1,006 research outputs found
Stationary phase slip state in quasi-one-dimensional rings
The nonuniform superconducting state in a ring in which the order parameter
vanishing at one point is studied. This state is characterized by a jump of the
phase by at the point where the order parameter becomes zero. In uniform
rings such a state is a saddle-point state and consequently unstable. However,
for non-uniform rings with e.g. variations of geometrical or physical
parameters or with attached wires this state can be stabilized and may be
realized experimentally.Comment: 6 pages, 7 figures, RevTex 4.0 styl
Properties of mesoscopic superconducting thin-film rings. London approach
Superconducting thin-film rings smaller than the film penetration depth (the
Pearl length) are considered. The current distribution, magnetic moment, and
thermodynamic potential for a flat, washer-shaped annular
ring in a uniform applied field perpendicular to the film are solved
analytically within the London approach for a state with winding number and
a vortex at radius between the inner and outer radii.Comment: Submitted to Phys. Rev.
Dependence of the vortex configuration on the geometry of mesoscopic flat samples
The influence of the geometry of a thin superconducting sample on the
penetration of the magnetic field lines and the arrangement of vortices are
investigated theoretically. We compare superconducting disks, squares and
triangles with the same surface area having nonzero thickness. The coupled
nonlinear Ginzburg-Landau equations are solved self-consistently and the
important demagnetization effects are taken into account. We calculate and
compare quantities like the free energy, the magnetization, the Cooper-pair
density, the magnetic field distribution and the superconducting current
density for the three geometries. For given vorticity the vortex lattice is
different for the three geometries, i.e. it tries to adapt to the geometry of
the sample. This also influences the stability range of the different vortex
states. For certain magnetic field ranges we found a coexistence of a giant
vortex placed in the center and single vortices toward the corners of the
sample. Also the H-T phase diagram is obtained.Comment: 9 pages, 17 figures (submitted to Phys. Rev. B
Flux transitions in a superconducting ring
We perform a numeric study of the flux transitions in a superconducting ring
at fixed temperature, while the applied field is swept at an ideally slow rate.
The current around the ring and its free energy are evaluated. We partially
explain some of the known experimental features, and predict a considerably
large new feature: in the vicinity of a critical field, giant jumps are
expected
Activity level DNA evidence evaluation: on propositions addressing the actor or the activity
More often than not, the source of DNA traces found at a crime scene is not disputed, but the activity or timing of events that resulted in their transfer is. As a consequence, practitioners are increasingly asked to assign a value to DNA evidence given propositions about activities provided by prosecution and defense counsel. Given that the dispute concerns the nature of the activity that took place or the identity of the actor that carried out the activity, several factors will determine how to formulate the propositions. Determining factors are (1) whether defense claims the crime never took place, (2) whether defense claims someone other than the accused (either an unknown individual or a known person) performed the criminal activity, and (3) whether it is claimed and disputed that the suspect performed an alternative, legitimate activity or has a relation to the victim, the object, or the scene of crime that implies a legitimate interaction. Addressing such propositions using Bayesian networks, we demonstrate the effects of the various proposition sets on the evaluation of the evidence.Criminal Justice: Legitimacy, accountability, and effectivit
The Similarity Hypothesis in General Relativity
Self-similar models are important in general relativity and other fundamental
theories. In this paper we shall discuss the ``similarity hypothesis'', which
asserts that under a variety of physical circumstances solutions of these
theories will naturally evolve to a self-similar form. We will find there is
good evidence for this in the context of both spatially homogenous and
inhomogeneous cosmological models, although in some cases the self-similar
model is only an intermediate attractor. There are also a wide variety of
situations, including critical pheneomena, in which spherically symmetric
models tend towards self-similarity. However, this does not happen in all cases
and it is it is important to understand the prerequisites for the conjecture.Comment: to be submitted to Gen. Rel. Gra
Diagnostic test strategies in children at increased risk of inflammatory bowel disease in primary care
Background: In children with symptoms suggestive of inflammatory bowel disease (IBD) who present in primary care, the optimal test strategy for identifying those who require specialist care is unclear. We evaluated the following three test strategies to determine which was optimal for referring children with suspected IBD to specialist care: 1) alarm symptoms alone, 2) alarm symptoms plus c-reactive protein, and 3) alarm symptoms plus fecal calprotectin. Methods: A prospective cohort study was conducted, including children with chronic gastrointestinal symptoms referred to pediatric gastroenterology. Outcome was defined as IBD confirmed by endoscopy, or IBD ruled out by either endoscopy or unremarkable clinical 12 month follow-up with no indication for endoscopy. Test strategy probabilities were generated by logistic regression analyses and compared by area under the receiver operating characteristic curves (AUC) and decision curves. Results: We included 90 children, of whom 17 (19%) had IBD (n = 65 from primary care physicians, n = 25 from general pediatricians). Adding fecal calprotectin to alarm symptoms increased the AUC significantly from 0.80 (0.67-0.92) to 0.97 (0.93-1.00), but adding c-reactive protein to alarm symptoms did not increase the AUC significantly (p > 0.05). Decision curves confirmed these patterns, showing that alarm symptoms combined with fecal calprotectin produced the diagnostic test strategy with the highest net benefit at reasonable threshold probabilities. Conclusion: In primary care, when children are identified as being at high risk for IBD, adding fecal calprotectin testing to alarm symptoms was the optimal strategy for improving risk stratification
Renormalizing Partial Differential Equations
In this review paper, we explain how to apply Renormalization Group ideas to
the analysis of the long-time asymptotics of solutions of partial differential
equations. We illustrate the method on several examples of nonlinear parabolic
equations. We discuss many applications, including the stability of profiles
and fronts in the Ginzburg-Landau equation, anomalous scaling laws in
reaction-diffusion equations, and the shape of a solution near a blow-up point.Comment: 34 pages, Latex; [email protected]; [email protected]
Superdeformed rotational bands in the Mercury region; A Cranked Skyrme-Hartree-Fock-Bogoliubov study
A study of rotational properties of the ground superdeformed bands in \Hg{0},
\Hg{2}, \Hg{4}, and \Pb{4} is presented. We use the cranked
Hartree-Fock-Bogoliubov method with the {\skm} parametrization of the Skyrme
force in the particle-hole channel and a seniority interaction in the pairing
channel. An approximate particle number projection is performed by means of the
Lipkin-Nogami prescription. We analyze the proton and neutron quasiparticle
routhians in connection with the present information on about thirty presently
observed superdeformed bands in nuclei close neighbours of \Hg{2}.Comment: 26 LaTeX pages, 14 uuencoded postscript figures included, Preprint
IPN-TH 93-6
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