75 research outputs found
Riscos geotécnicos e vulnerabilidades: aplicação de grade regular para representação espacial da população na zona costeira.
Considerando o contexto de riscos e vulnerabilidades (UNISDR, 2004; 2013; BRASIL/PNPDC, 2012; IPCC, 2012) e de mudanças climáticas (BRASIL/PNMC, 2009; IPCC, 2007; 2014) no âmbito da gestão ou de políticas públicas, caracterizar as situações de riscos e vulnerabilidades nas zonas costeiras tem sido fundamental para as agendas científicas relacionadas à temática das dimensões humanas das mudanças climáticas e ambientais. Nesse sentido que esse trabalho buscou, mais do que caracterizar essas situações, identificar possíveis padrões no perfil socioeconômico da população que influenciam sua situação de vulnerabilidade, trazendo também ao debate uma reflexão sobre as limitações dos métodos propostos para a análise da vulnerabilidade, que muitas vezes (ou quase sempre), é apenas tangencial (MARANDOLA Jr., 2009). Por meio de uma análise geoespacial, buscou-se identificar quais são os principais elementos indicativos de vulnerabilidade na zona costeira de São Paulo, por meio da integração de dois conjuntos de dados organizados em um Sistema de Informações Geográficas (SIG): riscos geotécnicos sobrepostos em uma grade regular de células de tamanho de 250 m para as áreas urbanas e de 1000 m para áreas rurais (proposta por BUENO, 2014 ? em prep.; BUENO; DAGNINO, 2011). As variáveis do meio físico consistiram em: (a) riscos geotécnicos associados com processos geológicos e hidrológicos ? escorregamentos, inundação e recalques ou subsidência do solo; (b) declividade; (c) altitude e modelo digital de elevação e variáveis. As variáveis sociodemográficas foram: (d) número de pessoas (moradores); (e) gênero (pessoas responsáveis pelo domicílio de sexo masculino e feminino); (f) renda; (g) idade; (h) raça ou cor e (i) alfabetização, todas agregadas por grades regulares ou células como unidade de análise
The chemical composition of red giants in 47 Tucanae I: Fundamental parameters and chemical abundance patterns
Context: The study of chemical abundance patterns in globular clusters is of
key importance to constrain the different candidates for intra-cluster
pollution of light elements. Aims: We aim at deriving accurate abundances for a
large range of elements in the globular cluster 47 Tucanae (NGC 104) to add new
constraints to the pollution scenarios for this particular cluster, expanding
the range of previously derived element abundances. Methods: Using tailored 1D
LTE atmospheric models together with a combination of equivalent width
measurements, LTE, and NLTE synthesis we derive stellar parameters and element
abundances from high-resolution, high signal-to-noise spectra of 13 red giant
stars near the tip of the RGB. Results: We derive abundances of a total 27
elements (O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr,
Mo, Ru, Ba, La, Ce, Pr, Nd, Eu, Dy). Departures from LTE were taken into
account for Na, Al and Ba. We find a mean [Fe/H] = and
in good agreement with previous studies. The
remaining elements show good agreement with the literature, but the inclusion
of NLTE for Al has a significant impact on the behaviour of this key element.
Conclusions: We confirm the presence of an Na-O anti-correlation in 47 Tucanae
found by several other works. Our NLTE analysis of Al shifts the [Al/Fe] to
lower values, indicating that this may be overestimated in earlier works. No
evidence for an intrinsic variation is found in any of the remaining elements.Comment: 22 pages, 16 figures. Accepted for publication in A&
Spitzer, Near-Infrared, and Submillimeter Imaging of the Relatively Sparse Young Cluster, Lynds 988e
We present {\it Spitzer} images of the relatively sparse, low luminosity
young cluster L988e, as well as complementary near-infrared (NIR) and
submillimeter images of the region. The cluster is asymmetric, with the western
region of the cluster embedded within the molecular cloud, and the slightly
less dense eastern region to the east of, and on the edge of, the molecular
cloud. With these data, as well as with extant H data of stars
primarily found in the eastern region of the cluster, and a molecular CO
gas emission map of the entire region, we investigate the distribution of
forming young stars with respect to the cloud material, concentrating
particularly on the differences and similarities between the exposed and
embedded regions of the cluster. We also compare star formation in this region
to that in denser, more luminous and more massive clusters already investigated
in our comprehensive multi-wavelength study of young clusters within 1 kpc of
the Sun.Comment: 21 pages, 6 tables, 13 figures. Full resolution figures at:
http://astro.pas.rochester.edu/~tom/Preprints/L988e.pd
The O-Na and Mg-Al Anticorrelations in Turn-Off and early Subgiants in Globular Clusters
High dispersion spectra (R>40,000) for a quite large number of stars at the
main sequence turn-off and at the base of the subgiant branch in NGC6397 and
NGC6752 were obtained with the UVES on Kueyen (VLT UT2). The [Fe/H] values we
found are -2.03+/-0.02+/-0.04 and -1.42+/-0.02+/-0.04 for NGC6397 and NGC6752
respectively, where the first error bars refer to internal errors and the
second ones to systematic errors. In both clusters the [Fe/H] obtained for
TO-stars agree perfectly (within a few per cents) with that obtained for stars
at the base of the RGB. The [O/Fe]=0.21+/-0.05 value we obtain for NGC6397 is
quite low, but it agrees with previous results obtained for giants in this
cluster; also, the star-to-star scatter in both O and Fe is very small,
indicating that this small mass cluster is chemically very homogenous. On the
other side, our results show clearly and for the first time that the O-Na
anticorrelation (up to now seen only for stars on the red giant branches of
globular clusters) is present among unevolved stars in the globular cluster
NGC6752, a more massive cluster than NGC6397. A similar anticorrelation is
present also for Mg and Al, and C and N. It is very difficult to explain the
observed Na-O, and Mg-Al anticorrelation in NGC6752 stars by a deep mixing
scenario; we think it requires some non internal mechanism.Comment: 20 pages, A&A Latex, including 7 .ps figures, tex-macro aa.cls, uses
psfig.tex. submitted to Astronomy & Astrophysic
EVIDENCE OF AGB POLLUTION IN GALACTIC GLOBULAR CLUSTERS FROM THE Mg-Al ANTICORRELATIONS OBSERVED BY THE APOGEE SURVEY
We study the formation of multiple populations in globular clusters (GC),
under the hypothesis that stars in the second generation formed from the winds
of intermediate-mass stars, ejected during the asymptotic giant branch (AGB)
phase, possibly diluted with pristine gas, sharing the same chemical
composition of first-generation stars. To this aim, we use the recent APOGEE
data, which provide the surface chemistry of a large sample of giant stars,
belonging to clusters that span a wide metallicity range. The APOGEE data set
is particularly suitable to discriminate among the various pollution scenarios
proposed so far, as it provides the surface abundances of Mg and Al, the two
elements involved in a nuclear channel extremely sensitive to the temperature,
hence to the metallicity of the polluters. The present analysis shows a
remarkable agreement between the observations and the theoretical yields from
massive AGB stars. In particular, the observed extension of the depletion of Mg
and O and the increase in Al is well reproduced by the models and the trend
with the metallicity is also fully accounted for. This study further supports
the idea that AGB stars were the key players in the pollution of the
intra-cluster medium, from which additional generations of stars formed in GC.Comment: Accepted on ApJ letter
Evolution of a 3 \msun star from the main sequence to the ZZ Ceti stage: the role played by element diffusion
The purpose of this paper is to present new full evolutionary calculations
for DA white dwarf stars with the major aim of providing a physically sound
reference frame for exploring the pulsation properties of the resulting models
in future communications. Here, white dwarf evolution is followed in a
self-consistent way with the predictions of time dependent element diffusion
and nuclear burning. In addition, full account is taken of the evolutionary
stages prior to the white dwarf formation. In particular, we follow the
evolution of a 3 \msun model from the zero-age main sequence (the adopted
metallicity is Z=0.02) all the way from the stages of hydrogen and helium
burning in the core up to the thermally pulsing phase. After experiencing 11
thermal pulses, the model is forced to evolve towards its white dwarf
configuration by invoking strong mass loss episodes. Further evolution is
followed down to the domain of the ZZ Ceti stars on the white dwarf cooling
branch. Emphasis is placed on the evolution of the chemical abundance
distribution due to diffusion processes and the role played by hydrogen burning
during the white dwarf evolution. Furthermore, the implications of our
evolutionary models for the main quantities relevant for adiabatic pulsation
analysis are discussed. Interestingly, the shape of the Ledoux term is markedly
smoother as compared with previous detailed studies of white dwarfs. This is
translated into a different behaviour of the Brunt-Vaisala frequency.Comment: 11 pages, 11 figures, accepted for publication in MNRA
Recuperação de seringais em Ouro Preto do Oeste - Rondônia (Relatório).
Este trabalho foi desenvolvido em Ouro Preto do Oeste com o objetivo de demonstrar aos produtores que a prática conjunta de controle de plantas invasoras, adubação e controle de doenças e pragas é um fator decisivo no sucesso da heveicultura
Whole Earth Telescope observations of the hot helium atmosphere pulsating white dwarf EC 20058-5234
We present the analysis of a total of 177h of high-quality optical
time-series photometry of the helium atmosphere pulsating white dwarf (DBV) EC
20058-5234. The bulk of the observations (135h) were obtained during a WET
campaign (XCOV15) in July 1997 that featured coordinated observing from 4
southern observatory sites over an 8-day period. The remaining data (42h) were
obtained in June 2004 at Mt John Observatory in NZ over a one-week observing
period. This work significantly extends the discovery observations of this
low-amplitude (few percent) pulsator by increasing the number of detected
frequencies from 8 to 18, and employs a simulation procedure to confirm the
reality of these frequencies to a high level of significance (1 in 1000). The
nature of the observed pulsation spectrum precludes identification of unique
pulsation mode properties using any clearly discernable trends. However, we
have used a global modelling procedure employing genetic algorithm techniques
to identify the n, l values of 8 pulsation modes, and thereby obtain
asteroseismic measurements of several model parameters, including the stellar
mass (0.55 M_sun) and T_eff (~28200 K). These values are consistent with those
derived from published spectral fitting: T_eff ~ 28400 K and log g ~ 7.86. We
also present persuasive evidence from apparent rotational mode splitting for
two of the modes that indicates this compact object is a relatively rapid
rotator with a period of 2h. In direct analogy with the corresponding
properties of the hydrogen (DAV) atmosphere pulsators, the stable low-amplitude
pulsation behaviour of EC 20058 is entirely consistent with its inferred
effective temperature, which indicates it is close to the blue edge of the DBV
instability strip. (abridged)Comment: 19 pages, 8 figures, 5 tables, MNRAS accepte
The lithium content of the globular cluster NGC 6397
We make use of high resolution, high signal-to-noise ratio spectra of 12
turn-off stars in the metal-poor globular cluster NGC 6397 to measure its
lithium content. We conclude that they all have the same lithium abundance
A(Li) = 2.34 with a standard deviation of 0.056 dex. We use this result,
together with Monte Carlo simulations, to estimate that the maximum allowed
intrinsic scatter is of the order of 0.035 dex. This is a new stringent
constraint to be fulfilled by stellar models which predict Li depletion. We
argue that although a mild depletion of 0.1 -- 0.2 dex, as predicted by recent
models, cannot be ruled out, there is no compelling reason for it. This fact,
together with the good agreement with the Li abundance observed in field stars,
supports the primordial origin of lithium in metal-poor stars. Taking the above
value as the primordial lithium abundance implies a cosmic baryonic density
which is either Omega_b h^2 = 0.016 +/- 0.004 or Omega_b h^2 = 0.005
^{+0.0026}_{-0.0006}, from the predictions of standard big bang
nucleosynthesis. The high baryonic density solution is in agreement with recent
results on the primordial abundance of deuterium and 3He and on the estimates
derived from the fluctuations of the cosmic microwave background.Comment: A&A, accepte
On mode trapping in pulsating DA white dwarf stars
The present work is designed to explore the effects of the time-dependent
element diffusion on the mode trapping properties of DA white dwarf models with
various thickness of the hydrogen envelope. Our predictions are compared with
the standard assumption of diffusive equilibrium in the trace element
approximation. We find that element diffusion markedly weakens the presence of
mode trapping originated in the outer layers of the models, even for the case
of thin hydrogen envelopes.Comment: 5 pages, 6 figures, to be published in MNRA
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