685 research outputs found
The conformal boundary states for SU(2) at level 1
For the case of the SU(2) WZW model at level one, the boundary states that
only preserve the conformal symmetry are analysed. Under the assumption that
the usual Cardy boundary states as well as their marginal deformations are
consistent, the most general conformal boundary states are determined. They are
found to be parametrised by group elements in SL(2,C).Comment: 22 pages, harvmac (b), 5 figure
Extended multiplet structure in Logarithmic Conformal Field Theories
We use the process of quantum hamiltonian reduction of SU(2)_k, at rational
level k, to study explicitly the correlators of the h_{1,s} fields in the
c_{p,q} models. We find from direct calculation of the correlators that we have
the possibility of extra, chiral and non-chiral, multiplet structure in the
h_{1,s} operators beyond the `minimal' sector. At the level of the vacuum null
vector h_{1,2p-1}=(p-1)(q-1) we find that there can be two extra non-chiral
fermionic fields. The extra indicial structure present here permeates
throughout the entire theory. In particular we find we have a chiral triplet of
fields at h_{1,4p-1}=(2p-1)(2q-1). We conjecture that this triplet algebra may
produce a rational extended c_{p,q} model. We also find a doublet of fields at
h_{1,3p-1}=(\f{3p}{2}-1)(\f{3q}{2}-1). These are chiral fermionic operators if
p and q are not both odd and otherwise parafermionic.Comment: 24 pages LATEX. Minor corrections and extra reference
Unitarity of rational N=2 superconformal theories
We demonstrate that all rational models of the N=2 super Virasoro algebra are
unitary. Our arguments are based on three different methods: we determine Zhu's
algebra (for which we give a physically motivated derivation) explicitly for
certain theories, we analyse the modular properties of some of the vacuum
characters, and we use the coset realisation of the algebra in terms of su_2
and two free fermions.
Some of our arguments generalise to the Kazama-Suzuki models indicating that
all rational N=2 supersymmetric models might be unitary.Comment: LaTeX (+amssym.def), 28 pages; minor changes in content, some
references added, final versio
Localization of quasiparticles in a disordered vortex
We study the diffusive motion of low-energy normal quasiparticles along the
core of a single vortex in a dirty, type-II, s-wave superconductor. The physics
of this system is argued to be described by a one-dimensional supersymmetric
nonlinear sigma model, which differs from the sigma models known for disordered
metallic wires. For an isolated vortex and quasiparticle energies less than the
Thouless energy, we recover the spectral correlations that are predicted by
random matrix theory for the universality class C. We then consider the
transport problem of transmission of quasiparticles through a vortex connected
to particle reservoirs at both ends. The transmittance at zero energy exhibits
a weak localization correction reminiscent of quasi-one-dimensional metallic
systems with symmetry index beta = 1. Weak localization disappears with
increasing energy over a scale set by the Thouless energy. This crossover
should be observable in measurements of the longitudinal heat conductivity of
an ensemble of vortices under mesoscopic conditions. In the regime of strong
localization, the localization length is shown to decrease by a factor of 8 as
the quasiparticle energy goes to zero.Comment: 38 pages, LaTeX2e + epsf, 4 eps figures, one reference adde
Iodine source apportionment in the Malawian diet
The aim of this study was to characterise nutritional-I status in Malawi. Dietary-I intakes were
assessed using new datasets of crop, fish, salt and water-I concentrations, while I status was
assessed for 60 women living on each of calcareous and non-calcareous soils as defined by urinary
iodine concentration (UIC). Iodine concentration in staple foods was low, with median concentrations
of 0.01 mg kgâ1 in maize grain, 0.008 mg kgâ1 in roots and tubers, but 0.155 mg kgâ1 in leafy
vegetables. Freshwater fish is a good source of dietary-I with a median concentration of 0.51 mg kgâ1.
Mean Malawian dietary-Iodine intake from food, excluding salt, was just 7.8 ÎŒg dâ1 compared to an
adult requirement of 150 ÎŒg dâ1. Despite low dietary-I intake from food, median UICs were 203 ÎŒg Lâ1
with only 12% defined as I deficient whilst 21% exhibited excessive I intake. Iodised salt is likely to
be the main source of dietary I intake in Malawi; thus, I nutrition mainly depends on the usage and
concentration of I in iodised salt. Drinking water could be a significant source of I in some areas,
providing up to 108 ÎŒg dâ1 based on consumption of 2 L dâ1
Tracking Parkinson's Disease over One Year with Multimodal Magnetic Resonance Imaging in a Group of Older Patients with Moderate Disease
Background & Objectives:
Cross-sectional magnetic resonance imaging (MRI) suggests that Parkinsonâs disease
(PD) is associated with changes in cerebral tissue volume, diffusion tensor imaging metrics,
and perfusion values. Here, we performed a longitudinal multimodal MRI studyâincluding
structural, diffusion tensor imaging (DTI), and perfusion MRIâto investigate progressive
brain changes over one year in a group of older PD patients at a moderate stage of disease
Pharmacologic intervention for prevention of fractures in osteopenic and osteoporotic postmenopausal women: Systemic review and meta-analysis
Objectives
Emerging evidence has indicated a role for pharmacologic agents in the primary prevention of osteoporotic fracture, but have not yet been systematically reviewed for meta-analysis. We conducted a meta-analysis to evaluate the efficacy of pharmacologic interventions in reducing fracture risk and increasing bone mineral density (BMD) in postmenopausal women with osteopenia or osteoporosis but without prevalent fragility fracture.
Method
The Medline, EMBASE, and CENTRAL databases were searched from inception to September 30, 2019. Only randomized placebo-controlled trials evaluating postmenopausal women with â1.0 > bone mineral density (BMD) T-score > â2.5 (low bone mass) and those with BMD T-score †â2.5 (osteoporosis) but without baseline fractures, who were receiving anti-osteoporotic agents, providing quantitative outcomes data and evaluating risk of vertebral and/or non-vertebral fragility fracture at follow-up. The PRISMA guidelines were followed, applying a random-effects model. The primary endpoint was the effect of anti-osteoporotic regimens in reducing the incidence of vertebral fractures. Secondary endpoints were percentage changes in baseline BMD at the lumbar spine and total hip at 1 and 2 years follow up.
Results
Full-text review of 144 articles yielded, 20 for meta-analysis. Bisphosphonates reduced the risk of vertebral fracture (pooled OR = 0.50, 95%CIs = 0.36â0.71) and significantly increased lumbar spine BMD after 1 year, by 4.42% vs placebo (95%CIs = 3.70%â5.14%). At the hip, this value was 2.94% (95%CIs = 2.13%â3.75%). Overall results of limited studies for non-bisphosphonate drugs showed increased BMD and raloxifene significantly decreases the risk of subsequent clinical vertebral fractures.
Conclusion
The bisphosphonates are efficacious and most evident for the primary prevention of osteoporotic vertebral fractures, reducing their incidence and improving BMD in postmenopausal women with osteopenia or osteoporosis
A Bayesian analysis of pentaquark signals from CLAS data
We examine the results of two measurements by the CLAS collaboration, one of
which claimed evidence for a pentaquark, whilst the other found no
such evidence. The unique feature of these two experiments was that they were
performed with the same experimental setup. Using a Bayesian analysis we find
that the results of the two experiments are in fact compatible with each other,
but that the first measurement did not contain sufficient information to
determine unambiguously the existence of a . Further, we suggest a
means by which the existence of a new candidate particle can be tested in a
rigorous manner.Comment: 5 pages, 3 figure
Quantifying atherogenic lipoproteins for lipid-lowering strategies : Consensus-based recommendations from EAS and EFLM
The joint consensus panel of the European Atherosclerosis Society (EAS) and the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) recently addressed present and future challenges in the laboratory diagnostics of atherogenic lipoproteins. Total cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, and calculated non-HDL cholesterol (= total - HDL cholesterol) constitute the primary lipid panel for estimating risk of atherosclerotic cardiovascular disease (ASCVD) and can be measured in the nonfasting state. LDL cholesterol is the primary target of lipid-lowering therapies. For on-treatment follow-up, LDL cholesterol shall be measured or calculated by the same method to attenuate errors in treatment decisions due to marked between-method variations. Lipoprotein(a)-cholesterol is part of measured or calculated LDL cholesterol and should be estimated at least once in all patients at risk of ASCVD, especially in those whose LDL cholesterol decline poorly upon statin treatment. Residual risk of ASCVD even under optimal LDL-lowering treatment should be also assessed by non-HDL cholesterol or apolipoprotein B, especially in patients with mild-to-moderate hypertriglyceridemia (2-10 mmol/L). Non-HDL cholesterol includes the assessment of remnant lipoprotein cholesterol and shall be reported in all standard lipid panels. Additional apolipoprotein B measurement can detect elevated LDL particle numbers often unidentified on the basis of LDL cholesterol alone. Reference intervals of lipids, lipoproteins, and apolipoproteins are reported for European men and women aged 20-100 years. However, laboratories shall flag abnormal lipid values with reference to therapeutic decision thresholds.Peer reviewe
First measurement of direct photoproduction on the proton
We report on the results of the first measurement of exclusive
meson photoproduction on protons for GeV and GeV. Data were collected with the CLAS detector at the Thomas
Jefferson National Accelerator Facility. The resonance was detected via its
decay in the channel by performing a partial wave analysis of the
reaction . Clear evidence of the meson
was found in the interference between and waves at GeV. The -wave differential cross section integrated in the mass range of
the was found to be a factor of 50 smaller than the cross section
for the meson. This is the first time the meson has been
measured in a photoproduction experiment
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