2,306 research outputs found
An Analytic Model with Critical Behavior in Black Hole Formation
A simple analytic model is presented which exhibits a critical behavior in
black hole formation, namely, collapse of a thin shell coupled with outgoing
null fluid. It is seen that the critical behavior is caused by the
gravitational nonlinearity near the event horizon. We calculate the value of
the critical exponent analytically and find that it is very dependent on the
coupling constants of the system.Comment: 21pp., ReVTeX, 7 figures (postscript, compressed and uuencoded),
TIT/HEP-266/COSMO-4
Uso de imagens de radar na estimativa do ar.
O objetivo deste boletim é apresentar uma metodologia para a geração de modelo numérico de terreno (MNT), com estimativa da temperatura do ar, a partir de dados do radar SRTM. O modelo digital de elevação, gerado pela missão SRTM, forneceu as coordenadas geográficas e as altitudes necessárias para estimar-se a temperatura média do ar, utilizando-se equações de regressão múltipla. A metodologia foi eficiente na geração do mapa de temperatura média do ar do Estado de São Paulo, produto que pode ser utilizado para os mais diversos fins, tais como zoneamentos agropecuários.bitstream/item/120540/1/2249.pd
Using SAR data for soil temperature regimes classifiction in São Paulo, Brazil.
The climatic variables are used in Soil Taxonomy (Soil Survey Staff, 1999) for soil classification, because it is important to plant germination and growth, soil formation and others soil properties. Synthetic aperture radar (SAR) interferometry has been shown to be a very cost effective tool for measuring digital topography (Zyl, 2001). The data of Shuttle Radar Topography Mission (SRTM) were the results of an international mission that generate a digital elevation model (DEM) with high resolution (Souza Filho, 2003). The data were generate and provided for South America with 90m spatial resolution. The SRTM was in February, 2000 and produced the most complete terrain map of the world (Foni, Seal, 2004). A radar interferometer images a scene from two slightly different positions. In the case of a single-pass interferometer, such as SRTM, these images are acquired simultaneously. This means that one needs to separate the antenna systems in space, but always know the relative positions of the antennas in order to reconstruct the topography correctly (Zyl, 2001). The SRTM actually flew two interferometers, a C-band system, and a X-band system. The DEM generate by SRTM has a good accuracy, and besides a great advantage in the homogeneous DEM quality. Therefore, it can be used to estimate the air temperature using multiple regression analysis, based on geographic coordinates and altitude as independent variables (Pinto et al., 1972; Pedro Júnior et al., 1991; Marin et al., 2003). The Soil Taxonomy criteria to define soil temperature regimes consider soil temperature at a depth of 50cm from the soil surface, these data are rare in Brasil, and are poor to classify soil temperature regimes in brazilian territory, classifying the major portion of the country in isohyperthermic regime. The objective of this paper is present a new perspective to classify soil temperature regimes based in air temperature estimated from SRTM data, for São Paulo State
Mosquito Surveillance Program Using Ovitraps Detected Aedes aegypti at the Honolulu International Airport in 2012
mosquito surveillance program using ovitraps at the Honolulu In- ternational Airport (HIA), Hawaii, USA May 2010 to June 2012 revealed that A. albopictus egg counts fluctuated over time during the surveillance program and the highest oviposition was observed from February to May 2011 and the lowest was from September to November 2011. Positive correlations found between a given week’s rainfall and egg counts 1 and 2 weeks later suggested that rainfall triggered the hatching of eggs which were laid before the rainfall, rather than di- rectly stimulating adult oviposition. In January and June 2012, Aedes aegypti was discovered from a small vegetated area located between terminals for out-of-state and within-state flights. This species had not been confirmed present on Oahu at least since 1948. This finding has led us to intensify our surveillance program at the airport, with the hope that we would improve our understanding of the nature of mosquito introductions at this important port of entry for the Hawaiian Islands
Perturbations and Critical Behavior in the Self-Similar Gravitational Collapse of a Massless Scalar Field
This paper studies the perturbations of the continuously self-similar
critical solution of the gravitational collapse of a massless scalar field
(Roberts solution). The perturbation equations are derived and solved exactly.
The perturbation spectrum is found to be not discrete, but occupying continuous
region of the complex plane. The renormalization group calculation gives the
value of the mass-scaling exponent equal to 1.Comment: 12 pages, RevTeX 3.1, 1 figur
An extreme critical space-time: echoing and black-hole perturbations
A homothetic, static, spherically symmetric solution to the massless
Einstein- Klein-Gordon equations is described. There is a curvature singularity
which is central, null, bifurcate and marginally trapped. The space-time is
therefore extreme in the sense of lying at the threshold between black holes
and naked singularities, just avoiding both. A linear perturbation analysis
reveals two types of dominant mode. One breaks the continuous self-similarity
by periodic terms reminiscent of discrete self-similarity, with echoing period
within a few percent of the value observed numerically in near-critical
gravitational collapse. The other dominant mode explicitly produces a black
hole, white hole, eternally naked singularity or regular dispersal, the latter
indicating that the background is critical. The black hole is not static but
has constant area, the corresponding mass being linear in the perturbation
amplitudes, explicitly determining a unit critical exponent. It is argued that
a central null singularity may be a feature of critical gravitational collapse.Comment: 6 revtex pages, 6 eps figure
Self-Similar Collapse of Scalar Field in Higher Dimensions
This paper constructs continuously self-similar solution of a spherically
symmetric gravitational collapse of a scalar field in n dimensions. The
qualitative behavior of these solutions is explained, and closed-form answers
are provided where possible. Equivalence of scalar field couplings is used to
show a way to generalize minimally coupled scalar field solutions to the model
with general coupling.Comment: RevTex 3.1, 15 pages, 3 figures; references adde
Mapeamento de áreas de preservação permanentes em topos de morros para a Amazônia Legal usando metodologia apropriada a grande volume de dados.
bitstream/item/65444/1/COT-57-Mapeamento-de-Areas-de.pd
Continuous Self-Similarity Breaking in Critical Collapse
This paper studies near-critical evolution of the spherically symmetric
scalar field configurations close to the continuously self-similar solution.
Using analytic perturbative methods, it is shown that a generic growing
perturbation departs from the critical Roberts solution in a universal way. We
argue that in the course of its evolution, initial continuous self-similarity
of the background is broken into discrete self-similarity with echoing period
, reproducing the symmetries of the critical
Choptuik solution.Comment: RevTeX 3.1, 28 pages, 5 figures; discussion rewritten to clarify
several issue
Pregnancy Outcome in Swiss-Webster Mice Infected With Chlamydia trachomatis
Objective: The objective of this study was to observe pregnancy
outcomes in mice infected transvaginally with Chlamydia trachomatis
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