IntroductionInterferon-gamma release assays (IGRAs) have been promoted as having a key role in contact tracing for tuberculosis (TB). In immunosuppressed patients T-SPOT is considered to be the test of choice for detection of latent TB infection. We describe a contact tracing exercise carried out...
钢球自由下落过程中,先后通过光电门A、B,计时装置测出钢球通过A、B的时间分别为tA、tB.用钢球通过光电门的平均速度表示钢球球心通过光电门的瞬时速度.测出两光电门间的距离为h,钢球直径为D,当地的重力加速度为g. (1)用20分度的游标卡尺测量钢球的直径,读数如图乙所示,钢球直径为D=cm....