| 释义 |
sedimentation|ˌsɛdɪmənˈteɪʃən|
[f. sediment n. + -ation.]
1. Deposition of sediment; spec. in Geol. (see sediment n. 2); also see quot. 1898.
1874H. A. Nicholson in Trans. Victoria Inst. IX. 215 There is no proof of any considerable pauses in the process of sedimentation during the same period. 1881Geikie in Nature 17 Feb. 358/1 That still comparatively narrow belt of sea to which sedimentation has always been mainly confined. 1896Pop. Sci. Monthly Dec. 243, I am inclined..to ascribe the greatest potency to the effects of erosion, transportation, and sedimentation on the earth's surface. 1898Syd. Soc. Lex., Sedimentation, production of quick deposition of a sediment, whether in sewage, or urine, &c., by means of some centrifugal apparatus. 1902Westm. Gaz. 20 Dec. 3/1 River water is usually purified by sedimentation and filtration.
2. Comb., as sedimentation coefficient, constant, a measure of the size of a microscopic particle, equal to the terminal outward velocity of the particle when centrifuged in a fluid medium divided by the centrifugal force acting on it; (expressed in units of time: cf. Svedberg); sedimentation rate, the rate of descent of particles suspended in a fluid; spec. in Med., of the red cells in drawn blood; sedimentation tank, a tank in which sewage is allowed to stand so that the solid matter in suspension may have time to settle.
1962H. Bloemendal et al. in A. Pirie Lens Metabolism Rel. Cataract 300, α-Crystallin, prepared by vertical starch block electrophoresis, has a sedimentation coefficient of 19 S (molecular weight 810,000). 1978Nature 12 Jan. 170/2 Nervous tissue and muscle in rat and chicken contain several molecular forms of acetylcholinesterase.., distinguishable by their sedimentation coefficient in sucrose gradient.
1929Svedberg & Katsurai in Jrnl. Amer. Chem. Soc. LI. 3577 The term ‘Sedimentation Constant’ has been adopted as a simplified means of expressing the old term ‘Specific Sedimentation Velocity’. 1966B. Pollara et al. in R. T. Smith et al. Phylogeny of Immunity ix. 94/2 The antibody produced by this animal is different from that of the other lower vertebrates, having a sedimentation constant of approximately 9S.
1946Nature 30 Nov. 794/2 In accordance with Stokes's law, sedimentation-rates of such red-cell aggregates will be greater than those of single non-polarized blood cells. 1978Ibid. 12 Oct. 532/1 To predict long-range trends in marsh stability, accurate measurements are needed of both subsidence and sedimentation rates.
1920Glasgow Herald 3 Nov. 13 The sewage passes into a sedimentation tank designed so as to bring down in the form of sludge as much of the suspended solids as possible. 1966McGraw-Hill Encycl. Sci. & Technol. XII. 221/2 In some [sewage] treatment plants screenings are passed through a grinder and returned to the flow so that they will settle out in the sedimentation tank. |