul, Pantanal,… (more)

Thaís Camilo Corrêa

2009-01-01

459

EM-MAC: A Dynamic Multichannel Energy-Efficient MAC Protocol for Wireless Sensor Networks  

E-print Network

-up scheduling. EM-MAC substantially enhances wireless channel uti- lization and transmission efficiency while resisting wireless inter- ference and jamming by enabling every node to dynamically op- timize the selection

Shihada, Basem

460

V.S. Ramachandran and E.M. Hubbard The Phenomenology of Synaesthesia  

E-print Network

V.S. Ramachandran and E.M. Hubbard The Phenomenology of Synaesthesia Abstract: This article the phenomenology of synaesthesia in greater detail, raise several new questions that have emerged from recent

Ramachandran, Vilayanur S.

461

EMDataBank.org: unified data resource for CryoEM  

PubMed Central

Cryo-electron microscopy reconstruction methods are uniquely able to reveal structures of many important macromolecules and macromolecular complexes. EMDataBank.org, a joint effort of the Protein Data Bank in Europe (PDBe), the Research Collaboratory for Structural Bioinformatics (RCSB) and the National Center for Macromolecular Imaging (NCMI), is a global ‘one-stop shop’ resource for deposition and retrieval of cryoEM maps, models and associated metadata. The resource unifies public access to the two major archives containing EM-based structural data: EM Data Bank (EMDB) and Protein Data Bank (PDB), and facilitates use of EM structural data of macromolecules and macromolecular complexes by the wider scientific community. PMID:20935055

Lawson, Catherine L.; Baker, Matthew L.; Best, Christoph; Bi, Chunxiao; Dougherty, Matthew; Feng, Powei; van Ginkel, Glen; Devkota, Batsal; Lagerstedt, Ingvar; Ludtke, Steven J.; Newman, Richard H.; Oldfield, Tom J.; Rees, Ian; Sahni, Gaurav; Sala, Raul; Velankar, Sameer; Warren, Joe; Westbrook, John D.; Henrick, Kim; Kleywegt, Gerard J.; Berman, Helen M.; Chiu, Wah

2011-01-01

462

História da ciência no estudo de modelos atômicos em livros didáticos de química.  

E-print Network

??Dissertação (mestrado)—Universidade de Brasília, Faculdade de Educação, Programa de Pós-Graduação em Educação, 2011. Esta dissertação tem por objetivo identificar a História da Ciência apresentada nos… (more)

Chaves, Lígia Maria Martinho Pereira

2011-01-01

463

Reserva de Recursos e Qualidade de Servio em Redes de Computadores de Dbito Elevado  

E-print Network

Reserva de Recursos e Qualidade de Serviço em Redes de Computadores de Débito Elevado Elisabete trabalho insere-se na área das redes de comunicação de alta velocidade com garantia de qualidade de serviço desenvolvimento e a integração de mecanismos de garantia de qualidade de serviço (QoS) em protocolos de rede e de

Monteiro, Edmundo

464

ARTIGO INTERNET Bioengenharia de Clulas Estaminais e Redes de Comunicaes em debate  

E-print Network

NewsSearch ARTIGO INTERNET Bioengenharia de Células Estaminais e Redes de Comunicações em debate://www.cienciapt.net/pt/in ... Bioengenharia de Células Estaminais e Redes de Comunicações em debate no IST Taguspark Com o objectivo de tecnológicas de vanguarda. Temáticas como a Bioengenharia de Células Estaminais, Redes de Comunicações, Gestão

Instituto de Sistemas e Robotica

465

SciMulator: Um Ambiente de Simulao de Workflows Cientficos em Redes P2P*  

E-print Network

SciMulator: Um Ambiente de Simulação de Workflows Científicos em Redes P2P* Jonas Dias1 , Carla desempenho ao utilizar a arquitetura SciMule para submissão de atividades de workflows científicos em redes P, equipe associada. VI Workshop de Redes Dinâmicas e Sistemas Peer-to-Peer 45 lirmm-00641030,version1-14Nov

Paris-Sud XI, Université de

466

Desenho e Avaliao do sistema BOA com base em Padres de Interfaces Sociais  

E-print Network

Desenho e Avaliação do sistema BOA com base em Padrões de Interfaces Sociais Alberto Rodrigues da-aprendizagem, como é o caso da plataforma Bolsa de Objectos de Aprendizagem (BOA). Este trabalho surge no seguimento dinamização e participação em comunidades suportadas pelo BOA. Este artigo, baseando-se na análise da

da Silva, Alberto Rodrigues

467

Circular Polarization Fractal Koch microstrip patch Antenna using single-fed EM coupled ring Resonators  

Microsoft Academic Search

This paper describes the design and analysis of a Circular Polarization Fractal Koch Antenna using single-fed electromagnetic (EM) coupled ring resonator at 2.4 GHz. By applying fractal Koch, the proposed antenna size is reduced about 5% compared to the square patch using single-fed EM coupled ring resonator antenna. The simulation process has been done by CST software. Simulation as well

M. A. M. Yusop; M. K. A. Rahim; M. F. Ismail; A. Wahid

2010-01-01

468

PROCEDIMENTOS PARA RECOLHIMENTO DE VALORES REFERENTES INSCRIO EM PROCESSOS SELETIVOS DOS CURSOS DE MESTRADO E DOUTORADO  

E-print Network

) 6) Competência: mês/ano do pagamento; 7) Vencimento: dia/mês/ano do pagamento; 8) CNPJ/CPF do interessado; 9) Nome do interessado; 12) Emitir GRU; 13) Imprimir; 14) Pagamento no Banco do Brasil em a impressão para posterior pagamento no Banco do Brasil. 4. Esta ordem de serviço entra em vigor a partir de

Paraná, Universidade Federal do

469

UNIVERSIDADE FEDERAL FLUMINENSE COORDENAO DE PS-GRADUAO EM ENFERMAGEM DO TRABALHO  

E-print Network

perante o Consulado do Brasil em seu País. Exige-se do candidato estrangeiro o Certificado de Proficiência carteira do Conselho Regional de Enfermagem ou franquia provisória; · Fotocópia do CPF (para brasileiros ou recolhida em: BANCO DO BRASIL ­ 3. DA SELE��O: 3.1 Análise do Curriculum Vitae Observação: a) A nota mínima

Souza, Max O.

470

Seminario Informal (mas Formal!) 2006 Estrategias da Teoria de Reescrita em PVS  

E-print Network

4o Semin´ario Informal (mas Formal!) 2006 Estrat´egias da Teoria de Reescrita em PVS: considerac Teoria da Computac¸ ~ao Campus de Catal~ao & Departamento de Matem´atica Universidade Federal de Goi. A especificac¸ ~ao em PVS ´e organizada como uma colec¸ ~ao de Teorias. Uma Teoria ´e essencialmente feita de

Ayala-Rincón, Mauricio

471

Examination on Temperature Distribution of a Pyramidal EM-wave Absorber Under High Power Injection  

Microsoft Academic Search

In this research, temperature distribution of a pyramidal EM-absorber under high power injection is computed by a coupled method called FDTD-SIMPLE-MR method. In this method, both electromagnetic field and all the heat transmission phenomena such as heat transportation, heat transfer by air convention and heat radiation can be calculated. Moreover, temperature distribution of a pyramidal EM-absorber is examined experimentally by

Tetsuhiro Sasagawa; O. Hashimoto; S. Watanabe; T. Saito; H. Kurihara

2007-01-01

472

Self-assembled monolayers improve protein distribution on holey carbon cryo-EM supports  

PubMed Central

Poor partitioning of macromolecules into the holes of holey carbon support grids frequently limits structural determination by single particle cryo-electron microscopy (cryo-EM). Here, we present a method to deposit, on gold-coated carbon grids, a self-assembled monolayer whose surface properties can be controlled by chemical modification. We demonstrate the utility of this approach to drive partitioning of ionotropic glutamate receptors into the holes, thereby enabling 3D structural analysis using cryo-EM methods. PMID:25403871

Meyerson, Joel R.; Rao, Prashant; Kumar, Janesh; Chittori, Sagar; Banerjee, Soojay; Pierson, Jason; Mayer, Mark L.; Subramaniam, Sriram

2014-01-01

473

Acceleration of germination of super-hard rice cultivar EM10 by soaking with red onion.  

PubMed

Red onion accelerated the germination of rice seeds and inhibited microbial infestation during germination. After germination with red onion for 16 h at 35 °C, super-hard rice EM10 showed a higher germination ratio (2.3 times), and it contained more GABA (2.3 times) and glucose (2.9 times) than that soaked without onion. Due to soaking with red onion, germinated EM10 was fortified with quercetin (18 mg/100 g). PMID:21389608

Nakamura, Sumiko; Ohtsubo, Ken'ichi

2011-01-01

474

Óleos essenciais no controle pós-colheita de Colletotrichum gloeosporioides em mamão  

Microsoft Academic Search

RESUMO: Os subprodutos de plantas medicinais têm sido estudados como uma alternativa para o controle de doenças de plantas visando amenizar e\\/ou reduzir o uso abusivo de agrotóxicos, principalmente em condições pós-colheita. Assim, este trabalho teve como objetivo avaliar, in vitro e in vivo, o controle de Colletotrichum gloeosporioides, agente causal da antracnose do mamão em pós-colheita, por óleos essenciais

475

Fast, simultaneous and robust VLF-EM data denoising and reconstruction via multivariate empirical mode decomposition  

NASA Astrophysics Data System (ADS)

The measurement of Very Low Frequency Electromagnetic (VLF-EM) is important in many different applications, i.e, environmental, archeological, geotechnical studies, etc. In recent years, improving and enhancing VLF-EM data containing complex numbers (bivariate) was presented by several authors in order to produce reliable models, generally using univariate empirical mode decomposition (EMD). Applying univariate EMD separately on each data is problematic. This results in a different number of misaligned Intrinsic Mode Functions (IMFs) which can complicate the selection of some IMFs for denoising process. Thus, a filtering method based on the multivariate empirical mode decomposition (MEMD) approach to decompose simultaneously bivariate data is proposed. In this paper we address two issues by employing the recently introduced noise assisted MEMD (N-A MEMD) for improving bivariate VLF-EM data. Firstly, the N-A MEMD to decompose bivariate measurement of the VLF-EM data into IMFs and a residue is defined as VLF-EM signal or unwanted noise. Secondly, the proposed method is used to enhance VLF-EM data and to reject unwanted noise. Finally, the proposed method is applied to a synthetic data with two added sinusoids. To demonstrate the robustness of the N-A MEMD method, the method was tested on added-noise synthetic data sets and the results were compared to the Ensemble EMD (EEMD) and Bivariate EMD (BEMD). The N-A MEMD gave more robust and accurate results than the EEMD and BEMD methods and the method required less CPU time to obtain the IMFs compared to EEMD. The method was also tested on several field data sets. The results indicate that the filtered VLF-EM data based on the N-A MEMD make the data easier to interpret and to be analyzed further. In addition, the 2D resistivity profile estimated from the inversion of filtered VLF-EM data results was appropriate to the geological condition.

Sungkono; Bahri, Ayi S.; Warnana, Dwa D.; Monteiro Santos, Fernando A.; Santosa, Bagus J.

2014-06-01

476

UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM NANOCINCIA E NANOBIOTECNOLOGIA  

E-print Network

Lunardi Gomes M/D clunardi@unb.br Denilson Rabelo M/D denilson@quimica.ufg.br Emília Celma de Oliveira Pereira Garcia M mgarcia@unb.br Patricia P. Confessori Sartoratto M/D patricia@quimica.ufg.br Paulo César@if.ufg.br Claure Nain Lunardi Gomes M/D clunardi@unb.br Denilson Rabelo M/D denilson@quimica.ufg.br Emília Celma de

Maier, Rudolf Richard

477

INPE-12145-TDI/969 ANLISE DE EPISDIOS DE TORNADO EM SANTA CATARINA  

E-print Network

INPE-12145-TDI/969 ANÁLISE DE EPIS�DIOS DE TORNADO EM SANTA CATARINA: CARACTERIZA��O SIN�TICA E. Análise de episódios de tornados em Santa Catarina: caracterização sinótica e mineração de dados / I. P. O. Marcelino. ­ São José dos Campos: INPE, 2003. 223p. ­ (INPE-12145-TDI/969). 1.Tornados. 2.Tempestades

478

Inactivation of the Cystatin E/M Tumor Suppressor Gene in Cervical Cancer  

PubMed Central

We have previously localized a cervical cancer tumor suppressor gene to a 300 kb interval of 11q13. Analysis of candidate genes revealed loss of expression of cystatin E/M, a lysosomal cysteine protease inhibitor, in 6 cervical cancer cell lines and 9 of 11 primary cervical tumors. Examination of the three exons in four cervical cancer cell lines, 19 primary tumors, and 21 normal controls revealed homozygous deletion of exon 1 sequences in one tumor. Point mutations were observed in six other tumors. Two tumors contained mutations at the consensus binding sites for cathepsin L, a lysosomal protease over-expressed in cervical cancer. Introduction of these two point mutations using site directed mutagenesis resulted in reduced binding of mutated cystatin E/M to cathepsin L. Although mutations were not observed in any cell lines, four cell lines and 12 of 18 tumors contained promoter hypermethylation. Re-expression of cystatin E/M was observed after 5?aza 2-deoxycytidiene and/or Trichostatin A treatment of cervical cancer cell lines, HeLa and SiHa, confirming promoter hypermethylation. Ectopic expression of cystatin E/M in these two cell lines resulted in growth suppression. There was also suppression of soft agar colony formation by HeLa cells expressing the cystatin E/M gene. Re-expression of cystatin E/M resulted in decreased intracellular and extracellular expression of cathepsin L. Over-expression of cathepsin L resulted in increased cell growth which was inhibited by the reintroduction of cystatin E/M. We conclude, therefore, that cystatin E/M is a cervical cancer suppressor gene and that the gene is inactivated by somatic mutations and promoter hypermethylation. PMID:18506750

Veena, Mysore S.; Lee, Grant; Keppler, Daniel; Mendonca, Marc S.; Redpath, J. Leslie; Stanbridge, Eric J.; Wilczynski, Sharon P.; Srivatsan, Eri S.

2010-01-01

479

AlmAnAc SUPPlEmEnT may 16, 1995 S-Making Connections  

E-print Network

AlmAnAc SUPPlEmEnT may 16, 1995 S- Making Connections Building Penn's electronic future Information #12;AlmAnAc SUPPlEmEnT may 16, 1995S- Abstract This statement of direction moves Penn toward a future and Computing, at may@pobox.upenn.edu or 5/898-0005. ©1995 Trustees of the University of Pennsylvania #12;AlmAnAc

Sharp, Kim

480

Colquio em homenagem ao centenrio da morte de Henri Poincar Rio de Janeiro  

E-print Network

Colóquio em homenagem ao centenário da morte de Henri Poincaré Rio de Janeiro 27 a 30 de novembro Henri Poincaré (Université Nancy 2) Em 2012, ocorrerá o primeiro centenário da morte do matemático morte de Poincaré, além de ser uma merecida homenagem a um cientista-filósofo, cujas idéias ainda hoje

Solodov, Mikhail V.

481

USING A HELICOPTER-BORNE EM-INDUCTION SYSTEM TO VALIDATE RADARSAT SEA ICE SIGNATURES  

Microsoft Academic Search

Field surveys over the past several winters in the Gulf of St. Lawrence and off Labrador use helicopter-borne sensors to validate SAR ice signatures in RADARSAT imagery. Ice-plus- snow thickness profiles were collected using an electromagnetic (EM) induction system towed 15-25m above the ice surface by helicopter. Measurements from the laser altimeter contained in the EM system were high-pass filtered

I. K. Peterson; S. J. Prinsenberg; J. S. Holladay

482

Tide-driven fluid mud transport in the Ems estuary  

NASA Astrophysics Data System (ADS)

The Ems estuary, located at the border between The Netherlands and Germany, experienced a significant change of the hydrodynamic regime during the past decades, as a result of extensive river engineering. With the net sediment transport now being flood-oriented, suspended sediment concentrations have increased dramatically, inducing siltation and formation of fluid mud layers, which, in turn, influence hydraulic flow properties, such as turbulence and the apparent bed roughness. Here, the process-based understanding of fluid mud is essential to model and predict mud accumulation, not only regarding the anthropogenic impact, but also in view of the expected changes of environmental boundary conditions, i.e., sea level rise. In the recent past, substantial progress has been made concerning the understanding of estuarine circulation and influence of tidal asymmetry on upstream sediment accumulation. While associated sediment transport formulations have been implemented in the framework of numerical modelling systems, in-situ data of fluid mud are scarce. This study presents results on tide-driven fluid mud dynamics, measured during four tidal cycles aside the navigation channel in the Ems estuary. Lutoclines, i.e., strong vertical density gradients, were detected by sediment echo sounder (SES). Acoustic Doppler current profiles (ADCP) of different acoustic frequencies were used to determine hydrodynamic parameters and the vertical distribution of suspended sediment concentrations in the upper part of the water column. These continuous profiling measurements were complemented by CTD, ADV, and OBS casts. SES and ADCP profiles show cycles of fluid mud entrainment during accelerating flow, and subsequent settling, and the reformation of a lutocline during decelerating flow and slack water. Significant differences are revealed between flood and ebb phase. Highest entrainment rates are measured at the beginning of the flood phase, associated with strong current shear and rapid vertical mixing, inducing the highest instantaneous suspended sediment flux measured during the tidal cycle. During decelerating flood currents a lutocline is again established at a certain distance above the consolidated river bed. During slack water after the flood phase the concentration gradient increases and the thickness of the fluid mud layer below is constant, also during a significant part of the ebb phase. As water depth decreases during ebb, entrainment occurs only at the upper part of the fluid mud layer. The suspended sediment flux is low compared to the flood phase. These observations are further elaborated using turbulence parameters obtained from ADV and ADCP, explaining the difference between ebb and flood concerning the vertical location of the maximum concentration gradient. This study is funded through DFG-Research Center / Excellence Cluster "The Ocean in the Earth System". The Senckenberg Institute and the Federal Waterways Engineering and Research Institute are acknowledged for technical support.

Becker, Marius; Maushake, Christian; Winter, Christian

2014-05-01

483

New Developments in the Technology Readiness Assessment Process in US DOE-EM - 13247  

SciTech Connect

A Technology Readiness Assessment (TRA) is a systematic, metric-based process and accompanying report that evaluates the maturity of the technologies used in systems; it is designed to measure technology maturity using the Technology Readiness Level (TRL) scale pioneered by the National Aeronautics and Space Administration (NASA) in the 1980's. More recently, DoD has adopted and provided systematic guidance for performing TRAs and determining TRLs. In 2007 the GAO recommended that the DOE adopt the NASA/DoD methodology for evaluating technology maturity. Earlier, in 2006-2007, DOE-EM had conducted pilot TRAs on a number of projects at Hanford and Savannah River. In March 2008, DOE-EM issued a process guide, which established TRAs as an integral part of DOE-EM's Project Management Critical Decision Process. Since the development of its detailed TRA guidance in 2008, DOE-EM has continued to accumulate experience in the conduct of TRAs and the process for evaluating technology maturity. DOE has developed guidance on TRAs applicable department-wide. DOE-EM's experience with the TRA process, the evaluations that led to recently developed proposed revisions to the DOE-EM TRA/TMP Guide; the content of the proposed changes that incorporate the above lessons learned and insights are described. (authors)

Krahn, Steven [Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN, 37235 (United States)] [Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN, 37235 (United States); Sutter, Herbert [Consultant, 910 Laurel Green Dr., North Canton, OH, 44720 (United States)] [Consultant, 910 Laurel Green Dr., North Canton, OH, 44720 (United States); Johnson, Hoyt [DOE-EM, 1000 Independence Ave., Washington, DC, 20585 (United States)] [DOE-EM, 1000 Independence Ave., Washington, DC, 20585 (United States)

2013-07-01

484

Mutagenic effectiveness and efficiency of EMS, DES and gamma-rays in rice.  

PubMed

Data on chlorophyll mutation frequency after treatment with EMS, DES and gamma-rays and sequential administration of gamma-rays and the two alkylating agents in three varieties of rice have been used to work out quantitatively the effectiveness and efficiency of each mutagen and combination treatment. For effectiveness, the order is EMS > DES and for efficiency it is EMS > DES > gamma-rays. In some sequential treatments (Gamma-rays + DES in 'IR8' and 'Basmati'; DES + gamma-rays in 'IR8' and 'Jhona'; Gamma-rays + EMS in 'IR8' and 'Basmati'; and EMS + gamma-rays in 'IR8', 'Jhona' and 'Basmati') mutation frequency is more than additive (synergistic) but these treatments are decisively less efficient because of their relatively high injurious effects in the M1. generation. EMS induces more albinas than gamma-rays do. The mutational spectrum patterns induced by gamma-rays and DES are alike. In general, combination treatments tend to increase the frequency of albinas over other types of chlorophyll mutants. PMID:24407841

Kaul, M L; Bhan, A K

1977-09-01

485

Anisotropic 3D inversion of towed streamer EM data from the Troll West oil province (Invited)  

NASA Astrophysics Data System (ADS)

Obviating the need for ocean bottom receivers, the towed streamer EM system enables CSEM data to be acquired simultaneously with seismic over very large areas in frontier and mature basins for higher production rates and more cost effective than conventional marine CSEM. The towed streamer EM data are currently processed and delivered as a spectrum of frequency-domain responses. We apply a 3D anisotropic inversion methodology for towed streamer EM data that includes a moving sensitivity domain. Our implementation is based on the 3D contraction integral equation method for computing the EM responses and Fréchet derivatives, and uses the re-weighted regularized conjugate gradient method for minimizing the objective functional with focusing regularization. We present an actual case study for the 3D anisotropic inversion of towed streamer EM data from the Troll West oil province in the North Sea, and demonstrate our ability to image the Troll West Oil and Gas Provinces. We conclude that 3D anisotropic inversion of the data from the current generation of towed streamer EM system can adequately recover both the vertical and horizontal resistivities in anisotropic hydrocarbon-bearing formations.

Mattsson, J.; Midgley, J.; Zhdanov, M. S.; ENDO, M.

2013-12-01

486

EM modeling for GPIR using 3D FDTD modeling codes  

SciTech Connect

An analysis of the one-, two-, and three-dimensional electrical characteristics of structural cement and concrete is presented. This work connects experimental efforts in characterizing cement and concrete in the frequency and time domains with the Finite Difference Time Domain (FDTD) modeling efforts of these substances. These efforts include Electromagnetic (EM) modeling of simple lossless homogeneous materials with aggregate and targets and the modeling dispersive and lossy materials with aggregate and complex target geometries for Ground Penetrating Imaging Radar (GPIR). Two- and three-dimensional FDTD codes (developed at LLNL) where used for the modeling efforts. Purpose of the experimental and modeling efforts is to gain knowledge about the electrical properties of concrete typically used in the construction industry for bridges and other load bearing structures. The goal is to optimize the performance of a high-sample-rate impulse radar and data acquisition system and to design an antenna system to match the characteristics of this material. Results show agreement to within 2 dB of the amplitudes of the experimental and modeled data while the frequency peaks correlate to within 10% the differences being due to the unknown exact nature of the aggregate placement.

Nelson, S.D.

1994-10-01

487

Exact solution of the EM radiation-reaction problem for classical finite-size and Lorentzian charged particles  

Microsoft Academic Search

.  An exact solution is given to the classical electromagnetic (EM) radiation-reaction (RR) problem, originally posed by Lorentz.\\u000a This refers to the dynamics of classical non-rotating and quasi-rigid finite-size particles subject to an external prescribed\\u000a EM field. A variational formulation of the problem is presented. It is shown that a covariant representation for the EM potential\\u000a of the self-field generated by

C. Cremaschini; M. Tessarotto

2011-01-01

488

Rock 'Em, Sock 'Em!  

ERIC Educational Resources Information Center

K-12-level competitive robotics is growing in popularity around the country and worldwide. According to one of the leading organizers of these events, FIRST--For Inspiration and Recognition of Science and Technology--250,000 students from 56 countries take part in its competitions. FIRST Tech Challenge (FTC) is a yearly event the organization puts…

Waters, John K.

2011-01-01

489

Accurate 2D/3D electromagnetic modeling for time-domain airborne EM systems  

NASA Astrophysics Data System (ADS)

The existing industry software cannot deliver correct results for 3D time-domain airborne EM responses. In this paper, starting from the Fourier transform and convolution, we compare the stability of different modeling techniques and analyze the reason for instable calculations of the time-domain airborne EM responses. We find that the singularity of the impulse responses of EM systems at very early time that are used in the convolution is responsible for the instability of the modeling (Fig.1). Based on this finding, we put forward an algorithm that uses step response rather than impulse response of the airborne EM system for the convolution and create a stable algorithm that delivers precise results and maintains well the integral/derivative relationship between the magnetic field B and the magnetic induction dB/dt. A three-step transformation procedure for the modeling is proposed: 1) output the frequency-domain EM response data from the existing software; 2) transform into step-response by digital Fourier/Hankel transform; 3) convolve the step response with the transmitting current or its derivatives. The method has proved to be working very well (Fig. 2). The algorithm can be extended to the modeling of other time-domain ground and airborne EM system responses.Fig. 1: Comparison of impulse and step responses for an airborne EM system Fig. 2: Bz and dBz/dt calculated from step (middle panel) and impulse responses (lower panel) for the same 3D model as in Fig.1.

Yin, C.; Hodges, G.

2012-12-01

490

Electrokinetic effect combined with surface-charge assumption: a possible generation mechanism of coseismic EM signals  

NASA Astrophysics Data System (ADS)

According to field observations, electromagnetic (EM) signals accompanying seismic waves can be recorded. The orders of magnitude of observed coseismic electric and magnetic signals associated with earthquakes are usually around 1 to 101 mV km-1 and 10-2 to 1 nT, respectively. In this paper, we carry out numerical simulation of coseismic EM signals associated with seismic waves due to electrokinetic effect and compare with field observations. The seismic source is represented by a finite fault measuring 15 × 9 km2 with a max slip displacement 1.5 m, corresponding to a Mw 5.9 earthquake. While using the EM surface boundary condition of continuous horizontal EM components, the magnetic signals only accompany the late-arriving S waves at receiver near the ground surface. This is obviously different from field observations. Thus, we adopt another EM surface boundary condition which assumes the ground surface carries surface charge. For the used half-space model, a surface-charge density magnitude |Qsc| in excess of 10-4 C m-2 is sufficient to make horizontal magnetic components clearly show up at the whole time duration of seismic waves. When |Qsc| increases, the contribution of surface-charge density to coseismic EM signals becomes more and more dominant comparing with that of the seismically induced streaming-current. We estimate the Qsc expected at the Earth's surface might be a value between -5 × 10-4 and -0.1 C m-2 by the comparison between numerical results and field observations. The vertical magnetic signals only accompany the late-arriving seismic waves, because they are theoretically only induced by SH wave. The field observation results of vertical magnetic signals may be resulted from the scattering effect or the seismic dynamo effect. We conclude that electrokinetic effect combined with surface-charge assumption is one possible generation mechanism of the observed coseismic EM signals.

Ren, Hengxin; Wen, Jian; Huang, Qinghua; Chen, Xiaofei

2015-02-01

491

Estudo de soluções locais e cosmológicas em teorias do tipo tensor-escalar  

NASA Astrophysics Data System (ADS)

Teorias do tipo tensor-escalar são a mais simples extensão possí vel da Relatividade Geral. Nessas teorias, cujo modelo padrão é a teoria de Brans-Dicke, a curvatura do espaço-tempo, descrita por componentes tensoriais, aparece acoplada a um campo escalar que, de certo modo, representa uma variação na constante de acoplamento da gravitação. Tais teorias apresentam soluções locais e cosmológicas que, em determinados limites, recaem nas apresentadas pela Relatividade Geral, mas que em outros limites trazem novidades, tais como conseqüências observacionais da evolução de flutuações primordiais distintas daquelas previstas pela Relatividade Geral (ver, por ex., Nagata et al., PRD 66, p. 103510 (2002)). Graças a esta possibilidade de trazer à luz novidades em relação à gravitação, teorias do tipo tensor-escalar podem ser vistas como um interessante campo alternativo de pesquisas para soluções dos problemas de massa faltante (ou escura) e/ou energia escura. Seguindo tal linha, este trabalho, ainda em sua fase inicial, apresenta soluções gerais de teorias do tipo tensor-escalar para diversas situações, verificando-se em que consiste a divergência dessas soluções dos casos tradicionais possí veis na Relatividade Geral. Como exemplos das soluções aqui apresentadas pode-se destacar uma expressão geral para diferentes soluções cosmológicas englobando diferentes tipos de matéria (representados por diferentes equações de estado), e a expressão para uma solução local representando um buraco negro com rotação, similar à solução de Kerr da Relatividade Geral. Por fim, é importante ressaltar que, embora aqui apresentem-se poucos resultados novos, na literatura sobre o assunto a maior parte das soluções apresentadas limita-se a uns poucos casos especí ficos, tal como soluções cosmológicas apenas com curvatura nula, e que mesmo as soluções disponí veis são, em geral, pouco divulgadas e, portanto, pouco conhecidas, e é tal situação que este trabalho busca, em parte, reverter.

Silva E Costa, S.

2003-08-01

492

EM-54 Technology Development In Situ Remediation Integrated Program. Annual report  

SciTech Connect

The Department of Energy (DOE) established the Office of Technology Development (EM-50) as an element of Environmental Restoration and Waste Management (EM) in November 1989. EM manages remediation of all DOE sites as well as wastes from current operations. The goal of the EM program is to minimize risks to human health, safety and the environment, and to bring all DOE sites into compliance with Federal, state, and local regulations by 2019. EM-50 is charged with developing new technologies that are safer, more effective and less expensive than current methods. The In Situ Remediation Integrated Program (the subject of this report) is part of EM-541, the Environmental Restoration Research and Development Division of EM-54. The In Situ Remediation Integrated Program (ISR IP) was instituted out of recognition that in situ remediation could fulfill three important criteria: Significant cost reduction of cleanup by eliminating or minimizing excavation, transportation, and disposal of wastes; reduced health impacts on workers and the public by minimizing exposure to wastes during excavation and processing; and remediation of inaccessible sites, including: deep subsurfaces; in, under, and around buildings. Buried waste, contaminated soils and groundwater, and containerized wastes are all candidates for in situ remediation. Contaminants include radioactive wastes, volatile and non-volatile organics, heavy metals, nitrates, and explosive materials. The ISR IP tends to facilitate development of in situ remediation technologies for hazardous, radioactive, and mixed wastes in soils, groundwater, and storage tanks. Near-term focus is on containment of the wastes, with treatment receiving greater effort in future years.

Not Available

1993-08-01

493

Canibalismo em fêmeas de camundongo swiss expostas à irradiação ionizante durante a prenhez: alterações morfoló gicas associadas.  

E-print Network

??Fêmeas de camundongos Swiss irradiadas apresentaram comportamento canibalístico inesperado durante um experimento para avaliação de teste de memória operacional e de referência, não mencionado em… (more)

Lúcia de Araújo Piúma

2007-01-01

494

Fraudes corporativas : uma análise das variáveis contábeis indicativas em empresas não financeiras de capital aberto no Brasil.  

E-print Network

??Trabalhos científicos com ferramental estatístico em contabilidade, utilizando variáveis contábeis indicativas, deram seus primeiros passos no estudo das fraudes corporativas no exterior no início da… (more)

Renato Ros

2011-01-01

495

Estratégia de escalonamento de controladores PID baseado em regras Fuzzy para redes industriais foundation fieldbus usando blocos padrões.  

E-print Network

??Com o objetivo de se manter a padronização Foundation Fieldbus, neste trabalho são apresentados procedimentos para se implementar estratégias de controle inteligente, baseadas em escalonamento… (more)

Fábio Soares de Lima

2004-01-01

496

Identificação fenotípica e molecular, perfil de suscetibilidade aos antifúngicos e detecção de glucuronoxilomanana em isolados clínicos de Trichosporon.  

E-print Network

??Infecções invasivas por Trichosporon spp. ocorrem com maior frequência em pacientes neutropênicos, principalmente portadores de doenças hematológicas malignas, e estão associadas a elevados índices de… (more)

Dulce Sachiko Yamamoto de Figueiredo

2013-01-01

497

Infecção por helmintos gastrintestinais em cães (Canis familiaris, Linnaeus, 1758) errantes procedentes do município de Recife - PE.  

E-print Network

??Os helmintos gastrintestinais assumem importância significativa na etiologia das gastrenterites em caninos, sendo as helmintoses de origem canina um problema mundial e de prevalência elevada,… (more)

Auxiliadora de Moraes Ostermann

2008-01-01

498

Over one-half billion years of head conservation? Expression of an ems class gene in Hydractinia symbiolongicarpus (Cnidaria: Hydrozoa)  

PubMed Central

We report the isolation of an empty spiracles class homeodomain-containing gene, Cn-ems, from the hydrozoan Hydractinia symbiolongicarpus, the first gene of this class characterized in a lower metazoan. Cn-ems was found to be expressed in the head of gastrozooids, specifically in endodermal epithelial cells of the taeniolae of the hypostome. Cn-ems is not expressed in gonozooids, which lack taeniolae. Experimental conversion of the posterior region of the planula larva into head structures up-regulates expression of the gene. These findings establish that the association of ems-class genes with head structures preceded the evolution of bilateral symmetry. PMID:9520424

Mokady, Ofer; Dick, Matthew H.; Lackschewitz, Dagmar; Schierwater, Bernd; Buss, Leo W.

1998-01-01

499

Elimination of error factors, affecting EM and seismic inversions  

NASA Astrophysics Data System (ADS)

EM or seismic data inversions are affected by many factors, which may conceal the responses from target objects. We address here the contributions from the following effects: 1) Pre-survey spectral sensitivity factor. Preliminary information about a target layer can be used for a pre-survey estimation of the required frequency domain and signal level. A universal approach allows making such estimations in real time, helping the survey crew to optimize an acquisition process. 2) Preliminary velocities' identification and their dispersions for all the seismic waves, arising in a stratified media became a fast working tool, based on the exact analytical solution. 3) Vertical gradients effect. For most layers the log data scatter, requiring an averaging pattern. A linear gradient within each representative layer is a reasonable compromise between required inversion accuracy and forward modeling complexity. 4) An effect from the seismic source's radial component becomes comparable with vertical part for explosive sources. If this effect is not taken into account, a serious modeling error takes place. This problem has an algorithmic solution. 5) Seismic modeling is often based on different representations for a source formulated either for a force or to a potential. The wave amplitudes depend on the formulation, making an inversion result sensitive to it. 6) Asymmetrical seismic waves (modified Rayleigh) in symmetrical geometry around liquid fracture come from S-wave and merge with the modified Krauklis wave at high frequencies. A detail analysis of this feature allows a spectral range optimization for the proper wave's extraction. 7) An ultrasonic experiment was conducted to show different waves appearance for a super-thin water-saturated fracture between two Plexiglas plates, being confirmed by comparison with theoretical computations. 8) A 'sandwich effect' was detected by comparison with averaged layer's effect. This opens an opportunity of the shale gas direct identification from the surface measurements.

Magomedov, M.; Zuev, M. A.; Korneev, V. A.; Goloshubin, G.; Zuev, J.; Brovman, Y.

2013-12-01

500

Pre-flight risk assessment in Emergency Medical Service (EMS) helicopters  

NASA Technical Reports Server (NTRS)

The Emergency Medical Service (EMS) industry has been the subject of several television and newspaper articles (Harvey and Jensen, 1987) which emphasized the negative aspects, (e.g., fatalities and high accident rates), rather than the life saving services performed. Until recently, the accident rate of the EMS industry has been five times as high as that of other civil helicopters. This high accident rate has been coupled with the dramatic rise in the number of programs. The industry has built from a single service at its inception in 1972, to over 180 in 1987 (Spray, 1987), to the point that 93 percent of the contiguous U.S. is now covered by some type of EMS service. These factors prompted the National Transportation Safety Board (NTSB) to study the accidents that occurred between May 11, 1978 and December 3, 1986 (NTSB, 1988). The NTSB report concluded that 'Sound pilot judgment is central to safe flight operations.' They further stated that '... factors unique to EMS helicopter operations--such as the influence of the mission itself, program competition, and EMS program management perspectives--can drastically influence pilot judgment during the EMS mission.' One of the most difficult decisions that a pilot must make is whether to accept or decline a mission. A pre-flight risk assessment system (SAFE) was developed at NASA-Ames Research Center for civil EMS operations to aid pilots in making this decision objectively. The ability of the SAFE system to predict mission risk profiles was tested at an EMS facility. The results of this field study demonstrated that the usefulness of SAFE was highly dependent on the type of mission flown. SAFE is now being modified so that it can 'learn' with each mission flown. For example, after flying a mission to a particular site, an EMS pilot would input information about this mission into the system, such as new buildings, wires, or approach procedures. Then, the next time a pilot flew a similar mission or one to the same area, this additional information would be taken into account in computing a risk assessment.

Shively, R. J.

1992-01-01