| CGGE | constant gradient gel electrophoresis |
|---|---|
| DGGE | denaturating gradient gel electrophoresis |
| ECPOG | electrochemical potential gradient |
| GE | gastric empyting; gastroemotional; gastroenteritis; gastroenterology; gastroenterostomy; gastroesoph... |
| GEPG | gastroesophageal pressure gradient |
| gradient perception | <cell biology> Problem faced by a cell that is to respond directionally to a gradient of, for example: a diffusible attractant chemical. In a spatial mechanism the cell would compare receptor occupancy at different sites on the cell surface, a temporal mechanism would involve comparison of concentrations at different times, the cell moving randomly between readings. In pseudospatial sensing, the cell would detect the gradient as a consequence of positive feedback to protrusive activity if receptor occupancy increased with time as the protrusion moved up gradient. Few cell types have been unambiguously shown to detect gradients. (18 Nov 1997) |
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| mitral gradient | The diastolic pressure difference between the left atrium and left ventricle. (05 Mar 2000) |
| concentration gradient | <chemistry> A column of liquid in which the density varies continually with position, usually as a consequence of variation of concentration of a solute. Such gradients may be established by progressive mixing of solutions of different density as for example: sucrose gradients) or by centrifuge induced redistribution of solute (as for caesium chloride gradients). Density gradients are widely used for centrifugal and gravity induced separations of cells, organelles and macromolecules. The separations may exploit density differences between particles or primarily differences in size, in which latter case the function of the gradient is chiefly to stabilise the liquid column against mixing. (12 Jan 1998) |
| critical gradient | <botany> The maximum stable inclination of an unsupported slope under the most adverse conditions that it will likely experience, as determined by current engineering technology. (09 Oct 1997) |
| pseudospatial gradient sensing | <cell biology> Mechanism for sensing a gradient of a diffusible chemical in which the cell sends protrusions out at random, up gradient protrusions are stabilised by positive feedback (because receptor occupancy is rising with time) and others are transitory because of adaptation. Possibly the mechanism by which neutrophils sense chemotactic gradients. (18 Nov 1997) |
| density gradient | <chemistry> A column of liquid in which the density varies continually with position, usually as a consequence of variation of concentration of a solute. Such gradients may be established by progressive mixing of solutions of different density as for example: sucrose gradients) or by centrifuge induced redistribution of solute (as for caesium chloride gradients). Density gradients are widely used for centrifugal and gravity induced separations of cells, organelles and macromolecules. The separations may exploit density differences between particles or primarily differences in size, in which latter case the function of the gradient is chiefly to stabilise the liquid column against mixing. (12 Jan 1998) |
| density gradient centrifugation | <technique> High-speed centrifugation inwhich molecules float at a point wheretheir density equals that in a gradient of cesium chloride or sucrose. (12 Jan 1998) |
| systolic gradient | The difference in pressure during systole between two communicating cardiovascular chambers, e.g., between the left ventricle and aorta in aortic stenosis. (05 Mar 2000) |
| electrochemical gradient | A measure of the tendency of an ion to move passively from one point to another, taking into consideration the differences in its concentration and in the electrical potentials between the two points; commonly expressed as the additional voltage needed to achieve equilibrium. (05 Mar 2000) |
| ficoll gradient | A density gradient of ficoll (synthetic sucrose polymer) in solution, where concentration of the ficoll varies continuously through the solution. It is often used to separate different types of cells from each other during the process of sedimentation. (09 Oct 1997) |
| auditory field | The space included within the limits of hearing of a definite sound, as of a tuning fork. (05 Mar 2000) |
| bright field illumination | <microscopy> The method of lighting the specimen with a solid cone of rays. Transmitted bright field illumination is performed by a substage condenser. Reflected bright field illumination is performed by a vertical illuminator. Compare: dark field illumination (05 Aug 1998) |
| bright field imaging | <microscopy> An imaging mode in a transmission electron microscopy that uses only unscattered Electrons to form the image. Contrast in such an image is due entirely to mass-thickness variations in amorphous samples, and may include diffraction contrast in crystalline samples. (05 Aug 1998) |
| bright field microscopy | <technique> Optical microscopy, in which absorption to a great extent and diffraction to a minor extent give rise to the image, as opposed to phase contrast or interference methods of microscopy. (18 Nov 1997) |
| Broca's field | The posterior part of the inferior frontal gyrus of the left or dominant hemisphere, corresponding approximately to Brodmann's area 44; Broca identified this region as an essential component of the motor mechanisms governing articulated speech. Synonym: Broca's area, Broca's field, motor speech centre. (05 Mar 2000) |