Whereas the engines in propeller-powered aircraft generally achieve their maximum efficiency at much lower speeds and altitudes, jet engines and aircraft achieve maximum efficiency (see specific impulse) at speeds close to or even well above the speed of sound. Jet aircraft generally cruise at faster than about M 0.8 (609mph, 981km/h or 273m/s) at altitudes around 10,000–15,000 metres (33,000–49,000ft) or more.
Frank Whittle, an English inventor and RAF officer, developed the concept of the jet engine in 1928,Hans von Ohain in Germany, a decade later developed the concept independently at the end of the 1930s. He wrote in February 1936 to Ernst Heinkel, telling him of the design and its possibilities. However, it can be argued that the English engineer A. A. Griffith, who published a paper in July 1926 on compressors and turbines, also deserves credit.
Uzbekistan (USi/ʊz.ˈbɛk.ɪ.ˌstæn/, UK/ʊz.ˌbɛk.ɪ.ˈstɑːn/), officially the Republic of Uzbekistan (Uzbek: Oʻzbekiston Respublikasi/Ўзбекистон Республикаси), is a doubly landlocked country in Central Asia. It is a unitary, constitutional, presidential republic, comprising 12 provinces, 1 autonomous republic, and 1 capital city. Uzbekistan is bordered by five countries: Kazakhstan to the north; Tajikistan to the southeast; Kyrgyzstan to the northeast; Afghanistan to the south; and Turkmenistan to the southwest.
Once part of the Turkic Khaganate and later Timurid Empires, the region that today includes the Republic of Uzbekistan was conquered in the early 16th century by Eastern Turkic-speaking nomads. The area was gradually incorporated into the Russian Empire during the 19th century, and in 1924 what is now Uzbekistan became a bordered constituent republic of the Soviet Union, known as the Uzbek Soviet Socialist Republic (Uzbek SSR). Following the breakup of the Soviet Union, it declared independence as the Republic of Uzbekistan on 31 August 1991 (officially celebrated the following day).
Karimova-Tillyaeva earned bachelor's and master's degrees in International Law from the University of World Economy and Diplomacy in Tashkent, and later received a doctorate degree in Psychology from Tashkent State University. In January 2008 she was appointed to her current role as Uzbekistan's Permanent Delegate to UNESCO. She is married to businessman Timur Tillyaev and they have three children: two daughters and a son (Mariam, Safia and Umar).
In July 2013, various media outlets reported that Karimova-Tillyaeva had purchased a home in Beverly Hills.
In an interview with the BBC Uzbek Service in 2013, Karimova-Tillyaeva stated that she had not been in contact with her sister Gulnara for 12 years and that "There are no family or friendly relations between us...We are completely different people."