A study of BIB designs through support matrices

This paper deals with the existence and nonexistence of BIB designs with repeated blocks. The approach is an algebraic one. The concept of a support matrix is introduced and some of its basic properties are noted. Some basic examples of support matrices are given when the block size is 3. The connection between full column rank proper support matrices and irreducible designs is explored and some examples of such matrices are given.     

A Longitudinal Study of Depressive Symptoms and Marijuana Use in a Sample of Inner‐City African Americans

The association between marijuana use and depressive symptoms was examined longitudinally in a sample of 622 African American youth, interviewed on six occasions, using hierarchical linear modeling (HLM). We considered whether depressive symptoms predicted changes in marijuana use and vice versa from high school through the transition into young adulthood. We also examined gender differences in these behaviors over time. The results indicated that depressive symptoms predicted later marijuana use only for males. Marijuana use did not predict later depressive symptoms for females or males. These findings are consistent with a unidirectional hypothesis indicating that marijuana use may play a role as mood regulator among young males, but not among females. Research findings also indicate that females with lower depressive symptoms use more marijuana than females who report high depressive symptoms. These findings did not change even after controlling for the effects of using other substances at previous stages, school achievement, and demographics factors. These results suggest that depressive symptoms may be an antecedent of marijuana use among African American males.     

Two-Event Model for Carcinogenesis: Biological, Mathematical, and Statistical Considerations

A two-mutation model for carcinogenesis is reviewed. General principles in fitting the model to epidemiologic and experimental data are discussed, and some examples are given. A general solution to the model with time-dependent parameters is developed, and its use is illustrated by application to data from an experiment in which rats exposed to radon developed lung tumors.     

A Stochastic Assessment of the Public Health Risks of the Use of Macrolide Antibiotics in Food Animals

Campylobacteriosis is an important food-borne illness with more than a million U.S. cases annually. Antibiotic treatment is usually not required. However, erythromycin, a macrolide antibiotic, is recommended for the treatment of severe cases. Therefore, it is considered a critically important antibiotic and given special attention as to the risk that food animal use will lead to resistant infections and compromised human treatment. To assess this risk, we used a retrospective approach; estimating the number of campylobacteriosis cases caused by specific meat consumption utilizing the preventable fraction. We then determined the number of cases with macrolide resistance Campylobacter spp. based on a linear model relating the resistance fraction to on-farm macrolide use. In this article, we considered the uncertainties in the parameter estimates, utilized a more elaborate model of resistance development and separated C. coli and C. jejuni . There are no published data for the probability of compromised treatment outcome due to macrolide resistance. Therefore, our estimates of compromised treatment outcome were based on data for fluoroquinolone-resistant infections. The conservative results show the human health risks are extremely low. For example, the predicted risk of suboptimal human treatment of infection with C. coli from swine is only 1 in 82 million; with a 95% chance it could be as high as 1 in 49 million. Risks from C. jejuni in poultry or beef are even less. Reduced antibiotic use can adversely impact animal health. These low human risks should be weighed against the alternative risks.     

The after-effects of a prolonged period of day-sleep on subjective sleep quality

The effects of day-sleep on the quality ofsleep are not restricted to the night-work period itself. Effects can be measured during night-sleep in the period following night-work. A study on these after-effects, using a self-report instrument to measure sleep quality, is described. A total of N=7O operators wcrc observed over five consecutive undisturbed nights after a working period of seven morning shifts (N= 35) and after a working period of seven night-shifts (N= 35). The quality of sleep during the third night after the night-shift period was still significantly worse than the third night after the rnorning-shift period. No differential (after-)effects were observed with respect to differences in sleep duration.     

THE RATE OF CONVERGENCE IN THE NORMAL APPROXIMATION FOR THE WILCOXON R-ESTIMATOR

We exploit the fact that the Wilcoxon score R-estimator of the slope in a linear regression model minimises Gini's mean difference of the residuals to obtain a Berry-Esseen rate of convergence result for the Wilcoxon R-estimator.     

Advocacy and ombudswork for children: implications of the Israeli experience

Israel's establishment of what is to be the first in a network of child advocacy councils is discussed in relation to child advocacy efforts in the United States. The work and structure of the Jerusalem Children's Council and its Ombudsman for Children is described. It is suggested that Israel's experience in establishing a well-functioning local child advocacy council provides a model for implementing the recommendation of the Joint Commission on the Mental Health of Children to establish a network of local child advocacy councils in the United States.     

Ideology and Social Movements: The Contributions of Habermas*

Theorists of social movements have not developed a sufficiently complex perspective of the role that ideology has in the dynamics of social movements. This essay demonstrates that Habermas’theory of the autonomy of normative structures is useful to explain the independent role of ideology in determining the direction taken by social movements. Habermas’emphasis on the interrelationship between cultural traditions, consensus formation, epistemologies, and differentiated rationalization processes furnishes an alternative to the instrumentalist and ahistorical assumptions that often characterize theorists’treatment of ideology in social movements. Empirical examples from studies of social movements are utilized to demonstrate the usefulness of Habermas’approach.