MOSCOW — Soviet scientist Nikolai N. Semyonov, whose work on the mechanism of chemical reactions won him the Nobel Prize in 1956, has died at age 90.
"Soviet science has suffered a heavy loss. A whole epoch in Soviet and world science is associated with Semyonov's name," said an obituary signed by Soviet leader Mikhail Gorbachev and other Soviet leaders and scientists.
The obituary, carried by the Tass news agency, said Semyonov died Thursday.
In 1956, Semyonov shared the Nobel Prize for Chemistry with Cyril Hinshelwood of Oxford, England, for demonstrating that branched and unbranched chain reactions are the general rule in the chemical transformation of matter.
Previously, it was believed that chemical processes followed simple laws and chain reactions were rare exceptions.
The work had applications for the refining of petroleum and natural gases and combustion in internal combustion and jet engines and contributed to theories on nuclear fission.
The Swedish Royal Academy of Sciences noted in its Nobel citation that the two men had done significant work exploring why chain reactions occur "and their importance in connection with the phenomenon of explosion."
Semyonov was nine times awarded the Order of Lenin, the nation's highest honor, and other state and scientific awards. He was a member of several foreign scientific academies and held honorary doctorates from Oxford University, Brussels University, the Polytechnical Institute of Milan and other prestigious schools.