The Physics
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Angular Speed of a Medical Centrifuge

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Schraer, William. Biology: The Study of Life. Englewood, NJ: Prentice Hall, 1991: 26. "The ultracentrifuge is much more powerful than a regular centrifuge. It spins at rates from 40,000 to 100,000 revolutions per minute." 40,000โ€“100,000 rpm
"Centrifuges turn from 800 to 6,000 times per minute." 800โ€“6,000 rpm
Cooper, Leon. Centrifuge. 1999: 357-358. "The ultracentrifuge is a newer kind of centrifuge with tremendous speed. It can spin around 80,000 turns per minute." 80,000 rpm
Laboratory Chromatography Spectroscopy Centrifugation. Kontron Instruments. 1996. "High Speed Centrifuges with speeds up to 20,000 rpm in a bench-top model." 20,000 rpm
Brooks & Tracy. Modern Physical Science. New York: Holt, 1957: 169. "One kind of centrifuge has been spun at 2,500,000 revolutions per minute." 2,500,000 rpm
Bloomfield, Victor. "Ultracentrifuge." McGraw Hill Encyclopedia of Science and Technology. New York: McGraw Hill, 1997: 3. "The most commonly used analytical ultracentrifuge can be run at speeds between about 2,000 and 60,000 revolutions per minute." 2,000โ€“60,000 rpm

Centrifuges are machines that rapidly spin fluids to separate substances of different densities by using centrifugal force to produce a form of artificial gravity. A very high speed centrifuge is called an ultracentrifuge. According to some companies that make centrifuges, the most commonly used medical centrifuge is a bench-top ultracentrifuge. The ultracentrifuge is widely used in the study of polymers, proteins, nucleic acids, viruses, and other organic macromolecules.Ultracentrifuges are used in biological and chemical laboratories and in medicine to prepare serums and plasma from blood. Ultracentrifuges are also used to separate gases and in the determination of molecular weights. This technique is used to separate uranium-235 for use in nuclear reactors.

The ultracentrifuge is balanced on a cushion of air and spins because a jet of compressed air touches the outer surface. An ultracentrifuge consists of a rotor, cell, drive mechanism, and temperature control. These parts are designed to achieve high centrifugal accelerations. A rotor of a typical ultracentrifuge is eighteen centimeters in diameter and carries ten ounces of liquid in a centrifugal field. The rotor spins in air or another type of gas at atmospheric pressure. The friction between the gas and the spinning of the rotor increases rapidly causing the power needed to drive the rotor to increase rapidly. This increase causes the temperature of the rotor to rise. This is where the temperature control device comes in. If the temperature rises too much it can cause the substance in the tube to remix and disturb sedimentation. Temperature control allows ultracentrifuges to have high rotational speeds.

Arika Bryant -- 1999

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