Abstract: A non-liquid scatter standard for use in nephelometry and turbidimetry systems which comprises a clear silicon rubber gel in which an effective light scattering amount of inorganic particles are suspended. The particles have an index of refraction greater than that of the silicon rubber gel.

Abstract: A method for use with liquid scintillation flow systems including flowing a mixture comprising a sample and a liquid scintillation medium through a flow detector, the liquid scintillation medium including a radionuclide marker having an energy distribution different from the sample. A pulse height distribution spectrum is determined and a unique point on the portion of the pulse height distribution spectrum representing the energy spectrum of the medium is found, a pulse height value related to such unique point providing a value related to the degree of quench present in the mixture. By comparing such pulse height value to a pulse height value obtained in a like manner for a calibration standard, a degree of quench present in the mixture is indicated.

Abstract: A prescaling device and method including a timer for generating a timing signal at the end of each of a plurality of timing periods and an integrator for integrating an input signal to generate an integrator output signal proportional thereto. The integrator can hold the integrator output signal in response to hold signal. A comparator is responsive to the integrator output signal for generating a signal when the integrator output exceeds a predetermined level. Control logic generates the hold signal in response to the comparator signal and the timing signal whereby integration is halted at the end of one of the timing periods. A counter counts the timing signals to thereby determine the number of timing periods elapsing prior to the halt of integration. The number of timing periods is indicative of an integration timing range which in turn is indicative of a scaling factor which may be applied to the held output of the integrator.

Abstract: A zero backlash device. The device includes a spring loaded bracket for providing a lateral force to the driving nut on a threaded rod. This lateral force is directed perpendicularly to the axis of the threaded shaft thus insuring continued intimate contact between the threads on the driving nut and the threads on the shaft.

Abstract: An apparatus and method for indicating the temperature of the environment into which a reaction vessel may be placed is provided by a container holding a thermally efficient fluid. The container has an identical external configuration substantially identical to the reaction vessel and is adapted to be positioned within the environment in place of the reaction vessel. A temperature sensor in thermal communication with the thermally efficient fluid provides an electrical parameter indicating the temperature of such fluid and thus the environment of the reaction vessel.

Abstract: A shear valve obtaining selective fluidic communication between fluid ports formed in a first member and fluid ports formed in a second member comprises a first seal with means for providing a fluidic seal between aligned ports and which separates the first and second members to form a passage, and a second sealing means to obtain a fluidic seal between the first and second members and enclose the passage. A fluid port is provided to introduce wash solution into the passage formed between the first and second members and a drain port is provided to remove the wash solution introduced between the first and second members, so that a wash and purge operation may be performed to cleanse the sealing surfaces of the valve.

Abstract: A kinetic assay method and apparatus for performing such method wherein a first sample containing predetermined concentrations of binary analytes is reacted with the reagent to form a reaction product. Reaction rates at first and second times are measured for the first reaction and a first ratio between such measured reaction rates is determined. A second reaction with a second sample and the reagent is also performed wherein the second sample contains predetermined concentrations of the binary analytes. Reaction rates at the first and second times are measured for the second reaction and a second ratio between such rates is determined. A third reaction with a third sample and the reagent is performed, the sample including unknown relative concentrations of the first and second analytes. Reaction rates are again measured at the first and second times and a third ratio between such measured reaction rates is determined.

Abstract: Methods for stray light measurement and compensation in spectrophotometers are disclosed. In one exemplary embodiment, stray light is determined as a convolution of a selected detected radiant power spectrum and a monochromator slit function. Such a stray light measurement may be made with or without the sample in an optical path between a source and detector within the spectrophotometer. When made with the sample in the optical path, the resulting stray light measurement may be used to compensate sample absorbance or transmittance measurements. In accordance with another embodiment of the present invention, sample absorbance or transmittance may be compensated in a method including measuring sample detected radiant power at a wavelength outside an interval of significant detected radiant power within which a sample measurement compensated for stray is desired.

Abstract: A device for starting and operating gas discharge tubes including a DC-to-AC inverter which generates a low voltage or a high voltage at an output thereof in response to first or second input signals, respectively. The output of the inverter is connected to a gas discharge tube and sensing means generates a signal proportional to the current flow through the tube. Suitable means provides a trigger or synchronizing signal to a driver. The driver, responsive to the sensed output signal and the trigger or synchronizing signal, generates a drive signal synchronized with the trigger or synchronizing signal and having a duration inversely related to the magnitude of the current flowing through the gas discharge tube. A high voltage switch applies a second input signal to the inverter in response to the drive signal to provide a decreasing high voltage duration during successive cycles of the inverter as the tube begins to conduct current.

Abstract: A method for driving a stepper motor. The method includes varying the width of the high level drive impulses of a bi-level drive system based on the desired speed to be achieved by the stepper motor. A microprocessor is used to vary the pulse width.

Abstract: A function generator responsive to clock pulses for developing an analog signal in the form of a digitally approximated parabola.

Abstract: A display system and method utilizing a common character generator among a plurality of display devices. Each display device generates address signals which are multiplexed and applied to the character generator. The output from the character generator is used to control the visual representation produced by each display device. A graphics memory of picture elements can be addressed for a composite display of graphics and alphanumeric characters by the various display devices.

Abstract: A video display memory expansion system for expanding the graphics memory within the video display. The memory expansion system is suited for increasing the resolution of a graphics display from a low-resolution to a high-resolution display. A video display device is adapted to receive a relatively simple graphics memory expansion accessory to thereby easily and inexpensively provide the increased graphics memory capability.

Abstract: A photomultiplier detector protection system and method utilizing a negative feedback loop to maintain the photomultiplier detector output below a predetermined output. The feedback loop comprises a comparator responsive to the photomultiplier detector output and also responsive to a predetermined limit signal. The comparator output is applied to a summing amplifier which also receives a voltage adjust signal. The output of the summing amplifier controls the output of a power supply which is in turn applied to the photomultiplier detector.

Abstract: A method of quench correction in liquid scintillation counting which compensates for the effect of sample quench. A quench corrected pulse height window is established for measuring sample scintillations. A pulse height threshold is established distinguishing regions for which a measure of sample quench, derived conventionally, is either proportional to or not proportional to the actual effect of quench on the sample pulse height spectrum. The quench corrected window is compared with the pulse height threshold, and the relative position of the corrected window is adjusted if the comparison step indicates that the window lies in the region of nonproportionality.

Abstract: A method and related apparatus for the determination of a random coincidence count attributable to chance coincidences of single-photon events which are each detected in only a single detector of a scintillation counter utilizing two detectors in a coincidence counting technique. Real and apparent coincidences of pulses are accumulated in a first counting device (28), and all pulses from the detectors (12) are accumulated in a second counting device (38), without regard for coincidence in time. The two counting devices are monitored during at least one random coincidence monitoring time occurring simultaneously with part of a sample counting period. The length and frequency of occurrence of the random coincidence monitoring times can be selected for particular counting measurement applications.