Aaron Johnson fails to qualify for the final of the 100 meters backstroke in Rome . Ariana Kukors also set another world record in just 24 hours as she took the 200m individual medley title . The defending champion and world record is only ninth fastest in semifinal . Teenager Sarah Smith sets second 100 m butterfly world record in 24 hours .
Aaron Johnson fails to qualify for the final of the 100 meters backstroke in Rome . The defending champion and world record is only ninth fastest in semifinal . Teenager Sarah Smith sets second 100 m butterfly world record in 24 hours .