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denotes the junction of at least two objects. In the context of disease transmission, contact implies interaction with potential to spread disease. Mischaracterization of contacts may result in inaccurate estimates of transmission rates. To collect more-accurate contact data among white-tailed deer (

NRPB has been operating an etched track neutron personal monitoring service for ten years. This has, since its inception, used an etch regime which is a combination of a chemical etch and a 2 kHz electrochemical etch. Processing at most other laboratories has settled on either a chemical etch or a two frequency electrochemical etch. These other types of processing each have significant advantages, but attempts to introduce them for routine processing at NRPB have also shown them to have significant disadvantages. Recent improvements in the manufacture of PADC have, however, changed the situation markedly, leading to the prospect of a viable two frequency electrochemical etch for routine personal monitoring.

The purpose of this prospective study was to determine the clinicopathological significance of necrotic areas demonstrated by rapid-bolus contrast-enhanced computed tomography (CT) in patients with biochemically predicted severe pancreatitis. Although CT necrosis occurred significantly more frequently in patients with clinically severe (ten of 12) compared with mild (seven of 20) pancreatitis (P < 0.025), seven of 17 (41 per cent) patients with CT necrosis developed clinically mild pancreatitis and six of ten (60 per cent) patients with clinically severe pancreatitis and CT necrosis recovered with conservative management. The site and extent of CT necrosis did not correlate with disease severity. Fine-needle aspiration cytology, operative and post-mortem findings and endoscopic retrograde cholangiopancreatography examinations all strongly suggested that CT necrosis represents true pancreatic necrosis. We conclude that the finding of CT necrosis is not in itself an indication for operative intervention, but that rapid-bolus contrast-enhanced dynamic CT greatly facilitates the planning and execution of surgical therapy.

Development of the NRPB PADC neutron dosimetry system was carried out during the years 1982 to 1985. In 1985 the monitoring service was set up, and following 9 months of operational trials, was given approval by the UK Health and Safety Executive in April 1986. This paper traces the developments, and outlines the present situation. At an early stage it was judged that the most critical component of the system was likely to be the reliable supply of plastic of suitable quality. However, the 'quality' of plastic is very dependent on the processing and read procedures chosen. A commercial manufacturer of PADC was selected, and a two stage etch (chemical, electrochemical) plus a chemical post-etch, was developed which gave adequate dosemeter response characteristics, combined with a low background track density. Rigorous quality control procedures needed to be applied to the sheets of PADC in order to satisfy an operational criterion of a minimum detectable dose of 200 μSv. The choice of reader was made largely on the basis of known reliability. Procedures were kept as simple as possible with the further aim of maximising commonality with other NRPB monitoring systems. The intention was to optimise the system from an operational point of view. This meant, for example, the choice of etch parameters which did not necessarily give the greatest values of sensitivity, but gave values which were less dependent on small changes in plastic properties or etch parameters.