Abstract: A method and apparatus for aspirating a liquid (e.g., blood) from a container uses an electrically biased thermistor element, mounted proximate the tip of a liquid-aspirating probe, to determine that the probe is safely submerged within a body of liquid to be aspirated at all times during the aspiration process. Also disclosed are different aspiration probe assemblies that are useful in the method and apparatus of the invention.

Abstract: A back-scatter detector for detecting light scattered backwardly (i.e., reflected) by an irradiated particle such as a blood cell comprises a plurality of optical fibers. A fiber optic holder having a centrally located opening for passing a light beam used to irradiate particles at a particle-interrogation zone serves to position the light-collecting ends at a desired position to collect back-scattered light. Preferably, the light-collecting ends of the optical fibers are positioned in a circular pattern centered about the irradiating light beam, and the respective axes of the supported portions of the optical fibers extend either parallel to the beam axis, or, more preferably, so that they converge at or near the location of the scattering source, i.e., the irradiated particle or cell. The latter configuration assures that the back-scatter light enters the fiber end substantially parallel to the fiber axis, thereby reducing optical transmission loses in the fiber.

Abstract: A shear valve assembly comprises a pair of valve pads having opposing planar surfaces supported for relative sliding engagement. Each valve pad defines a plurality of liquid pathways by which a liquid can be passed from one pad to the other. The planar surface of one of the valve pads has an open channel formed therein, such channel having dimensions to accommodate a prescribed volume of liquid. Liquid is introduced into such channel via a first pair of pathways formed in the other valve pad, and liquid is dispensed from the open channel by a second pair of pathways that are brought into alignment with the channel during sliding movement between the valve pads. The valve assembly is particularly useful in blood-analyzing instruments for isolating and dispensing relatively minute volumes (of the order of microliters) of whole blood for analysis.

Abstract: Blood cells of interest are readily distinguishable from other blood cells and look-a-like particles found in a blood sample by their back-scatter signature. A preferred method for differentiating platelets in a blood sample is to irradiate the cells and particles, one at a time, with a beam of radiation, and to detect back-scattered (reflected) radiation using a plurality of optical fibers to transmit the back-scattered radiation to a high-gain photodetector, e.g. a photomultiplier tube. Preferably, the back-scatter signal so obtained is combined with a second signal representing, for example, either the level of forward-scatter within a prescribed, relatively narrow angular range, or the level of side-scattered radiation, or the level of attenuation of the cell-irradiating beam caused by the presence of the irradiated cell or particle in the beam, or the electrical impedance of the irradiated cell or particle, to differentiate the cells of interest.

Abstract: A particle sizing method and apparatus of the PIDS type uses randomly polarized radiation to irradiate a particle sample. Portions of the resulting side scattering pattern are decomposed to simultaneously produce, for each decomposed portion, first and second linearly polarized beams of radiation in which the respective planes of polarization of the two beams are mutually perpendicular. Each of the polarized beams is focused onto a photodetector, and the respective photodetector outputs are differentiated to provide PIDS signals that are useful in calculating a particle size distribution for the sample.

Abstract: Apparatus for detecting light scattered by a small particle (e.g., a blood cell) irradiated by a light beam comprises one or more photodetectors and a plurality of optical fibers that serve to optically couple the scattered light and the photodetector(s). To enhance the efficiency of such optical coupling, a portion of each of the optical fibers in the vicinity of its light-collecting end is supported so that its optical axis extends towards the light-scattering source. By this arrangement, scattered light enters each fiber from a direction substantially parallel to the fiber axis. Preferably, the light-collecting ends of the optical fibers are supported on a concave surface and so that the respective optical axes of the fibers converge at a point representing the apparent position of the light-scattering source, taking into account the refractive effects of an optical flow cell through which scattering is detected.

Abstract: A method and apparatus for producing man-made snow without using either compressed air or high-speed fans. The method makes use of a special water nozzle that is designed to provide a high volume spray of water particles that, owing to their size distribution (having a median size of between about 100 and 200 microns) in the spray, are readily susceptible to conversion to ice crystals as they settle to earth under favorable ambient conditions. Preferably, water applied to the nozzle is seeded with artificial nucleation sites so that water particles in a spray containing such sites are more susceptible to conversion to ice crystals as the particles settle to earth.

Abstract: Blood cells of interest are readily distinguishable from other blood cells and look-a-like particles found in a blood sample by their back-scatter signature. A preferred method for differentiating platelets in a blood sample is to irradiate the cells and particles, one at a time, with a beam of radiation, and to detect back-scattered (reflected) radiation using a plurality of optical fibers to transmit the back-scattered radiation to a high-gain photodetector, e.g. a photomultiplier tube. Preferably, the back-scatter signal so obtained is combined with a second signal representing, for example, either the level of forward-scatter within a prescribed, relatively narrow angular range, or the level of side-scattered radiation, or the level of attenuation of the cell-irradiating beam caused by the presence of the irradiated cell or particle in the beam, or the electrical impedance of the irradiated cell or particle, to differentiate the cells of interest.

Abstract: A method for performing screening of one or more cell groups of interest obscured by a cell population such as one or more subsets of interest of a WBC population utilizing at least one light sensing parameter. The cell group of interest is enumerated by utilizing microspheres having monoclonal antibodies bound thereto to modify the sensed characteristics of specified cells to differentiate the cell group of interest from the obscuring cell population.

Abstract: Apparatus for precisely aspirating small volumes of liquid, e.g., a blood sample, contained in a vessel, e.g., a test tube or vial, includes a mechanism for sensing that the tip of an aspirating probe is contacting the bottom of the vessel during the aspiration process. Such a bottom-sensing mechanism is adapted to sense a predetermined forcible interaction between the probe tip and the vessel bottom. In a preferred embodiment, such forcible interaction is sensed by detecting movement of a movably mounted platform that supports the vessel during aspiration. In a second embodiment, the forcible interaction is sensed by detecting the back-emf in a motor winding used to advance the aspiration probe.

Abstract: A specimen carrier comprises a unitary structure for receiving and retaining a specimen container in an upright orientation. Such unitary structure is defined by a pedestal having upper and lower platforms connected by a stem. Extending upwardly from the upper platform is a plurality of rigid members which support a plurality of opposing flexible fingers adapted to engage and press upon the side wall of a specimen container received by the carrier. Preferably, the specimen carrier of the invention has a chamber formed therein for housing a pre-programmed, programmable or otherwise radio-frequency (RF) identification tag in the form of an RF transponder. Upon being energized by a suitable RF field provided by an RF reader antenna or sensor positioned adjacent the carrier's intended path of movement, the tag transmits a unique identification code, such code being received by the antenna or sensor and decoded by the reader.

Abstract: A method and apparatus for aspirating and dispensing precise volumes of liquid, e.g. whole blood, comprises an aspiration probe or needle having an internal volume precisely equal to a desired volume to be dispensed, and a computer-controlled shear valve for trapping aspirated liquid inside the probe for subsequent dispensing. A liquid sensor positioned downstream of the shear valve cooperates with a liquid level sensor on the probe tip to assure that the probe lumen is filled with the aspirated liquid.

Abstract: Apparatus for sensing and characterizing particles suspended in a liquid medium includes a particle-sensing structure having a continuous wall defining a hydrodynamically smooth conduit through which the liquid suspension of particles is caused to pass simultaneously with an electrical current. Particles passing through the conduit are sensed and characterized by monitoring changes in the electrical current through the conduit. According to the invention, the continuous, conduit-defining wall is made entirely of a material having an electrical resistivity less than or equal to that of the liquid medium. Thus, the apparatus of the invention is similar to the conventional Coulter aperture (conduit) except that the aperture is formed from an electrically conductive material instead of a dielectric material.

Abstract: A method and apparatus for differentiating and enumerating the five major sub-populations of leukocytes in a blood sample (i.e., lymphocytes, monocytes, eosinophils, neutrophils and basophils) uses multiangle light scatter and DC (Coulter) volume measurements. Light scattering characteristics of the leukocytes are determined within five different angular ranges, all being lower than 40 degrees. The invention is particularly useful in differentiating and enumerating the basophil sub-population which has heretofore required more complex apparatus and/or chemical processing.

Abstract: A blood analyzing instrument includes a single transducer for simultaneously measuring the DC volume, RF conductivity, light scattering and fluorescence characteristics of blood cells passing through a cell-interrogation zone. Preferably, the transducer includes an electro-optical flow cell which defines a cell-interrogation zone having a square transverse cross-section measuring approximately 50×50 microns, and having a length, measured in the direction of cell flow, of approximately 65 microns.

Abstract: A Coulter apparatus comprises a volumeter assembly containing a conduit through which a particle suspension is caused to pass simultaneously with an electrical current. In preferred embodiments the volumeter assembly comprises at least one traditional Coulter conduit wafer, i.e., a dielectric wafer containing a central circular conduit, and at least two electrically conductive collars. The conductive collars approximate the conduit diameter in thickness, are uninsulated, and are attached to opposite sides of the conduit wafer, the openings being congruent with the Coulter conduit. The Coulter conduit in the dielectric wafer and the openings in the conductive collars collectively form a hydrodynamically smooth conduit, in which the electric and hydrodynamic fields of the Coulter conduit are amended. The electric field is shaped to confine the particle-sensitive zone of the novel volumeter conduit within the conduit's physical boundaries, thereby decreasing the zone's coincidence volume.

Abstract: Apparatus for sensing and characterizing particles (e.g., blood cells or ceramic powders) suspended in a liquid medium comprises a conduit through which the particle suspension is caused to pass simultaneously with an electrical current. According to the invention, the interior wall of the conduit effectively varies in resistivity along the length of the conduit to define a delimited central region of high electrical resistivity which is smoothly contiguous on its opposing boundaries to uninsulated distal elements of lesser electrical resistivity. The delimited central region of the conduit functions as a Coulter volumeter conduit. The uninsulated distal elements of the conduit are made to have a dimension along the conduit wall which is at least equal to the axial extent of the effective ambit electric fields of a traditional Coulter volumeter conduit having a cross-sectional geometry identical to that of the delimited central region of high resistivity in the improved volumeter conduit.

Abstract: A device adapted for use with a conventional oral or nasopharyngeal airway for delivering an inhalant gas to a proximal end of said airway, and for sampling exhalant gas at a distal end of said airway, comprises a pair of conduits which are adapted to slide into an internal passage of the airway to provide an inhalant gas at the proximal end therof and/or to sample expired gas at the distal end thereof when the airway is being used.

Abstract: An open/close valve construction for use in solid-state fluid transport circuits having discrete fluid passageways formed in rigid substrates with a substrate land between port regions of the fluid passageways. The valve construction comprises a diaphragm disk having a dome portion overlying the substrate land and port regions and having a self-restoring resilience sufficient to maintain its dome configuration against substantial line vacuum. A valve actuator is located above the dome portion and spring biased to compress the dome into a flat configuration closing the port regions. Means for negating the spring force are provided to allow the dome portion to restore its configuration and open the valve.

Abstract: A method for a single-measurement quantification of multiple populations of white blood cells (WBC) is based upon the labeling of different pairs of cell populations, each pair containing mutually exclusive cell receptors which are expressed at substantially similar receptor densities with labeled ligands for each receptor. One cell population is labeled with a ligand capable of binding to a first cell surface receptor which ligand is directly conjugated to a fluorescent phycobiliprotein or tandem dye; and a second cell population is labeled with a ligand capable of binding to a second cell surface receptor, which ligand is cross-linked by an aminodextran to a fluorescent phycobiliprotein or tandem dye. The phycobiliproteins upon laser excitation produce a different detectable fluorescence intensity for each cell population. Use of such pairs of conjugates enable two populations of cells with similar receptor densities to be distinguished with the use of a single color marker.