5 research outputs found
Surface Scaling Analysis of a Frustrated Spring-network Model for Surfactant-templated Hydrogels
We propose and study a simplified model for the surface and bulk structures
of crosslinked polymer gels, into which voids are introduced through templating
by surfactant micelles. Such systems were recently studied by Atomic Force
Microscopy [M. Chakrapani et al., e-print cond-mat/0112255]. The gel is
represented by a frustrated, triangular network of nodes connected by springs
of random equilibrium lengths. The nodes represent crosslinkers, and the
springs correspond to polymer chains. The boundaries are fixed at the bottom,
free at the top, and periodic in the lateral direction. Voids are introduced by
deleting a proportion of the nodes and their associated springs. The model is
numerically relaxed to a representative local energy minimum, resulting in an
inhomogeneous, ``clumpy'' bulk structure. The free top surface is defined at
evenly spaced points in the lateral (x) direction by the height of the topmost
spring, measured from the bottom layer, h(x). Its scaling properties are
studied by calculating the root-mean-square surface width and the generalized
increment correlation functions C_q(x)= . The surface is
found to have a nontrivial scaling behavior on small length scales, with a
crossover to scale-independent behavior on large scales. As the vacancy
concentration approaches the site-percolation limit, both the crossover length
and the saturation value of the surface width diverge in a manner that appears
to be proportional to the bulk connectivity length. This suggests that a
percolation transition in the bulk also drives a similar divergence observed in
surfactant templated polyacrylamide gels at high surfactant concentrations.Comment: 17 pages RevTex4, 10 imbedded eps figures. Expanded discussion of
multi-affinit
A study of initial oxidation of Fe40Ni40P14B6 MET-glass using Auger electron spectroscopy
Study of thermal-field emission properties and investigation of temperature dependent noise in the field emission current from vertical carbon nanotube emitters
Global impact of COVID-19 on stroke care.
BACKGROUND: The COVID-19 pandemic led to profound changes in the organization of health care systems worldwide.
AIMS: We sought to measure the global impact of the COVID-19 pandemic on the volumes for mechanical thrombectomy, stroke, and intracranial hemorrhage hospitalizations over a three-month period at the height of the pandemic (1 March-31 May 2020) compared with two control three-month periods (immediately preceding and one year prior).
METHODS: Retrospective, observational, international study, across 6 continents, 40 countries, and 187 comprehensive stroke centers. The diagnoses were identified by their ICD-10 codes and/or classifications in stroke databases at participating centers.
RESULTS: The hospitalization volumes for any stroke, intracranial hemorrhage, and mechanical thrombectomy were 26,699, 4002, and 5191 in the three months immediately before versus 21,576, 3540, and 4533 during the first three pandemic months, representing declines of 19.2% (95%CI, -19.7 to -18.7), 11.5% (95%CI, -12.6 to -10.6), and 12.7% (95%CI, -13.6 to -11.8), respectively. The decreases were noted across centers with high, mid, and low COVID-19 hospitalization burden, and also across high, mid, and low volume stroke/mechanical thrombectomy centers. High-volume COVID-19 centers (-20.5%) had greater declines in mechanical thrombectomy volumes than mid- (-10.1%) and low-volume (-8.7%) centers (p \u3c 0.0001). There was a 1.5% stroke rate across 54,366 COVID-19 hospitalizations. SARS-CoV-2 infection was noted in 3.9% (784/20,250) of all stroke admissions.
CONCLUSION: The COVID-19 pandemic was associated with a global decline in the volume of overall stroke hospitalizations, mechanical thrombectomy procedures, and intracranial hemorrhage admission volumes. Despite geographic variations, these volume reductions were observed regardless of COVID-19 hospitalization burden and pre-pandemic stroke/mechanical thrombectomy volumes