( circadian ( ( rhythms ( ( ( ( ( the ( regular recurrence ) ) , ) ( in ( cycles ( of ( ( about 24 ) hours ) ) ) ) ) , ) ( of ( ( biological ( ( processes or ) activities ) ) ( especially ( known ( in sleep ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NN circadian)) (VP (VBZ rhythms) (NP (NP (DT the) (JJ regular) (NN recurrence)) (, ,) (PP (IN in) (NP (NP (NNS cycles)) (PP (IN of) (NP (QP (RB about) (CD 24)) (NNS hours))))) (, ,) (PP (IN of) (NP (NP (JJ biological) (NNS processes) (CC or) (NNS activities)) (VP (ADVP (RB especially)) (VBN known) (PP (IN in) (NP (NN sleep)))))))) (. .)))
circadian rhythms the regular recurrence, in cycles of about 24 hours, of biological processes or activities especially known in sleep.
(ROOT (S (NP (NP (JJ Regular) (NNS changes)) (PP (IN in) (NP (NN biology) (CC or) (NN behavior))) (SBAR (WHNP (WDT that)) (S (VP (VBP occur) (PP (IN in) (NP (DT a) (CD 24) (NN hour) (NN cycle))))))) (VP (VBP are) (NP (NP (NN part)) (PP (IN of) (NP (DT the) (NN circadian) (NN rhythm))))) (. .)))