Katherine Jones-Smith; Harsh Mathur; Tanmay Vachaspati
2010-01-25
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.
Quantum Faraday Effect in Double-Dot Aharonov-Bohm Ring
Kang, Kicheon
2011-01-01
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
Weder, Ricardo [Departamento de Metodos Matematicos y Numericos, Instituto de Investigaciones en Matematicas Aplicadas y en Sistemas, Universidad Nacional Autonoma de Mexico, Apartado Postal 20-726, Mexico DF 01000 (Mexico)
2011-05-15
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.
Optical Aharonov-Bohm effect: an inverse hyperbolic problems approach
Gregory Eskin
2007-10-18
We describe the general setting for the optical Aharonov-Bohm effect based on the inverse problem of the identification of the coefficients of the governing hyperbolic equation by the boundary measurements. We interpret the inverse problem result as a possibility in principle to detect the optical Aharonov-Bohm effect by the boundary measurements.
Photonic Aharonov–Bohm effect in photon–phonon interactions
Li, Enbang; Eggleton, Benjamin J.; Fang, Kejie; Fan, Shanhui
2014-01-01
The Aharonov–Bohm effect is one of the most intriguing phenomena in both classical and quantum physics, and associates with a number of important and fundamental issues in quantum mechanics. The Aharonov–Bohm effects of charged particles have been experimentally demonstrated and found applications in various fields. Recently, attention has also focused on the Aharonov–Bohm effect for neutral particles, such as photons. Here we propose to utilize the photon–phonon interactions to demonstrate that photonic Aharonov–Bohm effects do exist for photons. By introducing nonreciprocal phases for photons, we observe experimentally a gauge potential for photons in the visible range based on the photon–phonon interactions in acousto-optic crystals, and demonstrate the photonic Aharonov–Bohm effect. The results presented here point to new possibilities to control and manipulate photons by designing an effective gauge potential. PMID:24476790
Anomalous aharonov-bohm gap oscillations in carbon nanotubes.
Sangalli, Davide; Marini, Andrea
2011-10-12
The gap oscillations caused by a magnetic flux penetrating a carbon nanotube represent one of the most spectacular observations of the Aharonov-Bohm effect at the nanoscale. Our understanding of this effect is, however, based on the assumption that the electrons are strictly confined on the tube surface, on trajectories that are not modified by curvature effects. Using an ab initio approach based on density functional theory, we show that this assumption fails at the nanoscale inducing important corrections to the physics of the Aharonov-Bohm effect. Curvature effects and electronic density that is spilled out of the nanotube surface are shown to break the periodicity of the gap oscillations. We predict the key phenomenological features of this anomalous Aharonov-Bohm effect in semiconductive and metallic tubes and the existence of a large metallic phase in the low flux regime of multiwalled nanotubes, also suggesting possible experiments to validate our results. PMID:21805987
Is There an Aharonov-Bohm Effect for Neutrons?
NASA Astrophysics Data System (ADS)
Greenberger, Daniel M.; Atwood, D. K.; Arthur, J.; Shull, C. G.; Schlenker, M.
1981-09-01
A neutron interferometer experiment testing the existence of an Aharonov-Bohm effect has been performed and no measurable phase shift has been found upon reversal of the enclosed magnetic flux. A positive result would have provided evidence for a breakdown in the standard minimal-coupling scheme for the electromagnetic interaction of a neutron. The sensitivity of the experiment sets the ratio of the Aharonov-Bohm effect for a neutron to that of a particle of charge e to be less than 5×10-12.
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.
Aharonov-Bohm Oscillations in Singly Connected Disordered Conductors
NASA Astrophysics Data System (ADS)
Aleiner, I. L.; Andreev, A. V.; Vinokur, V.
2015-02-01
We show that the transport and thermodynamic properties of a singly connected disordered conductor exhibit quantum Aharonov-Bohm oscillations as a function of the total magnetic flux through the sample. The oscillations are associated with the interference contribution from a special class of electron trajectories confined to the surface of the sample.
Hydrino like states in graphene and Aharonov-Bohm field
Pulak Ranjan Giri
2008-01-01
We study the dynamics of fermions on graphene in presence of Coulomb impurities and Aharonov-Bohm field. Special emphasis is given to the formation of hydrino like states and its lifting of degeneracy due to the presence of AB field. The flux of the AB field can be tuned to make the low angular momentum hydrino states stable against decay. The
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.
Levinson theorem for Aharonov-Bohm scattering in two dimensions
NASA Astrophysics Data System (ADS)
Sheka, Denis D.; Mertens, Franz G.
2006-11-01
We apply the recently generalized Levinson theorem for potentials with inverse-square singularities [Sheka , Phys. Rev. A 68, 012707 (2003)] to Aharonov-Bohm systems in two dimensions (2D). By this theorem, the number of bound states in a given mth partial wave is related to the phase shift and the magnetic flux. The results are applied to 2D soliton-magnon scattering.
Flux effect in superconducting hybrid Aharonov-Bohm rings
Stoof, T.H.; Nazarov, Y.V. [Department of Applied Physics, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (The Netherlands)] [Department of Applied Physics, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (The Netherlands)
1996-07-01
We have extended the circuit theory of Andreev conductance [Phys. Rev. Lett. {bold 73}, 1420 (1994)] to diffusive superconducting hybrid structures that contain an Aharonov-Bohm ring. The electrostatic potential distribution in the system is predicted to be flux dependent with a period of the superconducting flux quantum {Phi}{sub 0}={ital h}/2{ital e}. When at least one tunnel barrier is present, the conductance of the system oscillates with the same period. {copyright} {ital 1996 The American Physical Society.}
Hydrino like states in graphene and Aharonov-Bohm field
Pulak Ranjan Giri
2008-01-01
We study the dynamics of fermions on graphene in presence of Coulomb\\u000aimpurities and Aharonov-Bohm field. Special emphasis is given to the formation\\u000aof hydrino like states and its lifting of degeneracy due to the presence of AB\\u000afield. The flux of the AB field can be tuned to make the low angular momentum\\u000ahydrino states stable against decay. The
Aharonov-Bohm Effect: a Quantum Variation and Classical Analogy
Vladan Pankovic; Darko Kapor; Stevica Djurovic; Milan Pantic
2014-04-23
In this work we consider a quantum variation of the usual Aharonov-Bohm effect with two solenoids sufficiently close one to the other so that (external) electron cannot propagate between two solenoids but only around both solenoids. Here magnetic field (or classical vector potential of the electromagnetic field) acting at quantum propagating (external) electron represents the quantum mechanical average value or statistical mixture. It is obtained by wave function of single (internal, quantum propagating within some solenoid wire) electron (or homogeneous ensemble of such (internal) electrons) representing a quantum superposition with two practically non-interfering terms. All this implies that phase difference and interference shape translation of the quantum propagating (external) electron represent the quantum mechanical average value or statistical mixture. On the other hand we consider a classical analogy and variation of the usual Aharonov-Bohm effect in which Aharonov-Bohm solenoid is used for the primary coil inside secondary large coil in the remarkable classical Faraday experiment of the electromagnetic induction.
Remarks on magnetic and electric Aharonov-Bohm effects
Gregory Eskin
2011-09-17
We give a direct proof of the magnetic Aharonov-Bohm effects without using the scattering theory and the theory of inverse boundary value problems. This proof can serve as a framework for a physical experiment to confirm the magnetic AB effect. We prove also the electric AB effect and we suggest a physical experiment to demonstrate the electric AB effect. In addition, we consider a combined electric and magnetic AB effect and we propose a new inverse problem for the time-dependent Schr\\"odinger equations. Finally we study the gravitational AB effect.
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.
Aharonov-Bohm conductance modulation in ballistic carbon nanotubes.
Lassagne, B; Cleuziou, J-P; Nanot, S; Escoffier, W; Avriller, R; Roche, S; Forró, L; Raquet, B; Broto, J-M
2007-04-27
We report on magnetoconductance experiments in ballistic multiwalled carbon nanotubes threaded by magnetic fields as large as 55 T. In the high temperature regime (100 K), giant modulations of the conductance, mediated by the Fermi level location, are unveiled. The experimental data are consistently analyzed in terms of the field-dependent density of states of the external shell that modulates the injection properties at the electrode-nanotube interface, and the resulting linear conductance. This is the first unambiguous experimental evidence of Aharonov-Bohm effect in clean multiwalled carbon nanotubes. PMID:17501520
Inelastic effects in Aharonov-Bohm molecular interferometers.
Hod, Oded; Baer, Roi; Rabani, Eran
2006-12-31
Inelastic effects arising from electron-phonon coupling in molecular Aharonov-Bohm (AB) interferometers are studied using the nonequilibrium Green's function method. Results for the magnetoconductance are compared for different values of the electron-phonon coupling strength. At low-bias voltages, the coupling to the phonons does not change the lifetime and leads mainly to scattering phase shifts of the conducting electrons. As a result of these dephasing processes, the magnetoconductance of the molecular AB interferometer becomes more sensitive to the threading magnetic flux as the electron-phonon coupling is increased, opposite to the behavior of an electric gate. PMID:17280449
Aharonov-Bohm Effect in a Rotating Acoustic Black Hole
NASA Astrophysics Data System (ADS)
Oliveira, E. S.; Crispino, L. C. B.; Dolan, S. R.
2015-01-01
A classical analogue to the Aharonov-Bohm (AB) effect occurs in a (idealized) draining bathtub (DBT) vortex system. The DBT vortex presents a sonic horizon, at which the flow rate exceeds the speed of sound. The sonic horizon is the analogue of a black hole event horizon. The DBT vortex also presents an ergoregion, similar to a rotating black hole. Because of the sonic event horizon, the AB effect is modified and has two tuning coefficients proportional to the flow draining and circulation couplings with the perturbation frequency.
Aharonov-Bohm effect without closing a loop
Retzker, A.; Nussinov, S.; Reznik, B. [Department of Physics and Astronomy, Tel-Aviv University, Tel Aviv 69978 (Israel); Aharonov, Y. [Department of Physics and Astronomy, Tel-Aviv University, Tel Aviv 69978 (Israel); Department of Physics, University of South Carolina, Columbia (United States); Botero, A. [Department of Physics, University of South Carolina, Columbia (United States); Departamento de Fisica, Universidad de Los Andes, Apartado Aereo 4976, Bogota (Colombia)
2006-03-15
We discuss the consequences of the Aharonov-Bohm (AB) effect in setups involving several charged particles, wherein none of the charged particles encloses a closed loop around the magnetic flux. We show that in such setups, the AB phase is encoded either in the relative phase of a bipartite or multipartite entangled photons states, or alternatively, gives rise to an overall AB phase that can be measured relative to another reference system. These setups involve processes of annihilation or creation of electron-hole pairs. We discuss the relevance of such effects in 'vacuum birefringence' in QED, and comment on their connection to other known effects.
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.
Interaction-induced dephasing of Aharonov-Bohm oscillations
NASA Astrophysics Data System (ADS)
Ludwig, T.; Mirlin, A. D.
2004-05-01
We study the effect of the electron-electron interaction on the amplitude of mesoscopic Aharonov-Bohm oscillations in quasi-one-dimensional (Q1D) diffusive rings. We show that the dephasing length LAB? governing the damping factor exp(-2?R/LAB?) of the oscillations is parametrically different from the common dephasing length for the Q1D geometry. This is due to the fact that the dephasing is governed by energy transfers determined by the ring circumference 2?R, making LAB? R-dependent.
What did we learn from the Aharonov-Bohm effect? Is spin 1/2 different?
Peshkin, M.
1994-06-01
I review what has been learned about fundamental issues in quantum mechanics from the Aharonov-Bohm effect. Following that, I consider the Aharonov-Casher effect and the Scalar Aharonov-Bohm effect, in both of which a spin-1/2 particle interacts with a local electromagnetic field through its magnetic moment, and conclude that those effects can be described as observable effects of local torques.
Stefano Longhi
2014-09-27
We suggest a method for trapping photons in quasi one-dimensional waveguide or coupled-resonator lattices, which is based on an optical analogue of the Aharonov-Bohm cages for charged particles. Light trapping results from a destructive interference of Aharonov-Bohm type induced by a synthetic magnetic field, which is realized by periodic modulation of the waveguide/resonator propagation constants/resonances.
On the Aharonov-Bohm Effect and Why Heisenberg Captures Nonlocality Better Than Schrödinger
NASA Astrophysics Data System (ADS)
Aharonov, Yakir
2014-01-01
This article is based on my lecture delivered at Tonomura FIRST International Symposium on "Electron Microscopy and Gauge Fields" held in Tokyo on May 9-10, 2012. I discuss in detail the history of the Aharonov-Bohm effect in Bristol and my encounters with Akira Tonomura later on. I then propose an idea that developed following the publication of the Aharonov-Bohm effect, namely the importance of modulo momentum and Heisenberg representation in dealing with non-local quantum phenomena.
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.
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
Magnetic edge states in Aharonov-Bohm graphene quantum rings
Farghadan, R., E-mail: rfarghadan@kashanu.ac.ir; Heidari Semiromi, E. [Department of Physics, University of Kashan, Kashan (Iran, Islamic Republic of); Saffarzadeh, A. [Department of Physics, Payame Noor University, P.O. Box 19395-3697 Tehran (Iran, Islamic Republic of); Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada)
2013-12-07
The effect of electron-electron interaction on the electronic structure of Aharonov-Bohm (AB) graphene quantum rings (GQRs) is explored theoretically using the single-band tight-binding Hamiltonian and the mean-field Hubbard model. The electronic states and magnetic properties of hexagonal, triangular, and circular GQRs with different sizes and zigzag edge terminations are studied. The results show that, although the AB oscillations in the all types of nanoring are affected by the interaction, the spin splitting in the AB oscillations strongly depends on the geometry and the size of graphene nanorings. We found that the total spin of hexagonal and circular rings is zero and therefore, no spin splitting can be observed in the AB oscillations. However, the non-zero magnetization of the triangular rings breaks the degeneracy between spin-up and spin-down electrons, which produces spin-polarized AB oscillations.
An Aharonov-Bohm interferometer for determining Bloch band topology
Lucia Duca; Tracy Li; Martin Reitter; Immanuel Bloch; Monika Schleier-Smith; Ulrich Schneider
2014-07-21
The geometric structure of an energy band in a solid is fundamental for a wide range of many-body phenomena in condensed matter and is uniquely characterized by the distribution of Berry curvature over the Brillouin zone. In analogy to an Aharonov-Bohm interferometer that measures the magnetic flux penetrating a given area in real space, we realize an atomic interferometer to measure Berry flux in momentum space. We demonstrate the interferometer for a graphene-type hexagonal lattice, where it has allowed us to directly detect the singular $\\pi$ Berry flux localized at each Dirac point. We show that the interferometer enables one to determine the distribution of Berry curvature with high momentum resolution. Our work forms the basis for a general framework to fully characterize topological band structures and can also facilitate holonomic quantum computing through controlled exploitation of the geometry of Hilbert space.
An Aharonov-Bohm interferometer for determining Bloch band topology
NASA Astrophysics Data System (ADS)
Duca, L.; Li, T.; Reitter, M.; Bloch, I.; Schleier-Smith, M.; Schneider, U.
2015-01-01
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.
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.
Free and bound spin-polarized fermions in the fields of Aharonov--Bohm kind
V. R. Khalilov; I. V. Mamsurov; Lee Ki Eun
2010-02-15
The scattering of electrons by an Aharonov--Bohm field is considered from the viewpoint of quantum-mechanical problem of constructing a self-adjoint Hamiltonian for the Pauli equation. The correct domain for the self-adjoint Hamiltonian, which takes into account explicitly the electron spin is found. A one-parameter self-adjoint extension of the Hamiltonian for spin-polarized electrons in the Aharonov--Bohm field is selected. The correct domain of the self-adjoint Hamiltonian can contain regular and singular (at the point ${\\bf r}=0$) square-integrable functions on the half-line with measure $rdr$. We argue that the physical reason of the existence of singular functions is the additional attractive potential, which appear due to the interaction between the spin magnetic moment of fermion and Aharonov--Bohm magnetic field. The scattering amplitude and cross section are obtained for spin-polarized electrons scattered by the Aharonov--Bohm field. It is shown that in some range of the extension parameter there appears a bound state. Since the Hamiltonian of the nonrelativistic Dirac--Pauli equation for a massive neutral fermion with the anomalous magnetic moment (AMM) in the electric field of a linear charge aligned perpendicularly to the fermion motion has the form of the Hamiltonian for the Pauli equation in the Aharonov--Bohm flux tube, we also calculate the scattering amplitude and cross section for the neutral fermion.
Aharonov-Bohm Effect and High-Velocity Estimates of Solutions to the Schrödinger Equation
Miguel Ballesteros; Ricardo Weder
2010-04-04
The Aharonov-Bohm effect is a fundamental and controversial issue in physics. At stake are what are the fundamental electromagnetic quantities in quantum physics, if magnetic fields can act at a distance on charged particles and if the magnetic potentials have a real physical significance. From the experimental side the issues were settled by the remarkable experiments of Tonomura et al. in 1982 and 1986 with toroidal magnets that gave a strong experimental evidence of the physical existence of the Aharonov-Bohm effect, and by the recent experiment of Caprez et al. in 2007 that shows that the results of these experiments can not be explained by a force. The Aharonov-Bohm Ansatz of 1959 predicts the results of the experiments of Tonomura et al. and of Caprez et al. In 2009 we gave the first rigorous proof that the Aharonov-Bohm Ansatz is a good approximation to the exact solution for toroidal magnets under the conditions of the experiments of Tonomura et al.. In this paper we prove that our results do not depend on the particular geometry of the magnets and on the velocities of the incoming electrons used on the experiments, and on the gaussian shape of the wave packets used to obtain our quantitative error bound. We consider a general class of magnets that are a finite union of handle bodies. We formulate the Aharonov-bohm Ansatz that is appropriate to this general case and 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 $v^\\rho, 0 effect and to its quantum nature.
The Aharonov-Bohm effect: A quantum or a relativistic phenomenon?
K. Wilhelm; B. N. Dwivedi
2014-08-23
The Aharonov-Bohm effect is considered by most authors as a quantum effect, but a generally accepted explanation does not seem to be available. The phenomenon is studied here under the assumption that hypothetical electric dipole distributions configured by moving charges in the solenoid act on the electrons as test particles. The relative motions of the interacting charged particles introduce relativistic time dilations. The massless dipoles are postulated as part of an impact model that has recently been proposed to account for the far-reaching electrostatic forces between charged particles described by Coulomb's law. The model provides a quantitative explanation of the Aharonov-Bohm effect.
A Simple Proof of Magnetic and Electric Aharonov-Bohm Effects
Gregory Eskin
2014-07-20
Magnetic Aharonov-Bohm effect (AB effect) was studied in hundreds of papers starting with the seminal paper of Aharonov and Bohm [AB] published in 1959. We give a new proof of the magnetic Aharonov-Bohm effect without using the scattering theory and the theory of inverse boundary value problems. We consider separately the cases of one and several obstacles. The electric AB effect was studied much less. We give the first proof of the electric AB effect in domains with moving boundaries. When the boundary does not move with the time the electric AB effect is absent.
Aharonov-Bohm interferometry with a tunnel-coupled wire
NASA Astrophysics Data System (ADS)
Aharony, A.; Takada, S.; Entin-Wohlman, O.; Yamamoto, M.; Tarucha, S.
2014-08-01
Recent experiments (Yamamoto et al 2012 Nature Nanotechnology 7 247) used the transport of electrons through an Aharonov-Bohm (AB) interferometer and two coupled channels (at both ends of the interferometer) to demonstrate a manipulable flying qubit. Results included in-phase and anti-phase (AB) oscillations of the two outgoing currents as a function of the magnetic flux, for strong and weak inter-channel coupling, respectively. Here we present new experimental results for a three terminal interferometer, with a tunnel coupling between the two outgoing wires. We show that in some limits, this system is an even simpler realization of the ‘two-slit’ experiment. We also present a simple tight-binding theoretical model which imitates the experimental setup. For weak inter-channel coupling, the AB oscillations in the current which is reflected from the device are very small, and therefore the oscillations in the two outgoing currents must cancel each other, yielding the anti-phase behavior, independent of the length of the coupling regime. Technically, the tight binding equations within the two coupled wires have four solutions for each electronic energy. In the ‘anti-phase’ region all of these solutions are wave-like, oscillating with the distance along the wires. As the coupling between the wires increases, two of these solutions become evanescent, and their amplitudes decay as the electron moves in the wires. In this regime, the amplitudes of the two remaining ‘running’ waves are proportional to each other, with a ratio which is practically flux-independent. As a result, the two outgoing currents are proportional to each other, yielding the ‘in phase’ behavior. For larger coupling all the solutions are evanescent, and the outgoing currents become very small.
The Aharonov-Bohm effect and its applications to electron phase microscopy
Tonomura, Akira
2006-01-01
The Aharonov-Bohm effect was conclusively established by a series of our electron interference experiments, with the help of some advanced techniques, such as coherent field-emission electron beams and microlithography. Using this fundamental principle behind the interaction of an electron wave with electromagnetic fields, new observation techniques were developed to directly observe microscopic objects and quantum phenomena previously unobservable.
Aharonov-Bohm effect in quantum-to-classical correspondence of the Heisenberg principle
De-Hone Lin; Jee-Gong Chang; Chi-Chuan Hwang
2003-01-01
The exact energy spectrum and wave function of a charged particle moving in the Coulomb field and Aharonov-Bohm's magnetic flux are solved by the nonintegrable phase factor. The universal formula for the matrix elements of the radial operator ralpha of arbitrary power alpha is given by an analytical solution. The difference between the classical limit of matrix elements of inverse
Gravitational Aharonov-Bohm effect due to noncommutative BTZ black hole
NASA Astrophysics Data System (ADS)
Anacleto, M. A.; Brito, F. A.; Passos, E.
2015-04-01
In this paper we consider the scattering of massless planar scalar waves by a noncommutative BTZ black hole. We compute the differential cross section via the partial wave approach, and we mainly show that the scattering of planar waves leads to a modified Aharonov-Bohm effect due to spacetime noncommutativity.
Stokes' theorem, gauge symmetry and the time-dependent Aharonov-Bohm effect
Macdougall, James, E-mail: jbm34@mail.fresnostate.edu; Singleton, Douglas, E-mail: dougs@csufresno.edu [Department of Physics, California State University Fresno, Fresno, California 93740-8031 (United States)] [Department of Physics, California State University Fresno, Fresno, California 93740-8031 (United States)
2014-04-15
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.
Alexander Moroz
1999-07-14
We show that the violation of rotational symmetry for differential cross section for Aharonov-Bohm effect with nonstandard boundary conditions has been known for some time. Moreover, the results were applied to discuss the Hall effect and persistent currents of fermions in a plane pierced by a flux tube.
Aharonov-Bohm Effect and High-Velocity Estimates of Solutions to the Schrödinger Equation
NASA Astrophysics Data System (ADS)
Ballesteros, Miguel; Weder, Ricardo
2011-04-01
The Aharonov-Bohm effect is a fundamental issue in physics that has been extensively studied in the literature and is discussed in most of the textbooks in quantum mechanics. The issues at stake are what are the fundamental electromagnetic quantities in quantum physics, if magnetic fields can act at a distance on charged particles and if the magnetic potentials have a real physical significance. The Aharonov-Bohm effect is a very controversial issue. From the experimental side the issues were settled by the remarkable experiments of Tonomura et al. (Phys Rev Lett 48:1443-1446, 1982; Phys Rev Lett 56:792-795, 1986) with toroidal magnets that gave a strong experimental evidence of the physical existence of the Aharonov-Bohm 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 can not be explained by the action of a force. Aharonov and Bohm (Phys Rev 115:485-491, 1959) proposed an Ansatz for the solution to the Schrödinger equation in simply connected regions of space where there are no electromagnetic fields. It consists of multiplying the free evolution by the Dirac magnetic factor. The Aharonov-Bohm Ansatz predicts the results of the experiments of Tonomura et al. and of Caprez et al. Recently in Ballesteros and Weder (Math Phys 50:122108, 2009) we gave the first rigorous proof that the Aharonov-Bohm Ansatz is a good approximation to the exact solution for toroidal magnets under the conditions of the experiments of Tonomura et al. We provided a rigorous, simple, quantitative, error bound for the difference in norm between the exact solution and the Aharonov-Bohm Ansatz. In this paper we prove that these results do not depend on the particular geometry of the magnets and on the velocities of the incoming electrons used on the experiments, and on the gaussian shape of the wave packets used to obtain our quantitative error bound. We consider a general class of magnets that are a finite union of handlebodies. Each handlebody is diffeomorphic to a torus or a ball, and some of them can be patched though the boundary. We formulate the Aharonov-Bohm Ansatz that is appropriate to this general case and we prove that the exact solution to the Schrödinger 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 v ? , 0 < ? < 1, with v the velocity. The results of Tonomura et al., of Caprez et al., our previous results and the results of this paper give a firm experimental and theoretical basis to the existence of the Aharonov-Bohm effect and to its quantum nature. Namely, that magnetic fields act at a distance on charged particles, and that this action at a distance is carried by the circulation of the magnetic potential which gives a real physical significance to magnetic potentials.
Aharonov-Bohm effect in quantum-to-classical correspondence of the Heisenberg principle
Lin, D.-H.; Chang, J.-G.; Hwang, C.-C. [National Center for High-Performance Computing, No. 21, Nan-ke 3rd Road, Hsin-Shi, Tainan County 744, Taiwan (China); Department of Engineering Science, National Cheng Kung University, Tainan, Taiwan (China)
2003-04-01
The exact energy spectrum and wave function of a charged particle moving in the Coulomb field and Aharonov-Bohm's magnetic flux are solved by the nonintegrable phase factor. The universal formula for the matrix elements of the radial operator r{sup {alpha}} of arbitrary power {alpha} is given by an analytical solution. The difference between the classical limit of matrix elements of inverse radius in quantum mechanics and the Fourier components of the corresponding quantity for the pure Coulomb system in classical mechanics is examined in reference to the correspondence principle of Heisenberg. Explicit calculation shows that the influence of nonlocal Aharonov-Bohm effect exists even in the classical limit. The semiclassical quantization rule for systems containing the topological effect is presented in the light of Heisenberg's corresponding principle.
Exotic electron states and tunable magneto-transport in a fractal Aharonov-Bohm interferometer
NASA Astrophysics Data System (ADS)
Nandy, Atanu; Pal, Biplab; Chakrabarti, Arunava
2014-08-01
A Sierpinski gasket fractal network model is studied in respect of its electronic spectrum and magneto-transport when each ‘arm' of the gasket is replaced by a diamond shaped Aharonov-Bohm interferometer, threaded by a uniform magnetic flux. Within the framework of a tight binding model for non-interacting, spinless electrons and a real space renormalization group method we unravel a class of extended and localized electronic states. In particular, we demonstrate the existence of extreme localization of electronic states at a special finite set of energy eigenvalues, and an infinite set of energy eigenvalues where the localization gets ‘delayed' in space (staggered localization). These eigenstates exhibit a multitude of localization areas. The two terminal transmission coefficient and its dependence on the magnetic flux threading each basic Aharonov-Bohm interferometer is studied in details. Sharp switch on-switch off effects that can be tuned by controlling the flux from outside, are discussed. Our results are analytically exact.
The time-dependent non-Abelian Aharonov-Bohm effect
Bright, Max
2015-01-01
In this article, we study the {\\it time-dependent} Aharonov-Bohm effect for non-Abelian gauge fields. We use two well known time-dependent solutions to the Yang-Mills field equations to investigate the Aharonov-Bohm phase shift. For both of the solutions, we find a cancellation between the phase shift coming from the non-Abelian "magnetic" field and the phase shift coming from the non-Abelian "electric" field, which inevitably arises in time-dependent cases. We compare and contrast this cancellation for the time-dependent non-Abelian case to a similar cancellation which occurs in the time-dependent Abelian case. We postulate that this cancellation occurs generally in time-dependent situations for both Abelian and non-Abelian fields.
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.
The Aharonov-Casher Theorem and the Axial Anomaly in the Aharonov-Bohm Potential
Alexander Moroz
1995-11-14
The spectral properties of the Dirac Hamiltonian in the the Aharonov-Bohm potential are discussed. By using the Krein-Friedel formula, the density of states (DOS) for different self-adjoint extensions is calculated. As in the nonrelativistic case, whenever a bound state is present in the spectrum it is always accompanied by a (anti)resonance at the energy. The Aharonov-Casher theorem must be corrected for singular field configurations. There are no zero (threshold) modes in the Aharonov-Bohm potential. For our choice of the 2d Dirac Hamiltonian, the phase-shift flip is shown to occur at only positive energies. This flip gives rise to a surplus of the DOS at the lower threshold coming entirely from the continuous part of the spectrum. The results are applied to several physical quantities: the total energy, induced fermion-number, and the axial anomaly.
Entanglement entropy as a witness of the Aharonov–Bohm effect in QFT
NASA Astrophysics Data System (ADS)
Arias, Raúl E.; Blanco, David D.; Casini, Horacio
2015-04-01
We study the dependence of the entanglement entropy with a magnetic flux and show that the former quantity witnesses an Aharonov–Bohm-like effect. In particular, we consider free charged scalar and Dirac fields living on a two-dimensional cylinder and study how the entanglement entropy for a strip-like region on the surface of the cylinder is affected by a magnetic field enclosed by it.
High-temperature Aharonov-Bohm effect in transport through a single-channel quantum ring
NASA Astrophysics Data System (ADS)
Dmitriev, A. P.; Gornyi, I. V.; Kachorovskii, V. Yu.; Polyakov, D. G.; Shmakov, P. M.
2015-02-01
We overview transport properties of an Aharonov-Bohm interferometer made of a single-channel quantum ring. Remarkably, in this setup, essentially quantum effects survive thermal averaging: the high-temperature tunneling conductance G of a ring shows sharp dips (antiresonances) as a function of magnetic flux. We discuss effects of the electron-electron interaction, disorder, and spin-orbit coupling on the Aharonov-Bohm transport through the ring. The interaction splits the dip into series of dips broadened by dephasing. The physics behind this behavior is the persistent-current-blockade: the current through the ring is blocked by the circular current inside the ring. Dephasing is then dominated by tunneling-induced fluctuations of the circular current. The short-range disorder broadens antiresonances, while the long-range one induces additional dips. In the presence of a spin-orbit coupling, G exhibits two types of sharp antiresonances: Aharonov-Bohm and Aharonov-Casher ones. In the vicinity of the antiresonances, the tunneling electrons acquire spin polarization, so that the ring serves as a spin polarizer.
Li, Jin-Liang; Li, Yu-Xian
2008-11-19
Using nonequilibrium Green's function techniques, we investigate Andreev reflection and Aharonov-Bohm oscillations through a parallel-coupled double quantum dot connected with a ferromagnetic lead and a superconductor lead. The possibility of controlling Andreev reflection and Aharonov-Bohm oscillations of the system is explored by tuning the interdot coupling, the gate voltage, the magnetic flux, and the intradot spin-flip scattering. When the spin-flip scattering increases, Fano resonant peaks resulting from the asymmetrical levels of the two quantum dots begin to split, and Aharonov-Bohm oscillations are suppressed. Due to the interdot coupling, one strongly and one weakly coupled state of the system can be formed. The magnetic flux can exchange the function of the two states, which leads to a swap effect. PMID:21693842
Higher-order topological phase: generalizations of the Aharonov-Bohm and Josephson effects
NASA Astrophysics Data System (ADS)
Buniy, Roman V.; Kephart, Thomas W.
2014-10-01
In the magnetic Aharonov-Bohm effect a semiclassical path of a charged particle is gaussian linked with a magnetic flux tube and one observes an interference phase angle proportional to the magnitude of the enclosed flux. We first generalize to the case of knotted paths. Then we argue that quantum mechanical wave functions with semiclassical paths that have higher order linking to multiple magnetic flux tubes have interference angle proportional to the product of the fluxes. Similar results hold for generalizing the Josephson effect.
Force-Free Gravitational Redshift: Proposed Gravitational Aharonov-Bohm Experiment
NASA Astrophysics Data System (ADS)
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.
Semiclassical theory of h/e Aharonov-Bohm oscillation for doubly connected ballistic cavities
Shiro Kawabata
2000-02-04
In Aharonov-Bohm (AB) cavities forming doubly connected ballistic structures, h/e AB oscillations that result from the interference among the complicated trapped paths in the cavity can be described by the framework of the semiclassical theory. We derive formulas of the correlation function C(\\Delta \\phi) of the nonaveraged magnetoconductance for chaotic and regular AB cavities. The different higher harmonics behaviors for C(\\Delta \\phi) are related to the differing distribution of classical dwelling times. The AB oscillation in ballistic regimes provides an experimental probe of quantum signatures of classical chaotic and regular dynamics.
Semiclassical Theory of h/e Aharonov-Bohm Oscillation in Ballistic Regimes
Shiro Kawabata
1999-09-01
We study the magneto-transport in Aharonov-Bohm (AB) billiards forming doubly connected structures. In these systems, non-averaged conductance oscillates as a function of magnetic flux with period h/e. We derive formulas of the correlation function C of the magneto-conductance for chaotic and regular AB billiards by use of the semiclassical theory. The different higher harmonics behaviors for C are related to the differing distribution of classical dwelling times. The AB oscillation in ballistic regimes provides an experimental probe of quantum signatures of classical chaotic and regular dynamics.
Quantum Faraday effect in a double-dot Aharonov-Bohm loop
NASA Astrophysics Data System (ADS)
Kang, Kicheon
2012-07-01
We investigate the role of Faraday's law of induction manifested in the quantum state of Aharonov-Bohm (AB) loops. In particular, a flux-switching experiment is proposed for a double-dot AB loop to verify the phase shift induced by Faraday's law. The induced Faraday phase is shown to be geometric and nontopological. This 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 contrast to the arbitrary local phase of an AB loop for a given flux.
Aharonov-Bohm oscillations in the local density of topological surface states
NASA Astrophysics Data System (ADS)
Fu, Zhen-Guo; Zhang, Ping; Li, Shu-Shen
2011-12-01
We study Aharonov-Bohm (AB) oscillations in the local density of states (LDOS) for topological insulator (TI) and conventional metal Au(111) surfaces with spin-orbit interaction, which can be probed by spin-polarized scanning tunneling microscopy. We show that the spacial AB oscillatory period in the total LDOS is a flux quantum ?0 = hc/e (weak localization) in both systems. Remarkably, an analogous weak antilocalization with ?0/2 periodic spacial AB oscillations in spin components of LDOS for TI surface is observed, while it is absent in Au(111).
Semiclassical theory of h/e Aharonov-Bohm oscillation for doubly connected ballistic cavities
NASA Astrophysics Data System (ADS)
Kawabata, Shiro
1998-09-01
In Aharonov-Bohm (AB) cavities forming doubly connected ballistic structures, h/e AB oscillations that result from the interference among the complicated trapped paths in the cavity can be described by the framework of the semiclassical theory. We derive formulas of the correlation function C(??) of the nonaveraged magnetoconductance for chaotic and regular AB cavities. The different higher harmonics behaviors for C(??) are related to the differing distribution of classical dwelling times. The AB oscillation in ballistic regimes provides an experimental probe of quantum signatures of classical chaotic and regular dynamics.
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
Electron Interferometry in the Quantum Hall Regime: Aharonov-Bohm Effect of Interacting Electrons
Lin, P.V.; Camino, F.; Goldman, V.J.
2009-09-01
An apparent h/fe Aharonov-Bohm flux period, where f is an integer, has been reported in coherent quantum Hall devices. Such subperiod is not expected for noninteracting electrons and thus is thought to result from interelectron Coulomb interaction. Here we report experiments in a Fabry-Perot interferometer comprised of two wide constrictions enclosing an electron island. By carefully tuning the constriction front gates, we find a regime where interference oscillations with period h/2e persist throughout the transition between the integer quantum Hall plateaus 2 and 3, including half-filling. In a large quantum Hall sample, a transition between integer plateaus occurs near half-filling, where the bulk of the sample becomes delocalized and thus dissipative bulk current flows between the counterpropagating edges ('backscattering'). In a quantum Hall constriction, where conductance is due to electron tunneling, a transition between forward and backscattering is expected near the half-filling. In our experiment, neither period nor amplitude of the oscillations show a discontinuity at half-filling, indicating that only one interference path exists throughout the transition. We also present experiments and an analysis of the front-gate dependence of the phase of the oscillations. The results point to a single physical mechanism of the observed conductance oscillations: Aharonov-Bohm interference of interacting electrons in quantum Hall regime.
Enhanced spin figure of merit in an Aharonov-Bohm ring with a double quantum dot
Zhou, Xingfei; Qi, Fenghua; Jin, Guojun, E-mail: gjin@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China)
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.
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.
Aharonov-Bohm and Aharonov-Casher tunneling effects and edge states in double-barrier structures
NASA Astrophysics Data System (ADS)
Bogachek, E. N.; Landman, Uzi
1994-07-01
The simultaneous occurrence of Aharonov-Bohm (AB) and Aharonov-Casher (AC) effects due to edge states in double-barrier two-dimensional wires formed by an electrostatic confinement potential, in the quantum Hall effect regime, is discussed. The AC effect is manifested via a shift of the AB conductance oscillations, and a method for measurement of the effect is proposed.
Energy Spectrum of a 2D Dirac Oscillator in the Presence of the Aharonov-Bohm Effect
N. Ferkous; A. Bounames
2008-01-30
We determine the energy spectrum and the corresponding eigenfunctions of a 2D Dirac oscillator in the presence of Aharonov-Bohm (AB) effect . It is shown that the energy spectrum depends on the spin of particle and the AB magnetic flux parameter. Finally, when the irregular solution occurs it is shown that the energy takes particular values. The nonrelativistic limit is also considered.
Levinson's theorem and higher degree traces for Aharonov-Bohm operators
NASA Astrophysics Data System (ADS)
Kellendonk, Johannes; Pankrashkin, Konstantin; Richard, Serge
2011-05-01
We study Levinson-type theorems for the family of Aharonov-Bohm models from different perspectives. The first one is purely analytical involving the explicit calculation of the wave-operators and allowing to determine precisely the various contributions to the left hand side of Levinson's theorem, namely, those due to the scattering operator, the terms at 0-energy and at energy +?. The second one is based on non-commutative topology revealing the topological nature of Levinson's theorem. We then include the parameters of the family into the topological description obtaining a new type of Levinson's theorem, a higher degree Levinson's theorem. In this context, the Chern number of a bundle defined by a family of projections on bound states is explicitly computed and related to the result of a 3-trace applied on the scattering part of the model.
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.
Wave-packet rectification in nonlinear electronic systems: A tunable Aharonov-Bohm diode
Li, Yunyun; Zhou, Jun; Marchesoni, Fabio; Li, Baowen
2014-01-01
Rectification of electron wave-packets propagating along a quasi-one dimensional chain is commonly achieved via the simultaneous action of nonlinearity and longitudinal asymmetry, both confined to a limited portion of the chain termed wave diode. However, it is conceivable that, in the presence of an external magnetic field, spatial asymmetry perpendicular to the direction of propagation suffices to ensure rectification. This is the case of a nonlinear ring-shaped lattice with different upper and lower halves (diode), which is attached to two elastic chains (leads). The resulting device is mirror symmetric with respect to the ring vertical axis, but mirror asymmetric with respect to the chain direction. Wave propagation along the two diode paths can be modeled for simplicity by a discrete Schrödinger equation with cubic nonlinearities. Numerical simulations demonstrate that, thanks to the Aharonov-Bohm effect, such a diode can be operated by tuning the magnetic flux across the ring. PMID:24691462
Anomalous Aharonov-Bohm Conductance Oscillations from Topological Insulator Surface States
NASA Astrophysics Data System (ADS)
Zhang, Yi; Vishwanath, Ashvin
2010-11-01
We study Aharonov-Bohm (AB) conductance oscillations arising from the surface states of a topological insulator nanowire, when a magnetic field is applied along its length. With strong surface disorder, these oscillations are predicted to have a component with anomalous period ?0=hc/e, twice the conventional period. The conductance maxima are achieved at odd multiples of (1)/(2)?0, implying that a ? AB phase for electrons strengthens the metallic nature of surface states. This effect is special to topological insulators, and serves as a defining transport property. A key ingredient, the surface curvature induced Berry phase, is emphasized here. We discuss similarities and differences from recent experiments on Bi2Se3 nanoribbons, and optimal conditions for observing this effect.
Aharonov-Bohm oscillations in coupled quantum dots: Effect of electron-electron interactions
NASA Astrophysics Data System (ADS)
Semenov, Andrew G.; Golubev, Dmitri S.; Zaikin, Andrei D.
2009-03-01
We theoretically analyze the effect of electron-electron interactions on Aharonov-Bohm (AB) current oscillations in ring-shaped systems with metallic quantum dots pierced by external magnetic field. We demonstrate that electron-electron interactions suppress the amplitude of AB oscillations IAB at all temperatures down to T=0 , and we formulate quantitative predictions which can be verified in future experiments. We argue that the main physical reason for such interaction-induced suppression of IAB is electron dephasing, while Coulomb blockade effects remain insignificant in the case of metallic quantum dots considered here. We also emphasize a direct relation between our results and the so-called P(E) theory describing tunneling of interacting electrons.
NASA Astrophysics Data System (ADS)
Zhang, G.; Li, X. Q.; Zhang, X. Z.; Song, Z.
2015-01-01
We study the effect of PT -symmetric imaginary potentials embedded in the two arms of an Aharonov-Bohm interferometer on the transmission phase by finding an exact solution for a concrete tight-binding system. It is observed that the spectral singularity always occurs at k =±? /2 for a wide range of fluxes and imaginary potentials. Critical behavior associated with the physics of the spectral singularity is also investigated. It is demonstrated that the quasispectral singularity corresponds to a transmission maximum and the transmission phase jumps abruptly by ? when the system is swept through this point. Moreover, we find that there exists a pulselike phase lapse when the imaginary potential approaches the boundary value of the spectral singularity.
Gaussian curvature and global effects: Gravitational Aharonov-Bohm effect revisited
NASA Astrophysics Data System (ADS)
Nouri-Zonoz, M.; Parvizi, A.
2013-07-01
By using the Gauss-Bonnet formula, the integral of the Gaussian curvature over a 2-surface enclosed by a curve in the asymptotically flat region of a static spacetime was found to be a measure of a gravitational analogue of the Aharonov-Bohm effect by Ford and Vilenkin in the linearized regime. Employing the 1+3 formulation of spacetime decomposition, we study the same effect in the context of the full Einstein field equations for stationary spacetimes. Applying our approach to static tubelike and cylindrical distributions of dust, not only do we recover their result but we also obtain an extra term which is interpreted to be representing the classical version of the Colella-Overhauser-Werner effect (the Colella-Overhauser-Werner experiment).
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.
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.
Effect of vacuum polarization of charged massive fermions in an Aharonov--Bohm field
V. R. Khalilov
2014-07-16
The effect of vacuum polarization of charged massive fermions in an Aharonov-Bohm (AB) potential in 2+1 dimensions is investigated. The causal Green's function of the Dirac equation with the AB potential is represented via the regular and irregular solutions of the two-dimensional radial Dirac equation. It is shown that the vacuum current density contains the contribution from free filled states of the negative energy continuum as well as that from a bound unfilled state, which can emerge in the above background due to the interaction of the fermion spin magnetic moment with the AB magnetic field while the induced charge density contains only the contribution from the bound state. The expressions for the vacuum charge and induced current densities are obtained (recovered for massless fermions) for the graphene in the field of infinitesimally thin solenoid perpendicular to the plane of a sample. We also find the bound state energy as a function of magnetic flux, fermion spin and the radius of solenoid as well as discuss the role of the so-called self-adjoint extension parameter and determine it in terms of the physics of the problem.
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 - Casher oscillations in strongly correlated electron systems at finite temperature
NASA Astrophysics Data System (ADS)
Schlottmann, P.
1997-09-01
Persistent charge and spin currents due to Aharonov - Bohm and Aharonov - Casher interferences of correlated electrons moving along a mesoscopic ring are discussed at finite temperature. As a function of applied flux the ground-state persistent currents have the shape of a generalized saw-tooth, i.e. they consist of piecewise straight segments. The periods and amplitudes of the oscillations are associated with the properties of the Fermi surface of the elementary excitations (two Dirac seas), namely the group velocities and the matrix of dressed generalized charges (Luttinger parameters). The temperature reduces the amplitudes of oscillation by smearing the Fermi surface in a similar way to that for the de Haas - van Alphen effect in 3D metals. The amplitude of higher harmonics decreases more quickly with T than the fundamental one, changing the saw-tooth to a more sinusoidal form with much smaller amplitude. The controlling parameters are the ratios of the thermal energy to the level spacings in the ring. The results are discussed in the context of the exact Bethe ansatz solutions for the Hubbard chain and the supersymmetric t - J model.
Observation of Optical Signature of the Aharonov-Bohm Phase in Type-II Quantum Dots
NASA Astrophysics Data System (ADS)
Kuskovsky, Igor; MacDonald, W.; Tamargo, M. C.; Govorov, A. O.; Wei, X.; Tadic, M.; Peeters, F. M.
2006-03-01
Recent theoretical studies^1,2 on the optical response of type-II excitons in the magnetic field have shown that the excitons will acquire the Aharonov-Bohm (AB) phase as the electrical dipole, formed due to carrier separation, interacts with the field, resulting in the field dependent exciton energy and the emission intensity. Experimentally, the former has been reported^3; however, the behavior of the intensity is still not fully understood. We present results of magneto-photoluminescence studies on type-II ZnTe/ZnSe quantum dots (QDs) formed in Zn-Se-Te multilayer systems^4; this ensures that electron move within the x-y plane. The observed strong oscillations in the intensity is explained in terms of the AB effect^1,2,5 due to the electron motion around a stack of QDs, when the hole is strongly localized in one them. This is in qualitative agreement with the theoretical predictions^2. 1. Kalameitsev, et al., JETP Lett. 68, 669 (1998); Govorov, et al., PRB R66, 081309 (2002); Janssens, et al., PRB 67, 235325 (2003). 2. Janssens, et al., PRB 69, 235320 (2004). 3. Ribeiro, et al., PRL 92, 126402 (2004). 4. Gu, et al.., PRB 71 045340 (2005). 5. Dias da Silva, et al., PRB 70, 155318 (2004).
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.
Amnon Aharony; Yasuhiro Tokura; Guy Z. Cohen; Ora Entin-Wohlman; Shingo Katsumoto
2011-03-11
Spin-1/2 electrons are scattered through one or two diamond-like loops, made of quantum dots connected by one-dimensional wires, and subject to both an Aharonov-Bohm flux and (Rashba and Dresselhaus) spin-orbit interactions. With some symmetry between the two branches of each diamond, and with appropriate tuning of the electric and magnetic fields (or of the diamond shapes) this device completely blocks electrons with one polarization, and allows only electrons with the opposite polarization to be transmitted. The directions of these polarizations are tunable by these fields, and do not depend on the energy of the scattered electrons. For each range of fields one can tune the site and bond energies of the device so that the transmission of the fully polarized electrons is close to unity. Thus, these devices perform as ideal spin filters, and these electrons can be viewed as mobile qubits; the device writes definite quantum information on the spinors of the outgoing electrons. The device can also read the information written on incoming polarized electrons: the charge transmission through the device contains full information on this polarization. The double-diamond device can also act as a realization of the Datta-Das spin field-effect transistor.
NASA Astrophysics Data System (ADS)
Aharony, Amnon; Tokura, Yasuhiro; Cohen, Guy Z.; Entin-Wohlman, Ora; Katsumoto, Shingo
2011-07-01
Spin-1/2 electrons are scattered through one or two diamond-like loops, made of quantum dots connected by one-dimensional wires, and subject to both an Aharonov-Bohm flux and (Rashba and Dresselhaus) spin-orbit interactions. With some symmetry between the two branches of each diamond, and with appropriate tuning of the electric and magnetic fields (or of the diamond shapes), this device completely blocks electrons with one polarization and allows only electrons with the opposite polarization to be transmitted. The directions of these polarizations are tunable by these fields, and do not depend on the energy of the scattered electrons. For each range of fields one can tune the site and bond energies of the device so that the transmission of the fully polarized electrons is close to unity. Thus, these devices perform as ideal spin filters, and these electrons can be viewed as mobile qubits; the device writes definite quantum information on the spinors of the outgoing electrons. The device can also read the information written on incoming polarized electrons: The charge transmission through the device contains full information on this polarization. The double-diamond device can also act as a realization of the Datta-Das spin field-effect transistor.
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
A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms
Ming-Xia Huo; Nie Wei; David A. W. Hutchinson; Leong Chuan Kwek
2014-08-11
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.
NASA Astrophysics Data System (ADS)
Petrosyan, L. S.; Shahbazyan, T. V.
2015-01-01
We study resonant tunneling through a periodic square array of quantum dots sandwiched between modulation-doped quantum wells. If a magnetic field is applied parallel to the quantum dot plane, the tunneling current exhibits a highly complex Aharonov-Bohm oscillation pattern due to the interference of multiple pathways traversed by a tunneling electron. Individual pathways associated with conductance beats can be enumerated by sweeping the magnetic field at various tilt angles. Remarkably, Aharonov-Bohm oscillations are aperiodic unless the magnetic field slope relative to the quantum dot lattice axes is a rational number.
Absence of localization in a disordered one-dimensional ring threaded by an Aharonov-Bohm flux
NASA Astrophysics Data System (ADS)
Heinrichs, Jean
2009-07-01
Absence of localization is demonstrated analytically to leading order in weak disorder in a one-dimensional Anderson model of a ring threaded by an Aharonov-Bohm (AB) flux. The result follows from adapting an earlier perturbation treatment of disorder in a superconducting ring subjected to an imaginary vector potential proportional to a depinning field for flux lines bound to random columnar defects parallel to the axis of the ring. The absence of localization in the ring threaded by an AB flux for sufficiently weak disorder is compatible with large free-electron-type persistent current obtained in recent studies of the above model.
NASA Astrophysics Data System (ADS)
Fu, Zhen-Guo; Zhang, Ping; Li, Shu-Shen
2012-03-01
We propose a scanning tunneling microscopy Aharonov-Bohm (AB) interferometer on the surface of a topological insulator (TI) to probe the crossover from analogous weak antilocalization to weak localization phenomenon via the AB oscillations in spin-resolved local density of states (LDOS). Based on our analytical and numerical results, we show that with increasing the energy gap of TI surface states, the ?0/2=hc/2e periodic AB oscillations in spin-resolved LDOS gradually transit into the ?0 periodic oscillations.
Correa, Francisco [Departamento de Fisica, Universidad de Santiago de Chile, Casilla 307, Santiago 2 (Chile)], E-mail: fco.correa.s@gmail.com; Jakubsky, Vit [Departamento de Fisica, Universidad de Santiago de Chile, Casilla 307, Santiago 2 (Chile)], E-mail: v.jakubsky@gmail.com; Plyushchay, Mikhail S. [Departamento de Fisica, Universidad de Santiago de Chile, Casilla 307, Santiago 2 (Chile)], E-mail: mplyushc@lauca.usach.cl
2009-05-15
We explain the origin and the nature of a special nonlinear supersymmetry of a reflectionless Poeschl-Teller system by the Aharonov-Bohm effect for a non-relativistic particle on the AdS{sub 2}. A key role in the supersymmetric structure appearing after reduction by a compact generator of the AdS{sub 2} isometry is shown to be played by the discrete symmetries related to the space and time reflections in the ambient Minkowski space. We also observe that a correspondence between the two quantum non-relativistic systems is somewhat of the AdS/CFT holography nature.
Magnetoresistance of nanoscale molecular devices based on Aharonov-Bohm interferometry.
Hod, Oded; Baer, Roi; Rabani, Eran
2008-09-24
Control of conductance in molecular junctions is of key importance in the growing field of molecular electronics. The current in these junctions is often controlled by an electric gate designed to shift conductance peaks into the low bias regime. Magnetic fields, on the other hand, have rarely been used due to the small magnetic flux captured by molecular conductors (an exception is the Kondo effect in single-molecule transistors). This is in contrast to a related field, electronic transport through mesoscopic devices, where considerable activity with magnetic fields has led to a rich description of transport. The scarcity of experimental activity is due to the belief that significant magnetic response is obtained only when the magnetic flux is of the order of the quantum flux, while attaining such a flux for molecular and nanoscale devices requires unrealistic magnetic fields. Here we review recent theoretical work regarding the essential physical requirements necessary for the construction of nanometer-scale magnetoresistance devices based on an Aharonov-Bohm molecular interferometer. We show that control of the conductance properties using small fractions of a magnetic flux can be achieved by carefully adjusting the lifetime of the conducting electrons through a pre-selected single state that is well separated from other states due to quantum confinement effects. Using a simple analytical model and more elaborate atomistic calculations we demonstrate that magnetic fields which give rise to a magnetic flux comparable to 10(-3) of the quantum flux can be used to switch a class of different molecular and nanometer rings, ranging from quantum corrals, carbon nanotubes and even a molecular ring composed of polyconjugated aromatic materials. The unique characteristics of the magnetic field as a gate is further discussed and demonstrated in two different directions. First, a three-terminal molecular router devices that can function as a parallel logic gate, processing two logic operations simultaneously, is presented. Second, the role of inelastic effects arising from electron-phonon couplings on the magnetoresistance properties is analyzed. We show that a remarkable difference between electric and magnetic gating is also revealed when inelastic effects become significant. The inelastic broadening of response curves to electric gates is replaced by a narrowing of magnetoconductance peaks, thereby enhancing the sensitivity of the device. PMID:21693808
NASA Astrophysics Data System (ADS)
Hou, Dong; Wang, Shikuan; Wang, Rulin; Ye, LvZhou; Xu, RuiXue; Zheng, Xiao; Yan, YiJing
2015-03-01
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.
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.
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
NASA Astrophysics Data System (ADS)
Zhang, Rong; Peng, Xiong-Feng; Han, Kui; Shen, Yi-Feng; Tang, Fu-Rong; Bai, Long
2013-02-01
Within the framework of non-equilibrium Green's functions, we investigate the spin-dependent Andreev reflection (AR) in a three-terminal Aharonov-Bohm interferometer with double quantum dot, taking account of the coherent indirect coupling via the superconducting reservoir. It is found that the time-reversal symmetry is broken by the crossed Andreev reflection (CAR) process, and moreover that the spin-value effect of the linear conductance, the spin-polarised AR current, and a pure spin current can be generated by means of the normal AR and the CAR. Expressions for the AR conductances (the transport coefficients) governing the AR properties of this system are derived analytically. The effect of the coherent indirect coupling on the conductance, the Andreev reflected tunneling magnetoresistance (ARTMR), and the spin-related current in the presence of the AR are amply analyzed. Our results indicate that the optimal properties of this system can be realised by tuning the external parameters.
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.
Bruno, Patrick
2012-06-15
The (Berry-Aharonov-Anandan) geometric phase acquired during a cyclic quantum evolution of finite-dimensional quantum systems is studied. It is shown that a pure quantum state in a (2J+1)-dimensional Hilbert space (or, equivalently, of a spin-J system) can be mapped onto the partition function of a gas of independent Dirac strings moving on a sphere and subject to the Coulomb repulsion of 2J fixed test charges (the Majorana stars) characterizing the quantum state. The geometric phase may be viewed as the Aharonov-Bohm phase acquired by the Majorana stars as they move through the gas of Dirac strings. Expressions for the geometric connection and curvature, for the metric tensor, as well as for the multipole moments (dipole, quadrupole, etc.), are given in terms of the Majorana stars. Finally, the geometric formulation of the quantum dynamics is presented and its application to systems with exotic ordering such as spin nematics is outlined. PMID:23004240
Khatua, Pradip; Bansal, Bhavtosh; Shahar, Dan
2014-01-10
In a "thought experiment," now a classic in physics pedagogy, Feynman visualizes Young's double-slit interference experiment with electrons in magnetic field. He shows that the addition of an Aharonov-Bohm phase is equivalent to shifting the zero-field wave interference pattern by an angle expected from the Lorentz force calculation for classical particles. We have performed this experiment with one slit, instead of two, where ballistic electrons within two-dimensional electron gas diffract through a small orifice formed by a quantum point contact (QPC). As the QPC width is comparable to the electron wavelength, the observed intensity profile is further modulated by the transverse waveguide modes present at the injector QPC. Our experiments open the way to realizing diffraction-based ideas in mesoscopic physics. PMID:24483873
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.
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.
NASA Astrophysics Data System (ADS)
Dey, Moumita; Maiti, Santanu K.; Karmakar, S. N.
2011-01-01
We address spin dependent transport through an array of diamonds in the presence of Rashba spin-orbit (SO) interaction where each diamond plaquette is penetrated by an Aharonov-Bohm (AB) flux ?. The diamond chain is attached symmetrically to two semi-infinite one-dimensional nonmagnetic metallic leads. We adopt a single particle tight-binding Hamiltonian to describe the system and study spin transport using Green's function formalism. After presenting an analytical method for the energy dispersion relation of an infinite diamond chain in the presence of Rashba SO interaction, we study numerically the conductance-energy characteristics together with the density of states of a finite sized diamond network. At the typical flux ? =?0/2, a delocalizing effect is observed in the presence of Rashba SO interaction, and, depending on the specific choices of SO interaction strength and AB flux the quantum network can be used as a spin filter. Our analysis may be inspiring in designing spintronic devices.
NASA Astrophysics Data System (ADS)
Peng, Ju; Yu, Hua-Ling; Wang, Zhi-Guo
2009-12-01
This paper theoretically reports the nonlocal Andreev reflection and spin current in a normal metal-ferromagnetic metal-superconducting Aharonov-Bohm interferometer. It is found that the electronic current and spin current are sensitive to systematic parameters, such as the gate voltage of quantum dots and the external magnetic flux. The electronic current in the normal metal lead results from two competing processes: quasiparticle transmission and nonlocal Andreev reflection. The appearance of zero spin-up electronic current (or spin-down electronic current) signals the existence of nonlocal Andreev reflection, and the presence of zero electronic current results in the appearance of pure spin current.
The optical Aharonov-Bohm effect and magneto-optical properties in type-II quantum dots
NASA Astrophysics Data System (ADS)
Whiteside, Vincent Ryan
We present a detailed experimental study of the magneto-optical properties of type-II quantum dots (QDs) in: (1) ZnTe/ZnSe superlattices grown by Molecular Beam Epitaxy (MBE)---these Zn(SeTe) QDs evolve from Te-clustering in the ZnSe matrix during growth; and (2) diluted magnetic semiconductor, (ZnMn)Se, QDs in a ZnSe matrix produced by migration enhanced epitaxy. In case (1) the Zn(SeTe) QDs display large and robust (with temperature) oscillations as a function of magnetic field in both the photoluminescence energy and intensity as a result of the optical Aharonov-Bohm effect. The large strength of these oscillations is attributed to a combination of the type-II symmetry and the columnar geometry of the structures; the oscillations persist until 180K. The type-II diluted magnetic semiconductor, (ZnMn)Te quantum dots display similar oscillatory effects in the emission intensity. Interestingly, the coherence of the Aharonov-Bohm phase in these magnetic dots is strongly related to the spin polarization of the system due to the Mn-exciton exchange interaction as shown by the disappearance of the oscillations at low magnetic fields. The enhanced coherence at high fields, which leads to strong oscillations in intensity, is attributed to removal of magnetic disorder by the applied magnetic field. While the magnetic nature of the QDs is clear from the polarization measurements there is the seemingly contradictory behavior of a very small Zeeman shift for material that has a corresponding large Zeeman shift for the comparable composition of bulk (ZnMn)Te. More importantly, a red shift greater than 30 meV is observed in the peak energy of the PL as function of time after excitation with a picosecond pulse. These results can be explained by postulating formation of bound magnetic polarons in the QDs. The overall red shift is identified as the magnetic polaron binding energy, EMP; it is roughly independent of temperature, persisting up to 150K. The large MP binding energy is apparently contradictory to the small observed Zeeman splitting and the temperature dependence of the optical polarization in the steady state. These apparently contradictory properties are interpreted in terms of a model that explains the temperature dependence as well as the polarization and Zeeman energy splitting, while fully taking into account the polaron formation energy. The model is based on the hole-Mn and the Mn-Mn exchange coupling and their role in the magnetic polaron formation with a crucial aspect being the formation of an antiferromagnetically ordered state of the Mn spin system in each of the QDs in the absence of photoinjected holes.
Alexander MOROZ
1994-05-05
In the nonrelativistic case we find that whenever the relation $mc^2/e^2 2$ (note that $g_m=2.00232$ for the electron), then the matter is unstable against formation of the flux $\\al$. The result persists down to $g_m=2$ provided the Aharonov-Bohm potential is supplemented with a short range attractive potential. We also show that whenever a bound state is present in the spectrum it is always accompanied by a resonance with the energy proportional to the absolute value of the binding energy. is considered. For the Klein-Gordon equation with the Pauli coupling which exists in (2+1) dimensions without any reference to a spin the matter is again unstable for $g_m>2$. The results are obtained by calculating the change of the density of states induced by the Aharonov-Bohm potential. The Krein-Friedel formula for this long-ranged potential is shown to be valid when supplemented with zeta function regularization. PACS : 03.65.Bz, 03-70.+k, 03-80.+r, 05.30.Fk
NASA Astrophysics Data System (ADS)
Chen, Xiong-Wen; Shi, Zhen-Gang; Song, Ke-Hui
2009-11-01
We theoretically investigate the Kondo effect of a quantum dot embedded in a mesoscopic Aharonov-Bohm (AB) ring in the presence of the spin flip processes by means of the one-impurity Anderson Hamiltonian. Based on the slave-boson mean-field theory, we find that in this system the persistent current (PC) sensitively depends on the parity and size of the AB ring and can be tuned by the spin-flip scattering (R). In the small AB ring, the PC is suppressed due to the enhancing R weakening the Kondo resonance. On the contrary, in the large AB ring, with R increasing, the peak of PC firstly moves up to max-peak and then down. Especially, the PC phase shift of ? appears suddenly with the proper value of R, implying the existence of the anomalous Kondo effect in this system. Thus this system may be a candidate for quantum switch.
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.
Chiao, R Y; Sundqvist, K M; Inan, N A; Munoz, G A; Singleton, D A; Kang, B S; Martinez, L A
2014-01-01
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-var...
NASA Astrophysics Data System (ADS)
Yarkony, David R.
1999-01-01
Recently there has been considerable interest, not to mention controversy, concerning a key aspect of the molecular Aharonov-Bohm (MAB) effect: the construction of the phase angle, induced by geometric phase effect, whose gradient is the vector potential characteristic of MAB theory. In the past this angle was constructed from explicit knowledge of the locus of the seam of conical intersection. Here it is shown how a phase angle that satisfies the requirements of MAB theory can be determined without a priori knowledge of the locus of points of conical intersection. This approach has important implications for direct dynamics. It is a corollary of a recent analysis that showed that diagonalizing the matrix of virtually any symmetric (real-valued Hermitian) electronic property operator in the subspace of states that intersect conically generates a transformation that removes all of the singularity of the derivative coupling at a conical intersection. Key aspects of this method are illustrated by considering the dipole moment operator near a point on the 1 3A?-23A? seam of conical intersection in CH2.
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
NASA Astrophysics Data System (ADS)
Bai, Long; Zhang, Rong; Duan, Chen-Long
2012-12-01
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.
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.
NASA Astrophysics Data System (ADS)
Tu, Matisse Wei-Yuan; Aharony, Amnon; Zhang, Wei-Min; Entin-Wohlman, Ora
2014-10-01
The spin-resolved nonequilibrium real-time electron transport through a double-quantum-dot (DQD) Aharonov-Bohm (AB) interferometer with spin-orbit interaction (SOI) is explored. The SOI and AB interference in the real-time dynamics of spin transport is expressed by effective magnetic fluxes. Analytical formulas for the time-dependent currents, for initially unpolarized spins, are presented. In many cases, there appear spin currents in the electrodes, for which the spins in each electrode are polarized along characteristic directions, predetermined by the SOI parameters and by the geometry of the system. Special choices of the system parameters yield steady-state currents in which the spins are fully polarized along these characteristic directions. The time required to reach this steady state depends on the couplings of the DQD to the leads. The magnitudes of the currents depend strongly on the SOI-induced effective fluxes. Without the magnetic flux, the spin-polarized current cannot be sustained to the steady states, due to the phase rigidity for this system. For a nondegenerate DQD, transient spin transport can be produced by the sole effects of SOI. We also show that one can extract the spin-resolved currents from measurements of the total charge current.
Alexander Moroz
1996-02-08
Both the nonrelativistic scattering and the spectrum in the presence of the Aharonov-Bohm potential are analyzed. The single-particle density of states (DOS) for different self-adjoint extensions is calculated. The DOS provides a link between different physical quantities and is a natural starting point for their calculation. The consequences of an asymmetry of the S matrix for the generic self-adjoint extension are examined. I. Introduction II. Impenetrable flux tube and the density of states III. Penetrable flux tube and self-adjoint extensions IV. The S matrix and scattering cross sections V. The Krein-Friedel formula and the resonance VI. Regularization VII. The R --> 0 limit and the interpretation of self-adjoint extensions VIII. Energy calculations IX. The Hall effect in the dilute vortex limit X. Persistent current of free electrons in the plane pierced by a flux tube XI. The 2nd virial coefficient of nonrelativistic interacting anyons XII. Discussion of the results and open questions
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.
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.
Spectral Zeta Functions for Spherical Aharonov-Bohm Quantum Bags
E. Elizalde; S. Leseduarte; A. Romeo
1992-12-16
We study the sum $\\ds\\zeta_H(s)=\\sum_j E_j^{-s}$ over the eigenvalues $E_j$ of the Schrdinger equation in a spherical domain with Dirichlet walls, threaded by a line of magnetic flux. Rather than using Green's function techniques, we tackle the mathematically nontrivial problem of finding exact sum rules for the zeros of Bessel functions $J_{\
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.
Comment on Macroscopic Test of the Aharonov-Bohm Effect
Tomislav Ivezic
2014-06-04
In this Comment it is shown that it cannot be argued that in the magnetic AB effect there is no force acting on the particle, i.e., that the observed phase shift is entirely due to nonzero vector potential. In stationary resistive conductors carrying constant currents there are quasistatic surface charges, which generate not only the electric field inside the wire driving the current, but also a static electric field outside it. These external static electric fields have nothing to do with Boyer's force picture and with his result for the existence of a time delay.
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 ...
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...
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...
Quantum transport in nonuniform magnetic fields: Aharonov-Bohm ring as a spin switch.
Frustaglia, D; Hentschel, M; Richter, K
2001-12-17
We study spin-dependent magnetoconductance in mesoscopic rings subject to an inhomogeneous in-plane magnetic field. We show that the polarization direction of transmitted spin-polarized electrons can be controlled via an additional magnetic flux such that spin flips are induced at half a flux quantum. This quantum interference effect is independent of the strength of the nonuniform field applied. We give an analytical explanation for one-dimensional rings and numerical results for corresponding ballistic microstructures. PMID:11736592
Anomalous Aharonov-Bohm-Type Effects in Square Array of Antidots
Katsumoto, Shingo
both in low and high magnetic field regimes [1-3]. The B-periodic oscillations reflect the modulation of the electronic density of states originating from the Bohr-Sommerfeld quantization of electron orbits pinned quantized orbits changes from pinned orbits in the low field regime to edge states in the quantum Hall (QH
Yannouleas, Constantine; Landman, Uzi
2015-01-01
The unique ultra-relativistic, massless, nature of electron states in two-dimensional extended graphene sheets, brought about by the honeycomb lattice arrangement of carbon atoms in two-dimensions, provides ingress to explorations of fundamental physical phenomena in graphene nanostructures. Here we explore the emergence of new behavior of electrons in atomically precise segmented graphene nanoribbons (GNRs) and graphene rings with the use of tight-binding calculations, non-equilibrium Green's function transport theory, and a newly developed Dirac continuum model that absorbs the valence-to-conductance energy gaps as position-dependent masses, including topological-in-origin mass-barriers at the contacts between segments. Through transport investigations in variable-width segmented GNRs with armchair, zigzag, and mixed edge terminations we uncover development of new Fabry-Perot-like interference patterns in segmented GNRs, a crossover from the ultra-relativistic massless regime, characteristic of extended gra...
Aharonov-Bohm Beats in Excitonic Luminescence from Quantum Rings and Type-II Quantum Dots
NASA Astrophysics Data System (ADS)
Dias da Silva, Luis; Shahbazyan, Tigran
2005-03-01
We study the absorption spectrum of neutral magnetoexcitons confined in ring-like structures. Despite their neutral character, excitons exhibit strong modulation effects on the energy and oscillator strength in the presence of magnetic fields [1] that have been recently observed [2]. We calculate the absorption coefficient ? for neutral excitons confined in circular ring geometries with radii Re for electrons and Rh for holes. A particularly interesting situation comes about when Re!=Rh and a net radial charge polarization arises. In this case, we consider an attractive Coulomb interaction proportional to (Re- Rh)-1 and the excitonic absorption peak shows oscillatory behavior as function of the applied magnetic field both in position and amplitude. Such oscillations strongly depend on the dipole moment P=e(Rh-Re) of the exciton and on the dielectric constant of the system. Such intensity changes could in principle be experimentally observed with single dot spectroscopy in quantum rings [3]. Supported by the NSF-IMC and NSF-RUI [1] A.O. Govorov et al. Phys. Rev. B 66 081309 (2002); A.O. Govorov et al. Physica E 13, 297 (2002). [2] E. Ribeiro et al. Phys Rev. Lett. 92 126402 (2004). [3] R.J. Warburton et al. Nature 405 (6789) 926 (2000).
Dynamics of a classical Hall system driven by a time-dependent AharonovBohm flux
the influence of a strong homogeneous magnetic field, an electrical background, and driven by a time is a cycloid around a center whose drift is outgoing, orthogonal to the electric field, diffusive, and without: generation, recombina- tion, lifetime, trapping, mean free paths 1 Introduction The motivation to study
Exciton storage in type-II quantum dots using the optical Aharonov-Bohm effect
Climente, Juan I.; Planelles, Josep, E-mail: josep.planelles@uji.es [Departament de Química Física i Analítica, Universitat Jaume I, E-12080 Castelló (Spain)
2014-05-12
We investigate the bright-to-dark exciton conversion efficiency in type-II quantum dots subject to a perpendicular magnetic field. To this end, we take the exciton storage protocol recently proposed by Simonin and co-workers [Phys. Rev. B 89, 075304 (2014)] and simulate its coherent dynamics. We confirm the storage is efficient in perfectly circular structures subject to weak external electric fields, where adiabatic evolution is dominant. In practice, however, the efficiency rapidly degrades with symmetry lowering. Besides, the use of excited states is likely unfeasible owing to the fast decay rates. We then propose an adaptation of the protocol which does not suffer from these limitations.
Berry, Michael Victor
for a light beam reflected by a mirror containing a step of height . A theory of this optical phenomenon, Olariuetal 1985), inaccessible magnetic flux diffracts electrons, producing interference fringes whose-dimensional) problem to be studied here. A monochromatic beam of electrons (charge -e) travelling in the r = (x, y
Iye, Yasuhiro
July 2003; published 5 December 2003 The Fano effect, which occurs through the quantum-mechanical probe to detect a quantum-mechanical phase of travers- ing electrons. DOI: 10.1103/PhysRevB.68 such a system, namely, a QD embedded in one arm of an AB ring. It was found that an electron at least partially
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.
Maxwell Duality, Lorentz Invariance, and Topological Phase
NASA Technical Reports Server (NTRS)
Dowling, J.; Williams, C.; Franson, J.
1999-01-01
We discuss the Maxwell electromagnetic duality relations between the Aharonov-Bohm, Aharonov-Casher, and He-McKellar-Wilkens topological phases, which allows a unified description of all three phenomena.
Quantum interference in an electron-hole graphene ring system
NASA Astrophysics Data System (ADS)
Smirnov, D.; Schmidt, H.; Haug, R. J.
2013-12-01
Quantum interference is observed in a graphene ring system via the Aharonov Bohm effect. As graphene is a gapless semiconductor, this geometry allows to study the unique situation of quantum interference between electrons and holes in addition to the unipolar quantum interference. The period and amplitude of the observed Aharonov-Bohm oscillations are independent of the sign of the applied gate voltage showing the equivalence between unipolar and dipolar interference.
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.
NASA Astrophysics Data System (ADS)
Kang, Kicheon
2014-02-01
We investigate the local geometric phase induced by Faraday's law of induction in a superconducting charge qubit threaded by an Aharonov-Bohm flux. A quantum-state reconstruction scheme, which is based on measurement of three complementary quantities, that is, the extra charge and two local currents, is introduced. We find that, while the variation of the local phase with magnetic field is determined by Faraday's law, incorporation of the time-reversal symmetry enables complete determination of the local phase. This procedure clearly demonstrates that the local geometric phase is a physical quantity (aside from a global phase factor), in contrast to the standard description of the Aharonov-Bohm effect.
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.
Equipment management system (EMS)
T. Yurtsever; M. Comerford
1995-01-01
Equipment Management System (EMS) is a software tool used to monitor and track equipment states, restrictions and PM schedules in real time. EMS has been designed and customized to support the MOS-2 die production facility. The system provides graphical representation of the entire factory. Color coded icons represent equipment's current state (i.e. qualification, production, unscheduled maintenance, etc.). Preventative maintenance schedules
Knott, Graham; Genoud, Christel
2013-10-15
Since electron microscopy (EM) first appeared in the 1930s, it has held centre stage as the primary tool for the exploration of biological structure. Yet, with the recent developments of light microscopy techniques that overcome the limitations imposed by the diffraction boundary, the question arises as to whether the importance of EM in on the wane. This Commentary describes some of the pioneering studies that have shaped our understanding of cell structure. These include the development of cryo-EM techniques that have given researchers the ability to capture images of native structures and at the molecular level. It also describes how a number of recent developments significantly increase the ability of EM to visualise biological systems across a range of length scales, and in 3D, ensuring that EM will remain at the forefront of biology research for the foreseeable future. PMID:24124192
ERIC Educational Resources Information Center
Matteucci, G.
2007-01-01
In the so-called electric Aharonov-Bohm effect, a quantum interference pattern shift is produced when electrons move in an electric field free region but, at the same time, in the presence of a time-dependent electric potential. Analogous fringe shifts are observed in interference experiments where electrons, travelling through an electrostatic…
V. Uski; B. Mehlig; R. A. Römer
1998-01-01
We have calculated wave functions and matrix elements of the dipole operator in the two- and three-dimensional Anderson model of localization and have studied their statistical properties in the limit of weak disorder. In particular, we have considered two cases. First, we have studied the fluctuations as an external Aharonov-Bohm flux is varied. Second, we have considered the influence of
Suppression of decoherence in a graphene monolayer ring
Smirnov, D., E-mail: smirnov@nano.uni-hannover.de; Rode, J. C.; Haug, R. J. [Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstr. 2, 30167 Hannover (Germany)
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.
Akira Inomata; Georg Junker; Raj Wilson
1993-01-01
The unified treatment of the Dirac monopole, the Schwinger monopole, and the Aharonov-Bohm problem by Barut and Wilson is revisited via a path integral approach. The Kustaanheimo-Stiefel transformation of space and time is utilized to calculate the path integral for a charged particle in the singular vector potential. In the process of dimensional reduction, a topological charge quantization rule is
Nontrivial systems and the necessity of the scalar quantum mechanics axioms
Kotulek, Jan [Mathematical Institute, Silesian University at Opava, Na Rybnicku 1, 746 01 Opava (Czech Republic)
2009-06-15
We discuss the necessity of the axioms of scalar quantum mechanics introduced by Paschke and clearly demonstrate their geometric and/or physical meaning. We show that reasonable nonrelativistic quantum mechanics is exactly specified by the axioms. A system describing the electric Aharonov-Bohm effect is presented. It illustrates the topological obstructions for the existence of a Hamiltonian.
Carbon nanotubes in confined magnetic fields: gap oscillations and
Marini, Andrea
Carbon nanotubes in confined magnetic fields: gap oscillations and persistent currents from a new;OutlineOutline Aharonov-Bohm oscillations in Carbon nanotubes Curvature effects Persistent currents #12 as a change in the interference pattern #12;The AB effect in carbon nano-tubes (CNTs) (I) A. Bachtold et al
Carbon nanotubes in confined magneticCarbon nanotubes in confined magnetic fields: thefields: the
Marini, Andrea
Carbon nanotubes in confined magneticCarbon nanotubes in confined magnetic fields: thefieldsOutline Aharonov-Bohm oscillations in Carbon nanotubes Confined and extended magnetic fields & Curvature effects as a change in the interference pattern #12;The AB effect in carbon nano-tubes A. Bachtold et al., Nature 397
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.
Topological interactions in broken gauge theories
Mark de Wild Propitius
1995-01-01
This thesis deals with planar gauge theories in which some gauge group G is spontaneously broken to a finite subgroup H. The spectrum consists of magnetic vortices, global H charges and dyonic combinations exhibiting topological Aharonov-Bohm interactions. Among other things, we review the Hopf algebra D(H) related to this residual discrete H gauge theory, which provides an unified description of
Quantum mechanical effects of topological origin
NASA Technical Reports Server (NTRS)
Duru, I. H.
1993-01-01
Following a brief review of the original Casimir and Aharonov-Bohm effects, some other effects of similar natures are mentioned. A Casimir interaction between AB fluxes is presented. Possible realizations of the Casimir effects for massive charged fields in solid state structures and a new AB effect for photons are suggested.
www.aspbs.com/enn odeling of arbon-Based Nanojunctions
Cuniberti, Gianaurelio
transform the tube from a metal into rnp_iY~,n semiconductor and vice versa. This was addressed a model Aharonov-Bohm oscillations [26] of the bandgap due to a flux the tube [27]. It has also been shown, and (d) controlled switches. PROPERTIES CARBON NANOTUBES (CNTs) In this we review the electronic
Magnetic Fields Effects on the Electronic Conduction Properties of Molecular Ring Structures
Dhurba Rai; Oded Hod; Abraham Nitzan
2011-01-01
While mesoscopic conducting loops are sensitive to external magnetic fields, as seen by observations of the Aharonov-Bohm (AB) effect in such structures, the field needed to observe the AB periodicity in small molecular rings is unrealistically large. The present study aims to identify conditions under which magnetic field dependence can be observed in electronic conduction through such molecules. We consider
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.
www.lpr-journal.org Temperature-dependent magneto-photoluminescence
Kono, Junichiro
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
Environmental Media Services (EMS)
NSDL National Science Digital Library
Environmental Media Services (EMS) is a nonprofit communications clearinghouse committed to the expansion of media coverage on critical environmental and public health issues. True to their mission, EMS staff "build relationships with top scientists, physicians, and other experts to bring journalists the latest and most credible information." EMS's modest homepage is free of clutter but full of content. While several sections are under construction and updates (currently) appear irregular, a series of available articles provides useful summaries of important environmental news issues over the past six months. Current articles include "The impacts of global warming on the oceans" and "Cool companies," among others.
Pascoal, Marta Margarida Braz
OPTIMIZAC¸ ~ AO EM REDES UMA VIS ~ AO GLOBAL Deolinda Dias Rasteiro, Jose Luis Santos, Marta Braz; Optimiza¸c~ao em Redes Uma Vis~ao Global N = fv 1 ; : : : ; v n g j f1; : : : ; ng conjunto de n'os (v; j) Rede (N ; A) grafo (N ; A) com um v'ertice inicial s e um v'ertice terminal t, a cujos arcos
Sayre, M R; White, L J; Brown, L H; McHenry, S D
2002-01-01
Now, more than ever before, the spirit of the emergency services professional is recognized by people everywhere. Individuals from every walk of life comprehend the reality of the job these professionals do each day. Placing the safety of others above their own is their acknowledged responsibility. Rescue and treatment of ill and injured patients are their purpose as well as their gratification. The men and women who provide prehospital care are well aware of the unpredictable nature of emergency medical services (EMS). Prehospital care is given when and where it is needed: in urban settings with vertical challenges and gridlock; in rural settings with limited access; in confined spaces; within entrapments; or simply in the street, exposed to the elements. Despite the challenges, EMS professionals rise to the occasion to do their best with the resources available. Despite more than 30 years of dedicated service by thousands of EMS professionals, academic researchers, and public policy makers, the nation's EMS system is treating victims of illness and injury with little or no evidence that the care they provide is optimal. A national investment in the EMS research infrastructure is necessary to overcome obstacles currently impeding the accumulation of essential evidence of the effectiveness of EMS practice. Funding is required to train new researchers and to help them establish their careers. Financial backing is needed to support the development of effective prehospital treatments for the diseases that drive the design of the EMS system, including injury and sudden cardiac arrest. Innovative strategies to make EMS research easier to accomplish in emergency situations must be implemented. Researchers must have access to patient outcome information in order to evaluate and improve prehospital care. New biomedical and technical advances must be evaluated using scientific methodology. Research is the key to maintaining focus on improving the overall health of the community in a competitive and cost-conscious health care market. Most importantly, research is essential to ensure that the best possible patient care is provided in the prehospital setting. The bravery and dedication of EMS professionals cannot be underestimated. Images of firefighters, EMS personnel, and others going into danger while others are evacuating will remain burned in our collective consciousness. These professionals deserve the benefit of research to assist them in providing the best possible care in the challenging circumstances they encounter. With this document, we are seeking support for elevating the science of EMS and prehospital care to the next level. It is essential that we examine innovative ways to deliver prehospital care. Strategies to protect the safety of both the patient and the public safety worker must be devised and tested. There are many questions that remain to be asked, many practices to be evaluated, and many procedures to be improved. Research is the key to obtaining the answers. PMID:12108581
O'Laughlin, Jay
#12;#12;#12;#12;#12;......... em o #12;'"''!.. . ' I The UNIVERSITY of IDAHO Moscow, Idaho Editors Donald W. Samuelson, who strode purposefully out of the North, became Idaho's leading gentle- man will determine his place in Idaho history. Perhaps no governor of a Western state has more complex
Peter König; Michael B. Braunfeld; John W. Sedat; David A. Agard
We have studied the in vitro reconstitution of sperm nuclei and small DNA templates to mitotic chroma- tin in Xenopus laevis egg extracts by three-dimensional (3D) electron microscopy (EM) tomography. Using specif- ically developed software, the reconstituted chromatin was interpreted in terms of nucleosomal patterns and the overall chromatin connectivity. The condensed chromatin formed
PROMETEUS FILOSOFIA EM REVISTA
VIVA VOX; João Roberto Barros II; Marcos Antonio da Silva
2010-01-01
Resumo: O uso heurístico do conceito de natureza é importante para os propósitos concernentes à ideia de uma história como palco para o desenvolvimento das disposições originárias do ser humano. Esse argumento torna possível falar do desenvolvimento ativo das disposições originárias do ser humano sem ferir o núcleo crítico que marca a filosofia kantiana em seu período áureo. Nosso argumento
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.
Bioterrorism awareness for EMS.
Patrick, Richard W
2004-04-01
It is important to understand that the issues surrounding bioterrorism and all weapons of mass destruction are complex. In an effort to enhance response to such events, EMS should handle all incidents from the perspective of an all-hazards approach. Prevention, preparation, response and recovery are essential to the safe mitigation of all incidents. Organizations must be prepared. Plan now for a safer tomorrow. Your personnel and communities depend on you. PMID:15131906
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
Identified EM Earthquake Precursors
NASA Astrophysics Data System (ADS)
Jones, Kenneth, II; Saxton, Patrick
2014-05-01
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 a number of custom rock experiments, two hypotheses were formed which could answer the EM wave model. The first hypothesis concerned a sufficient and continuous electron movement either by surface or penetrative flow, and the second regarded a novel approach to radio transmission. Electron flow along fracture surfaces was determined to be inadequate in creating strong EM fields, because rock has a very high electrical resistance making it a high quality insulator. Penetrative flow could not be corroborated as well, because it was discovered that rock was absorbing and confining electrons to a very thin skin depth. Radio wave transmission and detection worked with every single test administered. This hypothesis was reviewed for propagating, long-wave generation with sufficient amplitude, and the capability of penetrating solid rock. Additionally, fracture spaces, either air or ion-filled, can facilitate this concept from great depths and allow for surficial detection. A few propagating precursor signals have been detected in the field occurring with associated phases using custom-built loop antennae. Field testing was conducted in Southern California from 2006-2011, and outside the NE Texas town of Timpson in February, 2013. The antennae have mobility and observations were noted for recurrence, duration, and frequency response. At the Southern California field sites, one loop antenna was positioned for omni-directional reception and also detected a strong First Schumann Resonance; however, additional Schumann Resonances were absent. At the Timpson, TX field sites, loop antennae were positioned for directional reception, due to earthquake-induced, hydraulic fracturing activity currently conducted by the oil and gas industry. Two strong signals, one moderately strong signal, and approximately 6-8 weaker signals were detected in the immediate vicinity. The three stronger signals were mapped by a biangulation technique, followed by a triangulation technique for confirmation. This was the first antenna mapping technique ever performed for determining possible earthquake epicenters. Six and a half months later, Timpson experienced two M4 (M4.1 and M4.3) earthquakes on September 2, 2013 followed by a M2.4 earthquake three days later, all occurring at a depth of five kilometers. The Timpson earthquake activity now has a cyclical rate and a forecast was given to the proper authorities. As a result, the Southern California and Timpson, TX field results led to an improved design and construction of a third prototype antenna. With a loop antenna array, a viable communication system, and continuous monitoring, a full fracture cycle can be established and observed in real-time. In addition, field data could be reviewed quickly for assessment and lead to a much more improved earthquake forecasting capability. The EM precursors determined by this method appear to surpass all prior precursor claims, and the general public will finally receive long overdue forecasting.
College of Engineering EM Engineering Mechanics
MacAdam, Keith
College of Engineering EM Engineering Mechanics KEY: # = new course * = course changed = course or concur: MA 213. EM 302 MECHANICS OF DEFORMABLE SOLIDS. (3 of Engineering or consent of chairperson, and EM 221; prereq or concur: MA 214. EM 313 DYNAMICS. (3
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
B-EM: A Classifier Incorporating Bootstrap with EM Approach for Data Mining
Wu, Xintao
B-EM: A Classifier Incorporating Bootstrap with EM Approach for Data Mining Xintao Wu UNC that the more unlabeled examples are combined in learning, the more accurate the result. We then introduce B-EM
Direct observation of the Aharonov-Casher phase.
König, M; Tschetschetkin, A; Hankiewicz, E M; Sinova, Jairo; Hock, V; Daumer, V; Schäfer, M; Becker, C R; Buhmann, H; Molenkamp, L W
2006-02-24
Ring structures fabricated from HgTe/HgCdTe quantum wells have been used to study Aharonov-Bohm type conductance oscillations as a function of Rashba spin-orbit splitting strength. We observe nonmonotonic phase changes indicating that an additional phase factor modifies the electron wave function. We associate these observations with the Aharonov-Casher effect. This is confirmed by comparison with numerical calculations of the magnetoconductance for a multichannel ring structure within the Landauer-Büttiker formalism. PMID:16606124
Vacuum stress around a topological defect
De Lorenci, V A
2003-01-01
We show that a dispiration (a disclination plus a screw dislocation) polarizes the vacuum of a scalar field giving rise to an energy momentum tensor which, as seen from a local inertial frame, presents non vanishing off-diagonal components. Such a new effect resembles that where an induced vacuum current arises around a needle solenoid carrying a magnetic flux (the Aharonov-Bohm effect). The results may have applications in cosmology (chiral cosmic strings) and condensed matter physics (materials with linear defects).
On the Nonlocaity in the Goulomb Gauge External Field Problem
Péter Hraskó
2015-01-31
The apparent nonlocality of the Coulomb gauge external field problem in electrodynamics is illustrated with an example in which nonlocality is especially striking. Explanation of this apparent nonlocal behaviour based on a purely local picture is given. A gauge invariant decomposition of the Lorentz-force into two terms with clear physical meanings is pointed out. Based on this decomposition derivation of the Aharonov-Bohm effect in terms of field strengths alone is given.
Mark de Wild Propitius; F. Alexander Bais
1995-01-01
In these lecture notes, we present a self-contained discussion of planar\\u000agauge theories broken down to some finite residual gauge group H via the Higgs\\u000amechanism. The main focus is on the discrete H gauge theory describing the long\\u000adistance physics of such a model. The spectrum features global H charges,\\u000amagnetic vortices and dyonic combinations. Due to the Aharonov-Bohm
Topological interactions in broken gauge theories
Mark de Wild Propitius
1995-01-01
This thesis deals with planar gauge theories in which some gauge group G is\\u000aspontaneously broken to a finite subgroup H. The spectrum consists of magnetic\\u000avortices, global H charges and dyonic combinations exhibiting topological\\u000aAharonov-Bohm interactions. Among other things, we review the Hopf algebra D(H)\\u000arelated to this residual discrete H gauge theory, which provides an unified\\u000adescription of
Topological phase shift in a cold-atom interferometer
J. H. Müller; D. Bettermann; V. Rieger; K. Sengstock; U. Sterr; W. Ertmer
1995-01-01
Matter-wave interferences in a four-pulse version of a Ramsey-Bordé atom interferometer have been utilized to study phase shifts. A topological phase shift analogous to the scalar Aharonov-Bohm effect proposed for charged-particle interferences in the presence of a pulsed electrostatic potential has been investigated. The time-dependent potential has been generated by the interaction of a laser field with an induced atomic
Thank You and Farewell to Tonomura-kun
NASA Astrophysics Data System (ADS)
Fukuyama, Hidetoshi
2014-01-01
"Science triggers technology; technology inspires science" is true, so is your case, when you proved partially1 in 1982 and completely2,3 in 1986 the Aharonov-Bohm(AB) effect, the principal manifestation of gauge field, based on the state-of-the-art electron microscope that you developed. You put "period," i.e., an end, on the controversy associated with the AB effect...
Populações estelares em galáxias HII
NASA Astrophysics Data System (ADS)
Westera, P.; Cuisinier, F.; Telles, E.; Kehrig, C.
2003-08-01
Analisamos o conteúdo estelar de 74 galáxias HII a partir do contínuo observado nos espectros ópticos dessas galáxias, utilizando métodos de síntese de população estelar. Descobrimos que todas as galáxias para as quais encontramos soluções contêm uma população estelar velha que domina a massa estelar, e numa maioria dessas também encontramos evidência de uma população de idade intermediaria além da geração jovem que está se formando agora. Concluímos que a formação estelar dessas galáxias se realiza em surtos individuais, Esses surtos são interrompidos por longos períodos de inatividade, com os primeiros consumindo a maior parte do gás. Sugerimos, portanto, que as galáxias HII sejam galáxias anãs normais flagradas em um período de surto.
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
Burning the EMS candle. EMS shifts and worker fatigue.
McCallion, R; Fazackerley, J
1991-10-01
Has coffee become your best friend? Do you sleep only in your dreams? Is your bed merely an illusion? If so, you are not alone; sleep deprivation is a fact of life for many EMS personnel. Though widely accepted, isn't it time that we question the effects of those long days and nights? PMID:10116022
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
EM 306 Statics ABET EC2000 syllabus
Ben-Yakar, Adela
Edition Other Required Material: None Course Objectives: To be able to analyze systems of forcesEM 306 Â Statics Page 1 ABET EC2000 syllabus EM 306 Â Statics Fall and Spring 2009-10 Required Assignments: None Laboratory Projects: None #12;EM 306 Â Statics Page 2 ABET EC2000 syllabus Contribution
Project planning for EMS and SCADA systems
Charles T. Lindeberg; Wayne R. Block
1993-01-01
A typical supervisory control and data acquisition (SCADA) system or an energy management system (EMS) has an installed life of only 10 to 15 years. Because it can take five years or more to implement a new EMS or SCADA system, managing such projects is becoming a way of life for utilities. Project planning for EMS and SCADA systems is
Collins, R L
2006-01-01
An electron is a purely electromagnetic particle, a PEP. The biggest problem has been charge. Most simply put, charge is a source or sink of E fields. A way to assemble EM fields into a stable configuration that exhibits charge and other particle properties has been found, based in part on Weber's interpretation of the Faraday homopolar generator. A dipolar B field, spinning about its symmetry axis, creates a radial vxB electric field that falls off as 1/r^2. This paper suggests that pair production involves the rearrangement of the EM fields of each half a photon. The EM fields then oscillate at the Compton frequency between a dipolar B field and a toroidal E field. Electric and magnetic flux are quantized. An electron has angular momentum, and so the EM field assembly is spinning. The 1/r^2 E=vxB electric field, created by the spinning dipolar B field, is strongest at the waist and zero at the poles. Precession of the spin axis about a different axis and with the same rate as spin, produces charge. Otherwis...
NSDL National Science Digital Library
2014-09-14
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.
CURSO DE ESPECIALIZAO EM FISIOTERAPIA
Floeter, Sergio Ricardo
BioquÃmica FisiolÃ³gica Medicina do ExercÃcio em Pediatria Fisioterapia RespiratÃ³ria Fisioterapia na SaÃºde ginecolÃ³gica Nanotecnologia Â Atualidades e Perspectivas Vinculadas Ã Tecnologia dos Materiais BiomecÃ¢nica
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
Mestrado e Doutorado em Filosofia edital 2014
Mestrado e Doutorado em Filosofia PUC-Rio edital 2014 O Departamento de Filosofia da PontifÃcia PÃ³s-graduaÃ§Ã£o em Filosofia, nos nÃveis de mestrado e doutorado. Para a seleÃ§Ã£o de 2014, sÃ£o oferecidas Filosofia; o candidato ao doutorado deverÃ¡ ser mestre em Filosofia ou ter titulaÃ§Ã£o equivalente. 1.3. Os
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
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM COMBUSTÃO E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM COMBUSTÃO E PROPULSÃO Adaptação Obrigatórias para o mestrado PCP
EM international activities. February 1997 highlights
NONE
1997-02-01
EM International Highlights is a brief summary of on-going international projects within the Department of Energy`s Office of Environmental Management (EM). This document contains sections on: Global Issues, activities in Western Europe, activities in central and Eastern Europe, activities in Russia, activities in Asia and the Pacific Rim, activities in South America, activities in North America, and International Organizations.
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…
Analysis of EM Channel of Producing Well
Jintao Yu; Mingli Ding; Tingwei Liang
2008-01-01
Measurements while drilling (MWD) is a new technology by which we can observe the measurement values of the drilling parameters in the way of real-time. Use the results of searching the electromagnetic (EM) transmission channel for MWD for reference, an EM transmission model for the wireless transmission is set up. In addition, the model parameters are calculated by using the
Em que medida devem ser privados, em que medida devem ser pblicos o conhecimento e a informao?
Kuhlen, Rainer
Em que medida devem ser privados, em que medida devem ser pÃºblicos o conhecimento e a informaÃ§Ã£o? 1 TransparÃªncias com licenÃ§a Creative Commons Em que medida devem ser privados, em que medida devem ser pÃºblicos o as alternativas? codexKonstanz #12;Em que medida devem ser privados, em que medida devem ser pÃºblicos o
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.
EM International, July 1994, Volume 2
Not Available
1994-10-01
The Office of Environmental Management (EM) at the Department of Energy (DOE) is seeking out and leveraging foreign technology, data, and resources in keeping with EM`s mandate to protect public health and the environment through the safe and cost-effective remediation of the Department`s nuclear weapons sites. EM works closely with foreign governments, industry, and universities to obtain innovative environmental technologies, scientific and engineering expertise, and operations experience that will support EM`s objectives. Where appropriate, these international resources are used to manage the more urgent risks at our sites, secure a safe workplace, help build consensus on critical issues, and strengthen our technology development program. Through international agreements EM engages in cooperative exchange of information, technology, and individuals. Currently, we are managing agreements with a dozen countries in Europe, Latin America, and Asia. These agreements focus on environmental restoration, waste management, transportation of radioactive wastes, and decontamination and decommissioning. This publication contains the following articles: in situ remediation integrated program; in-situ characterization and inspection of tanks; multimedia environmental pollutant assessment system (MEPAS); LLNL wet oxidation -- AEA technology. Besides these articles, this publication covers: EU activities with Russia; technology transfer activities; and international organization activities.
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.
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 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
Investigao em clulas estaminais no Biocant deu origem a cinco patentes em dois anos
Instituto de Sistemas e Robotica
InvestigaÃ§Ã£o em cÃ©lulas estaminais no Biocant deu origem a cinco patentes em dois anos, nos Ãºltimos dois anos, em cinco patentes, duas delas jÃ¡ licenciadas a empresas, disse Ã Lusa o vias de dar origem a um projeto empresarial" no Ã¢mbito do rastreio e criaÃ§Ã£o de novos fÃ¡rmacos. As duas
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
EM-dissertations completed in 2007
Franssen, Michael
2007 #12;Virtual Thermo-Mechanical Prototyping of Microelectronics Devices Driel, W.D. van Advisors-90-9022179-3 EM research theme: Computational and Experimental Mechanics Thermomechanical fatigue failure
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).
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.
José E. P. Turco; Luiz F. S. A. Ferreira; Renato L. Furlan
2 FCAV\\/UNESP. Fone: (16) 3209-2637 3 FCAV\\/UNESP. Fone: (16) 3209-2654 Resumo: Resumo: Resumo: Resumo: Resumo: Este trabalho teve por objetivo analisar o consumo e o custo da energia elétrica em um galpão comercial de frangos de corte, durante dois ciclos de criação, inverno e verão. Foram realizadas medidas de consumo dos ventiladores, nebulizadores, lâmpadas e comedouros durante o manejo de
Tour of the Electromagnetic Spectrum (EMS) Videos
NSDL National Science Digital Library
Troy Benesch
2009-01-01
These videos introduce middle- and high school-age learners to the electromagnetic spectrum. The product consists of 8 animations including an introduction to electromagnetic waves and one animation for each wavelength of the EM spectrum (Radio, Microwave, Infrared, Visible, Ultraviolet, X-Rays and Gamma Rays). Each wavelength of the EM spectrum offers a construct to illustrate and teach about NASA sensors, missions, and science. Emphasis is placed on relevant science, such as lunar exploration, and hot science topics, such as climate change. The examples and narrative for each wavelength animation build on the learners’ prior knowledge then introduces examples from NASA missions. These examples explore the use of spectral analysis and visualizations that help scientists make discoveries about the world around us using EM waves.
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
ECE 341: Electromagnetic Fields I EM devices and systems
Schumacher, Russ
in material media - Electromagnetic induction - Inductance - Magnetic energy Applications: - ElectronicsECE 341: Electromagnetic Fields I EM devices and systems - Can compute and analyze potentials compositions - Can evaluate capacitance, inductance, resistance, and conductance of EM structures - Understands
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.
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
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 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
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 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
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
Influence of topology in a quantum ring
NASA Astrophysics Data System (ADS)
Netto, A. L. Silva; Chesman, C.; Furtado, C.
2008-05-01
In this Letter we study the quantum rings in the presence of a topological defect. We use geometric theory of defects to describe one and two-dimensional quantum rings in the presence of a single screw dislocation. In addition we consider some potential in a two dimensional ring and calculate their energy spectrum. It is shown that the energy spectrum depend on the parabolic way on the burgers vectors of the screw dislocation. We also show that the presence of a topological defect introduces a new contribution for the Aharonov-Bohm effect in the quantum ring.
Weak localization in mesoscopic hole transport: berry phases and classical correlations.
Krueckl, Viktor; Wimmer, Michael; Adagideli, ?nanç; Kuipers, Jack; Richter, Klaus
2011-04-01
We consider phase-coherent transport through ballistic and diffusive two-dimensional hole systems based on the Kohn-Luttinger Hamiltonian. We show that intrinsic heavy-hole-light-hole coupling gives rise to clear-cut signatures of an associated Berry phase in the weak localization which renders the magnetoconductance profile distinctly different from electron transport. Nonuniversal classical correlations determine the strength of these Berry phase effects and the effective symmetry class, leading even to antilocalization-type features for circular quantum dots and Aharonov-Bohm rings in the absence of additional spin-orbit interaction. Our semiclassical predictions are confirmed by numerical calculations. PMID:21561209
Dimensional crossover in quantum networks: from macroscopic to mesoscopic physics.
Schopfer, Félicien; Mallet, François; Mailly, Dominique; Texier, Christophe; Montambaux, Gilles; Bäuerle, Christopher; Saminadayar, Laurent
2007-01-12
We report on magnetoconductance measurements of metallic networks of various sizes ranging from 10 to 10(6) plaquettes, with an anisotropic aspect ratio. Both Altshuler-Aronov-Spivak h/2e periodic oscillations and Aharonov-Bohm h/e periodic oscillations are observed for all networks. For large samples, the amplitude of both oscillations results from the incoherent superposition of contributions of phase coherent regions. When the transverse size becomes smaller than the phase coherent length Lphi, one enters a new regime which is phase coherent (mesoscopic) along one direction and macroscopic along the other, leading to a new size dependence of the quantum oscillations. PMID:17358635
Synthetic Gauge Fields for Vibrational Excitations of Trapped ions
A. Bermudez; T. Schaetz; D. Porras
2011-11-12
The vibrations of a collection of ions in a microtrap array can be described in terms of hopping phonons. We show theoretically that the vibrational couplings may be tailored by using a gradient of the microtrap frequencies, together with a periodic driving of the trapping potential. These ingredients allow us to induce effective gauge fields on the vibrational excitations, such that phonons mimic the behavior of charged particles in a magnetic field. In particular, microtrap arrays are ideally suited to realize the famous Aharonov-Bohm effect, and observe the paradigmatic edge states typical from quantum-Hall samples and topological insulators.
Pure phase decoherence in a ring geometry
Zhu, Z. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia, V6T 1Z1 (Canada); Aharony, A.; Entin-Wohlman, O. [Department of Physics and the Ilse Katz Center for Meso- and Nano-Scale Science and Technology, Ben Gurion University, Beer Sheva 84105 (Israel); Pacific Institute of Theoretical Physics, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia, V6T 1Z1 (Canada); Stamp, P. C. E. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia, V6T 1Z1 (Canada); Pacific Institute of Theoretical Physics, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia, V6T 1Z1 (Canada)
2010-06-15
We study the dynamics of pure phase decoherence for a particle hopping around an N-site ring, coupled both to a spin bath and to an Aharonov-Bohm flux which threads the ring. Analytic results are found for the dynamics of the influence functional and of the reduced density matrix of the particle, both for initial single wave-packet states, and for states split initially into two separate wave packets moving at different velocities. We also give results for the dynamics of the current as a function of time.
NASA Astrophysics Data System (ADS)
Koga, M.; Matsumoto, M.; Kusunose, H.
2015-03-01
The Kondo effect plays an important role in emergence of electric polarization in a triangular triple-quantum-dot system, where one of the three dots is point-contacted with a single lead, and a magnetic flux penetrates through the triangular loop. The Kondo-induced electric polarization exhibits an Aharonov-Bohm type oscillation as a function of the magnetic flux. Our theoretical study shows various oscillation patterns associated with the field-dependent mixing of twofold orbitally degenerate ground states and their sensitivity to the point contact.
Noise-Induced Phase Transition in the Electronic Mach-Zehnder Interferometer
NASA Astrophysics Data System (ADS)
Levkivskyi, Ivan P.; Sukhorukov, Eugene V.
2009-07-01
We consider dephasing in the electronic Mach-Zehnder interferometer strongly coupled to current noise created by a voltage biased quantum point contact (QPC). We find the visibility of Aharonov-Bohm oscillations as a function of voltage bias and express it via the cumulant generating function of noise. In the large-bias regime, high-order cumulants of current add up to cancel the dilution effect of a QPC. This leads to an abrupt change in the dependence of the visibility on voltage bias which occurs at the QPC’s transparency T=1/2. Quantum fluctuations in the vicinity of this point smear out the sharp transition.
The Luther-Emery liquid: Spin gap and anomalous flux period
NASA Astrophysics Data System (ADS)
Seidel, Alexander; Lee, Dung-Hai
2005-01-01
We study the dependence of the ground state energy on an applied Aharonov-Bohm flux ? for the Luttinger model with large momentum scattering. Employing the method of finite size bosonization, we show that for systems with a spin gap but with gapless charge degrees of freedom, the ground state energy has an exact period of hc/2e , i.e., half a flux quantum, in the limit of large system size L . Finite size corrections are found to vanish exponentially in L . This behavior is contrasted to that of the spin gapless case, for both even and odd particle number. Generalizations to finite temperature are also discussed.
Non-reciprocal transmission in photonic lattices based on unidirectional coherent perfect absorption
Longhi, Stefano
2015-01-01
A method for realizing asymmetric (one-way) transmission of discretized light in modulated, linear and purely passive optical lattices is suggested, which exploits the idea of unidirectional coherent perfect absorption. The system consists of a linear photonic lattice of coupled resonators or waveguides, side coupled to a chain of lossy elements, in which light can avoid the occupation of the dissipative sites when propagating in one way, but not in the opposite one. Non-reciprocity requires modulation of the resonator/waveguide parameters, realizing a dissipative optical Aharonov-Bohm diode with non-reciprocal behavior.
Topological quantum computation via the quantum tunneling effect.
Kou, Su-Peng
2009-03-27
Quantum computers are predicted to utilize quantum states to process tasks far faster than those of conventional classical computers. In this Letter we show an alternative approach towards building topological quantum computers by tuning the quantum tunneling effect of degenerate quantum states in topological order, instead of braiding anyons. Using a designer Hamiltonian-the Wen-Plaquette model as an example, we study its quantum tunneling effect of the toric codes and show how to control the toric codes to realize topological quantum computation. In particular, we give a proposal to the measurement of the toric codes from Aharonov-Bohm interferences of quasiparticles. PMID:19392257
Conductivity and gating of silicon ringchains.
Speyer, Joseph L; Ovchinnikov, Igor V; Neuhauser, Daniel; Baugh, Delroy
2005-09-22
One-dimensional and two-dimensional conductivity calculations are done for a set of several closely spaced quantum silicon rings, following the development of bottom-up approaches for producing silicon rings. The transmission is easily influenced by electric and magnetic gatings and has band features even for two or three rings, showing its potential usefulness for logical devices. Analysis on different gatings shows that the electric-field gating would be as effective as the Aharonov-Bohm magnetic gating. PMID:16392508
Gauge Field Optics with Anisotropic Media
NASA Astrophysics Data System (ADS)
Liu, Fu; Li, Jensen
2015-03-01
By considering gauge transformations on the macroscopic Maxwell's equations, a two-dimensional gauge field, with its pseudomagnetic field in the real space, is identified as tilted anisotropy in the constitutive parameters. We show that the optical spin Hall effect with broadband response and one-way edge states become possible simply by using anisotropic media. The proposed gauge field also allows us to obtain unidirectional propagation for a particular pseudospin based on the Aharonov-Bohm effect. Our approach will be useful in spoof magneto-optics with arbitrary magnetic fields mimicked by metamaterials with subwavelength unit cells. It also serves as a generic way to design polarization-dependent devices.
NASA Astrophysics Data System (ADS)
Ermolaev, A. M.; Rashba, G. I.
2014-10-01
Kubo formula was obtained for conductivity tensor of electron gas on the surface of nanotube with superlattice in magnetic field. The high-frequency conductivity tensor components were calculated for quantum and quasiclassical cases. Electromagnetic wave Landau damping areas in the tube were determined. The conductivity tensor components show Aharonov-Bohm type oscillations and de Haas-van Alphen ones. When Fermi energy exceeds the miniband width, beatings are observed in the plot of conductivity vs. the tube parameters. Otherwise, the beatings are absent.
Period Halving in a Single-Mode Datta-Das Spin Field Effect Transistor
NASA Astrophysics Data System (ADS)
Lee, Hyun-Woo; ?ali?kan, S.; Park, Hyowon
2006-09-01
We study a nonballistic single-mode Datta-Das spin field effect transistor (SFET) subject to an external magnetic field parallel to the effective Rashba field. We map the SFET to an effective Aharonov-Bohm interferometer (ABI) and use this mapping to demonstrate that when the magnetic field is sufficiently strong, the Rashba-interaction-induced oscillation period of its conductance at sufficiently high temperature becomes a half of its zero temperature value while the temperature-induced period halving does not occur when the magnetic field is sufficiently weak.
Generation of uniform synthetic magnetic fields by split driving of an optical lattice
NASA Astrophysics Data System (ADS)
Creffield, C. E.; Sols, F.
2014-08-01
We describe a method to generate a synthetic gauge potential for ultracold atoms held in an optical lattice. Our approach uses a time-periodic driving potential based on quickly alternating two Hamiltonians to engineer the appropriate Aharonov-Bohm phases, and permits the simulation of a uniform tunable magnetic field. We explicitly demonstrate that our split-driving scheme reproduces the behavior of a charged quantum particle in a magnetic field over the complete range of field strengths, and obtain the Hofstadter butterfly band structure for the Floquet quasienergies.
Applications of the Complex Geometric "Phase" for Meta-stable Systems
S. Massar
1996-05-28
Garrison and Wright showed that upon undergoing cyclic quantum evolution a meta-stable state acquires both a geometric phase and a geometric decay probability. This is described by a complex geometric ``phase'' associated with the cyclic evolution of two states and is closely related to the two state formalism developed by Aharonov et al.. Applications of the complex geometric phase to the Born--Oppenheimer approximation and the Aharonov--Bohm effect are considered. A simple experiment based on the optical properties of absorbing birefringent crystals is proposed.
Surface state dominated transport in topological insulator Bi{sub 2}Te{sub 3} nanowires
Hamdou, Bacel, E-mail: bhamdou@physnet.uni-hamburg.de; Gooth, Johannes; Dorn, August; Nielsch, Kornelius, E-mail: knielsch@physnet.uni-hamburg.de [Institute of Applied Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany)] [Institute of Applied Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany); Pippel, Eckhard [Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Germany)] [Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Germany)
2013-11-04
We report on low temperature magnetoresistance measurements on single-crystalline Bi{sub 2}Te{sub 3} nanowires synthesized via catalytic growth and post-annealing in a Te-rich atmosphere. The observation of Aharonov-Bohm oscillations indicates the presence of topological surface states. Analyses of Subnikov-de Haas oscillations in perpendicular magnetoresistance yield extremely low two-dimensional carrier concentrations and effective electron masses, and very high carrier mobilities. All our findings are in excellent agreement with theoretical predictions of massless Dirac fermions at the surfaces of topological insulators.
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.
Quantum interference effects in antidot lattices in magnetic fields
NASA Astrophysics Data System (ADS)
Nakanishi, Takeshi; Ando, Tsuneya
1996-09-01
A numerical study is performed on quantum interference effects in antidot lattices in a weak magnetic field with the use of a recursive Green's function technique. An irregular Aharonov-Bohm (AB)-type oscillation varying sensitively with antidot diameters and periods is dominant in ideal antidot lattices. The AB-type oscillation disappears and an Al'tshuler, Aranov, and Spivak (AAS) oscillation manifests itself in the presence of fluctuations in the size or position of antidots. The AAS oscillation is much stronger in hexagonal lattices than in square lattices, in good agreement with experiments.
Quasiballistic transport of Dirac fermions in a Bi2Se3 nanowire.
Dufouleur, J; Veyrat, L; Teichgräber, A; Neuhaus, S; Nowka, C; Hampel, S; Cayssol, J; Schumann, J; Eichler, B; Schmidt, O G; Büchner, B; Giraud, R
2013-05-01
Quantum coherent transport of surface states in a mesoscopic nanowire of the three-dimensional topological insulator Bi(2}Se(3) is studied in the weak-disorder limit. At very low temperatures, many harmonics are evidenced in the Fourier transform of Aharonov-Bohm oscillations, revealing the long phase coherence length of spin-chiral Dirac fermions. Remarkably, from their exponential temperature dependence, we infer an unusual 1/T power law for the phase coherence length L(?)(T). This decoherence is typical for quasiballistic fermions weakly coupled to their environment. PMID:23683235
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.
On indices of the Dirac operator in a non-Fredholm case
Alexander Moroz
1996-03-15
The Dirac Hamiltonian with the Aharonov-Bohm potential provides an example of a non-Fredholm operator for which all spectral asymmetry comes entirely from the continuous spectrum. In this case one finds that the use of standard definitions of the resolvent regularized, the heat kernel regularized, and the Witten indices misses the contribution coming from the continuous spectrum and gives vanishing spectral asymmetry and axial anomaly. This behaviour in the case of the continuous spectrum seems to be general and its origin is discussed.
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.
Development of Em18-immunoblot and Em18-ELISA for specific diagnosis of alveolar echinococcosis.
Ito, Akira; Sako, Yasuhito; Yamasaki, Hiroshi; Mamuti, Wulamu; Nakaya, Kazuhiro; Nakao, Minoru; Ishikawa, Yuji
2003-02-01
Extensive experience has documented that Em2(plus)-ELISA, Em10-ELISA and Em18-immunoblot and Em18-ELISA are reliable serologic methods for detection of alveolar echinococcosis (AE) caused by the metacestodes of Echinococcus multilocularis. Among these, tests based on detection of antibodies to the specific Em18 antigen, either immunoblot or ELISA, appears to be the most specific for AE. Between 90 and 97% of AE cases with characteristic hepatic lesions detectable by image analysis have been positive in Em18-serology. In contrast Antigen B (8 kDa)-immunoblot is the most sensitive for all forms of echinococcosis, although it can not differentiate AE from cystic echinococcosis (CE). Primary serologic screening for echinococcosis, especially for CE using hydatid cyst fluid of Echinococcus granulosus appears to be highly sensitive in endemic areas. Glycoproteins (GPs) purified from cyst fluid of Taenia solium are highly specific for diagnosis of T. solium neuorcysticercosis (NCC). Using currently available antigens it is not difficult to differentiate these three larval cestodiases serologically. We recommend that (1) primary screening of CE in endemic areas should be carried out using hydatid cyst fluid of E. granulosus prepared from cysts in either sheep, human or mouse for immunoblot and from sheep or mouse for ELISA, (2) both primary screening and confirmation of AE in endemic areas should be carried out using Em18-ELISA, Em18-immunoblot or Em2(plus)-ELISA. Serodiagnosis in areas where both AE and CE are endemic, such as in China, should be carried out as a combination of (1) and (2), and (3) serology of NCC should be carried out using GP-ELISA or GP-immunoblot. All samples showing antibody to Em18 are exclusively from echinococcosis cases. There have been no false positive test reactions with sera from other diseases. Strongest Em18 responders are all from patients with AE but some weaker responses may be found in sera of persons with advanced complex lesions of CE. These highly reliable serodiagnostic methods using native, recombinant and synthetic antigens are briefly summarized and experiences with these methods in Japan is reviewed. We believe that use of these specific antigens in screening and confirmation programs for AE in Japan will improve specificity and reduce the confusion, anxiety and expense in persons whose sera give false positive reactions with crude echinococcal antigens. PMID:12606094
Metodos Matematicos em Financas Junho -Agosto 2005
Zubelli, Jorge Passamani
decimais (t = 5) usando truncamento (e.g. 1.23459 1.2345). Voce Â´e capaz de conseguir as duas raÂ´izes com 5 dÂ´igitos de precis~ao em tal aritmÂ´etica? (b) Encontre a raiz de menor valor absoluto da equa
Frmions ultra-frios em redes ticas
Liu, I-Shih
Efeito Zeeman BEEE Âµ=-= )()( |S MS >>>> | >>>> | >>>> Na presenÃ§a de um campo magnÃ©ticoNa presenÃ§a de um campo Corrida em busca do antiferromagnetismo #12;Experimentos Â· Schneider et al. Science 322, 1520 (2008
EMS Division Potential Benefits of Selected
Propulsion Systems have been Demonstrated Eg-Walters1: "In 1980 a 300 KW superconductive homopolar generator 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
Sheridan, Jennifer
are requested! If you have a news item, a request, an announcement etc. email it to geodept@geology at the University of New South Wales, Sydney, Australia. #12;GEOBULLETIN DEcEmBEr 16Th , 2011 - 3 - 1) Relationship Australia. The North Pole region hosts the oldest fossil life on Earth, as stromatolites in carbonates
Transportes em Revista.com Pas: Portugal
Instituto de Sistemas e Robotica
veículos Toyota Prius Plug-in (automóvel híbrido cujas baterias também são alimentadas por tomada elétrica 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
EM PROPAGATION IN JET ENGINE TURBINES
Eric Walton; Jonathan Young; Jim Moore; Kyle Davis
There is interest in the propagation of EM signals inside jet engine turbines for a number of reasons. Applications include radar scattering phenomenology and jet engine plasma plume formation studies. In our research, we are interested in the communication channel characteristics for micro-size wireless sensors attached to the turbine blades that measure parameters such as strain and temperature. Propagation measurements
CURSO DE PS-GRADUAO EM ASTROFSICA
CURSO DE PÓS-GRADUAÇÃO EM ASTROFÍSICA Coordenador Acadêmico Cláudia Vilega Rodrigues Conselho de curso André de Castro Milone Cláudia Vilega Rodrigues José Carlos Neves de Araújo Odylio Denys de Aguiar, Doutor, INPE, 1995 Cláudia Vilega Rodrigues, Doutora, USP, 1997 Dennis Bessada, Doutor, INPE, 2010 Emília
enhancem ent of em ission and absorption
Schaich, William L.
Resonant enhancem ent of em ission and absorption using frequency selective surfaces investigate the infrared properties of frequency selective surfaces consisting of alum inum patches on silicon Elsevier Science B.V. All rights reserved. Keywords: Frequency selective surfaces; Absorption; Infrared 1.I
DINÂMICA DA ESTRATÉGIA LOGÍSTICA EM EMPRESAS BRASILEIRAS
Peter Fernandes Wanke
RESUMO O objetivo do artigo é analisar a estratégia logística das empresas brasileiras a partir da mensuração do impacto de diferentes características do negócio sobre as principais decisões de produção e distribuição física de produtos acabados. Foi conduzida uma pesquisa de campo em empresas listadas no Ranking Exame para confrontar as quatro políticas propostas por Pagh e Cooper (1998), derivadas
FAGNER LUIZ DA C. FREITAS; ANDRÉ S. ZANETTI; CÉLIO R. MACHADO; ROSANGELA Z. MACHADO
1 ABSTRACT:- FREITAS, F.L. DA C.; ALMEIDA, K. DE S.; ZANETTI, A.S.; NASCIMENTO, A.A. DO; MACHADO, C. R.; MACHADO, R.Z. (Species of the genus Eimeria (Apicomplexa: Eimeriidae) in giant anteaters (Myrmecophaga tridactyla Linnaeus, 1758) in captivity). Espécies do gênero Eimeria (Apicomplexa: Eimeriidae) em Tamanduás-bandeira (Myrmecophaga tridactyla Linnaeus, 1758) em cativeiro. Revista Brasileira de Parasitologia Veterinária, v. 15, n. 1, p.
Marine EM in GOM: Advances and outlook
NASA Astrophysics Data System (ADS)
MacGregor, L. M.; Strack, K. M.
2005-05-01
Marine electromagnetic (EM) sounding methods provide valuable complementary information to conventional seismic exploration methods and success stories have been claimed by several oil companies: 1) as indicator of hydrocarbon presence derived from strong resistive anomalies 2) as complimentary tool in structural exploration. While 3D seismic identifies geological structures, it does not directly reveal the fluid content (hydrocarbons). Marine EM sounding exploits variations in electrical resistivity, and is directly sensitive to fluid saturation and thus resistive hydrocarbons. Under the right circumstances it can confirm the presence of hydrocarbons by identifying their resistive characteristics. This means that the possibility of drilling dry exploration wells is significantly reduced, as is the need for extensive appraisal drilling. EM data is used to resolve ambiguities in the structural interpretation of seismic data. For example, whereas the top of a diapiric salt body is often well constrained by seismic data, the position of the lower boundaries is often more elusive. Carbonate (or salt blankets, or resistive basalt) layers complicate the detection and characterization of deeper structure because of diffusive scattering in the layer. However, the resistivity contrast between these layers and the sediments below is an ideal target for EM sounding methods. Recently, two marine EM methods have become popular: The controlled source EM (CSEM) method and magnetotellurics (MT). The CSEM method uses an electric dipole source to transmit low frequency electromagnetic signals to an array of receivers that measure the electromagnetic field at the seafloor. Variation in amplitude and phase of the received signal as the source is towed through the receiver array yield the resistivity structure of the sub-surface to depths of several kilometers. The MT method uses naturally occurring electromagnetic source fields to determine the resistivity of the sub-surface. Thus, by studying the variation in response as a function of frequency, the variation in resistivity as a function of depth may be determined. These methods give complementary information about the resistivity structure of the sub-seafloor. Whereas CSEM data are primarily sensitive to resistive structures, and in particular to layers that are thin compared to their depth of burial, MT data can constrain larger scale conductive structure. By combining natural and controlled source methods better constraints on the geometry and properties of the seafloor can be gained than from either data type alone. Several case histories with large salt structures in the section illustrate that the techniques are useful for future exploration in the GOM. We see the technology moving from its present focus of deep water to include shallower water depths (where CSEM sounding is presently restricted). In addition, we envision the integration of complimentary EM techniques to get a better constrained resistivity image of the subsurface.
BUSCA LOCAL PARA POS-PROCESSAMENTO EM RESULTADOS DE OTIMIZAC~AO MULTI-OBJETIVO EM REDES DE FILAS
Cruz, Frederico
BUSCA LOCAL PARA P´OS-PROCESSAMENTO EM RESULTADOS DE OTIMIZA¸C~AO MULTI-OBJETIVO EM REDES DE FILAS otimiza¸c~ao de redes de filas finitas, a capacidade total do sistema em ´areas de espera deve ser a menor algoritmo simulated annealing foi desenvolvido, especialmente para redes de filas finitas, produzindo solu
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.
TandEM: Titan and Enceladus mission
A. Coustenis; S. K. Atreya; T. Balint; R. H. Brown; M. K. Dougherty; F. Ferri; M. Fulchignoni; D. Gautier; R. A. Gowen; C. A. Griffith; L. I. Gurvits; R. Jaumann; Y. Langevin; M. R. Leese; J. I. Lunine; C. P. McKay; X. Moussas; I. Müller-Wodarg; F. Neubauer; T. C. Owen; F. Raulin; E. C. Sittler; F. Sohl; C. Sotin; G. Tobie; T. Tokano; E. P. Turtle; J.-E. Wahlund; J. H. Waite; K. H. Baines; J. Blamont; A. J. Coates; I. Dandouras; T. Krimigis; E. Lellouch; R. D. Lorenz; A. Morse; C. C. Porco; M. Hirtzig; J. Saur; T. Spilker; J. C. Zarnecki; E. Choi; N. Achilleos; R. Amils; P. Annan; D. H. Atkinson; Y. Bénilan; C. Bertucci; B. Bézard; G. L. Bjoraker; M. Blanc; L. Boireau; J. Bouman; M. T. Capria; E. Chassefière; P. Coll; M. Combes; J. F. Cooper; A. Coradini; F. Crary; T. Cravens; I. A. Daglis; E. de Angelis; C. de Bergh; I. de Pater; C. Dunford; G. Durry; O. Dutuit; D. Fairbrother; F. M. Flasar; A. D. Fortes; R. Frampton; M. Fujimoto; M. Galand; O. Grasset; M. Grott; T. Haltigin; A. Herique; F. Hersant; H. Hussmann; W. Ip; R. Johnson; E. Kallio; S. Kempf; M. Knapmeyer; W. Kofman; R. Koop; T. Kostiuk; N. Krupp; M. Küppers; H. Lammer; L.-M. Lara; P. Lavvas; S. Le Mouélic; S. Lebonnois; S. Ledvina; J. Li; T. A. Livengood; R. M. Lopes; J.-J. Lopez-Moreno; D. Luz; P. R. Mahaffy; U. Mall; J. Martinez-Frias; B. Marty; T. McCord; C. Menor Salvan; A. Milillo; D. G. Mitchell; R. Modolo; O. Mousis; M. Nakamura; C. D. Neish; C. A. Nixon; D. Nna Mvondo; G. Orton; M. Paetzold; J. Pitman; S. Pogrebenko; W. Pollard; O. Prieto-Ballesteros; P. Rannou; K. Reh; L. Richter; F. T. Robb; R. Rodrigo; S. Rodriguez; P. Romani; M. Ruiz Bermejo; E. T. Sarris; P. Schenk; B. Schmitt; N. Schmitz; D. Schulze-Makuch; K. Schwingenschuh; A. Selig; B. Sicardy; L. Soderblom; L. J. Spilker; D. Stam; A. Steele; K. Stephan; D. F. Strobel; K. Szego; C. Szopa; R. Thissen; M. G. Tomasko; D. Toublanc; H. Vali; I. Vardavas; V. Vuitton; R. A. West; R. Yelle; E. F. Young
2009-01-01
TandEM was proposed as an L-class (large) mission in response to ESA’s Cosmic Vision 2015–2025 Call, and accepted for further\\u000a studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds\\u000a tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini–Huygens\\u000a mission. These
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.
Helicopter EMS: Research Endpoints and Potential Benefits
Thomas, Stephen H.; Arthur, Annette O.
2012-01-01
Patients, EMS systems, and healthcare regions benefit from Helicopter EMS (HEMS) utilization. This article discusses these benefits in terms of specific endpoints utilized in research projects. The endpoint of interest, be it primary, secondary, or surrogate, is important to understand in the deployment of HEMS resources or in planning further HEMS outcomes research. The most important outcomes are those which show potential benefits to the patients, such as functional survival, pain relief, and earlier ALS care. Case reports are also important “outcomes” publications. The benefits of HEMS in the rural setting is the ability to provide timely access to Level I or Level II trauma centers and in nontrauma, interfacility transport of cardiac, stroke, and even sepsis patients. Many HEMS crews have pharmacologic and procedural capabilities that bring a different level of care to a trauma scene or small referring hospital, especially in the rural setting. Regional healthcare and EMS system's benefit from HEMS by their capability to extend the advanced level of care throughout a region, provide a “backup” for areas with limited ALS coverage, minimize transport times, make available direct transport to specialized centers, and offer flexibility of transport in overloaded hospital systems. PMID:22203905
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.
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.
MICORRIZA ARBUSCULAR EM ESPÉCIES ARBÓREAS NATIVAS DA BACIA DO RIO TIBAGI, PARANÁ
Waldemar Zangaro; Silvio M. A. Nisizaki; Juliana C. B. Domingos; Emilia M. Nakano
RESUMO: Relata-se a incidência da colonização de micorriza arbuscular (MA) e a resposta à inocu- lação em 81 espécies arbóreas nativas da bacia do rio Tibagi (PR), em condições de casa de vegetação. Também é relatada a incidência da colonização de MA em 51 espécies arbóreas nativas coletadas em áreas em início de sucessão arbórea e no interior da floresta
An Effective EMS Hardware and Software Interface- The Trained Operator
Cherry, C. L.
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, ventilation, and air conditioning equip ment (HVAC). All computerized tools require three main components to function effectively: hardware, software, and an interface between the two - the operator. EMS owners recognize...
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM FILOSOFIA
Lucero, Jorge Carlos
1 UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM FILOSOFIA EDITAL No. 03/20011 SELEÃ?Ã?O DE CANDIDATOS Ã?S VAGAS DO PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM FILOSOFIA: CURSO DE MESTRADO ACADÃ?MICO, PARA INGRESSO NO PRIMEIRO PERÃODO LETIVO DE 2012 PREÃ?MBULO O Coordenador do Programa de PÃ³s-GraduaÃ§Ã£o em Filosofia, no uso
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS GRADUAO EM FILOSOFIA
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S GRADUAÃ?Ã?O EM FILOSOFIA EDITAL NÂº 2/2012 SELEÃ?Ã?O DE CANDIDATOS AO PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM FILOSOFIA PARA O CURSO DE MESTRADO ACADÃ?MICO, PARA O PRIMEIRO PERIODO LETIVO DE 2013 1. PREÃ?MBULO 1.1 O Coordenador do Programa de PÃ³s-GraduaÃ§Ã£o em Filosofia, no uso de
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM FILOSOFIA
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM FILOSOFIA EDITAL NÂº 1/2012 SELEÃ?Ã?O DE CANDIDATOS AO PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM FILOSOFIA PARA O CURSO DE MESTRADO ACADÃ?MICO, PARA INGRESSO NO SEGUNDO SEMESTRE LETIVO DE 2012 1. PREÃ?MBULO 1.1 O Coordenador do Programa de PÃ³s-GraduaÃ§Ã£o em Filosofia
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM FILOSOFIA
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM FILOSOFIA EDITAL No. 02/2010 SELEÃ?Ã?O DE CANDIDATOS Ã?S VAGAS DO PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM FILOSOFIA PARA OS CURSOS DE MESTRADO ACADÃ?MICO PARA O PRIMEIRO SEMESTRE LETIVO DE 2011 PREÃ?MBULO O Coordenador do Programa de PÃ³s-GraduaÃ§Ã£o em Filosofia, no uso
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM FILOSOFIA
Lucero, Jorge Carlos
1 UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM FILOSOFIA EDITAL No. 02/20011 SELEÃ?Ã?O DE CANDIDATOS Ã?S VAGAS DO PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM FILOSOFIA: CURSO DE MESTRADO ACADÃ?MICO, PARA INGRESSO NO PRIMEIRO PERÃODO LETIVO DE 2012 PREÃ?MBULO O Coordenador do Programa de PÃ³s-GraduaÃ§Ã£o em Filosofia, no uso
2. HI PAR (ACQUISITION RADAR) TOWER AND ENLISTED MEN (EM) ...
2. HI PAR (ACQUISITION RADAR) TOWER AND ENLISTED MEN (EM) BARRACKS WITH RADAR ATTACHED. - Nike Hercules Missile Battery Summit Site, Battery Control Administration & Barracks Building, Anchorage, Anchorage, AK
Freeman, Victoria A; Slifkin, Rebecca T; Patterson, P Daniel
2009-01-01
Maintaining an adequate staff is a challenge for rural emergency medical services (EMS) providers. This national survey of local EMS directors finds that rural EMS are more likely to be freestanding, that is, not affiliated with other public services, to employ only emergency medical technician-basics (EMT-Bs), and to be all volunteer. Rural EMS directors are more likely than urban ones to report that they are not currently fully staffed. The most common barriers to recruitment of EMTs in both urban and rural areas include unwillingness of community members to volunteer and lack of certified EMTs in the area. In rural areas, barriers to EMT training were noted more often than in urban areas as was the lack of employer support for employee volunteers. Similar rural training barriers affected retention of staff. Rural respondents reported that they lose staff to burnout and to difficulty in meeting continuing education requirements. Among rural respondents, those who direct all-volunteer EMS were the most likely to report recruitment and retention problems. The results suggest areas for further study including how volunteer EMS agencies can transition to paid agencies, how to bring EMS education to rural areas, and how EMS can work with other agencies to ensure EMS viability. PMID:19363405
Marine EM Reference Database http://marineemlab.ucsd.edu/~kkey/MarineEM
Key, Kerry
to document the peer-reviewed published papers that cover any aspect of marine electromagnetic induction. Techniques and instrumentation for study of natu- ral electromagnetic induction at sea. Physics Of The Earth. I started this database as part of a review paper that was presented at the 20th EM Induction
Marine EM Reference Database http://marineemlab.ucsd.edu/~kkey/MarineEM
Key, Kerry
to document the peer-reviewed published papers that cover any aspect of marine electromagnetic induction. I started this database as part of a review paper that was presented at the 20th EM Induction), Marine Electromagnetic Studies of Seafloor Resources and Tec- tonics, Surveys in Geophysics. http
FORMAÇÃO EM E-BUSINESS PARA PME'S: UMA APROXIMAÇÃO BAS EADA EM E- LEARNING
Sergio Castro; Nuno Caldeira; Eduardo Luís Cardoso
Introdução Novas formas de desenvolvimen to das actividades empresariais, associadas a grandes ganhos de produtividade, têm emergido baseadas nos progressos permanentes das tecnologias de informação e comunicação (TIC) e nomeadamente da internet. A adopção das práticas de 'e -business' no tecido empresarial e o aparecimento de novas empresas baseadas nestes modelos tem sido bastante mais limitado na Europa em relação
AVALIAÇÃO DA PRESENÇA DE ENDOSSIMBIONTES Cardinium em DIFERENTES ESPÉCIES DE ARTRÓPODES.
Technology Transfer Automated Retrieval System (TEKTRAN)
A presença de endossimbiontes do gênero Cardinium em alguns grupos de artrópodes foi recentemente relatada e relacionada com diversas alterações reprodutivas em seus hospedeiros, tais como feminilização de ácaros, partenogênese em parasitóides, incompatibilidade citoplasmática e aumento da fecundida...
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.
Communication - An Effective Tool for Implementing ISO 14001/EMS
Rachel Damewood; Bowen Huntsman
2004-04-01
The Idaho National Engineering and Environmental Laboratory (INEEL) received ISO 14001/EMS certification in June 2002. Communication played an effective role in implementing ISO 14001/EMS at the INEEL. This paper describes communication strategies used during the implementation and certification processes. The INEEL achieved Integrated Safety Management System (ISMS) and Voluntary Protection Program (VPP) Star status in 2001. ISMS implemented a formal process to plan and execute work. VPP facilitated worker involvement by establishing geographic units at various facilities with employee points of contact and management champions. The INEEL Environmental Management System (EMS) was developed to integrate the environmental functional area into its ISMS and VPP. Since the core functions of ISMS, VPP, and EMS are interchangeable, they were easy to integrate. Communication is essential to successfully implement an EMS. (According to ISO 14001 requirements, communication interacts with 12 other elements of the requirements.) We developed communication strategies that integrated ISMS, VPP, and EMS. For example, the ISMS, VPP, and EMS Web sites communicated messages to the work force, such as “VPP emphasizes the people side of doing business, ISMS emphasizes the system side of doing business, and EMS emphasizes the systems to protect the environment; but they all define work, identify and analyze hazards, and mitigate the hazards.” As a result of this integration, the work force supported and implemented the EMS. In addition, the INEEL established a cross-functional communication team to assist with implementing the EMS. The team included members from the Training and Communication organizations, VPP office, Pollution Prevention, Employee and Media Relations, a union representative, facility environmental support, and EMS staff. This crossfunctional team used various communication strategies to promote our EMS to all organization levels and successfully implemented EMS activities through VPP geographic units. In summary, the ISMS and VPP process at the INEEL provided the basic framework of management support and worker involvement to implement our EMS. A cross-functional communication team was established to facilitate the implementation with great success. Communication has been an effective tool for implementing an ISO 14001/EMS at the INEEL.
Klil H. Neori; Philip Goyal
2015-01-15
Quantization of multiply-connected spaces requires tools which take these spaces' global properties into account. Applying these tools exposes additional degrees of freedom. This was first realized in the Aharonov-Bohm effect, where this additional degree of freedom was a magnetic flux confined to a solenoid, which an electron cannot enter. Previous work using Feynman path integrals has either only dealt with specific cases, or was limited to spaces with finite fundamental groups, and therefore, was in fact inapplicable to the Aharonov-Bohm effect, as well as to interesting systems such as anyons. In this paper we start from the fundamental groupoid. This less familiar algebraic-topological object is oriented towards general paths. This makes it a more natural choice for the path integral approach than the more commonly known fundamental group, which is restricted to loops. Using this object, we provide a method that works for spaces with infinite fundamental groups. We adapt a tool used in the previous, restricted result, in order to clearly delineate physically significant degrees of freedom from gauge freedom. This allows us to explicitly build phases which take account of symmetries of the space, directly from topological considerations; we end by providing a pertinent example relating to anyons.
Surface-sensitive two-dimensional magneto-fingerprint in mesoscopic Bi2Se3 channels.
Kandala, Abhinav; Richardella, Anthony; Zhang, Duming; Flanagan, Thomas C; Samarth, Nitin
2013-06-12
Periodic Aharonov–Bohm and Altshuler–Aronov–Spivak oscillations have traditionally been observed in lateral transport through patterned mesoscopic loops of diffusive conductors. However, our studies of perpendicular-to-plane magnetotransport in straight-channel, diffusive devices of epitaxial Bi2Se3 surprisingly reveal signatures of Aharonov–Bohm orbits, periodic conductance fluctuation magneto-fingerprints, even though the devices are not explicitly patterned into loops. We show that the length scale of these orbits corresponds to the typical perimeter of triangular terraces found on the surface of these thin film devices, strongly suggesting that the periodic magneto-fingerprint arises from coherent scattering of electron waves from the step-edges. Our interpretation is bolstered by control measurements in devices without such surface morphology that only show a conventional, aperiodic magneto-fingerprint. These results show that lithographically patterned Bi2Se3 devices provide a novel class of mesoscopic physical systems for systematic studies of coherent surface sensitive transport. PMID:23642037
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.
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
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.
EM algorithm for sparse representation-based image inpainting
Mohamed-jalal Fadili; Jean-luc Starck
2005-01-01
We introduce an expectation-maximization (EM) algorithm for image inpainting based on a penalized likelihood formulated using linear sparse representations. Taking advantage of the sparsity of representations, a regularization through a prior penalty is imposed on the reconstructed coefficients. From a statistical point of view, the inpainting can be viewed as an estimation problem with missing data. The EM framework is
MESTRADO EM MICROBIOLOGIA BIOLOGIA ESTRUTURAL Instituto Superior Tcnico
Instituto de Sistemas e Robotica
MESTRADO EM MICROBIOLOGIA BIOLOGIA ESTRUTURAL Â Instituto Superior TÃ©cnico Objectivos: Introduzir e/ou aprofundar tÃ©cnicas avanÃ§adas de AnÃ¡lise Estrutural relevantes em Biologia e sua aplicaÃ§Ã£o na elucidaÃ§Ã£o de
ELEKTRA: Um Chatterbot para Uso em Ambiente Educacional
Michelle Denise Leonhardt; Daiane Dorneles de Castro; Liane Margarida; Rockenbach Tarouco
2003-01-01
**** Resumo. A E ducação à Distância vem despertando muito interesse de pesquisadores de diversas áreas. Por isso, também vem sendo muito a bordada em congressos, workshops e seminários. Muito se discute sobre a união entre tecnologia e educação visando complementar a formação de estudantes. Com a pesquisa em Inteligência Artificial, surgiram os chatterbots. Chatterbots são programas destinados a demonstrar
APLICAÇÃO DO CONVERSOR ZETA EM fONTES CHAVEADAS
Denizar Cruz Martins; Glaucio Nascimento de Abreu; Ivo Barbi
RESUMO Pretende-se neste artigo estudar em regime permanente o desempenho do conversor ZETA em modo de operação contínuo. Este conversor é derivado do conversor Forward pela substituição do diodo retificador por um capacitor de acoplamento. Ábacos serão gerados para auxiliar no projeto da estrutura de potência. Os estudos teóricos são confirmados por simulação. São apresentados resultados experimentais obtidos a partir
SALA DE AULA VIRTUAL EM INSTITUIÇÃO DE INTERNAÇÃO 1
JANAINA ABDALLA
2002-01-01
Resumo: Este texto apresenta três interfaces de estudo: instituição disciplinar\\/ sociedade de controle, tecnologia da comunicação e da informação e educomunicação partir de um objeto de pesquisa: Sala de Aula Virtual em Instituição de Internação de Adolescente em conflito com a lei sob o regime de internação. Busca compreender a natureza da instituição e sua relação com o poder disciplinar,
Using EM for Reinforcement Learning Peter Dayan Geoffrey E Hinton
Hinton, Geoffrey E.
return, even though it can make large changes in the values of the parameters. The proof is basedÂmaximization (EM) algorithm (Baum, Petrie, Soules & Weiss, 1970; Dempster, Laird & Rubin, 1977) and, as with EM . Our proof demonstrates that the RPP is wellÂfounded. 2 Theory The RPP operates to improve
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
Dirio Econmico -Universidades Como ser investigador em Portugal
Instituto de Sistemas e Robotica
DiÃ¡rio EconÃ³mico - Universidades Como Ã© ser investigador em Portugal Autor: N.D. Editora: ST e SF - Universidades Como Ã© ser investigador em Portugal Autor: N.D. Editora: ST e SF Id: 1646658 Data PublicaÃ§Ã£o: 19
International EMS systems in South Africa: past, present, and future
Campbell MacFarlane; Charl van Loggerenberg; Walter Kloeck
2005-01-01
Emergency medical services (EMS) in South Africa have developed rapidly over the last 20 years. However, there is inequitable distribution of services, with many rural areas being poorly resourced. This is partly as a result of the historical inequalities prevalent in the South African society of the past; efforts are being made to address this. EMS training is provided at
RFID-based flexible low-cost EM field probe
S. Capdevila; R. Serrano; A. Aguasca; S. Blanch; J. Romeu; L. Jofre
2008-01-01
The capability of the RFID tags as a low cost flexible device to measure the EM complex field distribution has been presented and some preliminary results presented. The devices do not need any kind of electrical connexion giving them a high versatility to act as a remote EM probing device under different conditions of positioning and accessibility. Sensitivity and dynamic
Recent development in open systems for EMS\\/SCADA
Yutaka Kokai; Fumio Masuda; Satoshi Horiike; Yasuji Sekine
1998-01-01
Based on the current situation and emerging trends of development of EMS\\/SCADA systems throughout the world, this report examines the `open system' concept from the viewpoints of users and suppliers. Current technologies for open distributed EMS\\/SCADAs and their possible future trends are described.
A European Land Mobile Satellite System via EMS
NASA Astrophysics Data System (ADS)
Ananasso, Fulvio; Mistretta, Ignazio
1991-10-01
The paper analyzes the technical and market issues that influence the strategy of implementation of a Land Mobile Satellite System via the payload EMS (European Mobile System) embarked on ITALSAT F-2. The final goal is to determine services, network architecture, and added value chain that make LMSS via EMS profitable for a typical telecommunication company.
The EM Algorithm and the Rise of Computational Biology
Xiaodan Fan; Yuan Yuan; Jun S. Liu
2009-01-01
In the past decade, computational biology has grown from a cottage industry with a handful of researchers to an attractive in- terdisciplinary eld, catching the attention and imagination of many quantitatively-minded scientists. Of interest to us is the key role played by the EM algorithm during this transformation. We survey the use of the EM algorithm in a few important
The EM Algorithm and the Rise of Computational Biology
Xiaodan Fan; Yuan Yuan; Jun S. Liu
2011-01-01
In the past decade computational biology has grown from a cottage industry with a handful of researchers to an attractive interdisciplinary field, catching the attention and imagination of many quantitatively-minded scientists. Of interest to us is the key role played by the EM algorithm during this transformation. We survey the use of the EM algorithm in a few important computational
EMS control chosen instead of refrigeration, HVAC upgrade
1984-01-01
A Wisconsin supermarket decided on the basis of costs to install an energy management system (EMS) to improve the store's energy efficiency rather than invest in new refrigerating equipment at this time. When the next remodeling occurs in two years, the store will purchase new equipment using energy savings from the EMS to help defray the costs. The store selected
DOE EM industry programs robotics development
Staubly, R.; Kothari, V. [Dept. of Energy, Morgantown, WV (United States)
1997-12-01
The Office of Science and Technology (OST) manages an aggressive program for RD&D, as well as testing and evaluation for the U.S. Department of Energy`s (DOE) Environmental Management (EM) organization. The goal is to develop new and improved environmental restoration and waste management technologies to clean up the inventory of the DOE weapons complex faster, safer, and cheaper than is possible with currently available technologies. OST has organized technology management activities along focus teams for each major problem area. There are currently five focus areas: decontamination and decommissioning, tanks, subsurface contaminants, mixed waste, and plutonium. In addition, OST is pursuing research and development (R&D) that cuts across these focus areas by having applications in two or more focus areas. Currently, there are three cross-cutting programs: the robotics technology development; characterization, monitoring, and sensor technologies; and efficient separations and processing.
Evaluation of Fracture Azimuth by EM Wave and Elastic Wave
NASA Astrophysics Data System (ADS)
Feng, X.; Wang, Q.; Liu, C.; Lu, Q.; Zeng, Z.; Liang, W.; Yu, Y.; Ren, Q.
2013-12-01
Fracture system plays an important role in the development of underground energy, for example enhanced geothermal system (EGS), oil shale and shale gas, etc. Therefore, it becomes more and more important to detect and evaluate the fracture system. Geophysical prospecting is an useful method to evaluate the characteristics of the subsurface fractures. Currently, micro-seismology, multi-wave seismic exploration, and electromagnetic (EM) survey are reported to be used for the purpose. We are studying a method using both elastic wave and EM wave to detect and evaluate the fracture azimuth in laboratory. First, we build a 3D horizontal transverse isotropy (HTI) model, shown in the figure 1, by dry parallel fractures system, which was constructed by plexiglass plates and papers. Then, we used the ultrasonic system to obtain reflected S-wave data. Depending on the shear wave splitting, we evaluated the fracture azimuth by the algorithm of Pearson correlation coefficient. In addition, we used the full Polarimetric ultra wide band electromagnetic (FP-UWB-EM) wave System, shown in the figure 2, to obtain full polarimetric reflected EM-wave data. Depending on the rotation of the EM wave polarimetry, we evaluated the fracture azimuth by the the ration between maximum amplitude of co-polarimetric EM wave and maximum amplitude of cross-polarimetric EM wave. Finally, we used both EM-wave data and S-wave data to evaluate the fracture azimuth by the method of cross plot and statistical mathematics. To sum up, we found that FP-UWB-EM wave can be used to evaluated the fracture azimuth and is more accurate than ultrasound wave. Also joint evaluation using both data could improve the precision.
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
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM COMUNICAO
Maier, Rudolf Richard
ExperiÃªncia profissional em comunicaÃ§Ã£o 5 ProduÃ§Ã£o cientÃfica na Ã¡rea de comunicaÃ§Ã£o (artigos, livros e capÃtulos) 10 ProduÃ§Ã£o cientÃfica em outras Ã¡reas de conhecimento (artigos, livros e capÃtulos) 5 (artigos, livros e 10 #12;3 capÃtulos) ProduÃ§Ã£o cientÃfica em outras Ã¡reas de conhecimento (artigos, livros
EMS control chosen instead of refrigeration, HVAC upgrade
Watson, F.
1984-05-07
A Wisconsin supermarket decided on the basis of costs to install an energy management system (EMS) to improve the store's energy efficiency rather than invest in new refrigerating equipment at this time. When the next remodeling occurs in two years, the store will purchase new equipment using energy savings from the EMS to help defray the costs. The store selected an EMS with distributed processing that can expand to control new equipment. It expects a 22% drop in energy bills and a two-year payback of the $50,000 investment. Details of the system's functions describe some of the 53 control points.
REGIMENTO DO CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS, REA DE CONCENTRAO
REGIMENTO DO CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS, ÁREA DE CONCENTRAÇÂO EM Espacial e Controle (CMC) do Curso de Pós-graduação em Engenharia e Tecnologia Espaciais (ETE) objetiva Conselho de Pós-Graduação, pelo Regimento do Curso de Pós-Graduação em Engenharia e Tecnologia Espaciais e
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
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 CONCENTRAÇÂO 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.
MESTRADO EM MICROBIOLOGIA BIOTECNOLOGIA AMBIENTAL Instituto Superior Tcnico
Instituto de Sistemas e Robotica
MESTRADO EM MICROBIOLOGIA BIOTECNOLOGIA AMBIENTAL Instituto Superior Técnico Objectivos: Na risco ambiental), e sobre a aplicação de métodos da biotecnologia na resolução de problemas ambientais, desde a monitorização dos poluentes no Ambiente até à biorremediação nos compartimentos ambientais
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.
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.
EM 1110-2-2100 1 December 2005
US Army Corps of Engineers
-3 Shear Strength Tests..................................................................... 2-8 2-3 Selection of Design Shear Strengths............................................. 2-9 2-5 Multiple Wedge Bearing Capacity........................................................... 3-10 3-6 #12;EM 1110-2-2100 1
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
suscetibilidade, isto é, mapas que indi- cam localizações com riscos de deslizamento em uma dada área e que usa o é demonstrado por um estudo de caso onde o sistema possui a responsabilidade de gerar mapas de
Nobel da Medicina em debate sobre a importncia da cincia
Instituto de Sistemas e Robotica
Nobel da Medicina em debate sobre a importÃ¢ncia da ciÃªncia lisboa O Nobel da Medicina e atual presidente da Royal Society (a congÃ©nere britÃ¢nica da Acade- mia das CiÃªncias) , Paul Nurse, estÃ¡ hoje em Lisboa para falar de ciÃªn- cia e da forma como ela pode ser eficaz e imprescindÃvel nas socie- dades
Decentralized autonomous object-oriented EMS\\/SCADA system
Toshibumi. Seki; H. Sato; T. Tanaka; H. Watanabe
1997-01-01
Energy management systems\\/supervisory control and data acquisition (EMS\\/SCADA) systems are usually geographically distributed and have operational organizations. They are changing in accordance with the various and varying environments, and they should be flexible enough to adapt to those changes quickly. The paper proposes a new architecture called SCOPE (System Configuration of Power Control System) to realize flexible and reliable EMS\\/SCADA
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.
Maximum likelihood noise cancellation using the EM algorithm
MEIR FEDER; ALAN V. OPPENHEIM; EHUD WEINSTEIN
1989-01-01
An approach to the two-microphone speech enhancement problem is discussed. Specifically, a maximum-likelihood (ML) problem is formulated for estimating the parameters needed for canceling the noise, and solved by the iterative EM (estimate-maximize) technique. The EM algorithm has been implemented for both a simplified and a more general scenario. The results improve upon those obtained with the classical least-squares approach
Waste fuel, EMS may save plant $1M yearly
Barber
1982-01-01
A mixture of paper trash and coal ash fueling an Erie, Pa. General Electric plant and a Network 90 microprocessor-based energy-management system (EMS) to optimize boiler efficiency will cost about $3 million and have a three-to-four-year payback. Over half the savings will come from the avoided costs of burning plant-generated trash. The EMS system will monitor fuel requirements in the
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.
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.
A eficiência de formação estelar em Musca
NASA Astrophysics Data System (ADS)
Hickel, G. R.; Vilas-Boas, J. W. S.; Roberto, A. J.., Jr.; Khan, R. P.
2003-08-01
Apresentamos os resultados de um survey no infravermelho próximo (bandas J e H), executado no Laboratório Nacional de Astrofísica, na direção da nuvem escura em forma de filamento de Musca (observamos ao longo de todo o filamento, além de todas as fontes pontuais IRAS e/ou fontes ROSAT brilhantes a uma distância de 2o da nuvem). Nosso objetivo é determinar a eficiência de formação estelar para esta nuvem escura (massa de estrelas formadas/massa da nuvem), procurando por objetos estelares jovens de pequena massa no seu interior e/ou evoluídos o suficiente para estarem afastados do local de nascimento, mas ainda mostrando características de objetos pré-seqüência principal como emissão de raios-X e excesso de emissão no infravermelho próximo. Este survey não estabeleceu nenhum viés na seleção de fontes pontuais IRAS ou fontes ROSAT, uma vez que a imensa maioria das fontes pontuais IRAS nesta região têm qualidade de fluxo ruim. Os candidatos a objetos estelares jovens foram selecionados pelo excesso no índice de cor (J-H), descontados os efeitos da extinção interestelar na linha de visada, determinada através da emissão estendida no infravermelho distante (IRAS). Estimativas de massa foram feitas para estes candidatos, através da relação massa-luminosidade, para calcular a eficiência de formação estelar de Musca.
FitEM2EM--tools for low resolution study of macromolecular assembly and dynamics.
Frankenstein, Ziv; Sperling, Joseph; Sperling, Ruth; Eisenstein, Miriam
2008-01-01
Studies of the structure and dynamics of macromolecular assemblies often involve comparison of low resolution models obtained using different techniques such as electron microscopy or atomic force microscopy. We present new computational tools for comparing (matching) and docking of low resolution structures, based on shape complementarity. The matched or docked objects are represented by three dimensional grids where the value of each grid point depends on its position with regard to the interior, surface or exterior of the object. The grids are correlated using fast Fourier transformations producing either matches of related objects or docking models depending on the details of the grid representations. The procedures incorporate thickening and smoothing of the surfaces of the objects which effectively compensates for differences in the resolution of the matched/docked objects, circumventing the need for resolution modification. The presented matching tool FitEM2EMin successfully fitted electron microscopy structures obtained at different resolutions, different conformers of the same structure and partial structures, ranking correct matches at the top in every case. The differences between the grid representations of the matched objects can be used to study conformation differences or to characterize the size and shape of substructures. The presented low-to-low docking tool FitEM2EMout ranked the expected models at the top. PMID:18974836
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
The EM-POGO: A simple, absolute velocity profiler
NASA Astrophysics Data System (ADS)
Terker, S. R.; Sanford, T. B.; Dunlap, J. H.; Girton, J. B.
2013-01-01
Electromagnetic current instrumentation has been added to the Bathy Systems, Inc. POGO transport sondes to produce a free-falling absolute velocity profiler called EM-POGO. The POGO is a free-fall profiler that measures a depth-averaged velocity using GPS fixes at the beginning and end of a round trip to the ocean floor (or a preset depth). The EM-POGO adds a velocity profile determined from measurements of motionally induced electric fields generated by the ocean current moving through the vertical component of the Earth's magnetic field. In addition to providing information about the vertical structure of the velocity, the depth-dependent measurements improve transport measurements by correcting for the non-constant fall-rate. Neglecting the variable fall rate results in errors O (1 cm s-1). The transition from POGO to EM-POGO included electrically isolating the POGO and electric-field-measuring circuits, installing a functional GPS receiver, finding a pressure case that provided an optimal balance among crush-depth, price and size, and incorporating the electrodes, electrode collar, and the circuitry required for the electric field measurement. The first EM-POGO sea-trial was in July 1999. In August 2006 a refurbished EM-POGO collected 15 absolute velocity profiles; relative and absolute velocity uncertainty was ˜1cms-1 and 0.5-5 cm s-1, respectively, at a vertical resolution of 25 m. Absolute velocity from the EM-POGO compared to shipboard ADCP measurements differed by ˜ 1-2 cm s-1, comparable to the uncertainty in absolute velocity from the ADCP. The EM-POGO is thus a low-cost, easy to deploy and recover, and accurate velocity profiler.
ERIC Educational Resources Information Center
Education Resource Strategies, 2010
2010-01-01
If your school district is facing a budget issue, it might surprise you to learn that the solution might very well lie in a game of cards. That certainly was the case earlier this year for the city schools of Memphis, Tennessee. The game is called Budget Hold'em, and it was developed by Education Resource Strategies (ERS) of Watertown,…
Quantitation of PET data with the EM reconstruction technique
Rosenqvist, G.; Dahlbom, M.; Erikson, L.; Bohm, C.; Blomqvist, G.
1989-02-01
The expectation maximization (EM) algorithm offers high spatial resolution and excellent noise reduction with low statistics PET data, since it incorporates the Poisson nature of the data. The main difficulties are long computation times, difficulties to find appropriate criteria to terminate the reconstruction and to quantify the resulting image data. In the present work a modified EM algorithm has been implements on a VAX 11/780. Its capability to quantify image data has been tested in phantom studies and in two clinical cases, cerebral blood flow studies and dopamine D2-receptor studies. Data from phantom studies indicate the superiority of images reconstructed with the EM technique compared to images reconstructed with the conventional filtered back-projection (FB) technique in areas with low statistics. At higher statistics the noise characteristics of the two techniques coincide. Clinical data support these findings.
Analyses of Subnanometer Resolution Cryo-EM Density Maps
Baker, Matthew L.; Baker, Mariah R.; Hryc, Corey F.; DiMaio, Frank
2011-01-01
Today, electron cryomicroscopy (cryo-EM) can routinely achieve subnanometer resolutions of complex macromolecular assemblies. From a density map, one can extract key structural and functional information using a variety of computational analysis tools. At subnanometer resolution, these tools make it possible to isolate individual subunits, identify secondary structures, and accurately fit atomic models. With several cryo-EM studies achieving resolutions beyond 5 Å, computational modeling and feature recognition tools have been employed to construct backbone and atomic models of the protein components directly from a density map. In this chapter, we describe several common classes of computational tools that can be used to analyze and model subnanometer resolution reconstructions from cryo-EM. A general protocol for analyzing subnanometer resolution density maps is presented along with a full description of steps used in analyzing the 4.3 Å resolution structure of Mm-cpn. PMID:20888467
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
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.
Low Bandwidth Vocoding using EM Sensor and Acoustic Signal Processing
Ng, L C; Holzrichter, J F; Larson, P E
2001-10-25
Low-power EM radar-like sensors have made it possible to measure properties of the human speech production system in real-time, without acoustic interference [1]. By combining these data with the corresponding acoustic signal, we've demonstrated an almost 10-fold bandwidth reduction in speech compression, compared to a standard 2.4 kbps LPC10 protocol used in the STU-III (Secure Terminal Unit, third generation) telephone. This paper describes a potential EM sensor/acoustic based vocoder implementation.
Speaker verification using combined acoustic and EM sensor signal processing
Ng, L C; Gable, T J; Holzrichter, J F
2000-11-10
Low Power EM radar-like sensors have made it possible to measure properties of the human speech production system in real-time, without acoustic interference. This greatly enhances the quality and quantity of information for many speech related applications. See Holzrichter, Burnett, Ng, and Lea, J. Acoustic. SOC. Am . 103 ( 1) 622 (1998). By combining the Glottal-EM-Sensor (GEMS) with the Acoustic-signals, we've demonstrated an almost 10 fold reduction in error rates from a speaker verification system experiment under a moderate noisy environment (-10dB).
Um Framework para Proviso de QoS em Redes Mveis Sem Fio1
Colcher, Sérgio
Um Framework para Provisão de QoS em Redes Móveis Sem Fio1 Luciana dos Santos Lima, Antônio Tadeu A provisão de QoS em redes móveis sem fio integrando soluções isoladas encontradas na literatura. Esses descrita através de um cenário simulado em que serviços integrados são oferecidos sobre uma rede IP Móvel
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UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM ANTROPOLOGIA SOCIAL
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Microanlise etnogrfica de interaces conversacionais: Atendimentos em Servios de Aco social
Paris-Sud XI, Université de
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UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM ANTROPOLOGIA SOCIAL
Maier, Rudolf Richard
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UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM ANTROPOLOGIA SOCIAL
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Imaging Gas Hydrate with Marine EM at Hydrate Ridge, Offshore Oregon
K. A. Weitemeyer; S. Constable; J. Behrens
2005-01-01
We present results from a marine controlled source electromagnetic experiment (CSEM) conducted at Hydrate Ridge, Oregon in August, 2004. Transmitted EM fields were measured by a dense array of 25 seafloor EM receivers spaced at 600 m intervals, allowing for redundant sampling of the spatially varying EM fields. The data heterogeneity is represented in simple form by using pseudosection approach,
Quasi-Monte Carlo Sampling to improve the Efficiency of Monte Carlo EM
Jank, Wolfgang
Quasi-Monte Carlo Sampling to improve the Efficiency of Monte Carlo EM Wolfgang Jank Department@rhsmith.umd.edu November 17, 2003 Abstract In this paper we investigate an efficient implementation of the Monte Carlo EM al- gorithm based on Quasi-Monte Carlo sampling. The Monte Carlo EM algorithm is a stochastic version
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...
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Paraná, Universidade Federal do
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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
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
REGIMENTO DO CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
REGIMENTO DO CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM e Tecnologia Espaciais (ETE) objetiva formar e aperfeiçoar pessoal nos níveis de Mestrado e de Curso de Pós- graduação em Engenharia e Tecnologia Espaciais e por este Regimento de Área de
REGIMENTO DO CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
REGIMENTO DO CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM e Tecnologia Espaciais (ETE) objetiva formar e aperfeiçoar pessoal nos níveis de Mestrado e de Curso de Pós-graduação em Engenharia e Tecnologia Espaciais e por este Regimento de Área de Concentração
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
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
REGIMENTO DO CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
REGIMENTO DO CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÂO EM e Tecnologia Espaciais (ETE) objetiva formar e aperfeiçoar pessoal nos níveis de Mestrado e de Curso de Pós- graduação em Engenharia e Tecnologia Espaciais e por este Regimento de Área de
MINISTRIO DA CINCIA, TECNOLOGIA E INOVAO (MCTI) CONCURSO PBLICO PARA PROVIMENTO DE VAGAS EM CARGOS
1 MINISTÉRIO DA CIÊNCIA, TECNOLOGIA E INOVAÇÃO (MCTI) CONCURSO PÚBLICO PARA PROVIMENTO DE VAGAS EM DA CIÊNCIA, TECNOLOGIA E INOVAÇÃO, tendo em vista o disposto na Portaria nº 553, de 8 de dezembro de, Planejamento e Infraestrutura em Ciência e Tecnologia e da Carreira de Desenvolvimento Tecnológico de que trata
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 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
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM TECNOLOGIAS QUMICA E
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM TECNOLOGIAS QUÍMICA E BIOLÓGICA EDITAL No . 1/2012 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS- GRADUAÇÃO EM TECNOLOGIAS QUÍMICA E BIOLÓGICA PARA O Programa de Pós-Graduação em Tecnologias Química e Biológica, no uso de suas atribuições legais, torna
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.
Properties of Light Waves, particles and EM spectrum
Wilkinson, Gerald S.
Properties of Light · Waves, particles and EM spectrum · Interaction with matter · Absorption related to wavelength (f = c / ) · Shares with sound the properties of spreading loss, attenuation molecules (visual pigments) make use of changes in electron orbital states #12;Absorption by water depends
The Economic Effect of Nature Farming by EM
B. N. Lee; C. K. Kang; K. H. Lee
Along with the increasing concern among farmers and the general public about the adverse effect of conventional farming, questions have been increasingly raised in recent years about the long-term sustainability of the current agricultural system that relies on agricultural chemicals such as fertilizers and pesticides. Effective Micro-organisms (EM), as a potentially valuable technology that pursues more ecologically oriented agriculture than
EMS-generated Rhizoctonia resistance in an adapted wheat
Technology Transfer Automated Retrieval System (TEKTRAN)
We report the first genetic resistance in wheat to Rhizoctonia solani AG-8 and R. oryzae, the causal agents of Rhizoctonia root rot and pre-emergence damping-off. Rhizoctonia resistance was generated in the spring wheat cultivar Scarlet using EMS mutagenesis. Resistant plants, named Scarlet-Rz1, d...
Under Review Scaling Down EM Using Graph Based
Davidson, Ian
, University of California, Davis, CA, USA. Abstract. The EM algorithm is used extensively in data mining reported in KAIS as being one of the top 10 data mining algorithms. Typical applications include indoor map building, mixture models and image mining. However, as data mining applications extend to deployment beyond
A experiência do dieese em pesquisa e conhecimento
SÉRGIO E. A. MENDONÇA
2002-01-01
Resumo: O texto situa o nascimento do Dieese com o objetivo singular de realizar pesquisas e estudos a partir da ótica da classe trabalhadora. O Dieese nasce para tentar produzir conhecimento em bases científicas, visan- do apoiar a disputa da classe trabalhadora pela distribuição de renda nacional. Relaciona os momentos de transformação da sociedade brasileira às principais pesquisas e atividades
An Innovative Tool to Assist in Rural EMS Response
Minnesota, University of
technologies for EMS -NextGeneration 911 -IP telephony -AACN -Mobile phones -Computer Aided Dispatch (CAD) -GPS/AVL/GIS of mobile computing (smartphones) !Leverage expansion of cell phone network !Leverage the web #12;CrashHelp System Prototype #12;CrashHelp System Architecture #12;#12;Mobile Phone Application !Secure login !Add
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…
Sonar-Based Mapping With Mobile Robots Using EM
Wolfram Burgard; Dieter Fox; Hauke Jans; Christian Matenar; Sebastian Thrun
This paper presents an algorithms for learn- ing occupancy grid maps with mobile robots equipped with range finders, such as sonar sen- sors. Our approach employs the EM algorithm to solve the concurrent mapping and localization problem. To accommodate the spatial nature of range data, it relies on a two-layered representa- tion of maps, where global maps are composed from
ISSN 0103-9741 Monografias em Cincia da Computao
Barbosa, Alberto
&P) activities, such as 3D geomodelling, seismic interpretation, real-time drilling follow-up and correction, offshore structures' design, static and dynamic simulations of these offshore structures, oil pipelines perfuração em tempo real, projeto de estruturas offshore, simulações estáticas e dinâmicas destas estruturas
Inhomogeneous Media 3D EM Modeling with Integral Equation Method
Q. di; R. Wang; Z. An; C. Fu; C. Xu
2010-01-01
In general, only the half space of earth is considered in electromagnetic exploration. However, for the long bipole source, because the length is close to the height of ionosphere and also most offsets between source and receivers are equal or larger than the height of ionosphere, the effect of ionosphere on the electromagnetic (EM) field should be considered when observation
Symmetry-restrained flexible fitting for symmetric EM maps.
Chan, Kwok-Yan; Gumbart, James; McGreevy, Ryan; Watermeyer, Jean M; Sewell, B Trevor; Schulten, Klaus
2011-09-01
Many large biological macromolecules have inherent structural symmetry, being composed of a few distinct subunits, repeated in a symmetric array. These complexes are often not amenable to traditional high-resolution structural determination methods, but can be imaged in functionally relevant states using cryo-electron microscopy (cryo-EM). A number of methods for fitting atomic-scale structures into cryo-EM maps have been developed, including the molecular dynamics flexible fitting (MDFF) method. However, quality and resolution of the cryo-EM map are the major determinants of a method's success. In order to incorporate knowledge of structural symmetry into the fitting procedure, we developed the symmetry-restrained MDFF method. The new method adds to the cryo-EM map-derived potential further restraints on the allowed conformations of a complex during fitting, thereby improving the quality of the resultant structure. The benefit of using symmetry-based restraints during fitting, particularly for medium to low-resolution data, is demonstrated for three different systems. PMID:21893283
Skin detection using the EM algorithm with spatial constraints
Gevers, Theo
Skin detection using the EM algorithm with spatial constraints A. Diplaros T. Gevers N. Vlassis,gevers,vlassis}@science.uva.nl Abstract Â In this paper, we propose a color-based method for skin detection and segmentation, which also takes into account the spatial coherence of the skin pixels. We treat the problem of skin detection
Using EM for Reinforcement Learning Peter Dayan Geoffrey E Hinton
Hinton, Geoffrey E.
return, even though it can make large changes in the values of the parameters. The proof is based) algorithm (Baum, Petrie, Soules & Weiss, 1970; Dempster, Laird & Rubin, 1977) and, as with EM, there can proof demonstrates that the RPP is well-founded. 2 Theory The RPP operates to improve the parameters Ã?
Germinação de Sementes de Forrageiras em Diferentes Profundidades de Semeadura
Adauton Vilela de Rezende; Hélio Henrique Vilela; Geraldo Benedito de Souza Almeida; Paulo Roberto; Correa Landgraf; Gustavo Augusto Andrade; Paulo de Figueiredo Vieira
3 Aluno de graduação em Agronomia - UNIFENAS Abstract: The experiment was conducted at José do Rosário Vellano University - UNIFENAS, in Alfenas, MG, with the purpose of evaluating the germination of forage seeds at different sowing depths. The experimental design was in randomized blocks with three replicates, four forages plants and four sowing depths being utilized, amounting to 20
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
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
DE JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22451-900 RIO DE JANEIRO - BRASIL #12;Monograas em, Computer Science Department, LES - Rio de Janeiro - Brazil 2 Federal University of Rio Grande do Norte Marquês de São Vicente, 225 - Gávea 22451-900 Rio de Janeiro RJ Brasil Tel. +55 21 3527-1516 Fax: +55 21
ISSN 0103-9741 Monografia em Cincia da Computao
Endler, Markus
Departamento de Informática PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22451-900 RIO DE JANEIRO #12;Monografias em Ciência da Computação, No. 10/10 ISSN: 0103 of Informatics PUC-Rio Rio de Janeiro, RJ Brazil {hpiccinini, melissa, casanova, furtado}@inf.puc-rio.br 2
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
Pereira de Lucena Departamento de Informática PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22451-900 RIO DE JANEIRO - BRASIL #12;Monografias em Ciência da Departamento de Informática Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
José Pereira de Lucena Departamento de Informática PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22453-900 RIO DE JANEIRO - BRASIL #12;Monografias em Ciência da Departamento de Informática Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
Departamento de Informática PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22451-900 RIO DE JANEIRO - BRASIL #12;Monografias em Ciência da Computação, No. 16/09 ISSN: 0103 Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brasil {mgatti, lucena, afgarcia}@inf.puc-rio.br Abstract
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22453-900 RIO DE JANEIRO - BRASIL #12;PUC RIO - DEPARTAMENTO DE INFORMÁTICA ISSN 0103-9741 Monografias em Ciência da Departamento de Informática Pontifícia Universidade Católica do Rio de Janeiro PUC-Rio Rua Marquês de São
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
Informática PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22453-900 RIO DE JANEIRO - BRASIL #12;PUC RIO - DEPARTAMENTO DE INFORMÁTICA ISSN 0103-9741 Monografias em-900 Rio de Janeiro RJ Brazil Tel. +55 21 3114-1516 Fax: +55 21 3114-1530 E-mail: bib-di@inf.puc-rio.br #12
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
Lucena Departamento de Informática PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22451-900 RIO DE JANEIRO - BRASIL #12;Monografias em Ciência da Computação, No. 03 Pereira de Lucena 2 1 PUC-Rio, Rio de Janeiro Brazil 2 PUC-Rio, Computer Science Department, LES - Rio
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22451-900 RIO DE JANEIRO - BRASIL #12;Monograas em Ciência Informática, LES - Rio de Janeiro - Brasil {ionunes,cnunes,lucena}@inf.puc-rio.br, guga@les.inf.puc-rio Marquês de São Vicente, 225 - Gávea 22451-900 Rio de Janeiro RJ Brasil Tel. +55 21 3527-1516 Fax: +55 21
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22453-900 RIO DE JANEIRO - BRASIL #12;PUC RIO - DEPARTAMENTO DE INFORMÁTICA ISSN 0103-9741 Monografias em Ciência da Rio de Janeiro PUC-Rio Rua Marquês de São Vicente, 225, 22453-900. Rio de Janeiro, Brasil. [lucena,hugo]@inf.puc-rio
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
Informática PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22453-900 RIO DE JANEIRO - BRASIL #12;PUC RIO - DEPARTAMENTO DE INFORMÁTICA ISSN 0103-9741 Monografias em PUC-Rio Departamento de Informática Rua Marquês de São Vicente, 225 - Gávea 22453-900 Rio de Janeiro
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
Departamento de Informática PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22451-900 RIO DE JANEIRO - BRASIL #12;Monografias em Ciência da Computação, No. 53/08 ISSN: 0103, Rio de Janeiro RJ Brasil {milene, mauserr}@les.inf.puc-rio.br {lucena}@inf.puc-rio.br Abstract
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22453-900 RIO DE JANEIRO - BRASIL #12;Monografias em Ciência Departamento de Informática PUC-Rio Rua Marquês de São Vicente, 225, Rio de Janeiro Brasil, 22453-900 {guga, Rio de Janeiro, Brasil, 22290-270 choren@de9.ime.br Abstract. In open multi-agent systems, in which
Online EM Algorithm for Hidden Markov Models Olivier Cappe
Paris-Sud XI, Université de
Online EM Algorithm for Hidden Markov Models Olivier Capp´e LTCI, Telecom ParisTech & CNRS Abstract likelihood estimator for large sample sizes. Keywords Hidden Markov Models, Expectation Hidden Markov modelling is a key concept of statistical time series analysis, which has had a wide
Online EM Algorithm for Hidden Markov Models Olivier Cappe
Online EM Algorithm for Hidden Markov Models Olivier CappÂ´e LTCI, TELECOM ParisTech & CNRS Abstract This paper is about the estimation of fixed model parameters in hidden Markov models us- ing an online (or evaluated through simulations in the case of a noisily observed Markov chain. Keywords Hidden Markov Models
A Generalized Partial Credit Model: Application of an EM Algorithm
Eiji Muraki
1992-01-01
The partial credit model (PCM) with a varying slope parameter is developed and called the generalized partial credit model (GPCM). The item step parameter of this model is decomposed to a location and a threshold parameter, following Andrich's (1978) rating scale formulation. The EM algorithm for estimating the model parameters is derived. The performance of this generalized model is compared
Cost-Effectiveness Analysis of Helicopter EMS for Trauma Patients
Peter A Gearhart; Richard Wuerz; A. Russell Localio
1997-01-01
Study objective: To evaluate the cost-effectiveness of helicopter EMS for trauma patients. Methods: We applied a cost-effectiveness analysis from the service provider's perspective to cost and effectiveness estimates. The cost estimates comprise direct operating costs and additional survivors' hospital costs. The effectiveness estimates were calculated with the TRISS methodology from literature sources and data from a cohort of patients transported
Nonlinear Cyclotron-Resonance Accelerations by a Generalized EM Wave
Boyer, Edmond
Nonlinear Cyclotron-Resonance Accelerations by a Generalized EM Wave AKIMOTO, Kazuhiro and HOJO that the well-known cyclotron resonance may be classified into three regimes as the length and/or the amplitude of the pulse are varied. Namely, as the pulse amplitude increases, the transit-time cyclotron
Communications technology guidelines for EMS\\/SCADA systems
Donald J. Marihart
2001-01-01
The purpose of this Guideline Technical Paper is to provide a summary of the different communications technologies available for use or application with EMS\\/SCADA system projects. All of the various communication media are addressed with a brief description along with tables of the advantages and disadvantages of each and recommendations for choosing the most appropriate communication technology. The technologies discussed
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
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
Life at Low Reynolds Number E.M. Purcell
Millis, Andrew
Life at Low Reynolds Number E.M. Purcell Lyman Laboratory, Harvard University, Cambridge, Mass elementary physics even if we don't throw much light on the other subjects. Now this is that kind know Viki's program of explaining everything including the height of mountains, with the elementary
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.
GPS computer navigators to shorten EMS response and transport times.
Ota, F S; Muramatsu, R S; Yoshida, B H; Yamamoto, L G
2001-05-01
GPS (global positioning satellite system to determine one's position on earth) units have become inexpensive and compact. The purpose of this study is to assess the effectiveness of a GPS enhanced computer street map navigator to improve the ability of EMS drivers in an urban setting to locate their destination and shorten response times. For part I, residential addresses in the city were randomly selected from a telephone directory. Two driver/navigator teams were assigned to drive to the address adhering to speed limits. One team used a standard street map, whereas the other team used a GPS computer navigator. The travel time and distance of the runs were compared. For part II, the computer GPS navigator was placed on an ambulance to supplement their normal methods of navigation to find the address requesting EMS. After the run was completed, EMS providers were interviewed to determine their opinion of whether the GPS navigator was helpful. For part I the results showed that in the 29 initial test runs, comparing the GPS team versus the standard map team, the mean distances traveled were 8.7 versus 9.0 kilometers (not significant) and the mean travel times were 13.5 versus 14.6 minutes (P=.02), respectively. The GPS team arrived faster in 72% runs. For part II the results showed that most EMS providers surveyed noted that the GPS computer navigator enhanced their ability to find the destination and all EMS providers acknowledged that it would enhance their ability to find a destination in an area in which they were unfamiliar. These results suggest that a portable GPS computer navigator system is helpful and can enhance the ability of prehospital care providers to locate their destination. Because these units are accurate and inexpensive, GPS computer navigators may be a valuable tool in reducing pre-hospital transport times. PMID:11326345
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.
Signals Attenuation and Application of EM-MWD in China
NASA Astrophysics Data System (ADS)
Wang, R.; Liu, H.; Yang, Q.; Li, J.; Wu, D.
2012-12-01
In the course of drilling utilizes directional well and horizontal well, it is indispensable to master timely and exact geological guide information, and offering services for such complicated drilling is electromagnetic Measurement While Drilling (EM-MWD) which can measure guide data of drilling tool in the hole and formation data while drilling. This knowledge allows the directional driller to make appropriate mechanical corrections in drill string orientation that will allow the advancing drill bit to hit an intended subsurface target area. Based on electromagnetic field theory, the paper has studied the propagation particularity and attenuation regularity that the signals of electromagnetic wave for EM-MWD transmit in stratum. The paper also gives a brief introduction of the containing, the work principle and the main technology parameter of EM-MWD. To check up the performance of EM-MWD, the field test of 5 wells were carried out in Shengli Oilfield and Liaohe Oilfield. Numerical simulation results indicate the signal attenuation will be added with the decrease of the stratum resistibility. In the frequency range from 1 to 10 Hz the stratum absorptivity is tiny and does not add noticeably with the increase of the electromagnetic wave frequency and the decrease of the stratum resistibility. In the frequency range from 1 to 10000 Hz the stratum absorptivity does not increase noticeably with the decrease of the dielectric constant of the stratum. Field test demonstrate that EM-MWD receives successfully signal emitted from depth underground 1600 meters in Shengli oilfield and 2400 meters in Liaohe oilfield. Our results indicate that numerical simulation methods are comparable to field test.
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
Carvalho, JoÃ£o Luiz
XXIII Congresso Brasileiro em Engenharia BiomÃ©dica Â XXIII CBEB 1 IDENTIFICAÃ?Ã?O DA DOENÃ?A DE CHAGAS-DF, Brasil joaoluiz@pgea.unb.br Abstract: Chagas' disease severely affects autonomic function, specially through the analysis of heart rate variability (HRV). This work aims at identifying Chagas' disease
Salomé Vieira Santos
RESUMO: No âmbito de um estudo mais vasto dirigido para o impacto do Síndrome Nefrótico e da Doença Celíaca na infância, pretende-se avaliar as percepções dos professores face às crianças em áreas específicas do contexto escolar. Para tal utilizam-se dois questionários: o primeiro, construído para o efeito, contempla conteúdos como a adaptação da criança à escola, a reacção dos professores
Neirotti, Juan Pablo
Approved Module Information for EM4005, 2014/5 Module Title/Name: Management of Change Module Code: To understand the theory of change and how we can manage it successfully in today?s engineering business environment. To explain the basic ideas behind change management and explore how they impact organizations
Neirotti, Juan Pablo
Approved Module Information for EM4003, 2014/5 Module Title/Name: Project Management Module Code Credits: 10 Module Management Information Module Leader Name Robin Clark Email Address r Information Module Aims: To explore the theory of project management and its application to real life
Composting of rice straw with effective microorganisms (EM) and its influence on compost quality
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
Application of Electromagnetic (EM) Separation Technology to Metal Refining Processes: A Review
NASA Astrophysics Data System (ADS)
Zhang, Lifeng; Wang, Shengqian; Dong, Anping; Gao, Jianwei; Damoah, Lucas Nana Wiredu
2014-12-01
Application of electromagnetic (EM) force to metal processing has been considered as an emerging technology for the production of clean metals and other advanced materials. In the current paper, the principle of EM separation was introduced and several schemes of imposing EM field, such as DC electric field with a crossed steady magnetic field, AC electric field, AC magnetic field, and traveling magnetic field were reviewed. The force around a single particle or multi-particles and their trajectories in the conductive liquid under EM field were discussed. Applications of EM technique to the purification of different liquid metals such as aluminum, zinc, magnesium, silicon, copper, and steel were summarized. Effects of EM processing parameters, such as the frequency of imposed field, imposed magnetic flux density, processing time, particle size, and the EM unit size on the EM purification efficiency were discussed. Experimental and theoretical investigations have showed that the separation efficiency of inclusions from the molten aluminum using EM purification could as high as over 90 pct. Meanwhile, the EM purification was also applied to separate intermetallic compounds from metal melt, such as ?-AlFeMnSi-phase from the molten aluminum. And then the potential industrial application of EM technique was proposed.
Development of the Emergency Medical Services Role Identity Scale (EMS-RIS).
Donnelly, Elizabeth A; Siebert, Darcy; Siebert, Carl
2015-03-01
This article describes the development and validation of the theoretically grounded Emergency Medical Services Role Identity Scale (EMS-RIS), which measures four domains of EMS role identity. The EMS-RIS was developed using a mixed methods approach. Key informants informed item development and the scale was validated using a representative probability sample of EMS personnel. Factor analyses revealed a conceptually consistent, four-factor solution with sound psychometric properties as well as evidence of convergent and discriminant validities. Social workers work with EMS professionals in crisis settings and as their counselors when they are distressed. The EMS-RIS provides useful information for the assessment of and intervention with distressed EMS professionals, as well as how role identity may influence occupational stress. PMID:25760489
Ilda de Fátima Ferreira Tinôco; Cecília de Fátima Souza; Paulo Armando Victoria de Oliveira; Robson Mendes de Paulo; Josiane Aparecida Campos; Cinara da Cunha Siqueira Carvalho; Marcelo Bastos Cordeiro
2007-01-01
RESUMO - Um estudo foi realizado com o objetivo de avaliar o sistema de criação em camas sobrepostas de maravalha e de casca de arroz, em comparação ao piso tradicional de concreto e sua influência no desempenho dos animais com base no ITGU (Índice de Temperatura de Globo negro e Umidade), no ganho de peso, no consumo de ração, na
Williamson, J D; Quatrano, R S; Cuming, A C
1985-10-15
The effect of abscisic acid (ABA) on the expression of the 'early-methionine-labeled' (Em) polypeptide was examined in cultured, immature wheat (Triticum aestivum, L.) embryos and in developing embryos in planta. A complementary DNA (cDNA) library was constructed from poly(A)-rich RNA from immature embryos cultured in the presence of ABA. ABA-enhanced sequences were first identified by differential colony-blot hybridization, and then verified using RNA slot-blot analysis. Dot-blot hybridization showed that one clone, p1015, was homologous to the previously isolated Em cDNA, pWG432. Electrophoretic analysis of the hybrid-select translation product of p1015 confirmed its identity as an Em sequence. Comparison of the p1015 cDNA insert size and the Em message size, from northern blot analysis, showed that p1015 contained about 87% of the Em sequence. RNA slot-blot analysis and protein electrophoresis showed that Em message, but not Em protein, accumulated at a low, basal level in immature embryos in the absence of ABA. Neither Em message nor Em protein was seen in three-day germinated seedlings. Steady-state levels of Em message and protein increased in immature embryos in the presence of ABA, both in culture and in planta. Regulation appeared to be primarily at the level of transcription or specific message stability. Regulation may also involve specific protein stability, since synthesis of Em protein continued in immature embryos in the absence of ABA, but Em protein did not accumulate in detectable amounts. We conclude that ABA specifically modulates Em message and protein levels in immature embryos, but is probably not responsible for the embryogenic specificity of Em expression. PMID:2932332
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.
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.
CARNEIRO DE PAIVA JUNIOR; RENZO GARCIA VON PINHO; ÉDILA VILELA DE RESENDE VON PINHO; SÉRGIO GERALDO DE RESENDE
RES UMO - Com o objetivo de avaliar a viabilidade técnica para a produção de milho verde no município de Lavras- MG, foram avaliadas treze cultivares de milho em três épocas (duas no verão e uma na safrinha) e em duas densidades (35 mil e 55 mil plantas\\/ha) de semeadura. Foram avaliadas as característic as de peso de espigas empalhadas,
Solé-Cava, Antonio M.
1 Submetido em 5 de janeiro de 2010. Aceito em 12 de junho de 2010. 2 Universidade Federal do Rio, 21941-590 Rio de Janeiro RJ, BRAZIL. 3 Bolsista de Doutorado CNPq. E-mail: almeida.d@gmail.com 4/UFRJ, Departamento de Invertebrados. Quinta da Boa Vista, São Cristovão, 20940-040, Rio de Janeiro RJ, BRAZIL
João Augusto; Alves Meira-Neto; Fernando Roberto Martins; Agostinho Lopes de Souza
RESUMO - (Influência da cobertura e do solo na composição florística do sub-bosque em uma floresta estacional semidecidual em Viçosa, MG, Brasil). A relação ecológica planta-luz tem sido estudada desde o início do século XX. As análises da relação da luminosidade ao nível das comunidades florestais têm se valido de medições indiretas por meio de índices de cobertura, mas sem
Demand-driven volume rendering of terascale EM data
Johanna Beyer; Markus Hadwiger; Won-Ki Jeong; Hanspeter Pfister; Jeff Lichtman
2011-01-01
In neuroscience, a very promising bottom-up approach to understanding how the brain works is built on acquiring and analyzing electron microscopy (EM) scans of brain tissue, an area known as Connectomics. This results in volume data of extremely high resolution of 3--5nm per pixel and 25--50nm slice thickness, overall leading to data sizes of many terabytes [Jeong et al. 2010].
Pesquisas Baseadas na Localizao e na Orientao em Dispositivos Mveis
Carmo, Maria Beatriz
Pesquisas Baseadas na LocalizaÃ§Ã£o e na OrientaÃ§Ã£o em Dispositivos MÃ³veis Hugo Aguiar, Maria Beatriz Carmo, Paulo Pombinho, Ana Paula Afonso Departamento de InformÃ¡tica, Faculdade de CiÃªncias, Universidade.di.fc.ul.pt,apa@di.fc.ul.pt SumÃ¡rio A crescente utilizaÃ§Ã£o de dispositivos mÃ³veis e a sua evoluÃ§Ã£o, com o surgimento de modelos
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
Position resolution and particle identification with the ATLAS EM calorimeter
J. Colas; L. Di Ciaccio; M. El Kacimi; O. Gaumer; M. Gouanère; D. Goujdami; R. Lafaye; C. Le Maner; L. Neukermans; P. Perrodo; L. Poggioli; D. Prieur; H. Przysiezniak; G. Sauvage; I. Wingerter-Seez; R. Zitoun; F. Lanni; H. Ma; S. Rajagopalan; S. Rescia; H. Takai; A. Belymam; D. Benchekroun; M. Hakimi; A. Hoummada; E. Barberio; Y. S. Gao; L. Lu; R. Stroynowski; M. Aleksa; J. Beck Hansen; T. Carli; P. Fassnacht; F. Gianotti; L. Hervas; W. Lampl; B. Belhorma; J. Collot; M. L. Gallin-Martel; J. Y. Hostachy; F. Ledroit-Guillon; P. Martin; F. Ohlsson-Malek; S. Saboumazrag; S. Viret; M. Leltchouk; J. A. Parsons; M. Seman; F. Barreiro; J. Del Peso; L. Labarga; C. Oliver; S. Rodier; P. Barrillon; C. Benchouk; F. Djama; P. Y. Duval; F. Henry-Couannier; F. Hubaut; E. Monnier; P. Pralavorio; D. Sauvage; C. Serfon; S. Tisserant; J. Toth; D. Banfi; L. Carminati; D. Cavalli; G. Costa; M. Delmastro; M. Fanti; L. Mandelli; M. Mazzanti; G. F. Tartarelli; K. Kotov; A. Maslennikov; G. Pospelov; Yu. Tikhonov; C. Bourdarios; C. de La Taille; L. Fayard; D. Fournier; L. Iconomidou-Fayard; M. Kado; M. Lechowski; G. Parrour; P. Puzo; D. Rousseau; R. Sacco; N. Seguin-Moreau; L. Serin; G. Unal; D. Zerwas; B. Dekhissi; J. Derkaoui; A. El Kharrim; F. Maaroufi; A. Camard; D. Lacour; B. Laforge; I. Nikolic-Audit; Ph. Schwemling; H. Ghazlane; R. Cherkaoui El Moursli; A. Idrissi Fakhr-Eddine; M. Boonekamp; B. Mansoulié; P. Meyer; J. Schwindling; B. Lund-Jensen; Y. Tayalati
2005-01-01
In the years between 2000 and 2002 several pre-series and series modules of the ATLAS EM barrel and end-cap calorimeter were exposed to electron, photon and pion beams. The performance of the calorimeter with respect to its finely segmented first sampling has been studied. The polar angle resolution has been found to be in the range 50–60 (mrad)\\/E(GeV). The ?0
Parameter estimation of superimposed signals using the EM algorithm
MEIR FEDER; EHUD WEINSTEIN
1988-01-01
A computationally efficient algorithm for parameter estimation of superimposed signals based on the two-step iterative EM (estimate-and-maximize, with an E step and an M step) algorithm is developed. The idea is to decompose the observed data into their signal components and then to estimate the parameters of each signal component separately. The algorithm iterates back and forth, using the current
Data management challenges in three-dimensional EM
Patwardhan, Ardan; Carazo, José-Maria; Carragher, Bridget; Henderson, Richard; Heymann, J Bernard; Hill, Emma; Jensen, Grant J; Lagerstedt, Ingvar; Lawson, Catherine L; Ludtke, Steven J; Mastronarde, David; Moore, William J; Roseman, Alan; Rosenthal, Peter; Sorzano, Carlos-Oscar S; Sanz-García, Eduardo; Scheres, Sjors H W; Subramaniam, Sriram; Westbrook, John; Winn, Martyn; Swedlow, Jason R; Kleywegt, Gerard J
2014-01-01
This report describes the outcomes of the Data Management Challenges in 3D Electron Microscopy workshop. Key topics discussed include data models, validation and raw-data archiving. The meeting participants agreed that the EMDataBank should take the lead in addressing these issues, and concrete action points were agreed upon that will have a substantial impact on the accessibility of three-dimensional EM data in biology and medicine. PMID:23211764
Da universidade para o mercado de trabalho em onze pases
Instituto de Sistemas e Robotica
Universia estÃ¡ a ser lanÃ§ado em vÃ¡rias instituiÃ§Ãµes de ensino superior portuguesas. Rede ibero-americana regista por mÃªs 195 mil ofertas ANA BELA FERREIRA Desde quinta-feira que os 23 mil alunos da Universidade a prÃ³-rei- tora, Ana Nunes de Almeida. Ao aderir a esta plataforma, que con- centra nÃ£o sÃ³ ofertas
A Biblioteca do IB em nmeros 2013 Acervo Total (publicaes)
Morandini, Andre C.
Total atual Livros * 347 33.796 Teses 259 3.483 TÃtulos de PeriÃ³dicos 2.132 Correntes ** 256 NÃ£o livros e teses) Biblioteca fornecedora 262 Biblioteca solicitante 100 NÂº de cÃ³pias fornecidas 3 a Biblioteca comprou 156 livros e recebeu em doaÃ§Ã£o 36. ** 256 por compra, 65 por doaÃ§Ã£o e 78 por permuta. #12;
ISSN 0103-9741 Monografia em Cincia da Computao
Endler, Markus
DO RIO DE JANEIRO RUA MARQUÊS DE SÃO VICENTE, 225 - CEP 22451-900 RIO DE JANEIRO #12;Monografias em , Vânia M.P. Vidal2 José A. F. de Macêdo2 1 Department of Informatics PUC-Rio Rio de Janeiro, RJ-900 Rio de Janeiro RJ Brasil Tel. +55 21 3527-1516 Fax: +55 21 3527-1530 E-mail: bib-di@inf.puc-rio.br Web
The boundary element method in EM-MWD
Chen Zhiyu
1992-01-01
The linear boundary element method for electromagnetic fields is taken to deal with the excitation of a non-symmetrical electric\\u000a dipole in a lossy half space. A simple and practical algorithm is offered to the Measurement While Drilling with Electromagnetic\\u000a waves (EM-MWD). The calculation for two models under the low frequency limits are compared with the experiments and the results\\u000a calculated
Supermarket eyes 1. 5-year payback on EMS
Barber
1982-01-01
A Honeywell W-7000 load control system has cut energy consumption at a Pittsburgh Shop and Save by 13% and should pay for itself in about 1.5 years. An 18.4% increase in utility rates, however, lowered the electricity savings to 10%. The energy management system (EMS) performs duty-cycling, demand limiting, and time-of-day scheduling functions in addition to controlling 25 loads. Monitoring
Improving EM&V for Energy Efficiency Programs (Fact Sheet)
Not Available
2012-07-01
This fact sheet describes the objectives of the U.S. Department of Energy Uniform Methods Project to bring consistency to energy savings calculations in U.S. energy efficiency programs. The U.S. Department of Energy (DOE) is developing a framework and a set of protocols for determining gross energy savings from energy efficiency measures and programs. The protocols represent a refinement of the body of knowledge supporting energy efficiency evaluation, measurement, and verification (EM&V) activities. They have been written by technical experts within the field and reviewed by industry experts. Current EM&V practice allows for multiple methods for calculating energy savings. These methods were developed to meet the needs of energy efficiency program administrators and regulators. Although they served their original objectives well, they have resulted in inconsistent and incomparable savings results - even for identical measures. The goal of the Uniform Methods Project is to strengthen the credibility of energy savings determinations by improving EM&V, increasing the consistency and transparency of how energy savings are determined.
Conjoined Use of EM and NMR in RNA Structure Refinement
Gong, Zhou; Schwieters, Charles D.; Tang, Chun
2015-01-01
More than 40% of the RNA structures have been determined using nuclear magnetic resonance (NMR) technique. NMR mainly provides local structural information of protons and works most effectively on relatively small biomacromolecules. Hence structural characterization of large RNAs can be difficult for NMR alone. Electron microscopy (EM) provides global shape information of macromolecules at nanometer resolution, which should be complementary to NMR for RNA structure determination. Here we developed a new energy term in Xplor-NIH against the density map obtained by EM. We conjointly used NMR and map restraints for the structure refinement of three RNA systems — U2/U6 small-nuclear RNA, genome-packing motif (?CD)2 from Moloney murine leukemia virus, and ribosome-binding element from turnip crinkle virus. In all three systems, we showed that the incorporation of a map restraint, either experimental or generated from known PDB structure, greatly improves structural precision and accuracy. Importantly, our method does not rely on an initial model assembled from RNA duplexes, and allows full torsional freedom for each nucleotide in the torsion angle simulated annealing refinement. As increasing number of macromolecules can be characterized by both NMR and EM, the marriage between the two techniques would enable better characterization of RNA three-dimensional structures. PMID:25798848
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)
Conjoined use of em and NMR in RNA structure refinement.
Gong, Zhou; Schwieters, Charles D; Tang, Chun
2015-01-01
More than 40% of the RNA structures have been determined using nuclear magnetic resonance (NMR) technique. NMR mainly provides local structural information of protons and works most effectively on relatively small biomacromolecules. Hence structural characterization of large RNAs can be difficult for NMR alone. Electron microscopy (EM) provides global shape information of macromolecules at nanometer resolution, which should be complementary to NMR for RNA structure determination. Here we developed a new energy term in Xplor-NIH against the density map obtained by EM. We conjointly used NMR and map restraints for the structure refinement of three RNA systems - U2/U6 small-nuclear RNA, genome-packing motif (?CD)2 from Moloney murine leukemia virus, and ribosome-binding element from turnip crinkle virus. In all three systems, we showed that the incorporation of a map restraint, either experimental or generated from known PDB structure, greatly improves structural precision and accuracy. Importantly, our method does not rely on an initial model assembled from RNA duplexes, and allows full torsional freedom for each nucleotide in the torsion angle simulated annealing refinement. As increasing number of macromolecules can be characterized by both NMR and EM, the marriage between the two techniques would enable better characterization of RNA three-dimensional structures. PMID:25798848
Yves Décanini; Antoine Folacci
2002-12-23
By using the complex angular momentum method, we provide a semiclassical analysis of electron scattering by a magnetic vortex of Aharonov-Bohm-type. Regge poles of the $S$-matrix are associated with surface waves orbiting around the vortex and supported by a magnetic field discontinuity. Rapid variations of sharp characteristic shapes can be observed on scattering cross sections. They correspond to quasibound states which are Breit-Wigner-type resonances associated with surface waves and which can be considered as quantum analogues of acoustic whispering-gallery modes. Such a resonant magnetic vortex could provide a new kind of artificial atom while the semiclassical approach developed here could be profitably extended in various areas of the physics of vortices.
NASA Astrophysics Data System (ADS)
Han, Yu; Gong, Wei-Jiang; Wei, Guo-Zhu
2009-12-01
Electron transport properties of a triple-terminal Aharonov-Bohm interferometer are theoretically studied. By applying a Rashba spin-orbit coupling to a quantum dot locally, we find that remarkable spin polarization comes about in the electron transport process with tuning the structure parameters, i.e., the magnetic flux or quantum dot levels. When the quantum dot levels are aligned with the Fermi level, there only appear spin polarization in this structure by the presence of an appropriate magnetic flux. However, in absence of magnetic flux spin polarization and spin separation can be simultaneously realized with the adjustment of quantum dot levels, namely, an incident electron from one terminal can select a specific terminal to depart from the quantum dots according to its spin state.
NASA Astrophysics Data System (ADS)
Lin, Xin; Pan, Hui; Xu, Huai-Zhe
2010-12-01
We have theoretically analyzed the quasibound states in a graphene quantum dot (GQD) with a magnetic flux ? in the centre. It is shown that the two-fold time reversal degeneracy is broken and the quasibound states of GQD with positive/negative angular momentum shifted upwards / downwards with increasing the magnetic flux. The variation of the quasibound energy depends linearly on the magnetic flux, which is quite different from the parabolic relationship for Schrödinger electrons. The GQD's quasibound states spectrum shows an obvious Aharonov—Bohm (AB) oscillations with the magnetic flux. It is also shown that the quasibound state with energy equal to the barrier height becomes a bound state completely confined in GQD.
Geometrically induced electric polarization in conical topological insulators
Jakson M. Fonseca; Winder A. Moura-Melo; Afranio R. Pereira
2011-11-29
We study the topological magnetoelectric effect on a conical topological insulator when a point charge $q$ is near the cone apex. The Hall current induced on the cone surface and the image charge configuration are determined. We also study a kind of gravitational Aharonov-Bohm effect in this geometry and realize a phase diference betwen the components of the wavefunctions (spinors) upon closed parallel transport around the (singular) cone tip. Concretely, a net current flowing towards cone apex (or botton) shows up, yielding electric polarization of the conical topological insulator. Such an effect may be detected, for instance, by means of the net accumulated Hall charge near the apex. Once it depends only on the geometry of the material (essetially, the cone apperture angle) this may be faced as a microscopic scale realization of (2+1)-dimensional Einstein gravity.
Resonances on hedgehog manifolds
Pavel Exner; Jiri Lipovsky
2013-02-21
We discuss resonances for a nonrelativistic and spinless quantum particle confined to a two- or three-dimensional Riemannian manifold to which a finite number of semiinfinite leads is attached. Resolvent and scattering resonances are shown to coincide in this situation. Next we consider the resonances together with embedded eigenvalues and ask about the high-energy asymptotics of such a family. For the case when all the halflines are attached at a single point we prove that all resonances are in the momentum plane confined to a strip parallel to the real axis, in contrast to the analogous asymptotics in some metric quantum graphs; we illustrate it on several simple examples. On the other hand, the resonance behaviour can be influenced by a magnetic field. We provide an example of such a `hedgehog' manifold at which a suitable Aharonov-Bohm flux leads to absence of any true resonance, i.e. that corresponding to a pole outside the real axis.
Geometric phase in Bohmian mechanics
Chou, Chia-Chun, E-mail: chiachun@mail.utexas.ed [Institute for Theoretical Chemistry and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Wyatt, Robert E., E-mail: wyattre@mail.utexas.ed [Institute for Theoretical Chemistry and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States)
2010-10-15
Using the quantum kinematic approach of Mukunda and Simon, we propose a geometric phase in Bohmian mechanics. A reparametrization and gauge invariant geometric phase is derived along an arbitrary path in configuration space. The single valuedness of the wave function implies that the geometric phase along a path must be equal to an integer multiple of 2{pi}. The nonzero geometric phase indicates that we go through the branch cut of the action function from one Riemann sheet to another when we locally travel along the path. For stationary states, quantum vortices exhibiting the quantized circulation integral can be regarded as a manifestation of the geometric phase. The bound-state Aharonov-Bohm effect demonstrates that the geometric phase along a closed path contains not only the circulation integral term but also an additional term associated with the magnetic flux. In addition, it is shown that the geometric phase proposed previously from the ensemble theory is not gauge invariant.
Transport of Massless Dirac Fermions in Non-topological Type Edge States
Latyshev, Yu I.; Orlov, A. P.; Volkov, V. A.; Enaldiev, V. V.; Zagorodnev, I. V.; Vyvenko, O. F.; Petrov, Yu V.; Monceau, P.
2014-01-01
There are two types of intrinsic surface states in solids. The first type is formed on the surface of topological insulators. Recently, transport of massless Dirac fermions in the band of “topological” states has been demonstrated. States of the second type were predicted by Tamm and Shockley long ago. They do not have a topological background and are therefore strongly dependent on the properties of the surface. We study the problem of the conductivity of Tamm-Shockley edge states through direct transport experiments. Aharonov-Bohm magneto-oscillations of resistance are found on graphene samples that contain a single nanohole. The effect is explained by the conductivity of the massless Dirac fermions in the edge states cycling around the nanohole. The results demonstrate the deep connection between topological and non-topological edge states in 2D systems of massless Dirac fermions. PMID:25524881
Optical conductivity of curved graphene
A. J. Chaves; T. Frederico; O. Oliveira; W. de Paula; M. C. Santos
2014-05-01
We compute the optical conductivity for an out-of-plane deformation in graphene using an approach based on solutions of the Dirac equation in curved space. Different examples of periodic deformations along one direction translates into an enhancement of the optical conductivity peaks in the region of the far and mid infrared frequencies for periodicities $\\sim100\\,$nm. The width and position of the peaks can be changed by dialling the parameters of the deformation profiles. The enhancement of the optical conductivity is due to intraband transitions and the translational invariance breaking in the geometrically deformed background. Furthemore, we derive an analytical solution of the Dirac equation in a curved space for a general deformation along one spatial direction. For this class of geometries, it is shown that curvature induces an extra phase in the electron wave function, which can also be explored to produce interference devices of the Aharonov-Bohm type.
Colloquium: Artificial gauge potentials for neutral atoms
Dalibard, Jean; Gerbier, Fabrice; Juzeliunas, Gediminas; Oehberg, Patrik [Laboratoire Kastler Brossel, CNRS, UPMC, Ecole normale superieure, 24 rue Lhomond, 75005, Paris (France); Institute of Theoretical Physics and Astronomy, Vilnius University, A. Gostauto 12, Vilnius 01108 (Lithuania); SUPA, Department of Physics, Heriot-Watt University, Edinburgh, EH14 4AS (United Kingdom)
2011-10-01
When a neutral atom moves in a properly designed laser field, its center-of-mass motion may mimic the dynamics of a charged particle in a magnetic field, with the emergence of a Lorentz-like force. In this Colloquium the physical principles at the basis of this artificial (synthetic) magnetism are presented. The corresponding Aharonov-Bohm phase is related to the Berry's phase that emerges when the atom adiabatically follows one of the dressed states of the atom-laser interaction. Some manifestations of artificial magnetism for a cold quantum gas, in particular, in terms of vortex nucleation are discussed. The analysis is then generalized to the simulation of non-Abelian gauge potentials and some striking consequences are presented, such as the emergence of an effective spin-orbit coupling. Both the cases of bulk gases and discrete systems, where atoms are trapped in an optical lattice, are addressed.
Locally induced quantum interference in scanning gate experiments
NASA Astrophysics Data System (ADS)
Kozikov, A. A.; Steinacher, R.; Rössler, C.; Ihn, T.; Ensslin, K.; Reichl, C.; Wegscheider, W.
2014-05-01
We present conductance measurements of a ballistic circular cavity influenced by a scanning gate. In contrast to previous studies, we demonstrate the use of scanning gate microscopy as a tool for tailoring the potential landscape of nanostructures with a high degree of control. When the tip depletes the electron gas below, we observe very pronounced and regular fringes covering the entire cavity. The fringes correspond to transmitted modes in constrictions formed between the tip-induced potential and the boundaries of the cavity. Moving the tip and counting the fringes gives us exquisite control over the transmission of these constrictions. We use this control to form a quantum ring with a specific number of modes in each arm showing the Aharonov-Bohm effect in low-field magnetoconductance measurements.
Gauge-invariant theory for semiclassical magnetotransport through ballistic microstructures
Wirtz, L.; Tang, J.; Burgdoerfer, J. [Department of Physics, University of Tennessee, Knoxville, Tennessee 37996-1200 (United States)] [Department of Physics, University of Tennessee, Knoxville, Tennessee 37996-1200 (United States); [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6377 (United States); [Institut fuer Theoretische Physik, Technische Universitaet Wien, Wiedner Hauptstrasse 8-10, A-1040 Wien (Austria)
1999-01-01
Within the semiclassical theory of magnetotransport through ballistic cavities, fluctuations in the transmission amplitude and in the conductance originate from the Aharonov-Bohm phase of directed areas. We formulate the semiclassical transmission amplitude in gauge-invariant form. The gauge invariant phases can be visualized in terms of areas enclosed by classical paths, which consist of the real path connecting the entrance point to the exit point and a virtual path leading back to the entrance point. We implement this method on different levels of a semiclassical description of magnetotransport with applications to magnetoconductance fluctuations and correlations. The validity of the semiclassical theories is analyzed. {copyright} {ital 1999} {ital The American Physical Society}
Topologically protected excitons in porphyrin thin films
Joel Yuen-Zhou; Semion S. Saikin; Norman Y. Yao; Alán Aspuru-Guzik
2014-06-05
The control of exciton transport in organic materials is of fundamental importance for the development of efficient light-harvesting systems. This transport is easily deteriorated by traps in the disordered energy landscape. Here, we propose and analyze a system that supports topological Frenkel exciton edge states. Backscattering of these chiral Frenkel excitons is prohibited by symmetry, ensuring that the transport properties of such a system are robust against disorder. To implement our idea, we propose a two-dimensional periodic array of tilted porphyrins interacting with a homogenous magnetic field. This field serves to break time-reversal symmetry and results in lattice fluxes that that mimic the Aharonov-Bohm phase acquired by electrons. Our proposal is the first blueprint for realizing topological phases of matter in molecular aggregates and suggests a paradigm for engineering novel excitonic materials.
NASA Astrophysics Data System (ADS)
Miller, J. H.; Wijesinghe, A. I.
2013-07-01
Aharonov-Bohm oscillations of period h/2 e in the charge density wave (CDW) magneto-conductance of TaS3 rings strongly support the hypothesis that CDW electron transport is a cooperative quantum phenomenon. In the picture discussed here, droplets or aggregates of solitons and antisolitons quantum-mechanically nucleate and carry current above a Coulomb blockade threshold for CDW transport. The Schrödinger equation is treated as a "classical" description of emerging order parameters, as in Feynman's description of Josephson tunneling. However, one key distinction of the proposed CDW model is that both the amplitudes and relative phases of the soliton droplet order parameters can vary with time. This ability to vary both amplitudes and phases of wave-function-like order parameters may prove critical to any viable quantum information processing strategies robust against decoherence.
Black Holes with Quantum Massive Spin-2 Hair
Gia Dvali
2006-05-31
We show that black holes can posses a long range quantum mechanical hair associated with a massive spin-2 field, which can be detected by a stringy generalization of the Aharovon-Bohm effect, in which a string loop lassoes the black hole. The long distance effect persist for arbitrarily high mass of the spin-2 field. An analogous effect is exhibited by a massive antisymmetric two-form field. We make a close parallel between the two and the ordinary Aharonov-Bohm phenomenon, and also show that in the latter case the effect can be experienced even by the electrically-neutral particles, provided some boundary terms are added to the action.
Black holes with quantum massive spin-2 hair
Dvali, Gia [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, New York 10003 (United States)
2006-08-15
We show that black holes can posses a long range quantum-mechanical hair associated with a massive spin-2 field, which can be detected by a stringy generalization of the Aharovon-Bohm effect, in which a string loop lassoes the black hole. The long distance effect persist for arbitrarily high mass of the spin-2 field. An analogous effect is exhibited by a massive antisymmetric two-form field. We make a close parallel between the two and the ordinary Aharonov-Bohm phenomenon, and also show that in the latter case the effect can be experienced even by the electrically-neutral particles, provided some boundary terms are added to the action.
NASA Astrophysics Data System (ADS)
Onorato, P.
2012-12-01
We study the quantum transport properties of cylindrical shaped wires, with submicrometric diameters and large aspect ratio. The zero bias conductance as a function of temperature, magnetic field and disorder is calculated for different kinds of nano cylinders, from semiconductor quantum wires to carbon nanotubes. A comparison between our findings and the experimental results allows the understanding of the charge carriers' localization, in the external surface or in the core of the wires, by highlighting the basic mechanism of charge transport. We discuss how we can infer that in InAs quantum wires the carriers move in the core. We examine the Aharonov-Bohm oscillations and the quenching that should be observed in the measured magneto conductivity of InAs nano cylinders and carbon nanotubes emphasizing the role of the angle between field and tube.
NASA Astrophysics Data System (ADS)
Onorato, P.
2011-03-01
An introduction to quantum mechanics based on the sum-over-paths (SOP) method originated by Richard P Feynman and developed by E F Taylor and coworkers is presented. The Einstein-Brillouin-Keller (EBK) semiclassical quantization rules are obtained following the SOP approach for bounded systems, and a general approach to the calculation of propagation amplitude is discussed for unbounded systems. These semiclassical results are obtained when the SOP is limited to the trajectories classically allowed. EBK semiclassical quantization and the topological Maslov index are used to deduce the correct quantum mechanical results for systems which live in a two-dimensional world as quantum dots and quantum rings. In the latter systems, the semiclassical propagation amplitude is used to discuss the Aharonov-Bohm effect. The development involves only elementary calculus and also provides a theoretical introduction to the quantum nature of low-dimensional nanostructures.
Control of Tripod-Scheme Cold-Atom Wavepackets by Manipulating a non-Abelian Vector Potential
Qi Zhang; Jiangbin Gong; C. H. Oh
2010-04-16
Tripod-scheme cold atoms interacting with laser beams have attracted considerable interest for their role in synthesizing effective non-Abelian vector potentials. Such effective vector potentials can be exploited to realize an all-optical imprinting of geometric phases onto matter waves. By working on carefully designed extensions of our previous work, we show that coherent lattice structure of cold-atom sub-wavepackets can be formed and that the non-Abelian Aharonov-Bohm effect can be easily manifested via the translational motion of cold atoms. We also show that by changing the frame of reference, effects due to a non-Abelian vector potential may be connected with a simple dynamical phase effect, and that under certain conditions it can be understood as an Abelian geometric phase in a different frame of reference. Results should help design better schemes for the control of cold-atom matter waves.
Control of tripod-scheme cold-atom wavepackets by manipulating a non-Abelian vector potential
Zhang Qi, E-mail: cqtzq@nus.edu.s [Centre of Quantum Technologies and Department of Physics, National University of Singapore, 117543 (Singapore); Gong Jiangbin, E-mail: phygj@nus.edu.s [Department of Physics and Centre for Computational Science and Engineering, National University of Singapore, 117542 (Singapore); NUS Graduate School for Integrative Sciences and Engineering, Singapore 117597 (Singapore); Oh, C.H., E-mail: phyohch@nus.edu.s [Centre of Quantum Technologies and Department of Physics, National University of Singapore, 117543 (Singapore); Institute of Advanced Studies, Nanyang Technological University, Singapore 639798 (Singapore)
2010-06-15
Tripod-scheme cold atoms interacting with laser beams have attracted considerable interest for their role in synthesizing effective non-Abelian vector potentials. Such effective vector potentials can be exploited to realize an all-optical imprinting of geometric phases onto matter waves. By working on carefully designed extensions of our previous work, we show that coherent lattice structure of cold-atom sub-wavepackets can be formed and that the non-Abelian Aharonov-Bohm effect can be easily manifested via the translational motion of cold atoms. We also show that by changing the frame of reference, effects due to a non-Abelian vector potential may be connected with a simple dynamical phase effect, and that under certain conditions it can be understood as an Abelian geometric phase in a different frame of reference. Results should help design better schemes for the control of cold-atom matter waves.
Three attempts at two axioms for quantum mechanics
Daniel Rohrlich
2011-11-04
The axioms of nonrelativistic quantum mechanics lack clear physical meaning. In particular, they say nothing about nonlocality. Yet quantum mechanics is not only nonlocal, it is twice nonlocal: there are nonlocal quantum correlations, and there is the Aharonov-Bohm effect, which implies that an electric or magnetic field h e r e may act on an electron t h e r e. Can we invert the logical hierarchy? That is, can we adopt nonlocality as an axiom for quantum mechanics and derive quantum mechanics from this axiom and an additional axiom of causality? Three versions of these two axioms lead to three different theories, characterized by "maximal nonlocal correlations", "jamming" and "modular energy". Where is quantum mechanics in these theories?
Dirac bound states of anharmonic oscillator in external fields
Hamzavi, Majid, E-mail: majid.hamzavi@gmail.com [Department of Physics, University of Zanjan, Zanjan (Iran, Islamic Republic of)] [Department of Physics, University of Zanjan, Zanjan (Iran, Islamic Republic of); Ikhdair, Sameer M., E-mail: sikhdair@gmail.com [Department of Physics, Faculty of Science, an-Najah National University, Nablus, West Bank, Palestine (Country Unknown); Department of Electrical and Electronic Engineering, Near East University, 922022 Nicosia, Northern Cyprus, Mersin 10 (Turkey); Falaye, Babatunde J., E-mail: fbjames11@physicist.net [Theoretical Physics Section, Department of Physics, University of Ilorin, P. M. B. 1515, Ilorin (Nigeria)
2014-02-15
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. -- Highlights: • Effect of the external fields on the energy levels of Dirac particle with the anharmonic oscillator is investigated. • The solutions are discussed in view of spin and pseudospin symmetries limits. • The energy levels and wave function are presented by the Nikiforov–Uvarov method.
Imaging coherent transport in a mesoscopic graphene ring
NASA Astrophysics Data System (ADS)
Cabosart, Damien; Faniel, Sébastien; Martins, Frederico; Brun, Boris; Felten, Alexandre; Bayot, Vincent; Hackens, Benoit
2014-11-01
Mesoscopic graphene devices often exhibit complex transport properties, stemming both from the peculiar electronic band structure of graphene and from the high sensitivity of transport to local disorder in this two-dimensional crystal. To disentangle contributions of disorder in the different transport phenomena at play in such devices, it is necessary to devise new local-probe methods and to establish links between transport and the microscopic structure of the devices. Here, we present a spatially resolved investigation of coherent transport inside a graphene quantum ring (QR), where Aharonov-Bohm conductance oscillations are observed. Thanks to scanning gate microscopy (SGM), we first identify spatial signatures of the Coulomb blockade, associated with disorder-induced localized states, and of charge-carrier interferences. We then image resonant states which decorate the QR local density of states (LDOS). Simulations of the LDOS in a model disorder graphene QR and temperature dependence of SGM maps confirm the presence of such scarred states.
Transport of massless Dirac fermions in non-topological type edge states.
Latyshev, Yu I; Orlov, A P; Volkov, V A; Enaldiev, V V; Zagorodnev, I V; Vyvenko, O F; Petrov, Yu V; Monceau, P
2014-01-01
There are two types of intrinsic surface states in solids. The first type is formed on the surface of topological insulators. Recently, transport of massless Dirac fermions in the band of "topological" states has been demonstrated. States of the second type were predicted by Tamm and Shockley long ago. They do not have a topological background and are therefore strongly dependent on the properties of the surface. We study the problem of the conductivity of Tamm-Shockley edge states through direct transport experiments. Aharonov-Bohm magneto-oscillations of resistance are found on graphene samples that contain a single nanohole. The effect is explained by the conductivity of the massless Dirac fermions in the edge states cycling around the nanohole. The results demonstrate the deep connection between topological and non-topological edge states in 2D systems of massless Dirac fermions. PMID:25524881
Two-dimensional Pauli operator in a magnetic field
NASA Astrophysics Data System (ADS)
Grinevich, P. G.; Mironov, A. E.; Novikov, S. P.
2011-10-01
The two-dimensional purely magnetic Schrödinger operator for the nonrelativistic particle with a spin of ½ in a magnetic field has some remarkable properties, that were discovered in the late 70s: its strongly degenerate in the ground state and it admits supersymmetry. In the present work we investigate the special case where the magnetic flux of the periodic field through the elementary cell equals zero. This case has not been covered in the previous publications. An interesting connection with the theory of solitons, in particular with Burgers-like systems and their two-dimensional analogues, is revealed. Their linearizability properties are simpler than some famous systems, such as KdV and KP. Members of the Aharonov-Bohm-type system with quantized magnetic flux play a special role in the investigation of this case.
Emergent geometry experienced by fermions in graphene in the presence of dislocations
G. E. Volovik; M. A. Zubkov
2015-03-11
In graphene in the presence of strain the elasticity theory metric naturally appears. However, this is not the one experienced by fermionic quasiparticles. Fermions propagate in curved space, whose metric is defined by expansion of the effective Hamiltonian near the topologically protected Fermi point. We discuss relation between both types of metric for different parametrizations of graphene surface. Next, we extend our consideration to the case, when the dislocations are present. We consider the situation, when the deformation is described by elasticity theory and calculate both torsion and emergent magnetic field carried by the dislocation. The dislocation carries singular torsion in addition to the quantized flux of emergent magnetic field. Both may be observed in the scattering of quasiparticles on the dislocation. Emergent magnetic field flux manifests itself in the Aharonov - Bohm effect while the torsion singularity results in Stodolsky effect.
Partial Phases in a Circling Electron
NASA Astrophysics Data System (ADS)
Englman, Robert; Yahalom, Asher
2012-11-01
An extended electronic cloud can acquire different Aharonov-Bohm (AB) phases in its parts when these parts experience different solenoidal fields. This is demonstrated by two models that describe an electron moving within a confining circular tube around a solenoidal vector potential and outside a magnetic field domain (just as in a usual AB set up): one in which the motion of the electron along the tube is restricted and moves adiabatically and another in which it extends freely and without restriction on its speed. When the electron cloud is split into two parts circling in opposite directions, we show that when the two parts of the electronic cloud rejoin, they do so with different phases. This set-up complements (and confirms the finding of) our previous work [Europhys. Lett.93, 20001 (2011)], in which the vector source was moving and the electron position was fixed.
Fault-tolerant quantum computation
John Preskill
1997-12-19
The discovery of quantum error correction has greatly improved the long-term prospects for quantum computing technology. Encoded quantum information can be protected from errors that arise due to uncontrolled interactions with the environment, or due to imperfect implementations of quantum logical operations. Recovery from errors can work effectively even if occasional mistakes occur during the recovery procedure. Furthermore, encoded quantum information can be processed without serious propagation of errors. In principle, an arbitrarily long quantum computation can be performed reliably, provided that the average probability of error per gate is less than a certain critical value, the accuracy threshold. It may be possible to incorporate intrinsic fault tolerance into the design of quantum computing hardware, perhaps by invoking topological Aharonov-Bohm interactions to process quantum information.
Asymmetric transmission through a flux-controlled non-Hermitian scattering center
NASA Astrophysics Data System (ADS)
Li, X. Q.; Zhang, X. Z.; Zhang, G.; Song, Z.
2015-03-01
We study the possibility of asymmetric transmission induced by a non-Hermitian scattering center embedded in a one-dimensional waveguide, motivated by the aim of realizing quantum diodes in a non-Hermitian system. It is shown that a PT -symmetric non-Hermitian scattering center always has symmetric transmission although the dynamics within the isolated center can be unidirectional, especially at its exceptional point. We propose a concrete scheme based on a flux-controlled non-Hermitian scattering center, which comprises a non-Hermitian triangular ring threaded by an Aharonov-Bohm flux. The analytical solution shows that such a complex scattering center acts as a diode at the resonant energy level of the spectral singularity, exhibiting perfect unidirectionality of the transmission. The connections between the phenomena of the asymmetric transmission and reflectionless absorption are also discussed.
NASA Astrophysics Data System (ADS)
Zhao, Hong-Kang; Wang, Jian; Wang, Qing
2014-04-01
The shot noise of a hybrid triple-quantum-dot (TQD) interferometer has been investigated by employing the nonequilibrium Green's function method, and the general shot noise formula has been derived. The oscillation behaviors of transmission coefficients and shot noise versus the Aharonov-Bohm phase ? exhibit asymmetric Fano resonance structure and blockade effect. Sub-Poissonian and super-Poissonian behaviors of shot noise appear in different regimes of terminal bias eV? contributed by the Andreev reflection, and correlation of Andreev tunneling with the normal electron transport. The inverse resonance and resonance structures emerge in the shot noise and Fano factor with respect to one of the gate voltages in different regimes of eV?. The asymmetric structure can be enhanced by modifying the energy levels and gate biases of the TQD. The self-correlation and cross-correlation of current components contribute to the enhancement and suppression of shot noise.
Is Quantum Mechanics Incompatible with Newton's First Law?
NASA Astrophysics Data System (ADS)
Rabinowitz, Mario
2008-04-01
Quantum mechanics (QM) clearly violates Newton’s First Law of Motion (NFLM) in the quantum domain for one of the simplest problems, yielding an effect in a force-free region much like the Aharonov-Bohm effect. In addition, there is an incompatibility between the predictions of QM in the classical limit, and that of classical mechanics (CM) with respect to NFLM. A general argument is made that such a disparity may be found commonly for a wide variety of quantum predictions in the classical limit. Alternatives to the Schrödinger equation are considered that might avoid this problem. The meaning of the classical limit is examined. Critical views regarding QM by Schrödinger, Bohm, Bell, Clauser, and others are presented to provide a more complete perspective.
Electric field geometries dominate quantum transport coupling in silicon nanoring
Lee, Tsung-Han, E-mail: askaleeg@gmail.com, E-mail: sfhu.hu@gmail.com; Hu, Shu-Fen, E-mail: askaleeg@gmail.com, E-mail: sfhu.hu@gmail.com [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China)
2014-03-28
Investigations on the relation between the geometries of silicon nanodevices and the quantum phenomenon they exhibit, such as the Aharonov–Bohm (AB) effect and the Coulomb blockade, were conducted. An arsenic doped silicon nanoring coupled with a nanowire by electron beam lithography was fabricated. At 1.47?K, Coulomb blockade oscillations were observed under modulation from the top gate voltage, and a periodic AB oscillation of ?B?=?0.178?T was estimated for a ring radius of 86?nm under a high sweeping magnetic field. Modulating the flat top gate and the pointed side gate was performed to cluster and separate the many electron quantum dots, which demonstrated that quantum confinement and interference effects coexisted in the doped silicon nanoring.
Topologically protected excitons in porphyrin thin films
NASA Astrophysics Data System (ADS)
Yuen-Zhou, Joel; Saikin, Semion K.; Yao, Norman Y.; Aspuru-Guzik, Alán
2014-11-01
The control of exciton transport in organic materials is of fundamental importance for the development of efficient light-harvesting systems. This transport is easily deteriorated by traps in the disordered energy landscape. Here, we propose and analyse a system that supports topological Frenkel exciton edge states. Backscattering of these chiral Frenkel excitons is prohibited by symmetry, ensuring that the transport properties of such a system are robust against disorder. To implement our idea, we propose a two-dimensional periodic array of tilted porphyrins interacting with a homogeneous magnetic field. This field serves to break time-reversal symmetry and results in lattice fluxes that mimic the Aharonov–Bohm phase acquired by electrons. Our proposal is the first blueprint for realizing topological phases of matter in molecular aggregates and suggests a paradigm for engineering novel excitonic materials.
Asymmetric coherent transmission for single particle diode and gyroscope
S. Yang; Z. Song; C. P. Sun
2009-12-02
We study the single particle scattering process in a coherent multi-site system consisting of a tight-binding ring threaded by an Aharonov-Bohm flux and several attaching leads. The asymmetric behavior of scattering matrix is discovered analytically in the framework of both Bethe Ansatz and Green's function formalism. It is found that, under certain conditions, a three-site electronic system can behave analogous to a perfect semiconductor diode where current flows only in one direction. The general result is also valid for a neutral particle system since the effective magnetic flux may be implemented by a globe rotation. This observation means that the three-site system can serve as an orientation measuring gyroscope due to the approximate linear dependence of the current difference of two output leads on the rotational angular velocity.
The Physical Interpretation of the Lanczos Tensor
Mark D. Roberts
1999-04-04
The field equations of general relativity can be written as first order differential equations in the Weyl tensor, the Weyl tensor in turn can be written as a first order differential equation in a three index tensor called the Lanczos tensor. The Lanczos tensor plays a similar role in general relativity to that of the vector potential in electro-magnetic theory. The Aharonov-Bohm effect shows that when quantum mechanics is applied to electro-magnetic theory the vector potential is dynamically significant, even when the electro-magnetic field tensor $F_{ab}$ vanishes. Here it is assumed that in the quantum realm the Lanczos tensor is dynamically significant, and this leads to an attempt to quantize the gravitational field by pursuing the analogy between the vector field and the Lanczos tensor.
NASA Astrophysics Data System (ADS)
Liew, T. C. H.; Shelykh, I. A.; Malpuech, G.
2011-07-01
We review the current hopes for applications of exciton-polaritons in semiconductor microcavities. These quasi-particles have become distinguished in recent years for a variety of different effects including Bose-Einstein condensation, ballistic spin current propagation and polarisation sensitive bistability. Bose-Einstein condensation is related to ultra low-threshold lasing, which has been demonstrated at room temperature and currently captures a significant research effort towards electrical carrier injection. Inspired by spintronics, the spin structure of polaritons gives rise to the field of spinoptronics, which presents optical analogues of the Datta and Das transistor and Aharonov-Bohm ring interferometer. Bistability, enhanced with the polarisation degree of freedom, gives rise to long-living spin memory elements, spin logic gates and polariton neurons for the construction of all-optical and hybrid optoelectronic circuits.
Astrophysical Bounds on the Photon Charge and Magnetic Moment
Brett Altschul
2007-11-13
If the photon possessed an electric charge or a magnetic moment, light waves propagating through magnetic fields would acquire new quantum mechanical phases. For a charged photon, this is an Aharonov-Bohm phase, and the fact that we can resolve distant galaxies using radio interferometry indicates that this phase must be small. This in turn constrains the photon charge to be smaller that 10^(-32) e if all photons have the same charge and smaller than 10^(-46) e if there are both positively and negatively charged photons. The best bound on the magnetic moment comes from the observed absence of wavelength-independent photon birefringence. Birefringence measurements, which compare the relative phases of right- and left-circularly polarized waves, restrict the magnetic moment to be less than 10^(-24) e cm. This is just a few orders of magnetude weaker than the experimental bounds on the electron and neutron electric dipole moments.
Topology and Gauge Theory in Physics
NASA Astrophysics Data System (ADS)
Yang, Chen Ning
2013-05-01
I am deeply touched by the short message that Tonomura recorded for all of us today. It reminded me of my first visit to his laboratory in the early 1980s and the many conferences that I attended that he had organized in Japan. It also recalled for me the many discussions that he and I had, not only about the Aharonov-Bohm effect, but also about flux movement in superconductors, especially after the 1987 discovery of high-temperature superconductors. He and I had in these years many warm and fruitful meetings in Japan, in China, and in the United States. Last winter I was very happy to have received a photograph of him standing in a garden a few months after his operation. I thought he was on his way to full recovery. But that was not to be...
Missing experiments in quantum mechanics
Miroslav Pardy
2008-01-16
We discuss the two-slit experiment and the Aharonov-Bohm (AB) experiment in the magnetic field. In such a case the electron moving in the magnetic field produces so called synchrotron radiation. In other words the photons are emitted from the points of the electron trajectory and it means that the trajectory of electron is visible in the synchrotron radiation spectrum. The axiomatic system of quantum mechanics does not enable to define the trajectory of the elementary particle. The two-slit experiment and AB experiment in a magnetic field was never performed and it means that they are the missing experiments of quantum mechanics. The extension of the discussion to the cosmical rays moving in the magnetic field of the Saturn magnetosphere and its rings is mentioned. It is related to the probe CASSINI. The solution of the problem in the framework of the hydrodynamical model of quantum mechanics and the nonlinear quantum mechanics is also mentioned.
Creation of two-dimensional coulomb crystals of ions in oblate Paul traps for quantum simulations
Bryce Yoshimura; Marybeth Stork; Danilo Dadic; W. C. Campbell; J. K. Freericks
2014-06-20
We develop the theory to describe the equilibrium ion positions and phonon modes for a trapped ion quantum simulator in an oblate Paul trap that creates two-dimensional Coulomb crystals in a triangular lattice. By coupling the internal states of the ions to laser beams propagating along the symmetry axis, we study the effective Ising spin-spin interactions that are mediated via the axial phonons and are less sensitive to ion micromotion. We find that the axial mode frequencies permit the programming of Ising interactions with inverse power law spin-spin couplings that can be tuned from uniform to $r^{-3}$ with DC voltages. Such a trap could allow for interesting new geometrical configurations for quantum simulations on moderately sized systems including frustrated magnetism on triangular lattices or Aharonov-Bohm effects on ion tunneling. The trap also incorporates periodic boundary conditions around loops which could be employed to examine time crystals.
Giant intrinsic spin and orbital hall effects in Sr2MO4 (M=Ru, Rh, Mo).
Kontani, H; Tanaka, T; Hirashima, D S; Yamada, K; Inoue, J
2008-03-01
We investigate the intrinsic spin Hall conductivity (SHC) and the d-orbital Hall conductivity (OHC) in metallic d-electron systems, by focusing on the t2g-orbital tight-binding model for Sr2MO4 (M=Ru, Rh, Mo). The conductivities obtained are one or 2 orders of magnitude larger than predicted values for p-type semiconductors with approximately 5% hole doping. The origin of these giant Hall effects is the "effective Aharonov-Bohm phase" that is induced by the d-atomic angular momentum in connection with the spin-orbit interaction and the interorbital hopping integrals. The huge SHC and OHC generated by this mechanism are expected to be ubiquitous in multiorbital transition metal compounds, which opens the possibility of realizing spintronics as well as "orbitronics" devices. PMID:18352738
Giant Intrinsic Spin and Orbital Hall Effects in Sr2MO4 (M=Ru, Rh, Mo)
NASA Astrophysics Data System (ADS)
Kontani, H.; Tanaka, T.; Hirashima, D. S.; Yamada, K.; Inoue, J.
2008-03-01
We investigate the intrinsic spin Hall conductivity (SHC) and the d-orbital Hall conductivity (OHC) in metallic d-electron systems, by focusing on the t2g-orbital tight-binding model for Sr2MO4 (M=Ru, Rh, Mo). The conductivities obtained are one or 2 orders of magnitude larger than predicted values for p-type semiconductors with ˜5% hole doping. The origin of these giant Hall effects is the “effective Aharonov-Bohm phase” that is induced by the d-atomic angular momentum in connection with the spin-orbit interaction and the interorbital hopping integrals. The huge SHC and OHC generated by this mechanism are expected to be ubiquitous in multiorbital transition metal compounds, which opens the possibility of realizing spintronics as well as “orbitronics” devices.
Gauge field optics with anisotropic media.
Liu, Fu; Li, Jensen
2015-03-13
By considering gauge transformations on the macroscopic Maxwell's equations, a two-dimensional gauge field, with its pseudomagnetic field in the real space, is identified as tilted anisotropy in the constitutive parameters. We show that the optical spin Hall effect with broadband response and one-way edge states become possible simply by using anisotropic media. The proposed gauge field also allows us to obtain unidirectional propagation for a particular pseudospin based on the Aharonov-Bohm effect. Our approach will be useful in spoof magneto-optics with arbitrary magnetic fields mimicked by metamaterials with subwavelength unit cells. It also serves as a generic way to design polarization-dependent devices. PMID:25815934
A non-qubit quantum adder as one-dimensional cellular automaton
NASA Astrophysics Data System (ADS)
Wu, C. H.; Cain, C. A.
2014-05-01
A complete quantum addition machine is presented and compared with methods employing unitary transformations first. A quantum half-adder circuit shown earlier can be implemented into each cell of a 1D cellular automaton. An electric Aharonov-Bohm effect version of the quantum circuit is used to illustrate this implementation. Whatever a quantum Turing machine can achieve is realized in the cellular automata architecture we propose here. The coherence requirement is limited to one cell area. The magnetic flux needed is 0.1?0, corresponding to 0.414 mT for a ring area of 1 square micron or an electric potential of 0.414 mV at 1 ps with an energy dissipation of 0.041 eV per iteration.
Decoherence and interactions in an electronic Mach-Zehnder interferometer
NASA Astrophysics Data System (ADS)
Chalker, J. T.; Gefen, Yuval; Veillette, M. Y.
2007-08-01
We develop a theoretical description of a Mach-Zehnder interferometer built from integer quantum Hall edge states, with an emphasis on how electron-electron interactions produce decoherence. We calculate the visibility of interference fringes and noise power as a function of bias voltage and of temperature. Interactions are treated exactly by using bosonization and considering edge states that are only weakly coupled via tunneling at the interferometer beam splitters. In this weak-tunneling limit, we show that the bias dependence of Aharonov-Bohm oscillations in source-drain conductance and noise power provides a direct measure of the one-electron correlation function for an isolated quantum Hall edge state. We find the asymptotic form of this correlation function for systems with either short-range interactions or unscreened Coulomb interactions, extracting a dephasing length ?? that varies with temperature T as ???T-3 in the first case and as ???T-1ln2(T) in the second case.
Dynamical features of interference phenomena in the presence of entanglement
Kaufherr, T. [Tel Aviv University, School of Physics and Astronomy, Tel Aviv 69978 (Israel); Physics Department, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Aharonov, Y. [Tel Aviv University, School of Physics and Astronomy, Tel Aviv 69978 (Israel); Chapman University, Schmid College of Sciences, Orange, California 92866 (United States); Nussinov, S. [Tel Aviv University, School of Physics and Astronomy, Tel Aviv 69978 (Israel); Popescu, S. [H.H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TK (United Kingdom); Tollaksen, J. [Chapman University, Schmid College of Sciences, Orange, California 92866 (United States)
2011-05-15
A strongly interacting, and entangling, heavy nonrecoiling external particle effects a significant change of the environment. Described locally, the corresponding entanglement event is a generalized electric Aharonov-Bohm effect, which differs from the original one in a crucial way. We propose a gedanken interference experiment. The predicted shift of the interference pattern is due to a self-induced or ''private'' potential difference experienced while the particle is in vacuum. We show that all nontrivial Born-Oppenheimer potentials are ''private'' potentials. We apply the Born-Oppenheimer approximation to interference states. Using our approach, we calculate the relative phase of the external heavy particle as well as its uncertainty throughout an interference experiment or entanglement event. We thus complement the Born-Oppenheimer approximation for interference states.
Berry's phases and topological properties in the Born-Oppenheimer approximation
Kazuo Fujikawa
2005-10-07
The level crossing problem is neatly formulated by the second quantized formulation, which exhibits a hidden local gauge symmetry. The analysis of geometric phases is reduced to a simple diagonalization of the Hamiltonian. If one diagonalizes the geometric terms in the infinitesimal neighborhood of level crossing, the geometric phases become trivial (and thus no monopole singularity) for arbitrarily large but finite time interval $T$. The topological proof of the Longuet-Higgins' phase-change rule, for example, thus fails in the practical Born-Oppenheimer approximation where $T$ is identified with the period of the slower system. The crucial difference between the Aharonov-Bohm phase and the geometric phase is explained. It is also noted that the gauge symmetries involved in the adiabatic and non-adiabatic geometric phases are quite different.
Cosmic strings in hidden sectors: 1. Radiation of standard model particles
NASA Astrophysics Data System (ADS)
Long, Andrew J.; Hyde, Jeffrey M.; Vachaspati, Tanmay
2014-09-01
In hidden sector models with an extra U(1) gauge group, new fields can interact with the Standard Model only through gauge kinetic mixing and the Higgs portal. After the U(1) is spontaneously broken, these interactions couple the resultant cosmic strings to Standard Model particles. We calculate the spectrum of radiation emitted by these ``dark strings'' in the form of Higgs bosons, Z bosons, and Standard Model fermions assuming that string tension is above the TeV scale. We also calculate the scattering cross sections of Standard Model fermions on dark strings due to the Aharonov-Bohm interaction. These radiation and scattering calculations will be applied in a subsequent paper to study the cosmological evolution and observational signatures of dark strings.
Dark matter in the SO(5) × U(1) gauge-Higgs unification
NASA Astrophysics Data System (ADS)
Funatsu, Shuichiro; Hatanaka, Hisaki; Hosotani, Yutaka; Orikasa, Yuta; Shimotani, Takuya
2014-11-01
In the SO(5){× }U(1) gauge-Higgs unification, the lightest neutral component of n_F SO(5)-spinor fermions (dark fermions), which are relevant as they have the observed unstable Higgs boson, becomes the dark matter of the universe. We show that the relic abundance of the dark matter determined by WMAP and Planck data is reproduced, below the bound placed by the direct-detection experiment by LUX, by a model with one light and three heavier (n_F=4) dark fermions with the lightest one with a mass from 2.3 TeV to 3.1 TeV. The corresponding Aharonov-Bohm phase ? _H in the fifth dimension ranges from 0.097 to 0.074. The case of n_F=3 (n_F = 5, 6) dark fermions yields a relic abundance smaller (larger) than the observed limit.
Experimental Realization of Strong Effective Magnetic Fields in an Optical Lattice
Aidelsburger, M.; Atala, M.; Trotzky, S.; Chen, Y.-A.; Bloch, I. [Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet, Schellingstrasse 4, 80799 Muenchen (Germany); Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Nascimbene, S. [Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet, Schellingstrasse 4, 80799 Muenchen (Germany); Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Laboratoire Kastler Brossel, CNRS, UPMC, Ecole Normale Superieure, 24 rue Lhomond, 75005 Paris (France)
2011-12-16
We use Raman-assisted tunneling in an optical superlattice to generate large tunable effective magnetic fields for ultracold atoms. When hopping in the lattice, the accumulated phase shift by an atom is equivalent to the Aharonov-Bohm phase of a charged particle exposed to a staggered magnetic field of large magnitude, on the order of 1 flux quantum per plaquette. We study the ground state of this system and observe that the frustration induced by the magnetic field can lead to a degenerate ground state for noninteracting particles. We provide a measurement of the local phase acquired from Raman-induced tunneling, demonstrating time-reversal symmetry breaking of the underlying Hamiltonian. Furthermore, the quantum cyclotron orbit of single atoms in the lattice exposed to the magnetic field is directly revealed.
Dynamic spin-flip shot noise of mesoscopic transport through a toroidal carbon nanotube
NASA Astrophysics Data System (ADS)
Zhao, H. K.; Zhang, J.; Wang, J.
2015-01-01
The shot noise in a toroidal carbon nanotube (TCN) interferometer under the perturbation of a rotating magnetic field (RMF) has been investigated. A general shot noise formula has been derived by calculating the current correlation. It was found that photon absorption and emission induce novel features of dynamic shot noise. The oscillatory behavior of shot noise and Fano factor vary with the Aharonov-Bohm (AB) magnetic flux, and they are sensitively dependent on the Zeeman energy, frequency of RMF, and source-drain bias. By adjusting the Zeeman energy, the AB oscillation structures of shot noise and Fano factor show valley-to-peak transformation. The shot noise increases nonlinearly with increasing the Zeeman energy and photon energy. The enhancement and asymmetry of shot noise can be attributed to the spin-flip effect.
Do the Laws of Nature and Physics Agree About What is Allowed and Forbidden?
Mario Rabinowitz
2001-03-31
There are countless examples in the history of science that not only were the laws of physics often incomplete and more limited in their domain of validity than was realized, but at times they missed the mark completely. Despite this, our collective memory is often short on such matters, focusing on present triumphs and quickly forgetting past failures. This makes us less tolerant to that which challenges present orthodoxy. It may be of value to recall such past deficiences as well as present shortcomings, particularly since science may always be encumbered with such limitations. We can avoid serious pitfalls if we let the past serve as a guide to the future. Subjects covered will include Godel's theorem, superconductivity, zero-point energy, the quantum and classical Aharonov-Bohm and similar effects, theories of general relativity, Mach's principle, black hole radiation, ball lightning, and the universe(s).
Quantum and Classical Variance in the Quantum Realm
Mario Rabinowitz
2008-07-18
This paper examines the variance of quantum and classical predictions in the quantum realm, as well as unexpected presence and absence of variances. Some features are found that share an indirect commonality with the Aharonov-Bohm and Aharonov-Casher effects in that there is a quantum action in the absence of a force. Variances are also found in the presence of a force that are more subtle as they are of higher order. Significant variances related to the harmonic oscillator and particle in a box periods are found. This paper raises the question whether apparent quantum self-inconsistency may be examined internally, or must be empirically ascertained. These inherent variances may either point to inconsistencies in quantum mechanics that should be fixed, or that nature is manifestly more non-classical than expected. For the harmonic oscillator it is proven that the second spatial moment is the same in QM and CM.
Is Quantum Mechanics Incompatible with Newton's First Law
Mario Rabinowitz
2008-04-11
Quantum mechanics (QM) clearly violates Newton's First Law of Motion (NFLM) in the quantum domain for one of the simplest problems, yielding an effect in a force-free region much like the Aharonov-Bohm effect. In addition, there is an incompatibility between the predictions of QM in the classical limit, and that of classical mechanics (CM) with respect to NFLM. A general argument is made that such a disparity may be found commonly for a wide variety of quantum predictions in the classical limit. Alternatives to the Schrodinger equation are considered that might avoid this problem. The meaning of the classical limit is examined. Critical views regarding QM by Schrodinger, Bohm, Bell, Clauser, and others are presented to provide a more complete perspective.
Quasiparticle scattering from vortices in d-wave superconductors I: Superflow contribution
M. Kulkarni; Sriram Ganeshan; A. C. Durst
2011-08-13
In the vortex state of a d-wave superconductor, massless Dirac quasiparticles are scattered from magnetic vortices via a combination of two basic mechanisms: effective potential scattering due to the superflow swirling about the vortices and Aharonov-Bohm scattering due to the Berry phase acquired by a quasiparticle upon circling a vortex. In this paper, we study the superflow contribution by calculating the differential cross section for a quasiparticle scattering from the effective non-central potential of a single vortex. We solve the massless Dirac equation in polar coordinates and obtain the cross section via a partial wave analysis. We also present a more transparent Born-limit calculation and in this approximation we provide an analytic expression for the differential cross section. The Berry phase contribution to the quasiparticle scattering is considered in a separate paper.
Ganeshan, S; Durst, A C
2010-01-01
In the vortex state of a d-wave superconductor, massless Dirac quasiparticles are scattered from magnetic vortices via a combination of two basic mechanisms: effective potential scattering due to the superflow swirling about the vortices and Aharonov-Bohm scattering due to the Berry phase acquired by a quasiparticle upon circling a vortex. In this paper, we study the scattering contribution of each of these mechanisms in the absence of the other. First, we consider the superflow contribution by calculating the differential cross section for a quasiparticle scattering from the effective non-central potential of a single vortex. Here we solve the massless Dirac equation in polar coordinates and obtain the cross section via a partial wave analysis. Next, we consider the Berry phase contribution, which results in branch cuts between neighboring vortices across which the quasiparticle wave function changes sign. Here, the simplest problem that captures the physics is that of scattering from a single finite branch ...
Hall, M Kennedy; Raven, Maria C; Hall, Jane; Yeh, Clement; Allen, Elaine; Rodriguez, Robert M; Tangherlini, Niels L; Sporer, Karl A; Brown, John F
2015-01-01
Abstract Objective. Emergency medical services (EMS) "superusers" -those who use EMS services at extremely high rates -have not been well characterized. Recent interest in the small group of individuals who account for a disproportionate share of health-care expenditures has led to research on frequent users of emergency departments and other health services, but little research has been done regarding those who use EMS services. To inform policy and intervention implementation, we undertook a descriptive analysis of EMS superusers in a large urban community. In this paper we compare EMS superusers to low, moderate, and high users to characterize factors contributing to EMS use. We also estimate the financial impact of EMS superusers. Methods. We conducted a retrospective cross-sectional study based on 1 year of data from an urban EMS system. Data for all EMS encounters with patients age ?18 years were extracted from electronic records generated on scene by paramedics. We identified demographic and clinical variables associated with levels of EMS use. EMS users were characterized by the annual number of EMS encounters: low (1), moderate (2-4), high (5-14), and superusers (?15). In addition, we performed a financial analysis using San Francisco Fire Department (SFFD) 2009 charge and reimbursement data. Results. A total of 31,462 adults generated 43,559 EMS ambulance encounters, which resulted in 39,107 transports (a 90% transport rate). Encounters for general medical reasons were common among moderate and high users and less frequent among superusers and low users, while alcohol use was exponentially correlated with encounter frequency. Superusers were significantly younger than moderate EMS users, and more likely to be male. The superuser group created a significantly higher financial burden/person than any other group, comprising 0.3% of the study population, but over 6% of annual EMS charges and reimbursements. Conclusions. In this retrospective study, adult EMS "superusers" emerged as a distinct, predominantly male population and their EMS encounters were associated with alcohol use. Continued analysis of this unique, high-cost, and frequently transported population will likely illuminate specific intervention strategies. PMID:25093273
Does EMS Perceived Anatomic Injury Predict Trauma Center Need?
Lerner, E. Brooke; Roberts, Jennifer; Guse, Clare E.; Shah, Manish N.; Swor, Robert; Cushman, Jeremy T.; Blatt, Alan; Jurkovich, Gregory J.; Brasel, Karen
2013-01-01
Objective Our objective was to determine the predictive value of the anatomic step of the 2011 Field Triage Decision Scheme for identifying trauma center need. Methods EMS providers caring for injured adults transported to regional trauma centers in 3 midsized communities were interviewed over two years. Patients were included, regardless of injury severity, if they were at least 18 years old and were transported by EMS with a mechanism of injury that was an assault, motor vehicle or motorcycle crash, fall, or pedestrian or bicyclist struck. The interview was conducted upon ED arrival and collected physiologic condition and anatomic injury data. Patients who met the physiologic criteria were excluded. Trauma center need was defined as non-orthopedic surgery within 24 hours, intensive care unit admission, or death prior to hospital discharge. Data were analyzed by calculating descriptive statistics including positive likelihood ratios (+LR) with 95% confidence intervals. Results 11,892 interviews were conducted. One was excluded because of missing outcome data and 1,274 were excluded because they met the physiologic step. EMS providers identified 1,167 cases that met the anatomic criteria, of which 307 (26%) needed the resources of a trauma center (38% sensitivity, 91% specificity, +LR 4.4; CI: 3.9 - 4.9). Criteria with a +LR ?5 were flail chest (9.0; CI: 4.1 - 19.4), paralysis (6.8; CI: 4.2 - 11.2), two or more long bone fractures (6.3; CI: 4.5 - 8.9), and amputation (6.1; CI: 1.5 - 24.4). Criteria with a +LR >2 and <5 were penetrating injury (4.8; CI: 4.2 - 5.6), and skull fracture (4.8; CI: 3.0 - 7.7). Only pelvic fracture (1.9; CI: 1.3 - 2.9) had a +LR less than 2. Conclusions The anatomic step of the Field Triage Guidelines as determined by EMS providers is a reasonable tool for determining trauma center need. Use of EMS perceived pelvic fracture as an indicator for trauma center need should be re-evaluated. PMID:23627418
Inhomogeneous Media 3D EM Modeling with Integral Equation Method
NASA Astrophysics Data System (ADS)
di, Q.; Wang, R.; An, Z.; Fu, C.; Xu, C.
2010-12-01
In general, only the half space of earth is considered in electromagnetic exploration. However, for the long bipole source, because the length is close to the height of ionosphere and also most offsets between source and receivers are equal or larger than the height of ionosphere, the effect of ionosphere on the electromagnetic (EM) field should be considered when observation is carried at a very far (about several thousands kilometers) location away from the source. At this point the problem becomes one which should contain ionosphere, atmosphere and earth that is “earth-ionosphere” case. There are a few of literatures to report the electromagnetic field results which is including ionosphere, atmosphere and earth media at the same time. We firstly calculate the electromagnetic fields with the traditional controlled source (CSEM) configuration using integral equation (IE) method for a three layers earth-ionosphere model. The modeling results agree well with the half space analytical results because the effect of ionosphere for this small scale bipole source can be ignorable. The comparison of small scale three layers earth-ionosphere modeling and half space analytical resolution shows that the IE method can be used to modeling the EM fields for long bipole large offset configuration. In order to discuss EM fields’ characteristics for complicate earth-ionosphere media excited by long bipole source in the far-field and wave-guide zones, we first modeled the decay characters of electromagnetic fields for three layers earth-ionosphere model. Because of the effect of ionosphere, the earth-ionosphere electromagnetic fields’ decay curves with given frequency show that there should be an extra wave guide zone for long bipole artificial source, and there are many different characters between this extra zone and far field zone. They are: 1) the amplitudes of EM fields decay much slower; 2) the polarization patterns change; 3) the positions better to measure Zxy and Zyx change; 4) there exits the polarization ellipse of electric and magnetic fields; 5) the long axis direction of the polarization ellipse in wave guide zone changes comparing to quasi static EM fields. In order to further model the EM fields for complex inhomogeneous media, we conducted the EM fields modeling for Biyang depressed basin of China. The bottom depth of the oil basin is about 8km. We added one ionosphere layer with thickness 100km and resistivity 104 Ohm-m and one atmosphere layer with thickness 100km and resistivity 1014 Ohm-m over the solid earth surface during the forward modeling. For easily to compare with the 2D seismic exploration result, we conducted the apparent resistivity modeling of equatorial array for the same survey line as seismic did for an 50km long bipole source with offset 400km and the same frequencies as that used for above three layers model. The modeling apparent resistivity pseudo-section has clearly shown the oil basin geology structure.
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM TECNOLOGIA AMBIENTAL E
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM TECNOLOGIA AMBIENTAL E RECURSOS HÃDRICOS EDITAL No. 1/2011 SELEÃ?Ã?O DE CANDIDATOS Ã?S VAGAS DO PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM TECNOLOGIA AMBIENTAL E Coordenador do Programa de PÃ³s-GraduaÃ§Ã£o em Tecnologia Ambiental e Recursos HÃdricos da Universidade de
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM PATOLOGIA MOLECULAR
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM PATOLOGIA MOLECULAR EDITAL PPGPM NÂº. 1/2013 SELEÃ?Ã?O DE CANDIDATOS Ã?S VAGAS DO PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM PATOLOGIA MOLECULAR PARA OS CURSOS DE Programa de PÃ³s-GraduaÃ§Ã£o em Patologia Molecular, no uso de suas atribuiÃ§Ãµes legais, torna pÃºblico e
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM BIOLOGIA MOLECULAR
Maier, Rudolf Richard
1 UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM BIOLOGIA MOLECULAR EDITAL No. 02/2010 SELEÃ?Ã?O DE CANDIDATOS Ã?S VAGAS DO PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM BIOLOGIA MOLECULAR PARA OS CURSOS DE Programa de PÃ³s GraduaÃ§Ã£o em Biologia Molecular, no uso de suas atribuiÃ§Ãµes legais, torna pÃºblico e
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM BIOLOGIA MOLECULAR
Lucero, Jorge Carlos
1 UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM BIOLOGIA MOLECULAR EDITAL No. 02/2011 SELEÃ?Ã?O DE CANDIDATOS Ã?S VAGAS DO PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM BIOLOGIA MOLECULAR PARA OS CURSOS DE Programa de PÃ³s GraduaÃ§Ã£o em Biologia Molecular, no uso de suas atribuiÃ§Ãµes legais, torna pÃºblico e
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM BIOLOGIA ANIMAL
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM BIOLOGIA ANIMAL EDITAL No. 01/2011 SELEÃ?Ã?O DE CANDIDATOS Ã?S VAGAS DO PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM BIOLOGIA ANIMAL PARA OS CURSOS DE MESTRADO ACADÃ?MICO E-GraduaÃ§Ã£o em Biologia Animal, no uso de suas atribuiÃ§Ãµes legais, torna pÃºblico e estabelece as normas do
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM BIOLOGIA ANIMAL EDITAL No. 02/2011
Lucero, Jorge Carlos
UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S- GRADUAÃ?Ã?O EM BIOLOGIA ANIMAL EDITAL No. 02/2011 SELEÃ?Ã?O DE CANDIDATOS Ã?S VAGAS DO PROGRAMA DE PÃ?S- GRADUAÃ?Ã?O EM BIOLOGIA ANIMAL PARA OS CURSOS DE MESTRADO PÃ³s-GraduaÃ§Ã£o em Biologia Animal, no uso de suas atribuiÃ§Ãµes legais, torna pÃºblico e estabelece
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM BIOLOGIA MICROBIANA
Lucero, Jorge Carlos
1 UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM BIOLOGIA MICROBIANA EDITAL No. 01/2011 SELEÃ?Ã?O DE CANDIDATOS Ã?S VAGAS DO PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM BIOLOGIA MICROBIANA PARA OS CURSOS DE Programa de PÃ³s GraduaÃ§Ã£o em Biologia Microbiana, no uso de suas atribuiÃ§Ãµes legais, torna pÃºblico e
PROGRAMA DE PS-GRADUAO EM FILOSOFIA DA UNIVERSIDADE DE BRASLIA
Lucero, Jorge Carlos
PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM FILOSOFIA DA UNIVERSIDADE DE BRASÃLIA EDITAL PPG EM FILOSOFIA NÂº 1/2011 SELEÃ?Ã?O DE CANDIDATOS AO PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM FILOSOFIA: CURSO DE MESTRADO ACADÃ?MICO, PARA Filosofia, no uso de suas atribuiÃ§Ãµes legais, torna pÃºblico e estabelece as normas do processo seletivo para
EM-Cube: an architecture for low-cost real-time volume rendering
Rtindy Osborne; Hanspeter Pfister; Hugh Lauer; TakaHide Ohkami; Neil McKenzie; Sarah Gibson; Wally Hiatt
1997-01-01
EM-Cube is a VLSI architecture for low-cost, high quality volume rendering at full video frame rates. Derived from the Cube-4 ar- chitecture developed at SUNY at Stony Brook, EM-Cube computes sample points and gradients on-the-fly to project 3-dimensional vol- ume data onto 2-dimensional images with realistic lighting and shading. A modest rendering system based on EM-Cube consists of a PCI
EMS-CO2 Welding: A New Approach to Improve Droplet Transfer Characteristics and Welding Formation
Jian Luo; Qian Luo; Xiangjie Wang; Xiaochuan Wang
2010-01-01
In this article, to improve the stability of droplet transfer and reduce the spatter of pure carbon dioxide gas shield welding (CO2 welding), we propose a new welding method called EMS-CO2 welding by applying an additional longitudinal electromagnetic field to a CO2 welding process (abbr. EMS-CO2 welding). The characteristics of droplet transfer, welding formation and microstructure between EMS-CO2 welding and
A Cramér-Rao Bound Characterization of the EM-Algorithm Mean Speed of Convergence
Cédric Herzet; Valéry Ramon; Alexandre Renaux; Luc Vandendorpe
2008-01-01
This paper deals with the mean speed of convergence of the expectation-maximization (EM) algorithm. We show that the asymptotic behavior (in terms of the number of observations) of the EM algorithm can be characterized as a function of the Cramer-Rao bounds (CRBs) associated to the so-called incomplete and complete data sets defined within the EM-algorithm framework. We particularize our result
1996-01-01
Hanford fiscal-year-to-date (FYTD) schedule performance remains unfavorable with a three percent schedule variance (-$36.6 million*) and a four percent cost variance (+$47.5 million). The schedule var-iance is attributed to EM-30, Office of Waste Management (-$21.6 million), EM-40, Office of Environmental Restoration (-$7.7 million), and EM-60, Office of Nuclear Material and Facility Stabilization (-$5.3 million). Sixty-one enforceable agreement milestones were scheduled
Detecção inesperada de efeitos de lentes fracas em grupos de galáxias pouco luminosos em raios-X
NASA Astrophysics Data System (ADS)
Carrasco, R.; Mendes de Oliveira, C.; Sodrã©, L., Jr.; Lima Neto, G. B.; Cypriano, E. S.; Lengruber, L. L.; Cuevas, H.; Ramirez, A.
2003-08-01
Obtivemos, como parte do programa de verificação científica do GMOS Sul, imagens profundas de três grupos de galáxias: G97 e G102 (z~0,4) e G124 (z = 0,17). Esses alvos foram selecionados a partir do catálogo de fontes extensas de Vikhlinin (1998), por terem luminosidades em raios X menores que 3´1043 ergs s-1, valor cerca de uma ou duas ordens de grandeza inferior ao de aglomerados de galáxias. O objetivo primário dessas observações é o estudo da evolução de galáxias em grupos. Grupos são ambientes menos densos que aglomerados, contêm a grande maioria das galáxias do Universo mas que, até o momento, foram estudados detalhadamente apenas no Universo local (z~0). Com esses dados efetuamos uma análise estatística da distorção na forma das galáxias de fundo (lentes gravitacionais fracas) como forma de inferir o conteúdo e a distribuição de massa nesses grupos apesar de que, em princípio, esse efeito não deveria ser detectado uma vez que os critérios de seleção adotados previlegiam sistemas de baixa massa. De fato, para G124 obtivemos apenas um limite superior para sua massa que é compatível com sua luminosidade em raios X. De modo contrário e surpreendente, os objetos G102 e G097, aparentam ter massas que resultariam em dispersões de velocidade maiores que 1000 km s-1, muito maiores do que se espera para grupos de galáxias. Com efeito, para G097 obtivemos, a partir de dados do satélite XMM, uma estimativa para a temperatura do gás intragrupo de kT = 2,6 keV, que é tipica de sistemas com dispersões de velocidade de ~ 600 km s-1, bem característica de grupos. Essas contradições aparentes entre lentes fracas e raios X podem ser explicadas de dois modos: i) a massa obtida por lentes estaria sobreestimada devido à superposição de estruturas massivas ao longo da linha de visada ou ii) a temperatura do gás do meio intra-grupo reflete o potencial gravitacional de estruturas menores que estariam se fundindo para formar uma estrutura maior.
NASA Astrophysics Data System (ADS)
Bagheri, Mehran
2010-07-01
The ground-state characteristics of spatially indirect excitons trapped in radially heteronanostructured type-II band alignment ZnSe/ZnTe nanotubes as functions of the magnetic field for nanotubes with a radial size both smaller and larger than the effective Bohr radius are theoretically investigated. In the former case, dominated by the net kinetic energy of the electron and hole, the magnetic field modifies the exciton spectrum through the well-known Zeeman splitting, intra-orbital-state Aharonov-Bohm oscillations and inter-orbital-state crossovers occurring in very strong magnetic field strengths. However, in the latter case, dominated by the electron-hole Coulomb attraction, the magnetic field adjusts the exciton lines only by means of the Zeeman splitting and inter-orbital-state transitions happening in typical magnetic fields. As a result, the angular momentum transitions occurr at lower magnetic fields when the radial size of the nanotube is increased. Most importantly, another consequence is the substantially unusual exciton oscillator strength in such heteronanostructures. It is shown that when the exciton is optically active, due to the full cylindrical symmetry of the problem, the exciton oscillator strength shows undamped oscillations. This effect is associated with the periodic redistribution of the exciton density as the magnetic field is varied. Also, the magnitude of the magnetically induced excitonic persistent current is decreased with increasing radial size of the nanotube. This study may provide a platform to investigate new photonic quantum interference as well as polarization-sensitive photodetector and photovoltaic devices based on the Aharonov-Bohm effect.
Magneto-optical studies of quantum dots
NASA Astrophysics Data System (ADS)
Russ, Andreas Hans
Significant effort in condensed matter physics has recently been devoted to the field of "spintronics" which seeks to utilize the spin degree of freedom of electrons. Unlike conventional electronics that rely on the electron charge, devices exploiting their spin have the potential to yield new and novel technological applications, including spin transistors, spin filters, and spin-based memory devices. Any such application has the following essential requirements: 1) Efficient electrical injection of spin-polarized carriers; 2) Long spin lifetimes; 3) Ability to control and manipulate electron spins; 4) Effective detection of spin-polarized carriers. Recent work has demonstrated efficient electrical injection from ferromagnetic contacts such as Fe and MnAs, utilizing a spin-Light Emitting Diode (spin-LED) as a method of detection. Semiconductor quantum dots (QDs) are attractive candidates for satisfying requirements 2 and 3 as their zero dimensionality significantly suppresses many spin-flip mechanisms leading to long spin coherence times, as well as enabling the localization and manipulation of a controlled number of electrons and holes. This thesis is composed of three projects that are all based on the optical properties of QD structures including: I) Intershell exchange between spin-polarized electrons occupying adjacent shells in InAs QDs; II) Spin-polarized multiexitons in InAs QDs in the presence of spin-orbit interactions; III) The optical Aharonov-Bohm effect in AlxGa1-xAs/AlyGa1-yAs quantum wells (QWs). In the following we introduce some of the basic optical properties of quantum dots, describe the main tool (spin-LED) employed in this thesis to inject and detect spins in these QDs, and conclude with the optical Aharonov-Bohm effect (OAB) in type-II QDs.
Phase diagram of the Bose-Hubbard model with T{sub 3} symmetry
Rizzi, Matteo; Fazio, Rosario [NEST CNR-INFM and Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Cataudella, Vittorio [COHERENTIA CNR-INFM and Dipartimento di Fisica, Universita Federico II, 80126 Naples (Italy)
2006-04-01
We study the quantum phase transition between the insulating and the globally coherent superfluid phases in the Bose-Hubbard model with T{sub 3} structure, the 'dice lattice'. Even in the absence of any frustration the superfluid phase is characterized by modulation of the order parameter on the different sublattices of the T{sub 3} structure. The zero-temperature critical point as a function of magnetic field shows the characteristic 'butterfly' form. At full frustration the superfluid region is strongly suppressed. In addition, due to the existence of the Aharonov-Bohm cages at f=1/2, we find some evidence for the existence of an intermediate insulating phase characterized by a zero superfluid stiffness but finite compressibility. In this intermediate phase bosons are localized due to the external frustration and the topology of the T{sub 3} lattice. We name this new phase the Aharonov-Bohm insulator. In the presence of charge frustration the phase diagram acquires the typical lobe structure. The form and hierarchy of the Mott insulating states with fractional fillings are dictated by the particular topology of the T{sub 3} lattice. The results presented were obtained by a variety of analytical methods: mean-field and variational techniques to approach the phase boundary from the superconducting side and a strongly coupled expansion appropriate for the Mott insulating region. In addition we performed quantum Monte Carlo simulations of the corresponding (2+1)-dimensional XY model to corroborate the analytical calculations with a more accurate quantitative analysis. We finally discuss experimental realization of the T{sub 3} lattice both with optical lattices and with Josephson junction arrays.
Covariance Matrix Estimation for the Cryo-EM Heterogeneity Problem*
Katsevich, E.; Katsevich, A.; Singer, A.
2015-01-01
In cryo-electron microscopy (cryo-EM), a microscope generates a top view of a sample of randomly oriented copies of a molecule. The problem of single particle reconstruction (SPR) from cryo-EM is to use the resulting set of noisy two-dimensional projection images taken at unknown directions to reconstruct the three-dimensional (3D) structure of the molecule. In some situations, the molecule under examination exhibits structural variability, which poses a fundamental challenge in SPR. The heterogeneity problem is the task of mapping the space of conformational states of a molecule. It has been previously suggested that the leading eigenvectors of the covariance matrix of the 3D molecules can be used to solve the heterogeneity problem. Estimating the covariance matrix is challenging, since only projections of the molecules are observed, but not the molecules themselves. In this paper, we formulate a general problem of covariance estimation from noisy projections of samples. This problem has intimate connections with matrix completion problems and high-dimensional principal component analysis. We propose an estimator and prove its consistency. When there are finitely many heterogeneity classes, the spectrum of the estimated covariance matrix reveals the number of classes. The estimator can be found as the solution to a certain linear system. In the cryo-EM case, the linear operator to be inverted, which we term the projection covariance transform, is an important object in covariance estimation for tomographic problems involving structural variation. Inverting it involves applying a filter akin to the ramp filter in tomography. We design a basis in which this linear operator is sparse and thus can be tractably inverted despite its large size. We demonstrate via numerical experiments on synthetic datasets the robustness of our algorithm to high levels of noise. PMID:25699132
EM-21 Retrieval Knowledge Center: Waste Retrieval Challenges
Fellinger, Andrew P.; Rinker, Michael W.; Berglin, Eric J.; Minichan, Richard L.; Poirier, Micheal R.; Gauglitz, Phillip A.; Martin, Bruce A.; Hatchell, Brian K.; Saldivar, Eloy; Mullen, O Dennis; Chapman, Noel F.; Wells, Beric E.; Gibbons, Peter W.
2009-04-10
EM-21 is the Waste Processing Division of the Office of Engineering and Technology, within the U.S. Department of Energy’s (DOE) Office of Environmental Management (EM). In August of 2008, EM-21 began an initiative to develop a Retrieval Knowledge Center (RKC) to provide the DOE, high level waste retrieval operators, and technology developers with centralized and focused location to share knowledge and expertise that will be used to address retrieval challenges across the DOE complex. The RKC is also designed to facilitate information sharing across the DOE Waste Site Complex through workshops, and a searchable database of waste retrieval technology information. The database may be used to research effective technology approaches for specific retrieval tasks and to take advantage of the lessons learned from previous operations. It is also expected to be effective for remaining current with state-of-the-art of retrieval technologies and ongoing development within the DOE Complex. To encourage collaboration of DOE sites with waste retrieval issues, the RKC team is co-led by the Savannah River National Laboratory (SRNL) and the Pacific Northwest National Laboratory (PNNL). Two RKC workshops were held in the Fall of 2008. The purpose of these workshops was to define top level waste retrieval functional areas, exchange lessons learned, and develop a path forward to support a strategic business plan focused on technology needs for retrieval. The primary participants involved in these workshops included retrieval personnel and laboratory staff that are associated with Hanford and Savannah River Sites since the majority of remaining DOE waste tanks are located at these sites. This report summarizes and documents the results of the initial RKC workshops. Technology challenges identified from these workshops and presented here are expected to be a key component to defining future RKC-directed tasks designed to facilitate tank waste retrieval solutions.
A compulsator driven rapid-fire EM-gun
Pratap, S.B.; Bird, W.L.
1984-03-01
A compulsator-driven railgun is an attractive alternative to the homopolar generator-inductor-switch configuration, especially for repetitive duty. A conceptual design of a rapid-fire EM-gun system is presented. The generator is sized to accelerate a 0.08-kg projectile to 2 to 3 km/s at a 60 pulse-per-second repetition rate. Initial design parameters are discussed, and example current and velocity waveforms are given. The generator is discharged at the proper phase angle to provide a current zero just as the projectile exits the muzzle of the railgun.
A compulsator driven rapid-fire EM gun
NASA Astrophysics Data System (ADS)
Pratap, S. B.; Bird, W. L.; Godwin, G. L.; Weldon, W. F.
1984-03-01
A computator-driven railgun is an attractive alternative to the homopolar generator-inductor-switch configuration, especially for repetitive duty. A conceptual design of rapid-fire EM-gun system is presented. The generator is sized to accelerate a 0.08-kg projectile to 2 to 3 km/s at a 60 pulse-per-second repetition rate. Initial design parameters are discussed, and example current and velocity waveforms are given. The generator is discharged at the proper phase angle to provide a current zero just as the projectile exits the muzzle of the railgun.
Caucasicosides E-M, furostanol glycosides from Helleborus caucasicus.
Muzashvili, Tamar; Perrone, Angela; Napolitano, Assunta; Kemertelidze, Ether; Pizza, Cosimo; Piacente, Sonia
2011-12-01
Nine furostanol glycosides, namely caucasicosides E-M, were isolated from the MeOH extract of the leaves of Helleborus caucasicus, along with 11 known compounds including nine furostanol glycosides, a bufadienolide and an ecdysteroid. Their structures were established by the extensive use of 1D and 2D NMR experiments along with ESIMS(n) analyses. The steroidal composition of leaves of H. caucasicus shows as particular feature the occurrence of steroidal compounds belonging to the 5? series, unusual for Helleborus species, and in particular, caucasicosides F-H are based on a 5?-polyhydroxylated steroidal aglycon never reported before. PMID:21893324