Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium - 235 or a similar fissile nuclide.
Ashkenazi Jews
In the Midrash compilation, Genesis Rabbah, Rabbi Berechiah mentions Ashkenaz, Riphath, and Togarmah as German tribes or as German lands. It may correspond to a Greek word that may have existed in the Greek dialect of the Palestinian Jews, or the text is corrupted from "Germanica." This view of Berechiah is based on the Talmud (Yoma 10a; Jerusalem Talmud Megillah 71b), where Gomer, the father of Ashkenaz, is translated by Germamia, which evidently stands for Germany, and which was suggested by the similarity of the sound.
Mesozoic
The climatic changes of the late Jurassic and Cretaceous provided for further adaptive radiation. The Jurassic was the height of archosaur diversity, and the first birds and eutherian mammals also appeared. Angiosperms radiated sometime in the early Cretaceous, first in the tropics, but the even temperature gradient allowed them to spread toward the poles throughout the period. By the end of the Cretaceous, angiosperms dominated tree floras in many areas, although some evidence suggests that biomass was still dominated by cycad and ferns until after the Cretaceous–Paleogene extinction.
Nuclear weapon design
ERWs were two-stage thermonuclears with all non-essential uranium removed to minimize fission yield. Fusion provided the neutrons. Developed in the 1950s, they were first deployed in the 1970s, by U.S. forces in Europe. The last ones were retired in the 1990s.
Uranium
Uranium-235 was the first isotope that was found to be fissile. Other naturally occurring isotopes are fissionable, but not fissile. On bombardment with slow neutrons, its uranium-235 isotope will most of the time divide into two smaller nuclei, releasing nuclear binding energy and more neutrons. If too many of these neutrons are absorbed by other uranium-235 nuclei, a nuclear chain reaction occurs that results in a burst of heat or (in special circumstances) an explosion. In a nuclear reactor, such a chain reaction is slowed and controlled by a neutron poison, absorbing some of the free neutrons. Such neutron absorbent materials are often part of reactor control rods (see nuclear reactor physics for a description of this process of reactor control).
Nuclear fuel
Most nuclear fuels contain heavy fissile elements that are capable of nuclear fission, such as uranium - 235 or plutonium - 239. When the unstable nuclei of these atoms are hit by a slow - moving neutron, they split, creating two daughter nuclei and two or three more neutrons. These neutrons then go on to split more nuclei. This creates a self - sustaining chain reaction that is controlled in a nuclear reactor, or uncontrolled in a nuclear weapon.
Continental drift
The widespread distribution of Permo-Carboniferous glacial sediments in South America, Africa, Madagascar, Arabia, India, Antarctica and Australia was one of the major pieces of evidence for the theory of continental drift. The continuity of glaciers, inferred from oriented glacial striations and deposits called tillites, suggested the existence of the supercontinent of Gondwana, which became a central element of the concept of continental drift. Striations indicated glacial flow away from the equator and toward the poles, based on continents' current positions and orientations, and supported the idea that the southern continents had previously been in dramatically different locations that were contiguous with one another.
Buddhism
The evidence of the early texts suggests that Siddhārtha Gautama was born in a community that was on the periphery, both geographically and culturally, of the northeastern Indian subcontinent in the fifth century BCE. It was either a small republic, in which case his father was an elected chieftain, or an oligarchy, in which case his father was an oligarch.
Neutron temperature
The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts. The term temperature is used, since hot, thermal and cold neutrons are moderated in a medium with a certain temperature. The neutron energy distribution is then adapted to the Maxwellian distribution known for thermal motion. Qualitatively, the higher the temperature, the higher the kinetic energy of the free neutrons. The momentum and wavelength of the neutron are related through the de Broglie relation. The large wavelength of slow neutrons allows for the large cross section.
State of matter
In physics, a state of matter is one of the distinct forms in which matter can exist. Four states of matter are observable in everyday life: solid, liquid, gas, and plasma. Many other states are known to exist, such as glass or liquid crystal, and some only exist under extreme conditions, such as Bose -- Einstein condensates, neutron - degenerate matter, and quark - gluon plasma, which only occur, respectively, in situations of extreme cold, extreme density, and extremely high - energy. Some other states are believed to be possible but remain theoretical for now. For a complete list of all exotic states of matter, see the list of states of matter.
Neolithic
Control of labour and inter-group conflict is characteristic of corporate-level or 'tribal' groups, headed by a charismatic individual; whether a 'big man' or a proto-chief, functioning as a lineage-group head. Whether a non-hierarchical system of organization existed is debatable, and there is no evidence that explicitly suggests that Neolithic societies functioned under any dominating class or individual, as was the case in the chiefdoms of the European Early Bronze Age. Theories to explain the apparent implied egalitarianism of Neolithic (and Paleolithic) societies have arisen, notably the Marxist concept of primitive communism.
James Chadwick
During the Second World War, Chadwick carried out research as part of the Tube Alloys project to build an atomic bomb, while his Manchester lab and environs were harassed by Luftwaffe bombing. When the Quebec Agreement merged his project with the American Manhattan Project, he became part of the British Mission, and worked at the Los Alamos Laboratory and in Washington, D.C. He surprised everyone by earning the almost-complete trust of project director Leslie R. Groves, Jr. For his efforts, Chadwick received a knighthood in the New Year Honours on 1 January 1945. In July 1945, he viewed the Trinity nuclear test. After this, he served as the British scientific advisor to the United Nations Atomic Energy Commission. Uncomfortable with the trend toward Big Science, Chadwick became the Master of Gonville and Caius College in 1948. He retired in 1959.
Beta decay
In nuclear physics, beta decay (β - decay) is a type of radioactive decay in which a beta ray (fast energetic electron or positron) and a neutrino are emitted from an atomic nucleus. For example, beta decay of a neutron transforms it into a proton by the emission of an electron, or conversely a proton is converted into a neutron by the emission of a positron (positron emission), thus changing the nuclide type. 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 (see below) or Q value must be positive.
Navajo
Archaeological and historical evidence suggests the Athabaskan ancestors of the Navajos and Apaches entered the Southwest around 1400 CE. The Navajo oral tradition is said to retain references of this migration.
Ashkenazi Jews
No evidence has yet been found of a Jewish presence in antiquity in Germany beyond its Roman border, nor in Eastern Europe. In Gaul and Germany itself, with the possible exception of Trier and Cologne, the archeological evidence suggests at most a fleeting presence of very few Jews, primarily itinerant traders or artisans. A substantial Jewish population emerged in northern Gaul by the Middle Ages, but Jewish communities existed in 465 CE in Brittany, in 524 CE in Valence, and in 533 CE in Orleans. Throughout this period and into the early Middle Ages, some Jews assimilated into the dominant Greek and Latin cultures, mostly through conversion to Christianity.[better source needed] King Dagobert I of the Franks expelled the Jews from his Merovingian kingdom in 629. Jews in former Roman territories faced new challenges as harsher anti-Jewish Church rulings were enforced.
Stellar rotation
A neutron star is a highly dense remnant of a star that is primarily composed of neutrons—a particle that is found in most atomic nuclei and has no net electrical charge. The mass of a neutron star is in the range of 1.2 to 2.1 times the mass of the Sun. As a result of the collapse, a newly formed neutron star can have a very rapid rate of rotation; on the order of a hundred rotations per second.
The God Who Wasn't There
The God Who Wasn't There is a 2005 independent documentary written and directed by Brian Flemming. The documentary questions the existence of Jesus, examining evidence that supports the Christ myth theory against the existence of a historical Jesus, as well as other aspects of Christianity.
C10orf76
C10orf76 or chromosome 10 open reading frame 76, also known as UPF0668, is a protein that in humans is encoded by the "c10orf76" gene. Its function is not currently known, but experimental evidence has suggested that it may be involved in transcriptional regulation. The protein contains a conserved proline-rich motif, suggesting that it may participate in protein-protein interactions via an SH3-binding domain, although no such interactions have been experimentally verified. The well-conserved gene appears to have emerged in Fungi approximately 1.2 billion years ago. The locus is alternatively spliced and predicted to yield five protein variants, three of which contain a protein domain of unknown function, DUF1741.
Discovery of the neutron
The essential nature of the atomic nucleus was established with the discovery of the neutron by James Chadwick in 1932 and the determination that it was a new elementary particle, distinct from the proton.
Domestication of the horse
A number of hypotheses exist on many of the key issues regarding the domestication of the horse. Although horses appeared in Paleolithic cave art as early as 30,000 BCE, these were wild horses and were probably hunted for meat. How and when horses became domesticated is disputed. The clearest evidence of early use of the horse as a means of transport is from chariot burials dated c. 2000 BCE. However, an increasing amount of evidence supports the hypothesis that horses were domesticated in the Eurasian Steppes approximately 3500 BCE; recent discoveries in the context of the Botai culture suggest that Botai settlements in the Akmola Province of Kazakhstan are the location of the earliest domestication of the horse. Regardless of the specific date of domestication, use of horses spread rapidly across Eurasia for transportation, agricultural work and warfare.
What was the person who provided evidence to suggest the existence of the neutron a participant of?
who provided evidence to suggest the existence of the neutron
James Chadwick
#1 >> participant in
Manhattan Project