49,260 research outputs found
Interplay between the ionic and electronic density profiles in liquid metal surfaces
First principles molecular dynamics simulations have been performed for the
liquid-vapor interfaces of liquid Li, Mg, Al and Si. We analize the oscillatory
ionic and valence electronic density profiles obtained, their wavelengths and
the mechanisms behind their relative phase-shift.Comment: Accepted for publication in Journal of Chemical Physic
R-Band Imaging of Fields Around 1<z<2 Radiogalaxies
We have taken deep -band images of fields around five radiogalaxies:
0956+47, 1217+36, 3C256, 3C324 and 3C294 with . 0956+47 is found to
show a double nucleus. Our data on 1217+36 suggest the revision of its
classification as a radiogalaxy. We found a statistically significant excess of
bright () galaxies on scales of 2 arcmin around the radiogalaxies
(which have ) in our sample. The excess has been determined
empirically to be at level. It is remarkable that this excess
is not present for galaxies within the same area, suggesting that
the excess is not physically associated to the galaxies but due to intervening
groups and then related to gravitational lensing.Comment: 20 pages, uuencoded compressed PostScript including tables. Figures
available upon request. To appear in the March 1995 issue of The Astronomical
Journa
Length-weight relationships of coral reef fishes from the Alacran Reef, Yucatan, Mexico
Length-weight relationships were computed for 42 species of coral reef fishes from 14 families from the Alacran Reef (Yucatan, Mexico). A total of 1 892 individuals was used for this purpose. The fish species were caught by different fishing techniques such as fishhooks, harpoons, gill and trawl nets. The sampling period was from March 1998 to January 2000
Solar proton forecast system and procedures used during the Mariner 5 mission
Solar proton forecast system and procedures used during Mariner 5 missio
How to excite the internal modes of sine-Gordon solitons
We investigate the dynamics of the sine-Gordon solitons perturbed by
spatiotemporal external forces. We prove the existence of internal (shape)
modes of sine-Gordon solitons when they are in the presence of inhomogeneous
space-dependent external forces, provided some conditions (for these forces)
hold. Additional periodic time-dependent forces can sustain oscillations of the
soliton width. We show that, in some cases, the internal mode even can become
unstable, causing the soliton to decay in an antisoliton and two solitons. In
general, in the presence of spatiotemporal forces the soliton behaves as a
deformable (non-rigid) object. A soliton moving in an array of inhomogeneities
can also present sustained oscillations of its width. There are very important
phenomena (like the soliton-antisoliton collisions) where the existence of
internal modes plays a crucial role. We show that, under some conditions, the
dynamics of the soliton shape modes can be chaotic. A short report of some of
our results has been published in [J. A. Gonzalez et al., Phys. Rev. E, 65
(2002) 065601(R)].Comment: 14 .eps figures.To appear in Chaos, Solitons and Fractal
Genus and spot density in the COBE DMR first year anisotropy maps
A statistical analysis of texture on the {\it COBE}-DMR first year sky maps
based on the genus and spot number is presented. A generalized
statistic is defined in terms of ``observable'' quantities: the genus and spot
density that would be measured by different cosmic observers. This strategy
together with the use of Monte Carlo simulations of the temperature
fluctuations, including all the relevant experimental parameters, represent the
main difference with previous analyses. Based on the genus analysis we find a
strong anticorrelation between the quadrupole amplitude and the
spectral index of the density fluctuation power spectrum at recombination
of the form K for fixed
, consistent with previous works. The result obtained based on the spot
density is consistent with this relation. In addition to the
previous results we have determined, using Monte Carlo simulations, the minimum
uncertainty due to cosmic variance for the determination of the spectral index
with the genus analysis. This uncertainty is .Comment: 5 pages, uuencode file containing text and 1 figure. MNRAS in press
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