Neighborhood Effects on AFDC Exits: Examining the Social Isolation, Relative Deprivation, and Epidemic Theories

Linking data from the Panel Study of Income Dynamics with the 1970 and 1980 censuses, the author finds that, in accordance with the social isolation theory, neighborhood conditions greatly affect the likelihood of exiting the Aid to Families with Dependent Children (AFDC) program. Neighborhood conditions are especially strong predictors of leaving the program for African Americans, high school dropouts, and for those who marry. Members of each of these groups stay on welfare significantly longer when they live in the most economically depressed neighborhoods of neighborhoods with a relatively high proportion of manufacturing relative to professional and executive workers. I test two additional theories of neighborhood effects: relative deprivation and epidemic theories

Childhood and Adolescent Neighborhood Effects on Adult Income: Using Siblings to Examine Differences in Ordinary Least Squares and Fixed-Effect Models

Using sibling data from the Panel Study of Income Dynamics, this article examines the effects of child and adolescent neighborhood conditions on adult income. Estimates from fixed-effect models and ordinary least squares regression (OLS) models are compared at four stages of childhood development, with three important findings. First, OLS models that include extensive control variables do not necessarily overstate the effects of neighborhoods. Second, neighborhoods have both linear and nonlinear relationships with adult economic well-being. Third, neighborhoods exert effects on even the youngest children

Work and Economic Outcomes After Welfare

Using data from the 1969 to 1993 Panel Study of Income Dynamics, this article examines a number of models to determine the characteristics of AFDC recipients who fare well economically after they initially leave the welfare system. The study includes analyses of income levels, time spent employed and not employed, and time spent below the poverty line. Hypotheses regarding state welfare payments, area economic conditions, human capital and time spent receiving welfare are examined. The findings indicate that area employment conditions and the ability to quickly find work greatly affect the likelihood of faring well economically after welfare. We found that time spent receiving welfare had some small negative effects on post-welfare economic outcomes. However, former welfare recipients living in states with more generous welfare payments are as likely to work, to not use welfare, and are generally as well off as those living in states with less generous welfare payments. These results indicate that high welfare benefit levels may not be a disincentive to work. The findings also indicate that women who have little job experience, who lack education, and who have many or more children after AFDC, fare economically worse than others

The Welfare Myth: Disentangling the Long-Term Effects of Poverty and Welfare Receipt for Young Single Mothers

This study investigates the effects of receiving welfare as a young woman on long-term economic and marital outcomes. Specifically, we examine if there are differences between young, single mothers who receive welfare and young, single mothers who are poor but do not receive welfare. Using the 1968-1997 Panel Study of Income Dynamics, our findings suggest those who receive welfare for an extended period as young adults have the same pre-transfer income over a 10 to 20 year period as those who are poor but do not receive welfare as young adults. While we found some differences between the two groups in income levels and the likelihood of having relatively low income when control variables were not included in our models, once appropriate controls were used, these differences became statistically insignificant. The only statistically significant difference found between the two groups in our 10, 15, and 20 year models was the likelihood of being married in year 15. Our results indicate that it is income level as a young adult, as well as such factors as the unemployment rate in the area of residence, but not welfare receipt, that affect long-term income and marital outcomes

Food Stamps and Dependency: Disentangling the Short-term and Long-term Economic Effects of Food Stamp Receipt and Low Income for Young Mothers

The Food Stamp Program (FSP) remains one of the most widely used of all U.S. social safety net programs. While a substantial body of research has developed around the primary goals of the program- improving food access, nutrition, and health among lowincome families-less attention has been paid to the broader goals of hardship and poverty reduction. Using 38 years of data from the Panel Study of Income Dynamics, we examine several immediate and longer-term economic outcomes of early adult FSP participation for a sample of3,848 young mothers. While FSP participation is associated with some negative outcomes in the immediate future in areas including family income-to-needs and transfer income, such effects are substantially reduced or disappear over the long run. These results suggest that concerns about the adverse economic effects of assistance, based solely on short-term outcomes or outcomes measured at a single point in time, do not hold for the long run. We find no evidence that food stamp recipients in early motherhood are any more or less dependent on public assistance programs than other young mothers who have low income but do not use food stamps

Geographic and species association of hepatitis B virus genotypes in non-human primates

AbstractInfection with hepatitis B virus (HBV) has been detected in human populations thoughout the world, as well as in a number of ape species (Pan troglodytes, Gorilla gorilla, gibbons [Nomascus and Hylobates species] and Pongo pygmaeus). To investigate the distribution of naturally occurring HBV infection in these species and other African Old World monkey species (Cercopithecidae), we screened 137 plasma samples from mainly wild caught animals by polymerase chain reaction (PCR) using several of highly conserved primers from the HB surface (HBs) gene, and for HBs antigen (HBsAg) by ELISA. None of the 93 Cercopithecidae screened (6 species) showed PCR or serology evidence for HBV infection; in contrast 2 from 8 chimpanzees and 5 from 22 gibbons were PCR-positive with each set of primers.Complete genome sequences from each of the positive apes were obtained and compared with all previously published complete and surface gene sequences. This extended phylogenetic analysis indicated that HBV variants from orangutans were interspersed by with HBV variants from southerly distributed gibbon species (H. agilis and H. moloch) occupying overlapping or adjacent habitat ranges with orangutans; in contrast, HBV variants from gibbon species in mainland Asia were phylogenetically distinct. A geographical rather than (sub)species association of HBV would account for the distribution of HBV variants in different subspecies of chimpanzees in Africa, and explain the inlier position of the previously described lowland gorilla sequence in the chimpanzee clade. These new findings have a number of implication for understanding the origins and epidemiology of HBV infection in non-human primates

Coevolved mutations reveal distinct architectures for two core proteins in the bacterial flagellar motor

Switching of bacterial flagellar rotation is caused by large domain movements of the FliG protein triggered by binding of the signal protein CheY to FliM. FliG and FliM form adjacent multi-subunit arrays within the basal body C-ring. The movements alter the interaction of the FliG C-terminal (FliGC) "torque" helix with the stator complexes. Atomic models based on the Salmonella entrovar C-ring electron microscopy reconstruction have implications for switching, but lack consensus on the relative locations of the FliG armadillo (ARM) domains (amino-terminal (FliGN), middle (FliGM) and FliGC) as well as changes during chemotaxis. The generality of the Salmonella model is challenged by the variation in motor morphology and response between species. We studied coevolved residue mutations to determine the unifying elements of switch architecture. Residue interactions, measured by their coevolution, were formalized as a network, guided by structural data. Our measurements reveal a common design with dedicated switch and motor modules. The FliM middle domain (FliMM) has extensive connectivity most simply explained by conserved intra and inter-subunit contacts. In contrast, FliG has patchy, complex architecture. Conserved structural motifs form interacting nodes in the coevolution network that wire FliMM to the FliGC C-terminal, four-helix motor module (C3-6). FliG C3-6 coevolution is organized around the torque helix, differently from other ARM domains. The nodes form separated, surface-proximal patches that are targeted by deleterious mutations as in other allosteric systems. The dominant node is formed by the EHPQ motif at the FliMMFliGM contact interface and adjacent helix residues at a central location within FliGM. The node interacts with nodes in the N-terminal FliGc α-helix triad (ARM-C) and FliGN. ARM-C, separated from C3-6 by the MFVF motif, has poor intra-network connectivity consistent with its variable orientation revealed by structural data. ARM-C could be the convertor element that provides mechanistic and species diversity.JK was supported by Medical Research Council grant U117581331. SK was supported by seed funds from Lahore University of Managment Sciences (LUMS) and the Molecular Biology Consortium

Randomization in Laboratory Procedure Is Key to Obtaining Reproducible Microarray Results

The quality of gene expression microarray data has improved dramatically since the first arrays were introduced in the late 1990s. However, the reproducibility of data generated at multiple laboratory sites remains a matter of concern, especially for scientists who are attempting to combine and analyze data from public repositories. We have carried out a study in which a common set of RNA samples was assayed five times in four different laboratories using Affymetrix GeneChip arrays. We observed dramatic differences in the results across laboratories and identified batch effects in array processing as one of the primary causes for these differences. When batch processing of samples is confounded with experimental factors of interest it is not possible to separate their effects, and lists of differentially expressed genes may include many artifacts. This study demonstrates the substantial impact of sample processing on microarray analysis results and underscores the need for randomization in the laboratory as a means to avoid confounding of biological factors with procedural effects

Randomization in Laboratory Procedure Is Key to Obtaining Reproducible Microarray Results

The quality of gene expression microarray data has improved dramatically since the first arrays were introduced in the late 1990s. However, the reproducibility of data generated at multiple laboratory sites remains a matter of concern, especially for scientists who are attempting to combine and analyze data from public repositories. We have carried out a study in which a common set of RNA samples was assayed five times in four different laboratories using Affymetrix GeneChip arrays. We observed dramatic differences in the results across laboratories and identified batch effects in array processing as one of the primary causes for these differences. When batch processing of samples is confounded with experimental factors of interest it is not possible to separate their effects, and lists of differentially expressed genes may include many artifacts. This study demonstrates the substantial impact of sample processing on microarray analysis results and underscores the need for randomization in the laboratory as a means to avoid confounding of biological factors with procedural effects