Faced with mounting deficits caused mainly by insufficient state aid to cover all its uninsured patients, officials at Muhlenberg Regional Medical Center in Plainfield said they will close the 130-year-old facility later this year. The Union County hospital plans to file formal papers with the state Department of Health and Senior Services on March 1 seeking the closure. If approved, programs and services will be phased out during a "wind down" period before Muhlenberg finally stops admitting patients.