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21 Crookes, Sir William
SUBJECT AREA: Electricity[br]b. 17 June 1832 London, Englandd. 4 April 1919 London, England[br]English chemist and physicist who carried out studies of electrical discharges and cathode rays in rarefied gases, leading to the development of the cathode ray tube; discoverer of the element thallium and the principle of the Crookes radiometer.[br]Crookes entered the Royal College of Chemistry at the age of 15, and from 1850 to 1854 held the appointment of Assistant at the college. In 1854 he became Superintendent of the Meteorological Department at the Radcliffe Observatory in Oxford. He moved to a post at the College of Science in Chester the following year. Soon after this he inherited a large fortune and set up his own private laboratory in London. There he studied the nature of electrical discharges in gases at low pressure and discovered the dark space (later named after him) that surrounds the negative electrode, or cathode. He also established that the rays produced in the process (subsequently shown by J.J.Thompson to be a stream of electrons) not only travelled in straight lines, but were also capable of producing heat and/or light upon impact with suitable anode materials. Using a variety of new methods to investigate these "cathode" rays, he applied them to the spectral analysis of compounds of selenium and, as a result, in 1861 he discovered the element thallium, finally establishing its atomic weight in 1873. Following his discovery of thallium, he became involved in two main lines of research: the properties of rarified gases, and the investigation of the elements of the "rare earths". It was also during these experiments that he discovered the principle of the Crookes radiometer, a device in which light is converted into rotational motion and which used to be found frequently in the shop windows of English opticians. Also among the fruits of this work were the Crookes tubes and the development of spectacle lenses with differential ranges of radiational absorption. In the 1870s he became interested in spiritualism and acquired a reputation for his studies of psychic phenomena, but at the turn of the century he returned to traditional scientific investigations. In 1892 he wrote about the possibility of wireless telegraphy. His work in the field of radioactivity led to the invention of the spinthariscope, an early type of detector of alpha particles. In 1900 he undertook investigations into uranium which led to the study of scintillation, an important tool in the study of radioactivity.While the theoretical basis of his work has not stood the test of time, his material discoveries, observations and investigations of new facts formed a basis on which others such as J.J. Thomson were to develop subatomic theory. His later involvement in the investigation of spiritualism led to much criticism, but could be justified on the basis of a belief in the duty to investigate all phenomena.[br]Principal Honours and DistinctionsKnighted 1897. Order of Merit 1910. FRS 1863. President, Royal Society 1913–15. Honorary LLD Birmingham. Honorary DSc Oxon, Cambridge, Sheffield, Durham, Ireland and Cape of Good Hope.Bibliography1874, On Attraction and Repulsion Resulting from Radiation.1874, "Researches in the phenomenon of spiritualism", Society of Metaphysics; reprinted in facsimile, 1986.For many years he was also Proprietor and Editor of Chemical News.Further ReadingE.E.Fournier D'Albe, 1923, Life of Sir William Crookes. Who Was Who II, 1916–28, London: A. \& C. Black. T.I.Williams, 1969, A Biographical Dictionary of Scientists. See also Braun, Karl Ferdinand.KF / MG -
22 Yagi, Hidetsugu
[br]b. 28 January 1886 Osaka, Japand. January 1976 Osaka, Japan[br]Japanese engineer who, with his student Shintaro Uda, developed the directional ultra-high frequency (UHF) aerial array that bears his name.[br]Yagi studied engineering at Tokyo Imperial University (now Tokyo University), graduating in 1910. For the next four years he taught at Engineering High School in Sendai, Honshu, then in 1914 he was sent to study resonance phenomena under Barkhausen at Dresden University. When the First World War broke out he was touring Europe, so he travelled to London to study under Ambrose Fleming at University College, London. Continuing his travels, he then visited the USA, studying at Harvard under G.W. Pierce, before returning to his teaching post at Sendai Engineering High School, which in 1919 was absorbed into Tohoku University. There, in 1921, he obtained his doctorate, and some years later he was appointed Professor of Electrical Engineering. Having heard of the invention of the magnetron, he worked with a student, Kinjiro Okabe; in 1927 they produced microwave energy at a wavelength of a few tens of centimetres. However, he is best known for his development with another student, Shintaro Uda, of a directional, multi-element ultrahigh frequency aerial, which he demonstrated during a tour of the USA in 1928. During the Second World War Yagi worked on radar systems. After his retirement he became Professor Emeritus at Tohoku and Osaka universities and formed the Yagi Antenna Company.[br]Principal Honours and DistinctionsYagi received various honours, including the Japanese Cultural Order of Merit 1976, and the Valdemar Poulsen Gold Medal.Bibliography1928, "Beam transmission of ultra-short waves", Proceedings of the Institute of Radio Engineers 6:715 (describes the Yagi-Uda aerial).Further ReadingF.E.Terman, 1943, Radio Engineers' Handbook, New York: McGraw-Hill (provides a review of aerials, including the Yagi system).KF
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