Science Advisor to the President War II by President Franklin Delano Roosevelt. Vannevar Bush chaired this office through Roosevelt's death in 1945, and continued under Roosevelt's successor Harry S. Truman until 1951. After the war, President Harry S. Truman replaced the OSRD with the Science Advisory Committee in 1951. The office was moved to the White House on November 21, 1957, by President Dwight D. Eisenhower to provide advice and recommendation in response to the Space Race started by the USSR's launch of the first artificial Earth satellite, Sputnik 1. President Richard M. Nixon eliminated the PSAC in 1973, rather than appointing a replacement for
President of Ukraine by acting president Oleksandr Turchynov, who then also served as Chairman of the Ukrainian Parliament, on 21 February 2014. Oleksandr Turchynov was the only acting president in Ukraine's modern history. Unlike in the US, where the vice president immediately receives all powers of the presidency upon assumption of the presidential office, in Ukraine the powers of an acting president are severely limited. On 18 June 2015, Yanukovych was officially deprived of the title of president of Ukraine. The current president is Petro Poroshenko who took the oath of office on 7 June 2014. The Government of Ukraine utilizes a Semi-presidential