| 释义 |
impacted, ppl. a.|ɪmˈpæktɪd|
[See impact v.]
1. a. Pressed closely in, firmly fixed.
1683Salmon Doron Med. ii. 463 To melt (as it were) any impacted humor, though never so tough. c1720W. Gibson Farrier's Dispens. i. (1734) 25 To ripen and dissolve hard impacted Humours. 1856Kane Arct. Expl. I. xxi. 267 The fine impacted snow-dust of winter.
b. Applied spec. to fæces lodged in the intestine (cf. impaction 2); also transf., applied to (a part of) the intestine when so blocked.
1844Boston Med. & Surg. Jrnl. XXX. 309 (heading) History of a case of impacted colon. 1850Lancet 19 Jan. 80/2 The bowel is found in a state of great distention from an impacted mass closely adhering to its walls. 1875Cincinnati Med. News VIII. 353 (heading) Remarkable case of impacted colon, with suppression of urine. 1902J. P. Tuttle Treat. Dis. Anus (1903) xiv. 545 Distressing symptoms are relieved either by the loosening up of an impacted fæcal mass, or possibly by the undoing of a volvulus or intussusception. 1972F. A. Jones in Jones & Godding Managem. Constipation iv. 128 In some patients, impaction may have already led to severe symptoms, with acute distress, and it is then necessary to organize the immediate removal of the impacted faeces.
c. Applied to a bone fracture in which the broken parts are driven together so as to become locked.
1850J. A. Orr Princ. Surg. ii. xi. 153 Impacted fracture is when one broken extremity of the bone is driven into and lodged in the other. 1921Baetjer & Waters Injuries & Dis. Bones & Joints v. 102 When the fracture is just behind the head [of the femur] or in the middle of the neck, impaction is relatively rare. Fracture at the base is generally impacted. 1967E. L. Ralston et al. Handbk. Fractures vii. 116 Impacted fractures [of the humeral neck] even with angulation of 25 to 30 degrees are best treated with the use of a sling and swathe and early active exercises.
d. Applied to a tooth which, owing to obstruction by another tooth or by bone, fails to erupt properly and remains partly or wholly within the jaw-bone.
1876H. Moon in T. Bryant Pract. Surg. (ed. 2) I. xiii. 546 In all cases where the impaction of a lower wisdom tooth is a source of irritation, the impaction should be at once got rid of... The serious results which may attend purulent inflammation about an impacted wisdom tooth, will receive notice later. 1928H. Prinz Dis. Soft Struct. Teeth i. 29 Impacted teeth usually do not cause painful symptoms unless they meet on their path of retarded eruption an obstruction or they exert pressure upon nerve fibers. 1971Costich & White Fund. Oral Surg. viii. 93/2 The maxillary third molars frequently fail to erupt but may not necessarily be regarded as impacted teeth.
2. a. That has impinged upon or struck something.
1952A.M.A. Arch. Industr. Hygiene & Occup. Med. V. 464 Although the size of impacted particles can be measured under a microscope, the impaction principle..is used more as a method of sampling than as a method of determining the particle-size distribution.
b. That has been struck by an impacting body; also fig. (U.S.) of an area: affected by a larger demand than usual on public services, esp. schools.
1924in Sci. Amer. (1974) July 12/1 One need only study a large raindrop falling into a still pool of water. There is first a surging outward of the impacted water. 1963Economist 25 May 777/2 The..scheme for aid to ‘impacted’ areas (where schools are over-loaded). 1967Compton Yearbk. 232/1 Funds were also earmarked for..federally ‘impacted’ areas, that is, areas where the families of federal workers had swollen school enrollments. 1970Time 6 Apr. 12 Nixon..proposed that $1.5 billion in federal funds be made available to ‘racially impacted areas’..to help desegregating school districts meet their special needs. 1971Nature 16 July 162/2 The shape of a newly formed impact crater is caused by the sudden release of the kinetic energy of the impacting mass within a small volume somewhat below the original impacted surface. |