| point-spread function | <microscopy> The mathematical representation of the image of a point source. For a diffraction-limited optical system operating in the absence of aberrations, the point-spread function is the Airy disk. See: three-dimensional diffraction pattern. (05 Aug 1998) |
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| state function | <chemistry> A property that is independent of the pathway, this function can be used to define or specify the state of the system. (09 Jan 1998) |
| discriminant function | A particular combination of continuous variable test results designed to achieve separation of groups; e.g., a single number representing a combination of weighted laboratory test results designed to discriminate between clinical classes. (05 Mar 2000) |
| distribution function | <radiobiology> Function characterising the density of particles located at a given point in phase space (a combination of velocity and/or position coordinates) at a given time. The velocity-space distribution function gives the number of particles with a particular velocity, the position-space distribution function is synonymous with the particle density in position-space. Different combinations of position and spatial coordinates are useful in different problems. (09 Oct 1997) |
| isomeric function | The individual function of an isolated segment of the spinal cord. (05 Mar 2000) |
| optical transfer function | <microscopy> The relationship between the image produced by an optical instrument and the amplitude and phase of a periodic specimen, measured at various spatial frequencies. The optical transfer function curve, which shows how well contrast is maintained for finer specimen details, is a complex function, of which the real term gives the ratio of amplitudes, and the imaginary term the phase relationships. When the brightness of the periodic specimen varies as a sine wave, the modulus or absolute value of the optical transfer function becomes the modulation transfer function, when the brightness varies as a square wave, the modulation transfer function is known as a contrast transfer function. Acronym: OTF (26 Mar 1998) |
| ovarian function tests | Methods used for assessment of ovarian function. (12 Dec 1998) |
| ecosystem function | The collective intraspecific and interspecific interactions of the biota, such as primary and secondary production and mutualistic relationships. The interactions between organisms and the physical environment, such as nutrient cycling, soil development, water budgeting, and flammability. (09 Oct 1997) |
| function | The special, normal or proper physiologic activity of an organ or part. Origin: L. Functio, from fungi = to do (18 Nov 1997) |
| function corrector | A removable orthodontic appliance utilizing oral and facial muscle forces to move teeth and possibly change the relationship of the dental arches. (05 Mar 2000) |
| line spread function | A measure of the ability of a system to form sharp images; in radiology, determined by measuring the spatial density distribution on film of the X-ray image of a narrow slit in a dense metal, such as uranium; from this can be calculated the modulation transfer function. (05 Mar 2000) |
| liver function test | <investigation> A test that measures the blood serum level of several enzymes produced by the liver. An elevated liver function test is a sign of possible liver damage. Examples include: prothrombin time, PTT, serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, gamma glutamyl transpeptidase, alkaline phosphatase and serum albumin. (14 Oct 1997) |
| lymphocyte function associated antigen | A member of the integrin family that is expressed on all leukocytes and binds to ICAM-1 and ICAM-2 on a variety of cells. (05 Mar 2000) |
| lymphocyte function-associated antigen-1 | A heterodimer molecule widely expressed on cells of haematopoietic origin. Cd11a antigen comprises the alpha chain and the CD18 antigen (antigens, CD18) the beta chain. Lfa-1 is a major receptor of T-cells, B-cells, and granulocytes. It mediates the leukocyte adhesion reactions underlying cytolytic conjugate formation, helper T-cell interactions, and antibody-dependent killing by natural killer cells and granulocytes. Intracellular adhesion molecule-1 (icam-1) has been defined as a ligand for lfa-1. (12 Dec 1998) |
| acute renal failure | <nephrology> A sudden decline in renal function may be triggered by a number of acute disease processes. Examples include sepsis (infection), shock, trauma, kidney stones, kidney infection, drug toxicity (aspirin or lithium), poisons or toxins (drug abuse) or after injection with an iodinated contrast dye (adverse effect). Chronic renal failure represents a slow decline in kidney function over time. Chronic renal failure may be caused by a number of disorders which include long-standing hypertension, diabetes, congestive heart failure, lupus or sickle cell anaemia. Both forms of renal failure result in a life-threatening metabolic derangement. (27 Sep 1997) |