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The oldest surviving written account of Popol Vuh (ms c. 1701 by Francisco Ximénez, O.P.). Popol Vuh (also Popul Vuh or Pop Vuj) [1] [2] is a text recounting the mythology and history of the Kʼicheʼ people of Guatemala, one of the Maya peoples who also inhabit the Mexican states of Chiapas, Campeche, Yucatan and Quintana Roo, as well as areas of Belize, Honduras and El Salvador.
The red ionizing radiation warning symbol (ISO 21482) was launched in 2007, and is intended for IAEA Category 1, 2 and 3 sources defined as dangerous sources capable of death or serious injury, including food irradiators, teletherapy machines for cancer treatment and industrial radiography units. The symbol is to be placed on the device housing ...
Neutron radiation is a form of ionizing radiation that presents as free neutrons.Typical phenomena are nuclear fission or nuclear fusion causing the release of free neutrons, which then react with nuclei of other atoms to form new nuclides—which, in turn, may trigger further neutron radiation.
Free neutrons do not directly ionize atoms, but they do indirectly cause ionizing radiation, so they can be a biological hazard, depending on dose. A small natural "neutron background" flux of free neutrons exists on Earth, caused by cosmic ray showers , and by the natural radioactivity of spontaneously fissionable elements in the Earth's crust .
The Books of Chilam Balam are referenced in The Falling Woman by Pat Murphy as source material for the description of sacrifices at Chichén Itzá. A poem from the Chilam Balam is prominently featured in a short story by the U.S.-born writer Lucia Berlin, who spent many years living and traveling in Latin America, including Chile and Mexico ...
In addition, high-energy (high-speed) neutrons have the ability to directly ionize atoms. One mechanism by which high energy neutrons ionize atoms is to strike the nucleus of an atom and knock the atom out of a molecule, leaving one or more electrons behind as the chemical bond is broken. This leads to production of chemical free radicals. In ...
Two examples of isotopes that emit neutrons are beryllium-13 (decaying to beryllium-12 with a mean life 2.7 × 10 −21 s) and helium-5 (helium-4, 7 × 10 −22 s). [ 1 ] In tables of nuclear decay modes, neutron emission is commonly denoted by the abbreviation n .
Some isotopes undergo spontaneous fission (SF) with emission of neutrons.The most common spontaneous fission source is the isotope californium-252. 252 Cf and all other SF neutron sources are made by irradiating uranium or a transuranic element in a nuclear reactor, where neutrons are absorbed in the starting material and its subsequent reaction products, transmuting the starting material into ...