2,533 research outputs found
Gravity with extra dimensions and dark matter interpretation: Phenomenological example via Miyamoto-Nagai galaxy
A configuration whose density profile coincides with the Newtonian potential
for spiral galaxies is constructed from a 4D isotropic metric plus extra
dimensional components. A Miyamoto-Nagai ansatz is used to solve Einstein
equations. The stable rotation curves of such system are computed and, without
fitting techniques, we recover with accuracy the observational data for flat or
not asymptotically flat galaxy rotation curves. The density profiles are
reconstructed and compared to that obtained from the Newtonian potential.Comment: 10 pages, 10 figures, submitted to Brazilian Journal of Physic
Analytical ray tracing system: introducing art, a C-library designed for seismic applications
Ray tracing technique is an important tool not only to forward but also for inverse problems in Geophysics, "which most of the seismic processing steps depend on. However, implementing ray tracing codes can be very time consuming. This article presents a computer library to trace rays in 2.5D media composed by a stack of layers. The velocity profile inside each layer is such that the eikonal equation can be analytically solved. Therefore, the ray tracing within such profile is Made fast and accurate. The great advantage of an analytical ray tracing library is the numerical precision of the quantities computed and the fast execution of the implemented codes. Even though ray tracing programs exist for a long time, for example the seis88 package by Cerveny, most of those programs use a numerical approach to compute the ray. Regardless of the fact that numerical methods can solve more general problems, the analytical ones could be part of a more sophisticated simulation process, where the ray tracing time is completely relevant. We demonstrate the feasibility of our codes using several examples (Miqueles et al., 2013) [1]. The library can also be used for other applications besides seismic, e.g., optics and tomography1851274293CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNP
Utilização da contagem de tosse e espirro como indicadores da ocorrência e severidade de pneumonias e rinite atrófica, respectivamente.
bitstream/CNPSA/15851/1/cot242.pd
Caracterização do sistema hidráulico e da qualidade da água em granjas de suínos da Região Sul do Brasil nas fases creche, crescimento e terminação.
bitstream/item/58382/1/CUsersPiazzonDocuments247.pdfAcesso em: 13 jun. 2007
Dielectron widths of the S-, D-vector bottomonium states
The dielectron widths of and vector decay
constants are calculated using the Relativistic String Hamiltonian with a
universal interaction. For the dielectron widths and
their ratios are obtained in full agreement with the latest CLEO data. For
and a good agreement with experiment is
reached only if the 4S--3D mixing (with a mixing angle ) and 6S--5D mixing (with ) are taken into
account. The possibility to observe higher "mixed -wave" resonances,
with is discussed. In particular,
, originating from the pure state,
can acquire a rather large dielectron width, eV, so that this
resonance may become manifest in the experiments. On the contrary, the
widths of pure -wave states are very small,
eV.Comment: 13 pages, no figure
Chemical characterization and antioxidant activity of sulfated polysaccharide from the red seaweed Gracilaria birdiae
Hydrocolloids from seaweeds have interesting functional properties, such as antioxidant activity and gelling ability. A polysaccharide was isolated by aqueous extraction at 90 C from the red seaweed
Gracilaria birdiae (Gb), with a yield of 27.2% of the seaweed dry weight. The sulfate content of the polysaccharide was 8.4% and the main sugars present were galactose (65.4 mol%), 3,6-anhydrogalactose
(25.1 mol%) and 6-O-methylgalactose (9.2 mol%). Gel permeation chromatography showed that Gb polysaccharide is a heterogeneous system, with molar mass at the main peak of 3.7 105 g mol1 and
a shoulder of 2.6 106 g mol1. The sulfated polysaccharide of Gb characterized by FTIR exhibits the characteristic bands of agarocolloids (at 1375 and 770 cm1).The rheological behavior of Gb sulfated polysaccharide exhibits a gel-like behavior close to the one observed in commercial agar.
The antioxidant properties of Gb sulfated polysaccharide were evaluated by measuring DPPH freeradical scavenging effect, showing that this polysaccharide has a moderate effect in inhibiting the
formation of those radicals.The author B. W. S. Souza was recipient of a fellowship from the Coordenaco de Aperfeicoamento de Pessoal de Nivel Superior (CAPES, Brazil). The authors M. A. Cerqueira, J.T. Martins and A. C. Pinheiro were recipient of fellowships from the Fundacao para a Ciencia e Tecnologia (FCT, Portugal) through grants SFRH/BD/23897/2005, SFRH/BD/32566/2006 and SFRH/BD/48120/2008, respectively. The authors thank the NGO Terramar for donating the algae. Thanks are also due to the financial support of FCT to the Research Unit 62/94-QOPNA
Fatores de risco associados aos problemas dos leitões no período pós-desmame.
Porque conhecer os fatores de risco?; Estudos desenvolvidos na Embrapa Suínos e Aves; Como usar esta tecnologia?bitstream/item/68657/1/DMeu-DiscoCNPSA-COM.-TEC.-226-98CNPSA-COM.-TEC.-226-98.pd
Anti-de Sitter curvature radius constrained by quasars in brane-world scenarios
This paper is intended to investigate the luminosity due to accretion of gas
in supermassive black holes (SMBHs) in the center of quasars, using a
brane-world scenario naturally endowed with extra dimensions, whereon theories
formulated introduce corrections in the field equations at high energies. SMBHs
possess the necessary highly energetic environment for the introduction of
these corrections, which are shown to produce small deviations in all SMBH
properties and, consequentely, corrections in the accretion theory that
supports quasars radiative processes. The radiative flux observed from quasars
indicates these deviations, from which the magnitude of the AdS bulk
curvature radius, and consequently the extra dimension compactification radius
is estimated.Comment: 11 pages, RevTeX, Eq.(2) and (3) expanded, and comments thereon
update
Hybridization in human evolution: Insights from other organisms
During the late Pleistocene, isolated lineages of hominins exchanged genes thus influencing genomic variation in humans in both the past and present. However, the dynamics of this genetic exchange and associated phenotypic consequences through time remain poorly understood. Gene exchange across divergent lineages can result in myriad outcomes arising from these dynamics and the environmental conditions under which it occurs. Here we draw from our collective research across various organisms, illustrating some of the ways in which gene exchange can structure genomic/phenotypic diversity within/among species. We present a range of examples relevant to questions about the evolution of hominins. These examples are not meant to be exhaustive, but rather illustrative of the diverse evolutionary causes/consequences of hybridization, highlighting potential drivers of human evolution in the context of hybridization including: influences on adaptive evolution, climate change, developmental systems, sex-differences in behavior, Haldane’s rule and the large X-effect, and transgressive phenotypic variation.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151330/1/evan21787.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151330/2/evan21787_am.pd
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