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.     

A Numerical Solution to the Nonhomogeneous Two-Stage MVK Model of Cancer

In this article, we describe a straightforward method for solving the probability of at least one malignant cell by time t, and the associated hazard function, in the general (i.e., nonhomogeneous) two-stage Moolgavkar-Venzon-Knudson (MVK) model of cancer. The method consists of solving four coupled ordinary differential equations derived from the Kolmogorov backward equations for this process. The relationship of this method to previously proposed solutions is discussed.     

中国蒙古文学史料学的起始与发展

蒙古文学研究的基础和前提是蒙古文学史料。随着国内外蒙古文学研究的不断拓展和深入,蒙古文学史料搜集整理已逐步发展成为蒙古文学史料学。蒙古文学史料学包括蒙古文学的田野调查、史料整理、考订、选录、笺释、校注、校勘、辑评等诸多研究内涵。中国蒙古文学研究取得巨大成就,得益于蒙古文学史料学的长足发展。我们应当总结以往蒙古文学史料学研究的经验,使蒙古文学史料学更加系统化、科学化和理论化。     

The Ecology of Family Guidance in Low-Income Mexican-American and European-American Families*

This two-part study applied an ecocultural perspective to socialization of daily and long-term goals in low-income Mexican-American and European-American families with children in third, fifth, and seventh grades. The first part of the study examined family members' participation and parents' socialization goals and guidance strategies for their children's daily household chores and homework activities. The second part of the study examined parents' long-term aspirations and guidance strategies for their children's educational, vocational, and moral development. For daily activities, results showed that in Mexican-American families both parents and siblings played important roles, whereas in European-American families parents were the primary socialization agents. As predicted, in both groups parents' expertise influenced their guidance strategies. Finally, Mexican-American and European-American parents differed in their relative endorsement of gender, relational, and self-reliance goals for household chores. For long-term goals, parents in both groups held high educational, vocational, and moral aspirations for their children. However, some parents of seventh-graders had lower educational and vocational aspirations than those of fifth- and third-graders. Although expertise consistently influenced Mexican-American parents' guidance strategies, the pattern for European-American parents was mixed. The discussion highlights between- and within-group differences in daily and long-term socialization practices with an emphasis on resources and vulnerabilities in the families.     

The impact of social networks on the occupational status of migrants

This paper postulates that there is a continuous exchange of information and knowledge between those who share the common bond of having migrated to the US. The individual components of this information exchange constitute social networks. The 2 hypotheses tested are 1) immediate social networks and people known in the US facilitate the flow of information both to new migrants and between established migrants, thus promoting upward social mobility; and 2) access to broader network ties, organization membership, extra-ethnic friendships, and familiarity with established institutions smooths the transition process, resulting in increased social position. The data used comes from a study conducted in 1982-1983 in 4 Mexican sending communities (2 rural, 2 urban), for a total of 440 migrants. Results show that migrants in every socioeconomic bracket reported access to some or all social network characteristics. There was contact with either a family member or acquaintances from the migrants' town of origin. Over 50% of migrants reported knowing many fellow townspeople. Twice as many migrants belong to a sports club as to a social or religious organization. Very few rural migrants report knowing no townspeople, while 32% of urban migrants claim no knowledge of fellow migrants from their town of origin. Urban origin migrants report more contacts with those of other ethnicity than rural migrants. Those employed in agriculture are least acquainted with social information and contacts, while those in skilled and service sectors are well acquainted with them. The results of fact and analysis show that 1) access to personal US networks results in an average 4.4 point advantage in occupational prestige scores over no access, and 2) utilizing institutional US networks combined with any cumulative US experience gives a migrant a 5 point advantage over a fellow migrant with identical experience level but no institutional network contacts. This is also true for institutional Mexican networks. Thus success or failure in migrating is partly due to migrants' societal infrastructure and the fact that available information and social networks are accessed and utilized differently by different migrants.     

The U.S. legalization program: a preliminary final report

The Immigration Reform and Control Act (IRCA) of 1986 made 4 types of aliens eligible to receive legalization benefits: 1) those who resided "continuously" in the US since January 1, 1982; 2) those who had worked in the US perishable-crop agriculture for 90 "man-days" in specified time periods (Special Agricultural Workers [SAWS]); 3) those who were in the US since before January 1, 1972; and 4) those classified as Cuban/Haitian entrants and who had been in the US since January 1, 1982. Estimates of the number of aliens eligible for legalization, not including SAWS, ranges from 1.834 million to 2.56 million. Estimates of undercounts of undocumented aliens are 10% for those who entered before 1975 and 37.5% for those who arrived after 1975. Other refinements in the estimates of undocumented aliens include adjustments for 1) ethnic group and location, 2) the growth of the undocumented population between the census date and the legalization eligibility date under IRCA, and 3) emigration and deportation rates. Out of the 1,581,800 applicants entered into the Immigration and Naturalization Service (INS) computers (from a total of 2.15 million applicants) as of May 20, 1988, 73.7% were Mexican nationals. Only 5 other countries contributed more than 1%: El Salvador (6.5%), Haiti (2.3%), Guatemala (2.2%), the Philippines (1%), and Colombia (1%). The Mexican percentage was unexpectedly high, perhaps because the legalization had been much more successful in the Southwest than anywhere else in the country. Reasons that Mexicans have a higher legalization participation rate than other nationalities include 1) the distant eligibility date; 2) ethnic differences among non-Mexican nationalities; 3) particularly in the northeast, fears of exposing one's illegal status to INS; 4) the difficulty of information reaching ethnic communities, 5) the reluctance of those already undergoing the naturalization process to risk the legalization process; and 6) the reluctance of employees to admit employment of undocumented aliens. In the end, more than 90% of applicants are expected to be granted temporary resident alien status (and about 70% of agricultural workers), for a total of more than 2 million people. Researchers estimate that 2.5 - 3 million more persons remain in an undocumented status in the US.     

Assimilation process and group integration of migrant families

This empirical analysis gives 1st answers to the question of which effects some specific types of interaction structures within migrant families have on the assimilation process of family members and their personal integration. The analysis is based on a sample of 92 Turkish women and 123 Turkish men in the Bonn-Cologne area of West Germany. Questionnaires examine variables such as 1) urbanization of the context of origin, 2) household complexity, 3) availability of ethnic infrastructure, 4) residential proximity of Turkish friends and relatives; 5) school education of respondent and spouse; and 6) occupational prestige before migration. The study considers the following dimensions of social and cultural assimilation: 1) housing quality, 2) use of ethnic and general infrastructure, and 3) use of ethnic minority and mainstream cultural facilities. Results of empirical analyses on the housing conditions of migrants show that 1) motivational factors of the migrant family are unrelated to choice of a housing area, but are related to apartment quality; and 2) housing conditions differ markedly, depending on the type of combination of task-allocation and decision-making power in the family. Use of infrastructure 1) declines in Turkish families in which women's participation in family tasks is relatively high, 2) is determined most by the opportunity structure of the housing area and the interaction structure within the family; and 3) is a necessary step between the reorganization of the family's interaction structure and the participation in a broader spectrum of institutions of the receiving society. The family structure has no significant effect on participation in the minority culture. The extent of minority-culture rise has no direct relationship to the individual assimilation of family members. The empirical data support the basic theoretical assumption that the group integration of the migrant family has considerable effects on the assimilation process of its individual members. In conclusion, 1) opportunities for assimilation are increased by the combined resources of the migrants family household, and 2) continuing individual autonomy contributes severely to a reduced personal integration.     

Enrich marital inventory: a discriminant validity and cross-validation assessment

To assess the validity and clinical utility of the marital inventory ENRICH, a discriminant validity study was conducted using a national sample of 5039 married couples. The sample was randomly split in order to form a cross-validation group. ENRICH is a multidimensional scale and two types of analysis were conducted to assess the value of these various scales. Results from discriminant analysis indicated that using either the individual scores or couples' scores, happily married couples could be discriminated from unhappily married couples with 85–95% accuracy. These results were cross-validated with a second sample. Using regression analysis, it was clearly demonstrated that background factors account for little of the variance in discriminating happy from unhappily married couples compared to their relationship dynamics, i.e., scale scores. All ENRICH scales except equalitarian roles proved significant, indicating the validity of a multidimensional inventory.