Dust in Supernovae and Supernova Remnants I : Formation Scenarios

Supernovae are considered as prime sources of dust in space. Observations of local supernovae over the past couple of decades have detected the presence of dust in supernova ejecta. The reddening of the high redshift quasars also indicate the presence of large masses of dust in early galaxies. Considering the top heavy IMF in the early galaxies, supernovae are assumed to be the major contributor to these large amounts of dust. However, the composition and morphology of dust grains formed in a supernova ejecta is yet to be understood with clarity. Moreover, the dust masses inferred from observations in mid-infrared and submillimeter wavelength regimes differ by two orders of magnitude or more. Therefore, the mechanism responsible for the synthesis of molecules and dust in such environments plays a crucial role in studying the evolution of cosmic dust in galaxies. This review summarises our current knowledge of dust formation in supernova ejecta and tries to quantify the role of supernovae as dust producers in a galaxy.Peer reviewe

Scholarly publishing depends on peer reviewers

The peer-review crisis is posing a risk to the scholarly peer-reviewed journal system. Journals have to ask many potential peer reviewers to obtain a minimum acceptable number of peers accepting reviewing a manuscript. Several solutions have been suggested to overcome this shortage. From reimbursing for the job, to eliminating pre-publication reviews, one cannot predict which is more dangerous for the future of scholarly publishing. And, why not acknowledging their contribution to the final version of the article published? PubMed created two categories of contributors: authors [AU] and collaborators [IR]. Why not a third category for the peer-reviewer?Scopu

Rural and Urban Differences in Welfare Exits: Minnesota Evidence 1986-1996

This article examines differences between rural and urban counties in the duration of welfare spells. We report evidence that suggests that parents from farming-dependent counties and rural counties are more likely to have shorter spells on welfare. The evidence appears consistent with the literature on rural low-income families in that there may be a concentration of low-wage jobs in rural counties. The difference between rural and urban areas is relevant to welfare policy as it pertains to caseload numbers, parents more likely to reach the sixty-month time limit, and parents more likely to trigger time-based policies, such as employment search. The study uses administrative data of Aid to Families With Dependent Children recipients from the state of Minnesota between 1986 and 1996. The methodology includes constructing descriptive statistics, calculating Kaplan-Meier estimates, and performing a Cox regression analysis with robustness checks across all three methods. Copyright 2005 Blackwell Publishing Ltd..