| 释义 |
beta|ˈbiːtə|
[a. L. beta, Gr. βῆτα.]
1. The second letter of the Greek alphabet, β, β.
a1300Cursor M. 12425 Bot sai þou me first o betha, And siþen i sal þe sai alpha.
2. In various scientific uses; esp.
a. Astron. Used to mark the second star in a constellation.
b. Chem. The second of two or more isomerous modifications of the same organic compound.
c. Nat. Hist. The second sub-species or permanent variety of a species.
d. In various other classifications. Cf. alpha.
1867Chambers Astron. vi. ii. (1877) 492 Amongst the conspicuous stars β Libræ (green) appears to be the only instance. 1877Watts Fownes' Chem. II. 497 Beta-orcin is obtained by dry distillation of usnic acid. 1877― Dict. Chem. IV. 235 Stenhouse designated the acid obtained from South American Roccella..as α-orsellic, and that prepared..from South African Roccella as β-orsellic.
e. Math. beta distribution, a distribution of a variate x of the form dF = xp - 1(1 - x)q - 1dx/B(p, q), where 0 ≤ x ≤ 1, p, q > 0; beta function, the function B(p, q) = ∫10xp - 1(1 - x)q - 1dx , where p, q > o; also called the complete beta function and the first Eulerian integral; also, the function Bx(p, q) = ∫x0 xp - 1(1 - x)q - 1dx (the incomplete beta function).
1888W. W. R. Ball Hist. Math. xviii. 368 The Beta and Gamma functions were invented by Euler. 1924C. H. Forsyth Introd. Math. Anal. Statistics iv. 61 The value of any Beta function for positive values of m and n can be expressed directly in terms of Gamma functions. 1941Biometrika XXXII. 153 The special character of the Beta-distribution..makes it necessary to vary the method of computation in different parts of the range of variables covered. 1967A. Battersby Network Analysis (ed. 2) 319 The method of calculating the expected value and variance of the duration of a job depends on the assumption that the duration follows a Beta distribution. The Beta distribution is derived from the Beta function.
f. Physics. beta (or β) radiation, the second of three types of radiation emitted by radioactive substances, having greater penetrating power than alpha radiation. So beta (or β) particle, beta ray.
1899Rutherford in Phil. Mag. XLVII. 116 These experiments show that uranium radiation is complex, and that there are present at least two distinct types of radiation—one that is very readily absorbed, which will be termed for convenience the α radiation, and the other of a more penetrative character, which will be termed the β radiation. 1902Rutherford & Grier in Phil. Mag. IV. 325 For brevity and convenience we will call the non-deviable rays of all radioactive substances α rays and the deviable rays β rays. 1904Rutherford in Nature 10 Mar. 437/1 It is to be expected that Röntgen rays would be set up at the sudden starting as well as the sudden stopping of the electron or β particle. 1909Soddy Interpr. Radium 55 In ordinary circumstances radium appears to be expelling both α- and β-particles together. 1922A. S. Eddington Theory of Relativity 19 The β particles shot off from radioactive substances are negative electrons which sometimes attain speeds of 100,000 miles a second. 1933Discovery Feb. 45/1 Beta radiations, which are streams of electrons. 1957Technology Mar. 14/2 Both beta and gamma rays can also be used for gauging thickness or height in the examination, for instance, of red-hot sheets of steel.
Hence denoting a process in which, or a substance from which, beta particles are emitted, as beta decay, beta disintegration, beta emission, beta emitter.
1931Rutherford in Proc. R. Soc. A. CXXXII. 674 There will be a broadening of the line by the Doppler effect due to recoil of the nucleus from the immediately preceding β-disintegration. 1933C. D. Ellis & Mott Ibid. CXLI. 502 The..upper limit of the β-ray spectrum is a significant parameter with which to classify a β-disintegration. 1934G. Gamow Ibid. CXLVI. 217 Every theory treating the β-decay as the transformation of a nuclear neutron into a proton. 1935Internat. Conference Physics 1934 I. 41 The final state of the nucleus after a β-emission is an excited one. 1947C. D. Coryell in C. Goodman Sci. & Engin. Nuclear Power I. 248 (heading) Long-lived β emitters without γ radiation. 1955Gloss. Terms Radiology (B.S.I.) 6 Beta decay, the radioactive decay process characterized by the emission of a beta particle. The parent atom involved is called a beta emitter.
g. Metallurgy. (a) Applied to the second of a series of allotropic forms of iron (see quot. 1949); (b) applied to the second of a range of alloys, as beta brass, the second of a series of alloys of copper and zinc, containing less copper than in alpha brass. Cf. alpha 3 d.
1885, etc. [see alpha 3 d]. 1895Jrnl. Iron & Steel Inst. XLVIII. 258 A special strong, hard, brittle, allotropic state called β iron. 1914Jrnl. Inst. Metals XI. 105 Plane sections through a bees' honeycomb..a benzene water-foam, and an over-annealed β brass are all very similar in appearance. 1949R. T. Rolfe Dict. Metallogr. (ed. 2) 24 Beta iron, formerly, a supposed allotropic form of i[ron] stable between..768° and about 900° C., of body-centred cubic form, and only very feebly magnetic. In reality, the change in magnetic susceptibility of α-iron occurring at 768° C. is not associated with any structural transformation and β-iron is no longer recognized as a distinct variety.
h. beta rhythm, beta waves, fast activity of the brain recorded in an electroencephalogram, having a frequency of fourteen to twenty-four cycles per second. Cf. alpha 3 f.
[1935Brain LVIII. 349 Berger describes a definite series of small oscillations—the b waves—superimposed on the primary a waves of the 10 a second rhythm. The frequency of the b waves is given as 35 a second.] 1936Archives Neurol. & Psychiatry XXXVI. 1215 Less prominent, because lower in voltage, is a faster rhythm, with a frequency of about 25 waves a second, called by Berger the ‘beta waves’. Ibid. 1220 A prominent fast (beta) rhythm. 1943Electronic Engin. XVI. 237 Faster rhythms, sometimes called ‘beta’ rhythms, have been described in the EEG.
i. beta receptor (Physiol.), one of two categories of adrenergic receptor on organs innervated by sympathetic nerves, which when stimulated increases cardiac action and blood flow and relaxes smooth muscle; beta-blocker (Pharm.), a drug that prevents the stimulation of beta receptors; so beta-blocking adj.
1948R. P. Ahlquist in Amer. Jrnl. Physiol. CLIII. 596 One type of [adrenotropic] receptor is associated with most of the excitatory functions and with at least one of the inhibitory functions (intestine). The other type is associated with most of the inhibitory functions and with one..excitatory function (myocardium)... Because of the opposite effects..the customary signs, E (excitatory) and I (inhibitory) cannot be applied. Therefore, for convenience they have been designated as the alpha adrenotropic receptors and the beta receptors. 1965J. H. Burn Lect. Notes Pharmacol. (ed. 8) 8 The β-blocking agents are those which prevent adrenaline from causing relaxation in smooth muscle. 1970Biol. Abstr. LI. 96372 Beta blockers exert a powerful physiological effect primarily on the cardiovascular system. 1977South China Morning Post (Hong Kong) 22 July 16/4 We're hoping that beta blockers will calm performers without taking the edge off their performance. 1983Oxf. Textbk. Med. II. xiii. 64 Inhibition of the beta receptor in bronchial smooth muscle is likely to produce a significant increase in airways resistance in asthmatic subjects. Ibid. 66/1 Beta-blocking agents may produce depression and other central nervous system side-effects, such as sleep-disturbances, insomnia, and nightmares. 1986Here's Health Dec. 28/3 With the advent of calcium channel blockers advertising has mentioned side-effects from beta blockers which were never mentioned during their peak of acceptability.
3. An examiner's second-class mark. Also transf.
1902[see alpha 4]. 1936‘N. Blake’ Thou Shell of Death vi. 104 He's quite a decent old trot, but definitely in the Beta class. 1958Oxf. Mag. 13 Mar. 362/1, I have mentioned twenty recent pictures..four have some alpha about them; the rest are gamma minus to beta plus (I have not mentioned deltas).
Add:j. beta test, a test of machinery, software, etc. in course of final development, carried out by a party or parties unconnected with the developer (freq. attrib.); so beta testing, beta-test v. trans., beta-tester. Cf. alpha test s.v. alpha n. 3 g.
1978Aviation Week 6 Feb. 243/3 A competition currently is under way to select a contractor to design and build a Beta testbed facility for evaluation during Fiscal 1980. 1981Electronics 24 Feb. 250/2 Xidak has added a symbolic debugger that is now at the beta test-site stage. 1982Inc. Jan. 68 The software is tested, usually by both an inhouse staff (called alpha-testers) and by outsiders (called beta-testers), and the manual is typeset and printed. 1982Electronics 24 Feb. 174/3 Only now, following beta testing at about a dozen installations, is the system ready for customer deliveries. 1982Computerworld 8 Mar. 63/3 The system is currently being beta tested and general customer deliveries are expected to begin this July. 1985Times 21 Mar. 39/1 (Advt.), Problem solving together with alpha and beta testing of new products require a minimum of 2 years experience of IBM Assembler or Z80 programming. 1985Austral. Personal Computer Nov. 77/1 The review software was a Beta-test version with a photocopied draft of the manual.
4. [Abbrev. Betamax n.] (With capital initial.) A name for one of the standard formats for videocassettes, orig. called Betamax (q.v.).
1977Fortune Sept. 180/2 There was a brief attempt by Sony back in 1975 to get Matsushita to adopt its Beta format, but by then the larger company was convinced it was perfecting a superior machine. 1984Listener 19 July 34/2 There are around 10,000 rental outlets for tapes, many already reluctantly stocking the same titles in two, or even three formats (VHS, Beta and V2000). 1987Which? June 286/2 Beta is gradually disappearing but you may find a few models in the shops.
[2.] [i.] For beta receptor read beta (or β) (adrenergic) receptor. Add before beta-blocker: beta-adrenergic a., pertaining to or affecting the beta receptors.
1959Pharmacol. Rev. XI. 462 These data seem to provide verification of Ahlquist's division of α- and β-adrenergic receptors. 1964Brit. Med. Jrnl. 19 Sept. 723/2 Beta-adrenergic blockade may be helpful in angina pectoris. 1994Sci. News 22 Oct. 262/2 Volunteers received either a placebo pill or propanolol, a drug that lowers blood pressure by blocking beta-adrenergic stress hormones.
▸ beta customer n. Business a person or company (usually a potential purchaser) involved in beta-testing a product.
1986Network World 6 Oct. 4/2 Malone was told to sign up *beta customers even though no resources were devoted to developing key product features. Three companies agreed to test the product. 2002R. Adams Good Hard Kick in Ass ii. 49 Many AV Labs startups recruit their first group of beta customers during market validation. |