A Semi-Analytical Analysis of Texture Collapse

This study presents a simplified approach to studying the dynamics of global texture collapse. We derive equations of motion for a spherically symmetric field configuration using a two parameter ansatz. Then we analyse the effective potential for the resulting theory to understand possible trajectories of the field configuration in the parameter space of the ansatz. Numerical results are given for critical winding and collapse time in spatially flat non-expanding, and flat expanding universes. In addition, the open non-expanding and open-expanding cases are studied.Comment: 12 pages, figures available from author, BROWN-HET-895, uses phyzz

Attractive Channel Skyrmions and the Deuteron

The deuteron is described as a quantum state on a ten-dimensional manifold $M_{10}$ of Skyrme fields of degree two, which are obtained by calculating the holonomy of $SU(2)$ instantons. The manifold $M_{10}$ includes both toroidal configurations of minimal energy and configurations which are approximately the product of two Skyrmions in the most attractive relative orientation. The quantum Hamiltonian is of the form $-\Delta +V$, where $\Delta$ is the covariant Laplace operator on $M_{10}$ and $V$ is the potential which $M_{10}$ inherits from the Skyrme potential energy functional. Quantum states are complex-valued functions on the double cover of $M_{10}$ satisfying certain constraints. There is a unique bound state with the quantum numbers of the deuteron, and its binding energy is approximately 6 MeV. Some of the deuteron's electrostatic and magnetostatic properties are also calculated and compared with experiment.Comment: 38 pages, latex, 9 figure

937-2 Safety and Efficacy of QW3600 (EchoGen®) in Producing LV Opacification During Stress Echocardiography in Normals

QW 3600 (EchoGen®) (EG) is a new ultrasonic contrast agent which produces intense LV cavity and even myocardial opacification following IV injection in animals. However, no data exists regarding the potential of this agent to be used in conjunction with stress echo in humans. Therefore, in 17 normals we compared the results of injecting equal volumes of normal saline and progressive doses of EG: 0.02 cc/kg (5 pts). 0.05cc/kg (4). and 0.1cc/kg (8) during stress echo performed to 85% of maximal heart rate. Echo was performed in apical 4 chamber view, and LV contrast opacification was assessed qualitatively (1 + weak and incomplete, 2+ complete cavity. 3+dense and complete) and by videodensitometry (0.3cm2) region of interest in mid cavity. All subjects tolerated the injections well without adverse events. No significant changes were observed in pulse oximetry, the ECG, or 25 laboratory studies. We analyzed the maximal change (Δ) in systolic (S) and diastolic (D) pressure (mmHg) and heart rate (HR) and peak videointensity (PVI) from baseline to post exertion following the injection of either saline or EG (Table, all p=NS for saline vs EG except PVI)DoseSalineEGΔHRΔSBPΔDBPPVIΔHRΔSBPΔDBPPVI0.0248431813424917280.0537351611434321420.13740191037441962LV opacification was absent with saline, was inconsistent at 0.02 and 0.05cc/kg doses, but was≥ 2+ in all but one 0.1cc/kg administration (mean 2.4). Peak LV videointensity after EG was 62 for 0.1cc/kg. Thus, EchoGen® is a new contrast agent which is well tolerated when used with stress echo in normals and results in complete LV opacification at a dose of 0.1cc/kg. EchoGen® should prove to be a useful adjunct to clinical stress echo

Reparametrising the Skyrme Model using the Lithium-6 Nucleus

The minimal energy B=6 solution of the Skyrme model is a static soliton with $D_{4d}$ symmetry. The symmetries of the solution imply that the quantum numbers of the ground state are the same as those of the Lithium-6 nucleus. This identification is considered further by obtaining expressions for the mean charge radius and quadrupole moment, dependent only on the Skyrme model parameters $e$ (a dimensionless constant) and $F_\pi$ (the pion decay constant). The optimal values of these parameters have often been deliberated upon, and we propose, for $B>2$, changing them from those which are most commonly accepted. We obtain specific values for these parameters for B=6, by matching with properties of the Lithium-6 nucleus. We find further support for the new values by reconsidering the $\alpha$-particle and deuteron as quantized B=4 and B=2 Skyrmions.Comment: 18 page

Rates of referable eye disease in the Scottish National Diabetic Retinopathy Screening Programme

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.Peer reviewedPublisher PD

Grafting from versus Grafting to Approaches for the Functionalization of Graphene Nanoplatelets with Poly(methyl methacrylate)

Graphene nanoplatelets (GNP) were exfoliated using a nondestructive chemical reduction method and subsequently decorated with polymers using two different approaches: grafting from and grafting to. Poly(methyl methacrylate) (PMMA) with varying molecular weights was covalently attached to the GNP layers using both methods. The grafting ratios were higher (44.6% to 126.5%) for the grafting from approach compared to the grafting to approach (12.6% to 20.3%). The products were characterized using thermogravimetric analysis–mass spectrometry (TGA-MS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The grafting from products showed an increase in the grafting ratio and dispersibility in acetone with increasing monomer supply; on the other hand, due to steric effects, the grafting to products showed lower absolute grafting ratios and a decreasing trend with increasing polymer molecular weight. The excellent dispersibility of the grafting from functionalized graphene, 900 μg/mL in acetone, indicates an increased compatibility with the solvent and the potential to increase graphene reinforcement performance in nanocomposite applications

Grafting from versus grafting to approaches for the functionalisation of graphene nanoplatelets with poly(methyl methacrylate)

Graphene nanoplatelets (GNP) were exfoliated using a nondestructive chemical reduction method and subsequently decorated with polymers using two different approaches: grafting from and grafting to. Poly(methyl methacrylate) (PMMA) with varying molecular weights was covalently attached to the GNP layers using both methods. The grafting ratios were higher (44.6% to 126.5%) for the grafting from approach compared to the grafting to approach (12.6% to 20.3%). The products were characterized using thermogravimetric analysis–mass spectrometry (TGA-MS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The grafting from products showed an increase in the grafting ratio and dispersibility in acetone with increasing monomer supply; on the other hand, due to steric effects, the grafting to products showed lower absolute grafting ratios and a decreasing trend with increasing polymer molecular weight. The excellent dispersibility of the grafting from functionalized graphene, 900 μg/mL in acetone, indicates an increased compatibility with the solvent and the potential to increase graphene reinforcement performance in nanocomposite applications

Polymorphism in <i>INSR</i> Locus Modifies Risk of Atrial Fibrillation in Patients on Thyroid Hormone Replacement Therapy

AimsAtrial fibrillation (AF) is a risk for patients receiving thyroid hormone replacement therapy. No published work has focused on pharmacogenetics relevant to thyroid dysfunction and AF risk. We aimed to assess the effect of L-thyroxine on AF risk stratified by a variation in a candidate gene.Methods and ResultsA retrospective follow-up study was done among European Caucasian patients from the Genetics of Diabetes Audit and Research in Tayside Scotland cohort (Scotland, United Kingdom). Linked data on biochemistry, prescribing, hospital admissions, demographics, and genetic biobank were used to ascertain patients on L-thyroxine and diagnosis of AF. A GWAS-identified insulin receptor-INSR locus (rs4804416) was the candidate gene. Cox survival models and sensitivity analyses by taking competing risk of death into account were used. Replication was performed in additional sample (The Genetics of Scottish Health Research register, GoSHARE), and meta-analyses across the results of the study and replication cohorts were done. We analyzed 962 exposed to L-thyroxine and 5,840 unexposed patients who were rs4804416 genotyped. The rarer G/G genotype was present in 18% of the study population. The total follow-up was up to 20 years, and there was a significant increased AF risk for patients homozygous carriers of the G allele exposed to L-thyroxine (RHR = 2.35, P = 1.6e–02). The adjusted increased risk was highest within the first 3 years of exposure (RHR = 9.10, P = 8.5e–04). Sensitivity analysis yielded similar results. Effects were replicated in GoSHARE (n = 3,190).ConclusionHomozygous G/G genotype at the INSR locus (rs4804416) is associated with an increased risk of AF in patients on L-thyroxine, independent of serum of free thyroxine and thyroid-stimulating hormone serum concentrations

Magnetic bubble refraction and quasibreathers in inhomogeneous antiferromagnets

The dynamics of magnetic bubble solitons in a two-dimensional isotropic antiferromagnetic spin lattice is studied, in the case where the exchange integral J(x,y) is position dependent. In the near continuum regime, this system is described by the relativistic O(3) sigma model on a spacetime with a spatially inhomogeneous metric, determined by J. The geodesic approximation is used to describe low energy soliton dynamics in this system: n-soliton motion is approximated by geodesic motion in the moduli space of static n-solitons, equipped with the L^2 metric. Explicit formulae for this metric for various natural choices of J(x,y) are obtained. From these it is shown that single soliton trajectories experience refraction, with 1/J analogous to the refractive index, and that this refraction effect allows the construction of simple bubble lenses and bubble guides. The case where J has a disk inhomogeneity (taking the value J_1 outside a disk, and J_2<J_1 inside) is considered in detail. It is argued that, for sufficiently large J_1/J_2 this type of antiferromagnet supports approximate quasibreathers: two or more coincident bubbles confined within the disk which spin internally while their shape undergoes periodic oscillations with a generically incommensurate period.Comment: Conference proceedings paper for talk given at Nonlinear Physics Theory and Experiment IV, Gallipoli, Italy, June 200