Exhibit 24.5

POWER OF ATTORNEY

               KNOW ALL MEN BY THESE PRESENTS, that the person's name whose signature appears below constitutes and appoints Marc W. Eller and Douglas P. Baker, and each of either of them, his true and lawful attorney-in-fact and agent, with full power of substitution and resubstitution, for him and in his name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this Registration Agreement and any subsequent registration statements relating to the offering to which this Registration Statement relates, and to file the same, with all exhibits thereto and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully and to intents and purposes as he might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or either of them, or their or his substitutes or substitute, may lawfully do or cause to be done by virtue hereof.

/s/ Robert Ronstadt            
Robert Ronstadt