Abstract: A stable blood serum bilirubin reference composition characterized in that the composition possess a pH of from about 8.2 to about 9.2 and comprises (a) a sulfhydryl compound in an amount sufficient to enhance the stability of the bilirubin and (b) a chelating agent in an amount sufficient to bind all the metals present in the blood serum moiety of the composition. This blood serum bilirubin composition when stored in a gas impervious vial under an inert atmosphere has an excellent shelf life.

Abstract: A method of closing or sealing a filler passage formed in a neck or stem protruding from the small access opening in the upper end of a substantially closed centrifuge tube. The neck is formed of a readily fusible material and a heat conductive cap member is positioned over the open end portion of the neck closely confining it therein. Heat and pressure are applied to the cap causing progressive portions of the neck to melt and fold into the filler passage where it forms a molten mass within the filler passage above the access opening to the tube. Heat and pressure are removed, permitting the cap to cool and the molten mass to solidify completely sealing or filler passage of the centrifuge tube. The cap is then removed and the centrifuge tube is fully prepared for centrifugation.

Abstract: A closed-loop drive system for variable speed induction motors for maintaining a constant slip frequency, regardless of motor speed. A slip frequency oscillator generates a signal having a frequency proportional to the desired slip of the motor and a tachometer generates a signal having a frequency proportional to the actual rotational speed of the motor. The stator frequency is the sum of the rotor speed and the slip frequency during acceleration and the difference between the rotor speed and the slip frequency during braking. Exclusive OR gates are used to add the slip frequency signal either to the tachometer signal or to the stator signal, the outputs of the gates being applied to a digital phase detector. The phase detector drives a voltage controlled oscillator which provides the stator signal. The output of the voltage controlled oscillator is used to trigger the slip frequency oscillator to prevent overlap of pulses to the digital phase detector.

Abstract: In an overspeed protection system for a centrifuge apparatus of the type including a rotor driven by a drive motor, a transducer for providing a signal whose frequency is a function of the rotational speed of the centrifuge rotor, an oscillator for generating a reference signal having a predetermined frequency, means for mixing the rotational speed signal with the reference signal to provide a difference frequency signal, a filter coupled to the output of the mixing means for passing signals having frequencies below a predetermined frequency, and means coupled to the filter for disconnecting power to the drive motor in response to an output signal from the filter, there is disclosed an improvement comprising a frequency comparator responsive to the rotational speed signal and the reference signal for generating an overspeed signal when the frequency of the rotational speed signal exceeds the frequency of the reference signal, and means for combining the outputs of the filter and the frequency comparator at th

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: An automatic transfer method and apparatus for a multi-variable control unit having at least two process control units is disclosed which initiates transfer from the selected controller to the non-selected controller through failure of the selected controller to produce transfer preventing signals.

Abstract: A solid state electrode for use in determining ion concentration in an aqueous solution comprising an electrically conductive element; a first lipophilic-hydrophobic (hereinafter referred to as LH) layer in intimate contact with the element; and a second LH layer in intimate contact with the first layer. The first LH layer comprises an adhesive, LH polymer having an intrinsic viscosity of from about 0.4 to about 0.9 ml/g; and an LH plasticizer. The second LH layer comprises a LH polymer having an intrinsic viscosity of from about 1 to about 1.5 ml/g; an LH plasticizer, and an LH ion-selective ligand of the ion to be determined.Preferably, the first LH layer further comprises an LH charge carrier.As used herein, the term "lipophilic-hydrophobic (LH)" denotes an organic solvent soluble-water insoluble substance.

Abstract: A method and apparatus for determining the wavelength of a light beam wherein the light beam is directed through a liquid crystal cell functioning as a variable retarder, wherein the voltage applied to the cell is ramped to vary the retardation of the cell between maximum and minimum values, wherein the light from the beam passing through the cell is detected, wherein the intensity of the detected light is monitored, which intensity alternately passes through maximum and minimum values as the retardation of the cell is varied between its maximum and minimum values, and wherein the number of times the intensity alternates between its maximum and minimum values is determined to provide an indication of the wavelength of the light beam.

Abstract: In a sulfur dioxide analyzer which measures the content of sulfur dioxide by fluorescence of sulfur dioxide molecules when illuminated by an ultraviolet light source, there is disclosed a converter containing vanadium pentoxide for removal of polynuclear aromatic hydrocarbons which produce interference when sulfur dioxide is measured by fluorescent methodology.

Abstract: A multi-contact rotary switch in which arcuate cam lobes on the planar faces of a rotatable disc-shaped cam rotor selectively engage a plurality of switch elements. Each switch element is attached to one of two switch blocks positioned adjacent to either cam rotor face. Slots in the switch blocks laterally confine the switch elements to preserve their alignment. A raised annular bearing on the cam rotor face maintains the position of the cam rotor relative to the switch blocks. Terminal extensions from the switch elements extend perpendicular to and away from the planar faces of the cam rotor.

Abstract: In a sulfur dioxide fluorescence analyzer, a method and apparatus for eliminating the fluorescence effects of nitric oxide is disclosed wherein a sample gas is mixed with a diluent which substantially quenches nitric oxide fluorescence.

Abstract: A membrane for use in the determination of calcium ion concentration in an aqueous solution, the membrane being of the type comprising a calcium ion selective component and a carrier material.

Abstract: In a system which measures a parameter of a sample and displays information relating thereto, a circuit including the component elements of the system for testing signal levels at test points within the system and for displaying the test signal levels. Switching means places the system in either a transducing mode for measuring the parameter or in a combined transducing/self-testing mode for simultaneous testing during transducing operation. The testing circuit includes an operator manipulated probe for contacting any of the test points and an analog multiplexer input of the system for multiplexing the probe test signal and the transducing signal. The multiplexed signals are converted to digital form and processed by the system's computer for display. In the combined transducing/self-testing mode, the probe test signal information is outputted to the system display while the transducing output thereto is inhibited.

Abstract: An electrochemical sensor for determining the O.sub.2 content of a fluid characterized in that the electrolyte employed therein is selected from a group consisting of amino alcohols having 2 to 12 carbon atoms, morpholine, and mixtures thereof. Optimally, the electrolyte can further comprise a supporting electrolyte selected from a group consisting of inorganic halides, organic supporting electrolytes, and mixtures thereof.

Abstract: A method of determining the concentration of antigen in a rate nephelometric immunochemical analysis wherein an observed maximum rate of change of a nephelometric signal is used to determine the antigen concentration by employing a mathematical expression derived on a semi-empirical basis.

Abstract: A multicharacter dot matrix gas discharge display panel utilizing a plurality of connector lines which provide direct connection to the same corresponding matrix bit within each dot matrix group in the display. The gas display panel allows direct addressing of each bit to achieve high luminescence and viewability. The display has very high resolution. The display also incorporates means for positioning each dot matrix group in such a manner to closely border adjacent dot matrix group, so that the overall display dimension is decreased for a multicharacter dot matrix display panel.

Abstract: A keyboard type switch is disclosed wherein a domed snap disc performs triatic functions of acting as a tactile feedback source for switch operation, of supplying a conductive path for electrical energy when depressed, and of providing a contact surface for manual operation. The disclosed switch is covered by a multilayered nonconductive membrane and spacer to provide maximum safety from electrical shock to the operator.

Abstract: In a system for analyzing the elemental or molecular composition of a sample where the sample components are excited through collision with an active metastable gaseous species, the excited sample components emitting a characteristic wavelength of light which may be detected, the system including a microwave cavity through which the gaseous species flows and a microwave source coupled to the cavity, the microwave discharge exciting the gaseous species, there is disclosed an improved gas and sample introduction system wherein a liquid sample and a water soluble compound are mixed with a diluent and aspirated into the flow, upstream of the microwave cavity, onto a heated filament, the compound being capable of releasing nitrogen or some other suitable gas molecules at high temperature and low pressure whereupon formation of nitrogen and vaporization of the sample occur simultaneously.

Abstract: An improved T.sub.3 uptake test procedure characterized in that the separating agent employed therein comprises precipitated nylon 6, precipitated nylon 66, or mixtures thereof.

Abstract: A liquid junction structure for an electrochemical reference electrode or a reference portion of an electrochemical combination electrode comprising an element of capillary material restrained between first and second plastic shrink tubes.