Abstract: A radiation aperture system where two sets of apertures are distributed in ring sections of like radius on two parallel rings. As one ring is rotated with respect to its counterpart, one aperture of each ring will align to pass a radiation beam through both apertures. Only a single aperture pair is formed at each unique time, allowing sequential measurements of all combinations of both aperture openings during rotation without halting the rotation.

Abstract: A diagnostic apparatus and method for clamping the blood glucose concentration of a subject at any one of a plurality of levels. A desired clamping level (BC) is selected and the value of the present blood glucose concentration, corrected to fit a least squares regression lines (GY) in the bloodstream of the subject is periodically determined. Dextrose is introduced into the bloodstream of the subject at a rate (DR) derived in accordance with ##EQU1## wherein: DR=dextrose infusion rate for clamp (mg/min)WT=body weight (kg)BC=desired clamp level (mg %)GY=present blood glucose level, corrected to fit a least squares regression line (mg %)M=slope of the least squares regression line fit for the last five glucose valuesKS=constant to allow adjustment for differences in metabolism ##EQU2## (Glucose utilization in mg/kg/min).

Abstract: In a method and apparatus for controlling the concentration of glucose in the blood stream of a subject at a desired level (BI) including controlling the supply of insulin (IR) by periodically measuring the blood glucose concentration (G) and selecting a predetermined basal infusion rate (RI) for the desired level, the step of selecting a predetermined basal infusion rate comprises periodically searching for the value of the basal infusion rate RI required for BI in accordance withRI=RI.sub.LAST (GY/BI)where (GY) is the present blood glucose level corrected to fit a least squares regression line, when the slope of the least squares regression line fit for the last five G values is less than 0.5 and GY is within .+-.50% of the desired BI level, and wherein the period between searches is equal to or greater than the period between glucose measurements.