| arterial switch operation | Operation for complete transposition of the great arteries; the most common way to repair this defect consists of switching the aorta and pulmonary arteries and implanting the coronary arteries into the neoaorta (the original pulmonary artery). (05 Mar 2000) |
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| genes, switch | Genes that cause the epigenotype (i.e., the interrelated developmental pathways through which the adult organism is realised) to switch to an alternate cell lineage-related pathway. Switch complexes control the expression of normal functional development as well as oncogenic transformation. (12 Dec 1998) |
| gene switch | <molecular biology> A situation in which a cell or organism stops expressing one gene orgene group and switches to expressing a different gene or group of genes. (09 Oct 1997) |
| class switch | Change in the isotype of antibody produced after a B-cell has encountered an antigen. (05 Mar 2000) |
| switch | 1. To strike with a switch or small flexible rod; to whip. 2. To swing or whisk; as, to switch a cane. 3. To trim, as, a hedge. 4. To turn from one railway track to another; to transfer by a switch; generally with off, from, etc.; as, to switch off a train; to switch a car from one track to another. 5. To shift to another circuit. Origin: Switched; Switching. 1. A small, flexible twig or rod. "Mauritania, on the fifth medal, leads a horse with something like a thread; in her other hand she holds a switch." (Addison) 2. A movable part of a rail; or of opposite rails, for transferring cars from one track to another. 3. A separate mass or trees of hair, or of some substance (at jute) made to resemble hair, worn on the head by women. 4. A mechanical device for shifting an electric current to another circuit. Safety switch, an arrangement of tracks whereby elevations otherwise insurmountable are passed. The track ascends by a series of zigzags, the engine running alternately forward and back, until the summit is reached. <physics> Switch board, a collection of switches in one piece of apparatus, so arranged that a number of circuits may be connected or combined in any desired manner. Switch grass. <botany> See Grass. Origin: Cf. OD. Swick a scourage, a whip. Cf. Swink, Swing. Source: Websters Dictionary (01 Mar 1998) |
| switch region | <molecular biology> The nucleotide sequences in heavy chain immunoglobulin genes located in the introns at the 5' end of each CH locus concerned with DNA recombination events that lead to changes in the type of heavy chain produced by a B-cell, for example IgM to IgG switching. These regions are highly conserved sequences. See: isotype switching. (19 Jan 1998) |
| immunoglobulin switch region | Site on a segment of a B-cell immunoglobulin heavy-chain gene where recombination or rearrangement can occur, expressed as isotype or allotype switching, maturation of immune response, or recombination of DNA molecules. It is found on genes encoding all five immunoglobulin heavy chains. (12 Dec 1998) |
| q-switch | <radiobiology> Optical switch used to rapidly change the Q of an optical resonator, utilised in the optical resonator of a laser to prevent lasing action until a high level of gain and energy storage are achieved in the laser medium. When the switch is triggered and rapidly increases the Q of the cavity, a stronger laser pulse is generated. See: oscillator. (09 Oct 1997) |
| radio frequency heating | <radiobiology> Process for heating the plasma by transferring energy to ions or electrons using waves generated by an external oscillator at an appropriate frequency. (This is similar to how a microwave oven heats food.) There are various types: See: ECRH, ICRH, and Lower Hybrid. (09 Oct 1997) |
| gross heating value | (GHV) The maximum potential energy in the fuel as received. It reflects the displacement of fibre by water present in the fuel. Expressed as: GHV = HHV (1 - MC / 100) (05 Dec 1998) |
| heating | That heats or imparts heat; promoting warmth or heat; exciting action; stimulating; as, heating medicines or applications. Heating surface, the aggregate surface exposed to fire or to the heated products of combustion, especially. Of all the plates or sheets that are exposed to water on their opposite surfaces. Synonym: fire surface. Source: Websters Dictionary (01 Mar 1998) |
| heating curve | <chemistry> A plot of temperature verses time for a substance where energy is added at a constant rate. (09 Jan 1998) |
| heating value | The maximum amount of energy that is available from burning a substance. (05 Dec 1998) |
| higher heating value | (HHV) The maximum potential energy in dry fuel. For wood, the range is 7,600 to 9,600 Btu/lb. (05 Dec 1998) |
| net heating value | The potential energy available in the fuel as received, taking into account the energy loss in evapourating and superheating the water in the sample. Expressed as NVH = (HHV x (1- MC / 100)) - (LH(2)O x MC / 100) (05 Dec 1998) |