The EPA Health Risk Assessment of Methylcyclopentadienyl Manganese Tricarbonyl (MMT)

This paper describes the U.S. Environmental Protection Agency's assessment of potential health risks associated with the possible widespread use of a manganese (Mn)-based fuel additive, methylcyclopentadienyl manganese tricarbonyl (MMT). This assessment was significant in several respects and may be instructive in identifying certain methodological issues of general relevance to risk assessment. A major feature of the inhalation health risk assessment was the derivation of Mn inhalation reference concentration (RfC) estimates using various statistical approaches, including benchmark dose and Bayesian analyses. The exposure assessment component used data from the Particle Total Exposure Assessment Methodology (PTEAM) study and other sources to estimate personal exposure levels of particulate Mn attributable to the permitted use of MMT in leaded gasoline in Riverside, CA, at the time of the PTEAM study; on this basis it was then possible to predict a distribution of possible future exposure levels associated with the use of MMT in all unleaded gasoline. Qualitative as well as quantitative aspects of the risk characterization are summarized, along with inherent uncertainties due to data limitations.     

Systematic planning and re-organization

In the last decade wages and salaries have more than doubled in most industrial countries. The amount of capital behind each person in industry has in many countries increased even more, partly to rationalize and compensate for the higher manpower costs. This high rate of investment made discount rates increase 50 – 100 per cent in most industrialized countries in the same period. On the other hand low-cost countries have steadily been pushing more and better products into the international markets. This increases competition. The strongest competition and challenge, however, may come from new technology, new materials, new products and above all from better management.

This development leads to a profit-squeeze for the static company. It gives smaller margins for slow and wrong decisions, and demands a dynamic forward-looking management that understands how to organize, how to develop and involve individual human resources, and how to draw up and use objectives, goals, plans, and programmes, both for present and future growth and progress.

In this article, which is based on management and consultant experience, the focus is put on the need of developing and using as management tools systematic planning and reorganization.     

Pathways to a Stable Union? Pregnancy and Childbearing Among Cohabiting and Married Couples

This study analyzes the stability of cohabiting and marital unions following a first birth. But unlike previous research, it compares the subsequent trajectories of unions that began with a pregnancy to those in which conceptions came after coresidence. The U.S. data from the 2006–2010 and 2011–2013 cross-sectional files of the National Survey of Family Growth indicate that roughly 1-in-5 first births were associated with rapid transitions from conception into either cohabitation or marriage. Moving in together following a pregnancy—especially an unintended one—is unlikely to lead to marital success or union stability. Compared with marital unions, dissolution rates following birth were particularly high for couples who entered a cohabiting union following conception. Only a small minority of these couples married (i.e., less than one-third), and these marriages experienced high dissolution rates. The results also suggest that the most committed cohabiting couples got married after finding themselves pregnant, leaving behind the most dissolution-prone cohabiting couples. The American family system is being transformed by newly emerging patterns of fertility among cohabiting couples.     

Multiversity of the twenty-first century – examining opportunities for integrating community engagement in planning curricula

Abstract

This paper examines student-community engagement activity in planning. This is a subset of university–community engagement, and is a point of overlap between such engagement and planning education. Community engagement activity enables students to learn in situ practical skills within live projects, while community partners may benefit from technical knowhow, and labour input. Based on a UK-wide survey and three in-depth case studies, the paper explores the pedagogical designs underpinning community engagement activities involving students, as well as the various capacities in which the different participants – students, instructors and community members – act. The analysis reveals considerable diversity in approaches. An alignment of student engagement activities in the planning curriculum with emerging transformative co-learning models of university-community engagement could offer novel opportunities for the discipline of planning and their impact on communities as well as the fields standing in today’s multiversities.     

Changes in Product Attributes and Costs as Drivers of New Product Diffusion and Substitution

Diffusion theory has typically focused on how communication, internal or external to a social system, leads to adoptions and diffusion of an innovation. We develop a diffusion and substitution model based on a somewhat different perspective. In some cases, progressive improvements in product attributes and/or continual cost reduction seem to be a key driver of the diffusion process. For example, after introduction of the 5.25‐inch disk drive, its capacity continually increased, and accordingly, so did customer willingness‐to‐pay. Our model is based on a linear reservation price framework, in which a product is described by its depth (defined as the difference between a product̂s maximum reservation price and its production cost), and its breadth (related to the slope of its reservation price curve), indicating how broadly it appeals across various customer segments. Because of changes in product depths and breadths over time, customers who previously preferred the old product may later prefer the new product, thus creating the diffusion process. While the Bass model describes diffusion as a function of the coefficients of innovation and imitation, in our model, it is described by the coefficients of depth and breadth (the rates of change in relative depth and breadth), along with an S‐coefficient that we associate with the technology S‐curve. We fit our model to data from the disk‐drive and the microprocessor industries.     

THE ROLE OF MARITAL STATUS IN HEALTH SERVICES EXPENDITURES FOR PSYCHIATRIC OUTPATTIENTS

This study tested the hypothesis that married psychiatric outpatients would have lower total health services expenditures than divorced or separated patients. Chart review of the 471 individuals attending an academic medical center outpatient psychiatric clinic during 1994 identified 131 married, 40 separated, and 93 divorced patients. Separated men had significantly higher average total charges ($16,890) than married ($5,279) or divorced ($5,539) men by one-way ANOVA (p < .05). The nonparametric Mann-Whitney test also showed that separated men had higher charges than married or divorced men. There were no differences between marital status groups for women.     

Union-Nonunion differentials and establishment size: Evidence from the NLSY

We provide new empirical evidence on union-nonunion differentials using the 1990 wave of the National Longitudinal Surveys of Youth (NLSY) data set which allows us to examine a broader set of fringe benefits than most other studies and provides a rich set of control variables. Our major finding is that the union effect decreases with establishment size for both components of the compensation structure, i.e., wages and fringe benefits. An earlier version of this paper was presented at the Southern Economic Association conference in Washington, DC in 1996. We thank Tom Hyclak and other session participants. We also acknowledge the financial support from Ade Howe Kent Fund. The usual disclaimer applies.