Both Web sites come from Science@NASA, an online source for news and information about NASA-funded research. The first article describes the work of researchers at the Center for Commercial Applications of Combustion in Space, who are developing artificial bones for long-lasting, pain-free hip and knee replacements. These ceramic bones are touted as "so much like the real thing that they could...

Offered through the John Moran Eye Center at the University of Utah, this Web site aims to "summarize the recent advances in knowledge and understanding of the mammalian retina." The Web site is arranged simply in a book-like fashion with chapters headings leading to well-referenced text and illustrations. The information presented is quite comprehensive, and would serve as a useful educational...