MCMC methods for putative pollution source problems in environmental epidemiology.

This paper demonstrates the use of the Gibbs Sampler and other Markov Chain Monte Carlo (MCMC) methods in two applications in environmental epidemiology. The first example concerns the application of a Metropolis-Hastings/Gibbs sampler to a Cox process with a direction-dependent cluster variance parameter. The second example consists of the estimation of the posterior (spatial) distribution of a putative location.

Tests for directional space-time interaction in epidemiological data.

Spatial incidence of disease is often recorded with time of occurrence as an ordering label. This ordering can be used to provide distance based tests for joint clustering of cases in space and time. Two different tests are proposed: one where a control disease is available, and the other where only standardized rates within census regions are available.

Assessing the breeding efficiency of broiler breeder flocks by measuring sperm transfer into laid eggs.

1. The breeding efficiency of broiler flocks was assessed by estimating the numbers of spermatozoa trapped in a 5.5 mm2 area of the perivitelline layer of laid eggs.

Interactions between killer yeasts and pathogenic fungi.

A total of 17 presumptive killer yeast strains were tested in vitro for growth inhibitory and killing activity against a range of fungal pathogens of agronomic, environmental and clinical significance. Several yeasts were identified which displayed significant activity against important pathogenic fungi. For example, isolates of the opportunistic human pathogen, Candida albicans, were generally very sensitive to Williopsis mrakii killer yeast activity, whilst killer strains of Saccharomyces cerevisiae and Pichia anomala markedly inhibited the growth of certain wood decay basidiomycetes and plant pathogenic fungi.

Evaluation of the use of induction in the development of a medical expert system.

In an earlier study, two medical expert systems for diagnosing thyroid disorders, developed by the application of induction on a sample of previously diagnosed cases and on expert-generated rules, diagnosed a set of test cases better than an expert system developed by the more traditional method of collaboration between a knowledge engineer and an expert. In this paper, an alternative measure of the accuracy of diagnosis of each system is used to evaluate the systems. Diagnoses for every distinct case represented by a combination of indicating factors are compared with diagnoses that the expert made.

A rapid colorimetric assay of killer toxin activity in yeast.

The pale yellow redox indicator 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) is reduced to a dark blue end-product, MTT-Formazan, by the mitochondrial dehydrogenases of living cells. MTT reduction can be measured spectrophotometrically at a wavelength of 570 nm and a method is described to assay the cidal activity of Williopsis mrakii killer toxin against sensitive cells of Candida glabrata. The MTT assay is rapid, quantitative and compares favourably with traditional plating techniques for the assessment of sensitive viability.

Frames of reference and motion aftereffects.

Evidence concerning the origin of the motion aftereffect (MAE) is assessed in terms of a model of levels of representation in visual motion perception proposed by Wade and Swanston. Very few experiments have been designed so as to permit unambiguous conclusions to be drawn. The requirements for such experiments are identified.

The roles of magnesium in biotechnology.

This review highlights the important roles played by magnesium in the growth and metabolic functions of microbial and animal cells, and therefore assigns a key role for magnesium ions in biotechnology. The fundamental biochemical and physiological actions of magnesium as a regulatory cation are outlined. Such actions are deemed to be relevant in an applied sense, because Mg2+ availability in cell culture and fermentation media can dramatically influence growth and metabolism of cells.