Valerie A. Tumins, 88, a retired University of California at Davis professor who was an expert on Russian history, religion and literature, died Jan. 21 at the Emeritus assisted living facility in Arlington. She had dementia. Dr. Tumins began her academic career at Regis College in Weston, Mass., and then taught at Brown University in Providence, R.I., before becoming a professor in 1965 at the University of California at Davis.