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1

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

2

Photonic Aharonov-Bohm effect in photon-phonon interactions.  

PubMed

The Aharonov-Bohm effect is one of the most intriguing phenomena in both classical and quantum physics, and associates with a number of important and fundamental issues in quantum mechanics. The Aharonov-Bohm effects of charged particles have been experimentally demonstrated and found applications in various fields. Recently, attention has also focused on the Aharonov-Bohm effect for neutral particles, such as photons. Here we propose to utilize the photon-phonon interactions to demonstrate that photonic Aharonov-Bohm effects do exist for photons. By introducing nonreciprocal phases for photons, we observe experimentally a gauge potential for photons in the visible range based on the photon-phonon interactions in acousto-optic crystals, and demonstrate the photonic Aharonov-Bohm effect. The results presented here point to new possibilities to control and manipulate photons by designing an effective gauge potential. PMID:24476790

Li, Enbang; Eggleton, Benjamin J; Fang, Kejie; Fan, Shanhui

2014-01-01

3

Aharonov-Bohm effect in optical activity  

NASA Astrophysics Data System (ADS)

Optically active media have the helical and dissymmetric crystal structure, which constrains the motions of the electrons to a helical path under the influence of the incident electric field. The charge flow along the helices induces a magnetic field in the direction of the axis of helices. The helical structure hence acts as natural micro-solenoids for the electromagnetic waves passing through them. Optical rotation is related to the difference in the accumulative Aharonov-Bohm (AB) phase between the right- and the left-circularly polarized waves. The AB phase is proportional to the angular momentum of an electron moving around the micro-solenoid. Originally the AB phase is shown to be a continuous function of the magnetic flux. However, quantization of the geometrical angular momentum leads to the quantized AB phase. The rotatory power and the Verdet constant are proportional to the refractive index of the medium. The quantized current in the micro-solenoid is proportional to the Bohr magneton and inversely proportional to the area of the helices.

Tan, C. Z.

2010-09-01

4

Aharonov-Bohm Superperiod in a Laughlin Quasiparticle Interferometer  

Microsoft Academic Search

We report an Aharonov-Bohm superperiod of five magnetic flux quanta (5h\\/e)\\u000aobserved in a Laughlin quasiparticle interferometer, where an edge channel of\\u000athe 1\\/3 fractional quantum Hall fluid encircles an island of the 2\\/5 fluid.\\u000aThis result does not violate the auge invariance argument of the Byers-Yang\\u000atheorem because the magnetic flux, in addition to affecting the Aharonov-Bohm\\u000aphase of

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

2005-01-01

5

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

6

Perturbative analysis of non-Abelian Aharonov-Bohm scattering  

SciTech Connect

We perform a perturbative analysis of the non-Abelian Aharonov-Bohm problem to one loop in the framework of a local field theory, and show the necessity of contact interactions for renormalizability of perturbation theory. Moreover at critical values of the contact interaction strength the theory is finite and preserves classical conformal invariance.

Bak, D.; Bergman, O. (Center for Theoretical Physics, Laboratory for Nuclear Science Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States))

1995-02-15

7

Gauge Equivalence and Inverse Scattering for Aharonov-Bohm Effect  

Microsoft Academic Search

We consider the Aharonov-Bohm effect for the Schroedinger operator and the related inverse problem in an exterior domain the 2-dim. Euclidean space with Dirichlet boundary condition. We study the structure and asymptotics of generalized eigenfunctions and show that the scattering operator determines the domain and the Hamiltonian up to Gauge equivalence under the equal flux condition. We also show that

Gregory Eskin; Hiroshi Isozaki; Stephen O'Dell

2008-01-01

8

The Aharonov–Bohm effect for a knotted magnetic solenoid  

Microsoft Academic Search

We show that the linking of a semiclassical path of a charged particle with a knotted magnetic solenoid results in the Aharonov–Bohm effect. The phase shift in the wave function is proportional to the flux intersecting a certain connected and orientable surface bounded by the knot (a Seifert surface of the knot).

Roman V. Buniy; Thomas W. Kephart

2009-01-01

9

The Aharonov-Bohm effect for a knotted magnetic solenoid  

NASA Astrophysics Data System (ADS)

We show that the linking of a semiclassical path of a charged particle with a knotted magnetic solenoid results in the Aharonov-Bohm effect. The phase shift in the wave function is proportional to the flux intersecting a certain connected and orientable surface bounded by the knot (a Seifert surface of the knot).

Buniy, Roman V.; Kephart, Thomas W.

2009-03-01

10

Aharonov-Bohm effect on the Poincare´ disk  

Microsoft Academic Search

We consider formal quantum Hamiltonian of a charged particle on the Poincare´ disk in the presence of an Aharonov-Bohm magnetic vortex and a uniform magnetic field. It is shown that this Hamiltonian admits a four-parameter family of self-adjoint extensions. Its resolvent and the density of states are calculated for natural values of the extension parameters.

Oleg Lisovyy

2007-01-01

11

Aharonov-Bohm effects on nearly-localized quantum states  

Microsoft Academic Search

The authors consider a charged particle confined to a ring encircling a magnetic flux. Supposing that the particle is trapped by a delta-function potential located on the ring, they examine the flux dependence of the energy and the wavefunction of the bound state. This offers a simple explicit model for the Aharonov-Bohm effect on a system localized, but not completely

Y. Nagoshi; S. Takagi

1991-01-01

12

Symmetry-protected many-body Aharonov-Bohm effect  

NASA Astrophysics Data System (ADS)

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 we examine an Aharonov-Bohm effect on a many-body wave function. Specifically, we study this many-body effect on the gapless edge states of a bulk gapped phase protected by a global symmetry (such as ZN)—the symmetry-protected topological (SPT) states. The many-body analog of spectral shifts, the twisted wave function, and the twisted boundary realization are identified in this SPT state. An explicit lattice construction of SPT edge states is derived, and a challenge of gauging its non-onsite symmetry is overcome. Agreement is found in the twisted spectrum between a numerical lattice calculation and a conformal field theory prediction.

Santos, Luiz H.; Wang, Juven

2014-05-01

13

Monte Carlo Evaluation of the Aharonov-Bohm Effect  

NASA Astrophysics Data System (ADS)

The electron propagator in the Aharonov-Bohm effect is investigated using the Feynman path integral formalism. The calculation of the propagator is effected using a variation of the Metropolis Monte Carlo algorithm. Unlike “exact” calculations, our approach permits us to include a nonvanishing solenoid radius. We investigate the dependence of the resulting interference pattern on the magnetic field as well as the solenoid radius. Our results agree with the exact case in the limit of an infinitesimally small solenoid radius.

John, George C.; Singh, Vijay A.

14

An experiment to test the gravitational Aharonov-Bohm effect  

NASA Astrophysics Data System (ADS)

The gravitational Aharonov-Bohm (AB) effect is examined in the weak-field approximation to general relativity. In analogy with the electromagnetic AB effect, we find that a gravitoelectromagnetic 4-vector potential gives rise to interference effects. A matter wave interferometry experiment, based on a modification of the gravity-induced quantum interference experiment of Colella, Overhauser and Werner (COW), is proposed to explicitly test the gravitoelectric version of the AB effect in a uniform gravitational field.

Ho, Vu B.; Morgan, Michael J.

15

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

16

Aharonov-Bohm conductance modulation in ballistic carbon nanotubes.  

PubMed

We report on magnetoconductance experiments in ballistic multiwalled carbon nanotubes threaded by magnetic fields as large as 55 T. In the high temperature regime (100 K), giant modulations of the conductance, mediated by the Fermi level location, are unveiled. The experimental data are consistently analyzed in terms of the field-dependent density of states of the external shell that modulates the injection properties at the electrode-nanotube interface, and the resulting linear conductance. This is the first unambiguous experimental evidence of Aharonov-Bohm effect in clean multiwalled carbon nanotubes. PMID:17501520

Lassagne, B; Cleuziou, J-P; Nanot, S; Escoffier, W; Avriller, R; Roche, S; Forró, L; Raquet, B; Broto, J-M

2007-04-27

17

Magnetic edge states in Aharonov-Bohm graphene quantum rings  

NASA Astrophysics Data System (ADS)

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.; Saffarzadeh, A.; Heidari Semiromi, E.

2013-12-01

18

A Critical Reexamination of the Electrostatic Aharonov-Bohm Effect  

NASA Astrophysics Data System (ADS)

This paper undertakes a critical reexamination of the electrostatic version of the Aharonov-Bohm (“AB”) effect. The conclusions are as follows: 1. Aharonov and Bohm’s 1959 exposition is invalid because it does not consider the wavefunction of the entire system, including the source of electrostatic potential. 2. As originally proposed, the electrostatic AB effect does not exist. Perhaps surprisingly, this conclusion holds despite the relativistic covariance of the electromagnetic four-potential combined with the well-established magnetic AB effect. 3. Although the authors attempted, in a 1961 paper, to demonstrate that consideration of the entire system would not change their result, they inadvertently assumed the desired outcome in their analysis. 4. An oft-cited claim to have experimentally detected the electrostatic AB effect is mistaken, because the observed interference effect is clearly due to electric forces acting directly on charged particles.

Walstad, Allan

2010-11-01

19

Aharonov-Bohm quantum rings in high-Q microcavities  

NASA Astrophysics Data System (ADS)

A single-mode microcavity with an embedded Aharonov-Bohm quantum ring, which is pierced by a magnetic flux and subjected to a lateral electric field, is studied theoretically. It is shown that external electric and magnetic fields provide additional means of control of the emission spectrum of the system. In particular, when the magnetic flux through the quantum ring is equal to a half-integer number of the magnetic flux quantum, a small change in the lateral electric field allows tuning of the energy levels of the quantum ring into resonance with the microcavity mode providing an efficient way to control the quantum ring-microcavity coupling strength. Emission spectra of the system are calculated for several combinations of the applied magnetic and electric fields.

Alexeev, A. M.; Shelykh, I. A.; Portnoi, M. E.

2013-08-01

20

Loop Quantum Gravity à la Aharonov-Bohm  

NASA Astrophysics Data System (ADS)

The state space of Loop Quantum Gravity admits a decomposition into orthogonal subspaces associated to diffeomorphism equivalence classes of spin-network graphs. In this paper I investigate the possibility of obtaining this state space from the quantization of a topological field theory with many degrees of freedom. The starting point is a 3-manifold with a network of defect-lines. A locally-flat connection on this manifold can have non-trivial holonomy around non-contractible loops. This is in fact the mathematical origin of the Aharonov-Bohm effect. I quantize this theory using standard field theoretical methods. The functional integral defining the scalar product is shown to reduce to a finite dimensional integral over moduli space. A non-trivial measure given by the Faddeev-Popov determinant is derived. I argue that the scalar product obtained coincides with the one used in Loop Quantum Gravity. I provide an explicit derivation in the case of a single defect-line, corresponding to a single loop in Loop Quantum Gravity. Moreover, I discuss the relation with spin-networks as used in the context of spin foam models.

Bianchi, Eugenio

2014-02-01

21

Aharonov Bohm quantum systems on a punctured 2-torus  

NASA Astrophysics Data System (ADS)

This paper deals with Aharonov-Bohm (A-B) quantum systems on a punctured two-dimensional torus from the geometric and the operator theoretic point of view. First, flat connections on the U(1)-bundles over the punctured 2-torus are studied, which serve as vector potentials for A-B effect magnetic fields. It is proved that the moduli space of flat connections is identified with the (N + 1)-dimensional torus TN+1, if the punctured torus has N > 0 pinholes at which solenoids are assumed to penetrate the 2-torus. For a given point of TN+1, an associated flat connection is constructed in terms of the Weierstrass zeta function on C together with an inhomogeneous linear function on R2. A-B quantum systems are defined in terms of position operators and momentum operators coupled with the A-B potentials. Necessary and sufficient conditions are given for two A-B quantum systems to be unitarily equivalent. Further, the A-B Hamiltonian is defined and analysed from the viewpoint of operator theory. The deficiency indices of the A-B Hamiltonian are determined to be (N + M, N + M), where M is the number of solenoids whose fluxes are not quantized. Finally, the eigenvalue problem is studied for the A-B Hamiltonian with all fluxes quantized to obtain eigenvalues together with eigenfunctions which are described in terms of the Weierstrass sigma functions.

Iwai, Toshihiro; Yabu, Yoshiro

2006-01-01

22

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

23

Double quantum wire Aharonov-Bohm interferometers for possible LN 2 temperature operation  

NASA Astrophysics Data System (ADS)

In this paper, we discuss the design of semiconductor electrostatic and magnetostatic Aharonov-Bohm interferometers that could operate at liquid nitrogen temperature. We find that for elevated temperature operation, one dimensional structures constructed from quantum wires are invariably the only choice, especially when transport is diffusive instead of ballistic. We have proposed such a structure which can be fabricated by present day technology. It may exhibit large conductance modulation in an electric field at 77 K and is an ideal configuration for "Quantum Interference Transistors" (QUITS) based on the electrostatic Aharonov-Bohm effect.

Bandyopadhyay, S.; Porod, W.

24

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

NASA Astrophysics Data System (ADS)

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; Singleton, Douglas

2014-04-01

25

Can the Aharonov-Bohm effect transmit signals faster than light?  

Microsoft Academic Search

The apparent conflict between the nonlocality of the magnetic Aharonov-Bohm effect (ABE) (described by Aharonov, 1984) and the requirement of relativity theory that no signals be transmitted faster than light (Greenberger, 1984) is investigated theoretically. It is shown that the electric field connected with the increase of magnetic flux in the impenetrable cylinder of the standard model configuration of the

N. G. van Kampen

1984-01-01

26

The Aharonov-Bohm effect and fractional statistics of distinguishable particles  

Microsoft Academic Search

In two-dimensional space, the topological coupling arising between charged particles with attached magnetic fluxes, via the Aharonov-Bohm effect, causes distinguishable particles to effectively acquire quantum statistics: a nontrivial quantum phase is generated when a particle of one species encircles one of a different species. We discuss a number of exact and numerical results concerning distinguishable particles with fractional statistics. Just

Stefan Mashkevich

2010-01-01

27

An experimental demonstration of winding number dependence of the Aharonov-Bohm effect  

Microsoft Academic Search

Measurements on a superconducting ring which twice encircles a long solenoid containing flux show quantized flux states with deltaphi = phi0\\/2 = h\\/4e. This explicity demonstrates the winding number dependence of the Aharonov-Bohm effect. Permanent address: Department of Applied Physics, University of Strathclyde, Glasgow G4, 0NG, Scotland.

Bascom S. Deaver; Gordon B. Donaldson

1982-01-01

28

Nucleon statistics in holographic QCD: Aharonov-Bohm effect in a matrix model  

NASA Astrophysics Data System (ADS)

We show that the Aharonov-Bohm effect in the nuclear matrix model [K. Hashimoto, N. Iizuka, and P. Yi, J. High Energy Phys.JHEPFG1029-8479 10 (2010), 3.10.1007/JHEP10(2010)003] derives the statistical nature of nucleons in holographic QCD. For Nc=odd (even), the nucleon is shown to be a fermion (boson).

Hashimoto, Koji; Iizuka, Norihiro

2010-11-01

29

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

30

The Aharonov-Bohm effect and Tonomura et al. experiments: Rigorous results  

SciTech Connect

The Aharonov-Bohm effect is a fundamental issue in physics. It describes the physically important electromagnetic quantities in quantum mechanics. Its experimental verification constitutes a test of the theory of quantum mechanics itself. The remarkable experiments of Tonomura et al. ['Observation of Aharonov-Bohm effect by electron holography', Phys. Rev. Lett 48, 1443 (1982) and 'Evidence for Aharonov-Bohm effect with magnetic field completely shielded from electron wave', Phys. Rev. Lett 56, 792 (1986)] are widely considered as the only experimental evidence of the physical existence of the Aharonov-Bohm effect. Here we give the first rigorous proof that the classical ansatz of Aharonov and Bohm of 1959 ['Significance of electromagnetic potentials in the quantum theory', Phys. Rev. 115, 485 (1959)], that was tested by Tonomura et al., is a good approximation to the exact solution to the Schroedinger equation. This also proves that the electron, that is, represented by the exact solution, is not accelerated, in agreement with the recent experiment of Caprez et al. in 2007 ['Macroscopic test of the Aharonov-Bohm effect', Phys. Rev. Lett. 99, 210401 (2007)], that shows that the results of the Tonomura et al. experiments can not be explained by the action of a force. Under the assumption that the incoming free electron is a Gaussian wave packet, we estimate the exact solution to the Schroedinger equation for all times. We provide a rigorous, quantitative error bound for the difference in norm between the exact solution and the Aharonov-Bohm Ansatz. Our bound is uniform in time. We also prove that on the Gaussian asymptotic state the scattering operator is given by a constant phase shift, up to a quantitative error bound that we provide. Our results show that for intermediate size electron wave packets, smaller than the ones used in the Tonomura et al. experiments, quantum mechanics predicts the results observed by Tonomura et al. with an error bound smaller than 10{sup -99}. It would be quite interesting to perform experiments with electron wave packets of intermediate size. Furthermore, we provide a physical interpretation of our error bound.

Ballesteros, Miguel; Weder, Ricardo [Projet POems, Domaine de Voluceau-Rocquencourt, Institut National de Recherche en Informatique et en Automatique Paris-Rocquencourt, BP 105, 78153 Le Chesnay Cedex France (France)

2009-12-15

31

Comment on ``Asymmetry of the Aharonov-Bohm diffraction pattern and Ehrenfest's theorem''  

NASA Astrophysics Data System (ADS)

In a recent paper [D. H. Kobe, V. C. Aguilera-Navarro, and R. M. Ricotta, Phys. Rev. A 45, 6192 (1992)], Kobe et al. have calculated the expectation values of position and momentum in the Aharonov-Bohm effect and have found that both are shifted by the Aharonov-Bohm potentials. Although these shifts appear to contradict certain ``no-shift'' theorems proved by various authors, we show that this apparent contradiction is the result of different assumptions. Specifically, one of the assumptions on which the no-shift theorems are based does not hold for the parameters used by Kobe et al.; that is, with their parameters, there is no reason to expect the no-shift theorems to hold. On the other hand, with the parameters of actual two-slit experiments, all of the conditions of the no-shift theorems do hold and the no-shift theorems do apply.

Semon, Mark D.; Taylor, John R.

1994-08-01

32

Spin-selective Aharonov-Bohm oscillations in a lateral triple quantum dot.  

PubMed

We present a theory of spin-selective Aharonov-Bohm oscillations in a lateral triple quantum dot. We show that to understand the Aharonov-Bohm (AB) effect in an interacting electron system within a triple quantum dot molecule (TQD) where the dots lie in a ring configuration requires one to not only consider electron charge but also spin. Using a Hubbard model supported by microscopic calculations we show that, by localizing a single electron spin in one of the dots, the current through the TQD molecule depends not only on the flux but also on the relative orientation of the spin of the incoming and localized electrons. AB oscillations are predicted only for the spin singlet electron complex resulting in a magnetic field tunable "spin valve." PMID:19113511

Delgado, F; Shim, Y-P; Korkusinski, M; Gaudreau, L; Studenikin, S A; Sachrajda, A S; Hawrylak, P

2008-11-28

33

Spin accumulation assisted by the Aharonov-Bohm-Fano effect of quantum dot structures  

PubMed Central

We investigate the spin accumulations of Aharonov-Bohm interferometers with embedded quantum dots by considering spin bias in the leads. It is found that regardless of the interferometer configurations, the spin accumulations are closely determined by their quantum interference features. This is mainly manifested in the dependence of spin accumulations on the threaded magnetic flux and the nonresonant transmission process. Namely, the Aharonov-Bohm-Fano effect is a necessary condition to achieve the spin accumulation in the quantum dot of the resonant channel. Further analysis showed that in the double-dot interferometer, the spin accumulation can be detailedly manipulated. The spin accumulation properties of such structures offer a new scheme of spin manipulation. When the intradot Coulomb interactions are taken into account, we find that the electron interactions are advantageous to the spin accumulation in the resonant channel.

2012-01-01

34

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

35

Suppression of the Aharonov-Bohm effect in hexagonal quantum rings  

NASA Astrophysics Data System (ADS)

Few-electron states of AlAs-GaAs-AlAs hexagonal quantum rings pierced by an axial magnetic field are computed through full configuration interaction calculations. The quantum ring is in the low-density regime, populated with N = 1 up to N = 7 electrons. Similar to circular rings, the energy spectra of the hexagonal ones reflect an integer and fractional Aharonov-Bohm regular oscillation pattern for N = 1 and N=2,3 , respectively. Deviations from the regular fractional period with increasing electron density become apparent for larger N. Remarkably, for N = 6 the Aharonov-Bohm effect is completely suppressed. This is a unique symmetry-related feature of hexagonal rings that only can emerge in the low-density regime.

Ballester, A.; Segarra, C.; Bertoni, A.; Planelles, J.

2013-12-01

36

Scattering theory and the Aharonov-Bohm effect in quasiclassical physics  

SciTech Connect

Research Highlights: > Scattering Aharonov-Bohm effect. > Short-wavelength limit of scattered nonrelativistic particles. > Fraunhofer diffraction in the forward direction. > Fresnel diffraction in the forward region in conical space. > Enclosed magnetic flux is a gate for the propagation of quasiclassical particles. - Abstract: Scattering of a nonrelativistic quantum-mechanical particle by an impenetrable magnetic vortex is considered. The nonvanishing transverse size of the vortex is taken into account, and the limit of short, as compared to this size, wavelengths of the scattered particle is analyzed. We show that the scattering Aharonov-Bohm effect persists in the quasiclassical limit owing to the diffraction persisting in the short-wavelength limit. As a result, the vortex flux serves as a gate for the propagation of short-wavelength, almost classical, particles. This quasiclassical effect is more feasible to experimental detection in the case when space outside the vortex is conical.

Sitenko, Yurii A., E-mail: yusitenko@bitp.kiev.ua [Bogolyubov Institute for Theoretical Physics, National Academy of Sciences, 03680 Kyiv (Ukraine); Vlasii, Nadiia D. [Bogolyubov Institute for Theoretical Physics, National Academy of Sciences, 03680 Kyiv (Ukraine); Physics Department, Taras Shevchenko National University of Kyiv, 01601 Kyiv (Ukraine)

2011-06-15

37

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

38

Momentum-transfer scattering cross section and the Aharonov-Bohm effect on a toroidal solenoid  

Microsoft Academic Search

The quantum-mechanical Aharonov-Bohm effect in the diffraction of charged particles by a toroidal solenoid containing a magnetic\\u000a field is investigated. The total and differential elastic scattering cross sections depend on the magnetic flux inside the\\u000a solenoid, even in the presence of a “black” ring-shaped screen which prevents charged particles from entering the region where\\u000a the magnetic field is localized. Relations

V. V. Lyuboshitz; V. L. Lyuboshitz

2000-01-01

39

The Aharonov-Bohm effect and time-dependent inverse scattering theory  

Microsoft Academic Search

We study the Aharonov–Bohm effect from the point of view of time-dependent inverse scattering theory. As this three-dimensional problem is invariant under translations along the vertical axis, it reduces to a problem in ?2. We first consider an unshielded magnetic field that has a singular part produced by a tiny solenoid and a regular part. The wavefunction is zero at

Ricardo Weder

2002-01-01

40

Aharonov-Bohm type effects and the interference of macro-molecules  

NASA Astrophysics Data System (ADS)

Given that it is now possible to observe the interference of molecules with comparatively numerous internal degrees of freedom, we might wonder what role these extra degrees of freedom play in the traditional double-slit experiment. Here we seek to understand the effect of these degrees of freedom in an Aharonov-Bohm type experiment. We find, perhaps unsurprisingly that an ionised object can exhibit the Aharonov-Bohm effect in a manner which is independent of its internal structure. Meanwhile, the Aharonov-Bohm type effects involving objects with magnetic, or electric dipole moments (the Aharonov-Casher and He-McKellar-Wilkens effects, respectively) depend explicitly upon the structure. When-due to some specified dynamics of the internal variables-an object's dipole moment changes during the experiment, we find that the corresponding phase shift depends upon the time average and variance of the internal dynamics. Furthermore, given that the internal dynamics are, to an extent, dependent upon the centre of mass motion there is also a small, transient loss of coherence associated with each internal degree of freedom.

Horsley, S. A. R.; Babiker, M.

2009-06-01

41

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

42

Axial anomaly in the presence of the Aharonov-Bohm gauge field  

SciTech Connect

We investigate on the plane the axial anomaly for Euclidean Dirac fermions in the presence of a background Aharonov-Bohm gauge potential. The nonperturbative analysis depends on the self-adjoint extensions of the Dirac operator and the result is shown to be influenced by the actual way of understanding the local axial vector current. The role of the quantum mechanical parameters involved in the expression for the axial anomaly is discussed. A derivation of the effective action by means of the stereographic projection is also considered.

Giacconi, P. (Dipartimento di Fisica A. Righi'' Bologna, Sezione I.N.F.N. Bologna (Italy)); Ouvry, S. (Division de Physique Theorique IPN.F-91406 Orsay (France) LPTPE, Universite Pierre et Marie Curie F-75252, Paris (France)); Soldati, R. (Dipartimento di Fisica A. Righi'' Bologna, Sezione I.N.F.N. Bologna (Italy))

1994-10-15

43

Analogue Aharonov-Bohm effect in a Lorentz-violating background  

NASA Astrophysics Data System (ADS)

In this paper, we consider the acoustic black hole metrics obtained from a relativistic fluid under the influence of constant background that violates the Lorentz symmetry to study the analogue of the Aharonov-Bohm (AB) effect. We show that the scattering of planar waves by a draining bathtub vortex leads to a modified AB effect and due to the Lorentz symmetry breaking, the phase shift persists even in the limit where the parameters associated with the circulation and draining vanish. In this limit, the Lorentz-violating background forms a conical defect, which is also responsible for the appearance of the analogue AB effect.

Anacleto, M. A.; Brito, F. A.; Passos, E.

2012-12-01

44

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

45

Current-conserving Aharonov-Bohm interferometry with arbitrary spin interactions  

NASA Astrophysics Data System (ADS)

We propose a general scattering-matrix formalism that guarantees the charge conservation at junctions between conducting arms with arbitrary spin interactions. By using our formalism, we find that the spin-flip scattering can happen even at nonmagnetic junctions if the spin eigenstates in arms are not orthogonal, which has been missed in previous similar studies. We apply our formalism to the Aharonov-Bohm interferometer consisting of an n-type semiconductor ring with both the Rashba spin-orbit coupling and the Zeeman splitting. We discuss the characteristics of the interferometer as a conditional (unconditional) spin switch in the weak (strong) -coupling limit.

Lee, Minchul; Stepanenko, Dimitrije

2012-02-01

46

Electron-electron correlations and the Aharonov-Bohm effect in mesoscopic rings  

NASA Astrophysics Data System (ADS)

We study the effect of correlations on the Aharonov-Bohm effect in small one-dimensional rings. We use the Luttinger and Hubbard models to describe electrons in the ring with two contacts on opposite sites and a magnetic field passing through the hole of the circuit. We show that correlations change the fundamental periodicity of the transmittance as a function of the magnetic flux. We interpret this new effect as a consequence of the charge and spin separation in the one-dimensional conductors.

Jagla, E. A.; Balseiro, C. A.

1993-02-01

47

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

48

Enhanced spin figure of merit in an Aharonov-Bohm ring with a double quantum dot  

NASA Astrophysics Data System (ADS)

We theoretically investigate the thermoelectric effects in an Aharonov-Bohm ring with a serially coupled double quantum dot embedded in one arm. An external magnetic field is perpendicularly applied to the two dots. Using the nonequilibrium Green's function method in the linear-response regime, we calculate the charge and spin figures of merit. When the energy levels of the two quantum dots are equal and the system is connected to two normal leads, a large spin figure of merit (ZsT ? 4.5) accompanying with a small charge figure of merit (ZcT ? 0) can be generated due to the remarkable bipolar effect. Further, when the system is connected to two ferromagnetic leads, the spin figure of merit can reach even a higher value about 9. Afterwards, we find that ZsT is enhanced while ZcT is reduced in the coaction of the Aharonov-Bohm flux and Rashba spin-orbit coupling. It is argued that the bipolar effect is positive (negative) to spin (charge) figure of merit in the presence of level detuning of the two quantum dots and intradot Coulomb interactions, respectively. Also, we propose a possible experiment to verify our results.

Zhou, Xingfei; Qi, Fenghua; Jin, Guojun

2014-04-01

49

Electron Interferometry in the Quantum Hall Regime: Aharonov-Bohm Effect of Interacting Electrons  

SciTech Connect

An apparent h/fe Aharonov-Bohm flux period, where f is an integer, has been reported in coherent quantum Hall devices. Such subperiod is not expected for noninteracting electrons and thus is thought to result from interelectron Coulomb interaction. Here we report experiments in a Fabry-Perot interferometer comprised of two wide constrictions enclosing an electron island. By carefully tuning the constriction front gates, we find a regime where interference oscillations with period h/2e persist throughout the transition between the integer quantum Hall plateaus 2 and 3, including half-filling. In a large quantum Hall sample, a transition between integer plateaus occurs near half-filling, where the bulk of the sample becomes delocalized and thus dissipative bulk current flows between the counterpropagating edges ('backscattering'). In a quantum Hall constriction, where conductance is due to electron tunneling, a transition between forward and backscattering is expected near the half-filling. In our experiment, neither period nor amplitude of the oscillations show a discontinuity at half-filling, indicating that only one interference path exists throughout the transition. We also present experiments and an analysis of the front-gate dependence of the phase of the oscillations. The results point to a single physical mechanism of the observed conductance oscillations: Aharonov-Bohm interference of interacting electrons in quantum Hall regime.

Lin, P.V.; Camino, F.; Goldman, V.J.

2009-09-01

50

Optically mediated spin current and Fano resonance in an Aharonov–Bohm ring with a quantum dot  

Microsoft Academic Search

We study the spin-polarized transport and Fano resonance in an Aharonov–Bohm (AB) interferometer with an embedded quantum dot, where the dot is irradiated by continuous circularly polarized light. Compared with the conventional Fano form, the resonance line shape is found to be deformed by the interplay between the external irradiation and the Coulomb repulsion. The Fano resonance peaks are split

Sha-Sha Ke; Hai-Feng Lü; Huai-Wu Zhang

2011-01-01

51

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

52

Electron matter optics of the Aharonov-Bohm and Stern-Gerlach effects  

NASA Astrophysics Data System (ADS)

Since the advent of quantum mechanics and the idea that massive particles exhibit wave properties, physicists have made efforts to make use of the short deBroglie wave length of matter waves for fundamental as well as practical studies. Among these are the precise measurements allowed by interference, diffraction, and microscopy as well as the study of more fundamental aspects of quantum theory such as the Aharonov-Bohm effects or the Stern-Gerlach effect, which are described below. However, in order to use matter waves to observe any of these effects it is necessary to produce and maintain coherence in the waves which are used for measurement. With a grasp of what coherence is and how it may be achieved and maintained one can move forward to study the interesting phenomena associated with coherent matter waves. More specifically in this work the interference and diffraction of electron matter waves are considered. The phenomena under consideration are those associated with the interaction of the electric charge and magnetic dipole moment of the electron with external fields and potentials while in the process of interfering or diffracting. Namely the focus of this dissertation is the Aharonov-Bohm effect, the Aharonov-Casher effect, and the Stern-Gerlach effect. Additionally, a wide-angle electron beam-splitter capable of producing two centimeter beam separation at the detection plane is discussed. The beam-splitter utilizes a nanofabricated periodic grating in combination with a bi-prism element. Contrary to devices utilizing only bi-prism elements, the use of the periodic grating causes amplitude, and not wave front, splitting. Even at maximum separation, beam profiles remain undistorted, providing evidence that coherence is intact. This is a step towards the realization of a large area electron interferometer using such a grating bi-prism combination. Such an interferometer could, in principle, be used to test the dispersionless nature of the Aharonov-Bohm effect. Work towards such an interferometer and possible future work are also discussed.

McGregor, Scot Cameron

53

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

54

Absence of the Aharonov-Bohm effect of chiral Majorana fermion edge states  

NASA Astrophysics Data System (ADS)

Majorana fermions in a superconductor hybrid system are charge neutral zero-energy states. For the detection of this unique feature, we propose an interferometry of a chiral Majorana edge channel, formed along the interface between a superconductor and a topological insulator under an external magnetic field. The superconductor is of a ring shape and has a Josephson junction that allows the Majorana state to enclose continuously tunable magnetic flux. Zero-bias differential electron conductance between the Majorana state and a normal lead is found to be independent of the flux at zero temperature, manifesting the Majorana feature of a charge neutral zero-energy state. In contrast, the same setup on graphene has no Majorana state and shows Aharonov-Bohm effects.

Park, Sunghun; Moore, Joel E.; Sim, H.-S.

2014-04-01

55

Aharonov–Bohm effect in the tunnelling of a quantum rotor in a linear Paul trap  

NASA Astrophysics Data System (ADS)

Quantum tunnelling is a common fundamental quantum mechanical phenomenon that originates from the wave-like characteristics of quantum particles. Although the quantum tunnelling effect was first observed 85 years ago, some questions regarding the dynamics of quantum tunnelling remain unresolved. Here we realize a quantum tunnelling system using two-dimensional ionic structures in a linear Paul trap. We demonstrate that the charged particles in this quantum tunnelling system are coupled to the vector potential of a magnetic field throughout the entire process, even during quantum tunnelling, as indicated by the manifestation of the Aharonov–Bohm effect in this system. The tunnelling rate of the structures periodically depends on the strength of the magnetic field, whose period is the same as the magnetic flux quantum ?0 through the rotor [(0.99±0.07) × ?0].

Noguchi, Atsushi; Shikano, Yutaka; Toyoda, Kenji; Urabe, Shinji

2014-05-01

56

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:

2011-01-01

57

Bound states in the continuum in open Aharonov-Bohm rings  

NASA Astrophysics Data System (ADS)

Using the formalism of the effective Hamiltonian, we consider bound states in a continuum (BIC). They are nonhermitian effective Hamiltonian eigenstates that have real eigenvalues. It is shown that BICs are orthogonal to open channels of the leads, i.e., disconnected from the continuum. As a result, BICs can be superposed to a transport solution with an arbitrary coefficient and exist in a propagation band. The one-dimensional Aharonov-Bohm rings that are opened by attaching single-channel leads to them allow exact consideration of BICs. BICs occur at discrete values of the energy and magnetic flux; however, it’s realization strongly depends on the way to the BIC point.

Bulgakov, E. N.; Pichugin, K. N.; Sadreev, A. F.; Rotter, I.

2006-12-01

58

The relativistic time-dependent Aharonov-Bohm effect in two spatial dimensions  

NASA Astrophysics Data System (ADS)

The Aharonov-Bohm (A-B) effect provides direct proof that the charged fermion fields are directly coupled to the gauge 4-vector potential. In this work the A-B effect is studied by means of the relativistic time-dependent Dirac equation coupled with static, external electromagnetic potentials. The staggered leap-frog numerical method is used and proven to be stable and accurate. The effect of possible residual Lorentz forces due to solenoid finite length is examined and compared to the pure A-B effect by means of the time-dependent interference patterns. The effect is also investigated inside quantum rings and shown to alter the fermion azimuthal probability distribution. There is a strong interaction A-B effect equivalent.

Petridis, Athanasios; Kertzman, Zachary

2009-11-01

59

Elementary Aharonov-Bohm system in three space dimensions: Quantum attraction with no classical force  

SciTech Connect

As a consequence of the Aharonov-Bohm effect, there is a quantum-induced attraction between a charged particle and a rigid, impenetrable hoop made from an arbitrarily thin tube containing a superconductor quantum of magnetic flux. This is remarkable because in classical physics there is no force between the two objects, and quantum-mechanical effects (associated with uncertainty-principle energy) generally are repulsive rather than attractive. For an incident spinless charged particle in a P wave (in a configuration with total angular momentum zero) we verify a resonance just above threshold using the Kohn variational principle in its S-matrix form. Even if optimistic choices of parameters describing a model system with these properties were feasible, the temperature required to observe the resonance would be far lower than has yet been attained in the laboratory.

Goldhaber, Alfred Scharff [C. N. Yang Institute for Theoretical Physics and Department of Physics and Astronomy, State University of New York, Stony Brook, New York 11794-3840, USA (United States); Stanford Linear Accelerator Center, Menlo Park, California 94025, USA (United States); Requist, Ryan [C. N. Yang Institute for Theoretical Physics and Department of Physics and Astronomy, State University of New York, Stony Brook, New York 11794-3840, USA (United States)

2003-07-01

60

An Elementary Aharonov-Bohm System in Three Space Dimensions: Quantum Attraction With No Classical Force  

SciTech Connect

As a consequence of the Aharonov-Bohm effect, there is a quantum-induced attraction between a charged particle and a rigid impenetrable hoop made from an arbitrarily thin tube containing a superconductor quantum of magnetic flux. This is remarkable because in classical physics there is no force between the two objects, and quantum-mechanical effects (associated with uncertainty-principle energy) generally are repulsive rather than attractive. For an incident spinless charged particle in a P wave, in a configuration with total angular momentum zero, we verify a resonance just above threshold using the Kohn variational principle in its S-matrix form. Even if optimistic choices of parameters describing a model system with these properties turned out to be feasible, the temperature required to observe the resonance would be far lower than has yet been attained in the laboratory.

Goldhaber, Alfred S.

2003-01-09

61

The role of internal degrees of freedom in Aharonov-Bohm-type interference phenomena  

NASA Astrophysics Data System (ADS)

We show that the pure Aharonov-Bohm (AB) effect, or its dual (DAB), depends only on the net electric, or magnetic charge of an interfering object, however many internal degrees of freedom that system may have. The reciprocal Aharonov-Casher (AC) and He-McKellar-Wilkens (HMW) effects, on the other hand, involve physical properties—the magnetic and electric polarization of the system—which couple a system’s internal degrees of freedom to its center-of-mass coordinate through the field. For composite systems this illustrates a fundamental difference between the two types of phenomenon, and one which could be important as the number of internal degrees of freedom become large. We show that, for a single internal degree of freedom, the result of this coupling is a transient loss of coherence in the observed interference of the center-of-mass coordinate.

Horsley, S. A. R.; Babiker, M.

2008-07-01

62

The interplay between the Aharonov-Bohm interference and parity selective tunneling in graphene nanoribbon rings  

NASA Astrophysics Data System (ADS)

We report on a numerical study of the Aharonov–Bohm (AB) effect and parity selective tunneling in pn junctions based on rectangular graphene rings where the contacts and ring arms are all made of zigzag nanoribbons. We find that when applying a magnetic field to the ring, the AB interference can reverse the parity symmetry of incoming waves and hence can strongly modulate the parity selective transmission through the system. Therefore, the transmission between two states of different parity exhibits the AB oscillations with a ??phase shift, compared to the case of states of the same parity. On this basis, it is shown that interesting effects, such as giant (both positive and negative) magnetoresistance and strong negative differential conductance, can be achieved in this structure. Our study thus presents a new property of the AB interference in graphene nanorings, which could be helpful for further understanding the transport properties of graphene mesoscopic systems.

Nguyen, V. Hung; Niquet, Y.-M.; Dollfus, P.

2014-05-01

63

Aharonov-Bohm effect and giant magnetoresistance in graphene nanoribbon rings  

NASA Astrophysics Data System (ADS)

We report a numerical study on the Aharonov-Bohm (AB) effect and giant magnetoresistance in rectangular rings made of graphene nanoribbons (GNRs). We show that in the low-energy regime where only the first subband of contact GNRs contributes to the transport, the transmission probability can be strongly modulated, i.e., almost fully suppressed, when tuning a perpendicular magnetic field. On this basis, strong AB oscillations with giant negative magnetoresistance can be achieved at room temperature. The magnetoresistance reaches thousands of percent in perfect GNR rings and a few hundred percent with edge-disordered GNRs. The design rules to observe such strong effects are also discussed. Our study hence provides guidelines for further investigations of the AB interference and to obtain high magnetoresistance in graphene devices.

Nguyen, V. Hung; Niquet, Y. M.; Dollfus, P.

2013-07-01

64

The interplay between the Aharonov-Bohm interference and parity selective tunneling in graphene nanoribbon rings.  

PubMed

We report on a numerical study of the Aharonov-Bohm (AB) effect and parity selective tunneling in pn junctions based on rectangular graphene rings where the contacts and ring arms are all made of zigzag nanoribbons. We find that when applying a magnetic field to the ring, the AB interference can reverse the parity symmetry of incoming waves and hence can strongly modulate the parity selective transmission through the system. Therefore, the transmission between two states of different parity exhibits the AB oscillations with a ?-phase shift, compared to the case of states of the same parity. On this basis, it is shown that interesting effects, such as giant (both positive and negative) magnetoresistance and strong negative differential conductance, can be achieved in this structure. Our study thus presents a new property of the AB interference in graphene nanorings, which could be helpful for further understanding the transport properties of graphene mesoscopic systems. PMID:24785639

Nguyen, V Hung; Niquet, Y-M; Dollfus, P

2014-05-21

65

Aharonov-Bohm effect in the tunnelling of a quantum rotor in a linear Paul trap.  

PubMed

Quantum tunnelling is a common fundamental quantum mechanical phenomenon that originates from the wave-like characteristics of quantum particles. Although the quantum tunnelling effect was first observed 85 years ago, some questions regarding the dynamics of quantum tunnelling remain unresolved. Here we realize a quantum tunnelling system using two-dimensional ionic structures in a linear Paul trap. We demonstrate that the charged particles in this quantum tunnelling system are coupled to the vector potential of a magnetic field throughout the entire process, even during quantum tunnelling, as indicated by the manifestation of the Aharonov-Bohm effect in this system. The tunnelling rate of the structures periodically depends on the strength of the magnetic field, whose period is the same as the magnetic flux quantum ?0 through the rotor [(0.99±0.07) × ?0]. PMID:24820051

Noguchi, Atsushi; Shikano, Yutaka; Toyoda, Kenji; Urabe, Shinji

2014-01-01

66

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

67

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

68

Interference Signatures of Abelian and Non-Abelian Aharonov-Bohm effect on Neutral Atoms in Optical Lattices  

NASA Astrophysics Data System (ADS)

We propose a scheme to generate an effective Abelian U(1) or non-Abelian SU(2) gauge field for cold neutral atoms in a ring- or square-shaped optical lattice by using Laguerre-Gauss lasers. The synthetic field produced is strongly localized, which allows us to study the Aharonov-Bohm effect on the neutral atoms. By preparing a coherent state of atoms initially and allowing them to evolve along two different paths enclosing the generated magnetic field, we obtain interference signatures of the Aharonov-Bohm effect with distinctly different patterns in the detection area for systems exposed to a zero, an Abelian U(1) or a non-Abelian SU(2) gauge field.

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

2013-03-01

69

Magnetic flux and gate-voltage dependence of Kondo effect in quantum dot embedded in Aharonov–Bohm ring  

Microsoft Academic Search

The Kondo effect is examined in a quantum dot embedded in an Aharonov–Bohm (AB) ring, based on the Haldane's two-stage scaling theory. In the small limit of the ring size, we derive analytical expressions for the Kondo temperature TK and conductance at temperatures T?TK, as functions of the magnetic flux penetrating the ring. The flux dependence of TK is drastically

R. Yoshii; M. Eto

2010-01-01

70

Aharonov-Bohm Ring Touching a Quantum Wire: How to Model it and to Solve the Inverse Problem  

NASA Astrophysics Data System (ADS)

An explicitly solvable model of the gated Aharonov-Bohm ring touching a quantum wire is constructed and investigated. The inverse spectral and scattering problems are discussed. It is shown that the Titchmarsh-Weyl matrix function associated with the boundary vertices determines a unique electric potential on the graph even though the graph contains a loop. This system gives another family of isospectral quantum graphs.

Kurasov, Pavel; Enerbäck, Magnus

2011-12-01

71

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

72

Scaling study of Kondo effect in a quantum dot embedded in an Aharonov-Bohm interferometer  

NASA Astrophysics Data System (ADS)

The Kondo effect is theoretically investigated in a quantum dot embedded in an Aharonov-Bohm (AB) ring, using the ``poor man's'' scaling method. First, we construct an equivalent model in which a quantum dot is coupled to a single lead. The AB interference effect is involved in the magnetic-flux dependence of the density of states in the lead. The scaling analysis of this model yields analytical expressions for the Kondo temperature TK and logarithmic corrections to the conductance at temperatures T TK.footnotetextR. Yoshii and M. Eto, J. Phys. Soc. Jpn. 77, 123714 (2008). We find that (i) TK is significantly modulated by the magnetic flux penetrating the ring when the ring size L is much smaller than the size of Kondo cloud, LK=vF/TK, with vF being the Fermi velocity. TK is hardly affected by the flux when L LK. (ii) When L LK, the flux dependence of TK is the smallest around the center of Coulomb valley and becomes remarkable near the edges of the valley.footnotetextR. Yoshii and M. Eto, Physica E, in press.

Yoshii, Ryosuke; Eto, Mikio

2010-03-01

73

Aharonov-Bohm-like scattering, localization, and novel electronic states in hydrogenated graphene  

NASA Astrophysics Data System (ADS)

Metallic nature of transport in graphene, which is fairly robust with respect to varying amounts of disorder, changes in an unexpected way when vacancies are introduced in this material. At low energies, near the Dirac point, electron scattering on vacancies mimics scattering on Aharonov-Bohm solenoids carrying unit flux. This type of scattering results in a very narrow band of states at the Dirac point with properties resembling those of zeroth Landau level, which is positioned in the middle of a (pseudo)gap created by vacancies and resembling the cyclotron gap around zeroth Landau level. The fictitious magnetic field describing vacancies has opposite signs for the valleys K and K'. As a result of this, an externally applied magnetic field has opposite effects in the two valleys, suppressing (reinforcing) the gap in the K (K') valley. We show that this picture is in agreement with the behavior observed in a recent study [1] of electronic properties of graphene, which can be transformed from metallic state to insulating state by hydrogenation. [1] D. C. Elias, R. R. Nair, T. M. G. Mohiuddin, S. V. Morozov, P. Blake, M. P. Halsall, A. C. Ferrari, D. W. Boukhvalov, M. I. Katsnelson, A. K. Geim, K. S. Novoselov, arXiv:0810.4706

Shytov, Andrey; Abanin, Dmitry; Levitov, Leonid

2009-03-01

74

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

NASA Astrophysics Data System (ADS)

We investigate the thermoelectric effects of an Aharonov-Bohm (AB) interferometer with a quantum dot (QD) embedded in each of its arms, where the intra-dot Coulomb interaction between electrons in each QD is taken into account. Using Green's function methods and the equation of motion (EOM) technique, we find that the Seebeck coefficient and Lorenz number can be strongly enhanced when the chemical potential sweeps the molecular states associated with the Fano line-shapes in the transmission spectra, due to quantum interference effects between the bonding and antibonding molecular states. It is found that enhancement of the thermoelectric effects occurs between the two groups of conductance peaks in the presence of strong intra-dot Coulomb interaction—the reason being that a transmission node is developed in the Coulomb blockade regime. In this case, the maximum value of the Lorenz number approaches 10?2kB2/(3e2). Its thermoelectric conversion efficiency in the absence of phonon thermal conductance, described by the figure of merit ZT, approaches 2 at room temperature. Therefore, it may be used as a high-efficiency solid-state thermoelectric conversion device under certain circumstances.

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

2011-06-01

75

The semi-classical limit of the Aharonov-Bohm effect: The actualized approach  

NASA Astrophysics Data System (ADS)

We suggest an approach, which formally allows us to describe the Aharonov-Bohm (AB) effect in the semi-classical language. In the framework of this approach, we keep the classical concepts of electromagnetic field and force. At the same time, instead of point-like classical charges, we introduce a finite-size elementary charge distribution, modelling the wave-like packet, associated with the motion of a given electron. In this case we derive the force on the wave-like packet on behalf of the solenoid via the minimization of action defined through the Lagrangian density (instead of the Lagrangian used in common classical electrodynamics of point-like charges). We show that this force due to the solenoid, being dependent on the vector potential, yields the common expression for the magnetic AB phase, when the original wave packet is splitted into a superposition of two packets encirling the solenoid. We also analyze in the classical language the implementation of total momentum conservation law for the isolated system "moving electrons plus elongated solenoid" and determine the properties of finite-size charge distribution, when this law is fulfilled. The results obtained are discussed.

Kholmetskii, A. L.; Yarman, T.

2013-03-01

76

Nonlocal phases of local quantum mechanical wavefunctions in static and time-dependent Aharonov-Bohm experiments  

NASA Astrophysics Data System (ADS)

We show that the standard Dirac phase factor is not the only solution of the usual gauge transformation equations. The full form of a general gauge function (that connects systems that move in different sets of scalar and vector potentials), apart from Dirac phases (spatial or temporal integrals over potentials), also contains terms of classical fields that act nonlocally (in spacetime) on the local solutions of the time-dependent Schrödinger equation. As a result, the phases of wavefunctions in the Schrödinger picture are affected nonlocally by spatially and temporally remote magnetic and electric fields, in specific ways that are fully explored. These contributions go beyond the usual Aharonov-Bohm effects (magnetic or electric). (i) Application to cases of particles passing through full static magnetic or electric fields leads to cancellations of Aharonov-Bohm phases at the observation point; these cancellations are linked to behaviors at the semiclassical level (i.e. the old Werner and Brill experimental observations, or their 'electric analogs'—or to more recent reports of Batelaan and Tonomura) but are shown to be far more general (true not only for narrow wavepackets but also for completely delocalized (spread-out) quantum states). By using these cancellations, certain previously unnoticed sign-errors in the literature are corrected. (ii) Application to time-dependent situations provides a remedy for erroneous results in the literature (concerning an uncritical use of Dirac phase factors) and leads to phases that contain an Aharonov-Bohm part and a field-nonlocal part: their competition is shown to recover relativistic causality in earlier 'paradoxes' (such as the van Kampen thought-experiment), while a more general consideration indicates that the temporal nonlocalities found here demonstrate in part a causal propagation of phases of quantum mechanical wavefunctions in the Schrödinger picture. This may open a new and direct way to address time-dependent double-slit experiments and the associated causal issues.

Moulopoulos, Konstantinos

2010-09-01

77

Aharonov-Bohm Excitons at Elevated Temperatures in Type-II ZnTe/ZnSe Quantum Dots  

NASA Astrophysics Data System (ADS)

Optical emission from type-II ZnTe/ZnSe quantum dots demonstrates large and persistent oscillations in both the peak energy and intensity indicating the formation of coherently rotating states. Furthermore, these Aharonov-Bohm oscillations are shown to be remarkably robust and persist until 180 K. This is at least one order of magnitude greater than the typical temperatures in lithographically defined rings. To our knowledge, this is the highest temperature at which the AB effect has been observed in solid-state and molecular nanostructures.

Sellers, I. R.; Whiteside, V. R.; Kuskovsky, I. L.; Govorov, A. O.; McCombe, B. D.

2008-04-01

78

Aharonov-Bohm excitons at elevated temperatures in type-II ZnTe/ZnSe quantum dots.  

PubMed

Optical emission from type-II ZnTe/ZnSe quantum dots demonstrates large and persistent oscillations in both the peak energy and intensity indicating the formation of coherently rotating states. Furthermore, these Aharonov-Bohm oscillations are shown to be remarkably robust and persist until 180 K. This is at least one order of magnitude greater than the typical temperatures in lithographically defined rings. To our knowledge, this is the highest temperature at which the AB effect has been observed in solid-state and molecular nanostructures. PMID:18517978

Sellers, I R; Whiteside, V R; Kuskovsky, I L; Govorov, A O; McCombe, B D

2008-04-01

79

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

NASA Astrophysics Data System (ADS)

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 second-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.

Kubo, T.; Tokura, Y.; Tarucha, S.

2010-09-01

80

Influence of transverse interdot coupling on transport properties of an Aharonov-Bohm structure composed by two dots and two reservoirs  

Microsoft Academic Search

We derive the modified rate equations for an Aharonov-Bohm (AB) ring with two transversely coupled quantum dots (QD's) embedded in two arms in the presence of a magnetic field. We find that the interdot coupling between the two QD's can cause a temporal oscillation in electron occupation at the initial stage of the quantum dynamics, while the source-drain current decays

Z. T. Jiang; J. Q. You; S. B. Bian; H. Z. Zheng

2002-01-01

81

Electron transmission in the Aharonov-Bohm Interferometer with (and without) a spin impurity: Effect of finite width of quantum wires  

Microsoft Academic Search

The Aharonov-Bohm interferometer (ABI) in a two-terminal configuration is a reliable tool to study electron transport in nanoscopic systems. Characterization of the ABI using the Griffith boundary conditions at the junctions of the leads and the ring reported earlier by Kumar and Sahoo (Inter. Jour. Mod. Phys. B 19, 3483 (2005)) are reanalyzed using improved boundary conditions recently proposed by

Chandan Setty; Satyaprasad P. Senanayak; K. Vijay Sai; K. Venkataramaniah; Debendranath Sahoo

2009-01-01

82

Magnetoresistance of nanoscale molecular devices based on Aharonov-Bohm interferometry.  

PubMed

Control of conductance in molecular junctions is of key importance in the growing field of molecular electronics. The current in these junctions is often controlled by an electric gate designed to shift conductance peaks into the low bias regime. Magnetic fields, on the other hand, have rarely been used due to the small magnetic flux captured by molecular conductors (an exception is the Kondo effect in single-molecule transistors). This is in contrast to a related field, electronic transport through mesoscopic devices, where considerable activity with magnetic fields has led to a rich description of transport. The scarcity of experimental activity is due to the belief that significant magnetic response is obtained only when the magnetic flux is of the order of the quantum flux, while attaining such a flux for molecular and nanoscale devices requires unrealistic magnetic fields. Here we review recent theoretical work regarding the essential physical requirements necessary for the construction of nanometer-scale magnetoresistance devices based on an Aharonov-Bohm molecular interferometer. We show that control of the conductance properties using small fractions of a magnetic flux can be achieved by carefully adjusting the lifetime of the conducting electrons through a pre-selected single state that is well separated from other states due to quantum confinement effects. Using a simple analytical model and more elaborate atomistic calculations we demonstrate that magnetic fields which give rise to a magnetic flux comparable to 10(-3) of the quantum flux can be used to switch a class of different molecular and nanometer rings, ranging from quantum corrals, carbon nanotubes and even a molecular ring composed of polyconjugated aromatic materials. The unique characteristics of the magnetic field as a gate is further discussed and demonstrated in two different directions. First, a three-terminal molecular router devices that can function as a parallel logic gate, processing two logic operations simultaneously, is presented. Second, the role of inelastic effects arising from electron-phonon couplings on the magnetoresistance properties is analyzed. We show that a remarkable difference between electric and magnetic gating is also revealed when inelastic effects become significant. The inelastic broadening of response curves to electric gates is replaced by a narrowing of magnetoconductance peaks, thereby enhancing the sensitivity of the device. PMID:21693808

Hod, Oded; Baer, Roi; Rabani, Eran

2008-09-24

83

Path integral action of a particle in a magnetic field in the noncommutative plane and the Aharonov-Bohm effect  

NASA Astrophysics Data System (ADS)

The formulation of noncommutative quantum mechanics as a quantum system represented in the space of Hilbert-Schmidt operators is used to systematically derive, using the standard time slicing procedure, the path integral action for a particle moving in the noncommutative plane and in the presence of a magnetic field and an arbitrary potential. Using this action, the equation of motion and the ground state energy for the particle are obtained explicitly. The Aharonov-Bohm phase is derived using a variety of methods and several dualities between this system and other commutative and noncommutative systems are demonstrated. Finally, the equivalence of the path integral formulation with the noncommutative Schrödinger equation is also established.

Gangopadhyay, Sunandan; Scholtz, Frederik G.

2014-02-01

84

Single-slit electron diffraction with Aharonov-Bohm phase: Feynman's thought experiment with quantum point contacts.  

PubMed

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. PMID:24483873

Khatua, Pradip; Bansal, Bhavtosh; Shahar, Dan

2014-01-10

85

Spin-dependent Andreev reflection in a three-terminal Aharonov-Bohm interferometer with coherent indirect coupling  

NASA Astrophysics Data System (ADS)

Within the framework of non-equilibrium Green's functions, we investigate the spin-dependent Andreev reflection (AR) in a three-terminal Aharonov-Bohm interferometer with double quantum dot, taking account of the coherent indirect coupling via the superconducting reservoir. It is found that the time-reversal symmetry is broken by the crossed Andreev reflection (CAR) process, and moreover that the spin-value effect of the linear conductance, the spin-polarised AR current, and a pure spin current can be generated by means of the normal AR and the CAR. Expressions for the AR conductances (the transport coefficients) governing the AR properties of this system are derived analytically. The effect of the coherent indirect coupling on the conductance, the Andreev reflected tunneling magnetoresistance (ARTMR), and the spin-related current in the presence of the AR are amply analyzed. Our results indicate that the optimal properties of this system can be realised by tuning the external parameters.

Zhang, Rong; Peng, Xiong-Feng; Han, Kui; Shen, Yi-Feng; Tang, Fu-Rong; Bai, Long

2013-02-01

86

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

87

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

88

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

NASA Astrophysics Data System (ADS)

The second-order Zeeman effect of the sodium clock transition in a weak magnetic field of less than 50 ?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 ?/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 ??=(0.222±0.003)×1012×B1.998±0.004 in a magnetic field of less than 50 ?T.

Numazaki, Kazuya; Imai, Hiromitsu; Morinaga, Atsuo

2010-03-01

89

Aharonov-Bohm rings with strong spin-orbit interaction: the role of sample-specific properties  

NASA Astrophysics Data System (ADS)

We present low-temperature transport experiments on Aharonov-Bohm (AB) rings fabricated from two-dimensional hole gases in p-type GaAs/AlGaAs heterostructures. Highly visible h/e (up to 15%) and h/2e oscillations, present for different gate voltages, prove the high quality of the fabricated devices. Like in previous work, a clear beating pattern of the h/e and h/2e oscillations is present in the magnetoresistance, producing split peaks in the Fourier spectrum. The magnetoresistance evolution is presented and discussed as a function of temperature and gate voltage. It is found that sample specific properties have a pronounced influence on the observed behaviour. For example, the interference of different transverse modes or the interplay between h/e oscillations and conductance fluctuations can produce the features mentioned above. In previous work they have occasionally been interpreted as signatures of spin-orbit interaction (SOI)-induced effects. In the light of these results, the unambiguous identification of SOI-induced phase effects in AB rings remains still an open and challenging experimental task.

Nichele, F.; Komijani, Y.; Hennel, S.; Gerl, C.; Wegscheider, W.; Reuter, D.; Wieck, A. D.; Ihn, T.; Ensslin, K.

2013-03-01

90

Magnetic-field-tuned Aharonov-Bohm oscillations and evidence for non-Abelian anyons at ? = 5/2.  

PubMed

We show that the resistance of the ? = 5/2 quantum Hall state, confined to an interferometer, oscillates with the magnetic field consistent with an Ising-type non-Abelian state. In three quantum Hall interferometers of different sizes, resistance oscillations at ? = 7/3 and integer filling factors have the magnetic field period expected if the number of quasiparticles contained within the interferometer changes so as to keep the area and the total charge within the interferometer constant. Under these conditions, an Abelian state such as the (3, 3, 1) state would show oscillations with the same period as at an integer quantum Hall state. However, in an Ising-type non-Abelian state there would be a rapid oscillation associated with the "even-odd effect" and a slower one associated with the accumulated Abelian phase due to both the Aharonov-Bohm effect and the Abelian part of the quasiparticle braiding statistics. Our measurements at ? = 5/2 are consistent with the latter. PMID:24237543

Willett, R L; Nayak, C; Shtengel, K; Pfeiffer, L N; West, K W

2013-11-01

91

Quantum non-locality vs. quasi-local measurements in the conditions of the Aharonov-Bohm effect  

NASA Astrophysics Data System (ADS)

Theoretical explanation of the Meissner effect involves proportionality between current density and vector potential, which has many deep consequences. As noticed by de Gennes, superconductors in a magnetic field "find an equilibrium state where the sum of kinetic and magnetic energies is minimum" and this state "corresponds to the expulsion of the magnetic field". This statement still leaves an open question: from which source is the superconducting current acquiring its kinetic energy? A naïve answer, perhaps, is from the energy of the magnetic field. However, one can consider situations (Aharonov-Bohm effect), where the classical magnetic field is locally absent in the area occupied by the current. Experiments demonstrate that despite the local absence of the magnetic field, current is, nevertheless, building up. From what source is it acquiring its energy then? Locally, only a vector potential is present. How does the vector potential facilitate the formation of the current? Is the current formation a result of a truly non-local quantum action, or does the local action of the vector potential have experimental consequences? We discuss possible experiments with a hybrid normal-metal superconductor circuitry, which can clarify this puzzling situation. Experimental answers will be important for further developments.

Gulian, Armen M.

2014-05-01

92

He-McKellar-Wilkens effect and scalar Aharonov-Bohm effect for a neutral particle based on the Lorentz symmetry violation  

NASA Astrophysics Data System (ADS)

In this contribution, we discuss the He-McKellar-Wilkens effect and the scalar Aharonov-Bohm effect for neutral particles based on the Lorentz symmetry violation background, by showing that the background of the Lorentz symmetry violation yields Abelian quantum phases for a neutral particle. We also study the non-relativistic bound states for a neutral particle interacting with a Coulomb-like potential based on the Lorentz symmetry violation background given by a fixed vector field parallel to the radial direction.

Bakke, K.; Silva, E. O.; Belich, H.

2012-05-01

93

Dynamics of One-Dimensional Bose Liquids: Andreev-Like Reflection at Y Junctions and the Absence of the Aharonov-Bohm Effect  

NASA Astrophysics Data System (ADS)

We study one-dimensional Bose liquids of interacting ultracold atoms in the Y-shaped potential when each branch is filled with atoms. We find that the excitation packet incident on a single Y junction should experience a negative density reflection analogous to the Andreev reflection at normal-superconductor interfaces, although the present system does not contain fermions. In a ring-interferometer-type configuration, we find that the transport is completely insensitive to the (effective) flux contained in the ring, in contrast with the Aharonov-Bohm effect of a single particle in the same geometry.

Tokuno, Akiyuki; Oshikawa, Masaki; Demler, Eugene

2008-04-01

94

Spin transfer in a ferromagnet-quantum dot and tunnel-barrier-coupled Aharonov-Bohm ring system with Rashba spin-orbit interactions  

NASA Astrophysics Data System (ADS)

The spin transfer effect in a ferromagnet-quantum dot (insulator)-ferromagnet Aharonov-Bohm (AB) ring system with Rashba spin-orbit (SO) interactions is investigated by means of the Keldysh nonequilibrium Green function method. It is found that both the magnitude and direction of the spin transfer torque (STT) acting on the right ferromagnet electrode can be effectively controlled by changing the magnetic flux threading the AB ring or the gate voltage on the quantum dot. The STT can be greatly augmented by matching a proper magnetic flux and an SO interaction at a cost of low electrical current. The STT, electrical current and spin current are uncovered to oscillate with the magnetic flux. The present results are expected to be useful for information storage in nanospintronics.

Chen, Xi; Zheng, Qing-Rong; Su, Gang

2010-05-01

95

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.

2012-01-01

96

Aharonov-Bohm Effect in Perturbation Theory.  

ERIC Educational Resources Information Center

The Aharonov-Bohn effect is obtained in first-order perturbation theory. It is shown that the effect occurs only when the initial state is a superposition of eigenstates of Lz corresponding to eigenvalues having opposite sign. (Author/GA)

Purcell, Kay M.; Henneberger, Walter C.

1978-01-01

97

Casimir force between two Aharonov-Bohm solenoids  

SciTech Connect

The vacuum structure for the massive charged scalar field in the region of two parallel, infinitely long and thin solenoids confining the fluxes n[sub 1] and n[sub 2] is studied. By using the Green function method, it is found that the vacuum expectation value of the system's energy has a finite mutual interaction term depending on the distance a between the solenoids, which implies an attractive force per unit length given by F[sub n1n2] = [minus]([h bar]c/[pi][sup 2])(n[sub 1]n[sub 2])[sup 2]/a[sup 3]. 11 refs.

Duru, I.H. (Edirne, Turkey, and Marmara Research Centre, Tubitak (Turkey))

1993-05-01

98

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

99

Anomalous Aharonov-Bohm effect in percolating superconducting films  

Microsoft Academic Search

We have studied the superconducting transition in thin films of Pb and Al as a function of temperature and magnetic field. Examination of the films in a transmission electron microscope shows a percolative structure with typical small loop sizes of a few thousand angstroms in Pb and about a thousand in Al. An ac current passing through the sample is

A. Gerber; G. Deutscher

1989-01-01

100

Extracting fractional statistics from superperiodic Aharonov-Bohm oscillations  

Microsoft Academic Search

We consider a quantum Hall interferometer in which the quasiparticles of a fractional quantum Hall (FQH) liquid with filling factor nu1=1\\/3 propagate around a large ring of radius r1, which is encircles an island with a smaller radius r2 occupied by FQH liquid with filling factor nu2=2\\/5. We study the conductance oscillations that result from the incompressibility of the FQH

Eun-Ah Kim; Steven Kivelson

2006-01-01

101

Aharonov-Bohm Conductance Modulation in Ballistic Carbon Nanotubes  

Microsoft Academic Search

We report on magnetoconductance experiments in ballistic multiwalled carbon nanotubes threaded by magnetic fields as large as 55 T. In the high temperature regime (100 K), giant modulations of the conductance, mediated by the Fermi level location, are unveiled. The experimental data are consistently analyzed in terms of the field-dependent density of states of the external shell that modulates the

B. Lassagne; J.-P. Cleuziou; S. Nanot; W. Escoffier; R. Avriller; S. Roche; L. Forró; B. Raquet; J.-M. Broto

2007-01-01

102

Acoustical indication of Aharonov-Bohm phase in metal oxide-A theoretical approach  

NASA Astrophysics Data System (ADS)

Phase of electron wave plays essential roles in quantum mechanical phenomena such as interference, absorption, and conductivity. Propagation of acoustical waves through materials with high free electron density causes absorption of acoustic waves by electron, phonon, coupled electron-phonon wave etc. Change of electron characteristics in material in presence of external stimuli such as temperature and magnetic field modifies the acoustic absorption coefficient. Here, we theoretically analyze the change of ultrasound attenuation due to absorption in aluminium oxide in presence of external magnetic field due to the evolution of 'Aharonov-Bohmphase' in electrons. This field induced variation of ultrasound attenuation in metal oxide utilizes to develop novel acoustic meta-material.

Brojabasi, Priyanka; Kumar, Anish; Jayakumar, T.

2013-06-01

103

Comment on "Aharonov-Casher and Scalar Aharonov-Bohm Topological Effects"  

NASA Astrophysics Data System (ADS)

In this Comment we point out (i) that the Hamiltonian, Eq. (17) in the Letter(Phys. Rev. Lett. 108, 070405 (2012)), is not a relativistic Hamiltonian, (ii) then that the conditions in the Letter are irrelevant for a topological AC and SAB effects, and (iii) conclusively that the non-relativistic Hamiltonian employed by Peshkin and Lipkin (Phys. Rev. Lett. 74, 2847 (1995)) has the same $U(1)_{mm}$ gauge structure for a fixed spin and then is not wrong, but their incorrect interpretation of the spin autocorrelations led to the incorrect conclusion.

Choi, Taeseung; Cho, Sam Young

2014-04-01

104

Aharonov-Bohm interference in neutral excitons: effects of built-in electric fields.  

PubMed

We report a comprehensive discussion of quantum interference effects due to the finite structure of neutral excitons in quantum rings and their first experimental corroboration observed in the optical recombinations. The signatures of built-in electric fields and temperature on quantum interference are demonstrated by theoretical models that describe the modulation of the interference pattern and confirmed by complementary experimental procedures. PMID:20366953

Teodoro, M D; Campo, V L; Lopez-Richard, V; Marega, E; Marques, G E; Gobato, Y Galvão; Iikawa, F; Brasil, M J S P; Abuwaar, Z Y; Dorogan, V G; Mazur, Yu I; Benamara, M; Salamo, G J

2010-02-26

105

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

NASA Astrophysics Data System (ADS)

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

2014-05-01

106

Single electron bipolar conductance switch driven by the molecular aharonov-bohm effect.  

PubMed

We demonstrate a conductance switch controlled by the spin-vibronic density of an odd electron on a single molecule. The junction current is modulated by the spin-flip bistability of the electron. Functional images are provided as wiring diagrams for control of the switch's frequency, amplitude, polarity, and duty-cycle. The principle of operation relies on the quantum mechanical phase associated with the adiabatic circulation of a spin-aligned electron around a conical intersection. The functional images quantify the governing vibronic Hamiltonian. PMID:24824563

Lee, Joonhee; Tallarida, Nicholas; Rios, Laura; Perdue, Shawn M; Apkarian, Vartkess Ara

2014-06-24

107

Iordanskii force and the gravitational Aharonov-Bohm effect for a moving vortex  

NASA Astrophysics Data System (ADS)

I discuss the scattering of phonons by a vortex moving with respect to a superfluid condensate. This allows us to test the compatibility of the scattering-theory derivation of the Iordanskii force with the Galilean invariance of the underlying fluid dynamics. In order to obtain the correct result we must retain O(v2s) terms in the sound-wave equation, and this reinforces the interpretation, due to Volovik, of the Iordanskii force as an analogue of the gravitational Bohm-Aharonov effect.

Stone, Michael

2000-05-01

108

Aharonov-Bohm Oscillations in Parallel Coupled Vertical Double Quantum Dot  

Microsoft Academic Search

We used a parallel coupled vertical double quantum dot device consisting of two laterally tunnel-coupled dots and a common source and drain electrodes to study the Aharanov-Bohm (AB) effects in the vertically flowing single electron tunneling current. In the charging diagram measured at a finite source-drain voltage a bonding state as a ground state, and an antibonding state as an

T. Hatano; T. Kubo; S. Amaha; S. Teraoka; Y. Tokura; S. Tarucha

2009-01-01

109

Aharonov-Bohm Oscillations in Parallel Coupled Vertical Double Quantum Dot  

NASA Astrophysics Data System (ADS)

We used a parallel coupled vertical double quantum dot device consisting of two laterally tunnel-coupled dots and a common source and drain electrodes to study the Aharanov-Bohm (AB) effects in the vertically flowing single electron tunneling current. In the charging diagram measured at a finite source-drain voltage a bonding state as a ground state, and an antibonding state as an excited state were distinguished for the one-electron state. We observed periodic magnetic oscillations for the current through the bonding state, due to the AB effect for the two tunnel-coupled dots.

Hatano, T.; Kubo, T.; Amaha, S.; Teraoka, S.; Tokura, Y.; Tarucha, S.

2009-06-01

110

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 ...

111

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...

112

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...

113

Influence of Coulomb interaction on the Aharonov-Bohm effect in an electronic Fabry-Pérot interferometer  

NASA Astrophysics Data System (ADS)

We study the role of Coulomb interaction in an electronic Fabry-Pérot interferometer (FPI) realized with chiral edge states in the integer quantum Hall regime in the limit of weak backscattering. Assuming that a compressible Coulomb island in a bulk region of the FPI is formed, we develop a capacitance model which explains the plethora of experimental data on the flux and gate periodicity of conductance oscillations. It is also shown that a suppression of finite-bias visibility stems from a combination of weak Coulomb blockade and a nonequilibrium dephasing by the quantum shot noise.

Ngo Dinh, Stéphane; Bagrets, Dmitry A.

2012-02-01

114

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

115

Aharonov-Bohm Effect on Charge Density Wave (CDW) Moving through Columnar Defects in NbSe3  

Microsoft Academic Search

The presence of columnar defects (CDs) in NbSe3 is shown to induce oscillations in the nonlinear charge density wave (CDW) conductivity as a function of magnetic field, when the field is oriented parallel to the axes of the defects. The period of oscillation corresponds to a change in the magnetic field flux in each CD by an amount phi0 =

Yu. I. Latyshev; O. Laborde; P. Monceau; S. Klaumünzer

1997-01-01

116

The Aharonov-Bohm effect for massless Dirac fermions and the spectral flow of Dirac-type operators with classical boundary conditions  

NASA Astrophysics Data System (ADS)

In topological terms, we compute the spectral flow of an arbitrary family of self-adjoint Dirac-type operators with classical (local) boundary conditions on a compact Riemannian manifold with boundary under the assumption that the initial and terminal operators of the family are conjugate by an automorphism of the bundle in which the operators act. We use this result to study conditions for the existence of a nonzero spectral flow of a family of self-adjoint Dirac-type operators with local boundary conditions in a two-dimensional domain with a nontrivial topology and discuss possible physical realizations of a nonzero spectral flow.

Katsnelson, M. I.; Nazaikinskii, V. E.

2012-09-01

117

Can Real Forces Be Induced by Interference of Quantum Wavefunctions?  

NASA Astrophysics Data System (ADS)

In 1958, a revolutionary paper by Aharonov and Bohm predicted a phase difference between two parts of an electron wavefunction even when being confined to a regime with no EM field. The Aharonov-Bohm effect was groundbreaking: proving that the EM vector potential is a real physical quantity, affecting the outcome of experiments not only through the EM fields extracted from it. But is the EM potential a real necessity for an Aharonov-Bohm-type effect? Can it exist in a potential-free system such as free-space? Here, we find self-accelerating wavepackets that are solutions of the free Dirac equation, for massive/massless fermions/bosons. These accelerating Dirac particles mimic the dynamics of a free-charge moving under a ``virtual'' EM field, even though no field is acting and there is no charge: the entire dynamics is a direct result of the initial conditions. We show that such particles display an effective Aharonov-Bohm effect caused by exactly the same ``virtual'' potential that also ``causes'' the acceleration. Altogether, along the trajectory, there is no way to distinguish between a real force and the self-induced force - it is real by all measurable quantities. This proves that one can create all effects induced by EM fields by only controlling the initial conditions of a wave pattern, while the dynamics is in free-space. These phenomena can be observed in various settings: e.g., optical waves in honeycomb photonic lattices or in hyperbolic metamaterials, and matter waves in honeycomb interference structures.

Kaminer, Ido; Nemirovsky, Jonathan; Rechtsman, Mikael; Bekenstein, Rivka; Segev, Mordechai

2013-04-01

118

Geometric phase for fermionic quasiparticles scattering by disgyration in superfluids  

NASA Astrophysics Data System (ADS)

We consider a Volovik's analogue model for the description of topological defects in a superfluid and we investigate the scattering of quasiparticles in this background. The analogue of the gravitational Aharonov-Bohm effect in this system is found. An analysis of this problem employing loop variables is considered and corroborates the existence of the Aharonov-Bohm effect in this system. The results presented here may be used to study the Aharonov-Bohm effect in superconductors.

Garcia de Andrade, L. C.; Carvalho, A. M. de M.; Furtado, C.

2004-08-01

119

Maxwell Duality, Lorentz Invariance, and Topological Phase  

NASA Technical Reports Server (NTRS)

We discuss the Maxwell electromagnetic duality relations between the Aharonov-Bohm, Aharonov-Casher, and He-McKellar-Wilkens topological phases, which allows a unified description of all three phenomena.

Dowling, J.; Williams, C.; Franson, J.

1999-01-01

120

Gate-Controlled Spin Transport Through GaAs Quantum Dots  

Microsoft Academic Search

We report measurements of transport through an Aharonov-Bohm ring, fabricated on a GaAs\\/AlGaAs heterostructure and containing a small quantum dot on each arm. Each dot is placed in the Coulomb-blockade (g << e^2\\/h) regime, and ground-state spin transitions are determined for each Coulomb-blockade peak using an in-plane magnetic field to control Zeeman energies. The amplitude of Aharonov-Bohm oscillations are measured

J. A. Folk; R. M. Potok; A. C. Johnson; S. M. Cronenwett; C. M. Marcus; W. G. van der Wiel; L. P. Kouwenhoven

2001-01-01

121

Temperature-Dependent Screening of the Edge State around Antidots in the Quantum Hall Regime  

Microsoft Academic Search

The Aharonov-Bohm effect in a small array of antidots with a large aspect ratio is investigated in the quantum Hall regime. The evolution with temperature of the Aharonov-Bohm oscillations in the magnetic field versus gate voltage (B-Vg) plane reveals the temperature dependence of the screening. The self-consistently screened potential of the compressible band surrounding an antidot is observed to gain

Masanori Kato; Akira Endo; Shingo Katsumoto; Yasuhiro Iye

2009-01-01

122

Quantum Effects of Electric Fields and Potentials on Electron Motion: An Introduction to Theoretical and Practical Aspects  

ERIC Educational Resources Information Center

In the so-called electric Aharonov-Bohm effect, a quantum interference pattern shift is produced when electrons move in an electric field free region but, at the same time, in the presence of a time-dependent electric potential. Analogous fringe shifts are observed in interference experiments where electrons, travelling through an electrostatic…

Matteucci, G.

2007-01-01

123

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

124

Quantum holonomies for an electric dipole moment  

NASA Astrophysics Data System (ADS)

In this Letter, we obtain the quantum holonomies for a neutral particle with a permanent electric dipole moment based on the analogue effects of the He-McKellar-Wilkens effect and the Scalar Aharonov-Bohm effect and show a new proposal for implementing one-qubit quantum gates.

Bakke, Knut; Furtado, Claudio

2011-10-01

125

Persistent current in an ordered-disordered separated cylinder  

NASA Astrophysics Data System (ADS)

The anomalous behavior of persistent current is examined in an ordered-disordered separated mesoscopic cylinder pierced by an Aharonov-Bohm (AB) flux J within a single-band non-interacting tight-binding framework. Our present analysis may be helpful for studying localization-delocalization transition in shell-doped nanotubes.

Dutta, Paramita; Maiti, Santanu K.; Karmakar, S. N.

2013-06-01

126

Influence of Interactions on Flux and Back-Gate Period of Quantum Hall Interferometers  

Microsoft Academic Search

In quantum Hall systems with two narrow constrictions, tunneling between opposite edges can give rise to quantum interference and Aharonov-Bohm like oscillations of the conductance. When there is an integer quantized Hall state within the constrictions, a region between them, with higher electron density, may form a compressible island. Electron tunneling through this island can lead to residual transport, modulated

B. Rosenowand; B. I. Halperin

2007-01-01

127

Triple Rashba dots as a spin filter: Bound states in the continuum and Fano effect  

NASA Astrophysics Data System (ADS)

We propose an efficient spin-filter device by exploiting bound states (BICs) in the continuum and Fano effect on a triple Rashba quantum dot molecule embedded in an Aharonov-Bohm interferometer. We find that the coexistence of a BIC and a Fano antiresonance result in polarizations close to 100% in wide regions in the space of parameters.

Vallejo, M. L.; Ladrón de Guevara, M. L.; Orellana, P. A.

2010-11-01

128

Ether drift experiments and electromagnetic momentum  

NASA Astrophysics Data System (ADS)

Propagation of Aharonov-Bohm matter waves and light waves in moving media is characterized by the interaction electromagnetic momentum. Thus, recent models of light propagation in moving rarefied media justify and call for an optical experiment of the Mascart-Jamin type, capable of testing the modern interpretations of ether drift experiments.

Spavieri, G.; Guerra, V.; de Abreu, R.; Gillies, G. T.

2008-05-01

129

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

130

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

131

Spectral Statistics of the Rectangular Billiard with a Flux Line  

Microsoft Academic Search

The density of states of a rectangular billiard with an AharonovBohm flux line in its center was calculated in the semiclassical approximation and was used for the calculation of the form factor in the diagonal approximation. The distribution of nearest level spacings and the form factor were calculated also numerically. For some values of the flux these were found to

Saar Rahav; Shmuel Fishman

2001-01-01

132

Spectral Statistics of the Rectangular Billiard with a Flux Line  

Microsoft Academic Search

The density of states of a rectangular billiard with an Aharonov–Bohm flux line in its center was calculated in the semiclassical approximation and was used for the calculation of the form factor in the diagonal approximation. The distribution of nearest level spacings and the form factor were calculated also numerically. For some values of the flux these were found to

Saar Rahav; Shmuel Fishman

2001-01-01

133

An Introduction to the Basics of Dephasing  

NSDL National Science Digital Library

This is a simplified introduction to the physics of dephasing of quantum systems. It covers the basics of interacting quantum systems, entanglement, dephasing, dissipation, and quantum measurements. Examples used include ensembles of spins, quantum Brownian motion, and the Aharonov-Bohm effect.

Marquardt, Florian

2004-03-29

134

EMS System Plan.  

National Technical Information Service (NTIS)

An Emergency Medical Service (EMS) system plan for an eight-county, primarily rural district of south central Oklahoma is presented. Demographic and area characteristics of the district are described. The existing EMS resources such as: manpower (physicia...

G. L. Dahl R. Eidson

1975-01-01

135

EMS Student Handbook.  

ERIC Educational Resources Information Center

This student guide is one of a series of self-contained materials for students enrolled in an emergency medical services (EMS) training program. Discussed in the individual sections of the guide are the following topics: the purpose and history of EMS professionals; EMS training, certification and examinations (national and state certification and…

Ogle, Patrick

136

Photovoltaic Detectors for Infrared Operation Detetor Fotovoltaico Crescimento de Cristais Juncao p-N.  

National Technical Information Service (NTIS)

Lead oxide semiconductors are discussed. They have a composition dependent energy gap which makes them, besides other optical and electrical characteristics, excellent candidates for tuned infrared detection. The results obtained for detectors of Pb(1-x)S...

C. Y. An I. N. Bandeira

1981-01-01

137

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

138

More than one mystery: Quantum interference with correlated charged particles and magnetic fields  

NASA Astrophysics Data System (ADS)

Examples of charged-particle interferometry are descibed whereby isolated magnetic fields-i.e., fields through which the particles do not pass-influence the clustering, as well as spatial distribution, of the particles. The configurations, which combine features characteristic of (i) Aharonov-Bohm and Hanbury Brown-Twiss experiments, and (ii) Aharonov-Bohm and Einstein-Podolsky-Rosen experiments, manifest simultaneously the effects of three distinct kinds of interference: (i) interference, dependent upon optical path length difference, resulting from wavelike propagation of particles; (ii) interference, dependent upon confined magnetic flux, resulting from particle charge and spatial topology; and (iii) interference, dependent upon quantum statistics, resulting from particle indistinguishability under exchange.

Silverman, M. P.

1993-06-01

139

Dynamics of dipoles and quantum phases in noncommutative coordinates  

NASA Astrophysics Data System (ADS)

The dynamics of a spin-(1/2) neutral particle possessing electric- and magnetic-dipole moments interacting with external electric and magnetic fields in noncommutative coordinates is obtained. Noncommutativity of space is interposed in terms of a semiclassical constrained Hamiltonian system. The relation between the quantum phase acquired by a particle interacting with an electromagnetic field and the (semi)classical force acting on the system is examined and generalized to establish a formulation of the quantum phases in noncommutative coordinates. The general formalism is applied to physical systems yielding the Aharonov-Bohm, Aharonov-Casher, He-McKellar-Wilkens and Anandan phases in noncommutative coordinates. Bounds for the noncommutativity parameter ? are derived comparing the deformed phases with the experimental data on the Aharonov-Bohm and Aharonov-Casher phases.

Dayi, Ö. F.

2009-02-01

140

Adiabatic Tracking of a State: A New Route to Nonequilibrium Physics  

NASA Astrophysics Data System (ADS)

We present a novel numerical approach to track the response of a quantum system to an external perturbation that is progressively switched on. The method is applied, within the framework of the density matrix renormalization group technique, to track current-carrying states of interacting fermions in one dimension and in the presence of an Aharonov-Bohm magnetic flux. This protocol allows us to access highly excited states. We also discuss the connection with the entanglement entropy of these excited states.

Moliner, M.; Schmitteckert, P.

2013-09-01

141

Flux Period Scaling in the Laughlin Quasiparticle Interferometer  

Microsoft Academic Search

Aharonov-Bohm superperiod was rececently reported for electron interferometer devices in the quantum Hall regime, where electron paths circle a 2D electron island. The electron island main confinement is produced by etch trenches, into which front gate metal is deposited. We determine experimentally the A-B period deltaB at several front gate voltages V for electrons (f =1) and Laughlin quasiparticles (2\\/5

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

2006-01-01

142

Dirac equation in magnetic-solenoid field  

Microsoft Academic Search

We consider the Dirac equation in the magnetic-solenoid field (the field of a solenoid and a collinear uniform magnetic field). For the case of Aharonov-Bohm solenoid, we construct self-adjoint extensions of the Dirac Hamiltonian using von Neumann’s theory of deficiency indices. We find self-adjoint extensions of the Dirac Hamiltonian and boundary conditions at the AB solenoid. Besides, for the first

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

2004-01-01

143

Solution of the Dirac equation with magnetic monopole and pseudoscalar potentials  

NASA Astrophysics Data System (ADS)

The Dirac equation in the presence of the Dirac magnetic monopole potential, the Aharonov-Bohm potential, a Coulomb potential and a pseudo-scalar potential, is solved by separation of variables using the spinweighted spherical harmonics. The energy spectrum and the form of the spinor functions are obtained. It is shown that the number j in spin-weighted spherical harmonics must be greater than.

Aghaei, Sohrab; Chenaghlou, Alireza

2014-04-01

144

Stable switch action based on quantum interference effect  

NASA Astrophysics Data System (ADS)

Although devices working on quantum principles can revolutionize the electronic industry, they have not been achieved yet as it is difficult to control their stability. We show that one can use evanescent modes to build stable quantum switches. The physical principles that make this possible is explained in detail. Demonstrations are given using a multichannel Aharonov-Bohm interferometer. We propose a new S matrix for multichannel junctions to solve the scattering problem.

Mukherjee, Sreemoyee; Yadav, Ashutosh; Singha Deo, P.

2013-01-01

145

General relativity in electrical engineering  

NASA Astrophysics Data System (ADS)

In electrical engineering metamaterials have been developed that offer unprecedented control over electromagnetic fields. Here we show that general relativity lends the theoretical tools for designing devices made of such versatile materials. We consider media that facilitate space-time transformations and include negative refraction. Our theory unifies the concepts operating behind the scenes of perfect invisibility devices, perfect lenses, the optical Aharonov-Bohm effect and electromagnetic analogs of the event horizon, and may lead to further applications.

Leonhardt, U.; Philbin, T. G.

2007-06-01

146

Magnetic field symmetries of nonlinear transport with elastic and inelastic scattering  

NASA Astrophysics Data System (ADS)

We study nonlinear electronic transport symmetries in Aharonov-Bohm interferometers subjected to inelastic-scattering effects and show that odd (even) conductance terms are even (odd) in the magnetic field when the junction is (left-right) spatially symmetric. This observation does not hold when spatial inversion symmetry is broken, as we show numerically. Under elastic dephasing effects, the Onsager-Casimir symmetry is maintained beyond linear response, irrespective of spatial asymmetries.

Bedkihal, Salil; Bandyopadhyay, Malay; Segal, Dvira

2013-10-01

147

Spectral analysis for the Sturm-Liouville operator on sun-type graphs  

NASA Astrophysics Data System (ADS)

A scattering problem is studied for second-order differential operators on noncompact graphs with a cycle and with standard matching conditions in the internal vertices. Moreover, a uniqueness theorem for a corresponding inverse problem is proved. Problems of this type appear in various applications of mathematical physics, in particular in connection with the study of the properties of Aharonov-Bohm rings connected to one or several wires.

Freiling, Gerhard; Ignatyev, Mikhail

2011-09-01

148

Magnetoconductance oscillations in graphene antidot arrays  

Microsoft Academic Search

Epitaxial graphene films have been formed on the C-face of semi-insulating 4H-SiC substrates by a high temperature sublimation process. Nanoscale square antidot arrays have been fabricated on these graphene films. At low temperatures, magnetoconductance in these films exhibits pronounced Aharonov-Bohm oscillations with the period corresponding to magnetic flux quanta added to the area of a single antidot. At low fields,

T. Shen; Y. Q. Wu; Leonid P Rokhinson; L. W. Engel; P. D. Ye

2008-01-01

149

Magnetoconductance oscillations in graphene antidot arrays  

Microsoft Academic Search

Epitaxial graphene films have been formed on the C-face of semi-insulating 4H-SiC substrates by a high temperature sublimation process. Nanoscale square antidot arrays have been fabricated on these graphene films. At low temperatures, magnetoconductance in these films exhibits pronounced Aharonov–Bohm oscillations with the period corresponding to magnetic flux quanta added to the area of a single antidot. At low fields,

T. Shen; Y. Q. Wu; M. A. Capano; L. P. Rokhinson; L. W. Engel; P. D. Ye

2008-01-01

150

Magnetic flux superperiods in fractional quantum Hall interferometers  

Microsoft Academic Search

Superperiodic Aharonov-Bohm oscillations in conductance of e\\/3 quasiparticles have been reported in three Fabry-Perot interferometer devices. Superperiods are observed in the FQH regime, when filling 1\\/3 edge channel encircles an island of 2\\/5 FQH fluid. Etch trenches define the devices, which consist of a 2D electron island connected to the 2DES bulk via two wide constrictions. An oscillatory signal in

F. E. Camino; P. V. Lin; V. J. Goldman

2010-01-01

151

Superperiods in interference of e\\/3 Laughlin quasiparticles encircling filling 2\\/5 fractional quantum Hall island  

Microsoft Academic Search

We report experiments in a large, 2.5mum diameter Fabry-Perot quantum Hall interferometer with two tunneling constrictions. Interference fringes are observed as conductance oscillations as a function of applied magnetic field (the Aharonov-Bohm flux through the electron island) or a global backgate voltage (electronic charge in the island). Depletion is such that in the fractional quantum Hall regime, filling 1\\/3 current-carrying

Ping V. Lin; F. E. Camino; V. J. Goldman

2009-01-01

152

Interference of e\\/3 quasiparticles encircling 2\\/5 fractional quantum Hall island  

Microsoft Academic Search

We report experiments in a large, 2.5 micron Fabry-Perot interferometer fabricated from a GaAs\\/AlGaAs heterostructure. Device is defined by etch trenches; front gates deposited in the trenches allow to tune the device. Tunneling in the two constrictions closes an Aharonov-Bohm path around the 2D electron island. Quantized plateaus in RXX and RXY allow to find out both: the bulk and

Ping V. Lin; F. E. Camino; V. J. Goldman

2010-01-01

153

Superperiods in Interference of eÃ3 Laughlin Quasiparticles Encircling Filling 2\\/5 FractionalQuantum Hall Island  

Microsoft Academic Search

We report experiments in a large, 2.5 μm diameter Fabry-Perot quantum Hall interferometer with two tunneling constrictions. Interference fringes are observed as conductance oscillations as a function of applied magnetic field (the Aharonov-Bohm flux through the electron island) or a global backgate voltage (electronic charge in the island). Depletion is such that in the fractional quantum Hall regime, filling 1\\/3

Ping V. Lin; F. E. Camino; V. J. Goldman

2009-01-01

154

Quantum phase of an electric dipole moving in a magnetic dipole field  

Microsoft Academic Search

It is shown that a neutral particle with an electric dipole moment acquires a quantum phase of Aharonov-Bohm type which is induced by a magnetic dipole field, in addition to the He-McKellar-Wilkens phase which requires a magnetic monopole field. Therefore this phase is measurable in principle. This phase is related to the Casella phase in the sense of the electromagnetic

Tae-Yeon Lee

2000-01-01

155

Bose-Einstein condensates in strong electric fields: Effective gauge potentials and rotating states  

Microsoft Academic Search

Magnetically trapped atoms in Bose-Einstein condensates are spin polarized. Since the magnetic field is inhomogeneous, the atoms acquire Berry phases of the Aharonov-Bohm type during adiabatic motion. In the presence of an electric field, there is an additional Aharonov-Casher effect. Taking into account the limitations on the strength of the electric fields due to the polarizability of the atoms, we

J. M. Kailasvuori; T. H. Hansson; G. M. Kavoulakis

2002-01-01

156

EM and beyond  

Microsoft Academic Search

The basic theme of the EM algorithm, to repeatedly use complete-data methods to solve incomplete data problems, is also a theme of several more recent statistical techniques. These techniques—multiple imputation, data augmentation, stochastic relaxation, and sampling importance resampling—combine simulation techniques with complete-data methods to attack problems that are difficult or impossible for EM.

Donald B. Rubin

1991-01-01

157

Exact solutions of the Klein Gordon equation in the presence of a dyon, magnetic flux and scalar potential in the spacetime of gravitational defects  

NASA Astrophysics Data System (ADS)

In this paper, we analyse the relativistic quantum motion of a charged spin-0 particle in the presence of a dyon, Aharonov Bohm magnetic field and scalar potential in the spacetimes produced by an idealized cosmic string and global monopole. In order to develop this analysis, we assume that the dyon and the Aharonov Bohm magnetic field are superposed to both gravitational defects. Two distinct configurations for the scalar potential, S(r), are considered: (i) the potential proportional to the inverse of the radial distance, i.e. S ~ 1/r, and (ii) the potential proportional to this distance, i.e. S ~ r. For both cases the centre of the potentials coincides with the dyon's position. In the case of the cosmic string the Aharonov Bohm magnetic field is considered along the defect, and for the global monopole this magnetic field pierces the defect. The energy spectra are computed for both cases and their dependence on the electrostatic and scalar coupling constants is explicitly shown. We also analyse scattering states of the Klein Gordon equations, and show how the phase shifts depend on the geometry of the spacetime and on the coupling constants parameter.

Cavalcanti de Oliveira, A. L.; Bezerra de Mello, E. R.

2006-09-01

158

Deterministic annealing EM algorithm.  

PubMed

This paper presents a deterministic annealing EM (DAEM) algorithm for maximum likelihood estimation problems to overcome a local maxima problem associated with the conventional EM algorithm. In our approach, a new posterior parameterized by `temperature' is derived by using the principle of maximum entropy and is used for controlling the annealing process. In the DAEM algorithm, the EM process is reformulated as the problem of minimizing the thermodynamic free energy by using a statistical mechanics analogy. Since this minimization is deterministically performed at each temperature, the total search is executed far more efficiently than in the simulated annealing. Moreover, the derived DAEM algorithm, unlike the conventional EM algorithm, can obtain better estimates free of the initial parameter values. We also apply the DAEM algorithm to the training of probabilistic neural networks using mixture models to estimate the probability density and demonstrate the performance of the DAEM algorithm. PMID:12662837

Ueda, N; Nakano, R

1998-03-01

159

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

160

emGain: Determination of EM gain of CCD  

NASA Astrophysics Data System (ADS)

The determination of the EM gain of the CCD is best done by fitting the histogram of many low-light frames. Typically, the dark+CIC noise of a 30ms frame itself is a sufficient amount of signal to determine accurately the EM gain with about 200 512x512 frames. The IDL code emGain takes as an input a cube of frames and fit the histogram of all the pixels with the EM stage output probability function. The function returns the EM gain of the frames as well as the read-out noise and the mean signal level of the frames.

Daigle, Olivier; Carignan, Claude; Blais-Ouellette, Sebastien

2012-01-01

161

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

162

EMS Course Coordinator's Implementation Guide.  

ERIC Educational Resources Information Center

This handbook is intended to clarify the responsibilities of an instructor-coordinator responsible for coordinating an emergency medical services (EMS) training program and to describe many of the materials now available for use in coordinating EMS training. Addressed in the individual chapters of the guide are the nature and scope of the…

Cockrum, Jim

163

Identified EM Earthquake Precursors  

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 a number of custom rock experiments, two hypotheses were formed which could answer the EM wave model. The first hypothesis concerned a sufficient and continuous electron movement either by surface or penetrative flow, and the second regarded a novel approach to radio transmission. Electron flow along fracture surfaces was determined to be inadequate in creating strong EM fields, because rock has a very high electrical resistance making it a high quality insulator. Penetrative flow could not be corroborated as well, because it was discovered that rock was absorbing and confining electrons to a very thin skin depth. Radio wave transmission and detection worked with every single test administered. This hypothesis was reviewed for propagating, long-wave generation with sufficient amplitude, and the capability of penetrating solid rock. Additionally, fracture spaces, either air or ion-filled, can facilitate this concept from great depths and allow for surficial detection. A few propagating precursor signals have been detected in the field occurring with associated phases using custom-built loop antennae. Field testing was conducted in Southern California from 2006-2011, and outside the NE Texas town of Timpson in February, 2013. The antennae have mobility and observations were noted for recurrence, duration, and frequency response. At the Southern California field sites, one loop antenna was positioned for omni-directional reception and also detected a strong First Schumann Resonance; however, additional Schumann Resonances were absent. At the Timpson, TX field sites, loop antennae were positioned for directional reception, due to earthquake-induced, hydraulic fracturing activity currently conducted by the oil and gas industry. Two strong signals, one moderately strong signal, and approximately 6-8 weaker signals were detected in the immediate vicinity. The three stronger signals were mapped by a biangulation technique, followed by a triangulation technique for confirmation. This was the first antenna mapping technique ever performed for determining possible earthquake epicenters. Six and a half months later, Timpson experienced two M4 (M4.1 and M4.3) earthquakes on September 2, 2013 followed by a M2.4 earthquake three days later, all occurring at a depth of five kilometers. The Timpson earthquake activity now has a cyclical rate and a forecast was given to the proper authorities. As a result, the Southern California and Timpson, TX field results led to an improved design and construction of a third prototype antenna. With a loop antenna array, a viable communication system, and continuous monitoring, a full fracture cycle can be established and observed in real-time. In addition, field data could be reviewed quickly for assessment and lead to a much more improved earthquake forecasting capability. The EM precursors determined by this method appear to surpass all prior precursor claims, and the general public will finally receive long overdue forecasting.

Jones, Kenneth, II; Saxton, Patrick

2014-05-01

164

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...

165

Measurement induced dephasing and suppression of persistent current in a lattice ring [rapid communication  

NASA Astrophysics Data System (ADS)

We investigate the effect of measurement on the persistent current density in a mesoscopic lattice ring with a threading Aharonov Bohm flux. A quantum dot coupled with the ring is continuously monitored by a point contact detector. It is demonstrated by explicit analysis of the time-evolution of current density that the persistent current in the lattice ring can be suppressed completely due to the effect of detector implying the dephasing of quantum states. Practical experiments to observe the measurement induced dephasing is proposed.

Zhang, Yong-Ping; Gao, Ying-Fang; Liang, J.-Q.

2005-10-01

166

Quantitatively probing two-electron entanglement with a spintronic quantum eraser  

NASA Astrophysics Data System (ADS)

We design a spintronic quantum eraser to quantitatively probe the two-electron entanglement. It is shown that the concurrence of two spin-entangled electrons is directly given by the Aharonov-Bohm oscillation amplitude of the Fano factor, a measurable current-current correlation, making it rather promising to experimentally quantify the two-electron entanglement. The singlet and triplet entangled states are distinguished by the opposite signs in the Fano factor. Since the main building blocks in the designed setup, an electronic Mach-Zehnder interferometer and a spin filter, have already been implemented, our proposal is particularly pertinent to experiments.

Chen, Wei; Shen, R.; Wang, Z. D.; Sheng, L.; Wang, B. G.; Xing, D. Y.

2013-04-01

167

Flux sensitivity of a piecewise normal and superconducting metal loop  

NASA Astrophysics Data System (ADS)

We consider a loop composed of a superconducting segment and a normal segment with an Aharonov-Bohm flux through the hole of the loop. The normal segment is assumed to be long compared to the superconducting coherence length ? but short compared to a mean inelastic diffusion length. The elementary excitation spectrum of the ground state of this loop is periodic with period hc/2e as long as the superconducting segment is larger than ?. If the superconducting segment length becomes of the order of ?, quasiparticles can tunnel through the superconducting gap and give rise to an excitation spectrum which is periodic with period hc/e. .AE

Büttiker, M.; Klapwijk, T. M.

1986-04-01

168

Electromagnetic potential vectors and the Lagrangian of a charged particle  

NASA Technical Reports Server (NTRS)

Maxwell's equations can be shown to imply the existence of two independent three-dimensional potential vectors. A comparison between the potential vectors and the electric and magnetic field vectors, using a spatial Fourier transformation, reveals six independent potential components but only four independent electromagnetic field components for each mode. Although the electromagnetic fields determined by Maxwell's equations give a complete description of all possible classical electromagnetic phenomena, potential vectors contains more information and allow for a description of such quantum mechanical phenomena as the Aharonov-Bohm effect. A new result is that a charged particle Lagrangian written in terms of potential vectors automatically contains a 'spontaneous symmetry breaking' potential.

Shebalin, John V.

1992-01-01

169

Quasiballistic transport of Dirac fermions in a Bi2Se3 nanowire.  

PubMed

Quantum coherent transport of surface states in a mesoscopic nanowire of the three-dimensional topological insulator Bi(2}Se(3) 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. PMID:23683235

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

170

Universalities: From Anderson Localization To Quantum Chaos  

Microsoft Academic Search

Contents1. Introduction 51.1. Impurity States 61.2. Impurity Bands 81.3. Anderson Model 92. Quantum Interference Effects in Disordered Conductors 112.1. Waves in Random Media 122.2. Aharonov-Bohm Oscillations 132.2.1. hc=e 132.2.2. hc=2e 152.3. Variations in Random Potential 162.4. Diffusion 172.5. Thouless Approach 193. Scaling Theory of Localization 204. Perturbation Theory of Disordered Metals 224.1. Green Functions 224.2. Random Potential 234.3. Diagrammatics 244.4....

Boris L. Altshuler; B. D. Simons

1985-01-01

171

Discrete gauge symmetry in continuum theories  

SciTech Connect

We point out that local symmetries can masquerade as discrete global symmetries to an observer equipped with only low-energy probes. The existence of the underlying local gauge invariance can, however, result in observable Aharonov-Bohm-type effects. Black holes can therefore carry discrete gauge charges: a form of nonclassical ''hair.'' Neither black-hole evaporation, wormholes, nor anything else can violate discrete gauge symmetries. In supersymmetric unified theories such discrete symmetries can forbid proton-decay amplitudes that might otherwise be catastrophic.

Krauss, L.M.; Wilczek, F.

1989-03-13

172

Test of the He-McKellar-Wilkens topological phase by atom interferometry. I. Theoretical discussion  

NASA Astrophysics Data System (ADS)

We have recently tested the topological phase predicted by He and McKellar and by Wilkens: this phase appears when an electric dipole propagates in a transverse magnetic field. In the present paper, we first recall the physical origin of this phase and its relations to the Aharonov-Bohm and Aharonov-Casher phases. We then explain possible detection schemes and we briefly describe the lithium atom interferometer we have used for this purpose. Finally, we analyze in great detail the phase shifts induced by electric and magnetic fields acting on such an interferometer, taking into account experimental defects. The experiment and its results are described in the following paper.

Lepoutre, S.; Gauguet, A.; Büchner, M.; Vigué, J.

2013-10-01

173

Gravitation: global formulation and quantum effects  

NASA Astrophysics Data System (ADS)

A non-integrable phase-factor global approach to gravitation is developed by using the similarity of teleparallel gravity to electromagnetism. The phase shifts of both the COW and the gravitational Aharonov Bohm effects are obtained. It is then shown, by considering a simple slit experiment, that in the classical limit the global approach yields the same result as the gravitational Lorentz force equation of teleparallel gravity. It represents, therefore, the quantum mechanical version of the classical description provided by the gravitational Lorentz force equation. As teleparallel gravity can be formulated independently of the equivalence principle, it will consequently require no generalization of this principle at the quantum level.

Aldrovandi, R.; Pereira, J. G.; Vu, K. H.

2004-01-01

174

General relativity in electrical engineering  

NASA Astrophysics Data System (ADS)

In electrical engineering metamaterials have been developed that offer unprecedented control over electromagnetic fields. Here, we show that general relativity provides the theoretical tools for designing devices made of such versatile materials. Given a desired device function, the theory describes the electromagnetic properties that turn this function into fact. We consider media that facilitate space-time transformations and include negative refraction. Our theory unifies the concepts operating behind the scenes of perfect invisibility devices, perfect lenses, the optical Aharonov Bohm effect and electromagnetic analogues of the event horizon, and may lead to further applications.

Leonhardt, Ulf; Philbin, Thomas G.

2006-10-01

175

Luttinger liquid theory of Coulomb drag in mesoscopic rings,(Supported in part by US DOE.)  

NASA Astrophysics Data System (ADS)

We develop a Luttinger liquid theory of the Coulomb drag of persistent currents, flowing in concentric mesoscopic rings, by incorporating non-linear corrections to the electron dispersion relation. We demonstrate that at low temperatures interactions between electrons in different rings generate an additional phase and thus alter the period of Aharonov-Bohm oscillations. The resulting nondissipative(A. G. Rojo and G. D. Mahan, Phys. Rev. Lett. 68) 2074 (1992). drag depends strongly on the relative parity of the electron numbers. We also show that interactions set a new temperature scale below which the linear response theory does not apply at certain values of external flux.

Shahbazyan, T. V.; Ulloa, S. E.

1997-03-01

176

Adiabatic tracking of a state: a new route to nonequilibrium physics.  

PubMed

We present a novel numerical approach to track the response of a quantum system to an external perturbation that is progressively switched on. The method is applied, within the framework of the density matrix renormalization group technique, to track current-carrying states of interacting fermions in one dimension and in the presence of an Aharonov-Bohm magnetic flux. This protocol allows us to access highly excited states. We also discuss the connection with the entanglement entropy of these excited states. PMID:24093238

Moliner, M; Schmitteckert, P

2013-09-20

177

Cloaking two-dimensional fermions  

SciTech Connect

A cloaking theory for a two-dimensional spin-(1/2) fermion is proposed. It is shown that the spinor of the two-dimensional fermion can be cloaked perfectly through controlling the fermion's energy and mass in a specific manner moving in an effective vector potential inside a cloaking shell. Different from the cloaking of three-dimensional fermions, the scaling function that determines the invisible region is uniquely determined by a nonlinear equation. It is also shown that the efficiency of the cloaking shell is unaltered under the Aharonov-Bohm effect.

Lin, De-Hone [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China)

2011-09-15

178

Field-periodic magnetoresistance oscillations in thin graphite single crystals with columnar defects  

NASA Astrophysics Data System (ADS)

The magnetoresistance of thin graphite single crystals with columnar defects has been studied. The field-periodic contribution to the magnetoresistance with a period of 7.5 T has been revealed. The atomic force microscope estimation of the columnar defect diameter shows that the period of the contribution oscillatory as a function of the flux is close to hc/ e per defect. The result agrees with the measurements of Aharonov-Bohm magnetoresistance oscillations in graphene mesoscopic rings [S. Russo et al., Phys. Rev. B 77, 085413 (2008)].

Latyshev, Yu. I.; Latyshev, A. Yu.; Orlov, A. P.; Shchekin, A. A.; Bykov, V. A.; Monceau, P.; van der Beck, K.; Kontsikovskii, M.; Monnet, I.

2009-11-01

179

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

180

The chiral anomalous Hall effect in PdFe and AuFe alloys  

NASA Astrophysics Data System (ADS)

We have made systematic measurements of the anomalous Hall effect in a PdFe and AuFe alloys. The Hall coefficient Rh has been measured as a function of applied magnetic field and temperature. The experimental results demonstrate that it is necessary to consider a negative contribution in addition to the canonical Karplus-Luttinger term. This difference term can be identified to the theoretically predicted chiral or real space Berry phase term and can be understood in terms of the Aharonov-Bohm-like intrinsic microscopic current loops arising from successive scatterings by canted local spins.

Wolff-Fabris, F.; Pureur, P.; Schaf, J.; Vieira, V.; Campbell, I. A.

2008-04-01

181

Nonquantized Dirac Monopoles and Strings in the Berry Phase of Anisotropic Spin Systems  

NASA Astrophysics Data System (ADS)

The Berry phase of an anisotropic spin system that is adiabatically rotated along a closed circuit C is investigated. It is shown that the Berry phase consists of two contributions: (i) a geometric contribution which can be interpreted as the flux through C of a nonquantized Dirac monopole, and (ii) a topological contribution which can be interpreted as the flux through C of a Dirac string carrying a nonquantized flux, i.e., a spin analogue of the Aharonov-Bohm effect. Various experimental consequences of this novel effect are discussed.

Bruno, Patrick

2004-12-01

182

Anyonlike particles in three dimensions  

NASA Astrophysics Data System (ADS)

We consider particles in three-dimensional space, which have a certain probability to find themselves in a thin layer (``plane''), where they are assumed to be well described by a planar Hamiltonian and are subjected to Aharonov-Bohm-type interaction. We demonstrate that their planar motion is then anyonlike, with the ``effective statistical parameter'' proportional essentially to the square of the probability. We also show that charge-flux composites with solenoids of finite length, provided they are themselves fermions, can form a bound state in which they behave like anyons, without any external potential confining them to a plane.

Gorbar, Edouard; Mashkevich, Stefan; Sharapov, Sergei

1995-12-01

183

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.

2012-01-01

184

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

185

Spatial EM jamming: A countermeasure against EM Analysis?  

Microsoft Academic Search

Electro-Magnetic Analysis has been identified as an efficient technique to retrieve the secret key of cryptographic algorithms. Although similar mathematically speaking, Power or Electro-Magnetic Analysis have different advantages in practice. Among the advantages of EM Analysis, the feasibility of attacking limited and bounded area of integrated systems is the key one. Within this context, the contribution of this paper is

Francois Poucheret; Lyonel Barthe; Pascal Benoit; Lionel Torres; Philippe Maurine; Michel Robert

2010-01-01

186

Alveolar Echinococcosis: Characterization of Diagnostic Antigen Em18 and Serological Evaluation of Recombinant Em18  

PubMed Central

The Echinococcus multilocularis protein Em18 is one of the most promising antigens for use in serodiagnosis of alveolar echinococcosis in human patients. Here we identify an antigenic relationship between Em18 and a 65-kDa immunodominant E. multilocularis surface protein previously identified as either EM10 or EmII/3. The NH2-terminal sequence of native Em18 was determined, revealing it to be a fragment of EM10. Experiments were undertaken to investigate the effect of proteinase inhibitors on the degradation of EM10 in crude extracts of E. multilocularis protoscoleces. Em18 was found to be the product of degradation of EM10 by cysteine proteinase. A recombinant Em18 (RecEm18, derived from 349K to 508K of EM10) was successfully expressed by using Escherichia coli expression system and then evaluated for use in serodiagnosis of alveolar echinococcosis. RecEm18 was recognized by 27 (87.1%) and 28 (90.3%) of 31 serum samples from clinically and/or pathologically confirmed alveolar echinococcosis patients by enzyme-linked immunosorbent assay and immunoblotting, respectively. Of 33 serum samples from cystic echinococcosis patients, 1 was recorded as having a weak positive reaction to RecEm18; however, none of the serum samples which were tested from neurocysticercosis patients (n = 10) or healthy people (n = 15) showed positive reactions. RecEm18 has the potential for use in the differential serodiagnosis of alveolar echinococcosis.

Sako, Yasuhito; Nakao, Minoru; Nakaya, Kazuhiro; Yamasaki, Hiroshi; Gottstein, Bruno; Lightowers, Marshall W.; Schantz, Peter M.; Ito, Akira

2002-01-01

187

Žem?s dangos skaitmenini? vaizd? identifikavimo analiz?  

NASA Astrophysics Data System (ADS)

Straipsnyje nagrin?jamas žem?s dangos skaitmenini? vaizd? identifikavimas taikant kovariacini? funkcij? ir Wavelet (bang?) teorij?. Dviej? skaitmenini? vaizd? arba pavieni? vaizd? autokovariacini? funkcij? ?ver?iai skai?iuojami pagal atsitiktines funkcijas, sudarytas iš skaitmenini? vaizd? pikseli? vektori? pavidalu. Pikseli? vektori? ?ver?iai gaunami skleidžiant skaitmenini? vaizd? pikseli? masyvus viena eilute. Tyrimams panaudoti HJ-DEM Ikonos palydoviniai vaizdai, kai kartografin? projekcija n?ra ortografin?, ir skaitmeninio vaizdo ta\\vsk? masteliai skirtingi. Kei?iant skaitmeninio vaizdo mastel? pavieni? pikseli? spalv? bang? dažniai lieka nekintantys, t. y. const, ir kovariacini? funkcij? skai?iavimo proced?rose mastelio kaitos ?taka nepasirei\\vskia. Vaizdams identifikuoti taikytas RGB formato spalv? spektras. Analizuota RGB spektro dedam?j? bei spalv? tenzoriaus ?taka skaitmenini? vaizd? kovariacini? funkcij? ?ver?iams. Skaitmenini? vaizd? tapatumas ?vertinamas pagal koreliacijos koeficient? reikšmi? kait? atitinkam? reikšmi? diapazone, taikant sudaryt? kompiuterin? program?.

Skeivalas, Jonas; Aleknien?, Edita; Ge?yt?, Silvija

2010-01-01

188

Deterministini? ir geostatistini? interpoliavimo metod? taikymas Žem?s paviršiui modeliuoti  

NASA Astrophysics Data System (ADS)

Analizuojamas Žem?s paviršiaus trimatis modeliavimas pagal geodezinius ir fotogrametrinius matavimo duomenis, taikant tiesin?, svorin? ir Kriging interpoliavimo metodus. Interpoliavimo algoritmai pertvarkyti ir pritaikyti MATLAB paketo vykdomajam kodui. Sudarytoji programa Geo3D skirta erdviniams duomenims vaizduoti pagal geodezinius ir fotogrametrinius duomenis. Geo3D programa sudaryti trima?iai Žem?s paviršiaus modeliai ?vertinti bei palyginti su modeliais, sukurtais reljefo vaizdavimo programa WinSurf.

Nareiko, Viktor; Ruzgien?, Birut?; ?selis, Adomas

2010-01-01

189

Three-wave mixing of volume EM, surface EM and surface acoustic waves  

Microsoft Academic Search

The authors have investigated the diffraction of volume EM waves into surface EM waves (or vice versa) by surface acoustic (SA) waves, i.e. the three-wave mixing of volume EM, surface EM and SA waves, using a Kretschmann (prism\\/Ag film\\/air) configuration with the SA waves propagating in the Ag film. The diffraction intensity was measured as a function of the angle

H. Talaat; W. P. Chen; E. Burstein

1982-01-01

190

Surface-sensitive two-dimensional magneto-fingerprint in mesoscopic Bi2Se3 channels.  

PubMed

Periodic Aharonov–Bohm and Altshuler–Aronov–Spivak oscillations have traditionally been observed in lateral transport through patterned mesoscopic loops of diffusive conductors. However, our studies of perpendicular-to-plane magnetotransport in straight-channel, diffusive devices of epitaxial Bi2Se3 surprisingly reveal signatures of Aharonov–Bohm orbits, periodic conductance fluctuation magneto-fingerprints, even though the devices are not explicitly patterned into loops. We show that the length scale of these orbits corresponds to the typical perimeter of triangular terraces found on the surface of these thin film devices, strongly suggesting that the periodic magneto-fingerprint arises from coherent scattering of electron waves from the step-edges. Our interpretation is bolstered by control measurements in devices without such surface morphology that only show a conventional, aperiodic magneto-fingerprint. These results show that lithographically patterned Bi2Se3 devices provide a novel class of mesoscopic physical systems for systematic studies of coherent surface sensitive transport. PMID:23642037

Kandala, Abhinav; Richardella, Anthony; Zhang, Duming; Flanagan, Thomas C; Samarth, Nitin

2013-06-12

191

DOE/EM Criticality Safety Needs Assessment  

SciTech Connect

The issue of nuclear criticality safety (NCS) in Department of Energy Environmental Management (DOE/EM) fissionable material operations presents challenges because of the large quantities of material present in the facilities and equipment that are committed to storage and/or material conditioning and dispositioning processes. Given the uncertainty associated with the material and conditions for many DOE/EM fissionable material operations, ensuring safety while maintaining operational efficiency requires the application of the most-effective criticality safety practices. In turn, more-efficient implementation of these practices can be achieved if the best NCS technologies are utilized. In 2002, DOE/EM-1 commissioned a survey of criticality safety technical needs at the major EM sites. These needs were documented in the report Analysis of Nuclear Criticality Safety Technology Supporting the Environmental Management Program, issued May 2002. Subsequent to this study, EM safety management personnel made a commitment to applying the best and latest criticality safety technology, as described by the DOE Nuclear Criticality Safety Program (NCSP). Over the past 7 years, this commitment has enabled the transfer of several new technologies to EM operations. In 2008, it was decided to broaden the basis of the EM NCS needs assessment to include not only current needs for technologies but also NCS operational areas with potential for improvements in controls, analysis, and regulations. A series of NCS workshops has been conducted over the past years, and needs have been identified and addressed by EM staff and contractor personnel. These workshops were organized and conducted by the EM Criticality Safety Program Manager with administrative and technical support by staff at Oak Ridge National Laboratory (ORNL). This report records the progress made in identifying the needs, determining the approaches for addressing these needs, and assimilating new NCS technologies into EM fissionable material operations. In addition, the report includes projections of future EM needs and associted recommendations.

Westfall, Robert Michael [ORNL; Hopper, Calvin Mitchell [ORNL

2011-02-01

192

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

193

Risco no mercado de arroz em casca  

Microsoft Academic Search

O presente trabalho avaliou as características das séries de retornos, normalmente encontradas em séries financeiras, para dados do mercado de arroz em casca ao produtor do Rio Grande do Sul. Um modelo da classe GARCH (1,1) tipo VaR foi utilizado para obter previsões da variância condicional e verificar o risco incorrido pelas posições comprada e vendida no mercado de arroz

Andreia Cristina de Oliveira Adami; Geraldo SantAna de Camargo Barros

2008-01-01

194

Ambiente e formação estelar em galáxias  

NASA Astrophysics Data System (ADS)

Estudamos o ambiente de galáxias com formação estelar inicialmente a partir de uma amostra limitada em volume proveniente do 2dF Galaxy Redshift Survey. Discriminamos as galáxias com formação estelar com base em distintas classes espectrais, utilizando para esta classificação as larguras equivalentes das linhas [OII]l3727 e Hd. O ambiente é caracterizado pela densidade espacial local de galáxias. Mostramos que a fração de galáxias com formação estelar é bastante reduzida em ambientes densos, enquanto a de galáxias passivas aumenta nestas regiões. Por outro lado, quando analisamos a fração de galáxias que apresentam um surto recente de formação estelar, notamos que ela independe do ambiente, sendo que em regiões mais densas alguns destes objetos apresentam distorções em sua morfologia. Estes resultados são confrontados com a análise da dependência ambiental da taxa de formação estelar, estimada pela emissão em Ha, de uma amostra extraída do Sloan Digital Sky Survey. Um declínio gradual da formação estelar também é observado nesta análise, sugerindo que as interações por efeitos de maré sejam responsáveis pela redução da formação estelar em ambientes densos através da remoção do reservatório de gás das galáxias. No entanto, estas interações também podem induzir surtos de formação estelar nas galáxias, além de peculiaridades morfológicas observadas nos objetos que habitam regiões mais densas.

Mateus, A., Jr.; Sodré, L., Jr.

2003-08-01

195

Evolução química em galáxias compactas azuis (BCGs)  

NASA Astrophysics Data System (ADS)

Neste trabalho, a formação estelar e evolução quí mica em galáxias Compactas Azuis (Blue Compact Galaxies - BCGs) foram estudadas através da comparação de previsões de modelos de evolução quí mica a várias razões de abundância quí mica observadas nestas galáxias. Modelos detalhados com recentes dados de nucleossí ntese e que levam em consideração o papel desempenahdo por supernovas de ambos os tipos (II e Ia) na evolução galáctica foram desenvolvidos para as BCGs permitindo seguir a evolução de vários elementos quí micos (H, D, He, C, N, O, Mg, Si, S, Ca, e Fe). O modelo é caracterizado pelas prescrições adotadas para a formação estelar, a qual ocorre em vários surtos de atividade separados por longos perí odos quiescentes. Após ajustar os melhores modelos aos dados observacionais, as previsões destes modelos foram comparadas também a razões de abundância observadas em sistemas Damped Lyman alpha (DLAs) e a origem do N (primária ou secundária) foi discutida. Alguns dos resultados obtidos são: i) as razões de abundância observadas nas BCGs são reproduzidas por modelos com 2 a 7 surtos de formação estelar com eficiência entre n = 0.2-0.9 Gano-1; ii) os baixos valores de N/O observados nestas galáxias são um resultado natural de uma formação estelar em surtos; iii) os modelos para BCGs podem reproduzir os dados dos DLAs, iv) uma quantidade "baixa" de N primário produzido em estrelas de alta massa pode ser uma explicação para os baixos valores de [N/a] observados em DLAs.

Lanfranchi, G. A.; Matteucci, F.

2003-08-01

196

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

197

Project X RFQ EM Design  

SciTech Connect

Project X is a proposed multi-MW proton facility at Fermi National Accelerator Laboratory (FNAL). The Project X front-end would consist of an H- ion source, a low-energy beam transport (LEBT), a CW 162.5 MHz radio-frequency quadrupole (RFQ) accelerator, and a medium-energy beam transport (MEBT). Lawrence Berkeley National Laboratory (LBNL) and FNAL collaboration is currently developing the designs for various components in the Project X front end. This paper reports the detailed EM design of the CW 162.5 MHz RFQ that provides bunching of the 1-10 mA H- beam with acceleration from 30 keV to 2.1 MeV.

Romanov, Gennady; /Fermilab; Hoff, Matthew; Li, Derun; Staples, John; Virostek, Steve; /LBNL

2012-05-09

198

Manufacturing Methods of Multi-ingredient Compost with EM  

Microsoft Academic Search

This project is performed for increasing the integrated effect of EM by reasonable mixing of EM solution and multi-ingredient compost in agriculture. This compost has been manufactured by treating organic materials with EM and culturing other beneficial bacteria with high density, and by adding some minerals. The organic substrates were fermented by EM. There was a definite difference between organic

H. G. Ryang; M. S. Rim; Y. H. Rim; C. U. Chang; C. G. Kang; D. C. Yang

199

Consumo e Fermentação Ruminal de Proteínas em Função de Suplementação Alimentar Energética e Protéica em Novilhos1  

Microsoft Academic Search

RESUMO - Objetivou-se analisar o efeito de suplementação energética sobre o consumo e a fermentação ruminal de proteínas em dois níveis de proteína dietética (6 e 20%). Quatro novilhos mestiços fistulados no rúmen foram utilizados em um quadrado latino e os tratamentos arranjados em um fatorial 2 × 2, em que as dietas testadas constituíram-se de: A. só feno; B.

Natália Guarino; Souza Barbosa; Rogério de Paula Lana; Gulab Newandram Jham; Arnaldo Chaer Borges; Antônio Bento Mâncio; José Carlos Pereira; Juliana Silva Oliveira

200

Fontes de metionina em rações formuladas com base em aminoácidos totais ou digestíveis para frangas de reposição leves e semipesadas  

Microsoft Academic Search

RESUMO - Foram conduzidos dois experimentos com o objetivo de avaliar a utilização de duas fontes de metionina (em pó ou líquida) em rações formuladas com base em aminoácidos digestíveis ou totais para frangas de reposição leves e semipesadas, nas fases inicial (de 1 a 6 semanas de idade) e de crescimento (de 11 a 16 semanas de idade). Em

Luiz Gustavo Rombola; Douglas Emygdio de Faria; Bruno José Deponti; Flávio Henrique Araujo Silva; Daniel Emygdio de Faria Filho; Otto Mack Junqueira

2008-01-01

201

Antibody responses against Em18 and Em16 serodiagnostic markers in alveolar and cystic echinococcosis patients from northwest China.  

PubMed

Western blot analysis was carried out in order to evaluate new serodiagnostic markers, Em18 and Em16, for differentiation of alveolar echinococcosis (AE) from cystic echinococcosis (CE) using 36 serum samples from hydatid patients from Xinjiang, China, where AE and CE are both endemic and one double infection case has been reported. All AE cases except one (5/6) who exhibited a calcified lesion and a single case of double infection showed antibody responses against Em18 and Em16. Some of CE patient sera (6/22) showed antibody response against Em16 except one who showed that against Em18. Analyses of IgG subclass responses against Em18 and Em16 were carried out using all serum samples showing antibody responses against Em18 and/or Em16 (seven CE, five AE, and one AE + CE) and additional samples of three CE and 22 AE from Sichuan, China. IgG4 was the most predominant antibody subclass. Em18 and Em16 were recognized by both IgG4 and IgG1 (in most cases) or by either IgG4 or IgG1 (in minor cases) or by IgG3 (in very rare cases). Neither Em18 nor Em16 was recognized by IgG2 antibodies. The usefulness of Em18 and Em16 as potential new markers for serological differentiation of human AE and CE, respectively, is discussed. PMID:9354966

Ito, A; Wen, H; Craig, P S; Ma, L; Nakao, M; Horii, T; Pang, X L; Okamoto, M; Itoh, M; Osawa, Y; Wang, X G; Liu, Y H

1997-02-01

202

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

203

Naval Electromagnetic (EM) Gun Technology Assessment.  

National Technical Information Service (NTIS)

The Naval Research Advisory Committee was asked in May 2003 to conduct an assessment of the current maturity of electromagnetic (EM) gun technology for the Assistant Secretary of the Navy (Research, Development & Acquisition). Specifically, the Committee ...

J. Bachkosky D. Katz R. Rumpf W. Weldon

2003-01-01

204

Naval Electromagnetic (EM) Gun Technology Assessment.  

National Technical Information Service (NTIS)

The Naval Research Advisory Committee was asked in May 2003 to conduct an assessment of the current maturity of electromagnetic (EM) gun technology for the Assistant Secretary of the Navy (Research, Development & Acquisition). Specifically, the Commit...

J. Bachkosky D. Katz R. Rumpf W. Weldon

2004-01-01

205

Evaluation of Em18-, Em16-, Antigen B-Western blots, Em2 plus-ELISA and four other tests for differential serodiagnosis of alveolar and cystic echinococcosis patients in Poland  

Microsoft Academic Search

Seven alveolar echinococcosis (AE) and 20 cystic echinococcosis (CE) cases in humans, confirmed clinically or pathologically, were analyzed serologically by Em18-, Em16-, Antigen B subunit (8 kDa)-Western blots (Em18-, Em16-, AgB-WBs) and five other serological tests including commercially available Em2plus-ELISA and IHA. Some serologically doubtful AE cases were rechecked parasitologically or histopathologically. In Em18-WB and Em2plus-ELISA, five and four of

Akira Ito; Liang Ma; Malgorzata Paul; Jerzy Stefaniak; Zbigniew S. Pawlowski

1998-01-01

206

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

207

de energia elétrica em equipamentos de energia elétrica em equipamentos de energia elétrica em equipamentos de energia elétrica em equipamentos de energia elétrica em equipamentos utilizados em galpão de frangos de corte utilizados em galpão de frangos de corte utilizados em galpão de frangos de corte utilizados em galpão de frangos de corte utilizados em galpão de frangos de corte  

Microsoft Academic Search

2 FCAV\\/UNESP. Fone: (16) 3209-2637 3 FCAV\\/UNESP. Fone: (16) 3209-2654 Resumo: Resumo: Resumo: Resumo: Resumo: Este trabalho teve por objetivo analisar o consumo e o custo da energia elétrica em um galpão comercial de frangos de corte, durante dois ciclos de criação, inverno e verão. Foram realizadas medidas de consumo dos ventiladores, nebulizadores, lâmpadas e comedouros durante o manejo de

José E. P. Turco; Luiz F. S. A. Ferreira; Renato L. Furlan

208

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 learnersâ 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.

Benesch, Troy

2009-01-01

209

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

210

Risk Communication Within the EM Program  

SciTech Connect

The U.S. Department of Energy Environmental Management program (EM) conducts the most extensive environmental remediation effort in the world. The annual EM budgets have exceeded $6,000,000,000 for approximately ten years and EM has assumed responsibility for the cleanup of the largest DOE reservations (i.e., at Hanford, Washington, Aiken, South Carolina, and Idaho Falls, Idaho) as well as the facilities at Rocky Flats, Colorado and in Ohio. Each of these sites has areas of extensive radioactive and chemical contamination, numerous surplus facilities that require decontamination and removal, while some have special nuclear material that requires secure storage. The EM program has been criticized for being ineffective (1) and has been repeatedly reorganized to address perceived shortcomings. The most recent reorganization was announced in 2001 to become effective at the beginning of the 2003 Federal Fiscal Year (i.e., October 2002). It was preceded by a ''top to bottom'' review (TTBR) of the program (2) that identified several deficiencies that were to be corrected as a result of the reorganization. One prominent outcome of the TTBR was the identification of ''risk reduction'' as an organizing principle to prioritize the activities of the new EM program. The new program also sought to accelerate progress by identifying a set of critical activities at each site that could be accelerated and result in more rapid site closure, with attendant risk, cost, and schedule benefits. This paper investigates how the new emphasis on risk reduction in the EM program has been communicated to EM stakeholders and regulators. It focuses on the Rocky Flats Environmental Technology Site (RFETS) as a case study and finds that there is little evidence for a new emphasis on risk reduction in EM communications with RFETS stakeholders. Discussions between DOE and RFETS stakeholders often refer to ''risk,'' but the word serves as a placeholder for other concepts. Thus ''risk'' communication at RFETS is lively and involves important issues, but often does not inform participants about true ''risk reduction.''

Edelson, M.

2003-02-26

211

Synthesis, characterization and adsorption capacities of microporous titanosilicate EMS3  

Microsoft Academic Search

A titanosilicate, named EMS-3, has been synthesized using the organic base TMAOH (tetramethylammonium hydroxide) and Na ion, as structure directing agents, under hydrothermal conditions. The XRD pattern of EMS-3 contains sharp and broad reflections typical of a partially disordered structure. EMS-3 has low thermal stability, indeed XRD pattern shows a decreased resolution after thermal treatment at 300°C. An amorphous phase

C. Rizzo; A. Carati; R. Millini; G. Bellussi; W. O. Parker Jr.; S. Zanardi

2006-01-01

212

EM21 Retrieval Knowledge Center: Waste Retrieval Challenges  

Microsoft Academic Search

EM-21 is the Waste Processing Division of the Office of Engineering and Technology, within the U.S. Department of Energys (DOE) Office of Environmental Management (EM). In August of 2008, EM-21 began an initiative to develop a Retrieval Knowledge Center (RKC) to provide the DOE, high level waste retrieval operators, and technology developers with centralized and focused location to share knowledge

Andrew P. Fellinger; Michael W. Rinker; Eric J. Berglin; Richard L. Minichan; Micheal R. Poirier; Phillip A. Gauglitz; Bruce A. Martin; Brian K. Hatchell; Eloy Saldivar; O Dennis Mullen; Noel F. Chapman; Beric E. Wells; Peter W. Gibbons

2009-01-01

213

EMS response to an airliner crash.  

PubMed

This report of an aircraft crash at a major airport in Kingston, Jamaica examines the response of the local Emergency Medical Services (EMS). Factors that impacted the response are discussed, and the need for more disaster simulation exercises is highlighted. The objective of this case report was to document the response of EMS personnel to the crash of American Airlines Flight 331, and to utilize the information to examine and improve the present protocol. While multiple errors can occur during a mass-casualty event, these can be reduced by frequent simulation exercises during which various personnel practice and learn designated roles. Efficient triage, proper communication, and knowledge of the roles are important in ensuring the best possible outcome. While the triage system and response of the EMS personnel were effective for this magnitude of catastrophe, more work is needed in order to meet predetermined standards. Ways in which this can be overcome include: (1) hosting more disaster simulation exercises; (2) encouraging more involvement with first responders; and (3) strengthening the links in the local EMS system. Vigorous public education must be instituted and maintained. PMID:22853919

Dasgupta, Shuvra; French, Simone; Williams-Johnson, Jean; Hutson, Rhonda; Hart, Nicole; Wong, Mark; Williams, Eric; Espinosa, Kurdell; Maycock, Celeste; Edwards, Romayne; McCartney, Trevor; Cawich, Shamir; Crandon, Ivor

2012-06-01

214

Áreas de Risco em Manaus: Inventário preliminar  

Microsoft Academic Search

O presente trabalho pautou-se em mapear as ocorrências registradas pela Defesa Civil Municipal (SEMDEC), nos anos de 2005 a 2008, com a finalidade de identificar as áreas mais afetadas por eventos adversos (alagação e deslizamento). Para tanto, foram utilizadas a base cartográfica Google Earth e QGIS. Uma das principais dificuldades foi a localização precisa dos eventos, pois as bases cartográficas

Denise Rodrigues Cruz; Karla R. Mendes Cassiano; Reinaldo Corrêa Costa

2009-01-01

215

O USO DE ANIMAIS EM PESQUISAS CIENTÍFICAS  

Microsoft Academic Search

Historicamente, atividades didáticas e de pesquisa utilizando animais são realizadas desde a Antigüidade. Inicialmente, muitas destas práticas eram executadas por pessoas interessadas em aprofundar o seu conhecimento sobre um determinado assunto, porém, sem a exigência da aplicação de um método sistematizado de investigação. Com o passar do tempo esta sistematização incorporou-se às práticas didático-científicas, sendo realizadas por pessoas capacitadas para

Marcia Mocellin Raymundo; José Roberto Goldim

216

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

217

Modelling and design for PM/EM magnetic bearings  

NASA Technical Reports Server (NTRS)

A mathematical model of a permanent magnet/electromagnet (PM/EM) radially active bearing is presented. The bearing is represented by both a reluctance model and a stiffness model. The reluctance model analyzes the magnetic circuit of the PM/EM bearings. By combining the two models, the performance of the bearing can be predicted given geometric dimensions, permanent magnet strength, and the parameters of the EM coils. The overall bearing design including the PM and EM design is subject to the performance requirement and physical constraints. A study of these requirements and constraints is discussed. The PM design is based on the required magnetic flux for proper geometric dimensions and magnet strength. The EM design is based on the stability and force slew rate consideration, and dictates the number of turns for the EM coils and the voltage and current of the power amplifier. An overall PM/EM bearing design methodology is proposed and a case study is also demonstrated.

Pang, D.; Kirk, J. A.; Anand, D. K.; Johnson, R. G.; Zmood, R. B.

1992-01-01

218

The association between EMS workplace safety culture and safety outcomes  

PubMed Central

Objective Prior studies have highlighted wide variation in EMS workplace safety culture across agencies. We sought to determine the association between EMS workplace safety culture scores and patient or provider safety outcomes. Methods We administered a cross-sectional survey to EMS workers affiliated with a convenience sample of agencies. We recruited these agencies from a national EMS management organization. We used the EMS Safety Attitudes Questionnaire (EMS-SAQ) to measure workplace safety culture and the EMS Safety Inventory (EMS-SI), a tool developed to capture self-reported safety outcomes from EMS workers. The EMS-SAQ provides reliable and valid measures of six domains: safety climate, teamwork climate, perceptions of management, perceptions of working conditions, stress recognition, and job satisfaction. A panel of medical directors, paramedics, and occupational epidemiologists developed the EMS-SI to measure self-reported injury, medical errors and adverse events, and safety-compromising behaviors. We used hierarchical linear models to evaluate the association between EMS-SAQ scores and EMS-SI safety outcome measures. Results Sixteen percent of all respondents reported experiencing an injury in the past 3 months, four of every 10 respondents reported an error or adverse event (AE), and 90% reported safety-compromising behaviors. Respondents reporting injury scored lower on 5 of the 6 domains of safety culture. Respondents reporting an error or AE scored lower for 4 of the 6 domains, while respondents reporting safety-compromising behavior had lower safety culture scores for 5 of 6 domains. Conclusions Individual EMS worker perceptions of workplace safety culture are associated with composite measures of patient and provider safety outcomes. This study is preliminary evidence of the association between safety culture and patient or provider safety outcomes.

Weaver, Matthew D.; Wang, Henry E.; Fairbanks, Rollin J.; Patterson, Daniel

2012-01-01

219

Crosshole EM in steel-cased boreholes  

SciTech Connect

The application of crosshole EM methods through steel well-casing was investigated in theoretical, laboratory and field studies. A numerical code was developed that calculates the attenuation and phase delay of an EM dipole signal propagated through a steel well casing lodged in a homogeneous medium. The code was validated with a scale model and used for sensitivity studies of casing and formation properties. Finally, field measurements were made in an oil field undergoing waterflooding. Our most important findings are that (1) crosshole surveys are feasible using a well pair with one metallic and one non-metallic casing. (2) The casing effect seems be localized within the pipe section that includes the sensor. (3) The effects of the casing can be corrected using simple means and (4) crosshole field data that are sensitive to both formation and casing were acquired in a working environment.

Wilt, M.; Lee, K.H.; Becker, A.; Spies, B.; Wang, B.

1996-07-01

220

Simplex EMS users knock company's service support  

Microsoft Academic Search

Simplex Tape Recorder Co. is not responding fast enough to please some of its energy management system (EMS) users who need service or new parts. The users complain that Simplex load-shedding, time-of-day control, and duty-cycling functions do not compare with the quality of its security and fire functions. Company spokesmen claim that service and parts are available on a 24-hour

Cohn

1982-01-01

221

Telescópio de patrulhamento solar em 12 GHz  

NASA Astrophysics Data System (ADS)

O telescópio de patrulhamento solar é um instrumento dedicado à observação de explosões solares com início de suas operações em janeiro de 2002, trabalhando próximo ao pico de emissão do espectro girossincrotrônico (12 GHz). Trata-se de um arranjo de três antenas concebido para a detecção de explosões e determinação em tempo real da localização da região emissora. Porém, desde sua implementação em uma montagem equatorial movimentada por um sistema de rotação constante (15 graus/hora) o rastreio apresentou pequenas variações de velocidade e folgas nas caixas de engrenagens. Assim, tornou-se necessária a construção de um sistema de correção automática do apontamento que era de fundamental importância para os objetivos do projeto. No segundo semestre de 2002 empreendemos uma série de tarefas com o objetivo de automatizar completamente o rastreio, a calibração, a aquisição de dados, controle de ganhos, offsets e transferência dos dados pela internet através de um projeto custeado pela FAPESP. O rastreio automático é realizado através de um inversor que controla a freqüência da rede de alimentação do motor de rastreio podendo fazer micro-correções na direção leste-oeste conforme os radiômetros desta direção detectem uma variação relativa do sinal. Foi adicionado também um motor na direção da declinação para correção automática da variação da direção norte-sul. Após a implementação deste sistema a precisão do rastreio melhorou para um desvio máximo de 30 segundos de arco, o que está muito bom para este projeto. O Telescópio se encontra em funcionamento automático desde março de 2003 e já conta com várias explosões observadas após a conclusão desta fase de automação. Estamos apresentando as explosões mais intensas do período e com as suas respectivas posições no disco solar.

Utsumi, F.; Costa, J. E. R.

2003-08-01

222

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

223

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

224

Current density waves in open mesoscopic rings driven by time-periodic magnetic fluxes.  

PubMed

Quantum coherent transport through open mesoscopic Aharonov-Bohm rings (driven by static fluxes) have been studied extensively. Here, by using quantum waveguide theory and the Floquet theorem we investigate the quantum transport of electrons along an open mesoscopic ring threaded by a time-periodic magnetic flux. We predicate that current density waves could be excited along such an open ring. As a consequence, a net current could be generated along the lead with only one reservoir, if the lead additionally connects to such a normal-metal loop driven by the time-dependent flux. These phenomena could be explained by photon-assisted processes, due to the interaction between the transported electrons and the applied oscillating external fields. We also discuss how the time-average currents (along the ring and the lead) depend on the amplitude and frequency of the applied oscillating fluxes. PMID:21393680

Yan, Cong-Hua; Wei, Lian-Fu

2010-05-12

225

Numerical finite size scaling approach to many-body localization.  

PubMed

We develop a numerical technique to study Anderson localization in interacting electronic systems. The ground state of the disordered system is calculated with quantum Monte Carlo simulations while the localization properties are extracted from the "Thouless conductance" g, i.e., the curvature of the energy with respect to an Aharonov-Bohm flux. We apply our method to polarized electrons in a two-dimensional system of size L. We recover the well-known universal beta(g)=dlogg/dlogL one parameter scaling function without interaction. Upon switching on the interaction, we find that beta(g) is unchanged while the system flows toward the insulating limit. We conclude that polarized electrons in two dimensions stay in an insulating state in the presence of weak to moderate electron-electron correlations. PMID:18352582

Fleury, Geneviève; Waintal, Xavier

2008-02-22

226

Effect of an electric field on the nonlinear optical rectification of a quantum ring  

NASA Astrophysics Data System (ADS)

We have studied the effects of an external electric field on the nonlinear optical rectification of a semiconductor quantum ring. An electric field applied in the ring plane destroys the rotational invariance. Calculations are performed by using the matrix diagonalization method and the compact density-matrix approach within the effective-mass approximation. The results indicate that an increase of electric field gives the red shift of the peak positions of nonlinear optical rectification. The roles of ring size and magnetic field strength as control parameters on this nonlinear property have been investigated. Our results show rich nonlinear optical rectification for quantum rings in the presence of electric fields, which effectively displays the signature of the Aharonov-Bohm oscillation.

Xie, Wenfang

2014-06-01

227

Observation of New Superconductivity and Performance Improvement by Employing Cyclotron of Electron Pairs  

NASA Astrophysics Data System (ADS)

A novel temperature-independent superconducting device that employs a doped semiconductor is presented in this study. The underlying theory of this superconductivity is confirmed by experimental results. Specifically, superconductivity generates a negative electric field with characteristics of both electrostatic and current-induced fields. This type of electric field creates a new paired interaction between two electrons and implies the existence of a new force. The negative electric field also exhibits the Meissner effect. Moreover, magnetic flux quanta are produced in the semiconductor. The Aharonov-Bohm effect is exhibited to create a superconducting current along the electric circuit of the superconducting system. Therefore, a load introduced to the circuit will also become superconductive. This finding has strong potential for practical applications. To solve the problem of critical current, a static magnetic field is applied. This field combines with the new electric field to yield cyclotron motion, which increases superconducting current.

Ishiguri, Shinichi

2013-05-01

228

Shot noise in the hybrid triple-quantum-dot interferometer coupled to superconductor and normal terminals  

NASA Astrophysics Data System (ADS)

The shot noise of a hybrid triple-quantum-dot (TQD) interferometer has been investigated by employing the nonequilibrium Green's function method, and the general shot noise formula has been derived. The oscillation behaviors of transmission coefficients and shot noise versus the Aharonov–Bohm phase ? exhibit asymmetric Fano resonance structure and blockade effect. Sub-Poissonian and super-Poissonian behaviors of shot noise appear in different regimes of terminal bias eV? contributed by the Andreev reflection, and correlation of Andreev tunneling with the normal electron transport. The inverse resonance and resonance structures emerge in the shot noise and Fano factor with respect to one of the gate voltages in different regimes of eV?. The asymmetric structure can be enhanced by modifying the energy levels and gate biases of the TQD. The self-correlation and cross-correlation of current components contribute to the enhancement and suppression of shot noise.

Zhao, Hong-Kang; Wang, Jian; Wang, Qing

2014-04-01

229

NRG study of the transmission phase shift through a two-level quantum dot with Kondo correlations  

NASA Astrophysics Data System (ADS)

The transmission phase shift through a Kondo quantum dot has been predicted to take the universal value ?/2 in the center of the Kondo valleyfootnotetextU. Gerland et al., Phys. Rev. Lett., 84, 3710 (2000).. Several experimental studies using a quantum dot embedded in an Aharonov-Bohm ring have aimed to check this prediction, which was finally verified in footnotetextM. Zaffalon et al., Phys. Rev. Lett., 100, 226601 (2008).. A recent experimentfootnotetextS. Takada et al., to be published (2012). has obtained particularly clean results for the transmission phase shift by eliminating the effect of backscattering. We provide a Numerical Renormalization Group study of a two-level quantum that shows very good qualitative agreement with these new experimental results. The effect of the second level, with width different from the first, is crucial for accounting for some of the observed experimental details.

Alex, Arne; Weichselbaum, Andreas; von Delft, Jan

2013-03-01

230

Photon-assisted Shot noise of the double quantum dot interferometer in weak Kondo regime  

NASA Astrophysics Data System (ADS)

The shot noise of a parallel double quantum dot (DQD) system under the perturbation of microwave fields is investigated in the weak Kondo regime. Peak-valley structures exhibit in the differential conductance and shot noise, and side resonant peaks emerge around the Kondo peak due to the absorption and emission of photons. The shot noise is sensitively dependent on the adjusting approach through changing the gate voltages. Large resonant Fano factor accompanying photon-induced side peaks appear by simultaneously varying the two gate voltages. The photon suppression and enhancement of shot noise have been evaluated corresponding to the coherent and incoherent current correlation. The destructive interference causes the suppression of shot noise by changing the Aharonov-Bohm phase.

Zhao, Li-Li; Zhao, Hong-Kang; Wang, Jian

2012-05-01

231

Coulomb stability of the 4?-periodic Josephson effect of Majorana fermions  

NASA Astrophysics Data System (ADS)

The Josephson energy of two superconducting islands containing Majorana fermions is a 4?-periodic function of the superconducting phase difference. If the islands have a small capacitance, their ground state energy is governed by the competition of Josephson and charging energies. We calculate this ground-state energy in a ring geometry, as a function of the flux ? enclosed by the ring, and show that the dependence on the Aharonov-Bohm phase 2e?/? remains 4? periodic regardless of the ratio of charging and Josephson energies—provided that the entire ring is in a topologically nontrivial state. If part of the ring is topologically trivial, then the charging energy induces quantum phase slips that restore the usual 2? periodicity.

van Heck, B.; Hassler, F.; Akhmerov, A. R.; Beenakker, C. W. J.

2011-11-01

232

Coulomb stability of the 4?-periodic Josephson effect of Majorana fermions  

NASA Astrophysics Data System (ADS)

The Josephson energy of two superconducting islands containing Majorana fermions is a 4?-periodic function of the superconducting phase difference. If the islands have a small capacitance, their ground state energy is governed by the competition of Josephson and charging energies. We calculate this ground state energy in a ring geometry, as a function of the flux ? enclosed by the ring, and show that the dependence on the Aharonov-Bohm phase 2e?/ remains 4?-periodic regardless of the ratio of charging and Josephson energies---provided that the entire ring is in a topologically nontrivial state. If part of the ring is topologically trivial, then the charging energy induces quantum phase slips that restore the usual 2?-periodicity [B. van Heck, F. Hassler, A. R. Akhmerov, and C. W. J. Beenakker, Phys. Rev. B 84, 180502(R) (2011)].

Hassler, Fabian; van Heck, Bernard; Akhmerov, Anton R.; Beenakker, C. W. J.

2012-02-01

233

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

234

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES Magnetic Manipulation of Massless Dirac Fermions in Graphene Quantum Dot  

NASA Astrophysics Data System (ADS)

We have theoretically analyzed the quasibound states in a graphene quantum dot (GQD) with a magnetic flux ? in the centre. It is shown that the two-fold time reversal degeneracy is broken and the quasibound states of GQD with positive/negative angular momentum shifted upwards / downwards with increasing the magnetic flux. The variation of the quasibound energy depends linearly on the magnetic flux, which is quite different from the parabolic relationship for Schrödinger electrons. The GQD's quasibound states spectrum shows an obvious Aharonov—Bohm (AB) oscillations with the magnetic flux. It is also shown that the quasibound state with energy equal to the barrier height becomes a bound state completely confined in GQD.

Lin, Xin; Pan, Hui; Xu, Huai-Zhe

2010-12-01

235

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Spin-Dependent Electron Properties of a Triple-Terminal Quantum Dot Structure  

NASA Astrophysics Data System (ADS)

Electron transport properties of a triple-terminal Aharonov-Bohm interferometer are theoretically studied. By applying a Rashba spin-orbit coupling to a quantum dot locally, we find that remarkable spin polarization comes about in the electron transport process with tuning the structure parameters, i.e., the magnetic flux or quantum dot levels. When the quantum dot levels are aligned with the Fermi level, there only appear spin polarization in this structure by the presence of an appropriate magnetic flux. However, in absence of magnetic flux spin polarization and spin separation can be simultaneously realized with the adjustment of quantum dot levels, namely, an incident electron from one terminal can select a specific terminal to depart from the quantum dots according to its spin state.

Han, Yu; Gong, Wei-Jiang; Wei, Guo-Zhu

2009-12-01

236

Antiresonance and bound states in the continuum in electron transport through parallel-coupled quantum-dot structures.  

PubMed

In this paper we make a theoretical study of electron transport through a multi-quantum-dot system, in which the peripheral quantum dots of a one-dimensional chain are embodied in the two arms of an Aharonov-Bohm interferometer. It is found that, in the absence of magnetic flux, all the even molecule states of odd-numbered quantum-dot structures decouple from the leads and in even-numbered quantum-dot systems all the odd molecule states decouple from the leads, which indicates the formation of remarkable bound states in the continuum. Meanwhile, what is interesting is that apparent antiresonance occurs in electron transport through this structure, the positions of which are accordant with all even (odd) eigenenergies of the sub-molecule of the even (odd)-numbered quantum dots without the peripheral dots. All these results are efficiently modified by the presence of magnetic flux through this system. PMID:21825434

Gong, Weijiang; Han, Yu; Wei, Guozhu

2009-04-29

237

Experimental realization of strong effective magnetic fields in an optical lattice.  

PubMed

We use Raman-assisted tunneling in an optical superlattice to generate large tunable effective magnetic fields for ultracold atoms. When hopping in the lattice, the accumulated phase shift by an atom is equivalent to the Aharonov-Bohm phase of a charged particle exposed to a staggered magnetic field of large magnitude, on the order of 1 flux quantum per plaquette. We study the ground state of this system and observe that the frustration induced by the magnetic field can lead to a degenerate ground state for noninteracting particles. We provide a measurement of the local phase acquired from Raman-induced tunneling, demonstrating time-reversal symmetry breaking of the underlying Hamiltonian. Furthermore, the quantum cyclotron orbit of single atoms in the lattice exposed to the magnetic field is directly revealed. PMID:22243087

Aidelsburger, M; Atala, M; Nascimbène, S; Trotzky, S; Chen, Y-A; Bloch, I

2011-12-16

238

Optical conductivity of curved graphene.  

PubMed

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 ?100 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. Furthermore, 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. PMID:24759188

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

2014-05-01

239

Confined electronic states and their modulations in graphene nanorings  

NASA Astrophysics Data System (ADS)

Confined electronic states in quantum rings formed by spatially modulated finite Dirac gap (FDGQR) in graphene are systematically studied by series-expansion method, and are compared with those in infinite-mass-boundary and one-dimensional quantum rings. The shape-size effect of FDGQR is illustrated to be distinct from that in graphene quantum dots. The Aharonov-Bohm effect in FDGQR is clearly shown by the energy spectrum and the optical-transition probabilities. The FDGQR coupled with the electrostatic-potential induced nanoring is found useful for modulating the Dirac electronic states and the optical-transition probabilities. These results may help us to understand and to control the quantum behaviors of confined electronic states in graphene.

Zhu, Jia-Lin; Wang, Xingyuan; Yang, Ning

2012-09-01

240

Noise thermometry in narrow two-dimensional electron gas heat baths connected to a quasi-one-dimensional interferometer  

NASA Astrophysics Data System (ADS)

Thermal voltage noise measurements are performed in order to determine the electron temperature in nanopatterned channels of a GaAs/AlGaAs heterostructure at bath temperatures of 4.2 and 1.4 K. Two narrow two-dimensional (2D) heating channels are connected by a quasi-1D quantum interferometer. Under dc current heating of the electrons in one heating channel, we perform cross-correlated noise measurements locally in the directly heated channel and nonlocally in the other channel, which is indirectly heated by hot electron diffusion across the quasi-1D connection. The temperature dependence of the electron energy-loss rate is reduced compared to wider 2D systems. Under nonlocal current heating, which establishes a thermal gradient across the quantum interferometer, we show the decoherence in this structure by Aharonov-Bohm measurements.

Buchholz, Sven S.; Sternemann, Elmar; Chiatti, Olivio; Reuter, Dirk; Wieck, Andreas D.; Fischer, Saskia F.

2012-06-01

241

Time-dependent solutions to the Dirac equation for interacting systems  

NASA Astrophysics Data System (ADS)

Time-dependent solutions to the minimally-coupled Dirac equation are obtained numerically using the staggered leap-frog method. The systems studied include: (1) Electromagnetically mutually interacting fermion-antifermion pairs propagating in free space and in medium representing mesons that undergo electromagnetic dissociation. The stability of the algorithm is challenged by the presence of time-retarded potentials generated by the 4-dimentional, fermionic currents. (2) Fermions interacting with fixed solenoidal magnetic vector potentials giving rise to a time-dependent Aharonov-Bohm effect especially inside quantum rings. The resulting interference patterns are evaluated to study the induced action. (3) Self-interacting fermions, emitting and re-absorbing photons. Their dynamic mass renormalization is studied and the ensuing problem of numerical stability and convergence is discussed.

Petridis, Athanasios; Kertzman, Zachary; Win, Khinlay

2008-10-01

242

Optical conductivity of curved graphene  

NASA Astrophysics Data System (ADS)

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 ?100 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. Furthermore, 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.

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

2014-05-01

243

Locally induced quantum interference in scanning gate experiments  

NASA Astrophysics Data System (ADS)

We present conductance measurements of a ballistic circular cavity influenced by a scanning gate. In contrast to previous studies, we demonstrate the use of scanning gate microscopy as a tool for tailoring the potential landscape of nanostructures with a high degree of control. When the tip depletes the electron gas below, we observe very pronounced and regular fringes covering the entire cavity. The fringes correspond to transmitted modes in constrictions formed between the tip-induced potential and the boundaries of the cavity. Moving the tip and counting the fringes gives us exquisite control over the transmission of these constrictions. We use this control to form a quantum ring with a specific number of modes in each arm showing the Aharonov–Bohm effect in low-field magnetoconductance measurements.

Kozikov, A. A.; Steinacher, R.; Rössler, C.; Ihn, T.; Ensslin, K.; Reichl, C.; Wegscheider, W.

2014-05-01

244

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

245

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

246

Mesoscopic Fano effect modulated by Rashba spin orbit coupling and external magnetic field  

NASA Astrophysics Data System (ADS)

By employing non-equilibrium Green's function method, the mesoscopic Fano effect modulated by Rashba spin orbit (SO) coupling and external magnetic field has been elucidated for electron transport through a hybrid system composed of a quantum dot (QD) and an Aharonov Bohm (AB) ring. The results show that the orientation of the Fano line shape is modulated by the Rashba spin orbit interaction kL variation, which reveals that the Fano parameter q will be extended to a complex number, although the system maintains time-reversal symmetry (TRS) under the Rashba SO interaction. Furthermore, it is shown that the modulation of the external magnetic field, which is applied not only inside the frame, but also on the QD, leads to the Fano resonance split due to Zeeman effect, which indicates that the hybrid is an ideal candidate for the spin readout device.

Yuan, R. Y.; Wang, R. Z.; Duan, Z. Q.; Song, X. M.; Wang, B.; Yan, H.

2007-05-01

247

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

248

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

249

Galilean covariant models of bosons coupled to a Chern Simons gauge field  

NASA Astrophysics Data System (ADS)

We construct non-relativistic models of complex scalar bosons coupled to Chern-Simons gauge fields by using a Galilean covariant formulation based on the embedding of the (d, 1) Newtonian spacetime into a (d + 1, 1) Minkowski manifold with light-cone coordinates. We also examine various generalizations of the Carroll-Field-Jackiw three-dimensional Chern-Simons term for which the usual Lorentz covariance is broken. Models with cubic Chern-Simons term and non-Abelian gauge fields are briefly discussed. Our main result is the application of this covariant formalism to the investigation of the Aharonov-Bohm effect, for which we retrieve the invariant scattering amplitude up to one-loop.

Abreu, L. M.; de Montigny, M.

2005-11-01

250

A pure spin-current injector of semiconductor quantum dots with Andreev reflection and Rashba spin—orbit coupling  

NASA Astrophysics Data System (ADS)

We propose a four-terminal device consisting of two parallel quantum dots with Rashba spin—orbit interaction (RSOI), coupled to two side superconductor leads and two common ferromagnetic leads, respectively. The two ferromagnetic leads and two quantum dots form a ring threaded by Aharonov—Bohm (AB) flux. This device possesses normal quasiparticle transmission between the two ferromagnetic leads, and normal and crossed Andreev reflections providing conductive holes. For the appropriate spin polarization of the ferromagnetic leads, RSOI and AB flux, the pure spin-up (or spin-down) current without net charge current in the right lead, which is due to the equal numbers of electrons and holes with the same spin-polarization moving along the same direction, can be obtained by adjusting the gate voltage, which may be used in practice as a pure spin-current injector.

Ye, Cheng-Zhi; Nie, Yi-Hang; Liang, Jiu-Qing

2011-12-01

251

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.

2013-01-01

252

The Chiral Anomalous Hall Effect in re-entrant AuFe alloys.  

NASA Astrophysics Data System (ADS)

The Hall Effect has been studied in a series of AuFe samples in the re-entrant concentration range, as well as in part of the spin glass range. The Hall coefficient has been measured in function of temperature and applied magnetic field. The present experimental data demonstrate that is indeed a negative contribution in addition to the canonical Karplus-Luttinger term. An anomalous Hall contribution linked to the tilting of the local spins can be identified, confirming theoretical predictions of a novel topological Hall term induced when chirality is present. This effect can be understood in terms of Aharonov-Bohm-like intrinsic current loops arising from successive scatterings by canted local spins. The experimental measurements indicate that the chiral signal persists, meaning scattering within the nanoscopic loops remains coherent, up to temperatures of the order of 150 K.

Fabris, Frederik; Zapf, Vivien; Lacerda, Alex; Pureur, Paulo; Schaf, Jacob; Vieira, Valdemar; Campbell, Ian

2007-03-01

253

Quantal Phase Factors Accompanying Adiabatic Changes  

NASA Astrophysics Data System (ADS)

A quantal system in an eigenstate, slowly transported round a circuit C by varying parameters R in its Hamiltonian hat{H}(R), will acquire a geometrical phase factor exp {i?(C)} in addition to the familiar dynamical phase factor. An explicit general formula for ?(C) is derived in terms of the spectrum and eigenstates of hat{H}(R) over a surface spanning C. If C lies near a degeneracy of hat{H}, ?(C) takes a simple form which includes as a special case the sign change of eigenfunctions of real symmetric matrices round a degeneracy. As an illustration ?(C) is calculated for spinning particles in slowly-changing magnetic fields; although the sign reversal of spinors on rotation is a special case, the effect is predicted to occur for bosons as well as fermions, and a method for observing it is proposed. It is shown that the Aharonov-Bohm effect can be interpreted as a geometrical phase factor.

Berry, M. V.

1984-03-01

254

Magnetoluminescence from trion and biexciton in type-II quantum dot  

PubMed Central

We theoretically investigate optical Aharonov-Bohm (AB) effects on trion and biexciton in the type-II semiconductor quantum dots, in which holes are localized near the center of the dot, and electrons are confined in a ring structure formed around the dot. Many-particle states are calculated numerically by the exact diagonalization method. Two electrons in trion and biexciton are strongly correlated to each other, forming a Wigner molecule. Since the relative motion of electrons are frozen, the Wigner molecule behaves as a composite particle whose mass and charges are twice those of an electron. As a result, the period of AB oscillation for trion and biexciton becomes h/2e as a function of magnetic flux penetrating the ring. We find that the magnetoluminescence spectra from trion and biexciton change discontinuously as the magnetic flux increases by h/2e. PACS: 71.35.Ji, 73.21.-b, 73.21.La, 78.67.Hc

2011-01-01

255

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

256

Current density waves in open mesoscopic rings driven by time-periodic magnetic fluxes  

NASA Astrophysics Data System (ADS)

Quantum coherent transport through open mesoscopic Aharonov-Bohm rings (driven by static fluxes) have been studied extensively. Here, by using quantum waveguide theory and the Floquet theorem we investigate the quantum transport of electrons along an open mesoscopic ring threaded by a time-periodic magnetic flux. We predicate that current density waves could be excited along such an open ring. As a consequence, a net current could be generated along the lead with only one reservoir, if the lead additionally connects to such a normal-metal loop driven by the time-dependent flux. These phenomena could be explained by photon-assisted processes, due to the interaction between the transported electrons and the applied oscillating external fields. We also discuss how the time-average currents (along the ring and the lead) depend on the amplitude and frequency of the applied oscillating fluxes.

Yan, Cong-Hua; Wei, Lian-Fu

2010-05-01

257

The Sagnac effect in conformal Weyl gravity  

NASA Astrophysics Data System (ADS)

We investigate the Sagnac effect, representing the difference in travel time or phase shift observed for relativistic matter or light beams counter-propagating in a rotating interferometer. This is done for the Schwarzschild-like and Kerr-like vacuum solutions of conformal gravity which describe the field around a massive static and rotating object respectively, in the fourth order theory. To do this we employ the formal analogy between the Sagnac and Aharonov-Bohm effects that has been used earlier to study this effect in flat and curved spacetimes in general relativity. In particular we show that the linear term in the static metric of conformal gravity has a diminishing effect on the Sagnac time delay. Moreover using the expression for the Sagnac effect in the rotating Kerr-like spacetime, we show that the detection of the Weyl gravity contributions to the Sagnac time delay in the case of the Earth, lies beyond the capability of current experiments.

Sultana, Joseph

2014-04-01

258

Perfect spin polarization in symmetric two-terminal mesoscopic rings  

NASA Astrophysics Data System (ADS)

Spin-polarized transport through an Aharonov-Bohm (AB) semiconductor mesoscopic ring is investigated in the presence of both the Rashba spin-orbit interaction (RSOI) and the Dresselhaus spin-orbit interaction (DSOI). The ring symmetrically bridges two input and output electrodes. Based on tight-binding model and Green's function formalism, we find that for AB fluxes other than integer or half-integer multiples of the flux quanta the ring acts as a spin selective device with unit efficiency only when the difference between strengths of RSOI and DSOI is nonzero and small. Results of this study can be used to design a nonmagnetic-material-based perfect spin filter.

Heidari Semiromi, Ebrahim

2014-02-01

259

Non-local coupling of two donor-bound electrons  

NASA Astrophysics Data System (ADS)

We report the results of an experiment investigating coherence and correlation effects in a system of coupled donors. Two donors are strongly coupled to two leads in a parallel configuration within a nano-wire field effect transistor. By applying a magnetic field we observe interference between two donor-induced Kondo channels, which depends on the Aharonov-Bohm phase picked up by electrons traversing the structure. This results in a non-monotonic conductance as a function of magnetic field and clearly demonstrates that donors can be coupled through a many-body state in a coherent manner. We present a model which shows good qualitative agreement with our data. The presented results add to the general understanding of interference effects in a donor-based correlated system which may allow us to create artificial lattices that exhibit exotic many-body excitations.

Verduijn, J.; Agundez, R. R.; Blaauboer, M.; Rogge, S.

2013-03-01

260

Magnetoconductance oscillations in graphene antidot arrays  

NASA Astrophysics Data System (ADS)

Epitaxial graphene films have been formed on the C-face of semi-insulating 4H-SiC substrates by a high temperature sublimation process. Nanoscale square antidot arrays have been fabricated on these graphene films. At low temperatures, magnetoconductance in these films exhibits pronounced Aharonov-Bohm oscillations with the period corresponding to magnetic flux quanta added to the area of a single antidot. At low fields, weak localization is observed and its visibility is enhanced by intervalley scattering on antidot edges. At high fields, we observe two distinctive minima in magnetoconductance, which can be attributed to commensurability oscillations between classical cyclotron orbits and antidot array. All mesoscopic features, surviving up to 70 K, reveal the unique electronic properties of graphene.

Shen, T.; Wu, Y. Q.; Capano, M. A.; Rokhinson, L. P.; Engel, L. W.; Ye, P. D.

2008-09-01

261

Electronic and optical properties of core-shell nanowires in a magnetic field  

NASA Astrophysics Data System (ADS)

The electronic and optical properties of zincblende nanowires are investigated in the presence of a uniform magnetic field directed along the [001] growth direction within the \\mathbf {k} \\boldsymbol {\\cdot } \\mathbf {p} method. We focus our numerical study on core-shell nanowires consisting of the III-V materials GaAs, AlxGa1-xAs and (AlyGa1-y)0.51In0.49P. Nanowires with electrons confined in the core exhibit a Fock-Darwin-like spectrum, whereas nanowires with electrons confined in the shell show Aharonov-Bohm oscillations. Thus, by properly choosing the core and the shell materials of the nanowire, the optical properties in a magnetic field can be tuned in very different ways.

Kishore, V. V. Ravi; Partoens, B.; Peeters, F. M.

2014-03-01

262

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

263

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

264

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

265

Modelling of patient EMS exposure: translating pharmacokinetics of EMS in vitro and in animals into patients.  

PubMed

In order to support the toxicological risk assessment for the ethyl methanesulfonate (EMS) exposure of patients ingesting contaminated Viracept tablets (Müller and Singer, 2009), there was a need to correlate the effects observed in in vivo genotoxicity studies with mice to EMS exposure and to estimate human exposure to EMS at the level of contamination of Viracept tablets. The species differences in volume of distribution of EMS, a key factor for determination of its C(max), were small in the species investigated (mouse, rat, monkey), the species differences in clearance, the key factor involved in AUC assessment, were large (Lavé et al., 2009). Because of this uncertainty in extrapolation of clearance across species we used a conservative approach for human exposure predictions in terms of AUC where clearance was assumed to solely reflect the chemical stability of EMS neglecting additional clearance pathways such as metabolism and exhalation. This approach was compared to the estimates obtained from allometric scaling based on rat clearance, the species leading to the lowest clearance predicted in man. We found that both approaches led to nearly identical predictions of the human AUC. Thus, we predict a human AUC of 13 microM h for patients ingesting the most contaminated Viracept tablets, corresponding to a maximal daily intake of 0.055 mg/kg of EMS. The C(max) of EMS in these patients is predicted to be 0.85 microM. In order to provide a basis for toxicological risk assessment, these maximal human AUC and C(max) values are to be compared to the AUC and C(max) values in mice at the EMS dose of 25mg/kg which was found to be the threshold dose for induction of mutagenic effects, i.e. the dose at which no mutagenic effects were observed (Gocke et al., 2009-a). We calculate AUC and C(max) in mice at the threshold dose to be 350 microM h and 315 microM, respectively. Thus we conclude that a large safety factor can be deduced, whatever the basis of comparison, as is discussed in detail by Müller et al. (2009). PMID:19695316

Lavé, Thierry; Paehler, Axel; Grimm, Hans Peter; Gocke, Elmar; Müller, Lutz

2009-11-12

266

Blind subspace-based channel estimation using the EM algorithm  

Microsoft Academic Search

We propose an application of the Expectation-Maximization (EM) algorithm to the problem of blind estimation of single-input multiple-output (SIMO), finite-impulse-response (FIR) channels. We first assume Gaussian input to formulate an EM-based estimation of the signal subspace of the output covariance matrix. This Gaussian assumption allows us to utilize knowledge from EM-based probabilistic principle component analysis (P-PCA). Next, we show that

Koji Harada; Hideaki Sakai

2009-01-01

267

A New Semi-Supervised EM Algorithm for Image Retrieval  

Microsoft Academic Search

One of the main tasks in content-based image retrieval (CBIR) is to reduce the gap between low-level visual features and high-level human concepts. This paper presents a new semi-supervised EM algorithm (NSS-EM), where the image distribution in feature space is modeled as a mixture of Gaussian densities. Due to the statistical mechanism of accumulating and process-ing meta knowledge, the NSS-EM

Anlei Dong; Bir Bhanu

2003-01-01

268

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

269

Immunoblot evaluation of the species-specificity of Em18 and Em16 antigens for serodiagnosis of human alveolar echinococcosis  

Microsoft Academic Search

An immunoblot study to confirm the species-specificity of the diagnostic antigens Em18 and Em16 of Echinococcus multilocularis protoscolex extract showed that both antigens cross-reacted with sera from cystic echinococcosis (CE) patients. The 18 kDa component was detectable by 75% of the sera from active alveolar echinococcosis (AE) patients, while only 31% detected Em16. Western blot analysis also showed that AE

Niroshini Nirmalan; Philip S. Craig

1997-01-01

270

Best Practices for Protecting EMS Responders during Treatment and Transport of Victims of Hazardous Substance Releases.  

National Technical Information Service (NTIS)

OSHA has developed a guide for emergency medical service (EMS) responders who provide medical assistance release. This guide is intended for employers of EMS responders and discusses the measures these employers need to take to protect their EMS responder...

2009-01-01

271

Doenças cerebrovasculares em pacientes entre 15 e 40 anos: achados neuropatológicos em 47 casos  

Microsoft Academic Search

RESUMO - As doenças cerebrovasculares em pacientes entre 15 e 40 anos são pouco estudadas na literatura latino americana, principalmente no que tange aos achados neuropatológicos. Analisamos 47 encéfalos provenientes de necrópsias completas realizadas no período de 1987 a 1997 selecionados com base na faixa etária e alteração neuropatológica básica envolvendo fenômenos vasculares. Destes 47 casos analisados, 26 eram (55,3%)

Everton M. Maggio; Mário R. Montemór-Netto; Emerson L. Gasparetto; Jorge S. Reis-Filho; Fábio A. Tironi; Luiz F. Bleggi Torres

2001-01-01

272

Via de parto em gestações sucessivas em adolescentes: estudo de 714 casos  

Microsoft Academic Search

Objetivo: analisar a associação da via de partos consecutivos de 714 gestantes adolescentes, que pariram na Maternidade do Hospital das Clínicas da Universidade Federal de Pernambuco, no período de janeiro a dezembro de 2001. Pacientes e Métodos: em estudo prospectivo, analítico, transversal, tipo incidência, foi analisada a sucessão das vias de parto da primeira até a quarta gestação de 714

Vamberto Oliveira de Azevedo Maia; Alessandra Costa de Azevedo Maia; Fábio Lima Queiroga; Vamberto Oliveira de Azevedo Maia Filho; Aline Brandão de Araújo; Luís André Marinho Lippo; Rivaldo Mendes de Albuquerque

2004-01-01

273

Communication - An Effective Tool for Implementing ISO 14001/EMS  

SciTech Connect

The Idaho National Engineering and Environmental Laboratory (INEEL) received ISO 14001/EMS certification in June 2002. Communication played an effective role in implementing ISO 14001/EMS at the INEEL. This paper describes communication strategies used during the implementation and certification processes. The INEEL achieved Integrated Safety Management System (ISMS) and Voluntary Protection Program (VPP) Star status in 2001. ISMS implemented a formal process to plan and execute work. VPP facilitated worker involvement by establishing geographic units at various facilities with employee points of contact and management champions. The INEEL Environmental Management System (EMS) was developed to integrate the environmental functional area into its ISMS and VPP. Since the core functions of ISMS, VPP, and EMS are interchangeable, they were easy to integrate. Communication is essential to successfully implement an EMS. (According to ISO 14001 requirements, communication interacts with 12 other elements of the requirements.) We developed communication strategies that integrated ISMS, VPP, and EMS. For example, the ISMS, VPP, and EMS Web sites communicated messages to the work force, such as “VPP emphasizes the people side of doing business, ISMS emphasizes the system side of doing business, and EMS emphasizes the systems to protect the environment; but they all define work, identify and analyze hazards, and mitigate the hazards.” As a result of this integration, the work force supported and implemented the EMS. In addition, the INEEL established a cross-functional communication team to assist with implementing the EMS. The team included members from the Training and Communication organizations, VPP office, Pollution Prevention, Employee and Media Relations, a union representative, facility environmental support, and EMS staff. This crossfunctional team used various communication strategies to promote our EMS to all organization levels and successfully implemented EMS activities through VPP geographic units. In summary, the ISMS and VPP process at the INEEL provided the basic framework of management support and worker involvement to implement our EMS. A cross-functional communication team was established to facilitate the implementation with great success. Communication has been an effective tool for implementing an ISO 14001/EMS at the INEEL.

Rachel Damewood; Bowen Huntsman

2004-04-01

274

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

275

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

10 Energy 2 2014-01-01 2014-01-01 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...

2014-01-01

276

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

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

2014-01-01

277

Tactical EMS: An emerging opportunity in graduate medical education  

Microsoft Academic Search

Objectives: Modification of traditional emergency medical services (EMS) principles and procedures for use in the tactical law enforcement setting is emerging as a subspecialty of emergency medicine. Few opportunities exist to train physicians in the principles of tactical medicine, and no studies demonstrate the effectiveness of physician-level training in tactical EMS. Methods: A standardized eight-hour CONTOMS (Counter Terrorism Operations Medical

William P. Bozeman; Edward R. Eastman

2002-01-01

278

Convergence Properties of the EM Algorithm for Gaussian Mixtures.  

National Technical Information Service (NTIS)

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 expl...

M. Jordan L. Xu

1995-01-01

279

Quality Improvement in EMS: A Unique and Challenging Necessity.  

PubMed

Quality Improvement (QI) is required in all aspects of the healthcare field. Emergency Medical Services (EMS) poses unique QI challenges. This article explores some of these challenges and provides some points to consider when performing QI in EMS services. [Full text available at http://rimed.org/rimedicaljournal-2014-08.asp, free with no login]. PMID:25083952

Tsai, Devin; Choi, Bryan; Sullivan, Francis; Williams, Kenneth A

2014-01-01

280

PROTECTIVE LAYERS OF MEMS FOR ELECTRO MAGNETIC (EM) DEVICES  

Microsoft Academic Search

Recent year's electromagnetic (EM) devices are used more frequently in a network by military as well as civilian applications for communications, navigation, sensing and data storage. This trend leads to an increasing use of EM devices which may result in a complex operation in the future. It creates electronic warfare and disturbances. This process can be prevented by imposing a

Himanshu Shekhar; J. Sam; Jeba Kumar; Joselin Retna Kumar

2009-01-01

281

THE DOE EM SCIENCE AND TECHNOLOGY PROGRAM VISION - AN OVERVIEW  

Microsoft Academic Search

The Department of Energy (DOE) Office of Environmental Management (EM) is in an era of shrinking budgets and increasing scrutiny of the budget that is provided. This is occurring at a time when EM has established a new, aggressive approach to environmental restoration and disposition of legacy waste inventory. This approach, as outlined in the guidance for the Accelerating Cleanup:

J. Walker USDOE

282

As implicações do trabalho em cooperativas de trabalhadores rurais  

Microsoft Academic Search

A cooperativa de trabalho é um meio pelo qual os trabalhadores rurais se organizam e gerenciam suas forças com maior poder de barganha no mercado, para alcançar melhores condições de trabalho, particularmente em situações em que se encontram desprovidos total ou parcialmente de direitos trabalhistas. Enquanto trabalhadores autônomos, por meio da assistência social da cooperativa, os associados podem melhor adequar

Geraldo Magela Braga; Leonardo Pinheiro Deboçã; José Mauro Ferraz Andrade; Rosiane Maria Lima Gonçalves

2007-01-01

283

Antibioticoterapia em Crianças com Pneumonia Antibioticoterapia em Crianças com Pneumonia Antibioticoterapia em Crianças com Pneumonia Antibioticoterapia em Crianças com Pneumonia Antibioticoterapia em Crianças com Pneumonia Therapy with Antibiotics in Childhood Pneumonia  

Microsoft Academic Search

Pneumonia é responsável por elevadas taxas de hospitalização e óbito na faixa etária pediátrica, especialmente em crianças menores de cinco anos. Um grande número de microorganismos pode causar pneumonia na infância; no entanto, há nítido predomínio dos agentes bacterianos, principalmente do Streptococcus pneumoniae, entre os casos fatais. A terapia antimicrobiana é, portanto, um importante meio de controle da mortalidade por

Adriana O. Rocha; Delano S. Valois; Jovita S. Araújo; Lívia M. B. Mendes; Lucas C. S. Oliveira; N. Alcântara

2007-01-01

284

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

285

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

286

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

287

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

288

LAN based data communication in modern energy management systems (EMS)  

SciTech Connect

The use of energy management systems (EMS) demands high reliability, real-time behavior and more and more economical systems. The last demand requires use of inexpensive standard components, whenever possible. The following article discusses realization of EMS, especially system communication, with respect to these constraints. Problems due to conventional use of standardized communication protocols in distributed supervisory systems in general and highly-reliable systems in particular are shown. Multicast communication concepts are presented as solutions, using standardized protocols in a problem specific way. The presented concepts fulfill the necessity of using standard components as well as the specific demands towards EMS.

Dieterle, W.; Kochs, H.D. [Univ. of Duisburg (Germany). Dept. of Computer Science] [Univ. of Duisburg (Germany). Dept. of Computer Science; Dittmar, E. [ABB Netzleittechnik Gmbh, Ladenburg (Germany)] [ABB Netzleittechnik Gmbh, Ladenburg (Germany)

1996-02-01

289

Application of the Chameleon Model to EM Field Momentum  

NASA Astrophysics Data System (ADS)

The Chameleon scalar field model proposed by Khoury and Weltman presents an alternative mechanism for circumventing the constraints from local tests of gravity by mediating a fifth force for cosmological expansion, which could result in experimental signatures detectable through modest improvements of current laboratory set-ups in the vicinity of oscillating matter. In this paper, the oscillation of a dielectric by a crossed EM field is investigated in light of the Chameleon model. An EM excited Chameleon field-force equation is developed and compared to several EM experiments using the Barium Titanate based dielectric material.

Robertson, Glen A.

2008-01-01

290

EMS control chosen instead of refrigeration, HVAC upgrade  

SciTech Connect

A Wisconsin supermarket decided on the basis of costs to install an energy management system (EMS) to improve the store's energy efficiency rather than invest in new refrigerating equipment at this time. When the next remodeling occurs in two years, the store will purchase new equipment using energy savings from the EMS to help defray the costs. The store selected an EMS with distributed processing that can expand to control new equipment. It expects a 22% drop in energy bills and a two-year payback of the $50,000 investment. Details of the system's functions describe some of the 53 control points.

Watson, F.

1984-05-07

291

Síndrome Metabólica em Crianças e Adolescentes Síndrome Metabólica em Crianças e Adolescentes Síndrome Metabólica em Crianças e Adolescentes Síndrome Metabólica em Crianças e Adolescentes Síndrome Metabólica em Crianças e Adolescentes Metabolic Syndrome in Children and Adolescents  

Microsoft Academic Search

A Síndrome Metabólica caracteriza-se pela associação de fatores de risco cardiovascular, como obesidade, resistência à insulina, dislipidemia e hipertensão arterial. Sua prevalência geral em crianças e adolescentes norte-americanos é de 3-4%, mas atinge 28,7% naqueles com Índice de Massa Corpórea (IMC) = percentil 95. Observa-se que os fatores predisponentes à síndrome se manifestam desde a vida intra-uterina. Apesar de bem

Cristhine L. Chagas; Diego G. Figuerôa; Ênio H. Rios; Gérson Carvalho; Gustavo Mascarenhas; Ives D. Barbosa; João M. Braghiroli; João N. Tupiná; Mariana F. Miranda; Naiara A. Fraga; Luis F. Adan

2007-01-01

292

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

293

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

294

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

295

Digital C4I Interoperability: The EM Protection Issue.  

National Technical Information Service (NTIS)

In this paper, a unified protection methodology is applied to a digital mobile C4I platform subjected to several human-generated and nature- generated EM environments and effects. The unclassified values for self-induced electromagnetic interference (EMI)...

R. Pfeffer

2000-01-01

296

Superconducting Electromagnetic Suspension (EMS) System for Grumman Maglev Concept.  

National Technical Information Service (NTIS)

The Grumman developed Electromagnetic Suspension (EMS) Maglev system has the following key characteristics: a large operating airgap--40 mm; levitation at all speeds; both high speed and low speed applications; no deleterious effects on SC coils at low ve...

S. S. Kalsi

1994-01-01

297

E.M. and Hadronic Shower Simulation with Fluka.  

National Technical Information Service (NTIS)

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.

G. Battistoni A. Fasso A. Ferrari J. Ranfit A. Rubbia P. R. Sala

2006-01-01

298

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

299

EM clustering analysis of diabetes patients basic diagnosis index.  

PubMed

Cluster analysis can group similar instances into same group and different instances into different groups. It assigns classes to samples without known the classes in advance. EM clustering algorithm can find number of distributions of generating data and build "mixture models". It identifies groups that are either overlapping or varying sizes and shapes. In this project, by using EM in Weka system, diabetes patient basic diagnosis index data have been analyzed for clustering. PMID:16779444

Wu, Cai; Steinbauer, Jeffrey R; Kuo, Grace M

2005-01-01

300

Preliminary Experiment of EM Technology on Waste Water Treatment  

Microsoft Academic Search

The objective of the experiment was to investigate the effect of EM4 on improving the quality of waste water. The experiment was conducted in two locations of candy factory, viz Nestle and Trebor Companies in Jakarta. The EM4 was treated in laboratory condition to the effluent of waste water of non adjusted pH (pH 4.0) and adjusted pH (pH 7.44)

Gede Ngurah Wididana

301

An LTCC design technique based on FDTD EM simulations  

Microsoft Academic Search

This paper described the Low Technology Co-fired Ceramic (LTCC) design methodology at TMRND based on FDTD EM simulations that are required when designing the RF\\/microwave circuit. In this paper, 3D EM analysis and optimization with Finite Different Time Domain (FDTD) software Empire XcCeltrade from IMST was applied to achieve accurate modeling of the RF\\/microwave circuit using LTCC technology. A multilayer

Zulkifli Ambak; Rosidah Alias; Azmi Ibrahim; Sabrina Mohd Shapee; Samsiah Ahmad; Mohamed Razman Yahya; A. Mat

2007-01-01

302

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

Microsoft Academic Search

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 ~2.75 mg\\/day (~0.055 mg\\/kg\\/day based on 50 kg patient).

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

2009-01-01

303

Electromagnetic divergence correction for 3D anisotropic EM modeling  

NASA Astrophysics Data System (ADS)

Until now, the application of divergence correction has been focusing on the electromagnetic (EM) isotropic modeling. However, in regions where the earth demonstrates strong electrical anisotropy due to lamina or faults saturated with water, the traditional divergence corrections may not be working for EM modeling. In this paper, based on the divergence-free property of the current density, we propose a divergence correction technique to speed up the EM modeling process for a 3D arbitrarily anisotropic earth. The volume current density weighting method is adopted for the discretization of divergence correction, so it can be applied to non-uniform grid model. By enforcing the constraints associated with the divergence-free property, the quasi-minimal residual (QMR) iterations and the total computational time for the EM modeling are largely reduced. Furthermore, we discuss how to divide the QMR process into sections and the influence of the number of iterations and the normalized residual on the solution process. We take a helicopter-borne EM system over a 3D earth with arbitrarily electrical anisotropy as an example to examine the effectiveness of our anisotropic divergence correction technique on the EM modelings.

Liu, Yun-He; Yin, Chang-Chun

2013-09-01

304

Análise da medição do raio solar em ultravioleta  

NASA Astrophysics Data System (ADS)

A medição acurada do raio solar em qualquer banda do espectro eletromagnético é de relevância na formulação e calibração de modelos da estrutura e atmosfera solar. Esses modelos atribuem emissão do contínuo do Sol calmo em microondas à mesma região da linha Ha do Hell. Apresentamos a medição do raio solar em UV com imagens do EIT (Extreme Ultraviolet Image Telescope) entre 1996 e 2002, no comprimento de onda 30,9 nm (Ha do Hell), que se forma na região de transição/cromosfera solar. A técnica utilizada para o cálculo do raio UV foi baseada na transformada Wavelet B3spline. Fizemos um banco de dados com 1 imagem por dia durante o período citado. Obtivemos como resultado o raio médio da ordem de 975.61" e uma diminuição do mesmo para o período citado variando em média -0,45" /ano. Comparamos estes dados com os valores obtidos pelo ROI (Radio Observatório de Itapetinga) em 22/48 GHz e Nobeyama Radio Heliograph em 17 GHz mostrando que os raios médios são muito próximos o que indica que a região de formação nessas freqüências é a mesma conforme os modelos. Comparamos os resultados também com outros índices de atividade solar.

Saraiva, A. C. V.; Giménez de Castro, C. G.; Costa, J. E. R.; Selhorst, C. L.; Simões, P. J. A.

2003-08-01

305

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

PubMed Central

To further evaluate recombinant Em18 antigen (rEm18) for immunodiagnosis of human alveolar echinococcosis, 208 serum samples were examined by enzyme-linked immunosorbent assay (ELISA). To comparatively 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.

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

2003-01-01

306

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

307

Immunoblot evaluation of the species-specificity of Em18 and Em16 antigens for serodiagnosis of human alveolar echinococcosis.  

PubMed

An immunoblot study to confirm the species-specificity of the diagnostic antigens Em18 and Em16 of Echinococcus multilocularis protoscolex extract showed that both antigens cross-reacted with sera from cystic echinococcosis (CE) patients. The 18 kDa component was detectable by 75% of the sera from active alveolar echinococcosis (AE) patients, while only 31% detected Em16. Western blot analysis also showed that AE sera recognized a band in the 18 kDa region of E. granulosus protoscolex extract, which was different from the 16/17 kDa subunit of antigen B. The results suggested that Em18 antigen is present in E. granulosus as well as E. multilocularis, and that some CE patients may have serum antibody against this antigen. PMID:9373662

Nirmalan, N; Craig, P S

1997-01-01

308

A History and Informal Assessment of the <em>Slacker Astronomyem> Podcast  

NASA Astrophysics Data System (ADS)

Slacker Astronomyem> is a weekly podcast that covers a recent astronomical news event or discovery. The show has a unique style consisting of irreverent, over-the-top humor combined with a healthy dose of hard science. According to our demographic analysis, the combination of this style and the unique podcasting distribution mechanism allows the show to reach audiences younger and busier than those reached via traditional channels. We report on the successes and challenges of the first year of the show, and provide an informal assessment of its role as a source for astronomical news and concepts for its approximately 15,500 weekly listeners.

Price, Aaron; Gay, Pamela; Searle, Travis; Brissenden, Gina

309

EM Task 9 - Centrifugal Membrane Filtration  

SciTech Connect

This project is designed to establish the utility of a novel centrifugal membrane filtration technology for the remediation of liquid mixed waste streams at US Department of Energy (DOE) facilities in support of the DOE Environmental Management (EM) program. The Energy and Environmental Research Center (EERC) has teamed with SpinTek Membrane Systems, Inc., a small business and owner of the novel centrifugal membrane filtration technology, to establish the applicability of the technology to DOE site remediation and the commercial viability of the technology for liquid mixed waste stream remediation. The technology is a uniquely configured process that makes use of ultrafiltration and centrifugal force to separate suspended and dissolved solids from liquid waste streams, producing a filtered water stream and a low-volume contaminated concentrate stream. This technology has the potential for effective and efficient waste volume minimization, the treatment of liquid tank wastes, the remediation of contaminated groundwater plumes, and the treatment of secondary liquid waste streams from other remediation processes, as well as the liquid waste stream generated during decontamination and decommissioning activities.

Stevens, B.G.; Stepan, D.J.; Hetland, M.D.

1998-11-01

310

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

311

Emergency medical service (EMS): A unique flight environment  

NASA Technical Reports Server (NTRS)

The EMS flight environment is unique in today's aviation. The pilots must respond quickly to emergency events and often fly to landing zones where they have never been before . The time from initially receiving a call to being airborne can be as little as two to three minutes. Often the EMS pilot is the only aviation professional on site, they have no operations people or other pilots to aid them in making decisons. Further, since they are often flying to accident scenes, not airports, there is often complete weather and condition information. Therefore, the initial decision that the pilot must make, accepting or declining a flight, can become very difficult. The accident rate of EMS helicopters has been relatively high over the past years. NASA-Ames research center has taken several steps in an attempt to aid EMS pilots in their decision making and situational awareness. A preflight risk assessment system (SAFE) was developed to aid pilots in their decision making, and was tested at an EMS service. The resutls of the study were promising and a second version incorporating the lessons learned is under development. A second line of research was the development of a low cost electronic chart display (ECD). This is a digital map display to help pilots maintain geographical orientation. Another thrust was undertaken in conjunction with the Aviation Safety Reporting System (ASRS). This involved publicizing the ASRS to EMS pilots and personnel, and calling each of the reporters back to gather additional information. This paper will discuss these efforts and how they may positively impact the safety of EMS operations.

Shively, R. Jay

1993-01-01

312

Degradation of Benzodiazepines after 120 Days of EMS Deployment.  

PubMed

Abstract 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

313

Astronomia para/com crianças carentes em Limeira  

NASA Astrophysics Data System (ADS)

Em 2001, o Instituto Superior de Ciências Aplicadas (ISCA Faculdades de Limeira) iniciou um projeto pelo qual o Observatório do Morro Azul empreendeu uma parceria com o Centro de Promoção Social Municipal (CEPROSOM), instituição mantida pela Prefeitura Municipal de Limeira para atender crianças e adolescentes carentes. O CEPROSOM contava com dois projetos: Projeto Centro de Convivência Infantil (CCI) e Programa Criança e Adolescente (PCA), que atendiam crianças e adolescentes em Centros Comunitários de diversas áreas da cidade. Esses projetos têm como prioridades estabelecer atividades prazerosas para as crianças no sentido de retirá-las das ruas. Assim sendo, as crianças passaram a ter mais um tipo de atividade - as visitas ao observatório. Este painel descreve as várias fases do projeto, que envolveu: reuniões de planejamento, curso de Astronomia para as orientadoras dos CCIs e PCAs, atividades relacionadas a visitas das crianças ao Observatório, proposta de construção de gnômons e relógios de Sol nos diversos Centros Comunitários de Limeira e divulgação do projeto na imprensa. O painel inclui discussões sobre a aprendizagem de crianças carentes, relatos que mostram a postura das orientadoras sobre a pertinência do ensino de Astronomia, relatos do monitor que fez o atendimento no Observatório e o que o número de crianças atendidas representou para as atividades da instituição desde o início de suas atividades e, em particular, em 2001. Os resultados são baseados na análise de relatos das orientadoras e do monitor do Observatório, registros de visitas e matérias da imprensa local. Conclui com uma avaliação do que tal projeto representou para as Instituições participantes. Para o Observatório, em particular, foi feita uma análise com relação às outras modalidades de atendimentos que envolvem alunos de escolas e público em geral. Também é abordada a questão do compromisso social do Observatório na educação do público em questão.

Bretones, P. S.; Oliveira, V. C.

2003-08-01

314

Thermal Insulation Performance Test with an EM Shielding MLI  

NASA Astrophysics Data System (ADS)

We have conducted a thermal insulation performance test with an EM (electromagnetic) shielding MLI (multi-layer insulator) and have compared its performances with a conventional MLI thermal insulation. The test was done in a vacuum chamber with a liquid nitrogen temperature shroud. The temperatures at various locations in the MLI were measured to obtain their effective emittances. The EM shielding provides an additional layer of copper fabric as an EM shielding layer, inserted in between conventional MLI layers to enhance EM shielding. The shielding MLI will be used for a lunar radar sounder to protect it from noise emitted by other instruments on board of the spacecraft in the SELENE mission, which is a collaboration mission between ISAS and NASDA. The lunar radar sounder has wide-band and highly sensitive radio wave receivers to detect weak signals in a ``noiseless'' environment on the far side of the moon. The desired signals are extremely weak, especially in the range between 1 MHz and 30 MHz. The EM shielding MLI was also tested and confirmed that its shielding effect was desirable in the specified range.

Iida, T.; Iijima, Y.; Nakazawa, S.

2004-06-01

315

International Space Station (ISS) Emergency Mask (EM) Development  

NASA Technical Reports Server (NTRS)

The Emergency Mask (EM) is considered a secondary response emergency Personal Protective Equipment (PPE) designed to provide respiratory protection to the International Space Station (ISS) crewmembers in response to a post-fire event or ammonia leak. The EM is planned to be delivered to ISS in 2012 to replace the current air purifying respirator (APR) onboard ISS called the Ammonia Respirator (AR). The EM is a one ]size ]fits ]all model designed to fit any size crewmember, unlike the APR on ISS, and uses either two Fire Cartridges (FCs) or two Commercial Off-the-Shelf (COTS) 3M(Trademark). Ammonia Cartridges (ACs) to provide the crew with a minimum of 8 hours of respiratory protection with appropriate cartridge swap ]out. The EM is designed for a single exposure event, for either post ]fire or ammonia, and is a passive device that cannot help crewmembers who cannot breathe on their own. The EM fs primary and only seal is around the wearer fs neck to prevent a crewmember from inhaling contaminants. During the development of the ISS Emergency Mask, several design challenges were faced that focused around manufacturing a leak free mask. The description of those challenges are broadly discussed but focuses on one key design challenge area: bonding EPDM gasket material to Gore(Registered Trademark) fabric hood.

Toon, Katherine P.; Hahn, Jeffrey; Fowler, Michael; Young, Kevin

2011-01-01

316

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.

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

2012-01-01

317

Discos de acresção em sistemas Be-X  

NASA Astrophysics Data System (ADS)

Alguns fenômenos de outbursts em Be-X sugerem a existência, mesmo que temporária, de um disco de acresção quando da passagem do objeto compacto pelo periastro orbital. Neste trabalho avaliamos a possibilidade de formação do disco de acresção em sistemas Be+estrela de neutrons e Be+anã branca, e a influência da excentricidade orbital na ocorrência deste fenômeno. Utilizamos a expressão analítica para o momento angular específico da matéria constituinte de um meio em expansão lenta, como é o caso do disco circunstelar das estrelas Be, proposta por Wang(1981), sob a condição básica de que o raio de circularização deva ser maior do que o raio de Alfvén. Concluímos que existe um limite para o período orbital do sistema acima do qual não é possível a formação do disco de acresção, e que este valor aumenta para sistemas com excentricidade orbital maior.

Lopes de Oliveira, R.; Janot-Pacheco, E.

2003-08-01

318

Influence of PCB and Attached Line of Hardware on Electromagnetic (EM) Information Leakage  

NASA Astrophysics Data System (ADS)

Electromagnetic (EM) radiation from information hardware under normal operating conditions can compromise secret information (EM information leakage), for example, operations or processed data contained in the hardware. Methods for analyzing EM radiation with the intention of extracting secret information have been proposed, and EM side-channel attacks on cryptographic hardware are a major concern. This paper investigates how EM information leakage changes with the configuration of information hardware, focusing on the frequency characteristics of the hardware. We assume that frequency characteristics of the EM radiation correspond to physical aspects of the hardware configuration. To address the issue of information leakage, this paper presents a novel analysis of EM radiation from information hardware by using a model circuit board. Through this model we show that the intensity of EM emission can be related to the layout of the hardware.

Hayashi, Yu-Ichi; Ohmura, Kouhei; Mizuki, Takaaki; Sone, Hideaki

319

Analytical Prediction of EM Scattering by Complex Obstacles Within Electrically Large Open Cavities.  

National Technical Information Service (NTIS)

The object of this paper is to describe an analytical technique for predicting the electromagnetic(EM) scattering by complex obstacles within electrically large open waveguide cavities. This topic is of relevance to EM scattering and EMC type applications...

P. H. Pathak

1991-01-01

320

How to migrate a proprietary EMS into an open system  

SciTech Connect

Energy Management Software (EMS) is a proprietary third party product and hence cannot be easily installed. One driving force behind every user`s effort to migrate is the significant need to get away from proprietary systems, including proprietary protocols. Manufacturing message specification (MMS) is an internationally standardized messaging system for exchanging real-time data and supervisory control information between networked devices and/or computer applications. It is independent of the application function being performed and the developer of the device or the application. This paper describes several utility company`s efforts in migrating to MMS-based EMS systems. 4 figs.

Tweedy, J.; McGinnis, D.; Hird, R.; Carr, D.

1996-02-01

321

Waste fuel, EMS may save plant $1M yearly  

SciTech Connect

A mixture of paper trash and coal ash fueling an Erie, Pa. General Electric plant and a Network 90 microprocessor-based energy-management system (EMS) to optimize boiler efficiency will cost about $3 million and have a three-to-four-year payback. Over half the savings will come from the avoided costs of burning plant-generated trash. The EMS system will monitor fuel requirements in the boiler and compensate for changes in steam demand. It will also monitor plant electrical needs and control the steam diverted for cogeneration. (DCK)

Barber, J.

1982-05-24

322

Noninvasive monitoring of CO2 sequestration sites using airborne EM technology  

Microsoft Academic Search

Usage of conventional airborne EM methods for studies related to CO2 sequestration reservoirs have been restricted up to date due to depth and system noise limitations. Recently a family of new EM systems was developed and launched in Canada, allowing superior depth of investigation to that of the conventional EM systems. Depending on the resistivity of the area such systems

V. Kaminski; W. P. Harbert; J. M. Legault

2009-01-01

323

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

324

An On-Line EM Algorithm Applied to Kernel PCA  

Microsoft Academic Search

Kernel principal component analysis (Pca) is a recent method for non-linear feature extraction. Applying kernel Pca to a data set with N patterns requires storing and nding the eigenvectors of a N N kernel matrix. This paper describes how an Expectation-Maximization (Em) algorithm for standard Pca can be adapted to kernel Pca without having to store the kernel matrix. Experimental

Perry Moerland

2000-01-01

325

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

326

Communications technology guidelines for EMS\\/SCADA systems  

Microsoft Academic Search

The purpose of this Guideline Technical Paper is to provide a summary of the different communications technologies available for use or application with EMS\\/SCADA system projects. All of the various communication media are addressed with a brief description along with tables of the advantages and disadvantages of each and recommendations for choosing the most appropriate communication technology. The technologies discussed

Donald J. Marihart

2001-01-01

327

Reservoir characterization and steam flood monitoring with crosshole EM  

SciTech Connect

Crosshole electromagnetic (EM) imaging is applied to reservoir characterization and steam flood monitoring in a central California oil field. Steam was injected into three stacked eastward-dipping, unconsolidated oil sands within the upper 200 m. The steam plume is expected to develop as an ellipse aligned with the regional northwest-southeast strike. EM measurements were made from two fiberglass-cased observation wells straddling the steam injector on a northeast-southwest profile using the LLNL frequency domain crosshole EM system. Field data were collected before the initiation of a steam drive to map the distribution of the oil sands and then 6 and 12 months later to monitor the progress of the steam chest. Resistivity images derived from the EM data before steam injection clearly delineate the distribution and dipping structure on the target oil sands. Difference images, from data collected before and after steam flooding, show resistivity changes that indicate that the steam chest has developed only in the deeper oil sands although steam injection occurred in all three sand layers.

Wilt, M. [Lawrence Livermore National Lab., CA (United States); Torres-Verdin, C. [Univ. of California, Berkeley, CA (United States)

1995-06-01

328

Sobre as bases dos procedimentos investigativos em psicanálise  

Microsoft Academic Search

Resumo O presente trabalho examina as bases da pesquisa psicanalítica. Parte das marcas deixadas nas investigações psicanalíticas pelos procedimentos científicos de disciplinas como a neurologia e a neurofisiologia no século XIX. Em seguida, acompanha o surgimento de um novo objeto, o sujeito do inconsciente, o qual, ainda que requeira operações que mantenham o rigor e a precisão característicos do pensamento

Anna Carolina; Lo Bianco

329

A connection between half-quadratic criteria and EM algorithms  

Microsoft Academic Search

Iteratively Reweighted Least Squares (IRLS) and Residual Steepest descent (RSD) algorithms of robust statistics arise as special cases of half-quadratic schemes . Here, we adopt a statistical framework and we show that both algorithms are instances of the EM algorithm. The augmented dataset respectively involves a scale and a location mixture of Gaussians. The sufficient conditions for the construction cover

Frédéric Champagnat; Jérôme Idier

2004-01-01

330

Germinação de Sementes de Forrageiras em Diferentes Profundidades de Semeadura  

Microsoft Academic Search

3 Aluno de graduação em Agronomia - UNIFENAS Abstract: The experiment was conducted at José do Rosário Vellano University - UNIFENAS, in Alfenas, MG, with the purpose of evaluating the germination of forage seeds at different sowing depths. The experimental design was in randomized blocks with three replicates, four forages plants and four sowing depths being utilized, amounting to 20

Adauton Vilela de Rezende; Hélio Henrique Vilela; Geraldo Benedito de Souza Almeida; Paulo Roberto; Correa Landgraf; Gustavo Augusto Andrade; Paulo de Figueiredo Vieira

331

Debris Avalanche Formation at Kick'em Jenny Submarine Volcano  

Microsoft Academic Search

Kick'em Jenny submarine volcano near Grenada is the most active volcanic center in the Lesser Antilles arc. Multibeam surveys of the volcano by NOAA in 2002 revealed an arcuate fault scarp east of the active cone, suggesting flank collapse. More extensive NOAA surveys in 2003 demonstrated the presence of an associated debris avalanche deposit, judging from their surface morphologic expression

H. Sigurdsson; S. N. Carey; D. Wilson

2005-01-01

332

Transparent EMI Shielding for EM Windows and Domes.  

National Technical Information Service (NTIS)

Shielding from electromagnetic interference (EMI) can be provided for EM windows and domes by application of a thin transparent conductive coating. Indium Tin Oxide (ITO) coatings 0.8 microns thick can be reactively sputtered onto many materials such as g...

W. T. Pawlewicz G. L. Brown R. H. Sobieske D. L. Jones B. L. Woodham

1983-01-01

333

Síndrome da cabeça caída em doença do neurônio motor  

Microsoft Academic Search

RESUMO - A síndrome da cabeça caída é causada por diminuição de força nos músculos extensores do pescoço sendo encontrada em diversas doenças neuro m u s c u l a res, bem como, na esclerose lateral amiotrófica. D e s c revemos o caso de três mulheres com diagnóstico de doença do neurônio motor com quadro clínico de disfagia

Paulo José Lorenzoni; Marcos Christiano Lange; Cláudia S. K. Kay; Luiz G. M. P. de Almeida; Hélio A. G. Teive; Rosana H. Scola; Lineu C. Werneck

2006-01-01

334

ML\\/EM Reconstruction Algorithm for Cosmic Ray Muon Tomography  

Microsoft Academic Search

Highly penetrating cosmic ray muons constantly shower the earth at a rate of about 1 muon per cm2 per minute. We have developed a technique which exploits the multiple Coulomb scattering of these particles to perform non-destructive inspection without the use of artificial radiation. In this paper we present a Maximum Likelihood \\/ Expectation Maximization (ML\\/EM) tomographic reconstruction algorithm designed

Larry Schultz; Gary Blanpied; Konstantin Borozdin; Andrew Fraser; Alexei Klimenko; Nicholas Hengartner; Chris Morris; Christopher Orum; Michael Sossong

2006-01-01

335

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

336

Modified Helical Method for Determining e\\/m  

Microsoft Academic Search

In the helical method a cathode-ray tube is inserted in a solenoid and e\\/m determined from the condition for focusing deflected electrons to a spot on the screen. This has been modified by substituting alternating current in the solenoid and simultaneously supplying a voltage to the deflection plates proportional to the solenoid current. As a result, all electrons move in

Bernard L. Miller

1959-01-01

337

Texas Hold 'em Online Poker: A Further Examination  

ERIC Educational Resources Information Center

Playing Texas Hold 'em Online Poker (THOP) is on the rise. However, there is relatively little research examining factors that contribute to problem gambling in poker players. The aim of this study was to extend the research findings of Hopley and Nicki (2010). The negative mood states of depression, anxiety and stress were found to be linked to…

Hopley, Anthony A. B.; Dempsey, Kevin; Nicki, Richard

2012-01-01

338

Alterações hepáticas em roedores com cisticercos de Taenia taeniformis  

Microsoft Academic Search

RESUMO A Taenia taeniformis é um parasito gastrointestinal, pertencente à classe Cestoda, ordem Cyclophilidea e família Taenidae. Este parasito, infecta roedores e felinos principalmente, embora em circunstância s anormais possa parasitar seres humanos. O objetivo deste trabalho foi relatar alterações nas enzimas hepáticas decorrentes de um surto por cisticercos de Taenia taeniformis no fígado de roedores. Ratos (Rattus norvergicus) e

Aleksandro S. SILVA; Patrícia WOLKMER; Carolina K. TRAESEL

339

Factors associated with the safety of EMS helicopters.  

PubMed

The accident rate for emergency medical service (EMS) helicopters is thought to be approximately twice the rate for other commercial (Part 135) helicopters. This observation has led to numerous news reports and to the publication of conclusions of a National Transportation Safety Board investigation. The data for these reports come from investigations of EMS helicopter accidents and incidents. The authors surveyed all listed civilian EMS helicopter programs to examine both helicopter ambulance mishaps and the number of safely completed missions. Epidemiological methods were then used to compare the safety records of different groups of EMS helicopters. The single most important factor identified was the number of flights made by the program during the study period: busy programs had an eightfold lower accident rate (P less than .0005) and a three-fold lower total mishap (accidents + incidents) rate (P less than .0005) than less active programs. Programs with the ability to fly under instrument flight rules (IFR) at the pilots discretion had no mishaps (P = .044) during the study period. Multivariate analysis shows this IFR capability to be marginally significant as an independent factor (P = .099). PMID:1994933

Low, R B; Dunne, M J; Blumen, I J; Tagney, G

1991-03-01

340

DESENVOLVIMENTO SUSTENTÁVEL E SOJICULTURA EM RORAIMA: TRAJETÓRIAS ANTAGÔNICAS OU CONCILIÁVEIS?  

Microsoft Academic Search

Quando há o entendimento de que crescimento e desenvolvimento são sinônimos, tende-se a prezar uma dimensão do desenvolvimento em detrimento das outras, o que acaba por prejudicar a população por meio de carências nas condições de vida e destruição do meio ambiente principalmente. O ideal do desenvolvimento sustentável surge na tentativa de harmonizar crescimento econômico, igualdade social e preservação ambiental.

Luciana Dal Gianluppi; Paulo Dabdab Waquil

2008-01-01

341

A shape constrained MAP-EM algorithm for colorectal segmentation  

NASA Astrophysics Data System (ADS)

The task of effectively segmenting colon areas in CT images is an important area of interest in medical imaging field. The ability to distinguish the colon wall in an image from the background is a critical step in several approaches for achieving larger goals in automated computer-aided diagnosis (CAD). The related task of polyp detection, the ability to determine which objects or classes of polyps are present in a scene, also relies on colon wall segmentation. When modeling each tissue type as a conditionally independent Gaussian distribution, the tissue mixture fractions in each voxel via the modeled unobservable random processes of the underlying tissue types can be estimated by maximum a posteriori expectation-maximization (MAP-EM) algorithm in an iterative manner. This paper presents, based on the assumption that the partial volume effect (PVE) could be fully described by a tissue mixture model, a theoretical solution to the MAP-EM segmentation algorithm. However, the MAP-EM algorithm may miss some small regions which also belong to the colon wall. Combining with the shape constrained model, we present an improved algorithm which is able to merge similar regions and reserve fine structures. Experiment results show that the new approach can refine the jagged-like boundaries and achieve better results than merely exploited our previously presented MAP-EM algorithm.

Wang, Huafeng; Li, Lihong; Song, Bowen; Han, Fangfang; Liang, Zhengrong

2013-02-01

342

Modelo Conceitual de Segurança para uma Arquitetura Multidomínio em Telemedicina  

Microsoft Academic Search

Resumo - A comunicação e a troca de informações de maneira rápida e segura entre centros hospitalares geograficamente distribuídos tornam-se cada vez mais importantes em um cenário de telemedicina. Nesse contexto, pode-se compartilhar informações clínicas sensíveis, como a história do paciente, a fim de se ob- ter maior qualidade e precisão no atendimento ao paciente, com custos relativos menores. Este

João F. M. Figueiredo; Eduardo P. Serafim; Walber J. A. Silva; Diego S. A. Pizzol; Gustavo H. M. B. Motta

343

Vision: EM-erging Motion-Detecting Circuits.  

PubMed

How does the brain compare visual inputs over space and time to extract motion? Electron microscopic (EM) and molecular analyses reveal a new circuit architecture for motion processing in Drosophila. An offset in the weighting of synaptic connections and differential use of fast and slow nicotinic receptors suggests a mechanism that can implement spatiotemporal comparisons. PMID:24845666

Silies, Marion; Clandinin, Thomas R

2014-05-19

344

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

345

EM calibration based on Post OPC layout analysis  

NASA Astrophysics Data System (ADS)

Design for Manufacturability (DFM) involves changes to the design and CAD tools to help increase pattern printability and improve process control. Design for Reliability (DFR) performs the same to improve reliability of devices from failures such as Electromigration (EM), gate-oxide break down, hot carrier injection (HCI), Negative Bias Temperature Insatiability (NBTI) and mechanical stress effects. Electromigration (EM) occurs due to migration or displacement of atoms as a result of the movement of electrons through a conducting medium. The rate of migration determines the Mean Time to Failure (MTTF) which is modeled as a function of temperature and current density. The model itself is calibrated through failure analysis (FA) of parts that are deemed to have failed due to EM against design parameters such as linewidth. Reliability Verification (RV) of a design involves verifying that every conducting line in a design meets certain MTTF threshold. In order to perform RV, current density for each wire must be computed. Current itself is a function of the parasitics that are determined through RC extraction. The standard practice is to perform the RC extraction and current density calculation on drawn, pre-OPC layouts. If a wire fails to meet threshold for MTTF, it may be resized. Subsequently, mask preparation steps such as OPC and PSM introduce extra features such as SRAFs, jogs,hammerheads and serifs that change their resistance, capacitance and current density values. Hence, calibrating EM model based on pre-OPC layouts will lead to different results compared to post-OPC layouts. In this work, we compare EM model calibration and reliability check based on drawn layout versus predicted layout, where the drawn layout is pre-OPC layout and predicted layout is based on litho simulation of post-OPC layout. Results show significant divergence between these two approaches, making a case for methodology based on predicted layout.

Sreedhar, Aswin; Kundu, Sandip

2010-03-01

346

A Hybrid EM and Monte Carlo EM Algorithm and Its Application to Analysis of Transmission of Infectious Diseases  

PubMed Central

Summary In epidemics of infectious diseases such as influenza, an individual may have one of four possible final states: prior immune, escaped from infection, infected with symptoms, and infected asymptomatically. The exact state is often not observed. In addition, the unobserved transmission times of asymptomatic infections further complicate analysis. Under the assumption of missing at random, data-augmentation techniques can be used to integrate out such uncertainties. We adapt an importance-sampling-based Monte Carlo EM (MCEM) algorithm to the setting of an infectious disease transmitted in close contact groups. Assuming the independence between close contact groups, we propose a hybrid EM-MCEM algorithm that applies the MCEM or the traditional EM algorithms to each close contact group depending on the dimension of missing data in that group, and discuss the variance estimation for this practice. In addition, we propose a bootstrap approach to assess the total Monte Carlo error and factor that error into the variance estimation. The proposed methods are evaluated using simulation studies. We use the hybrid EM-MCEM algorithm to analyze two influenza epidemics in the late 1970s to assess the effects of age and pre-season antibody levels on the transmissibility and pathogenicity of the viruses.

Yang, Yang; Longini, Ira M.; Halloran, M. Elizabeth; Obenchain, Valerie

2012-01-01

347

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.

de Vries, Sjoerd J.; Zacharias, Martin

2012-01-01

348

Composting of rice straw with effective microorganisms (EM) and its influence on compost quality  

PubMed Central

This study aims to assess the effect of EM application on the composting process of rice straw with goat manure and green waste and to evaluate the quality of both compost treatments. There are two treatment piles in this study, in which one pile was applied with EM and another pile without EM. Each treatment was replicated three times with 90 days of composting duration. The parameters for the temperature, pH, TOC and C/N ratio, show that decomposition of organic matter occurs during the 90-day period. The t-test conducted shows that there is a significant difference between compost with EM and compost without EM. The application of EM in compost increases the macro and micronutrient content. The following parameters support this conclusion: compost applied with EM has more N, P and K content (P?EM. Although the Fe in compost with EM is much higher (P?EM, for Zn and Cu, there is no significant difference between treatments. This study suggests that the application of EM is suitable to increase the mineralization in the composting process. The final resultant compost indicated that it was in the range of the matured level and can be used without any restriction.

2013-01-01

349

Erosão em compósitos à base de fibras de vidro\\/kevlar e resina epóxi de uso aeronáutico  

Microsoft Academic Search

Resumo: Este trabalho tem como objetivo principal o estudo e a análise da eficiência de dois diferentes tipos de recobrimentos usados na proteção contra o processo de desgaste por erosão em substratos fabricados em materiais compósitos poliméricos de uso aeronáutico, dando ênfase às peças fabricadas em fibras de vidro \\/ kevlar impregnadas com resina epóxi. Revestimentos protetores baseados em um

Rogério A. Silva; Mirabel C. Rezende

2003-01-01

350

Avaliação do índice de temperatura de globo negro e umidade e desempenho de suínos nas fases de crescimento e terminação criados em sistemas em camas sobrepostas em condições de verão  

Microsoft Academic Search

RESUMO - Um estudo foi realizado com o objetivo de avaliar o sistema de criação em camas sobrepostas de maravalha e de casca de arroz, em comparação ao piso tradicional de concreto e sua influência no desempenho dos animais com base no ITGU (Índice de Temperatura de Globo negro e Umidade), no ganho de peso, no consumo de ração, na

Ilda de Fátima Ferreira Tinôco; Cecília de Fátima Souza; Paulo Armando Victoria de Oliveira; Robson Mendes de Paulo; Josiane Aparecida Campos; Cinara da Cunha Siqueira Carvalho; Marcelo Bastos Cordeiro

2007-01-01

351

Lysis in the well-fixed shell: "hold 'em" or "fold 'em".  

PubMed

Periacetabular osteolysis is the greatest challenge for longevity of total hip arthroplasty. The generation of wear debris from the bearing surface is inevitably going to cause bone loss around the implants. The challenges for the arthroplasty surgeon in managing this problem are: detection, knowing when to intervene surgically, and choosing the best reconstructive option. From a surgical standpoint, the options for addressing osteolysis are: (1) liner exchange with or without bone grafting of lytic lesions; or (2) complete component revision. The advantages of "holding 'em" include a faster surgery, no bony disruption, a quicker recovery for the patient, and cost. The downside of isolated liner exchange is that there is a high rate of instability, there may be incomplete access to the lytic lesions, and the limitations of the existing component. There have been techniques developed to provide access to the retroacetabular lesions, particularly superolaterally via a trap-door technique. Alternatively, other surgeons have advocated injection of bone graft substitutes in the retroacetabular regions to fill osteolytic defects. However, one may not be able to take advantage of newer bearing materials, larger head sizes, or component reposition to improve stability and wear properties. The advantages of a complete component revision are access to lytic lesions, and the ability to modify component position and take advantage of newer technologies. The disadvantages are cost, a longer recovery, and bony disruption. Each method of addressing acetabular osteolysis has compelling reasons to use it; individual patient factors such as component type, size of lesion, and remaining bone will play a role in selecting the treatment. PMID:20839674

Su, Edwin P

2010-09-01

352

EM susceptibility studies and measurements on electro explosive devices  

NASA Astrophysics Data System (ADS)

Electroexplosive devices (EEDs) are susceptible to stray electromagnetic (EM) fields near high-power communications and radar transmitters. Experiments have been carried out to measure the exact susceptibility of EED resistive squibs in pulsed and continuous EM environments, respectively. The susceptibility test procedure consisted of individual measurements of direct current sensitivity (mA); impulse sensitivity; RF impedance measurements; and safety margin calculations. A stray energy monitor was used to evaluate the safe performance of a hybrid weapons system. It is found that the RF sensitivity of the squib was influenced by the transmission characteristics of the transmission line connected to it. RF absorption peaks were observed above the EED sensitivity threshold of 120 MHz. Methods of EMI control are discussed, including: low-pass pin filters; lossy line filters for all dc power line interconnections; and twisting and shielding of the wires.

Deb, G. K.; Mukherjee, M.

353

Magen David Adom--the EMS in Israel.  

PubMed

Israel is a small country with a population of around 7 million. The sole EMS provider for Israel is Magen David Adom (MDA) (translated as 'Red Shield of David'). MDA also carries out the functions of a National Society (similar to the Red Cross) and provides all the blood and blood product services for the country. Nationwide, the organisation responds to over 1000 emergency calls a day and uses doctors, paramedics, emergency medical technicians and volunteers. Local geopolitics has meant that MDA has to be prepared for anything from everyday emergency calls to suicide bombings and regional wars. MDA also prides itself in being able to rapidly assemble and dispatch mobile aid teams to scenes of international disasters. Such a broad range of activities is unusual for a single EMS organisation. PMID:17767990

Ellis, Daniel Y; Sorene, Eliot

2008-01-01

354

Superconducting Electromagnetic Suspension (EMS) system for Grumman Maglev concept  

NASA Technical Reports Server (NTRS)

The Grumman developed Electromagnetic Suspension (EMS) Maglev system has the following key characteristics: a large operating airgap--40 mm; levitation at all speeds; both high speed and low speed applications; no deleterious effects on SC coils at low vehicle speeds; low magnetic field at the SC coil--less than 0.35 T; no need to use non-magnetic/non-metallic rebar in the guideway structure; low magnetic field in passenger cabin--approximately 1 G; low forces on the SC coil; employs state-of-the-art NbTi wire; no need for an active magnet quench protection system; and lower weight than a magnet system with copper coils. The EMS Maglev described in this paper does not require development of any new technologies. The system could be built with the existing SC magnet technology.

Kalsi, Swarn S.

1994-01-01

355

Evolução temporal de discos circunstelares em estrelas Be  

NASA Astrophysics Data System (ADS)

A pesquisa do mecanismo que leva uma estrela do tipo Be a perder massa e formar um envelope circunstelar, nomeado como fenômeno Be, é uma questão em aberto, intrigante, e que adquire contornos interessantes em face às informações espectroscópicas de alta resolução. Nesta última década, consolida-se a idéia de que a forma destes envelopes é de tipo discóide, obedecendo a uma lei Kepleriana de velocidades, e mais ainda, recentemente há evidências de que a distribuição de matéria nestes discos pode assumir um caráter de anel. Medidas de algumas dimensões de discos circunstelares puderam ser obtidas pela análise de espectros de alta resolução e alta relação sinal-ruído para as estrelas Be: alpha Eri (HD 10144, B3Vpe), omicron And (HD 217675, B6IIIpe), e eta Cen (HD el972, B1.5Vne), no período dos anos de 1991 a 2001. Alguns modelos clássicos de envelope predizem uma distribuição de massa que decresce suavemente a partir da superfície estelar. Entretanto, considerando que a separação de picos de emissão em perfis de linhas do HeI e H-alpha, alargados por efeitos cinemáticos, é função do raio estelar e da velocidade rotacional projetada (vsini); nossos resultados sugerem a presença de um anel de matéria circunstelar, que aparece logo após a ejeção do material fotosférico, imediatamente acima da superfície estelar, e que se expande para raios maiores ao longo do tempo, eventualmente desconectando-se da superfície por uma região de densidade de matéria mínima. Tais interpretações revivem a idéia de que anéis de matéria circunstelar podem ser os responsáveis por algumas variabilidades em perfis de linhas de emissão, como as variações V/R.

Fernandes, M. V. M.; Leister, N. V.; Levenhagen, R. S.

2003-08-01

356

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

2014-01-01

357

Integrated EM & Thermal Simulations with Upgraded VORPAL Software  

Microsoft Academic Search

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

D. N. Smithe; D. Karipides; P. Stoltz; G. Cheng; H. Wang

2011-01-01

358

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

359

EMS Mutagenesis in the Pea Aphid Acyrthosiphon pisum  

PubMed Central

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.

Tagu, Denis; Le Trionnaire, Gael; Tanguy, Sylvie; Gauthier, Jean-Pierre; Huynh, Jean-Rene

2014-01-01

360

Partially supervised learning using an EM-boosting algorithm.  

PubMed

Training data in a supervised learning problem consist of the class label and its potential predictors for a set of observations. Constructing effective classifiers from training data is the goal of supervised learning. In biomedical sciences and other scientific applications, class labels may be subject to errors. We consider a setting where there are two classes but observations with labels corresponding to one of the classes may in fact be mislabeled. The application concerns the use of protein mass-spectrometry data to discriminate between serum samples from cancer and noncancer patients. The patients in the training set are classified on the basis of tissue biopsy. Although biopsy is 100% specific in the sense that a tissue that shows itself to have malignant cells is certainly cancer, it is less than 100% sensitive. Reference gold standards that are subject to this special type of misclassification due to imperfect diagnosis certainty arise in many fields. We consider the development of a supervised learning algorithm under these conditions and refer to it as partially supervised learning. Boosting is a supervised learning algorithm geared toward high-dimensional predictor data, such as those generated in protein mass-spectrometry. We propose a modification of the boosting algorithm for partially supervised learning. The proposal is to view the true class membership of the samples that are labeled with the error-prone class label as missing data, and apply an algorithm related to the EM algorithm for minimization of a loss function. To assess the usefulness of the proposed method, we artificially mislabeled a subset of samples and applied the original and EM-modified boosting (EM-Boost) algorithms for comparison. Notable improvements in misclassification rates are observed with EM-Boost. PMID:15032790

Yasui, Yutaka; Pepe, Margaret; Hsu, Li; Adam, Bao-Ling; Feng, Ziding

2004-03-01

361

Parameter estimation of superimposed signals using the EM algorithm  

Microsoft Academic Search

A computationally efficient algorithm for parameter estimation of superimposed signals based on the two-step iterative EM (estimate-and-maximize, with an E step and an M step) algorithm is developed. The idea is to decompose the observed data into their signal components and then to estimate the parameters of each signal component separately. The algorithm iterates back and forth, using the current

MEIR FEDER; EHUD WEINSTEIN

1988-01-01

362

Swine Waste Management Through Kyusei Nature Farming and EM  

Microsoft Academic Search

Ten swine farms were installed waste management systems. Farm size was different from 200 to 3,000 pigs. Pigs were managed under a fully automated system. Treatments were made with 2 x 3 Latin square arrangements. Two seasonal effects were hot summer (25 - 35 0C) and cold winter (10 - -15 0C). Three EM levels were 1:1,000, 1:5,000, 1:10,000 dilution

Sangsoo Sun; Byungjin Ahn; Kyuho Myung; Kwanghyun Kim

363

Transport quantique dans des nanostructures  

NASA Astrophysics Data System (ADS)

Quantum transport in nanostructures This work is devoted to the design, fabrication and magnetotransport investigations of mesoscopic devices. The sample are obtain by e-beam lithography and the measurements are performed at low temperature in a dilution refrigerator in the presence of a magnetic field. We have used MBE grown AlGaAs/GaAs heterojonctions as starting material to fabricate a bipartite tiling of rhombus called mathcal{T}3 lattice. We observe for the first time large amplitude h/e oscillations in this network as compared to the one measured in square lattices of similar size. These oscillations are the signature of a recently predited localization phenomenon induced by Aharonov-Bohm interferences on this peculiar topology. For particular values of the magnetic field the propagation of the electron wave function is bounded in a small number of cells, called Aharonov-Bohm cages. More strikingly, at high magnetic field, h/2e oscillations appear whose amplitude can be much higher than the fundamental period. Their temperature dependence is similar to that of the h/e signal. These observations withdraw a simple interpretation in terms of harmonics generation. The origin of this phenomenon is still unclear and needs more investigations. The influence electrical width of the wire defining the network and so the rule of the number of channels can be studied using a gate deposited over the lattice. In particular we have measured the amplitude dependence of the h/e and h/2e signal versus the gate voltage. Ce travail est consacré à la réalisation d'échantillons mésoscopiques à partir de la lithographie électronique ainsi qu'à leur caractérisation à très basse température en magnétotransport. Nous avons pour cela exploité le gaz bidimensionnel d'électrons situé à l'interface d'une hétérojonction AlGaAs/GaAs pour réaliser un réseau de boucle d'une géométrie particulière baptisée la géométrie mathcal{T}3. Nous avons observé sur cette structure des oscillations de conductance en fonction du flux du champ magnétique de période h/e dont l'amplitude est beaucoup plus importante que celle mesurée sur un réseau carré de même dimension. Cette différence constitue une signature d'un effet de localisation induit par le champ magnétique sur la topologie mathcal{T}3. Pour des valeurs spécifiques du champ magnétique, du fait des interférences destructives Aharonov-Bohm, la propagation des fonctions d'ondes est limitée à un ensemble fini de cellule du réseau appelé cage. De la dépendance en température des oscillations de période h/e mesurées sur le réseau mathcal{T}3 nous avons tiré une longueur caractéristique qui peut être rattachée au périmètre des cages. Un phénomène inattendu fut l'observation, pour des champs magnétiques plus importants, d'un doublement de fréquence des oscillations. Ces oscillations de période h/2e pouvant avoir une amplitude supérieure aux oscillations de période h/e, une interprétation en terme d'harmonique n'est pas possible. Enfin, l'influence de la largeur électrique des fils constituant le réseau et donc celle du nombre de canaux par brin a été étudiée en réalisant des grilles électrostatique. Les variations de l'amplitude des signaux en h/e et h/2e en fonction de la tension de grille ont été mesurés.

Naud, C.

2002-09-01

364

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.

Scheres, Sjors H.W.

2012-01-01

365

EMS-induced cytomictic variability in safflower (Carthamus tinctorius L.).  

PubMed

Seeds of safflower (Carthamus tinctorius L.) were subjected to three treatment durations (3h, 5h and 7h) of 0.5 % Ethyl Methane Sulphonate (EMS). Microsporogenesis was carried out in the control as well as in the treated materials. EMS treated plants showed interesting feature of partial inter-meiocyte chromatin migration through channel formation, beak formation or direct cell fusion. Another interesting feature noticed during the study was the fusion among tetrads due to wall dissolution. The phenomenon of cytomixis was recorded at nearly all the stages of microsporogenesis connecting from a few to several meiocytes. Other abnormalities such as laggards, precocious movement, bridge and non-disjunction of chromosomes were also recorded but in very low frequencies. The phenomenon of cytomixis increased along with the increase in treatment duration of EMS. Cells with these types of cytomictic disturbances may probably result in uneven formation of gametes or zygote, heterogenous sized pollen grains or even loss of fertility in future. PMID:21950142

Srivastava, P; Kumar, G

2011-01-01

366

Improving EM&V for Energy Efficiency Programs (Fact Sheet)  

SciTech Connect

This fact sheet describes the objectives of the U.S. Department of Energy Uniform Methods Project to bring consistency to energy savings calculations in U.S. energy efficiency programs. The U.S. Department of Energy (DOE) is developing a framework and a set of protocols for determining gross energy savings from energy efficiency measures and programs. The protocols represent a refinement of the body of knowledge supporting energy efficiency evaluation, measurement, and verification (EM&V) activities. They have been written by technical experts within the field and reviewed by industry experts. Current EM&V practice allows for multiple methods for calculating energy savings. These methods were developed to meet the needs of energy efficiency program administrators and regulators. Although they served their original objectives well, they have resulted in inconsistent and incomparable savings results - even for identical measures. The goal of the Uniform Methods Project is to strengthen the credibility of energy savings determinations by improving EM&V, increasing the consistency and transparency of how energy savings are determined.

Not Available

2012-07-01

367

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

368

Generalized EM-type reconstruction algorithms for emission tomography.  

PubMed

We provide a general form for many reconstruction estimators of emission tomography. These estimators include Shepp and Vardi's maximum likelihood (ML) estimator, the quadratic weighted least squares (WLS) estimator, Anderson's WLS estimator, and Liu and Wang's multi-objective estimator, and others. We derive a generic update rule by constructing a surrogate function. This work is inspired by the ML-EM (EM, expectation maximization), where the latter naturally arises as a special case. A regularization with a specific form can also be incorporated by De Pierro's trick. We provide a general and quite different convergence proof compared with the proofs of the ML-EM and De Pierro. Theoretical analysis shows that the proposed algorithm monotonically decreases the cost function and automatically meets nonnegativity constraints. We have introduced a mechanism to provide monotonic, self-constraining, and convergent algorithms, from which some interesting existing and new algorithms can be derived. Simulation results illustrate the behavior of these algorithms in term of image quality and resolution-noise tradeoff. PMID:22665503

Teng, Yueyang; Zhang, Tie

2012-09-01

369

Retrospectively exploring the importance of items in the decision to leave the emergency medical services (EMS) profession and their relationships to life satisfaction after leaving EMS and likelihood of returning to EMS.  

PubMed

An exit survey was returned by a sample of 127 respondents in fully compensated positions who left the EMS profession, most within 12 months prior to filling out the exit survey. A very high percentage continued to work after leaving EMS. Respondents were asked to rate the importance of each of 17 items in affecting their decision to leave EMS. A higher than anticipated response to a "not applicable" response choice affected the usability of 8 of these items. Nine of the 17 items had at least 65 useable responses and were used for further analysis. Within these 9, stress/burnout and lack of job challenges had the highest importance in affecting the decision to leave EMS, while desire for better pay and benefits had the lowest importance. Desire for career change was positively related to life satisfaction after leaving EMS and negatively related to likelihood of returning to EMS. Stress/burnout was positively related to life satisfaction after leaving EMS. Study limitations and future research issues are briefly discussed. PMID:21695362

Blau, Gary; Chapman, Susan

2011-01-01

370

What variables affect public perceptions for EMS meeting general community needs?  

PubMed

In the fall, 2010, a phone survey of 928 respondents examined two research questions: does the general public perceive Emergency Medical Services (EMS) as meeting their community needs? And what factors or correlates help to explain EMS meeting community needs? To maximize geographical representation across the contiguous United States, a clustered stratified sampling strategy was used based upon zip codes across the 48 states. Results showed strong support by the sample for perceiving that EMS was meeting their general community needs. 17 percent of the variance in EMS meeting community needs was collectively explained by the demographic and perceptual variables in the regression model. Of the correlates tested, the strongest relationship was found between greater admiration for EMS professionals and higher perception of EMS meeting community needs. Study limitations included sampling households with only landline (no cell) phones, using a simulated emergency situation, and not collecting gender data. PMID:22735824

Blau, Gary; Hochner, Arthur; Portwood, James

2012-01-01

371

A hybrid EM and Monte Carlo EM algorithm and its application to analysis of transmission of infectious diseases.  

PubMed

In epidemics of infectious diseases such as influenza, an individual may have one of four possible final states: prior immune, escaped from infection, infected with symptoms, and infected asymptomatically. The exact state is often not observed. In addition, the unobserved transmission times of asymptomatic infections further complicate analysis. Under the assumption of missing at random, data-augmentation techniques can be used to integrate out such uncertainties. We adapt an importance-sampling-based Monte Carlo Expectation-Maximization (MCEM) algorithm to the setting of an infectious disease transmitted in close contact groups. Assuming the independence between close contact groups, we propose a hybrid EM-MCEM algorithm that applies the MCEM or the traditional EM algorithms to each close contact group depending on the dimension of missing data in that group, and discuss the variance estimation for this practice. In addition, we propose a bootstrap approach to assess the total Monte Carlo error and factor that error into the variance estimation. The proposed methods are evaluated using simulation studies. We use the hybrid EM-MCEM algorithm to analyze two influenza epidemics in the late 1970s to assess the effects of age and preseason antibody levels on the transmissibility and pathogenicity of the viruses. PMID:22506893

Yang, Yang; Longini, Ira M; Halloran, M Elizabeth; Obenchain, Valerie

2012-12-01

372

EMS-CO2 Welding: A New Approach to Improve Droplet Transfer Characteristics and Welding Formation  

Microsoft Academic Search

In this article, to improve the stability of droplet transfer and reduce the spatter of pure carbon dioxide gas shield welding (CO2 welding), we propose a new welding method called EMS-CO2 welding by applying an additional longitudinal electromagnetic field to a CO2 welding process (abbr. EMS-CO2 welding). The characteristics of droplet transfer, welding formation and microstructure between EMS-CO2 welding and

Jian Luo; Qian Luo; Xiangjie Wang; Xiaochuan Wang

2010-01-01

373

An EM Algorithm for Estimating SPECT Emission and Transmission Parameters from Emission Data Only  

Microsoft Academic Search

A maximum-likelihood (ML) expectation-maximization (EM) algorithm (called EM-IntraSPECT) is presented for simultaneously estimating single photon emission computed tomography (SPECT) emission and attenuation parameters from emission data alone. The algorithm uses the activity within the patient as transmission tomography sources, with which attenuation coefficients can he estimated. For this initial study, EM-IntraSPECT was tested on computer-simulated attenuation and emission maps representing

Andrzej Król; James E. Bowsher; Stephen H. Manglos; David H. Feiglin; Martin P. Tornai; F. Deaver Thomas

2001-01-01

374

Comprehensive regional trauma\\/Emergency Medical Services (EMS) delivery systems: The United States experience  

Microsoft Academic Search

The early 1970's, as an outgrowth of the American military experience, several pioneer regional trauma\\/EMS programs showed the way for better planning, organization, and resource deployment for trauma\\/EMS systems in the civilian community. The experience of the mid and late 1970's has brought an even wider implementation and modeling of trauma\\/EMS care systems with identification of specific patient problems, designation

David R. Boyd; R. Adams Cowley

1983-01-01

375

EM-ANN models for microstrip vias and interconnects in dataset circuits  

Microsoft Academic Search

A novel approach for accurate and efficient modeling of monolithic microwave\\/millimeter wave integrated circuit (MMIC) components by using electromagnetically trained artificial neural network (EM-ANN) software modules is presented. Full-wave EM analysis is employed to characterize MMIC components. Structures for simulation are chosen using design of experiments (DOE) methodology. EM-ANN models are then trained using physical parameters as inputs and S-parameters

Paul M. Watson; Kuldip C. Gupta

1996-01-01

376

Effect of PU.1 Phosphorylation on Interaction with NF-EM5 and Transcriptional Activation  

Microsoft Academic Search

PU.1 recruits the binding of a second B cell-restricted nuclear factor, NF-EM5, to a DNA site in the immunoglobulin kappa 3' enhancer. DNA binding by NF-EM5 requires a protein-protein interaction with PU.1 and specific DNA contacts. Dephosphorylated PU.1 bound to DNA but did not interact with NF-EM5. Analysis of serine-to-alanine mutations in PU.1 indicated that serine 148 (Ser148) is required

Jagan M. R. Pongubala; Charles van Beveren; Sujatha Nagulapalli; Michael J. Klemsz; Scott R. McKercher; Richard A. Maki; Michael L. Atchison

1993-01-01

377

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

378

State-dependent classical potentials  

NASA Astrophysics Data System (ADS)

Since the inception of quantum mechanics, the classical limit has been an area of unease. Explanations proposed on this matter include the usage of Plank's constant, the decoherence parameter of the master's equation, or the quantum potential of Bohm's theory. An equally obscure related topic is the mixing of classical and quantum quantities in the dynamical equations. In this thesis, the subject of classical-quantum mixing will be studied. A method will be explored which will demonstrate one of several candidate methods whereby mixing may be removed and replaced by fully quantum non-relativistic equations. Through use of the quantum potential concept and the Feynman path integral, state-dependent forms of the classical scalar and vector potentials will be derived by assuming the existence of separate component wave functions for the particle and potential. The specific wave component psi e attributed to the potential, will hold the effects of an environment. The resulting equations are devoid of classical potentials and can therefore be considered as purely quantum---no mixing takes place. The standard classical potentials emerge from the state-dependent equations by a condition which will be referred to as state-dependence reduction (SDR). Through SDR, the semi-quantum and purely quantum equations are qualitatively and quantitatively equivalent. The new purely quantum equations will be used both to interpret gauge symmetry and to clarify the reasoning behind the Aharonov-Bohm effect. It will be argued that the freedom of gauge is related to the freedom to choose from many different and distinct environments which reproduce the same experimental outcome. Likewise, the AB-effect is understood through the environment from which the topological structure of the electromagnetic field is represented. Several aspects of the environment responsible for the effective potentials will be calculated numerically for well-known physical situations including one-dimensional scattering, two-dimensional double-slit setup, two-dimensional Aharonov-Bohm effect, and the two-dimensional Dirac equation. The proposal of using state-dependent potentials to replace the semi-quantum equation represents a consistent generalization and unification of the quantum and classical potentials, and may offer some experimental results yet untapped.

D'Amico, Mario

379

Efficient injection of spin-polarized electrons from manganese arsenide contacts into aluminum gallium arsenide/gallium arsenide spin LEDs  

NASA Astrophysics Data System (ADS)

In this thesis we describe two spectroscopic projects project on semiconductor heterostructures, as well as putting together and testing a micro-photoluminescence/7 tesla magnet system for the study of micron size two-dimensional crystals. Below we discuss the three parts in more detail. i) MnAs-based spin light emitting diodes. We have studied the injection of spin-polarized electrons from a ferromagnetic MnAs contact into an AlGaAs(n)/GaAs(i)/AlGaAs(p) n-i-p light emitting diode. We have recorder the emitted electroluminescence as function of magnetic field applied at right angles to the device plane in the 7-300 K temperature range. It was found that at 7 Kelvin the emitted light is circularly polarized with a polarization that is proportional to the MnAs contact magnetization with a saturation value of 26% for B > 1.25 tesla. The polarization persists up to room temperature with a saturation value of 6%. ii) Optical Aharonov-Bohm effect in InGaAs quantum wells. The excitonic photoluminescence intensity from InGaAs quantum wells as function of magnetic field exhibits two local maxima superimposed on a decreasing background. The maxima are attributed to the optical Aharonov-Bohm effect of electrons orbiting around a hole localized at the center of an Indium rich InGaAs islands detected by cross sectional scanning tunneling microscopy. Analysis of the position of the maxima yields a value of the electron orbit radius. iii) Micro-Photoluminescence. We have put together a micro-photoluminescence /7 tesla system for the study of two dimensional crystals. The samples are placed inside a continuous flow cryostat whose tail is positioned in the bore of the 7 tesla magnet. A microscope objective is used to focus the exciting laser light and collect the emitted photoluminescence. The system was tested by recording the photoluminescence spectra of WS2 and WSe 2 monolayers at T = 77 K.

Schweidenback, Lars

380

Epidemiology of major incidents: an EMS study from Pakistan  

PubMed Central

Background A major incident is defined as an event that owing to the number of casualties has the potential to overwhelm the available resources. This paper attempts to describe the incidence and epidemiology of major incidents dealt with by a government-run emergency medical service (EMS) in the Punjab province of Pakistan, a developing country in South Asia. A major incident in this EMS is defined as any incident that produces three or more patients, or any incident in which extraordinary resources are needed. Methods All the calls received by an EMS Rescue 1122 were studied over a 6-month period. Calls that were defined as major incidents were identified, and further details were sought from the districts regarding these incidents. Questions specifically asked were the type of incident, time of the incident, response time for the incident, the resources needed, and the number of dead and injured casualties. Retrospective data were collected from the submitted written reports. Results Road traffic crashes (RTCs) emerged as the leading cause of a major incident in the province of Punjab and also led to the greatest number of casualties, followed by fire incidents. The total number of casualties was 3,380, out of which 73.7% were RTC victims. There was a high rate of death on the scene (10.4%). Certain other causes of major incidents also emerged, including violence, gas explosions and drowning. Conclusion Road traffic crashes are the most common cause of a major incident in developing countries such as Pakistan. Injury prevention initiatives need to focus on RTCs.

2011-01-01

381

EM-21 Retrieval Knowledge Center: Waste Retrieval Challenges  

SciTech Connect

EM-21 is the Waste Processing Division of the Office of Engineering and Technology, within the U.S. Department of Energy’s (DOE) Office of Environmental Management (EM). In August of 2008, EM-21 began an initiative to develop a Retrieval Knowledge Center (RKC) to provide the DOE, high level waste retrieval operators, and technology developers with centralized and focused location to share knowledge and expertise that will be used to address retrieval challenges across the DOE complex. The RKC is also designed to facilitate information sharing across the DOE Waste Site Complex through workshops, and a searchable database of waste retrieval technology information. The database may be used to research effective technology approaches for specific retrieval tasks and to take advantage of the lessons learned from previous operations. It is also expected to be effective for remaining current with state-of-the-art of retrieval technologies and ongoing development within the DOE Complex. To encourage collaboration of DOE sites with waste retrieval issues, the RKC team is co-led by the Savannah River National Laboratory (SRNL) and the Pacific Northwest National Laboratory (PNNL). Two RKC workshops were held in the Fall of 2008. The purpose of these workshops was to define top level waste retrieval functional areas, exchange lessons learned, and develop a path forward to support a strategic business plan focused on technology needs for retrieval. The primary participants involved in these workshops included retrieval personnel and laboratory staff that are associated with Hanford and Savannah River Sites since the majority of remaining DOE waste tanks are located at these sites. This report summarizes and documents the results of the initial RKC workshops. Technology challenges identified from these workshops and presented here are expected to be a key component to defining future RKC-directed tasks designed to facilitate tank waste retrieval solutions.

Fellinger, Andrew P.; Rinker, Michael W.; Berglin, Eric J.; Minichan, Richard L.; Poirier, Micheal R.; Gauglitz, Phillip A.; Martin, Bruce A.; Hatchell, Brian K.; Saldivar, Eloy; Mullen, O Dennis; Chapman, Noel F.; Wells, Beric E.; Gibbons, Peter W.

2009-04-10

382

SEI: Junior E&M Course Materials - Electrostatics  

NSDL National Science Digital Library

This is a collection of resources for teaching electrostatics constructed over the course of four semesters of a transformed junior-level Electricity and Magnetism course. Included are homework questions, concept tests, student tutorials, lecture notes, 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.

Pollock, Steven J.; Chasteen, Stephanie V.

2010-06-29

383

SEI: Junior E&M I Course Materials - Math Fundamentals  

NSDL National Science Digital Library

This is a collection of resources for teaching mathematical fundamentals of electro- and magnetostatics constructed over the course of four semesters of a transformed junior-level Electricity and Magnetism course. Included are homework questions, concept tests, 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.

Pollock, Steven J.; Chasteen, Stephanie V.

2010-06-29

384

Testing For EM Upsets In Aircraft Control Computers  

NASA Technical Reports Server (NTRS)

Effects of transient electrical signals evaluated in laboratory tests. Method of evaluating nominally fault-tolerant, aircraft-type digital-computer-based control system devised. Provides for evaluation of susceptibility of system to upset and evaluation of integrity of control when system subjected to transient electrical signals like those induced by electromagnetic (EM) source, in this case lightning. Beyond aerospace applications, fault-tolerant control systems becoming more wide-spread in industry; such as in automobiles. Method supports practical, systematic tests for evaluation of designs of fault-tolerant control systems.

Belcastro, Celeste M.

1994-01-01

385

A compulsator driven rapid-fire EM gun  

NASA Astrophysics Data System (ADS)

A computator-driven railgun is an attractive alternative to the homopolar generator-inductor-switch configuration, especially for repetitive duty. A conceptual design of rapid-fire EM-gun system is presented. The generator is sized to accelerate a 0.08-kg projectile to 2 to 3 km/s at a 60 pulse-per-second repetition rate. Initial design parameters are discussed, and example current and velocity waveforms are given. The generator is discharged at the proper phase angle to provide a current zero just as the projectile exits the muzzle of the railgun.

Pratap, S. B.; Bird, W. L.; Godwin, G. L.; Weldon, W. F.

1984-03-01

386

Caucasicosides E-M, furostanol glycosides from Helleborus caucasicus.  

PubMed

Nine furostanol glycosides, namely caucasicosides E-M, were isolated from the MeOH extract of the leaves of Helleborus caucasicus, along with 11 known compounds including nine furostanol glycosides, a bufadienolide and an ecdysteroid. Their structures were established by the extensive use of 1D and 2D NMR experiments along with ESIMS(n) analyses. The steroidal composition of leaves of H. caucasicus shows as particular feature the occurrence of steroidal compounds belonging to the 5? series, unusual for Helleborus species, and in particular, caucasicosides F-H are based on a 5?-polyhydroxylated steroidal aglycon never reported before. PMID:21893324

Muzashvili, Tamar; Perrone, Angela; Napolitano, Assunta; Kemertelidze, Ether; Pizza, Cosimo; Piacente, Sonia

2011-12-01

387

SEI: Junior E&M 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

388

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

2008-04-01

389

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

390

An evaluation of success factors using the AHP to implement ISO 14001-based EMS  

Microsoft Academic Search

Today’s growing concern in environment awareness forces manufacturers to strive for implementing competitive strategies in environmental management. With the introduction of ISO 14001 Environmental Management System (EMS) standard in 1996, many manufacturing companies are facing a decision problem of whether or not to implement the ISO 14001 based EMS. The authors have studied the critical success factors to be considered

Kwai-Sang Chin; Simon Chiu; V. M. Rao Tummala

1999-01-01

391

Influência do veículo na eficácia da reposição de potássio em ratos hipocalêmicos  

Microsoft Academic Search

Resumo Introdução: Pacientes após cirurgia cardíaca são comumente tratados com diuréticos para controle de volume plasmático. A preocupação de distúrbios hipocalêmicos em adultos antes, durante ou após a cirurgia já foi ressaltada anteriormente, visto o risco de arritmias cardíacas. Clinicamente, a diluição da solução de potássio (K+) para administração por via intravenosa, em situações que requerem a sua reposição é

Márcio Petenusso; Vitor Engrácia Valenti; Luiz Carlos de Abreu; Eduardo Colombari; Fernando Luiz Affonso Fonseca; Monica Akemi Sato

2009-01-01

392

Estimation of Item Response Models Using the EM Algorithm for Finite Mixtures.  

ERIC Educational Resources Information Center

This paper presents a detailed description of maximum parameter estimation for item response models using the general EM algorithm. In this paper the models are specified using a univariate discrete latent ability variable. When the latent ability variable is discrete the distribution of the observed item responses is a finite mixture, and the EM…

Woodruff, David J.; Hanson, Bradley A.

393

Theoretical and experimental investigations of gravity modification by specially conditioned EM radiation  

Microsoft Academic Search

Ordinary electromagnetic (em) fields do not couple significantly with those that underlie gravitation and give rise to inertia, and it is suggested that this is because they are of different field essence and form. It is also suggested that a much stronger electro-gravitic coupling might be accomplished for effective propulsion by conditioning ordinary em fields into configurations that are similar

H. D. Froning; T. W. Barrett

2000-01-01

394

EmBOINC: An emulator for performance analysis of BOINC projects  

Microsoft Academic Search

BOINC is a platform for volunteer computing. The server component of BOINC embodies a number of schedul- ing policies and parameters that have a large impact on the projects throughput and other performance metrics. We have developed a system, EmBOINC, for studying these policies and parameters. EmBOINC uses a hybrid ap- proach: it simulates a population of volunteered clients (in-

Trilce Estrada; Michela Taufer; Kevin Reed; David P. Anderson

2009-01-01

395

DIFERENCIAÇÃO OU NECESSIDADE NA CERTIFICAÇÃO ISO 9001: UMA ANÁLISE EM DUAS EMPRESAS AGROINDUSTRIAIS  

Microsoft Academic Search

O presente estudo de caso foi realizado em duas organizações agroindustriais, a AGCO do Brasil Comércio e Indústria Ltda. e a Tecno Moageira S\\/A, tratando-se de um estudo de caso de natureza exploratória e descritiva, que objetivou analisar os motivos pelos quais essas organizações implementaram a certificação ISO 9001, em torno da seguinte problemática: Qual o real interesse da certificação

Alexandre Melo Abicht; Alessandra Carla Ceolin; Augusto Faria Correa; Paulo Rodrigo Pereira; Tania Nunes da Silva

2008-01-01

396

neuromuscular sobre o consumo máximo de oxigênio e salto vertical em atletas iniciantes de voleibol  

Microsoft Academic Search

RESUMO As alterações ocorridas na performance motora de jovens en- volvidos em treinamentos especializados ainda não são muito cla- ras. Este é um conhecimento de suma importância para a correta prescrição desses treinos. O objetivo deste estudo foi verificar a influência do treinamento nas variáveis neuromotoras e orgânicas de jovens atletas na modalidade voleibol em diferentes momen- tos do programa.

Alexandre Altini Neto; Ídico Luiz Pellegrinotti; Maria Imaculada; L. Montebelo

397

Evidence-based performance measures for emergency medical services systems: a model for expanded EMS benchmarking.  

PubMed

There are few evidence-based measures of emergency medical services (EMS) system performance. In many jurisdictions, response-time intervals for advanced life support units and resuscitation rates for victims of cardiac arrest are the primary measures of EMS system performance. The association of the former with patient outcomes is not supported explicitly by the medical literature, while the latter focuses on a very small proportion of the EMS patient population and thus does not represent a sufficiently broad selection of patients. While these metrics have their place in performance measurement, a more robust method to measure and benchmark EMS performance is needed. The 2007 U.S. Metropolitan Municipalities' EMS Medical Directors' Consortium has developed the following model that encompasses a broader range of clinical situations, including myocardial infarction, pulmonary edema, bronchospasm, status epilepticus, and trauma. Where possible, the benefit conferred by EMS interventions is presented in the number needed to treat format. It is hoped that utilization of this model will serve to improve EMS system design and deployment strategies while enhancing the benchmarking and sharing of best practices among EMS systems. PMID:18379908

Myers, J Brent; Slovis, Corey M; Eckstein, Marc; Goodloe, Jeffrey M; Isaacs, S Marshal; Loflin, James R; Mechem, C Crawford; Richmond, Neal J; Pepe, Paul E

2008-01-01

398

EMS Agenda for the Future: Where We Are … Where We Want to Be  

Microsoft Academic Search

During the past 30 years, emergency medical services (EMS) in the United States have experienced explosive growth. The American health care system is now transforming, providing an opportune time to examine what we have learned over the past three decades in order to create a vision for the future of EMS. Over the course of several months, a multidisciplinary steering

Theodore R Delbridge; Bob Bailey; John L Chew; Alasdair KT Conn; Jack J Krakeel; Dan Manz; David R Miller; Patricia J O'Malley; Susan D Ryan; Daniel W Spaite; Ronald D Stewart; Robert E Suter; E. Marie Wilson

1998-01-01

399

Bayesian reconstructions from emission tomography data using a modified EM algorithm  

Microsoft Academic Search

A novel method of reconstruction from single-photon emission computerized tomography data is proposed. This method builds on the expectation-maximization (EM) approach to maximum likelihood reconstruction from emission tomography data, but aims instead at maximum posterior probability estimation, which takes account of prior belief about smoothness in the isotope concentration. A novel modification to the EM algorithm yields a practical method.

PETER J. GREEN

1990-01-01

400

Multipurpose design optimization of EMS-type magnetically levitated vehicle based on genetic algorithm  

Microsoft Academic Search

A type of the magnetically levitated railway system with the electromagnetic suspension system (EMS), which is named HSST system, will be put into revenue service as an urban transport in Nagoya, Japan at the beginning of April 2005. To extend its operational velocity higher than 200 km\\/h for applications in other cities, the design of its EMS system is reexamined

Shinichi Kusagawa; Jumpei Baba; Katsuhiko Shutoh; Eisuke Masada

2004-01-01

401

Competência social e empatia: um estudo sobre resiliência com crianças em situação de pobreza  

Microsoft Academic Search

Social competence and empathy: Study about resilience with children in poverty Resumo O objetivo desse estudo foi avaliar a competência social e a empatia em crianças escolares que vivem em situação de po- breza. Participaram da pesquisa 100 crianças, de ambos os sexos, com idades entre seis e nove anos. Os instrumentos utilizados foram o Teste das Histórias Incompletas (THI)

Alessandra Marques Cecconello; Sílvia Helena Koller

2000-01-01

402

Programa em Educação a Distância para a Melhoria das Condições de Aprendizagem da Matemática  

Microsoft Academic Search

Resumo - A fim de fundamentar uma ação pedagógica diferenciada, frente ao elevado número de reprovações e desistências que ocorrem em disciplinas iniciais de Matemática na Universidade de Caxias do Sul, apresentamos um programa através do qual investigamos as reais possibilidades de constituir nova opção para alunos reprovados em Cálculo Diferencial e Integral I. Num ambiente virtual de aprendizagem os

Isolda G. De Lima; Laurete Z. Sauer

403

Influência da irrigação e do genótipo na produção de castanha em cajueiro-anão-precoce  

Microsoft Academic Search

(2) Resumo - Avaliou-se a influência da irrigação e do genótipo na produção de castanha em cajueiro-anão- precoce (Anacardium occidentale L.) durante três anos. Foram estudados três clones (CP 09, CP 76 e CP 1001) e quatro regimes hídricos (testemunha sem irrigação e intervalos de irrigação de um, três e cinco dias). O delineamento experimental foi em blocos ao acaso,

Vitor Hugo de Oliveira; Levi de Moura Barros; Raimundo Nonato de Lima

2003-01-01

404

Prevalência de sobrepeso\\/obesidade em crianças e adolescentes com constipação crônica funcional  

Microsoft Academic Search

RESUmO Objetivo: Avaliar a prevalência do sobrepeso\\/obesidade em um grupo de crianças com constipação crônica funcional. Métodos: Estudo retrospectivo com 257 crianças de dois a 15 anos com constipação crônica funcional diag- nosticada segundo critérios de Roma II, atendidas con- secutivamente em clínica terciária de gastroenterologia pediátrica. Informações demográficas, clínicas, diagnós - ticas e antropométricas foram obtidas de prontuários. O

Francisca Teresa V. Faleiros; Cristiane Camargo Omae; Cristiane Yoshie Nakazawa; Mary de Assis Carvalho; Nilton Carlos Machado

2008-01-01

405

NEW ISOTOPES OF EMANATION AND FRANCIUM: ²²³Em, ²²⁴Em, AND ²²⁴Fr  

Microsoft Academic Search

An examination of the products of the interaction of thorium with 230 ; Mev protons revealed evidence for the existence of the neutron-excess isotopes: ; Em²²³, Em²²⁴, and Fr²²⁴. The existence of these three new ; isotopes was confirmed by identification of their decay products: Ra²²³ and ; Ra²²⁴. (auth);

Bellido

1961-01-01

406

The simulated online EM algorithm for latent factor models  

NASA Astrophysics Data System (ADS)

The estimation of latent factor models are treated in an integrated maximum likelihood context where one parameter is marginalized and another is estimated. An extension to the online Expectation Maximization (EM) algorithm is employed the simulated online Expectation Maximization algorithm. Both these algorithms apply to exponential family models, but the simulated version of the algorithm can make use of Monte Carlo simulation to compute the stochastic E-steps while maintaining the convergence properties of the original online EM algorithm. A class of important latent factor models are identified that can be expressed in complete data exponential family form, the algorithm is applied to one of these models Itakura-Saito Non-negative Matrix Factorisation. An additional parameter is introduced into this model and it is conjectured if this is set to a high value the posterior variance of the parameters is reduced and estimation becomes easier. Simulations are provided that support this conjecture, although online estimation for models with even a modest number of components continues to be hampered by the presence of local minima.

Rohde, D.; Cappé, O.; Dikmen, O.

2012-10-01

407

Fabrication and EM shielding properties of electrospining PANi/MWCNT/PEO fibrous membrane and its composite  

NASA Astrophysics Data System (ADS)

In this paper, Polyaniline-based fibrous membranes were fabricated with multi-walled carbon nanotubes and polyethylene oxide (PEO) by the electrospinning method. And then PANi/PEO/MWCNT fibrous membranes reinforced epoxy based nanocomposite was then fabricated. The morphology and electrical properties of PANi /MWCNT /PEO fibrous membrane was characterized by scanning electron microscope (SEM). The morphologies of the membranes indicate that the electrospining method can fabricate well nano structures fibrous membrane. The EM properties of the composite reinforced with the electrospining fibrous membrane were measured by vector network analyzer. The results show that the permittivity real, image parts and permeability real part of the composite increase by filling with PANI/PEO and PANI/CNT/PEO membrane. The EM shielding and absorb performance is base on the dielectric dissipation. And different membranes made of different materials show different EM parameter, and different EM shielding performance, which can be used to the EM shielding and stealth material design and fabrication.

Zhang, Zhichun; Jiang, Xueyong; Liu, Yanju; Leng, Jinsong

2012-03-01

408

Qualidade de frutos de cinco híbridos de melão rendilhado em função do número de frutos por planta  

Microsoft Academic Search

RESUMO-Este trabalho teve por objetivo avaliar a qualidade de cinco híbridos de melão rendilhado, com dois e três frutos por planta, utilizando fibra da casca de coco e fertirrigação. Para tanto, foi instalado um experimento em casa de vegetação na UNESP-FCAV, Câmpus de Jaboticabal, com delineamento experimental em blocos ao acaso, em esquema fatorial 5 x 2, com quatro repetições.

Renata Castoldi; Hamilton César de Oliveira Charlo; Pablo Forlan Vargas; Leila Trevizan Braz

2008-01-01

409

Hybrid BEM\\/FEM Calculation of Thermal Rise in the Human Eye Exposed to Time Harmonic EM Waves  

Microsoft Academic Search

Human eye being unprotected by the layer of skin and bones is one of the most sensitive organs to EM radiation. The absorption of EM radiation is quantified in terms of SAR and to calculate the SAR the knowledge of complete electric field distribution inside the eye is necessary. In this paper the problem of distribution of near EM field

Hrvoje Dodig

2005-01-01

410

ON SPEEDING UP THE EM ALGORITHM IN PATTERN RECOGNITION: A COMPARISON OF INCREMENTAL AND MULTIRESOLUTION KD-TREE-BASED APPROACHES  

Microsoft Academic Search

Finite mixture models implemented via the EM algo- rithm are being increasingly used in a wide range of problems in the context of unsupervised statistical pattern recognition. As each E-step visits each feature vector on a given iteration, the EM algorithm requires considerable computation time in its application to large data sets. We consider two approaches, an incremental EM (IEM)

Shu Kay Ng; Geoffrey John McLachlan

2002-01-01

411

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

412

Linear array implementation of the EM algorithm for PET image reconstruction  

SciTech Connect

The PET image reconstruction based on the EM algorithm has several attractive advantages over the conventional convolution back projection algorithms. However, the PET image reconstruction based on the EM algorithm is computationally burdensome for today`s single processor systems. In addition, a large memory is required for the storage of the image, projection data, and the probability matrix. Since the computations are easily divided into tasks executable in parallel, multiprocessor configurations are the ideal choice for fast execution of the EM algorithms. In tis study, the authors attempt to overcome these two problems by parallelizing the EM algorithm on a multiprocessor systems. The parallel EM algorithm on a linear array topology using the commercially available fast floating point digital signal processor (DSP) chips as the processing elements (PE`s) has been implemented. The performance of the EM algorithm on a 386/387 machine, IBM 6000 RISC workstation, and on the linear array system is discussed and compared. The results show that the computational speed performance of a linear array using 8 DSP chips as PE`s executing the EM image reconstruction algorithm is about 15.5 times better than that of the IBM 6000 RISC workstation. The novelty of the scheme is its simplicity. The linear array topology is expandable with a larger number of PE`s. The architecture is not dependant on the DSP chip chosen, and the substitution of the latest DSP chip is straightforward and could yield better speed performance.

Rajan, K.; Patnaik, L.M.; Ramakrishna, J. [Indian Institute of Science, Bangalore (India)] [Indian Institute of Science, Bangalore (India)

1995-08-01

413

PREFACE: EmQM13: Emergent Quantum Mechanics 2013  

NASA Astrophysics Data System (ADS)

These proceedings comprise the invited lectures of the second international symposium on Emergent Quantum Mechanics (EmQM13), which was held at the premises of the Austrian Academy of Sciences in Vienna, Austria, 3–6 October 2013. The symposium was held at the ''Theatersaal'' of the Academy of Sciences, and was devoted to the open exploration of emergent quantum mechanics, a possible ''deeper level theory'' that interconnects three fields of knowledge: emergence, the quantum, and information. Could there appear a revised image of physical reality from recognizing new links between emergence, the quantum, and information? Could a novel synthesis pave the way towards a 21st century, ''superclassical'' physics? The symposium provided a forum for discussing (i) important obstacles which need to be overcome as well as (ii) promising developments and research opportunities on the way towards emergent quantum mechanics. Contributions were invited that presented current advances in both standard as well as unconventional approaches to quantum mechanics. The EmQM13 symposium was co–organized by Gerhard Grössing (Austrian Institute for Nonlinear Studies (AINS), Vienna), and by Jan Walleczek (Fetzer Franklin Fund, USA, and Phenoscience Laboratories, Berlin). After a very successful first conference on the same topic in 2011, the new partnership between AINS and the Fetzer Franklin Fund in producing the EmQM13 symposium was able to further expand interest in the promise of emergent quantum mechanics. The symposium consisted of two parts, an opening evening addressing the general public, and the scientific program of the conference proper. The opening evening took place at the Great Ceremonial Hall (Grosser Festsaal) of the Austrian Academy of Sciences, and it presented talks and a panel discussion on ''The Future of Quantum Mechanics'' with three distinguished speakers: Stephen Adler (Princeton), Gerard 't Hooft (Utrecht) and Masanao Ozawa (Nagoya). The articles contained in these proceedings represent the talks of the invited speakers as written immediately after the symposium. The volume starts with a contribution by organizers Jan Walleczek and Gerhard Grössing, essentially explaining why emergent quantum mechanics, and other deterministic approaches to quantum theory, must be considered viable approaches in quantum foundations today. This is followed by the exposition of Stephen Adler's talk who introduced to a general audience key questions at the current frontiers of quantum mechanics during the opening evening (with the contents of his conference talk appearing elsewhere). The conference proceedings then continues with the presentations as given in their chronological order i.e. starting with the opening talk of the scientific program by Gerard 't Hooft. While the page number was restricted for all invited speakers, the paper by Jeff Tollaksen was given more space, as his invited collaborator Yakir Aharonov was unable to deliver a separate talk, in order to represent both contributions in one paper. Note that the talks of all speakers, including the talks of those who could not be represented in this volume (M. Arndt, B. Braverman, C. Brukner, S. Colin, Y. Couder, B. Poirier, A. Steinberg, G. Weihs and H. Wiseman) are freely available on the conference website as video presentations (http://www.emqm13.org). The organizers wish to express their gratitude to Siegfried Fussy and Herbert Schwabl from AINS for the organizational support. The organizers also wish to thank Bruce Fetzer, President and CEO, John E. Fetzer Memorial Trust, and the Members of the Board of Trustees, for their strong support and for funding this symposium. We also wish to thank the Austrian Academy of Sciences for allowing the symposium to be held on their premises, and Anton Zeilinger, President of the Austrian Academy of Sciences, for his welcome address. The expertise of the Members of the Scientific Advisory Board of the EmQM13 symposium, Ana Maria Cetto (Mexico), Lajos Diósi (Budapest), Maurice de Gosson (Vienna), Edward Nelson (Princeton), The

2014-04-01

414

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

415

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

416

TrakEM2 Software for Neural Circuit Reconstruction  

PubMed Central

A key challenge in neuroscience is the expeditious reconstruction of neuronal circuits. For model systems such as Drosophila and C. elegans, the limiting step is no longer the acquisition of imagery but the extraction of the circuit from images. For this purpose, we designed a software application, TrakEM2, that addresses the systematic reconstruction of neuronal circuits from large electron microscopical and optical image volumes. We address the challenges of image volume composition from individual, deformed images; of the reconstruction of neuronal arbors and annotation of synapses with fast manual and semi-automatic methods; and the management of large collections of both images and annotations. The output is a neural circuit of 3d arbors and synapses, encoded in NeuroML and other formats, ready for analysis.

Cardona, Albert; Saalfeld, Stephan; Schindelin, Johannes; Arganda-Carreras, Ignacio; Preibisch, Stephan; Longair, Mark; Tomancak, Pavel; Hartenstein, Volker; Douglas, Rodney J.

2012-01-01

417

Speech articulator measurements using low power EM-wave sensors  

SciTech Connect

Very low power electromagnetic (EM) wave sensors are being used to measure speech articulator motions as speech is produced. Glottal tissue oscillations, jaw, tongue, soft palate, and other organs have been measured. Previously, microwave imaging (e.g., using radar sensors) appears not to have been considered for such monitoring. Glottal tissue movements detected by radar sensors correlate well with those obtained by established laboratory techniques, and have been used to estimate a voiced excitation function for speech processing applications. The noninvasive access, coupled with the small size, low power, and high resolution of these new sensors, permit promising research and development applications in speech production, communication disorders, speech recognition and related topics. {copyright} {ital 1998 Acoustical Society of America.}

Holzrichter, J.F.; Burnett, G.C.; Ng, L.C. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States)] [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States); Lea, W.A. [Speech Science Institute, P.O. Box 240428, Apple Valley, Minnesota 55124 (United States)] [Speech Science Institute, P.O. Box 240428, Apple Valley, Minnesota 55124 (United States)

1998-01-01

418

Imaging protein three-dimensional nanocrystals with cryo-EM.  

PubMed

Flash-cooled three-dimensional crystals of the small protein lysozyme with a thickness of the order of 100 nm were imaged by 300 kV cryo-EM on a Falcon direct electron detector. The images were taken close to focus and to the eye appeared devoid of contrast. Fourier transforms of the images revealed the reciprocal lattice up to 3 Å resolution in favourable cases and up to 4 Å resolution for about half the crystals. The reciprocal-lattice spots showed structure, indicating that the ordering of the crystals was not uniform. Data processing revealed details at higher than 2 Å resolution and indicated the presence of multiple mosaic blocks within the crystal which could be separately processed. The prospects for full three-dimensional structure determination by electron imaging of protein three-dimensional nanocrystals are discussed. PMID:23633595

Nederlof, Igor; Li, Yao Wang; van Heel, Marin; Abrahams, Jan Pieter

2013-05-01

419

Risk Factors for Hypothermia in EMS-treated Burn Patients.  

PubMed

Abstract Objective. Hypothermia has been associated with increased mortality in burn patients. We sought to characterize the body temperature of burn patients transported directly to a burn center by emergency medical services (EMS) personnel and identify the factors independently associated with hypothermia. Methods. We utilized prospective data collected by a statewide trauma registry to carry out a nested case-control study of burn patients transported by EMS directly to an accredited burn center between 2000 and 2011. Temperature at hospital admission ?36.5°C was defined as hypothermia. We utilized registry data abstracted from prehospital care reports and hospital records in building a multivariable regression model to identify the factors associated with hypothermia. Results. Forty-two percent of the sample was hypothermic. Burns of 20-39% total body surface area (TBSA) (OR 1.44; 1.17-1.79) and ?40% TBSA (OR 2.39; 1.57-3.64) were associated with hypothermia. Hypothermia was also associated with age > 60 (OR 1.50; 1.30-1.74), polytrauma (OR 1.58; 1.19-2.09), prehospital Glasgow Coma Scale <8 (OR 2.01; 1.46-2.78), and extrication (OR 1.49; 1.30-1.71). Hypothermia was also more common in the winter months (OR 1.54; 1.33-1.79) and less prevalent in patients weighing over 90 kg (OR 0.63; 0.46-0.88). Conclusions. A substantial proportion of burn patients demonstrate hypothermia at hospital arrival. Risk factors for hypothermia are readily identifiable by prehospital providers. Maintenance of normothermia should be stressed during prehospital care. PMID:24460465

Weaver, Matthew D; Rittenberger, Jon C; Patterson, P Daniel; McEntire, Serina J; Corcos, Alain C; Ziembicki, Jenny A; Hostler, David

2014-01-01

420

Ondas de choque em jatos de quasares e objetos BL Lacertae  

NASA Astrophysics Data System (ADS)

Este trabalho é parte de um projeto que vem sendo realizado há dois anos no CRAAM, cujos objetivos principais são analisar e aplicar um modelo generalizado de ondas de choque em jatos relativísticos de plasma, presentes em quasares e objetos BL Lacertae, para explicar a variabilidade observada nestes objetos. O método consiste em uma decomposição de curvas de luz em séries de explosões similares, em várias freqüências, baseando-se em uma evolução espectro-temporal média das explosões. A partir da evolução média, um ajuste de cada explosão é feito com base em equações empíricas, modificando-se apenas parâmetros específicos de cada explosão. Inicialmente o modelo foi aplicado ajustando-se as curvas de luz a explosões delineadas por uma evolução do choque em três estágios, segundo a predominância do processo de emissão: síncrotron, Compton e adiabático. Entretanto, nesta nova fase de projeto, visando uma parametrização mais concisa, uma otimização do algoritmo de ajuste e uma convergência mais rápida, a formulação para cada evento foi assumida com uma evolução em apenas dois estágios: subida e descida. Isto possibilitou uma ótima delineação das curvas de luz das fontes OV236, OJ287, 3C273 e BL Lac, entre 1980 e 2000, nas freqüências 4.8, 8.0, 14.5 e 22 GHz, utilizando-se dados do Observatório da Universidade de Michigan, do Observatório do Itapetinga (Atibaia SP) e do Observatório Metsähovi. Como conclusões importantes, verificou-se que: os parâmetros ajustados descrevem o comportamento do jato; os valores do índice que descreve a expansão do jato sugerem que o mesmo se expande de uma forma não-cônica; o campo magnético é turbulento atrás da frente de choque; e as peculiaridades das explosões são devidas à influência de grandezas tais como o coeficiente da distribuição espectral de energia dos elétrons, a intensidade de campo magnético e o fator de feixe Doppler, no início do choque.

Melo, F. E.; Botti, L. C. L.

2003-08-01

421

Abscesso pulmonar de aspiração: dados diagnósticos e resultados terapêuticos em 241 casos Primary lung abscess: diagnostic findings and results of the treatment in 241 cases  

Microsoft Academic Search

SINOPSE São mostrados aspectos diagnósticos e terapêuticos do abscesso pulmonar de aspiração. No período de 1968 a 2002 foram reunidos e estudados 241 casos da doença - 199 em homens e 42 em mulheres, com média de idade de 41,3 anos. Em 69% dos pacientes esteve presente a ingestão de álcool e em 64% o hábito tabágico. Tosse, expectoração, febre

ÂNGELA P. ZIEGLER; José S. Moreira; Rua Carlos Von Koseritz

422

An Ems-Sensitivity Factor in Maize Conditioning Albino Leaf Stripes  

PubMed Central

A description is given for a recessive EMS-sensitivity factor conditioning albino leaf stripes. In the homozygous condition, there is low frequency of spontaneous leaf stripes. EMS, depending on the concentration, increases markedly the frequency of the stripes in 100% of the treated plants. The effects of EMS, given to the seeds, starts to appear from the 6th to 7th leaf and persists in all the leaves throughout the life cycle of the M1 plants. Only about 20–25% of the M2 plants showed some variegation. These variegated M2 plants were not distributed at random among the different ear-to-row M2 rows.

Efron, Y.

1974-01-01

423

Integration of artificial intelligence applications in the EMS: Issues and solutions  

SciTech Connect

This paper discusses the issues which must be addressed when integrating Artificial Intelligence (AI) and, in particular, expert system applications in an Energy Management System (EMS) environment. It is argued that these issues can be resolved by creating an environment which supports all the interfaces between the Artificial Intelligence (AI) applications and the EMS. This environment should also be responsible for maintaining a model of the power system common to all the AI applications. Once this environment has been created, AI applications can be easily plugged into the EMS. The design of such an environment is described and case studies of its implementation are provided to illustrate its flexibility.

Bann, J.; Irisarri, G.; Kirschen, D.; Miller, B.; Mokhtari, S. [Empros Power Systems Control, Plymouth, MN (United States)] [Empros Power Systems Control, Plymouth, MN (United States)

1996-02-01

424

Reservoir characterization and process monitoring with EM methods. 1994 Annual report.  

National Technical Information Service (NTIS)

During the past five years at Lawrence Livermore National Laboratory (LLNL) the authors have applied the EM induction method to the problem of petroleum reservoir characterization and enhanced oil recovery (EOR) monitoring. The goal is to develop practica...

M. Wilt

1995-01-01

425

Use of low power EM radar sensors for speech articulator measurements.  

National Technical Information Service (NTIS)

Very low power electromagnetic (EM) wave sensors are being used to measure speech articulator motions such as the vocal fold oscillations, jaw, tongue, and the soft palate. Data on vocal fold motions, that correlate well with established laboratory techni...

J. F. Holzrichter G. C. Burnett

1997-01-01

426

Synthesis and formation of an EMS correlated contaminant in biotechnologically manufactured L-tryptophan.  

PubMed

Contaminants in biotechnologically manufactured L-Tryptophan (Trp) are suspected to be responsible for the outbreak of an unknown autoimmune disease in 1989. The contaminants, found in Trp-lots of a Japanese manufacturer, are classified in EMS-correlated and non EMS-correlated substances. Up to now six EMS-correlated substances are known. One of these compounds is 2-(3'-indolylmethyl)-indole (IMT). IMT was detected as a major contaminant in two investigated EMS-associated trp-samples. In a seven step chemical synthesis IMT was obtained for use as a reference substance. A model system to investigate the formation of IMT was created using Trp and 3-indolylmethanol (IM). IMT formation was observed at acidic and alkaline pH-values and the optimal molar ratio of Trp to IM is 100:1. In addition an IMT formation was observed from indole, formaldehyde and Trp as well as from Trp and 3-indolylacetaldehyde. PMID:10721091

Müller, B; Pacholski, C; Simat, T; Steinhart, H

1999-01-01

427

Applications of the EM Algorithm to the Estimation of Bayesian Hyperparameters.  

National Technical Information Service (NTIS)

Applications of the EM algorithm to the estimation of Bayesian hyperparameters are discussed and reviewed in the context of the author's philosophy involving the inductive and pragmatic modelling of sampling distributions and prior structures. Frequently ...

T. Leonard

1982-01-01

428

A Zernike-moment-based non-local denoising filter for cryo-EM images.  

PubMed

Cryo-electron microscopy (cryo-EM) plays an important role in determining the structure of proteins, viruses, and even the whole cell. It can capture dynamic structural changes of large protein complexes, which other methods such as X-ray crystallography and nuclear magnetic resonance analysis find difficult. The signal-to-noise ratio of cryo-EM images is low and the contrast is very weak, and therefore, the images are very noisy and require filtering. In this paper, a filtering method based on non-local means and Zernike moments is proposed. The method takes into account the rotational symmetry of some biological molecules to enhance the signal-to-noise ratio of cryo-EM images. The method may be useful in cryo-EM image processing such as the automatic selection of particles, orientation determination, and the building of initial models. PMID:23564187

Wang, Jia; Yin, Changcheng

2013-04-01

429

Observações simultâneas no óptico e infravermelho próximo dos BL Lacs PKS 2005-489 e PKS 2155-304 em diversas escalas de tempo  

NASA Astrophysics Data System (ADS)

A existência de variações rápidas de brilho em alguns blazares é um fenômeno bem comprovado, mas até agora não sabemos ao certo quais são os mecanismos físicos envolvidos. A maior dificuldade é a ausência de observações multibanda simultâneas que poderiam fornecer vínculos aos modelos. Buscando colaborar com a discussão estudamos o comportamento de dois BL Lacs, PKS 2005-489 e PKS 2155-304, em relação à variabilidade em diversas escalas de tempo, de poucos minutos até vários meses, com observações simultâneas em seis bandas espectrais (óptico e infravermelho próximo). Para tanto dois telescópios do LNA foram utilizados em conjunto nas campanhas observacionais realizadas em 2001 e 2002, cujos resultados são apresentados aqui. As duas fontes apresentaram características bastante diferentes, inclusive em relação à existência de variabilidade nos índices espectrais. Particularmente, registramos a primeira detecção de variações em escalas de tempo da ordem de poucos minutos em PKS 2005-489, com evidências da presença de um atraso entre as curvas de luz nas bandas V e R e a variação em R ocorrendo antes (o contrário do esperado no modelo de shock-in-jet). Em PKS 2155-304 detectamos pela primeira vez variabilidade em escalas de tempo de poucos minutos no infravermelho em um AGN. As observações indicam que as variações de brilho em blazares são o resultado da ação de mais de um fenômeno, especialmente em escalas de tempo muito curtas. Alguns cenários físicos são sugeridos para explicar os resultados observacionais.

Dominici, T. P.; Abraham, Z.; Galo, A. L.

2003-08-01

430

Experimental study of the E(m, ?)/E(m, 1064) ratio as a function of wavelength, fuel type, height above the burner and temperature  

NASA Astrophysics Data System (ADS)

The optical properties of soot have been studied for many years with a particular attention focused on refractive index. In the present study, the two-excitation wavelength laser-induced incandescence technique has been applied to determine the ratio of the soot absorption function as a function of the wavelength. The advantage of this technique is to provide the determination of the E(m) ratio using a non-intrusive laser-based method without being disturbed by scattering. Measurements have been carried out in a methane premixed flat flame and in a diesel turbulent spray one. Four pairs of wavelength have been used to evaluate the spectral behavior of E(m) ratios from ultraviolet (UV) to near infrared (NIR). The two-excitation wavelength LII method implies heating soot the same way using two different laser excitations. Particular operating conditions must be selected to insure the equality of the LII signals, such an equality being necessary to derive the E(m) ratio. A laser excitation at 1064 nm has been chosen as a reference, and the obtained results have been compared with those issued from the use of UV and visible wavelengths of 266, 355, 532 and 660 nm. Results show a significant decrease of the E(m) ratio from UV to visible while it tends to become constant from 532 nm to NIR. The use of different experimental conditions allows to analyze the dependence of the E(m) ratios with the height above the burner, the fuel type and the soot temperature. No significant influence of these parameters has been pointed out on the relative E(m) values determined in the flame conditions investigated here.

Bejaoui, S.; Lemaire, R.; Desgroux, P.; Therssen, E.

2013-10-01

431

Fully EM algorithms for the quasi-neutral, zero-electron-inertia model  

Microsoft Academic Search

An algorithm has been developed to compute the electromagnetic signature of impulsive currents in quasi-neutral, collisionless plasmas. Such plasmas are common in laser target chambers, space physics, and EMP generating events. Traditional models[1] used in this regime make the Darwin assumption that neglects purely EM waves. Computing electro-magnetic pulse behavior (EMP) requires the solution of the EM wave equations. Other

Dennis Hewett

2009-01-01

432

Parallel Electromagnetic Simulation for Electric Large Target by EMS-FMM  

Microsoft Academic Search

The development framework of parallel electromagnetic simulation software EMS-FMM based on multilevel fast multipole method (MLFMM) is present in this paper. EMS-FMM can solve large-scale scattering problem of 10 million scale with a complexity of O (Nlog N), so it's efficient for electric large target. It's implemented by C and Fortran with MPI communication on cluster DeepComp 7000. Implementation of

Wu Wang; Yangde Feng; Xuebin Chi

2010-01-01

433

Using EM to Obtain Asymptotic Variance-Covariance Matrices: The SEM Algorithm  

Microsoft Academic Search

The expectation maximization (EM) algorithm is a popular, and often remarkably simple, method for maximum likelihood estimation in incomplete-data problems. One criticism of EM in practice is that asymptotic variance–covariance matrices for parameters (e.g., standard errors) are not automatic byproducts, as they are when using some other methods, such as Newton–Raphson. In this article we define and illustrate a procedure

Xiao-Li Meng; Donald B. Rubin

1991-01-01

434

SELETIVIDADE E CONTROLE POR MISTURAS DE HERBICIDAS EM ALGODOEIRO HERBÁCEO1  

Microsoft Academic Search

RESUMO: Utilizam-se misturas de herbicidas para evitar a resistência de plantas daninhas a herbicidas e obter melhor eficiência de controle das plantas daninhas. Conduziu-se, no Campo Experimental da Embrapa Algodão, Barbalha, CE, experimento objetivando avaliar o efeito de misturas duplas, triplas e quádruplas de herbicidas, envolvendo Diuron, pendimethalin, metolachlor e oxadiazon, aplicadas em pré-emergência, no controle de plantas daninhas em

ANTONIA ELIENE DUARTE; JOSÉ RODRIGUES PEREIRA; JOÃO BOSCO PITOMBEIRA; MARIA ARLENE PESSOA DA SILVA; FANUEL PEREIRA DA SILVA

435

Direct EM based optimization of advanced waffle-iron and rectangular combline filters  

Microsoft Academic Search

A fast hybrid mode-matching (MM)\\/finite-element (FE) method is applied for the direct EM based optimization of advanced waffle-iron filters and coax-fed rectangular combline filters. The proposed technique, which combines the efficiency of the MM with the flexibility of the FE technique, achieves the direct EM based optimization of these components within typically an overnight run on a PC. The CAD

F. Arndt; Joem Brandt

2002-01-01

436

Crosshole EM for oil field characterization and EOR monitoring: Field examples  

Microsoft Academic Search

Crosshole and surface-to-borehole electromagnetic (EM) imaging is applied to reservoir characterization and steam flood monitoring in a central California oil field. Steam was injected into three stacked, eastward-dipping, unconsolidated oil sands within the upper 200 in. The steam plume is expected to develop as an ellipse aligned with the regional northwest-southeast strike. EM measurements were made from two flberglass-cased observation

M. Wilt; C. Schenkel; C. Torres-Verdin; Ki Ha Lee; Hung-Wen Tseng

1994-01-01

437

The Distance to SN 1999em in NGC 1637 from the Expanding Photosphere Method  

Microsoft Academic Search

We present 30 optical spectra and 49 photometric epochs sampling the first 517 days after discovery of supernova (SN) 1999em and derive its distance through the expanding photosphere method (EPM). SN 1999em is shown to be a Type II-plateau (II-P) event, with a photometric plateau lasting until about 100 days after explosion. We identify the dominant ions responsible for most

Douglas C. Leonard; Alexei V. Filippenko; Elinor L. Gates; Weidong Li; Ronald G. Eastman; Aaron J. Barth; Schelte J. Bus; Ryan Chornock; Alison L. Coil; Sabine Frink; Carol A. Grady; Alan W. Harris; Matthew A. Malkan; Thomas Matheson; Andreas Quirrenbach; Richard R. Treffers

2002-01-01

438

X-ray, Optical, and Radio Observations of SN 1999em and SN 1998S  

Microsoft Academic Search

Observations of the Type II-P (plateau) Supernova (SN) 1999em and Type IIn (narrow emission line) SN 1998S have enabled estimation of the profile of the SN ejecta, the structure of the circumstellar medium (CSM) established by the pre-SN stellar wind, and the nature of the shock interaction. SN 1999em is the first and only Type II-P detected at both X-ray

D. Pooley; W. H. G. Lewin; D. W. Fox; J. M. Miller; C. K. Lacey; S. D. Van Dyk; K. W. Weiler; R. A. Sramek; A. V. Filippenko; D. C. Leonard; S. Immler; R. A. Chevalier; A. C. Fabian; C. Fransson; K. Nomoto

2001-01-01

439

Pre-flight risk assessment in emergency medical service (EMS) helicopters  

NASA Technical Reports Server (NTRS)

A preflight risk assessment system (SAFE) was developed at NASA-Ames Research Center for civil EMS operations to assist pilots in making a decision objectively to accept or decline a mission. The ability of the SAFE system to predict risk profiles was examined at an EMS operator. Results of this field study showed that the usefulness of SAFE was largely dependent on the type of mission flown.

Shively, Robert J.

1990-01-01

440

Helicopter-borne measurements of sea ice thickness, using a small and lightweight, digital EM system  

Microsoft Academic Search

Sea ice is an important climate variable and is also an obstacle for marine operations in polar regions. We have developed a small and lightweight, digitally operated frequency-domain electromagnetic-induction (EM) system, a so-called EM bird, dedicated for measurements of sea ice thickness. It is 3.5 m long and weighs only 105 kg, and can therefore easily be shipped to remote places and

Christian Haas; John Lobach; Stefan Hendricks; Lasse Rabenstein; Andreas Pfaffling

2009-01-01

441

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

442

Two EM-type channel estimation algorithms for OFDM with transmitter diversity  

Microsoft Academic Search

We study channel estimation for orthogonal frequency-division multiplexing (OFDM) systems utilizing transmitter diversity and operating over multipath fading channels. Two expectation-maximization (EM)-type algorithms are introduced and compared with each other in terms of convergence rate. At each iteration and for every OFDM link, the EM-type algorithms partition the problem of estimating a multi-input channel into independent channel estimations for each

Yongzhe Xie; Costas N. Georghiades

2003-01-01

443

The Soils and Groundwater – EM-20 S&T Roadmap Quality Assurance Project Plan  

SciTech Connect

The Soils and Groundwater – EM-20 Science and Technology Roadmap Project is a U.S. Department of Energy, Office of Environmental Management-funded initiative designed to develop new methods, strategies and technology for characterizing, modeling, remediating, and monitoring soils and groundwater contaminated with metals, radionuclides, and chlorinated organics. This Quality Assurance Project Plan provides the quality assurance requirements and processes that will be followed by EM-20 Roadmap Project staff.

Fix, N. J.

2008-02-11

444

Very Fast EM-Based Mixture Model Clustering Using Multiresolution Kd-Trees  

Microsoft Academic Search

Clustering is important in many fields including manufacturing, biology,finance, and astronomy. Mixture models are a popular approachdue to their statistical foundations, and EM is a very popular methodfor finding mixture models. EM, however, requires many accesses ofthe data, and thus has been dismissed as impractical (e.g. (Zhang, Ramakrishnan,& Livny, 1996)) for data mining of enormous datasets.We present a new algorithm,

Andrew W. Moore

1998-01-01

445

Spin interference in quantum rings manipulated with quantum point contacts  

NASA Astrophysics Data System (ADS)

The Aharonov-Bohm (AB) and Aharonov-Casher (AC) effects are two well known interference phenomena that may appear in semiconductor quantum rings (QR's). Although the AB effect has been long observed, its counterpart, the AC effect has been only recently detected in clever magnetoconductance oscillations experiments on HgTe/HgCdTe based QR's exhibiting strong Rashba SO-interaction [1]. In this work, using the S-matrix formalism we study the role of the contacts between the leads and the QR on the AB and AC conductance oscillations of the device in the presence of Rashba and Dresselhaus type of SO interactions. We describe the backscattering and transparence of the conjunctions lead-to-ring through quantum point contacts (QPCs) modelled with gate-controllable saddle-point potentials. The variable transmitivity of the QPCs, adjusted in the experiment by gate voltages and/or applied magnetic fields, is readily incorporated in our approach. It is shown that manipulating electrostatically the confinement strength at the QPCs, may be of utility to implement a novel way to modulate spin interference effects in semiconductor quantum rings. [1] M. K"onig et al., PRL 96, 076804 (2006).

Mireles, Francisco; Diago, Leo

2009-03-01

446

Self-adjoint time operators and invariant subspaces  

NASA Astrophysics Data System (ADS)

The question of existence of self-adjoint time operators for unitary evolutions in classical and quantum mechanics is revisited on the basis of Halmos-Helson theory of invariant subspaces, Sz.-Nagy-Foia? dilation theory and Misra-Prigogine-Courbage theory of irreversibility. It is shown that the existence of self-adjoint time operators is equivalent to the intertwining property of the evolution plus the existence of simply invariant subspaces or rigid operator-valued functions for its Sz.-Nagy-Foia? functional model. Similar equivalent conditions are given in terms of intrinsic randomness in the context of statistical mechanics. The rest of the contents are mainly a unifying review of the subject scattered throughout an unconnected literature. A well-known extensive set of equivalent conditions is derived from the above results; such conditions are written in terms of Schrrdinger couples, the Weyl commutation relation, incoming and outgoing subspaces, innovation processes, Lax-Phillips scattering, translation and spectral representations, and spectral properties. Also the natural procedure dealing with symmetric time operators in standard quantum mechanics involving their self-adjoint extensions is illustrated by considering the quantum Aharonov-Bohm time-of-arrival operator.

Gómez, Fernando

2008-02-01

447

Backaction Dephasing Induced by a Quantum Dot Detector  

NASA Astrophysics Data System (ADS)

We theoretically investigate the backaction dephasing by a quantum dot detector (QDD) that couples to the quantum dot embedded in one arm of Aharonov-Bohm (AB) interferometer. We employ the nonequilibrium second-order perturbation theory and provide an analytical expression for the backaction dephasing rate, which characterizes the disturbance induced by coupling with an environment containing QDD. We show that the origin of backaction dephasing is a charge noise of QDD. In the linear transport regime through a QDD, this backaction dephasing induced by charge noise can be explained as a relaxation by an inelastic electron-electron scattering within the framework of Fermi liquid theory. In the low bias voltage regime, the increase or decrease of dephasing rate depends on the QDD energy level, the linewidth functions, and how to apply the bias voltage. Unlike quantum point contact detector, the dephasing rate would be insensitive to the bias voltage in a high bias voltage regime since the charge noise of a QDD is saturated. Moreover, such behaviors can be verified in terms of the visibility of AB oscillations by changing the bias voltage across the QDD.

Kubo, Toshihiro; Tokura, Yasuhiro

2013-03-01

448

Intrinsic spin Hall effect and orbital Hall effect in 4d and 5d transition metals  

NASA Astrophysics Data System (ADS)

We study the intrinsic spin Hall conductivity (SHC) in various 5d transition metals (Ta, W, Re, Os, Ir, Pt, and Au) and 4d transition metals (Nb, Mo, Tc, Ru, Rh, Pd, and Ag) based on the Naval Research Laboratory tight-binding model, which enables us to perform quantitatively reliable analysis. In each metal, the obtained intrinsic SHC is independent of resistivity in the low resistive regime (?<50??cm) whereas it decreases in proportion to ?-2 in the high resistive regime. In the low resistive regime, the SHC takes a large positive value in Pt and Pd, both of which have approximately nine d electrons per ion (nd=9) . On the other hand, the SHC takes a large negative value in Ta, Nb, W, and Mo, where nd<5 . In transition metals, a conduction electron acquires the trajectory-dependent phase factor that originates from the atomic wave function. This phase factor, which is reminiscent of the Aharonov Bohm phase, is the origin of the SHC in paramagnetic metals and that of the anomalous Hall conductivity in ferromagnetic metals. Furthermore, each transition metal shows huge and positive d -orbital Hall conductivity (OHC), independent of the strength of the spin-orbit interaction. Since the OHC is much larger than the SHC, it will be possible to realize an orbitronics device made of transition metals.

Tanaka, T.; Kontani, H.; Naito, M.; Naito, T.; Hirashima, D. S.; Yamada, K.; Inoue, J.

2008-04-01

449

Nonlocal momentum transfer in welcher Weg measurements  

NASA Astrophysics Data System (ADS)

A ``which-path'' (welcher Weg) measurement necessarily destroys the fringes in a double-slit interference experiment. We show that in all instances one may attribute this destruction to a disturbance of the particle's momentum by an amount equal to at least ??/2d, where d is the slit separation, in accordance with the uncertainty principle. However, this momentum transfer need not be local; that is, it need not act at either of the slits through which the particle passes. For well-known welcher Weg measurements such as Einstein's recoiling slit and Feynman's light microscope, the disturbance can be understood in terms of random classical momentum kicks that act locally. In some recent proposals, including that by Scully, Englert, and Walther [Nature (London) 351, 111 (1991)], the momentum transfer is of a peculiarly quantum, nonlocal nature. In this paper we introduce a formalism based on the Wigner function, as this describes both the local and nonlocal momentum transfer caused by any welcher Weg measurement. We show that for some examples, such as that of Scully, Englert, and Walther, there is no momentum disturbance at the slits even though the nonlocal momentum disturbance is sufficient to destroy the interference pattern. Finally, we discuss the experimental signatures of nonlocal versus local momentum transfer and demonstrate a strong similarity to the nonlocality of the Aharonov-Bohm effect.

Wiseman, H. M.; Harrison, F. E.; Collett, M. J.; Tan, S. M.; Walls, D. F.; Killip, R. B.

1997-07-01

450

Topological effects and particle physics analogies beyond the massless Dirac-Weyl fermion in graphene nanorings  

NASA Astrophysics Data System (ADS)

Armchair and zigzag edge terminations in planar hexagonal and trigonal graphene nanorings are shown to underlie one-dimensional topological states associated with distinctive energy gaps and patterns (e.g., linear dispersion of the energy of an hexagonal ring with an armchair termination versus parabolic dispersion for a zigzag terminated one) in the bands of the tight-binding spectra as a function of the magnetic field. A relativistic Dirac-Kronig-Penney model analysis of the tight-binding Aharonov-Bohm behavior reveals that the graphene quasiparticle in an armchair hexagonal ring is a condensed-matter realization of an ultrarelativistic fermion with a position-dependent mass term, akin to the zero-energy fermionic solitons with fractional charge familiar from quantum-field theory and from the theory of polyacetylene. The topological origins of the above behavior are highlighted by contrasting it with the case of a trigonal armchair ring, where we find that the quasiparticle excitations behave as familiar Dirac fermions with a constant mass. Furthermore, the spectra of a zigzag hexagonal ring correspond to the low-kinetic-energy nonrelativistic regime of a lepton-like massive fermion. A one-dimensional relativistic Lagrangian formalism coupling a fermionic and a scalar bosonic field via a Yukawa interaction, in conjunction with the breaking of the Z2 reflectional symmetry of the scalar field, is shown to unify the above dissimilar behaviors.

Romanovsky, Igor; Yannouleas, Constantine; Landman, Uzi

2013-04-01

451

Phase-dependent Andreev spectrum in a diffusive SNS junction: Static and dynamic current response  

NASA Astrophysics Data System (ADS)

A long phase coherent normal (N) wire between superconductors (S) is characterized by a dense phase-dependent Andreev spectrum. We investigate the current response of Andreev states of an NS ring to a time-dependent Aharonov Bohm flux superimposed to a dc one. The ring is modeled with a tight-binding Hamiltonian including a superconducting region with a BCS coupling between electron and hole states, in contact with a normal region with on-site disorder. Both dc and ac currents are determined from the computed eigenstates and energies using a Kubo formula approach. Beside the well-known Josephson current, we identify different contributions to the ac response: a low-frequency one related to the dynamics of the thermal occupations of the Andreev states and a higher-frequency one related to microwave induced transitions between levels. Both are characterized by phase dependencies with a high-harmonic content, opposite to one another. Our findings are successfully compared to the results of recent experiments.

Ferrier, M.; Dassonneville, B.; Guéron, S.; Bouchiat, H.

2013-11-01

452

Scaling analysis of Kondo screening cloud in a mesoscopic ring with an embedded quantum dot  

NASA Astrophysics Data System (ADS)

The Kondo effect is theoretically studied in a quantum dot embedded in a mesoscopic ring. The ring is connected to two external leads, which enables the transport measurement. Using the “poor man’s” scaling method, we obtain analytical expressions for the Kondo temperature TK as a function of the Aharonov-Bohm phase ? by the magnetic flux penetrating the ring. In this Kondo problem, there are two characteristic lengths. One is the screening length of the charge fluctuation, Lc=?vF/|?0|, where vF is the Fermi velocity and ?0 is the energy level in the quantum dot. The other is the screening length of the spin fluctuation, i.e., the size of the Kondo screening cloud, LK=?vF/TK. We obtain different expressions for 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 markedly modulated by ? in cases (ii) and (iii), whereas it hardly depends on ? in case (i). We also derive logarithmic corrections to the conductance at temperature T?TK and an analytical expression for the conductance at T?TK, on the basis of the scaling analysis.

Yoshii, Ryosuke; Eto, Mikio

2011-04-01

453

Snake orbits in graphene underneath an array of Ni0.80Fe0.20 nano-dots  

NASA Astrophysics Data System (ADS)

The existence of snake orbits in 2DEG formed at AlGaAs/GaAs heterojunction is theoretically predicted and experimentally demonstrated by creating a spatially inhomogeous magnetic field [1]. Due to its ambipolar nature, graphene opens up new possibilities to investigate snake orbits and other exotic phenomena by simply creating a p-n junction in a homogenous magnetic field. We have fabricated periodic arrays of Ni0.80Fe0.20 nano-dots on graphene with the dot diameter of 80 nm or 150 nm and the period of 160 nm or 300 nm, respectively. A quasi-periodic magneto-resistance oscillation is observed in the low-temperature magneto-transport measurement. We ascribe it to Aharonov-Bohm oscillations induced by snake orbits of carriers underneath the nano-dots. Due to the high work-function of Ni0.80Fe0.20, it is possible to generate local circular n-p and p--p junctions underneath the nanodots, which form the snake orbits of carriers in an external applied magnetic field. Dependence of these oscillations on temperature and carrier density and simulation work on snake orbits will be presented.[4pt] [1] J.E. Muller, Phys. Rev. Lett. 68, 385 (1992); P.D. Ye et al., Phys. Rev. Lett. 74, 3013 (1995).

Neal, Adam; Gu, Jiangjiang; Low, Tony; Ye, Peide

2011-03-01

454

Magnus force in superfluids and superconductors  

SciTech Connect

The forces on the vortex, transverse to its velocity, are considered. In addition to the superfluid Magnus force from the condensate (superfluid component), there are transverse forces from thermal quasiparticles and external fields violating the Galilean invariance. The forces between quasiparticles and the vortex originate from interference of quasiparticles with trajectories on the left and on the right from the vortex like similar forces for electrons interacting with the thin magnetic-flux tube (the Aharonov-Bohm effect). These forces are derived for phonons from the equations of superfluid hydrodynamics, and for BCS quasiparticles from the Bogolyubov{endash}de Gennes equations. The effect of external fields breaking Galilean invariance is analyzed for vortices in the two-dimensional Josephson junction array. The symmetry analysis of the classical equations for the array shows that the total transverse force on the vortex vanishes. Therefore the Hall effect which is linear in the transverse force is absent also. This means that the Magnus force from the superfluid component {ital exactly} cancels with the transverse force from the external fields. The results of other approaches are also brought together for discussion. {copyright} {ital 1997} {ital The American Physical Society}

Sonin, E.B. [Low Temperature Laboratory, Helsinki University of Technology, 02150 Espoo (Finland)] [Low Temperature Laboratory, Helsinki University of Technology, 02150 Espoo (Finland); [Ioffe Physical Technical Institute, St. Petersburg 194021 (Russia)

1997-01-01

455

Hybrid Superconducting Junctions of Bi2Se3 Topological Insulator Nanoribbons  

NASA Astrophysics Data System (ADS)

Topological insulators are exotic materials with bulk band gap and metallic edge states which are protected on their own boundary topologically. Here, we report on the fabrication and measurement results of the superconducting proximity junctions of topological insulator nanoribbons of Bi2Se3. Single-crystalline Bi2Se3 nanoribbons are synthesized using the vapor-liquid-solid method, while the superconducting Al electrodes are formed on top of the nanowire. When a magnetic field (H) is applied along the axial direction, the magneto-resistance data exhibit quasi-periodic oscillations with an average periodicity of H^* ˜ 0.4 T, which is consistent with the Aharonov-Bohm oscillations. In the superconducting state, the supercurrent branch with a critical current of Ic ˜ 90 nA is clearly observed in the current-voltage curve as a result of the superconducting proximity effect in Bi2Se3 nanoribbon. Quantized voltage steps of the Bi2Se3 nanoribbon Josephson junction under the microwave irradiation satisfy the ac Josephson relation.

Doh, Yong-Joo; Noh, Hyunho; Park, Lee-Seul; Jeon, Eun-Kyoung; Kim, Hong-Seok; Lee, Jeong-O.; Lee, Jin Seok; Kim, Jinhee

2012-02-01

456

Localized end states in density modulated quantum wires and rings.  

PubMed

We study finite quantum wires and rings in the presence of a charge-density wave gap induced by a periodic modulation of the chemical potential. We show that the Tamm-Shockley bound states emerging at the ends of the wire are stable against weak disorder and interactions, for discrete open chains and for continuum systems. The low-energy physics can be mapped onto the Jackiw-Rebbi equations describing massive Dirac fermions and bound end states. We treat interactions via the continuum model and show that they increase the charge gap and further localize the end states. The electrons placed in the two localized states on the opposite ends of the wire can interact via exchange interactions and this setup can be used as a double quantum dot hosting spin qubits. The existence of these states could be experimentally detected through the presence of an unusual 4? Aharonov-Bohm periodicity in the spectrum and persistent current as a function of the external flux. PMID:22540720

Gangadharaiah, Suhas; Trifunovic, Luka; Loss, Daniel

2012-03-30

457

Electrical control of a solid-state flying qubit  

NASA Astrophysics Data System (ADS)

Solid-state approaches to quantum information technology are attractive because they are scalable. The coherent transport of quantum information over large distances is a requirement for any practical quantum computer and has been demonstrated by coupling super-conducting qubits to photons. Single electrons have also been transferred between distant quantum dots in times shorter than their spin coherence time. However, until now, there have been no demonstrations of scalable `flying qubit' architectures--systems in which it is possible to perform quantum operations on qubits while they are being coherently transferred--in solid-state systems. These architectures allow for control over qubit separation and for non-local entanglement, which makes them more amenable to integration and scaling than static qubit approaches. Here, we report the transport and manipulation of qubits over distances of 6 µm within 40 ps, in an Aharonov-Bohm ring connected to two-channel wires that have a tunable tunnel coupling between channels. The flying qubit state is defined by the presence of a travelling electron in either channel of the wire, and can be controlled without a magnetic field. Our device has shorter quantum gates (<1 µm), longer coherence lengths (~86 µm at 70 mK) and higher operating frequencies (~100 GHz) than other solid-state implementations of flying qubits.

Yamamoto, Michihisa; Takada, Shintaro; Bäuerle, Christopher; Watanabe, Kenta; Wieck, Andreas D.; Tarucha, Seigo

2012-04-01

458

Neutron in a strong magnetic field: Finite volume effects  

NASA Astrophysics Data System (ADS)

We investigate the neutron's response to magnetic fields on a torus with the aid of chiral perturbation theory, and expose effects from nonvanishing holonomies. The determination of such effects necessitates nonperturbative treatment of the magnetic field; and, to this end, a strong-field power counting is employed. Using a novel coordinate-space method, we find the neutron propagates in a coordinate-dependent effective potential that we obtain by integrating out charged pions winding around the torus. Knowledge of these finite volume effects will aid in the extraction of neutron properties from lattice QCD computations in external magnetic fields. In particular, we obtain finite volume corrections to the neutron magnetic moment and magnetic polarizability. These quantities have not been computed correctly in the literature. In addition to effects from nonvanishing holonomies, finite volume corrections depend on the magnetic flux quantum through an Aharonov-Bohm effect. We make a number of observations that demonstrate the importance of nonperturbative effects from strong magnetic fields currently employed in lattice QCD calculations. These observations concern neutron physics in both finite and infinite volume.

Tiburzi, Brian C.

2014-04-01

459

Some global problems in gauge theories (Variations on a theme of Aharonov and Bohm)  

SciTech Connect

Several situations are discussed, in which the sort of global considerations made famous by Aharonov and Bohm in their discussion of the interaction of charged particles with magnetic flux tubes have important physical implications. It is argued that discrete gauge symmetries in the continuum make sense, and manifest themselves most clearly in Aharonov-Bohm type scattering of charged particles off string singularities. The existence of such discrete symmetries has important implications for the quantum mechanics of topologically non-trivial space-times in general and black holes in particular. It is argued that in the non-abelian case essentially new features arise, most notably that the symmetry group of the homogeneous ground state generally ceases to be globally defined in the presence of a string. When continuous rather than discrete symmetries are involved, a variety of fascinating and as yet poorly understood dynamical effects occur. Perhaps the most striking is a new form of string superconductivity, that exists for purely topological reasons, and is not well modeled by regarding the string as a superconducting wire. 8 refs., 2 figs.

Wilczek, F.

1989-12-01

460

Fano-Rashba effect in thermoelectricity of a double quantum dot molecular junction  

PubMed Central

We examine the relation between the phase-coherent processes and spin-dependent thermoelectric effects in an Aharonov-Bohm (AB) interferometer with a Rashba quantum dot (QD) in each of its arm by using the Green's function formalism and equation of motion (EOM) technique. Due to the interplay between quantum destructive interference and Rashba spin-orbit interaction (RSOI) in each QD, an asymmetrical transmission node splits into two spin-dependent asymmetrical transmission nodes in the transmission spectrum and, as a consequence, results in the enhancement of the spin-dependent thermoelectric effects near the spin-dependent asymmetrical transmission nodes. We also examine the evolution of spin-dependent thermoelectric effects from a symmetrical parallel geometry to a configuration in series. It is found that the spin-dependent thermoelectric effects can be enhanced by controlling the dot-electrode coupling strength. The simple analytical expressions are also derived to support our numerical results. PACS numbers: 73.63.Kv; 71.70.Ej; 72.20.Pa

2011-01-01

461

Quantizations on the circle and coherent states  

NASA Astrophysics Data System (ADS)

We present a possible construction of coherent states on the unit circle as configuration space. Our approach is based on Borel quantizations on S1 including the Aharonov-Bohm-type quantum description. Coherent states are constructed by Perelomov’s method as group-related coherent states generated by Weyl operators on the quantum phase space {Z} \\times 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} \\times {Z}_{M}. The coherent states constructed in this work are shown to satisfy the resolution of unity. To compare them with canonical coherent states, some of their further properties are also studied demonstrating similarities as well as substantial differences. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’.

Ch