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  1. Math

    A Magic Knight’s Tour

    For as long as chessboards have existed, there have been puzzles involving chessboards and chess pieces. Some of the most enduring conundrums involve knights. Example of a knight’s tour in which the rows and columns have the same sum (260), but the diagonals add up to 348 and 168. According to the rules of chess, […]

    By Ivars Peterson
  2. Health & Medicine

    Coronary Fix: Coated inserts keep vessels unclogged

    Mesh cylinders called stents, which doctors use to prop open coronary arteries, work better when they are coated with sirolimus, a drug that inhibits the accumulation of cells along the device.

    By Nathan Seppa
  3. Planetary Science

    News Splash: Strong evidence of lakes on Titan

    Using Earth-based radar to penetrate the thick atmosphere of Saturn's moon Titan, planetary scientists have the best evidence yet that the smog-shrouded moon has lakes or oceans of hydrocarbons over large stretches of its surface.