244 research outputs found
A Framework for Local Mechanical Characterization of Atherosclerotic Plaques: Combination of Ultrasound Displacement Imaging and Inverse Finite Element Analysis
Biomechanical models have the potential to predict plaque rupture. For reliable models, correct material properties of plaque components are a prerequisite. This study presents a new technique, where high resolution ultrasound displacement imaging and inverse finite element (FE) modeling is combined, to estimate material properties of plaque components. Iliac arteries with plaques were excised from 6 atherosclerotic pigs and subjected to an inflation test with pressures ranging from 10 to 120 mmHg. The arteries were imaged with high frequ
Current induced switching of magnetic domains to a perpendicular configuration
In a ferromagnet--normal-metal--ferromagnet trilayer, a current flowing
perpendicularly to the layers creates a torque on the magnetic moments of the
ferromagnets. When one of the contacts is superconducting, the torque not only
favors parallel or antiparallel alignment of the magnetic moments, as is the
case for two normal contacts, but can also favor a configuration where the two
moments are perpendicular. In addition, whereas the conductance for parallel
and antiparallel magnetic moments is the same, signalling the absence of giant
magnetoresistance in the usual sense, the conductance is greater in the
perpendicular configuration. Thus, a negative magnetoconductance is predicted,
in contrast with the usual giant magnetoresistance.Comment: 4 pages, 3 figures, major rewriting of the technical par
Spontaneous Spin Polarized Currents in Superconductor-Ferromagnetic Metal Heterostructures
We study a simple microscopic model for thin, ferromagnetic, metallic layers
on semi-infinite bulk superconductor. We find that for certain values of the
exchange spliting, on the ferromagnetic side, the ground states of such
structures feature spontaneously induced spin polarized currents. Using a
mean-field theory, which is selfconsistent with respect to the pairing
amplitude , spin polarization and the spontaneous current
, we show that not only there are Andreev bound states in the
ferromagnet but when their energies are near zero they support
spontaneous currents parallel to the ferromagnetic-superconducting interface.
Moreover, we demonstrate that the spin-polarization of these currents depends
sensitively on the band filling.Comment: 4 pages, 5 Postscript figures (included
Tachyonic Inflation in a Warped String Background
We analyze observational constraints on the parameter space of tachyonic
inflation with a Gaussian potential and discuss some predictions of this
scenario. As was shown by Kofman and Linde, it is extremely problematic to
achieve the required range of parameters in conventional string
compactifications. We investigate if the situation can be improved in more
general compactifications with a warped metric and varying dilaton. The
simplest examples are the warped throat geometries that arise in the vicinity
of of a large number of space-filling D-branes. We find that the parameter
range for inflation can be accommodated in the background of D6-branes wrapping
a three-cycle in type IIA. We comment on the requirements that have to be met
in order to realize this scenario in an explicit string compactification.Comment: Latex, JHEP class, 20 pages, 4 figures. v2: references added, small
error in section 7 corrected, published versio
Quasiclassical description of transport through superconducting contacts
We present a theoretical study of transport properties through
superconducting contacts based on a new formulation of boundary conditions that
mimics interfaces for the quasiclassical theory of superconductivity. These
boundary conditions are based on a description of an interface in terms of a
simple Hamiltonian. We show how this Hamiltonian description is incorporated
into quasiclassical theory via a T-matrix equation by integrating out
irrelevant energy scales right at the onset. The resulting boundary conditions
reproduce results obtained by conventional quasiclassical boundary conditions,
or by boundary conditions based on the scattering approach. This formalism is
well suited for the analysis of magnetically active interfaces as well as for
calculating time-dependent properties such as the current-voltage
characteristics or as current fluctuations in junctions with arbitrary
transmission and bias voltage. This approach is illustrated with the
calculation of Josephson currents through a variety of superconducting
junctions ranging from conventional to d-wave superconductors, and to the
analysis of supercurrent through a ferromagnetic nanoparticle. The calculation
of the current-voltage characteristics and of noise is applied to the case of a
contact between two d-wave superconductors. In particular, we discuss the use
of shot noise for the measurement of charge transferred in a multiple Andreev
reflection in d-wave superconductors
Applications of Thirring Model to Inhomogenous Rolling Tachyon and Dissipative Quantum Mechanics
We study the rolling tachyon and the dissipative quantum mechanics using the
Thirring model with a boundary mass. We construct a boundary state for the
dissipative quantum system in one dimension, which describes the system at the
off-critical points as well as at the critical point. Then we extend the
Thirring model with a boundary mass in order to depict the time evolution of an
unstable D-branes with one direction wrapped on a circle of radius , which
is termed the inhomogeneous rolling tachyon. The analysis based on the Thirring
model shows that the time dependent evolution of the inhomogeneous tachyon is
possible only when .Comment: 19 pages, 2 figures, This work supersedes the previous one,
arXiv:0705.3930 [hep-th
Pain and quality of life among older people with rheumatoid arthritis and/or osteoarthritis: a literature review
Cosmological implications of interacting polytropic gas dark energy model in non-flat universe
The polytropic gas model is investigated as an interacting dark energy
scenario. The cosmological implications of the model including the evolution of
EoS parameter , energy density and deceleration
parameter are investigated. We show that, depending on the parameter of
model, the interacting polytropic gas can behave as a quintessence or phantom
dark energy. In this model, the phantom divide is crossed from below to up. The
evolution of in the context of polytropic gas dark energy model represents
the decelerated phase at the early time and accelerated phase later. The
singularity of this model is also discussed. Eventually, we establish the
correspondence between interacting polytropic gas model with tachyon, K-essence
and dilaton scalar fields. The potential and the dynamics of these scalar field
models are reconstructed according to the evolution of interacting polytropic
gas.Comment: 19 pages, 3 figures, accepted by ijt
Polytropic gas scalar field models of dark energy
In this work we investigate the polytropic gas dark energy model in the non
flat universe. We first calculate the evolution of EoS parameter of the model
as well as the cosmological evolution of Hubble parameter in the context of
polytropic gas dark energy model. Then we reconstruct the dynamics and the
potential of the tachyon and K-essence scalar field models according to the
evolutionary behavior of polytropic gas model.Comment: 18 pages, 6 Figure
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