6,368 research outputs found
Metodologia de elaboração de mapas dos cenários climáticos futuros do terceiro relatório do IPCC para o Brasil.
O objetivo deste trabalho foi desenvolver um banco de dados de informações sobre o clima dos cenários futuros, utilizando um Sistema de Informação Geográfica (GIS). Cenários futuros centrados nas décadas de 2020, 2050 e 2080, do (cenários A2 e B2), foram obtidos a partir dos Modelos de Circulação Geral (GCM) disponÃveis no Data Distribution Centre do Terceiro Relatório de Avaliação (TAR) do Painel Intergovernamental sobre Mudanças Climáticas (IPCC). A TAR é composta por seis GCM com diferentes resoluções espaciais (ECHAM4: 2,8125 × 2,8125 º, HadCM3: 3,75 × 2,5 º, CGCM2: 3,75 × 3,75 º, CSIROMk2b: 5,625 × 3,214 º, e CCSR / NIES: 5,625 × 5,625 º) . A média aritmétrica dos modelos disponÃveis foi realizada as ferramentas de análise espacial (operação aritmética) do SIG. Mapas de médias mensais de temperatura média, temperatura mÃnima, temperatura máxima, precipitação, umidade relativa e radiação solar foram elaboradas adotando a resolução espacial de 0,5 ° x 0,5 ° latitude e longitude. O método de elaboração de mapas, utilizando ferramentas de SIG permitiu avaliar a distribuição espacial e das avaliações climáticas futuras
The Conformal Anomaly in General Rank 1 Symmetric Spaces and Associated Operator Product
We compute the one-loop effective action and the conformal anomaly associated
with the product of the Laplace type operators , acting in irreducible rank 1 symmetric spaces of non-compact
type. The explicit form of the zeta functions and the conformal anomaly of the
stress-energy momentum tensor is derived.Comment: 10 pages, LaTe
Análise de tendências de temperatura mÃnima do Brasil.
A concentração dos gases de efeito estufa vem aumentando consideravelmente nos últimos 150 anos e tem sido considerado como principal causa do aquecimento global no planeta nesse perÃodo. O objetivo do trabalho foi analisar as tendências de temperatura mÃnima nas cinco regiões do Brasil. Foram calculadas as temperaturas mÃnimas mensais e anuais de cada estação por meio da média aritmética dos valores diários e mensais, respectivamente. Calculou-se também a média móvel de cinco anos e o desvio da temperatura mÃnima em relação a média da temperatura mÃnima no perÃodo de estudo de cada estação meteorológica. As análises dos desvios da temperatura mÃnima anual, em relação à média da série de dados de cada estação meteorológica analisada, indicaram tendências de aumento significativo nas cinco regiões do paÃs.CBA 2009
No-horizon theorem for spacetimes with spacelike G1 isometry groups
We consider four-dimensional spacetimes which obey the
Einstein equations , and admit a global spacelike
isometry group. By means of dimensional reduction and local
analyis on the reduced (2+1) spacetime, we obtain a sufficient condition on
which guarantees that cannot contain apparent
horizons. Given any (3+1) spacetime with spacelike translational isometry, the
no-horizon condition can be readily tested without the need for dimensional
reduction. This provides thus a useful and encompassing apparent horizon test
for -symmetric spacetimes. We argue that this adds further evidence
towards the validity of the hoop conjecture, and signals possible violations of
strong cosmic censorship.Comment: 8 pages, LaTeX, uses IOP package; published in Class. Quantum Gra
Dynamo in the Intra-Cluster Medium: Simulation of CGL-MHD Turbulent Dynamo
The standard magnetohydrodynamic (MHD) description of the plasma in the hot,
magnetized gas of the intra-cluster (ICM) medium is not adequate because it is
weakly collisional. In such collisionless magnetized gas, the microscopic
velocity distribution of the particles is not isotropic, giving rise to kinetic
effects on the dynamical scales. These kinetic effects could be important in
understanding the turbulence, as so as the amplification and maintenance of the
magnetic fields in the ICM. It is possible to formulate fluid models for
collisonless or weakly collisional gas by introducing modifications in the MHD
equations. These models are often referred as kinetic MHD (KMHD). Using a KMHD
model based on the CGL-closure, which allows the adiabatic evolution of the two
components of the pressure tensor (the parallel and perpendicular components
with respect to the local magnetic field), we performed 3D numerical
simulations of forced turbulence in order to study the amplification of an
initially weak seed magnetic field. We found that the growth rate of the
magnetic energy is comparable to that of the ordinary MHD turbulent dynamo, but
the magnetic energy saturates in a level smaller than of the MHD case. We also
found that a necessary condition for the dynamo works is to impose limits to
the anisotropy of the pressure.Comment: 3 pages, 1 figure, 274 IAU Symposium: Advances in Plasma Astrophysic
Efeito do número de nós sobre o crescimento inicial de plantas de crajiru (Arrabidaea chica (Humb. & Bonpl.) B. Verl.).
O objetivo deste trabalho foi avaliar tipos de estacas e o efeito do número de brotações sobre o crescimento e produção de folhas de crajiru.bitstream/CPAF-RO-2010/12384/1/ct-99-crajiru.pd
Features of collisionless turbulence in the intracluster medium from simulated Faraday Rotation maps
Observations of the intracluster medium (ICM) in galaxy clusters suggest for
the presence of turbulence and the magnetic fields existence has been proved
through observations of Faraday Rotation and synchrotron emission. The ICM is
also known to be filled by a rarefied weakly collisional plasma. In this work
we study the possible signatures left on Faraday Rotation maps by collisionless
instabilities. For this purpose we use a numerical approach to investigate the
dynamics of the turbulence in collisionless plasmas based on an
magnetohydrodynamical (MHD) formalism taking into account different levels of
pressure anisotropy. We consider models covering the sub/super-Alfv\'enic and
trans/supersonic regimes, one of them representing the fiducial conditions
corresponding to the ICM. From the simulated models we compute Faraday Rotation
maps and analyze several statistical indicators in order to characterize the
magnetic field structure and compare the results obtained with the
collisionless model to those obtained using standard collisional MHD framework.
We find that important imprints of the pressure anisotropy prevails in the
magnetic field and also manifest in the associated Faraday Rotation maps which
evidence smaller correlation lengths in the collisionless MHD case. These
points are remarkably noticeable for the case mimicking the conditions
prevailing in ICM. Nevertheless, in this study we have neglected the decrease
of pressure anisotropy due to the feedback of the instabilities that naturally
arise in collisionless plasmas at small scales. This decrease may not affect
the statistical imprint differences described above, but should be examined
elsewhere.Comment: 24 pages, 15 figures, MNRAS accepte
- …