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Wikipedia talk:Selected anniversaries/April 3

 * 1860 - The first successful Pony Express run from Saint Joseph, Missouri to Sacramento, California is started (completed on April 13).
 * 1865 - American Civil War: Union forces capture Richmond, Virginia, the capital of the break-away Confederate States of America.
 * 1882 - Old West outlaw Jesse James is shot in the back and killed in Saint Joseph, Missouri by Robert Ford for a $5,000 reward.
 * 1942 - World War II: Japanese forces begin an all-out assault on the United States and Filipino troops on the Bataan Peninsula. Bataan fell on April 9 and the Bataan Death March began.
 * Let's save this for April 9th. -- PFHLai 04:02, 2005 Apr 2 (UTC)
 * 1946 - Japanese Lt. General Masaharu Homma is executed outside Manila in the Philippines for leading the Bataan Death March.
 * Let's save this for April 9th. -- PFHLai 04:02, 2005 Apr 2 (UTC)
 * 1948 - President Harry Truman signs the Marshall Plan which authorizes $5 billion in aid for 16 countries.
 * 1968 - Martin Luther King Jr. delivers his "mountaintop" speech.
 * 1974 - The Super Outbreak occurred. 148 tornadoes affected 13 states in 26 hours. It was the biggest tornado outbreak in the planet's recorded history.
 * 1986 - IBM unveils the PC Convertible, the first laptop computer.
 * 1996 - Suspected "Unabomber" Theodore Kaczynski is arrested at his Montana cabin.

re: tornado image
It is bad practice to place generic images in as representations of historical events. So I have removed the tornado image.

Let's try to use only images that are actually of the person or incident in question. Kingturtle 02:15, 3 Apr 2004 (UTC)

Super Outbreak
The link for La Niña needs to be fixed. The title of its article is actually ENSO, for "El Niño-Southern Oscillation". --Kitch 11:50, 3 April 2006 (UTC)

Addition to "On this Day"
Can someone modify the "On this Day" section" on the "Main Page". It should show that this day is observed as Rama Navami. This is a national holiday in India and one of the most auspicious day in Hinduism.Bmayuresh (talk) 04:45, 3 April 2009 (UTC)

2012 notes
— howcheng  {chat} 05:53, 2 April 2012 (UTC)
 * Omitted: Pony Express; Whitechapel murders; Jeju Uprising; Martin Cooper (inventor)
 * Included: Edward the Confessor (2nd appearance, last in 2010; rescued from Ineligible); Oscar Wilde (8th appearance, last in 2010); Kamen Rider Series (2nd appearance, last in 2008; rescued from Ineligible); YFZ Ranch (first appearance)
 * Repeats: Joseph Stalin (2nd consecutive appearance, 4 total)

2013 notes
— howcheng  {chat} 06:15, 2 April 2013 (UTC)
 * Omitted: Edward the Confessor; Oscar Wilde; Joseph Stalin; Kamen Rider Series; YFZ Ranch
 * Included: Whitechapel murders (2nd appearance, last in 2011); Richard Hauptmann (2nd appearance, last in 2006; rescued from Ineligible); Jeju Uprising (3rd appearance, last in 2011); Martin Cooper (inventor) (4th appearance, last in 2011; 40th anniversary); Osborne 1 (first appearance)

2014 notes
— howcheng  {chat} 10:19, 2 April 2014 (UTC)
 * Rescued from Ineligible (unused): Super Outbreak (there was another tornado outbreak article just on, so this is gets left out despite this being its 40th anniversary)
 * Omitted: Whitechapel murders; Richard Hauptmann; Jeju Uprising; Martin Cooper (inventor); Osborne 1
 * Included: Edward the Confessor (3rd appearance, last in 2012); Oscar Wilde (9th appearance, last in 2012); Joseph Stalin (5th appearance, last in 2012); Leadbeater's possum (first appearance); 1996 Croatia USAF CT-43 crash (3rd appearance, last in 2010)

2015 notes
— howcheng  {chat} 10:30, 1 April 2015 (UTC)
 * Moved to Ineligible: Osborne 1 (maintenance)
 * New articles (unused): Binghamton shootings
 * Omitted: Edward the Confessor; Oscar Wilde; Joseph Stalin; Leadbeater's possum; 1996 Croatia USAF CT-43 crash
 * Included: Pony Express (6th appearance, last in 2011); Whitechapel murders (3rd appearance, last in 2013); Marshall Plan (9th appearance, last in 2010; rescued from Ineligible); Kamen Rider Series (3rd appearance, last in 2012); 2013 Argentina floods (first appearance)

2016 notes
— howcheng  {chat} 16:01, 1 April 2016 (UTC)
 * Moved to Ineligible: 1974 Super Outbreak (maintenance)
 * Omitted: Pony Express; Whitechapel murders; Marshall Plan; Kamen Rider Series (ineligible—maintenance); 2013 Argentina floods
 * Included: Edward the Confessor (4th appearance, last in 2014); Oscar Wilde (10th appearance, last in 2014); Joseph Stalin (6th appearance, last in 2014); Masaharu Homma (first appearance; 70th anniversary); 1996 Croatia USAF CT-43 crash (4th appearance, last in 2014' 20th anniversary)

2017 notes
— howcheng  {chat} 02:40, 1 April 2018 (UTC)
 * Moved to Ineligible: Richard Hauptmann (maintenance); Marshall Plan (maintenance); Martin Cooper (inventor) (maintenance)
 * Omitted: Edward the Confessor; Oscar Wilde; Joseph Stalin; Masaharu Homma; 1996 Croatia USAF CT-43 crash
 * Included: Whitechapel murders (4th appearance, last in 2015); Jeju uprising (4th appearance, last in 2013); Leadbeater's possum (2nd appearance, last in 2014); Osborne 1 (2nd appearance, last in 2013; rescued from Ineligible); Mary Carpenter (first appearance); Tony Benn (first appearance); Graham Greene (first appearance)
 * Repeats: Pony Express (3rd consecutive appearance, 8 total)

2018 notes
— howcheng  {chat} 07:24, 3 April 2018 (UTC)
 * Omitted: Pony Express; Whitechapel murders; Leadbeater's possum; Osborne 1; Mary Carpenter; Tony Benn; Graham Greene
 * Included: Edward the Confessor (5th appearance, last in 2016; 10th anniversary); Italian War of 1551–1559 (first appearance); Joseph Stalin (7th appearance, last in 2016); YFZ Ranch (2nd appearance, last in 2012; 975th anniversary); Ernst Chladni (first appearance); Thomas C. Kinkaid (first appearance); Pál Teleki (first appearance)
 * Repeats: Jeju uprising (2nd consecutive appearance, 5 total; 70th anniversary)

2019 notes
— howcheng  {chat} 15:56, 3 April 2019 (UTC)
 * Moved to Ineligible: Leadbeater's possum (maintenance)
 * Omitted: Edward the Confessor; Joseph Stalin; Jeju uprising; YFZ Ranch (ineligible—maintenance); Ernst Chladni; Thomas C. Kinkaid; Pál Teleki
 * Included: Pony Express (9th appearance, last in 2017); Oscar Wilde (11th appearance, last in 2016); Masaharu Homma (2nd appearance, last in 2016); Binghamton shootings (first appearance; 10th anniversary); Al-Adil ibn al-Sallar (first appearance); Gus Grissom (first appearance); Mary Cartwright (first appearance)
 * Repeats: Italian War of 1551–1559 (2nd consecutive appearance, 2 total)

2020 notes
— howcheng  {chat} 17:54, 4 April 2020 (UTC)
 * New articles (unused): Panama Papers
 * Omitted: Italian War of 1551–1559; Oscar Wilde; Masaharu Homma; Binghamton shootings; Al-Adil ibn al-Sallar; Gus Grissom; Mary Cartwright
 * Included: Whitechapel murders (5th appearance, last in 2017); Joseph Stalin (8th appearance, last in 2018); Jeju uprising (6th appearance, last in 2018); United States v. Microsoft Corp. (first appearance; 20th anniversary); Richard of Chichester (first appearance); Cyrus K. Holliday (first appearance); Roza Shanina (first appearance)
 * Repeats: Pony Express (2nd consecutive appearance, 10 total)

2021 notes
— howcheng  {chat} 06:14, 6 April 2021 (UTC)
 * New articles (unused): SethBling
 * Omitted: Pony Express; Whitechapel murders; Joseph Stalin; Jeju uprising; United States v. Microsoft Corp.; Richard of Chichester; Cyrus K. Holliday; Roza Shanina
 * Included: Edward the Confessor (6th appearance, last in 2018); Italian War of 1551–1559 (3rd appearance, last in 2019); Masaharu Homma (3rd appearance, last in 2019; 75th anniversary); Osborne 1 (3rd appearance, last in 2017; 40th anniversary); 1996 Croatia USAF CT-43 crash (5th appearance, last in 2017; 25th anniversary); Thomas C. Kinkaid (2nd appearance, last in 2018); Pál Teleki (2nd appearance, last in 2018; 80th anniversary); Graham Greene (2nd appearance, last in 2017; 30th anniversary)

2022 notes
— howcheng  {chat} 03:47, 4 April 2022 (UTC)
 * New articles (unused): Houston–Mount Everest flight expedition
 * Omitted: Edward the Confessor; Italian War of 1551–1559; Masaharu Homma; Osborne 1; 1996 Croatia USAF CT-43 crash; Pál Teleki; Graham Greene
 * Included: Pony Express (11th appearance, last in 2020); Oscar Wilde (12th appearance, last in 2020); Joseph Stalin (9th appearance, last in 2020; 100th anniversary); Jeju uprising (11th appearance, last in 2020); Panama Papers (first appearance); George Herbert (first appearance); Ernst Chladni (2nd appearance, last in 2018); SethBling (first appearance)


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User:Denniswu

Dennis Wu is a Producer / Presenter in Radio 4, RTHK.

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

title: User:Denniswu


text:
Synthetic diamond

Laboratory-grown (LGD), also called lab-grown diamond, laboratory-created, man-made, artisan-created, artificial, synthetic, or cultured diamond, is diamond that is produced in a controlled technological process (in contrast to naturally formed diamond, which is created through geological processes and obtained by mining). Unlike diamond simulants (imitations of diamond made of superficially similar non-diamond materials), synthetic diamonds are composed of the same material as naturally formed diamonds—pure carbon crystallized in an isotropic 3D form—and share identical chemical and physical properties. the heaviest synthetic diamond ever made weighs 30.18 ct (6.0 g), and the heaviest natural diamond ever found weighs 3167 ct (633.4 g).

Numerous claims of diamond synthesis were reported between 1879 and 1928; most of these attempts were carefully analyzed but none was confirmed. In the 1940s, systematic research of diamond creation began in the United States, Sweden and the Soviet Union, which culminated in the first reproducible synthesis in 1953. Further research activity yielded the discoveries of high pressure high temperature diamond (HPHT) and CVD diamond, named for their production method (high-pressure high-temperature and chemical vapor deposition, respectively). These two processes still dominate synthetic diamond production. A third method in which nanometer-sized diamond grains are created in a detonation of carbon-containing explosives, known as detonation synthesis, entered the market in the late 1990s. A fourth method, treating graphite with high-power ultrasound, has been demonstrated in the laboratory, but as of 2008 had no commercial application.

The properties of synthetic diamonds depend on the manufacturing process. Some have properties such as hardness, thermal conductivity and electron mobility that are superior to those of most naturally formed diamonds. Synthetic diamond is widely used in abrasives, in cutting and polishing tools and in heat sinks. Electronic applications of synthetic diamond are being developed, including high-power switches at power stations, high-frequency field-effect transistors and light-emitting diodes. Synthetic diamond detectors of ultraviolet (UV) light or high-energy particles are used at high-energy research facilities and are available commercially. Due to its unique combination of thermal and chemical stability, low thermal expansion and high optical transparency in a wide spectral range, synthetic diamond is becoming the most popular material for optical windows in high-power lasers and gyrotrons. It is estimated that 98% of industrial-grade diamond demand is supplied with synthetic diamonds.

Both CVD and HPHT diamonds can be cut into gems and various colors can be produced: clear white, yellow, brown, blue, green and orange. The advent of synthetic gems on the market created major concerns in the diamond trading business, as a result of which special spectroscopic devices and techniques have been developed to distinguish synthetic and natural diamonds.

History
In the early stages of diamond synthesis, the founding figure of modern chemistry, Antoine Lavoisier, played a significant role. His groundbreaking discovery that a diamond's crystal lattice is similar to carbon's crystal structure paved the way for initial attempts to produce diamonds. After it was discovered that diamond was pure carbon in 1797, many attempts were made to convert various cheap forms of carbon into diamond. The earliest successes were reported by James Ballantyne Hannay in 1879 and by Ferdinand Frédéric Henri Moissan in 1893. Their method involved heating charcoal at up to 3500 C with iron inside a carbon crucible in a furnace. Whereas Hannay used a flame-heated tube, Moissan applied his newly developed electric arc furnace, in which an electric arc was struck between carbon rods inside blocks of lime. The molten iron was then rapidly cooled by immersion in water. The contraction generated by the cooling supposedly produced the high pressure required to transform graphite into diamond. Moissan published his work in a series of articles in the 1890s.

Many other scientists tried to replicate his experiments. Sir William Crookes claimed success in 1909. Otto Ruff claimed in 1917 to have produced diamonds up to 7 mm in diameter, but later retracted his statement. In 1926, Dr. J. Willard Hershey of McPherson College replicated Moissan's and Ruff's experiments, producing a synthetic diamond. Despite the claims of Moissan, Ruff, and Hershey, other experimenters were unable to reproduce their synthesis.

The most definitive replication attempts were performed by Sir Charles Algernon Parsons. A prominent scientist and engineer known for his invention of the steam turbine, he spent about 40 years (1882–1922) and a considerable part of his fortune trying to reproduce the experiments of Moissan and Hannay, but also adapted processes of his own. Parsons was known for his painstakingly accurate approach and methodical record keeping; all his resulting samples were preserved for further analysis by an independent party. He wrote a number of articles—some of the earliest on HPHT diamond—in which he claimed to have produced small diamonds. However, in 1928, he authorized Dr. C. H. Desch to publish an article in which he stated his belief that no synthetic diamonds (including those of Moissan and others) had been produced up to that date. He suggested that most diamonds that had been produced up to that point were likely synthetic spinel.

ASEA
The first known (but initially not reported) diamond synthesis was achieved on February 16, 1953, in Stockholm by ASEA (Allmänna Svenska Elektriska Aktiebolaget), Sweden's major electrical equipment manufacturing company. Starting in 1942, ASEA employed a team of five scientists and engineers as part of a top-secret diamond-making project code-named QUINTUS. The team used a bulky split-sphere apparatus designed by Baltzar von Platen and Anders Kämpe. Pressure was maintained within the device at an estimated 8.4 GPa and a temperature of 2400 C for an hour. A few small diamonds were produced, but not of gem quality or size.

Due to questions on the patent process and the reasonable belief that no other serious diamond synthesis research occurred globally, the board of ASEA opted against publicity and patent applications. Thus the announcement of the ASEA results occurred shortly after the GE press conference of February 15, 1955.

GE diamond project

In 1941, an agreement was made between the General Electric (GE), Norton and Carborundum companies to further develop diamond synthesis. They were able to heat carbon to about 3000 C under a pressure of 3.5 GPa for a few seconds. Soon thereafter, the Second World War interrupted the project. It was resumed in 1951 at the Schenectady Laboratories of GE, and a high-pressure diamond group was formed with Francis P. Bundy and H. M. Strong. Tracy Hall and others joined the project later.

The Schenectady group improved on the anvils designed by Percy Bridgman, who received a Nobel Prize in Physics for his work in 1946. Bundy and Strong made the first improvements, then more were made by Hall. The GE team used tungsten carbide anvils within a hydraulic press to squeeze the carbonaceous sample held in a catlinite container, the finished grit being squeezed out of the container into a gasket. The team recorded diamond synthesis on one occasion, but the experiment could not be reproduced because of uncertain synthesis conditions, and the diamond was later shown to have been a natural diamond used as a seed.

Hall achieved the first commercially successful synthesis of diamond on December 16, 1954, and this was announced on February 15, 1955. His breakthrough came when he used a press with a hardened steel toroidal "belt" strained to its elastic limit wrapped around the sample, producing pressures above 10 GPa and temperatures above 2000 C. The press used a pyrophyllite container in which graphite was dissolved within molten nickel, cobalt or iron. Those metals acted as a "solvent-catalyst", which both dissolved carbon and accelerated its conversion into diamond. The largest diamond he produced was 0.15 mm across; it was too small and visually imperfect for jewelry, but usable in industrial abrasives. Hall's co-workers were able to replicate his work, and the discovery was published in the major journal Nature. He was the first person to grow a synthetic diamond with a reproducible, verifiable and well-documented process. He left GE in 1955, and three years later developed a new apparatus for the synthesis of diamond—a tetrahedral press with four anvils—to avoid violating a U.S. Department of Commerce secrecy order on the GE patent applications.

Further development
Synthetic gem-quality diamond crystals were first produced in 1970 by GE, then reported in 1971. The first successes used a pyrophyllite tube seeded at each end with thin pieces of diamond. The graphite feed material was placed in the center and the metal solvent (nickel) between the graphite and the seeds. The container was heated and the pressure was raised to about 5.5 GPa. The crystals grow as they flow from the center to the ends of the tube, and extending the length of the process produces larger crystals. Initially, a week-long growth process produced gem-quality stones of around 5 mm (1 carat or 0.2 g), and the process conditions had to be as stable as possible. The graphite feed was soon replaced by diamond grit because that allowed much better control of the shape of the final crystal.

The first gem-quality stones were always yellow to brown in color because of contamination with nitrogen. Inclusions were common, especially "plate-like" ones from the nickel. Removing all nitrogen from the process by adding aluminum or titanium produced colorless "white" stones, and removing the nitrogen and adding boron produced blue ones. Removing nitrogen also slowed the growth process and reduced the crystalline quality, so the process was normally run with nitrogen present.

Although the GE stones and natural diamonds were chemically identical, their physical properties were not the same. The colorless stones produced strong fluorescence and phosphorescence under short-wavelength ultraviolet light, but were inert under long-wave UV. Among natural diamonds, only the rarer blue gems exhibit these properties. Unlike natural diamonds, all the GE stones showed strong yellow fluorescence under X-rays. The De Beers Diamond Research Laboratory has grown stones of up to 25 carat for research purposes. Stable HPHT conditions were kept for six weeks to grow high-quality diamonds of this size. For economic reasons, the growth of most synthetic diamonds is terminated when they reach a mass of 1 carat to 1.5 carat.

In the 1950s, research started in the Soviet Union and the US on the growth of diamond by pyrolysis of hydrocarbon gases at the relatively low temperature of 800 C. This low-pressure process is known as chemical vapor deposition (CVD). William G. Eversole reportedly achieved vapor deposition of diamond over diamond substrate in 1953, but it was not reported until 1962. Diamond film deposition was independently reproduced by Angus and coworkers in 1968 and by Deryagin and Fedoseev in 1970. Whereas Eversole and Angus used large, expensive, single-crystal diamonds as substrates, Deryagin and Fedoseev succeeded in making diamond films on non-diamond materials (silicon and metals), which led to massive research on inexpensive diamond coatings in the 1980s.

From 2013, reports emerged of a rise in undisclosed synthetic melee diamonds (small round diamonds typically used to frame a central diamond or embellish a band) being found in set jewelry and within diamond parcels sold in the trade. Due to the relatively low cost of diamond melee, as well as relative lack of universal knowledge for identifying large quantities of melee efficiently, not all dealers have made an effort to test diamond melee to correctly identify whether it is of natural or synthetic origin. However, international laboratories are now beginning to tackle the issue head-on, with significant improvements in synthetic melee identification being made.

Manufacturing technologies
There are several methods used to produce synthetic diamonds. The original method uses high pressure and high temperature (HPHT) and is still widely used because of its relatively low cost. The process involves large presses that can weigh hundreds of tons to produce a pressure of 5 GPa at 1500 C. The second method, using chemical vapor deposition (CVD), creates a carbon plasma over a substrate onto which the carbon atoms deposit to form diamond. Other methods include explosive formation (forming detonation nanodiamonds) and sonication of graphite solutions.

High pressure, high temperature
In the HPHT method, there are three main press designs used to supply the pressure and temperature necessary to produce synthetic diamond: the belt press, the cubic press and the split-sphere (BARS) press. Diamond seeds are placed at the bottom of the press. The internal part of the press is heated above 1400 C and melts the solvent metal. The molten metal dissolves the high purity carbon source, which is then transported to the small diamond seeds and precipitates, forming a large synthetic diamond.

The original GE invention by Tracy Hall uses the belt press wherein the upper and lower anvils supply the pressure load to a cylindrical inner cell. This internal pressure is confined radially by a belt of pre-stressed steel bands. The anvils also serve as electrodes providing electric current to the compressed cell. A variation of the belt press uses hydraulic pressure, rather than steel belts, to confine the internal pressure. Belt presses are still used today, but they are built on a much larger scale than those of the original design.

The second type of press design is the cubic press. A cubic press has six anvils which provide pressure simultaneously onto all faces of a cube-shaped volume. The first multi-anvil press design was a tetrahedral press, using four anvils to converge upon a tetrahedron-shaped volume. The cubic press was created shortly thereafter to increase the volume to which pressure could be applied. A cubic press is typically smaller than a belt press and can more rapidly achieve the pressure and temperature necessary to create synthetic diamond. However, cubic presses cannot be easily scaled up to larger volumes: the pressurized volume can be increased by using larger anvils, but this also increases the amount of force needed on the anvils to achieve the same pressure. An alternative is to decrease the surface area to volume ratio of the pressurized volume, by using more anvils to converge upon a higher-order platonic solid, such as a dodecahedron. However, such a press would be complex and difficult to manufacture.

The BARS apparatus is claimed to be the most compact, efficient, and economical of all the diamond-producing presses. In the center of a BARS device, there is a ceramic cylindrical "synthesis capsule" of about 2 cm3 in size. The cell is placed into a cube of pressure-transmitting material, such as pyrophyllite ceramics, which is pressed by inner anvils made from cemented carbide (e.g., tungsten carbide or VK10 hard alloy). The outer octahedral cavity is pressed by 8 steel outer anvils. After mounting, the whole assembly is locked in a disc-type barrel with a diameter about 1 m. The barrel is filled with oil, which pressurizes upon heating, and the oil pressure is transferred to the central cell. The synthesis capsule is heated up by a coaxial graphite heater, and the temperature is measured with a thermocouple.

Chemical vapor deposition
Chemical vapor deposition is a method by which diamond can be grown from a hydrocarbon gas mixture. Since the early 1980s, this method has been the subject of intensive worldwide research. Whereas the mass production of high-quality diamond crystals make the HPHT process the more suitable choice for industrial applications, the flexibility and simplicity of CVD setups explain the popularity of CVD growth in laboratory research. The advantages of CVD diamond growth include the ability to grow diamond over large areas and on various substrates, and the fine control over the chemical impurities and thus properties of the diamond produced. Unlike HPHT, CVD process does not require high pressures, as the growth typically occurs at pressures under 27 kPa.

The CVD growth involves substrate preparation, feeding varying amounts of gases into a chamber and energizing them. The substrate preparation includes choosing an appropriate material and its crystallographic orientation; cleaning it, often with a diamond powder to abrade a non-diamond substrate; and optimizing the substrate temperature (about 800 C) during the growth through a series of test runs. Moreover, optimizing the gas mixture composition and flow rates is paramount to ensure uniform and high-quality diamond growth. The gases always include a carbon source, typically methane, and hydrogen with a typical ratio of 1:99. Hydrogen is essential because it selectively etches off non-diamond carbon. The gases are ionized into chemically active radicals in the growth chamber using microwave power, a hot filament, an arc discharge, a welding torch, a laser, an electron beam, or other means.

During the growth, the chamber materials are etched off by the plasma and can incorporate into the growing diamond. In particular, CVD diamond is often contaminated by silicon originating from the silica windows of the growth chamber or from the silicon substrate. Therefore, silica windows are either avoided or moved away from the substrate. Boron-containing species in the chamber, even at very low trace levels, also make it unsuitable for the growth of pure diamond.

Detonation of explosives
Diamond nanocrystals (5 nm in diameter) can be formed by detonating certain carbon-containing explosives in a metal chamber. These are called "detonation nanodiamonds". During the explosion, the pressure and temperature in the chamber become high enough to convert the carbon of the explosives into diamond. Being immersed in water, the chamber cools rapidly after the explosion, suppressing conversion of newly produced diamond into more stable graphite. In a variation of this technique, a metal tube filled with graphite powder is placed in the detonation chamber. The explosion heats and compresses the graphite to an extent sufficient for its conversion into diamond. The product is always rich in graphite and other non-diamond carbon forms, and requires prolonged boiling in hot nitric acid (about 1 day at 250 C) to dissolve them. The recovered nanodiamond powder is used primarily in polishing applications. It is mainly produced in China, Russia and Belarus, and started reaching the market in bulk quantities by the early 2000s.

Ultrasound cavitation
Micron-sized diamond crystals can be synthesized from a suspension of graphite in organic liquid at atmospheric pressure and room temperature using ultrasonic cavitation. The diamond yield is about 10% of the initial graphite weight. The estimated cost of diamond produced by this method is comparable to that of the HPHT method but the crystalline perfection of the product is significantly worse for the ultrasonic synthesis. This technique requires relatively simple equipment and procedures, and has been reported by two research groups, but had no industrial use as of 2008. Numerous process parameters, such as preparation of the initial graphite powder, the choice of ultrasonic power, synthesis time and the solvent, were not optimized, leaving a window for potential improvement of the efficiency and reduction of the cost of the ultrasonic synthesis.

Crystallization inside liquid metal
In 2024, scientists announced a method that utilizes injecting methane and hydrogen gases onto a liquid metal alloy of gallium, iron, nickel and silicon (77.25/11.00/11.00/0.25 ratio) at approximately 1,025 °C to crystallize diamond at 1 atmosphere of pressure. The crystallization is a ‘seedless’ process, which further separates it from conventional high-pressure and high-temperature or chemical vapor deposition methods. Injection of methane and hydrogen results in a diamond nucleus after around 15 minutes and eventually a continuous diamond film after around 150 minutes.

Properties
Traditionally, the absence of crystal flaws is considered to be the most important quality of a diamond. Purity and high crystalline perfection make diamonds transparent and clear, whereas its hardness, optical dispersion (luster), and chemical stability (combined with marketing), make it a popular gemstone. High thermal conductivity is also important for technical applications. Whereas high optical dispersion is an intrinsic property of all diamonds, their other properties vary depending on how the diamond was created.

Crystallinity
Diamond can be one single, continuous crystal or it can be made up of many smaller crystals (polycrystal). Large, clear and transparent single-crystal diamonds are typically used as gemstones. Polycrystalline diamond (PCD) consists of numerous small grains, which are easily seen by the naked eye through strong light absorption and scattering; it is unsuitable for gems and is used for industrial applications such as mining and cutting tools. Polycrystalline diamond is often described by the average size (or grain size) of the crystals that make it up. Grain sizes range from nanometers to hundreds of micrometers, usually referred to as "nanocrystalline" and "microcrystalline" diamond, respectively.

Hardness
The hardness of diamond is 10 on the Mohs scale of mineral hardness, the hardest known material on this scale. Diamond is also the hardest known natural material for its resistance to indentation. The hardness of synthetic diamond depends on its purity, crystalline perfection and orientation: hardness is higher for flawless, pure crystals oriented to the [ 111 ]  direction (along the longest diagonal of the cubic diamond lattice). Nanocrystalline diamond produced through CVD diamond growth can have a hardness ranging from 30% to 75% of that of single crystal diamond, and the hardness can be controlled for specific applications. Some synthetic single-crystal diamonds and HPHT nanocrystalline diamonds (see hyperdiamond) are harder than any known natural diamond.

Impurities and inclusions
Every diamond contains atoms other than carbon in concentrations detectable by analytical techniques. Those atoms can aggregate into macroscopic phases called inclusions. Impurities are generally avoided, but can be introduced intentionally as a way to control certain properties of the diamond. Growth processes of synthetic diamond, using solvent-catalysts, generally lead to formation of a number of impurity-related complex centers, involving transition metal atoms (such as nickel, cobalt or iron), which affect the electronic properties of the material.

For instance, pure diamond is an electrical insulator, but diamond with boron added is an electrical conductor (and, in some cases, a superconductor), allowing it to be used in electronic applications. Nitrogen impurities hinder movement of lattice dislocations (defects within the crystal structure) and put the lattice under compressive stress, thereby increasing hardness and toughness.

Thermal conductivity
The thermal conductivity of CVD diamond ranges from tens of W/m2K to more than 2000 W/m2K, depending on the defects, grain boundary structures. As the growth of diamond in CVD, the grains grow with the film thickness, leading to a gradient thermal conductivity along the film thickness direction.

Unlike most electrical insulators, pure diamond is an excellent conductor of heat because of the strong covalent bonding within the crystal. The thermal conductivity of pure diamond is the highest of any known solid. Single crystals of synthetic diamond enriched in 12Carbon (99.9%), isotopically pure diamond, have the highest thermal conductivity of any material, 30 W/cm·K at room temperature, 7.5 times higher than that of copper. Natural diamond's conductivity is reduced by 1.1% by the 13Carbon naturally present, which acts as an inhomogeneity in the lattice.

Diamond's thermal conductivity is made use of by jewelers and gemologists who may employ an electronic thermal probe to separate diamonds from their imitations. These probes consist of a pair of battery-powered thermistors mounted in a fine copper tip. One thermistor functions as a heating device while the other measures the temperature of the copper tip: if the stone being tested is a diamond, it will conduct the tip's thermal energy rapidly enough to produce a measurable temperature drop. This test takes about 2–3 seconds.

Machining and cutting tools

Most industrial applications of synthetic diamond have long been associated with their hardness; this property makes diamond the ideal material for machine tools and cutting tools. As the hardest known naturally occurring material, diamond can be used to polish, cut, or wear away any material, including other diamonds. Common industrial applications of this ability include diamond-tipped drill bits and saws, and the use of diamond powder as an abrasive. These are by far the largest industrial applications of synthetic diamond. While natural diamond is also used for these purposes, synthetic HPHT diamond is more popular, mostly because of better reproducibility of its mechanical properties. Diamond is not suitable for machining ferrous alloys at high speeds, as carbon is soluble in iron at the high temperatures created by high-speed machining, leading to greatly increased wear on diamond tools compared to alternatives.

The usual form of diamond in cutting tools is micron-sized grains dispersed in a metal matrix (usually cobalt) sintered onto the tool. This is typically referred to in industry as polycrystalline diamond (PCD). PCD-tipped tools can be found in mining and cutting applications. For the past fifteen years, work has been done to coat metallic tools with CVD diamond, and though the work shows promise, it has not significantly replaced traditional PCD tools.

Thermal conductor
Most materials with high thermal conductivity are also electrically conductive, such as metals. In contrast, pure synthetic diamond has high thermal conductivity, but negligible electrical conductivity. This combination is invaluable for electronics where diamond is used as a heat spreader for high-power laser diodes, laser arrays and high-power transistors. Efficient heat dissipation prolongs the lifetime of those electronic devices, and the devices' high replacement costs justify the use of efficient, though relatively expensive, diamond heat sinks. In semiconductor technology, synthetic diamond heat spreaders prevent silicon and other semiconducting devices from overheating.

Optical material
Diamond is hard, chemically inert, and has high thermal conductivity and a low coefficient of thermal expansion. These properties make diamond superior to any other existing window material used for transmitting infrared and microwave radiation. Therefore, synthetic diamond is starting to replace zinc selenide as the output window of high-power CO2 lasers and gyrotrons. Those synthetic polycrystalline diamond windows are shaped as disks of large diameters (about 10 cm for gyrotrons) and small thicknesses (to reduce absorption) and can only be produced with the CVD technique. Single crystal slabs of dimensions of length up to approximately 10 mm are becoming increasingly important in several areas of optics including heatspreaders inside laser cavities, diffractive optics and as the optical gain medium in Raman lasers. Recent advances in the HPHT and CVD synthesis techniques have improved the purity and crystallographic structure perfection of single-crystalline diamond enough to replace silicon as a diffraction grating and window material in high-power radiation sources, such as synchrotrons. Both the CVD and HPHT processes are also used to create designer optically transparent diamond anvils as a tool for measuring electric and magnetic properties of materials at ultra high pressures using a diamond anvil cell.

Electronics
Synthetic diamond has potential uses as a semiconductor, because it can be doped with impurities like boron and phosphorus. Since these elements contain one more or one fewer valence electron than carbon, they turn synthetic diamond into p-type or n-type semiconductor. Making a p–n junction by sequential doping of synthetic diamond with boron and phosphorus produces light-emitting diodes (LEDs) producing UV light of 235 nm. Another useful property of synthetic diamond for electronics is high carrier mobility, which reaches 4500 cm2/(V·s) for electrons in single-crystal CVD diamond. High mobility is favorable for high-frequency operation and field-effect transistors made from diamond have already demonstrated promising high-frequency performance above 50 GHz. The wide band gap of diamond (5.5 eV) gives it excellent dielectric properties. Combined with the high mechanical stability of diamond, those properties are being used in prototype high-power switches for power stations.

Synthetic diamond transistors have been produced in the laboratory. They remain functional at much higher temperatures than silicon devices, and are resistant to chemical and radiation damage. While no diamond transistors have yet been successfully integrated into commercial electronics, they are promising for use in exceptionally high-power situations and hostile non-oxidizing environments.

Synthetic diamond is already used as radiation detection device. It is radiation hard and has a wide bandgap of 5.5 eV (at room temperature). Diamond is also distinguished from most other semiconductors by the lack of a stable native oxide. This makes it difficult to fabricate surface MOS devices, but it does create the potential for UV radiation to gain access to the active semiconductor without absorption in a surface layer. Because of these properties, it is employed in applications such as the BaBar detector at the Stanford Linear Accelerator and BOLD (Blind to the Optical Light Detectors for VUV solar observations). A diamond VUV detector recently was used in the European LYRA program.

Conductive CVD diamond is a useful electrode under many circumstances. Photochemical methods have been developed for covalently linking DNA to the surface of polycrystalline diamond films produced through CVD. Such DNA-modified films can be used for detecting various biomolecules, which would interact with DNA thereby changing electrical conductivity of the diamond film. In addition, diamonds can be used to detect redox reactions that cannot ordinarily be studied and in some cases degrade redox-reactive organic contaminants in water supplies. Because diamond is mechanically and chemically stable, it can be used as an electrode under conditions that would destroy traditional materials. As an electrode, synthetic diamond can be used in waste water treatment of organic effluents and the production of strong oxidants.

Gemstones
Synthetic diamonds for use as gemstones are grown by HPHT or CVD methods, and represented approximately 2% of the gem-quality diamond market as of 2013. However, there are indications that the market share of synthetic jewelry-quality diamonds may grow as advances in technology allow for larger higher-quality synthetic production on a more economic scale. Indeed, by 2023, synthetic diamonds' share had increased to 17% of the overall diamond market. They are available in yellow, pink, green, orange, blue and, to a lesser extent, colorless (or white). The yellow color comes from nitrogen impurities in the manufacturing process, while the blue color comes from boron. Other colors, such as pink or green, are achievable after synthesis using irradiation. Several companies also offer memorial diamonds grown using cremated remains.

Gem-quality diamonds grown in a lab can be chemically, physically and optically identical to naturally occurring ones. The mined diamond industry has undertaken legal, marketing and distribution countermeasures to try to protect its market from the emerging presence of synthetic diamonds. Synthetic diamonds can be distinguished by spectroscopy in the infrared, ultraviolet, or X-ray wavelengths. The DiamondView tester from De Beers uses UV fluorescence to detect trace impurities of nitrogen, nickel or other metals in HPHT or CVD diamonds.

At least one maker of laboratory-grown diamonds has made public statements about being "committed to disclosure" of the nature of its diamonds, and laser-inscribed serial numbers on all of its gemstones. The company web site shows an example of the lettering of one of its laser inscriptions, which includes both the words "Gemesis created" and the serial number prefix "LG" (laboratory grown).

In May 2015, a record was set for an HPHT colorless diamond at 10.02 carats. The faceted jewel was cut from a 32.2-carat stone that was grown in about 300 hours. By 2022, gem-quality diamonds of 16–20 carats were being produced.

Traditional diamond mining has led to human rights abuses in Africa and other diamond mining countries. The 2006 Hollywood movie Blood Diamond helped to publicize the problem. Consumer demand for synthetic diamonds has been increasing, albeit from a small base, as customers look for stones that are ethically sound and cheaper.

According to a report from the Gem & Jewellery Export Promotional Council, synthetic diamonds accounted for 0.28% of diamond produced for use as gemstones in 2014. In April 2022, CNN Business reported that engagement rings featuring a synthetic or a lab grown diamond jumped 63% compared to previous year, while the number of engagement rings sold with a natural diamond declined 25% in the same period.

Around 2016, the price of synthetic diamond gemstones (e.g., 1 carat stones) began dropping "precipitously" by roughly 30% in one year, becoming clearly lower than that of mined diamonds. As of 2017, synthetic diamonds sold as jewelry were typically selling for 15–20% less than natural equivalents; the relative price was expected to decline further as production economics improve.

In May 2018, De Beers announced that it would introduce a new jewelry brand called "Lightbox" that features synthetic diamonds.

In July 2018, the U.S. Federal Trade Commission approved a substantial revision to its Jewelry Guides, with changes that impose new rules on how the trade can describe diamonds and diamond simulants. The revised guides were substantially contrary to what had been advocated in 2016 by De Beers. The new guidelines remove the word "natural" from the definition of "diamond", thus including lab-grown diamonds within the scope of the definition of "diamond". The revised guide further states that "If a marketer uses 'synthetic' to imply that a competitor's lab-grown diamond is not an actual diamond, ... this would be deceptive." In July 2019, the third party diamond certification lab GIA (Gemological Institute of America) dropped the word 'synthetic' from its certification process and report for lab-grown diamonds, according to the FTC revision.

title: Synthetic diamond


text:
Talk:Hermann Weyl

Old thread
I replaced this sentence. It didn't sound right to me:

 * In 1913, Weyl published Die Idee der Riemannschen Fläche which unified analysis, geometry and topology in the standard model.

-- Walt Pohl 01:40, 2 Mar 2004 (UTC)
 * In this uncertain world, there is one thing certain: there will never be an English translation of The Idea of Riemannian Surfaces available at a reasonable price to anyone who wants to read it.Lestrade (talk) 15:48, 28 March 2011 (UTC)Lestrade

What are specifics of this wager?

 * George Polya and Weyl, during a mathematicians gathering in Zürich (February 9, 1918), made a bet concerning the least upper bound property. This discussion was on the completely vaguenes of the concepts concerning the construction of the real numbers, sets, and countability [and that the phrases of the least upper bound property is false]. What was in debate was that it may be irrelevant asking about truth of the least upper bound property, other than the basic assertions of Georg Hegel. When the friendly bet ended, the individuals gathered cited Polya as the victor (with Kurt Gödel not in concurrence).

If it's true, it needs to be more specific about the basic assertions of Georg Hegel. Note that neither Polya or Weyl were intuitionists so I doubt very much that any of them doubted the validity of the construction of the real numbers. This sounds very suspicious to me, and unless some reference is provided I think this paragraph should be removed. Moreover, the least upper bound property is not vague; by then it had been well established (for at least 50 years). CSTAR 19:48, 5 Jun 2004 (UTC)
 * I stumbled on this discussion and wondered what on earth the issue had to do with Hegel. I assumed the reference to Hegel was just an error, but I followed the links and found an explanation. In the 'wager' the notoriously obscure philosophy of Hegel was being used as a paradigm case of something too vague to be understood.  So the implication was that the LUB property was as hopelessly vague as Hegel. If they had waited a few years they might have used Heidegger as the paradigm instead!81.146.36.56 (talk) 00:37, 30 November 2019 (UTC)

Weyl did look quite closely at intuitionism, trying to connect it with Husserl's work and studying the effect of impredicativity. He gave up, around 1928/9 - this actually seems to me to be quite an important moment in the history of intuitionism. I'm not saying that Weyl was ever a 'true believer', in the Brouwer sense.

Charles Matthews 20:19, 5 Jun 2004 (UTC)

This is certainly interesting and should be icorporated into teh article (and if some specific assertions of Georg Hegel are quoted I'd suggest keeping the assertion on the wager too.)CSTAR 02:06, 6 Jun 2004 (UTC)

The wager is described bu Gurevich [] as having occurred in 1917. The full details are given in the article. Petrus 12:24, 31 October 2006 (UTC)

Small issues
Does the fragment:

 * Weyl left the professorship at the Technische Hochschule in Zürich, Switzerland, in the year of 1930 and he became  Hilbert's successor at Göttingen where he held the chair of mathematics.

mean

 * Weyl left the professorship at the Technische Hochschule in Zürich, Switzerland, in the year of 1930 to become Hilbert's successor at Göttingen where he held the chair of mathematics.

I was not sure. By the way, the "in the year of" thing sounds clumsy, and it shows up in many places.

Yes, those are meant to be the same, though it is certainly true that the first is awkward. At any rate, if you haven't made it already, I think it would be a good change. 71.183.198.26 (talk) 21:00, 26 December 2008 (UTC)

Does the fragment:

 * Weyl's research of Riemann surfaces and the associated definition of the complex manifold in one dimension. This is part of the theory of complex manifolds and of differential manifolds.

mean:

 * Weyl's research was on Riemann surfaces and the associated definition of the complex manifolds in one dimension. This is part of the theory of complex manifolds and of differential manifolds.

I again would have changed myself, but I am not sure.

This article needs some more stylistic edits. I will get to it sometimes. Oleg Alexandrov 21:15, 18 Jan 2005 (UTC)

Weyl's mathematics
I think the article mainly focuses on Weyl's contribution to physics, though he was more important as a mathematician. Unfortunately, I do not have the expertise to edit the article myself.

Weyl's first research, I believe, was in partial differential equations when he was a student of Hilbert. His most important work was in 1925-26 on the representation theory of compact Lie groups, in which he extended the work of Schur, Hurwitz and Cartan. He had a major influence on differential geometry, introducing the global viewpoint on Lie groups and homogenous spaces, which was then pursued vigorously by Elie Cartan. He invented the term "Lie algebra" in a lecture in the 30s, and that lecture inspired Jacobson to work on Lie algebras. Weyl also first defined principal fibre bundles and connections on them.

I am sure he had many more contributions in mathematics, but I know very little. :(

 * It's not well written, that's for sure. The Lie group work is sort of mentioned. His first research was on operator theory applied to singular cases for things like Sturm-Liouville equations. I'm not sure that's quite right about the topology of Lie groups, connections and bundles; Cartan knew plenty about those, too. Charles Matthews 09:52, 12 Feb 2005 (UTC)

 * Thanks. Well, let's then wait then for somebody who knows more about those things. Oleg Alexandrov 10:17, 12 Feb 2005 (UTC)

I have done something to make the article read better. (Oh, by the way, since I'm British. I'm not sure that's quite right is a little more assertive than it sounds!) I have just noticed that the introduction is also terrible. Charles Matthews 10:31, 12 Feb 2005 (UTC)

 * I had missed that fine point about I'm not sure that's quite right. :)

 * I know some things are not written well here even stylistically. I was not sure about touching the article since I know nothing of the guy. You are welcome to make at least the changes which seem obvious to you. Oleg Alexandrov 10:45, 12 Feb 2005 (UTC)

Hmm... I guess I have to check my sources more carefully then. I thought Weyl was the first person to get any result on the topology of Lie groups. (He proved the finiteness of the fundamental group of a compact Lie group in 1925-26.)

Thanks for editing the article; it looks more comprehensive now. Could you find some way of including the words "Unitary trick" in the section on Lie groups? 210.210.33.46 07:47, 13 Feb 2005 (UTC)

 * I wouldn't dispute what you say about the fundamental group; it can be read off something in the Weyl group theory, I guess (Stiefel diagram? - it's in Frank Adams' book on Lie groups). The whole business of what Elie Cartan knew and when is interesting and would bear writing up more carefully; and we should have an article topology of Lie groups one day that goes into it. It is probably true that an emerging understanding of Lie groups as global was important - as I recall, Hadamard said he could never hack it. Unitarian trick or such-like: in modern terms it says the unitary group is Zariski-dense in its general linear group? And so the representation theory carries across, in a certain sense? It would be good to support this with some of the other relevant articles on the site. Charles Matthews 08:26, 13 Feb 2005 (UTC)

Cassirer
The page states ''moved to a position closer not only to Hilbert but to that of Ernst Cassirer. Weyl however rarely refers to Cassirer, and wrote only brief articles and passages articulating this position.'' Do we have any sources for this? If Weyl rarely refers to Cassirer, how do we know he moved closer to his position? Tkuvho (talk) 19:19, 29 November 2011 (UTC)

Later attitude on Intuitionism?
The Foundations of Mathematics section dates Weyl's quote, "Mathematics with Brouwer gains its highest intuitive clarity..." to 1949, although it was present in the original 1927 version of Philosophie der Mathematik und Naturwissenschaft. Is there any evidence of Weyl's attitude toward intuitionism that can better support the article's claim that, "By 1949, Weyl was thoroughly disillusioned with the ultimate value of intuitionism"? 155.101.16.251 (talk) 20:05, 2 May 2017 (UTC)

Irrelevant information
Especially in the first few sections of this article, there is a lot of irrelevant information. Why? In many cases, this could be deleted or reduced to footnotes -- or reduced to a small section at the end.47.215.183.159 (talk) 09:52, 6 October 2017 (UTC)

title: Talk:Hermann Weyl


text:
The Book of Lost Tales

The Book of Lost Tales is a collection of early stories by the English writer J. R. R. Tolkien, published as the first two volumes of Christopher Tolkien's 12-volume series The History of Middle-earth, in which he presents and analyses the manuscripts of those stories, which were the earliest form (begun in 1917) of the complex fictional myths that would eventually comprise The Silmarillion. Each of the Tales is followed by notes and a detailed commentary by Christopher Tolkien.

For publication the book was split into two volumes: The Book of Lost Tales 1 (1983) and The Book of Lost Tales 2 (1984), but this is simply an editorial division. Each volume contains several "Lost Tales".

Inscriptions
There is an inscription in the Fëanorian characters (Tengwar, an alphabet Tolkien devised for High-Elves) in the first pages of every History of Middle-earth volume, written by Christopher Tolkien and describing the contents of the book. The inscription in Book I reads "This is the first part of the Book of the Lost Tales of Elfinesse which Eriol the Mariner learned from the Elves of Tol Eressëa, the Lonely Isle in the western ocean, and afterwards wrote in the Golden Book of Tavrobel. Herein are told the Tales of Valinor, from the Music of the Ainur to the Exile of the Noldoli and the Hiding of Valinor."

The inscription in Book II reads "This is the second part of the Book of the Lost Tales of Elfinesse which Eriol the Mariner learned from the Elves of Tol Eressëa, the Lonely Isle in the western ocean, and afterwards wrote in the Golden Book of Tavrobel. Herein are told the Tales of Beren and Tinúviel, of Turambar, of the Fall of Gondolin and of the Necklace of the Dwarves."

General
The science fiction author Colin Greenland reviewed The Book of Lost Tales I for Imagine magazine, and stated that "Those who prefer their fairy-tales sophisticated, in weighty prose with scholarly footnotes and appendices, will plunge joyously into J R R Tolkien's first Book of Lost Tales."

The science fiction critic Dave Langford reviewed The Book of Lost Tales II for White Dwarf #59, stating that he had mixed feelings about it, since while it provided some added depth, he was not sure that every detail was worth "annotating with such ghastly solemnity."

Scholarly
The Tolkien scholar Charles Noad, reviewing Part 1 in Mallorn in 1984, notes the mismatches between the names in the book and those in The Silmarillion, the many alternative names, and the varying attributes of the characters when the name remains unchanged. He likens the book's relationship to The Silmarillion to that of a charcoal sketch and the oil painting that it precedes: much work is evidently needed. Further, Tolkien's prose style is at this point still "immature and unsophisticated". Noad quotes Christopher Tolkien's remark that development was usually "by subtle transformation". He finds "very extraordinary" the revelation that the island that the wanderer Eriol sets foot on is what would become England. He notes, too, what he calls a major problem facing Tolkien: how "to present his mythology in the proper perspective", commenting that it was meant to be "a survival from the remotest antiquity". That, Noad writes, requires an indirect approach, which The Hobbit eventually provided: the legendarium became the distant past to the story in the foreground. He concludes that the book will be mainly of [literary] 'archaeological' interest "and cannot be recommended to the casual reader".

Noad, in his review of Part 2, comments that the reviewer's task faces the problem that the sort of comparisons a review would normally make have already all been made, in "abundant detail", by Christopher Tolkien in his commentary and notes. But it was still striking, he wrote, how Beren is here an Elf, not a Man; and Lúthien rescues him not from Sauron but from Tevildo, Prince of Cats. Noad finds it remarkable how much the story had changed, given that the tale of Lúthien and Beren was so important to Tolkien. Of the volume as a whole, Noad comments that it is less "cosmographic" than Part 1, but has a stronger narrative thread. All the same, he feels it is "more of use to the curious" or the researcher than a stand-alone work; he finds the writing "stilted", failing to achieve its intended effects. Evidently, he concludes, Tolkien did not acquire his finished prose style quickly or easily. Noad praises Christopher Tolkien's editing, setting out the complicated materials "astonishingly well".

The Tolkien scholar Vladimir Brljak, writing in Tolkien Studies in 2010, notes that Tolkien's comment in Beowulf: The Monsters and the Critics, that Beowulf was already antiquarian when written, and is now "an echo of an echo", bringing poignant vistas of sad times long gone by, was also a defence of his own writings, where he followed the Beowulf poet in deliberately seeking to create an impression of depth. He did this in the two Books of Lost Tales by creating "an intricate metafictional structure", embedding his works in a framework of "translations of redactions of ancient works, telling of things even more ancient." Brljak argues that this framework is "both the cornerstone and crowning achievement of Tolkien's mature literary work."

title: The Book of Lost Tales


text:
The Lays of Beleriand

The Lays of Beleriand, published in 1985, is the third volume of Christopher Tolkien's 12-volume book series, The History of Middle-earth, in which he analyzes the unpublished manuscripts of his father J. R. R. Tolkien.

Inscription
There is an inscription in the Fëanorian characters (Tengwar, an alphabet Tolkien has devised for High-Elves) in the first pages of every History of Middle-earth volume, written by Christopher Tolkien and describing the contents of the book. The inscription in Book III reads: "In the first part of this Book is given the Lay of the Children of Húrin by John Ronald Reuel Tolkien, in which is set forth in part the Tale of Túrin. In the second part is the Lay of Leithian, which is the Gest of Beren and Lúthien as far as the encounter of Beren with Carcharoth at the gate of Angband".

Contents
The book contains the long heroic lays or lyric poetry that Tolkien wrote: these are The Lay of the Children of Húrin about the saga of Túrin Turambar, and The Lay of Leithian (also called Release from Bondage) which tells the Tale of Beren and Lúthien. Although Tolkien abandoned them before their respective ends, they are both long enough to occupy many stanzas, each of which can last for over ten pages. The first poem is in alliterative verse, and the second is in rhyming couplets. Both exist in two versions.

In addition to these two poems, the book contains three short, soon-abandoned alliterative poems, The Flight of the Noldoli from Valinor, The Lay of Eärendel, and The Lay of the Fall of Gondolin.

The first versions of the long lays fit chronologically in with Tolkien's earliest writings, as recounted in The Book of Lost Tales, but the later version of The Lay of Leithian is contemporary with the writing of The Lord of the Rings.

The book is split into these main sections:

 * 1) The Lay of the Children of Húrin, the tale of Túrin in 2276 lines of verse.
 * 2) First version
 * 3) Second version
 * 4) Poems Early Abandoned:
 * 5) The Flight of the Noldoli
 * 6) Fragment of an alliterative Lay of Earendel
 * 7) The Lay of the Fall of Gondolin
 * 8) The Lay of Leithian (unfinished poem: the Tale of Beren and Lúthien in verse (over 4200 lines of iambic tetrameters, in rhyming couplets):
 * 9) The Gest of Beren son of Barahir and Lúthien the Fay called Tinúviel the Nightingale or the Lay of Leithian - Release from Bondage (split into fourteen cantos)
 * 10) Unwritten cantos
 * 11) Appendix: Commentary by C. S. Lewis
 * 12) The Lay of Leithian Recommenced

In the book Christopher Tolkien mentions a third Túrin poem, this time in rhyming couplets and incomplete. It is called The Children of Húrin and is only 170 lines long (compared to the 2276 lines of the first of the alliterative poems); that poem, however, has been omitted from the book.

Reception and legacy
David Langford reviewed The Lays of Beleriand for White Dwarf #70, stating that "A few gleams of humour come from C. S. Lewis's 15-page critique of an early draft: for the rest, poor old Tolkien lies entombed and fossilized in earnest commentary, like a set text for Eng Lit."

The fantasy novelist Suzannah Rowntree wrote that the book is a favourite of hers, and the only volume of the twelve that she had read in full and "[kept] coming back to for pleasure". In her view, "the book's main attraction is Part III, 'The Lay of Leithian'". She describes this as "a red-blooded, grand poem, written in a richly ornamented style bordering (in places) on the baroque. At worst this seems a little clumsy; at best it fits the lavish, heroic story and setting." She comments that Lewis "obviously enjoyed the poem hugely," going so far as to invent scholars Peabody and Pumpernickel who comment on what Lewis pretends is an ancient text.

The album Oath Bound by the Austrian band Summoning, known for its Tolkien-themed lyrics, contains several songs with lyrics derived from the Lay of Leithian.

Reviews

 * Review by Helen McNabb (1985) in Vector 128
 * Review by Ray Thompson (1986) in Fantasy Review, April 1986
 * Review by Don D'Ammassa (1986) in Science Fiction Chronicle, #80 May 1986
 * Review by Thomas A. Easton [as by Tom Easton] (1986) in Analog Science Fiction/Science Fact, August 1986
 * Review by Andy Sawyer (1987) in Paperback Inferno, #69
 * Review [Spanish] by Eugenio Sánchez Arrate (1998) in Gigamesh, 12, January 1998

title: The Lays of Beleriand


text:
The Shaping of Middle-earth

The Shaping of Middle-earth – The Quenta, The Ambarkanta and The Annals (1986) is the fourth volume of Christopher Tolkien's 12-volume series The History of Middle-earth in which he analysed the unpublished manuscripts of his father J. R. R. Tolkien.

Inscription
There is an inscription in the Fëanorian characters (Tengwar, an alphabet Tolkien has devised for High-Elves) in the first pages of every History of Middle-earth volume, written by Christopher Tolkien and describing the contents of the book. The inscription in Book IV reads: "Herein are the Quenta Noldorinwa, the History of the Gnomes, the Ambarkanta or Shape of the World by Rúmil, the Annals of Valinor and the Annals of Beleriand by Pengolod, the Wise of Gondolin with maps of the world in the Elder Days and translations made by Ælfwine the Mariner of England into the tongue of his own land".

Contents
In The Shaping of Middle-earth the gradual transition from the "primitive" legendarium of The Book of Lost Tales to what would become The Silmarillion is described, and it contains a text which could be seen as the first "Silmarillion": the "Sketch of the Mythology".

Three other parts are the Ambarkanta or "Shape of the World", a collection of maps and diagrams of the world described by Tolkien; and the Annals of Valinor and Beleriand, chronological works which started out as timelines but gradually turned into full narratives.

 * 1) Prose fragments following the Lost Tales — brief, uncompleted texts which continue on from The Book of Lost Tales
 * 2) The earliest "Silmarillion" — also referred to as the "Sketch of the Mythology", this is the start of the Silmarillion proper
 * 3) The Quenta Noldorinwa — a further developed version of the "Sketch", the first full narrative since the legends and the only instance where Tolkien completed it. It is notable for having the latest full narrative of the story of Tuor and the fall of the hidden Elven city of Gondolin.
 * 4) The first "Silmarillion" map — a reproduction of the first map of Beleriand
 * 5) The Ambarkanta — cosmological essays, maps, and diagrams
 * 6) The earliest Annals of Valinor
 * 7) The earliest Annals of Beleriand

The Annals of Valinor and Annals of Beleriand show the earliest outline of the chronology of the First Age as envisaged in the early 1930s. The next volume in the series, The Lost Road and Other Writings (1987), outlined revisions to both texts made c. 1937 as "The Later Annals of Valinor" and "The Later Annals of Beleriand".

title: The Shaping of Middle-earth


text:
Jōetsu Shinkansen

The Jōetsu Shinkansen (上越新幹線) is a high-speed shinkansen railway line connecting Tokyo and Niigata, Japan, via the Tōhoku Shinkansen, operated by the East Japan Railway Company (JR East). Despite its name, the line does not pass through the city of Jōetsu or the historical Jōetsu region, which instead are served by the Hokuriku Shinkansen. The name instead originates from the parallel Jōetsu Line, which in turn is named after the two provinces that it connects: Jōshū (an alternate name for Kōzuke Province which comprises today's Gunma Prefecture), and Echigo Province (modern day Niigata Prefecture).

Train services

 * Toki, Tokyo - Niigata (limited-stop/ mostly all-stations since 30 December 2002) (Although it was first introduced as an all-stations service from 1982 to 1997)
 * Tanigawa, Tokyo - Echigo-Yuzawa/ Gala-Yuzawa (Seasonal) (all-stations / mostly all-stations since 1 October 1997)

Discontinued services

 * Asahi, Tokyo - Niigata (discontinued 30 November 2002)
 * Max Asahi, Tokyo - Niigata (discontinued 30 November 2002)
 * Max Toki, Tokyo - Niigata (discontinued 17 October 2021)
 * Max Tanigawa, Tokyo - Echigo-Yuzawa/ Gala-Yuzawa (Seasonal) (discontinued 1 October 2021)

Stations
Legend:

The Gala-Yuzawa Line is a 1.8 km branch from Echigo-Yuzawa to Gala-Yuzawa Station. It operates in the winter months only, serving the adjoining ski resort.

As of 18 March 2023, the maximum line speed is 130.0 km/h between Tokyo and Omiya, and 275 km/h between Omiya and Niigata. The fastest Shinkansen from Tokyo to Niigata is 1 hour and 29 minutes, and 1 hour and 31 minutes from Niigata to Tokyo. Like all Shinkansen lines, the Jōetsu Shinkansen is standard gauge.

Rolling stock
the following train types operate on Jōetsu Shinkansen services.
 * E7 series: Toki / Tanigawa (since 3 March 2019)

Between fiscal 2018 and 2020, eleven 12-car E7 series train sets were introduced on Jōetsu Shinkansen services, replacing the E4 series trains, raising the speed from 240 km/h to 275 km/h. Additional sets were gradually introduced through 2023 for the replacement of E2 series trains.

Former rolling stock

 * 200 series: Toki / Tanigawa (1982 until March 2013)
 * E1 series: Max Asahi / Max Toki / Max Tanigawa (until September 2012)
 * E2 series: Toki / Tanigawa (January 2013 until March 2023)
 * E4 series: Max Toki / Max Tanigawa (until October 2021)

History
The program to build the new line was initiated in 1971 by Niigata-born prime minister Tanaka Kakuei; one popular anecdote is that Tanaka determined the line's routing by drawing it on a map with a red pencil. Built at a cost of $6.3 billion, it was built "to establish closer ties with Tokyo and promote regional development".

Trial runs over the line began in November 1980, and regular service began on 15 November 1982. The line was initially planned to terminate at Shinjuku Station, but economic considerations pushed Japanese National Railways (JNR) to merge the line with the existing Tōhoku Shinkansen line at Ōmiya.

In September 1991, a 400 Series Shinkansen train set a Japanese rail speed record of 345 km/h on the Jōetsu Shinkansen line, and in December 1993, the STAR21 experimental train recorded 425 km/h. The maximum speed for regular services on the line at the time was 245 km/h except for the section between Jomo-Kogen and Urasa which is 275 km/h for E2 series trains travelling towards Niigata. The urban section between Tokyo and Ōmiya is 110 km/h.

The Basic Plan specifies that the Jōetsu Shinkansen should actually start from Shinjuku, which would necessitate building 30 km of additional Shinkansen track from Ōmiya. While some land acquisitions along the existing Saikyō Line were made, no construction ever started.

The entire line was upgraded to 275 km/h, with construction starting in May 2019, and finished in 2023. Upgrades included improvements to the soundproofing system. This marks the first time that an E7 series train has operated commercially at more than 260 km/h, which is the maximum speed of the only other line served by this train, the Hokuriku Shinkansen. As a result of the upgrades, all trainsets on the Jōetsu Shinkansen operate exclusively with E7 series trainsets and the travel time on the line is projected to be reduced by 7 minutes compared to the former E2 and E4 series trainsets. The end of E2 series trainsets on Jōetsu Shinkansen services took take place on 17 March 2023 with the streamlining of all services to use the E7 series taking place the following day.

Future plans
The Niigata prefectural government has proposed building a new multi-modal terminal to directly connect the Shinkansen to the port of Niigata, potentially allowing direct transfers to ferries and cruise ships, and to potentially allow direct access between the Shinkansen and Niigata Airport. However this plan is foreseen to be completed only by the mid-2040s.

Special event train services
On 17 November 2012, a special Joetsu Shinkansen 30th Anniversary (上越新幹線開業30周年号) service ran as Toki 395 from Omiya to Niigata using 10-car 200 series set K47.

Also on 17 November 2012, a special Joetsu Shinkansen 30th Anniversary (上越新幹線開業30周年号) service ran from Niigata to Tokyo using E5 series set U8, with a special ceremony at Niigata Station before departure. This was the first revenue-earning service operated on the Joetsu Shinkansen by an E5 series trainset.

title: Jōetsu Shinkansen


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Pudendal nerve entrapment

Pudendal nerve entrapment (PNE), also known as Alcock canal syndrome,  is an uncommon  source of chronic pain in which the pudendal nerve (located in the pelvis) is entrapped or compressed in Alcock's canal. There are several different types of PNE based on the site of entrapment anatomically (see Anatomy). Pain is positional and is worsened by sitting. Other symptoms include genital numbness, fecal incontinence and urinary incontinence.

The term pudendal neuralgia (PN) is often used interchangeably with "pudendal nerve entrapment". This condition can greatly affect a person's quality of life. Pudendal neuralgia can be caused by many factors including inflammation, extreme cycling, and can be a "secondary condition to childbirth". A 2009 review study found both that "prevalence of PN is unknown and it seems to be a rare event" and that "there is no evidence to support equating the presence of this syndrome with a diagnosis of pudendal nerve entrapment," meaning that it could be possible to have all the symptoms of pudendal nerve entrapment (otherwise known as pudendal neuralgia) based on the criteria specified at Nantes in 2006, without having an entrapped pudendal nerve.

A 2015 study of 13 normal female cadavers found that the pudendal nerve was attached or fixed to the sacrospinous ligament (therefore "entrapped") in all cadavers studied, suggesting that the diagnosis of pudendal nerve entrapment may be overestimated.

Symptoms
There are no specific clinical signs or complementary test results for this condition.

Genito-anal numbness and fecal or urinary incontinence can occur. People may also experience a burning pain in perianal or genital areas.

In male competitive cyclists, it is often called "cyclist syndrome", in which cyclists rarely develop recurrent numbness of the penis and scrotum after prolonged cycling, or an altered sensation of ejaculation, with disturbance of micturition (urination) and reduced awareness of defecation. Nerve entrapment syndromes, presenting as genitalia numbness, are amongst the most common bicycling associated urogenital problems.

Pain, if present, is positional and typically caused by sitting and relieved by standing, lying down or sitting on a toilet seat. If the perineal pain is positional (changes with a person's position, for example sitting or standing), this suggests a tunnel syndrome. Anesthesiologist John S. McDonald of UCLA reports that sitting pain relieved by standing or sitting on a toilet seat is the most reliable diagnostic parameter.

A systematic review study found that PN may be implicated in various sexual dysfunctions such as persistent genital arousal disorder (PGAD), erectile dysfunction, premature ejaculation, and vestibulodynia. Additionally, another review that looked at cycling-related sexual dysfunction suggested that cycling may indirectly cause sexual dysfunction by disturbing the testosterone signaling aspect of the hypothalamic-pituitary-gonadal axis of the body.

Anatomy
The pudendal nerve carries both motor and sensory axons. It stems from the spinal nerves S2–S4 of the sacral plexus. The nerve progresses through the piriformis and coccygeus muscles and exits the pelvis by passing through the greater sciatic foramen. The pudendal nerve then re-enters the pelvic cavity by passing through the lesser sciatic foramen. After re-entering the pelvis, it breaks off into three branches known as the inferior rectal nerve, the perineal nerve, and the dorsal sensory nerve of the penis or clitoris. These three nerves are also referred to as the terminal branches, and they are more susceptible to injuries due to their locations.

There are also four levels of pudendal nerve entrapment compressions: entrapment below the piriformis muscle, entrapment that occurs between the sacrospinous ligament and sacrotuberous ligament (most common cause), entrapment in the Alcock canal, and entrapment of the terminal branches. Although there has been no evidence for a direct functional connection between the pudendal nerve and sacrotuberous ligament, many clinical studies have pointed at the sacrotuberous ligament as a potential cause of PNE. Around the ischial level of the spine, pudendal nerve runs between the sacrotuberous ligament and the sacrospinous ligament (posteriorly and anteriorly, respectively), giving way for potential compression of the pudendal nerve.

Causes
PNE is said to be caused by genitoanal surgical scarring and mishaps in the pelvic region, trauma to the pelvis, pregnancy, childbirth, bicycling and anatomic abnormalities. Vaginal birth may lead to pudendal nerve damage from the stretch during delivery and the likelihood increases when delivering larger-than-average babies. As the pudendal nerve lies in the pelvic region, surgical procedures that involve this area, such as a caesarean section, can cause nerve injury.

PNE can present in cyclists, likely due to both the compression and stretching of the pudendal nerve for prolonged time. Heavy and prolonged bicycling, especially if an inappropriately shaped or incorrectly positioned bicycle seat is used, may eventually thicken the sacrotuberous and/or sacrospinous ligaments and trap the nerve between them, resulting in PNE.

Anatomic abnormalities can result in PNE due to the pudendal nerve being fused to different parts of the anatomy, or trapped between the sacrotuberous and sacrospinalis ligaments.

Pathophysiology
Prolonged pressure on the pudendal nerve and chronic traction injuries interrupt the normal microvasculature of the pudendal nerve triggering a cascade of physiological changes. The sequence of physiologic changes are a breakdown of the blood-nerve barrier, followed by edema and connective tissue changes, followed by diffuse demyelination, and finally Wallerian degeneration. In the acute form, a metabolic block by an impaired blood supply will interrupt normal function of the pudendal nerve. In the chronic form, neuropraxia and axonmetesis (Sunderland type 1 and 2) injuries will create positive symptoms (e.g. pain and paresthesias) and negative symptoms (loss of sensation).

Diagnosis
Labat et al state that "there are no specific clinical signs or complementary test results of this disease". Kaur et al confirm that there are no specific and consistent radiological findings in patients with PNE.

Diagnostic tests that can be performed to suggest PNE are:

 * Pudendal nerve blocks to confirm the pudendal nerve is the source of pain through relief from the procedure. These diagnostic blocks can also be used in place of spinal anesthesia during delivery.
 * Quantitative sensory threshold testing to detect the inability to sense temperature changes.
 * High-frequency ultrasonography to identify the location of pudendal nerve compression.
 * Doppler ultra sound to detect vein compression, a result of nerve compression.
 * Pudendal nerve terminal motor latency test, an invasive diagnostic test that involves a rectal or vaginal exam.

Diagnoses are made through neurophysiological testing rather than imaging. However, MRI and CT imaging may be used to exclude other diagnoses.

Similar to a Tinel's sign digital palpation of the ischial spine may produce pain. In contrast, people may report temporary relief with a diagnostic pudendal nerve block (see Injections), typically infiltrated near the ischial spine. It is important to note that the duration of pain relief from pudendal nerve block is different per person. Imaging studies using MR neurography may be useful. In people with unilateral pudendal entrapment in the Alcock's canal, it is typical to see asymmetric swelling and hyperintensity affecting the pudendal neurovascular bundle.

Nantes Criteria
Pudendal nerve entrapment is difficult to diagnose and there are no specific examinations that can clearly confirm the diagnosis. A multidisciplinary group in Nantes, France developed a set of diagnostic criteria (the "Nantes Criteria") to serve as a guide to physicians in diagnosing PNE. It consists of inclusions, exclusions, and complementary characteristics of the syndrome. Some sources discourage the use of this guide due to errors found in the criteria.

Inclusion criteria are:

 * 1) The involved area corresponds to the area of supplied by the pudendal nerve (anus to the clitoris or penis).
 * 2) Pain worsened by sitting, because of increased pressure on the nerve.
 * 3) The patient is not awoken by pain during sleep.
 * 4) No objective loss of sensation on clinical examination. Loss of superficial sensation in the perineal area is more indicative of a lesion at the root of the sacral nerves.
 * 5) Pain relieved by an anesthetic block of the pudendal nerve.

Exclusion criteria are:

 * Imaging results used for exclusion
 * Unilateral pain
 * Abnormal diagnostic test results
 * Pain is acute

Complementary criteria are:

 * Nerve pain associated with extreme sensitivity to touch
 * Described as burning/shooting pain
 * Posterior pain following defecation

A systematic review by Indraccolo et al analyzed PN due to pudendal entrapment and PN without pudendal entrapment in women with chronic pelvic-perianal pain. The review classified the Nantes' criteria as the gold standard for diagnosing PN secondary to PNE. Because of this, the authors of the systematic review additionally suggest that the criteria may be useful in assessing the efficacy and effectiveness of the pudendal nerve entrapment treatments that people may undergo.

Differential diagnosis
Differential diagnosis should consider the far commoner conditions chronic prostatitis/chronic pelvic pain syndrome and interstitial cystitis. Other causes for similar symptoms of pudendal nerve entrapment include compression from a tumor, prostatitis in males, uterine diseases in females, complex regional pain syndrome (CRPS), superficial skin infections, and other neuropathies that share the same region as the pudendal nerve.

Treatment
Treatments include behavioral modifications, physical therapy, analgesics and other medications, pudendal nerve block, and surgical nerve decompression. A newer form of treatment is pulsed radiofrequency. Most medical treatments are intended for symptomatic relief, such as pain. If symptoms are not managed through this standard of care, surgery is considered.

Nerve protection
This is a form of self treatment to keep pressure off the pudendal nerve. It involves avoiding any activities that may increase pain in the pelvic area. A seat cushion with the center area removed may be used to provide relief and prevent further pain. A 2021 systematic review of preventative and therapeutic strategies found that cyclists who take precautions in maintaining proper posture may prevent the development of a more severe disorder. It is also suggested that using a wider seat when cycling could prevent damage to the nerve, but more evidence is necessary to show long-term benefit.

Physical therapy
Mobilization of the nerves and muscles in the pelvic region is a proposed way to treat symptoms associated with a nerve entrapment. An example of this is neural mobilization. The goal of neural mobilization is to restore the functionality of the nerve and muscles through a variety of exercises involving the lower extremities. Exercises to specifically target the pudendal nerve would be determined based on the anatomical layout of the nerve. It is important to note that evidence is limited to show support for this therapy.

Another possible treatment for nerve entrapments in the pelvic region would be stretching and strengthening exercises. A treatment plan would be determined by a physical therapist to specifically manipulate the pudendal nerve through a variety of stretches. Strengthening exercises may also be recommended to relieve the excessive pressure caused by the entrapment, but there is currently limited evidence to support this choice of therapy.

Medications
There are numerous pharmaceutical treatments for neuropathic pain associated with pudendal neuralgia. Drugs used include anti-epileptics (like gabapentin ), antidepressants (like amitriptyline ), and palmitoylethanolamide. Often times polypharmacy is used with consideration of medication history and side effects.

Injections
One way to identify and alleviate pain associated with the pudendal nerve is a "CT-guided nerve block." During this procedure, "a long-acting local anesthetic (bupivacaine hydrochloride) and a corticosteroid (e.g. methylprednisolone) are injected to provide immediate pudendal anesthesia." A pudendal nerve block can be inserted from several different anatomical locations including: transvaginal, transperitoneal, and perirectal. A reduction in pain following this injection is typically felt quickly. The most common side effect of a pudendal nerve block is injection site irritation. Relief from chronic pain may be achieved through this procedure due to the reduced inflammation from the steroid medication, and "steroid-induced fat necrosis" which "can reduce inflammation in the region around the nerve" to lessen strain on the pudendal nerve. This treatment may alleviate symptoms for up to 73% of people. Treatment of pudendal nerve entrapment by nerve block is not often prescribed due to "discomfort associated with the local injections as well as the risk of injuring critical structures."

Pulsed radiofrequency
This can be used instead of pudendal nerve perineural injections. In recent years, Pulsed radiofrequency (PRF) is starting to become more common for managing chronic pain, and has shown to have long-term benefits and low problem occurrences. Pulsed radiofrequency has also been successful in treating a refractory case of pudendal neuralgia, but additional research is needed to study the effectiveness of pulsed radiofrequency on treating pudendal nerve entrapment. Pudendal Nerve Stimulation (PNS) was found to significantly decrease subjective pain levels in people with pudendal neuralgia. A majority of people who underwent PNS reported "significant" or "remarkable" pain relief at 2 weeks after treatment.

Ergonomics
Various ergonomic devices can be used to allow an individual to sit while helping to take pressure off of the nerve. A few recommendations to decrease nerve compression while cycling include having soft, wide seat in a horizontal position and setting the handlebar height lower than the seat. There are also bicycle seats designed to prevent pudendal nerve compression, these seats usually have a narrow channel in the middle of them. Additionally, other recommendations include wearing padded bike shorts, standing on pedals periodically, shifting to higher gears, and taking frequent breaks. For sitting on hard surfaces, a cushion or coccyx cushion can be used to take pressure off the nerves.

Surgical
Decompression surgery is a "last resort", according to surgeons who perform the operation. It is highly controversial.

According to supporters of the theory of PNE, surgery is indicated when severe symptoms are present after exhausting all other forms of treatment. The surgery is also another option to confirm the diagnosis of pudendal nerve entrapment.

The surgery is performed by a small number of surgeons in a limited number of countries. The validity of decompression surgery as a treatment and the existence of entrapment as a cause of pelvic pain are highly controversial. While a few doctors will prescribe decompression surgery, most will not. Notably, in February 2003 the European Association of Urology in its Guidelines on Pelvic Pain said that expert centers in Europe have found no cases of PNE and that surgical success is rare:

"Pudendal nerve neuropathy is likely to be a probable diagnosis if the pain is unilateral, has a burning quality and is exacerbated by unilateral rectal palpation of the ischial spine, with delayed pudendal motor latency on that side only. However, such cases account for only a small proportion of all those presenting with perineal pain. Proof of diagnosis rests on pain relief following decompression of the nerve in Alcock's canal and is rarely achieved. The value of the clinical neurophysiological investigations is debatable; some centres in Europe claim that the investigations have great sensitivity, while other centres, which also have a specialized interest in pelvic floor neurophysiology, have not identified any cases."

There are several different approaches in order to perform a decompression surgery on the pudendal nerve. The different access areas include: superior transgluteal, superior retrosciatic, inferior retrosciatic, medial transgluteal, inferior transgluteal and transischial entry. The transgluteal entry involves "neurolysis of the PN at the infrapiriform canal and transection of the sacrospinal ligament." Another point of entry which is described as a "perineal para-anal pathway", "follows the inferior rectal nerve to the Alcock's canal."

If nerve damage is discovered, other surgery options may be considered like a "neurectomy" or "neuromodulation".

title: Pudendal nerve entrapment


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Tweed, Ontario

Tweed is a municipality located in central-eastern Ontario, Canada, in Hastings County.

History
The Municipality of Tweed is an amalgamated municipality comprising the former Village of Tweed and the former Hungerford Township and former Elzevir & Grimsthorpe Townships. The Municipality was incorporated on 1 January 1998 as a lower-tier municipality within the County of Hastings two-tier governing system.

The post office was established in 1852.

Elzevir Township (formed circa 1869, location of a major gold strike ) and Grimsthorpe Township (formed 22 February 1867 during the local gold rush) had been administered as one entity since before 1968 until amalgamation into the Municipality of Tweed.

As of 2004, the total land area was approximately 230,000 acre, 30% of which was Crown land. Lakes, rivers and streams account for approximately 4,650 acre. There are approximately 600 km of roads throughout the Municipality. The total 2004 property assessment for the Municipality of Tweed was $309,000,000. Its composition was 84% residential, 7% farm, 6% commercial and industrial, and 3% other categories.

A primary attraction in the Municipality of Tweed is a vacation destination located at 115 Varty Road, with cottages and campsites along the Skootamatta River, a part of the Moira River system. From 2000, it was managed as Tipper's Family Campground, run by the family of Canadian violist, Jayden Tipper. Purchased by the Haid family in 2018, it is managed as Haid's Hideaway Family Campground.

Immediately east of the Village of Tweed is Stoco Lake, home to a popular and uncommon sport-fish, the muskellunge or Muskie (Esox masquinongy). Stoco Lake is a part of the Moira River system; the Black River joins the Moira River near the Village of Tweed.

The Napanee, Tamworth and Quebec Railway (later the Bay of Quinte Railway) had a spur from Tamworth, Ontario to Tweed; the Tweed-Yarker and Tweed-Bannockburn segments were abandoned by 1941 and the former Napanee-Smiths Falls mainline abandoned in the late 1970s. From the 1880s, the Canadian Pacific Railway's Havelock Subdivision passed through Tweed to Glen Tay and Smith Falls. The line was abandoned from Glen Tay to Tweed in 1973 then Tweed to Havelock in 1987. A more westerly portion of the line still runs through Peterborough.

Communities
Besides the village proper of Tweed, the Municipality of Tweed comprises a number of villages and hamlets, including the following communities such as Actinolite, Bogart, Buller, Chapman, Cosy Cove, Coulters Hill, Duff Corners, East Hungerford ( 44.502°N, -77.151°W ), Elzevir, Farrell Corners ( 44.452°N, -77.134°W ), Hungerford, Larkins, Lime Lake, Lodgeroom Corners, Lost Channel ( 44.419°N, -77.316°W ), Marlbank, Moneymore, Otter Creek, Queensborough, Stoco, Sulphide, and Thomasburg ( 44.38896°N, -77.3459°W )

Approximately 30% of the population resides in the Village of Tweed, the only urban center. The remainder of the Municipality of Tweed consists of a large rural area which reaches from Wadsworth Lake in the north to Roslin in the south. The Municipality of Tweeds has five hamlets: (Actinolite, Marlbank, Queensborough, Stoco, and Thomasburg). The residents of the hamlets and the rural area comprise the other 70% of the population. In 2004, there were approximately 2870 households.

Demographics
In the 2021 Census of Population conducted by Statistics Canada, Tweed had a population of $6,067$ living in $2,591$ of its $3,042$ total private dwellings, a change of NaN% from its 2016 population of $6,044$. With a land area of 918.61 km2, it had a population density of in 2021.

Populations prior to amalgamation (1998):
 * Total Population in 1996: 5,706
 * Elzevir and Grimsthorpe township: 854
 * Hungerford township: 3,280
 * Tweed village: 1,572
 * Population in 1991:
 * Elzevir and Grimsthorpe township: 781
 * Hungerford township: 3,085
 * Tweed village: 1,626

Mother tongue:
 * English as first language: 95.8%
 * French as first language: 0.8%
 * English and French as first language: 0.4%
 * Other as first language: 3.0%

Forest fire protection history
The Tweed Forest Fire District was founded by the former Ontario Department of Lands and Forests (now the MNR) in 1922 as one of 17 districts to help protect Ontario's forests from fire by early detection from fire towers. The headquarters for the district were housed at Hungerford Road in town. It was the central headquarters for 21 fire lookout towers. When a fire was spotted in the forest a towerman would get the degree bearings from his respective tower and radio back the information to headquarters. When one or more towermen from other towers in the area would also call in their bearings, the forest rangers at headquarters could get a 'triangulation' read and plot the exact location of the fire on their map. This way a team of forest firefighters could be dispatched as soon as possible to get the fire under control. In 1958 the 100 ft-tall Hungerford firetower was erected beside the station. However, in the 1970s all the towers had been decommissioned as aerial firefighting techniques were employed. The Hungerford tower was disassembled in 1996 and placed behind the Tweed Heritage Centre.

Notable stories

 * Tweed made national news in 2010 when Colonel Russell Williams, a resident of Ottawa who had a cottage in Tweed, was arrested and accused of the murders of Jessica Lloyd and Corporal Marie-France Comeau. Williams was convicted in 2010 and received two life sentences for the first-degree murders. Williams is in prison in Port-Cartier, Quebec.
 * On December 14, 2017, a Hydro One helicopter working on a row of transmission towers crashed northeast of Tweed. All 4 people on board, the pilot and three electrical workers, were killed.
 * On March 10, 2021, a fire destroyed the landmark Tweedsmuir Hotel. Built in 1886 the hotel had many names and owners but was always a cornerstone of the community.

title: Tweed, Ontario