22,098 research outputs found
Bulk viscous Zel'dovich fluid model and it's asymptotic behavior
In this paper we have considered a flat FLRW universe with bulk viscous
Zel'dovich as the cosmic component. Being considered the bulk viscosity as per
the Eckart formalism, we have analyzed the evolution of the Hubble parameter
and constrained the model with the Type Ia Supernovae data thus extracting the
constant bulk viscous parameter and present Hubble parameter. Further we have
analyzed the scale factor, equation of state and deceleration parameter. The
model predicts the late time acceleration and is also compatible with the age
of the universe as given by the oldest globular clusters. We have also studied
the phase-space behavior of the model and found that a universe dominated by
bulk viscous Zel'dovich fluid is stable. But on the inclusion of radiation
component in addition to the Zel'dovich fluid, makes the model unstable. Hence,
even though the bulk viscous Zel'dovich fluid dominated universe is a feasible
one, the model as such failed to predict a prior radiation dominated phase.Comment: 14 pages, eight figure
Improving basic life support training for medical students
Mariam Lami, Pooja Nair, Karishma GadhviFaculty of Medicine, Imperial College, London, London, UKAbstract: Questions have been raised about basic life support (BLS) training in medical education. This article addresses the research evidence behind why BLS training is inadequate and suggests recommendations for improving BLS training for medical students.Keywords: medical education, basic life suppor
A differential memristive synapse circuit for on-line learning in neuromorphic computing systems
Spike-based learning with memristive devices in neuromorphic computing
architectures typically uses learning circuits that require overlapping pulses
from pre- and post-synaptic nodes. This imposes severe constraints on the
length of the pulses transmitted in the network, and on the network's
throughput. Furthermore, most of these circuits do not decouple the currents
flowing through memristive devices from the one stimulating the target neuron.
This can be a problem when using devices with high conductance values, because
of the resulting large currents. In this paper we propose a novel circuit that
decouples the current produced by the memristive device from the one used to
stimulate the post-synaptic neuron, by using a novel differential scheme based
on the Gilbert normalizer circuit. We show how this circuit is useful for
reducing the effect of variability in the memristive devices, and how it is
ideally suited for spike-based learning mechanisms that do not require
overlapping pre- and post-synaptic pulses. We demonstrate the features of the
proposed synapse circuit with SPICE simulations, and validate its learning
properties with high-level behavioral network simulations which use a
stochastic gradient descent learning rule in two classification tasks.Comment: 18 Pages main text, 9 pages of supplementary text, 19 figures.
Patente
A specialized inventory problem in banks: optimizing retail sweeps
Deposits held at Federal Reserve Banks are an essential input to the business activity of most depository institutions in the United States. Managing these deposits is an important and complex inventory problem, for two reasons. First, Federal Reserve regulations require that depository institutions hold certain amounts of such deposits at the Federal Reserve Banks to satisfy statutory reserve requirements against customers* transaction accounts (demand deposits and other checkable deposits). Second, some inventory of such deposits is essential for banks to operate one of their core lines of business: furnishing payment services to households and firms. including wire transfers, ACH payments, and check clearing settlement. Because the Federal Reserve does not pay interest on such deposits used to satisfy statutory reserve requirements, banks seek to minimize their inventory of such deposits. In 1994, the banking industry introduced a new inventory management tool for such deposits, the retail deposit sweep program, which avoids the statutory requirement by reclassifying transaction deposits as savings deposits. In this analysis, we examine two algorithms for operating such sweeps programs within the limits of Federal Reserve regulations.Banks and banking ; Retail trade
Plasmon interactions in the quark-gluon plasma
Yang-Mills theory at finite temperature is rewritten as a theory of plasmons
which provides a Hamiltonian framework for perturbation theory with resummation
of hard thermal loops.Comment: 12 pages, LaTeX, minor typos corrected, discussion adde
Large Magnetoresistance and Jahn Teller effect in SrFeCoO
Neutron diffraction measurement on the spin glass double perovskite
SrFeCoO reveals site disorder as well as Co intermediate spin
state. In addition, multiple valence states of Fe and Co are confirmed through
M\"{o}ssbauer and X-ray photoelectron spectroscopy. The structural disorder and
multiple valence lead to competing ferromagnetic and antiferromagnetic
interactions and subsequently to a spin glass state, which is reflected in the
form of an additional -linear contribution at low temperatures in specific
heat. A clear evidence of Jahn-Teller distortion at the Co-O complex
is observed and incorporating the physics of Jahn-Teller effect, the presence
of localized magnetic moment is shown. A large, negative and anomalous
magnetoresistance of 63% at 14K in 12T applied field is observed for
SrFeCoO. The observed magnetoresistance could be explained by applying
a semi-empirical fit consisting of a negative and a positive contribution and
show that the negative magnetoresistance is due to spin scattering of carriers
by localized magnetic moments in the spin glass phase
Spin Freezing in the Spin Liquid Compound FeAl2O4
Spin freezing in the -site spinel FeAlO which is a spin liquid
candidate is studied using remnant magnetization and nonlinear magnetic
susceptibility and isofield cooling and heating protocols. The remnant
magnetization behavior of FeAlO differs significantly from that of a
canonical spin glass which is also supported by analysis of the nonlinear
magnetic susceptibility term . Through the power-law analysis of
, a spin-freezing temperature, = 11.40.9~K and critical
exponent, = 1.480.59 are obtained. Cole-Cole analysis of magnetic
susceptibility shows the presence of broad spin relaxation times in
FeAlO, however, the irreversible dc susceptibility plot discourages an
interpretation based on conventional spin glass features. The magnetization
measured using the cooling-and-heating-in-unequal-fields protocol brings more
insight to the magnetic nature of this frustrated magnet and reveals
unconventional glassy behaviour. Combining our results, we arrive at the
conclusion that the present sample of FeAlO consists of a majority spin
liquid phase with "glassy" regions embedded.Comment: 5 pages, 6 figs, 2-column, Accepted to Phys. Rev.
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