302 research outputs found
The phase diagram of high-Tc's: Influence of anisotropy and disorder
We propose a phase diagram for the vortex structure of high temperature
superconductors which incorporates the effects of anisotropy and disorder. It
is based on numerical simulations using the three-dimensional Josephson
junction array model. We support the results with an estimation of the internal
energy and configurational entropy of the system. Our results give a unified
picture of the behavior of the vortex lattice, covering from the very
anysotropic BiSrCaCuO to the less anisotropic YBaCuO, and from the first order
melting ocurring in clean samples to the continuous transitions observed in
samples with defects.Comment: 8 pages with 7 figure
Quality of Life and Clinical Outcomes in Elderly Patients Treated with Ventricular Pacing as Compared with Dual-Chamber Pacing
ABSTRACT
Background Standard clinical practice permits the use of either single-chamber ventricular pacemakers or dual-chamber pacemakers for most patients who require cardiac pacing. Ventricular pacemakers are less expensive, but dual-chamber pacemakers are believed to be more physiologic. However, it is not known whether either type of pacemaker results in superior clinical outcomes.
Methods The Pacemaker Selection in the Elderly study was a 30-month, single-blind, randomized, controlled comparison of ventricular pacing and dualchamber pacing in 407 patients 65 years of age or older in 29 centers. Patients received a dual-chamber pacemaker that had been randomly programmed to either ventricular pacing or dual-chamber pacing. The primary end point was health-related quality of life as measured by the 36-item Medical Outcomes Study Short-Form General Health Survey.
Results The average age of the patients was 76 years (range, 65 to 96), and 60 percent were men. Quality of life improved significantly after pacemaker implantation (P0.001), but there were no differences between the two pacing modes in either the quality of life or prespecified clinical outcomes (including cardiovascular events or death). However, 53 patients assigned to ventricular pacing (26 percent) were crossed over to dual-chamber pacing because of symptoms related to the pacemaker syndrome. Patients with sinus-node dysfunction, but not those with atrioventricular block, had moderately better quality of life and cardiovascular functional status with dual-chamber pacing than with ventricular pacing. Trends of borderline statistical significance in clinical end points favoring dual-chamber pacing were observed in patients with sinus-node dysfunction, but not in those with atrioventricular block.
Conclusions The implantation of a permanent pacemaker improves health-related quality of life. The quality-of-life benefits associated with dualchamber pacing as compared with ventricular pacing are observed principally in the subgroup of patients with sinus-node dysfunction. (N Engl J Med 1998;338:1097-104.
Long-Lived Triplet State Charge Separation in Novel Piperidine-Bridged Donor−Acceptor Systems
Synthesis of Block Copolymers Containing Pendant Carbazole Groups via Living Ring-Opening Metathesis Polymerization
Three-Dimensional Chemical Characterization of Complex Silver Halide Microcrystals by Scanning Ion Microprobe Mass Analysis
Selective Inhibition of Bovine Plasma Amine Oxidase by Homopropargylamine, a New Inactivator Motif
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