Abstract: In a spectrophotometer including a photomultiplier tube responsive to light for producing an analog current proportional to the intensity thereof, an analog-to-digital converter, a signal path from the photomultiplier tube to the analog-to-digital converter, the analog-to-digital converter producing a digital signal as a function of the analog current, and computer means responsive to the digital signal for generating a signal for compensating for the dark current of the photomultiplier tube, there is disclosed a method and means for reducing the dark current correction error by temporarily increasing the gain of the signal path during calculation of the value of the compensating signal.

Abstract: Apparatus for utilizing the flotation separation process employs first and second chambers, the first chamber being positioned above the second chamber so that the tailings from the first chamber may be gravity fed into the second chamber. Both chambers include a plurality of spaced, air bubble infusers, each of which are fed by air and water pipes extending across the corresponding chamber. A plug and throat arrangement in a bulkhead between the first and second chambers allows control over the flow of tailings from the first chamber into the second chamber. Each infuser is designed so as to provide an even spread of the air bubbles emitted therefrom.

Abstract: There is disclosed a circuit for generating an error voltage which is proportional to the difference between a desired value of a physical parameter and the actual value of the physical parameter. The circuit operates by alternately switching the current from a source through a fixed reference resistor and a variable resistor, the resistance value of which changes as a function of the physical parameter to be controlled. The current is switched between the two resistors so that the average voltage generated across the variable resistor would be equal to the average voltage generated across the fixed resistor if the physical parameter had the desired value. By determining the difference between the average voltages across the resistors, the error voltage can be generated for controlling the physical parameter.

Abstract: A construction element having a high strength to weight ratio, particularly useful in the fabrication of a boat hull, the construction element comprising:A first face layer of resin impregnated glass fiber cloth or glass fiber matting;An intermediate stiffening member comprising a laminate of:A. a flexible top sheet, preferably of paper;B. an intermediate foam layer, bonded to the top sheet; andC. a flexible bottom sheet, preferably of paper, bonded to the intermediate foam layer on the side opposite the top paper sheet; the laminate having:I. a first series of spaced slits extending through the top sheet and intermediate foam layer but not through the bottom sheet;Ii. a second series of spaced slits parallel to the first series of spaced slits and extending through the bottom sheet and intermediate foam layer but not through the top sheet, the second series of spaced slits being offset from the first series of spaced slits;Iii.

Abstract: A threshold formed of an extruded aluminum shape and a plastic shape, the two shapes being interlocked and the plastic shape defining that part of the threshold inwardly of the bottom of a door and exposed to outside temperatures. The aluminum shape extends outwardly from the door and provides the base for the plastic threshold shape.