| Ficoll-Hypaque technique | A density-gradient centrifugation technique for separating lymphocytes from other formed elements in the blood; the sample is layered onto a Ficoll-sodium metrizoate gradient of specific density; following centrifugation, lymphocytes are collected from the plasma-Ficoll interface. (05 Mar 2000) |
|---|---|
| flicker fusion frequency technique | A technique of perimetry using the criterion of critical fusion frequency. Synonym: flicker fusion frequency technique. (05 Mar 2000) |
| fluorescent antibody technique | Test for tissue antigen using either a direct method, by conjugation of antibody with fluorescent dye (fluorescent antibody technique, direct) or an indirect method, by formation of antigen-antibody complex which is then labelled with fluorescein-conjugated anti-immunoglobulin antibody (fluorescent antibody technique, indirect). The tissue is then examined by fluorescence microscopy. (12 Dec 1998) |
| fluorescent antibody technique, direct | A form of fluorescent antibody technique utilizing a fluorochrome conjugated to an antibody, which is added directly to a tissue or cell suspension for the detection of a specific antigen. (12 Dec 1998) |
| fluorescent antibody technique, indirect | A form of fluorescent antibody technique commonly used to detect serum antibodies and immune complexes in tissues and microorganisms in specimens from patients with infectious diseases. The technique involves formation of an antigen-antibody complex which is labelled with fluorescein-conjugated anti-immunoglobulin antibody. (12 Dec 1998) |
| flush technique | <procedure> A technique for determining the systolic blood pressure in infants; the elevated limb is milked of blood from the hand or foot proximally; the blood pressure cuff is then inflated above the likely systolic pressure and the limb lowered; the cuff pressure is then gradually released until the blanched limb flushes. (05 Mar 2000) |
| long cone technique | The use of a cone distance of 14 inches or more in making oral roentgenographs. (05 Mar 2000) |
| alternating light test | Test to detect a relative afferent defect in one eye by watching pupillary movements. With the patient fixing in the distance, the light is held on each eye for about a second, and quickly moved to the other eye. Assuming no defect of the innervation to the iris sphincter in one eye (which would produce an anisocoria in light), the eye with the weaker light response has a relative afferent pupillary defect. This asymmetry of pupillomotor input can be estimated by holding neutral density filters in front of the better eye until the pupillary responses of the two eyes are balanced. Synonym: swinging light test. (05 Mar 2000) |
| gene rearrangement, b-lymphocyte, light chain | Ordered rearrangement of b-lymphocyte variable gene regions coding for the kappa or lambda light chains, thereby contributing to antibody diversity. It occurs during the second stage of differentiation of the immature b-lymphocyte. (12 Dec 1998) |
| ray, light | <microscopy> The term applied to the lines perpendicular to the wavefronts of waves of light to indicate their direction of travel in an isotropic medium. Note the wave normal and the ray do not coincide in isotropic media. (05 Aug 1998) |
| reflected light | Light directed backward from a mirror. (05 Mar 2000) |
| refracted light | Bent rays of light changed in passage from one transparent medium to another of unequal density. See: refraction. (05 Mar 2000) |
| visible light | <physics> Electromagnetic radiation with wavelengths between 400 nanometres and 750 nanometres. Electromagnetic radiation within this range can be detected by the human eye. Colours depend on the wavelength lengths, a short wavelength (the 400 nm side) looks blue and a long wavelength (the 750 nm side) looks red. (09 Oct 1997) |
| metals, light | Metals with low specific gravity, typically smaller than 5, characterised by a single valence (1, 2, or 3), a simple spectrum, strong electromotive force (positive), and colourless compounds. (12 Dec 1998) |
| minimum light | Threshold of visual sensation, the minimal light intensity evoking a visual sensation. Synonym: achromatic threshold, minimum light threshold. (05 Mar 2000) |