421 research outputs found
High pressure growth and electron transport properties of superconducting SmFeAsO1-xHx single crystals
We report the single crystal growth and characterization of the highest Tc
iron-based superconductor SmFeAsO1-xHx. Some sub-millimeter-sized crystals were
grown using the mixture flux of Na3As + 3NaH + As at 3.0 GPa and 1473 K. The
chemical composition analyses confirmed 10% substitution of hydrogen for the
oxygen site (x = 0.10), however, the structural analyses suggested that the
obtained crystal forms a multi-domain structure. By using the FIB technique we
fabricated the single domain SmFeAsO0.9H0.10 crystal with the Tc of 42 K, and
revealed the metallic conduction in in-plane (rhoab), while semiconducting in
the out-of-plane (rhoc). From the in-plane Hall coefficient measurements, we
confirmed that the dominant carrier of SmFeAsO0.9H0.10 crystal is an electron,
and the hydride ion occupied at the site of the oxygen ion effectively supplies
a carrier electron per iron following the equation: O2- = H- + e-.Comment: 4 figures, 2 table
Fibroblasts as Local Immune Modulators in Ocular Allergic Disease
ABSTRACTVernal keratoconjunctivitis (VKC), a severe form of ocular allergic disease, is characterized by the formation of giant papillae at the upper tarsal conjunctiva and corneal lesions that threaten vision. Recent evidence indicates that resident fibroblasts function as immune modulators in the pathogenesis of the chronic allergic inflammation associated with VKC. The T helper 2 (Th2) cell-derived cytokines interleukin (IL)-4 and IL-13 stimulate the migration and proliferation of conjunctival fibroblasts as well as protecting these cells from apoptotic cell death, effects that likely underlie the hyperplasia of fibroblasts that contributes to the formation of giant papillae. Conjunctival fibroblasts also synthesize extracellular matrix proteins and tissue inhibitors of metalloproteinases as well as down-regulate the expression of matrix metalloproteinases in response to these cytokines, effects that likely contribute to the excessive deposition of extracellular matrix that is characteristic of giant papillae. Stimulation of fibroblasts in the corneal stroma with the combination of a proinflammatory cytokine and either IL-4 or IL-13 results in up-regulation of the expression of the chemokine eotaxin and thymus- and activation-regulated chemokine as well as of vascular cell adhesion molecule-1, which together mediate the infiltration and activation of eosinophils and Th2 cells. Fibroblasts therefore appear to play a central role in the induction and amplification of ocular allergic inflammation and the consequent development of giant papillae and corneal disorders in individuals with VKC. Fibroblasts and fibroblast-derived factors thus represent new and potentially important therapeutic targets for treatment of the giant papillae and corneal disorders associated with VKC
Pareto law and Pareto index in the income distribution of Japanese companies
In order to study the phenomenon in detail that income distribution follows
Pareto law, we analyze the database of high income companies in Japan. We find
a quantitative relation between the average capital of the companies and the
Pareto index. The larger the average capital becomes, the smaller the Pareto
index becomes. From this relation, we can possibly explain that the Pareto
index of company income distribution hardly changes, while the Pareto index of
personal income distribution changes sharply, from a viewpoint of capital (or
means). We also find a quantitative relation between the lower bound of capital
and the typical scale at which Pareto law breaks. The larger the lower bound of
capital becomes, the larger the typical scale becomes. From this result, the
reason there is a (no) typical scale at which Pareto law breaks in the income
distribution can be understood through (no) constraint, such as the lower bound
of capital or means of companies, in the financial system.Comment: 12 pages, 8 figure
Network Working Group M. Day Request for Comments: 2778 Lotus Category: Informational
Abstract This document defines an abstract model for a presence and instant messaging system. It defines the various entities involved, defines terminology, and outlines the services provided by the system. The goal is to provide a common vocabulary for further work on requirements for protocols and markup for presence and instant messaging
String Theory as a Constrained Topological Sigma Model
It has been argued by Ishikawa and Kato that by making use of a specific
bosonization, string theory can be regarded as a constrained
topological sigma model. We generalize their construction for any
minimal model coupled to two dimensional (2d) gravity and show that the
energy--momentum tensor and the topological charge of a constrained topological
sigma model can be mapped to the energy--momentum tensor and the BRST charge of
string theory at zero cosmological constant. We systematically study
the physical state spectrum of this topological sigma model and recover the
spectrum in the absolute cohomology of string theory. This procedure
provides us a manifestly topological representation of the continuum Liouville
formulation of string theory.Comment: 12 pages, Latex file, UG-9/9
Topological Aspects of an Antisymmetric Background Field on Orbifolds
We study string theory on orbifolds in the presence of an antisymmetric
constant background field in detail and discuss some of new aspects of the
theory. It is pointed out that the term with the antisymmetric background field
can be regarded as a topological term like a Chern-Simons term or a Wess-Zumino
term. Detailed analysis in the operator formalism shows that orbifold models
with topologically nontrivial twists exhibit various anomalous behavior: Zero
mode variables obey nontrivial quantization conditions. Coordinate
transformations which define orbifolds are modified at quantum level. Wave
functions of twisted strings in general acquire nontrivial phases when they
move around non-contractible loops on orbifolds. Zero mode eigenvalues are
shifted from naively expected values, in favor of modular invariance.Comment: 45 pages, Latex file, NBI-HE-93-01, KOBE-TH-93-0
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