178 research outputs found
Proposals for Flashflood Management in Western Argentina: Case Study: The Metropolitan Area of Greater Mendoza
Las cuencas hidrográficas situadas en el oeste del Gran Mendoza (Argentina) son ejemplos típicos de las zonas directa o indirectamente afectadas por inundaciones repentinas. Gran Mendoza está invadiendo zonas con un relieve pronunciado (vertiente oriental de la Precordillera, el piedemonte y otras unidades menores) con fuertes presiones humanas en un entorno frágil. Hoy en día, la parte occidental del Gran Mendoza se cubre con superficies pavimentadas y edificios, poniendo en peligro la ciudad situada aguas abajo. Con el fin de mitigar los efectos negativos del uso y ocupación del piedemonte, un conjunto de medidas estructurales y no estructurales y un modelo de planificación urbana, con nuevas propuestas de desarrollo y arquitectura urbana, se han ideado. Estas medidas implican el control de inundaciones, control de la erosión, la repoblación forestal, la gestión del hábitat, control de las prácticas de extracción (agregados, fauna, vegetación, etc.) y la educación. El nuevo modelo de planificación urbana se basa en la preservación del carácter natural de la tierra y el manejo adecuado de los excedentes de agua (detección de escorrentía en el área de origen, la retención de sistema de drenaje, lo que aumenta la capacidad de drenaje y reducir al mínimo los impactos en entornos de aguas abajo, y la creación de áreas para amortiguar el escurrimiento). Muchas de estas medidas se han desarrollado y demostrado éxito a nivel local.Fil: Vich, Alberto Ismael Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Nacional de Cuyo. Facultad de Filosofía y Letras. Instituto de Estudios del Ambiente y los Recursos Naturales; ArgentinaFil: López Rodríguez, Mariela Beatriz. Universidad Nacional de Cuyo. Facultad de Filosofía y Letras. Instituto Cartografía, Investigación y Formación para el Ordenamiento Territorial; ArgentinaFil: Lauro, Carolina. Universidad Nacional de Cuyo. Facultad de Filosofía y Letras. Instituto de Estudios del Ambiente y los Recursos Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Vaccarino Pasquali, Emilce Liliana Belén. Universidad Nacional de Cuyo. Facultad de Filosofía y Letras. Instituto de Estudios del Ambiente y los Recursos Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentin
An empirical prediction for stellar metallicity distributions in nearby galaxies
We combine star-formation histories derived from observations of high
redshift galaxies with measurements of the z~0 relation between gas-phase
metallicity, stellar mass, and star formation rate to make an explicit and
completely empirical connection between near-field and distant galaxy
observations. Our approach relies on two basic assumptions: 1) galaxies'
average paths through time in stellar mass vs. star formation rate space are
represented by a family of smooth functions that are determined by the
galaxies' final stellar mass, and 2) galaxies grow and become enriched with
heavy elements such that they always evolve along the mass--metallicity--star
formation rate relation. By integrating over these paths, we can track the
chemical evolution of stars in galaxies in a model independent way, without the
need for explicit assumptions about gas inflow, outflow, or star formation
efficiency. Using this approach, we present predictions of stellar metallicity
(i.e., O/H) distribution functions for present day star-forming galaxies of
different stellar masses and the evolution of the alpha-element stellar
metallicity-mass relation since z~1. The metallicity distribution functions are
fairly well described as Gaussians, truncated at high metallicity, with
power-law tails to low metallicity. We find that the stellar metallicity
distribution for Milky Way mass galaxies is in reasonable agreement with
observations for our Galaxy, and that the predicted stellar mass vs. mean
stellar metallicity relation at z=0 agrees quite well with results derived from
galaxy surveys. This validates the assumptions that are implicit in our simple
approach. Upcoming observations will further test these assumptions and their
range of validity, by measuring the mean stellar mass-metallicity relation up
to z~1, and by measuring the stellar metallicity distributions over a range of
galaxy masses.Comment: 8 pages, 2 figures, 2 tables. MNRAS, in pres
Using Cepheids to determine the galactic abundance gradient I. The solar neighbourhood
A number of studies of abundance gradients in the galactic disk have been
performed in recent years. The results obtained are rather disparate: from no
detectable gradient to a rather significant slope of about -0.1 dex kpc -1. The
present study concerns the abundance gradient based on the spectroscopic
analysis of a sample of classical Cepheids. These stars enable one to obtain
reliable abundances of a variety of chemical elements. Additionally, they have
well determined distances which allow an accurate determination of abundance
distributions in the galactic disc. Using 236 high resolution spectra of 77
galactic Cepheids, the radial elemental distribution in the galactic disc
between galactocentric distances in the range 6-11 kpc has been investigated.
Gradients for 25 chemical elements (from carbon to gadolinium) are derived...Comment: 28 pages, 14 postscript figures, LaTeX, uses Astronomy and
Astrophysics macro aa.cls, graphicx package, to be published in Astronomy and
Astrophysics (2002) also available at
http://www.iagusp.usp.br/~maciel/index.htm
Efficacy of strain RB51 vaccine in protecting infection and vertical transmission against Brucella abortus in Sprague-Dawley rats
Immunizing animals in the wild against Brucella (B.) abortus is essential to control bovine brucellosis because cattle can get the disease through close contact with infected wildlife. The aim of this experiment was to evaluate the effectiveness of the B. abortus strain RB51 vaccine in protecting infection as well as vertical transmission in Sprague-Dawley (SD) rats against B. abortus biotype 1. Virgin female SD rats (n = 48) two months of age were divided into two groups: one group (n = 24) received RB51 vaccine intraperitoneally with 3 × 1010 colony forming units (CFU) and the other group (n = 24) was used as non-vaccinated control. Non-vaccinated and RB51-vaccinated rats were challenged with 1.5 × 109 CFU of virulent B. abortus biotype 1 six weeks after vaccination. Three weeks after challenge, all rats were bred. Verification of RB51-vaccine induced protection in SD rats was determined by bacteriological, serological and molecular screening of maternal and fetal tissues at necropsy. The RB51 vaccine elicited 81.25% protection in SD rats against infection with B. abortus biotype 1. Offspring from rats vaccinated with RB51 had a decreased (p < 0.05) prevalence of vertical transmission of B. abortus biotype 1 compared to the offspring from non-vaccinated rats (20.23% and 87.50%, respectively). This is the first report of RB51 vaccination efficacy against the vertical transmission of B. abortus in the SD rat model
Relationship between mental health and spiritual wellbeing among hemodialysis patients: a correlation study
Cross-cultural adaptation and validation of the instrument Diabetes - 39 (D-39): brazilian version for type 2 diabetes mellitus patients - stage 1
The Mice at play in the CALIFA survey: A case study of a gas-rich major merger between first passage and coalescence
We present optical integral field spectroscopy (IFS) observations of the
Mice, a major merger between two massive (>10^11Msol) gas-rich spirals NGC4676A
and B, observed between first passage and final coalescence. The spectra
provide stellar and gas kinematics, ionised gas properties and stellar
population diagnostics, over the full optical extent of both galaxies. The Mice
provide a perfect case study highlighting the importance of IFS data for
improving our understanding of local galaxies. The impact of first passage on
the kinematics of the stars and gas has been significant, with strong bars
likely induced in both galaxies. The barred spiral NGC4676B exhibits a strong
twist in both its stellar and ionised gas disk. On the other hand, the impact
of the merger on the stellar populations has been minimal thus far: star
formation induced by the recent close passage has not contributed significantly
to the global star formation rate or stellar mass of the galaxies. Both
galaxies show bicones of high ionisation gas extending along their minor axes.
In NGC4676A the high gas velocity dispersion and Seyfert-like line ratios at
large scaleheight indicate a powerful outflow. Fast shocks extend to ~6.6kpc
above the disk plane. The measured ram pressure and mass outflow rate
(~8-20Msol/yr) are similar to superwinds from local ULIRGs, although NGC4676A
has only a moderate infrared luminosity of 3x10^10Lsol. Energy beyond that
provided by the mechanical energy of the starburst appears to be required to
drive the outflow. We compare the observations to mock kinematic and stellar
population maps from a merger simulation. The models show little enhancement in
star formation during and following first passage, in agreement with the
observations. We highlight areas where IFS data could help further constrain
the models.Comment: 23 pages, 13 figures, accepted to A&A. A version with a complete set
of high resolution figures is available here:
http://www-star.st-and.ac.uk/~vw8/resources/mice_v8_astroph.pd
The role of major mergers in the size growth of intermediate-mass spheroids
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.We study of the role of ‘major’ mergers (mass ratios >1: 4) in driving size growth in high-redshift (1 1010.7 M⊙) SGs at z < 1, then major mergers are also likely to play an important role in the size growth of at least some massive SGs in this mass range.Peer reviewe
Gas Accretion and Star Formation Rates
Cosmological numerical simulations of galaxy evolution show that accretion of
metal-poor gas from the cosmic web drives the star formation in galaxy disks.
Unfortunately, the observational support for this theoretical prediction is
still indirect, and modeling and analysis are required to identify hints as
actual signs of star-formation feeding from metal-poor gas accretion. Thus, a
meticulous interpretation of the observations is crucial, and this
observational review begins with a simple theoretical description of the
physical process and the key ingredients it involves, including the properties
of the accreted gas and of the star-formation that it induces. A number of
observations pointing out the connection between metal-poor gas accretion and
star-formation are analyzed, specifically, the short gas consumption time-scale
compared to the age of the stellar populations, the fundamental metallicity
relationship, the relationship between disk morphology and gas metallicity, the
existence of metallicity drops in starbursts of star-forming galaxies, the
so-called G dwarf problem, the existence of a minimum metallicity for the
star-forming gas in the local universe, the origin of the alpha-enhanced gas
forming stars in the local universe, the metallicity of the quiescent BCDs, and
the direct measurements of gas accretion onto galaxies. A final section
discusses intrinsic difficulties to obtain direct observational evidence, and
points out alternative observational pathways to further consolidate the
current ideas.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics
and Space Science Library, eds. A. J. Fox & R. Dav\'e, to be published by
Springe
Mergers in Lambda-CDM: Uncertainties in Theoretical Predictions and Interpretations of the Merger Rate
Different methodologies lead to order-of-magnitude variations in predicted
galaxy merger rates. We examine and quantify the dominant uncertainties.
Different halo merger rates and subhalo 'destruction' rates agree to within a
factor ~2 given proper care in definitions. If however (sub)halo masses are not
appropriately defined or are under-resolved, the major merger rate can be
dramatically suppressed. The dominant differences in galaxy merger rates owe to
baryonic physics. Hydrodynamic simulations without feedback and older models
that do not agree with the observed galaxy mass function propagate factor ~5
bias in the resulting merger rates. However, if the model matches the galaxy
mass function, properties of central galaxies are sufficiently converged to
give small differences in merger rates. But variations in baryonic physics of
satellites also have dramatic effects. The known problem of satellite
'over-quenching' in most semi-analytic models (SAMs), whereby SAM satellites
are too efficiently stripped of gas, could lead to order-of-magnitude
under-estimates of merger rates for low-mass, gas-rich galaxies. Fixing the
satellite properties to observations tends to predict higher merger rates, but
with factor ~2 empirical uncertainties. Choice of mass ratio definition
matters: at low masses, most true major mergers (in baryonic/dynamical galaxy
mass) will appear to be minor mergers in their stellar or luminosity mass
ratio. Observations and models using these criteria may underestimate major
merger rates by factors ~5. Orbital parameters and gas fractions also introduce
factor ~3 differences in amount of bulge formed by mergers, even for fixed mass
ratio encounters.Comment: 32 Pages, 15 figures, accepted to ApJ (revised to match accepted
version and correct Fig. 12
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