| alpha radiation | <physics, radiobiology> The most easily absorbable type of radiation, it consists of a stream of alpha particles, doubly ionised helium nuclei which are electrically charged and produce intense ionisation in matter. Alpha radiation can be deflected in electromagnetic fields. (09 Oct 1997) |
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| alpha ray | <physics> A radioactive particle made up of two protons and two neutrons, these particles are created by the decay of a radioactive material or by nuclear bombardment, and they are the same as the nucleus of a helium-4 atom. (09 Oct 1997) |
| alpha rhythm | Brain waves in the encephalogram which have a frequency of 8 to 13 per second. They are typical of the normal person awake and in a quiet resting state, and occur principally in the occipital region. (12 Dec 1998) |
| alpha substance | A filamentous plasmatic material, beaded with granules, demonstrable by means of vital staining in the immature red blood cells. Synonym: alpha substance, filar mass, filar substance, substantia reticularis, substantia reticulofilamentosa. Synonym: reticular formation. (05 Mar 2000) |
| Alpha tests | A set of paper and pencil-administered mental tests first used in the United States Army in 1917-1918 to determine the mental ability of literate recruits; the set includes 8 different types of tests: i.e., directions, arithmetical problems, practical judgement, synonyms and antonyms, disarrayed sentences, number series completions, analogies, and information; they are designed especially for testing large groups of individuals simultaneously, and for rapid machine scoring; distinguished from the Army Beta tests, a complementary set for administration to recruits who could not read or write English, in which the instructions are given in signs and the test material is pictorial. See: Beta tests. Synonym: Army Alpha tests. (05 Mar 2000) |
| alpha thalassaemia | <haematology> A condition characterised by the reduced synthesis of the alpha chain of haemoglobin due to abnormality in one of two or more genes that code for the synthesis of alpha-globin chains. The severity of this condition can vary from mild anaemia to death, depending on the number of genes deleted. Heterozygous state: severe type, thalassaemia minor with 5 to 15% of Hb Barts at birth, only traces of Hb Barts in adult; mild type, 1 to 2% of Hb Barts at birth, not detectable in adult. Homozygous state: severe type, erythroblastosis foetalis and foetal death, only Hb Barts and Hb H present; mild type not clinically defined. See: haemoglobin H. (05 Mar 2000) |
| alpha units | Cytoplasmic glycogen granules arranged in rosettes. (05 Mar 2000) |
| alpha viruses | <virology> These are the major viruses in the Togavirus group and include eastern and western equine encephalitis viruses, the Sindbis virus and the Semliki Forest virus. The last two viruses are being researched as vectors for expressing heterologous genes. (09 Oct 1997) |
| alpha wave | Brain waves in the encephalogram which have a frequency of 8 to 13 per second. They are typical of the normal person awake and in a quiet resting state, and occur principally in the occipital region. (12 Dec 1998) |
| alpha(1-6)mannosidase | <enzyme> Human lysosomal enzyme highly specific for alpha 1-6 mannose residues; inhibited by swainsonine; not the same enzyme which is deficient in alpha-mannosidosis Registry number: EC 3.2.1.- (26 Jun 1999) |
| alpha(2,8)-sialyltransferase | <enzyme> Active towards gm1b, gd1a, gt1b, and gd3 gangliosides; genbank u91641 Registry number: EC 3.4.99.- Synonym: st8sia v, hst8sia v (26 Jun 1999) |
| alpha, alpha-phosphotrehalase | <enzyme> Forms glucose plus glucose-6-phosphate Registry number: EC 3.2.1.93 Synonym: trehalose-6-phosphate hydrolase, phospho-alpha(1,1)glucosidase, trea gene product, trec gene product (26 Jun 1999) |
| alpha,alpha-trehalose phosphorylase | <enzyme> Chemical name: alpha-d-glucopyranosyl-alpha-d-glucopyranose orthophosphate glucosyltransferase Registry number: EC 2.4.1.64 Synonym: trehalose phosphorylase (26 Jun 1999) |
| alpha,beta-ketoalkene reductase | <enzyme> Nadh is much less effective than NADPH; catalyses the reduction of the carbon-carbon double bond of five membered ring cpds which have two conjugated carbonyl groups on both sides of a double bond Registry number: EC 1.3.1.- Synonym: n-ethylmaleimide reducing enzyme, NADPH-linked alpha,beta-ketoalkene double bond reductase, n-ethylmaleimide reductase (26 Jun 1999) |
| alpha-(4-O-methyl)-D-glucuronidase | <enzyme> Removes 4-o-methyl-glucopyranosyl uronic acid residues from the 2-position of fungal cell wall xylans Registry number: EC 3.2.1.- Synonym: 4-o-methyl-glucuronidase (26 Jun 1999) |