The U.S. Department of Health and Human Services announced  Monday that it had found that Dong-Pyou Han, until recently an assistant professor at Iowa State University, falsified results of research he was conducting on a vaccine that could be used to prevent the spread of HIV. The agency found him to have engaged in "intentional spiking" of lab samples, and concluded that the results of these samples prompted considerable interest in the research involved -- including the awarding of more research grants. Han apparently added human blood to samples that were supposed to be rabbit blood, and the additional blood skewed the results, The Des Moines Register  reported. HHS said that Han had admitted his actions. The Register reported that he had resigned from Iowa State and that he could not be reached for comment.