194 research outputs found
Baryon Operators and Baryon Spectroscopy
The issues involved in a determination of the baryon resonance spectrum in
lattice QCD are discussed. The variational method is introduced and the need to
construct a sufficient basis of interpolating operators is emphasised. The
construction of baryon operators using group-theory techniques is outlined. We
find that the use both of quark-field smearing and link-field smearing in the
operators is essential firstly to reduce the coupling of operators to
high-frequency modes and secondly to reduce the gauge-field fluctuations in
correlators. We conclude with a status report of our current investigation of
baryon spectroscopy.Comment: Invited talk at Workshop on Computational Hadron Physics, Cyprus,
Sept. 14-17, 200
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A Case Report of Cognitive Processing Therapy Delivered over a Single Week.
Although evidence-based treatments for posttraumatic stress disorder (PTSD), such as Cognitive Processing Therapy (CPT), have been developed and widely disseminated, the rate of veterans engaging in and completing these therapies is low. Alternative methods of delivery may be needed to help overcome key barriers to treatment. Delivering evidence-based therapies intensively may address practical barriers to treatment attendance as well as problems with avoidance. This report details the case of a combat veteran who received 10 sessions of Cognitive Processing Therapy delivered twice per day over a single, five-day work week (CPT-5). Post-treatment, the veteran reported large and clinically meaningful decreases in PTSD and depression symptom severity as well as in guilt cognitions, which is a purported mechanism of successful treatment. These effects persisted six weeks after treatment ended. Despite the intensive nature of the treatment, the veteran found CPT-5 tolerable and could cite many benefits to completing therapy in one work week. In conclusion, CPT-5 holds promise as a way to efficiently deliver an evidence-based therapy that is both clinically effective and acceptable to patients, although more rigorous clinical trials are needed to test this treatment delivery format
Ab Initio Calculation of Relativistic Corrections to the Static Interquark potential I: SU(2) Gauge Theory
We test the capability of state-of-the-art lattice techniques for a precise
determination of relativistic corrections to the static interquark potential,
by use of SU(2) gauge theory. Emphasis is put on the short range structure of
the spin dependent potentials, with lattice resolution a ranging from a approx
0.04 fm (at beta=2.74) down to a approx 0.02 fm (at beta=2.96) on volumes of
32^4 and 48^4 lattice sites. We find a new short range Coulomb-like
contribution to the spin-orbit potential V_1'.Comment: 37 pages REVTeX with 20 encapsuled ps figure
Burning Rate of Liquid Fuel on Carpet (Porous Media)
Research paper published in the journal Fire Technology 2004The occurrence of a liquid fuel burning on carpet has been involved in many
incendiary and accidental fires. While the research on a liquid fuel fire on carpet is still
limited, much work on porous media has been performed using sand or glass beads
soaked with liquid fuel. In this study, a heat and mass transfer theory was first developed
to analyze the burning process of liquid on carpet, and then several small-scale tests were
performed to validate the theory. This analysis is valid for pool fires intermediate in size
(5-20 cm. in diameter). The experimental apparatus consisted of a circular pan (105mm)
and a load cell. Varying amounts of fuels (heptane, kerosene and methanol) were spilled
onto the carpet, which was allowed to burn in a quiescent environment. It was found that
due to the different controlling mechanisms, the liquid burning rate could be less or more
than that of a similarly spilled free-burning pool fire. For the worst-case scenario in fires,
the maximum enhancement of the burning rate due to the porous media is predictable
through the physical properties of the fuel. This analysis is valid for both combustion and
evaporation. Several similar results in the scientific literature are analyzed to further
describe the trend. This work explains the role of carpet in liquid pool fires and also helps
to explain special risks related to the presence of carpet involved in arsons and will be
useful in reconstruction of the early development of an incendiary or accidental fire
Retinal tissue engineering using mouse retinal progenitor cells and a novel biodegradable, thin-film poly(e-caprolactone) nanowire scaffold
Retinal progenitor cells (RPCs) can be combined with nanostructured polymer scaffolds to generate composite grafts in culture. One strategy for repair of diseased retinal tissue involves implantation of composite grafts of this type in the subretinal space. In the present study, mouse retinal progenitor cells (RPCs) were cultured on laminin-coated novel nanowire poly(e-caprolactone)(PCL) scaffolds, and the survival, differentiation, and migration of these cells into the retina of C57bl/6 and rhodospsin −/− mouse retinal explants and transplant recipients were analyzed. RPCs were cultured on smooth PCL and both short (2.5 μm) and long (27 μm) nanowire PCL scaffolds. Scaffolds with adherent mRPCs were then either co-cultured with, or transplanted to, wild-type and rhodopsin −/− mouse retina. Robust RPC proliferation on each type of PCL scaffold was observed. Immunohistochemistry revealed that RPCs cultured on nanowire scaffolds increased expression of mature bipolar and photoreceptor markers. Reverse transcription polymerase chain reaction revealed down-regulation of several early progenitor markers. PCL-delivered RPCs migrated into the retina of both wild-type and rhodopsin knockout mice. The results provide evidence that RPCs proliferate and express mature retinal proteins in response to interactions with nanowire scaffolds. These composite grafts allow for the migration and differentiation of new cells into normal and degenerated retina
Thermodynamics of SU(3) gauge theory on anisotropic lattices
Finite temperature SU(3) gauge theory is studied on anisotropic lattices
using the standard plaquette gauge action. The equation of state is calculated
on , and lattices with
the anisotropy , where and are the
spatial and temporal lattice spacings. Unlike the case of the isotropic lattice
on which data deviate significantly from the leading scaling behavior,
the pressure and energy density on an anisotropic lattice are found to satisfy
well the leading scaling from our coarsest lattice, . With
three data points at , 5 and 6, we perform a well controlled
continuum extrapolation of the equation of state. Our results in the continuum
limit agree with a previous result from isotropic lattices using the same
action, but have smaller and more reliable errors.Comment: RevTeX, 21 pages, 17 PS figures. A quantitative test about the
benefit of anisotropic lattices added, minor errors corrected. Final version
for PR
A calculation of the Lepage-Mackenzie scale for the lattice axial and vector currents
We calculate the perturbative scales (q*) for the axial and vector currents
for the Wilson action, with and without tadpole improvement, using Lepage and
Mackenzie's formalism. The scale for the pseudoscalar density (times the mass)
is computed as well. Contrary to naive expectation, tadpole improvement reduces
q* by only a small amount for the operators we consider. We also discuss the
use of a nonperturbative coupling to calculate the perturbative scale.Comment: 13 pages. One postscript figur
An estimate of the flavour singlet contributions to the hyperfine splitting in charmonium
We explore the splitting between flavour singlet and non-singlet mesons in
charmonium. This has implications for the hyperfine splitting in charmonium
Adjoint "quarks" on coarse anisotropic lattices: Implications for string breaking in full QCD
A detailed study is made of four dimensional SU(2) gauge theory with static
adjoint ``quarks'' in the context of string breaking. A tadpole-improved action
is used to do simulations on lattices with coarse spatial spacings ,
allowing the static potential to be probed at large separations at a
dramatically reduced computational cost. Highly anisotropic lattices are used,
with fine temporal spacings , in order to assess the behavior of the
time-dependent effective potentials. The lattice spacings are determined from
the potentials for quarks in the fundamental representation. Simulations of the
Wilson loop in the adjoint representation are done, and the energies of
magnetic and electric ``gluelumps'' (adjoint quark-gluon bound states) are
calculated, which set the energy scale for string breaking. Correlators of
gauge-fixed static quark propagators, without a connecting string of spatial
links, are analyzed. Correlation functions of gluelump pairs are also
considered; similar correlators have recently been proposed for observing
string breaking in full QCD and other models. A thorough discussion of the
relevance of Wilson loops over other operators for studies of string breaking
is presented, using the simulation results presented here to support a number
of new arguments.Comment: 22 pages, 14 figure
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