6,390 research outputs found
Study of the winter 2005 Antarctica polar vortex
During winter and springtime, the flow above Antarctica at high altitude
(upper troposphere and stratosphere) is dominated by the presence of a vortex
centered above the continent. It lasts typically from August to November. This
vortex is characterized by a strong cyclonic jet centered above the polar high.
In a recent study of our group (Hagelin et al., 2008) of four different sites
in the Antarctic internal plateau (South Pole, Dome C, Dome A and Dome F), it
was made the hypothesis that the wind speed strength in the upper atmosphere
should be related to the distance of the site to the center of the Antarctic
polar vortex. This high altitude wind is very important from an astronomical
point of view since it might trigger the onset of the optical turbulence and
strongly affect other optical turbulence parameters. What we are interested in
here is to localize the position of the minimum value of the wind speed at high
altitude in order to confirm the hypothesis of Hagelin et al. (2008).Comment: 3rd ARENA conference, 11-15 May 2009 EAS Publication Serie
Magnetic Resonance
Contains research objectives, summary of research and reports on one research project.National Science Foundation (Grant GP-19988)National Institutes of Health (Grant 5 RO1 GM16552-03
Magnetic Resonance
Contains research objectives.Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 28-043-AMC-02536(E
The CEDAR Project
We describe the plans and objectives of the CEDAR project (Combined e-Science
Data Analysis Resource for High Energy Physics) newly funded by the PPARC
e-Science programme in the UK. CEDAR will combine the strengths of the well
established and widely used HEPDATA database of HEP data and the innovative
JetWeb data/Monte Carlo comparison facility, built on the HZTOOL package, and
will exploit developing grid technology. The current status and future plans of
both of these individual sub-projects within the CEDAR framework are described,
showing how they will cohesively provide (a) an extensive archive of Reaction
Data, (b) validation and tuning of Monte Carlo programs against these reaction
data sets, and (c) a validated code repository for a wide range of HEP code
such as parton distribution functions and other calculation codes used by
particle physicists. Once established it is envisaged CEDAR will become an
important Grid tool used by LHC experimentalists in their analyses and may well
serve as a model in other branches of science where there is a need to compare
data and complex simulations.Comment: 4 pages, 4 postscript figures, uses CHEP2004.cls. Presented at
Computing in High-Energy Physics (CHEP'04), Interlaken, Switzerland, 27th
September - 1st October 200
Consistent thermodynamics for spin echoes
Spin-echo experiments are often said to constitute an instant of
anti-thermodynamic behavior in a concrete physical system that violates the
second law of thermodynamics. We argue that a proper thermodynamic treatment of
the effect should take into account the correlations between the spin and
translational degrees of freedom of the molecules. To this end, we construct an
entropy functional using Boltzmann macrostates that incorporates both spin and
translational degrees of freedom. With this definition there is nothing special
in the thermodynamics of spin echoes: dephasing corresponds to Hamiltonian
evolution and leaves the entropy unchanged; dissipation increases the entropy.
In particular, there is no phase of entropy decrease in the echo. We also
discuss the definition of macrostates from the underlying quantum theory and we
show that the decay of net magnetization provides a faithful measure of entropy
change.Comment: 15 pages, 2 figs. Changed figures, version to appear in PR
Doxycycline or Ofloxacin for Outpatient Chlamydial Pelvic Inflammatory Disease? A Cost-Benefit and Cost-Effectiveness Analysis
Objective: The current Centers for Disease Control and Prevention
(CDC) guidelines include 2 drugs, doxycycline and ofloxacin, for
treatment of the chlamydial component of outpatient pelvic
inflammatory disease (PID). Although ofloxacin costs about $90
more than doxycycline, doxycycline is frequently associated with
side effects and patient compliance with this drug is probably
poor. Because clinicians have little information by which to judge
the tradeoffs between price and compliance for these 2
antibiotics, we examined the impact of patient compliance in the
evaluation of the costs and benefits of using each drug
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