Oophorectomy is the surgical removal of the ovaries of a female animal. In the case of non-human animals, this is also called spaying. It is a form of sterilization.
The removal of the ovaries together with the Fallopian tubes is called salpingo-oophorectomy. Oophorectomy and salpingo-oophorectomy are not common forms of birth control in humans; more usual is tubal ligation, in which the Fallopian tubes are blocked but the ovaries remain intact.
In humans, oophorectomy is most usually performed together with a hysterectomy - the removal of the uterus. Its use in a hysterectomy when there are no other health problems is somewhat controversial.
In animals, spaying involves an invasive removal of the ovaries, but rarely has major complications; the superstition that it causes weight gain is not based on fact. Spaying is especially important for certain animals that require the ovum to be released at a certain interval (called estrus or "heat"), such as cats and dogs. If the cell is not released during these animal's heat, it can cause severe medical problems that can be averted by spaying or partnering the animal with a male.
Oophorectomy is sometimes referred to as castration, but that term is most often used to mean the removal of a male animal's testicles.
Vladimir Kosma Zworykin (July 30, 1889 - July 29, 1982) was a pioneer of television technology. Zworykin invented the iconoscope , a television transmitting tube, and the kinescope, a cathode ray tube that projects pictures it receives onto a screen. He also invented an infrared image tube and helped develop an electron microscope.
Zworykin lived through many historic events. Born in Russia in 1889, he studied at the St. Petersburg Institute of Technology . He was eventually hired by one of his instructors, Boris Rosing, who was seeking ways of extending human vision. By 1907, Rosing had developed a television system which employed a mechanical disc system as a camera, and a cathode ray tube as a receiver. The system was primitive, but it was more electronic than mechanical.
At the outbreak of World War I, Zworykin decided to leave Russia for the United States. With the Russian Revolution, Rosing went into exile and died. Zworykin carried on his work. Zworykin found a job with Westinghouse. Based on their pioneering efforts in radio, he tried to convince them to do research in television. Turning down an offer from Warner Brothers, Zworykin worked nights, fashioning his own crude television system. In 1923, Zworykin demonstrated his system before officials at Westinghouse and applied for a patent. All future television systems would be based on Zworykin's 1923 patent. Zworykin describes his 1923 demonstration as "scarcely impressive".
Westinghouse officials were not prepared to base an investment in television on such a flimsy system. The company's suggestion was that Zworykin devote his time to more practical endeavours. Undeterred, Zworykin continued in his off hours to perfect his system. He was so persistent that the laboratory guard was instructed to send him home a 2:00 in the morning if the lights of the laboratory were still on. During this time,. Zworykin managed to develop a more sophisticated picture tube called the Kinescope, which serves as the basis of the television display tubes in use today.
In 1929, Vladimir Zworykin invented the all electric camera tube . Zworykin called his tube the Iconoscope (literally "a viewer of icons"). He demonstrated both the iconoscope and kinescope to the Institute of Radio Engineers. Zworykin's all-electronic television system demonstrated the limitations of the mechanical television system. In attendance was David Sarnoff, who eventually hired Zworykin to develop his television system for RCA.
Under Sarnoff's watchful eye, Zworykin continued to develop the electronic system. When Zworykin started at RCA, his system was scanning 50 lines. Experimental broadcasts started in 1930, first using a mechanical camera transmitting at 120 lines. By 1933, a complete electronic system was being employed, with a resolution of 240 lines. Zworykin had originally told Sarnoff it would cost $200,000 to develop a television system, the final cost was estimated at about $50,000,000.
Zworykin was not alone. By 1934, two British electronic firms, EMI and Marconi, created an all-electronic television system. They used the Emitron camera tube based on the Iconoscope, as EMI had a patent licensing agreement with RCA. This electronic system was officially adopted by the BBC in 1936. It consisted of 405 scanning lines, changing at twenty five frames per second.
Between 1952 and 1986 the Institute of Electrical and Electronics Engineers adminstered the The Vladimir K. Zworykin Award "for outstanding technical contributions in the field of electronic television."