The VLBA Imaging and Polarimetry Survey at 5 GHz

We present the first results of the VLBA Imaging and Polarimetry Survey (VIPS), a 5 GHz VLBI survey of 1,127 sources with flat radio spectra. Through automated data reduction and imaging routines, we have produced publicly available I, Q, and U images and have detected polarized flux density from 37% of the sources. We have also developed an algorithm to use each source's I image to automatically classify it as a point-like source, a core-jet, a compact symmetric object (CSO) candidate, or a complex source. The mean ratio of the polarized to total 5 GHz flux density for VIPS sources with detected polarized flux density ranges from 1% to 20% with a median value of about 5%. We have also found significant evidence that the directions of the jets in core-jet systems tend to be perpendicular to the electric vector position angles (EVPAs). The data is consistent with a scenario in which ~24% of the polarized core-jets have EVPAs that are anti-aligned with the directions of their jet components and which have a substantial amount of Faraday rotation. In addition to these initial results, plans for future follow-up observations are discussed.Comment: 36 pages, 3 tables, 13 figures; accepted for publication in Ap

Stable isotope food-web analysis and mercury biomagnification in polar bears ( Ursus maritimus )

Mercury (Hg) biomagnification occurs in many ecosystems, resulting in a greater potential for toxicological effects in higher-level trophic feeders. However, Hg transport pathways through different food-web channels are not well known, particularly in high-latitude systems affected by the atmospheric Hg deposition associated with snow and ice. Here, we report on stable carbon and nitrogen isotope ratios, and Hg concentrations, determined for 26, late 19th and early 20th century, polar bear ( Ursus maritimus ) hair specimens, collected from catalogued museum collections. These data elucidate relationships between the high-latitude marine food-web structure and Hg concentrations in polar bears. The carbon isotope compositions of polar bear hairs suggest that polar bears derive nutrition from coupled food-web channels, based in pelagic and sympagic primary producers, whereas the nitrogen isotope compositions indicate that polar bears occupy > fourth-level trophic positions. Our results show a positive correlation between polar bear hair Hg concentrations and δ 15 N. Interpretation of the stable isotope data in combination with Hg concentrations tentatively suggests that polar bears participating in predominantly pelagic food webs exhibit higher mercury concentrations than polar bears participating in predominantly sympagic food webs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73930/1/j.1751-8369.2009.00114.x.pd

Reprodução de Nycticorax nycticorax (Linnaeus) no litoral de Santa Catarina, Brasil Reproduction of the Nycticorax nycticorax (Linnaeus) in the Santa Catarina's coast, Brazil

O savacu Nycticorax nycticorax (Linnaeus, 1758) é uma espécie de hábitos crepusculares e noturnos, com ampla distribuição geográfica. Sua biologia reprodutiva tem sido intensivamente estudada nos países de ocorrência, entretanto, no Brasil, é comumente citada nos levantamentos de ornitólogos, mas não existem informações disponíveis sobre seu ciclo de vida. Esse trabalho objetiva contribuir para o conhecimento da biologia reprodutiva dessa espécie no litoral catarinense. As amostragens foram realizadas nos anos de 2000 a 2002 na Ilha dos Pássaros e de 2002 na Ilha dos Lobos, Santa Catarina. As maiores abundâncias de exemplares e ninhos com ovos ocorreram em outubro, sendo que o comprimento médio dos ovos variou entre 5,02 &plusmn; 0,23 a 5,07 &plusmn; 0,21 cm e o volume 31,71 &plusmn; 2,64 a 35,92 &plusmn; 3,47 cm³ e as maiores freqüências de filhotes em novembro, culminando o abandono da colônia em meados de janeiro. Foram identificados sete itens nos regurgitos dos filhotes, sendo que os peixes marinhos representaram 44,4% da massa total. O principal predador na colônia foi o urubu-comum, que atuou sobre os ovos no início da temporada e os filhotes no final.<br>The black-crowned night heron N. nycticorax (Linnaeus, 1758) is a aquatic bird with twilight and night habits, with wide geographical distribution. His reproductive biology has been studied intensively at the occurrence countries, however, in Brazil, it is mentioned commonly in the ornithologists' risings, but available information don't exist on his life cycle. This work aims to contribute for the knowledge of the reproductive biology of that species in the Santa Catarina coast. The samplings were accomplished in the years from 2000 to 2002 in the Ilha dos Pássaros and of 2002 in the Ilha dos Lobos, Santa Catarina. The largest abundances of individuals and nests with eggs happened in October, and the medium length of the eggs varied between 5.02 &plusmn; 0.23 to 5.07 &plusmn; 0.21 cm and the volume 31.71 &plusmn; 2.64 to 35.92 &plusmn; 3.47 cm³ and the largest frequencies of nestlings in November, culminating the abandonment of the colony in the middle of January. They were identified seven items in the chick regurgitations of the nestlings, and the sea fish represented 44.4% of the total weight. The main predator in the colony was the black vulture, that it acted on the eggs in the beginning of the season and the nestlings in the end

Being cool is risky business: Young men’s within-peer-group status, heavy alcohol consumption and aggression in bars

Although research suggests that male peers play an important role in young men’s bar aggression, little is known about specific peer-related predictors of this behaviour. Both bar aggression and heavy alcohol consumption are associated with traditional masculinity and peer-acceptance among young men; thus, engagement in these behaviours may help young men maintain positive social standings within their male peer groups. Further, increased heavy alcohol consumption may, in turn, facilitate bar aggression. We conducted the first empirical analysis of the association between young men’s within-peer-group status and propensity to respond aggressively to provocation in bars. We also examined the mediating role of heavy episodic drinking in this relationship. In this study, male bar-going university students (N = 116; Mage = 19 years) completed self-reported measures of their within-peer-group status, frequency of heavy episodic drinking in the past month, and their likelihood to physically aggress in response to hypothetical provocation at a bar. As hypothesised, the higher participants’ within-peer-group status, the more likely they were to report that they would respond to provocation at a bar with physical aggression. Moreover, the positive association between status and bar aggression was explained by increased engagement in heavy alcohol consumption. Results suggest that future intervention efforts to prevent bar aggression and harmful drinking practices may benefit from addressing issues of status among young men