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Deuterium Gas
Deuterium (hydrogen-2, symbol H or D, also known as heavy hydrogen) is one of two stable isotopes of hydrogen; the other is protium, or hydrogen-1, H. The deuterium nucleus (deuteron) contains one proton and one neutron, whereas the far more common H has no neutrons. The name ''deuterium'' comes from Greek '' deuteros'', meaning "second". American chemist Harold Urey discovered deuterium in 1931. Urey and others produced samples of heavy water in which the H had been highly concentrated. The discovery of deuterium won Urey a Nobel Prize in 1934. Nearly all deuterium found in nature was synthesized in the Big Bang 13.8 billion years ago, forming the primordial ratio of H to H (~26 deuterium nuclei per 10 hydrogen nuclei). Deuterium is subsequently produced by the slow stellar proton–proton chain, but rapidly destroyed by exothermic fusion reactions. The deuterium–deuterium reaction has the second-lowest energy threshold, and is the most astrophysically accessi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tellus A
''Tellus Series A: Dynamic Meteorology and Oceanography'' is a peer-reviewed scientific journal that is published by Co-action Publishing on behalf of the International Meteorological Institute in Stockholm, Sweden. Since January 2012, the journal is published open access. Until that time it had been published as a subscription journal by Wiley-Blackwell, Blackwell Munksgaard. The journal publishes original articles, short contributions and correspondence encompassing dynamic meteorology, climatology and oceanography, including Mathematical model, numerical modelling, synoptic meteorology, weather forecasting, and climate analysis. ''Tellus A'' is the companion to ''Tellus B, Tellus Series B: Chemical and Physical Meteorology''. See also * List of scientific journals * List of scientific journals in earth and atmospheric sciences References External links * Previous websiteat Taylor and Francis (until 2022) Journal page at Blackwell Munksgaard (until 2012) Earth and a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stars
A star is a luminous spheroid of plasma held together by self-gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixed points of light. The most prominent stars have been categorised into constellations and asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated to stars. Only about 4,000 of these stars are visible to the naked eye—all within the Milky Way galaxy. A star's life begins with the gravitational collapse of a gaseous nebula of material largely comprising hydrogen, helium, and traces of heavier elements. Its stellar mass, total mass mainly determines its stellar evolution, evolution and eventual fate. A star shines for main sequence, most of its active life due to the thermonu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Isotope Biogeochemistry
Hydrogen isotope biogeochemistry (HIBGC) is the scientific study of biological, geological, and chemical processes in the environment using the distribution and relative abundance of hydrogen isotopes. Hydrogen has two stable isotopes, protium H and deuterium H, which vary in relative abundance on the order of hundreds of Per mille, permil. The ratio between these two species can be called the hydrogen isotopic signature of a substance. Understanding isotopic fingerprints and the sources of Isotope fractionation, fractionation that lead to variation between them can be applied to address a diverse array of questions ranging from ecology and hydrology to geochemistry and paleoclimate reconstructions. Since specialized techniques are required to measure natural hydrogen isotopic composition (HIC), HIBGC provides uniquely specialized tools to more traditional fields like ecology and geochemistry. History of hydrogen isotopes Earliest work The study of hydrogen stable isotopes began ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotopic Label
Isotopic labeling (or isotopic labelling) is a technique used to track the passage of an isotope (an atom with a detectable variation in neutron count) through chemical reaction, metabolic pathway, or a biological cell. The reactant is 'labeled' by replacing one or more specific atoms with their isotopes. The reactant is then allowed to undergo the reaction. The position of the isotopes in the products is measured to determine what sequence the isotopic atom followed in the reaction or the cell's metabolic pathway. The nuclides used in isotopic labeling may be stable nuclides or radionuclides. In the latter case, the labeling is called radiolabeling. In isotopic labeling, there are multiple ways to detect the presence of labeling isotopes; through their mass, vibrational mode, or radioactive decay. Mass spectrometry detects the difference in an isotope's mass, while infrared spectroscopy detects the difference in the isotope's vibrational modes. Nuclear magnetic resonance detects ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pressurized Heavy-water Reactor
A pressurized heavy-water reactor (PHWR) is a nuclear reactor that uses heavy water (deuterium oxide D2O) as its coolant and neutron moderator. PHWRs frequently use natural uranium as fuel, but sometimes also use very low enriched uranium. The heavy water coolant is kept under pressure to avoid boiling, allowing it to reach higher temperature (mostly) without forming steam bubbles, exactly as for a pressurized water reactor (PWR). While heavy water is very expensive to isolate from ordinary water (often referred to as ''light water'' in contrast to ''heavy water''), its low absorption of neutrons greatly increases the neutron economy of the reactor, avoiding the need for enriched fuel. The high cost of the heavy water is offset by the lowered cost of using natural uranium and/or alternative fuel cycles. As of the beginning of 2001, 31 PHWRs were in operation, having a total capacity of 16.5 GW(e), representing roughly 7.76% by number and 4.7% by generating capacity of all curre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutron Moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, ideally without capturing any, leaving them as thermal neutrons with only minimal (thermal) kinetic energy. These thermal neutrons are immensely more susceptible than fast neutrons to propagate a nuclear chain reaction of uranium-235 or other fissile isotope by colliding with their atomic nucleus. Water (sometimes called "light water" in this context) is the most commonly used moderator (roughly 75% of the world's reactors). Solid graphite (20% of reactors) and heavy water (5% of reactors) are the main alternatives. Beryllium has also been used in some experimental types, and hydrocarbons have been suggested as another possibility. Moderation Neutrons are normally bound into an atomic nucleus and do not exist free for long in nature. The unbound neutron has a half-life of 10 minutes and 11 seconds. The release of neutrons from the nucleus requires exceeding the binding ener ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fusion Power
Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices designed to harness this energy are known as fusion reactors. Research into fusion reactors began in the 1940s, but as of 2025, no device has reached net power. Fusion processes require fuel, in a state of plasma, and a confined environment with sufficient temperature, pressure, and confinement time. The combination of these parameters that results in a power-producing system is known as the Lawson criterion. In stellar cores the most common fuel is the lightest isotope of hydrogen (Protium (isotope), protium), and gravity provides the conditions needed for fusion energy production. Proposed fusion reactors would use the heavy hydrogen isotopes of deuterium and tritium for DT fusion, for which the Lawson criterion is the easiest to achieve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission or atomic bomb) or a combination of fission and fusion reactions (thermonuclear weapon), producing a nuclear explosion. Both bomb types release large quantities of energy from relatively small amounts of matter. Nuclear bombs have had yields between 10 tons (the W54) and 50 megatons for the Tsar Bomba (see TNT equivalent). Yields in the low kilotons can devastate cities. A thermonuclear weapon weighing as little as can release energy equal to more than 1.2 megatons of TNT (5.0 PJ). Apart from the blast, effects of nuclear weapons include firestorms, extreme heat and ionizing radiation, radioactive nuclear fallout, an electromagnetic pulse, and a radar blackout. The first nuclear weapons were developed by the Allied Manhattan Project during World War II. Their production continues to require a large scientific and industrial complex, pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Science (journal)
''Science'' is the peer review, peer-reviewed academic journal of the American Association for the Advancement of Science (AAAS) and one of the world's top academic journals. It was first published in 1880, is currently circulated weekly and has a subscriber base of around 130,000. Because institutional subscriptions and online access serve a larger audience, its estimated readership is over 400,000 people. ''Science'' is based in Washington, D.C., United States, with a second office in Cambridge, UK. Contents The major focus of the journal is publishing important original scientific research and research reviews, but ''Science'' also publishes science-related news, opinions on science policy and other matters of interest to scientists and others who are concerned with the wide implications of science and technology. Unlike most scientific journals, which focus on a specific field, ''Science'' and its rival ''Nature (journal), Nature'' cover the full range of List of academ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kathrin Altwegg
Kathrin Altwegg is an astrophysicist, who is an Associate Professor in the Department of Space Research and Planetology, and former director of the '' '' (CSH) at the University of Bern. She is a member of the International Astronomical Union. Early life Kathrin Altwegg was born on 11 December 1951 in Balsthal. Between 1957 and 1970, she completed her primary education in Balsthal and passed the High school diploma in Switzerland at the lycée in Solothurn. Education and research career In 1975, she graduated studying physics at University of Basel, where she was the only woman in her year. In 1980, she obtained her doctorate in experimental physics from the University of Basel and proceeded to undertake post-doctoral research in the physics-chemistry department of the University of Technology, Design and Architecture, in New York. In 1982, she returned to Switzerland, where she gained a position at the University of Bern, in the space exploration and planetology depart ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rosetta (spacecraft)
''Rosetta'' was a space probe built by the European Space Agency that launched on 2 March 2004. Along with ''Philae'', its lander module, ''Rosetta'' performed a detailed study of comet 67P/Churyumov–Gerasimenko (67P). During its journey to the comet, the spacecraft performed flybys of Earth, Mars, and the asteroids 21 Lutetia and 2867 Šteins. It was launched as the third cornerstone mission of the ESA's Horizon 2000 programme, after ''SOHO' Cluster'' and '' XMM-Newton''. On 6 August 2014, the spacecraft reached the comet and performed a series of manoeuvers to eventually orbit the comet at distances of . On 12 November, its lander module ''Philae'' performed the first successful landing on a comet, though its battery power ran out two days later. Communications with ''Philae'' were briefly restored in June and July 2015, but due to diminishing solar power, ''Rosetta'' communications module with the lander was turned off on 27 July 2016. On 30 September 2016, the ''Rosett ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
67P/Churyumov–Gerasimenko
67P/Churyumov–Gerasimenko (abbreviated as 67P or 67P/C–G) is a Jupiter-family comet. It is originally from the Kuiper belt and has an orbital period of 6.45 years as of 2012, a rotation period of approximately 12.4 hours, and a maximum velocity of . Churyumov–Gerasimenko is approximately at its longest and widest dimensions. It was first observed on photographic plates in 1969 by Soviet astronomers Klim Churyumov, Klim Ivanovych Churyumov and Svetlana Gerasimenko, Svetlana Ivanovna Gerasimenko, after whom it is Naming of comets, named. It most recently came to Perihelion and aphelion, perihelion (closest approach to the Sun) on 2 November 2021, and will next come to perihelion on 9 April 2028. Churyumov–Gerasimenko was the destination of the European Space Agency's Rosetta (spacecraft), ''Rosetta'' mission, launched on 2 March 2004. ''Rosetta'' space rendezvous, rendezvoused with Churyumov–Gerasimenko on 6 August 2014 and entered orbit on 10 September 2014. ''Rosetta' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
