• NUC (Turkish politics)

    Turkey: The National Unity Committee: From the outset a clear division existed between the officers who carried out the coup. One group, consisting predominantly of younger officers, believed that, to restore national unity and carry out major social and economic reforms, it would be necessary to retain…

  • nucellus (plant anatomy)

    seed: Angiosperm seeds: …part a region called the nucellus that in turn contains an embryo sac with eight nuclei, each with one set of chromosomes (i.e., they are haploid nuclei). The two nuclei near the centre are referred to as polar nuclei; the egg cell, or oosphere, is situated near the micropylar (“open”)…

  • Nuceria Alfaterna (Italy)

    Nocera Inferiore, town and episcopal see, Campania regione, southern Italy, in the Sarno River valley, northwest of Salerno. It originated as the Oscan and Roman town of Nuceria Alfaterna, which was sacked by the Carthaginian general Hannibal in 216 bc but was rebuilt by the emperor Augustus. In

  • Nucifraga (bird)

    nutcracker, (genus Nucifraga), either of two sharp-billed, short-tailed birds belonging to the family Corvidae (order Passeriformes), found in coniferous forests. The Eurasian nutcracker (Nucifraga caryocatactes) ranges from Scandinavia to Japan and has isolated populations in mountains farther

  • Nucifraga caryocatactes (bird)

    nutcracker: The Eurasian nutcracker (Nucifraga caryocatactes) ranges from Scandinavia to Japan and has isolated populations in mountains farther south. It is 32 cm (12.5 inches) long and brownish, with white streaking and a white tail tip. Clark’s nutcracker (N. columbiana) of western North America is pale gray,…

  • Nucifraga columbiana (bird)

    nutcracker: Clark’s nutcracker (N. columbiana) of western North America is pale gray, with a black tail and wings that show white patches in flight. Both species live chiefly on seeds and nuts, which they often store underground for winter use. Clark’s nutcracker hides several pine seeds…

  • Nuclear Age, The (novel by O’Brien)

    Tim O’Brien: Return from the war, journalism career, and early books: …from this subject matter in The Nuclear Age (1981), which is about a man’s lifelong fear of dying from a nuclear bombing.

  • nuclear astrophysics (astrophysics)

    Hans Bethe: Early work: …stars created the field of nuclear astrophysics and led to his being awarded the Nobel Prize.

  • nuclear atom (physics)

    Rutherford model, description of the structure of atoms proposed (1911) by the New Zealand-born physicist Ernest Rutherford. The model described the atom as a tiny, dense, positively charged core called a nucleus, in which nearly all the mass is concentrated, around which the light, negative

  • nuclear binding energy (physics)

    nuclear binding energy, the energy required to separate an atomic nucleus completely into its constituent protons and neutrons, or, equivalently, the energy that would be liberated by combining individual protons and neutrons into a single nucleus. For example, the nucleus of the hydrogen isotope

  • nuclear binding force (physics)

    nuclear binding energy, the energy required to separate an atomic nucleus completely into its constituent protons and neutrons, or, equivalently, the energy that would be liberated by combining individual protons and neutrons into a single nucleus. For example, the nucleus of the hydrogen isotope

  • nuclear ceramics

    nuclear ceramics, ceramic materials employed in the generation of nuclear power and in the disposal of radioactive nuclear wastes. In their nuclear-related functions, ceramics are of major importance. Since the beginning of nuclear power generation, oxide ceramics, based on the fissionable metals

  • nuclear chain reaction (physics)

    chain reaction: Nuclear chain reactions are series of nuclear fissions (splitting of atomic nuclei), each initiated by a neutron produced in a preceding fission. For example, 212 neutrons on the average are released by the fission of each uranium-235 nucleus that absorbs a low-energy neutron. Provided that…

  • nuclear clock (physics)

    nuclear clock, frequency standard (not useful for ordinary timekeeping) based on the extremely sharp frequency of the gamma emission (electromagnetic radiation arising from radioactive decay) and absorption in certain atomic nuclei, such as iron-57, that exhibit the Mössbauer effect. The aggregate

  • nuclear deterrence (war)

    international relations: Between the two world wars: Bernard Brodie’s treatise on nuclear deterrence was highly influential, as was the work of Herman Kahn, Glenn Snyder, Thomas C. Schelling, Henry A. Kissinger, and Albert Wohlstetter. Other issues that were addressed in the vast literature of international relations include international, and especially European, integration; alliances and alignment, such…

  • nuclear disaster

    Japan: Political developments: …the tsunami precipitated a serious nuclear accident at the Fukushima Daiichi power station along the coast of Fukushima prefecture that forced the evacuation of residents in a wide area around the plant.

  • Nuclear Disaster in the Urals, The (work by Medvedev)

    Zhores Medvedev: His book The Nuclear Disaster in the Urals (1979) provided the West with the first details of a major nuclear disaster that had occurred in the Soviet Union in 1957. His Soviet citizenship was restored in 1990, and his books began to be published in the Soviet…

  • nuclear division (biology)

    plant development: Nutritional dependence of the embryo: As nuclear division ends, the amount of DNA per nucleus increases still further, a condition comparable with that in various plant- and animal-gland nuclei, presumably connected with the nutritional function of the endosperm. Nuclear division takes place at first without cell-wall formation so that a coenocyte…

  • nuclear electromagnetic pulse (physics)

    nuclear electromagnetic pulse (EMP), a time-varying electromagnetic radiation resulting from a nuclear explosion. For a high-yield explosion of approximately 10 megatons detonated 320 km (200 miles) above the centre of the continental United States, almost the entire country, as well as parts of

  • nuclear emulsion (physics)

    nuclear photographic emulsion, radiation detector generally in the form of a glass plate thinly coated with a transparent medium containing a silver halide compound. Passage of charged subatomic particles is recorded in the emulsion in the same way that ordinary black and white photographic film

  • nuclear endosperm (plant anatomy)

    angiosperm: Fertilization and embryogenesis: In nuclear endosperm formation, repeated free-nuclear divisions take place; if a cell wall is formed, it will form after free-nuclear division. In cellular endosperm formation, cell-wall formation is coincident with nuclear divisions. In helobial endosperm formation, a cell wall is laid down between the first two…

  • nuclear energy

    nuclear energy, energy that is released in significant amounts in processes that affect atomic nuclei, the dense cores of atoms. It is distinct from the energy of other atomic phenomena such as ordinary chemical reactions, which involve only the orbital electrons of atoms. One method of releasing

  • nuclear engineering

    nuclear engineering, the field of engineering that deals with the science and application of nuclear and radiation processes. These processes include the release, control, and utilization of nuclear energy and the production and use of radiation and radioactive materials for applications in

  • nuclear envelope (biochemistry)

    cell: The nuclear envelope: The nuclear envelope is a double membrane composed of an outer and an inner phospholipid bilayer. The thin space between the two layers connects with the lumen of the rough endoplasmic reticulum (RER), and the outer layer is an extension of the outer…

  • Nuclear Exclusion Zones

    Humans have colonized nearly every corner of planet Earth, and each day more and more land once thought inhospitable or unusable is being utilized for transportation, agriculture, and buildings. By the early 21st century, it seems only the highest mountain peaks and the most remote parts of ice

  • nuclear explosion (physics)

    warning system: Detection of nuclear explosions: In 1963 a treaty banning nuclear weapon tests in the atmosphere, in outer space, and underwater was signed. Each signatory nation was to provide monitoring. A direct consequence was the development and construction of a wide variety of devices to monitor nuclear explosions.

  • nuclear explosive (nuclear physics)

    explosive: A nuclear explosive is one in which a sustained nuclear reaction can be made to take place with almost instant rapidity, releasing large amounts of energy. Experimentation has been carried on with nuclear explosives for possible petroleum extraction purposes. This article is concerned with chemical explosives,…

  • nuclear fallout (nuclear physics)

    fallout, deposition of radioactive materials on Earth from the atmosphere. The terms rain out and snow out are sometimes used to specify such deposition during precipitant weather. Radioactivity in the atmosphere may arise from (1) natural causes, (2) nuclear or thermonuclear bomb explosions, and

  • nuclear family (anthropology)

    nuclear family, in sociology and anthropology, a group of people who are united by ties of partnership and parenthood and consisting of a pair of adults and their socially recognized children. Typically, but not always, the adults in a nuclear family are married. Although such couples are most

  • nuclear fission (physics)

    nuclear fission, subdivision of a heavy atomic nucleus, such as that of uranium or plutonium, into two fragments of roughly equal mass. The process is accompanied by the release of a large amount of energy. In nuclear fission the nucleus of an atom breaks up into two lighter nuclei. The process may

  • nuclear football

    nuclear football, a specially designed briefcase that accompanies the president of the United States when the president is away from the White House and whose contents would enable the president to decide upon and order the use of nuclear weapons in the event of a national emergency. According to a

  • nuclear force (physics)

    strong force, a fundamental interaction of nature that acts between subatomic particles of matter. The strong force binds quarks together in clusters to make more-familiar subatomic particles, such as protons and neutrons. It also holds together the atomic nucleus and underlies interactions between

  • nuclear fuel

    actinoid element: Practical applications of the actinoids: …be allowed to generate an atomic explosion, or it can be controlled and used as a fuel to generate heat for the production of electrical power. Nuclear processes for power production give off no smoke, smog, noxious gases, or even carbon dioxide, as conventional coal- or gas-fueled plants do. Nuclear…

  • nuclear fuel cycle

    nuclear reactor: The nuclear fuel cycle: No discussion of nuclear power is complete without a brief exposition of the nuclear fuel cycle. The whole point of a reactor is, after all, to initiate and control the process of fission on a very large scale in nuclear fuel, and…

  • nuclear fusion (physics)

    nuclear fusion, process by which nuclear reactions between light elements form heavier elements (up to iron). In cases where the interacting nuclei belong to elements with low atomic numbers (e.g., hydrogen [atomic number 1] or its isotopes deuterium and tritium), substantial amounts of energy are

  • nuclear isomer (nuclear physics)

    isomer, in nuclear physics, any of two or more nuclides (species of atomic nuclei) that consist of the same number of protons and the same number of neutrons but differ in energy and manner of radioactive decay, and that exist for a measurable interval of time. The half-life of the more energetic

  • Nuclear Madness: What You Can Do! (work by Caldicott, Herrington, and Stiskin)

    Helen Caldicott: There she published Nuclear Madness: What You Can Do! (1978; with Nancy Herrington and Nahum Stiskin), in which she explained the consequences of nuclear technology in vivid, accessible language. She gave numerous public lectures and made television appearances.

  • nuclear magnetic moment (physics)

    magnetism: Paramagnetism: The size of the nuclear magnetic moment is only about one-thousandth that of an atom. Per kilogram mole, χn is on the order of 10−8/T; in solid hydrogen this just exceeds the electronic diamagnetism of 1 K.

  • nuclear magnetic resonance (scientific technique)

    nuclear magnetic resonance (NMR), selective absorption of very high-frequency radio waves by certain atomic nuclei that are subjected to an appropriately strong stationary magnetic field. This phenomenon was first observed in 1946 by the physicists Felix Bloch and Edward M. Purcell independently of

  • nuclear magnetic resonance spectroscopy (medicine)

    magnetic resonance spectroscopy (MRS), diagnostic imaging technique based on the detection of metabolites in tissues. Magnetic resonance spectroscopy (MRS) is related to magnetic resonance imaging (MRI) in that it uses the same machinery; however, instead of measuring blood flow, MRS measures the

  • nuclear magnetic resonance spectroscopy (chemistry)

    chemical analysis: Nuclear magnetic resonance: The absorption that occurs in different spectral regions corresponds to different physical processes that occur within the analyte. Absorption of energy in the radiofrequency region is sufficient to cause a spinning nucleus in some atoms to move to a different spin state…

  • nuclear magneton (physics)

    magneton: The nuclear magneton, calculated by using the mass of the proton (rather than that of the electron, used to calculate the Bohr magneton) equals 1/1,836 Bohr magneton. See magnetic dipole.

  • nuclear medicine

    nuclear medicine, medical specialty that involves the use of radioactive isotopes in the diagnosis and treatment of disease. Nuclear medicine enables clinicians to noninvasively and precisely identify specific molecular activity within tissues and organs of the body, facilitating the early

  • nuclear membrane (biology)

    eukaryote: The eukaryotic cell has a nuclear membrane that surrounds the nucleus, in which the well-defined chromosomes (bodies containing the hereditary material) are located. This compartmentalization allows for the separation of transcription (synthesis of RNA from DNA) and translation (synthesis of protein from RNA), increasing the

  • Nuclear Micronesian languages

    Micronesian languages: …all closely related, are the Nuclear Micronesian languages, including Marshallese, Gilbertese, Chuukese, Pohnpeian, Kosraean, Carolinean, and Ulithian. Two more languages of Micronesia that belong to the Polynesian group are Nukuoro and Kapingamarangi. Two languages spoken in Micronesia appear to be most closely related to the Western, or Indonesian, branch of…

  • nuclear model (physics)

    nuclear model, any of several theoretical descriptions of the structure and function of atomic nuclei (the positively charged, dense cores of atoms). Each of the models is based on a plausible analogy that correlates a large amount of information and enables predictions of the properties of nuclei.

  • Nuclear Non-Proliferation Treaty (international agreement)

    Treaty on the Non-Proliferation of Nuclear Weapons, agreement of July 1, 1968, signed by the United Kingdom, the United States, the Soviet Union, and 59 other states, under which the three major signatories, which possessed nuclear weapons, agreed not to assist other states in obtaining or

  • nuclear option (United States Senate procedure)

    Neil Gorsuch: Supreme Court nomination and confirmation: …to it as the “nuclear option.”

  • nuclear photoelectric effect (physics)

    photodisintegration, in physics, nuclear reaction in which the absorption of high-energy electromagnetic radiation (a gamma-ray photon) causes the absorbing nucleus to change to another species by ejecting a subatomic particle, such as a proton, neutron, or alpha particle. For example,

  • nuclear photographic emulsion (physics)

    nuclear photographic emulsion, radiation detector generally in the form of a glass plate thinly coated with a transparent medium containing a silver halide compound. Passage of charged subatomic particles is recorded in the emulsion in the same way that ordinary black and white photographic film

  • nuclear physics

    astronomy: The rise of astrophysics: …of the primitive state of nuclear physics at the time, he could not say in detail how this might occur, but he pointed to the mere existence of helium in the stars as the surest proof that such a process must exist. Nuclear physics gained a firm foundation in the…

  • Nuclear Polynesian languages

    Austronesian languages: Polynesian languages: …Tongic (Tongan and Niue) and Nuclear Polynesian (the rest). Nuclear Polynesian in turn contains Samoic-Outlier and Eastern Polynesian. Maori and Hawaiian, two Eastern Polynesian languages that are separated by some 5,000 miles of sea, appear to be about as closely related as Dutch and German. The closest external relatives of…

  • nuclear pore complex (biology)

    Günter Blobel: …to be known as the nuclear pore complex (NPC). The NPC is one of the largest protein-based components found in cells and provides the main method of transport for proteins between the cytoplasm and the nucleus. Blobel was primarily concerned with determining the structure of the NPC and employed various…

  • Nuclear Power (ProCon debate)

    From the discovery of the neutron by James Chadwick in England in 1932 to the nuclear weapons created by J. Robert Oppenheimer and his colleagues in the Manhattan Project (1942–45), many scientists contributed to the discovery of nuclear power and its uses. The first nuclear reactor was built by

  • nuclear power

    nuclear power, electricity generated by power plants that derive their heat from fission in a nuclear reactor. Except for the reactor, which plays the role of a boiler in a fossil-fuel power plant, a nuclear power plant is similar to a large coal-fired power plant, with pumps, valves, steam

  • nuclear power plant

    Fukushima accident: …the Fukushima Daiichi (“Number One”) plant in northern Japan, the second worst nuclear accident (after the Chernobyl disaster of 1986) in the history of nuclear power generation. The site is on Japan’s Pacific coast, in northeastern Fukushima prefecture about 100 km (60 miles) south of Sendai. The facility, operated by…

  • nuclear proliferation (military)

    nuclear proliferation, the spread of nuclear weapons, nuclear weapons technology, or fissile material to countries that do not already possess them. The term is also used to refer to the possible acquisition of nuclear weapons by terrorist organizations or other armed groups. During World War II

  • nuclear quadrupole reaction spectroscopy (physics)

    spectroscopy: General principles: … spin resonance (ESR) spectroscopy, and nuclear quadrupole resonance (NQR) spectroscopy. The first two arise, respectively, from the interaction of the magnetic moment of a nucleus or an electron with an external magnetic field. The nature of this interaction is highly dependent on the molecular environment in which the nucleus or…

  • nuclear reaction (physics)

    nuclear reaction, change in the identity or characteristics of an atomic nucleus, induced by bombarding it with an energetic particle. The bombarding particle may be an alpha particle, a gamma-ray photon, a neutron, a proton, or a heavy ion. In any case, the bombarding particle must have enough

  • nuclear reaction equilibrium (physics)

    chemical element: Reversible nuclear reaction equilibrium: Finally, at temperatures around 4 × 109 K, an approximation to nuclear statistical equilibrium may be reached. At this stage, although nuclear reactions continue to occur, each nuclear reaction and its inverse occur equally rapidly, and there is no further overall change…

  • nuclear reactor (device)

    nuclear reactor, any of a class of devices that can initiate and control a self-sustaining series of nuclear fissions. Nuclear reactors are used as research tools, as systems for producing radioactive isotopes, and most prominently as energy sources for nuclear power plants. Nuclear reactors

  • nuclear recoil (physics)

    Mössbauer effect: The second concept, that of nuclear recoil, may be illustrated by the behaviour of a rifle. If it is held loosely during firing, its recoil, or “kick,” will be violent. If it is firmly held against the marksman’s shoulder, the recoil will be greatly reduced. The difference in the two…

  • Nuclear Regulatory Commission (United States organization)

    Nuclear Regulatory Commission (NRC), an independent regulatory agency that is responsible for overseeing the civilian use of nuclear materials in the United States. The NRC was established on Oct. 11, 1974, by President Gerald Ford as one of two successor organizations to the Atomic Energy

  • nuclear shell (military technology)

    artillery: Nuclear shells, guided projectiles, and rocket assistance: Nuclear explosive was adapted to artillery by the United States’ “Atomic Annie,” a 280-millimetre gun introduced in 1953. This fired a 15-kiloton atomic projectile to a range of 17 miles, but, weighing 85 tons, it proved too cumbersome…

  • nuclear shield (military science)

    Strategic Defense Initiative: strategic defensive system against potential nuclear attacks—as originally conceived, from the Soviet Union. The SDI was first proposed by President Ronald Reagan in a nationwide television address on March 23, 1983. Because parts of the defensive system that Reagan advocated would be based in space, the…

  • nuclear species (physics)

    nuclide, species of atom as characterized by the number of protons, the number of neutrons, and the energy state of the nucleus. A nuclide is thus characterized by the mass number (A) and the atomic number (Z). To be regarded as distinct a nuclide must have an energy content sufficient for a m

  • nuclear strategy (military)

    nuclear strategy, the formation of tenets and strategies for producing and using nuclear weapons. Nuclear strategy is no different from any other form of military strategy in that it involves relating military means to political ends. In this case, however, the military means in question are so

  • nuclear submarine

    nuclear submarine, submarine that relies on a nuclear reactor to drive its propulsion system. A nuclear submarine may or may not be armed with nuclear weapons. The chief advantages afforded by nuclear power are increased speed (allowing submerged submarines to keep up with fast surface ships) and

  • Nuclear Suppliers Group (international organization)

    Nuclear Suppliers Group (NSG), voluntary association of 48 countries that are capable of exporting and transporting civilian nuclear technology and that have pledged to conduct the transfer of this technology under mutually agreed guidelines. The ultimate purpose of the NSG’s guidelines is to

  • Nuclear Test-Ban Treaty (1963)

    Nuclear Test-Ban Treaty, treaty signed in Moscow on August 5, 1963, by the United States, the Soviet Union, and the United Kingdom that banned all tests of nuclear weapons except those conducted underground. The origins of the treaty lay in worldwide public concern over the danger posed by

  • nuclear testing

    nuclear weapon: The weapons are tested: It was immediately clear to all scientists concerned that these new ideas—achieving a high density in the thermonuclear fuel by compression using a fission primary—provided for the first time a firm basis for a fusion weapon. Without hesitation, Los Alamos adopted the new program.…

  • Nuclear Threat Initiative (American organization)

    Sam Nunn: …in 2001 he cofounded the Nuclear Threat Initiative (NTI), a Washington, D.C., nonprofit organization established to reduce the threat posed to global security by weapons of mass destruction. Nunn was also a distinguished professor at the school of international affairs at Georgia Tech that bore his name.

  • nuclear transfer (genetics)

    nuclear transfer, the introduction of the nucleus from a cell into an enucleated egg cell (an egg cell that has had its own nucleus removed). This can be accomplished through fusion of the cell to the egg or through the direct removal of the nucleus from the cell and the subsequent transplantation

  • nuclear transformation (physics)

    transmutation, conversion of one chemical element into another. A transmutation entails a change in the structure of atomic nuclei and hence may be induced by a nuclear reaction (q.v.), such as neutron capture, or occur spontaneously by radioactive decay, such as alpha decay and beta decay (qq.v.).

  • nuclear transplantation (genetics)

    heredity: DNA as the agent of heredity: …to pass through cellular and nuclear membranes and then integrate into the chromosomal DNA of the recipient cell. Furthermore, using modern DNA technology, it is possible to isolate the section of chromosomal DNA that constitutes an individual gene, manipulate its structure, and reintroduce it into a cell to cause changes…

  • nuclear triad (military strategy)

    nuclear triad, a three-sided military-force structure consisting of land-launched nuclear missiles, nuclear-missile-armed submarines, and strategic aircraft with nuclear bombs and missiles. The triad was a central element of the U.S. military strategy (and, to a lesser degree, that of the Soviet

  • nuclear warfare

    doomsday machine: …in the event of a nuclear attack on the country maintaining the device. The former type of device might automatically launch a large number of ICBMs (intercontinental ballistic missiles) when it detected a nuclear explosion or an imminent nuclear attack, whereas the latter might detonate several very large thermonuclear bombs…

  • nuclear warhead (weapon)

    thermonuclear warhead, thermonuclear (fusion) bomb designed to fit inside a missile. By the early 1950s both the United States and the Soviet Union had developed nuclear warheads that were small and light enough for missile deployment, and by the late 1950s both countries had developed

  • nuclear waste

    nuclear power: Radioactive-waste disposal: Spent nuclear reactor fuel and the waste stream generated by fuel reprocessing contain radioactive materials and must be conditioned for permanent disposal. The amount of waste coming out of the nuclear fuel cycle is very small compared with the amount of waste generated…

  • nuclear weak force (physics)

    weak interaction, a fundamental force of nature that underlies some forms of radioactivity, governs the decay of unstable subatomic particles such as mesons, and initiates the nuclear fusion reaction that fuels the Sun. The weak interaction acts upon left-handed fermions—i.e., elementary particles

  • nuclear weapon

    nuclear weapon, device designed to release energy in an explosive manner as a result of nuclear fission, nuclear fusion, or a combination of the two processes. Fission weapons are commonly referred to as atomic bombs. Fusion weapons are also referred to as thermonuclear bombs or, more commonly,

  • Nuclear Weapons and Foreign Policy (work by Kissinger)

    Henry Kissinger: Early life, academic career, and initial government service: Kissinger’s Nuclear Weapons and Foreign Policy (1957) established him as an authority on U.S. strategic policy. He opposed Secretary of State John Foster Dulles’s policy of planning a nuclear “massive retaliation” to Soviet attack, advocating instead a “flexible response” combining the use of tactical nuclear weapons…

  • Nuclear Weapons Test-Ban Treaty (1963)

    Nuclear Test-Ban Treaty, treaty signed in Moscow on August 5, 1963, by the United States, the Soviet Union, and the United Kingdom that banned all tests of nuclear weapons except those conducted underground. The origins of the treaty lay in worldwide public concern over the danger posed by

  • nuclear winter

    nuclear winter, the environmental devastation that certain scientists contend would probably result from the hundreds of nuclear explosions in a nuclear war. The damaging effects of the light, heat, blast, and radiation caused by nuclear explosions had long been known to scientists, but such

  • nuclear-track recording (physics)

    technology of photography: Nuclear-track recording: Tracks of subatomic particles, such as protons, electrons, and mesons, produced by nuclear reactions can be recorded by photographic means. The most common technique is to photograph the visible traces of such tracks in bubble or spark chambers with special camera and lens…

  • nuclease (biology)

    nuclease, any enzyme that cleaves nucleic acids by breaking phosphodiester bonds between nucleotide molecules. Nucleases act via hydrolysis, using water to break bonds, and thus belong to the class of enzymes known as hydrolases. They serve a vital role in certain basic biological processes, namely

  • nucleated droplet mechanism (chemistry)

    industrial glass: Phase separation: …of phase separation exist, the nucleated droplet and the spinodal; the microstructures produced by these two mechanisms, as revealed by electron microscopy, are shown in Figure 4. In Figure 4A the interface between the droplets and the matrix is sharp, owing to a sharp change in composition. With time the…

  • nucleation (crystallography)

    nucleation, the initial process that occurs in the formation of a crystal from a solution, a liquid, or a vapour, in which a small number of ions, atoms, or molecules become arranged in a pattern characteristic of a crystalline solid, forming a site upon which additional particles are deposited as

  • nucleic acid (chemical compound)

    nucleic acid, naturally occurring chemical compound that serves as the main information-carrying molecule of the cell and that directs the process of protein synthesis, thereby determining the inherited characteristics of every living thing. Nucleic acids are further defined by their ability to be

  • nuclein (chemical compound)

    nucleic acid, naturally occurring chemical compound that serves as the main information-carrying molecule of the cell and that directs the process of protein synthesis, thereby determining the inherited characteristics of every living thing. Nucleic acids are further defined by their ability to be

  • nucleocapsid (biochemistry)

    nucleoprotein, molecule consisting of a protein linked to a nucleic acid, either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid). Nucleoproteins serve important functions in living organisms, owing to their involvement in essential processes, particularly replication, transcription, and

  • nucleoli (biology)

    nucleolus, spherical body within the nucleus of most eukaryotic cells, involved in the synthesis of ribosomal RNA (rRNA) and the formation of ribosomes. Nucleoli appear shortly after mitosis and form around specific repeating chromosome regions, known as nucleolar organizing regions, within the

  • nucleolus (biology)

    nucleolus, spherical body within the nucleus of most eukaryotic cells, involved in the synthesis of ribosomal RNA (rRNA) and the formation of ribosomes. Nucleoli appear shortly after mitosis and form around specific repeating chromosome regions, known as nucleolar organizing regions, within the

  • nucleon (physics)

    nucleon, either of the subatomic particles, the proton and the neutron, constituting atomic nuclei. Protons (positively charged) and neutrons (uncharged) behave identically under the influence of the short-range nuclear force, both in the way they are bound in nuclei and in the way they are

  • nucleon number (physics)

    mass number, in nuclear physics, the sum of the numbers of protons and neutrons present in the nucleus of an atom. The mass number is commonly cited in distinguishing among the isotopes of an element, all of which have the same atomic number (number of protons) and are represented by the same

  • nucleonics (physics)

    particle accelerator: …research on the structure of nuclei, the nature of nuclear forces, and the properties of nuclei not found in nature, as in the transuranium elements and other unstable elements. Accelerators are also used for radioisotope production, industrial radiography, radiation therapy, sterilization of biological materials, and a certain form of radiocarbon

  • nucleophile (chemistry)

    nucleophile, in chemistry, an atom or molecule that in chemical reaction seeks a positive centre, such as the nucleus of an atom, because the nucleophile contains an electron pair available for bonding. Examples of nucleophiles are the halogen anions (I-, Cl-, Br-), the hydroxide ion (OH-), the

  • nucleophilic addition (chemical reaction)

    aldehyde: Nucleophilic addition: Aldehydes undergo many different nucleophilic addition reactions. This is because the positive carbon atom of an aldehyde molecule, which always has one bond attached to the small hydrogen atom, is susceptible to attack by a nucleophilic reagent.

  • nucleophilic aromatic substitution (chemical reaction)

    organohalogen compound: Reactions: Nucleophilic aromatic substitution is a practical synthetic reaction only when the aryl halide bears a strongly electron-attracting substituent, such as a nitro group NO2, at a position ortho or para to the halogen, as in 1-chloro-4-nitrobenzene:

  • nucleophilic reactivity

    organometallic compound: Carbanion character: …is frequently referred to as nucleophilic or carbanion character. Thus, organometallic compounds containing highly active (electropositive) metals, such as lithium, magnesium, aluminum, and zinc, react rapidly and completely with water, liberating a hydrocarbon in the process. For example, dimethylzinc liberates methane gas along with solid zinc hydroxide. Zn(CH3)2 + 2H2O…