Abstract: Apparatus for controlling reaction temperatures in a chemical analyzer comprises a thermoelectric element operating in response to a temperature sensor, and control means capable of predicting a setpoint deviation for a future time period, and, when an overshoot is predicted, reducing a control signal for the element by an amount proportional to a current setpoint deviation. The apparatus includes at least one reaction cell and a buffer unit for thermally stabilizing a fluid that is fed, on demand, into the reaction cell, the cell and the buffer unit having separate thermoelectric elements and sensors. A microcomputer control system generates independent control signals for the elements.

Abstract: A device for generating a plurality of gas bubbles in a liquid. The device includes a conduit adapted to carry the liquid. A first gas chamber is formed near the conduit and an orifice proximate a side wall of the conduit defines a passageway between the first gas chamber and the conduit. A valve member is adapted to seat against and close the orifice. The device may include a second gas chamber and a diaphragm responsive to gas pressure in the second gas chamber. A conduit connecting the first and second chambers may include a variable vent for controlling the size and number of gas bubbles injected into the liquid flowing in the conduit.

Abstract: A novel competitive assay for theophylline wherein caffeine-like (7-substituted) labeled conjugates are used to detect the presence and/or amount of theophylline present in a test sample. The use of such conjugates in a competitive assay for theophylline results in improved sensitivity of the assay method. Where the assay method is a nephelometric or turbidimetric inhibition immunoassay procedure, the assay was found to be less temperature dependent than prior art immunoassays.

Abstract: In a centrifuge rotor with defined and discrete sample receiving cells, an improvement to the fastening of a lid on top of the rotor by a bolt for preserving gas pressure on sample is provided. The rotor is of the type having a rotor body and rotor adaptor for attachment to a drive hub. Typically, a male control surface on the drive hub mates with a corresponding female mating surface on the rotor adaptor. The mating surfaces include paired opposed pins on the rotor adaptor received in grooves on the drive hub. A central aperture along the spin axis of the rotor is provided through the rotor body. This aperture is provided for viewing the rotor coupling at the pins to the grooves in the drive hub as well as providing a path through which a bolt can attach a lid on the top of the rotor to the drive hub with the rotor compressed therebetween the lid and drive hub, a sample preserving atmosphere may be maintained in the rotor during centrifugation.

Abstract: A measuring system for use with automated pipettes for determining the presence or absence of a pipette tip. The central conduit of the pipette is connected to a source of pressure waves, such as a speaker and also connected to a pressure wave detector, such as a microphone. Changes in acoustic impedance between an open conduit when no tip is present, a partially constricted conduit when a tip is present, and a closed conduit when the liquid boundary layer is contacted determine the measured states of the apparatus.

Abstract: A centrifuge system includes a drive shaft bearing mounted to a drive shaft for engaging a solenoid actuated plunger in low friction contact over a predetermined angular velocity range of the drive shaft. The drive shaft bearing includes a frustoconical bearing surface that contacts a plunger bearing mounted in an end of the plunger when the solenoid actuates the plunger. The frustoconical bearing surface transforms vibrations of the drive shaft transverse to its axis of rotation into linear motion of the plunger relative to the drive shaft. The plunger is mounted inside the solenoid such that the solenoid, the plunger and the drive shaft are substantially concentric. The plunger is movable in the solenoid in response to application of an appropriate electrical current to the solenoid. However, the plunger fits sufficiently close within the solenoid that the force movement of the plunger arising from contact with the vibrating drive shaft bearing is damped by friction between the solenoid and the plunger.

Abstract: A flow cell for liquid scintillation counting having a spool wound with a length of light transparent tubing provides a variable volume of sample solution for analysis by selectively winding the spool with a select length of tubing, thus controlling sensitivity of anaysis and maintaining resolution of separated constituents in the sample. The flow cell comprises a spool rotatably held within a framework and which may be covered with a transparent material.

Abstract: A calibration method and apparatus for economical and rapid calibration of a scientific instrument utilizing a monochromator to generate monochromatic light utilizing controllable means for determining the angular position of a light dispersing element in the monochromator and a filter having a narrow absorption band(s) to determine a relationship between the wavelength of the monochromatic light generated by the monochromator and an angular position of the dispersing element so that the dispersing element can be rotated to an exact position for the monochromator to generate a selected wavelength of monochromatic light.

Abstract: To enable centrifuging to occur at precisely determined sample temperatures, a method of centrifuge calibration which permits rapid and accurate refrigeration of the rotor containing the sample is disclosed. A rotor with sample to be centrifuged is placed within a centrifuge can. Temperature of the radiometer T.sub.ra, and temperature of the surrounding refrigerating can T.sub.c is determined at a first time, t.sub.0. Thereafter, and at a second time t.sub.1, temperature of the radiometer T.sub.ra, and the temperature of the surrounding refrigerating can T.sub.c are equilibrated. The temperature excursion between t.sub.0 and t.sub.1 for the temperatures of the radiometer T.sub.ra and the temperature of the refrigerating can T.sub.c are measured to yield respective .DELTA. T.sub.ra and .DELTA. T.sub.c. The radio of .DELTA. T.sub.ra /.DELTA. T.sub.c is taken to give a constant which comprises the view factor from the radiometer for the particular shape of rotor and the surrounding can.

Abstract: The peak verify time for kinetic nephelometric measurements of reactions between antigens and antibodies is adjusted as a function of the magnitude of the peak rate order to reduce the time required for peak verification. The scatter signal is zeroed following the end of the peak verification period and the reaction is tested for antigen excess. Reactions during the antigen excess check having rates that exceed a threshold value are accepted as being valid, and no additional measurements are made for such samples. Reactions during the antigen excess check having rates that are less than the threshold value are rejected as being in antigen excess. Samples found to be in antigen excess are diluted and then reanalyzed.

Abstract: A centrifuge sample is optically scanned during centrifuging. The sample, placed in a centrifuge rotor having a cell with top and bottom windows, is spun until stratification and discrete layering occurs within the sample. Such layering occurs on layers that are precisely normal to the radius of the centrifuge at the point of sample and parallel to the spin axis of the centrifuge. A slit scanner having a slit normal to the sample plane transverse the width of the sample below the cell to detect with precision the precise location of the strata in the cell. A light source is reflected by a toroidal mirror having two radius of curvature. One radius of curvature is selected to collimate rays of light parallel to the layer of the sample. The mirror is ruled with respect to the other radius of curvature to chromatically classify light to preselect band width. Rotation of the mirror preserved collimation but enables selected scanning light frequency.

Abstract: An apparatus and method of protecting a centrifuge from rotor overspeed and resultant mishap by computation of the rotor moment of inertia is disclosed. In the preferred embodiment, a centrifuge is driven by a rotor mounted on a shaft which shaft is in turn driven by a constant current motor. A tachometer for detecting angular velocity of the drive shaft is used. A desired and ultimate centrifuge operating speed is selected by the operator. The times at which the rotor passes through discrete speeds are recorded and from the time difference the moment of inertia is computed. The moment of inertia can thereafter be utilized to discretely identify or "finger print" rotors to disqualify certain rotors from use in particular centrifuge protocols and establish gross limits of centrifuge operating speed.

Abstract: The present invention provides a mechanism for bolting a rotor to a hub without introducing excessive radial stress around the bolt holes when the rotor is operating at high speed. The rotor has a slot cut through its center to eliminate radial stress perpendicular to the slot and thereby avoid the problem of stress cracking of the otherwise weak section. The mounting bolts are necked down and not threaded at the surface of the hub. The bolts are threaded into the hub at a substantial distance from the top surface of the hub so that they can flex and so that the center of the rotor can move out relative to the hub. The hub rotor interface is lubricated to facilitate radial motion of the center of the rotor.

Abstract: An improved centrifuge. The centrifuge may be a conventional centrifuge having a rotor and a plurality of tube receiving adaptors inserted into the rotor in a circular configuration. The improvement comprises a flexible flap having a fixed end mounted on the rotor at an adaptor and having an opposing free end. The free end extends radially inward toward the center of the rotor when the rotor is not rotating and is folded by centrifugal force back to cover the opening in the adaptor when the rotor is rotating. By covering the opening in the adaptor, the flexible flap eliminates the high pitch whistle otherwise generated by the adaptor when rotating without a tube inserted.

Abstract: A salt belt for insertion into a centrifugal test rotor is provided which is used to hold and contain a plurality of test components during mechanical testing. The slat belt is a flat polymeric belt which adhesively affixes a plurality of L-shaped slat members to its upper surface. When the belt is laid flat, it accommodates the easy positioning of components into channels. As the belt is curled for insertion into the test rotor, the slats move closer to one another and clasp the components into channels formed by adjacent pairs of radially directed slat arms. Upon completion of the test run, the slat belt is removed from the rotor and unrolled whereby the components are easily removed from the belt.

Abstract: An electrophoretic gel comprising (a) at least one marine hydrocolloid processed from the class Rodophycea; and (b) a buffer. The electrophoretic gel is characterized in that the buffer (i) is selected from a group consisting of adipic acid, glutaric acid, itaconic acid, maleic acid, malic acid, malonic acid, succinic acid, succinamic acid, and tricarbalyllic acid and (ii) is present in a concentration of about 0.05 to about 0.09 M.

Abstract: The present invention provides an improved rotor for a centrifuge that operates by centrifugal elutriation. The rotor consists of a chamber assembly, a disk assembly, and a quick release mechanism. The chamber assembly is relatively light and it includes one or two separation chambers, tubing and a rotating seal. The disk assembly consists of the relatively heavy support structure. The two piece construction facilitates handling the parts of the rotor that generally need to be autoclaved. The chamber assembly has a novel structure that allows the rotor to easily be configured for operation with one or two chambers. The disk assembly has a unique strain relief that prevents structural cracking. The quick release mechanism is held in the latched position by centrifugal force during operation of the rotor.

Abstract: A composite material centrifuge rotor and process of construction of the rotor is disclosed. A rotor having high stiffness of fibers, preferably carbon, bound together with resin is disclosed. The rotor includes a top disk, a bottom disk and a spacer belt spacing the two disks apart to form a rotor assembly. The top and bottom disks are fabricated by overlying multiple layers of tape, the tape being made from longitudinally extending and parallel fibers held together with resin. Successive layers of tape are oriented so as to vary the longitudinal direction of the fiber with respect to a preselected radius vector from the spin axis of the rotor. When the tape is compiled in multiple layers to a thickness of the top and bottom disk, the tape is compressed between two metal plates and cured at a temperature well above the expected autoclave temperature of sterilization of the rotor. Thereafter, the entire assembly is wound by a peripheral belt with resin impregnated high stiffness fiber.

Abstract: A liquid boundary level detector employing an open-ended conduit which directs pressure waves toward a liquid boundary layer. The conduit is moved from a starting position toward the liquid boundary and, upon contact with the boundary, there is a change in acoustic impedance within the conduit. This change is monitored and a signal is generated indicative of such contact. Once the initial liquid boundary position is determined, that may become the reference position for subsequent liquid boundary measurements or motions.

Abstract: A springless floating coupling for a plunger type pump connecting the drive plunger to a driven piston.