▁he ▁was ▁at ▁the ▁Institut ▁Univers itaire ▁de ▁France . ▁He ▁is ▁today ▁at ▁the ▁Labor atoire ▁J . ▁A . ▁Die ud onn é ▁of ▁the ▁University ▁of ▁Nice . ▁( The ▁Labor atoire ▁J . ▁A . ▁D ied onn é ▁is ▁a ▁ ▁( UM R ) ▁of ▁the ▁C N RS .) ▁ ▁He ▁was ▁also ▁from ▁ 1 9 7 0 ▁to ▁ 1 9 8 5 ▁Ma ître ▁de ▁conf ér ences ▁at ▁the ▁É cole ▁Poly te chni que . ▁ ▁He ▁was ▁a ▁visit ing ▁professor ▁at ▁the ▁University ▁of ▁Minnesota ▁( 1 9 7 7 / 7 8 ), ▁at ▁the ▁University ▁of ▁California , ▁Ber keley ▁( 1 9 7 8 ), ▁and ▁at ▁the ▁University ▁of ▁Stuttgart ▁( 1 9 9 0 , ▁ 1 9 9 5 , ▁ 1 9 9 7 ), ▁where ▁he ▁collabor ated ▁with ▁Klaus ▁Kirch g ä ss ner ▁on ▁revers ible ▁dynam ical ▁systems . ▁ ▁Io oss ' s ▁research ▁de als ▁with ▁functional ▁analysis ▁of ▁the ▁Nav ier - Sto kes ▁equation , ▁non linear ▁hyd rod ynamic ▁stability ▁theory ▁and ▁water ▁waves ▁of ▁different ▁kinds , ▁and ▁general ▁behavior ▁( such ▁as ▁symmetry ▁breaking ▁and ▁normal ▁forms ) ▁of ▁b if ur c ations ▁( branch ing ▁of ▁solutions ) ▁in ▁dynamic ▁systems . ▁In ▁ 1 9 7 1 , ▁independently ▁of ▁David ▁H . ▁S att inger , ▁he ▁treated ▁the ▁H opf ▁b if ur cation ▁in ▁solutions