7,789 research outputs found
Magnetic component of Yang-Mills plasma
Confinement in non-Abelian gauge theories is commonly ascribed to percolation
of magnetic monopoles, or strings in the vacuum. At the deconfinement phase
transition the condensed magnetic degrees of freedom are released into gluon
plasma as thermal magnetic monopoles. We point out that within the percolation
picture lattice simulations can be used to estimate the monopole content of the
gluon plasma. We show that right above the critical temperature the monopole
density remains a constant function of temperature, as for a liquid, and then
grows, like for a gas.Comment: 4 pages, no figures; replaced to match published versio
Influenced of Fe buffer thickness on the crystalline quality and the transport properties of Fe/Ba(Fe1-xCox)2As2 bilayers
The implementation of an Fe buffer layer is a promising way to obtain
epitaxial growth of Co-doped BaFe2As2 (Ba-122). However, the crystalline
quality and the superconducting properties of Co-doped Ba-122 are influenced by
the Fe buffer layer thickness, dFe. The well-textured growth of the Fe/Ba-122
bilayer with dFe = 15 nm results in a high Jc of 0.45 MAcm at 12 K in
self-field, whereas a low Jc value of 61000 Acm is recorded for the
bilayer with dFe = 4 nm at the corresponding reduced temperature due to the
presence of grain boundaries
The Inhibition of Mixing in Chaotic Quantum Dynamics
We study the quantum chaotic dynamics of an initially well-localized wave
packet in a cosine potential perturbed by an external time-dependent force. For
our choice of initial condition and with small but finite, we find that
the wave packet behaves classically (meaning that the quantum behavior is
indistinguishable from that of the analogous classical system) as long as the
motion is confined to the interior of the remnant separatrix of the cosine
potential. Once the classical motion becomes unbounded, however, we find that
quantum interference effects dominate. This interference leads to a long-lived
accumulation of quantum amplitude on top of the cosine barrier. This pinning of
the amplitude on the barrier is a dynamic mechanism for the quantum inhibition
of classical mixing.Comment: 20 pages, RevTeX format with 6 Postscript figures appended in
uuencoded tar.Z forma
Magnetic Moments of Decuplet Baryons in Light Cone QCD
We calculate the magnetic moments of decuplet baryons containing strange
quarks within the framework of light cone QCD sum rules taking into account the
SU(3) flavor symmetry breaking effects. It is obtained that magnetic moments of
the neutral \sso and \xis0 baryons are mainly determined by the SU(3)
breaking terms. A comparison of our results on the magnetic moments of the
decuplet baryons with the predictions of other approaches is presented.Comment: Latex, 20 pages, 6 figure
Quest for Rare Events in three-dimensional Mesoscopic Disordered Metals
The study reports on the first large statistics numerical experiment
searching for rare eigenstates of anomalously high amplitudes in
three-dimensional diffusive metallic conductors. Only a small fraction of a
huge number of investigated eigenfunctions generates the far asymptotic tail of
their amplitude distribution function. The relevance of the relationship
between disorder and spectral averaging, as well as of the quantum transport
properties of the investigated mesoscopic samples, for the numerical
exploration of eigenstate statistics is divulged. The quest provides exact
results to serve as a reference point in understanding the limits of
approximations employed in different analytical predictions, and thereby the
physics (quantum vs semiclassical) behind large deviations from the universal
predictions of random matrix theory.Comment: 5 pages, 3 embedded EPS figures, figure 3 replaced with new findings
on spectral vs disorder averagin
Small Is Beautiful: Why Profundaplasty Should Not Be Forgotten
Background: Surgical profundaplasty (SP)is used mainly as an adjunct to endovascular management of peripheral vascular disease (PAD) today. Results from earlier series of profundaplasty alone have been controversial, especially regarding its hemodynamic effect. The question is: Can profundaplasty alone still be useful? Our aim was to evaluate its role in the modern management of vascular patients. Methods: This was a retrospective outcome study. A consecutive series of 97 patients (106 legs) from January 2000 through December 2003 were included. In 55 (52%) legs, the superficial femoral artery was occluded. These patients were included in the current analysis. Of these patients 14 (25%) were female. Mean age was 71 ((11) years. Nineteen (35%) were diabetic. The indication for operation was claudication in 29 (53%), critical leg ischemia (CLI) in 26 (47%), either with rest pain in 17 (31%), or ulcer/gangrene in 9 (16%). Endarterectomy with patch angioplasty with bovine pericardium was performed in all cases. Mean follow-up was 33(14 months. Mean preoperative ankle brachial index (ABI) was 0.6. Sustained clinical efficacy was defined as upward shift of 1 or greater on the Rutherford scale without repeat target limb revascularization (TLR) or amputation. Mortality, morbidity, need for TLR, or amputation were separate endpoints. Results: Postoperatively, ABI was significantly improved (mean=0.7), in 24 (44%) by more than 0.15. At three years, cumulative clinical success rate was 80%. Overall, patients with claudication had a better outcome than those with CLI (p=0.04). Two (4%) major amputations and 2 (4%) minor ones were performed, all in patients with CLI. None of the 9 (16%) ulcers healed. Conclusion: Profundaplasty is still a valuable option for patients with femoral PAD and claudication without tissue loss. It is a straightforward procedure that combines good efficacy with low complication rates. Further endovascular treatment may be facilitated. It is not useful for patients with the combination of critical ischemia and tissue los
Acute hypoglycemia impairs executive cognitive function in adults with and without type 1 diabetes
OBJECTIVE: Acute hypoglycemia impairs cognitive function in several domains. Executive cognitive function governs organization of thoughts, prioritization of tasks, and time management. This study examined the effect of acute hypoglycemia on executive function in adults with and without diabetes. RESEARCH DESIGN AND METHODS: Thirty-two adults with and without type 1 diabetes with no vascular complications or impaired awareness of hypoglycemia were studied. Two hyperinsulinemic glucose clamps were performed at least 2 weeks apart in a single-blind, counterbalanced order, maintaining blood glucose at 4.5 mmol/L (euglycemia) or 2.5 mmol/L (hypoglycemia). Executive functions were assessed with a validated test suite (Delis-Kaplan Executive Function). A general linear model (repeated-measures ANOVA) was used. Glycemic condition (euglycemia or hypoglycemia) was the within-participant factor. Between-participant factors were order of session (euglycemia-hypoglycemia or hypoglycemia-euglycemia), test battery used, and diabetes status (with or without diabetes). RESULTS: Compared with euglycemia, executive functions (with one exception) were significantly impaired during hypoglycemia; lower test scores were recorded with more time required for completion. Large Cohen d values (>0.8) suggest that hypoglycemia induces decrements in aspects of executive function with large effect sizes. In some tests, the performance of participants with diabetes was more impaired than those without diabetes. CONCLUSIONS: Executive cognitive function, which is necessary to carry out many everyday activities, is impaired during hypoglycemia in adults with and without type 1 diabetes. This important aspect of cognition has not received previous systematic study with respect to hypoglycemia. The effect size is large in terms of both accuracy and speed
Relaxation and Localization in Interacting Quantum Maps
We quantise and study several versions of finite multibaker maps. Classically
these are exactly solvable K-systems with known exponential decay to global
equilibrium. This is an attempt to construct simple models of relaxation in
quantum systems. The effect of symmetries and localization on quantum transport
is discussed.Comment: 32 pages. LaTex file. 9 figures, not included. For figures send mail
to first author at '[email protected]
Inversionless gain in a three-level system driven by a strong field and collisions
Inversionless gain in a three-level system driven by a strong external field
and by collisions with a buffer gas is investigated. The mechanism of
populating of the upper laser level contributed by the collision transfer as
well as by relaxation caused by a buffer gas is discussed in detail. Explicit
formulae for analysis of optimal conditions are derived. The mechanism
developed here for the incoherent pump could be generalized to other systems.Comment: RevTeX, 9 pages, 4 eps figure
Forming double-barred galaxies from dynamically cool inner disks
About one-third of early-type barred galaxies host small-scale secondary bars. The formation and evolution of such double-barred (S2B) galaxies remain far from being well understood. In order to understand the formation of such systems, we explore a large parameter space of isolated pure-disk simulations. We show that a dynamically cool inner disk embedded in a hotter outer disk can naturally generate a steady secondary bar while the outer disk forms a large-scale primary bar. The independent bar instabilities of inner and outer disks result in long-lived double-barred structures whose dynamical properties are comparable to those in observations. This formation scenario indicates that the secondary bar might form from the general bar instability, the same as the primary bar. Under some circumstances, the interaction of the bars and the disk leads to the two bars aligning or single, nuclear, bars only. Simulations that are cool enough of the center to experience clump instabilities may also generate steady S2B galaxies. In this case, the secondary bars are “fast,” i.e., the bar length is close to the co-rotation radius. This is the first time that S2B galaxies containing a fast secondary bar are reported. Previous orbit-based studies had suggested that fast secondary bars were not dynamically possibl
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