component of optical devices consisting of a surface ruled with close, equidistant, and parallel lines for the purpose of resolving light into spectra. A grating is said to be a ... [5 Related Articles]
(from the article "electron diffraction") As an analytic method, electron diffraction is used to identify a substance chemically or to locate the position of atoms in a substance. This information can be read from the ...
(from the article "spectroscopy") ...theta and crystal spacing d satisfy the Bragg condition, 2d sin theta = nlambda, where lambda is the wavelength of the X ray and n is an integer called the ...
(from the article "nebula") A recently recognized major component of interstellar gas has been discovered by means of its Halpha emission line at 6563 angstroms, produced by a hydrogen atom dropping from the third ...
(from the article "nebula") As noted above, clouds of gas and dust that contain stars hot enough to ionize their hydrogen are called diffuse nebulae, or H II regions. In contrast to dark or ...
(from the article "nervous system") The diffuse nervous system is the most primitive nervous system. In diffuse systems nerve cells are distributed throughout the organism, usually beneath the outer epidermal layer. Large concentrations of nerve ...
(from the article "atmosphere") ...its line of propagation by the intervening atmosphere. The image of the Sun's disk as a sharp and distinct object represents that portion of the solar radiation that reaches the ...
(from the article "attention") ...sustained, tonic shifts in an individual's level of involvement with the environment, including the control of sleep-wakefulness. One nonspecific route to the cerebral cortex via the thalamus, the diffuse thalamic ...
(from the article "tree") Hardwoods may be divided into ring-porous and diffuse-porous trees. In ring-porous trees the vessels laid down at the beginning of the growing season are much larger than subsequent vessels laid ...
(from the article "pump") Another type of radial flow centrifugal pump is the diffuser pump, in which, after the fluid has left the impeller, it is passed through a ring of fixed vanes that ...
process resulting from random motion of molecules by which there is a net flow of matter from a region of high concentration to a region of low concentration. A familiar ... [29 Related Articles]
(from the article "welding") This type of bonding relies on the effect of applied pressure at an elevated temperature for an appreciable period of time. Generally, the pressure applied must be less than that ...
(from the article "diffusion chamber") simple form of cloud chamber, a device used for radiation detection (see cloud chamber).cloud chamberscloud chamberIn a diffusion chamber, a ...
(from the article "gas") ...and in an equal countercurrent experiment this is balanced by an equal and opposite flow of the other component. The constant of proportionality is the same for both components and ...
(from the article "fluid mechanics") This is a diffusion equation. It indicates that, if the plate oscillates to and fro with frequency f, then the so-called boundary layer within which Omega3 is nonzero has a ...
(from the article "oxidation-reduction reaction") Diffusion flames, smoothly flowing (laminar) or turbulent, belong to the class of flames whose ingredients are not mixed prior to entering the burning zone. Molecular or turbulent diffusion is responsible ...
(from the article "economic forecasting") Some economists also use sets of statistics called diffusion indexes to calculate economic turning points. A diffusion index is a method of summarizing the common tendency of a group of ...
(from the article "integrated circuit") ...As a side effect of annealing, the implanted atoms usually move a little, diffusing into the surrounding material. The total area that contains implanted atoms after annealing is therefore called ...
(from the article "probability theory") ...it is quite difficult to write down explicitly a single example of a continuous, nowhere-differentiable function-they turn out to be typical of a large class of stochastic processes, called diffusion ...
(from the article "gas") There is also an effect that is the inverse of thermal diffusion, called the diffusion thermoeffect, in which an imposed concentration difference causes a temperature difference to develop. That is, ...
(from the article "photocopying machine") ...of light, heat, chemicals, or electrostatic charges. The need for a process other than wet photographic reproduction for copying documents stimulated the invention of various techniques, notably the diffusion-transfer and ...
(from the article "diffusion") ...dc/dx is the rate of change of concentration in the direction x, and the minus sign indicates the flow is from higher to lower concentration. D is called the diffusivity ...
one of the two principal sects of the Indian religion Jainism, whose male ascetics shun all property and wear no clothes. In accordance with their practice of nonviolence, the monks ... [8 Related Articles]
(from the article "Bentley, Richard") ...which were published after his death. Bentley made a particularly important scholarly contribution through his discovery that a sound (represented in transcriptions of some Greek dialects by the digamma, a ...
(from the article "Mishmi") ...century, the Mishmi live along the valleys of the Dibang (where they are known as Midu) and Luhit rivers. Those of the Luhit Valley are divided into two groups, the ...
(from the article "muscle") ...mandibulae, which replaces the hypobranchial muscles as the major jaw-opening muscle. The restructuring of the posterior jaw in mammals leads to the further replacement of this new muscle by the ...
town, seat of Digby county, western Nova Scotia, Canada. It is situated at the southern end of Annapolis Basin, an inlet of the Bay of Fundy. [1 Related Articles]
(from the article "flatworm") ...consists of suckerlets arranged in rows; excretory pore single and posterior; endoparasites of vertebrates, mollusks, and crustaceans; about 35 species.Oral and ventral suckers generally well-developed; development involves at least ...
Byzantine epic hero celebrated in folk ballads (Akritic ballads) and in an epic relating his parentage, boyhood adventures, manhood, and death. Based on historical events, the epic, a blend of ...
(from the article "immune system disorder") ...substance called an antigen.) The disease can be treated by periodic injections of large amounts of immunoglobulin G (IgG). The congenital, but not hereditary, T-cell deficiency disease called DiGeorge syndrome ...
(from the article "feed") ...protein or amino acids needed for growth or other body functions, either as a percentage of the diet or as the total grams or units required per day. The amounts ...
sequence by which food is broken down and chemically converted so that it can be absorbed by the cells of an organism and used to maintain vital bodily functions. This ... [17 Related Articles]
(from the article "thorium processing") Although monazite is very stable chemically, it is susceptible to attack by both strong mineral acids (e.g., sulfuric acid, H2SO4) and alkalies (e.g., sodium hydroxide, NaOH). In the acid treatment, ...
(from the article "hormone") In vertebrates, the muscular and secretory activities of the alimentary canal and its associated glands are regulated by nervous and hormonal mechanisms. The hormones comprise a self-contained complex that functions ...
(from the article "nervous system") ...most prominent. Two to five pairs of lateral nerves leave each ganglion to innervate the body wall of that segment. A subepidermal nerve plexus occurs over the whole body. Another ...
any of the diseases that affect the human digestive tract. Such disorders may affect the esophagus, stomach, small intestine, large intestine (colon), pancreas, liver, or biliary tract. A prevalent disorder ... [7 Related Articles]
the system used in the human body for the process of digestion. The human digestive system consists primarily of the digestive tract, or the series of structures and organs through ... [5 Related Articles]
any of the systems used by invertebrates for the process of digestion. Included are vacuolar and channel-network systems, as well as more specialized saccular and tubular systems. [13 Related Articles]
(from the article "animal development") ...an opening at its anterior end. This is also the case in some lower chordates and echinoderms, which are grouped together with vertebrates as the Deuterostomia, or animals with secondary ...
any of a group of agrarian communists who flourished in England in 1649-50 and were led by Gerrard Winstanley (q.v.) and William Everard. In April 1649 about 20 poor men ... [7 Related Articles]
(from the article "tunnels and underground excavations") The digger-shield type of machine is essentially a hydraulic-powered digger arm excavating ahead of a shield, whose protection can be extended forward by hydraulically operated poling plates, acting as retractable ...
(from the article "theodolite") basic surveying instrument of unknown origin but going back to the 16th-century English mathematician Leonard Digges; it is used to measure horizontal and vertical angles. In its modern form it ...
(from the article "plow") The antecedent of the plow is the prehistoric digging stick. The earliest plows were doubtless digging sticks fashioned with handles for pulling or pushing. By Roman times, light, wheelless plows ...
American politician whose service (1954-80) as a Democratic representative from Michigan helped pave the way for future African-American lawmakers but ended in disgrace after a conviction in a kickback scheme ...
in anatomy, finger or toe of land vertebrates, the skeleton of which consists of small bones called phalanges. The tips of the digits are usually protected by keratinous structures, such ...
(from the article "measurement system") The royal cubit (524 mm, or 20.62 inches) was subdivided in an extraordinarily complicated way. The basic subunit was the digit, doubtlessly a finger's breadth, of which there were 28 ...
(from the article "measurement system") ...Metrologists have come to differing conclusions concerning its exact length, but the currently accepted modern equivalents are 296 mm, or 11.65 inches. Expressed in terms of these equivalents, the digit ...
in human physiology, any of the isolated anomalies of the digits (fingers or toes) in an otherwise normal individual or as one symptom of a more generalized genetic abnormality. In ...
(from the article "ammeter") ...measure alternating current with accuracies of from 0.5 to 3 percent, the measured current heats a thermoconverter (thermocouple); the small voltage thus generated is used to power a millivoltmeter. Digital ...
(from the article "digital sound recording") ...signals. In the 1980s digital compact disc recordings became available that were played by using a laser beam to optically scan digital information encoded on the disc's surface. In the ...
device for making digital recordings of images. Texas Instruments Incorporated patented the first filmless electronic camera in 1972. In 1981 Sony Corporation brought out a commercial electronic model, which used ... [1 Related Articles]
(from the article "chess") ...and then falls straight down again. Until the introduction of the flag, an arbiter or judge had to determine whether the minute hand had passed 12. No further changes in ...
(from the article "electronics") Computers understand only two numbers, 0 and 1, and do all their arithmetic operations in this binary mode. Many electrical and electronic devices have two states: they are either off ...
(from the article "digital sound recording") ...by means of a microprocessor and converts the data back into analog audio signals that can be used by the amplifier of a conventional stereo sound system. The early 1990s ...
any of a class of devices capable of solving problems by processing information in discrete form. It operates on data, including magnitudes, letters, and symbols, that are expressed in binary ... [20 Related Articles]
(from the article "Digital Consumer Electronics Boom") The proliferation of consumer electronics gadgets continued in 2006 as it became routine to encounter people speaking on cellular phones, listening to digital music on headphones, or snapping countless pictures ...
(from the article "differential analyzer") ...with components that take up less space. The inherent lack of precision has been rectified in some cases by use of digital counting devices, giving rise to a subclass of ...
(from the article "music recording") Meanwhile, a new recording technique that boasted, among other things, a wider dynamic range had begun to revolutionize the market for quality recordings: the music was taped "digitally," via pulse-code ...
(from the article "Digital Consumer Electronics Boom") The digital divide, which separated those who could afford technology from those who could not, continued to exist in 2006. In an effort to reach more customers, cell phone companies ...
(from the article "Performing Arts") Technology continued to affect the position of classical music in the culture at large. Classical music downloads made up, by some estimates, upwards of 20% of the online music market ...
American manufacturer that created a new line of low-cost computers, known as minicomputers, especially for use in laboratories and research institutions. Founded in 1957, the company employed more than 120,000 ... [2 Related Articles]
(from the article "telephone and telephone system") ...the European Conference on Posts and Telecommunications (CEPT) began work on another personal communication system, which became known as the digital European cordless telephone (DECT) system. The DECT system was ...
(from the article "telephone and telephone system") Although the Group 2 fax machines proved to be successful in business applications where electronic transmission of documents containing nontextual information such as drawings, diagrams, and signatures was required, the ...
(from the article "information processing") ...to represent information electronically as digital signals and to manipulate it automatically at exceedingly high speeds. Information is stored in binary devices, which are the basic components of digital technology. ...
(from the article "Redefining the Library in the Digital Age") Broadly defined, a digital library is any collection of texts, sounds, or images stored in a digital format. The Digital Library Federation, a group of research libraries actively working on ...
(from the article "Media and Publishing") ...new HDTV units marketed during the year were a Sharp 165-cm (65-in) LCD TV, a Panasonic 262-cm (103-in) plasma-screen TV, and a Samsung 142-cm (56-in) rear-projection TV with a technology ...
(from the article "copyright") ...presented by technological advances. In most instances those adjustments have involved strengthening the entitlements of copyright owners. In 1998, for example, the United States passed the Digital Millennium Copyright Act, ...
(from the article "Computers and Information Systems") The growth of Apple Computer continued to be fueled by the iPod digital music player, which in turn benefited from Apple's dominance in online music sales through its iTunes service. ...
(from the article "stage design") By the early 21st century, digital projections had become the standard mode of projection in the theatre. The early generations of digital projectors, which first appeared in the 1980s, were ...
(from the article "media convergence") Some industry analysts see media convergence as marking the twilight of the "old media" of print and broadcasting and the rise of "new media" associated with digital publishing. Among the ...
(from the article "Media and Publishing") Some stations experimented with less-rigid music formats, and others took advantage of technology for digital radio broadcasting. In the United States some companies launched HD Radio stations. HD Radio-a system ...
(from the article "Media and Publishing") ...in other countries. Belgium-based TDPradio, the brainchild of program manager Daniel Versmissen, celebrated its third year as the first and only dance radio station that broadcast worldwide in Digital Radio ...
(from the article "colorectal cancer") Diagnoses of colon and rectal cancers are made by means of several techniques. During a digital rectal exam, the physician inserts a gloved finger into the rectum and feels its ...
(from the article "Computers and Information Systems") ...about 70% of the music-download market, introduced a major change in May in the way music was sold online. In an arrangement with EMI Group, Apple began to offer EMI ...
(from the article "earthquake") By the 1980s a further upgrading of permanent seismographic stations began with the installation of digital equipment by a number of organizations. Among the global networks of digital seismographic stations ...
(from the article "telecommunication") In order to transmit computer data and other digitized information over a communications channel, an analog carrier wave can be modulated to reflect the binary nature of the digital baseband ...
(from the article "information processing") ...recording of sound is important because speech is the most frequently used natural carrier of communicable information. Direct capture of sound into personal computers is accomplished by means of a ...
method of preserving sound in which audio signals are transformed into a series of pulses that correspond to patterns of binary digits (i.e., 0's and 1's) and are recorded as ... [7 Related Articles]
(from the article "diagnosis") Digital subtraction angiography (DSA), an electronic technique for imaging blood vessels, is useful in diagnosing arterial occlusion, including carotid artery stenosis and pulmonary artery thrombosis, and in detecting renal vascular ...
(from the article "computer") Digital tablets and touch pads are similar in purpose and functionality. In both cases, input is taken from a flat pad that contains electrical sensors that detect the presence of ...
(from the article "Media and Publishing") The International Telecommunications Union announced a pact between more than 100 countries across Europe, Africa, and the Middle East to switch from analog to digital audio and television broadcasting by ...
(from the article "Table 1: Standardized Digital Transmission Rates for the Synchronous Digital Hierarchy, the Synchronous Optical Network, and the Optical Carrier Hierarchy*") ...loss due to noise and interference. Figure 1 shows the basic components of a typical digital telecommunications system capable of transmitting voice, facsimile, data, radio, or television signals. Digital transmission ...
(from the article "Media and Publishing") ...terrestrial cellular networks. Alcatel signed up Samsung Electronics to develop mobile phones that would receive the satellite TV broadcasts. Germany's pilot cell phone TV project, which used the Digital Video ...
(from the article "Media and Publishing") ...mainstream. "Consumers will have more flexibility over what they watch and when they watch it," said Phillip Swann, president of TVPredictions.com. Swann pegged growing usage of HDTV, digital video recorders ...
(from the article "voltmeter") The instruments just described provide readings in analogue form, by moving a pointer that indicates voltage on a scale. Digital voltmeters give readings as numerical displays. They also provide outputs ...
(from the article "computer") ...of cycles per second). Another factor that affects performance is the "word" size-the number of bits that are fetched at once from memory and on which CPU instructions operate. Digital ...
(from the article "digital sound recording") ...with an analog-to-digital converter that transforms two channels of continuous audio signals into digital information, which is then recorded by a high-speed tape or disc machine. The system uses a ...
drug obtained from the dried leaves of the common foxglove (Digitalis purpurea) and used in medicine to strengthen contractions of the heart muscle. Belonging to a group ... [9 Related Articles]
(from the article "New Frontiers in Radio") ...bring the public's attention to satellite radio, an uncensored and still new outlet for radio programming. (Unlike regular, or terrestrial, radio, which is broadcast from Earth-based antennas, the digitally encoded ...
(from the article "crabgrass") any of about 300 species of grasses in the genus Digitaria (family Poaceae), especially D. sanguinalis or the slightly shorter D. ischaemum (smooth crabgrass). D. sanguinalis has long hairs covering ...
(from the article "cat, domestic") Cats are among the most highly specialized of the flesh-eating mammals. Their brains are large and well-developed. Cats are digitigrade; that is, they walk on their toes. Unlike the dog ...
(from the article "primate") ...is a single pattern of ground-living locomotion, which is called quadrupedalism. Within this category there are at least two variations on the theme: (a) knuckle-walking quadrupedalism, and (b) digitigrade quadrupedalism. ...
(from the article "Media and Publishing") ...success of the World eBook Fair, coordinated by Project Gutenberg. The five-week online giveaway of electronic books saw more than 30 million books downloaded worldwide. In addition, the amount of ...
(from the article "steroid") The most important cardiac glycosides, medicinally, are those occurring in foxglove (Digitalis): digitoxin, gitoxin, and digoxin. Each of these contains a specific aglycone (e.g., digitoxigenin [23] is the aglycone of ...
(from the article "drug") ...in 1785 by English physician William Withering, who successfully used an extract of foxglove leaves to treat heart failure. The two compounds most often used therapeutically are digoxin and digitoxin.plant ...
the coexistence of two forms of the same language in a speech community. Often, one form is the literary or prestige dialect, and the other is a common dialect spoken ... [2 Related Articles]
(from the article "fat") Monoglycerides and diglycerides are partial esters of glycerol and have one or two fatty-acid radicals, respectively. They are seldom found in natural fats except as the products of partial hydrolysis ...
