Abstract: Flexible wire loop slip ring brushes for use in miniaturized gyroscopes. A lurality of flexible wire loop brushes hug or embrace opposite peripheral sides of respective slip rings in resilient sliding contact over a substantial arc for establishing a redundancy of "a" spots for assured paths through which electrical current may pass with minimal resistance. The rings and the brushes are gold alloy which in sliding contact provide good electrical conductivity and low noise.

Abstract: A condensation nuclei counter for measurement of the concentrations of Aitken particles in gases by measurement of light scattered in a cloud chamber by water droplets formed on the particles in successive samples of a gas wherein the counter provides for sequential high speed sampling of the photodetector output during the cloud chamber growth of the droplets of each gas sample tested as a way of measuring the rate of increase of total droplet cross-section and wherein the counter provides for automatic ranging for particle population coordinated with the timed sampling during particle growth.