1,477 research outputs found
A study of the quenched bc mass spectrum at beta=6.2
We present an analysis of the mass spectrum of heavy quarkonia with
non-degenerate quark masses. The heavier (bottom) valence quark is treated in a
non-relativistic fashion and the other (charm) is a relativistic Wilson-like
quark using the improved SW action. Such states provide and interesting probe
between the relativistic B meson states and the non-relativistic bottomonium
states.Comment: 4 pages LaTeX, 4 postscript figures. requires espcrc2.sty and
epsf.sty. To be published in the proceedings of Lattice 97, Edinburgh,
Scotlan
On the growth of the Bergman kernel near an infinite-type point
We study diagonal estimates for the Bergman kernels of certain model domains
in near boundary points that are of infinite type. To do so, we
need a mild structural condition on the defining functions of interest that
facilitates optimal upper and lower bounds. This is a mild condition; unlike
earlier studies of this sort, we are able to make estimates for non-convex
pseudoconvex domains as well. This condition quantifies, in some sense, how
flat a domain is at an infinite-type boundary point. In this scheme of
quantification, the model domains considered below range -- roughly speaking --
from being ``mildly infinite-type'' to very flat at the infinite-type points.Comment: Significant revisions made; simpler estimates; very mild
strengthening of the hypotheses on Theorem 1.2 to get much stronger
conclusions than in ver.1. To appear in Math. An
Complementary vertices and adjacency testing in polytopes
Our main theoretical result is that, if a simple polytope has a pair of
complementary vertices (i.e., two vertices with no facets in common), then it
has at least two such pairs, which can be chosen to be disjoint. Using this
result, we improve adjacency testing for vertices in both simple and non-simple
polytopes: given a polytope in the standard form {x \in R^n | Ax = b and x \geq
0} and a list of its V vertices, we describe an O(n) test to identify whether
any two given vertices are adjacent. For simple polytopes this test is perfect;
for non-simple polytopes it may be indeterminate, and instead acts as a filter
to identify non-adjacent pairs. Our test requires an O(n^2 V + n V^2)
precomputation, which is acceptable in settings such as all-pairs adjacency
testing. These results improve upon the more general O(nV) combinatorial and
O(n^3) algebraic adjacency tests from the literature.Comment: 14 pages, 5 figures. v1: published in COCOON 2012. v2: full journal
version, which strengthens and extends the results in Section 2 (see p1 of
the paper for details
Noninvasively Predicting Hemodynamic Response to Carvedilol in Cirrhotic Patients With Varices: You Have Some Ex-Spleening to Do
Gastroesophageal varices are present in approximately 50% of patients with cirrhosis and variceal hemorrhage occurs at a rate of about 10%–15% per year (N Engl J Med 1988;319:983–989; Gastrointest Endosc 2007;65:82–88). Nonselective beta-blockers (NSBB) or variceal band ligation are currently recommended as primary prophylaxis against variceal hemorrhage in patients with large or high-risk varices (J Hepatol 2015;63:743–752; Hepatology 2017;65:310–335). The goal of NSBB therapy is to reduce portal pressures, which can formally be assessed by measuring the hepatic venous pressure gradient (HVPG)
Reversible magnetization of MgB2 single crystals with a two-gap nature
We present reversible magnetization measurements on MgB2 single crystals in
magnetic fields up to 2.5 T applied parallel to the crystal's c-axis. This
magnetization is analyzed in terms of the Hao-Clem model, and various
superconducting parameters, such as the critical fields [Hc(0) and Hc2(0)], the
characteristic lengths [xi(0) and lambda(0)], and the Ginzburg-Landau
parameter, kappa, are derived. The temperature dependence of the magnetic
penetration depth, lambda(T), obtained from the Hao-Clem analysis could not be
explained by theories assuming a single gap. Our data are well described by
using a two-gap model.Comment: 20 pages, 1 table, 4 figures, will be published in Phys. Rev.
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In-vessel flow characterization under severe accident conditions
The purpose of this study is to provide a parametric framework for characterization of flow and heat transfer regimes and their associated phenomenological uncertainties following severe accidents using a two dimensional, heterogenous, porous media formulation. This approach extends the understanding of buoyancy-induced flow characteristics in the uncovered region of the reactor core and the upper plenum of a PWR vessel. The results of this study can be used to augment the boil-off steam flow in integrated one-dimensional severe accident codes such as the Source Team Code Package (STCP)
Disruption of the leptomeningeal blood barrier in neuromyelitis optica spectrum disorder
OBJECTIVE: To describe leptomeningeal blood-barrier impairment reflected by MRI gadolinium-enhanced lesions in patients with aquaporin-4 immunoglobulin G (AQP4-IgG)-positive neuromyelitis optica spectrum disorder (NMOSD). METHODS: A retrospective case series of 11 AQP4-IgG-positive NMOSD patients with leptomeningeal enhancement (LME) were collected from 5 centers. External neuroradiologists, blinded to the clinical details, evaluated MRIs. RESULTS: LME was demonstrated on postcontrast T1-weighted and fluid-attenuated inversion recovery images as a sign of leptomeningeal blood-barrier disruption and transient leakage of contrast agent into the subarachnoid space in 11 patients, 6 in the brain and 6 in the spinal cord. The patterns of LME were linear or extensive and were accompanied by periependymal enhancement in 5 cases and intraparenchymal enhancement in all cases. The location of LME in the spinal cord was adjacent to intraparenchymal contrast enhancement with involvement of a median number of 12 (range 5-17) vertebral segments. At the time of LME on MRI, all patients had a clinical attack such as encephalopathy (36%) and/or myelopathy (70%) with median interval between symptom onset and LME of 12 days (range 2-30). LME occurred in association with an initial area postrema attack (44%), signs of systemic infection (33%), or AQP4-IgG in CSF (22%) followed by clinical progression. LME was found at initial clinical presentation in 5 cases and at clinical relapses leading to a diagnosis of NMOSD in 6 cases. CONCLUSION: This study suggests that altered leptomeningeal blood barrier may be accompanied by intraparenchymal blood-brain barrier breakdown in patients with AQP4-IgG-positive NMOSD during relapses
Instabilities of bulk fields and anomalies on orbifolds
Bulk matter modes of higher dimensional models generically become unstable in
the presence of additional matter multiplets at the branes. This quantum
instability is driven by localized Fayet-Iliopoulos terms that attract the bulk
zero modes towards the boundary branes. We study this mechanism in the
framework of a 5 dimensional S^1/Z_2 orbifold and give conditions for the
various possibilities of localization of (chiral) zero modes. This mechanism is
quite relevant for realistic model building, as the standard model contains
U(1) hypercharge with potentially localized FI-terms. The analysis is closely
related to localized anomalies in higher dimensional gauge theories. Five
dimensional gauge invariance of the effective action determines the anomaly
constraints and fixes the normalization of Chern-Simons terms. The localization
of the bulk modes does not effect the anomaly cancellation globally, but the
additional heavy Kaluza-Klein modes of the bulk fields may cancel the
Chern-Simons terms. We discuss also the potential appearance of the parity
anomaly that might render the construction of some orbifold models
inconsistent.Comment: 29 pages, LaTeX, with figure
Exotic optical elements generating 2D surface waves
We introduce exotic optical elements for 2D surface wave systems hosting Bloch surface waves (BSWs). First, we will study a 2D non-diffracting beam, second, a 2D array of the optical bottle beam via the Talbot effect and third, tight light confinement like a photonic nanojet. Investigations are carried out using a well-established BSW platform
Surgical stabilization for symptomatic carpometacarpal hypermobility; a randomized comparison of a dorsal and a volar technique and a cohort of the volar technique
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