U.S. researchers say that a new class of topical creams for impotence may be more effective than pills such as Viagra. The new cream include nanoparticles of the anti-impotence chemical nitric oxide, which are absorbed immediately into the skin. In a recent animal study, the cream appeared effective on five out of seven animals. And researchers say the benefit of applying the cream only where it's needed is that it reduces the side effects that can be caused by system-wide absorption from a...