16,081 research outputs found
Unique Quantum Stress Fields
We have recently developed a geometric formulation of the stress field for an
interacting quantum system within the local density approximation (LDA) of
density functional theory (DFT). We obtain a stress field which is invariant
with respect to choice of energy density. In this paper, we explicitly
demonstrate this uniqueness by deriving the stress field for different energy
densities. We also explain why particular energy densities give expressions for
the stress field that are more tractable than others, thereby lending
themselves more easily to first-principles calculations.Comment: To appear in Proceedings for Fundamental Physics of Ferroelectrics
(2001
Economic Evaluation of Catch Share Program: Rhode Island Fluke Fishery Sector Pilot Program
Catch share, sector allocation, fishery management, Demand and Price Analysis, Resource /Energy Economics and Policy, Q22, Q28,
Using Data to Drive State Improvement in Enrollment and Retention Performance
Outlines the RWJF Maximizing Enrollment program's core performance measures for Medicaid and Children's Health Insurance Program enrollment and retention, designed to assess state efforts to better utilize data to monitor and improve outreach and policy
Fast Characterization of Dispersion and Dispersion Slope of Optical Fiber Links using Spectral Interferometry with Frequency Combs
We demonstrate fast characterization (~1.4 microseconds) of both the
dispersion and dispersion slope of long optical fiber links (~25 km) using dual
quadrature spectral interferometry with an optical frequency comb. Compared to
previous spectral interferometry experiments limited to fiber lengths of
meters, the long coherence length and the periodic delay properties of
frequency combs, coupled with fast data acquisition, enable spectral
interferometric characterization of fibers longer by several orders of
magnitude. We expect that our method will be useful to recently proposed
lightwave techniques like coherent WDM and to coherent modulation formats by
providing a real time monitoring capability for the link dispersion. Another
area of application would be in stabilization of systems which perform
frequency and timing distribution over long fiber links using stabilized
optical frequency combs.Comment: 3 pages, 3 figures, Minor changes to tex
Plasma homocysteine, folate and vitamin B(12) compared between rural Gambian and UK adults.
The disease risk indicator plasma total homocysteine (tHcy) is influenced by genetic and environmental factors, including folate and vitamin B(12) status. Little is known about the determinants of tHcy in rural West Africa. We explored the hypothesis that tHcy in rural Gambian adults might vary between the sexes and physiological groups, and/or with folate and vitamin B(12) status. Comparisons were made with a British national survey. Non-pregnant Gambian women (n 158) had tHcy concentrations (geometric mean 9.0 micromol/l) similar to those of non-pregnant UK women (n 449; 9.4 micromol/l), whereas pregnant Gambian women (n 12) had significantly lower values (6.2 micromol/l). Gambian men (n 22) had significantly higher values (14.7 micromol/l) than British men (n 354; 10.8 micromol/l). Gambian lactating women and British men and women exhibited significant inverse relationships between log(e)(tHcy) and folate status; however, only the British subjects exhibited significant inverse relationships between loge(tHcy) and vitamin B(12) status. In the British sample, and in Gambian lactating women, folate and vitamin B(12) status variations together accounted for 20-25 % of the variation in log(e)(tHcy). Within the UK, black-skinned adults had folate and tHcy levels similar to those of their white-skinned counterparts, but significantly higher vitamin B(12) values. We conclude that, whereas folate and vitamin B(12) status are similar between British and rural Gambian populations, tHcy is higher in Gambian men and lower in pregnant Gambian women, and that serum vitamin B(12) values appear to be higher in black-skinned than white-skinned British subjects. Possible reasons are discussed
Ventricular tachycardia associated with lacosamide co-medication in drug-resistant epilepsy.
We report a case of sustained ventricular tachycardia following the initiation of lacosamide as adjunctive epilepsy treatment. A 49-year-old male with intractable frontal lobe seizures experienced severe ventricular tachycardia following the addition of 400Ā mg lacosamide to his existing regimen of carbamazepine, lamotrigine, clonazepam, and valproate. The tachycardia occurred during a cardiac stress test; stress tests prior to initiation of lacosamide were normal. Conduction defects, including QRS prolongation, persisted during hospitalization until lacosamide was discontinued. The patient had no prior history of cardiac arrhythmia but did possess cardiac risk factors, including hypertension, hypercholesterolemia, and low heart rate variability. This case represents one part of a growing body of literature suggesting a link between arrhythmia and use of lacosamide, which enhances slow inactivation of sodium channels in both the brain and the heart. We believe further study may be necessary to assess the safety of lacosamide in epilepsy patients with cardiac risk factors
Characteristics of magnetoacoustic sausage modes
Aims: We perform an advanced study of the fast magnetoacoustic sausage oscillations of coronal loops in the context of MHD coronal seismology to establish the dependence of the sausage mode period and cut-off wavenumber on the plasma- of the loop-filling plasma. A parametric study of the ratios for different harmonics of the mode is also carried out.
Methods: Full magnetohydrodynamic numerical simulations were performed using Lare2d, simulating hot, dense loops in a magnetic slab environment. The symmetric Epstein profile and a simple step-function profile were both used to model the density structure of the simulated loops. Analytical expressions for the cut-off wavenumber and the harmonic ratio between the second longitudinal harmonic and the fundamental were also examined.
Results: It was established that the period of the global sausage mode is only very weakly dependent on the value of the plasma- inside a coronal loop, which justifies the application of this model to hot flaring loops. The cut-off wavenumber kc for the global mode was found to be dependent on both internal and external values of the plasma-, again only weakly. By far the most important factor in this case was the value of the density contrast ratio between the loop and the surroundings. Finally, the deviation of the harmonic ratio P1/2P2 from the ideal non-dispersive case was shown to be considerable at low k, again strongly dependent on plasma density. Quantifying the behaviour of the cut-off wavenumber and the harmonic ratio has significant applications to the field of coronal seismology
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