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Occlusion effect The occlusion effect occurs when an object fills the outer portion of a person's ear canal, and that person perceives "hollow" or "booming" echo-like sounds of their own voice. It is caused by bone-conducted sound vibrations reverberating off the object filling the ear canal. When talking or chewing, t... | https://en.wikipedia.org/wiki?curid=14429491 |
Kraków School of Mathematics and Astrology The () was an influential mid-to-late-15th-century group of mathematicians and astrologers at the University of Kraków (later "Jagiellonian University"). | https://en.wikipedia.org/wiki?curid=14439044 |
Nuclear detection The threat of radiological attacks has led several organizations to develop specially designed nuclear detection systems. These systems differ in design and abilities. | https://en.wikipedia.org/wiki?curid=14439210 |
Lajos Abafi or Ludwig Abafi-Aigner (11 February 1840 in Nagyjécsa, Kingdom of Hungary, Austrian Empire – 19 June 1909 in Budapest, Austria-Hungary) was a Hungarian editor, a librarian and entomologist. His family, of German origin, moved to Pozsony (today Bratislava) in 1858. There, he learned the Hungarian language. H... | https://en.wikipedia.org/wiki?curid=14450665 |
Delta-v (physics) Delta comes as the 4th letter in the Greek alphabets which is spelled as 'D' in the English alphabets . In general physics, delta-"v" is simply a change in velocity. The Greek uppercase letter delta is the standard mathematical symbol to represent change in some quantity. Depending on the situation, d... | https://en.wikipedia.org/wiki?curid=14454695 |
Pollakanth A pollakanth is a plant that reproduces, flowers and sets seed recurrently during its life. The term was first used by Frans R. Kjellman. Other terms with the same meaning are "polycarpic" and "iteroparous". Its antonym is hapaxanth. | https://en.wikipedia.org/wiki?curid=14456810 |
Coalescence (chemistry) In chemistry, coalescence is a process in which two phase domains of the same composition come together and form a larger phase domain. In other words, the process by which two or more separate masses of miscible substances seem to "pull" each other together should they make the slightest contac... | https://en.wikipedia.org/wiki?curid=14458653 |
Planetarium software is application software that allows a user to simulate the celestial sphere at any time of day, especially at night, on a computer. Such applications can be as rudimentary as displaying a star chart or sky map for a specific time and location, or as complex as rendering photorealistic views of the ... | https://en.wikipedia.org/wiki?curid=14466034 |
Product-determining step The product-determining step is the step of a chemical reaction that determines the ratio of products formed via differing reaction mechanisms that start from the same reactants. The product determining step is not rate limiting if the rate limiting step of each mechanism is the same. | https://en.wikipedia.org/wiki?curid=14466384 |
Surface force denoted "f" is the force that acts across an internal or external surface element in a material body. can be decomposed into two perpendicular components: normal forces and shear forces. A normal force acts normally over an area and a shear force acts tangentially over an area. Since pressure is formula_2... | https://en.wikipedia.org/wiki?curid=14467558 |
Sándor Szalay (physicist) Sándor Szalay, Sr. (October 4, 1909 – October 11, 1987) was a pioneer of Hungarian nuclear physics. He discovered a natural mechanism for uranium enrichment, which led to the discovery of several uranium deposits including an enriched deposit in the Mecsek Mountains of Hungary. In 1955 he coll... | https://en.wikipedia.org/wiki?curid=14469689 |
Heng-O Corona is a corona in Guinevere Planitia on the planet Venus at Latitude 2° North, Longitude 355° East. It has a diameter of , and is the second largest corona on Venus. It is named for Heng O (also known as Chang'e), the Chinese goddess of the Moon. is located on the eastern Guinevere. Within the faulted ring s... | https://en.wikipedia.org/wiki?curid=14472512 |
Zisa Corona is a corona found on the planet Venus at Latitude 12° North, Longitude 221° East. It has a diameter of 850 kilometers, and is the 3rd largest corona on Venus. It is named for Zisa a German/Nordic harvest goddess and consort of Tyr. | https://en.wikipedia.org/wiki?curid=14473044 |
Quetzalpetlatl Corona is a corona in Lada Terra on the planet Venus. Latitude 68° South, Longitude 357° East. It has a diameter of 780 kilometers, and is the 4th largest corona on Venus. It lies in part on the Lada Rise, with part of the corona intersecting the Ammavuro-Quetzalpetlatl belt in the northwestern region of... | https://en.wikipedia.org/wiki?curid=14473293 |
Stephen Szára Stephen István Szára (born 21 March 1923) is a Hungarian chemist and psychiatrist who has made major contributions in the field of pharmacology. Szára was the first to scientifically study the psychotropic effects of "N,N"-Dimethyltryptamine (DMT), performing research with volunteers in the mid-1950s. Szá... | https://en.wikipedia.org/wiki?curid=14477052 |
Stephen Szára In recent years, Szára has argued that psychedelic drugs should be studied in a heuristic manner and that learning the mechanisms by which they affect the brain may "serve as keys to unlock the mysteries of the brain/mind relationship". Szára is an Emeritus Fellow of the American College of Neuropsychopha... | https://en.wikipedia.org/wiki?curid=14477052 |
Bernhard Eitel (born 31 August 1959) is a German earth scientist and geographer. Eitel was born in Baden. Since October 2007, he has been the Rector of Heidelberg University. | https://en.wikipedia.org/wiki?curid=14497677 |
Engin Arık (October 4, 1948 – November 30, 2007) was a Turkish particle physicist. She was a professor and head of the Experimental High Energy Physics group at the Boğaziçi University. Arık was born in Istanbul and received her BSc in 1969 in mathematics and physics from Istanbul University. Subsequently, she received... | https://en.wikipedia.org/wiki?curid=14498641 |
Health Sciences Descriptors DeCS – is a structured and trilingual thesaurus created by BIREME – Latin American and Caribbean Center on Health Sciences Information – in 1987 for indexing scientific journal articles, books, proceedings of congresses, technical reports and other types of materials, as well as for searchin... | https://en.wikipedia.org/wiki?curid=14499993 |
Health Sciences Descriptors Its main purpose is to serve as a unique language for indexing and recovery of information among the components of the Latin American and Caribbean Health Sciences Information System, coordinated by BIREME and that encompasses 37 countries in Latin America and the Caribbean, permitting a uni... | https://en.wikipedia.org/wiki?curid=14499993 |
Physiographic regions of the world are a means of defining the Earth's landforms into distinct regions, based upon the classic three-tiered approach by Nevin M. Fenneman in 1916, that separates landforms into physiographic divisions, physiographic provinces, and physiographic sections. The model became the basis for si... | https://en.wikipedia.org/wiki?curid=14500263 |
Physiographic regions of the world For the remainder of this article, emphasis will remain on the more "geomorphological" usage, which is based upon geological landforms, not on climate, vegetation, or other non-geological criteria. For the purposes of physiographic mapping, landforms are classified according to both t... | https://en.wikipedia.org/wiki?curid=14500263 |
Physiographic regions of the world In 1848, Mary Somerville published her book "Physical Geography" which gave detailed descriptions of the topography of each continent, along with the distribution of plant, animals and humans. This work gave impetus to further works along the field. In Germany, Oscar Peschel in 1870, ... | https://en.wikipedia.org/wiki?curid=14500263 |
Physiographic regions of the world In 1899, Albert Heim published his photographs and observations made during a balloon flight over the Alps; he is probably the first person to use aerial photography in geomorphological or physiographical research. The block diagrams of Fenneman, Raisz, Lobeck and many others were bas... | https://en.wikipedia.org/wiki?curid=14500263 |
Physiographic regions of the world Although the term has since been limited by some writers to one particular part of the subject, it seems best to maintain the original and literal meaning. In the stricter sense, physical geography is that part of geography which involves the processes of contemporary change in the cr... | https://en.wikipedia.org/wiki?curid=14500263 |
Physiographic regions of the world Even in the 21st century, some confusion remains as to exactly what "physiography" is. One source states "Geomorphology includes quaternary geology, physiography and most of physical geography", treating physiography as a separate field, but subservient to geomorphology. Another sourc... | https://en.wikipedia.org/wiki?curid=14500263 |
Physiographic regions of the world Partly due to this confusion over what "physiography" actually means, some scientists have refrained from using the term physiography (and instead use the similar term geomorphology) because the definitions vary from the American Geological Institute's "the study and classification of... | https://en.wikipedia.org/wiki?curid=14500263 |
The Natural History and Antiquities of Selborne The Natural History and Antiquities of Selborne, or just The Natural History of Selborne is a book by English naturalist and ornithologist Gilbert White. It was first published in 1789 by his brother Benjamin. It has been continuously in print since then, with nearly 300 ... | https://en.wikipedia.org/wiki?curid=14522051 |
The Natural History and Antiquities of Selborne The main part of the book, the "Natural History", is presented as a compilation of 44 letters nominally to Thomas Pennant, a leading British zoologist of the day, and 66 letters to Daines Barrington, an English barrister and Fellow of the Royal Society. In these letters, ... | https://en.wikipedia.org/wiki?curid=14522051 |
The Natural History and Antiquities of Selborne As a compilation of letters and other materials, the book as a whole has an uneven structure. The first part is a diary-like sequence of 'letters', with the breaks and wanderings that naturally follow. The second is a calendar, organized by phenological event around the y... | https://en.wikipedia.org/wiki?curid=14522051 |
The Natural History and Antiquities of Selborne There are 44 letters to White's friend Thomas Pennant (1726–1798), of which the first nine were never posted and are thus undated. Of those that were posted, the first, Letter 10 giving an overview of Selborne, is dated 4 August 1767; the last, Letter 44 on wood pigeons, ... | https://en.wikipedia.org/wiki?curid=14522051 |
The Natural History and Antiquities of Selborne Barrington, on the other hand, liked to theorize about the natural world, but had little interest in making observations himself, and tended to accept claimed facts uncritically. A character in some of the letters is a tortoise: Letter 65 describes the summer of 1783 as: ... | https://en.wikipedia.org/wiki?curid=14522051 |
The Natural History and Antiquities of Selborne He orders the canons of Selborne priory (Item 5th) "to take care that the doors of their church and priory be so attended to that no suspected and disorderly females, "suspectae at aliae inhonestae", pass through their choir and cloiser in the dark"; (Item 10th) to cease ... | https://en.wikipedia.org/wiki?curid=14522051 |
The Natural History and Antiquities of Selborne , and about fifty years before the general dissolution of the monasteries by Henry VIII." The final letter records that "No sooner did the priory .. become an appendage to the college, but it must at once have tended to swift decay." White notes that since then, even "the... | https://en.wikipedia.org/wiki?curid=14522051 |
The Natural History and Antiquities of Selborne For example, "Cuckoo "(Cuculus canorus)" heard" is recorded by White for 7—26 April, and by Markwick for 15 April and 3 May (presumably only once at the earlier date) and "last heard" by Markwick on 28 June. The table begins as follows: White's lifelong friend John Mulso ... | https://en.wikipedia.org/wiki?curid=14522051 |
The Natural History and Antiquities of Selborne Samuel Taylor Coleridge called it a "sweet, delightful book"; John Clare imitated its style of natural history letters. Thomas Carlyle wrote that "It is one of our most excellent books; White, a quiet country Parson, has preached a better sermon here than all the loud Bis... | https://en.wikipedia.org/wiki?curid=14522051 |
The Natural History and Antiquities of Selborne Samuel, who mounted the letters and bound the book in green Morocco leather. His library was sold in 1907. The manuscript was bought by the dealer A.S.W. Rosenbach in 1923, and passed into the collection of Arthur A. Houghton. The Houghton collection was auctioned by Chri... | https://en.wikipedia.org/wiki?curid=14522051 |
The Natural History and Antiquities of Selborne It was long held ("apocryphally", according to White's biographer, Richard Mabey) to be the fourth-most published book in the English language after the Bible, the works of Shakespeare, and John Bunyan's "The Pilgrim's Progress". White's frequent accounts in "The Natural ... | https://en.wikipedia.org/wiki?curid=14522051 |
The Natural History and Antiquities of Selborne The writer and zookeeper Gerald Durrell commented in "The Amateur Naturalist" that White "simply observed nature with a sharp eye and wrote about it lovingly." | https://en.wikipedia.org/wiki?curid=14522051 |
Budh Planitia is a large basin on Mercury located at 22.0° N, 150.9° W. It lies to the east of Odin Planitia. It falls within the Tolstoj quadrangle. It is named after the Hindu word for Mercury, Budha. | https://en.wikipedia.org/wiki?curid=14523900 |
Odin Planitia is a large basin on Mercury located in the Tolstoj quadrangle at 23.3° N, 171.6° W. It was named after the Norse god Odin in 1976 by the IAU. A large volcanic dome 7 km in diameter and 1.4 km high is situated near the center of Odin. | https://en.wikipedia.org/wiki?curid=14523957 |
SOFA (astronomy) The SOFA (Standards of Fundamental Astronomy) software libraries are a collection of subroutines that implement official International Astronomical Union algorithms for astronomical computations. As of February 2009 they are available in both Fortran and C source code format. The subroutines in the lib... | https://en.wikipedia.org/wiki?curid=14526771 |
Bris sextant The is not a sextant proper, but is a small angle-measuring device that can be used for navigation. The "Bris" is, however, a true reflecting instrument which derives its high accuracy from the same principle of double reflection which is fundamental to the octant, the true sextant, and other reflecting in... | https://en.wikipedia.org/wiki?curid=14528756 |
Bris sextant In use, one waits until an image's edge touches the horizon, and then records the time and reduces the sight using the recorded angle for that edge of the image. "Bris" is Swedish for "breeze". It would appear that the name "Bris" is used by Yrvind for a number of his sail boats and is a favourite of his. | https://en.wikipedia.org/wiki?curid=14528756 |
Sobkou Planitia is a large basin on the planet Mercury. It is named after the ancient Egyptian messenger deity Sobkou (whose name is more usually transliterated Sobek). He was associated by the Egyptians with the planet Mercury. was discovered after Sobkou, the basin, was recognized as a Pre-Tolstojan basin on images f... | https://en.wikipedia.org/wiki?curid=14529059 |
Suisei Planitia is a large basin on Mercury. Ghost craters are unusual forms that occur in the Suisei Planitia. They are buried and rounded in profile, with only their rim crests rising above the surrounding smooth plains. It has been suggested that the smooth plains that is part of (Caloris Planitia) might be ejecta f... | https://en.wikipedia.org/wiki?curid=14529154 |
Tir Planitia is a large basin on the planet Mercury. The name Tir (تیر) is the Persian word for "Mercury". | https://en.wikipedia.org/wiki?curid=14529260 |
Astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either observational (by analyzing the data) or theoretical astronomy. Example... | https://en.wikipedia.org/wiki?curid=580 |
Astronomer Today, that distinction has mostly disappeared and the terms "astronomer" and "astrophysicist" are interchangeable. Professional astronomers are highly educated individuals who typically have a PhD in physics or astronomy and are employed by research institutions or universities. They spend the majority of t... | https://en.wikipedia.org/wiki?curid=580 |
Astronomer Analysis of observed phenomena, along with making predictions as to the causes of what they observe, takes the majority of observational astronomers' time. Astronomers who serve as faculty spend much of their time teaching undergraduate and graduate classes. Most universities also have outreach programs incl... | https://en.wikipedia.org/wiki?curid=580 |
Atom An atom is the smallest constituent unit of ordinary matter that constitutes a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small; typical sizes are around 100 picometers (, a ten-millionth of a millimeter, or 1/254,000,000 of an inch). They ar... | https://en.wikipedia.org/wiki?curid=902 |
Atom This force is usually stronger than the electromagnetic force that repels the positively charged protons from one another. Under certain circumstances, the repelling electromagnetic force becomes stronger than the nuclear force. In this case, the nucleus shatters and leaves behind different elements. This is a kin... | https://en.wikipedia.org/wiki?curid=902 |
Atom In the early 1800s, John Dalton used the concept of atoms to explain why chemical elements seemed to combine in ratios of small whole numbers (the law of multiple proportions). For instance, there are two types of tin oxide: one is 88.1% tin and 11.9% oxygen, and the other is 78.7% tin and 21.3% oxygen. This means... | https://en.wikipedia.org/wiki?curid=902 |
Atom This was thought to be caused by water molecules knocking the grains about. In 1905, Albert Einstein proved the reality of these molecules and their motions by producing the first statistical physics analysis of Brownian motion. French physicist Jean Perrin used Einstein's work to experimentally determine the mass... | https://en.wikipedia.org/wiki?curid=902 |
Atom They expected all the alpha particles to pass straight through with little deflection, because Thomson's model said that the charges in the atom are so diffuse that their electric fields could not affect the alpha particles much. However, Geiger and Marsden spotted alpha particles being deflected by angles greater... | https://en.wikipedia.org/wiki?curid=902 |
Atom This quantization was used to explain why the electrons' orbits are stable (given that normally, charges in acceleration, including circular motion, lose kinetic energy which is emitted as electromagnetic radiation, see "synchrotron radiation") and why elements absorb and emit electromagnetic radiation in discrete... | https://en.wikipedia.org/wiki?curid=902 |
Atom When a beam of silver atoms was passed through a specially shaped magnetic field, the beam was split in a way correlated with the direction of an atom's angular momentum, or spin. As this spin direction is initially random, the beam would be expected to deflect in a random direction. Instead, the beam was split in... | https://en.wikipedia.org/wiki?curid=902 |
Atom Thus, the planetary model of the atom was discarded in favor of one that described atomic orbital zones around the nucleus where a given electron is most likely to be observed. The development of the mass spectrometer allowed the mass of atoms to be measured with increased accuracy. The device uses a magnet to ben... | https://en.wikipedia.org/wiki?curid=902 |
Atom In the 1950s, the development of improved particle accelerators and particle detectors allowed scientists to study the impacts of atoms moving at high energies. Neutrons and protons were found to be hadrons, or composites of smaller particles called quarks. The standard model of particle physics was developed that... | https://en.wikipedia.org/wiki?curid=902 |
Atom Thomson; see history of subatomic physics for details. Protons have a positive charge and a mass 1,836 times that of the electron, at . The number of protons in an atom is called its atomic number. Ernest Rutherford (1919) observed that nitrogen under alpha-particle bombardment ejects what appeared to be hydrogen ... | https://en.wikipedia.org/wiki?curid=902 |
Atom The quarks are held together by the strong interaction (or strong force), which is mediated by gluons. The protons and neutrons, in turn, are held to each other in the nucleus by the nuclear force, which is a residuum of the strong force that has somewhat different range-properties (see the article on the nuclear ... | https://en.wikipedia.org/wiki?curid=902 |
Atom Fermions obey the Pauli exclusion principle which prohibits "identical" fermions, such as multiple protons, from occupying the same quantum state at the same time. Thus, every proton in the nucleus must occupy a quantum state different from all other protons, and the same applies to all neutrons of the nucleus and... | https://en.wikipedia.org/wiki?curid=902 |
Atom The nucleus can also be modified through bombardment by high energy subatomic particles or photons. If this modifies the number of protons in a nucleus, the atom changes to a different chemical element. If the mass of the nucleus following a fusion reaction is less than the sum of the masses of the separate partic... | https://en.wikipedia.org/wiki?curid=902 |
Atom These more massive nuclei can not undergo an energy-producing fusion reaction that can sustain the hydrostatic equilibrium of a star. The electrons in an atom are attracted to the protons in the nucleus by the electromagnetic force. This force binds the electrons inside an electrostatic potential well surrounding ... | https://en.wikipedia.org/wiki?curid=902 |
Atom The electron can change its state to a higher energy level by absorbing a photon with sufficient energy to boost it into the new quantum state. Likewise, through spontaneous emission, an electron in a higher energy state can drop to a lower energy state while radiating the excess energy as a photon. These characte... | https://en.wikipedia.org/wiki?curid=902 |
Atom For example, all hydrogen atoms admit exactly one proton, but isotopes exist with no neutrons (hydrogen-1, by far the most common form, also called protium), one neutron (deuterium), two neutrons (tritium) and more than two neutrons. The known elements form a set of atomic numbers, from the single proton element h... | https://en.wikipedia.org/wiki?curid=902 |
Atom As a rule, there is only a handful of stable isotopes for each of these elements, the average being 3.2 stable isotopes per element. Twenty-six elements have only a single stable isotope, while the largest number of stable isotopes observed for any element is ten, for the element tin. Elements 43, 61, and all elem... | https://en.wikipedia.org/wiki?curid=902 |
Atom It is a positive integer and dimensionless (instead of having dimension of mass), because it expresses a count. An example of use of a mass number is "carbon-12," which has 12 nucleons (six protons and six neutrons). The actual mass of an atom at rest is often expressed in daltons (Da), also called the unified ato... | https://en.wikipedia.org/wiki?curid=902 |
Atom Atoms lack a well-defined outer boundary, so their dimensions are usually described in terms of an atomic radius. This is a measure of the distance out to which the electron cloud extends from the nucleus. However, this assumes the atom to exhibit a spherical shape, which is only obeyed for atoms in vacuum or free... | https://en.wikipedia.org/wiki?curid=902 |
Atom Atomic dimensions are thousands of times smaller than the wavelengths of light (400–700 nm) so they cannot be viewed using an optical microscope. However, individual atoms can be observed using a scanning tunneling microscope. To visualize the minuteness of the atom, consider that a typical human hair is about 1 m... | https://en.wikipedia.org/wiki?curid=902 |
Atom A few large nuclei explode into two or more charged fragments of varying masses plus several neutrons, in a decay called spontaneous nuclear fission. Each radioactive isotope has a characteristic decay time period—the half-life—that is determined by the amount of time needed for half of a sample to decay. This is ... | https://en.wikipedia.org/wiki?curid=902 |
Atom Due to the nature of electrons to obey the Pauli exclusion principle, in which no two electrons may be found in the same quantum state, bound electrons pair up with each other, with one member of each pair in a spin up state and the other in the opposite, spin down state. Thus these spins cancel each other out, re... | https://en.wikipedia.org/wiki?curid=902 |
Atom However, for certain elements (such as xenon-129) it is possible to polarize a significant proportion of the nuclear spin states so that they are aligned in the same direction—a condition called hyperpolarization. This has important applications in magnetic resonance imaging. The potential energy of an electron in... | https://en.wikipedia.org/wiki?curid=902 |
Atom ground state to first excited state, it must absorb or emit a photon at an energy matching the difference in the potential energy of those levels, according to the Niels Bohr model, what can be precisely calculated by the Schrödinger equation. Electrons jump between orbitals in a particle-like fashion. For example... | https://en.wikipedia.org/wiki?curid=902 |
Atom ) Spectroscopic measurements of the strength and width of atomic spectral lines allow the composition and physical properties of a substance to be determined. Close examination of the spectral lines reveals that some display a fine structure splitting. This occurs because of spin–orbit coupling, which is an intera... | https://en.wikipedia.org/wiki?curid=902 |
Atom That is, the wave patterns of the two photons are synchronized. This physical property is used to make lasers, which can emit a coherent beam of light energy in a narrow frequency band. Valency is the combining power of an element. It is equal to number of hydrogen atoms that atom can combine or displace in formin... | https://en.wikipedia.org/wiki?curid=902 |
Atom (The horizontal rows correspond to the filling of a quantum shell of electrons.) The elements at the far right of the table have their outer shell completely filled with electrons, which results in chemically inert elements known as the noble gases. Quantities of atoms are found in different states of matter that ... | https://en.wikipedia.org/wiki?curid=902 |
Atom Scanning one atom (taken as the tip) as it moves past the other (the sample) permits plotting of tip displacement versus lateral separation for a constant current. The calculation shows the extent to which scanning-tunneling-microscope images of an individual atom are visible. It confirms that for low bias, the mi... | https://en.wikipedia.org/wiki?curid=902 |
Atom The atom-probe tomograph has sub-nanometer resolution in 3-D and can chemically identify individual atoms using time-of-flight mass spectrometry. Spectra of excited states can be used to analyze the atomic composition of distant stars. Specific light wavelengths contained in the observed light from stars can be se... | https://en.wikipedia.org/wiki?curid=902 |
Atom High temperature inside stars makes most "atoms" fully ionized, that is, separates "all" electrons from the nuclei. In stellar remnants—with exception of their surface layers—an immense pressure make electron shells impossible. Electrons are thought to exist in the Universe since early stages of the Big Bang. Atom... | https://en.wikipedia.org/wiki?curid=902 |
Atom Isotopes such as lithium-6, as well as some beryllium and boron are generated in space through cosmic ray spallation. This occurs when a high-energy proton strikes an atomic nucleus, causing large numbers of nucleons to be ejected. Elements heavier than iron were produced in supernovae and colliding neutron stars ... | https://en.wikipedia.org/wiki?curid=902 |
Atom Transuranic elements have radioactive lifetimes shorter than the current age of the Earth and thus identifiable quantities of these elements have long since decayed, with the exception of traces of plutonium-244 possibly deposited by cosmic dust. Natural deposits of plutonium and neptunium are produced by neutron ... | https://en.wikipedia.org/wiki?curid=902 |
Atom In any case, superheavy elements (with "Z" > 104) would not exist due to increasing Coulomb repulsion (which results in spontaneous fission with increasingly short half-lives) in the absence of any stabilizing effects. Each particle of matter has a corresponding antimatter particle with the opposite electrical cha... | https://en.wikipedia.org/wiki?curid=902 |
Alloy An alloy is a combination of metals or metals combined with one or more other elements. For example, combining the metallic elements gold and copper produces red gold, gold and silver becomes white gold, and silver combined with copper produces sterling silver. Elemental iron, combined with non-metallic carbon or... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy An alloy may be a solid solution of metal elements (a single phase, where all metallic grains (crystals) are of the same composition) or a mixture of metallic phases (two or more solutions, forming a microstructure of different crystals within the metal). Intermetallic compounds are alloys with a defined stoichio... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy This is usually called the primary metal or the base metal, and the name of this metal may also be the name of the alloy. The other constituents may or may not be metals but, when mixed with the molten base, they will be soluble and dissolve into the mixture. The mechanical properties of alloys will often be quit... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy Although the elements of an alloy usually must be soluble in the liquid state, they may not always be soluble in the solid state. If the metals remain soluble when solid, the alloy forms a solid solution, becoming a homogeneous structure consisting of identical crystals, called a phase. If as the mixture cools th... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy However, in ancient times, it could only be created as an accidental byproduct from the heating of iron ore in fires (smelting) during the manufacture of iron. Other ancient alloys include pewter, brass and pig iron. In the modern age, steel can be created in many forms. Carbon steel can be made by varying only t... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy " If there are three types of atoms forming the mixture, such as iron, nickel and chromium, then it is called a "ternary alloy." An alloy with four constituents is a "quaternary alloy," while a five-part alloy is termed a "quinary alloy." Because the percentage of each constituent can be varied, with any mixture ... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy Great care is often taken during the alloying process to remove excess impurities, using fluxes, chemical additives, or other methods of extractive metallurgy. In practice, some alloys are used so predominantly with respect to their base metals that the name of the primary constituent is also used as the name of ... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy For example, in its liquid state, titanium is a very strong solvent capable of dissolving most metals and elements. In addition, it readily absorbs gases like oxygen and burns in the presence of nitrogen. This increases the chance of contamination from any contacting surface, and so must be melted in vacuum induc... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy The physical properties, such as density, reactivity, Young's modulus of an alloy may not differ greatly from those of its base element, but engineering properties such as tensile strength, ductility, and shear strength may be substantially different from those of the constituent materials. This is sometimes a re... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy The temperature at which melting begins is called the solidus, and the temperature when melting is just complete is called the liquidus. For many alloys there is a particular alloy proportion (in some cases more than one), called either a eutectic mixture or a peritectic composition, which gives the alloy a uniqu... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy When this diffusion happens, the carbon atoms are said to be in "solution" in the iron, forming a particular single, homogeneous, crystalline phase called austenite. If the steel is cooled slowly, the carbon can diffuse out of the iron and it will gradually revert to its low temperature allotrope. During slow coo... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy When heated to form a solution and then cooled quickly, these alloys become much softer than normal, during the diffusionless transformation, but then harden as they age. The solutes in these alloys will precipitate over time, forming intermetallic phases, which are difficult to discern from the base metal. Unlik... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy Instead, the smaller atoms become trapped in the spaces between the atoms of the crystal matrix, called the "interstices". This is referred to as an "interstitial alloy". Steel is an example of an interstitial alloy, because the very small carbon atoms fit into interstices of the iron matrix. Stainless steel is a... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy Around 10,000 years ago in the highlands of Anatolia (Turkey), humans learned to smelt metals such as copper and tin from ore. Around 2500 BC, people began alloying the two metals to form bronze, which was much harder than its ingredients. Tin was rare, however, being found mostly in Great Britain. In the Middle ... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy Many ancient civilizations alloyed metals for purely aesthetic purposes. In ancient Egypt and Mycenae, gold was often alloyed with copper to produce red-gold, or iron to produce a bright burgundy-gold. Gold was often found alloyed with silver or other metals to produce various types of colored gold. These metals ... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy These solutes were sometimes added individually in varying amounts, or added together, making a wide variety of objects, ranging from practical items such as dishes, surgical tools, candlesticks or funnels, to decorative items like ear rings and hair clips. The earliest examples of pewter come from ancient Egypt,... | https://en.wikipedia.org/wiki?curid=1187 |
Alloy Around 700 AD, the Japanese began folding bloomery-steel and cast-iron in alternating layers to increase the strength of their swords, using clay fluxes to remove slag and impurities. This method of Japanese swordsmithing produced one of the purest steel-alloys of the ancient world. While the use of iron started ... | https://en.wikipedia.org/wiki?curid=1187 |
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