135 research outputs found
VLT/UVES constraints on the carbon isotope ratio 12C/13C at z=1.15 toward the quasar HE 0515-4414
We analyzed the CI lines associated with the damped Ly-alpha system observed
at zabs = 1.15 in the spectrum of HE 0515-4414 to derive the 12C/13C ratio. The
spectrum was obtained by means of the UV-Visual Echelle Spectrograph (UVES) at
the ESO Very Large Telescope (VLT). The obtained lower limit 12C/13C > 80
(2sigma C.L.) shows for the first time that the abundance of 13C in the
extragalactic intervening clouds is very low. This rules out a significant
contribution from intermediate-mass stars to the chemical evolution of matter
sampled by this line of sight. The estimated low amount of 13C is in agreement
with low abundances of nitrogen observed in damped Ly-alpha systems - the
element produced in the same nuclear cycles and from about the same stars as
13C.Comment: 4 pages, 3 figures, published in A&A, 447, L21-L24, 200
Metal abundances and kinematics of quasar absorbers.- I. Absorption systems toward J2233-606
The metal line profiles of different ions observed in high HI column density
systems [N(HI) > 10^{16} cm^{-2}] in quasar spectra can be used to constrain
the ionization structure and kinematic characteristics of the absorbers. For
these purposes, a modified Monte Carlo Inversion (MCI) procedure was applied to
the study of three absorption systems in the spectrum of the HDF-South quasar
J2233-606 obtained with the UVES spectrograph at the VLT/Kueyen telescope. The
MCI does not confirm variations of metal abundances within separate systems
which were discussed in the literature. Instead, we found that an assumption of
a homogeneous metal content and a unique photoionizing background is sufficient
to describe the observed complex metal profiles. It was also found that the
linear size L and the line-of-sight velocity dispersion sigma_v measured within
the absorbers obey a scaling relation, namely, sigma_v increases with
increasing L, and that metal abundance is inversely proportional to the linear
size of the system: the highest metallicity was measured in the system with the
smallest L.Comment: 10 pages, 7 ps figures, accepted to A&
The influence of nova nucleosynthesis on the chemical evolution of the Galaxy
We adopt up-to-date yields of 7Li, 13C, 15N from classical novae and use a
well tested model for the chemical evolution of the Milky Way in order to
predict the temporal evolution of these elemental species in the solar
neighborhood. In spite of major uncertainties due to our lack of knowledge of
metallicity effects on the final products of explosive nucleosynthesis in nova
outbursts, we find a satisfactory agreement between theoretical predictions and
observations for 7Li and 13C. On the contrary, 15N turns out to be overproduced
by about an order of magnitude.Comment: 8 pages, latex, 3 figures. To appear in "The Chemical Evolution of
the Milky Way: Stars versus Clusters", eds. F. Giovannelli and F. Matteucci
(Kluwer: Dordrecht
A new 21-cm absorber identified with an galaxy
We present Giant Metrewave Radio Telescope (GMRT) observations of redshifted
21-cm absorption from the metal line absorption system towards PKS
1243-072. HI absorption is clearly detected; the absorption profile has a
velocity spread of km/s. Detection of 21-cm absorption indicates that
the absorber has an HI column density large enough to be classified as a damped
Lyman- system. Follow up ground based optical imaging and spectroscopy
allow us to identify the absorber with an galaxy at an impact
parameter of kpc from the line of sight to the QSO. The absorbing
galaxy is unusual in that it has bright emission lines. On the basis of the
optical spectrum we are unable to uniquely classify the galaxy since its
emission line ratios lie in the transition region between starburst and Seyfert
II type spectra.Comment: 5 pages, 3 figures. Accepted for publication in Astronomy &
Astrophysic
Sulphur and zinc abundances in Galactic stars and damped Lyman-alpha systems
High resolution spectra of 34 halo population dwarf and subgiant stars have
been obtained with VLT/UVES and used to derive sulphur abundances from the
8694.0, 8694.6 A and 9212.9, 9237.5 A SI lines. In addition, iron abundances
have been determined from 19 FeII lines and zinc abundances from the 4722.2,
4810.5 ZnI lines. The abundances are based on a classical 1D, LTE model
atmosphere analysis, but effects of 3D hydrodynamical modelling on the [S/Fe],
[Zn/Fe] and [S/Zn] ratios are shown to be small. We find that most halo stars
with metallicities in the range -3.2 < [Fe/H] < -0.8 have a near-constant
[S/Fe] = +0.3; a least square fit to [S/Fe] vs. {Fe/H] shows a slope of only
-0.04 +/- 0.01. Among halo stars with -1.2 < [Fe/H] < -0.8 the majority have
[S/Fe] ~ +0.3, but two stars (previously shown to have low [alpha/Fe] ratios)
have [S/Fe] ~ 0. For disk stars with [Fe/H] > -1, [S/Fe] decreases with
increasing [Fe/H]. Hence, sulphur behaves like other typical alpha-capture
elements, Mg, Si and Ca. Zinc, on the other hand, traces iron over three orders
of magnitude in [Fe/H], although there is some evidence for a small systematic
Zn overabundance ([Zn/Fe] ~ +0.1) among metal-poor disk stars and for halo
stars with [Fe/H] < -2.0. Recent measurements of S and Zn in ten damped
Ly-alpha systems (DLAs) with redshifts between 1.9 and 3.4 and zinc abundances
in the range -2.1 < [Zn/H] < -0.15 show an offset relative to the [S/Zn] -
[Zn/H] relation in Galactic stars. Possible reasons for this offset are
discussed, including low and intermittent star formation rates in DLAs.Comment: Accepted for publication in A&A. 16pages; 9 figure
Extremely metal-poor Lyman limit system at z = 2.917 toward the quasar HE 0940-1050
We report on detailed Monte Carlo inversion analysis of the Lyman limit
system observed at z = 2.917 in the VLT/UVES spectrum of the quasar HE
0940-1050. Metal absorption lines of carbon and silicon in three ionization
stages and numerous atomic hydrogen lines have been analyzed simultaneously. It
is found that in order to match the observations, the shape of the ultraviolet
background ionizing spectrum of Haardt & Madau (1996) should be modified: a
spectrum with a higher intensity of the emission feature at 3 Ryd is required.
It is also found that synthetic galactic spectra (or different mixtures of them
with power law spectra) cannot reproduce the observations, indicating that the
stellar contribution to the ionizing background is negligible at z ~= 3. For
the first time a very low carbon abundance of [C/H] = -2.93+/-0.13 and the
abundance ratio [Si/C] = 0.35+/-0.15 are directly measured in the Lyman limit
system with N(H I) = 3.2 10^{17} cm^{-2}. If the absorber at z = 2.917 provides
an example of a pristine gas enriched by the nucleosynthetic products of early
generations of stars, then the measured value of [Si/C] seems to indicate that
the initial mass functions for these stellar populations are constrained to
intermediate masses, M_up <= 25M_solar.Comment: 7 pages, 4 figures, A&A in pres
Pharmacological evaluation of Prosopis ruscifolia extract on lipid profile in hyperglycemic and hyperlipidemic mice
La diabetes es una patología crónica grave, con efectos a largo plazo que incluyen daño a los vasos sanguíneos o dislipidemia diabética. La dislipidemia diabética se caracteriza por el aumento de las concentraciones de triglicéridos de baja densidad y lipoproteínas y una disminución de las lipoproteínas de alta densidad HDL-colesterol (HDL-c). Este estudio tuvo como objetivo evaluar el efecto de Prosopis ruscifolia sobre el perfil lipídico en ratones suizos albinos con hiperglucemia e hiperlipidemia.CONACYT – Consejo Nacional de Ciencia y TecnologíaPROCIENCI
Clonal selection of Eucalyptus grandis x Eucalyptus globulus for productivity, adaptability, and stability, using SNP markers.
In Uruguay, reforestations with Eucalyptus sp. is of fundamental importance to supply paper, pulp, and wood production. This study investigates genetic, productivity, stability, and adaptability parameters in the selection of Eucalypts grandis x Eucalyptus globulus full-sib hybrid clones. The study was conducted in a clonal test, repeated in two different soils types, in Rio Negro State, Uruguay. The population was characterized phenotypically for diameter at breast height (dbh) and genotyped for SNP markers (EuCHIP60K chip). Mean dbh was similar between sites and the genotype?environment interaction was simple. We found high genotype correlation in clone performance between environments (0.708), indicating the possibility of selecting the same clones for both study locations. Mean heritability between clones (0.724), coefficient of individual genetic variation (10.9 %), and relative variation (0.916), suggest the possibility of gains (estimated at 3.1 % for both sites together) by selecting clones with higher growth rates. A total of 15,196 SNPs were used to confirm parentage and test a genomic selection model for dbh. The predictive capacity was negative (-0.15) given the small population size (78 individuals). The most adaptable material among the tested study sites presented higher values for SNP heterozygosity. Thus, using molecular markers to identify clones responsive to environmental changes can act as a powerful tool in Eucalyptus breeding programs. The hybrid population showed greater adaptability than E. globulus for this region
Glomerulopatías en el Paraguay. Reporte del Registro de Biopsias Renales en 1072 casos
La biopsia renal es el principal método de diagnóstico de las glomerulopatías. El Registro de biopsias renales es importante para conocer la situación epidemiológica y clínico-patológica de las enfermedades renales de un país y las variaciones geográficas entre los países o continentes. Para conocer la situación actual de las glomerulopatías del Paraguay se ha realizado el presenteestudio en 1.365 biopsias renales registradas entre agosto de 1989 a junio de 2005 en el Departamento de Patología del IICS, que es el Centro de Referencia y Registro de Biopsias Renales del país, analizando sus aspectos histológicos, demográficos y las diferencias entreperiodos quinquenales de estudio. Del total de casos, 1072 (75.5%) fueron glomerulopatías y, a diferencia de la mayoría de los países, se observó un predominio de glomerulonefritis secundarias (GNS) (57.3%) de las cuales 85.9% fueron nefritis lúpica (NL). En las glomerulonefritis primarias (GNP) la GN proliferativa mesangial (GNPM) y la membranoproliferativa (GNMP) fueron las mas frecuentes (39.8% y 28.2%), mientras que la Nefropatía por IgA (NIgA) y la Enfermedad decambios mínimos (ECM) fueron raras (1.9% y 1.3%). No se observaron cambios significativos de incremento o disminución de tipos histológicos a través de los periodos de estudio tanto en las GNP como en las GNS. La existencia de este registro de biopsias renales fue la base para lacreación del Registro de Glomerulopatías del Paraguay en el año 2004, cuyos datos son necesarios para establecer programas de tratamiento y prevención de las enfermedades glomerulares en nuestro país a fin de disminuir su progresión al estadío terminal
Early stages of Nitrogen enrichment in galaxies: Clues from measurements in damped Lyman alpha systems
We present 4 new measurements of nitrogen abundances and one upper limit in
damped Lyman alpha absorbers (DLAs) obtained by means of high resolution (FWHM
\~ 7 km/s) UVES/VLT spectra. In addition to these measurements we have compiled
data from all DLAs with measurements of nitrogen and alpha-capture elements (O,
S or Si) available in the literature, including all HIRES/Keck and UVES/VLT
data for a total of 33 systems, i.e. the largest sample investigated so far. We
find that [N/alpha] ratios are distributed in two groups: 75% of the DLAs show
a mean value of [N/alpha] = -0.87 with a scatter of 0.16 dex, while the
remaining 25% shows ratios clustered at [N/alpha] = -1.45 with an even lower
dispersion of 0.05 dex. The high [N/alpha] plateau is consistent with the one
observed in metal-poor HII regions of blue compact dwarf (BCD) galaxies
([N/alpha] = -0.73 +/- 0.13), while the [N/alpha] ~ -1.5 values are the lowest
ever observed in any astrophysical site. These low [N/alpha] ratios are real
and not due to ionization effects. They provide a crucial evidence against the
primary production of N by massive stars as responsible for the plateau at
-0.9/-0.7 dex observed in DLAs and BCD galaxies. The transition between the
low-N ([N/alpha] ~ -1.5) and high-N ([N/alpha] ~ -0.9) DLAs occurs at a
nitrogen abundance of [N/H] ~ -2.8, suggesting that the separation may result
from some peculiarity of the nitrogen enrichment history. The [N/alpha] ~ -1.5
values and their low dispersion are consistent with a modest production of
primary N in massive stars; however, due to the limited sample, specially for
the low-N DLAs, we cannot exclude a primary origin in intermediate mass stars
as responsible for the low N abundances observed.Comment: Accepted by A&A. 25 pages, including 9 tables and 10 figure
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