COUNCIL BLUFFS, Iowa (AP) – Authorities are crediting a federal DNA database for nabbing a Nebraska sex offender in a 10-year-old Iowa sexual assault case.   The Council Bluffs Nonpareil reports that Mark Sands, a registered sex offender from Omaha, Neb., pleaded guilty to third-degree kidnapping and third-degree sexual assault before his trial in Pottawattamie County was set to begin Tuesday. He had been charged with first- and second-degree kidnapping, burglary, sexual abuse and three assault charges for a 2001 home invasion in which a Council Bluffs mother was raped and beaten and her 16-year-old disabled daughter tied up.  Sands was sentenced Tuesday to 10 years in prison.  The 51-year-old Sands was arrested last year after police said the national DNA database identified him as the man who raped the woman in October 2001.