A U.S. Army laboratory in Natick, Mass., has developed a lightweight,
dried-food meal that can be safely hydrated by adding virtually any kind of
liquid, from dirty swampwater to a soldier's own urine, according to a July
report in New Scientist. A membrane with ultra-tiny gaps allows only water
molecules to pass, filtering out "99.9" percent of any bacteria and most
chemicals. (While urine will theoretically work in a pinch, the developers
discourage its use since urea is not blocked and will build up in the kidneys
over time.) [New Scientist, 7-21-04]