| backed | Having a back; fitted with a back; as, a backed electrotype or stereotype plate. Used in composition; as, broad- backed; hump-backed. Source: Websters Dictionary (01 Mar 1998) |
|---|---|
| backfill | <ecology> Soil, overburden, mine waste or imported material used to replace material removed during mining. (09 Oct 1997) |
| backflow | The reversal of the normal flow of a current. See: regurgitation. (05 Mar 2000) |
| backflushing | <procedure> A process used to clean filters or membranes of particles by reversing the flow of fluid through the system. (09 Oct 1997) |
| background level | The average amount of a substance present in the environment. Originally referring to naturally occurring phenomena. Used in toxic substance monitoring. (05 Dec 1998) |
| background radiation | <radiobiology> Level of environmental radation due to background sources. Background sources can be natural, such as cosmic rays and natural radioactive elements (principally radon, but including other elements such as isotopes of potassium (which people get substantial amounts of in foods like bananas)). They can also be man-made, such as from fossil-fuel combustion, everyday leakage from nuclear activities, and leftover from atmospheric nuclear weapons tests. Background radiation is usually distinguished from acute radiation, such as from medical X-rays, nuclear accidents, radioisotope therapy, or other short-term doses. The man-made contribution to background radiation is quite small compared to the natural contribution, medical uses dominate human exposure to acute radiation. (09 Oct 1997) |
| background retinopathy | <ophthalmology, pathology> Early stage of diabetic retinopathy, it usually does not impair vision. Origin: Gr. Pathos = disease (09 Oct 1997) |
| backing | In dentistry, a metal support which serves to attach a facing to a prosthesis. (05 Mar 2000) |
| backlash | <mechanics> The distance through which one part of connected machinery, as a wheel, piston, or screw, can be moved without moving the connected parts, resulting from looseness in fitting or from wear; also, the jarring or reflex motion caused in badly fitting machinery by irregularities in velocity or a reverse of motion. Origin: Back, adv. + lash. Source: Websters Dictionary (01 Mar 1998) |
| backlog | A large stick of wood, forming the of a fire on the hearth. "There was first a backlog, from fifteen to four and twenty inches in diameter and five feet long, imbedded in the ashes." (S. G. Goodrich) Origin: Back, a. + log. Source: Websters Dictionary (01 Mar 1998) |
| backprojection | In computed tomography or other imaging techniques requiring reconstruction from multiple projections, an algorithm for calculating the contribution of each voxel of the structure to the measured ray data, in order to generate an image; the oldest and simplest method of image reconstruction. Synonym: apical lordotic projection. (05 Mar 2000) |
| backscatter | Induced radiation deflected more than 90 |
| backscattered electron | <microscopy> Produced by an incident electron colliding with the nucleus of an atom in the specimen. The incident electron is then scattered backward about 180 degrees with no appreciable loss of energy, an elastic collision. (05 Aug 1998) |
| backscattered electron imaging | <microscopy> The production of backscattered electrons from a sample varies directly with the specimen's average atomic number, higher atomic number elements produce more backscattered electrons than lower atomic number ones. Detection of Backscattered Electrons is achieved by using a donut shaped solid state saemiconductor device mounted on the bottom of the objective lens. When Backscattered Electrons strike the detector electron-hole pairs are created which are then counted. This quantity is translated into a pixel intensity and displayed on the CRT, forming the image. By splitting the detector into halves (or quadrants) differences in the signal level on the individual detector segments provide surface topography information. (05 Aug 1998) |
| backscattering | <radiobiology> Deflection of incident particle / radiation through an angle greater than 90 degrees relative to the original direction of motion/propagation. (09 Oct 1997) |