Optimal mapping of terrestrial gamma dose rates using geological parent material and aerogeophysical survey data.

Regulatory authorities need ways to estimate natural terrestrial gamma radiation dose rates (nGy h⁻¹) across the landscape accurately, to assess its potential deleterious health effects. The primary method for estimating outdoor dose rate is to use an in situ detector supported 1 m above the ground, but such measurements are costly and cannot capture the landscape-scale variation in dose rates which are associated with changes in soil and parent material mineralogy. We investigate the potential for improving estimates of terrestrial gamma dose rates across Northern Ireland (13,542 km²) using measurements from 168 sites and two sources of ancillary data: (i) a map based on a simplified classification of soil parent material, and (ii) dose estimates from a national-scale, airborne radiometric survey. We used the linear mixed modelling framework in which the two ancillary variables were included in separate models as fixed effects, plus a correlation structure which captures the spatially correlated variance component. We used a cross-validation procedure to determine the magnitude of the prediction errors for the different models. We removed a random subset of 10 terrestrial measurements and formed the model from the remainder (n = 158), and then used the model to predict values at the other 10 sites. We repeated this procedure 50 times. The measurements of terrestrial dose vary between 1 and 103 (nGy h⁻¹). The median absolute model prediction errors (nGy h⁻¹) for the three models declined in the following order: no ancillary data (10.8) > simple geological classification (8.3) > airborne radiometric dose (5.4) as a single fixed effect. Estimates of airborne radiometric gamma dose rate can significantly improve the spatial prediction of terrestrial dose rate.

Speed-accuracy trade-off in planned arm movements with delayed feedback.

The Vector Integration to Endpoint (VITE) circuit describes a real-time neural network model simulating behavioral and neurobiological properties of planned arm and hand movements by the interaction of two populations of neurons. We analyze the speed-accuracy trade-off generated by this circuit, generalized to include delayed feedback. With delay, two important new properties of the circuit emerge: a breakdown of Fitts' law when the movement time is small relative to the delay; and a positive Fitts' law Y-intercept. This breakdown of Fitts' law for tasks with small Index of Difficulty has been previously observed experimentally, and we suggest it may be attributed at least in part to delay effects in the nervous system elaborated by the model. Additionally, this gives a theoretical explanation for why positive Fitts' law Y-intercept should occur, and that it is related to the delay within the movement circuit.

Allergic reaction to an amide local anaesthetic.

A 67-yr-old female patient gave a history of allergy to lignocaine. When she was challenge-tested with the intradermal injection of 0.5% bupivacaine 0.2ml she had a systemic reaction. This reaction was accompanied by a decrease in the concentration of complement C4 in the plasma, which indicated that the reaction was immunologically-mediated. This is the first report of allergy to a local anaesthetic drug which has been documented by concurrent immunological changes.

Adverse responses to i.v. anaesthetics.

The adverse reactions to i.v. anaesthetics which occurred during a 3-yr period in one hospital were investigated. Sixteen reactions were reported; 13 of these occurred in a total of 7906 administrations of Althesin, two in 45 546 administrations of thiopentone and one in 630 administrations of methohexitone. The pathological process was identified in 10 patients. Most reactions were caused by activation of the alternate pathway for complement conversion.

Prolonged infusion of chlormethiazole in intensive care.

Chlormethiazole has proved useful for prolonged sedation in patients receiving artificial ventilation of the lungs during intensive care. In short-term infusions sedation and unconsciousness can be produced quickly and reversal is rapid on stopping the administration. After prolonged infusion, however, recovery is much slower because of accumulation of the drug. The pharmacokinetics of chlormethiazole in both short and prolonged infusions were studied in four patients. Following brief administrations the drug disappeared very quickly from the blood as a result of re-distribution and the patients wakened after a few minutes. Unconsciousness was associated with plasma concentrations in the range of 3--5 micrograms ml-1. After 48 h administration, recovery was much slower, the elimination half-life varying from 3.5 to 12.1 h.

Delayed adverse responses to both methohexitone and Althesin.

A patient who reacted to both methohexitone and Althesin on separate occasions is described. On each occasion the reaction was delayed following anaesthesia. Underlying chronic infection had sensitised the patient's complement pathway, allowing it to be activated by two unrelated intravenous anaesthetic agents.

Effect of an inhibitor of dopamin-beta-hydroxylase on the acquistion and retention of four different avoidance tasks in mice.

The effect of [bis-(4-methyl-1-homopiperazinylthiocarbonyl)-disulfide] (FLA-63) (40 mg/kg, i.p.) on acquisition and retention in four different avoidance tasks was evaluated in mice. In all tasks animals were submitted to a training session on one day and to a retest session 24 h later. The drug or its vehicle were given either 2 h prior to training and/or retest (pretrial treatments) or immediately after the end of the training session (posttrial treatments). Two hours after injection, FLA-63 was found to lower brain norepinephrine (NE) levels by 51% without affecting those of dopamine (DA). Pretrial administration of the drug resulted in poorer performance of step-through and step-down passive avoidance as well as of step-up active avoidance in retest sessions. There was no apparent posttrial effect of the drug nor any effect on acquisition in these tasks. The drug was without influence on either acquisition or retention in an any-way passive avoidance task in which the response required from the animals was immobility. No evidence for state-dependent learning was detected in any of the tasks. The data are consistent with the hypothesis of an involvement of NE either in memory processes or in events parallel and related to memory processes. The present results rule out, however, several such possible parallel events (effects on acquisition, motor disturbances, and effects on reactivity to shocks).