CEDAR RAPIDS — A Minnesota man pleaded not guilty Tuesday to attempting to have sex with two Iowa teens after responding to an online ad from an undercover agent posing as a sex trafficker of minors. Terrance D. Nordwall, 50, of Faribault, Minn., was charged in U.S. District Court last week with one count each of attempted sex trafficking of children, attempted enticement of minors and travel for the purpose of engaging in illicit sexual conduct.A search warrant affidavit shows a Homeland Security Investigations agent placed an internet ad March 25 posing as a trafficker of minors in the Twin Cities and provided a phone number to contact him.