| beta particle | <physics, radiobiology> An electron or positron emitted from a radioactive nucleus during beta decay. (09 Oct 1997) |
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| beta pleated sheet | <cell biology> Beta secondary structure in proteins consists of two almost fully extended polypeptide chains lying side by side, linked by interchain hydrogen bonds between peptide C=O and N H groups. The chains may run in the same or opposite directions (yielding parallel or antiparallel structures, respectively). When multiple chains are involved, an extended sheet, the pleated sheet, is formed. (18 Nov 1997) |
| beta radiation | <radiobiology> Radiant energy from a source of beta rays. (05 Mar 2000) |
| beta ray | 1. <radiobiology> Original term used for electrons (and positrons) ejected from decaying nuclei via beta emission. (Label derives from the old days when we had various kinds of radiation emission, and they were labelled alpha, beta, and gamma (the first letters of the Greek Alphabet) because no one really knew what any of them were.) 2. A stream of positive or negative electrons ejected with high energy from a disintegrating atomic nucleus; most biomedically used isotopes emit negative particles (electrons or negatrons, rather than positrons). Cathode rays are low-energy negative electrons produced in cathode ray tubes, also called television tubes or oscilloscopes. (12 Sep 2000) |
| beta rhythm | <neurology> Brain waves in the electroencephalogram which have a frequency of 18 to 30 per second. They are typical during periods of intense activity of the nervous system, and occur principally in the parietal and frontal regions. (12 Dec 1998) |
| beta sheets | <biochemistry> A structure of proteins where the peptide is extended and stabilised by hydrogen bonding between NH and CO groups of different polypeptide chains or separate regions of the same chain. (05 Mar 2000) |
| Beta tests | <psychiatry> A set of pictorially administered mental tests first used in the United States Army in 1917-1918 to determine the relative mental ability of recruits who were illiterate or deficient in reading and writing English, the instructions being given in signs and the test material's pictorial in characters; distinguished from the Army Alpha tests, which were administered at the same time to literate recruits. Synonym: Army Beta tests. (05 Mar 2000) |
| beta thalassaemia | <haematology> Thalassaemia due to one of two or more genes that depress (partially or completely) synthesis of beta-globin chains by the chromosome bearing the abnormal gene. Heterozygous state (A2 t.): thalassaemia minor with Hb A2 increased, Hb F normal or variably increased, Hb A normal or slightly reduced. Homozygous state: thalassaemia major with Hb A reduced to very low but variable levels, Hb F very high level. A disorder characterised by reduced synthesis of the beta chains of haemoglobin. There is retardation of haemoglobin a synthesis in the heterozygous form (thalassaemia minor), which is asymptomatic, while in the homozygous form (thalassaemia major, cooley's anaemia, mediterranean anaemia, erythroblastic anaemia), which can result in severe complications and even death, haemoglobin a synthesis is absent. (05 Mar 2000) |
| beta wave | <neurology> Brain waves in the electroencephalogram which have a frequency of 18 to 30 per second. They are typical during periods of intense activity of the nervous system, and occur principally in the parietal and frontal regions. (12 Dec 1998) |
| beta, or beta-value | <radiobiology> Ratio of plasma kinetic pressure to magnetic-field pressure, proportional to the ratio of plasma kinetic energy density to magnetic field energy density. Beta is usually measured relative to the total, local field (loosely called beta toroidal), but sometimes the plasma pressure relative to only the poloidal component of the field (beta poloidal) or relative to some external field (like the maximum field at the magnetic coils) is more useful. There is also a normalised beta (beta_N) of interest when discussing the beta limit. (lots of help from Art Carlson with the above.) Because the cost of a reactor is strongly influenced by the strength of the magnetic field that must be provided, beta values are directly related to the economics of fusion power production. Beta is usually expressed as a percentage, with 5% generally believed to be the minimum value required for an economical fusion reactor. See: pressure, kinetic pressure, magnetic pressure, second stability. (09 Oct 1997) |
| beta-(2-furyl)-acryloyl phosphate hydrolase | <enzyme> Used as synthetic substrate for atpase assay Registry number: EC 3.6.1.- Synonym: bfa phosphatase (26 Jun 1999) |
| beta-1,3-galactosyl-0-glycosyl-glycoprotein beta-1,3-N-acetylglucosaminyltransferase | <enzyme> Capable of adding a glcnac residue to g1cnacman(3)g1cnac; from mung bean seedlings Registry number: EC 2.4.1.146 Synonym: n-acetylglucosaminyltransferase II, gal3-(glcnac6)galnac-mucin (glcnac--gal)3-glcnactransferase (26 Jun 1999) |
| beta-1,3-galactosyl-O-glycosyl-glycoprotein beta-1,6-acetylglucosaminyl transferase | <enzyme> With EC 2.4.1.148 this is called beta6-glcnac-transferase b Registry number: EC 2.4.1.102 Synonym: gal3-galnac-mucin-6-glcnac transferase, udp-glcnac-gal1-3galnac-r-(glcnac to galnac)-beta1-6glcnac transferase, core 2 glcnac transferase, core 2-n-acetylglucosaminyltransferase, core 2 beta6-gn-t (26 Jun 1999) |
| beta-1,4-mannosyl-glycoprotein beta-1,4-N-acetylglucosaminyltransferase | <enzyme> Induced in preneoplastic stage of liver carcinogenesis promoted by orotic acid in rats; adds "bisecting n-acetylglucosaminyl residue in beta 1,4 linkage to the beta-linked mannose of the core of asparagine-linked oligosaccharides Registry number: EC 2.4.1.144 Synonym: n-acetylglucosaminyltransferase III, udpgnac-glycopeptide beta4-n-acetylglucosaminyl transferase III, udpgnac-magtransferase III, udp-n-acetylglucosamine-beta-d-mannoside beta-1,4-n-acetylglucosaminyltransferase III (26 Jun 1999) |
| beta-adrenergic blocking agent | A class of drugs that compete with beta-adrenergic agonists for available receptor sites; some compete for both b1 and b2 receptors (e.g., propranolol) while others are primarily either b1 (e.g., metoprolol) or b2 blockers; used in the treatment of a variety of cardiovascular diseases where beta-adrenergic blockade is desirable. Synonym: beta-adrenergic receptor blocking agent, beta-adrenoreceptor antagonist, beta-blocker. (05 Mar 2000) |