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  • radio beacon
    Radio beacons, which first appeared in the 1920s, transmit in the frequency band of 285–315 kilohertz. In a characteristic signal lasting one minute, the station identification, in Morse code, is transmitted two or three times, followed by a period of continuous transmission during which a bearing can be taken by a ship’s direction-finding receiver. Bearing accuracy averages better t...
  • Radio Caroline (British radio station)
    In spring 1964, Radio Caroline began broadcasting from a ship anchored in international waters off the coast of Essex. Its nonstop pop was presented by young, effusive disc jockeys, punctuated by previously unheard American Top 40-style jingles and commercials, and unhindered by needle-time restrictions or royalty payments. A pirate radio armada gathered around the British coast, luring......
  • Radio Church of God
    Adventist church founded in 1933 as the Radio Church of God by Herbert W. Armstrong (1892–1986), an American newspaper advertising designer. Until the mid-1990s the church taught a non-Trinitarian theology, held Saturday worship services, and preached the imminent return of Jesus Christ....
  • Radio City Music Hall (building, New York City, New York, United States)
    ...for decorative purposes brought him acclaim and caught the attention of the Rockefeller Center, Inc., which in 1932 awarded him a large contract for the interior decoration and furnishings for Radio City Music Hall. The extraordinary results of this project helped the designer launch Donald Deskey Associates as a major consulting firm....
  • Radio City Rockettes (American dance troupe)
    world-famous American precision dance team....
  • radio compass (instrument)
    radio receiver and directional antenna system used to determine the direction of the source of a signal. It most often refers to a device used to check the position of a ship or aircraft, although it may also direct a craft’s course or be used for military or investigative purposes....
  • Radio Corporation of America (American firm)
    major American electronics and broadcasting conglomerate that is a unit of General Electric Company. Among its subsidiaries is the National Broadcasting Company (NBC). Headquarters are in New York City....
  • radio direction finder (instrument)
    radio receiver and antenna system for determining the direction of the source of a radio signal. A direction finder (DF) can be used by an aircraft or ship as a navigational aid. This is accomplished by measuring the direction (bearing) of at least two transmitters whose locations are already known. When the measured directions from each transmitter are plotted on a map, the intersection of the tw...
  • radio direction finder (instrument)
    radio receiver and directional antenna system used to determine the direction of the source of a signal. It most often refers to a device used to check the position of a ship or aircraft, although it may also direct a craft’s course or be used for military or investigative purposes....
  • radio emission (astronomy)
    Jupiter was the first planet found (in 1955) to be a source of radiation at radio wavelengths (see radio and radar astronomy). The radiation was recorded at a frequency of 22 megahertz (corresponding to a wavelength of 13.6 metres, or 1.36 decametres) in the form of noise bursts with peak intensities sometimes great enough to make Jupiter the brightest source in the sky at this wavelength,....
  • radio energy (physics)
    The radio altimeter measures the distance of an aircraft above the ground rather than above sea level. The altitude is equal to one-half the time that it takes a pulse of radio energy to travel from the aircraft to the ground and back multiplied by the speed of the pulse (equivalent to the speed of light). The measured altitude is displayed on a video screen. Radio altimeters are used in......
  • Radio Engineering (work by Terman)
    ...Valley. His other scientific contributions include work on long-distance electrical transmission and resonant transmission lines. From its initial publication in 1932 until the 1960s, Terman’s Radio Engineering was the leading book in its field....
  • Radio Free Europe
    ...for Christian Communications, set up in 1968 and based in London, and the Association Catholique Internationale pour la Radio, la Télévision, et l’Audiovisuel, based in Brussels. Radio Free Europe, based in Munich and financed by U.S. government funds, was established to broadcast pro-Western propaganda to eastern Europe....
  • radio frequency integrated circuit (electronics)
    Radio-frequency ICs (RFICs) are rapidly gaining importance in cellular telephones and pagers. RFICs are analog circuits that usually run in the frequency range of 900 MHz to 2.4 GHz (900 million hertz to 2.4 billion hertz). They are usually thought of as ASICs even though some may be configurable for several similar applications....
  • radio frequency modulation (electronics)
    (FM), variation of the frequency of a carrier wave in accordance with the characteristics of a signal. See modulation....
  • radio galaxy (astronomy)
    ...and that lie beyond the confines of the Galaxy were divided in the 1950s into two classes depending on whether they present spatially extended or essentially “starlike” images. Radio galaxies belong to the former class, and quasars (short for “quasi-stellar radio sources”) to the latter. The distinction is somewhat arbitrary, because the ability to distinguish......
  • Radio Golf (play by Wilson)
    ...which takes place in 1904 and centres on Aunt Ester, a 287-year-old spiritual healer mentioned in previous plays, and a man who seeks her help. Wilson completed the cycle with Radio Golf (first produced 2005). Set in the 1990s, the play concerns the fate of Aunt Ester’s house, which is slated to be torn down by real-estate developers. Music, particularly jazz and...
  • radio interferometer (astronomical instrument)
    apparatus consisting of two or more separate antennas that receive radio waves from the same astronomical object and are joined to the same receiver. The antennas may be placed close together or thousands of kilometres apart. (Using the Japanese VSOP satellite together with ground-based telescopes, the largest interferometer baselines have been up to 33,000 km [21,000 miles]).The principle of a ra...
  • radio jet (astronomy)
    A clue to the nature of the underlying source of power came from aperture-synthesis studies of the fine structure of double-lobed radio galaxies. It was found that many such sources possess radio jets that point from the nuclei of the parent galaxies to the radio lobes. It is now believed, largely because of the work of Sir Martin Rees and Roger Blandford, that the nucleus of an active galaxy......
  • Radio London (British radio station)
    Liverpool-born Maurice Cole changed his name to Kenny Everett as a legal precaution before making his broadcasting debut on pirate Radio London, the slickest of the illegal stations that ringed the coastline of the United Kingdom in the mid-1960s. A sometimes surreal sense of humour that was part Beatles and part Goon (the influential British radio comedy of the 1950s, The Goon Show,......
  • Radio Luxembourg (British radio station)
    Until the advent of pirate radio in 1964, the evenings-only English-language broadcasts from Radio Luxembourg—208 on the dial and transmitted from the grand duchy—represented the only pop music radio regularly available to British fans. Although the station’s policy of leasing airtime to record companies meant having to hear a sequence of forgettable records on, for example, t...
  • Radio Nacional Española (Spanish government station)
    Radio broadcasting began on a small scale in the 1920s. A government station, Radio Nacional de España (RNE), was set up by the Nationalists during the Spanish Civil War, but the government never established the same kind of monopoly over radio that it held over television. The number of privately owned radio stations increased markedly during the 1980s and ’90s, such that there were...
  • radio navigation
    Radio navigation...
  • Radio New Zealand Ltd.
    ...the New Zealand Broadcasting Corporation. In 1977 the Broadcasting Corporation of New Zealand was created, incorporating two previously independent networks. Dissolved in 1988, it was replaced by Radio New Zealand Ltd and Television New Zealand Ltd. Radio New Zealand has two radio medium-wave networks that include some broadcasts in Maori, Samoan, Tongan, Niuean, and Tokelauan. The......
  • Radio Normandy (private radio station)
    ...monopoly was declared in 1923 and state broadcasting remained a department of the Administration of Posts and Telegraphs until World War II, some private stations were granted licenses, including Radio Normandy, which broadcast to the United Kingdom. Some of these private commercial stations continued operation, broadcasting under government control until 1945, when their licenses were......
  • radio range (navigation)
    in aerial navigation, a system of radio transmitting stations, each of which transmits a signal that not only carries identification but also is of intrinsic value to a navigator in fixing his position. The older “A–N” type, dating from 1927, operates at low and medium frequencies. The only equipment needed in the aircraft is an ordinary radio receive...
  • radio reflector
    The largest single radio telescope in the world is the 305-metre (1,000-foot) fixed spherical reflector operated by Cornell University at the Arecibo Observatory near Arecibo, P.R. The antenna has an enormous collecting area, but the beam can be moved through only a limited angle of about 20° from the zenith. It is used for planetary radar astronomy, as well as for studying pulsars and......
  • radio relay (radio technology)
    Radio relay, born of the necessity for mobility, became the outstanding communication development of World War II. Sets employing frequency modulation and carrier techniques were developed and used, as were also radio relay sets that used radar pulse transmission and reception techniques and multiplex time-division methods for obtaining many voice channels from one radio carrier. Radio relay......
  • radio repeater (communications device)
    Satellites provide communications links via microwave radio, most commonly in the superhigh-frequency band of 3 to 30 gigahertz (3 billion to 30 billion hertz, or cycles per second). These frequencies correspond to wavelengths ranging from 10 cm to 1 cm (4 inches to 0.4 inch). Radio waves this short diverge along straight lines in narrow beams, rather than propagating in an expanding spherical......
  • Radio Research Laboratory (laboratory, Cambridge, Massachusetts, United States)
    During World War II Terman directed a staff of more than 850 at the Radio Research Laboratory at Harvard University; this organization was the source of Allied jammers to block enemy radar, tunable receivers to detect radar signals, and aluminum strips (“chaff”) to produce spurious reflections on enemy radar receivers. These countermeasures significantly reduced the effectiveness of....
  • Radio Research, Office of (research project, Princeton, New Jersey, United States)
    A Rockefeller Foundation grant for psychological research enabled Lazarsfeld to come to the United States in 1933, where he eventually obtained U.S. citizenship. He served as director of the Office of Radio Research, a Rockefeller project at Princeton University (1937–40), and, when the project was transferred to Columbia University in 1940 (it was later renamed the Bureau of Applied......
  • radio sensor (military science)
    Radio receivers can be used to detect and locate enemy radio. Enemy radars can be located in much the same way. Messages can be intercepted. This form of warning has been combated by radio silence and by spoofing, the transmission of signals intended to deceive. In 1967 the Israelis transmitted voluminous radio messages from empty airfields to hide the fact that aircraft had been moved to other......
  • radio serial (broadcasting)
    broadcast dramatic serial program, so called in the United States because most of its major sponsors for many years were manufacturers of soap and detergents. The soap opera is characterized by a permanent cast of actors, a continuing story, emphasis on dialogue instead of action, a slower-than-life pace, and a consistently sentimental or melodramatic treatment....
  • Radio Shack (American company)
    ...in 1977, when Apple Computer, Inc. (now Apple Inc.), founded by Steven P. Jobs and Stephen G. Wozniak, introduced the Apple II, one of the first pre-assembled, mass-produced personal computers. Radio Shack and Commodore Business Machines also introduced personal computers that year. These machines used 8-bit microprocessors (which process information in groups of 8 bits, or binary digits,......
  • radio source (astronomy)
    in astronomy, any of various objects in the universe that emit relatively large amounts of radio waves. Nearly all types of astronomical objects give off some radio radiation, but the strongest sources of such emissions include pulsars, certain nebulas, quasars, and radio galaxies....
  • radio spectrum (communications)
    Before 1930 the radio spectrum above 30 megahertz was virtually empty of man-made signals. Today, civilian radio signals populate the radio spectrum in eight frequency bands, ranging from very low frequency (VLF), starting at 3 kilohertz, and extending to extremely high frequency (EHF), ending at 300 gigahertz. The commercial radio spectrum and its applications are illustrated in Figure 3....
  • radio station
    Before 1930 the radio spectrum above 30 megahertz was virtually empty of man-made signals. Today, civilian radio signals populate the radio spectrum in eight frequency bands, ranging from very low frequency (VLF), starting at 3 kilohertz, and extending to extremely high frequency (EHF), ending at 300 gigahertz. The commercial radio spectrum and its applications are illustrated in Figure 3.......
  • radio technology
    transmission and detection of communication signals consisting of electromagnetic waves that travel through the air in a straight line or by reflection from the ionosphere or from a communications satellite. ...
  • Radio Telefís Éireann (Irish company)
    Best-known of the Irish classical composers are John Field, whose work influenced that of Frédéric Chopin, and Michael Balfe. Based in Dublin and maintained by Radio Telefís Éireann (RTÉ; the state-owned broadcasting company), the National Symphony Orchestra and the RTÉ Concert Orchestra are the country’s principal orchestral groups. Ireland’...
  • radio telescope (astronomical instrument)
    astronomical instrument consisting of a radio receiver and an antenna system that is used to detect radio-frequency radiation emitted by extraterrestrial sources. Because radio wavelengths are much longer than those of visible light, radio telescopes must be very large in order to attain the resolution of optical telescopes....
  • Radio Universidad (radio station, Mexico)
    ...Independiente de Mexico and is seen around the world, and the state-owned Imevision. Television, too, is nearly all commercial, though there are some university stations, of which the best-known is Radio Universidad, run by the Universidad Nacional Autónoma de México in Mexico City; in addition, the Instituto Politécnico Nacional operates a cultural station in the capital.....
  • radio wave (physics)
    Radio waves are used for wireless transmission of sound messages, or information, for communication, as well as for maritime and aircraft navigation. The information is imposed on the electromagnetic carrier wave as amplitude modulation (AM) or as frequency modulation (FM) or in digital form (pulse modulation). Transmission therefore involves not a single-frequency electromagnetic wave but......
  • Radio-activity (work by Rutherford)
    In his book Radio-activity (1904), Rutherford explained that radioactivity results from the spontaneous disintegration of an unstable element into a lighter element, which may decay further until a stable element is finally created. This process of radioactive decay involves the emission of positively charged particles (later to be recognized as helium nuclei) and negatively charged ones......
  • radio-frequency accelerating cavity (device)
    ...is small. As the field created by the ring magnets increases, the injection pulse is timed so that the field and the energy of the particles from the linear accelerator are properly matched. The radio-frequency accelerating devices, usually called cavities, operate on the same principle as a short section of a linear accelerator. The useful beam may be either the accelerated particles that......
  • radio-frequency amplifier (electronics)
    ...The circle traced out by the electron has a radius equal to mv/eB. This circular motion is exploited in many electron devices for generating or amplifying radio-frequency (RF) power....
  • radio-frequency current drive (physics)
    A technique known as radio-frequency (RF) current drive employs electromagnetic radiation to generate a steady-state current. Electromagnetic waves are injected into the plasma so that they propagate within the plasma in one direction around the torus. The speed of the waves is chosen to equal roughly the average speed of the electrons in the plasma. The wave electric field (which in a plasma......
  • radio-frequency heating (physics)
    process of heating materials through the application of radio waves of high frequency—i.e., above 70,000 hertz (cycles per second). Two methods of radio-frequency heating have been developed. One of these, induction heating, has proved highly effective for heating metals and other materials that are relatively good electric con...
  • radio-frequency spectroscopy (physics)
    The energy states of atoms, ions, molecules, and other particles are determined primarily by the mutual attraction of the electrons and the nucleus and by the mutual repulsion of the electrons. Electrons and nuclei have magnetic properties in addition to these electrostatic properties. The spin-orbit interaction has been discussed above (see Foundations of atomic spectra: Hydrogen atom states:......
  • radio-frequency spectrum (communications)
    Before 1930 the radio spectrum above 30 megahertz was virtually empty of man-made signals. Today, civilian radio signals populate the radio spectrum in eight frequency bands, ranging from very low frequency (VLF), starting at 3 kilohertz, and extending to extremely high frequency (EHF), ending at 300 gigahertz. The commercial radio spectrum and its applications are illustrated in Figure 3....
  • Radio-Keith-Orpheum Corporation of America (American film company)
    American motion-picture studio that made some notable films in the 1930s and ’40s. Radio-Keith-Orpheum originated in 1928 from the merger of the Radio Corporation of America, the Keith-Albee-Orpheum theatre chain, and the American Pathé production firm. Though it was one of the major studios in Hollywood, RKO spent much of its 25 years’ existence struggling for financial stab...
  • radio-pulse receiver (military science)
    For atmospheric or space explosions, radio-pulse receivers and light flash and acoustic detectors are used, as well as devices to measure fallout. Aircraft and rockets can be used to collect radioactive debris, while high-altitude satellites carry detectors for gamma rays and other emissions....
  • Radio-Televisión Española (Spanish government network)
    ...into Spain in 1956. During the Franco regime and the first few years of the constitutional monarchy, there were only two television stations, both part of the government-owned and -controlled Radio-Televisión Española (RTVE). They still broadcast today, solely in Castilian, and have been split into separate organizations: Radio Nacional de España (RNE) and......
  • radioactivation analysis (chemistry)
    Analytical methods involving activation analysis (production of artificial radioactivity) and mass spectroscopy (separation of atoms on the basis of mass) have made it possible to make accurate measurements of the relative abundances of these elements, even when they are present in extremely small amounts. Such measurements are of great interest to geophysicists because they supply valuable......
  • radioactive dating (chronology)
    In 1905, shortly after the discovery of radioactivity, the American chemist Bertram Boltwood suggested that lead is one of the disintegration products of uranium, in which case the older a uranium-bearing mineral the greater should be its proportional part of lead. Analyzing specimens whose relative geologic ages were known, Boltwood found that the ratio of lead to uranium did indeed increase......
  • radioactive decay
    property exhibited by certain types of matter of emitting energy and subatomic particles spontaneously. It is, in essence, an attribute of individual atomic nuclei....
  • radioactive dosage (medicine)
    Radioactive dosage forms, or radiopharmaceuticals, are substances that contain one or more radioactive atoms and are used for diagnosis or treatment of disease. In some cases the radioactive atoms are incorporated into a larger molecule. The larger molecule helps to direct the radioactive atoms to the organ or tissue of interest. In other cases the diagnostic or therapeutic molecule is the......
  • radioactive fallout (nuclear physics)
    deposition of radioactive materials on the Earth from the atmosphere. The terms rain out and snow out are sometimes used to specify such deposition during precipitant weather....
  • radioactive heat
    ...spontaneous decay (partial disintegration) of the nuclei of radioactive elements provides decay particles and energy. The energy, composed of emission kinetic energy and radiation, is converted to heat; it has been an important factor in affecting the temperature gradient and thermal evolution of the Earth. Deep-seated elevated temperatures provide the heat that causes rock to deform......
  • radioactive implant (medicine)
    Radioactive implants in the form of metal needles or “seeds” are used to treat some cancers, such as those of the prostate and uterine cervix. They can deliver high doses of radiation directly into the tumour with less effect on distant tissues....
  • radioactive isotope (chemistry)
    any of several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy by spontaneously emitting radiation in the form of alpha, beta, and gamma rays....
  • radioactive labelling (chemistry)
    Much of the experimental work on phloem transport now is done with the aid of radioactive substances; for example, when radioactive carbon dioxide administered to an illuminated leaf is incorporated into sugar during photosynthesis and carried from the leaf, the velocity of this movement can be measured by determining the arrival of radioactivity at given points along the stem. Whole plants, as......
  • radioactive nuclide (chemistry)
    ...RBE. At the same time, however, charged particles usually penetrate such a short distance in tissue that they pose relatively little hazard to tissues within the body unless they are emitted by a radionuclide, or radioactive isotope, that has been deposited internally....
  • radioactive nuclide cineangiography (medicine)
    ...all emit gamma rays, and a scintillation camera is used to detect gamma-ray emission. The data are assessed with the R wave of the electrocardiogram as a time marker for the cardiac cycle. Radionuclide cineangiography is a further development of radionuclide imaging. These techniques are used to assess myocardial damage, left ventricular function, valve regurgitation, and, with the use......
  • radioactive nuclide imaging (medicine)
    Radionuclide imaging (radioactive nuclides) provides a safe, quantitative evaluation of cardiac function and a direct measurement of myocardial blood flow and myocardial metabolism. Radionuclide imaging is used to evaluate the temporal progress of cardiac disease, hemodynamics, and the extent of myocardial damage during and after infarction and to detect pulmonary infarction following emboli.......
  • radioactive scanning (medicine)
    In isotope scanning, a radioisotope is introduced into the body, usually by means of intravenous injection. The isotope is then taken up in different amounts by different organs. Its distribution can be determined by recording the radiation it emits, and through charting its concentration it is often possible to recognize the presence, size, and shape of various abnormalities in body organs.......
  • radioactive series (chemical series)
    any of four independent sets of unstable heavy atomic nuclei that decay through a sequence of alpha and beta decays until a stable nucleus is achieved. These four chains of consecutive parent and daughter nuclei (shown in the ) begin and end among elements with atomic numbers higher than 81, which is the atomic weight of thallium; the members of each set are genetically related by alpha and beta ...
  • radioactive waste
    ...gases, as conventional coal- or gas-fueled plants do. Nuclear power plants, however, do yield waste heat that may be considered as thermal pollution, and they also yield useless and dangerous radioactive wastes which, although they are pollutants, may be less undesirable than those from fossil-fuel generators. For this and other reasons, such as economy of operation, there is a potential......
  • radioactivity
    property exhibited by certain types of matter of emitting energy and subatomic particles spontaneously. It is, in essence, an attribute of individual atomic nuclei....
  • radioautography (biology)
    ...depend on careful dissection, or cutting apart, of an organism and on accurate descriptions of the parts. The study of the structure of tissues and cells has been extended by the techniques of autoradiography and histochemistry. In the former, a tissue is supplied with a radioactive substance and allowed to utilize it for an appropriate period of time, after which the tissue is prepared......
  • radiobiology (biology)
    ...to X rays. These unfortunate early experiences eventually led to an awareness of radiation hazards for professional workers and stimulated the development of a new branch of science—namely, radiobiology....
  • Radiobras (Brazilian news agency)
    ...may be called upon to broadcast programs produced by the Agencia Nacional, consisting mainly of government statements and ministerial and presidential speeches. In 1975 the government created Radiobras, the Brazilian Broadcasting Company, which broadcasts to the remote regions of the Amazon Basin, bringing those regions into closer contact with the political and cultural mainstream of......
  • radiocarbon dating (scientific technology)
    method of age determination that depends upon the decay to nitrogen of radiocarbon (carbon-14). Carbon-14 is continually formed in nature by the interaction of neutrons with nitrogen-14 in the Earth’s atmosphere; the neutrons required for this reaction are produced by cosmic rays interacting with the atmosphere....
  • radiocarpal joint (anatomy)
    ...small, short bones (carpal bones) roughly arranged in two rows. The wrist is also made up of several component joints: the distal radioulnar joint, which acts as a pivot for the forearm bones; the radiocarpal joint, between the radius and the first row of carpal bones, involved in wrist flexion and extension; the midcarpal joint, between two of the rows of carpal bones; and various intercarpal....
  • radiochemical analysis (chemistry)
    During use of the radiochemical methods, spontaneous emissions of particles or electromagnetic radiation from unstable atomic nuclei are monitored. The intensity of the emitted particles or electromagnetic radiation is used for quantitative analysis, and the energy of the emissions is used for qualitative analysis. Emissions of alpha particles, electrons (negatrons and positrons), neutrons,......
  • Radiocommunications Sector (United Nations organization)
    ...which meets annually and is responsible for executing decisions of the Plenipotentiary Conference; (4) the General Secretariat, responsible for administrative and financial services; (5) the Radiocommunications Sector, which was formed by the merger of those activities of the former International Consultative Radio Committee and the former International Frequency Registration Board that......
  • radiodiagnosis
    X rays were discovered by Wilhelm Conrad Röntgen, a German professor of physics, in his laboratory in the University of Würzburg on Nov. 8, 1895. Early on, in radiodiagnosis, use was made of three of the properties of X rays—their ability to penetrate the tissues, their photographic effect, and their ability to cause certain substances to fluoresce. In penetrating the tissues,...
  • Radiodiffusion Télévision Algérienne (Algerian broadcasting)
    ...of magazines are also published in the country. The number and range of newspapers increased during the 1990s, despite frequent violent attacks directed against journalists by Islamic extremists. Radiodiffusion Télévision Algérienne operates as a broadcasting institution under the Ministry of Information and Culture. Its three radio channels offer programming in Arabic,......
  • Radiodiffusion Télévision Marocaine (Moroccan broadcasting network)
    Morocco’s government-owned radio and television network, Radiodiffusion Télévision Marocaine (RTM), broadcasts throughout the country. Radio broadcasts are in Arabic, French, Tamazight, Spanish, and English, while television is broadcast in Arabic, Tamazight, and French. In addition, a private television network is headquartered in Casablanca and a private radio network in......
  • “Radiografía de la pampa” (work by Martínez Estrada)
    ...and economic crises of the early 1930s and of what he saw as factors contributing to moral and social decay in Argentina led him to write Radiografía de la pampa (1933; X-Ray of the Pampa), a comprehensive psychological study of the Argentine character laden with fatalistic overtones. La cabeza de Goliat: Microscopía de Buenos Aires (1940;......
  • radiography
    Lower-energy betatrons in the 7–20-MeV range, however, have been specially constructed to serve as sources of energetic “hard” X-rays for use in medical and industrial radiography. Portable betatrons, operating at energy levels of approximately 7 MeV, have been designed for specialized applications in industrial radiography—for example, to examine concrete, steel, and.....
  • Radiohead (British rock group)
    British rock group that was arguably the most accomplished art-rock band of the early 21st century. This revered quintet made some of the most majestic—if most angst-saturated—music of the postmodern era. Formed in the mid-1980s at Abingdon School in Oxfordshire, Radiohead comprised singer-guitarist Thom Yorke ...
  • radioimmunoassay (medical procedure)
    American medical physicist and joint recipient (with Andrew V. Schally and Roger Guillemin) of the 1977 Nobel Prize for Physiology or Medicine, awarded for her development of the radioimmunoassay (RIA), an extremely sensitive technique for measuring minute quantities of biologically active substances....
  • radioisotope (chemistry)
    any of several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy by spontaneously emitting radiation in the form of alpha, beta, and gamma rays....
  • Radiolaria (protozoan)
    any protozoan of the class Polycystinea (superclass Actinopoda), found in the upper layers of all oceans. Radiolarians, which are mostly spherically symmetrical, are known for their complex and beautifully sculptured, though minute, skeletons, referred to as tests. Usually composed of silica, the test is elaborately perforated in a variety of patterns, forming a series either o...
  • radiolarian (protozoan)
    any protozoan of the class Polycystinea (superclass Actinopoda), found in the upper layers of all oceans. Radiolarians, which are mostly spherically symmetrical, are known for their complex and beautifully sculptured, though minute, skeletons, referred to as tests. Usually composed of silica, the test is elaborately perforated in a variety of patterns, forming a series either o...
  • radiolarian earth (geology)
    ...than chalk and will not effervesce in acid. Under a high-powered microscope the form of the diatoms can be distinguished. When well hardened, it is called diatomite. Similar siliceous rocks, called radiolarian earth and radiolarite, are formed from the latticelike opaline skeletons of Radiolaria....
  • radiolarian ooze (geology)
    ...the calcareous oozes include globigerina ooze, containing the shells of planktonic foraminifera, and pteropod ooze, made up chiefly of the shells of pelagic mollusks. The siliceous oozes include radiolarian ooze, comprising essentially brown clay with more than 30 percent of the skeletons of warm-water protozoa, and diatom ooze, containing the frustules (tiny shells) of diatoms. The......
  • radiology (medicine)
    branch of medicine using radiation for the diagnosis and treatment of disease. Radiology originally involved the use of X rays in the diagnosis of disease and the use of X rays, gamma rays, and other forms of ionizing radiation in the treatment of disease. In more recent years radiology has come also to embrace diagnosis by a method of organ scanning with the use of radioactive ...
  • radiology, diagnostic
    X rays were discovered by Wilhelm Conrad Röntgen, a German professor of physics, in his laboratory in the University of Würzburg on Nov. 8, 1895. Early on, in radiodiagnosis, use was made of three of the properties of X rays—their ability to penetrate the tissues, their photographic effect, and their ability to cause certain substances to fluoresce. In penetrating the tissues,...
  • radioluminescence (physics)
    Radioactive elements can emit alpha particles (helium nuclei), electrons, and gamma rays (high-energy electromagnetic radiation). The term radioluminescence, therefore, means that an appropriate material is excited to luminescence by a radioactive substance. When alpha particles bombard a crystal phosphor, tiny scintillations are visible to microscopic observation. This is the principle of the......
  • radiolysis (chemical reaction)
    ...may result in a large variety of chemical changes involving the positive ion, the outgoing electron, and the excited states resultant from charge neutralization, as well as (parent) positive-ion fragmentation and ion-molecule reactions. Some such consequences are summarized for a few cases....
  • radiometer (instrument)
    instrument for detecting or measuring radiant energy. The term is applied in particular to devices used to measure infrared radiation. Radiometers are of various types that differ in their method of measurement or detection. Those that function by means of an increase in the temperature of the device, such as Herschel’s thermometer, are called thermal detectors. Commonly...
  • radiometric analysis (chemistry)
    Solution of this equation by techniques of the calculus yields one form of the fundamental equation for radiometric age determination,...
  • radiometric dating (chronology)
    In 1905, shortly after the discovery of radioactivity, the American chemist Bertram Boltwood suggested that lead is one of the disintegration products of uranium, in which case the older a uranium-bearing mineral the greater should be its proportional part of lead. Analyzing specimens whose relative geologic ages were known, Boltwood found that the ratio of lead to uranium did indeed increase......
  • radiometric separation
    ...In addition, electro-optic detectors collect data on the responses of minerals when exposed to infrared, visible, and ultraviolet light. The same principle, only using gamma radiation, is called radiometric separation....
  • radionuclide (chemistry)
    ...RBE. At the same time, however, charged particles usually penetrate such a short distance in tissue that they pose relatively little hazard to tissues within the body unless they are emitted by a radionuclide, or radioactive isotope, that has been deposited internally....
  • radionuclide cineangiography (medicine)
    ...all emit gamma rays, and a scintillation camera is used to detect gamma-ray emission. The data are assessed with the R wave of the electrocardiogram as a time marker for the cardiac cycle. Radionuclide cineangiography is a further development of radionuclide imaging. These techniques are used to assess myocardial damage, left ventricular function, valve regurgitation, and, with the use......
  • radionuclide imaging (medicine)
    Radionuclide imaging (radioactive nuclides) provides a safe, quantitative evaluation of cardiac function and a direct measurement of myocardial blood flow and myocardial metabolism. Radionuclide imaging is used to evaluate the temporal progress of cardiac disease, hemodynamics, and the extent of myocardial damage during and after infarction and to detect pulmonary infarction following emboli.......
  • radiopharmaceutical (medicine)
    Radioactive dosage forms, or radiopharmaceuticals, are substances that contain one or more radioactive atoms and are used for diagnosis or treatment of disease. In some cases the radioactive atoms are incorporated into a larger molecule. The larger molecule helps to direct the radioactive atoms to the organ or tissue of interest. In other cases the diagnostic or therapeutic molecule is the......
  • radiosensitivity (biology)
    In general, dividing cells (such as cancer cells) are more radiosensitive than nondividing cells. As noted above, a dose of 1–2 Sv is sufficient to kill the average dividing cell, whereas nondividing cells can usually withstand many times as much radiation without overt signs of injury. It is when cells attempt to divide for the first time after irradiation that they are most apt to die......
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