Dust in Supernovae and Supernova Remnants II: Processing and survival

Observations have recently shown that supernovae are efficient dust factories, as predicted for a long time by theoretical models. The rapid evolution of their stellar progenitors combined with their efficiency in precipitating refractory elements from the gas phase into dust grains make supernovae the major potential suppliers of dust in the early Universe, where more conventional sources like Asymptotic Giant Branch (AGB) stars did not have time to evolve. However, dust yields inferred from observations of young supernovae or derived from models do not reflect the net amount of supernova-condensed dust able to be expelled from the remnants and reach the interstellar medium. The cavity where the dust is formed and initially resides is crossed by the high velocity reverse shock which is generated by the pressure of the circumstellar material shocked by the expanding supernova blast wave. Depending on grain composition and initial size, processing by the reverse shock may lead to substantial dust erosion and even complete destruction. The goal of this review is to present the state of the art about processing and survival of dust inside supernova remnants, in terms of theoretical modelling and comparison to observations

Prevalência de sorovares de Salmonella isolados de aves no Brasil Prevalence of Salmonella serovars isolated from birds in Brazil

Foram caracterizadas antigenicamente amostras de Salmonella isoladas de aves (portadoras e doentes) provenientes de diversas regiões do país durante o período de 1962 a 1991. Nas 2123 culturas analisadas foram reconhecidos 90 sorovares, distribuídos em 14 sorogrupos com predominância dos grupos O:9 (40,0%), O:4 (33,3%), O:7 (10,6%) e O: 3,10 (6,7%). A maior diversidade de sorovares foi reconhecida no sorogrupo O:7 com 22 tipos distintos, secundado por O:4, O:3,10 e O:9, constituídos de 19, 15 e 10 sorotipos, respectivamente. No computo geral, foi determinada a média de 10,8 sorovares isolados por ano. Os sorovares classificados como muito frequentes nos três decênios, representando 65 a 67%, dos isolamentos, foram S. Gallinarum, S. Pullorum, S. Typhimurium, S. Heidelberg, S. Enteritidis e S. Infantis. Considerações de natureza bacteriológica e epidemiológica foram discutidas em relação a alguns dos sorotipos prevalentes.<br>Salmonella strains were isolated from ill and shedding birds in several regions of Brazil between 1962 and 1991. Serotyping of 2123 isolates showed 90 serovars pertaining to 14 serogroups. There was a predominance of groups O:9 (40.0%), O:4 (33.3%), O:7 (10.6%) and O:3,10 (6.7%). Major serovar diversity was found to serogroup O:7 that accounted for 22 different types, followed by serogroups O:4, O:3,10 and O:9 with 19, 15 and 10 serotypes respectively. An average of 10.8 serovars was isolated per year. S. Gallinarum, S. Pullorum, S. Typhimurium, S. Heidelberg, S. Enteritidis and S. Infantis were the most frequent serovars found over the 30 years, representing 65% to 67% of the total of isolates. Bacteriological and epidemiological aspects concerning a number of serotypes are discussed