(19)

(11)

EP 0 540 694 A1

(12)

(43) Date of publication: 12.05.1993 Bulletin 1993/19 (21) Application number: 91917280.0 (22) Date of filing: 05.11.1990

(51) International Patent Classification (IPC):  G21B 3/ 00( . ) (86) International application number: PCT/US1990/006419 (87) International publication number: WO 1992/002020 (06.02.1992 Gazette 1992/04)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB IT LI LU NL SE (30) Priority: 20.07.1990 WO 1990US04122 (71) Applicant: UNIVERSITY OF HAWAII Honolulu, Hawaii 96822 (US)	(72) Inventors: LIEBERT, Bruce, E. Honolulu, HI 96822 (US) LIAW, Bor, Yann Honolulu, HI 96813 (US) (74) Representative: Pidgeon, Robert John, et al  Appleyard Lees & Co. 15 Clare Road Halifax West Yorkshire HX1 2HY Halifax West Yorkshire HX1 2HY (GB)