Infrared Observations of AGN

We present results from an imaging and spectroscopic study of the dust properties of Seyfert galaxies in the 1-10um range. The data are compared to state of the art models of torus emission to constrain geometrical and physical properties of the obscuring medium.Comment: 2 pages, to appear in the IAU Symp.No.222 proceedings:"The Interplay among Black Holes, Stars and ISM in Galactic Nuclei", Gramado, Brazil, March 1-5, 200

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

Biologia populacional de Macrobrachium jelskii (MIERS, 1778) (Crustacea, Decapoda, Palaemonidae) em uma planície inundável na Amazônia Oriental, Brasil.

A biologia populacional de M. jelskii foi investigada com ênfase na distribuição de frequência de comprimento, razão sexual, período reprodutivo e relação peso comprimento. A amostragem foi realizada durante o período de abril/2008 a maio/2009 junto às macrófitas, em um transecto de 50 m. As coletas foram obtidas com peneiras de 55 cm de diâmetro e malha de 2 mm, a cada 2 m, totalizando 25 amostras em todo o período de estudo. No laboratório, os exemplares de M. jelskii foram medidos, pesados, sexados e as fêmeas classificadas macroscopicamente quanto ao grau de maturação. Foram encontrados 910 exemplares, 505 machos e 405 fêmeas. O comprimento total variou de 9,7 a 50,3 mm e a maior frequência relativa de indivíduos ocorreu entre as classes de 19,7 a 21,7 mm e 37,7 a 39,7 mm. Os machos apresentaram tamanhos superiores e a proporção sexual foi instável entre os meses. A reprodução incidiu no período mais chuvoso. As fêmeas obtiveram crescimento isométrico e os machos alométrico negativo, demonstrando dimorfismo nas relações peso total/comprimento total de ambos os sexos

Reactivity Effects in a Very-High-Temperature Pebble-Bed Reactor

The very-high-temperature reactor (VHTR) is one of the most promising and innovative designs selected by the Generation IV International Forum. Although previous papers have focused on the study and optimization of several parameter of a VHTR conceptual design, there is still much work needed to achieve the commercial introduction of this technology. The primary aim of this study is to obtain the reactivity effects of such parameters as the temperature of the fuel, moderator, and reflector, and the poisoning by 135Xe and 149Sm in the VHTR critically. To reach this goal, the widely-used MCNP6 code was employed in order to simulate the neutronics of the VHTR. The viability of the utilization of the MCNP6 code and the developed model for the study of the physics of the VHTR core was confirmed through the calculation and comparison with benchmarks provided by the IAEA. Based on the results of the temperature coefficients of reactivity obtained, a negative reactivity effect on the system of about 12 pcm/K was found, as is expected in all the nuclear fission reactors, while the combined effect of fission products 135Xe and 149Sm implies a negative reactivity of 3475 pcm

The Reddening-Free Decline Rate Versus Luminosity Relationship for Type Ia Supernovae

We develop a method for estimating the host galaxy dust extinction for type Ia supernovae based on an observational coincidence first noted by Lira (1995), who found that the B-V evolution during the period from 30-90 days after V maximum is remarkably similar for all events, regardless of light curve shape. This fact is used to calibrate the dependence of the B(max)-V(max) and V(max)-I(max) colors on the light curve decline rate parameter delta-m15, which can, in turn, be used to separately estimate the host galaxy extinction. Using these methods to eliminate the effects of reddening, we reexamine the functional form of the decline rate versus luminosity relationship and provide an updated estimate of the Hubble constant of Ho = 63.3 +- 2.2(internal) +- 3.5(external) km/s/Mpc.Comment: 32 pages, 10 figures, AJ 1999 in pres

Ocorrência natural de fungos entomopatogênicos associados à broca-do-mogno, Hypsipyla grandella (Lepidoptera: Pyralidae).

Resumo

Cyanide contents in leaf tissues of Manihot Species with forage potential.

The aim of this study was to evaluate the hydrocyanic acid content in leaves of Manihot genus accessions with potential to animal feeding