| Abbe's law of limiting resolution | <physics> For a periodic structure of units separated by distance d and obliquely illuminated by the unrefracted ray and one of the two diffracted rays (extremely oblique illumination). Abbe applied the law of diffraction: d = 0.5 lambda /NA, where: lambda = wavelength of the monochromic light or shortest of mixed wavelengths NA = the limiting numerical aperture (NA) of objective or condenser. (05 Aug 1998) |
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| resolution | Complete return to normal structure and function: used, for example: of an inflammatory lesion or of a disease. (18 Nov 1997) |
| resolution acuity | The detection of a target having two or more parts, often measured by using the Snellen test types; indicated by two numbers: the first represents the distance at which an individual sees the test types (usually 6 meters or 20 feet), and the second, the distance at which the test types subtend an angle of 5 minutes; e.g., vision of 6/9 indicates a test distance of 6 meters and recognition of symbols which subtend an angle of 5 minutes at a distance of 9 meters. Synonym: visual acuity. (05 Mar 2000) |
| high-resolution banding | Banding, especially in prophase, which increases the clarity and number of discernible chromosome bands. (05 Mar 2000) |
| high resolution computed tomography | Computed tomography with narrow collimation to reduce volume-averaging and an edge-enhancing reconstruction algorithm to sharpen the image, sometimes with a restricted field of view to minimise the size of pixels in the region imaged; used particularly for lung imaging. Hypocycloidal tomography, body section radiography using a complex film and tube motion with a pattern resembling a three-leaf clover. (05 Mar 2000) |
| high-resolution imaging | <technique> High Resolution Electron Microscopy is phase contrast microscopy of the atomic structure of materials. In most crystalline inorganic materials and a number of polymeric materials HREM allows the imaging of individual atomic columns. The images can frequently be interpreted in terms of the projected crystal potential, although it is often necessary to match the experimental images with those calculated from multislice algorithms. Allows direct measurement of lattice parameters, inspection of individual defects and grain orientation. (05 Aug 1998) |
| limit of resolution | 1. <optics> The resolution of an optical system defines the closest proximity of two objects that can be seen as two distinct regions of the image. This limit depends upon the Numerical Aperture of the optical system, the contrast step between objects and background and the shape of the objects. The often quoted Airy limit applies only to self luminous discs. 2. <genetics> The smallest map distance measurable by an experiment involving a certain number of classified recombinant progency. (10 Mar 1998) |
| absolute intensity threshold acuity | The minimal light that can be seen. (05 Mar 2000) |
| absolute threshold | The lowest limit of any perception whatever. Compare: differential threshold. Synonym: stimulus threshold. (05 Mar 2000) |
| achromatic threshold | Threshold of visual sensation, the minimal light intensity evoking a visual sensation. Synonym: achromatic threshold, minimum light threshold. (05 Mar 2000) |
| anaerobic threshold | The oxygen consumption level above which aerobic energy production is supplemented by anaerobic mechanisms during exercise, resulting in a sustained increase in lactate concentration and metabolic acidosis. The anaerobic threshold is affected by factors that modify oxygen delivery to the tissues; it is low in patients with heart disease. Methods of measurement include direct measure of lactate concentration, direct measurement of bicarbonate concentration, and gas exchange measurements. (12 Dec 1998) |
| auditory threshold | The audibility limit of discriminating sound intensity and pitch. (12 Dec 1998) |
| brightness difference threshold | The smallest difference that can be perceived as a difference in brightness. Synonym: light difference. (05 Mar 2000) |
| pain threshold | Amount of stimulation required before the sensation of pain is experienced. (12 Dec 1998) |
| galvanic threshold | The minimal strength of an electrical stimulus of indefinite duration that is able to cause excitation of a tissue, e.g., muscle or nerve. See: chronaxie. Synonym: galvanic threshold. Origin: rheo-+ G. Basis, a base (05 Mar 2000) |