3,731 research outputs found
Variational Formulation of Macro-Particle Models for Electromagnetic Plasma Simulations
A variational method is used to derive a self-consistent macro-particle model
for relativistic electromagnetic kinetic plasma simulations. Extending earlier
work [E. G. Evstatiev and B. A. Shadwick, J. Comput. Phys., vol. 245, pp.
376-398, 2013], the discretization of the electromagnetic Low Lagrangian is
performed via a reduction of the phase-space distribution function onto a
collection of finite-sized macro-particles of arbitrary shape and
discretization of field quantities onto a spatial grid. This approach may be
used with both lab frame coordinates or moving window coordinates; the latter
can greatly improve computational efficiency for studying some types of
laser-plasma interactions. The primary advantage of the variational approach is
the preservation of Lagrangian symmetries, which in our case leads to energy
conservation and thus avoids difficulties with grid heating. Additionally, this
approach decouples particle size from grid spacing and relaxes restrictions on
particle shape, leading to low numerical noise. The variational approach also
guarantees consistent approximations in the equations of motion and is amenable
to higher order methods in both space and time. We restrict our attention to
the 1-1/2 dimensional case (one coordinate and two momenta). Simulations are
performed with the new models and demonstrate energy conservation and low
noise.Comment: IEEE Transaction on Plasma Science (TPS) Special Issue: Plenary and
Invited Papers of the Pulsed Power and Plasma Science Conference (PPPS 2013
Investigations of Pressure Distribution on Fast Flying Bodies
The question to be treated is: how high is the pressure in the bow wave caused by a body flying at supersonic speed, and how far reaching are the destructive effects of that wave? The pressure distribution on an s.S. and an S. projectile of normal speed has been ascertained already by the methods of measurement used at the Ballistic Institute of the Technical Academy of the German Air Forces. Now similar investigations of the conditions on especially fast-flying bodies were carried out
The relevance of ERTS-1 data to the state of Ohio
There are no author-identified significant results in this report
Solar System Objects in the ISOPHOT 170 micron Serendipity Survey
The ISOPHOT Serendipity Survey (ISOSS) covered approximately 15 % of the sky
at a wavelength of 170 micron while the ISO satellite was slewing from one
target to the next. By chance ISOSS slews went over many solar system objects
(SSOs). We identified the comets, asteroids and planets in the slews through a
fast and effective search procedure based on N-body ephemeris and flux
estimates. The detections were analysed from a calibration and scientific point
of view. Through the measurements of the well-known asteroids Ceres, Pallas,
Juno and Vesta and the planets Uranus and Neptune it was possible to improve
the photometric calibration of ISOSS and to extend it to higher flux regimes.
We were also able to establish calibration schemes for the important slew end
data. For the other asteroids we derived radiometric diameters and albedos
through a recent thermophysical model. The scientific results are discussed in
the context of our current knowledge of size, shape and albedos, derived from
IRAS observations, occultation measurements and lightcurve inversion
techniques. In all cases where IRAS observations were available we confirm the
derived diameters and albedos. For the five asteroids without IRAS detections
only one was clearly detected and the radiometric results agreed with sizes
given by occultation and HST observations. Four different comets have clearly
been detected at 170 micron and two have marginal detections. The observational
results are presented to be used by thermal comet models in the future. The
nine ISOSS slews over Hale-Bopp revealed extended and asymmetric structures
related to the dust tail. We attribute the enhanced emission in post-perihelion
observations to large particles around the nucleus. The signal patterns are
indicative of a concentration of the particles in trail direction.Comment: 15 pages, 6 figures, 6 tables; Accepted for publication in Astronomy
and Astrophysic
The Activity of the Serotonin Receptor 2C is Regulated by Alternative Splicing
The central nervous system-specific serotonin receptor 2C (5HT2C) controls key physiological functions, such as food intake, anxiety, and motoneuron activity. Its deregulation is involved in depression, suicidal behavior, and spasticity, making it the target for antipsychotic drugs, appetite controlling substances, and possibly anti-spasm agents. Through alternative pre-mRNA splicing and RNA editing, the 5HT2C gene generates at least 33 mRNA isoforms encoding 25 proteins. The 5HT2C is a G-protein coupled receptor that signals through phospholipase C, influencing the expression of immediate/early genes like c-fos. Most 5HT2C isoforms show constitutive activity, i.e., signal without ligand binding. The constitutive activity of 5HT2C is decreased by pre-mRNA editing as well as alternative pre-mRNA splicing, which generates a truncated isoform that switches off 5HT2C receptor activity through heterodimerization; showing that RNA processing regulates the constitutive activity of the 5HT2C system. RNA processing events influencing the constitutive activity target exon Vb that forms a stable double stranded RNA structure with its downstream intron. This structure can be targeted by small molecules and oligonucleotides that change exon Vb alternative splicing and influence 5HT2C signaling in mouse models, leading to a reduction in food intake. Thus, the 5HT2C system is a candidate for RNA therapy in multiple models of CNS disorders
Work-life conflicts and health among Swiss physicians--in comparison with other university graduates and with the general Swiss working population
QUESTION UNDER STUDY: The present study aimed to compare the prevalence of work-life conflicts and the health status of physicians, with a representative sample of university graduates as well as with a representative sample of the general Swiss working population. Furthermore, it aimed to analyse whether work-life conflicts correlate with the health of physicians, as it does in the general working population. METHODS: The present cross-sectional study analysed data from 2007 originating from the SwissMedCareer Study (a prospective cohort study of physicians who graduated in 2001; n = 543) and the Swiss Household Panel (a representative Swiss survey on living and working conditions; university graduates of the same age range: n = 172, general working population of the same age range: n = 670). Data were analysed with Chi2 tests, correlations and logistic regressions. RESULTS: Physicians reported strong time-based as well as strain-based work-life conflicts more frequently than university graduates and the general working population. Significantly more physicians reported "moderate" to "very poor" health than the other two samples. Surprisingly, on the other side of the scale ("very good" health), physicians outnumbered the other samples too. Strong associations between work-life conflict and self-rated health as well as various health complaints were found for physicians. CONCLUSION: The high prevalence of work-life conflicts may explain the comparably high prevalence of poor self-rated health in the physicians' sample
A statistical model of climates in the southwestern United States
EXTRACT (SEE PDF FOR FULL ABSTRACT):
We describe an empirical-statistical model of climates of the southwestern United States. Boundary conditions include sea surface temperatures, atmospheric transmissivity, and topography. Independent variables are derived from the boundary conditions along 1000-km paths of atmospheric circulation. ... Predictor equations are derived over a larger region than the application area to allow for the increased range of paleoclimate. This larger region is delimited by the autocorrelation properties of climatic data
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