( ( Nuclear reactors ) ( ( ( produce heat ) ( through ( ( the ( controlled ( chain reactions ) ) ) ( of ( nuclear fission ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Nuclear) (NNS reactors)) (VP (VBP produce) (NP (NN heat)) (PP (IN through) (NP (NP (DT the) (JJ controlled) (NN chain) (NNS reactions)) (PP (IN of) (NP (JJ nuclear) (NN fission)))))) (. .)))
Nuclear reactors produce heat through the controlled chain reactions of nuclear fission .
(ROOT (S (NP (NNP Control) (NNS rods)) (VP (VBP play) (NP (NP (DT an) (JJ important) (NN role)) (PP (IN in) (NP (NP (DT the) (NN modulation)) (PP (IN of) (NP (DT the) (JJ nuclear) (NN chain) (NN reaction))))))) (. .)))