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N Type connectors or Type N connectors are a form of high quality, screw-on, RF connector developed during the 1940's as a medium-sized, weatherproof, durable, RF connector that would exhibit consistent impedance - usually 50 ohms - at frequencies up to 11 ghz. The N Type connector was named after Paul Neill of the Bell Laboratories, and are widely used in military radio equipment for connecting aerials to receivers and transmitters.
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N-hexane is a chemical made from crude oil. It is used in laboratories, primarily when it is mixed with similar chemicals to produce solvents. Common names for these solvents are commercial hexane, mixed hexanes, petroleum ether, and petroleum naphtha. The major use for solvents containing n- hexane is to extract vegetable oils from crops such as soybeans, flax, peanuts, and safflower seed. They are also used as cleaning agents in the textile, furniture, shoemaking, and printing industries, particularly rotogravure printing.
N-hexane is also an ingredient of special glues that are used in the roofing, shoe, and leather industries. N-hexane is used in binding books, working leather, shaping pills and tablets, canning, manufacturing tyres, and making baseballs. Consumer products that contain small amounts of n-hexane include petrol, rubber cement, type over correction fluids, non-mercury thermometers, alcohol preparations, and aerosols in perfumes.
N-hexane is also a component of preparations such as paint thinners, general purpose solvents, degreasing agents, or cleaners. N-hexane is a colourless liquid with a slightly disagreeable odour. It evaporates very easily into the air and dissolves only slightly in water. It is highly flammable, and its vapours can be explosive. It may be ignited by heat, sparks, and flames. Flammable vapour may spread away from a spill.
N-hexane can react vigorously with oxidizing materials such as liquid chlorine, concentrated oxygen, and sodium hypochlorite. It will attack some forms of plastics, rubber, and coatings. It is insoluble in water and miscible with alcohol, chloroform, and ether. It is incompatible with strong oxidizers. N-hexane is also known as hexane and hexyl hydride.
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N-Nitrosodiphenylamine is a yellow or orange-brown solid with no odour. It is soluble in acetone, ethanol, benzene, and ethylene dichloride. Its flash point and flammability limits are unknown. It is not a naturally occurring substance; it is a man-made chemical that was used in rubber compounding as a retarder to prevent premature vulcanisation of rubber compounds during mixing and other processing operations. It was generally used with sulphenamide accelerators in tyre compounds and other mechanical goods.
N-Nitrosodiphenylamine was also used as an intermediate in the manufacture of p-nitrosodiphenylamine, which was subsequently used to produced N-phenyl-p-phenylenediamine and other rubber-processing chemicals. American manufacturers stopped producing N-nitrosodiphenylamine in the early 1980s because new and more efficient chemicals were found to replace it. It also had several undesirable side effects which do not occur with replacement chemicals.
N-nitrosodiphenylamine is also known as diphenylnitrosoamine, N-nitroso-n-phenylaniline, N-nitroso-n-phenylbenzenamine, N,n- diphenylnitrosoamine, nitrous diphenylamide, NDPA, and NDPhA.
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Nack (nak) is the 'Negative Acknowledge' character in many data codes; typically used to indicate receipt of a corrupted message, ordering retransmission.
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Nacre is the technical name for mother-of-pearl.
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The nadir is the point on the celestial sphere directly below an observer and diametrically opposite the zenith. It is 90 degrees away from the horizon and is approximately the direction in which a plumb-bob hangs. Because the Earth is not spherical the direction of the plumb-bob nadir would not in general pass through the Earth's centre. Furthermore, the plumb-bob can be deviated slightly by large local masses such as mountains so that for precise astronomical measurements corrections have to be made to clarify which nadir is being used.
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Nagana is a disease of hoofed animals of central and southern Africa, caused by the parasitic protozoa of the genus Trypanosoma that is transmitted by tsetse flies.
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Naloxone is a chemical substance that counteracts the effects of opiates by binding to opiate receptors on cells.
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A NAND gate is an electronic computer logic circuit having two or more input wires and one output wire that has an output signal if one or more of the input signals are at a low voltage.
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Naples yellow is a yellow pigment, used by artists. It is either lead antimonate or a similar pigment consisting of a mixture of zinc oxide with yellow colouring matter - originally it was found occuring naturally on the slopes of Mount Vesuvius.
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Naptha is a volatile and highly inflammable solvent, colourless to white in colour and with a disagreeable odour. Naptha is prepared from coal tar, petroleum or shale oil.
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Napthalene is a white solid hydrocarbon with a strong smell; is also called mothballs, moth flakes, white tar, and tar camphor. Naphthalene is a natural component of fossil fuels such as petroleum and coal; it is also formed when natural products such as wood or tobacco are burned. The principal use for naphthalene is as an intermediate in the production of phthalic anhydride, which is used as an intermediate in the production of phthalate plasticisers, resins, phthaleins, dyes, pharmaceuticals, insect repellents, and other materials; other products made from naphthalene are moth repellents, in the form of mothballs or crystals, and toilet and diaper pail deodorant blocks. Naphthalene is also used for making leather tanning agents, and the insecticide carbaryl. There are two common compounds related to naphthalene: 1-methylnaphthalene (C11H10), also called alpha- methylnaphthalene; and 2-methylnaphthalene (C11H10), called beta-methylnaphthalene. Naphthalene evaporates easily; when its vapours are mixed with air, the mixture can burn
easily. It is soluble in benzene, alcohol, ether, and acetone; it is soluble in water at 20 degrees C. It is a moderate fire hazard when exposed to heat or flame; it reacts with oxidizing materials and chromium anhydride. It is a moderate explosion hazard, in the form of dust, when exposed to heat or flame. Naphthalene is also known as naphthalin, naphthaline, tar camphor, white tar, NCI-C52904, albocarbon, and naphthene.
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Napthol exists in two varieties, alpha and beta, which are the mono-hydroxy derivatives of napthalene. Both are volatile, crystalline solids, somewhat resembling phenol. Beta napthol is an antiseptic, and both varieties are employed in producing dyes.
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Narceine or narceen is a narcotic alkaloid that occurs in opium.
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Narcotine is a non-narcotic alkaloid occurring in opium. It is decomposed by water into meconine and cotarnine.
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In chemistry, nascent is the condition of an element that has just been released in the monatomic state in a chemical reaction.
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The National Crime Information Computer (NCIC) is an American FBI computer system that maintains a database of information about such things as stolen cars, stolen boats, missing persons, wanted persons and arrest records. It provides quick access to these records by State, Local and Federal law enforcement agencies. NCIC is directly linked with the Treasury Department's TECS computer and many State computer systems.
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The National HRO was an American communications received introduced in the mid-1930's. The National HRO was a nine-valve superhet receiver with two RF amplifier stages, a mixer with a separate local oscillator, tow stages of IF amplification with variable selectivity and a crystal filter, diode detection, two stages of AF amplification and a beat frequency oscillator (BFO). Frequency coverage was selected with large plug-in coil-sets, these providing coverage of 1.7 - 4 Mhz, 3.5 to 7.3 Mhz, 7-14.4 Mhz and 14-30 Mhz with other sets available covering 50 - 100 khz, 100 -200 khz, 180 - 430 khz, 480 - 960 khz and 900 - 2050 khz. The National HRO could receive signals in AM and SSB modes,
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Natural fats are the group of oily substances of natural occurrence, such as butter, lard, tallow, etc., as distinguished from certain fat-like substances of artificial production, such as paraffin. Most natural fats are essentially mixtures of triglycerides of fatty acids.
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Natural gas is a naturally occurring gas consisting mainly of methane with smaller amounts of heavier hydrocarbons. It is widely used as a fuel and is obtained from underground reservoirs, often associated with oil deposits. It originates in the decomposition of animal matter.
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The natural order of colour is the order in which colours of maximum purity will occur if arranged in a circle so as to progress from the lightest tone (white) to the darkest (black), eg: white, yellow, orange, red, purple, violet, blue, blue-green, green, black
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Navar is a system of air navigation in which a ground radar station relays signals to each aircraft indicating the relative positions of neighbouring aircraft.
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Navigation is the science and technology of finding the position, course, and distance travelled by a ship, plane, or other craft. Traditional methods include the magnetic compass and sextant. Today the gyrocompass is usually used, together with highly sophisticated electronic methods, employing beacons of radio signals, such as Decca, Loran, and Omega. Satellite navigation uses satellites that broadcast time and position signals. The Phoenicians, Syrians, Carthaginians, Greeks and Romans conducted their voyages solely by the observation of the heavens, and by keeping as much as possible to the coast. It was not until the voyages made by direction of Prince Henry of Portugal, after 1418, that navigation seems to have been systematically conducted, and the sea-instruments and sea-charts then constructed formed the basis of maritime science until replaced by satellite
navigation equipment in the late 1990s. An early invention that marked progress was the cross-staff, first described by Werner in 1514. It was used for the determination of longitude, by observation of the distance between the moon and some star; and out of it grew the fore-staff and the back-staff.
In 1530 Gemma Frisius of Louvain devised the idea of using small clocks in conjunction with instrumental observation, and the nautical quadrant in some form was thenceforth part of every ship' s furniture. John Davis' quadrant (the back-staff) seems to have been generally preferred for many years. In the early 16th century there also cam into use at sea the astrolabe, for taking the altitude of the sun and stars. This instrument was made very heavy, so that it hung perpendicularly and steadily. The middle of the 16th century saw the invention of the log-line. Voyages were, however, conducted rather by guesswork and experience, and especially so previous to the discovery of methods of finding the longitude. Mercator's system of plane charts furthered
progress; and Edward Wright discovered the true method of dividing the meridian, and drew up a table for the use of navigators by which latitude could be determined.
The US global positioning system (GPS) was introduced 1992 and features 24 Navstar satellites that enable users to triangulate their position (from any three satellites) to within 15 m. In 1992, 85 nations agreed to take part in trials of a new navigation system which makes use of surplus military space technology left over from the Cold War. The new system, known as FANS or Future Navigation System, makes use of the 24 Russian Glonass satellites and the 24 US GPS satellites. Small computers will gradually be fitted to civil aircraft to process the signals from the satellite, allowing aircraft to navigate with pinpoint accuracy anywhere in the world. The signals from at least three satellites will guide the craft to within a few metres of accuracy. FANS will be used in conjunction with four Inmarsat satellites to provide worldwide communications between pilots and air-traffic controllers.
An Australian prototype for an electronic navigation system ECDIS (Electronic Chart Display Information System) is a single computer-based apparatus that combines information from existing navigational aids, such as charts, radar, sonar and satellites.
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A nebula is a cloud of gas and dust in space. Before the invention of the telescope, the term nebula was applied to all celestial objects of a diffuse appearance. As a result, many objects now known to be star clusters or galaxies were originally called nebulas.
Nebulas exist within other galaxies as well as in our own Milky Way galaxy. They are classified as planetary nebulas, supernova remnants, and diffuse nebulas, including reflecting, emission, and dark nebulas. Small, very bright nebulas called Herbig-Haro objects are found in dense interstellar clouds and are probably the products of gas jets expelled by new stars in the process of formation. Planetary nebulas, or planetaries, are so called because many of them superficially resemble planets through telescopes. They are actually shells of material that an old average star sheds during a late, red giant stage in its evolution, before becoming a white dwarf. The Ring nebula of the constellation Lyra, a typical planetary, has a rotational period of 132, 900 years and a mass calculated to be about 14 times that of the earth's sun. Several thousand planetaries have been discovered in the Milky Way. More spectacular but fewer in number are nebulas that are the fragments of supernova explosions, perhaps the most famous of which is the Crab nebula in
Taurus, now fading at the rate of about 0.4 percent per year. Nebulas of this kind are strong emitters of radio waves, as a result of the explosions that formed them and the probable pulsar remnants of the original star. Diffuse nebulas are extremely large structures, often many light-years wide, that have no definite outline and a tenuous, cloudlike appearance. They are either luminous or dark. The former shine as a result of the light of neighbouring stars. They include some of the most striking objects in the sky, such as the Great nebula in Orion. The tremendous streams of matter in the diffuse nebulas are intermingled in violent, chaotic currents. Many thousands of luminous nebulas are known. Spectral studies show that light emanating from them consists of reflected light from stars and also, in so-called emission nebulas, of stimulated radiation of ionised gases and dust from the nebulas themselves.
Dark, diffuse nebulas are observed as nonluminous clouds or faintly luminous, obscuring portions of the Milky Way and too distant from the stimulation of neighbouring stars to reflect or emit much light of their own. One of the most famous dark nebulas is the Horsehead nebula in Orion, so named for the silhouette of the dark mass in front of a more luminous nebular region. The longest dark rift observed on photographic plates of the star clouds of the Milky Way is a succession of dark nebulas. Both dark nebulas and luminous nebulas are considered likely sites for the processes of dust-cloud condensation and the formation of new stars.
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The Nebular Hypothesis is an hypothesis that the Solar System evolved from a nebula. Emanuel Swedenborg and Immanuel Kant both put forward explanations of this kind, but Pierre Laplace was the first to develop a nebular hypothesis on strictly scientific lines. Laplace's hypothesis was that rotating nebulae were first formed by the condensation of gaseous matter, and that the Sun was originally a nebula of this type. As the nebula continued to shrink, it rotated faster and faster, until fragments broke away from the main body of the Sun. These fragments condensed under their own gravitational attraction and formed the planets. Laplace's hypothesis is untenable, as it fails to explain the fact that nearly all the angular momentum of the Solar System resides in the planets. The tidal hypothesis of James Jeans, that the planets were formed from material torn out of the Sun by the close approach of a passing star, is also untenable, as the ejected material would disperse into space. Modern theories offer no unique solution, but agree that the Sun and planets condensed simultaneously from a rotating cloud of gas and dust.
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The needle is one of the oldest implements used by man. Some people still sew with awls of bone or of thorns or make needles of iron or steel, with a construction under the pin-like head around which the end of the thread is tied. The Chinese are believed to have been the first to use needles of steel, and the Moors are credited with bringing them to Europe.
By 1370 needle making was established in Nuremberg, Germany. In England during the reign of Queen Elizabeth I, the manufacture of needles was taken up on a considerable scale in small shops; after 1650 the manufacture of hand-sewing needles gradually became an important industry in England, and later in Germany. Subsequent developments included adding an eye to the needle and the gradual development of machines for the manufacture of needles. One such machine, introduced in 1785, produced a steel rod from which two joined needles were formed.
The first needles to have eyes drilled into them were made in 1826 on a stamping machine, but the mechanical process for the production of needles was not fully developed until 1885. Needles include those designed for hand and machine sewing and knitting.
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In engineering, a needle bearing is an antifriction roller bearing in which long rollers of very small diameter fill the race without a cage to provide spacers between them.
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The Neel temperature is the temperature at which the susceptibility of an antiferromagnetic material has a maximum value.
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Negative resistance is a characteristic of certain electronic components in which an increase in the applied voltage increases the resistance, producing a proportional decrease in current.
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Neodymium is a toxic silvery-white metallic element of the lanthanide series, occurring principally in monazite and used in colouring glass.
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Neon is a highly stable gaseous element with the symbol Ne. It is one of the rare components of the atmosphere and is used in some forms of discharge tubes and lamps, in which it gives a characteristic red glow.
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Neoprene is a synthetic rubber obtained by the polymerisation of chloroprene. It is resistant to oil and ageing and is used in waterproof products, such as diving suits, paints, and adhesives.
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A nephoscope is an instrument used in observing the altitude and motion of clouds.
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Neptunium is a silvery metallic transuranic element synthesized in the production of plutonium and occurring in trace amounts in uranium ores. It was the first element to be made synthetically, being artificially produced in 1940 by the bomardment of uranium with neutrons by Edwin McMillan and Philip Abelson.
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In thermodynamics, the Nernst heat theorem is the principle that reactions in crystalline solids involve changes in entropy that tend to zero as the temperature approaches absolute zero.
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The Nernst lamp was an early electric light bulb (circa 1905) which made use of a thread of yttrium oxide or zirconium oxide or similar earths. These wires do not conduct electricity until they are heated to a red heat, and so the Nernst lamp used a subsidiary heating arrangement consisting of a very fine platinum wire wound on a thin rod of porcelain. The lamp took roughly 30 seconds to light up.
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Neroli oil is a brown oil distilled from the flowers of various orange trees, especially the Seville orange and used in perfumery.
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NetMedic is a browser companion program for the Windows operating system that works with a user's browser to monitor, isolate, diagnose, and correct Internet or intranet performance problems. Net. Medic lets users identify the source of their network bottleneck, whether it is the PC, modem, Internet service provider (ISP), Internet backbone, or remote Web site server. Net.Medic identifies problems in split seconds, offers recommendations for solving them, and in many cases, automatically fixes them.
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Netstat is an application available with some computer operating systems that displays information about the networking subsystem. Uner Linux, the default for
netstat is to display a list of all open sockets. Under Linux netstat can be usefully used by web site system adminstrators to view the number of concurrent connections to the web server, for example with the command:
netstat -na
grep ^tcp
wc which filters out any non-tcp connections by using the grep program. Further, a simple count of the number of concurrent connections can be retrieved by again using netstat and piping its output through grep, so:
netstat -na
grep ^tcp
wc -l
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In engineering, a neutral axis is the line or plane through the section of a beam or plate which does not suffer extension or compression when the beam or plate bends.
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A neutrino is a short-lived uncharged particle of zero or near zero rest mass. They occur in certain nuclear reactions.
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Neutrino astronomy is the detection of neutrinos emitted by the sun from which information about the solar interior can be obtained.
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The neutron is a subatomic uncharged particle, of slightly greater mass than a proton and forming a constituent part of the nucleus of all atoms except hydrogen atoms, which consist of a single proton. It may be considered as the equivalent of one proton and one electron.
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In physics, a neutron gun is a device used for producing a beam of fast neutrons.
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The neutron number is the number of neutrons in the nucleus of an atom.
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A neutron poison is a nonfissionable material used to absorb neutrons and thus to control nuclear reactions.
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Newcastle disease is an acute viral disease of birds, especially poultry, characterized by pneumonia and inflammation of the central nervous system.
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Newton's first law of motion states: Every body continues in its state of rest or of uniform motion in a straight line unless compeled by some external force to act otherwise. It should be noted that Newton's laws apply only in the macro-world, at the atomic particle level and smaller, and at the planetary level, Newton's laws do not apply, for reasons which are as yet not understood.
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Newton's law of gravitation is the principle that two particles attract each other with forces directly proportional to the product of their masses divided by the square of the distance between them.
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Newton's laws of motion are three laws of mechanics describing the motion of a body. The first law states that a body remains at rest or in uniform motion in a straight line unless acted upon by a force. The second law states that a body's rate of change of momentum is proportional to the force causing it. The third law states that when a force acts on a body an equal and opposite force acts simultaneously on another body. It should be noted that Newton's laws apply only in the macro-world, at the atomic particle level and smaller, and at the planetary level, Newton's laws do not apply, for reasons which are as yet not understood.
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Newton's second law of motion states: The rate of change of momentum of a body is proportional to the applied force and takes place in the direction in which the force acts.
It should be noted that Newton's laws apply only in the macro-world, at the atomic particle level and smaller, and at the planetary level, Newton's laws do not apply, for reasons which are as yet not understood.
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Newton's third law of motion states: To every action there is an equal and opposite reaction. It should be noted that Newton's laws apply only in the macro-world, at the atomic particle level and smaller, and at the planetary level, Newton's laws do not apply, for reasons which are as yet not understood.
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The Newtonian telescope is a type of astronomical reflecting telescope in which light is reflected from a large concave mirror, onto a plane mirror, and through a hole in the side of the body of the telescope to form an image.
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Nichrome is a tradename used for various alloys containing nickel, iron, and chromium, with smaller amounts of other components. It is used in electrical heating elements, furnaces, etc.
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Nickel is a metal element with the symbol Ni. Nickel was discovered by Cronstedt in 1751 in the mineral copper-nickel.
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Nickel Silver (German Silver, Pack-Fong) is an alloy of copper, nickel and zinc in different proportions. Sometimes lead is added if the alloy is destined for making candlesticks or casts.
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Nickel steel is a type of steel containing between 0.5 and 6.0 percent nickel to increase its strength.
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A Nicol prism is a device composed of two prisms of Iceland spar or calcite cut at specified angles and cemented together with Canada balsam. It is used for producing plane-polarized light.
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Nicotinamide is the amide of nicotinic acid. It is a component of the vitamin B complex and is essential in the diet for the prevention of pellagra.
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Nicotinamide adenine dinucleotide (NAD) is a coenzyme that is a hydrogen carrier in metabolic reactions, especially in tissue respiration. It was formerly called DPN.
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Nicotinamide adenine dinucleotide phosphate (NADP) is a coenzyme with functions similar to those of NAD. It was formerly called TPN.
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Nicotine is an alkaloid derived from the leaves of tobacco.
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Niello is a black, metal, amalgam of sulphur added to copper, silver or lead and used for filling engraved lines in metal objects.
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Nigrosine is a class of black pigments and dyes obtained from aniline hydro-chlorates. They are used in inks and shoe polishes and for dyeing textiles.
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Niobium is a metal element with the symbol Nb.
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A nitrate is any salt of nitric acid.
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Nitric acid (Aqua fortis) is produced by the oxidation of ammonia.
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Nitro-glycerine is a powerful explosive produced from nitric acid and glycerol.
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Nitrogen (originally known as azote, a name given to the gas by Antoine Lavoisier) is a colourless, odourless, tasteless, gaseous element discovered about 1772 by Daniel Rutherford, though credit for the discovery of nitrogen in the atmosphere was claimed by Carl Scheele. The gas was renamed nitrogen in 1790 by J Chaptal. Nitrogen constitutes 78% of the atmosphere by volume, and occurs as a constituent of all living tissues in combined form. It is slightly soluble in water, but very soluble in liquid oxygen, and has the symbol N.
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No*Stop Suprdupe by Nonstop Networks Limited, is a computer program that makes two drives the same. It 'synchronizes' them. It works with any two drives, so long as the 'target' is large enough to hold the data on the 'source'. It can make a floppy disk look like a subdirectory of your hard disk, or make your RAMdrive look like a subdirectory of your hard disk. Scrub a complex data structure (such as a demo) from your hard disk. Dump important structures and data to a removable device for backup and safekeeping. It can be used to copy data only if the date/time, attributes or size are different.
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Nobelium is a radioactive metal element with the symbol No.
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In chemistry, the noble gases are a family of highly stable monoatomic gaseous elements, once though to be inert, consisting of helium, neon, argon, krypton, xenon and radon.
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In audio engineering a gate or noise gate is an audio switch used to mute signals below a set threshold level. It can be used to suppress background noise and hiss from valve amplifiers, effects pedals, and microphones.
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NoiseKiller by Jean-Pierre Menicucci is a computer program to spin IDE drives down when they are unused. The drives start spinning again as soon as they are accessed.
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The Nokia 1600 is a basic, non-nosense mobile phone for people who want a mobile phone for making and receiving calls and perhaps text messages. The Nokia 1600 features a 65,000 colour screen, MP3 and polyphonic ring tones for customisation. The Nokia 1600 includes a calendar, alarm and games, but is primarily a no-frills mobile telephone.
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The Nokia 8210 was a mobile telephone of the 1990s, and remains one of the smallest and lightest commercial mobile telephones ever produced. The Nokia 8210 was a dual-band telephone which featured changeable covers using the Nokia Xpress-on cover system enabling users to personalise their phone.
The Nokia 8210 was a quick and easy to use telephone featuring a phone book, selectable monophonic ring tones, built in calculator, diary, games and predictive text and picture messaging. The Nokia 8210 could be connected to other devices using an infrared link.
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The Nokia E90 Communicator is a quad-band mobile telephone able to be used on every continent of the world, featuring mobile office facilities and a battery stand-by time of up to fourteen days and a talk-time of up to 5.8 hours. The Nokia E90 Communicator incorporates a 3.2 megapixel digital camera, video faculties, music player, broadband internet connectivity and a full qwerty keyboard and a 800x352 pixel inner display supporting 16 million colours.
The Nokia E90 Communicator can be connected to a computer through a USB cable, and to other devices with an infra-red link or Bluetooth. The Nokia E90 Communicator provides a web browser and also support for the Adobe Acrobat Reader application for viewing PDF files.
The Nokia E90 Communicator also incorporates an FM radio and music player. The Nokia E90 Communicator supports the sending and receiving of emails through the usual POP3 and SMTP protocols, and also supports attachments with a built in ZIP manager and its own Quickoffice tools with editors for word processing, spreadsheets and presentations.
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A nonagon (or enneagon) is a nine-sided polygon.
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In chemistry, a nonelectrolyte is a compound whose water solution does not conduct an electric current.
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In chemistry, a normal solution is a solution which contains 1 gram-equivalent weight of a solute in 21 litres of solution.
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In civil engineering, notching is a method of excavating cuttings for roads or railways in a series of steps worked at the same time.
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Advanced NetWare was a powerful LAN operating system package that let you link up to 100 PCs to a file server to share files and network resources such as printers. With Advanced NetWare installed in an 80286 or better based PC, you could achieve minicomputer-like performance while you continued to use your PC-based applications.
Advanced NetWare could be configured as either a dedicated or non-dedicated system upon installation. Taking full advantage of the power of the processor, this product used up to 12Mb of RAM and more than 2Mb of hard disk storage to support up to 100 users per server. Because it is fully compatible with IBM's NetBIOS, it worked with the many multi-user applications available for the IBM Token-Ring and PC Network. Compatible with over 80 popular network hardware adapters and topologies, the package offered the utmost in flexibility. For example, if the layout of a building required multiple cable-types, you could connect an ARCNET segment in one part of the building, an Ethernet in another, and a Token-Ring somewhere else.
If you already had a non-Novell network installed, you could switch to Advanced or SFT NetWare and take advantage of the package's sophisticated security, power, and flexibility. Advanced NetWare provided operating system support for NetWare for Macintosh, a VAP (Value Added Process), and offered transparent protocol connectivity between IPX and Apple' s AFP. Using NetWare for Macintosh and Novell NL1000 AppleTalk network interface card, you could connect any AppleTalk network or network device (such as Apple LaserWriters) to a Novell file server running NetWare version 2.15.
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Novell ELS NetWare Level I is Novell's Entry Level Solution non-dedicated network operating system software for small workgroups or offices. Designed for those who need the advantages of networking but who are afraid that network installation is too complex. LAN operations such as file and resource sharing are supported. Much less expensive and easier to install than Novell's other LAN software, Novell ELS NetWare Level I is a non-dedicated LAN operating system that supports up to four network users simultaneously. The package includes many of the features of Novell's other LAN software, such as menu-driven operation, print spooling, and a custom menuing program, and supports up to five network server-attached printers. Novell ELS NetWare Level II supports up to eight concurrent users. Unlike ELS NetWare Level I, it includes many key features and network management tools of Novell Advanced NetWare, such as resource accounting, system security, basic system fault tolerance, and hardware independence.
ELS NetWare Level II offers the choice of dedicated or non- dedicated 80286 modes of operation. A read-after-write verification is performed whenever data is written to the network hard disk insuring that the data is re-readable. If the read-after-write verification finds a faulty area of the hard disk, Hot Fix labels it as bad, lists it in the bad block table, and automatically writes data to undamaged areas. ELS NetWare Level II provides operating system support for NetWare for Macintosh, a VAP (Value Added Process), and offers transparent protocol connectivity between IPX Apple's AFF. Using NetWare for Macintosh and Novell NL1000 AppleTalk network interface card, you can connect any AppleTalk network or network device (such as Apple LaserWriters) to a Novell file server running NetWare version 2.15.
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In a nuclear electricity generating installation the heat required for raising steam is provided by a nuclear reactor instead of a coal or gas furnace. A reactor consists of a strong steel pressure vessel enclosing a core made of graphite bricks. This graphite core has a number of vertical channels which are filled with rods of uranium. Interspersed among the uranium rods are a set of boron steel rods (the control rods) which may be raised or lowered in similar channels in the graphite. The uranium used in the reactor consists of a mixture of two different kinds of atoms, of which the most important are U-235. Quite spontaneously, some of these U-235 atoms explode or disintegrate to form other atoms of smaller mass. When this happens, energy is radiated from the central core or nucleus of the atom together with small high-speed particles called neutrons. If one of the neutrons happens to strike the nucleus of a neighbouring atom this may also disintegrate, with a further evolution of energy and the production of more neutrons. This
splitting up of the nucleus is called fission. The graphite of which the core is composed is called a moderator, and its function is to slow down the speed of the neutrons, as it is found that fission of U-235 is more likely to occur with slow neutrons than with fast ones. In a small piece of uranium mixed with moderator most of the neutrons escape through the surface. If, however, the amount of material is increased the chances that a neutron will collide with an atomic nucleus will also increase, since there are more atoms present. Each nuclear fission which occurs produces two or three fresh neutrons which are, in turn, capable of promoting the fission of further nuclei. When the lump of uranium and moderator is above a certain critical size the fission process proceeds cumulatively in what is called a chain reaction. This is where the boron steel rods play their part. Before the uranium rods are loaded into the graphite core the boron rods are already in position, and these have the property of being able to absorb neutrons which are shot out from the
uranium, and so prevent the chain reaction from starting. When sufficient uranium rods have been added to effect critical conditions the pressure vessel is sealed and the boron rods raised out of the core. The uranium rods are now freely bombarded by one another's neutrons and the chain reaction begins. The rate at which fission occurs can be controlled by raising or lowering the boron rods. If these are fully inserted into the graphite core the reaction shuts down completely, and only the normal spontaneous nuclear fission takes place. The heat energy released by the fission process is carried away in a stream of high-pressure carbon dioxide gas which is continuously pumped through the pressure vessel. This hot gas circulates through a special steam boiler, and the steam so raised is used to drive an electric turbo-generator in the usual way.
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Nucleic acid is a complex organic acid forming the basis of heredity.
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The nucleus is the positively charged central part of an atom.
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Nylon is a synthetic long-chain polymer plastic similar in chemical structure to protein.
Nylon was the first all-synthesized fibre, made from petroleum, natural gas, air, and water by the Du Pont firm in 1938. It is used in the manufacture of moulded articles, textiles, and medical sutures. Nylon fibres are stronger and more elastic than silk and are relatively insensitive to moisture and mildew. Nylon is used for hosiery and woven goods, simulating other materials such as silks and furs; it is also used for carpets.
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In audio engineering the Nyquist Sampling Theorem is a theorem that defines the process of sampling audio with a digital system. Amongst other things, it states that the sampling frequency of a digital audio system must be at least twice that of the highest audio frequency, otherwise aliasing will occur. The Nyquist theorem was developed at Bell Labs by C. Shannon and H. Nyquist.
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