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In physics, a Z particle is an elementary particle, one of the weakons responsible for carrying the weak nuclear force.
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The Z80 is an 8 bit microprocessor chip by Zilog widely used during the 1970's and 1980's - and still in widely used in 2004 - in early personal computers, and which formed the successor to the 8080 microprocessor with some Intel designers leaving Intel and designing the Z80. The Z80 retains all the 8080 instructions and added new instructions. In 2000 Zilog released the eZ80, an updated version of the Z80 microprocessor for modern embedded applications, which operates four times faster at the same clock speed as traditional Z80 microprocessors and can access 16mb of address space, as opposed to the 64 kb accessible by the original
Z80. It should be noted that the original Z80 microprocessor is still in production and use more than twenty years after its inception.
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Zaffre is a crude oxide of cobalt obtained by heating cobalt ore in a current of air. It was used to prepare smalt and to stain glass blue during Victorian times.
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The Zeeman effect is the splitting of the lines in a spectrum when the source of the spectrum is exposed to a magnetic field. It was discovered in 1896 by P. Zeeman. In the normal Zeeman effect a single line is split into three if the field is perpendicular to the light path or two lines if the field is parallel to the light path. This effect can be explained by classical electromagnetic principles in terms of the speeding up and slowing down of orbital electrons in the source as a result of the applied field. The anomalous Zeeman effect is a complicated splitting of the lines into several closely spaced lines, so called because it does not agree with classical predictions. This effect is explained by quantum mechanics in terms of electron spin.
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The zener diode is a type of semiconductor diode, consisting of a p-n junction with high doping concentrations on either side of the junction. It acts as a rectifier until the applied reverse voltage reaches a certain value, known as the Zener breakdown voltage, when the device becomes conducting. This effect occurs as a result of electrons being excited directly from the valence band into the conduction band. Zener diodes are used in voltage-limiting circuits and are named after C. M. Zener.
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Zeus for Windows V3.40 is a programmer's editor for the Windows operating system. It features support for version control using the Microsoft Common Source Code Control (SCC API) interface. This allows seamless integration with third party version control software like Microsoft Source Safe, CS-RCS, Perforce P4 and PVCS.
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The Ziegler process is an industrial process for manufacturing high-density polyethylene using catalysts of titanium(IV) chloride (TiCl4) and aluminium alkyls (e.g. triethylaluminium, Al(C2H5)3). The process was introduced in 1953 by the German chemist Karl Ziegler. It allowed the manufacture of polyethylene at lower temperatures (about 60 degrees C) and pressures (about 1atm) than used in the original process. Moreover, the polyethylene produced had more straight-chain molecules, giving the product more rigidity and a higher melting point than the earlier low-density polyethylene. The reaction involves the formation of a titanium alkyl in which the titanium can coordinate directly to the pi bond in ethene. In 1954 the process was developed further by the Italian chemist Giulio Natta, who extended the use of Ziegler' s catalysts (and similar catalysts) to other alkenes. In particular he showed how to produce stereospecific polymers of propene.
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The Ziesel reaction is a method of determining the number of methoxy (-OCH3) groups in an organic compound. The compound is heated with excess hydriodic acid, forming an alcohol and iodomethane. The iodomethane is distilled off and led into an alcoholic solution of silver nitrate, where it precipitates silver iodide. This is filtered and weighed, and the number of iodine atoms and hence methoxy groups can be calculated. The method was developed by S. Ziesel in 1886.
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Zinc is a metal element with the symbol Zn.
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Zinc chloride (formerly known as butter of zinc) is a white crystalline compound with the formula ZnCl2. The anhydrous salt, which is deliquescent, can be made by the action of hydrogen chloride gas on hot zinc. It has a relatively low melting point and sublimes easily, indicating that it is a molecular compound rather than ionic. Various hydrates also exist. Zinc chloride is used as a catalyst, dehydrating agent, a wood preservative for discouraging fungoid growths and as a flux for hard solder.
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Zinc oxide is a powder, white when cold and yellow when hot with the formula ZnO. It occurs naturally as a reddish orange ore - zincite, and can also be made by oxidizing hot zinc in air. It is amphoteric, forming zincates with bases. It is used as a brilliant permanent white pigment (Chinese white) and a mild antiseptic in zinc ointments. It was formerly known as philosopher's wool.
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Zinc sulphate is a white crystalline water-soluble compound made by heating zinc sulphide ore in air and dissolving out and recrystallizing the sulphate. The compound, which was formerly called white vitriol, is used as a mordant and as a styptic.
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Zinc sulphide is a yellow-white water-soluble solid with the formula ZnS. It occurs naturally as sphalerite (zinc blende) and wurtzite. It is used as a pigment and phosphor.
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Zipf's law is various principles that the frequency of occurrence of a word or other item is a function of that word or item's popularity, or rank, with an exponent close to unity (one) - that is if a graph is drawn of frequency against rank, the graph will be a straight line travelling through 45 degrees. The first example of Zipf's Law is that in the English language the most commonly used words are short in length, and the longer a word generally the less common its usage. Zipf's law is used for computer data compression systems.
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Zircon was a codename for a British spy satellite originally intended to be launched 1988. The revelation of the existence of the Zircon project (which had been concealed by the government) by the journalist Duncan Campbell, and the government's subsequent efforts to suppress a programme about it on BBC television, caused much controversy in 1987, not least for the bumbling way the security forces raided Campbell's office but failed to find his notes about the project which were concealed in computer files with anonymous names. Its intended function was to intercept radio and other signals from the USSR, Europe, and the Middle East and transmit them to the Government Communications Headquarters (GCHQ) in Cheltenham, England.
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Zirconium is a lustrous, greyish-white, strong, ductile, metallic element, with the symbol Zr. It occurs in nature as the mineral zircon (zirconium silicate), from which it is obtained commercially. It is used in some ceramics, alloys for wire and filaments, steel manufacture, and nuclear reactors, where its low neutron absorption is advantageous.
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Zodiacal light is cone-shaped light sometimes seen extending from the Sun along the ecliptic, and visible after sunset or before sunrise. It is due to thinly spread dust particles in the central plane of the Solar System. It is very faint, and requires a dark, clear sky to be seen.
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The zoetrope is an optical toy comprising a series of pictures on the inner surface of a cylinder. When the pictures are rotated and viewed through a slit, it gives the impression of continuous motion.
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Zoidogamy is a type of plant reproduction in which male gametes (antherozoids) swim in a film of water to the female gametes. Zoidogamy is found in algae, bryophytes, pteridophytes, and some gymnosperms (others use siphonogamy).
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Zone refining is a technique used to reduce the level of impurities in certain metals, alloys, semiconductors, and other materials. It is based on the observation that the solubility of an impurity may be different in the liquid and solid phases of a material. To take advantage of this observation, a narrow molten zone is moved along the length of a specimen of the material, with the result that the impurities are segregated at one end of the bar and the pure material at the other. In general, if the impurities lower the melting point of the material they are moved in the same direction as the molten zone moves, and vice versa.
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The zone system is a photographic system of exposure estimation invented by Ansel Adams that groups infinite tonal gradations into ten zones, zone 0 being black and zone 10 white. An f-stop change in exposure is required from zone to zone.
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Zwitterion is an ion that has both a positive and a negative charge, such as an amino acid in neutral solution.
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The ZX80 was a revolutionary computer invented by Clive Sinclair and released in 1980. It was based upon the Z80 microprocessor, and used few other chips. It had a built in BASIC interpreter and introduced computing for the first time to the masses by being affordable by any household. Video display was produced by a domestic television set which was connected by an aerial fly-lead to the computer. A year later the ZX80 was replaced by the improved ZX81 which in turn was replaced in 1982 by the far superior ZX Spectrum.
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The ZX81 was a revolutionary computer invented by Clive Sinclair and released in 1981. It was based upon the Z80 microprocessor, and used only three other chips in the basic model which had just 1K of RAM (enough to hold a functional player v computer chess game). It had a built in BASIC interpreter and introduced mass computing for the first time to the masses by being affordable by any household. Video display was produced by a domestic television set which was connected by an aerial fly-lead to the computer. Peripherals could be fitter to an exposed slot of the PCB, the most popular being a 16K RAM extension (RAM pack). Most remarkable was the award winning manual which accompanied the ZX81 which taught computing basics and the BASIC programming language in a clear and popular language for the first time. It replaced the ZX80 and was replaced itself in 1982 by the far superior ZX Spectrum.
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Zymase is an enzyme formed in yeast cells which converts sugar into alcohol and carbonic acid gas.
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A zymosocope is an apparatus used for determining the fermenting power of yeast by measuring the amount of carbonic acid produced from a given quantity of sugar.
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