382 research outputs found
Spectral analysis of the background in ground-based, long-slit spectroscopy
This paper examines the variations, because of atmospheric extinction, of
broad-band visible spectra, obtained from long-slit spectroscopy, in the
vicinity of some stars, nebulae, and one faint galaxy.Comment: 12 figure
Reddening law and interstellar dust properties along Magellanic sight-lines
This study establishes that SMC, LMC and Milky Way extinction curves obey the
same extinction law which depends on the 2200A bump size and one parameter, and
generalizes the Cardelli, Clayton and Mathis (1989) relationship. This suggests
that extinction in all three galaxies is of the same nature. The role of linear
reddening laws over all the visible/UV wavelength range, particularly important
in the SMC but also present in the LMC and in the Milky Way, is also
highlighted and discussed.Comment: accepted for publication in Astrophysics and Space Science. 16 pages,
12 figures. Some figures are colour plot
An analysis of spectra in the Red Rectangle nebula
This paper presents an analysis of a series of spectra in the Red Rectangle
nebula. Only the reddest part of the spectra can safely be attributed to light
from the nebula, and indicates Rayleigh scattering by the gas, in conformity
with the large angles of scattering involved and the proximity of the star. In
the blue, light from HD44179, refracted or scattered in the atmosphere,
dominates the spectra. This paper questions the reliability of ground-based
observations of extended objects in the blue.Comment: 25 figure
Effective Lagrangian Approach to the Theory of Eta Photoproduction in the Region
We investigate eta photoproduction in the resonance region
within the effective Lagrangian approach (ELA), wherein leading contributions
to the amplitude at the tree level are taken into account. These include the
nucleon Born terms and the leading -channel vector meson exchanges as the
non-resonant pieces. In addition, we consider five resonance contributions in
the - and - channel; besides the dominant , these are:
and . The amplitudes for the
and the photoproduction near threshold have significant
differences, even as they share common contributions, such as those of the
nucleon Born terms. Among these differences, the contribution to the
photoproduction of the -channel excitation of the is the most
significant. We find the off-shell properties of the spin-3/2 resonances to be
important in determining the background contributions. Fitting our effective
amplitude to the available data base allows us to extract the quantity
, characteristic of the
photoexcitation of the resonance and its decay into the
-nucleon channel, of interest to precise tests of hadron models. At the
photon point, we determine it to be from
the old data base, and from a
combination of old data base and new Bates data. We obtain the helicity
amplitude for to be from the old data base, and from the combination of the old data base and new Bates
data, compared with the results of the analysis of pion photoproduction
yielding , in the same units.Comment: 43 pages, RevTeX, 9 figures available upon request, to appear in
Phys. Rev.
Mesoscopic superpositions of vibronic collective states of N trapped ions
We propose a scalable procedure to generate entangled superpositions of
motional coherent states and electronic states in N trapped ions. Beyond their
fundamental importance, these states may be of interest for quantum information
processing and may be used in experimental studies of decoherence.Comment: Final version, as published in Physical Review Letters. See also
further developments and applications in quant-ph/020207
RPBS: a web resource for structural bioinformatics
RPBS (Ressource Parisienne en Bioinformatique Structurale) is a resource dedicated primarily to structural bioinformatics. It is the result of a joint effort by several teams to set up an interface that offers original and powerful methods in the field. As an illustration, we focus here on three such methods uniquely available at RPBS: AUTOMAT for sequence databank scanning, YAKUSA for structure databank scanning and WLOOP for homology loop modelling. The RPBS server can be accessed at and the specific services at
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