Matrix Theory Formalism for Event Tree Analysis: Application to Nuclear-Risk Analysis

It is pointed out that the familiar analytical device of "event tree", widely used in risk analysis, can be viewed as a transition matrix expressing the likelihood of going from "entry states" to "exit states". This point of view is shown to have numerous interesting conceptual and computational features which promise to make it a very useful addition to the arsenal of tools for risk analysis. The basic idea is explained first in terms of a simple, made-up example. The application of the idea to a very real and complicated problem, nuclear-plant risk assessment, is then outlined.     

An Alternative Approach to Dietary Exposure Assessment

The method of dietary exposure assessment currently used by the Environmental Protection Agency (EPA), the Dietary Residue Evaluation System (DRES), combines a consumption distribution derived from the United States Department of Agriculture (USDA) 1977-1978 Nationwide Food Consumption Survey (NFCS) with a single estimate of residue level. The National Academy of Sciences'¹' recommended that EPA incorporate both the distribution of residues and the distribution of consumption into their exposure assessment methodology and proposed using a Monte Carlo approach. This paper presents an alternative method, the Joint Distributional Analysis (JDA), that combines the consumption and residue distributions, without relying on random sampling or fitting theoretical distributions like the Monte Carlo method. This method permits simultaneous analysis of the entire diet, including assessing exposure from residues in different foods.     

The Rise and Fall of the Area Dental Officer

Reorganization of the NHS in 1974 sped up the process of professionalization of the leadership of the Community Dental Health Services. Since that event public dental officers have gained status through recognition of the need for specialists in community dental health. Nevertheless, by the beginning of 1982 no trainees had yet been appointed to begin the special training programme, thus far failing the efforts of those area dental officers who have striven since 1974 to raise the standards of their successors.     

Bat ecology and public health surveillance for rabies in an urbanizing region of Colorado

We describe use of Fort Collins, Colorado, and nearby areas by bats in 2001–2005, and link patterns in bat ecology with concurrent public health surveillance for rabies. Our analyses are based on evaluation of summary statistics, and information-theoretic support for results of simple logistic regression. Based on captures in mist nets, the city bat fauna differed from that of the adjacent mountains, and was dominated by big brown bats (Eptesicus fuscus). Species, age, and sex composition of bats submitted for rabies testing locally and along the urbanizing Front Range Corridor were similar to those of the mist-net captures and reflected the annual cycle of reproduction and activity of big brown bats. Few submissions occurred November- March, when these bats hibernated elsewhere. In summer females roosted in buildings in colonies and dominated health samples; fledging of young corresponded to a summer peak in health submissions with no increase in rabies prevalence. Roosting ecology of big brown bats in buildings was similar to that reported for natural sites, including colony size, roost-switching behavior, fidelity to roosts in a small area, and attributes important for roost selection. Attrition in roosts occurred from structural modifications of buildings to exclude colonies by citizens, but without major effects on long-term bat reproduction or survival. Bats foraged in areas set aside for nature conservation. A pattern of lower diversity in urban bat communities with dominance by big brown bats may occur widely in the USA, and is consistent with national public health records for rabies surveillance.