62,004 research outputs found
Teleporting bipartite entanglement using maximally entangled mixed channels
The ability to teleport entanglement through maximally entangled mixed states
as defined by concurrence and linear entropy is studied. We show how the
teleported entanglement depends on the quality of the quantum channel used, as
defined through its entanglement and mixedness, as well as the form of the
target state to be teleported. We present new results based on the fidelity of
the teleported state as well as an experimental set-up that is immediately
implementable with currently available technology.Comment: 8 pages, 7 figures, RevTeX4, Accepted for publication in the IJQI
special issue on Distributed Quantum Information Processin
Does the Sun shrink with increasing magnetic activity?
It has been demonstrated that frequencies of f-modes can be used to estimate
the solar radius to a good accuracy. These frequencies have been used to study
temporal variations in the solar radius with conflicting results. The variation
in f-mode frequencies is more complicated than what is assumed in these
studies. If a careful analysis is performed then it turns out that there is no
evidence for any variation in the solar radius.Comment: To appear in Astrophys.
The development of a prototype intelligent user interface subsystem for NASA's scientific database systems
The National Space Science Data Center (NSSDC) has initiated an Intelligent Data Management (IDM) research effort which has as one of its components the development of an Intelligent User Interface (IUI).The intent of the latter is to develop a friendly and intelligent user interface service that is based on expert systems and natural language processing technologies. The purpose is to support the large number of potential scientific and engineering users presently having need of space and land related research and technical data but who have little or no experience in query languages or understanding of the information content or architecture of the databases involved. This technical memorandum presents prototype Intelligent User Interface Subsystem (IUIS) using the Crustal Dynamics Project Database as a test bed for the implementation of the CRUDDES (Crustal Dynamics Expert System). The knowledge base has more than 200 rules and represents a single application view and the architectural view. Operational performance using CRUDDES has allowed nondatabase users to obtain useful information from the database previously accessible only to an expert database user or the database designer
Experimental study of wing leading-edge devices for improved maneuver performance of a supercritical maneuvering fighter configuration
Wind tunnel tests were conducted to examine the use of wing leading-edge devices for improved subsonic and transonic maneuver performance. These devices were tested on a fighter configuration which utilized supercritical-wing technology. The configuration had a leading-edge sweep of 45 deg and an aspect ratio of 3.28. The tests were conducted at Mach numbers of 0.60 and 0.85 with angles of attack from -0.5 deg to 22 deg. At both Mach numbers, sharp leading-edge flaps produced vortices which greatly altered the flow pattern on the wing and resulted in substantial reductions in drag at high lift. Underwing or pylon-type vortex generators also reduced drag at high lift. The vortex generators worked better at a Mach number of 0.60. The vortex generators gave the best overall results with zero toe-in angle and when mounted on either the outboard part of the wing or at both an outboard location and halfway out the semispan. Both the flaps and the vortex generators had a minor effect on the pitching moment. Fluorescent minitufts were found to be useful for flow visualization at transonic maneuver conditions
Protecting the Primordial Baryon Asymmetry From Erasure by Sphalerons
If the baryon asymmetry of the universe was created at the GUT scale,
sphalerons together with exotic sources of -violation could have erased
it, unless the latter satisfy stringent bounds. We elaborate on how the small
Yukawa coupling of the electron drastically weakens previous estimates of these
bounds.Comment: 41 pp., 4 latex figures included and 3 uuencoded or postscript
figures available by request, UMN-TH-1213-9
Tunnel magnetoresistance and interfacial electronic state
We study the relation between tunnel magnetoresistance (TMR) and interfacial
electronic states modified by magnetic impurities introduced at the interface
of the ferromagnetic tunnel junctions, by making use of the periodic Anderson
model and the linear response theory. It is indicated that the TMR ratio is
strongly reduced depending on the position of the -levels of impurities,
based on reduction in the spin-dependent -electron tunneling in the majority
spin state. The results are compared with experimental results for Cr-dusted
ferromagnetic tunnel junctions, and also with results for metallic multilayers
for which similar reduction in giant magnetoresistance has been reported.Comment: 5 pages, 4 figures, 2 column revtex4 format, ICMFS 2002 (Kyoto
Scaling and data collapse for the mean exit time of asset prices
We study theoretical and empirical aspects of the mean exit time of financial
time series. The theoretical modeling is done within the framework of
continuous time random walk. We empirically verify that the mean exit time
follows a quadratic scaling law and it has associated a pre-factor which is
specific to the analyzed stock. We perform a series of statistical tests to
determine which kind of correlation are responsible for this specificity. The
main contribution is associated with the autocorrelation property of stock
returns. We introduce and solve analytically both a two-state and a three-state
Markov chain models. The analytical results obtained with the two-state Markov
chain model allows us to obtain a data collapse of the 20 measured MET profiles
in a single master curve.Comment: REVTeX 4, 11 pages, 8 figures, 1 table, submitted for publicatio
Ethics, Genetic Technologies and Equine Sports: The Prospect of Regulation of a Modified Therapeutic Use Exemption Policy
This article critically reviews the current availability and selected use of genetic technologies for horses, before undertaking an ethical evaluation of current practice and regulatory positions in comparative relation to debates surrounding genetic testing, pre-implantation genetic testing and gene editing in humans. We argue that genetic testing for hereditary disorders is not only justified but should be encouraged on welfare grounds and that genetic testing for performance traits is ethically permissible based on a restricted imperative to genetically edit horses and horse embryos to reduce genetic predisposition to disease and injury. Given the current state of the science, where the effects of gene editing on health and welfare are currently undetermined, space is created for an analytical distinction between equine gene editing for ‘treatment’ and for ‘enhancement’. Gene editing is only justified for purposes of correcting/preventing disease and injury. Current regulation is challenged by apparently conflicting welfare-based ethical imperatives with respect to welfare-based gene editing. We propose modifications to the blanket bans on gene editing with a case-by-case assessment of applications to permit gene editing, based on best welfare interests underwritten by the aim of facilitating fair sport that adapt WADAs International Standard for Therapeutic Use Exemptions, adding an important reporting element. We reject the use of gene editing to obtain currently prohibited competitive advantages. In order to safeguard the welfare of human and equine athletes, we argue that regulatory institutions should urgently collaborate to develop cross-sport international regulations for the use of gene editing, including obligatory reporting of data about the health and welfare of genetically edited horses
BCS-BEC Crossover in Atomic Fermi Gases with a Narrow Resonance
We determine the effects on the BCS-BEC crossover of the energy dependence of
the effective two-body interaction, which at low energies is determined by the
effective range. To describe interactions with an effective range of either
sign, we consider a single-channel model with a two-body interaction having an
attractive square well and a repulsive square barrier. We investigate the
two-body scattering properties of the model, and then solve the Eagles-Leggett
equations for the zero temperature crossover, determining the momentum
dependent gap and the chemical potential self-consistently. From this we
investigate the dependence of the crossover on the effective range of the
interaction.Comment: 12 pages, 14 figure
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