Sunday, December 30, 2012
Bahcall's field was astrophysics. He worked on many problems in astrophysics, but he is most remembered for his work on stellar neutrinos. Stars produce energy by a series of different nuclear reactions converting hydrogen to helium. One of the products of these reactions are electron-neutrinos. Neutrinos are neutral subatomic particles and come in three "flavors", electron-neutrinos, muon-neutrinos and tau-neutrinos. Because they do not have a charge, they do not interact with other substances and generally pass directly through. It has been estimated that every centimeter of the earth, exposed to direct sunlight, has 65 billion neutrinos pass through it per second. To detect the neutrinos as they pass through the earth Bahcall, working with Raymond Davis Jr., did the theoretical calculations for a detector that was built in the Homestake Gold Mine in Lead, South Dakota, using a 380 cubic meter tank filled with dry cleaning fluid (tetrachloroethylene). The chlorine atoms in the dry cleaning fluid are transformed into argon when they are hit by an electron-neutrino. The argon is collected and the amount of electron-neutrinos hitting the tank can be counted. The initial results of the experiment, announced in 1968, found only one third of the amount of neutrinos predicted by theory. For thirty years Bahcall worked on the problem and it was eventually determined that some of the neutrinos change from electron-neutrinos into muon- and tau-neutrinos and were not detected by the chlorine in Bahcall and Davis' experiment.
Bahcall won many honors during his career, including the Comstock prize in physics from the National Academy of Science and the Gold Medal from the Royal Academy of Science. He is also responsible, with Lyman Spitzer Jr., for designing the Hubble Space Telescope put into orbit in 1990. In 1992 he received NASA's Public Service Medal for this work. Bahcall also worked on understanding how our galaxy is put together and the current model of our galaxy, with a super-massive black hole at its center, is called the Bahcall-Wolfe model.
Bahcall died on August 17, 2005.
Striker, Jeremiah P. and Bahcall, Neta A.; "John Norris Bahcall: 1934-2005"; Bulletin of the American Astronomical Society (2007)39:1053-4
Tremaine, Scott D.; "John Norris Bahcall: 1934-2005"; National Academy Press; 2011
John N. Bahcall Wikipedia Entry
Sunday, December 23, 2012
From 1943 to 1956 Jerne worked at the Danish National Serum Institute. During this time he proposed the theory of antibody selection, that the immune system produced a multitude of antibodies and through interactions with antigen (a molecule recognized by antibodies) antibodies were selected and the immune system produced more of them. This theory was later refined by David Talmadge and Frank Macfarlane Burnet, who separately proposed the genetic mechanism by which antibody producing cells each pick the DNA that will code for the cell's antibodies. Antibody producing cells are part of the body's humoral immune response. Antibodies are protein molecules that recognize and bind a particular antigen. Because they have multiple binding sites antibodies, when bound to antigen, can form large clumps. In a addition to their binding sites, antibodies have a site recognized by phagocytic cells. When large clumps of antibody/antigen complex form these recognition sites serve to signal phagocytic cells to devour it.
Starting in 1956 Jerne worked for the World Health Organization in Geneva. In 1962 he moved to the University of Pittsburg in Pittsburgh, Pennsylvania. From 1966 to 1969 he was director of the Paul-Erlich Institute and from 1969 to his retirement in 1980 he ran his own institute as director of the Basel Institute of Immunology. While there Jerne was the first to speculate about the role of the major histocompatability complex. This is a protein complex produced by cells that presents antigens on the cells surface. This is recognized by T-lymphocytes. When the antigen is recognized it means that it is foreign to the body and stimulates an immune response from the T-cell. T-cells then activate and secrete chemicals to stimulate the immune response.
Jerne's other major contribution to immunology was the idea that the immune system functions as a network, each part influencing the others. This is how the immune system is viewed today, where immune cells secrete an array of cytokines, hormones that influence the functions of the other cells of the body and the immune system. This paradigm has allowed immunologists to better understand immune cell dysfunction and the effects of the viral infection of immune cells in HIV infection. For his contributions to our understanding of immunology Jerne was awarded the 1984 Nobel Prize in Medicine, with Georges Kohler and Cesar Milstein.
Jerned died on October 7, 1994.
Hoffmann, Geoffrey, W.; "Niels Jerne, Immunologist: 1911-1994"; Vaccine Research (1994)3
Neils Gerne Wikipedia entry
Monday, December 17, 2012
Ritter's early research involved using the method of Luigi Galvani, using frog legs as an indicator of electrical current. Using a method involving two frog legs Ritter measured the activity series of metals. Ritter's explanation for the effect was closest to what we know today to be a chemical reaction where electrons are transferred from one chemical to another. These are called redox reactions because two processes are taking place, oxidation (where electrons are removed from a chemical) and reduction (where electrons are added to a chemical). For this Ritter is referred to as the father of electrochemistry. Ritter was also the first to separate the oxygen and hydrogen produced by the electrolysis of water. When an electrical current is run through water, water decomposes in to oxygen and hydrogen gases.
Ritter is most famous for his discovery of ultraviolet radiation. After William Herschel announced the discovery of infra-red radiation in 1801 Ritter believed that there was also radiation on the other end of the visible spectrum. Using silver nitrate he tested different colors of light and found that violet light caused more decomposition than red light. He also found that the greatest decomposition occurred using a wavelength of light that could not be seen. This is what today we call ultraviolet light. It is the region of the electromagnetic spectrum between visible light and x-ray radiation, with a wavelength between 4000 and 10 angstroms.
In addition to his scientific activities Ritter was also active in the German romantic movement. Because of his belief in the occult and reluctance to publish his results he was disregarded by most of his contemporaries. Beset by financial difficulties he died at the age of 33 on January 23, 1810.
Berg, Hermann; "Johann Wilhelm Ritter: the Founder of Scientific Electrochemistry"; Review of Polarography (2008)54:99-103
Davidson, Michael W., "Johann Wilhelm Ritter (1776-1810)"; retrieved from micro.magnet.fsu.edu
Johann Wilhelm Ritter Wikipedia Entry
Monday, December 10, 2012
Kendall's research involved using particle accelerators to probe the make up of the atom. In the 1960s and 70s Kendall worked with Jerome Friedman and Richard Taylor scattering electrons off of protons, neutrons, duterons and other heavier nuclei. These experiments confirmed the existence of quarks, small, sub-nuclear particles that protons and neutrons are made of. Quarks take their name from a line in Finnegan's Wake by James Joyce, and come in two kinds, up quarks and down quarks. Protons are made up of two up quarks and one down quark and neutrons are made up of two down quarks and one up quark. For their work confirming the existence of quarks Kendall, Friedman, and Taylor were awarded the 1990 Nobel Prize in physics.
In a addition to his work in physics, Kendall was also an avid outdoorsman, mountain climber and scuba diver. In the 1960s Kendall served as an adviser to the United States Department of Defense. In 1969 he co-founded the Union of Concerned Scientists and served for many years as its chairman. The Union of Concerned Scientists is a non-profit group that advocates sensible environmental and sustainable agricultural policies. He was elected to the National Academy of Sciences in 1977 and was inducted into the American Alpine Club's Hall of Mountaineering Excellence in 2012.
He died on February 15, 1999 as the result of a scuba diving accident while exploring an underwater cave in Wakulla Springs State Park in Florida.
Bjorken, James D., Friedman, Jerome I., Taylor, Gottfried, Kurt and Taylor, Richard B.; "Henry Way Kendal: 1926-1999"; National Academy Press; 2009
Kendall, Henry W., Nobel Autobiography
Kendall, Henry W. and Aasserud, Finn; "Oral History Transcript - Dr. Henry Kendall"; accessed at aip.org.
Henry Way Kendall Wikipedia Entry
Sunday, December 2, 2012
In 1922 he became physician-in-chief of Collis P. Huntington Memorial Hospital and in 1928 he became a professor of medicine at Harvard University. Minot published papers on many subjects, including vitamin B deficiency, blood coagulation, arthritis, leukemia, industrial blood poisoning, among others.
In 1914 he became interested in the work of George Whipple. Whipple was studying the effect of diet on anemic dogs and discovered that feeding dogs liver reversed the anemia. Minot, working with William Murphy of Johns Hopkins University, discovered that a diet of liver helped patients with pernicious anemia, a form of anemia characterized by improper red blood cell development. Later, working with William Cohn, he showed which fractions of the liver helped patients with pernicious anemia. Today it is known that pernicious anemia is caused by a deficit of vitamin B-12 or cobalamine. Vitamin B-12 is the only one of the B vitamins that contains an atom of the metallic element cobalt and it is involved in the DNA synthesis of developing red blood cells. For their discovery Whipple, Murphy and Minot were awarded the 1934 Nobel Prize in Medicine.
Minot died on February 15, 1950.
Castle, W.B.; "George Richards Minot: 1885-1950"; National Academy Press; 1974
George Minot Wikipedia Entry
George Minot Nobel Biography