Sentence:  The impact rate on 1958 Alpha for 153 events was * * f for particles of mass greater than * * f ( Dubin , 1960 ) ; this mass threshold was derived from the <WSD>detector</WSD> calibration and an assumed impact velocity of * * f . 
Meaning of the word marked with <WSD> tags:  any device that receives a signal or stimulus (as heat or pressure or light or motion etc.) and responds to it in a distinctive manner