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Duane's Hypothesis
In 1922, American physicist William Duane presented a discrete momentum-exchange model of the reflection of X-ray photons by a crystal lattice. Duane showed that such a model gives the same scattering angles as the ones calculated via a wave diffraction model, see Bragg's Law. The key feature of Duane's hypothesis is that a simple quantum rule based on the lattice structure alone determines the quanta of momentum that can be exchanged between the crystal lattice and an incident particle. In effect, the observed scattering patterns are reproduced by a model where the possible reactions of the crystal are quantized, and the incident photons behave as free particles, as opposed to models where the incident particle acts as a wave, and the wave then 'collapses' to one of many possible outcomes. Duane argued that the way that crystal scattering can be explained by quantization of momentum is not explicable by models based on diffraction by classical waves, as in Bragg's Law. Duane app ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Duane (physicist)
William Duane (February 17, 1872 – March 7, 1935) was an American physicist who conducted research on radioactivity and X-rays and their usage in the treatment of cancer. He developed the Duane-Hunt Law and Duane's hypothesis. He worked with Pierre and Marie Curie in their University of Paris laboratory for six years and developed a method for generating quantities of radon-222 "seeds" from radium for usage in early forms of brachytherapy. He was a professor at the University of Colorado Boulder, professor-emeritus and chair of biophysics at Harvard University and research fellow of physics at the Harvard Cancer Commission. He received the John Scott Medal and the Comstock Prize in Physics in 1922 and the Leonard Prize of the American Roentgen Ray Society in 1923. Early life and education Duane was born in Philadelphia, Pennsylvania to Charles William and Emma Cushman (Lincoln) Duane. He was a direct descendant of Benjamin Franklin from his father's side. He received an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paul Ehrenfest
Paul Ehrenfest (18 January 1880 – 25 September 1933) was an Austrian theoretical physicist, who made major contributions to the field of statistical mechanics and its relations with quantum mechanics, including the theory of phase transition and the Ehrenfest theorem. He bonded with Albert Einstein on a visit to Prague in 1912 and became a professor in Leiden, where he frequently hosted Einstein. Biography Paul Ehrenfest was born and grew up in Vienna to Jewish parents from Loštice in Moravia (now part of the Czech Republic). His parents, Sigmund Ehrenfest and Johanna Jellinek, ran a grocery store. Although the family was not overly religious, Paul studied Hebrew and the history of the Jewish people. Later, he always emphasized his Jewish roots. Ehrenfest excelled in grade school but did not do well at the Akademisches Gymnasium, his best subject being mathematics. After transferring to the Franz Josef Gymnasium, his marks improved. In 1899, he passed the final exams. He m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jagdish Mehra
Jagdish Mehra (April 8, 1931 – September 14, 2008) was an Indian-American historian of science. Academic career Mehra was educated at Allahabad University, the Max Planck Institut für Physik and the University of California at Los Angeles and obtained a Ph.D. in theoretical physics at the University of Neuchatel. He subsequently taught at Purdue University, Southeastern Massachusetts University, the University of Geneva, the Solvay Institute in Brussels, Rice University, the University of Houston and the International Center for Theoretical Physics. He is particularly well known for a book in 6 volumes on The Historical Development of Quantum Theory,Mehra, J. and Rechenberg, H. The Historical Development of Quantum Theory, Volumes 1-6. New York: Springer-Verlag which he wrote with Helmut Rechenberg. He also wrote a biography of Richard Feynman. He also wrote a book on the controversy surrounding the exact role David Hilbert played in the development of the gravitation th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carolyne Van Vliet
Carolyne Marina Van Vliet, van Vliet, (1929 – 2016) was a Dutch-American physicist notable for the theory of generation-recombination noise and for the theory of quantum transport in non-equilibrium statistical mechanics, as well as for her many contributions to the foundations of Linear Response Theory. She was a Fellow of the American Physical Society (APS) and of the Institute of Electrical and Electronics Engineers (IEEE). Education Van Vliet obtained a BS in physics and mathematics from Vrije Universiteit, Amsterdam in 1949. Van Vliet then obtained an MA in physics from the same university in 1953, and a PhD in 1956 for a thesis titled ''Current Fluctuations in Semiconductors and Photoconductors,'' under Gerardus J. Sizoo. Personal life As a teenager, Van Vliet lived in the Nazi-occupied Netherlands for 5 years. The name change from "K M van Vliet" to "C M Van Vliet" occurred in 1982. She moved to Minneapolis, Minnesota in 1956, then to Montreal, Quebec in 1969. Starti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Albert Messiah
Albert Messiah (23 September 1921, Nice – 17 April 2013, Paris) was a French physicist. He studied at the Ecole Polytechnique. He spent the Second World War in the Free France forces: he embarked on 22 June 1940 at Saint-Jean-de-Luz for England and participated in the Battle of Dakar with Charles de Gaulle in September 1940. He joined the Free French Forces in Chad, and the 2nd Armored Division in September 1944, and participated in the assault of Hitler's Eagle's nest at Berchtesgaden in 1945. As a French Jew who escaped France to fight in the Free French Army of de Gaulle, he was awarded a grant to study and work at the Institute for Advanced Study in Princeton, New Jersey in the US. The seminars at the Institute were incomprehensible to Messiah who had only a high-school education in physics, and he became depressed to the extent that he considered abandoning his plans to become a physicist. Fortunately he met Robert Marshak at a meeting of the American Physical Society i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Niels Bohr
Niels Henrik David Bohr (; 7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922. Bohr was also a philosopher and a promoter of scientific research. Bohr developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level (or orbit) to another. Although the Bohr model has been supplanted by other models, its underlying principles remain valid. He conceived the principle of complementarity: that items could be separately analysed in terms of contradictory properties, like behaving as a wave or a stream of particles. The notion of complementarity dominated Bohr's thinking in both science and philosophy. Bohr founded the Institute of Theoretical Physics at the University of Cope ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bragg's Law
In physics and chemistry , Bragg's law, Wulff–Bragg's condition or Laue–Bragg interference, a special case of Laue diffraction, gives the angles for coherent scattering of waves from a crystal lattice. It encompasses the superposition of wave fronts scattered by lattice planes, leading to a strict relation between wavelength and scattering angle, or else to the wavevector transfer with respect to the crystal lattice. Such law had initially been formulated for X-rays upon crystals. However, It applies to all sorts of quantum beams, including neutron and electron waves at atomic distances, as well as visible light at artificial periodic microscale lattices. History Bragg diffraction (also referred to as the Bragg formulation of X-ray diffraction) was first proposed by Lawrence Bragg and his father, William Henry Bragg, in 1913 in response to their discovery that crystalline solids produced surprising patterns of reflected X-rays (in contrast to that of, say, a liquid). They ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gregory Breit
Gregory Breit (russian: Григорий Альфредович Брейт-Шнайдер, ''Grigory Alfredovich Breit-Shneider''; July 14, 1899, Mykolaiv, Kherson Governorate – September 13, 1981, Salem, Oregon) was a Russian-born Jewish American physicist and professor at New York University (1929–1934), University of Wisconsin–Madison (1934–1947), Yale University (1947–1968), and University at Buffalo (1968–1973). In 1921, he was Paul Ehrenfest's assistant in Leiden University. Biography After completing his Ph.D. at age 22, he was from 1923 to 1924 an assistant professor at the University of Minnesota. In 1925, while at the Carnegie Institution of Washington, Breit joined with Merle Tuve in using a pulsed radio transmitter to determine the height of the ionosphere, a technique important later in radar development. Together with Eugene Wigner, Breit gave a description of particle resonant states with the relativistic Breit–Wigner distribution in 1929, and wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
David Bohm
David Joseph Bohm (; 20 December 1917 – 27 October 1992) was an American-Brazilian-British scientist who has been described as one of the most significant theoretical physicists of the 20th centuryPeat 1997, pp. 316-317 and who contributed unorthodox ideas to quantum theory, neuropsychology and the philosophy of mind. Among his many contributions to physics is his causal and deterministic interpretation of quantum theory, now known as De Broglie–Bohm theory. Bohm advanced the view that quantum physics meant that the old Cartesian model of reality—that there are two kinds of substance, the mental and the physical, that somehow interact—was too limited. To complement it, he developed a mathematical and physical theory of "implicate" and "explicate" order.David Bohm: ''Wholeness and the Implicate Order'', Routledge, 1980 (). He also believed that the brain, at the cellular level, works according to the mathematics of some quantum effects, and postulated that thought is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edgar Bright Wilson
Edgar Bright Wilson Jr. (December 18, 1908 – July 12, 1992) was an American chemist. Wilson was a prominent and accomplished chemist and teacher, recipient of the National Medal of Science in 1975, Guggenheim Fellowships in 1949 and 1970, the Elliott Cresson Medal in 1982, and a number of honorary doctorates. He was also the Theodore William Richards Professor of Chemistry, Emeritus at Harvard University. One of his sons, Kenneth G. Wilson, was awarded the Nobel Prize in physics in 1982. E. B. Wilson was a student and protégé of Nobel laureate Linus Pauling and was a coauthor with Pauling of ''Introduction to Quantum Mechanics'', a graduate level textbook in Quantum Mechanics. Wilson was also the thesis advisor of Nobel laureate Dudley Herschbach. Wilson was elected to the first class of the Harvard Society of Fellows. Wilson made major contributions to the field of molecular spectroscopy. He developed the first rigorous quantum mechanical Hamiltonian in internal coordi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linus Pauling
Linus Carl Pauling (; February 28, 1901August 19, 1994) was an American chemist, biochemist, chemical engineer, peace activist, author, and educator. He published more than 1,200 papers and books, of which about 850 dealt with scientific topics. ''New Scientist'' called him one of the 20 greatest scientists of all time, and as of 2000, he was rated the 16th most important scientist in history. For his scientific work, Pauling was awarded the Nobel Prize in Chemistry in 1954. For his peace activism, he was awarded the Nobel Peace Prize in 1962. He is one of five people to have won more than one Nobel Prize (the others being Marie Curie, John Bardeen, Frederick Sanger and Karl Barry Sharpless). Of these, he is the only person to have been awarded two unshared Nobel Prizes, and one of two people to be awarded Nobel Prizes in different fields, the other being Marie Curie. Pauling was one of the founders of the fields of quantum chemistry and molecular biology. His contributions t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Werner Heisenberg
Werner Karl Heisenberg () (5 December 1901 – 1 February 1976) was a German theoretical physicist and one of the main pioneers of the theory of quantum mechanics. He published his work in 1925 in a breakthrough paper. In the subsequent series of papers with Max Born and Pascual Jordan, during the same year, his matrix formulation of quantum mechanics was substantially elaborated. He is known for the uncertainty principle, which he published in 1927. Heisenberg was awarded the 1932 Nobel Prize in Physics "for the creation of quantum mechanics". Heisenberg also made contributions to the theories of the hydrodynamics of turbulent flows, the atomic nucleus, ferromagnetism, cosmic rays, and subatomic particles. He was a principal scientist in the German nuclear weapons program during World War II. He was also instrumental in planning the first West German nuclear reactor at Karlsruhe, together with a research reactor in Munich, in 1957. Following World War II, he was appointed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
