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Ultracentrifuge
An ultracentrifuge is a centrifuge optimized for spinning a rotor at very high speeds, capable of generating acceleration as high as (approx. ). There are two kinds of ultracentrifuges, the preparative and the analytical ultracentrifuge. Both classes of instruments find important uses in molecular biology, biochemistry, and polymer science.Susan R. Mikkelsen & Eduardo Cortón. Bioanalytical Chemistry, Ch. 13. Centrifugation Methods. John Wiley & Sons, Mar 4, 2004, pp. 247-267. History In 1924 Theodor Svedberg built a centrifuge capable of generating 7,000 g (at 12,000 rpm), and called it the ultracentrifuge, to juxtapose it with the Ultramicroscope that had been developed previously. In 1925-1926 Svedberg constructed a new ultracentrifuge that permitted fields up to 100,000 g (42,000 rpm). Modern ultracentrifuges are typically classified as allowing greater than 100,000 g. Svedberg won the Nobel Prize in Chemistry in 1926 for his research on colloids and proteins using the ultrac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Analytical Ultracentrifugation
Analytical ultracentrifugation is an analytical technique which combines an ultracentrifuge with optical monitoring systems. In an analytical ultracentrifuge (commonly abbreviated as AUC), a sample’s sedimentation profile is monitored in real time by an optical detection system. The sample is detected via ultraviolet light absorption and/or interference optical refractive index sensitive system, monitored by light-sensitive diode array or by film in the older machines. The operator can thus observe the change of sample concentration versus the axis of the rotation profile with time as a result of the applied centrifugal field. With modern instrumentation, these observations are electronically digitized and stored for further mathematical analysis. The information that can be obtained from an analytical ultracentrifuge includes the gross shape of macromolecules, conformational changes in macromolecules, and size distributions of macromolecules. With AUC it is possible to gain info ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theodor Svedberg
Theodor Svedberg (30 August 1884 – 25 February 1971) was a Swedish chemist and Nobel laureate for his research on colloids and proteins using the ultracentrifuge. Svedberg was active at Uppsala University from the mid 1900s to late 1940s. While at Uppsala, Svedberg started as a docent before becoming the university's physical chemistry head in 1912. After leaving Uppsala in 1949, Svedberg was in charge of the Gustaf Werner Institute until 1967. Apart from his 1926 Nobel Prize, Svedberg was named a Foreign Member of the Royal Society in 1944 and became part of the National Academy of Sciences in 1945. Early life and education Svedberg was born in Valbo, Sweden on 30 August 1884. He was the son of Augusta Alstermark and Elias Svedberg. Growing up, Svedberg enjoyed botany and other branches of science. While in grammar school, Svedberg conducted individual laboratorial research and performed scientific demonstrations. For his post-secondary education, Svedberg entered a c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centrifuge
A centrifuge is a device that uses centrifugal force to separate various components of a fluid. This is achieved by spinning the fluid at high speed within a container, thereby separating fluids of different densities (e.g. cream from milk) or liquids from solids. It works by causing denser substances and particles to move outward in the radial direction. At the same time, objects that are less dense are displaced and moved to the centre. In a laboratory centrifuge that uses sample tubes, the radial acceleration causes denser particles to settle to the bottom of the tube, while low-density substances rise to the top. A centrifuge can be a very effective filter that separates contaminants from the main body of fluid. Industrial scale centrifuges are commonly used in manufacturing and waste processing to sediment suspended solids, or to separate immiscible liquids. An example is the cream separator found in dairies. Very high speed centrifuges and ultracentrifuges able to prov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beckman Coulter
Beckman Coulter Inc. is a Danaher Corporation company that develops, manufactures, and markets products that simplify, automate and innovate complex biomedical testing. It operates in two industries: Diagnostics and Life Sciences. For more than 80 years, Beckman Coulter Inc. has helped healthcare and laboratory professionals, pharmaceutical and biotechnology companies, universities, medical schools, and research institutions worldwide. The company eventually grew to employ over 12,000 people, with $5.8 billion in annual sales by 2017. It is currently headquartered in Brea, California. Beckman Coulter was acquired by Danaher Corporation in 2011. History Founded by Caltech professor Arnold O. Beckman in 1935 as National Technical Laboratories to commercialize a pH meter that he had invented. In the 1940s, Beckman changed the name to Arnold O. Beckman, Inc. to sell oxygen analyzers, the ''Helipot'' precision potentiometer, and spectrophotometers. In the 1950s, the company ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beckman Instruments
Beckman Coulter Inc. is a Danaher Corporation company that develops, manufactures, and markets products that simplify, automate and innovate complex biomedical testing. It operates in two industries: Diagnostics and Life Sciences. For more than 80 years, Beckman Coulter Inc. has helped healthcare and laboratory professionals, pharmaceutical and biotechnology companies, universities, medical schools, and research institutions worldwide. The company eventually grew to employ over 12,000 people, with $5.8 billion in annual sales by 2017. It is currently headquartered in Brea, California. Beckman Coulter was acquired by Danaher Corporation in 2011. History Founded by Caltech professor Arnold O. Beckman in 1935 as National Technical Laboratories to commercialize a pH meter that he had invented. In the 1940s, Beckman changed the name to Arnold O. Beckman, Inc. to sell oxygen analyzers, the ''Helipot'' precision potentiometer, and spectrophotometers. In the 1950s, the company name c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Centrifuge
A gas centrifuge is a device that performs isotope separation of gases. A centrifuge relies on the principles of centrifugal force accelerating molecules so that particles of different masses are physically separated in a gradient along the radius of a rotating container. A prominent use of gas centrifuges is for the separation of uranium-235 (235U) from uranium-238 (238U). The gas centrifuge was developed to replace the gaseous diffusion method of uranium-235 extraction. High degrees of separation of these isotopes relies on using many individual centrifuges arranged in series, that achieve successively higher concentrations. This process yields higher concentrations of uranium-235 while using significantly less energy compared to the gaseous diffusion process. Centrifugal process The centrifuge relies on the force resulting from centrifugal acceleration to separate molecules according to their mass, and can be applied to most fluids. The dense (heavier) molecules move towards ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catastrophic Failure
A catastrophic failure is a sudden and total failure from which recovery is impossible. Catastrophic failures often lead to cascading systems failure. The term is most commonly used for structural failures, but has often been extended to many other disciplines in which total and irrecoverable loss occurs, such as a head crash occurrence on a hard disk drive. Such failures are investigated using the methods of forensic engineering, which aims to isolate the cause or causes of failure. For example, catastrophic failure can be observed in steam turbine rotor failure, which can occur due to peak stress on the rotor; stress concentration increases up to a point at which it is excessive, leading ultimately to the failure of the disc. In firearms, catastrophic failure usually refers to a rupture or disintegration of the barrel or receiver of the gun when firing it. Some possible causes of this are an out-of-battery gun, an inadequate headspace, the use of incorrect ammunition, the use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kinetic Energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body when decelerating from its current speed to a state of rest. Formally, a kinetic energy is any term in a system's Lagrangian which includes a derivative with respect to time. In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2. In relativistic mechanics, this is a good approximation only when ''v'' is much less than the speed of light. The standard unit of kinetic energy is the joule, while the English unit of kinetic energy is the foot-pound. History and etymology The adjective ''kinetic'' has its roots in the Greek word κίνησι� ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caesium
Caesium ( IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that are liquid at or near room temperature. Caesium has physical and chemical properties similar to those of rubidium and potassium. It is pyrophoric and reacts with water even at . It is the least electronegative element, with a value of 0.79 on the Pauling scale. It has only one stable isotope, caesium-133. Caesium is mined mostly from pollucite. The element has 40 known isotopes, making it, along with barium and mercury, one of the elements with the most isotopes. Caesium-137, a fission product, is extracted from waste produced by nuclear reactors. The German chemist Robert Bunsen and physicist Gustav Kirchhoff discovered caesium in 1860 by the newly developed method of flame spectroscopy. The first small-scale applications fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sucrose
Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refined from either sugarcane or sugar beet. Sugar mills – typically located in tropical regions near where sugarcane is grown – crush the cane and produce raw sugar which is shipped to other factories for refining into pure sucrose. Sugar beet factories are located in temperate climates where the beet is grown, and process the beets directly into refined sugar. The sugar-refining process involves washing the raw sugar crystals before dissolving them into a sugar syrup which is filtered and then passed over carbon to remove any residual colour. The sugar syrup is then concentrated by boiling under a vacuum and crystallized as the final purification process to produce crystals of pure sucrose that are clear, odorless, and sweet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gradient
In vector calculus, the gradient of a scalar-valued differentiable function of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p is the "direction and rate of fastest increase". If the gradient of a function is non-zero at a point , the direction of the gradient is the direction in which the function increases most quickly from , and the magnitude of the gradient is the rate of increase in that direction, the greatest absolute directional derivative. Further, a point where the gradient is the zero vector is known as a stationary point. The gradient thus plays a fundamental role in optimization theory, where it is used to maximize a function by gradient ascent. In coordinate-free terms, the gradient of a function f(\bf) may be defined by: :df=\nabla f \cdot d\bf where ''df'' is the total infinitesimal change in ''f'' for an infinitesimal displacement d\bf, and is seen to be maximal when d\bf is in the direction of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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