A Harvard physicist has concluded that superconductors generate an unanticipated resistance that jeopardizes some of their most highlytouted applications, and he will present some of his latest findings in a soon-to-be published article.

Rumford Professor of Physics Michael Tinkham has developed a theory during the last several months which predicts that using hightemperature superconductors to economize on transporting electricity will be a more difficult task than previously thought.

"My conclusion is that this [resistance] is enough to cause serious difficulty in using [the superconductors] to construct magnets," said Tinkham, who has spent three decades studying superconductors. "It's nothing wildly revolutionary, although I think most people don't understand it."

Tinkham published an early version of his theory in a Swiss journal several months ago, and has written "The Resistive Transition of High Temperature Superconductors," which willappear in next week's Physical Review, apublication of the American Physical Society.

To use the high-temperature superconductors tolevitate trains or power super magnets, scientistswill either have to find a way to counter theresistance, or spend energy to cool thesuperconductors down, Tinkham argues.

The superconductors that were first discoveredrequired much cooling before they reached atemperature at which they would work.Superconductors discovered more recently haveworked at higher temperatures, and less energy hasbeen necessary to cool them.

But according to Tinkham's theory, thesehigh-temperature superconductors will be moredifficult to work with than was first thought.

Tinkham said he developed the theory byexamining data produced by laboratories in Japan,at Stanford University, Ohio State University andat IBM.

Tinkham said his theory leaves open thepossibility that superconductors invented in thefuture will generate less resistance than thosewhich exist now