POPAN-6: Exploring convergence and estimate properties with SIMULATE

We describe some developments in the P OPAN system for the analysis of mark-recapture data from Jolly-Seber (JS) type experiments. The latest version, P OPAN-6, adopts the Design Matrix approach for specifying constraints and then uses it in the constrained maximization of the likelihood. We describe how this is done and the difference it makes to convergence and parameter identifiability over the constraint contrast-equation methods used in P OPAN-5. Then we show how the SIMULATE capabilities of P OPAN can be used to explore the properties of estimates, including their identifiability, precision, and robustness to model misspecification or capture heterogeneity.     

Distribution of Arsenic and Copper in Sediment Pore Water: An Ecological Risk Assessment Case Study for Offshore Drilling Waste Discharges

Due to the hydrophobic nature of synthetic based fluids (SBFs), drilling cuttings are not very dispersive in the water column and settle down close to the disposal site. Arsenic and copper are two important toxic heavy metals, among others, found in the drilling waste. In this article, the concentrations of heavy metals are determined using a steady state "aquivalence-based" fate model in a probabilistic mode. Monte Carlo simulations are employed to determine pore water concentrations. A hypothetical case study is used to determine the water quality impacts for two discharge options: 4% and 10% attached SBFs, which correspond to the best available technology option and the current discharge practice in the U.S. offshore. The exposure concentration ( C_E ) is a predicted environmental concentration, which is adjusted for exposure probability and bioavailable fraction of heavy metals. The response of the ecosystem  ( R_E )  is defined by developing an empirical distribution function of predicted no-effect concentration. The pollutants' pore water concentrations within the radius of 750 m are estimated and cumulative distributions of risk quotient  ( RQ = C_E / R_E )  are developed to determine the probability of RQ greater than 1.     

Robust estimation for longitudinal data under outcome‐dependent visit processes

In longitudinal data where the timing and frequency of the measurement of outcomes may be associated with the value of the outcome, significant bias can occur. Previous results depended on correct specification of the outcome process and a somewhat unrealistic visit process model. In practice, this will never exactly be the case, so it is important to understand to what degree the results hold when those assumptions are violated in order to guide practical use of the methods. This paper presents theory and the results of simulation studies to extend our previous work to more realistic visit process models, as well as Poisson outcomes. We also assess the effects of several types of model misspecification. The estimated bias in these new settings generally mirrors the theoretical and simulation results of our previous work and provides confidence in using maximum likelihood methods in practice. Even when the assumptions about the outcome process did not hold, mixed effects models fit by maximum likelihood produced at most small bias in estimated regression coefficients, illustrating the robustness of these methods. This contrasts with generalised estimating equations approaches where bias increased in the settings of this paper. The analysis of data from a study of change in neurological outcomes following microsurgery for a brain arteriovenous malformation further illustrate the results.     

Talking about Beauty: A Study of Everyday Aesthetics among Low‐Income Citizens of Milan

This paper reports on research undertaken into the aesthetics of the everyday. As well as the subject matter of aesthetic philosophy, art criticism and of the sociology of art, beauty, and beautiful are of course very ordinary matters too. To shed light on the meanings of beauty as used in everyday settings and in natural language, we use the data collected in a study conducted with a group of low‐income residents of the city of Milan. In this study we were interested in analyzing their lifestyle in terms of their relationship with aesthetics, i.e., with “beautiful” objects and/or experiences. Participants' self‐reported aesthetic appreciations suggest that conceptions of “beauty” are used as devices to narrate pieces of identity, memories, experiences, etc. Their aesthetic judgements take on an anthropological function, creating a framework of meanings that help the participants make sense of the world of objects and of their own lives with/through them.     

Region of Birth and Disability Among Recent U.S. Immigrants: Evidence from the 2000 Census

This study aimed to test the “healthy immigrant” hypothesis and assess health heterogeneity among newly arrived working-age immigrants (18–64 years) from various regions of origin. Using the 5% sample of the 2000 U.S. Census (PUMS), we found that, compared with their native-born counterparts, immigrants from all regions of the world were less likely to report mental disability and physical disability. Immigrants from selected regions of origin were, however, more likely to report work disability. Significant heterogeneity in disabilities exists among immigrants: Those from Eastern Europe and Southeast Asia reported the highest risk of mental and physical disability, and those from East Asia reported the lowest risk of physical disability. Furthermore, Mexican immigrants reported the lowest risk of mental disability, and Canadian immigrants reported the lowest risk of work disability. Socioeconomic status and English proficiency partially explained these differences. The health advantage of immigrants decreased with longer U.S. residence.     

Health Maintenance Organizations: Legislative and Training Implications

The Health Maintenance Organization Act of 1973 provides Americans with the opportunity to join prepaid group health plans. HMOs are not a panacea for the ills that beset our health delivery system but their emphasis on health maintenance and preventive interventions will provide new social work practice and student training opportunities. This article reviews and analyzes the major features of the HMO Act. Expanded roles for social work practitioners are discussed and suggestions are made for strengthening social work training programs in order to prepare social work professionals for practice in HMOs and in the health care field.     

Domain Effects and Financial Risk Attitudes

We investigated whether financial risk preferences are dependent on the financial domain (i.e., the context) in which the risky choice options are presented. Previous studies have demonstrated that risk attitudes change when gambles are framed as gains, losses, or as insurance. Our study explores this directly by offering choices between identical gambles, framed in terms of seven financial domains. Three factors were extracted, explaining 68.6% of the variance: Factor 1 (Positive)—opportunity to win, pension provision, and job salary change; Factor 2 (Positive‐Complex)—investments and mortgage buying; Factor 3 (Negative)—possibility of loss and insurance. Inspection of the solution revealed context effects on risk perceptions across the seven scenarios. We also found that the commonly accepted assumption that women are more risk averse cannot be confirmed with the context structure suggested in this research; however, it is acknowledged that in the students’ population the variance across genders might be considerably less. These results suggest that our financial risk attitude measures may be tapping into a stable aspect of “context dependence” of relevance to real‐world decision making.