| 释义 |
asymmetric, a.|æsɪˈmɛtrɪk|
[f. Gr. ἀ priv. + symmetric: see prec.]
a. = next.
1878Gurney Crystallog. 56 Forms with asymmetric faces occur in crystals of Topaz. 1881Syd. Soc. Lex. s.v., In Botany an organ is said to be asymmetric, when it cannot be divided into two similar halves by a vertical plane.
b. Chem. Exhibiting, pertaining to, or affected by asymmetry (sense 2 b below); = stereo-isomeric. Spec., asymmetric synthesis (see quots.). Cf. optical isomerism.
1875Jrnl. Chem. Soc. XXVIII. 862 The author [sc. J. H. van't Hoff] proceeds to show that combinations which possess an atom of carbon combined with four different univalent groups, and which he terms an asymmetric atom, present anomalies with respect to isomerism. 1881Nature XXIV. 41 One asymmetric carbon atom, i.e. an atom directly united with four different radicles. 1885Encycl. Brit. XIX. 314/2 A carbon atom combined with four different atoms or compound radicals may therefore be called an asymmetric carbon atom. 1902Ibid. XXVI. 722/1 The number of modifications of an asymmetric compound—which is not itself symmetric—is 2n, where n is the number of such carbon atoms. 1904Jrnl. Physical Chem. VIII. 528 By asymmetric synthesis is meant the synthesis of a substance containing an asymmetric carbon under such conditions that there shall be formed an excess either of the dextrorotatory or of the lævorotatory compound. 1949Thorpe's Dict. Appl. Chem. IX. 117/2 A molecule containing one asymmetric carbon atom possesses two isomeric structures, which are mirror images of each other. Ibid. 118/1 Asymmetric syntheses involving photochemical reactions under the influence of circularly polarised light have been successfully attempted. 1962P. J. & B. Durrant Adv. Inorg. Chem. viii. 237 A rotating molecule may..be regarded as a spinning top, and on this analogy a polyatomic molecule may be placed in one of the four following classes: a. Symmetric tops. b. Spherical tops. c. Linear molecules. d. Asymmetric tops.
▸ asymmetric bars n. Gymnastics (chiefly Brit.) a pair of horizontal rails placed close together and supported on posts, with one rail about 80 cm (approx. 30.5 inches) higher than the other, used in women's gymnastics (also occas. in sing.); (also) a competitive event consisting of individual performances on such an apparatus; cf. uneven parallel bars n. at uneven adj. Additions.
1961Times 27 Mar. 6/3 On both *asymmetric bars and vault she had made up ground lost on the beam. 1992Olympics 92 93/1 On the asymmetric bars the women go for consecutive releases, twisting long swings and ever more complex dismounts. 2002Mirror (Nexis) 9 Feb. 26 It took Olga five years to develop the famous Korbut Loop in which she threw herself backwards from the top asymmetric bar and caught it again.
▸ asymmetric conflict n. = asymmetric warfare n. at Additions.
1975World Politics 27 177 In such *asymmetric conflicts, insurgents may gain political victory from a situation of military stalemate or even defeat. 1994T. V. Paul Asymmetric Conflicts ii. 20 An ‘asymmetric conflict’ is defined as a conflict involving two or more states with unequal overall military and economic power resources.
▸ asymmetric digital subscriber line n. Computing and Telecomm. = ADSL n. at A n. Additions.
1991Telephony 10 June 27/1 *Asymmetric digital subscriber line (ADSL) capability transports a DSI bit stream..from the public telephone network to customers. 2000Independent 19 Sept. 17/3 ADSL or asymmetric digital subscriber line technology speeds computer data and images over BT's existing copper wire telephone lines at up to 500 kilobits per second—almost 10 times faster than current 56 kbs internet access.
▸ asymmetric warfare n. warfare between forces unequal in size, composition, or means; spec. warfare in which a smaller or ostensibly inferior force uses unexpected, unconventional tactics to its advantage in combating a larger or apparently superior adversary.
1991Press Assoc. (Nexis) 9 Feb. It was what we call today ‘*asymetric [sic] warfare’—and I think we're going to see quite a bit of asymetric [sic] warfare..soon. 1997M. C. Libicki Defending Cyberspace Introd. 8 Today's asymmetric warfare is about points, blots, and gated fences, topological forms with particular applicability to information warfare. 2001Times 5 Dec. i. 8/2 After September 11, Geoff Hoon, the Defence Secretary, ordered a defence strategy review to ensure that the Armed Forces could deal with the so-called asymmetric warfare threat posed by international terrorists. |
