Abstract: A rotary fluid-displacement assembly having a housing and a rotor positioned within an internal cavity of the housing. The rotor being configured to rotate about a rotor axis of rotation eccentric to a housing longitudinal axis. A gate is also provided that is slidably mounted therewith the rotor and movable axially about and between a first position, in which a distal end of the gate is positioned at a first distance from the peripheral surface of the rotor, and a second position, in which the distal end of the gate is positioned at a second distance from the peripheral surface of the rotor. The distal end of the gate being constrained to be spaced proximate from the inner wall surface of the housing as the rotor rotates about the rotor axis of rotation.

Abstract: The present invention provides a method for measuring a blood analyte concentration of a body part comprising removing a portion or all of the blood from the body part to produce a modified body part, and recording a first absorbance value of the modified body part. This is followed by filling the body part with blood to produce a filled body part, and recording a second absorbance value of the filled body part. A difference spectrum is obtained by subtracting the first absorbance values from the second absorbance values, and a calibration algorithm for the blood analyte is applied to the difference spectrum, thereby measuring the concentration of the blood analyte. Also provided is an apparatus for determining the concentration of a blood analyte of a body part. The apparatus comprising a chamber of a size and shape to receive the body part, where the chamber comprises an element for withdrawing and reintroducing blood from the body part, when the body part is inserted within the chamber.