a/u ablaut

As for the a/u alternation, I wonder if the original vowel was a nasal /a,/; /a,/ -> /u/ is known from Russian, /a,/ -> /a/ would be no sensation, positing an original /a,/ in *akW-/*ap-/*up- (*a,kW-? *a,n,W-?) would explain the occasional nasal reflex in that word, and an original *stra,n,W- would explain the /u:/ of stru:ctus.


Torsten