(Portland, OR)  --  Portland police have a man in custody in connection with a string of robberies at Plaid Pantry convenience stores.  Authorities say they saw the suspect leave a Plaid Pantry on Northeast 15th Avenue early yesterday morning and jump into a stolen vehicle.  After a brief chase, police say they set out spike strips and stopped the car in the area of Northeast 96th and Sandy Boulevard.  Police say Demarcus Yordell Vance may be connected to as many as five armed robberies at Plaid Pantry stores within a 24-hour period.