| 释义 |
nucleus, n.|ˈnjuːklɪəs|
Pl. nuclei |ˈnjuːklɪaɪ| and nucleuses.
[a. L. nucleus (nuculeus) kernel, inner part, f. nucula or nuc-, nux nut. So F. nucleus, It., Sp., and Pg. nucleo.]
I.
1. Astr. a. The more condensed portion of the head of a comet.[1704J. Harris Lex. Techn. I. Nucleus..is by Hevelius and others used for the Head of a Comet.] 1708Whiston The. Earth (ed. 2) ii. 76 The lowest part next the Nucleus, or Dense Body, seems to be Opake. 1766Phil. Trans. LV. 310, I compared the nucleus of the comet with two new stars that were just by. 1837J. F. Cooper Europe II. v. 99 The astronomers tell us that some of these comets have no visible nucleuses. 1868Lockyer Elem. Astron. §291 The brighter part of the comet is called the head, or coma, and sometimes the head contains a brighter portion still, called the nucleus.
fig.1759Sterne Tr. Shandy ii. ix, Would not such a phenomenon..have been a subject of juster apprehension..than the worst of Whiston's comets?—To say nothing of the Nucleus; that is, of Obadiah and the coach-horse.
b. A more condensed, usu. brighter, central part of a galaxy or nebula.
1784W. Herschel in Phil. Trans. R. Soc. LXXIV. 442, I have seen double and treble nebulæ, variously arranged; large ones with small, seeming attendants;..others of the cometic shape, with a seeming nucleus in the center. 1849J. F. W. Herschel Outlines Astron. xvii. 601 The nebula in Andromeda is visible to the naked eye... Mr. G. P. Bond, assistant at the observatory of Cambridge, U.S., describes and figures it as..very suddenly condensed at the nucleus almost to the semblance of a star. 1898A. M. Clerke et al. Concise Knowledge Astron. iv. vi. 534 The photograph shows both nuclei of the nebula to be stellar. 1955Sci. Amer. May 48/3 Because of heavy dust clouds this nucleus [of the Milky Way] has not been observed visually or photographically; it was discovered by radio astronomy. 1970Sci. Jrnl. Feb. 61/1 The emission line spectrum of a Seyfert nucleus is rather like that from typical hot clouds of gas such as the Orion Nebula.
†2. A supposed interior crust of the earth. Obs.
1715tr. Gregory's Astron. I. i. §69. 144 He [Kepler] found it necessary to suppose an interior Crust (which might be like a Nucleus, in regard of the exterior). Ibid. 145 And within this Nucleus, or rather Crust, he is forced to suppose again another interior Nucleus. 1727Pope Mem. Mart. Scriblerus i. xiv, A Proposal..to pierce the first crust or Nucleus of this our Earth, quite through, to the next Concentrical Sphere.
3. A central part or thing around which other parts or things are grouped, collected, or compacted; that which forms the centre or kernel of some aggregate or mass.
a. Of material (esp. more or less solid) things.
1762Phil. Trans. LII. 470 The nucleus of the nearest light will appear whitest and brightest. 1764Ibid. LIV. 42 The conical cavity and its nucleus are always proportioned to the bulk of the Belemnite. 1797M. Baillie Morbid Anat. (1807) 306 Some extraneous body, which becomes the nucleus of the calculus. Ibid., The nuclei which I have seen. 1826S. Cooper First Lines Surg. (ed. 5) 66 Every portion of the gangrenous cellular membrane, nucleus, or core, [should be] extracted. 1878Huxley Physiogr. xxi. 366 There may sometimes be detected a yet darker part [of a sun-spot] which is called the nucleus.
b. Of communities or groups of persons.
1798W. Hutton Life 120 About 700 individuals..were the nucleus of his colony of Georgia. 1853Merivale Rom. Repub. v. (1867) 150 The few hundred families, which formed the original nucleus of her citizenship. 1868Blunt Ref. Ch. Eng. II. 95 A Protestant party which crystallized around the nucleus of antisacerdotalists.
attrib.1904Westm. Gaz. 10 Dec. 11/1 They will have a nucleus crew of two-fifths of their war complement. 1905Fortn. Rev. 2 Jan. 15 The officers and men withdrawn..from distant squadrons will be utilised as nucleus crews in the Reserve ships. 1914C. F. Tweney Dict. Naval & Mil. Terms 163 Nucleus crew, the essential members of a ship's crew, such as petty officers, gunners, etc., the crew being raised to full strength in case of mobilisation. 1926in Fowler Mod. Eng. Usage 713/2 Ships with nucleus crews were not so efficient as ships fully manned. 1965M. Morse Unattached i. 57 The mood of each rehearsal..depended very much on the attitude of the nucleus group.
c. Of immaterial things.
1820Edin. Rev. XXXIII. 314 The nucleus of fine thought is there. 1835Thirlwall Greece I. vi. 248 They manifestly formed the basis or nucleus of the epic cycle. 1876Geo. Eliot Dan. Der. li, Each nucleus of pain or pleasure.
d. Of places, buildings, etc.
1839James Louis XIV, I. 266 A town was the nucleus round which a province, a kingdom, an empire was gathered together. 1865Lecky Ration. II. vi. 261 When a monastery was planted, it soon became the nucleus around which the inhabitants of the neighbourhood clustered. 1872Baker Nile Trib. v. 73 It formed a nucleus for the general gathering of the people with their flocks.
e. Of collections of things.
1866Cornh. Mag. Nov. 575 There are little nuclei of future collections. 1875J. H. Bennet Shores Medit. i. vii. 200 There is already a very fair collection of modern books in hand, as the nucleus of a library. a1878Scott Lect. Archit. (1879) I. 149 These may in their turn be made the nucleus round which detached..shafts may be grouped.
4. Archæol. A block of flint or other stone from which early implements have been made.
1869Lubbock Preh. Times iv. 87 These ‘livres de beurre’ appear to have been the blocks or nuclei from which they were obtained. 1899R. Munro Preh. Scotl. v. 143 Nuclei of obsidian have also been found in Greece.
II.
5. Bot. a. The kernel of a nut. Now rare or Obs.
1704J. Harris Lex. Techn. I, Nucleus is the Edible part of the Kernel of any Nut, which is contained within the Skin of the Kernel; and in a larger sense is by Botanists used for any Fruit or Seed contained within an Husk or Shell. 1727–38Chambers Cycl. s.v. Nut, An hard cortex, or shell; which contains a softer edible nucleus, or kernel. 1785Martyn tr. Rousseau's Bot. (1794) 439 The fruit is a drupe containing a nut, with a furrowed shell, within which is a four-lobed irregularly furrowed nucleus. 1846–50A. Wood Class-bk. Bot. 490 White Walnut..; nucleus oblong, acuminate, deeply..furrowed.
b. The kernel of a seed (see quots.).
1829Clinton tr. Richard's Elem. Bot. (ed. 4) 387 The kernel or nucleus is the whole of the ripe and perfect seed contained in the cavity of the episperm. 1849Balfour Man. Bot. §577 The seed..consists of a nucleus or kernel, and integuments. 1861Bentley Man. Bot. 343 The nucleus of the seed may either consist of the embryo alone,..or of the embryo enclosed in albumen or perisperm.
c. The central part of an ovule.
1829Clinton tr. Richard's Elem. Bot. (ed. 4) 383 The nucleus contained within both the integuments of the ovule is a cellular body. 1832Lindley Introd. Bot. i. ii. 155 The central part is a fleshy, pointed, pulpy mass, called the nucleus or nucelle. 1861Bentley Man. Bot. 330 As development proceeds, a cavity is formed at or near the apex of the nucleus..in which the embryo..is developed.
d. In Lichens: (see quot. 1832).
1832Lindley Introd. Bot. i. iii. 206 Nucleus, is the disk of the shield which contains the sporules and their cases. Asci, are tubes, in which the sporules are contained while in the nucleus. 1882Encycl. Brit. XIV. 554/2 When the pyrenium quite covers the nucleus it is said to be entire.
e. In Fungi: (see quots.).
1832Lindley Introd. Bot. i. iii. 209 Nucleus, is the central part of a perithecium. 1866Treas. Bot. II, Nucleus,..the gelatinous mass of asci or spores which is found in the perithecia of Sphæriæ or the analogous fungi. 1875Cooke & Berkeley Fungi 79 Fruit consisting of sporidia,..contained in asci,..forming a hymenium or nucleus = Ascomycetes.
f. The hilum of a starch-granule.
1861Bentley Man. Bot. 23 Starch granules, when fully formed, usually present a small rounded spot, which is commonly situated at one end..; this is called the hilum or nucleus.
6. a. The rudiments of the shell in certain molluscs.
1851Woodward Mollusca i. 36 A rudimental shell..which becomes the nucleus of the adult shell. 1866R. Tate British Mollusks iii. 64 The operculum is horny with the nucleus lateral. 1889Nicholson Palæont. (ed. 3) I. 682 In the Spiral Gastropods the embryonic shell, or ‘nucleus’, is placed at the apex of the permanent shell.
b. Any discrete mass of grey matter in the central nervous system.
The term is used in numerous English and mod.L. combs. distinguishing the various different nuclei.
1828J. Quain Elem. Anat. x. 622 If a vertical section be made of one of the lobes of the cerebellum, in such a way as that two-thirds of its breadth shall lie external to the incision, an oval nucleus of grey substance (corpus dentatum, vel rhomboideum) will be exposed. 1856Ibid. (ed. 6) II. 493 Another division passes directly up, its fibres embracing the olivary nucleus. 1875Encycl. Brit. I. 878/1 The upper mass of grey matter projects into the lateral ventricle, and is called the intra-ventricular portion or nucleus caudatus. 1881Mivart Cat 271 The third pair of nerves..arise deeply from a grey nucleus..close to the origin of the fourth nerve. 1896Cleland & Mackay Anat. 614 The superior peduncles..turn down..and reach the red nucleus. 1899[see hypothalamus]. 1968Passmore & Robson Compan. Med. Stud. I. xix. 12/1 Masses of grey matter are called nuclei, some of which, e.g. the basal nuclei, are large and embedded in the depths of the brain. 1972Sci. Amer. Dec. 73/1 A sensory pathway consists of peripheral sense organs and several clusters of nerve cells called nuclei. Sensory information is processed in several stages, so that each nucleus receives input from the preceding one, processes the input and sends an output to the next nucleus.
7. Biol. A cell organelle present in most of the cells of all organisms except the most primitive, usu. as a single subspherical structure, and consisting (except when undergoing division) of a membrane enclosing a ground substance (the nuclear sap) in which lie the chromosomes, one or more nucleoli, etc., and functioning as the repository of genetic information and as the director of metabolic and synthetic activity of the cell. Hence, by extension, applied by some writers to an organelle in some of the more primitive organisms, esp. bacteria, which is analogous in function but structurally simpler (cf. nucleoid a. B. b).
1831R. Brown in Trans. Linn. Soc. (1833) XVI. 710 This areola, or nucleus of the cell as perhaps it might be termed. 1842Carpenter Hum. Phys. §735. 618 At first having but one nucleus and afterwards presenting several; these nuclei..it is probable..are to be regarded as cytoblasts. 1847–9Todd's Cycl. Anat. IV. 120/2 No cell, or nucleus-stage having pre-existed. 1849Balfour Man. Bot. §16 Each cell is found to contain, at some period of its existence, a small body, called a nucleus. 1857G. Bird's Urin. Deposits (ed. 5) 362 A regularly organized body, consisting of a granular membrane enveloping transparent nuclei; being in fact a nucleated cell. 1861Bentley Man. Bot. 18 Almost all young cells contain one or more bodies called Nuclei or Cytoblasts... In cells of the higher classes of plants the nucleus consists of a rounded or lenticular granular-looking body. 1880Bastian Brain 35 Nerve cells are more or less granular bodies, each of which contains a large nucleus. 1882Vines tr. Sachs' Bot. 551 In most Monocotyledons the large central nucleus divides, and two fresh nuclei make their appearance. 1888Rolleston & Jackson Anim. Life Introd. p. xxii, The nucleus is limited externally by a nuclear membrane. 1889[see nucleoid a.]. 1962Brit. Med. Bull. XVIII. 31/1 (heading) Morphology of the bacterial nucleus. 1965[see nucleoid n. b]. 1968Passmore & Robson Compan. Med. Stud. I. xxvi. 2/1 The mature red [blood] cell..appears as a biconcave disc with no nucleus. 1970Ambrose & Easty Cell Biol. v. 163 This may also explain how acridine dyes penetrate the nucleus without staining the cytoplasm.
8. Chem. An arrangement of atoms, esp. a ring structure, characteristic of a number of organic compounds.
1845W. Gregory Outl. Chem.: Org. Chem. 512 Laurent considers benzole as in some measure the fundamental compound, or nucleus, and calls it phene. 1886E. F. Smith tr. V. von Richter's Chem. Carbon Compounds 465 The azo-group, N{b2}N, decomposes, each nitrogen atom remaining attached as NH2 to a benzene nucleus. 1932Jrnl. Chem. Soc. 1132 Table III summarises the effect of varying the nature of the side-chain halogen in the compounds with an unsubstituted phenyl nucleus. 1951I. L. Finar Org. Chem. x. 185 If one acetic acid nucleus is blocked off, the fragment required is ethyl chloroacetate. 1971Nature 7 May 25/1 Many psychoto⁓mimetic substances possess an indole nucleus.
9. A particle on which crystals, droplets, or bubbles can form in a fluid.
1857Miller Elem. Chem., Org. ii. §1 (1862) 90 Small pieces of wood are then introduced to act as nuclei upon which the crystals of lactose are deposited. 1886Proc. R. Soc. Edin. XIII. 79 If this were the case, no nucleus would be absolutely requisite for the formation either of liquid from vapour or of vapour from liquid. 1906[see nucleation]. 1939Q. Jrnl. R. Meteorol. Soc. LXV. 411 If supersaturation is attained the fogs may thicken considerably owing to the deposition of water on the sea-salt nuclei. 1952Industr. & Engin. Chem. June 1273/1 A nucleus in water⁓fog formation consists of about 80 water molecules. 1957G. E. Hutchinson Treat. Limnol. I. ix. 583 In a free volume of water containing no minute masses of gas that can act as nuclei, an enormous excess tension is needed for bubble formation. 1967[see nucleation].
10. A small group of bees, including a queen, used as the foundation of a new colony.
1886F. R. Cheshire Bees & Bee-keeping II. vii. 306 These small nuclei will sustain themselves, in average seasons. 1915E. F. Phillips Beekeeping iii. 39 A mere handful of bees (perhaps 200) may constitute a small colony (usually called a nucleus). 1952H. Mace Bee-Keeper's Handbk. xxxiii. 154 Nucleus hives can be purchased or made, either to hold a single nucleus up to four combs, or two or more separate nuclei, separated by partitions. 1963F. G. Smith Beekeeping vii. 60 A nucleus is a very small colony of bees. It consists of a queen and up to four or six frames of brood and food, well covered with bees.
11. Physics. The positively charged central constituent of the atom, comprising nearly all its mass but occupying only a very small part of its volume and now known to be composed of protons and neutrons.
In Rutherford's 1911 paper called merely a ‘central charge’. In the examples in the first paragraph nucleus is used for various speculative notions concerning the atom.
[1844Faraday in Phil. Mag. XXIV. 141 If, in the ordinary view of atoms, we call the particle of matter away from the powers a, and the system of powers or forces in and around it m, then in Boscovitch's theory a disappears, or is a mere mathematical point... To my mind..the a or nucleus vanishes, and the substance consists of the powers or m. 1851W. J. M. Rankine in Phil. Mag. I. 443 The fundamental suppositions of the hypothesis of molecular vortices are the following:—First. That each atom of matter consists of a nucleus or central physical point enveloped by an elastic atmosphere, which is retained around it by attraction. Ibid., If an indefinitely extended vibrating medium..consist of a system of atomic nuclei. 1900Rep. Brit. Assoc. Adv. Sci. 1900 619 The material atom must be some kind of permanent nucleus that retains around itself an æthereal field of physical influence. Ibid., If..the distances at which they [sc. atoms] are kept apart are large compared with the diameters of the atomic nuclei. 1903O. Lodge Mod. Views on Matter 5 If the charge of electricity usually associated with a single monad atom of matter were concentrated on to a spherical nucleus one hundred-thousandth of an atom's dimension in diameter, it would thereby possess a mass about one-thousandth of that of the lightest atom known... Such a hypothetical concentrated unit of electricity it has become customary to call an ‘electron’. ]
1912E. Rutherford in Phil. Mag. XXIV. 461 In a previous paper [sc. Phil. Mag. (1911) XXI. 669] I have given reasons for believing that the atom consists of a positively charged nucleus of very small dimensions, surrounded by a distribution of electrons in rapid motion, possibly of rings of electrons rotating in one plane. 1919Conquest I. i. 36/2 An atom is a sort of solar system in miniature, and comprises a central core or nucleus..and a number of particles, called corpuscles, circulating round the nucleus. 1942J. D. Stranathan ‘Particles’ of Mod. Physics xi. 417 The nucleus must be very small, not larger than 10-12 cm. 1955C. G. Darwin in W. Pauli Niels Bohr 6 In 1911 he [sc. Rutherford] tried the idea of a heavy central electric charge repelling the α-particle—it was I think several months before it was called the nucleus—and at once the whole theory of the nuclear atom emerged. 1962H. D. Bush Atomic & Nuclear Physics iii. 62 The hypothesis that every nucleus consisted of protons and neutrons, was first suggested by Heisenberg (1932).
12. a. Phonetics. The syllable of a word (spoken in isolation) that bears the primary accent; in an utterance, the syllable or syllables given particular emphasis.
1922H. E. Palmer English Intonation ii. 7 Each Tone-Group contains a Nucleus, which is the stressed syllable of the most prominent word in the Tone-Group. The nucleus corresponds to what is usually called sentence-stress. Ibid. 8 In Southern English there are four characteristic Nucleus Tones. 1924― Gram. Spoken Eng. 6 If..tonetic transcription is used, the syllable [´] will be replaced by the appropriate nucleus-symbol. Ibid. 14 Instead of the rise taking place in the nucleus-syllable itself, it is distributed over the nucleus and tail. 1941Language XVII. 224 The present study..will deal with junctures, stresses, and consonants only in summary, and then devote itself to the syllabic nuclei. 1942English Studies XXIV. 157 In combinations of noun + adjective (like French master, black bird) the marking of the nucleus tone (i.e. the point at which the pitch begins to rise or fall) is an excellent device to bring home to students the two meanings such combinations may express. 1962A. C. Gimson Introd. Pronunc. Eng. x. 244 The primary accent (or accents) in a sentence is shown by initiating a change of pitch direction, with the nucleus (falling, rising, or a combination of the two) on the appropriate syllable of the word (or words) on which attention is particularly to be concentrated. 1962S. Stubelius in F. Behre Contrib. Eng. Syntax 151 The main features of intonation, particularly whether the sentences studied had a falling or a rising end intonation (nucleus). 1973Archivum Linguisticum IV. 21 Tonality, tonicity, and tone, which refer to the number of tone-groups, the location of the tonic, or nucleus, and the choice of tone used, respectively.
b. Linguistics. The main word or words in a combination, phrase, or sentence; also = kernel n.1 8 b.
1934[see determinant a. and n. B. 2 c]. 1949E. A. Nida Morphol. (ed. 2) 83 The nucleus of a morphological construction consists of (1) a root or (2) a combination of roots... The nonnucleus is made up of nonroots. In the construction boyishness the element boy is the nucleus and -ishness constitutes the nonnucleus. 1961R. B. Long Sentence & its Parts i. 20 Isolates sometimes take adjunct modifiers, much as nucleuses do. Ibid. 497 Nucleuses, minimal sequences made up of subjects, predicators, and complements, or of such of these as occur... In come in! the nucleus is made up of the predicator come and the complement in. 1961Y. Olsson Syntax Eng. Verb iv. 77 The relationship between a group of nuclei (like London, etc.) and equivalent members of the paradigms based on them (like London-er, etc.) give rise to an expectancy which may or may not be met in the same way. 1968J. Lyons Introd. Theoretical Linguistics viii. 334 The subject and the predicate together form the nucleus of the sentence.
Hence ˈnucleus v. trans., to make into a nucleus, to concentrate.
1899Kipling Stalky 252 They'd withdrawn all the troops they could, but I nucleused about forty Pathans. |