title: Ancient Roman architecture

text: The most frequent dam types were earth- or rock-filled embankment dams and masonry gravity dams. These served a wide array of purposes, such as irrigation, flood control, river diversion, soil-retention, or a combination of these functions. The impermeability of Roman dams was increased by the introduction of waterproof hydraulic mortar and especially "opus caementicium" in the Concrete Revolution. These materials also allowed for bigger structures to be built, like the Lake Homs Dam, possibly the largest water barrier today, and the sturdy Harbaqa Dam, both of which consist of a concrete core.


title: Ancient Roman architecture

text: Roman builders were the first to realize the stabilizing effect of arches and buttresses, which they integrated into their dam designs. Previously unknown dam types introduced by the Romans include arch-gravity dams, arch dams,; buttress dams, and multiple-arch buttress dams.


title: Ancient Roman architecture

text: The Romans generally fortified cities rather than fortresses, but there are some fortified camps such as the Saxon Shore forts like Porchester Castle in England. City walls were already significant in Etruscan architecture, and in the struggle for control of Italy under the early Republic many more were built, using different techniques. These included tightly fitting massive irregular polygonal blocks, shaped to fit exactly in a way reminiscent of later Inca work. The Romans called a simple rampart wall an agger; at this date great height was not necessary. The Servian Wall around Rome was an ambitious project of the early 4th century BC. The wall was up to 10 metres (32.8 ft) in height in places, 3.6 metres (12 ft) wide at its base, 11 km (7 mi) long, and is believed to have had 16 main gates, though many of these are mentioned only from writings, with no other known remains. Some of it had a "fossa" or ditch in front, and an agger behind, and it was enough to deter Hannibal. Later the Aurelian Wall replaced it, enclosing an expanded city, and using more sophisticated designs, with small forts at intervals.


title: Ancient Roman architecture

text: The Romans walled major cities and towns in areas they saw as vulnerable, and parts of many walls remain incorporated in later defensive fortifications, as at Córdoba (2nd century BC), Chester (earth and wood in the 70s AD, stone from c. 100), and York (from 70s AD). Strategic walls across open country were far rarer, and Hadrian's Wall (from 122) and the Antonine Wall (from 142, abandoned only 8 years after completion) are the most significant examples, both on the Pictish frontier of Roman Britain.


title: Ancient Roman architecture

text: On his return from campaigns in Greece, the general Sulla brought back what is probably the best-known element of the early imperial period: the mosaic, a decoration made of colourful chips of stone inserted into cement. This tiling method took the empire by storm in the late first century and the second century and in the Roman home joined the well-known mural in decorating floors, walls, and grottoes with geometric and pictorial designs.


title: Ancient Roman architecture

text: There were two main techniques in Greco-Roman mosaic. "Opus vermiculatum" used tiny "tesserae", typically cubes of 4 millimeters or less, and was produced in workshops in relatively small panels, which were transported to the site glued to some temporary support. The tiny "tesserae" allowed very fine detail and an approach to the illusionism of painting. Often small panels called "emblemata" were inserted into walls or as the highlights of larger floor-mosaics in coarser work. The normal technique, however, was "opus tessellatum", using larger tesserae, which were laid on site. There was a distinct native Italian style using black on a white background, which was no doubt cheaper than fully coloured work.


title: Ancient Roman architecture

text: A specific genre of Roman mosaic obtained the name "asaroton" (Greek "unswept floor"). It represented an optical illusion of the leftovers from a feast on the floor of rich houses.


title: Ancient Roman architecture

text: A hypocaust was an ancient Roman system of underfloor heating, used to heat houses with hot air. The Roman architect Vitruvius, writing about the end of the 1st century BC, attributes their invention to Sergius Orata. Many remains of Roman hypocausts have survived throughout Europe, western Asia, and northern Africa. The hypocaust was an invention which improved the hygiene and living conditions of citizens, and was a forerunner of modern central heating.


title: Ancient Roman architecture

text: Hypocausts were used for heating hot baths ("thermae"), houses and other buildings, whether public or private. The floor was raised above the ground by pillars, called pilae stacks, with a layer of tiles, then a layer of concrete, then another of tiles on top; and spaces were left inside the walls so that hot air and smoke from the furnace would pass through these enclosed areas and out of flues in the roof, thereby heating but not polluting the interior of the room.


title: Ancient Roman architecture

text: In Magna Graecia truss roofs presumably appeared as early as 550 BC. Their potential was fully realized in the Roman period, which saw trussed roofs over 30 wide spanning the rectangular spaces of monumental public buildings such as temples, basilicas, and later churches. Such spans were three times as wide as the widest prop-and-lintel roofs and only surpassed by the largest Roman domes.


title: Ancient Roman architecture

text: The largest truss roof by span of ancient Rome covered the Aula Regia (throne room) built for emperor Domitian (81–96 AD) on the Palatine Hill, Rome. The timber truss roof had a width of 31.67 m, slightly surpassing the postulated limit of 30 m for Roman roof constructions. Tie-beam trusses allowed for much larger spans than the older prop-and-lintel system and even concrete vaulting. Nine out of the ten largest rectangular spaces in Roman architecture were bridged this way, the only exception being the groin vaulted Basilica of Maxentius.


title: Ancient Roman architecture

text: The spiral stair is a type of stairway which, due to its complex helical structure, was introduced relatively late into architecture. Although the oldest example dates back to the 5th century BC, it was only in the wake of the influential design of Trajan's Column that this space-saving new type permanently caught hold in Roman architecture.


title: Ancient Roman architecture

text: Apart from the triumphal columns in the imperial cities of Rome and Constantinople, other types of buildings such as temples, thermae, basilicas and tombs were also fitted with spiral stairways. Their notable absence in the towers of the Aurelian Wall indicates that although used in medieval castles, they did not yet figure prominently in Roman military engineering. By late antiquity, separate stair towers were constructed adjacent to the main buildings, as in the Basilica of San Vitale.


title: Gomer Pyle

text: Gomer Pyle is a fictional character played by Jim Nabors and introduced in the middle of the third season of "The Andy Griffith Show".


title: Gomer Pyle

text: A naïve and gentle auto mechanic, he became a character in the January 1963 episode, "Man in a Hurry". Nabors played Pyle for 23 episodes, from 1962 to 1964.


title: Gomer Pyle

text: After two seasons on "The Andy Griffith Show", the character was spun off to "Gomer Pyle, U.S.M.C." in 1964 which ran until 1970.


title: Gomer Pyle

text: Gomer is a naïve, extremely moral auto mechanic turned United States Marine Corps PFC, from Mayberry, North Carolina. The only apparent employee at Wally's Filling Station, he initially lived there in a back room; and, according to Andy, was "saving up for college" and wanted to be a doctor. Wide-eyed and slack jawed, he usually wore a service station uniform and a baseball cap with an upturned bill; a handkerchief dangled from his back pocket. He initially displayed scant knowledge of automotive mechanics: in "The Great Filling Station Robbery", for example, he thought a carburetor was a hood ornament. In the same episode, he admitted all he knew how to do was fill cars with gas, oil, water and air. However, he learned over time; in other episodes, he was able to diagnose mechanical problems for the average layperson. In his first appearance, the episode "The Bank Job", Gomer is shown operating a blow torch to cut through a bank's vault. In another episode, Gomer diagnoses a problem with a car belonging to an out of town visitor who is delayed by a mechanical breakdown. In "Barney's First Car", Andy calls Gomer to tow Barney's disabled car, implying that Gomer knows how to operate Wally's tow truck. In "Gomer The House Guest", Wally fires Gomer causing Gomer to move in with Andy. Wally's former customers then bring their cars to Andy's house so Gomer can diagnose mechanical problems and repair them. Realizing the success of his business depends on Gomer, Wally re-hires him.


title: Gomer Pyle

text: Like his cousin Goober, Gomer provided comic relief, awestruck by the simplest of things, resulting in the exclamation of his catchphrases, "Shazam!", "Golly", "Sur-prise, sur-prise, sur-prise!", and "shame, shame, shame!", as appropriate.


title: Gomer Pyle

text: Gomer was sometimes deputized by Deputy Barney Fife, when Sheriff Taylor was otherwise occupied. Though always compliant, Gomer's ineptitude usually made him more of a hindrance than a help in the line of duty. However, in the eyes of his friends, especially Sheriff Andy Taylor, his shortcomings were generally outweighed by his gentle, generous spirit.


title: Gomer Pyle

text: In the last episode of the fourth season, Gomer tells Andy he has joined the Marines, because he realized he would eventually be drafted into military service.


title: Gomer Pyle

text: Gomer's Mayberry roots were evident in the spin-off series "Gomer Pyle, U.S.M.C.", where his countrified, backward nature served as the mainstay for the show's humor, making him a comic foil to the hard-nosed drill instructor (later platoon sergeant) Gunnery Sergeant Vince Carter, played by Frank Sutton. Both series also included several episodes displaying Gomer's skill as a baritone singer. In one episode, Gomer stated that his birthday was on Feb 26.


title: Gomer Pyle

text: At first Sergeant Carter was rankled and "extremely" irritated by the slow-witted Pyle, and dreamed of ways to rid himself of the private's presence. Over the course of the series, however, Carter began to tolerate Pyle, and even grew to respect him. Pyle, though always unconventional, developed into a good Marine, yet never went an episode without causing some degree of irritation for Carter. In the final episode, Gomer requests a transfer after realizing he is nothing but a source of constant anxiety for Carter. Carter, initially pleased with the request, later arranges for the transfer to be denied; and the episode ends with Carter insisting the two shake hands, not knowing Gomer's hand is covered in shellac.


title: Gomer Pyle

text: As a Marine, Gomer's romantic interest is Lou Ann Poovie, a fellow North Carolinian who came to California for a singing career, although she proves to be tone deaf. Like Gomer, Lou Ann is innocent and naive, and is a willing participant in many of Gomer's misadventures.


title: Gomer Pyle

text: Both "The Andy Griffith Show" and "Gomer Pyle, U.S.M.C." ended their runs by the late 1960s. While Mayberry R.F.D. continued from 1968 to 1971, where "The Andy Griffith Show" left off, the concept of returning Gomer to Mayberry was nixed, as the actor was given a CBS variety show of his own (which lasted two seasons). Gomer eventually returned, along with most of the original cast of "The Andy Griffith Show", to the 1986 television movie "Return to Mayberry". Gomer and Goober Pyle run a gas station/car repair shop called "G & G Garage", implying that Gomer's Marine career had, at some point, ended.


title: Gomer Pyle

text: On an episode of "The Lucy Show", "Lucy Gets Caught Up in the Draft", Nabors has a cameo role as "Gomer Pyle".


title: Gomer Pyle

text: When both "The Carol Burnett Show" and "Gomer Pyle, U.S.M.C." were running on CBS first-run, there would be an annual crossover between the series – with a character played by Burnett appearing on "Gomer Pyle, U.S.M.C.", and Nabors appearing on Burnett's variety show on the first episode of every season.


title: Gomer Pyle

text: The following is a list of "The Andy Griffith Show" episodes featuring Gomer before his spinoff series:


title: History of radio

text: The early history of radio is the history of technology that produces and uses radio instruments that use radio waves. Within the timeline of radio, many people contributed theory and inventions in what became radio. Radio development began as "wireless telegraphy". Later radio history increasingly involves matters of broadcasting.


title: History of radio

text: In an 1864 presentation, published in 1865, James Clerk Maxwell proposed theories of electromagnetism, with mathematical proofs, that showed that light and predicted that radio and x-rays were all types of electromagnetic waves propagating through free space.


title: History of radio

text: Between 1886 and 1888 Heinrich Rudolf Hertz published the results of experiments wherein he was able to transmit electromagnetic waves (radio waves) through the air, proving Maxwell's electromagnetic theory. Thus, given Hertz comprehensive discoveries, radio waves were referred to as "Hertzian waves".


title: History of radio

text: After the discovery of what came to be called "Hertzian waves" (it would take almost 20 years for the term "radio" to be universally adopted for this type of electromagnetic radiation) many scientists and inventors experimented with transmitting and detecting them. Maxwell's theory showing that light and Hertzian electromagnetic waves were the same phenomenon at different wavelengths led "Maxwellian" scientists such as John Perry, Frederick Thomas Trouton and Alexander Trotter to assume they would be analogous to optical light.


title: History of radio

text: Following Hertz' untimely death in 1894, Professors Oliver Lodge presented a widely covered lecture on Hertzian (radio) waves at the Royal Institution on June 1 of the same year. Lodge focused on the optical qualities of the waves and demonstrated how to transmit, reflect, and detect them (using an improved variation of French physicist Édouard Branly's detector Lodge named the "coherer"). During part of the demonstration radio waves were sent from the neighboring Clarendon Laboratory building, and received by apparatus in the lecture theater.


title: History of radio

text: Building on the work of Lodge, the Bengali Indian physicist Jagadish Chandra Bose further explored the optical nature these waves. He conducted his experiments using very short wavelengths (closer to visible light in the microwave range) which allowed him to explore the relationship between radio waves and light while using much smaller antennas, reflectors, and prisms as test equipment. He published the paper "On polarisation of electric rays by double-refracting crystals" in May 1895 followed by a second paper sent to the Royal Society of London in October 1895. Bose would latter write an essay, "Adrisya Alok" ("Invisible Light") on how during 1895 he conducted a public demonstration at the Town Hall of Kolkata, India using millimeter-range-wavelength microwaves to trigger detectors that ignited gunpowder and rang a bell at a distance.


title: History of radio

text: Between 1890 and 1892 physicists such as John Perry, Frederick Thomas Trouton and William Crookes proposed electromagnetic or Hertzian waves as a navigation aid or means of communication, with Crookes writing on the possibilities of wireless telegraphy based on Hertzian waves in 1892. Among physicist, what were perceived as technical limitations to using these new waves, such as delicate equipment, the need for large amounts of power to transmit over limited ranges, and its similarity to already existent optical light transmitting devices, lead them to a belief that applications were very limited. The Serbian American engineer Nikola Tesla considered Hertzian waves relatively useless for long range transmission since "light" could not transmit further than line of sight. There was speculation that this fog and stormy weather penetrating "invisible light" could be used in maritime applications such as lighthouses, including the London journal "The Electrician" (December 1895) commenting on Bose's achievements, saying "we may in time see the whole system of coast lighting throughout the navigable world revolutionized by an Indian Bengali scientist working single handed[ly] in our Presidency College Laboratory."


title: History of radio

text: In 1895, adapting the techniques presented in Lodge's published lectures, Russian physicist Alexander Stepanovich Popov built a lightning detector that used a coherer based radio receiver. He presented it to the Russian Physical and Chemical Society on May 7, 1895. A depiction of the lightning detector was printed in the "Journal of the Russian Physical and Chemical Society" the same year (publication of the minutes 15/201 of this session – December issue of the journal RPCS).


title: History of radio

text: In 1894, the young Italian inventor Guglielmo Marconi began working on the idea of building long-distance wireless transmission systems based on the use of Hertzian waves (radio waves), a line of inquiry that he noted other inventors did not seem to be pursuing. Marconi read through the literature and used the ideas of others who were experimenting with radio waves but did a great deal to develop devices such as portable transmitters and receiver systems that could work over long distances, turning what was essentially a laboratory experiment into a useful communication system. By August 1895, Marconi was field testing his system but even with improvements he was only able to transmit signals up to one-half mile, a distance Oliver Lodge had predicted in 1894 as the maximum transmission distance for radio waves. Marconi raised the height of his antenna and hit upon the idea of grounding his transmitter and receiver. With these improvements the system was capable of transmitting signals up to and over hills. Marconi's experimental apparatus proved to be the first engineering-complete, commercially successful radio transmission system. Marconi's apparatus is also credited with saving the 700 people who survived the tragic "Titanic" disaster.


title: History of radio

text: In 1896, Marconi was awarded British patent 12039, "Improvements in transmitting electrical impulses and signals and in apparatus there-for", the first patent ever issued for a Hertzian wave (radio wave) base wireless telegraphic system. In 1897, he established a radio station on the Isle of Wight, England. Marconi opened his "wireless" factory in the former silk-works at Hall Street, Chelmsford, England, in 1898, employing around 60 people. Shortly after the 1900s, Marconi held the patent rights for radio. Marconi would go on to win the Nobel Prize in Physics in 1909 and be more successful than any other inventor in his ability to "commercialize" radio and its associated equipment into a global business. In the US some of his subsequent patented refinements (but not his original radio patent) would be overturned in a 1935 court case (upheld by the US Supreme Court in 1943).


title: History of radio

text: In June 1912 Marconi opened the world's first purpose-built radio factory at New Street Works in Chelmsford, England.


title: History of radio

text: Through the end of the 19th century Canadian-American inventor Reginald Fessenden worked on the possibility of making audio radio transmissions, in contrast to the early spark-gap transmissions that could only transmit Morse code messages. To this end he worked on developing a high-speed alternator (referred to as "an alternating-current dynamo") that generated "pure sine waves" and produced "a continuous train of radiant waves of substantially uniform strength", or, in modern terminology, a continuous-wave (CW) transmitter. While working for the United States Weather Bureau on Cobb Island, Maryland, Fessenden began research on audio transmissions via radio. Because he did not yet have a continuous-wave transmitter, initially he worked with an experimental "high-frequency spark" transmitter, taking advantage of the fact that the higher the spark rate, the closer a spark-gap transmission comes to producing continuous waves. He later reported that, in the fall of 1900, he successfully transmitted speech over a distance of about 1.6 kilometers (one mile), which appears to have been the first successful audio transmission using radio signals. Although successful, the sound transmitted was far too distorted to be commercially practical. According to some sources, notably Fessenden's wife Helen's biography, on Christmas Eve 1906, Reginald Fessenden used an Alexanderson alternator and rotary spark-gap transmitter to make the first radio audio broadcast, from Brant Rock, Massachusetts. Ships at sea heard a broadcast that included Fessenden playing "O Holy Night" on the violin and reading a passage from the Bible. However, Fessenden himself never mentioned that date: rather, he wrote of experiments with voice as early as 1902. And some of his experiments with voice and music, which occurred in mid-to-late December 1906, were reported in the "American Telephone Journal".


title: History of radio

text: The Dutch company "Nederlandsche Radio-Industrie" and its owner engineer, Hanso Idzerda, made the first regular wireless broadcast for entertainment from its workshop in The Hague on 6 November 1919. The company manufactured both transmitters and receivers. Its popular program was broadcast four nights per week on AM 670 metres, until 1924 when the company ran into financial troubles.


title: History of radio

text: On 27 August 1920, regular wireless broadcasts for entertainment began in Argentina, pioneered by Enrique Telémaco Susini and his associates, and spark gap telegraphy stopped. On 31 August 1920 the first known radio news program was broadcast by station 8MK, the unlicensed predecessor of WWJ (AM) in Detroit, Michigan under ownership of the CBS network. The first college radio station began broadcasting on October 14, 1920, from Union College, Schenectady, New York under the personal call letters of Wendell King, an African-American student at the school.


title: History of radio

text: Also in October 1920, 2ADD (renamed WRUC in 1947), aired what is believed to be the first public entertainment broadcast in the United States, a series of Thursday night concerts initially heard within a radius and later for a radius. In November 1920, it aired the first broadcast of a sporting event. At 9 pm on August 27, 1920, Sociedad Radio Argentina aired a live performance of Richard Wagner's opera "Parsifal" from the Coliseo Theater in downtown Buenos Aires. Only about twenty homes in the city had receivers to tune in this radio program. In 1922 regular audio broadcasts for entertainment began in the UK from the Marconi Research Centre 2MT at Writtle near Chelmsford, England.


title: History of radio

text: In the early 1930s, single sideband and frequency modulation were invented by amateur radio operators.


title: History of radio

text: In early radio, and to a limited extent much later, the transmission signal of the radio station was specified in meters, referring to the wavelength, the length of the radio wave. This is the origin of the terms long wave, medium wave, and short wave radio. Portions of the radio spectrum reserved for specific purposes were often referred to by wavelength: the 40-meter band, used for amateur radio, for example. The relation between wavelength and frequency is reciprocal: the higher the frequency, the shorter the wave, and vice versa.


title: History of radio

text: As equipment progressed, precise frequency control became possible; early stations often did not have a precise frequency, as it was affected by the temperature of the equipment, among other factors. Identifying a radio signal by its frequency rather than its length proved much more practical and useful, and starting in the 1920s this became the usual method of identifying a signal, especially in the United States. Frequencies specified in number of cycles per second (kilocycles, megacycles) were replaced by the more specific designation of hertz (cycles per second) about 1965.


title: History of radio

text: Using various patents, the British Marconi company was established in 1897 by Guglielmo Marconi and began communication between coast radio stations and ships at sea. A year after, in 1898, they successfully introduced their first radio station in Chelmsford. This company, along with its subsidiaries Canadian Marconi and American Marconi, had a stranglehold on ship-to-shore communication. It operated much the way American Telephone and Telegraph operated until 1983, owning all of its equipment and refusing to communicate with non-Marconi equipped ships. Many inventions improved the quality of radio, and amateurs experimented with uses of radio, thus planting the first seeds of broadcasting.


title: History of radio

text: The company Telefunken was founded on May 27, 1903, as "Telefunken society for wireless telefon" of Siemens & Halske (S & H) and the Allgemeine Elektrizitäts-Gesellschaft ("General Electricity Company") as joint undertakings for radio engineering in Berlin. It continued as a joint venture of AEG and Siemens AG, until Siemens left in 1941. In 1911, Kaiser Wilhelm II sent Telefunken engineers to West Sayville, New York to erect three 600-foot (180-m) radio towers there. Nikola Tesla assisted in the construction. A similar station was erected in Nauen, creating the only wireless communication between North America and Europe.


title: History of radio

text: The invention of amplitude-modulated (AM) radio, so that more than one station can send signals (as opposed to spark-gap radio, where one transmitter covers the entire bandwidth of the spectrum) is attributed to Reginald Fessenden and Lee de Forest.


title: History of radio

text: The most common type of receiver before vacuum tubes was the crystal set, although some early radios used some type of amplification through electric current or battery. Inventions of the triode amplifier, motor-generator, and detector enabled audio radio. The use of amplitude modulation (AM), by which soundwaves can be transmitted over a continuous-wave radio signal of narrow bandwidth (as opposed to spark-gap radio, which sent rapid strings of damped-wave pulses that consumed much bandwidth and were only suitable for Morse-code telegraphy) was pioneered by Fessenden and Lee de Forest.


title: History of radio

text: The art and science of crystal sets is still pursued as a hobby in the form of simple un-amplified radios that 'runs on nothing, forever'. They are used as a teaching tool by groups such as the Boy Scouts of America to introduce youngsters to electronics and radio. As the only energy available is that gathered by the antenna system, loudness is necessarily limited.


title: History of radio

text: During the mid-1920s, amplifying vacuum tubes (or "thermionic valves" in the UK) revolutionized radio receivers and transmitters. John Ambrose Fleming developed a vacuum tube diode. Lee de Forest placed a screen, added a "grid" electrode, creating the triode.


title: History of radio

text: Early radios ran the entire power of the transmitter through a carbon microphone. In the 1920s, the Westinghouse company bought Lee de Forest's and Edwin Armstrong's patent. During the mid-1920s, Amplifying vacuum tubes (US)/thermionic valves (UK) revolutionized radio receivers and transmitters. Westinghouse engineers developed a more modern vacuum tube.


title: History of radio

text: Following development of transistor technology, bipolar junction transistors led to the development of the transistor radio. In 1954, the Regency company introduced a pocket transistor radio, the TR-1, powered by a "standard 22.5 V Battery." In 1955, the newly formed Sony company introduced its first transistorized radio, the TR-55. It was small enough to fit in a vest pocket, powered by a small battery. It was durable, because it had no vacuum tubes to burn out. In 1957, Sony introduced the TR-63, the first mass-produced transistor radio, leading to the mass-market penetration of transistor radios. Over the next 20 years, transistors replaced tubes almost completely except for high-power transmitters.


title: History of radio

text: By the mid-1960s, the Radio Corporation of America (RCA) were using metal–oxide–semiconductor field-effect transistors (MOSFETs) in their consumer products, including FM radio, television and amplifiers. Metal–oxide–semiconductor (MOS) large-scale integration (LSI) provided a practical and economic solution for radio technology, and was used in mobile radio systems by the early 1970s.


title: History of radio

text: Telegraphy did not go away on radio. Instead, the degree of automation increased. On land-lines in the 1930s, teletypewriters automated encoding, and were adapted to pulse-code dialing to automate routing, a service called telex. For thirty years, telex was the cheapest form of long-distance communication, because up to 25 telex channels could occupy the same bandwidth as one voice channel. For business and government, it was an advantage that telex directly produced written documents.


title: History of radio

text: Telex systems were adapted to short-wave radio by sending tones over single sideband. CCITT R.44 (the most advanced pure-telex standard) incorporated character-level error detection and retransmission as well as automated encoding and routing. For many years, telex-on-radio (TOR) was the only reliable way to reach some third-world countries. TOR remains reliable, though less-expensive forms of e-mail are displacing it. Many national telecom companies historically ran nearly pure telex networks for their governments, and they ran many of these links over short wave radio.


title: History of radio

text: Documents including maps and photographs went by radiofax, or wireless photoradiogram, invented in 1924 by Richard H. Ranger of Radio Corporation of America (RCA). This method prospered in the mid-20th century and faded late in the century.


title: History of radio

text: One of the first developments in the early 20th century was that aircraft used commercial AM radio stations for navigation, AM stations are still marked on U.S. aviation charts. Radio navigation played an important role during war time, especially in World War II. Before the discovery of the crystal oscillator, radio navigation had many limits. However, as radio technology expanding, navigation is easier to use, and it provides a better position. Although there are many advantages, the radio navigation systems often comes with complex equipment such as the radio compass receiver, compass indicator, or the radar plan position indicator. All of these require users to obtain certain knowledge.


title: History of radio

text: In the 1960s VOR systems became widespread. In the 1970s, LORAN became the premier radio navigation system. Soon, the US Navy experimented with satellite navigation. In 1987, the Global Positioning System (GPS) constellation of satellites was launched.


title: History of radio

text: In 1933, FM radio was patented by inventor Edwin H. Armstrong. FM uses frequency modulation of the radio wave to reduce static and interference from electrical equipment and the atmosphere. In 1937, W1XOJ, the first experimental FM radio station after Armstrong's W2XMN in Alpine, New Jersey, was granted a construction permit by the US Federal Communications Commission (FCC).


title: History of radio

text: After World War II, FM radio broadcasting was introduced in Germany. At a meeting in Copenhagen in 1948, a new wavelength plan was set up for Europe. Because of the recent war, Germany (which did not exist as a state and so was not invited) was only given a small number of medium-wave frequencies, which were not very good for broadcasting. For this reason Germany began broadcasting on UKW ("Ultrakurzwelle", i.e. ultra short wave, nowadays called VHF) which was not covered by the Copenhagen plan. After some amplitude modulation experience with VHF, it was realized that FM radio was a much better alternative for VHF radio than AM. Because of this history FM Radio is still referred to as "UKW Radio" in Germany. Other European nations followed a bit later, when the superior sound quality of FM and the ability to run many more local stations because of the more limited range of VHF broadcasts were realized.


title: History of radio

text: In the 1930s, regular analog television broadcasting began in some parts of Europe and North America. By the end of the decade there were roughly 25,000 all-electronic television receivers in existence worldwide, the majority of them in the UK. In the US, Armstrong's FM system was designated by the FCC to transmit and receive television sound.


title: History of radio

text: By 1963, color television was being broadcast commercially (though not all broadcasts or programs were in color), and the first (radio) communication satellite, "Telstar", was launched. In the 1970s,


title: History of radio

text: In 1947 AT&T commercialized the Mobile Telephone Service. From its start in St. Louis in 1946, AT&T then introduced Mobile Telephone Service to one hundred towns and highway corridors by 1948. Mobile Telephone Service was a rarity with only 5,000 customers placing about 30,000 calls each week. Because only three radio channels were available, only three customers in any given city could make mobile telephone calls at one time. Mobile Telephone Service was expensive, costing US$15 per month, plus $0.30–0.40 per local call, equivalent to (in 2012 US dollars) about $176 per month and $3.50–4.75 per call. The Advanced Mobile Phone System analog mobile phone system, developed by Bell Labs, was introduced in the Americas in 1978, gave much more capacity. It was the primary analog mobile phone system in North America (and other locales) through the 1980s and into the 2000s.


title: History of radio

text: In 1947, AT&T commercialized the Mobile Telephone Service. From its start in St. Louis in 1946, AT&T then introduced Mobile Telephone Service to one hundred towns and highway corridors by 1948. Mobile Telephone Service was a rarity with only 5,000 customers placing about each week. Because only three radio channels were available, only three customers in any given city could make mobile telephone calls at one time. Mobile Telephone Service was expensive, costing US$15 per month, plus $0.30–0.40 per local call, equivalent to (in 2012 US dollars) about $176 per month and $3.50–4.75 per call.


title: History of radio

text: The development of metal–oxide–semiconductor (MOS) large-scale integration (LSI) technology, information theory and cellular networking led to the development of affordable mobile communications. The Advanced Mobile Phone System analog mobile phone system, developed by Bell Labs and introduced in the Americas in 1978, gave much more capacity. It was the primary analog mobile phone system in North America (and other locales) through the 1980s and into the 2000s.


title: History of radio

text: The British government and the state-owned postal services found themselves under massive pressure from the wireless industry (including telegraphy) and early radio adopters to open up to the new medium. In an internal confidential report from February 25, 1924, the "Imperial Wireless Telegraphy Committee" stated:


title: History of radio

text: When radio was introduced in the early 1920s, many predicted it would kill the phonograph record industry. Radio was a free medium for the public to hear music for which they would normally pay. While some companies saw radio as a new avenue for promotion, others feared it would cut into profits from record sales and live performances. Many record companies would not license their records to be played over the radio, and had their major stars sign agreements that they would not perform on radio broadcasts.


title: History of radio

text: Indeed, the music recording industry had a severe drop in profits after the introduction of the radio. For a while, it appeared as though radio was a definite threat to the record industry. Radio ownership grew from two out of five homes in 1931 to four out of five homes in 1938. Meanwhile, record sales fell from $75 million in 1929 to $26 million in 1938 (with a low point of $5 million in 1933), though the economics of the situation were also affected by the Great Depression.


title: History of radio

text: The copyright owners were concerned that they would see no gain from the popularity of radio and the ‘free’ music it provided. What they needed to make this new medium work for them already existed in previous copyright law. The copyright holder for a song had control over all public performances ‘for profit.’ The problem now was proving that the radio industry, which was just figuring out for itself how to make money from advertising and currently offered free music to anyone with a receiver, was making a profit from the songs.


title: History of radio

text: The test case was against Bamberger's Department Store in Newark, New Jersey in 1922. The store was broadcasting music from its store on the radio station WOR. No advertisements were heard, except at the beginning of the broadcast which announced "L. Bamberger and Co., One of America's Great Stores, Newark, New Jersey." It was determined through this and previous cases (such as the lawsuit against Shanley's Restaurant) that Bamberger was using the songs for commercial gain, thus making it a public performance for profit, which meant the copyright owners were due payment.


title: History of radio

text: With this ruling the American Society of Composers, Authors and Publishers (ASCAP) began collecting licensing fees from radio stations in 1923. The beginning sum was $250 for all music protected under ASCAP, but for larger stations the price soon ballooned to $5,000. Edward Samuels reports in his book "The Illustrated Story of Copyright" that "radio and TV licensing represents the single greatest source of revenue for ASCAP and its composers […] and [a]n average member of ASCAP gets about $150–$200 per work per year, or about $5,000-$6,000 for all of a member's compositions." Not long after the Bamberger ruling, ASCAP had to once again defend their right to charge fees, in 1924. The Dill Radio Bill would have allowed radio stations to play music without paying and licensing fees to ASCAP or any other music-licensing corporations. The bill did not pass.


title: History of radio

text: Radio technology was first used for ships to communicate at sea. To ensure safety, the Wireless Ship Act of 1910 marks the first time the U.S. government implies regulations on radio systems on ships. This act requires ships to have a radio system with a professional operator if they want to travel more than 200 miles offshore or have more than 50 people on board. However, this act had many flaws including the competition of radio operators including the two majors company (British and American Marconi). They tended to delay communication for ships that used their competitor's system. This contributed to the tragic incident of the sinking of the Titanic in 1912.


title: History of radio

text: In 1912, distress calls to aid the sinking "Titanic" were met with a large amount of interfering radio traffic, severely hampering the rescue effort. Subsequently, the US government passed the Radio Act of 1912 to help mitigate the repeat of such a tragedy. The act helps distinguish between normal radio traffic and (primarily maritime) emergency communication, and specifies the role of government during such an emergency.


title: History of radio

text: The Radio Act of 1927 gave the Federal Radio Commission the power to grant and deny licenses, and to assign frequencies and power levels for each licensee. In 1928 it began requiring licenses of existing stations and setting controls on who could broadcast from where on what frequency and at what power. Some stations could not obtain a license and ceased operations. In section 29, the Radio Act of 1927 mentioned that the content of the broadcast should be freely present, and the government cannot interfere with this.


title: History of radio

text: The introduction of the Communications Act of 1934 led to the establishment of the Federal Communications Commissions (FCC). The FCC's responsibility is to control the industry including "telephone, telegraph, and radio communications." Under this Act, all carriers have to keep records of authorized interference and unauthorized interference. This Act also supports the President in time of war. If the government needs to use the communication facilities in time of war, they are allowed to.


title: History of radio

text: The Telecommunications Act of 1996 was the first significant overhaul in over 60 years amending the work of theThe Communications Act of 1934. Coming only two dozen years after the breakup of AT&T, the act sets out to move telecommunications into a state of competition with their markets and the networks they are a part of. Up to this point the effects of the Telecommunications Act of 1996 have been seen, but some of the changes the Act set out to fix are still ongoing problems, such as being unable to create an open competitive market.


title: History of radio

text: The question of the 'first' publicly targeted licensed radio station in the U.S. has more than one answer and depends on semantics. Settlement of this 'first' question may hang largely upon what constitutes 'regular' programming


title: Niobium

text: Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has similar ductility to iron. Niobium oxidizes in Earth's atmosphere very slowly, hence its application in jewelry as a hypoallergenic alternative to nickel. Niobium is often found in the minerals pyrochlore and columbite, hence the former name "columbium". Its name comes from Greek mythology: Niobe, daughter of Tantalus, the namesake of tantalum. The name reflects the great similarity between the two elements in their physical and chemical properties, which makes them difficult to distinguish.


title: Niobium

text: English chemist Charles Hatchett reported a new element similar to tantalum in 1801 and named it columbium. In 1809, English chemist William Hyde Wollaston wrongly concluded that tantalum and columbium were identical. German chemist Heinrich Rose determined in 1846 that tantalum ores contain a second element, which he named niobium. In 1864 and 1865, a series of scientific findings clarified that niobium and columbium were the same element (as distinguished from tantalum), and for a century both names were used interchangeably. Niobium was officially adopted as the name of the element in 1949, but the name columbium remains in current use in metallurgy in the United States.


title: Niobium

text: It was not until the early 20th century that niobium was first used commercially. Niobium is an important addition to high-strength low-alloy steels. Brazil is the leading producer of niobium and ferroniobium, an alloy of 60–70% niobium with iron. Niobium is used mostly in alloys, the largest part in special steel such as that used in gas pipelines. Although these alloys contain a maximum of 0.1%, the small percentage of niobium enhances the strength of the steel by scavenging carbide and nitride. The temperature stability of niobium-containing superalloys is important for its use in jet and rocket engines.


title: Niobium

text: Niobium is used in various superconducting materials. These alloys, also containing titanium and tin, are widely used in the superconducting magnets of MRI scanners. Other applications of niobium include welding, nuclear industries, electronics, optics, numismatics, and jewelry. In the last two applications, the low toxicity and iridescence produced by anodization are highly desired properties. Niobium is considered a technology-critical element.


title: Niobium

text: Niobium was identified by English chemist Charles Hatchett in 1801. He found a new element in a mineral sample that had been sent to England from Connecticut, United States in 1734 by John Winthrop F.R.S. (grandson of John Winthrop the Younger) and named the mineral "columbite" and the new element "columbium" after "Columbia", the poetic name for the United States. The "columbium" discovered by Hatchett was probably a mixture of the new element with tantalum.


title: Niobium

text: Subsequently, there was considerable confusion over the difference between columbium (niobium) and the closely related tantalum. In 1809, English chemist William Hyde Wollaston compared the oxides derived from both columbium—columbite, with a density 5.918 g/cm, and tantalum—tantalite, with a density over 8 g/cm, and concluded that the two oxides, despite the significant difference in density, were identical; thus he kept the name tantalum. This conclusion was disputed in 1846 by German chemist Heinrich Rose, who argued that there were two different elements in the tantalite sample, and named them after children of Tantalus: "niobium" (from Niobe) and "pelopium" (from Pelops). This confusion arose from the minimal observed differences between tantalum and niobium. The claimed new elements "pelopium", "ilmenium", and "dianium" were in fact identical to niobium or mixtures of niobium and tantalum.


title: Niobium

text: The differences between tantalum and niobium were unequivocally demonstrated in 1864 by Christian Wilhelm Blomstrand and Henri Étienne Sainte-Claire Deville, as well as Louis J. Troost, who determined the formulas of some of the compounds in 1865 and finally by Swiss chemist Jean Charles Galissard de Marignac in 1866, who all proved that there were only two elements. Articles on "ilmenium" continued to appear until 1871.


title: Niobium

text: De Marignac was the first to prepare the metal in 1864, when he reduced niobium chloride by heating it in an atmosphere of hydrogen. Although de Marignac was able to produce tantalum-free niobium on a larger scale by 1866, it was not until the early 20th century that niobium was used in incandescent lamp filaments, the first commercial application. This use quickly became obsolete through the replacement of niobium with tungsten, which has a higher melting point. That niobium improves the strength of steel was first discovered in the 1920s, and this application remains its predominant use. In 1961, the American physicist Eugene Kunzler and coworkers at Bell Labs discovered that niobium–tin continues to exhibit superconductivity in the presence of strong electric currents and magnetic fields, making it the first material to support the high currents and fields necessary for useful high-power magnets and electrical power machinery. This discovery enabled—two decades later—the production of long multi-strand cables wound into coils to create large, powerful electromagnets for rotating machinery, particle accelerators, and particle detectors.


title: Niobium

text: "Columbium" (symbol Cb) was the name originally given by Hatchett upon his discovery of the metal in 1801. The name reflected that the type specimen of the ore came from America (Columbia). This name remained in use in American journals—the last paper published by American Chemical Society with "columbium" in its title dates from 1953—while "niobium" was used in Europe. To end this confusion, the name "niobium" was chosen for element 41 at the 15th Conference of the Union of Chemistry in Amsterdam in 1949. A year later this name was officially adopted by the International Union of Pure and Applied Chemistry (IUPAC) after 100 years of controversy, despite the chronological precedence of the name "columbium". This was a compromise of sorts; the IUPAC accepted tungsten instead of wolfram in deference to North American usage; and "niobium" instead of "columbium" in deference to European usage. While many US chemical societies and government organizations typically use the official IUPAC name, some metallurgists and metal societies still use the original American name, ""columbium".


title: Niobium

text: Niobium is a lustrous, grey, ductile, paramagnetic metal in group 5 of the periodic table (see table), with an electron configuration in the outermost shells atypical for group 5. Similary atypical configurations occur in the neighborhood of ruthenium (44), rhodium (45), and palladium (46).


title: Niobium

text: Although it is thought to have a body-centered cubic crystal structure from absolute zero to its melting point, high-resolution measurements of the thermal expansion along the three crystallographic axes reveal anisotropies which are inconsistent with a cubic structure. Therefore, further research and discovery in this area is expected.


title: Niobium

text: Niobium becomes a superconductor at cryogenic temperatures. At atmospheric pressure, it has the highest critical temperature of the elemental superconductors at 9.2 K. Niobium has the greatest magnetic penetration depth of any element. In addition, it is one of the three elemental Type II superconductors, along with vanadium and technetium. The superconductive properties are strongly dependent on the purity of the niobium metal.


title: Niobium

text: The metal has a low capture cross-section for thermal neutrons; thus it is used in the nuclear industries where neutron transparent structures are desired.


title: Niobium

text: The metal takes on a bluish tinge when exposed to air at room temperature for extended periods. Despite a high melting point in elemental form (2,468 °C), it is less dense than other refractory metals. Furthermore, it is corrosion-resistant, exhibits superconductivity properties, and forms dielectric oxide layers.


title: Niobium

text: Niobium is slightly less electropositive and more compact than its predecessor in the periodic table, zirconium, whereas it is virtually identical in size to the heavier tantalum atoms, as a result of the lanthanide contraction. As a result, niobium's chemical properties are very similar to those for tantalum, which appears directly below niobium in the periodic table. Although its corrosion resistance is not as outstanding as that of tantalum, the lower price and greater availability make niobium attractive for less demanding applications, such as vat linings in chemical plants.


title: Niobium

text: Niobium in Earth's crust comprises one stable isotope, Nb. By 2003, at least 32 radioisotopes had been synthesized, ranging in atomic mass from 81 to 113. The most stable is Nb with half-life 34.7 million years. One of the least stable is Nb; estimated half-life 30 milliseconds. Isotopes lighter than the stable Nb tend to β decay, and those that are heavier tend to β decay, with some exceptions. Nb, Nb, and Nb have minor β-delayed proton emission decay paths, Nb decays by electron capture and positron emission, and Nb decays by both β and β decay.


title: Niobium

text: At least 25 nuclear isomers have been described, ranging in atomic mass from 84 to 104. Within this range, only Nb, Nb, and Nb do not have isomers. The most stable of niobium's isomers is Nb with half-life 16.13 years. The least stable isomer is Nb with a half-life of 103 ns. All of niobium's isomers decay by isomeric transition or beta decay except Nb, which has a minor electron capture branch.


title: Niobium

text: Niobium is estimated to be the 34th-most common element in Earth's crust, at 20 ppm. Some believe that the abundance on Earth is much greater, and that the element's high density has concentrated it in Earth's core. The free element is not found in nature, but niobium occurs in combination with other elements in minerals. Minerals that contain niobium often also contain tantalum. Examples include columbite () and columbite–tantalite (or "coltan", ). Columbite–tantalite minerals (the most common species being columbite-(Fe) and tantalite-(Fe), where "-(Fe)" is the Levinson suffix indicating the prevalence of iron over other elements such as manganese) that are most usually found as accessory minerals in pegmatite intrusions, and in alkaline intrusive rocks. Less common are the niobates of calcium, uranium, thorium and the rare earth elements. Examples of such niobates are pyrochlore () (now a group name, with a relatively common example being, e.g., fluorcalciopyrochlore) and euxenite (correctly named euxenite-(Y)) (). These large deposits of niobium have been found associated with carbonatites (carbonate-silicate igneous rocks) and as a constituent of pyrochlore.


title: Niobium

text: The three largest currently mined deposits of pyrochlore, two in Brazil and one in Canada, were found in the 1950s, and are still the major producers of niobium mineral concentrates. The largest deposit is hosted within a carbonatite intrusion in Araxá, state of Minas Gerais, Brazil, owned by CBMM (Companhia Brasileira de Metalurgia e Mineração); the other active Brazilian deposit is located near Catalão, state of Goiás, and owned by China Molybdenum, also hosted within a carbonatite intrusion. Together, those two mines produce about 88% of the world's supply. Brazil also has a large but still unexploited deposit near São Gabriel da Cachoeira, state of Amazonas, as well as a few smaller deposits, notably in the state of Roraima.


title: Niobium

text: The third largest producer of niobium is the carbonatite-hosted Niobec mine, in Saint-Honoré, near Chicoutimi, Quebec, Canada, owned by Magris Resources. It produces between 7% and 10% of the world's supply.


title: Niobium

text: After the separation from the other minerals, the mixed oxides of tantalum and niobium are obtained. The first step in the processing is the reaction of the oxides with hydrofluoric acid:


title: Niobium

text: The first industrial scale separation, developed by Swiss chemist de Marignac, exploits the differing solubilities of the complex niobium and tantalum fluorides, dipotassium oxypentafluoroniobate monohydrate () and dipotassium heptafluorotantalate () in water. Newer processes use the liquid extraction of the fluorides from aqueous solution by organic solvents like cyclohexanone. The complex niobium and tantalum fluorides are extracted separately from the organic solvent with water and either precipitated by the addition of potassium fluoride to produce a potassium fluoride complex, or precipitated with ammonia as the pentoxide:


title: Niobium

text: Several methods are used for the reduction to metallic niobium. The electrolysis of a molten mixture of [] and sodium chloride is one; the other is the reduction of the fluoride with sodium. With this method, a relatively high purity niobium can be obtained. In large scale production, is reduced with hydrogen or carbon. In the aluminothermic reaction, a mixture of iron oxide and niobium oxide is reacted with aluminium:


title: Niobium

text: Small amounts of oxidizers like sodium nitrate are added to enhance the reaction. The result is aluminium oxide and ferroniobium, an alloy of iron and niobium used in steel production. Ferroniobium contains between 60 and 70% niobium. Without iron oxide, the aluminothermic process is used to produce niobium. Further purification is necessary to reach the grade for superconductive alloys. Electron beam melting under vacuum is the method used by the two major distributors of niobium.


title: Niobium

text: , CBMM from Brazil controlled 85 percent of the world's niobium production. The United States Geological Survey estimates that the production increased from 38,700 tonnes in 2005 to 44,500 tonnes in 2006. Worldwide resources are estimated to be 4.4 million tonnes. During the ten-year period between 1995 and 2005, the production more than doubled, starting from 17,800 tonnes in 1995. Between 2009 and 2011, production was stable at 63,000 tonnes per year, with a slight decrease in 2012 to only 50,000 tonnes per year.


title: Niobium

text: In many ways, niobium is similar to tantalum and zirconium. It reacts with most nonmetals at high temperatures; with fluorine at room temperature; with chlorine at 150 °C and hydrogen at 200 °C; and with nitrogen at 400 °C, with products that are frequently interstitial and nonstoichiometric. The metal begins to oxidize in air at 200 °C. It resists corrosion by fused alkalis and by acids, including aqua regia, hydrochloric, sulfuric, nitric and phosphoric acids. Niobium is attacked by hydrofluoric acid and hydrofluoric/nitric acid mixtures.


title: Niobium

text: Although niobium exhibits all of the formal oxidation states from +5 to −1, the most common compounds have niobium in the +5 state. Characteristically, compounds in oxidation states less than 5+ display Nb–Nb bonding. In aqueous solutions, niobium only exhibit the +5 oxidation state. It is also readily prone to hydrolysis and is barely soluble in dilute solutions of hydrochloric, sulfuric, nitric and phosphoric acids due to the precipitation of hydrous Nb oxide. Nb(V) is also slightly soluble in alkaline media due to the formation of soluble polyoxoniobate species.


title: Niobium

text: Niobium forms oxides in the oxidation states +5 (), +4 (), and the rarer oxidation state, +2 (NbO). Most common is the pentoxide, precursor to almost all niobium compounds and alloys. Niobates are generated by dissolving the pentoxide in basic hydroxide solutions or by melting it in alkali metal oxides. Examples are lithium niobate () and lanthanum niobate (). In the lithium niobate is a trigonally distorted perovskite-like structure, whereas the lanthanum niobate contains lone ions. The layered niobium sulfide () is also known.


title: Niobium

text: Materials can be coated with a thin film of niobium(V) oxide chemical vapor deposition or atomic layer deposition processes, produced by the thermal decomposition of niobium(V) ethoxide above 350 °C.


title: Niobium

text: Niobium forms halides in the oxidation states of +5 and +4 as well as diverse substoichiometric compounds. The pentahalides () feature octahedral Nb centres. Niobium pentafluoride () is a white solid with a melting point of 79.0 °C and niobium pentachloride () is yellow (see image at left) with a melting point of 203.4 °C. Both are hydrolyzed to give oxides and oxyhalides, such as . The pentachloride is a versatile reagent used to generate the organometallic compounds, such as niobocene dichloride (). The tetrahalides () are dark-coloured polymers with Nb-Nb bonds; for example, the black hygroscopic niobium tetrafluoride () and brown niobium tetrachloride ().


title: Niobium

text: Anionic halide compounds of niobium are well known, owing in part to the Lewis acidity of the pentahalides. The most important is [NbF], an intermediate in the separation of Nb and Ta from the ores. This heptafluoride tends to form the oxopentafluoride more readily than does the tantalum compound. Other halide complexes include octahedral []:


title: Niobium

text: As with other metals with low atomic numbers, a variety of reduced halide cluster ions is known, the prime example being [].


title: Niobium

text: Other binary compounds of niobium include niobium nitride (NbN), which becomes a superconductor at low temperatures and is used in detectors for infrared light. The main niobium carbide is NbC, an extremely hard, refractory, ceramic material, commercially used in cutting tool bits.


title: Niobium

text: Out of 44,500 tonnes of niobium mined in 2006, an estimated 90% was used in high-grade structural steel. The second-largest application is superalloys. Niobium alloy superconductors and electronic components account for a very small share of the world production.


title: Niobium

text: Niobium is an effective microalloying element for steel, within which it forms niobium carbide and niobium nitride. These compounds improve the grain refining, and retard recrystallization and precipitation hardening. These effects in turn increase the toughness, strength, formability, and weldability. Within microalloyed stainless steels, the niobium content is a small (less than 0.1%) but important addition to high-strength low-alloy steels that are widely used structurally in modern automobiles. Niobium is sometimes used in considerably higher quantities for highly wear-resistant machine components and knives, as high as 3% in Crucible CPM S110V stainless steel.


title: Niobium

text: Quantities of niobium are used in nickel-, cobalt-, and iron-based superalloys in proportions as great as 6.5% for such applications as jet engine components, gas turbines, rocket subassemblies, turbo charger systems, heat resisting, and combustion equipment. Niobium precipitates a hardening γ<nowiki>"</nowiki>-phase within the grain structure of the superalloy.


title: Niobium

text: One example superalloy is Inconel 718, consisting of roughly 50% nickel, 18.6% chromium, 18.5% iron, 5% niobium, 3.1% molybdenum, 0.9% titanium, and 0.4% aluminium. These superalloys were used, for example, in advanced air frame systems for the Gemini program. Another niobium alloy was used for the nozzle of the Apollo Service Module. Because niobium is oxidized at temperatures above 400 °C, a protective coating is necessary for these applications to prevent the alloy from becoming brittle.


title: Niobium

text: C-103 alloy was developed in the early 1960s jointly by the Wah Chang Corporation and Boeing Co. DuPont, Union Carbide Corp., General Electric Co. and several other companies were developing Nb-base alloys simultaneously, largely driven by the Cold War and Space Race. It is composed of 89% niobium, 10% hafnium and 1% titanium and is used for liquid-rocket thruster nozzles, such as the main engine of the Apollo Lunar Modules.


title: Niobium

text: The nozzle of the Merlin Vacuum series of engines developed by SpaceX for the upper stage of its Falcon 9 rocket is made from a niobium alloy.


title: Niobium

text: The reactivity of niobium with oxygen requires it to be worked in a vacuum or inert atmosphere, which significantly increases the cost and difficulty of production. Vacuum arc remelting (VAR) and electron beam melting (EBM), novel processes at the time, enabled the development of niobium and other reactive metals. The project that yielded C-103 began in 1959 with as many as 256 experimental niobium alloys in the "C-series" (C arising possibly from columbium) that could be melted as buttons and rolled into sheet. Wah Chang Corporation had an inventory of hafnium, refined from nuclear-grade zirconium alloys, that it wanted to put to commercial use. The 103rd experimental composition of the C-series alloys, Nb-10Hf-1Ti, had the best combination of formability and high-temperature properties. Wah Chang fabricated the first 500 lb heat of C-103 in 1961, ingot to sheet, using EBM and VAR. The intended applications included turbine engines and liquid metal heat exchangers. Competing niobium alloys from that era included FS85 (Nb-10W-28Ta-1Zr) from Fansteel Metallurgical Corp., Cb129Y (Nb-10W-10Hf-0.2Y) from Wah Chang and Boeing, Cb752 (Nb-10W-2.5Zr) from Union Carbide, and Nb1Zr from Superior Tube Co.


title: Niobium

text: Niobium-germanium (), niobium–tin (), as well as the niobium–titanium alloys are used as a type II superconductor wire for superconducting magnets. These superconducting magnets are used in magnetic resonance imaging and nuclear magnetic resonance instruments as well as in particle accelerators. For example, the Large Hadron Collider uses 600 tons of superconducting strands, while the International Thermonuclear Experimental Reactor uses an estimated 600 tonnes of NbSn strands and 250 tonnes of NbTi strands. In 1992 alone, more than US$1 billion worth of clinical magnetic resonance imaging systems were constructed with niobium-titanium wire.


title: Niobium

text: The superconducting radio frequency (SRF) cavities used in the free-electron lasers FLASH (result of the cancelled TESLA linear accelerator project) and XFEL are made from pure niobium. A cryomodule team at Fermilab used the same SRF technology from the FLASH project to develop 1.3 GHz nine-cell SRF cavities made from pure niobium. The cavities will be used in the linear particle accelerator of the International Linear Collider. The same technology will be used in LCLS-II at SLAC National Accelerator Laboratory and PIP-II at Fermilab.


title: Niobium

text: The high sensitivity of superconducting niobium nitride bolometers make them an ideal detector for electromagnetic radiation in the THz frequency band. These detectors were tested at the Submillimeter Telescope, the South Pole Telescope, the Receiver Lab Telescope, and at APEX, and are now used in the HIFI instrument on board the Herschel Space Observatory.


title: Niobium

text: Lithium niobate, which is a ferroelectric, is used extensively in mobile telephones and optical modulators, and for the manufacture of surface acoustic wave devices. It belongs to the ABO structure ferroelectrics like lithium tantalate and barium titanate. Niobium capacitors are available as alternative to tantalum capacitors, but tantalum capacitors still predominate. Niobium is added to glass to obtain a higher refractive index, making possible thinner and lighter corrective glasses.


title: Niobium

text: Niobium and some niobium alloys are physiologically inert and hypoallergenic. For this reason, niobium is used in prosthetics and implant devices, such as pacemakers. Niobium treated with sodium hydroxide forms a porous layer that aids osseointegration.


title: Niobium

text: Like titanium, tantalum, and aluminium, niobium can be heated and anodized ("reactive metal anodization") to produce a wide array of iridescent colours for jewelry, where its hypoallergenic property is highly desirable.


title: Niobium

text: Niobium is used as a precious metal in commemorative coins, often with silver or gold. For example, Austria produced a series of silver niobium euro coins starting in 2003; the colour in these coins is created by the diffraction of light by a thin anodized oxide layer. In 2012, ten coins are available showing a broad variety of colours in the centre of the coin: blue, green, brown, purple, violet, or yellow. Two more examples are the 2004 Austrian €25 150-Year Semmering Alpine Railway commemorative coin, and the 2006 Austrian €25 European Satellite Navigation commemorative coin. The Austrian mint produced for Latvia a similar series of coins starting in 2004, with one following in 2007. In 2011, the Royal Canadian Mint started production of a $5 sterling silver and niobium coin named "Hunter's Moon" in which the niobium was selectively oxidized, thus creating unique finishes where no two coins are exactly alike.


title: Niobium

text: The arc-tube seals of high pressure sodium vapor lamps are made from niobium, sometimes alloyed with 1% of zirconium; niobium has a very similar coefficient of thermal expansion, matching the sintered alumina arc tube ceramic, a translucent material which resists chemical attack or reduction by the hot liquid sodium and sodium vapour contained inside the operating lamp.


title: Niobium

text: Niobium is used in arc welding rods for some stabilized grades of stainless steel and in anodes for cathodic protection systems on some water tanks, which are then usually plated with platinum.


title: Niobium

text: Niobium is an important component of high-performance heterogeneous catalysts for the production of acrylic acid by selective oxidation of propane.


title: Niobium

text: Niobium is used to make the high voltage wire of the solar corona particles receptor module of the Parker Solar Probe.


title: Niobium

text: Niobium has no known biological role. While niobium dust is an eye and skin irritant and a potential fire hazard, elemental niobium on a larger scale is physiologically inert (and thus hypoallergenic) and harmless. It is often used in jewelry and has been tested for use in some medical implants.


title: Niobium

text: Short- and long-term exposure to niobates and niobium chloride, two water-soluble chemicals, have been tested in rats. Rats treated with a single injection of niobium pentachloride or niobates show a median lethal dose (LD) between 10 and 100 mg/kg. For oral administration the toxicity is lower; a study with rats yielded a LD after seven days of 940 mg/kg.


title: Injective function

text: In mathematics, an injective function (also known as injection, or one-to-one function) is a function that maps distinct elements of its domain to distinct elements; that is, implies . (Equivalently, implies in the equivalent contrapositive statement.) In other words, every element of the function's codomain is the image of one element of its domain. The term must not be confused with that refers to bijective functions, which are functions such that each element in the codomain is an image of exactly one element in the domain.


title: Injective function

text: A homomorphism between algebraic structures is a function that is compatible with the operations of the structures. For all common algebraic structures, and, in particular for vector spaces, an is also called a . However, in the more general context of category theory, the definition of a monomorphism differs from that of an injective homomorphism. This is thus a theorem that they are equivalent for algebraic structures; see for more details.


title: Injective function

text: Let formula_1 be a function whose domain is a set formula_3 The function formula_1 is said to be injective provided that for all formula_5 and formula_6 in formula_7 if formula_8 then formula_9; that is, formula_10 implies formula_11 Equivalently, if formula_12 then formula_13 in the contrapositive statement.


title: Injective function

text: More generally, when formula_16 and formula_36 are both the real line formula_37 then an injective function formula_21 is one whose graph is never intersected by any horizontal line more than once. This principle is referred to as the .


title: Injective function

text: Functions with left inverses are always injections. That is, given formula_39 if there is a function formula_40 such that for every formula_41, formula_42, then formula_1 is injective. In this case, formula_26 is called a retraction of formula_45 Conversely, formula_1 is called a section of formula_47


title: Injective function

text: Conversely, every injection formula_1 with non-empty domain has a left inverse formula_49 which can be defined by fixing an element formula_5 in the domain of formula_1 so that formula_52 equals the unique pre-image of formula_53 under formula_1 if it exists and formula_55 otherwise.


title: Injective function

text: The left inverse formula_26 is not necessarily an inverse of formula_57 because the composition in the other order, formula_58 may differ from the identity on formula_59 In other words, an injective function can be "reversed" by a left inverse, but is not necessarily invertible, which requires that the function is bijective.


title: Injective function

text: In fact, to turn an injective function formula_60 into a bijective (hence invertible) function, it suffices to replace its codomain formula_36 by its actual range formula_62 That is, let formula_63 such that formula_64 for all formula_41; then formula_26 is bijective. Indeed, formula_1 can be factored as formula_68 where formula_69 is the inclusion function from formula_70 into formula_59


title: Injective function

text: A proof that a function formula_1 is injective depends on how the function is presented and what properties the function holds.


title: Injective function

text: Proof: Let formula_121 Suppose formula_122 So formula_123 implies formula_124 which implies formula_119 Therefore, it follows from the definition that formula_1 is injective.


title: Injective function

text: There are multiple other methods of proving that a function is injective. For example, in calculus if formula_1 is a differentiable function defined on some interval, then it is sufficient to show that the derivative is always positive or always negative on that interval. In linear algebra, if formula_1 is a linear transformation it is sufficient to show that the kernel of formula_1 contains only the zero vector. If formula_1 is a function with finite domain it is sufficient to look through the list of images of each domain element and check that no image occurs twice on the list.


title: Injective function

text: A graphical approach for a real-valued function formula_1 of a real variable formula_53 is the horizontal line test. If every horizontal line intersects the curve of formula_133 in at most one point, then formula_1 is injective or one-to-one.


title: Feminist theory

text: Feminist theory is the extension of feminism into theoretical, fictional, or philosophical discourse. It aims to understand the nature of gender inequality. It examines women's and men's social roles, experiences, interests, chores, and feminist politics in a variety of fields, such as anthropology and sociology, communication, media studies, psychoanalysis, political theory, home economics, literature, education, and philosophy.


title: Feminist theory

text: Feminist theory often focuses on analyzing gender inequality. Themes often explored in feminist theory include discrimination, objectification (especially sexual objectification), oppression, patriarchy, stereotyping, art history and contemporary art, and aesthetics.


title: Feminist theory

text: Feminist theories first emerged as early as 1794 in publications such as "A Vindication of the Rights of Woman" by Mary Wollstonecraft, "The Changing Woman", "Ain't I a Woman", "Speech after Arrest for Illegal Voting", and so on. "The Changing Woman" is a Navajo Myth that gave credit to a woman who, in the end, populated the world. In 1851, Sojourner Truth addressed women's rights issues through her publication, "Ain't I a Woman". Sojourner Truth addressed the issue of women having limited rights due to men's flawed perception of women. Truth argued that if a woman of color can perform tasks that were supposedly limited to men, then any woman of any color could perform those same tasks. After her arrest for illegally voting, Susan B. Anthony gave a speech within court in which she addressed the issues of language within the constitution documented in her publication, "Speech after Arrest for Illegal voting" in 1872. Anthony questioned the authoritative principles of the constitution and its male-gendered language. She raised the question of why women are accountable to be punished under law but they cannot use the law for their own protection (women could not vote, own property, nor maintain custody of themselves in marriage). She also critiqued the constitution for its male-gendered language and questioned why women should have to abide by laws that do not specify women.


title: Feminist theory

text: Nancy Cott makes a distinction between "modern feminism" and its antecedents, particularly the struggle for suffrage. In the United States she places the turning point in the decades before and after women obtained the vote in 1920 (1910–1930). She argues that the prior "woman movement" was primarily about woman as a "universal" entity, whereas over this 20-year period it transformed itself into one primarily concerned with social differentiation, attentive to "individuality" and diversity. New issues dealt more with woman's condition as a social construct, gender identity, and relationships within and between genders. Politically, this represented a shift from an ideological alignment comfortable with the right, to one more radically associated with the left.


title: Feminist theory

text: Susan Kingsley Kent says that Freudian patriarchy was responsible for the diminished profile of feminism in the inter-war years, others such as Juliet Mitchell consider this to be


title: Feminist theory

text: overly simplistic since Freudian theory is not wholly incompatible with feminism. Some feminist scholarship shifted away from the need to establish the origins of family, and towards analyzing the process of patriarchy. In the immediate postwar period, Simone de Beauvoir stood in opposition to an image of "the woman in the home". De Beauvoir provided an existentialist dimension to feminism with the publication of "Le Deuxième Sexe" ("The Second Sex") in 1949.


title: Feminist theory

text: As the title implies, the starting point is the implicit inferiority of women, and the first question de Beauvoir asks is "what is a woman"?


title: Feminist theory

text: A woman she realizes is always perceived of as the "other", "she is defined and differentiated with reference to man and not he with reference to her". In this book and her essay, "Woman: Myth & Reality", de Beauvoir anticipates Betty Friedan in seeking to demythologize the male concept of woman. "A myth invented by men to confine women to their oppressed state. For women, it is not a question of asserting themselves as women, but of becoming full-scale human beings." "One is not born, but rather becomes, a woman", or as Toril Moi puts it "a woman defines herself through the way she lives her embodied situation in the world, or in other words, through the way in which she makes something of what the world makes of her". Therefore, the woman must regain subject, to escape her defined role as "other", as a Cartesian point of departure.


title: Feminist theory

text: In her examination of myth, she appears as one who does not accept any special privileges for women. Ironically, feminist philosophers have had to extract de Beauvoir herself from out of the shadow of Jean-Paul Sartre to fully appreciate her. While more philosopher and novelist than activist, she did sign one of the "Mouvement de Libération des Femmes" manifestos.


title: Feminist theory

text: The resurgence of feminist activism in the late 1960s was accompanied by an emerging literature of concerns for the earth and spirituality, and environmentalism. This, in turn, created an atmosphere conducive to reigniting the study of and debate on matricentricity, as a rejection of determinism, such as Adrienne Rich and Marilyn French while for socialist feminists like Evelyn Reed, patriarchy held the properties of capitalism. Feminist psychologists, such as Jean Baker Miller, sought to bring a feminist analysis to previous psychological theories, proving that "there was nothing wrong with women, but rather with the way modern culture viewed them".


title: Feminist theory

text: Elaine Showalter describes the development of feminist theory as having a number of phases. The first she calls "feminist critique" – where the feminist reader examines the ideologies behind literary phenomena. The second Showalter calls "Gynocritics" – where the "woman is producer of textual meaning" including "the psychodynamics of female creativity; linguistics and the problem of a female language; the trajectory of the individual or collective female literary career and literary history". The last phase she calls "gender theory" – where the "ideological inscription and the literary effects of the sex/gender system" are explored". This model has been criticized by Toril Moi who sees it as an essentialist and deterministic model for female subjectivity. She also criticized it for not taking account of the situation for women outside the west.


title: Feminist theory

text: From the 1970s onwards, psychoanalytical ideas that have been arising in the field of French feminism have gained a decisive influence on feminist theory. Feminist psychoanalysis deconstructed the phallic hypotheses regarding the Unconscious. Julia Kristeva, Bracha Ettinger and Luce Irigaray developed specific notions concerning unconscious sexual difference, the feminine, and motherhood, with wide implications for film and literature analysis.


title: Feminist theory

text: There are a number of distinct feminist disciplines, in which experts in other areas apply feminist techniques and principles to their own fields. Additionally, these are also debates which shape feminist theory and they can be applied interchangeably in the arguments of feminist theorists.


title: Feminist theory

text: In western thought, the body has been historically associated solely with women, whereas men have been associated with the mind. Susan Bordo, a modern feminist philosopher, in her writings elaborates the dualistic nature of the mind/body connection by examining the early philosophies of Aristotle, Hegel, and Descartes, revealing how such distinguishing binaries such as spirit/matter and male activity/female passivity have worked to solidify gender characteristics and categorization. Bordo goes on to point out that while men have historically been associated with the intellect and the mind or spirit, women have long been associated with the body, the subordinated, negatively imbued term in the mind/body dichotomy.


title: Feminist theory

text: The notion of the body (but not the mind) being associated with women has served as a justification to deem women as property, objects, and exchangeable commodities (among men). For example, women's bodies have been objectified throughout history through the changing ideologies of fashion, diet, exercise programs, cosmetic surgery, childbearing, etc. This contrasts to men's role as a moral agent, responsible for working or fighting in bloody wars.


title: Feminist theory

text: The race and class of a woman can determine whether her body will be treated as decoration and protected, which is associated with middle or upper-class women's bodies. On the other hand, the other body is recognized for its use in labor and exploitation which is generally associated with women's bodies in the working-class or with women of color.


title: Feminist theory

text: Second-wave feminist activism has argued for reproductive rights and choice. The women's health movement and lesbian feminism are also associated with this Bodies debate.


title: Feminist theory

text: The standard sex determination and gender model consists of evidence based on the determined sex and gender of every individual and serve as norms for societal life. The model that the sex-determination of a person exists within a male/female dichotomy, giving importance to genitals and how they are formed via chromosomes and DNA-binding proteins (such as the sex-determining region Y genes), which are responsible for sending sex-determined initialization and completion signals to and from the biological sex-determination system in fetuses. Occasionally, variations occur during the sex-determining process, resulting in intersex conditions. The standard model defines gender as a social understanding/ideology that defines what behaviors, actions, and appearances are normal for males and females. Studies into biological sex-determining systems also have begun working towards connecting certain gender conducts such as behaviors, actions, and desires with sex-determinism.


title: Feminist theory

text: The socially biasing children's sex and gender model broadens the horizons of the sex and gender ideologies. It revises the ideology of sex to be a social construct that is not limited to either male or female. The Intersex Society of North America which explains that "nature doesn't decide where the category of 'male' ends and the category of 'intersex' begins, or where the category of 'intersex' ends and the category of 'female' begins. Humans decide. Humans (today, typically doctors) decide how small a penis has to be, or how unusual a combination of parts has to be before it counts as intersex". Therefore, sex is not a biological/natural construct but a social one instead since, society and doctors decide on what it means to be male, female, or intersex in terms of sex chromosomes and genitals, in addition to their personal judgment on who or how one passes as specific sex. The ideology of gender remains a social construct but is not as strict and fixed. Instead, gender is easily malleable and is forever changing. One example of where the standard definition of gender alters with time happens to be depicted in Sally Shuttleworth's "Female Circulation" in which the "abasement of the woman, reducing her from an active participant in the labor market to the passive bodily existence to be controlled by male expertise is indicative of the ways in which the ideological deployment of gender roles operated to facilitate and sustain the changing structure of familial and market relations in Victorian England". In other words, this quote shows what it meant growing up into the roles of a female (gender/roles) changed from being a homemaker to being a working woman and then back to being passive and inferior to males. In conclusion, the contemporary sex gender model is accurate because both sex and gender are rightly seen as social constructs inclusive of the wide spectrum of sexes and genders and in which nature and nurture are interconnected.


title: Feminist theory

text: Questions about how knowledge is produced, generated, and distributed have been central to Western conceptions of feminist theory and discussions on feminist epistemology. One debate proposes such questions as "Are there 'women's ways of knowing' and 'women's knowledge'?" And "How does the knowledge women produce about themselves differ from that produced by patriarchy?" Feminist theorists have also proposed the "feminist standpoint knowledge" which attempts to replace the "view from nowhere" with the model of knowing that expels the "view from women's lives". A feminist approach to epistemology seeks to establish knowledge production from a woman's perspective. It theorizes that from personal experience comes knowledge which helps each individual look at things from a different insight.


title: Feminist theory

text: It is central to feminism that women are systematically subordinated, and bad faith exists when women surrender their agency to this subordination (for example, acceptance of religious beliefs that a man is the dominant party in a marriage by the will of God). Simone de Beauvoir labels such women "mutilated" and "immanent".


title: Feminist theory

text: Intersectionality is the examination of various ways in which people are oppressed, based on the relational web of dominating factors of race, sex, class, nation and sexual orientation. Intersectionality "describes the simultaneous, multiple, overlapping, and contradictory systems of power that shape our lives and political options". While this theory can be applied to all people, and more particularly all women, it is specifically mentioned and studied within the realms of black feminism. Patricia Hill Collins argues that black women in particular, have a unique perspective on the oppression of the world as unlike white women, they face both racial and gender oppression simultaneously, among other factors. This debate raises the issue of understanding the oppressive lives of women that are not only shaped by gender alone but by other elements such as racism, classism, ageism, heterosexism, ableism etc.


title: Feminist theory

text: In this debate, women writers have addressed the issues of masculinized writing through male gendered language that may not serve to accommodate the literary understanding of women's lives. Such masculinized language that feminist theorists address is the use of, for example, "God the Father", which is looked upon as a way of designating the sacred as solely men (or, in other words, biblical language glorifies men through all of the masculine pronouns like "he" and "him" and addressing God as a "He"). Feminist theorists attempt to reclaim and redefine women through a deeper thinking of language. For example, feminist theorists have used the term "womyn" instead of "women". Some feminist theorists have suggested using neutral terminology when naming jobs (for example, police officer versus policeman or mail carrier versus mailman). Some feminist theorists have reclaimed and redefined such words as "dyke" and "bitch".


title: Feminist theory

text: Feminist psychology is a form of psychology centered on societal structures and gender. Feminist psychology critiques the fact that historically psychological research has been done from a male perspective with the view that males are the norm. Feminist psychology is oriented on the values and principles of feminism. It incorporates gender and the ways women are affected by issues resulting from it. Ethel Dench Puffer Howes was one of the first women to enter the field of psychology. She was the executive secretary of the National College Equal Suffrage League in 1914.


title: Feminist theory

text: One major psychological theory, "relational-cultural theory", is based on the work of Jean Baker Miller, whose book "Toward a New Psychology of Women" proposes that "growth-fostering relationships are a central human necessity and that disconnections are the source of psychological problems". Inspired by Betty Friedan's "Feminine Mystique", and other feminist classics from the 1960s, relational-cultural theory proposes that "isolation is one of the most damaging human experiences and is best treated by reconnecting with other people", and that a therapist should "foster an atmosphere of empathy and acceptance for the patient, even at the cost of the therapist's neutrality". The theory is based on clinical observations and sought to prove that "there was nothing wrong with women, but rather with the way modern culture viewed them".


title: Feminist theory

text: Psychoanalytic feminism and feminist psychoanalysis are based on Freud and his psychoanalytic theories, but they also supply an important critique of it. It maintains that gender is not biological but is based on the psycho-sexual development of the individual, but also that sexual difference and gender are different notions. Psychoanalytical feminists believe that gender inequality comes from early childhood experiences, which lead men to believe themselves to be masculine, and women to believe themselves feminine. It is further maintained that gender leads to a social system that is dominated by males, which in turn influences the individual psycho-sexual development. As a solution it was suggested by some to avoid the gender-specific structuring of the society coeducation. From the last 30 years of the 20th century, the contemporary French psychoanalytical theories concerning the feminine, that refer to sexual difference rather than to gender, with psychoanalysts like Julia Kristeva, Maud Mannoni, Luce Irigaray, and Bracha Ettinger that invented the concept matrixial space and matrixial Feminist ethics, , , have largely influenced not only feminist theory but also the understanding of the subject in philosophy, art, aesthetics and ethics and the general field of psychoanalysis itself. These French psychoanalysts are mainly post-Lacanian. Other feminist psychoanalysts and feminist theorists whose contributions have enriched the field through an engagement with psychoanalysis are Jessica Benjamin, Jacqueline Rose, Ranjana Khanna, and Shoshana Felman.


title: Feminist theory

text: Feminist literary criticism is literary criticism informed by feminist theories or politics. Its history has been varied, from classic works of female authors such as George Eliot, Virginia Woolf, and Margaret Fuller to recent theoretical work in women's studies and gender studies by "third-wave" authors.


title: Feminist theory

text: In the most general terms, feminist literary criticism before the 1970s was concerned with the politics of women's authorship and the representation of women's condition within literature. Since the arrival of more complex conceptions of gender and subjectivity, feminist literary criticism has taken a variety of new routes. It has considered gender in the terms of Freudian and Lacanian psychoanalysis, as part of the deconstruction of existing power relations.


title: Feminist theory

text: Many feminist film critics, such as Laura Mulvey, have pointed to the "male gaze" that predominates in classical Hollywood film making. Through the use of various film techniques, such as shot reverse shot, the viewers are led to align themselves with the point of view of a male protagonist. Notably, women function as objects of this gaze far more often than as proxies for the spectator. Feminist film theory of the last twenty years is heavily influenced by the general transformation in the field of aesthetics, including the new options of articulating the gaze, offered by psychoanalytical French feminism, like Bracha Ettinger's feminine, maternal and matrixial gaze.


title: Feminist theory

text: Linda Nochlin and Griselda Pollock are prominent art historians writing on contemporary and modern artists and articulating Art history from a feminist perspective since the 1970s. Pollock works with French psychoanalysis, and in particular with Kristeva's and Ettinger's theories, to offer new insights into art history and contemporary art with special regard to questions of trauma and trans-generation memory in the works of women artists. Other prominent feminist art historians include: Norma Broude and Mary Garrard; Amelia Jones; Mieke Bal; Carol Duncan; Lynda Nead; Lisa Tickner; Tamar Garb; Hilary Robinson; Katy Deepwell.


title: Feminist theory

text: Feminist history refers to the re-reading and re-interpretation of history from a feminist perspective. It is not the same as the history of feminism, which outlines the origins and evolution of the feminist movement. It also differs from women's history, which focuses on the role of women in historical events. The goal of feminist history is to explore and illuminate the female viewpoint of history through rediscovery of female writers, artists, philosophers, etc., in order to recover and demonstrate the significance of women's voices and choices in the past.


title: Feminist theory

text: Feminist geography is often considered part of a broader postmodern approach to the subject which is not primarily concerned with the development of conceptual theory in itself but rather focuses on the real experiences of individuals and groups in their own localities, upon the geographies that they live in within their own communities. In addition to its analysis of the real world, it also critiques existing geographical and social studies, arguing that academic traditions are delineated by patriarchy, and that contemporary studies which do not confront the nature of previous work reinforce the male bias of academic study.


title: Feminist theory

text: The Feminist philosophy refers to a philosophy approached from a feminist perspective. Feminist philosophy involves attempts to use methods of philosophy to further the cause of the feminist movements, it also tries to criticize and/or reevaluate the ideas of traditional philosophy from within a feminist view. This critique stems from the dichotomy Western philosophy has conjectured with the mind and body phenomena. There is no specific school for feminist philosophy like there has been in regard to other theories. This means that Feminist philosophers can be found in the analytic and continental traditions, and the different viewpoints taken on philosophical issues with those traditions. Feminist philosophers also have many different viewpoints taken on philosophical issues within those traditions. Feminist philosophers who are feminists can belong to many different varieties of feminism. The writings of Judith Butler, Rosi Braidotti, Donna Haraway, Bracha Ettinger and Avital Ronell are the most significant psychoanalytically informed influences on contemporary feminist philosophy.


title: Feminist theory

text: Feminist sexology is an offshoot of traditional studies of sexology that focuses on the intersectionality of sex and gender in relation to the sexual lives of women. Feminist sexology shares many principles with the wider field of sexology; in particular, it does not try to prescribe a certain path or "normality" for women's sexuality, but only observe and note the different and varied ways in which women express their sexuality. Looking at sexuality from a feminist point of view creates connections between the different aspects of a person's sexual life.


title: Feminist theory

text: From feminists' perspectives, sexology, which is the study of human sexuality and sexual relationship, relates to the intersectionality of gender, race and sexuality. Men have dominant power and control over women in the relationship, and women are expected to hide their true feeling about sexual behaviors. Women of color face even more sexual violence in the society. Some countries in Africa and Asia even practice female genital cutting, controlling women's sexual desire and limiting their sexual behavior. Moreover, Bunch, the women's and human rights activist, states that society used to see lesbianism as a threat to male supremacy and to the political relationships between men and women. Therefore, in the past, people viewed being a lesbian as a sin and made it death penalty. Even today, many people still discriminate homosexuals. Many lesbians hide their sexuality and face even more sexual oppression.


title: Feminist theory

text: Monosexual Paradigm is a term coined by Blasingame, a self-identified African American, bisexual female. Blasingame used this term to address the lesbian and gay communities who turned a blind eye to the dichotomy that oppressed bisexuals from both heterosexual and homosexual communities. This oppression negatively affects the gay and lesbian communities more so than the heterosexual community due to its contradictory exclusiveness of bisexuals.