SUMMARY / RELATED TOPICS

Beta decay

In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atomic nucleus, transforming the original nuclide to an isobar. For example, beta decay of a neutron transforms it into a proton by the emission of an electron accompanied by an antineutrino. Neither the beta particle nor its associated neutrino exist within the nucleus prior to beta decay, but are created in the decay process. By this process, unstable atoms obtain a more stable ratio of protons to neutrons; the probability of a nuclide decaying due to beta and other forms of decay is determined by its nuclear binding energy. The binding energies of all existing nuclides form what is called the nuclear band or valley of stability. For either electron or positron emission to be energetically possible, the energy release or Q value must be positive. Beta decay is a consequence of the weak force, characterized by lengthy decay times. Nucleons are composed of up quarks and down quarks, the weak force allows a quark to change its flavour by emission of a W boson leading to creation of an electron/antineutrino or positron/neutrino pair.

For example, a neutron, composed of two down quarks and an up quark, decays to a proton composed of a down quark and two up quarks. Electron capture is sometimes included as a type of beta decay, because the basic nuclear process, mediated by the weak force, is the same. In electron capture, an inner atomic electron is captured by a proton in the nucleus, transforming it into a neutron, an electron neutrino is released; the two types of beta decay are known as beta beta plus. In beta minus decay, a neutron is converted to a proton, the process creates an electron and an electron antineutrino. Β+ decay is known as positron emission. Beta decay conserves a quantum number known as the lepton number, or the number of electrons and their associated neutrinos; these particles have lepton number +1, while their antiparticles have lepton number −1. Since a proton or neutron has lepton number zero, β+ decay must be accompanied with an electron neutrino, while β− decay must be accompanied by an electron antineutrino.

An example of electron emission is the decay of carbon-14 into nitrogen-14 with a half-life of about 5,730 years: 146C → 147N + e− + νeIn this form of decay, the original element becomes a new chemical element in a process known as nuclear transmutation. This new element has an unchanged mass number A, but an atomic number Z, increased by one; as in all nuclear decays, the decaying element is known as the parent nuclide while the resulting element is known as the daughter nuclide. Another example is the decay of hydrogen-3 into helium-3 with a half-life of about 12.3 years: 31H → 32He + e− + νeAn example of positron emission is the decay of magnesium-23 into sodium-23 with a half-life of about 11.3 s: 2312Mg → 2311Na + e+ + νeβ+ decay results in nuclear transmutation, with the resulting element having an atomic number, decreased by one. The beta spectrum, or distribution of energy values for the beta particles, is continuous; the total energy of the decay process is divided between the electron, the antineutrino, the recoiling nuclide.

In the figure to the right, an example of an electron with 0.40 MeV energy from the beta decay of 210Bi is shown. In this example, the total decay energy is 1.16 MeV, so the antineutrino has the remaining energy: 1.16 MeV − 0.40 MeV = 0.76 MeV. An electron at the far right of the curve would have the maximum possible kinetic energy, leaving the energy of the neutrino to be only its small rest mass. Radioactivity was discovered in 1896 by Henri Becquerel in uranium, subsequently observed by Marie and Pierre Curie in thorium and in the new elements polonium and radium. In 1899, Ernest Rutherford separated radioactive emissions into two types: alpha and beta, based on penetration of objects and ability to cause ionization. Alpha rays could be stopped by thin sheets of paper or aluminium, whereas beta rays could penetrate several millimetres of aluminium. In 1900, Paul Villard identified a still more penetrating type of radiation, which Rutherford identified as a fundamentally new type in 1903 and termed gamma rays.

Alpha and gamma are the first three letters of the Greek alphabet. In 1900, Becquerel measured the mass-to-charge ratio for beta particles by the method of J. J. Thomson used to identify the electron, he found that m/e for a beta particle is the same as for Thomson's electron, therefore suggested that the beta particle is in fact an electron. In 1901, Rutherford and Frederick Soddy showed that alpha and beta radioactivity involves the transmutation of atoms into atoms of other chemical elements. In 1913, after the products of more radioactive decays were known and Kazimierz Fajans independently proposed their radioactive displacement law, which states that beta emission from one element produces another element one place to the right in the periodic table, while alpha emission produces an element two places to the left; the study of beta decay provided the first physical evidence for the existence of the neutrino. In both alpha and gamma decay, the resulting alpha or gamma particle has a narrow energy distribution, since the particle carries the energy from the difference between the init

Cut Knife, Saskatchewan

Cut Knife is a town located in the Canadian province of Saskatchewan on Highway 40, northwest of Saskatoon and 55 km west of North Battleford. The population of Cut Knife in 2011 was 517. Nearby are Poundmaker Cree Nation and Little Pine First Nation to the north in Paynton, Sweetgrass First Nation to the east and Hillsvale Hutterite Colony located to the northwest of the town. Cut Knife is named after Cut Knife Hill situated on the Poundmaker reserve; the hill was named. The town is located close to the site of the Battle of Cut Knife which occurred during the Northwest Rebellion of 1885. At Cut Knife is the "World's Largest Tomahawk", the Poundmaker Historical Centre and the Big Bear monument. There is now located, a cairn erected by the Historic Sites and Monuments Board of Canada upon Cut Knife Hill overlooking the Poundmaker Battle site and Battle River valley; the tomahawk is located in the Tomahawk Park next to the Clayton McLain Memorial Museum. It was built in 1971 as a symbol of friendship with the First Nations of the area.

It was designed in 1970 by UMA Engineering of Saskatoon, Saskatchewan

Garvey's Ghost

Garvey's Ghost is the fourth album by the reggae group Burning Spear, released in 1976 on Island Records, ILPS 9382. Each track is a dub version of its correspondent song on Marcus Garvey; this album was fashioned by Island Record engineers John Burns and Dick Cuthell in their Hammersmith studio. It features prominently the backing musicians, whom Lindo named The Black Disciples band, assembled from members of the session group The Soul Syndicate and Bob Marley's touring band, The Wailers. John Corbett has suggested that "dub" could derive from "duppie," a Jamaican patois word for ghost, as Lee Perry has been quoted stating that dub is "the ghost in me coming out," this connection further illustrated by Winston Rodney having named this album as the ghost of Garvey. On July 27, 2010, this album was remastered and released by Universal's Hip-O Records reissue imprint in tandem with the original Marcus Garvey LP on one compact disc. For "The Ghost", the dub counterpart to "Marcus Garvey", instead of dubbing straight from the track as all the others were, "The Ghost" was instead replayed and made to design itself to be the official dub of the tune.

A more official dub version was released on the original 7" single releases of "Marcus Garvey". All tracks written by Phillip Fullwood except as indicated. "The Ghost" — 3:56 "I and I Survive" — 3:55 "Black Wa-Da-Da" — 3:53 "John Burns Skank" — 3:49 "Brain Food" — 3:11 "Farther East of Jack" — 4:26 "2000 Years" — 3:49 "Dread River" — 3:13 "Workshop" — 4:34 "Reggaelation" — 3:43 Winston Rodney - lead vocals Delroy Hines - harmony vocals Rupert Willington - harmony vocals Bobby Ellis - trumpet Vincent "Trommie" Gordon - trombone, clavinet Carlton "Sam" Samuels - flute Herman Marquis - alto saxophone Richard "Dirty Harry" Hall - tenor saxophone Tyrone "Organ D" Downie - piano, organ Bernard "Touter" Harvey - piano, clavinet Earl "Chinna" Smith - lead guitar Valentine "Tony" Chin – rhythm guitar Robbie "Rabbi" Shakespeare - bass Aston "Family Man" Barrett - bass Leroy "Horsemouth" Wallace - drums Engineers: George Philpott and Errol Thompson Dubbing engineers: John Burns and Dick Cuthell Recorded at Randy's Recording Studio, North Parade, Jamaica Mixed at Joe Gibbs Studio, Retirement Crescent, Jamaica Dub mix at Island Studios, Hammersmith Special thanks to Lloyd Coxone