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, kit and a solution for assaying enzyme, such as prostate acid phosphatase (PAP), in a sample. The sample is contacted with a first antibody (Ab.sub.1) against the enzyme and incubated. The resulting Ab.sub.1 -enzyme complex is contacted with a second antibody (Ab.sub.2) specific for Ab.sub.1. The resulting Ab.sub.2 -Ab.sub.1 -enzyme complex precipitates out of the medium. The precipitated complex is separated and solubilized with a pH controlled solution of gamma globulin. The resulting solution is then assayed for enzyme activity.

Abstract: Sample handling apparatus for circulating one or more sample holders along a rectilinear path in a sample holder storage compartment and past an operating station at which the holders may be removed from and then returned to the compartment. First and second parallel conveyors on opposite sides of the operating station drive the holders toward and away from the operating station. Lateral drivers engage the holders in longitudinal stop positions at opposite ends of the conveyors and drive them laterally between conveyors to lateral stop positions, one of the holders during lateral movement being driven into and away from an operative position at the operating station. A movable sample compartment divider between the conveyors is indexed in synchronism with the lateral drivers to engage and stabilize the sample holder at the operating station.

Abstract: Sample handling apparatus for circulating one or more sample holders along a rectilinear path in a sample holder storage compartment and past an operating station at which the holders may be removed from and then returned to the compartment. First and second parallel conveyors on opposite sides of the operating station drive the holders toward and away from the operating station. Lateral drivers engage the holders in longitudinal stop positions at opposite ends of the conveyors and drive them laterally between conveyors to lateral stop positions, one of the holders during lateral movement being driven into and away from an operative position at the operating station. A movable sample compartment divider between the conveyors is indexed in synchronism with the lateral drivers to engage and stabilize the sample holder at the operating station.

Abstract: In an optical instrument including a birefringent liquid crystal cell of the type consisting of a pair of transparent plates and a zero-twist, nematic-phase, liquid crystal material with a positive dielectric anisotropy between the plates, the liquid crystal molecules being oriented in and tilting in a plane perpendicular to the cell plates, a beam of light being conducted through the cell, generally normal to the plates thereof, it has been observed that if all of the rays of the beam are not collimated, each ray will suffer a different retardation in passing through the cell and this is unacceptable in most applications. This problem is minimized, according to the present invention, by using a filament light source positioned with the filament axis normal to the plane of the tilting molecule axes or by using two liquid crystal cells between a pair of polarizers, one of the cells being rotated 180.degree.

Abstract: Apparatus for transporting elongated sample holders in a sample holder storage compartment past an operating station at which sample tubes contained in the sample holders may be removed and then returned to the sample holders. First and second parallel conveyors on opposite sides of the operating station drive the holders toward and away from the operating station. A lateral drive system engages the holders in longitudinal stop positions at opposite ends of the conveyors and drives them laterally between the conveyors to lateral stop positions, one of the holders during lateral movement being driven into and away from an operative position at the operating station. Encoded labels are displayed on each sample holder for indicating the incremental spacing between the sample tubes carried in the sample holder.

Abstract: A double beam photometric flow cell for high pressure liquid chromatography having illuminated sample and reference passageways therein, the sample passageway receiving flowing fluid sample fractions for analysis. Regulating apertures control the relative amount of light passed through the passageways such that the light energy through the reference passageway exceeds that through the sample passageway. This reduces the contribution of the reference path to "shot noise" in the photometer output signal.

Abstract: A liquid transfer valve including a movable valve portion. A second valve portion is movable with respect to a first valve portion to allow probes to extend therethrough to pick up a liquids. Upon probe retraction, the second valve portion is movable to a position which allows the liquids to be injected into the valve where they are diluted, mixed, and carried to a remote detector or delivery point.

Abstract: A wavelength calibration solution comprising from about 0.025 to about 0.140 molar neodymium and from about 0.135 to about 0.550 molar samarium, wherein the neodymium is present as a neodymium ionized constituent and the samarium is present as a samarium ionized constituent.A method for checking the wavelength accuracy of spectrometers or spectrophotometers of the type comprising measuring the absorbance (A) or percent transmittance (% T) of a wavelength calibration check solution versus a blank at more than one wavelength. The method is characterized in that the above solution is employed therein as the wavelength calibration check solution.

Abstract: Apparatus for transporting elongated sample holders in a sample holder storage compartment past an operating station at which sample tubes contained in the sample holders may be removed and then returned to the sample holders. First and second parallel conveyors on opposite sides of the operating station drive the holders toward and away from the operating station. Lateral drive means engage the holders in longitudinal stop positions at opposite ends of the conveyors and drive them laterally between the conveyors to lateral stop positions, one of the holders during lateral movement being driven into and away from an operative position at the operating station. Encoded label means are displayed on each sample holder for indicating the incremental spacing between the sample tubes carried in the sample holder.

Abstract: There is disclosed a method and apparatus for implementing a narrow band rejection filter utilizing a liquid crystal cell. A liquid crystal cell is positioned in the path of a light beam between a pair of crossed or parallel polarizers with the optical axis of the cell at a 45.degree. angle to the optical axes of the polarizers. A voltage is applied to the cell to tune the cell to reject a given wavelength and to pass other wavelengths. In order to reject the given wavelength and pass all other wavelengths, the order of the cell is stepped to maintain rejection of a fixed wavelength and the detected signal from the light passing through the cell is averaged.

Abstract: Plunger operated pipet operable to execute different lengths of plunger movement during successive fluid pickup and fluid discharge operations or strokes. A stop member is movable between first and second locations in the pipet body to halt plunger movement at two different positions. A drive spring for driving the stop member from one location to the other is energized by a manually operable arming element and is retained in one location against action of the drive spring during a first plunger stroke. A release mechanism responsive to plunger movement during the first stroke disables the retaining means allowing the drive spring to move the stop member to the second location at which position the plunger is halted during the succeeding discharge stroke. The arming element is actuated by and in response to positioning of a replaceable tip on the pipet body.

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: Gain hysteresis exhibited by the photomultiplier detector of a single beam spectrophotometer is reduced by illuminating the detector and applying dynode voltage thereto during the normal "off" or "idle" interval of the spectrophotometer.

Abstract: Gain hysteresis exhibited by the photomultiplier detector of a single beam spectrophotometer is reduced by illuminating the detector and applying dynode voltage thereto during the normal "off" or "idle" interval of the spectrophotometer.

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 fluid pump mechanism for delivering a smooth output of fluids to a system utilizing at least one piston in a chamber reciprocative therewithin. The piston has strokes that fill and empty the chamber in conjunction with the action of valve means located at the inlet and outlet of the chamber. Motive means causes reciprocation of the piston within the chamber. Control means is also included for minimizing the time during the piston cycle in which the piston is not emptying the chamber. The invention's scope also encompasses a pressure metering device for a fluid forcing means motivated by an electrical motor.