Abstract: In a valve assembly exhibiting zero dead volume the port head is mounted on a solenoid and defines an inlet port on one side of the valve seat, and two outlet ports on the opposite side of the valve seat. A flexible diaphragm is seated across the valve seat between the port head and the solenoid, and is sealed along its peripheral edge. A spring-biased valve rod is coupled to the opposite side of the diaphragm relative to the valve seat, and the solenoid is actuated to move the valve rod and diaphragm between open and closed positions. The valve assembly is opened by actuating the solenoid to drive the valve rod and diaphragm away from the valve seat and permit the passage of fluid across the valve seat between the inlet and outlet ports.

Abstract: The present invention provides a novel lytic reagent composition highly selective in its interactions with the cell membranes of blood cells and also provides a method of using the reagent composition in a semi-automated or an automated system to effect a significantly improved white blood cell differential determination. The lytic reagent composition is characterized by an ability to selectively shrink the white blood cells into the increasing size order of lymphocytes, a midregion consisting mainly of monocytes, other mononuclear cells, some basophils and eosinophils, and neutrophils and can readily be optimized to effect a significantly improved three component separation on the histogram of commercially available semi-automated and automated blood analyzers when compared to the reagents conventionally employed on such instruments.

Abstract: An apparatus for hematology testing, which has a sensing unit defining a counting orifice for the flow of a blood sample through the counting orifice to analyze the blood sample, and a pump unit having three syringes. A first syringe is coupled in fluid communication with the sensing unit on the inlet side of the counting orifice for injecting a stream of blood sample through the counting orifice. A second syringe is coupled in fluid communication with the sensing chamber on the inlet side of the counting orifice for simultaneously injecting a sheath of fluid surrounding the sample stream on the inlet side of the counting orifice. And a third syringe is coupled to the sensing chamber on the outlet side of the counting orifice for aspirating a sheath of fluid from the sensing chamber surrounding the sample stream on the outlet side of the counting orifice.

Abstract: A method and apparatus for determining the parameters (i.e., proportion, mean, and standard deviation) of constituent subpopulations within a sample population of particles which contains overlapping populations. The invention includes the use of the EM algorithm, an iterative process which estimates the probability that a particle belongs to any given overlapping subpopulation.

Abstract: A lytic reagent composition highly selective in its interactions with the cell membranes of white blood cells and also provides a method of using the reagent composition in a particle analyzing system to effect a significantly improved white blood cell differential determination. The lytic reagent composition is characterized by an ability to selectively shrink the white blood cells into the increasing size order of lymphocytes, basophils, monocutes, eosinophils and neutrophils, and effect a five component separation of these major subpopulations of white blood cells on the histogram of an automated blood analyzer when used in conjunction with a suitable blood diluent.

Abstract: A lytic reagent composition highly selective in its interactions with the cell membranes of white blood cells and also provides a method of using the reagent composition in a particle analyzing system to effect a significantly improved white blood cell differential determination. The lytic reagent composition is characterized by an ability to selectively shrink the white blood cells into the increasing size order of lymphocytes, basophils, monocytes, eosinophils and neutrophils, and effect a five component separation of these major subpopulations of white blood cells on the histogram of an automated blood analyzer when used in conjunction with a suitable blood diluent.

Abstract: A lytic reagent composition highly selective in its interactions with the cell membranes of blood cells and also provides a method of using the reagent composition in a semi-automated or an automated system to effect a significantly improved white blood cell differential determination. The lytic reagent composition is characterized by an ability to selectively shrink the white blood cells into the increasing size order of lymphocytes, a midregion consisting mainly of monocytes, other mononuclear cells, some basophils and eosinophils, and neutrophils and can readily be optimized to effect a significantly improved three component separation on the histogram of commercially available semi-automated and automated blood analyzers when compared to the reagents conventionally employed on such instruments.

Abstract: A method and appartatus for determining the parameters (i.e., proportion, mean, and standard deviation) of constituent subpopulations within a sample population of particles which contains overlapping populations. The invention includes the use of the EM algorithm, an iterative process which estimates the probability that a particle belongs to any given overlapping subpopulation.

Abstract: A lysing reagent is employed for stromatolysing the red cells in a blood sample and differentiating the leukocytes into subpopulations. The lysing reagent contains a dodecyltrimethylammonium halide and an aromatic second cationic agent which is either a benzyltrialkylammonium halide or an alkylpyridinium halide. In some methods, the lysing reagent is mixed in the reaction chamber with a major proportion of the diluent, and the blood sample with a minor proportion of the diluent is added to the reaction chamber.

Abstract: A system that is particularly useful in biological fluid analysis includes a face plate member and a mating flexible member, one of which has a plurality of passages. Selected motion of the flexible member provides a valving action to control fluid flow into, through, and out of the passages. An analysis chamber in a surface of the face plate member is in fluid communication with a passage and has an analyzer which, for a hematology analyzer, is preferably an impedance-type particle counter.