| 释义 |
polycyclic, a.|pɒlɪˈsaɪklɪk|
[f. poly- + cyclic a.]
†1. Math. (See quots.) Obs.
1869W. Thomson in Trans. R. Soc. Edin. XXV. 253 When the function is cyclic with reference to several different mutually irreconcilable circuits, it is called polycyclic. Ibid., Irrotational motion may be either acyclic or cyclic. If cyclic it is monocyclic if there is only one distinct circuit, or polycyclic if there are several distinct circuits, in which there is circulation. 1888A. B. Basset Treat. Hydrodynamics I. iv. 74 If ϕ be a polycyclic velocity potential, the circulation round any closed curve, which does not cut any of the barriers is..zero. Ibid. 75 Every polycyclic function may be expressed as the sum of..monocyclic functions.
2. [Gr. κύκλος circle.] Having or consisting of many rounds, turns, or whorls.
1890Cent. Dict., Polycyclic. 1899Allbutt's Syst. Med. VIII. 553 A curved figure, having a polycyclic outline.
3. Chem. Having more than one ring of atoms in the molecule. Also as n., a polycyclic compound.
1903Chem. News 13 Mar. 130/2 (heading) A method for the synthesis of polycyclic hydrocarbides. 1909C. A. Keane Mod. Org. Chem. xv. 414 The most important of these polycyclic substances are built up of benzene rings. 1943Endeavour Jan. 32/2 Carcinogenic potency is by no means confined to polycyclic compounds. 1968I. L. Finar Org. Chem. (ed. 4) II. xi. 462 This is only possible if rings B and C are fused together in a trans manner (cf. polycyclics, §11 d. IV). 1971Daily Tel. (Colour Suppl.) 28 May 27/2 Other potential dangers in exhaust fumes are polycyclic hydrocarbons—which can cause cancer in laboratory animals. 1976Nature 9 Sept. 93/1 Binding of carcinogenic polycylics to DNA..has been well established.
4. Electr. Engin. Involving the simultaneous transmission along a conductor of currents of different frequencies and voltages.
1903Jrnl. Inst. Electr. Engin. XXXII. 751 The advantages of low frequency for power work and of high frequency for lighting are combined in this polycyclic system. 1906A. Russell Treat. Theory Alternating Currents II. xvii. 478 (heading) Three phase polycyclic system of distribution. 1913S. P. Smith tr. La Cour & Bragstad's Theory & Calculation Electr. Currents xvi. 289 The object of the polycyclic system..is to simultaneously transmit electrical energy by means of currents at different pressures and frequencies through one and the same conductor, and to distribute the same without their affecting one another.
5. Geol. [ad. F. polycyclique (E. Argand 1922, in Compt. Rend. XIII Session, Congrès Géol. Internat. (1924) I. 365).] Produced by or having undergone many cycles, esp. of erosion and deposition. Cf. multicyclic adj. s.v. multi- 1 a.
1935H. Baulig Changing Sea Level ii. 13 (caption) Block-diagram of a polycyclic valley. 1947Trans. R. Geol. Soc. Cornwall XVII. 341 Polycyclic forms in the valleys still witness the later Pliocene stillstands despite intense peri-glacial solifluction. 1958[see morphometry]. 1968R. W. Fairbridge Encycl. Geomorphol. 554/2 A lateritic crust..reflects a polycyclic regime, usually as a result of repeated alternation of hot, humid conditions..with dry, evaporating conditions. 1975Nature 13 Feb. 502/3 Such sediments may incorporate..duplicated or polycyclic layers.
6. Biol. Producing several generations during a year by sexual reproduction.
1957New Biol. XXIII. 58 These polycyclic populations are found in complex environments like ponds where there are successive outbursts of different planktonic algae which cause fluctuations in the amount of food available. 1965J. Johnston tr. Danilevskii's Photoperiodism & Seasonal Devel. Insects vii. 194 They are all potentially polycyclic, and in southern provinces may have several generations a year. 1970Amer. Naturalist CIV. 398 In most polycyclic insects of the temperate zone, long days cause continuous development, while short days cause diapause. |