Abstract: A diluted whole blood sample is hydrodynamically focused to a given point. A light beam is transversely focused on the same point and the principles of dark field microscopy are utilized, detecting scattered light and thereby discriminating platelets from red blood cells based on cell volume and refractivity.

Abstract: Latex material disposed in a solvent is injected into a sheath fluid into which the solvent is soluble, but the latex is not. The solvent being jetted from a vibrating nozzle forms droplets within the flowing sheath, which is then delivered onto an inclined hydrophobic surface reposing at a low angle to the jet. As the droplet containing stream strikes and flows down the surface, its velocity is taken up as the phase separation process for forming microparticles begins.

Abstract: A core/sheath vibrating system is utilized to produce core droplets within the sheath, which in turn form into microparticles through phase separation. The flow momentum is first arrested by means of an inclined surface, and the combination is thence deposited, in a continuous, helical channel extending from one end to the other of the inside of a hollow, rotating drum. Rotation of the drum moves the forming microspheres through the channel. At the exit end of the drum, the sheath fluid which carries suspended microspheres, may be filtered, and the microspheres collected and utilized.

Abstract: Latex material disposed in a solvent is injected into a sheath fluid into which the solvent is soluble, but the latex is not. The solvent being jetted from a vibrating nozzle forms droplets within the flowing sheath, which is then delivered onto an inclined hydrophobic surface reposing at a low angle to the jet. As the droplet containing stream strikes and flows down the surface, its velocity is taken up as the phase separation process for forming microparticles begins.

Abstract: Methods and reagents for determination of Rh.sub.o (D), C, c, E, e, and K antigens in human blood. The reagents are low-protein compositions containing reduced and S-alkylated IgG antibody to the selected antigen maintained at a pH of between about 7.5 and 8.3. These reagents meet or exceed FDA standards for potency and specificity of the respective antisera.

Abstract: A novel method is disclosed for detecting and controlling the flow rate of a perturbed, droplet-forming stream in an electrostatic particle sorting apparatus. Detection apparatus is located at two points along the stream, at a first particle sensing point for sensing the presence of particles within a core portion of the stream, and at a second downstream point, preferably the stream breakpoint, for sensing light scatter and extinction characteristics which are proportional to the surface characteristics of the sheath portion of the stream. Changes in phase shift, pulse width, duty cycle, pulse area, or breakpoint location are detected by analyzing these sheath surface-related characteristics. An error signal is produced in response to such changes which drives an electromechanical fluid flow regulator to increase or decrease the fluid flow rate in a direction which tends to minimize the error signal. The flow rate is thus maintained at a reference flow rate setting.

Abstract: A novel method for positioning the point of droplet formation in the jetting fluid of an electrostatic sorting device is disclosed. The formation of the uniform droplets is carried out via the application of vibrational energy inparted by a transducer to a jetting laminar flow stream. Previously sensed particles contained within the core portion of the laminar stream are subsequently sorted from the stream as part of a subsequently formed droplet. The disclosed method uses the dependency of the droplet formation point on the amplitude of the wave form applied to the transducer and the modulation of this amplitude to control the droplet formation point distance. The position of the droplet formation point is detected via the use of a light source and photodetector focused on the jetting stream at the position at which the droplet formation point is to be located, and a method for automatically maintaining the breakpoint at that position is described.

Abstract: In order to initiate the charging of droplets at a specific point in time with respect to the formation of those droplets in an electrostatic flow sorting system, the charge phase of the system of the present invention is continuously and automatically adjusted by droplet break point monitoring. The charge phase is therefore flow rate and fluid velocity independent. The break point is monitored by a light source which is focused onto the jet stream at the droplet formation break point, or close to it, and the modulation of light caused by the scatter induced by the sheath stream portion as it passes the focused beam of light is detected via the use of a suitable electro-optical detector. From the output of the electro-optical detector, after appropriate signal conditioning, an electrical wave form is obtained which shape depends upon the shape of the fluid column passing the focus beam.

Abstract: A method for the measurement of fluid velocity and fluid flow rate is described which may be applied to a system in which fluid is caused to exit through an orifice to form a free jet. Optical as well as fluidic properties of the jetting fluids are used to determine the mean velocity of the jet between its point of exit from the orifice and at least a preselected detection point. From the mean velocity determination, the fluid flow rate may also be determined. A marker signal perturbation is applied to the jetting fluid at the orifice, and is detected downstream at a stream sensing point which is located a preselected distance from that orifice.

Abstract: A novel method and apparatus for automatically setting the time delay for relatively charging droplets in an electrostatic particle sorting system is disclosed. By utilizing a movable sheath sensing means for sensing the light scatter and extinction of this stream, the flow rate and distance to breakpoint are automatically measured and used to calculate and set the timing delay circuitry. This insures that droplet charging at the breakpoint will occur synchronously to produce selective relative charging of those droplets containing particles to be sorted.

Abstract: A novel method and system are disclosed for detecting the breakpoint of a perturbed flow stream. The scattering and extinction of light caused by a perturbed stream at a preselected flow stream sensing point therealong is measured to produce a real time waveform proportional thereto. The real time waveform is differentiated to produce a differentiated waveform, which is then selectively monitored to distinguish a waveform exhibiting substantially three (positive and negative) peaks per cycle, whereby such detection indicates that at least a portion of the breakpoint region of said flow stream corresponds with said flow stream sensing point. In order to align the stream sensing point with respect to a preselected point within the breakpoint region of the flow stream, the breakpoint region of the stream is caused to move with respect to the stream sensing point until the breakpoint pulse width of one of the peaks corresponds with a preselected pulse width reference.

Abstract: Disclosed is a procedure for conducting anti-thrombin III assays in which the conventional thrombin-anti-thrombin III treatment step is conducted at a pH of 7.9 to 8.5 maintained at the level by a buffer system comprising a buffering amount of N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid, N-2-hydroxyethylpiperazine-N'-3-propanesulfonic acid, N-tris-(hydroxymethyl)-methyl-2-amino-ethanesulfonic acid, N-tris-(hydroxymethyl)-methylglycine, or N,N-bis (2-hydroxymethyl)-glycine or a salt thereof. The compositions may also contain bacteriostatic agents.

Abstract: Methods and reagents for determination of Rh (D) antigen in human blood. The reagent is a low-protein composition containing reduced and S-alkylated anti-D IgG maintained at pH of between about 7.5 and 8.3. This reagent meets or exceeds FDA standards for potency of anti-D for the slide test of rapid tube test.

Abstract: A hermetically sealed ampoule containing blood gas control fluid is provided wherein the fluid occupies the entire ampoule with no appreciable head space. The ampoule is provided with a plunger-like seal adapted to be directed against the contents of the ampoule and a pierceable seal through which may extend a hollow needle to act as a conduit for the contents upon expulsion from the ampoule. A syringe is also provided for expelling the contents from the ampoule.

Abstract: A one-stage prothrombin assay which measures the exponential rate of thrombin production in thromboplastin-treated, recalcified plasma. A serum reagent reduces the lag time before thrombin production substantially to zero for both normal and abnormal plasma, thus allowing measurements to be made in just a few minutes.

Abstract: Fluorescence volume exclusion signals are utilized to evaluate cell volume. Cells are suspended in a medium which is furnished with a fluorescent dye which neither penetrates nor adheres to the cells. Cells are analyzed by an optical flow cytometer, with illumination which causes the dye medium to fluoresce. Passage of a cell through the sensing zone therefore reduces the amount of fluorescent medium being illuminated, and proportionally reduces the fluorescence output signal. Fluorescence volume exclusion pulse height and area are related to cell volume.

Abstract: Specified subclasses of blood cells, such as of lymphocytes, are automatically identified based on utilization of antigenic determinants on the cell surface, their reactivity with antibodies which fluoresce under known circumstances, and utilization of principles of flow cytometry. A blood sample is first incubated with a reagent including antibodies to the lymphocyte subclass to be identified, the antibodies being directly or indirectly made fluorescently responsive to particular light (e. g. argon ion laser). The sample is illuminated, a cell at a time, by such focused coherent light, and forward light scatter, right angle light scatter, and fluorescence are detected and used to identify and enumerate cells of the specified subclass.

Abstract: Input pulses are coupled through a delay network to a pulse amplifier. The amplifier includes feedback circuitry for correcting its output to a particular baseline level, generally zero volts. Within the amplifier feedback path is a gate, which is normally closed. Input pulses are also coupled to a pulse detector; whenever an input pulse is detected, the baseline gate in the amplifier feedback path is open, and the dynamic feedback operation is temporarily inhibited. During this time, the most recent previous level of baseline correction is retained.

Abstract: A fluid sampling nozzle is spatially fixed, and adapted to be supplied by fluid to be sampled. A nearby actuating switch, manipulated by the operator, energizes a sequence of sampling, cleaning, and drying steps. In particular, once fluid is withdrawn, the sample is removed. A waste removal sink pivots to a point beneath the nozzle, and in a series of motions by a probe washer assembly, the nozzle is successively washed, inside and out. The apparatus is then returned to its initial position, ready for successive sampling operations.