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.     

Economic Adversity and Voter Turnout: Evidence from Turkish Parliamentary Elections

Social Indicators Research - This paper investigates the relationship between economic adversity and voter participation in Turkish parliamentary elections. We employ a dynamic model of voter...     

Ground beetle (Coleoptera: Carabidae) communities on green roofs in Switzerland: synthesis and perspectives

Urban Ecosystems - Green roofs have recently gained recognition for their potential contribution to urban ecosystems by providing, among other services, habitat for plants and animals, and stepping...     

Children's Experiences of Time When a Parent Travels for Work

This qualitative study focuses on the different ways time is experienced by children in families who face time challenges because of a family member's job that required work travel. Data are from a family‐level study that includes interviews of all family members older than age 7. Using grounded theory methodology, this study illustrates the ways in which job demands and family processes interact. The analysis centers on 75 children's perspectives from 43 families. Holding together assessments of having enough time while wanting more time with their parents, children express emotion, generally unrecognized by parents, around the topic of family time. Children's experience of time with parents is rushed or calm, depending on the activities done in time and the gender of the parent with whom they spend time. Findings are interpreted through a feminist social constructionist lens.     

Examining educational inequalities in two national systems: a comparison of the North African second generation in France and the Mexican second generation in the United States

This paper aims to compare the educational outcomes of children of immigrants in France and in the United States to highlight the ethnic educational inequalities in both countries. The comparison focuses on children from two groups: North Africans in France and Mexicans in the United States. By using two longitudinal datasets, the French Educational Panel Survey and Add Health, we examine aspirations, expectations, and secondary attainment in the two contexts. We explore in particular the role of parental education on attainment. Immigrant families have high educational aspirations in both contexts. North-African families express higher aspirations than native French with similar background, while there are no significant differences between second-generation Mexicans and the majority group net of parental education. Second-generation children are disadvantaged in school in both countries; they are more likely to drop out and less likely to graduate from high school, but most of the disadvantage is related to their social background. Net of social background, the Mexican second generation does not differ from the majority group while the North African second generation is more likely to get the French high school diploma than their peers of French origins, in line with their high aspirations. However, North Africans are more likely to receive the technological baccalauréat than the general baccalauréat.     

Adolescent group therapy membership selection

Conclusions Social agency practitiooners can employ adolescent group therapy as an effective treatment mode, as long as a great deal of attention and planning is put into the details of group membership selection. The authors have presented suggestions and guidelines that can be used in overcoming the logistic problems inherent in forming an adolescent therapy group. We feel that proper pregroup planning is just as important in determining group results as is the ongoing group process. Group treatment does not necessarily incease a therapist's productivity or reduce the amount of time spent in therapy, but it does offer a unique experience which has certain qualitative advantages for teenagers experiencing behavioral and relationship problems within and, particularly, outside of the family system.     

The Safeguarding Effect of Governance Mechanisms in Inter‐firm Exchange: The Decisive Role of Mutual Opportunism

This study empirically investigates the safeguarding effect of (1) administrative control, (2) a dominant power position and (3) relational norms, on opportunistic behaviour of suppliers, by means of a survey among 624 information and communication technology professionals in Dutch municipalities. The findings indicate that individual effectiveness of relational norms, particularly in terms of flexibility and solidarity, was most prominent. Administrative control and power did not show a significant impact on supplier opportunism in our sample. Research into the simultaneous use of several safeguards against opportunism generated the finding that different relational norms fortify each other's safeguarding effect. Furthermore, we demonstrate that supplier opportunism is only mitigated by a dominant power position when the buyer does not exploit its favourable position and the buyer does not behave opportunistically. Hence, power seems to have a safeguarding effect only when it is not used.     

The analytic construction of D-optimal designs for the two-variable binary logistic regression model without interaction

Candidate locally D-optimal designs for the binary two-variable logistic model with no interaction, which comprise 3 and 4 support points lying in the first quadrant of the two-dimensional Euclidean space, were introduced by Haines et al. (D-optimal designs for logistic regression in two variables. In: Lopez-Fidalgo J, Rodrigez-Diaz JM, Torsney B, editors. MODA8 – advances in model-oriented designs and analysis. Heidelberg: Physica-Verlag; 2007. p. 91–98). The authors proved algebraically the global D-optimality of the 3-point design for the special case in which the intercept parameter is equal to?1.5434. However for other selected values of the intercept parameter, the global D-optimality of the proposed 3- and 4-point designs was only demonstrated numerically. In this paper, we provide analytical proofs of the D-optimality of these 3- and 4-point designs for all negative and zero intercept parameters of the binary two-variable logistic model with no interaction. The results are extended to the construction of D-optimal designs on a rectangular design space and illustrated by means of two examples of which one is a real example taken from the literature.