School dropout and injecting drug use in a national sample of white non-Hispanic American adults

In this study we sought to extend our previous finding of an association between school dropout and injecting drug use (IDU) among African Americans by testing the association in a sample of White non-Hispanic Americans. A nationally representative sample of White non-Hispanic Americans age eighteen years and older was drawn from public use data files of the 1995-1996 National Household Surveys on Drug Abuse (NHSDA). Adults with a self-report history of IDU were identified, and were matched to non-IDU adults in the same neighborhoods of residence. Conditional logistic regression was used to estimate the association between dropping out of high school and the occurrence of IDU. White non-Hispanic American high school dropouts were more likely than high school graduates to have injected a drug at least once. The findings of this research on non-Hispanic Whites are generally consistent with our earlier evidence on the association between educational status and a history of IDU among African-American adults. School dropout prevention programs may merit attention in an overall strategy of preventing injecting drug use and HIV/AIDS.     

Evaluation of a family-based substance abuse prevention program targeted for the middle school years

A family-based substance abuse prevention program was evaluated which emphasizes family cohesion, school and peer attachment, self-esteem, and attitudes about adolescent use of alcohol and tobacco. The program was implemented in rural communities and targeted families with students entering middle or junior high school. Baseline surveys were conducted with students and parents in four schools and were readministered one year later. Because the program was voluntary, a quasi-experimental design was used to compare participants (29 students and 28 parents) and nonparticipants (268 students and 134 parents). Analyses of covariance indicated that student participants, as compared to nonparticipants, had higher family cohesion, less family fighting, greater school attachment, higher self-esteem, and believed that alcohol should be consumed at an older age at the one year follow-up. There were fewer significant results for parent participants. Strategies for involving parents in prevention programs are discussed.     

Marijuana use and depression

The primary goal of this study is to examine the association between marijuana use and adult depressive symptomatology. The key independent variables examined are age of marijuana initiation, frequency of current marijuana use, the use of other licit and illicit drugs, and whether marijuana was used to cope with problems. The relationships among these variables are assessed using data from the Young Men and Drugs Survey (n = 1,941), a nationally representative sample of men from the 1944-1954 birth cohort. Results show that early marijuana initiation appears to be weakly associated with increased depression in adulthood. This effect, however, is mediated by educational attainment, employment status, marital status, and other drug use, notably alcohol and tobacco use. Adult frequency of marijuana use is not significantly associated with increased depression in adulthood. Finally, marijuana users who use the drug to cope with problems are more depressed than those who do not use to cope with problems.     

The role of friends, in-laws, and other kin in father-perpetrated child physical abuse

Thirty-five physically abusive fathers were matched with a comparison sample to test multiple systemic explanations for child physical abuse, using an ecological perspective, and to show the relationship between the structure of social ties and the function of those ties. The physically abusive fathers were found to have received significantly fewer emotional and instrumental supports from their friends, in-laws, and other kin than the comparison fathers, and were only weakly linked to members of their social networks--members who might have discouraged the fathers' aggressive impulses or provided additional support to them and to their families.     

Data-based organizational change: the use of administrative data to improve child welfare programs and policy

Administrative databases hold the potential to have a significant impact on the development of effective child welfare programs and policies. This article discusses the strengths and weaknesses of administrative databases, issues with their implementation and data analysis, and effective presentation of their data at different levels in child welfare organizations.     

Use of Markov Chain Monte Carlo Analysis with a Physiologically-Based Pharmacokinetic Model of Methylmercury to Estimate Exposures in U.S. Women of Childbearing Age

A Bayesian approach, implemented using Markov Chain Monte Carlo (MCMC) analysis, was applied with a physiologically‐based pharmacokinetic (PBPK) model of methylmercury (MeHg) to evaluate the variability of MeHg exposure in women of childbearing age in the U.S. population. The analysis made use of the newly available National Health and Nutrition Survey (NHANES) blood and hair mercury concentration data for women of age 16–49 years (sample size, 1,582). Bayesian analysis was performed to estimate the population variability in MeHg exposure (daily ingestion rate) implied by the variation in blood and hair concentrations of mercury in the NHANES database. The measured variability in the NHANES blood and hair data represents the result of a process that includes interindividual variation in exposure to MeHg and interindividual variation in the pharmacokinetics (distribution, clearance) of MeHg. The PBPK model includes a number of pharmacokinetic parameters (e.g., tissue volumes, partition coefficients, rate constants for metabolism and elimination) that can vary from individual to individual within the subpopulation of interest. Using MCMC analysis, it was possible to combine prior distributions of the PBPK model parameters with the NHANES blood and hair data, as well as with kinetic data from controlled human exposures to MeHg, to derive posterior distributions that refine the estimates of both the population exposure distribution and the pharmacokinetic parameters. In general, based on the populations surveyed by NHANES, the results of the MCMC analysis indicate that a small fraction, less than 1%, of the U.S. population of women of childbearing age may have mercury exposures greater than the EPA RfD for MeHg of 0.1 μg/kgg/day, and that there are few, if any, exposures greater than the ATSDR MRL of 0.3 μgg/kgg/day. The analysis also indicates that typical exposures may be greater than previously estimated from food consumption surveys, but that the variability in exposure within the population of U.S. women of childbearing age may be less than previously assumed.     

A graph coloring approach for image segmentation

In this paper we develop a segmentation scheme for digital images based upon an iterative binary coloring technique that takes into account changing behavior of adjacent pixels. The output is a hierarchical structure of images which allows a better understanding of complex images. In particular, we propose two algorithms that should be considered as image preprocessing techniques.     

Cell-to-switch level planning in mobile wireless networks for efficient management of radio resources

A major step in effectively managing radio resources in a cellular network is to design an appropriate scheme for assigning cells to a location area (LA), serviced by a switch, and allocate resources for individual switches. However, this assignment is already proven in the literature to be an NP-hard problem [Merchant A, Sengupta B. Assignment of cells to switches in PCS networks. IEEE/ACM Transactions on Networking 3(5) (1995) 521–6] that requires efficient heuristic search techniques for obtaining real-time solutions. This work presents a state-space search technique, which is a variant of best first search heuristic technique. The algorithm called the block depth first search (BDFS), allocates cells to switches during switch level resource planning. Under various simulated performance criteria, we compare the performance of the proposed technique with other similar procedures in the literature. Our results indicate that the BDFS outperforms the meta-heuristic procedures in terms of both efficiency and quality of solutions. Hence, we conclude that our proposed technique can be effectively used for switch level planning leading to an efficient management of scarce radio resource in cellular networks.     

Decompositions of λ K v

In a series of 2 papers, Kang, Du and Tian solved the existence problem for G-decomposition of λ K _n when G is any simple graph with 6 vertices and 7 edges, except when G is the graph T=K ₄∪K ₂. Notice that a T-decomposition can be considered to be a Pairwise Balanced Design in which each block of size 4 has been matched to a block of size 2. In this paper we remove this exception for all λ≥2. The case when λ=1 is also addressed. This paper is written in honor of Frank Hwang on the occasion of his 65th birthday.