353 research outputs found
Exactly solvable path integral for open cavities in terms of quasinormal modes
We evaluate the finite-temperature Euclidean phase-space path integral for
the generating functional of a scalar field inside a leaky cavity. Provided the
source is confined to the cavity, one can first of all integrate out the fields
on the outside to obtain an effective action for the cavity alone.
Subsequently, one uses an expansion of the cavity field in terms of its
quasinormal modes (QNMs)-the exact, exponentially damped eigenstates of the
classical evolution operator, which previously have been shown to be complete
for a large class of models. Dissipation causes the effective cavity action to
be nondiagonal in the QNM basis. The inversion of this action matrix inherent
in the Gaussian path integral to obtain the generating functional is therefore
nontrivial, but can be accomplished by invoking a novel QNM sum rule. The
results are consistent with those obtained previously using canonical
quantization.Comment: REVTeX, 26 pages, submitted to Phys. Rev.
Fecal Viral Load and Norovirus-associated Gastroenteritis
We report the median cDNA viral load of norovirus genogroup II is >100-fold higher than that of genogroup I in the fecal specimens of patients with norovirus-associated gastroenteritis. We speculate that increased cDNA viral load accounts for the higher transmissibility of genogroup II strains through the fecal-oral route
Three dimensional resonating valence bond liquids and their excitations
We show that there are two types of RVB liquid phases present in
three-dimensional quantum dimer models, corresponding to the deconfining phases
of U(1) and Z_2 gauge theories in d=3+1. The former is found on the bipartite
cubic lattice and is the generalization of the critical point in the square
lattice quantum dimer model found originally by Rokhsar and Kivelson. The
latter exists on the non-bipartite face-centred cubic lattice and generalizes
the RVB phase found earlier by us on the triangular lattice. We discuss the
excitation spectrum and the nature of the ordering in both cases. Both phases
exhibit gapped spinons. In the U(1) case we find a collective, linearly
dispersing, transverse excitation, which is the photon of the low energy
Maxwell Lagrangian and we identify the ordering as quantum order in Wen's
sense. In the Z_2 case all collective excitations are gapped and, as in d=2,
the low energy description of this topologically ordered state is the purely
topological BF action. As a byproduct of this analysis, we unearth a further
gapless excitation, the pi0n, in the square lattice quantum dimer model at its
critical point.Comment: 9 pages, 2 figure
How parents perceive and feel about participation in community activities: The comparison between parents of preschoolers with and without autism spectrum disorders
The present study compared how parents of preschoolers with and without Autism Spectrum Disorders (ASD) perceived and felt about participation in community activities. A questionnaire survey was conducted with 380 Hong Kong parents of preschoolers with ASD and 214 Hong Kong parents of preschoolers without ASD. The two groups were not different in their willingness and frequency of participation in community activities. However, the psychological processes underneath their willingness were very different. Among the parents of preschoolers with ASD, their willingness was associated with how they perceived the difficulty and importance of the participation and what emotions they experienced during the activities. This pattern of association was not evident among the parents of preschoolers without ASD. Copyright © The Author(s), 2010.published_or_final_versio
Biochemical parameters of silver catfish (Rhamdia quelen) after transport with eugenol or essential oil of Lippia alba added to the water
The transport of live fish is a routine practice in aquaculture and constitutes a considerable source of stress to the animals. The addition of anesthetic to the water used for fish transport can prevent or mitigate the deleterious effects of transport stress. This study investigated the effects of the addition of eugenol (EUG) (1.5 or 3.0 mu L L-1) and essential oil of Lippia alba (EOL) (10 or 20 mu L L-1) on metabolic parameters (glycogen, lactate and total protein levels) in liver and muscle, acetylcholinesterase activity (AChE) in muscle and brain, and the levels of protein carbonyl (PC), thiobarbituric acid reactive substances (TBARS) and nonprotein thiol groups (NPSH) and activity of glutathione-S-transferase in the liver of silver catfish (Rhamdia quelen; Quoy and Gaimard, 1824) transported for four hours in plastic bags (loading density of 169.2 g L-1). The addition of various concentrations of EUG (1.5 or 3.0 mu L L-1) and EOL (10 or 20 mu L L-1) to the transport water is advisable for the transportation of silver catfish, since both concentrations of these substances increased the levels of NPSH antioxidant and decreased the TBARS levels in the liver. In addition, the lower liver levels of glycogen and lactate in these groups and lower AChE activity in the brain (EOL 10 or 20 mu L L-1) compared to the control group indicate that the energetic metabolism and neurotransmission were lower after administration of anesthetics, contributing to the maintenance of homeostasis and sedation status.Fundacao de Amparo a Pesquisa do Estado do Rio Grande do Sul (FAPERGS/PRONEX) [10/0016-8]; Conselho Nacional de Pesquisa e Desenvolvimento Cientifico (CNPq) [470964/2009-0]; Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES); CNPqinfo:eu-repo/semantics/publishedVersio
Specific Heat of Liquid Helium in Zero Gravity very near the Lambda Point
We report the details and revised analysis of an experiment to measure the
specific heat of helium with subnanokelvin temperature resolution near the
lambda point. The measurements were made at the vapor pressure spanning the
region from 22 mK below the superfluid transition to 4 uK above. The experiment
was performed in earth orbit to reduce the rounding of the transition caused by
gravitationally induced pressure gradients on earth. Specific heat measurements
were made deep in the asymptotic region to within 2 nK of the transition. No
evidence of rounding was found to this resolution. The optimum value of the
critical exponent describing the specific heat singularity was found to be a =
-0.0127+ - 0.0003. This is bracketed by two recent estimates based on
renormalization group techniques, but is slightly outside the range of the
error of the most recent result. The ratio of the coefficients of the leading
order singularity on the two sides of the transition is A+/A- =1.053+ - 0.002,
which agrees well with a recent estimate. By combining the specific heat and
superfluid density exponents a test of the Josephson scaling relation can be
made. Excellent agreement is found based on high precision measurements of the
superfluid density made elsewhere. These results represent the most precise
tests of theoretical predictions for critical phenomena to date.Comment: 27 Pages, 20 Figure
Quasinormal modes of Schwarzschild black holes in four and higher dimensions
We make a thorough investigation of the asymptotic quasinormal modes of the
four and five-dimensional Schwarzschild black hole for scalar, electromagnetic
and gravitational perturbations. Our numerical results give full support to all
the analytical predictions by Motl and Neitzke, for the leading term. We also
compute the first order corrections analytically, by extending to higher
dimensions, previous work of Musiri and Siopsis, and find excellent agreement
with the numerical results. For generic spacetime dimension number D the
first-order corrections go as . This means that
there is a more rapid convergence to the asymptotic value for the five
dimensional case than for the four dimensional case, as we also show
numerically.Comment: 12 pages, 5 figures, RevTeX4. v2. Typos corrected, references adde
Encoding and retrieval in a CA1 microcircuit model of the hippocampus
Recent years have witnessed a dramatic accumulation of
knowledge about the morphological, physiological and molecular characteristics,
as well as connectivity and synaptic properties of neurons in
the mammalian hippocampus. Despite these advances, very little insight
has been gained into the computational function of the different neuronal
classes; in particular, the role of the various inhibitory interneurons in
encoding and retrieval of information remains elusive. Mathematical and
computational models of microcircuits play an instrumental role in exploring
microcircuit functions and facilitate the dissection of operations
performed by diverse inhibitory interneurons. A model of the CA1 microcircuitry
is presented using biophysical representations of its major cell
types: pyramidal, basket, axo-axonic, bistratified and oriens lacunosummoleculare
cells. Computer simulations explore the biophysical mechanisms
by which encoding and retrieval of spatio-temporal input patterns
are achieved by the CA1 microcircuitry. The model proposes functional
roles for the different classes of inhibitory interneurons in the encoding
and retrieval cycles
Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS
We present the results of a search for new, heavy particles that decay at a
significant distance from their production point into a final state containing
charged hadrons in association with a high-momentum muon. The search is
conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV
and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS
detector operating at the Large Hadron Collider. Production of such particles
is expected in various scenarios of physics beyond the standard model. We
observe no signal and place limits on the production cross-section of
supersymmetric particles in an R-parity-violating scenario as a function of the
neutralino lifetime. Limits are presented for different squark and neutralino
masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final
version to appear in Physics Letters
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