| | - optical ceramics
- advanced industrial materials developed for use in optical applications.
- optical character recognition
- (from the article "computerized typesetting") An optical character recognition (OCR) system "reads" typed copy and records the characters on a machine-readable tape. It converts the tape into electronic signals that enter the recognition unit and ...
- optical communication
- (from the article "telecommunications media") Optical communication employs a beam of modulated monochromatic light to carry information from transmitter to receiver. The light spectrum spans a tremendous range in the electromagnetic spectrum, extending from the ...
- optical crystallography
- branch of crystallography that deals with the optical properties of crystals. It is of considerable interest theoretically and has the greatest practical importance. The science of petrography is largely based ...
- optical depth
- (from the article "Saturn") The structure of the rings is broadly described by their optical depth as a function of distance from Saturn. Optical depth is a measure of the amount of electromagnetic radiation ...
- optical disc
- (from the article "information processing") An entirely different kind of recording and storage medium, the optical disc, became available during the early 1980s. The optical disc makes use of laser technology: digital data are recorded ...
- optical double resonance
- (from the article "spectroscopy") ...(usually a vapour in a glass cell) within the coil of an oscillator and tuning the device until a change is seen in the absorption of energy from the oscillator ...
- optical engineering
- (from the article "motion-picture technology") Lenses have gone through a continuous evolution in the last half century, for both still and motion-picture photography. The two major objectives have been to focus properly all the colours ...
- optical fibre
- (from the article "materials science") ...for transmission over optical fibres. Electronic switching therefore is seen as the principal barrier to achieving higher switching speeds. One approach to solving this problem would be to introduce optics ...
- optical fibre channel
- (from the article "telecommunications media") In contrast to wire transmission, in which an electric current flows through a copper conductor, in optical fibre transmission an electromagnetic (optical) field propagates through a fibre made of a ...
- optical fibre communications link
- (from the article "telecommunications media") An optical fibre communications link consists of the following elements: an electro-optical transmitter, which converts analog or digital information into a modulated beam of light; a light-carrying fibre, which spans ...
- optical frequency chain
- (from the article "Hall, John L.") Working with Hansch, Hall conducted prizewinning research on measuring optical frequencies (frequencies of visible light). Although a procedure (the optical frequency chain) had already been developed to make such measurements, ...
- optical frequency comb technique
- (from the article "Hall, John L.") ...chain) had already been developed to make such measurements, it was so complex that it could be performed in only a few laboratories. The two men focused on developing Hansch's ...
- optical gyroscope
- (from the article "gyroscope") Optical gyroscopes, with virtually no moving parts, are replacing mechanical gyroscopes in commercial jetliners, booster rockets, and orbiting satellites. Such devices are based on the Sagnac effect, first demonstrated by ...
- optical illusion
- (from the article "illusion") Numerous optical illusions are produced by the refraction (bending) of light as it passes through one substance to another in which the speed of light is significantly different. A ray ...
- optical image
- the apparent reproduction of an object, formed by a lens or mirror system from reflected, refracted, or diffracted light waves. There are two kinds of images, real and virtual. In ... [7 Related Articles]
- optical interferometer
- instrument for making precise measurements for beams of light of such factors as length, surface irregularities, and index of refraction. It divides a beam of light into a number of ... [2 Related Articles]
- optical invariant
- (from the article "optics") It is frequently as important to determine the size of an image as it is to determine its location. To obtain an expression for the magnification-that is, the ratio of ...
- optical isomerism
- (from the article "isomerism") Two classes of stereoisomeric compounds are generally recognized: optical isomers and geometric isomers. Optical isomers occur in pairs that are nonsuperimposable mirror images of each other, like right- and left-handed ...
- optical lever system
- (from the article "perception") It is not feasible to eliminate eye movements, but it is possible to stabilize or fix the location of the retinal image by coupling the source of the image to ...
- optical microscope
- (from the article "microscope") Optical microscopesmetallographymetallurgyOptical microscopyThe simplest, and oldest, type of metallography (though hardly a century old) involves polishing the surface to a ...
- optical model
- in physics, description of atomic nuclei as similar to cloudy crystal balls in that, when struck by a beam of particles, they partially absorb the beam, partially scatter it, and ...
- optical molasses
- (from the article "Chu, Steven") In 1985 Chu and his coworkers used an array of intersecting laser beams to create an effect they called "optical molasses," in which the speed of target atoms was reduced ...
- optical observatory
- (from the article "astronomical observatory") ...to observe celestial objects. Observatories can be classified on the basis of the part of the electromagnetic spectrum in which they are designed to observe. The largest number of observatories ...
- optical path difference
- (from the article "optics") ...the y0 coordinate lying in the meridian plane containing the object point and the lens axis. The departure of the wave from the ideal sphere is generally called OPD, meaning ...
- optical printer
- (from the article "motion-picture technology") The most important resource of the special effects department is the optical printer, essentially a camera and projector operating in tandem, which makes it possible to photograph a photograph. In ...
- optical printing
- (from the article "motion-picture technology") Printing takes a number of different forms. In contact printing, the master film (or negative) is pressed against the raw stock; this combination is exposed to light on the master ...
- optical pumping
- in physics, the use of light energy to raise the atoms of a system from one energy level to another. A system may consist of atoms having a random orientation ... [4 Related Articles]
- optical pyrometer
- (from the article "pyrometer") ...in furnaces. Most pyrometers work by measuring radiation from the body whose temperature is to be measured. Radiation devices have the advantage of not having to touch the material being ...
- optical range finder
- (from the article "range finder") any of several instruments used to measure the distance from the instrument to a selected point or object. One basic type is the optical range finder modeled after a ranging ...
- optical resonator
- (from the article "laser") An optical resonator is needed to build up the light energy in the beam. The resonator is formed by placing a pair of mirrors facing each other so that light ...
- optical separation
- (from the article "mineral processing") This process is used for the concentration of particles that have sufficiently different colours (the best contrast being black and white) to be detected by the naked eye. In addition, ...
- optical sound recording
- use of an optical system for registering sound on photographic film; it is a technique widely used in making the sound track (q.v.) of motion pictures. [4 Related Articles]
- optical spectroscopy
- (from the article "spectroscopy") Survey of optical spectroscopy
- optical storage
- electronic storage medium that uses low-power laser beams to record and retrieve digital (binary) data. In optical-storage technology, a laser beam encodes digital data onto an optical, or laser, disk ... [1 Related Articles]
- optical system
- (from the article "optics") Optical systems
- optical telescope
- (from the article "Table 1: Some Important Ground-Based Optical Telescopes") Optical telescopesastronomyastronomyTelescopic observationsOptical telescopes are either refractors or reflectors that use lenses or mirrors, respectively, for their main light-collecting elements ...
- optical waveguide
- (from the article "industrial glass") Optical waveguides (OWGs), which transmit information signals in the form of pulses of light, consist of a core glass fibre clad by glass of a lower refractive index. As is ...
- optical-mechanical scanner
- (from the article "Earth exploration") Thermal infrared energy is detected by an optical-mechanical scanner. The detector is cooled by a liquid-nitrogen (or liquid-helium) jacket that encloses it, making the instrument sensitive at long wavelengths and ...
- optical-pumping magnetometer
- (from the article "Earth exploration") ...is the magnetic compass, which measures the field direction. Other instruments include magnetic balances and fluxgate magnetometers. Most magnetic surveys are made with proton-precession or optical-pumping magnetometers, which are appreciably ...
- optician
- (from the article "optometry") The optician, another optical specialist, makes, fits, and sells optical devices, particularly the corrective lenses prescribed by optometrists and ophthalmologists.ophthalmology
- optics
- science concerned with the genesis and propagation of light, the changes that it undergoes and produces, and other phenomena closely associated with it. There are two major branches of optics, ... [37 Related Articles]
- optimal allocation
- (from the article "economics") ...combinations, while a household attempts to maximize product combinations. From the maximizing point of view, some combinations are better than others, and the best combination is called the "optimal" or ...
- optimal filter
- (from the article "dead reckoning") ...over distance, celestial observations are taken intermittently to determine a more reliable position (called a fix), from which a new dead reckoning is begun. Dead reckoning is also embedded in ...
- optimal linear predictor
- (from the article "probability theory") ...of the expression for b is called the covariance of X and Y and is denoted Cov(X, Y). Let Y = a + bX denote the optimal linear predictor. The mean square error of prediction ...
- optimal mean square predictor
- (from the article "probability theory") There is one important case in which the optimal mean square predictor actually is the same as the optimal linear predictor. If X and Y are jointly normally distributed, the ...
- optimal strategy
- (from the article "game theory") ...game of go. In 1912 the German mathematician Ernst Zermelo proved that such games are strictly determined; by making use of all available information, the players can deduce strategies that ...
- optimality model
- (from the article "nature, philosophy of") A much more controversial method is the use of so-called "optimality models." The researcher begins by assuming that natural selection works optimally, in the sense that the feature (or set ...
- Optimates and Populares
- (Latin: respectively, "Best Ones," or "Aristocrats", and "Demagogues," or "Populists"), two principal patrician political groups during the later Roman Republic from about 133 to 27 BC. The members of both ... [3 Related Articles]
- Optimisticheskaya Cave
- (from the article "cave") ...regions such as West Texas, western Oklahoma, and eastern New Mexico. Caves formed by the dissolution of gypsum are much like limestone caves in the size, shape, and pattern of ...
- optimization
- collection of mathematical principles and methods used for solving quantitative problems in many disciplines, including physics, biology, engineering, economics, and business. The subject grew from a realization that quantitative problems ... [6 Related Articles]
- optimization study
- (from the article "systems engineering") ...essentially the same final level of performance in many different ways. Limited performance by one subsystem may be offset by superior performance somewhere else. These optimization studies, called trade-offs, are ...
- option contract
- (from the article "security") An option contract is an agreement enabling the holder to buy a security at a fixed price for a limited period of time. One form of option contract is the ...
- Optional Municipal Code
- (from the article "Washington") ...the legislature. The governing body in most counties is the board of county commissioners, whose three members act as both the chief executive officers and the legislative body for the ...
- Optional Protocol to the Convention against Torture
- (from the article "torture") Attention in the early 21st century turned to preventive mechanisms. In 2002 the Optional Protocol to the Convention against Torture (OPCAT) established a Subcommittee on Prevention, an expert body that, ...
- optional referendum
- (from the article "referendum and initiative") ...a popular vote for approval or rejection. For example, constitutional amendments proposed by legislatures in most of the states of the United States are subject to obligatory referendum. Under the ...
- optoelectronic receiver
- (from the article "telecommunications media") The two most common kinds of optoelectronic receivers for optical links are the positive-intrinsic-negative (PIN) photodiode and the avalanche photodiode (APD). These optical receivers extract the baseband signal from a ...
- optoelectronics
- (from the article "electronics") A new direction in electronics employs photons (packets of light) instead of electrons. By common consent these new approaches are included in electronics, because the functions that are performed are, ...
- optokinetic nystagmus
- (from the article "photoreception") During fixations the eyes are stabilized against movements of the head and body by two reflexes, the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR). In VOR the semicircular canals ...
- optometry
- health-care profession concerned with examining the eyes for defects of vision and diagnosing and treating such conditions. Optometrists prescribe and supply eyeglasses, contact lenses, and other optical aids that correct ... [1 Related Articles]
- Optype
- (from the article "printing") Optype is a hybrid process that simultaneously carries out the operation of justifying a text typed directly in cold type and transmits it to photographic film. By means of optical ...
- Opuntia
- largest genus of the family Cactaceae, native to the New World, with some 200 species. It has characteristic glochidia-small bristles with backward-facing barbs in the areoles. (These barbs are difficult ... [2 Related Articles]
- Opus
- in ancient Greece, the chief city of the Locri Opuntii. Its site may have been at modern Atalandi or at Kiparissi. Homer in his Iliad mentioned Opus, and Pindar devoted ...
- opus Alexandrinum
- in mosaic, type of decorative pavement work widely used in Byzantium in the 9th century. It utilized tiny, geometrically shaped pieces of coloured stone and glass paste that were arranged ... [1 Related Articles]
- opus anglicanum
- (Latin: "English work"), embroidery done in England between about 1100 and about 1350 and of a standard unsurpassed anywhere. The technical skill that was shown by English workers in handling ... [1 Related Articles]
- opus caementicum
- (from the article "building construction") ...as forms to lay the pozzolana into place. Finally, the mortar of lime, sand, water, and pozzolana was mixed with stones and broken brick to form a true concrete, called ...
- Opus Dei
- Roman Catholic lay and clerical organization whose members seek personal Christian perfection and strive to implement Christian ideals and values in their occupations and in society as a whole. Theologically ... [2 Related Articles]
- opus incertum
- (from the article "Western architecture") ...is, ordinary stone walling-was used as a facing especially for important public buildings under the earlier empire (for example, the exterior of the Colosseum). (2) Opus incertum ...
- opus interassile
- metalwork technique developed in Rome and widely used during the 3rd century AD, especially appropriate for making arabesques and other nonrepresentational ornamental designs. Probably of Syrian origin, the technique consists ... [2 Related Articles]
- opus mixtum
- (from the article "Western architecture") ...appearance of a wall built of thin bricks. Bonding courses of bipedales were employed at intervals of 2 or 3 feet (60 or 90 cm). (5) Mixed brick and stone ...
- opus quadratum
- (from the article "Western architecture") ...or bricks laid with ends toward the face of the wall) and stretchers (stones or bricks laid with lengths parallel to the face of the wall). This type of masonry ...
- opus sectile
- type of mosaic work in which figural patterns are composed of pieces of stone or, sometimes, shell or mother-of-pearl cut in shapes to fit the component parts of the design, ...
- opus signinum
- in mosaic, type of simple, unpatterned or roughly patterned pavement commonly used in Roman times. It was composed of river gravel, small pieces of stone, or terra-cotta fragments cemented in ...
- opus tessellatum
- mosaic technique that involves the use of tesserae (small cubes of stone, marble, glass, ceramic, or other hard material) of uniform size applied to a ground to form pictures and ... [1 Related Articles]
- opus testaceum
- (from the article "reticulated work") ...of the Mausoleum of Augustus; and on the terraces of the country villa built by Herod the Great (d. 4 BC) at Jericho, Jordan. Reticulated work was replaced by a ...
- opus vermiculatum
- type of mosaic work frequently used in Hellenistic and Roman times, in which part or all of a figural mosaic is made up of small, closely set tesserae (cubes of ... [3 Related Articles]
- Opusztaszer
- (from the article "Csongrad") According to traditional history, the village Opusztaszer was the site of the first council of the seven conquering Magyar tribes that formed the Arpad dynasty in the late 9th century. ...
- Oquendo, Antonio de
- (from the article "Tromp, Maarten") ...of the republic. In February 1639, he defeated a fleet of Dunkirk privateers; he then met a large Spanish armada that was transporting some 13,000 Spanish recruits to Flanders. Commanded ...
- Oquirrh Mountains
- mountain range that extends about 30 miles (50 km) southward from the southern end of the Great Salt Lake, Utah, U.S., overlooking the Tooele and Salt Lake valleys. The mountains ...
- or
- (from the article "heraldry") ...figures mimicking the fur of a species of squirrel). Two other colours appear occasionally in British heraldry, murrey (a tint between red and purple) and tenne (orange-tawny). Gold and silver ...
- OR gate
- (from the article "applied logic") current flows out to the right only when current is present in both inputs; otherwise there is no output. In an OR gate, current is output when a current is ...
- Or San Michele
- (from the article "Donatello") The full power of Donatello first appeared in two marble statues, "St. Mark" and "St. George" (both completed c. 1415), for niches on the exterior of Or San Michele, the ...
- ora serrata
- (from the article "eye, human") The ciliary body is the forward continuation of the choroid. It is a muscular ring, triangular in horizontal section, beginning at the region called the ora serrata and ending, in ...
- oracle
- (Latin oraculum from orare, "to pray," or "to speak"), divine communication delivered in response to a petitioner's request; also, the seat of prophecy itself. Oracles were a branch of divination ... [16 Related Articles]
- oracle bone
- (from the article "chronology") ...findings, however, have established an authentic chronology beginning with the Shang dynasty, though the exact date of its end remains a controversial topic among experts. The so-called oracle-bone inscriptions of ...
- Oracle Corporation
- (from the article "Computers and Information Systems") Database firm Oracle, which had been buying up corporate software firms, acquired Hyperion Solutions for $3.3 billion. Hyperion provided "business-intelligence" software that analyzed corporate data to reveal business trends. Following ...
- Oracular Chinese language
- (from the article "Chinese writing") ...began to develop in the early 2nd millennium BC. The earliest known inscriptions, each of which contains between 10 and 60 characters incised on pieces of bone and tortoiseshell that ...
- Oradea
- city, capital of Bihor judet (county), northwestern Romania. It lies about 8 miles (13 km) east of the Hungarian border, along the Crisul Repede River where it leaves the western ...
- Oradour-sur-Glane
- village, Haute-Vienne departement, Limousin region, south-central France. It is located 14 miles (23 km) northwest of Limoges.
- Oraefajokull
- ice-covered volcanic massif, southeastern Iceland. It lies at the southern end of the giant ice field of Vatnajokull (q.v.). Its highest peak, Mount Hvannadals, reaches an elevation of 6,952 feet ...
- Orage, Alfred Richard
- influential English editor and social thinker. [2 Related Articles]
- Orai
- (from the article "Jalaun") ...is bounded on the north by the Yamuna River. The Betwa Canal system provides irrigation water; crops include wheat, gram, and mustard. There are acacia tree plantations near the town ...
- Oraibi
- Hopi pueblo (village), Navajo county, northeastern Arizona, U.S. The pueblo is situated on the narrow, rocky Third Mesa of the Hopi Indian Reservation. It is the unofficial capital of the ... [1 Related Articles]
- Oral
- city, western Kazakhstan, along the Ural (Zhayyq) River. Founded in 1613 or 1622 by Cossacks fleeing a tsarist punitive campaign, it was known as Yaitsky Gorodok until 1775, when its ...
- oral and maxillofacial surgery
- dental specialty that deals with the diagnosis and surgical treatment of the diseases, injuries, and defects of the human mouth, jaw, and associated structures. The most common oral surgery procedure ... [1 Related Articles]
- oral cancer
- disease characterized by the growth of cancerous cells in the mouth, including the lips. Oral cancer is often associated with cancers of the cavity located behind the tonsils and the ... [1 Related Articles]
- oral contraceptive
- (from the article "contraception") There are several types of drugs that alter hormonal levels in women; these drugs suppress the hormonal signal sent by the pituitary gland for the ovaries to release an egg. ...
- Oral law
- (from the article "Judah ha-Nasi") Because the Written Law of the Jews (found in the Pentateuch, or Five Books of Moses) could not cover all exigencies, over the centuries a body of Oral Law had ...
- oral literature
- (from the article "African American literature") Behind the achievements of individual African American writers during the antislavery era lies the communal consciousness of millions of slaves, whose oral tradition in song and story has given form ...
- oral microbiology
- (from the article "dentistry") Oral microbiology, which is concerned with the effects of the more than 600 different species of oral bacteria on the teeth, gums, mouth, and other parts of the body that ...
- oral pathology
- (from the article "dentistry") Oral pathology is the study of the causes, processes, and effects of oral disease, together with the resultant alterations of oral structure and functions. The oral pathologist provides diagnoses on ...
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