| 释义 |
impaction|ɪmˈpækʃən|
[ad. L. impactiōn-em, n. of action f. impingĕre to impinge.]
I.
1. The action of becoming, or condition of being, impacted or firmly fixed in.
1739J. Huxham Fevers (1750) 176 To prevent the further Impaction of the obstructing Lentor. 1853Kane Grinnell Exp. xxiv. (1856) 197 In case of accident or impaction further north. 1873T. H. Green Introd. Pathol. (ed. 2) 42 Sudden obstruction of the circulation by the impaction of an embolus in one of the larger arteries. 1876[see impacted ppl. a. 1 d]. 1921[see impacted ppl. a. 1 c]. 1957J. G. Bonnin Textbk. Fractures i. 8 Impaction is important in aiding fixation and indicates, as a rule, that little displacement has occurred. 1972D. E. Waite Textbk. Pract. Oral Surg. xi. 141 They also vary widely in degree of impaction; some are partially erupted, while others are completely encased in bone.
2. spec. in Med.
a. The lodging of a mass of (usu. hardened) fæces in the intestine so that defecation is prevented or impeded; hence, the obstruction of (a part of) the intestine in this way.
1853Assoc. Med. Jrnl. I. 606 (heading) Impaction of the rectum from unground wheat. 1866Clin. Lect. & Rep. (London Hospital) III. 193 Three cases of obstruction of the bowels..produced by the impaction of hardened fæces in the rectum, and colon. 1902J. P. Tuttle Treat. Dis. Anus xiv. 543 In simple constipation and in impaction there is always a channel for the escape of gases from the bowels. 1943Niles & Martin in E. J. Stieglitz Geriatric Med. xxxv. 599 Rectal impaction is much more common in the aged. Ibid. Colonic impaction (scybala) is seen occasionally in old people, especially among those who are bedridden. 1972[see impacted ppl. a. 1 b].
b. concr. A mass of (usu. hardened) fæces lodged in the intestine so as to impede defecation.
1902J. P. Tuttle Treat. Dis. Anus xiv. 542 The author has known a patient to suffer from a continuous diarrhœa for six weeks..apparently from no other cause than an impaction of fæces in the sigmoid flexure. 1931M. C. Pruitt Mod. Proctology xviii. 350 It is important to determine..whether the impaction is hard or soft. 1958A. F. R. Andresen Office Gastroenterol. 442 Small impactions can usually be induced to pass by means of a cleansing enema.
II.
3. The process of causing something to impinge or impact on something else (cf. impact v. 4); also, the action of so impinging (cf. impact v. 3).
1945[see impactor 2]. 1952A.M.A. Arch. Industr. Hygiene & Occup. Med. V. 476 Larger and heavier particles are thrown onto a collecting surface in front of the jet, while smaller and lighter particles escape impaction. 1956P. L. Magill et al. Air Pollution Handbk. xiii. 32 The impaction of aerosol particles on cylinders has been given considerable attention since it provides an insight into the functioning of fibrous filters. 1972J. O. Ledbetter Air Pollution A. vi. 230 Impaction devices..that depend upon the wind to carry out the impaction. |