# General Information (X-Z)

X-band
The X-band is the frequency band from 5200 to 10,900 mhz employed in radar.

Xanthine
Xanthine is a nitrogenous compound closely allied to uric acid, that occurs in extract of meat and in tea. It forms a colourless powder slightly soluble in water, and yields alloxan and urea on oxidation.

Xebec
A xebec is a small, sharp-built three-masted vessel with lateen sails. They were used for coasting voyages in the Mediterranean and on the ocean coasts of Spain and Portugal. It differs from the felucca in possessing both square and lateen sails, the felucca having only lateen sails. The xebec was formerly much used by Algerian pirates.

Xenon
Xenon is a rare, inert gaseous element. It's symbol is Xe.

Xerography
Xerography is an electrostatic dry-printing process for the reproduction of images or documents, widely employed in commerce and industry in copying machines, such as photo-copiers. The process was invented by the American printer Chester F Carlson in 1937 and first commercially developed in 1950. It makes use of the principle of photoconductivity, that is, that certain substances resist passage of an electric current except when struck by light. Silicon, germanium, and selenium are poor conductors of electricity, but when light energy is absorbed by some of their electrons, the electrons are able to pass from one atom to another, thus allowing a current to flow when a voltage is applied. When the light is removed, their conductivity again becomes low. Xerography employs a photoconductive insulating layer, such as selenium, on an aluminum or other conductive metal support. The layer is charged electrostatically, either with positive or negative ions ( see Ion ), the polarity of the charge depending on the type of photoconductive insulating layer selected. When the plate is exposed, in a camera or photographic machine, those areas of the coating subjected to light lose a varying portion of the charge, depending upon the intensity of the illumination. Thus, the variation of the amount of charge retained on the coated metal plate is established as an electrical or electrostatic pattern of the image. The image is rendered visible by sprinkling over the exposed plate a special, charged powder, which carries an opposite charge to the initial charge applied to the plate and insulating layer. The powder adheres to those areas that have retained their charge. The print is obtained by covering the plate with paper, then applying a charge over the back of the paper of the same polarity as the initial charge applied to the photoconductive insulating layer. In this way the opposite charged powders are transferred to the paper surface. The powder image is then fused onto the
er by exposure to solvent vapors or heat to make the image permanent. The entire xerographic process can be carried out, in high-speed mechanized equipment, in less than 5 seconds, and it is comparatively inex pensive to make these images because the photoconductive insulating layer can be recycled many thousand times. The process has found its primary usefulness in copying office documents and in low-volume duplication of data. The xerographic method also permits the making, quickly and cheaply, of paper offset masterplates for low-to-medium-volume runs on office offset-printing presses. The method has also been applied to the production of X-ray images in a technique that is known as xeroradiography and is used in mammography for the early detection of breast cancer.

Xerox FormBase
Xerox FormBase is a computer forms management program. It combines forms management with database techniques, which can be accessed from within the Microsoft Windows environment. FormBase creates professional quality forms while providing facilities to enter, sort, search, retrieve, and print data. Unlike typical forms management packages which allow usars to create a single form per file, FormBase lets you create multiple forms, or views, per database file. Each form created is considered a different view of the database. FormBase lets you create subforms and subtables within a form which facilitate entering multiple entries into a field. For example, in a database containing customer information you may want to create a data-entry form containing all the invoices for each customer. Because the information varies for each customer, this form may need to store dozens of entries. FormBase contains features usually found in database packages. The product can perform a lookup from one file to another. Information entered into one database can be retrieved in another form. Mathematical computations can be built into a form which are similar to formulae found in spreadsheet programs. Formulae can also be created to validate information entered into forms to provide accuracy and consistency during data entry. FormBase allows you to import graphic images from other software programs into a database and to create forms with logos and pictures. FormBase can print out columnar reports and supports laser, dot-matrix, and colour printers.

Xylazine
see "Ketamine"

Xylophone
The xylophone is a percussion musical instrument.

Yacht
A yacht is a light sailing vessel built for racing.

Yagi Aerial
A Yagi aerial is a particular form of directive, end-fire aerial array in which the director and reflector elements are parasitically excited. Most television aerials are of this type.

Yale University
Yale University is a famous and respected American university. It was chartered as the Collegiate School of Connecticut in 1701. The college was first established at Saybrook, but was removed to New Haven in 1717, and the name of Yale College was adopted in honour of Elihu Yale who had made large gifts to the school. A new charter was obtained in 1745, and in 1887 the title of Yale University was authorised by the legislature.

Yapp
Yapp is a type of bookbinding of limp leather with overlapping edges. It was first made for Yapp, a London bookseller in 1860, hence the name.

Yard
The yard is a unit of the imperial scale of measurement of length equivalent to three feet, 36 inches or 0.9144 metres. The yard was a British measurement of butter equal to 1 lb.

Yardley
Yardley was an English soap and cosmetic firm. It was established in 1770 and went into receivership in 1998.

Yards
see "Yard"

Yarn
Yarn is a fibre, such as cotton, wool, silk or flax which has been spun and prepared for use in weaving or knitting.

Yawl
A yawl is a two-masted sailing ship. The aftermast is much smaller than the mainmast and is placed far aft.

Yearling
A yearling is a one-year old animal. The term is generally applied to sheep, calves and foals.

Yeoman of the Guard
Yeomen of the Guard is a play by Gilbert and Sullivan written in 1888.

Yerukala
Yerukala is a dialect of Tamil.

Yiddish
Yiddish is a kind of jargon Hebrew spoken by lower class Jews.

Yolk
Yolk is a food store found in eggs.

Yom Kippur
Yom Kippur (Day of Atonement) is the most solemn day in the Jewish calendar, occurring always on Tishri 10th, corresponding with the end of September. It is a full fast day of 24 hours, observed from sunset to star-rise of the following day, in which neither food nor drink is taken, in accordance with Biblical command. It was observed in ancient times by an elaborate sacrificial ritual, in which the High Priest, representing the whole of Israel, interceded for Divine Pardon.

Youthful Offenders Act
The Youthful Offenders Act was an act of Parliament passed in 1901 making a parent liable for the misdeeds of his child.

Ytterbium
Ytterbium is a bivalent or trivalent metallic element of the rare-earth elements that resembles yttrium and occurs with it and related elements in several minerals such as gadolinite. It has the symbol Yb.

Ytterium
Ytterium is a trivalent metallic element usually included among the rare earth elements which it resembles chemically and with which it occurs in minerals. It has the symbol Y.

Yttrium
Yttrium is a metal element with the symbol Y.

Yurt
The yurt is the dwelling place of Yakutsks, it is a wooden house with sloping turf-clad walls.

Zaffre
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.

Zetran
Zetran is a tradename for Chlordiazepoxide hydrochloride.

Zheng Fen
Zheng Fen ("competing for points") is an interesting hybrid card game between a climbing game and a point-trick game. The mechanics are like those of Zheng Shangyou or Big Two but the primary aim is to win points rather than necessarily to get rid of cards as quickly as possible. The point values of cards are the same as in the popular Chinese point-trick game Da Bai Fen (Hundred). From three to six people can play and a 54 card pack is used, consisting of the standard 52 cards plus two distinguishable jokers, big and small. Generally the red or colourful joker is agreed to be the big one. The object is to win valuable cards in tricks. The fives are worth 5 points each, and the tens and kings are worth 10 points each. All the other cards are worthless. There are therefore 100 points in total to be won on each hand. A target score for the game is agreed - generally 500 or (for a longer game) 1000. The winner is the first player whose score reaches or exceeds the target.

Zheng Shangyou
Zheng Shangyou is a Chinese card game whose name can be roughly translated as Struggling Upstream. The game exists in several variations, and has various alternative names. According to Zhang Shutai, the most interesting version is the partnership game for six players, also known as San jia xi (family of three) or Huojian (rocket). This is a skilful and light-hearted card game for four or more players, probably best with 5 or 6. Zheng Shangyou was brought to the UK by John McLeod, who learned it during a visit to China by some British Go players in 1979 from an interpreter Zhang Chuansheng. In Britain it was given the name Pits, which is easier to pronounce, and refers to the predicament of the losing players, who find themselves in a pit which is hard to escape from. A couple to whom Jonathan Norris taught it reported that they call it "Unto him...". It is closely related to several other games - the Japanese Dai Hin Min (or Dai Fugo), Vietnamese Tieng Len, Chinese Big Two and the Western derivative usually called Asshole or President. In fact you could argue that these are really all versions of the same game. Zheng Shangyou uses a 54-card pack consisting of the standard 52 cards with the addition of two distinguishable jokers, referred to as Red and Black. The object of each hand is to be the first to play out all one's cards and thereby gain 2 points, or second and gain 1, towards a rubber-winning total of (usually) 11.

Zinc
Zinc is a metal element with the symbol Zn.

Zirconium
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.

Zither
The zither is an Austrian musical instrument.

Zodiac
The zodiac is the name given by the Greeks to the heavens.

Zoology
Zoology is the science which deals with the structure, life-history, habits and activities of animals.

Zwitterion
Zwitterion is an ion that has both a positive and a negative charge, such as an amino acid in neutral solution.

ZX80
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.

ZX81
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.

Zyklon-B
Zyklon-B was a poison gas used in Nazi extermination camps. It was a cyanide compound originally developed for fumigation purposes in the 1920s. It was actually a crystalline compound which gave off hydrogen cyanide gas when exposed to the air. It was first used against humans in a euthanasia programme in 1939, aimed at ridding Germany of lunatics, incurable invalids, and other 'undesirables'. The victims were induced to enter a 'shower bath', Zyklon-B was released, and the gas killed them in a few minutes. When the extermination camps were set up, this method was adopted as standard and was responsible for several million deaths. The inventor, Dr Bruno Tesch, was convicted of war crimes and executed for his manufacture and supply of the substance to the camps.

Zymase
Zymase is an enzyme formed in yeast cells which converts sugar into alcohol and carbonic acid gas.

Copyright 1997,1998 Servile Software Enquiries to Matthew Probert

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