OMAHA, Neb. — Union Pacific announced several executive assignments effective Jan. 1: Dennis J. Duffy, currently executive vice president – Operations, will become vice chairman – Operations of the Union Pacific Railroad, remaining as the senior operations executive of the company. Lance M. Fritz, currently vice president – Labor Relations, will become vice president – Operations of the railroad, reporting to Duffy. William R. (Rick) Turner, currently assistant vice president – Labor Relations, will succeed Fritz as vice president – Labor Relations. Robert M. Grimaila, currently senior assistant vice president – Safety, Security and Environment, will be named vice president