( But ( ( decay rates ) ( ( are ( ( fixed , ) ( resulting ( in ( ( a ( characteristic ( , ( unchanging half-life ) ) ) ) ( for ( ( each isotope ) ( that ( is ( ( the time ) ( ( needed ( for ( one-half ( of ( the isotope ) ) ) ) ) ( to decay ) ) ) ) ) ) ) ) ) ) ) ) . ) ) )
(ROOT (S (CC But) (NP (NN decay) (NNS rates)) (VP (VBP are) (VP (VBN fixed) (, ,) (S (VP (VBG resulting) (PP (IN in) (NP (NP (DT a) (JJ characteristic) (, ,) (JJ unchanging) (NN half-life)) (PP (IN for) (NP (NP (DT each) (NN isotope)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (NP (NP (DT the) (NN time)) (VP (VBN needed) (PP (IN for) (NP (NP (NN one-half)) (PP (IN of) (NP (DT the) (NN isotope))))) (PP (TO to) (NP (NN decay)))))))))))))))) (. .)))
But decay rates are fixed, resulting in a characteristic, unchanging half-life for each isotope that is the time needed for one-half of the isotope to decay.
(ROOT (S (NP (DT The) (NN term) (NN half-life)) (VP (VBZ decribes) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN time)) (VP (VBN required) (PP (IN for) (NP (NP (NN half)) (PP (IN of) (NP (DT the) (JJ original) (NN material))))) (PP (TO to) (NP (NP (NN decay)) (PP (IN in) (NP (DT an) (NN isotope)))))))))) (. .)))