1,546 research outputs found
Recuperação de áreas degradadas como instrumento para a conservação das florestas nativas.
Palestra
O papel das populações tradicionais na conservação da biodiversidade.
bitstream/CNPF-2009-09/42622/1/Doc153.pdf1 CD-ROM
Deterministic and probabilistic models for the estimation of nitrate loads in a rural basin
En este trabajo se desarrolló un modelo
probabilístico que utiliza la teoría de la función de
densidad de probabilidades derivada para estimar
la carga media anual de nitratos transportada
por el escurrimiento superficial, utilizando una
relación funcional entre el escurrimiento y la carga
de nitratos. El modelo determinístico hidrológico
y de calidad de agua denominado Simulator for
Water Resources in Rural Basins - Water Quality
(SWRRB-WQ) fue utilizado para estimar la carga
de nitratos en el escurrimiento superficial. Este
modelo emplea como variable de entrada la
precipitación diaria observada en la Estación
del Aeropuerto de Olavarría durante el período
1988 a 2002. Para la calibración del modelo
se aplicó una nueva metodología que estima
la incertidumbre en los valores observados.
Ambos modelos probabilístico y determinístico
se aplican en una subcuenca rural del arroyo
Tapalqué (provincia de Buenos Aires, Argentina)
y finalmente se comparan los valores de la carga
de nitratos estimados con los dos modelos con
las observaciones realizadas en la sección del
arroyo motivo de este estudio. Los resultados
muestran que la carga media de nitratos obtenida
con el modelo probabilístico es del mismo orden
de magnitud que los valores medios observados y
estimados con el modelo hidrológico y de calidad
de agua SWRRB-WQ.In this work a new probabilistic model
was developed. The new model applies the
derived density function theory to estimate
nitrate mean annual load transported by
surface runoff. A functional relationship
between runoff and nitrate load was used.
The deterministic hydrologic and water quality
model Simulator for Water Resources in Rural
Basins - Water Quality (SWRRB-WQ) was
used to estimate nitrate load in surface runoff.
This model uses, as input variable, daily
precipitation observed at Olavarría Airport
Meteorological Station, for the 1988-2002
period. For model calibration a new method
that estimates uncertainty in observed values
is applied. Both probabilistic and deterministic
hydrologic models are applied in a rural
subbasin of Tapalqué River (province of
Buenos Aires, Argentina). Finally, estimated
and observed nitrate loads are compared
at the outlet section of the subbasin under
study. The results of applying the selected
probabilistic model show that the mean
nitrate loads obtained, are of the same order
of magnitude that the mean nitrate loads
observed and estimated with the SWRRB-WQ
hydrologic and water quality model.Fil: Gelmi, Mónica E..
Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería.Fil: Seoane, Rafael.
Universidad de Buenos Aires. Facultad de Ingeniería. Instituto Nacional del Agua
Estudos fitossociológicos em agroflorestas e regeneração natural na floresta atlântica densa.
Editores técnicos: Marcílio José Thomazini, Elenice Fritzsons, Patrícia Raquel Silva, Guilherme Schnell e Schuhli, Denise Jeton Cardoso, Luziane Franciscon. EVINCI. Resumos
Otimização de protocolo para extração do DNA de endosperma de sementes de Araucaria angustifolia.
bitstream/item/25642/1/177-10.pd
The distribution of stars around the Milky Way's central black hole II: Diffuse light from sub-giants and dwarfs
This is the second of three papers that search for the predicted stellar cusp
around the Milky Way's central black hole, Sagittarius A*, with new data and
methods. We aim to infer the distribution of the faintest stellar population
currently accessible through observations around Sagittarius A*. We use
adaptive optics assisted high angular resolution images obtained with the NACO
instrument at the ESO VLT. Through optimised PSF fitting we remove the light
from all detected stars above a given magnitude limit. Subsequently we analyse
the remaining, diffuse light density. The analysed diffuse light arises from
sub-giant and main-sequence stars with KS ~ 19 - 20 with masses of 1 - 2 Msol .
These stars can be old enough to be dynamically relaxed. The observed power-law
profile and its slope are consistent with the existence of a relaxed stellar
cusp around the Milky Way's central black hole. We find that a Nuker law
provides an adequate description of the nuclear cluster's intrinsic shape
(assuming spherical symmetry). The 3D power-law slope near Sgr A* is \gamma =
1.23 +- 0.05. At a distance of 0.01 pc from the black hole, we estimate a
stellar mass density of 2.3 +- 0.3 x 10^7 Msol pc^-3 and a total enclosed
stellar mass of 180 +- 20 Msol. These estimates assume a constant mass-to-light
ratio and do not take stellar remnants into account. The fact that no cusp is
observed for bright (Ks 16) giant stars at projected distances of roughly
0.1-0.3 pc implies that some mechanism has altered their appearance or
distribution.Comment: Accepted for publication A&
The distribution of old stars around the Milky Way's central black hole I: Star counts
(abridged) In this paper we revisit the problem of inferring the innermost
structure of the Milky Way's nuclear star cluster via star counts, to clarify
whether it displays a core or a cusp around the central black hole. Through
image stacking and improved PSF fitting we push the completeness limit about
one magnitude deeper than in previous, comparable work. Contrary to previous
work, we analyse the stellar density in well-defined magnitude ranges in order
to be able to constrain stellar masses and ages. The RC and brighter giant
stars display a core-like surface density profile within a projected radius
R<0.3 pc of the central black hole, in agreement with previous studies, but
show a cusp-like surface density distribution at larger R. The surface density
of the fainter stars can be described well by a single power-law at R<2 pc. The
cusp-like profile of the faint stars persists even if we take into account the
possible contamination of stars in this brightness range by young pre-main
sequence stars. The data are inconsistent with a core-profile for the faint
stars.Finally, we show that a 3D Nuker law provides a very good description of
the cluster structure. We conclude that the observed stellar density at the
Galactic Centre, as it can be inferred with current instruments, is consistent
with the existence of a stellar cusp around the Milky Way's central black hole,
Sgr A*. This cusp is well developed inside the influence radius of about 3 pc
of Sgr A* and can be described by a single three-dimensional power-law with an
exponent gamma=1.23+-0.05. The apparent lack of RC stars and brighter giants at
projected distances of R < 0.3 pc (R<8") of the massive black hole may indicate
that some mechanism has altered their distribution or intrinsic luminosity.Comment: Accepted for publication A&
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