440 research outputs found
A new Proposal for a Quasielectron Trial Wavefunction for the FQHE on a Disk
In this letter, we propose a new quasielectron trial wavefunction for
interacting electrons in two dimensions moving in a strong magnetic field in a
disk geometry. Requiring that the trial wavefunction exhibits the correct
filling factor of a quasielectron wavefunction, we obtain angular
momentum eigenfunctions. The expectation values of the energy are calculated
and compared with the data of an exact numerical diagonalization.Comment: 8 page
Extrinsic Curvature Embedding Diagrams
Embedding diagrams have been used extensively to visualize the properties of
curved space in Relativity. We introduce a new kind of embedding diagram based
on the {\it extrinsic} curvature (instead of the intrinsic curvature). Such an
extrinsic curvature embedding diagram, when used together with the usual kind
of intrinsic curvature embedding diagram, carries the information of how a
surface is {\it embedded} in the higher dimensional curved space. Simple
examples are given to illustrate the idea.Comment: 22 pages, 4 figure
Expanding Cosmologies in Brane Geometries
Five dimensional gravity coupled, both in the bulk and on a brane, to a
scalar Liouville field yields a geometry confined to a strip around the brane
and with time dependent scale factors for the four geometry. In various limits
known models can be recovered as well as a temporally expanding four geometry
with a warp factor falling exponentially away from the brane. The effective
theory on the brane has a time dependent Planck mass and ``cosmological
constant''. Although the scale factor expands, the expansion is not an
acceleration.Comment: 7 pages, LaTex/RevTex
Factors associated with intracerebral hemorrhage after thrombolytic therapy for ischemic stroke pooled analysis of placebo data from the Stroke-Acute Ischemic NXY Treatment (SAINT) I and SAINT II trials
<p><b>Background and Purpose:</b> A number of factors have been associated with postthrombolysis intracerebral hemorrhage, but these have varied across studies.</p>
<p><b>Methods:</b> We examined patients with acute ischemic stroke treated with intravenous tissue plasminogen activator within 3 hours of symptom onset who were enrolled in the placebo arms of 2 trials (Stroke-Acute Ischemic NXY Treatment [SAINT] I and II Trials) of a putative neuroprotectant. Early CT changes were graded using the Alberta Stroke Program Early CT Score (ASPECTS). Post–tissue plasminogen activator symptomatic intracerebral hemorrhage was defined as a worsening in National Institutes of Health Stroke Scale of ≥4 points within 36 hours with evidence of hemorrhage on follow-up neuroimaging. Good clinical outcome was defined as a modified Rankin scale of 0 to 2 at 90 days.</p>
<p><b>Results:</b> Symptomatic intracerebral hemorrhage occurred in 5.6% of 965 patients treated with tissue plasminogen activator. In multivariable analysis, symptomatic intracerebral hemorrhage was increased with baseline antiplatelet use (single antiplatelet: OR, 2.04, 95% CI, 1.07 to 3.87, P=0.03; double antiplatelet: OR, 9.29, 3.28 to 26.32, P<0.001), higher National Institutes of Health Stroke Scale score (OR, 1.09 per point, 1.03 to 1.15, P=0.002), and CT changes defined by ASPECTS (ASPECTS 8 to 9: OR, 2.26, 0.63 to 8.10, P=0.21; ASPECTS ≤7: OR, 5.63, 1.66 to 19.10, P=0.006). Higher National Institutes of Health Stroke Scale was associated with decreased odds of good clinical outcome (OR, 0.82 per point, 0.79 to 0.85, P<0.001). There was no relationship between baseline antiplatelet use or CT changes and clinical outcome.</p>
<p><b>Conclusions:</b> Along with higher National Institutes of Health Stroke Scale and extensive early CT changes, baseline antiplatelet use (particularly double antiplatelet therapy) was associated with an increased risk of post–tissue plasminogen activator symptomatic intracerebral hemorrhage. Of these factors, only National Institutes of Health Stroke Scale was associated with clinical outcome.</p>
Berry phases for composite fermions: effective magnetic field and fractional statistics
The quantum Hall superfluid is presently the only viable candidate for a
realization of quasiparticles with fractional Berry phase statistics. For a
simple vortex excitation, relevant for a subset of fractional Hall states
considered by Laughlin, non-trivial Berry phase statistics were demonstrated
many years ago by Arovas, Schrieffer, and Wilczek. The quasiparticles are in
general more complicated, described accurately in terms of excited composite
fermions. We use the method developed by Kjonsberg, Myrheim and Leinaas to
compute the Berry phase for a single composite-fermion quasiparticle, and find
that it agrees with the effective magnetic field concept for composite
fermions. We then evaluate the "fractional statistics", related to the change
in the Berry phase for a closed loop caused by the insertion of another
composite-fermion quasiparticle in the interior. Our results support the
general validity of fractional statistics in the quantum Hall superfluid, while
also giving a quantitative account of corrections to it when the quasiparticle
wave functions overlap. Many caveats, both practical and conceptual, are
mentioned that will be relevant to an experimental measurement of the
fractional statistics. A short report on some parts of this article has
appeared previously.Comment: 14 pages, 9 figure
A maximum density rule for surfaces of quasicrystals
A rule due to Bravais of wide validity for crystals is that their surfaces
correspond to the densest planes of atoms in the bulk of the material.
Comparing a theoretical model of i-AlPdMn with experimental results, we find
that this correspondence breaks down and that surfaces parallel to the densest
planes in the bulk are not the most stable, i.e. they are not so-called bulk
terminations. The correspondence can be restored by recognizing that there is a
contribution to the surface not just from one geometrical plane but from a
layer of stacked atoms, possibly containing more than one plane. We find that
not only does the stability of high-symmetry surfaces match the density of the
corresponding layer-like bulk terminations but the exact spacings between
surface terraces and their degree of pittedness may be determined by a simple
analysis of the density of layers predicted by the bulk geometric model.Comment: 8 pages of ps-file, 3 Figs (jpg
Thermodynamics of Quantum Hall Ferromagnets
The two-dimensional interacting electron gas at Landau level filling factor
and temperature is a strong ferromagnet; all spins are
completely aligned by arbitrarily weak Zeeman coupling. We report on a
theoretical study of its thermodynamic properties using a many-body
perturbation theory approach and concentrating on the recently measured
temperature dependence of the spin magnetization. We discuss the interplay of
collective and single-particle aspects of the physics and the opportunities for
progress in our understanding of itinerant electron ferromagnetism presented by
quantum Hall ferromagnets.Comment: REVTex, 10 pages, 3 uuencoded, compressed and tarred PostScript
figures appende
Rationale and design of the AXIOMATIC-SSP phase II trial: Antithrombotic treatment with factor XIa inhibition to Optimize Management of Acute Thromboembolic events for Secondary Stroke Prevention
MRI; Milvexian; Stroke preventionResonancia magnética; Milvexian; Prevención de ictusRessonà ncia magnètica; Milvexian; Prevenció d'ictusBackground
Individuals with ischemic stroke or transient ischemic attack (TIA) have a high early risk of ischemic stroke despite dual antiplatelet therapy. The risk of ischemic stroke, and associated disability, represents a significant unmet clinical need. Genetic variants resulting in reduced factor XI levels are associated with reduced risk for ischemic stroke but are not associated with increased intracranial bleeding. Milvexian is an oral small-molecule inhibitor of FXIa that binds activated factor XI with high affinity and selectivity and may reduce the risk of stroke when added to antiplatelet drugs without significant bleeding. We aimed to evaluate the dose-response relationship of milvexian in participants treated with dual antiplatelets.
Methods
We began a phase II, double-blinded, randomized, placebo-controlled trial at 367 sites in 2019. Participants (N = 2366) with ischemic stroke (National Institutes of Health Stroke Scale score ≤7) or high-risk TIA (ABCD2 score ≥6) were randomized to 1 of 5 doses of milvexian or placebo for 90 days. Participants also received clopidogrel 75 mg daily for the first 21 days and aspirin 100 mg for 90 days. The efficacy endpoint was the composite of ischemic stroke or incident infarct on magnetic resonance imaging. Major bleeding, defined as type 3 or 5 bleeding according to the Bleeding Academic Research Consortium, was the safety endpoint. Participant follow-up will end in 2022.
Conclusion
The AXIOMATIC-SSP trial will evaluate the dose-response of milvexian for ischemic stroke occurrence in participants with ischemic stroke or TIA.This study is sponsored by Bristol Myers Squibb and Janssen Research & Development, LLC
A Snapshot of J. L. Synge
A brief description is given of the life and influence on relativity theory
of Professor J. L. Synge accompanied by some technical examples to illustrate
his style of work
Brane World Cosmology In Jordan-Brans-Dicke Theory
We consider the embedding of 3+1 dimensional cosmology in 4+1 dimensional
Jordan-Brans-Dicke theory. We show that exponentially growing and power law
scale factors are implied. Whereas the 4+1 dimensional scalar field is
approximately constant for each, the effective 3+1 dimensional scalar field is
constant for exponentially growing scale factor and time dependent for power
law scale factor.Comment: 11 page
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