Abstract: An improved reagent combination of the type comprising a first solution comprising an aryl amine and an acid; and a second solution comprising a nitrite compound. The regent combination is characterized in that is further comprises a salt, wherein the salt is present in any preselected distribution in the solutions.Also, an improved method for colorimetrically determining bilirubin in a sample comprising mixing an aliquot of the above first solution with an aliquot of the above second solution to form a stable diazo reagent; contacting a sample to be assayed with a total bilirubin accelerator buffer system to form a prereaction medium; contacting the prereaction medium with the stable diazo reagent; and measuring the color of the azobilirubin formed form the coupling reaction of the stable diazo reagent with the bilirubin present in said sample.In addition, an improved method for producing a diazo reagent of the type comprising reacting an aryl amine with a nitrite compound in the presence of an acid.

Abstract: A method and means for stabilizing the difference in frequencies between the frequency components of a two frequency laser beam influenced by Zeeman effect frequency splitting, accurately determines the frequency separation independently of the individual frequencies or intensities of either of the frequency components. Frequency stabilization is accomplished by mechanical and thermal adjustments to the lasing chamber length of the laser by a closed loop servo control referencing the frequency difference between laser beam components and a reference signal having a frequency equal to the desired frequency difference.

Abstract: A swinging bucket centrifuge rotor including seating surfaces having shapes which cause buckets seating thereon to be relieved of side loading forces. Each bucket is symmetrical and is pivotally supported by bucket pins that rest in respective spring-loaded carrier assemblies. The spring constants of the springs of the carrier assemblies are selected so that the leading edge of each bucket bottom rests upon a curved surface and clears the respective seating surface before the trailing edge thereof contacts the same. The resulting bucket orientation assures that, upon seating, each bucket rotates until its bucket pins lift slightly off of the surfaces of the respective carrier assemblies.

Abstract: A method comprising (a) applying a sample to at least two application areas on an electrophoretic gel; (b) electrophoresing the gel; (c) aligning a template onto the electrophoresed gel, the template having a template slot corresponding to each electrophoresed area; (d) applying a composition capable of fixing proteins in situ to at least one template slot and applying an antisera capable of reacting with one protein to at least one of the remaining template slots; (e) incubating the resultant product of step (d); (f) removing the template from the incubated, electrophoresed gel; (g) washing the incubated electrophoresed gel of step (f); (h) drying the washed gel of step (g); (i) staining the dryed gel of step (h); (j) destaining the stained gel of step (i); (k) drying the destained gel of step (j); and (l) analyzing the dryed gel of step (k).

Abstract: An improved composition of the type comprising a known concentration of at least one enzyme. The composition is characterized in that substantially all of at least one of the enzymes is combined with a stabilizing amount of a reversible inhibitor thereof to form an inhibitor-enzyme complex, thereby stabilizing the enzyme moiety of the complex.A method of stabilizing a composition comprising a known concentration of at least one enzyme. The method comprising combining substantially all of at least one of the enzymes with a stabilizing amount of a reversible inhibitor thereof to form an inhibitor-enzyme complex, thereby stabilizing the enzyme moiety of the complex.

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 multicomponent quantitative analytical method and apparatus wherein the method includes the steps of and the apparatus is capable of performing steps of obtaining a plurality of calibration spectra, transforming the calibration spectra using a transform with orthogonal basis vectors, obtaining a calibration matrix relating the transform spectra to concentrations of analytes in the calibration samples, obtaining a spectrum for an unknown sample, transforming the unknown sample spectrum, and relating the transformed unknown sample spectrum to the calibration matrix to thereby determine the concentration of analytes in the unknown sample.

Abstract: A centrifuge rotor is presented having a pivotal mount for a sample container upwardly offset from the radial plane of maximal strength of the rotor permitting a smaller diameter rotor container assembly and reducing exposed surface area of the rotor container assembly.

Abstract: An improved mirror scan control for driving a movable mirror in an interferometer with a constant scan velocity comprises a closed loop servo control which provides constant velocity mirror scan in response to a phase comparison of a signal derived from the beat frequency of a two frequency laser beam passing through the interferometer and a selected frequency reference signal, wherein the difference in frequencies or beat frequency of the two frequency laser beam is stabilized at a specified difference in frequencies. The mirror scan control employs a phase lock control loop which locks the frequency of the referenced signal with the frequency of the signal derived from the laser beam to provide precise mirror velocity control.

Abstract: A liquid flow monitor. The device includes a thermistor placed in the path of liquid flow. A circuit including the thermistor in a Wheatstone bridge is used to sense the liquid flow by sensing the change in resistance of the thermistor. A transistor connected to the bridge is used to maintain the thermistor within predetermined levels to prevent overheating of the device.

Abstract: A liquid chromatographic analytical column includes an end cap that is abutted with an end edge of a holder body when the analytical column is fully inserted into a bore in the holder body. An end cap mounted to a precolumn is compressed between the end cap of the analytical column and an end nut connected to a holder union. The holder union has a central passage that admits the precolumn therethrough and a stop that engages a ferrule placed around the precolumn to compress the ferrule against the analytical column end cap to form a seal.

Abstract: A tube-cutting apparatus and method for separating centrifuged materials are shown in which a resilient axial compressive force is exerted on the tube during cutting by spaced tube-holding members; and the cutting knife has flat upper and lower sides against which the severed portions of the tube are held in sealing engagement by the axial force. Independent adjustment is provided for (a) the relative positions of the tube and the cutting knife, and (b) the relative positions of the spaced tube-holding members.

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: Spectrophotometer purge apparatus comprising a sample compartment including a plurality of walls defining a first sample purge volume. The apparatus may further include a volume reducing wall and fastening means for removably fixing the volume reducing wall within the sample compartment to thereby define a second sample purge volume smaller than the first sample purge volume. A purge gas inlet introduces purge gas into the sample purge volumes. Further the apparatus may comprise a movable partition forming one of the plurality of walls and the volume reducing wall. In such an embodiment, the fastening means may further include means for removably fixing the movable partition to thereby define the first sample purge volume. The apparatus advantageously enables the sample purge volume to be adjusted as required to thereby optimize purge efficiency in a spectrophotometer.

Abstract: An immunoassay for assaying an antigenic substance (Ag) in a fluid. The immunoassay is the type which comprises contacting the fluid with at least one first entity selected from a group consisting of an antibody (Ab) to the Ag, a soluble, labeled antibody (L-Ab.sub.a) to the Ag, and an antibody (Ab.sub.b) to the Ag bound to a solid support (SC). The immunoassay is characterized in that the fluid is contacted with at least one additional entity selected from a group consisting of at least one different type of soluble, labeled antibody (L-Ab.sub.c) to the Ag, at least one different type of antibody (Ab.sub.d) bound to a solid carrier (SC.sub.1), and at least one different type of antibody (Ab.sub.e) to the Ag. The SC.sub.1 is selected from a group consisting of SC, at least one different solid carrier (SC.sub.2), and mixtures thereof (SC and SC.sub.2). Each type of L-Ab.sub.c, Ab.sub.d -SC.sub.1, and Ab.sub.e has a lower average affinity constant (K) for Ag than each respective K of L-Ab.sub.a, Ab.sub.

Abstract: A direct particle agglutination immunoassay for assaying an antigenic substance (Ag) in a fluid. The immunoassay is the type which comprises:(a) contacting the fluid with an antibody (Ab) coated particle (P) to agglutinate the Ab coated particles; and(b) detecting the presence of agglutination.The immunoassay is characterized in that the fluid is contacted with at least one additional entity selected from a group consisting of at least one different type of antibody (Ab.sub.a) coated particle (P.sub.1) and at least one different type of antibody (Ab.sub.b). The P.sub.1 is selected from a group consisting of P, at least one different particle (P.sub.2), and mixtures thereof (P and P.sub.2). Each type of Ab.sub.a -P.sub.1 and Ab.sub.b has a lower average affinity constant (K) for Ag than the K of Ab-P and the additional entity is present in an amount sufficient to avoid a high antigen false negative effect.Also, a reagent of the type comprising Ab-P.

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: A transfer mechanism for movement of sample containing vials from a first position to a second position in an analyzer instrument such as a liquid scintillation or a gamma counting device. The apparatus is particularly adaptable where available space is limited. A flexible transport member permits the transformation of movement in one direction into movement in another direction. Sensors and adjusting screws are incorporated into the apparatus for precisely controlling the travel distance of the transport member as well as precisely orienting the direction of the transport member.

Abstract: In a liquid scintillation counter a standard radioactive source is supported within the tubular bore of a flexible coil spring conveyor. Spacer elements within the coil spring retain the source at a predetermined axial position along the spring. The coil spring is disposed in sliding engagement along a conveyor guideway. A drive roller drivingly engages the spring for conveying the source along the guideway between an operating position adjacent the counting chamber and a remote shielded position.