(Portland, OR)  --  Federal agents say they've arrested a Portland man in connection with a child sex-trafficking case.  The FBI says 33-year-old Aaron Barnes was arrested earlier this week at a motel in Lincoln, Nebraska.  Authorities say they're looking for a second suspect in the case, who's identified as 28-year-old Kamau Curnal.  KATU-TV reports both men were indicted last month for sex trafficking of a child and transportation of a minor with the purpose of prostitution.