Amino acid requirements for growth of two isolates of Chlamydia pneumoniae were studied and compared with those for one strain of Chlamydia trachomatis in a HeLa 229 cell culture. It was shown that among 13 amino acids in Eagle minimum essential medium, C. pneumoniae required all amino acids except lysine. A true requirement for arginine, isoleucine, leucine, threonine, and valine could not be ...

Dominoes is a popular and well-known game possibly dating back three millennia. Players are given a set of domino tiles, each with two labeled square faces, and take turns connecting them into a growing chain of dominoes by matching identical faces. We show that singleplayer dominoes is in P, while multiplayer dominoes is hard: when players cooperate, the game is NP-complete, and when players c...