Abstract: Improved apparatus for automatically calibrating and verifying the calibration of a chemical analyzer of the type which determines the concentration of a component in chemical or biological samples, e.g. concentration of glucose in blood or urine, wherein a sample changer sequentially advances samples into position for analysis. Calibration of the analyzer is performed by measuring a calibration standard of known concentration and generating a conversion factor therefor which converts the measured value of the standard to the known value thereof. Means is provided for storing conversion factors and proper calibration of the analyzer is verified by comparing successive conversion factors. If the compared conversion factors differ by more than a predetermined amount, the sample changer is halted and the calibration standard is remeasured.

Abstract: An air driven centrifuge including a rotor chamber having a rotor seat mounted in the bottom thereof and including a rotor having a plurality of turbine flutes formed in an under side thereof. The rotor seat includes driving air jet means for impinging pressurized air streams against the turbine flutes of the rotor for supporting and spinning the rotor on an air cushion above the rotor seat. Support air jet means are also provided in the seat for directing pressurized air streams against the under side of the rotor for supporting the rotor when the driving air jet streams are inactivated. A brake and stabilizing means is included for decelerating the spinning rotor and includes a friction bearing means on the bottom portion of the rotor and a stabilizer means movable into engagement with the bearing means and cooperating with the bearing means to produce a frictional load against the bearing means thereby causing the rotor to decelerate and also stabilizing the rotor as it slows to a stop.

Abstract: Sheep or horse blood is specially treated to produce an antigen which is readily agglutinable by heterophil type antibodies present in the patient's serum. This antigen possesses properties of stability, sensitivity and agglutinability which are utilized in a serological diagnostic test for infectious mononucleosis. Two other antigens, prepared from beef blood from guinea pig tissues, are used in the test to differentiate the infectious mononucleosis type antibody from the Forssman type.

Abstract: A semiconductor material is doped or alloyed under vacuum with an impurity by thermal decomposition and by sedimentation resulting from centrifugal force. The doping material is alternatively applied by evaporation before being subjected to centrifugal force and may be heated up to the melting point before completion of the centrifugal action. A centrifuge is provided having a thermal insulating layer between the outer wall of a rotor and a support for basic semiconductor material to be doped. The doping impurity material to be evaporated onto the basic solid state material is placed in the center of the centrifuge rotor.

Abstract: Improved liquid crystal compositions comprise a major portion by weight of at least three different p-alkoxybenzylidene-p'-aminophenylalkanoates and a minor portion by weight of p-methoxybenzylidene-p'-butylaniline and p-ethoxybenzylidene-p'-butylaniline. The compositions have broader nematic ranges than either ternary mixtures of the alkanoates or binary mixtures of the other two compounds. In addition, when certain dopants are added to the compositions, optimum improvement in properties is obtained using less dopant than that required by prior art compositions.

Abstract: A small ball valve for chemically active materials is provided which does not require the strength of metal parts and which permits the use of brittle material such as glass or ceramic as well as materials such as fluorocarbon polymers and polytetrafluoroethylene which are resistant to the action of chemically active fluids. A free-floating construction is provided without requiring a stem packing gland and permitting the stem to be integral with the ball. Identical sealing rings are provided with clamping screws which press the sealing rings inward against the ball and outward against the openings in the valve body, the diameter of the valve stem being smaller than the opening in the sealing ring and clamping screw therefor so that the portion of the ball surrounding the valve stem may also float freely under the sealing means with the seal around the ball stem being against the ball itself instead of against the valve stem.

Abstract: A vacuum bushing for an ultracentrifuge that minimizes excessive oil loss due to the high pressure differential across the bushing and allows automatic reclaiming and reusing of a major portion of the uncontaminated oil flow. The bushing is provided with first and second annular chambers, one chamber being connected to an atmospheric oil reservoir and the other chamber being connected to a vacuum oil reservoir. The major oil flow is from the atmospheric reservoir to the first chamber, along the rotor drive shaft to the second chamber, and then to the vacuum reservoir. The vacuum reservoir is connected to the atmospheric reservoir by a one-way check valve so that the oil is automatically returned to the atmospheric reservoir when the centrifuge is deactivated and the vacuum released.

Abstract: A spectrophotometer system having a first stepper motor driving a wavelength scanning mechanism and a second stepper motor driving a chart recorder, both motors being operative in response to pulses from a system clock. The clock frequency is successively divided by first and second cascaded, switch-selectable sets of frequency dividers. The output of the first divider is applied to the wavelength motor and determines wavelength scan speed. The output of the second divider is applied to the chart motor and determines chart scale expansion. A decoder monitors the frequency selections of the first and second sets of frequency dividers, and upon detection of a frequency selection outside the capability of the chart motor, the decoder provides an output which inhibits both motors. The decoder output additionally actuates a visual indicator to inform an operator of the invalid selection.

Abstract: A densitometer for providing an output which is a function of the density of a film badge in a photodosimeter system. The light passing through the film badge is received by a photodiode which generates a current signal which is directly proportional to the intensity of the received light. The current signal is converted to a voltage signal, the converting means being biased so that the voltage signal is zero when no light is received by the photodiode. The voltage signal is applied, together with a reference voltage, to a log-ratio circuit which generates an output signal proportional to the log of the ratio of the reference voltage to the voltage signal, the output of the log-ratio circuit being displayed. A circuit is operative, when the film badge is removed from the light path, to adjust the reference voltage until the output of the log-ratio circuit is zero.

Abstract: A light beam is passed through a cuvette, through which flows liquid to be analyzed optically for concentration of color reacted amino acids. The emergent beam is directed through a series of dichroic beam separators and pass band filters to produce three beams of substantially three different wavelengths. Photoelectric detectors produce electrical signals corresponding to each of the three wavelengths. Two of the signals are characteristic of the substance to be detected. The third is subtracted from the other two wavelength signals to produce a pair of output signals from which base line noise has been substantially eliminated.

Abstract: An electronic process controller is disclosed having analog circuitry for generating an analog control signal, a digital memory for generating a manual control signal and digital circuitry for sequencing of the analog functions. This controller provides drift-free manual control in the manual control mode, tracking of the process control signal in the automatic mode to allow bumpless transfer from automatic mode to manual mode and output ramping to allow bumpless transfer to and from direct digital control mode.

Abstract: An electronic process controller is disclosed having automatically bumpless operation. Changes such as transfer between manual and automatic modes, switching between set point sources and adjustment of control parameter values are all accomplished bumplessly with the aid of a settle circuit which adjusts the automatic control signal for bumpless switching while the manual memory freezes the process control signal at its last value before the change was initiated.

Abstract: An electrode housing for a fluid conductivity cell contains a chamber in which electrodes are securely positioned, the walls of the housing being electrically nonconducting and having at least one chamber duct penetrating the walls of the housing for the ingress and egress of fluid to be measured. The chamber duct is located relative to the electrodes such that it is substantially coincident with at least a portion of a line of equipotential established at the inside surface of the chamber in response to a voltage applied to the electrodes. The chamber duct is a size and shape to provide a negligible voltage drop across any dimension thereby substantially confining a conduction of current between the electrodes to the chamber of the electrode housing.

Abstract: A centrifuge test tube cap assembly for a thin flexible test tube including a stem member having a stud adapted to extend out the mouth of the test tube and having a cylindrically shaped skirt dimensioned to fit snugly within the inner surface of the mouth of the test tube, the stem member also having a slanting annular surface between the skirt and the stud, slanting outwardly in the downward direction, and the assembly also including a crown member having a depending outer lip, the outer diameter of which is substantially the same as the outer diameter of the thin flexible tube and having an annular inner surface slanting outwardly in the downward direction, the slanting surface of the lip conforming to the shape and slant of the slanting annular surface of the stem member so that when the crown is positioned over the stem and tightened axially on the stem member the upper edge of the flexible tube is deformed inwardly to squeeze the upper edge of the tube between the respective slanting surfaces of the ste

Abstract: To compensate for the nonspecific absorption in an atomic absorption spectral photometer an auxiliary illuminating source is provided in addition to the principal illuminating source. The need for moving parts and mirrors is obviated by mounting the principal and auxiliary radiation sources in fixed positions along a common ray path. The auxiliary source is constructed so that it is optically transparent and mounted adjacent the optical input with the radiation concentrated in an emission center common to both sources coinciding with the emission center of the auxiliary source. The sources are pulsed so that they are energized alternately.

Abstract: A gaseous glow discharge display tube having a plurality of digits positioned within a common envelope is filled with a gas mixture of such a composition so as to reduce the blanking requirements for streamer elimination. Within a prescribed range of current densities, and applied voltage, blanking requirements may be entirely elininated.

Abstract: A method of analyzing nitric oxide (NO) in a gas stream containing nitrogen dioxide (NO.sub.2) and a scrubber apparatus for selectively removing nitrogen dioxide from a gas stream containing nitric oxide. The scrubber apparatus comprises a container having an inlet port for the gas stream and an outlet port. The scrubber material in the container includes silver carbonate whereby the scrubber has an efficiency of at least about 99% and a capacity of about 11.5 parts per million hours of 99% nitrogen dioxide removal per gram of silver carbonate. The method involves passing the gas stream through a scrubber material containing silver carbonate so as to remove nitrogen dioxide from the gas stream while passing the nitric oxide unattenuated and thereafter conveying the gas stream from the scrubber material to an analyzer for nitric oxide. The gas stream is analyzed with the analyzer to determine the nitric oxide concentration therein.

Abstract: A portable, automated chemical analyzer having a polarographic oxygen electrode submerged in a batch of stirred solution. The signal from the electrode is directly differentiated and amplified to produce a signal proportional to the time rate of change of oxygen concentration. The membrane of the polarographic sensor is stretched very tightly over the cathode surface to provide a high signal-to-noise ratio. Methods for analyzing glucose-glucose oxidase, catalase-H.sub.2 O.sub.2 and various other enzyme systems by the polarographic electrode oxygen sensing apparatus include the steps of converting the sensed signal into time rate of change of oxygen concentration and recording the maximum rate of change of oxygen concentration.

Abstract: A shutter assembly for a radioactivity measuring apparatus having a sample counting chamber, the assembly having a bulky solid lead cylinder with a sample access port extending therethrough for alignment with the sample chamber. The cylinder is rotated by a Geneva wheel arrangement having a drive wheel with a plurality of equi-angularly disposed pins perpendicular to the surface thereof engaging radially extending open-ended slots in a driven wheel secured to the lead cylinder for concurrent rotation therewith. The drive wheel is rotated at a constant speed with the driven wheel accelerating as a pin traverses the slot from the open end toward the driven wheel center and then decelerating as the pin traverses the reverse direction to provide precise positioning with adjacent pins engaging the open ends of adjacent slots in the stop position of the cylinder.

Abstract: A thermistor material which, when screened and fired upon ceramic substrates by thick film techniques, exhibits a substantially constant temperature coefficient of electrical resistance. The thermistor composition or ink, before screening, comprises from 30 to 80% by weight of an oxide of vanadium VO.sub.X, where X varies from 1.5 to 2.5, mixed with 70 to 20% by weight of a glass frit.