1,963 research outputs found
Padrão de frugivoria por Tapirus terrestris na Mata Atlântica do norte do Espírito Santo, Brasil
A anta Tapirus terrestris (Linnaeus, 1758), último representante da megafauna Pleistocênica na região Neotropical, representa um importante grupo funcional, pois se alimentam de uma grande variedade de espécies vegetais, especialmente frutos. No entanto, o padrão de frugivoria da espécie pode variar entre diferentes áreas. Dessa forma, nosso interesse foi investigar o grau de frugivoria da espécie em duas diferentes áreas no estado do Espírito Santo e a sua importância para a dinâmica florestal. Para isso, foram coletadas amostras fecais, através de busca ativa em diferentes ambientes na Reserva Biológica do Córrego do Veado (Rebio Córrego do Veado) e na Reserva Particular do Patrimônio Natural Recanto das Antas (RPPN Recanto das Antas), durante o período de janeiro de 2011 a novembro de 2013. Após a triagem do material biológico, as sementes foram individualizadas, classificadas quanto às características e grupos ecológicos e identificadas até o menor nível taxonômico possível. Foi obtido um esforço amostral de 130 dias, resultando em 325 amostras fecais coletadas, sendo 53,2% da Rebio Córrego do Veado e 46,8% da RPPN Recanto das Antas. Do total de amostras, 41,8% estavam depositadas dentro ou próximas a corpos dágua e 58,2% na serrapilheira/substrato seco. A dieta da anta foi composta por 94,1% de fibras e 5,9% de frutos. Foram encontradas duas vezes mais amostras contendo sementes na RPPN Recanto das Antas do que na Rebio Córrego do Veado. Das 30 morfoespécies encontradas nas amostras, 15 foram identificadas em nível específico, as quais estão distribuídas em oito famílias. As famílias mais representativas foram Anacardiaceae, Fabaceae e Myrtaceae. As espécies mais freqüentemente encontradas nas amostras foram Spondias macrocarpa Engl. e S. venulosa (Engl.) Engl. Do total de sementes encontradas 60% apresentam dispersão zoocórica e 46,7% são sementes grandes e muito grandes e 50% possuem fruto do tipo carnoso. Das morfoespécies encontradas, sete foram registradas em ambas as unidades de conservação, 21 foram encontradas apenas na RPPN Recanto das Antas e duas foram encontradas na Rebio Córrego do Veado. Isso pode indicar que o ambiente na RPPN Recanto das Antas pode fornecer mais frutos que na Rebio Córrego do Veado, o que pode ser um resultado do histórico de perturbações da última
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reserva. Na década de 1980, 80% da Rebio Córrego do Veado foi queimada em um incêndio e, atualmente, o entorno da reserva é composto principalmente por pastagens. Ao contrário, a RPPN Recanto das Antas, apesar de sua área ter sofrido extração seletiva na década de 50, está inserida no maior remanescente de Mata Atlântica do Espírito Santo. Ainda que a anta possua uma dieta composta por uma variedade de frutos nas áreas de estudo, ela aparenta ser menos frugívora do que em outras áreas da Mata Atlântica. Contudo, é evidente a importância de T. terrestris na dispersão de um grande número de espécies vegetais, especialmente as espécies com sementes grandes, aumentando o recrutamento de espécies de plantas que não são dispersadas por outras espécies animais
Numerical Approximation of the Transport Equation: Comparison of Five Positive Definite Algorithms
IIASA's Regional Acidification INformation and Simulation (RAINS) model will be used to develop and assess international control strategies to reduce emissions of acidifying pollutants. These strategies will involve the expenditure of large sum of money; it is important, therefore, to assess the effect of uncertainties in the model on its results. An important component of the RAINS model is its atmospheric transport component; this paper reports the results of examining several algorithms for solution of the atmospheric transport equation. It also represents a joint effort between IIASA scientists and those in the Institute of Meteorology and Water Management in Warsaw and Central Institute for Meteorology and Geodynamics in Vienna
Synthetic Mudscapes: Human Interventions in Deltaic Land Building
In order to defend infrastructure, economy, and settlement in Southeast Louisiana, we must construct new land to
mitigate increasing risk. Links between urban environments and economic drivers have constrained the dynamic delta
landscape for generations, now threatening to undermine the ecological fitness of the entire region. Static methods of
measuring, controlling, and valuing land fail in an environment that is constantly in flux; change and indeterminacy are
denied by traditional inhabitation.
Multiple land building practices reintroduce deltaic fluctuation and strategic deposition of fertile material to form the
foundations of a multi-layered defence strategy. Manufactured marshlands reduce exposure to storm surge further
inland. Virtual monitoring and communication networks inform design decisions and land use becomes determined
by its ecological health. Mudscapes at the threshold of land and water place new value on former wastelands. The
social, economic, and ecological evolution of the region are defended by an expanded web of growing land
Value of uncertain streamflow observations for hydrological modelling
Previous studies have shown that hydrological models can be parameterised using a
limited number of streamflow measurements. Citizen science projects can
collect such data for otherwise ungauged catchments but an important question
is whether these observations are informative given that these streamflow
estimates will be uncertain. We assess the value of inaccurate streamflow estimates for calibration of a
simple bucket-type runoff model for six Swiss catchments. We pretended that
only a few observations were available and that these were affected by
different levels of inaccuracy. The level of inaccuracy was based on a
log-normal error distribution that was fitted to streamflow estimates of 136
citizens for medium-sized streams. Two additional levels of inaccuracy, for
which the standard deviation of the error distribution was divided by 2 and
4, were used as well. Based on these error distributions,
random errors were added to the measured hourly streamflow data. New time
series with different temporal resolutions were created from these synthetic
streamflow time series. These included scenarios with one observation each
week or month, as well as scenarios that are more realistic for crowdsourced
data that generally have an irregular distribution of data points throughout
the year, or focus on a particular season. The model was then calibrated for
the six catchments using the synthetic time series for a dry, an average and
a wet year. The performance of the calibrated models was evaluated based on
the measured hourly streamflow time series. The results indicate that
streamflow estimates from untrained citizens are not informative for model
calibration. However, if the errors can be reduced, the estimates are
informative and useful for model calibration. As expected, the model
performance increased when the number of observations used for calibration
increased. The model performance was also better when the observations were
more evenly distributed throughout the year. This study indicates that
uncertain streamflow estimates can be useful for model calibration but that
the estimates by citizen scientists need to be improved by training or more
advanced data filtering before they are useful for model calibration.</p
Thermal quark production in ultra-relativistic nuclear collisions
We calculate thermal production of u, d, s, c and b quarks in
ultra-relativistic heavy ion collisions. The following processes are taken into
account: thermal gluon decay (g to ibar i), gluon fusion (g g to ibar i), and
quark-antiquark annihilation (jbar j to ibar i), where i and j represent quark
species. We use the thermal quark masses, ,
in all the rates. At small mass (), the production is largely
dominated by the thermal gluon decay channel. We obtain numerical and analytic
solutions of one-dimensional hydrodynamic expansion of an initially pure glue
plasma. Our results show that even in a quite optimistic scenario, all quarks
are far from chemical equilibrium throughout the expansion. Thermal production
of light quarks (u, d and s) is nearly independent of species. Heavy quark (c
and b) production is quite independent of the transition temperature and could
serve as a very good probe of the initial temperature. Thermal quark production
measurements could also be used to determine the gluon damping rate, or
equivalently the magnetic mass.Comment: 14 pages (latex) plus 6 figures (uuencoded postscript files);
CERN-TH.7038/9
It's a wonderful tail: the mass loss history of Mira
Recent observations of the Mira AB binary system have revealed a surrounding
arc-like structure and a stream of material stretching 2 degrees away in
opposition to the arc. The alignment of the proper motion vector and the
arc-like structure shows the structures to be a bow shock and accompanying
tail. We have successfully hydrodynamically modelled the bow shock and tail as
the interaction between the asymptotic giant branch (AGB) wind launched from
Mira A and the surrounding interstellar medium. Our simulations show that the
wake behind the bow shock is turbulent: this forms periodic density variations
in the tail similar to those observed. We investigate the possiblity of
mass-loss variations, but find that these have limited effect on the tail
structure. The tail is estimated to be approximately 450,000 years old, and is
moving with a velocity close to that of Mira itself. We suggest that the
duration of the high mass-loss phase on the AGB may have been underestimated.
Finally, both the tail curvature and the rebrightening at large distance can be
qualitatively understood if Mira recently entered the Local Bubble. This is
estimated to have occured 17 pc downstream from its current location.Comment: 12 pages, 3 colour figures, accepted by ApJ Part II (Letters
GALEX, Optical and IR Light Curves of MQ Dra: UV Excesses at Low Accretion Rates
Ultraviolet light curves constructed from NUV and FUV detectors on GALEX
reveal large amplitude variations during the orbital period of the Low
Accretion Rate Polar MQ Dra (SDSSJ1553+55). This unexpected variation from a UV
source is similar to that seen and discussed in the Polar EF Eri during its low
state of accretion, even though the accretion rate in MQ Dra is an order of
magnitude lower than even the low state of EF Eri. The similarity in phasing of
the UV and optical light curves in MQ Dra imply a similar location for the
source of light. We explore the possibilities of hot spots and cyclotron
emission with simple models fit to the UV, optical and IR light curves of MQ
Dra. To match the GALEX light curves with a single temperature circular hot
spot requires different sizes of spots for the NUV and FUV, while a cyclotron
model that can produce the optical harmonics with a magnetic field near 60 MG
requires multipoles with fields > 200 MG to match the UV fluxes.Comment: accepted for ApJ; 15 pages, 7 tables, 8 fig
Extinction law variations and dust excitation in the spiral galaxy NGC 300
We investigate the origin of the strong radial gradient in the
ultraviolet-to-infrared ratio in the spiral galaxy NGC 300, and emphasize the
importance of local variations in the interstellar medium geometry, concluding
that they cannot be neglected with respect to metallicity effects. This
analysis is based upon a combination of maps from GALEX and Spitzer, and from
the ground (UBVRI, Halpha and Hbeta). We select ionizing stellar clusters
associated with HII regions of widely varying morphologies, and derive their
fundamental parameters from population synthesis fitting of their spectral
energy distributions, measured to eliminate local backgrounds accurately. From
these fits, we conclude that the stellar extinction law is highly variable in
the line of sight of young clusters of similar ages. In the particular model
geometry that we consider most appropriate to the sampled regions, we checked
that our findings are not significantly altered by the correct treatment of
radiative transfer effects. The variations are systematic in nature: extinction
laws of the Milky Way or LMC type are associated with compact HII regions (the
compacity being quantified in two different ways), while clusters surrounded by
diffuse HII regions follow extinction laws of the 30 Doradus or SMC type. The
Calzetti starburst attenuation law, although most often degenerate with the 30
Doradus extinction law, overpredicts ionizing photon fluxes by large amounts.
We also find that the extinction law variations are correlated with the column
density of dust species emitting in the near- and mid-infrared. Finally, we
briefly discuss the nebular to stellar extinction ratios, and the excitation of
aromatic band carriers, invalidating their claimed association with cold dust.Comment: accepted for publication in ApJ -- figure 6 abridged her
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