Vladimir Valentinovich Alexandrov was a Soviet/Russian physicist who created a mathematical model for the nuclear winter theory. He disappeared while at a conference on "nuclear-free zones" in Cordoba, Spain on March 31 and his ultimate fate remains unknown, with much speculation continuing. Wikipedia*
On the C-SPAN Networks:
Vladimir Alexandrov has one video in the C-SPAN Video Library; the first appearance was a 2013 Speech.