Late last month, Sergei Khrushchev, Russian scholar, scientist, and son of Soviet leader Nikita Khrushchev, died at age 84 in his home in Rhode Island. In addition to his half century in the Soviet Union, where he was born and educated, the younger Khrushchev spent almost 30 years here as a naturalized U.S. citizen. During that time, he established himself as a preeminent authority on U.S.-Russia relations and Cold War history, writing several books on the subject, lecturing across the country, and serving in distinguished positions at some of the nation’s top colleges, including Brown and Harvard University.