12,524 research outputs found
On the exposure to mobile phone radiation in trains
This report presents theoretical estimates of the Power Density levels which
may be reached inside trains. Two possible sources of high levels of radiation
are discussed. The first one arises since the walls of the wagons are metallic
and therefore bounce back almost all radiation impinging on them. The second is
due to the simultaneous emission of a seemingly large number of nearby
telephones. The theoretical study presented here shows that Power Densities
stay at values below reference levels always.Comment: 9 pages, 1 figur
The spectroscopic orbits and the geometrical configuration of the symbiotic binary AR Pavonis
We analyze optical and near infrared spectra of intermediate and high
resolution of the eclipsing symbiotic system AR Pavonis. We have obtained the
radial velocity curves for the red and the hot component from the M-giant
absorption lines and from the wings of Halpha, H and He II4686 emission
profiles, respectively. From the orbital elements we have derived the masses,
Mgiant=2.5 and Mhot =1.0 solar masses, for the red giant and the hot component,
respectively. We also present and discuss radial velocity patterns in the blue
cF absorption spectrum as well as various emission lines. In particular, we
confirm that the blue absorption lines are associated with the hot component.
The radial velocity curve of the blue absorption system, however, does not
track the hot companion's orbital motion in a straightforward way, and its
departures from an expected circular orbit are particularly strong when the hot
component is active. We suggest that the cF-type absorption system is formed in
material streaming from the giant presumably in a region where the stream
encounters an accretion disk or an extended envelope around the hot component.
The broad emission wings originate from the inner accretion disk or the
envelope around the hot star.We also suggest that the central absorption in H
profiles is formed in a neutral portion of the cool giant's wind which is
strongly concentrated towards the orbital plane. The nebula in AR Pav seems to
be bounded by significant amount of neutral material in the orbital plane. The
forbidden emission lines are probably formed in low density ionized regions
extended in polar directions and/or the wind-wind interaction zone.Comment: 12 pages, 5 figures, accepted by A&
Effects of Bose-Einstein Condensation on forces among bodies sitting in a boson heat bath
We explore the consequences of Bose-Einstein condensation on
two-scalar-exchange mediated forces among bodies that sit in a boson gas. We
find that below the condensation temperature the range of the forces becomes
infinite while it is finite at temperatures above condensation.Comment: 10 pages, 2 figure
Gluon Vortices and Induced Magnetic Field in Compact Stars
The natural candidates for the realization of color superconductivity are the
extremely dense cores of compact stars, many of which have very large magnetic
fields, especially the so-called magnetars. In this paper we discuss how a
color superconducting core can serve to generate and enhance the stellar
magnetic field without appealing to a magnetohydrodynamic dynamo mechanism.Comment: To appear in the Proceedings of the VII Latin American Symposium on
Nuclear Physics and Applications. Cusco (Peru) June 200
Symmetry-induced interference effects in metalloporphyrin wires
Organo-metallic molecular structures where a single metallic atom is embedded
in the organic backbone are ideal systems to study the effect of strong
correlations on their electronic structure. In this work we calculate the
electronic and transport properties of a series of metalloporphyrin molecules
sandwiched by gold electrodes using a combination of density functional theory
and scattering theory. The impact of strong correlations at the central
metallic atom is gauged by comparing our results obtained using conventional
DFT and DFT+U approaches. The zero bias transport properties may or may not
show spin-filtering behavior, depending on the nature of the d state closest to
the Fermi energy. The type of d state depends on the metallic atom and gives
rise to interference effects that produce different Fano features. The
inclusion of the U term opens a gap between the d states and changes
qualitatively the conductance and spin-filtering behavior in some of the
molecules. We explain the origin of the quantum interference effects found as
due to the symmetry-dependent coupling between the d states and other molecular
orbitals and propose the use of these systems as nanoscale chemical sensors. We
also demonstrate that an adequate treatment of strong correlations is really
necessary to correctly describe the transport properties of metalloporphyrins
and similar molecular magnets
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