Topics in Microbial Risk Assessment: Dynamic Flow Tree Process

Microbial risk assessment is emerging as a new discipline in risk assessment. A systematic approach to microbial risk assessment is presented that employs data analysis for developing parsimonious models and accounts formally for the variability and uncertainty of model inputs using analysis of variance and Monte Carlo simulation. The purpose of the paper is to raise and examine issues in conducting microbial risk assessments. The enteric pathogen Escherichia coli O157:H7 was selected as an example for this study due to its significance to public health. The framework for our work is consistent with the risk assessment components described by the National Research Council in 1983 (hazard identification; exposure assessment; dose-response assessment; and risk characterization). Exposure assessment focuses on hamburgers, cooked a range of temperatures from rare to well done, the latter typical for fast food restaurants. Features of the model include predictive microbiology components that account for random stochastic growth and death of organisms in hamburger. For dose-response modeling, Shigella data from human feeding studies were used as a surrogate for E. coli O157:H7. Risks were calculated using a threshold model and an alternative nonthreshold model. The 95% probability intervals for risk of illness for product cooked to a given internal temperature spanned five orders of magnitude for these models. The existence of even a small threshold has a dramatic impact on the estimated risk.     

“A La Recherche Du” Quality of Life

This essay examines the stages of inquiry when we seek to formulate quality of life in an era before our own. There arises the question of the extent to which today’s formulation of quality of life can be applied to an era far removed from our own. Implicitly, there is the nature of the time interval, T₁···T_n, and the causal significance of intervening events. Data of a numerical sort can be hard to retrieve due to fires, wars, and mishandling. Quantitative data can be found in censuses and military records. Information in its raw form is referred to here as protodata. Figure 1 provides a schematic overview of the search for quality of life by subjective and objective modes of inquiry.     

Aboriginal and Torres Strait Islander employment policy and Welfare to Work: The Community Development Programme and the need for new narratives,new alliances and new institutions

The way Australian federal governments have approached Aboriginal and Torres Strait Islander employment and welfare policy over the last two decades has been a paradigmatic example of what not to do in policymaking. In the absence of effective engagement or consultation, a series of decisions under Coalition and Australian Labor Party governments have had a range of negative consequences for Aboriginal and Torres Strait Islander peoples. These changes – centred around the closure of the Community Development Employment Projects (CDEP) scheme and implementation of the Community Development Programme (CDP) – have resulted in increased unemployment, inadequate support for job creation, a dramatic over‐application of income penalties to social security recipients and reduced capacity in many community organisations. This article argues that these outcomes constitute policy failure, especially given that genuine engagement with Aboriginal and Torres Strait Islander people could have prevented many of these consequences. It then turns to an exploration of three ways in which Aboriginal and Torres Strait Islander people are responding to such policy failure: through promotion of new narratives, new alliances, and new institutions. The study concludes that while we should avoid “specious hope”, there is room for optimism in a renewed push for Aboriginal and Torres Strait Islander sovereignty.     

Book Review

Abstract

Kim Witte, Gary Meyer, and Dennis Martell. Effective Health Risk Messages: A Step-by-Step Guide: Thousand Oaks, CA: Sage; 2000. 216 pps; paper, $24.95, cloth, $64.95.     

Teaching Students to Perform Assessments

In recent years, assessment methods and skills have been increasingly emphasized in the social work literature. Little information, however, has been provided about how to teach students assessment skills in a classroom setting. This article addresses that gap in the literature and presents an integrative skills assessment approach for teaching students to perform assessments. This approach is based on technical eclecticism and combines assessment methods and skills from three practice models: (1) psychosocial, (2) cognitive—behavioral, and (3) systems. Knowledge and skills about measurement, computerized assessment models and expert systems also are included in this approach to teaching assessment skills. The authors provide suggestions and tools for teaching assessment skills in a classroom, including an integrative skills assessment protocol and several techniques that may be used to teach students to gather assessment data. In teaching assessment skills, possible links may be developed with the field practicum and the classroom experience of students. In addition, the authors suggest that students benefit from the integrative skills approach. The approach is comprehensive, flexible, competency based, technological, and empirically based. However, shortcomings are that the approach is a clinical practice approach that excludes other forms of practice and that the integrative skills assessment approach does not help students develop skills for performing the rapid assessments frequently required for brief interventions.     

Urbanization and the fertility transition in Ghana

This paper examines the way in which migration and urban residence operate to alter fertility outcomes. While urban-rural fertility differentials have long been established for most developing societies, the nature of these differences among migrants and between migrants and those of succeeding generations is not well understood. The evidence presented here suggests that rural-urban migration and urbanization may contribute positively to processes of fertility transition. Using data from the 1998 Kumasi Peri-Urban Survey, which included a 5-year retrospective monthly calendar of childbearing, we suggest that migrants adapt quickly to an urban environment. Our results also reveal generational differences in recent and cumulative fertility. While migrants exhibit higher cumulative fertility than urban residents of the second and third generation, their fertility is significantly lower than rural averages in Ghana. Children of migrants exhibit childbearing patterns quite similar to those in higher-order generations. Most noteworthy is the nature of the disparities in childbearing patterns between migrants and the succeeding generations. Migrant women have higher lifetime fertility than urban natives. Migrant women also exhibit higher fertility over the last 5 years than second generation or high-order urban natives. But these first generation women exhibit lower fertility (vs. urban natives) for the year immediately prior to the survey. These patterns lend support to an interpretation that combines rather than opposes theories of selectivity, disruption, adaptation and socialization. We conclude by discussing mechanisms that might explain these interrelated processes of fertility adjustment and suggest that policies discouraging rural-urban migration need to be revisited.     

“L'Homme Moyen”: Estimating the quality of life for British adults, 1815–1914, an index

The potential value of a numerical, summating index to estimate the quality of Victorian people's lives is described. Variables in three domains, Health, Economic and Social, are drawn on to describe the circumstances of life for Britons in the era 1815–1914. A range of variables is indexed to their 1914 value for each of the years between 1815 and 1914. The potential value of the index for the assessment of events, trends and policy initiatives is described.     

Using interviews to understand the assignment mechanism in a nonexperimental study: the case of eighth grade algebra

Many inquiries regarding the causal effects of policies or programs are based on research designs where the treatment assignment process is unknown, and thus valid inferences depend on tenuous assumptions about the assignment mechanism. This article draws attention to the importance of understanding the assignment mechanism in policy and program evaluation studies, and illustrates how information collected through interviews can develop a richer understanding of the assignment mechanism. Focusing on the issue of student assignment to algebra in 8th grade, I show how a preliminary data collection effort aimed at understanding the assignment mechanism is particularly beneficial in multisite observational studies in education. The findings, based on ten interviews and administrative data from a large school district, draw attention to the often ignored heterogeneity in the assignment mechanism across schools. These findings likely extend beyond the current research project in question to related educational policy issues such as ability grouping, tracking, differential course taking, and curricular intensity, as well as other social programs in which the assignment mechanism can differ across sites.     

Setups and effective capacity: the impact of lot sizing techniques in an MRP environment

This study investigates how lot sizing techniques influence the profit performance, inventory level, and order lardiness of an assembly job shop controlled by MRP. Four single-level lot sizing techniques are compared by simulation analysis under two levels of master schedule instability and two levels of end item demand. A second analysis investigates the influence of a multilevel lot sizing technique, the generalized constrained-K (GCK) cost modification, on the four single-level techniques at low demand and low nervousness. The analyses reveal a previously unreported phenomenon. Given the same inventory costs, the single-level lot sizing techniques generate substantially different average batch sizes. The lot sizing techniques maintain the following order of increasing average batch size (and decreasing total setup time):

economic order quantity (EOQ)

period order quantity (POQ)

least total cost (LTC)

Silver-Meal heuristic (SML)

The causes for different average batch sizes among the lot sizing techniques are analysed and explained. Demand lumpiness, inherent in multilevel manufacturing systems controlled by MRP, is found to be a major factor. The number of setups each lot sizing technique generates is the primary determinant of profit performance, inventory level, and order tardiness. EOQ, a fixed order quantity technique, is less sensitive to nervousness than the discrete lot sizing techniques. EOQ_, however, generates the smallest average batch size, and, therefore, the most setups. Since setups consume capacity, EOQ, is more sensitive to higher demand. SML generates the largest average batch sizes, and is, therefore, less sensitive to increased demand. At low demand, the other lot sizing techniques perform better on all criteria. They generate smaller batches and, therefore, shorter actual lead times. The GCK cost modification increases the average batch size generated by each lot sizing technique. GCK improves the profit and customer service level of EOQ the lot sizing technique with the smallest batches. GCK causes the other lot sizing techniques to generate excessively large batches and, therefore, excessively long actual lead times.