 Complete the following phrase:  Silver was nominated by President Bill Clinton on September 14, 1994, to a seat on the United States District Court for the District of Arizona vacated by Earl H. Carroll. She was confirmed by the United States Senate on October 7, 1994, and received her commission on October 11, 1994. She took senior status on September 3, 2013. Silver became Chief Judge in January 2011 after the shooting death of previous Chief Judge John Roll during the 