( ( Liquid nitrogen ) ( ( is ( used ( for cooling ) ) ) . ) )
(ROOT (S (NP (NN Liquid) (NN nitrogen)) (VP (VBZ is) (VP (VBN used) (PP (IN for) (S (VP (VBG cooling)))))) (. .)))
Liquid nitrogen is used for cooling.
(ROOT (S (NP (NN Liquid) (NN nitrogen)) (VP (VBZ is) (VP (VBN used) (PP (IN for) (NP (NP (VBG cooling) (NNS detectors)) (PP (IN of) (NP (JJ infrared) (NNS telescopes))))))) (. .)))