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# Carrier battle group
`{{Naval units}}`{=mediawiki} A **carrier battle group** (**CVBG**) is a naval fleet consisting of an aircraft carrier capital ship and its large number of escorts, together defining the group. The *CV* in *CVBG* is the United States Navy hull classification code for an aircraft carrier.
The first naval task forces built around carriers appeared just prior to and during World War II. The Imperial Japanese Navy (IJN) was the first to assemble many carriers into a single task force, known as the *Kido Butai*. This task force was used with devastating effect in the Japanese attack on Pearl Harbor. The Kido Butai operated as the IJN\'s main carrier battle group until four of its carriers were sunk at the Battle of Midway. In contrast, the United States Navy deployed its large carriers in separate formations, with each carrier assigned its own cruiser and destroyer escorts. These single-carrier formations would often be paired or grouped together for certain assignments, most notably the Battle of the Coral Sea and Midway. By 1943, however, large numbers of fleet and light carriers became available, which required larger formations of three or four carriers. These groups eventually formed the Fast Carrier Task Force, which became the primary battle unit of the U.S. Third and Fifth Fleets.
With the construction of the large \"supercarriers\" of the Cold War era, the practice of operating each carrier in a single formation was revived. During the Cold War, the main role of the CVBG in case of conflict with the Soviet Union would have been to protect Atlantic supply routes between the United States and its NATO allies in Europe, while the role of the Soviet Navy would have been to interrupt these sea lanes, a fundamentally easier task. Because the Soviet Union had no large carriers of its own, a situation of dueling aircraft carriers would have been unlikely. However, a primary mission of the Soviet Navy\'s attack submarines was to track every allied battle group and, on the outbreak of hostilities, sink the carriers. Understanding this threat, the CVBG expended enormous resources in its own anti-submarine warfare mission.
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# Carrier battle group
## Carrier battle groups in crises {#carrier_battle_groups_in_crises}
In the late 20th and early 21st centuries, most uses of carrier battle groups by the United States as well as that of other Western nations have been in situations where their use has been uncontested by other comparable forces. During the Cold War, an important battle scenario was an attack against a CVBG using numerous anti-ship missiles.
### 1956 Suez Crisis {#suez_crisis}
British and French carrier battle groups were involved in the 1956 Suez Crisis.
### 1971 Indo-Pakistan war {#indo_pakistan_war}
During the Indo-Pakistani War of 1971, India used its carrier strike group centered on `{{INS|Vikrant|1961|6}}`{=mediawiki} to impose a naval blockade on East Pakistan. Air strikes were carried out initially on shipping in the harbors of Chittagong and Cox\'s Bazar, sinking or incapacitating most ships there. Further strikes were carried out on Cox\'s Bazar from 60 nautical miles (110 km) offshore. On the evening of 4 December, the air group again struck Chittagong harbor. Later strikes targeted Khulna and the Port of Mongla. Air strikes continued until 10 December 1971.
### 1982 Falklands War {#falklands_war}
The first attempted use of anti-ship missiles against a carrier battle group was part of Argentina\'s efforts against British armed forces during the Falklands War. This was the last conflict so far in which opposing belligerents employed aircraft carriers, although Argentina made little use of its sole carrier, `{{ship|ARA|Veinticinco de Mayo|V-2|6}}`{=mediawiki}, which was originally built in the United Kingdom as HMS *Venerable* and later served with the Royal Netherlands Navy (1948--1968).
### Lebanon
The United States Sixth Fleet assembled a force of three carrier battle groups and a battleship during the Lebanese Civil War in 1983. Daily reconnaissance flights were flown over the Bekaa Valley and a strike was flown against targets in the area resulting in loss of an A-6 Intruder and an A-7 Corsair.
### Gulf of Sidra {#gulf_of_sidra}
Carrier battle groups routinely operated in the Gulf of Sidra inside the \"Line of Death\" proclaimed by Libya resulting in aerial engagements in 1981, 1986 and 1989 between U.S. Navy Tomcats and Libyan Su-22 aircraft, SA-5 surface-to-air missiles and MiG-23 fighters. During the 1986 clashes, three carrier battle groups deployed to the Gulf of Sidra and ultimately two of them conducted strikes against Libya in Operation El Dorado Canyon.
### 2011 military intervention in Libya {#military_intervention_in_libya}
During the international military intervention in the 2011 Libyan civil war, the French Navy deployed its aircraft carrier, `{{ship|French aircraft carrier|Charles de Gaulle|R91|2}}`{=mediawiki}, off Libya. The *Charles de Gaulle* was accompanied by several frigates as `{{ship|French frigate|Forbin|D620|2}}`{=mediawiki}, `{{ship|French frigate|Dupleix|D641|2}}`{=mediawiki}, `{{ship|French frigate|Aconit|F 713|2}}`{=mediawiki}, the replenishment tanker *Meuse* and two `{{sclass|Rubis|submarine|0}}`{=mediawiki} nuclear attack submarines.
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# Carrier battle group
## Applications
### China
China plans to set up several carrier battle groups in the future. At present China\'s two aircraft carriers, `{{ship|Chinese aircraft carrier|Liaoning||2}}`{=mediawiki} and `{{ship|Chinese aircraft carrier|Shandong||2}}`{=mediawiki}, use Type 055 destroyers for area air defence with anti-submarine warfare, Type 052C or Type 052D destroyers for air defence, Type 054A frigates for anti-submarine and anti-ship warfare, one to two Type 093 nuclear attack submarines, and one Type 901 supply ship. China is building a third carrier, as well as a nuclear-powered fourth carrier planned for construction and expected to be completed by the late 2020s. China is also building a new larger class of air defence destroyers, the Type 055.
### France
The only serving French carrier is the `{{ship|French aircraft carrier|Charles de Gaulle||2}}`{=mediawiki}, which also serves as the flagship of the French Navy. The carrier battle group of the *\[\[Force d\'Action Navale\]\]* is known as the *Groupe Aéronaval* (GAN) and is usually composed, in addition to the aircraft carrier, of:
- a carrier air wing (Groupe Aérien Embarqué, GAE, in French), a complement composed of about 40 aircraft:
- Rafale F3 (up to 30)
- E-2C Hawkeye (2)
- SA365 Dauphin (3) for RESCO and EC725 Caracal for CSAR (2)
- one `{{sclass|Rubis|submarine|1}}`{=mediawiki}
- two anti-submarine destroyers (currently FREMM ASM or `{{sclass|Georges Leygues|frigate|4}}`{=mediawiki})
- one or two anti-air destroyers (`{{sclass2|Horizon|frigate|5}}`{=mediawiki} or `{{sclass|Cassard|frigate|4}}`{=mediawiki})
- one stealth frigate in forward patrol (usually a `{{sclass|La Fayette|frigate|4}}`{=mediawiki})
- one supply ship (currently a `{{sclass|Durance|tanker|2}}`{=mediawiki})
This group is commanded by a rear admiral (*contre-amiral\]\]*) on board the aircraft carrier. The commanding officer of the air group (usually a *capitaine de frégate*---equivalent to commander) is subordinate to the commanding officer of the aircraft carrier, a senior captain. The escort destroyers (called frigates in the French denomination) are commanded by more junior captains.
France also operates three `{{sclass|Mistral|amphibious assault ship|2}}`{=mediawiki}s. While incapable of operating fixed-winged aircraft, they function as helicopter carriers and form the backbone of France\'s amphibious force. These ships are typically escorted by the same escorts *Charles De Gaulle* uses.
### India
The Indian Navy has operated all types of aircraft carriers including CATOBAR configured `{{INS|Vikrant|1961|3}}`{=mediawiki}, STOVL configured `{{INS|Viraat||2}}`{=mediawiki} and STOBAR configured `{{INS|Vikramaditya||2}}`{=mediawiki} and `{{INS|Vikrant|2013|3}}`{=mediawiki} and CBGs centered on them. The Indian Navy has been operating carrier battle groups since 1961, with its first carrier battle group formed around the now decommissioned *Vikrant* (1961). *Viraat* was an updated `{{sclass|Centaur|aircraft carrier|0}}`{=mediawiki} light carrier originally built for the Royal Navy as `{{HMS|Hermes|R12|6}}`{=mediawiki}, which was laid down in 1944 and commissioned in 1959. It was purchased by India in May 1987, and was decommissioned in March 2017. India commissioned *Vikramaditya* in 2013 followed by the new *Vikrant* (2013) in 2022. *Vikramaditya* is the modified `{{sclass|Kiev|aircraft carrier|1}}`{=mediawiki} `{{ship|Soviet aircraft carrier|Admiral Gorshkov||2}}`{=mediawiki}, *Vikrant* is the first indigenous aircraft carrier built in India. India plans to have three carrier battle groups by 2035, each centered on *Vikrant* (2013), *Vikramaditya* and `{{INS|Vishal||2}}`{=mediawiki}, another planned carrier. As of 2023, the Indian Navy operates two carrier battle groups centred on *Vikramaditya* and *Vikrant*.
The Indian Navy\'s carrier battle group centred on *Viraat* consisted of two destroyers, usually of the `{{sclass|Delhi|destroyer|4}}`{=mediawiki} (previously `{{sclass|Rajput|destroyer|5}}`{=mediawiki}s), two or more frigates, usually of the `{{sclass|Brahmaputra|frigate|5}}`{=mediawiki}, `{{sclass|Godavari|frigate|5}}`{=mediawiki} or `{{sclass|Nilgiri|frigate|4||1972}}`{=mediawiki}es, and one support ship.
The Carrier Battle Group (CBG) led by *Vikramaditya* includes `{{sclass|Kolkata|destroyer|1}}`{=mediawiki}s, `{{sclass|Talwar|frigate|1}}`{=mediawiki}s and the support ship `{{INS|Deepak|A50|6}}`{=mediawiki} among others. While the independent CBG of *Vikrant* is expected to consist of `{{sclass|Visakhapatnam|destroyer|1}}`{=mediawiki}s, `{{sclass|Nilgiri|frigate|1||2019}}`{=mediawiki}s, `{{sclass|Kamorta|corvette|1}}`{=mediawiki}s and the support ship `{{INS|Shakti|A57|6}}`{=mediawiki}.
### Italy
The CVS--ASW (Aircraft Carrier with Anti-Submarine Warfare) `{{ship|Italian aircraft carrier|Giuseppe Garibaldi|551|6}}`{=mediawiki} was Italy\'s first carrier. The battle group based at Taranto called COMFORAL was formed by the carrier *Giuseppe Garibaldi*, two `{{sclass|Durand de la Penne|destroyer|1}}`{=mediawiki}s, two support ships (*Etna* and *Elettra*), and three amphibious/support ships (*San Giusto*, *San Marco* and *San Giorgio*).
After 2010, the Italian battle group will be formed by the new `{{ship|Italian aircraft carrier|Cavour||2}}`{=mediawiki}, 5--6 new warships (including Orizzonte-class destroyers and frigates), one new support ship, some minehunters and new submarines (the COMFORAL will be a reserve group).
### Russia
*Admiral Kuznetsov* has been observed sailing together with a `{{sclass|Kirov|battlecruiser|2}}`{=mediawiki} (CBGN), `{{sclass|Slava|cruiser|1}}`{=mediawiki} (CG), `{{sclass|Sovremenny|destroyer|2}}`{=mediawiki} (ASuW), `{{sclass|Udaloy|destroyer|2}}`{=mediawiki} (ASW) and *Krivak* I/II FFG (ASW). These escorts, especially the heavily armed *Kirov*-class battlecruiser, use advanced sensors and carry a variety of weaponry. During *Admiral Kuznetsov*{{\'}}s deployment to Syria in November 2016 on her first combat tour, the carrier was escorted by a pair of *Udaloy*-class destroyers and a *Kirov*-class battlecruiser en route, while additional Russian Navy warships met her off Syria.
*Admiral Kuznetsov* is designed specifically to sail alone and carries greater firepower than her U.S. counterparts. This includes 12x SS-N-19 \'Shipwreck\' (long range, high speed, sea-skimming) SSMs, 24 x VLS units loaded with 192 SA-N-9 \'Gauntlet\' SAMs, and 8 x Kashtan CIWS with dual 30 mm guns, and 8 × AK-630 CIWS. Compared to the 4 × Phalanx CIWS and 4 × Sea Sparrow launchers, each with 8 missiles carried by the *Nimitz* class, *Admiral Kuznetsov* is well armed for both air-defence and offensive operations against hostile shipping.
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# Carrier battle group
## Applications
### United Kingdom {#united_kingdom}
As one of the pioneers of aircraft carriers, the Royal Navy has maintained a carrier strike capability since the commissioning of `{{HMS|Argus|I49|6}}`{=mediawiki} in 1918. However, the capability was temporarily lost between 2010 and 2018, following the retirement of the `{{sclass|Invincible|aircraft carrier|1}}`{=mediawiki} and Harrier GR9s. During this period, the Royal Navy worked to regenerate its carrier strike capability based on the Carrier-Enabled Power Projection (CEPP) concept by ordering two `{{sclass|Queen Elizabeth|aircraft carrier|1}}`{=mediawiki}s and the F-35B Lightning aircraft to operate from them. To maintain its skills and experience, the Royal Navy embedded personnel and ships with partner navies, in particular the United States Navy.
In 2017, the first *Queen Elizabeth*-class aircraft carrier, `{{HMS|Queen Elizabeth|R08|6}}`{=mediawiki}, entered service followed by her sister ship, `{{HMS|Prince of Wales|R09|6}}`{=mediawiki}, in 2019. The first carrier strike group took to sea in September 2019 as part of an exercise known as Westlant 19. HMS *Queen Elizabeth* and her air group of F-35B Lightning jets operated alongside two surface escorts and a fleet tanker off the east coast of the United States. The deployment was in preparation for the first operational deployment in 2021, which is expected to involve HMS *Queen Elizabeth* alongside four Royal Navy escorts, two support ships and a submarine.
Under current plans, a Royal Navy carrier strike group will typically comprise a *Queen Elizabeth*-class aircraft carrier, two air defence destroyers, two anti-submarine frigates, a submarine, solid stores ship and a fleet tanker. However, the composition varies depending on the operational tasking. While *Queen Elizabeth*{{\'}}s initial deployment will be as part of an all-British carrier group, it is envisaged in the longer term that the UK\'s carriers will usually form the centre of a multi-national operation -- in 2018, it was announced that the British and Dutch governments had come to an agreement that would see escort vessels of the Royal Netherlands Navy operating as part of the UK Carrier Strike Group. Command of the UK carrier strike group is the responsibility of Commander United Kingdom Carrier Strike Group. A June 2020 National Audit Office report however provided a critical review of the forthcoming Carrier Strike Group, especially noting the delay to the Crowsnest system.
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# Carrier battle group
## Applications
### United States {#united_states}
#### Carrier strike group {#carrier_strike_group}
In modern United States Navy carrier air operations, a carrier strike group (CSG) normally consists of one aircraft carrier, one guided missile cruiser (for air defense), two LAMPS-capable warships (focusing on anti-submarine and surface warfare), and one to two anti-submarine destroyers or frigates. The large number of CSGs used by the United States reflects, in part, a division of roles and missions allotted during the Cold War, in which the United States assumed primary responsibility for blue-water operations and for safeguarding supply lines between the United States and Europe, while the NATO allies assumed responsibility for less costly brown- and green-water operations. The CSG has replaced the old term of carrier battle group (CVBG or CARBATGRU).`{{when|date=March 2019}}`{=mediawiki} The US Navy maintains 11 carrier strike groups,`{{clarify timeframe|date=March 2016}}`{=mediawiki} 10 of which are based in the United States and one that is forward deployed in Yokosuka, Japan.
#### Expeditionary strike group {#expeditionary_strike_group}
An expeditionary strike group is composed of an amphibious assault ship (landing helicopter assault/landing helicopter dock), a dock landing ship, an amphibious transport dock, a Marine expeditionary unit, AV-8B Harrier II or, more the newer Lockheed Martin F-35B Lightning II aircraft, CH-53E Super Stallion and CH-46E Sea Knight helicopters or, more recently, MV-22B tiltrotors. Cruisers, destroyers and attack submarines are deployed with either an Expeditionary Strike Group or a Carrier Strike Group.
#### Battleship battle group {#battleship_battle_group}
During the period when the American navy recommissioned all four of its `{{sclass|Iowa|battleship|1}}`{=mediawiki}s, it sometimes used a similar formation centered on a battleship, referred to as a battleship battle group. It was alternately referred to as a surface action group. The battleship battle group typically consisted of one modernized battleship, one `{{sclass|Ticonderoga|cruiser|1}}`{=mediawiki}, one `{{sclass|Kidd|destroyer|1}}`{=mediawiki} or `{{sclass|Arleigh Burke|destroyer|1}}`{=mediawiki}, one `{{sclass|Spruance|destroyer|1}}`{=mediawiki}, three `{{sclass|Oliver Hazard Perry|frigate|1}}`{=mediawiki}s and one auxiliary ship such as a replenishment oiler.
#### Surface action group {#surface_action_group}
A surface action group is \"a temporary or standing organization of combatant ships, other than carriers, tailored for a specific tactical mission\".
## Underway replenishment {#underway_replenishment}
Since its origins, the viability of the carrier battle group has been dependent on its ability to remain at sea for extended periods. Specialized ships were developed to provide underway replenishment of fuel (for the carrier and its aircraft), ordnance, and other supplies necessary to sustain operations. Carrier battle groups devote a great deal of planning to efficiently conduct underway replenishment to minimize the time spent conducting replenishment. The carrier can also provide replenishment on a limited basis to its escorts, but typically a replenishment ship such as a fast combat support ship (AOE) or replenishment oiler (AOR) pulls alongside a carrier and conducts simultaneous operations with the carrier on its port side and one of the escorts on its starboard side. The advent of the helicopter provides the ability to speed replenishment by lifting supplies at the same time that fueling hoses and lines are delivering other goods.
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# Carrier battle group
## Debate on future viability {#debate_on_future_viability}
There is debate in naval warfare circles as to the viability of carrier battle groups in 21st century naval warfare. Proponents of the CVBG argue that it provides unmatched firepower and force projection capabilities. Opponents argue that CVBGs are increasingly vulnerable to arsenal ships and cruise missiles, especially those with supersonic or even hypersonic flight and the ability to perform radical trajectory changes to avoid anti-missile systems. It is also noted that CVBGs were designed for Cold War scenarios, and are less useful in establishing control of areas close to shore. It is argued however that such missiles and arsenal ships pose no serious threat as they would be eliminated due to increasing improvement in ship defenses such as Cooperative Engagement Capability (CEC), DEW technology and missile technology.
Additionally, carrier battle groups proved to be vulnerable to diesel-electric submarines owned by many smaller naval forces. Examples are the German *U24* of the conventional 206 class which in 2001 \"sank\" USS *Enterprise* during the exercise JTFEX 01-2 in the Caribbean Sea by firing flares and taking a photograph through its periscope or the Swedish *Gotland* which managed the same feat in 2006 during JTFEX 06-2 by penetrating the defensive measures of Carrier Strike Group 7 undetected and snap several pictures of `{{USS|Ronald Reagan}}`{=mediawiki}.
However, carriers have been called upon to be first responders even when conventional land-based aircraft were employed. During Desert Shield, the U.S. Navy sortied additional carriers to augment the on-station assets, eventually maintaining six carriers for Desert Storm. Although the U.S. Air Force sent fighters such as the F-16 to theater in Desert Shield, they had to carry bombs with them as no stores were in place for sustained operations, whereas the carriers arrived on scene with full magazines and had support ships to allow them to conduct strikes indefinitely.
The Global War on Terror has shown the flexibility and responsiveness of the carrier on multiple occasions when land-based air was not feasible or able to respond in a timely fashion. After the 11 September terrorist attacks on the U.S., carriers immediately headed to the Arabian Sea to support Operation Enduring Freedom and took up station, building to a force of three carriers. Their steaming location was closer to the targets in Afghanistan than any land-based assets and thereby more responsive. The `{{USS|Kitty Hawk|CV-63|6}}`{=mediawiki} was adapted to be a support base for special operations helicopters. Carriers were used again in Operation Iraqi Freedom and even provided aircraft to be based ashore on occasion and have done so periodically when special capabilities are needed. This precedent was established during World War II in the Battle of Guadalcanal.
Regardless of the debate over viability, the United States has made a major investment in the development of a new carrier class---the `{{sclass|Gerald R. Ford|aircraft carrier|}}`{=mediawiki}s (formerly designated CVN-X, or the X Carrier)---to replace the existing `{{sclass|Nimitz|aircraft carrier}}`{=mediawiki}s. The new *Ford*-class carriers are designed to be modular and are easily adaptable as technology and equipment needed on board changes
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# Costa Smeralda
The **Costa Smeralda** (`{{IPA|it|ˈkɔsta zmeˈralda|lang}}`{=mediawiki}, `{{lit|Emerald Coast}}`{=mediawiki}; *\'\'\'Monti di Mola\'\'\'*; *\'\'\'Montes de Mola\'\'\'*) is a coastal area and tourist destination in northern Sardinia, Italy, with a length of some 20 km, although the term originally designated only a small stretch in the commune of Arzachena.
With white sand beaches, golf clubs, private jet and helicopter services, and exclusive hotels, the area has drawn celebrities, business and political leaders, and other affluent visitors.
Costa Smeralda is one of the most expensive locations in Europe. Prime home prices in the area increased by 18% in 2023, while prime rents were double their pre-Covid levels. On a per square metre basis, prime residential prices in Sardinia reached nearly €12,500.
The main towns and villages in the area, built according to a detailed urban plan, are Porto Cervo, Liscia di Vacca, Capriccioli, and Romazzino. Archaeological sites include the necropolis of Li Muri.
Each September the Sardinia Cup sailing regatta is held off the coast. Polo matches are held between April and October at Gershan near Arzachena.
Development of the area started in 1961, and was financed by a consortium of companies led by Prince Karim Aga Khan. Spiaggia del Principe, one of the beaches along the Costa Smeralda, was named after this Ishmaelite prince. Architects involved in the project included Michele Busiri Vici, Jacques Couëlle, Savin Couëlle, and Vietti
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# Chianti
**Chianti** is an Italian red wine produced in the Chianti region of central Tuscany, principally from the Sangiovese grape. It was historically associated with a squat bottle enclosed in a straw basket, called a *fiasco* (\"flask\"; `{{plural form}}`{=mediawiki}: *fiaschi*). However, the *fiasco* is now only used by a few makers of the wine; most Chianti is bottled in more standard-shaped wine bottles. In the late 19th century, Baron Bettino Ricasoli (later Prime Minister of the Kingdom of Italy) helped establish Sangiovese as the blend\'s dominant grape variety, creating the blueprint for today\'s Chianti wines.
The first definition of a wine area called *Chianti* was made in 1716. It described the area near the villages of Gaiole, Castellina and Radda; the so-called *Lega del Chianti* and later *Provincia del Chianti* (Chianti province). In 1932 the Chianti area was completely redrawn and divided into seven sub-areas: Classico, Colli Aretini, Colli Fiorentini, Colline Pisane, Colli Senesi, Montalbano and Rùfina. Most of the villages that in 1932 were added to the newly defined Chianti Classico region added *in Chianti* to their names, for example Greve in Chianti, which amended its name in 1972. Wines labelled Chianti Classico come from the largest sub-area of Chianti, which includes the original Chianti heartland. Only Chianti from this sub-zone may display the black rooster (*gallo nero*) seal on the neck of the bottle, which indicates that the producer of the wine is a member of the Chianti Classico Consortium, the local association of producers. Other variants, with the exception of Rufina north-east of Florence and Montalbano south of Pistoia, originate in the named provinces: Siena for the Colli Senesi, Florence for the Colli Fiorentini, Arezzo for the Colli Aretini and Pisa for the Colline Pisane. In 1996 part of the Colli Fiorentini sub-area was renamed *Montespertoli*.
During the 1970s producers started to reduce the quantity of white grapes in Chianti. In 1995 it became legal to produce a Chianti with 100% Sangiovese. For a wine to retain the name of Chianti it must be produced with at least 80% Sangiovese grapes. Aged Chianti (at least 6 months in barrel and 3 more in bottle before release, instead of 6 months aging without barreling necessary) may be labelled as Riserva. Chianti that meets more stringent requirements (lower yield, higher alcohol content and dry extract) may be labelled as Chianti Superiore, although Chianti from the Classico sub-area is not allowed in any event to be labelled as Superiore.
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# Chianti
## History
The earliest documentation of a \"Chianti wine\" dates back to the 14th century, when viticulture was known to flourish in the *\"Chianti Mountains\"* around Florence. A military league called *Lega del Chianti* (League of Chianti) was formed around 1250 between the townships of Castellina, Gaiole and Radda, which would lead to the wine from this area taking on a similar name. In 1398 the earliest-known record notes Chianti as a white wine, though the red wines of Chianti were also discussed around the same time in similar documents.
The first attempt to classify Chianti wine in any way came in 1427, when Florence developed a tariff system for the wines of the surrounding countryside, including an area referred to as \"Chianti and its entire province\". In 1716 Cosimo III de\' Medici, Grand Duke of Tuscany, issued an edict legislating that the three villages of the *Lega del Chianti* (Castellina in Chianti, Gaiole in Chianti and Radda in Chianti) as well as the village of Greve and a 2 mi of hillside north of Greve near Spedaluzzo as the only officially recognised producers of Chianti. This delineation existed until July 1932, when the Italian government expanded the Chianti zone to include the outlying areas of Barberino Val d\'Elsa, Chiocchio, Robbiano, San Casciano in Val di Pesa and Strada. Subsequent expansions in 1967 would eventually result in the Chianti zone covering a very large area all over central Tuscany.
By the 18th century Chianti was widely recognised as a red wine, but the exact composition and grape varieties used to make Chianti at this point is unknown. Ampelographers find clues about which grape varieties were popular at the time in the writings of Italian writer Cosimo Villifranchi, who noted that Canaiolo was a widely planted variety in the area along with Sangiovese, Mammolo and Marzemino. It was not until the work of the Italian statesman Bettino Ricasoli that the modern Chianti recipe as a Sangiovese-based wine would take shape.
Prior to Ricasoli, Canaiolo was emerging as the dominant variety in the Chianti blend with Sangiovese and Malvasia Bianca Lunga playing supporting roles. In the mid-19th century, Ricasoli developed a recipe for Chianti that was based primarily on Sangiovese. Though he is often credited with creating and disseminating a specific formula (typically reported as 70% Sangiovese, 20% Canaiolo, 10% Malvasia Bianca Lunga), a review of his correspondence of the time does not corroborate this. In addition, his efforts were quickly corrupted by other local winemakers (for example, replacing Malvasia with Trebbiano Toscano, or relying too heavily on the latter), leading to further misunderstanding of the \"Ricasoli formula\". In 1967, the *Denominazione di origine controllata* (DOC) regulation set by the Italian government was based on a loose interpretation of Ricasoli\'s \"recipe\", calling for a Sangiovese-based blend with 10--30% Malvasia and Trebbiano.
The late 19th century saw a period of economic and political upheaval. First came oidium and then the phylloxera epidemic would take its toll on the vineyards of Chianti just as they had ravaged vineyards across the rest of Europe. The chaos and poverty following the *Risorgimento* heralded the beginning of the Italian diaspora that would take Italian vineyard workers and winemakers abroad as immigrants to new lands. Those that stayed behind and replanted choose high-yielding varieties like Trebbiano and Sangiovese clones such as the *Sangiovese di Romagna* from the nearby Romagna region. Following the Second World War, the general trend in the world wine market for cheap, easy-drinking wine saw a brief boom for the region. With over-cropping and an emphasis on quantity over quality, the reputation of Chianti among consumers eventually plummeted. By the 1950s, Trebbiano (which is known for its neutral flavours) made up to 30% of many mass-market Chiantis.
By the late 20th century, Chianti was often associated with basic Chianti sold in a squat bottle enclosed in a straw basket, called a *fiasco*. However, during the same period, a group of ambitious producers began working outside the boundaries of DOC regulations to make what they believed would be a higher-quality wine. These wines eventually became known as the \"Super Tuscans\".
Many of the producers behind the Super Tuscan movement were originally Chianti producers who were rebelling against what they felt were antiquated DOC regulations. Some of these producers wanted to make Chiantis that were 100% varietal Sangiovese. Others wanted the flexibility to experiment with blending French grape varieties such as Cabernet Sauvignon and Merlot or to not be required to blend in any white grape varieties. The late 20th century saw a flurry of creativity and innovation in the Chianti zones as producers experimented with new grape varieties and introduced modern wine-making techniques such as the use of new oak barrels. The prices and wine ratings of some Super Tuscans would regularly eclipse those of DOC-sanctioned Chiantis. The success of the Super Tuscans encouraged government officials to reconsider the DOC regulations in order to bring some of these wines back into the fold labelled as Chianti.
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# Chianti
## Chianti subregions {#chianti_subregions}
The Chianti region covers a vast area of Tuscany and includes within its boundaries several overlapping *Denominazione di origine controllata* (DOC) and *Denominazione di Origine Controllata e Garantita* (DOCG) regions. Other well known Sangiovese-based Tuscan wines such as Brunello di Montalcino and Vino Nobile di Montepulciano could be bottled and labelled under the most basic designation of \"Chianti\" if their producers chose to do so. Within the collective Chianti region more than 8 million cases of wines classified as DOC-level or above are produced each year. Today, most Chianti falls under two major designations of Chianti DOCG, which includes basic level Chianti, as well as that from seven designated sub-zones, and Chianti Classico DOCG. Together, these two Chianti zones produce the largest volume of DOC/G wines in Italy.
The Chianti DOCG covers all the Chianti wine and includes a large stretch of land encompassing the western reaches of the province of Pisa near the coast of the Tyrrhenian Sea, the Florentine hills in the province of Florence to the north, to the province of Arezzo in the east and the Siena hills to the south. Within this regions are vineyards that overlap the DOCG regions of Brunello di Montalcino, Vino Nobile di Montepulciano and Vernaccia di San Gimignano. Any Sangiovese-based wine made according to the Chianti guidelines from these vineyards can be labelled and marked under the basic Chianti DOCG should the producer wish to use the designation.
Within the Chianti DOCG there are eight defined sub-zones that are permitted to affix their name to the wine label. Wines that are labelled as simply Chianti are made either from a blend from these sub-zones or include grapes from peripheral areas not within the boundaries of a sub-zone. The sub-zones are (clockwise from the north): the Colli Fiorentini which is located south of the city of Florence; Chianti Rufina in the northeastern part of the zone located around the commune of Rufina; Classico in the centre of Chianti, across the provinces of Florence and Siena; Colli Aretini in the Arezzo province to the east; Colli Senesi south of Chianti Classico in the Siena hills, which is the largest of the sub-zones and includes the Brunello di Montalcino and Vino Nobile di Montepulciano areas; Colline Pisane, the westernmost sub-zone in the province of Pisa; Montespertoli located within the Colli Fiorentini around the commune of Montespertoli; Montalbano in the north-west part of the zone which includes the Carmignano DOCG.
, there were 786 acre under production in Montalbano, 2236 acre in the Colli Fiorentini, 140 acre in Montespertoli, 1840 acre in Rufina, 8780 acre in the Colli Senesi, 380 acre in Colline Pisane, 1603 acre in the Colli Aretini, and an additional 25511 acre in the peripheral areas that do not fall within one of the sub-zone classifications. Wines produced from these vineyards are labelled simply \"Chianti\".
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# Chianti
## Chianti subregions {#chianti_subregions}
### Chianti Classico {#chianti_classico}
The original area dictated by the edict of Cosimo III de\' Medici would eventually be considered the heart of the modern \"Chianti Classico\" subregion. `{{As of|2006}}`{=mediawiki}, there were 17640 acre of vineyards in the Chianti Classico subregion. The Chianti Classico subregion covers an area of approximate 100 sqmi between the city of Florence to the north and Siena to the south. The four communes of Castellina in Chianti, Gaiole in Chianti, Greve in Chianti and Radda in Chianti are located entirely within the boundaries of the Classico area with parts of Barberino Val d\'Elsa, San Casciano in Val di Pesa and Tavarnelle Val di Pesa in the province of Florence as well as Castelnuovo Berardenga and Poggibonsi in the province of Siena included within the permitted boundaries of Chianti Classico.
The soil and geography of this subregion can be quite varied, with altitudes ranging from 820 to, and rolling hills producing differing macroclimates. There are two main soil types in the area: a weathered sandstone known as *alberese* and a bluish-gray chalky marlstone known as *galestro*. The soil in the north is richer and more fertile with more *galestro*, with the soil gradually becoming harder and stonier with more *albarese* in the south. In the north, the Arno River can have an influence on the climate, keeping the temperatures slightly cooler, an influence that diminishes further south in the warmer Classico territory towards Castelnuovo Berardenga.
Chianti Classico are premium Chianti wines that tend to be medium-bodied with firm tannins and medium-high to high acidity. Floral, cherry and light nutty notes are characteristic aromas with the wines expressing more notes on the mid-palate and finish than at the front of the mouth. As with Bordeaux, the different zones of Chianti Classico have unique characteristics that can be exemplified and perceived in some wines from those areas. According to Master of Wine Mary Ewing-Mulligan, Chianti Classico wines from the Castellina area tend to have a very delicate aroma and flavour, Castelnuovo Berardegna wines tend to be the most ripe and richest tasting, wines from Gaiole tend to have been characterised by their structure and firm tannins while wines from the Greve area tend to have very concentrated flavours.
The production of Chianti Classico is realised under the supervision of Consorzio del Vino Chianti Classico, a union of producers in the Chianti Classico subregion. The Consorzio was founded with the aim of promoting the wines of the subregion, improving quality and preventing wine fraud. Since the 1980s, the foundation has sponsored extensive research into the viticultural and winemaking practice of the Chianti Classico area, particularly in the area of clonal research. In the last three decades, more than 50% of the vineyards in the Chianti Classico subregion have been replanted with improved Sangiovese clones and modern vineyard techniques as part of the Consorzio Chianti Classico\'s project \"Chianti 2000\".
In 2014, a new category of Chianti Classico was introduced: Chianti Classico Gran Selezione. Gran Selezione is made exclusively from a winery\'s own grapes grown according to stricter regulations compared to regular Chianti Classico. Gran Selezione is granted to a Chianti Classico after it passes a suitability test conducted by authorised laboratories, and after it is approved by a special tasting committee. The creation of the Chianti Classico Gran Selezione DOCG has been criticized, with some describing it as being \"Needless; an extra layer of confusion created by marketing people hoping to help Chianti Classico out of a sales crisis.\"
### Greater Chianti region {#greater_chianti_region}
Outside of the Chianti Classico area, the wines of the Chianti sub-zone of Rufina are among the most widely recognised and exported from the Chianti region. Located in the Arno valley near the town of Pontassieve, the Rufina region includes much area in the Pomino region, an area that has a long history of wine production. The area is noted for the cool climate of its elevated vineyards located up to 2950 ft. The vineyard soils of the area are predominantly marl and chalk. The Florentine merchant families of the Antinori and Frescobaldi own the majority of the vineyards in Rufina. Chianti from the Rufina area is characterised by its multi-layered complexity and elegance.
The Colli Fiorentini subregion has seen an influx of activity and new vineyard development in recent years as wealthy Florentine business people move to the country to plant vineyards and open wineries. Many foreign \"flying winemakers\" have had a hand in this development, bringing global viticulture and wine-making techniques to the Colli Fiorentini. Located in the hills between the Chianti Classico area and Arno valley, the wines of the Colli Fiorentini vary widely depending on producer, but tend to have a simple structure with strong character and fruit notes. The Montespertoli sub-zone was part of the Colli Fiorentini sub-zone until 2002 when it became its own tiny enclave.
The Montalbano subregion is located in the shadow of the Carmignano DOCG, with much of the best Sangiovese going to that wine. A similar situation exists in the Colli Senesi which includes the well known DOCG region of Vino Nobile di Montepulciano. Both regions rarely appear on wine labels that are exported out of Tuscany. The Colli Pisane area produces typical Chiantis with the lightest body and color. The Colli Aretini is a relatively new and emerging area that has seen an influx of investment and new winemaking in recent years.
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# Chianti
## Grapes and classification {#grapes_and_classification}
Since 1996 the blend for Chianti and Chianti Classico has been 75--100% Sangiovese, up to 10% Canaiolo and up to 20% of any other approved red grape variety such as Cabernet Sauvignon, Merlot or Syrah. Since 2006, the use of white grape varieties such as Malvasia and Trebbiano have been prohibited in Chianti Classico. Chianti Classico must have a minimum alcohol level of 12% with a minimum of 7 months aging in oak, while Chianti Classicos labeled *riserva* must be aged at least 24 months at the winery, with a minimum alcohol level of 12.5%. The harvest yields for Chianti Classico are restricted to no more than 7.5 tonne/ha. For basic Chianti, the minimum alcohol level is 11.5% with yields restricted to 9 tonne/ha.
The aging for basic Chianti DOCG is much less stringent with most varieties allowed to be released to the market on 1 March following the vintage year. The sub-zones of Colli Fiorentini, Montespertoli and Rufina must be aged for a further three months and not released until 1 June. All Chianti Classicos must be held back until 1 October in the year following the vintage.
normal Classico Colli Aretini Colli Fiorentini Colli Senesi Colline Pisane Montalbano Montespertoli Rùfina Superiore
------------------------------- -------- ---------- --------------- ------------------ -------------- ---------------- ------------ --------------- -------- -----------
Max. grape prod. (t/ha) 9.0 7.5 8.0 8.0 8.0 8.0 8.0 8.0 8.0 7.5
Max. grape prod. (kg/vine) 4.0 3.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 2.2
Min. vines/ha 3,300 3,350 3,300 3,300 3,300 3,300 3,300 3,300 3,300 4,000
Min. age of vineyards (years) 3 4 4 4 4 4 4 4 4 4
Min. wine dry extract (g/L) 19 23 21 21 21 21 21 21 21 22
Min. alcohol cont. (%) 11.5 12.0 11.5 12.0 11.5 11.5 11.5 12.0 12.0 12.0
Min. aging (months) 3 10 3 9 3 3 3 6 9 9
: Comparative table of Chianti *laws of production*
Jancis Robinson notes that Chianti is sometimes called the \"Bordeaux of Italy\" but the structure of the wines is very different from any French wine. The flexibility in the blending recipe for Chianti accounts for some of the variability in styles among Chiantis. Lighter-bodied styles will generally have a higher proportion of white grape varieties blended in, while Chiantis that have only red grape varieties will be fuller and richer. While only 15% of Cabernet Sauvignon is permitted in the blend, the nature of the grape variety can have a dominant personality in the Chianti blend and be a strong influence in the wine.
Chianti Classico wines are characterised in their youth by their predominantly floral and cinnamon spicy bouquet. As the wine ages, aromas of tobacco and leather can emerge. Chiantis tend to have medium-high acidity and medium tannins. Basic level Chianti is often characterised by its juicy fruit notes of cherry, plum and raspberry and can range from simple quaffing wines to those approaching the level of Chianti Classico. Wine expert Tom Stevenson notes that these basic everyday-drinking Chiantis are at their peak drinking qualities often between three and five years after vintage, with premium examples having the potential to age for four to eight years. Well-made examples of Chianti Classico often have the potential to age and improve in the bottle for six to twenty years.
### Chianti Superiore {#chianti_superiore}
Chianti Superiore is an Italian DOCG wine produced in the provinces of Arezzo, Florence, Pisa, Pistoia, Prato and Siena, in Tuscany. Superiore is a specification for wines produced with a stricter rule of production than other Chianti wines. Chianti Superiore has been authorised since 1996. Chianti Superiore wines can be produced only from grapes cultivated in the Chianti wine areas except from those vineyards that are registered in the Chianti Classico sub-zone. Vineyards registered in Chianti sub-zones other than Classico can produce Chianti Superiore wines but must omit the sub-zone name on the label. Aging is calculated from 1 January after the picking. Chianti Superiore cannot be sold to the consumer before nine months of aging, of which three must be in the bottle. Therefore, it cannot be bottled before the June after picking or sold to consumers before the next September.
Chianti Superiore Other Chianti \% Ch. Superiore
--------------------------- ------------------- --------------- ------------------
Registered vineyards (ha) 297.98 25,333.67 1.18%
Grape production (t) 1,808.51 184,023.10 0.98%
Wine production (L) 1,166,169 106,124,871 1.09%
: 2004 production
## Special editions {#special_editions}
Chianti Classico was promoted as the \"Official wine of the 2013 UCI Road World Championships\" and sold bottles dedicated to the Championships with special labels
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# Claude Louis Berthollet
**Claude Louis Berthollet** (`{{IPA|fr|klod lwi bɛʁtɔlɛ}}`{=mediawiki}, 9 December 1748 -- 6 November 1822) was a Savoyard-French chemist who became vice president of the French Senate in 1804. He is known for his scientific contributions to the theory of chemical equilibria via the mechanism of reverse chemical reactions, and for his contribution to modern chemical nomenclature. On a practical basis, Berthollet was the first to demonstrate the bleaching action of chlorine gas, and was first to develop a solution of sodium hypochlorite as a modern bleaching agent.
## Biography
Claude Louis Berthollet was born in Talloires, near Annecy, then part of the Duchy of Savoy, in 1749.
He started his studies at Chambéry and then in Turin where he graduated in medicine. Berthollet\'s great new developments in works regarding chemistry made him, in a short period of time, an active participant of the Academy of Science in 1780.
Berthollet, along with Antoine Lavoisier and others, devised a chemical nomenclature, or a system of names, which serves as the basis of the modern system of naming chemical compounds.
He also carried out research into dyes and bleaches, being first to introduce the use of chlorine gas as a commercial bleach in 1785. He first produced a modern bleaching liquid in 1789 in his laboratory on the quay Javel in Paris, France, by passing chlorine gas through a solution of sodium carbonate. The resulting liquid, known as \"*Eau de Javel*\" (\"Javel water\"), was a weak solution of sodium hypochlorite. Another strong chlorine oxidant and bleach which he investigated and was the first to produce, potassium chlorate (KClO~3~), is known as *Berthollet\'s Salt*.
Berthollet first determined the elemental composition of the gas ammonia, in 1785.
Berthollet was one of the first chemists to recognize the characteristics of a reverse reaction, and hence, chemical equilibrium.
Berthollet was engaged in a long-term battle with another French chemist, Joseph Proust, on the validity of the law of definite proportions. While Proust believed that chemical compounds are composed of a fixed ratio of their constituent elements irrespective of the methods of production, Berthollet believed that this ratio can change according to the ratio of the reactants initially taken. Although Proust proved his theory by accurate measurements, his theory was not immediately accepted partially due to Berthollet\'s authority. His law was finally accepted when Berzelius confirmed it in 1811, but it was found later that Berthollet was not completely wrong because there exists a class of compounds that do not obey the law of definite proportions. These non-stoichiometric compounds are also named *berthollides* in his honor.
Berthollet was one of several scientists who went with Napoleon to Egypt and was a member of the physics and natural history section of the Institut d\'Égypte.
## Awards and honours {#awards_and_honours}
In April, 1789 Berthollet was elected a Fellow of the Royal Society of London. In 1801, he was elected a foreign member of the Royal Swedish Academy of Sciences. In 1809, Berthollet was elected an associate member first class of the Royal Institute of the Netherlands, predecessor of the Royal Netherlands Academy of Arts and Sciences. He was elected an Honorary Fellow of the Royal Society of Edinburgh in 1820 and a Foreign Honorary Member of the American Academy of Arts and Sciences in 1822.
Claude-Louis Berthollet\'s 1788 publication entitled *Méthode de Nomenclature Chimique*, published with colleagues Antoine Lavoisier, Louis Bernard Guyton de Morveau, and Antoine François, comte de Fourcroy, was honored by a Citation for Chemical Breakthrough Award from the Division of History of Chemistry of the American Chemical Society, presented at the Académie des Sciences (Paris) in 2015.
A French High School located in Annecy is named after him (Lycée Claude Louis Berthollet).
<File:Méthode> de Nomenclature Chimique-1.jpg\|1787 copy of \"Méthode de Nomenclature Chimique\" <File:Méthode> de Nomenclature Chimique-2.jpg\|Title page of \"Méthode de Nomenclature Chimique\" <File:Méthode> de Nomenclature Chimique-3.jpg\|Table of contents for \"Méthode de Nomenclature Chimique\"
## Personal life {#personal_life}
Berthollet married Marie Marguerite Baur in 1788. Their son, Amédée-Barthélémy Berthollet, died in 1811 of carbon monoxide poisoning via charcoal-burning suicide in which he had recorded his physiological and psychological experiences as a final scientific contribution before losing consciousness and succumbing to the fumes.
Berthollet was accused of being an atheist.
He died in Arcueil, France in 1822
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# Chilean Constitution of 1980
The **Political Constitution of the Republic of Chile of 1980** (*Constitución Política de la República de Chile*) is the fundamental law in force in Chile. It was approved and promulgated under the military dictatorship headed by Augusto Pinochet, being ratified by the Chilean citizenry through a referendum on September 11, 1980, although being held under restrictions and without electoral registers. While 69% of the population was reported to have voted yes, the vote was questioned by hundreds of denunciations of irregularities and fraud. The constitutional text took effect, in a transitory regime, on March 11, 1981, and then entered into full force on March 11, 1990, with the return to electoral democracy. It was amended for the first time in 1989 (through a referendum), and afterward in 1991, 1994, 1997, each year from 1999 to 2001, 2003, each year from 2007 to 2015, and each year from 2017 to 2021, with the last three amendments concerning the constituent process of 2020--2022. In September 2005, under Ricardo Lagos\'s presidency, a large amendment of the Constitution was approved by parliamentarians, removing from the text some of the less democratic dispositions coming from Pinochet\'s regime, such as senators-for-life and appointed senators, as well as the armed forces\' warranty of the democratic regime.
On November 15, 2019, following a series of popular protests in October 2019, a political agreement between parties with parliamentary representation called for a national referendum on the proposal of writing a new Constitution and on the mechanism to draft it. A plebiscite held on October 25, 2020, approved drafting a new fundamental charter, as well as choosing by popular vote delegates to a Constitutional Convention which was to fulfill this objective. The members of the convention were elected in May 2021, and first convened on July 4, 2021. However, on September 4, 2022, voters rejected the new constitution in the constitutional referendum. Following the rejection, the Expert Commission drafted another new constitution for the Constitutional Council to amend. However, on December 15, 2023, voters rejected the constitution in the 2023 Chilean constitutional referendum.
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# Chilean Constitution of 1980
## Background
The Commission for the Study of the New Political Constitution of the Republic of Chile\', commonly known as the Ortúzar Commission\', was a body established in 1973 by the Military Government Junta that ruled the country during the military dictatorship of Augusto Pinochet, following the coup against the Socialist President Salvador Allende. Its purpose was to draft the preliminary project for the 1980 Constitution. It met from September 24, 1973, to October 5, 1978. The name \"Ortúzar Commission\" is due to its chairman, Enrique Ortúzar Escobar, who previously served as Minister of Justice and Minister of Foreign Affairs during the administration of Jorge Alessandri.
The following people were part of the commission: Rafael Eyzaguirre Echeverría (secretary), Sergio Diez Urzúa, Enrique Evans de la Cuadra, Jaime Guzmán Errázuriz, Gustavo Lorca Rojas, Jorge Ovalle Quiroz, Alejandro Silva Bascuñán, Alicia Romo Román, Raúl Gormaz Molina and later on Luz Bulnes Aldunate, Raúl Bertelsen Repetto, Juan de Dios Carmona.
Despite what is commonly believed, the Ortúzar Commission was not a constituent assembly and did not draft the 1980 Constitution; rather, it merely prepared a preliminary draft that was subsequently reviewed by the Council of State and the Government Junta before being formally submitted for popular approval via a plebiscite.
Nevertheless, there is no denying the importance of the discussion carried out by the Ortúzar Commission regarding the final text of the 1980 Constitution. Although many of the commission\'s proposals were not adopted by the Council of State and the Government Junta, a large portion of the new Constitution\'s text was analyzed and debated within the commission.
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# Chilean Constitution of 1980
## Legitimacy
According to the law professor Camel Cazor Aliste, the Constitution of 1980 has problems of legitimacy stemming from two facts. First, the constitutional commission was not representative of the political spectrum of Chile: its members had been handpicked by the Pinochet dictatorship, and opponents of the regime had been deliberately excluded. Secondly, the constitution\'s approval was achieved by the government in a controversial and tightly controlled referendum in 1980. Campaigning for the referendum was irregular, with the government calling people to vote positively on the reform, and also using radio and television commercial spots, while the opposition urging people to vote negatively were only able of doing small public demonstrations, without access to television time and limited radio access. There was no electoral roll for this vote, as the register had been burned during the dictatorship. There were multiple cases of double voting, with at least 3000 CNI agents doing so.
Since the return to democracy, the constitution has been amended nearly 60 times.
A document from September 13, 1973, shows that Jaime Guzmán had by then already been tasked by the Junta to study the creation of a new constitution.
It has been argued the 1980 Constitution was designed to favor the election of right-wing legislative majorities. Several rounds of constitutional amendments have been enacted since 1989 to address this concern.
A referendum held in 2020 after waves of popular protests approved the drafting of a new constitution. In September 2022, a proposed left-wing replacement constitution was rejected, 62% to 38%. Following a second process, in December 2023, a proposed right-wing replacement was also rejected, 55.8% to 44.2%. These outcomes effectively granted the 1980 charter democratic legitimacy.
## Attempted replacement {#attempted_replacement}
In July 2022, a proposed replacement constitution was submitted for national debate and general referendum, but it was rejected on September 4 despite having had the support of left-leaning President Gabriel Boric. The document had faced intense criticism that it was \"too long, too left-wing and too radical\", and was rejected by a margin of 62% to 38%.
On March 6, 2023, a group of experts appointed by Congress began a second attempt to prepare a preliminary draft of a new constitution. The group, with lawyer Veronica Undurraga serving as its president, was scheduled to work for three months on 12 institutional bases agreed to by lawmakers, after which the draft would be given to an elected Constitutional Council, whose members would be voted upon on May 7, 2023. At the same time, a 14-member Technical Admissibility Committee began serving as arbitrator.
On December 17, 2023, Chileans voted 55.8% to 44.2% against the second proposed constitution. President Boric stated that he would not seek a third referendum; this outcome effectively guaranteed the 1980 charter would remain in effect
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# Crystallography
**Crystallography** is the branch of science devoted to the study of molecular and crystalline structure and properties. The word *crystallography* is derived from the Ancient Greek word `{{wikt-lang|grc|κρύσταλλος}}`{=mediawiki} (`{{grc-transl|κρύσταλλος}}`{=mediawiki}; \"clear ice, rock-crystal\"), and `{{wikt-lang|grc|γράφειν}}`{=mediawiki} (`{{grc-transl|γράφειν}}`{=mediawiki}; \"to write\"). In July 2012, the United Nations recognised the importance of the science of crystallography by proclaiming 2014 the International Year of Crystallography.
Crystallography is a broad topic, and many of its subareas, such as X-ray crystallography, are themselves important scientific topics. Crystallography ranges from the fundamentals of crystal structure to the mathematics of crystal geometry, including those that are not periodic or quasicrystals. At the atomic scale it can involve the use of X-ray diffraction to produce experimental data that the tools of X-ray crystallography can convert into detailed positions of atoms, and sometimes electron density. At larger scales it includes experimental tools such as orientational imaging to examine the relative orientations at the grain boundary in materials. Crystallography plays a key role in many areas of biology, chemistry, and physics, as well new developments in these fields.
## History and timeline {#history_and_timeline}
Before the 20th century, the study of crystals was based on physical measurements of their geometry using a goniometer. This involved measuring the angles of crystal faces relative to each other and to theoretical reference axes (crystallographic axes), and establishing the symmetry of the crystal in question. The position in 3D space of each crystal face is plotted on a stereographic net such as a Wulff net or Lambert net. The pole to each face is plotted on the net. Each point is labelled with its Miller index. The final plot allows the symmetry of the crystal to be established.
The discovery of X-rays and electrons in the last decade of the 19th century enabled the determination of crystal structures on the atomic scale, which brought about the modern era of crystallography. The first X-ray diffraction experiment was conducted in 1912 by Max von Laue, while electron diffraction was first realized in 1927 in the Davisson--Germer experiment and parallel work by George Paget Thomson and Alexander Reid. These developed into the two main branches of crystallography, X-ray crystallography and electron diffraction. The quality and throughput of solving crystal structures greatly improved in the second half of the 20th century, with the developments of customized instruments and phasing algorithms. Nowadays, crystallography is an interdisciplinary field, supporting theoretical and experimental discoveries in various domains. Modern-day scientific instruments for crystallography vary from laboratory-sized equipment, such as diffractometers and electron microscopes, to dedicated large facilities, such as photoinjectors, synchrotron light sources and free-electron lasers.
## Methodology
Crystallographic methods depend mainly on analysis of the diffraction patterns of a sample targeted by a beam of some type. X-rays are most commonly used; other beams used include electrons or neutrons. Crystallographers often explicitly state the type of beam used, as in the terms *X-ray diffraction, neutron diffraction* and *electron diffraction*. These three types of radiation interact with the specimen in different ways.
- X-rays interact with the spatial distribution of electrons in the sample.
- Neutrons are scattered by the atomic nuclei through the strong nuclear forces, but in addition the magnetic moment of neutrons is non-zero, so they are also scattered by magnetic fields. When neutrons are scattered from hydrogen-containing materials, they produce diffraction patterns with high noise levels, which can sometimes be resolved by substituting deuterium for hydrogen.
- Electrons are charged particles and therefore interact with the total charge distribution of both the atomic nuclei and the electrons of the sample.
It is hard to focus x-rays or neutrons, but since electrons are charged they can be focused and are used in electron microscope to produce magnified images. There are many ways that transmission electron microscopy and related techniques such as scanning transmission electron microscopy, high-resolution electron microscopy can be used to obtain images with in many cases atomic resolution from which crystallographic information can be obtained. There are also other methods such as low-energy electron diffraction, low-energy electron microscopy and reflection high-energy electron diffraction which can be used to obtain crystallographic information about surfaces.
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# Crystallography
## Applications in various areas {#applications_in_various_areas}
### Materials science {#materials_science}
Crystallography is used by materials scientists to characterize different materials. In single crystals, the effects of the crystalline arrangement of atoms is often easy to see macroscopically because the natural shapes of crystals reflect the atomic structure. In addition, physical properties are often controlled by crystalline defects. The understanding of crystal structures is an important prerequisite for understanding crystallographic defects. Most materials do not occur as a single crystal, but are poly-crystalline in nature (they exist as an aggregate of small crystals with different orientations). As such, powder diffraction techniques, which take diffraction patterns of samples with a large number of crystals, play an important role in structural determination.
Other physical properties are also linked to crystallography. For example, the minerals in clay form small, flat, platelike structures. Clay can be easily deformed because the platelike particles can slip along each other in the plane of the plates, yet remain strongly connected in the direction perpendicular to the plates. Such mechanisms can be studied by crystallographic texture measurements. Crystallographic studies help elucidate the relationship between a material\'s structure and its properties, aiding in developing new materials with tailored characteristics. This understanding is crucial in various fields, including metallurgy, geology, and materials science. Advancements in crystallographic techniques, such as electron diffraction and X-ray crystallography, continue to expand our understanding of material behavior at the atomic level.
In another example, iron transforms from a body-centered cubic (bcc) structure called ferrite to a face-centered cubic (fcc) structure called austenite when it is heated. The fcc structure is a close-packed structure unlike the bcc structure; thus the volume of the iron decreases when this transformation occurs.
Crystallography is useful in phase identification. When manufacturing or using a material, it is generally desirable to know what compounds and what phases are present in the material, as their composition, structure and proportions will influence the material\'s properties. Each phase has a characteristic arrangement of atoms. X-ray or neutron diffraction can be used to identify which structures are present in the material, and thus which compounds are present. Crystallography covers the enumeration of the symmetry patterns which can be formed by atoms in a crystal and for this reason is related to group theory. Further information: Oligocrystalline material
### Biology
X-ray crystallography is the primary method for determining the molecular conformations of biological macromolecules, particularly protein and nucleic acids such as DNA and RNA. The first crystal structure of a macromolecule was solved in 1958, a three-dimensional model of the myoglobin molecule obtained by X-ray analysis. Neutron crystallography is often used to help refine structures obtained by X-ray methods or to solve a specific bond; the methods are often viewed as complementary, as X-rays are sensitive to electron positions and scatter most strongly off heavy atoms, while neutrons are sensitive to nucleus positions and scatter strongly even off many light isotopes, including hydrogen and deuterium. Electron diffraction has been used to determine some protein structures, most notably membrane proteins and viral capsids.
Macromolecular structures determined through X-ray crystallography (and other techniques) are housed in the Protein Data Bank (PDB)--a freely accessible repository for the structures of proteins and other biological macromolecules. There are many molecular graphics codes available for visualising these structures.
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# Crystallography
## Notation
- Coordinates in *square brackets* such as **\[100\]** denote a direction vector (in real space).
- Coordinates in *angle brackets* or *chevrons* such as **\<100\>** denote a *family* of directions which are related by symmetry operations. In the cubic crystal system for example, **\<100\>** would mean \[100\], \[010\], \[001\] or the negative of any of those directions.
- Miller indices in *parentheses* such as **(100)** denote a plane of the crystal structure, and regular repetitions of that plane with a particular spacing. In the cubic system, the normal to the (hkl) plane is the direction \[hkl\], but in lower-symmetry cases, the normal to (hkl) is not parallel to \[hkl\].
- Indices in *curly brackets* or *braces* such as **{100}** denote a family of planes and their normals. In cubic materials the symmetry makes them equivalent, just as the way angle brackets denote a family of directions. In non-cubic materials, is not necessarily perpendicular to {hkl}.
## Reference literature {#reference_literature}
The *International Tables for Crystallography* is an eight-book series that outlines the standard notations for formatting, describing and testing crystals. The series contains books that covers analysis methods and the mathematical procedures for determining organic structure through x-ray crystallography, electron diffraction, and neutron diffraction. The International tables are focused on procedures, techniques and descriptions and do not list the physical properties of individual crystals themselves. Each book is about 1000 pages and the titles of the books are:
: Vol A - *Space Group Symmetry*,
: Vol A1 - *Symmetry Relations Between Space Groups*,
: Vol B - *Reciprocal Space*,
: Vol C - *Mathematical, Physical, and Chemical Tables*,
: Vol D - *Physical Properties of Crystals*,
: Vol E - *Subperiodic Groups*,
: Vol F - *Crystallography of Biological Macromolecules*, and
: Vol G - *Definition and Exchange of Crystallographic Data*
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# Critical psychology
**Critical psychology** is a perspective on psychology that draws extensively on critical theory. Critical psychology challenges the assumptions, theories and methods of mainstream psychology and attempts to apply psychological understandings in different ways.
The field of critical psychology does not fall under a monolithic category`{{Clarify|date=September 2024}}`{=mediawiki}. One can observe different starting points of critiques, similarities, as well as substantial differences. Thus, critical psychology should be perceived as an "umbrella term" that includes various critiques against the status quo of mainstream psychology. A common theme of critical approaches in psychology is the assessment of the social effects of psychological theories and practices. Critical psychology is a movement that challenges psychology to work towards emancipation and social justice, and that opposes the uses of psychology to perpetuate oppression and injustice.
Critical psychologists believe that mainstream psychology fails to consider how power differences and discrimination between social classes and groups can impact an individual\'s or a group\'s mental and physical well-being. Mainstream psychology does this only in part by attempting to explain behavior at the individual level. However, it largely ignores institutional racism, postcolonialism and deficits in social justice for minority groups based on differences in observable characteristics such as gender, ethnicity, religious minority, sexual orientation, or disability.
## Origins
Psychology, draws a history filled with theoretical and political conflict. Within its history various stream of critiques have emerged, some of them sharing similarities, as well as different starting points and substantial differences. Criticisms of mainstream psychology consistent with current critical psychology usage have existed since psychology\'s modern development in the late 19th century. Use of the term *critical psychology* started in the 1970s at the Freie Universität Berlin. The German branch of critical psychology predates and has developed largely separately from the rest of the field. As of May 2007, only a few works have been translated into English. The German Critical Psychology movement is rooted in the post-war student revolt of the late 1960s; see German student movement. Marx\'s *Critique of Political Economy* played an important role in the German branch of the student revolt, which was centered in West Berlin. At that time, the capitalist city of West Berlin was surrounded by communist-ruled East Germany, and represented a \"hot spot\" of political and ideological controversy for the revolutionary German students. The sociological foundations of critical psychology are decidedly Marxist.
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# Critical psychology
## Origins
### Klaus Holzkamp {#klaus_holzkamp}
One of the most important and sophisticated books in the German development of the field is the *Grundlegung der Psychologie* (*Foundations of Psychology*) by Klaus Holzkamp, who might be considered the theoretical founder of German critical psychology. Holzkamp wrote two books on theory of science and one on sensory perception before publishing the *Grundlegung der Psychologie* in 1983. Holzkamp believed his work provided a solid paradigm for psychological research because he viewed psychology as a pre-paradigmatic scientific discipline (T.S. Kuhn had used the term \"pre-paradigmatic\" for social science).
Holzkamp mostly based his sophisticated attempt to provide a comprehensive and integrated set of categories defining the field of psychological research on Aleksey Leontyev\'s approach to cultural--historical psychology and activity theory. Leontyev had seen human action as a result of biological as well as cultural evolution and, drawing on Marx\'s materialist conception of culture, stressed that individual cognition is always part of social action which in turn is mediated by man-made tools (cultural artifacts), language and other man-made systems of symbols, which he viewed as a major distinguishing feature of human culture and, thus, human cognition. Another important source was Lucien Séve\'s theory of personality, which provided the concept of \"social activity matrices\" as mediating structure between individual and social reproduction. At the same time, the *Grundlegung* systematically integrated previous specialized work done at Free University of Berlin in the 1970s by critical psychologists who also had been influenced by Marx, Leontyev, and Seve. This included books on animal behavior/ethology, sensory perception, motivation and cognition. He also incorporated ideas from Freud\'s psychoanalysis and Merleau-Ponty\'s phenomenology into his approach.
One core result of Holzkamp\'s historical and comparative analysis of human reproductive action, perception and cognition is a very specific concept of meaning that identifies symbolic meaning as historically and culturally constructed, purposeful conceptual structures that humans create in close relationship to material culture and within the context of historically specific formations of social reproduction.
Coming from this phenomenological perspective on culturally mediated and socially situated action, Holzkamp launched a methodological attack on behaviorism (which he termed S--R (stimulus--response) psychology) based on linguistic analysis, showing in minute detail the rhetorical patterns by which this approach to psychology creates the illusion of \"scientific objectivity\" while at the same time losing relevance for understanding culturally situated, intentional human actions. Against this approach, he developed his own approach to generalization and objectivity, drawing on ideas from Kurt Lewin in Chapter 9 of **Grundlegung der Psychologie**.
His last major publication before his death in 1995 was about learning. It appeared in 1993 and contained a phenomenological theory of learning from the standpoint of the subject. One important concept Holzkamp developed was \"reinterpretation\" of theories developed by conventional psychology. This meant to look at these concepts from the standpoint of the paradigm of critical psychology, thereby integrating their useful insights into critical psychology while at the same time identifying and criticizing their limiting implications, which in the case of S--R psychology were the rhetorical elimination of the subject and intentional action, and in the case of cognitive psychology which did take into account subjective motives and intentional actions, methodological individualism.
The first part of the book thus contains an extensive look at the history of psychological theories of learning and a minute re-interpretation of those concepts from the perspective of critical psychology, which focuses on intentional action situated in specific socio-historical/cultural contexts. The conceptions of learning he found most useful in his own detailed analysis of \"classroom learning\" came from cognitive anthropologists Jean Lave (situated learning) and Edwin Hutchins (distributed cognition).
The book\'s second part contained an extensive analysis on the modern state\'s institutionalized forms of \"classroom learning\" as the cultural--historical context that shapes much of modern learning and socialization. In this analysis, he heavily drew upon Michel Foucault\'s *Discipline and Punish*. Holzkamp felt that classroom learning as the historically specific form of learning does not make full use of student\'s potentials, but rather limits her or his learning potentials by a number of \"teaching strategies.\" Part of his motivation for the book was to look for alternative forms of learning that made use of the enormous potential of the human psyche in more fruitful ways. Consequently, in the last section of the book, Holzkamp discusses forms of \"expansive learning\" that seem to avoid the limitations of classroom learning, such as apprenticeship and learning in contexts other than classrooms.
This search culminated in plans to write a major work on *life leadership* in the specific historical context of modern (capitalist) society. Due to his death in 1995, this work never got past the stage of early (and premature) conceptualizations, some of which were published in the journals *Forum Kritische Psychologie* and *Argument*.
### 1960s--1970s
In the 1960s and 1970s the term *radical psychology* was used by psychologists internationally to denote a branch of the field which rejected mainstream psychology\'s focus on the individual as the basic unit of analysis and sole source of psychopathology. Instead, radical psychologists examined the role of society in causing and treating problems and looked towards social change as an alternative to therapy to treat mental illness and as a means of preventing psychopathology. Within psychiatry the term *anti-psychiatry* was often used and now British activists prefer the term *critical psychiatry*. *Critical psychology* is currently the preferred term for the discipline of psychology keen to find alternatives to the way the discipline of psychology reduces human experience to the level of the individual and thereby strips away possibilities for radical social change.
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# Critical psychology
## Origins
### 1990s
Starting in the 1990s a new wave of books started to appear on critical psychology, the most influential being the edited book *Critical Psychology* by Dennis Fox and Isaac Prilleltensky. Various introductory texts to critical psychology written in the United Kingdom have tended to focus on discourse, but this has been seen by some proponents of critical psychology as a reduction of human experience to language which is as politically dangerous as the way mainstream psychology reduces experience to the individual mind. Attention to language and ideological processes, others would argue, is essential to effective critical psychology -- it is not simply a matter of applying mainstream psychological concepts to issues of social change.
### Ian Parker {#ian_parker}
In 1999 Ian Parker published an influential manifesto in both the online journal *Radical Psychology* and the *Annual Review of Critical Psychology*. This manifesto argues that critical psychology should include the following four components:
1. Systematic examination of how some varieties of psychological action and experience are privileged over others, how dominant accounts of \"psychology\" operate ideologically and in the service of power;
2. Study of the ways in which all varieties of psychology are culturally historically constructed, and how alternative varieties of psychology may confirm or resist ideological assumptions in mainstream models;
3. Study of forms of surveillance and self-regulation in everyday life and the ways in which psychological culture operates beyond the boundaries of academic and professional practice; and
4. Exploration of the way everyday \"ordinary psychology\" structures academic and professional work in psychology and how everyday activities might provide the basis for resistance to contemporary disciplinary practices.
### Critical psychology today {#critical_psychology_today}
There are a few international journals devoted to critical psychology and critical discussions in Psychology, including *Psychology in Society*, *Theory & Psychology*, *Culture & Psychology*, *Feminism & Psychology*, *Human Development*, *Annual Review of Critical Psychology and* the no longer published *International Journal of Critical Psychology* (continued in the journal *Subjectivity*) and *Radical Psychology Journal* (published for ten years until its final issue in 2011). The journals still tend to be directed to an academic audience, though the *Annual Review of Critical Psychology* and *Psychology in Society* runs as an open-access online journal. There are close links between critical psychologists and critical psychiatrists in Britain through the Asylum Collective. David Smail was one of the founders of The Midlands Psychology Group, a critical psychology collective who produced a manifesto for a social materialist psychology of distress. Critical psychology courses and research concentrations are available at Manchester Metropolitan University, York St John University, the University of East London, the University of Edinburgh, the University of KwaZulu Natal, the City University of New York Graduate Center, the University of West Georgia, Point Park University, University of Guelph, York University, and Prescott College. Undergraduate concentrations can also be found at the California Institute of Integral Studies, Prescott College, and at the University of Notre Dame Australia (Fremantle).
## Extensions
Like many critical applications, critical psychology has expanded beyond Marxist and feminist roots to benefit from other critical approaches. Consider ecopsychology and transpersonal psychology. Critical psychology and related work has also sometimes been labelled *radical psychology* and *liberation psychology*. In the field of developmental psychology, the work of Erica Burman has been influential.
Various sub-disciplines within psychology have begun to establish their own critical orientations. Perhaps the most extensive are critical health psychology, community psychology, and social psychology.
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# Critical psychology
## Aims of Critical Psychology {#aims_of_critical_psychology}
Central themes of critical psychology is the concept of "oppression" and "emancipation". Critical psychology reflects not only on the connection of mainstream psychology with power, but also work toward emancipation (or liberation). Oppression refers to "a state of asymmetric power relations characterized by domination, subordination, and resistance, where the dominating persons or groups exercise their power by restricting access to material resources and by implanting in the subordinated persons or groups fear or self-deprecating views about themselves". Emancipation (or liberation) refer to the possibilities of individuals within the social inequalities, doing justice to both, individual and societal domains. Consequently, the aims of critical psychology is the understanding of "oppression" and "liberation" in relation with "Power".
The spectrum through which the aims of critical psychology is expressed is divided into three different levels of intervention : The micro-level, meso-level, and macro level. Micro-level context refer to the relation of psychology with individuals and groups, the meso-level context refer to the critical reflections of critical psychology on psychology and the re-formation of a psychology not *about* but *for* the people, and the macro-level context refer to interventions of critical psychology to create a more equitable society, inviting larger social-agents. A similar reflection is the one that divides possibilities of liberation in relation with power into: aesthetic, interaction, and labor dimension. Aesthetic dimension refer to very personal and individual possibility of liberation through self-expression, the dimension of interaction refer to the deconstruction of oppression in the symbolic and communicative dimension of power (e.g. books, texts, media) and labor refer to liberation from larger socio-political expressions of power (schools, work, health-care). To sum-up, power is practiced in a spectrum from individual- to larger societal level, and thus oppression and possibilities of liberation is also identified within this spectrum. Thus, the aims of critical psychology toward emancipation exceeds from the individual, to the larger societal level of reflection and action.
## Forms of Critical Psychology {#forms_of_critical_psychology}
Understanding and action, is an ongoing debate in the field of critical psychology. The understanding of oppression and the \"praxis\" of emancipation is two different domains, which is the domain of theory and the domain of action. For this reason it is proposed to divide Critical Psychology into four different forms : (a) critical theoretical psychology, (b) critical theoretical psychology with a practical emancipatory intention, (c) critical empirical psychology, and (d) critical applied psychology. Critical theoretical psychology (a), and critical empirical psychology (c) refers to the theoretical understanding and development of the field, while critical theoretical psychology with practical emancipatory intention, (b) and critical applied psychology (d), has to do with practice and move toward a social change.
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# Critical psychology
## Internationally
An early international overview of critical psychology perspectives can be found in *Critical Psychology: Voices for Change*, edited by Tod Sloan (Macmillan, 2000). In 2015, Ian Parker edited the *Handbook of Critical Psychology*.
### Germany
At FU-Berlin, critical psychology was not really seen as a division of psychology and followed its own methodology, trying to reformulate traditional psychology on an unorthodox Marxist base and drawing from Soviet ideas of cultural--historical psychology, particularly Aleksey Leontyev. Some years ago `{{When|date=May 2023|reason=When was "Some years ago"?}}`{=mediawiki} the department of critical psychology at FU-Berlin was merged into the traditional psychology department.
An April 2009 issue of the journal *Theory & Psychology* (edited by Desmond Painter, Athanasios Marvakis, and Leendert Mos) is devoted to an examination of German critical psychology.
### South Africa {#south_africa}
The complex sociopolitical history of South Africa, and its relationship with mainstream psychology, created a setting in which critical psychology could be impactful. South Africa is a good example of a context in which mainstream psychology positioned itself alongside neo-colonialism, racism, and capitalist exploitation - during the country\'s Apartheid era - which led to the need for critical alternatives within the field that could challenge ideological complicities. During apartheid, mainstream psychology supported the oppressive political system - some psychologists actively and others passively. In the early 1980s, at the height of apartheid, progressive white psychologists and a growing number of black psychologists began to research and practice alternative programmes to critique and resist mainstream psychology\'s role in perpetuating apartheid in South Africa. In this way, critical psychology started to develop in South Africa.
As is the case in other parts of the world, critical psychology in South Africa was born from interrogating psychology in relation to politics. Firstly, psychology was accused of being a product of, and supporter of, an oppressive political system in which its supposed neutrality and scientific objectivity were informed by the sectors of society that benefited from the ideological and economic dominance that it upheld. Secondly, once critical psychologists in South Africa revealed the ideological flaws in mainstream psychology within the country\'s context, work began to reconfigure the field as a progressive and socially relevant practice with theoretical and methodological approaches that could benefit all members of South African society.
The establishment of critical psychology in South Africa took various forms between 1980 and 1994. Although the field was not necessarily fully formalised during this time, spaces and organisations were created for its ideas to be expressed and developed: such as in the University of Cape Town\'s (UCT) psychology department, the formation of the Organisation for Appropriate Social Services in South Africa (OASSSA), Psychologists Against Apartheid, the South African Health and Social Services Organisation (SAHSSO), and the establishment of the academic journal *Psychology in Society (PINS)*. Some of the main theoretical and practical achievements of these developments were: the forging of a way to critique the categories of class, race, gender, and other structural factors impacting the discipline of psychology, the encouragement of students to think critically about the politics of psychology, and rebuilding international links as well as relationships with other social and health sciences in South Africa.
However, not all these initiatives continued after the end of political struggle and the transition to democracy. After 1994, professional psychology in South Africa was reorganised through the establishment of the Professional Board for Psychology that exists within the Health Professions Council of South Africa (HPCSA). This statutory body regulates the profession with its systems of licensing and certification. Within these systems, critical psychology is more of an approach to the field than it is a professional category on its own. From the 2000s until recent times, critical psychology moved more toward studying certain domains, such as gender or race, and in the process, the overarching project of establishing a formalised field of critical psychology has either been discarded or broadened to refer to anything that is \'non-mainstream\' in psychology. Critical psychology in South Africa is therefore mostly applied as a theoretical approach.
### United States and Canada {#united_states_and_canada}
The doctoral program in Critical Social/Personality Psychology and Environmental Psychology at the CUNY Graduate Center and the doctoral program in Critical Psychology at Point Park University, in Pittsburgh, PA are the only critical psychology specific doctoral programs in the United States. Prescott College in Prescott, Arizona offers an online Master\'s program in Critical Psychology and Human Services and has a critically oriented undergraduate program. The California Institute of Integral Studies in San Francisco also offers the Bachelor\'s Completion Program with a minor in Critical Psychology, and critical perspectives are sometimes encountered in traditional universities, perhaps especially within community psychology programs. The University of West Georgia offers a Ph.D. in Consciousness and Society with critical psychology being one of the main three theoretical orientations. North American efforts include the 1993 founding of RadPsyNet, the 1997 publication of *Critical Psychology: An Introduction* (edited by Dennis Fox and Isaac Prilleltensky; expanded 2009 edition edited by Dennis Fox, Isaac Prilleltensky, and Stephanie Austin), the 2001 Monterey Conference on Critical Psychology, and in underlying themes of many contributions to the *Journal of Social Action in Counseling and Psychology*
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# Crossfire
`{{wiktionary}}`{=mediawiki} A **crossfire** (also known as **interlocking fire**) is a military term for the siting of weapons (often automatic weapons such as assault rifles or sub-machine guns) so that their arcs of fire overlap. This tactic came to prominence in World War I.
Siting weapons this way is an example of the application of the defensive principle of *mutual support*. The advantage of siting weapons that mutually support one another is that it is difficult for an attacker to find a covered approach to any one defensive position. Use of armour, air support, indirect fire support, and stealth are tactics that may be used to assault a defensive position. However, when combined with land mines, snipers, barbed wire, and air cover, crossfire became a difficult tactic to counter in the early 20th century.
## Early modern warfare {#early_modern_warfare}
The concept of overlapping arcs of fire drove major developments in the use of cannon in early modern Europe. The star fort forced attackers approaching the walls into the overlapping enfilade of the protruding bastions; attempts to achieve a similar effect through maneuver on the battlefield were limited by the weight and size of the artillery of the time. The earliest experiments in mobile artillery, such as the leather cannon, were generally flawed due to the limitations of the materials science of the period, but eventually gave rise to the regimental gun.
Perhaps the most famous example of crossfire tactics in early modern warfare occurred in the final stages of the First Battle of Breitenfeld. Swedish cavalry under Gustavus Adolphus outflanked and seized the artillery pieces of the Imperial army. As the battle had progressed, the Imperial guns were now well-positioned to fire upon the bulk of the Imperial army, and the crossfire of Swedish and captured cannon shattered the Imperial forces.
## Trench warfare {#trench_warfare}
The tactic of using overlapping arcs of fire came to prominence during World War I where it was a feature of trench warfare. Machine guns were placed in groups, called machine-gun nests, and they protected the front of the trenches. Many people died in futile attempts to charge across the no man\'s land where these crossfires were set up. After these attacks many bodies could be found in the no man\'s land.
## \"Caught in the crossfire\" {#caught_in_the_crossfire}
To be \"caught in the crossfire\" is an expression that often refers to unintended casualties (bystanders, etc.) who were killed or wounded by being exposed to the gunfire of a battle or gun fight, such as in a position to be hit by bullets of either side. The phrase has come to mean any injury, damage or harm (physical or otherwise) caused to a third party due to the action of belligerents (collateral damage)
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# Cavitation
thumb\|upright=1\|right\|Cavitating propeller model in a water tunnel experiment thumb\|upright=1\|Cavitation damage on a valve plate for an axial piston hydraulic pump thumb\|upright=1\|This video shows cavitation in a gear pump right\|thumb\|upright=1\|Cavitation damage evident on the propeller of a personal watercraft
**Cavitation** in fluid mechanics and engineering normally is the phenomenon in which the static pressure of a liquid reduces to below the liquid\'s vapor pressure, leading to the formation of small vapor-filled cavities in the liquid. When subjected to higher pressure, these cavities, called \"bubbles\" or \"voids\", collapse and can generate shock waves that may damage machinery. These shock waves are strong when they are very close to the imploded bubble, but rapidly weaken as they propagate away from the implosion. Cavitation is a significant cause of wear in some engineering contexts. Collapsing voids that implode near to a metal surface cause cyclic stress through repeated implosion. This results in surface fatigue of the metal, causing a type of wear also called \"cavitation\". The most common examples of this kind of wear are to pump impellers, and bends where a sudden change in the direction of liquid occurs.
Cavitation is usually divided into two classes of behavior. *Inertial (or transient) cavitation* is the process in which a void or bubble in a liquid rapidly collapses, producing a shock wave. It occurs in nature in the strikes of mantis shrimp and pistol shrimp, as well as in the vascular tissues of plants. In manufactured objects, it can occur in control valves, pumps, propellers and impellers. *Non-inertial cavitation* is the process in which a bubble in a fluid is forced to oscillate in size or shape due to some form of energy input, such as an acoustic field. The gas in the bubble may contain a portion of a different gas than the vapor phase of the liquid. Such cavitation is often employed in ultrasonic cleaning baths and can also be observed in pumps, propellers, etc.
Since the shock waves formed by collapse of the voids are strong enough to cause significant damage to parts, cavitation is typically an undesirable phenomenon in machinery. It may be desirable if intentionally used, for example, to sterilize contaminated surgical instruments, break down pollutants in water purification systems, emulsify tissue for cataract surgery or kidney stone lithotripsy, or homogenize fluids. It is very often specifically prevented in the design of machines such as turbines or propellers, and eliminating cavitation is a major field in the study of fluid dynamics. However, it is sometimes useful and does not cause damage when the bubbles collapse away from machinery, such as in supercavitation.
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# Cavitation
## Physics
### Inertial cavitation {#inertial_cavitation}
Inertial cavitation was first observed in the late 19th century, considering the collapse of a spherical void within a liquid. When a volume of liquid is subjected to a sufficiently low pressure, it may rupture and form a cavity. This phenomenon is coined *cavitation inception* and may occur behind the blade of a rapidly rotating propeller or on any surface vibrating in the liquid with sufficient amplitude and acceleration. A fast-flowing river can cause cavitation on rock surfaces, particularly when there is a drop-off, such as on a waterfall.
Vapor gases evaporate into the cavity from the surrounding medium; thus, the cavity is not a vacuum at all, but rather a low-pressure vapor (gas) bubble. Once the conditions which caused the bubble to form are no longer present, such as when the bubble moves downstream, the surrounding liquid begins to implode due its higher pressure, building up momentum as it moves inward. As the bubble finally collapses, the inward momentum of the surrounding liquid causes a sharp increase of pressure and temperature of the vapor within. The bubble eventually collapses to a minute fraction of its original size, at which point the gas within dissipates into the surrounding liquid via a rather violent mechanism which releases a significant amount of energy in the form of an acoustic shock wave and as visible light. At the point of total collapse, the temperature of the vapor within the bubble may be several thousand Kelvin, and the pressure several hundred atmospheres.
The physical process of cavitation inception is similar to boiling. The major difference between the two is the thermodynamic paths that precede the formation of the vapor. Boiling occurs when the local temperature of the liquid reaches the saturation temperature, and further heat is supplied to allow the liquid to sufficiently phase change into a gas. Cavitation inception occurs when the local pressure falls sufficiently far below the saturated vapor pressure, a value given by the tensile strength of the liquid at a certain temperature.
In order for cavitation inception to occur, the cavitation \"bubbles\" generally need a surface on which they can nucleate. This surface can be provided by the sides of a container, by impurities in the liquid, or by small undissolved microbubbles within the liquid. It is generally accepted that hydrophobic surfaces stabilize small bubbles. These pre-existing bubbles start to grow unbounded when they are exposed to a pressure below the threshold pressure, termed Blake\'s threshold. The presence of an incompressible core inside a cavitation nucleus substantially lowers the cavitation threshold below the Blake threshold.
The vapor pressure here differs from the meteorological definition of vapor pressure, which describes the partial pressure of water in the atmosphere at some value less than 100% saturation. Vapor pressure as relating to cavitation refers to the vapor pressure in equilibrium conditions and can therefore be more accurately defined as the equilibrium (or saturated) vapor pressure.
Non-inertial cavitation is the process in which small bubbles in a liquid are forced to oscillate in the presence of an acoustic field, when the intensity of the acoustic field is insufficient to cause total bubble collapse. This form of cavitation causes significantly less erosion than inertial cavitation, and is often used for the cleaning of delicate materials, such as silicon wafers.
Other ways of generating cavitation voids involve the local deposition of energy, such as an intense focused laser pulse (optic cavitation) or with an electrical discharge through a spark. These techniques have been used to study the evolution of the bubble that is actually created by locally boiling the liquid with a local increment of temperature.
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# Cavitation
## Physics
### Hydrodynamic cavitation {#hydrodynamic_cavitation}
Hydrodynamic cavitation is the process of vaporisation, bubble generation and bubble implosion which occurs in a flowing liquid as a result of a decrease and subsequent increase in local pressure. Cavitation will only occur if the local pressure declines to some point below the saturated vapor pressure of the liquid and subsequent recovery above the vapor pressure. If the recovery pressure is not above the vapor pressure then flashing is said to have occurred. In pipe systems, cavitation typically occurs either as the result of an increase in the kinetic energy (through an area constriction) or an increase in the pipe elevation.
Hydrodynamic cavitation can be produced by passing a liquid through a constricted channel at a specific flow velocity or by mechanical rotation of an object through a liquid. In the case of the constricted channel and based on the specific (or unique) geometry of the system, the combination of pressure and kinetic energy can create the hydrodynamic cavitation cavern downstream of the local constriction generating high energy cavitation bubbles.
Based on the thermodynamic phase change diagram, an increase in temperature could initiate a known phase change mechanism known as boiling. However, a decrease in static pressure could also help one pass the multi-phase diagram and initiate another phase change mechanism known as cavitation. On the other hand, a local increase in flow velocity could lead to a static pressure drop to the critical point at which cavitation could be initiated (based on Bernoulli\'s principle). The critical pressure point is vapor saturated pressure. In a closed fluidic system where no flow leakage is detected, a decrease in cross-sectional area would lead to velocity increment and hence static pressure drop. This is the working principle of many hydrodynamic cavitation based reactors for different applications such as water treatment, energy harvesting, heat transfer enhancement, food processing, etc.
There are different flow patterns detected as a cavitation flow progresses: inception, developed flow, supercavitation, and choked flow. Inception is the first moment that the second phase (gas phase) appears in the system. This is the weakest cavitating flow captured in a system corresponding to the highest cavitation number. When the cavities grow and becomes larger in size in the orifice or venturi structures, developed flow is recorded. The most intense cavitating flow is known as supercavitation where theoretically all the nozzle area of an orifice is filled with gas bubbles. This flow regime corresponds to the lowest cavitation number in a system. After supercavitation, the system is not capable of passing more flow. Hence, velocity does not change while the upstream pressure increase. This would lead to an increase in cavitation number which shows that choked flow occurred.
The process of bubble generation, and the subsequent growth and collapse of the cavitation bubbles, results in very high energy densities and in very high local temperatures and local pressures at the surface of the bubbles for a very short time. The overall liquid medium environment, therefore, remains at ambient conditions. When uncontrolled, cavitation is damaging; by controlling the flow of the cavitation, however, the power can be harnessed and non-destructive. Controlled cavitation can be used to enhance chemical reactions or propagate certain unexpected reactions because free radicals are generated in the process due to disassociation of vapors trapped in the cavitating bubbles.
Orifices and venturi are reported to be widely used for generating cavitation. A venturi has an inherent advantage over an orifice because of its smooth converging and diverging sections, such that it can generate a higher flow velocity at the throat for a given pressure drop across it. On the other hand, an orifice has an advantage that it can accommodate a greater number of holes (larger perimeter of holes) in a given cross sectional area of the pipe.
The cavitation phenomenon can be controlled to enhance the performance of high-speed marine vessels and projectiles, as well as in material processing technologies, in medicine, etc. Controlling the cavitating flows in liquids can be achieved only by advancing the mathematical foundation of the cavitation processes. These processes are manifested in different ways, the most common ones and promising for control being bubble cavitation and supercavitation. The first exact classical solution should perhaps be credited to the well-known solution by Hermann von Helmholtz in 1868. The earliest distinguished studies of academic type on the theory of a cavitating flow with free boundaries and supercavitation were published in the book *Jets, wakes and cavities* followed by *Theory of jets of ideal fluid*. Widely used in these books was the well-developed theory of conformal mappings of functions of a complex variable, allowing one to derive a large number of exact solutions of plane problems. Another venue combining the existing exact solutions with approximated and heuristic models was explored in the work *Hydrodynamics of Flows with Free Boundaries* that refined the applied calculation techniques based on the principle of cavity expansion independence, theory of pulsations and stability of elongated axisymmetric cavities, etc. and in *Dimensionality and similarity methods in the problems of the hydromechanics of vessels*.
A natural continuation of these studies was recently presented in *The Hydrodynamics of Cavitating Flows* -- an encyclopedic work encompassing all the best advances in this domain for the last three decades, and blending the classical methods of mathematical research with the modern capabilities of computer technologies. These include elaboration of nonlinear numerical methods of solving 3D cavitation problems, refinement of the known plane linear theories, development of asymptotic theories of axisymmetric and nearly axisymmetric flows, etc. As compared to the classical approaches, the new trend is characterized by expansion of the theory into the 3D flows. It also reflects a certain correlation with current works of an applied character on the hydrodynamics of supercavitating bodies.
Hydrodynamic cavitation can also improve some industrial processes. For instance, cavitated corn slurry shows higher yields in ethanol production compared to uncavitated corn slurry in dry milling facilities.
This is also used in the mineralization of bio-refractory compounds which otherwise would need extremely high temperature and pressure conditions since free radicals are generated in the process due to the dissociation of vapors trapped in the cavitating bubbles, which results in either the intensification of the chemical reaction or may even result in the propagation of certain reactions not possible under otherwise ambient conditions.
### Acoustic cavitation and ultrasonic cavitation {#acoustic_cavitation_and_ultrasonic_cavitation}
Inertial cavitation can also occur in the presence of an acoustic field. Microscopic gas bubbles that are generally present in a liquid will be forced to oscillate due to an applied acoustic field. If the acoustic intensity is sufficiently high, the bubbles will first grow in size and then rapidly collapse. Hence, inertial cavitation can occur even if the rarefaction in the liquid is insufficient for a Rayleigh-like void to occur.
Ultrasonic cavitation inception will occur when the acceleration of the ultrasound source is enough to produce the needed pressure drop. This pressure drop depends on the value of the acceleration and the size of the affected volume by the pressure wave. The dimensionless number that predicts ultrasonic cavitation is the Garcia-Atance number. High power ultrasonic horns produce accelerations high enough to create a cavitating region that can be used for homogenization, dispersion, deagglomeration, erosion, cleaning, milling, emulsification, extraction, disintegration, and sonochemistry.
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# Cavitation
## Physics
### Aerodyamic cavitation {#aerodyamic_cavitation}
Although predominant in liquids, cavitation exists to an extent in gas as it has fluid dynamics at high speeds. For example, a bullet with a flat tip moves faster underwater as it creates cavitation compared to a bullet with a sharp tip. A dune shape is very useful for managing aerodynamic cavitation. The shape of a dune provides minimal resistance to the wind. With small dunes installed on the surfaces of aircraft and other high speed vehicles, friction against the air decreases by several times. The dune surface pushes the air upwards, underneath and behind areas where the air pressure drops, reducing friction. The dune may increase frontal resistance, but that will be compensated for by a decrease in the total friction area, as also happens with an underwater bullet. As a result, the speed of the aircraft or vehicle will increase significantly.
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# Cavitation
## Applications
### Chemical engineering {#chemical_engineering}
In industry, cavitation is often used to homogenize, or mix and break down, suspended particles in a colloidal liquid compound such as paint mixtures or milk. Many industrial mixing machines are based upon this design principle. It is usually achieved through impeller design or by forcing the mixture through an annular opening that has a narrow entrance orifice with a much larger exit orifice. In the latter case, the drastic decrease in pressure as the liquid accelerates into a larger volume induces cavitation. This method can be controlled with hydraulic devices that control inlet orifice size, allowing for dynamic adjustment during the process, or modification for different substances. The surface of this type of mixing valve, against which surface the cavitation bubbles are driven causing their implosion, undergoes tremendous mechanical and thermal localized stress; they are therefore often constructed of extremely strong and hard materials such as stainless steel, Stellite, or even polycrystalline diamond (PCD).
Cavitating water purification devices have also been designed, in which the extreme conditions of cavitation can break down pollutants and organic molecules. Spectral analysis of light emitted in sonochemical reactions reveal chemical and plasma-based mechanisms of energy transfer. The light emitted from cavitation bubbles is termed sonoluminescence.
Use of this technology has been tried successfully in alkali refining of vegetable oils.
Hydrophobic chemicals are attracted underwater by cavitation as the pressure difference between the bubbles and the liquid water forces them to join. This effect may assist in protein folding.
### Biomedical
Cavitation plays an important role for the destruction of kidney stones in shock wave lithotripsy. Currently, tests are being conducted as to whether cavitation can be used to transfer large molecules into biological cells (sonoporation). Nitrogen cavitation is a method used in research to lyse cell membranes while leaving organelles intact.
Cavitation plays a key role in non-thermal, non-invasive fractionation of tissue for treatment of a variety of diseases and can be used to open the blood-brain barrier to increase uptake of neurological drugs in the brain.
Cavitation also plays a role in HIFU, a thermal non-invasive treatment methodology for cancer.
In wounds caused by high velocity impacts (like for example bullet wounds) there are also effects due to cavitation. The exact wounding mechanisms are not completely understood yet as there is temporary cavitation, and permanent cavitation together with crushing, tearing and stretching. Also the high variance in density within the body makes it hard to determine its effects.
Ultrasound sometimes is used to increase bone formation, for instance in post-surgical applications.
It has been suggested that the sound of \"cracking\" knuckles derives from the collapse of cavitation in the synovial fluid within the joint.
Cavitation can also form Ozone micro-nanobubbles which shows promise in dental applications.
### Cleaning
In industrial cleaning applications, cavitation has sufficient power to overcome the particle-to-substrate adhesion forces, loosening contaminants. The threshold pressure required to initiate cavitation is a strong function of the pulse width and the power input. This method works by generating acoustic cavitation in the cleaning fluid, picking up and carrying contaminant particles away in the hope that they do not reattach to the material being cleaned (which is a possibility when the object is immersed, for example in an ultrasonic cleaning bath). The same physical forces that remove contaminants also have the potential to damage the target being cleaned.
### Food and beverage {#food_and_beverage}
#### Eggs
Cavitation has been applied to egg pasteurization. A hole-filled rotor produces cavitation bubbles, heating the liquid from within. Equipment surfaces stay cooler than the passing liquid, so eggs do not harden as they did on the hot surfaces of older equipment. The intensity of cavitation can be adjusted, making it possible to tune the process for minimum protein damage.
#### Vegetable oil production {#vegetable_oil_production}
Cavitation has been applied to vegetable oil degumming and refining since 2011 and is considered a proven and standard technology in this application. The implementation of hydrodynamic cavitation in the degumming and refining process allows for a significant reduction in process aid, such as chemicals, water and bleaching clay, use.
### Biofuels
#### Biodiesel
Cavitation has been applied to Biodiesel production since 2011 and is considered a proven and standard technology in this application. The implementation of hydrodynamic cavitation in the transesterification process allows for a significant reduction in catalyst use, quality improvement and production capacity increase.
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# Cavitation
## Cavitation damage`{{anchor|Cavitation erosion}}`{=mediawiki} {#cavitation_damage}
thumb\|right\|upright=1.05\|Cavitation damage to a Francis turbine
Cavitation is usually an undesirable occurrence. In devices such as propellers and pumps, cavitation causes a great deal of noise, damage to components, vibrations, and a loss of efficiency. Noise caused by cavitation can be particularly undesirable in naval vessels where such noise may render them more easily detectable by passive sonar. Cavitation has also become a concern in the renewable energy sector as it may occur on the blade surface of tidal stream turbines.
When the cavitation bubbles collapse, they force energetic liquid into very small volumes, thereby creating spots of high temperature and emitting shock waves, the latter of which are a source of noise. The noise created by cavitation is a particular problem for military submarines, as it increases the chances of being detected by passive sonar.
Although the collapse of a small cavity is a relatively low-energy event, highly localized collapses can erode metals, such as steel, over time. The pitting caused by the collapse of cavities produces great wear on components and can dramatically shorten a propeller\'s or pump\'s lifetime.
After a surface is initially affected by cavitation, it tends to erode at an accelerating pace. The cavitation pits increase the turbulence of the fluid flow and create crevices that act as nucleation sites for additional cavitation bubbles. The pits also increase the components\' surface area and leave behind residual stresses. This makes the surface more prone to stress corrosion.
### Pumps and propellers {#pumps_and_propellers}
Major places where cavitation occurs are in pumps, on propellers, or at restrictions in a flowing liquid.
As an impeller\'s (in a pump) or propeller\'s (as in the case of a ship or submarine) blades move through a fluid, low-pressure areas are formed as the fluid accelerates around and moves past the blades. The faster the blade moves, the lower the pressure can become around it. As it reaches vapor pressure, the fluid vaporizes and forms small bubbles of gas. This is cavitation. When the bubbles collapse later, they typically cause very strong local shock waves in the fluid, which may be audible and may even damage the blades.
Cavitation in pumps may occur in two different forms: suction cavitation and discharge cavitation.
#### Suction cavitation {#suction_cavitation}
Suction cavitation occurs when the pump suction is under a low-pressure/high-vacuum condition where the liquid turns into a vapor at the eye of the pump impeller. This vapor is carried over to the discharge side of the pump, where it no longer sees vacuum and is compressed back into a liquid by the discharge pressure. This imploding action occurs violently and attacks the face of the impeller. An impeller that has been operating under a suction cavitation condition can have large chunks of material removed from its face or very small bits of material removed, causing the impeller to look spongelike. Both cases will cause premature failure of the pump, often due to bearing failure. Suction cavitation is often identified by a sound like gravel or marbles in the pump casing.
Common causes of suction cavitation can include clogged filters, pipe blockage on the suction side, poor piping design, pump running too far right on the pump curve, or conditions not meeting NPSH (net positive suction head) requirements.
In automotive applications, a clogged filter in a hydraulic system (power steering, power brakes) can cause suction cavitation making a noise that rises and falls in synch with engine RPM. It is fairly often a high pitched whine, like set of nylon gears not quite meshing correctly.
#### Discharge cavitation {#discharge_cavitation}
Discharge cavitation occurs when the pump discharge pressure is extremely high, normally occurring in a pump that is running at less than 10% of its best efficiency point. The high discharge pressure causes the majority of the fluid to circulate inside the pump instead of being allowed to flow out the discharge. As the liquid flows around the impeller, it must pass through the small clearance between the impeller and the pump housing at extremely high flow velocity. This flow velocity causes a vacuum to develop at the housing wall (similar to what occurs in a venturi), which turns the liquid into a vapor. A pump that has been operating under these conditions shows premature wear of the impeller vane tips and the pump housing. In addition, due to the high pressure conditions, premature failure of the pump\'s mechanical seal and bearings can be expected. Under extreme conditions, this can break the impeller shaft.
Discharge cavitation in joint fluid is thought to cause the popping sound produced by bone joint cracking, for example by deliberately cracking one\'s knuckles.
#### Cavitation solutions {#cavitation_solutions}
Since all pumps require well-developed inlet flow to meet their potential, a pump may not perform or be as reliable as expected due to a faulty suction piping layout such as a close-coupled elbow on the inlet flange. When poorly developed flow enters the pump impeller, it strikes the vanes and is unable to follow the impeller passage. The liquid then separates from the vanes causing mechanical problems due to cavitation, vibration and performance problems due to turbulence and poor filling of the impeller. This results in premature seal, bearing and impeller failure, high maintenance costs, high power consumption, and less-than-specified head and/or flow.
To have a well-developed flow pattern, pump manufacturer\'s manuals recommend about (10 diameters?) of straight pipe run upstream of the pump inlet flange. Unfortunately, piping designers and plant personnel must contend with space and equipment layout constraints and usually cannot comply with this recommendation. Instead, it is common to use an elbow close-coupled to the pump suction which creates a poorly developed flow pattern at the pump suction.
With a double-suction pump tied to a close-coupled elbow, flow distribution to the impeller is poor and causes reliability and performance shortfalls. The elbow divides the flow unevenly with more channeled to the outside of the elbow. Consequently, one side of the double-suction impeller receives more flow at a higher flow velocity and pressure while the starved side receives a highly turbulent and potentially damaging flow. This degrades overall pump performance (delivered head, flow and power consumption) and causes axial imbalance which shortens seal, bearing and impeller life. To overcome cavitation: Increase suction pressure if possible. Decrease liquid temperature if possible. Throttle back on the discharge valve to decrease flow-rate. Vent gases off the pump casing.
### Control valves {#control_valves}
Cavitation can occur in control valves. If the actual pressure drop across the valve as defined by the upstream and downstream pressures in the system is greater than the sizing calculations allow, pressure drop flashing or cavitation may occur. The change from a liquid state to a vapor state results from the increase in flow velocity at or just downstream of the greatest flow restriction which is normally the valve port. To maintain a steady flow of liquid through a valve the flow velocity must be greatest at the vena contracta or the point where the cross sectional area is the smallest. This increase in flow velocity is accompanied by a substantial decrease in the fluid pressure which is partially recovered downstream as the area increases and flow velocity decreases. This pressure recovery is never completely to the level of the upstream pressure. If the pressure at the vena contracta drops below the vapor pressure of the fluid bubbles will form in the flow stream. If the pressure recovers after the valve to a pressure that is once again above the vapor pressure, then the vapor bubbles will collapse and cavitation will occur.
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# Cavitation
## Cavitation damage`{{anchor|Cavitation erosion}}`{=mediawiki} {#cavitation_damage}
### Spillways
When water flows over a dam spillway, the irregularities on the spillway surface will cause small areas of flow separation in a high-speed flow, and, in these regions, the pressure will be lowered. If the flow velocities are high enough the pressure may fall to below the local vapor pressure of the water and vapor bubbles will form. When these are carried downstream into a high pressure region the bubbles collapse giving rise to high pressures and possible cavitation damage.
Experimental investigations show that the damage on concrete chute and tunnel spillways can start at clear water flow velocities of between 12 and, and, up to flow velocities of 20 m/s, it may be possible to protect the surface by streamlining the boundaries, improving the surface finishes or using resistant materials.
When some air is present in the water the resulting mixture is compressible and this damps the high pressure caused by the bubble collapses. If the flow velocities near the spillway invert are sufficiently high, aerators (or aeration devices) must be introduced to prevent cavitation. Although these have been installed for some years, the mechanisms of air entrainment at the aerators and the slow movement of the air away from the spillway surface are still challenging.
The spillway aeration device design is based upon a small deflection of the spillway bed (or sidewall) such as a ramp and offset to deflect the high flow velocity flow away from the spillway surface. In the cavity formed below the nappe, a local subpressure beneath the nappe is produced by which air is sucked into the flow. The complete design includes the deflection device (ramp, offset) and the air supply system.
### Engines
Some larger diesel engines suffer from cavitation due to high compression and undersized cylinder walls. Vibrations of the cylinder wall induce alternating low and high pressure in the coolant against the cylinder wall. The result is pitting of the cylinder wall, which will eventually let cooling fluid leak into the cylinder and combustion gases to leak into the coolant.
It is possible to prevent this from happening with the use of chemical additives in the cooling fluid that form a protective layer on the cylinder wall. This layer will be exposed to the same cavitation, but rebuilds itself. Additionally a regulated overpressure in the cooling system (regulated and maintained by the coolant filler cap spring pressure) prevents the forming of cavitation.
From about the 1980s, new designs of smaller gasoline engines also displayed cavitation phenomena. One answer to the need for smaller and lighter engines was a smaller coolant volume and a correspondingly higher coolant flow velocity. This gave rise to rapid changes in flow velocity and therefore rapid changes of static pressure in areas of high heat transfer. Where resulting vapor bubbles collapsed against a surface, they had the effect of first disrupting protective oxide layers (of cast aluminium materials) and then repeatedly damaging the newly formed surface, preventing the action of some types of corrosion inhibitor (such as silicate based inhibitors). A final problem was the effect that increased material temperature had on the relative electrochemical reactivity of the base metal and its alloying constituents. The result was deep pits that could form and penetrate the engine head in a matter of hours when the engine was running at high load and high speed. These effects could largely be avoided by the use of organic corrosion inhibitors or (preferably) by designing the engine head in such a way as to avoid certain cavitation inducing conditions.
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# Cavitation
## In nature {#in_nature}
### Geology
Some hypotheses`{{by whom|date=December 2019}}`{=mediawiki}`{{example needed|date=December 2019}}`{=mediawiki} relating to diamond formation posit a possible role for cavitation---namely cavitation in the kimberlite pipes providing the extreme pressure needed to change pure carbon into the rare allotrope that is diamond. The loudest three sounds ever recorded, during the 1883 eruption of Krakatoa, are now`{{when|date=December 2019}}`{=mediawiki} understood as the bursts of three huge cavitation bubbles, each larger than the last, formed in the volcano\'s throat. Rising magma, filled with dissolved gasses and under immense pressure, encountered a different magma that compressed easily, allowing bubbles to grow and combine.
### Vascular plants {#vascular_plants}
Cavitation can occur in the xylem of vascular plants. The sap vaporizes locally so that either the vessel elements or tracheids are filled with water vapor. Plants are able to repair cavitated xylem in a number of ways. For plants less than 50 cm tall, root pressure can be sufficient to redissolve the vapor. Larger plants direct solutes into the xylem via *ray cells*, or in tracheids, via osmosis through bordered pits. Solutes attract water, the pressure rises and vapor can redissolve. In some trees, the sound of the cavitation is audible, particularly in summer, when the rate of evapotranspiration is highest. Some deciduous trees have to shed leaves in the autumn partly because cavitation increases as temperatures decrease.
### Spore dispersal in plants {#spore_dispersal_in_plants}
Cavitation plays a role in the spore dispersal mechanisms of certain plants. In ferns, for example, the fern sporangium acts as a catapult that launches spores into the air. The charging phase of the catapult is driven by water evaporation from the annulus cells, which triggers a pressure decrease. When the compressive pressure reaches approximately 9 MPa, cavitation occurs. This rapid event triggers spore dispersal due to the elastic energy released by the annulus structure. The initial spore acceleration is extremely large -- up to 10`{{sup|5}}`{=mediawiki} times the gravitational acceleration.
### Marine life {#marine_life}
Just as cavitation bubbles form on a fast-spinning boat propeller, they may also form on the tails and fins of aquatic animals. This primarily occurs near the surface of the ocean, where the ambient water pressure is low.
Cavitation may limit the maximum swimming speed of powerful swimming animals like dolphins and tuna. Dolphins may have to restrict their speed because collapsing cavitation bubbles on their tail are painful. Tuna have bony fins without nerve endings and do not feel pain from cavitation. They are slowed down when cavitation bubbles create a vapor film around their fins. Lesions have been found on tuna that are consistent with cavitation damage.
Some sea animals have found ways to use cavitation to their advantage when hunting prey. The pistol shrimp snaps a specialized claw to create cavitation, which can kill small fish. The mantis shrimp (of the *smasher* variety) uses cavitation as well in order to stun, smash open, or kill the shellfish that it feasts upon.
Thresher sharks use \'tail slaps\' to debilitate their small fish prey and cavitation bubbles have been seen rising from the apex of the tail arc.
### Coastal erosion {#coastal_erosion}
In the last half-decade,`{{when|date=December 2019}}`{=mediawiki} coastal erosion in the form of inertial cavitation has been generally accepted. Bubbles in an incoming wave are forced into cracks in the cliff being eroded. Varying pressure decompresses some vapor pockets which subsequently implode. The resulting pressure peaks can blast apart fractions of the rock.
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# Cavitation
## History
As early as 1754, the Swiss mathematician Leonhard Euler (1707--1783) speculated about the possibility of cavitation. In 1859, the English mathematician William Henry Besant (1828--1917) published a solution to the problem of the dynamics of the collapse of a spherical cavity in a fluid, which had been presented by the Anglo-Irish mathematician George Stokes (1819--1903) as one of the Cambridge \[University\] Senate-house problems and riders for the year 1847. In 1894, Irish fluid dynamicist Osborne Reynolds (1842--1912) studied the formation and collapse of vapor bubbles in boiling liquids and in constricted tubes.See:
-
-
The term *cavitation* first appeared in 1895 in a paper by John Isaac Thornycroft (1843--1928) and Sydney Walker Barnaby (1855--1925)---son of Sir Nathaniel Barnaby (1829 -- 1915), who had been Chief Constructor of the Royal Navy---to whom it had been suggested by the British engineer Robert Edmund Froude (1846--1924), third son of the English hydrodynamicist William Froude (1810--1879). Early experimental studies of cavitation were conducted in 1894--5 by Thornycroft and Barnaby and by the Anglo-Irish engineer Charles Algernon Parsons (1854--1931), who constructed a stroboscopic apparatus to study the phenomenon.See:
- Parsons, Charles A. (1934) \"Motive power --- high-speed navigation steam turbines \[address to the Royal Institution of Great Britain, delivered on 26 January 1900\]\". Parsons, G.L. (ed.). *Scientific Papers and Addresses of the Hon. Sir Charles A. Parsons*. Cambridge England: Cambridge University Press. pp. 26--35.
-
-
- Thornycroft and Barnaby were the first researchers to observe cavitation on the back sides of propeller blades.
In 1917, the British physicist Lord Rayleigh (1842--1919) extended Besant\'s work, publishing a mathematical model of cavitation in an incompressible fluid (ignoring surface tension and viscosity), in which he also determined the pressure in the fluid. The mathematical models of cavitation which were developed by British engineer Stanley Smith Cook (1875--1952) and by Lord Rayleigh revealed that collapsing bubbles of vapor could generate very high pressures, which were capable of causing the damage that had been observed on ships\' propellers.Stanley Smith Cook (1875--1952) was a designer of steam turbines. During the First World War, Cook was a member of a six-member committee that had been organized by the Royal Navy to investigate the deterioration (\"erosion\") of ship propellers. The erosion was attributed primarily to cavitation. See:
- \"Erosion of propellers.\" Propeller Sub-Committee (Section III). Report of the Board of Invention and Research (September 17, 1917) London, England.
-
-
- ; see pp. 123--124.
Experimental evidence of cavitation causing such high pressures was initially collected in 1952 by Mark Harrison (a fluid dynamicist and acoustician at the U.S. Navy\'s David Taylor Model Basin at Carderock, Maryland, USA) who used acoustic methods and in 1956 by Wernfried Güth (a physicist and acoustician of Göttigen University, Germany) who used optical Schlieren photography.
In 1944, Soviet scientists Mark Iosifovich Kornfeld (1908--1993) and L. Suvorov of the Leningrad Physico-Technical Institute (now: the Ioffe Physical-Technical Institute of the Russian Academy of Sciences, St. Petersburg, Russia) proposed that during cavitation, bubbles in the vicinity of a solid surface do not collapse symmetrically; instead, a dimple forms on the bubble at a point opposite the solid surface and this dimple evolves into a jet of liquid. This jet of liquid damages the solid surface. This hypothesis was supported in 1951 by theoretical studies by Maurice Rattray Jr., a doctoral student at the California Institute of Technology. Kornfeld and Suvorov\'s hypothesis was confirmed experimentally in 1961 by Charles F. Naudé and Albert T. Ellis, fluid dynamicists at the California Institute of Technology.
A series of experimental investigations of the propagation of strong shock wave (SW) in a liquid with gas bubbles, which made it possible to establish the basic laws governing the process, the mechanism for the transformation of the energy of the SW, attenuation of the SW, and the formation of the structure, and experiments on the analysis of the attenuation of waves in bubble screens with different acoustic properties were begun by pioneer works of Soviet scientist prof.V.F. Minin at the Institute of Hydrodynamics (Novosibirsk, Russia) in 1957--1960, who examined also the first convenient model of a screen - a sequence of alternating flat one-dimensional liquid and gas layers. In an experimental investigations of the dynamics of the form of pulsating gaseous cavities and interaction of SW with bubble clouds in 1957--1960 V.F. Minin discovered that under the action of SW a bubble collapses asymmetrically with the formation of a cumulative jet, which forms in the process of collapse and causes fragmentation of the bubble
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# Cyprinodontiformes
**Cyprinodontiformes** `{{IPAc-en|ˌ|s|ɪ|p|r|ᵻ|n|oʊ-|ˈ|d|ɒ|n|t|ᵻ|f|ɔːr|m|iː|z}}`{=mediawiki} is an order of ray-finned fish, comprising mostly small, freshwater fish. Many popular aquarium fish, such as killifish and live-bearers, are included. They are closely related to the Atheriniformes and are occasionally included with them. A colloquial term for the order as a whole is **toothcarps**, though they are not actually close relatives of the true carps -- the latter belong to the superorder Ostariophysi, while the toothcarps are Acanthopterygii.
The families of Cyprinodontiformes can be informally divided into three groups based on reproductive strategy: viviparous and ovoviviparous (all species give live birth), and oviparous (all species are egg-laying). The live-bearing groups differ in whether the young are carried to term within (ovoviviparous) or without (viviparous) an enclosing eggshell. Phylogenetically however, one of the two suborders -- the Aplocheiloidei -- contains oviparous species exclusively, as do two of the four superfamilies of the other suborder (the Cyprinodontoidea and Valencioidea of the Cyprinodontoidei). Vivipary and ovovivipary have evolved independently from oviparous ancestors, the latter possibly twice.
The oldest fossil record of the group is the extinct ?*Cyprinodon primulus*, a *nomen vanum* known from isolated fossil scales from the Late Paleocene of Argentina. Its exact taxonomic identity is uncertain, although it is generally considered to at least be a true cyprinodontiform.
## Description
Some members of this order are notable for inhabiting extreme environments, such as saline or very warm waters, heavily polluted waters, rain water pools devoid of minerals and made acidic by decaying vegetation, or isolated situations where no other types of fish occur.
They are typically carnivores, and often live near the surface, where the oxygen-rich water compensates for environmental disadvantages. Scheel (1968) observed the gut contents were invariably ants, others have reported insects, worms and aquatic crustaceans. Aquarium specimens are invariably seen eating protozoans from the water column and the surfaces of leaves, however these are not apparent as stomach contents. Many members of the family Cyprinodontidae (the pupfishes) eat plant material as well and some have adapted to a diet very high in algae to the point where one, the Flagfish also known as American flagfish, is a renowned algae eater in the aquarium, in spite of belonging to an order of fishes that do not generally consume any plant material. In addition, killifish derive some of the carotenoids and other chemicals required to make their body pigments from pollen grains on the surface of and in the gut of insects they eat from the surface of the water; this can be simulated in culture by the use of special color enhancing foods that contain these compounds.
Although the Cyprinodontiformes are a diverse group, most species contained within are small to medium-sized fish, with small mouths, large eyes, a single dorsal fin, and a rounded caudal fin. The largest species is the *cuatro ojos* (*Anableps dowei*), which measures 34 cm in length, while the smallest, the least killifish (*Heterandria formosa*), is just 8 mm long as an adult.
## Systematics
Based on *Eschmeyer\'s Catalog of Fishes* (2025): **CYPRINODONTIFORMES**
- Suborder Aplocheiloidei (all oviparous)
- Family Aplocheilidae - Asian killifishes
- Family Nothobranchiidae - African killifishes
- Family †Kenyaichthyidae (Miocene of Kenya)
- Family Rivulidae - New World killifishes
- Suborder Cyprinodontoidei
- Family Pantanodontidae - spine killifishes (oviparous)
- Family Fundulidae - topminnows (oviparous)
- Family Cyprinodontidae - pupfishes (oviparous)
- Family Profundulidae - Middle American killifishes (oviparous)
- Family Goodeidae - splitfins or goodeids (largely viviparous)
- Family Fluviphylacidae - American lampeyes (oviparous)
- Family Anablepidae - four-eyed fish (largely ovoviviparous)
- Family Poecilidae - livebearers (viviparous)
- Family Aphaniidae - Oriental killifishes (oviparous)
- Family Valenciidae - Valencia toothcarps (oviparous)
- Family Procatopodidae - African lampeyes (oviparous)
The family Aplocheilidae has been expanded by some authorities to include all the killifishes with three subfamilies, Aplocheilinae, Cynolebiinae and Nothobranchiinae, but this is not the classification adopted in the 5th Edition of *Fishes of the World*
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# Click consonant
**Click consonants**, or **clicks**, are speech sounds that occur as consonants in many languages of Southern Africa and in three languages of East Africa. Examples familiar to English-speakers are the *tut-tut* (British spelling) or *tsk! tsk!* (American spelling) used to express disapproval or pity (IPA `{{IPA|[ǀ]}}`{=mediawiki}), the *tchick!* used to spur on a horse (IPA `{{IPA|[ǁ]}}`{=mediawiki}), and the *clip-clop!* sound children make with their tongue to imitate a horse trotting (IPA `{{IPA|[ǃ]}}`{=mediawiki}). However, these paralinguistic sounds in English are not full click consonants, as they only involve the front of the tongue, without the release of the back of the tongue that is required for clicks to combine with vowels and form syllables.
Anatomically, clicks are obstruents articulated with two closures (points of contact) in the mouth, one forward and one at the back. The enclosed pocket of air is rarefied by a sucking action of the tongue (in technical terminology, clicks have a lingual ingressive airstream mechanism). The forward closure is then released, producing what may be the loudest consonants in the language, although in some languages such as Hadza and Sandawe, clicks can be more subtle and may even be mistaken for ejectives.
## Phonetics and IPA notation {#phonetics_and_ipa_notation}
Click consonants occur at six principal places of articulation. The International Phonetic Alphabet (IPA) provides five letters for these places (there is as yet no dedicated symbol for the sixth).
- The easiest clicks for English speakers are the dental clicks written with `{{angbr IPA|ǀ}}`{=mediawiki}. These are sharp (high-pitched) squeaky sounds made by sucking on the front teeth. A simple dental click is used in English to express pity or to shame someone, or to call a cat or other animal, and is written *tut!* in British English and *tsk!* in American English. In many cultures around the Mediterranean a simple dental click is used for \"no\" in answer to a direct question. They are written with the letter *c* in Zulu and Xhosa.
- Next most familiar to English speakers are the lateral clicks, which are written with `{{angbr IPA|ǁ}}`{=mediawiki}. They are also squeaky sounds, though less sharp than `{{IPA|[ǀ]}}`{=mediawiki}, made by sucking on the molars on either side (or both sides) of the mouth. A simple lateral click is made in English to get a horse moving, and is conventionally written *tchick!*. They are written with the letter *x* in Zulu and Xhosa.
- Then there are the bilabial clicks, written with `{{angbr IPA|ʘ}}`{=mediawiki}. These are lip-smacking sounds, but often without the pursing of the lips found in a kiss, that occur in words in only a few languages.
The above clicks sound like affricates, in that they involve a lot of friction. The next two families of clicks are more abrupt sounds that do not have this friction.
- With the alveolar clicks, written with `{{angbr IPA|ǃ}}`{=mediawiki}, the tip of the tongue is pulled down abruptly and forcefully from the roof of the mouth, sometimes using a lot of jaw motion, and making a hollow *pop!* like a cork being pulled from an empty bottle. Something like these sounds may be used for a \'clip-clop\' sound as noted above. These sounds can be quite loud. They are written with the letter *q* in Zulu and Xhosa.
- The palatal clicks, `{{angbr IPA|ǂ}}`{=mediawiki}, are made with a flat tongue that is pulled backward rather than downward, and are sharper cracking sounds than the `{{IPA|[ǃ]}}`{=mediawiki} clicks, like sharply snapped fingers. They are not found in Zulu but are very common in the San languages of southern Africa.
- Finally, the retroflex clicks are poorly known, being attested from only a single language, Central !Kung. The tongue is curled back in the mouth, and they are both fricative and hollow sounding, but descriptions of these sounds vary between sources. This may reflect dialect differences. They are perhaps most commonly written `{{angbr IPA|‼}}`{=mediawiki}, but that is an *ad hoc* transcription. The expected IPA letter is `{{angbr IPA|𝼊}}`{=mediawiki} (`{{angbr IPA|ǃ}}`{=mediawiki} with retroflex tail), and the IPA supported the addition of that letter to Unicode.
Technically, these IPA letters transcribe only the forward articulation of the click, not the entire consonant. As the *Handbook* states, `{{blockquote|Since any click involves a velar or uvular closure [as well], it is possible to symbolize factors such as voicelessness, voicing or nasality of the click by combining the click symbol with the appropriate velar or uvular symbol: {{IPA|[k͡ǂ ɡ͡ǂ ŋ͡ǂ]}}, {{IPA|[q͡ǃ]}}.<ref>Instead of a tie bar, a superscript velar or uvular letter is sometimes seen: {{angbr IPA|ᵏǂ ᶢǂ ᵑǂ 𐞥ǂ}} etc.</ref>}}`{=mediawiki} Thus technically `{{IPA|[ǂ]}}`{=mediawiki} is not a consonant, but only one part of the articulation of a consonant, and one may speak of \"ǂ-clicks\" to mean any of the various click consonants that share the `{{IPA|[ǂ]}}`{=mediawiki} place of articulation. In practice, however, the simple letter `{{angbr IPA|ǂ}}`{=mediawiki} has long been used as an abbreviation for `{{IPA|[k͡ǂ]}}`{=mediawiki}, and in that role it is sometimes seen combined with diacritics for voicing (e.g. `{{angbr IPA|ǂ̬}}`{=mediawiki} for `{{IPA|[ɡ͡ǂ]}}`{=mediawiki}), nasalization (e.g. `{{angbr IPA|ǂ̃}}`{=mediawiki} for `{{IPA|[ŋ͡ǂ]}}`{=mediawiki}), etc. These differing transcription conventions may reflect differing theoretical analyses of the nature of click consonants, or attempts to address common misunderstandings of clicks.
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# Click consonant
## Languages with clicks {#languages_with_clicks}
### Southern Africa {#southern_africa}
Clicks occur in all three Khoisan language families of southern Africa, where they may be the most numerous consonants. To a lesser extent they occur in three neighbouring groups of Bantu languages---which borrowed them, directly or indirectly, from Khoisan. In the southeast, in eastern South Africa, Eswatini, Lesotho, Zimbabwe and southern Mozambique, they were adopted from a Tuu language (or languages) by the languages of the Nguni cluster (especially Zulu, Xhosa and Phuthi, but also to a lesser extent Swazi and Ndebele), and spread from them in a reduced fashion to the Zulu-based pidgin Fanagalo, Sesotho, Tsonga, Ronga, the Mzimba dialect of Tumbuka and more recently to Ndau and urban varieties of Pedi, where the spread of clicks continues. The second point of transfer was near the Caprivi Strip and the Okavango River where, apparently, the Yeyi language borrowed the clicks from a West Kalahari Khoe language; a separate development led to a smaller click inventory in the neighbouring Mbukushu, Kwangali, Gciriku, Kuhane and Fwe languages in Angola, Namibia, Botswana and Zambia. These sounds occur not only in borrowed vocabulary, but have spread to native Bantu words as well, in the case of Nguni at least partially due to a type of word taboo called hlonipha. Some creolised varieties of Afrikaans, such as Oorlams, retain clicks in Khoekhoe words.
### East Africa {#east_africa}
Three languages in East Africa use clicks: Sandawe and Hadza of Tanzania, and Dahalo, an endangered South Cushitic language of Kenya that has clicks in only a few dozen words. It is thought the latter may remain from an episode of language shift.
### Damin
The only non-African language known to have clicks as regular speech sounds is Damin, a ritual code once used by speakers of Lardil in Australia. In addition, one consonant in Damin is the egressive equivalent of a click, using the tongue to compress the air in the mouth for an outward (egressive) \"spurt\".
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# Click consonant
## Use
### Spread of clicks from loanwords {#spread_of_clicks_from_loanwords}
Once clicks are borrowed into a language as regular speech sounds, they may spread to native words, as has happened due to *hlonipa* word-taboo in the Nguni languages. In Gciriku, for example, the European loanword *tomate* (tomato) appears as *cumáte* with a click `{{IPA|[ǀ]}}`{=mediawiki}, though it begins with a *t* in all neighbouring languages. It has also been argued that click phonemes have been adopted into some languages through the process of *hlonipha*, women refraining from saying certain words and sounds that were similar to the name of their husband, sometimes replacing local sounds by borrowing clicks from a nearby language.
### Marginal usage of clicks {#marginal_usage_of_clicks}
Scattered clicks are found in ideophones and mimesis in other languages, such as Kongo `{{IPA|/ᵑǃ/}}`{=mediawiki}, Mijikenda `{{IPA|/ᵑǀ/}}`{=mediawiki} and Hadza `{{IPA|/ᵑʘʷ/}}`{=mediawiki} (Hadza does not otherwise have labial clicks). Ideophones often use phonemic distinctions not found in normal vocabulary.
English and many other languages may use bare click releases in interjections, without an accompanying rear release or transition into a vowel, such as the dental \"tsk-tsk\" sound used to express disapproval, or the lateral *tchick* used with horses. In a number of languages ranging from the central Mediterranean to Iran, a bare dental click release accompanied by tipping the head upwards signifies \"no\". Libyan Arabic apparently has three such sounds. A voiceless nasal back-released velar click `{{IPA|[ʞ]}}`{=mediawiki} is used throughout Africa for backchanneling. This sound starts off as a typical click, but the action is reversed and it is the rear velar or uvular closure that is released, drawing in air from the throat and nasal passages.
Lexical clicks occasionally turn up elsewhere. In West Africa, clicks have been reported allophonically, and similarly in French and German, faint clicks have been recorded in rapid speech where consonants such as `{{IPA|/t/}}`{=mediawiki} and `{{IPA|/k/}}`{=mediawiki} overlap between words. In Rwanda, the sequence `{{IPA|/mŋ/}}`{=mediawiki} may be pronounced either with an epenthetic vowel, `{{IPA|[mᵊ̃ŋ]}}`{=mediawiki}, or with a light bilabial click, `{{IPA|[m𐞵̃ŋ]}}`{=mediawiki}---often by the same speaker.
Speakers of Gan Chinese from Ningdu county, as well as speakers of Mandarin from Beijing and Jilin and presumably people from other parts of the country, produce flapped nasal clicks in nursery rhymes with varying degrees of competence, in the words for \'goose\' and \'duck\', both of which begin with `{{IPA|/ŋ/}}`{=mediawiki} in Gan and until recently began with `{{IPA|/ŋ/}}`{=mediawiki} in Mandarin as well. In Gan, the nursery rhyme is,
: 天上一隻鵝 \'a goose in the sky\'
: 地下一隻鴨 \'a duck on the ground\'
: 天上一隻鴨 \'a duck in the sky\'
: 地下一隻鵝 \'a goose on the ground\'
: 鵝生鵝蛋鵝孵鵝 \'a goose lays a goose egg, a goose hatches a goose\'
: 鴨生鴨蛋鴨孵鴨 \'a duck lays a duck egg, a duck hatches a duck\'
where the `{{IPA|/ŋ/}}`{=mediawiki} onsets are all pronounced `{{IPA|[ᵑǃ¡]}}`{=mediawiki}.
Occasionally other languages are claimed to have click sounds in general vocabulary. This is usually a misnomer for ejective consonants, which are found across much of the world.
### Position in word {#position_in_word}
For the most part, the Southern African Khoisan languages only use root-initial clicks. Hadza, Sandawe and several Bantu languages also allow syllable-initial clicks within roots. In no language does a click close a syllable or end a word, but since the languages of the world that happen to have clicks consist mostly of CV syllables and allow at most only a limited set of consonants (such as a nasal or a glottal stop) to close a syllable or end a word, *most* consonants share the distribution of clicks in these languages.
### Number of click-types in languages {#number_of_click_types_in_languages}
Most languages of the Khoesan families (Tuu, Kxʼa and Khoe) have four click types: `{{IPA|{ ǀ ǁ ǃ ǂ }}`{=mediawiki}} or variants thereof, though a few have three or five, the last supplemented with either bilabial `{{IPA|{ ʘ }}`{=mediawiki}} or retroflex `{{IPA|{ 𝼊 }}`{=mediawiki}}. Hadza and Sandawe in Tanzania have three, `{{IPA|{ ǀ ǁ ǃ }}`{=mediawiki}}. Yeyi is the only Bantu language with four, `{{IPA|{ ǀ ǁ ǃ ǂ }}`{=mediawiki}}, while Xhosa and Zulu have three, `{{IPA|{ ǀ ǁ ǃ }}`{=mediawiki}}, and most other Bantu languages with clicks have fewer.
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# Click consonant
## Types of clicks {#types_of_clicks}
Like other consonants, clicks can be described using four parameters: place of articulation, manner of articulation, phonation (including glottalisation) and airstream mechanism. As noted above, clicks necessarily involve at least two closures, which in some cases operate partially independently: an anterior articulation traditionally represented by the special click symbol in the IPA---and a posterior articulation traditionally transcribed for convenience as oral or nasal, voiced or voiceless, though such features actually apply to the entire consonant. The literature also describes a contrast between velar and uvular rear articulations for some languages.
In some languages that have been reported to make this distinction, such as Nǁng, all clicks have a uvular rear closure, and the clicks explicitly described as uvular are in fact cases where the uvular closure is independently audible: contours of a click into a pulmonic or ejective component, in which the click has two release bursts, the forward (click-type) and then the rearward (uvular) component. \"Velar\" clicks in these languages have only a single release burst, that of the forward release, and the release of the rear articulation isn\'t audible. However, in other languages all clicks are velar -- for example Hadza, or uvular -- for example Xhosa; and a few languages, such as Taa, have a true velar--uvular distinction that depends on the place rather than the timing of rear articulation and that is audible in the quality of the vowel.
Regardless, in most of the literature the stated place of the click is the anterior articulation (called the *release* or *influx),* whereas the manner is ascribed to the posterior articulation (called the *accompaniment* or *efflux).* The anterior articulation defines the *click type* and is written with the IPA letter for the click (dental `{{angbr IPA|ǀ}}`{=mediawiki}, alveolar `{{angbr IPA|ǃ}}`{=mediawiki}, etc.), whereas the traditional term \'accompaniment\' conflates the categories of manner (nasal, affricated), phonation (voiced, aspirated, breathy voiced, glottalised), as well as any change in the airstream with the release of the posterior articulation (pulmonic, ejective), all of which are transcribed with additional letters or diacritics, as in the *nasal alveolar click*, `{{angbr IPA|ǃŋ}}`{=mediawiki} or `{{angbr IPA|ᵑǃ}}`{=mediawiki} or---to take an extreme example---the *voiced (uvular) ejective alveolar click*, `{{angbr IPA|ᶢǃ͡qʼ}}`{=mediawiki}.
The size of click inventories ranges from as few as three (in Sesotho) or four (in Dahalo), to dozens in the Kxʼa and Tuu (Northern and Southern Khoisan) languages. Taa, the last vibrant language in the latter family, has 45 to 115 click phonemes, depending on analysis (clusters vs. contours), and over 70% of words in the dictionary of this language begin with a click.
Clicks appear more stop-like (sharp/abrupt) or affricate-like (noisy) depending on their place of articulation: In southern Africa, clicks involving an apical alveolar or laminal postalveolar closure are acoustically abrupt and sharp, like stops, whereas labial, dental and lateral clicks typically have longer and acoustically noisier click types that are superficially more like affricates. In East Africa, however, the alveolar clicks tend to be flapped, whereas the lateral clicks tend to be more sharp.
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# Click consonant
## Transcription
The six places of articulation of clicks that have dedicated letters in the International Phonetic Alphabet (IPA) are labial `{{angbr IPA|ʘ}}`{=mediawiki}, dental `{{angbr IPA|ǀ}}`{=mediawiki}, lateral `{{angbr IPA|ǁ}}`{=mediawiki}, palatal (\"palato-alveolar\") `{{angbr IPA|ǂ}}`{=mediawiki}, (post)alveolar (\"retroflex\") `{{angbr IPA|ǃ}}`{=mediawiki} and retroflex, with the \'implicit\' letter `{{angbr IPA|𝼊}}`{=mediawiki}. In most languages, the alveolar and palatal types involve an abrupt release; that is, they are sharp popping sounds with little frication (turbulent airflow). The labial, dental and lateral types, on the other hand, are typically noisy: they are longer, lip- or tooth-sucking sounds with turbulent airflow, and are sometimes called affricates. (This applies to the forward articulation; both may also have either an affricate or non-affricate rear articulation as well.) The apical places, `{{IPA|ǃ}}`{=mediawiki} and `{{IPA|ǁ}}`{=mediawiki}, are sometimes called \"grave\", because their pitch is dominated by low frequencies; whereas the laminal places, `{{IPA|ǀ}}`{=mediawiki} and `{{IPA|ǂ}}`{=mediawiki}, are sometimes called \"acute\", because they are dominated by high frequencies. (At least in the Nǁng language and Juǀʼhoan, this is associated with a difference in the placement of the rear articulation: \"grave\" clicks are uvular, whereas \"acute\" clicks are pharyngeal.) Thus the alveolar click `{{IPA|[kǃ]}}`{=mediawiki} sounds something like a cork pulled from a bottle (a low-pitch pop), at least in Xhosa; whereas the dental click `{{IPA|[kǀ]}}`{=mediawiki} is like English *tsk! tsk!,* a high-pitched sucking on the incisors. The lateral clicks are pronounced by sucking on the molars of one or both sides. The labial click `{{IPA|[kʘ]}}`{=mediawiki} is different from what many people associate with a kiss: the lips are pressed more-or-less flat together, as they are for a `{{IPA|[p]}}`{=mediawiki} or an `{{IPA|[m]}}`{=mediawiki}, not rounded as they are for a `{{IPA|[w]}}`{=mediawiki}.
The most populous languages with clicks, Zulu and Xhosa, use the letters *c, q, x,* by themselves and in digraphs, to write click consonants. Most Khoisan languages, on the other hand (with the notable exceptions of Naro and Sandawe), use a more iconic system based on the pipe `{{angbr|<nowiki>|</nowiki>}}`{=mediawiki}. (The exclamation point for the \"retroflex\" click was originally a pipe with a subscript dot, along the lines of *ṭ, ḍ, ṇ* used to transcribe the retroflex consonants of India.) There are also two main conventions for the second letter of the digraph as well: voicing may be written with *g* and uvular affrication with *x*, or voicing with *d* and affrication with *g* (a convention of Afrikaans). In two orthographies of Juǀʼhoan, for example, voiced `{{IPA|/ᶢǃ/}}`{=mediawiki} is written *g!* or *dq*, and `{{IPA|/ᵏǃ͡χ/}}`{=mediawiki} *!x* or *qg*. In languages without `{{IPA|/ᵏǃ͡χ/}}`{=mediawiki}, such as Zulu, `{{IPA|/ᶢǃ/}}`{=mediawiki} may be written *gq*.
labial laminal apical
-------------------------- ---------------------------- ---------- -------------------------------------------------------------------- -----------
dental palatal alveolar lateral retroflex
Lepsius (1855)
Bantuist *`{{IPA|pc}}`{=mediawiki}* *`{{IPA|v ç tc<br />qc}}`{=mediawiki}* `{{ref|pal|b}}`{=mediawiki}
IPA (1921)
expanded IPA (1926-1984)
IPA (1989)
: Competing orthographies
1. `{{angbr IPA|ʞ}}`{=mediawiki} was proposed as the IPA letter for a palatal click by Daniel Jones, but in his writing he called it \'velar\', which was evidently misunderstood by other phoneticians. Replacement with `{{angbr|🡣}}`{=mediawiki} was proposed by Clement Doke, and with `{{angbr IPA|𝼋}}`{=mediawiki} by Beach. (The former is not supported by Unicode, and is here substituted with an arrow.) Doke and Beach used additional letters for voiced and nasal clicks, but these did not catch on.
2. The labial and palatal clicks do not occur in written Bantu languages. However, the palatal clicks have been romanized in Naron, Juǀʼhõasi and !Xun,`{{which|date=December 2012}}`{=mediawiki} where they have been written `{{angbr|tc}}`{=mediawiki}, `{{angbr|ç}}`{=mediawiki} and `{{angbr|qc}}`{=mediawiki}, respectively. In the 19th century, palatal clicks were sometimes written with the letter `{{angbr|v}}`{=mediawiki}, which may have been the source of the Doke letter `{{angbr|🡣}}`{=mediawiki}.
There are a few less-well-attested articulations. A reported subapical retroflex articulation `{{angbr IPA|𝼊}}`{=mediawiki} in Grootfontein !Kung turns out to be alveolar with lateral release, `{{angbr IPA|ǃ𐞷}}`{=mediawiki}; Ekoka !Kung has a fricated alveolar click with an s-like release, provisionally transcribed `{{angbr IPA|ǃ͡s}}`{=mediawiki}; and Sandawe has a \"slapped\" alveolar click, provisionally transcribed `{{angbr IPA|ǃ¡}}`{=mediawiki} (in turn, the lateral clicks in Sandawe are more abrupt and less noisy than in southern Africa). However, the Khoisan languages are poorly attested, and it is quite possible that, as they become better described, more click articulations will be found.
Formerly when a click consonant was transcribed, two symbols were used, one for each articulation, and connected with a tie bar. This is because a click such as `{{IPA|[ɢ͡ǀ]}}`{=mediawiki} was analysed as a voiced uvular rear articulation `{{IPA|[ɢ]}}`{=mediawiki} pronounced simultaneously with the forward ingressive release `{{IPA|[ǀ]}}`{=mediawiki}. The symbols may be written in either order, depending on the analysis: `{{angbr IPA|ɢ͡ǀ}}`{=mediawiki} or `{{angbr IPA|ǀ͡ɢ}}`{=mediawiki}. However, a tie bar was not often used in practice, and when the manner is tenuis (a simple `{{IPA|[k]}}`{=mediawiki}), it was often omitted as well. That is, `{{angbr IPA|ǂ}}`{=mediawiki} = `{{angbr IPA|kǂ}}`{=mediawiki} = `{{angbr IPA|ǂk}}`{=mediawiki} = `{{angbr IPA|k͡ǂ}}`{=mediawiki} = `{{angbr IPA|ǂ͡k}}`{=mediawiki}. Regardless, elements that do not overlap with the forward release are usually written according to their temporal order: Prenasalisation is always written first (`{{angbr IPA|ɴɢ͡ǀ}}`{=mediawiki} = `{{angbr IPA|ɴǀ͡ɢ}}`{=mediawiki} = `{{angbr IPA|ɴǀ̬}}`{=mediawiki}), and the non-lingual part of a contour is always written second (`{{angbr IPA|k͡ǀʼqʼ}}`{=mediawiki} = `{{angbr IPA|ǀ͡kʼqʼ}}`{=mediawiki} = `{{angbr IPA|ǀ͡qʼ}}`{=mediawiki}).
However, it is common to analyse clicks as simplex segments, despite the fact that the front and rear articulations are independent, and to use diacritics to indicate the rear articulation and the accompaniment. At first this tended to be `{{angbr IPA|ᵏǀ, ᶢǀ, ᵑǀ}}`{=mediawiki} for `{{angbr IPA|k͡ǀ, ɡ͡ǀ, ŋ͡ǀ}}`{=mediawiki}, based on the belief that the rear articulation was velar; but as it has become clear that the rear articulation is often uvular or even pharyngeal even when there is no velar--uvular contrast, voicing and nasalisation diacritics more in keeping with the IPA have started to appear: `{{angbr IPA|ǀ̥, ǀ̬, ǀ̃, ŋǀ̬}}`{=mediawiki} for `{{angbr IPA|ᵏǀ, ᶢǀ, ᵑǀ, ŋᶢǀ}}`{=mediawiki}.
Tenuis Aspirated Voiced Nasal Delayed (\"uvular\") True uvular
-------------- -------- ----------- -------- ------- ---------------------- -------------
Tie bars etc.
etc.
Digraphs etc.
Superscripts etc.
Diacritics NA NA
: Variation in the transcription of accompaniments
In practical orthography, the voicing or nasalisation is sometimes given the anterior place of articulation: *dc* for `{{IPA|ᶢǀ}}`{=mediawiki} and *mʘ* for `{{IPA|ᵑʘ}}`{=mediawiki}, for example.
In the literature on Damin, the clicks are transcribed by adding `{{angbr|!}}`{=mediawiki} to the homorganic nasal: `{{angbr|m!, nh!, n!, rn!}}`{=mediawiki}.
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# Click consonant
## Places of articulation {#places_of_articulation}
Places of articulation are often called click *types, releases,* or *influxes,* though \'release\' is also used for the accompaniment/efflux. There are seven or eight known places of articulation, not counting slapped or egressive clicks. These are *(bi)labial affricated* `{{IPA|ʘ}}`{=mediawiki}, or \"bilabial\"; *laminal denti-alveolar affricated* `{{IPA|ǀ}}`{=mediawiki}, or \"dental\"; *apical (post)alveolar plosive* `{{IPA|ǃ}}`{=mediawiki}, or \"alveolar\"; *laminal palatal plosive* `{{IPA|ǂ}}`{=mediawiki}, or \"palatal\"; *laminal palatal affricated* `{{IPA|ǂᶴ}}`{=mediawiki} (known only from Ekoka !Kung); *subapical postalveolar* `{{IPA|𝼊}}`{=mediawiki}, or \"retroflex\" (only known from Central !Kung and possibly Damin); and *apical (post)alveolar lateral* `{{IPA|ǁ}}`{=mediawiki}, or \"lateral\".
Labial Dental Alveolar Slapped Retroflex Domed Palatal Lateral Linguolabial Velar
-------- -------- ---------- -------------- ----------- --------------------------- --------- --------- -------------------- -------
(`{{IPA|𝼋}}`{=mediawiki})
(allophonic) (paralexical only)
: Place of articulation of initial release
Languages illustrating each of these articulations are listed below. Given the poor state of documentation of Khoisan languages, it is quite possible that additional places of articulation will turn up. No language is known to contrast more than five.
+------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------------------------------------------------------------------------------------------------------------------+
| Click place\ | Languages | Notes |
| inventory | | |
+==========================================================================================================================================+==================================+=======================================================================================================================+
| 1 release, variable `{{IPA|ǀ ~ ǁ}}`{=mediawiki} | Dahalo | Various nasal clicks only. |
+------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------------------------------------------------------------------------------------------------------------------+
| 1 release, variable `{{IPA|ǀ ~ ǃ}}`{=mediawiki} | Sotho, Swazi | In Sotho the clicks tend to be alveolar, in Swazi dental. |
+------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------------------------------------------------------------------------------------------------------------------+
| 1 release, variable `{{IPA|ǀ ~ ǃ ~ ǁ or ǂ}}`{=mediawiki} | Fwe, Gciriku | Tend to be dental. |
+------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------------------------------------------------------------------------------------------------------------------+
| 3 releases, `{{IPA|ǀ}}`{=mediawiki}, `{{IPA|ǂ}}`{=mediawiki}, `{{IPA|ǁ}}`{=mediawiki} | Kwadi | and `{{IPA|ǁ}}`{=mediawiki} not found with all manners, but these may be accidental gaps, as Kwadi is poorly attested |
+------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------------------------------------------------------------------------------------------------------------------+
| 3 releases, `{{IPA|ǀ}}`{=mediawiki}, `{{IPA|ǃ}}`{=mediawiki}, `{{IPA|ǁ}}`{=mediawiki} | Sandawe, Hadza, Xhosa, Zulu | In Sandawe, `{{IPA|ǃ}}`{=mediawiki} is often \"slapped\" `{{IPA|[ǃ¡]}}`{=mediawiki}. |
+------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------------------------------------------------------------------------------------------------------------------+
| 3--4 releases, `{{IPA|ʘ}}`{=mediawiki}, `{{IPA|ǀ}}`{=mediawiki}, (`{{IPA|ǃ}}`{=mediawiki},) `{{IPA|ǁ}}`{=mediawiki} | ǁXegwi | reacquired in loans |
+------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------------------------------------------------------------------------------------------------------------------+
| 4 releases, `{{IPA|ǀ}}`{=mediawiki}, `{{IPA|ǂ}}`{=mediawiki}, `{{IPA|ǃ}}`{=mediawiki}, `{{IPA|ǁ}}`{=mediawiki} | Korana, Khoekhoe, Yeyi, Juǀʼhoan | |
+------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------------------------------------------------------------------------------------------------------------------+
| 4 releases, `{{IPA|ǀ}}`{=mediawiki}, `{{IPA|ǂᶴ}}`{=mediawiki}, `{{IPA|ǃ}}`{=mediawiki}, `{{IPA|ǁ}}`{=mediawiki} | Ekoka !Kung | |
+------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------------------------------------------------------------------------------------------------------------------+
| 5 releases, `{{IPA|ʘ}}`{=mediawiki}, `{{IPA|ǀ}}`{=mediawiki}, `{{IPA|ǂ}}`{=mediawiki}, `{{IPA|ǃ}}`{=mediawiki}, `{{IPA|ǁ}}`{=mediawiki} | ǂHõã, Nǀu, ǀXam, Taa | |
+------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------------------------------------------------------------------------------------------------------------------+
| 5 releases, `{{IPA|ǀ}}`{=mediawiki}, `{{IPA|ǂ}}`{=mediawiki}, `{{IPA|ǃ}}`{=mediawiki}, `{{IPA|𝼊}}`{=mediawiki}, `{{IPA|ǁ}}`{=mediawiki} | Grootfontein !Kung | |
+------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------------------------------------------------------------------------------------------------------------------+
| 5 releases, `{{IPA|ʘ}}`{=mediawiki}, `{{IPA|ʘ↑}}`{=mediawiki}, `{{IPA|ǀ}}`{=mediawiki}, `{{IPA|ǃ}}`{=mediawiki}, `{{IPA|𝼊}}`{=mediawiki} | Damin | Aside from `{{IPA|/ʘ↑/}}`{=mediawiki}, which is not technically a click, all are nasal. |
+------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----------------------------------------------------------------------------------------------------------------------+
Extra-linguistically, Coatlán Zapotec of Mexico uses a linguolabial click, `{{IPA|[ǀ̼ʔ]}}`{=mediawiki}, as mimesis for a pig drinking water, and several languages, such as Wolof, use a velar click `{{IPA|[ʞ]}}`{=mediawiki}, long judged to be physically impossible, for backchanneling and to express approval. An extended dental click with lip pursing or compression (\"sucking-teeth\"), variable in sound and sometimes described as intermediate between `{{IPA|[ǀ]}}`{=mediawiki} and `{{IPA|[ʘ]}}`{=mediawiki}, is found across West Africa, the Caribbean and into the United States.
The exact place of the alveolar clicks varies between languages. The lateral, for example, is alveolar in Khoekhoe but postalveolar or even palatal in Sandawe; the central is alveolar in Nǀuu but postalveolar in Juǀʼhoan.
### Names found in the literature {#names_found_in_the_literature}
The terms for the click types were originally developed by Bleek in 1862. Since then there has been some conflicting variation. However, apart from \"cerebral\" (retroflex), which was found to be an inaccurate label when true retroflex clicks were discovered, Bleek\'s terms are still considered normative today. Here are the terms used in some of the main references.
Click type Bleek (1862) Doke (1926) IPA (1928) Beach (1938) IPA (1949) IPA (1989) Unicode Miller et al. (2009) Vossen (2013) other
------------ -------------- ----------------- ------------------ -------------------------- ------------ -------------------- ----------- ---------------------- ------------------ ----------------------------------------------------------
dental dental dental dental affricative dental dental dental denti-pharyngeal dental alveolar affricated; denti-alveolar; apico-lamino-dental
cerebral palato-alveolar cerebral alveolar implosive retroflex (post-)alveolar retroflex central alveo-uvular alveolar palatal; palatal retroflex; apico-palatal
lateral lateral alveolar lateral lateral affricative lateral (alveolar) lateral lateral lateral alveo-uvular lateral-alveolar post-alveolar lateral; lateral apico-alveo-palatal
palatal alveolar velar denti-alveolar implosive velar palatoalveolar alveolar palato-pharyngeal palatal alveolar instantaneous; dental
bilabial bilabial labio-uvular bilabial labial
: Names in the literature
The dental, lateral and bilabial clicks are rarely confused, but the palatal and alveolar clicks frequently have conflicting names in older literature, and non-standard terminology is fossilized in Unicode. However, since Ladefoged & Traill (1984) clarified the places of articulation, the terms listed under Vossen (2013) in the table above have become standard, apart from such details as whether in a particular language `{{IPA|ǃ}}`{=mediawiki} and `{{IPA|ǁ}}`{=mediawiki} are alveolar or postalveolar, or whether the rear articulation is velar, uvular or pharyngeal, which again varies between languages (or may even be contrastive within a language).
| 759 |
Click consonant
| 5 |
7,816 |
# Click consonant
## Manners of articulation {#manners_of_articulation}
Click manners are often called click *accompaniments* or *effluxes*, but both terms have met with objections on theoretical grounds.
There is a great variety of click manners, both simplex and complex, the latter variously analysed as consonant clusters or contours. With so few click languages, and so little study of them, it is also unclear to what extent clicks in different languages are equivalent. For example, the `{{IPA|[ǃkˀ]}}`{=mediawiki} of Khoekhoe, `{{IPA|[ǃkˀ ~ ŋˀǃk]}}`{=mediawiki} of Sandawe and `{{IPA|[ŋ̊ǃˀ ~ ŋǃkˀ]}}`{=mediawiki} of Hadza may be essentially the same phone; no language distinguishes them, and the differences in transcription may have more to do with the approach of the linguist than with actual differences in the sounds. Such suspected allophones/allographs are listed on a common row in the table below.
Some Khoisan languages are typologically unusual in allowing mixed voicing in non-click consonant clusters/contours, such as `{{IPA| ̬d̥sʼk͡x}}`{=mediawiki}, so it is not surprising that they would allow mixed voicing in clicks as well. This may be an effect of epiglottalised voiced consonants, because voicing is incompatible with epiglottalisation.
### Phonation
As do other consonants, clicks vary in phonation. Oral clicks are attested with four phonations: tenuis, aspirated, voiced and breathy voiced (murmured). Nasal clicks may also vary, with plain voiced, breathy voiced / murmured nasal, aspirated and unaspirated voiceless clicks attested (the last only in Taa). The aspirated nasal clicks are often said to have \'delayed aspiration\'; there is nasal airflow throughout the click, which may become voiced between vowels, though the aspiration itself is voiceless. A few languages also have pre-glottalised nasal clicks, which have very brief prenasalisation but have not been phonetically analysed to the extent that other types of clicks have.
All languages have nasal clicks, and all but Dahalo and Damin also have oral clicks. All languages but Damin have at least one phonation contrast as well.
### Complex clicks {#complex_clicks}
Clicks may be pronounced with a third place of articulation, glottal. A glottal stop is made during the hold of the click; the (necessarily voiceless) click is released, and then the glottal hold is released into the vowel. Glottalised clicks are very common, and they are generally nasalised as well. The nasalisation cannot be heard during the click release, as there is no pulmonic airflow, and generally not at all when the click occurs at the beginning of an utterance, but it has the effect of nasalising preceding vowels, to the extent that the glottalised clicks of Sandawe and Hadza are often described as prenasalised when in medial position. Two languages, Gǀwi and Yeyi, contrast plain and nasal glottalised clicks, but in languages without such a contrast, the glottalised click is nasal. Miller (2011) analyses the glottalisation as phonation, and so considers these to be simple clicks.
Various languages also have prenasalised clicks, which may be analysed as consonant sequences. Sotho, for example, allows a syllabic nasal before its three clicks, as in *nnqane* \'the other side\' (prenasalised nasal) and *seqhenqha* \'hunk\'.
There is ongoing discussion as to how the distinction between what were historically described as \'velar\' and \'uvular\' clicks is best described. The \'uvular\' clicks are only found in some languages, and have an extended pronunciation that suggests that they are more complex than the simple (\'velar\') clicks, which are found in all. Nakagawa (1996) describes the extended clicks in Gǀwi as consonant clusters, sequences equivalent to English *st* or *pl*, whereas Miller (2011) analyses similar sounds in several languages as click--non-click contours, where a click transitions into a pulmonic or ejective articulation within a single segment, analogous to how English *ch* and *j* transition from occlusive to fricative but still behave as unitary sounds. With ejective clicks, for example, Miller finds that although the ejective release follows the click release, it is the rear closure of the click that is ejective, not an independently articulated consonant. That is, in a simple click, the release of the rear articulation is not audible, whereas in a contour click, the rear (uvular) articulation is audibly released after the front (click) articulation, resulting in a double release.
These contour clicks may be *linguo-pulmonic*, that is, they may transition from a click (lingual) articulation to a normal pulmonic consonant like `{{IPAblink|ɢ}}`{=mediawiki} (e.g. `{{IPA|[ǀ͡ɢ]}}`{=mediawiki}); or *linguo-glottalic* and transition from lingual to an ejective consonant like `{{IPAblink|qʼ}}`{=mediawiki} (e.g. `{{IPA|[ǀ͡qʼ]}}`{=mediawiki}): that is, a sequence of ingressive (lingual) release + egressive (pulmonic or glottalic) release. In some cases there is a shift in place of articulation as well, and instead of a uvular release, the uvular click transitions to a velar or epiglottal release (depending on the description, `{{IPA|[ǂ͡kxʼ]}}`{=mediawiki} or `{{IPA|[ǂᴴ]}}`{=mediawiki}). Although homorganic `{{IPA|[ǂ͡χʼ]}}`{=mediawiki} does not contrast with heterorganic `{{IPA|[ǂ͡kxʼ]}}`{=mediawiki} in any known language, they are phonetically quite distinct (Miller 2011).
Implosive clicks, i.e. velar `{{IPA|[ɠ͡ʘ ɠ͡ǀ ɠ͡ǃ ɠ͡ǂ ɠ͡ǁ]}}`{=mediawiki}, uvular `{{IPA|[ʛ͡ʘ ʛ͡ǀ ʛ͡ǃ ʛ͡ǂ ʛ͡ǁ]}}`{=mediawiki}, and *de facto* front-closed palatal `{{IPA|[ʄ͡ʘ ʄ͡ǀ ʄ͡ǃ ʄ͡ǁ]}}`{=mediawiki} are not only possible but easier to produce than modally voiced clicks. However, they are not attested in any language.
The \'Khoisan\' languages, as well as Bantu Yeyi, have glottalized nasal clicks. Contour clicks are restricted to southern Africa, but are very common there: they are found in all members of the Tuu, Kxʼa and Khoe families, as well as in the Bantu language Yeyi.
| 884 |
Click consonant
| 6 |
7,816 |
# Click consonant
## Manners of articulation {#manners_of_articulation}
### Variation among languages {#variation_among_languages}
In a comparative study of clicks across various languages, using her own field work as well as phonetic descriptions and data by other field researchers, Miller (2011) posits 21 types of clicks that contrast in manner or airstream. The homorganic and heterorganic affricated ejective clicks do not contrast in any known language, but are judged dissimilar enough to keep separate. Miller\'s conclusions differ from those of the primary researcher of a language; see the individual languages for details.
- Taa (ǃXóõ) and Nǁng (Nǀuu) are Tuu languages, from the two branches of that family.
- ǂʼAmkoe (ǂHoan) and Juǀʼhoan (ǃKung) are Kxʼa languages, from the two branches of that family.
- Korana and Gǀui (Gǁana) are Khoe languages, from the two branches of that family.
(all spoken primarily in South Africa, Namibia and Botswana; Khoekhoe is similar to Korana except it has lost ejective `{{IPA|/ᵏꞰ͡χʼ/}}`{=mediawiki})
- Sandawe and Hadza are language isolates spoken in Tanzania
- Dahalo is a Cushitic language of Kenya
- Xhosa and Yeyi are Bantu languages, from the two geographic areas of that family that have acquired clicks.
(Zulu is similar to Xhosa apart from not having `{{IPA|/ᵑꞰˀ/}}`{=mediawiki})
- Damin was an initiation jargon in northern Australia.
Each language below is illustrated with Ʞ as a placeholder for the different click types. Under each language are the orthography (in italics, with old forms in parentheses), the researchers\' transcription (in `{{angbr|angle brackets}}`{=mediawiki}), or allophonic variation (in \[brackets\]). Some languages also have labialised or prenasalised clicks in addition to those listed below.
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| Language | | | Tuu | | Kxʼa | | Khoe | |
+==============================+======================================+===================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================================+========================================================================================================================================+================================================================================================+=========+=======================================================================+=======================================================================+======+
| Taa | Nǁng | ǂʼAmkoe | Juǀʼhoan | Korana | Gǀui | Dahalo | Xhosa | Yeyi |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| Manner | | | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| Simple\ | *Tenuis* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞ}}`{=mediawiki}\* \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[ᵏꞰ]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *Ʞ (c, ç, q, x)* \| bgcolor=\"#f0c0c0\" align=center \| *Ʞg* \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|kꞰ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *c, q, x* \| bgcolor=\"#f0c0c0\" align=center \| *c, q, x (Ʞ)* | \| bgcolor=\"#f0c0c0\" align=center \| *c, q, x* \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞ}}`{=mediawiki} | | | | | |
| oral\ | | | | | | | | |
| click | | | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Voiced* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|gꞰ}}`{=mediawiki}\* \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|ᶢꞰ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[ᶢꞰ]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *gꞰ (dq etc.)* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|gꞰ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *gq etc.*\ | | | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|gꞰ}}`{=mediawiki} | | |
| | | | `{{IPA|[ᶢꞰ}}`{=mediawiki} \~ `{{IPA|ŋᶢꞰ]}}`{=mediawiki} | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Aspirated* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞh}}`{=mediawiki}\* \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞʰ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[ᵏꞰʰ]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *Ʞh (qh etc.)* \| bgcolor=\"#f0c0c0\" align=center \| *Ʞkh* \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|kꞰh}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *qh etc.* \| bgcolor=\"#f0c0c0\" align=center \| *qh etc. (Ʞh)* | \| bgcolor=\"#f0c0c0\" align=center \| *qh etc.* \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞh}}`{=mediawiki} (= Ʞx ?) | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Breathy-voiced* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|gꞰh}}`{=mediawiki}\* | | \| bgcolor=\"#f0c0c0\" align=center \| *gꞰh (dqh etc.)*\ | | | | |
| | | | | `{{IPA|[ᶢꞰʱ ~ ᶢꞰˠ]}}`{=mediawiki} | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| Simple\ | *Voiceless* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|nhꞰ}}`{=mediawiki}\*\ | | | | | | |
| nasal\ | | `{{IPA|[ŋ̊ᵑꞰ]}}`{=mediawiki} | | | | | | |
| click | | | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Voiced* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|nꞰ}}`{=mediawiki}\*\ | | | | | | |
| | | `{{IPA|[ŋ̈ᵑꞰ]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|ᵑꞰ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[ᵑꞰ]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *nꞰ (nq etc.)* \| bgcolor=\"#f0c0c0\" align=center \| *Ʞn* \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|ŋꞰ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *nq etc.* \| bgcolor=\"#f0c0c0\" align=center \| *nq etc. (nꞰ)* \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|/ᵑǀ/}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *nq etc.* \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|ŋꞰ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Nǃ}}`{=mediawiki} | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *(Delayed) aspiration\ | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞhh}}`{=mediawiki}\ | | | | | | |
| | (prenasalised between vowels)* | `{{IPA|[ŋ̊↓Ʞh]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|ᵑ̊Ʞʰ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[ᵑ̊Ʞʱ ~ ŋᵑ̊Ʞʱ]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *Ʞʼh (qʼh etc.)* \| bgcolor=\"#f0c0c0\" align=center \| *Ʞh* \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|ŋꞰh}}`{=mediawiki} | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Breathy-voiced* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|nꞰhh}}`{=mediawiki} | | \| bgcolor=\"#f0c0c0\" align=center \| *nꞰh (nqh etc.)* | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| *Preglottalised nasal click* | | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|ʼnꞰ}}`{=mediawiki}\* | \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[ʔᵑꞰ]}}`{=mediawiki} | (in Ekoka) | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| Glottalised\ | *Oral / velar ejective* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞʼ}}`{=mediawiki}\* | | | | \| \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|kꞰʼ}}`{=mediawiki} | | |
| click | | | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Creaky-voiced oral* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|gꞰʼ}}`{=mediawiki}\* | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Nasal (silent initially,\ | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞʼʼ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|ᵑ̊Ʞˀ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[Ʞˀ ~ ŋˀꞰ]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *Ʞʼ (qʼ etc.)*\ | | | | | | |
| | prenasalised after vowels)* | (w/ nasal vowels) \| bgcolor=\"#f0c0c0\" align=center \| *Ʞ* \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|kꞰʔ}}`{=mediawiki} (`{{IPA|ŋ̊Ʞʔ}}`{=mediawiki}) \| bgcolor=\"#f0c0c0\" align=center \| *qʼ etc.*\ | | | | | | |
| | | `{{IPA|[Ʞˀʔ}}`{=mediawiki} \~ `{{IPA|ŋʔꞰˀ]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *qq etc.*\ | | | | | | |
| | | *(Ʞʼ \~ nꞰʼ)* \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|/ᵑǀˀ/}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *nkq etc.* ? \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|ŋꞰʼ}}`{=mediawiki} | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Nasal (prenasalised initially)* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|nꞰʼʼ}}`{=mediawiki} | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| Pulmonic\ | *Tenuis stop* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞq}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞq}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[Ʞq]}}`{=mediawiki} | | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|qꞰ}}`{=mediawiki} | | | | |
| contour | | | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Voiced (and prenasalised)* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|gꞰq}}`{=mediawiki}\ | | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|ɢꞰ}}`{=mediawiki}\ | | | | |
| | | `{{IPA|[ᶰꞰɢ ~ Ʞɢ]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[Ʞɢ]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| (`{{IPA|[ᶰꞰɢ]}}`{=mediawiki}) | | `{{IPA|[ᶰꞰɢ]}}`{=mediawiki} | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Aspirated stop* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞqh}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞqʰ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[Ʞqʰ]}}`{=mediawiki} | | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|qꞰh}}`{=mediawiki} | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Breathy-voiced* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|gꞰqh}}`{=mediawiki} | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Voiceless fricative* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞx}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞχ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[Ʞq͡χ]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| *Ʞx (qg etc.)* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|qꞰχ}}`{=mediawiki} | | | | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞx}}`{=mediawiki} (?) | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Voiced fricative (prenasalised)* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|gꞰx}}`{=mediawiki}\ | | \| bgcolor=\"#f0c0c0\" align=center \| *gꞰx (dqg etc.)* | | | | |
| | | `{{IPA|[ᶢꞰ͡χ ~ ɴᶢꞰ͡ʁ]}}`{=mediawiki} | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| Ejective\ | *Ejective stop* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞqʼ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[Ʞqʼ]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[Ʞqʼ]}}`{=mediawiki} | | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|qꞰʼ}}`{=mediawiki} | | | | |
| contour | | | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Voiced ejective stop* | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|gꞰqʼ}}`{=mediawiki} | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Ejective fricative* | | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞχʼ}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{IPA|[Ʞq͡χʼ]}}`{=mediawiki} | \| bgcolor=\"#f0c0c0\" align=center rowspan=2 \| *Ʞkhʼ* | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Heterorganic affricate /\ | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|Ʞqxʼ}}`{=mediawiki} | | \| bgcolor=\"#f0c0c0\" align=center \| *Ʞk (qgʼ etc.)*\ | | | | |
| | epiglottalised* | | | `{{IPA|[Ʞᵸ]}}`{=mediawiki} \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|qꞰχʼ}}`{=mediawiki} | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | *Voiced heterorganic\ | \| bgcolor=\"#f0c0c0\" align=center \| `{{angbr|gꞰqxʼ}}`{=mediawiki} | | \| bgcolor=\"#f0c0c0\" align=center \| *gꞰk (dqgʼ etc.)*\ | | | | |
| | affricate / epiglottalised* | | | `{{IPA|[ᶢꞰˤ]}}`{=mediawiki} | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| Egressive | *(Voiceless \"spurt\"; labial only)* | | | | | | | |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
| | | IPA | Taa | Nǁng | ǂʼAmkoe | Juǀʼhoan | Korana | Gǀui |
+------------------------------+--------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------+---------+-----------------------------------------------------------------------+-----------------------------------------------------------------------+------+
Yeyi also has prenasalised `{{IPA|/ŋᶢꞰ/}}`{=mediawiki}. The original researchers believe that `{{IPA|[Ʞʰ]}}`{=mediawiki} and `{{IPA|[Ʞχ]}}`{=mediawiki} are allophones.
A DoBeS (2008) study of the Western ǃXoo dialect of Taa found several new manners: creaky voiced (the voiced equivalent of glottalised oral), breathy-voiced nasal, prenasalised glottalised (the voiced equivalent of glottalised) and a (pre)voiced ejective. These extra voiced clicks reflect Western ǃXoo morphology, where many nouns form their plural by voicing their initial consonant. DoBeS analyses most Taa clicks as clusters, leaving nine basic manners (marked with asterisks in the table). This comes close to Miller\'s distinction between simple and contour clicks, shaded light and medium grey in the table.
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# Click consonant
## Phonotactics
Languages of the southern African Khoisan families only permit clicks at the beginning of a word root. However, they also restrict other classes of consonant, such as ejectives and affricates, to root-initial position. The Bantu languages, Hadza and Sandawe allow clicks within roots.
In some languages, all click consonants within known roots are the same phoneme, as in Hadza *cikiringcingca* `{{IPA|/ǀikiɺiN.ǀiN.ǀa/}}`{=mediawiki} \'pinkie finger\', which has three tenuis dental clicks. Other languages are known to have the occasional root with different clicks, as in Xhosa *ugqwanxa* `{{IPA|/uᶢ̊ǃʱʷaᵑǁa/}}`{=mediawiki} \'black ironwood\', which has a slack-voiced alveolar click and a nasal lateral click.
No natural language allows clicks at the ends of syllables or words, but then no languages with clicks allows many consonants at all in those positions. Similarly, clicks are not found in underlying consonant clusters apart from /Cw/ (and, depending on the analysis, /Cχ/), as languages with clicks do not have other consonant clusters than that. Due to vowel elision, however, there are cases where clicks are pronounced in cross-linguistically common types of consonant clusters, such as Xhosa `{{IPA|[sᵑǃɔɓilɛ]}}`{=mediawiki} *Snqobile*, from *Sinqobile* (a name), and `{{IPA|[isǁʰɔsa]}}`{=mediawiki} *isXhosa*, from *isiXhosa* (the Xhosa language).
Like other articulatorily complex consonants, clicks tend to be found in lexical words rather than in grammatical words, but this is only a tendency. In Nǁng, for example, there are two sets of personal pronouns, a full one without clicks and a partial set with clicks (*ńg* \'I\', *á* \'thou\', *í* \'we all\', *ú* \'you\', vs. *nǀǹg* \'I\', *gǀà* \'thou\', *gǀì* \'we all\', *gǀù* \'you\'), as well as other grammatical words with clicks such as *ǁu* \'not\' and *nǀa* \'with, and\'.
### The back-vowel constraint {#the_back_vowel_constraint}
In several languages, including Nama and Juǀʼhoan, the alveolar click types `{{IPA|[ǃ]}}`{=mediawiki} and `{{IPA|[ǁ]}}`{=mediawiki} only occur, or preferentially occur, before back vowels, whereas the dental and palatal clicks occur before any vowel. The effect is most noticeable with the high front vowel `{{IPA|[i]}}`{=mediawiki}. In Nama, for example, the diphthong `{{IPA|[əi]}}`{=mediawiki} is common but `{{IPA|[i]}}`{=mediawiki} is rare after alveolar clicks, whereas the opposite is true after dental and palatal clicks. This is a common effect of uvular or uvularised consonants on vowels in both click and non-click languages. In Taa, for example, the back-vowel constraint is triggered by both alveolar clicks and uvular stops, but not by palatal clicks or velar stops: sequences such as `{{IPA|*/ǃi/}}`{=mediawiki} and `{{IPA|*/qi/}}`{=mediawiki} are rare to non-existent, whereas sequences such as `{{IPA|/ǂi/}}`{=mediawiki} and `{{IPA|/ki/}}`{=mediawiki} are common. The back-vowel constraint is also triggered by labial clicks, though not by labial stops. Clicks subject to this constraint involve a sharp retraction of the tongue during release.
+------------------------------+---------+---------+
| | Abrupt\ | Noisy\ |
| | release | release |
+==============================+=========+=========+
| ballistic tongue retraction\ | | |
| & back-vowel constraint | | |
+------------------------------+---------+---------+
| no retraction, no constraint | | |
+------------------------------+---------+---------+
Miller and colleagues (2003) used ultrasound imaging to show that the rear articulation of the alveolar clicks (`{{IPA|[ǃ]}}`{=mediawiki}) in Nama is substantially different from that of palatal and dental clicks. Specifically, the shape of the body of the tongue in palatal clicks is very similar to that of the vowel `{{IPA|[i]}}`{=mediawiki}, and involves the same tongue muscles, so that sequences such as `{{IPA|[ǂi]}}`{=mediawiki} involved a simple and quick transition. The rear articulation of the alveolar clicks, however, is several centimetres further back, and involves a different set of muscles in the uvular region. The part of the tongue required to approach the palate for the vowel `{{IPA|[i]}}`{=mediawiki} is deeply retracted in `{{IPA|[ǃ]}}`{=mediawiki}, as it lies at the bottom of the air pocket used to create the vacuum required for click airstream. This makes the transition required for `{{IPA|[ǃi]}}`{=mediawiki} much more complex and the timing more difficult than the shallower and more forward tongue position of the palatal clicks. Consequently, `{{IPA|[ǃi]}}`{=mediawiki} takes 50 ms longer to pronounce than `{{IPA|[ǂi]}}`{=mediawiki}, the same amount of time required to pronounce `{{IPA|[ǃəi]}}`{=mediawiki}.
Languages do not all behave alike. In Nǀuu, the simple clicks `{{IPA|/ʘ, ǃ, ǁ/}}`{=mediawiki} trigger the `{{IPA|[əi]}}`{=mediawiki} and `{{IPA|[æ]}}`{=mediawiki} allophones of `{{IPA|/i/}}`{=mediawiki} and `{{IPA|/e/}}`{=mediawiki}, whereas `{{IPA|/ǀ, ǂ/}}`{=mediawiki} do not. All of the affricated contour clicks, such as `{{IPA|/ǂ͡χ/}}`{=mediawiki}, do as well, as do the uvular stops `{{IPA|/q, χ/}}`{=mediawiki}. However, the occlusive contour clicks pattern like the simple clicks, and `{{IPA|/ǂ͡q/}}`{=mediawiki} does not trigger the back-vowel constraint. This is because they involve tongue-root raising rather than tongue-root retraction in the uvular-pharyngeal region. However, in Gǀwi, which is otherwise largely similar, both `{{IPA|/ǂ͡q/}}`{=mediawiki} and `{{IPA|/ǂ͡χ/}}`{=mediawiki} trigger the back-vowel constraint (Miller 2009).
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# Click consonant
## Click genesis and click loss {#click_genesis_and_click_loss}
One genetic study concluded that clicks, which occur in the languages of the genetically divergent populations Hadza and !Kung, may be an ancient element of human language. However, this conclusion relies on several dubious assumptions (see Hadza language), and most linguists assume that clicks, being quite complex consonants, arose relatively late in human history. How they arose is not known, but it is generally assumed that they developed from sequences of non-click consonants, as they are found allophonically for doubly articulated consonants in West Africa, for `{{IPA|/tk/}}`{=mediawiki} sequences that overlap at word boundaries in German, and for the sequence `{{IPA|/mw/}}`{=mediawiki} in Ndau and Tonga. Such developments have also been posited in historical reconstruction. For example, the Sandawe word for \'horn\', `{{IPA|/tɬana/}}`{=mediawiki}, with a lateral affricate, may be a cognate with the root `{{IPA|/ᵑǁaː/}}`{=mediawiki} found throughout the Khoe family, which has a lateral click. This and other words suggests that at least some Khoe clicks may have formed from consonant clusters when the first vowel of a word was lost; in this instance \*`{{IPA|[tɬana]}}`{=mediawiki} \> \*`{{IPA|[tɬna]}}`{=mediawiki} \> `{{IPA|[ǁŋa] ~ [ᵑǁa]}}`{=mediawiki}.
On the other side of the equation, several non-endangered languages in vigorous use demonstrate click loss. For example, the East Kalahari languages have lost clicks from a large percentage of their vocabulary, presumably due to Bantu influence. As a rule, a click is replaced by a consonant with close to the manner of articulation of the click and the place of articulation of the forward release: alveolar click releases (the `{{IPA|[ǃ]}}`{=mediawiki} family) tend to mutate into a velar stop or affricate, such as `{{IPA|[k], [ɡ], [ŋ], [k͡x]}}`{=mediawiki}; palatal clicks (the `{{IPA|[ǂ]}}`{=mediawiki} family) tend to mutate into a palatal stop such as `{{IPA|[c], [{{thin space}}ɟ], [{{thin space}}ɲ], [cʼ]}}`{=mediawiki}, or a post-alveolar affricate `{{IPA|[tʃ], [dʒ]}}`{=mediawiki}; and dental clicks (the `{{IPA|[ǀ]}}`{=mediawiki} family) tend to mutate into an alveolar affricate `{{IPA|[ts]}}`{=mediawiki}.
## Difficulty
Clicks are often presented as difficult sounds to articulate within words. However, children acquire them readily; a two-year-old, for example, may be able to pronounce a word with a lateral click `{{IPA|[ǁ]}}`{=mediawiki} with no problem, but still be unable to pronounce `{{IPA|[s]}}`{=mediawiki}. Lucy Lloyd reported that after long contact with the Khoi and San, it was difficult for her to refrain from using clicks when speaking English
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# The Cider House Rules
***The Cider House Rules*** (1985) is a *Bildungsroman* by American writer John Irving that was later adapted into a 1999 film by Lasse Hallström and a stage play by Peter Parnell. Set in the pre-- and post--World War II era, the story tells of a young man named Homer Wells growing up in an orphanage under the guidance of Dr. Wilbur Larch, an obstetrician and abortion provider. It shows Homer\'s coming of age as he eventually sets off on his own.
## Plot
Homer Wells is shown growing up in an orphanage where he spends his childhood trying to be \"of use\" as a medical assistant to director Dr. Wilbur Larch, whose history is told in flashbacks: After a traumatic misadventure with a prostitute as a young man, Wilbur turns his back on sex and love, choosing instead to help women with unwanted pregnancies give birth and then keeping the babies in an orphanage.
He makes a point of maintaining an emotional distance from the orphans, so that they can more easily make the transition into an adoptive family, but when it becomes clear that Homer is going to spend his childhood at the orphanage, Wilbur trains the orphan as an obstetrician and comes to love him like a son.
Wilbur\'s and Homer\'s lives are complicated by the abortions Wilbur provides. Wilbur came to this work reluctantly, but is driven by having seen the horrors of back-alley operations. Homer, upon learning Wilbur\'s secret, considers it morally wrong.
As a young man, Homer befriends a young couple, Candy Kendall and Wally Worthington, who come to St. Cloud\'s for an abortion. Homer leaves the orphanage, and returns with them to Wally\'s family\'s orchard in Heart\'s Rock, near the Maine coast. Wally and Homer become best friends and Homer develops a secret love for Candy. Wally goes off to serve in the Second World War and his plane is shot down over Burma. He is declared missing by the military, but Homer and Candy both believe he is dead and move on with their lives, which includes beginning a romantic relationship. When Candy becomes pregnant, they go back to St. Cloud\'s Orphanage, where their son is born and named Angel.
Subsequently, Wally is found in Burma and returns home, paralyzed from the waist down. He is still able to have sexual intercourse but is sterile due to an infection caught in Burma. Homer and Candy lie to the family about Angel\'s parentage, claiming that Homer had adopted him. Wally and Candy marry shortly afterward, but Candy and Homer maintain a secret affair that lasts some 15 years.
Many years later, teenaged Angel falls in love with Rose, the daughter of the head migrant worker at the apple orchard. Rose becomes pregnant by her father, and Homer aborts her fetus. Homer decides to return to the orphanage after Wilbur\'s death, to work as the new director. Though he maintains his distaste for abortions, he continues Dr. Larch\'s legacy of performing the procedure for those in need, and he dreams of the day when abortions are legal.
The name \"The Cider House Rules\" refers to the list of rules that migrant workers are supposed to follow at the Ocean View Orchards. However, none of them can read, and they are completely unaware of the rules -- which have been posted for years.
A subplot follows the character Melony, who grew up alongside Homer in the orphanage. She was Homer\'s first girlfriend. After Homer leaves the orphanage, so does she in an effort to find him. She eventually becomes an electrician and takes a female lover, Lorna. Melony is stoic, who refuses to press charges against a man who brutally broke her nose and arm. She intends to later take revenge. She is the catalyst that transforms Homer from his comfortable, but not entirely admirable, position at the apple orchard into Dr. Larch\'s replacement.
## Background
Wally\'s experience getting shot down over Burma was based in part on that of Irving\'s biological father (whom he never met), who was shot down over Burma and survived.
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# The Cider House Rules
## Film adaptation {#film_adaptation}
The novel was adapted into a film of the same name released in 1999 directed by Lasse Hallström. It starred Tobey Maguire as Homer Wells
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# Civilian Conservation Corps
The **Civilian Conservation Corps** (**CCC**) was a voluntary government work relief program that ran from 1933 to 1942 in the United States for unemployed, unmarried men ages 18--25 and eventually expanded to ages 17--28. The CCC was a major part of President Franklin D. Roosevelt\'s New Deal that supplied manual labor jobs related to the conservation and development of natural resources in rural lands owned by federal, state, and local governments. The CCC was designed to supply jobs for young men and to relieve families who had difficulty finding jobs during the Great Depression in the United States. There was eventually a smaller counterpart program for unemployed women called the She-She-She Camps, which were championed by Eleanor Roosevelt.
Robert Fechner was the first director of this agency, succeeded by James McEntee following Fechner\'s death. The largest enrollment at any one time was 300,000. Through the course of its nine years in operation, three million young men took part in the CCC, which provided them with shelter, clothing, and food, together with a monthly wage of \$30 (`{{Inflation|US|30|1933|fmt=eq}}`{=mediawiki}), \$25 of which (`{{Inflation|US|25|1933|fmt=eq}}`{=mediawiki}) had to be sent home to their families.
The American public made the CCC the most popular of all the New Deal programs. Sources written at the time claimed an individual\'s enrollment in the CCC led to improved physical condition, heightened morale, and increased employability. The CCC also led to a greater public awareness and appreciation of the outdoors and the nation\'s natural resources, and the continued need for a carefully planned, comprehensive national program for the protection and development of natural resources.
thumb\|upright=1.6\|154th Co.. CCC, Eagle Lake Camp NP-1-Me. Bar harbor Maine, February 1940
thumb\|upright=1.6\|CCC camps in Michigan; the tents were soon replaced by barracks built by Army contractors for the enrollees.
The CCC operated separate programs for veterans and Native Americans. Approximately 15,000 Native Americans took part in the program, helping them weather the Great Depression.
By 1942, with World War II raging and the draft in effect, the need for work relief declined, and Congress voted to close the program.
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# Civilian Conservation Corps
## Founding
As governor of New York, Franklin D. Roosevelt had run a similar program on a much smaller scale, known as the Temporary Emergency Relief Administration (TERA). It was started in early 1932 to \"use men from the lists of the unemployed to improve our existing reforestation areas.\" In its first year alone, more than 25,000 unemployed New Yorkers were active in its paid conservation work. Long interested in conservation, as president Roosevelt proposed a full-scale national program to Congress on March 21, 1933: `{{blockquote|I propose to create [the CCC] to be used in complex work, not interfering with normal employment and confining itself to forestry, the prevention of soil erosion, flood control, and similar projects. I call your attention to the fact that this type of work is of definite, practical value, not only through the prevention of great present financial loss but also as a means of creating future national wealth.}}`{=mediawiki}
He promised this law would provide 250,000 young men with meals, housing, workwear, and medical care in exchange for their work in the national forests and other government properties. The Emergency Conservation Work (ECW) Act was introduced to Congress the same day and enacted by voice vote on March 31. Roosevelt issued Executive Order 6101 on April 5, 1933, which established the CCC organization and appointed a director, Robert Fechner, a former labor union official who served until 1939. The organization and administration of the CCC was a new experiment in operations for a federal government agency. The order directed that the program be supervised jointly by four government departments: Labor, which recruited the young men; War, which operated the camps; the Agriculture; and Interior, which organized and supervised the work projects. A CCC Advisory Council was composed of a representative from each of those departments. In addition, the Office of Education and Veterans Administration participated in the program. To overcome opposition from labor unions, which wanted no training programs started when so many of their members were unemployed, Roosevelt chose Robert Fechner, vice president of the International Association of Machinists and Aerospace Workers, as director of the Corps. William Green, head of the American Federation of Labor, was taken to the first camp to see that there was no job training involved beyond simple manual labor.
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# Civilian Conservation Corps
## U.S. Army {#u.s._army}
Officers from the U.S. Army were in charge of the camps, but there was no military training. The Chief of Staff of the United States Army, General Douglas MacArthur, was placed in charge of the program. Initially, about 3,800 of the Regular Army\'s 13,000 officers and 4,600 of its 120,000 enlisted men were assigned in the spring of 1933 to administer the CCC. The troops were pulled from just about every source possible, but usually from the Army's combat regiments and battalions, and Army instructors on duty with ROTC, Organized Reserve, and National Guard organizations. In at least one case each, district personnel were drawn from an engineer regiment and an Air Corps group. MacArthur soon said that the number of Regular Army personnel assigned to the CCC was affecting military readiness.
Only 575 Organized Reserve officers initially received orders for CCC duty. CCC tours were initially six months long, but were later lengthened to one year. In July 1933, the War Department ordered that Regular Army officers assigned as instructors with ROTC and Organized Reserve units be returned to their former duties. By the end of September 1933, the number of Regular officers on CCC duty had dropped to about 2,000 and the number of Reservists had increased to 2,200. By June 1934, only 400 Regular officers remained on CCC duty, and by October, Reserve officers had assumed command of almost all CCC companies and sub-districts. Effective on 1 January 1938, the War Department limited the number of Regular officers assigned to CCC duty to only 117.
Due to a ruling that Reserve officers on CCC duty had to have the same housing and subsistence benefits as Regular officers, President Roosevelt directed that all Reservists be relieved from CCC duty effective 1 July 1939. The changeover was complete by September 1939, but it was a change largely in name only because many of the Reservists merely took off their uniforms and continued their jobs with the CCC as civilians, albeit with lower pay.
The Army found numerous benefits in the program. Through the CCC, the Regular Army could assess the leadership performance of both Regular and Reserve officers. In mobilizing, clothing, feeding, and controlling thousands of men, the CCC provided lessons which the Army used in developing its wartime mobilization plans for training camps. When the draft began in 1940, the policy was to make CCC alumni corporals and sergeants. The CCC also provided command experience to Reserve officers, who normally interacted almost exclusively with other officers during training and did not have the chance to lead large numbers of enlisted men. Future Chief of Staff of the Army General George C. Marshall \"embraced\" the CCC, unlike many of his brother officers.
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# Civilian Conservation Corps
## History
An implicit goal of the CCC was to restore morale in an era of 25% unemployment for all men and much higher rates for poorly educated teenagers. Jeffrey Suzik argues in \"\'Building Better Men\': The CCC Boy and the Changing Social Ideal of Manliness\" that the CCC provided an ideology of manly outdoor work to counter the Depression, as well as cash to help the family budget. Through a regime of heavy manual labor, civic and political education, and an all-male living and working environment, the CCC tried to build \"better men\" who would be economically independent and self-reliant. By 1939, there was a shift in the ideal from the hardy manual worker to the highly trained citizen soldier ready for war.
### Early years, 1933--1937 {#early_years_19331937}
thumb\|right\|upright=2\|A CCC map of the planned route of a parkway in Texas, drafted in 1934. The Corps worked in numerous parks throughout the state during the early 1930s, constructing everything from benches to highways.\|alt=A blue-grey map of a road, covered with assorted lines
The legislation and mobilization of the program occurred quite rapidly. Roosevelt made his request to Congress on March 21, 1933; the legislation was submitted to Congress the same day; Congress passed it by voice vote on March 31; Roosevelt signed it the same day, then issued an executive order on April 5 creating the agency, appointing Fechner its director, and assigning War Department corps area commanders to begin enrollment. The first CCC enrollee was selected April 8, and lists of unemployed men were subsequently supplied by state and local welfare and relief agencies for immediate enrollment. On April 17, the first camp, NF-1, Camp Roosevelt, was established at George Washington National Forest near Luray, Virginia. On June 18, the first of 161 soil erosion control camps was opened in Clayton, Alabama. By July 1, 1933, there were 1,463 working camps with 250,000 junior enrollees 18--25 years of age; 28,000 veterans; 14,000 Native Americans; and 25,000 adults in the Local Experienced Men (LEM) program.
### Enrollees
The typical CCC enrollee was a U.S. citizen, unmarried, unemployed male, 18--25 years of age. Normally his family was on local relief. Each enrollee volunteered and, upon passing a physical exam and/or a period of conditioning, was required to serve a minimum six-month period, with the option to serve as many as four periods, or up to two years if employment outside the Corps was not possible. Enrollees worked 40 hours per week over five days, sometimes including Saturdays if poor weather dictated. In return they received \$30 per month (`{{Inflation|US|30|1933|r=-1|fmt=eq}}`{=mediawiki}) with a compulsory allotment of \$25 (about `{{Inflation|US|25
|1933|r=-1|fmt=eq}}`{=mediawiki}) sent to a family dependent, as well as housing, food, clothing, and medical care.
#### Veterans Conservation Corps {#veterans_conservation_corps}
Following the second Bonus Army march on Washington, D.C., President Roosevelt amended the CCC program on May 11, 1933, to include work opportunities for veterans. Veteran qualifications differed from the junior enrollee; one needed to be certified by the Veterans Administration by an application. They could be any age, and married or single as long as they were in need of work. Veterans were generally assigned to entire veteran camps. Enrollees were eligible for the following \"rated\" positions to help with camp administration: senior leader, mess steward, storekeeper and two cooks; assistant leader, company clerk, assistant educational advisor and three second cooks. These men received additional pay ranging from \$36 to \$45 per month depending on their rating.
### Camps
Each CCC camp was located in the area of particular conservation work to be performed and organized around a complement of up to 200 civilian enrollees in a designated numbered \"company\" unit. The CCC camp was a temporary community in itself, structured to have barracks (initially Army tents) for 50 enrollees each, officer/technical staff quarters, medical dispensary, mess hall, recreation hall, educational building, lavatory and showers, technical/administrative offices, tool room/blacksmith shop and motor pool garages.
The company organization of each camp had a dual-authority supervisory staff: firstly, Department of War personnel or Reserve officers (until July 1, 1939), a \"company commander\" and junior officer, who were responsible for overall camp operation, logistics, education and training; and secondly, ten to fourteen technical service civilians, including a camp \"superintendent\" and \"foreman\", employed by either the Departments of Interior or Agriculture, responsible for the particular fieldwork. Also included in camp operation were several non-technical supervisor LEMs, who provided knowledge of the work at hand, \"lay of the land,\" and paternal guidance for inexperienced enrollees. Enrollees were organized into work detail units called \"sections\" of 25 men each, according to the barracks they resided in. Each section had an enrollee \"senior leader\" and \"assistant leader\" who were accountable for the men at work and in the barracks.
### Work classifications {#work_classifications}
The CCC performed 300 types of work projects in nine approved general classifications:
1. Structural improvements: bridges, fire lookout towers, service buildings
2. Transportation: truck trails, minor roads, foot trails and airfields
3. Erosion control: check dams, terracing, and vegetable covering
4. Flood control: irrigation, drainage, dams, ditching, channel work, riprapping
5. Forest culture: tree planting, fire prevention, fire pre-suppression, firefighting, insect and disease control
6. Landscape and recreation: public camp and picnic ground development, lake and pond site clearing and development
7. Range: stock driveways, elimination of predatory animals
8. Wildlife: stream improvement, fish stocking, food and cover planting
9. Miscellaneous: emergency work, surveys, mosquito control
The responses to this seven-month experimental conservation program were enthusiastic. On October 1, 1933, Director Fechner was directed to arrange for the second period of enrollment. By January 1934, 300,000 men were enrolled. In July 1934, this cap was increased by 50,000 to include men from Midwest states that had been affected by drought. The temporary tent camps had also developed to include wooden barracks. An education program had been established, emphasizing job training and literacy.
Approximately 55% of enrollees were from rural communities, a majority of which were non-farm; 45% came from urban areas. Level of education for the enrollee averaged 3% illiterate; 38% had less than eight years of school; 48% did not complete high school; and 11% were high school graduates. At the time of entry, 70% of enrollees were malnourished and poorly clothed. Few had work experience beyond occasional odd jobs. Peace was maintained by the threat of \"dishonorable discharge\". \"This is a training station; we\'re going to leave morally and physically fit to lick \'Old Man Depression,\'\" boasted the newsletter, *Happy Days,* of a North Carolina camp.
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# Civilian Conservation Corps
## History
### African American people {#african_american_people}
Because of the power of conservative Solid South white Democrats in Congress, who insisted on racial segregation, most New Deal programs were racially segregated; African American and white people rarely worked alongside each other. At this time, all the states of the South had passed legislation imposing racial segregation and, since the turn of the century, laws and constitutional provisions that disenfranchised most African Americans; they were excluded from formal politics. Because of discrimination by white officials at the local and state levels, African Americans in the South did not receive as many benefits as white people from New Deal programs.
In the first few weeks of operation, CCC camps in the North were integrated. By July 1935, however, all camps in the United States were segregated. Enrollment peaked at the end of 1935, when there were 500,000 men in 2,600 camps in operation in every state. All received equal pay and housing. Black leaders lobbied to secure leadership roles. Adult white men held the major leadership roles in all the camps. Director Fechner refused to appoint Black adults to any supervisory positions except that of education director in the all-Black camps.
### Indian Division {#indian_division}
The CCC operated a separate division for members of federally recognized tribes: the \"Indian Emergency Conservation Work Division\" (IECW or CCC-ID). Native men from reservations worked on roads, bridges, clinics, shelters, and other public works near their reservations. Although they were organized as groups classified as camps, no permanent camps were established for Native Americans. Instead, organized groups moved with their families from project to project and were provided with an additional rental allowance. The CCC often provided the only paid work, as many reservations were in remote rural areas. Enrollees had to be between the ages of 17 and 35.
During 1933, about half the male heads of households on the Sioux reservations in South Dakota were employed by the CCC-ID. With grants from the Public Works Administration (PWA), the Indian Division built schools and conducted a road-building program in and around many reservations to improve infrastructure. The mission was to reduce erosion and improve the value of Indian lands. Crews built dams of many types on creeks, then sowed grass on the eroded areas from which the damming material had been taken. They built roads and planted shelter-belts on federal lands. The steady income helped participants regain self-respect, and many used the funds to improve their lives. John Collier, the federal Commissioner of Indian Affairs and Daniel Murphy, the director of the CCC-ID, both based the program on Indian self-rule and the restoration of tribal lands, governments, and cultures. The next year, Congress passed the Indian Reorganization Act of 1934, which ended allotments and helped preserve tribal lands, and encouraged tribes to re-establish self-government.
Collier said of the CCC-Indian Division, \"no previous undertaking in Indian Service has so largely been the Indians\' own undertaking\". Educational programs trained participants in gardening, stock raising, safety, native arts, and some academic subjects. IECW differed from other CCC activities in that it explicitly trained men in skills to be carpenters, truck drivers, radio operators, mechanics, surveyors, and technicians. With the passage of the National Defense Vocational Training Act of 1941, enrollees began participating in defense-oriented training. The government paid for the classes and after students completed courses and passed a competency test, guaranteed automatic employment in defense work. A total of 85,000 Native Americans were enrolled in this training. This proved valuable social capital for the 24,000 alumni who later served in the military and the 40,000 who left the reservations for city jobs supporting the war effort.
### Expansion, 1935--1936 {#expansion_19351936}
Responding to public demand to alleviate unemployment, Congress approved the Emergency Relief Appropriation Act of 1935, on April 8, 1935, which included continued funding for the CCC program through March 31, 1937. The age limit was expanded to 17--28 to include more men. April 1, 1935, to March 31, 1936, was the period of greatest activity and work accomplished by the CCC program. Enrollment peaked at 505,782 in about 2,900 camps by August 31, 1935, followed by a reduction to 350,000 enrollees in 2,019 camps by June 30, 1936. During this period the public response to the CCC program was overwhelmingly popular. A Gallup poll of April 18, 1936, asked: \"Are you in favor of the CCC camps?\"; 82% of respondents said \"yes\", including 92% of Democrats and 67% of Republicans.
### Change of purpose, 1937--1938 {#change_of_purpose_19371938}
On June 28, 1937, the Civilian Conservation Corps was legally established and transferred from its original designation as the Emergency Conservation Work program. Funding was extended for three more years by Public Law No. 163, 75th Congress, effective July 1, 1937. Congress changed the age limits to 17--23 years old and changed the requirement that enrollees be on relief to \"not regularly in attendance at school, or possessing full-time employment.\" The 1937 law mandated the inclusion of vocational and academic training for a minimum of 10 hours per week. Students in school were allowed to enroll during summer vacation. During this period, the CCC forces contributed to disaster relief following 1937 floods in New York, Vermont, and the Ohio and Mississippi river valleys, and response and clean-up after the 1938 hurricane in New England.
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# Civilian Conservation Corps
## History
### From conservation to defense, 1939--1940 {#from_conservation_to_defense_19391940}
In 1939 Congress ended the independent status of the CCC, transferring it to the control of the Federal Security Agency. The National Youth Administration, U.S. Employment Service, the Office of Education, and the Works Progress Administration also had some responsibilities. About 5,000 reserve officers serving in the camps were affected, as they were transferred to federal Civil Service, and military ranks and titles were eliminated. Despite the loss of overt military leadership in the camps by July 1940, with war underway in Europe and Asia, the government directed an increasing number of CCC projects to resources for national defense. It developed infrastructure for military training facilities and forest protection. By 1940 the CCC was no longer wholly a relief agency, was rapidly losing its non-military character, and it was becoming a system for work-training, as its ranks had become increasingly younger and inexperienced.
### Decline and disbandment 1941--1942 {#decline_and_disbandment_19411942}
Although the CCC was probably the most popular New Deal program, it never was authorized as a permanent agency. The program was reduced in scale as the Depression waned and employment opportunities improved. After conscription began in 1940, fewer eligible young men were available. Following the attack on Pearl Harbor in December 1941, the Roosevelt administration directed all federal programs to emphasize the war effort. Most CCC work, except for wildland firefighting, was shifted onto U.S. military bases to help with construction.
The CCC disbanded one year earlier than planned, as the 77th United States Congress ceased funding it. Operations were formally concluded at the end of the federal fiscal year on June 30, 1942. The end of the CCC program and closing of the camps involved arrangements to leave the incomplete work projects in the best possible state, the separation of about 1,800 appointed employees, the transfer of CCC property to the War and Navy Departments and other agencies, and the preparation of final accountability records. Liquidation of the CCC was ordered by Congress by the Labor-Federal Security Appropriation Act (56 Stat. 569) on July 2, 1942, and virtually completed on June 30, 1943. Liquidation appropriations for the CCC continued through April 20, 1948.
Some former CCC sites in good condition were reactivated from 1941 to 1947 as Civilian Public Service camps where conscientious objectors performed \"work of national importance\" as an alternative to military service. Other camps were used to hold Japanese, German and Italian Americans interned under the Western Defense Command\'s Enemy Alien Control Program, as well as Axis prisoners of war. Most of the Japanese American internment camps were built by the people held there. After the CCC disbanded, the federal agencies responsible for public lands organized their own seasonal fire crews, modeled after the CCC. These have performed a firefighting function formerly done by the CCC and provided the same sort of outdoor work experience for young people. Approximately 47 young men have died while in this line of duty.
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# Civilian Conservation Corps
## Museums
- Civilian Conservation Corps Museum at DeSoto State Park, Fort Payne, Alabama
- Civilian Conservation Corps Museum and Memorial, at Monte Sano State Park, Huntsville, Alabama
- Colossal Cave Mountain Park, Vail, Arizona
- Conservation Corps State Museum at Camp San Luis Obispo, San Luis Obispo, California
- North East States Civilian Conservation Corps Museum, Camp Conner, Stafford, Connecticut
- Florida Civilian Conservation Corps Museum at Highlands Hammock State Park, Sebring, Florida
- Civilian Conservation Corps Museum, Vogel State Park, Blairsville, Georgia
- Civilian Conservation Corps Camp in Kokeʻe State Park, Waimea, Kauai County, Hawaii
- Starved Rock State Park (CCC Section in the visitors\' center) Oglesby, Illinois
- Black Hawk State Historic Site, Rock Island, Illinois (The Refectory, located in the east end of Watch Tower Lodge houses a permanent exhibit on the Civilian Conservation Corps.)
- Iowa Civilian Conservation Corps Museum at Backbone State Park, Strawberry Point, Iowa
- Houghton\'s Pond, Blue Hills Reservation, Milton, Massachusetts
- Michigan Civilian Conservation Corps Museum, Roscommon, Michigan
- Bear Brook State Park Civilian Conservation Corps (CCC) Camp Historic District, Allenstown, New Hampshire
- New York State Civilian Conservation Corps Museum at Gilbert Lake State Park, New Lisbon, New York
- Masker Museum at Promised Land State Park, Greentown, Pennsylvania
- Lou and Helen Adams Civilian Conservation Corps Museum, Parker Dam State Park, Huston Township, Clearfield County, Pennsylvania
- Civilian Conservation Corps Museum at Lake Greenwood State Recreation Area, Ninety Six, South Carolina
- Civilian Conservation Corps Museum at Pocahontas State Park, Chesterfield, Virginia
- Civilian Conservation Corps Legacy, Edinburg, Virginia
- Civilian Conservation Corps Museum, Rhinelander, Wisconsin
- West Virginia CCC Museum, Harrison County, West Virginia
- Civilian Conservation Corps Museum, Guernsey State Park, Guernsey, Wyoming
- James F. Justin Civilian Conservation Corps Museum
- Civilian Conservation Corps History Center at the Minnesota Discovery Center Museum in Chisholm Minnesota
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# Civilian Conservation Corps
## Notable alumni and administrators {#notable_alumni_and_administrators}
- David \"Stringbean\" Akeman, enrollee, country music singer
- Norman Borlaug, leader, agronomist, Nobel Peace Prize recipient
- Raymond Burr, enrollee, actor
- Borden Deal, enrollee
- Hutton Gibson, author
- Archie Green, enrollee, folklorist
- Henry Gurke, enrollee
- Ralph Hauenstein. Army officer in charge of camp
- Hubert D. Humphreys, historian
- Aldo Leopold, former technical forester, ecologist, environmentalist
- Stanley Makowski, enrollee
- Walter Matthau, enrollee, actor
- Robert Mitchum, enrollee, actor
- Archie Moore, enrollee, the Light Heavyweight Boxing Champion of the World
- Stan Musial, enrollee, professional baseball player
- Edward R. Roybal, enrollee, politician
- Red Schoendienst, enrollee, baseball player/manager
- Dan White, enrollee, American actor in vaudeville, theater, radio, film and television
- Conrad L. Wirth, U.S. administrator, National Park Service supervisor of CCC Program
- Chuck Yeager, enrollee, test pilot
- Alvin C. York, a project superintendent
## Statues
In several cities where CCC workers worked, statues were erected to commemorate them.
## In media {#in_media}
- *Pride of the Bowery* (1940), the fourth movie in the East Side Kid series, is a movie about friendship, trouble, and boxing at a CCC camp.
- *The American Experience* PBS series showcased documentaries on American history; it portrayed the life in Civilian Conservation Corps in 2009, in the first episode of Season 22.
- Jeanette Ingold\'s novel *Hitch* (2012) is a young adult book about a teenager in the CCC.
## Inspired programs {#inspired_programs}
The CCC program was never officially terminated. Congress provided funding for closing the remaining camps in 1942 with the equipment being reallocated. It became a model for conservation programs that were implemented in the period after World War II. Present-day corps are national, state, and local programs that engage primarily youth and young adults (ages 16--25) in community service, training, and educational activities. The nation\'s approximately 113 corps programs operate in 41 of the 50 states and Washington, D.C. During 2004, they enrolled more than 23,000 young people. The Corps Network, known originally as the National Association of Service and Conservation Corps (NASCC), works to expand and enhance corps-type programs throughout the country. The Corps Network began in 1985 when the nation\'s first 24 Corps directors banded together to secure an advocate at the federal level and a repository of information on how best to start and manage a corps. Early financial assistance from the Ford, Hewlett and Mott Foundations was critical to establishing the association.
Similar active programs in the United States are: the National Civilian Community Corps, part of the AmeriCorps program, a team-based national service program in which young adults ages 18--26 spend 10 months working for non-profit and government organizations; and the Civilian Conservation Corps, USA, (CCCUSA) managed by its president, Thomas Hark, in 2016. Hark, his co-founder Mike Rama, currently the Deputy Director of the Corporate Eco Forum (CEF) founded by M. R. Rangaswami, and their team of strategic advisors have reimagined the federal Civilian Conservation Corps program of the 1930s as a private, locally governed, national social franchise. The goal of this recently established CCCUSA is to enroll a million young people annually, building a core set of values in each enrollee, who will then become the catalyst in their own communities and states to create a more civil society and stronger nation.
### Student Conservation Association {#student_conservation_association}
The CCC program became a model for the creation of team-based national service youth conservation programs such as the Student Conservation Association (SCA). The SCA, founded in 1959, is a nonprofit organization that offers conservation internships and summer trail crew opportunities to more than 4,000 people each year.
### California Conservation Corps {#california_conservation_corps}
In 1976, Governor of California Jerry Brown established the California Conservation Corps. This program had many similar characteristics - residential centers, high expectations for participation, and emphasis on hard work on public lands. Young adults from different backgrounds were recruited for a term of one year. Corps members attended a training session called the Corpsmember Orientation Motivation Education and Training (COMET) program before being assigned to one of the various centers. Project work is also similar to the original CCC of the 1930s - work on public forests, state and federal parks.
### Nevada Conservation Corps {#nevada_conservation_corps}
The Nevada Conservation Corps is a non-profit organization that partners with public land management agencies such as the Bureau of Land Management, United States Forest Service, National Park Service, and Nevada State Parks to complete conservation and restoration projects throughout Nevada. Conservation work includes fuel reductions through thinning, constructing and maintaining trails, invasive species removal, and performing biological surveys. The Nevada Conservation Corps was created through the Great Basin Institute and is part of the AmeriCorps program.
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# Civilian Conservation Corps
## Inspired programs {#inspired_programs}
### Minnesota Conservation Corps {#minnesota_conservation_corps}
Conservation Corps Minnesota & Iowa provides environmental stewardship and service-learning opportunities to youth and young adults while accomplishing conservation, natural resource management projects and emergency response work through its Young Adult Program and the Summer Youth Program. These programs emphasize the development of job and life skills by conservation and community service work.
### Montana Conservation Corps {#montana_conservation_corps}
The Montana Conservation Corps (MCC) is a non-profit organization with a mission to equip young people with the skills and values to be vigorous citizens who improve their communities and environment. Collectively, MCC crews contribute more than 90,000 work hours each year. The MCC was established in 1991 by Montana\'s Human Resource Development Councils in Billings, Bozeman and Kalispell. Originally, it was a summer program for disadvantaged youth, although it has grown into an AmeriCorps-sponsored non-profit organization with six regional offices that serve Montana, Idaho, Wyoming, North Dakota, and South Dakota. All regions also offer Montana YES (Youth Engaged in Service) summer programs for teenagers who are 14 to 17 years old.
### Texas Conservation Corps {#texas_conservation_corps}
Established in 1995, Environmental Corps, now Texas Conservation Corps (TxCC), is an American YouthWorks program which allows youth, ages 17 to 28, to contribute to the restoration and preservation of parks and public lands in Texas. The only conservation corps in Texas, TxcC is a nonprofit corporation based in Austin, Texas, which serves the entire state. Their work ranges from disaster relief to trail building to habitat restoration. TxCC has done projects in national, state, and city parks.
### Washington Conservation Corps {#washington_conservation_corps}
The Washington Conservation Corps (WCC) is a sub-agency of the Washington State Department of Ecology. It employs men and women 18 to 25 years old in a program to protect and enhance Washington\'s natural resources. WCC is a part of the AmeriCorps program.
### Vermont Youth Conservation Corps {#vermont_youth_conservation_corps}
The Vermont Youth Conservation Corps (VYCC) is a non-profit, youth service and education organization that hires Corps Members, aged 16--24, to work on high-priority conservation projects in Vermont. Through these work projects, Corps Members develop a strong work ethic, strengthen their leadership skills, and learn how to take personal responsibility for their actions. VYCC Crews work at VT State Parks, U.S. Forest Service Campgrounds, in local communities, and throughout the state\'s backcountry. The VYCC has also given aid to a similar program in North Carolina, which is currently in its infancy.
### Youth Conservation Corps {#youth_conservation_corps}
The Youth Conservation Corps is a youth conservation program present in federal lands around the country. The program gives youth aged 13--17 the opportunity to participate in conservation projects in a team setting. YCC programs are available in land managed by the National Park Service, the Forest Service, and the Fish and Wildlife Service. Projects can last up to 10 weeks and typically run over the summer. Some YCC programs are residential, meaning the participants are given housing on the land they work on. Projects may necessitate youth to camp in backcountry settings in order to work on trails or campsites. Most require youth to commute daily or house youth for only a few days a week. Youth are typically paid for their work. YCC programs contribute to the maintenance of public lands and instill a value for hard work and the outdoors in those who participate.
### Conservation Legacy {#conservation_legacy}
Conservation Legacy is a non-profit employment, job training, and education organization with locations across the United States including Arizona Conservation Corps in Tucson and Flagstaff, Arizona; Conservation Corps New Mexico in Las Cruces, New Mexico; Southwest Conservation Corps in Durango and Salida, Colorado; and Southeast Conservation Corps in Chattanooga, Tennessee. Conservation Legacy also operates an AmeriCorps VISTA team serving to improve the environment and economies of historic mining communities in the American West and Appalachia. Conservation Legacy also hosts the Environmental Stewards Program - providing internships with federal, state, municipal and NGO land management agencies nationwide. Conservation Legacy formed as a merger of the Southwest Youth Corps, San Luis Valley Youth Corps, The Youth Corps of Southern Arizona, and Coconino Rural Environmental Corps.
Conservation Legacy engages young adults ages 14 to 26 and U.S. military veterans of all ages in personal and professional development experiences involving conservation projects on public lands. Corp members live, work, and learn in teams of six to eight for terms of service ranging from 3 months to 1 year.
### Sea Ranger Service {#sea_ranger_service}
The Sea Ranger Service is a social enterprise, based in Netherlands, that has taken its inspiration from the Civilian Conservation Corps in running a permanent youth training program, supported by veterans, to manage ocean areas and carry out underwater landscape restoration. Unemployed youths are trained up as Sea Rangers during a bootcamp and subsequently offered full-time employment to manage and regenerate Marine Protected Areas and aid ocean conservation. The Sea Ranger Service works in close cooperation with the Dutch government and national maritime authorities.
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# Civilian Conservation Corps
## Inspired programs {#inspired_programs}
### Aina Corps {#aina_corps}
The Aina Corps performed environmental restoration work in Hawaii in 2020, funded by the CARES Act.
### American Climate Corps {#american_climate_corps}
The American Climate Corps is an organization created by the Joe Biden administration. It was inspired by the Civilian Conservation Corps and aims to mobilize young people to stop climate change, while giving them a job at the same time. It is financed from the Inflation Reduction Act and the federal budget. It should have 9,000 members by the end of June 2024. Later, the number of participants should rise to 20,000
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# Caribbean Sea
The **Caribbean Sea** is a sea of the North Atlantic Ocean in the tropics of the Western Hemisphere, located south of the Gulf of Mexico and southwest of the Sargasso Sea. It is bounded by the Greater Antilles to the north from Cuba to Puerto Rico, the Lesser Antilles to the east from the Virgin Islands to Trinidad and Tobago, South America to the south from the Venezuelan coastline to the Colombian coastline, and Central America and the Yucatán Peninsula to the west from Panama to Mexico. The geopolitical region around the Caribbean Sea, including the numerous islands of the West Indies and adjacent coastal areas in the mainland of the Americas, is known as the Caribbean.
The Caribbean Sea is one of the largest seas on Earth and has an area of about 2754000 km2. The sea\'s deepest point is the Cayman Trough, between the Cayman Islands and Jamaica, at 7686 m below sea level. The Caribbean coastline has many gulfs and bays: the Gulf of Gonâve, the Gulf of Venezuela, the Gulf of Darién, Golfo de los Mosquitos, the Gulf of Paria and the Gulf of Honduras.
The Caribbean Sea has the world\'s second-largest barrier reef, the Mesoamerican Barrier Reef. It runs 1000 km along the Mexico, Belize, Guatemala, and Honduras coasts.
## History
The name *Caribbean* derives from the Caribs, one of the region\'s dominant native people at the time of European contact during the late-15th century. After Christopher Columbus landed in The Bahamas in 1492 and later discovered some of the islands in the Caribbean, the Spanish term *Antillas* applied to the lands; stemming from this, the *Sea of the Antilles* became a common alternative name for the \"Caribbean Sea\" in various European languages. Spanish dominance in the region remained undisputed during the first century of European colonization.
From the 16th century, Europeans visiting the Caribbean region distinguished the \"South Sea\" (the Pacific Ocean south of the isthmus of Panama) from the \"North Sea\" (the Caribbean Sea north of the same isthmus).
The Caribbean Sea had been unknown to the populations of Eurasia until after 1492, when Christopher Columbus sailed into Caribbean waters to find a sea route to Asia. At that time, the Americas were generally unknown to most Europeans, although they had been visited in the 10th century by the Vikings. After Columbus\'s discovery of the islands, the area was quickly colonized by several Western cultures (initially Spain, then later England, the Dutch Republic, France, Courland and Denmark). After colonization of the Caribbean islands, the Caribbean Sea became a busy area for European-based marine trading and transports. The commerce eventually attracted pirates such as Samuel Bellamy and Blackbeard.
the area is home to 22 island territories and borders 12 continental countries.
## Extent
The International Hydrographic Organization defines the limits of the Caribbean Sea as follows:
:
: *On the North.* In the Windward Channel -- a line joining Caleta Point (74°15′W) in Cuba and Pearl Point (19°40′N) in Haiti. In the Mona Passage -- a line joining Cape Engaño and the extreme of Agujereada (18 31 N 67 08 W display=inline) in Puerto Rico.
```{=html}
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:
: *Eastern limits.* From Point San Diego (Puerto Rico) northward along the meridian thereof (65°39′W) to the 100-fathom line, thence eastward and southward, in such a manner that all islands, shoals and narrow waters of the Lesser Antilles are included in the Caribbean Sea as far as but not including Trinidad. From before Trinidad to Baja Point (9 32 N 61 0 W display=inline) in Venezuela.
Although Trinidad and Tobago and Barbados are on the same continental shelf, they are considered to be in the Atlantic Ocean rather than in the Caribbean Sea.
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# Caribbean Sea
## Geology
The Caribbean Sea is an oceanic sea on the Caribbean Plate. The Caribbean Sea is separated from the ocean by several island arcs of various ages. The youngest stretches from the Lesser Antilles to the Virgin Islands to north of Trinidad and Tobago, which is in the Atlantic. This arc was formed by a collision of the South American Plate with the Caribbean Plate. It included active and extinct volcanoes such as Mount Pelee, the Quill on Sint Eustatius in the Caribbean Netherlands, La Soufrière in Saint Vincent and the Grenadines and Morne Trois Pitons on Dominica. The larger islands in the northern part of the sea Cuba, Hispaniola, Jamaica and Puerto Rico lie on an older island arc.
thumb\|upright=1.4\|The shaded relief map of the Caribbean Sea and the Gulf of Mexico area
The geological age of the Caribbean Sea is estimated to be 160 million to 180 million years and was formed by a horizontal fracture called Pangaea that split the supercontinent in the Mesozoic Era. It is assumed the proto-Caribbean basin existed in the Devonian period and, in the early Carboniferous movement of Gondwana to the north and its convergence with the Euramerica basin, decreased in size. The next stage of the Caribbean Sea\'s formation began in the Triassic. Powerful rifting led to the formation of narrow troughs, stretching from modern Newfoundland to the Gulf of Mexico\'s west coast, forming siliciclastic sedimentary rocks. In the early Jurassic due to powerful marine transgression, water broke into the current area of the Gulf of Mexico, creating a vast shallow pool. Deep basins emerged in the Caribbean during the Middle Jurassic rifting. The emergence of the basins marked the beginning of the Atlantic Ocean and contributed to the destruction of Pangaea at the end of the late Jurassic. During the Cretaceous, the Caribbean acquired a shape close to today\'s. In the early Paleogene, due to marine regression, the Caribbean became separated from the Gulf of Mexico and the Atlantic Ocean by the lands of Cuba and Haiti. The Caribbean remained like this for most of the Cenozoic until the Holocene, when rising water levels of the oceans restored communication with the Atlantic Ocean.
The Caribbean\'s floor is composed of suboceanic sediments of deep red clay in the deep basins and troughs. On continental slopes and ridges, calcareous silts are found. Clay minerals have likely been deposited by the mainland river Orinoco and the Magdalena River. Deposits on the bottom of the Caribbean Sea and the Gulf of Mexico have thicknesses of about 1 km. Upper sedimentary layers relate to the period from the Mesozoic to the Cenozoic (250 million years ago) and the lower layers from the Paleozoic to the Mesozoic.
thumb\|upright=1.6\|Caribbean plate tectonics
The Caribbean seafloor is divided into five basins separated from one another by underwater ridges and mountain ranges. Atlantic Ocean water enters the Caribbean through the *Anegada Passage* between the Lesser Antilles and the Virgin Islands and the *Windward Passage* between Cuba and Haiti. The Yucatán Channel between Mexico and Cuba links the Gulf of Mexico with the Caribbean. The deepest points of the sea lie in Cayman Trough, with depths reaching approximately 7686 m. Despite that, the Caribbean Sea is considered a relatively shallow sea compared with other bodies of water. The pressure of the South American Plate to the east of the Caribbean causes the region of the Lesser Antilles to have high volcanic activity, and a very serious eruption of Mount Pelée in 1902 caused many casualties.
The Caribbean seafloor is also the home of two oceanic trenches: the Cayman Trench and the Puerto Rico Trench, which put the area at a high risk of earthquakes. Underwater earthquakes pose a threat of generating tsunamis, which could have devastating effects on the Caribbean islands. Scientific data reveals that during the past 500 years, the area has seen a dozen earthquakes above 7.5 magnitude. Most recently, a 7.1-magnitude earthquake struck Haiti, on January 12, 2010.
- List of islands in the Caribbean
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# Caribbean Sea
## Oceanography
The hydrology of the sea has a high level of homogeneity. Annual variations in monthly average water temperatures at the surface do not exceed 3 C-change. In the past 50 years, the Caribbean has gone through three stages: cooling until 1974, a cold phase with peaks during 1974--1976 and 1984--1986, and, finally, a warming phase with an increase in temperature of 0.6 C-change per year. Virtually all temperature extremes were associated with the phenomena of El Niño and La Niña. The salinity of the seawater is about 3.6%, and its density is 1023.5 -. The surface water color is blue-green to green.
The Caribbean\'s depth in its wider basins and deep-water temperatures are similar to those of the Atlantic Ocean. Atlantic deepwater is thought to spill into the Caribbean and contribute to the general deepwater of its sea. The surface water (30 m; 100 ft) acts as an extension of the northern Atlantic as the Guiana Current and part of the North Equatorial Current enter the sea on the east. On the western side of the sea, the trade winds influence a northerly current, which causes an upwelling and a rich fishery near Yucatán.
## Ecology
The Caribbean is the home of about 9% of the world\'s coral reefs, covering about 50000 km2, most of which are located off the Caribbean islands and the Central American coast. Among them, the Belize Barrier Reef stands out, with an area of 963 km2, which was declared a World Heritage Site in 1996. It forms part of the Great Mayan Reef (also known as the MBRS) and, being more than 1000 km in length, is the world\'s second longest. It runs along the Caribbean coasts of Mexico, Belize, Guatemala and Honduras.
Since 2005, unusually warm Caribbean waters have been increasingly threatening the coral reefs. Coral reefs support some of the most diverse marine habitats in the world, but they are fragile ecosystems. When tropical waters become unusually warm for extended periods of time, microscopic plants called zooxanthellae, which are symbiotic partners living within the coral polyp tissues, die off. These plants provide food for the corals and give them their color. The result of the death and dispersal of these tiny plants is called coral bleaching and can lead to the devastation of large areas of reef. More than 42% of corals are completely bleached, and 95% are experiencing some type of whitening. Historically, the Caribbean is thought to contain 14% of the world\'s coral reefs.
thumb\|center\|upright=2.75\|The Belize Barrier Reef viewed from the International Space Station in 2016
The habitats supported by the reefs are critical to such tourist activities as fishing and scuba diving, and they provide an annual economic value to Caribbean nations of US\$3.1--4.6 billion. Continued destruction of the reefs could severely damage the region\'s economy. The *Convention for the Protection and Development of the Marine Environment of the Wider Caribbean Region* came into effect in 1986 to protect the various endangered marine life of the Caribbean by forbidding human activities that would advance the continued destruction of such marine life in various areas. Currently, the convention has been ratified by 15 countries. Also, several charitable organizations have been formed to preserve Caribbean marine life, such as Sea Turtle Conservancy, which seeks to study and protect sea turtles while educating about them.
In connection with the foregoing, the Institute of Marine Sciences and Limnology of the National Autonomous University of Mexico conducted a regional study funded by the Department of Technical Cooperation of the International Atomic Energy Agency, in which specialists from 11 Latin American countries (Colombia, Costa Rica, Cuba, the Dominican Republic, Guatemala, Haiti, Honduras, Mexico, Nicaragua, Panama, and Venezuela) plus Jamaica participated. The study\'s findings indicate that heavy metals such as mercury, arsenic, and lead have been identified in the coastal zone of the Caribbean Sea. Analysis of toxic metals and hydrocarbons is based on investigation of coastal sediments that have accumulated less than 50 meters deep during the past 150 years. Project results were presented in Vienna at the forum \"Water Matters\", and the 2011 General Conference of that multilateral organization.
After the Mediterranean Sea, the Caribbean Sea is the second-most-polluted sea. Pollution in the form of up to 300,000 tonnes of solid garbage dumped into the Caribbean Sea each year is progressively endangering marine ecosystems, wiping out species, and harming the livelihoods of local people, who rely primarily on tourism and fishing.
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# Caribbean Sea
## Climate
The climate of the Caribbean is driven by the low latitude and tropical ocean currents that run through it. The principal ocean current is the North Equatorial Current, which enters the region from the tropical Atlantic. The climate of the area is tropical, varying from tropical rainforest in some areas to tropical savanna in others. There are also some locations that are arid climates with considerable drought in some years.
Rainfall varies with elevation, size, and water currents (cool upwelling keep the ABC islands arid). Warm, moist trade winds blow consistently from the east, creating both rainforest and semi-arid climates across the region. The tropical rainforest climates include lowland areas near the Caribbean Sea from Costa Rica north to Belize, as well as the Dominican Republic and Puerto Rico, while the more seasonal dry tropical savanna climates are found in Cuba, northern Venezuela, and southern Yucatán, Mexico. Arid climates are found along the extreme northern coast of Venezuela out to the islands including Aruba and Curaçao, as well as the northern tip of Yucatán
Tropical cyclones are a threat to the nations that rim the Caribbean Sea. While landfalls are infrequent, the resulting loss of life and property damage makes them a significant hazard to life in the Caribbean. Tropical cyclones that impact the Caribbean often develop off the West coast of Africa and make their way west across the Atlantic Ocean toward the Caribbean, while other storms develop in the Caribbean itself. The Caribbean hurricane season as a whole lasts from June through November, with the majority of hurricanes occurring during August and September. On average around nine tropical storms form each year, with five reaching hurricane strength. According to the National Hurricane Center 385 hurricanes occurred in the Caribbean between 1494 and 1900.
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# Caribbean Sea
## Flora and fauna {#flora_and_fauna}
The region has a high level of biodiversity and many species are endemic to the Caribbean.
### Vegetation
The vegetation of the region is mostly tropical but differences in topography, soil and climatic conditions increase species diversity. Where there are porous limestone terraced islands these are generally poor in nutrients. It is estimated that 13,000 species of plants grow in the Caribbean of which 6,500 are endemic. For example, guaiac wood (*Guaiacum officinale*), the flower of which is the national flower of Jamaica and the Bayahibe rose (*Pereskia quisqueyana*) which is the national flower of the Dominican Republic and the ceiba which is the national tree of both Puerto Rico and Guatemala. The mahogany is the national tree of the Dominican Republic and Belize. The caimito (*Chrysophyllum cainito*) grows throughout the Caribbean. In coastal zones there are coconut palms and in lagoons and estuaries are found thick areas of black mangrove and red mangrove (*Rhizophora mangle*).
In shallow water flora and fauna is concentrated around coral reefs where there is little variation in water temperature, purity and salinity. Leeward sides of lagoons provide areas of growth for sea grasses. Turtle grass (*Thalassia testudinum*) is common in the Caribbean as is manatee grass (*Syringodium filiforme*) which can grow together as well as in fields of single species at depths up to 20 m. Another type shoal grass (*Halodule wrightii*) grows on sand and mud surfaces at depths of up to 5 m. In brackish water of harbours and estuaries at depths less than 2.5 m widgeongrass (*Ruppia maritima*) grows. Representatives of three species belonging to the genus *Halophila*, (*Halophila baillonii*, *Halophila engelmannii* and *Halophila decipiens*) are found at depths of up to 30 m except for *Halophila engelmani* which does not grow below 5 m and is confined to the Bahamas, Florida, the Greater Antilles and the western part of the Caribbean. *Halophila baillonii* has been found only in the Lesser Antilles.
### Fauna
Marine biota in the region have representatives of both the Indian and Pacific oceans which were caught in the Caribbean before the emergence of the Isthmus of Panama four million years ago. In the Caribbean Sea there are around 1,000 documented species of fish, including sharks (bull shark, tiger shark, silky shark and Caribbean reef shark), flying fish, giant oceanic manta ray, angel fish, spotfin butterflyfish, parrotfish, Atlantic Goliath grouper, tarpon and moray eels. Throughout the Caribbean there is industrial catching of lobster and sardines (off the coast of Yucatán Peninsula).
There are 90 species of mammals in the Caribbean including sperm whales, humpback whales and dolphins. The island of Jamaica is home to seals and manatees. The Caribbean monk seal which lived in the Caribbean is considered extinct. Solenodons and hutias are mammals found only in the Caribbean; only one extant species is not endangered.
There are 500 species of reptiles (94% of which are endemic). Islands are inhabited by some endemic species such as rock iguanas and American crocodile. The blue iguana, endemic to the island of Grand Cayman, is endangered. The green iguana is invasive to Grand Cayman. The Mona ground iguana which inhabits the island of Mona, Puerto Rico, is endangered. The rhinoceros iguana from the island of Hispaniola which is shared between Haiti and the Dominican Republic is also endangered. The region has several types of sea turtle (loggerhead, green turtle, hawksbill, leatherback turtle, Atlantic ridley and olive ridley). Some species are threatened with extinction. Their populations have been greatly reduced since the 17th century -- the number of green turtles has declined from 91 million to 300,000 and hawksbill turtles from 11 million to less than 30,000 by 2006.
All 170 of the amphibian species that live in the region are endemic. The habitats of almost all members of the toad family, poison dart frogs, tree frogs and leptodactylidae (a type of frog) are limited to only one island. The golden coqui is in serious threat of extinction.
In the Caribbean, 600 species of birds have been recorded, of which 163 are endemic such as todies, Fernandina\'s flicker and palmchat. The American yellow warbler is found in many areas, as is the green heron. Of the endemic species 48 are threatened with extinction including the Puerto Rican amazon, and the Zapata wren. According to BirdLife International in 2006 in Cuba 29 species of bird were in danger of extinction and two species officially extinct. The black-fronted piping guan is endangered. The Antilles along with Central America lie in the flight path of migrating birds from North America so the size of populations is subject to seasonal fluctuations. Parrots and bananaquits are found in forests. Over the open sea can be seen frigatebirds and tropicbirds.
## Economy and human activity {#economy_and_human_activity}
The Caribbean region has seen a significant increase in human activity since the colonization period. The sea is one of the largest oil production areas in the world, producing approximately 170 million `{{clarify|text=tons|reason=metric tonnes, long tons or short tons?|date=June 2017}}`{=mediawiki} per year. The area also generates a large fishing industry for the surrounding countries, accounting for 500000 t of fish a year.
Human activity in the area also accounts for a significant amount of pollution. The Pan American Health Organization estimated in 1993 that only about 10% of the sewage from the Central American and Caribbean Island countries is properly treated before being released into the sea.
The region has been famous for its rum production - the drink is first mentioned in records from Barbados in around 1650, although it was likely to have been produced beforehand across the other islands.
The Caribbean region supports a large tourism industry. The Caribbean Tourism Organization calculates that about 12 million people a year visit the area, including (in 1991--1992) about 8 million cruise ship tourists. Tourism based upon scuba diving and snorkeling on coral reefs of many Caribbean islands makes a major contribution to their economies.
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# Caribbean Sea
## Gallery
<File:Jamaica> sunrise.JPG\|Sunrise over the south beach of Jamaica <File:Village> Gran Roque.jpg\|Los Roques Archipelago, Venezuela <File:Marie> Galante - on the beach (407689602).jpg\|Marie Galante, Guadeloupe <File:Strand> Auf Klein Curacao (213574363).jpeg\|Beach of Curaçao <File:Mona> Island, Puerto Rico.JPG\|Mona Island, Puerto Rico <File:Palm> Beach, Aruba (4901990402).jpg\|Palm Beach, Aruba <File:Beach> Of Cayo Coco (108034377).jpeg\|Cayo Coco, Cuba <File:Grosse> Roche Beach in Saint-Marc, Haiti.jpg\|Saint-Marc, Haiti <File:Sunset> over the Caribbean Sea
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# Colin Maclaurin
**Colin Maclaurin** (`{{IPAc-en|m|ə|ˈ|k|l|ɔː|r|ə|n}}`{=mediawiki}; *Cailean MacLabhruinn*;`{{pronunciation needed|date=September 2024}}`{=mediawiki} February 1698 -- 14 June 1746) was a Scottish mathematician who made important contributions to geometry and algebra. He is also known for being a child prodigy and holding the record for being the youngest professor. The Maclaurin series, a special case of the Taylor series, is named after him.
Owing to changes in orthography since that time (his name was originally rendered as **M\'Laurine**), his surname is alternatively written **MacLaurin.**
## Early life {#early_life}
Maclaurin was born in Kilmodan, Argyll. His father, John Maclaurin, minister of Glendaruel, died when Maclaurin was in infancy, and his mother died before he reached nine years of age. He was then educated under the care of his uncle, Daniel Maclaurin, minister of Kilfinan. A child prodigy, he entered university at age 11.
## Academic career {#academic_career}
At eleven, Maclaurin, a child prodigy at the time, entered the University of Glasgow. He graduated Master of Arts three years later by defending a thesis on *the Power of Gravity,* and remained at Glasgow to study divinity until he was 19, when he was elected professor of mathematics in a ten-day competition at Marischal College and University in Aberdeen. This record as the world\'s youngest professor endured until March 2008, when the record was officially given to Alia Sabur.
In the vacations of 1719 and 1721, Maclaurin went to London, where he became acquainted with Isaac Newton, Benjamin Hoadly, Samuel Clarke, Martin Folkes, and other philosophers. He was admitted as a member of the Royal Society.
In 1722, having provided a locum for his class at Aberdeen, he travelled on the Continent as tutor to George Hume, the son of Alexander Hume, 2nd Earl of Marchmont. During their time in Lorraine, he wrote his essay on the percussion of bodies (*Demonstration des loix du choc des corps*), which gained the prize of the Royal Academy of Sciences in 1724. Upon the death of his pupil at Montpellier, Maclaurin returned to Aberdeen.
In 1725, Maclaurin was appointed deputy to the mathematical professor at the University of Edinburgh, James Gregory (brother of David Gregory and nephew of the esteemed James Gregory), upon the recommendation of Isaac Newton. On 3 November of that year Maclaurin succeeded Gregory, and went on to raise the character of that university as a school of science. Newton was so impressed with Maclaurin that he had offered to pay his salary himself.
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# Colin Maclaurin
## Contributions to mathematics {#contributions_to_mathematics}
Maclaurin used Taylor series to characterize maxima, minima, and points of inflection for infinitely differentiable functions in his *Treatise of Fluxions*. Maclaurin attributed the series to Brook Taylor, though the series was known before to Newton and Gregory, and in special cases to Madhava of Sangamagrama in fourteenth century India. Nevertheless, Maclaurin received credit for his use of the series, and the Taylor series expanded around 0 is sometimes known as the *Maclaurin series*. Maclaurin also made significant contributions to the gravitation attraction of ellipsoids, a subject that furthermore attracted the attention of d\'Alembert, A.-C. Clairaut, Euler, Laplace, Legendre, Poisson and Gauss. Maclaurin showed that an oblate spheroid was a possible equilibrium in Newton\'s theory of gravity. The subject continues to be of scientific interest, and Nobel Laureate Subramanyan Chandrasekhar dedicated a chapter of his book *Ellipsoidal Figures of Equilibrium* to Maclaurin spheroids. Maclaurin corresponded extensively with Clairaut, Maupertuis, and d\'Ortous de Mairan.
Independently from Euler and using the same methods, Maclaurin discovered the Euler--Maclaurin formula. He used it to sum powers of arithmetic progressions, derive Stirling\'s formula, and to derive the Newton--Cotes numerical integration formulas which includes Simpson\'s rule as a special case.
Maclaurin contributed to the study of elliptic integrals, reducing many intractable integrals to problems of finding arcs for hyperbolas. His work was continued by d\'Alembert and Euler, who gave a more concise approach.
In his *Treatise of Algebra* (Ch. XII, Sect 86), published in 1748 two years after his death, Maclaurin proved a rule for solving square linear systems in the cases of 2 and 3 unknowns, and discussed the case of 4 unknowns. This publication preceded by two years Cramer\'s publication of a generalization of the rule to *n* unknowns, now commonly known as Cramer\'s rule.
## Personal life {#personal_life}
In 1733, Maclaurin married Anne Stewart, the daughter of Walter Stewart, the Solicitor General for Scotland, by whom he had seven children. His eldest son John Maclaurin studied law, was a Senator of the College of Justice, and became Lord Dreghorn; he was also joint founder of the Royal Society of Edinburgh.
Maclaurin actively opposed the Jacobite rising of 1745 and superintended the operations necessary for the defence of Edinburgh against the Highland army. Maclaurin compiled a diary of his exertions against the Jacobites, both within and without the city. When the Highland army entered the city, however, he fled to York, where he was invited to stay by the Archbishop of York.
On his journey south, Maclaurin fell from his horse, and the fatigue, anxiety, and cold to which he was exposed on that occasion laid the foundations of dropsy. He returned to Edinburgh after the Jacobite army marched south, but died soon after his return.
He is buried at Greyfriars Kirkyard, Edinburgh. The simple table stone is inscribed simply \"C. M. Nat MDCXCVIII Ob MDCCXLVI\" and stands close to the south-west corner of the church but is supplemented by a more wordy memorial on the outer wall of the church.
The mathematician and former MIT President Richard Cockburn Maclaurin was from the same family.
The Maclaurin Society (MacSoc), the Mathematics and Statistics Society at Glasgow University, is named in his honour.
Colin MacLaurin Road within Edinburgh University\'s King\'s Buildings complex is named in his honour.
## Notable works {#notable_works}
Some of his important works are:
- *Geometria Organica* -- 1720
- *De Linearum Geometricarum Proprietatibus* -- 1720
- *Treatise on Fluxions* -- 1742 (763 pages in two volumes. The first systematic exposition of Newton\'s methods.)
- *Treatise of Algebra* -- 1748 (two years after his death.)
- *Account of Newton\'s Discoveries* -- Incomplete upon his death and published in 1748
-
Colin Maclaurin was the name used for the new Mathematics and Actuarial Mathematics and Statistics Building at Heriot-Watt University, Edinburgh.
<File:MacLaurin> - Treatise of algebra, 1753 - 1429142.jpg\|French edition of the *Treatise of algebra* (1748) <File:MacLaurin>, Colin -- Account of Sir Isaac Newton\'s philosophical discoveries, 1749 -- BEIC 743185
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# Concord, Michigan
**Concord** is a village in Jackson County in the U.S. state of Michigan. The population was 1,050 at the 2010 census. The village is within Concord Township.
Settled in 1831, much of the village\'s downtown area is designated as part of the Concord Village Historic District. The village is located along M-60 about 15 mi southwest of Jackson.
## History
Concord first received a post office in 1836. It was incorporated as a village in 1871.
The Michigan Historical Center operates a museum in Concord called the Mann House. The Mann House is an excellent example of typical middle-class domestic architecture of the early 1880s and features the family\'s sleigh and buggy as well as Jackson\'s Michigan State Prison made furniture.
## Government
Concord is a general-law village incorporated within the Concord Township.
## Geography
According to the United States Census Bureau, the village has a total area of 1.62 sqmi, of which 1.50 sqmi is land and 0.12 sqmi (7.41%) is water.
The village is located within the T3S R3W survey township.
## Demographics
Concord Community Schools (Enrollment 900) participate in Class C and Division 4 of MHSAA athletics. Their teams are known as the Yellow Jackets and play in the Big 8 Conference. The schools\' colors are purple and gold. The boys\' cross country and track & field teams both claimed MHSAA State Championships during the 2009--10 school year, as well as back to back MHSAA State Championships in the 2014 and 2015 school years. In 2011 and 2012, the boys cross country team won back to back MHSAA State Championships.
### 2010 census
As of the census of 2010, there were 1,050 people, 412 households, and 293 families living in the village. The population density was 700.0 PD/sqmi. There were 484 housing units at an average density of 322.7 /sqmi. The racial makeup of the village was 99.0% White, 0.3% African American, 0.1% Native American, 0.1% Asian, 0.1% from other races, and 0.4% from two or more races. Hispanic or Latino of any race were 1.8% of the population.
There were 412 households, of which 33.7% had children under the age of 18 living with them, 54.6% were married couples living together, 10.4% had a female householder with no husband present, 6.1% had a male householder with no wife present, and 28.9% were non-families. 25.7% of all households were made up of individuals, and 12.6% had someone living alone who was 65 years of age or older. The average household size was 2.55 and the average family size was 3.02.
The median age in the village was 40.9 years. 26% of residents were under the age of 18; 8.3% were between the ages of 18 and 24; 21.4% were from 25 to 44; 28.7% were from 45 to 64; and 15.6% were 65 years of age or older. The gender makeup of the village was 48.9% male and 51.1% female.
### 2000 census {#census_1}
As of the census of 2000, there were 1,101 people, 428 households, and 308 families living in the village. The population density was 748.4 PD/sqmi. There were 499 housing units at an average density of 339.2 /sqmi. The racial makeup of the village was 97.91% White, 0.09% Black or African American, 0.27% Native American, 0.73% Asian, 0.64% from other races, and 0.36% from two or more races. 0.82% of the population were Hispanic or Latino of any race.
There were 428 households, out of which 34.3% had children under the age of 18 living with them, 57.9% were married couples living together, 10.7% had a female householder with no husband present, and 28.0% were non-families. 25.0% of all households were made up of individuals, and 10.5% had someone living alone who was 65 years of age or older. The average household size was 2.57 and the average family size was 3.09.
In the village, the population was spread out, with 28.1% under the age of 18, 7.5% from 18 to 24, 28.2% from 25 to 44, 21.7% from 45 to 64, and 14.5% who were 65 years of age or older. The median age was 37 years. For every 100 females, there were 92.8 males. For every 100 females age 18 and over, there were 87.7 males.
The median income for a household in the village was \$46,500, and the median income for a family was \$54,531. Males had a median income of \$39,167 versus \$23,594 for females. The per capita income for the village was \$19,348. About 4.8% of families and 5.2% of the population were below the poverty line, including 3.1% of those under age 18 and 7.1% of those age 65 or over
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# Complete metric space
In mathematical analysis, a metric space `{{mvar|M}}`{=mediawiki} is called **complete** (or a **Cauchy space**) if every Cauchy sequence of points in `{{mvar|M}}`{=mediawiki} has a limit that is also in `{{mvar|M}}`{=mediawiki}.
Intuitively, a space is complete if there are no \"points missing\" from it (inside or at the boundary). For instance, the set of rational numbers is not complete, because e.g. $\sqrt{2}$ is \"missing\" from it, even though one can construct a Cauchy sequence of rational numbers that converges to it (see further examples below). It is always possible to \"fill all the holes\", leading to the *completion* of a given space, as explained below.
## Definition
**Cauchy sequence**
A sequence $x_1, x_2, x_3, \ldots$ of elements from $X$ of a metric space $(X, d)$ is called **Cauchy** if for every positive real number $r > 0$ there is a positive integer $N$ such that for all positive integers $m, n > N,$ $d(x_m, x_n) < r.$
**Complete space**
A metric space $(X, d)$ is **complete** if any of the following equivalent conditions are satisfied:
1. Every Cauchy sequence in $X$ converges in $X$ (that is, has a limit that is also in $X$).
2. Every decreasing sequence of non-empty closed subsets of $X,$ with diameters tending to 0, has a non-empty intersection: if $F_n$ is closed and non-empty, $F_{n+1} \subseteq F_n$ for every $n,$ and $\operatorname{diam}\left(F_n\right) \to 0,$ then there is a unique point $x \in X$ common to all sets $F_n.$
## Examples
The space $\Q$ of rational numbers, with the standard metric given by the absolute value of the difference, is not complete. Consider for instance the sequence defined by
$$x_1 = 1\;$$ and $\;x_{n+1} = \frac{x_n}{2} + \frac{1}{x_n}.$ This is a Cauchy sequence of rational numbers, but it does not converge towards any rational limit: If the sequence did have a limit $x,$ then by solving $x = \frac{x}{2} + \frac{1}{x}$ necessarily $x^2 = 2,$ yet no rational number has this property. However, considered as a sequence of real numbers, it does converge to the irrational number $\sqrt{2}$.
The open interval `{{open-open|0,1}}`{=mediawiki}, again with the absolute difference metric, is not complete either. The sequence defined by $x_n = \tfrac{1}{n}$ is Cauchy, but does not have a limit in the given space. However the closed interval `{{closed-closed|0,1}}`{=mediawiki} is complete; for example the given sequence does have a limit in this interval, namely zero.
The space $\R$ of real numbers and the space $\C$ of complex numbers (with the metric given by the absolute difference) are complete, and so is Euclidean space $\R^n$, with the usual distance metric. In contrast, infinite-dimensional normed vector spaces may or may not be complete; those that are complete are Banach spaces. The space C`{{closed-closed|''a'', ''b''}}`{=mediawiki} of continuous real-valued functions on a closed and bounded interval is a Banach space, and so a complete metric space, with respect to the supremum norm. However, the supremum norm does not give a norm on the space C`{{open-open|''a'', ''b''}}`{=mediawiki} of continuous functions on `{{open-open|''a'', ''b''}}`{=mediawiki}, for it may contain unbounded functions. Instead, with the topology of compact convergence, C`{{open-open|''a'', ''b''}}`{=mediawiki} can be given the structure of a Fréchet space: a locally convex topological vector space whose topology can be induced by a complete translation-invariant metric.
The space **Q**~*p*~ of *p*-adic numbers is complete for any prime number $p.$ This space completes **Q** with the *p*-adic metric in the same way that **R** completes **Q** with the usual metric.
If $S$ is an arbitrary set, then the set `{{math|''S''<sup>'''N'''</sup>}}`{=mediawiki} of all sequences in $S$ becomes a complete metric space if we define the distance between the sequences $\left(x_n\right)$ and $\left(y_n\right)$ to be $\tfrac{1}{N}$ where $N$ is the smallest index for which $x_N$ is distinct from $y_N$ or $0$ if there is no such index. This space is homeomorphic to the product of a countable number of copies of the discrete space $S.$
Riemannian manifolds which are complete are called geodesic manifolds; completeness follows from the Hopf--Rinow theorem.
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# Complete metric space
## Some theorems {#some_theorems}
Every compact metric space is complete, though complete spaces need not be compact. In fact, a metric space is compact if and only if it is complete and totally bounded. This is a generalization of the Heine--Borel theorem, which states that any closed and bounded subspace $S$ of `{{math|'''R'''<sup>''n''</sup>}}`{=mediawiki} is compact and therefore complete.
Let $(X, d)$ be a complete metric space. If $A \subseteq X$ is a closed set, then $A$ is also complete. Let $(X, d)$ be a metric space. If $A \subseteq X$ is a complete subspace, then $A$ is also closed.
If $X$ is a set and $M$ is a complete metric space, then the set $B(X, M)$ of all bounded functions `{{mvar|f}}`{=mediawiki} from `{{mvar|X}}`{=mediawiki} to $M$ is a complete metric space. Here we define the distance in $B(X, M)$ in terms of the distance in $M$ with the supremum norm $d(f, g) \equiv \sup\{d[f(x), g(x)]: x \in X\}$
If $X$ is a topological space and $M$ is a complete metric space, then the set $C_b(X, M)$ consisting of all continuous bounded functions $f : X \to M$ is a closed subspace of $B(X, M)$ and hence also complete.
The Baire category theorem says that every complete metric space is a Baire space. That is, the union of countably many nowhere dense subsets of the space has empty interior.
The Banach fixed-point theorem states that a contraction mapping on a complete metric space admits a fixed point. The fixed-point theorem is often used to prove the inverse function theorem on complete metric spaces such as Banach spaces.
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# Complete metric space
## Completion
For any metric space *M*, it is possible to construct a complete metric space *M′* (which is also denoted as $\overline{M}$), which contains *M* as a dense subspace. It has the following universal property: if *N* is any complete metric space and *f* is any uniformly continuous function from *M* to *N*, then there exists a unique uniformly continuous function *f′* from *M′* to *N* that extends *f*. The space *M*\' is determined up to isometry by this property (among all complete metric spaces isometrically containing *M*), and is called the *completion* of *M*.
The completion of *M* can be constructed as a set of equivalence classes of Cauchy sequences in *M*. For any two Cauchy sequences $x_{\bull} = \left(x_n\right)$ and $y_{\bull} = \left(y_n\right)$ in *M*, we may define their distance as $d\left(x_{\bull}, y_{\bull}\right) = \lim_n d\left(x_n, y_n\right)$
(This limit exists because the real numbers are complete.) This is only a pseudometric, not yet a metric, since two different Cauchy sequences may have the distance 0. But \"having distance 0\" is an equivalence relation on the set of all Cauchy sequences, and the set of equivalence classes is a metric space, the completion of *M*. The original space is embedded in this space via the identification of an element *x* of *M*\' with the equivalence class of sequences in *M* converging to *x* (i.e., the equivalence class containing the sequence with constant value *x*). This defines an isometry onto a dense subspace, as required. Notice, however, that this construction makes explicit use of the completeness of the real numbers, so completion of the rational numbers needs a slightly different treatment.
Cantor\'s construction of the real numbers is similar to the above construction; the real numbers are the completion of the rational numbers using the ordinary absolute value to measure distances. The additional subtlety to contend with is that it is not logically permissible to use the completeness of the real numbers in their own construction. Nevertheless, equivalence classes of Cauchy sequences are defined as above, and the set of equivalence classes is easily shown to be a field that has the rational numbers as a subfield. This field is complete, admits a natural total ordering, and is the unique totally ordered complete field (up to isomorphism). It is *defined* as the field of real numbers (see also Construction of the real numbers for more details). One way to visualize this identification with the real numbers as usually viewed is that the equivalence class consisting of those Cauchy sequences of rational numbers that \"ought\" to have a given real limit is identified with that real number. The truncations of the decimal expansion give just one choice of Cauchy sequence in the relevant equivalence class.
For a prime $p,$ the `{{math|''p''}}`{=mediawiki}-adic numbers arise by completing the rational numbers with respect to a different metric.
If the earlier completion procedure is applied to a normed vector space, the result is a Banach space containing the original space as a dense subspace, and if it is applied to an inner product space, the result is a Hilbert space containing the original space as a dense subspace.
## Topologically complete spaces {#topologically_complete_spaces}
Completeness is a property of the *metric* and not of the *topology*, meaning that a complete metric space can be homeomorphic to a non-complete one. An example is given by the real numbers, which are complete but homeomorphic to the open interval `{{open-open|0,1}}`{=mediawiki}, which is not complete.
In topology one considers *completely metrizable spaces*, spaces for which there exists at least one complete metric inducing the given topology. Completely metrizable spaces can be characterized as those spaces that can be written as an intersection of countably many open subsets of some complete metric space. Since the conclusion of the Baire category theorem is purely topological, it applies to these spaces as well.
Completely metrizable spaces are often called *topologically complete*. However, the latter term is somewhat arbitrary since metric is not the most general structure on a topological space for which one can talk about completeness (see the section Alternatives and generalizations). Indeed, some authors use the term *topologically complete* for a wider class of topological spaces, the completely uniformizable spaces.
A topological space homeomorphic to a separable complete metric space is called a Polish space.
## Alternatives and generalizations {#alternatives_and_generalizations}
Since Cauchy sequences can also be defined in general topological groups, an alternative to relying on a metric structure for defining completeness and constructing the completion of a space is to use a group structure. This is most often seen in the context of topological vector spaces, but requires only the existence of a continuous \"subtraction\" operation. In this setting, the distance between two points $x$ and $y$ is gauged not by a real number $\varepsilon$ via the metric $d$ in the comparison $d(x, y) < \varepsilon,$ but by an open neighbourhood $N$ of $0$ via subtraction in the comparison $x - y \in N.$
A common generalisation of these definitions can be found in the context of a uniform space, where an entourage is a set of all pairs of points that are at no more than a particular \"distance\" from each other.
It is also possible to replace Cauchy *sequences* in the definition of completeness by Cauchy *nets* or Cauchy filters. If every Cauchy net (or equivalently every Cauchy filter) has a limit in $X,$ then $X$ is called complete. One can furthermore construct a completion for an arbitrary uniform space similar to the completion of metric spaces. The most general situation in which Cauchy nets apply is Cauchy spaces; these too have a notion of completeness and completion just like uniform spaces
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# Chain reaction
A **chain reaction** is a sequence of reactions where a reactive product or by-product causes additional reactions to take place. In a chain reaction, positive feedback leads to a self-amplifying chain of events.
Chain reactions are one way that systems which are not in thermodynamic equilibrium can release energy or increase entropy in order to reach a state of higher entropy. For example, a system may not be able to reach a lower energy state by releasing energy into the environment, because it is hindered or prevented in some way from taking the path that will result in the energy release. If a reaction results in a small energy release making way for more energy releases in an expanding chain, then the system will typically collapse explosively until much or all of the stored energy has been released.
A macroscopic metaphor for chain reactions is thus a snowball causing a larger snowball until finally an avalanche results (\"snowball effect\"). This is a result of stored gravitational potential energy seeking a path of release over friction. Chemically, the equivalent to a snow avalanche is a spark causing a forest fire. In nuclear physics, a single stray neutron can result in a prompt critical event, which may finally be energetic enough for a nuclear reactor meltdown or (in a bomb) a nuclear explosion.
Another metaphor for a chain reaction is the domino effect, named after the act of domino toppling, where the simple action of toppling one domino leads to all dominoes eventually toppling, even if they are significantly larger.
Numerous chain reactions can be represented by a mathematical model based on Markov chains.
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# Chain reaction
## Chemical chain reactions {#chemical_chain_reactions}
### History
In 1913, the German chemist Max Bodenstein first put forth the idea of chemical chain reactions. If two molecules react, not only molecules of the final reaction products are formed, but also some unstable molecules which can further react with the parent molecules with a far larger probability than the initial reactants. (In the new reaction, further unstable molecules are formed besides the stable products, and so on.)
In 1918, Walther Nernst proposed that the photochemical reaction between hydrogen and chlorine is a chain reaction in order to explain what is known as the *quantum yield* phenomena. This means that one photon of light is responsible for the formation of as many as 10^6^ molecules of the product HCl. Nernst suggested that the photon dissociates a Cl~2~ molecule into two Cl atoms which each initiate a long chain of reaction steps forming HCl.
In 1923, Danish and Dutch scientists J. A. Christiansen and Hendrik Anthony Kramers, in an analysis of the formation of polymers, pointed out that such a chain reaction need not start with a molecule excited by light, but could also start with two molecules colliding violently due to thermal energy as previously proposed for initiation of chemical reactions by van\' t Hoff.
Christiansen and Kramers also noted that if, in one link of the reaction chain, two or more unstable molecules are produced, the reaction chain would branch and grow. The result is in fact an exponential growth, thus giving rise to explosive increases in reaction rates, and indeed to chemical explosions themselves. This was the first proposal for the mechanism of chemical explosions.
A quantitative chain chemical reaction theory was created later on by Soviet physicist Nikolay Semyonov in 1934. Semyonov shared the Nobel Prize in 1956 with Sir Cyril Norman Hinshelwood, who independently developed many of the same quantitative concepts.
### Typical steps {#typical_steps}
The main types of steps in chain reaction are of the following types.
- Initiation (formation of active particles or chain carriers, often free radicals, in either a thermal or a photochemical step)
- Propagation (may comprise several elementary steps in a cycle, where the active particle through reaction forms another active particle which continues the reaction chain by entering the next elementary step). In effect the active particle serves as a catalyst for the overall reaction of the propagation cycle. Particular cases are:
- chain branching (a propagation step where one active particle enters the step and two or more are formed);
- chain transfer (a propagation step in which the active particle is a growing polymer chain which reacts to form an inactive polymer whose growth is terminated and an active small particle (such as a radical), which may then react to form a new polymer chain).
- Termination (elementary step in which the active particle loses its activity; e. g. by recombination of two free radicals).
The *chain length* is defined as the average number of times the propagation cycle is repeated, and equals the overall reaction rate divided by the initiation rate.
Some chain reactions have complex rate equations with fractional order or mixed order kinetics.
### Detailed example: the hydrogen-bromine reaction {#detailed_example_the_hydrogen_bromine_reaction}
The reaction H~2~ + Br~2~ → 2 HBr proceeds by the following mechanism:
- Initiation
: Br~2~ → 2 Br• (thermal) or Br~2~ + hν → 2 Br• (photochemical)
: each Br atom is a free radical, indicated by the symbol \"•\" representing an unpaired electron.
- Propagation (here a cycle of two steps)
: Br• + H~2~ → HBr + H•
: H• + Br~2~ → HBr + Br•
: the sum of these two steps corresponds to the overall reaction H~2~ + Br~2~ → 2 HBr, with catalysis by Br• which participates in the first step and is regenerated in the second step.
- Retardation (inhibition)
: H• + HBr → H~2~ + Br•
: this step is specific to this example, and corresponds to the first propagation step in reverse.
- Termination 2 Br• → Br~2~
: recombination of two radicals, corresponding in this example to initiation in reverse.
As can be explained using the steady-state approximation, the thermal reaction has an initial rate of fractional order (3/2), and a complete rate equation with a two-term denominator (mixed-order kinetics).
### Further chemical examples {#further_chemical_examples}
- The reaction 2 H~2~ + O~2~ → 2 H~2~O provides an example of chain branching. The propagation is a sequence of two steps whose net effect is to replace an H atom by another H atom plus two OH radicals. This leads to an explosion under certain conditions of temperature and pressure.
- H• + O~2~ → •OH + •O•
- •O• + H~2~ → •OH + H•
- In chain-growth polymerization, the propagation step corresponds to the elongation of the growing polymer chain. Chain transfer corresponds to transfer of the activity from this growing chain, whose growth is terminated, to another molecule which may be a second growing polymer chain. For polymerization, the kinetic chain length defined above may differ from the degree of polymerization of the product macromolecule.
- Polymerase chain reaction, a technique used in molecular biology to amplify (make many copies of) a piece of DNA by *in vitro* enzymatic replication using a DNA polymerase.
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# Chain reaction
## Chemical chain reactions {#chemical_chain_reactions}
### Acetaldehyde pyrolysis and rate equation {#acetaldehyde_pyrolysis_and_rate_equation}
The pyrolysis (thermal decomposition) of acetaldehyde, CH~3~CHO (g) → CH~4~ (g) + CO (g), proceeds via the Rice-Herzfeld mechanism:
- Initiation (formation of free radicals):
: CH~3~CHO (g) → •CH~3~ (g) + •CHO (g) k~1~
The methyl and CHO groups are free radicals.
- Propagation (two steps):
: •CH~3~ (g) + CH~3~CHO (g) → CH~4~ (g) + •CH~3~CO (g) k~2~
This reaction step provides methane, which is one of the two main products.
: •CH~3~CO (g) → CO (g) + •CH~3~ (g) k~3~
The product •CH~3~CO (g) of the previous step gives rise to carbon monoxide (CO), which is the second main product.
The sum of the two propagation steps corresponds to the overall reaction CH~3~CHO (g) → CH~4~ (g) + CO (g), catalyzed by a methyl radical •CH~3~.
- Termination:
: •CH~3~ (g) + •CH~3~ (g) → C~2~H~6~ (g) k~4~
` This reaction is the only source of ``ethane`` (minor product) and it is concluded to be the main chain ending step.`
Although this mechanism explains the principal products, there are others that are formed in a minor degree, such as acetone (CH~3~COCH~3~) and propanal (CH~3~CH~2~CHO).
Applying the Steady State Approximation for the intermediate species CH~3~(g) and CH~3~CO(g), the rate law for the formation of methane and the order of reaction are found:
The rate of formation of the product methane is
$(1)... \frac{d\ce{[CH4]}}{dt} = k_2\ce{[CH3]} \ce{[CH3CHO]}$
For the intermediates
$(2)... \frac{d\ce{[CH_3]}}{dt} = k_1 \ce{[CH3CHO]} - k_2 \ce{[CH3]} \ce{[CH3CHO]} + k_3 \ce{[CH3CO]} - 2 k_4 \ce{[CH3]}^2 = 0$ and
$(3)... \frac{d\ce{[CH3CO]}}{dt} = k_2 \ce{[CH3]} \ce{[CH3CHO]} - k_3 \ce{[CH3CO]} = 0$
Adding (2) and (3), we obtain $k_1 \ce{[CH3CHO]} - 2 k_4 \ce{[CH3]}^2 = 0$
so that $(4)...\ce{[CH3]} = \frac{k_1}{2k_4}\ce{[CH3CHO]}^{1/2}$
Using (4) in (1) gives the rate law $(5) \frac{d\ce{[CH4]}}{dt} = \frac{k_1}{2k_4} k_2 \ce{[CH3CHO]}^{3/2}$, which is order 3/2 in the reactant CH~3~CHO.
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# Chain reaction
## Nuclear chain reactions {#nuclear_chain_reactions}
A *nuclear* chain reaction was proposed by Leo Szilard in 1933, shortly after the neutron was discovered, yet more than five years before nuclear fission was first discovered. Szilárd knew of *chemical* chain reactions, and he had been reading about an energy-producing nuclear reaction involving high-energy protons bombarding lithium, demonstrated by John Cockcroft and Ernest Walton, in 1932. Now, Szilárd proposed to use neutrons theoretically produced from certain nuclear reactions in lighter isotopes, to induce further reactions in light isotopes that produced more neutrons. This would in theory produce a chain reaction at the level of the nucleus. He did not envision fission as one of these neutron-producing reactions, since this reaction was not known at the time. Experiments he proposed using beryllium and indium failed.
Later, after fission was discovered in 1938, Szilárd immediately realized the possibility of using neutron-induced fission as the particular nuclear reaction necessary to create a chain-reaction, so long as fission also produced neutrons. In 1939, with Enrico Fermi, Szilárd proved this neutron-multiplying reaction in uranium. In this reaction, a neutron plus a fissionable atom causes a fission resulting in a larger number of neutrons than the single one that was consumed in the initial reaction. Thus was born the practical nuclear chain reaction by the mechanism of neutron-induced nuclear fission.
Specifically, if one or more of the produced neutrons themselves interact with other fissionable nuclei, and these also undergo fission, then there is a possibility that the macroscopic overall fission reaction will not stop, but continue throughout the reaction material. This is then a self-propagating and thus self-sustaining chain reaction. This is the principle for nuclear reactors and atomic bombs.
Demonstration of a self-sustaining nuclear chain reaction was accomplished by Enrico Fermi and others, in the successful operation of Chicago Pile-1, the first artificial nuclear reactor, in late 1942.
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# Chain reaction
## Electron avalanche in gases {#electron_avalanche_in_gases}
An electron avalanche happens between two unconnected electrodes in a gas when an electric field exceeds a certain threshold. Random thermal collisions of gas atoms may result in a few free electrons and positively charged gas ions, in a process called impact ionization. Acceleration of these free electrons in a strong electric field causes them to gain energy, and when they impact other atoms, the energy causes release of new free electrons and ions (ionization), which fuels the same process. If this process happens faster than it is naturally quenched by ions recombining, the new ions multiply in successive cycles until the gas breaks down into a plasma and current flows freely in a discharge.
Electron avalanches are essential to the dielectric breakdown process within gases. The process can culminate in corona discharges, streamers, leaders, or in a spark or continuous electric arc that completely bridges the gap. The process may extend huge sparks --- streamers in lightning discharges propagate by formation of electron avalanches created in the high potential gradient ahead of the streamers\' advancing tips. Once begun, avalanches are often intensified by the creation of photoelectrons as a result of ultraviolet radiation emitted by the excited medium\'s atoms in the aft-tip region. The extremely high temperature of the resulting plasma cracks the surrounding gas molecules and the free ions recombine to create new chemical compounds.
The process can also be used to detect radiation that initiates the process, as the passage of a single particles can be amplified to large discharges. This is the mechanism of a Geiger counter and also the visualization possible with a spark chamber and other wire chambers.
## Avalanche breakdown in semiconductors {#avalanche_breakdown_in_semiconductors}
An avalanche breakdown process can happen in semiconductors, which in some ways conduct electricity analogously to a mildly ionized gas. Semiconductors rely on free electrons knocked out of the crystal by thermal vibration for conduction. Thus, unlike metals, semiconductors become better conductors the higher the temperature. This sets up conditions for the same type of positive feedback---heat from current flow causes temperature to rise, which increases charge carriers, lowering resistance, and causing more current to flow. This can continue to the point of complete breakdown of normal resistance at a semiconductor junction, and failure of the device (this may be temporary or permanent depending on whether there is physical damage to the crystal). Certain devices, such as avalanche diodes, deliberately make use of the effect.
## Living organisms {#living_organisms}
Examples of chain reactions in living organisms include excitation of neurons in epilepsy and lipid peroxidation. In peroxidation, a lipid radical reacts with oxygen to form a peroxyl radical (L• + O~2~ → LOO•). The peroxyl radical then oxidises another lipid, thus forming another lipid radical (LOO• + L--H → LOOH + L•). A chain reaction in glutamatergic synapses is the cause of synchronous discharge in some epileptic seizures
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# Caddie
In golf, a **caddie** (or **caddy**) is a companion to the player, providing both practical support and strategic guidance on the course. Caddies are responsible for carrying the player's bag, managing clubs, and assisting with basic course maintenance like repairing divots and raking bunkers. Their role extends well beyond these physical tasks, going into emotional and behavioural moral support. Whether at local clubs, public courses, or prestigious tournaments---caddies offer valuable insight on course strategy, advising on everything from club selection to reading greens and evaluating weather conditions. They often serve as a steadying presence, offering encouragement and helping players maintain focus under pressure.
Caddies are trusted for their course knowledge, adaptability, and close understanding of a player's game, and their role is integral at every level of play. In professional and amateur golf alike, caddies often build lasting partnerships with players, developing a rapport that contributes to overall performance.
Other nicknames for the role are looper or jock.
## Etymology
The Scots word *caddie* or **cawdy** was derived in the 17th century from the French word *cadet* and originally meant a student military officer. It later came to refer to someone who did odd jobs. By the 19th century, it had come to mean someone who carried clubs for a golfer, or in its shortened form, cad, a man of disreputable behaviour.
## History
The first recorded use of a caddie was in Edinburgh in 1681 by the future James VII of Scotland when taking part in the first international golf contest.`{{Better source|reason=User-generated content |date=January 2023}}`{=mediawiki}
## Earnings
Caddies pay is variable and is usually based on an allocated percentage share of prize money. At a professional level, caddies work in a high level partnership with golfers, some work as contractors to individual players in events. In 2020, caddies on the PGA European Tour became eligible to earn bonuses through sponsors\' logos on their gear. In 2024, Golf Digest reported that Scottie Scheffler's caddie Ted Scott earned \$2.6 million over the season with the world number 1. Caddying fees range throughout courses across the world, however is a popular role for low handicap golfers which can provide opportunities to work with a variety of people.
## In popular culture {#in_popular_culture}
Caddies have been depicted in television, films, and books, including:
- *The Caddy*, a 1953 musical comedy film starring Dean Martin and Jerry Lewis
- *McAuslan in the Rough*, a 1974 short story by George MacDonald Fraser in which a disreputable Scottish soldier caddies for his regimental sergeant major
- *Caddyshack*, a 1980 comedy film featuring Bill Murray
- *Brown\'s Requiem*, a 1981 crime novel by James Ellroy, who worked as a caddie while writing his first books
- *The Legend of Bagger Vance*, a 2000 film based on the 1995 book by Steven Pressfield, *The Legend of Bagger Vance: A Novel of Golf and the Game of Life*, features Vance as an angelic caddie.
- *The Greatest Game Ever Played*, a 2005 film about 1913 US open where Francis Ouimet (Shia LaBeouf) wins with his caddie Eddie Lowery (Josh Flitter)
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# Stellar corona
*Pandoc failed*: ```
Error at (line 115, column 24):
unexpected 't'
{| class="wikitable" | title="Typical length of observable coronal features"
^
``
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# Planned economy
A **planned economy** is a type of economic system where investment, production and the allocation of capital goods takes place according to economy-wide economic plans and production plans. A planned economy may use centralized, decentralized, participatory or Soviet-type forms of economic planning. The level of centralization or decentralization in decision-making and participation depends on the specific type of planning mechanism employed.
Socialist states based on the Soviet model have used central planning, although a minority such as the former Socialist Federal Republic of Yugoslavia have adopted some degree of market socialism. Market abolitionist socialism replaces factor markets with direct calculation as the means to coordinate the activities of the various socially owned economic enterprises that make up the economy. More recent approaches to socialist planning and allocation have come from some economists and computer scientists proposing planning mechanisms based on advances in computer science and information technology.
Planned economies contrast with unplanned economies, specifically market economies, where autonomous firms operating in markets make decisions about production, distribution, pricing and investment. Market economies that use indicative planning are variously referred to as planned market economies, mixed economies and mixed market economies. A command economy follows an administrative-command system and uses Soviet-type economic planning which was characteristic of the former Soviet Union and Eastern Bloc before most of these countries converted to market economies. This highlights the central role of hierarchical administration and public ownership of production in guiding the allocation of resources in these economic systems.
## Overview
In the Hellenistic and post-Hellenistic world, \"compulsory state planning was the most characteristic trade condition for the Egyptian countryside, for Hellenistic India, and to a lesser degree the more barbaric regions of the Seleucid, the Pergamenian, the southern Arabian, and the Parthian empires\". Scholars have argued that the Incan economy was a flexible type of command economy, centered around the movement and utilization of labor instead of goods. One view of mercantilism sees it as involving planned economies.
The Soviet-style planned economy in Soviet Russia evolved in the wake of a continuing existing World War I war-economy as well as other policies, known as war communism (1918--1921), shaped to the requirements of the Russian Civil War of 1917--1923. These policies began their formal consolidation under an official organ of government in 1921, when the Soviet government founded Gosplan. However, the period of the New Economic Policy (c. 1921 to c. 1928) intervened before the planned system of regular five-year plans started in 1928. Leon Trotsky was one of the earliest proponents of economic planning during the NEP period. Trotsky argued that specialization, the concentration of production and the use of planning could \"raise in the near future the coefficient of industrial growth not only two, but even three times higher than the pre-war rate of 6% and, perhaps, even higher\". According to historian Sheila Fitzpatrick, the scholarly consensus was that Stalin appropriated the position of the Left Opposition on such matters as industrialisation and collectivisation.
After World War II (1939--1945) France and Great Britain practiced dirigisme -- government direction of the economy through non-coercive means. The Swedish government planned public-housing models in a similar fashion as urban planning in a project called Million Programme, implemented from 1965 to 1974. Some decentralized participation in economic planning occurred across Revolutionary Spain, most notably in Catalonia, during the Spanish Revolution of 1936.
### Relationship with socialism {#relationship_with_socialism}
In the May 1949 issue of the *Monthly Review* titled \"Why Socialism?\", Albert Einstein wrote:
> I am convinced there is only one way to eliminate these grave evils, namely through the establishment of a socialist economy, accompanied by an educational system which would be oriented toward social goals. In such an economy, the means of production are owned by society itself and are utilized in a planned fashion. A planned economy, which adjusts production to the needs of the community, would distribute the work to be done among all those able to work and would guarantee a livelihood to every man, woman, and child. The education of the individual, in addition to promoting his own innate abilities, would attempt to develop in him a sense of responsibility for his fellow-men in place of the glorification of power and success in our present society.
While socialism is not equivalent to economic planning or to the concept of a planned economy, an influential conception of socialism involves the replacement of capital markets with some form of economic planning in order to achieve *ex-ante* coordination of the economy. The goal of such an economic system would be to achieve conscious control over the economy by the population, specifically so that the use of the surplus product is controlled by the producers. The specific forms of planning proposed for socialism and their feasibility are subjects of the socialist calculation debate.
### Computational economic planning {#computational_economic_planning}
In 1959 Anatoly Kitov proposed a distributed computing system (Project \"Red Book\", *Красная книга*) with a focus on the management of the Soviet economy. Opposition from the Defence Ministry killed Kitov\'s plan.
In 1971 the socialist Allende administration of Chile launched Project Cybersyn to install a telex machine in every corporation and organization in the economy for the communication of economic data between firms and the government. The data was also fed into a computer-simulated economy for forecasting. A control room was built for real-time observation and management of the overall economy. The prototype-stage of the project showed promise when it was used to redirect supplies around a trucker\'s strike, but after CIA-backed Augusto Pinochet led a coup in 1973 that established a military dictatorship under his rule the program was abolished and Pinochet moved Chile towards a more liberalized market economy.
In their book *Towards a New Socialism* (1993), the computer scientist Paul Cockshott from the University of Glasgow and the economist Allin Cottrell from Wake Forest University claim to demonstrate how a democratically planned economy built on modern computer technology is possible and drives the thesis that it would be both economically more stable than the free-market economies and also morally desirable.
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# Planned economy
## Overview
### Cybernetics
The use of computers to coordinate production in an optimal fashion has been variously proposed for socialist economies. The Polish economist Oskar Lange (1904--1965) argued that the computer is more efficient than the market process at solving the multitude of simultaneous equations required for allocating economic inputs efficiently (either in terms of physical quantities or monetary prices).
In the Soviet Union, Anatoly Kitov had proposed to the Central Committee of the Communist Party of the Soviet Union a detailed plan for the re-organization of the control of the Soviet armed forces and of the Soviet economy on the basis of a network of computing centers in 1959. Kitov\'s proposal was rejected, as later was the 1962 OGAS economy management network project. Soviet cybernetician, Viktor Glushkov argued that his OGAS information network would have delivered a fivefold savings return for the Soviet economy over the first fifteen-year investment.
Salvador Allende\'s socialist government pioneered the 1970 Chilean distributed decision support system Project Cybersyn in an attempt to move towards a decentralized planned economy with the experimental viable system model of computed organisational structure of autonomous operative units through an algedonic feedback setting and bottom-up participative decision-making in the form of participative democracy by the Cyberfolk component.
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# Planned economy
## Central planning {#central_planning}
### Advantages
Supporters of a planned economy argue that the government can harness land, labor, and capital to serve the economic objectives of the state. Consumer demand can be restrained in favor of greater capital investment for economic development in a desired pattern. In international comparisons, supporters of a planned economy have said that state-socialist nations have compared favorably with capitalist nations in health indicators such as infant mortality and life expectancy. However, according to Michael Ellman, the reality of this, at least regarding infant mortality, varies depending on whether official Soviet or WHO definitions are used.
The state can begin building massive heavy industries at once in an underdeveloped economy without waiting years for capital to accumulate through the expansion of light industry and without reliance on external financing. This is what happened in the Soviet Union during the 1930s when the government forced the share of gross national income dedicated to private consumption down from 80% to 50%. As a result of this development, the Soviet Union experienced massive growth in heavy industry, with a concurrent massive contraction of its agricultural sector due to the labor shortage.
### Disadvantages
#### Economic instability {#economic_instability}
Studies of command economies of the Eastern Bloc in the 1950s and 1960s by both American and Eastern European economists found that contrary to the expectations of both groups they showed greater fluctuations in output than market economies during the same period.
#### Inefficient resource distribution {#inefficient_resource_distribution}
Critics of planned economies argue that planners cannot detect consumer preferences, shortages and surpluses with sufficient accuracy and therefore cannot efficiently co-ordinate production (in a market economy, a free price system is intended to serve this purpose). This difficulty was notably written about by economists Ludwig von Mises and Friedrich Hayek, who referred to subtly distinct aspects of the problem as the economic calculation problem and local knowledge problem, respectively. These distinct aspects were also present in the economic thought of Michael Polanyi.
Whereas the former stressed the theoretical underpinnings of a market economy to subjective value theory while attacking the labor theory of value, the latter argued that the only way to satisfy individuals who have a constantly changing hierarchy of needs and are the only ones to possess their particular individual\'s circumstances is by allowing those with the most knowledge of their needs to have it in their power to use their resources in a competing marketplace to meet the needs of the most consumers most efficiently. This phenomenon is recognized as spontaneous order. Additionally, misallocation of resources would naturally ensue by redirecting capital away from individuals with direct knowledge and circumventing it into markets where a coercive monopoly influences behavior, ignoring market signals. According to Tibor Machan, \"\[w\]ithout a market in which allocations can be made in obedience to the law of supply and demand, it is difficult or impossible to funnel resources with respect to actual human preferences and goals\".
Historian Robert Vincent Daniels regarded the Stalinist period to represent an abrupt break with Lenin\'s government in terms of economic planning in which an deliberated, scientific system of planning that featured former Menshevik economists at Gosplan had been replaced with a hasty version of planning with unrealistic targets, bureaucratic waste, bottlenecks and shortages. Stalin\'s formulations of national plans in terms of physical quantity of output was also attributed by Daniels as a source for the stagnant levels of efficiency and quality.
#### Suppression of economic democracy and self-management {#suppression_of_economic_democracy_and_self_management}
Economist Robin Hahnel, who supports participatory economics, a form of socialist decentralized planned economy, notes that even if central planning overcame its inherent inhibitions of incentives and innovation, it would nevertheless be unable to maximize economic democracy and self-management, which he believes are concepts that are more intellectually coherent, consistent and just than mainstream notions of economic freedom. Furthermore, Hahnel states:
> Combined with a more democratic political system, and redone to closer approximate a best case version, centrally planned economies no doubt would have performed better. But they could never have delivered economic self-management, they would always have been slow to innovate as apathy and frustration took their inevitable toll, and they would always have been susceptible to growing inequities and inefficiencies as the effects of differential economic power grew. Under central planning neither planners, managers, nor workers had incentives to promote the social economic interest. Nor did impeding markets for final goods to the planning system enfranchise consumers in meaningful ways. But central planning would have been incompatible with economic democracy even if it had overcome its information and incentive liabilities. And the truth is that it survived as long as it did only because it was propped up by unprecedented totalitarian political power.
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# Planned economy
## Central planning {#central_planning}
### Command economy {#command_economy}
Planned economies contrast with command economies in that a planned economy is \"an economic system in which the government controls and regulates production, distribution, prices, etc.\" whereas a command economy necessarily has substantial public ownership of industry while also having this type of regulation. In command economies, important allocation decisions are made by government authorities and are imposed by law.
This is contested by some Marxists. Decentralized planning has been proposed as a basis for socialism and has been variously advocated by anarchists, council communists, libertarian Marxists and other democratic and libertarian socialists who advocate a non-market form of socialism, in total rejection of the type of planning adopted in the economy of the Soviet Union.
Most of a command economy is organized in a top-down administrative model by a central authority, where decisions regarding investment and production output requirements are decided upon at the top in the chain of command, with little input from lower levels. Advocates of economic planning have sometimes been staunch critics of these command economies. Leon Trotsky believed that those at the top of the chain of command, regardless of their intellectual capacity, operated without the input and participation of the millions of people who participate in the economy and who understand/respond to local conditions and changes in the economy. Therefore, they would be unable to effectively coordinate all economic activity.
Historians have associated planned economies with Marxist--Leninist states and the Soviet economic model. Since the 1980s, it has been contested that the Soviet economic model did not actually constitute a planned economy in that a comprehensive and binding plan did not guide production and investment. The further distinction of an administrative-command system emerged as a new designation in some academic circles for the economic system that existed in the former Soviet Union and Eastern Bloc, highlighting the role of centralized hierarchical decision-making in the absence of popular control over the economy. The possibility of a digital planned economy was explored in Chile between 1971 and 1973 with the development of Project Cybersyn and by Aleksandr Aleksandrovich Kharkevich, head of the Department of Technical Physics in Kiev in 1962.
While both economic planning and a planned economy can be either authoritarian or democratic and participatory, democratic socialist critics argue that command economies under modern-day communism is highly undemocratic and totalitarian in practice. Indicative planning is a form of economic planning in market economies that directs the economy through incentive-based methods. Economic planning can be practiced in a decentralized manner through different government authorities. In some predominantly market-oriented and Western mixed economies, the state utilizes economic planning in strategic industries such as the aerospace industry. Mixed economies usually employ macroeconomic planning while micro-economic affairs are left to the market and price system.
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# Planned economy
## Decentralized planning {#decentralized_planning}
A decentralized-planned economy, occasionally called horizontally planned economy due to its horizontalism, is a type of planned economy in which the investment and allocation of consumer and capital goods is explicated accordingly to an economy-wide plan built and operatively coordinated through a distributed network of disparate economic agents or even production units itself. **Decentralized planning** is usually held in contrast to centralized planning, in particular the Soviet-type economic planning of the Soviet Union\'s command economy, where economic information is aggregated and used to formulate a plan for production, investment and resource allocation by a single central authority. Decentralized planning can take shape both in the context of a mixed economy as well as in a post-capitalist economic system. This form of economic planning implies some process of democratic and participatory decision-making within the economy and within firms itself in the form of industrial democracy. Computer-based forms of democratic economic planning and coordination between economic enterprises have also been proposed by various computer scientists and radical economists. Proponents present decentralized and participatory economic planning as an alternative to market socialism for a post-capitalist society.
Decentralized planning has been a feature of anarchist and socialist economics. Variations of decentralized planning such as economic democracy, industrial democracy and participatory economics have been promoted by various political groups, most notably anarchists, democratic socialists, guild socialists, libertarian Marxists, libertarian socialists, revolutionary syndicalists and Trotskyists. During the Spanish Revolution, some areas where anarchist and libertarian socialist influence through the CNT and UGT was extensive, particularly rural regions, were run on the basis of decentralized planning resembling the principles laid out by anarcho-syndicalist Diego Abad de Santillan in the book *After the Revolution*. Trotsky had urged economic decentralisation between the state, oblast regions and factories during the NEP period to counter structural inefficiency and the problem of bureaucracy.
### Models
#### Negotiated coordination {#negotiated_coordination}
Economist Pat Devine has created a model of decentralized economic planning called \"negotiated coordination\" which is based upon social ownership of the means of production by those affected by the use of the assets involved, with the allocation of consumer and capital goods made through a participatory form of decision-making by those at the most localized level of production. Moreover, organizations that utilize modularity in their production processes may distribute problem solving and decision making.
#### Participatory planning {#participatory_planning}
The planning structure of a decentralized planned economy is generally based on a consumers council and producer council (or jointly, a distributive cooperative) which is sometimes called a consumers\' cooperative. Producers and consumers, or their representatives, negotiate the quality and quantity of what is to be produced. This structure is central to guild socialism, participatory economics and the economic theories related to anarchism.
### Practice
#### Kerala
Some decentralized participation in economic planning has been implemented in various regions and states in India, most notably in Kerala. Local level planning agencies assess the needs of people who are able to give their direct input through the Gram Sabhas (village-based institutions) and the planners subsequently seek to plan accordingly.
#### Revolutionary Catalonia {#revolutionary_catalonia}
Some decentralized participation in economic planning has been implemented across Revolutionary Spain, most notably in Catalonia, during the Spanish Revolution of 1936.
#### Similar concepts in practice {#similar_concepts_in_practice}
##### Community participatory planning {#community_participatory_planning}
The United Nations has developed local projects that promote participatory planning on a community level, requiring opportunities for all people to be politically involved and share in the community development process.
## Portrayals in fiction {#portrayals_in_fiction}
The 1888 novel *Looking Backward* by Edward Bellamy depicts a fictional planned economy in a United States around the year 2000 which has become a socialist utopia. Other literary portrayals of planned economies include Yevgeny Zamyatin\'s *We* (1924)
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# Crystallographic defect
A **crystallographic defect** is an interruption of the regular patterns of arrangement of atoms or molecules in crystalline solids. The positions and orientations of particles, which are repeating at fixed distances determined by the unit cell parameters in crystals, exhibit a periodic crystal structure, but this is usually imperfect. Several types of defects are often characterized: point defects, line defects, planar defects, bulk defects. Topological homotopy establishes a mathematical method of characterization.
## Point defects {#point_defects}
Point defects are defects that occur only at or around a single lattice point. They are not extended in space in any dimension. Strict limits for how small a point defect is are generally not defined explicitly. However, these defects typically involve at most a few extra or missing atoms. Larger defects in an ordered structure are usually considered dislocation loops. For historical reasons, many point defects, especially in ionic crystals, are called *centers*: for example a vacancy in many ionic solids is called a luminescence center, a color center, or F-center. These dislocations permit ionic transport through crystals leading to electrochemical reactions. These are frequently specified using Kröger--Vink notation.
- Vacancy defects are lattice sites which would be occupied in a perfect crystal, but are vacant. If a neighboring atom moves to occupy the vacant site, the vacancy moves in the opposite direction to the site which used to be occupied by the moving atom. The stability of the surrounding crystal structure guarantees that the neighboring atoms will not simply collapse around the vacancy. In some materials, neighboring atoms actually move away from a vacancy, because they experience attraction from atoms in the surroundings. A vacancy (or pair of vacancies in an ionic solid) is sometimes called a Schottky defect.
- Interstitial defects are atoms that occupy a site in the crystal structure at which there is usually not an atom. They are generally high energy configurations. Small atoms (mostly impurities) in some crystals can occupy interstices without high energy, such as hydrogen in palladium.
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- A nearby pair of a vacancy and an interstitial is often called a Frenkel defect or Frenkel pair. This is caused when an ion moves into an interstitial site and creates a vacancy.
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- Due to fundamental limitations of material purification methods, materials are never 100% pure, which by definition induces defects in crystal structure. In the case of an impurity, the atom is often incorporated at a regular atomic site in the crystal structure. This is neither a vacant site nor is the atom on an interstitial site and it is called a **substitutional defect**. The atom is not supposed to be anywhere in the crystal, and is thus an impurity. In some cases where the radius of the substitutional atom (ion) is substantially smaller than that of the atom (ion) it is replacing, its equilibrium position can be shifted away from the lattice site. These types of substitutional defects are often referred to as off-center ions. There are two different types of substitutional defects: Isovalent substitution and aliovalent substitution. Isovalent substitution is where the ion that is substituting the original ion is of the same oxidation state as the ion it is replacing. Aliovalent substitution is where the ion that is substituting the original ion is of a different oxidation state than the ion it is replacing. Aliovalent substitutions change the overall charge within the ionic compound, but the ionic compound must be neutral. Therefore, a charge compensation mechanism is required. Hence either one of the metals is partially or fully oxidised or reduced, or ion vacancies are created.
- **Antisite defects** occur in an ordered alloy or compound when atoms of different type exchange positions. For example, some alloys have a regular structure in which every other atom is a different species; for illustration assume that type A atoms sit on the corners of a cubic lattice, and type B atoms sit in the center of the cubes. If one cube has an A atom at its center, the atom is on a site usually occupied by a B atom, and is thus an antisite defect. This is neither a vacancy nor an interstitial, nor an impurity.
- Topological defects are regions in a crystal where the normal chemical bonding environment is topologically different from the surroundings. For instance, in a perfect sheet of graphite (graphene) all atoms are in rings containing six atoms. If the sheet contains regions where the number of atoms in a ring is different from six, while the total number of atoms remains the same, a topological defect has formed. An example is the Stone Wales defect in nanotubes, which consists of two adjacent 5-membered and two 7-membered atom rings.
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- Amorphous solids may contain defects. These are naturally somewhat hard to define, but sometimes their nature can be quite easily understood. For instance, in ideally bonded amorphous silica all Si atoms have 4 bonds to O atoms and all O atoms have 2 bonds to Si atom. Thus e.g. an O atom with only one Si bond (a dangling bond) can be considered a defect in silica. Moreover, defects can also be defined in amorphous solids based on empty or densely packed local atomic neighbourhoods, and the properties of such \'defects\' can be shown to be similar to normal vacancies and interstitials in crystals.
- Complexes can form between different kinds of point defects. For example, if a vacancy encounters an impurity, the two may bind together if the impurity is too large for the lattice. Interstitials can form \'split interstitial\' or \'dumbbell\' structures where two atoms effectively share an atomic site, resulting in neither atom actually occupying the site.
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# Crystallographic defect
## Line defects {#line_defects}
Line defects can be described by gauge theories.
Dislocations are linear defects, around which the atoms of the crystal lattice are misaligned. There are two basic types of dislocations, the *edge* dislocation and the *screw* dislocation. \"Mixed\" dislocations, combining aspects of both types, are also common.
Edge dislocations are caused by the termination of a plane of atoms in the middle of a crystal. In such a case, the adjacent planes are not straight, but instead bend around the edge of the terminating plane so that the crystal structure is perfectly ordered on either side. The analogy with a stack of paper is apt: if a half a piece of paper is inserted in a stack of paper, the defect in the stack is only noticeable at the edge of the half sheet.
The screw dislocation is more difficult to visualise, but basically comprises a structure in which a helical path is traced around the linear defect (dislocation line) by the atomic planes of atoms in the crystal lattice.
The presence of dislocation results in lattice strain (distortion). The direction and magnitude of such distortion is expressed in terms of a Burgers vector (b). For an edge type, b is perpendicular to the dislocation line, whereas in the cases of the screw type it is parallel. In metallic materials, b is aligned with close-packed crystallographic directions and its magnitude is equivalent to one interatomic spacing.
Dislocations can move if the atoms from one of the surrounding planes break their bonds and rebond with the atoms at the terminating edge.
It is the presence of dislocations and their ability to readily move (and interact) under the influence of stresses induced by external loads that leads to the characteristic malleability of metallic materials.
Dislocations can be observed using transmission electron microscopy, field ion microscopy and atom probe techniques. Deep-level transient spectroscopy has been used for studying the electrical activity of dislocations in semiconductors, mainly silicon.
Disclinations are line defects corresponding to \"adding\" or \"subtracting\" an angle around a line. Basically, this means that if you track the crystal orientation around the line defect, you get a rotation. Usually, they were thought to play a role only in liquid crystals, but recent developments suggest that they might have a role also in solid materials, e.g. leading to the self-healing of cracks.
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# Crystallographic defect
## Planar defects {#planar_defects}
- Grain boundaries occur where the crystallographic direction of the lattice abruptly changes. This usually occurs when two crystals begin growing separately and then meet.
- Antiphase boundaries occur in ordered alloys: in this case, the crystallographic direction remains the same, but each side of the boundary has an opposite phase: For example, if the ordering is usually ABABABAB (hexagonal close-packed crystal), an antiphase boundary takes the form of ABABBABA.
- Stacking faults occur in a number of crystal structures, but the common example is in close-packed structures. They are formed by a local deviation of the stacking sequence of layers in a crystal. An example would be the ABABCABAB stacking sequence.
- A twin boundary is a defect that introduces a plane of mirror symmetry in the ordering of a crystal. For example, in cubic close-packed crystals, the stacking sequence of a twin boundary would be ABCABCBACBA.
- On planes of single crystals, steps between atomically flat terraces can also be regarded as planar defects. It has been shown that such defects and their geometry have significant influence on the adsorption of organic molecules
## Bulk defects {#bulk_defects}
- Three-dimensional macroscopic or bulk defects, such as pores, cracks, or inclusions
- Voids --- small regions where there are no atoms, and which can be thought of as clusters of vacancies
- Impurities can cluster together to form small regions of a different phase. These are often called precipitates.
## Mathematical classification methods {#mathematical_classification_methods}
A successful mathematical classification method for physical lattice defects, which works not only with the theory of dislocations and other defects in crystals but also, e.g., for disclinations in liquid crystals and for excitations in superfluid ^3^He, is homotopy theory, a branch of topology.
## Computer simulation methods {#computer_simulation_methods}
Density functional theory, classical molecular dynamics and kinetic Monte Carlo simulations are widely used to study the properties of defects in solids with computer simulations. Simulating jamming of hard spheres of different sizes and/or in containers with non-commeasurable sizes using the Lubachevsky--Stillinger algorithm can be an effective technique for demonstrating some types of crystallographic defects
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# Chomsky normal form
In formal language theory, a context-free grammar, *G*, is said to be in **Chomsky normal form** (first described by Noam Chomsky) if all of its production rules are of the form:
: *A* → *BC*, or
: *A* → *a*, or
: *S* → ε,
where *A*, *B*, and *C* are nonterminal symbols, the letter *a* is a terminal symbol (a symbol that represents a constant value), *S* is the start symbol, and ε denotes the empty string. Also, neither *B* nor *C* may be the start symbol, and the third production rule can only appear if ε is in *L*(*G*), the language produced by the context-free grammar *G*.
Every grammar in Chomsky normal form is context-free, and conversely, every context-free grammar can be transformed into an equivalent one which is in Chomsky normal form and has a size no larger than the square of the original grammar\'s size.
## Converting a grammar to Chomsky normal form {#converting_a_grammar_to_chomsky_normal_form}
To convert a grammar to Chomsky normal form, a sequence of simple transformations is applied in a certain order; this is described in most textbooks on automata theory. The presentation here follows Hopcroft, Ullman (1979), but is adapted to use the transformation names from Lange, Leiß (2009). Each of the following transformations establishes one of the properties required for Chomsky normal form.
### START: Eliminate the start symbol from right-hand sides {#start_eliminate_the_start_symbol_from_right_hand_sides}
Introduce a new start symbol *S*~0~, and a new rule
: *S*~0~ → *S*,
where *S* is the previous start symbol. This does not change the grammar\'s produced language, and *S*~0~ will not occur on any rule\'s right-hand side.
### TERM: Eliminate rules with nonsolitary terminals {#term_eliminate_rules_with_nonsolitary_terminals}
To eliminate each rule
: *A* → *X*~1~ \... *a* \... *X*~*n*~
with a terminal symbol *a* being not the only symbol on the right-hand side, introduce, for every such terminal, a new nonterminal symbol *N*~*a*~, and a new rule
: *N*~*a*~ → *a*.
Change every rule
: *A* → *X*~1~ \... *a* \... *X*~*n*~
to
: *A* → *X*~1~ \... *N*~*a*~ \... *X*~*n*~.
If several terminal symbols occur on the right-hand side, simultaneously replace each of them by its associated nonterminal symbol. This does not change the grammar\'s produced language.
### BIN: Eliminate right-hand sides with more than 2 nonterminals {#bin_eliminate_right_hand_sides_with_more_than_2_nonterminals}
Replace each rule
: *A* → *X*~1~ *X*~2~ \... *X*~*n*~
with more than 2 nonterminals *X*~1~,\...,*X*~*n*~ by rules
: *A* → *X*~1~ *A*~1~,
: *A*~1~ → *X*~2~ *A*~2~,
: \... ,
: *A*~*n*-2~ → *X*~*n*-1~ *X*~*n*~,
where *A*~*i*~ are new nonterminal symbols. Again, this does not change the grammar\'s produced language.
### DEL: Eliminate ε-rules {#del_eliminate_ε_rules}
An ε-rule is a rule of the form
: *A* → ε,
where *A* is not *S*~0~, the grammar\'s start symbol.
To eliminate all rules of this form, first determine the set of all nonterminals that derive ε. Hopcroft and Ullman (1979) call such nonterminals *nullable*, and compute them as follows:
- If a rule *A* → ε exists, then *A* is nullable.
- If a rule *A* → *X*~1~ \... *X*~*n*~ exists, and every single *X*~*i*~ is nullable, then *A* is nullable, too.
Obtain an intermediate grammar by replacing each rule
: *A* → *X*~1~ \... *X*~*n*~
by all versions with some nullable *X*~*i*~ omitted. By deleting in this grammar each ε-rule, unless its left-hand side is the start symbol, the transformed grammar is obtained.
For example, in the following grammar, with start symbol *S*~0~,
: *S*~0~ → *AbB* \| *C*
: *B* → *AA* \| *AC*
: *C* → *b* \| *c*
: *A* → *a* \| ε
the nonterminal *A*, and hence also *B*, is nullable, while neither *C* nor *S*~0~ is. Hence the following intermediate grammar is obtained:
: *S*~0~ → *`{{color|#006000|A}}`{=mediawiki}b`{{color|#006000|B}}`{=mediawiki}* \| *`{{color|#006000|A}}`{=mediawiki}b`{{color|#ffc0c0|<s>B</s>}}`{=mediawiki}* \| *`{{color|#ffc0c0|<s>A</s>}}`{=mediawiki}b`{{color|#006000|B}}`{=mediawiki}* \| *`{{color|#ffc0c0|<s>A</s>}}`{=mediawiki}b`{{color|#ffc0c0|<s>B</s>}}`{=mediawiki}* \| *C*
: *B* → *`{{color|#006000|AA}}`{=mediawiki}* \| *`{{color|#ffc0c0|<s>A</s>}}`{=mediawiki}`{{color|#006000|A}}`{=mediawiki}* \| *`{{color|#006000|A}}`{=mediawiki}`{{color|#ffc0c0|<s>A</s>}}`{=mediawiki}* \| *`{{color|#ffc0c0|<s>A</s>}}`{=mediawiki}ε`{{color|#ffc0c0|<s>A</s>}}`{=mediawiki}* \| *`{{color|#006000|A}}`{=mediawiki}C* \| *`{{color|#ffc0c0|<s>A</s>}}`{=mediawiki}C*
: *C* → *b* \| *c*
: *A* → *a* \| ε
In this grammar, all ε-rules have been \"inlined at the call site\". In the next step, they can hence be deleted, yielding the grammar:
: *S*~0~ → *AbB* \| *Ab* \| *bB* \| *b* \| *C*
: *B* → *AA* \| *A* \| *AC* \| *C*
: *C* → *b* \| *c*
: *A* → *a*
This grammar produces the same language as the original example grammar, viz. {*ab*,*aba*,*abaa*,*abab*,*abac*,*abb*,*abc*,*b*,*ba*,*baa*,*bab*,*bac*,*bb*,*bc*,*c*}, but has no ε-rules.
### UNIT: Eliminate unit rules {#unit_eliminate_unit_rules}
A unit rule is a rule of the form
: *A* → *B*,
where *A*, *B* are nonterminal symbols. To remove it, for each rule
: *B* → *X*~1~ \... *X*~*n*~,
where *X*~1~ \... *X*~*n*~ is a string of nonterminals and terminals, add rule
: *A* → *X*~1~ \... *X*~*n*~
unless this is a unit rule which has already been (or is being) removed. The skipping of nonterminal symbol *B* in the resulting grammar is possible due to *B* being a member of the unit closure of nonterminal symbol *A*.
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# Chomsky normal form
## Converting a grammar to Chomsky normal form {#converting_a_grammar_to_chomsky_normal_form}
### Order of transformations {#order_of_transformations}
+----------------------------------------------------------------------------------------------+
| Transformation *X* `{{color|#004000|always preserves}}`{=mediawiki} (`{{Aye}}`{=mediawiki})\ |
| resp. `{{color|#400000|may destroy}}`{=mediawiki} (`{{Nay}}`{=mediawiki}) the result of *Y*: |
+----------------------------------------------------------------------------------------------+
| |
+----------------------------------------------------------------------------------------------+
| START |
+----------------------------------------------------------------------------------------------+
| TERM |
+----------------------------------------------------------------------------------------------+
| BIN |
+----------------------------------------------------------------------------------------------+
| DEL |
+----------------------------------------------------------------------------------------------+
| UNIT |
+----------------------------------------------------------------------------------------------+
| ^\*^**UNIT** preserves the result of **DEL**\ |
| if **START** had been called before. |
+----------------------------------------------------------------------------------------------+
: Mutual preservation\
of transformation results
When choosing the order in which the above transformations are to be applied, it has to be considered that some transformations may destroy the result achieved by other ones. For example, **START** will re-introduce a unit rule if it is applied after **UNIT**. The table shows which orderings are admitted.
Moreover, the worst-case bloat in grammar size depends on the transformation order. Using \|*G*\| to denote the size of the original grammar *G*, the size blow-up in the worst case may range from \|*G*\|^2^ to 2^2\ \|G\|^, depending on the transformation algorithm used. The blow-up in grammar size depends on the order between **DEL** and **BIN**. It may be exponential when **DEL** is done first, but is linear otherwise. **UNIT** can incur a quadratic blow-up in the size of the grammar. The orderings **START**,**TERM**,**BIN**,**DEL**,**UNIT** and **START**,**BIN**,**DEL**,**UNIT**,**TERM** lead to the least (i.e. quadratic) blow-up.
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# Chomsky normal form
## Example
The following grammar, with start symbol *Expr*, describes a simplified version of the set of all syntactical valid arithmetic expressions in programming languages like C or Algol60. Both *number* and *variable* are considered terminal symbols here for simplicity, since in a compiler front end their internal structure is usually not considered by the parser. The terminal symbol \"\^\" denoted exponentiation in Algol60.
: {\|
\|- \| *Expr* \| → *Term* \| \| \| *Expr* *AddOp* *Term* \| \| \| *AddOp* *Term* \|- \| *Term* \| → *Factor* \| \| \| *Term* *MulOp* *Factor* \|- \| *Factor* \| → *Primary* \| \| \| *Factor* \^ *Primary* \|- \| *Primary* \| → *number* \| \| \| *variable* \| \| \| ( *Expr* ) \|- \| *AddOp* \| → + \| \| \| − \|- \| *MulOp* \| → \* \| \| \| / \|}
In step \"START\" of the above conversion algorithm, just a rule *S*~0~→*Expr* is added to the grammar. After step \"TERM\", the grammar looks like this:
: {\|
\|- \| *S*~0~ \| → *Expr* \|- \| *Expr* \| → *Term* \| \| \| *Expr* *AddOp* *Term* \| \| \| *AddOp* *Term* \|- \| *Term* \| → *Factor* \| \| \| *Term* *MulOp* *Factor* \|- \| *Factor* \| → *Primary* \| \| \| *Factor* *PowOp* *Primary* \|- \| *Primary* \| → *number* \| \| \| *variable* \| \| \| *Open* *Expr* *Close* \|- \| *AddOp* \| → + \| \| \| − \|- \| *MulOp* \| → \* \| \| \| / \|- \| *PowOp* \| → \^ \|- \| *Open* \| → ( \|- \| *Close* \| → ) \|}
After step \"BIN\", the following grammar is obtained:
: {\|
\|- \| *S*~0~ \| → *Expr* \|- \| *Expr* \| → *Term* \| \| \| *Expr* *AddOp_Term* \| \| \| *AddOp* *Term* \|- \| *Term* \| → *Factor* \| \| \| *Term* *MulOp_Factor* \|- \| *Factor* \| → *Primary* \| \| \| *Factor* *PowOp_Primary* \|- \| *Primary* \| → *number* \| \| \| *variable* \| \| \| *Open* *Expr_Close* \|- \| *AddOp* \| → + \| \| \| − \|- \| *MulOp* \| → \* \| \| \| / \|- \| *PowOp* \| → \^ \|- \| *Open* \| → ( \|- \| *Close* \| → ) \|- \| *AddOp_Term* \| colspan=3 \| → *AddOp* *Term* \|- \| *MulOp_Factor* \| colspan=3 \| → *MulOp* *Factor* \|- \| *PowOp_Primary* \| colspan=3 \| → *PowOp* *Primary* \|- \| *Expr_Close* \| colspan=3 \| → *Expr* *Close* \|}
Since there are no ε-rules, step \"DEL\" does not change the grammar. After step \"UNIT\", the following grammar is obtained, which is in Chomsky normal form:
: {\|
\|- \| *S*~0~ \| → *number* \| \| \| *variable* \| \| \| *Open* *Expr_Close* \| \| \| *Factor* *PowOp_Primary* \| \| \| *Term* *MulOp_Factor* \| \| \| *Expr* *AddOp_Term* \| \| \| *AddOp* *Term* \|- \| *Expr* \| → *number* \| \| \| *variable* \| \| \| *Open* *Expr_Close* \| \| \| *Factor* *PowOp_Primary* \| \| \| *Term* *MulOp_Factor* \| \| \| *Expr* *AddOp_Term* \| \| \| *AddOp* *Term* \|- \| *Term* \| → *number* \| \| \| *variable* \| \| \| *Open* *Expr_Close* \| \| \| *Factor* *PowOp_Primary* \| \| \| *Term* *MulOp_Factor* \|- \| *Factor* \| → *number* \| \| \| *variable* \| \| \| *Open* *Expr_Close* \| \| \| *Factor* *PowOp_Primary* \|- \| *Primary* \| → *number* \| \| \| *variable* \| \| \| *Open* *Expr_Close* \|- \| *AddOp* \| → + \| \| \| − \|- \| *MulOp* \| → \* \| \| \| / \|- \| *PowOp* \| → \^ \|- \| *Open* \| → ( \|- \| *Close* \| → ) \|- \| *AddOp_Term* \| colspan=3 \| → *AddOp* *Term* \|- \| *MulOp_Factor* \| colspan=3 \| → *MulOp* *Factor* \|- \| *PowOp_Primary* \| colspan=3 \| → *PowOp* *Primary* \|- \| *Expr_Close* \| colspan=3 \| → *Expr* *Close* \|}
The *N*~*a*~ introduced in step \"TERM\" are *PowOp*, *Open*, and *Close*. The *A*~*i*~ introduced in step \"BIN\" are *AddOp_Term*, *MulOp_Factor*, *PowOp_Primary*, and *Expr_Close*.
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# Chomsky normal form
## Alternative definition {#alternative_definition}
### Chomsky reduced form {#chomsky_reduced_form}
Another way to define the Chomsky normal form is:
A formal grammar is in **Chomsky reduced form** if all of its production rules are of the form:
: $A \rightarrow\, BC$ or
: $A \rightarrow\, a$,
where $A$, $B$ and $C$ are nonterminal symbols, and $a$ is a terminal symbol. When using this definition, $B$ or $C$ may be the start symbol. Only those context-free grammars which do not generate the empty string can be transformed into Chomsky reduced form.
### Floyd normal form {#floyd_normal_form}
In a letter where he proposed a term Backus--Naur form (BNF), Donald E. Knuth implied a BNF \"syntax in which all definitions have such a form may be said to be in \'Floyd Normal Form\'\",
: $\langle A \rangle ::= \, \langle B \rangle \mid \langle C \rangle$ or
: $\langle A \rangle ::= \, \langle B \rangle \langle C \rangle$ or
: $\langle A \rangle ::=\, a$,
where $\langle A \rangle$, $\langle B \rangle$ and $\langle C \rangle$ are nonterminal symbols, and $a$ is a terminal symbol, because Robert W. Floyd found any BNF syntax can be converted to the above one in 1961. But he withdrew this term, \"since doubtless many people have independently used this simple fact in their own work, and the point is only incidental to the main considerations of Floyd\'s note.\" While Floyd\'s note cites Chomsky\'s original 1959 article, Knuth\'s letter does not.
## Application
Besides its theoretical significance, CNF conversion is used in some algorithms as a preprocessing step, e.g., the CYK algorithm, a bottom-up parsing for context-free grammars, and its variant probabilistic CKY
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# Diatomic molecule
**Diatomic molecules** (`{{ety|el|di-|two}}`{=mediawiki}) are molecules composed of only two atoms, of the same or different chemical elements. If a diatomic molecule consists of two atoms of the same element, such as hydrogen (`{{chem2|H2}}`{=mediawiki}) or oxygen (`{{chem2|O2}}`{=mediawiki}), then it is said to be homonuclear. Otherwise, if a diatomic molecule consists of two different atoms, such as carbon monoxide (`{{chem2|CO}}`{=mediawiki}) or nitric oxide (`{{chem2|NO}}`{=mediawiki}), the molecule is said to be heteronuclear. The bond in a homonuclear diatomic molecule is non-polar.
thumb\|upright=2.5\|A periodic table showing the elements that exist as homonuclear diatomic molecules under typical laboratory conditions.
The only chemical elements that form stable homonuclear diatomic molecules at standard temperature and pressure (STP) (or at typical laboratory conditions of 1 bar and 25 °C) are the gases hydrogen (`{{chem2|H2}}`{=mediawiki}), nitrogen (`{{chem2|N2}}`{=mediawiki}), oxygen (`{{chem2|O2}}`{=mediawiki}), fluorine (`{{chem2|F2}}`{=mediawiki}), and chlorine (`{{chem2|Cl2}}`{=mediawiki}), and the liquid bromine (`{{chem2|Br2}}`{=mediawiki}).
The noble gases (helium, neon, argon, krypton, xenon, and radon) are also gases at STP, but they are monatomic. The homonuclear diatomic gases and noble gases together are called \"elemental gases\" or \"molecular gases\", to distinguish them from other gases that are chemical compounds.
At slightly elevated temperatures, the halogens bromine (`{{chem2|Br2}}`{=mediawiki}) and iodine (`{{chem2|I2}}`{=mediawiki}) also form diatomic gases. All halogens have been observed as diatomic molecules, except for astatine and tennessine, which are uncertain.
Other elements form diatomic molecules when evaporated, but these diatomic species repolymerize when cooled. Heating (\"cracking\") elemental phosphorus gives diphosphorus (`{{chem2|P2}}`{=mediawiki}). Sulfur vapor is mostly disulfur (`{{chem2|S2}}`{=mediawiki}). Dilithium (`{{chem2|Li2}}`{=mediawiki}) and disodium (`{{chem2|Na2}}`{=mediawiki}) are known in the gas phase. Ditungsten (`{{chem2|W2}}`{=mediawiki}) and dimolybdenum (`{{chem2| Mo2}}`{=mediawiki}) form with sextuple bonds in the gas phase. Dirubidium (`{{chem2|Rb2}}`{=mediawiki}) is diatomic.
## Heteronuclear molecules {#heteronuclear_molecules}
All other diatomic molecules are chemical compounds of two different elements. Many elements can combine to form heteronuclear diatomic molecules, depending on temperature and pressure.
Examples are gases carbon monoxide (CO), nitric oxide (NO), and hydrogen chloride (HCl).
Many 1:1 binary compounds are not normally considered diatomic because they are polymeric at room temperature, but they form diatomic molecules when evaporated, for example gaseous MgO, SiO, and many others.
## Occurrence
Hundreds of diatomic molecules have been identified in the environment of the Earth, in the laboratory, and in interstellar space. About 99% of the Earth\'s atmosphere is composed of two species of diatomic molecules: nitrogen (78%) and oxygen (21%). The natural abundance of hydrogen (H~2~) in the Earth\'s atmosphere is only of the order of parts per million, but H~2~ is the most abundant diatomic molecule in the universe. The interstellar medium is dominated by hydrogen atoms.
## Molecular geometry {#molecular_geometry}
All diatomic molecules are linear and characterized by a single parameter which is the bond length or distance between the two atoms. Diatomic nitrogen has a triple bond, diatomic oxygen has a double bond, and diatomic hydrogen, fluorine, chlorine, iodine, and bromine all have single bonds.
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# Diatomic molecule
## Historical significance {#historical_significance}
Diatomic elements played an important role in the elucidation of the concepts of element, atom, and molecule in the 19th century, because some of the most common elements, such as hydrogen, oxygen, and nitrogen, occur as diatomic molecules. John Dalton\'s original atomic hypothesis assumed that all elements were monatomic and that the atoms in compounds would normally have the simplest atomic ratios with respect to one another. For example, Dalton assumed water\'s formula to be HO, giving the atomic weight of oxygen as eight times that of hydrogen, instead of the modern value of about 16. As a consequence, confusion existed regarding atomic weights and molecular formulas for about half a century.
As early as 1805, Gay-Lussac and von Humboldt showed that water is formed of two volumes of hydrogen and one volume of oxygen, and by 1811 Amedeo Avogadro had arrived at the correct interpretation of water\'s composition, based on what is now called Avogadro\'s law and the assumption of diatomic elemental molecules. However, these results were mostly ignored until 1860, partly due to the belief that atoms of one element would have no chemical affinity toward atoms of the same element, and also partly due to apparent exceptions to Avogadro\'s law that were not explained until later in terms of dissociating molecules.
At the 1860 Karlsruhe Congress on atomic weights, Cannizzaro resurrected Avogadro\'s ideas and used them to produce a consistent table of atomic weights, which mostly agree with modern values. These weights were an important prerequisite for the discovery of the periodic law by Dmitri Mendeleev and Lothar Meyer.
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# Diatomic molecule
## Excited electronic states {#excited_electronic_states}
Diatomic molecules are normally in their lowest or ground state, which conventionally is also known as the $X$ state. When a gas of diatomic molecules is bombarded by energetic electrons, some of the molecules may be excited to higher electronic states, as occurs, for example, in the natural aurora; high-altitude nuclear explosions; and rocket-borne electron gun experiments. Such excitation can also occur when the gas absorbs light or other electromagnetic radiation. The excited states are unstable and naturally relax back to the ground state. Over various short time scales after the excitation (typically a fraction of a second, or sometimes longer than a second if the excited state is metastable), transitions occur from higher to lower electronic states and ultimately to the ground state, and in each transition results a photon is emitted. This emission is known as fluorescence. Successively higher electronic states are conventionally named $A$, $B$, $C$, etc. (but this convention is not always followed, and sometimes lower case letters and alphabetically out-of-sequence letters are used, as in the example given below). The excitation energy must be greater than or equal to the energy of the electronic state in order for the excitation to occur.
In quantum theory, an electronic state of a diatomic molecule is represented by the molecular term symbol $^{2S+1} \Lambda (v)^{+/-}_{(g/u)}$ where $S$ is the total electronic spin quantum number, $\Lambda$ is the total electronic angular momentum quantum number along the internuclear axis, and $v$ is the vibrational quantum number. $\Lambda$ takes on values 0, 1, 2, \..., which are represented by the electronic state symbols $\Sigma$, $\Pi$, $\Delta$, \... For example, the following table lists the common electronic states (without vibrational quantum numbers) along with the energy of the lowest vibrational level ($v=0$) of diatomic nitrogen (N~2~), the most abundant gas in the Earth\'s atmosphere.
The subscripts and superscripts after $\Lambda$ give additional quantum mechanical details about the electronic state. The superscript $+$ or $-$ determines whether reflection in a plane containing the internuclear axis introduces a sign change in the wavefunction. The sub-script $g$ or $u$ applies to molecules of identical atoms, and when reflecting the state along a plane perpendicular to the molecular axis, states that does not change are labelled $g$ (gerade), and states that change sign are labelled $u$ (ungerade).
State Energy ($T_0$, cm^−1^)
------------------- ------------------------
$X ^1\Sigma_g^+$ 0.0
$A ^3\Sigma_u^+$ 49754.8
$B ^3\Pi_g$ 59306.8
$W ^3\Delta_u$ 59380.2
$B' ^3\Sigma_u^-$ 65851.3
$a' ^1\Sigma_u^-$ 67739.3
$a ^1\Pi_g$ 68951.2
$w ^1\Delta_u$ 71698.4
The aforementioned fluorescence occurs in distinct regions of the electromagnetic spectrum, called \"emission bands\": each band corresponds to a particular transition from a higher electronic state and vibrational level to a lower electronic state and vibrational level (typically, many vibrational levels are involved in an excited gas of diatomic molecules). For example, N~2~ $A$-$X$ emission bands (a.k.a. Vegard-Kaplan bands) are present in the spectral range from 0.14 to 1.45 μm (micrometres). A given band can be spread out over several nanometers in electromagnetic wavelength space, owing to the various transitions that occur in the molecule\'s rotational quantum number, $J$. These are classified into distinct sub-band branches, depending on the change in $J$. The $R$ branch corresponds to $\Delta J = +1$, the $P$ branch to $\Delta J = -1$, and the $Q$ branch to $\Delta J = 0$. Bands are spread out even further by the limited spectral resolution of the spectrometer that is used to measure the spectrum. The spectral resolution depends on the instrument\'s point spread function.
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# Diatomic molecule
## Energy levels {#energy_levels}
The molecular term symbol is a shorthand expression of the angular momenta that characterize the electronic quantum states of a diatomic molecule, which are also eigenstates of the electronic molecular Hamiltonian. It is also convenient, and common, to represent a diatomic molecule as two-point masses connected by a massless spring. The energies involved in the various motions of the molecule can then be broken down into three categories: the translational, rotational, and vibrational energies. The theoretical study of the rotational energy levels of the diatomic molecules can be described using the below description of the rotational energy levels. While the study of vibrational energy level of the diatomic molecules can be described using the harmonic oscillator approximation or using the quantum vibrational interaction potentials. These potentials give more accurate energy levels because they take multiple vibrational effects into account.
Concerning history, the first treatment of diatomic molecules with quantum mechanics was made by Lucy Mensing in 1926.
### Translational energies {#translational_energies}
The translational energy of the molecule is given by the kinetic energy expression: $E_\text{trans} = \frac{1}{2}mv^2$ where $m$ is the mass of the molecule and $v$ is its velocity.
### Rotational energies {#rotational_energies}
Classically, the kinetic energy of rotation is $E_\text{rot} = \frac{L^2}{2 I}$ where
- $L \,$ is the angular momentum
- $I \,$ is the moment of inertia of the molecule
For microscopic, atomic-level systems like a molecule, angular momentum can only have specific discrete values given by $L^2 = \ell(\ell+1) \hbar^2$ where $\ell$ is a non-negative integer and $\hbar$ is the reduced Planck constant.
Also, for a diatomic molecule the moment of inertia is $I = \mu r_0^2$ where
- $\mu \,$ is the reduced mass of the molecule and
- $r_0 \,$ is the average distance between the centers of the two atoms in the molecule.
So, substituting the angular momentum and moment of inertia into `{{math|''E''<sub>rot</sub>}}`{=mediawiki}, the rotational energy levels of a diatomic molecule are given by: $E_\text{rot} = \frac{\ell (\ell + 1) \hbar^2}{2 \mu r_0^2}, \quad \ell = 0, 1, 2, \dots$
### Vibrational energies {#vibrational_energies}
Another type of motion of a diatomic molecule is for each atom to oscillate---or vibrate---along the line connecting the two atoms. The vibrational energy is approximately that of a quantum harmonic oscillator: $E_\text{vib} = \left(n + \tfrac{1}{2} \right)\hbar \omega, \quad n = 0, 1, 2, \dots,$ where
- $n$ is an integer
- $\hbar$ is the reduced Planck constant and
- $\omega$ is the angular frequency of the vibration.
### Comparison between rotational and vibrational energy spacings {#comparison_between_rotational_and_vibrational_energy_spacings}
The spacing, and the energy of a typical spectroscopic transition, between vibrational energy levels is about 100 times greater than that of a typical transition between rotational energy levels.
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# Diatomic molecule
## Hund\'s cases {#hunds_cases}
The good quantum numbers for a diatomic molecule, as well as good approximations of rotational energy levels, can be obtained by modeling the molecule using Hund\'s cases.
## Mnemonics
The mnemonics *BrINClHOF*, pronounced \"Brinklehof\", *HONClBrIF*, pronounced \"Honkelbrif\", "HOBrFINCl", pronounced "Hoberfinkel", and *HOFBrINCl*, pronounced \"Hofbrinkle\", have been coined to aid recall of the list of diatomic elements. Another method, for English-speakers, is the sentence: \"*Never Have Fear of Ice Cold Beer*\" as a representation of Nitrogen, Hydrogen, Fluorine, Oxygen, Iodine, Chlorine, Bromine
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# Disbarment
**Disbarment**, also known as **striking off**, is the removal of a lawyer from a bar association or the practice of law, thus revoking their law license or admission to practice law. Disbarment is usually a punishment for unethical or criminal conduct but may also be imposed for incompetence or incapacity. Procedures vary depending on the law society; temporary disbarment may be called suspension.
## Australia
In Australia, states regulate the Legal Profession under state law despite many participating in a uniform scheme. Admission as a lawyer is the business of the admissions board and the Supreme Court. Disciplinary proceedings may be commenced by the Bar Association, the Law Society of which one is a member, or the board itself.
## Germany
In Germany, a *Berufsverbot* is a ban on practicing a profession, which the government can issue to a lawyer for misconduct, *Volksverhetzung* or for serious mismanagement of personal finances.
In April 1933, the Nazi government issued a *Berufsverbot* forbidding the practice of law by Jews, Communists, and other political opponents, except for those protected by the *Frontkämpferprivileg*.
## United Kingdom {#united_kingdom}
In the United Kingdom, the removal of the licence to practise of a barrister or Scottish advocate is called being \"disbarred\", whilst the removal of a solicitor from the rolls in England and Wales, Scotland, or Northern Ireland is called being \"struck off\".
## United States {#united_states}
### Overview
Generally, disbarment is imposed as a sanction for conduct indicating that an attorney is not fit to practice law, willfully disregarding a client\'s interests, commingling funds, or engaging in fraud that impedes the administration of justice. In some states, any lawyer who is convicted of a felony is automatically suspended pending further disciplinary proceedings, or, in New York, automatically disbarred. Automatic disbarment, although opposed by the American Bar Association, has been described as a convicted felon\'s just deserts .
In the United States legal system, disbarment is specific to regions; one can be disbarred from some courts while still being a member of the bar in another jurisdiction. However, under the American Bar Association\'s Model Rules of Professional Conduct, which have been adopted in most states, disbarment in one state or court is grounds for disbarment in a jurisdiction which has adopted the Model Rules.
Disbarment is quite rare: in 2011, only 1,046 lawyers were disbarred. Instead, lawyers are usually sanctioned by their clients through civil malpractice proceedings, or via fine, censure, suspension, or other punishments from the disciplinary boards. To be disbarred is considered a great embarrassment and shame, even if one no longer wishes to continue a career in law.
Because disbarment rules vary by area, different rules can apply depending on where a lawyer is disbarred. Notably, most US states have no procedure for permanently disbarring a person. Depending on the jurisdiction, a lawyer may reapply to the bar immediately, after five to seven years, or be banned for life.
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# Disbarment
## United States {#united_states}
### Notable U.S. disbarments {#notable_u.s._disbarments}
In the 20th and 21st centuries, one former U.S. president and one former U.S. vice president have been disbarred, and another former president has been suspended from one bar and forced to resign from another bar rather than face disbarment.
Former vice president Spiro Agnew, having pleaded no contest (which subjects a person to the same criminal penalties as a guilty plea but is not an admission of guilt for a civil suit) to charges of bribery and tax evasion, was disbarred from Maryland, the state of which he had previously been governor.
Former president Richard Nixon was disbarred from New York in 1976 for obstruction of justice related to the Watergate scandal. He had attempted to resign from the New York bar, as he had done with California and the Supreme Court, but his resignation was not accepted as he would not acknowledge that he was unable to defend himself from the charges brought against him.
In 2001, following a 5-year suspension by the Arkansas bar, the United States Supreme Court suspended Bill Clinton from the United States Supreme Court bar, providing 40 days for him to contest disbarment. He resigned before the end of the 40 days, thus avoiding disbarment.
Alger Hiss was disbarred for a felony conviction but later became the first person reinstated to the bar in Massachusetts after disbarment.
In 2007, Mike Nifong, the District Attorney of Durham County, North Carolina who presided over the 2006 Duke University lacrosse case, was disbarred for prosecutorial misconduct related to his handling of the case.
In April 2012, a three-member panel appointed by the Arizona Supreme Court voted unanimously to disbar Andrew Thomas, former County Attorney of Maricopa County, Arizona, and a former close confederate of Maricopa County Sheriff Joe Arpaio. According to the panel, Thomas \"outrageously exploited power, flagrantly fostered fear, and disgracefully misused the law\" while serving as Maricopa County Attorney. The panel found \"clear and convincing evidence\" that Thomas brought unfounded and malicious criminal and civil charges against political opponents, including four state judges and the state attorney general. \"Were this a criminal case,\" the panel concluded, \"we are confident that the evidence would establish this conspiracy beyond a reasonable doubt.\"
Jack Thompson, the Florida lawyer noted for his activism against Howard Stern, video games, and rap music, was permanently disbarred for various charges of misconduct. The action resulted from several grievances claiming that Thompson had made defamatory, false statements and attempted to humiliate, embarrass, harass, or intimidate his opponents. The order was made on September 25, 2008, effective October 25. However, Thompson tried to appeal to the higher courts to avoid the penalty taking effect. Neither the US District Court nor the US Supreme Court would hear his appeal, rendering the judgment of the Florida Supreme Court final.
Ed Fagan, a New York lawyer who prominently represented Holocaust victims against Swiss banks, was disbarred in New York (in 2008) and New Jersey (in 2009) for failing to pay court fines and fees; and for misappropriating client and escrow trust funds.
F. Lee Bailey, noted criminal defense attorney, was disbarred by Florida in 2001, with reciprocal disbarment in Massachusetts in 2002. The Florida disbarment resulted from his stock handling in the DuBoc marijuana case. Bailey was found guilty of 7 counts of attorney misconduct by the Florida Supreme Court. Bailey had transferred a large portion of DuBoc\'s assets into his own accounts, using the interest gained on those assets to pay for personal expenses. In March 2005, Bailey filed to regain his law license in Massachusetts. The book *Florida Pulp Nonfiction* details the peculiar facts of the DuBoc case and extended interviews with Bailey, including his own defense. Bailey is also best known for representing murder suspect O. J. Simpson in 1994.
Richard P. Liebowitz, a New York attorney focused on copyrights held by photographers, was disbarred by the state of New York in 2024 following suspension from the practice of law in the Southern District of New York. His disbarment followed what was described as a \"pattern and practice of failing to comply with court orders and making false statements to the court\" and multiple lawsuits wherein Liebowitz was sanctioned for misconduct.
Rudy Giuliani was disbarred in New York and Washington, D.C., for false allegations about mass voter fraud and his participation in the January 6, 2021, attack on the United States Capitol to subvert the 2020 Presidential Election
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# Dead Kennedys
**Dead Kennedys** are an American punk rock band that formed in San Francisco, California, in 1978. The band was one of the defining punk bands during its initial eight-year run.
Initially consisting of lead guitarist East Bay Ray, bassist Klaus Flouride, lead vocalist Jello Biafra, drummer Ted and rhythm guitarist 6025, 6025 left in 1979, and Ted left the following year after the band recorded their acclaimed first album *Fresh Fruit for Rotting Vegetables* (1980). The band\'s longest-serving drummer was D. H. Peligro, who replaced Ted in 1981 and remained until his death in 2022. Dead Kennedys recorded the EP *In God We Trust Inc.* (1981), followed by three more studio albums, *Plastic Surgery Disasters* (1982), *Frankenchrist* (1985), and *Bedtime for Democracy* (1986), the latter of which was recorded and released shortly after announcing their breakup in January 1986. Most of the band\'s recordings were released on Alternative Tentacles, an independent record label founded by Biafra and East Bay Ray.
Following Dead Kennedys\' dissolution, Biafra continued to run Alternative Tentacles, and went on to collaborate and record with other artists, including D.O.A., NoMeansNo and his own bands Lard and the Guantanamo School of Medicine, as well as releasing several spoken word performances. In 2000 (upheld on appeal in 2003), Biafra lost an acrimonious legal case initiated by his former Dead Kennedys bandmates over songwriting credits and unpaid royalties. In 2001, the band reformed without Biafra; various singers have since been recruited for vocal duties. Although Dead Kennedys have continued to perform over the years, they have not released any more studio albums since *Bedtime for Democracy*.
Dead Kennedys\' lyrics were usually political in nature, satirizing political figures and authority in general, as well as popular culture and even the punk movement itself. During their initial incarnation between 1978 and 1986, they attracted considerable controversy for their provocative lyrics and artwork. Several stores refused to stock their recordings, provoking debate about censorship in rock music; in the mid-1980s, vocalist and primary lyricist Jello Biafra became an active campaigner against the Parents Music Resource Center (PMRC). This culminated in an obscenity trial between 1985 and 1986, which resulted in a hung jury and also hastened the band\'s demise.
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# Dead Kennedys
## History
### Formation of the band (1978--1979) {#formation_of_the_band_19781979}
Dead Kennedys were formed in June 1978 in San Francisco, California, when East Bay Ray (Raymond Pepperell) advertised for bandmates in the newspaper *The Recycler*. The original band lineup consisted of East Bay Ray on lead guitar, Klaus Flouride (Geoffrey Lyall) on bass, Jello Biafra (Eric Reed Boucher) on vocals, Ted (Bruce Slesinger) on drums and 6025 (Carlos Cadona) on rhythm guitar. This lineup recorded their first demos. Their first live show was on July 19, 1978 at Mabuhay Gardens in San Francisco, California. They were the opening act on a bill that included DV8 and Negative Trend with The Offs headlining.
Dead Kennedys played numerous shows at local venues afterward. Due to the provocative name of the band, they sometimes played under pseudonyms, including \"The DK\'s\", \"The Sharks\", \"The Creamsicles\" and \"The Pink Twinkies\". *San Francisco Chronicle* columnist Herb Caen wrote in November 1978, \"Just when you think tastelessness has reached its nadir, along comes a punk rock group called \'The Dead Kennedys\', which will play at Mabuhay Gardens on Nov. 22, the 15th anniversary of John F. Kennedy\'s assassination.\" Despite mounting protests, the owner of Mabuhay declared, \"I can\'t cancel them NOW---there\'s a contract. Not, apparently, the kind of contract some people have in mind.\" However, despite popular belief, the name was not meant to insult the Kennedy family, but according to Ray, \"the assassinations were in much more poor taste than our band. We actually respect the Kennedy family. . . . When JFK was assassinated, when Martin Luther King was assassinated, when RFK was assassinated, the American Dream was assassinated. . . . Our name is actually homage to the American Dream.\"
6025 left the band in March 1979 under somewhat unclear circumstances, generally considered to be musical differences. In June, the band released their first single, \"California Über Alles\", on Biafra and East Bay Ray\'s independent label, Alternative Tentacles. The band followed with a poorly attended East Coast tour, being a new and fairly unknown band at the time, without a full album release.
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# Dead Kennedys
## History
### *Fresh Fruit for Rotting Vegetables* (1980--1981) {#fresh_fruit_for_rotting_vegetables_19801981}
In early 1980, they recorded and released the single \"Holiday in Cambodia\". In June, the band recorded their debut album, *Fresh Fruit for Rotting Vegetables*, released in September of that year on the UK label Cherry Red. The album reached number 33 on the UK Albums Chart. Since its initial release, it has been re-released by several other labels, including IRS, Alternative Tentacles, and Cleopatra. The 2005 reissue---the special 25th-anniversary edition---features the original artwork and a bonus 55-minute DVD documenting the making of the album as well as the band\'s early years.
On March 25, 1980, Dead Kennedys were invited to perform at the Bay Area Music Awards in an effort to give the event some \"new wave credibility\", in the words of the organizers. The day of the performance was spent practicing the song they were asked to play, the underground hit \"California über alles\". The band became the talking point of the ceremony when after about 15 seconds into the song, Biafra stopped the band---in a manner reminiscent of Elvis Costello\'s *Saturday Night Live* appearance---and said, \"Hold it! We\'ve gotta prove that we\'re adults now. We\'re not a punk rock band, we\'re a new wave band.\" The band, all wearing white shirts with a big, black S painted on the front, pulled black ties from around the backs of their necks to form a dollar sign, then started playing a new song titled \"Pull My Strings\", a barbed, satirical attack on the ethics of the mainstream music industry, which contained the lyrics, \"Is my cock big enough, is my brain small enough, for you to make me a star?\". The song also referenced The Knack\'s song \"My Sharona\". \"Pull My Strings\" was never recorded for a studio release, though the performance at the Bay Area Music Awards, which was one of only two times that the song was ever performed, was released on the band\'s 1987 compilation album *Give Me Convenience or Give Me Death*. In a 2017 interview about the show Klaus stated, \"We did one other performance of it at The Mabuhay and that was the only other time we performed it\... like within a week of the Bammies\" It's unknown if this performance was ever recorded.
In January 1981, Ted announced that he wanted to leave to pursue a career in architecture and would help look for a replacement. He played his last concert in February 1981. His replacement was D. H. Peligro (Darren Henley). Around the same time, East Bay Ray had tried to pressure the rest of the band to sign to the major record label Polydor Records; Biafra stated that he was prepared to leave the group if the rest of the band wanted to sign to the label, though East Bay Ray asserts that he recommended against signing with Polydor. Polydor decided not to sign the band after they learned that Dead Kennedys\' next single was to be entitled \"Too Drunk to Fuck\".
When \"Too Drunk to Fuck\" came out in May 1981 it caused controversy in the UK, as the BBC feared the single would reach the Top 30, which would necessitate its title being mentioned on *Top of the Pops*. It was never played, although it was simply called \"\'Too Drunk\' by the Kennedys\" by presenter Tony Blackburn.
### *In God We Trust, Inc.*, *Plastic Surgery Disasters* and Alternative Tentacles Records (1981--1985) {#in_god_we_trust_inc._plastic_surgery_disasters_and_alternative_tentacles_records_19811985}
After Peligro joined the band, the extended play *In God We Trust, Inc.* (1981) saw them move toward a more aggressive hardcore/thrash sound. In addition to the EP\'s controversial artwork depicting a gold Christ figure on a cross of dollar bills, the lyrics contained Biafra\'s most biting social and political commentary yet, and songs such as \"Moral Majority\", \"Nazi Punks Fuck Off!\" and \"We\'ve Got a Bigger Problem Now\" placed Dead Kennedys as the spokesmen of social protest, while \"Dog Bite\", a cover version of *Rawhide* and various joke introductions showed a much more whimsical side. In 1982, they released their second studio album, *Plastic Surgery Disasters*. The album\'s cover features a withered starving African child\'s hand being held and dwarfed by a white man\'s hand, a picture that had won the World Press Photo award in 1980, taken in Karamoja district in Uganda by Mike Wells.
The band\'s music had evolved considerably in a short time, moving away from hardcore formulae toward a more innovative jazz-informed style, featuring musicianship and dynamics far beyond other bands in the genre (thus effectively removing the music from that genre). By now the group had become a de facto political force, pitting itself against rising elements of American social and political life such as the religious right, Ronald Reagan and the idle rich. The band continued touring all over the United States, as well as Europe and Australia, and gained a large underground following. While they continued to play live shows during 1983 and 1984, they took a break from releasing new records to concentrate on the Alternative Tentacles record label, which would become synonymous with DIY alternative culture. The band continued to write and perform new material during this time, which would appear on their next album (some of these early performances can be seen in the *DMPO\'s on Broadway* video, originally released by Dirk Dirksen and later reissued on Rhino).
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# Dead Kennedys
## History
### *Frankenchrist* and obscenity trial (1985--1986) {#frankenchrist_and_obscenity_trial_19851986}
The release of the album *Frankenchrist* in 1985 showed the band had grown in musical proficiency and lyrical maturity. While there were still a number of loud/fast songs, much of the music featured an eclectic mix of instruments including trumpets and synthesizers. Around this time Klaus Flouride released the similarly experimental solo EP *Cha Cha Cha With Mr. Flouride*. Lyrically, the band continued their trademark social commentary, with songs such as \"MTV Get Off The Air\" and \"Jock-O-Rama (Invasion of the Beef Patrol)\" poking fun at mainstream America.
However, the controversy that erupted over H.R. Giger\'s *Penis Landscape*, included as an insert with the album, dwarfed the notoriety of its music. The artwork caused a furor with the newly formed Parents Music Resource Center (PMRC). In December 1985 a teenage girl purchased the album at the Wherehouse Records store in Los Angeles County. The girl\'s mother wrote letters of complaint to the California Attorney General and to Los Angeles prosecutors. In June 1986, members of the band, along with other parties involved in the distribution of *Frankenchrist*, were charged criminally with distribution of harmful matter to minors. The store where the teen actually purchased the album was never named in the lawsuit. The criminal charges focused on an illustration by H.R. Giger, titled \"Work 219: Landscape XX\" (also known as *Penis Landscape*). Included as a poster with the album, *Penis Landscape* depicts nine copulating penises and vaginas.
Members of the band and others in the chain of distribution were charged with violating the California Penal Code on a misdemeanor charge carrying a maximum penalty of up to a year in county jail and a base fine of up to \$2,000. Biafra says that during this time government agents invaded and searched his home. The prosecution tried to present the poster to the jury in isolation for consideration as obscene material, but Judge Susan Isacoff ruled that the poster must be considered along with the music and lyrics. The charges against three of the original defendants, Ruth Schwartz (owner of Mordam Records), Steve Boudreau (a distributor involved in supplying *Frankenchrist* to the Los Angeles Wherehouse store), and Salvatore Alberti (owner of the factory where the record was pressed), were dismissed for lack of evidence.
In August 1987, the case went to the jury with two remaining defendants: Jello Biafra and Michael Bonanno (former Alternative Tentacles label manager). However, the criminal trial ended with a hung jury, split 7 to 5 in favor of acquittal. District Attorneys Michael Guarino and Ira Riener made a motion for a retrial which was denied by Judge Isacoff, Superior Court Judge for the County of Los Angeles. The album, however, was banned from many record stores nationwide.
After the break up of the band, Jello Biafra brought up the court case on *The Oprah Winfrey Show*. Biafra was on the show with Tipper Gore as part of a panel discussion on the issues of \"controversial music lyrics\" and censorship.
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# Dead Kennedys
## History
### *Bedtime for Democracy* and break-up (1986) {#bedtime_for_democracy_and_break_up_1986}
In addition to the obscenity lawsuit, the band became increasingly disillusioned with the underground scene as well. The hardcore scene, which had been a haven for free-thinking intellectuals and downtrodden nonconformists, was attracting a more violent audience that imposed an increasing level of brutality on other concertgoers and began to alienate many of the bands and individuals who had helped pioneer the movement in the early 1980s. In earlier years the band had criticized neo-Nazi skinheads for trying to ruin the punk scene, but just as big a problem was the popularity of increasingly macho hardcore bands, which brought the group (and their genre) an audience that had little to do with the ideas/ideals they stood for. Biafra penned new songs such as \"Chickenshit Conformist\" and \"Anarchy for Sale\" that articulated the band\'s feelings about the \"dumbing down\" of punk rock. During the summer they recorded these for their final album, *Bedtime for Democracy*, which was released in November. The artwork, depicting a defaced Statue of Liberty overrun with Nazis, media, opportunists, Klan members, corrupt government officials, and religious zombies, echoed the idea that neither America itself nor the punk scene were safe havens any more for \"your tired, your poor, your huddled masses yearning to breathe free\". The album contains a number of fast/short songs interspersed with jazz (\"D.M.S.O.\"), spoken word (\"A Commercial\") and psychedelia (\"Cesspools In Eden\").
The band decided to split up in January 1986, prior to the recording and release of *Bedtime for Democracy*, and played their last live show with the original lineup on 21 February. Biafra went on to speak about his political beliefs on numerous television shows and he released a number of spoken-word albums. Ray, Flouride, and Peligro also went on to solo careers. As of 2025, it remains the band\'s final studio album.
### Band reformation and death of Peligro (2001--present) {#band_reformation_and_death_of_peligro_2001present}
In 2001, Ray, Peligro, and Flouride reformed the Dead Kennedys, with former Dr. Know singer Brandon Cruz replacing Biafra on vocals. The band played under the name \"DK Kennedys\" for a few concerts, but later reverted to \"Dead Kennedys\" permanently. They played across the continental United States, Europe, Asia, South America, and Russia. Brandon Cruz left the band in May 2003 and was replaced by Jeff Penalty. The band has released two live albums of archival performances on Manifesto Records: *Mutiny on the Bay*, compiled from various live shows including a recording from their last show with Biafra in 1986, and *Live at the Deaf Club*, a recording of a 1979 performance at the Deaf Club in San Francisco which was greeted with more enthusiasm.
On October 9, 2007, a best of album titled *Milking the Sacred Cow* was released. It includes two previously unreleased live versions of \"Soup Is Good Food\" and \"Jock-O-Rama\", originally found on *Frankenchrist*.
Jeff Penalty left the band in March 2008 in what he describes as a \"not amicable split.\" In a statement released, Jeff said that, following a series of disputes, the band had secretly recruited a new singer and played a gig in his neighbourhood, although he also stated he was \"really proud of what we were able to accomplish with Dead Kennedys\". He was replaced by former Wynona Riders singer Ron \"Skip\" Greer. D. H. Peligro also left the band to \"take some personal time off\". He was replaced for a tour by Translator drummer Dave Scheff.
On August 21, 2008, the band announced an extended break from touring due to the health-related issues of Flouride and Peligro. They stated their plans to collaborate on new projects. The band performed a gig in Santa Rosa, California in June 2009, with Peligro returning to the drum kit.
In August 2010, Dead Kennedys announced plans for a short East Coast tour. The lineup assembled for this tour contained East Bay Ray, Peligro, Greer, and bassist Greg Reeves replacing Flouride, who was taking \"personal time off\" from the band. The tour dates included performances in Philadelphia, New York City, Boston, Washington, D.C., Portland, Maine and Hawaii. The band has played a reworked version of their song \"MTV Get Off the Air\", re-titled \"MP3 Get Off the Web\", with lyrics criticizing music piracy during their October 16, 2010, concert at the Rock and Roll Hotel in Washington, D.C.
Dead Kennedys had world tours in 2013 and in 2014, the latter mostly in North American cities. In 2015 and 2016 they toured again, including South America, where they had not played since 2001.
In 2017, East Bay Ray revealed that the band and Jello Biafra had been approached by the Punk-oriented music festival Riot Fest about a potential reunion. While Ray and the rest of the band expressed interest in the concept, Biafra refused.
On April 26, 2019, the group released *DK40*, a live compilation album celebrating 40 years since the band formed.
On October 28, 2022, D.H. Peligro died from an overdose of heroin and fentanyl, although it was initially believed to have been from possible head trauma from a fall at his home that day. Since Peligro\'s death, the band has performed in the UK with Santi Guardiola and the United States with Steve Wilson (who had played in D. H. Peligro\'s band Peligro before) filling in on drums.
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