Jones-Smith, Katherine; Vachaspati, Tanmay
2009-01-01
A solenoid oscillating in vacuum will pair produce charged particles due to the Aharonov-Bohm (AB) interaction. We calculate the radiation pattern and power emitted for charged scalar particles. We extend the solenoid analysis to cosmic strings, and find enhanced radiation from cusps and kinks on loops. We argue by analogy with the electromagnetic AB interaction that cosmic strings should emit photons due to the gravitational AB interaction of fields in the conical spacetime of a cosmic string. We calculate the emission from a kink and find that it is of similar order as emission from a cusp, but kinks are vastly more numerous than cusps and may provide a more interesting observational signature.
NASA Astrophysics Data System (ADS)
Jones-Smith, Katherine; Mathur, Harsh; Vachaspati, Tanmay
2010-02-01
A solenoid oscillating in vacuum will pair produce charged particles due to the Aharonov-Bohm (AB) interaction. We calculate the radiation pattern and power emitted for charged scalar particles. We extend the solenoid analysis to cosmic strings and find enhanced radiation from cusps and kinks on loops. We argue by analogy with the electromagnetic AB interaction that cosmic strings should emit photons due to the gravitational AB interaction of fields in the conical spacetime of a cosmic string. We calculate the emission from a kink and find that it is of similar order as emission from a cusp, but kinks are vastly more numerous than cusps and may provide a more interesting observational signature.
Quantum Faraday Effect in Double-Dot Aharonov-Bohm Ring
Kicheon Kang
2011-02-25
We investigate Faraday's law of induction manifested in the quantum state of Aharonov-Bohm loops. In particular, we propose a flux-switching experiment for a double-dot AB ring to verify the phase shift induced by Faraday's law. We show that the induced {\\em Faraday phase} is geometric and nontopological. Our study demonstrates that the relation between the local phases of a ring at different fluxes is not arbitrary but is instead determined by Faraday's inductive law, which is in strong contrast to the arbitrary local phase of an Aharonov-Bohm ring for a given flux.
The Electric Aharonov-Bohm Effect
Ricardo Weder
2011-07-14
In their seminal paper Aharonov and Bohm (1959) 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. They proposed two experiments to verify their theoretical conclusions. The magnetic effect, that has been extensively studied, and the electric 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. The existence of electric Aharonov-Bohm effect, 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 estimulate the experimental research on the electric Aharonov-Bohm effect.
Tests of the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Caprez, Adam Preston
The Aharonov-Bohm effect was first proposed in 1959, and has stimulated discussion and controversy since the start. Seen by many as a purely quantum mechanical effect, it nevertheless involves such issues as gauge invariance and relativistic dynamics. This multi-faceted nature has led it to be considered a keystone of modern quantum theory. Over the past half-century, interest has remained strong in what many believe is still an open debate as to the purely quantum nature. Additionally, discovery of similar effects for particles other than electrons has further driven curiosity. To better understand the issues such as electromagnetic mass and relativistic effects involved in the Aharonov-Bohm effect, a theoretical study of a simpler two particle system was done. The goal was to understand the manner in which mass of the system behaved strictly classically as compared to a relativistically. As a result of this, a Gedanken experiment is presented which serves as a test for covariance. The two particle system was extended to a spherical shell interacting with a single particle, and a second thought experiment put forth to explore a coupling between electromagnetism and gravitation. In the course of searching for simpler systems which involved the same issues as the Aharonov-Bohm effect, a system presented in the Feynman Lectures of Physics was found to be appropriate. We conduct a complete relativistic analysis of this system as a step towards a full relativistic analysis of the Aharonov-Bohm effect. Given the history and significance of the Aharonov-Bohm effect, it is perhaps surprising that relevant experimental tests had not been completed. For the first time, we searched for time delays as an electron passes a macroscopic solenoid. Such time delays are characteristic of classical forces acting on the electron. No such delays were found, seemingly confirming the standard viewpoint. It is still possible a classical explanation may exist for microscopic solenoids, though our experiment has served to place an upper limit for any such explanation. The definitive experiment concerning the Aharonov-Bohm Effect has yet to be completed. Proposed by Zeilinger, it consists of showing the dispersionless nature of the effect. To accomplish this requires an electron interferometer capable of enclosing a larger area and operating at lower energies than any which currently exist. We are attempting to construct such an interferometer using a hybrid approach with a nanofabricated grating and electron bi-prism. We have shown that experimentally that this combination can produce a large beam separation and still retain sufficient coherence to function as an interferometer.
Gravitational Dressing of Aharonov-Bohm Amplitudes
G. Amelino-Camelia; I. I. Kogan; R. J. Szabo
1996-10-09
We investigate Aharonov-Bohm scattering in a theory in which charged bosonic matter fields are coupled to topologically massive electrodynamics and topologically massive gravity. We demonstrate that, at one-loop order, the transmuted spins in this theory are related to the ones of ordinary Chern-Simons gauge theory in the same way that the Knizhnik-Polyakov-Zamolodchikov formula relates the Liouville-dressed conformal weights of primary operators to the bare weights in two-dimensional conformal field theories. We remark on the implications of this connection between two-dimensional conformal field theories and three-dimensional gauge and gravity theories for a topological membrane reformulation of strings. We also discuss some features of the gravitational analog of the Aharonov-Bohm effect.
The electric Aharonov-Bohm effect
Weder, Ricardo
2011-05-15
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.
Quantum chaos in Aharonov-Bohm oscillations
Berman, G.P.; Campbell, D.K.; Bulgakov, E.N.; Krive, I.V.
1995-10-01
Aharonov-Bohm oscillations in a mesoscopic ballistic ring are considered under the influence of a resonant magnetic field with one and two frequencies. The authors investigate the oscillations of the time-averaged electron energy at zero temperature in the regime of an isolated quantum nonlinear resonance and at the transition to quantum chaos, when two quantum nonlinear resonances overlap. It is shown that the time-averaged energy exhibits resonant behavior as a function of the magnetic flux, and has a ``staircase`` dependence on the amplitude of the external field. The delocalization of the quasi-energy eigenfunctions is analyzed.
Aharonov-Bohm radiation of fermions
NASA Astrophysics Data System (ADS)
Chu, Yi-Zen; Mathur, Harsh; Vachaspati, Tanmay
2010-09-01
We analyze Aharonov-Bohm radiation of charged fermions from oscillating solenoids and cosmic strings. We find that the angular pattern of the radiation has features that differ significantly from that for bosons. For example, fermionic radiation in the lowest harmonic is approximately isotropically distributed around an oscillating solenoid, whereas for bosons the radiation is dipolar. We also investigate the spin polarization of the emitted fermion-antifermion pair. Fermionic radiation from kinks and cusps on cosmic strings is shown to depend linearly on the ultraviolet cutoff, suggesting strong emission at an energy scale comparable to the string energy scale.
Aharonov-Bohm phase for an electromagnetic wave background
Max Bright; Douglas Singleton; Atsushi Yoshida
2015-09-05
The canonical Aharonov-Bohm effect is usually studied with time-independent potentials. In this work, we investigate the Aharonov-Bohm phase acquired by a charged particle moving in {\\it time-dependent} potentials . In particular, we focus on the case of a charged particle moving in the time varying field of a plane electromagnetic wave. We work out the Aharonov-Bohm phase using both the potential ({\\it i.e.} $\\oint A_\\mu dx ^\\mu$) and field ({\\it i.e.} $\\frac{1}{2}\\int F_{\\mu \
Aharonov-Bohm phase for an electromagnetic wave background
Bright, Max; Yoshida, Atsushi
2015-01-01
The canonical Aharonov-Bohm effect is usually studied with time-independent potentials. In this work, we investigate the Aharonov-Bohm phase acquired by a charged particle moving in {\\it time-dependent} potentials . In particular, we focus on the case of a charged particle moving in the time varying field of a plane electromagnetic wave. We work out the Aharonov-Bohm phase using both the potential ({\\it i.e.} $\\oint A_\\mu dx ^\\mu$) and field ({\\it i.e.} $\\frac{1}{2}\\int F_{\\mu \
Calculation of the Aharonov-Bohm wave function
Alvarez, M.
1996-08-01
A calculation of the Aharonov-Bohm wave function is presented. The result is an asymptotic series of confluent hypergeometric functions which is finite at the forward direction. {copyright} {ital 1996 The American Physical Society.}
New formulae for the Aharonov-Bohm wave operators
S. Richard
2008-11-24
It is proved that the wave operators corresponding to Schroedinger operators with Aharonov-Bohm type magnetic fields can be rewritten in terms of explicit functions of the generator of dilations and of the Laplacian.
On the feasibility of detecting an Aharonov-Bohm phase shift in neutral matter
Sato, Yuki
On the feasibility of detecting an Aharonov-Bohm phase shift in neutral matter Yuki Sato state. This surprising result arises from non-cancellation of the Aharonov-Bohm phase shifts associated would exhibit an Aharonov-Bohm (AB) type phase shift when moving in a magnetic field. However
Group-theoretical derivation of Aharonov-Bohm phase shifts
Hagen, C. R. [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627-0171 (United States)] [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627-0171 (United States)
2013-02-15
The phase shifts of the Aharonov-Bohm effect are generally determined by means of the partial wave decomposition of the underlying Schroedinger equation. It is shown here that they readily emerge from an o(2,1) calculation of the energy levels employing an added harmonic oscillator potential which discretizes the spectrum.
Group-Theoretical Derivation of Aharonov-Bohm Phase Shifts
C. R. Hagen
2012-11-16
The phase shifts of the Aharonov-Bohm effect are generally determined by means of the partial wave decomposition of the underlying Schrodinger equation. It is shown here that they readily emerge from an o(2,1) calculation of the energy levels employing an added harmonic oscillator potential which discretizes the spectrum.
Symmetry-protected many-body Aharonov-Bohm effect
Santos, Luiz H.
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 ...
Noiseless Quantum Transmission of Information via Aharonov - Bohm Effect
Jian-Zu Zhang
2008-10-24
The possibility of quantum transmission of information via the induced fractional angular momentum by the Aharonov - Bohm vector potential is revealed. Its special advantage is that it is noiseless: Stray magnetic fields of environments influence the energy spectrum of the ion, but cannot contribute the fractional angular momentum to cause noise.
The Aharonov–Bohm effect in scattering theory
Sitenko, Yu.A.; Vlasii, N.D.
2013-12-15
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.
The Aharonov-Bohm effect for a knotted magnetic solenoid
Roman V. Buniy; Thomas W. Kephart
2008-08-13
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).
Aharonov Bohm effect on noncommutative plane: A coherent state approach
NASA Astrophysics Data System (ADS)
Anacleto, M. A.; Nascimento, J. R.; Petrov, A. Yu.
2006-06-01
We formulate in a systematic manner the coherent state approach and apply it to study Aharonov-Bohm effect in the field theory context. Within this approach, we verify that the scattering amplitude is ultraviolet finite. Also, we prove that introduction of a quartic self-interaction for the scalar field allows to obtain a smooth commutative limit.
Symmetry-protected many-body Aharonov-Bohm effect
Luiz H. Santos; Juven Wang
2014-08-19
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 wavefunction. Specifically, we study this many-body effect on the gapless edge states of a bulk gapped phase protected by a global symmetry (such as $\\mathbb{Z}_{N}$) - the symmetry-protected topological (SPT) states. The many-body analogue of spectral shifts, the twisted wavefunction 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.
Effects of external radiation on biased Aharonov-Bohm rings
NASA Astrophysics Data System (ADS)
Entin-Wohlman, O.; Imry, Y.; Aharony, A.
2004-08-01
We consider the currents flowing in a solid-state interferometer under the effect of both an Aharonov-Bohm phase and a bias potential. Expressions are obtained for these currents, allowing for electronic or electron-boson interactions, which may take place solely on a quantum dot placed on one of the interferometer arms. The boson system can be out of equilibrium. The results are used to obtain the transport current through the interferometer, and the current circulating around it under the effect of the Aharonov-Bohm flux. The modifications of both currents, brought about by coupling the quantum dot to an incoherent sonic or electromagnetic source, are then analyzed. By choosing the appropriate range of the boson source intensity and its frequency, the magnitude of the interference-related terms of both currents can be controlled.
An experiment to test the gravitational Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Ho, Vu B.; Morgan, Michael J.
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.
Spectroscopic version of the Aharonov-Bohm effect
C. Laganá
2015-06-01
An experiment is proposed in which the Aharonov-Bohm effect can be veryfied through a spectroscopic measurement. The apparatus consists of gaseous hydrochloric acid (HCl) immersed in the constant vector potential ${\\bf A}=A_0{\\bf z}$ present in the center of a toroidal coil, where ${\\bf B}=0$. Changes due to ${\\bf A}$ in the absorption spectrum of the gas are investigated.
Magnetotransport in Aharonov-Bohm interferometers: Exact numerical simulations
NASA Astrophysics Data System (ADS)
Bedkihal, Salil; Segal, Dvira
2014-12-01
The linear conductance of a two-terminal Aharonov-Bohm interferometer is an even function of the applied magnetic flux, as dictated by the Onsager-Casimir symmetry. Away from linear response this symmetry may be broken when many-body interactions are in effect. Using a numerically exact simulation tool, we study the dynamics and the steady-state behavior of the out-of-equilibrium double-dot Aharonov-Bohm interferometer, while considering different types of interactions: Model I includes a closed interferometer with an interdot electron-electron repulsion energy. In model II the interferometer is interacting with a dissipative environment, possibly driven away from equilibrium. In both cases we show that depending on the (horizontal, vertical) mirror symmetries of the setup, nonlinear transport coefficients obey certain magnetosymmetries. We compare numerically exact simulations to phenomenological approaches and special limits: The behavior of model I is compared to self-consistent mean-field calculations and master equation results in the Coulomb blockade regime. Model II, allowing heat dissipation to a thermal bath, is mimicked by an Aharonov-Bohm junction with a voltage probe. In both cases we find that phenomenological treatments capture the relevant transport symmetries, yet significant deviations in magnitude may show up.
M. Chaichian; A. Demichev; P. Presnajder; M. M. Sheikh-Jabbari; A. Tureanu
2001-01-01
After discussing the peculiarities of quantum systems on noncommutative (NC) spaces with nontrivial topology and the operator representation of the ?-product on them, we consider the Aharonov–Bohm and Casimir effects for such spaces. For the case of the Aharonov–Bohm effect, we have obtained an explicit expression for the shift of the phase, which is gauge invariant in the NC sense.
Discrete gauge symmetry and Aharonov-Bohm radiation in string theory
NASA Astrophysics Data System (ADS)
Ookouchi, Yutaka
2014-01-01
We investigate cosmological constraints on phenomenological models with discrete gauge symmetries by discussing the radiation of standard model particles from Aharonov-Bohm strings. Using intersecting D-brane models in Type IIA string theory, we demonstrate that Aharonov-Bohm radiation, when combined with cosmological observations, imposes constraints on the compactification scales.
Gravitational Aharonov-Bohm effect and gravitational lensing
A. Tartaglia
2000-03-08
Considering the spacetime around a rotating massif body it is seen that the time of flight of a light ray is different whether it travels on one side of the source or on the other. The difference is proportional to the angular momentum of the body. In the case that a compact rapidly rotating object is the source of a gravitational lensing effect, the contribution coming from the above mentioned gravitational Aharonov-Bohm effect should be added to the other causes of phase difference between light rays coming from different images of the same object.
The incident wave in Aharonov-Bohm scattering wavefunction
Sahng-Kyoon Yoo; D. K. Park
1997-07-02
It is shown that only the infinite angular momentum quantum states contribute to the incident wave in Aharonov-Bohm (AB) scattering. This result is clearly shown by recalculating the AB calculation with arbitrary decomposition of summation over the angular momentum quantum numbers in wave function. It is motivated from the fact that the pole contribution in the integral representation used by Jackiw is given by only the infinite angular momentum states, in which the closed contour integration involving this pole gives just the incident wave.
Combined Electric and Magnetic Aharonov-Bohm Effects
Samuel Marcovitch; Yakir Aharonov; Tirza Kaufferr; Benni Reznik
2007-09-11
It is well-known that the electric and magnetic Aharonov-Bohm effects may be formally described on equal footing using the four-vector potential in a relativistic framework. We propose an illustrative manifestation of both effects in a single configuration, in which the specific path of the charged particle determines the weight of the electric and magnetic acquired relative phases. The phases can be distinctively obtained in the Coulomb gauge. The scheme manifests the pedagogical lesson that though each of the relative phases is gauge-dependent their sum is gauge-invariant.
Complemetarity of Phases in Aharonov-Bohm Solenoid Effect
Y. Ben-Aryeh
2011-12-21
In the present Note it is suggested that there should be a certain complementarity of phases between Aharonov-Bohm (AB) solenoid phase calculation on one part of the system and a phase calculation about another part of the physical system. Assuming a unique value for the function of the total system, after a complete circulation of the electron around the solenoid, the sum of these two phase changes should vanish. Such assumption leads to a compatibility relation between our previous calculations for the AB solenoid phase effect and that of the original calculation by AB.
L-Dependence of Particle Radiation in Magnetic-Solenoid Field as Aharonov-Bohm Effect
NASA Astrophysics Data System (ADS)
Bagrov, V. G.; Gitman, D. M.; Tlyachev, V. B.
Aharonov-Bohm solenoid changes the energy spectrum of charge particles in pure magnetic field. In particular, the degeneracy with respect to azimuthal quantum number l is partially lifted. In turn, this complicates the radiation spectrum of a charged particle in magnetic field in the presence of the solenoid (Aharonov-Bohm effect). In particular, the degeneracy of the radiation intensity with respect to the azimuthal quantum number is lifted completely. In the present work we study l-dependence (induced by Aharonov-Bohm solenoid) of synchrotron radiation intensity in semiclassical approximation.
Aharonov-Bohm effect in a mesoscopic metallic ring with a microwave induced superstructure
NASA Astrophysics Data System (ADS)
Aronov, I. E.; Bogachek, E. N.; Krive, I. V.
1992-04-01
Aharonov-Bohm oscillations in a mesoscopic metallic ring exposed to a microwave electromagnetic field are considered. It is shown that the oscillation amplitude decreases periodically with the radiation intensity.
Iye, Yasuhiro
Resistance Fluctuations and AharonovBohm-Type Oscillations in Antidot Arrays in the Quantum Hall, 2008; published September 10, 2008) Resistance fluctuation phenomenon in antidot lattices plateau transition regime exhibits two types of oscillatory effect. One is the aperiodic resistance
Revisiting the Marton, Simpson, and Suddeth experimental confirmation of the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Macdougall, James; Singleton, Douglas; Vagenas, Elias C.
2015-09-01
We perform an "archeological" study of one of the original experiments used as evidence for the static, time-independent Aharonov-Bohm effect. Since the experiment in question [1] involved a time varying magnetic field we show that there are problems with the explanation of this experiment as a confirmation of the static Aharonov-Bohm effect - specifically the previous analysis ignored the electric field which arises in conjunction with a time-varying magnetic flux. We further argue that the results of this experiment do in fact conform exactly to the recent prediction [2,3] of a cancellation between the magnetic and electric phase shifts for the time-dependent Aharonov-Bohm effect. To resolve this issue a new time-dependent Aharonov-Bohm experiment is called for.
Propagators for Spinless and Spin-1/2 Aharonov-Bohm-Coulomb Systems
NASA Astrophysics Data System (ADS)
Park, D. K.; Yoo, Sahng-Kyoon
1998-03-01
The propagator of the spinless Aharonov-Bohm-Coulomb system is derived by following the Duru-Kleinert method. We use this propagator to explore the spin-1/2 Aharonov-Bohm-Coulomb system which contains a point interaction as a Zeeman term. Incorporation of the self-adjoint extension method into the Green's function formalism properly allows us to derive the finite propagator of the spin-1/2 Aharonov-Bohm-Coulomb system. As a by-product, the relation between the self-adjoint extension parameter and the bare coupling constant is obtained. Bound-state energy spectra of both spinless and spin-1/2 Aharonov-Bohm-Coulomb systems are examined.
Gravito-electromagnetic Aharonov-Bohm effect: some rotation effects revised
Ruggiero, Matteo Luca
2010-01-01
By means of the description of the standard relative dynamics in terms of gravito-electromagnetic fields, in the context of natural splitting, we formally introduce the gravito-magnetic Aharonov-Bohm effect. Then, we interpret the Sagnac effect as a gravito-magnetic Aharonov-Bohm effect and we exploit this formalism for studying the General Relativistic corrections to the Sagnac effect in stationary and axially symmetric geometries.
Gravito-electromagnetic Aharonov-Bohm effect: some rotation effects revised
Matteo Luca Ruggiero
2010-07-22
By means of the description of the standard relative dynamics in terms of gravito-electromagnetic fields, in the context of natural splitting, we formally introduce the gravito-magnetic Aharonov-Bohm effect. Then, we interpret the Sagnac effect as a gravito-magnetic Aharonov-Bohm effect and we exploit this formalism for studying the General Relativistic corrections to the Sagnac effect in stationary and axially symmetric geometries.
Impact of Aharonov-Bohm Solenoid on Particle Radiation in Magnetic Field
NASA Astrophysics Data System (ADS)
Bagrov, V. G.; Gitman, D. M.; Levin, A. D.; Tlyachev, V. B.
We study the impact of Aharonov-Bohm solenoid on the radiation of a charged particle moving in a constant uniform magnetic field. Radiation peculiarities caused by the presence of the solenoid may be considered as a manifestation of Aharonov-Bohm effect in the radiation. In particular, new spectral lines appear in the radiation spectrum. Due to angular distribution peculiarities of the radiation intensity, these lines can in principle be isolated from basic cyclotron and synchrotron radiation spectra.
Radiation of supersymmetric particles from Aharonov-Bohm R-string
NASA Astrophysics Data System (ADS)
Ookouchi, Yutaka; Yonemoto, Takahiro
2015-02-01
We study radiation of supersymmetric particles from an Aharonov-Bohm string associated with a discrete R-symmetry. Radiation of the lightest supersymmetric particle, when combined with the observed dark matter density, imposes constraints on the string tension or the freeze-out temperature of the particle. We also calculate the amplitude for Aharonov-Bohm radiation of massive spin 3/2 particles.
Magnetism in a Wigner solid and Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Okamoto, Tohru; Kawaji, Shinji
1998-06-01
Thermal activation energy EA in an insulation phase of a two-dimensional electron system formed in an Si inversion layer has been studied. All the results which depend both on total strength Btot and normal component B? of a magnetic field are quantitatively explained by a model based on exchange interactions in a Wigner solid ( rs?8). We attribute the observed peculiar B?-dependence of EA in which two minima appear at B??0.6 Ns?0 and B??1.1 Ns?0 for ?0= h/ e to the Aharonov-Bohm effect on the three-electron ring exchange interaction of which exchange constant is in the same order as that from the multidimensional WKB calculation of Roger (Phys. Rev. B 30 (1984) 6432).
An Aharonov-Bohm interferometer for determining Bloch band topology.
Duca, L; Li, T; Reitter, M; Bloch, I; Schleier-Smith, M; Schneider, U
2015-01-16
The geometric structure of a single-particle energy band in a solid is fundamental for a wide range of many-body phenomena and is uniquely characterized by the distribution of Berry curvature over the Brillouin zone. We realize an atomic interferometer to measure Berry flux in momentum space, in analogy to an Aharonov-Bohm interferometer that measures magnetic flux in real space. We demonstrate the interferometer for a graphene-type hexagonal optical lattice loaded with bosonic atoms. By detecting the singular ? Berry flux localized at each Dirac point, we establish the high momentum resolution of this interferometric technique. Our work forms the basis for a general framework to fully characterize topological band structures. PMID:25525160
NASA Astrophysics Data System (ADS)
Chiao, Raymond Y.; Haun, Robert W.; Inan, Nader A.; Kang, Bong-Soo; Martinez, Luis A.; Minter, Stephen J.; Munoz, Gerardo A.; Singleton, Douglas A.
A thought experiment is proposed to demonstrate the existence of a gravitational, vector Aharonov-Bohm effect. We begin the analysis starting from four Maxwell-like equations for weak gravitational fields interacting with slowly moving matter. A connection is made between the gravitational, vector Aharonov-Bohm effect and the principle of local gauge invariance for nonrelativistic quantum matter interacting with weak gravitational fields. The compensating vector fields that are necessitated by this local gauge principle are shown to be incorporated by the DeWitt minimal coupling rule. The nonrelativistic Hamiltonian for weak, time-independent fields interacting with quantum matter is then extended to time-dependent fields, and applied to the problem of the interaction of radiation with macroscopically coherent quantum systems, including the problem of gravitational radiation interacting with superconductors. But first we examine the interaction of EM radiation with superconductors in a parametric oscillator consisting of a superconducting wire placed at the center of a high Q superconducting cavity driven by pump microwaves. Some room-temperature data will be presented demonstrating the splitting of a single microwave cavity resonance into a spectral doublet due to the insertion of a central wire. This would represent an unseparated kind of parametric oscillator, in which the signal and idler waves would occupy the same volume of space. We then propose a separated parametric oscillator experiment, in which the signal and idler waves are generated in two disjoint regions of space, which are separated from each other by means of an impermeable superconducting membrane. We find that the threshold for parametric oscillation for EM microwave generation is much lower for the separated configuration than the unseparated one, which then leads to an observable dynamical Casimir effect. We speculate that a separated parametric oscillator for generating coherent GR microwaves could also be built. [Editor's note: for a video of the talk given by Prof. Chiao at the Aharonov-80 conference in 2012 at Chapman University, see http://quantum.chapman.edu/talk-20.
The Aharonov-Bohm effect in Möbius rings
NASA Astrophysics Data System (ADS)
Li, Zehao; Ram-Mohan, L.; Center for Computational NanoScience Team
2013-03-01
Electron transmission through finite-width 2D ring structures is calculated for cylindrical, flat (Aharonov-Bohm), and Möbius rings. In the presence of an external magnetic field, curves of constructive transmission display a pattern similar to that for a 1D ring. The periodicity in the magnetic flux, in units of h / e , is weakly broken on 2D rings of finite width, so that a description with a 1D-path is very acceptable. The unusual states with half-integer values of
Loop Quantum Gravity a la Aharonov-Bohm
Eugenio Bianchi
2009-09-10
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.
Aharonov-Bohm interference in topological insulator nanoribbons.
Peng, Hailin; Lai, Keji; Kong, Desheng; Meister, Stefan; Chen, Yulin; Qi, Xiao-Liang; Zhang, Shou-Cheng; Shen, Zhi-Xun; Cui, Yi
2010-03-01
Topological insulators represent unusual phases of quantum matter with an insulating bulk gap and gapless edges or surface states. The two-dimensional topological insulator phase was predicted in HgTe quantum wells and confirmed by transport measurements. Recently, Bi(2)Se(3) and related materials have been proposed as three-dimensional topological insulators with a single Dirac cone on the surface, protected by time-reversal symmetry. The topological surface states have been observed by angle-resolved photoemission spectroscopy experiments. However, few transport measurements in this context have been reported, presumably owing to the predominance of bulk carriers from crystal defects or thermal excitations. Here we show unambiguous transport evidence of topological surface states through periodic quantum interference effects in layered single-crystalline Bi(2)Se(3) nanoribbons, which have larger surface-to-volume ratios than bulk materials and can therefore manifest surface effects. Pronounced Aharonov-Bohm oscillations in the magnetoresistance clearly demonstrate the coherent propagation of two-dimensional electrons around the perimeter of the nanoribbon surface, as expected from the topological nature of the surface states. The dominance of the primary h/e oscillation, where h is Planck's constant and e is the electron charge, and its temperature dependence demonstrate the robustness of these states. Our results suggest that topological insulator nanoribbons afford promising materials for future spintronic devices at room temperature. PMID:20010826
Loop Quantum Gravity à la Aharonov-Bohm
NASA Astrophysics Data System (ADS)
Bianchi, Eugenio
2014-02-01
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.
Quantum interference and Aharonov-Bohm oscillations in topological insulators
NASA Astrophysics Data System (ADS)
Bardarson, Jens H.; Moore, Joel E.
2013-05-01
Topological insulators (TIs) have an insulating bulk but a metallic surface. In the simplest case, the surface electronic structure of a three-dimensional (3D) TI is described by a single two-dimensional (2D) Dirac cone. A single 2D Dirac fermion cannot be realized in an isolated 2D system with time-reversal symmetry, but rather owes its existence to the topological properties of the 3D bulk wavefunctions. The transport properties of such a surface state are of considerable current interest; they have some similarities with graphene, which also realizes Dirac fermions, but have several unique features in their response to magnetic fields. In this review we give an overview of some of the main quantum transport properties of TI surfaces. We focus on the efforts to use quantum interference phenomena, such as weak anti-localization and the Aharonov-Bohm effect, to verify in a transport experiment the Dirac nature of the surface state and its defining properties. In addition to explaining the basic ideas and predictions of the theory, we provide a survey of recent experimental work.
Gravito-electromagnetic Aharonov-Bohm effect: some rotation effects revised
Matteo Luca Ruggiero
2010-01-01
By means of the description of the standard relative dynamics in terms of\\u000agravito-electromagnetic fields, in the context of natural splitting, we\\u000aformally introduce the gravito-magnetic Aharonov-Bohm effect. Then, we\\u000ainterpret the Sagnac effect as a gravito-magnetic Aharonov-Bohm effect and we\\u000aexploit this formalism for studying the General Relativistic corrections to the\\u000aSagnac effect in stationary and axially symmetric geometries.
The Crucial Role of Inert Source in the Magnetic Aharonov-Bohm Effect
E. Comay
2009-10-17
The role of the inert magnetic source used in the Tonomura experiment that has confirmed the magnetic Aharonov-Bohm effect is discussed. For this purpose, an analysis of a thought experiment is carried out. Here the permanent magnet is replaced by a classical source which is made of an ideal coil. A detailed calculation of this noninert source proves that in this case the effect disappears. This outcome provides another support for the crucial role of an inert source in the Aharonov-Bohm effect. A new aspect of quantum nonlocality is pointed out.
The Aharonov-Bohm solenoids in a constant magnetic eld Takuya Mine
The Aharonov-Bohm solenoids in a constant magnetic #12;eld Takuya Mine Department of Mathematics, Faculty of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan. (e-mail: mine associated to the form closure of D(LN ), see [Re-Si, Theorem X.23]) by H AB N , which is called the standard
Modular Momentum of the Aharonov-Bohm Effect on Noncommutative Lattices
Takeo Miura
2012-07-23
Based on the technique of noncommutative geometry, it is shown that, by means of the concept of the theta quantization, there is an equivalence between the notion of the modular momentum of the Aharonov-Bohm effect and the notion of a noncommutative lattice over a circle poset.
Stokes' theorem, gauge symmetry and the time-dependent Aharonov-Bohm effect
Macdougall, James Singleton, Douglas
2014-04-15
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.
Eigenvalue estimates for the Aharonov-Bohm operator in a domain
Rupert L. Frank; Anders Hansson
2007-10-04
We prove semi-classical estimates on moments of eigenvalues of the Aharonov-Bohm operator in bounded two-dimensional domains. Moreover, we present a counterexample to the generalized diamagnetic inequality which was proposed by Erdos, Loss and Vougalter. Numerical studies complement these results.
The Sagnac Phase Shift Suggested by the Aharonov-Bohm Effect for Relativistic Matter Beams
Guido Rizzi; Matteo Luca Ruggiero
2003-01-01
The phase shift due to the Sagnac Effect, for relativistic matter beams counter-propagating in a rotating interferometer, is deduced on the bases of a formal analogy with the Aharonov-Bohm effect. A procedure outlined by Sakurai, in which non relativistic quantum mechanics and Newtonian physics appear together with some intrinsically relativistic elements, is generalized to a fully relativistic context, using the
Phase evolution of the transmission coefficient in an Aharonov-Bohm ring with Fano resonance
Chang-Mo Ryu; Sam Young Cho
1998-01-01
Phase of the transmission coefficient for a mesoscopic loop with Fano resonance has been investigated by using the scattering matrix method, for a model of an Aharonov-Bohm ring with a double barrier coupled to a t-stub resonator in one arm. It is found that the phase varies rapidly by pi on the shoulder of a resonance peak. In addition, it
Revisiting the Marton, Simpson, and Suddeth experimental confirmation of the Aharonov-Bohm effect
James Macdougall; Douglas Singleton; Elias C. Vagenas
2015-05-16
We perform an "archeological" study of one of the original experiments used as evidence for the static, time-independent Aharonov-Bohm effect. Since the experiment in question [L. Marton, J. A. Simpson, and J. A. Suddeth, Rev. Sci. Instr. 25, 1099 (1954)] involved a time varying magnetic field we show that there are problems with the explanation of this experiment as a confirmation of the static Aharonov-Bohm effect -- specifically the previous analysis ignored the electric field which arises in conjunction with a time-varying magnetic flux. We further argue that the results of this experiment do in fact conform exactly to the recent prediction [D. Singleton and E. Vagenas, Phys. Lett. B723, 241 (2013); J. MacDougall and D. Singleton, J. Math. Phys. 55, 042101 (2014)] of a cancellation between the magnetic and electric phase shifts for the time-dependent Aharonov-Bohm effect. To resolve this issue a new time-dependent Aharonov-Bohm experiment is called for.
Path integral for relativistic Aharonov-Bohm-Coulomb system on the pseudo-sphere
NASA Astrophysics Data System (ADS)
Nouicer, Kh.; Chetouani, L.
2001-03-01
The Green's function for relativistic spinless Aharonov-Bohm-Coulomb (ABC) system on the pseudo-sphere ?(2) is calculated using Kleinert's path integral representation for relativistic spinless particles. The energy spectrum and the corresponding wave functions are extracted for bound and scattering states. The results in the nonrelativistic and flat space limits are considered.
Nucleon statistics in holographic QCD: Aharonov-Bohm effect in a matrix model
Hashimoto, Koji [Mathematical Physics Lab., RIKEN Nishina Center, Saitama 351-0198 (Japan); Iizuka, Norihiro [Theory Division, CERN, CH-1211 Geneva 23 (Switzerland)
2010-11-15
We show that the Aharonov-Bohm effect in the nuclear matrix model [K. Hashimoto, N. Iizuka, and P. Yi, J. High Energy Phys. 10 (2010), 3.] derives the statistical nature of nucleons in holographic QCD. For N{sub c}=odd (even), the nucleon is shown to be a fermion (boson).
Nucleon statistics in holographic QCD: Aharonov-Bohm effect in a matrix model
NASA Astrophysics Data System (ADS)
Hashimoto, Koji; Iizuka, Norihiro
2010-11-01
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).
The phase of Hidden Momentum in Aharonov-Bohm solenoid effect
Y. Ben-Aryeh
2012-01-03
It is shown that the phase of the hidden momentum in Aharonov-Bohm (AB) solenoid effect is equal in magnitude to the phase of the electron but with opposite sign. The phase of the hidden momentum is equal to that obtained by the energy of interference calculated in our previous paper (J.Opt.Soc.Am. B 17, 2052 2000).
Revisiting the Marton, Simpson, and Suddeth experimental confirmation of the Aharonov-Bohm effect
Macdougall, James; Vagenas, Elias C
2015-01-01
We perform an "archeological" study of one of the original experiments used as evidence for the static, time-independent Aharonov-Bohm effect. Since the experiment in question [L. Marton, J. A. Simpson, and J. A. Suddeth, Rev. Sci. Instr. 25, 1099 (1954)] involved a time varying magnetic field we show that there are problems with the explanation of this experiment as a confirmation of the static Aharonov-Bohm effect -- specifically the previous analysis ignored the electric field which arises in conjunction with a time-varying magnetic flux. We further argue that the results of this experiment do in fact conform exactly to the recent prediction [D. Singleton and E. Vagenas, Phys. Lett. B723, 241 (2013); J. MacDougall and D. Singleton, J. Math. Phys. 55, 042101 (2014)] of a cancellation between the magnetic and electric phase shifts for the time-dependent Aharonov-Bohm effect. To resolve this issue a new time-dependent Aharonov-Bohm experiment is called for.
The Sagnac effect in curved space-times from an analogy with the Aharonov-Bohm effect
Matteo Luca Ruggiero
2005-01-01
In the context of the natural splitting, the standard relative dynamics can be expressed in terms of gravito-electromagnetic fields, which allow to formally introduce a gravito-magnetic Aharonov-Bohm effect. We showed elsewhere that this formal analogy can be used to derive the Sagnac effect in flat space-time as a gravito-magnetic Aharonov-Bohm effect. Here, we generalize those results to study the General
The Sagnac effect in curved space-times from an analogy with the Aharonov-Bohm effect
Matteo Luca Ruggiero
2005-01-01
In the context of the natural splitting, the standard relative dynamics can be expressed in terms of gravito-electromagnetic\\u000a fields, which allow to formally introduce a gravito-magnetic Aharonov-Bohm effect. We showed elsewhere that this formal analogy\\u000a can be used to derive the Sagnac effect in flat space-time as a gravito-magnetic Aharonov-Bohm effect. Here, we generalize\\u000a those results to study the General
Reply to "Comment on `Role of potentials in the Aharonov-Bohm effect' "
NASA Astrophysics Data System (ADS)
Vaidman, Lev
2015-08-01
The preceding Comment challenged my claim that potentials might be just auxiliary mathematical tools and that they are not necessary for explaining physical phenomena. The Comment did not confront my explanation without the potentials of the Aharonov-Bohm effects that appeared in the original article, but stated that I cannot apply this explanation for seven other examples. In my reply, using my method, I provide explanations of one of the examples, show that two other examples are not relevant, and agree that the remaining examples require further analysis. However, I argue that none of the examples provides robust counterexamples to my claim, similar to the original Aharonov-Bohm setups which were explained in my article, so the Comment does not refute my claim.
Noncommutative correction to Aharonov-Bohm scattering: A field theory approach
Anacleto, M.A.; Gomes, M.; Silva, A.J. da [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318, 05315-970, Sao Paulo, SP (Brazil); Spehler, D. [Universite Louis Pasteur, I.U.T. Allee d'Athenes, 67300 Schiltigheim (France)
2004-10-15
We study a noncommutative nonrelativistic theory in 2+1 dimensions of a scalar field coupled to the Chern-Simons field. In the commutative situation this model has been used to simulate the Aharonov-Bohm effect in the field theory context. We verified that, contrary to the commutative result, the inclusion of a quartic self-interaction of the scalar field is not necessary to secure the ultraviolet renormalizability of the model. However, to obtain a smooth commutative limit the presence of a quartic gauge invariant self-interaction is required. For small noncommutativity we fix the corrections to the Aharonov-Bohm scattering and prove that up to one loop the model is free from dangerous infrared/ultraviolet divergences.
Aharonov-Bohm effect and resonances in the circular quantum billiard with two leads
Ree, S.; Reichl, L.E.
1999-03-01
We calculate the conductance through a circular quantum billiard with two leads and a point magnetic flux at the center. The boundary element method is used to solve the Schr{umlt o}dinger equation of the scattering problem, and the Landauer formula is used to calculate the conductance from the transmission coefficients. We use two different shapes of leads, straight and conic, and find that the conductance is affected by lead geometry, the relative positions of the leads and the magnetic flux. The Aharonov-Bohm effect can be seen from shifts and splittings of fluctuations. When the flux is equal to h/2e and the angle between leads is 180{degree}, the conductance tends to be suppressed to zero in the low-energy range due to the Aharonov-Bohm effect. {copyright} {ital 1999} {ital The American Physical Society}
The Aharonov-Bohm effect in scattering of nonrelativistic electrons by a penetrable magnetic vortex
Yurii A. Sitenko
2014-11-17
Quantum-mechanical theory for scattering of nonrelativistic charged particles with spin by a penetrable magnetic vortex is elaborated. The scattering differential cross section is shown to consist of two terms, one describing diffraction on the vortex in the forward direction and another one describing penetration through the vortex. The Aharonov-Bohm effect is manifested as a fringe shift in the diffraction pattern. The penetration effect is analyzed for the case of the uniform distribution of the magnetic field strength inside the vortex. We find that the penetrability of the magnetic vortex does not affect the diffraction pattern, and, hence, the Aharonov-Bohm effect is the same for a penetrable vortex as for an impenetrable one.
NASA Astrophysics Data System (ADS)
Matityahu, Shlomi; Aharony, Amnon; Entin-Wohlman, Ora; Katsumoto, Shingo
2013-05-01
In an earlier paper [A. Aharony, Y. Tokura, G. Z. Cohen, O. Entin-Wohlman, and S. Katsumoto, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.84.035323 84, 035323 (2011)], we proposed a spin filter that was based on a diamond-like interferometer, subject to both an Aharonov-Bohm flux and (Rashba and Dresselhaus) spin-orbit interactions. Here, we show that the full polarization of the outgoing electron spins remains the same even when one allows leakage of electrons from the branches of the interferometer. Once the gate voltage on one of the branches is tuned to achieve an effective symmetry between them, this polarization can be controlled by the electric and/or magnetic fields, which determine the spin-orbit interaction strength and the Aharonov-Bohm flux.
Time-dependent Pauli equation in the presence of the Aharonov-Bohm effect
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
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.
Effects of broken time-reversal symmetry on transmission zeros in the Aharonov-Bohm interferometer
Tae-Suk Kim; Sam Young Cho; Chul Koo Kim; Chang-Mo Ryu
2002-01-01
In this paper, we study the behavior of the transmission zeros in the closed Aharonov-Bohm (AB) interferometer with an embedded scattering center in one arm and the corresponding change in the transmission phase when the time-reversal symmetry is broken by magnetic fields. Specifically, we consider three embedded scattering centers: one discrete energy level, a double-barrier well, and a t stub.
The Aharonov-Bohm effect: the role of tunneling and associated forces
G. C. Hegerfeldt; J. T. Neumann
2008-02-27
Through tunneling, or barrier penetration, small wavefunction tails can enter a finitely shielded cylinder with a magnetic field inside. When the shielding increases to infinity the Lorentz force goes to zero together with these tails. However, it is shown, by considering the radial derivative of the wavefunction on the cylinder surface, that a flux dependent force remains. This force explains in a natural way the Aharonov-Bohm effect in the idealized case of infinite shielding.
Gravitational Aharonov-Bohm radiation in string-generated conical space-time.
NASA Astrophysics Data System (ADS)
Aliev, A. N.; Gal'Tsov, D. V.
1989-07-01
The scalar, electromagnetic, gravitational radiation in a conical space-time generated by an infinite straight cosmic string is considered. It is shown that freely moving particles in a conical space emit radiation. Though there is no local force acting upon particles, radiation arises due to the topological properties of space-time and it can be interpreted as the radiative gravitational Aharonov-Bohm effect. The string-modified magnetobremsstrahlung is also discussed.
A charged particle in a homogeneous magnetic field accelerated by a time-periodic Aharonov-Bohm flux
Kalvoda, T. [Department of Theoretical Computer Science, Faculty of Information Technology, Czech Technical University in Prague, Kolejni 2, 160 00 Praha (Czech Republic); Stovicek, P., E-mail: stovicek@kmlinux.fjfi.cvut.cz [Department of Mathematics, Faculty of Nuclear Science, Czech Technical University in Prague, Trojanova 13, 120 00 Praha (Czech Republic)
2011-10-15
We consider a nonrelativistic quantum charged particle moving on a plane under the influence of a uniform magnetic field and driven by a periodically time-dependent Aharonov-Bohm flux. We observe an acceleration effect in the case when the Aharonov-Bohm flux depends on time as a sinusoidal function whose frequency is in resonance with the cyclotron frequency. In particular, the energy of the particle increases linearly for large times. An explicit formula for the acceleration rate is derived with the aid of the quantum averaging method, and then it is checked against a numerical solution and a very good agreement is found. - Highlights: > A nonrelativistic quantum charged particle on a plane. > A homogeneous magnetic field and a periodically time-dependent Aharonov-Bohm flux. > The quantum averaging method applied to a time-dependent system. > A resonance of the AB flux with the cyclotron frequency. > An acceleration with linearly increasing energy; a formula for the acceleration rate.
The Sagnac Effect in curved space-times from an analogy with the Aharonov-Bohm Effect
Matteo Luca Ruggiero
2005-10-28
In the context of the natural splitting, the standard relative dynamics can be expressed in terms of gravito-electromagnetic fields, which allow to formally introduce a gravito-magnetic Aharonov-Bohm effect. We showed elsewhere that this formal analogy can be used to derive the Sagnac effect in flat space-time as a gravito-magnetic Aharonov-Bohm effect. Here, we generalize those results to study the General Relativistic corrections to the Sagnac effect in some stationary and axially symmetric geometries, such as the space-time around a weakly gravitating and rotating source, Kerr space-time, G\\"{odel} universe and Schwarzschild space-time.
A charged particle in a homogeneous magnetic field accelerated by a time periodic Aharonov-Bohm flux
T. Kalvoda; P. Stovicek
2011-07-14
We consider a nonrelativistic quantum charged particle moving on a plane under the influence of a uniform magnetic field and driven by a periodically time-dependent Aharonov-Bohm flux. We observe an acceleration effect in the case when the Aharonov-Bohm flux depends on time as a sinusoidal function whose frequency is in resonance with the cyclotron frequency. In particular, the energy of the particle increases linearly for large times. An explicit formula for the acceleration rate is derived with the aid of the quantum averaging method, and then it is checked against a numerical solution with a very good agreement.
Comment on Experiments Related to the Aharonov-Bohm Phase Shift
Timothy H. Boyer
2007-08-23
Recent experiments undertaken by Caprez, Barwick, and Batelaan should clarify the connections between classical and quantum theories in connection with the Aharonov-Bohm phase shift. It is pointed out that resistive aspects for the solenoid current carriers play a role in the classical but not the quantum analysis for the phase shift. The observed absence of a classical lag effect for a macroscopic solenoid does not yet rule out the possibility of a lag explanation of the observed phase shift for a microscopic solenoid.
Absence of the Electric Aharonov-Bohm Effect due to Induced Charges
Wang, Rui-Feng
2015-01-01
This paper states that the induced charge should not be neglected in the electric Aharonov-Bohm (A-B) effect. If the induced charge is taken into account, the interference pattern of the moving charge will not change with the potential difference between the two metal tubes. It means that the scalar potential itself can not affect the phase of the moving charge, and the true factor affecting the phase of the moving charge is the energy of the system including the moving charge and the induced charge. PMID:26392302
The Sagnac Phase Shift suggested by the Aharonov-Bohm effect for relativistic matter beams
Guido Rizzi; Matteo Luca Ruggiero
2003-05-13
The phase shift due to the Sagnac Effect, for relativistic matter beams counter-propagating in a rotating interferometer, is deduced on the bases of a a formal analogy with the the Aharonov-Bohm effect. A procedure outlined by Sakurai, in which non relativistic quantum mechanics and newtonian physics appear together with some intrinsically relativistic elements, is generalized to a fully relativistic context, using the Cattaneo's splitting technique. This approach leads to an exact derivation, in a self-consistently relativistic way, of the Sagnac effect. Sakurai's result is recovered in the first order approximation.
The Sagnac Phase Shift suggested by the Aharonov-Bohm effect for relativistic matter beams
Rizzi, G; Rizzi, Guido; Ruggiero, Matteo Luca
2003-01-01
The phase shift due to the Sagnac Effect, for relativistic matter beams counter-propagating in a rotating interferometer, is deduced on the bases of a a formal analogy with the the Aharonov-Bohm effect. A procedure outlined by Sakurai, in which non relativistic quantum mechanics and newtonian physics appear together with some intrinsically relativistic elements, is generalized to a fully relativistic context, using the Cattaneo's splitting technique. This approach leads to an exact derivation, in a self-consistently relativistic way, of the Sagnac effect. Sakurai's result is recovered in the first order approximation.
Effects of broken time-reversal symmetry on transmission zeros in the Aharonov-Bohm interferometer
Tae-Suk Kim; Sam Young Cho; Chul Koo Kim; Chang-Mo Ryu
2002-01-01
In this paper, we study the behavior of the transmission zeros in the closed\\u000aAharonov-Bohm(AB) interferometer with an embedded scattering center in one arm\\u000aand the corresponding change in the transmission phase when the time-reversal\\u000asymmetry is broken by magnetic fields. Specifically, we consider three embedded\\u000ascattering centers: one discrete energy level, a double-barrier well, and a\\u000a$t$-stub. We find
Force-Free Gravitational Redshift: Proposed Gravitational Aharonov-Bohm experiment
Michael A. Hohensee; Brian Estey; Paul Hamilton; Anton Zeilinger; Holger Mueller
2012-06-07
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.
Force-free gravitational redshift: proposed gravitational Aharonov-Bohm experiment.
Hohensee, Michael A; Estey, Brian; Hamilton, Paul; Zeilinger, Anton; Müller, Holger
2012-06-01
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
Scattering of a charged particle from a hard cylindrical solenoid: Aharonov-Bohm Effect
Oktay Yilmaz
2014-02-26
The scattering amplitude of a charged particle from a long hard cylinderical solenoid is derived by solving the time independent Schr\\"{o}dinger equation on a double connected plane. It is a summation over the angular momentum quantum number (partial wave summation). It is shown that only negative mechanical angular momenta contribute to the amplitude when the radius of the solenoid goes to zero limit without varying the magnetic induction flux (Flux line). Original Aharonov-Bohm result is obtained with this limit.
Two-particle nonlocal Aharonov-Bohm effect from two single-particle emitters.
Splettstoesser, Janine; Moskalets, Michael; Büttiker, Markus
2009-08-14
We propose a mesoscopic circuit in the quantum Hall effect regime comprising two uncorrelated single-particle sources and two distant Mach-Zehnder interferometers with magnetic fluxes, which allows us in a controllable way to produce orbitally entangled electrons. Two-particle correlations appear as a consequence of erasing of which-path information due to collisions taking place at distant interferometers and in general at different times. The two-particle correlations manifest themselves as an Aharonov-Bohm effect in noise, while the current is insensitive to magnetic fluxes. In an appropriate time interval the concurrence reaches a maximum and a Bell inequality is violated. PMID:19792674
NASA Astrophysics Data System (ADS)
Entin-Wohlman, O.; Imry, Y.; Aharony, A.
2003-07-01
We consider an Aharonov-Bohm interferometer, connected to two electronic reservoirs, with a quantum dot embedded on one of its arms. We find a general expression for the persistent current at steady state, valid for the case where the electronic system is free of interactions except on the dot. The result is used to derive the modification in the persistent current brought about by coupling the quantum dot to a phonon source. The magnitude of the persistent current is found to be enhanced in an appropriate range of the intensity of the acoustic source.
Entin-Wohlman, O; Imry, Y; Aharony, A
2003-07-25
We consider an Aharonov-Bohm interferometer, connected to two electronic reservoirs, with a quantum dot embedded on one of its arms. We find a general expression for the persistent current at steady state, valid for the case where the electronic system is free of interactions except on the dot. The result is used to derive the modification in the persistent current brought about by coupling the quantum dot to a phonon source. The magnitude of the persistent current is found to be enhanced in an appropriate range of the intensity of the acoustic source. PMID:12906684
Aharonov-Bohm oscillations in a quasi-ballistic three-dimensional topological insulator nanowire
NASA Astrophysics Data System (ADS)
Cho, Sungjae; Dellabetta, Brian; Zhong, Ruidan; Schneeloch, John; Liu, Tiansheng; Gu, Genda; Gilbert, Matthew J.; Mason, Nadya
2015-07-01
Aharonov-Bohm oscillations effectively demonstrate coherent, ballistic transport in mesoscopic rings and tubes. In three-dimensional topological insulator nanowires, they can be used to not only characterize surface states but also to test predictions of unique topological behaviour. Here we report measurements of Aharonov-Bohm oscillations in (Bi1.33Sb0.67)Se3 that demonstrate salient features of topological nanowires. By fabricating quasi-ballistic three-dimensional topological insulator nanowire devices that are gate-tunable through the Dirac point, we are able to observe alternations of conductance maxima and minima with gate voltage. Near the Dirac point, we observe conductance minima for zero magnetic flux through the nanowire and corresponding maxima (having magnitudes of almost a conductance quantum) at magnetic flux equal to half a flux quantum; this is consistent with the presence of a low-energy topological mode. The observation of this mode is a necessary step towards utilizing topological properties at the nanoscale in post-CMOS applications.
Aharonov-Bohm oscillations in a quasi-ballistic three-dimensional topological insulator nanowire.
Cho, Sungjae; Dellabetta, Brian; Zhong, Ruidan; Schneeloch, John; Liu, Tiansheng; Gu, Genda; Gilbert, Matthew J; Mason, Nadya
2015-01-01
Aharonov-Bohm oscillations effectively demonstrate coherent, ballistic transport in mesoscopic rings and tubes. In three-dimensional topological insulator nanowires, they can be used to not only characterize surface states but also to test predictions of unique topological behaviour. Here we report measurements of Aharonov-Bohm oscillations in (Bi1.33Sb0.67)Se3 that demonstrate salient features of topological nanowires. By fabricating quasi-ballistic three-dimensional topological insulator nanowire devices that are gate-tunable through the Dirac point, we are able to observe alternations of conductance maxima and minima with gate voltage. Near the Dirac point, we observe conductance minima for zero magnetic flux through the nanowire and corresponding maxima (having magnitudes of almost a conductance quantum) at magnetic flux equal to half a flux quantum; this is consistent with the presence of a low-energy topological mode. The observation of this mode is a necessary step towards utilizing topological properties at the nanoscale in post-CMOS applications. PMID:26158768
Quantum Measurement and the Aharonov-Bohm Effect with Superposed Magnetic Fluxes
Bradonjic, Kaca
2011-01-01
In the standard Aharonov-Bohm effect, the magnetic flux involved is taken to be classical and with a well-defined value. Here, we consider what happens if the magnetic flux is in a quantum mechanical superposition of two values. We find that the interference pattern in the Aharonov-Bohm effect contains information about the nature of the superposition, allowing information about the state of the flux to be extracted without disturbing it. The approach is novel in that the information is obtained by a non-local operation involving the vector potential without transfer of energy or momentum. The information is also not obtained via a single interaction of a charged particle with the vector potential, but rather by the accumulated interactions of many particles which form the interference pattern. Suggestions are made as to how an experiment to test this effect could be done using superposed currents in a superconducting ring which has already been experimentally realized. Broader implications of the result are ...
Enhanced spin figure of merit in an Aharonov-Bohm ring with a double quantum dot
Zhou, Xingfei; Qi, Fenghua; Jin, Guojun
2014-04-21
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 (Z{sub s}T???4.5) accompanying with a small charge figure of merit (Z{sub c}T???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 Z{sub s}T is enhanced while Z{sub c}T 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.
The Aharonov-Bohm Effect in a 3D topological insulator nanowire
NASA Astrophysics Data System (ADS)
Cho, Sungjae; Dellabetta, Brian; Yang, Alina; Schneeloch, John; Xu, Zhijun; Gu, Genda; Gilbert, Matthew; Mason, Nadya
2014-03-01
The three dimensional topological insulator (3D TI) is a new class of material having metallic surface states characterized by gapless Dirac dispersions and novel properties such as momentum-spin locking. A TI nanowire with an insulating bulk can be described as a hollow metallic cylinder, showing Aharonov-Bohm oscillations when a magnetic flux is threaded through the axis. The magneto-conductance of a TI nanowire near the Dirac point is expected to have a minimum at zero magnetic field and an oscillation period of one magnetic flux quantum, ? (due to a Berry phase of ? acquired by electron waves upon 2 ? rotation of electron spin around the surface of the nanowire). In this talk, we discuss magneto-conductance measurements of TI (Bi2Se3) nanowires, measured as the gate voltage is tuned through the Dirac point. The Aharonov-Bohm oscillations switch from a conductance maximum to a minimum at zero field as the Dirac point is approached, consistent with the existence of a Berry phase in the nanowire.
Aharonov-Bohm Oscillations in a Quasi-Ballistic 3D Topological-Insulator Nanowire , B. Dellabetta2
Gilbert, Matthew
1 Aharonov-Bohm Oscillations in a Quasi-Ballistic 3D Topological-Insulator Nanowire S. Cho1 , B, this signature has been missing in transport experiments reported to date.9-11 Here, we report measurements surface transport. The use of low-doped, quasi- ballistic devices allows us to observe a minimum
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
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.
The manifestly covariant Aharonov-Bohm effect in terms of the 4D fields
Tomislav Ivezic
2014-11-21
In this paper it is presented a manifestly covariant formulation of the Aharonov-Bohm (AB) phase difference for the magnetic AB effect . This covariant AB phase is written in terms of the Faraday 2-form F and using the decomposition of F in terms of the electric and magnetic fields as four-dimensional (4D) geometric quantities. It is shown that there is a static electric field outside a stationary solenoid with resistive conductor carrying steady current, which causes that the AB phase difference in the magnetic AB effect may be determined by the electric part of the covariant expression, i.e. by the local influence of the 4D electric field and not, as generally accepted,in terms of nonzero vector potential.
Spin transport in an Aharonov-Bohm ring with exchange interaction
NASA Astrophysics Data System (ADS)
Savenko, I. G.; Polozkov, R. G.; Shelykh, I. A.
2013-11-01
We investigate spin-dependent conductance through a quantum Aharonov-Bohm ring containing localized electrons which interact with the propagating flow of electrons via exchange interaction of the ferromagnetic or antiferromagnetic type. We analyze the conductance oscillations as a function of both the chemical potential (particle concentration) and external magnetic field. It is demonstrated that the amplitude of the conductance oscillations in the ballistic regime is determined by the value of the noncompensated spin localized in the ring. The results are in agreement with the concept of fractional quantization of the ballistic conductance, proposed by us earlier [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.71.113311 71, 113311 (2005)].
Phase evolution of the transmission coefficient in an Aharonov-Bohm ring with Fano resonance
NASA Astrophysics Data System (ADS)
Ryu, Chang-Mo; Cho, Sam Young
1998-08-01
Phase of the transmission coefficient for a mesoscopic loop with Fano resonance has been investigated by using the scattering matrix method, for a model of an Aharonov-Bohm ring with a double barrier coupled to a t-stub resonator in one arm. It is found that the phase varies rapidly by ? on the shoulder of a resonance peak. In addition, it is found that there is a sudden phase jump by ? near the tail of a resonance peak. Each resonance peak is found to return to the same phase via two processes; in one process, the phase shift by ? occurs rather smoothly through the excitation of the h/2e oscillation near the resonance peak, and in the other process, the same amount of phase shift occurs very abruptly across the zero transmission of the resonator. These phase behaviors show some resemblance to the ones found in the recent phase measurement of a quantum dot via double-slit interference experiment.
Bedkihal, Salil
2012-01-01
We study the real time dynamics of electron coherence in a double quantum dot two-terminal Aharonov-Bohm geometry, taking into account repulsion effects between the dots' electrons. The system is simulated by extending a numerically exact path integral method, suitable for treating transport and dissipation in biased impurity models [Phys. Rev. B 82, 205323 (2010)]. Numerical simulations at finite interaction strength are supported by master equation calculations in two other limits: assuming non-interacting electrons, and working in the Coulomb blockade regime. Focusing on the intrinsic coherence dynamics between the double-dot states, we find that its temporal characteristics are preserved under weak-to-intermediate inter-dot Coulomb interaction. In contrast, in the Coulomb blockade limit, a master equation calculation predicts coherence dynamics and a steady-state value which notably deviate from the finite interaction case.
Salil Bedkihal; Dvira Segal
2012-01-13
We study the real time dynamics of electron coherence in a double quantum dot two-terminal Aharonov-Bohm geometry, taking into account repulsion effects between the dots' electrons. The system is simulated by extending a numerically exact path integral method, suitable for treating transport and dissipation in biased impurity models [Phys. Rev. B 82, 205323 (2010)]. Numerical simulations at finite interaction strength are supported by master equation calculations in two other limits: assuming non-interacting electrons, and working in the Coulomb blockade regime. Focusing on the intrinsic coherence dynamics between the double-dot states, we find that its temporal characteristics are preserved under weak-to-intermediate inter-dot Coulomb interaction. In contrast, in the Coulomb blockade limit, a master equation calculation predicts coherence dynamics and a steady-state value which notably deviate from the finite interaction case.
Aharonov-Bohm effect in the tunnelling of a quantum rotor in a linear Paul trap.
Noguchi, Atsushi; Shikano, Yutaka; Toyoda, Kenji; Urabe, Shinji
2014-01-01
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
Nguyen, V Hung; Niquet, Y-M; Dollfus, P
2014-05-21
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
Topological phases reviewed: The Aharonov Bohm, Aharonov Casher, and He McKellar Wilkens phases
McKellar, B. H. J. [ARC Centre of Excellence for Particle Physics at the Terrascale, School of Physics, University of Melbourne (Australia); He, X-G. [Department of Physics, National Taiwan University, Taipei, Taiwan (China); Klein, A. G. [School of Physics, University of Melbourne (Australia)
2014-03-05
There are three topological phases related to electromagnetic interactions in quantum mechanics: 1. The Aharonov Bohm phase acquired when a charged particle encircles a magnetic field but travels through a field free region. 2. The Aharonov Casher phase acquired when a magnetic dipole encircles electric charges but travels through a charge free region. 3. The He McKellar Wilkens phase acquired when an electric dipole encircles magnetic charges but travels through a charge free region. We review the conditions under which these phases are indeed topological and their experimental realisation. Because the He McKellar Wilkens phase has been recently observed we pay particular attention to how the basic concept of 'an electric dipole encircles magnetic charges' was realised experimentally, and discuss possible future experimental realisations.
A possible interplay between electron beams and magnetic fluxes in the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Wang, Rui-Feng
2015-06-01
Most studies on the magnetic Aharonov-Bohm (A-B) effect focus on the action exerted by the magnetic flux on the electron beam, but neglect the back-action exerted by the electron beam on the magnetic flux. This paper focuses on the latter, which is the electromotive force ? U across the solenoid induced by the time-dependent magnetic field of the electron beam. Based on the back-action analysis, we observe that the magnetic A-B effect arises owing to the interaction energy between the magnetic field of the electron beam and the magnetic field of the solenoid. We also demonstrate that the interpretation attributing the magnetic A-B effect to the vector potential violates the uncertainty principle.
The manifestly covariant Aharonov-Bohm effect in terms of the 4D fields
NASA Astrophysics Data System (ADS)
Ivezi?, T.
2015-05-01
In this paper it is presented a manifestly covariant formulation of the Aharonov-Bohm (AB) phase difference for the magnetic AB effect. This covariant AB phase is written in terms of the Faraday 2-form F and using the decomposition of F in terms of the electric and magnetic fields as four-dimensional (4D) geometric quantities. It is shown that there is a static electric field outside a stationary solenoid with resistive conductor carrying steady current, which causes that the AB phase difference in the magnetic AB effect may be determined by the electric part of the covariant expression, i.e., by the local influence of the 4D electric field and not, as generally accepted, in terms of nonzero vector potential.
Electromagnetism, local covariance, the Aharonov-Bohm effect and Gauss' law
Ko Sanders; Claudio Dappiaggi; Thomas-Paul Hack
2014-03-26
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. 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.
NASA Astrophysics Data System (ADS)
Belov, V. V.; Kondrat'eva, M. F.
1992-10-01
Approximate (as h ? 0) dynamic states in the form of nondiffusing wave packets, localized in the vicinity of a classical trajectory (nonintersecting the solenoid), quasiclassical nonstationary trajectory-coherent states, are constructed for nonrelativistic electron motion in a uniform magnetic field in the presence of an infinitely thin and long solenoid. The occurrence of the Aharonov-Bohm effect in such states is investigated. Special cases of electron motion — in a uniform magnetic field and in the solenoid field — are considered.
Aharonov-Bohm Effect and High-Momenta Inverse Scattering for the Klein-Gordon Equation
Miguel Ballesteros; Ricardo Weder
2015-06-03
We analyze spin-0 relativistic scattering of charged particles propagating in the exterior, $\\Lambda \\subset \\mathbb{R}^3$, of a compact obstacle $K \\subset \\mathbb{R}^3$. The connected components of the obstacle are handlebodies. The particles interact with an electro-magnetic field in $\\Lambda$ and an inaccessible magnetic field localized in the interior of the obstacle (through the Aharonov-Bohm effect). We obtain high-momenta estimates, with error bounds, for the scattering operator that we use to recover physical information: We give a reconstruction method for the electric potential and the exterior magnetic field and prove that, if the electric potential vanishes, circulations of the magnetic potential around handles (or equivalently, by Stokes' theorem, magnetic fluxes over transverse sections of handles) of the obstacle can be recovered, modulo $2 \\pi$. We additionally give a simple formula for the high-momenta limit of the scattering operator in terms of certain magnetic fluxes, in the absence of electric potential. If the electric potential does not vanish, the magnetic fluxes on the handles above referred can be only recovered modulo $\\pi$ and the simple expression of the high-momenta limit of the scattering operator does not hold true.
The Aharonov-Bohm scattering the role of the incident wave
Sakoda, S
1996-01-01
The scattering problem under the influence of the Aharonov-Bohm (AB) potential is reconsidered. By solving the Lippmann-Schwinger (LS) equation we obtain the wave function of the scattering state in this system. In spite of working with a plane wave as an incident wave we obtain the same wave function as was given by Aharonov and Bohm. Another method to solve the scattering problem is given by making use of a modified version of Gordon's idea which was invented to consider the scattering by the Coulomb potential. These two methods give the same result to guarantee the validity of the analyses. The scattering problem by a solenoid of finite radius is also discussed, and we find that the vector potential of the solenoid affects the charged particles even when the magnitude of the flux is an odd integer as well as noninteger. It is shown that the unitarity of the S matrix does holds by virtue of taking a plane wave as an incident one.
A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms
NASA Astrophysics Data System (ADS)
Huo, Ming-Xia; Nie, Wei; Hutchinson, David A. W.; Kwek, Leong Chuan
2014-08-01
Cold neutral atoms provide a versatile and controllable platform for emulating various quantum systems. Despite efforts to develop artificial gauge fields in these systems, realizing a unique ideal-solenoid-shaped magnetic field within the quantum domain in any real-world physical system remains elusive. Here we propose a scheme to generate a ``hairline'' solenoid with an extremely small size around 1 micrometer which is smaller than the typical coherence length in cold atoms. Correspondingly, interference effects will play a role in transport. Despite the small size, the magnetic flux imposed on the atoms is very large thanks to the very strong field generated inside the solenoid. By arranging different sets of Laguerre-Gauss (LG) lasers, the generation of Abelian and non-Abelian SU(2) lattice gauge fields is proposed for neutral atoms in ring- and square-shaped optical lattices. As an application, interference patterns of the magnetic type-I Aharonov-Bohm (AB) effect are obtained by evolving atoms along a circle over several tens of lattice cells. During the evolution, the quantum coherence is maintained and the atoms are exposed to a large magnetic flux. The scheme requires only standard optical access, and is robust to weak particle interactions.
Constantine Yannouleas; Igor Romanovsky; Uzi Landman
2015-02-16
The unique ultra-relativistic, massless, nature of electron states in two-dimensional extended graphene sheets, brought about by the honeycomb lattice arrangement of carbon atoms in two-dimensions, provides ingress to explorations of fundamental physical phenomena in graphene nanostructures. Here we explore the emergence of new behavior of electrons in atomically precise segmented graphene nanoribbons (GNRs) and graphene rings with the use of tight-binding calculations, non-equilibrium Green's function transport theory, and a newly developed Dirac continuum model that absorbs the valence-to-conductance energy gaps as position-dependent masses, including topological-in-origin mass-barriers at the contacts between segments. Through transport investigations in variable-width segmented GNRs with armchair, zigzag, and mixed edge terminations we uncover development of new Fabry-Perot-like interference patterns in segmented GNRs, a crossover from the ultra-relativistic massless regime, characteristic of extended graphene systems, to a massive relativistic behavior in narrow armchair GNRs, and the emergence of nonrelativistic behavior in zigzag-terminated GNRs. Evaluation of the electronic states in a polygonal graphene nanoring under the influence of an applied magnetic field in the Aharonov-Bohm regime, and their analysis with the use of a relativistic quantum-field theoretical model, unveils development of a topological-in-origin zero-energy soliton state and charge fractionization. These results provide a unifying framework for analysis of electronic states, coherent transport phenomena, and the interpretation of forthcoming experiments in segmented graphene nanoribbons and polygonal rings.
Berman, G.P.; Bulgakov, E.N.; Campbell, D.K.; Krive, I.V.
1997-10-01
We consider Aharonov-Bohm oscillations in a mesoscopic semiconductor ring threaded by both a constant magnetic flux and a time-dependent, resonant magnetic field with one or two frequencies. Working in the ballistic regime, we establish that the theory of {open_quotes}quantum nonlinear resonance{close_quotes} applies, and thus that this system represents a possible solid-state realization of {open_quotes}quantum nonlinear resonance{close_quotes} and {open_quotes}quantum chaos.{close_quotes} In particular, we investigate the behavior of the time-averaged electron energy at zero temperature in the regimes of (i) an isolated quantum nonlinear resonance and (ii) the transition to quantum chaos, when two quantum nonlinear resonances overlap. The time-averaged energy exhibits sharp resonant behavior as a function of the applied constant magnetic flux, and has a staircase dependence on the amplitude of the external time-dependent field. In the chaotic regime, the resonant behavior exhibits complex structure as a function of flux and frequency. We compare and contrast the quantum chaos expected in these mesoscopic {open_quotes}solid-state atoms{close_quotes} with that observed in Rydberg atoms in microwave fields, and discuss the prospects for experimental observation of the effects we predict. {copyright} {ital 1997} {ital The American Physical Society}
NonAbelian Vortices, Large Winding Limits and Aharonov-Bohm Effects
Stefano Bolognesi; Chandrasekhar Chatterjee; Kenichi Konishi
2015-03-20
Remarkable simplification arises from considering vortex equations in the large winding limit. This was recently used in [1] to display all sorts of vortex zeromodes, the orientational, translational, fermionic as well as semi-local, and to relate them to the apparently distinct phenomena of the Nielsen-Olesen-Ambjorn magnetic instabilities. Here we extend these analyses to more general types of BPS nonAbelian vortices, taking as a prototype a system with gauged U(1) x SU(N) x SU(N) symmetry where the VEV of charged scalar fields in the bifundamental representation breaks the symmetry to SU(N)_{l+r} . The presence of the massless SU(N)_{l+r} gauge fields in 4D bulk introduces all sorts of non-local, topological phenomena such as the nonAbelian Aharonov-Bohm effects, which in the theory with global SU(N)_r group (g_r=0) are washed away by the strongly fluctuating orientational zeromodes in the worldsheet. Physics changes qualitatively at the moment the right gauge coupling constant g_r is turned on.
A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms
Huo, Ming-Xia; Nie, Wei; Hutchinson, David A. W.; Kwek, Leong Chuan
2014-01-01
Cold neutral atoms provide a versatile and controllable platform for emulating various quantum systems. Despite efforts to develop artificial gauge fields in these systems, realizing a unique ideal-solenoid-shaped magnetic field within the quantum domain in any real-world physical system remains elusive. Here we propose a scheme to generate a “hairline” solenoid with an extremely small size around 1 micrometer which is smaller than the typical coherence length in cold atoms. Correspondingly, interference effects will play a role in transport. Despite the small size, the magnetic flux imposed on the atoms is very large thanks to the very strong field generated inside the solenoid. By arranging different sets of Laguerre-Gauss (LG) lasers, the generation of Abelian and non-Abelian SU(2) lattice gauge fields is proposed for neutral atoms in ring- and square-shaped optical lattices. As an application, interference patterns of the magnetic type-I Aharonov-Bohm (AB) effect are obtained by evolving atoms along a circle over several tens of lattice cells. During the evolution, the quantum coherence is maintained and the atoms are exposed to a large magnetic flux. The scheme requires only standard optical access, and is robust to weak particle interactions. PMID:25103877
Aharonov-Bohm-like scattering, localization, and novel electronic states in hydrogenated graphene
NASA Astrophysics Data System (ADS)
Shytov, Andrey; Abanin, Dmitry; Levitov, Leonid
2009-03-01
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
Aharonov-Bohm interference in gate-defined ring of high-mobility graphene
NASA Astrophysics Data System (ADS)
Kim, Minsoo; Lee, Hu-Jong
2015-03-01
Recent progress in preparing a high-quality graphene layer enables one to investigate the intrinsic carrier transport nature in the material. Here, we report the signature of conservation of the Berry's phase with preserved valley symmetry in Aharonov-Bohm (AB) interferometers fabricated on monolayer graphene with high carrier mobility, where the graphene was sandwiched between two thin hexagonal boron nitride (h-BN) layers. In measurements, charge carriers were confined in an AB ring-shaped potential well formed by the dual-gate operation of the bottom and top gates and the four-terminal magneto-conductance (MC) was measured with varying charge carrier density and temperature. Graphene in the device was in the ballistic regime as confirmed by the conductance quantization in steps of ?G = 4e2/ h in a constricted conducting channel of separate measurements. We observed h/e periodic modulation of MC and the zero-field conductance minimum with a negative MC background. The phase information of AB interference strongly suggests that carriers in the graphene in our devices preserve the intrinsic Dirac transport nature, which would be conveniently utilized for valleytronics in graphene.
NASA Astrophysics Data System (ADS)
Marengo, Edwin A.; Ziolkowski, Richard W.
2002-12-01
A new characterization of nonradiating (NR) sources is derived that is based on electromagnetic potentials. In the new description a hierarchy of NR sources is systematically created that includes certain nonlocalized NR sources having the property that their curl is localized. The important class of spatially localized NR sources, whose fields vanish everywhere in the exterior of the source, corresponds to a special case of the general theory. The new NR source developments are discussed in connection with the question of measurability of electromagnetic potentials as enabled by the Aharonov-Bohm (A-B) effect, whereby quantum mechanical effects of the potentials can be observed in regions of vanishing electromagnetic fields but nonvanishing electromagnetic potentials. A necessary condition is derived for an electrodynamic A-B effect in the exterior of a spatially localized NR source. By exploring this condition, it is concluded that for time-varying, information-carrying fields (as required, e.g., in communications and remote sensing applications) the required A-B conditions of vanishing fields and nonvanishing potentials are not possible in the exterior of a NR source; i.e., electrodynamically, if the fields vanish everywhere outside the source, then the potentials also vanish there. This does not necessarily hold under static conditions in which nontrivial potentials with physically observable quantum effects can exist in the exterior of a source having zero external fields.
Kubo, T; Tarucha, S
2010-01-01
We theoretically investigated the dephasing in an Aharonov-Bohm interferometer containing a lateral double quantum dot induced by coupling with a quantum dot charge sensor. We employed the interpolative 2nd-order perturbation theory to include the charge sensing Coulomb interaction. It is shown that the visibility of the Aharonov-Bohm oscillation of the linear conductance decreases monotonically as the sensing Coulomb interaction increases. In particular, for a weak sensing interaction regime, the visibility decreases parabolically, and it behaves linearly for a strong sensing interaction regime.
T. Kubo; Y. Tokura; S. Tarucha
2010-05-12
We theoretically investigated the dephasing in an Aharonov-Bohm interferometer containing a lateral double quantum dot induced by coupling with a quantum dot charge sensor. We employed the interpolative 2nd-order perturbation theory to include the charge sensing Coulomb interaction. It is shown that the visibility of the Aharonov-Bohm oscillation of the linear conductance decreases monotonically as the sensing Coulomb interaction increases. In particular, for a weak sensing interaction regime, the visibility decreases parabolically, and it behaves linearly for a strong sensing interaction regime.
Aharonov-Bohm-type electron interference in the presence of one-mode SU(1,1) coherent state
NASA Astrophysics Data System (ADS)
Zou, Jian; Shao, Bin; Xing, Xiu-San
1998-03-01
Dynamic behaviour of Aharonov-Bohm-type electron interference in the presence of a nonclassical electromagnetic field is investigated. The visibility of the time-averaged interference pattern is discussed for SU(1,1) coherent state (CS) and a comparison with other states is made. It is shown that the dynamic behaviour of the electron interference exhibits collapse and revival (CR) phenomenon for SU(1,1) CS. It is also shown that CR phenomenon of electron interference is closely related to the fluctuation of a nonclassical electromagnetic field.
Quantum Mechanical Inclusion of the Source in the Aharonov-Bohm Effect
Philip Pearle; Anthony Rizzi
2015-06-30
The standard treatment of the magnetic Aharonov-Bohm (A-B) effect assumes one can calculate the phase without accounting for the source (solenoid) quantum mechanically. Recently, Vaidman, using a semi-classical calculation, showed that the source may indeed matter. He argued for what might be called a local field hypothesis---the idea that in quantum theory, as in classical physics, only field-producing potentials have physical effects. His calculation indicates that the electron's non-relativistic electric field, acting on a semi-classically treated solenoid, produces the A-B phase shift. Here, employing a model of the solenoid consisting of charged particles, we give a quantum mechanical treatment of their contribution to the phase shift under the influence of the circulating electron's electric field. We show that the phase shift of the field-producing non-relativistic vector potential gives the A-B phase shift, and how this confirms Vaidman's semi-classical prediction of that phase shift. However, we also show that the phase shift of the field-producing relativistic (retarded) scalar potential gives the negative of the A-B phase shift. This cancellation allows one to effectively treat the source as a classical entity as is done in the standard derivation of the A-B effect. We close by remarking that the apparent necessity for relativistic considerations suggests the possibility that the A-B phase shift may yet be explained in terms of field-producing potentials alone, which may vindicate the local field hypothesis.
High-Velocity Estimates for the Scattering Operator and Aharonov-Bohm Effect in Three Dimensions
Miguel Ballesteros; Ricardo Weder
2007-11-16
We obtain high-velocity estimates with error bounds for the scattering operator of the Schr\\"odinger equation in three dimensions with electromagnetic potentials in the exterior of bounded obstacles that are handlebodies. A particular case is a finite number of tori. We prove our results with time-dependent methods. We consider high-velocity estimates where the direction of the velocity of the incoming electrons is kept fixed as its absolute value goes to infinity. In the case of one torus our results give a rigorous proof that quantum mechanics predicts the interference patterns observed in the fundamental experiments of Tonomura et al. that gave a conclusive evidence of the existence of the Aharonov-Bohm effect using a toroidal magnet. We give a method for the reconstruction of the flux of the magnetic field over a cross-section of the torus modulo $2\\pi$. Equivalently, we determine modulo $2\\pi$ the difference in phase for two electrons that travel to infinity, when one goes inside the hole and the other outside it. For this purpose we only need the high-velocity limit of the scattering operator for one direction of the velocity of the incoming electrons. When there are several tori -or more generally handlebodies- the information that we obtain in the fluxes, and on the difference of phases, depends on the relative position of the tori and on the direction of the velocities when we take the high-velocity limit of the incoming electrons. For some locations of the tori we can determine all the fluxes modulo 2$\\pi$ by taking the high-velocity limit in only one direction. We also give a method for the unique reconstruction of the electric potential and the magnetic field outside the handlebodies from the high-velocity limit of the scattering operator.
On the Aharonov-Bohm Operators with Varying Poles: The Boundary Behavior of Eigenvalues
NASA Astrophysics Data System (ADS)
Noris, Benedetta; Nys, Manon; Terracini, Susanna
2015-07-01
We consider a magnetic Schrödinger operator with magnetic field concentrated at one point (the pole) of a domain and half integer circulation, and we focus on the behavior of Dirichlet eigenvalues as functions of the pole. Although the magnetic field vanishes almost everywhere, it is well known that it affects the operator at the spectral level (the Aharonov-Bohm effect, Phys Rev (2) 115:485-491, 1959). Moreover, the numerical computations performed in (Bonnaillie-Noël et al., Anal PDE 7(6):1365-1395, 2014; Noris and Terracini, Indiana Univ Math J 59(4):1361-1403, 2010) show a rather complex behavior of the eigenvalues as the pole varies in a planar domain. In this paper, in continuation of the analysis started in (Bonnaillie-Noël et al., Anal PDE 7(6):1365-1395, 2014; Noris and Terracini, Indiana Univ Math J 59(4):1361-1403, 2010), we analyze the relation between the variation of the eigenvalue and the nodal structure of the associated eigenfunctions. We deal with planar domains with Dirichlet boundary conditions and we focus on the case when the singular pole approaches the boundary of the domain: then, the operator loses its singular character and the k-th magnetic eigenvalue converges to that of the standard Laplacian. We can predict both the rate of convergence and whether the convergence happens from above or from below, in relation with the number of nodal lines of the k-th eigenfunction of the Laplacian. The proof relies on the variational characterization of eigenvalues, together with a detailed asymptotic analysis of the eigenfunctions, based on an Almgren-type frequency formula for magnetic eigenfunctions and on the blow-up technique.
Two-Particle Nonlocal Aharonov-Bohm Effect from Two Single-Particle Emitters
NASA Astrophysics Data System (ADS)
Splettstoesser, Janine
2010-03-01
High-frequency single-particle emitters have been realized experimentally in the integer quantum Hall effect regime [1]: the particles are injected into edge states, operating as wave guides, and encounter splitters realized by quantum point contacts. These tools allow for the implementation of complex interferometers in mesoscopic systems showing two-particle interference effects. An example for tunable two-particle correlations is manifest in the electronic analogue of the Hong-Ou-Mandel interferometer [2], where a noise suppression is found due to the Pauli principle. In the work presented here we explore the entanglement production from two uncorrelated sources. We therefore propose a mesoscopic circuit in the quantum Hall effect regime comprising two independent single-particle sources and two distant Mach-Zehnder interferometers with magnetic fluxes. This and the tunability of the single-particle sources allow in a controllable way to produce orbitally entangled electrons [3]. Two-particle correlations appear as a consequence of erasing of which-path information due to collisions taking place at distant interferometers and in general at different times. While the current in this setup is insensitive to the magnetic flux, the two-particle correlations manifest themselves as an Aharonov-Bohm effect in the noise. In an appropriate time-interval the concurrence reaches a maximum and a Bell inequality is violated, proving the existence of time-bin entanglement.[4pt] [1] G. Fève, A. Mah'e, J.-M. Berroir, T. Kontos, B. Placais, D. C. Glattli, A. Cavanna, B. Etienne, and Y. Jin, Science 316, 1169 (2007).[0pt] [2] S. Ol'Khovskaya, J. Splettstoesser, M. Moskalets, and M. Buttiker, Phys. Rev. Lett. 101, 166802 (2008).[0pt] [3] J. Splettstoesser, M. Moskalets, and M. Buttiker, Phys. Rev. Lett.103, 076804 (2009).
Hod, Oded
in molecular junctions is of key importance in the growing field of molecular electronics. The current by molecular conductors (an exception is the Kondo effect in single-molecule transistors). This is in contrastMagnetoresistance of nanoscale molecular devices based on Aharonov-Bohm interferometry This article
Magnetism in a Wigner solid and the Aharonov-Bohm effect: Experiment and theory
NASA Astrophysics Data System (ADS)
Okamoto, Tohru; Kawaji, Shinji
1998-04-01
We have measured the magnetic field dependence of thermal activation energy EA in an insulating phase of a two-dimensional electron system formed in a Si inversion layer to investigate magnetic interactions among electrons. Experimental results are summarized as follows. (1) In a magnetic field parallel to the two-dimensional plane, EA increases linearly with the total strength Btot of the magnetic field for Btot<~3 T, while it takes a saturation value in the complementary high-Btot region. (2) The normal component B? of the magnetic field causes a peculiar change in EA, where two minima appear at B?~0.6Ns?0 and B?~1.1Ns?0 for ?0=h/e. All the results are quantitatively explained by a model based on exchange interactions in a Wigner solid (WS) formed at rs~8. We assume that a three-particle ring exchange among localized electrons in the WS and a standard two-particle exchange between a thermally created mobile electron and a localized electron in the WS play dominant roles in determining the magnetic behavior of the system. At B?=0, the three-particle ring exchange interaction leads to the ferromagnetically ordered ground state of the WS. The antiferromagnetic two-particle exchange interaction favors magnetic states of a mobile electron different from the lowest spin-valley state of the localized electrons. Thermal activation, which involves a spin flip at low Btot or a transition between the valley states which we call a ``pseudo-spin-flip'' at high Btot, explains the experimental result (1). Magnetic flux through the exchange path can change the nature of the ring exchange interaction due to the Aharonov-Bohm effect. A simple calculation using an exchange constant of 0.3 K, which is consistent with the WKB calculation of Roger [Phys. Rev. B 30, 6432 (1984)], for the three-electron ring exchange interaction reproduces the experimental result (2). Theoretical values of B?N-1s/?0 at magnetic-flux-induced antiferromagnetic phase transitions, which occur in the pseudospin system for large values of Btot, agree with the observed minima in EA(B?).
Fano effect in the Andreev reflection of the Aharonov-Bohm-Fano ring with Majorana bound states
NASA Astrophysics Data System (ADS)
Jiang, Cui; Zheng, Yi-Song
2015-06-01
The Andreev reflection in an Aharonov-Bohm-Fano ring induced by Majorana bound states (MBSs) is theoretically investigated. We find that compared with the Fano effect in the normal electron tunneling process, the Fano effect here is more determined by the structural parameters, i.e., the quantum dot level, the dot-MBS coupling, and the dot-MBS and MBS-lead couplings. By transforming the ring into its Nambu representation, we present a comprehensive analysis about the quantum interference in the Andreev reflection, and then explain the reason for the occurrence of the Fano effect. These results will be helpful for understanding the quantum interference in the MBS-assisted Andreev reflection.
NASA Astrophysics Data System (ADS)
Khatua, Pradip; Bansal, Bhavtosh; Shahar, Dan
2014-01-01
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.
NASA Astrophysics Data System (ADS)
Gangopadhyay, Sunandan; Scholtz, Frederik G.
2014-02-01
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.
NASA Astrophysics Data System (ADS)
Royo, Miquel; Segarra, Carlos; Bertoni, Andrea; Goldoni, Guido; Planelles, Josep
2015-03-01
We use spin-density-functional theory within an envelope function approach to calculate electronic states in a GaAs/InAs core-shell nanowire pierced by an axial magnetic field. Our fully three-dimensional quantum modeling includes explicitly a description of the realistic cross section and composition of the sample, and the electrostatic field induced by external gates in two different device geometries: gate-all-around and back-gate. At low magnetic fields, we investigate Aharonov-Bohm oscillations and signatures therein of the discrete symmetry of the electronic system, and we critically analyze recent magnetoconductance observations. At high magnetic fields, we find that several charge and spin transitions occur. We discuss the origin of these transitions in terms of different localization and Coulomb regimes, and we predict their signatures in magnetoconductance experiments.
NASA Astrophysics Data System (ADS)
Roy, Bidisha; Ji, Haojie; Dhomkar, Siddharth; Cadieu, Fred J.; Peng, Le; Moug, Richard; Tamargo, Maria C.; Kuskovsky, Igor L.
2013-02-01
A spectral analysis of the Aharonov-Bohm (AB) oscillations in photoluminescence intensity was performed for stacked type-II ZnTe/ZnSe quantum dots (QDs) fabricated within multilayered Zn-Se-Te system with sub-monolayer insertions of Te. Robust AB oscillations allowed for fine probing of distinguishable QDs stacks within the ensemble of QDs. The AB transition magnetic field, B AB , changed from the lower energy side to the higher energy side of the PL spectra revealing the presence of different sets of QDs stacks. The change occurs within the spectral range, where the contributing green and blue bands of the spectra overlapped. "Bundling" in lifetime measurements is seen at transition spectral regions confirming the results.
Hou, Dong; Wang, Shikuan; Wang, Rulin; Ye, LvZhou; Xu, RuiXue; Zheng, Xiao; Yan, YiJing
2015-03-14
Several recent advancements for the hierarchical equations of motion (HEOM) approach are reported. First, we propose an a priori estimate for the optimal number of basis functions for the reservoir memory decomposition. Second, we make use of the sparsity of auxiliary density operators (ADOs) and propose two ansatzs to screen out all the intrinsic zero ADO elements. Third, we propose a new truncation scheme by utilizing the time derivatives of higher-tier ADOs. These novel techniques greatly reduce the memory cost of the HEOM approach, and thus enhance its efficiency and applicability. The improved HEOM approach is applied to simulate the coherent dynamics of Aharonov-Bohm double quantum dot interferometers. Quantitatively accurate dynamics is obtained for both noninteracting and interacting quantum dots. The crucial role of the quantum phase for the magnitude of quantum coherence and quantum entanglement is revealed. PMID:25770531
Jian-Zu Zhang
2007-11-02
The induced fractional zero-point canonical angular momentum on charged particles by the Aharonov - Bohm (AB) vector potential is realized via modified combined traps. It explores new features for this type of quantum effects: In a limit of vanishing mechanical kinetic energy the AB vector potential alone cannot induce a fractional zero-point canonical angular momentum on charged particles at the quantum mechanical level in the AB magnetic field-free region; But for the case of the AB vector potential with another one of a "spectator" magnetic field the AB vector potential induces a fractional zero-point canonical angular momentum in the same limit. The "spectator" one does not contribute to such a fractional zero-point quantity, but plays essential role in guaranteeing non-trivial dynamics survived in this limit at the quantum mechanical level. These results are significance in investigations of the AB effects and related fields for both theories and experiments.
A. G. Smirnov
2014-12-15
We develop a general technique for finding self-adjoint extensions of a symmetric operator that respect a given set of its symmetries. Problems of this type naturally arise when considering two- and three-dimensional Schr\\"odinger operators with singular potentials. The approach is based on constructing a unitary transformation diagonalizing the symmetries and reducing the initial operator to the direct integral of a suitable family of partial operators. We prove that symmetry preserving self-adjoint extensions of the initial operator are in a one-to-one correspondence with measurable families of self-adjoint extensions of partial operators obtained by reduction. The general scheme is applied to the three-dimensional Aharonov-Bohm Hamiltonian describing the electron in the magnetic field of an infinitely thin solenoid. We construct all self-adjoint extensions of this Hamiltonian, invariant under translations along the solenoid and rotations around it, and explicitly find their eigenfunction expansions.
NASA Astrophysics Data System (ADS)
Bagrov, V. G.; Gitman, D. M.; Skarzhinskii, V. D.
The paper is concerned with the Aharonov-Bohm effect arising in the quantum mechanical description of electron motion in a magnetic field in the presence of an infinitely thin and long solenoid. Under stationary conditions, this effect is observed as the appearence of an additional series of energy levels shifted relative to the Landau levels by a value depending on the magnetic field flux in the solenoid. Quantum states describing the quasi-classical motion of an electron are obtained which are close to the coherent states. In these states, the presence of a solenoid leads to additional electron oscillations relative to the classical orbit and to changes in the relationships between classical motion parameters.
Schütz, G; Rembold, A; Pooch, A; Prochel, H; Stibor, A
2015-11-01
We propose an experiment for the first proof of the type I electric Aharonov-Bohm effect in an ion interferometer for hydrogen. The performances of three different beam separation schemes are simulated and compared. The coherent ion beam is generated by a single atom tip (SAT) source and separated by either two biprisms with a quadrupole lens, two biprisms with an einzel-lens or three biprisms. The beam path separation is necessary to introduce two metal tubes that can be pulsed with different electric potentials. The high time resolution of a delay line detector allows to work with a continuous ion beam and circumvents the pulsed beam operation as originally suggested by Aharonov and Bohm. We demonstrate that the higher mass and therefore lower velocity of ions compared to electrons combined with the high expected SAT ion emission puts the direct proof of this quantum effect for the first time into reach of current technical possibilities. Thereby a high detection rate of coherent ions is crucial to avoid long integration times that allow the influence of dephasing noise from the environment. We can determine the period of the expected matter wave interference pattern and the signal on the detector by determining the superposition angle of the coherent partial beams. Our simulations were tested with an electron interferometer setup and agree with the experimental results. We determine the separation scheme with three biprisms to be most efficient and predict a total signal acquisition time of only 80s to measure a phase shift from 0 to 2? due to the electric Aharonov-Bohm effect. PMID:26188995
Georg Schütz; Alexander Rembold; Andreas Pooch; Henrike Prochel; Alexander Stibor
2015-07-28
We propose an experiment for the first proof of the type I electric Aharonov-Bohm effect in an ion interferometer for hydrogen. The performances of three different beam separation schemes are simulated and compared. The coherent ion beam is generated by a single atom tip (SAT) source and separated by either two biprisms with a quadrupole lens, two biprisms with an einzel-lens or three biprisms. The beam path separation is necessary to introduce two metal tubes that can be pulsed with different electric potentials. The high time resolution of a delay line detector allows to work with a continuous ion beam and circumvents the pulsed beam operation as originally suggested by Aharonov and Bohm. We demonstrate, that the higher mass and therefore lower velocity of ions compared to electrons combined with the high expected SAT ion emission puts the direct proof of this quantum effect for the first time into reach of current technical possibilities. Thereby a high coherent ion detection rate is crucial to avoid long integration times that allow the influence of dephasing noise from the environment. We can determine the period of the expected matter wave interference pattern and the signal on the detector by determining the superposition angle of the coherent partial beams. Our simulations were tested with an electron interferometer setup and agree with the experimental results. We determine the separation scheme with three biprisms to be most efficient and predict a total signal acquisition time of only 80 s to measure a phase shift from 0 to 2$\\pi$ due to the electric Aharonov-Bohm effect.
Numazaki, Kazuya; Imai, Hiromitsu; Morinaga, Atsuo [Department of Physics, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510 (Japan)
2010-03-15
The second-order Zeeman effect of the sodium clock transition in a weak magnetic field of less than 50 {mu}T was measured as the scalar Aharonov-Bohm phase by two-photon stimulated Raman atom interferometry. The ac Stark effect of the Raman pulse was canceled out by adopting an appropriate intensity ratio of two photons in the Raman pulse. The Ramsey fringes for the pulse separation of 7 ms were obtained with a phase uncertainty of {pi}/200 rad. The nondispersive feature of the scalar Aharonov-Bohm phase was clearly demonstrated through 18 fringes with constant amplitude. The Breit-Rabi formula of the sodium clock transition was verified to be {Delta}{nu}=(0.222{+-}0.003)x10{sup 12}xB{sup 1.998{+-}0.004} in a magnetic field of less than 50 {mu}T.
Bias dependence of h/e and h/2e Aharonov-Bohm oscillations in topological insulators
NASA Astrophysics Data System (ADS)
Upadhyaya, Pramey; Xiu, Faxian; Fan, Yabin; Ovchinnikov, Igor; Wang, Kang; University of California Los Angeles Team
2011-03-01
Recently Aharonov-Bohm (AB) oscillations were observed in Bi 2 Se 3 nanoribbons by Peng et al. as a direct evidence for the existence of surface states in topological insulator. However, the resistance showed only h/e oscillations with a minimum in resistance at zero flux while the ballistic and diffusive theory predicts either h/e oscillations with a maximum in resistance at zero flux or h/2e oscillations with a minimum in resistance at zero flux respectively. A possible explanation of the results of Peng et al. was given in the theory of disordered topological insulators proposed by Bardarson et al . and Zhang et al. where they attributed the results of Peng et al. to presence of weak disorder. Furthermore authors of and studied dependence of h/e and h/2e oscillations on disorder strength and doping using their proposed theory. In this work we look at the effect of doping by studying bias dependence of AB oscillations using a gated device and observe both h/e and h/2e oscillations whose relative strength depends on the applied bias and compare the proposed theory of ref. and with the experimental results. This work was in part supported by Marco Focus Center on FENA -Functional Engineered Nano Architectoncis.
Miyamoto, Satoru; Ishikawa, Toyofumi; Eto, Mikio; Itoh, Kohei M.; Moutanabbir, Oussama; Haller, Eugene E.; Sawano, Kentarou; Shiraki, Yasuhiro
2010-08-15
We report on a magnetophotoluminescence study of isotopically pure {sup 70}Ge/Si self-assembled type-II quantum dots. Oscillatory behaviors attributed to the Aharonov-Bohm effect are simultaneously observed for the emission energy and intensity of excitons subject to an increasing magnetic field. When the magnetic flux penetrates through the ringlike trajectory of an electron moving around each quantum dot, the ground state of an exciton experiences a change in its angular momentum. Our results provide the experimental evidence for the phase coherence of localized electron wave functions in group-IV Ge/Si self-assembled quantum structures.
Tokuno, Akiyuki [Institute for Solid State Physics, University of Tokyo, Kashiwa 227-8581 (Japan); Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro-ku, Tokyo 152-8551 (Japan); Oshikawa, Masaki [Institute for Solid State Physics, University of Tokyo, Kashiwa 227-8581 (Japan); Demler, Eugene [Department of Physics, Harvard University, Massachusetts 02138 (United States)
2008-04-11
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.
NASA Astrophysics Data System (ADS)
Wu, C. H.; Tran, L.; Cain, C. A.
2012-05-01
Electron transport and the exact scaling relations for two irreducibly coupled Aharonov-Bohm (AB) rings with two external terminals attached are investigated. In coupled AB rings, a center common path exists where the phase of the electron wave function can be modulated by two applied fluxes simultaneously. The two coupled rings can be considered as two coupled atoms where Fermi level crossings exist not only between bonding states but also between bonding and anti-bonding states when the applied flux is varied in one of the two cases studied. We show that when the smallest atomic-sized coupled rings are scaled up any odd number of times, an identical electron transmission is preserved. When two terminals are attached to isolated coupled AB rings, there is a further redistribution of bond-charge stored within the center common path. The shift of the electron charge distribution to favor one end of the common path is accompanied by the redistribution of the two partial waves that traverse through the two arms from the input to the output terminal. The flux can control which arm the electron traverses through more favorably, and hence, the center path behaves like a flux-controlled charge reservoir for the electron transport. The unbalanced charge in the entire structure creates a space-charge effect much like a p-n junction. The paradox of the delocalization of the electron wave when two AB rings are coupled and the subsequent localization effect of the electron transport in a quantum network are described.
Thiago Prudencio
2015-07-02
Generation of Aharonov-Bohm (AB) phase has achieved a state-of-the-art in mesoscopic systems with manipulation and control of the AB effect. The possibility of transfer information enconded in such systems to light increases the possible scenarios where the information can be manipulated and transfered. In this paper we discuss a bit-enconding of AB phases and propose a quantum transfer of the AB phase generated in a topological spin transistor (TST) to coherent state superposition in high-Q cavity. We demonstrate that the AB phase generated in the TST can be stored in a non-classical state of light, a coherent state superposition, by interacting dispersivelly the spin state carrying the AB phase with the cavity state initially in a coherent state. We also discuss the storage of bits enconded by AB phases in high-Q and multimode cavities.
NSDL National Science Digital Library
De Raedt, Hans
This web page illustrates the effect of a magnetic flux on the interference of a quantum double-slit experiment. The time-dependent scattering patterns are shown with and without a magnetic field. In addition, the effects of changing the topology of the system are discussed and displayed. The webpage includes animations which demonstrate the concept.
NASA Astrophysics Data System (ADS)
Maamache, M.; Lahoulou, C.; Saadi, Y.
2009-05-01
Invariant operator method for discrete or continuous spectrum eigenvalue and unitary transformation approach are employed to study the two-dimensional time-dependent Pauli equation in presence of the Aharonov-Bohm effect (AB) and external scalar potential. For the spin particles the problem with the magnetic field is that it introduces a singularity into wave equation at the origin. A physical motivation is to replace the zero radius flux tube by one of radius R, with the additional condition that the magnetic field be confined to the surface of the tube, and then taking the limit R ? 0 at the end of the computations. We point that the invariant operator must contain the step function ?(r - R). Consequently, the problem becomes more complicated. In order to avoid this difficulty, we replace the radius R by ?(t)R, where ?(t) is a positive time-dependent function. Then at the end of calculations we take the limit R ? 0. The qualitative properties for the invariant operator spectrum are described separately for the different values of the parameter C appearing in the nonlinear auxiliary equation satisfied by ?(t), i.e., C > 0, C = 0, and C < 0. Following the C's values the spectrum of quantum states is discrete (C > 0) or continuous (C <= 0).
Matisse Wei-Yuan Tu; Amnon Aharony; Wei-Min Zhang; Ora Entin-Wohlman
2014-10-02
The spin-resolved non-equilibrium real-time electron transport through a double-quantum-dot (DQD) Aharonov-Bohm (AB) interferometer with spin-orbit interaction (SOI) is explored. The SOI and AB interference in the real-time dynamics of spin transport is expressed by effective magnetic fluxes. Analytical formulae for the time-dependent currents, for initially unpolarized spins, are presented. In many cases, there appear spin currents in the electrodes, for which the spins in each electrode are polarized along characteristic directions, pre-determined by the SOI parameters and by the geometry of the system. Special choices of the system parameters yield steady-state currents in which the spins are fully polarized along these characteristic directions. The time required to reach this steady state depends on the couplings of the DQD to the leads. The magnitudes of the currents depend strongly on the SOI-induced effective fluxes. Without the magnetic flux, the spin-polarized current cannot be sustained to the steady states, due to the phase rigidity for this system. For a non-degenerate DQD, transient spin transport can be produced by the sole effects of SOI. We also show that one can extract the spin-resolved currents from measurements of the total charge current.
2012-01-01
Using the nonequilibrium Green’s function method, we theoretically study the Andreev reflection(AR) in a four-terminal Aharonov-Bohm interferometer containing a coupled double quantum dot with the Rashba spin-orbit interaction (RSOI) and the coherent indirect coupling via two ferromagnetic leads. When two ferromagnetic electrodes are in the parallel configuration, the spin-up conductance is equal to the spin-down conductance due to the absence of the RSOI. However, for the antiparallel alignment, the spin-polarized AR occurs resulting from the crossed AR (CAR) and the RSOI. The effects of the coherent indirect coupling, RSOI, and magnetic flux on the Andreev-reflected tunneling magnetoresistance are analyzed at length. The spin-related current is calculated, and a distinct swap effect emerges. Furthermore, the pure spin current can be generated due to the CAR when two ferromagnets become two half metals. It is found that the strong RSOI and the large indirect coupling are in favor of the CAR and the production of the strong spin current. The properties of the spin-related current are tunable in terms of the external parameters. Our results offer new ways to manipulate the spin-dependent transport. PMID:23228047
R. Y. Chiao
2012-06-23
The flux as measured by the Josephson effect in a SQUID-like configuration with a ferromagnetic core inserted into its center, is shown to be sensitive to the vector potential arising from the central ferromagnetic core, even when the core is covered with a superconducting material that prevents any magnetic field lines from ever reaching the perimeter of the SQUID-like configuration. This leads to a macroscopic, Aharonov-Bohm-like effect that is observable in an asymmetric hysteresis loop in the response of the SQUID-like configuration to an externally applied magnetic field.
R. Y. Chiao; X. H. Deng; K. M. Sundqvist; N. A. Inan; G. A. Munoz; D. A. Singleton; B. S. Kang; L. A. Martinez
2014-11-13
In this paper we investigate the scalar Aharonov-Bohm (AB) effect in two of its forms, i.e., its electric form and its gravitational form. The standard form of the electric AB effect involves having particles (such as electrons) move in regions with zero electric field but different electric potentials. When a particle is recombined with itself, it will have a different phase, which can show up as a change in the way the single particle interferes with itself when it is recombined with itself. In the case where one has quasi-static fields and potentials, the particle will invariably encounter fringing fields, which makes the theoretical and experimental status of the electric AB effect much less clear than that of the magnetic (or vector) AB effect. Here we propose using time varying fields outside of a spherical shell, and potentials inside a spherical shell to experimentally test the scalar AB effect. In our proposal a quantum system will always be in a field-free region but subjected to a non-zero time-varying potentials. Furthermore, our system will not be spatially split and brought back together as in the magnetic AB experiment. Therefore there is no spatial interference and hence no shift in a spatial interference pattern to observe. Rather, there arises purely temporal interference phenomena. As in the magnetic AB experiments, these effects are non-classical. We present two versions of this idea: (i) a Josephson temporal interferometry experiment inside a superconducting spherical shell with a time-varying surface charge; (ii) a two-level atom experiment in which the atomic spectrum acquires FM sidebands when it is placed inside a spherical shell whose exterior mass is sinusoidally varying with time. The former leads to a time-varying internal magnetic field, and the latter leads to a time-varying gravitational redshift.
NASA Astrophysics Data System (ADS)
Vaidman, Lev; Dennis, Mark; Popescu, Sandu
2010-01-01
This is a call for contributions to a special issue of Journal of Physics A: Mathematical and Theoretical dedicated to the subject of quantum phases and highlighting the impact of the discovery of the Aharonov--Bohm effect and of the Berry phase across physics. Researchers working in the area are invited to submit papers of original research to this issue. Editorial policy The Editorial Board has invited Lev Vaidman, Mark Dennis and Sandu Popescu to serve as Guest Editors for the special issue. The criteria for acceptance of contributions are as follows: Contributions will be refereed and processed according to the usual procedure and high standards of the journal. Papers should be original and should contain substantial new results. All contributions will be refereed and processed according to the usual procedure of the journal. Papers should report original and significant research that has not already been published. Guidelines for preparation of contributions The DEADLINE for contributed papers will be 1 February 2010. This deadline will allow the special issue to appear in September 2010. Advice on publishing your work in Journal of Physics A: Mathematical and Theoretical www.iop.org/Journals/jphysa. Contributions to the special issue should be submitted electronically, if possible, by web upload at www.iop.org/Journals/jphysa, or by email to jphysa@iop.org, quoting 'JPhysA Special Issue— Quantum Phases'. Submissions should ideally be in standard LaTeX form. Please see the website for further information on electronic submissions. Authors unable to submit electronically may send hard-copy contributions to: Publishing Administrators, Journal of Physics A, IOP Publishing, Dirac House, Temple Back, Bristol BS1 6BE, UK. Please quote 'JPhysA Special Issue— Quantum Phases'. All contributions should be accompanied by a read-me file or covering letter giving the postal and e-mail addresses for correspondence. The Publishing Office should be notified of any subsequent change of address. This special issue will be published in the paper and online version of the journal.
Aharonov-Bohm Effect in Perturbation Theory.
ERIC Educational Resources Information Center
Purcell, Kay M.; Henneberger, Walter C.
1978-01-01
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)
Mathematical justification of the Aharonov-Bohm hamiltonian
describing the quantum motion of this charged particle is given by (with = 1) HAB = p - q c A 2 , p = -i , with Dirichlet boundary conditions, i.e., the functions in the domain of HAB are supposed to vanish = 0 at the solenoid boundary (the precise domain of HAB is described just before Proposition ??). Observable effects
Semifluxon degeneracy choreography in Aharonov-Bohm billiards
NASA Astrophysics Data System (ADS)
Berry, M. V.; Popescu, S.
2010-09-01
Every energy level of a charged quantum particle confined in a region threaded by a magnetic flux line with quantum flux one-half must be degenerate for some position of the semifluxon within the boundary B. This is illustrated by computations for which B is a circle and a conformal transformation of a circle without symmetry. As the shape of B is varied, two degeneracies between the same pair of levels can collide and annihilate. Degeneracy of three levels requires three shape parameters, or the positions of three semifluxons; degeneracy of N levels can be generated by int{N(N + 1)/4} semifluxons. The force on the semifluxon is derived.
Aharonov-Bohm radiation Katherine Jones-Smith,1
Akerib, Daniel S.
purely topological, as it arises from the nontrivial change in the phase of the wave function radiation rate from oscillating cosmic string loops. The disadvantage of this perturbative approach.e. we expand in the velocity of the solenoid. The advantage now is that we explicitly see the periodic
Aharonov-Bohm effect on Aharonov-Casher scattering
Lin Qionggui
2010-01-15
The scattering of relativistic spin-1/2 neutral particles with a magnetic dipole moment by a long straight charged line and a magnetic flux line at the same position is studied. The scattering cross sections for unpolarized and polarized particles are obtained by solving the Dirac-Pauli equation. The results are in general the same as those for pure Aharonov-Casher scattering (by the charged line alone) as expected. However, in special cases when the incident energy, the line charge density, and the magnetic flux satisfy some relations, the cross section for polarized particles is dramatically changed. Relations between the polarization of incident particles and that of scattered ones are presented, both in the full relativistic case and the nonrelativistic limit. The characteristic difference between the general and special cases lies in the backward direction: in the general cases the incident particles are simply bounced while in the special cases their polarization is turned over simultaneously. For pure Aharonov-Casher scattering there exist cases where the helicities of all scattered particles are reversed. This seems to be remarkable but appears unnoticed previously. Two mathematical approaches are employed to deal with the singularity of the electric and magnetic field and it turns out that the physical results are essentially the same.
Detecting Noncommutative Phase Space by Aharonov-Bohm Effect
Shi-Dong Liang; Haoqi Li; Guang-Yao Huang
2015-02-02
Noncommutative phase space plays an essential role in particle physics and quantum gravity at the Planck scale. However, direct experimental evidence or observation to demonstrate the existence of noncommutative phase space is still lacking.We study a quantum ring in noncommutative phase space based on the Seiberg-Witten map and give the effective magnetic potential and field coming from the noncommutative phase space, which induces the persistent current in the ring. We introduce two variables as two signatures to detect the noncommutative phase space and propose an experimental scheme to detect the noncommutative phase space as long as we measure the persistent current and the external magnetic flux.
Induced current and Aharonov-Bohm effect in graphene
Jackiw, Roman
The effect of vacuum polarization in the field of an infinitesimally thin solenoid at distances much larger than the radius of solenoid is investigated. The induced charge density and induced current are calculated. Though ...
AZO DYES ARE MAJOR CONTRIBUTORS TO THE MUTAGENIC ACTIVITY DETECTED IN THE CRISTAIS RIVER WATERS
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...
THE CONTRIBUTION OF AZO DYES TO THE MUTAGENIC ACTIVITY OF THE CRISTAIS RIVER
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 ...
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...
Aharonov-Bohm effect and geometric phase And all I wanted was a complex carrot.
Johannesson, Henrik
through regions where the David Bohm (1917-1992) was a major figure in 20th century physics. He also led discoveries, it made its entrance amidst myriad precursor and complementary studies. It was not as original
Canonical Quantization on a Doubly Connected Space and the AharonovBohm Phase
isp k = exp [\\Gammaist~ffi jk ] e isp k e itq j ; e itq j e isq k = e isq k e itq j ; e itp j e isp k = e isp k e itp j (1.2) (s; t 2 R; j; k = 1; \\Delta \\Delta \\Delta ; N) determines fp j ; q j g
Feng Li; HuJun Jiao; Hui Wang; JunYan Luo; Xin-Qi Li
2009-06-19
For the solid state double-dot interferometer, the phase shifted interference pattern induced by the interplay of inter-dot Coulomb correlation and multiple reflections is analyzed by harmonic decomposition. Unexpected result is uncovered, and is discussed in connection with the which-path detection and electron loss.
Fano resonances through quantum dots in tunable Aharonov-Bohm rings
Y. S. Joe; J. S. Kim; E. R. Hedin; R. M. Cosby; A. M. Satanin
2004-01-01
The main goal of the present work is to investigate novel resonant phenomena which may arise in the AB rings with specially-designed dots. First, we investigate the total transmission probability through the coupled double quantum dots (QDs) embedded in one of the arms of the AB ring with a magnetic flux passing through its center. We calculate the electron transmission
Foundations of Physics, Vol. 18, No. 7, 1988 The Aharonov-Bohm Effect: Still a
Semon, Mark D.
is that a two-slit interference pattern is altered by shifting the relative phase of the two transmitted waves, electromagnetic potentials alter the two-slit inter- ference pattern formed by an electron beam. We discuss here a curious feature of this effect, namely that, even though the interference pattern changes, none of its
Coherent and semiclassical states in magnetic field in the presence of the Aharonov-Bohm solenoid
V. G. Bagrov; S. P. Gavrilov; D. M. Gitman; D. P. Meira Filho
2011-08-25
A new approach to constructing coherent states (CS) and semiclassical states (SS) in 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 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.
Self-adjoint Schrodinger and Dirac operators with Aharonov-Bohm and magnetic-solenoid fields
D. M. Gitman; A. Smirnov; I. V. Tyutin; B. L. Voronov
2009-11-04
We study all the s.a. Schrodinger and Dirac operators (Hamiltonians) both with pure AB field and with magnetic-solenoid field. Then, we perform a complete spectral analysis for these operators, which includes finding spectra and spectral decompositions, or inversion formulas. In constructing the Hamiltonians and performing their spectral analysis, we respectively follow the von Neumann theory of s.a. extensions of symmetric differential operators and the Krein method of guiding functionals. The examples of similar consideration are given by us in arXiv:0903.5277, where a nonrelativistic particle in the Calogero potential field is considered and in Theor. Math. Phys. 150 (1) (2007) 34, where a Dirac particle in the Coulomb field of arbitrary charge is considered. However, due to peculiarities of the three-dimensional problems under consideration, we elaborated a generalization of the approach used in the study of the Dirac particle.
Coherent and semiclassical states in a magnetic field in the presence of the Aharonov-Bohm solenoid
NASA Astrophysics Data System (ADS)
Bagrov, V. G.; Gavrilov, S. P.; Gitman, D. M.; Meira Filho, D. P.
2011-02-01
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.
Semon, Mark D.
~nctic- potentials. e,en if the electrons Ilcn'r enter the region in which the Iidlls ,ire nonz('ro. In this papl'll \\'('10111'by the introtlllctioll of ma!!nl'tic or ('!Petrie pott'!!liaJ..;. A or ft. TIll' main [lointtion. As AIL\\RO,,"O\\' and GOlD! Tll;idt, ('!t'ar, thl' pr('~l'nce of nonZl'ro pot('ntials ran shift
NASA Astrophysics Data System (ADS)
Sarkar, Daipayan
The objective of this research is to understand the temperature variation in dielectric materials of different geometry. The work is divided into three major segments. The Thermal Wave model has been taken into consideration as the classical Fourier law of heat conduction breaks down when a dielectric material of sub-micron geometry is heated rapidly. The first part of the work discusses primarily about the temperature distribution in a semi-infinite dielectric material, followed by the temperature profile in a finite body (plate) and finally mathematical formulation is presented for a two-layered body. The thermal wave equation is used because in dielectric materials the lag time due to temperature (taut) is much less than the lag time due to heat flux (tauq), ( taut <
Chords: Em 022000 Em Em Em Em C C C C
Reiners, Peter W.
Verse 1 Chorus Verse 2 Chorus Verse 3 Chords: Em 022000 C 035553 G 320002 F 133211 Intro: Em Em Em Em C C C C Em Em Em Em C C C C Em Em Em Em C C C C Em Em Em Em C C C C Verse: Em Em Em Em C C C C G G G G G G G G Em Em Em Em C C C C G G G G G G G G Em Em Em Em C C C C G G G G G G G G Em Em Em Em C C
Optical analog of the Iordanskii force in a Bose-Einstein condensate
Leonhardt, U.; Oehberg, P. [School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, Scotland (United Kingdom)
2003-05-01
A vortex in a Bose-Einstein condensate generates the optical analog of the Aharonov-Bohm effect when illuminated with slow light. In contrast to the original Aharonov-Bohm effect the vortex will exchange forces with the light that leads to a measurable motion of the vortex.
Goldman, Vladimir J.
Flux-period scaling in the Laughlin quasiparticle interferometer Wei Zhou, F. E. Camino, and V. J is deposited. We find a linear dependence of the Aharonov-Bohm period on gate voltage for electrons integer, we find the magnetic field period and its slope scale with the radius of the Aharonov-Bohm orbit
Meir, Yigal
and the Orthogonality Catastrophe in Tunneling through a Quantum Dot: The "Which Path?" Interferometer I. L. Aleiner,1 of the Aharonov-Bohm oscillations which is caused by both measurement dephasing and the orthogonality catastrophe
JÃ¼ngel, Ansgar
Perfectly Matched Layers versus discrete transparent boundary conditions in quantum device Abstract Discrete transparent boundary conditions (DTBC) and the Perfectly Matched Lay- ers (PML) method transparent boundary conditions, transient simulations, quantum waveguides, Aharonov-Bohm effect 1
THE INSTITUTE FOR SOLID STATE PHYSICS 2014 Division of New Materials Science
Katsumoto, Shingo
processes such as chemical reaction at surfaces, and creation of new material phases, Epitaxial growth and Aharonov-Bohm effect. In the quantum Hall regime, where electron solid (stripe and bubble) phases
Two Further Experiments on Electron Interference
ERIC Educational Resources Information Center
Matteucci, G.; Pozzi, G.
1978-01-01
Presents the results of two experiments concerning the phenomena of the interference of probabilities and of the so called Aharonov-Bohm effect. An electron biprism and a standard electron microscope have been used for the experiments. (Author/GA)
chapter five Magnetic properties
Natelson, Douglas
119 chapter five Magnetic properties Junichiro Kono Rice University Stephan Roche Commissariat à l.2.3.1 Fermi's golden rule and mean free path....................129 5.2.3.2 AharonovBohm phenomena: ballistic
Quantum mechanics : Intellectually delicious;
Peshkin, M.; Vaidman, L. (Physics); (Tel-Aviv Univ.)
2010-03-01
It is 50 years since the discovery of the Aharonov-Bohm effect, and 25 years since that of the Berry phase. A celebration of this double anniversary at the University of Bristol made evident that these discoveries still offer much food for thought. The meeting celebrating the fiftieth anniversary of the Aharonov-Bohm effect and the twenty-fifth anniversary of the Berry phase was held on 14-15 December 2009 in the historic H. H.
NASA Astrophysics Data System (ADS)
Li, Hai-Tao; Liu, Li-Zhe; Liu, Jian-Jun
2008-11-01
We calculate the energy states and Aharonov-Bohm oscillations of an electron in elliptical quantum rings in the presence of a uniform magnetic Geld by using an exact numerical diagonalization. The calculated results show that the elliptical quantum rings are flatter, larger amplitudes and periods of the Aharonov-Bohm oscillations are observed. In addition, in the limits of a circular quantum ring, the results of our approach are in good agreement with those of earlier theories.
Ludwig-Maximilians-Universität, München
, Heisenbergstraße 1, 70569 Stuttgart, Germany (Received 1 November 2000; published 29 November 2001) We define two s and ns 1.7 3 1015 m22 . By electron beam writing and Au evaporation Schottky gates are de- fined which
A Note on the Sagnac Effect and Current Terrestrial Experiments
Matteo Luca Ruggiero; Angelo Tartaglia
2014-06-04
We focus on the Sagnac effect for light beams in order to evaluate if the higher order relativistic corrections of kinematic origin could be relevant for actual terrestrial experiments. Moreover, we discuss to what extent the analogy with the Aharonov-Bohm effect holds true in a fully relativistic framework. We show that the analogy with the Aharonov-Bohm is not true in general, but is recovered in a suitable low order approximation, and that even though the Sagnac effect is influenced by both the position of the interferometer in the rotating frame and its extension, these effects are negligible for current terrestrial experiments.
Nonrelativistic molecular models under external magnetic and AB flux fields
Sameer M. Ikhdair; Babatunde J. Falaye; Majid Hamzavi
2014-12-21
By using the wave function ansatz method, we study the energy eigenvalues and wave function for any arbitrary $m$-state in two-dimensional Schr\\"{o}dinger wave equation with various power interaction potentials in constant magnetic and Aharonov-Bohm (AB) flux fields perpendicular to the plane where the interacting particles are confined. We calculate the energy levels of some diatomic molecules in the presence and absence of external magnetic and AB flux fields using different potential models. We found that the effect of the Aharonov-Bohm field is much as it creates a wider shift for $m\
Exciton splitting in semiconducting carbon nanotubes in ultrahigh magnetic fields above 300 T
NASA Astrophysics Data System (ADS)
Nakamura, Daisuke; Sasaki, Tatsuya; Zhou, Weihang; Liu, Huaping; Kataura, Hiromichi; Takeyama, Shojiro
2015-06-01
In high magnetic fields, the exciton absorption spectrum of a semiconducting single-walled carbon nanotube splits as a result of Aharonov-Bohm magnetic flux. A magnetic field of 370 T, generated by the electromagnetic flux compression destructive pulsed magnet-coil technique, was applied to single-chirality semiconducting carbon nanotubes. Using streak spectroscopy, we demonstrated the separation of the independent band-edge exciton states at the K and K' points of the Brillouin zone after the mixing of the dark and bright states above 150 T. These results enable a quantitative discussion of the whole picture of the Aharonov-Bohm effect in single-walled carbon nanotubes.
Hartman effect in presence of Aharanov Bohm flux
Swarnali Bandopadhyay; Raishma Krishnan; A. M. Jayannavar
2003-12-03
The Hartman effect for the tunneling particle implies the independence of group delay time on the opaque barrier width, with superluminal velocities as a consequence. This effect is further examined on a quantum ring geometry in the presence of Aharonov-Bohm flux. We show that while tunneling through an opaque barrier the group delay time for given incident energy becomes independent of the barrier thickness as well as the magnitude of the flux. The Hartman effect is thereby extended beyond one dimension and in the presence of Aharonov-Bohm flux.
Not Available
1993-07-01
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.
Testing Atom and Neutron Neutrality with Atom Interferometry
Asimina Arvanitaki; Savas Dimopoulos; Andrew A. Geraci; Jason Hogan; Mark Kasevich
2007-11-29
We propose an atom-interferometry experiment based on the scalar Aharonov-Bohm effect which detects an atom charge at the 10^{-28}e level, and improves the current laboratory limits by 8 orders of magnitude. This setup independently probes neutron charges down to 10^{-28}e, 7 orders of magnitude below current bounds.
Hidden supersymmetry in quantum bosonic systems
Francisco Correa; Mikhail S. Plyushchay
2006-12-11
We show that some simple well studied quantum mechanical systems without fermion (spin) degrees of freedom display, surprisingly, a hidden supersymmetry. The list includes the bound state Aharonov-Bohm, the Dirac delta and the Poschl-Teller potential problems, in which the unbroken and broken N=2 supersymmetry of linear and nonlinear (polynomial) forms is revealed.
nature physics | VOL 6 | MARCH 2010 | www.nature.com/naturephysics 151 perspective
Loss, Daniel
nature physics | VOL 6 | MARCH 2010 | www.nature.com/naturephysics 151 perspective Dynamical quantum non-locality Sandu Popescu During the 50 years since its discovery, the AharonovBohm effect hasBohm (AB) effect1 , one of the most surprising and quintessential effects in quantum mechanics. Since its
Remarks about Hardy inequalities on metric trees
Tomas Ekholm; Rupert L. Frank; Hynek Kovarik
2007-11-13
We find sharp conditions on the growth of a rooted regular metric tree such that the Neumann Laplacian on the tree satisfies a Hardy inequality. In particular, we consider homogeneous metric trees. Moreover, we show that a non-trivial Aharonov-Bohm magnetic field leads to a Hardy inequality on a loop graph.
Foundations of Physics, Vol. 12, No. 1, 1982 Experimental Verification
Semon, Mark D.
in Rotating Reference Frames Mark D. Semon ~ Received January 26, 1981 A thought experiment is reviewed whichFoundations of Physics, Vol. 12, No. 1, 1982 Experimental Verification of an Aharonov-Bohm Effect shows two things. First, in a region of a rotating frame that is not simply connected, the inertial
A Note on the Sagnac Effect and Current Terrestrial Experiments
Ruggiero, Matteo Luca
2014-01-01
We focus on the Sagnac effect for light beams in order to evaluate if the higher order relativistic corrections of kinematic origin could be relevant for actual terrestrial experiments. Moreover, we discuss to what extent the analogy with the Aharonov-Bohm effect holds true in a fully relativistic framework.
Energy levels and far-infrared spectra of oval-shaped nanorings
Gutiérrez, W.; García, L. F.; Mikhailov, I. D. [Escuela de Física, Universidad Industrial de Santander, A. A. 678, Bucaramanga (Colombia)
2014-05-15
The evolution of the Aharonov-Bohm oscillation of low-lying states and far infrared spectrum associated to variation of the path curvature for electron motion along nanorings with centerlines in a form of a set of Cassini ovals, whose shape is changed continuously from a single elongated loop to two separated loops is theoretically investigated.
Suppression of decoherence in a graphene monolayer ring
Smirnov, D. Rode, J. C.; Haug, R. J.
2014-08-25
The influence of high magnetic fields on coherent transport is investigated. A monolayer graphene quantum ring is fabricated and the Aharonov-Bohm effect is observed. For increased magnitude of the magnetic field, higher harmonics appear. This phenomenon is attributed to an increase of the phase coherence length due to reduction of spin flip scattering.
arXiv:cond-mat/0504756v226Sep2005 The Multimode Conductance Formula
Cohen, Doron
of an electro motive force (EMF) such that the voltage drop is concentrated across a segment of the device. More EMF by changing in time an Aharonov-Bohm magnetic flux, or we can change the potential in some region. The current is measured via the section x = x1. The Electro motive force (EMF) is realized by time dependent
arXiv:cond-mat/0510289v211Jan2006 Quantum stirring of particles in closed devices
Cohen, Doron
in this ring. If the particles are charged then one way to do it is by creating an electro motive force (EMF). This can be induced by varying an Aharonov-Bohm flux , such that by Faraday's law EMF = - . But there is another way to create a current that does not involve EMF, and hence does not assume charged particles
Kane, Charles
Telegraph Noise and Fractional Statistics in the Quantum Hall Effect C. L. Kane Department of Physics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA (Received 28 October 2002 for an Aharonov- Bohm ring with a third contact in the middle of the ring. Because of their fractional statistics
Effects of dephasing on shot-noise in an electronic Mach-Zehnder interferometer Florian Marquardt
Bruder, Christoph
Effects of dephasing on shot-noise in an electronic Mach-Zehnder interferometer Florian Marquardt study of the influence of dephasing on shot noise in an electronic Mach- Zehnder interferometer" or "Mach-Zehnder" interferometers, often employ- ing the Aharonov-Bohm phase due to a magnetic flux
Role of interactions in an electronic FabryPerot interferometer operating in the quantum
Heiblum, Mordehai "Moty"
in an electronic version of a Fabry Perot interferometer (FPI) (13, 14) or in a similar MachZehnder of the interfering quasiparticles controlled by the AharonovBohm effect. Our main finding is that Coulomb with a biased metallic gate and observing the periodicity of the interference pattern, charges e (for integer
The reality of loops Alexander Afriat
Paris-Sud XI, Université de
The reality of loops Alexander Afriat January 3, 2013 Abstract The transformation properties of the electromagnetic four-potential can make one wonder whether it has any physical reality. But it is felt (with the Aharonov-Bohm effect in mind) that the reality in question has to be somewhere, `thereabouts
How to test atom and neutron neutrality with atom interferometry.
Arvanitaki, Asimina; Dimopoulos, Savas; Geraci, Andrew A; Hogan, Jason; Kasevich, Mark
2008-03-28
We propose an atom-interferometry experiment based on the scalar Aharonov-Bohm effect which detects an atom charge at the 10{-28}e level, and improves the current laboratory limits by 8 orders of magnitude. This setup independently probes neutron charges down to 10{-28}e, 7 orders of magnitude below current bounds. PMID:18517846
Testing atom and neutron neutrality with atom interferometry
NASA Astrophysics Data System (ADS)
Arvanitaki, Asimina
We propose an atom-interferometry experiment based on the scalar Aharonov-Bohm effect which detects an atom charge at the 10 -28e level, and improves the current laboratory limits by 8 orders of magnitude. This setup independently probes neutron charges down to 10 -28e, 7 orders of magnitude below current bounds.
How to Test Atom and Neutron Neutrality with Atom Interferometry
NASA Astrophysics Data System (ADS)
Arvanitaki, Asimina; Dimopoulos, Savas; Geraci, Andrew A.; Hogan, Jason; Kasevich, Mark
2008-03-01
We propose an atom-interferometry experiment based on the scalar Aharonov-Bohm effect which detects an atom charge at the 10-28e level, and improves the current laboratory limits by 8 orders of magnitude. This setup independently probes neutron charges down to 10-28e, 7 orders of magnitude below current bounds.
Quantum Corrections to Scattering Amplitude in Conical Space-time
Shiraishi, Kiyoshi
2015-01-01
It is known that the vacuum polarization of zero-point field arises around a conical singularity generated by an infinite, straight cosmic string. In this paper we study quantum electromagnetic corrections to the gravitational Aharonov-Bohm effect around a cosmic string. We find the scattering amplitude from a conical defect for charged Klein-Gordon field.
www.lpr-journal.org Temperature-dependent magneto-photoluminescence
Natelson, Douglas
LASER & PHOTONICS REVIEWS www.lpr-journal.org REPRINT Temperature-dependent magneto-photoluminescence-walled carbon nanotubes; photoluminescence; excitons; Aharonov-Bohm effect PACS 78.67.Ch, 71.35.Ji, 78.55.-m We-dependent photoluminescence studies of excitons in SWNTs in a varying magnetic field have thus provided one of the most
MESTRADO EM TEOLOGIA Edital 2016
Díaz, Lorenzo J.
MESTRADO EM TEOLOGIA Edital 2016 Este edital se destina especificamente a candidatos ao Mestrado em Teologia, com início em março de 2016. 1. Objetivo O Programa de Mestrado em Teologia visa o universitários de Teologia e de assessores teológicos a organismos internacionais e nacionais, civis e
Guide d'utilisation EM-PREMIUM
Brest, Université de
EM-PREMIUM Guide d'utilisation #12;EM-PREMIUM Présentation EM Premium est la bibliothèque numérique domaine sont enrichis de vidéos, d'illustrations, de grilles d'auto-évaluation interactives.. #12;EM-PREMIUM Accès à partir d'UBODOC #12;EM-PREMIUM #12;EM-PREMIUM Entrez vos identifiant et mot de passe de l
Escenario EM Modelo Matematico
Majós, Antonio Badía
negativa ? Difusi´on magn´etica hacia el EC #12;j - 2012 CAB Escenario EM Modelo Matem´atico Problemas F E(J) (E = J o bien Fdiss = J2 2 ) µ0 t - 2 H = 0 Ecuaci´on de difusi´on magn´etica en un metal #12
NASA Astrophysics Data System (ADS)
Jones, K. B., II; Saxton, P. T.
2013-12-01
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.
EM Diffusion for a Time-Domain Airborne EM System
NASA Astrophysics Data System (ADS)
Yin, C.; Qiu, C.; Liu, Y.; Cai, J.
2014-12-01
Visualization of EM diffusion for an airborne EM (AEM) system is important for understanding the transient procedure of EM diffusion. The current distribution and diffusion features also provide effective means to evaluate EM footprint, depth of exploration and further help AEM system design and data interpretation. Most previous studies on EM diffusion (or "smoke ring" effect) are based on the static presentation of EM field, where the dynamic features of EM diffusion were not visible. For visualizing the dynamic feature of EM diffusion, we first calculate in this paper the frequency-domain EM field by downward continuation of the EM field at the EM receiver to the deep earth. After that, we transform the results to time-domain via a Fourier transform. We take a homogeneous half-space and a two-layered earth induced by a step pulse to calculate the EM fields and display the EM diffusion in the earth as 3D animated vectors or time-varying contours. The "smoke ring" effect of EM diffusion, dominated by the resistivity distribution of the earth, is clearly observed. The numerical results for an HCP (vertical magnetic dipole) and a VCX (horizontal magnetic dipole) transmitting coil above a homogeneous half-space of 100 ohm-m are shown in Fig.1. We display as example only the distribution of EM field inside the earth for the diffusion time of 0.05ms. The detailed EM diffusion will be shown in our future presentation. From the numerical experiments for different models, we find that 1) the current for either an HCP or a VCX transmitting dipole propagates downward and outward with time, becoming wider and more diffuse, forming a "smoke ring"; 2) for a VCX transmitter, the underground current forms two ellipses, corresponding to the two polarities of the magnetic flux of a horizontal magnetic dipole, injecting into or ejected from the earth; 3) for a HCP transmitter, however, the underground current forms only one circle, corresponding to the polarity of the magnetic flux for a vertical magnetic dipole, injecting into the earth; 4) there exists no vertical current in an isotropic homogeneous half-space. The currents for both HCP and VCX transmitting dipole flow horizontally.
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM CINCIAS E TECNOLOGIAS EM SADE
Maier, Rudolf Richard
1 UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM CIÊNCIAS E TECNOLOGIAS EM SAÚDE EDITAL No. 003/2015 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM CIÊNCIAS E TECNOLOGIAS EM O Coordenador do Programa de Pós-Graduação em Ciências e Tecnologias em Saúde, no uso de suas
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM CINCIAS E TECNOLOGIAS EM SADE
Maier, Rudolf Richard
1 UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM CIÊNCIAS E TECNOLOGIAS EM SAÚDE EDITAL N. 01/2015 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM CIÊNCIAS E TECNOLOGIAS EM. PREÂMBULO 1.1. O Coordenador do Programa de Pós-Graduação em Ciências e Tecnologias em Saúde (PPGCTS
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM CINCIAS E TECNOLOGIAS EM SADE
Maier, Rudolf Richard
1 UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM CIÊNCIAS E TECNOLOGIAS EM SAÚDE EDITAL N. 01/2011 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM CIÊNCIAS E TECNOLOGIAS EM. PREÂMBULO 1.1 A Coordenadora do Programa de Pós-Graduação em Ciências e Tecnologias em Saúde, no uso de suas
MESTRADO EM MICROBIOLOGIA INOVAO, EMPREENDEDORISMO E TRANSFERNCIA DE TECNOLOGIA EM
Instituto de Sistemas e Robotica
MESTRADO EM MICROBIOLOGIA INOVAÇÃO, EMPREENDEDORISMO E TRANSFERÊNCIA DE TECNOLOGIA EM MICROBIOLOGIA conceitos sobre os princípios e metodologias da moderna Transferência de Tecnologia. Assim, inclui-se numa alunos aprendem por realização real e directa do processo de transferência de tecnologia, utilizando
Fleuret, F; Schwemling, P
1999-01-01
We present in this note a method to construct a correction function of the EM accordion calorimeter energy to take into account the lead plates inhomegeneous thickness distribution. After having derived the method, the results of the analysis of the real Module 0 plates distribution are presented and discussed. We show that the knowledge of the lead plate thickness can be used to correct the reconstructed energy such as the residual constant term due to lead thickness fluctuation can be reduced. We show that the connection between two modules with two different mean thickness can be also very well corrected resulting in a very small constant term contribution.
ESPECIAO ESPONTNEA EM POPULAES ESPACIALMENTE
de Aguiar, Marcus A. M.
público em geral. Em 1859 Charles Darwin deu passo fundamental para a solução desse problema com Charles Darwin a franchi le pas pour la solution de ce problème avec la publication de son oeuvre majeure do livro A origem das Espécies de Charles Darwin e muito se tem falado a respeito de teoria da
Busca de estruturas em grandes escalas em altos redshifts
NASA Astrophysics Data System (ADS)
Boris, N. V.; Sodrã©, L., Jr.; Cypriano, E.
2003-08-01
A busca por estruturas em grandes escalas (aglomerados de galáxias, por exemplo) é um ativo tópico de pesquisas hoje em dia, pois a detecção de um único aglomerado em altos redshifts pode por vínculos fortes sobre os modelos cosmológicos. Neste projeto estamos fazendo uma busca de estruturas distantes em campos contendo pares de quasares próximos entre si em zÂ Â3Â 0.9. Os pares de quasares foram extraídos do catálogo de Véron-Cetty & Véron (2001) e estão sendo observados com os telescópios: 2,2m da University of Hawaii (UH), 2,5m do Observatório de Las Campanas e com o GEMINI. Apresentamos aqui a análise preliminar de um par de quasares observado nos filtros i'(7800 Å) e z'(9500 Å) com o GEMINI. A cor (i'-z') mostrou-se útil para detectar objetos "early-type" em redshifts menores que 1.1. No estudo do par 131046+0006/J131055+0008, com redshift ~ 0.9, o uso deste método possibilitou a detecção de sete objetos candidatos a galáxias "early-type". Num mapa da distribuição projetada dos objetos para 22 < i' < 25 observou-se que estas galáxias estão localizadas próximas a um dos quasares e há indícios de que estejam aglomeradas dentro de um área de ~ 6 arcmin2. Se esse for o caso, estes objetos seriam membros de uma estrutura em grande escala. Um outro argumento em favor dessa hipótese é que eles obedecem uma relação do tipo Kormendy (raio equivalente X brilho superficial dentro desse raio), como a apresentada pelas galáxias elípticas em z = 0.
DOUTORADO EM TEOLOGIA Edital 2015/02
Díaz, Lorenzo J.
DOUTORADO EM TEOLOGIA Edital 2015/02 Este edital se destina especificamente a candidatos ao Doutorado em Teologia, com início em agosto de 2015. 1. Objetivo: O Programa de Doutorado em Teologia visa o universitários de Teologia e de assessores teológicos a organismos internacionais e nacionais, civis e
Falta de investimento prejudica sector em Portugal
Instituto de Sistemas e Robotica
.car*alF»o@ecOnomlco.pt Portugal tem condições para se tornar um exemplo de sucesso no desenvolvimento da biotecnologia, mas ainda- estruturas físicas e o "investi- mento descontinuado" - a biotecnologia re- quer investimento de longo prazo, "falta verdadeiro capital de risco investidor em ciências da vida em ge- ral, e em biotecnologia em
Portugueses em Formula 1 universitria
Instituto de Sistemas e Robotica
de carbono fazem do carro FST 05 o mais leve e tecnológico alguma vez fabricado em Portugal no currículo uma vitória na edição do ano passado, na categoria de projeto. Na sua quinta versão, o carro tem o
EPA LABORATORIES IMPLEMENT EMS PROGRAM
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...
Spatial based Expectation Maximizing (EM)
2011-01-01
Background Expectation maximizing (EM) is one of the common approaches for image segmentation. Methods an improvement of the EM algorithm is proposed and its effectiveness for MRI brain image segmentation is investigated. In order to improve EM performance, the proposed algorithms incorporates neighbourhood information into the clustering process. At first, average image is obtained as neighbourhood information and then it is incorporated in clustering process. Also, as an option, user-interaction is used to improve segmentation results. Simulated and real MR volumes are used to compare the efficiency of the proposed improvement with the existing neighbourhood based extension for EM and FCM. Results the findings show that the proposed algorithm produces higher similarity index. Conclusions experiments demonstrate the effectiveness of the proposed algorithm in compare to other existing algorithms on various noise levels. PMID:22029864
Coherent states of non-relativistic electron in magnetic-solenoid field
V. G. Bagrov; S. P. Gavrilov; D. M. Gitman; D. P. Meira Filho
2010-07-07
We construct coherent states of a nonrelativistic electron in the magnetic-solenoid field, which is a superposition of the Aharonov-Bohm field and a collinear uniform magnetic field. In the problem under consideration there are two kind of coherent states, the first kind corresponds to classical trajectories which embrace the solenoid and the second one to trajectories which do not. Mean coordinates in the constructed coherent states are moving along classical trajectories, the coherent states maintain their form under the time evolution, and represent a complete set of functions, which can be useful in semi classical calculations. In the absence of the Aharonov-Bohm filed these states are reduced to the well-known in the case of uniform magnetic field Malkin-Man'ko coherent states.
Berry's phase for coherent states of Landau levels
Wen-Long Yang; Jing-Ling Chen
2007-06-14
The Berry phases for coherent states and squeezed coherent states of Landau levels are calculated. Coherent states of Landau levels are interpreted as a result of a magnetic flux moved adiabatically from infinity to a finite place on the plane. The Abelian Berry phase for coherent states of Landau levels is an analog of the Aharonov- Bohm effect. Moreover, the non-Abelian Berry phase is calculated for the adiabatic evolution of the magnetic field B.
Theoretical Errors in Contemporary Physics
E. Comay
2005-09-09
Errors pertaining to the following physical theories are discussed: the Dirac magnetic monopole theory; the Klein-Gordon equation; the Yukawa theory of nuclear force; the idea of Vector Meson Dominance; the Aharonov-Bohm effects; the idea of diffraction-free electromagnetic beams; Quantum Chromodynamics. Implications of the theoretical errors are discussed briefly. In particular, relations between the Dirac monopole theory, the idea of Vector Meson Dominance and Quantum Chromodynamics cast doubt on the current interpretation of strong interactions.
Dirac bound states of anharmonic oscillator in external fields
Majid Hamzavia; Sameer M. Ikhdair; Babatunde J. Falaye
2014-01-28
We explore the effect of the external magnetic and Aharonov-Bohm (AB) flux fields on the energy levels of Dirac particle subjects to mixed scalar and vector anharmonic oscillator field in the two-dimensional (2D) space. We calculate the exact energy eigenvalues and the corresponding un-normalized two-spinor-components wave functions in terms of the chemical potential parameter, magnetic field strength, AB flux field and magnetic quantum number by using the Nikiforov-Uvarov (NU) method.
Is magnetic flux quantized inside a solenoid?
F. Darabi
2009-01-13
In some textbooks on quantum mechanics, the description of flux quantization in a superconductor ring based on the Aharonov-Bohm effect may lead some readers to a (wrong) conclusion that flux quantization occurs as well for a long solenoid with the same quantization condition in which the charge of cooper pair $2e$ is replaced by the charge of one electron $e$. It is shown how this confusion arises and how can one avoid it.
Berry's phase for coherent states of Landau levels
Yang, Wen-Long; Chen, Jing-Ling [Theoretical Physics Division, Chern Institute of Mathematics, Nankai University, Tianjin 300071 (China)
2007-02-15
The Berry phases for coherent states and squeezed coherent states of Landau levels are calculated. Coherent states of Landau levels are interpreted as a result of a magnetic flux moved adiabatically from infinity to a finite place on the plane. The Abelian Berry phase for coherent states of Landau levels is an analog of the Aharonov-Bohm effect. Moreover, the non-Abelian Berry phase is calculated for the adiabatic evolution of the magnetic field B.
Real-time Observation of Vortices in Superconductors by Lorentz Microscopy
Akira Tonomura
2005-01-01
The dynamics of individual quantized vortices in superconducting thin films became observable using coherent Lorentz microscopy with our field-emission transmission electron microscopes (1). The observation principle is based on the Aharonov-Bohm effect (2) Since a phase shift of 2pi is produced between two electron beams enclosing a magnetic flux of h\\/e, a vortex having magnetic flux of h\\/(2e) is a
REGIMENTO DO CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS, REA DE CONCENTRAO EM
REGIMENTO DO CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS, ÁREA DE CONCENTRAÇÂO EM Propulsão (PCP) do Curso de Pós-graduação em Engenharia e Tecnologia Espaciais (ETE) objetiva formar e de Pós-Graduação, pelo Regimento do Curso de Pós- Graduação em Engenharia e Tecnologia Espaciais e
Instituto Brasileiro de Informao em Cincia e Tecnologia
Paraná, Universidade Federal do
ibict Instituto Brasileiro de Informação em Ciência e Tecnologia OJS em uma Hora 1 OJS em uma hora Meinert 06 de outubro de 2006 #12;ibict Instituto Brasileiro de Informação em Ciência e Tecnologia OJS Brasileiro de Informação em Ciência e Tecnologia OJS em uma Hora 3 Visão GeralVisão GeralVisão Geral
Transportes em Revista.com Pas: Portugal
Instituto de Sistemas e Robotica
Transportes em Revista.com País: Portugal Period.: Diária Âmbito: Online Pag.: 1 de 2ID: 41904396 22-05-2012 Receba gr átis a Transportes Online | Assinar a Transportes em Revista | Fazer da TR a sua Transport Rodas de mudança Et si nos villes #12;Transportes em Revista.com País:
The European Mobile System (EMS)
NASA Technical Reports Server (NTRS)
Jongejans, A.; Rogard, R.; Mistretta, I.; Ananasso, F.
1993-01-01
The European Space Agency is presently procuring an L band payload in order to promote a regional European L band system coping with the specific needs of the European market. The payload, and the two communications systems to be supported, are described below. The potential market for EMS in Europe is discussed.
NSDL National Science Digital Library
COMET
2013-09-25
This lesson illustrates how numerical guidance from the Weather Research and Forecasting Model - Environmental Modeling System (WRF-EMS) can be added to surface observations, satellite graphics, and conceptual models of important aviation phenomena, to produce TAFs. Specifically, the lesson describes how visibility, cloud ceilings, and the flight categories variables provide values for aviation forecasts in Africa.
Correlation of the NBME Advanced Clinical Examination in EM and the National EM M4 exams
Hiller, Katherine; Miller, Emily S.; Lawson, Luan; Wald, David; Beeson, Michael; Heitz, Corey; Morrissey, Thomas; House, Joseph; Poznanski, Stacey
2015-01-01
Introduction Since 2011 two online, validated exams for fourth-year emergency medicine (EM) students have been available (National EM M4 Exams). In 2013 the National Board of Medical Examiners offered the Advanced Clinical Examination in Emergency Medicine (EM-ACE). All of these exams are now in widespread use; however, there are no data on how they correlate. This study evaluated the correlation between the EM-ACE exam and the National EM M4 Exams. Methods From May 2013 to April 2014 the EM-ACE and one version of the EM M4 exam were administered sequentially to fourth-year EM students at five U.S. medical schools. Data collected included institution, gross and scaled scores and version of the EM M4 exam. We performed Pearson’s correlation and random effects linear regression. Results 303 students took the EM-ACE and versions 1 (V1) or 2 (V2) of the EM M4 exams (279 and 24, respectively). The mean percent correct for the exams were as follows: EM-ACE 74.8 (SD-8.83), V1 83.0 (SD-6.41), V2 78.5 (SD-7.70). Pearson’s correlation coefficient for the V1/EM-ACE was 0.51 (0.42 scaled) and for the V2/EM-ACE was 0.59 (0.41 scaled). The coefficient of determination for V1/EM-ACE was 0.72 and for V2/EM-ACE = 0.71 (0.86 and 0.49 for scaled scores). The R-squared values were 0.25 and 0.30 (0.18 and 0.13, scaled), respectively. There was significant cluster effect by institution. Conclusion There was moderate positive correlation of student scores on the EM-ACE exam and the National EM M4 Exams. PMID:25671023
Complaints against an EMS system.
Colwell, Christopher B; Pons, Peter T; Pi, Randy
2003-11-01
Complaints against Emergency Medical Services (EMS) agencies represent a concerning and potentially time-consuming problem for all involved in the delivery of prehospital emergency medical care. The objective of this study was to identify the source of complaints against an EMS system to help focus quality and performance improvement and customer service efforts. We conducted a retrospective review of complaints filed against a busy urban EMS agency over a 6-year period. All complaints were included, totaled by season and by year, and categorized by originator and nature of the complaint. A total of 286 complaints were registered during the 6-year period, with an average of 48 per year and 9.3 per 10,000 responses. The most common originators of complaints were patients (53%) followed by medical personnel (19%) and family members or friends (12%). Rude behavior accounted for 23% of the complaints registered, followed by technical skills (20%), transport problems (18%), and loss of belongings (13%). The identification of areas of dissatisfaction will allow focused quality and performance improvement programs directed at customer service and risk management. PMID:14654181
Universidade de Braslia Programa de Ps-Graduao em Cincias e Tecnologias em Sade -PGCTS/FCE
Maier, Rudolf Richard
Universidade de Brasília Programa de Pós-Graduação em Ciências e Tecnologias em Saúde - PGCTS/FCE Edital n. 01/2013 1 UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM CIÊNCIAS E TECNOLOGIAS EM SAÚDE EDITAL Nº 01/2013 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM CIÊNCIAS E TECNOLOGIAS
ALTERNATIVE DERIVATION OF EM CLOAKS AND CONCENTRATORS
Maryland at College Park, University of
ALTERNATIVE DERIVATION OF EM CLOAKS AND CONCENTRATORS Arthur D. Yaghjian AFRL (Consultant), Hanscom;ALTERNATIVE DERIVATION OF EM CLOAKS AND CONCENTRATORS (r), (r) V r Je inc, Jm inc O and are continuous al. 2007-08 #12;GOOD NEWS · Perfect cloaks and nonscatterers, such as concentrators
School Budget Hold'em Facilitator's Guide
ERIC Educational Resources Information Center
Education Resource Strategies, 2012
2012-01-01
"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…
TECHNICAL REPORT Explaining slow convergence of EM
, they are able to demonstrate several points: (i) In the low noise limit, EM is freezing in the sense that An+1 using the EM algorithm . . . . . . . . . . . 4 3 Saddle Point Approximation 4 3.1 Approximation of an Integral . . . . . . . . . . . . . . . . . . . . 5 3.2 Finding the Saddle Point
View of Spacelab engineering Model (EM)
NASA Technical Reports Server (NTRS)
1981-01-01
View of Spacelab engineering Model (EM) as it is being brought in the O and C bldg at Kenndey Space Center (27464); view of the EM as it is being offloaded from the C-54 aircraft. Kennedy Space Center alternative photo number is 108-KSC-80-OC-666 (27465); model taken out to launch pad (27466).
EMS: part three. Preventive medicine for EMS maladies
Hyfantis, J.F.
1983-05-01
Shakeout problems in the fast-growing field of energy-management systems (EMS) are gorwing pains and neither unexpected nor insoluble. A National Bureau of Standards (NBS) survey found user complaints ranging from problems with food spoilage to poorly trained service people. But blame can be placed on users, manufacturers, and distributors. Involving operators and managers in load-control strategies can alleviate some problems and save some money. Allowing for realistic testing time in the installation phase can also save in the long run, as will initiating a maintenance schedule and maintaining operating logs. Software maintenance can present a serious problem. Another NBS study result indicates there is perceptible improvement in system performance when good training accompanies installation, particularly when the training is provided at the user facility. User education is probably the best key to avoiding most of the potential pitfalls. 2 figures, 2 tables.
Romanov, Gennady; /Fermilab; Hoff, Matthew; Li, Derun; Staples, John; Virostek, Steve; /LBNL
2012-05-09
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.
Abundâncias em estrelas de Bário
NASA Astrophysics Data System (ADS)
Allen, D. M.
2003-08-01
Estrelas de Bário apresentam linhas intensas de elementos produzidos pelo processos (ex: Ba, Y, Sr, Zr) e bandas intensas de CN, C2 e CH. A hipótese mais aceita sobre a origem deste grupo peculiar é a de que essas estrelas façam parte de sistemas binários, tendo recebido material enriquecido em elementos pesados da companheira mais evoluída. Apresentamos neste trabalho uma análise detalhada de uma amostra de estrelas desta classe, incluindo determinação de parâmetros atmosféricos e cálculo de abundâncias. As temperaturas efetivas foram determinadas a partir de dados fotométricos obtidos com o Fotrap instalado no telescópio Zeiss do LNA (Laboratório Nacional de Astrofísica) (B-V, V-I, R-I, V-R), e coletados na literatura nos catálogos Hipparcos (B-V), 2MASS (Two Micron All Sky Survey) (V-K) e The General Catalogue Photometric Data (sistema Geneva). Obtivemos uma faixa de temperaturas de 4400 £ Tef £ 6500. As metalicidades foram determinadas a partir de linhas de Fe I e Fe II, estando os resultados no intervalo -1 £ [Fe/H] £ +0.1. O log g foi determinado pelo equilíbrio de ionização e pela relação com a magnitude bolométrica, a temperatura e a massa, sendo os resultados na faixa 1.5 £ log g £ 4.5. As distâncias utilizadas foram determinadas com o auxílio das paralaxes Hipparcos, e as massas determinadas por modelos de isócronas. Os espectros utilizados foram obtidos com o espectrógrafo FEROS no Telescópio de 1,5m do ESO (European Southern Observatory). As abundâncias foram calculadas por meio de síntese espectral de linhas individuais incluindo elementos alfa, pico do Fe, s e r. Encontramos um excesso de elementos pesados em relação ao Fe, como esperado para estrelas de Bário.
Ambiente e formação estelar em galáxias
NASA Astrophysics Data System (ADS)
Mateus, A., Jr.; Sodré, L., Jr.
2003-08-01
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.
Evolução química em galáxias compactas azuis (BCGs)
NASA Astrophysics Data System (ADS)
Lanfranchi, G. A.; Matteucci, F.
2003-08-01
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.
EM Algorithms Charles Byrne (Charles Byrne@uml.edu)
Byrne, Charles
EM Algorithms Charles Byrne (Charles Byrne@uml.edu) Department of Mathematical Sciences University of Massachusetts Lowell Lowell, MA 01854, USA March 6, 2011 Abstract The EM algorithm is not a single algorithm algorithm based on the EM framework we refer to as an "EM algorithm". Because there is no inclusive theory
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM ENGENHARIA E;2 CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM ENGENHARIA E Tecnologia de Satélites petronio.souza@lit.inpe.br CSE-201-4 Introdução à Engenharia de Sistemas Espaciais
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM
Maier, Rudolf Richard
1 UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM PSICOLOGIA CLÍNICA E CULTURA EDITAL Nº 01 Programa de Pós-Graduação em Psicologia Clínica e Cultura, no uso de suas atribuições legais, torna público Acadêmico do Programa de Pós- Graduação em Psicologia Clínica e Cultura, em conformidade com as exigências
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM ENGENHARIA E PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM ENGENHARIA E GERENCIAMENTO Tecnologia de Satélites petronio.souza@lit.inpe.br CSE-201-4 Introdução à Engenharia de Sistemas Espaciais
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM CIÊNCIA E TECNOLOGIA DE MATERIAIS E SENSORES Coordenador Acadêmico do Curso Evandro Marconi Rocco Coordenador Acadêmico, França, 2003 #12;2 CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM
FACULDADE DE CEILNDIA CAMPUS UnB CEILNDIA PROGRAMA DE PS-GRADUAO EM CINCIAS E TECNOLOGIAS EM SADE
Lucero, Jorge Carlos
1 FACULDADE DE CEILÂNDIA CAMPUS UnB CEILÂNDIA PROGRAMA DE PÓS-GRADUAÇÃO EM CIÊNCIAS E TECNOLOGIAS TECNOLOGIAS EM SAÚDE PARA OS CURSOS DE MESTRADO ACADÊMICO E DOUTORADO PARA O PRIMEIRO PERÍODO LETIVO DE 2012 1. PREÂMBULO 1.1. A Coordenadora do Programa de Pós-Graduação em Ciências e Tecnologias em Saúde, no uso de
EMS offshore. A new horizon for paramedics.
Mallard, A S
1991-10-01
The difficulty in getting medical aid to offshore drilling platforms can be a source of life-threatening delays. Recently, some companies have charted new waters by actually stationing EMS crews on their rigs. PMID:10116023
Licenciatura em Engenharia Electrotcnica e de Computadores
da Silva, Alberto Rodrigues
arquitectura. No campo das tecnologias baseadas em agentes estudou-se de forma aprofundada o sistema de agentes-chave Agentes de Software, Comércio Electrónico, Shopping Mall, Java #12;Trabalho Final de Curso E
Fast PET EM reconstruction from linograms
James Hamill; Christian Michel; Paul Kinahan
2002-01-01
The approximate discrete Radon transform (ADRT) is a fast forward projection technique for generating linograms. It uses a succession of nearest-neighbor interpolations in a butterfly algorithm analogous to the one used in fast Fourier transforms to gain a (log N)\\/N speed advantage. We have used matched forward and backward ADRT projectors to perform ML-EM reconstructions for PET (EM-ADRT). Accuracy is
Estudo em microondas do aprisionamento e precipitação de elétrons em explosões solares
NASA Astrophysics Data System (ADS)
Rosal, A. C.; Costa, J. E. R.
2003-08-01
Uma explosão solar é uma variação rápida e intensa do brilho que ocorre nas chamadas regiões ativas da atmosfera, constituídas por um plasma magnetizado com intensa indução magnética. Os modelos de explosões solares atuais, discutidos na literatura, apresentam características de aprisionamento e precipitação de elétrons em ambientes magnéticos simplificados. Neste trabalho, nos propusemos a separar a emissão dos elétrons aprisionados da emissão dos elétrons em precipitação apenas a partir da emissão em microondas, melhorando portanto o controle sobre o conjunto de parâmetros inferidos. A emissão em microondas da população em precipitação é bastante fraca e portanto da nossa base de dados de 130 explosões observadas pelo Rádio Polarímetro de Nobeyama, em sete freqüências, apenas para 32 foi possível separar as duas componentes de emissão com uma boa razão sinal/ruído. A partir de estudos das escalas de tempo das emissões devidas à variação gradual da emissão no aprisionamento e da variação rápida da emissão dos elétrons em precipitação foi possível obter a separação utilizando um filtro temporal nas emissões resultantes. Em nossa análise destas explosões estudamos os espectros girossincrotrônicos da emissão gradual, a qual associamos provir do topo dos arcos magnéticos e da emissão de variação rápida associada aos elétrons em precipitação. Estes espectros foram calculados e dos quais inferimos que a indução magnética efetiva do topo e dos pés foi em média, Btopo = 236 G e Bpés = 577 G, inferidas das freqüências de pico dos espectros em ntopo = 11,8 GHz e npés = 14,6 GHz com leve anisotropia (pequeno alargamento espectral). O índice espectral da distribuição não-térmica de elétrons d, inferido do índice espectral de fótons da emissão em regime opticamente fino, foi de dtopo = 3,3 e dpés = 3,9. Estes parâmetros são típicos da maioria das análises realizadas em ambiente único de emissão e a relação dos índices espectrais, dpés > dtopo prioriza as interpretações com difusão em ângulo de passo devida a colisões Coulombianas. Nesta difusão o déficit de elétrons energéticos na precipitação seria uma conseqüência natural da dependência em e-3/2 das colisões elétron-próton (onde e é a energia dos elétrons).
Wolfe, Patrick J.
EM results from the simulation EM results on a real data Gibbs results from the simulation, 2010 #12;EM results from the simulation EM results on a real data Gibbs results from the simulation are and µ. #12;EM results from the simulation EM results on a real data Gibbs results from the simulation
Condições físicas em galáxias HII
NASA Astrophysics Data System (ADS)
Kehrig, C.; Telles, E.; Cuisinier, F.
2003-08-01
Galáxias HII são galáxias anãs de baixa luminosidade que apresentam alta taxa de formação estelar. Seus espectros são dominados por intensas linhas de emissão devido à fotoionização pela presença de um grande número de estrelas do tipo O e B. Nós apresentamos um catálogo espectrofotométrico de 111 galáxias HII observadas no telescópio 1.52m do ESO com o espectrógrafo Boller & Chivens. Determinamos propriedades estatísticas da amostra e derivamos condições físicas (temperatura eletrônica, densidade eletrônica) e abundâncias químicas. Para algumas galáxias, fomos também capazes de resolver espacialmente regiões de formação estelar individuais e determinar propriedades espectroscópicas para estas regiões separadamente, o que nos permitiu avaliar as flutuações das condições físico-químicas dentro das galáxias HII. Em particular, vimos que apesar das galáxias HII apresentarem formação estelar espalhada ao longo do corpo da galáxia, são objetos quimicamente homogêneos. A fim de estudar a evolução temporal dos objetos durante o tempo de vida das estrelas ionizantes construimos também alguns diagramas relacionando razões de linhas de emissão com a largura equivalente de Hb (EW(Hb)). Para interpretar tais diagramas utilizamos modelos de fotoionização para populações estelares integradas. Concluímos que as galáxias HII não correspondem a simples idéia de um burst instantâneo envolvido por um gás opaco aos fótons ionizantes e com densidade constante. As relações observadas entre razões de linhas e EW(Hb) podem ser melhor compreendidas se as galáxias HII apresentarem populações estelares mais velhas, que contribuem para o contínuo óptico observado.
Hanazaki, Natalia
Redação Aprovada em Reunião do Colegiado do Programa de Pós-Graduação em Ciência da Informação Programa de Pós-Graduação em Ciência da Informação EEDDIITTAALL NNºº 000066//PPGGCCIINN//22001133 para bolsa de pós-doutorado do PGCIN. 2 A inscrição será recebida na Secretaria do Programa de Pós
Capitulo 32 Alguns Topicos Especiais em Topologia e Analise
Barata, JoÃ£o Carlos Alves
.1.1 Conjuntos Densos em EspaÂ¸cos TopolÂ´ogicos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1443 32.1.2 A NoÂ¸c~ao de Conjunto Conexo em EspaÂ¸cos TopolÂ´ogicos . . . . . . . . . . . . . . . . . . . . . . 1444
Captulo 32 Alguns Topicos Especiais em Topologia e Analise
Barata, JoÃ£o Carlos Alves
.1.1 Conjuntos Densos em Espaâ?ºcos Topolâ??ogicos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1443 32.1.2 A Noâ?ºcâ?ao de Conjunto Conexo em Espaâ?ºcos Topolâ??ogicos . . . . . . . . . . . . . . . . . . . . . . 1444
EM2: A Scalable Shared-Memory Multicore Architecture
Khan, Omer
2010-06-12
We introduce the Execution Migration Machine (EM2), a novel, scalable shared-memory architecture for large-scale multicores constrained by off-chip memory bandwidth. EM2 reduces cache miss rates, and consequently off-chip ...
EM-ONE : an architecture for reflective commonsense thinking
Singh, Pushpinder, 1972-2006.
2005-01-01
This thesis describes EM-ONE, an architecture for commonsense thinking capable of reflective reasoning about situations involving physical, social, and mental dimensions. EM-ONE uses as its knowledge base a library of ...
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM COMBUSTÃO E Mendonça do IAE/CTA, Univ. Pennsylvania, USA, 1997 #12;CURSO DE ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE
Risk Communication Within the EM Program
Edelson, M.
2003-02-26
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.''
População estelar jovem em galáxias irregulares próximas
NASA Astrophysics Data System (ADS)
Guimarães, T. A.; Telles, E.
2003-08-01
A análise do conteúdo estelar de galáxias próximas através da fotometria das suas estrelas resolvidas nos fornece informações importantes sobre a história de formação estelar e os processos de formação estelar em galáxias, que estão diretamente ligados ao estudo de evolução de galáxias. Quando nenhuma estrela puder ser resolvida o método mais poderoso consiste na análise do conteúdo estelar integrado das galáxias através das suas cores integradas em conjunto com informação espectroscópica que combinados com modelos de síntese evolutiva podem restringir simultaneamente a função de massa inicial (IMF) e a taxa de formação estelar (SFR). Nesse contexto, galáxias do tipo tardio, em particular, irregulares, são relevantes por várias razões: elas são objetos relativamente simples, com alta atividade de formação estelar e são objetos relativamente jovens (geralmente apresentam baixas abundâncias de elementos pesados e grande quantidade de gás). Apresentamos uma análise fotométrica de uma amostra de 7 galáxias do tipo tardio do universo local (NGC 2366, NGC 4395, NGC 4656, NGC 4214, NGC 4236, HOII, IC2574) que foram observadas com uma boa resolução espacial nas bandas B, V e R no telescópio Isaac Newton de 2.5m de Roque de los Muchachos nas Ilhas Canárias, Espanha. A distribuição espacial da população estelar jovem dessas galáxias é discutida sobre os pontos de vista dos íindices de cor integrados e dos seus diagramas cor magnitude, que comparados com isócronas teóricas, nos fornecem informações sobre os eventos de formação estelar, como por exemplo, indicações sobre a idade dos mesmos. As principais conclusões do trabalho podem ser resumidas em: (i) As galáxias irregulares possuem formação estelar recente (FE) espalhada ocorrendo nos últimos 50 Manos; (ii) A formação estelar em galáxias irregulares não é auto-propagante em escalas globais ( > 100 pc) ; (iii) A FE pode ser auto-regulável em escalas espaciais de poucas dezenas de parsec; (iv) As galáxias irregulares sofreram um evento principal de FE há 1010 anos atrás, o que implica que houve um momento na evolução do universo onde a maior parte das estrelas se formaram em galáxias.
A emissão em 8mm e as bandas de Merrill-Sanford em estrelas carbonadas
NASA Astrophysics Data System (ADS)
de Mello, A. B.; Lorenz-Martins, S.
2003-08-01
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.
1.2 Electromagnetic (EM) properties Physical properties
Zhang, Guifu
1.2 Electromagnetic (EM) properties · Physical properties: PSD/density/shape/velocity · EM properties: - propagation, absorption, scattering - light (EM wave) refraction and reflection · Reflectivity: ! " = # 5 $4 m2 %1 m2 + 2 2 Ze = &(D)N(D)dD' Refractivity and dielectric constant · Complex form: refractive
Marvin, robô construtor para competição em robótica móvel
André Martin Narciso; Carlos Augusto; Bentes da Silva; Jackson Paul Matsuura
renatohsp@gmail .com Resumo: Este artigo é sobre a construção do robô autônomo Marvin o Construtor, que foi construído para participar da IV Competição IEEE Brasileira de Robô. A tarefa consiste em empilhar blocos em uma área predeterminada em um menor tempo possível, ganha a torre mais alta. O robô, construído por alunos do Instituto Tecnológico de Aeronáutica (ITA), foi construído
Motivac~ao Consist^encia: modelos baseados em dados
Rodriguez, Noemi
Motiva¸c~ao Consist^encia: modelos baseados em dados Consist^encia: modelos baseados do cliente;Motiva¸c~ao Consist^encia: modelos baseados em dados Consist^encia: modelos baseados do cliente;Motiva¸c~ao Consist^encia: modelos baseados em dados Consist^encia: modelos baseados do cliente
Infer^encia em Modelos Hierarquicos Generalizados sob Planos Amostrais
Ravines, Romy R.
UFRJ Infer^encia em Modelos HierÂ´arquicos Generalizados sob Planos Amostrais Informativos Romy Moura Rio de Janeiro MarÂ¸co de 2003 #12;Infer^encia em Modelos HierÂ´arquicos Generalizados sob Planos^encia em Modelos HierÂ´arquicos Generalizados sob Planos Amostrais Informativos/ Romy Elena Rodriguez
On Convergence Properties of the EM Algorithm for Gaussian Mixtures
Lei Xu; Michael I. Jordan
1996-01-01
We build up the mathematical connection between the Expectation-Maximization (EM) algorithm and gradient-based approaches for maximum likelihood learning of finite gaussian mixtures. We show that the EM step in parameter space is obtained from the gradient via a projection matrix P, and we provide an explicit expression for the matrix. We then analyze the convergence of EM in terms of
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM Design
Maier, Rudolf Richard
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UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM SOCIOLOGIA
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Hanazaki, Natalia
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Maier, Rudolf Richard
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Maier, Rudolf Richard
UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM AGRONOMIA EDITAL No. 02/2014 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM AGRONOMIA, PARA OS CURSOS DE MESTRADO ACADÊMICO E DOUTORADO PARA O PRIMEIRO PERÍODO LETIVO DE 2015 PREÂMBULO O Coordenador do Programa de Pós-Graduação em
Meta 4: Transcodificao MPEG-2/H.264 em software
Carvalho, João Luiz
11/06/2012 1 Meta 4: Transcodificação MPEG-2/H.264 em software Coordenador: Prof. Ricardo Lopes de. Ricardo Queiroz, Ph.D. Prof. João Luiz Carvalho, Ph.D. (fev'09-jun'12) Prof. Leonardo Aguayo, Dr. (mai'11 · Fazer transcodificação MPEG-2 / H.264 Em tempo real Em software Com a melhor qualidade possível
EM Algorithms from a Non-Stochastic Perspective Charles Byrne
Byrne, Charles
EM Algorithms from a Non-Stochastic Perspective Charles Byrne August 27, 2013 Abstract The EM algorithm is not a single algorithm, but a template for the con- struction of iterative algorithms. While for estimat- ing parameters in statistics, the essence of the EM algorithm is not stochastic. The conventional
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM ENGENHARIA E ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM ENGENHARIA E GERENCIAMENTO DE SISTEMAS ESPACIAIS 1º Período Obrigatória para o Mestrado e o Doutorado CSE-200-4 Introdução à Tecnologia de Satélites otavio
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM CIÊNCIA E TECNOLOGIA DE MATERIAIS E SENSORES Coordenador Acadêmico do Curso Evandro Marconi Rocco Coordenador Acadêmico TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM CIÊNCIA E TECNOLOGIA DE MATERIAIS E SENSORES 1o Período Letivo
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM MECÂNICA TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM MECÂNICA ESPACIAL E CONTROLE RELAÇÃO DAS DISCIPLINAS SEPARADAS Ciência, Engenharia e Tecnologia I CMC-325-3 Teoria de Visualização Gráfica Tridimensional I: Algoritmos
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM ECONOMIA
Maier, Rudolf Richard
1/4 UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM ECONOMIA EDITAL No. 02/2011 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM ECONOMIA PARA O CURSO DE DOUTORADO PARA O PRIMEIRO PERÍODO LETIVO DE 2012 1. PREÂMBULO 1.1. O Coordenador do Programa de Pós-Graduação em Economia, no uso de
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM PSICOLOGIA
Maier, Rudolf Richard
1 UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM PSICOLOGIA CLÍNICA E CULTURA EDITAL Nº 01-2012 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM PSICOLOGIA CLÍNICA E CULTURA PARA O CURSO Pós-Graduação em Psicologia Clínica e Cultura, no uso de suas atribuições legais, torna público e
Clustering of EM radiation source based on eigenvector
I. Takumi; S. Murakami; A. Shimura; M. Hata; H. Yasukawa
2002-01-01
Our goal is to locate anomalous electromagnetic (EM) sources caused by seismic activity for earthquake prediction. For the purpose, we have measured the EM wave of 223Hz at 35 sites in Japan. The measured signal contains much noise caused by lightning around the equator, human activity, near field lightning and so on. EM noises from far sources can be eliminated
Study on analysis of EM radiation source based on eigenvector
S. Murakami; I. Takumi; M. Hata; H. Yasukawa
2003-01-01
Occurrence of anomalous Electro-Magnetic (EM) radiation is known as a precursor of earthquakes. Our goal is to locate anomalous EM source caused by seismic activity for earthquake prediction. For the purpose, we have been measuring EM wave of 223 Hz at about 40 sites in Japan. Measured signal contains much noise caused by far thunder lightning around equators, human activities,
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM ENGENHARIA E, ITA, Brasil, 1990 #12;2 CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE Doutorado CSE-200-4 Introdução à Tecnologia de Satélites CSE-201-4 Introdução à Engenharia de Sistemas
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM CIÊNCIA E TECNOLOGIA DE MATERIAIS E SENSORES Coordenador Acadêmico do Curso Evandro Marconi Rocco Coordenador Acadêmico ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM CIÊNCIA E TECNOLOGIA DE MATERIAIS E SENSORES 1o
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM ENGENHARIA E GERENCIAMENTO DE SISTEMAS ESPACIAIS 1º Período Obrigatória para o Mestrado e o Doutorado CSE-200-4 Introdução à Tecnologia de Satélites petronio
Gravitation: global formulation and quantum effects
NASA Astrophysics Data System (ADS)
Aldrovandi, R.; Pereira, J. G.; Vu, K. H.
2004-01-01
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.
Single molecular shuttle-junction: Shot noise and decoherence
NASA Astrophysics Data System (ADS)
Lai, Wenxi; Zhang, Chao; Ma, Zhongshui
2015-02-01
Single molecular shuttle-junction is one kind of nanoscale electromechanical tunneling system. In this junction, a molecular island oscillates depending on its charge occupation, and this charge dependent oscillation leads to modulation of electron tunneling through the molecular island. This paper reviews recent development on the study of current, shot noise and decoherence of electrons in the single molecular shuttle-junction. We will give detailed discussion on this topic using the typical system model, the theory of fully quantum master equation and the Aharonov-Bohm interferometer.
The origin of the hidden supersymmetry
Vit Jakubsky; Luis-Miguel Nieto; Mikhail S. Plyushchay
2010-09-08
The hidden supersymmetry and related tri-supersymmetric structure of the free particle system, the Dirac delta potential problem and the Aharonov-Bohm effect (planar, bound state, and tubule models) are explained by a special nonlocal unitary transformation, which for the usual N=2 supercharges has a nature of Foldy-Wouthuysen transformation. We show that in general case, the bosonized supersymmetry of nonlocal, parity even systems emerges in the same construction, and explain the origin of the unusual N=2 supersymmetry of electron in three-dimensional parity even magnetic field. The observation extends to include the hidden superconformal symmetry.
NASA Astrophysics Data System (ADS)
Shech, Elay
2015-09-01
This paper looks at the nature of idealizations and representational structures appealed to in the context of the fractional quantum Hall effect, specifically, with respect to the emergence of anyons and fractional statistics. Drawing on an analogy with the Aharonov-Bohm effect, it is suggested that the standard approach to the effects—(what we may call) the topological approach to fractional statistics—relies essentially on problematic idealizations that need to be revised in order for the theory to be explanatory. An alternative geometric approach is outlined and endorsed. Roles for idealizations in science, as well as consequences for the debate revolving around so-called essential idealizations, are discussed.
Interlayer interference in double wells in a tilted magnetic field
NASA Astrophysics Data System (ADS)
Gusev, G. M.; Duarte, C. A.; Lamas, T. E.; Bakarov, A. K.; Portal, J. C.
2008-10-01
Magnetotransport measurements on bilayer electron systems reveal repeated reentrance of the resistance minima at filling factors ?=4N+1 and ?=4N+3 , where N is the Landau index number, in the tilted magnetic field. At high filling factors, the Shubnikov-de Haas oscillations exhibit beating effects at certain tilt angles. We attribute such behavior to oscillations of the tunneling gap due to Aharonov-Bohm interference effect between cyclotron orbits in different layers. The interplay between quantum and quasiclassical regimes is established.
A Note on the Sagnac Effect for Matter Beams
Matteo Luca Ruggiero; Angelo Tartaglia
2015-04-09
We study the Sagnac effect for matter beams, in order to estimate the kinematic corrections to the basic formula, deriving from the position and the extent of the interferometer, and discuss the analogy with the Aharonov-Bohm effect. We show that the formula for the Sagnac time delay is the same for matter and light beams in arbitrary stationary space-times, provided that a suitable condition on the speed of the beams is fulfilled. Hence, the same results obtained for light beams apply to matter beams.
A Note on the Sagnac Effect for Matter Beams
Ruggiero, Matteo Luca
2014-01-01
We study the Sagnac effect for matter beams, in order to estimate the kinematic corrections to the basic formula, deriving from the position and the extension of the interferometer, and discuss the analogy with the Aharonov-Bohm effect. We show that the formula for the Sagnac time delay is the same for matter and light beams in arbitrary stationary space-times, provided that a suitable condition on the speed of the beams is fulfilled. Hence, the same results obtained for light beams apply to matter beams.
A General Method for Deriving Vector Potentials Produced by Knotted Solenoids
V. V. Sreedhar
2015-01-06
A general method for deriving exact expressions for vector potentials produced by arbitrarily knotted solenoids is presented. It consists of using simple physics ideas from magnetostatics to evaluate the magnetic field in a surrogate problem. The latter is obtained by modelling the knot with wire segments carrying steady currents on a cubical lattice. The expressions for a 31 (trefoil) and a 41 (figure-eight) knot are explicitly worked out. The results are of some importance in the study of the Aharonov-Bohm effect generalised to a situation in which charged particles moving through force-free regions are scattered by fluxes confined to the interior of knotted impenetrable tubes.
Quantum Interference of Electrons in a Ring: Tuning of the Geometrical Phase
NASA Astrophysics Data System (ADS)
Capozza, R.; Giuliano, D.; Lucignano, P.; Tagliacozzo, A.
2005-11-01
We calculate the oscillations of the dc conductance across a mesoscopic ring, simultaneously tuned by applied magnetic and electric fields orthogonal to the ring. The oscillations depend on the Aharonov-Bohm flux and of the spin-orbit coupling. They result from mixing of the dynamical phase, including the Zeeman spin splitting, and of geometric phases. By changing the applied fields, the geometric phase contribution to the conductance oscillations can be tuned from the adiabatic (Berry) to the nonadiabatic (Ahronov-Anandan) regime. To model a realistic device, we also include nonzero backscattering at the connection between ring and contacts, and a random phase for electron wave function, accounting for dephasing effects.
Sameer M. Ikhdair; Majid Hamzavi
2012-05-18
We study the effects of the perpendicular magnetic and Aharonov-Bohm (AB) flux fields on the energy levels of a two-dimensional (2D) Klein-Gordon (KG) particle subjects to equal scalar and vector pseudo-harmonic oscillator (PHO). We calculate the exact energy eigenvalues and normalized wave functions in terms of chemical potential parameter, magnetic field strength, AB flux field and magnetic quantum number by means of the Nikiforov-Uvarov (NU) method. The non-relativistic limit, PHO and harmonic oscillator solutions in the existence and absence of external fields are also obtained.
Surface state dominated transport in topological insulator Bi2Te3 nanowires
NASA Astrophysics Data System (ADS)
Hamdou, Bacel; Gooth, Johannes; Dorn, August; Pippel, Eckhard; Nielsch, Kornelius
2013-11-01
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.
R. P. Woodard
2015-06-13
A recent paper by Fr\\"ob employs the linearized Weyl-Weyl correlator to construct the tensor power spectrum. Although his purpose was to argue that infrared divergences and secular growth in the graviton propagator are gauge artefacts, a closer examination of the problem leads to the opposite conclusion. The analogies with the BMS symmetries of graviton scattering on a flat background, and with the Aharonov-Bohm effect of quantum mechanics, suggest that de Sitter breaking secular growth is likely to be observable in graviton loop effects. And a recent result for the vacuum polarization does seem to show it.
Woodard, R P
2015-01-01
A recent paper by Fr\\"ob employs the linearized Weyl-Weyl correlator to construct the tensor power spectrum. Although his purpose was to argue that infrared divergences and secular growth in the graviton propagator are gauge artefacts, a closer examination of the problem leads to the opposite conclusion. The analogies with the BMS symmetries of graviton scattering on a flat background, and with the Aharonov-Bohm effect of quantum mechanics, suggest that de Sitter breaking secular growth is likely to be observable in graviton loop effects. And a recent result for the vacuum polarization does seem to show it.
Alternative expression for the electromagnetic Lagrangian
Saldanha, Pablo L
2015-01-01
We propose an alternative expression for the Lagrangian density that governs the interaction of a charged particle with external electromagnetic fields. The proposed Lagrangian is written in terms of the local superposition of the particle fields with the applied electromagnetic fields, not in terms of the particle charge and of the electromagnetic potentials as is usual. The total Lagrangian for a set of charged particles assumes a simple elegant form with the alternative formulation, giving an aesthetic support for it. The proposed Lagrangian is equivalent to the traditional one in their domain of validity and provides an interesting description of the Aharonov-Bohm effect.
Large time behavior of the heat kernel of two-dimensional magnetic Schroedinger operators
Hynek Kovarik
2010-07-12
We study the heat semigroup generated by two-dimensional Schroedinger operators with compactly supported magnetic field. We show that if the field is radial, then the large time behavior of the associated heat kernel is determined by its total flux. We also establish some on-diagonal heat kernel estimates and discuss their applications for solutions to the heat equation. An exact formula for the heat kernel, and for its large time asymptotic, is derived in the case of the Aharonov-Bohm magnetic field.
NASA Astrophysics Data System (ADS)
Omidi, Mahboubeh; Faizabadi, Edris
2015-09-01
We use a simple model to study the electron-phonon interaction influences on persistent current in a one-dimensional quantum ring enclosed by a magnetic flux. With increasing the temperature, persistent current amplitude is reduced, especially in a quantum ring with two ions per primitive cell (diatomic ring) because of the participation of optical phonons. Furthermore, the periodicity of the Aharonov-Bohm oscillations changes to ?0 / 2?(?0 is magnetic flux quantum). In a diatomic ring, by increasing the difference between left and right nearest-neighbor hopping integrals at zero temperature, persistent current variations show a transition from metallic to insulator against distinctive behavior at nonzero temperature.
Thévenin equivalence in disorderless quantum networks
NASA Astrophysics Data System (ADS)
Cain, C. A.; Wu, C. H.
2015-01-01
We outline the procedure of extending the Thévenin equivalence principle for classical electric circuits to reducing Aharonov-Bohm-based quantum networks into equivalent models. With examples, we show from first principles how the requirements are related to the electron band structure's Fermi level and the lattice spacing of the network. Quantum networks of varying degrees of coupling strength from four basic classifications of single and double entangled loops sharing symmetry and highly correlated band structures are used to demonstrate the concept. We show the limitations of how the principle may be applied. Several classes of examples are given and their equivalent forms are shown.
Conformal field theory description of mesoscopic phenomena in the fractional quantum Hall effect
Lachezar S. Georgiev
2006-01-12
We give a universal description of the mesoscopic effects occurring in fractional quantum Hall disks due to the Aharonov-Bohm flux threading the system. The analysis is based on the exact treatment of the flux within the conformal field theory framework and is relevant for all fractional quantum Hall states whose edge states CFTs are known. As an example we apply this scheme for the parafermion Hall states and extract the main characteristics of the low- and high- temperature asymptotic behavior of the persistent currents.
Multipole modes and spin features in the Raman spectrum of nanoscopic quantum rings
NASA Astrophysics Data System (ADS)
Emperador, Agustí; Pi, Martí; Barranco, Manuel; Lipparini, Enrico
2001-10-01
We present a systematic study of ground state and spectroscopic properties of many-electron nanoscopic quantum rings. Addition energies at zero magnetic field (B) and electrochemical potentials as a function of B are given for a ring hosting up to 24 electrons. We find discontinuities in the excitation energies of multipole spin and charge density modes, and a coupling between the charge and spin density responses that allow to identify the formation of ferromagnetic ground states in narrow magnetic field regions. These effects can be observed in Raman experiments, and are related to the fractional Aharonov-Bohm oscillations of the energy and of the persistent current in the ring.
Dirac oscillator interacting with a topological defect
Carvalho, J.; Furtado, C.; Moraes, F. [Unidade Academica de Tecnologia de Alimentos, CCTA, Universidade Federal de Campina Grande, Pereiros, 58840-000, Pombal, Paraiba (Brazil); Departamento de Fisica, CCEN, Universidade Federal da Paraiba, Cidade Universitaria, 58051-970 Joao Pessoa, Paraiba (Brazil)
2011-09-15
In this work we study the interaction problem of a Dirac oscillator with gravitational fields produced by topological defects. The energy levels of the relativistic oscillator in the cosmic string and in the cosmic dislocation space-times are sensible to curvature and torsion associated to these defects and are important evidence of the influence of the topology on this system. In the presence of a localized magnetic field the energy levels acquire a term associated with the Aharonov-Bohm effect. We obtain the eigenfunctions and eigenvalues and see that in the nonrelativistic limit some results known in standard quantum mechanics are reached.
Coherence of Single Electron Sources from Mach-Zehnder Interferometry
Géraldine Haack; Michael Moskalets; Janine Splettstoesser; Markus Büttiker
2011-03-11
A new type of electron sources has emerged which permits to inject particles in a controllable manner, one at a time, into an electronic circuit. Such single electron sources make it possible to fully exploit the particles' quantum nature. We determine the single-particle coherence length from the decay of the Aharonov-Bohm oscillations as a function of the imbalance of a Mach-Zehnder interferometer connected to a single electron source. The single-particle coherence length is of particular importance as it is an intrinsic property of the source in contrast to the dephasing length.
Electromagnetic potential vectors and the Lagrangian of a charged particle
NASA Technical Reports Server (NTRS)
Shebalin, John V.
1992-01-01
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.
Topological properties of linear circuit lattices
Victor V. Albert; Leonid I. Glazman; Liang Jiang
2015-03-10
Motivated by the topologically insulating (TI) circuit of capacitors and inductors proposed and tested in arXiv:1309.0878, we present a related circuit with less elements per site. The normal mode frequency matrix of our circuit is unitarily equivalent to the hopping matrix of a quantum spin Hall insulator (QSHI) and we identify perturbations that do not backscatter the circuit's edge modes. The idea behind these models is generalized, providing a platform to simulate tunable and locally accessible lattices with arbitrary complex spin-dependent hopping of any range. A simulation of a non-Abelian Aharonov-Bohm effect using such linear circuit designs is discussed.
Again on coherent states in magnetic-solenoid field
V. G. Bagrov; S. P. Gavrilov; D. M. Gitman; K. Gorska
2011-08-25
This article completes our study of coherent states in the so-called magnetic-solenoid field (a colinear combination of a constant uniform magnetic field and Aharonov-Bohm solenoid field) presented in JPA 2010 and 2011. Here we succeeded to prove nontrivial completeness relations for non-relativistic and relativistic coherent states in such a field. In addition, we solve here the relevant Stieltjes moment problem and present a comparative analysis of our coherent states and the well-known in the case of pure uniform magnetic field Malkin-Man'ko coherent states.
Transportes em Revista.com Pas: Portugal
Instituto de Sistemas e Robotica
Comentar artigo Imprimir PDF Enviar a um amigo 09 -10 -2012 Toyota aposta no hidrogénio para ve ículos Plug-in em Paris 21 -08 -2012 Toyota lan ça novo Auris com motoriza ção híbrida 20 -08 -2012 MAN Toyota Veículos híbridos Estatísticas deste artigo Passageiros & Mobilidade voltar Os utilizadores
EM algorithms for ML factor analysis
Donald B. Rubin; Dorothy T. Thayer
1982-01-01
The details of EM algorithms for maximum likelihood factor analysis are presented for both the exploratory and confirmatory models. The algorithm is essentially the same for both cases and involves only simple least squares regression operations; the largest matrix inversion required is for aq ×q symmetric matrix whereq is the matrix of factors. The example that is used demonstrates that
Novo modelo em 2015 para financiar
Instituto de Sistemas e Robotica
entre universidades O Governo propôs ontem às univer- sidades e politécnicos os fundamen- tos de um novo estabelecimen- tos de ensino superior. A ideia está ainda numa fase em- brionária e, se for adiante, introdu- tos Superiores Politécnicos, consi- dera que o Governo não ofereceu informação suficiente sobre a ques
PRMIO PRIMUS INTER PARES Construir em equipa
Instituto de Sistemas e Robotica
, como o imagi- nam. Como vão poder resumir o seu percurso profissional daqui a 25 anos, em 2038? Nas pouco mais de 20 anos co- meçam a dar os primeiros passos no seu currículo profissional. São alunos de escolas de ne- gócios de prestígio (como as espa- nholas lESE ou IE) aos três pri- meiros classificados
Book Reviews EMS Newsletter September 2012 61
Bishop, Christopher
Book Reviews EMS Newsletter September 2012 61 Donald C. Spencer. In a very short essay "Some recol to several books by Eric Temple Bell, in particular his fa- mous book Men of Mathematics, thereby recorded in the essay "Olé!" by the Spanish mathematician José L. Fernández. The essay takes the point
ANÁLISE DA TRANSPOSIÇÃO DIDÁTICA EM SOFTWARES EDUCACIONAIS
Rosana Janete
Resumo. Este trabalho analisa como ocorre a transposição didática nos softwares educacionais usados nas escolas do município de Passo Fundo. Investiga junto aos professores\\/coordenadores dos laboratórios de informática das escolas os elementos significativos que envolvem a utilização do software educacional em suas atividades diárias, identificando formas de apresentação e estratégias de ensino nos conteúdos presentes nesses materiais e os recursos
Physiological Aspects of Em.otional Knowledge
Levenson, Robert W.
CHAPTER 2 Physiological Aspects of Em.otional Knowledge and Rapport Robert W Levenson AnnaM. Ruef physiology with emotional knowledge and rapport. However, human emotion is clearly a phenomenon of both body mind-body phenomenon. Be- cause physiology is such a crucial ingredient, we believe that all emotion
EMS Division Potential Benefits of Selected
Validation Program for ONR 300 KW Test Stand Motor 3.7 MW Motor Operated Successfully with SC magnet at full Homopolar Motors & Projections for Ship Propulsion Topics NOTE: Search for the interplay of technical disciplines!!!!! #12;EMS Division Homopolar Motor Outline ·Homopolar Motor Basics ·Homopolar Motor Technology
EMS: Group: Date: REVISED 04/09
Carter, John
is responsible for filling out a State Accident Report as well as an accident report with Public SafetyEMS: Group: Date: REVISED 04/09 TERMS OF USAGE: Violation(s) of any of the following terms may responsibility for all financial obligations incurred as a result of 1) failure to return vehicle as indicated, 2
Electro Magnetic (EM) Uses Radio Waves
Naik, Naren
- Doppler/velocity of targets - Angle (azimuth and/or elevation) · Special-purpose radars also measure Spectra; Modulation of Doppler shift by target motion Synthetic Aperture Radar; Conversion of Doppler#12;RADAR Electro Magnetic (EM) SENSOR Uses Radio Waves Used for Detection of Objects Finding
CURSO DE PS-GRADUAO EM METEOROLOGIA
, 1993 Clóvis Angeli Sansigolo, Doutor, USP, 1986 Daniel Alejandro Vila, Doutor, Universidad de Buenos Célia dos Santos Alvalá, Doutora, INPE, 1993 Saulo Ribeiro de Freitas, Doutor, IF-USP, 1999 Simone Pezzi Dra. Regina Célia dos Santos Alvalá MET-560-3 Métodos Matemáticos em Meteorologia Dr. Luiz
Modelling and design for PM/EM magnetic bearings
NASA Technical Reports Server (NTRS)
Pang, D.; Kirk, J. A.; Anand, D. K.; Johnson, R. G.; Zmood, R. B.
1992-01-01
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.
Crosshole EM in steel-cased boreholes
Wilt, M.; Lee, K.H.; Becker, A.; Spies, B.; Wang, B.
1996-07-01
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.
Telescópio de patrulhamento solar em 12 GHz
NASA Astrophysics Data System (ADS)
Utsumi, F.; Costa, J. E. R.
2003-08-01
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.
Cryo-EM: Spinning the Micelles Away.
Singh, Satinder K; Sigworth, Fred J
2015-09-01
Structural characterization of integral membrane proteins (MPs) demands that the samples be pure, monodisperse, and stable. Detergents are required to extract MPs from the lipid bilayer in which they reside and to stabilize them for downstream biophysical analyses. Some of the best MP-stabilizing detergents pose problems for cryo-EM studies, but in this issue of Structure, Hauer et al. (2015) now offer a solution called GraDeR. PMID:26331455
TandEM: Titan and Enceladus mission
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
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.
TandEM: Titan and Enceladus mission
NASA Astrophysics Data System (ADS)
Coustenis, A.; Atreya, S. K.; Balint, T.; Brown, R. H.; Dougherty, M. K.; Ferri, F.; Fulchignoni, M.; Gautier, D.; Gowen, R. A.; Griffith, C. A.; Gurvits, L. I.; Jaumann, R.; Langevin, Y.; Leese, M. R.; Lunine, J. I.; McKay, C. P.; Moussas, X.; Müller-Wodarg, I.; Neubauer, F.; Owen, T. C.; Raulin, F.; Sittler, E. C.; Sohl, F.; Sotin, C.; Tobie, G.; Tokano, T.; Turtle, E. P.; Wahlund, J.-E.; Waite, J. H.; Baines, K. H.; Blamont, J.; Coates, A. J.; Dandouras, I.; Krimigis, T.; Lellouch, E.; Lorenz, R. D.; Morse, A.; Porco, C. C.; Hirtzig, M.; Saur, J.; Spilker, T.; Zarnecki, J. C.; Choi, E.; Achilleos, N.; Amils, R.; Annan, P.; Atkinson, D. H.; Bénilan, Y.; Bertucci, C.; Bézard, B.; Bjoraker, G. L.; Blanc, M.; Boireau, L.; Bouman, J.; Cabane, M.; Capria, M. T.; Chassefière, E.; Coll, P.; Combes, M.; Cooper, J. F.; Coradini, A.; Crary, F.; Cravens, T.; Daglis, I. A.; de Angelis, E.; de Bergh, C.; de Pater, I.; Dunford, C.; Durry, G.; Dutuit, O.; Fairbrother, D.; Flasar, F. M.; Fortes, A. D.; Frampton, R.; Fujimoto, M.; Galand, M.; Grasset, O.; Grott, M.; Haltigin, T.; Herique, A.; Hersant, F.; Hussmann, H.; Ip, W.; Johnson, R.; Kallio, E.; Kempf, S.; Knapmeyer, M.; Kofman, W.; Koop, R.; Kostiuk, T.; Krupp, N.; Küppers, M.; Lammer, H.; Lara, L.-M.; Lavvas, P.; Le Mouélic, S.; Lebonnois, S.; Ledvina, S.; Li, J.; Livengood, T. A.; Lopes, R. M.; Lopez-Moreno, J.-J.; Luz, D.; Mahaffy, P. R.; Mall, U.; Martinez-Frias, J.; Marty, B.; McCord, T.; Menor Salvan, C.; Milillo, A.; Mitchell, D. G.; Modolo, R.; Mousis, O.; Nakamura, M.; Neish, C. D.; Nixon, C. A.; Nna Mvondo, D.; Orton, G.; Paetzold, M.; Pitman, J.; Pogrebenko, S.; Pollard, W.; Prieto-Ballesteros, O.; Rannou, P.; Reh, K.; Richter, L.; Robb, F. T.; Rodrigo, R.; Rodriguez, S.; Romani, P.; Ruiz Bermejo, M.; Sarris, E. T.; Schenk, P.; Schmitt, B.; Schmitz, N.; Schulze-Makuch, D.; Schwingenschuh, K.; Selig, A.; Sicardy, B.; Soderblom, L.; Spilker, L. J.; Stam, D.; Steele, A.; Stephan, K.; Strobel, D. F.; Szego, K.; Szopa, C.; Thissen, R.; Tomasko, M. G.; Toublanc, D.; Vali, H.; Vardavas, I.; Vuitton, V.; West, R. A.; Yelle, R.; Young, E. F.
2009-03-01
TandEM was proposed as an L-class (large) mission in response to ESA’s Cosmic Vision 2015-2025 Call, and accepted for further studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini-Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TandEM is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini-Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time). In the current mission architecture, TandEM proposes to deliver two medium-sized spacecraft to the Saturnian system. One spacecraft would be an orbiter with a large host of instruments which would perform several Enceladus flybys and deliver penetrators to its surface before going into a dedicated orbit around Titan alone, while the other spacecraft would carry the Titan in situ investigation components, i.e. a hot-air balloon (Montgolfière) and possibly several landing probes to be delivered through the atmosphere.
Gradientes de abundâncias em galáxias espirais
NASA Astrophysics Data System (ADS)
Dors, O. L.., Jr.; Copetti, M. V. F.
2003-08-01
Gradientes de abundâncias obtidos através de observações de regiões H II têm um papel importante no estudo de formação e evolução de galáxias espirais. Determinações diretas de abundâncias somente são obtidas quando linhas de emissão sensíveis à temperatura eletrônica (e.g., [O III]l4363) são detectadas. Infelizmente estas linhas são fracas ou não observadas em regiões H II de baixa excitação. Nestes casos métodos empíricos são utilizados para estimar as abundâncias químicas. Entretanto, diferentes métodos têm produzido diferentes estimativas de gradientes de abundâncias. Neste trabalho, nós construímos modelos de fotoionização com o objetivo de descrever diagramas de diagnósticos construídos com dados publicados de algumas galáxias espirais normais e barradas. Comparações entre nossas estimativas de abundâncias e de outros métodos mostram que quando não há acordo entre eles, nossos modelos superestimam as abundâncias de O/H e N/H por um fator de 0.3 dex em relação a estimativas diretas de abundâncias, e por fator de 0.2 dex em relação a outros métodos empíricos. A origem da produção de nitrogênio nas galáxias estudadas é discutida.
Universidade Federal do Rio de Janeiro UM ESQUEMA EFICIENTE DE AMOSTRAGEM EM MODELOS DIN ^AMICOS
Ravines, Romy R.
Universidade Federal do Rio de Janeiro UM ESQUEMA EFICIENTE DE AMOSTRAGEM EM MODELOS DIN ^AMICOS ESQUEMA EFICIENTE DE AMOSTRAGEM EM MODELOS DIN ^AMICOS GENERALIZADOS COM APLICACÂ¸ ~OES EM FUNCÂ¸ ~OES DE EFICIENTE DE AMOSTRAGEM EM MODELOS DIN ^AMICOS GENERALIZADOS COM APLICACÂ¸ ~OES EM FUNCÂ¸ ~OES DE TRANSFER
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM EDUCAO FSICA
Maier, Rudolf Richard
instrumental, emitido por escola de idiomas ou Comprovante de aprovaÃ§Ã£o em Exame de proficiÃªncia em lÃngua por escola de idiomas ou Comprovante de aprovaÃ§Ã£o em Exame de proficiÃªncia em lÃngua inglesa obtido em
Galp investe em cincia no Brasil Margarida Davim
Instituto de Sistemas e Robotica
Galp investe em ciÃªncia no Brasil Margarida Davim margarida.davim@sol.pt Lei brasileira obriga dÃ³lares em investiga- Ã§Ã£o e projectos cientÃficos no Brasil atÃ© 2017. O investimento - cerca de 102 devem ser aplica- dos em Â«projectos de explora- Ã§Ã£o e produÃ§Ã£o no BrasilÂ» e estÃ¡ nos planos da empresa
Rio Internet TV ---AulaNet^TM Videoconferncia em WebBased Learning
Endler, Markus
conjunto com o uso maciço dos computadores por pessoas em seus ambientes profissional e doméstico, vêm. A forma tradicional de aprendizado em um ambiente confinado como a escola, onde um professor em uma
EM threat analysis for wireless systems.
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
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.
e/m Experiment Analysis Refinement
NASA Astrophysics Data System (ADS)
Harmon, Michael; Pruitt, Bryce; Velasquez, Kevin; Schelp, Rich
2011-10-01
Thomson's e/m experiment is widely popular in undergraduate courses to help gain an understanding of the properties of the electron. Our results using a standard apparatus, however, reveal significant systematic errors. We examine possible reasons for the discrepancy with the aim of modeling effects that were not included in the original analysis. We conclude that the energy loss of the electron beam as it travels through the helium and the distortion of the beam radius measurement by the curved glass of the tube are the two factors which dominate the discrepancy.
Slab melting as an origin of EMs reservoirs
NASA Astrophysics Data System (ADS)
Shimoda, G.
2010-12-01
It has been widely accepted that at least three enriched geochemical reservoirs must exist in the mantle to explain the isotopic variations observed in ocean island basalts (OIBs). These reservoirs are known as enriched mantle 1 (EM1), enriched mantle 2 (EM2) and HIMU (238U/204Pb) (e.g., Zindler and Hart, 1986). As these reservoirs have been considered to be produced by the major differentiation process(es) of Earth, many studies have been conducted to evaluate their origins. As a result, the reservoirs are considered to be formed by the recycling of continental/oceanic crustal materials (e.g., Zindler and Hart, 1986; Hofmann, 1997; Stracke et al., 2005). Among the mantle reservoirs, EM1 and EM2 should have a particularly close chemical connection because many island chains have Sr and Nd isotopic compositions that form linear arrays extending from DMM (depleted MORB mantle) or FOZO (focus zone; Hart et al., 1992) to intermediate composition between EM1 and EM2. Furthermore, it has been suggested that the source material of EM1- and EM2-type magmas could have specific trace element compositions at each hot spot (Willbold and Stracke, 2006). These geochemical features could imply that a process capable of producing the isotopic difference between EM1 and EM2 may have operated. Thus, the development of a model that can account for both EM1 and EM2 compositions would be a significant step forward in understanding the origins of two reservoirs. In this study, geochemical modeling for the origin of EM1 and EM2 is conducted from the perspective of slab melting, i.e., adakite production. For the model, the average composition of adakites is re-estimated from published data for eighteen trace elements. The average composition of adakites can be explained by melting of oceanic crust with no sediment contribution. Calculations using mantle AFC suggest that the mantle-slab melt reaction could selectively increase HREE concentration. In addition, crystal fractionation at shallow depth could produce additional chemical variations in adakites. To examine the effect of chemical variations on the isotopic composition of recycled adakites, correlations between trace elements and SiO2 concentrations, and the MELTS program are employed. The results suggest that recycling of a basic adakite (SiO2 = 55%) can account for EM1 isotopic signatures with storage times of about 2.0 Gyr. The isotopic compositions of less-basic adakites and their evolved magmas shift towards EM2 values with increasing SiO2 concentrations. In particular, evolved acidic adakite can yield EM2 isotopic signatures. These lines of evidence suggest that the recycling of adakites at various stages of evolution can produce the entire isotopic range between EM1 and EM2 reservoirs. Consequently, adakite recycling via sediment subduction or subduction erosion can account for the origins of EM1 and EM2 reservoirs.
ANLISE DE DESEMPENHO E CONSUMO DE POTNCIA NA COMUNICAO INTERPROCESSOS EM SOFTWARE EMBARCADO
Wagner, Flávio Rech
um microcontrolador Java de aplicação específica. Um sistema de controle embarcado de guindaste foi mensagens. Estes mecanismos foram avaliados em uma plataforma arquitetural baseada em um microcontrolador
Aquisição de Estreptococos Mutans e Desenvolvimento de Cárie Dental em Primogênitos
NOCE, Erica; RUBIRA, Cassia Maria Fischer; da Silva ROSA, Odila Pereira; da SILVA, Salete Moura Bonifácio; BRETZ, Walter Antonio
2011-01-01
Objetivo Avaliar o momento de aquisição de estreptococos mutans (EM), desenvolvimento de cárie dental e as variáveis a eles associadas no decorrer de 23 meses, em primogênitos de famílias de baixo nível socioeconômico, desde os sete meses de idade. Método A amostra foi selecionada com base em mães densamente colonizadas por EM, incluindo todos os membros de 14 famílias que conviviam na mesma casa. Foram envolvidos no estudo 14 mães, pais e primogênitos e 8 parentes, na maioria avós. Exames clínicos e radiográficos iniciais determinaram os índices de cárie e condição periodontal dos adultos. Contagens de EM foram feitas em todos os adultos nas duas primeiras visitas. Nas crianças foram avaliados os níveis de EM, o número de dentes e de cáries, em quatro visitas. Resultados A prevalência de EM nos adultos foi alta, estando ausente em apenas um dos pais. EM foram detectados em 1, 2, 3 e 10 crianças, respectivamente nas visitas #1, 2, 3 e 4. A cárie dental foi detectada em apenas três crianças na última visita (aos 30 meses de idade), as quais apresentaram escores de EM significantemente maiores que as crianças sem cárie, na mesma visita. Conclusão Exclusivamente a condição social de baixa renda e mães densamente colonizadas por EM não são sinônimo de colonização precoce e alta atividade de cárie em crianças cuidadas em casa. O desenvolvimento de cárie está significantemente associado a escores elevados de EM nas crianças. PMID:22022218
Sobre o uso das séries de Puiseux em mecanica celeste
NASA Astrophysics Data System (ADS)
Miloni, O. I.
2003-08-01
Neste trabalho é apresentada uma demonstração do uso dos diferentes desenvolvimentos em séries para as equações de perturbação em Mecânica Celeste no marco Hamiltoniano. Em trabalhos clássicos como os de Poincaré (Poincaré, 1893) por exemplo, já esta planteado o uso de potências não inteiras no pequeno parâmetro, o que evidencia a não analiticidade das funções quando uma ressonância ocorre. Nestes trabalhos os desenvolvimentos são na raíz quadrada da massa de Júpiter (o pequeno parâmetro). Mais recentemente (Ferraz-Mello, 1985) outros tipos de desenvolvimentos foram aplicados modificando substancialmente as ordens de grandeza e a velocidade de convergência das séries. Com esta abordagem, os desenvolvimentos foram expressados em termos da raíz cúbica do pequeno parâmetro. Neste trabalho apresentamos um enfoque geral, onde os diferentes tipos de desenvolvimentos em séries de Puiseux (Valiron, 1950) são obtidos a partir da aplicação de Teorema de Preparação de Weierstrass (Goursat, 1916) considerando a equação de Hamilton-Jacobi como uma equação algébrica. Os resultados são aplicados ao problema restrito dos três corpos em ressonância de primeira ordem e, dependendo da grandeza da excentricidade do asteróide em relação à de Júpiter, obtemos os diferentes desenvolvimentos, em raíz quadrada ou raíz cúbica da massa de Júpiter.
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM ECOLOGIA
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM ECOLOGIA EDITAL No. 02/2015 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM ECOLOGIA PARA OS CURSOS DE MESTRADO ACADÊMICO E DOUTORADO ECOLOGIA, no uso de suas atribuições legais, estabelece e torna público as normas do processo seletivo para
CURSO DE BACHARELA CURSO DE LICENCIATURA EM EDUCAO FSICA
Floeter, Sergio Ricardo
Fundamental e Médio) e Educação Profissional. O Licenciado em Educação Física deverá estar capacitado para o pleno exercício profissional no componente curricular Educação Física na Educação Básica e Profissional em suas exigências gerais, tais como inserção social da escola, domínio de teorias e processos
EMS quality assurance: a computerized incident reporting system.
Pointer, J E; Osur, M A
1987-01-01
Incident reports are an extremely valuable quality assurance vehicle in Emergency Medical Services (EMS) Systems. Appropriate identification, analysis, and followup of incidents can identify trends and recurrent problems, and change system policy. An urban EMS System utilized a computerized data base program to expedite its handling of a large number of incident reports. PMID:3429823
10 CFR Appendixes E-M to Part 52 - [Reserved
Code of Federal Regulations, 2010 CFR
2010-01-01
10 Energy 2 2010-01-01 2010-01-01 false [Reserved] E Appendixes E-M to Part 52 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS Appendixes E-M to Part 52...
Levantamento Webométrico Na Produção Científica em Mestrado da Furb 1
Roseméri LAURINDO
2008-01-01
A Internet tem desenvolvido a propagação das comunicações científicas, transformando métodos científicos tradicionais. O crescente uso de buscadores gera preocupações em relação aos novos hábitos dos pesquisadores. No campo da leitura pretendemos entender, com a presente pesquisa, as novas problemáticas comunicacionais que se revelam na produção científica. Escolhemos para análise preliminar produtores de dissertações realizadas no Mestrado em Ciências Contábeis
Background and Foreground Modelling Using an Online EM Algorithm
Johan Lindström; Finn Lindgren; Kalle Åström; Jan Holst; Ulla Holst
novel approach to background\\/foreground segmentation using an online EM algorithm is presented. The method models each layer as a Gaussian mixture, with local, per pixel, parameters for the background layer and global parameters for the foreground layer, utilising information from the entire scene when estimating the foreground. Additionally, the online EM algorithm uses a progressive learning rate where the relative
Asymptotic Convergence Properties of EM-Type Algorithms1
Fessler, Jeffrey A.
Asymptotic Convergence Properties of EM-Type Algorithms1 Alfred O. Hero and Je rey A. Fessler Dept Arbor, MI 48109 ABSTRACT We analyze the asymptotic convergence properties of a general class of EM. A theorem is given which provides conditions for monotone convergence with respect to a given norm and speci
US Army Corps of Engineers
EM 1110-1-1804 1 January 2001 US Army Corps of Engineers ENGINEER MANUAL Geotechnical Investigations ENGINEERING AND DESIGN #12;AVAILABILITY Electronic copies of this and other U.S. Army Corps;DEPARTMENT OF THE ARMY EM 1110-1-1804 U.S. Army Corps of Engineers CECW-ET Washington, DC 20314-1000 Manual
BENJAMIN FRANKLIN E A HISTÓRIA DA ELETRICIDADE EM LIVROS DIDÁTICOS
Cibelle Celestino Silva; Ana Carolina Pimentel
Introdução Nos últimos anos, a história da ciência vem sendo introduzida em materiais didáticos utilizados em sala de aula. Uma das razões para isso é a pressão de órgãos governamentais, tais como a Secretaria de Educação Básica, responsável pela avaliação destes livros dentro do Programa Nacional de Livros Didáticos para o ens ino fundamental e médio. Os editais destes programas
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
modelling, logic programming. Resumo: Sistemas de informação com um componente de banco de dados devem ser estático refere-se às classes de fatos a serem representados no banco de dados. O nível dinâmico trata do computadores, os arquivos de dados armazenados externamente, em geral em fitas ou discos, eram considerados
Inferring O set Normal Shape Distributions with EM Max Welling
Welling, Max
Inferring O#11;set Normal Shape Distributions with EM Max Welling University of Toronto 6 King normal shape distribution. Abstract An EM algorithm for inferring the parameters of the o#11;set normal shape distribution is derived. Update rules for mixtures of o#11;set normal shape distributions are also
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM
Maier, Rudolf Richard
1 UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM PSICOLOGIA SOCIAL, DO TRABALHO E DAS PSICOLOGIA SOCIAL, DO TRABALHO E DAS ORGANIZAÇÕES PARA OS CURSOS DE MESTRADO ACADÊMICO E DE DOUTORADO PARA O SEGUNDO PERÍODO LETIVO DE 2012 1 PREÂMBULO 1.1 O Coordenador do Programa de Pós-Graduação em Psicologia
Um SGBD com Armazenamento Distribuido de Dados Baseado em DHT
Hara, Carmem Satie
tabelas. Unindo as propriedades da DHT `as propriedades do banco de dados, Â´e possÂ´ivel desenvolver umUm SGBD com Armazenamento DistribuÂ´ido de Dados Baseado em DHT Eduardo Augusto Ribas1 , Roney Uba1- namento baseado em Tabelas de Espalhamento DistribuÂ´idas (DHT) para um Sistema Gerenciador de Banco de
STM: Memoria Transacional em Software Distribuida e Confiavel
Rodrigues, Luís E.T.
D2 STM: Mem´oria Transacional em Software Distribu´ida e Confi´avel Maria Couceiro, Paolo Romano@gsd.inesc-id.pt, nonius@gsd.inesc-id.pt, ler@ist.utl.pt Resumo Os sistemas de Mem´oria Transacional em Software (MTS) t consider´aveis. Abstract. Software Transactional Memory (STM) systems have emerged as a powerful paradigm
Mennemann, Jan-Frederik Jüngel, Ansgar
2014-10-15
Discrete transparent boundary conditions (DTBC) and the Perfectly Matched Layers (PML) method for the realization of open boundary conditions in quantum device simulations are compared, based on the stationary and time-dependent Schrödinger equation. The comparison includes scattering state, wave packet, and transient scattering state simulations in one and two space dimensions. The Schrödinger equation is discretized by a second-order Crank–Nicolson method in case of DTBC. For the discretization with PML, symmetric second-, fourth-, and sixth-order spatial approximations as well as Crank–Nicolson and classical Runge–Kutta time-integration methods are employed. In two space dimensions, a ring-shaped quantum waveguide device is simulated in the stationary and transient regime. As an application, a simulation of the Aharonov–Bohm effect in this device is performed, showing the excitation of bound states localized in the ring region. The numerical experiments show that the results obtained from PML are comparable to those obtained using DTBC, while keeping the high numerical efficiency and flexibility as well as the ease of implementation of the former method. -- Highlights: •In-depth comparison between discrete transparent boundary conditions (DTBC) and PML. •First 2-D transient scattering state simulations using DTBC. •First 2-D transient scattering state simulations of the Aharonov–Bohm effect.
D. Ebert; K. G. Klimenko; P. B. Kolmakov; V. Ch. Zhukovsky
2015-09-27
In this paper we consider a class of (2+1)D schematic models with four-fermion interactions that are effectively used in studying condensed-matter systems with planar crystal structure, and especially graphene. Symmetry breaking in these models occurs due to a possible appearance of condensates. Special attention is paid to the symmetry properties of the appearing condensates in the framework of discrete chiral and $\\mathcal C$, $\\mathcal P$ and $\\mathcal T$ transformations. Moreover, boundary conditions corresponding to carbon nanotubes are considered and their relations with the effect of an applied external magnetic field are studied. To this end we calculated the effective potential for the nanotube model including effects of finite temperature, density and an external magnetic field. As an illustration we made numerical calculations of the chiral symmetry properties in a simpler Gross--Neveu model with only one condensate taken into account. We also investigated the phase structure of the nanotube model under the influence of the Aharonov--Bohm effect and demonstrated that there is a nontrivial relation between the magnitude of the Aharonov--Bohm phase, compactification of the spatial dimension and thermal restoration of the originally broken chiral symmetry.
Magnetosymmetries of nonlinear transport in dissipative conductors
NASA Astrophysics Data System (ADS)
Bedkihal, Salil; Segal, Dvira
2014-03-01
We demonstrate with numerically exact simulations that nonlinear transport coefficients obey certain magnetic field symmetries. Our model includes a two terminal Aharonov-Bohm interferometer with a quantum dot located at each of its arms. One quantum dot is interacting electrostatically with a reservoir, a fermionic environment made of a quantum dot coupled to one or more leads. We study the dynamics and steady state properties of this many-body out of equilibrium setup, by using a numerically exact influence functional path integral technique (Phys. Rev.B 82, 205323 (2010)). We show that, in agreement with phenomenological treatments of dephasing and mean field approaches, even (odd) conductance terms obey odd (even) symmetry with threading magnetic flux, as long as system acquires spatial inversion symmetry. When spatial asymmetry is introduced, magnetic field symmetries are broken, but more general symmetries with respect to left-right interchange are obeyed. Finally we also numerically demonstrate that double quantum dot Aharonov-Bohm interferometer coupled electrostatically to a fermionic environment can act as a charge current rectifier when two conditions are met simultaneously (I)broken time reversal and (II) many body effects. Authors acknowledge funding from NSERC, University of Toronto Department of Chemistry, Queen Elizabeth II graduate scholarship, Gilchrist fellowship.
Self-accelerating Dirac particles and prolonging the lifetime of relativistic fermions
NASA Astrophysics Data System (ADS)
Kaminer, Ido; Nemirovsky, Jonathan; Rechtsman, Mikael; Bekenstein, Rivka; Segev, Mordechai
2015-03-01
The Aharonov-Bohm effect predicts that two parts of the electron wavefunction can accumulate a phase difference even when they are confined to a region in space with zero electromagnetic field. Here we show that engineering the wavefunction of electrons, as accelerating shape-invariant solutions of the potential-free Dirac equation, fundamentally acts as a force and the electrons accumulate an Aharonov-Bohm-type phase--which is equivalent to a change in the proper time and is related to the twin-paradox gedanken experiment. This implies that fundamental relativistic effects such as length contraction and time dilation can be engineered by properly tailoring the initial conditions. As an example, we suggest the possibility of extending the lifetime of decaying particles, such as an unstable hydrogen isotope, or altering other decay processes. We find these shape-preserving Dirac wavefunctions to be part of a family of accelerating quantum particles, which includes massive/massless fermions/bosons of any spin.
Uma grade de perfis teóricos para estrelas massivas em transição
NASA Astrophysics Data System (ADS)
Nascimento, C. M. P.; Machado, M. A.
2003-08-01
Na XXVIII Reunião Anual da Sociedade Astronômica Brasileira (2002) apresentamos uma grade de perfis calculados de acordo com os pontos da trajetória evolutiva de metalicidade solar, Z = 0.02 e taxa de perda de massa () padrão, para estrelas com massa inicial de 25, 40, 60, 85 e 120 massas solares. Estes perfis foram calculados com o auxílio de um código numérico adequado para descrever os ventos de objetos massivos, supondo simetria esférica, estacionaridade e homogeneidade. No presente trabalho, apresentamos a complementação da grade com os perfis teóricos relativos às trajetórias de Z = 0.02 com taxa de perda de massa dobrada em relação a padrão (2´), e de metalicidade Z = 0.008. Para cada ponto das três trajetórias obtemos os perfis teóricos de Ha, Hb, Hg e Hd, e como esperado eles se apresentam em pura emissão, pura absorção ou em P-Cygni. Para valores de taxa de perda de massa muito baixos (~10-7) não há formação de linhas, o que é visto nos primeiros pontos em todas as trajetórias. Em geral, para um mesmo ponto a componente de emissão diminui e a absorção aumenta de Ha para Hd. É verificado que as trajetórias com Z = 0.02 e padrão possuem menos circuitos (loops) do que as com metalicidade Z = 0.02 e 2´ padrão, e seus perfis são, em geral, menos intensos. Em relação a trajetória de Z = 0.008, verifica-se menos circuitos e maior variação em luminosidade, e seus perfis mostram-se em, algumas trajetórias, mais intensos. Verificamos também que, pontos distintos em uma mesma trajetória, apresentam perfis diferentes para valores similares de luminosidade e temperatura efetiva. Sendo assim, uma grade de perfis teóricos parece ser útil para fornecer uma informação preliminar sobre o estágio evolutivo de uma estrela massiva.
Incentives for P2P-Assisted Content Distribution: If You Can't Beat 'Em, Join 'Em
Wierman, Adam
Incentives for P2P-Assisted Content Distribution: If You Can't Beat 'Em, Join 'Em Vinod Ramaswamy. In particular, we evaluate the benefits of a hybrid revenue-sharing system that combines a legitimate P2P swarm. Motivated by recent work using lottery schemes to promote societally beneficial conduct [6], we suggest
Internal EM Field and Absorbed Power Density in Human Torsos Induced by 1-500MHz EM Waves
Kun-Mu Chen; B. S. Guru
1977-01-01
Numerical results on the internal electromagnetic (EM) field and absorbed power density inside a human torso induced by EM waves of frequencies ranging from 1 to 500 MHz and of both vertical and horizontal polarizations are presented. The induced fields inside the torso are shown to be dependent on the frequency and the torso geometry. Theoretical results are obtained based
Neirotti, Juan Pablo
Approved Module Information for EM4019, 2014/5 Module Title/Name: Research Methods Module Code: EM will enable students to develop knowledge of, and competence in, research methods appropriate to engineering of the basic principles, concepts, terminology, and techniques of qualitative research methods; as appropriate
Online EM with weight-based forgetting.
Celaya, Enric; Agostini, Alejandro
2015-05-01
In the online version of the EM algorithm introduced by Sato and Ishii ( 2000 ), a time-dependent discount factor is introduced for forgetting the effect of the old estimated values obtained with an earlier, inaccurate estimator. In their approach, forgetting is uniformly applied to the estimators of each mixture component depending exclusively on time, irrespective of the weight attributed to each unit for the observed sample. This causes an excessive forgetting in the less frequently sampled regions. To address this problem, we propose a modification of the algorithm that involves a weight-dependent forgetting, different for each mixture component, in which old observations are forgotten according to the actual weight of the new samples used to replace older values. A comparison of the time-dependent versus the weight-dependent approach shows that the latter improves the accuracy of the approximation and exhibits much greater stability. PMID:25710091
Hanford Site performance summary: EM funded programs
Edwards, C.
1995-09-01
Hanford performance at fiscal year end reflects a three percent unfavorable schedule variance ($46.3 million*) which was an improvement over August 1995 ($46.3 million for September versus $65.9 million for August) and is below established reporting thresholds (greater than 3 percent). The majority of the behind schedule condition (53 percent) is attributed to EM-40 (Office of Environmental Restoration [ER]) and is a result of late receipt of funds, procurement delays, and US Army Corps of Engineers (USACE) work planned but not accomplished. Other primary contributors to the behind schedule condition are associated with tank farm upgrades, high-level waste disposal and work for others (support to the US Department of Energy-Headquarters [DOE-HQ]). The remaining behind schedule condition is distributed throughout the remaining Hanford programs and do not share common causes. A breakdown of individuals listed on page 8.
Electromagnetic optimization of EMS-MAGLEV systems
Andriollo, M.; Martinelli, G.; Morini, A.; Tortella, A.
1998-07-01
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.
Queda dos homicídios em São Paulo, Brasil: uma análise descritiva
Peres, Maria Fernanda Tourinho; Vicentin, Diego; Nery, Marcelo Batista; de Lima, Renato Sérgio; de Souza, Edinilsa Ramos; Cerda, Magdalena; Cardia, Nancy; Adorno, e Sérgio
2012-01-01
Objetivo Descrever a evolução da mortalidade por homicídios no Município de São Paulo segundo tipo de arma, sexo, raça ou cor, idade e áreas de exclusão/inclusão social entre 1996 e 2008. Métodos Estudo ecológico de série temporal. Os dados sobre óbitos ocorridos no Município foram coletados da base de dados do Programa de Aprimoramento das Informações sobre Mortalidade, seguindo a Classificação Internacional de Doenças, Décima Revisão (CID-10). Foram calculadas as taxas de mortalidade por homicídio (TMH) para a população total, por sexo, raça ou cor, faixa etária, tipo de arma e área de exclusão/inclusão social. As TMH foram padronizadas por idade pelo método direto. Foram calculados os percentuais de variação no período estudado. Para as áreas de exclusão/inclusão social foram calculados os riscos relativos de morte por homicídio. Resultados As TMH apresentaram queda de 73,7% entre 2001 e 2008. Foi observada redução da TMH em todos os grupos analisados, mais pronunciada em homens (?74,5%), jovens de 15 a 24 anos (?78,0%) e moradores de áreas de exclusão social extrema (?79,3%). A redução ocorreu, sobretudo, nos homicídios cometidos com armas de fogo (?74,1%). O risco relativo de morte por homicídio nas áreas de exclusão extrema (tendo como referência áreas com algum grau de exclusão social) foi de 2,77 em 1996, 3,9 em 2001 e 2,13 em 2008. Nas áreas de alta exclusão social, o risco relativo foi de 2,07 em 1996 e 1,96 em 2008. Conclusões Para compreender a redução dos homicídios no Município, é importante considerar macrodeterminantes que atingem todo o Município e todos os subgrupos populacionais e microdeterminantes que atuam localmente, influenciando de forma diferenciada os homicídios com armas de fogo e os homicídios na população jovem, no sexo masculino e em residentes em áreas de alta exclusão social. PMID:21390415
Pirmasis lietuvi\\vskas Suvalkijos žem?lapis
NASA Astrophysics Data System (ADS)
Girkus, Romualdas; Lukoševi?ius, Viktoras
2009-01-01
Po ilgo paie\\vskos laikotarpio, dr. N. Lietuvninkaitei padedant, KTU bibliotekos Ret? knyg? skyriaus kartografiniame archyve aptiktas 1915 m. JAV išleistas B. K. Balu?io M 1:252 000 Suvalkijos žem?lapis. Lietuvi? išeivijos instituto B. K. Balu?io fonde žem?lapio sudarymo medžiagos nerasta. Paie\\vska atrod? bevilti\\vska d?l tarpukario Lietuvi\\vskosios enciklopedijos klaidinan?ios informacijos, kad prasid?jus Pirmajam pasauliniam karui žem?lapis nebuvo išleistas, tad aprašomas ir publikuojamas pirm? kart?.
Lietuvos Teritorijos Gravimetrinio Žem?lapio Tikslumo Vertinimas
NASA Astrophysics Data System (ADS)
Birvydien?, Rosita; Krikštaponis, Boleslovas; Obuchovski, Romuald; Paršeli?nas, Eimuntas; Petroškevi?ius, Petras; Šlikas, Dominykas
2010-01-01
Remiantis matavim?, atlikt? Lietuvos gravimetrinio tinklo punktuose, duomenimis, ?vertintas Lietuvos teritorijos 1:200 000 mastelio Bouguer anomalij? gravimetrinio žem?lapio tikslumas. Vertinimui naudota 686 gravimetrini? punkt? sunkio pagrei?io reikšm?s, kuri? vidutin? kvadratin? paklaida neviršija 9 ?Gal. Nustatytos teritorijos, kuriose sunkio pagreitis, apskai?iuotas pagal žem?lap?, turi sisteming?sias paklaidas. Gautas vidutinis skirtumas tarp žem?lapyje taikomos Potsdamo sunkio sistemos ir IGSN 71 sistemos, apibr?žtos Lietuvos gravimetriniame tinkle atliktais absoliu?iaisiais gravimetriniais matavimais.
INVERSION OF EM DATA TO RECOVER 1-D CONDUCTIVITY AND A GEOMETRIC SURVEY PARAMETER
Oldenburg, Douglas W.
INVERSION OF EM DATA TO RECOVER 1-D CONDUCTIVITY AND A GEOMETRIC SURVEY PARAMETER By Sean Eugene electromagnetic (EM) data. There are two types of data which are of particular interest: airborne EM (AEM) and ground based horizontal loop EM (HLEM). When dealing with AEM data there is a potential for errors
REGIMENTO DO CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS, REA DE
REGIMENTO DO CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS, ÁREA DE CONCENTRAÇÃO EM Espacial e Controle (CMC) do Curso de Pós-graduação em Engenharia e Tecnologia Espaciais (ETE) objetiva de Pós-Graduação, pelo Regimento do Curso de Pós- Graduação em Engenharia e Tecnologia Espaciais e
Environmental Education and Development Division (EM-522). Annual report, Fiscal year 1993
Not Available
1993-12-31
The Environmental Education and Development Division (EM-522) is one of three divisions within the Office of Technology Integration and Environmental Education and Development (EM-52) in Environmental Restoration and Waste Management`s (EM`s) Office of Technology Development (EM-50). The primary design criterion for EM-522 education activities is directly related to meeting EM`s goal of environmental compliance on an accelerated basis and cleanup of the 1989 inventory of inactive sites and facilities by the year 2019. Therefore, EM-522`s efforts are directed specifically toward stimulating knowledge and capabilities to achieve the goals of EM while contributing to DOE`s overall goal of increasing scientific, mathematical, and technical literacy and competency. This report discusses fiscal year 1993 activities.
CURSO DE PS-GRADUAO EM GEOFSICA ESPACIAL
CURSO DE PÓS-GRADUAÇÃO EM GEOFÍSICA ESPACIAL Coordenador Acadêmico Maria Virgínia Alves Docentes, Brasil Walter D. Gonzalez Alarcon, Ph.D., Univ. Cal. Berkeley, 1973- MAGHEL #12;Docentes Colaboradores
7 CFR 759.6 - EM to be made available.
Code of Federal Regulations, 2014 CFR
2014-01-01
...the FSA Administrator to make a determination that a natural disaster has occurred in a county, resulting in severe physical...If the FSA Administrator determines that such a natural disaster has occurred, then EM can be made available...
7 CFR 759.6 - EM to be made available.
Code of Federal Regulations, 2013 CFR
2013-01-01
...the FSA Administrator to make a determination that a natural disaster has occurred in a county, resulting in severe physical...If the FSA Administrator determines that such a natural disaster has occurred, then EM can be made available...
Comparison of different marine EM methods for reservoir monitoring
NASA Astrophysics Data System (ADS)
ENDO, M.; Black, N.; Wilson, G. A.; Zhdanov, M. S.
2011-12-01
Recent studies have inferred the feasibility of controlled-source electromagnetic (CSEM) methods for the monitoring of offshore oil and gas fields. These studies have focused on CSEM methods where a transmitter is towed above an array of seafloor receivers. Recently, a towed streamer EM system capable to simultaneous seismic and CSEM data acquisition has been developed and tested in the North Sea. In this paper, we use 3D modeling and inversion to compare conventional CSEM with towed EM for monitoring of the Harding field, which is representative of a typical North Sea target. The 3D model of the Harding field itself was constructed from dynamic reservoir simulations. We observe similarities in the recovered models, suggesting that the towed streamer EM system could be used for reservoir monitoring. Obviating the need for ocean bottom receivers, the towed-streamer EM system enables CSEM data to be acquired simultaneously with seismic for higher production rates and relatively lower cost than conventional CSEM.
EMS Newsletter March 2014 39 Open Access Four Opinions
Greuel, Gert-Martin
Discussion EMS Newsletter March 2014 39 Open Access Four Opinions In the last few issues of the newsletter,we have published more than one article on publication-related topics. The editorial board wishes
E.M. and Hadronic Shower Simulation with FLUKA
Battistoni, G.; Fasso, A.; Ferrari, A.; Ranft, J.; Rubbia, A.; Sala, P.R.; /INFN, Milan /SLAC /CERN /Siegen U. /Zurich, ETH
2005-10-03
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.
EMS: A framework for data acquisition and analysis
NASA Astrophysics Data System (ADS)
Nogiec, J. M.; Sim, J.; Trombly-Freytag, K.; Walbridge, D.
2001-08-01
The Extensible Measurement System (EMS) is a universal Java framework for building data analysis and test systems. The objective of the EMS project is to replace a multitude of different existing systems with a single expandable system, capable of accommodating various test and analysis scenarios and varying algorithms. The EMS framework is based on component technology, graphical assembly of systems, introspection and flexibility to accommodate various data processing and data acquisition components. Core system components, common to many application domains, have been identified and designed together with the domain-specific components for the measurement of accelerator magnets. The EMS employs several modern technologies and the result is a highly portable, configurable, and potentially distributed system, with the capability of parallel signal data processing, parameterized test scripting, and run-time reconfiguration.
GENERAL PHYSICS EM FIELDS NUMERICAL SOLUTION FOR FREDHOLM
Fernandez, Thomas
GENERAL PHYSICS EM FIELDS NUMERICAL SOLUTION FOR FREDHOLM FIRST KIND INTEGRAL EQUATIONS OCCURRING IN SYNTHESIS OF ELECTROMAGNETIC FIELDS ELENA BÃUTU, ELENA PELICAN "Ovidius" University, Constanta, 900527. INTRODUCTION Problems in the classical theory of electromagnetic fields come from two fundamental groups
NASA EM Followup of LIGO-Virgo Candidate Events
NASA Technical Reports Server (NTRS)
Blackburn, Lindy L.
2011-01-01
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.
Geodesicas Nulas em Relatividade Geral Francisco Jo~ao Lopes
NatÃ¡rio, JosÃ©
GeodÂ´esicas Nulas em Relatividade Geral Francisco Jo~ao Lopes Instituto Superior TÂ´ecnico, LisboaÂ¸co de 2013 Resumo Pretende-se estudar raios de luz, ou seja, geodÂ´esicas nulas, em Relatividade GeralÂ´icio do sÂ´eculo XX, com a criaÂ¸c~ao da Teoria da Relatividade Restrita, por Einstein (que postulou que
EM Telemetry Tool for Deep Well Drilling Applications
Jeffrey M. Gabelmann
2005-11-15
This final report discusses the successful development and testing of a deep operational electromagnetic (EM) telemetry system, produced under a cooperative agreement with the United States Department of Energy's National Energy Technology Laboratory. This new electromagnetic telemetry system provides a wireless communication link between sensors deployed deep within oil and gas wells and data acquisition equipment located on the earth's surface. EM based wireless telemetry is a highly appropriate technology for oil and gas exploration in that it avoids the need for thousands of feet of wired connections. In order to achieve the project performance objectives, significant improvements over existing EM telemetry systems were made. These improvements included the development of new technologies that have improved the reliability of the communications link while extending operational depth. A key element of the new design is the incorporation of a data-fusion methodology which enhances the communication receiver's ability to extract very weak signals from large amounts of ambient environmental noise. This innovative data-fusion receiver based system adapts advanced technologies, not normally associated with low-frequency communications, and makes them work within the harsh drilling environments associated with the energy exploration market. Every element of a traditional EM telemetry system design, from power efficiency to reliability, has been addressed. The data fusion based EM telemetry system developed during this project is anticipated to provide an EM tool capability that will impact both onshore and offshore oil and gas exploration operations, for conventional and underbalanced drilling applications.
Análise da medição do raio solar em ultravioleta
NASA Astrophysics Data System (ADS)
Saraiva, A. C. V.; Giménez de Castro, C. G.; Costa, J. E. R.; Selhorst, C. L.; Simões, P. J. A.
2003-08-01
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.
Išmatuot? aukš?i? skirtum? redukavimas ivertinant vertikaliuosius žem?s paviršiaus judesius
NASA Astrophysics Data System (ADS)
Zakarevi?ius, Algimantas; Puzien?, R?ta
2010-01-01
Atliekant niveliavimo matavimus darbai dažnai t?siasi kelet? met?. D?l šios priežasties niveliavimo matavim? duomenims ?takos gali tur?ti vertikalieji Žem?s plutos judesiai. Siekiant išvengti šios ?takos, išmatuoti aukš?i? skirtumai turi b?ti redukuojami atsižvelgiant ? pasirinkt? epoch?. Tyrimai atlikti Lietuvos vertikaliojo geodezinio tinklo pavyzdžiu. Nustatyta, kad eksperimentiniame objekte niveliavimo matavimo rezultat? redukavimo, atsižvelgiant ? pasirinkt? epoch?, pataisos yra reikšmingos ir didesn?s už kitas apdorojant niveliavimo matavim? rezultatus skai?iuotas pataisas. Patais? d?l vertikali?j? Žem?s plutos judesi? ?tak? skai?iuoti niveliaciniuose ?jimuose rekomenduojama taikant regresinius vertikali?j? judesi? grei?i? prognozavimo arba judesi? grei?i? horizontali?j? gradient? modelius.
Elected medical staff leaders: who needs 'em?
Thompson, R E
1994-03-01
Authority, influence, and power are not synonyms. In working with elected medical staff leaders, a physician executive who chooses to exert authority may soon find him- or herself relatively powerless. But one who chooses to downplay authority, to influence through persuasion, and to coach leaders to lead effectively soon generates support for his or her ideas. The need to coax, cajole, explain, persuade, and "seek input" frustrates many leaders in all kinds of organizations. It would be much easier just to order people about. It's so tempting to think: "Who needs 'em? I'm the 'chief physician.' I know what needs to be done. Let's weigh anchor, take her out, and do what it takes to sail those rough, uncharted seas." If you really enjoy sailing a large ship in rough seas without a crew, go right ahead. Or if you think it makes sense to run an organization with only an executive staff and no knowledgeable middle managers, by all means let clinician leaders know that, now that you're aboard, they're just window-dressing. If you can make this approach work, well and good. Your life will be much less complicated, each day will have far fewer frustrations, and progress toward established goals will be much faster. However, given the reality of traditionally thinking physicians, it would be best to keep an up-dated resume in the locked lower left-hand drawer of your desk. PMID:10161050
DOE EM industry programs robotics development
Staubly, R.; Kothari, V.
1998-12-31
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.
Perfis de temperatura eletrônica em regiões HII
NASA Astrophysics Data System (ADS)
Copetti, M. V. F.
2003-08-01
As flutuações de temperatura eletrônica em regiões HII, inicialmente propostas para explicar as discrepâncias entre os valores de temperatura obtidos por diferentes métodos, têm sido apontadas como a causa mais provável das enormes diferenças encontradas entre as abundâncias químicas medidas através de linhas excitadas colisionalmente e de linhas de recombinação. Recentemente têm sido reportadas tentativas de detecção e quantificação diretas das flutuações de temperatura eletrônica através de medidas ponto a ponto, obtidas por meio de espectroscopia de fenda longa, das razões de linhas [OIII]l4263/l5007 e [NII]l5755/l6584, principais sensores de temperatura. Neste trabalho, utilizamos o código numérico de fotoionização Cloudy para avaliar a confiabilidade desse procedimento. Concluímos que, para valores de densidade eletrônica e de temperatura efetiva da estrela ionizante típicos das regiões HII, os perfis superficiais de temperatura obtidos via medidas do sensor [OIII]l4263/l5007 são bons traçadores dos gradientes internos de temperatura eletrônica. Já os perfis de temperatura eletrônica medidos por meio da razão [NII]l5755/l6584 não reproduzem os gradientes verdadeiros de temperatura.
Development of a Powerful EM Transmitter
NASA Astrophysics Data System (ADS)
Ahmad, Nur Azliza; Yahya, Noorhana; Zakariah, Muhammad Hanis; Puspitasari, Poppy
2009-06-01
Antenna is used as a transmitter and device for radiating or receiving electromagnetic waves in free space is applied in Seabed Logging (SBL). However, designing an antenna to propagate strong electromagnetic (EM) wave remains a challenge. This paper discussed the design and optimization of antenna types namely dipole, triangle, rectangle and hexagon with various materials and length. Simulation using Applied Wave Research (AWR) Design Environment Evaluation shows the radiation pattern of antenna and phase (0-360 degree) was carried out. The highest power of antenna obtained via simulation is 2.835 W which was for hexagon. Aluminum rods (100 mm diameter) and copper wire (0.8 mm diameter) with different length of 20 cm, 40 cm and 60 cm were used to investigate patterns of voltage peak-to-peak (Vp-p) at the detector. It was found that the copper wire gave that a higher Vp-p. Nickel Zinc Ferrite has been successfully synthesized by self combustion technique. X-Ray Diffraction of the nickel zinc ferrites demonstrated that it can be used as a magnetic feeder for the transmitter.
EM Task 9 - Centrifugal Membrane Filtration
Stevens, B.G.; Stepan, D.J.; Hetland, M.D.
1998-11-01
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.
Fu, J C; Chen, C C; Chai, J W; Wong, S T C; Li, I C
2010-06-01
We propose an automatic hybrid image segmentation model that integrates the statistical expectation maximization (EM) model and the spatial pulse coupled neural network (PCNN) for brain magnetic resonance imaging (MRI) segmentation. In addition, an adaptive mechanism is developed to fine tune the PCNN parameters. The EM model serves two functions: evaluation of the PCNN image segmentation and adaptive adjustment of the PCNN parameters for optimal segmentation. To evaluate the performance of the adaptive EM-PCNN, we use it to segment MR brain image into gray matter (GM), white matter (WM) and cerebrospinal fluid (CSF). The performance of the adaptive EM-PCNN is compared with that of the non-adaptive EM-PCNN, EM, and Bias Corrected Fuzzy C-Means (BCFCM) algorithms. The result is four sets of boundaries for the GM and the brain parenchyma (GM+WM), the two regions of most interest in medical research and clinical applications. Each set of boundaries is compared with the golden standard to evaluate the segmentation performance. The adaptive EM-PCNN significantly outperforms the non-adaptive EM-PCNN, EM, and BCFCM algorithms in gray mater segmentation. In brain parenchyma segmentation, the adaptive EM-PCNN significantly outperforms the BCFCM only. However, the adaptive EM-PCNN is better than the non-adaptive EM-PCNN and EM on average. We conclude that of the three approaches, the adaptive EM-PCNN yields the best results for gray matter and brain parenchyma segmentation. PMID:20042313
Astronomia para/com crianças carentes em Limeira
NASA Astrophysics Data System (ADS)
Bretones, P. S.; Oliveira, V. C.
2003-08-01
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.
Degradation of Benzodiazepines after 120 Days of EMS Deployment
McMullan, Jason T.; Jones, Elizabeth; Barnhart, Bruce; Denninghoff, Kurt; Spaite, Daniel; Zaleski, Erin; Silbergleit, Robert
2014-01-01
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
Emergency medical service (EMS): A unique flight environment
NASA Technical Reports Server (NTRS)
Shively, R. Jay
1993-01-01
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.
International Space Station (ISS) Emergency Mask (EM) Development
NASA Technical Reports Server (NTRS)
Toon, Katherine P.; Hahn, Jeffrey; Fowler, Michael; Young, Kevin
2011-01-01
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.
Flutuações da temperatura eletrônica em NGC 2438 e NGC 2440
NASA Astrophysics Data System (ADS)
Krabbe, A. C.; Copetti, M. V. F.
2003-08-01
Tradicionalmente, as abundâncias em nebulosas planetárias e regiões HII têm sido obtidas de linhas excitadas colisionalmente, as quais são fortemente dependentes da temperatura eletrônica. Alternativamente, as abundâncias químicas podem ser determinadas de linhas de recombinação, as quais são quase independententes da temperatura eletrônica. Entretanto, consideráveis diferenças têm sido encontradas entre estes dois métodos. Estas discrepâncias têm sido atribuídas às flutuações espaciais da temperatura eletrônica. Entretanto, as magnitudes necessárias de flutuações de temperatura eletrônica são consideravelmente mais altas do que aquelas preditas pelos modelos padrões de fotoionização e os mecânismos físicos que poderiam explicar as grandes flutuações de temperatura são desconhecidas. Desta forma, o estudo de variações da temperatura eletrônica em regiões HII e nebulosas planetárias tem ganho um renovado interesse. Neste trabalho apresentamos os resultados preliminares de um estudo observacional sobre variações internas da temperatura eletrônica nas nebulosas planetárias NGC 2440 e NGC 2438. Analisamos dados espectrofotométricos de fenda longa, com alta razão sinal-ruído, na faixa de 3300-6800 Å, com o espectrógrafo Cassegrain Boller & Chivens acoplado ao telescópio de 1.52 m do European Southern Observatory (ESO). Temperaturas eletrônicas foram derivadas da razão [OIII](l4959+l5007)/l4363 em diferentes posições em cada nebulosa planetária. Flutuações da temperatura eletrônica foram detectadas e suas magnitudes foram estimadas em NGC 2440 e NGC 2438.
Goodloe, Jeffrey M; Crowder, Christopher J; Arthur, Annette O; Thomas, Stephen H
2012-01-01
Purpose. There is a paucity of data regarding EMS stretcher-operation-related injuries. This study describes and analyzes characteristics associated with undesirable stretcher operations, with or without resultant injury in a large, urban EMS agency. Methods. In the study agency, all stretcher-related "misadventures" are required to be documented, regardless of whether injury results. All stretcher-related reports between July 1, 2009 and June 30, 2010 were queried in retrospective analysis, avoiding Hawthorne effect in stretcher operations. Results. During the year studied, 129,110 patients were transported. 23 stretcher incidents were reported (0.16 per 1,000 transports). No patient injury occurred. Four EMS providers sustained minor injuries. Among contributing aspects, the most common involved operations surrounding the stretcher-ambulance safety latch, 14/23 (60.9%). From a personnel injury prevention perspective, there exists a significant relationship between combative patients and crew injury related to stretcher operation, Fisher's exact test 0.048. Conclusions. In this large, urban EMS system, the incidence of injury related to stretcher operations in the one-year study period is markedly low, with few personnel injuries and no patient injuries incurred. Safety for EMS personnel and patients could be advanced by educational initiatives that highlight specific events and conditions contributing to stretcher-related adverse events. PMID:22606379
Discos de acresção em sistemas Be-X
NASA Astrophysics Data System (ADS)
Lopes de Oliveira, R.; Janot-Pacheco, E.
2003-08-01
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.
07/2014 -PPGSAN/SD/UFPR Deferimento das matrculas em disciplina isolada.
Paraná, Universidade Federal do
. A Coordenação do Programa de Pós-Graduação em Segurança Alimentar e Nutricional do Setor de Ciências da Saúde da isolada no Programa de Pós-graduação em Segurança Alimentar e Nutricional para o 2º semestre de 2014
Universidade Federal do Paran Programa de Ps-graduao em Fsica
Sharipov, Felix
Universidade Federal do Paraná Programa de Pós-graduação em Física Dissertação de Mestrado Victor;Universidade Federal do Paraná Programa de Pós-graduação em Física Dissertação de Mestrado Victor Juan Benites
Instituto de Sistemas e Robotica
em abundância naquela escola superior. O tra- balho, pintado em azul, branco e preto, as cores do dos materiais" nota Ca- rolina Azevedo. Daniel Matos, 19 anos, aluno do i s ano de Escultura da Escola
Developments in the EM-CCD camera for OGRE
NASA Astrophysics Data System (ADS)
Tutt, James H.; McEntaffer, Randall L.; DeRoo, Casey; Schultz, Ted; Miles, Drew M.; Zhang, William; Murray, Neil J.; Holland, Andrew D.; Cash, Webster; Rogers, Thomas; O'Dell, Steve; Gaskin, Jessica; Kolodziejczak, Jeff; Evagora, Anthony M.; Holland, Karen; Colebrook, David
2014-07-01
The Off-plane Grating Rocket Experiment (OGRE) is a sub-orbital rocket payload designed to advance the development of several emerging technologies for use on space missions. The payload consists of a high resolution soft X-ray spectrometer based around an optic made from precision cut and ground, single crystal silicon mirrors, a module of off-plane gratings and a camera array based around Electron Multiplying CCD (EM-CCD) technology. This paper gives an overview of OGRE with emphasis on the detector array; specifically this paper will address the reasons that EM-CCDs are the detector of choice and the advantages and disadvantages that this technology offers.
An Effective EMS Hardware and Software Interface- The Trained Operator
Cherry, C. L.
1986-01-01
stream_source_info ESL-IE-86-06-14.pdf.txt stream_content_type text/plain stream_size 17499 Content-Encoding ISO-8859-1 stream_name ESL-IE-86-06-14.pdf.txt Content-Type text/plain; charset=ISO-8859-1 AN EFFECTIVE EMS... HARDWARE AND SOFTWARE THE TRAINED OPER~TQR Christene ~. Cherry Johnson Controls Institute INTERFACE Milwaukee, ABSTRAC'l' A computerized Energy Management Sys tem (EMS) is a tool that allows the user to moni tor and control building heating...
SE1EM11 Differentiation and Integration Part A Dr Richard Mitchell, 2014 1
Mitchell, Richard
SE1EM11 Differentiation and Integration Part A © Dr Richard Mitchell, 2014 1 p1 RJM 10/09/14 SE1EM11 Differentiation and Integration Part A © Dr Richard Mitchell 2014 SE1EM11 - Engineering Maths Dr will see maths applied in module SE1CC11, for instance p2 RJM 10/09/14 SE1EM11 Differentiation
EM-based Joint Estimation and Detection for Multiple Antenna Cognitive Radios
Champagne, Benoît
EM-based Joint Estimation and Detection for Multiple Antenna Cognitive Radios Ayman Assra for multiantenna assisted cognitive radio (CR) us- ing the expectation-maximization (EM) algorithm. Considering), the EM-based JED scheme enhances the detection process of the multiple antenna CR with few iterations
EmSe: Supporting Children's Information Needs within a Hospital Environment
Theune, Mariët
Vries PuppyIR http://www.puppyir.eu Abstract. The Emma Search (EmSe) demonstrator developed for the Emma, and sensitive to the child's physical and emotional state. To address these, we developed the Emma Search (EmSe) engine for Emma Kinderziekenhuis (EKZ) at the Amsterdam Medical Centre1 . The goal of the EmSe service
EM Attack Is Non-Invasive? -Design Methodology and Validity Verification
International Association for Cryptologic Research (IACR)
EM attack sensor utilizes LC oscillators which detect vari- ations in the EM field around be therefore scaled together with the cryptographic LSI to be protected. The sensor prototype is designed based, side-channel information, such as power dissipation, electromagnetic (EM) radiation, and/or the timing
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM BIOTECNOLOGIA E BIODIVERSIDADE
Maier, Rudolf Richard
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Maier, Rudolf Richard
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Convergence results for the EM approach to mixtures of experts architectures
Michael I. Jordan; Lei Xu
1995-01-01
The Expectation-Maximization (EM) algorithm is an iterative approach to maximum likelihood parameter estimation. Jordan and Jacobs recently proposed an EM algorithm for the mixture of experts architecture of Jacobs, Jordan, Nowlan and Hinton (1991) and the hierarchical mixture of experts architecture of Jordan and Jacobs (1992). They showed empirically that the EM algorithm for these architectures yields significantly faster convergence
ANÁLISE DAS ESTRATÉGIAS DE MARKETING EM UMA FECULARIA DA REGIÃO DE TUPÃ-SP
Joao Guilherme de Camargo Ferraz Machado; Timoteo Ramos Queiroz; Andrea Rossi Scalco
2008-01-01
Nas últimas décadas, verificou-se uma mudança no comportamento do consumidor no sentido de adotar uma postura mais consciente em relação aos produtos que adquire. No setor alimentício, essa evolução é nítida, em função da busca por uma maior qualidade de vida, agregando à dieta questões de saúde, incluindo produtos com menor conteúdo de gorduras e calorias, rico em fibras, pobre
COLOR IMAGE SEGMENTATION USING A SELF-INITIALIZING EM Dana Elena Ilea and Paul F. Whelan
Whelan, Paul F.
COLOR IMAGE SEGMENTATION USING A SELF-INITIALIZING EM ALGORITHM Dana Elena Ilea and Paul F. Whelan-Maximization (EM) algorithm that we apply for color image segmentation. Since this algorithm partitions the data based on an initial set of mixtures, the color segmentation provided by the EM algorithm is highly
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Floeter, Sergio Ricardo
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Paraná, Universidade Federal do
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UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM EDUCAO FSICA
Maier, Rudolf Richard
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Hanazaki, Natalia
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Hanazaki, Natalia
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Maier, Rudolf Richard
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Technology Transfer Automated Retrieval System (TEKTRAN)
Em B. phoenicis (Geijskes) (Acari: Tenuipalpidae), ácaro vetor de importantes fitovírus, a presença de endossimbiontes do gênero Cardinium relaciona-se ao processo de feminilização dos machos, acarretando em elevada proporção de fêmeas em populações naturais. Até o momento, não é conhecido se este e...
On the Origin of the Standardization Sensitivity in RegEM Climate Field Reconstructions*
Kaplan, Alexey
On the Origin of the Standardization Sensitivity in RegEM Climate Field Reconstructions* JASON E April 2008) ABSTRACT The regularized expectation maximization (RegEM) method has been used in recent millennium. Original pseudoproxy experiments that tested RegEM [with ridge regression regularization (Reg
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO PROFISSIONAL EM DESENVOLVIMENTO
Maier, Rudolf Richard
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Maier, Rudolf Richard
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Maier, Rudolf Richard
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Maier, Rudolf Richard
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Paterson, Kenny
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ICE-EM RNSA 2007 Workshop on Pairing Based Cryptography 1 Certificateless Cryptography I
Paterson, Kenny
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Maier, Rudolf Richard
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UNIVERSIDADE DE BRASLIA PROGRAMA DE RESIDNCIA EM MEDICINA VETERINRIA/REA PROFISSIONAL
Maier, Rudolf Richard
1 UNIVERSIDADE DE BRASÍLIA PROGRAMA DE RESIDÊNCIA EM MEDICINA VETERINÁRIA/ÁREA PROFISSIONAL EDITAL "Lato sensu" EM ÁREA PROFISSIONAL DE SAÚDE/MEDICINA VETERINÁRIA PARA O PRIMEIRO PERÍODO LETIVO DE 2015 1. PREÂMBULO 1.1. O Coordenador do Programa de Residência em Medicina Veterinária COREMEV/UnB, vinculado à
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM TECNOLOGIA AMBIENTAL E
Maier, Rudolf Richard
1 UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM TECNOLOGIA AMBIENTAL E RECURSOS HÍDRICOS EDITAL N°2/2014 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM TECNOLOGIA AMBIENTAL E.1 O Coordenador do Programa de Pós-Graduação em Tecnologia Ambiental e Recursos Hídricos da
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM TECNOLOGIAS QUMICA E
Lucero, Jorge Carlos
UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM TECNOLOGIAS QUÍMICA E BIOLÓGICA EDITAL Nº 2/2012 SELEÇÃO DE CANDIDATOS AO PROGRAMA DE PÓS-GRADUAÇÃO EM TECNOLOGIAS QUÍMICA E BIOLÓGICA PARA O CURSO DE-Graduação em Tecnologias Química e Biológica, no uso de suas atribuições legais, torna público e estabelece
Centro de Cincias Agrrias Coordenao do Curso de Graduao em Cincia e Tecnologia de Alimentos
Floeter, Sergio Ricardo
Centro de Ciências Agrárias Coordenação do Curso de Graduação em Ciência e Tecnologia de Alimentos-2728 Regimento Interno do Curso de Graduação em Ciência e Tecnologia de alimentos Capítulo I Das disposições iniciais Art. 1º - O Curso de Graduação em Ciência e Tecnologia de Alimentos, instituído pela Resolução 005
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM TECNOLOGIA AMBIENTAL E
Lucero, Jorge Carlos
UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM TECNOLOGIA AMBIENTAL E RECURSOS HÍDRICOS EDITAL N°2/2011 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM TECNOLOGIA AMBIENTAL E. PREÂMBULO 1.1 O Coordenador do Programa de Pós-Graduação em Tecnologia Ambiental e Recursos Hídricos da
RESOLUO No Fixa o Currculo Pleno do Curso de Tecnologia em
Paraná, Universidade Federal do
RESOLUÇÃO No 51/11-CEPE Fixa o Currículo Pleno do Curso de Tecnologia em Orientação Comunitária do/2010-01 e por unanimidade de votos, RESOLVE: Art. 1 o - O Currículo Pleno do Curso de Tecnologia em, Artes e Linguagem e Comunicação. Art. 2 0 A integralização do currículo do Curso de Tecnologia em
RESOLUO N45/11CEPE Fixa o currculo do Curso de Tecnologia em Gesto de
Paraná, Universidade Federal do
RESOLUÇÃO Nº45/11CEPE Fixa o currículo do Curso de Tecnologia em Gestão de Turismo, do Setor unanimidade de votos, RESOLVE: Art. 1º O Currículo do curso de Graduação em Tecnologia em Gestão de Turismo Turismo I Cultura, História e Patrimônio C.2. MUNDO DO TRABALHO Tecnologia da Informação no Turismo D
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM TECNOLOGIA AMBIENTAL E
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM TECNOLOGIA AMBIENTAL E RECURSOS HÍDRICOS EDITAL No. 1/2011 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM TECNOLOGIA AMBIENTAL E Coordenador do Programa de Pós-Graduação em Tecnologia Ambiental e Recursos Hídricos da Universidade de
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM TECNOLOGIA AMBIENTAL E
Maier, Rudolf Richard
1 UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM TECNOLOGIA AMBIENTAL E RECURSOS HÍDRICOS EDITAL N°1/2014 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM TECNOLOGIA AMBIENTAL E Coordenador do Programa de Pós-Graduação em Tecnologia Ambiental e Recursos Hídricos da Universidade de
Airborne EM for geothermal and hydrogeological mapping
NASA Astrophysics Data System (ADS)
Menghini, A.; Manzella, A.; Viezzoli, A.; Montanari, D.; Maggi, S.
2012-12-01
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.
Investigation of Array E Experiment EM! Test Data Validity
Rathbun, Julie A.
of the qualification testing of changes made to this experiment. These changes will be incorporated in the Protu LMS and a change in the Housekeeping Multiplexer are planned as a part of the qualification testing for this newInvestigation of Array E Experiment EM! Test Data Validity NO. ATMllOO PAGE 1 REV. NO. OF__§__ DATE
492 BOOK REVIEWS the missing data paradigm, and the EM
Neumaier, Arnold
492 BOOK REVIEWS the missing data paradigm, and the EM algorithm. The book is well organized an annoying habit of omitting articles. The level of the book is that of advanced undergraduate courses for the book: researchers studyÂ ing Monte Carlo methods, scientists using Monte Carlo, and graduate students
Texas Hold 'em Online Poker: A Further Examination
ERIC Educational Resources Information Center
Hopley, Anthony A. B.; Dempsey, Kevin; Nicki, Richard
2012-01-01
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…
Reservoir characterization and steam flood monitoring with crosshole EM
Wilt, M. [Lawrence Livermore National Lab., CA (United States); Torres-Verdin, C. [Univ. of California, Berkeley, CA (United States)
1995-06-01
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.
ISSN 0103-9741 Monografias em Cincia da Computao
Barbosa, Alberto
ISSN 0103-9741 Monografias em Ciência da Computação n° 24/06 Emergency Environments for the Oil Environments for the Oil & Gas Exploration and Production Industry * Enio Emanuel Ramos Russo1 Alberto Barbosa challenges faced when defining and building virtual workspaces for oil & gas Exploration & Production (E
A shape constrained MAP-EM algorithm for colorectal segmentation
NASA Astrophysics Data System (ADS)
Wang, Huafeng; Li, Lihong; Song, Bowen; Han, Fangfang; Liang, Zhengrong
2013-02-01
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.
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
little attention. This work analyzes, from the perspective of CMMI, methods used to generate software, Function Point Analysis, Software Project Management, CMMI. Resumo. Estimativas documentadas constituem baseada em CMMI, métodos utilizados para geração de estimativas de tamanho de projetos de software
58 EMS Newsletter March 2011 Letters to the Editor
Kutateladze, Semen Samsonovich
58 EMS Newsletter March 2011 Letters to the Editor litical, racial, and social differences.-P. Bourguignon, R. Remmert & F. Hirzebruch "Henri Cartan 19042008", European Mathematical Society Newsletter of this newsletter. Fortunately Haggstrom's concerns are rather straightforward to ad- dress and I hope
Um método de avaliação para interfaces baseadas em mapas
Maria Lúcia Arraes Seixas; Clarisse Sieckenius de Souza
RESUMO A integração da informação geográfica e dos mapas digitais nos Sistemas de Informação Geográfica (SIGs) produz soluções para vários grupos de usuários. Porém, vem crescendo o número de usuários não especializados que utilizam SIGs na Web ou em desktop para localizar endereços, planejar rotas, planejar viagens, encontrar lugares, e assim por diante. Estas aplicações menos complexas e destinadas a
Life at Low Reynolds Number E.M. Purcell
Millis, Andrew
Life at Low Reynolds Number E.M. Purcell Lyman Laboratory, Harvard University, Cambridge, Mass transparent vessel of corn syrup, projected by an overhead projector turned on its side. Some essential hand that of water. The viscosities have a big range but they stop at the same place. I don't understand that. That
A Science Service Feature 1 WHYTHE"EmHER ?
A Science Service Feature 1 WHYTHE"EmHER ? Dr. Charles F. Erooks, Secretary, American the plain white f l a g has a dark trh@&aLr f l a g above i t the prophesy is fair and warmer by Science Service Science Service, 1115 Conn. Ave., Washington, D .C . #12;
AO DO FLUXO DE POT ENCIA EM AMBIENTE VETORIAL USANDO
Coutinho, Alvaro L. G. A.
SOLU Â¸ C ~ AO DO FLUXO DE POT â?? ENCIA EM AMBIENTE VETORIAL USANDO O M ' ETODO DO GRADIENTE BI--970, Brasil. Resumo Este trabalho apresenta um m'etodo de soluÂ¸c~ao do problema de Fluxo de Potâ??encia usando o. Palavras Chaves: Fluxo de Potâ??encia, M'etodos tipo Gradiente Conjugado, Processamento Vetorial. 1 Introdu
Hierarchical Mixtures of Experts and the EM Algorithm
Michael I. Jordan; Robert A. Jacobs
1994-01-01
We present a tree-structured architecture for supervised learning. The statistical model underlying the architecture is a hierarchical mixture model in which both the mixture coefficients and the mixture components are generalized linear models (GLIM's). Learning is treated as a maximum likelihood problem; in particular, we present an Expectation-Maximization (EM) algorithm for adjusting the parameters of the architecture. We also develop
Hierarchical mixtures of experts and the EM algorithm
Michael I. Jordan; Robert A. Jacobs
1993-01-01
We present a tree-structured architecture for supervised learning. The statistical model underlying the architecture is a hierarchical mixture model in which both the mixture coefficients and the mixture components are generalized linear models (GLIMs). Learning is treated as a maximum likelihood problem; in particular, we present an expectation-maximization (EM) algorithm for adjusting the parameters of the architecture. We also develop
AO EFICIENTE A PADR ~ COMPARTILHAMENTO EM SOFTWARE DSMS
Bianchini, Ricardo
TO SHARING PATTERNS IN SOFTWARE DSMS Luiz Rodolpho Rocha Monnerat December of 1997 Advisor: Ricardo BianchiniADAPTACÂ¸ ~ AO EFICIENTE A PADR ~ OES DE COMPARTILHAMENTO EM SOFTWARE DSMS Luiz Rodolpho Rocha. Ricardo Bianchini, Ph.D. Prof. Cl'audio Amorim, Ph.D. Prof. Jairo Panetta, Ph.D. Prof. S'ergio Takeo
14 EMS Newsletter September 2008 Seminar Sophus Lie
Fialowski, Alice
, Budapest, Hungary) and Ãgnes SzilÃ¡rd (AlfrÃ©d RÃ©nyi Institute of Mathematics, Budapest, Hungary) About was particularly important Marius Sophus Lie (1842Â1899) Seminar Sophus Lie XXXV, Budapest, Hungary #12;News EMS
Statistical Physics, Mixtures of Distributions, and the EM Algorithm
Alan L. Yuille; Paul E. Stolorz; Joachim Utans
1994-01-01
We show that there are strong relationships between approaches to optmization and learning based on statistical physics or mixtures of experts. In particular, the EM algorithm can be interpreted as converging either to a local maximum of the mixtures model or to a saddle point solution to the statistical physics system. An advantage of the statistical physics approach is that
Tecnologia Adaptativa Aplicada à Otimização de Código em Compiladores
Júlio C. Luz; João J. Neto
The programming memory space of embedded microcontrolled systems is usually limited. Although, compilers nowadays apply optimizing transformations to the embedded software, the lack of memory space can become a critical probl em to the designer with the introduction of new features and corrections in the original softwa re. In contrast, workstations hosting development systems for embedded applications are faster and
DISSERTAO DE MESTRADO EM ENGENHARIA REDUO DE COMPLEXIDADE
de Queiroz, Ricardo L.
TECNOLOGIA #12;#12;UNIVERSIDADE DE BRASÍLIA Faculdade de Tecnologia DISSERTAÇÃO DE MESTRADO EM ENGENHARIA Dissertação de mestrado submetida ao Departamento de Engenharia Elétrica da Faculdade de Tecnologia da Processamento de Sinais, 2008). Dissertação de Mestrado. Universidade de Brasília. Faculdade de Tecnologia
TESE DE DOUTORADO EM ENGENHARIA DE SISTEMAS ELETRNICOS E AUTOMAO
de Queiroz, Ricardo L.
BRASÍLIA FACULDADE DE TECNOLOGIA #12;#12;UNIVERSIDADE DE BRASÍLIA FACULDADE DE TECNOLOGIA DEPARTAMENTO DE Tecnologia TESE DE DOUTORADO EM ENGENHARIA DE SISTEMAS ELETRÔNICOS E AUTOMAÇÃO REALCE DE VÍDEO PARA de Engenharia Elétrica da Faculdade de Tecnologia da Universidade de Brasília, como parte dos
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
por gerar dados de forma automática e inseri-los em bancos de dados criados a partir de diferen- tesDB foi utilizado. Palavras-chave: Geração de Dados, Banco de Dados, Testes, JMeter. #12;ii In charge Geração de Dados Janaina de Souza Horácio Andrew Diniz da Costa Carlos José Pereira de Lucena Soeli
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
esquema é uma questão fundamental em aplicações de banco de dados, tais como, mediação de consultas e armazéns de dados. Neste tra- balho, assumimos que os esquemas de bancos de dados a serem alinhados são. Palavras-chave: banco de dados, alinhamento, esquema, similaridade. ___________________ * This work has
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
-Sintonia do Projeto Físico de Banco de Dados José Maria Monteiro Sérgio Lifschitz Ângelo Brayner Departamento Projeto F´isico de Banco de Dados Jos´e Maria Monteiro, S´ergio Lifschitz, ^Angelo Brayner1 1 Mestrado em Design Resumo. O desempenho dos servidores de bancos de dados ´e fator chave para o sucesso das aplica
Interoperabilidade de Objetos em Sistemas de Bancos de Dados Heterogneos
Endler, Markus
Interoperabilidade de Objetos em Sistemas de Bancos de Dados Heterogêneos Elvira Maria Antunes@inf.pucrio.br PUCRioInf.MCC45/96 Dezembro, 1996 Resumo Sistemas de bancos de dados heterogêneos têm sido apontados informações, interligados por redes de comunicação. Na arquitetura dos sistemas de bancos de dados
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
banco de dados através de uma interface ODBC. Finalmente levando a um estágio operacional, fornece memória principal quanto sobre o banco de dados em Oracle. Palavras-chave: Especificação Conceitual, Modelo Entidades-Relacionamentos, Bancos de Dados Relacionais, Geração de Planos, Simulação, Programação
Learning Context Cues for Synapse Segmentation in EM Volumes
Fua, Pascal
the numer- ous other organelles that appear within an EM volume, including those whose local textural methods either require first finding cell membranes [2] or operate on individual 2D slices [3], thus vector ni. 2 Related Work Several fully automated approaches to reliable segmentation of organelles
A Greedy EM Algorithm for Gaussian Mixture NIKOS VLASSIS1
Likas, Aristidis
A Greedy EM Algorithm for Gaussian Mixture Learning NIKOS VLASSIS1 and ARISTIDIS LIKAS2 1 RWCP a Gaussian mixture which tries to overcome these limitations. In particular, starting with a single component and adding components sequentially until a maximum number k, the algorithm is capable of achieving solutions
ECE 341: Electromagnetic Fields I EM devices and systems
Connors, Daniel A.
ECE 341: Electromagnetic Fields I EM devices and systems - Can compute and analyze potentials conditions to solve complex static and low-frequency electromagnetic-field problems - Can mathematically-frequency electromagnetic- field problems utilizing physical conceptual reasoning and mathematical synthesis of solutions
ISSN 0103-9741 Monografias em Cincia da Computao
Barbosa, Simone Diniz Junqueira
- CEP 22451-900 RIO DE JANEIRO - BRASIL #12;Monograas em Ciência da Computação, No. 25/09 ISSN: 0103, Personal Agents, User Preferences. Resumo. Agentes pessoais estão se tornando populares por automatizar tarefas para usuários. Dado que estes agentes representam indivíduos, existe a necessidade de cap- turar
EM Effects on Semiconductor Devices, Gates and Integrated Circuit
Anlage, Steven
characterize microwave coupling on integrated circuits and its effect on device and circuit performance Method. · Task 1 focuses on detailed modeling of MOSFETs to understand their internal mechanisms of EM induced. Electron Transport Physics Include: -Acoustic & Optical Phonons -Band Structure -Ionized Impurities -Impact
RURALSIM: the design and implementation of a rural EMS simulator.
Shuman, L J; Wolfe, H; Gunter, M J
1992-01-01
Why were these applications of simulation technology unsuccessful? Parochialism, the volunteer nature of EMS planning, and limited regional commitment to resolve such complex problems at the local level all combined to present significant barriers to implementation. Political factors which posed the most significant barriers included: conservative attitudes concerning the funding and regulation of EMS activities by local governments; general opposition to governmental intervention in the private sector; strong resistance to mandatory standards for EMS; jurisdictional disputes between EMS-related agencies; lack of cooperation between the local governments; competition between prehospital-care providers and between hospitals; overemphasis on local jurisdictional boundaries in the planning and delivery of services; and the allocation of EMS resources, such as ambulances, according to political priorities, rather than more objective criteria. Based upon the results of the four field tests, the following observations are relevant: 1. RURALSIM is a very complex simulator. While every effort was made to assure generalizability, for any given situation, it required extensive modification and tailoring. The result was a model capable of handling a rather diverse set of situations, but one that could not be turned over to the general public for use. To implement RURALSIM required the participation of the University of Pittsburgh research team. The newer simulation languages now available alleviate this problem somewhat. 2. RURALSIM's complexity was needed to examine the different alternatives proposed by local planners. It was particularly needed in order to simulate each region's existing system. Such "base-line" simulations were required in order to achieve face validity and provide a basis for comparing alternatives. 3. With hindsight, a major weakness was the limited amount of face-to-face interaction between local planners and decision makers and the University of Pittsburgh staff. Only two trips to the region were budgeted. This proved to be insufficient and placed too much responsibility for model interpretation and analysis on the local contractors. 4. In none of the four test sites did the contractors and/or local health planners have the authority, influence and/or incentives necessary to develop regional EMS systems. In particular, none of the contractors were in the position to be decision makers, nor was there ever only one decision maker. This is not a criticism of the contractors, who did their best under difficult circumstances. Rather, it is a criticism of the state of eMS system development in the US in the early 1980s. There were few examples where regional systems developed successfully in the face of serious opposition from local interests.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1391744
Persistent topology for cryo-EM data analysis.
Xia, Kelin; Wei, Guo-Wei
2015-08-01
In this work, we introduce persistent homology for the analysis of cryo-electron microscopy (cryo-EM) density maps. We identify the topological fingerprint or topological signature of noise, which is widespread in cryo-EM data. For low signal-to-noise ratio (SNR) volumetric data, intrinsic topological features of biomolecular structures are indistinguishable from noise. To remove noise, we employ geometric flows that are found to preserve the intrinsic topological fingerprints of cryo-EM structures and diminish the topological signature of noise. In particular, persistent homology enables us to visualize the gradual separation of the topological fingerprints of cryo-EM structures from those of noise during the denoising process, which gives rise to a practical procedure for prescribing a noise threshold to extract cryo-EM structure information from noise contaminated data after certain iterations of the geometric flow equation. To further demonstrate the utility of persistent homology for cryo-EM data analysis, we consider a microtubule intermediate structure Electron Microscopy Data (EMD 1129). Three helix models, an alpha-tubulin monomer model, an alpha-tubulin and beta-tubulin model, and an alpha-tubulin and beta-tubulin dimer model, are constructed to fit the cryo-EM data. The least square fitting leads to similarly high correlation coefficients, which indicates that structure determination via optimization is an ill-posed inverse problem. However, these models have dramatically different topological fingerprints. Especially, linkages or connectivities that discriminate one model from another, play little role in the traditional density fitting or optimization but are very sensitive and crucial to topological fingerprints. The intrinsic topological features of the microtubule data are identified after topological denoising. By a comparison of the topological fingerprints of the original data and those of three models, we found that the third model is topologically favored. The present work offers persistent homology based new strategies for topological denoising and for resolving ill-posed inverse problems. Copyright © 2015?John Wiley & Sons, Ltd. PMID:25851063
População estelar nuclear e extranuclear em galáxias Seyfert 2
NASA Astrophysics Data System (ADS)
Raimann, D. I.; Storchi-Bergmann, T.; Cid Fernandes, R., Jr.; Delgado, R. M. G.; Schmitt, H.; Heckman, T.; Leitherer, C.
2003-08-01
A luz das estrelas foi, historicamente, vista por observadores de AGNs como uma poluição inconveniente. Conseqüentemente, a informação contida nas características estelares foi, durante muito tempo, largamente omitida. Nos primeiros estudos, o método empregado para remover esta contaminação estelar foi representá-la por um template de galáxia elíptica e subtraí-la do espectro observado, restando o puro AGN como um resíduo. Hoje sabemos que não é tão simples representar essa população. Vários estudos têm mostrado a presença de formação estelar recente próxima a região nuclear de galáxias Seyfert. Neste trabalho foi revisada a abordagem tradicional, tendo-se focalizado a análise na luz estelar. Espectros óticos de fenda longa, com alta razão sinal/ruído, foram usados para estudar a variação radial das larguras equivalentes de linhas de absorção e cores do contínuo. Utilizando o método de síntese espectral de populações estelares, foram estimadas as contribuições de populações estelares de diferentes idades (e de um contínuo tipo lei de potência) para a luz integrada das galáxias, em 4020A. As principais conclusões deste trabalho são: na região nuclear, mais da metade das galáxias Seyfert 2 da amostra (57%) apresenta contribuições das populações com 100 milhões de anos ou mais jovens superior a 20% do fluxo em 4020A, enquanto que em cerca de 40% delas a componente de 3 milhões de anos (e/ou luz que provem de um núcleo ativo) tem contribuição significativa (maior do que 10%). Estas contribuições em geral decrescem quando se vai para regiões mais distantes do centro das galáxias, respectivamente 53% e 30% a 1kpc, 40% e 15% a 3kpc do centro das galáxias. Estes resultados foram comparados com aqueles obtidos para uma amostra de galáxias não ativas de mesmo tipo de Hubble das Seyfert. Em uma análise inicial nota-se que em geral as galáxias Seyfert apresentam contribuições das populações de 100 milhões de anos maiores do que aquelas encontradas nas galáxias não ativas, sugerindo uma ligação entre a formação estelar e a atividade em galáxias.
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.
An Evaluation of DOE-EM Public Participation Programs
Bradbury, Judith A.; Branch, Kristi M.; Malone, Elizabeth L.
2003-02-28
This report evaluates the scope and effectiveness of the public participation pr ograms, including Site-Specific Advisory Boards (SSABs), at seven U.S. Departmen t of Energy (DOE) sites: Fernald, Hanford, Los Alamos, Nevada, Oak Ridge, Paduc ah, and Savannah River. The primary purpose of the study is to assist both DOE Field and Headquarters managers in reviewing and understanding lessons learned o ver the past decade concerning public participation programs administered by the DOE Office of Environmental Management (EM). The evaluation provides a snapsh ot of selected EM public participation programs at a particular point of time. It is based on interviews and site visits conducted between January and June 200 2- a time of change within the program. The study focuses on public participati on programs that incorporate a variety of activities and address a wide range of individual site activities and decisions. It uses the Acceptability Diamond as an evaluative framework to answer questions about stakeholders' experiences wit h, and assessment of, DOE-EM's public participation programs. The Acceptability Diamond, which was developed by researchers from the Pacific Northwest National Laboratory in previous research, identifies four program dimensions - substanti ve issues, decision-making process, relationships, and accountability - that det ermine the effectiveness of an agency's interactions with local communities. Es sentially, a public participation program may be deemed effective to the extent that it provides for open disclosure and addresses all four acceptability dimens ions in ways that are appropriate and effective for a particular community and s ituation. This framework provides a guide for agencies to 1) set objectives, 2) design public participation and oversight programs, and 3) set criteria for eva luating program effectiveness. In the current study, where the framework is use d as a means of assessing program effectiveness, the focus is on stakeholders' p erspectives of public participation: on the nature of DOE-EM's public disclosure and the four interrelated dimensions of DOE-EM's interactions with its neighbor ing communities
Neirotti, Juan Pablo
Approved Module Information for EM4031, 2014/5 Module Title/Name: Logistics and Transportation Module Learning Information Module Aims: This module will explore the role of logistics, applications and systems in all aspects of logistics (e.g. inventory management, warehousing) - Analyse supply
de Vries, Sjoerd J.; Zacharias, Martin
2012-01-01
Many of the most important functions in the cell are carried out by proteins organized in large molecular machines. Cryo-electron microscopy (cryo-EM) is increasingly being used to obtain low resolution density maps of these large assemblies. A new method, ATTRACT-EM, for the computational assembly of molecular assemblies from their components has been developed. Based on concepts from the protein-protein docking field, it utilizes cryo-EM density maps to assemble molecular subunits at near atomic detail, starting from millions of initial subunit configurations. The search efficiency was further enhanced by recombining partial solutions, the inclusion of symmetry information, and refinement using a molecular force field. The approach was tested on the GroES-GroEL system, using an experimental cryo-EM map at 23.5 Å resolution, and on several smaller complexes. Inclusion of experimental information on the symmetry of the systems and the application of a new gradient vector matching algorithm allowed the efficient identification of docked assemblies in close agreement with experiment. Application to the GroES-GroEL complex resulted in a top ranked model with a deviation of 4.6 Å (and a 2.8 Å model within the top 10) from the GroES-GroEL crystal structure, a significant improvement over existing methods. PMID:23251350
Yang, Yang; Longini, Ira M.; Halloran, M. Elizabeth; Obenchain, Valerie
2012-01-01
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. PMID:22506893
Composting of rice straw with effective microorganisms (EM) and its influence on compost quality.
Jusoh, Mohd Lokman Che; Manaf, Latifah Abd; Latiff, Puziah Abdul
2013-01-01
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. PMID:23390930
NASA Astrophysics Data System (ADS)
Dos Santos, L. C.; Kintopp, J. A.; Jatenco-Pereira, V.; Opher, R.
2003-08-01
Ondas Alfvén em plasma astrofísico têm sido objeto de intenso estudo nas últimas décadas pelo fato de apresentarem papel importante em muitas áreas de pesquisa na astrofísica. Particularmente são importantes no mecanismo de aquecimento da coroa solar; em ventos estelares; em jatos galácticos e extragalácticos; em discos protoestelares, etc. A formulação para diferenças finitas no domínio do tempo (FDTD), aplicada a plasma magnetizado é desenvolvida para estudo das propriedades de ondas Alfvén em três dimensões (3D-FDTD). O método é aplicado inicialmente a um plasma homogêneo e isotérmico imerso em uma região com campo magnético externo B0, que sofre uma pequena perturbação. Uma vez gerada a onda, esta perturbação é retirada e, então analisamos a evolução temporal das ondas, bem como a forma de seu amortecimento.
Hara, Carmem Satie
Um Estudo sobre Bancos de Dados em Grafos Nativos Raqueline R. M. Penteado, Rebeca Schroeder, Diego. Resumo. Sistemas de banco de dados em grafos suportam aplicacÂ¸~oes baseadas em modelos de dados cuja, bancos de dados em grafos classificados como nativos s~ao capazes de executar consultas de forma
População nuclear e extranuclear em rádio-galáxias
NASA Astrophysics Data System (ADS)
Raimann, D. I.; Storchi-Bergmann, T.; Quintana, H.; Alloin, D.; Hunstead, R.; Wisotzki, L.
2003-08-01
A natureza do contínuo UV/ótico em rádio-galáxias é muito importante para o seu entendimento. Em baixos redshifts existem evidências de que muitas delas são dominadas no ótico por luz de estrelas velhas, características de galáxias early-type e em altos redshifts a característica dominante é um excesso de luz no UV, freqüentemente associado com estruturas que estão alinhadas aos eixos das estruturas rádio em grande escala. Inicialmente esse excesso foi interpretado como devido a episódios intensos de formação estelar nas galáxias hospedeiras. Entretanto, as descobertas dos alinhamentos entre as estruturas UV e rádio modificaram essa idéia. Foi proposto que a formação estelar é iniciada pela passagem do jato rádio através do meio interestelar das galáxias hospedeiras. A natureza do excesso UV começou a ser compreendida em um estudo detalhado do continuo ótico da 3C321, onde se concluiu que o contínuo desta galáxia tem origem multicomponente, com contribuições de populações velhas e intermediárias, de luz espalhada oriunda de um quasar obscurecido e do contínuo nebular. No presente trabalho estudamos a população nuclear e extranuclear de uma amostra de 24 rádio-galáxias, utilizando espectros óticos de fenda longa, com alta razão sinal/ruído. Através do método de síntese espectral de populações estelares, foram estimadas as contribuições de populações estelares de diferentes idades (e de um contínuo tipo lei de potência devido a um AGN, FC) para a luz integrada das galáxias, em 4020Å. As principais conclusões deste trabalho são: apenas quatro dos objetos estudados têm contribuições significativas (maiores do que 10%) das populações de 100 milhões de anos ou mais jovens (ou de FC) ao longo da região espacial estudada (6 kpc centrais); nenhuma das rádio-galáxias de tipo FRI estudadas tem contribuição significativa destas populações ao longo desta região; duas (de oito) de tipo FRII tem contribuições significativas da luz que vem do AGN, na região nuclear; uma tem contribuição significativa das populações de 100 milhões de anos e mais jovens ao longo dos 4 kpc centrais, indicando claramente a presença de formação estelar recente. Comparando estes resultados com aqueles obtidos para uma amostra de galáxias não ativas de mesmo tipo de Hubble das rádio, encontramos que a principal diferença entre as duas amostras está na contribuição da população de 1 bilhão de anos, geralmente maior nas rádio-galáxias.
Sanjay M. Wagh
2004-09-12
In non-relativistic as well as in special relativistic quantum theory, {\\em mass} and {\\em charge} are {\\em pure numbers} appearing in various (quantum) operators and admit {\\em any values}, {\\it ie}, values for these quantities are to be prescribed {\\em by hand}. This is, in a theory of probability, understandable since we need to {\\em assume} some {\\em intrinsic} properties of the object we are calculating the probability about. Then, if we {\\em specify}, in some satisfactory manner, mass and charge for a point of the space in a suitable general-relativistic framework, the quantum theoretical framework could, in principle, be {\\em obtainable} within it. Heuristic arguments are presented to show that a {\\em natural unification} of the quantum theory and the general theory of relativity is achievable in this manner.
Magnetic field effects on endcap EM calorimetry in SDC
Green, D.
1993-01-25
The SDC calorimeter will be immersed in a strong magnetic field in the endcap region because of the solenoid which supplies the SDC tracking field. This flux must be returned through the endcap region of the electromagnetic (EM) and hadronic (HAD) calorimeters. Since magnetic fields are known to induce changes in the light output of plastic scintillator, the endcap will need to be recalibrated once the solenoid is energized. In addition, gradients in the field will create nonuniformities in the calorimetric response. The ``induced constant term`` in the EM and HAD calorimeters due to the inhomogeneities induced by the magnetic field are here evaluated in order to see that SDC performance specifications are not compromised.
Magnetic field effects on endcap EM calorimetry in SDC
Green, D.
1993-01-25
The SDC calorimeter will be immersed in a strong magnetic field in the endcap region because of the solenoid which supplies the SDC tracking field. This flux must be returned through the endcap region of the electromagnetic (EM) and hadronic (HAD) calorimeters. Since magnetic fields are known to induce changes in the light output of plastic scintillator, the endcap will need to be recalibrated once the solenoid is energized. In addition, gradients in the field will create nonuniformities in the calorimetric response. The induced constant term'' in the EM and HAD calorimeters due to the inhomogeneities induced by the magnetic field are here evaluated in order to see that SDC performance specifications are not compromised.
Instabilidade de Kelvin-Helmholtz em Raios Cometários
NASA Astrophysics Data System (ADS)
Matsuura, O. T.; Shigueoka, H.; Voelzke, M. R.
1995-08-01
Raios cometários são estruturas finas e longas da cauda de cometas do Tipo I (ou de plasma). Como eles apresentam simetria cilíndrica, admitem modelos MHD simples. Este trabalho explora essa possibilidade, apresentando um estudo sistemático da estabilidade e das oscilações de raios cometários na aproximação de plasma homogêneo. O critério de estabilidade, combinado com dados observacionais de perturbações (ondas, hélices, rupturas etc), constitui um importante diagnóstico da velocidade do plasma cometário em relação ao vento solar circundante, contribuindo assim para esclarecer questões fundamentais, tais como, o papel da instabilidade de Kelvin-Helmholtz na aceleração do plasma cometário, a propagação, conversão de modos e amortecimento de certas ondas do espectro MHD nos raios cometários. Os resultados deste estudo nortearão a análise de um grande número de imagens do Cometa Halley arquivadas em CD-ROM pela equipe dos fenômenos de grande escala do International Halley W!
Environmental Restoration and Waste Management (EM) program: An introduction
Not Available
1990-12-01
This booklet introduces the reader to the mission and functions of a major new unit within the US Department of Energy (DOE): the Office of Environmental Restoration and Waste Management (EM). The Secretary of Energy established EM in November 1989, implementing a central purpose of DOE's first annual Environmental Restoration and Waste Management Five-Year Plan, which had appeared three months earlier. The contents of this booklet, and their arrangement, reflect the annual update of the Five-Year Plan. The Five-Year Plan supports DOE's strategy for meeting its 30-year compliance and cleanup goal. This strategy involves: focusing DOE's activities on eliminating or reducing known or recognized potential risks to worker and public health and the environment, containing or isolating, removing, or detoxifying onsite and offsite contamination, and developing technology to achieve DOE's environmental goals.
Superconducting Electromagnetic Suspension (EMS) system for Grumman Maglev concept
NASA Technical Reports Server (NTRS)
Kalsi, Swarn S.
1994-01-01
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.
Tataris, Katie; Mercer, Mary; Brown, John
2015-01-01
Since 2009, the seminal text in emergency medical services (EMS) medicine has been used to guide the academic development of the new subspecialty but direct application of the material into EMS oversight has not been previously described. The EMS/Disaster Medicine fellowship program at our institution scheduled a monthly meeting to systematically review the text and develop a study guide to assist the fellow and affiliated faculty in preparation for the board examination. In addition to the summary of chapter content, the review included an assessment of areas from each chapter subject where our EMS system did not exhibit recommended characteristics. A matrix was developed in the form of a gap analysis to include specific recommendations based on each perceived gap. Initial review and completion dates for each identified gap enable tracking and a responsible party. This matrix assisted the fellow with development of projects for EMS system improvement in addition to focusing and prioritizing the work of other interested physicians working in the system. By discussing expert recommendations in the setting of an actual EMS system, the faculty can teach the fellow how to approach system improvements based on prior experiences and current stakeholders. This collaborative environment facilitates system-based practice and practice-based learning, aligning with ACGME core competencies. Our educational model has demonstrated the success of translating the text into action items for EMS systems. This model may be useful in other systems and could contribute to the development of EMS system standards nationwide. PMID:25290737
Neirotti, Juan Pablo
Approved Module Information for SE11EM, 2014/5 Module Title/Name: Transition Mathematics for Engineers Module Code: SE11EM School: Engineering and Applied Science Module Type: Standard Module New Information Module Aims: Consolidate core mathematical skills required in a specified range of first year SEAS
Neirotti, Juan Pablo
Approved Module Information for SE12EM, 2014/5 Module Title/Name: Mathematics for 1st year Engineers Module Code: SE12EM School: Engineering and Applied Science Module Type: Standard Module New (Enhanced Honours) Programmes in which available: BEng Mechanical Engineering Systems. BEng
Neirotti, Juan Pablo
Approved Module Information for AM21EM, 2014/5 Module Title/Name: Engineering Mathematics 2 Module engineering mathematics which are necessary in order to understand the modelling of the statistics Code: AM21EM School: Engineering and Applied Science Module Type: Standard Module New Module? No Module
Paraná, Universidade Federal do
. A Coordenação do Programa de Pós-Graduação em Segurança Alimentar e Nutricional do Setor de Ciências da Saúde da isolada no Programa de Pós- graduação em Segurança Alimentar e Nutricional para o 1º semestre de 2015 - Farmácia Aiane B. Sereno SAN 706 - Diagnóstico da Situação Alimentar e Nutricional I Laboratório de
Razik, M A; Quatrano, R S
1997-01-01
Templates constructed from the wheat Em and maize rab28 promoters are efficiently and accurately transcribed in the well-characterized cell-free transcription system prepared from HeLa nuclei. Deletion analysis of the Em promoter indicates that a G-box (CACGTG) element (Em1b) is required for transcription. USF, a Myc transcription factor in HeLa nuclear extracts, activates transcription by binding to Em1b, as shown by the ability of an antibody raised against USF to inhibit transcription and to interfere with Em1b complex formation in an electrophoretic mobility shift assay. The addition of the recombinant Viviparous1 protein from maize to HeLa nuclear extracts specifically stimulated transcription of the Em promoter but was dependent on the presence of USF in the extract. In USF-depleted extracts, the addition of recombinant EmBP1, a basic leucine zipper transcription factor from wheat, activated transcription through Em1b as well as from a similar G-box in the adenovirus major late promoter. Our study demonstrates that the basic transcriptional apparatus in HeLa nuclear extract supports transcription from plant promoters and can be used to assay the function of certain plant nuclear proteins, thereby helping to determine their effects on transcription. PMID:9368416
EMS Mutagenesis in the Pea Aphid Acyrthosiphon pisum
Tagu, Denis; Le Trionnaire, Gaël; Tanguy, Sylvie; Gauthier, Jean-Pierre; Huynh, Jean-René
2014-01-01
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
EMS mutagenesis in the pea aphid Acyrthosiphon pisum.
Tagu, Denis; Le Trionnaire, Gaël; Tanguy, Sylvie; Gauthier, Jean-Pierre; Huynh, Jean-René
2014-04-01
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
Evolução temporal de discos circunstelares em estrelas Be
NASA Astrophysics Data System (ADS)
Fernandes, M. V. M.; Leister, N. V.; Levenhagen, R. S.
2003-08-01
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.
The US DOE-EM International Program - 13004
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
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)