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It is still possible for two sounds of indefinite pitch to clearly be higher or lower than one another. For instance, a snare drum sounds higher pitched than a bass drum though both have indefinite pitch, because its sound contains higher frequencies. In other words, it is possible and often easy to roughly discern the relative pitches of two sounds of indefinite pitch, but sounds of indefinite pitch do not neatly correspond to any specific pitch. A special type of pitch often occurs in free nature when sound reaches the ear of an observer directly from the source, and also after reflecting off a sound-reflecting surface. This phenomenon is called repetition pitch, because the addition of a true repetition of the original sound to itself is the basic prerequisite.
For example, one might refer to the A above middle C as a', A4, or 440 Hz. In standard Western equal temperament, the notion of pitch is insensitive to "spelling": the description "G4 double sharp" refers to the same pitch as A4; in other temperaments, these may be distinct pitches. Human perception of musical intervals is approximately logarithmic with respect to fundamental frequency: the perceived interval between the pitches "A220" and "A440" is the same as the perceived interval between the pitches A440 and A880. Motivated by this logarithmic perception, music theorists sometimes represent pitches using a numerical scale based on the logarithm of fundamental frequency. For example, one can adopt the widely used MIDI standard to map fundamental frequency, f, to a real number, p, as follows
Temporal theories offer an alternative that appeals to the temporal structure of action potentials, mostly the phase-locking and mode-locking of action potentials to frequencies in a stimulus. The precise way this temporal structure helps code for pitch at higher levels is still debated, but the processing seems to be based on an autocorrelation of action potentials in the auditory nerve. However, it has long been noted that a neural mechanism that may accomplish a delay—a necessary operation of a true autocorrelation—has not been found. At least one model shows that a temporal delay is unnecessary to produce an autocorrelation model of pitch perception, appealing to phase shifts between cochlear filters; however, earlier work has shown that certain sounds with a prominent peak in their autocorrelation function do not elicit a corresponding pitch percept, and that certain sounds without a peak in their autocorrelation function nevertheless elicit a pitch. To be a more complete model, autocorrelation must therefore apply to signals that represent the output of the cochlea, as via auditory-nerve interspike-interval histograms. Some theories of pitch perception hold that pitch has inherent octave ambiguities, and therefore is best decomposed into a pitch chroma, a periodic value around the octave, like the note names in western music—and a pitch height, which may be ambiguous, that indicates the octave the pitch is in.
The motif of the England national football team has three lions passant guardant, the emblem of King Richard I, who reigned from 1189 to 1199. The lions, often blue, have had minor changes to colour and appearance. Initially topped by a crown, this was removed in 1949 when the FA was given an official coat of arms by the College of Arms; this introduced ten Tudor roses, one for each of the regional branches of the FA. Since 2003, England top their logo with a star to recognise their World Cup win in 1966; this was first embroidered onto the left sleeve of the home kit, and a year later was moved to its current position, first on the away shirt.
Although England's first away kits were blue, England's traditional away colours are red shirts, white shorts and red socks. In 1996, England's away kit was changed to grey shirts, shorts and socks. This kit was only worn three times, including against Germany in the semi-final of Euro 96 but the deviation from the traditional red was unpopular with supporters and the England away kit remained red until 2011, when a navy blue away kit was introduced. The away kit is also sometimes worn during home matches, when a new edition has been released to promote it.
England failed to qualify for the World Cup in 1974, 1978 and 1994. The team's earliest exit in the competition itself was its elimination in the first round in 1950, 1958 and most recently in the 2014 FIFA World Cup, after being defeated in both their opening two matches for the first time, versus Italy and Uruguay in Group D. In 1950, four teams remained after the first round, in 1958 eight teams remained and in 2014 sixteen teams remained. In 2010, England suffered its most resounding World Cup defeat (4–1 to Germany) in the Round of 16, after drawing with the United States and Algeria and defeating Slovenia 1–0 in the group stage.
Their first ever defeat on home soil to a foreign team was an 0–2 loss to the Republic of Ireland, on 21 September 1949 at Goodison Park. A 6–3 loss in 1953 to Hungary, was their second defeat by a foreign team at Wembley. In the return match in Budapest, Hungary won 7–1. This still stands as England's worst ever defeat. After the game, a bewildered Syd Owen said, "it was like playing men from outer space". In the 1954 FIFA World Cup, England reached the quarter-finals for the first time, and lost 4–2 to reigning champions Uruguay.
In February 2012, Capello resigned from his role as England manager, following a disagreement with the FA over their request to remove John Terry from team captaincy after accusations of racial abuse concerning the player. Following this, there was media speculation that Harry Redknapp would take the job. However, on 1 May 2012, Roy Hodgson was announced as the new manager, just six weeks before UEFA Euro 2012. England managed to finish top of their group, winning two and drawing one of their fixtures, but exited the Championships in the quarter-finals via a penalty shoot-out, this time to Italy.
The England national football team represents England and the Crown Dependencies of Jersey, Guernsey and the Isle of Man for football matches as part of FIFA-authorised events, and is controlled by The Football Association, the governing body for football in England. England are one of the two oldest national teams in football; alongside Scotland, whom they played in the world's first international football match in 1872. England's home ground is Wembley Stadium, London, and the current team manager is Roy Hodgson.
To begin with, England had no permanent home stadium. They joined FIFA in 1906 and played their first ever games against countries other than the Home Nations on a tour of Central Europe in 1908. Wembley Stadium was opened in 1923 and became their home ground. The relationship between England and FIFA became strained, and this resulted in their departure from FIFA in 1928, before they rejoined in 1946. As a result, they did not compete in a World Cup until 1950, in which they were beaten in a 1–0 defeat by the United States, failing to get past the first round in one of the most embarrassing defeats in the team's history.
England is quite a successful nation at the UEFA European Football Championship, having finished in third place in 1968 and reached the semi-final in 1996. England hosted Euro 96 and have appeared in eight UEFA European Championship Finals tournaments, tied for ninth-best. The team has also reached the quarter-final on two recent occasions in 2004 and 2012. The team's worst result in the competition was a first-round elimination in 1980, 1988, 1992 and 2000. The team did not enter in 1960, and they failed to qualify in 1964, 1972, 1976, 1984, and 2008.
England qualified for the 1970 FIFA World Cup in Mexico as reigning champions, and reached the quarter-finals, where they were knocked out by West Germany. England had been 2–0 up, but were eventually beaten 3–2 after extra time. They failed in qualification for the 1974, leading to Ramsey's dismissal, and 1978 FIFA World Cups. Under Ron Greenwood, they managed to qualify for the 1982 FIFA World Cup in Spain (the first time competitively since 1962); despite not losing a game, they were eliminated in the second group stage.
Sven-Göran Eriksson took charge of the team between 2001 and 2006, and was the first non–English manager of England. Despite controversial press coverage of his personal life, Eriksson was consistently popular with the majority of fans.[citation needed] He guided England to the quarter-finals of the 2002 FIFA World Cup, UEFA Euro 2004, and the 2006 FIFA World Cup. He lost only five competitive matches during his tenure, and England rose to an No.4 world ranking under his guidance. His contract was extended by the Football Association by two years, to include UEFA Euro 2008. However, it was terminated by them at the 2006 FIFA World Cup's conclusion.
All England matches are broadcast with full commentary on BBC Radio 5 Live. From the 2008–09 season until the 2017–18 season, England's home and away qualifiers, and friendlies both home and away are broadcast live on ITV (often with the exception of STV, the ITV affiliate in central and northern Scotland). England's away qualifiers for the 2010 World Cup were shown on Setanta Sports until that company's collapse. As a result of Setanta Sports's demise, England's World Cup qualifier in Ukraine on 10 October 2009 was shown in the United Kingdom on a pay-per-view basis via the internet only. This one-off event was the first time an England game had been screened in such a way. The number of subscribers, paying between £4.99 and £11.99 each, was estimated at between 250,000 and 300,000 and the total number of viewers at around 500,000.
England first appeared at the 1950 FIFA World Cup and have appeared in 14 FIFA World Cups, they are tied for sixth-best in terms of number of wins alongside France and Spain. The national team is one of eight national teams to have won at least one FIFA World Cup title. The England team won their first and only World Cup title in 1966. The tournament was played on home soil and England defeated Germany 4–2 in the final. In 1990, England finished in fourth place, losing 2–1 to host nation Italy in the third place play-off after losing on penalties to champions Germany in the semi-final. The team has also reached the quarter-final on two recent occasions in 2002 and 2006. Previously, they reached this stage in 1954, 1962, 1970 and 1986.
In August 1836, two real estate entrepreneurs—Augustus Chapman Allen and John Kirby Allen—from New York, purchased 6,642 acres (26.88 km2) of land along Buffalo Bayou with the intent of founding a city. The Allen brothers decided to name the city after Sam Houston, the popular general at the Battle of San Jacinto, who was elected President of Texas in September 1836. The great majority of slaves in Texas came with their owners from the older slave states. Sizable numbers, however, came through the domestic slave trade. New Orleans was the center of this trade in the Deep South, but there were slave dealers in Houston. Thousands of enslaved African-Americans lived near the city before the Civil War. Many of them near the city worked on sugar and cotton plantations, while most of those in the city limits had domestic and artisan jobs. In 1860 forty-nine percent of the city's population was enslaved. A few slaves, perhaps as many as 2,000 between 1835 and 1865, came through the illegal African trade. Post-war Texas grew rapidly as migrants poured into the cotton lands of the state. They also brought or purchased enslaved African Americans, whose numbers nearly tripled in the state from 1850 to 1860, from 58,000 to 182,566.
When World War II started, tonnage levels at the port decreased and shipping activities were suspended; however, the war did provide economic benefits for the city. Petrochemical refineries and manufacturing plants were constructed along the ship channel because of the demand for petroleum and synthetic rubber products by the defense industry during the war. Ellington Field, initially built during World War I, was revitalized as an advanced training center for bombardiers and navigators. The Brown Shipbuilding Company was founded in 1942 to build ships for the U.S. Navy during World War II. Due to the boom in defense jobs, thousands of new workers migrated to the city, both blacks and whites competing for the higher-paying jobs. President Roosevelt had established a policy of non-discrimination for defense contractors, and blacks gained some opportunities, especially in shipbuilding, although not without resistance from whites and increasing social tensions that erupted into occasional violence. Economic gains of blacks who entered defense industries continued in the postwar years.
One wave of the population boom ended abruptly in the mid-1980s, as oil prices fell precipitously. The space industry also suffered in 1986 after the Space Shuttle Challenger disintegrated shortly after launch. There was a cutback in some activities for a period. In the late 1980s, the city's economy suffered from the nationwide recession. After the early 1990s recession, Houston made efforts to diversify its economy by focusing on aerospace and health care/biotechnology, and reduced its dependence on the petroleum industry. Since the increase of oil prices in the 2000s, the petroleum industry has again increased its share of the local economy.
Underpinning Houston's land surface are unconsolidated clays, clay shales, and poorly cemented sands up to several miles deep. The region's geology developed from river deposits formed from the erosion of the Rocky Mountains. These sediments consist of a series of sands and clays deposited on decaying organic marine matter, that over time, transformed into oil and natural gas. Beneath the layers of sediment is a water-deposited layer of halite, a rock salt. The porous layers were compressed over time and forced upward. As it pushed upward, the salt dragged surrounding sediments into salt dome formations, often trapping oil and gas that seeped from the surrounding porous sands. The thick, rich, sometimes black, surface soil is suitable for rice farming in suburban outskirts where the city continues to grow.
In the 1960s, Downtown Houston consisted of a collection of mid-rise office structures. Downtown was on the threshold of an energy industry–led boom in 1970. A succession of skyscrapers were built throughout the 1970s—many by real estate developer Gerald D. Hines—culminating with Houston's tallest skyscraper, the 75-floor, 1,002-foot (305 m)-tall JPMorgan Chase Tower (formerly the Texas Commerce Tower), completed in 1982. It is the tallest structure in Texas, 15th tallest building in the United States, and the 85th tallest skyscraper in the world, based on highest architectural feature. In 1983, the 71-floor, 992-foot (302 m)-tall Wells Fargo Plaza (formerly Allied Bank Plaza) was completed, becoming the second-tallest building in Houston and Texas. Based on highest architectural feature, it is the 17th tallest in the United States and the 95th tallest in the world. In 2007, downtown Houston had over 43 million square feet (4,000,000 m²) of office space.
In 2006, the Houston metropolitan area ranked first in Texas and third in the U.S. within the Category of "Best Places for Business and Careers" by Forbes magazine. Foreign governments have established 92 consular offices in Houston's metropolitan area, the third highest in the nation. Forty foreign governments maintain trade and commercial offices here and 23 active foreign chambers of commerce and trade associations. Twenty-five foreign banks representing 13 nations operate in Houston, providing financial assistance to the international community.
Many annual events celebrate the diverse cultures of Houston. The largest and longest running is the annual Houston Livestock Show and Rodeo, held over 20 days from early to late March, is the largest annual livestock show and rodeo in the world. Another large celebration is the annual night-time Houston Pride Parade, held at the end of June. Other annual events include the Houston Greek Festival, Art Car Parade, the Houston Auto Show, the Houston International Festival, and the Bayou City Art Festival, which is considered to be one of the top five art festivals in the United States.
Of the 10 most populous U.S. cities, Houston has the most total area of parks and green space, 56,405 acres (228 km2). The city also has over 200 additional green spaces—totaling over 19,600 acres (79 km2) that are managed by the city—including the Houston Arboretum and Nature Center. The Lee and Joe Jamail Skatepark is a public skatepark owned and operated by the city of Houston, and is one of the largest skateparks in Texas consisting of 30,000 (2,800 m2) square foot in-ground facility. The Gerald D. Hines Waterwall Park—located in the Uptown District of the city—serves as a popular tourist attraction, weddings, and various celebrations. A 2011 study by Walk Score ranked Houston the 23rd most walkable of the 50 largest cities in the United States. Wet'n'Wild SplashTown is a water park located north of Houston.
The city of Houston has a strong mayoral form of municipal government. Houston is a home rule city and all municipal elections in the state of Texas are nonpartisan. The City's elected officials are the mayor, city controller and 16 members of the Houston City Council. The current mayor of Houston is Sylvester Turner, a Democrat elected on a nonpartisan ballot. Houston's mayor serves as the city's chief administrator, executive officer, and official representative, and is responsible for the general management of the city and for seeing that all laws and ordinances are enforced.
The Houston–The Woodlands–Sugar Land metropolitan area is served by one public television station and two public radio stations. KUHT (HoustonPBS) is a PBS member station and is the first public television station in the United States. Houston Public Radio is listener-funded and comprises two NPR member stations: KUHF (KUHF News) and KUHA (Classical 91.7). KUHF is news/talk radio and KUHA is a classical music station. The University of Houston System owns and holds broadcasting licenses to KUHT, KUHF, and KUHA. The stations broadcast from the Melcher Center for Public Broadcasting, located on the campus of the University of Houston.
Houston (i/ˈhjuːstən/ HYOO-stən) is the most populous city in Texas and the fourth most populous city in the United States, located in Southeast Texas near the Gulf of Mexico. With a census-estimated 2014 population of 2.239 million people, within a land area of 599.6 square miles (1,553 km2), it also is the largest city in the Southern United States, as well as the seat of Harris County. It is the principal city of Houston–The Woodlands–Sugar Land, which is the fifth most populated metropolitan area in the United States.
By 1860, Houston had emerged as a commercial and railroad hub for the export of cotton. Railroad spurs from the Texas inland converged in Houston, where they met rail lines to the ports of Galveston and Beaumont. During the American Civil War, Houston served as a headquarters for General John Bankhead Magruder, who used the city as an organization point for the Battle of Galveston. After the Civil War, Houston businessmen initiated efforts to widen the city's extensive system of bayous so the city could accept more commerce between downtown and the nearby port of Galveston. By 1890, Houston was the railroad center of Texas.
In August 2005, Houston became a shelter to more than 150,000 people from New Orleans who evacuated from Hurricane Katrina. One month later, approximately 2.5 million Houston area residents evacuated when Hurricane Rita approached the Gulf Coast, leaving little damage to the Houston area. This was the largest urban evacuation in the history of the United States. In September 2008, Houston was hit by Hurricane Ike. As many as forty percent refused to leave Galveston Island because they feared the traffic problems that happened after Hurricane Rita.
Though Houston is the largest city in the United States without formal zoning regulations, it has developed similarly to other Sun Belt cities because the city's land use regulations and legal covenants have played a similar role. Regulations include mandatory lot size for single-family houses and requirements that parking be available to tenants and customers. Such restrictions have had mixed results. Though some have blamed the city's low density, urban sprawl, and lack of pedestrian-friendliness on these policies, the city's land use has also been credited with having significant affordable housing, sparing Houston the worst effects of the 2008 real estate crisis. The city issued 42,697 building permits in 2008 and was ranked first in the list of healthiest housing markets for 2009.
The Houston area is a leading center for building oilfield equipment. Much of its success as a petrochemical complex is due to its busy ship channel, the Port of Houston. In the United States, the port ranks first in international commerce and tenth among the largest ports in the world. Unlike most places, high oil and gasoline prices are beneficial for Houston's economy, as many of its residents are employed in the energy industry. Houston is the beginning or end point of numerous oil, gas, and products pipelines:
The Houston Theater District, located downtown, is home to nine major performing arts organizations and six performance halls. It is the second-largest concentration of theater seats in a downtown area in the United States. Houston is one of few United States cities with permanent, professional, resident companies in all major performing arts disciplines: opera (Houston Grand Opera), ballet (Houston Ballet), music (Houston Symphony Orchestra), and theater (The Alley Theatre). Houston is also home to folk artists, art groups and various small progressive arts organizations. Houston attracts many touring Broadway acts, concerts, shows, and exhibitions for a variety of interests. Facilities in the Theater District include the Jones Hall—home of the Houston Symphony Orchestra and Society for the Performing Arts—and the Hobby Center for the Performing Arts.
The Theater District is a 17-block area in the center of downtown Houston that is home to the Bayou Place entertainment complex, restaurants, movies, plazas, and parks. Bayou Place is a large multilevel building containing full-service restaurants, bars, live music, billiards, and Sundance Cinema. The Bayou Music Center stages live concerts, stage plays, and stand-up comedy. Space Center Houston is the official visitors' center of NASA's Lyndon B. Johnson Space Center. The Space Center has many interactive exhibits including moon rocks, a shuttle simulator, and presentations about the history of NASA's manned space flight program. Other tourist attractions include the Galleria (Texas's largest shopping mall, located in the Uptown District), Old Market Square, the Downtown Aquarium, and Sam Houston Race Park.
Minute Maid Park (home of the Astros) and Toyota Center (home of the Rockets), are located in downtown Houston. Houston has the NFL's first retractable-roof stadium with natural grass, NRG Stadium (home of the Texans). Minute Maid Park is also a retractable-roof stadium. Toyota Center also has the largest screen for an indoor arena in the United States built to coincide with the arena's hosting of the 2013 NBA All-Star Game. BBVA Compass Stadium is a soccer-specific stadium for the Dynamo, the Texas Southern University football team, and Dash, located in East Downtown. In addition, NRG Astrodome was the first indoor stadium in the world, built in 1965. Other sports facilities include Hofheinz Pavilion (Houston Cougars basketball), Rice Stadium (Rice Owls football), and Reliant Arena. TDECU Stadium is where the University of Houston Houston Cougars football team plays. Houston has hosted several major sports events: the 1968, 1986 and 2004 Major League Baseball All-Star Games; the 1989, 2006 and 2013 NBA All-Star Games; Super Bowl VIII and Super Bowl XXXVIII, as well as hosting the 2005 World Series and 1981, 1986, 1994 and 1995 NBA Finals, winning the latter two. Super Bowl LI is currently slated to be hosted in NRG Stadium in 2017.
Several private institutions of higher learning—ranging from liberal arts colleges, such as The University of St. Thomas, Houston's only Catholic university, to Rice University, the nationally recognized research university—are located within the city. Rice, with a total enrollment of slightly more than 6,000 students, has a number of distinguished graduate programs and research institutes, such as the James A. Baker Institute for Public Policy. Houston Baptist University, affiliated with the Baptist General Convention of Texas, offers bachelor's and graduate degrees. It was founded in 1960 and is located in the Sharpstown area in Southwest Houston.
Houston is the seat of the internationally renowned Texas Medical Center, which contains the world's largest concentration of research and healthcare institutions. All 49 member institutions of the Texas Medical Center are non-profit organizations. They provide patient and preventive care, research, education, and local, national, and international community well-being. Employing more than 73,600 people, institutions at the medical center include 13 hospitals and two specialty institutions, two medical schools, four nursing schools, and schools of dentistry, public health, pharmacy, and virtually all health-related careers. It is where one of the first—and still the largest—air emergency service, Life Flight, was created, and a very successful inter-institutional transplant program was developed. More heart surgeries are performed at the Texas Medical Center than anywhere else in the world.
Houston was the headquarters of Continental Airlines until its 2010 merger with United Airlines with headquarters in Chicago; regulatory approval for the merger was granted in October of that year. Bush Intercontinental became United Airlines' largest airline hub. The airline retained a significant operational presence in Houston while offering more than 700 daily departures from the city. In early 2007, Bush Intercontinental Airport was named a model "port of entry" for international travelers by U.S. Customs and Border Protection.
Houston's economy has a broad industrial base in energy, manufacturing, aeronautics, and transportation. It is also leading in health care sectors and building oilfield equipment; only New York City is home to more Fortune 500 headquarters within its city limits. The Port of Houston ranks first in the United States in international waterborne tonnage handled and second in total cargo tonnage handled. Nicknamed the Space City, Houston is a global city, with strengths in business, international trade, entertainment, culture, media, fashion, science, sports, technology, education, medicine and research. The city has a population from various ethnic and religious backgrounds and a large and growing international community. Houston is the most diverse city in Texas and has been described as the most diverse in the United States. It is home to many cultural institutions and exhibits, which attract more than 7 million visitors a year to the Museum District. Houston has an active visual and performing arts scene in the Theater District and offers year-round resident companies in all major performing arts.
Houston has mild winters in contrast to most areas of the United States. In January, the normal mean temperature at Intercontinental Airport is 53.1 °F (11.7 °C), while that station has an average of 13 days with a low at or below freezing. Snowfall is rare. Recent snow events in Houston include a storm on December 24, 2004 when one inch (2.5 cm) of snow accumulated in parts of the metro area. Falls of at least one inch on both December 10, 2008 and December 4, 2009 marked the first time measurable snowfall had occurred in two consecutive years in the city's recorded history. The coldest temperature officially recorded in Houston was 5 °F (−15 °C) on January 18, 1940. Houston has historically received an ample amount of rainfall, averaging about 49.8 in (1,260 mm) annually per 1981–2010 normals. Localized flooding often occurs, owing to the extremely flat topography and widespread typical clay-silt prairie soils, which do not drain quickly.
The University of Houston System's annual impact on the Houston area's economy equates to that of a major corporation: $1.1 billion in new funds attracted annually to the Houston area, $3.13 billion in total economic benefit and 24,000 local jobs generated. This is in addition to the 12,500 new graduates the U.H. System produces every year who enter the workforce in Houston and throughout the state of Texas. These degree-holders tend to stay in Houston. After five years, 80.5% of graduates are still living and working in the region.
Houston was founded in 1836 on land near the banks of Buffalo Bayou (now known as Allen's Landing) and incorporated as a city on June 5, 1837. The city was named after former General Sam Houston, who was president of the Republic of Texas and had commanded and won at the Battle of San Jacinto 25 miles (40 km) east of where the city was established. The burgeoning port and railroad industry, combined with oil discovery in 1901, has induced continual surges in the city's population. In the mid-twentieth century, Houston became the home of the Texas Medical Center—the world's largest concentration of healthcare and research institutions—and NASA's Johnson Space Center, where the Mission Control Center is located.
Located in the American South, Houston is a diverse city with a large and growing international community. The metropolitan area is home to an estimated 1.1 million (21.4 percent) residents who were born outside the United States, with nearly two-thirds of the area's foreign-born population from south of the United States–Mexico border. Additionally, more than one in five foreign-born residents are from Asia. The city is home to the nation's third-largest concentration of consular offices, representing 86 countries.
In 1900, after Galveston was struck by a devastating hurricane, efforts to make Houston into a viable deep-water port were accelerated. The following year, oil discovered at the Spindletop oil field near Beaumont prompted the development of the Texas petroleum industry. In 1902, President Theodore Roosevelt approved a $1 million improvement project for the Houston Ship Channel. By 1910 the city's population had reached 78,800, almost doubling from a decade before. African-Americans formed a large part of the city's population, numbering 23,929 people, or nearly one-third of the residents.
According to the United States Census Bureau, the city has a total area of 656.3 square miles (1,700 km2); this comprises 634.0 square miles (1,642 km2) of land and 22.3 square miles (58 km2) of water. The Piney Woods is north of Houston. Most of Houston is located on the gulf coastal plain, and its vegetation is classified as temperate grassland and forest. Much of the city was built on forested land, marshes, swamp, or prairie which resembles the Deep South, and are all still visible in surrounding areas. Flatness of the local terrain, when combined with urban sprawl, has made flooding a recurring problem for the city. Downtown stands about 50 feet (15 m) above sea level, and the highest point in far northwest Houston is about 125 feet (38 m) in elevation. The city once relied on groundwater for its needs, but land subsidence forced the city to turn to ground-level water sources such as Lake Houston, Lake Conroe and Lake Livingston. The city owns surface water rights for 1.20 billion gallons of water a day in addition to 150 million gallons a day worth of groundwater.
During the summer months, it is common for temperatures to reach over 90 °F (32 °C), with an average of 106.5 days per year, including a majority from June to September, with a high of 90 °F or above and 4.6 days at or over 100 °F (38 °C). However, humidity usually yields a higher heat index. Summer mornings average over 90 percent relative humidity. Winds are often light in the summer and offer little relief, except in the far southeastern outskirts near the Gulf coast and Galveston. To cope with the strong humidity and heat, people use air conditioning in nearly every vehicle and building. In 1980, Houston was described as the "most air-conditioned place on earth". Officially, the hottest temperature ever recorded in Houston is 109 °F (43 °C), which was reached both on September 4, 2000 and August 28, 2011.
Houston is considered to be a politically divided city whose balance of power often sways between Republicans and Democrats. Much of the city's wealthier areas vote Republican while the city's working class and minority areas vote Democratic. According to the 2005 Houston Area Survey, 68 percent of non-Hispanic whites in Harris County are declared or favor Republicans while 89 percent of non-Hispanic blacks in the area are declared or favor Democrats. About 62 percent Hispanics (of any race) in the area are declared or favor Democrats. The city has often been known to be the most politically diverse city in Texas, a state known for being generally conservative. As a result, the city is often a contested area in statewide elections. In 2009, Houston became the first US city with a population over 1 million citizens to elect a gay mayor, by electing Annise Parker.
According to the 2010 Census, whites made up 51% of Houston's population; 26% of the total population were non-Hispanic whites. Blacks or African Americans made up 25% of Houston's population. American Indians made up 0.7% of the population. Asians made up 6% (1.7% Vietnamese, 1.3% Chinese, 1.3% Indian, 0.9% Pakistani, 0.4% Filipino, 0.3% Korean, 0.1% Japanese), while Pacific Islanders made up 0.1%. Individuals from some other race made up 15.2% of the city's population, of which 0.2% were non-Hispanic. Individuals from two or more races made up 3.3% of the city. At the 2000 Census, there were 1,953,631 people and the population density was 3,371.7 people per square mile (1,301.8/km²). The racial makeup of the city was 49.3% White, 25.3% African American, 5.3% Asian, 0.7% American Indian, 0.1% Pacific Islander, 16.5% from some other race, and 3.1% from two or more races. In addition, Hispanics made up 37.4% of Houston's population while non-Hispanic whites made up 30.8%, down from 62.4% in 1970.
The Houston–The Woodlands–Sugar Land MSA's gross domestic product (GDP) in 2012 was $489 billion, making it the fourth-largest of any metropolitan area in the United States and larger than Austria's, Venezuela's, or South Africa's GDP. Only 26 countries other than the United States have a gross domestic product exceeding Houston's regional gross area product (GAP). In 2010, mining (which consists almost entirely of exploration and production of oil and gas in Houston) accounted for 26.3% of Houston's GAP up sharply in response to high energy prices and a decreased worldwide surplus of oil production capacity, followed by engineering services, health services, and manufacturing.
The Baylor College of Medicine has annually been considered within the top ten medical schools in the nation; likewise, the MD Anderson Cancer Center has consistently ranked as one of the top two U.S. hospitals specializing in cancer care by U.S. News & World Report since 1990. The Menninger Clinic, a renowned psychiatric treatment center, is affiliated with Baylor College of Medicine and The Methodist Hospital System. With hospital locations nationwide and headquarters in Houston, the Triumph Healthcare hospital system is the third largest long term acute care provider nationally.
In 2013, Houston was identified as the #1 U.S. city for job creation by the U.S. Bureau of Statistics after it was not only the first major city to regain all the jobs lost in the preceding economic downturn, but after the crash, more than two jobs were added for every one lost. Economist and vice president of research at the Greater Houston Partnership Patrick Jankowski attributed Houston's success to the ability of the region's real estate and energy industries to learn from historical mistakes. Furthermore, Jankowski stated that "more than 100 foreign-owned companies relocated, expanded or started new businesses in Houston" between 2008 and 2010, and this openness to external business boosted job creation during a period when domestic demand was problematically low. Also in 2013, Houston again appeared on Forbes' list of Best Places for Business and Careers.
Three community college districts exist with campuses in and around Houston. The Houston Community College System serves most of Houston. The northwestern through northeastern parts of the city are served by various campuses of the Lone Star College System, while the southeastern portion of Houston is served by San Jacinto College, and a northeastern portion is served by Lee College. The Houston Community College and Lone Star College systems are within the 10 largest institutions of higher learning in the United States.
METRO began light rail service on January 1, 2004, with the inaugural track ("Red Line") running about 8 miles (13 km) from the University of Houston–Downtown (UHD), which traverses through the Texas Medical Center and terminates at NRG Park. METRO is currently in the design phase of a 10-year expansion plan that will add five more lines. and expand the current Red Line. Amtrak, the national passenger rail system, provides service three times a week to Houston via the Sunset Limited (Los Angeles–New Orleans), which stops at a train station on the north side of the downtown area. The station saw 14,891 boardings and alightings in fiscal year 2008. In 2012, there was a 25 percent increase in ridership to 20,327 passengers embarking from the Houston Amtrak station.
The second-largest commercial airport is William P. Hobby Airport (named Houston International Airport until 1967) which operates primarily short- to medium-haul domestic flights. However, in 2015 Southwest Airlines launched service from a new international terminal at Hobby airport to several destinations in Mexico, Central America, and the Caribbean. These were the first international flights flown from Hobby since 1969. Houston's aviation history is showcased in the 1940 Air Terminal Museum located in the old terminal building on the west side of the airport. Hobby Airport has been recognized with two awards for being one of the top five performing airports in the world and for customer service by Airports Council International.
The Houston area has over 150 active faults (estimated to be 300 active faults) with an aggregate length of up to 310 miles (500 km), including the Long Point–Eureka Heights fault system which runs through the center of the city. There have been no significant historically recorded earthquakes in Houston, but researchers do not discount the possibility of such quakes having occurred in the deeper past, nor occurring in the future. Land in some areas southeast of Houston is sinking because water has been pumped out of the ground for many years. It may be associated with slip along the faults; however, the slippage is slow and not considered an earthquake, where stationary faults must slip suddenly enough to create seismic waves. These faults also tend to move at a smooth rate in what is termed "fault creep", which further reduces the risk of an earthquake.
Houston was incorporated in 1837 under the ward system of representation. The ward designation is the progenitor of the eleven current-day geographically oriented Houston City Council districts. Locations in Houston are generally classified as either being inside or outside the Interstate 610 Loop. The inside encompasses the central business district and many residential neighborhoods that predate World War II. More recently, high-density residential areas have been developed within the loop. The city's outlying areas, suburbs and enclaves are located outside of the loop. Beltway 8 encircles the city another 5 miles (8.0 km) farther out.
Centered on Post Oak Boulevard and Westheimer Road, the Uptown District boomed during the 1970s and early 1980s when a collection of mid-rise office buildings, hotels, and retail developments appeared along Interstate 610 west. Uptown became one of the most prominent instances of an edge city. The tallest building in Uptown is the 64-floor, 901-foot (275 m)-tall, Philip Johnson and John Burgee designed landmark Williams Tower (known as the Transco Tower until 1999). At the time of construction, it was believed to be the world's tallest skyscraper outside of a central business district. The new 20-story Skanska building and BBVA Compass Plaza are the newest office buildings built in Uptown after 30 years. The Uptown District is also home to buildings designed by noted architects I. M. Pei, César Pelli, and Philip Johnson. In the late 1990s and early 2000s decade, there was a mini-boom of mid-rise and high-rise residential tower construction, with several over 30 stories tall. Since 2000 more than 30 high-rise buildings have gone up in Houston; all told, 72 high-rises tower over the city, which adds up to about 8,300 units. In 2002, Uptown had more than 23 million square feet (2,100,000 m²) of office space with 16 million square feet (1,500,000 m²) of Class A office space.
Houston is recognized worldwide for its energy industry—particularly for oil and natural gas—as well as for biomedical research and aeronautics. Renewable energy sources—wind and solar—are also growing economic bases in the city. The Houston Ship Channel is also a large part of Houston's economic base. Because of these strengths, Houston is designated as a global city by the Globalization and World Cities Study Group and Network and global management consulting firm A.T. Kearney. The Houston area is the top U.S. market for exports, surpassing New York City in 2013, according to data released by the U.S. Department of Commerce's International Trade Administration. In 2012, the Houston–The Woodlands–Sugar Land area recorded $110.3 billion in merchandise exports. Petroleum products, chemicals, and oil and gas extraction equipment accounted for approximately two-thirds of the metropolitan area's exports last year. The Top 3 destinations for exports were Mexico, Canada, and Brazil.
In 2008, Houston received top ranking on Kiplinger's Personal Finance Best Cities of 2008 list, which ranks cities on their local economy, employment opportunities, reasonable living costs, and quality of life. The city ranked fourth for highest increase in the local technological innovation over the preceding 15 years, according to Forbes magazine. In the same year, the city ranked second on the annual Fortune 500 list of company headquarters, first for Forbes magazine's Best Cities for College Graduates, and first on their list of Best Cities to Buy a Home. In 2010, the city was rated the best city for shopping, according to Forbes.
Houston has sports teams for every major professional league except the National Hockey League (NHL). The Houston Astros are a Major League Baseball (MLB) expansion team formed in 1962 (known as the "Colt .45s" until 1965) that made one World Series appearance in 2005. The Houston Rockets are a National Basketball Association (NBA) franchise based in the city since 1971. They have won two NBA Championships: in 1994 and 1995 under star players Hakeem Olajuwon, Otis Thorpe, Clyde Drexler, Vernon Maxwell, and Kenny Smith. The Houston Texans are a National Football League (NFL) expansion team formed in 2002. The Houston Dynamo are a Major League Soccer (MLS) franchise that has been based in Houston since 2006 after they won two MLS Cup titles in 2006 and 2007. The Houston Dash play in the National Women's Soccer League (NWSL). The Scrap Yard Dawgs, a women's pro softball team, is expected to play in the National Pro Fastpitch (NPF) from 2016.
The original city council line-up of 14 members (nine district-based and five at-large positions) was based on a U.S. Justice Department mandate which took effect in 1979. At-large council members represent the entire city. Under the city charter, once the population in the city limits exceeded 2.1 million residents, two additional districts were to be added. The city of Houston's official 2010 census count was 600 shy of the required number; however, as the city was expected to grow beyond 2.1 million shortly thereafter, the two additional districts were added for, and the positions filled during, the August 2011 elections.
Four separate and distinct state universities are located in Houston. The University of Houston is a nationally recognized Tier One research university, and is the flagship institution of the University of Houston System. The third-largest university in Texas, the University of Houston has nearly 40,000 students on its 667-acre campus in southeast Houston. The University of Houston–Clear Lake and the University of Houston–Downtown are stand-alone universities; they are not branch campuses of the University of Houston. Located in the historic community of Third Ward is Texas Southern University, one of the largest historically black colleges and universities in the United States.
Houston is served by the Houston Chronicle, its only major daily newspaper with wide distribution. The Hearst Corporation, which owns and operates the Houston Chronicle, bought the assets of the Houston Post—its long-time rival and main competition—when Houston Post ceased operations in 1995. The Houston Post was owned by the family of former Lieutenant Governor Bill Hobby of Houston. The only other major publication to serve the city is the Houston Press—a free alternative weekly with a weekly readership of more than 300,000.
Houston's highway system has a hub-and-spoke freeway structure serviced by multiple loops. The innermost loop is Interstate 610, which encircles downtown, the medical center, and many core neighborhoods with around a 8-mile (13 km) diameter. Beltway 8 and its freeway core, the Sam Houston Tollway, form the middle loop at a diameter of roughly 23 miles (37 km). A proposed highway project, State Highway 99 (Grand Parkway), will form a third loop outside of Houston, totaling 180 miles in length and making an almost-complete circumference, with the exception of crossing the ship channel. As of June 2014, two of eleven segments of State Highway 99 have been completed to the west of Houston, and three northern segments, totaling 38 miles, are actively under construction and scheduled to open to traffic late in 2015. In addition to the Sam Houston Tollway loop mentioned above, the Harris County Toll Road Authority currently operates four spoke tollways: The Katy Managed Lanes of Interstate 10, the Hardy Toll Road, the Westpark Tollway, and the Fort Bend Parkway Extension. Other spoke roads either planned or under construction include Crosby Freeway, and the future Alvin Freeway.
The primary city airport is George Bush Intercontinental Airport (IAH), the tenth-busiest in the United States for total passengers, and twenty eighth-busiest worldwide. Bush Intercontinental currently ranks fourth in the United States for non-stop domestic and international service with 182 destinations. In 2006, the United States Department of Transportation named IAH the fastest-growing of the top ten airports in the United States. The Houston Air Route Traffic Control Center stands on the George Bush Intercontinental Airport grounds.
In the Roman era, copper was principally mined on Cyprus, the origin of the name of the metal from aes сyprium (metal of Cyprus), later corrupted to сuprum, from which the words copper (English), cuivre (French), Koper (Dutch) and Kupfer (German) are all derived. Its compounds are commonly encountered as copper(II) salts, which often impart blue or green colors to minerals such as azurite, malachite and turquoise and have been widely used historically as pigments. Architectural structures built with copper corrode to give green verdigris (or patina). Decorative art prominently features copper, both by itself and in the form of pigments.
Copper occurs naturally as native copper and was known to some of the oldest civilizations on record. It has a history of use that is at least 10,000 years old, and estimates of its discovery place it at 9000 BC in the Middle East; a copper pendant was found in northern Iraq that dates to 8700 BC. There is evidence that gold and meteoric iron (but not iron smelting) were the only metals used by humans before copper. The history of copper metallurgy is thought to have followed the following sequence: 1) cold working of native copper, 2) annealing, 3) smelting, and 4) the lost wax method. In southeastern Anatolia, all four of these metallurgical techniques appears more or less simultaneously at the beginning of the Neolithic c. 7500 BC. However, just as agriculture was independently invented in several parts of the world, copper smelting was invented locally in several different places. It was probably discovered independently in China before 2800 BC, in Central America perhaps around 600 AD, and in West Africa about the 9th or 10th century AD. Investment casting was invented in 4500–4000 BC in Southeast Asia and carbon dating has established mining at Alderley Edge in Cheshire, UK at 2280 to 1890 BC. Ötzi the Iceman, a male dated from 3300–3200 BC, was found with an axe with a copper head 99.7% pure; high levels of arsenic in his hair suggest his involvement in copper smelting. Experience with copper has assisted the development of other metals; in particular, copper smelting led to the discovery of iron smelting. Production in the Old Copper Complex in Michigan and Wisconsin is dated between 6000 and 3000 BC. Natural bronze, a type of copper made from ores rich in silicon, arsenic, and (rarely) tin, came into general use in the Balkans around 5500 BC.[citation needed]
The gates of the Temple of Jerusalem used Corinthian bronze made by depletion gilding. It was most prevalent in Alexandria, where alchemy is thought to have begun. In ancient India, copper was used in the holistic medical science Ayurveda for surgical instruments and other medical equipment. Ancient Egyptians (~2400 BC) used copper for sterilizing wounds and drinking water, and later on for headaches, burns, and itching. The Baghdad Battery, with copper cylinders soldered to lead, dates back to 248 BC to AD 226 and resembles a galvanic cell, leading people to believe this was the first battery; the claim has not been verified.
Despite competition from other materials, copper remains the preferred electrical conductor in nearly all categories of electrical wiring with the major exception being overhead electric power transmission where aluminium is often preferred. Copper wire is used in power generation, power transmission, power distribution, telecommunications, electronics circuitry, and countless types of electrical equipment. Electrical wiring is the most important market for the copper industry. This includes building wire, communications cable, power distribution cable, appliance wire, automotive wire and cable, and magnet wire. Roughly half of all copper mined is used to manufacture electrical wire and cable conductors. Many electrical devices rely on copper wiring because of its multitude of inherent beneficial properties, such as its high electrical conductivity, tensile strength, ductility, creep (deformation) resistance, corrosion resistance, low thermal expansion, high thermal conductivity, solderability, and ease of installation.
Copper is biostatic, meaning bacteria will not grow on it. For this reason it has long been used to line parts of ships to protect against barnacles and mussels. It was originally used pure, but has since been superseded by Muntz metal. Similarly, as discussed in copper alloys in aquaculture, copper alloys have become important netting materials in the aquaculture industry because they are antimicrobial and prevent biofouling, even in extreme conditions and have strong structural and corrosion-resistant properties in marine environments.
Copper, silver and gold are in group 11 of the periodic table, and they share certain attributes: they have one s-orbital electron on top of a filled d-electron shell and are characterized by high ductility and electrical conductivity. The filled d-shells in these elements do not contribute much to the interatomic interactions, which are dominated by the s-electrons through metallic bonds. Unlike metals with incomplete d-shells, metallic bonds in copper are lacking a covalent character and are relatively weak. This explains the low hardness and high ductility of single crystals of copper. At the macroscopic scale, introduction of extended defects to the crystal lattice, such as grain boundaries, hinders flow of the material under applied stress, thereby increasing its hardness. For this reason, copper is usually supplied in a fine-grained polycrystalline form, which has greater strength than monocrystalline forms.
Copper is synthesized in massive stars and is present in the Earth's crust at a concentration of about 50 parts per million (ppm), where it occurs as native copper or in minerals such as the copper sulfides chalcopyrite and chalcocite, the copper carbonates azurite and malachite, and the copper(I) oxide mineral cuprite. The largest mass of elemental copper discovered weighed 420 tonnes and was found in 1857 on the Keweenaw Peninsula in Michigan, US. Native copper is a polycrystal, with the largest described single crystal measuring 4.4×3.2×3.2 cm.
In Greece, copper was known by the name chalkos (χαλκός). It was an important resource for the Romans, Greeks and other ancient peoples. In Roman times, it was known as aes Cyprium, aes being the generic Latin term for copper alloys and Cyprium from Cyprus, where much copper was mined. The phrase was simplified to cuprum, hence the English copper. Aphrodite and Venus represented copper in mythology and alchemy, because of its lustrous beauty, its ancient use in producing mirrors, and its association with Cyprus, which was sacred to the goddess. The seven heavenly bodies known to the ancients were associated with the seven metals known in antiquity, and Venus was assigned to copper.
Compounds that contain a carbon-copper bond are known as organocopper compounds. They are very reactive towards oxygen to form copper(I) oxide and have many uses in chemistry. They are synthesized by treating copper(I) compounds with Grignard reagents, terminal alkynes or organolithium reagents; in particular, the last reaction described produces a Gilman reagent. These can undergo substitution with alkyl halides to form coupling products; as such, they are important in the field of organic synthesis. Copper(I) acetylide is highly shock-sensitive but is an intermediate in reactions such as the Cadiot-Chodkiewicz coupling and the Sonogashira coupling. Conjugate addition to enones and carbocupration of alkynes can also be achieved with organocopper compounds. Copper(I) forms a variety of weak complexes with alkenes and carbon monoxide, especially in the presence of amine ligands.
The uses of copper in art were not limited to currency: it was used by Renaissance sculptors, in photographic technology known as the daguerreotype, and the Statue of Liberty. Copper plating and copper sheathing for ships' hulls was widespread; the ships of Christopher Columbus were among the earliest to have this feature. The Norddeutsche Affinerie in Hamburg was the first modern electroplating plant starting its production in 1876. The German scientist Gottfried Osann invented powder metallurgy in 1830 while determining the metal's atomic mass; around then it was discovered that the amount and type of alloying element (e.g., tin) to copper would affect bell tones. Flash smelting was developed by Outokumpu in Finland and first applied at Harjavalta in 1949; the energy-efficient process accounts for 50% of the world's primary copper production.
Copper's greater conductivity versus other metals enhances the electrical energy efficiency of motors. This is important because motors and motor-driven systems account for 43%-46% of all global electricity consumption and 69% of all electricity used by industry. Increasing the mass and cross section of copper in a coil increases the electrical energy efficiency of the motor. Copper motor rotors, a new technology designed for motor applications where energy savings are prime design objectives, are enabling general-purpose induction motors to meet and exceed National Electrical Manufacturers Association (NEMA) premium efficiency standards.
Chromobacterium violaceum and Pseudomonas fluorescens can both mobilize solid copper, as a cyanide compound. The ericoid mycorrhizal fungi associated with Calluna, Erica and Vaccinium can grow in copper metalliferous soils. The ectomycorrhizal fungus Suillus luteus protects young pine trees from copper toxicity. A sample of the fungus Aspergillus niger was found growing from gold mining solution; and was found to contain cyano metal complexes; such as gold, silver, copper iron and zinc. The fungus also plays a role in the solubilization of heavy metal sulfides.
Copper-alloy touch surfaces have natural intrinsic properties to destroy a wide range of microorganisms (e.g., E. coli O157:H7, methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus, Clostridium difficile, influenza A virus, adenovirus, and fungi). Some 355 copper alloys were proven to kill more than 99.9% of disease-causing bacteria within just two hours when cleaned regularly. The United States Environmental Protection Agency (EPA) has approved the registrations of these copper alloys as "antimicrobial materials with public health benefits," which allows manufacturers to legally make claims as to the positive public health benefits of products made with registered antimicrobial copper alloys. In addition, the EPA has approved a long list of antimicrobial copper products made from these alloys, such as bedrails, handrails, over-bed tables, sinks, faucets, door knobs, toilet hardware, computer keyboards, health club equipment, shopping cart handles, etc. (for a comprehensive list of products, see: Antimicrobial copper-alloy touch surfaces#Approved products). Copper doorknobs are used by hospitals to reduce the transfer of disease, and Legionnaires' disease is suppressed by copper tubing in plumbing systems. Antimicrobial copper alloy products are now being installed in healthcare facilities in the U.K., Ireland, Japan, Korea, France, Denmark, and Brazil[citation needed] and in the subway transit system in Santiago, Chile, where copper-zinc alloy handrails will be installed in some 30 stations between 2011–2014.
Copper compounds in liquid form are used as a wood preservative, particularly in treating original portion of structures during restoration of damage due to dry rot. Together with zinc, copper wires may be placed over non-conductive roofing materials to discourage the growth of moss.[citation needed] Textile fibers use copper to create antimicrobial protective fabrics, as do ceramic glazes, stained glass and musical instruments. Electroplating commonly uses copper as a base for other metals such as nickel.
Copper has been in use at least 10,000 years, but more than 95% of all copper ever mined and smelted has been extracted since 1900, and more than half was extracted in only the last 24 years. As with many natural resources, the total amount of copper on Earth is vast (around 1014 tons just in the top kilometer of Earth's crust, or about 5 million years' worth at the current rate of extraction). However, only a tiny fraction of these reserves is economically viable, given present-day prices and technologies. Various estimates of existing copper reserves available for mining vary from 25 years to 60 years, depending on core assumptions such as the growth rate. Recycling is a major source of copper in the modern world. Because of these and other factors, the future of copper production and supply is the subject of much debate, including the concept of peak copper, analogous to peak oil.
The cultural role of copper has been important, particularly in currency. Romans in the 6th through 3rd centuries BC used copper lumps as money. At first, the copper itself was valued, but gradually the shape and look of the copper became more important. Julius Caesar had his own coins made from brass, while Octavianus Augustus Caesar's coins were made from Cu-Pb-Sn alloys. With an estimated annual output of around 15,000 t, Roman copper mining and smelting activities reached a scale unsurpassed until the time of the Industrial Revolution; the provinces most intensely mined were those of Hispania, Cyprus and in Central Europe.
The major applications of copper are in electrical wires (60%), roofing and plumbing (20%) and industrial machinery (15%). Copper is mostly used as a pure metal, but when a higher hardness is required it is combined with other elements to make an alloy (5% of total use) such as brass and bronze. A small part of copper supply is used in production of compounds for nutritional supplements and fungicides in agriculture. Machining of copper is possible, although it is usually necessary to use an alloy for intricate parts to get good machinability characteristics.
The softness of copper partly explains its high electrical conductivity (59.6×106 S/m) and thus also high thermal conductivity, which are the second highest (to silver) among pure metals at room temperature. This is because the resistivity to electron transport in metals at room temperature mostly originates from scattering of electrons on thermal vibrations of the lattice, which are relatively weak for a soft metal. The maximum permissible current density of copper in open air is approximately 3.1×106 A/m2 of cross-sectional area, above which it begins to heat excessively. As with other metals, if copper is placed against another metal, galvanic corrosion will occur.
Most copper is mined or extracted as copper sulfides from large open pit mines in porphyry copper deposits that contain 0.4 to 1.0% copper. Examples include Chuquicamata in Chile, Bingham Canyon Mine in Utah, United States and El Chino Mine in New Mexico, United States. According to the British Geological Survey, in 2005, Chile was the top mine producer of copper with at least one-third world share followed by the United States, Indonesia and Peru. Copper can also be recovered through the in-situ leach process. Several sites in the state of Arizona are considered prime candidates for this method. The amount of copper in use is increasing and the quantity available is barely sufficient to allow all countries to reach developed world levels of usage.
Like aluminium, copper is 100% recyclable without any loss of quality, regardless of whether it is in a raw state or contained in a manufactured product. In volume, copper is the third most recycled metal after iron and aluminium. It is estimated that 80% of the copper ever mined is still in use today. According to the International Resource Panel's Metal Stocks in Society report, the global per capita stock of copper in use in society is 35–55 kg. Much of this is in more-developed countries (140–300 kg per capita) rather than less-developed countries (30–40 kg per capita).
The metal's distinctive natural green patina has long been coveted by architects and designers. The final patina is a particularly durable layer that is highly resistant to atmospheric corrosion, thereby protecting the underlying metal against further weathering. It can be a mixture of carbonate and sulfate compounds in various amounts, depending upon environmental conditions such as sulfur-containing acid rain. Architectural copper and its alloys can also be 'finished' to embark a particular look, feel, and/or color. Finishes include mechanical surface treatments, chemical coloring, and coatings.
Gram quantities of various copper salts have been taken in suicide attempts and produced acute copper toxicity in humans, possibly due to redox cycling and the generation of reactive oxygen species that damage DNA. Corresponding amounts of copper salts (30 mg/kg) are toxic in animals. A minimum dietary value for healthy growth in rabbits has been reported to be at least 3 ppm in the diet. However, higher concentrations of copper (100 ppm, 200 ppm, or 500 ppm) in the diet of rabbits may favorably influence feed conversion efficiency, growth rates, and carcass dressing percentages.
Britain's first use of brass occurred around the 3rd–2nd century BC. In North America, copper mining began with marginal workings by Native Americans. Native copper is known to have been extracted from sites on Isle Royale with primitive stone tools between 800 and 1600. Copper metallurgy was flourishing in South America, particularly in Peru around 1000 AD; it proceeded at a much slower rate on other continents. Copper burial ornamentals from the 15th century have been uncovered, but the metal's commercial production did not start until the early 20th century.
There are 29 isotopes of copper. 63Cu and 65Cu are stable, with 63Cu comprising approximately 69% of naturally occurring copper; they both have a spin of 3⁄2. The other isotopes are radioactive, with the most stable being 67Cu with a half-life of 61.83 hours. Seven metastable isotopes have been characterized, with 68mCu the longest-lived with a half-life of 3.8 minutes. Isotopes with a mass number above 64 decay by β−, whereas those with a mass number below 64 decay by β+. 64Cu, which has a half-life of 12.7 hours, decays both ways.
The alloy of copper and nickel, called cupronickel, is used in low-denomination coins, often for the outer cladding. The US 5-cent coin called a nickel consists of 75% copper and 25% nickel and has a homogeneous composition. The alloy consisting of 90% copper and 10% nickel is remarkable for its resistance to corrosion and is used in various parts that are exposed to seawater. Alloys of copper with aluminium (about 7%) have a pleasant golden color and are used in decorations. Some lead-free solders consist of tin alloyed with a small proportion of copper and other metals.
Polyols, compounds containing more than one alcohol functional group, generally interact with cupric salts. For example, copper salts are used to test for reducing sugars. Specifically, using Benedict's reagent and Fehling's solution the presence of the sugar is signaled by a color change from blue Cu(II) to reddish copper(I) oxide. Schweizer's reagent and related complexes with ethylenediamine and other amines dissolve cellulose. Amino acids form very stable chelate complexes with copper(II). Many wet-chemical tests for copper ions exist, one involving potassium ferrocyanide, which gives a brown precipitate with copper(II) salts.
Alloying copper with tin to make bronze was first practiced about 4000 years after the discovery of copper smelting, and about 2000 years after "natural bronze" had come into general use[citation needed]. Bronze artifacts from the Vinča culture date to 4500 BC. Sumerian and Egyptian artifacts of copper and bronze alloys date to 3000 BC. The Bronze Age began in Southeastern Europe around 3700–3300 BC, in Northwestern Europe about 2500 BC. It ended with the beginning of the Iron Age, 2000–1000 BC in the Near East, 600 BC in Northern Europe. The transition between the Neolithic period and the Bronze Age was formerly termed the Chalcolithic period (copper-stone), with copper tools being used with stone tools. This term has gradually fallen out of favor because in some parts of the world the Chalcolithic and Neolithic are coterminous at both ends. Brass, an alloy of copper and zinc, is of much more recent origin. It was known to the Greeks, but became a significant supplement to bronze during the Roman Empire.
Copper is an essential trace element in plants and animals, but not some microorganisms. The human body contains copper at a level of about 1.4 to 2.1 mg per kg of body mass. Stated differently, the RDA for copper in normal healthy adults is quoted as 0.97 mg/day and as 3.0 mg/day. Copper is absorbed in the gut, then transported to the liver bound to albumin. After processing in the liver, copper is distributed to other tissues in a second phase. Copper transport here involves the protein ceruloplasmin, which carries the majority of copper in blood. Ceruloplasmin also carries copper that is excreted in milk, and is particularly well-absorbed as a copper source. Copper in the body normally undergoes enterohepatic circulation (about 5 mg a day, vs. about 1 mg per day absorbed in the diet and excreted from the body), and the body is able to excrete some excess copper, if needed, via bile, which carries some copper out of the liver that is not then reabsorbed by the intestine.
The concentration of copper in ores averages only 0.6%, and most commercial ores are sulfides, especially chalcopyrite (CuFeS2) and to a lesser extent chalcocite (Cu2S). These minerals are concentrated from crushed ores to the level of 10–15% copper by froth flotation or bioleaching. Heating this material with silica in flash smelting removes much of the iron as slag. The process exploits the greater ease of converting iron sulfides into its oxides, which in turn react with the silica to form the silicate slag, which floats on top of the heated mass. The resulting copper matte consisting of Cu2S is then roasted to convert all sulfides into oxides:
Together with caesium and gold (both yellow), and osmium (bluish), copper is one of only four elemental metals with a natural color other than gray or silver. Pure copper is orange-red and acquires a reddish tarnish when exposed to air. The characteristic color of copper results from the electronic transitions between the filled 3d and half-empty 4s atomic shells – the energy difference between these shells is such that it corresponds to orange light. The same mechanism accounts for the yellow color of gold and caesium.
Copper has been used since ancient times as a durable, corrosion resistant, and weatherproof architectural material. Roofs, flashings, rain gutters, downspouts, domes, spires, vaults, and doors have been made from copper for hundreds or thousands of years. Copper's architectural use has been expanded in modern times to include interior and exterior wall cladding, building expansion joints, radio frequency shielding, and antimicrobial indoor products, such as attractive handrails, bathroom fixtures, and counter tops. Some of copper's other important benefits as an architectural material include its low thermal movement, light weight, lightning protection, and its recyclability.
A psychological identity relates to self-image (one's mental model of oneself), self-esteem, and individuality. Consequently, Weinreich gives the definition "A person's identity is defined as the totality of one's self-construal, in which how one construes oneself in the present expresses the continuity between how one construes oneself as one was in the past and how one construes oneself as one aspires to be in the future"; this allows for definitions of aspects of identity, such as: "One's ethnic identity is defined as that part of the totality of one's self-construal made up of those dimensions that express the continuity between one's construal of past ancestry and one's future aspirations in relation to ethnicity" (Weinreich, 1986a).
The description or representation of individual and group identity is a central task for psychologists, sociologists and anthropologists and those of other disciplines where "identity" needs to be mapped and defined. How should one describe the identity of another, in ways which encompass both their idiosyncratic qualities and their group memberships or identifications, both of which can shift according to circumstance? Following on from the work of Kelly, Erikson, Tajfel and others Weinreich's Identity Structure Analysis (ISA), is "a structural representation of the individual's existential experience, in which the relationships between self and other agents are organised in relatively stable structures over time … with the emphasis on the socio-cultural milieu in which self relates to other agents and institutions" (Weinreich and Saunderson, (eds) 2003, p1). Using constructs drawn from the salient discourses of the individual, the group and cultural norms, the practical operationalisation of ISA provides a methodology that maps how these are used by the individual, applied across time and milieus by the "situated self" to appraise self and other agents and institutions (for example, resulting in the individual's evaluation of self and significant others and institutions).[citation needed]
Weinreich's identity variant similarly includes the categories of identity diffusion, foreclosure and crisis, but with a somewhat different emphasis. Here, with respect to identity diffusion for example, an optimal level is interpreted as the norm, as it is unrealistic to expect an individual to resolve all their conflicted identifications with others; therefore we should be alert to individuals with levels which are much higher or lower than the norm – highly diffused individuals are classified as diffused, and those with low levels as foreclosed or defensive. (Weinreich & Saunderson, 2003, pp 65–67; 105-106). Weinreich applies the identity variant in a framework which also allows for the transition from one to another by way of biographical experiences and resolution of conflicted identifications situated in various contexts – for example, an adolescent going through family break-up may be in one state, whereas later in a stable marriage with a secure professional role may be in another. Hence, though there is continuity, there is also development and change. (Weinreich & Saunderson, 2003, pp 22–23).
Anthropologists have contributed to the debate by shifting the focus of research: One of the first challenges for the researcher wishing to carry out empirical research in this area is to identify an appropriate analytical tool. The concept of boundaries is useful here for demonstrating how identity works. In the same way as Barth, in his approach to ethnicity, advocated the critical focus for investigation as being "the ethnic boundary that defines the group rather than the cultural stuff that it encloses" (1969:15), social anthropologists such as Cohen and Bray have shifted the focus of analytical study from identity to the boundaries that are used for purposes of identification. If identity is a kind of virtual site in which the dynamic processes and markers used for identification are made apparent, boundaries provide the framework on which this virtual site is built. They concentrated on how the idea of community belonging is differently constructed by individual members and how individuals within the group conceive ethnic boundaries.
The inclusiveness of Weinreich's definition (above) directs attention to the totality of one's identity at a given phase in time, and assists in elucidating component aspects of one's total identity, such as one's gender identity, ethnic identity, occupational identity and so on. The definition readily applies to the young child, to the adolescent, to the young adult, and to the older adult in various phases of the life cycle. Depending on whether one is a young child or an adult at the height of one's powers, how one construes oneself as one was in the past will refer to very different salient experiential markers. Likewise, how one construes oneself as one aspires to be in the future will differ considerably according to one's age and accumulated experiences. (Weinreich & Saunderson, (eds) 2003, pp 26–34).
Although the self is distinct from identity, the literature of self-psychology can offer some insight into how identity is maintained (Cote & Levin 2002, p. 24). From the vantage point of self-psychology, there are two areas of interest: the processes by which a self is formed (the "I"), and the actual content of the schemata which compose the self-concept (the "Me"). In the latter field, theorists have shown interest in relating the self-concept to self-esteem, the differences between complex and simple ways of organizing self-knowledge, and the links between those organizing principles and the processing of information (Cote & Levin 2002).

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