sentences:  He graduated from the Physics Department of Tsinghua in June 1929, and served as an assistant professor from 1929 to 1930.In his thesis ""On the daily change of radon gas"" (《清华园周围氡气的强度及每天的变化》), he was the first Chinese scientist to publish on atmospheric research and radioactive experiments.In 1930 he went to study at the University of Berlin in Germany.