economical fractions

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• petroleum refining — Introduction  conversion of crude oil into useful products. History Distillation of kerosene and naphtha       The refining of crude petroleum owes its origin to the successful drilling of the first oil well in Titusville, Pa., in 1859. Prior to… …   Universalium

• technology, history of — Introduction       the development over time of systematic techniques for making and doing things. The term technology, a combination of the Greek technē, “art, craft,” with logos, “word, speech,” meant in Greece a discourse on the arts, both… …   Universalium

• rare-earth element — /rair errth /, Chem. any of a group of closely related metallic elements, comprising the lanthanides, scandium, and yttrium, that are chemically similar by virtue of having the same number of valence electrons. Also called rare earth metal. [1955 …   Universalium

• Argentine Constitution of 1853 — The Argentine Constitution of 1853 was the first constitution of Argentina, approved with the support of the governments of the provinces mdash;though without that of the Buenos Aires Province, who remained separated of the Argentine… …   Wikipedia

• Constitution of Argentina of 1853 — Argentine Constitution of 1853 Cover of the original manuscript of the 1853 Constitution Ratified …   Wikipedia

• Field (mathematics) — This article is about fields in algebra. For fields in geometry, see Vector field. For other uses, see Field (disambiguation). In abstract algebra, a field is a commutative ring whose nonzero elements form a group under multiplication. As such it …   Wikipedia

• Start-stop system — This article refers to the automotive technology. For the use of start stop systems in telecommunication, see asynchronous serial communication. In automobiles, a start stop system or stop start system automatically shuts down and restarts the… …   Wikipedia

• History of German settlement in Eastern Europe — The presence of German speaking populations in Central and Eastern Europe is rooted in centuries of history, that of the independent German states (particularly Prussia), and later German Empire but also Austria Hungary, Poland, and other multi… …   Wikipedia

• printing — /prin ting/, n. 1. the art, process, or business of producing books, newspapers, etc., by impression from movable types, plates, etc. 2. the act of a person or thing that prints. 3. words, symbols, etc., in printed form. 4. printed material. 5.… …   Universalium

• monopoly and competition — ▪ economics Introduction       basic factors in the structure of economic markets.In economics monopoly and competition signify certain complex relations among firms in an industry. A monopoly implies an exclusive possession of a market by a… …   Universalium

• petroleum production — Introduction       recovery of crude oil and, often, associated natural gas from the Earth.        petroleum is a naturally occurring hydrocarbon material that is believed to have formed in deep sedimentary (sedimentary rock) beds from animal and …   Universalium