(1) Read a TST result 48 to 96 (ideally 72) hours after administration. Palpate and measure induration (not redness). An alternative method is to use a ballpoint pen to draw a line starting at 1 cm from both sides of the skin reaction and moving toward...
如图所示,边长为L、不可形变的正方形导线框内有半径为r的圆形磁场区域,其磁感应强度B随时间t的变化关系为B= kt(常量k>0)。回路中滑动变阻器R的最大阻值为R0,滑动片P位于滑动变阻器中央,定值电阻R1=R0、R2=(框及导线电阻不计)。闭合开关S,电压表的示数为U,不考虑虚线MN右侧导体的感应电动势...