1,512 research outputs found
Galaxy Clusters in the Line of Sight to Background Quasars: I. Survey Design and Incidence of MgII Absorbers at Cluster Redshifts
We describe the first optical survey of absorption systems associated with
galaxy clusters at z= 0.3-0.9. We have cross-correlated SDSS DR3 quasars with
high-redshift cluster/group candidates from the Red-Sequence Cluster Survey. We
have found 442 quasar-cluster pairs for which the MgII doublet might be
detected at a transverse (physical) distance d<2 Mpc from the cluster centers.
To investigate the incidence (dN/dz) and equivalent-width distribution n(W) of
MgII systems at cluster redshifts, two statistical samples were drawn out of
these pairs: one made of high-resolution spectroscopic quasar observations (46
pairs), and one made of quasars used in MgII searches found in the literature
(375 pairs). The results are: (1) the population of strong MgII systems
(W_0>2.0 Ang.) near cluster redshifts shows a significant (>3 sigma)
overabundance (up to a factor of 15) when compared with the 'field' population;
(2) the overabundance is more evident at smaller distances (d<1 Mpc) than
larger distances (d<2 Mpc) from the cluster center; and, (3) the population of
weak MgII systems (W_0<0.3 Ang.) near cluster redshifts conform to the field
statistics. Unlike in the field, this dichotomy makes n(W) in clusters appear
flat and well fitted by a power-law in the entire W-range. A sub-sample of the
most massive clusters yields a stronger and still significant signal. Since
either the absorber number density or filling-factor/cross-section affects the
absorber statistics, an interesting possibility is that we have detected the
signature of truncated halos due to environmental effects. Thus, we argue that
the excess of strong systems is due to a population of absorbers in an
overdense galaxy environment, and the lack of weak systems to a different
population, that got destroyed in the cluster environment. (Abridged)Comment: Accepted for publication in the Astrophysical Journa
Perfil fitoquÃmico do órgão subterrâneo de Jacaratia Corumbensis Kuntze (Caricaceae).
Jacaratia corumbensis, vulgarmente conhecida como "mamãozinho", e um arbusto que atinge até quatro metro de altura, de ocorrência escassa nas caatingas nordestinas, cujo órgão subterrâneo, de proporções gigantescas, armazena grande quantidade de água, sendo utilizado no preparo de doce caseiro. O estudo aqui apresentado em camada delgada de modo a definir as principais moléculas ou grupos de moleculas presentes. Investigou-se a presença de: alcaloides; esteroides/triterpenoides; cumarinas; flavanoides; proantocianidinas; saponinas; e oses. Constatou-se a presença unicamente de esteroides/triterpenoides, majoritariamente B-sitosterol, e oses (redutores e não redutores), com predominância de glicose (CAPE 5)
Turbulence generation by a shock wave interacting with a random density inhomogeneity field
When a planar shock wave interacts with a random pattern of pre-shock density
non-uniformities, it generates an anisotropic turbulent velocity/vorticity
field. This turbulence plays an important role at the early stages of the
mixing process in the compressed fluid. This situation emerges naturally in
shock interaction with weakly inhomogeneous deuterium-wicked foam targets in
Inertial Confinement Fusion (ICF) and with density clumps/clouds in
astrophysics. We present an exact small-amplitude linear theory describing such
interaction. It is based on the exact theory of time and space evolution of the
perturbed quantities behind a corrugated shock front for a single-mode
pre-shock non-uniformity. Appropriate mode averaging in 2D results in closed
analytical expressions for the turbulent kinetic energy, degree of anisotropy
of velocity and vorticity fields in the shocked fluid, shock amplification of
the density non-uniformity, and sonic energy flux radiated downstream. These
explicit formulas are further simplified in the important asymptotic limits of
weak/strong shocks and highly compressible fluids. A comparison with the
related problem of a shock interacting with a pre-shock isotropic vorticity
field is also presented.Comment: This article corresponds to a presentation given at the Second
International Conference and Advanced School "Turbulent Mixing and Beyond,"
held on 27 July - 07 August 2009 at the Abdus Salam International Centre for
Theoretical Physics, Trieste, Italy. That Conference Proceeding will be
published as a Topical Issue of the Physica Scripta IOP scienc
Desempenho produtivo de cultivares de girassol (Helianthus annuus L.) sob condições irrigadas no Rio Grande do Norte.
Este trabalho teve como objetivo avaliar o desempenho produtivo de cultivares de girassol em regime de irrigação. O ensaio foi conduzido na Estação Experimental da EMPARN, (Ipanguaçu,RN, 05º37? S 36º50? W , 70 m). O solo foi é um Neossolo de alta fertilidade, com adubação de 50-20-20 kg/ha + 2kg de Boro.. Utilizou-se irrigaçãoi por sulco e durante o ciclo da cultura foram aplicados 510 mm de água.. Foram avaliadas 26 cultivares, sendo 24 hÃbridos e 02 variedades em foi blocos ao acaso, com 04 repetições. As médias de rendimentos de grãos (aquênios) variaram de 2.110 kg/ha a 4.120 kg/ha, com média de 3.218 kg/ha. SobressaÃram-se os hÃbridos GRIZZLY, T 700, MG 52, NEON, HLS 03 e o HÉLIO 358, com respectivamente, 4.120 kg/ha, 4.097kg/ha, 3.705kg/ha, 3.638 kg/ha, 3.633 kg/ha e 3.610 kg/ha. Os maiores rendimentos de óleo foram obtidos com os genótipos MG 52, HÉLIO 358, HLS 03 e BRS-Gira 11, acima de 1.500kg/ha
Desempenho de cultivares de girassol (Helianthus annuus. L.) no Estado do Rio Grande do Norte.
Este trabalho teve como objetivo avaliar o comportamento produtivo de diversas cultivares de girassol. O ensaio foi instalado no MunicÃpio de Canguaretama/RN no ano agrÃcola de 2007( 6º22 ? S, 35º 07? W, altitude de 5m, temperatura média anual de 25 ºC O solo é classificado como latossolo amarelo de textura arenosa. A precipitação ocorrida durante a condução do ensaio foi de 904,6 mm. O delineamento experimental foi blocos ao acaso, com quatro repetições. Fez-se uma adubação utilizando-se a fórmula: 60-80-60 kg/ha mais 2 kg/ha de boro.Os materiais avaliados mostraram-se precoces, com uma média de 39 dias para atingir o florescimento inicial. Os rendimentos médios de grãos das cultivares ficaram entre 1.356 kg/ha e 2.581 kg/ha, com média geral de 1.829 kg/ha.Três cultivares apresentaram rendimentos médios de grãos acima de 2.200 kg/ha, sobressaindo-se os materiais M 734, HLA 863 e GIRA 19 e com o teor de óleo superior a 42 %
An Application of Simple and Compact Genetic Algorithms for Estimating Harmonic Components
This work presents an approach for the harmonic components estimation problem present in electrical power systems by making use of evolutionary algorithms. The referential data were obtained by the ATP (Alternative Transients Program) software. Compact and simple genetic algorithms were applied to estimate the parameters of non-linear function to generate a waveform as similar as possible to the one provided by the ATP software. The results yielded by the aforementioned evolutionary algorithms were then compared with one another in a number of scenarios, using the values obtained by the waveform of reference generated by the ATP software. The comparisons were used to seek evidence of which algorithm solved the problem in a setting with limited availability of computational resources. Based on the generated results, it has been found that compact genetic algorithm satisfactorily solves the proposed problem and it is the most indicated method, when less computational effort is required
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