HARARE (Reuters) - Zimbabwe President Robert Mugabe arrived at a university graduation ceremony in the capital on Friday, his first public appearance since a military seizure of power that political sources say is aimed at ending his 37 years in office. Wearing a blue and yellow academic gown and mortar board hat, the 93-year-old sat in large wooden chair at the front the hall. He was greeted by ululations from the crowd as he declared the ceremony open. 