Abstract: Electronic damping may be provided to an electrostatic positioner by developing a signal proportional to the velocity of the movable positioner plate and then changing the voltage applied to the positioner in proportion to this velocity signal to oppose the velocity of the movable plate. This velocity signal is obtained by subtracting from a first voltage proportional to the total current through the positioner a second voltage proportional to the current through the static capacitance of the positioner. The first voltage is obtained by a resistor in series with the positioner. The second voltage is not obtainable directly but is equal to a third voltage synthesized by a model impedance including a capacitor and a resistor in series having the same impedance and RC time constant as that of the positioner static capacitance and the resistor in series with the positioner where both resistor and capacitance are energized by the voltage driving the positioner.

Abstract: Electronic damping may be provided to an electrostatic positioner by developing a signal proportional to the velocity of the movable positioner plate and then changing the voltage applied to the positioner in proportion to this velocity signal to oppose the velocity of the movable plate. This velocity signal is obtained by subtracting from a first voltage proportional to the total current through the positioner a second voltage proportional to the current through the static capacitance of the positioner. The first voltage is obtained by a resistor in series with the positioner. The second voltage is not obtainable directly but is equal to a third voltage synthesized by a model impedance comprising a capacitor and a resistor in series having the same impedance and RC time constant as that of the positioner static capacitance and the resistor in series with the positioner where both resistor and capacitance are energized by the voltage driving the positioner.

Abstract: A particle counter volume sensor for sensing by the electrical resistance puplse method the volume of particles in a fluid suspension passing through an orifice assembly which includes an orifice member made of electrically insulating material and electrically resistive material disposed before, within, and after the orifice. The orifice is cylindrical with well rounded entry and exit corners. The resistive material has a conduit for the passage of particles through it generally centered with the orifice. The resistive material has an electrical resistivity matching that of the particle suspending fluid. Thus the electric field within the orifice is substantially the same with or without the resistive material. The conduit restricts particles to trajectories through the orifice where the maximum electric field intensity is substantially uniform thus accurately sizing the particles.

Abstract: Electronic damping may be provided to a piezoelectric positioner by developing a voltage signal proportional to the current through the dynamic impedance portion of the positioner impedance and then reducing the voltage applied to the positioner in proportion to this voltage signal. This dynamic impedance portion of the positioner impedance consists of an inductance, a resistance, and a capacitance in series. The inductance is the electrical equivalent of the positioner distributed mass and its load mass. The capacitor is the electrical equivalent of the compliance of the positioner and its support structure. The resistor is the electrical equivalent of the damping of the positioner and its load. The voltage signal proportional to the current through this dynamic impedance is obtained by subtracting from a first voltage proportional to the total current through the positioner a second voltage proportional to the current through the static capacitance portion of the positioner impedance.

Abstract: An ordinary vacuum blood collection tube assembly is rotated about its longitudinal axis to partition a blood sample into serum and formed elements by centrifugation. While still rotating a higher density, immiscible, inert liquid is pumped into the vacuum blood collection tube assembly thereby displacing the lower density serum towards the axis of rotation and thence out of the vacuum blood collection tube assembly to a serum receiver vessel. A contaminant detector located on the serum delivery conduit controls a 3 way valve to divert contaminants from the removed serum to a waste vessel so only clean serum is delivered to the serum receiver vessel. The serum delivery conduits, serum cannula, contaminant detector, and diverter valve are washed and dried between successive samples to limit sample carryover effects to acceptably low levels.

Abstract: An orifice arrangement for sensing by the electrical resistance pulse method the volume of particles in a fluid suspension passing through an orifice which comprises an orifice member made of electrically insulating material (1) and electrically resistive material (2) disposed before, within, and after the orifice. The orifice is cylindrical with well rounded entry and exit corners. The resistive material has an aperture for the passage of particles through it and the orifice generally centered with the orifice center. The resistive material has an electrical resistivity matching that of the particle suspending fluid. Thus the electric field within the orifice is substantially the same with or without the resistive material. The aperture restricts particles to trajectories through the orifice where the maximum electric field intensity is substantially uniform thus accurately sizing the particles.

Abstract: An ordinary vacuum blood collection tube assembly is rotated about its longitudinal axis to partition a blood sample into serum and formed elements by centrifugation. While still rotating a higher density, immiscible inert liquid is pumped into the vacuum blood collection tube assembly thereby displacing lower density serum towards the axis of rotation and thence out of the vacuum blood collection tube assembly to a serum receiver vessel. A contaminant detector located on the serum delivery conduit controls a 3 way valve to divert contaminants from the removed serum to a waste vessel so only clean serum is delivered to the serum receiver vessel. The serum delivery conduits, serum cannula, and contaminant detector are washed and dried between successive samples to limit sample carryover effects to acceptably low levels.

Abstract: An apparatus and method are disclosed to wash blood cells in a discrete manner that is compatible with automated sample preparation systems. The test tube containing the cells to be washed is mounted on a rotatable spindle. The spindle includes central passageways for the introduction of wash fluid and air into the test tube, and radial exit passageways at the bottom of the spindle. The test tube is first spun about its vertical axis to centrifuge cells against the inner wall of the test tube. A vacuum is then applied to the exit passageways so cell supernatant is aspirated out through the exit passageways. Wash fluid is then introduced into the test tube, and aspirated out through the exit passageways, thereby washing the cells. Rotational acceleration and deceleration of the test tube then resuspends the cells in wash fluid.

Abstract: A method for control of the drive means for a reciprocating piston pump delivering liquid to a spring loaded piston liquid accumulator providing high volume compliance whereby the accumulator liquid volume is controlled within narrow limits by continuous control of power to the pump drive motor. The accumulator achieves high volume compliance by arranging the kinematics of a main spring loading the accumulator piston to have a negative spring rate equal to the sum of all other positive spring rates produced by a second spring used to adjust the accumulator pressure, by the diaphragm (piston), and by a flexure support for a sensor lever. This sensor lever moves with the accumulator diaphragm to actuate an optical sensor producing an electric signal indicative of small changes in liquid volume in the accumulator.

Abstract: A method for control of the drive means for a reciprocating piston pump delivering liquid to a spring loaded piston liquid accumulator providing high volume compliance whereby the accumulator liquid volume is controlled within narrow limits by continuous control of power to the pump drive motor. The accumulator achieves high volume compliance by arranging the kinematics of a main spring loading the accumulator piston to have a negative spring rate equal to the sum of all other positive spring rates produced by a second spring used to adjust the accumulator pressure, by the diaphragm (piston), and by a flexure support for a sensor lever. This sensor lever moves with the accumulator diaphragm to actuate an optical sensor producing an electric signal indicative of small changes in liquid volume in the accumulator.

Abstract: A liquid supply system including a diaphragm pump, a novel liquid accumulator providing exceptionally high volume compliance, and a control of accumulator volume within narrow limits by continuous control of the pump motor. The accumulator achieves high volume compliance by arranging the kinematics of a main spring loading the accumulator to have a negative spring rate equal to the sum of all other positive spring rates produced by a second spring used to adjust the accumulator pressure, by the diaphragm, and by a pivot for a sensor lever. This lever moves with the diaphragm to actuate an optical sensor producing an signal indicative of small changes in liquid volume in the accumulator. This signal continuously modulates the power to the motor driving the pump so as to maintain the accumulator volume lose to a datum valve. This close control of liquid volume in a high compliance accumulator provides substantially pulse-free constant pressure liquid delivery from a pulsatile pump.

Abstract: A liquid supply system for flow cytometry apparatus including a diaphragm pump, a novel liquid accumulator providing exceptionally high volume compliance, and a control of accumulator volume within narrow limits by continuous control of power to the pump motor. The accumulator achieves high volume compliance by arranging the kinematics of a main spring loading the accumulator to have a negative spring rate equal to the sum of all other positive spring rates produces by a second spring used to adjust the accumulator pressure, by the diaphragm, and by a flexure pivot support for a sensor lever. This sensor lever moves with the accumulator diaphragm to actuate an optical sensor producing an electric signal indicative of small changes in liquid volume in the accumulator. This signal in turn continuously modulates the power to the motor driving the pump so as to maintain the accumulator liquid volume close to a datum value even during a portion of the pump delivery cycle.

Abstract: An apparatus and method are disclosed to wash blood cells in a discrete manner that is compatible with automated sample preparation systems. The test tube containing the cells to be washed is mounted on a rotatable spindle. The spindle includes central passageways for the introduction of wash fluid and air into the test tube, and radial exit passageways at the bottom of the spindle. The test tube is first spun about its vertical axis to centrifuge cells against the inner wall of the test tube. A vacuum is then applied to the exit passageways so cell supernatant is aspirated out through the exit passageways. Wash fluid is then introduced into the test tube, and aspirated out through the exit passageways, thereby washing the cells. Rotational acceleration and deceleration of the test tube then resuspends the cells in wash fluid.

Abstract: A flow apparatus for the analysis of particles passing substantially one at a time through an analysis region includes a flow rate control responsive to changes in the pressure used to drive the particles through the analysis region. The flow rate control automatically regulates the flow to a preset value throughout the analysis by adjusting the particle driving pressure to be uniform even though the sheathe liquid supply is depleted during the analysis. A method for controlling the flow of a supply of particles to be analyzed includes steps of sensing differential pressure and regulating the differential pressure to a preset reference.

Abstract: A sorter with a body member passageway has analysis, pre-analysis and post analysis portions for particles. An elongate catcher tube carried on the body member, and mounted with its axis to be selectively aligned with the analysis portion for intermittently receiving analyzed particles. An operator receives a signal from the analysis portion relative to one or more particle characteristics and selectively aligns the catcher tube in fluid communication with the analysis portion. The signal is an electrical pulse of strength and timing sufficient to cause a driver mounted to the body member and associated with the catcher tube to align the catcher for sorting particles. A resilient support attaches the catcher tube to the body member and provides a pivot for the catcher tube. A method for sorting includes generating a signal representative of one or more characteristics of the particles and applying the signal to a driver to change the position of the catcher tube.

Abstract: A flow cytometry apparatus for determining one or more characteristics of particles or the like flowing in a liquid stream includes a nozzle for generating a liquid flow stream for moving particles therethrough substantially one at a time. A light source provides a beam of focused light to illuminate the particles moving in the stream. A beam steering member is positioned to adjust the focal point of the light beam on the particles by refracting the light beam to cause a displacement of the focal point. At least one detector is provided for detecting light and for associating that light with one or more characteristics of each particle.

Abstract: A housing for a particle flow-through apparatus comprises a body member having a passageway therethrough including a region through which substantially one particle at a time may pass in a normal direction of flow. An operative plunger is positioned in the passageway so that the plunger is depressible into the passageway. Depression of the plunger creates increased pressure in the passageway for dislodging clogged particles or debris from the region in a direction reverse to the normal direction of particle flow.

Abstract: A door assembly for a sterilizer includes a rectangular door on which is a vertical rail assembly movable horizontally toward and away from the door on threaded posts. Nuts carried by the rail assembly are rotated on the posts by sprockets entraining a motor driven chain. The rail assembly carries spring mounted axially retractable horizontal pairs of locking bars. The bars are inserted into and removed from sockets in a doorway frame by turning angularly as the rail assembly moves horizontally. A pressure responsive locking mechanism engages the sprockets to prevent their turning when the sterilizer is above a predetermined pressure. Cables carried by the locking bars actuate a switch in an alarm circuit for indicating that any one or more bars is not engaged properly in its respective socket. Limit switches stop operation of the motor when the rail assembly reaches extremes of inward and outward movement.

Abstract: An improved multi-purpose blood diluent is provided which is isotonic, with a neutral pH for avoiding cell volume change. The diluent of the invention provides balance between the effects on cell volume of a preservative for the solution, and the effects of a surfactant. The diluent of the invention is particularly useful as a carrier for blood samples in instruments which automatically provide medical diagnostic determinations of blood samples. The diluent herein includes conventional sodium and potassium chlorides as electrolytes, pH buffers, such as monobasic and dibasic phosphate, and ethylene diamine tetraacetic acid to control and chelate the divalent cations. The balanced preservative-surfactant combination may include, for example, 2-phenoxyethanol with certain ethylene oxide-polypropylene glycol condensation products.

Abstract: A manometer is provided for metering samples of fluid flowing in devices wherein particle concentration in the fluid is being counted or measured. Such devices include particle counters for determining blood cell concentration in body fluid. The device includes low permeable stretchable diaphragms in the device connections for containing the mercury therein, and a slide valve in the vent connection to restrict the movement of the mercury during storage or shipment. The arrangement herein includes, also, a one-way valve downstream of the "stop" point to stop flow substantially immediately upon the cessation of the measurement interval to reduce unwanted airflow to the counting aperture. A start and stop arrangement in the mercury flow path for causing the leading edge of the mercury meniscus at the axis thereof to engage the electrode contacts includes simple wire tips extending into the mercury flow path to the axis thereof for engaging the axis of the mercury meniscus.