Exposure Reconstruction for the TCDD-Exposed NIOSH Cohort Using a Concentration- and Age-Dependent Model of Elimination

Recent studies demonstrating a concentration dependence of elimination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) suggest that previous estimates of exposure for occupationally exposed cohorts may have underestimated actual exposure, resulting in a potential overestimate of the carcinogenic potency of TCDD in humans based on the mortality data for these cohorts. Using a database on U.S. chemical manufacturing workers potentially exposed to TCDD compiled by the National Institute for Occupational Safety and Health (NIOSH), we evaluated the impact of using a concentration- and age-dependent elimination model (CADM) (Aylward et al., 2005) on estimates of serum lipid area under the curve (AUC) for the NIOSH cohort. These data were used previously by Steenland et al. (2001) in combination with a first-order elimination model with an 8.7-year half-life to estimate cumulative serum lipid concentration (equivalent to AUC) for these workers for use in cancer dose-response assessment. Serum lipid TCDD measurements taken in 1988 for a subset of the cohort were combined with the NIOSH job exposure matrix and work histories to estimate dose rates per unit of exposure score. We evaluated the effect of choices in regression model (regression on untransformed vs. ln-transformed data and inclusion of a nonzero regression intercept) as well as the impact of choices of elimination models and parameters on estimated AUCs for the cohort. Central estimates for dose rate parameters derived from the serum-sampled subcohort were applied with the elimination models to time-specific exposure scores for the entire cohort to generate AUC estimates for all cohort members. Use of the CADM resulted in improved model fits to the serum sampling data compared to the first-order models. Dose rates varied by a factor of 50 among different combinations of elimination model, parameter sets, and regression models. Use of a CADM results in increases of up to five-fold in AUC estimates for the more highly exposed members of the cohort compared to estimates obtained using the first-order model with 8.7-year half-life. This degree of variation in the AUC estimates for this cohort would affect substantially the cancer potency estimates derived from the mortality data from this cohort. Such variability and uncertainty in the reconstructed serum lipid AUC estimates for this cohort, depending on elimination model, parameter set, and regression model, have not been described previously and are critical components in evaluating the dose-response data from the occupationally exposed populations.     

Africa's expanding population: old problems,new policies

Sub-Saharan Africa faces an historic challenge: to achieve economic and social progress while experiencing extraordinary population growth. With an estimated 1989 population of 512 million, the 42 countries of sub-Saharan Africa have the highest birth and death rates of any major world region. While death rates have fallen since the 1960s, persistently high birth rates yield annual growth rates above 3% in many countries. The United Nations projects that the region's population will increase 2.7 times by 2025--to 1.4 billion. Throughout the region, population has outstripped economic growth since the mid-1970s. In addition, many African countries are experiencing an epidemic of AIDS (Acquired Immunodeficiency Syndrome). The extent and demographic impact of the epidemic still are unknown, but disturbing social and political effects are already being felt. The region's population growth will slow only when African couples begin to have fewer children. The average number of children per woman ranges from 6 to 8 for most countries. The Africans' preference for large families is deeply rooted in the culture and fed by the perceived economic benefits they receive from their children. Economic stagnation during the 1980s prompted many national governments to recognize that rapid population growth was hindering their socioeconomic development. The political climate has shifted away from pronatalist or laissez-faire attitudes toward official policies to slow population growth. The policy formation process--detailed here for 4 countries (Zambia, Nigeria, Zaire, and Liberia)--is ponderous and beset with political and bureaucratic pitfalls, However, policy shifts in more and more countries combined with evidence of increased contraceptive use and fertility downturns in a few countries give some hope that the region's extraordinary population growth may have peaked and will start a descent. Whatever the case, the decade of the 1990s will be crucial for the future of sub-Saharan Africa.     

India: ‘Brain Drain’ or the Migration of Talent?

2 views on "brain drain" exist: 1) LDCs lose their enormous investments on higher education when skilled people migrate to other countries and 2) LDCs are exaggerating the problem and only a few skilled people migrate at 1 time. India does not completely lose its investment in education when professionals migrate, since the migrants still contribute to knowledge and also send remittances to relatives in India. Unemployed educated people would cause a greater drain on India's resources than educated migrants. The author prefers the phrase migration of talent to brain drain, since the former indicates a 2-way movement. Most migrants from LDCs are students. About 11,000 university graduates leave India every year for advanced study and/or work. A conservative estimate is that 2500 will remain abroad permanently. Most professionals who migrate go to the US and Canada. Factors promoting migration include 1) unemployment, 2) immigration rules, 3) colonial links, 4) financial incentives and material benefits, 5) pursuit of higher education, 6) improvement of working conditions and facilities, 7) avoidance of excessive bureaucratic procedures, and 8) compensation for the mismatch between Indian education and employment. Reasons for returning to India include 1) deference to wives who were unable to adjust to a foreign way of life, 2) contributing to Indian development, and 3) racial discrimination. It will probably not be possible to lure back migrants who left for material reasons. Attractive job offers could entice back those who left for advanced training. To encourage the return of those who left to pursue high quality research, India must 1) increase expenditure on research and development, possibly through the private industrial sector, 2) promote travel to other countries for professional enrichment, and 3) improve conditions of research work. The article concludes with an analysis of migration of talent from 3 perspectives: 1) the individual, 2) the nation-state, and 3) the world as a whole.     

Immigration and the evolution of economic theory

This is a review of "the limited and scant contributions made to immigration theory in the context of the evolution of economic thought over a protracted historical time span." The economic theories considered include those of the mercantilists, Adam Smith, the classical economists, and J. M. Keynes. (SUMMARY IN FRE AND SPA)     

Social choice theory in the case of von Neumann-Morgenstern utilities

Part I of this paper offers a novel result in social choice theory by extending Harsanyi's well-known utilitarian theorem into a multi-profile context. Harsanyi was contented with showing that if the individuals' utilities u _i are von Neumann-Morgenstern, and if the given utility u of the social planner is VNM as well, then the Pareto indifference rule implies that u is affine in terms of the u _i. We provide a related conclusion by considering u as functionally dependent on the u _i, through a suitably restricted social welfare functional (u ₁,...,u _n)u=f(u ₁,...,u _n). We claim that this result is more in accordance with contemporary social choice theory than Harsanyi's single-profile theorem is. Besides, harsanyi's initial proof of the latter was faulty. Part II of this paper offers an alternative argument which is intended to be both general and simple enough, contrary to the recent proofs published by Fishburn and others. It finally investigates the affine independence problem on the u _i discussed by Fishburn as a corollary to harsanyi's theorem.The authors are indebted to L. Haddad, A. Sen and two anonymous referees for useful written comments. They also benefited from stimulating remarks in seminars and helpful conversations with their colleagues. The usual caveat of course applies. One of the authors acknowledges partial financial support from the ARI Communication of the C.N.R.S., Paris.     

A quantitative theory of preferences: Some results on transition functions

We investigate a general theory of combining individual preferences into collective choice. The preferences are treated quantitatively, by means of preference functions (a,b), where 0(a,b) expresses the degree of preference of a to b. A transition function is a function (x,y) which computes (a,c) from (a,b) and (b,c), namely (a,c)=((a,b),(b,c)). We prove that given certain (reasonable) conditions on how individual preferences are aggregated, there is only one transition function that satisfies these conditions, namely the function (x,y)=x·y (multiplication of odds). We also formulate a property of transition functions called invariance, and prove that there is no invariant transition function; this impossibility theorem shows limitations of the quantitative method.Research supported in part by the National Science Foundation.     

Therapeutic compliments: setting the stage for successful therapy

Compliments are often viewed primarily as a linear event in which one person expresses approval or admiration of another. Far less attention has been given to the circular nature of compliments and the manner in which they enhance the positions of both the giver and the receiver of the compliment. Therapeutic compliments have proven to be highly effective means of motivating clients, while at the same time increasing therapeutic leverage. This article proposes that compliments should be purposefully given, and that the type of compliment should vary with the stage of therapy and the intended response of the client to the compliment.     

Selecting a family therapy model: the role of personality attributes in eclectic practice*

The expanding knowledge and skill bases within the interdisciplinary family therapy profession pose a significant challenge for evolving practitioners, at whatever stage along the professional development process they find themselves. This challenge raises a basic question regarding whether there are any constraining forces to the level of eclecticism in practice towards which one can aspire. This paper empirically explores the role played by the personality attributes of the family therapist in facilitating and/or inhibiting one's adherence to a variety of approaches to family practice.     

The prediction of learning in family therapy training programs*

Research on family therapy training has produced very little data regarding the kinds of trainees that do best in family therapy training programs. This study attempts to provide some rough and preliminary data on that issue. One hundred and seventy trainees, drawn from seven different structural!strategic training experiences, were evaluated as to how much they learned by taking the Family Therapy Assessment Exercise pre- and posttraining. Their performance was correlated using a hierarchical regression analysis with a number of trainee variables such as amount of conjugal family experience, amount of experience doing family or individual therapy, or prior knowledge of family therapy. The results indicate that, as predicted, conjugal family experience was positively related, and prior knowledge was negatively related to performance. Prior experience doing individual therapy was also positively related to performance.