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Fluorometric biochemical analyses based on the enzyme coupled NAD-NADH reaction are limited in sensitivity by sample background fluorescence. An order of magnitude improvement in sensitivity has been achieved with a fluorometer designed to automatically measure sample fluorescence with high precision, before and after the enzymatic reaction, to give a precise value for a small change in the fluorescence level. The design of this instrument has been optimized for precision of photometric measurement and includes automatic processing of 20 samples, automatic reagent addition, and digital signal processing. Performance tests show a capability for measuring changes in sample fluorescence of 1% with a precision of about 5%.

A precision thermistor bridge and thermistor is described for use in a thermal titration calorimeter or a high-speed stopped- or continuous-flow calorimeter of the Roughton type. These are compared and evaluated with regard to several other types of detectors, including the platinum resistance thermometer, thermocouple, transistor thermometer, and capacitance thermometers. At this time the best detection for our purpose seems to be a specially constructed 20-100 kΩ thermistor used in conjunction with a new ac lock-in amplifier bridge. The sensitivity of the system is equivalent to a peak-to-peak noise of 25 x 10-6 °C, with a 100-ms time constant and 1 µW power dissipation in the thermistor. Long-term drift of the bridge, without an oven, was 1 x 10-6 °C/min.

A method of using a field effect transistor to record single cell discharges through a closed system from the cerebral cortex of human patients is described. There have been no complications encountered in six patients under investigation.

Functional, electrical and structural details of an aversive stimulator for autistic children are presented. Design considerations and compromises needed to obtain satisfactory size, cost, convenience, safety, reliability and effectiveness are discussed. Limited clinical trials are reported.