a nasty aftertaste but little clear memory of its operational mechanics 
(ROOT (NP (NP (DT a) (JJ nasty) (NN aftertaste)) (CC but) (NP (NP (JJ little) (JJ clear) (NN memory)) (PP (IN of) (NP (PRP$ its) (JJ operational) (NN mechanics))))))
(ROOT (NP (NP (DT ) (JJ ) (NN )) (CC ) (NP (NP (JJ ) (JJ ) (NN )) (PP (IN ) (NP (PRP$ ) (JJ ) (NN ))))))