Welfare Reform and Immigrant Participation in the Supplemental Security Income Program

We examine the effect of the 1996 welfare reform legislation on participation in the Supplemental Security Income (SSI) program by immigrants. Although none of the immigrants on the SSI rolls before welfare reform lost eligibility, the potential exists for future impacts on the SSI caseload and the well-being of recent immigrants. We use microdata files from the Social Security Administration’s Continuous Work History Sample matched to administrative data on SSI participation for the period 1993 to 1999. We estimate simple models of SSI participation and compare our results to the existing literature. We then estimate a series of difference-in-differences models of SSI participation. These models compare SSI participation by immigrants relative to nativeborn individuals, and among affected immigrants relative to unaffected immigrants and native-born individuals, before and after welfare reform. Descriptive results indicate that the percentage of immigrants and natives receiving SSI decreased after welfare reform, but by a larger percentage for natives than for immigrants. The probability of SSI participation decreased after welfare reform for immigrants who were affected by the legislation relative to immigrants who were unaffected. The difference-in-differences estimate is positive for immigrants relative to otherwise similar natives, but the estimated effect among affected immigrants is about half as large as the effect for unaffected immigrants. When the sample is limited to low earners as a proxy for the SSI means test, the results are qualitatively unchanged but quantitatively much stronger. Authors’ Acknowledgements We are grateful to Ulyses Balderas for assisting with the collection of some data used here. A previous version of this paper was presented at the 2004 Western Regional Science Association Annual Meeting, February 25-28, 2004, Maui, HI.

Myeloperoxidase-derived oxidation: mechanisms of biological damage and its prevention

There is considerable interest in the role that mammalian heme peroxidase enzymes, primarily myeloperoxidase, eosinophil peroxidase and lactoperoxidase, may play in a wide range of human pathologies. This has been sparked by rapid developments in our understanding of the basic biochemistry of these enzymes, a greater understanding of the basic chemistry and biochemistry of the oxidants formed by these species, the development of biomarkers that can be used damage induced by these oxidants in vivo, and the recent identification of a number of compounds that show promise as inhibitors of these enzymes. Such compounds offer the possibility of modulating damage in a number of human pathologies. This reviews recent developments in our understanding of the biochemistry of myeloperoxidase, the oxidants that this enzyme generates, and the use of inhibitors to inhibit such damage

Overlooked examples of cloud self-organization at the mesoscale

Stratocumulus clouds are common in the tropical and subtropical marine boundary layer, and understanding these clouds is important due to their significant impact on the earth's radiation budget. Observations show that the marine boundary layer contains complex, but poorly understood processes, which, from time to time, result in the observable self-organization of cloud structures at scales ranging from a few to a few thousand kilometers. Such shallow convective cloud features, typically observed as hexagonal cells, are known generally as mesoscale cellular convection (MCC). Actinoform clouds are rarer, but visually more striking forms of MCC, which possess a radial structure. Because mesoscale cloud features are typically too large to be observed from the ground, observations of hexagonal cells historically date only to the beginning of satellite meteorology. Examples of actinoform clouds were shown in the venerable “Picture of the Month” series in Monthly Weather Review in the early 1960s, but these clouds were generally forgotten as research focused on hexagonal cells. Recent high-resolution satellite images have, in a sense, “rediscovered” actinoform clouds, and they appear to be much more prevalent than had been previously suspected. We show a number of examples of actinoform clouds from a variety of locations worldwide. In addition, we have conducted a detailed case study of an actinoform cloud system using data from the Multiangle Imaging SpectroRadiometer (MISR) and the Geostationary Operational Environmental Satellite (GOES), including analysis of cloud heights, radiative properties, and the time-evolution of the cloud system. We also examine earlier theories regarding actinoform clouds in light of the new satellite data

Are Recent Peculiar Velocity Surveys Consistent?

We compare the bulk flow of the SMAC sample to the predictions of popular cosmological models and to other recent large-scale peculiar velocity surveys. Both analyses account for aliasing of small-scale power due to the sparse and non-uniform sampling of the surveys. We conclude that the SMAC bulk flow is in marginal conflict with flat COBE-normalized Lambda-CDM models which fit the cluster abundance constraint. However, power spectra which are steeper shortward of the peak are consistent with all of the above constraints. When recent large-scale peculiar velocity surveys are compared, we conclude that all measured bulk flows (with the possible exception of that of Lauer & Postman) are consistent with each other given the errors, provided the latter allow for `cosmic covariance'. A rough estimate of the mean bulk flow of all surveys (except Lauer & Postman) is ~400 km/s towards l=270, b=0.Comment: 8 pages, 3 figures. To appear in Proceedings of the Cosmic Flows Workshop, Victoria, B. C., Canada, July 1999, eds. S. Courteau, M. Strauss, and J. Willic