23,422 research outputs found
Identification and molecular characterization of Pear blister canker viroid isolates in Campania (Southern Italy)
A new Viola (Violaceae) from the Argentinian Andes
Viola beati, a hitherto unknown species of V. sect. Andinium (Violaceae) is described and illustrated. It is an inconspicuous, diminutive, perennial forb currently known from only one locality in NW Argentina. We draw attention to its morphology, ecology, rarity and endemism. The differences between V. beati and its apparently only close relative, V. singularis J. M. Watson & A. R. Flores, are defined
Experimental proposal for accurate determination of the phase relaxation time and testing a formation of thermalized non-equilibrated matter in highly excited quantum many-body systems
We estimate how accurate the phase relaxation time of quantum many-body
systems can be determined from data on forward peaking of evaporating protons
from a compound nucleus. The angular range and accuracy of the data needed for
a reliable determination of the phase relaxation time are evaluated. The
general method is applied to analyze the inelastic scattering of 18 MeV protons
from Pt for which previously measured double differential cross sections for
two angles in the evaporating domain of the spectra show a strong forward
peaking. A new experiment for an improved determination of the phase relaxation
time is proposed. The experiment is also highly desirable for an accurate test
of a formation of thermalized non-equilibrated matter in quantum many-body
systems.Comment: 5 pages, 3 figure
Signatures of rocky planet engulfment in HAT-P-4. Implications for chemical tagging studies
Aims. To explore the possible chemical signature of planet formation in the
binary system HAT-P-4, by studying abundance vs condensation temperature Tc
trends. The star HAT-P-4 hosts a planet detected by transits while its stellar
companion does not have any detected planet. We also study the Lithium content,
which could shed light on the problem of Li depletion in exoplanet host stars.
Conclusions. The exoplanet host star HAT-P-4 is found to be ~0.1 dex more metal
rich than its companion, which is one of the highest differences in metallicity
observed in similar systems. This could have important implications for
chemical tagging studies, disentangling groups of stars with a common origin.
We rule out a possible peculiar composition for each star as lambda Boo, delta
Scuti or a Blue Straggler. The star HAT-P-4 is enhanced in refractory elements
relative to volatile when compared to its stellar companion. Notably, the
Lithium abundance in HAT-P-4 is greater than in its companion by ~0.3 dex,
which is contrary to the model that explains the Lithium depletion by the
presence of planets. We propose a scenario where, at the time of planet
formation, the star HAT-P-4 locked the inner refractory material in
planetesimals and rocky planets, and formed the outer gas giant planet at a
greater distance. The refractories were then accreted onto the star, possibly
due to the migration of the giant planet. This explains the higher metallicity,
the higher Lithium content, and the negative Tc trend detected. A similar
scenario was recently proposed for the solar twin star HIP 68468, which is in
some aspects similar to HAT-P-4. We estimate a mass of at least Mrock ~ 10
Mearth locked in refractory material in order to reproduce the observed Tc
trends and metallicity.Comment: 5 pages, 6 figures, A&A Letters accepte
Apple dimple fruit viroid sequence variability and its specific detection by multiplex fluorescent RT-PCR in the presence of apple scar skin viroid.
How was the Hubble sequence 6 Gyrs ago?
The way galaxies assemble their mass to form the well-defined Hubble sequence
is amongst the most debated topic in modern cosmology. One difficulty is to
link distant galaxies to those at present epoch. We aim at establishing how
were the galaxies of the Hubble sequence, 6 Gyrs ago. We intend to derive a
past Hubble sequence that can be causally linked to the present-day one. We
selected samples of nearby galaxies from the SDSS and of distant galaxies from
the GOODS survey. We verified that each sample is representative of galaxies.
We further showed that the observational conditions necessary to retrieve their
morphological classification are similar in an unbiased way. Morphological
analysis has been done in an identical way for all galaxies in the two samples.
We found an absence of number evolution for elliptical and lenticular galaxies,
which strikingly contrasts with the strong evolution of spiral and peculiar
galaxies. Spiral galaxies were 2.3 times less abundant in the past, that is
exactly compensated by the strong decrease by a factor 5 of peculiar galaxies.
It strongly suggests that more than half of the present-day spirals had
peculiar morphologies, 6 Gyrs ago, and this has to be accounted by any scenario
of galactic disk evolution and formation. The past Hubble sequence can be used
to test these scenarios as well as to test evolution of fundamental planes for
spirals and bulges.Comment: Version accepted by Astronomy and Astrophysics, October 21 2009.
Including low resolution images. 11 pages, 8 figure
The Evolution of the Baryonic Tully-Fisher Relation over the past 6 Gyr
Scaling relations are salient ingredients of galaxy evolution and formation
models. I summarize results from the IMAGES survey, which combines
spatially-resolved kinematics from FLAMES/GIRAFFE with imaging from HST/ACS and
other facilities. Specifically, I will focus on the evolution of the stellar
mass and baryonic Tully-Fisher Relations (TFR) from z=0.6 down to z=0. We found
a significant evolution in zero point and scatter of the stellar mass TFR
compared to the local Universe. Combined with gas fractions derived by
inverting the Schmidt-Kennicutt relation, we derived for the first time a
baryonic TFR at high redshift. Conversely to the stellar mass TFR, the baryonic
relation does not appear to evolve in zero point, which suggests that most of
the reservoir of gas converted into stars over the past 6 Gyr was already
gravitationally bound to galaxies at z=0.6.Comment: To be published in the proceedings of the IAU Symposium 277 "Tracing
the Ancestry of Galaxies"; 4 pages, 1 figur
Cluster Cores, Gravitational Lensing, and Cosmology
Many multiply--imaged quasars have been found over the years, but none so far
with image separation in excess of 8\arcsec. The absence of such large
splittings has been used as a test of cosmological models: the standard Cold
Dark Matter model has been excluded on the basis that it predicts far too many
large--separation double images. These studies assume that the lensing
structure has the mass profile of a singular isothermal sphere. However, such
large splittings would be produced by very massive systems such as clusters of
galaxies, for which other gravitational lensing data suggest less singular mass
profiles. Here we analyze two cases of mass profiles for lenses: an isothermal
sphere with a finite core radius (density , and a Hernquist profile (). We find that small core radii
kpc, as suggested by the cluster data, or large a \gsim 300 h^{-1} kpc, as
needed for compatibility with gravitational distortion data, would reduce the
number of large--angle splittings by an order of magnitude or more. Thus, it
appears that these tests are sensitive both to the cosmological model (number
density of lenses) and to the inner lens structure, which is unlikely to depend
sensitively on the cosmology, making it difficult to test the cosmological
models by large--separation quasar lensing until we reliably know the structure
of the lenses themselves.Comment: 17 pages, uuencoded compressed tarred postscript file including text
and 1 figure. To appear in January 20, 1996 issue of ApJ Letter
- …