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Band gap

In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to the energy difference (often expressed in electronvolts) between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. It is the energy required to promote an electron from the valence band to the conduction band. The resulting conduction-band electron (and the electron hole in the valence band) are free to move within the crystal lattice and serve as charge carriers to conduct electric current. It is closely related to the HOMO/LUMO gap in chemistry. If the valence band is completely full and the conduction band is completely empty, then electrons cannot move within the solid because there are no available states. If the electrons are not free to move within the crystal lattice, then there is no generated current due to no net charge carrier mobility. However, if some electrons transfer from the valence band (mostly full) to the conduction band (mostly empty), then current can flow (see carrier generation and recombination). Therefore, the band gap is a major factor determining the electrical conductivity of a solid. Substances having large band gaps (also called "wide" band gaps) are generally insulators, those with small band gaps (also called "narrow" band gaps) are semiconductor, and conductors either have very small band gaps or none, because the valence and conduction bands overlap to form a continuous band.

In semiconductor physics
Every solid has its own characteristic energy-band structure. This variation in band structure is responsible for the wide range of electrical characteristics observed in various materials. Depending on the dimension, the band structure and spectroscopy can vary. The different types of dimensions are as listed: one dimension, two dimensions, and three dimensions.

In semiconductors and insulators, electrons are confined to a number of bands of energy, and forbidden from other regions because there are no allowable electronic states for them to occupy. The term "band gap" refers to the energy difference between the top of the valence band and the bottom of the conduction band. Electrons are able to jump from one band to another. However, in order for a valence band electron to be promoted to the conduction band, it requires a specific minimum amount of energy for the transition. This required energy is an intrinsic characteristic of the solid material. Electrons can gain enough energy to jump to the conduction band by absorbing either a phonon (heat) or a photon (light).

A semiconductor is a material with an intermediate-sized, non-zero band gap that behaves as an insulator at T=0K, but allows thermal excitation of electrons into its conduction band at temperatures that are below its melting point. In contrast, a material with a large band gap is an insulator. In conductors, the valence and conduction bands may overlap, so there is no longer a bandgap with forbidden regions of electronic states.

The conductivity of intrinsic semiconductors is strongly dependent on the band gap. The only available charge carriers for conduction are the electrons that have enough thermal energy to be excited across the band gap and the electron holes that are left off when such an excitation occurs.

Band-gap engineering is the process of controlling or altering the band gap of a material by controlling the composition of certain semiconductor alloys, such as GaAlAs, InGaAs, and InAlAs. It is also possible to construct layered materials with alternating compositions by techniques like molecular-beam epitaxy. These methods are exploited in the design of heterojunction bipolar transistors (HBTs), laser diodes and solar cells.

The distinction between semiconductors and insulators is a matter of convention. One approach is to think of semiconductors as a type of insulator with a narrow band gap. Insulators with a larger band gap, usually greater than 4 eV, are not considered semiconductors and generally do not exhibit semiconductive behaviour under practical conditions. Electron mobility also plays a role in determining a material's informal classification.

The band-gap energy of semiconductors tends to decrease with increasing temperature. When temperature increases, the amplitude of atomic vibrations increase, leading to larger interatomic spacing. The interaction between the lattice phonons and the free electrons and holes will also affect the band gap to a smaller extent. The relationship between band gap energy and temperature can be described by Varshni's empirical expression (named after Y. P. Varshni),
 * $$E_g(T)=E_g(0)-\frac{\alpha T^2}{T+\beta}$$, where Eg(0), α and β are material constants.

Furthermore, lattice vibrations increase with temperature, which increases the effect of electron scattering. Additionally, the number of charge carriers within a semiconductor will increase, as more carriers have the energy required to cross the band-gap threshold and so conductivity of semiconductors also increases with increasing temperature. The external pressure also influences the electronic structure of semiconductors and, therefore, their optical band gaps.

In a regular semiconductor crystal, the band gap is fixed owing to continuous energy states. In a quantum dot crystal, the band gap is size dependent and can be altered to produce a range of energies between the valence band and conduction band. It is also known as quantum confinement effect.

Band gaps can be either direct or indirect, depending on the electronic band structure of the material.

It was mentioned earlier that the dimensions have different band structure and spectroscopy. For non-metallic solids, which are one dimensional, have optical properties that are dependent on the electronic transitions between valence and conduction bands. In addition, the spectroscopic transition probability is between the initial and final orbital and it depends on the integral. φi is the initial orbital, φf is the final orbital, ʃ φf*ûεφi is the integral, ε is the electric vector, and u is the dipole moment.

Two-dimensional structures of solids behave because of the overlap of atomic orbitals. The simplest two-dimensional crystal contains identical atoms arranged on a square lattice. Energy splitting occurs at the Brillouin zone edge for one-dimensional situations because of a weak periodic potential, which produces a gap between bands. The behavior of the one-dimensional situations does not occur for two-dimensional cases because there are extra freedoms of motion. Furthermore, a bandgap can be produced with strong periodic potential for two-dimensional and three-dimensional cases.

Direct and indirect band gap
Based on their band structure, materials are characterised with a direct band gap or indirect band gap. In the free-electron model, k is the momentum of a free electron and assumes unique values within the Brillouin zone that outlines the periodicity of the crystal lattice. If the momentum of the lowest energy state in the conduction band and the highest energy state of the valence band of a material have the same value, then the material has a direct bandgap. If they are not the same, then the material has an indirect band gap and the electronic transition must undergo momentum transfer to satisfy conservation. Such indirect "forbidden" transitions still occur, however at very low probabilities and weaker energy. For materials with a direct band gap, valence electrons can be directly excited into the conduction band by a photon whose energy is larger than the bandgap. In contrast, for materials with an indirect band gap, a photon and phonon must both be involved in a transition from the valence band top to the conduction band bottom, involving a momentum change. Therefore, direct bandgap materials tend to have stronger light emission and absorption properties and tend to be better suited for photovoltaics (PVs), light-emitting diodes (LEDs), and laser diodes; however, indirect bandgap materials are frequently used in PVs and LEDs when the materials have other favorable properties.

Light-emitting diodes and laser diodes
LEDs and laser diodes usually emit photons with energy close to and slightly larger than the band gap of the semiconductor material from which they are made. Therefore, as the band gap energy increases, the LED or laser color changes from infrared to red, through the rainbow to violet, then to UV.

Photovoltaic cells

The optical band gap (see below) determines what portion of the solar spectrum a photovoltaic cell absorbs. Strictly, a semiconductor will not absorb photons of energy less than the band gap; whereas most of the photons with energies exceeding the band gap will generate heat. Neither of them contribute to the efficiency of a solar cell. One way to circumvent this problem is based on the so-called photon management concept, in which case the solar spectrum is modified to match the absorption profile of the solar cell.

List of band gaps
Below are band gap values for some selected materials. For a comprehensive list of band gaps in semiconductors, see List of semiconductor materials.

Optical versus electronic bandgap
In materials with a large exciton binding energy, it is possible for a photon to have just barely enough energy to create an exciton (bound electron–hole pair), but not enough energy to separate the electron and hole (which are electrically attracted to each other). In this situation, there is a distinction between "optical band gap" and "electronic band gap" (or "transport gap"). The optical bandgap is the threshold for photons to be absorbed, while the transport gap is the threshold for creating an electron–hole pair that is not bound together. The optical bandgap is at lower energy than the transport gap.

In almost all inorganic semiconductors, such as silicon, gallium arsenide, etc., there is very little interaction between electrons and holes (very small exciton binding energy), and therefore the optical and electronic bandgap are essentially identical, and the distinction between them is ignored. However, in some systems, including organic semiconductors and single-walled carbon nanotubes, the distinction may be significant.

Band gaps for other quasi-particles
In photonics, band gaps or stop bands are ranges of photon frequencies where, if tunneling effects are neglected, no photons can be transmitted through a material. A material exhibiting this behaviour is known as a photonic crystal. The concept of hyperuniformity has broadened the range of photonic band gap materials, beyond photonic crystals. By applying the technique in supersymmetric quantum mechanics, a new class of optical disordered materials has been suggested, which support band gaps perfectly equivalent to those of crystals or quasicrystals.

Similar physics applies to phonons in a phononic crystal.

Materials

 * Aluminium gallium arsenide
 * Boron nitride
 * Indium gallium arsenide
 * Indium arsenide
 * Gallium arsenide
 * Gallium nitride
 * Germanium
 * Metallic hydrogen

List of electronics topics

 * Electronics
 * Bandgap voltage reference
 * Condensed matter physics
 * Direct and indirect bandgaps
 * Electrical conduction
 * Electron hole
 * Field-effect transistor
 * Light-emitting diode
 * Photodiode
 * Photoresistor
 * Photovoltaics
 * Solar cell
 * Solid state physics
 * Semiconductor
 * Semiconductor devices
 * Strongly correlated material
 * Valence band

title: Band gap


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Arkhangelsk

Arkhangelsk (, ; Арха́нгельск, ), also known as Archangel and Archangelsk, is a city and the administrative center of Arkhangelsk Oblast, Russia. It lies on both banks of the Northern Dvina near its mouth into the White Sea. The city spreads for over 40 km along the banks of the river and numerous islands of its delta. Arkhangelsk was the chief seaport of medieval and early modern Russia until 1703, when it was replaced by the newly founded Saint Petersburg.

A 1133 km railway runs from Arkhangelsk to Moscow via Vologda and Yaroslavl, and air travel is served by the Talagi Airport and the smaller Vaskovo Airport. As of the 2021 Census, the city's population was 301,199.

Coat of arms
The arms of the city display the Archangel Michael in the act of defeating the Devil. Legend states that this victory took place near where the city stands, hence its name, and that Michael still stands watch over the city to prevent the Devil's return.

Early history
Vikings knew the area around Arkhangelsk as Bjarmaland. Ohthere of Hålogaland told circa 890 of his travels in an area by a river and the White Sea with many buildings. This was probably the place later known as Arkhangelsk. According to Snorri Sturluson, Vikings led by Thorir Hund raided this area in 1027.

In 1989, an unusually impressive silver treasure was found by local farm workers by the mouth of Dvina, right next to present-day Arkhangelsk.

Most of the findings comprised a total of 1.6 kg of silver, largely in the form of coins. Jewelry and pieces of jewelry come from Russia or neighboring areas. The majority of the coins were German, but the hoard also included a smaller number of Kufan, English, Bohemian, Hungarian, Danish, Swedish and Norwegian coins. It is hard to place this find historically until further research is completed. There are at least two possible interpretations. It may be a treasure belonging to the society outlined by the Norse source material. Generally such finds, whether from Scandinavia, the Baltic area, or Russia, are closely tied to well-established agricultural societies with considerable trade activity.

Alternatively, like the Russian scientists who published the find in 1992, one may see it as evidence of a stronger case of Russian colonization than previously thought.

Novgorodian arrival
In the 12th century, the Novgorodians established a monastery dedicated to Archangel Michael in the estuary of the Northern Dvina. The main trade center of the area at that time was Kholmogory, located 75 km southeast of Arkhangelsk, up the Dvina River, about 10 km downstream from where the Pinega River flows into the Dvina. Written sources indicate that Kholmogory existed early in the 12th century, but there is no archeological material of this period. It is not known whether the origin of this settlement was Russian, or if it goes back to pre-Russian times. In the center of the small town (or Gorodok) that is there today is a large mound of building remains and river sand, but it has not been archeologically excavated.

Norwegian–Russian conflict

The area of Arkhangelsk came to be important in the rivalry between Norwegian and Russian interests in the northern areas. From Novgorod, the spectrum of Russian interest was extended far north to the Kola Peninsula in the 12th century. However, here Norway enforced taxes and rights to the fur trade. A compromise agreement entered in 1251 which was soon broken.

In 1411, Yakov Stepanovich from Novgorod went to attack northern Norway. This was the beginning of a series of clashes. In 1419, Norwegian ships with five hundred soldiers entered the White Sea. The "Murmaners", as the Norwegians were called (cf. Murmansk), plundered many Russian settlements along the coast, among them the Archangel Michael Monastery.

Novgorod managed to drive the Norwegians back. However, in 1478 the area was taken over by Ivan III and passed to the Grand Duchy of Moscow with the rest of the Novgorod Republic.

Trade with England, Scotland, and the Netherlands
Three English ships the Bona Esperanza, Edward Bonaventure, and Bona Confidentia set out to find the Northeast passage to China in 1553; two disappeared, and one, the Edward Bonaventure ended up in the White Sea at Nyonoksa, eventually coming across the area of Arkhangelsk at the mouth of the Dvina River where the St. Nicolas Monastery stood. Subsequently, the English gave the name St. Nicolas Bay to the sea now known as the White Sea. Ivan the Terrible found out about this, and brokered a trade agreement with the ship's captain, Richard Chancellor.

Trade privileges were granted to English merchants in 1555, leading to the founding of the Company of Merchant Adventurers, which began sending ships annually into the estuary of the Northern Dvina. Dutch merchants also started bringing their ships into the White Sea from the 1560s. Scottish and English merchants also traded in the 16th century; however, by the 17th century it was mainly the Dutch that sailed to the White Sea area.

Founding and further development
In 1584, Ivan ordered the founding of New Kholmogory (which would later be renamed after the nearby Archangel Michael Monastery). At the time access to the Baltic Sea was still mostly controlled by Sweden, so while Arkhangelsk was icebound in winter, it remained Moscow's almost sole link to the sea-trade. Local inhabitants, called Pomors, were the first to explore trade routes to Northern Siberia as far as the trans-Urals city of Mangazeya and beyond. In December 1613, during the Time of Troubles, Arkhangelsk was besieged by Polish-Lithuanian marauders commanded by Stanislaw Jasinski (Lisowczyks), who failed to capture the fortified town. In 1619, and again in 1637, fires broke out, and the entire city burned down.

In 1693, Peter the Great ordered the creation of a state shipyard in Arkhangelsk. A year later the ships Svyatoye Prorochestvo (Holy Prophecy), Apostol Pavel (Apostle Paul), and the yacht Svyatoy Pyotr (Saint Peter) were sailing in the White Sea. However, he also realized that Arkhangelsk would always be limited as a port due to the five months of ice cover, and after a successful campaign against Swedish armies in the Baltic area, he founded Saint Petersburg in May 1703. Nonetheless, Arkhangelsk continued to be an important naval base and maritime centre in the Russian north.

In 1722, Peter the Great decreed that Arkhangelsk should no longer accept goods that amounted to more than was sufficient for the town (for so-called domestic consumption). It was due to the Tsar's will to shift all international marine trade to Saint Petersburg. This factor greatly contributed to the deterioration of Arkhangelsk that continued up to 1762 when this decree was cancelled.

Arkhangelsk declined in the 18th century as the Baltic trade became ever more important. Its economy revived at the end of the 19th century when a railway to Moscow was completed and timber became a major export. The city resisted Bolshevik rule from 1918 to 1920 and was a stronghold of the anti-Bolshevik White Army. The White Army was supported by an Allied intervention in which British, French, Italian, and American troops helped to defend against the Bolsheviks. The Allied forces, led by British Lieutenant General Frederick Poole, suffered numerous set-backs and eventually withdrew from Russia. Without Allied support, the poorly disciplined White Army quickly collapsed and the Bolsheviks entered Arkhangelsk on February 21, 1920. Arkhangelsk was also the scene of the Mudyug concentration camp.

During both world wars, Arkhangelsk was a major port of entry for Allied aid. During World War II, the city became known in West Europe as one of the two main destinations (along with Murmansk) of the Arctic convoys bringing supplies in to assist the Soviet Union. During Operation Barbarossa, the German invasion of the Soviet Union in 1941, Arkhangelsk was one of two cities (the other being Astrakhan) selected to mark the envisioned eastern limit of German control. This military operation was to be halted at this A-A line, but never reached it, as the German armies failed to capture either of these two cities and also failed to capture Moscow.

Arkhangelsk was also the site of Arkhangelsk ITL, or the Arkhangelsk Labour Camp, in the 1930s and 1940s.

Today, Arkhangelsk remains a major seaport, now open year-round due to improvements in icebreakers. The city is primarily a center for the timber and fishing industries.

On 16 March 2004, 58 people were killed in an explosion at an apartment building in the city.

Administrative and municipal status
Arkhangelsk is the administrative center of the oblast and, within the framework of administrative divisions, it also serves as the administrative center of Primorsky District, even though it is not a part of it. As an administrative division, it is, together with five rural localities, incorporated separately as the city of oblast significance of Arkhangelsk—an administrative unit with the status equal to that of the districts. As a municipal division, the city of oblast significance of Arkhangelsk is incorporated as Arkhangelsk Urban Okrug.

City divisions
For administrative purposes, the city is divided into nine territorial okrugs:
 * Isakogorsky
 * Lomonosovsky
 * Maymaksansky
 * Mayskaya Gorka
 * Oktyabrsky
 * Severny
 * Solombalsky
 * Tsiglomensky
 * Varavino-Faktoriya

Transportation
Arkhangelsk is the final destination of Northern Railway. In addition, the city is host to two airports, Vaskovo Airport and Talagi Airport where they host the 2nd Arkhangelsk United Aviation Division and Smartavia Airline, respectively. M8 highway provides a direct link to Moscow, Yaroslavl and Severodvinsk, the administrative center of the oblast. Local public transit is provided by buses and minibuses called marshrutkas. Until 2004 there were also streetcars (trams), and until 2008, trolleybuses.

Education

Arkhangelsk was home to Pomorsky State University and Arkhangelsk State Technical University which merged with several other institutions of higher learning in 2010 to form the Northern (Arctic) Federal University.

Arkhangelsk is home to the Northern State Medical University, Makarov state Maritime Academy, and a branch of the All-Russian Distance Institute of Finance and Economics.

Culture
Mikhail Lomonosov came from a Pomor village near Kholmogory. A monument to him was installed to a design by Ivan Martos in 1829. A monument to Peter the Great was designed by Mark Antokolsky in 1872 and installed in 1914.

After its historic churches were destroyed during Joseph Stalin's rule, the city's main extant landmarks are the fort-like Merchant Yards (1668–1684) and the New Dvina Fortress (1701–1705). The Assumption Church on the Dvina embankment (1742–1744) was rebuilt in 2004.

In 2008, it was decided that the city's cathedral, dedicated to the Archangel Michael, which had been destroyed under the Soviets, would be rebuilt. The foundation stone was laid in November 2008 by the regional Bishop Tikhon. The cathedral, situated near the city's main bus station and river port, is expected to be completed and consecrated in 2019.

Another remarkable structure is the Arkhangelsk TV Mast, a 151 m tall guyed mast for FM-/TV-broadcasting built in 1964. This tubular steel mast has six crossbars equipped with gangways, which run in two levels from the central mast structure out to each of the three guys. On these crossbars there are also several antennas installed (image).

An unusual example of local "vernacular architecture" was the so-called Sutyagin House. This thirteen-story, 44 m tall residence of the local entrepreneur Nikolay Petrovich Sutyagin was reported to be the world's, or at least Russia's, tallest wooden house. Constructed by Sutyagin and his family over fifteen years (starting in 1992), without plans or a building permit, the structure deteriorated while Sutyagin spent a few years in prison on racketeering charges. In 2008, it was condemned by local authorities as a fire hazard, and the courts ordered it to be demolished by 1 February 2009. On 26 December 2008, the tower was pulled down, and the remainder of the building was dismantled manually by early February 2009. The cultural life of Arkhangelsk includes:
 * The Arkhangelsk Lomonosov Drama Theater
 * Arkhangelsk Philarmonia
 * Arkhangelsk Youth Theater
 * Arkhangelsk Oblast Museum
 * Arkhangelsk Art Museum
 * Stepan Pisakhov Museum

An airstrip in Arkhangelsk was the fictional setting for a level in the 1997 hit videogame Goldeneye 007.

Literature
The Russian North, and, in particular, the area of Arkhangelsk, is notable for its folklore. Until the mid-20th century, fairy tales and bylinas were still performed on the daily basis by performers who became professionals. Starting from the 1890s, folkloric expeditions have been organized to the White Sea area and later to other areas of the Arkhangelsk Governorate in order to write down the tales and the bylinas, especially in Pomor dialects.

In the 1920s, mostly due to the efforts of Anna Astakhova, these expeditions became systematic. By the 1960s, the performing art was basically extinct. These folkloric motives and fairy tales inspired the literary works of Stepan Pisakhov and Boris Shergin, who were both natives of Arkhangelsk.

Climate
Arkhangelsk experiences a subarctic climate (Köppen climate classification Dfc), with long (November–March), very cold winters and short (June–August), mildly warm summers. More extreme climates at this high latitude- such as Fairbanks, Alaska or Oymyakon, Sakha Republic- have much colder winters than Arkhangelsk, indicating that there is still significant moderation from the Atlantic Ocean.

Snowfall during winter is heavy, while summers are very rainy. Precipitation is very reliable year round.

Demographics
According to the 2021 Census, Arkhangelsk has a population of 301,199 people, which makes it the 68th largest city in Russia.

In the 2010 Census, the following ethnic groups were listed:

Sports

Bandy is the biggest sport in the city and is considered a national sport in Russia. Vodnik, the local team, nine times became the Russian champion (1996–2000 and 2002–2005). Their home arena has the capacity of 10000. Arkhangelsk hosted the Bandy World Championship in 1999 and 2003. The 2011–2012 season Russian Bandy League final was played here on March 25, 2012. The 2016 Youth-17 Bandy World Championship was played in Arkhangelsk between 28 and 31 January.

Notable people

 * Mikhail Lomonosov (1711–1765), Russian polymath
 * Piter Poel (1760–1837), Dutch diplomat and publisher
 * Johann Abraham Nüske (1796–1865), German-British guitarist and composer
 * Ilya Shumov (1819–1881), Russian chess master and officer in the Russian Navy
 * Wilhelm Greiffenhagen (1821–1890), Baltic German journalist and politician
 * Eduard Schensnovich (1852–1911), Polish admiral in the Imperial Russian Navy
 * Stepan Pisakhov (1879–1960), Russian and Soviet writer
 * Stepan Balmashov (1882–1902), Russian student and assassin
 * Boris Shergin (1896–1973), Russian and Soviet writer
 * Władysław Pobóg-Malinowski (1899–1962), Polish soldier and historian
 * Monja Danischewsky (1911–1994) British film producer
 * Boris Lukoshkov (1922–1989), Russian painter
 * Timur Gaidar (1926–1999), Soviet and Russian admiral
 * Mikhail Kalik (1927–2017), Soviet and Israeli film director and screenwriter
 * Vladimir Tarasov (born 1939), Russian percussionist and constellation artist
 * Boris Skrynnik (born 1948), President in Federation of International Bandy and Russian Bandy Federation
 * Slava Polunin (born 1950), Russian clown
 * Vladimir Malaniuk (1957–2017), Ukrainian chess player (GM)
 * Mikhail Pletnev (born 1957), Russian pianist and conductor
 * Alexander Dobrunov (1959–2006), Russian judo fighter
 * Victor Ferin (born 1969), Russian actor and filmmaker
 * Alexander Kravchenko (born 1971), Russian poker player
 * Anatoli Tebloyev (born 1974), Russian football player
 * Yuliya Fomenko (born 1979), Russian athlete (middle-distance runner)
 * Illya Haliuza (born 1979), Ukrainian football player
 * Sergei Bykov (born 1983), Russian basketball player
 * Nadezhda Kosintseva (born 1985), Russian chess player (GM)
 * Andrei Pervyshin (born 1985), Russian ice hockey player
 * Tatiana Kosintseva (born 1986), Russian chess player (GM)
 * Alex Gilbert (born 1992), Russian-born New Zealand adoption advocate

Twin towns – sister cities
Arkhangelsk is twinned with:

 * 🇺🇸 Portland, Maine, United States (1988)
 * 🇳🇴 Vardø, Norway (1989)
 * 🇩🇪 Emden, Germany (1989)

 * Sukhumi, Georgia (2011)
 * 🇮🇱 Ashdod, Israel (2012)
 * 🇦🇲 Jermuk, Armenia (2018)

Former twin towns:
 * 🇵🇱 Słupsk, Poland (1989–2022, terminated as a result of the Russian invasion of Ukraine)
 * 🇳🇴 Tromsø, Norway (2011–2022); Norwegian authorities gave 3 reasons for cutting Tromsø's ties with Arkhangelsk
 * 🇫🇮 Oulu, Finland (1993–2022)
 * 🇸🇪 Kiruna, Sweden (1999–2022)

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Arkhangelsk


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Robert Bork

Robert Heron Bork (March 1, 1927 – December 19, 2012) was an American legal scholar who served as solicitor general of the United States from 1973 until 1977. A professor by training, he was acting United States Attorney General and a judge on the U.S. Court of Appeals for the D.C. Circuit from 1982 to 1988. In 1987, President Ronald Reagan nominated Bork to the U.S. Supreme Court, but the Senate rejected his nomination after a contentious and highly publicized confirmation hearing.

Bork was born in Pittsburgh, Pennsylvania, and received both his undergraduate and legal education at the University of Chicago. After working at the law firms of Kirkland & Ellis and Willkie Farr & Gallagher, he served as a professor at Yale Law School. He became a prominent advocate of originalism, calling for judges to adhere to the original understanding of the United States Constitution, and an influential antitrust scholar, arguing that consumers often benefited from corporate mergers and that antitrust law should focus on consumer welfare rather than on ensuring competition. Bork wrote several notable books, including a scholarly work titled The Antitrust Paradox and a work of cultural criticism titled Slouching Towards Gomorrah.

From 1973 to 1977, he served as Solicitor General under Presidents Richard Nixon and Gerald Ford, successfully arguing several cases before the Supreme Court. During the October 1973 Saturday Night Massacre, Bork became acting U.S. Attorney General after his superiors in the U.S. Justice Department chose to resign rather than fire Special Prosecutor Archibald Cox, who was investigating the Watergate scandal. Following an order from President Nixon, Bork fired Cox as his first assignment as Acting Attorney General. Bork served as Acting Attorney General until January 4, 1974, and was succeeded by Ohio U.S. Senator William B. Saxbe.

In 1982, President Reagan appointed Bork to the Court of Appeals for the District of Columbia Circuit. In 1987, Reagan nominated Bork to replace retiring Supreme Court Justice Lewis Powell. His nomination attracted unprecedented media attention and efforts by interest groups to mobilize opposition to his confirmation, primarily due to his outspoken criticism of the Warren and Burger Courts and his role in the Saturday Night Massacre. His nomination was ultimately rejected in the Senate, 42–58, and the vacancy was filled by Anthony Kennedy. Bork resigned from his judgeship in 1988, taking up a career as an author. He served as a professor at various institutions, including the George Mason University School of Law. He advised presidential candidate Mitt Romney, and was a fellow at the American Enterprise Institute and at the Hudson Institute.

Early life and education
Bork was born on March 1, 1927, in Pittsburgh, Pennsylvania. He was the only child of Harry Philip Bork Jr. (1897–1974), a steel company purchasing agent, and Elizabeth (née Kunkle; 1898–2004), a schoolteacher. His father was of German and Irish ancestry, while his mother was of Pennsylvania German descent.

Bork attended the Hotchkiss School in Lakeville, Connecticut. He later recalled that he spent his time there "reading books and arguing with people". He then attended the University of Chicago, where he was a member of the international social fraternity Phi Gamma Delta and graduated with a Bachelor of Arts in 1948. He then attended the University of Chicago Law School, where he was an editor of the University of Chicago Law Review. He graduated in 1953 with a Juris Doctor and membership in the Order of the Coif and Phi Beta Kappa. While in law school, Bork took a two-year leave of absence to serve in the U.S. Marine Corps during the Korean War.

Academia
After law school, Bork spent another year in military service. From 1954 to 1962, he was in private practice at the law firms Kirkland & Ellis and Willkie Farr & Gallagher. In 1962, Bork left private practice and joined the faculty of Yale Law School as a professor. He taught at Yale from 1962 to 1981, with a four-year break from 1973 to 1977 when he served as U.S. Solicitor General. Among Bork's students at Yale Law were Bill Clinton, Hillary Clinton, Anita Hill, Robert Reich, Jerry Brown, Linda Greenhouse, John Bolton, Samuel Issacharoff, and Cynthia Estlund.

As a law professor, Bork was best known for his 1978 book The Antitrust Paradox, in which he argued that consumers often benefited from corporate mergers, and that many contemporary readings of the antitrust laws were economically irrational and hurt consumers. He posited that the primary focus of antitrust laws should be on consumer welfare, including producer welfare and consumer welfare, rather than ensuring competition, for fostering competition of companies within an industry has a natural built-in tendency to allow, and even help, many poorly run companies with methodologies and practices that are both inefficient and expensive to continue in business simply for the sake of competition, to the detriment of both consumers and society. Bork's writings on antitrust law, with those of Richard Posner and other law and economics and Chicago School thinkers, have been influential in causing a shift in the Supreme Court's approach to antitrust laws since the 1970s. Bork also supports using anticompetitive practices within the text as useful business practices. (e.g. exclusive deals, mergers, price fixing, etc.)

Solicitor General
Bork served as Solicitor General in the U.S. Department of Justice from March 1973 until 1977. As Solicitor General, he argued several high-profile cases before the Supreme Court in the 1970s, including 1974's Milliken v. Bradley, where his brief in support of the State of Michigan was influential among the justices. Chief Justice Warren Burger called Bork the most effective counsel to appear before the court during his tenure. Bork hired many young attorneys as assistants who went on to have successful careers, including judges Danny Boggs and Frank H. Easterbrook as well as Robert Reich, later Secretary of Labor in the Clinton administration.

Saturday Night Massacre
On October 20, 1973, Solicitor General Bork was part of the "Saturday Night Massacre" when President Richard Nixon ordered the firing of Watergate Special Prosecutor Archibald Cox following Cox's request for tapes of his Oval Office conversations. Nixon initially ordered U.S. Attorney General Elliot Richardson to fire Cox. Richardson resigned rather than carry out the order. Richardson's top deputy, Deputy Attorney General William Ruckelshaus, also considered the order "fundamentally wrong" and resigned, making Bork Acting Attorney General.

When Nixon reiterated his order, Bork complied and fired Cox. Bork claimed he carried out the order under pressure from Nixon's attorneys and intended to resign immediately afterward, but was persuaded by Richardson and Ruckelshaus to stay on for the good of the Justice Department. Bork remained Acting Attorney General until the appointment of William B. Saxbe on January 4, 1974. In his posthumously published memoirs, Bork claimed that after he carried out the order, Nixon promised him the next seat on the Supreme Court, though Bork did not take the offer seriously as he believed Watergate had left Nixon too politically compromised to appoint another justice. Nixon never had the chance to carry out his promise, as the next Supreme Court vacancy came after Nixon resigned and Gerald Ford assumed the presidency, with Ford instead nominating John Paul Stevens following the 1975 retirement of William O. Douglas. Ford planned to nominate Bork to replace William Colby as CIA Director, but his advisors convinced him to turn first to Edward Bennett Williams and then George H. W. Bush instead due to Bork's unpopularity and lack of experience in intelligence.

United States Circuit Judge
Bork was a circuit judge for the United States Court of Appeals for the District of Columbia Circuit from 1982 to 1988. He was nominated by President Ronald Reagan on December 7, 1981, was confirmed via voice vote by the Senate on February 8, 1982, and received his commission on February 9, 1982.

One of Bork's opinions while on the D.C. Circuit was Dronenburg v. Zech, 741 F.2d 1388, decided in 1984. The case involved James L. Dronenburg, a sailor who had been administratively discharged from the United States Navy for engaging in homosexual conduct. Dronenburg argued that his discharge violated his right to privacy. His argument was rejected in an opinion written by Bork and joined by Antonin Scalia, in which Bork critiqued the line of Supreme Court cases upholding a right to privacy.

In rejecting Dronenburg's suggestion for a rehearing en banc, the D.C. Circuit issued four separate opinions, including one by Bork (again joined by Scalia), who wrote that "no principle had been articulated [by the Supreme Court] that enabled us to determine whether appellant's case fell within or without that principle."

In 1986, President Reagan considered nominating Bork to the Supreme Court after Chief Justice Warren Burger retired. Reagan ultimately nominated then-Associate Justice William Rehnquist to be the next Chief Justice and Bork's D.C. Circuit colleague, Antonin Scalia, for Rehnquist's Associate Justice seat. Some journalists and correspondents believed that if Reagan nominated Bork in 1986, Bork would have likely reached the Supreme Court, for the Senate at that time was led by the Republicans. However, the Senate Democrats might still have fought to defeat Bork in 1986, and the Republicans' Senate majority at the time was narrow (53–47), which implies that maybe Bork still would have been defeated in 1986, especially when the six Republicans who voted against Bork's 1987 nomination were not first elected in the November 1986 Senate elections.

U.S. Supreme Court nomination

President Reagan nominated Bork for associate justice of the Supreme Court on July 1, 1987, to replace retiring Associate Justice Lewis F. Powell Jr. A hotly contested United States Senate debate over Bork's nomination ensued. Opposition was partly fueled by civil rights and women's rights groups, concerned about Bork's opposition to the authority claimed by the federal government to impose standards of voting fairness upon states (at his confirmation hearings for the position of solicitor general, he supported the rights of Southern states to impose a poll tax), and his stated desire to roll back civil rights decisions of the Warren and Burger courts. Bork is one of four Supreme Court nominees (along with William Rehnquist, Samuel Alito, and Brett Kavanaugh) to have been opposed by the American Civil Liberties Union. Bork was criticized for being an "advocate of disproportionate powers for the executive branch of Government, almost executive supremacy", most notably, according to critics, for his role in the Saturday Night Massacre.

Before Justice Powell's expected retirement on June 27, 1987, some Senate Democrats had asked liberal leaders to "form a 'solid phalanx' of opposition" if President Reagan nominated an "ideological extremist" to replace him, assuming it would tilt the court rightward. Democrats warned Reagan there would be a fight if Bork were nominated. Nevertheless, Reagan nominated Bork for Powell's seat on July 1, 1987.

Following Bork's nomination, Senator Ted Kennedy took to the Senate floor with a strong condemnation of him, declaring:

"Robert Bork's America is a land in which women would be forced into back-alley abortions, blacks would sit at segregated lunch counters, rogue police could break down citizens' doors in midnight raids, schoolchildren could not be taught about evolution, writers and artists could be censored at the whim of the Government, and the doors of the Federal courts would be shut on the fingers of millions of citizens for whom the judiciary is--and is often the only--protector of the individual rights that are the heart of our democracy. ... The damage that President Reagan will do through this nomination, if it is not rejected by the Senate, could live on far beyond the end of his presidential term. President Reagan is still our president. But he should not be able to reach out from the muck of Irangate, reach into the muck of Watergate and impose his reactionary vision of the Constitution on the Supreme Court and the next generation of Americans. No justice would be better than this injustice."

Bork responded, "There was not a line in that speech that was accurate." In an obituary of Kennedy, The Economist remarked that Bork may well have been correct, "but it worked". Bork contended in his book, The Tempting of America, that the brief prepared for then-Senator Joe Biden, Chairman of the Senate Judiciary Committee, "so thoroughly misrepresented a plain record that it easily qualifies as world class in the category of scurrility." Opponents of Bork's nomination found the arguments against him justified, claiming that Bork believed the Civil Rights Act was unconstitutional, and he supported poll taxes, literacy tests for voting, mandated school prayer, and sterilization as a requirement for a job, while opposing free speech rights for non-political speech and privacy rights for gay conduct. In 1988, an analysis published in The Western Political Quarterly of amicus curiae briefs filed by U.S. Solicitors General during the Warren and Burger courts found that during Bork's tenure in the position during the Nixon and Ford Administrations (1973–1977), Bork took liberal positions in the aggregate as often as Thurgood Marshall did during the Johnson Administration (1965–1967) and more often than Wade H. McCree did during the Carter Administration (1977–1981), in part because Bork filed briefs in favor of the litigants in civil rights cases 75 percent of the time.

Television advertisements produced by People For the American Way and narrated by Gregory Peck attacked Bork as an extremist. Kennedy's speech successfully fueled widespread public skepticism of Bork's nomination. The rapid response to Kennedy's "Robert Bork's America" speech stunned the Reagan White House, and the accusations went unanswered for $2 1/2$ months.

During debate over his nomination, Bork's video rental history was leaked to the press. His video rental history was unremarkable, and included such harmless titles as A Day at the Races, Ruthless People, and The Man Who Knew Too Much. Writer Michael Dolan, who obtained a copy of the hand-written list of rentals wrote about it for the Washington City Paper. Dolan justified accessing the list on the ground that Bork himself had stated that Americans had only such privacy rights as afforded them by direct legislation. The incident led to the enactment of the 1988 Video Privacy Protection Act.

To pro-choice rights legal groups, Bork's originalist views and his belief that the Constitution did not contain a general "right to privacy" were viewed as a clear signal that, should he become a justice of the Supreme Court, he would vote to completely overrule the Court's 1973 decision in Roe v. Wade. Accordingly, a large number of groups mobilized to press for Bork's rejection, and the 1987 Senate confirmation hearings became an intensely partisan battle.

On October 23, 1987, the Senate denied Bork's confirmation, with 42 senators voting in favor and 58 senators voting against. Two Democratic senators (David Boren of Oklahoma, and Fritz Hollings of South Carolina) voted in favor of his nomination, while six Republican senators (John Chafee of Rhode Island, Bob Packwood of Oregon, Arlen Specter of Pennsylvania, Robert Stafford of Vermont, John Warner of Virginia, and Lowell Weicker of Connecticut) voted against it. His defeat in the Senate was the worst of any Supreme Court nominee since George Washington Woodward was defeated 20–29 in 1845, and the third-worst on record.

The seat to which Bork had been nominated went to Judge Anthony Kennedy, who was unanimously approved by the Senate, 97–0. Bork, unhappy with his treatment in the nomination process, resigned his appellate court judgeship in 1988.

"Bork" as a verb
According to columnist William Safire, the first published use of "bork" as a verb was possibly in The Atlanta Journal-Constitution of August 20, 1987, two months prior to the final vote: "Let's just hope something enduring results for the justice-to-be, like a new verb: Borked." A well known use of the verb "to bork" occurred in July 1991 at a conference of the National Organization for Women in New York City. Feminist Florynce Kennedy addressed the conference on the importance of defeating the nomination of Clarence Thomas to the U.S. Supreme Court, saying: "We're going to bork him. We're going to kill him politically. This little creep, where did he come from?" Thomas was confirmed after the most divisive confirmation hearing in Supreme Court history to that point.

In March 2002, the Oxford English Dictionary added an entry for the verb "bork" as U.S. political slang, with this definition: "To defame or vilify (a person) systematically, esp. in the mass media, usually to prevent his or her appointment to public office; to obstruct or thwart (a person) in this way." Supreme Court Justice Brett Kavanaugh used the term during his own contentious Senate confirmation hearing testimony, when he stated: "The behavior of several of the Democratic members of this committee at my hearing a few weeks ago was an embarrassment. But at least it was just a good old-fashioned attempt at borking."

Later work
Following his failure to be confirmed, Bork resigned his seat on the U.S. Court of Appeals for the D.C. Circuit, and was for several years both a professor at George Mason University School of Law and a senior fellow at the American Enterprise Institute for Public Policy Research. He consulted for Netscape in the Microsoft litigation.

Bork later served as a fellow at the Hudson Institute, a visiting professor at the University of Richmond School of Law and a professor at Ave Maria School of Law in Naples, Florida. In 2011, he worked as a legal adviser for the presidential campaign of Republican Mitt Romney.

Advocacy of originalism
Bork is known by American conservatives for his theory that the best way to reconcile the role of the judiciary in the U.S. government against what he terms the "Madisonian" or "counter-majoritarian" dilemma of the judiciary making law without popular approval is for constitutional adjudication to be guided by the framers' original understanding of the United States Constitution. Reiterating that it is a court's task to adjudicate and not to "legislate from the bench," he advocated that judges exercise restraint in deciding cases, emphasizing that the role of the courts is to frame "neutral principles" (a term borrowed from Herbert Wechsler) and not simply ad hoc pronouncements or subjective value judgments. Bork once said, "The truth is that the judge who looks outside the Constitution always looks inside himself and nowhere else."

Bork built on the influential critiques of the Warren Court authored by Alexander Bickel, who criticized the Supreme Court under Earl Warren, alleging shoddy and inconsistent reasoning, undue activism, and misuse of historical materials. Bork's critique was harder-edged than Bickel's, writing: "We are increasingly governed not by law or elected representatives but by an unelected, unrepresentative, unaccountable committee of lawyers applying no will but their own." Bork's writings influenced judges such as Associate Justice Antonin Scalia and Chief Justice William Rehnquist of the U.S. Supreme Court, and sparked vigorous debate within legal academia about how to interpret the Constitution.

Some conservatives criticized Bork's approach. Conservative scholar Harry Jaffa criticized Bork (along with Rehnquist and Scalia) for failing to adhere to natural law principles, and therefore believing that the Constitution says nothing about abortion or gay rights (Jaffa believed that the Constitution prohibited these things.) Robert P. George explained Jaffa's critique this way: "He attacks Rehnquist and Scalia and Bork for their embrace of legal positivism that is inconsistent with the doctrine of natural rights that is embedded in the Constitution they are supposed to be interpreting." Jaffa attacked Bork as insufficiently conservative. Bork, in turn, described adherents of natural law constitutionalism as fanatical.

Works and views
Bork wrote several books, including the two best-sellers The Tempting of America, about his judicial philosophy and his nomination battle, and Slouching Towards Gomorrah: Modern Liberalism and American Decline, in which he argued that the rise of the New Left in the 1960s in the U.S. undermined the moral standards necessary for civil society, and spawned a generation of intellectuals who oppose Western civilization. During the period these books were written, as well as most of his adult life, Bork was an agnostic, a fact used pejoratively behind the scenes by Southern Democrats when speaking to their evangelical constituents during his Supreme Court nomination process. Bork's 1971 Indiana Law Journal article "Neutral Principles and Some First Amendment Problems" has been identified as one of the most cited legal articles of all time.

In The Tempting of America, p. 82, Bork explained his support for the Supreme Court's desegregation decision in Brown v. Board of Education: "By 1954, when Brown came up for decision, it had been apparent for some time that segregation rarely if ever produced equality. Quite aside from any question of psychology, the physical facilities provided for blacks were not as good as those provided for whites. That had been demonstrated in a long series of cases… The Court's realistic choice, therefore, was either to abandon the quest for equality by allowing segregation or to forbid segregation in order to achieve equality. There was no third choice. Either choice would violate one aspect of the original understanding, but there was no possibility of avoiding that. Since equality and segregation were mutually inconsistent, though the ratifiers did not understand that, both could not be honored. When that is seen, it is obvious the Court must choose equality and prohibit state-imposed segregation. The purpose that brought the fourteenth amendment into being was equality before the law, and equality, not separation, was written into the law."Bork opposed the Civil Rights Act of 1964, saying that the provisions within the Act which prohibited racial discrimination by public accommodations were based on a principle of "unsurpassed ugliness". He came to repudiate his earlier views, saying in his 1987 confirmation hearing that the Civil Rights Act and other racial equality legislation of the 1960s "helped bring the nation together in ways which otherwise would not have occurred."

Bork opposed the 1965 Supreme Court ruling in Griswold v. Connecticut, which struck down a Connecticut Comstock Act of 1873 that prohibited the use of contraceptives for married couples. Bork said the decision was "utterly specious", "unprincipled" and "intellectually empty". Bork argued that the Constitution only protected speech that was "explicitly political", and that there were no free speech protections for "scientific, literary or that variety of expression we call obscene or pornographic."

Bork was known for his disregard for the Ninth Amendment. When asked about his views on unenumerated constitutional rights during his confirmation hearings by Arizona Senator Dennis DeConcini, Bork famously compared the Ninth Amendment to an uninterpretable inkblot, too vague for judges to meaningfully enforce.

In 1998, he reviewed High Crimes and Misdemeanors: The Case Against Bill Clinton, conservative pundit Ann Coulter's book on impeaching Clinton, pointing out that "'High crimes and misdemeanors' are not limited to actions that are crimes under federal law."

In 1999, Bork wrote an essay about Thomas More and attacked jury nullification as a "pernicious practice". Bork once quoted More in summarizing his judicial philosophy. In 2003, he published Coercing Virtue: The Worldwide Rule of Judges, an American Enterprise Institute book that includes Bork's philosophical objections to the phenomenon of incorporating international ethical and legal guidelines into the fabric of domestic law. In particular, he focused on problems he viewed as inherent in the federal judiciaries of Israel, Canada, and the United States— countries where he believes courts have exceeded their discretionary powers, discarded precedent and common law and instead substituted their own liberal judgment.

Bork advocated modifying the Constitution to allow Congressional supermajorities to override Supreme Court decisions, similar to the Canadian Charter of Rights and Freedoms' notwithstanding clause. Though Bork had many liberal critics, some of his arguments have earned criticism from conservatives as well. Although an opponent of gun control, Bork denounced what he called the "NRA view" of the Second Amendment, something he described as the "belief that the constitution guarantees a right to Teflon-coated bullets." Instead, he argued that the Second Amendment merely guarantees a right to participate in a government militia, that its intent was to guarantee the right of militia membership, not an individual right to bear arms. He is quoted as saying that the gun lobby's interpretation of the Second Amendment was intentional deception, not "law as integrity," and that states could technically pass a ban on assault weapons.

Bork converted to Catholicism from Presbyterianism in 2003.

In October 2005, Bork publicly criticized the nomination of Harriet Miers to the Supreme Court, saying her nomination was "a disaster on every level."

On June 6, 2007, Bork filed suit in federal court in New York City against the Yale Club over an incident that had occurred a year earlier. Bork alleged that, while trying to reach the dais to speak at an event, he fell, because of the Yale Club's failure to provide any steps or handrail between the floor and the dais. (After his fall, he successfully climbed to the dais and delivered his speech.) According to the complaint, Bork's injuries required surgery, immobilized him for months, forced him to use a cane, and left him with a limp. In May 2008, Bork and the Yale Club reached a confidential, out-of-court settlement.

On June 7, 2007, Bork with several others authored an amicus brief on behalf of Scooter Libby arguing that there was a substantial constitutional question regarding the appointment of the prosecutor in the case, reviving the debate that had previously resulted in the Morrison v. Olson decision.

On December 15, 2007, Bork endorsed Mitt Romney for president in the 2012 presidential election. He repeated this endorsement on August 2, 2011, during Romney's second campaign for the White House.

A 2008 issue of the Harvard Journal of Law and Public Policy collected essays in tribute to Bork. Authors included Frank H. Easterbrook, George Priest, and Douglas Ginsburg.

Personal life
Bork was married to Claire Davidson from 1952 until her death from cancer in 1980. They had a daughter, Ellen, and two sons, Robert Bork Jr. and Charles Bork. In 1982, he married Mary Ellen Pohl, a Catholic religious sister turned activist. Bork Jr. is a prominent conservative activist who is currently president of the Antitrust Education Project.

Death
Bork died of complications from heart disease at the Virginia Hospital Center in Arlington County, Virginia, on December 19, 2012, at age 85. Following his death, Scalia referred to Bork as "one of the most influential legal scholars of the past 50 years" and "a good man and a loyal citizen". He is interred at Fairfax Memorial Park in Fairfax, Virginia.

Selected writings

 * — (1978). The Antitrust Paradox. New York: Free Press. ISBN 0-465-00369-9; 2nd edition (1993).
 * — (1990). The Tempting of America. New York: Free Press. ISBN 0-684-84337-4.
 * — (1996). Slouching Towards Gomorrah: Modern Liberalism and American Decline. New York: ReganBooks. ISBN 0-06-039163-4.
 * — (2003). Coercing Virtue: The Worldwide Rule of Judges. Washington, DC: American Enterprise Institute Press. ISBN 0-8447-4162-0.
 * — (ed.) (2005). A Country I Do Not Recognize: The Legal Assault on American Values. Stanford: Hoover Institution Press. ISBN 0-8179-4602-0.
 * — (2008) A Time to Speak: Selected Writings and Arguments. Wilmington, DL: ISI Books. ISBN 978-1-933859-68-2
 * — (2013) Saving Justice: Watergate, the Saturday Night Massacre, and Other Adventures of a Solicitor General. New York: Encounter Books. ISBN 978-1-59403-681-1
 * — (ed.) (2005). A Country I Do Not Recognize: The Legal Assault on American Values. Stanford: Hoover Institution Press. ISBN 0-8179-4602-0.
 * — (2008) A Time to Speak: Selected Writings and Arguments. Wilmington, DL: ISI Books. ISBN 978-1-933859-68-2
 * — (2013) Saving Justice: Watergate, the Saturday Night Massacre, and Other Adventures of a Solicitor General. New York: Encounter Books. ISBN 978-1-59403-681-1

title: Robert Bork


text:
Parse tree

A parse tree or parsing tree or derivation tree or concrete syntax tree is an ordered, rooted tree that represents the syntactic structure of a string according to some context-free grammar. The term parse tree itself is used primarily in computational linguistics; in theoretical syntax, the term syntax tree is more common.

Concrete syntax trees reflect the syntax of the input language, making them distinct from the abstract syntax trees used in computer programming. Unlike Reed-Kellogg sentence diagrams used for teaching grammar, parse trees do not use distinct symbol shapes for different types of constituents.

Parse trees are usually constructed based on either the constituency relation of constituency grammars (phrase structure grammars) or the dependency relation of dependency grammars. Parse trees may be generated for sentences in natural languages (see natural language processing), as well as during processing of computer languages, such as programming languages.

A related concept is that of phrase marker or P-marker, as used in transformational generative grammar. A phrase marker is a linguistic expression marked as to its phrase structure. This may be presented in the form of a tree, or as a bracketed expression. Phrase markers are generated by applying phrase structure rules, and themselves are subject to further transformational rules. A set of possible parse trees for a syntactically ambiguous sentence is called a "parse forest."

Nomenclature
A parse tree is made up of nodes and branches. In the picture the parse tree is the entire structure, starting from S and ending in each of the leaf nodes (John, ball, the, hit). In a parse tree, each node is either a root node, a branch node, or a leaf node. In the above example, S is a root node, NP and VP are branch nodes, while John, ball, the, and hit are all leaf nodes.

Nodes can also be referred to as parent nodes and child nodes. A parent node is one which has at least one other node linked by a branch under it. In the example, S is a parent of both NP and VP. A child node is one which has at least one node directly above it to which it is linked by a branch of the tree. Again from our example, hit is a child node of V.

A nonterminal function is a function (node) which is either a root or a branch in that tree whereas a terminal function is a function (node) in a parse tree which is a leaf.

For binary trees (where each parent node has two immediate child nodes), the number of possible parse trees for a sentence with n words is given by the Catalan number $$C_n$$.

Constituency-based parse trees
The constituency-based parse trees of constituency grammars (phrase structure grammars) distinguish between terminal and non-terminal nodes. The interior nodes are labeled by non-terminal categories of the grammar, while the leaf nodes are labeled by terminal categories. The image below represents a constituency-based parse tree; it shows the syntactic structure of the English sentence John hit the ball:

The parse tree is the entire structure, starting from S and ending in each of the leaf nodes (John, hit, the, ball). The following abbreviations are used in the tree:

 * S for sentence, the top-level structure in this example

 * NP for noun phrase. The first (leftmost) NP, a single noun "John", serves as the subject of the sentence. The second one is the object of the sentence.

 * VP for verb phrase, which serves as the predicate

 * V for verb. In this case, it's a transitive verb hit.

 * D for determiner, in this instance the definite article "the"

 * N for noun

Each node in the tree is either a root node, a branch node, or a leaf node. A root node is a node that does not have any branches on top of it. Within a sentence, there is only ever one root node. A branch node is a parent node that connects to two or more child nodes. A leaf node, however, is a terminal node that does not dominate other nodes in the tree. S is the root node, NP and VP are branch nodes, and John (N), hit (V), the (D), and ball (N) are all leaf nodes. The leaves are the lexical tokens of the sentence. A parent node is one that has at least one other node linked by a branch under it. In the example, S is a parent of both N and VP. A child node is one that has at least one node directly above it to which it is linked by a branch of a tree. From the example, hit is a child node of V. The terms mother and daughter are also sometimes used for this relationship.

Dependency-based parse trees
The dependency-based parse trees of dependency grammars see all nodes as terminal, which means they do not acknowledge the distinction between terminal and non-terminal categories. They are simpler on average than constituency-based parse trees because they contain fewer nodes. The dependency-based parse tree for the example sentence above is as follows:

 * Parse2.jpg

This parse tree lacks the phrasal categories (S, VP, and NP) seen in the constituency-based counterpart above. Like the constituency-based tree, constituent structure is acknowledged. Any complete sub-tree of the tree is a constituent. Thus this dependency-based parse tree acknowledges the subject noun John and the object noun phrase the ball as constituents just like the constituency-based parse tree does.

The constituency vs. dependency distinction is far-reaching. Whether the additional syntactic structure associated with constituency-based parse trees is necessary or beneficial is a matter of debate.

Phrase markers
Phrase markers, or P-markers, were introduced in early transformational generative grammar, as developed by Noam Chomsky and others. A phrase marker representing the deep structure of a sentence is generated by applying phrase structure rules. Then, this application may undergo further transformations.

Phrase markers may be presented in the form of trees (as in the above section on constituency-based parse trees), but are often given instead in the form of "bracketed expressions", which occupy less space in the memory. For example, a bracketed expression corresponding to the constituency-based tree given above may be something like:

 * $$[_S\ [_\mathit{N}\ \text{John}]\ [_\mathit{VP}\ [_V\ \text{hit}]\ [_\mathit{NP}\ [_\mathit{D}\ \text{the}]\ [_N\ \text{ball}]]]]$$

As with trees, the precise construction of such expressions and the amount of detail shown can depend on the theory being applied and on the points that the query author wishes to illustrate.

title: Parse tree


text:
Howard Keel

Harold Clifford Keel (April 13, 1919 – November 7, 2004), professionally Howard Keel, was an American actor and singer known for his rich bass-baritone singing voice. He starred in a number of MGM musicals in the 1950s and in the television series Dallas from 1981 to 1991.

Early life
Keel was born in Gillespie, Illinois, the younger of two sons born to Navyman-turned-coalminer Homer Keel and his wife, Grace Margaret (née Osterkamp). Howard's elder brother was Frederick William Keel. After his father's death in 1930, Keel and his mother moved to California, where he graduated from Fallbrook High School at age 17. He worked various odd jobs until settling at Douglas Aircraft Company as a "traveling representative". He was a long haul truck driver.

In the 1950s, the MGM publicity department stated that Keel's birth name was Harold Leek.

Career
At age 20, Keel was overheard singing by his landlady Mom Rider and was encouraged to take vocal lessons. One of his music heroes was the great baritone Lawrence Tibbett. Keel later remarked that learning that his own voice was a basso cantante was one of the greatest disappointments of his life. Nevertheless, his first public performance took place in the summer of 1941 when he played the role of Samuel the Prophet in Handel's oratorio Saul (singing a duet with bass-baritone George London).

In 1945, he made his Broadway debut as a vacation replacement for John Raitt in Carousel, playing the role of Billy Bigelow from August 20 - September 8, 1945. Two weeks later, on September 24, he took over the lead role of Curly in Oklahoma!, playing across the street at the St. James Theatre. He temporarily left Oklahoma! to fill-in once again for John Raitt, this time from June 3 - August 31, 1946, returning to Oklahoma! afterwards. In 1947, Oklahoma! became the first American postwar musical to travel to London, England, and Keel joined the production. On April 30, 1947, at the Drury Lane Theatre, the capacity audience (which included the future Queen Elizabeth II) demanded 14 encores.

Keel made his film debut as Harold Keel at the British Lion studio in Elstree, in The Small Voice (1948), released in the United States as The Hideout. He played an escaped convict holding a playwright and his wife hostage in their English country cottage. Additional Broadway credits include Saratoga, No Strings, and Ambassador. He appeared at The Muny in St. Louis as Adam in Seven Brides for Seven Brothers (1978), Emile de Becque in South Pacific (1992), and as General Waverly in White Christmas (2000).

MGM
From London's West End, Keel went to Hollywood in 1949 where he was engaged by the Metro-Goldwyn-Mayer film studio. He made his musical film debut as Frank Butler in the film version of Irving Berlin's Annie Get Your Gun (1950), co-starring with Betty Hutton. The film was a big hit and established Keel as a star.

MGM put him with Esther Williams in Pagan Love Song (1950), which was successful, but not as profitable as most Esther Williams films because it went over budget. Keel had a third hit in a row with the comedy Three Guys Named Mike (1951), supporting Van Johnson and Jane Wyman.

Even more popular was Show Boat (1951), where Keel played the male lead with Kathryn Grayson and Ava Gardner. Keel was reunited with Williams in Texas Carnival (1952). He had his first flop at MGM with the comedy Callaway Went Thataway (1952) co-starring Fred MacMurray and Dorothy McGuire. Lovely to Look At (1952), with Grayson and based on the stage musical Roberta, was popular but lost money.

MGM tried him in the adventure film Desperate Search (1953), which was poorly received. So too was the comedy Fast Company (1953). More popular was Ride, Vaquero! (1953), with Gardner and Robert Taylor.

Warner Bros borrowed Keel to play Wild Bill Hickok with Doris Day in Calamity Jane (1953), another hit. Back at MGM, he and Grayson made Kiss Me Kate (1953), which again was liked by the public but unprofitable. The same went for Rose Marie (1954) which Keel made with Ann Blyth. However Seven Brides for Seven Brothers (1954) with Jane Powell was a huge success, and it made MGM over $3 million in profit.

Keel was one of many guest stars in Deep in My Heart (1954). He and Williams made Jupiter's Darling (1955), which lost MGM over $2 million - the first Williams movie to lose money. Kismet (1955) with Blyth also lost over $2 million, and Keel was released from his MGM contract.

Post-MGM
He returned to his first love, the stage. In 1957, he was in a short-lived revival of Carousel. Keel's next film was made in Britain, the thriller Floods of Fear (1959). He returned to Hollywood to play Simon-Peter in the Biblical epic The Big Fisherman (1960). In 1959–1960, he was in the short-lived Broadway musical Saratoga. Keel went to Europe to make the low-budget film Armored Command (1961). In England, he starred in The Day of the Triffids (1962).

As America's taste in entertainment changed, finding jobs became more difficult for Keel. The 1960s held limited prospects for career advancement and consisted primarily of nightclub work, B-Westerns and summer stock. He did Carousel in 1962 and 1966. He replaced Richard Kiley on Broadway in No Strings (1962). Keel starred in Westerns for A. C. Lyles: Waco (1966), Red Tomahawk (1966) and Arizona Bushwhackers (1968). He had a supporting part in the John Wayne movie The War Wagon (1967).

In early 1970, Keel met Judy Magamoll, who was 25 years younger than he and who knew nothing about his stardom. Years later, Keel called the relationship love at first sight, but the age difference bothered him tremendously. For Magamoll, however, it was not a problem, and with the aid of Robert Frost's poem "What Fifty Said", she convinced him to proceed with their relationship. He resumed his routine of nightclub, cabaret and summer stock.

From 1971 to 1972, Keel appeared briefly in the West End and Broadway productions of the musical Ambassador, which flopped. In 1974, Keel became a father for the fourth time with the birth of his daughter Leslie Grace. In January 1986, he underwent double heart bypass surgery.

Dallas
Keel continued to tour with his wife and daughter in tow, but by 1980 had decided to make his life change. He moved his family to Oklahoma with the intention of joining an oil company. The family had barely settled down when Keel was called to California to appear with Jane Powell on an episode of The Love Boat. While there, he was told that the producers of the television series Dallas wanted to speak with him.

In 1981, after several guest appearances, Keel joined the show permanently as the dignified but hot-tempered oil baron Clayton Farlow. Starting with an appearance on the fourth season, the character had been meant as a semi-replacement patriarch for the series' Jock Ewing played by Jim Davis, who had died. However, Clayton was such a hit among viewers that he was made a series regular and stayed until its end in 1991. Not only did Dallas revive his acting career, it revived his recording endeavors.

Recording career
With renewed fame, Keel commenced his first solo recording career, at age 64, as well as a successful concert career in the UK. He released the album With Love in 1984, which sold poorly. However, his album And I Love You So reached #6 in the UK Albums Chart and #37 in Australia in 1984. The follow-up album, Reminiscing – The Howard Keel Collection peaked at #20 in the UK Albums Chart, spending 12 weeks in this listing in 1985 and 1986. The album also peaked at #83 in Australia. In 1988, the album Just for You reached #51 in the UK Albums Chart.

In 1994, Keel and Magamoll moved to Palm Desert, California. The Keels were active in community charity events, and attended the annual Howard Keel Golf Classic at Mere Golf Club in Cheshire, England, which raised money for the National Society for the Prevention of Cruelty to Children (NSPCC). Keel attended the event for many years until 2004.

Honors
Keel received a star on the Hollywood Walk of Fame on 8 February 1960. It is located at 6253 Hollywood Boulevard.

A Golden Palm Star on the Walk of Stars was dedicated to him in 1996.

Keel was a member of the Grand Order of Water Rats.

In 2019, he was inducted into the Western Performers Hall of Fame at the National Cowboy & Western Heritage Museum in Oklahoma City, Oklahoma.

Personal life and death
In 1943, Keel met and married actress Rosemary Cooper. They divorced in 1948. During the London run of Oklahoma! Keel met Helen Anderson, a member of the show's chorus, and they married in January 1949. Keel and Helen divorced in 1970. Keel married airline flight attendant Judy Magamoll in December 1970.

Keel had four children: three with second wife, Helen Anderson (two daughters, Kaija Liane and Kirstine Elizabeth; and a son, Gunnar Louis; one by his third wife of 34 years, Judy (a daughter, Leslie Grace); and 10 grandchildren.

Keel died at his Palm Desert home on November 7, 2004, six weeks after being diagnosed with colon cancer.

Stage work

 * Oklahoma! (1945–46; 1947)
 * Carousel (1946; 1957; 1962; 1966)
 * South Pacific (1957; 1965; 1978; 1992)
 * Mister Roberts (1959)
 * Saratoga (1959)
 * Kismet (1962)
 * No Strings (1962–63)
 * Show Boat (1963)
 * Camelot (1964)
 * Kiss Me, Kate (1964)
 * On a Clear Day You Can See Forever (1967)
 * The Fantasticks (1968)
 * The Unsinkable Molly Brown (1971–1972; 1973)
 * Ambassador (1971–72)
 * The Most Happy Fella (1971)
 * Man of La Mancha (1972)
 * Seven Brides for Seven Brothers (1978)
 * Paint Your Wagon (1979)
 * I Do! I Do! (1980)
 * My Fair Lady (1996)
 * White Christmas (2000)

title: Howard Keel


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London postal district

The London postal district is the area in England of 241 sqmi to which mail addressed to the London post town is delivered. The General Post Office under the control of the Postmaster General directed Sir Rowland Hill to devise the area in 1856 and throughout its history it has been subject to reorganisation and division into increasingly smaller postal units, with the early loss of two compass points and a minor retraction in 1866. It was integrated by the Post Office into the national postcode system of the United Kingdom during the early 1970s and corresponds to the E, EC, N, NW, SE, SW, W and WC postcode areas. The postal district has also been known as the London postal area. The County of London was much smaller, at 117 mi2, but Greater London is much larger at 607 mi2.

Origins
By the 1850s, the rapid growth of the metropolitan area meant it became too large to operate efficiently as a single post town. A Post Office inquiry into the problem had been set up in 1837 and a House of Commons committee was initiated in 1843. In 1854 Charles Canning, the Postmaster General, set up a committee at the Post Office in St. Martin's Le Grand to investigate how London could best be divided for the purposes of directing mail. In 1856, of the 470 million items of mail sent in the United Kingdom during the year, approximately one fifth (100 million) were for delivery in London and half of these (50 million items) also originated there.

The General Post Office under the control of the Postmaster General devised the area in 1856. Sir Rowland Hill produced an almost perfectly circular area of 12 mi radius from the central post office at St. Martin's Le Grand in central London. As originally devised, it extended from Waltham Cross in the north to Carshalton in the south and from Romford in the east to Sunbury in the west — six counties at the time if including the City of London. Within the district it was divided into two central areas and eight compass points which operated much like separate post towns. Each was named "London" with a suffix (EC, WC, N, NE, E, SE, S, SW, W, and NW) indicating the area it covered; each had a separate head office. The system was introduced during 1857 and completed on 1 January 1858.

Abolition of NE and S divisions and retraction of E division
During the 1860s, following an official report by Anthony Trollope, the E division subsumed the original NE division (which became defunct) and the S division was split between the SE and SW divisions. In 1866, NE was abolished; large districts transferred to E included Walthamstow, Wanstead and Leytonstone. The remaining eight letter prefixes (excluding all numbers) were not changed. In 1868 the S district was abolished and split between SE and SW.

At the same time, the London postal district boundary was retracted in the east, when some Essex areas, including around Ilford, became part of other postal towns.

The NE and S codes have been re-used in the national postcode system and now refer to the NE postcode area around Newcastle upon Tyne and the S postcode area around Sheffield.

Numbered divisions
In 1917, as a wartime measure to improve efficiency, the districts were further subdivided with a number applied to each sub-district. This was achieved by designating a sub-area served most conveniently by the head office in each district "1" and then allocating the rest alphabetically by the name of the location of each delivery office. Exceptionally, W2 and SW11 are also 'head districts'.

The boundaries of each sub-district rarely correspond to any units of civil administration: the parishes and hamlets/chapelries with chapels that traditionally define settlement names everywhere in England and Wales or the generally larger boroughs; despite this, postal sub-districts have developed over time into a primary reference frame. The numbered sub-districts became the "outward code" (first half) of the postcode system as expanded into longer codes during the 1970s.

Changes
Ad hoc changes have taken place to the organisation of the districts, such as the creation of SE28 from existing districts because of the construction of the high-density Thamesmead development.

High-density districts
Owing to heavier demand, seven high-density postcode districts in central London have been subdivided to create new, smaller postcode districts. This is achieved by adding a letter after the original postcode district, for example W1P. Where such sub-districts are used elsewhere such as on street signs and maps, the original unsuffixed catch-all versions often remain in use instead. The districts subdivided are E1, N1, EC (EC1, EC2, EC3, EC4) SW1, W1, WC1 and WC2 (each with several subdivisions). Similarly, there are solely non-geographic suffixed sub-districts for PO boxes in NW1 (e.g. NW1W) and SE1 (e.g. SE1P).
 * Subdivisions of postcode sub-districts

Relationship to London boundary
The London postal district has never been aligned with the London boundary. When the initial system was designed, the London boundary was restricted to the square mile of the small, ancient City of London. The wider metropolitan postal area covered parts of Middlesex, Surrey, Kent, Essex and Hertfordshire.

In 1889 a County of London, which was smaller than the postal district, was created from parts of Middlesex, Surrey and Kent. The bulk of 40 fringe sub-districts (having been numbered in 1917) lay outside its boundary including, for example: Leyton, Ealing, Totteridge and Wimbledon

In 1965 the creation of Greater London boundary went beyond these postal districts except for part of the parish of Waltham Holy Cross. The General Post Office was unwilling to follow this change and expand the postal district to match because of the cost. Places in London's outer boroughs such as Harrow, Barnet, Wembley, Enfield, Ilford, Romford, Bexleyheath, Bromley, Hounslow, Richmond, Croydon, Sutton, Kingston and Uxbridge are therefore covered by parts of twelve adjoining postcode areas (EN, IG, RM, DA, BR, TN, CR, SM, KT, TW, HA and UB) from postal districts of 5 different counties including Middlesex whose county council was abolished upon the creation of the Greater London Council.

Royal Mail has a seemingly settled policy of changing postcodes only if there is an operational advantage to doing so, unlike the postal services of other countries, and so has no plan to change the postcode system to correlate with the Greater London boundary. In 2003 the then Mayor of London expressed support for revision of postal addresses in Greater London. Similarly, organisations on the fringes of the London postal district have lobbied to be excluded or included in an attempt to decrease their insurance premiums (SE2→DA7) or raise the prestige of their business (IG1-IG6→E19). This is generally futile as Royal Mail changes postcodes only in order to facilitate the delivery of post, and not to illustrate geographical boundaries like the postal services of other countries.

The London postal district includes all of the City of London, Camden, Hackney, Hammersmith and Fulham, Haringey, Islington, Kensington and Chelsea, Southwark, Tower Hamlets, Wandsworth and Westminster. Almost entirely included are Greenwich, Lambeth, Lewisham, Newham and Waltham Forest, except for a few streets. Barking and Dagenham, Barnet, Bexley, Brent, Bromley, Croydon, Ealing, Enfield, Harrow, Hounslow, Kingston upon Thames, Merton, Redbridge, and Richmond upon Thames are partly in the postal district. Havering, Hillingdon and Sutton are completely outside the postal district. Sewardstone, in postal district E4 and in the Epping Forest District of Essex is anomalously the only place to be outside Greater London but in the London postal area.

Under early abandoned price differentials it formed the inner area of the London postal region, one now obscure definition of Inner London — the term has however lost economic significance from the consumer viewpoint with the standardisation of Royal Mail pricing.

Significance
It is common to use postal sub-districts as placenames in London, particularly in the property market: a property may be described as being "in N11", especially where this can be synonymous with a desirable location but also covers other less prestigious places. Thus sub-districts are a convenient shorthand indicator towards social status, such that a 'desirable' postcode may add significantly to the value of property, and property developers have tried to no avail to have Royal Mail alter the boundaries of postal districts so that new developments will sound as though they are in a richer area, whether in capital, personal income or both.

Parliament, which first established the London postal district, then created the narrower County of London (1889–1965) and replaced it with the much larger Greater London. However, there has been very little change in London postal district boundaries. Being in a London postcode inaccurately gives a broad definition of Inner London.

Presentation
All London postal districts were traditionally prefixed with the post town 'LONDON' and full stops were commonly placed after each character, e.g. LONDON S.W.1. Use of the full stops ended with the implementation of the national postcode system. In addition, integration of the London postal districts into postcodes means that as postcodes should be on a separate address line (in line with other postcodes in the national system) the postal district should not now appear after LONDON on the same line but as the first part of the full postcode.

The presentation of the postal districts on street signs in London is commonplace, although not universal as each borough is individually responsible for street signs. Current regulations date from 1952 and were originally for the County of London, but were extended to Greater London in 1965. The section relating to postal districts reads "The appropriate postal district shall be indicated in the nameplate in signal red".

List of London postal districts

 * The postcode district names refer to the original delivery office. Some postcode districts have been further subdivided. The postcode area articles give the full coverage of each district.

Map

The area covered is 241 sqmi.

London postal region
The E, EC, N, NW, SE, SW, W and WC postcode areas (the eight London postal districts) comprise the inner area of the London postal region and correspond to the London post town.

The BR, CM, CR, DA, EN, HA, IG, SL, TN, KT, RM, SM, TW, UB, and WD (the 15 outer London postcode areas) comprise the outer area of the London postal region.

The inner and outer areas together comprised the London postal region.

title: London postal district