Abstract : When an explosion occurs in the atmosphere above a water surface, most of the energy in the resulting shock wave will be reflected upon striking the air-water interface; however, some portion of the energy will be transmitted through the interface and propagate into the water. The experimental study, designed to provide quantitative information on the induced water shock as well as verigy theoretical findings, was conducted in a trapezoidal-shaped test basin 250 ft long, 150 ft wide (midpoint), and 20 ft deep. It involved the detonation of some sixty 21-lb spheres of TNT positioned at various distances above the water surface, and pressure-time histories of the induced water shocks were measured at spatial positions underwater for depths ranging from just beneath the surface to middepth. (Author)
AIM:To compare hemorrhoidectomy with a bipolar electrothermal device or hemorrhoidectomy using an ultrasonically activated scalpel.METHODS:Sixty patients with grade Ⅲ or Ⅳ hemorrhoids were prospectively randomized to undergo closed hemorrhoidectomy assisted by bipolar diathermy(group 1) or hemorrhoidectomy with the ultrasonic scalpel(group 2).Operative data were recorded,and patients were followed at 1,3,and 6 wk to evaluate complications.Independent assessors were assigned to obtain postoperative pain scores,oral analgesic requirement and satisfaction scores.RESULTS:Reduced intraoperative blood loss median 0.9 mL(95% CI:0.8-3.7) vs 4.6 mL(95% CI:3.8-7.0),P = 0.001 and a short operating time median 16(95% CI:14.6-18.2) min vs 31(95% CI:28.1-35.3) min,P < 0.0001 was observed in group 1 compared with group 2.There was a trend towards lower postoperative pain scores on day 1 group 1 median 2(95% CI:1.8-3.5) vs group 2 median 3(95% CI:2.6-4.2),P = 0.135.Reduced oral analgesic requirement during postoperative 24 h after operation median 1(95% CI:0.4-0.9) tablet vs 1(95% CI:0.9-1.3) tablet,P = 0.006 was observed in group 1 compared with group 2.There was no difference between the two groups in the degree of patient satisfaction or number of postoperative complications.CONCLUSION:Bipolar diathermy hemorrhoidectomy is quick and bloodless and,although as painful as closed hemorrhoidectomy with the ultrasonic scalpel,is associated with a reduced analgesic requirement immediately after operation.
