title: Père Lachaise Cemetery

text: This strategy achieved its desired effect: people began clamoring to be buried among the famous citizens. Records show that the Père Lachaise contained more than 33,000 graves in 1830. Père Lachaise was expanded five times: in 1824, 1829, 1832, 1842 and 1850. Presently there are more than 1 million bodies buried there, and many more in the columbarium, which holds the remains of those who had requested cremation.


title: Père Lachaise Cemetery

text: The Communards' Wall ("Mur des Fédérés"), located within the cemetery, was the site where 147 Communards were executed by the French Army during the Semaine sanglante, "The Bloody Week", following the final battles between the Army and the Paris Commune. The Commune soldiers had been captured in earlier battles by the French Army, were taken to the prisons of Mazas and la Roquette, where they were quickly tried by military courts and sentenced to death. They were then taken to Pere Lachaise, where they were lined up against the wall and shot, and buried in common graves. the site is a traditional rallying point for members of the French political Left. Adolphe Thiers, the second elected President of France, and the first President of the French Third Republic, who led the suppression of the Commune, is also interred in the cemetery.


title: Père Lachaise Cemetery

text: A funerary chapel was erected in 1823 by Étienne-Hippolyte Godde at the exact place of the ancient Jesuit house. This same Neoclassical architect created the monumental entrance a few years later.


title: Père Lachaise Cemetery

text: A columbarium and a crematorium of a Byzantine Revival architecture were designed in 1894 by Jean-Camille Formigé in one building. The roof consists of a large brick and sandstone dome, three small domes and two chimneys. In the 1920s, the main dome was decorated with stained glass windows by Carl Maumejean. The final columbarium is composed of four levels: two in the basement and two exterior levels, both can contain more than 40,800 cases.


title: Père Lachaise Cemetery

text: The crematorium was the first built in France. The first cremation took place on 30 January 1889, a little over a year after the law of 15 November 1887 proclaimed freedom of funerals and thus authorized cremations. Nonetheless, cremation remained uncommon until the end of the 20th century. With the work of anticlerical and free-thinkers (Charles-Ange Laisant, André Lorulot), the use of cremation became more popular after overturning of the ban by the Catholic Church in 1963. From 49 cremations in 1889, there were about 5,000 cremations at the beginning of the 21st century. In 2012, cremation represents 45% of funerals in Paris.


title: Père Lachaise Cemetery

text: Inside the columbarium rest the remains of numerous celebrities including the director Max Ophuls and the comedian Pierre Dac. The box inscribed with Maria Callas’ name is only a cenotaph.


title: Père Lachaise Cemetery

text: An 1804 law put in place by Napoleon addressed the question of cemetery organization relating to religious beliefs. It was required that an entire cemetery be built, or at least a section of a large cemetery, should be dedicated to a specific religion. Another law in 1881 repealed the former law but by that time at Père Lachaise, a Jewish enclosure and a Muslim enclosure already existed.


title: Père Lachaise Cemetery

text: The law of separation of church and state on 9 December 1905 had no impact on Père Lachaise because religious emblems were still allowed on private funeral monuments. The cemetery cross was removed in June 1883.


title: Père Lachaise Cemetery

text: Where the former house of Père Lachaise stood, Alexandre-Theodore Brongniart envisioned an outstanding pyramid to be used by all Christian denominations. It was never constructed but the Parisian architect Etienne Hippolyte Godde began building a chapel in 1820. It was sanctified by the Catholic Church in 1834 and is supported by the basilique Notre-Dame du Perpetuel Secours.


title: Père Lachaise Cemetery

text: In 1804, a law was passed which allowed the sharing of cemeteries between diverse religions. The Jewish enclosure in Père Lachaise opened on 18 February 1810 in the 7th division. Enclosed by a wall, this part of the cemetery included a purification room and a pavilion for the caretaker.


title: Père Lachaise Cemetery

text: From 1865 to 1887 the 87th division also served as the Jewish enclosure. After the revocation of segregation within cemeteries in 1881, the walls of the enclosure were destroyed, and the Jewish dead were buried in the 96th division.


title: Père Lachaise Cemetery

text: Some noteworthy individuals buried in the 19th century include the actress Rachel Felix, the first French rabbi, David Sintzheim, and Robles, Singer and Fould Rothschild.


title: Père Lachaise Cemetery

text: In 1856, a Muslim enclosure was opened in the 85th division – part of this section of the cemetery was newly acquired in the last extension in 1850. Work on the mosque started in 1855 based on the plans created by Marie-Gabriel Jolivet. The monument included a waiting room, a lavatorium intended for the purification of Muslims, and a counter for religious effects.


title: Père Lachaise Cemetery

text: The Muslim enclosure opened on 1 January 1857, making it the first Muslim cemetery in France. Between 1856 and 1870, there were only 44 burials – 6 perpetual concessions, 7 temporary and 31 free of charge. The enclosure was reduced multiple times and in 1871, an unused part was dedicated to the Jewish religion.


title: Père Lachaise Cemetery

text: The law of 14 November 1881 made segregation in cemeteries illegal. The fence of the enclosure was removed but the plant hedge was preserved. Despite the law, the mosque was conserved but the Ottoman Empire, responsible for maintenance, lapsed in their responsibility. Plans for reconstruction were made, but during WWI, when the Ottomans became an ally to Germany and an enemy to France, those plans were cancelled. The mosque was destroyed in 1914 and a plan for reconstruction was abandoned in 1923 in lieu of the project to build the Grand Mosque of Paris.


title: Père Lachaise Cemetery

text: In 1899, the Monument aux Morts by Albert Bartholomé was erected in Père Lachaise as a memorial to unidentified deceased Parisians. The monument holds a communal ossuary. In addition to the elaborate tombs, there are various monuments dedicate to individuals or groups of people including:


title: Père Lachaise Cemetery

text: Behind the "Aux Morts" (To the Dead) monument sculpted by Paul-Albert Bartholomé lies an ossuary of the bones of Parisians from cemeteries all over the city, a smaller kind of modern-day catacombs. Although the monument is well known, it is not general knowledge that it is also an ossuary, and its doors usually remain closed and locked to the public. When it became overcrowded recently, the bones were removed for cremation and returned to the ossuary after the incineration process. In the Père Lachaise ossuary, efforts are made to store bones and ashes in separate boxes.


title: Père Lachaise Cemetery

text: Père Lachaise is still an operating cemetery and accepting new burials. However, the rules to be buried in a Paris cemetery are rather strict: people may be buried in one of these cemeteries if they die in the French capital city or if they lived there. Being buried in Père Lachaise is even more difficult nowadays as there is a waiting list: very few plots are available. The grave sites at Père Lachaise range from a simple, unadorned headstone to towering monuments and even elaborate mini chapels dedicated to the memory of a well-known person or family. Many of the tombs are about the size and shape of a telephone booth, with just enough space for a mourner to step inside, kneel to say a prayer, and leave some flowers.


title: Père Lachaise Cemetery

text: The cemetery manages to squeeze an increasing number of bodies into a finite and already crowded space. One way it does this is by combining the remains of multiple family members in the same grave. At Père Lachaise, it is not uncommon to reopen a grave after a body has decomposed and inter another coffin. Some family mausoleums or multi-family tombs contain dozens of bodies, often in several separate but contiguous graves. Shelves are usually installed to accommodate their remains.


title: Père Lachaise Cemetery

text: During relatively recent times, the Père Lachaise has adopted a standard practice of issuing 30-year leases on gravesites, so that if a lease is not renewed by a family, the remains can be removed, space made for a new grave, and the overall deterioration of the cemetery minimized. Abandoned remains are boxed, tagged and moved to "Aux Morts" ossuary, still in the Père Lachaise cemetery.


title: Père Lachaise Cemetery

text: Plots can be bought in perpetuity or for 50, 30 or 10 years, the last being the least expensive option. Even for the case of mausoleums and chapels, coffins are usually below ground.


title: Père Lachaise Cemetery

text: Although some sources incorrectly estimate the number of interred as 300,000 in Père Lachaise, according to the official website of the city of Paris, one million people have been buried there to date. Along with the stored remains in the "Aux Morts" ossuary, the number of human remains exceeds 2–3 million.


title: Père Lachaise Cemetery

text: Père Lachaise is often referenced in French culture and has been included in various films, literary works, video games and songs. A number of English-language works also make reference to the cemetery.


title: Binary code

text: A binary code represents text, computer processor instructions, or any other data using a two-symbol system. The two-symbol system used is often "0" and "1" from the binary number system. The binary code assigns a pattern of binary digits, also known as bits, to each character, instruction, etc. For example, a binary string of eight bits (which is also called a byte) can represent any of 256 possible values and can, therefore, represent a wide variety of different items.


title: Binary code

text: In computing and telecommunications, binary codes are used for various methods of encoding data, such as character strings, into bit strings. Those methods may use fixed-width or variable-width strings. In a fixed-width binary code, each letter, digit, or other character is represented by a bit string of the same length; that bit string, interpreted as a binary number, is usually displayed in code tables in octal, decimal or hexadecimal notation. There are many character sets and many character encodings for them.


title: Binary code

text: A bit string, interpreted as a binary number, can be translated into a decimal number. For example, the lower case "a", if represented by the bit string codice_1 (as it is in the standard ASCII code), can also be represented as the decimal number "97".


title: Binary code

text: The modern binary number system, the basis for binary code, was invented by Gottfried Leibniz in 1689 and appears in his article "Explication de l'Arithmétique Binaire". The full title is translated into English as the "Explanation of the binary arithmetic", which uses only the characters 1 and 0, with some remarks on its usefulness, and on the light it throws on the ancient Chinese figures of Fu Xi. Leibniz's system uses 0 and 1, like the modern binary numeral system. Leibniz encountered the "I Ching" through French Jesuit Joachim Bouvet and noted with fascination how its hexagrams correspond to the binary numbers from 0 to 111111, and concluded that this mapping was evidence of major Chinese accomplishments in the sort of philosophical visual binary mathematics he admired. Leibniz saw the hexagrams as an affirmation of the universality of his own religious belief.


title: Binary code

text: Binary numerals were central to Leibniz's theology. He believed that binary numbers were symbolic of the Christian idea of "creatio ex nihilo" or creation out of nothing. Leibniz was trying to find a system that converts logic verbal statements into a pure mathematical one. After his ideas were ignored, he came across a classic Chinese text called "I Ching" or ‘Book of Changes’, which used 64 hexagrams of six-bit visual binary code. The book had confirmed his theory that life could be simplified or reduced down to a series of straightforward propositions. He created a system consisting of rows of zeros and ones. During this time period, Leibniz had not yet found a use for this system.


title: Binary code

text: Binary systems predating Leibniz also existed in the ancient world. The aforementioned "I Ching" that Leibniz encountered dates from the 9th century BC in China. The binary system of the "I Ching", a text for divination, is based on the duality of yin and yang. Slit drums with binary tones are used to encode messages across Africa and Asia. The Indian scholar Pingala (around 5th–2nd centuries BC) developed a binary system for describing prosody in his "Chandashutram".


title: Binary code

text: The residents of the island of Mangareva in French Polynesia were using a hybrid binary-decimal system before 1450. In the 11th century, scholar and philosopher Shao Yong developed a method for arranging the hexagrams which corresponds, albeit unintentionally, to the sequence 0 to 63, as represented in binary, with yin as 0, yang as 1 and the least significant bit on top. The ordering is also the lexicographical order on sextuples of elements chosen from a two-element set.


title: Binary code

text: In 1605 Francis Bacon discussed a system whereby letters of the alphabet could be reduced to sequences of binary digits, which could then be encoded as scarcely visible variations in the font in any random text. Importantly for the general theory of binary encoding, he added that this method could be used with any objects at all: "provided those objects be capable of a twofold difference only; as by Bells, by Trumpets, by Lights and Torches, by the report of Muskets, and any instruments of like nature".


title: Binary code

text: George Boole published a paper in 1847 called 'The Mathematical Analysis of Logic' that describes an algebraic system of logic, now known as Boolean algebra. Boole's system was based on binary, a yes-no, on-off approach that consisted of the three most basic operations: AND, OR, and NOT. This system was not put into use until a graduate student from Massachusetts Institute of Technology, Claude Shannon, noticed that the Boolean algebra he learned was similar to an electric circuit. In 1937, Shannon wrote his master's thesis, "A Symbolic Analysis of Relay and Switching Circuits", which implemented his findings. Shannon's thesis became a starting point for the use of the binary code in practical applications such as computers, electric circuits, and more.


title: Binary code

text: The bit string is not the only type of binary code: in fact, a binary system in general, is any system that allows only two choices such as a switch in an electronic system or a simple true or false test.


title: Binary code

text: Braille is a type of binary code that is widely used by the blind to read and write by touch, named for its creator, Louis Braille. This system consists of grids of six dots each, three per column, in which each dot has two states: raised or not raised. The different combinations of raised and flattened dots are capable of representing all letters, numbers, and punctuation signs.


title: Binary code

text: The "bagua" are diagrams used in "feng shui," Taoist cosmology and "I Ching" studies. The "ba gua" consists of 8 trigrams; "bā" meaning 8 and "guà" meaning divination figure. The same word is used for the 64 guà (hexagrams). Each figure combines three lines ("yáo") that are either broken ("yin") or unbroken ("yang"). The relationships between the trigrams are represented in two arrangements, the primordial, "Earlier Heaven" or "Fuxi" "bagua", and the manifested, "Later Heaven,"or "King Wen" "bagua." (See also, the King Wen sequence of the 64 hexagrams).


title: Binary code

text: The Ifá/Ifé system of divination in African religions, such as of Yoruba, Igbo, Ewe, consists of an elaborate traditional ceremony producing 256 oracles made up by 16 symbols with 256 = 16 x 16. An initiated priest "babalowo" who had memorized oracles, would request sacrifice from consulting clients and make prayers. Then, divination nuts or a pair of chains are used to produce random binary numbers, which are drawn with sandy material on an "Opun" figured wooden tray representing the totality of fate.


title: Binary code

text: Through the spread of Islamic culture, Ifé/Ifá was assimilated as the "Science of Sand" (ilm al-raml), which then spread further and became "Science of Reading the Signs on the Ground" (Geomancy) in Europe.


title: Binary code

text: This was thought to be another possible route from which computer science was inspired, as Geomancy arrived at Europe at an earlier stage (about 12th Century, described by Hugh of Santalla) than I Ching (17th Century, described by Gottfried Wilhelm Leibniz).


title: Binary code

text: The American Standard Code for Information Interchange (ASCII), uses a 7-bit binary code to represent text and other characters within computers, communications equipment, and other devices. Each letter or symbol is assigned a number from 0 to 127. For example, lowercase "a" is represented by codice_2 as a bit string (which is "97" in decimal).


title: Binary code

text: Binary-coded decimal (BCD) is a binary encoded representation of integer values that uses a 4-bit nibble to encode decimal digits. Four binary bits can encode up to 16 distinct values; but, in BCD-encoded numbers, only ten values in each nibble are legal, and encode the decimal digits zero, through nine. The remaining six values are illegal and may cause either a machine exception or unspecified behavior, depending on the computer implementation of BCD arithmetic.


title: Binary code

text: BCD arithmetic is sometimes preferred to floating-point numeric formats in commercial and financial applications where the complex rounding behaviors of floating-point numbers is inappropriate.


title: Binary code

text: Most modern computers use binary encoding for instructions and data. CDs, DVDs, and Blu-ray Discs represent sound and video digitally in binary form. Telephone calls are carried digitally on long-distance and mobile phone networks using pulse-code modulation, and on voice over IP networks.


title: Binary code

text: The weight of a binary code, as defined in the table of constant-weight codes, is the Hamming weight of the binary words coding for the represented words or sequences.


title: Castellammarese War

text: The Castellammarese War () was a bloody power struggle for control of the Italian-American Mafia that took place in New York City, New York, from February 1930 until April 15, 1931, between partisans of Joe "The Boss" Masseria and those of Salvatore Maranzano. The war was named after the Sicilian town of Castellammare del Golfo, the birthplace of Maranzano. Maranzano's faction won and divided New York's crime families into the Five Families; Maranzano declared himself "capo di tutti i capi" ("boss of all bosses"). However, Maranzano was murdered in September 1931 on orders of Lucky Luciano, who established a power-sharing arrangement called the Commission, a group of Mafia families of equal stature, to avoid such wars in the future.


title: Castellammarese War

text: In the 1920s, Mafia operations in the United States were controlled by Giuseppe "Joe The Boss" Masseria, whose faction consisted mainly of gangsters from Sicily, along with Calabria (the 'Ndrangheta) and Campania (the Camorra) regions of southern Italy. Masseria's faction included Charles "Lucky" Luciano, Albert "Mad Hatter" Anastasia, Vito Genovese, Alfred Mineo, Willie Moretti, Joe Adonis, and Frank Costello. However, powerful Sicilian Don Vito Ferro decided to make a bid for control of Mafia operations. He sent Salvatore Maranzano from his base in Castellammare del Golfo to seize control. The Castellammarese faction in the U.S. included Joseph "Joe Bananas" Bonanno, Stefano "The Undertaker" Magaddino, Joseph Profaci, and Joe Aiello. As it became more and more evident that the two factions would clash for leadership of the Mafia, they each sought to recruit more followers to support them.


title: Castellammarese War

text: Outwardly, the Castellammarese War was between the forces of Masseria and Maranzano. Underneath, however, there was also a generational conflict between the old guard Sicilian leadership known as the "Mustache Petes" for their long mustaches and old-world ways, such as refusing to do business with non-Italians and the "Young Turks", a younger and more diverse Italian-American group who, unlike the "Mustache Petes", had grown up in the U.S., were more forward-thinking, and were willing to work with non-Italians. This approach led Masseria's followers to question whether he was even capable of making the Mafia prosper in the world of the 1930s. Led by Luciano, the aim of this group was to end the war as soon as possible in order to resume their businesses, viewing the conflict as unnecessary. Luciano's objective was to modernize the mob and do away with unnecessary orthodox norms. This was a vision that enabled Luciano to attract followers, who had seen the inadequacies of Masseria's traditionalist leadership. Therefore, both factions were fluid, with many mobsters switching sides or killing their own allies during the war. Tensions between the Maranzano and Masseria factions were evident as far back as 1928, with one side frequently hijacking the other's alcohol trucks (alcohol production being illegal in the U.S. at that time due to Prohibition).


title: Castellammarese War

text: As the war became more violent, gunmen clashed on the streets of New York City. According to Bonanno, in February 1930 Masseria ordered the death of Gaspar Milazzo, a Castellemmarese native who was the president of Detroit's chapter of . Masseria had reportedly been humiliated by Milazzo's refusal to support him in a dispute involving the Chicago Outfit and Al Capone.


title: Castellammarese War

text: The opening salvo in the war was fired within the Masseria faction when, on February 26, 1930, Masseria ordered the murder of an ally, Gaetano Reina. Masseria gave the job to a young Genovese, who killed Reina with a shotgun. Masseria's intent was to protect his secret allies Tommy Gagliano, Tommy Lucchese, and Dominick "The Gap" Petrilli. Later his treachery would come back to haunt him, as the Reina family then threw its support behind Maranzano. Vito Bonventre also became a target, as Castellammarese-born members of Nicolo Schiro's gang began to threaten Masseria's domination over Mafia gangs. Masseria forced Schiro to pay him US$10,000 (approximately US$170,000 in 2022) and step down as boss of the gang. On July 15, 1930, Bonventre was gunned down outside his garage.


title: Castellammarese War

text: On August 15, 1930, Castellammerese loyalists executed a key Masseria enforcer, Giuseppe Morello, at Morello's East Harlem office (a visitor, Giuseppe Peraino, was also killed). Two weeks later, Masseria suffered another blow. After Reina's murder, Masseria had appointed Joseph Pinzolo to take over the ice-distribution racket. However, on September 9, the Reina family shot and killed Pinzolo at a Times Square office rented by Lucchese. After these two murders, the Reina crew formally joined forces with the Castellammarese.


title: Castellammarese War

text: Masseria soon struck back. On October 23, 1930, Castellammarese ally Joe Aiello, president of the Chicago Unione Siciliane, was murdered in Chicago.


title: Castellammarese War

text: Following the murder of Aiello, the tide of war rapidly turned in favor of the Castellammarese. On November 5, 1930, Mineo and a key member of Masseria's gang, Steve Ferrigno, were murdered. Francesco Scalice inherited control of Mineo's gang and subsequently defected to the Maranzano faction. At this point, many other members of Masseria's gang also began defecting to Maranzano, rendering the original battle lines of the conflict (Castellammarese "versus" non-Castellammarese) meaningless. On February 3, 1931, another important Masseria lieutenant, Joseph Catania, was gunned down, dying two days later.


title: Castellammarese War

text: Given the worsened situation, Masseria allies Luciano and Genovese started communicating with Castellammarese leader Maranzano. The two men agreed to betray Masseria if Maranzano would end the war. A deal was struck, based on which Luciano would arrange for Masseria to be murdered and Maranzano would bring the Castellammarese War to an end. On April 15, 1931, Masseria was killed at Nuova Villa Tammaro, a restaurant in Coney Island, Brooklyn. While they played cards, Luciano allegedly excused himself to the bathroom, with the gunmen reportedly being Anastasia, Genovese, Joe Adonis, and Benjamin "Bugsy" Siegel; Ciro "The Artichoke King" Terranova drove the getaway car, but legend has it that he was too shaken up to drive away and had to be shoved out of the driver's seat by Siegel.


title: Castellammarese War

text: However, according to "The New York Times", "[A]fter that, the police have been unable to learn definitely [what happened]". Reputedly Masseria was "seated at a table playing cards with two or three unknown men" when he was fired upon from behind. He died from gunshot wounds to his head, back, and chest. Masseria's autopsy report shows that he died on an empty stomach. No witnesses came forward, though "two or three" men were observed leaving the restaurant and getting into a stolen car. No one was convicted in Masseria's murder as there were no witnesses and Luciano had an alibi.


title: Castellammarese War

text: With the death of Masseria, the war ended. Maranzano organized the Mafia in New York City using a clear structure and hierarchy by dividing the main Italian gangs in New York into Five Families. Each family had a boss, underboss, consigliere, capos, soldiers, and associates. While associates could come from any background, the higher ranks had to be "made men", required in most eras to be full-blooded Italian Americans. Shortly after Masseria's death, Maranzano announced that the Five Families would be led by Luciano, Joe Bonanno, Joseph Profaci, Vincent Mangano and Thomas Gagliano.


title: Castellammarese War

text: Except for New York City, the major urban areas in the Northeast and Midwest were organized into one family per city by Maranzano; due to the size of organized crime in New York, it was organized into five separate families. The bosses of the Five Families of New York were to be Luciano (now the Genovese crime family), Profaci (now the Colombo crime family), Gagliano (now the Lucchese crime family), Maranzano (now the Bonanno crime family), and Frank Scalice (now the Gambino crime family). Maranzano called a meeting of crime bosses in Wappingers Falls, New York, where he declared himself "capo di tutti capi" ("boss of all bosses").


title: Castellammarese War

text: Each crime "family" was to be headed by a "boss", who was assisted by an "underboss" (the third-ranking position of "consigliere" was added somewhat later). Below the underboss, the family was divided into crews, each headed by a "caporegime", or "capo", and staffed by "soldiers". The soldiers would often be assisted by associates, who were not yet members. Associates could also include non-Italians who worked with the family, and would include Meyer Lansky and Benjamin "Bugsy" Siegel.


title: Castellammarese War

text: Maranzano's reign as "capo di tutti capi" was short-lived. Although Maranzano was slightly more forward-thinking than Masseria, Luciano had come to believe that Maranzano was even more greedy and hidebound than Masseria had been. On September 10, 1931, he was shot and stabbed to death in his Manhattan office by a team of Jewish triggermen (recruited by Lansky), which included Samuel "Red" Levine, Bo Weinberg, and Bugsy Siegel.


title: Castellammarese War

text: With both Maranzano and Masseria out of the way, it was easier for the Young Turks, led by Luciano, to assume control of the way things functioned in New York City. The first agenda on the table was the reformation and restructuring of the American Mafia. Luciano envisioned the future of the American Mafia in the form of a major corporation. He believed that this would increase cooperation, reduce conflict and ensure plain sailing governance by the Mafia as a whole. Since Maranzano had formed a basic structure that was in the process of being put into effect, Luciano decided to retain the concept to a large extent. Owing to his clear disregard for orthodox ideologies that did not have any profitable consequences, Luciano allowed for more flexibility in the structure, allowing for the inclusion of other societal groups like the Jews to involve themselves with the families. In Joe Bonanno's autobiography "A Man of Honor", he states: "We revised the old custom of looking toward one man, one supreme leader for advice and the settling of disputes. We replaced leadership by one man with leadership by committee. We opted for a parliamentary arrangement whereby a group of the most important men in our world would assume the function formerly performed by one man."


title: Castellammarese War

text: In the aftermath of the Maranzano hit, there was believed to have been a massive purge of "old-timer" mafiosi, the so-called "Night of the Sicilian Vespers". These rumors were seemingly confirmed by the testimony of Joseph Valachi, but a later study found no signs of such massive violence occurring. Luciano formed "The Commission" to oversee all Mafia activities in the United States and serve to mediate conflicts between families, eliminating the "capo di tutti capi" position.


title: Castellammarese War

text: In the end, both of the traditional factions in the New York Mafia lost the war. The real winners were the younger and more ruthless generation of mobsters, headed by Luciano. With their ascension to power, organized crime was poised to expand into a truly national and multi-ethnic combination.


title: Carboxylic acid

text: In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is ' or ', with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion.


title: Carboxylic acid

text: Carboxylic acids are commonly identified by their trivial names. They at oftentimes have the suffix "-ic acid". IUPAC-recommended names also exist; in this system, carboxylic acids have an "-oic acid" suffix. For example, butyric acid (CHCOH) is butanoic acid by IUPAC guidelines. For nomenclature of complex molecules containing a carboxylic acid, the carboxyl can be considered position one of the parent chain even if there are other substituents, such as 3-chloropropanoic acid. Alternately, it can be named as a "carboxy" or "carboxylic acid" substituent on another parent structure, such as 2-carboxyfuran.


title: Carboxylic acid

text: The carboxylate anion (R–COO or RCO) of a carboxylic acid is usually named with the suffix "-ate", in keeping with the general pattern of "-ic acid" and "-ate" for a conjugate acid and its conjugate base, respectively. For example, the conjugate base of acetic acid is acetate.


title: Carboxylic acid

text: Carbonic acid, which occurs in bicarbonate buffer systems in nature, is not generally classed as one of the carboxylic acids, despite that it has a moiety that looks like a COOH group.


title: Carboxylic acid

text: Carboxylic acids are polar. Because they are both hydrogen-bond acceptors (the carbonyl –C=O) and hydrogen-bond donors (the hydroxyl –OH), they also participate in hydrogen bonding. Together, the hydroxyl and carbonyl group form the functional group carboxyl. Carboxylic acids usually exist as dimers in nonpolar media due to their tendency to "self-associate". Smaller carboxylic acids (1 to 5 carbons) are soluble in water, whereas bigger carboxylic acids have limited solubility due to the increasing hydrophobic nature of the alkyl chain. These longer chain acids tend to be soluble in less-polar solvents such as ethers and alcohols. Aqueous sodium hydroxide and carboxylic acids, even hydrophobic ones, react to yield water-soluble sodium salts. For example, enanthic acid has a low solubility in water (0.2 g/L), but its sodium salt is very soluble in water.


title: Carboxylic acid

text: Carboxylic acids tend to have higher boiling points than water, because of their greater surface areas and their tendency to form stabilised dimers through hydrogen bonds. For boiling to occur, either the dimer bonds must be broken or the entire dimer arrangement must be vaporised, increasing the enthalpy of vaporization requirements significantly.


title: Carboxylic acid

text: Carboxylic acids are Brønsted–Lowry acids because they are proton (H) donors. They are the most common type of organic acid.


title: Carboxylic acid

text: Carboxylic acids are typically weak acids, meaning that they only partially dissociate into HO cations and RCOO anions in neutral aqueous solution. For example, at room temperature, in a 1-molar solution of acetic acid, only 0.001% of the acid are dissociated (i.e. 10 moles out of 1 mol). Electron-withdrawing substituents, such as -CF group, give stronger acids (the pK of formic acid is 3.75 whereas trifluoroacetic acid, with a trifluoromethyl substituent, has a pK of 0.23). Electron-donating substituents give weaker acids (the pK of formic acid is 3.75 whereas acetic acid, with a methyl substituent, has a pK of 4.76)


title: Carboxylic acid

text: Deprotonation of carboxylic acids gives carboxylate anions; these are resonance stabilized, because the negative charge is delocalized over the two oxygen atoms, increasing the stability of the anion. Each of the carbon–oxygen bonds in the carboxylate anion has a partial double-bond character. The carbonyl carbon's partial positive charge is also weakened by the -/ negative charges on the 2 oxygen atoms.


title: Carboxylic acid

text: Carboxylic acids often have strong sour odours. Esters of carboxylic acids tend to have fruity, pleasant odours, and many are used in perfume.


title: Carboxylic acid

text: Carboxylic acids are readily identified as such by infrared spectroscopy. They exhibit a sharp band associated with vibration of the C=O carbonyl bond ("ν") between 1680 and 1725 cm. A characteristic "ν" band appears as a broad peak in the 2500 to 3000 cm region. By H NMR spectrometry, the hydroxyl hydrogen appears in the 10–13 ppm region, although it is often either broadened or not observed owing to exchange with traces of water.


title: Carboxylic acid

text: Many carboxylic acids are produced industrially on a large scale. They are also frequently found in nature. Esters of fatty acids are the main components of lipids and polyamides of aminocarboxylic acids are the main components of proteins.


title: Carboxylic acid

text: Carboxylic acids are used in the production of polymers, pharmaceuticals, solvents, and food additives. Industrially important carboxylic acids include acetic acid (component of vinegar, precursor to solvents and coatings), acrylic and methacrylic acids (precursors to polymers, adhesives), adipic acid (polymers), citric acid (a flavor and preservative in food and beverages), ethylenediaminetetraacetic acid (chelating agent), fatty acids (coatings), maleic acid (polymers), propionic acid (food preservative), terephthalic acid (polymers). Important carboxylate salts are soaps.


title: Carboxylic acid

text: In general, industrial routes to carboxylic acids differ from those used on a smaller scale because they require specialized equipment.


title: Carboxylic acid

text: Preparative methods for small scale reactions for research or for production of fine chemicals often employ expensive consumable reagents.


title: Carboxylic acid

text: Many reactions produce carboxylic acids but are used only in specific cases or are mainly of academic interest.


title: Carboxylic acid

text: The most widely practiced reactions convert carboxylic acids into esters, amides, carboxylate salts, acid chlorides, and alcohols. Carboxylic acids react with bases to form carboxylate salts, in which the hydrogen of the hydroxyl (–OH) group is replaced with a metal cation. For example, acetic acid found in vinegar reacts with sodium bicarbonate (baking soda) to form sodium acetate, carbon dioxide, and water:


title: Carboxylic acid

text: Carboxylic acids also react with alcohols to give esters. This process is widely used, e.g. in the production of polyesters. Likewise, carboxylic acids are converted into amides, but this conversion typically does not occur by direct reaction of the carboxylic acid and the amine. Instead esters are typical precursors to amides. The conversion of amino acids into peptides is a significant biochemical process that requires ATP.


title: Carboxylic acid

text: The hydroxyl group on carboxylic acids may be replaced with a chlorine atom using thionyl chloride to give acyl chlorides. In nature, carboxylic acids are converted to thioesters.


title: Carboxylic acid

text: Like esters, most carboxylic acids can be reduced to alcohols by hydrogenation, or using hydride transferring agents such as lithium aluminium hydride. Strong alkyl transferring agents, such as organolithium compounds but not Grignard reagents, will reduce carboxylic acids to ketones along with transfer of the alkyl group.


title: Carboxylic acid

text: "N","N"-Dimethyl(chloromethylene)ammonium chloride (ClHC=N(CH)Cl) is a highly chemoselective agent for carboxylic acid reduction. It selectively activates the carboxylic acid to give the carboxymethyleneammonium salt, which can be reduced by a mild reductant like lithium tris("t"-butoxy)aluminum hydride to afford an aldehyde in a one pot procedure. This procedure is known to tolerate reactive carbonyl functionalities such as ketone as well as moderately reactive ester, olefin, nitrile, and halide moieties.


title: Carboxylic acid

text: The carboxyl radical, •COOH, only exists briefly. The acid dissociation constant of •COOH has been measured using electron paramagnetic resonance spectroscopy. The carboxyl group tends to dimerise to form oxalic acid.


title: Metamorphoses

text: The Metamorphoses (, from : "Transformations") is a Latin narrative poem from 8 CE by the Roman poet Ovid. It is considered his "magnum opus". The poem chronicles the history of the world from its creation to the deification of Julius Caesar in a mythico-historical framework comprising over 250 myths, 15 books, and 11,995 lines.


title: Metamorphoses

text: Although it meets some of the criteria for an epic, the poem defies simple genre classification because of its varying themes and tones. Ovid took inspiration from the genre of metamorphosis poetry and some of the "Metamorphoses" derives from earlier treatment of the same myths; however, he diverged significantly from all of his models.


title: Metamorphoses

text: One of the most influential works in Western culture, the "Metamorphoses" has inspired such authors as Dante Alighieri, Giovanni Boccaccio, Geoffrey Chaucer, and William Shakespeare. Numerous episodes from the poem have been depicted in works of sculpture, painting, and music. Although interest in Ovid faded after the Renaissance, there was a resurgence of attention to his work towards the end of the 20th century. Today the "Metamorphoses" continues to inspire and be retold through various media. Numerous English translations of the work have been made, the first by William Caxton in 1480.


title: Metamorphoses

text: Ovid's decision to make myth the primary subject of the "Metamorphoses" was influenced by Alexandrian poetry. In that tradition myth functioned as a vehicle for moral reflection or insight, yet Ovid approached it as an "object of play and artful manipulation". The model for a collection of metamorphosis myths was found in the metamorphosis poetry of the Hellenistic tradition, which is first represented by Boio(s)' "Ornithogonia"—a now-fragmentary poem of collected myths about the metamorphoses of humans into birds.


title: Metamorphoses

text: There are three examples of "Metamorphoses" by later Hellenistic writers, but little is known of their contents. The "Heteroioumena" by Nicander of Colophon is better known, and clearly an influence on the poem—21 of the stories from this work were treated in the "Metamorphoses". However, in a way that was typical for writers of the period, Ovid diverged significantly from his models. The "Metamorphoses" was longer than any previous collection of metamorphosis myths (Nicander's work consisted of probably four or five books) and positioned itself within a historical framework.


title: Metamorphoses

text: Some of the "Metamorphoses" derives from earlier literary and poetic treatment of the same myths. This material was of varying quality and comprehensiveness—while some of it was "finely worked", in other cases Ovid may have been working from limited material. In the case of an oft-used myth such as that of Io in Book I, which was the subject of literary adaptation as early as the 5th century BC, and as recently as a generation prior to his own, Ovid reorganises and innovates existing material in order to foreground his favoured topics and to embody the key themes of the "Metamorphoses".


title: Metamorphoses

text: Scholars have found it difficult to place the "Metamorphoses" in a genre. The poem has been considered as an epic or a type of epic (for example, an anti-epic or mock-epic); a that pulls together a series of examples in miniature form, such as the epyllion; a sampling of one genre after another; or simply a narrative that refuses categorization.


title: Metamorphoses

text: The poem is generally considered to meet the criteria for an epic; it is considerably long, relating over 250 narratives across fifteen books; it is composed in dactylic hexameter, the meter of both the ancient "Iliad" and "Odyssey", and the more contemporary epic "Aeneid"; and it treats the high literary subject of myth. However, the poem "handles the themes and employs the tone of virtually every species of literature", ranging from epic and elegy to tragedy and pastoral. Commenting on the genre debate, Karl Galinsky has opined that "... it would be misguided to pin the label of any genre on the "Metamorphoses"".


title: Metamorphoses

text: The "Metamorphoses" is comprehensive in its chronology, recounting the creation of the world to the death of Julius Caesar, which had occurred only a year before Ovid's birth; it has been compared to works of universal history, which became important in the 1st century BC. In spite of its apparently unbroken chronology, scholar Brooks Otis has identified four divisions in the narrative:


title: Metamorphoses

text: Ovid works his way through his subject matter, often in an apparently arbitrary fashion, by jumping from one transformation tale to another, sometimes retelling what had come to be seen as central events in the world of Greek mythology and sometimes straying in odd directions. It begins with the ritual "invocation of the muse", and makes use of traditional epithets and circumlocutions. But instead of following and extolling the deeds of a human hero, it leaps from story to story with little connection.


title: Metamorphoses

text: The recurring theme, as with nearly all of Ovid's work, is love—be it personal love or love personified in the figure of "Amor" (Cupid). Indeed, the other Roman gods are repeatedly perplexed, humiliated, and made ridiculous by Amor, an otherwise relatively minor god of the pantheon, who is the closest thing this putative mock-epic has to a hero. Apollo comes in for particular ridicule as Ovid shows how irrational love can confound the god out of reason. The work as a whole inverts the accepted order, elevating humans and human passions while making the gods and their desires and conquests objects of low humor.


title: Metamorphoses

text: The "Metamorphoses" ends with an epilogue (Book XV.871–879), one of only two surviving Latin epics to do so (the other being Statius' "Thebaid"). The ending acts as a declaration that everything except his poetry—even Rome—must give way to change:


title: Metamorphoses

text: The different genres and divisions in the narrative allow the "Metamorphoses" to display a wide range of themes. Scholar Stephen M. Wheeler notes that "metamorphosis, mutability, love, violence, artistry, and power are just some of the unifying themes that critics have proposed over the years".


title: Metamorphoses

text: Metamorphosis or transformation is a unifying theme amongst the episodes of the "Metamorphoses". Ovid raises its significance explicitly in the opening lines of the poem: "In nova fert animus mutatas dicere formas / corpora;" ("I intend to speak of forms changed into new entities;"). Accompanying this theme is often violence, inflicted upon a victim whose transformation becomes part of the natural landscape. This theme amalgamates the much-explored opposition between the hunter and the hunted and the thematic tension between art and nature.


title: Metamorphoses

text: There is a great variety among the types of transformations that take place: from human to inanimate objects (Nileus), constellations (Ariadne's Crown), animals (Perdix); from animals (ants) and fungi (mushrooms) to human; of sex (hyenas); and of colour (pebbles). The metamorphoses themselves are often located metatextually within the poem, through grammatical or narratorial transformations. At other times, transformations are developed into humour or absurdity, such that, slowly, "the reader realizes he is being had", or the very nature of transformation is questioned or subverted. This phenomenon is merely one aspect of Ovid's extensive use of illusion and disguise.


title: Metamorphoses

text: The "Metamorphoses" has exerted a considerable influence on literature and the arts, particularly of the West; scholar A. D. Melville says that "It may be doubted whether any poem has had so great an influence on the literature and art of Western civilization as the "Metamorphoses"." Although a majority of its stories do not originate with Ovid himself, but with such writers as Hesiod and Homer, for others the poem is their sole source.


title: Metamorphoses

text: The influence of the poem on the works of Geoffrey Chaucer is extensive. In "The Canterbury Tales", the story of Coronis and Phoebus Apollo (Book II 531–632) is adapted to form the basis for The Manciple's Tale. The story of Midas (Book XI 174–193) is referred to and appears—though much altered—in The Wife of Bath's Tale. The story of Ceyx and Alcyone (from Book IX) is adapted by Chaucer in his poem "The Book of the Duchess", written to commemorate the death of Blanche, Duchess of Lancaster and wife of John of Gaunt.


title: Metamorphoses

text: The "Metamorphoses" was also a considerable influence on William Shakespeare. His "Romeo and Juliet" is influenced by the story of Pyramus and Thisbe ("Metamorphoses" Book IV); and, in "A Midsummer Night's Dream", a band of amateur actors performs a play about Pyramus and Thisbe. Shakespeare's early erotic poem "Venus and Adonis" expands on the myth in Book X of the "Metamorphoses". In "Titus Andronicus", the story of Lavinia's rape is drawn from Tereus' rape of Philomela, and the text of the "Metamorphoses" is used within the play to enable Titus to interpret his daughter's story. Most of Prospero's renunciative speech in Act V of "The Tempest" is taken word-for-word from a speech by Medea in Book VII of the "Metamorphoses". Among other English writers for whom the "Metamorphoses" was an inspiration are John Milton—who made use of it in "Paradise Lost", considered his "magnum opus", and evidently knew it well—and Edmund Spenser. In Italy, the poem was an influence on Giovanni Boccaccio (the story of Pyramus and Thisbe appears in his poem "L'Amorosa Fiammetta") and Dante.


title: Metamorphoses

text: During the Renaissance and Baroque periods, mythological subjects were frequently depicted in art. The "Metamorphoses" was the greatest source of these narratives, such that the term "Ovidian" in this context is synonymous for mythological, in spite of some frequently represented myths not being found in the work. Many of the stories from the "Metamorphoses" have been the subject of paintings and sculptures, particularly during this period. Some of the most well-known paintings by Titian depict scenes from the poem, including "Diana and Callisto", "Diana and Actaeon", and "Death of Actaeon". These works form part of Titian's ""poesie"", a collection of seven paintings derived in part from the "Metamorphoses", inspired by ancient Greek and Roman mythologies, which were reunited in the Titian exhibition at The National Gallery in 2020. Other famous works inspired by the "Metamorphoses" include Pieter Brueghel's painting "Landscape with the Fall of Icarus" and Gian Lorenzo Bernini's sculpture "Apollo and Daphne". The "Metamorphoses" also permeated the theory of art during the Renaissance and the Baroque style, with its idea of transformation and the relation of the myths of Pygmalion and Narcissus to the role of the artist.


title: Metamorphoses

text: Though Ovid was popular for many centuries, interest in his work began to wane after the Renaissance, and his influence on 19th-century writers was minimal. Towards the end of the 20th century his work began to be appreciated once more. Ted Hughes collected together and retold twenty-four passages from the "Metamorphoses" in his "Tales from Ovid", published in 1997. In 1998, Mary Zimmerman's stage adaptation "Metamorphoses" premiered at the Lookingglass Theatre, and the following year there was an adaptation of "Tales from Ovid" by the Royal Shakespeare Company. In the early 21st century, the poem continues to inspire and be retold through books, films and plays. A series of works inspired by Ovid's book through the tragedy of Diana and Actaeon have been produced by French-based collective LFKs and his film/theatre director, writer and visual artist Jean-Michel Bruyere, including the interactive 360° audiovisual installation "Si poteris narrare, licet" ("if you are able to speak of it, then you may do so") in 2002, 600 shorts and "medium" film from which 22,000 sequences have been used in the 3D 360° audiovisual installation "La Dispersion du Fils" from 2008 to 2016 as well as an outdoor performance, "Une Brutalité pastorale" (2000).


title: Metamorphoses

text: In spite of the "Metamorphoses" enduring popularity from its first publication (around the time of Ovid's exile in 8 AD) no manuscript survives from antiquity. From the 9th and 10th centuries there are only fragments of the poem; it is only from the 11th century onwards that complete manuscripts, of varying value, have been passed down.


title: Metamorphoses

text: The poem retained its popularity throughout late antiquity and the Middle Ages, and is represented by an extremely high number of surviving manuscripts (more than 400); the earliest of these are three fragmentary copies containing portions of Books 1–3, dating to the 9th century.


title: Metamorphoses

text: But the poem's immense popularity in antiquity and the Middle Ages belies the struggle for survival it faced in late antiquity. "A dangerously pagan work," the "Metamorphoses" was preserved through the Roman period of Christianization, but was criticized by the voices of Augustine and Jerome, who believed the only real metamorphosis was transubstantiation. Though the "Metamorphoses" did not suffer the ignominious fate of the "Medea", no ancient scholia on the poem survive (although they did exist in antiquity), and the earliest complete manuscript is very late, dating from the 11th century.


title: Metamorphoses

text: Influential in the course of the poem's manuscript tradition is the 17th-century Dutch scholar Nikolaes Heinsius. During the years 1640–52, Heinsius collated more than a hundred manuscripts and was informed of many others through correspondence.


title: Metamorphoses

text: Collaborative editorial effort has been investigating the various manuscripts of the "Metamorphoses", some forty-five complete texts or substantial fragments, all deriving from a Gallic archetype. The result of several centuries of critical reading is that the poet's meaning is firmly established on the basis of the manuscript tradition or restored by conjecture where the tradition is deficient. There are two modern critical editions: William S. Anderson's, first published in 1977 in the Teubner series, and R. J. Tarrant's, published in 2004 by the Oxford Clarendon Press.


title: Metamorphoses

text: The full appearance of the "Metamorphoses" in English translation (sections had appeared in the works of Chaucer and Gower) coincides with the beginning of printing, and traces a path through the history of publishing. William Caxton produced the first translation of the text on 22 April 1480; set in prose, it is a literal rendering of a French translation known as the "Ovide Moralisé".


title: Metamorphoses

text: In 1567, Arthur Golding published a translation of the poem that would become highly influential, the version read by Shakespeare and Spenser. It was written in rhyming couplets of iambic heptameter. The next significant translation was by George Sandys, produced from 1621 to 1626, which set the poem in heroic couplets, a metre that would subsequently become dominant in vernacular English epic and in English translations.


title: Metamorphoses

text: In 1717, a translation appeared from Samuel Garth bringing together work "by the most eminent hands": primarily John Dryden, but several stories by Joseph Addison, one by Alexander Pope, and contributions from Tate, Gay, Congreve, and Rowe, as well as those of eleven others including Garth himself. Translation of the "Metamorphoses" after this period was comparatively limited in its achievement; the Garth volume continued to be printed into the 1800s, and had "no real rivals throughout the nineteenth century".


title: Metamorphoses

text: Around the later half of the 20th century a greater number of translations appeared as literary translation underwent a revival. This trend has continued into the twenty-first century. In 1994, a collection of translations and responses to the poem, entitled "", was produced by numerous contributors in emulation of the process of the Garth volume.


title: Rhodium

text: Rhodium is a chemical element with the symbol Rh and atomic number 45. It is a very rare, silvery-white, hard, corrosion-resistant transition metal. It is a noble metal and a member of the platinum group. It has only one naturally occurring isotope: Rh. Naturally occurring rhodium is usually found as a free metal or as an alloy with similar metals and rarely as a chemical compound in minerals such as bowieite and rhodplumsite. It is one of the rarest and most valuable precious metals.


title: Rhodium

text: Rhodium is found in platinum or nickel ores with the other members of the platinum group metals. It was discovered in 1803 by William Hyde Wollaston in one such ore, and named for the rose color of one of its chlorine compounds.


title: Rhodium

text: The element's major use (consuming about 80% of world rhodium production) is as one of the catalysts in the three-way catalytic converters in automobiles. Because rhodium metal is inert against corrosion and most aggressive chemicals, and because of its rarity, rhodium is usually alloyed with platinum or palladium and applied in high-temperature and corrosion-resistive coatings. White gold is often plated with a thin rhodium layer to improve its appearance, while sterling silver is often rhodium-plated to resist tarnishing. Rhodium is sometimes used to cure silicones: a two-part silicone in which one part containing a silicon hydride and the other containing a vinyl-terminated silicone are mixed; one of these liquids contains a rhodium complex.


title: Rhodium

text: Rhodium detectors are used in nuclear reactors to measure the neutron flux level. Other uses of rhodium include asymmetric hydrogenation used to form drug precursors and the processes for the production of acetic acid.


title: Rhodium

text: Rhodium (Greek "rhodon" (ῥόδον) meaning "rose") was discovered in 1803 by William Hyde Wollaston, soon after he discovered palladium. He used crude platinum ore presumably obtained from South America. His procedure dissolved the ore in aqua regia and neutralized the acid with sodium hydroxide (NaOH). He then precipitated the platinum as ammonium chloroplatinate by adding ammonium chloride (). Most other metals like copper, lead, palladium, and rhodium were precipitated with zinc. Diluted nitric acid dissolved all but palladium and rhodium. Of these, palladium dissolved in aqua regia but rhodium did not, and the rhodium was precipitated by the addition of sodium chloride as . After being washed with ethanol, the rose-red precipitate was reacted with zinc, which displaced the rhodium in the ionic compound and thereby released the rhodium as free metal.


title: Rhodium

text: For decades, the rare element had only minor applications; for example, by the turn of the century, rhodium-containing thermocouples were used to measure temperatures up to 1800 °C. They have exceptionally good stability in the temperature range of 1300 to 1800 °C.


title: Rhodium

text: The first major application was electroplating for decorative uses and as corrosion-resistant coating. The introduction of the three-way catalytic converter by Volvo in 1976 increased the demand for rhodium. The previous catalytic converters used platinum or palladium, while the three-way catalytic converter used rhodium to reduce the amount of NO in the exhaust.


title: Rhodium

text: Rhodium is a hard, silvery, durable metal that has a high reflectance. Rhodium metal does not normally form an oxide, even when heated. Oxygen is absorbed from the atmosphere only at the melting point of rhodium, but is released on solidification. Rhodium has both a higher melting point and lower density than platinum. It is not attacked by most acids: it is completely insoluble in nitric acid and dissolves slightly in aqua regia.


title: Rhodium

text: Rhodium belongs to group 9 of the periodic table, but the configuration of electrons in the outermost shells is atypical for the group. This anomaly is also observed in the neighboring elements, niobium (41), ruthenium (44), and palladium (46).


title: Rhodium

text: Unlike ruthenium and osmium, rhodium forms no volatile oxygen compounds. The known stable oxides include , , , , and . Halogen compounds are known in nearly the full range of possible oxidation states. Rhodium(III) chloride, rhodium trifluoride, rhodium pentafluoride and rhodium hexafluoride are examples. The lower oxidation states are stable only in the presence of ligands.


title: Rhodium

text: The best-known rhodium-halogen compound is the Wilkinson's catalyst chlorotris(triphenylphosphine)rhodium(I). This catalyst is used in the hydroformylation or hydrogenation of alkenes.


title: Rhodium

text: Naturally occurring rhodium is composed of only one isotope, Rh. The most stable radioisotopes are Rh with a half-life of 3.3 years, Rh with a half-life of 207 days, Rh with a half-life of 2.9 years, and Rh with a half-life of 16.1 days. Twenty other radioisotopes have been characterized with atomic weights ranging from 92.926 u (Rh) to 116.925 u (Rh). Most of these have half-lives shorter than an hour, except Rh (20.8 hours) and Rh (35.36 hours). Rhodium has numerous meta states, the most stable being Rh (0.141 MeV) with a half-life of about 2.9 years and Rh (0.157 MeV) with a half-life of 4.34 days (see isotopes of rhodium).


title: Rhodium

text: In isotopes weighing less than 103 (the stable isotope), the primary decay mode is electron capture and the primary decay product is ruthenium. In isotopes greater than 103, the primary decay mode is beta emission and the primary product is palladium.


title: Rhodium

text: Rhodium is one of the rarest elements in the Earth's crust, comprising an estimated 0.0002 parts per million (2 × 10). Its rarity affects its price and its use in commercial applications. The concentration of rhodium in nickel meteorites is typically 1 part per billion. Rhodium has been measured in some potatoes with concentrations between 0.8 and 30 ppt.


title: Rhodium

text: The industrial extraction of rhodium is complex because the ores are mixed with other metals such as palladium, silver, platinum, and gold and there are very few rhodium-bearing minerals. It is found in platinum ores and extracted as a white inert metal that is difficult to fuse. Principal sources are located in South Africa; in river sands of the Ural Mountains in Russia; and in North America, including the copper-nickel sulfide mining area of the Sudbury, Ontario, region. Although the rhodium abundance at Sudbury is very small, the large amount of processed nickel ore makes rhodium recovery cost-effective.


title: Rhodium

text: The main exporter of rhodium is South Africa (approximately 80% in 2010) followed by Russia. The annual world production is 30 tonnes. The price of rhodium is highly variable. In 2007, rhodium cost approximately eight times more than gold, 450 times more than silver, and 27,250 times more than copper by weight. In 2008, the price briefly rose above $10,000 per ounce ($350,000 per kilogram). The economic slowdown of the 3rd quarter of 2008 pushed rhodium prices sharply back below $1,000 per ounce ($35,000 per kilogram); the price rebounded to $2,750 by early 2010 ($97,000 per kilogram) (more than twice the gold price), but in late 2013, the prices were less than $1,000. Political and financial problems led to very low oil prices and over supply, causing most metals to drop in price. The economies of China, India and other emerging countries slowed in 2014 and 2015. In 2014 alone, 23,722,890 motor vehicles were produced in China, excluding motorbikes. This resulted in a rhodium price of 740.00 US-$ per Troy ounce (31.1 grams) in late November 2015.


title: Rhodium

text: Owners of rhodium—a metal with a highly volatile market price—are periodically put in an extremely advantageous market position: extracting more rhodium-containing ore from the ground will necessarily also extract other much more abundant precious metals—notably platinum and palladium—which would oversupply the market with those other metals, lowering their prices. Since it is economically infeasible to simply extract these other metals just to obtain rhodium, the market is often left hopelessly squeezed for rhodium supply, causing prices to spike. Recovery from this supply-deficit position may be quite problematic in the future for many reasons, notably because it is not known how much rhodium (and other precious metals) actually was placed in catalytic converters during the many years when manufacturers' emissions-cheating software was in use. Much of the world supply of rhodium is obtained from recycled catalytic converters obtained from scrapped vehicles. As of early November 2020, the spot price of rhodium was US$14,700 per troy ounce. In early March 2021, rhodium reached a price of US$29,400 per troy ounce on Metals Daily (a precious metals commodity listing).


title: Rhodium

text: Rhodium is a fission product of uranium-235: each kilogram of fission product contains a significant amount of the lighter platinum group metals. Used nuclear fuel is therefore a potential source of rhodium, but the extraction is complex and expensive, and the presence of rhodium radioisotopes requires a period of cooling storage for multiple half-lives of the longest-lived isotope (Rh with a half-life of 3.3 years, and Rh with a half-life of 2.9 years), or about 10 years. These factors make the source unattractive and no large-scale extraction has been attempted.


title: Rhodium

text: The primary use of this element is in automobiles as a catalytic converter, changing harmful unburned hydrocarbons, carbon monoxide, and nitrogen oxide exhaust emissions into less noxious gases. Of 30,000 kg of rhodium consumed worldwide in 2012, 81% (24,300 kg) went into this application, and 8,060 kg was recovered from old converters. About 964 kg of rhodium was used in the glass industry, mostly for production of fiberglass and flat-panel glass, and 2,520 kg was used in the chemical industry.


title: Rhodium

text: Rhodium is preferable to the other platinum metals in the reduction of nitrogen oxides to nitrogen and oxygen:


title: Rhodium

text: In 2008, net demand (with the recycling accounted for) of rhodium for automotive converters made up 84% of the world usage, with the number fluctuating around 80% during in 2015−2021.


title: Rhodium

text: Rhodium catalysts are used in a number of industrial processes, notably in catalytic carbonylation of methanol to produce acetic acid by the Monsanto process. It is also used to catalyze addition of hydrosilanes to molecular double bonds, a process important in manufacture of certain silicone rubbers. Rhodium catalysts are also used to reduce benzene to cyclohexane.


title: Rhodium

text: The complex of a rhodium ion with BINAP is a widely used chiral catalyst for chiral synthesis, as in the synthesis of menthol.


title: Rhodium

text: Rhodium finds use in jewelry and for decorations. It is electroplated on white gold and platinum to give it a reflective white surface at time of sale, after which the thin layer wears away with use. This is known as rhodium flashing in the jewelry business. It may also be used in coating sterling silver to protect against tarnish (silver sulfide, AgS, produced from atmospheric hydrogen sulfide, HS). Solid (pure) rhodium jewelry is very rare, more because of the difficulty of fabrication (high melting point and poor malleability) than because of the high price. The high cost ensures that rhodium is applied only as an electroplate.


title: Rhodium

text: Rhodium has also been used for honors or to signify elite status, when more commonly used metals such as silver, gold or platinum were deemed insufficient. In 1979 the "Guinness Book of World Records" gave Paul McCartney a rhodium-plated disc for being history's all-time best-selling songwriter and recording artist.


title: Rhodium

text: Rhodium is used as an alloying agent for hardening and improving the corrosion resistance of platinum and palladium. These alloys are used in furnace windings, bushings for glass fiber production, thermocouple elements, electrodes for aircraft spark plugs, and laboratory crucibles. Other uses include:


title: Rhodium

text: Being a noble metal, pure rhodium is inert and harmless in elemental form. However, chemical complexes of rhodium can be reactive. For rhodium chloride, the median lethal dose (LD) for rats is 198 mg () per kilogram of body weight. Like the other noble metals, rhodium has not been found to serve any biological function.


title: Rhodium

text: People can be exposed to rhodium in the workplace by inhalation. The Occupational Safety and Health Administration (OSHA) has specified the legal limit (Permissible exposure limit) for rhodium exposure in the workplace at 0.1 mg/m over an 8-hour workday, and the National Institute for Occupational Safety and Health (NIOSH) has set the recommended exposure limit (REL), at the same level. At levels of 100 mg/m, rhodium is immediately dangerous to life or health. For soluble compounds, the PEL and REL are both 0.001 mg/m.


title: Helstrom (TV series)

text: Helstrom is an American television series created by Paul Zbyszewski for the streaming service Hulu, based on the Marvel Comics characters Daimon and Satana Hellstrom. The series is produced by Marvel Television and ABC Signature Studios, with Zbyszewski serving as showrunner.


title: Helstrom (TV series)

text: Tom Austen and Sydney Lemmon respectively star as Daimon and Ana Helstrom, the children of a powerful serial killer, who hunt the worst of humanity. Elizabeth Marvel, Robert Wisdom, June Carryl, Ariana Guerra, and Alain Uy also star. "Helstrom" was officially announced with a series order at Hulu in May 2019, planned as the first series in Marvel Television's Adventure into Fear franchise, which would exist within the Marvel Cinematic Universe (MCU) but would not cross over with the films or other television series of the franchise. However, upon its release, Zbyszewski stated that "Helstrom" was not part of the MCU. Filming took place in Vancouver from October 2019 until March 2020. Oversight of the series was moved to Marvel Studios in December 2019 when Marvel Television was folded into that company.


title: Helstrom (TV series)

text: "Helstrom" was released on Hulu on October 16, 2020, and consists of 10 episodes. It was met with largely negative reviews, feeling the characters and plot were uninteresting, though the series' visual effects were considered impressive. "Helstrom" was canceled on December 14, 2020.


title: Helstrom (TV series)

text: In May 2019, Hulu ordered "Marvel's Helstrom" to series, based on the Marvel Comics characters Daimon and Satana Hellstrom; their names are Daimon and Ana Helstrom in the series. Paul Zbyszewski, who previously served as an executive producer on Marvel's ABC series "Agents of S.H.I.E.L.D.", was set as showrunner and executive producer of "Helstrom" alongside Marvel Television head Jeph Loeb and Karim Zreik. Marvel Television and ABC Signature Studios were set to co-produce "Helstrom". Zbyszewski said the series would be adding "scares" to the Marvel formula of "heart, humor, and action", and that he would use the Helstroms' story to "dissect some of our deepest fears", with Loeb saying the series is moving into a new, "chilling" corner of the Marvel Universe. The series consists of 10 episodes.


title: Helstrom (TV series)

text: In December 2019, Marvel Television was folded into Marvel Studios, with some executives from Marvel Television moving over to Marvel Studios to oversee the completion of production on "Helstrom", including Zreik. In April 2020, Marvel terminated Zbyszewski's overall deal with them, in part because of the COVID-19 pandemic, but Zbyszewski continued post-production work on the series. By July, the series was no longer officially titled "Marvel's Helstrom", with Disney changing the title to simply "Helstrom" in order to distance the Marvel brand from the series' horror-based content, not wanting viewers to "stumble upon the show while looking for something in the tone" of the Marvel Cinematic Universe films. The Marvel logo is also not featured before each episode as was the case with Marvel Television's other series, with Zbyszewski saying this was "a way of telling the audience that this is something different" from the other Marvel series. On December 14, 2020, Hulu canceled the series, making it the final live-action Marvel series produced through Marvel Television, following its absorption back into Marvel Studios.


title: Helstrom (TV series)

text: Marvel announced the series' cast at the start of production in October 2019: Tom Austen and Sydney Lemmon star as Daimon and Ana Helstrom, with Elizabeth Marvel as their mother Victoria, Robert Wisdom as Caretaker, June Carryl as Dr. Louise Hastings, Ariana Guerra as Gabriella Rosetti, and Alain Uy as Chris Yen. Daniel Cudmore and David Meunier were cast in the recurring roles as Nurse Keith Spivey and Finn Miller, respectively in November.


title: Helstrom (TV series)

text: Production on the series began on October 7, 2019, in Vancouver, under the working title "Omens". Filming wrapped on March 14, 2020.


title: Helstrom (TV series)

text: Hulu and Marvel announced both "Helstrom" and a Ghost Rider series in May 2019, referring to them as the cornerstone of the "Spirits of Vengeance" and intending on them being interconnected in a similar fashion to Marvel's Netflix television series. Marvel revealed that the two series would exist within the Marvel Cinematic Universe but would not cross over with the films or other television series of the franchise. In August, Loeb revealed that the fear-based series at Hulu were being collectively referred to as Adventure into Fear. Hulu was no longer moving forward with "Ghost Rider" by the end of September, but other Adventure into Fear series were still planned. Development on any further series was cancelled in December 2019 when Marvel Television was shut down.


title: Helstrom (TV series)

text: Roxxon Corporation, a company from the Marvel Comics that has been featured throughout the MCU, is referenced in the series. Josh Bell of "Comic Book Resources" added that outside of the Roxxon inclusions, the series "bears essentially no connection to the Marvel Cinematic Universe" films or the other Marvel Television series. Regarding the series' place relative to the MCU, Zbyszewski explained "Helstrom" is "siloed off" in part because of it being a "darker-themed show", further adding that the series was "not tied to the MCU" and "our own separate thing". Zbyszewski called it "freeing" not being a part of the MCU or its canon, instead "hav[ing] just this little pocket of the universe". Zbyszewski also stated that Easter eggs in the series hinted at the cancelled Adventure into Fear franchise.


title: Helstrom (TV series)

text: Zbyszewski and the series' cast took part in a panel for the series during the virtual convention Comic-Con@Home in July 2020, where the first teaser for the series was released. An official trailer was released on September 23. Ben Pearson of "/Film" said the series "looks a lot like something that would have aired on The CW circa 2006. Which, sadly, means it looks kinda terrible". Though he felt there were good actors in "Helstrom", he added that the trailer made the series look "super cheap" and "bland". As well, he noted there were hardly any indications it was a Marvel series, and compared it to the film "The New Mutants", both "holdover[s] from... different era[s]"–"New Mutants" with the acquisition of 21st Century Fox by Disney and "Helstrom" with Marvel Television being dissolved. Hulu released the first 10 minutes of the series at the New York Comic Con online panel held in October the same year.


title: Helstrom (TV series)

text: "Helstrom" was released on Hulu on October 16, 2020, as part of Hulu's "Huluween" programming block, consisting of 10 episodes. Internationally, the series premiered on Disney+ under the dedicated streaming hub Star as an original series, on February 23, 2021.


title: Helstrom (TV series)

text: For the series, review aggregator Rotten Tomatoes reported an approval rating of 27% based on 26 reviews, with an average rating of 5/10. The website's critics consensus reads, ""Helstrom" strong visual effects can't save it from the fact that its characters simply aren't interesting enough to overcome their familiar setting." Metacritic, which uses a weighted average, assigned a score of 40 out of 100 based on 9 critics, indicating "mixed or average reviews".


title: Helstrom (TV series)

text: In his review, Bell from "Comic Book Resources" stated "Helstrom" "seems to have been completed largely out of contractual obligation" calling it "a generic, dull supernatural drama with a few names that may sound familiar to dedicated comics fans". Bell pointed out the pacing issues the series faced, comparing it to Marvel Television's other streaming series that also faced similar issues, and felt the series had a dull color palette. As well, "Helstrom" "doesn’t much resemble a superhero story, and aside from an occasional swear word and a bit of blood, it could be a mid-level CW supernatural drama about photogenic people going after standard-issue demons." He enjoyed Lemmon as Ana Helstrom, since she was "more charismatic than Daimon" and "the most prominent LGBTQ character in any Marvel TV series to date", but he was disappointed she would not become a fully realized version of her comic counterpart. Because the series was once meant to be part of the planned Adventure into Fear, Bell concluded "Helstrom" is "in an uninspired middle ground, and it seems likely to end up as nothing more than a footnote in the history of the MCU". Charles Pulliam-Moore at "io9" said, "In another universe, the show’s focus on shadowy magics and ugly family drama might make it one of Marvel’s standouts, but here the series barely manages to make a strong argument in defense of its own existence." He added it was "telling" that Marvel's name was hardly featured in the series' marketing and the content of the series made it seem like this was by design". Sadie Gennis at "TV Guide" however found "Helstrom" the "perfect TV cocktail for right now ... with compelling mythology and morally complicated characters," recommending it as "a horror binge that goes down easy".


title: Superconductivity

text: Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered even down to near absolute zero, a superconductor has a characteristic critical temperature below which the resistance drops abruptly to zero.


title: Superconductivity

text: The superconductivity phenomenon was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes. Like ferromagnetism and atomic spectral lines, superconductivity is a phenomenon which can only be explained by quantum mechanics. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor during its transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of "perfect conductivity" in classical physics.


title: Superconductivity

text: In 1986, it was discovered that some cuprate-perovskite ceramic materials have a critical temperature above . Such a high transition temperature is theoretically impossible for a conventional superconductor, leading the materials to be termed high-temperature superconductors. The cheaply available coolant liquid nitrogen boils at 77 K, and thus the existence of superconductivity at higher temperatures than this facilitates many experiments and applications that are less practical at lower temperatures.


title: Superconductivity

text: A superconductor can be "Type I", meaning it has a single critical field, above which all superconductivity is lost and below which the magnetic field is completely expelled from the superconductor; or "Type II", meaning it has two critical fields, between which it allows partial penetration of the magnetic field through isolated points. These points are called vortices. Furthermore, in multicomponent superconductors it is possible to have a combination of the two behaviours. In that case the superconductor is of Type-1.5.


title: Superconductivity

text: It is "conventional" if it can be explained by the BCS theory or its derivatives, or "unconventional", otherwise. Alternatively, a superconductor is called unconventional if the superconducting order parameter transforms according to a non-trivial irreducible representation of the point group or space group of the system.


title: Superconductivity

text: A superconductor is generally considered "high-temperature" if it reaches a superconducting state above a temperature of 30 K (−243.15 °C); as in the initial discovery by Georg Bednorz and K. Alex Müller. It may also reference materials that transition to superconductivity when cooled using liquid nitrogen – that is, at only "T" > 77 K, although this is generally used only to emphasize that liquid nitrogen coolant is sufficient. Low temperature superconductors refer to materials with a critical temperature below 30 K, and are cooled mainly by liquid helium ("T" > 4.2 K). One exception to this rule is the iron pnictide group of superconductors which display behaviour and properties typical of high-temperature superconductors, yet some of the group have critical temperatures below 30 K.


title: Superconductivity

text: Superconductor material classes include chemical elements (e.g. mercury or lead), alloys (such as niobium–titanium, germanium–niobium, and niobium nitride), ceramics (YBCO and magnesium diboride), superconducting pnictides (like fluorine-doped LaOFeAs) or organic superconductors (fullerenes and carbon nanotubes; though perhaps these examples should be included among the chemical elements, as they are composed entirely of carbon).


title: Superconductivity

text: Several physical properties of superconductors vary from material to material, such as the critical temperature, the value of the superconducting gap, the critical magnetic field, and the critical current density at which superconductivity is destroyed. On the other hand, there is a class of properties that are independent of the underlying material. The Meissner effect, the quantization of the magnetic flux or permanent currents, i.e. the state of zero resistance are the most important examples. The existence of these "universal" properties is rooted in the nature of the broken symmetry of the superconductor and the emergence of off-diagonal long range order. Superconductivity is a thermodynamic phase, and thus possesses certain distinguishing properties which are largely independent of microscopic details.


title: Superconductivity

text: Off diagonal long range order is closely connected to the formation of Cooper pairs. An article by V.F. Weisskopf presents simple physical explanations for the formation of Cooper pairs, for the origin of the attractive force causing the binding of the pairs, for the finite energy gap, and for the existence of permanent currents.


title: Superconductivity

text: The simplest method to measure the electrical resistance of a sample of some material is to place it in an electrical circuit in series with a current source "I" and measure the resulting voltage "V" across the sample. The resistance of the sample is given by Ohm's law as "R = V / I". If the voltage is zero, this means that the resistance is zero.


title: Superconductivity

text: Superconductors are also able to maintain a current with no applied voltage whatsoever, a property exploited in superconducting electromagnets such as those found in MRI machines. Experiments have demonstrated that currents in superconducting coils can persist for years without any measurable degradation. Experimental evidence points to a current lifetime of at least 100,000 years. Theoretical estimates for the lifetime of a persistent current can exceed the estimated lifetime of the universe, depending on the wire geometry and the temperature. In practice, currents injected in superconducting coils have persisted for more than 27 years (as of August, 2022) in superconducting gravimeters. In such instruments, the measurement principle is based on the monitoring of the levitation of a superconducting niobium sphere with a mass of 4 grams.


title: Superconductivity

text: In a normal conductor, an electric current may be visualized as a fluid of electrons moving across a heavy ionic lattice. The electrons are constantly colliding with the ions in the lattice, and during each collision some of the energy carried by the current is absorbed by the lattice and converted into heat, which is essentially the vibrational kinetic energy of the lattice ions. As a result, the energy carried by the current is constantly being dissipated. This is the phenomenon of electrical resistance and Joule heating.


title: Superconductivity

text: The situation is different in a superconductor. In a conventional superconductor, the electronic fluid cannot be resolved into individual electrons. Instead, it consists of bound "pairs" of electrons known as Cooper pairs. This pairing is caused by an attractive force between electrons from the exchange of phonons. This pairing is very weak, and small thermal vibrations can fracture the bond. Due to quantum mechanics, the energy spectrum of this Cooper pair fluid possesses an "energy gap", meaning there is a minimum amount of energy Δ"E" that must be supplied in order to excite the fluid. Therefore, if Δ"E" is larger than the thermal energy of the lattice, given by "kT", where "k" is Boltzmann's constant and "T" is the temperature, the fluid will not be scattered by the lattice. The Cooper pair fluid is thus a superfluid, meaning it can flow without energy dissipation.


title: Superconductivity

text: In a class of superconductors known as type II superconductors, including all known high-temperature superconductors, an extremely low but nonzero resistivity appears at temperatures not too far below the nominal superconducting transition when an electric current is applied in conjunction with a strong magnetic field, which may be caused by the electric current. This is due to the motion of magnetic vortices in the electronic superfluid, which dissipates some of the energy carried by the current. If the current is sufficiently small, the vortices are stationary, and the resistivity vanishes. The resistance due to this effect is tiny compared with that of non-superconducting materials, but must be taken into account in sensitive experiments. However, as the temperature decreases far enough below the nominal superconducting transition, these vortices can become frozen into a disordered but stationary phase known as a "vortex glass". Below this vortex glass transition temperature, the resistance of the material becomes truly zero.


title: Superconductivity

text: In superconducting materials, the characteristics of superconductivity appear when the temperature "T" is lowered below a critical temperature "T". The value of this critical temperature varies from material to material. Conventional superconductors usually have critical temperatures ranging from around 20 K to less than 1 K. Solid mercury, for example, has a critical temperature of 4.2 K. As of 2015, the highest critical temperature found for a conventional superconductor is 203 K for HS, although high pressures of approximately 90 gigapascals were required. Cuprate superconductors can have much higher critical temperatures: YBaCuO, one of the first cuprate superconductors to be discovered, has a critical temperature above 90 K, and mercury-based cuprates have been found with critical temperatures in excess of 130 K. The basic physical mechanism responsible for the high critical temperature is not yet clear. However, it is clear that a two-electron pairing is involved, although the nature of the pairing (formula_1 wave vs. formula_2 wave) remains controversial.


title: Superconductivity

text: Similarly, at a fixed temperature below the critical temperature, superconducting materials cease to superconduct when an external magnetic field is applied which is greater than the "critical magnetic field". This is because the Gibbs free energy of the superconducting phase increases quadratically with the magnetic field while the free energy of the normal phase is roughly independent of the magnetic field. If the material superconducts in the absence of a field, then the superconducting phase free energy is lower than that of the normal phase and so for some finite value of the magnetic field (proportional to the square root of the difference of the free energies at zero magnetic field) the two free energies will be equal and a phase transition to the normal phase will occur. More generally, a higher temperature and a stronger magnetic field lead to a smaller fraction of electrons that are superconducting and consequently to a longer London penetration depth of external magnetic fields and currents. The penetration depth becomes infinite at the phase transition.


title: Superconductivity

text: The onset of superconductivity is accompanied by abrupt changes in various physical properties, which is the hallmark of a phase transition. For example, the electronic heat capacity is proportional to the temperature in the normal (non-superconducting) regime. At the superconducting transition, it suffers a discontinuous jump and thereafter ceases to be linear. At low temperatures, it varies instead as "e" for some constant, α. This exponential behavior is one of the pieces of evidence for the existence of the energy gap.


title: Superconductivity

text: The order of the superconducting phase transition was long a matter of debate. Experiments indicate that the transition is second-order, meaning there is no latent heat. However, in the presence of an external magnetic field there is latent heat, because the superconducting phase has a lower entropy below the critical temperature than the normal phase. It has been experimentally demonstrated that, as a consequence, when the magnetic field is increased beyond the critical field, the resulting phase transition leads to a decrease in the temperature of the superconducting material.


title: Superconductivity

text: Calculations in the 1970s suggested that it may actually be weakly first-order due to the effect of long-range fluctuations in the electromagnetic field. In the 1980s it was shown theoretically with the help of a disorder field theory, in which the vortex lines of the superconductor play a major role, that the transition is of second order within the type II regime and of first order (i.e., latent heat) within the type I regime, and that the two regions are separated by a tricritical point. The results were strongly supported by Monte Carlo computer simulations.


title: Superconductivity

text: When a superconductor is placed in a weak external magnetic field H, and cooled below its transition temperature, the magnetic field is ejected. The Meissner effect does not cause the field to be completely ejected but instead, the field penetrates the superconductor but only to a very small distance, characterized by a parameter "λ", called the London penetration depth, decaying exponentially to zero within the bulk of the material. The Meissner effect is a defining characteristic of superconductivity. For most superconductors, the London penetration depth is on the order of 100 nm.


title: Superconductivity

text: The Meissner effect is sometimes confused with the kind of diamagnetism one would expect in a perfect electrical conductor: according to Lenz's law, when a "changing" magnetic field is applied to a conductor, it will induce an electric current in the conductor that creates an opposing magnetic field. In a perfect conductor, an arbitrarily large current can be induced, and the resulting magnetic field exactly cancels the applied field.


title: Superconductivity

text: The Meissner effect is distinct from thisit is the spontaneous expulsion that occurs during transition to superconductivity. Suppose we have a material in its normal state, containing a constant internal magnetic field. When the material is cooled below the critical temperature, we would observe the abrupt expulsion of the internal magnetic field, which we would not expect based on Lenz's law.


title: Superconductivity

text: The Meissner effect was given a phenomenological explanation by the brothers Fritz and Heinz London, who showed that the electromagnetic free energy in a superconductor is minimized provided


title: Superconductivity

text: This equation, which is known as the London equation, predicts that the magnetic field in a superconductor decays exponentially from whatever value it possesses at the surface.


title: Superconductivity

text: A superconductor with little or no magnetic field within it is said to be in the Meissner state. The Meissner state breaks down when the applied magnetic field is too large. Superconductors can be divided into two classes according to how this breakdown occurs. In Type I superconductors, superconductivity is abruptly destroyed when the strength of the applied field rises above a critical value "H". Depending on the geometry of the sample, one may obtain an intermediate state consisting of a baroque pattern of regions of normal material carrying a magnetic field mixed with regions of superconducting material containing no field. In Type II superconductors, raising the applied field past a critical value "H" leads to a mixed state (also known as the vortex state) in which an increasing amount of magnetic flux penetrates the material, but there remains no resistance to the flow of electric current as long as the current is not too large. At a second critical field strength "H", superconductivity is destroyed. The mixed state is actually caused by vortices in the electronic superfluid, sometimes called fluxons because the flux carried by these vortices is quantized. Most pure elemental superconductors, except niobium and carbon nanotubes, are Type I, while almost all impure and compound superconductors are Type II.


title: Superconductivity

text: Conversely, a spinning superconductor generates a magnetic field, precisely aligned with the spin axis. The effect, the London moment, was put to good use in Gravity Probe B. This experiment measured the magnetic fields of four superconducting gyroscopes to determine their spin axes. This was critical to the experiment since it is one of the few ways to accurately determine the spin axis of an otherwise featureless sphere.


title: Superconductivity

text: Superconductivity was discovered on April 8, 1911 by Heike Kamerlingh Onnes, who was studying the resistance of solid mercury at cryogenic temperatures using the recently produced liquid helium as a refrigerant. At the temperature of 4.2 K, he observed that the resistance abruptly disappeared. In the same experiment, he also observed the superfluid transition of helium at 2.2 K, without recognizing its significance. The precise date and circumstances of the discovery were only reconstructed a century later, when Onnes's notebook was found. In subsequent decades, superconductivity was observed in several other materials. In 1913, lead was found to superconduct at 7 K, and in 1941 niobium nitride was found to superconduct at 16 K.


title: Superconductivity

text: Great efforts have been devoted to finding out how and why superconductivity works; the important step occurred in 1933, when Meissner and Ochsenfeld discovered that superconductors expelled applied magnetic fields, a phenomenon which has come to be known as the Meissner effect. In 1935, Fritz and Heinz London showed that the Meissner effect was a consequence of the minimization of the electromagnetic free energy carried by superconducting current.


title: Superconductivity

text: The theoretical model that was first conceived for superconductivity was completely classical: it is summarized by London constitutive equations.


title: Superconductivity

text: It was put forward by the brothers Fritz and Heinz London in 1935, shortly after the discovery that magnetic fields are expelled from superconductors. A major triumph of the equations of this theory is their ability to explain the Meissner effect, wherein a material exponentially expels all internal magnetic fields as it crosses the superconducting threshold. By using the London equation, one can obtain the dependence of the magnetic field inside the superconductor on the distance to the surface.


title: Superconductivity

text: During the 1950s, theoretical condensed matter physicists arrived at an understanding of "conventional" superconductivity, through a pair of remarkable and important theories: the phenomenological Ginzburg–Landau theory (1950) and the microscopic BCS theory (1957).


title: Superconductivity

text: In 1950, the phenomenological Ginzburg–Landau theory of superconductivity was devised by Landau and Ginzburg. This theory, which combined Landau's theory of second-order phase transitions with a Schrödinger-like wave equation, had great success in explaining the macroscopic properties of superconductors. In particular, Abrikosov showed that Ginzburg–Landau theory predicts the division of superconductors into the two categories now referred to as Type I and Type II. Abrikosov and Ginzburg were awarded the 2003 Nobel Prize for their work (Landau had received the 1962 Nobel Prize for other work, and died in 1968). The four-dimensional extension of the Ginzburg–Landau theory, the Coleman-Weinberg model, is important in quantum field theory and cosmology.


title: Superconductivity

text: Also in 1950, Maxwell and Reynolds "et al." found that the critical temperature of a superconductor depends on the isotopic mass of the constituent element. This important discovery pointed to the electron-phonon interaction as the microscopic mechanism responsible for superconductivity.


title: Superconductivity

text: The complete microscopic theory of superconductivity was finally proposed in 1957 by Bardeen, Cooper and Schrieffer. This BCS theory explained the superconducting current as a superfluid of Cooper pairs, pairs of electrons interacting through the exchange of phonons. For this work, the authors were awarded the Nobel Prize in 1972.


title: Superconductivity

text: The BCS theory was set on a firmer footing in 1958, when N. N. Bogolyubov showed that the BCS wavefunction, which had originally been derived from a variational argument, could be obtained using a canonical transformation of the electronic Hamiltonian. In 1959, Lev Gor'kov showed that the BCS theory reduced to the Ginzburg–Landau theory close to the critical temperature.


title: Superconductivity

text: Generalizations of BCS theory for conventional superconductors form the basis for the understanding of the phenomenon of superfluidity, because they fall into the lambda transition universality class. The extent to which such generalizations can be applied to unconventional superconductors is still controversial.


title: Superconductivity

text: The first practical application of superconductivity was developed in 1954 with Dudley Allen Buck's invention of the cryotron. Two superconductors with greatly different values of the critical magnetic field are combined to produce a fast, simple switch for computer elements.